Muscle fluorometry: A determination of the depth of penetration

Summary Fluorometric recordings of NADH (nicotinamide adenine dinucleotide) were made on rabbit papillary muscles. The specimens were placed between the UV light source and a small window of the detection stage. As the muscle was moved over the window in a transverse direction, simultaneous measurement could be taken of transmitted UV light and fluorescent light for various thicknesses of tissue. It is concluded that a muscle thinckness of 0.65 mm, is optimal before absorption of the incident light decreases the fluorescence signal.     

No sex difference in the waveform of the pulse type electric fish,Gnathonemus petersii (Mormyridae)

Summary A communication signal in an African freshwater electric fish, its pulse-like Electric Organ Discharge (EOD), was investigated in order to determine whether inter- or intraindividual variability of the EOD waveform provides a putative cue for communication, in addition to the electric cues already identified. In contrast to an individual's highly stereotyped EODs showing extremely low variation (fig. 1), variability between individuals was considerable (fig. 2). The dependence of an individual's EOD duration on temperature was weak with a Q₁₀ of close to 1.5. In none of four quantitative EOD waveform measures can a sexual dimorphism be discerned (table).Gnathonemus petersii very likely relies on mechanisms other than discrimination of intraspecific EOD waveforms for mate recognition.     

Primary structure of bovine thyroglobulin deduced from the sequence of its 8,431-base complementary DNA

In mammals, an adequate supply of thyroid hormones is essential for normal growth and neurological development. The biosynthesis of thyroid hormones involves an iodinated precursor protein, thyroglobulin, which may be considered an extreme example of a pro-hormone. Thyroglobulin is a dimeric glycoprotein of relative molecular mass (Mr) 660,000 (660K), which is secreted by the thyrocyte and stored in the lumen of the thyroid follicle. The hormonogenic reaction is extracellular, and involves iodination of tyrosyl residues of thyroglobulin and the intramolecular coupling of a subset of these into thyroxine (T4) and triiodothyronine (T3), which remain part of the polypeptide chain. Secretion of hormones results from the endocytosis of thyroglobulin followed by its complete hydrolysis in lysosomes. Considering that the maximum yield of hormones is approximately 6-8 per 660K protein, the whole process is apparently wasteful. However, the efficiency of thyroglobulin as a thyroid hormone precursor is extremely high when the supply of iodine is short; in such conditions, almost all the iodine incorporated is found in iodothyronine. Hence it is suggested that the thyroglobulin structure has evolved to allow for the preferential and efficient iodination and coupling of the hormonogenic tyrosines. Here we report the complete primary structure of bovine thyroglobulin, derived from the sequence of its 8,431-base-pair complementary DNA. The 2,769-amino-acid sequence is characterized by a pattern of imperfect repeats derived from three cysteine-rich motifs. Four hormonogenic tyrosines have been precisely localized near the amino and carboxyl ends of the protein.     

Pituitary growth hormone and hypothalamic somatostatin in young female rats versus old constant estrous female rats

Pituitary content and concentration of growth hormone was significantly reduced, and hypothalamic somatostatin content significantly increased, in old constant estrous as compared to young female rats. Increased levels of somatostatin may contribute to the decrease in pituitary growth hormone levels in these animals.     

Wound-induced alterations in survival of 60Co irradiated mice: importance of wound timing

Wounding mice shortly before or shortly after lethal 60Co irradiation enhances survival. Survival of wounded-irradiated mice may be due to enhanced hematopoietic recovery as measured by endogenous spleen colony (E-CFU-s) formation.     

Intergeneric interactions between Eimeria separata (Apicomplexa) and Nippostrongylus brasiliensis (Nematoda) in the rat

Ova production in Nippostrongylus brasiliensis infected rats was significantly greater than in rats singly infected with the helminth when Eimeria separata infections were introduced 4, 6 and 11 days postinoculation with N. brasiliensis. Patent periods were unaltered during concurrent infections. These results suggest that the presence of E. separata affects helminth fecundity but does not increase N. brasiliensis longevity as has been shown with E. nieschulzi.     

Mutations in a delta 8-delta 7 sterol isomerase in the tattered mouse and X-linked dominant chondrodysplasia punctata. jderry@immunex.com.

Tattered (Td) is an X-linked, semi-dominant mouse mutation associated with prenatal male lethality. Heterozygous females are small and at 4-5 days of age develop patches of hyperkeratotic skin where no hair grows, resulting in a striping of the coat in adults. Craniofacial anomalies and twisted toes have also been observed in some affected females. A potential second allele of Td has also been described. The phenotype of Td is similar to that seen in heterozygous females with human X-linked dominant chondrodysplasia punctata (CDPX2, alternatively known as X-linked dominant Conradi-Hünermann-Happle syndrome) as well as another X-linked, semi-dominant mouse mutation, bare patches (Bpa). The Bpa gene has recently been identified and encodes a protein with homology to 3beta-hydroxysteroid dehydrogenases that functions in one of the later steps of cholesterol biosynthesis. CDPX2 patients display skin defects including linear or whorled atrophic and pigmentary lesions, striated hyperkeratosis, coarse lusterless hair and alopecia, cataracts and skeletal abnormalities including short stature, rhizomelic shortening of the limbs, epiphyseal stippling and craniofacial defects (MIM 302960). We have now identified the defect in Td mice as a single amino acid substitution in the delta8-delta7 sterol isomerase emopamil binding protein (Ebp; encoded by Ebp in mouse) and identified alterations in human EBP in seven unrelated CDPX2 patients.     

Neuron numbers in hypothalamic nuclei in young,middle-aged and aged male rats

Summary Morphologic analysis of nine hypothalamic areas revealed significant decreases in the number of neurons per unit area in the ventral medial and arcuate nuclei. These data suggest that altered neuron numbers in the VMW and perhaps the ARC may participate in the well documented reductions in endocrine and neuroendocrine function observed in aging rats.