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Biomedical subjects

C Clark

Publications and source records attributed to C Clark.

At least 253 records · Page 14Linked to original sources
PubMed1981

Developmental follow-up of hyperventilated neonates: preliminary observations.

A group of 13 newborn infants greater than 37 weeks' gestation were selected to be hyperventilated because of severe hypoxemia refractory to conventional mechanical ventilation, ie, failure to maintain PaO2 greater than 50 torr with an FIO2 of 1.0, despite PaCO2 less than or equal to 40 torr and pH greater than or equal to 7.40. Eleven survived; nine were available for follow-up evaluations. As a group, the nine infants were exposed to a PaCO2 less than or equal to 20 torr for 51.8 +/- 11.8 (mean +/- SEM) hours, to PaCO2 less than or equal to 15 torr for 11.8 +/- 3.3 hours, to a pH greater than 7.50 for 64.4 +/- 18.6 hours, and to a pH greater than or equal to 7.60 for 6.1 +/- 2.9 hours. One infant was lost to follow-up after a normal assessment at nine months. the other eight infants (seven AGA, one markedly SGA) were at least 1 1/4 years old at the time of evaluation. The seven AGA infants had a normal developmental quotient (mean 110 [range 96-130] by Stanford-Binet or Bayley assessment); the one SGA infant had a Bayley score of 89. All eight had normal neurologic examinations. These preliminary findings are reassuring with respect to neurologic and developmental outcome following prolonged hyperventilation.

Child Development↗
PubMed1980

Coronary artery ligation in anesthetized rats as a method for the production of experimental dysrhythmias and for the determination of infarct size.

Coronary artery ligation in anesthetized rats was assessed as a method for the production of experimental dysrhythmias and for the determination of infarct size. Following occlusion of the left main coronary artery, very marked ventricular dysrhythmias occurred in two distinct phases, an early and a late phase, at 0-30 minutes and at 1 1/2--4 hours after ligation respectively. Infarct size was measured at 4 hours after ligation using nitroblue tetrazolium to stain for the depletion of two cytoplasmic enzymes, lactate dehydrogenase and NADPH diaphorase. In this model, lignocaine (10 mg/kg plus an infusion of 5 mg/kg/hr) and ORG 6001 (10 mg/kg plus an infusion of 2.5 mg/kg/hr) had marked antidysrhythmic activity but neither drug influenced infarct size. The model, because of its simplicity, reproducibility, and low cost, should be useful for the screening of potential antidysrhythmic agents and may also be used to determine infarct size following coronary artery ligation.

Androstanols↗
PubMed1979

Student voluntarism in transition.

The university student volunteer as a social change agent is in a period of transition. There is no returning to the idealism and activism of the 1960s if this and future generations of students continue to see self-preservation and individual advancement as their only viable option here in America. In view of the changing nature of today's students, the conventional definitions of volunteers, such as Shultz's (1972) altruist, average, and pseudo-volunteer, must be reconsidered. Does the acceptance of minimal pay or demand for academic credit preclude one's being a true altruist? Further, is altruism a necessary or sufficient condition of voluntarism? While we must attempt to answer these questions, the purpose here was to suggest viable first steps in reviving and enhancing student voluntarism. Some of the most salient points are: (1) Student volunteers provide critically needed services to the community, (2) Students are increasingly demanding tangible personal and educational gains for services through voluntarism, (3) Faculty support is vital to student voluntarism and they should be encouraged to actively design their classes to integrate classroom theory and practice through volunteering, and (4) The community agencies served should be active participants in the faculty, student, agency triad, and not merely passive recipients of services. The future of student voluntarism must be viewed in the larger context of changes occurring in the society-at-large, such as cynicism, mistrust of authority figures and leaders, and a move away from altruism and toward symbiosis and/or individualism. There is widespread disillusionment with "band-aid" approaches to solving enormous social problems, i.e., trying to help the few while some of society's most fundamental structures guarantee the perpetuation of poverty, crime, and general anomie. The rekindling of the ideology of cooperative altruism will take ingenuity and tireless effort. Meanwhile, if community psychology and related disciplines are to continue to utilize student volunteers, programs must be oriented toward new trends in student and faculty values and interests, and evolving community needs.

Altruism↗
PubMed1979

The effect of topical crude coal tar treatment on unstimulated hairless hamster skin.

Topical treatment of hairless hamster skin with crude coal tar has been shown to induce epidermal thickening, an increased labelling index in the basal cell layer, an elevation in NADP-dependent glucose-6-phosphate dehydrogenase activity throughout the epidermis, an increased squame count, comedo formation, and atrophy of the sebaceous glands. Ultraviolet light fluorescence microscopy of sections of treated skin suggests that the hair follicle is an important route for skin penetration by coal tar.

Acne Vulgaris↗
PubMed1979

Characterization and quantitation of murine-delayed hypersensitivity responses elicted with particle-associated human gamma-globulin.

Parameters delineating the utilization of particle-associated human gamma-globulin to quantitate murine-delayed hypersensitivity (DHS) responses include: (1) the conditions used to prepare HGG-coated polystyrene latex particles; (2) the marked increase in sensitivity of detection of delayed immune responsiveness using particle-bound HGG; (3) a histologic analysis of the lesions induced by HGG-latex in DHS mice, and (4) the increased retention of particle-associated as opposed to soluble HGG at the site of challenge. The potential utilization of particle-bound antigens as a sensitive method of assessing the role of delayed-type responsiveness in tumor and transplantation immunity is discussed.

Animals↗
PubMed1979

Recovery of the gastric mucosa from bile-induced injury.

Bile salts are known to injure the gastric mucosa and may be involved in the pathogenesis of gastric stress ulceration, a feared sequela of shock. Although the induction of bile injury to the stomach has been extensively studied, recovery from such an injury has not. In the studies reported here the period after removal of bile was examined to see whether the mucosa could return to pre-bile-exposure status under various circumstances. Recovery from a bile salt-induced injury was studied in three mongrel dogs with Heidenhain pouches. Net acid back diffusion (NABD) was measured with a recirculating system incorporating a pH stat and was measured with a recirculating system incorporating a pH stat and autoburette, and transmucosal electrical potential difference (PD) was measured by usual methods. The effects of exposure to 5 mM taurodeoxycholate at pH 2 for 30 minutes were studied. This exposure increased net acid back diffusion from 23 +/- 5 to 184 +/- 16 micro Eq/10 min (P less than 0.01) and reduced PD from 56 +/- 2 to 18 +/- 2 mV (P less than 0.01). After injury the pouches were copiously irrigated with saline to remove bile, and then recovery was observed as the pouches were perfused with pH 1, 2, or 7 HCl solution made isotonic with NaCl. The recovery values were compared with the same dog's preinjury values at the same pH perfusion. The data showed that at pH 2 and pH 7, PD and NABD returned to preinjury levels within 90 minutes after bile injury. At pH 1, however, recovery did not occur. The pH dependence of recovery from bile-induced injury may have relevance to patients with episodic reflux of bile into the stomach.

Animals↗
PubMed1978

Niemann-Pick disease: prenatal diagnoses and studies of sphingomyelinase activities.

Five pregnancies were monitored for couples at-risk for having a child with some form of Niemann-Pick disease (NPD). Three of these were for the classic Type A form in which affected children usually have less than 1% of normal sphingomyelinase activity. Two of these pregnancies were terminated after the cultured amniotic-fluid cells were determined to have less than 1% of normal sphingomyelinase activity (0.4 and 0.6 nmole/mg protein/hr versus the control mean of 61.7). In the other pregnancy at risk for Type A NPD near normal activity was measured and it was continued to term. The two other pregnancies were monitored for couples in which severely affected children were found to have partially deficient sphingomyelinase activity (about 20% of normal) in cultured skin fibroblasts. Cultural amniotic-fluid cells from one of these pregnancies also had about 20% of control sphingomyelinase activity, but the woman underwent a spontaneous abortion soon after the cells were received and no studies on the fetus were done. The other sample was taken at the time of abortion for social reasons. In this case the cultured amniotic-fluid cells and cultured fetal skin fibroblasts gave normal sphingomyelinase activity. Enzymatic studies on tissues from the two fetuses predicted to be affected with Type A NPD confirmed the prenatal diagnosis. Studies of sphingomyelinase activity in the brains from these fetuses and from a child who died with Type A NPD indicated significant levels of activity when measured at pH 7.4 in the presence of magnesium. The higher level of the pH 7.4 sphingomyelinase activity in developing brain may indicate some important role in normal brain development.

Adult↗
PubMed1978

The measurement of histochemically-stained NADP-dependent isocitrate dehydrogenase in the sebaceous glands of hairless hamster.

The effect of substrate, co-factor and Nitroblue Tetrazolium concentration on the production of formazan by the action of NADP-dependent isocitrate dehydrogenase was studied in the sebaceous glands of the hairless hamster. The measurement (in average optical density units per unit area) of formazan in histochemically stained skin sections was carried out by television scanning microdensitometry (Quantimet 720D). Having established optimal conditions for this enzyme, a second study was carried out to determine the effect of different power objectives and wide-band wavelength light instead of white light on the average optical density per unit area, recorded by the instrument, of the formazan produced in a defined number of sebaceous glands in a single skin section. It was found that there was no difference in the average optical density per unit area recorded by the instrument at different power objectives and a peak value of average optical density per unit area could be obtained using a K4 or a K5 Balzer filter (550-650 nm).

Animals↗
PubMed1978

Hypoglycorrhachia and coxsackie B3 meningoencephalitis.

The case of a 3-week-old infant with Coxsackie B3 meningoencephalitis is discussed. Hypoglycorrhachia and neutrophils in the cerebrospinal fluid characterized the first ten days of her illness. Coxsackie B3 should be added to the list of enteroviruses that can cause hypoglycorrhachia during infections of the central nervous system in children.

Cerebrospinal Fluid↗
PubMed1978

Relation between pressure difference across the aortic valve and left ventricular outflow.

Equations are presented to relate left ventricular-aortic pressure difference and flow. The relative importance of fluid inertia and friction are evaluated and the errors introduced by the neglect of compliance are estimated. The equations are used to calculate pressure differences for both normal conditions and simulated aortic stenosis and to explain the timing of the reversal of the pressure difference.

Aortic Valve↗