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Biomedical subjects

D M Smith

Publications and source records attributed to D M Smith.

At least 415 records · Page 23Linked to original sources
PubMed1978

Servo control of end-tidal CO2 in paralyzed animals.

We are reporting an electronic circuit which uses the peak end-tidal CO2 signal from a rapid infrared CO2 analyzer to vary the motor rate of a fixed volume respirator. It contains variable gain and a lag compensation network which permits critical damping to prevent oscillation. The CO2 analyzer, circuitry, and respirator are connected in a closed-loop servo system that allows automatic control of the CO2 level. The system's gain and performance are such that it can accommodate large changes of CO2 return to the lungs with no more than +/- 0.5 Torr carbon dioxide pressure (PCO2) error signal. It has proved useful in experiments on neural respiratory control in paralyzed animals where it is desired to keep PCO2 constant despite changes in cardiac output and venous and CO2 return to the lungs, and to monitor the approximate magnitude of these changes.

Carbon Dioxide↗
PubMed1978

Influences of season and age on maturation in vitro of rhesus monkey oocytes.

Oocytes obtained from antral follicles of adult and adolescent rhesus monkeys during the annual breeding season extruded polar bodies in vitro at significantly higher rates (50--60%) than oocytes from animals of similar age during the non-breeding season ((20--30%) or from infant and prepubertal females at any time of the year (20--30%). The proportion of oocytes degenerating in culture was greatest in groups where maturation was highest.

Age Factors↗
PubMed1978

Effects of medium composition and progesterone on maturation in vitro of rabbit oocytes from Graafian follicles of different sizes.

Rabbit oocytes from large (1-1.5 mm diam.), medium (0.5 mm) and small (0.15-0.25 mm) antral follicles were cultured in five chemically defined media. In all media, oocytes from large antral follicles showed the highest incidence of meiotic activity followed by those from follicles of medium size. Most oocytes from small follicles did not resume meiosis in culture. The addition of glutamine to a standard medium for ovum culture significantly improved maturation of oocytes from medium-sized follicles but did not affect those from large or small follicles. When polyvinylpyrrolidone was substituted for bovine serum albumin, maturation of oocytes from large and medium-sized follicles was reduced. Progesterone at a concentration of 10 micrometer did not affect maturation, but 100 micrometer-progesterone blocked germinal vesicle breakdown in oocytes from medium-sized follicles and reduced both germinal vesicle breakdown and polar body formation in oocytes from large follicles. This effect was reversible.

Animals↗
PubMed1978

The effect of cold shock on mouse oocyte maturation in vitro.

Maintenance of mouse ovaries in ice-cold medium for 1, 2 or 4 h before removing the oocytes did not alter the incidence of spontaneous maturation or increase the number of oocytes degenerating, fragmenting or forming 2 equal blastomeres in culture.

Animals↗
PubMed1977

In vitro behavior of granule cells from Staggerer and Weaver mutants of mice.

The survival, in monolayer culture, of cerebellar granule cells from the cerebellar mutants Staggerer and Weaver was studied to examine whether the observed in vivo granule cell degeneration is intrinsic or environmentally induced. Granule cells in vitro can be identified by means of a combination of criteria including their size, shape, nuclear morphology, relative proportion of the total cell population, and failure to take up gamma-aminobutyric acid (GABA) in the presence of several other cell types which do. Cultures from both Staggerer and Weaver cerebella had surviving granule cells for at least 3 weeks in vitro. Therefore, since the mice used as the source of the cells were 7 days of age, the degeneration observed in vivo cannot be a case of irreversibly programmed cell death determined before postnatal day 7. While the behavior of Weaver granule cells is essentially the same as littermate controls, cells from Staggerer cerebella both clump less and survive considerably longer than those from wild-type. The role of intrinsic granule cell differences vs. primary changes in some other cell type is discussed.

Animals↗
PubMed1977

The duration of gestation in the squirrel monkey (Saimiri sciureus).

A restricted mating period was used to determine the duration of gestation in the squirrel monkey (Saimiri sciureus) of Colombian-Brazilian origin. Ten pregnancies were observed. The length of the gestation period was found to range from 141 to 154 days with a mean of 146.9 +/- 3.28 SD, a median of 146.5, and a modal length of 146.

Animals↗
PubMed1976

Some characteristics of homosexual men.

Although recognition of homosexuals is often important, many doctors lack the necessary skill or experience, so to assist them a group of 5,302 men was surveyed using a computer-based data system and 9-1 per cent. were recorded as homosexual. Analysis showed a relatively high proportion of homosexuals among men with syphilis and gonorrhoea, and a low proportion among men with nonspecific genital infection (non-specific urethritis and proctitis) and other infections. All men with secondary syphilis were homosexual. A relatively high proportion of men born in Eire, Spain, and North America were homosexual and a relatively high proportion of men living in the West End of London were homosexual. While these findings will be of most value to those working in STD clinics in London they may also be helpful to those working elsewhere and in other disciplines.

Adolescent↗
PubMed1976

Age and activity effects on rate of bone mineral loss.

It has been postulated that the rate of mineral loss in postmenopausal women remains constant with aging and that the decreased activities of daily living associated with aging contribute to mineral loss. These hypothese were examined by measuring the bone mineral content at the midshaft of the radius with the photon absorption technique. The estimated rate of loss was calculated in a cross-sectional study as the regression coefficient of bone mineral content vs. age and in a longitudinal study as the regression coefficient of bone mineral content vs. time. In the cross-sectional study, Group A, which consisted of 264 women aged 50-72 yr, had an estimated rate of loss of -0.0114 +/- 0.0014 (SE) g/cm per yr. Group B, which consisted of 266 women aged 73-96 yr, had an estimated rate of loss of -0.0055 +/- 0.0017 g/cm per yr. In the longitudinal study, Group C consisted of 33 women aged 51-65 yr who were followed for an average of 4.5 yr with a mean number of 16 visits per subject; they were found to have a mean rate of loss of -0.00990 +/- 0.00107 g/cm per yr. Group D consisted of 38 women aged 70-91 yr who were followed for an average of 3.8 yr with a mean number of 31 visits per subjects; they were found to have a mean rate of loss of -0.00020 +/- 0.00236 g/cm per yr. The estimated and directly measured rates of loss were more rapid in the younger groups than in the older groups (A vs. B, P less than 0.001; C vs. D, P less than 0.001). These data demonstrate that the mean rate of mineral loss is not constant with aging and that in elderly subjects it is significantly slower than that of the earlier postmenopausal years. Since the elderly women were the less active, these findings suggest that factors other than decreased physical activity are more important in determining the rates of mineral loss.

Activities of Daily Living↗
PubMed1976

Hormonal responsiveness of adenylate cyclase activity in cartilage.

Adenylate cyclase activity was measured in a crude particulate fraction of hyaline cartilage obtained from the xiphoid process of the rat. Bovine parathyroid hormone (PTH) at concentrations as low as 1.3 x 10(-7)M and porcine calcitonin (CT) at concentrations as low as 2.3 x 10(-5)M significantly increased adenylate cyclase activity. Glucagon, prostaglandin E1 (PGE1) and E2 (PG2), and epinephrine at concentrations of 10(-5)M also increased activity, whereas, no increased activity was seen with the additions of somatotrophin (10 mug/ml), PGF1alpha, PGF2alpha, or T3 at 10(-5)M. The combination of doses of PTH and CT, which individually produced maximal responses, was not additive. These data provide evidence that cartilage in growing rats responds directly to PTH and CT.

Adenylyl Cyclases↗
PubMed1976

Femoral trabecular-pattern index and bone mineral content measurement by photon absorption in senile osteoporosis.

A comparative study of the usefulness of the femoral trabecular-pattern index (Singh index) and bone mineral content measurement by photon absorption in senile osteoporosis was performed in 106 white women, seventy to ninety-five years old. In 17% of the subjects adequate hip roentgenograms could not be obtained. Interpretation of the Singh index was not found to be simple and easily reproducible. A positive correlation was noted between the bone mineral content and the Singh index. The incidence of previous vertebral and non-vertebral fracture was noted to be inversely related to both bone mineral content and the Singh index, but neither method clearly separated subjects with fracture from those without fracture.

Aged↗
PubMed1976

The measurement of rates of mineral loss with aging.

The photon absorption technique was used to measure bone mineral content in the radius repeatedly with time to determine the feasibility of using this method in studies on the rate of loss with aging. Two groups of postmenopausal women were followed, a younger group for an average of 3.74 years and an older group for an average of 2.37 years. It was determined that estimates of rate over periods less than two years were too low in precision to be useful. There were significant differences in rates among individuals. The loss of mineral from the midshaft site was determined to be linear within the precision of the method and over an average interval of 3.74 years. From these data the size of groups and length of time needed for a study to determine the effect of a treatment upon inhibition of bone loss was predicted. When the inhibition is 50 per cent of the control rate, it would be possible to detect a significant (alpha=0.05) inhibition with a certainty of 95 per cent (1-beta = 0.95), if 56 subjects were followed in each group for a period averaging 2.70 years. A more potent inhibition or more frequent visits would reduce the number of subjects and duration of study needed. The separation of individuals into groups of significantly more rapid and slower rates of loss was demonstrated. From these data, it is possible to predict that one-third of a sample could be so characterized after 3.5 years. The photon absorption technique can be applied to the measurement of the rate of loss of mineral with aging with a precision that is sufficicient for certain types of clinical investigations.

Adult↗