To examine the baroreflex response in humans during acute high-altitude exposure, the carotid baroreflex cardiac responsiveness was studied using a neck chamber in seven unacclimatized male subjects. Measurements were made in a high-altitude chamber on separate days at sea level and during 1-h exposure at two different altitudes of 3,800 m [partial pressure of oxygen in inspired air (Pi O2 ) = 90 mmHg] and 4,300 m (Pi O2  = 82 mmHg). R-R intervals were plotted against neck chamber pressures, and the baroreceptor response was analyzed by applying a four-parameter sigmoidal logistic function. The baroreceptor response curve shifted downward in either altitude, reflecting a tachycardic response at high altitude, and the magnitude of the shift was greater at 4,300 m than at 3,800 m. There was no change in the sigmoidal parameters at 3,800 m compared with sea level except for a reduction ( P < 0.05) of the minimum R-R interval. At 4,300 m the maximal R-R range, slope coefficient, minimum R-R interval, and maximal gain of the curve decreased significantly ( P < 0.05) compared with sea level values, whereas the centering point of the curve remained unchanged. These results suggest that hypoxia (Pi O2  = 82 mmHg) reduces the sensitivity of carotid baroreflex cardiac response.

Inadequate obstetric services are associated with maternal mortality in Japan. Reducing single-obstetrician only delivery patterns and establishing regional 24-hour inpatient obstetrics facilities for high-risk cases may reduce maternal mortality in Japan. JAMA. 2000;283:2661-2667.

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Background Glycated albumin (GA) reflects glycemic control in patients with neonatal diabetes mellitus (NDM). However, GA in NDM patients is apparently low in relation to glycemia. Objective To establish the reference intervals for GA in healthy infants. Subjects and Methods Fifty‐eight healthy, full‐term newborn infants were used to define the GA reference values and to investigate its relationship to plasma glucose (PG) and serum albumin. The infants were categorized into three groups according to age: group A, 5 (4–6) median (range) d: n = 18; group B, 33 (30–38) d: n = 19; and group C, 181 (50–352) d: n = 21. We also studied 212 non‐diabetic adults [group D, 53 (28–78) yr old] and the 5 NDM patients previously reported for GA comparisons. Results In the infants, GA was strongly positively correlated with logarithmic transformation of age [log (age)] (p = 0.831, p < 0.0001). The GA in groups A, B, C, and D were 7.3 ± 1.0%, 8.6 ± 1.1%, 10.9 ± 0.8%, and 14.0 ± 1.1%, respectively. The GA was more strongly positively correlated with serum albumin (r = 0.768, p < 0.0001) than with PG (r = 0.596, p < 0.0001). When GA levels were compared with the age‐dependent reference values, GA in the transient NDM patient was normalized although GA in the four permanent NDM patients decreased but remained high after insulin therapy. Conclusions This study showed that the reference range for GA in infants is lower than that of adults and increases with age, with which we confirmed that GA in the NDM patients reflected the clinical course. Consequently, GA in NDM patients should be compared with the age‐based reference values to assess the accurate glycemic status.

These experiments were conducted to examine whether changes in central and peripheral hemodynamics were proportional to muscle sympathetic nerve activity (MSNA) during graded head-down tilt (HDT). Twelve healthy males (19-42 yr old) underwent HDT at 15 degrees and 30 degrees for 10 min each with a 10-min rest period between the trials. MSNA at 15 degrees HDT declined by 31 +/- 5% (P < 0.05) for burst rate and by 37 +/- 3% (P < 0.05) for total activity. At 30 degrees HDT, the reduction in MSNA was 51 +/- 5% for burst rate (P < 0.05 vs. 15 degrees HDT) and 46 +/- 5% for total activity (P < 0.05 vs. 15 degrees HDT). Stroke volume increased (P < 0.05) during both 15 degrees and 30 degrees HDT, but heart rate and blood pressure remained unchanged. A concurrent increase in central venous pressure (P < 0.05) and stroke volume with a reduction of thoracic impedance (P < 0.05) suggests that both pressure and volume in the atrium were elevated during HDT, and the magnitude of these changes was greater (P < 0.05) at 30 degrees HDT than at 15 degrees HDT. Forearm blood flow increased during HDT at both 15 degrees and 30 degrees, and the magnitude of the increase was greater (P < 0.05) at 30 degrees HDT. It is concluded that the magnitude of the loading of the cardiopulmonary mechanoreceptors during HDT was higher at 30 degrees in comparison to 15 degrees. This increased the afferent firing rate by the cardiopulmonary receptors and probably inhibited sympathetic outflow in the central nervous system.(ABSTRACT TRUNCATED AT 250 WORDS)