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Biomedical subjects

K T Ng

Publications and source records attributed to K T Ng.

At least 91 records · Page 5Linked to original sources
PubMed1988

Hydronephrosis in rats associated with postnatal exposure to a fatty acid oxidation inhibitor.

Methyl palmoxirate, an inhibitor of long-chain fatty acid oxidation, was administered by gavage (0, 1, 5, or 20 mg/kg/day) to female rats over the last third of gestation and throughout lactation. Weight gain (mid- and high-dosage group) and survivability (high-dosage group) were significantly (p less than or equal to 0.05) reduced in offspring of methyl palmoxirate-treated dams as compared to control offspring. Mid- and high-dosage male offspring found dead after Day 4 of lactation exhibited grossly distended bladders and renal pelves. A dosage-related increased incidence of dilated renal pelves was observed in both sexes at necropsy of 21-day-old mid- and high-dosage group pups. Microscopic examination of the urinary tracts of a number of affected pups revealed renal parenchymal atrophy and urethral obstruction. Drug disposition studies indicated lactating pups were exposed to significant amounts of methyl palmoxirate via mammary secretions. Cross-fostering experimentation suggested that some of the adverse effects observed in offspring were due to lactational, rather than in utero, exposure.

Animals↗
PubMed1987

Intra blood-cerebrospinal fluid-barrier detection of hepatitis B virus.

Hepatitis B, a major public health concern worldwide, is caused by hepatitis type B virus, a hepdnavirus that infects only human and certain nonhuman primates, and replicates strictly in hepatocytes. By using the techniques of slot and Southern blot DNA hybridization, and electron microscopy, the presence of HBV was identified in the cerebrospinal fluid of three affected individuals.

Blood-Brain Barrier↗
PubMed1987

Inhibition of memory in the chick using a monoclonal anti-Thy-1 antibody.

One-day-old chicks trained on a single trial passive avoidance task were administered a monoclonal anti-chick Thy-1 antibody, either intracranially or subcutaneously, at various times before and after learning and retention tested at various times post-learning. This procedure resulted in profound amnesia when anti-Thy-1 antibody was administered immediately before learning (5 min) in the case of the subcutaneous injections or 5 min before until 5 min after the learning process with intracranial injections. Antibody administered at other times, either before or after learning had little or no effect on retention. Retention levels were normal until 50 min post-learning, then declined sharply and remained at control levels for the duration of the test period. Chicks injected with anti-chick cerebellum or anti-rat Thy-1 antibodies showed no evidence of amnesia for the concentration of the antibodies used.

Animals↗
PubMed1987

Sex differences in acetaldehyde on body temperature and open-field performance in the rat.

Using the open field, for making an overall assessment of behavioural change in response to acetaldehyde (AcH) treatment, the results from the present study demonstrate that AcH produces behavioural and physiological effects similar to those of ethanol. High doses of AcH produced a similar degree of change as high doses of ethanol. Both compounds render the animal incapable of locomotor activities, such as ambulation and rearing and both produce a decrease of 2-3 degrees C in body temperature. AcH, however, appears to be a much more potent compound as behavioural and physiological changes are exhibited even after a dose of 10 mg/kg, while the dose of ethanol necessary to produce a decrease in open-field behaviour is at least 10 times as much. Females were more sensitive to the effects of AcH at the 100 mg/kg dose.

Acetaldehyde↗
PubMed1987

Effect of excess intracranial amino acids on memory: a behavioural survey.

Nineteen naturally occurring amino acids were administered intracranially to day-old chicks at various times before and after a single trial passive avoidance learning task. The results suggest a consistent and simple difference between essential and non-essential amino acids. Except for arginine, phenylalanine, tryptophan and tyrosine, the essential amino acids had no effect on memory formation when administered 5 min before or immediately after learning. However, arginine, phenylalanine and tryptophan yielded amnesia after 60 min following learning, when given between 5 min before and 2.5 min after learning. In the case of tryptophan, amnesia was only temporary, lasting from 60 min to 240 min post-learning. All non-essential amino acids, when administered between 5 min before and 5 min after learning yielded amnesia by 60 min post-learning, with no evidence of recovery by 24 hr post-learning. Alanine-, asparagine-, cysteine- and glutamate-treated chicks, however, showed signs of generalized avoidance shortly after administration. The retention time courses after injection of glutamine, proline, serine and taurine were similar to that obtained with the non-metabolizable amino acid alpha-amino-isobutyric acid, and amnesia arising from administration of these amino acids was counteracted by diphenylhydantoin, as was amnesia induced by phenylalanine and tyrosine. The retention function obtained with tryptophan was similar to that obtained with 5-hydroxytryptamine, and DPH had no effect on the action of tryptophan or the actions of arginine, alanine or asparagine. The findings were interpreted in the context of a three-stage model of memory formation.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1986

Automated capillary gas chromatographic assay using nitrogen-phosphorus ionization detection for the determination of bepridil in human plasma.

A highly sensitive and specific capillary gas chromatographic method for the determination of the antianginal drug bepridil in plasma is described. The capillary gas chromatograph and nitrogen-selective detector combination provides excellent sensitivity for clinical samples. The lowest concentration of bepridil which can be measured accurately and precisely in a 1-ml plasma sample is 1 ng/ml. Standard curves are linear over the concentration range 1-60 ng/ml. Accuracy and precision of the assay, expressed as relative deviation from the true value and relative standard deviation (inter-run) are less than 15% at all concentrations in the linear range. No interfering peaks are observed. Using an automatic injector and a laboratory computer system, sixty samples can be analyzed routinely in one day. The present assay has been successfully cross-validated with a published high-performance liquid chromatographic assay.

Bepridil↗
PubMed1986

Effect of testosterone on intermediate memory in day-old chicks.

Day-old chicks trained on a single trial passive avoidance discrimination task show three well-defined behavioural stages in memory formation: short-term, intermediate and long-term memory. Testosterone (2 mg), given subcutaneously, yielded results which may be tentatively interpreted as an extension of the time of availability of recall from the intermediate stage by between 20 and 50 min, provided the hormone is administered no earlier than 90 min before learning. A higher dose (12.5 mg) of testosterone administered 30 min before learning had a similar effect. The findings with testosterone are comparable to those reported for pituitary-adrenal hormones.

Animals↗
PubMed1986

Effect of stress-related hormones on short term memory.

Adrenocorticotropic hormone (ACTH)1-24, ACTH4-10, corticosterone (CS) or arginine vasopressin (AVP) was administered subcutaneously to one day-old chicks immediately after learning a single trial passive avoidance task. Chicks were pretreated with 2 mM KC1 or 4 mM monosodium glutamate 5 min before learning. With KC1 or monosodium glutamate alone, no evidence of memory was observed on retention tests carried out as early as 5 min and as late as 24 h postlearning. However, the addition of ACTH1-24, ACTH4-10 or AVP to KC1-pretreated animals yielded normal retention levels up till 10 min, 10 min and 20 min after learning, respectively. Similar results were obtained with ACTH1-24 and AVP given to glutamate-pretreated birds. CS had no effect on KC1- or glutamate-induced amnesia. The calcium channel blocker, lanthanum chloride, also inhibited the formation of short-term memory, with amnesia still present as late as 24 h following learning. ACTH1-24, but not CS or AVP, yielded normal retention levels until 10 min postlearning in the presence of lanthanum chloride. Thus ACTH1-24 and AVP can overcome KC1 or glutamate inhibition of STM formation but will not prevent subsequent amnesia. The mechanisms underlying this action of ACTH1-24 and AVP are different. The possibility that the effect of ACTH1-24 is related to the role of calcium in STM formation is explored.

Animals↗
PubMed1986

A single-dose pharmacokinetic study of the antisickling agent cetiedil.

Cetiedil citrate is an antisickling agent shown to be effective in reducing the severity and duration of acute sickle cell crisis. With the use of a sensitive GC/MS assay, the pharmacokinetic profile of cetiedil was studied in normal men and in men with sickle cell anemia who were not in crisis at the time of study. A peak cetiedil concentration of 70 to 200 ng/ml was found immediately after a 30-minute drug infusion. The plasma level then gradually declined to approximately 10 ng/ml during a 3-hour distributive phase. Computer analysis of the data was most consistent with a three-compartment model. No pharmacokinetic differences were found between the normal men and the subjects with sickle cell. Because the cetiedil plasma levels achieved during this in vivo study are well below concentrations that exhibit antisickling activity in vitro, additional clinical studies will be necessary before an optimal dosing regimen can be established.

Adult↗