Biomedical subjects

J D Oliver

Publications and source records attributed to J D Oliver.

At least 55 records · Page 3Linked to original sources

PubMed1994

Proteinuria and impaired glomerular permselectivity in uninephrectomized fawn-hooded rats.

Previous studies of glomerular permselectivity have indicated that both size selectivity and charge selectivity changes play a role in the pathogenesis of proteinuria. In this study, we measured Ficoll sieving coefficients, hemodynamic parameters, and urinary protein excretion rates in the FHH strain of fawn-hooded rats. These animals spontaneously develop systemic and glomerular hypertension, proteinuria, and focal and segmental glomerulosclerosis at a relatively young age. Three groups of FHH rats were studied: two-kidney controls (2K), untreated uninephrectomized rats (CON-NX), and uninephrectomized rats treated with the angiotensin I converting enzyme inhibitor enalapril (ENA-NX). CON-NX rats had higher glomerular transcapillary pressures (delta P) and higher urinary excretion rates of both total protein (UpV) and albumin (UaV) than did 2K rats, whereas treatment with enalapril prevented both glomerular hypertension and the increased proteinuria. Ficoll sieving coefficients were significantly higher in both groups of NX rats compared with 2K rats only for Stokes-Einstein radii (rs) > or = 46 A. Fits of sieving data to pore models showed a small increase in the number of large, nonselective pores in NX, which was not prevented by enalapril treatment. Total clearances of Ficoll with rs = 36 A (the size of albumin) in CON-NX and ENA-NX groups were unchanged compared with 2K animals. In contrast, UaV in CON-NX rats was more than six times that of 2K and ENA-NX rats. Across groups, UpV, UaV, and the ratio (UaV)/(UpV) all correlated strongly with delta P.(ABSTRACT TRUNCATED AT 250 WORDS)

Albuminuria↗

PubMed1994

Effect of osmotic variation on the outer membrane proteins of Vibrio vulnificus: identification of a major heat-modifiable protein.

Cells of the moderately halophilic bacterium Vibrio vulnificus showed marked morphological changes, manifested primarily by pronounced cell elongation when grown in a defined medium with increased salt concentrations of 0.5 to 2.0%. These morphological changes were not accompanied by changes in outer membrane proteins (Omp). A similar lack of Omp variation was observed when cells were grown in heart infusion broth containing 1-2% NaCl. Osmotic upshock during growth also had no effect on Omp profiles. A heat modifiable protein with a molecular weight of 38 kD similar to Omp A of Escherichia coli, was identified in cells grown in heart infusion broth. The results suggest that under these osmotic conditions V. vulnificus may not need to regulate transport through modification of its outer membrane proteins.

Bacterial Outer Membrane Proteins↗

PubMed1993

Stimulation of lipoprotein lipase synthesis by refeeding, insulin and dexamethasone.

Lipoprotein lipase synthesis in adipose tissue was greater in rats fed ad libitum or refed than in fasted rats. Insulin alone and together with dexamethasone increased lipoprotein lipase synthesis in adipose tissue incubated in vitro. The changes in relative lipoprotein lipase synthesis (immunoprecipitable 35S-labelled lipoprotein lipase as a fraction of general [35S]protein after pulse-labelling with [35S]methionine) indicate that insulin and dexamethasone exert a selective effect on lipoprotein lipase synthesis. There was no evidence for an inverse relationship between lipoprotein lipase synthesis and activity for any of the conditions studied.

Adipose Tissue↗

PubMed1993

Purification, crystallization and preliminary X-ray investigation of aqualysin I, a heat-stable serine protease.

Aqualysin I, a thermostable protease found in the culture medium of Thermus aquaticus YT-1, has been purified to homogeneity using a combination of ion-exchange and affinity chromatography. It is a polypeptide with a molecular weight of 28 350 [Kwon, Terada, Matsuzawa & Ohta (1988). Eur. J. Biochem. 173, 491-497] and is most active at 343-353 K and pH about 10.0 [Matsuzawa, Tokugawa, Hamaoki, Mizoguchi, Taguchi, Terada, Kwon & Ohta (1988). Eur. J. Biochem. 171, 441-447]. Crystals of the enzyme are monoclinic, space group P2(1), with cell dimensions a = 40.80 (5), b = 64.39 (6), c = 45.51 (6) A and beta = 109.1 (1) degrees. The asymmetric unit consists of a single molecule (V(m) = 1.99 A(3)Da(-1)). The crystals are stable to X-radiation and scatter to at least 2.8 A resolution.

Journal Article↗

PubMed1993

Effects of retinoic acid on lipoprotein lipase activity and mRNA level in vitro and in vivo.

This study was designed to determine whether all-trans retinoic acid altered lipoprotein lipase (LPL) activity and mRNA levels in vitro and tissue LPL mRNA levels in vivo. Incubation of adipocytes or adipose tissue for up to 12 hr with 10(-6) or 10(-5) M all-trans retinoic acid did not decrease LPL activity. There was no change in LPL mRNA levels following 3 hr incubation of adipocytes with all-trans retinoic acid. Feeding all-trans retinoic acid for 4 days led to a significant decrease in adipose tissue LPL activity but no change in heart enzyme activity. Retinoic acid did not alter the increase in heart LPL activity observed with fasting. There were no changes in LPL mRNA levels in adipose tissue, heart or liver. Retinoic acid does not have an acute direct effect on adipose tissue LPL activity. The observed decrease in adipose tissue LPL activity in vivo is not due to alterations in mRNA levels and may be a secondary effect of retinoic acid.

Adipose Tissue↗

PubMed1993

Regulation of proteolytic activity of Vibrio vulnificus by iron-containing compounds.

Previous studies have shown that the Vibrio vulnificus is able to use hemoglobin and the hemoglobin-haptoglobin complex to reverse iron limitation. In addition, we report here that free hemin, as well as hemin bound to albumin, will reverse iron-limited growth. While protease negative mutants were able to use hemin and hemoglobin, they were unable to compete as successfully for albumin-bound hemin. Using Luria broth with the iron chelator ethylenediamine-di(o-hydroxyphenylacetic acid) (EDDA), no changes in proteolytic activity were seen. In contrast, growth in a low iron defined medium resulted in a loss of proteolytic activity. This loss was reversed by the addition of hemin or hemoglobin but not by inorganic iron or globin alone. Since one portal of entry of this organism is pre-existing wounds, hemoglobin released during cell damage may be important in activating extracellular proteases leading to the massive cell damage seen with this vibrio.

Albumins↗

PubMed1993

Starvation-induced thermal tolerance as a survival mechanism in a psychrophilic marine bacterium.

Carbon-starved cultures of strain Ant-300, a psychrophilic marine vibrio isolated from the Antarctic Convergence, were compared with their nonstarved counterparts for resistance to heat. Specifically, starved and unstarved cells were exposed to 17 degrees C, which is 4 degrees C above the maximum growth temperature, and compared with cells maintained at the optimum temperature (5 to 7 degrees C). Total cell counts, direct viable-cell counts, and plate counts were monitored. At a temperature of 17 degrees C, viability (as indicated by plate counts) was lost within 40 h, with direct viable-cell counts indicating less than 5% viability at this time. However, when cells were carbon starved for 1 week prior to heat challenge, significant plateability was maintained for more than 6 days; direct viable-cell counts of starved cells maintained at 17 degrees C indicated the presence of viable cells for at least 12 days. Because starvation is the normal physiological state of copiotrophic, heterotrophic bacteria in oligotrophic marine waters, these data suggest that starvation conditions may be a significant factor in providing heat tolerance to psychrophiles.

Journal Article↗

PubMed1992

Low temperature induced non-culturability and killing of Vibrio vulnificus.

Vibrio vulnificus cells progressively lose culturability during incubation at 5 degrees C. This process is accelerated by the addition of supernatants from non-culturable cells obtained by incubation at 5 degrees C for 17 days. Thus the organism apparently produces a factor upon cold incubation which is triggering or causing the decline in culturability. Reversing the temperature shift can restore a culturable population comparable in numbers to the original population, but this process is largely due to regrowth. A few cells retaining the ability to grow apparently utilize the substrates released by the moribund cells, thus mimicking resuscitation of the whole population.

Cold Temperature↗

PubMed1992

Reversal of hypotension induced by Vibrio vulnificus lipopolysaccharide in the rat by inhibition of nitric oxide synthase.

Intravenous infusion of Vibrio vulnificus lipopolysaccharide (LPS) (1 mg/kg body wt) in rats caused a dramatic drop in mean arterial pressure within 10 min and a further decline in mean arterial pressure and heart rate which lead to death between 25 and 70 min. Rats treated with LPS followed 10 min later by the intravenous infusion of NG-monomethyl-L-arginine (L-NMMA, 20 mg/kg body wt) showed an initial drop in mean arterial pressure owing to the LPS infusion, followed by a transient rise in mean arterial pressure which lasted for approximately 40 min after the infusion of L-NMMA. The pressure values then remained level for at least 150 min post-LPS infusion. Control rats treated with equivalent volumes of saline infusion showed stable values of mean arterial pressure and heart rate. Additional control rats receiving L-NMMA alone showed the transient rise in mean arterial pressure, followed by a return to the baseline values. The results indicate that the symptoms of endotoxic shock resulting from V. vulnificus LPS may result in part from the stimulation of the activity of nitric oxide synthase. Inhibition of nitric oxide synthase by L-NMMA is a possible treatment for toxic shock induced by V. vulnificus.

Amino Acid Oxidoreductases↗

PubMed1992

Use of colistin-polymyxin B-cellobiose agar for isolation of Vibrio vulnificus from the environment.

Colistin-polymyxin B-cellobiose agar was employed for the isolation of Vibrio vulnificus from shellfish. Isolates were examined phenotypically and with a gene probe and monoclonal antibody specific for V. vulnificus. Results indicated that colistin-polymyxin B-cellobiose agar is superior to both sodium dodecyl sulfate-polymyxin B-sucrose agar and thiosulfate-citrate-bile salts-sucrose agar in its ability to select and differentiate this species from background vibrios.

Agar↗

PubMed1992

Starvation Response of the Marine Barophile CNPT-3.

The psychrophilic marine barophile CNPT-3 underwent a starvation-survival response similar to that reported for the marine bacteria Ant-300, DW1, and S-14. The number of culturable cells increased initially and then decreased gradually over a 24-day starvation period, with corresponding decreases in total cell number and direct viability count. A significant reduction in cell size and biovolume accompanied these changes. Starved cells demonstrated a greater tendency to attach at the in situ pressure (400 atm; ca. 40.5 MPa) and temperature (5 degrees C) than at 1 atm (ca. 101 kPa), and the extent of attachment increased with increasing duration of starvation. The membrane fatty acid profile of the marine barophile CNPT-3 was studied as the cells were subjected to starvation conditions. A 37.5% increase in saturated fatty acids was observed during the first 8 days of starvation, with a concomitant decrease in unsaturated fatty acids. There was also an increase in the amount of short-chain (<C(15:0)) fatty acids.

Journal Article↗

PubMed1992

Effects of temperature abuse on survival of Vibrio vulnificus in oysters.

Opaque and translucent morphotypes of a TnphoA-containing strain of Vibrio vulnificus were fed to oysters, which were subsequently stored at temperatures ranging from 0.5 to 22 degrees C for 10 days. Samples of oysters were homogenized and plated at intervals to determine the cell density of V. vulnificus and total aerobic population of bacteria present. At all temperatures, the numbers of V. vulnificus (both morphotypes) declined over the 10-day study period. The same observation was made with a lower inoculum of V. vulnificus. Identical experiments with shucked oysters showed a more rapid decrease in V. vulnificus. Identical experiments with shucked oysters showed a more rapid decrease in V. vulnificus to levels below limits of detection. Little change in the total bacterial counts was observed in shellstock oysters at any of the test temperatures, whereas incubation at the higher temperatures (17 and 22 degrees C) resulted in large increases in total counts in shucked oysters. These data suggest that temperature abuse of oysters may not be a factor in increasing the public health risk of V. vulnificus through raw oyster consumption. However, the data also suggest that even with proper storage, indigenous levels of V. vulnificus may remain sufficiently higher in shellstock oysters to produce infection in compromised hosts.

Aerobiosis↗

PubMed1992

Determination of glomerular size-selectivity in the normal rat with Ficoll.

Diffusion studies in vitro indicate that Ficoll behaves more like an ideal spherical molecule than does dextran, suggesting that Ficoll would be a better probe of glomerular pore size than the commonly used dextran. To examine the differences between these macromolecules in vivo, the fractional clearances of tritiated Ficoll and dextran were measured over a wide range of molecular sizes (Stokes-Einstein radius, rs, from 19 to 65 A) in normal euvolemic Munich-Wistar rats. Whole-kidney and single-nephron hemodynamic conditions were characterized through a combination of clearance and micropuncture measurements. The fractional clearance, or sieving coefficient (theta), for dextran significantly exceeded that of Ficoll at all molecular sizes examined, theta for dextran being approximately 10 times that for Ficoll for rs greater than 30 A. Thus, the results with Ficoll imply a more size-restrictive barrier than do the results with dextran. The values of theta for Ficoll approximated previously reported values for uncharged globular proteins. Although theta for Ficoll at rs = 35 A was much smaller than the corresponding value for dextran, it was still approximately 30 times greater than typical values of the filtrate-to-plasma concentration ratio reported for serum albumin (a polyanion) in the rat, in agreement with the concept that glomerular charge-selectivity normally plays an important role in the prevention of albuminuria. Three membrane-pore models were compared in their ability to represent the dextran and Ficoll sieving data. A lognormal pore-size distribution in parallel with a nonselective "shunt" pathway was found to be more effective than either an isoporous membrane with a shunt or a purely lognormal distribution. On the basis of these laboratory results and computations, Ficoll may be preferred over dextran in future studies of glomerular size-selectivity.

Animals↗

PubMed1991

Formation of nonculturable Vibrio vulnificus cells and its relationship to the starvation state.

Entry into the viable but nonculturable state by the human bacterial pathogen Vibrio vulnificus in artificial seawater microcosms was studied. In contrast to the long-term culturability exhibited by cells incubated under these starvation conditions at room temperature, cells exposed to a temperature downshift to 5 degrees C exhibited an immediate decrease in culturability. Cells incubated at low temperature exhibited a morphological change from rods to cocci but demonstrated no reductive division. Of 10 factors studied which might affect the nonculturable response in V. vulnificus, only the physiological age of the cells was found to significantly affect the rate at which cells became nonculturable. The nonculturable response appears to be related to the starvation response, as prestarvation at room temperature for 24 h was found to eliminate the nonculturable response of cells subsequently incubated at 5 degrees C. This observation suggests that the synthesis of starvation proteins may repress the viable but nonculturable program displayed during low-temperature incubation. The possible ecological significance of these findings is discussed.

Colony Count, Microbial↗

PubMed1991

Use of the polymerase chain reaction in detection of culturable and nonculturable Vibrio vulnificus cells.

Vibrio vulnificus is a human pathogen associated with consumption of raw oysters. During the colder months the organism apparently enters a viable but nonculturable state and thus cannot be cultured by ordinary bacteriological methods. For this reason, another means of detecting this bacterium is necessary. In the present study we utilized the polymerase chain reaction (PCR) to detect V. vulnificus DNA, thus eliminating the problem of nonculturability. DNA from both culturable and nonculturable cells of V. vulnificus was amplified by PCR with primers flanking a 340-bp fragment of the cytotoxin-hemolysin gene. As little as 72 pg of DNA from culturable cells and 31 ng of DNA from nonculturable cells could be detected. Fifty cycles of a two-step reaction (30 s [each] at 94 and 65 degrees C) were found to be optimal as well as more time efficient than the three-step PCR. The total procedure from the point of DNA extraction to observation on a gel required less than 8 h. Possible reasons for the difficulties encountered in amplifying DNA from nonculturable cells, e.g., gene rearrangement or loss of the hemolysin gene, are discussed.

Base Sequence↗

PubMed1991

Resuscitation of Vibrio vulnificus from the viable but nonculturable state.

Stationary-phase-grown cells of the estuarine bacterium Vibrio vulnificus became nonculturable in nutrient-limited artificial seawater microcosms after 27 days at 5 degrees C. When the nonculturable cells were subjected to temperature upshift by being placed at room temperature, the original bacterial numbers were detectable by plate counts after 3 days, with a corresponding increase in the direct viable counts from 3% to over 80% of the total cell count. No increase in the total cell count was observed during resuscitation, indicating that the plate count increases were not due to growth of a few culturable cells. Chloramphenicol and ampicillin totally inhibited resuscitation of the nonculturable cells when added to samples that had been at room temperature for up to 24 h. After 72 h of resuscitation, the inhibitors had an easily detectable but reduced effect on the resuscitated cells, indicating that protein and peptidoglycan synthesis were still ongoing. Major changes in the morphology of the cells were discovered. Nonculturable cells of V. vulnificus were small cocci (approximately 1.0 micron in diameter). Upon resuscitation, the cells became large rods with a size of mid-log-phase cells (3.0 microns in length). Four days after the cells had become fully resuscitated, the cell size had decreased to approximately 1.5 micron in length and 0.7 micron in width. The cells were able to go through at least two cycles of nonculturability and subsequent resuscitation without changes in the total cell count. This is the first report of resuscitation, without the addition of nutrient, of nonculturable cells, and it is suggested that temperature may be the determining factor in the resuscitation from this survival, or adaptation, state of certain species in estuarine environments.

Ampicillin↗

PubMed1991

Physiological effects of the lipopolysaccharide of Vibrio vulnificus on mice and rats.

Vibrio vulnificus is a pathogenic, marine, Gram-negative bacterium which commonly enters and infects humans via open wounds or the ingestion of raw seafood. The lipopolysaccharide (LPS) of V. vulnificus has recently been characterized, but the biological activity of this putative endotoxin is unknown. Three treatment groups were used to test its activity: saline (negative control), the LPS of Salmonella typhimurium (a known endotoxin), and the LPS of V. vulnificus. Whereas, intravenous injections of the S. typhimurium LPS caused mortality in two strains of mice, V. vulnificus LPS was not lethal. However, intraperitoneal injections into rats of both V. vulnificus and S. typhimurium LPS were pyrogenic. Intravenous injections of V. vulnificus LPS in rats caused decreased mean arterial pressure within 10 min which further declined, leading to death in 30 to 60 min. S. typhimurium LPS caused similar responses at the same concentration. The data suggest that the LPS of V. vulnificus may be a factor contributing to the virulence of this organism.

Animals↗

PubMed1991

Comparison of fifteen production batches of house dust mite extract (Dermatophagoides pteronyssinus).

An important measurement of quality of allergenic extracts is the batch to batch uniformity. Using different methods of protein and immunobiochemical analysis, we could demonstrate, that 15 production batches of house dust mite Dermatophagoides pteronyssinus extract prepared during the course of 4 years from different lots of the source material, (purified whole mite bodies) showed reproducible data.

Allergens↗