Clofibrate-induced antidiuresis

Normal subjects and patients with antidiuretic hormone (ADH) deficiency were studied to determine the mechanism of the antidiuretic action of clofibrate. Before clofibrate treatment, the patients' ability to concentrate urine with a standardized dehydration procedure correlated with the amount of ADH which was excreted. During clofibrate administration all six patients with ADH deficiency developed an antidiuresis which was like that of ADH, since there was no change in sodium, potassium, total solute, or creatinine excretion. There was a correlation between the patients' ability to concentrate urine during dehydration and the subsequent response to clofibrate, and the excretion of ADH during dehydration correlated with the excretion of ADH on clofibrate therapy. Clofibrate-induced antidiuresis in these patients was partially overcome by ethanol and by water loading. Clofibrate interfered with the ability of patients and subjects to excrete a water load and prevented the water load from inhibiting ADH excretion in the normal subjects. These studies suggested that clofibrate was acting through endogenous ADH and this thesis was supported by the failure of clofibrate to produce an antidiuresis when injected into rats with total ADH deficiency (Brattleboro strain) although an antidiuresis was produced in water-loaded normal rats. When the drug was injected into Brattleboro rats with exogenous ADH, clofibrate either did not alter or it inhibited the action of the ADH. The data demonstrate that clofibrate has a significant ADH-like action. This action appears to be mediated through the release of endogenous ADH.

Differential renal protein clearance in diabetes

Measurements of differential renal protein clearance (ratio of the renal clearance of immunoglobulin-G to that of transferrin) have been performed in long-standing diabetics with varying amounts of proteinuria. In seventy-one diabetics the IgC-transferrin clearance ratio (0.44 ± 0.04, mean ± S.E.M.) was significantly lower than in seventeen normal subjects (1.85 ± 0.24). The mean IgG-transferrin clearance ratio was significantly lower in fourteen of these diabetics with normal amounts of proteinuria than in normal subjects. A further decrease in clearance ratio was apparent when nonproteinuric (125 mg./24 hr.) and minimally proteinuric (500 mg./24 hr.) diabetics were compared. Deterioration of renal function in proteinuric diabetics was associated with an increase in the IgG-transferrin clearance ratio. The results taken overall suggest that an initial fall and a delayed rise in the clearance ratio occurs in individuals who progress to terminal renal failure. The initial fall in the IgG-transferrin clearance ratio may reflect the earliest renal changes of diabetic nephropathy. The relationship of this fall to the onset of carbohydrate intolerance remains to be clarified.

Experimental papillary necrosis of the kidney. II. Electron microscopic and histochemical studies

Renal papillary necrosis was induced in rats by bromoethylamine hydrobromide and studied electron microscopically and histochemically. Morphologic changes appear to develop in vessels and tubules simultaneously, rather than tubular lesions preceding and leading to vascular lesions, or vice versa. Abnormalities are recognized as early as 3 hours, but platelets do not make their appearance until 12 hours, eliminating primary vascular thrombosis as the source of papillary injury.

Hydroxyproline heterooligosaccharides in Chlamydomonas

Most of the hydroxyproline in Chlamydomonas reinhardtii is glycosidically linked to oligosaccharides and a monosaccharide that are different from the arabinosides found in hydroxyproline-containing plant cell walls previously examined. Of particular interest is the presence of hydroxyproline-O-galactose. These differences may be common to the volvocalean green algae and may be related to lower tensile strength of the cell walls of this group of plants.

Fatty acid oxidation, oxidative phosphorylation and ultrastructure of mitochondria in the diabetic rat liver. Hepatic factors in diabetic ketosis

Oxidative phosphorylation, maximum rate of palmitate xidation and ultrastructure of mitochondria (MT) were tudied in livers of ketotic, nonketotic and insulin-treated liabetic rats. Significant changes in oxidative phosphorylaion were found only in ketotic diabetes. Respiratory control atios were decreased for all of the substrates studied and vere primarily due to increased state 4 respiration with lalmitylcarnitine and 2-oxoglutarate, and lowered state 3 espiration in the case of succinate. ADP/O ratio was only partially lowered with 2-step oxidation of 2-oxoglutarate. The naximum rate of palmitate oxidation to acetoacetate was ncreased 90 per cent in MT of rats with ketotic diabetes ind 50 per cent in MT from animals with nonketotic diabetes. Accompanying these changes were ultrastructural alteritions of MT. The average size of MT in the diabetic rat liver was 50 per cent larger in cut sections. MT within hepacocytes in ketotic diabetes were distorted, enlarged, and had irregular shapes and contours. Cristae tended to be deranged; when isolated, crescentic MT were predominant, In the insulin-treated diabetic rats, these functional and morphological changes were not observed. The results imply that in diabetic ketosis, increased availability of free fatty acid(s) (FFA) in hepatocytes together with increased capacity of mitochondrial FA oxidation produces more acetyl CoA which in turn results in an overproduction of ketone bodies. Since a significant increase in state 4 respiration of MT isolation from ketotic diabetic rats was observed, FA oxidation may proceed independently of ADP availability because of “loose” coupling of respiration to phosphorylation.

Segmental aneuploidy and the genetic gross structure of the Drosophila genome

By combining elements of two Y-autosome translocations with displaced autosomal breakpoints, it is possible to produce zygotes heterozygous for a deficiency for the region between the breakpoints, and also, as a complementary product, zygotes carrying a duplication for precisely the same region. A set of Y-autosome translocations with appropriately positioned breakpoints, therefore, can in principle be used to generate a non-overlapping set of deficiencies and duplications for the entire autosomal complement.-Using this method, we have succeeded in examining segmental aneuploids for 85% of chromosomes 2 and 3 in order to assess the effects of aneuploidy and to determine the number and location of dosage-sensitive loci in the Drosophila genome (Figure 5). Combining our data with previously reported results on the synthesis of Drosophila aneuploids (see Lindsley and Grell 1968), the following generalities emerge.-1. The X chromosome contains no triplo-lethal loci, few or no haplo-lethal loci, at least seven Minute loci, one hyperploid-sensitive locus, and one locus that is both triplo-abnormal and haplo-abnormal. 2. Chromosome 2 contains no triplo-lethal loci, few or no haplo-lethal loci, at least 17 Minute loci, and at least four other haplo-abnormal loci. 3. Chromosome 3 contains one triplo-lethal locus that is also haplo-lethal, few or no other haplo-lethal loci, at least 16 Minute loci, and at least six other haplo-abnormal loci. 4. Chromosome 4 contains no triplo-lethal loci, no haplo-lethal loci, one Minute locus, and no other haplo-abnormal loci.-Thus, the Drosophila genome contains 57 loci, aneuploidy for which leads to a recognizable effect on the organism: one of these is triplo-lethal and haplo-lethal, one is triplo-abnormal and haplo-abnormal, one is hyperploid-sensitive, ten are haplo-abnormal, 41 are Minutes, and three are either haplo-lethals or Minutes. Because of the paucity of aneuploid-lethal loci, it may be concluded that the deleterious effects of aneuploidy are mostly the consequence of the additive effects of genes that are slightly sensitive to abnormal dosage. Moreover, except for the single triplo-lethal locus, the effects of hyperploidy are much less pronounced than those of the corresponding hypoploidy.

Ergonomic evaluation of a redesigned surgical instrument

Some problems have been encountered with the current design of the bayonet forceps, one of the more frequently used instruments of the neurosurgeon. By studying its function and operational use, a new design was conceived to make the instrument more amenable to the surgeon's hand, ie ergonomically suitable. This was tested in the laboratory and the operating room, and was found superior to the old one in comfort, stability-in-use, and ease of operation. This method of ergonomic redesign and evaluation can be used for other similar problems.

Diabetes in the Pima Indians. Evidence of bimodality in glucose tolerance distributions

Venous plasma glucose levels two hours after a 75 gm. carbohydrate load were determined on over 2,900 Pima Indians, a population known to have an extremely high prevalence of diabetes mellitus. In each sex and in each decade above twenty-five years of age, the frequency distributions of the logarithms of the glucose levels were clearly bimodal, but below this age a single symmetrical unimodal distribution was found. A maximum likelihood procedure was used to derive the best fitting theoretical gaussian distributions for each group of data, together with the parameters of each distribution.

The observed bimodal distributions were found to be in satisfactory agreement with a model of two overlapping gaussian distributions, indicating that a logical separation between those with normal and high levels of glucose is possible, although the presence of overlap indicates that some misclassification will occur if any finite level is used to subdivide the population.

The data indicate that among the Pima: 1. The frequency distributions of two-hour glucose tolerance levels can be used to identify objectively and describe a hyperglycemic population without recourse to other criteria for diabetes. 2. There are small changes in the parameters of “normal” glucose tolerance between the ages of twenty-five and sixtyfour years. 3. The increase in mean glucose level found with rising age in this population is mainly the result of an increasing proportion of subjects who are in the group characterized by marked glucose intolerance.

The bimodal distributions of plasma glucose levels The bimodal distributions of plasma glucose levels among the Pima Indians contrast with those described so far in other groups. It seems likely that differences are attributable to the lower prevalence of diabetes elsewhere which would obscure the identification of bimodality.