摘要:

AbstractPeptide maps and amino acid composition of LDH crystallized from skeletal muscle extracts of brook trout (Salvelinus fontinalis) and lake trout (S. namaycush) are similar to those of the hybrid splake trout. The molecular weights are identical to mammalian LDH on the basis of sucrose density gradient centrifugation. The five A′–A isozymes are restricted to LDH from trout muscle and migrate very slowly toward the anode. The B′–B subunit series of isozymes are ubiquitous in trout tissues, although cell specific proportions of isozymes occur. While the A′–A subunit genes must be present in all trout cells, they are active only in the muscle where their products are responsible for essentially all of the LDH activity in this tissue.Isozyme patterns reveal that B subunit‐containing tetramers (less anodal) predominate in LDH from liver, whereas B′ subunit molecules (more anodal) prevail in LDH from trout heart. Therefore, extracts from heart, muscle, and liver tissues were utilized to characterize and compare the duplicated subunit tetramers of LDH in terms of several physico‐chemical and physiological parameters.Substrate kinetics show that trout B′ subunit tetramers are very sensitive to increases in pyruvate and lactate. These isozymes attain maximum initial velocity at about 0.8 μmole of pyruvate, while substrate inhibition begins at 7 μmoles. The B and the A′–A tetramers reach maximum initial velocity at 1.3 and 3.5 μmoles of pyruvate, respectively, and inhibition does not begin until substrate concentrations of about 20 μmoles are reached. Results are similar with lactate as substrate. Only the B′ tetramers exhibit substrate inhibition with lactate.An analysis of competitive pyruvate and oxamate inhibition reveals that the LDH active site(s) binds one molecule of inhibitor (or substrate).The inactivating temperature for trout B′ subunit tetramers is 70–75°C; for B subunit tetramers, 65–70°C; and for A′–A tetramers, 46–54°. The A′–A and the B subunit‐containing tetramers possess the generally lower thermal stability characteristic associated with LDH‐5 from most other animals, but thermolability is much more pronounced in the A′–A tetramers. Kinetics of the thermal inactivation process show that it is a first‐order, unimolecular event consistent with protein denaturation.Homologies of trout LDH isozymes with those of

ISSN:0022-104X    

DOI:10.1002/jez.1401740302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractSmall fragments of 0.1 mm3to 0.03 mm3, too small to regenerate the whole organism and yet containing a variety of tissues were taken from the prepharyngeal portion of a fresh‐water planaria,Dugesia dorotocephala. They were cultured in saline solution and histologically examined at intervals. Morphological rearrangement of tissues was completed in two days, coinciding with the time reported as necessary for the formation of an ordinary regeneration blastema. This was the result of the interactions of isotypically aggregating epidermis, gastrodermis and inner composite‐tissue, and involved neither dedifferentiation nor differentiation. The parenchyma accounted for most of the motility of the inner composite‐tissue layer. Furthermore, fixed parenchyma cells and neoblasts segregated in the portion of the parenchymal aggregate which was exposed to the saline solution, resulting in the aggregation of neoblasts in the periphery. This parenchymal segregation is considered due to differences in susceptibility to environmental conditions of these two parenchymal cells in addition to differences in motility and adhesiveness. The population of neoblasts thus aggregated was observed to increase by mitosis. A regeneration blastema appears to from by the local cellular segregation triggered by an injury under hypotonic conditions and not by the extensive migration of any particular cell type to the site of the wound. Less motile tissues, such as muscles and nerves, may account for the regional characteristics of the regeneration field. A possibility of involvement of the old tissues in the growth of a blastema and in its histogenesis is disc

ISSN:0022-104X    

DOI:10.1002/jez.1401740303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractResting membrane potentials were recorded from developing thing muscle cells of the chick at different stages from the third day of incubation. During the early stages the membrane potentials were lower than in the adult animal. No significant changes in potentials were observed until after the fifteenth day. There was a marked increase between the fifteenth and nineteenth days, and the membrane potential reached values comparable to those of the adult. In a study of the concomitant morphological development, the increase in membrane potentials was found to coincide with the transformation of the majority of the cells from myotubes to myocytes.

ISSN:0022-104X    

DOI:10.1002/jez.1401740304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractThe histology and ultrastructure of 48 hour renal transplants between unrelated canines was studied. Included in the investigation were eight normal, four autografted, and four allografted kidneys. The autografted organs showed no histological or ultrastructural changes when compared to normal contralateral controls. Light microscopy of the 48 hour allografts revealed extensive leukocytic infiltration and general cellular disruption with accumulations of lipid material and desquamated cytoplasm. Ultrastructural changes in glomeruli of allografted organs included thickening of the capillary basal lamina, enlargement and fusion of podocyte processes, accumulation of debris in the capillary lumens, and increase in blood platelets within the capillaries. Cells of both proximal and distal convoluted tubules showed mitochondrial swelling and disruption, cytoplasmic vacuolization, and accumulations of lipid material. Evidence of endothelial disruption in intertubular capillaries was observed. No changes were observed in the loops of Henle, collecting ducts or larger blood vessels. The results showed that tissue destruction reached an irreversible state by the 48 hour stage of allografting. The presence of plasma cells at this early stage implicated them in the rejection reaction.

ISSN:0022-104X    

DOI:10.1002/jez.1401740305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractA study was made of the ability of ammonium ions to stimulate active sodium extrusion in toad skeletal muscle. In sodium‐rich muscles, 15 mM ammonium induced a net loss of sodium against a concentration gradient slightly larger than 5 mM potassium. Similar results were obtained when a sodium efflux was considered. The activation curve of ammonium‐stimulated sodium efflux was strongly S‐shaped, reaching a plateau at 10–15 mM ammonium; this could be due to more than one activation site on the outside membrane, or to some cooperative effect of ions. The increment in the rate constant for sodium efflux produced by both ammonium and potassium was completely abolished by 10−4M ouabain. The extent of the inhibition by a submaximal dose of this glycoside was independent of the external ammonium concentration up to 30 mM. This behavior corresponds to a non‐competitive type of

ISSN:0022-104X    

DOI:10.1002/jez.1401740306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractThe effects of hibernation and 1, 2, 4, 8, 12, 16, and 20 weeks of cold‐exposure (5 ± 1° C) were studied on the testes of 100 adult, male hamsters (Mesocrietus auratus, Waterhouse), having initial body weights of 80 to 100 gm. Half of these animals were maintained on an eight‐hour photoperiod and half on a 14‐hour photoperiod. Control animals, at both photoperiods, were kept at 25 ± 1° C. At the time of autopsy, the wet weights of the testes were determined and the tissue was prepared for quantitative histological evaluation (diameter of the seminiferous tubules and spermatogenic activity). In animals kept at 25° C and 14 hours of light, the testes remained unchanged. With eight hours of light at the same temperature, however, the testes: (1) were unaffected for four weeks; (2) exhibited a 90% loss in wet weight at eight weeks; and (3) recovered to about 66% of the initial level at 12 and 20 weeks. In cold‐exposed hamsters, the testes decreased rapidly in activity between two to four weeks, reaching the lowest weight at eight weeks. Those cold‐exposed animals on 14 hours of light returned to the control level by 16 weeks, but those on eight hours showed only slight recovery. The testes of the 14‐hour light, cold‐exposed animals were larger than those of the eight‐hour light, cold‐exposed animals at each week tested. Only with the 14‐hour photoperiod were the testes of the hibernators significantly smaller than those of the cold

ISSN:0022-104X    

DOI:10.1002/jez.1401740307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractThe specific activities ofthreo‐Ds‐Isocitrate:NAD oxidoreductase (E.C.1.1.1.41; NAD‐ICDH) andthreo‐Ds‐Isocitrate:NADP oxidoreductase (E.C. 1.1.1.42; NADP‐ICDH) were measured in the brachial spinal cord of chick embryos ranging in development from 3.5 to 21 days' incubation. The activity of NAD‐ICDH increased gradually throughout the developmental period studied and appeared to be similar ontogenetically, with other enzymes of the citric acid cycle. The ontogenetic pattern of NADP‐ICDH, on the other hand, was quite different. The enzymatic activity increased rapidly from 3.5 to 7 days' incubation and then increased at a slower rate throughout the remainder of development. The temporal changes in activity of both enzymes are discussed in relation to other enzymes of intermediary carbohydrate metabolism and to the processes of neuroblastic growth and differentiation. The results of this study suggest that NADP‐ICDH is the major source of reduced NADP for the reductive syntheses associated with neuroblastic growth and differentiation whereas glucose‐6‐phosphate dehydrogenase and the pentose cycle provide the major source of NADPH during the preceding period of rapid proliferation and

ISSN:0022-104X    

DOI:10.1002/jez.1401740308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractThe radula protractor can be made to be spontaneously rhythmic, although it is normally a quiescent, phasic muscle, with apparently multi‐unit organization. Acetylcholine and potassium depolarize with contracture. Once a radula muscle has been put into a long‐lasting contracture by acetylcholine, tryptamine can repolarize it with accompanying relaxation. In the continued presence of acetylcholine and tryptamine, the repolarization and relaxation gradually taper off while membrane oscillation accompanied by mechanical rhythmicity develops. Contrariwise, if a radula protractor is in a potassium contracture, tryptamine will potentiate the contracture without affecting the level of membrane depolarization. Potentiation of potassium contracture, without changing potential level, can also be effected by increased calcium concentrations or by caffeine. After a muscle has been soaked in artificial sea water lacking calcium, its twitch tension, tetanic tension, potassium contracture, and acetylcholine contracture become directly dependent on external calcium concentrat

ISSN:0022-104X    

DOI:10.1002/jez.1401740309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractPrevious investigations have shown that through day 15 of incubation behavior of the chick was not influenced by sensory input. Behavior of chick embryos after this period has been reported to be controlled by integration of stimuli at centers located in different regions of the central nervous system. In this investigation experiments were designed to determine when sensory input of the vestibular system demonstrates an overt influence on the development of behavior and to determine how integration of stimuli at different levels of the CNS was affected by early extirpation of the otocysts.Unilateral and bilateral extirpations of the chick otocysts were made on day 3 or 4 of the incubation period. Embryonic motility was qualitatively and quantitatively monitored through 15 weeks post‐hatching. (Behavior of embryos was compared with unoperated controls and the ablated regions of the nervous system of experimentals were histologically compared with each other as well as with controls.)Primary losses of peripheral vestibular (inner ear) receptors and ganglia with little secondary degeneration of vestibular motor nuclei showed no influence on embryonic behavior until hatching. However, gross secondary degenerative changes of vestibular nuclei due to removal of the otocysts influenced behavior of the chick embryos around day 17. Presumably, the early acquisition of sensory capacity by the vestibular system does not influence the development of behavior until the end of the incubation period, but loss of interrelations between vestibular motor centers and other centers of the CNS influences behavior around day 1

ISSN:0022-104X    

DOI:10.1002/jez.1401740310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

ISSN:0022-104X    

DOI:10.1002/jez.1401740311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY