Homocarnosinosis: Hypercarnosinuria

Abstract: Homocarnosine (γ-aminobutyrylhistidine) is a brain-specific dipeptide. Homocarnosinosis is a familial metabolic disorder in which spastic paraplegia, progressive mental deficiency, and retinal pigmentation coexist with increased CSF homocarnosine levels, i.e. approximately 20 times higher than the mean control level. In the present study, the urinary excretion of carnosine ( β -alanylhistidine) and anserine ( β -alanyl-1-methylhistidine) was determined in patients with homocarnosinosis and in their close relatives. Both the patients and their relatives were also loaded with chicken meat, which is rich in anserine and carnosine. The results were compared with those obtained in childhood hypercarnosinuria with serum carnosinase deficiency. Somewhat surprisingly, patients with homocarnosinosis were also shown to have hypercarnosinuria. Chicken meat loading in healthy individuals results in increased excretion of carnosine and anserine and, in addition, 1-methylhistidine in the urine. Homocarnosinosis patients and patients with serum carnosinase deficiency also showed an increased excretion of carnosine and anserine, but 1-methylhistidine was not detected in serum carnosinase deficiency, and it was present only in very small amounts in homocarnosinosis. This defect seems to be due to lack of the hydrolyzing enzyme activity. The biochemical and clinical similarities between adult homocarnosinosis and infantile serum carnosinase deficiency are intriguing. A complete insight into the relationship between them must await further investigation.     

The mathematics of tanning

Background  

The pigment melanin is produced by specialized cells, called melanocytes. In healthy skin, melanocytes are sparsely spread among the other cell types in the basal layer of the epidermis. Sun tanning results from an UV-induced increase in the release of melanin to neighbouring keratinocytes, the major cell type component of the epidermis as well as redistribution of melanin among these cells. Here we provide a mathematical conceptualization of our current knowledge of the tanning response, in terms of a dynamic model. The resolution level of the model is tuned to available data, and its primary focus is to describe the tanning response following UV exposure.     

Fluid endocytosis in isolated rat parenchymal and non-parenchymal liver cells

Fluid endocytosis in rat liver parenchymal (hepatocytes) and non-parenchymal cells was studied by measuring uptake of [¹²⁵I]polyvinylpyrrolidone (PVP). Radioactive sucrose preparations were also tested but turned out to be unsuitable because of impurities of radioactive glucose and fructose. Fluid endocytosis was temperature dependent without any transition temperature. The rate of endocytosis was inhibited by inhibitors of the glycolytic and the respiratory pathway. Colchicine, but not cytochalasin B, inhibited the uptake of [¹²⁵I]PVP in hepatocytes. Therefore, intact microtubuli, but not microfilaments may be required for normal rate of fluid endocytosis in hepatocytes. Colchicine reduced the rate of fluid endocytosis in the non-parenchymal liver cells. Subcellular fractionation by isopycnic centrifugation in sucrose gradients indicated that [¹²⁵I]PVP taken up by the hepatocytes accumulated in the lysosomes. The rate of uptake expressed as volume of fluid internalized per unit time (endocytic index) was calculated to 0.08 μl/h/10⁶ cells for hepatocytes and 0.07 μl/h/10⁶ cells for non-parenchymal liver cells.     

Ultrastructural and ultrahistochemical studies on ventricular endocardial cells in teleosts (Pisces)

The ultrastructure of the ventricular endocardial cells in 17 bony-fish species representing eight families, is described. In species of Characidae, Cobitidae, Cyprinidae, and Gyrinocheilidae these cells are flat (1–2 µm at nucleus) and contain numerous ribosomes, some few bristle-coated vesicles (BCV) and small (0.243 pm) electron dense inclusion bodies. However, in species of Cichlidae, Gadidae, and Poeciliidae most endocardial cells appear relatively thicker (2–5 µm at nucleus) and contain numerous BCV, tubules of agranular endoplasmic reticulum, and large (0.5-1.5 µm) moderately electron dense bodies (MDB). In the MDB occur a number of small (20–150 nm) electron dense granules. Within the family Anabantidae, most endocardial cells seem to be of the first type in Colisa laliu and Trichogaster leeri. whereas in Helosioma iemmincki there are numerous cells of the second type. When glutaraldehyde/tannic acid fixed heart tissue of Pollachius virens is treated with ferrous chloride, ferric chloride, or osmium tetroxide, and grid stained by uranyl and lead solutions, damaged endocardial cells appear highly electron dense, whereas undamaged ones are electron lucent. Further, when glutaraldehyde fixed tissue is treated with osmium tetroxide/potassium ferrocyanide the subendocardial space is filled by a highly electron dense material. The methods described in this study make it possible to distinguish between those endocardial vacuoles having structural contact with the cell membrane, and those lacking such contact, and also to determine whether the lumen of the former is continuous with the subendocardial space, or with the intertrabecular lumen.     

Growth and sex ratio of nestlings in two species of crows: how important is hatching asynchrony?

Summary In experimental studies of avian hatching paterns offspring sex has been neglected. This may be a problem if nestling growth and mortality is sex biased, and if this bias is influenced by hatching spread. In a field study of two crow species, the magpie Pica pica and the hooded crow Corvus corone cornix, we manipulated hatching spread. Both species have asynchronous hatching, and adult males are larger than females by 12–14%. The sex ratios obtained from the different experimental groups on day 24 post-hatch (total sample n = 403) did not deviate significantly from unity, nor did the sex ratios obtained among young newly hatched in an incubator (total sample n = 305). Male and female offspring were of similar size at hatching but males were larger on day 24 post-hatch. Males seemed to be more costly to rear than females, judging by the 20% difference in the mean amounts of food found in the gizzards of the young on day 24 post-hatch. Dimorphism in body size did not seem to be influenced by degree of hatching spread. Asynchronous hatching did not seem to be needed to produce high quality offspring of the larger sex (i.e. males), nor did asynchronous hatching help to ensure equal parental investment in male and female progeny. One reason for the latter negative results may be that the size dimorphism of the two crow species studied were relatively small.