摘要:

AbstractAplysia brasilianais an osmoconforming mollusc; the osmolality of its extracellular fluid follows that of the external media. This investigation analyzes the volume changes of isolated neuron bodies exposed to hypotonic shocks. The abdominal ganglion was isolated, and the volumes of neuron bodies as well as intracellular K+concentration were measured. Hypotonic shocks induce a rapid swelling followed by a slower restoration of cell volume. The regulatory volume decrease (RVD) restores cell volume to its control value. Ba2+slows RVD without blocking it. Furosemide (in the μM range) completely and reversibly blocks the regulatory volume decrease. On return to isotonic solution after RVD, cell shrinkage was only detected when furosemide was present. It is concluded that neuron bodies ofA. brasilianadisplay efficient processes for volume regulation, based on a conductive pathway and a furosemide‐sensitive transport mechanism, which is probably the Na‐2Cl‐K cotransporter. A model simulation provides additional support to this hypothesis. © 1995 Wiley‐

ISSN:0022-104X    

DOI:10.1002/jez.1402720502

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

年代:1995

数据来源: WILEY

摘要:

AbstractPopulations of cells ofParamecium bursariaexposed to a light‐dark cycle (LD; 12:12 hr) show mating reactivity during the light period but not during the dark period. After transfer to constant light (LL) or constant darkness (DD), they continue to show a circadian rhythm of mating reactivity. When cells in the non‐reactive phase of DD were exposed to light pulse (from 5 sec to 6 hr in duration), they expressed mating ability 1.5 hr after the light pulse. Three wavelengths (416 nm, 547 nm, 626 nm) of light (5‐sec pulse) were most effective for inducing the mating ability. Light pulses of more than 2 hr were sufficient to shift the phase of the circadian mating rhythm in DD, but phase shifts did not occur after light pulses of less than 1 hr. We obtained a phase response curve (PRC) for light pulses of 6‐hr duration.To investigate the intracellular light‐transduction pathway, we examined whether inositol triphosphate (IP3) could induce the mating activity in DD. Cells in the non‐reactive phase of DD were injected with 10 pl of a solution of IP3(120 μM) under dim green light (480 nm, 8 μW/cm2) which did not induce mating ability. The cells begin to show mating activity 30 min after the injection and the extent of the activity was greater than that obtained by exposing cells to a 3 hr light pulse. However, injection of IP3did not cause phase shifting in DD. Thus, circadian clock appeared not to be influenced by the injection of IP3. © 1995 W

ISSN:0022-104X    

DOI:10.1002/jez.1402720503

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

年代:1995

数据来源: WILEY

摘要:

AbstractIn a previous study we showed that formation of deer pedicle and first antler proceeded through four ossification pattern change stages: intramembranous, transition, pedicle endochondral, and antler endochondral. In the present study antlerogenic tissues (antlerogenic periosteum, apical periosteum/perichondrium, and apical perichondria of pedicle and antler) taken from four developmental stages were cultivated in diffusion chambers in vivo as autografts for 42–68 days. The results showed that all the cultivated tissues without exception formed trabecular bone de novo, irrespective of whether they were forming osseous, osseocartilaginous, or cartilaginous tissue at the time of initial implant surgery; in two cases in the apical perichondria from antler group, avascularized cartilage also formed. Therefore, the antlerogenic cells, like the progenitor cells of somatic secondary type cartilage, have a tendency to differentiate into osteoblasts and then form trabecular bone. Consequently, the differentiation pathway whereby antlerogenic cells change from forming osteoblasts to forming chondroblasts during pedicle formation is caused by extrinsic factors. Both oxygen tension and mechanical pressure are postulated to be the factors that cause this alteration of the differentiation pathway. © 1995 Wiley‐Liss,

ISSN:0022-104X    

DOI:10.1002/jez.1402720504

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe various somatic cell layers (surface epithelium, theca, and follicle cells) that envelope the amphibian oocyte were removed one by one. The various follicular preparations thus obtained were tested for their ability to undergo germinal vesicle breakdown (GVBD) in the presence or absence of progesterone during different seasonal periods. Intact follicles, follicles without epithelium, or defolliculated oocytes (without epithelium and theca layers) did not undergo GVBD when cultured in Ringer solution, unless progesterone was added to the culture medium. In contrast, denuded oocytes (lacking all follicular layers) cultured in a medium with no hormones underwent GVBD in percentages similar to those of denuded oocytes incubated with progesterone. This ability of denuded oocytes to undergo spontaneous maturation was found to be related to the respiratory activity of the oocyte, which is in turn a seasonal variable inBufo arenarum. The different respiratory activity of the full‐grown oocyte according to the seasonal period was expressed by the respiratory control quotient (around 1.0 during winter and 4.0 during summer). In fact, only those oocytes with a respiratory control quotient over 2.0 were able to undergo spontaneous nuclear maturation. The maturation obtained without exogenous hormonal stimulus was genuine as indicated by the ability of these oocytes to induce pronuclear formation after sperm injection. © 1995 Wiley‐Liss,

ISSN:0022-104X    

DOI:10.1002/jez.1402720505

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

年代:1995

数据来源: WILEY

摘要:

AbstractOur previous studies showed that mammalian follicle‐stimulating hormone (FSH) stimulated the proliferation and differentiation of secondary spermatogonia into primary spermatocytes in organ culture of testes fragments fromCynops pyrrhogaster. To elucidate how FSH stimulates spermatogonial proliferation, we studied the interaction of spermatogonia with somatic cells in the presence or absence of FSH in cultures of aggregated cells derived from fractionated cell populations.When spermatogonia or those with somatic cells were cultured, they formed aggregates with themselves or with somatic cells, respectively. Most of the somatic cells in the aggregates were Sertoli cells, judged by the lipid droplets in their cytoplasm.[3H]thymidine incorporation into aggregates and autoradiography demonstrated spermatogonial proliferation that was enhanced in the presence of FSH and somatic cells (most probably Sertoli cells), but not in the absence of FSH or in the presence of luteinizing hormone (LH).To examine whether direct contact between spermatogonia and Sertoli cells is indispensable for the stimulation of spermatogonial proliferation by Sertoli cells, the two cell types were separated by a 0.4 μm pore filter in two compartments of a bicameral chamber. In this case, Sertoli cells did not stimulate spermatogonial proliferation in the presence of FSH, indicating that direct contact between spermatogonia and Sertoli cells is indispensable for the stimulation of spermatognial proliferation by Sertoli cells.Finally, Sertoli cells isolated from the testes from the primary spermatocyte stage did not stimulate spermatogonial proliferation in the presence of FSH. This result indicated that the function of Sertoli cells with respect to their stimulation of proliferation was stage‐specific. © 1995 Wiley‐Li

ISSN:0022-104X    

DOI:10.1002/jez.1402720506

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

年代:1995

数据来源: WILEY

摘要:

AbstractOur previous studies showed that mammalian follicle‐stimulating hormone (FSH) promoted the differentiation of primary spermatocytes into elongated spermatids in organ culture of testes fragments fromCynops pyrrhogaster. To elucidate the mechanism of FSH action, in this study the testes in the primary spermatocyte stage were dissociated and fractionated into germ and somatic cells, the latter comprising more than 80% Sertoli cells. Radioreceptor assays showed that FSH bound to somatic cells, very probably Sertoli cells, but not to germ cells. FSH elevated intracellular cyclic AMP levels in somatic but not germ cells.In cultures of cell aggregates somatic cells stimulated the differentiation of primary spermatocytes into round spermatids even in the absence of FSH, but to a greater extent in the presence of FSH. However, in the absence of somatic cells the extent of differentiation was similar, irrespective of the presence of FSH. Luteinizing hormone (LH) had no stimulatory effects. Most, if not all, of the somatic cells adherent to germ cells were Sertoli cells based on the criterion that they contained lipid droplets. This indicates that FSH stimulates the differentiation of primary spermatocytes via Sertoli cells.To examine if direct contact between Sertoli cells and germ cells is required for the promotion of differentiation, Sertoli and germ cells were cultured in two different compartments which were separated by a permeable membrane. Under these conditions Sertoli cells did not promote the differentiation of primary spermatocytes either in the absence or presence of FSH, indicating that direct contact between germ and Sertoli cells is required for Sertoli cells to promote the differentiation of primary spermatocytes. © 1995 Wiley‐Liss,

ISSN:0022-104X    

DOI:10.1002/jez.1402720507

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe proteins secreted by the male genital tract were analyzed in the seasonally breeding rodentOctodon degus. The protein patterns from the fluids collected from sexually active animals were compared with those from animals in resting period, with others which were previously castrated, and with castrated animals which received testosterone replacement treatment. Fluids from cauda epididymides (CE), seminal vesicles (SV) and prostate glands (PG) were collected, and analyzed by polyacrylamide gel electrophoresis followed by different staining methods and densitometry. Modifications were detected in the protein patterns of resting or castrated animals. In CE fluid, the decrease of one protein band (45 Kda) and the uprising of another (210 Kda) were recognized after castration. In animals during resting period the changes were not as marked as in castrated animals. SV secretion demonstrated a similar response to resting phase and castration, because Protein SVS I (200 Kda) decreased or were not observed when these conditions occurred. PG fluid proteins were also modified after castration. In general, the more severe changes in the protein spectrum were induced by castration, despite radioimmunoassay showing that testosterone fall is even higher in resting period animals than in those castrated. Testosterone replacement resulted in recovery of a protein profile which is very similar to that of sexually active males. Results suggest that the androgenic control of male tract secretions would be rather different in this seasonal hystrichomorph when compared to the regulation system described for myomorph rodents. © 1995 Wiley‐Liss, I

ISSN:0022-104X    

DOI:10.1002/jez.1402720508

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

年代:1995

数据来源: WILEY

摘要:

AbstractGonadal histology and plasma levels of sex steroids were investigated during the period of sex differentiation and the annual cycle of grey mullet,Mugil cephalus. Primordial germ cells were observed in the gonads of 3‐month‐old grey mullet and appeared to be undifferentiated in fish at 3 to 6 months of age. At 7 to 14 months of age 23.3% of the fish examined had differentiated into males and females whereas 70–90% of 15‐ to 17‐month‐old fish and more than 95% of 18‐ to 24‐month‐old fish had completed gonadal differentiation. Differentiation into females occurred earlier than males. In 15‐ to 17‐month‐old fish, spermatogonia and primary oocytes in the perinucleolus stage were observed in the testes and ovaries, respectively. Testes underwent intensive spermatogenesis at 18 to 24 months whereas ovaries during this period contained both primary and well developed vitellogenic oocytes. There was no sexual dimorphism in the annual cycle of plasma estradiol‐17β (E2), testosterone (T) and 17α‐hydroxyprogesterone (17α‐OH P) in 7‐to 24‐month‐old grey mullet. Plasma E2levels significantly decreased in 9‐ to 12‐month‐old presumptively female and male grey mullet. On the contrary, peak levels of plasma T were observed in both female and male grey mullet at 10 to 11 months. Plasma 17α‐OH P levels did not show significant profiles in the annual cycle of grey mullet. The data conclude that few gonads at 7 to 14 months begin to differentiate, but sex differentiation mainly occurs at the age of 15 months. It is 9 to 12 months of age when the decreases of plasma E2and increases of T levels significantly occur in both female and male

ISSN:0022-104X    

DOI:10.1002/jez.1402720509

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

年代:1995

数据来源: WILEY

摘要:

AbstractBlood volume in the hemoglobinless Antarctic icefishChionodraco hamatus(Channichthyidae) has been determined by the Evans blue dye dilution technique. A mean blood volume of 127.0 ± 5.0 ml kg−1body weight was found, a value even higher than that previously found in another icefish,Chaenocephalus aceratus(mean blood volume, 89.7 ml kg−1body weight; Hemmingsen and Douglas [1970] Comp. Biochem. Physiol.,33:733–744; Twelves [1972] Br. Antarct. Surv. Bull.37:85–92). This extraordinary hypervolemia appears unique among teleosts and may compensate for the absence of hemoglobin in the icefish. © 1995 Wiley

ISSN:0022-104X    

DOI:10.1002/jez.1402720510

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe honeybee (Apis mellifera) is likely to become the major model system for resolving the genetic basis of advanced perceptual and behavioural abilities of highly social insects because of the high level of knowledge regarding its physiology and social behaviour and its ease of handling. Here we report for the first time genetic transformation of honeybees by the production of chimeric larvae obtained by nuclear transplantation, identified by use of a genetic marker. Two chimeras expressed only the genotype of the donor indicating developmental totipotency of nuclei up to the 11th cleavage mitosis. © 1995 Wiley‐Liss, I

ISSN:0022-104X    

DOI:10.1002/jez.1402720511

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

年代:1995

数据来源: WILEY