bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen excretion by embryos of an altricial bird, the redwing blackbird (Agelaius phoeniceus)
Authors: Packard Gary C. , Packard Mary J.
Published: June 2005

Small quantities of urea and soluble urates are present in eggs of redwing blackbirds at oviposition, but no ammonia can be detected in eggs before the ninth day of a 12‐day incubation. Urea‐nitrogen accumulates relatively slowly in eggs during development, whereas urate‐nitrogen accumulates more rapidly. At hatching, 71% of the waste‐nitrogen accumulated in eggs is in the form of urates, 26% in urea, and 3% in ammonia. Thus, the general pattern of nitrogen excretion described for embryos of precocial birds applies also to those of an altricial species.
Developmental profile of the heat shock response in early embryos of Drosophila
Authors: Bergh Sandra , Arking Robert
Published: June 2005

Drosophila melanogaster embryos reared at 22°C were subjected to a mild heat shock (40 min at 37°C) at various ages in order to determine whether there are changes in the heat shock response during embryogenesis. The effects of the heat shock were measured by assaying (1), subsequent developmental abnormalities (2), developmental time (3), hatchability, and (4), the ability to synthesize the heat shock proteins as assayed by 35S‐methionine pulse labeling followed by protein separations using both one and two‐dimensional polycrylamide gel electrophoresis. Our data show that, first, proteins with molecular weights similar to those of six of the seven major heat shock proteins are normally found in the embryo at control temperatures (22°C); second, that the pregastrula embryo (stages 2–6) is not capable of displaying any aspect of the heat shock response upon treatment, although it may possess all of the so‐called heat shock proteins; third, that the complete heat shock response is acquired very rapidly by early gastrula embryos; and fourth, that the heat shock treatment brings about developmental delays and/or abnormalities, depending on the developmental stage of the embryo at the time of the treatment. These developmental abnormalities appear to stem from the failure of early embryos to completely inhibit their synthesis of non‐heat‐shock proteins. In the light of these findings, it becomes important not to base conclusions about the putative presence of a heat shock response in a particular tissue or developmental stage solely on the presence or absence of the heat shock proteins.
Cyclic GMP levels during regeneration in Hydra oligactis and its distribution in steady‐state animals
Authors: Berkowitz Michele S. , Lesh‐Laurie Georgia E.
Published: June 2005

To assess the involvement of cyclic guanosine 3′, 5′‐monophos‐phate (cGMP) in regulating cell division versus cell differentiation in regenerating systems, a radioimmunoassay study of the distribution and concentration of cGMP in steady‐state and regenerating Hydra oligactis was undertaken. In steady‐state animals, uniformly low cGMP levels were observed in the hypos‐tome‐tentacle, and upper‐, mid‐, and lower‐gastric regions. The peduncle/basal disc region, however, evidenced markedly higher levels of this cyclic nucleotide. Removal of the animal's interstitial cell population, using nitrogen mustard, did not alter this distribution. Animals lacking interstitial cells, however, exhibited greater concentrations of cGMP/cell than did untreated controls. During distal, whole animal regeneration increased cGMP concentrations were noted during wound healing and 3 hr antecedent to tentacle elaboration. A similar pattern was observed in the distal 1 mm of regenerating tissue. Basal disc regeneration was accompanied by only a single elevation in cGMP levels, concomitant with basal disc reformation. Wounded, but nonregenerating, animals likewise showed only a single rise in cGMP levels; this increase occurred during wound healing. The data, therefore, are consistent with changes in cGMP concentrations occurring in association with periods of DNA synthesis (e.g., tentacle elaboration and restructuring of the wounded surface). The distribution data and nitrogen mustard studies allow the further conclusion that the changes in cGMP recorded reflect activities of the epithelial cell population.
Electrical stimulation of the starfish's radial nerve in vitro induces the release of a gonadotrophin
Authors: Desantis Mark , Cloud J. G.
Published: June 2005

In starfish a neuropeptide responsible for the induction of ovulation and the reinitiation of meiotic maturation in fully grown oocytes appears to be released from the radial nerves at the time of spawning. The objectives of this investigation were to determine if the radial nerve would release this gonadotrophin when electrically stimulated in vitro and to locate other possible sources of this factor. Electrical stimulation of radial nerves isolated from the starfish, Pycnopodia helianthoides, resulted in the release of the gonadotrophin. Significant amounts of this neuropeptide were detected neither in other tissues of the starfish nor in mammalian nervous tissue.
Photoperiod perception in the blind mole rat (Spalax ehrenbergi, Nehring): Involvement of the Harderian gland, atrophied eyes, and melatonin
Authors: Pevet P. , Heth G. , Hiam A. , Nevo E.
Published: June 2005

The involvement of the Harderian gland, atrophied eyes, and melatonin in the perception of photoperiodic changes has been studied in the mole rat, a fossorial blind mammal the thermoregulatory capacity of which is photoperiod‐dependent. When transferred from a long photoperiod to a short one, mole rats increase their resistance to cold, a perfectly reversible phenomenon.

After 2 weeks under short photoperiod the thermoregulatory capacities of animals without Harderian glands are less than those of the controls. The Harderian gland appears thus to be implicated in the detection of photoperiodic changes. After 5 weeks, however, the Harderianectomized animals had perfectly integrated the photoperiodic change, so demonstrating that other photoreceptor organs exist. The atrophied eyes, which, under these conditions, do not seem to play an important role, are involved when the animals are transferred from short photoperiod to long photoperiod. Melatonin, but not 5‐methoxytryptamine, appears to be a crucial compound in such a phenomenon.

These results, which demonstrate that in mammals (at least in the mole rat, as in nonmammalian vertebrates), nonocular photoreceptors exist, suggest that the mechanism by which mammals integrate photoperiodic changes is not the same when the animals are transferred from long to short photoperiod as when transferred from short photoperiod to long photoperiod.
A nerve‐conditioning lesion accelerates limb regeneration in the newt
Authors: Maier C. Eberhardt , McQuarrie Irvine G. , Singer Marcus
Published: June 2005

A nerve‐conditioning lesion induced sustained acceleration of limb regeneration. Newt limb nerves were subjected to a conditioning lesion by unilateral axotomy at the elbow 2 weeks prior to amputating both limbs above the elbows. Limbs on the side that had received a conditioning lesion began the regeneration process 3–4 days earlier than contralateral controls and this difference was observed up to recognizable digit formation. Limb buds on the conditioned sides had a twofold greater axonal density than contralateral counterparts at 2 weeks after amputation. Since limb bud formation is dependent on a sufficient quantity of axonal regrowth, accelerated limb regeneration is apparently due to accelerated reinnervation.
Evidence that the ectoderm is the affected germ layer in the wingless mutant chick embryo
Authors: Carrington Jill L. , Fallon John F.
Published: June 2005

We grafted normal flank ectoderm to the denuded presumptive wing bud mesoderm of stages 14–15 wingless embryos. When this was done, the wingless wing bud mesoderm was capable of inducing a ridge in the grafted ectoderm, maintaining that ridge, and growing out to form a wing. However, when stage 17–18 wingless wing bud mesoderm was combined with a normal leg bud ectodermal jacket, the recombinant bud failed to grow out to form a wing (Zwilling, '56a; and this report). When normal ectoderm was first grafted to a wingless host at stages 14–15, and the resulting stage 18 wing bud was removed and then the mesoderm recombined with a normal ectodermal jacket, the double recombinant bud could form a distally complete wing. However, these wings had some deficiencies compared to similar double recombinants made with normal mesoderm. These results show, first, that the ectoderm is affected by the wingless gene and, second, that there may be a prelimb bud stage interaction between wingless ectoderm and mesoderm such that, by stage 17, the wingless mesoderm becomes defective as a result of the ectodermally expressed mutation. Deficiencies in wingless mesoderm double recombinants indicate that the mesoderm may be sensitive to manipulation, possibly because the ectoderm has affected the mesoderm to some extent before stage 14. We believe it is not possible to determine the affected germ layer in wingless after the limb bud arises. However, after using the prelimb bud recombinant technique which we have designed, it becomes apparent that the ectoderm is affected by the wingless gene.
Cell death in the posterior necrotic zone of the developing chick wing measured by the loss of membrane integrity
Authors: MacCabe Jeffrey A. , Brewton Randolph G.
Published: June 2005

Cell death in the posterior necrotic zone (PNZ) of the developing chick wing was examined in organ culture using a 51chromium release assay. This isotope is incorporated into the cytoplasm of mesenchymal cells and is released from the tissue very slowly. A sudden increase in 51Cr release coincides with cell death and lysis. There is no evidence of an increase in membrane permeability prior to histological evidence of cell lysis. Lysis begins at late stage 22 or early stage 23 and lasts for 9 hours. Approximately 3,500 cells lyse in the PNZ during this period of time, resulting in a considerable decrease in cell density in the tissue.
Neuronal organization of the avian paraventricular nucleus: Intrinsic, afferent, and efferent connections
Authors: Korf Horst‐W.
Published: June 2005

The heterogeneous paraventricular nucleus (PVN) of birds offers favorable conditions for the analysis of intrinsic, afferent, and efferent connections of neuroendocrine systems. Paraventricular neurons are successfully impregnated with the Golgi‐technique. The findings indicate a direct influence of the cerebrospinal fluid (CSF) on the magnocellular neurons that, via their axon terminals in the neural lobe of the pituitary, are also exposed to the hemal milieu. The magnocellular neurons are intermingled with parvocellular elements which may represent local interneurons. A group of parvocellular nerve cells is identified as CSF‐contacting neurons. This type of cell forms a basic morphologic component of the avian neuroendocrine apparatus.

Immunocytochemical and ultrastructural studies further support the concept of neuronal interactions between parvocellular and magnocellular elements. Moreover, these findings speak in favor of the existence of recurrent collaterals of the magnocellular neurons.

Nerve cells giving rise to afferent connections to the PVN are located in the limbic system and autonomic areas of the upper and lower brainstem. Further afferents may originate from the subfornical organ, the organon vasculosum laminae terminalis, the ventral tegmentum, and the area postrema. Via efferent projections, the PVN is connected to the nucleus accumbens, lateral septum, several hypothalamic nuclei, the neural lobe of the pituitary, the organon vasculosum laminae terminalis, the subfornical organ, the pineal organ, the area postrema, the lateral habenular complex, and various autonomic areas of the reticular formation in the upper and lower brainstem and the spinal cord.

In conclusion, the PVN may be regarded as an integral component of the neuroendocrine apparatus reciprocally coupled to the limbic system, several circumventricular organs, and various autonomic centers of the brain.
Effects of gonadal steroids and adrenergic agonists on avian growth and feed efficiency
Authors: Weppelman R. M.
Published: June 2005

The effects of gonadal steroids and adrenergic agonists in growing poultry are reviewed. Estrogens, used commercially to caponize, improve muscle palatability and weight gain but are hyperlipidemic and adversely affect feed efficiency. Their ability to caponize results from the fact that negative feedback regulation of gonadotropin secretion is mediated by estrogen synthesized within the male's central nervous system. Androgens are strongly anabolic in avian species but are deleterious to growing bone. Thus, androgens depress growth and efficiency when given before epiphyseal closure but stimulate gain and improve efficiency when given afterwards. The beta‐adrenergic agonist clenbuterol improves the growth and efficiency of broiler chickens. The effects of beta‐agonists on muscle, adipogenic tissue, and the endocrine system are presented as possible mechanisms for these actions.
Organization and activation of behavior in quail: Role of testosterone metabolism
Authors: Balthazart Jacques , Schumacher Michael
Published: June 2005

In quail, the hypothalamus enzymatically transforms testosterone (T) into estradiol (E2) estradiol (E2), 5α‐dihydrotestosterone (5α‐DHT). During the embryonic life, the 5β‐androstanes are inactive androgens. The decrease of 5β reductase with age during sexual maturation corresponds to a potentiation of the effects of T as shown by experiments that compared the effects of T and 5α‐DHT in adult and young quail. T metabolism is also involved in the activation of male behavior in the adult. T aromatization is probably essential for behavioral activation, but nonaromatizable androgens such as methyltrienolone, and to some extent 5α‐DHT, can also stimulate sexual behavior in castrates. These enzymatic activities show a clear neuroanatomical localization and are sexually dimorphic. Males produce more active metabolites (E2, 5α‐DHT) than females, which could explain the male's greater sensitivity to T treatments. It thus appears that T metabolism is involved in the differentiation and activation of behavior in quail.
Prolactin and parenting in the pigeon family
Authors: Silver Rae
Published: June 2005

The relationship between plasma prolactin and: (1) crop growth; (2) incubation; (3) brooding; and (4) feeding young in Columbiformes is reviewed. There is a good parallel between changes in crop growth and plasma prolactin fluctuations during the breeding cycle. Prolactin does not play a role in the initiation of incubation, though it can maintain the response. Toward the end of breeding, a decline in prolactin precedes the decline in incubation (of infertile eggs) or brooding (of young), while exogenously administered prolactin can prolong the response. There is no evidence of a necessary relationship between prolactin secretion and parental feeding of young, as this behavior can precede and outlast the secretion of the hormone during breeding.
Interrelation of the avian immune and neuroendocrine systems
Authors: Glick Bruce
Published: June 2005

Our understanding of immunology and endocrinology has been enriched by studies with different avian species. Numerous experiments have identified the role of the avian thymus and bursa of Fabricius in the immune response and the interrelation of these glands and their cellular products with the neural endocrine system. The growth pattern of the thymus and bursa are influenced by steroids. Increases in thymi growth appear to be controlled, in part, by fluctuations in thyroid activity. Sex‐linked dwarf (SLD) chicks have lower T3levels than normal chicks, but normal levels of growth hormone. The poor agglutinin response of SLD chickens to low concentrations of sheep red blood cells (0.1–1.0%) may be overcome by increasing the percentage of sheep erythrocytes to 5 or injecting growth hormone, which may enhance the conversion of T4to T3. Castration impaired cell‐mediated immunity but surgical removal of the thyroid did not significantly influence the humoral response to sheep erythrocytes orBrucella. Embryonic hypophysectomy reduced the number of B cells in the late embryo. Lesioning the anterior pituitary in 9‐day‐old chicks markedly reduced several parameters of cell‐mediated immunity. In ovo bursectomy at 68 hr markedly increased the size of the adrenals and testes, numbers of Leydig cells, and levels of circulating testosterone but not corticosterone. On the basis of identification of lymphokines or cytoplasmic granules, lymphocytes and other cells of the lymphomyeloid complex are candidates for an endocrine role. A circuitry between the lymphocyte and neuroendocrine system has been identified in mammals and should be extended to Aves.
Renal handling of sodium chloride and its control in birds
Authors: Nishimura Hiroko , Miwa Toichiro , Bailey John R.
Published: June 2005

Avian kidneys show features of both mammalian and non‐mammalian kidneys, possessing 1) cortical reptilian‐type (RT) and medullary mammalian‐type (MT) nephrons, 2) blood supplies from renal arterial and renal portal systems, and 3) a primitive macula densa. To determine how these morphological characteristics contribute to unique renal functions, we examined first a possible functional link between the renal tubules and the preglomerular vasculature and, second, the function of the loop of Henle of the MT nephrons. Infusion of 5% NaCl (2.0 ml/kg/h) into the renal portal system of the pullet Gallus domesticus caused diuresis and natriuresis in the infused side, whereas infusion of the same dose into the systemic circulation showed no effect. Infusion of 10% NaCl at a higher flow rate into either the renal portal or systemic routes caused hypernaturemia and a prolonged antidiuresis, presumably due to a release of arginine vasotocin. Plasma renin activity (PRa) decreased during renal portal infusion of hypertonic saline, suggesting that increases in intratubular or peritubular NaCl levels may suppress PRA. The thick limb of the loop of Henle (TLH) isolated from the MT nephron of the quail Coturnix coturnix revealed a lumen‐positive, furosemide‐sensitive transepithelial voltage (Vt) that requires the presence of both Na and Cl. Net water flux (Jv) was nearly zero when the TLH was perfused and bathed with isosmotic solution. Net water flux increased only slightly and osmotic water permeability (Lp) was low when the osmotic gradient was imposed. Vasotocin altered neither Vt, Jv, nor Lp. Chloride efflux was higher than Cl influx, and net Cl absorption was comparable to that of the TLH of the mammalian kidney. Thus, it appears that the TLH of MT nephrons acts as a diluting segment that contributes to the diluting and concentrating functions of the bird kidney.
Role of protein synthesis and ninhydrin‐positive substances in acclimation of Paramecium tetraurelia to high NaCl
Authors: Cronkite D. L. , Gustafson A. N. , Bauer B. F.
Published: June 2005

Paramecium tetraurelia, stock 51s, will not survive if shifted from normal medium to medium with 80–100 mM NaCl. But, if first kept in medium with 50 mM NaCl for at least 45–60 min, cells survive in medium with 80–100 mM NaCl. After shifting to medium with 50 mM NaCl, cells increase internal levels of ninhydrin‐positive substances (NPS) for the first 30 min, then decrease them again over the next 90 min. Total internal osmolarity probably remains constant over this 90 min since contractile vacuole output is constant. Treatment with the protein synthesis inhibitor G418 (geneticin) prevents acclimation in cells in 50 mM NaCl, but does not prevent the changes in NPS levels. Thus NPS are not sufficient to account for acclimation, nor is there evidence that they are required.
Phospholipase A2 from liver microsomal membranes of thermally acclimated rainbow trout
Authors: Neas N. P. , Hazel J. R.
Published: June 2005

Hydrolysis of exogenous one‐acyl,2[3H]‐oleoyl phosphatidyl choline by intracellular phospholipase A2 to yield free [3H]‐oleate and lysophosphatidylcholine was measured in isolated liver microsomes from warm (20°)‐ and cold (5°C)‐acclimated rainbow trout, Salmo gairdneri. Unlike mammalian phospholipase A2, which is not typically microsomal, over 18% of the total phospholipase A2 activity from trout liver occurred in the microsomes. Specific activity in microsomal preparations (4.07 nmole · hr−1 · mg−1) represented a 1.4‐fold purification of clarified liver homogenates (2.93 nmole· hr−1mg−1). The accumulation of free fatty acid was a function of both the duration and the protein concentration of the assay. Activity was enhanced fourfold in the presence of 0.1% Triton X‐100. Free Ca++ stimulated activity up to 100 μM, but was not an absolute requirement of the enzyme. Maximal activity occurred at pH 8.0–8.5 at 20°C assay temperature and pH 9.0 at 5°C. Acclimation history did not influence the pH optima of the enzyme. Thermal acclimation did, however, result in perfect compensation of enzymatic rate; phospholipase A2 activity from cold‐acclimated trout was not significantly different from that of warm‐acclimated trout when measurements were made at their respective acclimation temperatures. This perfect compensation for temperature as well as the unique intracellular localization of trout liver phospholipase A2 implicate the enzyme in a deacylation‐reacylation cycle that could be partially responsible for the thermally modulated restructuring previously observed in microsomal membranes of this species.
Pattern regulation during regeneration of limb stumps bearing partial circumferences of flank skin in the newt, Notophthalmus viridescens
Authors: Tank Patrick W.
Published: June 2005

The regenerative ability of limb stumps bearing partial circumferences of flank skin was tested in the newt, Notophthalmus viridescens. Skin dorsal to the lateral line of the flank was removed and used to replace 1/4, 1/2, or 3/4 of the skin of the upper forelimb. Grafts were placed at anterior, posterior, dorsal, or ventral positions relative to the axes of the limb. After 30 days of graft healing the limbs were amputated through the grafts and were permitted to regenerate for 60 days. Limb stumps bearing 1/4 circumference of flank skin regenerated complete limbs in 85% of the experimental cases. After 1/2 circumference of limb skin was replaced, 57% regenerated complete limbs. When 3/4 of the limb skin was replaced by flank skin, 29% regenerated complete limbs. Only 2% of experimental limbs bearing a full circumference of flank skin regenerated complete limbs in an earlier study [Tank, P.W. (1984) J. Exp. Zool., 229:143–153]. The greatest effect on pattern formation was observed when flank skin grafts were placed at the ventral position of the limb stump regardless of graft size. These results are discussed in light of the idea that short‐range cellular interactions between limb cells are essential for pattern formation during limb regeneration.
Putative extraocellar photoreceptors in the outer nerve ring of Polyorchis penicillatus
Authors: Satterlie Richard A.
Published: June 2005

Putative sensory cells have been described in the outer nerve ring of the hydrozoan jellyfish Polyorchis penicillatus that resemble ocellar photoreceptors characteristic of this animal group. Each receptor cell bears an apical structure consisting of verticillate lamellae representing evaginations of ciliary membranes (9 + 2 axonemes). Verticils are grouped in clusters of three or more and are distributed throughout the outer nerve ring. Individual lamellae of each verticil are up to 0.2 μM wide and are frequently reflexly folded to form a tightly packed whorl. Multiple axonemes contribute to each verticil. Each receptor cell body contributes a single axon (up to 1.75 μm in diameter) to the neuronal tracts of the outer nerve ring. The structural similarity between the described cells and hydrozoan photoreceptors, and the close agreement between the location of these cells and the localized photoresponse in Polyorchis and related medusae suggest that the putative receptor cells function as photoreceptors.
Effect of hypoxic hypoxia on taurine concentrations in ventricles of mouse hearts
Authors: Eldridge Stuart A. , Hilton Fredrick K. , Hilton Mary A.
Published: June 2005

The effect of hypoxic hypoxia on the concentration of taurine in right ventricles was studied in the hearts of male CF1 mice caged individually and maintained for 16 hr per day in a hypobaric chamber evacuated to an air pressure of 307 mm Hg. After 23 days hearts were excised and right and left ventricles were separated and lyophilized. Hematocrits in chamber animals were 77‐82%, compared to 45–49% for control mice. Mean weights of right ventricles of animals from the chamber were 11.2 ± 0.9, compared to control values of 7.0 ± 0.4, mg dry weight. The mean dry weights of left ventricles in both groups of animals were the same. There were no significant differences in the nmoles taurine per mg dry tissue in either heart chamber, with mean values ± S.E.M. of 124.0 ± 4.6 and 135.0 ± 4.5 in right ventricles and 128.0 ± 4.3 and 110.9 ± 15.3 in left ventricles of experimental and control animals respectively. Thus, hypertrophy which results from hypoxia is not accompanied by increased concentrations of taurine in right ventricles.
Kinetics of cell cycle entry in innervated and denervated forelimb stumps of larval Ambystoma
Authors: Barger Philip M. , Tassava Roy A.
Published: June 2005

Pulse and continuous labeling with 3H‐thymidine were used to examine the kinetics of cell cycle entry and progression in innervated, regenerating and denervated, nonregenerating limbs of larval axolotls. In innervated limbs the labeling index (LI) increased from a relatively low level after a pulse (30%) to 60% and 80% after 26 and 50 hr, respectively, of continuous labeling, at both preblastema and blastema stages. Thus a considerably larger proliferative fraction was revealed by continuous labeling data than was predicted from pulse labeling data. Much cycling heterogeneity was shown to exist in the blastema cell population, primarily in the G‐1 phase. These results show that many cells of regenerating limbs are transiently quiescent for periods of up to and perhaps longer than 50 hr. The proliferative fraction in denervated limbs on days 4‐6 postamputation was somewhat less than that of innervated limbs but also larger than predicted from pulse labeling data. The data show that most of the dedifferentiated cells enter the proliferative fraction even in the absence of nerves. Most of these initially cycling cells subsequently leave the proliferative fraction; the LI was less than 20% even after 50 hr of continuous labeling on days 8–10 postamputation.
Experimental analysis on the capacity of several larval tissues to promote lens‐forming transformations in the cornea of Xenopus laevis Tadpoles
Authors: Bosco Luigi , Filoni Sergio , Cioni Carla
Published: June 2005

Fragments of iris ring, spleen, kidney, tail, tail blastema, tentacle, tentacle blastema, and spinal cord were implanted between the outer and the inner cornea in normal eyes of Xenopus laevis tadpoles at stage 50 (according to Nieuwkoop and Faber, '56).

Results show that tail blastema, tentacle blastema, and spinal cord can induce varying degrees of lens‐forming transformations in the outer cornea, while the iris ring, spleen, kidney, tail, and tentacle do not produce any significant response from the cornea, thus demonstrating that the lens‐inducing capacity is not widely distributed in the larval tissues of Xenopus.

The causes of the different degrees of lens‐inducing capacity in the various larval tissues are discussed.
Electron microscopic observations on sperm entry into eggs of the bitterling during cross‐fertilization
Authors: Ohta Tadayuki
Published: June 2005

In the cross‐fertilization of the two bitterlings Acheilognathus lanceolata (spermatozoa) and Rhodeus ocellatus ocellatus (eggs), the morphology of the gametes and the process of sperm entry were observed using transmission and scanning electron microscopy (TEM and SEM). The spermatozoon (total length, about 30 μm) had a round head (about 1.8 μm), two centrioles, a single large mitochondrion, and a flagellum. The micropyle of the egg did not permit simultaneous passage of two spermatozoa. The chorion was mainly composed of an outer and an inner layer and progressively decreased in thickness away from the vicinity of the micropyle where it was thickest. Filamentous structures were observed in microplicae and microvilli on the egg cortex. After a fertilizing spermatozoon attached to the specialized sperm entry site, it appeared to be incorporated into the egg by membrane fusion. At this time the site swelled and plugged the micropyle. The swollen cytoplasm appeared to be a fertilization cone which did not retract in this fish. With the advance of the cortical change, the egg cytoplasm was detached from the chorion except in the area of and around the sperm entry site. About 20 min after insemination, the egg cytoplasm devoid of cortical alveoli was torn away from the other cytoplasm and adhered to the inside of the chorion. These observations showed that the process of sperm entry in cross‐fertilization was similar to that in homologous fertilization of R. ocellatus.
Extracellular localization of cyclic GMP in the house cricket male accessory reproductive gland and its fate in mating
Authors: Murtaugh Michael P. , Kapoor C. Lal , Denlinger David L.
Published: June 2005

The male accessory reproductive gland (ARG) of the house cricket, Acheta domesticus (L.), contains an exceedingly high concentration of cyclic GMP, about 1,000 pmol/mg protein. Immunofluorescent localization and radioimmunoassay measurements show that cyclic GMP is concentrated in a small number of tubules. It accumulates in the tubule lumina where it is protected from degradation by phosphodiesterases. Cyclic GMP is secreted by the ARG and is incorporated into spermatophores. Over 80% of spermatophore cyclic GMP is found in the handle‐capillary tube, a thin conduit through which sperm pass during transfer to the female. The concentration of cyclic GMP in the insemination fluid is about 20 μM but does not appear to be specifically associated with the sperm. Cyclic GMP enters the female spermatheca during insemination but disappears rapidly. Physiological effects of cyclic GMP on sperm were not observed nor was an effect of cyclic GMP observed on egg laying by mated females. Cyclic AMP was localized on sperm flagella in the spermatophore and in the spermatheca. These studies indicate that cyclic nucleotides have important roles in insect reproduction and that the house cricket is a good model for elucidating these functions.
Cross fertilization in vivo and in vitro between three species of vesper mice, Calomys (Rodentia, Cricetidae)
Authors: Roldan E. R. S. , Vitullo A. D. , Merani M. S. , Von Lawzewitsch I.
Published: June 2005

Cross fertilization was tested between oocytes of Calomys callidus and spermatozoa from C. callidus, C. musculinus and C. laucha by both in vivo and in vitro insemination. After in vivo and in vitro insemination, respectively, percentages of oocytes fertilized were 68.8 and 46.6 (C. callidus × C. callidus), 20.3 and 12.7 (C. callidus × C. musculinus), 26.7 and 4.3 (C. callidus × C. laucha). Thus, the percentages obtained after in vitro insemination were always lower than those obtained with in vivo insemination. It was found that 23.9% and 44.4% of two‐cell hybrid embryos were present in oviducts 30 hr after in vivo insemination of C. callidus females with C. musculinus or C. laucha spermatozoa, respectively. At a later stage (56 hr postinsemination), development did not progress further, and abnormal embryos were found both at 30 and 56 hr postinsemination, suggesting some kind of cleavage arrest or degeneration of the embryos. We suggest that fertilization is not strictly species‐specific, at least among the species we studied, but that there are some factors that reduce the efficiency of interspecific fertilization.
Developmental mutants isolated from wild‐caught Xenopus laevis by gynogenesis and inbreeding
Authors: Krotoski Danuta M. , Reinschmidt Dana C. , Tompkins Robert
Published: June 2005

Xenopus laevis obtained from indigenous African populations are a rich source of mutants affecting development. Gynogenesis and inbreeding were used to isolate mutants affecting development from wild‐caught Xenopus laevis females. Fourteen mutants were recovered from eight females tested. One mutant was recovered from each of two females. This load of 1.875 developmental mutants per female is similar to that found in the axolotl (Ambystoma mexicanum), a urodele amphibian, and is only slightly less than the load of mutants with major developmental effects found in Drosophila and man. These results suggest that the anuran amphibian Xenopus laevis, an ancestrally tetraploid species, has undergone extensive diploidization of developmentally important loci and that gynogenesis and inbreeding of wild‐caught animals can provide adequate mutants at diploid loci for developmental genetic studies.
Effects of exposing Drosophila melanogaster parents to ethanol on expression of vestigial in their progeny
Authors: Giesel James T. , Niemann Mark M.
Published: June 2005

When parental Drosophila melanogaster were chronically exposed at 28°C or 24°C to ethanol during their larval and pupal stages of development, their progeny, produced when parents were 5–16‐day‐old adults, showed modified expression of vestigial alleles in heterozygous and homozygous combinations. Parental alcohol effects were dependent on parental rearing temperature. We conclude that parental environment (alcohol, temperature) causes heritable but transitory changes in progeny phenotype that are elicited by exposure of germ cells to alcohol.
Inverse effects of ethidium bromide on superoxide dismutase and lactate dehydrogenase of Artemia salina embryos
Authors: Bremner Theodore A. , Edwards Kimberly A.
Published: June 2005

Development of Artemia salina embryos in the presence of ethidium bromide, an inhibitor of mitochondrial transcription, results in a dose dependent increase in the specific activity of lactate dehydrogenase, and a concomitant decrease in the specific activity of a cyanide‐resistant superoxide dismutase. The inhibition of mitochondrial function by ethidium bromide appears to exert opposite effects on the nuclear cistrons encoding lactate dehydrogenase and superoxide dismutase, and suggests that a common mitochondrial signal may exert diametric effects on nuclear cistrons whose products are characteristic of alternate states of respiration.
Organic matrixlike macromolecules associated with the mineral phase of sea urchin skeletal plates and teeth
Authors: Weiner Stephen
Published: June 2005

The skeletal plates and teeth of the echinoid Paracentrotus lividus contain a heterogeneous assemblage of macromolecules that are not part of the connective tissue, but are presumably intimately associated with the mineral phase. Upon dissolution of the Mg‐calcite mineral phase, some of these molecules are insoluble. The insoluble fractions of the teeth and skeletal plates are quite different, the former being predominantly protein and the latter, primarily some unknown nonproteinaceous material. The soluble constituents are similar in both tissues. These hydrophilic macromolecules have been partially separated and characterized. In both hard parts, two distinct classes of macromolecules are present, as indicated by the amino acid compositions of their protein constituents. These two classes of macromolecules are also present in the shells of a foraminifer and in various mollusks, both of which are formed by the “organic matrix‐mediated” biomineralization process. The locations of these macromolecules in the teeth and skeletal plates are not known, nor whether they form coherent structures. It is therefore premature to conclude that these macromolecules do function as an organic matrix, although the results presented are in agreement with such an interpretation.
Heterogeneity of myofibrillar proteins in lobster fast and slow muscles: Variants of troponin, paramyosin, and myosin light chains comprise four distinct protein assemblages
Authors: Mykles Donald L.
Published: June 2005

Fast and slow muscles from the claws and abdomen of the American lobster Homarus americanus were examined for adenosine triphosphatase (ATPase) activity and for differences in myofibrillar proteins. Both myosin and actomyosin ATPase were correlated with fiber composition and contractile speed. Four distinct patterns of myofibrillar proteins observed in sodium dodecyl sulfate‐polyacrylamide gels were distinguished by different assemblages of regulatory and contractile protein variants. A total of three species of troponin‐T, five species of troponin‐I, and three species of troponin‐C were observed. Lobster myosins contained two groups of light chains (LC), termed “alpha” and “beta.” There were three α‐LC variants and two β‐LC variants. There were no apparent differences in myosin heavy chain, actin, and tropomyosin. Only paramyosin showed a pattern completely consistent with muscle fiber type: slow fibers contained a species (105 kD) slightly smaller than the principle variant (110 kD) in fast fibers. It is proposed that the type of paramyosin present could provide a biochemical marker to identify the fiber composition of muscles that have not been fully characterized. The diversity of troponin and myosin LC variants suggests that subtle differences in physiological performance exist within the broader categories of fast‐ and slow‐twitch muscles.
Neural fold and neural crest movement in the mexican salamander Ambystoma mexicanum
Authors: Brun Rudolf B.
Published: June 2005

In studies of amphibian neurulation, the terms “neural ridge,” “neural fold,” and “neural crest” are sometimes used as synonyms. This has occasionally led to the misconception that grafting of the neural crest is equivalent to grafting of the neural fold. The neural fold, however, is composed of three parts: the neural crest, prospective neural tube tissue, and epidermis. In order to investigate how these neural fold components move during neurulation, time‐lapse photography, electron microscopy, and grafting were performed. Ambystoma mexicanum embryos were photographed during neurulation at regular intervals. The photographs were analyzed to find the position of those cells at beginning of neurulation that end up on the line of fusion as the neural folds close. Posteriorly, these cells are already on the emerging neural fold. In the anterior neural folds, however, these cells are located in the lateral epidermis. Electron microscopy of the neural folds confirms the presence of epidermis. To follow the movement of the cells differentiating into melanophores (neural crest), neural fold parts were grafted into albino hosts. The crest cells differentiating into melanophores following ectopic grafting are located in the flank of the neural fold that is in contact with the neural plate. In grafts from the outside (distal) flank, no melanophores developed. Semithin sections show that the third part of the neural fold consists of apically constricted cells known to differentiate into neural tissue. Because the neural folds consist of epidermis, neural tissue, and neural crest, neural fold and neural crest cannot be used as synonyms.
An egg envelope component induces the acrosome reaction in sturgeon sperm
Authors: Cherr Gary N. , Clark Jr. Wallis H.
Published: June 2005

The acrosome reaction in Acipenser transmontanus sperm can be induced by a 66,000 dalton glycoprotein that is present in Layer 3 (L3) of the egg envelope and in egg water only following exposure of the eggs to fresh water. When egg water is fractionated on Sepharose CL 6B, the 66,000 dalton glycoprotein‐containing fractions possess acrosome reaction inducing activity. Egg water may be species‐specific in its ability to elicit the acrosome reaction, as demonstrated by the fact that it has no effect on the sperm of Acipenser fulvescens. Egg jelly possesses no acrosome reaction, inducing activity. The major carbohydrate‐containing component of the egg envelope is L3, a layer that contains galactose residues. L3 possesses a 70,000 dalton glycoprotein prior to freshwater exposure and lacks the 66,000 dalton component. If isolated from polyacrylamide gels, the 70,000 dalton glycoprotein elicits acrosome reactions in what appears to be a species specific manner. After freshwater exposure, L3 contains both the 70,000 dalton glycoprotein and the 66,000 dalton glycoprotein that is also present in egg water. The appearance of the 66,000 dalton inducer can be blocked by the incubation of eggs in fresh water containing inhibitors of trypsin activity. Thus, the soluble inducer in egg water may be proteolytically derived from a higher molecular weight complex in the egg envelope.
Placental lactogen secretion in the mouse: In vitro responses and ovarian and hormonal influences
Authors: Soares Michael J. , Talamantes Frank
Published: June 2005

In vivo and in vitro methodologies were utilized to study the regulation of placental lactogen (PL) secretion in the mouse. Chorioallantoic placental explants obtained from midpregnant (day 10 of gestation) C3H/HeN or Swiss Webster mouse conceptuses behaved differently in culture than explants of chorioallantoic placentas obtained later in pregnancy. Midpregnant placental explants maintained or showed an increasing amount of PL output per day for 5–6 days of culture, while gestationally older placental explants demonstrated a progressive decline in PL output per day over the 5–6‐day culture period. On selected days of gestation, bilaterally ovariectomized C3H/HeN or Swiss Webster mice were shown to have significantly higher serum PL concentrations than sham operated mice. Reduction of serum progesterone concentrations by unilateral ovariectomy and/or partial lutectomy had no significant effect on serum PL concentrations. Progesterone significantly reduced PL production by midpregnant placental explants from both C3H/HeN and Swiss Webster mice, whereas 17 β‐estradiol did not significantly affect PL release in vitro. PL production by mouse chorioallantoic placentas has gestational specific characteristics in vitro and is responsive to regulatory influences of the maternal ovaries and progesterone.
Regulation in the neural plate ofXenopus laevisdemonstrated by genetic markers
Authors: Szaro Ben , Ide Charles , Kaye Cynthia , Tompkins Robert
Published: June 2005

To follow the subsequent history of grafted tissue in experiments designed to study regulation and commitment in the amphibian neural plate, previous workers have relied on graft scars, vital dyes applied externally to cells, or xenoplastic grafts. Each of these methods has been criticized on the grounds that they do not indicate unambiguously the origins of individual cells within the operated host. To overcome these difficulties, homoplastic, genetically marked embryonic grafts were taken from the prospective spinal neuroectoderm of triploid and tetraploidXenopus laevisfrogs and transplanted to presumptive eye and prosencephalic regions of the neural plate of diploidX. laevisembryos. Orthotopic presumptive eye grafts also were done. Marked cells were scored in section either by nucleolar number or computerized nuclear size analysis. Of 28 heterotopically grafted embryos that survived to stage 41, when the retina has differentiated, prospective spinal cord neuroectoderm in eight animals gave rise to cell types unique to the eye. The remaining 20 survivors appeared to be mosaic. These results substantiate claims of regulation in the neural plate and extend these observations to the level of individual cell types, a level of resolution not previously obtained in other studies.
Amino acids can induce nondisjunction during maturation of mammalian oocytes in vitro
Authors: McGaughey Robert W.
Published: June 2005

Certain chromosomal disorders in mammalian embryos are traceable to meiotic errors during oocyte maturation. This report evaluates the influence of amino acids on meiotic maturation in vitro of oocytes from pigs, hamsters, and rats. The results indicate that maturing porcine oocytes respond not only to 1‐glutamine (1‐gln) but also to 1‐isoleucine (1‐ileu) in complex or chemically defined media by exhibiting significantly (P < .05) increased incidences of nondisjunction when compared with oocytes in control medium. Nondisjunction was highly correlated (r = 0.981) with dose of 1‐gln in porcine oocytes (incidences of maturing oocytes exhibiting nondisjunction were 19.3%, 39.7%, 41.5%, 66.2%, and 88.5% at l‐gln concentrations of 0 mM, 0.5 mM, 1.0 mM, 3.0 mM and 10.0 mM, respectively). Hamster oocytes also exhibited significantly (P < .05) increased nondisjunction when cultured in medium containing l‐gln (52% of maturing cumulus‐enclosed oocytes exhibited nondisjunction in medium with 3.0 mM l‐gln vs. 6.3% in control medium). Denuded hamster oocytes also responded to l‐gln (35% exhibited nondisjunction in 4.0 mM l‐gln, 8% in control medium). In contrast the incidence of nondisjunction in rat oocytes was not increased significantly by l‐gln over a concentration range of 0–12.0 mM. This study demonstrates that maturing oocytes respond to certain environmental conditions by undergoing chromo‐somally abnormal maturation. Specifically, amino acids can induce nondisjunction when present in elevated concentrations during oocyte maturation. The amino acid influence not only was dose dependent for porcine oocytes but also was species specific. These findings suggest that an unbalanced maternal environment might promote chromosomally abnormal meiotic maturation in vivo, and that culture media must be carefully selected to allow chromosomally normal oocyte maturation in vitro. This study defines a potentially useful experimental system for the further analysis of nondisjunction in mammalian oocytes.
Patterns of energy metabolism in the stone crab, Menippe mercenaria, during severe hypoxia and subsequent recovery
Authors: Albert J. L. , Ellington W. R.
Published: June 2005

Specimens of the stone crab, Menippe mercenaria, survived severe hypoxia (PO2 < 8mm Hg) for at least 12 hr at 28–30°C. During the time course of 12 hr of hypoxia, hemolymph L‐lactate levels rose to 30–50 μmoles/g wet wt. There was a slight elevation of L‐alanine levels, whereas succinate was found in only trace quantities in the hemolymph. Pronounced metabolic changes took place in the heart, cheliped closer, and leg socket muscles during severe hypoxia. L‐lactate accumulated to levels ranging from 16–20 μmoles/g wet wt. There were pronounced changes in high‐energy phosphate levels in the cheliped closer and leg socket muscles. Taking into account expected intra‐ and extracellular water content, the calculated intracellular lactate content in the three muscles investigated is substantially less than the hemolymph lactate concentrations. Part of this reverse concentration gradient may be accounted for by the reduction in lactate activity due to cation‐lactate complex formation. Hemolymph calcium and magnesium concentrations rose considerably during severe hypoxia. During recovery from severe hypoxia, approximately 50% of the accumulated lactate in the hemolymph was cleared in 6 hr. Hemolymph lactate and alanine levels returned to near control levels after 24 hr of recovery. This study shows that the stone crab, M. mercenaria, survives severe hypoxia by a reliance on glycogen fermentation to lactate. This species is capable of tolerating high levels of accumulated lactate.