摘要:

AbstractAngiogenesis is important to such processes as normal embryonic development and tissue growth, and is also a central feature of diseases such as diabetic retinopathy and the growth of solid tumors. Understanding the basic events governing angiogenesis has therefore attracted great interest. The ion channel blocking agent, amiloride, has been shown to inhibit angiogenesis in an in vivo model (Lansing et al., '91). This suggested a vital role for Na+‐coupled transport processes in angiogenesis. A large number of structural analogues of amiloride have been synthesized (Kleyman and Cragoe, '88), and many of these are well characterized with respect to biological activity. These analogues present an opportunity to dissect the process of angiogenesis and identify potentially important physiological events. In this report we describe the effects of amiloride on an in vitro model for angiogenesis employing vascularized tissue explants. Amiloride inhibits capillary morphogenesis completely and reversibly at concentrations as low as 134 μM. It appears to act by blocking endothelial cell proliferation, but not migration. Inhibition is heightened by the introduction of hydrophobic groups on the terminal guanidino nitrogen atom, or on the 5‐amino position. An analogue substituted at both of these positions is 30‐fold more potent than the parent compound. Of amiloride's known biological activities, these results most closely correlate with the inhibition of Ca2+transport processes, and thereby suggest an important role for Ca2+transport in capillary morphogenesis. © 1993 Wiley‐

ISSN:0022-104X    

DOI:10.1002/jez.1402670302

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

年代:1993

数据来源: WILEY

摘要:

AbstractEmbryonic cardiomyocytes can both beat and divide. They assemble cardiac musclespecific proteins into sarcomeric myofibrils and contract. In addition, they periodically synthesize DNA, complete mitosis, disassemble sarcomeric myofibrils in the area of the mitotic spindle, assemble cytoplasmic isoform‐specific proteins into a cleavage furrow contractile ring, undergo cytokinesis, and then reform sarcomeric myofibrils in daughter cells. Little is known about how embryonic cardiomyocytes disassemble their myofibrils as they traverse the cell cycle and divide. In the present study, beating embryonic avian ventricular cardiomyocytes in primary culture were stimulated to initiate DNA synthesis without subsequent mitosis or cytokinesis by infection with the lytic avian polyomavirus, Budgerigar Fledgling Disease Virus (BFDV). Within 48 hours, infected, adherent cardiomyocytes disassemble most of their sarcomeric myofibrils, retaining cardiac myosin only in thin myofibrils with disrupted sarcomeric periodicity and in amorphous nonfibrillar pools. By 72 hours, infected cardiomyocytes contain no myofibrils and no longer react with antibodies to cardiac myosin. In contrast, infected cardiomyocytes continue to display cytoplasmic myosin localized in stress‐fiber‐like‐structures in adherent cells, or in disrupted fibers and dispersed pools in detaching cells. Infected cardiomyocytes also continue to display interphase‐like arrays of polymerized microtubules, even when rounded‐up just prior to lysis. These results suggest that polyomavirus infection may provide a useful model system for further study of the regulation of myofibrils disassembly in embryonic cardiomyocytes. © 1993 Wil

ISSN:0022-104X    

DOI:10.1002/jez.1402670303

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe structural evolution of nervous tissues during the postembryonic development ofPieris brassicaehas already been described in same detail but the effects of diapause on this process have not been examined. In this report, we demonstrate that the nervous system of a diapausing insect is characterized by a typical pattern of morphogenesis, which includes the arrest of the differentiation of the brain and the ventral nerve cord. This arrest occurs at a specific phase of pupation (third day of diapause) and persists throughout diapause, being independent of the storage temperture. No sign of progressive adult differentiation, referred to in other insect species as “diapause development,” is apparent. Rapid breakdown of this arrest occurred when diapausing pupae were exposed to summer conditions after an initial 2 month period at 4°C. Resumption of the morphogenesis of the nervous system was evident within 4 to 5 days in most experimental batches, with resultant differentiation to the adult state. © 1993 Wiley‐Li

ISSN:0022-104X    

DOI:10.1002/jez.1402670304

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe steroid secretory activity of cultured ovarian follicles ofRana dybowskiiand the activities of relevant steroidogenic enzymes were examined during the natural hibernation period (October‐February). Enzyme activities were measured indirectly by monitoring the conversion of exogenous substrates to products by isolated follicles. Follicles were incubated for 6 h in amphibian Ringer in the presence or absence of frog pituitary homogenate (FPH, 0.1 pituitary/2 ml) and/or various steroid precursors. Progesterone (P4), 17α‐hydroxyprogesterone (17α‐OHP) or testosterone (T) secreted by the follicles into the medium were measured by RIA. In the presence of FPH, high levels of P4were produced by follicles at the early and mid‐hibernation period (695 and 898 pg/follicle, respectively) whereas markedly elevated levels of P4were produced during late hibernation (1,393 pg/follicle) (just prior to or breeding season, February). In contrast, high levels of T were produced by the follicles early in hibernation (1,206 pg/follicle) while negligible levels were produced in late hibernation (69 pg/follicle). Higher levels of 17α‐OHP were produced by follicles at early and mid hibernation (594 and 705 pg/follicle, respectively) than in later hibernation (221 pg/follicle). Addition of exogenous pregnenolone markedly increased P4levels in a dose‐dependent manner when added to follicles at early and late stages of hibernation: FPH addition further enhanced conversion of pregnenolone. Similarly, addition of androstenedione (AD) increased T levels in a dose‐dependent manner by these follicles. However, following addition of exogenous P4, less 17α‐OHP was produced by follicles collected in late hibernation as compared to those collected earlier. Likewise, addition of 17α‐OHP to follicles during late hibernation produced a small increase in T accumulation while a marked increase occurred when follicles were obtained in early hibernation. Taken together, the data indicate that steroidogenesis shifts from T to P4late in hibernation and this is probably due to decreases in 17α‐hydroxylase and C17, 20‐lyase activit

ISSN:0022-104X    

DOI:10.1002/jez.1402670305

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

年代:1993

数据来源: WILEY

摘要:

AbstractSerum concentrations of the steroid hormone corticosterone were monitored over a four‐year period in two male and two female immature captive whitetip reef sharks,Triaenodon obesus. Corticosterone concentrations in the serum ranged from 69–999 pg/ml (319.8 ± 31.9; n = 36) for males and 3–246 pg/ml (116.0 ± 15.1; n = 32) for females. Males had significantly higher values than females (P<0.001). No significant difference was detected between females; however, a significant difference was observed between the two males. No seasonality was observed in corticosterone levels. Corticosterone levels in elasmobranchs are only 10% the levels of the principal glucocorticoid, 1α‐hydroxycorticosterone, but the assay is inexpensive and readily available, and, once individual ranges are established, the corticosterone concentrations have utility. Our data suggest that, after these baseline levels are established for individual sharks, long‐term monitoring of serum corticosterone in captive populations may be utilized to monitor health or, conversely, stress. © 1993 Wi

ISSN:0022-104X    

DOI:10.1002/jez.1402670306

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

年代:1993

数据来源: WILEY

摘要:

AbstractFrom mid‐April to late November, i.e., during antler growth phase and main breeding season, a group of four (later three) male fallow deer was treated with increasing doses of the antiandrogen cyproterone acetate (CA). Throughout the treatment period, plasma testosterone levels of the bucks were either undetectable or only slightly above the detection limit of 0.1 ng/ml. In marked contrast to controls, testicular volumes and neck girths of the CA treated bucks were basal during the application period, proving the strong antigonadotropic effect of CA (testicular volume) and the absence of androgen action at the normal target organs (neck girths), respectively. Antler growth in the CA treated bucks occurred during the normal time span for fallow deer and the antlers produced were of species specific shape. From this it is concluded that in fallow deer, onset, duration, and termination of antler growth are independent of androgen action. Velvet shedding in the CA treated bucks however did not occur at the normal time (late August/early September), but was postponed until late December/early January, i.e., about 5 weeks after the termination of CA application. Activity of alkaline phosphatase in the experimental animals increased during the antler growth phase, but was markedly lower than in controls. Maximum body weight in the CA treated bucks was reached already in June, i.e., about 3 months prior to controls. Furthermore, the rut associated, drastic decline in body weight observed in controls did not occur in the experimental animals. © 1993 Wiley‐Liss,

ISSN:0022-104X    

DOI:10.1002/jez.1402670307

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

年代:1993

数据来源: WILEY

摘要:

AbstractCrinoids have remarkable regenerative capacities. After traumatic or self‐induced amputation they can replace one or several arms through a complex sequence of morphogenetic events which lead quickly to the complete reconstruction of the lost part. These phenomena are well known in their general aspects and a comprehensive description of arm regeneration was previously provided (Candia Carnevali et al., Recent Trends in Regeneration Research. Plenum Press, New York, '89). However, there is a considerable gap in knowledge of the early regenerative phases which are particularly significant for the following development. The aim of the present work is to describe and interpret the different aspects of these early stages of arm regeneration inAntedon mediterranea. According to our results the regenerative development ofAntedonarm seems to consist of an epimorphic process which essentially implies the involvement of proliferating undifferentiated cells. The early stages of this process can be distinguished in a first repair phase, which includes the overall 24 hr post‐amputation period and is characterized mainly by the processes of wound healing and tissue repair, and in a second regenerative phase, which includes the 24–72 hr post‐amputation period and is characterized by the first regenerative events. The different arm components involved in the amputation/regeneration phenomena seem to play different and specific roles in these initial phases. © 1993 Wiley

ISSN:0022-104X    

DOI:10.1002/jez.1402670308

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

年代:1993

数据来源: WILEY

摘要:

AbstractBy observing numerous living eggs from the lesser spotted dogfishScyliorhinus canicula(L.) caught near Roscoff (France) and reared at recorded temperatures as they developed from first cleavage to hatching, the first reasonably complete developmental table was worked out for this classical material in vertebrate embryology. The successive stages, described and numbered from 1 to 34, correct and replace the incomplete stages A–Q proposed by Balfour (J.Anat. Physiol.,10:555–576,1876) and other even less complete series later published, and is unique in the inclusion of a timetable at 16°C. The stages can be identified, usually through the cleared eggshell wall, with naked eye or low magnification. This table of normal stages ofScyliorhinuscan be adapted with slight modification to other chondrichthyan fishes. © 1993 Wiley‐Li

ISSN:0022-104X    

DOI:10.1002/jez.1402670309

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe two cell populations of the day 5 mouse blastocyst–the inner cell mass (ICM) and trophectoderm (TE)–were isolated by immunosurgery and TE biopsy. The uptake of glucose and pyruvate and the production of lactate were measured in the isolated cell populations and in single day 5 blastocysts, using a non‐invasive ultramicrofluorescence technique. The number of cells in isolated ICMs, TE vesicles, and intact blastocysts were counted after differential labeling with fluorochromes. The uptake of glucose and the formation of lactate were approximately three and five times greater, respectively, in the ICM cells compared with the TE cells. All the glucose consumed by the ICM could be accounted for by lactate formation, whereas the value for TE was 55%. The uptake of pyruvate was low in both cell types. The results are consistent with the proposition that the TE acts as a transporting epithelium, sparing nutrients for metabolism by the ICM. © 1993 Wiley‐L

ISSN:0022-104X    

DOI:10.1002/jez.1402670310

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

年代:1993

数据来源: WILEY

摘要:

AbstractTo examine the factors affecting the survival of refrigerated embryos, rabbit and mouse morulae were stored at 0°C in modified phosphate‐buffered saline (PB1) or in PB1 containing 0.75 M sucrose. Survival was defined as the ability to develop into an expanded blastocyst in culture. The data was analyzed with special reference to the presence of a mucin coat around the embryos. When rabbit morulae were stored in isotonic PB1 for 2, 4, 6, and 8 days, survival rates were 98%, 88%, 85%, and 50%, respectively. However, if the mucin coat had been removed before storage, the rates were lower (95%, 75%, 36%, and 3%, respectively). Sucrose impaired the survival of rabbit morulae irrespective of the presence of the mucin coat. Only 11% of mouse morulae survived 2 days of storage in PB1 medium, but if the medium contained sucrose, survival rates after storage for 2, 3, 4, and 5 days were higher (83%, 55%, 31%, and 7%, respectively). To provide them with a mucin coat around the zona pellucida, mouse embryos were incubated in a rabbit oviduct. Survival rates of these embryos after storage in the presence of sucrose did not decrease over 4 days of refrigeration (98–92%), and the rates after storage for 5, 6, and 7 days were 65%, 40%, and 30%, respectively; embryos that had been stored for 5 days were transferred to recipient mice, and live young were born. Agar embedding of mouse morulae did not have the same effect as the mucin coat. These results show that the rabbit embryo mucin coat can protect refrigerated embryos, but in mouse morulae, this effect was manifest only when sucrose was present in the storage medium. © 1993 Wiley‐Li

ISSN:0022-104X    

DOI:10.1002/jez.1402670311

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

年代:1993

数据来源: WILEY