bluuebunny/crossref_metadata_2025_split huggingface dataset:
Baroreflex sensitivity in an amphibian, Rana catesbeiana, and a reptilian, Pseudemys scripta elegans
Authors: Millard Ronald W. , Moalli Richard 
Published: June 2005

AbstractAn inverse relationship between heart rate and systematic arterial pressure is demonstrated in unanesthetized bullfrogs (Rana catesbeiana) and red‐eared turtles (Pseudemys scripta elegans). Drug‐induced elevation of systemic blood pressure resulted in proportional decreases in heart rate and lengthening of the pulse interval. Conversely, nitroglycerin‐induced decreases in blood pressure produced compensatory increases in heart rate. This relationship in frogs is defined by y = 25.4x + 1684, and in turtles by y = 64.8x + 1686, where y is pulse interval in msec and x is systolic blood pressure in mmHg. Resting and drug‐induced systolic pressure limits were not different in the two species. However, both resting and reflexly altered heart rates were significantly lower in turtles than in frogs (p<.05). The heart rate responses were abolished by atropinization, without effect on the blood pressure responses. While anatomic identification of the baroreceptor site sensing the pressure changes remains to be made, the translation of pressure information via reflex pathways analogous to mammalian baroreceptor reflex arc system is evidenced in these lower vertebrates.
Formation of tetraploid mouse blastocysts following blastomere fusion with polyethylene glycol
Authors: Eglitis Martin A. 
Published: June 2005

AbstractA rapid method to produce tetraploid embryos by blastomere fusion using polyethylene glycol (PEG) has been developed. Individual four‐cell stage blastomeres were aggregated into pairs with phytohemagglutinin (PHA) and then treated with 45% (w/v) PEG (MW 1,000). 56.8% (804/1,416) of treated blastomere pairs fused. Tetraploid blastomeres were aggregated into quartets or doublets to restore cell number equivalent to that of whole or half diploid embryos, respectively. Best development was obtained with quartets, 72.9% (78/107) of which cavitated. 46.4% (13/28) of doublets and 31.7% (13/41) of singly cultured tetraploid blastomeres formed cavitated structures. Uniform tetraploidy was confirmed by fixing cavitated embryos and analyzing their metaphase plates. The fusion method described here replaces Sendai virus with a chemically defined fusogen and confirms earlier observations (Snow, '73; Graham, '71) that tetraploidy does not prohibit preimplantation development. This fusion method obviates some of the drawbacks of cytochalasin B‐induced tetraploidy, namely the blocking of cleavage and the potential of diploid/tetraploid mosaicism.
Four new proteins of the eumelanosome matrix of the chick pigment epithelium
Authors: Zimmerman Joel 
Published: June 2005

AbstractA new procedure is presented for the isolation of electron microscopically clean melanosomes. The procedure provides melanosomes which have been stripped of their membrane components so that only matrix elements are examined. Solubilization of these melanosomes is by 8 M urea‐1% Triton X‐100 treatment with reduction and alkylation. The proteins are examined on sodium dodecyl sulfate‐polyacrylamide gels and on acid‐urea polyacrylamide gels. Evidence is presented indicating the presence of four low‐molecular‐weight proteins which have not previously been reported. Data indicate that these proteins are the major components of the melanosome matrix, that they are not histones and that at least one of them is a glycoprotein.
In vitro steroid production in the postovulatory follicles of the amago salmon, Oncorhynchus rhodurus, in response to salmon gonadotropin
Authors: Nagahama Yoshitaka , Kagawa Hirohiko 
Published: June 2005

AbstractPartially purified chinook salmon gonadotropin (SG‐G100) was used to investigate estradiol‐17β and progesterone production in vitro in the isolated postovulatory follicles of the amago salmon, Oncorhynchus rhodurus, at varying intervals after ovulation. Chinook salmon gonadotropin stimulated progesterone production in vitro in the young postovulatory follicles, but not in the older ones. In contrast, estradiol‐17β production was not stimulated in either young or older postovulatory follicles. Morphological observations indicate that young postovulatory follicles are more glandular than older ones. Thus, it is concluded that the young postovulatory follicles of the amago salmon are steroidogenic.
The effect of limiting light to the pineal on the rate of forelimb regeneration in the newt
Authors: Maier C. Eberhardt , Singer Marcus 
Published: June 2005

AbstractNewts with bilaterally amputated forelimbs were exposed to either continuous light (LL), total darkness (DD), or continuous light with the dorsal head epithelium painted with an India ink and Nile blue sulfate mixture (LL‐II‐NBS) that limited light penetration through the skull to the pineal. The LL‐II‐NBS animals regenerated their forelimbs more slowly than their counterparts in LL.
Water loss and survival in embryos of the domestic chicken
Authors: Snyder Gregory K. , Birchard Geoffrey F. 
Published: June 2005

AbstractIn this report we show that the amount of water lost during incubation is an important determinant of hatchability in embryos of the domestic chicken. However, when the loss of water is restricted to the first half versus the second half of the total incubation period, it is the loss of water during the first half that affects hatching success. We propose that regulating the permeability of the egg shell may be important in preventing excessive drying of the inner shell membrane during early development along with limiting the total amount of water lost from the embryo during incubation.
Na+ and Cl− transport and intercellular junctions in the isolated skin of a marine teleost (Blennius pholis L.)
Authors: Nonnotte G. , Colin D. A. , Nonnotte L. 
Published: June 2005

AbstractElectrical parameters were simultaneously measured with unidirectional fluxes of Cl− and Na+ through isolated short‐circuited skin of a marine teleost, the shanny (Blennius pholis L.). The mean transepithelial potential TEP developed across the skin was 10.6 ± 0.4 mV (n = 6) in open‐circuit conditions. When the skin was short circuited, the mean short circuit current Isc was 35.1 ± 2.7 μamp·cm−2, which represented the difference between mean Cl− and Na+ net fluxes (1.2 ± 0.2 μEq·hour−1·cm−2 equivalent to 32.5 ± 5.4 μamp·cm−2). The junctional complexes between the different cells of the epidermis were also studied. Epithelial cells were linked to each other by tight junctions as well as epithelial and accessory cells. In contrast, junctions between chloride and accessory cells were characterized as shallow junctions. The Na+ and Cl− transport through the skin of the shanny is discussed with reference to the implication of the junctional complexes of the epidermis.
Circadian rhythmicity in Bulla gouldiana: Role of the eyes in controlling locomotor behavior
Authors: Block Gene D. , Davenport Philip A. 
Published: June 2005

AbstractThe eyes of Bulla express a circadian rhythm in optic nerve impulse frequency. Bulla also exhibit a circadian rhythm in locomotor behavior. In order to determine what role the ocular oscillators play in controlling rhythmic behavior, the eyes were removed and locomotor activity was recorded during free runs and while entrained to light‐dark cycles. We find that eye removal leads to a disorganization of the free‐running locomotor rhythm, suggesting that the ocular oscillators are involved in timing this behavior. Eyeless Bulla in the presence of light cycles exhibit locomotor rhythmicity but there is a switch from predominantly nocturnal to diurnal activity. While diurnal behavior in eyeless Bulla reveals the presence of extraocular photoreceptors, we presently find no evidence that a circadian pacemaker mediates this diurnal activity.
Differentiation of muscle fiber types in aneurogenic brachial muscles of the chick embryo
Authors: Butler Jane , Cosmos Ethel , Brierley Joyce 
Published: June 2005

AbstractCross‐reinnervation studies performed ex ovo with newly hatched chicks demonstrate that peripheral motor neurons control the phenotypic characteristics of avian muscles. The present experiments were designed to determine whether or not nerves play a similar role during the initial expression of muscle fiber types. Previous experiments indicated that differentiation of specific fiber types occurs during the first week of embryogenesis, temporally coincident with the penetration of nerves within muscle masses. These observations suggested that peripheral nerves may be associated with the initial differentiation of fiber types. To test this hypothesis directly, anterior limb buds of the chick embryo were rendered aneurogenic by deletion of the brachial segment of the neural tube. To ensure a completely aneurogenic environment for developing brachial muscles, surgery was performed at day 2 in ovo before the exit of ventral root fibers. Experimental and control embryos from Stage (St) 25 (4.5 d) through St 45 (19d) were analyzed histochemically by a silver‐cholinesterase reaction to detect nerves and by the myosin ATPase reaction, following alkali and acid preincubation, to determine the fiber type composition of the muscles. In addition, the total volume of aneurogenic and control muscles was compared. Results demonstrate that the characteristic myosin ATPase profiles of individual aneurogenic and innervated (control) muscles were identical throughout the entire period analyzed. Therefore, we conclude that these enzymic profiles are endogenously expressed and are not under neuronal control during early embryogenesis. Furthermore, the entire sequence of events from the migration of myogenic cells to the anterior limb bud through the division of the primary muscle masses to form individual brachial muscles proceeded on schedule in the absence of nerves. Since the growth of aneurogenic muscles was impaired, we conclude that during embryogenesis peripheral motor nerves are necessary initially for the proper growth of muscles and ultimately, for their survival. They are not involved, however, with either the initial formation or initial differentiation of individual brachial muscles.
Resumption of DNA synthesis in delayed implanting mouse blastocysts during activation in vitro
Authors: Given Randall L. , Weitlauf Harry M. 
Published: June 2005

AbstractThe resumption of DNA synthesis in delayed implanting mouse embryos undergoing metabolic activation in vitro was examined. Blastocysts were recovered from ovariectomized mice, incubated for various intervals in basal Eagle's medium, exposed to 3H‐ thymidine, and prepared for light microscopic autoradiography. Following incubation the proportion of labeled cells increased from 4% at 1 hr to 30% by 24 hr. This increase in labeling was not uniform in all regions of the blastocyst, i.e., labeling was initially highest over the inner cell mass (ICM) but remained low over the polar and proximal mural trophoblast for 6 and 12 hr, respectively, and then began to increase. This pattern in the resumption of DNA synthesis during activation in vitro is similar to that reported in vivo (Given and Weitlauf, '81) and suggests that the mechanism responsible is intrinsic to the blastocyst rather than being a differential response to the intrauterine milieu. Furthermore, it appears that the ICM may play an essential role in the resumption of synthesis in the surrounding trophoblast.
Extraintestinal calcium uptake in the killifish, Fundulus heteroclitus
Authors: Mayer‐Gostan Nicole , Bornancin Michel , de Renzis Guy , Naon Robert , Yee John A. , Shew Ronald L. , Pang Peter K. T. 
Published: June 2005

AbstractExtraintestinal calcium influxes were measured in the killifish, Fundulus heteroclitus, in solutions with different calcium concentrations, from distilled water level (near 0) to seawater level (approximately 12 mM). The extraintestinal influx is modified by the concentration of calcium in the medium during the adaptive period. In freshwater‐adapted fish, calcium depletion resulted in an increase in calcium uptake. Such an adaptation was not observed in calcium‐depleted fish in artificial calcium‐deficient seawater. Calcium depletion in either medium seems to increase the calcium permeability. No correlation was found between Ca‐ATPase activity in the gill tissue and calcium uptake.
Cardiovascular events associated with spontaneous apnea in the Australian short‐finned eel, Anguilla australis
Authors: Hipkins Scott F. , Smith David G. 
Published: June 2005

AbstractHeart output, arterial pressures, and buccal pressure were measured in conscious, unrestrained eels (Anguilla australis). The branchial ventilatory pattern comprised alternating periods of eupnea and apnea. The transition from eupnea to apnea was always associated with significant decreases in ventral aortic blood pressure (−20%), dorsal aortic blood pressure (−16%), ventral aortic blood flow (−39%) and heart rate (−27%), and a significant increase in systemic vascular resistance (+39%). Although there were, significant decreases in cardiac stroke volume in some animals, heart output was primarily determined by heart rate. The rapidity of the transition to apnea and the occasional occurrence of Mayer waves in the circulation of A. australis is considered as evidence in favour of the neural regulation of systemic vascular resistance.
The ionic concentrations in the mitochondria‐rich or chloride cell of Fundulus heteroclitus
Authors: Potts W. T. W. , Oates K. 
Published: June 2005

AbstractThe intracellular concentrations of sodium, potassium, and chloride ions, together with total phosphorous, in the cytoplasm of the chloride cells of the opercular epithelium of Fundulus heteroclitus have been estimated by X‐ray emission analysis of bulk frozen hydrated tissue. The estimated concentrations are Na, 171 ± 12; Cl, 155 ± 6; K, 62 ± 4 mE/kg water, together with 80 ± 6 mM P/kg water. It is shown that these high concentrations are consistent, with the Silva model of chloride secretion in which a sodium‐chloride linked carrier, driven by the inward diffusion of sodium ions, concentrates chloride in the cytoplasm. The intracellular concentration of chloride is such that if the potential across the apical membrane is greater than 34 mV, inside negative, there will be a net efflux of chloride ions out of the cell. If the linkage between sodium and chloride on the carrier is one to one, it is shown that energy dissipation is minimal when the product of the cytoplasmic concentrations of sodium and chloride approaches the product of those in the plasma and it would be energetically disadvantageous to maintain low intracellular concentrations of these ions. In practice, however, optimum concentrations are not attainable because of other intracellular solutes that contribute substantially to the osmotic pressure.
Contractile responses of single fibers in lobster claw closer muscles: Correlation with structure, histochemistry, and innervation
Authors: Costello Walter J. , Govind C. K. 
Published: June 2005

AbstractThis study incorporates contractile, structural (sarcomere length), histochemical (myofibrillar ATPase and NADH diaphorase), and physiological (fast and slow axon innervation) parameters to define fiber types in lobster muscle. Single fibers were examined in the closer muscle of adult cutter and crusher claws and of developing larval claws of the lobster Homarus americanus. Fibers with short sarcomeres ( < 4 μm) had rise times of 50–160 msec for attaining maximum tension which either was maintained for the period of stimulation (fatigue‐resistant) or declined (fatiguable). Fibers with long sarcomeres ( > 6 μm) had rise times of 90–800 msec for reaching maximum tension, which either was subsequently held at this level or continued to increase. The contractile properties and sarcomere length of single fibers were correlated with their enzymatic properties such that fast‐contracting, short‐sarcomere fibers had high myofibrillar ATPase activity and low oxidative capacity compared to their slow‐contracting, long‐sarcomere counterparts. The slow fibers were also further differentiated into subcategories based on contractile and histochemical properties. Fibers with the fastest rise times tended to be innervated primarily by the fast axon, and those with the slowest rise times were supplied solely by the slow axon. The organization of the massive closer muscle into discrete bundles in which fibers have uniform contractile, structural, and physiological properties leads to functional subdivision within the muscle. The contractile properties of developing fibers were similar to the adult except that larval fibers did not possess very slow rise times.
A unilateral cleavage furrow in embryos of S. droebachiensis
Authors: Anstrom John A. , Summers Robert G. 
Published: June 2005

AbstractEmbryos of the sea urchin, Strongylocentrotus droebachiensis, develop normally at temperatures ranging from 8°C to 0°C. An embyro cultured at 8°C cleaves symmetrically about its equator whereas one cultured at 0°C cleaves unilaterally. In embryos cultured at 8°C the mitotic apparatus (MA) occupies the entire cell volume at late anaphase whereas at 0°C the MA at the same stage is 20% smaller (Anstrom and Summers, '83). At 8°C the MA is centered within the zygote whereas at 0°C it is located eccentrically. The cleavage furrow always forms at the cell surface closest to the eccentric MA. We attribute the unilateral cleavage furrow in the 0°C embryo to the small size and eccentric placement of the mitotic apparatus within it. Both symmetrical and unilateral cleavage are apparently normal in this species, suggesting a common mechanism for both types of cleavage.
Proliferation of epidermal melanocytes during the healing of skin wounds in newborn mice
Authors: Hirobe Tomohisa 
Published: June 2005

AbstractA full‐thickness cut 7 mm long was made on the middorsal skin of C57BL/10J mice using fine iridectomy scissors. Specimens from the wounded skins were fixed at various days after wounding and were subjected to the dopa reaction and to the combined dopa‐premelanin reaction. In the epidermis within 1 mm from the wound edge, the melanocyte population positive to the dopa reaction as well as the melanoblast‐melanocyte population positive to the combined dopa‐premelanin reaction increased dramatically until the third day, then gradually decreased. In contrast, both populations in the regenerating wound epidermis appeared on the third day and increased until the seventh day, then gradually decreased. However, the maximal population density in the regenerating epidermis did not exceed the initial density. The size of the melanocyte population in both the epidermis within 1 mm from the wound edge and the regenerating epidermis did not differ from that of the melanoblast‐melanocyte population in all stages of wound healing. Moreover, pigment‐producing melanocytes in mitosis were found immediately after wounding in the epidermis within 1 mm from the wound edge, but not in the regenerating epidermis and control epidemis. These results indicate that the epidermal melanocytes in neonatal mouse skin can be stimulated to undergo mitosis immediately adjacent to a skin wound and, thèreafter, to migrate into the regenerating epidermis.
The effects of amino acids, cumulus cells, and bovine serum albumin on in vitro fertilization and first cleavage of hamster eggs
Authors: Juetten Jacquline , Bavister Barry D. 
Published: June 2005

AbstractThree factors were studied for their effects on the first cleavage division of in vitro fertilized hamster eggs. Eggs from superovulated females were inseminated with precapacitated epididymal hamster sperm in medium containing either fatty acid‐free (FAF) or fraction V (V) bovine serum albumin (BSA), in the presence or absence of cumulus cells. After incubation for 3 to 4 h with sperm, eggs were transferred to culture medium containing FAF‐ or V‐BSA, with or without amino acids (glutamine, isoleucine, methionine, and phenylalanine), and the percentages of eggs cleaving to two cells were recorded after a further 20 h of incubation. Fatty acid‐free BSA was found to support a significantly higher percentage of eggs cleaving than V‐BSA and was used in all further experiments. The presence of cumulus cells during fertilization was found to have a beneficial effect on cleavage when no amino acids were added to the culture medium, but when amino acids were included, eggs fertilized with or without cumulus present cleaved equally well. These results represent another step toward defining the optimal environmental conditions for obtaining the first cleavage division of hamster eggs in vitro.
Changes in body water and plasma constituents during bullfrog development: Effects of temperature and hormones
Authors: Brown Stephen C. , Horgan Elizabeth A. , Savage Lynne M. , Brown Patricia Stocking 
Published: June 2005

AbstractThe osmoregulatory responses to warmer temperatures and hormone treatment in cold‐adapted (5° C) Rana catesbeiana tadpoles and newly metamorphosed frogs were examined. Tadpoles transferred to 11° C and 18° C and left for 5 days lost 7% and 10% of their body weight. Plasma [Na+] was elevated 28% and 21%, respectively. Control (5° C) animals maintained their body weight and plasma [Na+] constant. Daily treatment with either ovine prolactin (oPRL) or ovine growth hormone (oGH) prevented the weight loss and the increase in extracellular [Na+] that occurred when tadpoles were transferred to 18° C. Neither propylthiouracil (PTU) nor arginine vasotocin (AVT) were effective in countering temperature‐induced weight loss in tadpoles. Newly metamorphosed frogs transferred to 18° C also lost weight; this was not prevented by daily treatment with saline, oPRL, oGH or PTU. However, in frogs treated daily with AVT, initial BW was regained by day 6. When warm‐adapted (18° C) tadpoles were treated daily for 18 days with saline, bPRL, bGH, thyroxine (T4), ergocornine, cortisol, or cortisol + T4, bPRL was most effective in retarding weight loss and maintaining body water content, whereas T4 + cortisol caused the greatest loss of weight and body water. By day 20, the correlations between weight loss and both body water content and hematocrit were highly significant. These data suggest that reported increases in plasma solute concentrations in larval amphibians may actually reflect decreases in extracellular fluid volume, rather than increased amounts of solutes, per se.