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The rumen has several important physiological functions: absorption, transport, metabolic activity, and protection. To clarify the molecular basis underlying the physiological function of the rumen, reticulum, omasum, and abomasum, we used mRNA differential display to isolate and identify differentially expressed genes in these tissues. We isolated 18 transcripts that coexpressed in the rumen, reticulum, and omasum. Five genes, ribosomal protein 19 (RPS19), basic helix-loop-helix domain containing class B2 (BHLHB2), NADH dehydrogenase flavoprotein 2 (NDUFV2), exosome component 9 (EXOSC9), and ribosomal protein 23 (RPS23), were highly expressed in the rumen of adult Holstein and Japanese Black cattle. Significant differences of expression were observed in the abomasum compared with the rumen, reticulum, and omasum. To investigate the expression pattern of these genes during the neonatal growth stage, the relative levels of gene expression were analyzed in the rumen and abomasum of 3-wk-, 13-wk-, and 18- to 20-mo-old Holstein cattle. The expression level of RPS19 did not change with age in the rumen and abomasum. The levels of BHLHB2, NDUFV2, and EXOSC9 mRNA in the abomasum decreased (P< 0.05) after weaning and declined (P< 0.05) further in adults; in contrast, expression in the rumen was not altered. Interestingly, the levels of RPS23 mRNA in the rumen increased (P< 0.05) after weaning and further increased in the adult; however, the level of expression of this gene decreased (P< 0.05) in the abomasum with weaning and age. This indicates that the 4 tissues, especially the rumen and abomasum, have different developmental pathways after birth and subsequent onset of rumination.

The synthesis of narrow diameter (&lt;10 nm) straight and branched PbSe nanowires (NWs) using a seeded solution approach is described. Solution-based PbSe NWs are obtained by injecting a solution consisting of trioctylphosphine selenide (TOPSe) and Au/Bi core/shell nanoparticles (NPs) into a mixture composed primarily of a mild coordinating solvent, a fatty acid, and a Pb precursor at moderate temperatures. The resulting NWs have diameters between 5 and 10 nm and lengths ranging from 1 to 5 μm. High-resolution transmission electron microscopy (TEM) reveals that the NWs exhibit a high degree of crystallinity and grow along the 〈100〉 directions of the lattice. By varying the initial reaction conditions, in particular the Pb to Se precursor ratio, branched NWs can be obtained. The growth mechanism appears similar to the case of analogous (branched) CdSe NWs, although the underlying rock salt structure of PbSe leads to right angles and t-shapes as opposed to CdSe, where v-shape, y-shape, and tripod morphologies are observed due to its underlying zinc blende and wurtzite lattices. In addition, “merged-y” NWs and higher order structures exhibiting multiple branching points are observed. Both straight and branched NWs have radii well below the bulk exciton Bohr radius of PbSe (46 nm), opening up opportunities for interesting optical and electrical studies of strong confinement in this system. The current investigation also sheds additional light on the mechanism behind self-induced branching in one-dimensional (1D) nanowires.

From metabolic considerations and prediction of an inhibitor-induced conformational change, novel adenosine deaminase (ADA) inhibitors with improved activities and oral bioavailability have been developed on the basis of our originally designed non-nucleoside ADA inhibitors. They demonstrated in vivo efficacy in models of inflammation and lymphoma. Furthermore, X-ray crystal structure analysis has revealed a novel induced fit to ADA.

Confined straight and branched CdSe nanowires (NWs) are synthesized using a solution-based approach which leverages advances in the synthesis of colloidal CdSe quantum dots (QDs) with incipient approaches for the seeded (solution) synthesis of semiconductor NWs. The resulting straight and branched NWs have typical diameters below 10 nm with accompanying lengths between 1 and 10 μm. In the case of branched NWs, tripod, v-shaped, and y-shaped morphologies are observed. Variations in this preparation lead to higher order structures with multiple arms. The branching transition is discussed, and a possible mechanism based upon geminate NW nucleation is proposed. Such solution-grown straight, branched, and higher-order NWs exhibit potentially interesting optical, electrical, and transport properties due to their narrow radii below the corresponding bulk exciton Bohr radius of CdSe. Furthermore, this transition from straight to branched morphologies opens up avenues for investigating not only size- but also shape-dependent optical/electrical properties of one-dimensional (1D) and quasi-1D materials.

We disclose herein optimization efforts around the novel, highly potent non-nucleoside adenosine deaminase (ADA) inhibitor, 1-[(R)-1-hydroxy-4-(6-(3-(1-methylbenzimidazol-2-yl)propionylamino)indol-1-yl)-2-butyl]imidazole-4-carboxamide 1 (Ki = 7.7 nM), which we recently reported. Structure-based drug design (SBDD) utilizing the crystal structure of the 1/ADA complex was performed in order to obtain structure−activity relationships (SAR) for this type of compound rationally and effectively. To utilize the newly formed hydrophobic space (F2), replacement of the benzimidazole ring of 1 with a n-propyl chain (4b) or a simple phenyl ring (4c) was tolerated in terms of binding activity, and the length of the methylene-spacer was shown to be optimal at two or three. Replacement of an amide with an ether as a linker was also well tolerated in terms of binding activity and moreover improved the oral absorption (6a and 6b). Finally, transformation of indol-1-yl to indol-3-yl resulted in discovery of a novel highly potent and orally bioavailable ADA inhibitor, 1-[(R)-4-(5-(3-(4-chlorophenyl)propoxy)-1-methylindol-3-yl)-1-hydroxy-2-butyl]imidazole-4-carboxamide 8c.

We disclose optimization efforts based on the novel non-nucleoside adenosine deaminase (ADA) inhibitor, 4 (Ki = 680 nM). Structure-based drug design utilizing the crystal structure of the 4/ADA complex led to discovery of 5 (Ki = 11 nM, BA = 30% in rats). Furthermore, from metabolic considerations, we discovered two inhibitors with improved oral bioavailability [6 (Ki = 13 nM, BA = 44%) and 7 (Ki = 9.8 nM, BA = 42%)]. 6 demonstrated in vivo efficacy in models of inflammation and lymphoma.

High-quality colloidal mercury sulfide quantum dots (QDs) are synthesized at room temperature using a strategy combining the effects of strongly binding Hg(II) ligands and metal/chalcogen precursor phase separation. This combination prevents both the rapid precipitation of bulk HgS in preparations involving only weak Hg(II) ligands and the reduction of mercury that takes place when only strongly binding ligands are used to slow the growth kinetics. Both the linear absorption and complementary band edge emission of the synthesized HgS QDs exhibit narrow, size-dependent transitions between 500 and 800 nm for sizes ranging from 1 to 5 nm in diameter. The metastable zinc blende phase of HgS is verified by wide-angle X-ray diffraction experiments and suggests potentially large tunable band edges if larger HgS nanocrystals that approach the bulk (zero energy) gap can be made. Growth of HgS QDs can be arrested by subsequent addition of Cd or Zn to the surface, after which the QDs can be stabilized with long-chain thiols or amines.

ABSTRACTT-705 (6-fluoro-3-hydroxy-2-pyrazinecarboxamide) has been found to have potent and selective inhibitory activity against influenza virus. In an in vitro plaque reduction assay, T-705 showed potent inhibitory activity against influenza A, B, and C viruses, with 50% inhibitory concentrations (IC50s) of 0.013 to 0.48 μg/ml, while it showed no cytotoxicity at concentrations up to 1,000 μg/ml in Madin-Darby canine kidney cells. The selectivity index for influenza virus was more than 2,000. It was also active against a neuraminidase inhibitor-resistant virus and some amantadine-resistant viruses. T-705 showed weak activity against non-influenza virus RNA viruses, with the IC50s being higher for non-influenza virus RNA viruses than for influenza virus, and it had no activity against DNA viruses. Orally administered T-705 at 100 mg/kg of body weight/day (four times a day) for 5 days significantly reduced the mean pulmonary virus yields and the rate of mortality in mice infected with influenza virus A/PR/8/34 (3 × 102PFU). These results suggest that T-705 may be a compound that is useful and highly selective against influenza virus infections and that has a mode of action different from those of commercially available drugs, such as amantadine, rimantadine, and neuraminidase inhibitors.

Fluorescence “blinking” kinetics of isolated colloidal InP quantum dots (QDs) are investigated via confocal single molecule microscopy. Analysis of fluorescence trajectories reveals inverse power law behavior (∝ 1/τ^m) in on/off time probability densities with mon ≈ 2.0(2) and moff ≈ 1.5(1). Such an inverse power law in both on/off times is inconsistent with a static distribution of electron/hole trapping sites and highlights the role of fluctuations in the QD nanoenvironment.

Ca2+ entry through plasma membrane has been considered to play a significant role in elevating cytosolic free Ca2+ concentrations during stimulus-secretion coupling in mast cells, but electrophysiological evidence of the Ca2+ channels is lacking. We examined the properties of secretagogue (compound 48/80)-induced currents in rat peritoneal mast cells, using the patch-clamp technique. In the whole cell recordings, the addition of compound 48/80 induced transient currents that were suppressed by Cd or reduced by ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). In Ringer solution containing 2 mM Ca2+, the current-voltage relation was fairly linear from -100 to 50 mV and the reversal potential was 14 +/- 10.1 mV (n = 9). When the external Ca2+ was approximately 1 microM, the compound 48/80-induced currents were marginal, but readmission of Ca2+ or Ba2+ to the bath solution led to an appearance of the currents. In the cell-attached patches, the stimulation enhanced the activity of inward current mediated by Ba2+. The unitary inward Ba2+ current was characterized by the unitary conductance of 10.5 +/- 2.0 pS (n = 10) with isotonic BaCl2 pipette solution, the extrapolated reversal potential of 60.7 +/- 16.0 mV (n = 10) positive to the resting membrane potentials. The percent open time of the inward Ba2+ current channel was not appreciably changed by voltage. In some whole cell recordings, an increase in openings of the cation-selective channel (20-45 pS) was identified in the stimulated cells. When the external Na+ was completely replaced by choline+, the compound 48/80-induced currents had a fairly linear current-voltage relation.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigenic stimulation of rat basophilic leukemia (RBL-2H3) cells, a tumor mast cell line, is associated with an increase in intracellular free Ca2+ concentrations ([Ca2+]i) and membrane polarization. We recorded whole cell and single-channel currents through the inwardly rectifying K+ channel, a major resting conductance of cells, using the patch-clamp technique, and we examined interactions between channel activity and [Ca2+]i. With 10 microM Ca2+ in the pipette, the amplitude of whole cell currents gradually declined within 5 min to 48 +/- 13% of that immediately after rupture of the patch membrane, in the presence of 1 mM ATP which minimized intrinsic rundown. In inside-out patches, activity of the channel was reduced by increasing the concentration of Ca2+ in the internal medium, both in the presence and absence of 1 mM ATP, with no apparent change in single-channel conductance. Time-averaged mean current activity in inside-out patches in the presence of 5 microM Ca2+ was less than 50% of that with Ca2+ of 100 nM or less. These results suggest that a rise in [Ca2+]i leads to a closure of the inwardly rectifying K+ channel. In some inside-out patches, inward currents characterized by burst composed of rapid transitions between open and closed states were observed (flickering currents). Single-channel properties of the flickering currents are similar to the inwardly rectifying K+ channel except for kinetics (single-channel conductance of 24.5 +/- 7.9 pS, inward rectification, and permeability to K+).(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract.: Effects of the extracellular Ca2+ concentration ([Ca2+] o ) on whole cell membrane currents were examined in mouse osteoclastic cells generated from bone marrow/stromal cell coculture. The major resting conductance in the presence of 1 mm Ca2+ was mediated by a Ba2+-sensitive, inwardly rectifying K+ (IRK) current. A rise in [Ca2+] o (5–40 mm) inhibited the IRK current and activated an 4,4′-diisothiocyano-2,2′-stilbenedisulfonate (DIDS)-sensitive, outwardly rectifying Cl− (ORCl) current. The activation of the ORCl current developed slowly and needed higher [Ca2+] o than that required to inhibit the IRK current. The inhibition of the IRK current consisted of two components, initial and subsequent late phases. The initial inhibition was not affected by intracellular application of guanosine 5′-O-(3-thiotriphosphate) (GTPγS) or guanosine 5′-O-(2-thiodiphosphate) (GDPβS). The late inhibition, however, was enhanced by GTPγS and attenuated by GDPβS, suggesting that GTP-binding proteins mediate this inhibition. The activation of the ORCl current was suppressed by pretreatment with pertussis toxin, but not potentiated by GTPγS. An increase in intracellular Ca2+ level neither reduced the IRK current nor activated the ORCl current. Staurosporine, an inhibitor for protein kinase C, did not modulate the [Ca2+] o -induced changes in the IRK and ORCl conductances. These results suggest that high [Ca2+] o had a dual action on the membrane conductance of osteoclasts, an inhibition of an IRK conductance and an activation of an ORCl conductance. The two conductances modulated by [Ca2+] o may be involved in different phases of bone resorption because they differed in Ca2+ sensitivity, temporal patterns of changes and regulatory mechanisms.

1. Motoneurone death induced by axotomy in the rat was studied following section of the medial gastrocnemius nerve near the muscle 4 days after birth. 2. The maximum twitch tension of the medial gastrocnemius muscle achieved by motor reinnervation after section of its nerve was about 70% of that measured on the contralateral, intact side. 3. The number of motor units counted at 35‐45 days of age in the animals whose medial gastrocnemius nerves had been sectioned on day 4 was 62% of that observed in normal rats. 4. The number of medial gastrocnemius motoneurones retrogradely labelled with horseradish peroxidase (HRP) 30‐40 days after section of the medial gastrocnemius nerve was 77% of that labelled on the contralateral, intact side. 5. When the medial gastrocnemius nerve had been sectioned on day 4 and prevented from peripheral reinnervation, the number of medial gastrocnemius motoneurones labelled with HRP was, on the average, only 18% of that labelled on the control side. 6. Decreased number of medial gastrocnemius motoneurones labelled with HRP following prevention of peripheral reinnervation was associated with a decrease in the neurone density of the motor cell column, indicating the occurrence of motoneurone death. 7. The majority of medial gastrocnemius motoneurones axotomized 4 days after birth appear to maintain their survival for about 2 weeks without target contact. 8. The area of the compound action potential of medial gastrocnemius motor fibres once decreased after axotomy on day 4 began to recover from the 12th day after the operation if reinnervation by the cut peripheral nerve had been allowed, whereas the compound action potential continued to decrease in those axotomized motoneurones whose reinnervation had been prevented. 9. It is concluded that target dependence of motoneurone survival previously observed at embryonic stages is still present during the early post‐natal period.

1. The electrophysiological properties were compared between sexually dimorphic motoneurones in the spinal nucleus of the bulbocavernosus (SNB) and those innervating hindlimb muscles by the whole‐cell recording technique in thin slices of the neonatal rat spinal cord. 2. The mean duration of action potentials in SNB motoneurones was significantly longer than that in hindlimb motoneurones. 3. The spike duration of motoneurones was inversely related to the magnitude of transient K+ currents (IA), and in this relation, there was a continuous gradation between SNB and hindlimb motoneurones. 4. The mean duration of spike after‐hyperpolarization (AHP) in female SNB motoneurones was significantly longer than that in male SNB motoneurones. 5. In both SNB and hindlimb motoneurones, sustained, Ca(2+)‐dependent K+ currents (IAHP) appear to be responsible for the generation of AHP. When IAHP was recorded as a tail current following an identical depolarizing pulse, the magnitude and time course of IAHP were relatively uniform, regardless of the type of motoneurone. 6. In both SNB and hindlimb motoneurones, voltage‐gated Ca2+ currents showed an initial transient phase followed by a sustained phase. The mean magnitude of sustained Ca2+ currents was larger in female SNB motoneurones than in male SNB motoneurones, whereas the mean magnitude of transient Ca2+ currents showed no significant different between male and female SNB motoneurones. 7. It is concluded that SNB and hindlimb motoneurones cannot be classified into two distinct neurone types in terms of their electrophysiological properties. 8. It is suggested that the predominant occurrence of natural cell death in female SNB motoneurones during early development may be due in part to high densities of sustained Ca2+ channels in these neurones.

Auditory evoked responses (AERs) were recorded from the primary cortex, medial geniculate body (MG), inferior colliculus (IC) and cochlear nucleus (CN) of the cat anesthetized with sodium pentobarbitone to examine the effects of increased intracranial pressure (ICP) on neural activity in the different levels of auditory centres. ICP was increased by injecting saline solution into the intracranial space and a tone burst was used for activating the auditory centres. Cortical response (ACR) began to decrease in amplitude from about 30-40 mmHg of ICP. A decrease in amplitude of MG response and that of IC response followed in the order with a further increase in ICP. CN response was most resistant and usually remained even when ACR and MG responses were totally abolished. Recovery of the AERs followed a release of the increased pressure in the reversed order to the decrease in the AERs. When an increase was repeated with a short interval of pressure release such as 5 to 10 min, recovery of ACR became much slower and no recovery was sometimes observed 30-60 min after the release of ICP increased to a level below 100 mmHg. A discussion was conducted on the origin of the changes in AERs in response to increased ICP. We concluded from the results that the higher auditory centres are more susceptible to an increase in ICP to suppress the neural activities without apparent influence on the lower centres. A clinical test of ABR may be available to predict the prognosis of the auditory disorders.

1. The properties of medial gastrocnemius (fast alpha) and soleus (slow alpha) motoneurones of the cat were examined with intracellular electrodes 33–154 days after self‐ or cross‐union of the muscle nerves.

1. Electrophysiological properties of soleus motoneurones in adult cats were examined with intracellular electrodes following alterations of activity of the soleus muscle induced by transection of the thoracic spinal cord or by conduction block of the muscle nerve with tetrodotoxin (TTX) cuffs. Attempts were also made to maintain muscle activity by daily stimulation of the maintain muscle activity by daily stimulation of the peripheral nerve. 2. Within 8 days after transection of the thoracic cord, soleus motoneurones showed a significant decrease in the duration of afterhyperpolarization following action potentials. This change in motoneurone properties induced by cord transection was prevented by daily stimulation of the sciatic nerve. 3. Soleus motoneurones showed a significant decrease in the duration of after‐hyperpolarization within 8 days after conduction block of the soleus nerve with TTX. This change in montoneurone properties was prevented by daily stimulation of the nerve peripheral to the TTX cuff but not central to the cuff. 4. The soleus muscle showed a significant decrease in weight relative to body weight within 8 days after transection of the thoracic cord. This decrease in muscle weight following cord transection was prevented by daily stimulation of the sciatic nerve. 5. No fibrillation was detected in the soleus muscle 8 days after conduction block of the soleus nerve with TTX. The maximum twitch tension of the soleus muscle evoked by nerve stimulation showed no significant difference between the two sides treated and untreated with TTX. Fast axoplasmic transport measured with cholinesterase as a marker was not affected by TTX. Thus, there was no sign of functional although morphological abnormalities were found in some nerve fibres. 6. It is concluded that motoneurone properties in an adult depend partly upon some factors associated with activity of the innervated muscles and that such trophic signals are retrogradely carried by the motor axons.

1. The spinal cord of kittens, 3‐‐5 days of age, was transected at the lower thoracic level. Isometric contractions of the medial gastrocnemius and soleus muscles as well as intracellular potentials of their motoneurones were recorded after varying post‐operative periods of up to 110 days. Similar observations were made 52‐‐59 days after cord transection in adult cats. 2. In cord‐transected kittens, contraction time of the gastrocnemius muscle showed normal development, whereas the soleus muscle failed to maintain slow contraction. In adult cats, cord transection increased the speed of contraction in the soleus muscle without significant changes in contraction times of the gastrocnemius muscle. 3. Soleus motoneurones showed a normal post‐natal increase in the duration of afterhyperpolarization (a.h.p.) up to a certain stage (61‐‐71 days in age) following cord transection. However, the subsequent increase in the duration of a.h.p. of soleus motoneurones observed in normal kittens was lacking in cord‐transected kittens. It is suggested that soleus motoneurones show two stages of differentiation in terms of the duration of a.h.p. 4. In adult cats, cord transection caused a decrease in the duration of a.h.p. of soleus motoneurones approximately to the value observed at the end of the first stage of differentiation in kittens. 5. The duration of a.h.p. of gastrocnemius motoneurones remained virtually unchanged follwoing cord transection in both kittens and adult cats. 6. The positive correlation between the duration of a.h.p. of soleus motoneurones and contraction time of the innervated muscle fibres normally observed in kittens and adult cats was absent following cord transection. 7. It was assumed that alteration s in contraction time of the muscle following cord transection are due to virtual elimination of motoneurone discharge and that the duration of a.h.p. reflects the discharge pattern of motoneurones under normal conditions. Based on these assumptions, a possible process for normal post‐natal differentiation of motoneurone and muscle is proposed.

1. Monosynaptic excitatory post‐synaptic potentials (e.p.s.p.s) were recorded from medial (m.g.) and lateral gastrocnemius (l.g.) motoneurones in the cat 2‐30 weeks after crushing the m.g. nerve.

1. Monosynaptic excitatory post‐synaptic potentials (e.p.s.p.s.) were recorded from triceps surae motoneurones of the cat 2‐8 months after section of the medial gastrocnemius nerve whose regeneration into the muscle was prevented. In other animals, the cut nerve was reunited to the muscle with a post‐denervation delay varying from 2 to 6 months, and the e.p.s.p.s were recorded 2 months later. The e.p.s.p.s were evoked by stimulation of the medial gastrocnemius nerve central to the site of the section or reunion. 2. The mean amplitudes of the e.p.s.p.s decreased with time after nerve section, virtually disappearing by the eighth post‐operative month. The decrement of the e.p.s.p. amplitude occurred more quickly in soleus motoneurones than in medial or lateral gastrocnemius motoneurones. 3. The e.p.s.p.s evoked in medial or lateral gastrocnemius motoneurones from the cut medial gastrocnemius nerve returned to normal levels 2 months after reunion of the cut nerve even following a post‐denervation delay of 6 months. However, in soleus motoneurones the e.p.s.p. recovery was incomplete. 4. The degree of functional motor reinnervation of the medial gastrocnemius muscle depended upon the post‐denervation delay preceding the reunion operation. With a delay of 6 months before the reunion, the muscle showed no or only weak contractions in response to nerve stimulation. 5. Axotomized medial gastrocnemius motoneurones showed a significant decrease in conduction velocity and significant increase in the amplitude of overshoot of action potentials. The changes persisted even when the cut nerve was reunited to the muscle 2‐6 months after denervation. 6. When the cut medial gastrocnemius nerve was reunited to the muscle 4 months after denervation, most of the sensory fibres, tested 2 months later, failed to respond to muscle stretch. 7. It is concluded that recovery of monosynaptic e.p.s.p.s following reconnexion of the cut nerve with its muscle does not require recovery of muscle activity, full restoration of sensory activity or the recovery of normal motoneurone properties. 8. It is also suggested that the degree to which central synaptic efficacy declines and recovers following section and regeneration of a peripheral nerve depends partly upon the type of motoneurone (fast phasic or slow tonic) with which the sensory fibres form synaptic connexions.

The brain stem, cervical cord and attached phrenic nerve were excised from neonatal rats and superfused in vitro. Respiratory activity was recorded from the phrenic nerve following transection of all the cranial nerves and dorsal roots. The frequency of spontaneous periodic activity recorded from the phrenic nerve was 6‐14/min during superfusion with a saline solution equilibrated with 5% CO2 in O2 at 25 degrees C (pH 7.3). The magnitude of respiration was estimated from the peak value of phrenic activity integrated for each 0.1 s period. When the pH of the superfusion fluid was altered by changing the HCO3‐concentration at constant PCO2, respiratory activity increased in low pH and decreased in high pH. These changes were maintained as long as a given pH was held. Respiratory changes observed under these conditions were characterized by alterations in both respiratory frequency and magnitude. When the CO2 level of the superfusion fluid was altered, maintaining constant pH by modified HCO3‐concentrations, respiratory activity increased at high PCO2 and decreased at low PCO2. These changes were transient and lasted only for a few minutes after exposure to a new level of PCO2. Respiratory changes observed under these conditions were characterized by alterations in magnitude but not in frequency. At constant PCO2 an increase in the HCO3‐concentration occasionally enhanced the magnitude of respiration before respiratory activity was depressed by the increased pH. This suggests that HCO3‐ may act independently as a stimulus to the central chemoreceptor. It is concluded that the mammalian central chemoreceptor for respiratory control is responsive independently to H+ and CO2 and that H+ and CO2 exert differential effects on the respiratory centre in terms of frequency and magnitude. It is suggested that frequency modulation and magnitude (tidal volume) modulation for respiratory control are triggered at different regions in the respiratory centre and/or rely on different mechanisms.

Electrophysiological properties of the ventral giant axon in the abdominal nerve cord of the cockroach were studied by recording intracellular potentials following partial or complete block of the K+ conductance. When the K+ conductance was completely blocked by tetraethylammonium (TEA) and 3,4-diaminopyridine, the intensity of depolarizing currents necessary for eliciting the action potential was markedly decreased, and the action potential was followed by a prolonged plateau potential. During the plateau potential following the spike, the input resistance was significantly reduced. The plateau potential was not affected by changing the external Ca2+ concentration but depended on the external Na+ concentration in a manner expected from the Nernst equation and was blocked by tetrodotoxin (TTX). During the plateau potential, the Na+ conductance responsible for the spike was inactivated, whereas immediately after the plateau potential a newly evoked spike was not followed by a plateau potential, suggesting different inactivation kinetics between the spike and plateau Na+ conductances. When the K+ conductance was partially blocked by TEA alone, slow depolarizing responses were evoked at voltage levels a few millivolts more positive than the resting potential. The "threshold" for the slow potential was much lower than that for the spike potential. The slow potential produced after partial block of the K+ conductance was not affected by alterations of the external Ca2+ concentration but was blocked by TTX or in a Na+-free solution. Even in normal medium, a small TTX-sensitive depolarizing response was discernible. This response was similar in its time course and threshold to the slow potential observed after partial block of the K+ conductance. It is concluded that the cockroach giant axon has two populations of Na+ channels, which can be distinguished by differences in time course and voltage levels for activation and that the slow, low-threshold Na+-dependent potential is largely masked by delayed increases in the K+ conductance under normal conditions. It remains uncertain whether the low-threshold slow potential and the plateau potential originate from the same or different populations of Na+ channels.

Responses were recorded extra- or intracellularly from single, small afferent fibers of the goldfish saccule, that is, S2 fibers, to clarify how the spontaneous and sound-evoked firings in these fibers are initiated from generator potentials. Spontaneously active units randomly selected from the saccular nerve of five goldfish (total 78 units) were classified by the coefficient of variation (CV) of interspike intervals into irregular (59 units; CV greater than 0.3), intermediate (10 units), and regular types (9 units; CV less than 0.23). The irregular type showed a burst (38 units) or random (21 units) pattern of firing in spontaneous activity. In cases where a clear generator potential could be recorded in response to each sound wave, spontaneous generator potentials could also be observed in the absence of stimulus sound. These spontaneous potentials were irregular in amplitude and time course, and often contained components much slower than the sound-evoked generator potentials. The sound-evoked generator potentials in S2 fibers were produced with a delay of 0.4-0.85 ms following each sound wave, and had a time course comparable to the sound-evoked excitatory postsynaptic potentials (EPSPs) of large S1 fibers. They also shared other properties such as adaptive decline in amplitude, incremental and decremental responses, and off-suppression. The mean amplitude of the sound-evoked generator potentials in S2 fibers was linearly related to the rate of afferent firing. There was no apparent difference in the action potential threshold amplitude for spontaneous and sound-evoked generator potentials. It may be concluded that the generator potentials that underlie the spontaneous and sound-evoked firing of S2 fibers are produced by the release of transmitter by hair cells.

1. Isometric contractions of the medial gastrocnemius (fast switch) and soleus (slow twitch) muscles were recorded in kittens ranging in age from 3 to 112 days, as well as in adult cats. 2. It was confirmed that the speed of contraction of the gastrocnemius muscle becomes progressively faster during the first few weeks after birth, whereas contraction times of the soleus muscle show little changes or a slight prolongation during the period of post‐natal development. 3. The properties of gastrocnemius (fast alpha) and soleus (slow alpha) motoneurons were examined with intracellular electrodes in kittens at three different stages; 16‐20, 61‐71 and 100‐112 days in age. 4. The axonal conduction velocities of both gastrocnemius and soleus motoneurones increased monotonically throughout the period of development and showed no correlation with post‐natal changes in contraction times of the innervated muscles. 5. The duration of after‐hyperpolarization in soleus motoneurones became progressively longer with age, while that in gastrocnemius motoneurones remained virtually unchanged during development. 6. The relation between the duration of after‐hyperpolarization and the axonal conduction velocity in kitten motoneurones was similar to that observed in axotomized motoneurones of adult cats. 7. It is suggested that fast and slow alpha motoneurones show postnatal differentiation in terms of the duration of after‐hyperpolarization and that axotomy leads to 'dedifferentiation' of the motoneurone properties. 8. Post‐natal changes in the contractile properties of skeletal muscles were independent of the changes in the duration of after‐hyperpolarization of the innervating motoneurones. However, it remains uncertain whether muscle differentiation is independent of the discharge pattern of the innervating motoneurones.

1. The properties of medial gastrocnemius (m.g., fast α) and soleus (sol., slow α) motoneurones of the cat were examined with intracellular electrodes 8–119 days after section of the muscle nerves.

1. The properties of spinal motoneurones of normal and dystrophic mice (129/ReJ) were examined with intracellular electrodes. 2. The following parameters of spinal motoneurones showed no significant differences between normal and dystrophic mice: resting and action potentials, the amplitude and duration of after‐hyperpolarization, rheobasic current for excitation, threshold for excitation of the somadendritic membrane (IS‐SD inflexion) and input resistance. 3. The changes in motoneurone properties observed 13–16 days after section of the sciatic nerve (axotomy) were similar in both normal and dystrophic mice. 4. The axonal conduction velocity of motoneurones in dystrophic mice was about ten times slower than that in normal mice. The conduction velocity of the sciatic nerve was only about 25% slower in dystrophic mice than in the normal animal. The estimated ventral root conduction velocity as well as the observed dorsal root conduction velocity in dystrophic mice was at least twenty times slower than that in normal mice. 5. In dystrophic mice, spinal motoneurones often showed multiple discharges in response to single, antidromic stimuli. The site of initiation of multiple discharge was located in the motor axon rather than in the motoneurone cell body. 6. In dystrophic mice, nerve impulses were transmitted from fibre to fibre (‘cross‐talk’). The site of impulse transmission among nerve fibres was near the distal portion of the spinal roots. 7. Synaptic potentials and peripheral reflex discharges evoked by stimulation of the dorsal roots showed a longer latency and were more prolonged in dystrophic mice than in the control mice. 8. The motoneurone properties of dystrophic mice showed no tendency of progressive changes with age ranging from 63 to 148 days. 9. It is concluded that the properties of motoneurone cell bodies examined in dystrophic mice are indistinguishable from those in normal mice and that the only abnormality in motoneurones of the former residues in the motor axon. 10. It is suggested that integrity of the discharge pattern of spinal motoneurones in dystrophic mice is interfered by anomalous impluse transmission in the motor axons and that the motoneurones in dystrophic mice are a homogeneous group rather than a mixture of "normal" and "abnormal" neurones.

1. The properties of soleus motoneurones of the cat were examined with intracellular electrodes about 3 weeks after partial denervation of the soleus muscle. Soleus motoneurones whose axons had been left intact were distinguished from those whose axons had been sectioned by the presence or absence of muscle contraction in response to intracellular stimulation of each motoneurone. 2. The average twitch tension of motor units evoked by intracellular stimulation of intact soleus motoneurones after partial denervation of the muscle was not significantly different from that observed in control, unoperated cats. Therefore, it was assumed that the majority of intact motoneurones had not been subject to injuries in their axons upon partial denervation. 3. Soleus motoneurones whose axons had been sectioned showed a significant increase in overshoot of action potentials and a significant decrease in resting membrane potential, in axonal conduction velocity and in the duration of after‐hyperpolarization. 4. Soleus motoneurones whose axons had been left intact also showed a significantly shorter after‐hyperpolarization than that seen in control, unoperated cats. Other electrophysiological properties of the intact soleus motoneurones were indistinguishable from those observed in unoperated animals. 5. The decrease of the duration of after‐hyperpolarization in intact soleus motoneurones was greater in highly denervated preparations than in moderately denervated preparations. 6. The decrease of the duration of after‐hyperpolarization in intact soleus motoneurones was associated with a decrease in contraction times of the innervated muscle fibres, the former preceding the latter by one to two weeks. 7. It is concluded that motoneurone properties can be modified without injury to their axons and that alterations in the properties of intact motoneurones depend upon the degree of partial denervation of the muscle. The possible signal for alterations of motoneurone properties is discussed. 8. It is also concluded that the contractile properties of muscle fibres can be modified without cross‐union of the nerves. It is suggested that the contractile properties of muscle fibres may be linked to the duration of after‐hyperpolarization or to some mechanism related to this factor in the innervating motoneurones.

1. The properties of dorsal root ganglion cells in the lumbosacral segments were examined with intracellular electrodes about 3 weeks after section of the central (dorsal roots) or peripheral processes in the cat.

1. The fast‐twitch flexor digitorum (the lateral head; equivalent to the flexor hallucis longus) and slow‐twitch soleus muscles of the cat were denervated, and the two nerves immediately reunited to one or the other muscle. Contraction times of the dually reinnervated muscle were examined 9 weeks post‐operatively in response to separate stimulation of its own and the foreign nerve. Over a 5 week period before the terminal experiment, a variety of artificial activity patterns was imposed on the two nerves.

1. On application of a step decrement in the sound intensity, the amplitude of excitatory post‐synaptic potentials (e.p.s.p.s) recorded intracellularly from large afferent auditory fibres in goldfish's sacculus showed a decremental response in which the amplitude of the e.p.s.p.s was temporarily reduced to a very low level, but soon returned to a new steady level appropriate to the decreased sound intensity. This response seems to underlie the temporary reduction in the rate of afferent discharge observed in the mammalian cochlea upon cessation of sound or upon reduction of its intensity 2. A statistical analysis revealed that reduction in the size of the mean quantal content (m) during the decremental response was associated with reduction in the size of binomial population (n), but not that of the probability (p) of any one of the available quanta actually being used. 3. The temporary reduction in the size of n during the decremental responses can be explained if it is assumed that replenishment to vacant release sites was channelled to high threshold sites and that the low threshold sites were bypassed. The mechanism underlying this special type of replenishment is discussed in relation to the ultrastructural features of presynaptic sites in the hair cell.

The lumbar spinal cord excised from neonatal rats was superfused with an oxygenated saline, and monosynaptic excitatory post‐synaptic potentials (e.p.s.p.s) were recorded from the lumbar motoneurones following stimulation of muscle nerves of the hind leg. The amplitude of monosynaptic e.p.s.p.s increased with an increase in the external Ca2+ concentration ([Ca2+]o). In [Ca2+]o of 0.5‐2 mM, the relation between the e.p.s.p. amplitude and [Ca2+]o was linear with a slope of 1.6 on double logarithmic co‐ordinates. An increase in [Mg2+]o in a range of 1‐5 mM reduced the e.p.s.p. amplitude without affecting the slope of the relation between log e.p.s.p. amplitude and log [Ca2+]o, suggesting competitive interaction between Ca2+ and Mg2+. When [Ca2+]o was increased to 4‐12 mM, the latency of monosynaptic e.p.s.p.s was prolonged, and the antidromic action potential failed to invade the cell body or initial segment of motoneurones. Under these conditions, the monosynaptic e.p.s.p.s were still present. It is concluded that at near‐normal levels of [Ca2+]o the effects of Ca2+ and Mg2+ on the e.p.s.p. amplitude are accounted for entirely by their competitive interaction for the probability of transmitter release without altering the mode of impulse propagation at central terminals of the Group Ia sensory fibres. It is suggested that impulses of Ia sensory fibres normally invade their terminals without intermittent blocks at their terminal branch points.

1. The amount of calcitonin gene‐related peptide (CGRP) released from the isolated rat soleus muscle was measured by enzyme immunoassay. 2. When the soleus muscle was exposed to a solution containing high K+ (20‐100 mM) in the presence of tetrodotoxin, the amount of CGRP released into the bathing medium increased with an increase in the K+ concentration. 3. The exposure to 100 mM‐K+ did not increase CGRP release from chronically denervated soleus muscles or from pieces of the soleus nerve separated from the muscle. 4. The amount of CGRP released from the isolated muscle by 100 mM‐K+ depended on the external Ca2+ concentration. The slope of the relation between the amount of CGRP release and the Ca2+ concentration was less than one on double logarithmic co‐ordinates. 5. Following chronic section of the lumbar ventral roots, the mean amount of CGRP released from the soleus muscle by 100 mM‐K+ was reduced by 28%, compared with that observed in normal muscle. 6. Antidromic stimulation of the lumbar dorsal roots at an intensity three times the threshold for most excitable sensory fibres failed to induce CGRP release from the soleus muscle, whereas stimulation at intensities 50‐100 times the threshold increased significantly the amount of CGRP release from the muscle. 7. Stimulation of the muscle nerve at an intensity sufficient to activate the alpha‐motor fibres did not release CGRP from the soleus muscle or from the diaphragm. 8. It is concluded that the major source of CGRP released from skeletal muscle is A delta‐ and/or C sensory terminals and that the Ca2+ dependence of CGRP release is less steep than that reported for acetylcholine release at neuromuscular junctions.

1. Rat facial motoneurones axotomized on the day after birth were examined morphologically, and their electrical properties were characterized using the whole‐cell recording technique in thin slices of the brainstem. 2. About 40% of facial motoneurones were lost within 4 days of axotomy, and only about 20% of the neurones survived 9 days after axotomy. 3. The surviving facial motoneurones examined 4 or 6 days after axotomy were reduced in size, and this was associated with a decrease in their input capacitance. 4. Both the resting potential and the amplitude of action potentials remained unchanged in axotomized facial motoneurones. 5. Facial motoneurones examined 4 or 6 days after axotomy showed an increase in the spike duration. When the preparation was superfused with a Ca(2+)‐free solution, the spike duration of axotomized facial motoneurones was shortened, whereas the spike duration of control facial motoneurones was prolonged. 6. The voltage‐gated transient K+ current (IA) density was significantly reduced in axotomized motoneurones, whereas the Ca(2+)‐dependent transient K+ current (IK, Ca) density was not affected. 7. Voltage‐gated Ca2+ currents in facial motoneurones showed inactivation, displaying an initial transient phase followed by a sustained phase. The rate of inactivation of Ca2+ currents was significantly faster in axotomized neurones than in control neurones. 8. A small subpopulation of facial motoneurones examined 4 or 6 days after axotomy had a disproportionately high input resistance and a significantly longer after‐hyperpolarization. The probability of this occurring was correlated with the time course of cell death induced by axotomy. 9. It is concluded that facial motoneurones axotomized in neonatal rats comprise two subpopulations. The subpopulation characterized by a markedly high input resistance is suggested to represent the neurones which are at the ‘prelethal’ stage or in the process of cell death.

Inositol-1,4,5,-trisphosphate (IP₃)-activated calcium-permeable channels were recorded from inside-out patches of cultured cerebellar Purkinje cells. When 2-5 µM of IP₃ was applied to the internal surface of the inside-out patches, inward Ba2+ currents were activated within 10 sec following the application in 11 out of 24 patches. In the presence of heparin (100 µg/ml), activation of Ba2+ currents by IP₃ was inhibited. Unitary currents with different amplitudes and kinetics were observed; small and large unitary currents, and rapid fluctuations with various amplitudes. The small unitary currents (single channel conductance; 5.6 pS) were most frequent. Addition of inositol 1,3,4-trisphosphate (2-5 µM) slightly activated Ba2+ currents in 2 out of 10 patches, but the amount of the increment was much smaller than that produced by IP₃. These results suggest a possibility that IP₃ directly activates Ca2+-permeable channels in the plasma membrane of cerebellar Purkinje cells.Copyright 1994, 1999 Academic Press

Abstract: Electrophysiological properties of mouse bone marrow-derived mast cells (BMMC) were studied under the whole-cell clamp configuration. About one third of the cells were quiescent, but others expressed either inward or outward currents. Inwardly rectifying (IR) currents were predominant in 14% of the cells, and outwardly rectifying (OR) currents in 24%. The rest (22%) of the cells exhibited both inward and outward currents. The IR currents were eliminated by 1 mm Ba2+, and were partially inhibited by 100 mgrm quinidine. The reversal potential was dependent on extracellular K+, thereby indicating that K+ mediated the IR currents. The negative conductance region was seen at potentials positive to E K. The OR currents did not apparently depend on the extracellular K+ concentration, but were reduced by lowering the extracellular Cl– concentration. The OR currents were partially blocked by 1 mm Ba2+, and were further blocked by a Cl– channel blocker, 4,4prime-diisothiocyano-2, 2prime-stilbenedisulfonate (DIDS). In addition, the reversal potential of the OR currents was positively shifted by decreasing the ratio of external and internal Cl– concentrations, suggesting that Cl– was a major ion carrier. In cells exhibiting IR currents, the membrane potential varied among cells and tended to depolarize by elevating the external K+ concentration. In cells with OR currents, the resting potential was hyperpolarized in association with an increase in conductance. These results suggest that BMMC have a heterogeneous electrophysiological profile that may underlie a variety of ion channels expressed in different phenotypes of mast cells. Activities of both the inwardly rectifying K+ channel and the outwardly rectifying Cl– channel seem to contribute to the regulation of the membrane potential.

Hippocampal slices prepared from neonatal rats were cultured for several weeks, and excitotoxicity induced in CA1 pyramidal neurons byN-methyl-d-aspartate was evaluated at different culture stages. CA1 neurons cultured for one week exhibited cell death predominantly within 1–3 h after a 15-minN-methyl-d-aspartate insult (early death), whereas those cultured for three weeks showed cell death mainly a few hours to 24 h after the insult (delayed death). CA1 neurons cultured for two weeks were in a transitional state, expressing only weak early and delayed forms of cell death in response toN-methyl-d-aspartate. TheN-methyl-d-aspartate-induced early cell death observed in the one-week group depended on external Cl− but did not require external Ca2+; rather, early cell death was enhanced in Ca2+-free solution. This early cell death was accompanied by cell swelling, but cell swelling alone produced by osmotic changes failed to induce cell death. There was no evidence that CA1 neurons in the one-week group were more responsive toN-methyl-d-aspartate than those in the two other groups. Delayed cell death examined in the three-week group depended on external Ca2+ but was independent of Cl−. The density ofN-methyl-d-aspartate-induced whole-cell currents recorded from CA1 neurons in Mg2+-free solution remained unchanged during three weeks of culture. However, theN-methyl-d-aspartate receptor channel in the three-week group was more resistant to Mg2+ block than that in the one- or two-week group. The incidence ofN-methyl-d-aspartate-induced delayed cell death was higher in the three-week group than in the two-week group in normal solution but not in Mg2+-free solution. Thus, Mg2+, block-resistant properties of theN-methyl-d-aspartate receptor channel acquired during prolonged culture may account for the high incidence ofN-methyl-d-aspartate-induced delayed cell death in the three-week group. However, theN-methyl-d-aspartate receptor subunits expressed in the CA1 subfield did not show any feature specific to the three-week group.

Relationship between the firing rate in the auditory fibers and the amplitude of the excitatory postsynaptic potentials (EPSPs) that trigger afferent impulses was investigated. The unitary EPSPs and spike potentials were extracellularly recorded from the goldfish large auditory fibers by means of a microelectrode placed close to the distal terminals. The relation between the firing rate and the amplitude of the EPSPs was studied using a variety of stimulus conditions. The firing probability of phase-locked impulses was linearly related to the mean amplitude of the EPSPs determined for the same time bins. The same linear relation was applicable for the firings elicited by different intensities of sound and observed at various times after onset and also for the firings produced by applying step increments in intensity. The threshold amplitude of the EPSPs required for initiation of afferent impulses was unchanged in these different situations. Random changes in the amplitude of successively evoked EPSPs were found to underlie the probabilistic nature of the sequence of afferent firings. The present results indicate that the per stimulus adaptation and incremental and decremental responses, as observed in the firing probability of afferent impulses, are largely attributable to adaptive changes in the mean amplitude of the evoked EPSPs and not to changes in excitability of the auditory fibers.

1. The depressant actions of taurine applications on lumbar motoneurons in the isolated frog spinal cord were studied using conventional intracellular recordings and the two-electrode voltage-clamp technique. 2. With microelectrodes containing K+-acetate, 0.75-2 mM taurine mostly induced a hyperpolarization that often faded or turned into depolarization during the continuous application. A higher concentration (5-7.5 mM) depolarized a majority of cells. The effects on the membrane potential were associated with an increase in input conductance (approximately 285%). 3. The reversal potential of the taurine-induced currents was approximately -70 mV, with microelectrodes containing K+-acetate. In recordings using KCl-filled electrodes, taurine (less than or equal to 2 mM) produced a large depolarization (greater than or equal to 20 mV) at resting potentials near -50 mV, thereby indicating that the reversal potential was positively shifted by loading the cell with Cl-. These results suggest that the taurine potentials were mediated predominantly by an increased Cl- permeability. 4. Voltage-dependent relaxations of taurine currents were observed in 10 of 14 neurons. 5. A linear relation was found between the input conductance and the amount of current required to generate a 1-mV increment in EPSP at resting potential. 6. Polysynaptic excitatory postsynaptic potentials (EPSPs) and currents (EPSCs) were more susceptible to taurine than the monosynaptic responses. Taurine (less than 1 mM) seemed to suppress the interneurons mediating polysynaptic pathways. 7. Monosynaptic EPSPs and EPSCs were decreased with higher concentrations of taurine (greater than 1 mM). The percent reduction of EPSPs and that of the corresponding EPSCs had a positive correlation (r = 0.95), whereas, there was no significant correlation between changes in EPSPs and in input conductance, and between changes in EPSCs and in input conductance. The amount of current required to produce a 1-mV increment of EPSP was increased in the presence of taurine, in association with the increased input conductance. 8. Taurine suppressed synaptic potentiation of EPSPs evoked by paired stimuli, at an interval of 60-180 ms. Gamma-D-glutamylglycine, an antagonist of receptors for excitatory amino acids, greatly reduced the amplitude of EPSPs, but had little effect on synaptic potentiation. 9. Taurine suppressed glutamate currents evoked at membrane potentials, clamped near rest in low Ca2+, high Mg2+ solution. 10. These findings suggest that the taurine-induced reduction of EPSPs is due mainly to suppression of EPSCs, through both presynaptic and postsynaptic mechanisms.(ABSTRACT TRUNCATED AT 400 WORDS)

Wear volume, surface area and coefficient of friction of UHMWPE cup crosslinked with gamma radiation of 0, 50, 75, 100, 125, 150 and 200 Mrad sliding against an alumina ball were measured using a sphere-on-flat reciprocating type tribology testing machine. The effects of gamma radiation were scarcely observed in coefficient of friction. The coefficient of friction under lubricated (distilled water) and non-lubricated testing conditions was 0.08 to 0.12 and 0.20 to 0.25, respectively. The wear volume of UHMWPE with radiation of 50 Mrad, 75 to 150 Mrad, and 200 Mrad was 70 to 80%, 18 to 25%, and 12 to 15%, respectively, in comparison to non-irradiated specimens. Elongation and tensile strength of UHMWPE with radiation of 100 Mrad decreased to 6%, and 50% of that without radiation, respectively. The hardness increased with increase of the radiation dose. From several kinds of tribological findings, mechanical strength tests, and studies of long-term clinical findings, it is concluded that approximately 200 Mrad is the optimum dose of gamma radiation for clinical use in total hip prostheses.

1. Monosynaptic excitatory post‐synaptic potentials (e.p.s.p.s) were recorded from triceps surae motoneurones in the cat following section or chronic conduction block of the medial gastrocnemius (m.g.) nerve with tetrodotoxin (TTX) or after daily stimulation of the sciatic nerve. 2. The mean maximum amplitudes of homonymous and heteronymous monosynaptic e.p.s.p.s evoked by stimulation of the mg. nerve were reduced significantly between 1 and 2 weeks after section of the muscle nerve. The mean amplitudes of monosynaptic e.p.s.p.s produced in the same motoneurones by afferent volleys from the intact synergists showed no significant alterations. 3. Reduction of the amplitude of monosynaptic e.p.s.p.s. evoked by the sectioned m.g. afferent volleys was not prevented by daily stimulation of the sciatic nerve. The chronic stimulation of the sciatic nerve did not increase the amplitude of monosynaptic e.p.s.p.s evoked by stimulation of the intact, lateral gastrocnemius (l.g.) or soleus nerve. 4. Chronic conduction block of the intact m.g. nerve with TTX cuffs for 2 weeks resulted in a significant increase in the homonymous e.p.s.p. amplitude. The amplitude of the heteronymous e.p.s.p.s evoked in the same m.g. motoneurones by stimulation of the intact l.g. or soleus nerve showed no significant changes. 5. It is concluded that decreased central synaptic transmission following section of the peripheral nerve is not due to elimination of impulse activity (disuse) of the sensory input and that prolonged disuse of the sensory fibres causes an increase, rather than a decrease, in central synaptic efficacy.