bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in pituitary responsiveness during the ovulatory cycle of the Japanese quail, in vitro
Authors: Connolly Peter B. , Callard Ian P.
Published: June 2005

Anterior pituitary glands from ovulating Japanese quail (Coturnix coturnix) were used to investigate variation in sensitivity to chicken luteinizing hormone‐releasing hormone (cLHRH I; Gln8‐LHRH). Grouping the pituitaries by ovulatory stage provided preliminary evidence of changes in sensitivity to LHRH during the ovulatory cycle. Pituitaries taken from quail before the preovulatory LH surge were responsive to cLHRH I, while pituitaries from the other times of the cycle showed minimal response to cLHRH I. Female pituitary glands release less LH than those of males. These data indicate a change in sensitivity to LHRH in the female quail that may be due to changes in gonadal steroids or the pool of releaseable LH from the pituitary.
Protein‐free culture medium containing polyvinylalcohol, vitamins, and amino acids supports development of eight‐cell hamster embryos to hatching blastocysts
Authors: Kane Michael T. , Bavister Barry D.
Published: June 2005

In vitro development of eight‐cell hamster embryos to hatching blastocysts requires the presence of amino acids and a group of water‐soluble vitamins in the culture medium. The present studies investigated the effect of type of macromolecule on blastocyst hatching and on the requirement for vitamins. Embryos were cultured for 3 days in the presence of the synthetic macromolecule polyvinylalcohol (PVA) and of different types of bovine serum albumin (BSA), both with and without vitamins. The results showed that eight‐cell embryos develop to hatching blastocysts in the presence of vitamins and amino acids with PVA as the only macromolecule in the medium. The presence of certain types of BSA reduced but did not eliminate the need for vitamins. Glutamine alone was as efficient as a complete amino acid supplement in supporting blastocyst hatching. These results demonstrate for the first time that eight‐cell hamster embryos can be cultured to hatching blastocysts in a chemically defined medium.
Coronary drainage in the Octopus vulgaris systemic heart
Authors: Agnisola C. , Zummo G. , Tota B.
Published: June 2005

The vascular architecture of the coronary system of the systemic heart of the octopus (Octopus vulgaris) has been studied by means of both the corrosion‐cast method and scanning electron microscopy. It is shown that the Octopus systemic heart myocardium is supplied through a very rich capillary network, the complexity of which probably reflects the complex organization of the ventricular wall. Drainage occurs by way of a classic venous system that originates from this capillary network. Morphological evidences are reported indicating that the coronary bed communicates directly with the ventricular lumen. In the isolated perfused systemic heart, the flow through this system is related directly to cardiac contractility. In an in situ preparation of the systemic heart, where for the first time simultaneous records have been obtained, ventricular pressure, coronary vein pressure, and coronary flow appear to be time related. It is suggested that in Octopus the venous coronary flow is not dependent on the systemic arterial pressure, as in the vertebrate heart, but it is directly dependent on intraventricular pressure.
Unexpected divergence among identified interneurons in different abdominal segments of the crayfish Procambarus clarkii
Authors: Larimer James L. , Pease Craig M.
Published: June 2005

The command elements that initiate and coordinate the abdominal movements in crayfish show little similarity between the various abdominal segments. Our criteria for similarity among interneurons were based on both cell morphology and electrophysiology. By contrast, previously published evidence shows much greater intersegmental similarity in the skeletal, muscular, motoneuronal, and sensory components of the abdominal system in crayfish, structures that are controlled by or send information to the command elements. Therefore, unlike the command elements, these structures have retained nearly identical form and function in the various segments.

We also found in different ganglia examples of interneurons involved with abdominal positioning behavior that have similar morphology but different function and vice versa. Such interneurons could represent divergent pairs of serial homologues. It is unknown why so many of the abdominal positioning interneurons have become different. The various ganglia may perform subtly different functions, requiring differences in the positioning interneurons but not in the motor neurons or muscles. Alternatively, some of the abdominal positioning interneurons underlie more than one behavior; consequently, selection acting on these multiple functions may have changed these interneurons through evolution.
Feminization of the hepatic microsomal cytochrome P‐450 system in brook trout by estradiol, testosterone, and pituitary factors
Authors: Pajor Ana M. , Stegeman John J. , Thomas Peter , Woodin Bruce R.
Published: June 2005

The effects of estradiol, testosterone, and pituitary extract on hepatic microsomal enzymes were studied in sham‐operated and gonadectomized immature brook trout. Estradiol reduced the specific content of cytochromes P‐450 and b5 by 70% or more in both groups. Testosterone and pituitary extract also decreased the levels of total P‐450 and b5, but to a lesser extent. These latter effects were not evident when the contents of P‐450 and b5 were normalized per g liver. Immunoblot analysis with antibodies to P‐450 forms from a teleost (scup) showed the presence of cross‐reacting proteins in control fish, presumed counterparts to the scup forms. Levels of a trout counterpart to P‐450A (a putative testosterone 6β‐hydroxylase) were strongly suppressed in estradiol‐treated fish. A trout P‐450B counterpart was suppressed in estradiol‐treated fish, but less strongly than was the P‐450A counterpart. The trout orthologue of hydrocarbon‐inducible P‐450E (P‐450IA1), the aryl hydrocarbon hydroxylase (AHH) catalyst, was undetectable in any group, consistent with very low levels of AHH activity in these fish. Estradiol or pituitary extract also decreased the levels of NADH‐cytochrome b5 and NADPH‐cytochrome P‐450 reductase activities in sham‐operated but not in gonadectomized fish. Gonadectomy alone also lowered the levels of reductase activities but not of total P‐450 or b5, suggesting an influence of gonads in maintaining normal levels of the reductases. The results support a prominent suppressive role for estrogens in producing the general sex differences in microsomal enzymes in fish liver and indicate that there could be affects on several P‐450 forms. However, the mechanism of hormone action in this regulation is uncertain. The results also suggest the existence of unidentified, possibly gonadal, factors which contribute to the regulation of reductases in teleost liver.
Developmental change in follicular cell‐enhanced amino acid uptake into mouse oocytes that depends on intact gap junctions and transport system gly
Authors: Haghighat Nasrin , Van Winkle Lon J.
Published: June 2005

Uptake of L‐alanine, L‐lysine, and choline into both preantral and antral mouse oocytes was enhanced by follicular cells. Follicular cells also enhanced glycine uptake into oocytes at the preantral stage of development, but no effect of these cells was observed at the antral stage. Glycine uptake was predominantly Na+ dependent and inhibited almost completely by 10 mM sarcosine, moderately by proline and its analog pipecolate, and poorly or not at all by other amino acids. By these criteria, glycine transport was mainly via system Gly in follicular cells and the oolemma at both the preantral and antral stages. Moreover, an increase in glycine transport via the oolemma between the preantral and antral stages was more than threefold larger than was the increase in transport of alanine or lysine. This relatively large increase in glycine‐specific transport in the oolemma appears to obscure the ability of follicular cells to enhance glycine uptake into antral oocytes. In contrast to other amino acids, leucine uptake into oocytes was not enhanced by follicular cells unless 14 other amino acids were also present at their concentrations in mouse serum. An inhibitor of gap junctional communication, 18‐α‐glycyrrhetinic acid, abolished follicular cell‐enhanced uptake of glycine and choline into preantral oocytes. Therefore, the extent to which follicular cells enhance uptake of a particular amino acid into oocytes depends on at least three physiologically important variables. Namely, enhancement may depend on the stage of follicular development, the presence of other amino acids in the environment, and gap junctional communication.
Lactate production in the gills of the mudskipper Periophthalmodon schlosseri exposed to hypoxia
Authors: Ip Y. K. , Low W. P.
Published: June 2005

Fish gills are generally regarded as lactate‐consuming organs. However, the mudskipper, Periophthalmodon schlosseri, which is euryhaline, amphibious, and frequently exposed to environmental hypoxia in its natural habitat, accumulated significantly greater (P < 0.01) amount of lactate in its gills under experimental hypoxic condition (4.82 ± 1.22 μmol/g) than those of the control normoxic fish (2.43 ± 0.22 μmol/g). Perfused gills incubated in vitro under hypoxia for 1 hr also contained a greater amount of lactate (8.77 ± 0.25 μmol/g) than those incubated in normoxic condition (2.39 ± 0.75 μmol/g). These results proved that the branchial tissues of P. schlosseri can produce lactate under hypoxia from some endogenous substrates, which have yet to be determined. Lactate dehydrogenase extracted from the gills of the mudskipper also showed high ratio of pyruvate‐reducing activity to lactate‐oxidizing activity, indicating that its brachial tissues have a greater capacity for lactate production than those of other fishes.
Tissue‐specific regulation of pyruvate kinase during environmental anoxia in Concholepas concholepas (Gastropoda: Muricidae)
Authors: Carvajal Nelson , González Ruby , Kessi Eduardo
Published: June 2005

The effects of anoxia on pyruvate kinases (PK) from the heart and foot muscle of Concholepas concholepas, as well as the presence and levels of phosphoenolpyruvate carboxykinase (PEPCK) in the aerobic and anoxic tissues, were examined. In response to anoxia, the maximal activity of pyruvate kinase decreased in the heart but was not altered in the foot muscle. Phosphoenolpyruvate carboxykinase was not detected in the foot muscle and anoxic stress had no effect on the activity of this enzyme in the heart tissue. Anoxic stress altered the kinetic and regulatory properties of heart PK without any change in the foot muscle enzyme. Anoxic heart PK was much more dependent of fructose 1,6‐diphosphate for significant activity at low concentrations of phos‐phoenolpyruvate and had a higher sensitivity to inhibition by alanine and ATP than the aerobic enzyme from. All changes were reversed when the animals were transferred to well‐aerated seawater. The results are compatible with the operation of a succinate pathway of glycogen degradation during prolonged environmental anoxia in the heart, but not in the foot muscle tissue of C. concholepas.
Effects of temperature acclimation on muscle relaxation in the carp: A mechanical, biochemical, and ultrastructural study
Authors: Fleming J. R. , Crockford T. , Altringham J. D. , Johnston I. A.
Published: June 2005

Common carp (Cyprinus carpio L.) were acclimated to either 5–8°C or 20–25°C for a minimum of 1 month, and the twitch contraction kinetics of a myotomal nerve‐muscle preparation were investigated. A significant compensation for the acute effects of temperature was achieved in twitch kinetics by acclimation to 8°C. An acute drop in temperature from 20 to 8°C in preparations from warm‐acclimated fish led to approximately two‐ to three‐fold increases in the half‐times for activation and relaxation. At 8°C, values were 50% faster in 8°C‐ than in 20°C‐acclimated fish, indicating a partial capacity adaptation in rates of both twitch activation and relaxation.

The mechanisms underlying temperature compensation of twitch contraction kinetics were investigated. A quantitative ultrastructural study was performed on the sarcoplasmic reticulum (S.R.) of fast and slow myotomal muscles. No differences were found in the surface and volume densities of the S.R. in fast‐twitch fibres between cold‐ and warm‐acclimated fish. The surface densities of terminal cisternae and S.R. were higher in slow‐twitch fibres from the warm‐acclimated fish. Parvalbumin concentration in fast fibres was found to be independent of acclimation temperature (0.61–0.68 mmol/kg wet weight). Although the relative proportions of parvalbumin isoforms (I–IV) showed considerable individual variation this was not correlated with environmental temperature. The Ca2+‐ATPase activity of S.R.‐enriched microsomes prepared from fast myotomal muscle was 60% higher at 8°C in cold‐ than warm‐acclimated carp. This suggests that changes in the kinetics and/or density of Ca2+ pumps contribute to the observed capacity adaptation in relaxation rate with temperature acclimation. Other possible mechanisms underlying the plasticity of twitch contraction kinetics in carp are briefly discussed.
Oxygen reduction metabolism by the digestive gland of the common marine mussel, Mytilus edulis L.
Authors: Winston Gary W. , Livingstone David R. , Lips Franz
Published: June 2005

Partial reduction of molecular oxygen (O2) produces reactive oxygen species such as the superoxide anion radical (O−2) and H2O2. Redox cycling of iron promotes the conversion of O−2 and H2O2 to the highly reactive and potentially destructive hydroxyl radical (·OH). These processes of one‐electron metabolism of O2 were studied in digestive gland microsomes of the marine mussel, M. edulis L. by using the free radical scavengers benzoate and 2‐keto‐4‐methiolbutyric acid (KMBA) to detect ·OH. Benzoate was decarboxylated and 2‐keto‐4‐methiolbutyric acid (KMBA) was oxidized to ethylene by M. edulis microsomal electron transport (MET) in a reaction that was stimulated by ferric‐EDTA and sodium azide (an inhibitor of catalase), suggesting that H2O2 was the precursor of the oxidizing species. In contrast to previous reports on rat liver microsomes (Jewell and Winston, '89), NADH supported a two to three times higher rate of oxyradical production than did NADPH. After a 10 min lag phase, NADH‐dependent KMBA oxidation was linear up to at least 60 min. NADPH‐dependent KMBA oxidation showed no lag phase and was linear for 30–40 min. In the presence of ferric‐EDTA, NADH‐dependent KMBA oxidation was weakly inhibited by superoxide dismutase (approximately 15%) whereas NADPH‐dependent KMBA oxidation was inhibited nearly 40%. As ferrous iron is required for ·OH from H2O2, ferric iron is at least in part reduced directly by MET and to a greater extent with NADH as electron donor than with NADPH. These data show that M. edulis microsomes generate superoxide/H2O2 during MET and in the presence of ferric‐EDTA can oxidize ·OH scavengers, albeit via different mechanisms.

Cytosol accounted foremost of the oxyradical‐generating capacity of digestive gland post 9,000g supernatant. A substantial nonpyridine nucleotide‐dependent oxyradical‐generating activity was found in cytosol that was removed by G‐25 Sephadex filtration. Protective antioxidant enzymes were present in digestive gland, indicating an in vivo scenario for oxyradical production.
Fate mapping the avian epiblast with focal injections of a fluorescent‐histochemical marker: Ectodermal derivatives
Authors: Schoenwolf Gary C. , Sheard Philip
Published: June 2005

A microinjection technique is described for fate mapping the epiblast of avian embryos. It consists of injecting the epiblast of cultured blastoderms with a fluorescent‐histochemical marker, examining rhodamine fluorescence at the time of injection in living blastoderms, and assaying for horseradish peroxidase activity in histological sections obtained from the same embryos collected 24 h postinjection. Our results demonstrate that this procedure routinely marks cells, allowing their fates to be determined and prospective fate maps to be constructed. Two such maps are presented for ectodermal derivatives of the epiblast: one for late stages of Hensen's node progression (stages 3c through 4) and one for early stages of node regression (stages 4 + through 5). These new maps have six significant features. First, they show that regardless of whether the node is progressing or regressing, the flat neural plate extends at least 300 μm cranial to, 300 μm bilateral to and 1 mm caudal to the center of Hensen's node. Second, they confirm our previous fate mapping studies based on quail/chick chimeras. Namely, they show that the prenodal midline region of the epiblast forms the floor of the forebrain and the ventrolateral part of the optic vesicles as well as MHP cells (i.e., mainly wedge‐shaped neurepithelial cells contained within the median hinge point of the bending neural plate); in contrast, paranodal and postnodal regions contribute L cells (i.e., mainly spindle‐shaped neurepithelial cells constituting the lateral aspects of the neural plate). Third, they reveal a second source of MHP cells, Hensen's node, verifying previous studies of others based on tritiated thymidine labeling. Fourth, they demonstrate, in contrast to studies of others based on vital staining, carbon marking, and choriolallantoic grafting but in accordance with our previous studies based on quail/chick chimeras, that the cells contributing to the four craniocaudal subdivisions of the neural tube (i.e., forebrain, midbrain, hindbrain, and spinal cord) are not yet spatially segregated from one another at the flat neural plate stage, although more cranial neural plate cells tend to form more cranial subdivisions and more caudal cells tend to form more caudal subdivisions. Thus, single injections routinely mark multiple neural tube subdivisions. Probable reasons for the discrepancy between our present results and the previous results of others is discussed. Fifth, they suggest that cells contributing to the surface ectoderm and neural plate are not yet completely spatially segregated from one another at the flat neural plate stage, particularly in caudal postnodal regions. Sixth, they delineate the locations of the otic placodes. Therefore, the microinjection technique has contributed important new information about the avian epiblast and, in particular, about the neural plate and its subdivisions.
Sexual dimorphism in the hindlimb of Eleutherodactylus coqui: Does behavior predict morphology?
Authors: Townsend Daniel S. , Wassersug Richard J. , King V. Ann , Elder Geoffrey C. B.
Published: June 2005

Eleutherodactylus coqui differs from most other anuran amphibians in that it has internal fertilization. This requires close apposition of male and female cloacae during amplexus, achieved by a reverse hindleg clasp (RHLC) where—rather than the male clasping the female with his forelimbs, as occurs in most anurans—the female adducts her hindlimbs around the male. Since normal amplexus in anurans is associated with enlarged forelimb muscles in males of some species, we asked whether the RHLC of E. coqui was associated with enlarged hindlimb adductors in the female or with other sexually dimorphic myological specializations. Several features, such as muscle fiber number, size, type, and overall cross‐sectional area were compared between male and female adult E. coqui for two muscles essential to the RHLC and a control hindlimb muscle not used in the behavior. No sexual dimorphism was found that could be specifically related to the RHLC. While muscles in all cases were larger in the females than in the males, this was accounted for by the larger body size of females in this species.
Prey transport in the tiger salamander: Quantitative electromyography and muscle function in tetrapods
Authors: Reilly Stephen M. , Lauder George V.
Published: June 2005

A quantitative analysis of the muscle activity patterns (motor patterns) used by tiger salamanders (Ambystoma tigrinum) during terrestrial feeding is presented to provide comparative data on motor output during prey transport in amphibians, compare prey transport motor patterns to those used during initial prey capture, and test the generality of previously proposed models of the feeding cycle in tetrapods.

Simultaneous electromyographic and kinematic recordings during prey transport reveal four phases in the prey transport cycle. The Preparatory phase precedes prey transport with activity found mainly in muscles of the buccal floor (genioglossus, geniohyoideus, interhyoideus, and inter‐mandibularis), but with all muscles silent at the end of this phase. Prey transport occurs during the Fast Opening and Closing phases. The Fast Opening phase begins with near simultaneous onset of activity in all jaw and hyoid muscles, including anatomical antagonists such as the depressor mandibulae and adductor mandibulae. The subarcualis rectus one muscle is active during the Fast Opening and Closing phases of transport despite the lack of accompanying tongue projection and may function to stabilize the hyobranchial apparatus. The motor pattern of terrestrial prey transport differs considerably from that of initial prey capture, but appears to be similar to the motor pattern used during aquatic prey capture and hydraulic prey transport. We hypothesize that post‐metamorphic tiger salamanders accomplish terrestrial prey transport by retaining the larval motor pattern employed during suction feeding. The motor pattern and kinematics of prey transport in Ambystoma tigrinum differ in nearly all aspects from previous models of the generalized tetrapod feeding cycle.
Accumulation of 45Ca in the freshwater unionids Anodonta anatina and Unio tumidus, as influenced by water hardness, protons, and aluminum
Authors: Pynnönen Kirsi
Published: June 2005

Previous studies have revealed that freshwater bivalves subjected to acid stress suffer from severe electrolyte imbalance. A typical initial reaction is a transitory increase in concentration of Ca in the hemolymph during the first few days of exposure to such stress. Although this calcium obviously originates from the CaCO3 reserves in the clam, a possible ambient origin has never been ruled out. In the present study the uptake of Ca was studied under both circumneutral and acid conditions: two freshwater unionids, Anodonta anatina and Unio tumidus, were exposed to a bathing medium that contained 45Ca for a period of 24 hrs. In order to study the effect of the ambient Ca concentration on the efficiency of uptake of Ca, two media with different Ca concentrations (35 and 3.5 mg Ca/1; 4 × 106 cpm 45Ca/1 and 4 × 105 cpm 45Ca/1, respectively) were used. The role of the ingested food as a source of Ca was evaluated by feeding the clams with algae labeled with 45Ca. After the clams had been exposed for 24 hrs to 45Ca, the accumulation of 45Ca in the soft parts, including hemolymph, calcium concretions and glochidial larvae, was measured. Low pH (4–4.5) significantly decreased the uptake of 45Ca from the medium, whereas the addition of aluminum (900 μg/1) had only a minor effect on the uptake of 45Ca. The sites of accumulation of 45Ca under acidified conditions did not change: in all cases highest values for 45Ca concentration were measured in the gills, where the calcium concretions sequestered a large part of the 45Ca. A 90% decrease in the ambient Ca concentration caused a similar decrease in the uptake of 45Ca. Clams were able to utilize both dietary and waterborne Ca.
Precambrian oxygen levels, the sulfide biosystem, and the origin of the metazoa
Authors: Mangum Charlotte
Published: June 2005

The Berkner and Marshall hypothesis suggests that the atmosphere was virtually anoxic until the late Precambrian, and that the abrupt and coincidental appearance in the fossil record of the major animal phyla reflects the rise of PO2 to a level that supported animal life. In a more recent version the rise of PO2 is supposed to permit previously soft‐bodied animals, which had arisen during the anoxic period, to form fossilizable hard parts. The animal kingdom is conceived as fundamentally and primitively anaerobic and only secondarily aerobic. These ideas were incorporated into the Thiobiotic Theory, which supposes that a meiofauna endemic to the anoxic sulfide layer in marine sediments is a relict community of the pre‐normoxic Precambrian. This fauna consists of a number of simple metazoan phyla, including free‐living platyhelminths (but not cnidarians) which this theory regards as representatives of the ancestral Eumetazoa.

The development of geological and ecological thinking about these hypotheses is summarized and the pertinent physiological evidence for and against them is briefly reviewed. I conclude that the available information does not support either the Berkner and Marshall Hypothesis or the Thiobiotic Theory, and is inconclusive on the identity of the ancestral animals. Moreover, several aspects of respiratory and metabolic biology are far more consistent with a fundamentally aerobic than anaerobic way of animal life.
Vitellogenesis in Anolis pulchellus: Induction of VTG‐like protein in liver explants from male and immature lizards
Authors: Morales Magda H. , Osuna Roberto , Sánchez Eric
Published: June 2005

Vitellogenin (VTG) synthesis has been described as an ideal system to study the hormonal regulation of gene expression. In Xenopus the molecular aspects of this control have been analyzed; however, in other non‐mammalian species such as reptiles, very few studies approaching this level have been undertaken. We report on the induction by estradiol‐17β of VTG‐like proteins in liver explants from adult males and immature male and female lizards (A. pulchellus). A concentration of 10−7 M was optimum for adult males while a higher concentration (10−6 M) is required for the immature animals. No differences were observed in the hormonal induction in male and female immature animals, suggesting that there are no sexual distinctions in the liver at this stage.

The effect of the hormone in male liver appears to be primarily on mRNA synthesis, since increases in 3H‐uridine incorporation in total RNA were prevented by addition of 1 μg/ml of the RNA polmerase II inhibitor α‐Amanitin; however, rRNA synthesis was also increased as observed by agarose gel analysis. A 48 hr lag period was required for the detection of the intracellular as well as the secreted VTG‐like protein. Electrophoretical analysis of the secretory products revealed the induction of a group of phosphoproteins immunologically related to yolk lipovitellin whose molecular weights range from 116,000 to 200,000.
Regenerative capacity of forelimb buds after amputation in mouse embryos at the early‐organogenesis stage
Authors: Chan W. Y. , Lee K. K. H. , Tam P. P. L.
Published: June 2005

The ability of mouse forelimb buds at stage 1 (Wanek et al., '89a) of development to regenerate after amputation was investigated. The findings were as follows: 1. Outgrowths in the form of hillocks were found at the sites of amputation in 116 (95%) out of 122 embryos examined 24 hours after amputation. Examination of the amputated region after various intervals of time revealed that the outgrowths were established from flank tissues at the anterior and posterior borders of the wound. 2. Ectodermal thickening was found on the distal margin of the outgrowths in 21 (66%) out of 32 specimens examined. These thickenings were histologically similar to the apical ectodermal ridge (AER) present on the control limb buds. 3. Alkaline phosphatase activity was detected on the ectodermal thickening in 11 (79%) out of 14 experimental limb buds examined. The pattern of expression of alkaline phosphatase activity was similar to that observed in control limb buds. 4. There was no correlation between the size of the outgrowths and the presence of the ectodermal thickening or the enzymatic activity. The outgrowths developed despite the absence of ectodermal thickening and enzymatic activity, suggesting that the thickening and the presence of alkaline phosphatase are not crucial for the initiation and formation of the outgrowths. 5. Explants of the outgrowths, when grafted beneath adult kidney capsules, differentiated extensively into various tissues, which included bones, epiphyseal plates, skeletal muscles, and skin derivatives. Control explants also gave rise to the same spectrum of tissues. Hence, the flank tissues surrounding the site of amputation in E10 mouse embryos can regenerate to form a structure that is morphologically and histochemically similar to a limb bud and the mesenchyme within the structure is histogenetically competent to produce the variety of tissues that is normally found in the adult limb.
Specific, concentration‐dependent uptake of vitellin by the oocytes of Nereis virens (Annelida, Polychaeta) in vitro
Authors: Fischer A. , Rabien H. , Heacox A. E.
Published: June 2005

One purpose of this study was the development of methods for radioactive labeling and handling of the yolk protein of Nereis virens, another, the utilization of this tracer in nereid oocyte cultures to describe the kinetics and specificity of yolk protein uptake. Accumulation of labeled yolk protein by growing oocytes is linear over time, specific for yolk protein, and dependent on tracer concentration in the medium. Incorporation of yolk protein follows saturation kinetics which allows us to reproducibly determine the characteristics of this process. The apparent KM of ∼ 1 × 10−8 M indicates the high affinity of the transport system; the Vmax (160–400 pg protein/day × oocyte) reveals that transport of yolk protein into the nereid oocyte is very slow compared with a vertebrate system. The low Vmax corresponds to the very slow sexual maturation in this worm. Since nereid oocytes grow freely in the coelom, the experimental system described is suitable for a quantitative study of the transfer of biomass from soma to growing oocytes.
Slow locomotion in chameleons: Histochemical and ultrastructural characteristics of muscle fibers isolated from the iliofibularis muscle of Jackson's Chameleon (Chamaeleo jacksonii)
Authors: Mutungi Gabriel
Published: June 2005

The histochemical and ultrastructural characteristics of the fiber types present in the iliofibularis muscle isolated from Jackson's chameleon, Chamaeleo jacksonii, have been characterized in an attempt to explain the slow locomotion of these lizards. On the basis of their histochemical characteristics and nerve endings, four types of fibers were identified corresponding to the fast glycolytic (FG), fast oxidative glycolytic (FOG), slow oxidative (SO), and tonic fibers of other lower vertebrates. Three of these fiber types (FG, FOG, and SO) were focally innervated, and the other type (tonic fibers) multiply innervated. All the fibers isolated from the clear region and most of the fibers isolated from the yellow region had single well‐defined endplates. However, 20 to 28% of the fibers isolated from the yellow region possessed an average of 13 ± 0.6 endplates per fiber. The endplates in these fibers were poorly defined, 62 ± 2 μm in length, and 952 ± 40 μm apart. The mitochondrial volume of fibers isolated from the yellow region (8 ± 0.5%) was three times higher than that of fibers isolated from the clear region (2.45 ± 0.2%). In addition, the fibers isolated from the yellow region had three times the number of capillaries surrounding them as those recorded for fibers isolated from the clear region (1.95 ± 0.12 and 0.67 ± 0.09 capillaries per fiber, respectively). Fibers isolated from both regions had similar myofibrillar volume densities (91 ± 0.57, clear; 95 ± 0.87, yellow). © 1992 Wiley‐Liss, Inc.
Uptake of L‐ and D‐alanine by a brackish‐water Bivalve, Corbicula japonica, with special reference to their transport pathways and the salinity effect
Authors: Matsushima Osamu , Yamada Ayumu
Published: June 2005

The uptake of L‐ and D‐alanine by intact animals or isolated gills of a brackish‐water bivalve, Corbicula japonica, was investigated in relation to their transport pathways and the possible physiological roles. The animals took up L‐alanine at concentrations as low as 10 μM. Both the net transport and the influx were strongly affected by external salinity; animals acclimated to fresh water showed much lower rates of net transport and influx than did animals acclimated to 250 mOsm. Patterns of accumulation of 14C‐L‐alanine in different tissues of intact animals revealed that the gill was the principal site for the transport of the amino acid. Influx of both 14C‐L‐ and 14C‐D‐alanine into isolated gills was inhibited by α‐neutral amino acids, but not by α‐acidic or β‐amino acids; all α‐neutral amino acids examined (glycine, L‐glutamine, L‐leucine, L‐valine, and even D‐ and L‐alanine) inhibited the influx of D‐alanine more strongly than the influx of L‐alanine. Kinetic analysis of the influx indicated that D‐ and L‐alanine were transported via the same carrier(s), but that the carrier(s) had a higher affinity for L‐alanine than for D‐alanine. The transport mechanism appears to play a significant role in the net uptake of D‐ and L‐alanine or in the re‐uptake of the amino acids diffused from the integument according to the ambient concentrations of the substrates. © 1992 Wiley‐Liss, Inc.
Differential molt‐induced atrophy in the dimorphic claws of male fiddler crabs, Uca pugnax
Authors: Ismail Safaa Z. M. , Mykles Donald L.
Published: June 2005

Molt‐induced atrophy was examined in the closer muscles of the dimorphic claws of the fiddler crab, Uca pugnax. In adult males, the major claw, which is about 30 times larger than the minor claw, contains primarily S1 fibers and some S2 fibers, while the minor claw contains exclusively S2 fibers. Ultrastructurally, both S1 and S2 fibers resembled slow fibers of other crustacean species: high ratios of thin:thick myofilaments, thickened Z‐lines, and myofibrils with long sarcomeres. However, the S1 fibers had higher thin:thick myofilament ratios (9:1 vs. 6:1), longer sarcomeres (6 μm vs. 4.5–5 μm) and fewer mitochondria than the S2 fibers. During proecdysis, the muscle of the major claw underwent a greater atrophy than that of the minor claw. Furthermore, atrophy of the major claw muscle was enhanced by the number of walking legs being regenerated. The weight of the major claw muscle in animals regenerating one walking leg decreased about 50%, while that in animals regenerating eight walking legs decreased about 67%. The weight of the minor claw muscle decreased about 25% in animals regenerating either one or eight walking legs. Changes in myofibrillar cross‐sectional areas paralleled the reductions in muscle mass. In S1 fibers, cross‐sectional area decreased 43% in animals regenerating one walking leg and 78% in animals regenerating eight walking legs. In S2 fibers, cross‐sectional area decreased 27% and 32%, respectively. Increases in the thick myofilament packing density and decreases in the thin:thick myofilament and actin:myosin heavy chain ratios suggest that this atrophy involves a preferential hydrolysis of thin myofilaments. The ultrastructural changes in S2 fibers from major and minor claws were similar, suggesting that the preferential atrophy of the major claw muscle results, at least in part, from a differential sensitivity of S1 and S2 fibers to factor(s) that trigger protein degradation. © 1992 Wiley‐Liss, Inc.
In vivo magnetic resonance imaging of the blue crab, Callinectes sapidus: Effect of cadmium accumulation in tissues on proton relaxation properties
Authors: Brouwer Marius , Engel David W. , Bonaventura Joseph , Johnson G. Allan
Published: June 2005

Nuclear magnetic resonance imaging (MRI) has been used to visualize the internal anatomy of a living blue crab. The resolution obtained in these studies was sufficient to distinguish individual organs by the differences in their proton densities and proton relaxation properties. T1 (spin‐lattice relaxation time)‐weighted imaging revealed the lipid‐rich nature of the hepatopancreas and gonadal tissue. To evaluate the effect of metal‐induced stress on the different organs, crabs were exposed to elevated levels of cadmium in their diet, which resulted in increased concentrations of both cadmium and copper in the hepatopancreas. The spin‐spin relaxation time, T2, of mobile protons in the metal‐exposed tissue was significantly greater than T2 in the control tissues. These measurements suggest that the excess copper in the exposed tissues was diamagnetic [Cu(I)], since the presence of paramagnetic copper [Cu(II)] would result in a decrease of observed T2 values. We hypothesize that the increased T2 value is a reflection of increased free water in the hepatopancreas. These studies show that magnetic resonance imaging is an important nondestructive tool for the study of morphological and physiological changes that occur in marine invertebrates in response to anthropogenic and natural stresses. © 1992 Wiley‐Liss, Inc.
Diisopropylfluorophosphate inhibits acetylcholinesterase activity and disrupts somitogenesis in the Zebrafish
Authors: Hanneman Eric H.
Published: June 2005

Acetylcholinesterase (AChE) activity, localized histochemically, appeared in the nuclei of presumptive somitic mesodermal cells prior to the onset of somitogenesis. AChE activity appeared in a rostro‐caudal sequence, in cells located the equivalent of five somite lengths caudal to the last formed somite. To investigate whether AChE activity was required for somitogenesis, several inhibitors of AChE activity were tested for their ability to block somitogenesis.

Diisopropylfluorophosphate (DFP), a broad spectrum inhibitor of serine proteases and related enzymes, was the only AChE inhibitor tested that disrupted somitogenesis. Gastrulae at 50% epiboly exposed continuously to DFP at concentrations between 40 μM and 90 μM completed epiboly, but exhibited a dose‐dependent decrease in the number of somites formed, and a parallel decrease in the caudal extent of somite innervation, by 24 hours post‐fertilization (h).

Fifteen somite (15h) embryos exposed to DFP at the ED50 of 70 μM for 3 hours, followed by recovery to 24h, developed abnormal somites. Approximately five normal somites formed after drug treatment before the first abnormal somite formed. The abnormal somites corresponded in location to that area of the presumptive somitic mesoderm that would have initiated AChE activity while the DFP was present. While exposed to 70 μM DFP, presumptive somites formed and motoneurons extended processes that had initiated AChE activity at the time of treatment with DFP, although at a slower than normal rate. However, embryos exposed to 1 mM DFP for 30 minutes at both the 5 and 15 somite stages, followed by recovery to 24h, developed the normal number of somites but were reduced in the caudal extent of somite innervation, and occasionally developed abnormal primary motoneurons. As with the abnormal somites, the abnormal motoneurons would have initiated AChE activity while the DFP was present.

Presumptive somitic mesoderm unable to initiate AChE activity due to inhibition by DFP developed abnormally. While the effects of DFP are not limited to inhibiting AChE, the data support the “clock and wavefront” model proposed for somite formation, and support the hypothesis that AChE activity has a role in somitogenesis in zebrafish. © 1992 Wiley‐Liss, Inc.
Genetic linkage analysis of the murine developmental mutant velvet coat (Ve) and the distal chromosome 15 developmental genes Hox‐3.1, Rar‐g, Wnt‐1, and Krt‐2
Authors: Hart Charles P. , Compton John G. , Langley Stephen H. , Hunihan Lisa , LeClair Kenneth P. , Zelent Arthur , Roderick Thomas H. , Ruddle Frank H.
Published: June 2005

We have identified restriction fragment length polymorphisms between Mus musculus and Mus spretus for the Chromosome 15 loci Hox‐3, Wnt‐1, Krt‐2, Rar‐g, and Ly‐6. We followed the inheritance of these alleles in interspecific genetic test crosses between velvet coat (Ve) heterozygotes and M. spretus. The results suggest a gene order and recombination distances (in cM) of Ly‐6—22—Wnt‐1—2—Ve/Krt‐2/Rar‐g—3—Hox‐3. No recombination was found between Ve, Krt‐2, and Rar‐g. The data also provide evidence for the hypothesis of a large‐scale genomic duplication involving homologous gene pairs on mouse Chromosomes 15 and 11. © 1992 Wiley‐Liss, Inc.
MHC class II molecules and immunoglobulins on peripheral blood lymphocytes of the bottlenosed dolphin, Tursiops truncatus
Authors: Romano Tracy A. , Ridgway Sam H. , Quaranta Vito
Published: June 2005

The immune system of marine mammals is of comparative interest because of its adaptation to the aquatic environment. Little information, however, is available on its cellular and molecular components. Here, we used a cross‐reactive antibody to MHC class II molecules and an immunoglobulin‐specific antiserum for identifying these molecular species on lymphocytes of the bottlenosed dolphin, Tursiops truncatus. Limited structural analyses indicated that class II molecules and immunoglobulins of dolphin closely resemble those of other vertebrates. In the peripheral blood of most land mammals both class II and immunoglobulins are usually found on B but not T lymphocytes. Expression of immunoglobulins on dolphin peripheral blood lymphocytes suggests a ratio of B cells to T cells comparable to that of land mammals. However, unlike the majority of land mammals, virtually 100% of the peripheral T cells display pronounced expression of class II molecules, generally considered an indication of T cell activation. It is therefore possible that the physiology of T cell activation has unusual attributes in the dolphin. It is especially interesting that some land mammals, namely swine (ungulates) and dogs and cats (carnivores), also express class II molecules on peripheral blood T lymphocytes. Since ungulates and carnivores are thought to share a common distant ancestry with toothed whales, the evolutionary history may be more relevant than the environmental history in determining these unusual attributes. © 1992 Wiley‐Liss, Inc.
Incidents of rejection and indifference in Fu/HC incompatible protochordate colonies
Authors: Rinkevich Baruch , Weissman Irving L.
Published: June 2005

We test here for the existence of specific alloimmune memory in the rejection responses of the colonial tunicate Botryllus schlosseri. Colony specificity in these organisms is controlled by the Fu/HC locus. Rejection occurs only between colonies that do not share any allelic determinant at this locus. Two sets of experiments were conducted: 1) Forty‐nine pairs of nonfusible oozooids were interacted naturally along a period of several months. They rejected, disconnected, and in 20% of the cases, interacted again. 2) Repeated colony allorecognition assays were done on 15 pairs of interacting subclones (up to 5 consecutive tests/pair). Major results indicate: 1) Not all ampulla‐ampulla interactions resulted in necrotic areas, points of rejection (PORs). 2) A full repertoire of PORs was attained within the first 10 days. Thereafter, no more PORs were added. 3) The outcome of indifference (cases where ampulla‐ampulla contacts did not result in rejection) was repeatedly recorded in multiple tests, and its frequency increased in the secondary and tertiary tests along a set of 5 consecutive tests. It is concluded that allospecific memory, as measured by an accelerated production of PORs and amplification in their number, was not characteristic of the Botryllus rejection phenomenon, which, however, reveals the qualities of a low responder. These results are discussed in the light of some aspects of tolerance in the mammalian system. © 1992 Wiley‐Liss, Inc.
Teratogenic and morphogenetic effects of retinoic acid on the regenerating pectoral fin in zebrafish
Authors: Géraudie Jacqueline , Brulfert Annie , Monnot Marie J. , Ferretti Patrizia
Published: June 2005

Following amputation, the pectoral fin undergoes a regenerative process which leads to an apparently faithful replacement, both in shape and in size, of the missing part. However, analysis of the fin skeleton in whole mount preparations of normal and regenerated fins has revealed that fin regenerates are not perfect copies of the missing part, and that the distance and the number of ray segments between the amputation plane and the first dichotomy are higher in regenerated than in unamputated fins. This suggests that a respecification of positional values may be induced by amputation. Since retinoic acid (RA) induces duplication of structures in the regenerating amphibian limb, and affects pattern formation in the zebrafish nervous system, we have investigated whether RA could affect regeneration of the pectoral fin in zebrafish. We report that, depending on the concentration and the experimental schedule, RA can have both teratogenic (narrowing of the fin and fusion of rays) and morphogenetic (increased number of ray segments) effects on the regenerating fin, but, unlike in the amphibian limb, these effects often overlap. Furthermore, while the teratogenic effect seems to affect mainly the dorsoventral axis, the morphogenetic effect is observed on the proximodistal axis. Our work suggests that the zebrafish fin may provide another valuable model to study regeneration and pattern formation of animal appendages. © Wiley‐Liss, Inc.
The pseudoblastema in the wound healing process of the leech Hirudo medicinalis L. (Hirudinea): Changes in cell junctions
Authors: Huguet G. , Molinas M.
Published: June 2005

The role of the connective tissue cells and their migratory behavior have been investigated in the formation and evolution of the pseudoblastema during wound healing in the leech Hirudo medicinalis. In H. medicinalis the healing process shows first a flow of cells that effectively seal the wound and form a temporary cellular clump, the pseudoblastema, which contributes to the phagocytotic process and apparently regenerates the extracellular matrix. The migratory cells forming the pseudoblastema are connective tissue cells known as vasocentral cells, which, when in a resting state, are associated with the vasofibrous cells. During the formation and evolution of the pseudoblastema several changes affect vasocentral cell junctions. At rest, vasocentral cells do not show cell to cell junctions but they show adhering junctions in contact with the extracellular matrix. These junctions disrupt during the migratory phase. When vasocentral cells regroup in the pseudoblastema, adhering junctions are formed between them, and adhering junctions making contact with the matrix appear again. As the pseudoblastema evolves, cell to cell adhering junctions become more conspicuous and undergo other changes. During the next stage of retraction, close contacts develop between pseudoblastema cells and neighboring nondamaged muscle fibers, which probably serve as points of anchorage for the approaching movement of the wound edges. Finally, cell to cell and cell to matrix junctions disappear and the pseudoblastema disintegrates. © Wiley‐Liss, Inc.