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Biomedical subjects

R M Smith

Publications and source records attributed to R M Smith.

At least 397 records · Page 22Linked to original sources
PubMed1977

Heart rate response to breath holding at 18.6 ATA.

The heart rate (HR) responses to breath-holding (BH) with the without face immersion (FI) in 31 or 27 degrees C water was studied in 1 ATA air and hyperbaric He-O2 environments in 4 male subjects during a dry saturation dive to simulated depth of 580 ft (18.6 ATA). When a 60 sec BH or FI was performed while leaning forward, there was a significant linear correlation between the maximal bradycardial response (delta HRmax) and ambient pressure for simple BH (r-0.08, P less than 0.05) and 31 degrees C FI (r = 0.91, P less than 0.01), but not for 27 degrees C FI. A similar trend was seen during 30 sec BH's while seated erect. The facial cold-dependent component of the FI bradycardia was not significantly altered by pressure. In general, there were significant correlations between the initial HR and the initial thoracic conductive volume (TCV; measured by the four-electrode Minnesota impedance cardiograph), and between the initial TCV and delta HRmax observed during seated erect BH's. Since the TCV was generally higher at depth, it is suggested that a mechanical effect due to increased TCV at depth, possibly related to increased gas density, is at least partly responsible for the pressure dependence of BH bradycardia.

Atmospheric Pressure↗
PubMed1977

Thermal comfort of patients in hospital ward areas.

The patient is identified as being of prime importance for comfort standards in hospital ward areas, other ward users being expected to adjust their dress to suit the conditions necessary for patients comfort. A study to identify the optimum steady state conditions for patients comfort is then described. Although this study raises some doubts as to the applicability of the standard thermal comfort assessment techniques to ward areas, it is felt that its results give a good indication of the steady-state conditions preferred by the patients. These were an air temperature of between 21-5 degrees and 22 degrees C and a relative humidity of between 30% and 70%, where the air velocity was less than 0-1 m/s and the mean radiant temperature was close to air temperature.

Adolescent↗
PubMed1977

Nature of the genetic determinant controlling encapsulation in Staphylococcus aureus Smith.

Two strains of Staphylococcus aureus, Smith and M, were studied for the elimination of encapsulation. For S. aureus M, encapsulation was stable. For S. aureus Smith, spontaneous loss of encapsulation was 1.3% and increased markedly in medium containing surface-active agents. In the presence of sodium dodecyl sulfate, unencapsulated cells had a considerable selective advantage. Attempts to demonstrate covalently closed circular plasmid deoxyribonucleic acid were unsuccessful. In cultures of unencapsulated cells, encapsulated cells were observed occasionally. These data argue against a plasmid location for the determinants controlling encapsulation in this organism in spite of a high spontaneous loss of this character.

Chromosomes, Bacterial↗
PubMed1977

Amino acid nutrition of the fetal lamb.

With three exceptions amino acids were retained by the fetal lamb from the maternal circulation in proportions appropriate for the synthesis of whole blody protein. Only glutamate, aspartate and serine, amino acids involved in the synthesis of nucleic acids, seemed to be produced by the fetus itself.

Amino Acids↗
PubMed1977

Hana Kai II: a 17-day dry saturation dive at 18.6 ATA. I. Objectives, design, and scope.

The dive (Hana Kai II) described in these papers was designed to determine the effects on man of a prolonged exposure to a dry helium-oxygen hyperbaric environment. Comprehensive studies on energy balance, body fluid balance, cardiorespiratory functions, maximal oxygen uptake, psychological performance, and physiological responses to cold were performed at a simulated depth of 580 ft (18.6 ATA) over a 30-day period in March-April 1975. Following a 3-day predive control period at 1 ATA air (period 1), 5 male divers spent 17 days at 18.6 ATA in a helium-oxygen environment (periods 2-6), and returned to 1 ATA air after 7 days of decompression (periods 7-8). They stayed an additional 3 days inside the chamber for postdive control measurements (period 9). The chamber temperature was maintained at 25-27 degrees C during periods 1 and 9, 30-31 degrees C during periods 2-5, and 27-28 degrees C during period 6. At 18.6 ATA, the PO2 and PCO2 of the chamber gas were maintained at approximately 225 and 2 mmHg, respectively. In this introductory paper, physical and physiological characteristics of individual subjects, the major daily activity schedule, and the scope of investigation are presented.

Activities of Daily Living↗
PubMed1977

Hana kai ii: a 17-day dry saturation dive at 18.6 ATA. II. Energy balance.

Since previous saturation dives have caused loss of body weight despite apparently adequate-to-high food intake, a complete study of energy balance was undertaken during the saturation dive Hana Kai II. Over a 30-day period in the hyperbaric chamber (3 days of predive control, 1 day of compression, 16 days at 18.6 ATA, 7 days of decompression, and 3 days of postdive control), all food, urine, and feces for five men were analyzed by bomb calorimetry; 24-h energy expenditure (M) was measured from continuous VO2, VCO2, and urine N. Body weight was taken daily; body composition was assessed from density, total body water, and skinfold thickness. Food intake was high throughout the 30 days (about 3500 kcal/day) while fecal and urinary losses were a normal 6-8% of intake. Energy expenditure was increased a little by the hyperbaric condition, but averaged only 2431 kcal/day for the 30 days and yet there was an average loss of adipose tissue of 0.8 kg for each man for the entire period. Nitrogen balance was positive. There was no evidence of heat gain or loss. The energy balance, total fuel compared with energy expenditure, required an additional 919 kcal/man-day for 30 days, an unidentified term which is not measured by conventional techniques.

Adult↗
PubMed1977

Hana kai ii: a 17-day dry saturation dive at 18.6 ATA. III. Body fluid balance.

Comprehensive studies on body fluid balance on 5 divers were conducted during the Hana Kai II dive (17 days at 18.6 ATA and 7 days of decompression). Daily urine flow increased from about 2000 ml at 1 ATA to 2600 ml at 18.6 ATA, at 31 degrees C. This diuresis was accompanied by a reduction in urine osmolality (from 650 to 500 mOsm) and a slight increase in osmolal clearance. Endogenous creatinine clearance remained at about 173 ml/min throughout the dive. Despite such a sustained diuresis, neither daily water intake nor total body water volume changed significantly. The plasma renin activity changed little, while both plasma aldosterone concentration and urinary aldosterone excretion increased significantly during the first week at 18.6 ATA. The plasma prolactin concentration showed a significant decrease during the first 3 days at 18.6 ATA. The daily excretion of antidiuretic hormone (ADH) decreased significantly (by 40%) 4 days after compression and remained low throughout the rest of the dive. Insensible waterloss at 18.6 ATA was 35% lower than that at 1 ATA. It is suggested that the observed hyperbaric diuresis is due primarily to suppression of ADH as a result of suppression of insensible water loss.

Aldosterone↗
PubMed1977

Hana Kai II: a 17-day dry saturation dive at 18.6 ATA. IV. Cardiopulmonary functions.

Impedance plethysmography was used to measure resting cardiac stroke volume (SV) and thoracic conductive volume (TCV) in four divers at intervals during a prolonged dry saturation dive (17 days at 18.6 ATA and 7 days' decompression). Resting heart rate (HR), blood pressure (BP), and pulmonary minute ventilation (VE) were measured 4 times per day for the duration of the 30-day experiment. The vital capacity (VC) and its subdivisions IC and ERV were measured by spirometry every 3 days. In nonsmokers, VC fell significantly with time (r = 0.64), while VC in smokers increased nearly 400 ml during the first week at pressure before tending to fall with time. Compared to predive, the mean ERV was increased 629 ml at pressure, while VE and respiratory rate were not changed. The increased ERV did not persist postdive and was probably the result of the increased work of breathing a dense gas (4.1 g/liters). Residual volume (RV) measured by nitrogen dilution before and after the dive increased 38% and remained significantly increased (22%) even after one year in 4 divers. It is suggested that hyperoxia (0.3 ATA PO2) combined with increased gas flow resistance caused the VC to fall and RV to increase. The major cardiovascular findings were a transient bradycardia associated with increased stroke volume leading to a significant increase in resting cardiac output associated with an increased rate of rapid ventricular filling, TCV, and BP at depth. Lowering the ambient temperature for 3 days did not re-establish the bradycardia, suggesting that hyperbaric bradycardia is not due to a subtle cold stress.

Adult↗
PubMed1977

Hana kai ii: a 17-day dry saturation dive at 18.6 ATA. V. Maximal oxygen uptake.

Cardiorespiratory responses of four men to submaximal and maximal cycling exercise were observed during 17 days at 18.6 ATA. Inspired gas at pressure consisted of hyperoxic (PO2 = 232 mmHg) and normoxic (PO2 = 159 mmHg) helium mixtures with relative gas densities of 3.8 and 2.8, respectively. The average of pre- and postdive VO2max (1 ATA air), which were not significantly different, was 3.10 liters - min-1. During 5 min of submaximal exercise at 50% of VO2max, no significant difference in work rate, VO2, VCO2, VE, respiratory rate, heart rate (HR), stroke volume, blood pressures, or rectal temperature was noted at 18.6 ATA compared to 1 ATA with either gas mixture. Submaximal HR tended to decrease by 5 to 10 beats - min-1 at pressure, and in hyperoxia the VO2/HR ratio was significantly higher. Maximal exercise was performed to exhaustion at work rates requiring about 120% of VO2max. Significant increased in VO2max of 0.10 liter - min-1 (3%) and in endurance time of 2 min (48%) were found during hyperoxic gas breathing, whereas normoxic values at 18.6 ATA were similar to those at 1 ATA. Significant reductions in maximal HR of 8 beats - min-1 (4%) were observed with both gas mixtures at pressure, and VE was significantly decreased by 36 liters - min-1 (26%) in hyperoxia and 29 liters - min-1 (21%) in normoxia. No change was found in the calculated cardiac output. Maximal voluntary ventilation, which was measured only for the hyperoxic gas, fell significantly by 80 liters - min-1 (40%). Results indicate that aerobic power and endurance performance were affected by oxygen pressure. Normoxic work capacity, however, was not decreased at 18.6 ATA, despite marked reductions in HR and VE.

Adult↗
PubMed1976

Subjective odour levels in an air - conditioned hospital ward.

Tests were carried out in an experimental air-conditioned hospital ward to determine what effect the mechanical ventilation and recirculation rates had on subjective odour levels in the ward. Odour conditions in the ward were not found to deteriorate with decreasing mechanical ventilation rate or increasing recirculation rate, but to fall into two distinct categories, which have been termed 'Acute' and 'Intermittent Background' conditions. 'Acute' conditions, where a particularly foul malodour prevailed in one or more rooms of the ward, were a rarity in the experimental general surgical ward; they occurred only twice during the testing period of approximately two years, and the mechanical ventilation rates tested were incapable of dealing with them. 'Intermittent Background' conditions, which are not attributable to a general prevailing odour level but rather to specific low level odour producing events, were satisfactory even under the most extreme test condition of three mechanical air changes per hour and 80% recirculation.

Journal Article↗
PubMed1976

Deldrin toxicity and successive discrimation reversal in squirrel monkeys (Saimiri sciureus).

Seven squirrel monkeys were systematically exposed to dieldrin (C12H10DC16) at two oral doses: 0.10 and 0.01 mg/kg-day. Two zero-dose controls were included. After 55 days of exposure dose assignments were shifted and continued for an additional 54 days. The higher dose group was shifted to zero exposure and lower dose group was shifted to high-dose exposure. Controls continued at zero exposure. The monkeys were presented with a visual nonspatial successive discrimination reversal task. During the first 55 days (preshift), control and low-dose monkeys learned the task; high-dose monkeys did not (p less than 0.001). During the subsequent 54 days (postshift), all groups performances remained at the approximate level achieved at the end of the preshift period. It was concluded that the high dose disrupted learning acquisition. This effect is speculated to be attributed to disruption of hippocampal activity. The low dose had no effect on task acquisition or maintenance.

Animals↗
PubMed1975

Ultrastructural localization of insulin receptors on adipocytes.

The method for preparing a stable, biologically active, covalently linked ferritin--insulin complex has been modified to provide a 25-fold increase in yield compared to the original procedure while reducing the molar fatio of ferritin to insulin to 1:1 from 40:1. Ultrastructural studies of isolated adipocytes revealed specific binding of ferritin--insulin to the cell surface in irregular clusters associated with the glycocalyx coating. The number of ferritin--insulin molecules observed was consistent with the number of sulin molecules observed was consistent with the number of receptors calculated from 125I-labeled insulin binding studies. The ferritin--insulin was not observed in the cytoplasm of the cell but was found on the convave side of surface connected vesicles. These surface connected vesicles were part of an alveolar-like system of plasma membrane invaginations which project in various directions in the cytoplasm and by thin sectioning can appear as pinocytotic-like microvesicles. The morphological observations on ferritin--insulin binding were supported by the finding that 125I-labeled insulin binding was almost exclusively localized to highly purified plasma membranes isolated by fractionation of adipocytes after incubation with 125I-labeled insulin. These data supported the theory that insulin did not need to enter a cell to cause biological effects and was consistent with the negative cooperativity concept of insulin binding to cell receptors.

Adipose Tissue↗