bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expression of a sex‐linked gene in standard and fusion‐chimeric mice
Authors: Dunn G. R. 
Published: June 2005

AbstractThe single‐active‐X hypothesis states that in any mammal with more than one X chromosome per cell, only one X is active in each cell. The hypothesis further states that X‐chromosome differentiation occurs randomly in each cell early in development and subsequently is stable. The phenotype of a mammal heterozygous for a sex‐linked gene will thus be mosaic, and any interaction of different X alleles can occur only on the intercellular level. Another hypothesis, the “complemental‐X” hypothesis, explains the phenotype of a sex‐linked gene heterozygote in terms of intracellular allelic interaction.The validity of intercellular interaction in sex‐linked gene heterozygotes was tested in the mouse by making fusion chimeras of embryos carrying different X‐linked alleles and comparing the chimeric phenotype to that of a standard heterozygote.The X‐chromosome marker Greasy (Gs) was shown to affect ten parameters of hair structure, four of which were chosen to establish a series of hair types. It was found that Gs/ +. mice had almost the entire range of hair types, while wild‐type and Gs/ mice showed restricted hair type distributions, significantly different from each other and from Gs/ +. It was also found that the Gs/ + phenotype could not be accounted for by additivity of the wild‐type and mutant hair‐type distributions.Some of the fusion chimeras had phenotypes similar, if not identical, to that of standard Gs/ + mice in all respects except the rate of change in the distribution of hair types with age. This discrepancy could be accounted for on the basis of cell selection.These data support the conclusion that intercellular interaction can account for the observed phenotypes of sex‐linked gene heterozygotes.
Epidermal‐mesodermal interaction during morphogenesis of the limb regeneration blastema in larval salamanders
Authors: Stocum David L. , Dearlove George E. 
Published: June 2005

AbstractThe question was asked whether the proximo‐distal regional organization of regenerating urodele limbs is the result of an epidermal‐mesodermal interaction, as is the case in the embryonic limb bud. Epidermal deletion experiments on regeneration blastemas of various stages have answered this question in the affirmative. The mechanisms involved in the morphogenesis of the regeneration blastema are therefore very similar to those operating in the morphogenesis of embryonic limb buds.
The influence of olfaction on sexual behavior in the male golden hamster (Mesocricetus auratus)
Authors: Lisk Robert D. , Zeiss Jacob , Ciaccio Leonard A. 
Published: June 2005

AbstractAblation of the olfactory bulbs terminates the sexually oriented behavior patterns shown by the male hamster towards the female. All aspects of overt copulatory behavior including mounting are immediately eliminated. Investigatory behavior is decreased significantly and orientation of attention to the hindquarters of the animal being investigated (sexual orientation) is lost over a one to two week interval. This disruption of sexually oriented behavior patterns occurs regardless of the degree of experience of the male in mating prior to the bulbectomy. Unilateral bulbectomy or sham bulbectomy does not disrupt, even temporarily, the mating pattern.Evidence that the lack of mating behavior following bulbectomy is indeed due to anosmia was provided by rendering animals temporarily anosmic by use of zinc sulfate in the nasal cavities. Full recovery of sexual activity occurred within four to six days following this treatment. A second treatment produced a similar result.Naive males, raised in isolation, can show a normal copulatory pattern on first exposure to a receptive female. Naive males do not distinguish between diestrus (non receptive) and estrus (receptive) vaginal secretions from the female.The release of sexual arousal requires olfactory input in the male hamster, conditioning to other cues does not occur. However, differentiation between receptive and non‐receptive females appears to be a positive learned response. The absolute dependence of the male hamster on olfactory cues for sexual arousal has an obvious adaptive value in a species where the female tends to be dominant in encounters and the male, if unable to escape, can be maimed or killed during the course of a fight.
Light microscopic and fine structural changes in the brown adipose tissue from torpid and aroused pigmy mice (Baiomys taylori)
Authors: Hudecki M. S. , Privitera C. A. 
Published: June 2005

AbstractChanges in the composition and morphology of interscapular brown adipose tissue (BAT) are described for the adult pigmy mouse, Baiomys taylori, in its short‐term, cold‐torpor cycle. The study includes an analysis of tissues from, (1) room temperature (RT) controls, (2) RT, 24 hour starvation animals, (3) mice exposed on 15°C for six hours, (4) torpid animals (24, 48, and 72 hours at 15°C), and (5) mice allowed to arouse from torpor at RT for 1, 2, 5, 9, 24, and 288 hours. Control brown fat is composed predominately of lipid vacuoles, glycogen particles, and mitochondria with lamellaelike cristae. Starvation at RT has no marked effect on either the BAT energy stores, or the mitochondrial morphometry. Short exposure to 15°C brings about a pronounced depletion in the lipid and glycogen content, and a significant swelling in the mitochondria. Brown fat from torpid mice is deplete of lipid and glycogen. Mitochondria remain enlarged, and have parallel, closely‐packed cristae. The lipid and glycogen reappear in the early hours of arousal. The multilocular character of the control BAT is reached in five to nine hours after initiation of arousal. Throughout the arousal the mitochondria retain their cold‐induced morphological alterations. Pinocytotic microvesicles in the capillary endothelium and in the brown adipocytes are observed in different degrees, in all experimental groups. With the histological changes in evidence, the participation of pigmy mouse brown fat in non‐shivering thermogenesis in situations of cold exposure, and arousal from torpor, is discussed.
Development of pigmentation in the eyeless mutant of the Mexican axolotl, Ambystoma mexicanum, Shaw
Authors: Epp Leonard G. 
Published: June 2005

AbstractThe development of pigment pattern in the eyeless mutant of Ambystoma mexicanum is described. Pigmentation, is much enhanced in this mutant through increased size and branching of melanophores. The eyeless mutant does not possess the ability to adapt to its background, nor does it blanch in darkness.Reciprocal neural crest transplants between eyeless mutants and eyed siblings indicate no intrinsic neural crest differences in the eyeless mutant. Normal optic functioning after implantation of an eye in the mutant leads to diminished pigmentation. Enhanced pigmentation in the eyeless mutant is postulated as due to abnormally high secretion of MSH by the pituitary causing normal pigment‐producing systems to operate beyond normal limitations.
Avian scale development. I. Histogenesis and morphogenesis of the epidermis and dermis during formation of the scale ridge
Authors: Sawyer Roger H. 
Published: June 2005

AbstractScale development in the chick embryo can be considered as consisting of two major phases. First, a definitive scale ridge is formed from a simple two‐layered epidermis. This phase consists of five stages: preplacode, placode, asymmetrical placode, hump stage, and definitive scale ridge. The second phase involves the elongation of the definitive scale ridge to give rise to the overlapping scales of the adult bird. During elongation a new (inner) epidermal surface is formed, which is histologically less differentiated than the outer epidermal surface. A timed‐sequence study has shown that the placode gives rise mainly to the outer epidermal surface of the definitive scale ridge, while the inter‐placode region becomes the thinner epidermis at the scale apex.
Avian scale development. II. A study of cell proliferation
Authors: Sawyer Roger H. 
Published: June 2005

AbstractThe spatial and temporal distribution of DNA synthesis and the cell cycle duration change during scale development in the chick embryo. Previous histological studies indicated that the two epidermal surfaces of the scale, outer and inner, originated from the placode and interplacode regions, respectively. The present autoradiographic study demonstrated that the epidermal placodes did not incorporate tritiated thymidine for 20–35 hours after their appearance, while the interplacode regions incorporate continuously during this period. The synthetic indices (number of labeled nuclei/total number of basal nuclei) of the two surfaces of the scale also differed early in formation. An explanation for this observation became evident, when it was found that the generation time of the cells constituting the outer and inner surfaces of the scale differed during development. The DNA synthetic phase was constant, whereas the G1‐phase varied concurrently with the generation time.
In vitro fertilization and capacitation‐like interaction in the hydroid Campanularia flexuosa
Authors: O'Rand Michael G. 
Published: June 2005

AbstractFertilization in Campanularia flexuosa is internal. In both freshly collected colonies and laboratory cultured colonies eggs may be removed from the gonangium still attached to the blastostyle as a single packet surrounded by epithelial cells. Packets from mature gonangia of freshly collected colonies contain spermatozoa although the eggs are immature. The spermatozoa remain inside the packet to await egg maturation. Packets from mature gonangia of laboratory cultured colonies do not contain spermatozoa if male and female colonies are cultured separately. Eggs in such packets may be fertilized by the addition of spermatozoa. Removal of the epithelial cells which surround the eggs in the egg packet results in loss of fertilizability. Treatment of the egg packets with 0.75% trypsin also results in a loss of fertilizability. However, fertilizability may be restored by exposure of spermatozoa to non‐trypsin treated female epithelial cells. Thus, apparently a definite interaction must occur between female epithelial cells and spermatozoa prior to fertilization. This interaction may be analogous to mammalian capacitation and the necessary conditioning of amphibian sperm prior to fertilization.
The developmental biology of annual fishes. III. Pre‐embryonic and embryonic diapause of variable duration in the eggs of annual fishes
Authors: Wourms John P. 
Published: June 2005

AbstractAnnual fishes can maintain permanent populations in temporary aquatic habitats since the population survives dry seasons in the form of diapausing eggs. Populations persist even though subject to erratic environmental cycles and recurrent ecological catastrophes.Developmental arrest occurs at one or all of the following stages: Diapause I (Dispersed cell phase); Diapause II (Long somite embryo); Diapause III (Prehatching). In Austrofundulus, Diapause I is facultative. Diapause II and III are obligate, long and variable (105 ± 20 days each). Subpopulations (about 10%) of “escape eggs” bypass Diapause II and/or Diapause III. Pterolebias and Rachovia eggs behave much like those of Austrofundulus. In Rachovia, the duration of Diapause II is 80 ± 33 days and of Diapause III at least 61 ± 23 days. Subpopulations of “escape eggs” are present. Cynolebias and Nothobranchius can undergo facultative arrest at Diapause I and II and enter obligate arrest at Diapause III. Annual species of Aphyosemion can undergo facultative arrest at Diapause I and II, and an obligate arrest at Diapause III. A few species may also experience obligate arrest at Diapause II. A short term arrest phenomenon, “retarded hatching,” sometimes is encountered among non‐annual Aphyosemions and other non‐annual cyprinodonts.Survival strategy is based on the “multiplier effect”; i.e., interposition into the developmental pathway of three branch points containing diapause stages of prolonged, variable duration generates eight different distributions of total developmental time. Thus, a single egg population of identical age can generate several subpopulations, all of which develop according to different schedules. A developmental program is established which permits the repeated loss of individual eggs under conditions which may initiate hatching but do not allow for maturation and successful reproduction. The “multiplier effect” augmented by other adaptations guarantees that some portion of the egg population will survive to reproduce.
Response of the toad, Xenopus laevis, to circulating antigens. I. Cellular changes in the spleen
Authors: Turner Rodney J. , Manning Margaret J. 
Published: June 2005

AbstractThe localization, cytology and proliferation of lymphoid cells in the spleen of Xenopus laevis were investigated in normal toads and in toads stimulated with sheep erythrocytes (SRBC) or human gamma globulin (HGG). In toads given HGG in adjuvant, considerable increase in spleen weight was found both before and during serum antibody production; autoradiographic and histological examination showed that cell proliferation and formation of pyroninophilic cells had markedly increased in the splenic lymphoid tissue, particularly in the white pulp, but to a considerable extent also in the red pulp. Cell proliferation was also present, although less pronounced, after injections of HGG in saline. In toads given SRBC, most proliferation occurred in the white pulp, particularly towards the periphery of the follicles.Light and electron microscopy revealed that the lymphoid cells in the Xenopus spleen — in particular small lymphocytes and large pyroninophilic cells — are similar to those implicated in the mammalian immune response. However, cell clusters resembling mammalian germinal centres were absent. Furthermore, cells resembling the mammalian plasma cell were rare in both normal and immunized toads.
Polyspermic fertilization in pigs after tubal deposition of excessive numbers of spermatozoa
Authors: Hunter R. H. F. 
Published: June 2005

AbstractThe incidence of polyspermy has been examined in mature pigs in relation to the site of deposition of whole semen. Oestrous gilts were inseminated surgically some 12 hours before induced ovulation, semen being introduced into the Fallopian tube on one side of the tract and into the contralateral uterine horn adjacent to the utero‐tubal junction as a control. Animals were slaughtered between five hours 30 minutes and ten hours five minutes after completion of ovulation.There was no detrimental effect of instilling whole semen directly into the tubal isthmus on the proportion of eggs recovered. Ninety‐three per cent of the 145 eggs examined were fertilized. Twenty‐nine eggs recovered from nine animals had undergone polyspermic fertilization: 33.8% of the fertilized eggs from the inseminated tubes were polyspermic compared with 5.2% of the eggs from the side of uterine insemination (p < 0.001). Penetration of the vitellus by two spermatozoa constituted the principal anomaly of fertilization, but trispermy, tetraspermy and higher forms were also found. In such eggs, the female and only a single male pronucleus were conjugating. It is concluded that the incidence of polyspermic fertilization in pigs is significantly increased when large numbers of capacitated spermatozoa confront the newly‐ovulated eggs. The rate of capacitation of boar sperm has been discussed, as has the fate of polyspermic eggs.
Morphometrics of sexual dimorphism in an arrhenotokous mite, Ornithonyssus bacoti (acari:mesostigmata)
Authors: Oliver James H. , Herrin C. Selby 
Published: June 2005

AbstractDiploid Ornithonyssus bacoti females from an inbred laboratory colony are more variable in more external morphological characters than haploid males maintained under identical colony conditions. Prejudiced selection of characters or use of a small sample size can provide data suggesting greater variability in males. When large numbers of characters on many mite specimens are compared by F‐tests of variances, coefficients of variation, generalized variances (determinant of variance‐covariance matrices) and tests of homogeneity of variance‐covariance matrices, general phenotypic variation is greater in females. The agreement between univariate and multivariate tests allows additional confidence in the conclusion (tables 2–7).
T3‐ and T4‐induced rates of metamorphosis in immature and sexually mature larvae of Ambystoma tigrinum (amphibia: Caudata)
Authors: Norris David O. , Platt James E. 
Published: June 2005

AbstractRates of T3‐ and T4‐induced metamorphosis in sexually mature and immature tiger salamander larvae (Ambystoma tigrinum) from a single local population were proportional to daily injected doses (1.0, 10 1, 10 2, or 10 3 μg T3, or T4). Larvae were maintained at 16° C on 12L:12D photoperiod, and were fed beef liver daily. Metamorphic rates were compared as the mean number of days to achieve 50% resorption of the gills (GR50). Saline‐injected and untreated control larvae exhibited no metamorphic tendencies during the experiments. Immature larvae were induced to metamorphose with as little as 0.05 ng T3 or T4/g body weight/day. Small, sexually mature larvae were less sensitive to a given dose of T4, especially at the lowest doses. Large sexually mature larvae did not differ from small larvae. It is presumed that the observed differences in sensitivity would not account solely for the observations of neoteny in this species. Metamorphosis was not influenced by sex. T3 and T4 are equipotent inducers of metamorphosis in immature larvae under conditions of this experiment except that some animals receiving the lowest dose of T3 did not undergo metamorphosis. Larvae receiving 10−1 μg T4/day did not metamorphose at 5° C, and gill resorption was slower for larvae at 10° C as compared to 16° C. GR50 for larvae maintained at 21° C was not different from 16° C.
Hamster sperm hyaluronidase. I. A bioassay procedure based on cumulus dispersion rate
Authors: Talbot Prudence , Franklin Luther E. 
Published: June 2005

AbstractAn in vitro bioassay for hyaluronidase activity has been developed based on cumulus dispersion rate. It was found that the logarithm of the time for complete cumulus dispersion and the logarithm of hyaluronidase activity are linearly related in three incubation media. These data have been used in constructing standard curves for the prediction of hyaluronidase activity from the observed time for complete cumulus dispersion. The technique is sensitive to low levels of hyaluronidase activity, is compatible with complex incubation media, and requires small volumes of test solution.
Aberrent regeneration in carcinogen‐treated earthworms (Eisenia foetida)
Authors: Andrews Edwin J. 
Published: June 2005

AbstractGroups of earthworms (Eisenia foetida) were injected either with 1% methyleholanthrene (MCA), 0.5% 7–12, Dimethylbenz (a) anthracene (DMBA) or 3 × 10−4 mg of N‐methyl‐N‐nitrosoguanadine (NMNG), After one week, the posterior ten segments were removed from all worms. Twenty‐five days after amputation the mumber of regenerated segments were counted. A statistically significant overgrowth of segments occurred in MCA‐treated worms as compared to controls. DMBA treatment failed to alter the mumber of regenerating segments and worms treated with NMNG had statistically fewer regenerating segments than controls. An overgrowth of segments also occurred in certain groups of vehicle‐injected control worms. The groups receiving oil‐based vehicles had significantly greater growth than Hank's Balanced Salt Solution injected controls. A new theory of the mechanism of regeneration is offered to explain the seemingly paradoxical results.
Effects of sperm concentration on the capacitation of rat spermatozoa
Authors: Niwa K. , Chang M. C. 
Published: June 2005

AbstractRat epididymal spermatozoa were preincubated for various times in concentrated (9.6–14.9 × 106 sperm/ml) or diluted form (0.7–1.2 × 106 sperm/ml) and mixed at similar concentrations with eggs recovered from superovulated immature rats. When the eggs were examined at various times after insemination, the penetration rates, the time of sperm penetration, and the fertilizing capacity of sperm were greatly reduced following the preincubation of spermatozoa in a concentrated form for 5–7.5 hours. By preincubation of sperm in diluted form, capacitation of spermatozoa was achieved in 3–5.5 hours, the penetration rates were increased, and the interval between insemination and sperm penetration was progressively reduced as the duration of preincubation increased up to 7.5 hours. It appears that the sperm concentration plays an important role for the capacitation of rat spermatozoa in vitro and the maintenance of their fertilizing capacity.
Intrinsic rhythmic contractions in insect skeletal muscle
Authors: Hoyle Graham , O'Shea Michael 
Published: June 2005

AbstractA constant slow rhythm of contraction and relaxation has been discovered in the extensor tibiae (jumping muscle) of saltatory orthopterans. The rhythm is present in the intact insect and persist in the isolated leg, but is abolished when the leg is perfused with saline. The amplitudes and durations of contractions and also the intervals between them, are subject to central nervous modulation. The rhythm may serve to exercise muscle fibers and to promote movement.
In vitro secretion of α‐ecdysone by prothoracic glands of a hemimetabolous insect, Leucophaea maderae (Blattaria)
Authors: Borst David W. , Engelmann Franz 
Published: June 2005

AbstractProthoracic glands of the cockroach Leucophaea maderae were maintained in organ culture under defined conditions. Examination of the culture medium from mid‐instar glands revealed material which gave a positive response in an ecdysone radioimmune assay and the Musca bioassay. The material was identified as α‐ecdysone on the basis of its co‐chromatography with α‐ecdysone on thin layer chromatography and gas liquid chromatography using the highly selective electrone capture detector. Only very low amounts of secreted material were detected from glands of early last instar nymphs or 1 day adults. No material was secreted from several control tissues.
Growth of crustacean muscle: Asymmetric development of the claw closer muscles in the lobster, Homarus americanus
Authors: Goudey Linda R. , Lang Fred 
Published: June 2005

AbstractMuscle fiber types were examined in lobsters using sarcomere length measurements. In the adult, the slender cutter claw was comprised of fast and slow fibers, while the broader crusher contained only slow fibers. In the juvenile lobster, both the cutter and crusher contained fast and slow fibers. Lengthening of sarcomeres is postulated for some fibers during growth and development of crustacean muscle.
Cell migration into the “established” lateral motor column in Rana pipiens larvae. II. Lumbosacral spinal cord and comparative aspects
Authors: Pollack Emanuel D. , Kollros Jerry J. 
Published: June 2005

AbstractNeuronal turnover has been demonstrated during the period of differentiation and maturation of motor neurons in the developing lateral motor columns of Rana pipiens larvae. As determined by thymidine‐3H labeling, cells continued to migrate into the lateral motor column (LMC) while there was a concurrent reduction in LMC cell numbers. Notably, cells in the lumbosacral LMC ceased to be labeled following thymidine‐3H injection at an earlier time than for the brachial LMC. This is consistent with a caudo‐cephalic direction of development among the two pairs of motor columns in the spinal cord.Since neuronal turnover occurs following the initial formation of the LMC and continues after the maximum number of cells has been attained, it is proposed that neuronal turnover may be a mechanism that allows for neural readjustment and refinement during spinal cord development.