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Biomedical subjects

J M Walsh

Publications and source records attributed to J M Walsh.

At least 55 records · Page 3Linked to original sources
PubMed1986

Maturational steroids and gonadotropin in upstream migratory sockeye salmon.

The circulating serum concentrations of various steroid hormones in mature sockeye salmon were measured at four different developmental stages in their upstream migration to spawn at Adams River in British Columbia, Canada. In females, a high level of estradiol-17 beta was found in fish at the first location, and it persisted until immediately before reaching the spawning grounds, 485 km upstream, where it decreased to a minimal level. Free testosterone was extremely high throughout the migration but decreased significantly after spawning while its glucuronide changed reciprocally. Free and conjugated 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (17 alpha, 20 beta-P) peaked at the last location before spawning with the glucuronide only 20% of the free steroid in concentration. After spawning, the concentration of free steroid declined but the glucuronide remained constant. 17 alpha-hydroxyprogesterone increased significantly in serum before and after the fish had spawned. During the migration 11-deoxycortisol was present in the serum at all stages but maximal levels were found in postspawned fish. Throughout the migration, the males had high serum levels of 11-ketotestosterone. Lesser amounts of free testosterone were also consistently present but the ratio of free: conjugated decreased from 1.7 at the beginning of the migration to 0.15 on the arrival at the Adams River and 0.10 in postspawned fish. Only low levels of 11 beta-hydroxytestosterone were found except in the postspawned males where the value was equal to one-half that of free testosterone. As in the females, there was a substantial increase in the levels of 17 alpha, 20 beta-P and its glucuronide in the males captured at the spawning grounds. In both sexes gonadotropin levels were low during the migration and high in the postspawned fish.

Animals↗
PubMed1985

Progestogens, androgens and their glucuronides in the terminal stages of oocyte maturation in landlocked Atlantic salmon.

Peripheral serum levels of free and conjugated steroids were correlated with seven terminal stages of oocyte maturation in female landlocked Atlantic salmon. Pregnenolone levels were maximal at stage 1, and there was a surge in testosterone after initiation of germinal vesicle migration. Testosterone remained high, above 25 ng/ml until ovulation, and its glucuronide was always lower than the corresponding free form. 17 alpha,20 beta-Dihydroxy-4-pregnen-3-one increased progressively from 0.71 to 68 ng/ml from oocyte stage 1 to 6, with the glucuronide predominating in stages 1 to 4 and the free steroid in stages 5 to 7. Thus, very low levels of free 17 alpha,20 beta-dihydroxy-4-pregnen-3-one were present when migration of the germinal vesicle was initiated but considerable free steroid was present at and after germinal vesicle breakdown. Negligible amounts of progesterone, 17 alpha-hydroxypregnenolone, 5-pregnene-3 beta,17 alpha,20 beta-triol were found in the serum during final maturation. In male salmon with expressible milt, 17 alpha,20 beta-dihydroxy-4-pregnen-3-one was present with a gradual increase of both free and conjugated form at the advent of spawning, suggesting that this steroid may also play a role in reproduction in male fish. The action of steroids in vitro on oocytes at various stages was consistent with conclusions based on blood levels.

Androgens↗
PubMed1983

Effect of acute exposure to crude petroleum on some reproductive hormones in salmon and flounder.

1. The concentration of total (free + conjugated) androgens in plasma of sexually mature male salmon and flounder was generally lower in oil-exposed fish. 2. Exposure to crude oil inhibited some testicular development of salmon during the final stages of maturation. 3. Oil exposure had no effect on levels of total plasmatic androgens or estradiol in male and female flounder during gonadal recrudescence. 4. Aryl hydrocarbon hydroxylase activity increased in liver and kidney of both species. 5. Sperm, collected from salmon exposed to oil, fertilized eggs from non-exposed females to produce normal alevins.

Androgens↗
PubMed1981

Histone modifications in the yeast S. Cerevisiae.

The content of the acetylated histone species associated with the highly transcriptionally active chromatin of yeast was examined. We found yeast chromatin to contain very high levels of the acetylated species for histones H3, H4 and possibly the H2B variants, H2B-1 and H2B-2. Sixty-three percent of the histone H4 species was represented by the di-, tri- and tetra-acetylated forms. These results make yeast chromatin among the most highly acetylated of any chromatins reported thus far. In addition, the results are consistent with the idea that hyperacetylation of histones allows chromatin to be transcribed at an increased rate.

Acetylation↗
PubMed1980

Behavioral effects of morphine on free-operant avoidance under hyperbaric pressure.

Morphine sulfate was tested under hyperbaric pressure to assess its effects on behavior. Four male hooded rats were trained to avoid brief electric shocks under a free-operant unsignalled avoidance procedure. Using an individual organism design, we injected each rat subcutaneously with morphine sulfate (2.0, 4.0, 6.0, 8.0 mg/kg body wt.) or saline (0.1 ml/100 g body wt.). Rats were tested at 1.0 and 7.1 atmospheres absolute (ATA) in a dry hyperbaric chamber while breathing a mixture of helium and oxygen. Each session lasted 60 min. Overall, the analgesic effects of morphine at 1.0 and 7.1 ATA were found to be similar. Shock avoidance by a rat was found to be a monotonic function of the drug dose; the fewest shocks were associated with the 2.0 mg/kg dose. Increased pressure did not significantly affect the number of shocks received by a rat across doses. Total responding remained stable throughout the study, but the temporal pattern of responding was differentially influenced by drug dose.

Animals↗
PubMed1978

Reduction of the incidence of decompression sickness in rats by smooth-muscle activating factor (SMAF).

Normal rats were injected with a smooth-muscle activating factor (SMAF) to examine the dose-response relationshio of SMAF to the incidence of decompression sickness. After injections of saline or 1.0, 5.0, or 10.0 mg/kg SMAF, the animals were compressed to 6 ATA breathing air for 1 h and were then rapidly decompressed to 1 ATA. Results indicate that predive injections of SMAF or exposure to the SMAF substance protected rats against decompression sickness and that higher doses appear to offer more protection.

Animals↗
PubMed1977

Reduction of the behavioral effects of delta9-tetrahydrocannabinol by hyperbaric pressure.

Delta9-tetrahydrocannabinol in doses of 0.5, 1.0, 2.0 and 4.0 mg/kg was administered to rats under normal (1 ATA) and increased (3, 5 and 7 times normal) atmospheric pressure. Behavior was maintained by a food-reinforced differential-reinforcemnet-of-low-rate (DRL) schedule. Dose-dependent decrements in performance was observed at the 1 ATA conditions, in which response rates increased and the well-established temporal discrimination disintegrated. Under the elevated pressure conditions, however, a reversal of behavioral toxicity occurred during which performance improved as a function of pressure. The behavioral disruptions occurring at the 5- and 7-ATA pressures were minimal compared with those occurring at 1 ATA under equivalent doses of the drug. The present experiment has demonstrated that delta9-tetrahydrocannabinol produces significant behavioral changes at 1 ATA pressure, but when atmospheric pressure is increased the drug effects are reduced.

Animals↗
PubMed1976

Studies on the control of 4-aminobutyrate metabolism in 'synaptosomal' and free rat brain mitochondria.

1. The specific activities of 4-aminobutyrate aminotransferase (EC 2.6.1.19) and succinate semialdehyde dehydrogenase (EC 1.2.1.16) were significantly higher in brain mitochondria of non-synaptic origin (fraction M) than those derived from the lysis of synaptosomes (fraction SM2). 2. The metabolisms of 4-aminobutyrate in both 'free' (non-synaptic, fraction M) and 'synaptic' (fraction SM2) rat brain mitochondria was studied under various conditions. 3. It is proposed that 4-aminobutyrate enters both types of brain mitochondria by a non-carrier-mediated process. 4. The rate of 4-aminobutyrate metabolism was in all cases higher in the 'free' (fraction M) brain mitochondria than in the synaptic (fraction SM2) mitochondria, paralleling the differences in the specific activities of the 4-aminobutyrate-shunt enzymes. 5. The intramitochondrial concentration of 2-oxoglutarate appears to be an important controlling parameter in the rate of 4-aminobutyrate metabolism, since, although 2-oxoglutarate is required, high concentrations (2.5 mM) of extramitochondrial 2-oxoglutarate inhibit the formation of aspartate via the glutamate-oxaloacetate transaminase. 6. The redox state of the intramitochondrial NAD pool is also important in the control of 4-aminobutyrate metabolism; NADH exhibits competitive inhibition of 4-aminobutyrate metabolism by both mitochondrial populations with an apparent Ki of 102 muM. 7. Increased potassium concentrations stimulate 4-aminobutyrate metabolsim in the synaptic mitochondria but not in 'free' brain mitochondria. This is discussed with respect to the putative transmitter role of 4-aminobutyrate.

4-Aminobutyrate Transaminase↗
PubMed1976

Mitochondrial DNA in yeast recombination and subsequent modification following mating between a Grande and a suppressive Petite.

The fate of mitochondrial DNA, following mating between a grande and suppressive petite of Saccharomyces cerevisiae, has been followed for up to 60 generations. The buoyant density of the mitochondrial DNA was seen to change in a manner explicable by a combination of recombination and subsequent modification phenomena whilst the suppressivity of the petite zygotic clones always remained high. These findings are consistent with current models of mitochondrial DNA metabolism in which petite strains have been observed to undergo deletion and reamplification of certain parts of their genomes.

Centrifugation, Density Gradient↗