摘要:

AbstractSubsequent to incomplete surgical removal of the dorsal pancreatic rudiment ofRana pipiensembryos, islets of Langerhans arise in the pancreas, but in smaller amount than normal. Conpensatory hypertrophy of the beta cells occurs, and the islets are transformed from a larval into an adult histological type. Larval growth and metamorphosis is otherwise unaffected. The evidence supports the hypothesis that metamorphic maturation of the islets of Langerhans is a consequence of an increase in the functional demand on the islets of the frog as compared to the tadpole, and not to direct metamorphic effects of thyroxine. Possible causes for a relatively higher insulin requirement of the frog include (1) an increase in the carbohydrate load on the islets, (2) an increase in the secretion of hyperglycemic hormones, and (3) a higher rate of insulin inactivation.

ISSN:0022-104X    

DOI:10.1002/jez.1401580202

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

年代:1965

数据来源: WILEY

摘要:

AbstractMorphological, cytochemical and developmental studies were undertaken of the adipose cells present in third instar larvae and in adult females ofDrosophila melanogaster. The adipose cells of the adult type in the abdomens of recently emerged and seven‐day‐old adult females contain deposits of lipid and glycogen. Although the cells increase in size during this period, their nuclei do not. During the third instar the larval adipose cells and their nuclei undergo a five‐ and twofold increase in average cross‐sectional area, respectively. Deposits of lipid and glycogen are present throughout this period. Proteinaceous globules first appear in the middle of the third instar. They increase in diameter and number until just before pupation they comprise one fourth of the cytoplasm of the cells. In the young adult the surviving larval adipose cells and their nuclei have decreased in average cross‐sectional area by two and three times, respectively, from the late third instar values. The surviving larval adipose cells contain droplets of unsaturated lipids, protein globules, and deposits of glycogen which completely fill the remaining cytoplasmic area. By the third day of adult life these cells histolyze. When late second instar larvae are starved for three days, the average cross‐sectional area of their fat body cells decreases ten times. Despite the absence of glycogen and a huge decrease in lipid, protein globules form, and by the third day of starvation comprise one fourth of the cytoplasm. Transplantation experiments demonstrate that a hormone produced by the ring gland during the late third instar induces the formation of these prote

ISSN:0022-104X    

DOI:10.1002/jez.1401580203

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

年代:1965

数据来源: WILEY

摘要:

AbstractMyotis lucifugusfirst learned to catch mealworms mechanically projected into the air in a laboratory flight room, and were then trained to distinguish mealworms from small metal or plastic disks (3.0 × 12.5 mm and 0.5 × 6.3 mm). These three targets were presented singly in a semi‐random sequence, traveling along very similar trajectories. The most skillful bats caught 98% of the mealworms while avoiding any contact with 85 to 90% of the two types of disks. Echoes of 100–20 kc pulses (similar to the bats' orientation sounds) were measured from all three targets in almost all possible angular orientations. There was great overlap in intensity both in the peak amplitudes and in each of the ten 8 kc bands from 100–20 kc. These bats thus seem capable of some qualitative discrimination based on the “fine structure” of echoes from small mov

ISSN:0022-104X    

DOI:10.1002/jez.1401580204

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

年代:1965

数据来源: WILEY

摘要:

AbstractOogenesis in rabbits was investigated by examining the development of germ cells after birth. The transformation of oogonia to oocytes begins in the one day old animal. The appearance of the different stages of meiotic prophase was noted and their differential distribution in the germ cell population determined. The early stages of meiotic prophase develop within the first two weeks of life, however, they are transitory and have transformed into the “stationary” phase of prophase by the end of the third week of life, when all nuclei of oocytes are in diplotene.DNA synthesis in germ cells was studied with the aid of H3‐thymidine, which was injected into animals within the first ten days of life. The number of labeled germ cells varies with the age of the animal at the time of injection. Injection between the day of birth and the age of four days results in the labeling of 20 to 35% of the germ cells. After this age the labeling index falls, reaching 3% in the ten day old animal.The synthesis of the oocyte DNA takes place in the premeiotic interphase and may extend into the early phase of prophase, i.e. lept

ISSN:0022-104X    

DOI:10.1002/jez.1401580205

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

年代:1965

数据来源: WILEY

摘要:

AbstractDissociated monolayer cell cultures of chick embryonic spinal ganglia were set up on collagen‐coated coverslips and incubated in 5% CO2atmosphere at 38°C. Neurons were maintained in good condition for approximately three weeks and showed regeneration of nerve fibers as well as recovery from chromatolysis to normal Nissl pattern.Synthesis and transport of nucleic acids and protein in neurons and in spindle cells were studied with tritiated precursors by means of autoradiography.Less than 3% (10 of 318) of nerve cells from 12‐day‐old chick embryo spinal ganglia showed tritiated thymidine incorporation, whereas 27% (511 of 1880) of spindle cells from the same source incorporated tritiated thymidine. Thus, under our cultural conditions most neurons did not synthesize DNA.Both neurons and spindle cells incorporated tritiated uridine. Newly synthesized RNA appeared in the nucleus, and after several hours it was distributed over the perikaryon of neurons and the cytoplasm of spindle cells. The label was never found in nerve fibers, even after prolonged tritiated uridine treatment. A conclusion is thus made that RNA is absent in the nerve fibers.In neurons, protein was synthesized only in the perikaryon. Nerve fibers did not show protein synthesis. Newly synthesized protein was transported from perikaryon distally along nerve fibers at a rate of approximately 10 mm p

ISSN:0022-104X    

DOI:10.1002/jez.1401580206

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

年代:1965

数据来源: WILEY

摘要:

AbstractThein vitroprolactin‐secreting capacities of adenohypophyses ofColumba livia(pigeon) andNecturus maculosus(salamander) were compared with those of living and dead rat adenohypophyses over an eight‐day culture period. The living rat adenohypophysis produced prolactin at a constantly high rate. The dead rat tissue showed no evidence of active prolactin secretion. The secretion rate of prolactin by the pigeon adenohypophysis decreased rapidly with timein vitroand closely resembled the performance of dead rat adenohypophysis.Necturusadenohypophysis showed a slight initial decrease in prolactin secretion rate, which then plateaued at a constantly low level. The effects of acid extracts of cerebral and hypothalamic tissues ofAgelaius tricolor(blackbird) on prolactin secretionin vitrobyAgelaiusadenohypophysis were examined. The extract of cerebral tissue had no effect, but the hypothalamic extract increased prolactin secretion, indicating that the blackbird hypothalamus contains a stimulator of prolactin secretion. These results indicate that the neural mechanism which controls prolactin secretion inColumbaandAgelaiusis different from that which exists in rats and other laboratory mammals. No definite conclusions can be drawn regarding neural regulation of prolactin secretion inNectu

ISSN:0022-104X    

DOI:10.1002/jez.1401580207

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

年代:1965

数据来源: WILEY

摘要:

AbstractPrimordia of organs of the male reproductive system develop abnormally in response to near lethal temperatures when thermal pressure is applied at a time of cellular differentiation during embryogeny and postembryogeny. This paper is concerned primarily with the thermally induced imaginal deformities effected during embryogeny. All parts of the masculine system may be affected except the gonads. Part or all of the tract and accessory glands may be deleted by regulating the time and duration of exposure to critical temperatures. The critical period for the inhibition of development of the reproductive tract in the embryo occurs primarily during the fourth and fifth days of ontogeny. Morphogenesis of imaginal female organs was unaffected by excessive embryogenic temperatures in either genetic females or genetic males. Certain primordia of larval parts developed abnormally when embryos were subjected to temperatures somewhat above those permitting survival beyond the first larval instar.

ISSN:0022-104X    

DOI:10.1002/jez.1401580208

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

年代:1965

数据来源: WILEY

摘要:

AbstractTwenty‐three structurally related compounds were tested as choline substitutes in the diet ofD. melanogasterto determine the specificity of different structural groups in the growth action of the choline molecule. None of the substitutes completely replaced choline in the diet, indicating that the intact choline molecule is essential for maximal growth action. The single most important group is the hydroxyl group. It must be located terminally and on the 2‐carbon for the maximal growth effect. Three methyl groups are essential for maximal growth action, but they are not employed in transmethylation. The sulfur analogue is effective at low concentrations but is toxic at higher concentrations, indicating the importance of the nitrogen atom.A comparison of dietary requirements indicated that the choline requirements for the growth of Drosophila, the growth of Neurospora choline‐requiring mutants, perosis‐prevention in the chick, and fatty liver prevention in the rat have a basic similarity. It is suggested that choline is required as a phospholipid entity by all of these organisms.The insects differ in their abilities to utilize quaternary ammonium compounds which have carbon groups associated with the 2‐carbon.D. melanogastercan use carnitine, deoxycarnitine, and β‐methylcholine in place of choline, apparently converting deoxycarnitine to carnitine and carnitine in turn to β‐methylcholine. This contrasts with the specific carnitine requirement of the beetles of the family Tenebrionidae.D. melanogastercan also convert betaine alde

ISSN:0022-104X    

DOI:10.1002/jez.1401580209

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

年代:1965

数据来源: WILEY

摘要:

AbstractSheep eggs were obtained at appointed times from 4 to 16 hours after ovulation and examined for evidence of penetration by spermatozoa. The following observations were made: (1) The fertilizing spermatozoon makes a curved slit in the zona as a result of traversing it. The slit seems to be an open passage. (2) The sperm head of the ram has ventral‐dorsal asymmetry. The flat side of the sperm head always faces the vitellus as it passes through the zona. (3) A fine filament‐like structure was observed extending from the anterior tip of sperm heads embedded in the zona. (4) The site on the zona at which spermatozoa penetrate into the egg is ran

ISSN:0022-104X    

DOI:10.1002/jez.1401580210

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

年代:1965

数据来源: WILEY

摘要:

AbstractThe ontogeny of the enzyme LDH has been studied in two species of amphibians (Amblystoma gracileandRana aurora) as it provides a sensitive gauge of the state of differentiation of the organism, since the number and proportions of LDH isozymes present exhibit temporal and species specificity, thereby reflecting the degree of activity of the controlling genes. The presence of LDH in all stages of both species examined was establishd by assaying embryo homogenates for LDH activity, and the LDH was resolved into isozymic patterns by the methods of starch gels and disc electrophoresis. Specific enzyme activity for each developmental stage was correlated with the developmental events then occurring and the isozyme patterns obtained were discussed in terms of an increase in complexity during Anuran ontogeny while an extension of the current LDH isozyme hypothesis was advanced to account for some of the Urodele experimental findings.

ISSN:0022-104X    

DOI:10.1002/jez.1401580211

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

年代:1965

数据来源: WILEY