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Biomedical subjects

L D Smith

Publications and source records attributed to L D Smith.

At least 127 records · Page 7Linked to original sources
PubMed1977

Synthesis of heterogeneous nuclear RNA in full-grown oocytes of Xenopus laevis (Daudin).

At various times following injection of either 3H-GTP or 32PO4 into full-grown (stage 6) Xenopus laevis oocytes, RNA has been extracted and fractionated on polyacrylamide gels. Based on size, base composition and incorporation data, we have defined the kinetics of synthesis and accumulation of ribosomal RNA (40S, 28S, 18S), heterogeneous RNA of high molecular weight (greater than 40S) and heterogeneous RNA migrating with molecular weights of from 4S to 40S. Nuclear isolations have been performed to determine the cellular distribution of these classes of RNA as a function of time. Evidence is presented which shows that stage 6 oocytes synthesize RNA which by virtue of its size, base composition, rapid turnover and nuclear location is equivalent to the heterogeneous nuclear RNA observed in somatic cells. In addition, the data suggest synthesis of a class of nuclear RNA with a half-life of several hours. A small fraction (5%) of the nuclear RNA is stable, enters the cytoplasm and may represent RNA added to the stockpile of maternal transcripts known to be present in stage 6 oocytes.

Animals↗
PubMed1976

Inhibition of oocyte maturation by theophylline: possible mechanism of action.

Theophylline, a competitive inhibitor of cAMP phosphodiesterase, inhibits the maturation of oocytes previously exposed to progesterone. Cyclic AMP levels remain constant both during normal maturation and in response to theophylline, even though the latter effectively inhibits phosphodiesterase activity in the oocyte. Thus, the inhibition is not attributable to elevated cAMP levels. Rather, we suggest that theophylline may exert its inhibitory effects on maturation either by reducing rates of protein synthesis or possibly through effects at the oocyte surface.

Animals↗
PubMed1975

The efficacy of carbamazepine combinations in epilepsy.

The efficacy and bioavailability, and tolerance to carbamazepinee when administered with phenobarbital or phenytoin or with both drugs were evaluated in a prospective, double-blind study of patients whose seizures were not completely controlled by currently available antiepileptic drugs in usually therapeutic dosages as determined by serum levels. During each of four 21-day treatment periods, one fourth of the patients received daily doses of: (1) carbamazepine (1,200 mg) and phenytoin (300 mg); (2) carbamazepine (1,200 mg) and phenobarbital (300 mg); (3) phenytoin (300 mg) and phenobarbital (300 mg); or (4) carbamazepine (1,200 mg), with phenytoin (300 mg) and phenobarbital (300 mg). The treatment periods were separated by 2 wk of each patient's usual prestudy medication. Treatment with all three drugs was the most efficacious for seizure control. Serum carbamazepine concentration was significantly decreased when the drug was administered with either phenytoin or phenobarbital or both.

Adult↗
PubMed1975

A single-dose study of mexiletine (Kö 1173).

Serum concentrations of mexiletine after a single dose were determined in 8 adult Caucasian males with complex partial seizures who were continuing to receive other antiepileptic drugs. Two patients each received a single dose of either 100, 200, 300, or 400 mg mexiletine. Serum concentrations were determined by two gas chromatographic methods. Serum concentrations ranged up to 795 ng/ml. Peak concentrations occurred 1 to 3 hr after administration of the drug and were significantly different between the 100- and 300-mg, 100- and 400-mg, 200- and 300-mg, and 200- and 400-mg doses. Differences between the other doses were not significant. Serum concentrations declined monoexponentially. Half-life ranged from 2.7 to 7.2 hr. Numerous papers have appeared in the European literature on the use of mexiletine to treat cardiac arrhythmias. Preliminary studies in the United States suggest the use of mexiletine as an adjunct for therapy of epilepsy.

Adult↗
PubMed1975

A multiple-dose study of mexiletine (Kö 1173).

In preparation for a prospective controlled study of mexiletine in the treatment of epilepsy, a preliminary study of serum concentrations after multiple doses was performed with 8 institutionalized Caucasian adult males with uncontrolled seizures and similar weight, medical regimen, and seizure classification. Two patients each received daily dosages of 200, 400, 600 or 800 mg mexiletine administered in capsules four times a day for 7 days, in addition to their usual medication. Serum concentrations of mexiletine were determined by the Kupferberg-Yonekawa method. After the first day, serum concentrations of mexiletine were significantly higher for the 600 and 800-mg dosages than for the 200- and 400-mg dosages. The differences in serum concentration between the 200- and 400-mg dosages and between the 600- and 800-mg dosages were not significant. Serum concentrations for the 200-mg and 400-mg dosages were generally below 400 ng/ml, whereas at dosages of 600- and 800-mg, serum concentrations ranged from 400 to over 1,100 ng/ml, after the first day. Optimal dosage for this population appeared to be at least 800 mg/day. Half-life ranged from 3.5 to 7.8 hr.

Adult↗
PubMed1975

Common mesophilic anaerobes, including Clostridium botulinum and Clostridium tetani, in 21 soil specimens.

A relatively rich medium was markedly superior to a dilute medium for the isolation of anaerobic bacteria from soil. The obligate anaerobes isolated from 21 soil samples were all clostridia and the counts ranged from 2.7 X 10-2 to 3.3 X 10-6 per g. The organisms most frequently isolated were Clostridium subterminate, C. sordelii, C. sporogenes, C. indolis, C. bifermentans, C. mangenoti, and C. perfringens. Seventeen other species were also recognized but almost one-third of the isolates could not be identified with any known species of Clostridium. C. botulinum type A was demonstrated in six soil samples, and type B in one. These soils were neutral to alkaline in reaction (average pH 7.9) and low in organic matter content (1.4%). The association of C. botulinum types A and B with neutral to alkaline soils was statistically significant (P = 0.001) as was their association with soils low in organic matter (P = 0.005). C. botulinum types E and F were found in one soil sample, pH 4.5, with organic matter 13.7%. C. tetani was isolated from two soil samples, both of intermediate pH value and higher than average organic matter content.

Anaerobiosis↗
PubMed1975

Inhibition of Clostridium botulinum by strains of Clostridium perfringens isolated from soil.

Thirty-one soil samples were examined for the presence of organisms capable of inhibiting growth and toxin production of strains of Clostridium botulinum type A. Such organisms were found in eight samples of soil. Inhibiting strains of C. perfringens were found in five samples, of C. sporogenes in three and of Bacillus cereus in three. Three of the C. perfringens strains produced an inhibitor effective on all 11 strains of C. botulinum type A against which they were tested, seven of eight proteolytic type B strains, one nonproteolytic type B strain, five of nine type E strains and all seven type F strains, whether proteolytic or nonproteolytic. They did not inhibit any of 26 type C strains, 6 type D strains, 4 type E strains, or 24 C. sporogenes strains. In mixed culture, an inhibitor strain of C. perfringens repressed growth and toxin production by a C. botulinum type A strain even though it was outnumbered by the latter about 40 times. It also repressed growth and toxin production of C. botulinum in mixed culture of soils in which this latter organism naturally occurred when cooked meat medium but not when trypticase medium was used.

Antibiosis↗