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M Schumer

Publications and source records attributed to M Schumer.

5 recordsLinked to original sources
PubMed1997

Cardiovascular autonomic nervous system tests: determination of normative values and effect of confounding variables.

OBJECTIVE: To determine normative values for heart rate variation to deep breathing (VAR) and Valsalva ratio (VAL) as well as the effect of various confounding variables on these measures using data from a large group of normal subjects collected from multiple centers. RESEARCH DESIGN AND METHODS: VAR and VAL were measured on 611 normal subjects, age range 9-79, from 63 centers and was analyzed at a single Autonomic Nervous System Reading Center. Using simple and stepwise logistic regression the effect of age, gender, height, weight, mean arterial blood pressure (MAP) and body mass index (BMI), on VAR and VAL was evaluated. RESULTS: The 95% normative values range (values at 2.5 to 97.5 percentile) for VAR (n = 580) was 12.8-103.5 (mean 49.7) and for VAL (n = 425) was 1.31-2.97 (mean 1.97). No gender effect was found for either VAR or VAL (p > 0.05). VAR correlated inversely with both age and MAP, while VAL correlated inversely with both age and BMI. Since age is the principal confounding variable for both VAR and VAL, normative values are also presented stratified by age. CONCLUSION: Normative values for VAR and VAL based on a large population sample are presented. However, the values presented may not be valid in patients with morbid obesity or malignant hypertension. These data are applicable for either individual patients or for use in multicenter research trials.

Adolescent↗
PubMed1992

Morphologic, biochemical, and molecular evidence of apoptosis during the reperfusion phase after brief periods of renal ischemia.

A multiparametric analysis to demonstrate that even brief periods of arterial clamping can initiate extensive cell loss in a rat kidney through the process of apoptosis during the 48-hour period after reperfusion was performed. Microscopic examination of rat renal tissues subject to a 5-, 30-, or 45-minute period of complete ischemia showed the presence of apoptotic bodies both within and occasionally between renal tubules, appearing as early 12 hours after reperfusion, and increasing in numbers at 24 hours. Furthermore, DNA extracted from such reperfused renal tissue demonstrated the appearance of a distinct "ladder" pattern of DNA fragments after electrophoresis in agarose gels, a phenomenon commonly associated with cells undergoing apoptosis and in contrast to the predominant smear pattern obtained after electrophoresis of DNA extracted from necrotic renal tissue. Finally, messenger RNA (mRNA) encoding sulfated glycoprotein-2, a gene product previously identified to apoptotic renal cells, was found to be highly expressed in the 30-minute arterial clamped rat kidney after 24 hours of reperfusion, but was not detectable in mRNA extracted from renal tissue after 24 hours chronic infarction. This study demonstrates that a combination of morphologic, biochemical, and molecular markers can be used to distinguish predominant modes of cell death in varying forms of tissue injury. Application of these analytical techniques to renal vascular injury has distinguished that brief periods of complete ischemia initiates a form of cell death (apoptosis) during a subsequent reperfusion phase that is drastically different from cellular necrosis induced by prolonged severe ischemia.

Animals↗
PubMed1988

Diabetic autonomic neuropathy--Part I. Autonomic nervous system data analysis by a computerized central unit in a multicenter trial.

To determine the feasibility of utilizing a central, computerized unit to analyze autonomic nervous system function tests for a 10-year, multicenter, clinical trial, the Autonomic Nervous System Reading Center was established. The Reading Center selected and standardized testing methods, designed the testing protocol, developed testing equipment, computerized data analysis, and instituted measures to monitor data quality. Three cardiovascular testing methods, RR-variation, Valsalva maneuver, and postural testing, were selected because each is a simple, non-invasive, quantitative, sensitive, and reproducible test. Furthermore, a hierarchy of sensitivity has been established with these cardiovascular autonomic nervous system measurements: RR-variation, Valsalva maneuver, and finally postural testing. Confounding variables were minimized by prescribing eligibility criteria. Testing equipment, designed to record time between RR intervals in a form easily read into a computer, has been in 21 clinics for three years and a total of 54 technicians have been trained. Over 85 percent of the autonomic nervous system tests performed have been usable at initial testing. A central reading center is an efficient and necessary means of collecting and analyzing data for a multicenter clinical trial.

Autonomic Nervous System Diseases↗
PubMed1988

Diabetic autonomic neuropathy--Part II. Coefficient of variation of RR-variation and Valsalva maneuver tests.

To confirm the reliability and validity of cardiovascular autonomic nervous system tests, RR-variation and Valsalva maneuver, coefficient of variation for triplicate tests was calculated. The testing data were collected from patients participating in the Statil Neuropathy Trial. Triplicate testing was done within a three-week period at three different time points: baseline, 12 months, and 18 months. BMDP Statistical Software was used in the analysis. There is no significant difference between the coefficients of variation between clinics for either RR-variation or Valsalva maneuver tests. The coefficient of variation of pooled data was not significantly different from the coefficient of variation of individual clinics. Furthermore, there was no evidence that there was a significant worsening of coefficient of variation with time. Thus, RR-variation and Valsalva maneuver provide reliable and reproducible results that do not vary in consistency over time.

Autonomic Nervous System Diseases↗