Transformation is an alternative to normal skeletal muscle development

The differentiation of skeletal muscle is characterized by cessation of proliferation and fusion of single myoblasts to form non-replicating multinucleate fibers (myotubes). If termination of proliferation is an obligate requirement for further differentiation, myoblasts defective in this stage of development should fail to fuse or exhibit any further characteristics of myotubes. Furthermore, myoblasts which have lost the ability to control and cease proliferation may represent a transformed, potentially tumorigenic population. Formation of the neoplastic state may therefore be viewed as an alternate path, antithetical to the normal differentiation of skeletal muscle. To test this hypothesis, we isolated 13 clones of non-fusing cells from the myogenic L₈ line of rat myoblasts. In contrast to the L₈ line, all of the non-fusing clones maintain their proliferative capacity, do not form myotubes, nor elevated creatine kinase activity nor increased myosin, but do develop into tumors when injected into athymic mice. L₈ cells do not produce tumors in these mice. Analysis of cell growth and serum requirements, plasminogen activator, hexose transport, adhesiveness, LETS protein and growth in soft agar, indicates that these non-fusing cells are transformed and clearly distinguished from the parent L₈ cells. Whereas the L₈ line maintains a near diploid complement of chromosomes, all non-fusing clones were polyploid. In addition, 12 of 13 non-fusing clones (but not the L₈ cells) express an endogenous type C virus. Although all clones defective in differentiation formed tumors, no single in vitro characteristic was found to be a constant index of this tumorigenic capacity. We conclude that cessation of proliferation is an obligate requirement for skeletal myogenesis, that transformation is an alternative to normal skeletal muscle development and that the phenotype of these transformed cells may be quite varied.     

Specificity in the recognition of crystals by antibodies

We show that IgG molecules isolated from the serum of rabbits injected with crystals of monosodium urate monohydrate, magnesium urate octahydrate and allopurinol, can each catalyze the nucleation of the same type of crystal to which they were exposed. These results generalize previous findings related to monosodium urate monohydrate and assess the idea that the invasion of a foreign crystal into an organism may amplify a population of antibodies which bear in their binding sites an imprint of the crystal surface structure. Such antibodies further act as nucleating templates which accelerate crystal formation in vitro. Antibodies from rabbitscan injected with sodium urate crystals do not cross-react or cross-react only to a low extent with antibodies isolated from rabbits injected with crystals of either magnesium urate or allopurinol. These results indicate a high specificity of the elicited antibodies, as these can distinguish between nuclei of crystals having similar molecular and structural characteristics.     

Psoriasis vulgaris and genetic markers

Summary In a sample of n=160 nonrelated male and female patients suffering from psoriasis vulgaris, blood, serum protein, and enzyme group typings have been carried out and compared with healthy controls from the same area (Rheinland-Pfalz). Marked statistically significant differences between patients and controls were found in none of the genetic blood polymorphisms considered here. However, combining previously published data from various authors with our own, significant associations between this skin disease and genetic polymorphisms such as MN, Gc, Gm(2), red cell acid phosphatase, and red cell phosphoglucomutase (PGM₁) were seen. The possible reasons for these associations are discussed.     

Serum depletion of corticosteroid binding activities,an early marker of human septic shock

We report that human sera within 24 hours after the onset of septic shock are virtually depleted of the corticosteroid binding activities characteristic for transcortin. By contrast, transcortin activities are not changed significantly in cases of acute inflammation, though septic shock and inflammatory sera are comparable in other respects: they show similar responses of their haptoglobin, thyroxine binding prealbumin, endogenous cortisol and progesterone levels. The physiological meaning and clinical interest of these results are discussed.     

Cell-to-cell channels with two independently regulated gates in series: Analysis of junctional conductance modulation by membrane potential,calcium, and pH

We study cell-to-cell channels, in cell pairs isolated from Chironomus salivary gland, by investigating the dependence of junctional conductance (gj) on membrane potentials (E1, E2), on Ca2+, and on H+, and we explore the interrelations among these dependencies; we use two separate voltage clamps to set the membrane potentials and to measure gj. We find gj to depend on membrane potentials whether or not a transjunctional potential is present. The pattern of gj dependence on membrane potentials suggests that each channel has two closure mechanisms (gates) in series. These gates pertain, respectively, to the two cell faces of the junction. By treating the steady-state gj as the resultant of two simultaneous but independent voltage-sensitive open/closed equilibria, one within each population of gates (i.e., one on either face of the junction), we develop a model to account for the steady-state gj vs. E relationship. Elevation of cytosolic Ca2+ or H+ at fixed E lowers gj, but at moderate concentrations of these ions this effect can be completely reversed by clamping to more negative E. Overall, the effect of a change in pCai or pHi takes the form of a parallel shift of the gj vs. E curve along the E axis, without change in slope. We conclude (1) that the patency of a cell-to-cell channel is determined by the states of patency of its two gates; (2) that the patency of the gates depends on membrane potentials (not on transjunctional potential), on pCai, and on pHi; (3) that pCai and pHi determine the position of the gj vs. E curve on the E axis; and (4) that neither Ca2+ nor H+ at moderate concentrations alters the voltage sensitivity of gj.     

Beta-globin gene cluster haplotype distribution in five Brazilian Indian tribes

Haplotypes derived from five polymorphic restriction sites in the beta-globin gene cluster were investigated in 139 individuals from five different Brazilian Indian tribes by the polymerase chain reaction (PCR). Eight haplotypes were identified. Haplotypes 2 (+????) and 6 (?++?+) were the most frequent and were common to all tribes. Their prevalences ranged from 60% to 93% and from 3% to 18%, respectively. Average heterozy-gosity measured by the Gini-Simpson index is markedly reduced among these Brazilian Indians when compared with Europeans (56%), but much less (8%) in relation to Asiatics, suggesting the absence of an important bottleneck effect in the early colonization of South America. The coefficient of gene differentiation (GST′) was estimated as 0.082 among six Brazilian Indian tribes, but when only three Tupi-Mondé-speaking tribes were considered, this estimate was reduced to 0.030. © 1995 Wiley-Liss, Inc.     

Hydrolysis of N'-benzoyl-d-arginine-p-nitroanilide by members of the Haloanaerobiaceae: additional evidence that Haloanaerobium praevalens is related to endospore-forming bacteria

Abstract Three out of the four described halophilic obligately anaerobic bacteria of the family Haloanaerobiaceae hydrolyze d -BAPA (N'-benzoyl- d -arginine-p-nitroanilide), while showing no or little l -BAPA hydrolyzing activity. This property was shown earlier to be characteristic only of non-halophilic Gram-positive endospore-forming bacteria of the genera Bacillus and Clostridium . These results suggest that Haloanaerobium praevalens , which has never been shown to produce endospores, but was shown to be related to the endosphere-forming representatives of the Haloanaerobiaceae on the basis of 16S rRNA nucleotide sequence data, shares other properties characteristics of the endospore-forming bacteria. Neither significant d -BAPA nor l -BAPA hydrolyzing activity was found in Sporohalobacter lortetii .     

Localization and Characterization of Nitric Oxide Synthase in the Rat Suprachiasmatic Nucleus: Evidence for a Nitrergic Plexus in the Biological Clock

Abstract: Behavioral and electrophysiological evidence indicates that the biological clock in the hypothalamic suprachiasmatic nuclei (SCN) can be reset at night through release of glutamate from the retinohypothalamic tract and subsequent activation of nitric oxide synthase (NOS). However, previous studies using NADPH-diaphorase staining or immunocytochemistry to localize NOS found either no or only a few positive cells in the SCN. By monitoring conversion of l -[³H]arginine to l -[³H]citrulline, this study demonstrates that extracts of SCN tissue exhibit NOS specific activity comparable to that of rat cerebellum. The enzymatic reaction requires the presence of NADPH and is Ca²⁺/calmodulin-dependent. To distinguish the neuronal isoform (nNOS; type I) from the endothelial isoform (type III), the enzyme activity was assayed over a range of pH values. The optimal pH for the reaction was 6.7, a characteristic value for nNOS. No difference in nNOS levels was seen between SCN collected in day versus night, either by western blot or by enzyme activity measurement. Confocal microscopy revealed for the first time a dense plexus of cell processes stained for nNOS. These data demonstrate that neuronal fibers within the rat SCN express abundant nNOS and that the level of the enzyme does not vary temporally. The distribution and quantity of nNOS support a prominent regulatory role for this nitrergic component in the SCN.