Calcium-dependent interactions of F-actin filaments under the influence of troponin components.

The effect of three components of troponin (TN C, I, T) on the gelation of F-actin was investigated by measuring the increase in viscosity at a very low velocity gradient in a rotating viscometer. TN I or TN T greatly enhanced the generation of F-actin. The effect of TN I-C or T-C complex became Ca-dependent: in the absence of Ca, the complex increased the rate of viscosity rise of F-actin, but in its presence this enhancing effect was almost absent. For these actions, the presence of tropomyosin or heat treatment at 45 degrees was not required. These results can be explained in terms of strengthened interactions of F-actin particles bound with TN T or TN I and the release of TN I-C or TN T-C in the presence of Ca.     

Genetics of acheiropodia (the handless and footless families of Brazil). VII. Population dynamics.

Since carriers of the acheiropodia gene cannot be distinguished from noncarriers, parents and normal sibs of affected individuals have been used to estimate the fitness of heterozygotes. No significant difference in biologic fitness (viability and fertility) between normal sibs and the general population could be detected. A comparison between acheiropods and their normal sibs showed the following: (1) a nonsignificant difference in stillbirth rate; (2) a higher mortality rate of acheiropods in the first 5 years of life; (3) a relative viability not larger than .7; (4) a relative fertility no greater than .14, due to "cosmetic effects"; and (5) a fitness of .10 or lower. The total number of acheiropodia genes in Brazil has been calculated as 25,000 in the 1970s. The data are compatible with an extremely low mutation rate and a very stable locus. It is suggested that all Brazilian acheiropods can be traced to a single mutation. A conservative estimate of the number of acheiropods to appear in the future in Brazil is 14,000 with an extinction time of no less than 2,300 generations or almost 70,000 years. A variety of other parameters have been calculated.     

Selective degradation of altered tomato β-fructofuranosidase molecules by neutral protease

Evidence is presented for the selective breakdown of altered tomato β-fructofuranosidase molecules by a neutral protease from Bacillus subtilis.     

An intermediate state of G-actin between native and denatured: polymerization rate decreases but extent of polymerization remains unchanged

The rate of actin polymerization gradually decreased without changing the final level of polymerization, when incubated in the presence of 0.2 mM ATP at pH 8.0 and 25 degrees C. This change was much faster in Mg2+-actin than Ca2+-actin, and Mg2+-actin became denatured and unpolymerizable on prolonged incubation. The drop in the polymerization rate was due both to weakened nucleation and a slowed elongation rate in the incubated actin. The change in the polymerization rate was partially reversible by storing the sample at 0 degrees C. When the rate of polymerization dropped markedly on prolonged incubation, a gel filtration profile showed that Ca2+-actin existed as monomer not as oligomer. On the other hand, Mg2+-actin formed dimers, and other oligomers, as revealed by crosslinking analysis. There were changes in fluorescence intensities due to tyrosine and/or tryptophan residues of the actin molecule, and in difference absorption spectra, suggesting that conformational changes intermediate between native and denatured states occurred during incubation.     

Isolation and Characterization of a Filamentous Phage,Vf33, Specific for Vibrio parahaemolyticus

Phage Vf33, a filamentous phage about 1,400 nm long and 7 nm wide, specific for Vibrio parahaemolyticus, was isolated and characterized. The buoyant density of Vf33 in CsCl was 1.292 g/cm³. As with other filamentous phages, the lytic activity of Vf33 was resistant to heating below 80 C and to treatment with diethylether, acetone or methanol but sensitive to chloroform. The nucleic acid of this phage is single-stranded circular DNA 8.4 kb in size. The viral genome was converted to a double-stranded replicative form in the host cell. Among the strains tested, only V. parahaemolyticus strains possessing K38 antigen was sensitive to the phage.     

Plasma normetanephrine: A biochemical marker of sympathetic nerve function in man

The concentration of the catecholamines in plasma are regarded by many investigators as biochemical markers of sympathoadrenal activity in man. This study was designed to: 1) assess the relationship of normetanephrine (NMN), the metabolite of norepinephrine (NE) most likely to represent degration of newly synthesized and released “active” norepinephrine, to that of norepinephrine in plasma of normal volunteers and 2) to determine regional variations in plasma normetanephrine concentrations at venous and arterial sites of patients undergoing cardiac catherization. The findings suggest that 1) plasma normetanephrine reflects sympathoadrenal activity and neurotransmitter production at both peripheral neuronal and adrenal medullary sites and 2) there is net removal of normetanephrine by liver and kidney. Plasma normetanephrine should provide assistance in the biochemical assessment of sympathoadrenal tone in man and in patients with various autonomic disorders.     

Gamma-Actinin, a new regulatory protein from rabbit skeletal muscle. I. Purification and characterization.

A new regulatory protein which we have designated as gamma-actinin has been isolated from native thin filaments of rabbit skeletal muscle. Depolymerized native thin filaments were fractionated by salting out with ammonium sulfate, and the precipitates obtained at 40--60% ammonium sulfate saturation were further subjected to DEAE-Sephadex and Sephadex G-200 column chromatography. The purified gamma-actinin was shown to have a chain weight of 35,000 daltons and had a strong inhibitory action on the polymerization of G-actin. The results of amino acid analysis indicated a unique amino acid composition of gamma-actinin as compared with other structural proteins of muscle. Non-polar and neutral amino acid residues were abundant. One cysteine residue was contained per one molecule of gamma-actinin and played a critical role in the maintenance of the inhibitory activity. Pelleting of gamma-actinin with F-actin showed that gamma-actinin binds to F-action.     

Some observations on the fine structure of the mantis shrimp heart

Summary The electron microscopic structure of the myocardium of the mantis shrimp is descriped. Particular attention is paid to the organization of the nerve terminal and the sarcotubular system. The general appearance of this myocardium is characterized by deep invagination of the plasma membrane at the level of Z-band and large irregular shaped mitochondria. It possesses a very well developed sarcotubular system, consisting of the longitudinal system and two transverse elements making two sets of contact to each other. One forms dyad and the other forms triad at the level of M- and Z-band, respectively. The organization of the myoneural junction in this muscle is very simple and undifferentiated. In general, a special structural differentiation is invariably observed at both sides of the contact area. In spite of the fact that synaptic vesicles and a differentiated membrane are found at the naked process of this cardiac nerve, specialization such as subsynaptic fold formation has not been observed at the muscle side which is in contact with the nerve process. Observations made on the sarcotubular system and the nerve termination have been discussed with reference to their physiological significance. This investigation was supported by the Public Health Service Research Grants HE 06968-04 and NB 03348-04 of the National Institutes of Health, Bethesda, and the U. S. Department of the Army through its Far East Research Office.