摘要:

AbstractTestes from adultRana pipienswere maintained for five days in organ culture in a chemically defined medium consisting of CulturSTAT 199 organics dissolved in amphibian Ringer's solution. Various steroid hormones and vitamins, when added individually to testicular organ cultures, were found to be toxic. Toxicity of these substances was reduced or abolished by the simultaneous addition of protein hormones. Most combinations of protein hormones resulted in improved maintenance of cultured testes over that obtained in hormone‐free media. The combinations FSH + LH, and FSH + LH + insulin + testosterone, resulted in almost complete testicular maintenancein vitroand, in some circumstances, even stimulation of spermatogenesis. However, in no case were secondary spermatocytes maintained in these organ cultures, and spermatogenesis could be stimulated only through the first meiotic division.Testosterone, previously demonstratedin vivoto inhibit spermatogenesis at the secondary spermatogonial level, exerted no such inhibitory actionin vitro. At the dose level used, testosterone appeared to have a slightly deleterious, but nonspecific, effect on testicular maintenance.Seasonal variations in the sensitivity of the testis to hormones and other conditionsin vitrowere noted. Testicular maintenance was relatively poor, even in hormone‐supplemented media, during the period of active spermatogenesis (summer). In contrast, gonadotropin‐induced stimulation of spermatogenesisin vitrooccurred only in testes taken from winter frogs, at a time when the testicular epithelium is presumed to be maximally sensitive to gonadotropic a

ISSN:0022-104X    

DOI:10.1002/jez.1401620302

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe protein fractions of 7–18 day chick serum, allantoic and amniotic fluid and egg white were demonstrated by acrylamide gel electrophoresis.The similarity in protein fractions suggests that most of the amniotic fluid proteins are derived from egg white while serum contributes most of the allantoic fluid proteins.Several protein fractions which are unique to the respective fluids may be produced by components of the extraembryonic membranes.The nature of the proteins found in both serum and allantoic fluid suggests a selective transfer of protein between the two fluid

ISSN:0022-104X    

DOI:10.1002/jez.1401620303

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

年代:1966

数据来源: WILEY

摘要:

AbstractTwo experiments were conducted to test the influence of ambient light and the pineal gland on the pituitary‐thyroidal and pituitary‐gonadal axes of female golden hamsters. The results show that the thyroid glands of dark‐exposed [light:dark (LD) 1:23 in hours], goitrogen‐treated (1% aqueous thiourea as drinking fluid) animals hypertrophy less than those of similarly treated animals maintained in long daily periods of illumination (LD 16:18). Goitrogen‐induced thyroidal hypertrophy is accompanied by hypothyroidism. The hypertrophic response of the thyroid glands in either light cycle was not affected by removal of the pineal gland. Microscopically the thyroid glands of goitrogen‐treated animals kept in either long or short daily photoperiod exhibited changes normally associated with hypertrophy and concomitant hypofunction of the gland.The exposure of intact female hamsters to LD cycles of 1:23 caused a significant reduction in the weight of the uteri and adrenal glands within 35 days. Likewise, removal of the eyes led to atrophy of the same organs. Although darkness caused a variable change in ovarian weight, histological studies of ovaries from dark‐exposed and blinded animals suggested minimal hormonal output. The atrophic responses of the ovaries, uteri and adrenal glands were prevented by pinealectomy. These data suggest that darkness activates the pineal gland to secrete a substance(s) which modified pituitary‐target organ relationships.Hypothyroidism induced by the administration of thiourea to intact female hamsters in both long (LD 16:8) and short (LD 1:23) daily light cycles caused a reduction in weight of the ovaries, uteri and adrenal glands. With one exception, these responses were not altered by pineal removal. The uterine weights of the dark‐exposed hypothyroid animals that were pinealectomized were comparable to those of animals given fresh drinking water and maintained in LD cycles of 16:8 (normal controls). The relationship of the secretion of thyroid stimulating hormone to adrenocorticotrophic and gonadotrophic hormone release by the pitui

ISSN:0022-104X    

DOI:10.1002/jez.1401620304

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe effect of tetracycline on developing bones was explored in organotypic tissue culture. Such culture conditions proved to be suitable for certain experiments dealing with the “teratogenic” effect of drugs, and the first part of the paper examines the possibilities, limitations and fallacies of this technique.Embryonic mouse bones cultivatedin vitroshow rapid incorporation of tetracycline, and after 30 minutes of cultivation a definite fluorescence is seen. The drug is incorporated at least into two fractions: one which is rapidly released after the withdrawal of tetracycline and one which remains in the calcium‐containing zones of the bone.Tetracycline in concentrations of the order of 5 μg/ml completely inhibits the elongation of the calcified zone of the bone rudiments and the increase of their total calcium. However, experiments with labeled calcium still show an incorporation in the presence of tetracycline although no cumulative uptake is seen. The results thus indicate the existence of a rapidly incorporated calcium fraction which is independent of tetracycline.The inhibition of calcification is reversible up to some five days of treatment, whereafter a transfer to normal medium does not lead to a recovery, and the mineralization seems to be irreversibly blocked.It is concluded that the results speak in favor of the theory of a direct action of tetracycline on the formations of the bone salts, rather than interference with enzymatic activity dependent on divalent c

ISSN:0022-104X    

DOI:10.1002/jez.1401620305

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

年代:1966

数据来源: WILEY

摘要:

AbstractRecent modifications in the biochemical method for determining hydroxyproline have improved its accuracy. The increasing use of fibroblasts from chick embryos for production of collagen necessitates the reinvestigation of hydroxyproline production in chick embryos. The levels of proline and free and bound hydroxyproline were determined in embryonated hen eggs by the method of Prockop and Udenfriend. Determinations on the yolk, white, and embryo were done separately. Analysis of specimens taken from the onset of incubation to the thirteenth day of incubation revealed the presence of 20 to 80 μMoles of proline in each compartment throughout the period of study. Free hydroxyproline was present in the yolk and white at a constant low level of less than 1 μMole per egg. Hydroxyproline (total: bound and free) was first detected in five day embryos. By nine days the level was 0.5 μMoles; at 11 days, 1.5 μMoles, and at 13 days, 4.25 μMoles. The increase in hydroxyproline when calculated per milligram of wet weight of embryo approximated a straight

ISSN:0022-104X    

DOI:10.1002/jez.1401620306

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

年代:1966

数据来源: WILEY

摘要:

AbstractTail blastemas of larval anurans and urodeles were implanted into 106 lentectomized larval eyes to test claims that lenses develop from blastemas in an eye environment. None of these eyes regenerate a lens from the dorsal iris. Lentectomy was complete in all 35Amblystoma tigrinum, in 34 of 36Rana pipiensand 21 of 35Rana clamitanseyes.After complete lentectomy, blastema grafts formed spherical masses of mesenchyme cells sometimes enclosed in epithelial vesicles, but never associated with lens fibers. Lens fragments not removed were easily identified. They were usually fused with the blastema. Their appearance was the same from one to many days after implantation.Leg and tail blastemas were implanted into 64 completely lentectomized adultTriturus viridescenseyes which regenerate a lens from the dorsal iris. The grafts formed spherical compact groups of epithelial and mesenchyme cells, loose cultures of cells and fibers, or cartilage and muscle, but never lens fibers. One of 13 brain segments implanted into lentectomized newt eyes carried dorsal iris cells on its surface. They formed a small lens gving a false picture of blastema origin.From an analysis of the literature and of the results of these experiments it is concluded that the claims so far made for lens formation from blastema cells are an incorrect interpretation of a mere fusion of lens fragments and implanted tissues and that regenerating tissues of anurans and urodeles are not competent to form lens as has been claimed.

ISSN:0022-104X    

DOI:10.1002/jez.1401620307

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

年代:1966

数据来源: WILEY

摘要:

AbstractAfter total extirpation of the caudal neurosecretory system in the teleostTilapia mossambicaby ligature and removal of the caudal peduncle, a new system regenerates rapidly. The new neurosecretory cells differentiate from ependyma. A series of transitional stages between slightly modified ependymal cells and fully developed caudal neurosecretory neurons can be readily constructed. Immediately after the operation, the distal part of the remaining spinal cord undergoes degeneration, during which no traces of the caudal system can be found. Eleven days after the operation the first signs of the new system appear, and after three weeks a potentially functional, although much reduced, system has developed, the elements of which are detectable with the electron microscope. After 5–6 months, an extensive system has regenerated; however, the neurohemal area equivalent to the normal urophysis is contained within the spinal cord. There is strong cytologic evidence for a considerable release of elementary neurosecretory granules into the cerebrospinal fluid in the regenerating and regenerated system, possibly by several different mechanisms. Prominent tubular reticula occur in the distal (preterminal) parts of the neurosecretory axons, and the possibility of local axonal production of vesicles and granules is strongly supported. Signs of secretion into the central canal and of distal production of neurosecretory material are also present in normalTilapia, but both phenomena are much more strikingly demonstrated in regenerating system

ISSN:0022-104X    

DOI:10.1002/jez.1401620308

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

年代:1966

数据来源: WILEY

摘要:

Abstract1. The growth of a wild strain ofDrosophila melanogasterhas been studied from the time of hatching from the egg to the adult. Wet and dry weights, protein and protein fractions, lipids, RNA and DNA have been determined at successive intervals. 2. All estimates have been carried out on animals grown axenically on defined medium. The medium has been shown to permit growth which is as fast as on live yeast medium when the larvae can burrow freely. 3. Insoluble protein and chitin nitrogen reach a maximum of about 70% total nitrogen in the late pupa, at which time the soluble nitrogen reaches its lowest level. The amino acid fraction reaches a maximum in the early third instar. 4. The water content declines from 70–75% of the live weight at the end of the first instar, rises to a maximum during the second instar and declines sharply to about 66% at the prepupal stage. 5. Total lipids represent an increasing proportion of body weight during larval growth, increasing from about 6% in young larvae to about 15% at pupation. 6. The curve of RNA increase follows the dry weight and protein curves during larval life. The ratio of RNA to protein declines during the first two instars. 7. The increase in DNA content follows a path similar to that of RNA. The RNA/DNA ratio reaches a maximum 24 hours after hatching from the egg, declines to about half this value by 84 hours, and remains more or less constant thereafter. 8. The rates of increase of protein, RNA and DNA during successive periods of larval life show striking differences. For protein the rate is high and increasing until about 36 hours after which it declines rapidly during the rest of larval life. For both nucleic acids the rate of increase falls to a minimum in the early third instar, about the time of the critical size, then increases during proliferation of the imaginal discs and finally declines at the end of larval life. 8. The data are compared with evidence from other strains ofDrosophilaand from other species of insect. In the latter case, it appears that all theDiptera, so far examined, follow a similar trend in the increase of the nucleic acids during growth. 9. RNA synthesis has been followed during development from egg to adult with the aid of pulse‐labeling and sucrose gradient analysis. Developmental stages differ in the amount of rapidly labeled high molecular weight material which is most evident in newly hatched larvae and in mid‐third instar larvae, at times when the rate of synthesis of total RNA is

ISSN:0022-104X    

DOI:10.1002/jez.1401620309

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

年代:1966

数据来源: WILEY

摘要:

AbstractAn autoradiographic study of the pattern of DNA synthesis in Wolffian lens regeneration of adult newtTriturus viridescenswas carried out. Animals were injected with thymidine‐H3at different stages of lens regeneration, and killed after different time intervals ranging between 2 hours to 15 days. The temporal pattern of incorporation and localization of labeled cells was studied with autoradiograms.DNA synthesis, which is not detectable in the normal iris, is activated in the dorsal as well as in the ventral iris within five days after lens removal when the cells are still heavily pigmented. When the dorsal iris cells become depigmented, all depigmented cells show a high labeling frequency. Cessation of DNA synthesis is indicated immediately before the depigmented cells start to elongate and differentiate into fibers. At later stages of regeneration, when the regenerate is composed of fibers, lens epithelium, and stalk, DNA synthesis is limited to the latter two. It has been pointed out that cells synthesizing a detectable amount of gamma crystallins never synthesize DNA.The data suggest that all the cells which form the new lens pass through a period of DNA synthesis, which starts approximately five days following lens removal. However, not all cells which are activated to DNA synthesis participate in lens formation. Thus, DNA synthesis is a necessary but not sufficient condition for transformation of iris cells into the lens cell

ISSN:0022-104X    

DOI:10.1002/jez.1401620310

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

年代:1966

数据来源: WILEY

ISSN:0022-104X    

DOI:10.1002/jez.1401620301

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

年代:1966

数据来源: WILEY