Search PubMed⌕ Search

Biomedical subjects

C T Johnson

Publications and source records attributed to C T Johnson.

At least 37 records · Page 2Linked to original sources
PubMed1987

Purification of human liver aldehyde dehydrogenase by high-performance liquid chromatography and identification of isoenzymes by immunoblotting.

Human liver aldehyde dehydrogenase (ALDH) exists in multiple molecular forms. Two different isoenzymes of ALDH have been purified which will oxidize acetaldehyde to acetate. ALDH1 is localized principally in hepatocyte cytosol and exhibits a Km for acetaldehyde of about 0.1 mM at pH 9.5. ALDH2 is mitochondrial in origin and exhibits low Km for acetaldehyde, about 1 microM. We have developed rapid purification procedures for ALDH1 and ALDH2 by use of agarose-AMP affinity chromatography and high-performance anion-exchange liquid chromatography (HPLC). The method takes less time and affords higher yields of the labile ALDH isoenzymes than conventional column chromatography methods. A previously uncharacterized ALDH form has been identified by anion-exchange HPLC which exhibits high Km for acetaldehyde, about 1 mM, and is very labile. Polyclonal antibodies to the purified ALDH1 and ALDH2 isoenzymes have been prepared. As evidenced by immunoblotting of starch gels containing the purified isoenzymes, anti-ALDH1 does not crossreact with ALDH2 and anti-ALDH2 does not crossreact with ALDH1. The anti-ALDH2 antibody identifies the "inactive" variant of ALDH2 in Japanese livers exhibiting the "deficient" ALDH2 phenotype. The sensitivity of detection of ALDH isoenzymes in liver homogenate-supernatants by immunoblotting of starch gels is about 10-fold greater than that by activity staining.

Aldehyde Dehydrogenase↗
PubMed1984

Alterations in regulatory and locomotor behaviors following trimethyltin exposure in the rat: a time and dose analysis.

Adult male hooded rats were tested pretreatment for spontaneous alternation and open-field behaviors. Animals were then intubated with either 5 or 7 mg/kg trimethyltin chloride (TMT Cl) or the isotonic saline vehicle. Post-treatment, animals were again tested for spontaneous alternation and open-field behaviors during three separate 5-day periods: days 14-18, days 56-60 and days 106-110. Additionally, both body weight and water intake were assessed. The larger dose of TMT Cl resulted in significant, but temporary reduction in body weight, elevated water intake for approximately 3 weeks, and a persistent increase in open-field activity. The smaller dose of TMT Cl resulted in elevated water intake for approximately 3 weeks and a temporary increase in open-field activity. Since the tendency to enter choice arms decreased in all groups across testing sessions, the effects of TMT Cl on spontaneous alternation could not be accurately assessed.

Animals↗
PubMed1981

Endocrine and ovarian changes in dairy cattle fed a low beta-carotene diet during an oestrus synchronisation regime.

Twelve Friesian cows, 76 to 110 days calved, with blood cell counts and Compton metabolic profile values in the normal range throughout, were housed and fed a marginal diet for varying periods before being injected twice, 11 days apart, with cloprostenol. Artificial insemination was carried out 72 and 96 hours after the second injection. Plasma concentrations of progesterone, oestradiol 17 beta, luteinising hormone, follicle stimulating hormone, and beta-carotene were monitored during this regime as were uterine and ovarian changes. Progesterone profiles were followed for a further 21 days by assay of milk samples. Subsequent rectal examinations showed that five of the 12 cows conceived at controlled oestrus and another four within 52 days of this time. No correlation was observed between time of conception and condition score, metabolic profiles or haematological parameters; there was a correlation between time of conception and plasma beta-carotene concentrations and cows with lower beta-carotene values showed cyclic irregularities or appeared to have depressed steroid hormone production.

Animals↗
PubMed1979

Influence of stage of oestrous cycle on time of oestrus following cloprostenol treatment in the bovine.

The first of 2 injections of 0.5 mg cloprostenol (PG1 and PG2) eleven days apart was given to 19 Friesian-Hereford cross heifers between days 8-14 of their cycle (Treatment A) and 16 similar animals between days 0-4 (Treatment B). Oestrus show was monitored by Kamar Heat Mount detectors and vasectomised bulls with chin-ball markers. Blood samples taken at PG1, six days later, at PG2 and four days later were assayed for progesterone to confirm that luteolysis had occurred as expected. Four hourly rectal examinations of the ovaries were carried out from 56-112 hours after PG2 and four hourly blood samples from 36-96 hours after PG2 were collected for FSH and LH assay. Mean time in hours from PG2 to oestrus onset, LH peak and ovulation respectively was 57.4 +/- 2.9, 60.2 +/- 2.0, 91.7 +/- 1.8 for Treatment A and 64.9 +/- 4.1, 68.9 +/- 2.4, 96.7 +/- 1.3 for Treatment B. Treatment A animals showed significantly higher (p<0.01) FSH levels at PG2 than Treatment B. Time from PG2 to LH peak was significantly shorter in animals treated either on days 7 and 8 (p<0.01) or days 15-16 (p<0.05) of their cycle compared with treatment on days 12-14 and it is suggested that these shorter response times correspond to an early and late cycle wave of follicular growth. Secondary FSH peaks some 28 hours after that occurring synchronously with the pre-ovulatory LH peak were observed to be significantly (p<0.01) higher at oestrus associated with the early cycle follicular growth wave as compared with that later in the cycle which may argue a difference in endocrine control of the two periods of follicular maturation.

Journal Article↗
PubMed1979

Alcohol-induced alterations in hippocampal afterdischarges and afterdischarge thresholds: dose-reponse studies.

The hippocampal afterdischarge (AD) has been suggested as an index of toxicant-induced CNS change [1]. The present experiments report raised AD thresholds, decreased AD durations, shorter post-stimulation latencies to AD onset, decreased numbers of AD spike complexes and increased numbers of spikes/complex following alcohol administration. Results are discussed in light of single-unit data concerning alcohol effects upon hippocampal cells, and the biphasic effects of alcohol upon behavior.

Animals↗
PubMed1978

Time to onset of oestrus after the injection of heifers with cloprostenol.

When two injections of 500 microgram cloprostenol are given 11 days apart to unselected cycling heifers the onset of oestrus behaviour is significantly earlier, and more compact, after the second injection than after the first. The time from treatment to the onset of oestrus following this second injection was not significantly different from that obtaining in animals given a single injection on day 8 of the oestrous cycle. It is suggested that the more precise onset of oestrus after the second of two cloprostenol injections is due to the majority of animals being at a comparable stage of the oestrous cycle when the treatment is given. The earlier oestrus after two cloprostenol injections may be due to the greater number of heifers at days 7, 8 and 9 of the oestrous cycle at the time the second injection is given.

Animals↗
PubMed1977

Damage to hippocampus and hippocampal connections: effects on DRL and spontaneous alternation.

Male albino rats were tested both pre- and postoperatively either on a schedule of differential reinforcement of low-rate responding (DRL 20 sec; Experiment 1) or for spontaneous alternation (Experiment 2). Selective lesions were produced in the hippocampus and its fiber connections. Performance of both behaviors was consistently disrupted by total fornix, medial fornix, and septum lesions, while neither behavior was significantly disrupted by postcommissural fornix or entorhinal cortex lesions. Anterior hippocampus lesions consistently disrupted only DRL performance, while neither posterior hippocampus nor lateral fornix lesions resulted in consistently impaired performance of either behavior. These data are discussed as representing a possible functional differentiation between anterior and posterior portions of the hippocampal system.

Animals↗
PubMed1976

Active avoidance and brain DNA after postnatal food deprivation in rats.

Fond deprivation was produced in infant rats, from 2 to 20 days of age, by a procedure designed to minimize reduction in maternal care. Body weights in the deprived animals were 60% of control weights at 7 days, 65% at 20 days, and, after ad lib feeding, 89% at 4 months. No change was observed in the rate of acquistion of a conditioned active avoidance response in the food-deprived rats when compared with their littermate controls when tested as adults. No lasting reduction in cerebral desoxynucleic acid (DNA) was observed despote a 9% reduction in cerebellar DNA.

Animals↗
PubMed1975

Impairment of conditioned active avoidance in adult rats given corticosterone in infancy.

Intensive corticosterone treatment given to rats during the 1st postnatal week irreversibly decreases DNA accumulation in the cerebrum and cerebellum. After such hypercorticism in infancy rats were tested as adults in 2 conditioned active avoidance tasks. In comparison with litter-mate controls, the treated rats were impaired in the acquisition of 2-way active avoidance but not in the acquisition of 1-way active avoidance. These data are consistent with other observations suggesting a hyperresponsiveness or hyperemotionality following corticosterone treatment in infancy.

Animals↗
PubMedDate not supplied

The use of an antimicrobial and competitive exclusion combination in Salmonella-infected pullet flocks.

Replacement pullets which had been found infected with Salmonella were treated with antibiotics for 12 days, moved to a clean house by the 11th day and given 2 treatments with a competitive exclusion (CE) preparation on the 13th and 15th day. It was found necessary to supply a small amount of feed to generate a thirst in the birds and ensure efficient and rapid consumption of the CE preparation. Salmonella could not be grown from the intestines or other organs of birds after this procedure had been carried out.

Animal Husbandry↗