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Biomedical subjects

C A Schroeder

Publications and source records attributed to C A Schroeder.

8 recordsLinked to original sources
PubMed1999

Inhibition of NO synthesis or endothelium removal reveals a vasoconstrictor effect of insulin on isolated arterioles.

In this study we tested the hypothesis that insulin may differentially affect isolated arterioles from red (RGM) and white gastrocnemius muscles (WGM) because of their differences in function and metabolic profile. We also determined whether the responses of these arterioles are endothelium dependent and mediated by either prostaglandins or nitric oxide (NO). Arterioles were isolated, pressurized to 85 mmHg, equilibrated in Krebs bicarbonate-buffered solution (pH 7.4) gassed with 10% O2 (5% CO2-85% N2), and studied in a no-flow state. Control diameters for first-order arterioles from RGM averaged 77 +/- 8 micrometers and from WGM averaged 77 +/- 5 micrometers. Cumulative dose-response curves to insulin (10 microU/ml, 100 microU/ml, 1 mU/ml, and 10 mU/ml) were obtained in arterioles before and after endothelium removal or administration of either indomethacin (Indo, 10(-5) M) or NG-nitro-L-arginine (L-NNA, 10(-4) M). Insulin evoked concentration-dependent increases in control diameter of intact RGM and WGM arterioles of 6-26% and 9-28%, respectively. Indo was without any effect on insulin-induced dilation in RGM and WGM arterioles. Insulin-evoked dilation in both RGM and WGM arterioles was completely inhibited and converted to vasoconstriction by endothelium removal and administration of L-NNA. These results indicate that in endothelium-intact arterioles from RGM and WGM, insulin evokes an endothelium-dependent dilation that is equivalent and mediated by NO. In contrast, in the absence of a functional endothelium, insulin evokes arteriolar constriction. The finding that insulin can constrict arterioles, at physiological concentrations, suggests that insulin may play a more significant role in the regulation of vascular tone and total peripheral resistance than previously appreciated.

Animals↗
PubMed1996

Preconditioning with ischemia or adenosine protects skeletal muscle from ischemic tissue reperfusion injury.

Prolonged tissue ischemia and subsequent reperfusion results in significant tissue injury due to the ischemic-reperfusion (IR) syndrome. Ischemic preconditioning (IPC) or adenosine (ADO) pretreatment are known to protect IR injury in cardiac muscle. Our aim was to determine whether IPC or ADO pretreatment attenuates and protects against ischemic tissue reperfusion injury in skeletal muscle. Rats were anesthetized and global hindlimb ischemia was induced by 60 min of suprarenal aortic clamping followed by 30 min of reperfusion period. The degree of skeletal muscle dysfunction was determined by decreases in maximum contractile force, and adenosine triphosphate (ATP) and creatine phosphate (CP) levels of extensor digitorum longus (EDL) muscle. The distal tendon of the EDL was attached to a force transducer for maximum isometric force measurement. Samples were taken from the EDL for measurement of ATP and CP levels. The following were protective protocols prior to the IR challenge: (1) four consecutive 5-min periods of ischemia separated by 5-min reperfusion periods (PC/I) or (2) i.v. adenosine infusion (350 microg/kg/min x 10 min, PC/A). Our data suggest that pretreatment with brief periods of ischemia or systemic ADO infusion attenuates ischemic tissue reperfusion injury in skeletal muscle. [Table: see text]

Adenosine Diphosphate↗
PubMed1996

Women's experience of bed rest in high-risk pregnancy.

OBJECTIVE: To explore women's experience of bed rest in high risk pregnancy. DESIGN: Naturalistic, qualitative. SAMPLE, SETTING: Twelve adult, pregnant women on prescribed bed rest of a minimum of 20 hours per day and for at least 3-weeks duration were interviewed in one Western state of the U.S.A. regarding their experiences. FINDINGS: Three major themes were perceptions of high risk pregnancy, perceptions of bed rest, and the experience of time and restricted movement. The women described a high level of physical, emotional, familial, and economic hardship resulting from the bed-rest experience. Having adequate income, health insurance, and a supportive relative to take over household responsibilities were dimensions of successful maintenance of bed rest in the women. CONCLUSIONS: The routine obstetric procedure of bed-rest should be reevaluated in light of its lack of demonstrated effectiveness and potential to seriously harm women and their families. CLINICAL IMPLICATIONS: Women should be fully informed about controversies surrounding the efficacy of bed rest in pregnancy and encouraged to participate in decisions when complications occur regarding the prescription of prolonged bed rest.

Adult↗
PubMed1991

Movement and time: exertion and perceived duration.

This study examined differences in consciousness indexes (perceived duration of time) at different levels of physical exertion within the framework of Newman's model of health and with emphasis on Prigogine's theory of dissipative structures. The sample consisted of 100 volunteers participating in regular aerobic exercise. Instruments included 817E Monarch Stationary Bicycles, 1800 Dynamap Automatic Blood Pressure/Pulse Monitors, the production method of time estimation, and the Perceived Exertion Scale. Repeated measures ANOVA revealed significant differences in consciousness indexes during exertion (p less than .00001). Paired t-tests yielded significant differences between the resting consciousness index and consciousness indexes at preferred, increased, and decreased exertion levels (p = .000). Results indicate that the consciousness index decreased with physical exertion regardless of actual exertion level. In addition, changes in perceived exertion and in physiological parameters suggest a pattern of expanding consciousness that is consistent with the theoretical framework.

Adolescent↗
PubMed1989

Consciousness as a dissipative structure: an extension of the Newman model.

Newman's model of health as the expansion of consciousness and Prigogine's theory of dissipative structures provide the framework for the development of a model of consciousness as a dissipative structure. Relationships among Type A behavior, temporal orientation, and death anxiety are examined and explicated within the human field pattern of consciousness as a dissipative structure. Type A behavior, future orientation, and death anxiety are proposed as manifestations of consciousness with the potential to evolve to higher levels in accordance with Prigogine's theory. Preliminary research findings related to the model and suggestions for future research are also presented.

Attitude to Death↗