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Biomedical subjects

S W Smith

Publications and source records attributed to S W Smith.

At least 127 records · Page 7Linked to original sources
PubMed1978

Reverse transcriptase-associated RNase H activity. II. Inhibition by natural and synthetic RNA.

The RNase H activity associated with purified avian myeloblastosis virus and Rauscher murine leukemia virus DNA polymerases is inhibited by homopolymeric RNA molecules, although the efficiency of inhibition by each homopolymer appears enzyme specific. Formation of duplex RNA molecules abolished the inhibitory activity. In contrast to these results, DNA polymerase-independent RNase H activities, such as the RNase H-II from Rauscher murine leukemia virus and calf thymus RNase H, were unaffected by the addition of exogenous RNA molecules to reaction mixtures. These results support the concept (M. J. Modak and S. L. Marcus, J. Virol. 22:253--256, 1977) that the catalytic site of DNA polymerase-associated RNase H activity may be that which is also involved in template binding. Naturally occurring RNA molecules of oncornaviral, procaryotic, or eucaryotic origin also proved to be efficient inhibitors of avian myeloblastosis virus DNA polymerase-associated RNase H activity. In contrast to this result, naturally occurring RNA molecules, at concentrations which inhibited the avian myeloblastosis virus enzyme, did not inhibit Rauscher murine leukemia virus DNA polymerase-catalyzed RNase H activity. This finding represents a new biochemical distinction between the two reverse transcriptases, and may be indicative of differences in the relative affinities of these enzymes for natural RNA molecules.

Avian Leukosis Virus↗
PubMed1978

Studies on acid lipase, and E 600-resistant acid esterase activities in human tissue homogenates.

Detailed comparison of acid lipase and acid esterase activities of human spleen, liver and kidney homogenates has been carried out by means of the following substrates: 14C-tripalmitin, alpha-naphthyl acetate, alpha-naphthyl butyrate, alpha-naphthyl laurate, p-nitro-phenyl acetate, butyrate and laurate. In addition, homogenates of the three tissues were subjected to isoelectric focusing in polyacrylamide gels and histochemical staining with the above mentioned naphthyl substrates in the presence and absence of the organophosphate esterase inhibitor diethyl-p-nitrophenyl phosphate (E 600). These studies provide extensive support for the proposal that E 600-resistant acid naphthyl butyryl and lauryl esterase activities in human tissues derive largely from the enzyme acid lipase. The studies suggest that the most specific chromogenic substrate for this enzyme at a biochemical and histochemical level is alpha-napthyl laurate in the presence of E600 (3 X 10(-6) M).

Carboxylic Ester Hydrolases↗
PubMed1977

Patterns of plasma free fatty acid concentrations in fasted, resting dogs.

Free fatty acid (FFA) concentrations were determined in arterial plasma samples obtained during short or prolonged fasts from resting, conscious adult male mongrel dogs. Arterial blood was continuously collected during experiments ranging from 2.25 to 15 h, from dogs fasted 1 or 5 days. Each continuous collection stream was divided at 45 equal intervals into separate sequential samples. In 18 experiments, no consistent pattern was found in plasma FFA concentrations: the concentrations were never constant, and fluctuations were only rarely periodic. Large, spontaneous, seemingly random level changes with amplitudes of 200-600 mueq/liter were observed in 14 experiments, that took from 1 to 8 h to complete. There was no apparent relation between these fluctuations and time of day or rectal temperature, and glucose concentrations remained unchanged during the FFA fluctuations. The inconstancy of plasma FFA levels and the irregularity of their fluctuations suggests that FFA production rates may be unregulated or only loosely regulated within a wide regulation band during the first few days of starvation. No current model of FFA metabolism preducts the observed patterns of FFA levels.

Animals↗
PubMed1977

Lack of a circannual cycle of daytime serum prolactin in man and monkey.

Serum samples were obtained from 7 subjects (6 men and 1 woman) in the morning (09.00 h) and in the afternoon (15.00 h) of each week for a period of 13 months and assayed for prolactin by RIA. In addition, 4 female monkeys were sampled once weekly in the afternoon for approximately two years. The data were analyzed for cyclicity by power spectrum analysis. In both species a serum prolactin circannual cycle was not obvious. In most subjects statistically significant (P less than 0.05) cycles were observed; however, there was considerable variability among individuals in the duration of the cycle, which ranged between 4 and 50 weeks. A similar result was also observed for the monkey data; here the cycles ranged between 7 and 51 weeks. The physiologic significance of these cycles is unknown at present. It is suggested that although there appears to be no diurnal serum prolactin circannual cycle, this does not rule out the possibility that there may be a nocturnal circannual cycle.

Adult↗
PubMed1977

Influence of restraint on plasma prolactin and corticosterone in female rats.

The effect of restraint on plasma prolactin and corticosterone concentrations was investigated in chronically catheterized, ovariectomized (OVX) or ovariectomized, oestrogen-treated (OVX-PEP) rats. Restraint was induced by tying the hind legs together. In OVX rats, prolactin levels were unchanged following restraint, either during the morning (10.00 h) or afternoon (14.00 h). Prolactin levels increased in OVX-PEP animals when restraint was initiated in the morning; when restraint was initiated in the afternoon the prolactin response depended upon the level of prolactin before restraint. If levels were low (pre-surge) the response to restraint was similar to that observed in the morning; if prolactin levels were high (surge) the response to restraint was reversed and the prolactin level declined. The morning prolactin response to restraint was significantly inhibited and the afternoon surge was retarded in adrenalectomized OVX-PEP (OVX-PEP-ADX) rats; however, in OVX-PEP animals maintained on 0-9% NaCl drinking solution, the morning prolactin response to restraint was also blunted, although the afternoon surge was normal. In OVX-PEP-ADX animals injected with either vehicle alone, or 2 or 4 mg corticosterone for 4 days, and sampled on the morning of day 5, the prolactin response to restraint was absent. Furthermore, when OVX-PEP animals were injected daily with either vehicle or 4 mg corticosterone/day, they showed no increase in prolactin in response to restraint when values were compared with those of uninjected animals. Corticosterone levels after restraint were higher than initial values in all of the above experimental conditions.

Adrenalectomy↗
PubMed1976

Therapeutic trial of aniline mustard in patients with advanced cancer. Comparison of therapeutic response with cytochemical assessment of tumor cell beta-glucuronidase activity.

Seventy-eight patients with advanced cancer received an adequate therapeutic trial with aniline mustard (NSC 18429). Significant anticancer activity with clinical benefit was demonstrated in five patients with cancer of the prostate and one patient with renal cancer. beta-glucuronidase levels in aspirate and imprint preparations of tumor cells were assessed by a timed cytochemical technique. A partial correlation appeared to exist between very intense glucuronidase staining and tumor regression in prostate and kidney lesions; however, these high levels were observed only rarely. Sequential observations in two patients demonstrated loss of enzymatic activity concomitant with development of clinical relapse.

Aniline Mustard↗
PubMed1975

Effect of dietary Mo on Cu metabolism. Evidence for the involvement of Mo in abnormal binding of Cu to plasma proteins.

The effects of feeding Mo at concentrations of 17 mug/g to sheep and 100 mug/g to guinea pigs in the presence of adequate dietary Cu, on the distribution of Cu within plasma have been studied. The creation of a fraction of plasma Cu which is insoluble in trichloroacetic acid has been confirmed and it has been shown that this fraction also contains Mo. Complete removal of Cu and Mo from this protein cannot be achieved under acid conditions without at least partial hydrolysis of the protein. The estimated atomic ratio of Cu:Mo in the fraction was 1.7. It is suggested that the formation of such a stable Cu-Mo-protein compound may explain the observed low tissue uptake of Cu in the presence of high plasma total and "direct-reacting" Cu concentrations.

Animals↗