bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pancreatic hormones, insulin/glucagon molar ratios, and somatostatin as determinants of avian carbohydrate metabolism
Authors: Hazelwood Robert L. 
Published: June 2005

AbstractThe endocrine pancreas of birds contains cell populations similar, if not identical, to those found in mammalian pancreata, although the topographical distributions of these cell types differ to some extent. Insulin‐secreting (b) cells, glucagon‐secreting (a) cells, somatostatin‐secreting (D) cells, and pancreatic polypeptide‐secreting (PP or F) cells are distributed unequally among the four pancreatic lobes, with most of the A cells located in the third and splenic lobes and PP cells residing in both islet tissue and in acinar tissue. Glucagon appears to be a (the?) major pancreatic hormone involved in metabolic glucoregulation in birds. Yet the essentiality of insulin for this regulatory purpose also has been established. As a result, current thought is directed toward the molar ratio of insulin to glucagon (I/G) as a dominant force in homeostasis rather than toward either of the two hormones separately. Molar I/G ratios have been useful in mammals in studying the needs of the organism to produce glucose to meet a metabolic crisis/need and, when compared with that found in normal Aves, a value of 1.8–2.2 has been established. Such a molar ratio is indicative of a catabolic recovery of nutrients in mammals, suggesting that birds normally are in a catabolic mode (like diabetic, starving, or exercising mammals). Somatostatin (SRIF) is known to inhibit the release of all pancreatic hormones but has a greater inhibitory action on glucagon secretion than it does on any of the other peptides. (It has least effect on APP.) Recent studies have provided evidence indicating that SRIF may be very important in Aves in regulating the I/G molar ratio appropriate for the metabolic condition present at any given time. Such “fine tuning” of the endocrine pancreas by SRIF would allow the appropriate hormone mixture to be released against any metabolic background to effect carbohydrate homeostasis.
Gastrointestinal hormones in birds: Morphological, chemical, and developmental aspects
Authors: Rawdon B. B. 
Published: June 2005

AbstractHistorically, the enterochromaffin cell was the first endocrine cell type detected in avian gut; subsequently, a number of types of such cells were distinguished on the basis of the ultrastructural features of the secretory granules. More recently, immunocytochemical procedures have revealed somatostatin‐, pancreatic polypeptide (PP)‐, polypeptide YY‐, glucagon‐, secretin‐, vasoactive intestinal peptide (VIP)‐, gastrin‐, cholecystokinin‐, neurotensin‐, bombesin‐, substance P‐, enkephalin‐, motilin‐, and FMRFamide‐like immunoreactivity in avian gastrointestinal endocrine cells. Most endocrine cells are located in the antrum; there are a number in the proventriculus and small intestine but few in the gizzard, cecum, and recum, Several avian gastroenteropancreatic hormones, including glucagon, VIP, secretin, bombesin, neurotensin, and PP, have been isolated and sequenced. They resemble the equivalent mammalian peptides in terms of molecular size but differ in amino acid composition and sequence; some (e.g., VIP) differ only in minor respects, others (e.g., secretin) more radically. Gastrointestinal endocrine cells appear late in development; available data indicate that few types are recognized by either immunocytochemistry or electron microscopy before 16 days of incubation. Experimental evidence has shown that at least the majority of gut endocrine cells are of endodermal origin and are not derived from the neural crest or neuroectoderm as earlier proposed. In early embryos, the progenitors of gastrointestinal endocrine cells are more widespread than are the differentiated cells in chicks at hatching. This, along with other observations, raises the question of factors that might influence the differentiation of gut endocrine cells.
Plasma hormones (arginine vasotocin, prolactin, aldosterone, and corticosterone) in relation to hydration state, NaCl intake, and egg laying in fowls
Authors: Arad Zeev , Skadhauge Erik 
Published: June 2005

AbstractThis review surveys our latest research dealing with the involvement of arginine vasotocin (AVT), the avian antidiuretic hormone, and other hormones in the regulation of water and salt balance in fowl. We examined the effect of dehydration, salt loading, high‐ and low‐salt diets, and oviposition on plasma hormone levels and analyzed them in light of our knowledge of avian osmoregulatory responses to changes in water and salt balance. Gradual dehydration and hyperosmotic loading in domestic fowl revealed consistent differences in the AVT response between groups adapted to low‐ and high‐NaCl diets. In birds on a low‐NaCl diet the sensitivity of the AVT release was significantly higher than in birds on a high‐NaCl diet. These results support the concept that the link between osmotic and volume regulation is established via varying sensitivity of the AVT release. We determined the half‐life of the AVT in fowls (6.3 min), a value similar to that of ADH in mammals. We found that during oviposition, plasma AVT increases by a factor of four over the normal level, a magnitude consistent with the maximal responses revealed in osmotic stimulations. We have shown that as long as drinking water is available, heat exposure has no effect on the plasma osmotic constituents and the regulatory hormones. However, combined dehydration and heat exposure resulted in pronounced osmoregulatory responses integrated with the thermoregulatory responses to maintain water and salt balance without jeopardizing the birds' ability to cope with the thermoregulatory demands. We now have ample evidence that AVT does not release prolactin from the pituitary and that probably hyperosmolality (or high sodium) as such releases prolactin.
Endocrine regulation of avian renal function
Authors: Braun Eldon J. , Dantzler William H. 
Published: June 2005

AbstractThe avian kidney contains reptilian‐type (RT) nephrons that do not function in concert and mammalian‐type (MT) nephrons that do function in concert to permit production of concentrated urine. Significant data on endocrine regulation of renal function are available only for antidiuretic hormone (arginine vasotocin, AVT) and parathyroid hormone (PTH). Plasma AVT increases and number of filtering RT nephrons decrease when plasma osmolality increases. Small doses of AVT reduce the number of filtering RT nephrons, and all RT nephrons filter following acute neurohypophysectomy. In addition to changing tubule permeability to water, AVT affects the concentrating mechanism by reducing the number of filtering RT nephrons and flow through collecting ducts. Both net tubular reabsorption and net tubular secretion of PO4 occur. Parathyroidectomy (PTX) stimulates PO4 reabsorption, and PTH replacement decreases reabsorption and stimulates secretion, apparently in proximal tubules of RT nephrons. PTX stimulates and PTH replacement inhibits Na‐dependent PO4 transport by renal brush border membrane vesicles. PTH also stimulates Ca2+ reabsorption but apparently not along the proximal tubule of RT nephrons.
Antidiuretic effect of [Sar1, Val5, Ala8] angiotensin II in Lophius americanus
Authors: Churchill Paul , Malvin Richard , Churchill Monique , Beasley Debbie , Shier David 
Published: June 2005

AbstractWe have reported previously that angiotensin II increases urine flow and Na and K excretion rates in the aglomerular goosefish Lophius americanus. The present experiments were undertaken to determine if antagonism of endogenous angiotensin has the opposite renal effects. Arterial blood pressure, urine flow, and plasma and urine electrolytes were measured during two consecutive clearance periods in two groups of goosefish. The control group (n = 7) received saline intravenously during both periods; the experimental group (n = 8) received saline during the first period and a competitive antagonist of angiotensin II (saralasin, or [Sar1, Val5, Ala8] angiotension II) dissolved in saline during the second period. The control group exhibited no significant change over time in any of the measured variables: arterial blood pressure; plasma [Na], [K], [Mg], [Ca]; osmolality; urine flow; and excretion rates of Na, K, Ca, and Mg. Arterial blood pressure and plasma electrolytes and osmolality were stable over time in the experimental group also. However, during saralasin infusion there were significant decreases in urine flow and in excretion rates of K, Mg, and Ca. Taken together with our previous results, these observations suggest that endogenous levels of angiotensin in goosefish are sufficient to have direct renal effects. The mechanisms of action of angiotensin are not clear, but involve neither changes in systemic blood pressure nor filtration but might involve inhibitory effects of angiotensin on tubular reabsorptive processes.
Temporal variations in gonadal and body fat responses to daily injections of 5‐hydroxytryptophan (5‐HTP) and dihydroxyphenylalanine (DOPA) in the gulf killifish, Fundulus grandis
Authors: Emata Arnil C. , Meier Albert H. , Spieler Richard E. 
Published: June 2005

AbstractDaily injections of dihydroxyphenylalanine (DOPA), a dopamine precursor, stimulate large increases in reproductive and body fat indices in gulf killifish, Fundulus grandis, when given 20 hours after daily injections of 5‐hydroxytryptophan (5‐HTP), a serotonin precursor. However, DOPA injections are inhibitory when given 8 hours after 5‐HTP. The drug effects persist for at least 3 weeks following drug treatment indicating a possible resetting of an endogenous mechanism involved in seasonality.
Structural and functional development of cricket wing muscles
Authors: Ready Neal E. , Najm Ramzi E. 
Published: June 2005

AbstractThe sizes of the unifunctional dorsal longitudinal (DLM) and bifunctional subalar (Sa) metathoracic flight muscles of the cricket Teleogryllus oceanicus increase by more than an order of magnitude between the second instar before the terminal molt and the tenth day of adult life. During the same developmental period isometric twitch duration (onset to 50% relaxation, 25°C) varies little, while muscle mitochondrial content increased by a factor of ten as measured by stereological analysis of electron micrographs and citrate synthase activity (μmoles citrate·min−1· gm protein−1, 25°C). The wing muscles of adults have abundant sarcoplasmic reticulum (SR), narrow myofibrils, and a high volume density of mitochondria. At two molts from adulthood muscles that will later be used in flight behavior also have narrow myofibrils and abundant SR, but unlike muscles at later stages, nymphal muscles have a low volume density of mitochondria. At the terminal molt muscles have at least as much SR as is seen in muscles at the tenth day of adult life, and the myofibrils are also more narrow at the earlier stage. Since there is significant variation in muscle structure and little change in twitch duration during late development, the efficacy of the SR in releasing and resequestering CA2+ is seemingly lower in muscles at the terminal molt, a time of rapid muscle growth.
Functional connections are established between giant nerve fibers in grafted earthworms
Authors: Vining Elizabeth P. , Drewes Charles D. 
Published: June 2005

AbstractGiant fiber interconnections were examined in successful grafts between two posterior portions of earthworms (Eisenia foetida). Electrophysiological and histological results indicated that cell‐specific interanimal connections were formed between the medial giant fibers (MGF) in these preparations. Similar interconnections were formed between the paired lateral giant fibers (LGF), except that these involved the apposed left and right LGFs. Establishment of reliable and bidirectional conduction of LGF and MGF spikes across the graft occurred 2–4 days and 7–14 days after grafting, respectively. Subsequently, conduction across the graft remained effective for at least 6 weeks. These results are consistent with a hypothesis that grafted giant fibers are joined by a direct electrical connection, involving either fusion or an electrical synapse.
Pregnancy diagnosis by vaginal lavage in deer mice, Peromyscus maniculatus
Authors: Paull Judith A. , Fairbrother Anne 
Published: June 2005

AbstractWe developed a method for diagnosing pregnancy in the deer mouse (Peromyscus maniculatus) using vaginal lavage. We first clearly defined stages of the estrous cycle by using the ratio of the cell types observed. The distribution of cells found in vaginal smears prepared from visibly pregnant females matched the cell ratio of the metestrous stage. Two females were monitored through consecutive pregnancies; no significant variation of the cell types from the metestrous cell ratio was observed. We tested the accuracy of this predictive method using 67 breeding females. Because the vaginal smear of a pregnant mouse is indistinguishable from the smear of a mouse in cyclic metestrus, we lavaged mice twice at a 2‐day interval to eliminate false positives (mice in cyclic metestrus). We obtained an 86.6% accuracy rate and concluded that the method can predict pregnancy in deer mice.
Respiratory properties of the haemolymph of the intertidal prawn Palaemon elegans (Rathke)
Authors: Morris S. , Taylor A. C. , Bridges C. R. , Grieshaber M. K. 
Published: June 2005

AbstractThe properties of the haemolymph of Palaemon elegans for oxygen and carbon dioxide transport were studied with respect to the considerable fluctuation in the environmental conditions normally experienced by this prawn in intertidal rock pools. The haemolymph was found to have a high oxygen affinity (P50 = 3.6 Torr, 15°C, pH 8.0) and a large oxygen carrying capacity (1.17 mmol.L−1), as well as a marked Bohr shift (φ = ‐ 1.7). Under some conditions, the affinity appeared to be independent of temperature as did the n50 value (n50 = 2.8). Experiments in which the pH of the haemolymph was varied using fixed acid together with two different CO2 tensions demonstrated a specific CO2 effect on O2 affinity, which did not affect the Bohr factor. The nonbicarbonate buffer value of the haemolymph was found to be high (16.02 mmol.L−1.pH unit−1). The in vivo postbranchial haemolymph pH at 15°C was 7.89 with a calculated Pco2 of 1.26 Torr. A large functional Haldane coefficient was observed (1.25), which was only moderately temperature dependent. The haemolymph exhibited an extremely high capacitance for CO2 at low Pco2 values (βCO2 = 8.4 mmol.L−1.Torr−1). Some functional implications of linkage between the large Bohr and Haldane effects are discussed in light of present knowledge.
Salinity‐induced changes in gill Na, K‐ATPase activity in the mud fiddler crab, Uca pugnax
Authors: Holliday Charles W. 
Published: June 2005

AbstractMale mud fiddler crabs (Uca pugnax) were shown to hyperosmoregulate in 10% and 50% seawater (SW) and to hypoosmoregulate in 150% and 200% SW. Crabs fully immersed in the media did not osmoregulate as well as those that were free to enter or leave the medium at will (“natural” environment). Gill sodium‐plus‐potassium ATPase (Na,K‐ATPase) enzyme specific activity was characterized in crude homogenates. After acclimation (21 days) in 10% SW, all six gill pairs in immersed crabs showed significantly higher enzyme specific activity (ESA) than 100% SW controls; crabs in 50% SW had significantly higher ESA in gills 3 through 6. With one exception, a decrease, acclimation to 150% or 200% SW did not significantly change gill ESA in immersed crabs. In all media, gills 5 and 6 had approximately 75% of the total ESA in the crabs' gills. Crabs in the “natural” environment showed a similar pattern of changes in gill ESA. Thus, changes in gill ESA appear to be important only in hyperosmotic regulation and in active sodium uptake by the gills from dilute media. The time‐course of changes in crude homogenate ESA in gills 5 and 6, after transfer of 100% SW crabs to 10% SW, was relatively rapid (significantly increased after 1 day) and correlated well with changes in hemolymph osmolality. Three different microsomal preparations from gills 5 and 6 did not show significantly increased ESA until between 3 and 7 days after transfer. Therefore, gill Na,K‐ATPase activity may be altered both by rapid modulation of existing enzyme and by longer term synthesis of new enzyme.
Commitment to sexual and asexual phases in Paramecium multimicronucleatum
Authors: Shimomura Fumiyo , Takagi Yoshiomi 
Published: June 2005

AbstractSexually mature cells of Paramecium multimicronucleatum, syngen 2, which have been starved 1 day, can be artificially controlled to select either the sexual phase or the asexual phase by putting them either in autogamy‐inducing medium (AIM) or in culture medium (CM). Simultaneous treatment with AIM and CM was found to bring the cells into the sexual phase. When cells were first treated with AIM for T hr and then with CM, they all reverted to the asexual phase if T ≦ 1.5 hr; they were increasingly determined to undergo nuclear activation with the increase of T; and virtually all of them were determined if T ≧ 2.5 hr. Cells lost their capacity to feed and divide with the same kinetics. It was demonstrated by using the same single cells that there was a complete correspondence between the final loss of capacity to feed and nuclear activation, and between nuclear activation and the loss of capacity to divide. When cells were first treated with CM for t hr and then with AIM, they could be pulled back to the sexual phase if t < 2 hr, with decreasing possibility with time. Within this time interval, longer pretreatment of CM required longer posttreatment of AIM to set the competent cells back to the sexual phase. Incubation in CM for t ≧ 2 hr made all of the cells insensitive to AIM, while incubation in CM for at least 4 hr was necessary to let them actually pass through the asexual phase.
Cross‐phyletic bioactivity of arthropod neurohormones and molluscan ganglion extracts: Evidence of an extended peptide family
Authors: Greenberg M. J. , Rao K. R. , Lehman H. K. , Price D. A. , Doble K. E. 
Published: June 2005

AbstractTwo structurally related arthropod neuropeptides, red pigment concentrating hormone (RPCH) and adipokinetic hormone (AKH), are potent excitors of the heart of the clam Mercenaria mercenaria. The response is bimodal: whereas the threshold for affected hearts is 1–3 × 10−9 M, about 40% of the preparations are virtually unresponsive. Aqueous extracts of Mercenaria ganglia contain a substance which concentrates the red pigment in the erythrophores of intact destalked Uca pugilator and even of its isolated legs. This substance is retained on Sephadex G‐15 and co‐elutes with synthetic shrimp RPCH. The active fractions also concentrate the erythrophores and the leucophores of destalked shrimp (Penaeus). Neither dopamine nor the molluscan neuropeptide FMRFamide had any chromatophorotropic effect in these assays. The activity of the ganglion extracts was abolished by digestion with chymotrypsin. In conclusion, molluscan ganglion extracts contain a peptide factor, possibly an analog of RPCH, that concentrates the pigments of crustacean chromatophores by a direct action on the cells.
Growth and aging in the rat: Changes in total protein, cellularity, and polyploidy in various organs
Authors: Bohman R. , Tamura C. T. , Doolittle M. H. , Cascarano J. 
Published: June 2005

AbstractThe objectives of this study were to determine the influence of growth and aging on ploidy, cell number, and protein content of various organs. Tissue homogenates were prepared at 3, 8, 25, 50, and 100 weeks of age. Samples were analyzed for DNA per nucleus (by flow cytofluorometry), nuclei number, and protein content. Livers of 8‐ and 100‐week‐old animals were also perfused with collagenase and the released cells separated into parenchymal and nonparenchymal populations by unit gravity sedimentation. Nuclei of these cells were also analyzed for DNA. In all four zones of the kidney and in thyroid, 4n nuclei diminished in percentage between 3 and 50 weeks and increased at 100 weeks. In the growth phase these probably are cycling cells and after 50 weeks represent an increasing population of nuclei arrested after synthesis of DNA. Constant levels of ploidy were found in brain, heart, rectus abdominis, and adrenal throughout the 3–100 weeks. A dramatic increase in 4n nuclei occurred between 3 and 8 weeks in liver with little change occurring thereafter. Ploidy is a property of only parenchymal cells in liver and this probably is also true in other organs. The 4n nuclei that remain in constant proportion to the total population are established early in life and are not related to aging. They are probably tetraploid and replicate into 4n daughter cells during growth. Cerebrum shows no changes in nuclei number but exhibits a 70% increase in protein between 3 and 100 weeks. Although kidney, liver and adrenal show large increases in number of nuclei (≈ fourfold) with growth, these are not as great as increases in body weight (≈ 11‐fold). With regard to organ protein, only liver shows increases approximating those in body weight. Increases in organ nuclei appear to occur in concert for adrenal, kidney, and liver whereas increases in organ protein bear no relationship to each other. Protein content remains at stable levels in organs of 100‐week‐old animals and little (adrenal, liver) or no (brain, kidney) diminution occurs in nuclei numbers.
Isolation of intact sperm asters from fertilized sea urchin eggs
Authors: Hinkley Robert E. , Wright Brent D. 
Published: June 2005

AbstractWe have developed a procedure for isolating intact sperm asters in quantity from fertilized sea urchin eggs. This procedure is based on detergent‐extraction methods developed previously for the bulk isolation of mitotic apparatuses. Using this protocol it is possible to isolate sperm asters as soon as they appear in the fertilized egg or at any subsequent point in their brief existence.
Lack of renal effects of DOCA, ACTH, spironolactone, and angiotensin II in Squalus acanthias
Authors: Churchill Paul C. , Malvin Richard L. , Churchill Monique C. 
Published: June 2005

AbstractAngiotensin II was infused intravenously in spiny dogfish sharks (Squalus acanthias). There were no significant effects on arterial blood pressure, glomerular filtration rate, urine flow, or Na excretion either in comparison with pre‐ and postinfusion values or in comparison with values measured in a control group of fish given elasmobranch saline intravenously. In other dogfish, glomerular filtration rate, urine flow, and Na and K excretory rates were measured for 3 days following implantation of desoxycorticosterone (DOCA), adrenocorticotropin (ACTH), or spironolactone; a control group was given no drug. There were no significant differences between these four groups of fish with respect to any of the measured parameters. These results suggest that the dogfish kidney is not a target organ for several substances known to affect renal function, either directly or indirectly, in other animals.