bluuebunny/crossref_metadata_2025 huggingface dataset:
Nuclear protein changes in the maternally and paternally derived chromatin at fertilization
Authors: Kunkle Mel , Longo Frank J. , Magun Bruce E.
Published: June 2005

The proteins which become associated with the paternally derived chromatin during fertilization may be instrumental in its activation and in the dramatic structural metamorphosis of the sperm nucleus during pronuclear development. Proteins associated with sperm and zygote nuclei and male and female pronuclei of fertilized sea urchin eggs were analysed by polyacrylamide gel electrophoresis in order to examine nuclear protein changes in the paternally and maternally derived chromatin following insemination. Results demonstrate major changes in both the solubility characteristics and polypeptide profiles of sperm nuclei upon insemination. Evidence is presented which indicates that at fertilization the paternally derived chromatin acquires proteins of molecular weights greater than 80,000 and a nuclear protein composition similar to that of the female pronucleus. The nuclear proteins associated with zygote nuclei were compared to those of combined male and female pronuclei and showed many similarities and some differences. Several polypeptides were present in zygote nuclei which were not observed in pronuclear extracts.
Regulation of the oxidative NADP‐enzyme tissue levels in Drosophila melanogaster. II. The biochemical basis of dietary carbohydrate and D‐glycerate modulation
Authors: Geer B. W. , Woodward C. G. , Marshall S. D.
Published: June 2005

When cultured on a series of casein‐synthetic diets constituting a dietary sucrose gradient, the tissue levels of glucose‐6‐phosphate dehydrogenase (EC 1.1.1.49) and 6‐phosphogluconate dehydrogenase (EC 1.1.1.43) in the third instar larvae of Drosophila melanogaster paralleled the dietary sucrose concentration. The tissue level of malic enzyme (EC 1.1.1.40) was increased only by very high concentrations of dietary sucrose; whereas, the tissue level of NADP‐isocitrate dehydrogenase (EC 1.1.1.42) was negatively correlated with the dietary sucrose concentration. Dietary supplements convertible to the intermediates of the initial steps of glycolysis stimulated high tissue levels of glucose‐6‐phosphate dehydrogenase; D‐glycerate was the most effective inducer. Dietary sucrose increased the tissue concentrations of the intermediates of glycolysis that yield lipid substrate. As a result, lipid synthesis, pentose shunt activity and the tissue levels of the oxidative pentose shunt enzymes were elevated. In contrast, D‐glycerate increased the concentrations of the intermediates of the initial part of glycolysis and stimulated high tissue levels of the oxidative shunt enzymes without concurrent increases in pentose shunt activity or lipid synthesis. Thus, the activity of the pentose shunt is a function of lipid synthesis; whereas, the tissue levels of glucose‐6‐phosphate dehydrogenase and 6‐phosphogluconate dehydrogenase are dependent on the concentrations of one or more metabolites derived from the initial part of glycolysis.
Characteristics of resting ventilation and response to hypoxia, hypercapnia, and emersion in the blue crab Callinectes sapidus (Rathbun)
Authors: Batterton Carol V. , Cameron James N.
Published: June 2005

Ventilation volume was monitored in the blue crab Callinectes sapidus using an electromagnetic flow probe. The mean resting ventilation volume for a 200 g crab was 111 ± 78 ml. min−1, mean oxygen consumption was 62 ± 27 ml. kg−1. hr−1, and mean extraction efficiency was 53 ± 15%. Blue crabs continued to ventilate in air for at least eight hours at room temperature and were able to maintain oxygen consumption during exposure to air. The crabs did not change ventilation, oxygen consumption or extraction efficiency significantly in response to hypercapnia (7.5 or 15 torr Pco2), whether breathing air, fresh water, or sea water. Ventilation increased 37% at reduced oxygen tensions (24–65 torr), but since the extraction efficiency remained the same, oxygen consumption fell more sharply at lower O2 tensions. Pecularities of the ventilatory system, such as apnea, reversals, unilateral apnea or reversals, and variable phasing of the two scaphognathites were observed. Ventilation volume varied linearly with scaphognathite frequency and pressure differential; the scaphognathite stroke volume and gill sieve resistance appeared to be constant.
A comparison of amino acid accumulation during high salinity adaptation with anaerobic metabolism in the ribbed mussel, Modiolus demissus demissus
Authors: Baginski Richard M. , Pierce Sidney K.
Published: June 2005

The metabolic alterations leading to accumulation of amino acids during the initial stages of acclimation to high salinity and anaerobiosis appear to be different in Modiolus demissus demissus. First, the major metabolic event (activation of phosphenolpyruvate carboxykinase) does not appear to occur during acclimation to high salinity since increased incorporation of 14C‐bicarbonate into succinate of isolated gills occurred only in anaerobic treatment. Secondly, the cellular changes in concentrations of amino acids and succinate observed in isolated ventricles and gills after exposure to high salinity and anaerobiosis were not similar. Thirdly, during anaerobiosis the total amino‐acid pool remained constant largely because of decreased aspartic acid concentrations.

Although different from the response to anaerobiosis, the mechanism of intracellular free amino acid accumulation during the initial stages of high salinity acclimation also depends on an alteration of intracellular metabolism. Thus, isolated ventricles exposed to salinity increases showed significantly lower levels of radioactivity in glycogen than ventricles maintained in low salinity. Similarly, radioactive glucose was selectively incorporated into the major osmotic solute (alanine) used initially during acclimation to high salinity.

These results suggest that the intracellular free alanine accumulated during acclimation to high salinity is synthesized using glycogen as the carbon source.
The nasal gland of the Montpellier snake Malpolon monspessulanus: Fine structure, secretion composition, and a possible role in reduction of dermal water loss
Authors: Dunson William A. , Dunson Margaret K. , Keith Alec D.
Published: June 2005

A study was made of the structure and function of the enlarged lateral nasal gland of the Montpellier snake (Malpolon monspessulanus). This unusual gland opens directly to the exterior via a duct on the nasal valve. The secretion is spread over the skin surface by a series of stroking movements with the head. An ultrastructural examination showed that the gland does not have the specialized cytological features associated with salt secretion, the only previously known function for nasal glands in reptiles. The principal tubule cells are filled with clear secretory vacuoles of various sizes, moderate numbers of mitochondria, and have few interdigitations with adjacent cells. The nuclei are basal. In one snake the cells had numerous membrane bound lamellar bodies (LB) in the basal region. These LB stained darkly with toluidine blue and strongly resembled lamellar bodies found in the mammalian lung. Although LB were not seen in nasal glands of five other snakes, membrane bound globular structures found in some might well be earlier or later stages of the same organelle, possibly a lysosome. A major portion of the gland is a system of anastomosing ducts lined with simple columnar or cuboidal epithelium. The ducts not only connect with the secretory tubules but also with blind vessels lined with squamous epithelium. The glands go through cyclic increases in size, which are externally visible as swellings posterior to the nares. Gentle pressure on the swollen glands expelled fluid through the duct on the exterior aspect of the nasal valve. At certain times the glands also responded to subcutaneous injections of the parasympathetic agent pilocarpine by pronounced swelling. The secretion was quite watery but contained a complex mixture of fatty acids, proteins, and variable amounts of sodium and potassium. The spreading of this material over the skin might be related to retardation of dermal evaporative water loss, since long chain fatty acids are known to have this effect when applied as films on an aqueous surface. In partial confirmation of this hypothesis, rates of total evaporative water loss were found to be extremely low (0.2–0.5% body weight/day for 0.2–1.0 kg snakes at 33°C). In dry air at 33°C, the dermal loss was only about 30% of the total evaporative loss.
A comparison of lactate dehydrogenase isozymes in tissues of immature and mature Coho salmon (Oncorhynchus kisutch)
Authors: Márquez Ernest D.
Published: June 2005

Lactate dehydrogenase (LDH) isozymes from various tissues of mature and immature (fry) Coho salmon (Oncorhynchus kisutch) were compared. Brain isozymes from both appeared identical while minor differences were seen with isozymes from liver and heart. The most dramatic differences were observed in isozymes from muscle. Adult muscle displayed 8 discernible LDH isozymes while fry muscle displayed 7. Of these, fry muscle contained 2 predominant isozymes, one of which was specified by the B locus while the other was specified by the A locus. In adult muscle 3 predominant isozymes were seen and all were A locus associated. In addition, none of the predominant isozymes from adult and fry muscle were seen to comigrate.
Epidermal regeneration and percutaneous water loss following cellophane stripping of reptile epidermis
Authors: Maderson P. F. A. , Zucker A. H. , Roth S. I.
Published: June 2005

The histological and physiological effects of the removal of superficial corneous epidermal materials have been studied in several squamate species and a caiman.

The gross and microscopic anatomy of the squamate integument has characteristics which make cellophane stripping inherently variable, but in general, when corneous materials are removed, they are replaced over a period of one to two weeks, by a tissue with the histological characteristics of the normal α‐layer. This tissue may be produced by stimulated germinal activity and/or metaplasia of other presumptive cell populations.

In caiman, the thickness of the corneous tissues of the outer scale surface is reduced by stripping and the tissue is restored to normal in approximately two weeks by stimulated germinal proliferation.

Measurements of cutaneous water loss (CWL) before, immediately after, and during two weeks post‐trauma revealed the following. There is a sudden rise in CWL immediately after stripping, and values decline over the next two weeks as the corneous tissues are replaced.

The results are interpreted as indicating that, as in mammals, the impermeability of the epidermis depends on the thickness of the corneous materials. In squamates it appears that the physiological barrier is the αlayer of the epidermal generation, and while the β‐layer cannot be excluded as playing some role in reducing the permeability of the integument, its role appears to be primarily mechanical.
Alterations in growth, function and composition of Rana pipiens oocytes and follicles associated with microsporidian parasites
Authors: Schuetz Allen W. , Selman Kelly , Samson Douglas
Published: June 2005

A class of unique, abnormally enlarged and discolored follicles and oocytes were identified in ovaries of sexually mature Rana pipiens. Various parameters of the composition, function and structure of these “large” oocytes were analyzed and compared to that of normal, fully grown oocytes and follicles obtained from the same ovary. Large oocytes in contrast to normal oocytes contained markedly elevated concentrations of potassium and decreased levels of calcium ions. Sodium and magnesium concentrations, in contrast, were relatively the same in both types of oocytes. The ratio of sodium to potassium in large oocytes was markedly depressed from that seen in normal oocytes. Treatment of normal, immature (germinal vesicle stage) oocytes with EDTA produced: (1) loss of potassium, (2) an influx of sodium and (3) an elevated Na/K ratio. Similar alterations were not observed when large oocytes recovered from the ovary or the body cavity following ovulation were treated with EDTA. Progesterone pre‐treatment of normal and large oocytes recovered from the ovary inhibited the response of the normal but not large oocytes to EDTA. Normal immature and large oocytes recovered from the ovary extensively incorporated yolk protein precursor 3H‐vitellogenin. Following ovulation 3H‐vitellogenin incorporation was markedly depressed in normal oocytes whereas large oocytes continued to incorporate at a much higher rate per unit surface area and did not undergo ultrastructural changes (retraction of microvilli) which are associated with suppression of vitellogenin incorporation. Ultrastructural analysis revealed that large oocytes in contrast to normal oocytes were devoid of cortical granules, contained few yolk platelets and numerous lipid droplets. In addition, the cytoplasm of large oocytes contained numerous microsporidia at various stages of differentiation. The results indicate that large oocytes are viable cells but undergo drastic alterations in their development, composition and function, in association with the parasitic infection. The significance of these interrelated changes are discussed in relation to the mechanisms of infection and those of gamete differentiation.
Timing of sperm transport, sperm penetration and cleavage in the rat
Authors: Shalgi R. , Kraicer P. F.
Published: June 2005

Times of sperm entry into the oviduct from the uterus, into the ampulla from the isthmus; of sperm penetration into oocytes, and of cleavage, were determined using three mating regions. Time intervals and their errors of estimation were calculated. Spermatozoa were first found in the isthmus of the oviduct no earlier than 15 minutes after coitus, but required four hours to ascend the oviduct to the ampulla. The rate of sperm arrival was equal to the rate of sperm penetration, i.e., about 3 sperms/hour. Time of cleavage in vivo was 20.6 hours after sperm penetration in ad libitum mated animals. In culture, oocytes cleaved at exactly the same time as in vivo. Delaying sperm arrival to the site of fertilization (by delaying mating) shortened the time interval between median time of sperm penetration and median time of cleavage. It was concluded that the time of cleavage of the oocyte reflects primarily the time of sperm penetration, but is also influenced by the postovulatory age of the oocyte.
Renal regulation of acid‐base balance in a freshwater fish
Authors: Wood Chris M. , Caldwell Forrest H.
Published: June 2005

Intra‐arterial injection of a fixed acid load caused only a short‐lived (< 2h) disturbance of blood pH but a long lived (2–3 days) elevation of urinary acid excretion in freshwater trout (Salmo gairdneri). The renal response comprised an immediate increase in acid output in the form of titratable acidity minus bicarbonate, and a slower rise in acid output in the form of ammonia. The total elevation in urinary acid efflux over 72h was such that no other mechanism besides renal function is needed to explain the ultimate compensation of this experimental acid‐base disturbance.
Site‐specific sperm agglutination and the timed release of a sperm chemo‐attractant by the egg of the leptomedusan, Orthopyxis caliculata
Authors: Miller Richard L.
Published: June 2005

In Orthopyxis sperm entry apparently occurs at the site of emission of the polar bodies. If sperm are present from the time of spawning of the egg, they agglutinate head to head shortly after emission of the second polar body but only at a point on the egg surface under the second polar body. Since sperm agglutination does not occur elsewhere on the egg, it appears that this part of the surface of the egg of Orthopyxis and probably other hydromedusae is a special membrane patch which causes sperm to bind reversibly both to it, and to each other. The patch develops at a specific time during egg maturation and ceases function at or just after fertilization. Concomitant with the appearance of the patch is the production of a species‐specific sperm attractant by the egg. These results imply that the egg has strict control not only of the site and timing of sperm penetration but also of the time during which sperm are attracted to the egg.
Testosterone and 5α‐dihydrotestosterone inhibit both growth and spermatogenesis in the remaining testis in partially castrated adult newts, Notophthalmus viridescens
Authors: Scadding Steven R.
Published: June 2005

The testis of the newt, Notophthalmus viridescens, undergoes hypertrophy following partial castration. Injections of either testosterone or 5α‐dihydrotestosterone are equally effective in inhibiting the increase in testis weight which follows partial castration. In addition, both of these androgens inhibit spermatogenesis, i.e., spermatogonia appear to be inhibited resulting in early cessation of spermatogenesis and a precocious division of the testis into separate spermatogonia and sperm compartments.
Effects of continual mechanical agitation prior to cleavage in echinoderm eggs
Authors: Rappaport R.
Published: June 2005

The force necessary to accomplish animal cell division is exerted by a ring of specialized cytoplasm which is rapidly established at the equatorial surface by the mitotic apparatus. Although the structure of the cleavage mechanism is not demonstrable before it is functional, the geometrical relation between the mitotic apparatus and the equatorial surface is established early in the mitotic cycle and remains unchanged. In order to learn more about the process by which the mitotic apparatus establishes the division mechanism, regions of cleaving echinoderm eggs (Echinarachnius parma, Lytechinus pictus) were continually agitated or stretched while establishment took place. Normal cleavage occurred despite stroking and vibration of the equatorial surface at different frequencies. Cells continually stretched at right angles to the future cleavage plane produced temporally and morphologically normal furrows. Subsurface cytoplasm was agitated by moving the mitotic apparatus back and forth parallel to its axis and by a vibrating needle inserted between the mitotic apparatus and the equatorial margin of flattened cells. Neither of these operations blocked cleavage. Cells held and shaped by the nozzle of a pipette were pierced by a needle inserted through the polar surface and into the zone between the mitotic apparatus and the equatorial surface. The needle was then swept around the entire mitotic apparatus. Furrows developed in these cells; they appeared later than in controls and did not appear completely normal. Furrow establishment does not seem to depend upon a precise, long‐standing, stable arrangement of sub‐surface cytoplasmic components.
The effect of oxygen on the development of preimplantation mouse embryos in vitro
Authors: Quinn P. , Harlow Gaye M.
Published: June 2005

The optimal oxygen tension for development of preimplantation mouse embryos to the blastocyst stage in vitro was found to be between 2.5% and 5%. One‐ and two‐cell embryos had a more sharply defined range of oxygen tension capable of supporting development than 8‐cell and morula stages. At all stages of development, more embryos developed to the blastocyst stage under 5% O2 compared to the numbers of developing under higher oxygen tensions (20% and 40% O2). The blastocysts developing under 20% O2 had fewer blastomeres than those which developed under 5% O2. As the time required for development to the blastocyst stage in vitro increased, there were fewer blastomeres present at the blastocyst stage.

These results indicate that the cleaving mouse embryo has an optimal oxygen requirement in vitro of about 5%. At higher oxygen tensions, fewer embryos develop to the blastocyst stage and in those which do develop, there are fewer cell divisions. If a gradient of oxygen tension exists across the blastomeres from the outside of the embryo to its centre, the blastomeres might be using this gradient to obtain information about their location within the embryo and respond accordingly. Thus blastomeres on the outside at a higher oxygen tension would divide at a slower rate and form trophectoderm whereas those on the inside at a lower oxygen tension would divide more rapidly and contribute to the inner cell mass.
Contraction in a muscle with negligible sarcoplasmic reticulum: The longitudinal retractor of the sea cucumber Isostichopus badionotus (Selenka), holothuria aspidochirota
Authors: Hill Robert B. , Sanger Joseph W. , Yantorno Robert E. , Deutsch Carol
Published: June 2005

The longitudinal retractor muscles of the body wall of the sea cucumber Isostichopus badionotus have small cells joined in small bundles by extensive areas of tight surface contact between the cells and on projections at the center of the bundles. The cells have only a few small mitochondria and negligible sarcoplasmic reticulum. It might be expected that such cells would be poor in intracellular storage sites for calcium for excitation‐contraction coupling. However, we have found that it requires up to ten hours incubation of the isolated muscles in calcium‐free solutions of chelating agents to abolish contractility in the calcium‐free solutions. After that, contraction is directly calcium dependent. Contractility was assessed by measuring either force or shortening during potassium depolarization across a sucrose gap. Caffeine induces contraction even in calcium‐free solutions. Thus the physiological evidence indicates that there are internal storage sites for calcium, even though there is scarcely any sarcoplasmic reticulum. On morphological grounds we suggest that there are also superficial sarcolemmic storage sites for calcium. This is suggested by the great increase in sarcolemmic area provided by extraordinary extensions of each cell into the lumen of the bundle.
Temporal aspects of starfish oocyte maturation and 1‐methyladenine metabolism in vitro
Authors: Glad R. W. , Schuetz A. W.
Published: June 2005

The temporal relation between hormone uptake, metabolism, and reinitiation of meiosis was investigated following in vitro incubation of immature starfish oocytes with the maturation inducing hormone 1‐methyladenine (1‐MA) and/or 3H‐1‐methyladenine (3H‐1‐MA).

Oocyte incorporation of the radioactive marker occurred in a dose dependent fashion and in excess of that required for maturation. Uptake and metabolism of the hormone by oocytes took place at subthreshold doses of 1‐MA as well as maturation inducing doses. Oocytes also concentrated radioactivity following incubation with physiologic doses of 3H‐1‐MA. Chromatographic analysis of oocyte radioactivity indicated that greater than 90% of the hormone incorporated by the oocytes existed as a single metabolite and this percentage remained constant over a 6‐hour time period. Metabolite was also isolated from the culture media and the quantity in the media increased with increased duration of incubation. After six hours, the metabolite accounted for 28% of the total culture media radioactivity. Determination of the rate of release of 3H‐marker from preloaded oocytes indicated that release was insufficient to account for the levels of metabolite found in the culture media. Such results suggest that at least a portion of 1‐MA metabolism occurred to the exterior of the cell membrane. Oocyte uptake as well as release of incorporated radioactivity were both suppressed by incubation at 0°C. However, at 0°C the proportion of oocyte incorporated radioactivity isolated as metabolite was similar to that following incubation at 22°C. The high and constant level of metabolism of incorporated hormone by oocytes, as well as the continued metabolism despite suppression of uptake suggests that a close association exists, possibly at the level of the oocyte cell membrane, between 1‐MA uptake and formation of metabolite in the starfish oocyte.
Continuance of circannual reproductive refractoriness in pinealectomized parthenogenetic whiptails (Cnemidophorus uniparens)
Authors: Cuellar Hector S.
Published: June 2005

Twelve control and thirteen pinealectomized lizards (Cnemidophorus uniparens) were exposed to a temperature gradient of 27°C to 42°C and a 10L:14D photothermal regime for nearly one year starting during the latter part (late October‐early November) of their reproductive refractory period. This lizard is refractory to photothermal stimulation in captivity from early July to mid‐December. Two pinealectomized animals became reproductive by mid‐November but the remaining in both groups became reproductive as usual starting in December. These results conflict with those reported for another lizard in which pinealectomy in the winter resulted in significant ovarian activity. The data presented here demonstrate that the pineal organ does not play a role in the endogenous circannual cycle of this lizard but may be involved in thermoregulation as reported for other lizards.
Blood viscosity in annelids
Authors: Snyder Gregory K.
Published: June 2005

The intrinsic viscosity of hemoglobin from the marine annelid Arenicola marina is less than 25% of the value predicted for a linear polymer of comparable molecular weight. The relatively low Viscosity, which appears to be related to the subunit arrangement in annelid hemoglobins, provides a much higher than predicted blood oxygen transport capacity.
Facial development in normal and mutant chick embryos. I. Scanning electron microscopy of primary palate formation
Authors: Yee G. Wendel , Abbott Ursula K.
Published: June 2005

Early facial development in normal chick embryos was studied by scanning electron microscopy, and compared to the abnormal facial development of a mutant in which primary palate formation does not occur, thus resulting in bilateral cleft lip. In both normal and “cleft primary palate” mutant embryos, subsequent to the appearance of the nasal placodes, the surrounding tissues elevate to give rise to the presumptive facial primordia. As the facial primordia grow forward, they gradually assume the configuration of a square which is most pronounced at five days development.

In normal embryos, the square configuration is then lost as the facial primordia become aligned in preparation for primary palate formation. The primary palate is formed at six days development by fusion of the “free‐ended” medial nasal processes with the combined lateral nasal and maxillary processes across the nasal grooves. Just prior to fusion, long, slender filaments extend from the apposing surfaces of the facial primordia in the regions of prefusion contact. It is speculated that these “prefusion filaments” may function in alignment or adhesion of the facial primordia.

In “cleft primary palate” embryos, facial morphogenesis appears to arrest at five days development, so that the square configuration persists. The medial nasal processes never contact the lateral nasal and maxillary processes, but instead remain separated from them by wide nasal grooves. Furthermore, facial primordia of mutant embryos do not exhibit the “prefusion filaments” characteristic of normal embryos.
NA++K+‐ATPase in the osmoregulating clam Rangia cuneata
Authors: Saintsing David G. , Towle David W.
Published: June 2005

Of six tissues sampled from the osmoregulating clam Rangia cuneata, mantle contained the highest concentration of Na++K+‐ATPase activity and ouabain binding sites. Acclimation to low salinities was accompanied by adaptive increases in Na++K+‐ATPase activity in mantle but not in gill. Since the number of ouabain binding sites did not show parallel increases, the mechanism of acclimation to reduced salinity in Rangia appears to involve activation of pre‐existing pump sites in the mantle epithelium.
Effect of acclimation temperature on plasma levels of glucose and lactate in rainbow trout, Salmo gairdneri
Authors: Connors Thomas J. , Schneider Mark J. , Genoway Robert G. , Barraclough Stephen A.
Published: June 2005

Baseline plasma glucose and lactate levels were determined in unstressed rainbow trout (Salmo gairdneri) acclimated to 8°, 12°, and 16°C. The 8°C acclimated fish had the highest plasma glucose level (75.7 mg/dl), which is significantly greater than the 16°C acclimated fish (59.7 mg/dl) but not the 12°C fish (66.7 mg/dl). The plasma glucose levels of the 12°C and 16°C acclimated fish were not statistically different. The plasma lactate levels of 8°C fish (5.3 gm/dl), 12°C fish (4.2 mg/dl) and 16°C fish (5.3 mg/dl) were not significantly different. There was significant positive correlation between weight and length and significant negative correlation between plasma glucose and both weight and length. No other significant correlations between parameters were detected.
Satellite cells are mitotically quiescent in mature mouse muscle: An EM and radioautographic study
Authors: Schultz Edward , Gibson Marcia C. , Champion Thomas
Published: June 2005

Normal adult mouse tibialis anterior muscles were perfused continuously with 3H‐thymidine for nine days. Quantitation of the satellite cell population in these muscles reveals that not only is the frequency of satellite cell nuclei low, but that those present are mitotically quiescent.
Scanning electron microscopy of primordial germ cells in early chick embryos
Authors: Lee Hsin‐Yi , Nagele Robert G. , Goldstein Mark M.
Published: June 2005

Primordial germ cells (PGCs) of the early chick embryo were examined using scanning electron microscopy. Temporal changes in the form and distribution of surface projections were found to be correlated with migratory phases of PGCs. Non‐migrating PGCs were spherical to ovoid with relatively smooth surfaces. Their transition to the migratory phase was first evidenced by a burst of membrane activity. Migrating PGCs became somewhat flattened against the underlying hypoblast (which serves as the substratum for their migration) and exhibited blebs and lamellar processes. The lamellar processes were most prominent at the leading edges of actively migrating PGCs. Overall results of the present study indicate that PGCs found in the germinal crescent area of early chick embryos actively migrate on the dorsal surface of the hypoblast towards posterior embryonic regions.
Glucose effect on respiration: Possible mechanism for capacitation in guinea pig spermatozoa
Authors: Rogers B. Jane , Chang Lana , Yanagimachi Ryuzo
Published: June 2005

Guinea pig sperm respiration was determined in minimal capacitation medium (MCM) with different energy sources. The ZO2 observed for spermatozoa suspended in media containing pyruvate and lactate was 35.7 ± 5.9, pyruvate alone, 27.9 ± 3.8 and D‐glucose alone 3.4 ± 1.1. When D‐glucose was added to spermatozoa rapidly respiring in media containing pyruvate as the only exogenous energy source, an immediate suppression in respiration was observed. Further reduction was caused by continued addition of D‐glucose. Fructose and mannose also produced a suppression in respiratory rate. However, lactose, fucose, sucrose, L‐glucose, and galactose did not alter the respiratory rate. The suppression of respiration by metabolizable sugars is paralleled by a suppression of acrosome reaction in guinea pig spermatozoa. The possibility that suppression of respiration is the mechanism for retardation of capacitation and the subsequent acrosome reaction by D‐glucose and other metabolizable sugars is suggested.
Peroxidase absorption in the ascidian gut
Authors: Burighel Paolo
Published: June 2005

Protein absorption in the colonial ascidian Botryllus schlosseri was investigated by electron microscopic cytochemistry using horseradish peroxidase (HRP) as a tracer. Colonies were kept in HRP dissolved in seawater; entire guts were excised at selected intervals and processed for electron microscopy using the technique of Graham and Karnovsky for demonstration of HRP activity.

The absorption of HRP takes place in cells of the stomach and intestine, characterized by brush borders and large supranuclear vacuoles (vacuolated cells). Zymogenic cells and mucous cells did not show evidence of HRP uptake.

In the vacuolated cells HRP is absorbed by pinocytic invaginations of the apical plasmalemma and appears to be localized in numerous apical microvesicles, in subapical macrovesicles and in the large supranuclear vacuoles. It appears probable that the macrovesicles and vacuoles are important sites of intracellular digestion. However, some differences in ultrastructure and in the pattern of HRP uptake were observed between vacuolated cells of the distal intestine and those of the stomach and proximal intestine.

The results indicate that ascidians are able to absorb macromolecules which are naturally occurring in the gut or derive from incomplete extracellular digestion.
Histochemical evidence for enzyme differences in crustacean fast and slow muscle
Authors: Ogonowski Mark M. , Lang Fred
Published: June 2005

Histochemical techniques were developed for characterizing fast and slow muscles of crustaceans. When crayfish or lobster abdominal muscles were tested for myofibrillar ATPase activity, fast muscle stained darkly and slow muscle stained lightly. When tested for NADH diaphorase activity, as a sign of oxidative capacity, slow muscle stained darkly around the sarcolemma while fast muscle stained lightly. In contrast, the results suggested that swimmeret muscles are more heterogenous in their properties. These histochemical techniques provide a simple but efficient method for elucidating the enzymatic profile of crustacean muscles. They should prove useful for characterizing the diversity of these muscles and for investigating the causes of this diversity.
Sexual differentiation and germ cell transfer in the colonial ascidian Botryllus schlosseri
Authors: Sabbadin Armando , Zaniolo Giovanna
Published: June 2005

The sexual differentiation in the colonial ascidian Botryllus schlosseri was considered with respect to colony sexualization and sexualization of the single zooids of the same blastogenic generation.

The colony sexualization was investigated histologically in a series of young colonies reared in the laboratory and fixed periodically throughout a sequence of blastogenic generations. The newly set colonies lack gonad blastemata; next, germ cells appear and several generations are involved in various phases of hyposexuality prior to the appearance of generations in which mature both eggs and sperm.

The sexual contribution of the zooids of the same generation was found to vary according to an intrinsic bilateral asymmetry (the gonadogenic potential differs both contralaterally in each zooid and between zooids of a different, dextral or sinistral, parental origin) and in proportion to the quantity of germ cells that have been transferred from preceding generations.

The transfer of germ cells from one to the following generations was investigated by fusing colonies of opposite pigment genotypes, then crossing the separated parabionts to a common genotype, and scoring the offspring pigment phenotypes. This experiment has shown that not only immature oocytes but also undifferentiated cells were exchanged between the parabionts and then gradually matured as eggs or sperm in a prolonged series of generations.

The primordial germ cells differ in size from hemoblasts, the source of hemocytes. However, further experiments are needed in order to decide between the two contrasting hypotheses of germ cell origin: either segregation from the atrial epithelium of buds or development from hemoblasts.
Rathke's pouch morphogenesis in the chick embryo
Authors: Jacobson Antone G. , Miyamoto David M. , Mai S.‐H.
Published: June 2005

Origin of Rathke's pouch ectoderm is complex. Anterior neural ridge and plate extend and reflect ventrally, then caudad, under the head into the subcephalic pocket. At least pouch roof and part of the walls form from ventral neural ridge. Pouch roof anchors to brain floor along the ventral suture line. Pouch tip, floor, and the rest of the walls are from stomodeal ectoderm. Pouch tip anchors to prechordal plate, and floor to Seessel's pocket along the midline.

The prosencephalon bulges ventrally, bending attached pouch roof at right angles to pouch floor. The pouch tip is a pivotal point about which the head of the embryo enfolds. Cranial flexure bends the head ventrally, then caudad, folding the pouch roof parallel to its floor. Prosencephalon floor elongation stretches attached pouch roof. That these forces help form the pouch is shown in experiments in which parts are surgically altered, or glass rods are placed in brain cavity or in the foregut to stop the movements and thereby affect pouch formation.

Pouch wall formation is due to accumulation of mesenchyme beneath lateral, unattached ectoderm. The full length of pouch floor ectoderm is present in early embryos and is gradually incorporated into the pouch as the walls form. The pouch does not invaginate nor change its position relative to the brain floor. The true infundibulum evaginates from brain floor over the pouch tip on the fifth day of incubation, which also is when an earlier, more caudal structure called “infundibulum” disappears.
The induction of collagenase and acid phosphatase by thyroxine in resorbing tadpole gills in vitro
Authors: Derby Albert , Jeffrey John J. , Eisen Arthur Z.
Published: June 2005

Explants of tadpole gills were cultured in Hanks balanced salt solution or in Hanks supplemented with thyroid hormone. Gills in control media maintain their integrity in vitro while those treated with thyroxine undergo resorption. The activity of collagenase in the media increases in parallel with thyroxine induced resorption and is accompanied by a decrease in tissue collagen levels. T4 induced gill resorption is also associated with an increase in the specific activity of acid phosphatase. However, this increase is not the result of a significant increase in total enzyme activity but rather the result of a differential loss in total protein concentration in thyroxine treated gills as compared to control.
Anhydrobiosis in nematodes: Permeability during rehydration
Authors: Crowe John H. , O'Dell Steven J. , Armstrong David A.
Published: June 2005

1. Inorganic ions and primary amines are leaked from anhydrobiotic and quick‐dried nematodes, Aphelenchus avenae, when they are plunged from dry air into water.

2. Anhydrobiotic nematodes leak about one‐third as fast as quick‐dried ones.

3. When the water content is increased above about 20% by exposing the animals to moist air before immersing them in water, the leakage rate in both anhydrobiotic and quick‐dried worms is diminished.

4. The rate of leakage is inversely correlated with the glycerol contents of the worms at the time they are placed in water.
In vitro development of core cells of the inner cell mass of the mouse blastocyst: Effects of conditioned medium
Authors: Atienza‐Samols Sui Bi , Sherman Michael I.
Published: June 2005

Blastocysts submitted to two rounds of immunosurgery give rise to cores of presumptive ectoderm cells, many of which do not survive for more than 48 hours when cultured individually. Precoating of the culture plates with conditioned medium (CM) from PYS‐2 cells increases the incidence with which cores regenerate an outer layer. This procedure also improves the survival frequency of the cores, but only for a limited period of time. The small number of cores which survive for two weeks or more, either in uncoated or CM‐coated plates, give rise to an array of cell types, including giant cells resembling trophoblast.
Gonadotropin stimulation of the expansion of cumulus oophori isolated from mice: General condition for expansion in vitro
Authors: Eppig John J.
Published: June 2005

Gonadotropin Stimulation of the Expansion of Cumulus Oophori Isolated from Mice: General Conditions for Expansion In Vitro

The hormonal stimulation of cumulus expansion (mucification) was studied using oocyte‐cumulus cell complexes isolated from Graafian follicles of C57BL/6J mice. Cumulus expansion was stimulated in vitro with human chorionic gonadotropin (HCG) and highly purified rat follicle stimulating hormone (FSH) in Whitten's medium containing fetal bovine serum (FBS). Highly purified rat luteinizing hormone failed to stimulate cumulus expansion. The 50% maximal stimulating concentration of FSH was found to be about 3–4 ng/ ml. Cumulus expansion was also stimulated by dibutyryl cyclic adenosine monophosphate (DBcAMP), but not by dibutyryl cyclic guanosine monophosphate or butyrate. Neither progesterone, testosterone, nor 17β‐estradiol stimulated cumulus expansion. Expanded cumuli were dispersed by hyaluronidase.

The stimulation of cumulus expansion by FSH, HCG or DBcAMP required the presence of FBS. The active component of serum had a molecular weight greater than 10,000 daltons and did not require the association of a steroid for activity. Since DBcAMP does not stimulate cumulus expansion in the absence of FBS, it is suggested that the serum factor(s) is involved after the step of FSH stimulation of cAMP production by the complex.

The cumulus does not expand if FSH is added to cultures after seven hours of spontaneous oocyte maturation, when the oocytes are at late metaphase I or early anaphase I of meiosis. Therefore, the changes which occur in the oocytecumulus cell complex during spontaneous oocyte maturation affect the ability of the complex to respond to FSH and bring about the expansion of the cumulus.
The Focal differentiation of pigment cells
Authors: Whimster I. W.
Published: June 2005

A study has been made of the normal development and of the regeneration after excision of the groups of large pigment cells which form the spotted skin pattern of the gecko Eublepharis macularius, together with the effects of neonatal graft transplantation on this pattern. The results all indicate strongly that such groups of specialized pigment cells are not clones but the product of an induction process. This is then compared with the neural reflex mechanism by which the skin pattern of Chamaeleo dilepis is formed.
Autoradiographic and electron microscopic studies of minced cardiac muscle regeneration in the adult newt, Notophthalmus viridescens
Authors: Bader David , Oberpriller John
Published: June 2005

The regenerative response of minced cardiac muscle grafts in the adult newt was studied using autoradiography and electron microscopy. One‐sixteenth to one‐eighth of the newt ventricle was amputated, minced, and returned to the wounded ventricle. At five days after grafting, no reorganization of graft muscle pieces was apparent and there was degeneration of much of the muscle graft. Another, smaller population of 5‐day myocytes had euchromatic nuclei and intact sarcolemmae. In 10‐ and 16‐day grafts, continuity between ventricular and graft lumina was established and coalescence of graft pieces was apparent. Ultrastructurally, 10‐ and 16‐day graft myocytes appeared to have fewer myofibrillae and increased amounts of rough endoplasmic reticulum, polyribosomes, Golgi complexes, and dense bodies when compared to uninjured ventricular myocytes. The peak of proliferative activity of graft cells was observed at 16 days. Electron microscopic autoradiography revealed breakdown of myofibrillar structure in labeled myocytes, whereas in myocytes in the later stages of mitosis only scattered myofilaments and no Z bands were present. By 30 days, grafts appeared as an integrated structure composed primarily of cardiac muscle. Myocytes of 30‐day grafts were observed in various stages of myofibrillogenesis and contained numerous 10‐nm filaments. Seventy‐day graft myocytes had numerous well organized myofibrillae and intercellular junctions similar to those seen in uninjured ventricular myocytes.
Light‐induced acceleration of retina development in a mouth‐brooding teleost
Authors: Grün Gerd
Published: June 2005

Rearing animals in the dark had been shown to be either without effect on the development of the retina or to result in a reduction or a delay of retinal maturation. In the present study, the influence of light on a retina which normally develops under contitions of very dim light has been investigated. When 3‐day‐old embryos of the mouth‐brooding teleost Tilapia leucosticta are placed into a continuously lighted environment, from day 6 on, optic tract diameter and inner plexiform layer thickness increase up to day 10 or 12. In the dark‐reared retina, this increase occurs only after day 10. Similarly, synaptic junctions of the inner plexiform layer appear at about day 6 in the light‐reared retina and increase continuously on following days, whereas in the retina of embryos reared in darkness, they appear at day 7 and do not increase essenially before day 11. These and other data suggest that continuous light induces a precocious growth of retinal structures. The first differences between light‐ and dark‐reared retinae appear synchronously with the beginning of receptor cell development and prior to the first synaptic junctions. A nonneurally mediated effect of light on the retinal ganglion cells in consequently assumed.
Acrosin does not appear to be bound to the inner acrosomal membrane of bull spermatozoa
Authors: Shams‐Borhan Gabriele , Huneau Daniel , Fléchon Jacques‐Edmond
Published: June 2005

Ferritin‐conjugated soybean tryps in inhibitor was used for the ultrastructural localization of acrosin in bull spermatozoa following acrosomal disruption. The ferritin label was observed in the anterior segment of the acrosome in disrupted cells only. Emptied acrosomes were labeled, mostly on the external surface of their outer membrane. Labeling was also found on the material bound to detached acrosomal caps. However, at no time could the ferritin label be found on the inner acrosomal membrane. It is concluded that acrosin activity is not present on the inner acrosomal membrane but is lost from the acrosomal matrix as the acrosomal reaction proceeds.
Feeding in water snakes: An electromyographic study
Authors: Cundall David , Gans Carl
Published: June 2005

Synchronized cinematography and electromyography were used to study feeding behavior in water snakes, Nerodia rhombifera and Nerodia fasciata. While these species swallow their prey by alternate movements of the right and left toothed bones of the skull, the muscles show bilateral asymmetric activity during each movement.

Opening of one side of the mouth is initiated by protraction of the palatomaxillary arch and slight depression of the mandible. These movements serve to disengage the teeth from the surface of the prey and correlate with activity of the protractors of the palatomaxillary arch and quadrate. Continued opening results primarily from rotation of the braincase around its longitudinal axis. During the latter half of the opening phase, the rates of protraction of both palatomaxillary arch and mandible increase; this correlates with increased activity of the depressor mandibulae, several of the mandibular adductors and three of the four cervical muscles analyzed. The cervical muscles appear to restrain the prey during the fast segment of mouth opening when the toothed bones reach their maximum displacements from the surface of the prey.

Closing of the mouth is initiated by rapid depression of the palatopterygoid joint which correlates with a cessation of activity of the levator pterygoidei. Immediately thereafter, the posterior end of the maxilla is depressed and slightly retracted and the mandible tends to be protracted and slightly adducted. These movements correlate with synchronized activity of the palato‐maxillary protractors, the pterygoideus and the depressor mandibulae. The rest of the closing phase consists primarily of adduction and retraction of the palatomaxillary and mandibular elements relative to the braincase; the toothed bones remain fixed to the surface of the prey while the braincase is moved forward. EMGs indicate that the complex bone movements of the latter stage of mouth opening and the initial stage of mouth closing are dependent upon the simultaneous firing of a number of morphologically antagonistic muscles.