Preparation of membrane vesicles from isolated myelin: studies on functional and structural properties.

Myelin membranes purified from bovine brain are shown to form membrane vesicles when incubated in hypotonic buffer. Following restoration of isotonicity a resealing of the membrane occurs as judged by a significant decrease in 22Na+ permeability. Electron spin resonance measurements using stearic acid spin label I indicate a small decrease in membrane fluidity with increasing ionic strength between 50 and 80 mM NaCl. Iodination of myelin membrane vesicles by lactoperoxidase shows a four-fold increase in the amount of iodine incorporation into the myeline basic protein from 0--150 mM NaCl, while the iodination of the proteolipid protein remains essentially unaffected by the change in ionic strength. This dependence of the iodination of the myelin basic protein on the ionic strength can be explained by the electrostatic interactions of this protein with membrane lipids. In view of striking analogies with studies on model membranes correlating protein binding with membrane permeability changes, we suggest a similar structure-function relationship for the myelin basic protein.     

Seasonal fluctuations of food intake and bodyweight in the dormouse Glis glis (author's transl)]

Cycles of body weight lasting a few weeks occurred in dormice fed ad libitum, throughout the year with the same food. The pattern of the fluctuations suggests an oscillation between an upper and a lower limit. When the lower limit is reached, compensatory mechanisms acting on the food intake are induced which cause an increase in body weight to the upper one; when this upper limit is reached, other mechanisms cause the body weight to decrease to the lower one. Thus, body weight and variations in food intake may well be controlled by the difference between the body weight and the limit it will reach. In a warm environment (23-25 degrees C) these fluctuations are smaller than in the cold (5-6 degrees C). They are also smaller during summer than during winter in animals placed in natural climatic conditions. In summer, the body weight stays near the upper limit; in this season, as in the warm environment, the lower limit approaches the upper one. Thus, the main circannual variation of body weight regulation in dormice may be the elevation during summer of the lower body weight limit.     

Characterization of the cDNA coding for mouse prothrombin and localization of the gene on mouse chromosome 2

A series of overlapping cDNAs coding for mouse prothrombin (coagulation factor II) have been isolated and the composite DNA sequence has been determined. The complete prothrombin cDNA is 1,987 bp in length [excluding the poly(A) tail] and codes for 18 bp of 5' untranslated sequence, an open reading frame coding for 618 amino acids, a stop codon, and a 3' untranslated region of 112 bp followed by a poly(A) tail. The translated amino acid sequence predicts a molecular weight of 66,087, which includes 10 residues of gamma-carboxyglutamic acid. There are five potential N-linked glycosylation sites. Mouse prothrombin is 81.4% and 77.3% identical to the human and bovine proteins, respectively. Comparison of the cDNA coding for mouse prothrombin to the human and bovine cDNAs indicates 79.9% and 76.5% identity, respectively. Amino acid residues important for the structure and function of human prothrombin are conserved in the mouse and bovine proteins. In the adult mouse and rat, prothrombin is primarily synthesized in the liver, where is constitutes 0.07% of total mRNA as determined by solution hybridization analysis. The genetic locus for mouse prothrombin, Cf-2, has been mapped using an interspecies backcross and DNA fragment differences between the two species. The prothrombin locus lies on mouse chromosome 2, 1.8 +/- 1.3 map units proximal to the catalase locus. The gene order in this region is Cen-Acra-Cf-2-Cas-1-A-Tel. This localization extends the proximal boundary of the known region of homology between mouse chromosome 2 and human chromosome 11p from Cas-1 about 2 map units toward the centromere.     

Hormonally induced elevations of alpha- and beta-casein mRNA levels are blocked by cyclic adenine nucleotide and prostaglandins

Normal mammary gland development during pregnancy follows a coordinated program of morphological development (formation of lobuloalveoli) and biochemical differentiation (casein production). In culture, whole mammary glands of Balb/c mice can be similarly induced by application of a mixture of insulin, prolactin, aldosterone and hydrocortisone (IPAH) for 7 days. Our previous reports have shown that lobuloalveolar development, induced by IPAH, is competitively inhibited by the simultaneous presence of dibutyryl cyclic AMP (Bt2cAMP), prostaglandins (PGs) E1, E2, and B1, and papaverine (pap). However, if this mixture is not added until day 4, lobuloalveolar development is relatively unaffected but casein synthesis is repressed. This report explores the mechanism by which cyclic adenine nucleotides and prostaglandins interfere with the normal developmental pathway. The accumulation of alpha- and beta-casein mRNAs induced by prolactin, hydrocortisone and aldosterone is blocked by the combination of Bt2cAMP, PGs E1, E2, and B1, and pap added to the medium for the final 3 days (days 4-7). Under these conditions the glands retain their lobuloalveoli, and little squamous metaplasia can be discerned. Furthermore, de novo synthesis of both caseins is selectively inhibited, despite the continued presence of casein mRNAs in the glands and normal protein synthesis. In contrast, the synthesis of keratin is stimulated. Incomplete mixtures of Bt2cAMP and pap or the combination of PGs E1, E2, and B1, are only partly effective in preventing the accumulation of casein mRNAs. All three mixtures bring about similar effects on both alpha- and beta-casein mRNAs.(ABSTRACT TRUNCATED AT 250 WORDS)     

On the computation of in vivo transmural mean stress of patient-specific aortic wall

Biomechanics and Modeling in Mechanobiology - It is well known that residual deformations/stresses alter the mechanical behavior of arteries, e.g., the pressure–diameter curves. In an effort...     

Sociosexual behavioral patterns involving nulliparous female orangutans (Pongo sp.) reflect unique challenges during the adolescent period

The primate adolescent period is characterized by a series of changes in physiology, behavior, and social relationships. Orangutans have the slowest life history and the longest period of dependency of all primates. As members of a semisolitary species with high levels of sexual coercion, adolescent female orangutans face a unique combination of challenges when achieving independence from their mother. This study examined the mating behavior of adolescent female orangutans and compared it with that of adult females to assess whether mating behavior reflects distinct strategies at these different points in the life cycle. Data were collected in Gunung Palung National Park on the island of Borneo over 20 years. Mating events from adolescent (n = 19) and adult females (n = 26) were scored and compared. Adolescent female mating events had significantly higher mating scores (indicating more proceptivity) than those of adult females (β = 1.948, p = .001). Adolescent females also engaged in elaborate sociosexual interactions with different flanged males, behaviors that were never observed during mating events of adult females. These interactions involved characteristic behavior on the part of both the adolescent females and the flanged males. Given these findings and the documentation of similar accounts of adolescent female–flanged male mating from the island of Sumatra, we propose that adolescent female orangutans display distinctive behavioral repertoires throughout the genus Pongo which serves to overcome male ambivalence toward nulliparous females, establish familiarity, and evaluate coercive tendencies in flanged males. We suggest that these behavioral patterns are an integral part of female social development in a female philopatric, but highly dispersed species where consistent social support is absent after ranging independence is achieved.