bluuebunny/crossref_metadata_2025 huggingface dataset:
Sperm release evoked by electrical stimulation of the fish brain: A functional‐anatomical study
Authors: Demski Leo S. , Bauer Diana H. , Gerald Jerry W.
Published: June 2005

Acute brain stimulation experiments were carried out in anesthetized male green sunfish, Lepomis cyanellus. Semen discharge was evoked consistently by low level electrical stimulation (100 μA or less) in the following areas: the preoptic region, dorsal hypothalamus, thalamus, midbrain tegmentum and the basolateral midbrain and medulla. Areas which were stimulated repeatedly at 100 μA and were always negative for sperm release included: the telencephalon with the exception of the preoptic region, the optic tectum, the cerebellum, the inferior lobe of the hypothalamus, the nucleus rotundus and the dorsal medulla. Removal of most of the optic tectum and cerebellum failed to block responses evoked from the preoptic area; however, they were usually eliminated by transecting the rostral spinal cord. Electrical stimulation of an isolated 4 mm segment of spinal cord located at the third vertebral level resulted in sperm release, indicating that adequate mechanisms for semen discharge are present within the upper spinal cord. The results of this study suggest that a sperm release system in the green sunfish extends from the preoptic area to the spinal cord passing through the hypothalamus, midbrain tegmentum and basal midbrain and medulla.
An analysis of nuclear numbers in individual muscle fibers during differentiation and growth: A satellite cell‐muscle fiber growth unit
Authors: Cardasis Constance A. , Cooper George W.
Published: June 2005

A numerical analysis of changes in the populations of nuclei in individual, intact muscle fibers was made to study how multinucleation arises during normal differentiation and growth. Gastrocnemius muscle fibers from pre‐ and post‐natal mice were isolated with guanidine (Cardasis and Cooper, '75) and examined.

Satellite cells associated with muscle fibers were first observed at 19 days of gestation. The number of nuclei per muscle fiber (muscle + satellite cell nuclei) averages 83 at this age, 157 at birth and continues to increase to 354 by 63 days of age. However, the rate of increase during growth is not constant. Estimates of satellite cell and muscle nuclei in histological cross sections indicate that there is a decrease in the percentage of satellite cells from 32% at birth to 6% in the adult. However, the numbers of satellite cells associated with individual muscle fibers, calculated from these percentages and the nuclear counts on whole fibers, decreases only between 2 and 4 weeks of age.

Cytosine arabinoside was injected subcutaneously during the first two weeks of age. Pairs of satellite cells, abnormal nuclei and elevated percentages of satellite cells were observed. This evidence as well as the numerical analysis of nuclear populations in whole fibers lends further support to the hypothesis that satellite cells account for the increase in muscle nuclei from birth to maturity.
Hybrid desmosomes in aggregated chick and mouse cells
Authors: Overton Jane , Kapmarski Rita
Published: June 2005

Mouse embryo skin epidermis has been examined during maturation, and stages have been found when desmosomes are first scarce, then increasing in frequency and finally numerous. Cells of skin epithelium from these stages have been combined in reaggregates with cells of the 15‐day chick corneal epithelium which also form desmosomes readily. When these two cell types are reaggregated in the presence of cytochalasin B which inhibits cell sorting, they form numerous junctions with each other. Desmosomes in mouse and chick appear similar morphologically except for certain cytoplasmic components. Mouse skin epidermis cells combined with cardiac muscle or intestinal epithelium formed imperfect or no specialized contacts. The possible role of junctions in cell sorting in reaggregates is discussed.
Urea excretion in the hibernating columbian ground squirrel (Spermophilus columbianus)
Authors: Passmore J. C. , Pfeiffer E. W. , Templeton J. R.
Published: June 2005

Hibernation was induced in Columbian ground squirrels by placing them in refrigerated cages equipped with urine‐collection pans. On arousal, urine and blood were collected from each animal, which was then allowed to reenter hibernation. After several days the animal was sacrificed and bladder urine and another blood sample were taken. In addition, four active non‐hibernating ground squirrels were placed in a cage at room temperature with neither food nor water. Urine was collected at 9 and 26 hours and blood was collected at 0 and 26 hours. Although only seven of ten hibernating squirrels had a higher blood‐urea level when sacrificed than during the previous arousal, the other three had very high levels in the arousal period and probably further excreted urea before entering hibernation. When total body urea was calculated on a body weight basis, all except one animal showed a greater level of urea during hibernation than in the previous arousal. During their period of dehydration, the non‐hibernating summer squirrels showed a marked decrease in blood urea. The osmotic concentration of the urine from these squirrels was due less to urea than that excreted during arousal by hibernating squirrels. Thus, it appears that urea accumulates in the blood during hibernation and is excreted in the urine during arousal.
Ultrastructural analysis of artificially activated rabbit eggs
Authors: Longo Frank J.
Published: June 2005

Ultrastructural investigations have been carried out on parthenogenetic rabbit eggs in an effort to elucidate events occurring during artificial activation and their similarity to processes of fertilization and embryogenesis. Rabbit eggs were artificially activated by culturing at 10°C for 24 hours followed by incubation at 37°C for 2 to 24 hours. Examination of eggs immediately after incubation at 10°C for 24 hours indicates that activation is initiated when the chromosomes coalesce to form a reticulum which is either surrounded completely by two parallel membranes or incompletely by cisternae of smooth endoplasmic reticulum. Aggregation of the chromosomes occurs as a result of a reduction in the number of microtubules making up the meiotic spindle. When cold treated ova are subsequently incubated at 37°C a nucleus is formed which moves centrad where it may participate in the cleavage of the egg. Formation of a second polar body and release of the contents of the cortical granules as reported for inseminated eggs was not found to be a part of activation of the egg by cold treatment. Approximately 95% of the ova cultured at 10°C for 24 hours followed by 37°C for 12 hours were activated, i.e., they possessed a nucleus or they had cleaved. Many of the activated eggs cultured for short periods at 37°C were structurally similar to fertilized ova, with further incubation fragmented eggs and abnormal multicellular stages predominated.
Mitosis in presumptive primordial germ cells in post‐blastula embryos of Xenopus laevis
Authors: Dziadek M. , Dixon K. E.
Published: June 2005

In X. laevis embryos injected with (3H) thymidine between early gastrula and late neurula, the presumptive primordial germ cell nuclei were labelled and some were observed in mitosis, confirming that division occurs throughout this developmental period. In all labelled and mitotic cells, the germ plasm adjoined the nucleus, an observation which invalidates the hypothesis that germ plasm inhibits mitosis in presumptive primordial germ cells after gastrula. In embryos which had been irradiated with UV at the vegetal pole at the 2‐cell stage, the presumptive primordial germ cells also incorporated (3H) thymidine and divided during the same developmental period.
Considerations of symmetry in the cortical integration of Tetrahymena doublets
Authors: Nanney D. L. , Chow Margaret , Wozencraft Barbara
Published: June 2005

Homopolar doublets of syngen 1, T. pyriformis, may be induced by treatment of conjugating pairs with immobilizing antiserum. These doublets have geometric properties and basal body populations generally indicative of separate autonomous integrative systems in the two halves. The duplex system, though metastable, is transformed through a process of “simplification” back to the simplex state. The transformation is not a single event, but a series involving changes at different times for different structures and processes; for the micronuclei and the macronuclei; for the capacity to generate two oral apparatuses through stomatogenesis and the capacity to develop them through oral replacement; for the structures at the anterior and posterior ends of the cell; for the numbers of ciliary rows and for the numbers of basal bodies which make up the rows.

Although the two semicells composing a doublet are in important respects independent of each other, they are coordinated in significant ways. The positions of the contractile vacuole pores and their numbers depend not only on the number of ciliary rows in a semicell, but also on the number of ciliary rows in the opposing twin. Most notably, the probability for dual stomatogenesis, and hence the perpetuation of the doubled oral apparatus, depends on the symmetry of the semicells. The cell as a whole is maintained as an integrated unit over a prolonged interval as various aspects of duplex structure and function are progressively consolidated.
In vitro fertilization of rat and mouse eggs by ejaculated sperm and the effect of energy sources on in vitro fertilization of rat eggs
Authors: Tsunoda Y. , Chang M. C.
Published: June 2005

In vitro fertilization of rat and mouse eggs by ejaculated or epididymal spermatozoa in chemically defined media was studied. Penetration rates by ejaculated sperm was very low (0 to 8%) in the rat, but 11 to 41% of eggs were penetrated by ejaculated sperm in the mouse. The optimal concentration of sperm for in vitro fertilization appears to be similar whether ejaculated or epididymal sperm were used. The time of sperm penetration in the mouse eggs, however, was delayed for one‐half to one hour when ejaculated sperm were used.

The importance of sodium pyruvate, sodium lactate and glucose in the medium containing bovine serum albumin for in vitro fertilization of rat eggs was examined. When rat eggs in cumulus clot were exposed to epididymal sperm preincubated for five hours, the presence of sodium pyruvate, sodium lactate and glucose was found to play an important role. When exposed to non‐incubated epididymal sperm sodium pyruvate could be omitted without much decline of the fertilization rate. When the denuded eggs were exposed to non‐incubated sperm, penetration rates were very low (0 and 5%) in the absence of pyruvate. It appears that although lactate, pyruvate and glucose are all important for in vitro fertilization of rat eggs, pyruvate can be supplied by the follicular cells surrounding the eggs.
Tooth replacement in the upper jaw of the rainbow trout (Salmo gairdneri)
Authors: Berkovitz B. K. B. , Moore M. H.
Published: June 2005

The present paper describes the pattern of tooth replacement in the upper jaw of two size ranges of rainbow trout (standard lengths 12–15 cm and 20–23 cm) as determined from wax impressions of the dentitions taken twice weekly on anaesthetised fish. There was considerable variation in the nature of replacement waves (lines constructed on dental charts linking eruption times of alternate teeth) between fish for both the premaxillary/maxillary and vomerine/palatine rows. The wave patterns obtained showed the same consistency of form for any one animal which is to be expected when consecutive generations show constant or proportionately changing life spans. Data relating to the life span of the teeth is given. The results are compared with those derived for the lower jaw and the significance of wave form discussed.
In vitro development of t6/t6 embryos
Authors: Erickson Robert P. , Pedersen Roger A.
Published: June 2005

Embryos from matings in which approximately a third of the zygotes were expected to be t6/t6, a condition known to be lethal at the egg cylinder stage in vivo, were compared to normal control embryos during post‐implantation culture. The percentage success of trophoblast out growths was the same in both groups while the experimental group showed a 25% deficiency of embryos with inner cell masses. Those experimental embryos which did have inner cell masses developed comparably to the control group and both groups showed roughly similar numbers of morphologically abnormal egg cylinders. Autoradiography disclosed no deficiency in 3H‐thymidine and 3H‐uridine labeling in disorganized egg cylinder embryos.
Synthesis of octopamine by insect dorsal median unpaired neurons
Authors: Hoyle Graham , Barker David L.
Published: June 2005

Dorsal unpaired median (DUM) neurons of locusts and grasshoppers inhibit the instrinsic rhythm of contraction of metathoracic extensor tibia muscle fibers. This physiological action is mimicked by very low concentrations of octopamine and by higher concentrations of dopamine and noradrenaline. We have examined the synthesis of biogenic amines from tritiated tyrosine by these neurons. DUM cell bodies and a peripheral nerve containing the DUM axon which terminates in the extensor tibia both produced octopamine, but neither noradrenaline nor dopamine synthesis was detected. The observations support the suggestion that the dorsal unpaired median neurons are octopaminergic.
Normal development of the chick wing following removal of the polarizing zone
Authors: Fallon John F. , Crosby Gayle M.
Published: June 2005

The negative results of assays for polarizing activity along the posterior border of the chick wing 24 and 48 hours after removal of the polarizing zone demonstrate that this zone is not regenerated following removal. These results, and the fact that normal wing development can occur after polarizing zone removal from stages 15 through 24 wing buds, indicate that during these stages the polarizing zone has no direct role in normal development of the limb bud. It isspeculated that the polarizing zone is effective only during limb induction and that after this time it exists latentor residual form.
Purification and molecular properties of the (sodium + potassium)‐adenosinetriphosphatase and reconstitution of coupled sodium and potassium transport in phospholipid vesicles containing purified enzyme
Authors: Hokin Lowell E.
Published: June 2005

Recent work in our laboratory on the purification and characterization of the (sodium + potassium)‐activated adenosinetriphosphatase (NaK ATPase) has been reviewed. Two enzymes have been purified, that from the rectal salt gland of the spiny dogfish, Squalus acanthias and that from the electric organ of the electric eel, Electrophorus electricus. The enzyme appears to consist of two catalytic subunits of molecular weight of about 95,000 and one glycoprotein with a molecular weight of about 50,000. The amino acid composition, N‐terminal amino acids, and the carbohydrate composition of these subunits have been determined. The phospholipid composition of the holoenzyme has also been determined. The protein component shows very little variation with evolution, but the carbohydrate and phospholipid components show considerable variation. It has been possible to form vesicles from the purified enzyme from Squalus acanthias and to demonstrate the ATP‐dependent, ouabain inhibitable, coupled uphill transports of Na+ and K+. The properties of these transports are very similar to those observed previously in intact erythrocytes or resealed erythrocyte ghosts with respect to asymmetries of binding sites, stoichiometries of Na+ and K+ transported, Na+−Na+ exchange, and K+−K+ exchange. It is concluded that the NaK ATPase is the molecular machine for effecting Na+ and K+ transport in the intact cell membrane.
Comparative physiology of cellular ion and volume regulation
Authors: Schmidt‐Nielsen Bodil
Published: June 2005

Intracellular [K+]i in most cells is around 100–150 mOs. This is true in invertebrate or vertebrate muscle or any other tissue, and the only known exceptions being the axons of some invertebrates (Burton, '73).

When cell volume is increased due to hypoosmotic swelling, cell volume is regulated back toward normal in almost all cells. In cells with an osmolality of 300–350 mOs, the regulatory volume decrease is caused primarily by a passive efflux of potassium and anions due to increased membrane permeability to potassium. In cells with a higher osmolality, regulatory volume decrease is caused by the passive efflux of small organic molecules.

When cell volume is decreased due to hyperosmotic shrinking, volume is not always regulated back toward normal in in vitro experiments carried out for several hours. However, it appears from the in vivo experiments that some cell volume control is always present. The volume control in the flounder red cells took place through increased sodium influx brought about by a relative increase in cell membrane permeability to sodium. This mechanism also appears to be dominant in the mammalian renal papilla, where the [Na+]i increases in proportion to the increase in cellular osmolality with no change in [K+]i.

Cells which remain shrunken in vitro, or cells which only partly restore their volume in vivo, do not exhibit increased [K+]i. This finding means that potassium is lost from the cell and, in most cases, exchanged for sodium when the volume is decreased, even though the osmotic concentration in the extracellular fluid is elevated.

Finally, it appears that the maintenance of a rather constant [K+]i is important for all cells. This constancy may be due to the fact that certain enzymes are sensitive to the intracellular potassium concentration. Thus, the DNA synthesis is blocked in mammalian kidney cells when [K+]i is increased (Bygrave, '67). Furthermore, Lubin ('64) has shown that low [K+]i concentrations also cause a decrease in DNA, RNA, and protein synthesis. An optimal concentration appears to be necessary for protein synthesis.
Versatility of hydraulic systems
Authors: Chapman G.
Published: June 2005

The use of fluid or easily deformable materials for force transmission in a variety of animals is reviewed and its role in muscular antagonism is shown. The hydraulics of cells and developing embryos is mentioned and animals employing hydraulic systems are classified as having open, closed or external fluid compartments and simple or complex muscular arrangements. The importance of hydraulically antagonized muscle systems in movement and locomotion is described, and the application of force to the substratum discussed, including the concentration of force from a large muscle field on a smaller area of application. The jet propulsion of cephalopods and medusae is described and their short time scale of action is compared with the long time scale of operation of other hydraulic systems. The pumping operation of the nematode pharynx, the mechanism of suctorial feeding in insects and the energetic demands of tube irrigation in feeding are outlined.
Cell proliferation in the digestive tract of Styela clava (Urochordata: Ascidiacea) as revealed by autoradiography with tritiated thymidine
Authors: Ermak Thomas H.
Published: June 2005

The DNA‐synthesizing cells in the digestive tract of Styela clava were labeled with tritiated thymidine and detected at increasing time intervals with autoradiography. Most of the epithelia consist of renewing cell populations. These are the dorsal tubercle, dorsal lamina, branchial bars, zone 1 of the endostyle, stigmata, esophagus, stomach, intestine, and rectum. Expanding populations are the branchial tentacles, unspecialized pharyngeal cells, and pylorictubules. In the renewing populations, cell proliferation occurs in restricted germinal zones of pseudostratified cells. In the postbranchial digestive tract, these germinal zones usually occur at the bases of folds or grooves. Germinal cell nuclei migrate into the cell apex and undergo mitosis there. With time, germinal cells migrate as a band of labeled cells over the underlying connective tissue into non‐proliferating mature zones of ciliated, secretory, or absorptive cells. Aging mature cells are presumably extruded into the gut lumen, maintaining the system in a steady state. Transit times are about ten days for the stigmata; two and a half weeks for the dorsal tubercle, esophageal mucous population, stomach crest population, and stomach groove population; five weeks for the intestine and rectum; and several months for zone 1 of the endostyle and esophageal band population.
The ubiquitous occurrence of chondroitin sulfates in chick embryos
Authors: Abrahamsohn Paulo A. , Lash James W. , Kosher Robert A. , Minor Ronald R.
Published: June 2005

The synthesis of sulfated glycosaminoglycans has been studied in a wide variety of embryonic chick tissues. All tissues studied have the capability to manufacture, but not necessarily accumulate, the chondroitin sulfates as well as other glycosaminoglycans. The relative distribution of glycosaminoglycans differs between tissues and changes with age.
Annual cycle of plasma luteinizing hormone concentrations in wild mallard drakes
Authors: Haase E. , Sharp P. J. , Paulke E.
Published: June 2005

Plasma LH concentrations were followed in 9 individually marked wild mallard drakes in Kiel (54°N) for one year at monthly intervals. Mean LH levels increased during the spring and reached the annual maximum in April and May. In June when testicular regression occurs, the LH titer sharply decreased and was lower than at any other phase of the annual cycle. In late fall mean plasma LH concentrations increased and, whilst not reaching the values observed during the breeding season, remained relatively high during the winter. Thus, in the mallard LH can be released under short and long daily photo‐periods.
Regulation of the oxidative NADP‐enzyme tissue levels in Drosophila melanogaster. I. Modulation by dietary carbohydrate and lipid
Authors: Geer B. W. , Kamiak S. N. , Kidd K. R. , Nishimura R. A. , Yemm S. J.
Published: June 2005

Wild‐type third instar larvae of Drosophila melanogaster fed a casein‐sucrose synthetic diet supplemented with phosphatidylcholine (4 mg/ml) possessed 33% more tissue lipid and a modified fatty acid profile compared to larvae fed a fat free‐sucrose diet. The rates of lipid synthesis and pentose shunt activity were 2.1 and 2.2 times greater respectively in larvae fed the fat free‐sucrose diet than in fat‐sucrose fed animals. The tissue concentrations of acetyl‐CoA and acytl‐CoA were 80 and 61% higher respectively, CoA 49% lower, and the NADPH/NADP+ ratio greater in fat‐sucrose fed larvae than in larvae fed a fat free‐sucrose diet. Thus, larvae effectively utilized dietary lipid for lipid synthesis and as a supplementary energy source to carbohydrate. Larval oxidative NADP‐enzyme tissue levels were dependent upon the interaction of at least three regulatory systems. Dietary carbohydrate induced high tissue levels of glucose‐6‐phosphate dehydrogenase (EC 1.1.1.49) and 6‐phospho‐gluconate dehydrogenase (EC 1.1.1.43), ostensibly via a glycolytic derivative. High tissue levels of malic enzyme (EC 1.1.1.40) and NADP‐isocitrate dehydrogenase (EC 1.1.1.42) were induced by an acetate derivative postulated to be formed by the Krebs cycle. In contrast, a fatty acid derivative, presumably a product of β‐oxidation, repressed the tissue levels of all four oxidative NADP‐enzymes in larvae. A model of induction and repression regulatory systems that are dependent on regulatory gene products is proposed.
Variation in the effects of antidiuretic hormone on the isolated skin of the toad, Scaphiopus couchi
Authors: Hillyard Stanley D.
Published: June 2005

The rate of active sodium transport as measured by short‐circuit current across the isolated skin of the toad, Scaphiopus couchi, was elevated following vasopressin (0.2 units/ml) or arginine vasotocin (0.1 units/ml) treatment of skins from active animals at all times of the year tested. Skins from dormant animals showed no such elevation at any time of the year. The rate of active sodium transport was elevated following treatment with dibutyryl cyclic AMP (2.5 mM) plus theophylline (10 mM) in all skins tested.

The hydraulic conductivity of isolated skins from both active and dormant animals showed no significant change following treatment with vasopressin (0.2 units/ml) or arginine vasotocin (0.1 units/ml) except on the first day following emergence from dormancy in the field. A correlation was, therefore, observed between the occurrence of a hydroosmotic response to antidiuretic hormones and the seasonal exposure of S. couchi to standing water.

A small but significant elevation of hydraulic conductivity was observed across the skins of dormant toads following treatment with dibutyryl cyclic AMP (2.5 mM) plus theophylline (10 mM) whereas a substantial elevation was observed with the skins of active animals.
Hormone induction of specific protein synthesis in midpregnant mouse mammary cell culture
Authors: Ceriani Roberto L.
Published: June 2005

Monolayer primary cell cultures of midpregnant mouse mammary cells were subjected to hormone stimulation under strictly defined conditions. Hormonal response was measured in terms of increase in rate of synthesis of mouse casein, using a double antibody precipitation technique. Cells stimulated by insulin plus prolactin plus cortisol plus estradiol plus progesterone showed a marked increase in rate of mouse casein synthesis over the controls. This specific product synthesis, which remains inducible in these cells for at least ten days, was detected either by labelled phosphoric acid or labelled amino acid incorporation. The mouse casein synthesized was identical, as judged by the identification techniques used, to that of mouse milk.

Mouse midpregnant mammary explants in organ culture require insulin plus prolactin plus cortisol to express their full lactogenic capabilities. Nevertheless, when the same cells are dispersed and grown in monolayers they require ovarian steroids to elicit a lactogenic response as shown in this study. Ovarian steroids, therefore, are necessary in lactogenesis, although the fundamental nature of their action remains to be established.
Ventilation and metabolic rate of young rainbow trout (Salmo gairdneri) exposed to sublethal environmental pH
Authors: Hargis Jack R.
Published: June 2005

Differences between ventilatory response and metabolic rates of young rainbow trout tested within the sublethal range of pH 6 to pH 9 were observed using a flowing water respirometer. The oxygen consumption was monitored at swimming speeds of 12 cm/sec and 24 cm/sec. The oxygen consumption rates at 24 cm/sec and pH 6 (423 mg/kg‐hr) and pH 9 (367 mg/kg‐hr) were considerably higher than those determined near neutrality (328 mg/kg‐hr). Ventilation rate increased to either side of neutrality, but significantly fewer respiratory reversals, or “coughs,” were obseved at pH 6 and a greater number at pH 9 than occurred at pH 7 and 8 or in untested fish. The respiratory‐cough response is shown to be pH‐dependent in rainbow trout and may therefore not be as reliable an indication of pollutant‐caused stress in studies where the experimental pH has not been specified or controlled.
The role of the copulatory plug in reproduction of the guinea pig
Authors: Martan Jan , Shepherd Benjamin A.
Published: June 2005

Two methods of artificial insemination and removal of copulatory plugs were used to investigate the role of the plug in the guinea pig. In addition, the effectiveness of the copulatory plug in blocking the passage of spermatozoa from the second mating was tested in albino females, where coat color was used as a genetic marker.

Thirteen female guinea pigs that were either in proestrus, estrus, or metestrus, and inseminated with freshly collected copulatory plugs containing living spermatozoa, did not conceive. In a group of six females from which the copulatory plug was immediately removed, five conceived. Of nine estrous females artificially inseminated, five conceived. In five albino females, copulatory plugs from albino males completely blocked spermatozoa deposited by colored males, and 20 offspring, all albino were born. In a second group of four albino females where the plugs of albino males were removed prior to copulation with colored males, resulting litters were sired by either male or a combination of both males.
Maturation and sperm penetration of canine ovarian oocytes in vitro
Authors: Mahi Cherrie Ann , Yanagimachi Ryuzo
Published: June 2005

Canine ovarian oocytes were cultured in a medium consisting of TC medium 199, fetal calf serum and antibiotics. Ninety‐nine percent of the apparently healthy oocytes were in the germinal vesicle (dictyate) stage when recovered from the ovaries; 25% of them reached metaphase I or II by 72 hours of culture. Washed ejaculated spermatozoa were added to BWW medium containing oocytes which had either been removed directly from the follicles or which had been cultured for 24‐72 hours. The earliest acrosome reaction and zona penetration by spermatozoa were seen at seven hours after insemination. Seventy‐four percent of the oocytes examined between 11 and 24 hours after insemination showed evidence of zona penetration by spermatozoa. Neither the condition of the oocyte vitellus nor the stage of nuclear maturation influenced the incidence of zona penetration. Decondensing sperm nuclei were found in the vitellus of 27% of the oocytes which had not been cultured and in the vitellus of 20% of those which had been cultured for 24–72 hours and were in various stages of maturation. These results indicate that (1) canine ovarian oocytes can be matured in vitro, (2) the spermatozoa require capacitation which takes approximately seven hours in vitro and (3) maturation of the oocytes is not required for sperm passage through the zona pellucida or entry into the vitellus nor for sperm nuclear decondensation.
Regeneration from different levels along the tail of the newt, Notophthalmus viridescens
Authors: Iten Laurie E. , Bryant Susan V.
Published: June 2005

Some aspects of the influence of position on regeneration have been examined by comparing regeneration from different levels along the newt tail. Tails amputated such that either three‐fourths, one‐half or one‐fourth of the tail was removed pass through the same morphological and histological stages at the same times after amputation. In tails amputated at these three different levels, the rate of elongation of regenerates from more proximal levels is greater than that of regenerates from more distal levels. The total lengths of regenerates from different levels are proportional to the lengths of tail removed by amputation. Furthermore, the number of vertebrae formed in a tail regenerate is directly proportional to the number of vertebrae removed by amputation. When a tail blastema is transplanted to a more proximal level tail stump, intercalary regeneration between the stump and transplant occurs and the resulting regenerate has a complement of vertebrae appropriate to its new level along the tail. The results indicate that position along the appendage does not influence the developmental sequence of events of regeneration, but that it does influence the rate of growth and the structures to be replaced.
Duration of the cycle of the seminiferous epithelium in the prairie vole (Microtus ochrogaster ochrogaster)
Authors: Schuler Harold M. , Gier Herschel T.
Published: June 2005

The cycle of the seminiferous epithelium in M. o. ochrogaster was divided into eight readily recognizable stages based on the morphology of the developing spermatid. The mean relative frequencies of Stages I through VIII were 11.66, 19.25, 20.00, 19.00, 8.42, 6.17, 9.25 and 6.58%, respectively.

The duration of one cycle of the seminiferous epithelium in this species, as determined from autoradiographs of thymidine‐H3 injected testes was 7.17 days (S.E. ± 0.03). This is the shortest spermatogenic cycle reported for any mammal to date. The approximate durations of the meiotic prophase, meiotic divisions, and spermiogenesis were 8.8, 0.4 and 12.2 days, respectively. The entire process of spermatogenesis was estimated to span approximately 28.68 days.

The number of cycles that spermiogenesis spanned in this species was compared to values calculated for other species. Values within groups of related species appear relatively constant, but between groups the values are variable.
Scanning electron microscope studies of sea urchin fertilization I. Eggs with vitelline layers
Authors: Tegner Mia J. , Epel David
Published: June 2005

The surface coats of sea urchin eggs and the events of fertilization which take place on these surfaces were examined with the scanning electron microscope (SEM). Gametes of Strongylocentrotus purpuratus and Lytechinus pictus were considered in detail; eggs of seven other echinoids were examined for comparative purposes. Jelly coats, preserved by varying the pH of fixation, were found to vary in morphology and solubility properties between species. The vitelline layers of the nine echinoids are characterized by arrays of projections which are impressions of cytoplasmic microvilli in the vitelline layer. After sperm bind to the egg surface via the acrosomal process, fine filaments, apparently an egg response to insemination, further connect some sperm heads and tails to the egg. The cortical reactions spread out as a wave from where the fertilizing sperm fused with the egg; separation of the vitelline layer proceeds as a smooth wave front in S. purpuratus eggs and as a series of localized separations in L. pictus eggs. The fertilization membranes of S. purpuratus and Allocentrotus fragilis zygotes are expanded replicas of their respective vitelline layers, suggesting that fertilization membranes are formed by an unfolding of the vitelline layer.
Mammalian carbonic anhydrase isozymes : Evidence for A third locus
Authors: Holmes Roger S.
Published: June 2005

Starch gel electrophoretic patterns of carbonic anhydrase (CA) isozymes were examined from tissue extracts of sheep, mice, rabbits, and chickens. In addition to the widely distributed and extensively studied B and C isozymes, an additional isozyme (called CA‐A) was observed, which was predominantly localized in muscle tissue. Immunochemical studies showed the A isozyme to be homologous with CA‐B. Developmental and tissue distribution analyses suggested that a third locus (A) is involved in carbonic anhydrase synthesis in mammals.
Photoperiodic control of antler cycles in deer. III. Decreasing versus increasing day lengths
Authors: Goss Richard J.
Published: June 2005

Deer were exposed for three years to photoperiods which increased or decreased two hours every four months, starting at 4L/20D or 20L/4D, respectively. Under both sets of conditions, antlers were repeatedly shed and replaced, usually in synchrony with every other time the day lengths were changed. On decreasing days, antler cycles were omitted as the photoperiod passed the equinox (12L/12D). On increasing days, the equinoctial photoperiod induced prolonged episodes of antler growth.

The tendency for the antler replacement cycle to lock onto alternate changes in artificial photoperiods is consistent with the seasonal growth of antlers every other time the day lengths change in the natural environment. It is suggested that antler replacement is triggered neither by shortening nor lengthening days, but by the alternation of such changes irrespective of the direction of the shift in the photoperiod.
Effects of various low temperatures, cryoprotective agents and cooling rates on the survival, fertilizability and development of frozen‐thawed mouse eggs
Authors: Parkening T. A. , Tsunoda Y. , Chang M. C.
Published: June 2005

Frozen mouse eggs were examined to determine the effects of low temperatures, concentration of cryoprotective agents and cooling rates on their survival, fertilizability in vitro and subsequent development. Dimethyl sulfoxide administered at 1.5 M concentration was found to be the most effective cryoprotective agent. Upon thawing, 51% and 56% of the eggs appeared to be normal after having been cooled at 0.33°C/min to − 30°C and −50°C, but only 18% of the eggs appeared to be normal after having been cooled at the same rate to − 75°C. When eggs were cooled at 0.33°C/min to −45°C and the cooling rate increased to 1°C/min from −45°C to −75°C, 44% and 72% appeared normal upon thawing. Of the normal eggs fertilized in vitro from C3H mice, 65% cleaved to the 2‐cell stage and 24% of the 2‐cell eggs developed into blastocysts. Following the transfer of 17 blastocysts into three recipient mice, one mouse delivered three normal young.
Qualitative patterns of protein synthesis in the mouse oocyte
Authors: Golbus Mitchell S. , Stein Madelyn P.
Published: June 2005

Mouse oocytes were found to sythesize proteins actively at the germinal vesicle, metaphase I, metaphase II, and pronuclear (6 hours post‐fertilization) stages. The qualitative pattern of protein components being sythesized in vitro, as demonstrated using polyacrylamide gel electrophoresis, changed throughout maturation and fertilization. Oocytes were arrested at metaphase I by ≥ 0.1 μg/ml cycloheximide or actinomycin D. The protein pattern in oocytes cultured in the presence of actinomycin D progresses to a metaphase II pattern in spite of the nuclear maturation arrest, indicating a dissociation between meiotic maturation and the changes in the pattern of proteins synthesized at different stages of maturation.
Role of asterosaponin A in starfish spawning induced by gonad‐stimulating substance and 1‐methyladenine
Authors: Ikegami Susumu
Published: June 2005

A polypeptide hormone, gonad‐stimulating substance (GSS), induces oocyte maturation and spawning in starfish through the production of 1‐methyladenine (1‐MA) in the follicle cells. Asterosaponin A (ASA) obtained from the ovary of Asterias amurensis inhibits the spawning induced by the application of GSS on isolated ovarian fragments of Asterias. The action of ASA is not ascribable to its surface‐active property since various natural and synthetic surface‐active agents failed to affect GSS‐induced spawning. ASA antagonized the action of 1‐MA in inducing spawning of isolated ovarian fragments. However, ASA did not inhibit 1‐MA‐induced maturation of isolated oocytes. When ovarian fragments were placed in sea water containing ASA and GSS or 1‐MA, oocytes inside the fragments underwent germinal vesicle breakdown. The application of acetylcholine to these ovarian fragments resulted in an immediate shedding of mature oocytes. ASA did not affect calcium‐induced spawning in the ovarian fragments which were pretreated with calcium‐free sea water to dissolve the follicular envelope.
Analysis of mouse oogenesis in vitro. Oocyte isolation and the utilization of exogenous energy sources by growing oocytes
Authors: Eppig John J.
Published: June 2005

A method is described for the dissociation of mouse ovaries and the isolation of oocytes free of somatic cells by agitating pieces of ovary in collagenase and deoxyribonuclease in a calcium and magnesium free salt solution. This method yielded about 50% of the growing oocytes from immature mice.

The utilization of exogenously administered 14C‐labelled energy sources by oocytes in various growth stages was determined by measurement of evolved 14CO2. Little or no evolution of 14CO2 was detected from oocytes of any size incubated in 14C‐glucose, lactate or succinate. The production of 14CO2 from 14C‐pyruvate increased logarithmically when plotted against increasing oocyte volume with a plateau occurring after oocytes reached a volume of 65,500 μm3 (50 μ diameter). Thus, the pattern of energy metabolism for oocyte maturation and early egg cleavage, wherein glucose and lactate are not utilized as efficiently as pyruvate, has been established by the earliest stages of oocyte growth.
Preparation of tissue‐specific cell‐aggregating factors from embryonic neural tissues
Authors: Hausman R. E. , Knapp L. W. , Moscona A. A.
Published: June 2005

Tissue‐specific cell‐aggregating factors were previously obtained from the supernatant media of embryonic cell cultures. We describe here that such factors can be extracted from cell‐membrane preparations derived directly from embryonic tissues: neural retina, cerebrum, and spinal cord of chick embryos.
Relation between nerve fiber number and pectoral fin regeneration in the teleost
Authors: Ǵeraudie Jacqueline , Singer Marcus
Published: June 2005

The number of nerve fibers per unit of amputation surface area has been determined in four teleosts capable of regenerating their fins (Gobius paganellus, Gobius minutus, Ictalurus nebulosus and Fundulus heteroclitus) and in two non‐regenerating ones (Cottus bubalis and Blennius pholis.) The number of nerve fibers is about 16 in the non‐regenerating fins and varies between 25 and 35 in the regenerating ones. These data, correlated with previous ones obtained on tetrapods, affirm the principle that there is a phylogenetic decline in the quantitative innervation of the vertebrate appendage. Moreover, they show that in the fish a quantitative neuronal threshold must also be satisfied in order for fin regeneration to occur. The threshold, in terms of fiber number, is higher than in the urodele amphibian. However, the fibers appear to be of smaller caliber; and so, the total amount of neuroplasm at the amputation surface which is required for regeneration may be similar to that for the amphibian.
Environmental influence on ovulation and embryonic development in Rana pipiens
Authors: Lehman Grace C.
Published: June 2005

Environmental effects on ovulation and embryogenesis in Rana pipiens were assessed using both freshly‐captured fall animals and laboratory‐conditioned females which had undergone vitellogenesis in the laboratory. Frogs in both categories were divided into two groups. Ovulation was hormonally induced in one group of females prior to cold exposure and in the second group of animals following an 8‐week period at 4°C with an 8L 16D photoperiod. The incidence of both ovulation and normal embryonic development was increased following exposure of the animals to low temperatures and short daylength. Those animals which only partially ovulated prior to cold treatment did not respond to hormone injections following the period of cold exposure. Examination of the ovaries of these females revealed a much greater degree of oocyte resorption than was found in frogs whose initial ovulation was induced only after exposure to cold temperatures. The administration of ovulation‐inducing hormones prior to artificial hibernation may thus have initiated a phase of oocyte resorption which progressed even at 4°C.

The incidence of ovulation was similar in wild‐caught and laboratory‐conditioned females, but eggs from the latter showed a much lower percentage of development to Shumway stage 20. This effect may have been related to differences in the environmental factors to which the two groups were exposed during oogenesis.
Inhibition of hamster sperm acrosome reaction and fertilization by oligomycin, antimycin A, and rotenone
Authors: Rogers B. Jane , Ueno Marilynn , Yanagimachi Ryuzo
Published: June 2005

Effects of respiratory inhibitors (oligomycin, antimycin A and rotenone) on hamster sperm acrosome reaction and fertilization were studied. Hamster spermatozoa were incubated in a mixture of a modified Tyrode's solution and heat‐treated human serum in the presence and absence of inhibitors. Oligomycin (2.4 × 10−6 M), antimycin A (2.5 × 10−6 M) and rotenone (2.5 × 10−6 M) all reduced the incidence of the sperm acrosome reaction and fertilization without markedly affecting sperm motility. Antimycin A was the most effective in reducing the incidence of acrosome reaction. A reduction in the rate of fertilization was found in the presence of all of these respiratory inhibitors. The reduction in the incidence of acrosome reaction and fertilization by respiratory inhibitors implies an intimate relationship between high energy production (via respiration and oxidative phosphorylation) and capacitation and the acrosome reaction of spermatozoa. The necessity of oxidative metabolism for efficient capacitation and acrosome reaction of spermatozoa is suggested.
Factors influencing ovulation in the Mexican axolotl as revealed by induced spawnings
Authors: Humphrey Rufus R.
Published: June 2005

Axolotl females may be induced to spawn by injecting them with small doses of FSH prior to mating. Data on the different categories of spawnings obtained by this procedure have established the following points.

Spawnings of injected females completely without fertile eggs are small (173 eggs average). Courtship occurred in some of the matings (spermatophores found) but not in all. Spawnings of injected but uninseminated females re‐mated with a second (or third) male, not becoming inseminated, but all having some eggs fertilized by contact with spermatophores (showing courtship) are likewise small (219). It can be concluded that courtship of the injected female, even by two successive males, does not stimulate ovulation of additional eggs.

Insemination of injected females induced additional ovulation more or less frequently, depending upon whether the female was inseminated by the first, or a subsequent male with whom she was mated. Insemination by the first male, within 15 hours after the female had been injected with FSH, resulted in stimulation of ovulation in 36 of 54 spawnings (67%). The 36 spawnings averaged 593 eggs per spawning. In contrast, insemination by a second or third male, more than 15 hours after the female was injected with FSH, resulted in stimulation of additional ovulation in only 4 of 21 spawnings (19%).

Survival time of spermatozoa in inseminated females has been established. Considerable numbers of spermatozoa capable of fertilizing eggs survive for about one week. A few survive for 11 to 12 days, but none was found after 14 days.
Stages in the post‐hatching development of Aplysia californica
Authors: Kriegstein Arnold R.
Published: June 2005

In order to study the development of the nervous system of the marine mollusc, Aplysia californica, it is necessary objectively to assess the maturity of individual specimens. This can be done by defining stages in the life cycle. The post‐hatching development can be divided into four phases: planktonic, metamorphic, juvenile, and adult. These phases can be further subdivided into 13 stages on the basis of behavioral and morphological characteristics visible in living specimens: Stage 1, newly hatched; Stage 2, eyes develop; Stage 3, the larval heart beats; Stage 4, maximum shell size is reached; Stage 5, the propodium develops; Stage 6, red spots appear; Stage 7, the velum is shed; Stage 8, eyebrows appear; Stage 9, pink color develops; Stage 10, white spots appear; Stage 11, rhinophores grow; Stage 12, the genital groove forms; Stage 13, egg laying begins.

Reconstructions from serial sections taken from specimens fixed at each of these stages reveal the sequence of formation of the major organ systems. The nervous system develops gradually. The cerebral and pedal ganglia are present at Stage 1, the optic ganglia develop at Stage 2, the abdominal, pleural, and osphradial ganglia at Stage 3, the buccal ganglia at Stage 5, and the genital ganglion at Stage 13.

Because Aplysia develops gradually, it is possible to analyze the contribution which gastropod torsion makes to the different phases of the life cycle. The Aplysia embryo undergoes 120° torsion prior to Stage 1. The major visceral organs, the digestive system, heart, gill, and visceral nervous system, develop subsequently in their post‐torsional positions. After metamorphosis, there is a partial de‐torsion which involves only the digestive system. Torsion of the digestive system may therefore be beneficial only to the pre‐metamorphic larva, and not to the postmetamorphic juvenile.