Laboratory tests of renal function

The kidneys are vital organs in the management of fluid balance, waste product removal, electrolyte homeostasis, acid–base balance and endocrine function. Waste products removed by the kidney are urea, uric acid and creatinine; other foreign products with similar physiochemical properties are also excreted. Urea and uric acid are by products of protein metabolism and creatinine is generated by the metabolism of creatine compounds from muscle. The kidney regulates fluid and electrolyte balance through controlling the composition and volume of urine. In the proximal convoluted tubule and the loop of Henle, 90% of sodium, potassium, calcium and magnesium are reabsorbed. Acid–base balance is achieved by regulating the excretion of hydrogen ions and bicarbonate buffering. The kidney also has a number of endocrine functions including the production of renin and erythropoietin as well as hydroxylation of vitamin D. The kidneys receive 25% of cardiac output, generating 170–200 litres of ultrafiltrate per day. Urine output is approximately 1.5 litres per day, which is concentrated ultrafiltrate through selective reabsorption of solutes and water. In this article we will discuss tests frequently used to assess renal function.     

Selective Attention Effects on the Reflex Blink

Past work has shown that facilitation of reflex blinking accompanies cardiac deceleration when the attention of subjects is directed to a reflex-eliciting stimulus. The present studies showed that when warning stimuli directed attention instead to weak (tactile) stimuli presented simultaneously with reflex-eliciting (acoustic) stimuli, cardiac deceleration was still present but reflex magnitude was unchanged or inhibited. However, latency to reflex onset remained facilitated, i.e., latency and magnitude changes were discordant. The findings were interpreted as evidence for two independent processes: a process capable of selectively enhancing or attenuating sensory input and a non-selective process presumably facilitating motor pathways.     

微波体模

用水、盐,聚氯乙烯粉和羧甲基纤维钠四种材料配制成一种适用的微波体模(模拟肌肉组织)。该体模的复介电系数在300～2500MHz范围内与实际人体肌肉组织的误差≤5％。这种体模的优点是材料立足国内,价廉,室温下配制,使用方便。本文也给出这种体模的温度特性,稳定性和热学特性,供电磁场生物效应和微波热疗等研究使用。     

A more realistic approach to the cumulative pregnancy rate after in-vitro fertilization

As most studies overestimate the cumulative pregnancy rate,a method is proposed to estimate a more realistic cumulativepregnancy rate by taking into account the reasons for an earlycessation of treatment with in-vitro fertilization (IVF). Threemethods for calculating cumulative pregnancy rates were compared.The first method assumed that those who stopped treatment hadno chance at all of pregnancy. The second method, the one usedmost often, assumed the same probability of pregnancy for thosewho stopped as for those who continued. The third method assumedthat only those who stopped treatment, because of a medicalindication, had no chance at all of pregnancy and that the otherswho stopped had the same probability of pregnancy as those whocontinued treatment Data were used from 616 women treated atthe University Hospital Nijmegen, Nijmegen, The Netherlands.The cumulative pregnancy rates after five initiated IVF cyclesfor the three calculation methods were in the ranges 37–51%for the positive pregnancy test result, 33–55% for a clinicalpregnancy and 30–56% for an ongoing pregnancy. As expected,the first method underestimated the cumulative pregnancy rateand the second overestimated it The third method produced themost realistic cumulative pregnancy rates.     

红霉素缓释微囊的制备及其释药机理的研究

本文旨在探讨红霉素微囊的制备及体外缓释机理。以明胶等为囊材,用红霉素制成微囊,研究微囊的厚度及孔隙度对药物释放速率的影响。进行理论分析,与实验结果相符性较好。     

Solar heat load: heat balance during exercise in clothed subjects

Summary Six subjects exercised for 60 min on a cycle ergometer. Their backs were exposed to an artificial sun with a spectral distribution similar to sunlight and an intensity of 724 W m^–2. Each subject took part in four experiments in random order: wearing suits of polyester (insulation value = 0.5 clo), white (WP) or black (BP), or cotton (0.6 clo), white (WC) or black (BC). Measured by partitional calorimetry, the calculated heat losses and gains for the four conditions balanced within less than 10%. The differences between the short-wave radiation gains of subjects in white or black garments were small. This is due to the transparency of the white materials, which allows a larger percentage of the radiation to penetrate the clothing. The surface temperatures of the sun-exposed areas were very high, especially in the black suits. This promotes dry heat loss. Therefore the sweat loss in the black suits and the differences between the black and white clothes became relatively small. The physiological strain in steady-state exercise, as expressed by average heart rates, was 142 (WP), 154 (BP), 151 (WC), and 160 (BC) beats min^–1; the sweat losses were 649 (WP), 666 (BP), 704 (WC), and 808 (BC) g. For both of these measures values for white polyester were significantly less than those for black cotton.     

Renal functional reserve in children with reduced renal mass: study by two dietary periods

It has been suggested that the renal functional reserve (RFR) defined by the rise in glomerular filtration rate (GFR) after a protein load could disappear in patients with severe nephron loss but with a normal GFR. This study compared, in 17 children, inulin clearance (C _in) measured by the plasma inulin plateau at the end of two 14-day randomized periods differing in protein intake: 100% (low protein, LP), or 200% (high protein, HP) of recommended dictary allowances (RDA). Diets were aimed at maintaining food habits and energy intake. Compliance was assessed by records of the last 3–4 days, an interview with the dietician and by urinary nitrogen measurements. Mean actual protein intake was 109% (56%–139%) RDA for the LP period and 220% (163%–319%) RDA for the HP period.C _in did not change in 14 children with GFR below (n=7) or within (n=7) the normal range.C _in was higher in the HP period than in the LP period (+32, 50, 63%) in 3 children who had a 50% (single kidneys) or a 25% (sclerosed glomeruli) nephron loss. Non-responding children had a GFR below 105 ml/min per 1.73 m². Nephron loss (70% sclerosed glomeruli) was estimated in only 1 child with no RFR. The results suggest that GFR measurement after prolonged dietary stimulation could help in evaluating the severity of nephron loss in children with normal or borderline GFR. The prognostic value of this test has to be confirmed by long-term follow-up.