摘要:

AbstractFemale hamsters maintained in groups of 4 to 12 animals continue to show four‐day ovulatory cycles. However, when placed with males on the evening of proestrus, only 40% of these grouped females mate. Ninety‐five per cent of females caged singly or in groups of two, mate in less than ten minutes when placed with males on the evening of proestrus. Thus, grouping of female hamsters blocks reproduction in some individuals through a behavioral mechanism which does not apparently affect the ovulatory cycle. Receptivity cannot be reinitiated in such animals by administration of exogenous progesterone on the afternoon of proest

ISSN:0022-104X    

DOI:10.1002/jez.1401890102

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

年代:1974

数据来源: WILEY

摘要:

AbstractInjection of ergocornine into larval tiger salamanders (Ambystoma tigrinum) placed on a black background prevented the increase in melanophore index observed in saline‐injected controls. Larvae pre‐adapted to a black background showed a significant drop in their melanophores indices which persisted for up to 11 days following a single injection of 25 μg ergocornine (2.5 μg/g body weight). Dark‐adapted, ergocornine‐treated larvae with melanin concentrated in the melanophores responded to a single injection of 20 μg mammalian ACTH with rapid and complete dispersion of melanin within the melanophores. The same larvae did not respond similarly to a single injection of 25 μg ovine prolactin. These results support the hypothesis that ergocornine blocked the secretion of pituitary MSH inAmbysto

ISSN:0022-104X    

DOI:10.1002/jez.1401890103

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

年代:1974

数据来源: WILEY

摘要:

AbstractRemoval of an abdominal ganglion or a segment of a connective of the ventral nerve cord in crayfish (Procambarus simulans) resulted in little regenerative outgrowth from cut ends of CNS axons and no replacement of ablated cell bodies, even after 9–12 months. A few small‐diameter interneurons, but no giant axons, showed physiological and/or morphological evidence for regeneration across the lesion site. No behavioral, physiological or morphological evidence for degeneration of severed axonal segments of any interneuron (except for a few damaged segments of the septate lateral giant axons) was seen 2–3 weeks after lesioning and survival of isolated segments of medial giant axons was associated with hypertrophy of their glial‐connective tissue sheaths. Very little morphological degeneration of severed CNS interneurons was seen even 9–12 months after lesioning, except for isolated distal stumps of medial giant axons.Physiological evidence for degenerative changes was obtained after 9–12 months for CNS synapses posterior to the lesion site in that these synapses rapidly fatigued with repeated stimulation whereas synapses anteror to the lesion continued to function normally. This difference in synaptic efficacy might be explained by an interruption of a rostral‐caudal transport of axoplasmic proteins in these ventral nerve cords (Fernandez et al., '70, '71). A rostral‐caudal flow of trophic substances might also account for the 9–12 month survival of some anterior segments of lateral giant axons which were disconnected from their original cell bodies but which remained in contact with rostral cell bodies via

ISSN:0022-104X    

DOI:10.1002/jez.1401890104

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

年代:1974

数据来源: WILEY

摘要:

AbstractAntibody prepared in rabbits against saline extracts of hamster ovary forms a precipitate on the zona pellucida surface of oviducal eggs and immature oocytes of adult and prepubertal females. The precipitate appears in a net‐like arrangement on the outer surface only and reflects the heterogeneity of the zona. The antibody diffuses through the cumulus cells of oviducal eggs but not the cumulus cells of ovarian oocytes. Trypsin digests the inner nonprecipitated portion of the antibody treated zona but not the outer precipitated region.An important role for the zona antigen in sperm to zona attachment and in zona penetration is indicated by: (a) the failure of sperm to attach to the zona pellucida surface following treatment of eggs with antibody; (b) the polarity of the distribution of antigen in the zona; (c) the species‐specificity of the antigen; (d) the attachment of sperm to only the outer surface of zona ghosts; (e) and the concentration of the antigen at the surface of the sperm slits in the z

ISSN:0022-104X    

DOI:10.1002/jez.1401890105

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

年代:1974

数据来源: WILEY

摘要:

AbstractCorneal epithelium isolated with EDTA from 5–11 day old chick embryos was grown on a variety of substrata in organ culture to judge the effect of the substratum on the ability of the epithelium to produce a corneal stroma. When grown on the capsule of either living or frozen‐killed lens, the corneal epithelium synthesized and secreted a proline‐rich product (as judged by autoradiography) which was shown by electron microscopy to accumulate under and within the epithelium in the form of striated collagen fibrils, many of which were 250 Å in diameter and arranged at right angles to one another as in the normal corneal stroma. Basal lamina formed, but was not continuous under the epithelium. On EDTA‐treated frozen‐killed corneal stroma, new basal lamina formation was difficult to detect because of the persistence of the old basal lamina on the stroma. When this old basal lamina was digested by trypsin, the remaining corneal stroma failed to promote new basal lamina formation by the epithelium unless the stroma contained living fibroblasts. When grown on rat tendon collagen gels, epithelia produced a proline‐rich product which seemed to polymerize in the gel instead of forming a cornea‐like stroma. Millipore filter failed to elicit any basal lamina or collagen fibril formation. The data presented in this paper are consistent with the hypothesis that juxtaepithelial extracellular matrix may provide cell surface‐stabilizing factors which promote corneal epithelial

ISSN:0022-104X    

DOI:10.1002/jez.1401890106

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe origin of the dental lamina (DL) in the regenerating lower jaws of seven species of larval and adult urodeles was examined by various transverse amputation procedures.Collectively the results indicate that jaw and DL regeneration following experimental amputation is a widespread phenomenon in urodeles. In 1/4 and 1/2 amputated jaws of larvae (DL present in the stump), the dental epithelium was replaced from both the anterior and posterior ends of the regenerate area, while in adults it was replaced from the posterior stump tissues only. In 1/4 and 1/2 jaw removals (no DL present in the stump), larval forms exhibited a posterior regrowth of the DL, while in adults DL accumulated at the edge of the regenerate area, resulting in 1/4 and 1/2 edentulous jaws. Removal of all DL in both stumps in larval and adult forms resulted in completely edentulous jaws.The DL does not arisede novoduring regeneration, nor is it a direct outgrowth of the DL in the stump. Serial sections made in various planes of the area of the regenerating tip of the DL indicated that DL formation in the regenerate is an epithelio‐mesenchymal interaction caused by the inductive influence of remnant DL in the stump on the adjacent regenerating oral epithelium, resulting in a chain of proliferating and invading cells developing serially and sequentially through time. The mechanism involved in the inductive event remains undetermine

ISSN:0022-104X    

DOI:10.1002/jez.1401890107

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

年代:1974

数据来源: WILEY

摘要:

AbstractIn the crayfish, eyestalk extirpation produced noticeable blood dilution within three to four hours when maintained in tap water. Microscopic examination of kidney labyrinth cells following this treatment revealed an increase in the width and number of intercellular spaces and a decreased cell volume. Conversely, exposure of the intact animal to 50% sea water for the same interval concentrated the blood, and intercellular spaces and cell volumes did not change. Finally, with both treatments together (i.e., eyestalk extirpation and immersion in 50% sea water), blood became concentrated, but intercellular spaces increased in width and cells shrunk, as occurred with eyestalk extirpation alone. Effects of these whole‐animal treatments on mitochondria, intracellular compartments and basal invaginations among labyrinth cells are also noted. The findings suggest two conclusions. First, it is proposed that the dilation of intercellular spaces is due to an efflux of fluid from the cells into the lateral compartments. Such movements may be part of a mechanism effecting isotonic transepithelial fluid flow from lumen to blood as demonstrated in other systems. Second, since eyestalk extirpation is known to induce hormonal conditions simulating ecdysis, and since the morphological changes in the labyrinth following extirpation occur whether the blood has become diluted or concentrated, it is suggested that solute reabsorption by the crayfish kidney is under direct hormonal control. Such a mechanism could be especially useful during molt‐induced water uptake to enhance reabsorption of solutes and prevent loss of fl

ISSN:0022-104X    

DOI:10.1002/jez.1401890108

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

年代:1974

数据来源: WILEY

摘要:

AbstractThis study was designed to determine the effect of denervation on RNA and protein precursor incorporation into polyribosomes of nerve‐independent regenerates of the adult newt,Notophthalmus viridescens.The three stages of regeneration chosen for experimentation were the late paddle‐early digit stage (day 21), the 2–3 digit stage (day 28) and the 3–4 digit stage (day 35). Right forelimbs were denervated two days prior to polyribosome extraction while left forelimbs served as controls. To measure precursor incorporation, each newt was given either (1) H3‐uridine (six hours), (2) Na3P32O4(90 minutes), or (3) H3‐amino acids (60 minutes). Following incorporation, regenerates were prepared for examination of either polysome profiles or polysomal RNA profiles. A technique was used which yielded undegraded, non‐membrane bound polyribosomes relatively uncontaminated by labeled cosedimenting material. It was found that denervation reduced the incorporation of RNA precursors into both ribosomal and putative messenger RNA of polyribosomes of all three stages examined. Of the three stages tested, the 35 day stage was least affected by denervation. Amino acid incorporation into polysomal nascent peptides of regenerates was also adver

ISSN:0022-104X    

DOI:10.1002/jez.1401890109

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

年代:1974

数据来源: WILEY

摘要:

AbstractKinetochores are demonstrated for the first time in mitotic chromosomes that have been spread on a hypophase and selectively contrasted. The kinetochores have comparable characteristics to those seen in thin sections.

ISSN:0022-104X    

DOI:10.1002/jez.1401890110

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

年代:1974

数据来源: WILEY

摘要:

AbstractA procedure has been developed whereby cell proliferation during early embryogenesis of the monkey can be studied radioautographically following in vivo exposure to relatively small amounts of3H‐thymidin

ISSN:0022-104X    

DOI:10.1002/jez.1401890111

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

年代:1974

数据来源: WILEY