bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multiple hemoglobins of the cutthroat trout, Salmo clarki
Authors: Southard Jonathan N. , Berry Charles R. , Farley Thomas M. 
Published: June 2005

AbstractNine hemoglobins were purified from blood of Salmo clarki by ion‐exchange chromatography and preparative isoelectric focusing. The subunit structures of eight of the purified hemoglobins were studied by electrophoresis of globins in the presence of urea. Six are α2 β2 tetramers while two appear to be heterotetramers of the type αα′ β2 and αα′ββ′.The effects of pH, nucleotides, and temperature on the oxygen equilibria of the purified hemoglobins were studied. Five hemoglobins with isoelectric points from 9.1 to 7.1 and one minor hemoglobin with an isoelectric point of 5.9 appear to have essentially identical oxygen binding properties. All have similar oxygen equilibria which are independent of pH and temperature and not affected by saturating amounts of ATP. Another minor hemoglobin with an isoelectric point below 5.9 has similar oxygen equilibria except for a possible pH dependence. Two hemoglobins, with isoelectric points of 6.5 and 6.4, have oxygen binding properties which are strongly pH and temperature dependent. Addition of ATP or GTP causes a large decrease in the oxygen affinity without affecting the cooperativity of oxygen binding. The effect of GTP is slightly greater than that of ATP. No significant differences were observed in the oxygen equilibria of these two hemoglobins.The red blood cells of S. clarki were found to contain large amounts of both ATP and GTP, with an ATP:GTP ratio of 3:1. Both nucleotides may be important modulators of hemoglobin oxygen affinity in S. clarki, in contrast to the situation in S. gairdneri, in which red blood cell GTP concentrations are considerably lower.The presence of six or possibly seven hemoglobins with identical oxygen binding properties in S. clarki suggests that, to a large extent, the physiological role of multiple hemoglobins in this species involves phenomena not directly related to the oxygen binding properties of the hemoglobins.
Influence of calcium‐perturbing agents on schistosomes: Comparison of effects of praziquantel and verapamil on worm tegument
Authors: Senft A. W. , Gibler W. B. , Guterman J. J. 
Published: June 2005

AbstractA “slow calcium channel” blocking agent, Verapamil (VPL), induces tegumental disruption in schistosomes. The response of worms to VPL was compared to that caused by a widely used antischistosomal drug, Praziquantel (PZQ), whose mode of action has been related to a rapid influx Ca++.Scanning microscopy of worms exposed to micromolar concentrations of either PZQ or VPL in vitro revealed a striking similarity of tegumental damage. At high dosage (10−5 M × 1 h), both compounds cause extensive surface bleb formation, which can proceed to shredding and denudation of the tegument. Early VPL‐induced changes in male Schistosoma mansoni appear to consist of small intertubercular lesions, as well as head and neck microblebs and bullae. After longer exposure, the bleb formations develop into large lesions, which after fixation for scanning microscopy, appear as flower‐like outgrowths on and around the tubercles. Females show much less surface disruption than males.Physiologically, PZQ typically causes quick contraction of worm pairs into a tight, agonal coil. While VPL also induces spasm and clonic jerking, worms soon lengthen into a gentle coil. Both drugs kill the parasites in vitro.The findings suggest that both PZQ and VPL have a surface target, whose disruption can be noted visually as lipoidal oozing and eventual tegumental blebbing. The inference drawn is that a direct affect on worm internal calcium metabolism, or on calcium channel activities, can lead to pathological changes which are grossly indistinguishable. These two drugs have markedly dissimilar structures, and thus probably different mechanisms of action. Yet, they result in similar final pathological events. These studies raise the possibility that various calcium‐perturbing agents might be useful candidates in a search for alternative or synergistic chemotherapeutic agents against trematodes and cestodes.
The determination of the shell field cells during the first hour in the sixth cleavage cycle of eggs of Ilyanassa obsoleta
Authors: Labordus V. , van der Wal U. P. 
Published: June 2005

AbstractTo investigate the possibility of a relation between the moment of deletion of macromeres and the morphogenetic potential of the resulting embryo, the 2D‐, the 3D‐, or the 3(A–D)‐macromeres were deleted at regular intervals during the fifth or the sixth cleavage cycle. Ectoblasts, ‐3(A–D), are capable of extensive cellular differentiation and the formation of several organs. The developmental capacity of the ectoblasts is independent of the stage of deletion.Deletions of the D‐macromere at successive stages result in a decreasing number of internal shells; a minimum is reached 40–60 min after the fifth cleavage (24‐cell stage). Simultaneously, the number of external shells increases.Deletions of the 3D‐macromere during the first 60 min of the sixth cleavage cycle (24‐cell stage) lead to highly teratomorphic larvae; rather normal‐shaped larvae, but without heart and intestine, develop following deletions after 60 min. The moment of deletion of the D‐macromere affects morphogenesis.These results lead to the following hypothesis: each quadrant may induce an internal shell, irrespective of factors derived from the polar lobe; an internal shell is a differentiated non‐evaginated shell gland. During the first hour of the sixth cleavage cycle the 3D‐macromere suppresses shell field formation in the A‐, B‐, and C‐quadrants, and induces evagination of the shell gland in the D‐quadrant resulting in the formation of an external shell. At the same time the morphogenetic potential of the embryo is enhanced.
Stress‐induced suppression of testosterone secretion in male alligators
Authors: Lance Valentine A. , Elsey Ruth M. 
Published: June 2005

AbstractIn order to test the effect of acute stress on gonadal hormone secretion in reptiles, six mature male alligators were captured, and a blood sample was taken within 5 min of capture. Additional blood samples were taken at timed intervals for up to 41 hr, and plasma testosterone and corticosterone were measured by radioimmunoassay. Plasma testosterone declined to 50% of the initial value by 4 hr and dropped to less than 10% of initial by 24 hr. Plasma corticosterone increased during the first 12 hr, declined at 24 hr, and rose again at 40 hr. Blood samples from male alligators collected in North and South Carolina, south Florida, and in south Louisiana in two consecutive breeding seasons were also assayed for testosterone and corticosterone. In these populations there were significant differences in mean plasma testosterone and corticosterone levels. Elevated corticosterone levels were consistently seen in alligators caught in traps and from which a blood sample was taken several hours later. Plasma testosterone, although consistently lower in trapped alligators, did not show a negative correlation with plasma corticosterone. Farm‐reared alligators bled once, released, and bled again at 24 hr also showed a highly significant suppression of testosterone secretion. These results demonstrate that stress has a rapid and dramatic effect on testicular steroid secretion in both farm‐reared and wild alligators.
Mouse embryos develop normally Exo utero
Authors: Muneoka K. , Wanek N. , Bryant S. V. 
Published: June 2005

AbstractSurgical procedures are described which permit direct experimental access to postimplantation mouse embryos. These procedures arose from our finding that development proceeds normally to term after embryos have been released from the confines of the uterus, while remaining attached to it via the placenta. Embryos continue to develop exo utero, within the abdominal cavity of the mother, and are capable of surviving a variety of different surgical manipulations. This finding opens the way for experimental analyses of mouse development in vivo.
Abnormal regeneration in the planarian Dugesia tigrina as a function of the length: Width ratio of the regenerating fragment
Authors: Mead Robert W. , Krump Martha A. 
Published: June 2005

AbstractRegeneration was examined in different regions of planaria (Dugesia tigrina) in order to determine the effect that the shape of a section exerts on regenerative success. Length:width ratios were used as an index of tissue proportion, and overall regenerative success was measured by percent of abnormal regenerates and number of abnormalities per abnormal regenerate. Frequency and number of abnormalities increased as section width exceeded section length. Frequency of specific abnormalities varied with changes in length:width ratios and followed a predictable pattern. As ratios decreased below 1.0, abnormalities typically consisted of characteristics regarded as being due to excess head formation. These included the presence of two heads, the “head hump” syndrome, and/or lack of pharynx. This excess head formation was due to the proportional shape of the section rather than to overall segment size, and the frequency of such abnormalities increased in proportion to decreases in length:width ratios. Abnormalities which were more typically seen at ratios over 1.0 consisted of the lack of head, pharynx, and/or polarity.
Dependence of GnRH action on Na+, K+, and Ca2+ in the frog, Rana pipiens, pituitary
Authors: Porter David A. , Licht Paul 
Published: June 2005

AbstractThe roles of K+, Ca2+, and Na+ ions in the mechanism of gonadotropin releasing hormone (GnRH) action on frog (Rana pipiens) hemipituitaries were studied using an in vitro superfusion system. The effects of elevated K+ alone or in combination with Ca2+ ‐depleted medium, tetrodotoxin (TTX), or with 100 ng/ml GnRH were examined. The involvement of K+ was also studied indirectly through the use of tetraethyl ammonium chloride (TEA). The importance of Ca2+ was established by the loss of responsiveness to GnRH in Ca2+ ‐depleted medium, or in the presence of the Ca2+ competitor CoCl2. The absence of a major dependence of GnRH on Na+ was revealed by the continued gonadotropin secretion after addition of 1 μM TTX to medium containing GnRH or 36.3 mM KCl, or by replacement of NaCL with choline chloride. High (10 × normal) KCl (36.3 mM) stimulated gonadotropin‐both LH and FSH‐secretion, but the response was more gradual than for GnRH. The inclusion of TEA (to block K+ efflux) in medium with GnRH accentuated the effect of GnRH, and the effects of elevated (36.3 mM) KCl and 100 ng/ml GnRH (a relatively high dose) were additive. Responses to high K+, like GnRH, were abolished by removal of Ca2+ from the medium. Overall, the roles of K+, Ca2+, and Na+ ions in the mechanism of GnRH action are very similar between mammals and frogs; Ca2+ apparently serves a critical function in the mechanism of GnRH action, while Na+ appears not to be involved. K+ can induce gonadotropin secretion, but it is not clear that it plays a direct role in the mediation of the action of GnRH.
Calcium effects on progesterone accumulation and oocyte maturation in cultured follicles of Rana pipiens
Authors: Francisco Susan Kleis‐San , Schuetz Allen W. 
Published: June 2005

AbstractPituitary homogenates (FPH) provoke a cascade of responses in the amphibian ovarian follicle, culminating in progesterone biosynthesis and oocyte maturation (GVBD). Calcium may play an important role as an intracellular second messenger in regulating these physiological responses. Experiments were carried out on cultured, isolated follicles of Rana pipiens to assess the effects of varying extracellular calcium on follicular progesterone accumulation and oocyte maturation. In hormonally unstimulated follicles, an increase in extracellular Ca2+ alone produced a significant increase in progesterone in methanol extracts of follicles after 4 hours of culture, and in some cases also provoked oocyte maturation assessed after 24 hours of culture. In no case did elevated Ca2+ alone stimulate maximal progesterone accumulation as compared with FPH‐stimulated follicles, although the time‐course of accumulation was similar. The calcium ionophore, A‐23187, similarly increased progesterone accumulation in a dose‐dependent manner when introduced in amphibian Ringer's (1.35 mM Ca2+), but inhibited progesterone elevation caused by increasing calcium concentrations in the culture media and FPH stimulation. Depleting free calcium from the culture medium with graded doses of the chelator EGTA decreased FPH‐induced progesterone accumulation and inhibited FPH‐ and progesterone‐induced GVBD. The calcium channel blocker, verapamil, also inhibited FPH‐induced progesterone accumulation and GVDB in a dose‐dependent manner, while having no effect on progester‐one‐induced meiotic resumption. These data strongly implicate intracellular calcium levels regulating progesterone production by ovarian follicle cells and subsequent oocyte maturation.
Impact of symbiotic algae on sea anemone metabolism: Analysis by in vivo 31P nuclear magnetic resonance spectroscopy
Authors: Steen R. Grant 
Published: June 2005

AbstractHigh‐field pulsed Fourier‐transform nuclear magnetic resonance spectroscopy (NMR) was used to quantify the adenylate levels of sea anemones (Aiptasia pulchella) with and without symbiotic dinoflagellates (Symbiodinium sp.). Animals were fed to repletion, then starved in darkness for up to six days before collection of in vivo NMR spectra. The host adenylate ration of ATP: (ATP + ADP) declined significantly with increasing perioids of starvation in both symbiotic and aposymbiotic hosts (P<0.05). However, the decline in the animal adenylate ratio was significantly more rapid in animals bearing symbiotic algae (P<0.05). This suggests that symbiotic algae in darkness cause more rapid depletion of host energy reserves, possibly by drawing on host pools of organic substrates. In vivo NMR spectroscopy was also used to evaluate the effect on A. pulchella of photosynthesis by zooxanthellae. Symbiotic anemones were fed to repletion, then starved under high irradiance (300 to 320 μEin m−2 s−1) or low irradiance (70 to 80 μEin m−2 s−1) conditions for up to five days. The host adenylate ratio declined significantly (P<0.01) with starvation under both treatments, but no significant difference was detected between treatments (P<0.35). Blotted wet weight of anemones under high and low irradiance declined by 50% over eight days of starvation, but there was no significant difference in the rate of weight loss by anemones in the two treatments. There results suggest that translocation of photosynthate from symbiotic zooxanthellae does not significantly affect host adenylate ratio or have a sparing effect on host biomass during starvation in this symbiotic sea anemone.
Expression of homeotic genes in Bombyx mori estimated from asymmetry of dorsal closure in mutant/normal mosaics
Authors: Shimada Toru , Ebinuma Hiroyasu , Kobayashi Masahiko 
Published: June 2005

AbstractGenetic mosaics of homeotic genes, ENk and ESw, in the silkworm, Bombyx mori, were made using a hereditary mosaic gene, mo. Deformed segmentation, due to asymmetric integumental fusion during dorsal closure, was observed in the mosaics. Left and right integuments that contained an ENk or ESw gene on either side did not fuse symmetrically on the dorsal center line. The asymmetric fusion was observed only in places where the dorsal center lines corresponded to the border line between genotypes. In mosaics of ENk and +E, the sides of segments containing ENk genes frequently fused with anterior parts of the wild‐type side, in the region from the metathorax to the fourth adbominal segment, while on the sixth through eighth abdominal segments they fused with the posterior parts of the opposite sides. In mosaics of ENk and +E, asymmetric fusion was observed in a narrower region, from the metathorax to the second abdominal segment. In this region, the sides containing ESw genes frequently fused with posterior parts of the wild‐type side, in contrast to the fusion observed for ENk mosaics. The cause of asymmetric fusion and expression of the homoeotic genes in degmental differentiation are discussed in terms of a quantitive analysis of the relationship between mosaic patterns and asymmetric patterns of fusion.
Factors involved in the testicular development from fetal mouse ovaries following transplantation
Authors: Taketo‐Hosotani Teruko 
Published: June 2005

AbstractWe have previously shown that fetal mouse ovaries develop testicular structures after transplantation into adult male mice. The mechanisms of gonadal sex reversal is poorly understood. In the present study, we examined how a host environment is involved in the induction of testicular development in ovarian grafts. Fetal ovaries on the twelfth day of gestation were microencapsulated with semipermeable membranes, transplanted beneath the kidney capsules of adult male mice, and fixed for histological examinations between the sixteenth and twenty‐second day after transplantation. Fifteen of forty‐seven ovarian grafts were found to be completely enclosed in microcapsules, whereas the microcapsule membranes of other grafts were partly broken or had been lost. These differences of microencapsulation conditions made it possible to study the role of host factors in gonadal sex reversal. All ovarian grafts surrounded by microcapsule membranes developed ovarian structures. In contrast, most ovarian grafts which had lost the microcapsules developed testicular structures in addition to ovarian structures. When ovarian grafts were partially enclosed in microcapsule membranes, testicular structures developed only in the area in contact with the host kidney. These results suggest that direct interaction between the ovarian graft and cells or large macromolecules from the host is involved in the development of testicular structures in ovarian grafts.
Post‐testicular change in the reptile sperm surface with particular reference to the snake, Natrix fasciata
Authors: Esponda P. , Bedford J. M. 
Published: June 2005

AbstractSperm surface changes occurring in the reptile Wolffian duct have been explored with particular references to the snake, Natrix fasciata. In the snake Wolffian duct there are several proteins not present in serum, the pattern of which changes in concert with the seasonal testicular cycle. Whereas testicular spermatozoa did not bind antibody to duct secretions, all Wolffian duct spermatozoa did so over both head and tail, according to immunofluorescence patterns. Thus, on entering the Wolffian duct, the entire surface of N. fasciata spermatozoa acquires one of more of the duct's secretory components.As indicated by immunofluorescence, immunoelectrophoresis, and immunodiffusion, epitopes on at least some molecules that bind to spermatozoa or that remain free in the duct fluid are shared with those in other Natrix species, but not in more distant reptiles (turtle, anole lizard), nor chicken, rat, or rabbit. In regard to glycoproteins, one prominent con A‐reactive band was present in polyacrylamide gel electrophoresis (PAGE) of snake fluid and more were evident in fluid collected from the turtle duct. However, such lectin‐reactive elements did not bind to spermatozoa as judged by an absence of any change in snake, turtle and lizard sperm lectin‐binding patterns in passing from the testis into and through the Wolffian duct.In all, evidence from these and other species studied begins to suggest that the nature of the post‐testicular sperm surface modification displayed in most vertebrates that fertilize internally may differ in sub‐therian and therian groups, respectively. There appears to be a relative emphasis on glycosyl‐rich surface elements in the latter. The possible significance of these changes for sperm function in the different groups is discussed briefly in terms of sperm survival/storage, as well as capacitation and sperm binding to the zona.
Reexamination of metabolic potential in the toadfish sonic muscle
Authors: Walsh Patrick J. , Bedolla Cindy , Mommsen Thomas P. 
Published: June 2005

AbstractActivities of eight enzymes were measured in the sonic muscle of the gulf toadfish, Opsanus beta, to determine the metabolic poise of this unique tissue and to evaluate potential sex related differences in metabolism. In contrast to a prior study (Pennypacker et al., '85, J. Exp. Zool., 239:259–264), we observed substantial activities of M4‐lactate dehydrogenase, 333 to 482 units/g wet sonic muscle weight. This observation and the presence of high activities of other enzymes of glycolytic and anaerobic metabolism (pyruvate kinase and creatine phosphokinase) lead us to conclude that this tissue has high anaerobic capacity. Also in contrast to the observations of Pennypacker et al. ('85), we found that the activities of some enzymes indicative of aerobic metabolism are relatively low. For example, the activities of citrate synthase found in sonic muscle (1.5 to 2.7 units/g) are only slightly higher than values obtained for toadfish white skeletal muscle (1.2 units/g). The discrepancies between the results obtained by the two studies appear to be methodological ones. Lastly, significant differences in enzyme activities between males and females were observed for lactate dehydrogenase, malate dehydrogenase, and citrate synthase, and possible explantions for these differences are discussed.
Temperature‐sensitive periods of sex determination in a lizard: Similarities with turtles and crocodilians
Authors: Bull J. J. 
Published: June 2005

AbstractThe sex of leopard geckoes is determined by incubation temperature. This study identified their temperature‐sensitive period of sex determination by incubating embryos at a male‐producing temperature (32°C) and a female‐producing temperature (26°C) for various intervals of development and comparing the sex ratios from the different experiments. Eggs incubated at 26° for 14 days (to stage 32) could still develop as either sex, but eggs incubated 30 days (through stage 34) necessarily became female; incubation at 32° did not guarantee male development until 20 days of incubation (to stage 37). The temperature‐sensitive period of irreversible sex determination therefore lies between stages 32–37 and occupies much of the first half of development. The temperature‐sensitive period in geckoes is similar to those in turtles and alligators, which are only distantly related to geckoes, but the reasons for these similarities are obscure.
Role of carbonic anhydrase in calcification in the gorgonian Leptogorgia virgulata
Authors: Kingsley Roni J. , Watabe Norimitsu 
Published: June 2005

AbstractThe relationship between carbonic anhydrase and calcification in the gorgonian Leptogorgia virgulata was examined by analysis of the enzyme's activity, its cellular locations and its response to inhibition by Diamox. Enzyme activity was 2.7 nmol μg−1 protein s−1 at 4°C. Carbonic anhydrase localization at the light level using immunofluorescent techniques and at the ultrastructural level using Hansson's method showed activity in the scleroblasts and axial epithelium. Specifically, at the electron microscopic level this activity was found to be very high on the membranes of the spicule‐forming vacuole and electron‐dense bodies. Membranes of the microvilli and plasma membranes of the desmocytes showed high activity of this enzyme. The activity on the scleroblast plasma membranes was variable. This enzyme is possibly present in the axis. Regenerated branch tips incubated in seawater containing 10−4 M and 10−6 M Diamox showed an increase in 45Ca uptake into the spicules and axes. The tissue o fbranch tips incubated in 10−6 M Diamox showed a decrease in 45Ca uptake. The observation that carbonic anhydrase is located adjacent to calcifying structures and organelles associated with spicule formation suggests that the enzyme is involved in calcification. The increase in 45Ca uptake from enzyme inhibition may suggest that carbonic anhydrase is involved in the regulation of HCO3.