bluuebunny/crossref_metadata_2025 huggingface dataset:
Urea transport in the dogfish kidney
Authors: Hays Richard M. , Levine Sherman D. , Myers Jack D. , Heinemann Henry O. , Kaplan Michael A. , Franki Nicholas , Berliner Henry
Published: June 2005

There is increasing evidence that urea movement across many epithelia involves more than passive diffusion. Of particular interest is the observation that urea transport across the erythrocyte membrane and across the vasopressin‐stimulated urinary bladder of the toad occurs by facilitated diffusion, and can be selectively inhibited by phloretin and chromate. These inhibitory agents have been employed in studies of renal urea reabsorption by the spiny dogfish Squalus acanthias. Both agents inhibit urea reabsorption; the effect of chromate is of particular interest, since it blocks urea reabsorption to a proportionately greater extent than sodium reabsorption, and does so irreversibly.
Microtubules in the “chloride cell” of the gill and disruptive effects of colchicine on the salt balance of the sea water adapted Mugil capito
Authors: Maetz J. , Pic P.
Published: June 2005

Electron‐microscopic examination of the gill of the grey mullet, Mugil capito adapted to sea water, reveals the presence of numerous microtubules in the apical region of the mitochondria‐rich cells. No microtubules are found in other types of epithelial cell. Exposure of the fish to colchicine (10−4M) for four hours induces a 20% increase of plasma Na and Cl. Colchicine leaves the water permeability of the gill unchanged but Cl and Na exchange fluxes are inhibited by 30–50% and the gill potential pattern is altered. Salt gain replaces salt excretion across the gill. The K dependent Na and Cl efflux components, independent of the gill potential shift produced by K, are totally inhibited by colchicine. Exposure to lumicolchicine is not followed by a significant change of these Na and Cl efflux‐components and potential pattern. The possibility that microtubules intervene in the salt excretion process across the chloride cells is discussed.
Characterization of gill (Na+ K)–activated adenosine triphosphatase from chinook salmon, Oncorhynchus tshawytscha
Authors: Johnson S. L. , Ewing R. D. , Lichatowich J. A.
Published: June 2005

(Na +K)‐activated ATPase activity from gills of yearling spring chinook was examined using a new rapid assay method. Characterization of the enzyme activity was performed. Optimal activity was obtained at pH 7.2 in the presence of 240 mM NaCl, 120 mM KCl, 20 mM MgCl2 and 10 mM Na2ATP. Maximal inhibition of the enzyme was observed in the presence of 0.5 mM ouabain. Differential centrifugation indicated that 75% of the enzymatic activity was sedimented at 1000 × g. Only 8% of the activity was found in the microsomal pellet. Treatment with 0.1% sodium deoxycholate liberated activity from the 1000 × g pellet and elevated the activity of the microsomal pellet from 8% to 51% of the total activity. This treatment caused a loss of 20% of the original activity of the preparation.

Statistical analysis of the sampling procedure for gill (Na +K)‐activated ATPase activity indicated that there was small variation in the technique itself when compared to variation between the individual gill arches and between individual fish. Results indicate that for meaningful comparisons of groups of fish, the sampling of the gill arches must be standardized and a large number of individual fish must be sampled.
Killifish opercular skin: A flat epithelium with a high density of chloride cells
Authors: Karnaky Karl J. , Kinter William B.
Published: June 2005

In teleosts the head region, particularly the gills, plays the key role in osmoregulatory NaCl transport, presumably by mechanisms located in the chloride cell. As interest has focused on specific mechanisms of chloride cell function, two classical preparations, the intact fish and the isolated, perfused gill, have continued to serve as the only available model systems. However, both of these preparations have severe limitations, e.g., as they are not flat sheets, they cannot be studied readily under the ideal thermodynamic conditions achieved with the short‐circuit current technique. The present study describes the histology and ultrastructure of a particular area of skin in the head region of both killifish (Fundulus heteroclitus) and sea raven (Hemitripterus americanus). This skin lies on the inside of the operculum and possesses a flat epithelium containing chloride cells. In the present study the identity of the chloride cell in this epithelium was definitively established with the electron microscope. Although the opercular epithelium from the marine sea raven contains few chloride cells, that from the euryhaline killifish adapted to pond water, 100%‐, and 200% artificial seawater is predominately chloride cells. Significantly, the teleost gill has never been reported to contain more than 10% chloride cells. Thus the opercular skin of the killifish can serve as a model to study the adaptive role of chloride cells in euryhaline teleosts. A separate electrophysiological study has demonstrated that the short‐circuit current technique can be applied to this skin.
Renal tubule ion transport and collecting duct function in the elasmobranch little skate, Raja erinacea
Authors: Stolte H. , Galaske R. G. , Eisenbach G. M. , Lechene C. , Schmidt‐Nielsen B. , Boylan J. W. , Antkowiak D. , Patel Y. , Niermann U.
Published: June 2005

Renal micropuncture and microdissection techniques with ultra‐micro fluid analysis have been applied to evaluate single nephron function in the skate, Raja erinacea.

We have divided the skate nephron into three proximal tubular segments (PTS I‐III), three distal coilings (DC I‐III), and a countercurrent loop system located between the proximal segments and the distal coilings.

The collecting duct is the principal site of urinary dilution. Following exposure of the fish to 75% seawater for about 24 hours, the sodium concentration difference between the end collecting duct lumen and plasma is decreased sufficiently to account for the urinary dilution. The principal site for magnesium, phosphate and sulphate secretion appears to be PTS II. This segment is located on the ventral surface of the kidney. PTS II is also the main nephron site for reabsorption of sodium and chloride in excess of water.
Free amino acids in tissues of the skate Raja erinacea and the stingray Dasyatis sabina: Effects of environmental dilution
Authors: Boyd Thomas A. , Cha Chung‐Ja , Forster Roy P. , Goldstein Leon
Published: June 2005

Concentrations of individual free amino acids were determined in various tissues of the skate (Raja erinacea) and the stingray (Dasyatis sabina), and the relationship of cellular free amino acid concentrations to intracellular osmoregulation was investigated by adapting these elasmobranchs to halfstrength seawater. Each tissue characteristically had high levels of certain specific amino acids. Skate wing muscle contained high concentrations of sarcosine and β‐alanine, skate heart had high concentrations of taurine, and skate erythrocytes had high levels of taurine and β‐alanine. Amino acid levels in skate plasma were very low. High concentrations of taurine and glutamate were found in stingray brain. Adaptation of skates and stingrays to half‐strength seawater was accompanied by significant decreases in concentrations of the major free amino acids in skate wing muscle and erythrocytes and in stingray brain, but not in skate heart. The data suggest that in these elasmobranchs certain specific free amino acids are selectively involved in intracellular osmoregulatory mechanisms.
Cyclic AMP regulation of active chloride transport in the rectal gland of marine elasmobranchs
Authors: Stoff Jeffrey S. , Silva Patricio , Field Michael , Forrest John , Stevens Arthur , Epstein Franklin H.
Published: June 2005

Active transport of chloride in the salt secreting rectal gland of the dogfish Squalus acanthias is markedly stimulated by the addition of theophylline (0.01 to 5 mM) or dibutyryl cyclic AMP (0.05 mM) during in vitro perfusion. The effect occurs promptly and may persist for two hours. Specific hormonal effectors have not yet been identified. The isolated perfused rectal gland thus offers a unique opportunity to examine the cellular mechanisms of active chloride secretion.
Hemodynamics in the pink abalone, Haliotis corrugata (mollusca, gastropoda). I. Pressure relations and pressure gradients in intact animals
Authors: Bourne George B. , Redmond James R.
Published: June 2005

After establishing basic anatomical relationships in the circulatory system of the pink abalone, Haliotis corrugata, blood‐pressure measurements were made in the ventricle, aorta, left epipodial artery, afferent ctenidial veins, efferent ctenidial veins, and the pericardial chamber with strain‐gauge manometers on unrestrained specimens at 15°C. All sites showed pulsatile pressures of low magnitude. Intraventricular pressure normally ranged from slightly above ambient during diastole to about 8 cm water at systole, and produced a mean pressure gradient of 5.5 cm water between the aorta and the efferent ctenidial veins. Pressure variations and pulse waves recorded from structures within the pericardium support a constant‐volume mechanism for cardiac filling. There is no clear evidence that body movement enhanced venous return.
Hemodynamics in the pink abalone, Haliotis corrugata (mollusca, gastropoda). II. Acute blood‐flow measurements and their relationship to blood pressure
Authors: Bourne George B. , Redmond James R.
Published: June 2005

In the pink abalone, Haliotis corrugata, pulsatile flow and pulsatile pressure were measured at 15°C by electromagnetic and Doppler ultrasonic flowmeters and strain gauge manometers. Flow was pulsatile in all areas of the arterial system investigated, i.e., the aorta, the cephalic arterial sinus and pedal arteries. Flow rates of approximately 2.9 ml/min were measured in the aorta of animals after surgical implantation of electromagnetic flowprobes. The events of the cardiac cycle are correlated with aortic blood flow. Simultaneous recording of pressure and flow suggested that the action of the aortic bulb maintained aortic flow during ventricular diastole.
Accumulation and degradation of three major yolk proteins in Drosophila melanogaster
Authors: Bownes M. , Hames B. D.
Published: June 2005

In contrast to previous findings, three major yolk proteins have been identified in the oocytes and eggs of Drosophila melanogaster. They are also present as major proteins in the haemolymph of mature females and in trace amounts in the haemolymph of young females; the male haemolymph lacked all three proteins. Female fat body contained the three proteins and, surprisingly, trace amounts were also present in the male fat body. The accumulation and degradation of the three yolk proteins by oocytes and embryos was asynchronous suggesting that independent controls may exist.
Immunofluorescent localization of acrosin in mammalian spermatozoa
Authors: Garner Duane L. , Easton Marlys P.
Published: June 2005

Acrosin was detected by immunofluorescence in the spermatozoan acrosomes of artiodactyla (bull, ram and boar), perissodactyla (horse), carnivora (dog and cat), lagomorpha (rabbit) and primates (human) using anti‐bovine acrosin immunoglobulins. The results indicate that the acrosin molecules of several mammalian species possess antigenic similarities.
Changes in cyclic GMP levels during forelimb regeneration in adult notophthalmus viridescens
Authors: Liversage Richard A. , Rathbone Michel P. , McLaughlin Hooley M. G.
Published: June 2005

Cyclic 3′,5′‐guanosine monophosphate (cGMP) was measured at eight stages of forelimb regeneration in adult newts and compared with the cGMP levels of non‐regenerating control limbs. There was a significant increase in cGMP content during dedifferentiation followed by a sharp decrease to minimal levels at the cone stage. A second smaller increase in cGMP occurred between the cone stage and mid‐differentiation, followed by a decrease to relatively constant levels approaching control values as differentiation progressed. The changes in cGMP during dedifferentiation and during the period of highest cell proliferation indicate that cGMP may play a role in these processes. The smaller increases in cGMP levels during differentiation may reflect a reduced rate of cell division in the differentiating tissues.
A Mg++ dependent cortical reaction in the eggs of penaeid shrimp
Authors: Clark Wallis H. , Lynn John W.
Published: June 2005

Mature penaeid oocytes contain large cortical specializations (rods) in their cortex. These rods reside in membrane crypts and are isolated from the external environment by a thin investment coat which surrounds the oocyte. When oocytes contact seawater, at spawning, their cortical rods are expelled and form a striking investment layer which subsequently dissipates. During cortical rod dissipation a hatching membrane forms around the egg. Oocytes spawned into Mg++ free seawater do not exhibit cortical rod explusion. If oocytes spawned into Mg++ free seawater are returned to normal seawater cortical rod explusion proceeds, however the expelled rods do not dissipate.
Cytodifferentiation in the accessory glands of Tenebrio molitor. I. Ultrastructure of the tubular gland in the post‐ecdysial adult male
Authors: Gadzama Njidda M. , Happ Christine M. , Happ George M.
Published: June 2005

The tubular accessory reproductive glands of the male mealworm beetle consist of a secretory epithelium surrounded by a thin muscular sheath. Each columnar secretory cell is divisible into three zones: basal which is adjacent to the muscle layer and contains rough endoplasmic reticulum and Golgi, intermediate, which contains endoplasmic reticulum and Golgi zones in the immature gland and is filled with secretory vesicles in the mature gland, and apical. Maturation also involves proliferation and organization of the rough endoplasmic reticulum in the basal and intermediate zone. The process appears to be complete at four days after ecdysis. Parallels with other insect glands and with the mammalian prostate are striking.
The genetic control of the pituitary‐gonadal axis in the platyfish, Xiphophorus maculatus
Authors: Schreibman Martin P. , Kallman Klaus D.
Published: June 2005

A sex‐linked gene controls the age at which the gonadotropic zone of the pituitary gland develops and becomes physiologically active. The alleles for early (Pe) and late(Pl) differentiation are linked to pigment genes that serve as genetic markers. Pe may be marked by Sp, Dr, Sr, Ir and + and Pl by Br and N. Ir females (PePe) matured between 10 to 15 weeks of age and Br (PePl) females between 16 to 20 weeks. Dr (PePe) females had ripe ovaries six to eight weeks earlier than N Dr (PePl) females (8 to 12 weeks versus 16 to 20 weeks). The average age of sexual maturation was 12.5 weeks for Ir Ir (PePe) males, 20 weeks for Ir Br (PePl) and 26.5 weeks for Br Br (PlPl) males. Dr Sr (PePe) males reached maturity at 13.5 weeks and N Sr (PePl) males at 27.5 weeks. The transformation of the anal fin into a gonopodium which is under androgenic control, takes longest in the late maturing fish (Ir Ir, 3.8 weeks; Ir Br, 4.8; Br Br, 6.5; Dr Sr, 4.2; N Sr, 6.4). Similarly, the rate of development of the gonadotropic zone and of the gonad is protracted in the late genotypes. Eventually, the gonadotropic zone of early and late maturing fish are indistinguishable. The Pl factor linked to N delays sexual maturity to a greater extent than the one linked to Br suggesting that not all Pl factors are identical and that important allelic interactions may exist. The growth rate of immature males and females is the same, however it declines sharply in males (but not females) at the time of sexual maturity. This leads to significant differences in adult size between male genotypes. Female genotypes do not exhibit size differences and eventually become larger than all males. The development of the gonadotropic zone precedes, and is essential for, complete gonadal maturation. In the absence of a functional gonadotropic zone, oocytes developed through the oil droplet stage and were surrounded by active follicle cells and a prominent zona pellucida. Spermatogenesis proceeded up to the spermatocyte stage and the cells lining the efferent ducts displayed a modicum of activity. Some of our data suggest that low levels of androgens are present in all males as early as five weeks of age prior to the development of gonadotrops. The genes regulating the development of the pituitary‐gonadal axis may be an important factor in explaining the evolution of poeciliid fish.
Embryotoxic effects of heterologous antisera against rat reichert's membrane
Authors: Leung Christopher C. K.
Published: June 2005

Parietal yolk‐sacs of rat embryos at the fifeenth day of gestation were obtained by microdissection. A Reichert's membrane (RM) preparation was isolated by treating the parietal yolk‐sacs with the chelating agent tetrasodium salt of ethylenediaminetetraacetic acid (EDTA) combined with mechanical shaking. Less than 1% of the membrane preparation was DNA and phosphorus contaminants. The membrane purity was also evaluated by electron microscopic examination. Rabbit Ig G directed against the RM preparation when injected ip into ninth day pregnant rats produced malformations, fetal growth retardation and resorption. Fluorescent‐labeled antibody localization studies demonstrated that the teratogenic antibodies localized in RM. It is postulated that RM antibodies induce teratogenesis by interfering with the function of RM.
Some effects of mating in female tsetse, Glossina austeni newst
Authors: Ejezie G. C. , Davey K. G.
Published: June 2005

Virgin females of G. austeni were mated at carefully chosen physiological states to determine the effect of mating on ovulation, neurosecretion and blood meal size. The results suggest that ovulation and larviposition are controlled by neurosecretion, and that the release of neurosecretion requires both a mating stimulus and the presence of a mature egg in one of the ovarioles. The mating stimulus was also found to lead to an increase in blood meal size. Unmated female flies do not ovulate and their mature eggs eventually disintegrate. Virgin blood meal sizes remain relatively low.
Influence of the thyroid and adrenal glands on the growth of the intestine of the suckling rat, and on the development of intestinal alkaline phosphatase and disaccharidase activities
Authors: Yeh Kwo‐Yih , Moog Florence
Published: June 2005

Previous investigations have shown that cortisone or thyroxine can promote maturation of the intestinal epithelium in rats hypophysectomized at six days of age. This indication that either the thyroid or the adrenocortical hormone can act in the absence of the other has been pursued by study of intestinal maturation in rats deprived of the thyroid or adrenal glands during the suckling period. At 24 days of age, rats that have been thyroidectomized at six days retain the short villi and low mitotic index characteristic of neonatal life. Thyroxine elevates the mitotic index; neither thyroxine nor cortisone promote lengthening of the villi, but both cause some deepening of the crypts. Duodenal alkaline phosphatase and jejunal maltase remain at very low levels, but sucrase, which is absent at six days, does appear in the thyroidectomized pups at 24 days. Thyroxine raises phosphatase and maltae activity to the normal 24‐day level, but cortisone is only partly effective. Sucrase is raised above the normal maximum by cortisone but not by thyroxine. After adrenalectomy at 14 days, cortisone corrects deficiencies in villus height, crypt depth, and mitotic index, but thyroxine is without effect. Phosphatae, maltase, and sucrase activities rise only to subnormal levels in adrenalectomized pups. Thyroxine restores phosphatase activity to the control level, but is only partly successful in normalizing disaccharidase activities. Periodic acid‐Schiff stainability of the brush border is weak in specimens deprived of either thyroid or adrenals. Both thyroxine and cortisone restore normal intensity after thyroidectomy; after adrenalectomy only cortisone was able to restore normal stainability. Plasma corticosteroid concentration is elevated by thyroxine only if the hypophysis is present. These results demonstrate that the intestinal epithelium is able to respond to each hormone in the absence of the other.
The effect of ascorbic acid on growth and synthesis of matrix components by cultured chick embryo chondrocytes
Authors: Hajek Anthony S. , Solursh Michael
Published: June 2005

Fifty μg/ml ascorbic acid was found to accelerate the growth of logarithmically growing chick embryo sternal chondrocytes in cell culture. Differences in the number of cells between control and ascorbate‐treated cultures were apparent by the fourth day of treatment when a 58% increase in the number of cells and a 35% increase in protein per culture were observed in ascorbate‐treated cultures. Under these conditions, the cell size and protein content per cell was reduced in ascorbate‐treated cultures.

Collagen synthesis, which was measured by the amount of collagenase‐sensitive counts released from 3H‐proline labeled protein, was increased by 116% over controls after 24 hours of ascorbate treatment. Observations with scanning and transmission electron microscopy are consistent with the idea that ascorbate has a much greater effect on collagen secretion and demonstrate an ascorbate‐mediated change in matrix morphology.

35S incorporation into hyaluronidase‐sensitive or cetylpyridinium chloride precipitates was accelerated by 57% by 24 hours of ascorbate treatment whereas two, four and six days of treatment caused decreases in this parameter of 19%, 57% and 35%, respectively. This effect was dependent on cell density. 35S incorporation probably reflects synthesis of new glycosaminoglycan similar results were observed when either 35S or 14C‐glucose incorporation was monitored. An effect of ascorbate on both collagen and glycosaminoglycan synthesis is consistent with the possibility that collagen and glycosaminoglycan synthesis can be coregulated under some circumstances.
Molecular aspects of temperature acclimation in fish: Contributions of changes in enzyme activities and isozyme patterns to metabolic reorganization in the green sunfish
Authors: Shaklee James B. , Christiansen James A. , Sidell Bruce D. , Prosser C. Ladd , Whitt Gregory S.
Published: June 2005

Spectrophotometric and electrophoretic techniques were used to monitor qualitative and quantitative aspects of changes in 12 enzymes from five different tissues of green sunfish after thermal acclimation. Changes in dissolved oxygen concentrations over the range 5–25 ppm had no significant effect on qualitative or quantitative aspects of enzyme distributions.

In response to differences in environmental temperature, however, significant changes in the levels of activity of fructose‐biphosphate aldolase, pyruvate kinase, lactate dehydrogenase, malate dehydrogenase, succinate dehydrogenase, cytochrome oxidase, cytochrome c, and glucose‐6‐phosphate dehydrogenase were observed in one or more tissues. Enzymes in a single metabolic pathway (e.g., glycolysis) usually exhibited parallel changes in a given tissue. Enzymes in different pathways, on the other hand, frequently exhibited changes in opposite directions, one group of enzymes increased in the cold while the other group decreased, indicating that major metabolic reorganizations were occurring. The patterns of change among tissues were distinctly different, therefore changes observed in one tissue cannot readily be generalized to other tissues.

No changes in isozyme patterns were seen for lactate dehydrogenase, creatine kinase, fructose‐biphosphate aldolase, malate dehydrogenase, glucosephosphate isomerase, phosphoglucomutase, glycerol‐3‐phosphate dehydrogenase, or alcohol dehydrogenase in any of the tissues examined. However, some changes in the isozyme patterns of esterases in both liver and eye tissue were observed. These observations indicate that major changes in isozyme repertories do not necessarily accompany the thermoacclimatory responses of all fishes.
Anhydrobiosis in nematodes: Metabolism during resumption of activity
Authors: Crowe John H. , Madin K. A. C. , Loomis Stephen H.
Published: June 2005

Changes in chemical composition, water content, respiration, and ability to survive rapid dehydration in dry air were studied in nematodes, Aphelenchus avenae, recovering from anhydrobiosis, in water. Water content rises rapidly, from about 0.02 mg H2O/mg dry weight to 2.0 mg/mg after five minutes and 2.9 mg/mg after four hours. Glycogen increases from 5 μg/mg to about 25 μg/mg after one hour. Glycerol and trehalose fall from 45 μg/mg and 125 μg/mg respectively to undetectable levels and 70 μg/mg after four hours. Oxygen uptake rises from about 25 nl/mg/min after ten minutes to 450 nl/mg/min after 1.5 hours and then falls to about 150 nl/mg min after four hours. Lipid content declines from 124 μg/mg to 51 μg/mg after 24 hours. Correlations were observed between survival in dry air and glycerol, trehalose, and water contents.
Accumulation of glucocorticoids in regenerating areas of limbs of the newt, Notophthalmus viridescens
Authors: Bromley Stephen C
Published: June 2005

Evidence is presented that regenerating portions of newt limbs preferentially accumulate 3H‐labelled exogeneous cortisol and corticosterone. The ability of such regions to accumulate glucocorticoids is maximal about seven days after amputation and is abolished by interrupting the spinal nerves innervating the limb. Either hypophysectomy or ablation of interrenal tissue is without marked effect. The accumulation effect is not shown by aldosterone, testosterone, glucose, cholesterol, or leucine but estradiol does accumulate to a some‐what lesser extent than do the glucocorticoids examined.
An early step in initiation of fertilization in Paramecium: Early micronuclear migration
Authors: Fujishima Masahiro , Hiwatashi K.
Published: June 2005

Micronuclear behavior in the early stage of conjugation in P. caudatum was observed. In stationary phase, the micronucleus is in a concavity of the macronucleus, but within 30 minutes after the mating reaction occurs or the cells are transferred into KCl solution for chemical induction of conjugation, the micronucleus leaves the concavity and moves into the cytoplasm. This phenomenon, called “early micronuclear migration” (EMM), occurs in about 90% of the cells prior to formation of holdfast union. The proportion of cells undergoing EMM is the same as the proportion of conjugants. Micronuclear migration is delayed by treatment with 5 mM colchicine, suggesting a role for microtubules in the phenomenon.
Photoreceptor degeneration in the eyes of an amphisbaenian in response to constant light or constant darkness
Authors: Gundy G. Craig
Published: June 2005

Eye morphology and behavioral responses were studied in Bipes biporus (Cope) exposed to normal photoperiods, constant light, and constant darkness. Control animals had retinas with a reduced number of outer segments relative to the typical vertebrate retina. In addition, many of these outer segments were poorly formed, suggesting a capability for light detection but not for image formation. Constant light led to detached retinas and eventual degeneration of outer segments. Earliest signs of detachment appeared in younger animals, but no subsequent age differences were found. Constant dark‐induced changes were similar to light‐induced changes except that dark‐induced changes were not so severe, did not depend on age, and included loss of pigment from cells in the pigmented epithelium. Retinal damage in constant dark animals suggests that free‐living Bipes biporus are occasionally exposed to light. Dark‐seeking behavior of normal animals diminishes after exposure to constant light.
Tail (end) bud contributions to the posterior region of the chick embryo
Authors: Schoenwolf Gary C.
Published: June 2005

Chick tail buds labeled with tritiated thymidine were transplanted homotopically to unlabeled embryos to determine the specific body levels and structures formed by tail buds. In addition, labeling patterns of posterior structures were studied in normal embryos labeled for progressively longer time periods.

Tail buds contributed labeled cells primarily to tail neural tube, somites, mesenchyme, and caudal arteries, but not to tail notochord, skin ectoderm, hindgut, or tail gut. Labeled somites were often located three to four somite levels anterior to labeled portions of neural tubes. In labeled normal embryos central notochordal cells were labeled only occasionally. This labeling pattern extended posteriorly into a region designated as prospective notochord, which merged posteriorly with the tail bud. The tail bud labeled uniformly and contained about the same density of labeled cells as the segmental plates, indicating that proliferation was not excessive in the former.

Defects in operated embryos occurred primarily in the neural tube, somites, and notochord. The tail portion of the notochord, presumably formed from the prospective notochordal region, was never isolated from the trunk portion. The tail portion of the neural tube rarely seemed isolated from the trunk portion. Large, unpaired midline somites frequently developed. They appeared to form only when a space was available in which paired segmental plates could approach the midline and fuse.
Tensiometric studies of cytokinesis in cleaving sand dollar eggs
Authors: Rappaport R.
Published: June 2005

Tensions exerted by cleavage furrows of Echinarachnius parma were measured by means of calibrated, flexible glass needles. The tensions exerted by the first and second furrows in isometric contraction were, respectively, 1.58 × 10−3 dyne (S.D. 0.41 × 10−3 dyne) and 1.43 × 10−3 dyne (S.D. 0.44 × 1.0−3 dyne). The difference between the two means is not significant. The tensions exerted by the same cleavage furrow at two different lengths, of which the shorter was about 66% the length of the longer, were not significantly different. When the progress of a second cleavage furrow was mechanically blocked, it continued to exert maximum tension up to 9 minutes after its companion blastomere, which served as a time control, completed cleavage.
Photoperiodic control of antler cycles in deer. IV. Effects of constant light:dark ratios on circannual rhythms
Authors: Goss Richard J.
Published: June 2005

Yearling sika deer, when exposed to constant unequal photoperiods since the autumnal equinox, replace their antlers the next spring and at irregular intervals thereafter. On equatorial light cycles (12L: 12D) they retain their original antlers indefinitely. The changeover occurs between constant day lengths of 12 3/4 and 13 hours. Since yearlings held on 6L:6D:6L:6D are able to replace their antlers on schedule, the failure to do so on 12L:12D is not due to light:dark parity, but to the 12‐hour durations of the days and/or nights.
Self‐organizational capacity of distally transplanted limb regeneration blastemas in larval salamanders
Authors: Stocum David L. , Melton Douglas A.
Published: June 2005

Previous autografting and homografting experiments (Iten and Bryant, '75; Stocum, '75b) showed that, when progressively later stages of upper arm blastemas were transplanted to either the distal radio‐ulna or the wrist, surviving grafts of each stage formed wrist and hand parts in 100% of the cases. However, the earliest stages transplanted formed the humerus and radio‐ulna at a low frequency, with an increase in this frequency when later stages were transplanted. These results can be interpreted in two ways: (1) The proximal‐distal organization of the blastema is stable at the earliest stages with the low frequency of humeral and radio‐ulnar formation being attributable to artifacts introduced by surgical trauma, artifacts which would not have as much effect on later stages; (2) The proximal‐distal organization of the early blastema is initially labile and can interact with the stump to conform to the level of transplantation. This lability would decrease in later stages. The present study describes the results of new experiments which argue against the latter alternative. In addition, differences between autograft and homograft development are described which could be attributable to an immune response directed at homografts.
A scanning electron microscopic and X‐ray microanalytic study of cell surface material during amphibian neurulation
Authors: Rice Robert W. , Moran Denis J.
Published: June 2005

Treatment with lanthanum (La3+) after fixation in phosphate (PO4−3)‐buffered glutaraldehyde results in the deposition of a cell surface material (CSM) primarily on the developing urodele amphibian neural axis. X‐ray probe microanalysis indicates that calcium (CA2+) levels are considerably higher in the neural fold region. La3+ displaces Ca2+ from negatively‐charged moieties on biological membranes. Once bound, La3+ likely interacts with residual phosphate(s) resulting in deposition of CSM. Elemental X‐ray microanalysis shows CSM contains mostly lanthanum and phosphorus. The high level of regional La3+ binding is correlated with inherently greater Ca2+ levels in the developing neural axis.
Genetic and experimental studies on three associated mutant genes in the Mexican axolotl: st (for stasis), mi (for microphthalmic) and h (for hand lethal),
Authors: Humphrey R. R. , Chung Hae‐Moon
Published: June 2005

Three mutant genes, st, mi, and h, were discovered in an axolotl male received from Mexico City. All three are recessive to their normal alleles, and appear to segregate independently.

Larvae homozygous for st (for stasis) suffer blockage of the circulation at hatching or shortly after, and the majority soon die; any surviving live only a few weeks at most. The mi/mi (microphthalmic) can be identified at the feeding stage. None survives more than a few days. The h/h (hand lethals) live until the digits have appeared on the forelimb. They may then be recognized by the thumb‐like orientation of digit 1.

Transplants from st/st embryos into normal produce normal structures which persist indefinitely. Those from mi/mi and h/h donors do not survive. The structures (forelimb, gills) derived from h/h donors grow for a relatively long time, and their final death and degeneration result in defects leading to death of most of the recipients.

Parabiosis is of no benefit to st/st or h/h mutants and leads to the death of the normal twin; mi/mi mutants undergo a gradual absorption by the normal twin.
Timing of sperm penetration, pronuclear formation, pronuclear DNA synthesis, and first cleavage in naturally ovulated mouse eggs
Authors: Krishna Maryala , Generoso Walderico M.
Published: June 2005

Timing of development of naturally ovulated mouse eggs from sperm penetration to first cleavage, including that of DNA synthesis, was established. In an attempt to limit variability, partial synchronization of ovulation was accomplished by shortening the length of the dark period to five hours, and partial synchronization of sperm entry was attempted by mating the females soon after the ovulated eggs reached the ampulla and by limiting the period at which mating could occur to only 20 minutes.

Evidence of sperm penetration (presence of one or more sperm in perivitelline space or inside the vitellus) was found beginning 1.75 hours after the end of the mating period. Pronuclei were formed three to four hours after sperm entry. Pronuclear DNA synthesis began about eight hours postmating, 3.25 to 4.5 hours after pronuclear formation, or about 6.25 to 8.5 hours after sperm entry; it was completed in almost all zygotes by 16 hours postmating. The first completed cleavage division was found 17 to 18 hours postmating, and almost all eggs had cleaved by 20 hours.
Development of sodium regulation and de novo synthesis of Na+K‐activated ATPase in larval brine shrimp, Artemia salina
Authors: Conte F. P. , Droukas P. C. , Ewing R. D.
Published: June 2005

The development of brine shrimp embryos, A. salina, incubated in media of increasing salinity is delayed as evidenced by decreased emergence and lengthening of the time for excystment. Prehydration of cysts at low temperature (3°C) for four to ten hours in distilled water eliminates asynchrony of the population in regard to emergence and hatching times. Internal concentration glycerol, which controls the rate of hydration of the cyst stage, is markedly affected by external salinity. Water balance in the cyst stage is maintained via the trehalose‐glycerol mechanism which generates a simple passive diffusional gradient across the chitinous shell allowing water to pass. Non‐gaseous solutes, such as sodium and glycerol, do not pass through the chitin‐membrane barrier. Rupturing the shell by emergence initiates the onset of the prenaupliar stage; it is accompanied by the appearance of large amounts of free glycerol in the external media, decreasing levels of internal glycerol, increased concentrations of internal sodium and the first detectable levels of the cationic transport enzyme, Na + K‐ATPase. Continual loss of free glycerol through the cellular and hatching membranes causes the excysting embryo to convert from a trehalose‐glycerol mechanism to a sodium‐mediated transport system in order to maintain larval water balance. Ontogeny of the sodium regulating mechanism requires formation of Na + K‐ATPase. The production of new Na + K‐ATPase, as evidenced by incorporation of 14C‐amino acids into polypeptide subunits and density‐gradient centrifugation of radioactive membrane vesicles rich in Na + K‐ATPase, may play an important role and, if so, it appears to be initiated between E‐1 and E‐2 stages.
Periodic respiratory and circulatory performance in the red rock crab Cancer productus
Authors: McMahon B. R. , Wilkens J. L.
Published: June 2005

Periods of simultaneous arrest in both cardiac and scaphognathite (ventilatory) pumps of up to 20 minutes duration occur spontaneously and repetitively in resting restrained Cancer productus. Measurement of cardiac and scaphognathite beat frequencies, ventilation volume, oxygen uptake and circulating blood oxygen tensions indicate that oxygen exchange is more effective in this species than has previously been reported for other brachyuran decapods and compensation for long pauses involves only short periods of moderate hyperventilation and enhanced oxygen uptake. The initiation, importance and control of pausing behaviour is discussed. During periods of repetitive pausing a stereotyped pattern of heart and scaphognathite responses occurs. The pattern is easily modified by such factors as activity and oxygen availability. This study suggests that higher neural control centers coordinate the beating of heart and scaphognathites thus allowing regulation of gas transport and exchange.
Endocrine control of vitellogenesis in Drosophila melanogaster: Effects of the brain and corpus allatum
Authors: Handler Alfred M. , Postlethwait John H.
Published: June 2005

The endocrine control of yolk deposition in Drosophila melanogaster was studied by ligation and transplantation techniques. Endocrine events associated with the initiation of vitellogenesis were found to be synchronized with eclosion rather than the completion of adult development. Decapitation experiments showed that a cephalic event occurring at about the time of eclosion is necessary for each animal to initiate vitellogenesis. The morphogenetic effect of the head could be replaced by a juvenile hormone analog (JHA).

In addition to the cephalic event, a thoracic factor is required for each follicle to initiate vitellogenesis, since preparation of isolated abdomens before 16 hours after eclosion prevented vitellogenesis. In abdomens isolated after this time, no early vitellogenic stages were formed. The suppression of vitellogenesis in isolated abdomens was reversed by implanting corpora allata or by treating these preparations with JHA, but not by implanting corpora cardiaca. Ovaries that were artificially induced to mature by treating isolated abdomens with JHA still displayed the normal complement of ovarian proteins after electrophoresis in polyacrylamide gels.

These results show that a circadian clock triggers vitellogenesis via a cephalic signal at eclosion, which in turn triggers events in the thorax or abdomen. The cephalic signal can be superseded by juvenile hormone, whose presence is necessary for each follicle to become vitellogenic.
On the diversity of sperm histones in the vertebrates. III. Electrophoretic variability of testis‐specific histone patterns in Anura contrasts with relative constancy in Squamata
Authors: Kasinsky H. E. , Huang S. Y. , Kwauk S. , Mann M. , Sweeney M. A. J. , Yee B.
Published: June 2005

A starch gel electrophoretic survey of testis‐specific histones in frogs, snakes and lizards reveals a multiple banded pattern in most of these vertebrates whether the proteins are extracted from the testis cell suspension of a single animal or from chromatin pooled from the testes of several animals. Hence, the multiple banded pattern is probably typical for each individual in a particular species. When such testis‐specific histones of Anura are compared with those of Squamata, a notable difference emerges. Thus, the principal Xenopus, Bufo and Rana testicular proteins show entirely different patterns from each other upon starch gel electrophoresis while in Squamata, each of the species examined shows a similar 2‐banded pattern in the protamine region of the electrophoretogram. In the anurans Xenopus and Scaphiopus, the testis‐specific histone patterns are different even amongst several congeneric species. Although the present survey examines only a limited number of species, the electrophoretic data do point to the order Squamata as one place in vertebrate phylogeny where the diversity of testis‐specific histones in fish and amphibians appears to give way to a relative constancy of such proteins in reptiles. Such an evolutionary trend may be consistent with a modified version of Bloch's ('69) hypothesis that relates sperm histone variability to genetically based sex determination.
Disintegration of the vitelline coat during the hatching process in the frog
Authors: Yoshizaki Norio
Published: June 2005

In the frog, Rana japonica, the volume enclosed by the vitelline coat (VC) does not change during embryonic development up to stage 16 but increases during stages 17–18. During these latter stages, approximately one‐third of the VC material is lost as determined by its dry weight, proteins and neutral sugars. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis showed that two high molecular weight proteins disappear from the VC during stages 18–20. Electron microscopic observation of the VC revealed that the network of filament bundles which runs parallel to the egg surface disintegrates or diminishes during stages 17–20. Besides the VC, the innermost jelly layer (J1) becomes susceptible to UV irradiation at stage 18. All the changes observed in the present study prove that the partial disintegration of the VC and J1 by the hatching enzyme occurs during stages 17–20, three days before embryonic hatching.
Air‐breathing in a California sculpin
Authors: Wright W. G. , Raymond J. A.
Published: June 2005

The intertidal sculpin Clinocottus recalvus has been observed emerged and showing signs of air‐breathing near tidepools in a cave on the central California coast. In the laboratory the fish consumed oxygen at nearly equal rates in water and air, but release of carbon dioxide was retarded in air. The cause of emergence appeared to be low oxygen levels in the tidepools. This is the first report of air‐breathing in the sculpin family.
Interaction of immunoglobulin fragments with the mammalian sperm acrosome
Authors: Allen G. J. , Bourne F. J.
Published: June 2005

A study was made of the interaction of immunoglobulins and immunoglobulin fragments from sera of rabbits and pigs with the acrosomes of ten species of mammalian spermatozoa to investigate previous reports of an interaction between normal serum and the acrosome. It was shown that this could be predominantly attributed to IgC, although there was weak staining due to IgM. Further, it was shown that IgG interacted through the Fc fragment, the Fab fragment causing only weak staining of homologous spermatozoa.
Transformation of amphibian xanthophores into melanophores in clonal culture
Authors: Ide Hiroyuki
Published: June 2005

Xanthophores isolated from bullfrog tadpoles were successfully cloned. The rapid disappearance of the yellow pigment‐containing organelles (pterinosomes) occurred in proliferating xanthophores and many black granules were newly synthesized in the cells. The granules were electronmicroscopically identified as melanin granules. These chromatophores showed melanin dispersion by the addition of the alkali‐treated ACTH. The findings suggest that xanthophores transform into melanophores in vitro.
Chick somite determination: The role of factors in young somites and the segmental plate
Authors: Packard David S.
Published: June 2005

One class of hypotheses proposed to explain the anterior to posterior sequence of chick somite formation envisions the movement of morphogenetic substances or processes along the segmental plate prior to somite formation. An effort was made to demonstrate any such phenomena in the region of somite formation by placing grafts that contained forming somites into the segmental plates of cultured host embryos. No somite‐inducing properties on the part of the grafts were detected. Host somite formation proceeded in a normal manner. In additional experiments, posterior portions of segmental plates were isolated from the more anterior parts of the segmental plate which might contain the hypothetical morphogenetic factors. It was found that anterior portions of the segmental plate representing as many as eight prospective somites could be removed without impairing the ability of the remaining posterior portion to form somites in vitro. It is concluded that other hypotheses of the type studied here are not likely to be useful and that the present data further strengthen the argument that the cells of the chick segmental plate present at any time between the 8‐ and 20‐somite stages of development are committed to form somites. In addition, the explant experiments described here indicate that a somite pattern representing about 11 prospective somites, becomes established in the segmental plate.
Urea levels in plasma and erythrocytes of the southern fiddler skate, Trygonorhina fasciata guanerius
Authors: Browning J.
Published: June 2005

Plasma and erythrocyte esamples from Trygonorhina fasciata guanerius were analysed for urea content. The erythrocyte urea concentration is higher than plasma urea concentration. The difference in concentration is probably due to the presence of urea normally bound to protein within the erythrocyte. Erythrocyte urea concentrations followed environmentally induced changes in plasma urea concentrations. Naturally occurring plasma urea concentrations, exceeding 500 mMolar, are some of the highest recorded for an elasmobranch.
Allosteric modifiers of fish hemoglobins: In vitro and in vivo studies of the effect of ambient oxygen and pH on erythrocyte ATP concentrations
Authors: Greaney George S. , Powers Dennis A.
Published: June 2005

Fundulus heteroclitus decreases erythrocyte adenosine triphosphate and increases blood hematocrit when acclimated to hypoxic conditions. A defined medium has been developed which allows isolated F. heteroclitus erythrocytes to be maintained for several hours without an appreciable loss of cellular ATP. The effect of oxygen tension, pH and metabolic inhibitors on the cellular concentration of ATP of fish red cells has been investigated as an in vitro model to explain in vivo responses to environmental changes. The isolated red cells significantly decrease their ATP/Hb molar ratio when exposed either to anaerobiosis or metabolic inhibitors. It is concluded that the in vivo response is mediated at the red cell level via decreased oxidative phosphorylation in the presence of low environmental oxygen. The length of time necessary to elicit the response both in vivo and in vitro is also discussed.