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S L Evans

Publications and source records attributed to S L Evans.

36 records · Page 2Linked to original sources
PubMed1995

Physiological determinants of 10-km performance in highly trained female runners of different ages.

Endurance exercise performance declines with age; however, there is little information on the mechanisms responsible, especially in women. We tested the hypothesis that this performance decline in women is associated with decreases in maximal O2 consumption (VO2max), blood lactate threshold (LT), and running economy (RE). We determined a 10-km race pace, VO2max, LT, and RE in 31 highly trained female runners aged 23-56 yr with similar relative (i.e., age-adjusted) competitive performances. Absolute 10-km race pace declined with age (r = -0.83). Both 10-km performance and age were correlated with VO2max (P < 0.05) and with the running velocity and O2 consumption at LT but not with RE. The runners then were divided into three age groups: group I (23-35 yr), group II (37-47 yr), and group III (49-56 yr). Stepwise regression analyses performed on subjects pooled from groups I and II and from groups II and III indicated that the majority (60%) of the variability in performance for runners aged 23-47 yr was explained by the running velocity at which LT occurred, whereas VO2max explained the majority (74%) of the variability for the runners aged 37-56 yr. We conclude that decreases in VO2max and running velocity at LT are the two physiological phenomena most closely associated with declines in 10-km performance with age in highly trained female runners. However, the contributions of these two mechanisms to the declines in performance are not uniform with advancing age.

Adult↗
PubMed1994

Cadmium-induced sexual dysfunction does not involve increased hepatic metabolism of testosterone nor increased circulating levels of corticosterone.

Sexually experienced male rats were injected IP with 0, 0.3, 1.5, 3.0, or 6.0 mg/kg cadmium chloride. The highest dose was fatal within 48 h of injection. A dose-related deficit in erectile function was observed in ex copula tests 48 h after injection. Copulatory dysfunction was evident in mating tests 72 h after injection. Hepatic mixed function oxidase activity after 0.3 mg/kg injections was not different from controls, but was diminished by 50% in rats treated with 3.0 mg/kg. The higher cadmium doses (1.5 and 3.0 mg/kg) were associated with equivalent and marked reductions in circulating testosterone levels, and lesser decrements in circulating corticosterone levels. The rats treated with 1.5 or 3.0 mg/kg cadmium chloride lost weight (32 +/- 12 and 39 +/- 9 g, respectively). Relative decapsulated adrenal gland weights were markedly increased in rats treated with 3.0 mg/kg. These data indicate that exposure to cadmium is associated with alterations in sexual, hepatic, and adrenal function, with erectile dysfunction occurring at the lowest dose. The effects on copulatory behavior are especially striking because it requires some weeks for copulatory behavior to wane following castration.

Adrenal Glands↗
PubMed1991

The effect of exercise at various temperatures on salivary levels of immunoglobulin A.

The purpose of this investigation was to determine the effect of ambient temperature on the salivary immunoglobulin A (s-IgA) response to submaximal exercise. Nine adult males (x age +/- SD = 22 +/- 2 yrs) volunteered to perform an incremental treadmill test to exhaustion for the determination of VO2max and three 30-minute treadmill runs at 80% VO2max in an environmental chamber at temperatures of approximately 6, 19 and 34 degrees C. Saliva samples were collected prior to each submaximal workbout as well as immediately and 1 hr post-exercise. A 2 within subjects factors (temperature, sample time) repeated measures ANOVA indicated no significant interaction or main effects for sampling time or temperature. The results of this study indicated that 30 minutes of non-competitive exercise at temperatures ranging from 6 to 34 degrees C had no effect on s-IgA. These findings suggest that moderate intensity exercises at a wide range of ambient temperatures does not increase the susceptibility to upper respiratory infection by decreasing s-IgA.

Adult↗
PubMed1991

The prevalence and nature of podiatric problems in elderly diabetic patients.

To determine if diabetes in the elderly is associated with increased prevalence of podiatric problems, a random sample of diabetic patients (n = 74) was compared to a group of elderly non-diabetic patients (n = 79). The two groups were comparable in age (range 70-90 years), smoking habits, and consumption of alcohol. The mean duration of diabetes was 14.5 +/- 11.7 years (+/- SD), and mean serum fructosamine level was 3.3 +/- 0.66 mmol/L. The number of medical diagnoses and medications used was significantly higher in the diabetic group. Diabetic patients had modestly higher prevalence of neuropathy, vascular disease, kidney disease, and eye complications. The most common podiatric problem in both groups was elongated toenails. The prevalence of podiatric problems such as cellulitis, amputation, tinea pedia, onychomycosis, calluses, bunions, and hammer toe deformity were not increased in diabetic patients. Active foot ulcers were more common in diabetic patients (13/74 vs 5/79, P less than 0.05). It is concluded that diabetes in the elderly, unlike in young patients, increases the risk of foot problems only marginally.

Aged↗
PubMed1987

Local cerebral glucose utilization in fetal sheep exposed to noise.

Rate of local cerebral glucose utilization in fetal sheep was measured in conditions of normal laboratory ambient sound (65 to 70 dB sound pressure levels) and broadband noise (105 and 120 dB sound pressure levels) delivered by two earphones situated on the abdominal surface of the ewe. Broadband noise had neither a visible effect on the ewe nor specific effects on the fetal arterial pH, PaO2, PaCO2, and plasma glucose concentration. However, glucose utilization of many cerebral structures was elevated in noise-exposed fetuses.

Animals↗
PubMed1986

Calcium modulation of growth of Streptococcus mutans.

The steady-state growth yield of Streptococcus mutans (in a Teflon chemostat using a chemically defined medium that was treated to lower trace metal contamination and supplemented with high-purity trace metals) was doubled by addition of 0.63 microM calcium. Subsequent increases in calcium concentration to 1.3 microM and 2.5 microM lowered steady-state growth yield below the level with no added calcium, suggesting that calcium has dose-dependent stimulatory and inhibitory effects on S. mutans.

Calcium↗
PubMed1986

Enhanced toxicity of copper for Streptococcus mutans under anaerobic conditions.

Copper inhibition of 11 strains (serotypes a through g) of Streptococcus mutans was increased by anaerobic incubation. Anaerobic toxicity was reversed by cuprous, but not by cupric, chelators. Susceptibility to aerobic copper inhibition was related to serotype; serotypes c, e, and f (biotype I) were most sensitive.

Anaerobiosis↗
PubMed1986

Ferrous iron transport in Streptococcus mutans.

Radioiron uptake from 59FeCl3 by Streptococcus mutans OMZ176 was increased by anaerobiosis, sodium ascorbate, and phenazine methosulfate (PMS), although there was a 10-min lag before PMS stimulation was evident. The reductant ascorbate may have provided ferrous iron. The PMS was reduced by the cells, and the reduced PMS then may have generated ferrous iron for transport; reduced PMS also may have depleted dissolved oxygen. We conclude that S. mutans transports only ferrous iron, utilizing reductants furnished by glucose metabolism to reduce iron prior to its uptake.

Anaerobiosis↗
PubMed1984

Oxygen toxicity in Streptococcus mutans: manganese, iron, and superoxide dismutase.

When cultured anaerobically in a chemically defined medium that was treated with Chelex-100 to lower its trace metal content, Streptococcus mutans OMZ176 had no apparent requirement for manganese or iron. Manganese or iron was necessary for aerobic cultivation in deep static cultures. During continuous aerobic cultivation in a stirred chemostat, iron did not support the growth rate achieved with manganese. Since the dissolved oxygen level in the chemostat cultures was higher than the final level in the static cultures, manganese may be required for growth at elevated oxygen levels. In medium supplemented with manganese, cells grown anaerobically contained a low level of superoxide dismutase (SOD) activity; aerobic cultivation increased SOD activity at least threefold. In iron-supplemented medium, cells grown anaerobically also had low SOD activity; aerobic incubation resulted in little increase in SOD activity. Polyacrylamide gel electrophoresis of the cell extracts revealed a major band and a minor band of SOD activity in the cells grown with manganese; however, cells grown with iron contained a single band of SOD activity with an Rf value similar to that of the major band found in cells grown with manganese. None of the SOD activity bands were abolished by the inclusion of 2 mM hydrogen peroxide in the SOD activity strain. S. mutans may not produce a separate iron-containing SOD but may insert either iron or manganese into an apo-SOD protein. Alternatively, iron may function in another activity (not SOD) that augments the defense against oxygen toxicity at low SOD levels.

Anaerobiosis↗
PubMed1984

Occupational asthma from nickel sensitivity: I. Human serum albumin in the antigenic determinant.

Occupational asthma from nickel sensitivity was confirmed in a male worker (SB) by allergy skin tests and inhalational challenge. In an ammonium sulphate coprecipitation test 63Ni was selectively precipitated from SB plasma indicating antibody with nickel related specificity. Preincubation of 63Ni with human serum albumin (HSA) increased the specificity of the coprecipitation test. Blocking experiments with nickel and copper(II) salts effectively inhibited the binding of 63Ni to antibody of SB plasma but did not affect control tests or that for antibodies to an unrelated antigen, ampicillin. Co2+ slightly inhibited the binding of 63Ni, while Zn2+ and Mn2+ failed to inhibit. This deactivation pattern corresponds to the known sequence of binding of these metals to the primary copper binding site of HSA. It is concluded that the antigenic determinant depends on the combination of Ni2+ with HSA at this specific copper/nickel plasma transport site.

Antibody Specificity↗
PubMed1984

Occupational asthma from nickel sensitivity: II. Factors influencing the interaction of Ni2+, HSA, and serum antibodies with nickel related specificity.

Serum from an individual with occupational asthma from nickel sulphate inhalation was shown by ammonium sulphate (Farr) and anti-IgG coprecipitation tests to contain antibodies which bind 63Ni2+. This binding was absent from 30 control sera. Ligand competition studies with serum and plasma from the propositus and controls are described, and include serial additions of HSA, L-histidine, EDTA, and the tripeptide gly-gly-L-his. The results, like those from metal ion blocking experiments, clearly showed that the formation of the reactive antigenic determinant depends on the selective binding of Ni2+ at the native Cu2+/Ni2+ transport site of HSA. Corroborating evidence is derived from the similar dependence on pH of the Ni2+-HSA formation and the ammonium sulphate 63Ni2+ coprecipitation reactions.

Antibodies↗
PubMed1984

Cellular binding and/or uptake of nickel(II) ions.

L-Histidine (L-His) and human serum albumin (HSA) at physiological concentrations, like the exogenous ligands D-penicillamine (D-PEN) and EDTA, are shown to inhibit the uptake of physiological levels of Ni2+ by B-lymphoblasts of human origin, human erythrocytes and rabbit alveolar macrophages. Evidence is also presented that illustrates the ability of these ligands to sequester Ni2+ from cells preloaded with this ion. The experimental observations are interpreted to indicate that serum concentrations of HSA and amino acids (especially L-His) exert a controlling influence on the cellular accumulation of Ni2+ in vitro, and further suggest the necessity to standardize the concentrations of these and related constituents in cell-culture media for meaningful comparisons of cellular uptake and toxicity of Ni2+ and other metal ions. Cells were lysed and the fractional distribution of 63Ni2+ in the lysate and residual pellet were assessed. About 60% of the radiolabel occurred in the pellet and 40% in the lysate for B-lymphoblasts, compared to 70 and 30% respectively for the alveolar macrophages. Diethyldithiocarbamate (DDC), unlike the other complexing agents, enhanced the cellular uptake of Ni2+ and prevented its removal from loaded cells. DDC also induced a transfer of the 63Ni2+ from the lysate to the residual pellet, suggesting that it promotes the deposition of Ni2+ in the lipid-rich components of cells (tissues). It is concluded that cellular association of Ni2+ is favoured by ligands forming lipophilic complexes, and extracellular localization by those giving hydrophilic complex compounds. The relevance of these contrasting roles in nickel detoxification by endogenous ligands and chelating drugs is discussed.

Animals↗
PubMed1982

Midtrimester intrauterine exchange transfusion of the fetus.

Thirty-seven fetuses, 15 to 23 weeks' gestation, were subjected to intrauterine exchange transfusion under direct vision with a fetoscope prior to therapeutic abortion. A maximum of 30 ml of blood was exchanged, so that as much as 95% of the blood in the fetoplacental circulation was of donor origin. The technique clearly has potential value in the management of severe rhesus-hemolytic disease of newborn infants.

Blood Transfusion, Intrauterine↗
PubMed1977

Cyclic vomit in children: seen through the psychiatrist's eye.

Sixteen patients have been seen since 1956 at the Children's Hospital of Pittsburgh with a disgnosis of cyclic vomiting. Five of these patients were reverred for psychiatric consultation or treatment. Four of the 16 had laparotomies and no specific pathological condition was found; seven of the patients did not have surgery or psychiatric intervention. Descriptive follow-up is given for all patients, as well as various methods of handling the problem. The psychological conflicts were found to be parental anxiety, a prolonged symbiotic relationship with the mother, and the failure of the child to separate and individuate.

Child↗
PubMed1975

Cyclopentyl ketones: identification and function in Azteca ants.

The anal gland secretions of dolichoderine ants in the genus Azteca are fortified with cyclopentyl ketones. Since these compounds, 2-methylcyclopentanone, cis-1-acetyl-2-methylcyclopentane, and 2-acetyl-3-methylcyclopentene, release sustained alarm behavior in ant workers, they constitute a new chemical class of insect pheromones. The ketones probably also function as defensive compounds and thus are part of the ants' alarm-defense system.

Animals↗