bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperature as a selective factor in protein evolution: The adaptational strategy of “compromise”
Authors: Somero George N. 
Published: June 2005

AbstractMost of the important functional and structural properties of enzymes are affected by temperature. In order to maintain critical enzymic properties such as regulatory sensitivity, catalytic potential and structural stability, significant changes have been made in enzymes during evolution in different thermal regimes.Regulatory function, as typified by substrate binding ability, has been especially conservative. For a given enzyme, substrate binding ability is maintained at a relatively stable level over the entire temperature range experienced by the organism (enzyme), in spite of wide variation in substrate affinity at temperatures outside the biological range. Similarities in substrate affinity among homologues and analogues of enzymes from bacteria, invertebrates, fishes and mammals, at respective physiological temperatures for the enzymes, demonstrate the crucial importance of regulatory abilities in enzymes. Two facts, (a) that enzymes function at sub‐maximal rates, and (b) that low temperature compensation is not effected by wholesale reductions in apparent Km values, argue that regulation outweighs sheer catalytic potential in enzymic function.The efficiency of an enzyme to catalyze a reaction at a rapid rate appears highest in low cell‐temperature forms. The finding that catalytic efficiency is inversely correlated with enzymic heat stability suggests that enzymes with relatively great abilities to undergo conformational changes during catalysis are capable of supplying the most energy for activation events, this energy arising in part from the exergonic formation of weak bonds during the activation step in catalysis. Energy changes due to conformational changes may also be used to reduce the net enthalpy change which occurs during ligand binding, a mechanism we refer to as “coupled‐compensating enthalpy changes.”Comparisons of amino acid compositions of enzyme homologues and analogues from differently thermally adapted species do not reveal major differences, for example, in the overall hydrophobicity of enzymes. We propose that observed differences in enzyme thermal stability derive more from quantitative differences, i.e., differences in total numbers of secondary interactions, than from qualitative differences, i.e., differences in the relative importance of different classes of weak bonds.
Scaling in biology: The consequences of size
Authors: Schmidt‐Nielsen Knut 
Published: June 2005

AbstractA review of major ideas pertaining to the importance of the body size of animals. It discusses the size range of living organisms and the possibilities and constraints that result from the design of animals and the materials used in their supporting structures. The change in size of similarly organized animals is considered in the light of the principles of scaling, with examples chosen both from morphology and physiology. The mechanical consequences of body size in relation to locomotion is also discussed.
Salinity tolerance and desiccation resistance of the gemmules of the brackish‐water sponge, Haliclona loosanoffi
Authors: Fell Paul E. 
Published: June 2005

AbstractGemmules of Haliclona loosanoffi were collected in the fall and stored in sea water at 5°C for seven to ten months before being used in experiments. Extensive gemmule germination occurred at salinities ranging from 20 to 40o/oo (at 20°C), and salinities of 25 and 30o/oo appeared to be optimal. No germination occurred at 5, 10, 15 or 45o/oo, but extensive germination took place when the gemmules were subsequently transferred to 25o/oo. It is suggested that gemmules may play an important role in the survival of the sponge during extreme conditions of salinity. The gemmules were found to have little resistance to desiccation.
Effects on adult newt limb regeneration of partial and complete skin flaps over the amputation surface
Authors: Mescher Anthony L. 
Published: June 2005

AbstractThe influence of the wound epithelium on the cellular events preceding blastema formation was examined by comparing dedifferentiation, DNA labeling indices, and mitotic indices of the distal mesodermal tissues in control regenerating newt forelimbs and in amputated forelimbs covered with a flap of full thickness skin. Three kinds of results were seen following the skin‐flap graft operations. Epidermal migration across the amputation surface was completely inhibited in 22% (8) of the cases and these limbs repaired the amputation wound but did not form regeneration blastemas. In 11% (4) of the experimental limbs, essentially normal wound epithelia displaced the skin flaps and the limb stumps formed blastemas and regenerated. The majority of the skin grafts (67%) exhibited epidermal migration restricted to the free edges of the flaps. These limbs formed eccentric blastemas on the ventral side of the limb next to the dermis‐free epidermis and regenerated laterally in that direction.Despite these differences caused by the skin‐flap grafts, the experimental limbs all resembled control regenerating limbs one week after the operations in the dedifferentiated appearance of the distal mesodermal tissues and in the DNA labeling and mitotic indices of the mesodermal cells. While the labeling and mitotic indices increased by two weeks after the operations in limbs with wound epithelia, these parameters decreased in limbs with complete skin grafts which lacked dermis‐free epidermis. When labeling and mitotic indices were determined two weeks after the operations in the limbs with partial skin flaps, these values had increased over those a week earlier in the areas next to the lateral wound epithelia, but decreased in the opposite areas contacting the complete skin of the graft.These results suggest that the epidermal influence in promoting blastema formation may serve to keep the dedifferentiating cells in the cell cycle and prevent their early redifferentiation.
Sex reversal in a freshwater sponge
Authors: Gilbert John J. , Simpson Tracy L. 
Published: June 2005

AbstractSpongilla lacustris exhibits a type of alternative hermaphroditism, new to the phylum, in which a sponge may be exclusively male or female during the period of sexual reproduction one year and the opposite sex the next year. This form of sexuality may facilitate larva production and thus dispersal following colonization of a new habitat. Gametogenesis occurs shortly after gemmule hatching in both males and females but slightly later in males.
Spontaneous maturation of oocytes isolated from ovaries of immature hypophysectomized rats
Authors: Erickson Gregory F. , Ryan Kenneth J. 
Published: June 2005

AbstractOocytes were collected from preantral follicles (200–300 μ in diameter) from 30‐day‐old immature rats 7 days after hypophysectomy. The ova were cultured in vitro for 17 hrs in a chemically defined medium and scored cytologically for meiotic maturation. Of 534 oocytes that were cultured 89% resumed meiosis; however, 98% of these oocytes arrested in either metaphase or anaphase I. In contrast, 82% of the oocytes isolated from preovulatory follicles (∼600 μ in diameter) of adult proestrus rats progressed to metaphase II. These results are discussed in terms of functional FSH and LH receptors on the granulosa cells.
Changes in the free adenylate nucleotide pattern in relation to the longitudinal axis of earthworms and during their regeneration
Authors: Chapron Claude , Chapron Jacqueline 
Published: June 2005

AbstractThe contents of free adenylate nucleotides (ATP, ADP and AMP) were measured in the earthworm Eisenia foetida at different levels of the body, at various stages of regeneration. The nucleotide concentrations are highest in normal segment 9. AMP level decreases anteroposteriorly. In the first days of cephalic regeneration characterized by DNA synthesis the level of AMP decreases. Conversely AMP level increases during caudal regeneration. The nucleotide AMP might be the substance which specifically inhibits cephalic regeneration.
Selective reinnervation in skin rotation grafts in Rana pipiens
Authors: Bloom Emanuel M. , Tompkins Robert 
Published: June 2005

AbstractSkin rotation grafts were performed in Rana pipiens tadpoles producing misdirected reflexes in adult frogs. The pattern of innervation fields of dorsal and ventral rami of segmental nerves 3, 4, 5 and 6 were investigated by recording from the severed rami with suction electrodes. Innervation patterns of regenerated fields were influenced by graft borders and adjacent fields. Misdirected reflexes were found for ventral skin on the dorsal side only when innervated by ventral rami in a manner never seen in normal or sham operated animals. This suggested that selective reinnervation has occurred.
Sperm concentration dependency in the fertilization and zonae sperm binding properties of mouse eggs inseminated in vitro
Authors: Wolf D. P. , Inoue M. 
Published: June 2005

AbstractSperm penetration of zonae and fertilization of mouse eggs in vitro was studied as a function of sperm concentration over the range 103−106 cells/ml. Maximal fertilization was obtained at 105 sperm/ml with markedly reduced levels seen at lower concentrations. Eggs inseminated at low sperm concentrations were, however, characterized by the absence of multiple sperm penetrations of their zonae and by the retention of an intact cumulus oophorus during culture. Penetration levels were similar in eggs inseminated with and without an intact cumulus, although increases in supernumerary and supplemental sperm were observed with partly denuded ova. The distribution of sperm found within eggs inseminated in vitro was compared with a distribution predicted by chance alone. The similarity in observed and expected distributions indicated that a functional zona reaction was absent in eggs inseminated in vitro. Sperm binding to zonae of cumulus‐free unfertilized mouse eggs was shown to be related to sperm concentration over the range 103‐106 cells/ml. Zonae sperm binding sites, while too numerous for accurate quantitation, exceeded 100 per zona. The interrelationships between sperm penetration of and sperm binding to the zonae of cumulus‐free eggs were examined. At low sperm concentrations, the ratio of sperm/zonae with bound sperm to sperm/penetrated egg approached one, although the total number of bound sperm exceeded the total number of penetrating sperm. That proportion of cells in a preincubated epididymal sperm suspension capable of binding to the zona was determined and employed in an estimation of the extent of sperm capacitation.
The influence of the otic capsule in Ambystomid skull formation
Authors: Leibel Wayne S. 
Published: June 2005

AbstractIn the absence of the otic capsule, or in the presence of capsular materials of varying volume or placement, the bones and cartilages of the contiguous skull showed several sorts of responses.
The parietal and squamosal bones, and possibly the parasphenoid bone and parachordal cartilage apparently used the capsule as a substrate, spreading over its surface.
The parietal, squamosal, and exoccipital bones, and the quadrate cartilage were displaced when otic capsule material was absent or oversized.
The squamosal bone developed at first independently of the capsule but was modified in its shape and size by the capsule in later, possibly inductive, response.
Stresses resulting from paired otic capsules of unequal size bent the parasphenoid bone and the parachordal cartilage through angles of predictable direction relative to the notochord.
The paired exoccipital bones developed at different rates when one otic capsule was absent or oversized.
The results obtained following manipulation of the otocyst indicate the major role of extrinsic (epigenetic) parameters in normal skeletogenesis and emphasize an apparent discrepancy between the normal and potential expansion of a bone.
Evidence for a polyspermy block at the level of sperm‐egg plasma membrane fusion in Urechis caupo
Authors: Paul Miles , Gould‐Somero Meredith 
Published: June 2005

AbstractThe results of sperm binding experiments reveal no change in the sperm binding properties of the egg surface coat at fertilization of Urechis caupo eggs. When fertilized eggs are reinseminated, sperm continue to attach to the egg surface coat. The acrosomal tubules of supernumerary sperm are observed in the perivitelline space closely apposed to the egg membrane. Thus, the polyspermy block in Urechis eggs involves neither alteration of sperm binding sites nor inhibition of the acrosome reaction. Our results suggest that the block is at the level of sperm‐egg membrane fusion.
The fine structural development of preimplantation mouse parthenotes
Authors: van Blerkom Jonathan , Runner Meredith N. 
Published: June 2005

AbstractThe normality of the preimplantation development of 2‐cell to expanded blastocyst stage mouse parthenotes, derived from oocytes activated in vivo, or in vitro, has been assessed at the fine structural level. Major changes in the organization of the cellular organelles, i.e., nucleoli, mitochondria, ribosomes, RER and junctional complexes, follow the same developmental sequences observed in embryos obtained from normally fertilized oocytes. One difference between parthenotes and controls is the scarcity of crystalloid bodies in parthenotes at the blastocyst stage. Because the embryos examined in this study had been cultured in vitro, in a simple salt and albumin medium in the absence of maternal influences, our observations on parthenotes indicate that developmental, preimplantation changes in the subcellular organization of the embryo do not require the continued presence of “maternal” factors or the participation of the paternal genome.
Extra cytoproct mutant in Paramecium tetraurelia: Morphogenetical analysis of proters and opisthes
Authors: Ng Stephen F. 
Published: June 2005

AbstractTo account for the differences between proters and opisthes with regard to extra cytoproct morphogenesis in Paramecium tetraurelia, two hypotheses have been proposed and tested. (i) The differences may be a result of different actions of proter‐macronucleus and opisthe‐macronucleus. This hypothesis has been tested by cytoplasmically connecting the proter with the opisthe in the form of chains, some of which have only one macronucleus per chain. However, the connected proters and opisthes remain different in extra cytoproct morphogenesis, thus arguing against the hypothesis. (ii) The differences may be a result of differences between the proter and the opisthe with regard to the development of their posterior‐ventral cortex: proters have a newly‐developed posterior‐ventral cortex whereas opisthes receive the posterior‐ventral cortex from the pre‐fission mother animal. This hypothesis has been tested by surgically producing an opisthe with a newly‐regenerated posterior cortex. Such opisthes, however, remain different from proters in extra cytoproct morphogenesis. Thus no direct support for the second hypothesis is obtained. Also, proteropisthe difference in morphogenesis may be understood in terms of Wolpert's positional information hypothesis, by assuming that the anterior and posterior ends of a dividing animal serve as reference points for establishing a gradient and that positional information before separation of the two daughter animals leads to differences in extra cytoproct morphogenesis between them after separation.
Changes in the tail of Ambystoma maculatum at different stages of metamorphosis: Observations on tissue remodeling and its relationship to hydrolytic enzymes
Authors: Derby A. , McEldoon W. 
Published: June 2005

AbstractA system for staging A. maculatum during growth and metamorphosis was devised, based on several parameters of body size; body length, tail length and tail width. Animals at various stages of metamorphosis were empolyed to study the relationship between specific biochemical and histological changes that occur in the tail of this urodele during metamorphosis. The specific and total activity of two hydrolytic enzymes, acid phosphatase and β‐N‐acetyl‐glucosaminidase, were measured in tail tissues at progressive stages of development. The activites of these enzymes increased in both the fins and muscular portion of the tail during metamorphosis. These activities can be correlated with resorption of the tail fins and the remodeling of tissues in the muscular portion of the tail.
Regenerative abnormalities in Notophthalmus viridescens induced by repeated amputations
Authors: Dearlove G. E. , Dresden M. H. 
Published: June 2005

AbstractThe fidelity of the regenerative response in the adult newt, Notophthalmus viridescens, was examined following repeated amputations at the level of the distal one‐third of humerus. Three to four months following amputation, all regenerates were scored for gross morphology, reamputated, and stained with methylene blue for skeletal elements. The occurrence of abnormal regeneration with respect both to gross morphology and to skeletal structure was found to increase directly with the number of times the limb stumps were required to initiate dedifferentiation and repair. The initial amputation‐regeneration process produced structurally normal replacement limbs in 91% of the cases examined. Reamputations of 4‐digit regenerates (3‐4 months after the previous transection) resulted in structurally abnormal regenerates in 28% of the cases following two amputation; 50% of the cases following three amputations; 65% of the cases following four amputations; and 81% of the cases following five amputations. The relationship between repeated dedifferentiation, proliferation, and redifferentiation and normal limb development are discussed.
Retention of ova in oviducts of senescent mice and hamsters
Authors: Parkening Terry A. 
Published: June 2005

AbstractYoung (3–5 months of age) and senescent (12–17 months of age depending on the species) female mice, hamsters and rats were mated with young mature males and examined for numbers of degenerating ova. Young female mice, hamsters, rats and senescent rats exhibited normal numbers of ova following ovulation and, in general, normal numbers of blastocysts before implantation. In contrast, on the morning of ovulation some senescent mice and hamsters exhibited degenerating ova in the isthmus or isthmic‐utero‐tubal region of the oviduct, while normal ova were found in the ampulla. Degenerating ova were also located in the uterine horns of one mouse and hamster before implantation (day 3 of pregnancy). Another hamster at the same stage of pregnancy exhibited 24 degenerating ova and nine blastocysts, all of which remained in the oviducts except for one blastocyst recovered from the uterus. In a previous study (Parkening and Soderwall, '75), a histological examination of the number of corpora lutea from ovaries removed from senescent female hamsters whose oviducts contained large numbers of degenerating ova indicated the deteriorating ova were not ovulated following mating. Why ova from the previous unmated estrous cycle(s) remain in the oviducts of some senescent mice and hamsters remains to be determined.
The effect of hypothalamic thermal stimulation on respiration in the turtle
Authors: Siegel Eliot B. , Privitera C. A. 
Published: June 2005

AbstractCumulative Oxygen Consumption (VO2) and Oxygen Consumption per Unit Time were measured for fresh water turtles (Pseudemy scripta elegans) as hypothalamic stimulation was applied. Stimulation was provided by means of a thermode at 0–2° C (cold), 27° C (sham), and 55–60° C (hot). A statistically significant increase in mean cumulative oxygen consumption was noted for hot stimulation as compared to control value. A less dramatic but significant decrease in mean cumulative oxygen consumption was noted for cold stimulation. Both the increase and decrease, for hot and cold application, respectively, were proportional to the temperature of the thermode. Mean cumulative oxygen consumption per unit time did not show any corresponding statistically significant increase or decrease for hot or cold stimulation, respectively. Application of thermode at room temperature (sham) produced no significant change in respiration. This study indicates that reptiles have evolved a neural input mechanism sensitive to temperature change before mammalian and avian endothermy had developed.
Regeneration in the fiddler crab, Uca pugilator, after injury or removal of limb buds
Authors: Weis Judith S. 
Published: June 2005

AbstractAfter autotomy of seven appendages and partial regeneration, crabs (Uca pugilator) were subjected to removal of one, three, or six developing limb buds at different stages of limb growth. Removal of one limb had no effect on the growth of the remaining limb buds or the time of ecdysis, and the limb bud removed was not replaced before ecdysis. Removal of six limb buds early in the regenerative period caused a retardation of growth in the remaining bud until the reamputated buds could be replaced. Ecdysis was postponed in these animals. Removal of six limb buds at a later stage, or removal of three limb buds at any stage, produced a slight delay in growth of the remaining bud(s) which was not always statistically significant. The inhibition of growth in the remaining bud(s) was greatest in those individuals which went on to replace the reamputated buds. Such individuals also exhibited a longer time to ecdysis.No inhibition of growth or delay in ecdysis was produced in small crabs (11–12 mm carapace width) by removal of one, three, or six limb buds. These were generally not replaced.Animals which had six limb buds removed early in regeneration showed a greater inhibition of growht in the remaining limb bud than those which had eyestalks as well as six limb buds removed. This latter group, however, did show a significant retardation. This is considered evidence for the production of limbgrowth inhibiting substances in other sites in addition to the eyestalks.Limb buds which had been injured grew more slowly than contralateral control limbs initially, but the difference diminished as the crabs approached ecdysis. Ecdysis was not delayed by the presence of this one incomplete limb bud. This is consistent with the lack of effect of removal of a single limb bud, seen in the previous experiments.
An analytical model for ovarian follicle dynamics
Authors: Faddy M. J. , Jones Esther C. , Edwards R. G. 
Published: June 2005

AbstractDifferential counts of follicles of different sizes in the ovaries of intact and hypophysectomized strain A mice of various ages have been analysed statistically. The influence of age on the number of follicles in each size group is described. The number of small follicles in the ovarian pool declined exponentially, whereas number of follicles in other groups displayed two peaks, one during immaturity and the other in adult life. These appeared sequentially in follicles in successive groups.The proportion of follicles growing and dying was estimated and age dependent fluctuations in the time spent by follicles in each group were demonstrated. Further calculations then determined the mean inflow and outflow of follicles to and from the various groups throughout the lifespan.Hypophysectomy during post‐puberty decreased only slightly the utilization of small follicles from the pool and did not prevent their subsequent development to the two‐layered stage. Many follicles then died at this stage of development, indicating that the initial main site of gonadotrophic action may be on medium sized follicles with two layers of granulosa cells.