Fiber types and some contractile properties of extensor digitorum longus and soleus muscles in different animal species

We studied the fiber types and contractile properties of the extensor digitorum longus (EDL) and soleus (SOL) muscles from young adult mice, rats and guinea pigs, and the correlation between these two parameters. Individual fibers in both muscles were classified as fast-twitch glycolytic (FG), fast-twitch oxidative glycolytic (FOG) or slow-twitch oxidative (SO) fibers according to Peter et al., and type II B, II A, or I fibers according to Brooke & Kaiser. Contractile properties were measured in situ at 37 degrees C. The isometric twitch contraction time (CT) and one-half relaxation time (1/2 RT) tended to be shortened in proportion to the area occupied by type II fibers, and type II B fibers. However, the differences between CT and fiber types were not always uniform among the three species. The CT of the rat EDL, in spite of its higher proportion of type II B fibers about 10% was the same as that of the guinea-pig EDL. The SOL of the mouse, composed of about 50% type I (SO) fibers, had a CT about as short as that of the EDL. In the case of the classification by Peter et al., the relationship between the percentage of subgroups of fast-twitch fibers and the CT or 1/2 RT, but not the resistance to fatigue, was not obvious. The resistance to fatigue tended to be enhanced in proportion to the area occupied by FOG in the EDL and by SO (type I) in the SOL. These results suggest that the contractile properties of individual fibers identified histochemically are distinct among animal species, producing interspecies differences in fiber types along with different contractile properties. However, it may be possible to compare the difference between fiber types and CT or 1/2 RT in the classification based on the pH lability of myosin ATPase, and also the difference between fiber types and resistance to fatigue in the classification based on the oxidative enzyme.     

Embryonic hemoglobins of different animal species

Summary The existence of embryonic hemoglobins is demonstrated in sheep-, calf and pig embryos. The occurrence and disappearance of these hemoglobins is quantitatively determined by cellulose acetate gel electrophoresis; hemoglobins as well as the globin chains, dissociated in 8 molar urea were quantitated. Sedimentation and diffusion experiments in the analytical ultracentrifuge revealed a S₂₀ of 4.3 and a D₂₀ of 6.6 for the examined hemoglobins. Therefore it is concluded that all hemoglobins occurring at different stages of embryonic and fetal development consist of 4 polypeptide chains with a total molecular weight of 66,000. The subsequent formation of the different polypeptide chains during ontogenesis is shown: At first only -chains are formed as demonstrated by the existence of Hb Gower I, consisting of four identical -chains. Subsequently the -chain appears, which leads to Hb Gower 2 (₂₂). The third polypeptide chain formed during the ontogenesis the -chain results finally in the appearance of HbF.In addition the existence of a HbF pig is demonstrated by the fingerprint technique.     

Immunogenicity of Trypanosoma cruzi in different animal species

The immunogenicity of two fractions (1 500 F and 10 000 F) from epimastigotes of Trypanosoma cruzi as well as the supernatant from culture media (SF) were studied using hens, rabbits and opossums. For comparative purposes, sera from individuals with chronic Chagas' disease were also used. A similar, positive response was obtained for the fractions in all the animal species studied using indirect hemagglutination test. Supernatants from culture media were the least immunogenic. By double immunodiffusion test, it was possible to detect a positive response to a different number as well as to different antigens in the three animal species, but there was response to a common antigen by all the different animal species. The common antigen called here major, was present in all the fractions assayed. Human sera from individuals chronically infected showed a variable response. When assayed by double immunodiffusion technique, the major antigen could be detected in just a few samples.     

Fluorescence polarization studies of different forms of angiotensin-converting enzyme

The interaction of three forms of bovine angiotensin-converting enzyme (ACE) with the competitive peptide inhibitor lisinopril with a fluorescent label was studied by the fluorescence polarization technique. The dissociation constants K _d of the enzyme-inhibitor complexes in 50 mM Hepes-buffer, pH 7.5, containing 150 mM NaCl and 1 M ZnCl₂ at 37°C were (2.3 ± 0.4)·10^–8, (2.1 ± 0.3)·10^–8, and (2.1 ± 0.2)·10^–8 M for two-domain somatic ACE, single-domain testicular ACE, and for the N-domain of the enzyme, respectively. The interaction of the enzyme with the inhibitor strongly depended on the presence of chloride in the medium, and the apparent dissociation constant of the ACE-chloride complex was (1.3 ± 0.2)·10^–3 M for the somatic enzyme. The dissociation kinetics of the complex of the inhibitor with somatic ACE did not fit the kinetics of a first-order reaction, but it was approximated by a model of simultaneous dissociation of two complexes with the dissociation rate constants (0.13 ± 0.01) sec^–1 and (0.026 ± 0.001) sec^–1 that were present at approximately equal initial concentrations. The dissociation kinetics of the single-domain ACE complexes with the inhibitor were apparently first-order, and the dissociation rate constants were similar: (0.055 ± 0.001) and (0.041 ± 0.001) sec^–1 for the N-domain and for testicular ACE, respectively.     

Fluorescence depolarization studies of melanosomal membranes from different sources

In the present paper we report a comparative study of physical properties and biochemical composition of isolated melanosomal membranes extracted from bovine eyes and from an equine spleen melanoma. Some biophysical characteristics of such membranes were obtained by steady-state and time resolved fluorescence spectroscopy using DPH as fluorescent probe. By these methods we have measured both static fluorescence polarization and fluorescence lifetimes and from the experimental data we have calculated the rotational correlation times by Perrin's equation. Since dynamic and static parameters, such as fluidity and molecular order, can be determined by these methods, the results are discussed on the basis of the recent theories of the role of the biochemical composition in the molecular structure and properties of membranes.