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Biomedical subjects

D H Taylor

Publications and source records attributed to D H Taylor.

At least 73 records · Page 4Linked to original sources
PubMed1983

The effects of lead on the developing central nervous system of the rat.

Biochemical and structural development of the cerebral cortex of rat pups is delayed by low levels of lead administered in the dam's drinking water during gestation and suckling periods. These changes in brain development coincide with delays in the development of exploratory and locomotor activity and impaired learning. Subsequent cross-fostering experiments have shown that delays in synaptogenesis and in the development of exploratory behavior were attributed entirely to the prenatal, as opposed to the postnatal, exposure to lead at the low dose levels utilized. Examination of the variations in blood lead concentrations in pups and dams during gestation and until weaning at 21 days of postnatal age indicated that a substantial increase in blood lead concentrations occurred late in pregnancy. At 200 mg of Pb/liter of drinking water, peak blood Pb concentrations were observed to be approximately 60 micrograms/dl in dams and 80 micrograms/dl in pups on the 20th day of gestation. By the 10th postnatal day blood Pb concentrations had decreased to 35 micrograms/dl in dams and 40 microgram/dl in pups despite an increased consumption of drinking water containing the same concentration of Pb during this period. (Delays in cerebral cortical development were observed after 10 days of postnatal age). Tracer studies utilizing 203Pb indicate that the rate of Pb absorption was substantially increased in the pregnant, relative to the non-pregnant, dam. Although a similar increase in 45Ca absorption was also observed during pregnancy, increases in Pb absorption were enhanced by Pb-pretreatment, whereas Ca absorption was independent of Pb-pretreatment. From this data it is concluded that the apparently greater sensitivity of postnatal development on prenatal Pb exposure is secondary to enhanced Pb absorption in the pregnant rat. In vitro metabolic studies in isolated cerebral cortex slices taken from 15 day old rat pups exposed to Pb revealed increased glucose and oxygen consumption in response to elevations in the potassium concentration of the incubation media. This evidence of metabolic uncoupling in the immature rat cerebral cortex may be causally related to the measured delays in brain development.

Animals↗
PubMed1982

Effect of Tween 80 on exploratory behavior and locomotor activity in rats.

Exploratory behavior and locomotor activity is enhanced in male rat pups (aged 10 to 20 days) whose dams received a chronic dose (1.25 ml/l) of Tween 80 via their drinking water. This enhancement manifests itself during the diurnal period of the day. These data suggest that Tween 80 has an effect on the CNS which could lead to misinterpretation of results in toxicology studies that use this compound as a dosage vehicle.

Analysis of Variance↗
PubMed1982

Adsorption of reovirus by minerals and soils.

Adsorption of [35S]methionine-labeled reovirus by 30 dry soils, minerals, and finely ground rocks suspended in synthetic freshwater at pH 7 was investigated to determine the conditions necessary for optimum virus removal during land application of wastewaters. All of the minerals and soils studied were excellent adsorbents of reovirus, with greater than 99% of the virus adsorbed after 1 h at 4 degrees C. Thereafter, virus remaining in suspension was significantly inactivated, and within 24 h a three to five log10 reduction in titer occurred. The presence of divalent cations, i.e., Ca2+ and Mg2+, in synthetic freshwater enhanced removal, whereas soluble organic matter decreased the amount of virus adsorbed in secondary effluent. The amount of virus adsorbed by these substrates was inversely correlated with the amount of organic matter, capacity to adsorb cationic polyelectrolyte, and electrophoretic mobility. Adsorption increased with increasing available surface area, as suspended infectivity was reduced further by the more finely divided substrates. However, the organic content of the soils reduced the level of infectious virus adsorbed below that expected from surface area measurements alone. The inverse correlation between virus adsorption and substrate capacity for cationic polyelectrolyte indicates that the adsorption of infectious reovirus particles is predominately a charged colloidal particle-charged surface interaction. Thus, adsorption of polyelectrolyte may be useful in predicting the fate of viruses during land application of sewage effluents and sludges.

Adsorption↗
PubMed1981

Measurement of the electrokinetic properties of vaccinia and reovirus by laser-illuminated whole-particle microelectrophoresis.

The electrokinetics of vaccinia virus and reovirus type 3 were studied in dilute electrolyte solutions by whole-particle microelectrophoresis with dark-field laser illumination. The electrophoretic mobilities were dependent upon pH and electrolyte composition. The isoelectric point of vaccinia virus in dilute NaCl was 4.8 +/- 0.1; that of reovirus was 3.8 +/- 0.1. The mobility of reovirus was -2.65 +/- 0.30 micrometer . S-1 . V-1 . cm-1. Treatments known to cause irreversible changes in the structure of vaccinia, such as heating to 90 degrees C or exposure to pH 10, altered the virus's mobility under the reference conditions. The practical range of whole-particle microelectrophoresis thus extends to microorganisms as small as reovirus, allowing their electrokinetic and related surface properties to be studied.

Bicarbonates↗
PubMed1981

Poliovirus adsorption by 34 minerals and soils.

The adsorption of radiolabeled infectious poliovirus type 2 by 34 well-defined soils and mineral substrates was analyzed in a synthetic freshwater medium containing 1 mM CaCl(2) and 1.25 mM NaHCO(3) at pH 7. In a model system, adsorption of poliovirus by Ottawa sand was rapid and reached equilibrium within 1 h at 4 degrees C. Near saturation, the adsorption could be described by the Langmuir equation; the apparent surface saturation was 2.5 x 10(6) plaque-forming units of poliovirus per mg of Ottawa sand. At low surface coverage, adsorption was described by the Freundlich equation. The soils and minerals used ranged from acidic to basic and from high in organic content to organic free. The available negative surface charge on each substrate was measured by the adsorption of a cationic polyelectrolyte, polydiallyldimethylammonium chloride. Most of the substrates adsorbed more than 95% of the virus. In general, soils, in comparison with minerals, were weak adsorbents. Among the soils, muck and Genesee silt loam were the poorest adsorbents; among the minerals, montmorillonite, glauconite, and bituminous shale were the least effective. The most effective adsorbents were magnetite sand and hematite, which are predominantly oxides of iron. Correlation coefficients for substrate properties and virus adsorption revealed that the elemental composition of the adsorbents had little effect on poliovirus uptake. Substrate surface area and pH, by themselves, were not significantly correlated with poliovirus uptake. A strong negative correlation was found between poliovirus adsorption and both the contents of organic matter and the available negative surface charge on the substrates as determined by their capacities for adsorbing the cationic polyelectrolyte, polydiallyldimethylammonium chloride.

Adsorption↗
PubMed1981

Influence of pH and electrolyte composition on adsorption of poliovirus by soils and minerals.

The pH and the nature an concentration of simple electrolytes influenced the interaction of poliovirus type 2 with three soils, a sand, and a clay mineral. In electrolytes above pH 9 the virus was not adsorbed extensively to the substrates, but below pH 7 almost all virus was bound. For each adsorbent there was a characteristic pH region of transition from strong to weak uptake. Differences between the soils in virus uptake were shown to parallel their pH-dependent mineral. In electrolytes above pH 9 the virus was not adsorbed extensively to the substrates, but below pH 7 almost all virus was bound. For each adsorbent there was a characteristic pH region of transition from strong to weak uptake. Differences between the soils in virus uptake were shown to parallel their pH-dependent mineral. In electrolytes above pH 9 the virus was not adsorbed extensively to the substrates, but below pH 7 almost all virus was bound. For each adsorbent there was a characteristic pH region of transition from strong to weak uptake. Differences between the soils in virus uptake were shown to parallel their pH-dependent charge properties, as determined by whole-particle microelectrophoresis. Only when the pH was close to or above the critical region was uptake increased with electrolyte concentration. The transition region for all substrates was above pH 7.5 the isoelectric point of the virus. Thus, it appears that when both the virus and substrate are highly negative charged, repulsive electrostatic effects may exceed inherent attractive interactions, thereby inhibiting adsorption.

Adsorption↗
PubMed1976

Effects of Sevin on the reproductive biology of the Coturnix.

Adult Coturnix quail (Coturnix coturnix japonica) were subjected to three levels of carbaryl pesticide treatment (Sevin-20 p.p.m., 40 p.p.m., and 400 p.p.m) and monitored to observe any modifications in either their reproductive biology or behavior. There was an increase in the amount of pesticide excreted with increasing treatment levels during the first 48 hours following intubation, after which pesticide levels in the fecal material for all groups approached zero. Addditionally, significant amounts of the pesticide were detected in the egg yolks after pesticide ingestion (treatment levels, 20, 40, and 400 p.p.m. resulted in pesticide residues of 1.58, 2.03, and 3.15 p.p.m., respectively). Egg production was significantly reduced (p less than or equal to 0.05), although egg viability was not affected by the pesticide stress. Agonistic behavior decreased in males while it increased in the females following pesticide ingestion.

Aggression↗
PubMed1970

Extraoptic celestial orientation in the southern cricket frog Acris gryllus.

Celestial orientation and setting of the biological clock in the southern cricket frog Acris gryllus can be cued by light stimuli received by extraoptic receptors in the brain. These extraoptic photoreceptors may also be used in learning new orientational directions. A mechanism for a light-activated biological clock is discussed.

Animals↗