Garcia & Koelling (1966) showed that if rats are poisoned after ingesting a flavored solution in the presence of audiovisual cues, they will subsequently avoid only the taste stimulus, whereas if they are shocked, they learn to avoid only the audiovisual cues. The present experiments replicated these findings with one major change in experimental conditions: both taste and nongustatory CSs were presented in the absence of approach and ingestive behaviors to minimize involvement of ingestion in the associative process. (The taste CS was presented by flushing the oral cavity with a saccharin solution under conditions in which the rat would not drink.) Despite these changes, Garcia and Koelling's results were confirmed.

Rats tasting but not ingesting a flavored solution prior to toxicosis acquired weaker aversions to the flavor than subjects that actively consumed the CS during conditioning. Taste was isolated from ingestion either by curarizing the subjects or by infusing a flavored solution very rapidly into the oral cavity of non-water-deprived rats. Control groups showed that the facilitatory effect of ingestion on taste-aversion learning did not depend on the consumption of very much of the CS solution.

Glomerular filtration rate (GFR) and urine and serum concentrations of cystatin C and creatinine were measured in 40 boys and 42 girls. The fractional excretion of cystatin C (FE Cyst C) increased in proportion to the decrease in GFR. Since serum creatinine concentration (S-Creatinine) in the numerator of the fractional excretion equation and serum cystatin C concentration (S-Cystatin C) in the denominator have similar numerical values, they cancel out. The result is an equation in which the FE Cyst C is equal to the ratio of urinary cystatin C to urinary creatinine (u[cystatin-C/Cr]). The ratio of u[cystatin C/Cr] was compared with GFR. Using a receiving operating characteristic (ROC) plot, the data showed that a ratio of u[cystatin C/Cr]*100 that is > or =0.100 has a sensitivity of 90.0% for identification of children with GFR < or =60 ml/min per 1.73 m(2). The false-positive rate is 16.1%. The u[cystatin C/Cr] ratio is a reliable screening tool for detecting decreased GFR that does not require a serum sample.

Renal functional reserve was measured during 89 studies in 78 children as the difference between the baseline glomerular filtration rate (GFR) and that following a protein meal. GFR was measured using creatinine as the filtration marker in children pre-treated with cimetidine. The children had been on a diet free of meat, fish, and fowl for 24 h. The protein meal to stimulate GFR was derived from milk, cheese, eggs, and baked goods. The increase in GFR following the protein meal was due mainly to an increase in the glomerular filtration of creatinine, with a small contribution by decreased serum creatinine concentration. This study confirmed that renal functional reserve can be measured using a meat-free protein meal to stimulate GFR. The protocol employed is a relatively noninvasive and inexpensive procedure for identifying glomerular hyperfiltration in children.

ELISAs for measuring the urinary excretion of collagen crosslinks and related peptides appear to show marked differences in sensitivity to anti-resorptive therapy. This presumably reflects variations in specificity of the anylate being detected in these assays, and the way in which they respond to treatment. To clarify these points, we used HPLC analysis to assess the effect of four weeks treatment with the amino-bisphosphonate, neridronate, on free and peptide-bound fractions of the collagen cross-links deoxypyridinoline (Dpd) and pyridinoline (Pyd). Six postmenopausal women, in whom two hour morning urine samples were obtained at baseline (x2), and one, two and four weeks after commencing treatment, were included. We found that neridronate had relatively little effect on peptide-bound or free urinary Pyd. but markedly reduced peptide-bound urinary Dpd. However, urinary excretion of free Dpd was not significantly affected. As a consequence of these differential effects on collagen cross-link excretion, neridronate led to a striking increase in the free/total Dpd ratio, and in the peptide-bound Pyd/Dpd ratio. We conclude that neridronate, and presumably other bisphosphonates, selectively suppresses peptide-bound Dpd excretion, possibly reflecting altered processing of collagen crosslinks released during bone resorption.

No abstract

The purpose of this study was to describe the reproducibility of timed-urine collections for renal clearance studies and the effect variations in urine collection has on measurement of glomerular filtration rate (GFR). Data from 222 cimetidine clearance studies (GFR-Cim) were obtained from 32 pediatric renal patients over a period of 8 years. There were three to 18 studies per child aged 4.8 years to 21 years at the time of a study. The urinary creatinine excretion rate is measured during supervised urine collection periods. The creatinine excretion rates in each child were compared to obtain data on the reproducibility of the urine collections. The coefficient of variation (CV) of the creatinine excretion rate is approximately 10% in both children and adults. The variation in GFR to be expected during repeated renal clearance studies in subjects with stable GFR, using voided urine collections, was similar in children and adults, with a CV of 12% to 14%.

Rats exposed to inescapable heat stress maintained a controlled hyperthermia while increasing heat loss by cutaneous vasodilatation and by grooming behavior. In nonpregnant rats, the evaporation of saliva groomed onto the body surfaces increased exponentially as a function of ambient temperature above 36 °C. In contrast, rats in an advanced stage of pregnancy became dependent on grooming behavior for thermoregulation at ambient temperatures of 30-36 °C. This was associated with a decrease in the body temperature threshold for salivary secretion from the submaxillary gland, which then began at approximately the same body temperature as cutaneous vasodilatation. In addition, the pregnant rats maintained a lower level of controlled hyperthermia during heat stress than did nonpregnant rats. This appeared to result from a decreased production of metabolic heat, reduced insulation on the ventral surface, and an increased motivation to keep cool during heat stress. These changes met the increased need for thermolysis during pregnancy and provided for thermal homeostasis both in the pregnant rat and in the unborn fetuses.Rats exposed to inescapable heat stress maintain a controlled hyperthermia while increasing heat loss by cutaneous vasodilatation and by grooming behavior (see review by . Heat loss by radiation and conduction, primarily from vascularized exposed surfaces such as the tail (Knoppers, 1942;Rand, Burton, & Ing, 1965), is a particularly important avenue of thermolysis in female rats, whose long tails make them less dependent than males on the cooling that results from evaporation of saliva groomed onto the body surfaces (Hainsworth, 1967(Hainsworth, ,1968. During pregnancy, however, their increased girth reduces the relative size of the "thermal window" that is provided by