Biomedical subjects

S Zeger

Publications and source records attributed to S Zeger.

22 records · Page 2Linked to original sources

PubMed1984

The effect of a keto acid-amino acid supplement to a restricted diet on the progression of chronic renal failure.

We treated 24 patients who had chronic renal failure with a low-phosphorus diet containing 20 to 30 g of mixed-quality protein, supplemented by amino acids and their keto analogues. Seventeen patients had well-defined rates of progression before treatment, as assessed by serial determinations of serum creatinine levels. By extrapolating these rates of progression, we found that 10 of the 17 (59 per cent) had a clinically important slower rise in creatinine levels during long-term treatment (average, 20 months) than predicted; none had a faster rise than predicted. Seven of the 17 patients began treatment before creatinine reached the level of 8 mg per deciliter; in six of the seven, followed for an average of 22 months, creatinine has remained at or below the level at the start of treatment. Nutrition, as assessed by body weight, nitrogen balance, serum albumin, and serum transferrin, has been well maintained. This regimen slowed or arrested the rise in creatinine levels and thus must have slowed or halted the progression of renal insufficiency in a majority of cases, especially when treatment was initiated before creatinine had reached the level of 8 mg per deciliter. The mechanism underlying this effect remains to be determined.

Adult↗

PubMed1984

Comparison of cerebrovascular response to hypoxic and carbon monoxide hypoxia in newborn and adult sheep.

Cerebral blood flow (CBF) responses to two types of isocapnic hypoxia, hypoxic hypoxia (HH) and carbon monoxide hypoxia (COH), were examined in seven unanesthetized adult sheep by the radiolabeled microsphere technique. Comparisons were made with newborn lambs (5-12 days old) previously studied under similar conditions. The arterial O2 content (CaO2) was reduced in a graded manner to 50-60% of the control value. During HH, CBF increased to maintain cerebral O2 delivery (CaO2 X CBF) in both adults and newborns; however, cerebral O2 uptake (CMRO2) did not change. Although CMRO2 was higher in newborns, the responses of CBF/CMRO2 to HH did not differ significantly in newborns and adults. In newborns, regional CBF showed that brainstem areas were particularly responsive to HH. In both age groups, CBF increased to a greater extent with COH than with HH for similar reductions in CaO2. This resulted in an increase in cerebral O2 delivery with COH. The degree to which COH differed from HH correlated with the magnitude of the leftward shift of the oxyhemoglobin dissociation curve that accompanies COH. In adults, CMRO2 fell by 16% with COH but was maintained in newborns. We conclude that maintenance of cerebral O2 delivery during acute, isocapnic HH is a property of CBF regulation common to both newborn and adult sheep. During COH, the position of the oxyhemoglobin dissociation curve is an additional factor that sets the level of O2 delivery. The fetal conditions of low CaO2 and a left-shifted oxyhemoglobin dissociation curve may have provided the newborn with a microcirculation better suited for maintaining CMRO2 during COH.

Animals↗

PubMedDate not supplied

Diminished pulse pressure under mental stress characterizes normotensive adolescents with parental high blood pressure.

An exaggerated blood pressure response to mental stress is believed to characterize young adults with genetic risk of essential hypertension, suggesting that stress-induced changes might provide a useful index of pathogenetic processes. We explored this by studying pressor responsivity to competitive tasks in adolescents drawn from a large urban population. Individuals with systolic or diastolic pressures persistently between the 85th and 95th percentiles were evaluated on basal blood pressure, parental history of hypertension, and pressor and heart rate response to a challenging video game. Basal pressure was measured again at 6, 10, and 14 months. A persistently diminished pulse pressure was the cardiovascular characteristic that most reliably typified normotensive subjects with familial hypertension. Response to the video game was the best indicator of risk status. Contrary to expectations derived from research with convenience samples, epidemiologic investigation points to an increased peripheral resistance and lower cardiac output as the cardiovascular pattern more prominently associated with genetic risk in the normotensive adolescent.

Adolescent↗

PubMedDate not supplied

Relationship of somatosensory evoked potentials and cerebral oxygen consumption during hypoxic hypoxia in dogs.

The effects of hypoxic hypoxia on cerebral hemodynamics and somatosensory evoked potential (SEP) were studied in 10 pentobarbital anestheteized dogs. Cerebral blood flow (CBF) was measured using the venous outflow technique and cerebral oxygen consumption (CMRO2) was calculated from the arterio-cerebro-venous oxygen difference times CBF. SEP was evaluated by percutaneous stimulation of an upper extremity nerve and was recorded over the contralateral somatosensory cortex. The latencies of the initial negative wave (N1), second positive wave (P2) and the amplitude of the primary complex (P1N1) were measured. Animals were breathed sequentially with oxygen concentrations of 21, 10, 6, 5, and 4.5% for five minutes each. Animals were returned to room air breathing when the amplitude of the SEP decreased to less than 20% of control and were observed for 30 minutes following reoxygenation. Severe hypoxia (4.5% O2) increased CBF to 200% of control, decreased CMRO2 to 45% of control, decreased amplitude and increased latency of SEP. Following reoxygenation, as CMRO2 increased toward control, latency of SEP decreased and amplitude increased and CBF returned to baseline within 30 min. During hypoxia and reoxygenation, the latencies of N1 and P2 and the amplitude of P1N1 were correlated with CMRO2 in individual animals. We conclude that changes in SEP amplitude and latency reflect changes in CMRO2 despite high CBF during rapidly progressive hypoxic hypoxia and following reoxygenation.

Animals↗