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C T Johnson

Publications and source records attributed to C T Johnson.

16 recordsLinked 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↗
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↗