bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on cell differentiation: Inducing capacity of sulfhydryl‐containing amino acids on post‐nodal pieces of chick blastoderms
Authors: Lee Hsin‐yi , Kalmus Gerhard W.
Published: June 2005

The inducing capacity of sulfhydryl (SH)‐containing amino acids (cysteine and glutathione) on post‐nodal pieces (PNPs) of stage 4 chick blastoderms was investigated. PNPs were treated for different lengths of time with chick Ringer's solution (control group) or chick Ringer's solution containing cysteine or glutathione, followed by culturing for 2–10 days on Spratt‐Haas agar medium or on the chorioallantoic membrane of 8‐day chick embryos. Control PNPs rarely showed differentiation, but those treated with the amino acids for six hours or longer developed structures such as neural tissue, notochord, somite mesoderm, and nephric tubules. The pulsatile tissue was only seen in the PNPs cultured for four days or longer. Two‐four hours of treatment was too short to provoke induction in a statistically significant number of PNPs. The highest frequency of induction was noted in those pretreated with glutathione (8 μg/ml) for eight hours, followed by culturing for four days. The magnitude of the inducing capacity and toxicity of the amino acids were concentration dependent: a deleterious effect was observed at 14 μg/ml, the highest frequency of induction occurred at 8 μg/ml, but the frequency decreased as the concentration decreased; at 2 μg/ml all PNPs remained viable, but only a few (9–14%) showed differentiation. The inducing capacity of the amino acids was counteracted by equimolar concentrations of p‐chloromercuribenzoic acid or w‐chloroacetophenone. The effects of glutathione (8 μg/ml) differed from those of Hensen's node grafts in that the former caused sublethal cytolysis and inhibited H3‐uridine uptake in competent ectodermal cells during the first 18 hours of cultivation.
Properties of the hatching enzyme from frog embryos
Authors: Katagiri Chiaki
Published: June 2005

The stage 18 Rana chensinensis embryos were deprived of their envelopes, and were reared until stage 21. The culture medium concentrated by lyophilization contains the enzyme (hatching enzyme; HE) which digests the whole egg‐envelopes of the homologous species. The enzyme also digests the outer egg‐jelly layers of a closely related species, but does not affect its inner layers and the whole envelopes of the less‐related anuran species. HE is a protease, as defined by its activity towards casein. Successive fractionation by (NH4)2SO4 precipitation, Sephadex gel‐filtration, and DEAE‐cellulose chromatography yielded a 100‐fold increase of proteolytic activity in the original culture medium. The molecular weight estimation by gel‐filtration gave a value of 55,000–60,000 for the HE. The pH optimum for the enzyme is 7.4–7.8. The enzyme is easily inactivated by preincubation at temperatures higher than 50°C, but is quite stable to autodigestion at pH 7.4. Its activity is unaffected by Na+, K+, and the soybean trypsin inhibitor, but is strongly inhibited by Ca++, Mg++, ethylenediaminetetraacetic acid, and diisopropyl‐fluorophosphate. The properties of the HE demonstrated here provide a basis for the view that this enzyme can be regarded as a unique protein functioning at the particular stage of embryogenesis.
The dicyemid mesozoa as an integrated system for morphogenetic studies. I. Description isolation and maintenance
Authors: Lapan Elliot A. , Morowitz Harold J.
Published: June 2005

The morphological simplicity of the dicyemid Mesozoa is such as to allow mapping of every individual cell during the development of the organisms. Individual cells are of a size amenable to micromanipulation and a number of potential morphogenetic markers is readily apparent. The possibility of raising the animals in vitro and obtaining developmental mutants makes these organisms excellent candidates for use as an integrated system to correlate cytodifferentiation and morphogenesis with genetic control.

An axenic, nearly defined, medium in which the mesozoans can be kept for over three months has been developed. Methods for isolating and maintaining the organisms are described.
Coelomic fluid and blood serum proteins of the metamorphosing bullfrog tadpole
Authors: Thornburg Kent L. , Hillemann Howard H. , Martin Gordon W.
Published: June 2005

Bullfrog (Rana catesbeiana) tadpoles were divided into four groups containing Gosner ('60) stages as follows: I, 27–31; II, 32–36; III, 37–41; IV, 42–46. Extractable coelomic fluid volume from late metamorphic tadpoles (Group IV) was found to have a highly significant (p<0.001) negative correlation with stage; tadpole weight also had a negative correlation with stage (p<0.025). No significant correlation was found between coelomic fluid volume and tadpole weight. Group IV blood serum protein levels (x = 1.30 ± SEM 0.10 g/100 ml serum) were shown to be significantly higher than corresponding coelomic fluid serum protein levels (x = 0.80 ± 0.06 g/100 ml). Electrophoresis data demonstrated an increase in the albumin fraction of both blood serum and coelomic fluid during metamorphosis. I‐125 labeled human serum albumin equilibrated with the blood serum at equal concentrations about ten hours after an intracoelomic injection. A coelomic fluid turnover time of 26% per hour was calculated from the tracer data. We hypothesize that a slight sieving occurs at the coelomic fluid inflow site with none at the outflow site.
Parathyroid hormone preparations, salmon calcitonin, and urine flow in the South American lungfish, Lepidosiren paradoxa
Authors: Pang Peter K. T. , Sawyer Wilbur H.
Published: June 2005

In the South American lungfish, Lepidosiren paradoxa, injections of salmon calcitonin or bovine parathyroid extract have no effect on serum calcium levels. However, salmon calcitonin elicits a distinct diuresis. Crude or purified parathyroid extract or synthetic parathyroid hormone (1–34 fraction) produce a distinct antidiuresis.
Extensive and intensive factors determining the performance of striated muscle
Authors: Josephson Robert K.
Published: June 2005

Striated muscle is obviously a versatile tissue, one which has been malleable to selective pressure and has become modified for many specific tasks. The variations which adapt striated muscle to particular functions involve both changes in its structural organization and changes in the chemical nature of its components. Although a number of factors have been identified which contribute to the diversity of muscle performance, it is not yet possible to account adequately for the wide range in muscle performance throughout the animal kingdom. While not a new direction in comparative physiology, developing quantitative explanations for the diversity of muscle performance is still an obvious, remaining task.
Hemoglobins and hemocyanins: Comparative aspects of structure and function
Authors: Bonaventura Joseph , Bonaventura Celia , Sullivan Bolling
Published: June 2005

Comparative studies of protein structure and function can be quite interesting by themselves, and even more interesting when interpreted with respect to an animal's physiology. In the case of fish hemoglobins, some success in the latter has been achieved but there are still many unsolved problems. It appears that comparative physiology and biochemistry have entered an era where results from comparative studies can shed a great deal of light on biochemical mechanisms in general. The trout hemoglobin system is an example. Distinctive hemoglobins in this system are presently being used as high resolution probes of the ligand‐binding mechanism. Characterization of the multiple, structurally distinct subunits of the 60S Limulus hemocyanin molecule may similarly aid in understanding its function.

Our studies suggest the possibility of using Limulus hemocyanin and other hemocyanins as structural homologs and analogs of more complex macromolecular arrays. The rapid development of molecular structural data from X‐ray crystallographers combined with the vast data of comparative physiology and biochemistry makes this one of the most exciting areas in present day science.
Temperature as a selective factor in protein evolution: The adaptational strategy of “compromise”
Authors: Somero George N.
Published: June 2005

Most 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

A 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

Gemmules 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

The 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

Spongilla 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

Oocytes 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

The 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

Skin 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

Sperm 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

In 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

The 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

The 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

To 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

A 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

The 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

Young (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

Cumulative 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

After 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

Differential 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.
Protein synthesis in lethal nucleocytoplasmic hybrids between the species Pleurodeles waltlii Michahelles and Ambystoma mexicanum shaw (Urodele amphibians) obtained by nuclear grafting
Authors: Aimar C. , Desvaux F. X. , Chalumeau‐Le‐Foulgoc M. Th.
Published: June 2005

Using Polyacrylamide gel electrophoresis, proteins stemming from the nucleus of the donor species in nucleocytoplasmic hybrids were determined. The interspecific lethal nucleocytoplasmic hybrids of Pleurodeles waltlii and Ambystoma mexicanum were studied. The presence of these proteins at the blastula or early gastrula stages attests to the early nuclear control of their synthesis.
Phagocytosis of chloroplasts in Placida dendritica (Gastropoda: Sacoglossa)
Authors: McLean N.
Published: June 2005

Phagocytosis of algal chloroplasts by digestive gland cells in the sacoglossan opisthobranch Placida dendritica is described. It is suggested that engulfment of chloroplasts is accomplished by veils of cytoplasm which are derived from elongating microvilli.
Respiratory behaviour of sea‐urchin spermatozoa. I. Effect of pH and egg water on the respiratory rate
Authors: Ohtake Hideki
Published: June 2005

Effects of pH and egg water on the respiration of sea‐urchin spermatozoa were polarographically studied in three sea‐urchins and one starfish species. Sea‐urchin sperm respiration is extremely sensitive to change in the pH of the suspending medium over a wide range. In normal‐sea water, the pH of the sperm suspension decreased from 8.02 to 7.62, after four to five minutes' incubation at 18°C. The Respiratory Dilution Effect could be recognized in the same medium. However, when sea water was buffered with HEPES at pH 8.2, the Effect was no longer observed. The diffusate from egg water (jelly coat solution) brought about a striking increase in the respiration when added to moderately respiring spermatozoa in HEPES‐sea water of pH values lower than 7.9. No increase in the respiration was observed when the diffusate was added to vigorously respiring spermatozoa in HEPES‐sea water of pH values higher than 8.2. Sperm motility was also inhibited by acid pH, and this inhibition was reversed by the addition of the diffusate. It does not seem that there is any species‐specificity among three sea‐urchins and one starfish used. The role of the diffusate is discussed in relation to the penetration of spermatozoa through the jelly coat to the egg surface.
The role of calcium in the acrosome reaction: An analysis using ionophore A23187
Authors: Talbot P. , Summers R. G. , Hylander B. L. , Keough E. M. , Franklin L. E.
Published: June 2005

The role of Ca+2 in the acrosome reaction of echinoid and mammalian sperm was investigated using the Ca+2 transporting ionophore A23187. The ionophore induced morphologically normal acrosome reactions in both types of sperm (as assessed by electron microscopic observation of echinoid sperm and phase contrast microscopic observation of mammalian sperm). In echinoids, these reactions were immediate. In the guinea pig and hamster, ionophore significantly decreased the capacitation interval; early reactions were accompanied by activation of motility. Ionophore induced reactions were affected by sperm, ionophore and Ca+2 concentrations. Since both ionophore induced and natural reactions require extracellular Ca+2, it is suggested that an influx of Ca+2 represents the initial step of the acrosome reaction. Under natural conditions, the permeability change which results in Ca+2 influx may be induced in echinoid sperm by egg jelly and may occur in mammalian sperm during capacitation.

Ionophore A23187 should prove an experimentally useful drug for further study of the acrosome reaction since its effect on cells is understood, it induces synchronous reactions in a high percentage of sperm, and it conveniently reduces the capacitation interval in mammalian sperm.
Biosynthesis of crustacean lipovitellin. III. The incorporation of labeled amino acids into the purified lipovitellin of the crab Pachygrapsus crassipes
Authors: Lui Chung W. , O'Connor John D.
Published: June 2005

Electrophoretically pure subunits were obtained from the lipovitellin (LV) of the intertidal crab, Pachygrapsus crassipes. The molecular weights of these subunits were determined. In addition, it was demonstrated that the ovaries of Pachygrapsus, incubated in vitro, incorporated 3H‐leucine into the two principal subunits of lipovitellin. At the end of a 30 hour incubation the specific activity of each of the principal subunits was approximately 30,000 dpm/mg protein. It is concluded that the ovaries of Pachygrapsus crassipes are capable of synthesizing the proteinaceous yolk found in the mature egg.
Esterase isozyme patterns in developing embryos of Brachydanio rerio (zebra danio), Brachydanio abolineatus (pearl danio), and their hybrids
Authors: Hart Nathan H. , Cook Marie
Published: June 2005

The ontogeny of esterase isozymes in Brachydanio rerio (zebra danio), Brachydanio albolineatus (pearl danio), and hybrids formed by their reciprocal crosses was investigated using polyacrylamide disc electrophoresis. Seven esterase isozymes were identified in each species from the unfertilized egg stage to nine days posthatch. Electrophoretic analysis of qualitative changes in enzyme pattern indicated that some esterases were present at all stages of development while other esterases abruptly appeared at a specific stage of morphological differentiation. The esterases of both species were classified on the basis of differential substrate and inhibitor specificities.

In developing hybrids formed by B. rerio eggs inseminated with B. albolineatus sperm, the maternal isozyme pattern persisted until Stage 17 (gastrulation). Embryonic extracts from Stage 17 onward showed a slow‐moving, DFP‐sensitive carboxylesterase of paternal origin. In developing hybrids fromed by B. albolineatus eggs inseminated with B. rerio sperm, a paternal contribution to the esterase pattern was probably present by the end of gastrulation; esterase activity of distinctively paternal origin was present by Stage 22 (retinal pigmentation). The maternal contribution to the total esterase profile appeared to remain high through hatching.

Additional evidence for gene activity at gastrulation was obtained in experiments utilizing actinomycin‐D and cycloheximide. Results of exposing embryos of B. rerio to 15μg/ml of actinomycin‐D indicated that transcription of the template RNA coding for cholinesterase occurred during gastrulation or some 20–30 hours prior to the appearance of the isozyme at Stage 22. This template RNA was translated sometime during the 10‐hour interval immediately preceding Stage 22.
Base composition of DNA from some reptiles
Authors: Olmo Ettore , Odierna Gaetano
Published: June 2005

The DNA base composition was studied in 9 reptilian species (4 chelonians, 3 saurians, and 2 ophidians) by the thermal denaturation method. This preliminary investigation has brought to light differences in GC percentages and in the shape of melting curves between chelonian DNA and that from saurians and ophidians.
Involvement of a trypsin‐like activity in sperm penetration of zona‐free mouse ova
Authors: Wolf Don P.
Published: June 2005

The presence of trypsin inhibitors during insemination reduced penetration of zona‐intact and zona‐free mouse ova by capacitated sperm. This inhibition was dependent upon both concentration of inhibitor and sperm. Preincubation of gametes in inhibitors did not markedly influence their subsequent fertility, nor did it alter sperm motility. Trypsin inhibitors may exert an effect on penetration by interfering with the induction of the sperm acrosome reaction or with the process of sperm‐egg fusion.
Tail regeneration in the plethodontid salamander, Plethodon cinereus: Induced autotomy versus surgical amputation
Authors: Dinsmore Charles E.
Published: June 2005

Regeneration of the tail in the plethodontid salamander, Plethodon cinereus, occurs following either surgical amputation or induced autotomy. Autotomy may occur along any one of the caudal myosepta which form natural cleavage planes. The distally attached myofibers break away from the myoseptum which then becomes part of the stump surface remaining intact during subsequent regeneration of the distal segments. Under these conditions, therefore, muscle fibers do not normally participate in tail regeneration. If, however, the myofibers of a caudal myotome are interrupted as in mid‐segment amputation, the damaged fibers undergo hyaline degeneration and are largely replaced by connective tissue often as far proximally as the next myoseptum. Other tissues at the amputation surface are concurrently engaged in the epimorphic regeneration of the tail, including myogenesis, though at a slower initial rate than that following autotomy. Muscle cells, therefore, appear not to participate in epimorphic tail regeneration in Plethodon cinereus following either surgical amputation or induced autotomy.
Turnover of cytochrome C in skeletal muscle of green sunfish (Lepomis cyanellus, R.) during thermal acclimation
Authors: Sidell Bruce D.
Published: June 2005

The concentration of cytochrome c in the skeletal muscle of the green sunfish (Lepomis cyanellus) increases with decreasing temperature of acclimation: 1.51 ± 0.09, 1.17 ± 0.03, and 0.98 ± 0.07 nanomnoles per gram wet weight from muscle of animals acclimated to 5°, 15°, and 25°C, respectively.

The roles of synthesis and degradation of cytochrome c during thermal acclimation were investigated by measurement of loss of specific radioactivity from cytochrome c and from total mitochondrial heme protein, and by analysis of the rate of change in concentration of cytochrome c. The radioisotope used was 14C‐δ‐aminolevulinic acid, a non‐reutilizable heme precursor.

At 25°C, the half‐life of cytochrome c was 7.1 days based on radioactivity measurements and 5.6 days based on change in concentration. Statistical analysis showed no significant difference in half‐lives obtained by the two methods. The half‐life of total mitochondrial heme protein was determined to be 5.7 days on the basis of radioactivity data, under the same conditions. No significant difference was found between the rate of turnover of the heme protein pool from mitochondria and either measurement for cytochrome c at 25°C.

At an acclimation temperature of 5°C, the half‐life of cytochrome c from skeletal muscle was 13.7 days based upon changes in concentration. At low acclimation temperature, radioactive label was retained in acid‐soluble form by fish for many days, precluding measurement of half‐life by this technique.

Transfer of fish from 25° to 5°C resulted in a rapid decrease of approximately 40% in rates of synthesis of skeletal muscle cytochrome c, and a concomitant decrease in the degradation rate constant for this molecule of approximately 60%. The disproportionality in temperature‐sensitivities of these two processes leads to an approximately 50% net increase in the concentration of cytochrome c during acclimation. In transfer from 5° to 25°C, the converse, rapid readjustments in synthetic and degradative parameters occur, resulting in the observed decrease in cytochrome c content.
Volume regulation by Flounder red blood cells: The role of the membrane potential
Authors: Cala Peter M.
Published: June 2005

The nucleated red blood cells of the Winter Flounder Pseudopleuronectes americanus demonstrate a volume regulatory response subsequent to osmotic perturbation. The net water movements associated with the response are secondary to net inorganic cation flux. The increased net cation fluxes occur in response to increased cation permeability (Pcation). While ionic strength and cell volume do not appear to be the stimulus for the volume regulatory response i.e. increased Pcation, changes in the cell membrane potential (Vm), as calculated from the chloride distribution ratio, do appear to result in increased Pcation. These studies demonstrate that manipulations leading to membrane hyperpolarization result in net loss of cellular K and water. In contrast treatments which depolarize Vm lead to cellular uptake of Na, K, Cl and water.
Correlation of structure and active transport in the teleost nephron
Authors: Trump Benjamin F. , Jones Raymond T.
Published: June 2005

In the present study we have extended our investigations concerning the correlation between ultrastructure and active transport in the isolated flounder nephron. The composition of the fish nephron is defined in ultrastructural terms and its behavior when incubated in vitro under short term and long term culture conditions is described. Using the in vitro system originally described by Forster, a variety of inhibitors and conditions which modify cell structure and function were tested. Ultrastructure was correlated with chlorphenol red dye transport. In general, conditions altering active transport also markedly altered cellular ultrastructure. The principal alterations consisted of membrane changes involving various organelles — most importantly the plasma membrane and the mitochondria. Conditions associated with irreversible cell injury could be rapidly produced by interference either with mitochondrial ATP synthesis or with the integrity of the plasma membrane. Both of these rapidly lead to irreversible events which are preceded by reversible structural changes. Organelle changes progress in a rather well‐defined sequence of reversible and irreversible stages which are defined. One difference between the two types of interactions is the presence of intramitochondrial calcification which does not occur with direct modification of the mitochondrial electron transport system. The concept of utilizing long term explant organ cultures of fish nephrons for environmental studies is introduced.
Interdependence of active Na+ and Cl− transport by the isolated urinary bladder of the teleost, Pseudopleuronectes americanus
Authors: Renfro J. Larry
Published: June 2005

The relationship between transepithelial Na+ and Cl− active transport from the mucosal toward the serosal surface was studied by ion substitution experiments in the isolated, perfused urinary bladder of the winter flounder, Pseudopleuronectes americanus. The tissue behaves as a simple ohmic resistance of about 1000 ohm·cm2 which was not significantly changed by perfusion of the lumen (mucosal surface) with Na‐free or Cl‐free solutions. Transepithelial electrical potential difference and short‐circuit current were reversed (mucosa positive to negative) by Cl‐free perfusion but unaltered by Na‐free medium. Short‐circuit current did not agree with isotopically measured net Na+ and Cl− flux in either control or ion‐substituted medium. Cl‐free perfusion depressed net Na+ flux more than 50% and a similar effect was seen on net Clflux upon Na‐free perfusion. A kinetic analysis of the relationship of Na+ or Clflux to the concentration of Na+ or Cl− in the perfusate in the presence and absence of Cl− or Na+, respectively, indicated that Cl‐free medium acted as a non‐competitive inhibitor of Na+ transport, and the effect of Na‐free medium on Cl− transport could be interpreted similarly. This inter‐dependence of Na+ and Cl− transport was taken as an indication of co‐transport of these two ions. Amiloride (10−4 M) seemed to inhibit a component of Na flux distinct from the Cl‐dependent flux. It had no effect on Cl− transport.
Ouabain inhibition of gill Na‐K‐ATPase: Relationship to active chloride transport
Authors: Silva Patricio , Solomon Richard , Spokes Katherine , Epstein Franklin H.
Published: June 2005

Ouabain circulating in blood inhibits Na‐K‐ATPase in the gills of seawater eels at a concentration similar to that necessary for inhibition in vitro. By contrast, a much higher concentration is required when ouabain is applied to the exterior of the gill. Inhibition by external ouabain occurs only when the drug gains access to the circulation of the fish, as evidenced by simultaneous inhibition of Na‐K‐ATPase in the kidney. These results suggest that the Na‐K‐ATPase of gill chloride cells faces inward, lining intracytoplasmic tubular channels continuous with the extracellular fluid.

Inhibition of gill Na‐K‐ATPase by ouabain in intact salt water eels results in almost complete inhibition of the efflux of both Na+ and Cl−. The efflux of tritiated water was much less reduced, to 60% of normal. Since chloride is actively transported outward across the gill of seawater teleosts, it is suggested that active chloride transport is coupled to Na‐K‐ATPase. A neutral sodium chloride carrier is postulated that is energized by the movement of sodium from extracellular fluid down its electrochemical gradient into the chloride cell.