bluuebunny/crossref_metadata_2025_split huggingface dataset:
A spider fibroin and its synthesis
Authors: Candelas Graciela C. , Cintron José 
Published: June 2005

AbstractThe tissue‐specific fibroin product of the large ampullate glands of the spider Nephila clavipes was isolated and analyzed with respect to homogeneity and size. The solubilized luminar contents of the glands migrate as a homogeneous band in SDS electrophoresis. Its molecular mass has been estimated to be approximately 323,600 daltons. Excised glands have been manintained metabolically active under rather simple culture conditions. Protein synthesis, monitored by incorporation of labeled alanine and glycine, has been elicited through exposure to a cholinergic agent in the culture medium as well as by depleting the animals of their store of silks.
Distribution of polyamines and ornithine decarboxylase activity in the tissues of the lizard, Calotes versicolor
Authors: Baby T. G. , Reddy S. Raghupathi Rami 
Published: June 2005

AbstractThe distribution of polyamines, putrescine, spermidine, and spermine is reported in the tissues of the lizard, Calotes versicolor. The levels of spermidine and spermine are higher than those of putrescine in all tissues and most tissues have more spermine than spermidine. Enzymatic decarboxylation of L‐ornithine is also demonstrated in the lizard tissues. Liver orthinine decarboxylase has optimal activity at about pH 6.8 and apparent Km (Michaelis constant) of 1.23 to 1.73 mM for L‐ornithine.
Cortical vesicle breakdown in fertilized eggs of Fundulus heteroclitus
Authors: Brummett Anna Ruth , Dumont James N. 
Published: June 2005

AbstractA scanning and transmission electron microscope study has been made of the cortical alveoli of the egg of Fundulus heteroclitus. The study includes both unactivated eggs and fertilized eggs fixed at intervals of 1 second to 10 minutes after insemination.The alveoli appear to vary considerably in size, in contents, and in morphological aspects of their breakdown. As it undergoes dehiscence, each vesicle may form one or several openings in the egg surface; dense granules and particulate, fibrous, or membranous material, apparently in any combination, are liberated to the nascent perivitelline space. It appears that much of the excess membrane externalized during the reaction is strung out in threads and probably lost to the perivitelline space. The evidence does not suggest that the excess membrane either “dissolves” or is retrieved by the egg cytoplasm. That part of the cortical vesicle membrane which remains continuous with the oolemma gradually becomes microvillous and loses its morphological identity.Granules and particulate matter, presumably liberated from the cortical alveoli, are seen adhering to the inner surface of chorions removed from activated eggs. The micropyle appears to be sealed with similar material. Supernumerary sperm are observed inside the chorion in some instances.The cortical reaction appears to play a secondary role in the prevention of polyspermy and to be somehow related to the subsequent formation of a normal embryonic blastodisc.
Active immunization of rats with cumulus‐free mouse ova: Induction of infertility and antibody titers
Authors: Aitken R. J. , Richardson D. W. 
Published: June 2005

AbstractActive immunization of rats with cross‐reacting zona pellucida antigens derived from cumulus‐free mouse ova resulted in the induction of infertility without adverse side effects. Half of the immunized animals never regained their fertility despite repeated matings with fertile males. Two of the remaining animals conceived when antibody titers fell to basal levels and gave birth to litters of normal healthy young. Post mortem examination of immunized animals 24 hours after finding sperm in the vaginal smears resulted in the recovery of tubal ova exhibiting the presence of a precipitate on the outer surface of the zona pellucida. Some of these ova appeared to have been fertilized, suggesting that anti‐zona antibodies may also inhibit fertility through a post‐fertilization mechanism of action.
Cyclic AMP in mammalian follicle cells and oocytes during maturation
Authors: Moor R. M. , Heslop J. P. 
Published: June 2005

AbstractIntact ovarian follicles and isolated oocytes were cultured for 30 sec to 18 hr in the presence of gonadotrophins, and the cyclic AMP content in the follicle and oocyte was measured. The basal content of cyclic AMP in ovine oocytes before gonadotrophic stimulation was 6.3 ± 0.7 fmol/oocyte or 8 μM. There was no fall in oocyte cyclic AMP concentration as an immediate response to the gonadotrophins, but at 1, and 12–18 hr after stimulation, the concentration in both the oocytes and follicle cells was considerably elevated. There was no comparable increase in intracellular cyclic AMP in oocytes denuded of follicle cells before culture, even when both gonadotrophins and phosphodiesterase inhibitors were included in the medium. We conclude that the signal which initiates oocyte maturation in mammals differs from that of amphibia, where an early fall in intracellular cyclic AMP is essential for the resumption of meiosis. Moreover, cellular interactions within the mammalian follicle are necessary for the characteristic periods of increased cyclic AMP in oocytes during maturation.
Altered acetylcholinesterase isozyme patterns in mice with hereditary muscular dystrophy
Authors: Kuhn D. E. , Logan D. M. , Rathbone M. P. 
Published: June 2005

AbstractNormal and dystrophic mouse muscles were separated into a predominantly white muscle fraction (gastrocnemius, extensor digitorum longus) and a predominantly red muscle fraction (diaphragm). Acetylcholinesterase (AChE) was extracted from each muscle fraction using a Triton X‐100/NaCl buffer. Six forms of AChE were separated from each muscle homogenate by velocity sedimentation on linear sucrose gradients. Their apparent sedimentation coefficients in each case were 19.7S, 16.0S, 13.3S, 10.4S, 7.6S, and 3.9S. Gel electrophoresis of crude muscle homogenates under nondenaturing conditions (native gels) and of each separate isozyme fraction gave one band of AChE activity with a consistent Rf (relative mobility) value. Reelectrophoresis of native gel bands on SDS/acrylamide slab gels revealed a similar monomeric subunit protein from either crude muscle homogenates or isozyme fractions with an apparent molecular weight of approximately 69,000 daltons.Our results indicate that the AChE distribution and activity are severely affected in dystrophic “white” muscles (anaerobic) but much less so in “red” muscles (aerobic). Dystrophic predominantly white muscles weigh less, contain less protein, and have a decreased total AChE activity in comparison with their normal counterparts. Furthermore, the relative proportions of AChE activity in each isozyme fraction is altered between normal white and dystrophic white muscle fractions: i.e., dystrophic white muscle contains a decreased proportion of a low molecular weight form (7.6S) and increased proportions of higher molecular weight forms (16.0S, 19.7S). In contrast, no significant differences occur in AChE activity or distribution between normal and dystrophic predominantly red muscle.The changes in white muscle AChE are toward a pattern common to red muscle. This suggests that the effect of muscular dystrophy and its related stress on mouse white muscle is at least in part a shift from a predominantly anaerobic, fatigable metabolism to an aerobic, fatigue‐resistant metabolism.
Newt forelimb regeneration blastemas in vitro: Cellular response to explantation and effects of various growth‐promoting substances
Authors: Mescher Anthony L. , Loh Jee‐Joon 
Published: June 2005

AbstractMacromolecular synthesis was studied in cultured newt forelimb blastemas. Late bud stage blastemas were explanted into organ culture and thus denervated. When the response of the blastemas to explantation was examined, it was found that a peak in 3H‐leucine incorporation occurred at 2 hr of incubation, and a similar peak in 3H‐thymidine incorporation occurred at 3–4 hr. After these initial increases, both parameters declined to levels lower than those determined at the time of explantation. The peaks in macromolecular synthesis reported here in vitro are similar to those observed in blastemas in vivo after denervation (Singer, '74). In the second part of the study, the ability of various growth‐promoting substances to stimulate DNA synthesis in cultured blastemas was investigated. Increasing concentrations of fetal bovine serum caused increased levels of 3H‐thymidine incorporation, with maximal stimulation at 30% serum. Newt brain extract (NBE) was as effective as additional serum, with optimal stimulation at 100 μg total NBE protein per ml culture medium. Fibroblast growth factor (FGF), derived from brain tissue, at a concentration of 10 ng/ml was as effective as both 30% serum and the optimal concentration of NBE. Epidermal growth factor (EGF) produced a maximal effect at 1 ng/ml. Neither nerve growth factor nor the platelet‐derived growth factor were stimulatory. Bovine insulin was highly active in stimulating DNA synthesis at concentrations from 1–10 μg/ml. The requirement of nerves for blastemal development, as well as the possible roles of the various growth‐promoting substances in this process, are discussed.
Oxidative metabolism of spermatozoa from inbred and random bred mice
Authors: Carey Joan E. , Olds‐Clarke Patricia , Storey Bayard T. 
Published: June 2005

AbstractEpididymal spermatozoa from the random‐bred CFW and from the inbred C57BL/6 strains of mice were treated either hypotonically or with the antibiotic filipin in order to study the mitochondrial oxidative activities of the two strains in the absence of permeability barriers imposed by the plasma membrane. The percentage of motile spermatozoa from C57BL/6 mice was consistently higher than that from CFW mice, but sperm from the latter fertilized a higher percentage of eggs in vitro. In vivo, there was no apparent difference in fertilizing capacity in vivo: no significant difference between strains was observed. There is a strategy of oxidative metabolism in mouse spermatozoa which is common to the two genetic strains of the species tested, but which differs from that of rabbit and bull spermatozoa. The mitochondria of mouse spermatozoa oxidize L‐3‐glycerolphosphate but not glutamate in the presence of malate; both activities are present in bull spermatozoa but neither are present in rabbit spermatozoa. In common with those of the mammalian species thus far studied, the mitochondria of mouse spermatozoa readily oxidize lactate and pyruvate in the presence of malate. They also oxidize acetyl CoA, acetyl carnitine, and long‐chain acyl CoA esters directly, without the intermediacy of the carnitine esters. Mouse spermatozoa, therefore, have access to endogenous acyl CoA esters as a source of metabolic energy, which is consistent with their ability to maintain motility for 4–6 hours in the absence of added energy sources. Mouse spermatozoa are self‐sufficient with regard to oxidative metabolism, which suggests that energy sources are not readily available to them in the mouse female reproductive tract.
Photoperiodic control of seasonal reproduction in tropical weaver bird
Authors: (Nee Pavgi) Sushama Singh , Chandola Asha 
Published: June 2005

AbstractExperiments were performed in order to provide information on the extent of involvement of daylength, if any, in the control of seasonal breeding in the tropical weaver bird. The reproductive cycle was completely abolished in both short and long photoperiods. The cycle was suppressed in short photoperiods, and in long photoperiods gonads were maintained in a stimulated state indefinitely. These results indicated a definite photoperiodic requirement for gonadal development in the weaver bird. the photoperiodic response threshold was found to be 11 hours daily. Gonads in a period of 12L/12D exhibited cyclicity, though at a low level, indicating that a light period of 12 hours daily allows gonadal regression which is abolished in longer photoperiods. On correlating these laboratory observations with the natural reproductive cycle, it seems that the annual timing of reproduction in the weaver bird may coincide with the time in the spring when the increasing day length reaches the photoperiodic response threshold.
Induced locomotion by midbrain stimulation in restrained skipjack tuna, Katsuwonus pelamis, L.
Authors: Kashin S. M. , Brill R. W. , Ikehara W. N. , Dizon A. E. 
Published: June 2005

AbstractWe show that electrical stimulation of the midbrain of restrained and sedated skipjack tuna (Katsuwonus pelamis) produces coordinated locomotory activity. Therefore, our preparation is a viable alternative for creating normal swimming movements which can be closely controlled by the experimentalist, and demonstrates that a midbrain “locomotory center” is present in skipjack tuna, as in other teleosts.
Microvascular pressures in gill filaments of lingcod (Ophiodon elongatus)
Authors: Farrell A. P. , Smith D. G. 
Published: June 2005

AbstractDynamic intravascular pressures were measured in the afferent and efferent filament arteries of Ophiodon elongatus using micropipettes. Measurements from anesthetized fish and from isolated, saline‐perfused preparations indicated that the major site of gill resistance was located in the lamellar complex (secondary lamella and associated arterioles). The presence of a postlamellar cholinergic constrictor site was also supported by efferent arterial pressure measurements during acetylcholine administration.
A possible stress‐warning marker in Ambystomatid salamanders
Authors: Hedberg Thomas G. 
Published: June 2005

AbstractWhen placed under thermal and mechanical stress, individuals of Ambystoma tigrinum may produce a chemical substance which elicits aversive movements, increases negative phototaxis, and inhibits swimming coordination in conspecifics in an aquatic environment. Introduction of water in which three individuals were kept under stress elicited these responses in conspecifics kept in another container. Under natural conditions, the proposed substance may serve as a stress‐warning marker during the spring migrations of this species.
Effect of seasonal variations on the immune system of the snake, Psammophis schokari
Authors: Ridi R. El , Badir N. , Rouby S. El 
Published: June 2005

AbstractIn spring and autumn, the lymphoid complex of the colubrid snake, Psammophis schokari is well developed and the humoral response to intraperitoneally administered rat erythrocytes (RRBC), human serum albumin (HSA), or polyvinyl pyrrolidone (PVP) is quick and vigorous. In contrast, in summer and winter, lymphoid elements of the thymus, spleen, and part of the gut‐associated lymphoid tissue are highly depleted. Humoral reactivity to RRBC and HSA is poor in summer presumably due to the deleterious effect of seasonal factors on the thymus and thymus‐derived helper lymphocytes. This assumption is supported by the fact that, in summer, P. schokari responds powerfully to the T‐independent antigen PVP. Humoral response to RRBC, HSA, and PVP is, however, weak in winter suggesting that a further mechanism of immunosuppression is involved.
Cortical control of macronuclear positioning in the ciliate Stentor
Authors: De Terra Noël 
Published: June 2005

AbstractIn the ciliate Stentor, the chain macronucleus has a fixed position within the cell; it is located just beneath the region of narrow cortical striping to the right of the gullet (nuclear site). Stentor therefore lends itself well to experiments on control of nuclear positioning. I have studied this problem by microsurgically producing various abnormalities of nuclear positioning and determining how these are corrected. Breaks in the nuclear chain were repaired by segregation of broken parts into the two daughter cells at division. When a second nucleus was transplanted into a stentor, the abnormality was eventually corrected because the two parallel chains tended to move during oral development (regeneration or division) so that one was anterior to the other. The two nuclei were then segregated into the anterior and posterior daughter cells at division. When a doublet stentor, which has two nuclear sites and two macronuclei, was deprived of one nucleus, it acquired a second one because the remaining nucleus was attracted to both nuclear sites when it elongated during oral development. This phenomenon first produced doublets with a single nuclear chain sharing the two nuclear sites at opposite ends of the cell, a break in the chain then presumably created two nuclei. These latter observations indicate that one mechanism by which the nucleus is positioned involves its attraction toward the nuclear site, a differentiated region of cell cortex, during oral development. Other experiments have shown that the nuclear site also holds the nucleus firmly in place.
Rapid nasal pit formation in mouse embryos stimulated by ATP‐containing medium
Authors: Smuts Marybeth S. 
Published: June 2005

AbstractThe primary palate in the mouse is composed of epithelium and mesenchyme. Most studies on primary palate formation have concentrated on the role of the mesenchyme based upon the hypothesis that mesenchymal accumulation elevated the sides of the nasal placodes, thereby creating the depressed nasal pits.This study demonstrates that the epithelium is actively participating in formation of the nasal pits. Mouse heads from embryos of 14 to 24 pairs of body somites were placed in medium 199 and photographed. The medium was replaced with medium containing 1.0 mM ATP and 0.05% Triton‐X. Within 5 minutes, the placodes either thickened or invaginated. Control heads exposed to medium 199 containing only Triton‐X or ATP did not show any invaginations.The rapid thickening and invagination stimulated by ATP‐containing medium demonstrates that the epithelium is the dominant tissue in nasal pit formation. Although mesenchymal accumulation certainly contributes to the formation of the primary palate, it is the placodal epithelial invagination that appears to shape the nasal pits.
Histone synthesis in preimplantation mouse embryos
Authors: Kaye Peter L. , Wales Raymond G. 
Published: June 2005

AbstractThe synthesis of histones by preimplantation mouse embryos was examined by electrophoresis of [3H]‐lysine‐labeled acid extracts of cleavage stage embryos. Histones were synthesized by fertilized zygotes, two‐cell, eight‐cell, and morula stage embryos. Their identity was confirmed by coextraction and coelectrophoresis in a number of systems and differential labeling with [3H]‐tryptophan. There was evidence of post‐translational modifications of the embryonic histones. The estimated histone synthetic rate was sufficient to provide the chromatin requirements of cleavage division as related to DNA synthesis. The results are discussed in relation to coordination of histone and DNA synthesis in the preimplantation embryo.
An intrabursal injection procedure for the in vivo study of ovulation in hamsters
Authors: Martin Gary G. , Talbot Prudence , Pendergrass Paula 
Published: June 2005

AbstractA new procedure for studying the effect of various drugs on ovulation in vivo is described. In golden hamsters (Mesocricetus auratus), each ovary is enclosed within a complete bursa that is continuous with the oviduct. Drugs can be applied topically to ovaries by injection of a solution into a bursal cavity of an anesthetized hamster several hours before ovulation: the contralateral ovary serves as an in vivo control and receives no treatment. After ovulation, the number of ruptured follicles on experimental and control ovaries are compared. Data presented show that: (1) the operation and injection procedure per se do not affect ovulation; (2) normal saline is a suitable vehicle for administration of drugs by this route; (3) compounds with molecular weights of less than 1,000 daltons rapidly penetrate all layers of the follicle wall; (4) solutions injected into the bursal cavity 6 hours before ovulation remain there until ovulation. The advantages and limitations of this technique are discussed.
The role of follicular smooth muscle cells in hamster ovulation
Authors: Martin Gary G. , Talbot Prudence 
Published: June 2005

AbstractThe role of contractile cells in mammalian ovulation is uncertain. In this study, we examined the morphology and distribution of cells within the theca externa of hamster follicles at various times during ovulation. Cells with all the ultrastructural features of smooth muscle (SMC) were found only in the basal hemisphere of the follicle. In contrast, the theca externa in the top half of the follicle was composed of fibroblasts. We next examined living hamster follicles during in vitro ovulation for morphological evidence of follicular contraction. The following changes in follicle shape were observed: (1) The base of the follicle moved apically; (2) follicles, which were initially spherical, became taller and thinner; and (3) after rupture, the apical follicle wall collapsed onto the surface of the ovary. To analyze the cause of these changes, sections of fixed follicles were examined by light and electron microscopy. During the final minutes before rupture, a V‐shaped constriction formed in the base of the follicle. This constriction continued to narrow and by the time of rupture, it obliterated the basal part of the antrum. We concluded that the apical movement of the base of the follicle seen in living ovaries corresponds to the formation of the basal constriction seen in fixed sections. To determine if follicular SMC were involved in formation of the constriction, the ultrastructure of SMC was examined before, during, and after the constriction formed. The morphology of the SMC changed from the characteristic of relaxed or stretched SMC to that of contracted SMC when the constriction began to form. No other type of cell in the follicle wall showed these changes in morphology. We conclude that the formation of this constriction, and possibly the increase in height of preovulatory follicles and the collapse of the follicle wall after rupture, are due to contraction of SMC in the theca externa in the basal hemisphere of the follicle. This is the first morphological demonstration that follicular SMC contract prior to rupture of the follicle. The significance of these observations in mammalian ovulation is discussed.
Mouse alcohol dehydrogenase isozymes: Products of closely localized duplicated genes exhibiting divergent kinetic properties
Authors: Holmes Roger S. , Albanese Rico , Whitehead Faye D. , Duley John A. 
Published: June 2005

AbstractElectrophoretic variants for the stomach isozyme (ADH‐C2) and liver isozyme (ADH‐A2) of alcohol dehydrogenase in strains of Mus musculus have been used in genetic analyses to demonstrate close linkage between the structural genes (Ahd‐3 and Adh‐1, respectively) encoding these enzymes. No recombinants were observed between these loci among 126 backcross animals, which places them less than 0.8 centimorgans apart. Previous studies have positioned Adh‐3, and a temporal locus (Adh‐3t), on chromosome 3 (Holmes, '79; Holmes et al., '80). Kinetic analyses on partially purified preparations of these isozymes have demonstrated widely divergent catalytic properties and inhibitor specificities. The liver isozyme exhibited Michaelis constants that were nearly 3 orders of magnitude lower than the stomach isozyme for various alcohol and aldehyde substrates. Moreover, aminopropyl pyrazole strongly inhibited ADH‐A2 (Ki = 1.2 M), whereas ADH‐C2 was insensitive to inhibition under the conditions used. It is proposed that Adh‐1 and Adh‐3 are products of a recent gene duplication event during mammalian evolution and that considerable divergence in the active sites of these enzymes and the “temporal” genes controlling loci expression in differentiated tissues has subsequently occurred.