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Endothelium-derived prostaglandins appear to play an important role in myogenic contraction of the cerebral arteries in response to increased transmural pressure. The goal of this study was to determine whether prostaglandins contribute to the autoregulatory response of cerebral blood flow (CBF) during acute hypertension in normotensive and chronically hypertensive animals. In 4-5 months old Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) anesthetized with pentobarbital sodium (45 mg/kg, i.p.), regional CBF of the right parietal cortex was monitored by laser-Doppler flowmetry. Acute hypertension was induced by intravenous infusion of phenylephrine and the elevated arterial pressure was maintained for 50 seconds for the measurement of CBF. In the control group of WKY rats, CBF increased by 5.6% per 10-mmHg increase in arterial pressure. Changes in CBF were similar between the initial state (0-10 seconds) and the steady state (30-40 seconds) of acute hypertension. In WKY rats pretreated with indomethacin (10 mg/kg, i.v.), increases in CBF in the initial state were slightly but significantly greater than that in the steady state. Indomethacin also tended to enhance the increases in CBF in both the initial state and the steady state; however, the effect was not significant. In the control group and indomethacin-pretreated group of SHR, acute hypertension produced similar increases in CBF. In both groups, no significant difference between changes in CBF in the initial state and the steady state was observed. Thus our findings suggest that 1) in normotensive animals, the early autoregulatory response of CBF during acute hypertension is partially mediated by prostaglandins and 2) the role of prostaglandins in the regulation of CBF during acute hypertension is altered in chronically hypertensive animals.

Continuous production of a recombinant murine granulocyte-macrophage colony-stimulating factor (GM-CSF) by Saccharomyces cerevisiae strain XV2181 (a/a, Trp 1) containing plasmid palphaADH2 and immobilized on porous glass beads in a fluidized bed bioreactor was studied. Kinetic models for plasmid stability, cell growth, and protein production in the three-phase fluidized bed bioreactor were developed and used to study the effects of solid loading or cell immobilization on plasmid stability and recombinant protein production. With increasing cell immobilization or solid loading in the bioreactor, plasmid stability and protein production improved significantly. The improvements could be attributed to the decreased theta value, which is the plasmid loss probability during cell division and is an indication of segregational instability of the recombinant cell, and the increased alpha value, which is the ratio of the specific growth rate of a plasmid-carrying cell to that of a plasmid-free cell and is indicative of competitive stability of the recombinant cell culture. theta decreased from 0.552 to 0.042 and alpha increased from 0.351 to 0.991 when solid loading in the bioreactor was increased from 5% (v/v) to 33%. The model simulation also showed that the specific growth rate of cells in the bioreactor was lower at higher solid loading. This indicated that there was significant mass transfer limitation, particularly for oxygen transfer, when the total cell density in the bioreactor was high at high solid loading. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 470-477, 1997.

We describe an efficient and highly stable injection-locked, laser-diode end-pumped cw Nd:YAG laser. With 22.3-W pump input from two fiber-coupled laser diodes, combined with 700 mW of power injected by a singlefrequency master laser, the injection-locked slave laser emits 10 W of linearly polarized, TEM(00)-mode output in a single longitudinal mode. In addition to high efficiency, the injection-locked laser also possesses excellent output stability. At 300 Hz, the measured relative intensity noise and the frequency-noise spectral density are 2 x 10(-5)/ radicalHz and 50 Hz/ radicalHz, respectively. To improve frequency stability further, we lock the frequency of the injection-locked laser to an external high-finesse reference cavity. When the frequency was stabilized, a minimum frequency-noise spectral density of 40 mHz/ radicalHz was measured at the frequency-stabilization loop error point at 1 kHz.

Continuous production of a recombinant murine granulocyte-macrophage colony-stimulating factor (MuGM-CSF) by immobilized yeast cells, Saccharomyces cerevisiae strain XV2181 (a/a, Trp1) containing plasmid palphaADH2, in a fluidized bed bioreactor was studied at a 0.03 h(-1) dilution rate and various particle loading rates ranging from 5% to 33% (v/v). Cells were immobilized on porous glass beads fluidized in an air-lift draft tube bioreactor. A selective medium containing glucose was used to start up the reactor. After reaching a stable cell concentration, the reactor feed was switched to a rich, nonselective medium containing ethanol as the carbon source for GM-CSF production. GM-CSF production increased initially and then dropped gradually to a stable level. During the same period, the fraction of plasmid-carrying cells declined continuously to a lower level, depending on the particle loading. The relatively stable GM-CSF production, despite the large decline in the fraction of plasmid-carrying cells, was attributed to cell immobilization. As the particle loading rate increased, the plasmid stability also increased. Also, as the particle loading increased from 5% to 33%, total cell density in the bioreactor increased from 16 to 36 g/L, and reactor volumetric productivity increased from 0.36 to 1.31 mg/L.h. However, the specific productivity of plasmid-carrying cells decreased from 0.55 to 0.07 mg/L.g cell. The decreased specific productivity at higher particle loading rates was attributed to reduced growth efficiency caused by nutrient limitations at higher cell densities. Both the reactor productivity and specific cell productivity increased by two- to threefold or higher when the dilution rate was increased from 0.03 to 0.07 h(-1).

Continuous production of murine GM-CSF by recombinant Saccharomyces cerevisiae in an airlift bioreactor was studied at three different dilution rates. The reactor was initially fed with a selective medium to increase cell concentration, and then was fed with a rich, nonselective medium for GM-CSF production. Ethanol was used as the main carbon source to provoke GM-CSF expression. In continuous culture, GM-CSF production was maintained for over 150 h, even though the fraction of plasmid-carrying cells continuously dropped to lower than 20%. The stable GM-CSF production during the later phase of the continuous culture was attributed to increased specific cell productivity possibly resulting from an increase in the plasmid copy number in plasmid-carrying cells. This also indicated the possibility of natural selection of high-copy number cells in continuous culture. Plasmid stability was found to be growth rate (dilution rate) dependent; it increased with the dilution rate. Reactor productivity and specific productivity also increased with the dilution rate. A two-parameter kinetic equation was used to model the plasmid stability kinetics. The growth rate ratio between plasmid-carrying and plasmid-free cells increased from 0.996 to 0.998 while the segregational instability or the probability of plasmid loss from each cell division increased from 1.1% to 16% as the dilution rate decreased from 0.11 h-1 to 0.05 h-1. Oscillation of the dilution rate between 0.05 h-1 and 0.11 h-1 stabilized the plasmids and gave a higher productivity than that achieved without oscillation.

The continuous production of murine granulocyte-macrophage colony-stimulating factor (GM-CSF) by recombinant yeast cells immobilized in a fibrous-bed bioreactor was studied. A high cell density of approximately 68 g/L and a GM-CSF productivity of approximately 3.5 mg/L.h were attained in the fibrous-bed bioreactor-fed with a rich (nonselective, pH 6.7) medium at a dilution rate of 0.16 h-1. The GM-CSF production was stable even though the fraction of plasmid-carrying cells in the reactor effluent gradually dropped below 5% over a period of 2 weeks. At the end of that period, the immobilized cells in the fibrous matrix still had a high fraction, approximately 26%, of plasmid-carrying cells. Similar results were obtained with reactors operated at 0.05 h-1 dilution rate and pH 4.0. Although the GM-CSF production was lower at pH 4, the reactor was stably operated for over 4 weeks without contamination or significant loss of productivity. The stable long-term GM-CSF production from the fibrous-bed bioreactor was attributed to the effect of cell immobilization on plasmid stability. Because GM-CSF production was growth-associated, as was found in batch fermentation with free cells, this stabilization effect cannot be attributed solely to the reduced cell growth in the immobilized cell environment. Plasmid-carrying cells were preferentially retained in the fibrous matrix, perhaps because their abilities to adhere to the fiber surface and to form cell aggregates were higher than those of plasmid-free cells.

The dynamic response of temperature-regulated gene expression in the recombinant yeast Saccharomyces cerevisiae, strain XK1-C2 carrying plasmid pSXR125, to temperature changes during fed-batch and continuous (chemostat) cultures was studied. The production of the gene product, beta-galactosidase, in the yeast cell is sensitive to the growth temperature. Gene expression of this product was fully turned on or off by temperature shifts between 24 and 30 degrees C. However, the response for gene turn-on and turn-off in this recombinant yeast was slow, requiring from several hours to over 10 h to fully appear. The continuous reactor took 30-60 h after the temperature shift to reach a new steady state. A dynamic process model was developed to simulate the reactor and cell responses to temperature shift. A first-order model was used to account for the effect of dilution rate on the change of protein concentration in the chemostat. It was found that cell response in gene expression to temperature shift followed first-order plus dead-time dynamics. Also, the response time for gene expression to temperature shift varied with specific growth rate or dilution rate of the continuous reactor. In general, the response was slower at a higher dilution rate and for gene turn-on than for gene turn-off.

The influence of nitric oxide (NO) on basal vascular tone varies with different hypertensive models or vascular beds. The goal of the present study was to examine the role of NO in the maintenance of resting cerebral blood flow (CBF) during chronic hypertension. In 9-10 months old Wistar-Kyoto (WKY) rats (n=47) and spontaneously hypertensive rats (SHR;n=47) anesthetized with pentobarbital sodium (60 mg/kg i.p.), regional CBF of the right parietal cortex was monitored by laser-Doppler flowmetry. Reductions in CBF in response to intravenous infusion of the NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME; 1, 3, 10, and 30 mg/kg) were similar between WKY rats (17 +/- 6 approximately 43 +/- 6%; means +/- SE) and SHR (15 +/- 6 approximately 48 +/- 6%) while arterial blood pressure was maintained on the baseline level by controlled hemorrhage. Effects of L-NAME (3 mg/kg i.v.) on arterial blood pressure and CBF were almost completely inhibited by L-arginine (300 mg/kg i.v.), but not by D-arginine (300 mg/kg i.v.). In addition, intravenous infusion of L-arginine (300 mg/kg) alone did not affect resting CBF in both WKY rats and SHR. Thus, these findings suggest that 1) NO plays an important role in the maintenance of resting CBF in both normotensive and chronically hypertensive rats and 2) the contribution of NO to the maintenance of resting CBF is not altered during chronic hypertension.

The cheese industry produces large amounts of lactose in the form of cheese whey and whey permeate, generating approximately 27 million tonnes/yr in the US alone. Many uses have been found for whey and lactose, including uses in infant formula; bakery, dairy, and confectionery products; animal feed; and feedstocks for lactose derivatives and several industrial fermentations. Lactose use in food products, however, is somewhat limited because of its low solubility and indigestibility in many individuals. For this reason, lactose is often hydrolyzed before use. Still, demand is insufficient to use all available whey lactose. The result is a low market value for lactose; almost half of the whey produced each year remains unused and is a significant waste disposal problem. Several approaches are possible for transforming lactose into value-added products. For example, galactooligosaccharides can be produce through enzymatic treatments of lactose and may be used as a probiotic food ingredient. Organic acids or xanthan gum may be produced via whey fermentation, and the fermented whey product can be used as a food ingredient with special functionality. This paper reviews the physical characteristics, production techniques, and current uses of lactose, whey, and lactose derivatives. Also examined are novel fermentation and separation technologies developed in our laboratory for the production of lactate, propionate, acetate, and xanthan gum from whey.

The purpose of this study is to investigate the hypothesis that ketamine, a non-competitive antagonist of the N-methyl-D-aspartate (NMDA) receptor, attenuates hypoxia-induced striatal dopamine release in vivo. High-speed chronoamperometric recording techniques, using Nafion-coated carbon fiber electrodes, were used to evaluate extracellular dopamine (DA) concentration in the striatum. KCl and DA were locally applied directly to the striatum of urethane-anesthetized Sprague-Dawley rats, in order to measure release and clearance, respectively, of DA. These anesthetized animals were paralyzed with D-tubocurarine and connected to a respirator to allow controlled respiration. Systemic concentrations of oxygen and carbon dioxide were altered by changing the partial pressure of O2, CO2, N2 of inspired air and the rate of the respirator. Our data indicate that lowering the respiratory rate from 90 to 20 times/min for 5 min, in room air, caused a decrease in blood O2 while increasing the CO2 concentration. These changes in blood gas concentration were reversible and reproducible. We also found that lowering the respiratory rates potentiated K(+)-induced DA release but not DA clearance in the striatum. In an attempt to induce hypercapnia, the room air was replaced with high CO2-containing air (15% CO2 + 20% O2 + 65% N2), and this change resulted in increased blood CO2 levels without lowering O2 concentration. The hypercapnia did not alter K(+)-induced DA release in the striatum. Next, we attempted to simulate anoxic hypoxia in the absence of hypercapnia. Respiration with pure N2 for 30 s resulted in lowering blood O2 without increasing CO2 levels. Both basal and K(+)-evoked DA releases were increased during N2-induced anoxic hypoxia. These data suggested that transient hypoxia facilitates DA release in the striatum. It has been suggested that NMDA is involved in many hypoxia-mediated responses. We also found that systemic application of ketamine, which itself did not affect blood O2 or CO2 levels, antagonized hypoxia-induced electrochemical responses. These data suggest that the increase in DA release in vivo during short-term hypoxia may probably be mediated through NMDA receptors.

Background: The objective of this study is to reassess the validity of plain film diagnosis for pediatric intussusception with consideration of the combinations of radiologic findings., Methods: Sixty-six cases of intussusception and 81 controls of gastroenteritis were collected. Their films were read blindly by three radiologists together, with emphasis on nine radiologic findings: sparse colon gas (F1), sparse fecaloid content in colon (F2), gas-filled small bowel loops in right hypochondrium (F3), small bowel obstruction (F4), difficulty in assessing cecum position (F5), pneumoperitoneum (F6), discernible mass lesion (F7), target sign (F8) and crescent sign (F9). The sensitivity and specificity of individual findings and combinations of findings were analyzed., Results: No cases showed F6. Listed in decreasing order of sensitivity, the other eight findings were F1, F5, F2, F7, F3, F4, F9 and F8. The sensitivity and specificity of these eight findings were inversely proportional with significant p-values (F8: < 0.005; the other seven findings: < 0.001). Sixty-three films (95%) in case group displayed combination of at least three radiologic findings. If the diagnostic criteria must consist of at least three radiologic findings, 60 cases (74%) of control group can be excluded., Conclusions: After eliminating the confounding effect of small bowel obstruction on the percentage of gas-filled small bowel loops in right hypochondrium and excluding the data agreed by only one radiologist from the study by Ratcliffe et al, the results of plain film findings were consistent with those of previous reports. The plain abdominal film can play an active role in the diagnosis of pediatric intussusception. Its validity increases when combinations of radiologic findings rather than individual signs are emphasized.

Recycle batch fermentations using immobilized cells of Propionibacterium acidipropionici were studied for propionate production from whey permeate, de-lactose whey permeate, and acid whey. Cells were immobilized in a spirally wound fibrous sheet packed in a 0.5-L column reactor, which was connected to a 5-L stirred tank batch fermentor with recirculation. The immobilized cells bioreactor served as a breeder for these recycle batch fermentations. High fermentation rates and conversions were obtained with these whey media without nutrient supplementation. It took approximately 55 h to ferment whey permeate containing approximately 45 g/L lactose to approximately 20 g/L propionic acid. Higher propionate concentrations can be produced with various concentrated whey media containing more lactose. The highest propionic acid concentration obtained with the recycle batch reactor was 65 g/L, which is much higher than the normal maximum concentration of 35 to 45 g/L reported in the literature. The volumetric productivity ranged from 0.22 g/L x h to 0.47 g/L x h, depending on the propionate concentration and whey medium used. The corresponding specific cell productivity was 0.033 to 0.07 g/L x g cell. The productivity increased to 0.68 g/L x h when whey permeate was supplemented with 1% (w/v) yeast extract. Compared with conventional batch fermentation, the recycle batch fermentation with the immobilized cell bioreactor allows faster fermentation, produces a higher concentration of product, and can be run continually without significant downtime. The process also produced similar fermentation results with nonsterile whey media.

Butylated hydroxyanisole (BHA), Butylated hydroxytoluene (BHT) and tertiary butylhydroquinone (TBHQ) alone in cultural media were tested for the inhibition of growth and luteoskyrin production by two toxigenic strains ofPenicillium islandicum UST-11 andP. islandicum HLT-6. In potato dextrose agar, the concentrations of BHA and TBHQ from 0.2 mg/disc, BHT from 5.0 mg/disc did affect the growth of both tested strains, but the initial concentrations of these antioxidants to reduced luteoskyrin production by UST-11 strain were BHA 0.5 mg/disc, BHT 1.0 mg/disc and TBHQ 0.4 mg/disc, while for HLT-6, BHA 0.4 mg/disc, BHT and TBHQ were 0.2 mg/disc, respectively. In grainy and powdery rice media, the effects of BHA, BHT and TBHQ on luteoskyrin production byP. islandicum UST-11 and HLT-6 were clearly demonstrated. The efficiency of the inhibitory effect was not only closely related to the concentration of antioxidants, but also completely inhibited the luteoskyrin production at a concentration of 200 mg/kg or higher. Also, the antioxidants at a concentration higher than 20 mg/kg reduced significantly the growth and luteoskyrin production by both strains ofP. islandicum.

Dynamic light scattering (DLS) is a useful technique for analyzing the size, shape, and other structural characteristics of protein molecules in solution. The effects of various environmental conditions on the structure and activity of Aspergillus oryzae beta-galactosidase were studied. DLS was used to determine protein particle size under various salt, pH, and temperature conditions. Changes in the activity and stability of this enzyme caused by different environmental conditions were found to correlate well with the size changes of the protein particles. This change in protein size can be attributed to protein unfolding and aggregation under extreme conditions. The presence of the enzyme substrate, lactose, in the protein solution greatly enhanced enzyme stability by inhibiting aggregation.

Fiber optic sensors for nitrite were prepared by first electrochemically depositing a film of cobalt(II) tetrakis(o-aminophenyl)porphyrin, [Co(o-NH(2))TPP], on the surface of indium(tin) oxide glass slides. Then, the slides with the immobilized porphyrin were positioned at the tip of an optical fiber bundle. The response of the sensors was based on a change in absorbance caused by the interaction between nitrite and the poly[Co(o-NH(2))TPP] film. The sensors had a detection limit of 6 x 10(-9)M nitrite. The selectivity of the sensors was determined under both separate solutions and fixed interference conditions. The sensor had a long lifetime and was reversible.

Continuous production of propionate from whey lactose by Propionibacterium acidipropionici immobilized in a novel fibrous bed bioreactor was studied. In conventional batch propionic acid fermentation, whey permeate without nutrient supplementation was unable to support cell growth and failed to give satisfactory fermentation results for over 7 days. However, with the fibrous bed bioreactor, a high fermentation rate and high conversion were obtained with plain whey permeate and de-lactose whey permeate. About 2% (wt/vol) propionic acid was obtained from a 4.2% lactose feed at a retention time of 35 to 45 h. The propionic acid yield was approximately 46% (wt/vol) from lactose. The optimal pH for fementation was 6.5, and lower fermentation rates and yields were obtained at lower pH values. The optimal temperature was 30 degrees C, but the temperature effect was not dramatic in the range of 25 to 35 degrees C. Addition of yeast extract and trypticase to whey permeate hastened reactor startup and increased the fermentation rate and product yields, but the addition was not required for long-term reactor performance. The improved fermentation results with the immobilized cell bioreactor can be attributed to the high cell density, approximately 50 g/L, attained in the bioreactor, Cells were immobilized by loose attachement to fiber surfaces and entrapment in the void spaces within the fibrous matrix, thus allowing constant renewal of cells. Consequently, this bioreactor was able to operate continuously for 6 months without encountering any clogging, degeneration, or contamination problems. Compared to conventional batch fermentors, the new bioreactor offers many advantages for industrial fermentation, including a more than 10-fold increase in productivity, acceptance of low-nutrient feedstocks such as whey permeate, and resistance to contamination. (c) 1994 John Wiley & Sons, Inc.

We report high-power and single-frequency operation of a continuous-wave singly resonant potassium titanyl phosphate (KTiOPO(4)) optical parametric oscillator in a ring-cavity configuration. The ring singly resonant optical parametric oscillator threshold is 4.3 W. When the oscillator is pumped by 6.7 W of 532-nm radiation from an 11.2-W single-frequency resonantly doubled Nd:YAG laser, 1.9 W of single-axial-mode output is generated at the idler wavelength of 1039 nm.

A fiber optic sensor that exploits the natural selectivity of the Ca(2+)-binding protein calmodulin (CaM) is described. In this sensor, a dialysis membrane is used to entrap a fluorescein-labeled CaM (F-CaM) solution at the common end of a bifurcated fiber optic bundle. Ca2+ ions in a sample solution can diffuse through the membrane and bind to the F-CaM. Upon binding with Ca2+, CaM undergoes a conformational change that induces a change in the fluorescence of the attached fluorescein tag. This change in fluorescence can be related to the concentration of Ca2+ in the sample solution. The detection limit for the sensor is 5 x 10(-8) M Ca2+. The sensor has no interference by Mg2+ at concentrations as high as 10(-2) M.

Endothelium-dependent dilatation of cerebral arterioles is impaired during chronic hypertension. The goal of this study was to determine the effects of an angiotensin converting enzyme inhibitor, cilazapril, on endothelium-dependent dilatation in pial arterioles. Four-month-old Wistar-Kyoto (WKY) rats and stroke-prone spontaneously hypertensive rats (SHRSP) received cilazapril in their drinking water (500 mg/L) for 3 to 6 months. Treatment with cilazapril reduced mean arterial pressure in both WKY rats and SHRSP and had no significant effect on baseline diameter of pial arterioles measured with a cranial window. Responses to bradykinin and A23187, but not to nitroglycerin and adenosine, were impaired in SHRSP. Cilazapril did not affect responses to bradykinin (3 x 10(-7) M) and A23187 (10(-5) M) in WKY rats but significantly increased cerebral vasodilatation in response to bradykinin (52 +/- 4% vs 27 +/- 5%) and A23187 (19 +/- 3% vs 8 +/- 3%) in SHRSP. Cilazapril also tended to increase dilator responses to nitroglycerin and adenosine in SHRSP. In another group of SHRSP, treatment with cilazapril for 4 days produced a moderate reduction in blood pressure and increased cerebral vasodilatation in response to bradykinin, A23187, and adenosine. Topical application of the active form of cilazapril (cilazaprilat) for 40 minutes also increased cerebral vasodilatation in response to bradykinin, A23187, and nitroglycerin in SHRSP. The data indicate that an angiotensin converting enzyme inhibitor enhances cerebral vasodilatation in response to endothelium-dependent agonists in SHRSP and may also increase responses to endothelium-independent agonists.

We report what is to our knowledge the first demonstration of a continuous-wave singly resonant optical parametric oscillator based on potassium titanyl phosphate. The pump source used is a single-frequency resonantly doubled Nd:YAG laser. By double passing the pump through the crystal, we achieved a minimum oscillation threshold of 1.4 W. With 3.2 W of incident pump power, a maximum 1.07 W of nonresonant idler power was generated. Spectral measurement reveals that the singly resonant optical parametric oscillator operates consistently in a single axial mode with much relaxed axial mode hop tolerance to cavity length and pump-frequency fluctuations compared with doubly resonant optical parametric oscillators previously demonstrated.

The authors present a case of fetus-in-fetu in which the CT findings are compatible with an earlier description by Nocera et al., i.e., a "round or tubular collection of very low density fat surrounding a central bony structure (probably one of the legs)." Additionally, sonography showed a heterogeneous mass with limb-like structures in the left lateral ventricle. Plain films can confirm the presence of a vertebral column and identify specific bony structures, but CT is a valuable aid in cases where plain films were not obtained or are inconclusive.

Continuous propionic acid fermentations of lactate by Propionibacterium acidipropionici were studied in spiral wound fibrous bed bioreactors. Cells were imobilized by natural attachment to fiber surfaces and entrapment in the void volume within the fibrous matrix. A high cell density of approximately 37 g/L was attained in the reactor and the reactor productivity was approximately 4 times higher than that from a conventional batch fermentation. The bioreactor was able to operate continuously for 4 months without encountering any clogging, degeneration, or contamination problems. Also, the reactor could accept low-nutrient and low-pH feed without sacrificing much in reactor productivity. This new type of immobilized cell bioreactor is scalable and thus is suitable for industrial production of propionate.

We report 6.5 W of TEM(00) cw 532-nm radiation generated by external resonant doubling in a LiB(3)O(5) crystal. An 18-W, cw, injection-locked single-frequency Nd:YAG laser was used to generate 532-nm second-harmonic output with a 3-dB heterodyne linewidth of 15 kHz.

Bradykinin produces less dilatation of pial arterioles in stroke-prone spontaneously hypertensive rats than in normotensive Wistar-Kyoto rats. The goals of this study were to determine the mediator of bradykinin-induced dilatation in cerebral arterioles of rats and to determine whether responses to this mediator are altered in hypertensive rats. Diameter of pial arterioles (20-65 microns) was measured using intravital microscopy in 18 normotensive and 17 hypertensive rats. Superfusion of 3 x 10(-7) M bradykinin dilated pial arterioles by 53 +/- 4% (mean +/- SEM) in normotensive rats but only 33 +/- 6% in hypertensive rats (p less than 0.05 versus normotensive rats). Vasodilatation in response to bradykinin was almost completely inhibited by 280 units/ml catalase in both normotensive and hypertensive rats (n = 7 and n = 7, respectively) whereas 150 units/ml superoxide dismutase (n = 6 and n = 5, respectively) and 1 mM deferoxamine (n = 5 and n = 5, respectively) did not attenuate bradykinin-induced vasodilatation. These findings suggest that hydrogen peroxide is the mediator of bradykinin-induced dilatation in cerebral arterioles of rats. We also examined responses of cerebral arterioles to hydrogen peroxide in five normotensive and six hypertensive rats. Dilator responses of cerebral arterioles to 3.2 x 10(-5) M to 1.6 x 10(-4) M hydrogen peroxide did not differ in normotensive and hypertensive rats, which suggests that impaired dilatation of cerebral arterioles in response to bradykinin is not related to altered responsiveness of smooth muscle to an endothelium-derived relaxing factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Batch propionic acid fermentation of lactose by Propionibacterium acidipropionici were studied at various pH values ranging from 4.5 to 7.12. The optimum pH range for cell growth was between 6.0 and 7.1, where the specific growth rate was approximately 0.23 h(-1). The specific growth rate decreased with the pH in the acids have been identified as the two major fermentation products from lactose. The production of propionic acid was both growth and nongrowth associated, while acetic acid formation was closely associated with cell growth. The propionic acid yield increased with decreasing pH; It changed from approximately 33% (w/w) at pH 6.1-7.1 to approximately 63% at pH 4.5-5.0. In contrast, the acetic acid yield was not significantly affected by the pH; it remained within the range of 9%-12% at all pH values. Significant amounts of succinic and pyruvic acids were also formed during propionic acid fermentation of lactose. However, pyruvic acid was reconsumed and disappeared toward the end of the fermentation. The succinic acid yield generally decreased with the pH, from a high value of 17% at pH 7.0 to a low 8% at pH 5.0 Effects of growth nutrients present in yeast ex-tract on the fermentation were also studied. In general, the same trend of pH effects was found for fermentations with media containing 5 to 10 g/L yeast extract. However, More growth nutrients would be required for fermentations to be carried out efficienytly at acidic pH levels.

Acetylcholine produces less dilatation of pial arterioles in stroke-prone spontaneously hypertensive rats (SHRSP) than in normotensive (WKY) rats. Responses of cerebral vessels to acetylcholine and bradykinin appear to involve different mechanisms. Our first goal was to determine whether responses of pial arterioles to bradykinin are impaired in SHRSP. Diameter of pial arterioles (20-60 microns) was measured using intravital microscopy in WKY rats and SHRSP (9-12 months old). Superfusion of bradykinin (3 x 10(-7) M) dilated pial arterioles by 35 +/- 6% (mean +/- SEM) in WKY rats, but only 21 +/- 3% in SHRSP (p less than 0.05 versus WKY rats). Both nitric oxide (5 x 10(-7) M) and nitroglycerin (10(-5) M) produced similar vasodilatation in WKY rats and SHRSP. Our second goal was to determine whether alteration of postreceptor mechanisms contributes to impairment of endothelium-dependent cerebral vasodilatation in SHRSP. Calcium ionophore A23187 (10(-5) M) produced more vasodilatation in WKY rats than in SHRSP (32 +/- 8% versus 9 +/- 4%, p less than 0.05). Responses to A23187 (10(-5) M) were inhibited by indomethacin (46 +/- 13% versus 15 +/- 5%, p less than 0.05) in WKY rats, whereas responses to A23187 (10(-6) M) were potentiated modestly by indomethacin (-3 +/- 2% versus 4 +/- 2%, p less than 0.05) in SHRSP.(ABSTRACT TRUNCATED AT 250 WORDS)

Batch fermentation kinetics of xanthan gum production from glucose by Xanthomonas campestris at temperatures between 22 degrees C and 35 degrees C were studied to evaluate temperature effects on cell growth and xanthan formation. These batch xanthan fermentations were modeled by the logistic equation for cell growth, the Luedeking-Piret equation for xanthan production, and a modified Luedeking-Piret equation for glucose consumption. Temperature dependence of the parameters in this model was evaluated. Growth-associated rate constants increased to a maximum at approximately 30 degrees C and then decreased to zero at approximately 35 degrees C. This temperature effect can be modeled using a square-root model. On the contrary, non-growth-associated rate constants increased with increasing temperature, following the Arrhenius relationship, in the entire temperature range studied. The model developed in this work fits the experimental data very well and can be used in a simulation study. However, due to the empirical nature of the model, the parameter values need to be reevaluated if the model is to be applied to different growth conditions.

The fermentation kinetics of methane production from whey permeate in a packed bed immobilized cell bioreactor at mesophilic temperatures and pHs around neutral was studied. Propionate and acetate were the only two major organic intermediates found in the methanogenic fermentation of lactose. Based on this finding, a three-step reaction mechanism was proposed: lactose was first degraded to propionate, acetate, CO(2), and H(2) by fermentative bacteria; propionate was then converted to acetate by propionate-degrading bacteria; and finally, CH(4) and CO(2) were produced from acetate, H(2), and CO(2) by methanogenic bacteria. The second reaction step was found to be the rate-limiting step in the overall methanogenic fermentation of lactose. Monod-type mathematical equations were used to model these three step reactions. The kinetic constants in the models were sequentially determined by fitting the mathematical equations with the experimental data on acetate, propionate, and lactose concentrations. A mixed-culture fermentation model was also developed. This model simulates the methanogenic fermentation of whey permeate very well.

Batch xanthan fermentations by Xanthomonas campestris NRRL B-1459 at various temperatures ranging between 22 degrees C and 35 degrees C were studied. At 24 degrees C or lower, xanthan formation lagged significantly behind cell growth, resembling typical secondary metabolism. However, at 27 degrees C and higher, xanthan biosynthesis followed cell growth from the beginning of the exponential phase and continued into the stationary phase. Cell growth at 35 degrees C was very slow; the specific growth rate was near zero. The specific growth rate had a maximum value of 0.26 h(-1) at temperatures between 27 degrees C and 31 degrees C. Cell yield decreased from 0.53 g/g glucose at 22 degrees C to 0.28 g/g glucose at 33 degrees C, whereas xanthan yield increased from 54% at 22 degrees C to 90% at 33 degrees C. The specific xanthan formation rate also increased with increasing temperature. The pyruvate content of xanthan produced at various temperatures ranged between 1.9% and 4.5%, with the maximum occurring between 27 degrees C and 30 degrees C. These results suggest that the optimal temperatures for cell growth are between 24 degrees C and 27 degrees C, whereas those for xanthan formation are between 30 degrees C and 33 degrees C. For single-stage batch fermentation, the optimal temperature for xanthan fermentation is thus dependent on the design criteria (i. e., fermentation rate, xanthan yield, and gum qualities). However, a two-stage fermentation process with temperature shift-up from 27 degrees C to 32 degrees C is suggested to optimize both cell growth and xanthan formation, respectively, at each stage, and thus to improve overall xanthan fermentation.

Clostridium formicoaceticum homofermentatively converts lactate to acetate at 37 degrees C and pH 6.6-9.6. However, this fermentation is strongly inhibited by acetic acid at acidic pH. The specific growth rate of this organism decreased from a maximum at pH 7.6 to zero at pH 6.6. This inhibition effect was found to be attributed to both H(+) and undissociated acetic acid. At pH values below 7.6, the H(+) inhibited the fermentation following non-competitive inhibition kinetics. The acetic acid inhibition was found to be stronger at a lower medium pH. At pH 6.45-6.8, cell growth was found to be primarily limited by a maximum undissociated acetic acid concentration of 0.358 g/L (6mM). This indicates that the undissociated acid, not the dissociated acid, is the major acid inhibitor. At pH 7.6 or higher, this organism could tolerate acetate concentrations of higher than 0.8M, but salt (Na(+)) became a strong inhibitor at concentrations of higher than 0.4M. Acetic acid inhibition also can be represented by noncompetitive inhibition kinetics. A mathematical model for this homoacetic fermentation was also developed. This model can be used to simulate batch fermentation at any pH between 6.9 and 7.6.

Clostridium formicoaceticum homofermentatively converted lactate to acetate at mesophilic temperatures (30 to 42 degrees C) and at pHs between 6.6 and 9.6. The production of acetate was found to be growth associated. Approximately 0.96 g of acetic acid and 0.066 g of cells were formed from each gram of lactic acid consumed at 37 degrees C. The concentration of the substrate (lactate) had little or no effect on the growth rate; however, the fermentation was inhibited by acetic acid. The bacterium grew at an optimal pH of 7.6 and an optimal temperature of 37 degrees C. Small amounts of bicarbonate were stimulatory to bacterial growth. Bacterial growth was enhanced, however, by the use of higher concentrations of bicarbonate in the media, only because higher buffer capacities were obtained and proper medium pH could be maintained for growth. Based on its ability to convert lactate to acetate, this homoacetic bacterium may be important in the anaerobic methanogenic process when lactate is a major intermediary metabolite.

The defined microbial cultures for methane generation from lactose were investigated. A mixed culture consisting of homolactic (Streptococcus lactis), homoacetic (Clostridium formicoaceticum), and acetate-utilizing methanogenic (Methanococcus mazei) bacteria was used to convert lactose and whey permeate to methane at mesophilic temperatures (35-37 degrees C) and a pH around 7.0. Lactose was first converted to lactic acid by S. lactis, then to acetic acid by C. formicoaceticum, and finally to methane and CO(2) by M. mazei. About 5.3 mol methane were obtained from each mole of lactose consumed, and the conversion of acetate to methane was the rate-limiting step for this mixed-culture fermentation.

Fermentation kinetics of Clostridium formicoaceticum grown on lactate at pH 7.0 and 35 degrees C was studied. Acetate was the only fermentation product and its production was growth associated. The growth of this bacterium was insensitive to the lactate concentrations studied, but was inhibited by acetic acid. A Monod-type expression with product inhibition similar to the noncompetitive inhibition of enzyme kinetics was used to model the batch fermentation. An integrated equation was developed and used to help estimating the kinetic parameters in the model. This mathematical model can be used to simulate the homoacetic fermentation of lactate by C. formicoaceticum at pH 7.0 and 35 degrees C.

Stimulation of macrophages to lyse tumor cells is a property common to lipopolysaccharide (LPS) extracted from a variety of smooth and rough bacterial strains by several different preparative procedures. The relationship between macrophage stimulation and the structural characteristics of LPS is defined. In protein-free LPS, lipid A bears the stimulatory signal which results in the differentiation of elicited macrophages into killer cells. The polysaccharide moiety is neither stimulatory itself nor does it block the activity of complete LPS on macrophages. Extraction of LPS by the butanol or Boivin procedures produces preparations in which LPS is complexed through its lipid A moiety to a protein rich component, LAP. Isolated LAP delivers a macrophage differentiation signal which is independent of lipid A. The presence of these two structurally distinct constituents in the cell walls of gram-negative bacteria broadens the biological environments in which they can stimulate macrophages in vivo.

A new graphical method was developed to determine the kinetic parameters in the Michaelis-Menten-type equation. This method was then applied to studying the kinetics of lactose hydrolysis by Aspergillus niger beta-galactosidase. In this study, the reaction temperature ranged between 8 and 60 degrees C, and the initial lactose concentration ranged between 2.5 and 20%. A kinetic model similar to the conventional Michaelis-Menten equation with competitive product inhibition by galactose was tested using this graphical method as well as a nonlinear computer regression method. The experimental data and the model fit together fairly well at 50 degrees C. However, a relative large disparity was found for reactions at 30 degrees C. A three-parameter integrated model derived from the reversible reaction mechanism simulates the experimental data very well at all temperatures studied. However, this reversible reaction model does not follow the Arrhenius temperature dependence. Nevertheless, reaction rate constants for the proposed model involving the enzyme-galactose complex (in addition to the Michaelis complex) as an intermediate in lactose hydrolysis follow the Arrhenius temperature dependence fairly well, suggesting that this model can be best used for describing the enzymatic lactose hydrolysis. The lack of fit between the model predictions and data may be largely attributed to the effects of galactose mutarotation and oligosaccharide formation during lactose hydrolysis.

The hydrolysis of lactose using immobilized beta-galactosidase (from Aspergillus niger) on phenol-formaldehyde resin was studied at temperatures between 8 and 60 degrees C and initial lactose concentrations ranging from 2.5 to 20.0%. A model involving enzyme-galactose complex similar to Michaelis-Menten kinetics with competitive product (galactose) inhibition is suitable to describe the lactose hydrolysis reaction. A small degree of lack of fit between the model and the data was found to be due to the formation of oligosaccharides. Thermal deactivation of lactase follows first-order reaction mechanism. The effect of temperature on the reaction and the deactivation rate constants follows the Arrhenius relationship. The Oligosaccharide formation was not significantly affected by the temperature when the initial lactose concentration was 5%. A design equation for the plug-flow immobilized lactase reactor was developed from the reaction and the deactivation kinetics and was used to find the optimal operating temperature. The optimal temperature was found to be dependent on the operating time but not on the lactose concentration or the conversion. The optimal operating temperature is 60 degrees C when operating time is short but is close to 35 degrees C for a long operating time. A preliminary economic analysis indicates that the optimal operating temperature is 43, 38.5, and 33 degrees C when the operating time is 300 days, 1000 days, and infinity, respectively.

When 0.1% gentamicin solution was applied to full-thickness skin wounds of dogs, the wounds became smaller by contraction during the first 7 days and continued to contract over the next 14 days. Wounds treated with 0.1% gentamicin cream enlarged during the first 7 days, followed by wound contraction over the next 14 days. The wounds treated with gentamicin solution also had more epithelialization at 7 days than did the cream-treated wounds; however, epithelialization of the 2 types of wounds was similar at 14 and at 21 days. Gentamicin solution and cream were effective in controlling bacterial growth on wounds when compared with the bacterial growth on the control wounds (not treated with antibiotics).

The stability of eseroline, the hydrolysis product of physostigmine under aerobic conditions, was studied by liquid chromatography. A reversed-phase, ion-pair technique was used to separate eseroline from its degradation products. The degradation of eseroline in phosphate buffer solutions of pH 6.91, 7.40, 7.98, 8.41 and 8.94 appears to follow first-order kinetics; the rate constant increased with an increase in pH. The degradation appears to follow specific base catalysis.

A lamp-pumped, 13-W cw Nd:YAG ring laser at 1.064 microm is injection locked using a 40-mW single-frequency diodelaser-pumped Nd:YAG laser as the master oscillator. The phase fidelity of the injected slave to the master is measured using an all-optical technique.

Kinetics of methanogenesis from acetate was studied using pure cultures of Methanosarcina barkeri and Methanosarcina mazei. Methane formation was found to be associated with cell growth. Nearly equimolar methane was produced from acetate during the methanogenic growth, and about 1.94 g of cells were formed from each mole of acetate consumed. Cell growth can be estimated from methane production. Significant substrate inhibition was found when acetate concentration was higher than 0.12 M. Among the three methanogenic strains studied, M. mazei strain S6 had the highest specific growth rate at all acetate concentrations studied and was least sensitive to environmental factors investigated (e.g., acetate concentration). The maximum specific growth rate found for strain S6 was 0.022 hr(-1) at acetic acid concentration around 7 g/L. The other two strains studied were M. barkeri strain 227 and strain MS. Growth of M. barkeri was completely inhibited at sodium acetate concentrations higher than 0.24 M. The maximum specific growth rate found for strains 227 and MS was 0.019 and 0.021 h(-1) at acetic acid concentrations of 3.6 and 6.8 g/L, respectively. A kinetic model with substrate inhibition was developed and can be used to simulate the methane formation from M. mazei strain S6 grown on acetate at 35 degrees C, pH 7.