摘要:

AbstractThe formation of multivesicular and lamellar bodies, organelles characteristic of arthropod photoreceptor cells, is shown in the mosquito eye to be dependent upon light. The organelles are nearly absent from light deprived eyes; they form in large numbers when such eyes are first illuminated. Multivesicular bodies form adjacent to the rhabdomere, then move proximally into the body of the cell, ultimately being transformed into lamellar and probably dense bodies. Experiments in which ferritin was injected into the hemolymph of the head confirmed the hypothesis that the coated vesicles of the rhabdomere are pinocytotic vesicles. Ferritin taken into the cell by rhabdomeric vesicles is sequestered in multivesicular bodies.

ISSN:0022-104X    

DOI:10.1002/jez.1401690302

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

年代:1968

数据来源: WILEY

摘要:

AbstractLow doses of l‐thyroxin promote feather regeneration and lead to significant reduction in the mean weight of the gonad of adult normal and thyroidectomized Spotted Munia,Uroloncha punctulata, in the breeding phase. At moderately high doses of thyroxin complete molting occurs, and the mean weight of the gonoduct is also significantly reduced. The effect of l‐thyroxin increases as the duration of administration is increased. There is practically no difference between the response of normal and thyroidless birds.It is suggested that whereas the effects of l‐thyroxin on the plumage are by way of body metabolism, those on the gonad, gonoduct and body weight are due to a direct influence on the output of the gonad‐stimulating and growth‐promoting hormones from the adenoh

ISSN:0022-104X    

DOI:10.1002/jez.1401690303

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe newt,Triturus viridescens, shows a polymorphism for the genes controlling the synthesis of the enzyme lactate dehydrogenase (LDH). Homozygotes have either of two electrophoretically fast migrating bands. In heterozygotes, the isozymes present in both homozygote classes appear along with three additional isozymes of intermediate mobilities. An additional slowly migrating isozyme is found in all animals. The relationship between the three phenotypic distributions of isozymes in the population is consistent with the predicted phenotypic frequencies made in accordance with the Hardy‐Weinberg Law. No difference in the Km for pyruvate reduction or the thermal denaturation characteristics was noted between homogenates containing different isozyme distributions. The electrophoretically fast moving isozymes in all homogenates are inactivated at a higher temperature than the slowly migrating isozyme. The evolutionary significance of polymorphism for alleles controlling isozyme synthesis is discusse

ISSN:0022-104X    

DOI:10.1002/jez.1401690304

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe changes in fine structure of the growing female germ cell ofArbacia lixulaandParacentrotus lividuswere examined by light and electron microscopy. During the previtellogenic growth stage of the oocyte, when the ribosome population in the cytoplasm increases several thousand times, the nucleolus also increases considerably in volume. A large number of ribosome‐like granules are concentrated in these nucleoli. Although particularly during this stage a passage of “informative” material from the nucleus to the cytoplasm is to be expected, at present, evidence of any kind of extrusion has not been observed in these species. The only indirect morphological evidence for passage of material out of the nuclei might be the many newly formed pore complexes in the nuclear envelope. There is, however, strong evidence that they do not represent patent openings, since a dense, almost homogeneous, material is observed within the pore. Thus it is assumed that small molecules might pass through the pores freely, but not large particles the size of ribosomes.Dense aggregates of two different types have been observed in secondary oogonia and in oocytes at the growth stage: one shows densely packed fibrils of about 80 Å and the other granules of 300 to 400 Å.At the end of vitellogenesis, the major nucleolus becomes vacuolated and disappears. At the same time several minor “agranular” nucleoli are formed. At meiosis these too disappear. In the mature egg few “agranular” nucleoli are seen. During cleavage the several “agranular” nucleoli are fibrillar, without ribosome‐like granules. From the blastula stage on, at a time when the cell divisions stop almost completely, the one or two nucleoli which can be observed in each nucleus have a small number of granules. During the following development the number of granules increases gradually up to gastrula, whereas the number of fibrils becomes

ISSN:0022-104X    

DOI:10.1002/jez.1401690305

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

年代:1968

数据来源: WILEY

摘要:

AbstractExperiments are described in which the differentiative capacity of the posterior embryonic shield of the teleost,Fundulus heteroclitus, was investigated by means of deletion‐transplantation techniques.The posterior embryonic shield, removed from early gastrulae to immediate postgastrulae and grafted into the pericardial cavity of slightly older embryos, exhibits considerable growth and differentiates typical trunk and tail structures involving all germ layers.The donor embryos, in general, develop normal heads to pectoral fin regions. They lack all trunk structures except for gut and some gut derivatives. They frequently differentiate a very small “tail” with unpaired somites. The “tail” sometimes flattens and forms fin rays.Collateral experiments involving the deletion and grafting of various parts of the germ ring provide data in agreement with the conclusion that the posterior embryonic shield supplies the bulk of material for the formation of the trunk and tail in teleosts.The experiments are discussed from the standpoint of their elucidation of gastrulation, trunk and tail formation, embryonic regulation of defects, and endoderm formation in

ISSN:0022-104X    

DOI:10.1002/jez.1401690306

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe activities of 17β‐hydroxysteroid dehydrogenase and of some NADPH‐generating enzymes in the fetal mouse testis during the formation of the accessory reproductive glands indicate that Leydig cells synthesize androgens before gonadotropins are secreted. In the neonatal testis the seminiferous tubules grow rapidly and the relative volume of the intertubular tissues decreases. At the same time the absolute activity of 17βSDH also decreases but there is no evident loss of enzyme activity as the primary spermatocytes begin meiotic prophase. High levels of NADPH‐generating malic enzyme activity coincide with the onset of meiosis and the development of the spermatids, although the activity of 17βSDH remains constant. Both glucose‐6‐phosphate and isocitrate dehydrogenases, which can be activated by gonadotropin, show strong activity prior to spermiogenesis.Significantly increased activities of 17βSDH and the ME occur in 10‐day postpartum intact mice four hours after a single injection of 0.25 unit ICSH. Exogenous gonadotropin stimulates G6PDH and IDH activities during divisions of spermatogonia five days after birth. The pituitary‐Leydig cell axis is stabilized after the beginning of meiosis so exogenous ICSH has little effect on testicular enzymes during the remainder of the first wave of spermatogenesis. Dependence of Leydig cell activities on pituitary gonadotropin seems to occur during pachytene or the early stages of spermatid formation. Androgen synthesis in the murine testis may be associated with the NADPH‐generating ME and IDH as well as G6PDH which has been implicated in other st

ISSN:0022-104X    

DOI:10.1002/jez.1401690307

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

年代:1968

数据来源: WILEY

摘要:

AbstractMethods for the isolation of ribosomal RNA (rRNA) from three crustacean tissue have been devised. These include precipitation of rRNA from total RNA preparations with 1M sodium chloride, to remove both melanin and ATP, or solubilization in buffer containing EDTA, to chelate Mg++and Ca++which, when present, form alcohol‐insoluble complexes with ATP. By cosedimentation or gel electrophoresis with rRNA of known S20,w, the sedimentation constants of crab rRNA have been determined to be 28 S and 18 S. The base compositions of the 28 S and 18 S rRNA's have been determined. Muscle, midgut gland and epidermis have been found to have higher concentrations of rRNA in the premolt period than in the intermolt period, with the maxima corresponding to the periods of maximum protein synthesis. Premolt epidermis has the highest rRNA content of the three tissue

ISSN:0022-104X    

DOI:10.1002/jez.1401690308

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe determination of the mesonephric kidney inTaricha torosainvolves both inductive and suppressive interactions between the kidney mesoderm and other embryonic tissues. The analysis of kidney determination was made by explanting the mesonephrogenic mesenchyme in epidermal vesicles either alone or in combination with the endoderm, notochord, neural tube, neural crest, lateral plate mesoderm, somite or nephric duct. It was found that the endoderm, notochord, early somite, and early lateral plate mesoderm are inductors of the mesonephros. Also, both premigratory and migratory neural crest cells, neural tube, older somite, and older lateral plate mesoderm were identified as suppressors of the development of the mesonephros.Most of the above interactions occur before the nephric duct makes contact with the mesonephrogenic mesenchyme. Too much emphasis has been placed on the nephric duct as beingtheinductor of the mesonephros. The mesonephric kidney is determined by late tailbud stages; a result of the inductive and suppressive interactions it has experienced.

ISSN:0022-104X    

DOI:10.1002/jez.1401690309

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

年代:1968

数据来源: WILEY

摘要:

AbstractLymphocystis, a virus caused, tumor producing disease of marine and fresh water fish was studied using various cytochemical methods for general proteins, histones, both classes of nucleic acids (DNA and RNA), and polysaccharides including mucopolysaccharides and acid mucopolysaccharides. Special interest is afforded the Feulgen‐positive cytoplasmic inclusions which accompany the virus infection of the cells, and concomitant increases in RNA and protein. Particular attention is given the chemistry and formation of the acid mucopolysaccharide capsule which develops around individual cells following viral infection. Possible significance of the capsule is discusse

ISSN:0022-104X    

DOI:10.1002/jez.1401690310

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe growth of White Leghorn tibiotarsi, measured as an increase in length, total protein and DNA content, is significantly lower when co‐cultured in the presence of 6.5‐7‐day Creeper tibiotarsi. The growth of White Leghorn tibiotarsi is not affected with increasing age of the Creeper donor. Quantitative measurements ofin situgrowth of Creeper and White Leghorn tibiotarsi were made for a comparison with thein vitroeffect. Creeper rudiments do not accumulate protein as fast as White Leghorn rudiments. Creeper rudiments show a lag phase in DNA accumulation up to the eighth day and then accumulate DNA at the same rate as White Leghorn rudiments. The evidence suggests that Creeper is acting primarily on protein metab

ISSN:0022-104X    

DOI:10.1002/jez.1401690311

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

年代:1968

数据来源: WILEY