bluuebunny/crossref_metadata_2025_split huggingface dataset:
Roles of ectodermal and endodermal epithelial cells in hydra morphogenesis: Analysis of chimeras
Authors: Wanek Nancy 
Published: June 2005

AbstractChimeric hydra were constructed from ectoderm of one strain and endoderm of a morphologically different strain. Body size and budding rate were assayed in three pairs of ectoderm/endoderm chimeras, which were chosen on the basis of their differences in size and budding rates. Reciprocal chimeras of one parental pair were the same size as their endodermal parent, while chimeras of another pair were closer to the ectodermal parents in size. Chimeras of the third pair were similar to one another in size, and intermediate in size between the parental strains. The budding rates of the three reciprocal pairs were similar to their ectodermal parents. This suggests that ectoderm exerts more influence than endoderm on budding rate, while both ectoderm and endoderm are capable of influencing the size of a hydra. The morphology of these three pairs of reciprocal chimeras and of a fourth pair of chimeras constructed from normal H. attenuata and a mutant strain which produces multiple basal discs were compared to the parental morphologies. Both ectoderm and endoderm contribute to the morphology of the chimeric strains.
Origin of permanently altered epithelial cells of the vagina in neonatally estrogen‐treated mice
Authors: Mori Takao , Iguchi Taisen , Takasugi Noboru 
Published: June 2005

AbstractIn adult mice, neonatal injections of estrogen induce persistent, estrogen‐independent cornification of the vaginal epithelium. Since the occurrence of nodules composed of affected epithelial cells (B cells) is a prodromic phenomenon of the irreversible vaginal alterations, the relationship between the occurrence of B‐cell nodules and the time of DNA synthesis in the vaginal epithelial cells was examined by means of the techniques of serial mapping and autoradiography. B‐cell nodules appeared in the epithelium of mullerian vagina 3–5 days after the initiation of neonatal estrogen treatment, without spatial continuity to cuboidal epithelial cells of the sinus vagina. The time of DNA synthesis was different in B cells from that in both columnar mullerian and cuboidal sinus cells, suggesting that the mother cells of B cells.
Effect of an estrogen antagonist on development of blastocysts and implantation in the hamster
Authors: Sengupta Jayasree , Paria Bibhas C. , Manchanda S. K. 
Published: June 2005

AbstractCI 628 citrate, an estrogen antagonist, was given as a single intraluminal injection (5 μg) on day 3 to ovariectomized, progesterone‐treated hamsters. This significantly reduced embryo cleavage rate, transformation of morula into blastocyst, and completely inhibited implantation. The effects of the drug could be reversed by estradiol‐17B (1 μg) but not estradiol‐17α (1 μg) injected intraluminally with CI 628 citrate. Our finding suggests a role of estrogen present in hamster preimplantation embryo in the triggering of embryonic differentiation and implantation of the blastocyst.
Gene expression during mammalian spermatogenesis. II. Evidence for stage‐specific differences in mRNA populations
Authors: Gold Bert , Stern Leslie , Bradley Francis M. , Hecht Norman B. 
Published: June 2005

AbstractGene expression during murine spermatogenesis has been studied using highly enriched populations of cells obtained by velocity sedimentation at unit gravity and further purified by density gradient centrifugation through Percoll. Polypeptides whose synthesis was directed by total cytoplasmic RNA from round spermatids, pachytene spermatocytes, primitive type A spermatogonia, and Sertoli cells in cell‐free translation systems have been compared by two‐dimensional polyacrylamide gel electrophoresis, followed by fluorography. At the level of detection provided by the electrophoretic methods used, each population of cells contained mRNAs encoding over 200 polypeptides, many of wich were present in high abundance in all four cell types. However, for each cell type examined, a minimum of 5–10% of these polypeptides appear to be either specific to or greatly enriched within a particular cell type. Analysis of the polysomal and nonpolysomal cell fractions from pachytene spermatocytes and round spermatids revealed that the two compartments share many identical mRNAs but specific mRNAs are selectively compartmentalized between the cell fractions and between the two cell types. Movement between compartments was seen; e.g., some polypeptides encoded by mRNA found primarily in the nonpolysomal fraction of pachytene cells were later seen in the polysomal fraction from round spermatids. Virtually every other combination was also observed. These results suggest that the control of gene expression at the level of selective production of mRNA and selective utilization of mRNA are among the mechanisms involved in regulation of spermatogenic cell differentiation.
Videotape analysis of hamster ovulation in vitro
Authors: Talbot Prudence 
Published: June 2005

AbstractVideotape recordings were made of hamster follicles ovulating in vitro. These recordings were analyzed to characterize the morphological changes occurring in ovulating follicles and to time various events in the ovulation sequence. Before rupture, the shape of the follicle is transformed from a low to tall profile as shown previously (Martin and Talbot, '81). The complete transition from a low to tall profile required about 22.5 min. During the profile transition, the smooth muscle cells (SMC) in the base of the follicle contract (Martin and Talbot, '81), and the following events were observed. The base of the follicle moved apically. This pressed the cumulus and oocyte against the apical follicle wall, which appeared granular rather than smooth. The size of the antrum decreased presumably due to obliteration of the basal part of the antrum and movement of follicular fluid through the developing rupture site in the apex. The pressing of the cumulus against the apical wall appeared to cause final thinning and opening of the rupture site. The cumulus was extruded in two phases. Phase 1 was rapid (10–60 sec) and resulted in evacuation of about 25% of the cumulus and usually the oocyte from the antrum. Phase 2 required 2–10 min for completion and was accompanied by collapse of the follicle wall. After collapse, the cumulus remained with its follicle and could not be removed by pulling with Watchmaker's forceps. These observations provide new information on the role of SMC in hamster ovulation and characterize extrusion of the cumulus as a two‐phase event.
Nocturnal rhabdom cycling and retinal hemocyte functions in crayfish (Procambarus) compound eyes. I. Light microscopy
Authors: Piekos W. Barry , Waterman Talbot H. 
Published: June 2005

AbstractIn addition to the previously known photoreceptor membrane cycle coupled to light and dark adaptation, detailed study of the late‐night period (24:00 to 06:00 h) in Procambarus compound eyes demonstrates that a second cycle of degradation (about 14% decrease in maximum rhabdom diameter) and resynthesis takes place completely in the dark between midnight and dawn.Invasive granular hemocytes are present in the retina throughout the latenight period in winter. Their distribution around the retinulas during the degradative phase (24:00 to 02:00 h) of the turnover cycle differs significantly from that characteristic of both the synthetic (02:00 to 04:00 h) and resting (04:00 to 06:00 h) phases. This correlation provides an important way of identifying retinal areas in the process of net photoreceptor membrane degradation. Retinal hemocytes are highly significantly more numerous in the resting stage than in either of the other two.Certain associated changes differ between winter and summer series. Total hemocyte numbers in our winter experiments show a positive linear correlation with rhabdom diameters. In the summer series, retinal hemocytes are rare or absent, and rhabdom diameters are significantly smaller than in winter. No hemocytes are associated with the smallest (June) rhabdoms. Yet the latter do show the late‐night breakdown and regeneration. Correlation between hemocyte numbers and rhabdom size becomes almost perfect if our summer and winter series are pooled.
Regulation of tadpole spinal nerve fiber growth by the regenerating limb blastema in tissue culture
Authors: Richmond Mary J. , Pollack Emanuel D. 
Published: June 2005

AbstractExplants of frog tadpole spinal cord cocultured with blastemas of regenerating hindlimbs provide in vitro evidence that the mesenchymelike cells of the blastema may serve to elicit nerve fiber growth and sprouting into the limb stump. The present study indicates that (1) blastemal mesenchyme results in enhanced, directed nerve fiber growth and its extended survival in defined tissue culture medium; (2) the amount of nerve growth decreases in the presence of blastemas from limbs incapable of complete regeneration; and (3) the quantity of nerve fiber outgrowth decreases as the developmental stage of the spinal cord increases. It is hypothesized that one of the requisites for limb regeneration is the production of a distal population of dedifferentiated cells capable of eliciting nerve fiber outgrowth from competent neural tissue in an amount that is sufficient to promote nerve‐dependent regeneration.
Epigenesis in developing avian scales. I. Qualitative and quantitative characterization of finite cell populations
Authors: Tanaka Shoji , Kato Yoshihiro 
Published: June 2005

AbstractThroughout a period from day 8.5 to day 12.5 of incubation of a chick embryo, a finite cell population of scale epidermis was characterized from various view points such as cellular organization, position, shape, area, number of constituent cells, density, and cell proliferation activity. In this study, the preparation of whole mount specimens was found to be quite valuable. On day 8.5, cells in the prospective scale region could be morphologically distinguished in the tarsometatarsus at a certain distance proximally away from the tarsometatarsal–phalangeal joint.—On day 9.25, about 1,100 cells became highly columnar in shape and densely associated, forming a placode structure. In both distally and proximally adjacent regions of this placode, the cells were semiquadrate in shape and loosely associated, leading to the formation of the interplacode structures. Such contrasting difference in cell organization between placode and interplacode was preserved from day 9.25 to day 11. During this period, both the area and number of constituent cells increased greatly in the placode and only slightly in the interplacode. However, cell proliferation activity was completely suppressed in the placode, and quite active in the interplacode. The activity in cell proliferation proved to be inversely correlated with the density of basal cells. Throughout the present study, it has been demonstrated that the early development of scale epidermis is achieved through a coordinated activity of the two discrete cell populations: the placode and interplacode.
Availability time of tritium‐labeled DNA Precursors in newt eyes following intraperitoneal injection of 3H‐thymidine
Authors: Reyer Randall W. 
Published: June 2005

AbstractFollowing intraperitoneal injection of 3H‐thymidine into host newts, iris together with a regenerating lens was transplanted from a donor eye into a lentectomized host eye at frequent intervals for 20 hours and then every 1 or 2 days for 14 days. The eyes were fixed 2 hours and 1 or 2 days after implantation and autoradiographs prepared. Following fixation 2 hours after operation, incorporation of 3H‐thymidine into DNA, as evidenced by grain counts over nuclei, fell rapidly for 3.5 hours after injection and was no longer apparent after 4.5 hours. However, almost one‐half of the implants were lightly labeled when they remained in the host eyes for 1 or 2 days beginning from 1 to 14 days after isotope injection. When these implanted, regenerating lenses were left in the host eyes for longer periods of time, then a light label was found over nuclei in most of the implants remaining in the eye for 3 to 24 days. When 3H‐thymidine was injected from 1 to 3 days after extirpation of both lens and neural retina, before DNA synthesis had been initiated in the pigmented retinal epithelium or iris, there were numerous cases of labeled nuclei among depigmenting cells of the pigmented retinal epithelium which was regenerating a new neural retina from 2 to 25 days after isotope injection. Depigmenting cells of the dorsal iris and regenerating lens were similarly labeled. These results provide evidence for the continued availability of small amounts of tritiated DNA‐precursor molecules which can be incorporated in DNA of proliferating cells long after the initial injection of 3H‐thymidine.
Thermoperiodism in the Gulf killifish, Fundulus grandis
Authors: Weld Madeline M. , Meier Albert H. 
Published: June 2005

AbstractMale Gulf killifish, Fundulus grandis, were held on various photoperiodic and thermoperiodic regimens for 2 to 4 weeks and examined with respect to body fat stores and testes weights. Groups offish kept on a 24‐hr (LD 12:12) photoperiodic regimen were provided a water temperature of 28°C except for a 4‐hr daily interval of 20°C given at one of six different times during the photocycle. Similarly, fish kept on a 48‐hr (LD 12:36) photocycle and 28–30°C were provided 4‐hr cryophases (20°C) once during each photocycle in various phase relations to the photoperiodic regimen. In addition, some groups were held at 20°C and provided 4‐hr thermophase (28–30°C) interruptions. Fat stores and gonad weights varied among the groups as a function of the time of day when the temperature interruptions occurred. The photoperiod appears to entrain a circadian rhythm of thermosensitivity, so that the coincidence of a temperature change with a thermosensitive phase alters metabolic and reproductive indices. The circadian mechanism in thermoperiodism appears similar to that involved in photoperiodism.
Proliferation in vitro of melanophores from Xenopus laevis
Authors: Fukuzawa T. , Ide H. 
Published: June 2005

AbstractMelanophores of wild‐type and periodic albino mutants of Xenopus laevis were successfully cultured in vitro. They proliferated in the presence of α‐melanocyte‐stimulating hormone (α‐MSH) or cyclic adenosine monophosphate (cAMP) at a doubling time of 8–10 days. These proliferating melanophores retained their phenotypes, ability to synthesize melanin, and melanin‐dispersing response to MSH stimulation. Neither depigmentation nor selective cell death of periodic albino melanophores was observed for at least 4 months during the cultivation.
Changes in subcellular elemental distributions accompanying the acrosome reaction in sea urchin sperm
Authors: Cantino M. E. , Schackmann R. W. , Johnson D. E. 
Published: June 2005

AbstractEnergy‐dispersive x‐ray microanalysis was used to analyze changes in the subcellular distributions of Na, Mg, P, S, Cl, K, and Ca associated with the acrosome reaction of sea urchin sperm. Within 5 sec after induction of the acrosome reaction, nuclear Na and mitochondrial Ca increased and nuclear and mitochondrial K decreased. Uptake of mitochondrial P was detected after several minutes, and increases in nuclear Mg were detected only after 5–10 min of incubation following induction of the reaction. The results suggest that sudden permeability changes in the sperm plasma membrane are associated with the acrosome reaction, but that complete breakdown of membrane and cell function does not occur for several minutes.
Male fertility in Drosophila melanogaster: Lesions of spermatogenesis associated with male sterile mutations of the vermilion region
Authors: Dybas Linda K. , Harden Kathryn K. , Machnicki Joy L. , Geer Billy W 
Published: June 2005

AbstractOf the four male sterile, ms, loci that have been identified in the vermilion region, 9F4 to 10C2, of Drosophila melanogaster, one specifically affects male fertility, whereas three influence male and female fertility and viability. Mutations at a testis‐specific locus (10A2‐5; 1‐33.44) blocked postmeiotic spermatid maturation at or before the coiling stage. Improper associations of the axonemal sheath with the axoneme and with the mitochondrial derivatives were common to spermiogenesis in adult ms (l)v3/Y and ms (l)v 6/Y males representing the locus. Abnormalities in premeiotic events of spermatogenesis were detected in the testes of ms (l) v7/Y (9F4 to 9F8‐9; 1‐32.82), ms (l) v1/Y (1‐B4‐5 to 10B16; 1‐34.61), and ms (l) v22/Y and l (l) v73/Y males (10B4‐5 to 10B16; 1‐35.31). Differences in the characteristics of the premeiotic ms mutations suggested that each influences spermatogenesis in a unique way.
Increase in mitotic activity of regenerating axolotl limbs by growth factor‐impregnated implants
Authors: Chew Keith E. , Cameron Jo Ann 
Published: June 2005

AbstractThis study was designed to investigate the effects of pituitary fibroblast growth factor (FGF), endothelial cell growth supplement (ECGS), and human serum albumin (HSA) on the mitotic indices of dedifferentiating stump cells in regenerating limbs deprived of a wound epidermis. These cells would normally contribute to blastema cell formation but have been prevented from doing so by the placement of a full thickness skin flap over the amputation site. FGF, ECGS, and HSA were released from copolymer implants inserted between full thickness skin flaps and tibia‐fibula amputation sites in axolotls, Ambystoma mexicanum. The implants were plain or contained either FGF or ECGS or HSA. After 2 wk the mitotic indices of the area of dedifferentiation within these experimental limbs were determined and compared to the mitotic indices of normal regeneration blastemas. Histological analysis revealed that the technique of suturing the full thickness skin flaps into position prevented the formation of dermis‐free areas that can permit, regeneration. Full thickness skin flaps alone, or with a plain implant, or with an HSA‐impregnated implant completely inhibited blastema formation in axolotl hindlimbs. The mitotic indices of these animals showed significant decreases compared to mitotic indices of normal regeneration blastemas. The mitotic indices of animals treated with full thickness skin flaps and implants impregnated with either FGF or ECGS showed significant increases compared to those of normal regeneration blastemas. Precocious cartilage development was found in limbs which contained FGF implants.
An electrophoretic and immunological reinvestigation of the cytosolic di‐ and tripeptidases of the guinea pig
Authors: Frick Lloyd 
Published: June 2005

AbstractElectrophoretic and immunological techniques have been used to analyze the cytosolic di‐ and tripeptidases of guinea pigs. In contrast to previous reports utilizing intestinal mucosa extracts, cavian peptidases were found to be similar to peptidases described in other mammals and in fishes. Earlier papers are in error owing to coelectrophoresis of enzymes and to impure enzyme preparations. Guinea pigs are unusual in that they appear to lack peptidase C.
Muscle and cartilage differentiation in axolotl limb regeneration blastema cultures
Authors: Hinterberger Timothy J. , Cameron Jo Ann 
Published: June 2005

AbstractA tissue culture system is described for explants of mesenchyme from Ambystoma mexicanum limb regeneration blastemas. Explants were cultured on collagen substrate for 3 weeks in minimal essential medium supplemented with the hormones insulin, thyroxine, somatotropin, and hydrocortisone, plus beef embryo extract (EE), 2%. This medium supported extensive cell migration onto the substrate followed by cell proliferation and differentiation of both cartilage matrix and myotubes. Cultures on plastic substrate, rather than on collagen, displayed similar cell outgrowth and cartilage formation, but relatively little myotube formation. Differentiation in EE‐supplemented medium was compared with that in two defined media: Explants in medium containing only the hormones showed little outgrowth or cartilage development and never formed myotubes; medium containing the hormones plus fibroblast growth factor, 50 ng/ml, supported an intermediate degree of outgrowth and cartilage development and occasional myotube formation. Explant size was also a factor: Smaller explants survived and formed myotubes less frequently, even when on collagen in EE‐supplemented medium.
Experimental studies on a lethal gene (t) in the Mexican axolotl, Ambystoma mexicanum
Authors: Armstrong John B. , Gillespie Laura L. , Cooper Gillian 
Published: June 2005

AbstractIn the Mexican axolotl, Ambystoma mexicanum, the developmental mutation lethal t is inherited as a simple Mendelian recessive. Mutant larvae failed to feed and died, on the average, 17 days after hatching. Unfed wild‐type larvae died an average of 23 days after hatching. By 15 days, forelimb development had progressed further in the wild type; a cartilaginous scapula and humerus were present, but no cartilage was seen in the mutant limb. Histological examination indicated that the visceral cartilage may also be abnormal, and the rectus cervicus muscle was found to have fewer and smaller fibers. Though the mutant was not rescued by parabiosis with wild‐type embryos, transplants of presumptive gill and limb tissue to wild‐type hosts survived, indicating that the mutaion is not an autonomous cell lethal.
Fertilizability of in vitro matured oocytes from golden hamsters
Authors: Leibfried M. Lorraine , Bavister Barry D. 
Published: June 2005

AbstractThe fertilizability of hamster oocytes matured in vitro was examined along with two factors potentially affecting nuclear maturation in culture. The four amino acids (isoleucine, methionine, phenylalanine, and glutamine) necessary for nuclear maturation of cumulus‐free oocytes (Gwatkin and Haidri, '74) were not required if oocytes recovered on the morning of proestrus (day 4) were cultured with intact cumuli. Although follicular oocytes recovered on day 3 of the estrous cycle (late diestrus) had somewhat lower frequencies of maturation in vitro compared to those recovered on day 4 (76 vs. 95%, respectively), they still had a substantial frequency of spontaneous maturation.Follicular oocytes recovered on day 3 and matured in vitro were fertilized at frequencies equivalent to oviducal oocytes (80 vs. 82%, respectively) when incubation of oocytes with precapacitated sperm was continued for 6 h. Penetration of follicular oocytes was lower (37.4%) after only 4 h of sperm/egg incubation, indicating a delay in sperm penetration with follicular oocytes matured in vitro. Incubation for 4 h is sufficient time for penetration of 80% or more of oviducal oocytes. While 98% of penetrated oviducal oocytes were fertilized normally, only 2% of penetrated follicular oocytes were normal. The majority (85%) of follicular oocytes, unlike oviducal oocytes, were unable to cause decondensation of sperm nuclei after 6 h of sperm/egg incubation. Use of a highly defined system for in vitro fertilization of hamster gametes has provided rigorous proof that isolated cumulus‐oocytes complexes do not undergo complete maturation in vitro.