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Current therapeutics are not effective for orofacial neuropathic pain, and better options are needed. The present study used inferior orbital nerve (ION)-injured mice to investigate the effect of inhibiting monoacylglycerol lipase (MAGL), an enzyme that degrades the major endocannabinoid 2-arachydonoylgycerol (2-AG) in orofacial neuropathic pain. The head-withdrawal threshold to mechanical stimulation of the whisker pad was reduced on days 3, 5, and 7 after ION injury. Injection of JZL184, a selective inhibitor of MAGL, on day 7 after ION injury attenuated the reduction in head-withdrawal threshold at 2 h after administration. Moreover, the numbers of MAGL-immunoreactive neurons in the trigeminal subnucleus caudalis (Vc) and upper cervical spinal cord (C1-C2) were significantly greater in ION-injured mice than in sham-operated mice but were reduced after administration of JZL184. The increase in MAGL immunoreactivity suggests that increased 2-AG production is followed by rapid enzymatic degradation of 2-AG. JZL184 inhibited this degradation and thus increased 2-AG concentration in the brain, particularly in the Vc and C1-C2 regions, thus attenuating pain. Our findings suggest that inhibition of 2-AG degradation by MAGL inhibitors is a promising therapeutic option for treatment of orofacial neuropathic pain.

To evaluate the mechanisms underlying orofacial motor dysfunction associated with trigeminal nerve injury, we studied the astroglial cell activation following chronic constriction injury (CCI) of the infraorbital nerve (ION) immunohistochemically, nocifensive behavior in ION-CCI rats, and the effect of the glutamine synthase (GS) blocker methionine sulfoximine (MSO) on the jaw-opening reflex (JOR), and also studied whether glutamate-glutamine shuttle mechanism is involved in orofacial motor dysfunction. GFAP-immunoreactive (IR) cells were observed in the trigeminal motor nucleus (motV) 3 and 14 days after ION-CCI, and the nocifensive behavior and JOR amplitude were also strongly enhanced at these times. The number of GS- and GFAP-IR cells was also significantly higher in ION-CCI rats on day 7. The amplitude and duration of the JOR were strongly suppressed after MSO microinjection (m.i.) into the motV compared with that before MSO administration in ION-CCI rats. After MSO administration, the JOR amplitude was strongly suppressed, and the duration of the JOR was shortened. Forty minutes after m.i. of glutamine, the JOR amplitude was gradually returned to the control level and the strongest attenuation of the suppressive effect of MSO was observed at 180 min after glutamine m.i. In addition, glutamine also attenuated the MSO effect on the JOR duration, and the JOR duration was extended and returned to the control level thereafter. The present findings suggest that astroglial glutamate-glutamine shuttle in the motV is involved in the modulation of excitability of the trigeminal motoneurons affecting the enhancement of various jaw reflexes associated with trigeminal nerve injury.

Flavonoids are biologically active polyphenolic compounds widely distributed in plants. Recent research has focused on high dietary intake of flavonoids because of their potential to reduce the risks of diseases such as cardiovascular diseases, diabetes, and cancers. We report here the effects of plant flavonoids on catecholamine signaling in cultured bovine adrenal medullary cells used as a model of central and peripheral sympathetic neurons. Daidzein (0.01 – 1.0 μM), a soy isoflavone, stimulated 14C-catecholamine synthesis through plasma membrane estrogen receptors. Nobiletin (1.0 – 100 μM), a citrus polymethoxy flavone, enhanced 14C-catecholamine synthesis through the phosphorylation of Ser19 and Ser40 of tyrosine hydroxylase, which was associated with 45Ca2+ influx and catecholamine secretion. Treatment with genistein (0.01 – 10 μM), another isoflavone, but not daidzein, enhanced [3H]noradrenaline uptake by SK-N-SH cells, a human noradrenergic neuroblastoma cell line. Daidzein as well as nobiletin (≥ 1.0 μM) inhibited catecholamine synthesis and secretion induced by acetylcholine, a physiological secretagogue. The present review shows that plant flavonoids have various pharmacological potentials on the catecholamine system in adrenal medullary cells, and probably also in sympathetic neurons. Keywords:: adrenal medulla, catecholamine, flavonoid, membrane estrogen receptor, tyrosine hydroxylase

Nicotine acts on nicotinic acetylcholine receptors in the adrenal medulla and brain, thereby stimulating the release of monoamines such as norepinephrine (NE). In the present study, we examined the effects of prolonged exposure to nicotine on NE transporter (NET) activity in cultured bovine adrenal medullary cells. Treatment of adrenal medullary cells with nicotine increased [(3)H]NE uptake in both a time- (1-5 days) and concentration-dependent (0.1-10 muM) manner. Kinetic analysis showed that nicotine induced an increase in the V (max) of [(3)H]NE uptake with little change in K (m). This increase in NET activity was blocked by cycloheximide, an inhibitor of ribosomal protein synthesis, but not by actinomycin D, a DNA-dependent RNA polymerase inhibitor. [(3)H]NE uptake induced by nicotine was strongly inhibited by hexamethonium and mecamylamine but not by alpha-bungarotoxin, and was abolished by elimination of Ca(2+) from the culture medium. KN-93, an inhibitor of Ca(2+)/calmodulin-dependent protein kinase II, attenuated not only nicotine-induced [(3)H]NE uptake but also (45)Ca(2+) influx in the cells. The present findings suggest that long-term exposure to nicotine increases NET activity through a Ca(2+)-dependent post-transcriptional process in the adrenal medulla.

We previously isolated RA-A47, which is recognized as an antigen of rheumatoid arthritis (RA), from a human chondrosarcoma-derived cell line (HCS-2/8). The N-terminal 21-amino-acid sequence of RA-A47 had 81% homology to the deduced amino acid sequence of the human heat-shock protein (HSP) 47 gene, the colligin gene, and 100% homology to that of the colligin-2 gene. Moreover, as is HSP47, RA-A47 was a heat-inducible collagen-binding protein. To further characterize RA-A47, we isolated ra-a47 cDNA from HCS-2/8 cells and human periodontal ligament fibroblast (HPLF) cells. The isolated ra-a47 cDNAs from both cells were almost the same as that of colligin-2. C504 and G505 in the cDNA sequences of both cells and C598 in the cDNA of HCS-2/8 were different from the corresponding bases of colligin-2 cDNA. These differences were also observed in genomic DNA. colligin cDNA was not isolated. To show that the isolated cDNA encodes RA-A47 protein, it was expressed in Cos-7 cells. The produced protein was 47kDa and was recognized both with RA sera and antirat HSP47 antibody, indicating that it is RA-A47 and has structural similarity to HSP47. These results taken together with our previous findings show that RA-A47 is the putative colligin-2 gene product and behaves as a human HSP47. Although colligin has been considered the human HSP47 gene, failure to detect the colligin gene and its mRNA suggests that colligin does not exist in human cells and that the HSP47 gene is identical with colligin-2, which encodes RA-A47.

To clarify the mechanism of cartilage degradation induced by mechanical stress, we investigated the influence of cyclic tension force (CTF) on the metabolism of cultured chondrocytes. The chondrocytes were exposed to CTF using a Flexercell strain unit. Five or 15 kPa of high frequency CTF significantly inhibited the syntheses of DNA, proteoglycan, collagen, and protein. Fifteen kPa of high frequency CTF induced the expression of interleukin-1 (IL-1), matrix metalloproteinase (MMP)-2 and -9 mRNA, and increased the production of pro- and active-MMP-9. The degradation of proteoglycan was inhibited by and MMP inhibitor, indicating that MMPs are involved in the degradation of proteoglycans induced by high frequency CTF. Moreover, reducing the frequency of CTF from high to low decreased the inhibition of proteoglycan synthesis. These findings suggest that the CTF frequency is one of the key determinants of chondrocyte metabolism. Low magnitude CTF, whether high or low frequency, did not cause the gene expression of cartilage degradation factors, suggesting that this CTF magnitude causes only minor changes in the cartilage matrix. High magnitude and frequency CTF caused the gene expression of IL-1 and MMP-9, followed by increases in the production of MMP-2 and -9 proteins, suggesting that excessive and continuous cyclic mechanical stress induces the production of IL-1 and MMP-9, resulting in cartilage degradation.

To determine the cooperative effect of laryngeal afferent signals on the swallowing reflex, we examined whether afferent signals originating from the left and right superior laryngeal nerve (SLN) modulates elicitation of the swallowing reflex in urethane-anesthetized rats. Mylohyoid electromyographic activity was recorded to quantify the swallowing reflex. The onset latency of the swallowing reflex and the time intervals between successive swallows were used to quantify and compare the effects of unilateral and bilateral electrical stimulations of the SLN. The mean latency of the first swallow and the mean time interval between swallows evoked with low frequency stimulation were both significantly different between unilateral and bilateral stimulations of the SLN. These findings suggest that facilitatory effect of afferent signals originating from the SLN bilaterally increase the motoneuronal activity in the medullary swallowing center and enhance the swallowing reflex.

Prolonged incubation with interleukin-1 beta (IL-1) induced the release of large amounts of NO and subsequently inhibited DNA synthesis and the biosynthesis and accumulation of proteoglycans in cultured rabbit articular chondrocytes (RAC). IL-1 also inhibited DNA synthesis in bovine aortic endothelial cells (BAE). On the other hand, DNA synthesis in BAE cocultured with RAC was not inhibited by prolonged incubation with IL-1. Moreover, conditioned media from RAC incubated for a long period with IL-1 stimulated DNA synthesis in BAE alone. This growth stimulatory activity was mainly due to the release of basic fibroblast growth factor, a heparin-binding growth factor, into RAC culture. Gelatin zymography of the RAC culture medium revealed that IL-1 increased the production of matrix metalloproteinase-2 (MMP-2) and MMP-9. NG-Monomethyl-L-arginine, an inhibitor of NO synthesis, inhibited all of these actions of IL-1. These results indicate that NO from RAC treated with IL-1 stimulates MMPs, which, in turn, degrade the extracellular matrix produced by RAC, resulting in the release of large amounts of basic fibroblast growth factor stored in the matrix, which then stimulates adjacent BAE proliferation. Thus, NO produced from RAC treated with IL-1 may modulate angiogenesis in the synovium of arthritic patients.

Endothelin (ET) receptors on chondrocytes were demonstrated using cultured rabbit costal chondrocytes. After crosslinking the receptors on the cells with 125 I-ET-1, two major bands of 43 kDa and 46 kDa were separated by SDS-PAGE. Scatchard analysis demonstrated two classes of ET receptors with K d values of 1 × 10 -10 M and 5 × 10 -9 M. The numbers of high- and low- affinity receptors were 1 × 10 4 and 2 × 10 5 per cell, respectively. The binding of ET-1 to chondrocytes was increased by treatment with PTH, DBcAMP, TGF-β1, IL-1β, RA and EGF. ET-1 stimulated DNA synthesis in cultured rabbit chondrocytes. ET-1 also stimulated calcium incorporation through the cell membrane of chondrocytes. These findings indicate that ET-1 has a physiological effect on chondrocytes via its receptors on the cells.

In a cultured osteoblastic cell line, MC3T3-E1 derived from newborn mouse calvaria, the mRNA encoding TRKC, which is the receptor molecule of neurotrophin-3 (NT-3), was detected by the polymerase chain reaction (PCR) method. The mRNAs of the normal type and one alternative form (C14) were highly expressed in the exponential growth phase of MC3T3-E1 cells and decreased as the cells reached the differentiation stage. NT-3, but not nerve growth factor (NGF), stimulated the proliferation of MC3T3-E1 cells in a dose-dependent manner. NT-3 also stimulated calcium incorporation through the surface of MC3T3-E1 cells, indicating the association of NT-3 and its receptor on the cell surface.

Norepinephrine transporter (NET) regulates noradrenergic synaptic transmission by controlling extracellular levels of norepinephrine (NE). The small GTPase, RhoA, and its downstream effector Rho kinase (ROCK) are involved in the regulation of actin cytoskeleton and focal adhesion/stress fiber formation, which may play an important role in various functions of the sympathetic nervous system. We report here the effect of fasudil, a ROCK inhibitor, on the functions of NET in cultured bovine adrenal medullary cells as a model of sympathetic neurons. Treatment of bovine adrenal medullary cells with fasudil caused an increase in [(3)H]NE uptake in time (8-120 h) and concentration (10-100 μM)-dependent manner. Another ROCK inhibitor, Y-27632 (10-100 μM, 1 day), also increased [(3)H]NE uptake by the cells. Kinetics analysis of the effect of fasudil on NE transport showed a significant increase in the V (max) of NE transport with little change in K (m). When both extracellular and intracellular Ca(2+) were removed by the deprivation of extracellular Ca(2+) and BAPTA-AM, a cell-permeable Ca(2+) chelator, [(3)H]NE uptake induced by fasudil was completely abolished. Nocodazole, an inhibitor of microtubule polymerization, but not cytochalasin D, an inhibitor of actin polymerization, suppressed the stimulatory effect of fasudil on [(3)H]NE uptake. The present findings suggest that the ROCK inhibitor fasudil up-regulates NET function in a Ca(2+)-dependent and/or nocodazole-sensitive pathway in adrenal medullary cells.

The use of injectable generic antineoplastic agents has been increasing. Few studies have compared the quality and adverse reactions of generic and branded antineoplastic agents; and therefore, generic agents have not gained wide acceptance. Paclitaxel injections, which are used for treating solid cancers, are being marketed by some companies in Japan. The degree of hypersensitive reactions to these drugs may vary because of the differences in chemical properties of the polyoxyethylene castor oil that is used as a solvent in the paclitaxel preparations. Therefore, we investigated the incidence of pulmonary edema occurring as a hypersensitive reaction in rats administered branded and generic paclitaxel injections. Moreover, we compared the chemical properties of these preparations. We found that the pH of branded and generic paclitaxel preparations diluted with saline was different. This difference in pH may be attributed to a difference in chemical properties from the additive. We observed no significant differences in pulmonary vascular permeability, arterial partial pressure of oxygen, or leakage of protein in the pulmonary alveolus, between paclitaxel preparations administered to rats. These results suggest that both paclitaxel preparations induced pulmonary edema of a similar level in rats, irrespective of the differences in their chemical properties.

Nobiletin, a compound of polymethoxy flavones found in citrus fruits, possesses a wide range of pharmacological activities. Here we report the effects of nobiletin on catecholamine secretion in cultured bovine adrenal medullary cells. Nobiletin (1.0-100 microM) concentration-dependently stimulated catecholamine secretion and (45)Ca(2+) influx. Its stimulatory effect of nobiletin on catecholamine secretion was abolished by deprivation of extracellular Ca(2+) and partially inhibited by specific inhibitors of voltage-dependent Ca(2+) channels and Na(+)/Ca(2+) exchangers. On the other hand, nobiletin suppressed catecholamine secretion and (22)Na(+) and (45)Ca(2+) influx induced by acetylcholine, an agonist of nicotinic acetylcholine receptors, in a concentration-dependent manner. It also inhibited catecholamine secretion, (22)Na(+) influx and/or (45)Ca(2+) influx induced by veratridine, an activator of voltage-dependent Na(+) channels, and 56 mM K(+), an activator of voltage-dependent Ca(2+) channels. In Xenopus oocytes expressing alpha3beta4 neuronal acetylcholine receptors, nobiletin directly inhibited the current evoked by acetylcholine in a concentration-dependent manner similar to that observed in catecholamine secretion. The present findings suggest that nobiletin, by itself, stimulates catecholamine secretion via activation of voltage-dependent Ca(2+) channels or Na(+)/Ca(2+) exchangers, whereas it inhibits catecholamine secretion induced by acetylcholine through the suppression of Na(+) influx and Ca(2+) influx in cultured bovine adrenal medullary cells.

We examined the effects of genistein, one of the major soy phytoestrogens, on the activity of noradrenaline transporter (NAT) and serotonin transporter. Treatment with genistein (10 nM-10 microM) for 20 min stimulated [(3)H]noradrenaline (NA) uptake by SK-N-SH cells. Genistein also stimulated [(3)H]NA uptake and [(3)H]serotonin uptake by NAT and serotonin transporter transiently transfected COS-7 cells, respectively. Kinetics analysis of the effect of genistein on NAT activity in NAT-transfected COS-7 cells revealed that genistein significantly increased the maximal velocity of NA transport with little or no change in the affinity. Scatchard analysis of [(3)H]nisoxetine binding to NAT-transfected COS-7 cells showed that genistein increased the maximal binding without altering the dissociation constant. Although genistein is also known to be an inhibitor of tyrosine kinases, daidzein, another soy phytoestrogen and an inactive genistein analogue against tyrosine kinases, had little effect on [(3)H]NA uptake by SK-N-SH cells. The stimulatory effects on NAT activity were observed by treatment of tyrphostin 25, an inhibitor of epidermal growth factor receptor tyrosine kinase, whereas orthovanadate, a protein tyrosine phosphatase inhibitor, suppressed [(3)H]NA uptake by NAT-transfected COS-7 cells. These findings suggest that genistein up-regulates the activity of neuronal monoamine transporters probably through processes involving protein tyrosine phosphorylation.

The glucoamylase enzyme (GAase) gene from Aspergillus shirousami was cloned and sequenced from genomic and cDNA libraries. The genomic gene was located in the 5.4 kb EcoRI fragment. The deduced amino acid sequence of GAase contained 639 amino acid residues with a relative molecular mass of approximately 68,000 daltons (non-glycosylated form). The genomic gene of A. shirousami GAase was introduced into Aspergillus oryzae. These transformants had increased GAase and raw starch degradation (RSD) activity in culture media and in rice-koji extracts. Analysis by Southern, Northern, SDS-PAGE, and Western blot techniques confirmed the foreign gene was correctly transcribed, translated, and expressed in A. oryzae.

We report here the effects of capsaicin, a flavoring ingredient in the hot pepper Capsicum family, on catecholamine secretion and synthesis in cultured bovine adrenal medullary cells. Capsaicin inhibited catecholamine secretion (IC(50)=9.5, 11.8, and 62 microM) stimulated by carbachol, an agonist of the nicotinic acetylcholine receptor, by veratridine, an activator of voltage-dependent Na(+) channels, and by high K(+), an activator of voltage-dependent Ca(2+) channels, respectively. Capsaicin also suppressed carbachol-induced (22)Na(+) influx (IC(50)=5.0 microM) and (45)Ca(2+) influx (IC(50)=24.4 muM), veratridine-induced (22)Na(+) influx (IC(50)=2.4 microM) and (45)Ca(2+) influx (IC(50)=1.1 microM), and high K(+)-induced (45)Ca(2+) influx (IC(50)=5.8 microM). The reduction in catecholamine secretion caused by capsaicin was not overcome by increasing the concentration of carbachol. Furthermore, capsazepine (10 microM), a competitive antagonist for the transient receptor potential vanilloid 1, and ruthenium red (30 microM), a nonselective cation channel antagonist, did not block the inhibition by capsaicin of catecholamine secretion. Capsaicin also suppressed both basal and carbachol-stimulated (14)C-catecholamine synthesis (IC(50)=10.6 and 26.4 microM, respectively) from [(14)C] tyrosine but not from L: -3, 4-dihydroxyphenyl [3-(14)C] alanine ([(14)C] DOPA) as well as tyrosine hydroxylase activity (IC(50)=8.4 and 39.0 microM, respectively). The present findings suggest that capsaicin inhibits catecholamine secretion and synthesis via suppression of Na(+) and Ca(2+) influx through a vanilloid receptor-independent pathway.

Incubation of cultured bovine adrenal medullary cells with 17beta-estradiol (E(2)) (0.3-100nM) or membrane-impermeable E(2)-bovine serum albumin (100nM) acutely increased (14)C-catecholamine synthesis from [(14)C]tyrosine. The stimulatory effect of E(2) was not inhibited by ICI182,780, a nuclear estrogen receptor inhibitor. E(2) also increased tyrosine hydroxylase activity and p44/42MAPK phosphorylation, the former of which was attenuated by U0126, an inhibitor of p44/42MAPK kinase. The plasma membrane isolated from the gland showed two classes of specific binding sites of [(3)H]E(2) with apparent K(d)s of 3.2 and 106nM, and B(max)s of 0.44 and 8.5pmol/mg protein, respectively. The high-affinity binding of [(3)H]E(2) was most strongly inhibited by E(2) and phytoestrogens, and to lesser extents by other steroid hormones, while it was enhanced by ICI182,780 and environmental estrogenic pollutants. These findings suggest that E(2) acutely stimulates catecholamine synthesis via activation of p44/42MAPK through unique estrogen receptors in the plasma membrane of bovine adrenal medulla.

We recently reported that nitric oxide (NO), which is produced by chondrocytes treated with interleukin-1beta (IL-1), releases basic fibroblast growth factor (bFGF) stored in the matrix of articular chondrocytes. To clarify the mechanism of the IL-1-induced bFGF release, we investigated the production and gene expression of bFGF, matrix metalloproteinases (MMPs), syndecan 3, and inducible NO synthase (iNOS) by IL-1-treated rabbit articular chondrocytes. IL-1 stimulated not only the release of bFGF but also the production of it. Gelatin and casein zymography revealed that IL-1 stimulated the production of not only MMP-9 but also MMP-3. The increase in the production of these MMPs preceded the IL-1-stimulated bFGF release. An MMP inhibitor partially suppressed the release of bFGF, indicating that matrix degradation is at least partially involved in the IL-1-stimulated bFGF release even if increased production of bFGF is related to the release. IL-1 sequentially stimulated mRNA expression of iNOS, membrane type 1-MMP, MMP-9 and -3, and bFGF, in that order. NG-Monomethyl-L-arginine, an inhibitor of NO production, inhibited gene expression of MMP-9 and bFGF. These findings suggest that elevation of the NO level via iNOS mRNA expression stimulated by IL-1 mediates gene expression and production of MMPs and bFGF, resulting in the release of bFGF, and also reveal molecular mechanisms implicating the degradation of articular cartilage followed by angiogenesis in the synovium in arthritic joints.

Both insulin-like growth factor (IGF)-I and IGF-II increased the synthesis of cartilage-type, large proteoglycan in a human chondrosarcoma-derived chondrocyte cell line, HCS-2/8. In contrast to the stimulatory effects of IGFs on costal chondrocytes of the young rabbit, the stimulatory effect of IGF-II on proteoglycan synthesis in HCS-2/8 cells was more potent than that of IGF-I. IGF-II, but not IGF-I, increased calcium influx into HCS-2/8 cells, and there was a close relation between the stimulation of proteoglycan synthesis and the calcium influx. [125I]IGF-I bound to HCS-2/8 cells, and this binding was competitively inhibited by low concentrations of unlabeled IGF-I, higher concentrations of IGF-II, and much higher concentrations of insulin. [125I]IGF-II also bound to the cells, and its binding was competitively inhibited by IGF-II and slightly inhibited by higher concentrations of IGF-I and much higher concentrations of insulin. When radioligand-receptor complexes were separated by SDS-PAGE and subjected to autoradiography, two major bands at 260 and 130 kDa were observed, which correspond to the IGF type II receptor (IGF-IIR) and the alpha subunit of the IGF type I receptor (IGF-IR), indicating the presence of both receptors. When confluent cultures of HCS-2/8 cells were maintained in serum-free medium, proteoglycan synthesis did not decrease unless the medium was repeatedly replaced. Conditioned medium of HCS-2/8 cells stimulated the HCS-2/8 cells to synthesize proteoglycans. RIA revealed that the cells produced both IGF-II and IGF-I. Transcripts of messenger RNAs of both IGF-I and IGF-II and both IGF-IR and IGF-IIR also were detectable by Northern analysis. Both anti-IGF-IR antibody and anti-IGF-II antibody inhibited proteoglycan synthesis. Mannose-6-phosphate, which is known to bind to IGF-IIR, stimulated proteoglycan synthesis, potentiated IGF-II-stimulated proteoglycan synthesis, and enhanced the binding affinity for IGF-II but not for IGF-I. Even in the presence of anti-IGF-IR antibody, IGF-II and mannose-6-phosphate stimulated proteoglycan synthesis in the cells. [Leu27]IGF-II, an IGF-II analogue with high affinity only for IGF-IIR, strongly stimulated proteoglycan synthesis in HCS-2/8 cells but [Arg54, Arg55]IGF-II, which binds to only IGF-IR, also stimulated proteoglycan synthesis in the cells. These findings indicate that IGF-I and IGF-II act as autocrine differentiation factors for this chondrocytic permanent cell line, HCS-2/8, mainly via respective receptors.

With cultured osteoblastic cells, clone MC3T3-E1 derived from newborn mouse calvaria, the mRNAs encoding three representative neurotrophins, namely, nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3), were proved in estimation by the polymerase chain reaction (PCR) method. The increase and then subsequent decrease of all three mRNAs within the proliferation phase were followed by their gradual increase in the differentiation phase, with a tendency of enhancement by exogenous TGF-beta as was particularly evident in the case of NGF. These findings were further substantiated by identification of NGF-like neutrophils in the conditioned medium of the osteoblastic cells by an immunoblotting and neurite extension assay.

Mouse osteoblastic clone MC3T3-E1 was proved as a target cell for retinoic acid (RA) in bone tissues through the demonstration of RA-receptor gene expression by the northern blot analysis. The effect of RA on the cell growth of MC3T3-E1 was repressive for both subconfluent and confluent growth, whereas RA enhancement of alkaline phosphatase expression was observed at the confluent stage. This implies that RA is a regulatory factor leading osteogenesis of the cells after the confluent stage. RA exhibited simultaneously the stage-dependent effects on EGF-dependent mitogenesis: promotive at the subconfluent, but repressive at the confluent stage.

The V of horse liver aldehyde dehydrogenase is enhanced twofold in the presence of 0.5 m m Mg 2+ ions when assayed in the dehydrogenase reaction. The mechanism of this activation appears to be related to the fact the enzyme changes from functioning with half-of-the-sites reactivity to functioning with all-of-the-sites reactivity. That is, the presteady-state burst magnitude increases from 2 mol NADH formed per mole of tetrameric enzyme to 4 mol formed per mole ( K. Takahashi and H. Weiner, J. Biol. Chem. , 1980 , 255 , 8206–8209). Whether this twofold enhancement correlates, in fact, to a change from half-of-the-sites to all-of-the-sites reactivity of the enzyme by Mg 2+ ions was investigated by determining the Stoichiometry of coenzyme binding by fluorescence quenching and enhancement methods in the absence and presence of the metal ions. The biphasic Scatchard plots for NAD binding to the enzyme were similar in the absence and presence of Mg 2+ ions, while that of NADH binding was monophasic (-Mg 2+ ) and biphasic (+Mg 2+ ). In the presence of p -methoxyacetophenone, a competitive inhibitor for substrate, the stoichiometric titration of coenzyme binding to the ternary complexes (enzyme-NAD(H)-inhibitor) revealed that only 2 mol of NAD or NADH bind in the absence of Mg 2+ ions but 4 bind per mole of tetrameric enzyme in the presence of added metal. The fluorescence intensity of NAD's fluorescent derivative, 1, N 6 -ethenoadenine dinucleotide, bound to the enzyme was also doubled by the addition of Mg 2+ ions. The combined binding data show that the stoichiometry of coenzyme binding to aldehyde dehydrogenase in the ternary complex increases from 2 to 4 mol binding per mole of tetrameric enzyme with the addition of Mg 2+ ions. This increase in stoichiometry corresponds to the observed changes of burst magnitude obtained from the presteady-state and V in the steady-state kinetics assays. From both results of the kinetics and stoichiometry, we show that horse liver aldehyde dehydrogenase exhibits half-of-the-sites reactivity when in the tetrameric state in the absence of Mg 2+ ions, and all-of-the-sites reactivity in the dimeric state in the presence of the metal.

The reactivity of the mitochondrial (pI = 5) isoenzyme of horse liver aldehyde dehydrogenase was determined by studying the effects of pH on steady-state velocity, burst magnitude, and molecular weight of the enzyme in the absence and presence of Mg2+ ions. The Mg2+ ion activation of the steady-state velocity at pH 7.5 has been explained through a mechanism involving alteration of the tetrameric enzyme, functioning with half-of-the-sites reactivity, to a dimeric enzyme, functioning with all-of-the-sites reactivity [Takahashi, K., & Weiner, H. (1980) J. Biol. Chem. 255, 8206-8209]. With increasing pH, the tetrameric enzyme dissociated even in the absence of Mg2+ ions to the more active dimeric state. The pH-dependent dissociation was governed by proton release from a group with pK = 9.5. After correcting for the increased number of functioning active sites, determined from the pre-steady-state burst, we calculated that elevated pH also caused an increase in the velocity of the rate-limiting step, hydrolysis of the acyl-enzyme intermediate. This event was governed by the ionization of two groups, with pK = 7.2 and 9.5, respectively. If these groups are directly involved in the catalytic step, a mechanism involving histidine acting as a general base can be proposed for the former group. The latter group may be involved in a charge relay activation process which only occurs at elevated, nonphysiological pH. The importance of the latter is questionable, as there is only a 3-fold increase in Vmax when this group is involved in catalysis.

The 31P NMR method was first applied to characterize in vivo phosphorylation of H1 and H5 in calf thymus and chicken erythrocytes as well as in vitro phosphorylation of H1 and H5 by cAMP-dependent protein kinase. The amino acid residues phosphorylated in vivo in the histones were exclusively serine residues, and the mole fraction of phosphoserine was estimated to be 0.34 and 0.27 per molecule of calf thymus H1 and chicken erythrocyte H5, respectively. Interestingly, chicken erythrocyte H1 was not phosphorylated in vivo. Three H1 subtypes from calf thymus H1 varied in the 31P NMR spectra, and the bisected fragments of calf thymus H1 and chicken erythrocyte H5 exhibited characteristic spectral patterns, indicating that there are considerable diversities of the degree of phosphorylation and phosphorylation sites in very-lysine-rich histones. Furthermore, it was found that the microenvironment of phosphoserine residues phosphorylated in vivo in calf thymus H1 and chicken erythrocyte H5 is quite distinct from that of phosphoserine residues phosphorylated in vitro by bovine heart cAMP-dependent protein kinase.

The sodium dodecyl sulfate (SDS) concentration dependence of spectral changes in circular dichroism (CD) and in absorbance of cytochrome c were examined in the far-ultraviolet region, aromatic region, and the Soret band. The Soret peak obtained in 0.60 mM SDS was nine times greater than that of the native state. (The critical micelle concentration, CMC, of SDS was 2.2 mM in the phosphate buffer used.) The results indicated that the drastic change at the Soret band did not accompany the corresponding large-scale change in secondary structure of the protein. In the stopped-flow measurements, two and three processes were followed at 406 nm below and above the CMC, respectively. At 289 nm only one process was observed, and this corresponded to the second process at 406 nm. Therefore, the second process at 406 nm was considered to be a change in tertiary structure around the heme group. The first process and the third process seemed to reflect a change in the heme environment; the former appeared to be due to a solvent effect and the latter due to a binding effect of a large number of dodecyl sulfate ions.

The effects of Mg2+ and Ca2+ ions on the activities of mitochondrial and cytosolic aldehyde dehydrogenases isolated from horse, rat, and beef livers were investigated in 0.1 M sodium phosphate, pH 7.5, at 25 degrees C. As with the Mg2+-enhancement of the horse liver mitochondrial enzyme [17], Mg2+-activation was observed for the mitochondrial enzymes from rat and beef. The cytosolic enzymes from horse, rat, and beef livers were inhibited in the presence of Mg2+ ions. The effects of Ca2+ ions on the activity were essentially the same as those observed in the presence of Mg2+ ions; the mitochondrial isozymes were activated while the cytosolic isozymes were inhibited. The fact that only the activity of mitochondrial forms of mammalian liver aldehyde dehydrogenase was enhanced by Ca2+ or Mg2+ ions may be related to the in vivo regulation of aldehyde metabolism, a presumed mitochondrial event.