bluuebunny/crossref_metadata_2025 huggingface dataset:
Amiloride inhibition of angiogenesis in vitro
Authors: Alliegro Mark C. , Alliegro Mary Anne , Cragoe Edward J. , Glaser Bert M.
Published: September 2005

Angiogenesis is important to such processes as normal embryonic development and tissue growth, and is also a central feature of diseases such as diabetic retinopathy and the growth of solid tumors. Understanding the basic events governing angiogenesis has therefore attracted great interest. The ion channel blocking agent, amiloride, has been shown to inhibit angiogenesis in an in vivo model (Lansing et al., '91). This suggested a vital role for Na+ ‐coupled transport processes in angiogenesis. A large number of structural analogues of amiloride have been synthesized (Kleyman and Cragoe, '88), and many of these are well characterized with respect to biological activity. These analogues present an opportunity to dissect the process of angiogenesis and identify potentially important physiological events. In this report we describe the effects of amiloride on an in vitro model for angiogenesis employing vascularized tissue explants. Amiloride inhibits capillary morphogenesis completely and reversibly at concentrations as low as 134 μM. It appears to act by blocking endothelial cell proliferation, but not migration. Inhibition is heightened by the introduction of hydrophobic groups on the terminal guanidino nitrogen atom, or on the 5‐amino position. An analogue substituted at both of these positions is 30‐fold more potent than the parent compound. Of amiloride's known biological activities, these results most closely correlate with the inhibition of Ca2+ transport processes, and thereby suggest an important role for Ca2+ transport in capillary morphogenesis. © 1993 Wiley‐Liss, Inc.
Infection with the avian polyomavirus, bfdv, selectively affects myofibril structure in embryonic chick ventricle cardiomyocytes
Authors: Conrad Abigail H. , Consigli Richard A. , Conrad Gary W.
Published: September 2005

Embryonic cardiomyocytes can both beat and divide. They assemble cardiac musclespecific proteins into sarcomeric myofibrils and contract. In addition, they periodically synthesize DNA, complete mitosis, disassemble sarcomeric myofibrils in the area of the mitotic spindle, assemble cytoplasmic isoform‐specific proteins into a cleavage furrow contractile ring, undergo cytokinesis, and then reform sarcomeric myofibrils in daughter cells. Little is known about how embryonic cardiomyocytes disassemble their myofibrils as they traverse the cell cycle and divide. In the present study, beating embryonic avian ventricular cardiomyocytes in primary culture were stimulated to initiate DNA synthesis without subsequent mitosis or cytokinesis by infection with the lytic avian polyomavirus, Budgerigar Fledgling Disease Virus (BFDV). Within 48 hours, infected, adherent cardiomyocytes disassemble most of their sarcomeric myofibrils, retaining cardiac myosin only in thin myofibrils with disrupted sarcomeric periodicity and in amorphous nonfibrillar pools. By 72 hours, infected cardiomyocytes contain no myofibrils and no longer react with antibodies to cardiac myosin. In contrast, infected cardiomyocytes continue to display cytoplasmic myosin localized in stress‐fiber‐like‐structures in adherent cells, or in disrupted fibers and dispersed pools in detaching cells. Infected cardiomyocytes also continue to display interphase‐like arrays of polymerized microtubules, even when rounded‐up just prior to lysis. These results suggest that polyomavirus infection may provide a useful model system for further study of the regulation of myofibrils disassembly in embryonic cardiomyocytes. © 1993 Wiley‐Liss, Inc.
Steroidogenic shift by cultured ovarian follicles of Rana dybowskii at breeding season
Authors: Ahn Ryun S. , Ko Sun K. , Bai Dong G. , Yoon Yong D. , Kwon Hyuk B.
Published: September 2005

The steroid secretory activity of cultured ovarian follicles of Rana dybowskii and the activities of relevant steroidogenic enzymes were examined during the natural hibernation period (October‐February). Enzyme activities were measured indirectly by monitoring the conversion of exogenous substrates to products by isolated follicles. Follicles were incubated for 6 h in amphibian Ringer in the presence or absence of frog pituitary homogenate (FPH, 0.1 pituitary/2 ml) and/or various steroid precursors. Progesterone (P4), 17α‐hydroxyprogesterone (17α‐OHP) or testosterone (T) secreted by the follicles into the medium were measured by RIA. In the presence of FPH, high levels of P4 were produced by follicles at the early and mid‐hibernation period (695 and 898 pg/follicle, respectively) whereas markedly elevated levels of P4 were produced during late hibernation (1,393 pg/follicle) (just prior to or breeding season, February). In contrast, high levels of T were produced by the follicles early in hibernation (1,206 pg/follicle) while negligible levels were produced in late hibernation (69 pg/follicle). Higher levels of 17α‐OHP were produced by follicles at early and mid hibernation (594 and 705 pg/follicle, respectively) than in later hibernation (221 pg/follicle). Addition of exogenous pregnenolone markedly increased P4 levels in a dose‐dependent manner when added to follicles at early and late stages of hibernation: FPH addition further enhanced conversion of pregnenolone. Similarly, addition of androstenedione (AD) increased T levels in a dose‐dependent manner by these follicles. However, following addition of exogenous P4, less 17α‐OHP was produced by follicles collected in late hibernation as compared to those collected earlier. Likewise, addition of 17α‐OHP to follicles during late hibernation produced a small increase in T accumulation while a marked increase occurred when follicles were obtained in early hibernation. Taken together, the data indicate that steroidogenesis shifts from T to P4 late in hibernation and this is probably due to decreases in 17α‐hydroxylase and C17, 20 ‐lyase activities. © 1993 Wiley‐Liss, Inc.
Serum corticosterone concentrations in immature captive whitetip reef sharks, Triaenodon obesus
Authors: Rasmussen L. E. L. , Crow Gerald L.
Published: September 2005

Serum concentrations of the steroid hormone corticosterone were monitored over a four‐year period in two male and two female immature captive whitetip reef sharks, Triaenodon obesus. Corticosterone concentrations in the serum ranged from 69–999 pg/ml (319.8 ± 31.9; n = 36) for males and 3–246 pg/ml (116.0 ± 15.1; n = 32) for females. Males had significantly higher values than females (P < 0.001). No significant difference was detected between females; however, a significant difference was observed between the two males. No seasonality was observed in corticosterone levels. Corticosterone levels in elasmobranchs are only 10% the levels of the principal glucocorticoid, 1α‐hydroxycorticosterone, but the assay is inexpensive and readily available, and, once individual ranges are established, the corticosterone concentrations have utility. Our data suggest that, after these baseline levels are established for individual sharks, long‐term monitoring of serum corticosterone in captive populations may be utilized to monitor health or, conversely, stress. © 1993 Wiley‐Liss, Inc.
A series of normal stages for development of Scyliorhinus canicula, the lesser spotted dogfish (Chondrichthyes: Scyliorhinidae)
Authors: Ballard William W. , Mellinger Jean , Lechenault Henri
Published: September 2005

By observing numerous living eggs from the lesser spotted dogfish Scyliorhinus canicula (L.) caught near Roscoff (France) and reared at recorded temperatures as they developed from first cleavage to hatching, the first reasonably complete developmental table was worked out for this classical material in vertebrate embryology. The successive stages, described and numbered from 1 to 34, correct and replace the incomplete stages A–Q proposed by Balfour (J.Anat. Physiol., 10:555–576,1876) and other even less complete series later published, and is unique in the inclusion of a timetable at 16°C. The stages can be identified, usually through the cleared eggshell wall, with naked eye or low magnification. This table of normal stages of Scyliorhinus can be adapted with slight modification to other chondrichthyan fishes. © 1993 Wiley‐Liss, Inc.
Influence of the mucin coat on the survival of rabbit and mouse embryos stored at 0°c
Authors: Kasai M. , Hiraishi M. , Nureki I. , Zhu S. E. , Sakurai T. , Machida T.
Published: September 2005

To examine the factors affecting the survival of refrigerated embryos, rabbit and mouse morulae were stored at 0°C in modified phosphate‐buffered saline (PB1) or in PB1 containing 0.75 M sucrose. Survival was defined as the ability to develop into an expanded blastocyst in culture. The data was analyzed with special reference to the presence of a mucin coat around the embryos. When rabbit morulae were stored in isotonic PB1 for 2, 4, 6, and 8 days, survival rates were 98%, 88%, 85%, and 50%, respectively. However, if the mucin coat had been removed before storage, the rates were lower (95%, 75%, 36%, and 3%, respectively). Sucrose impaired the survival of rabbit morulae irrespective of the presence of the mucin coat. Only 11% of mouse morulae survived 2 days of storage in PB1 medium, but if the medium contained sucrose, survival rates after storage for 2, 3, 4, and 5 days were higher (83%, 55%, 31%, and 7%, respectively). To provide them with a mucin coat around the zona pellucida, mouse embryos were incubated in a rabbit oviduct. Survival rates of these embryos after storage in the presence of sucrose did not decrease over 4 days of refrigeration (98–92%), and the rates after storage for 5, 6, and 7 days were 65%, 40%, and 30%, respectively; embryos that had been stored for 5 days were transferred to recipient mice, and live young were born. Agar embedding of mouse morulae did not have the same effect as the mucin coat. These results show that the rabbit embryo mucin coat can protect refrigerated embryos, but in mouse morulae, this effect was manifest only when sucrose was present in the storage medium. © 1993 Wiley‐Liss, Inc.
Initiation of the human sperm acrosome reaction by thapsigargin
Authors: Meizel Stanley , Turner Kenneth O.
Published: September 2005

Previous studies have established that the mammalian sperm acrosome reaction (AR) is dependent upon an influx of extracellular Ca2+, but the involvement of a mobilizable store of intracellular Ca2+ has not been shown. In many other cells, the endoplasmic reticulum is the site of such a Ca2+ ‐store. Here, we show that thapsigargin, a highly specific inhibitor of the endoplasmic reticulum Ca2+ ‐ATPase Ca2+ ‐pump (and thus a mobilizer of intracellular Ca2+) in other cells, can initiate the AR in capacitated human sperm. Thapsigargin at concentrations from 50–500 nM significantly increased the AR to the same extent when incubated with capacitated sperm for 1 min (assayed by indirect immunofluorescence). Transmission electron microscopy confirmed the occurrence of normal morphologyin the AR initiated by thapsigargin. Thapsigargin (200 nM) did not initiate the AR in noncapacitated sperm. Inititation of the AR by thapsigargin apparently requires an influx of Ca2+ since 1 min preincubation with the calcium channel blockers La3+ (250 μM) or Ni2+ (250 μM) prior to addition of thapsigargin completely inhibits AR‐initiation. Mobilization of an intracellular Ca2+ ‐store by thapsigargin in capacitated human sperm may lead to an influx of extracellular Ca2+ and subsequently the AR. Putative sites for thapsigargin‐sensitive intracellular Ca2+ ‐stores in human sperm include the cytoplasmic droplet, the sperm nucleus and the acrosome. © 1993 Wiley‐Liss, Inc.
Auditory receptor organs in the forelegs of Gampsocleis gratiosa (Tettigoniidae): Morphology and function of the organs in comparison to the frequency parameters of the conspecific song
Authors: Lin Yuzhen , Kalmring Klaus , Jatho Martin , Sickmann Thomas , Rössler Wolfgang
Published: September 2005

The morphology and the physiology of the auditory receptor organs in the forelegs of the tettigoniid species Gampsocleis gratiosa were investigated in detail. According to the tonotopic organization of the receptor cells of the crista acoustica in bushcrickets the threshold curves of all receptors found in the organs were correlated with the morphology of the auditory receptor cells. This was done by arranging them in relation to their frequency tuning with the receptors along the chain of cells in both organs starting proximally with the extreme low frequency cell up to the highest ultrasonic cells at the distal end of the crista acoustica.

This investigation reveals that the auditory receptor organs of Gampsocleis gratiosa possess a broard banded hearing threshold curve including very low frequency parts.

Also the conspecific stridulatory song is very broard banded with extraordinarily low frequency components. Therefore the sender and the receiver of this species‐specific communication system seem to be well adapted to each other. © 1993 wiley‐Liss, Inc.
Comparison of motor patterns in larval and adult stage of a beetle, Zophobas morio
Authors: Kutsch W. , Urbach R. , Breidbach O.
Published: September 2005

For a holometabolous insect, the beetle Zophobas morio, several motor patterns were recorded, using EMGs, for several homologous metathoracic muscles of the larval and adult stage. In the larva, most muscles are employed during walking, while in the adult, only the remotor coxae muscle (M119) will be activated during leg movements. Segmental bendings of the larva are mainly due to contractions of the dorsal longitudinal muscles. For adults, the myogenically driven thoracic flight muscles display a phase preference within the wing‐beat cycle, resulting in not only a functional but also activity‐dependent classification of wing depressor and elevator muscles. Time interval histograms of the excitatory junctional potentials (ejp's) show several peaks separated by about 20 ms, representing the wing‐beat period. Application of chlordimeform (CDM), an agonist of the neuromodulator octopamine, elicits in adults longer “flight” sequences without wing movement. During such sequences the 20 ms modulation of the ejp intervals is missing. This points to wing‐beat dependent afferences involved in patterning of the output during normal flight. Application of CDM in the larva results in a tonic activation, which shows several similarities with the adult ‘flight’ without wing‐beat. This finding suggests that the basic neuronal circuitry underlying the imago's flight is present precociously, before the dramatic reorganization of the animal during metamorphosis. © 1993 wiley‐Liss, Inc.
Cyclic postural behavior in the crayfish, Procambarus clarkii: Properties of the pattern‐initiating network
Authors: Moore Darrell , Larimer James L.
Published: September 2005

Crayfish exhibit complex cyclical adjustments in abdominal posture during certain forms of backward walking. An isolated nerve cord preparation was used to investigate the properties of the interneurons which direct this alternation of abdominal flexion and extension.

The command function for this cyclic postural behavior appears to be the domain of a distributed network of multiple pattern‐initiating interneurons: each interneuron may be viewed as a command element within a command system. The cyclic pattern may be elicited by stimulation of small axon bundles pulled from the ventrolateral margins of any of the abdominal connectives. As few as one stimulus pulse to the axon bundle can elicit a single cycle of patterned output, although more pulses are generally necessary. This suggests some convergence or amplification step in the pattern‐initiating interneurons. The amplification may be accomplished by several pattern‐initiating interneurons that are coupled to one another and converge on pattern generating circuits in each ganglion. Evidence supporting this interpretation is presented.

Experiments involving resection of the cord reveal that the pattern‐initiating signals transfer laterally across all of the abdominal ganglia, but the network contains a bias for descending signal conduction once a lateral transfer is made. This finding agrees with other results. For example, recordings from pattern‐initiating axon bundles at rostral and caudal locations in the abdominal nerve cord show several descending but only one ascending unit activated during cyclic pattern generation.

We also show that an isolated ganglion is capable of producing the cyclic motor program, although the outputs are much weaker than those elicited in the intact abdominal cord. Therefore, the pattern‐initiating system is both central and distributed. © 1993 wiley‐Liss, Inc.
Hepatic extraction of circulating insulin and glucagon in brown trout (Salmo trutta fario) after glucose and arginine injection
Authors: Carneiro N. M. , Navarro I. , Gutiérrez J. , Plisetskaya E. M.
Published: September 2005

To investigate whether nutritional state and induced changes of plasma hormone levels may affect hepatic extraction of hormones, plasma levels of insulin and glucagon were measured in the portal vein, hepatic vein, and caudal vessel of brown trout, Salmo trutta fario. In spring, when fish were actively feeding, glucose (30 mg/100 g weight) injection was followed by a decrease in glucagon presented to the liver (11.7 ng/min vs. 34.3 ng/min) and in hepatic extraction of glucagon. As a result, systemic glucagon concentration remained unchanged. High circulation levels of insulin and its hepatic uptake remained unaffected by glucose. In autumn, when maturing fish were fasting, their systemic plasma insulin levels decreased from 6.9 ng/ml to 1.8 ng/ml. Injected glucose increased both insulin quantity presented to the liver (81.3 ng/min vs. 43.6 ng/min) and systemic concentration of insulin (4.0 ng/ml vs. 1.8 ng/ml). Glucagon levels and hepatic extraction of insulin and glucagon remained unchanged after glucose injection. Injection of arginine (139 mg/100 g) elevated plasma circulating levels of both peptides. However, their hepatic extraction (especially the extraction of glucagon) decreased as compared to the control fish. This resulted in very high levels of insulin (>20 ng/ml) and glucagon (3.8 ng/ml) in the systemic circulation of arginine‐treated trout. We conclude that hepatic uptake of pancreatic hormones in fish is a dynamic process depending on experimental as well as nutritional conditions. © 1993 wiley‐Liss, Inc.
Effects of ions and bioactive substances on ovarian contraction in Fundulus heteroclitus
Authors: Leonard Jill B. K. , Bartley Susan M. , Taylor Malcolm H.
Published: September 2005

The effects of potassium, calcium, angiotensin II, urotensin II, melatonin, gonadotropin releasing hormone analogue (GnRH‐a), and human chorionic gonadotropin (hCG) on in vitro ovarian smooth muscle contraction were observed in Fundulus heteroclitus. Calcium induced contractions and modified spontaneous contractions in a dose‐dependent manner. Potassium, angiotensin II and urotension II induced dose‐dependent contractions while melatonin, GnRH‐a and HCG had no observable effect on the system. These data highlight the integral role of calicum in ovarian contraction and suggest possible roles in reproduction for angiotensin II and urotensin II. © 1993 wiley‐Liss, Inc.
Purification and properties of the fatty acid‐binding VHDL from the hemolymph of the spider Eurypelma californicum
Authors: Stratakis Emmanoel , Fragkiadakis Georgios , Tentes Ioannis
Published: September 2005

An abundant, very high density lipoprotein (VHDL) was isolated from the hemolymph of male and female tarantula Eurypelma californicum. The purification procedure involved density gradient ultracentrifugation and gel permeation chromatography on Bio‐Gel A‐1.5m. The tarantula VHDL has a hydrated density of 1.23 gml−1 and contains 16.5% lipids. The native molecular mass determined by pore limit electrophoresis and gel permeation chromatography was 380 kDa, which differs from the molecular mass calculated for its SDS‐PAGE subunits (110 and 95 kDa, plus 16.5% lipids). The tetrameric structure of the VHDL is discussed. Both the 110 and the 95 kDa subunit are glycosylated, containing 1.8% carbohydrate, indicating that the difference in molecular mass between them is not due to the level of glycosylation. Treatment of VHDL with reducing agents (β‐mercaptoethanol) decreased the apparent molecular mass of the 110 kDa subunit, while the 95 kDa subunit was not affected, indicating the presence of intra‐molecular disulfide bonds in the 110 kDa subunit. Indeed, cyst(e)ine analysis showed that the molecule contains five disulfide bonds persubunit. Both subunits are antigenically similar, as demonstrated by immunoblotting. Amino acid analysis showed that the VHDL has a relatively high aromatic amino acid content, tyrosine, and phenylalanine (14.5%). Phospholipids (46%) and free fatty acids (35%) were the major lipid components of the VHDL, indicating that this protein is the principal free fatty acid carrier in the hemolymph. The capacity of the purified VHDL to accept free fatty acids from the hepatopancreas was demonstrated in vitro. Phosphatidylcholine (60%) and phosphatidylethanolamine (14%) were the predominant phospholipids. The possible multiple role of tarantula VHDL in carrying fatty acids and carbonic anhydrase is discussed. Fatty acid analysis showed that the fatty acids and non‐polar lipids predominantly contain saturated fatty acids, whereas the phospholipids contain unsaturated fatty acids. © 1993 wiley‐Liss, Inc.
Regulation of mealworm fat body glucose metabolism in vitro: Effects of natural and synthetic catabolic neurohormones
Authors: Mtioui A. , Moreau R. , Bahjou A. , Gourdoux L.
Published: September 2005

Glucose metabolism by Tenebrio molitor larval fat body tissue was studied in vitro by means of a microradiorespirometric method and the effects of either natural or synthetic catbolic hormones were evaluated.

The use of this microradiorespirometric method allowed us to measure glucose catabolism in small pieces of tissue with good sensitivity.

The metabolic modifications (relative and absolute) induced in the activities of the pentose cycle and glycolysis‐Krebs cycle, by larval mealworm Corpora cardiaca (CC) purified extracts, were compared with those produced by synthetic locust AKH I and mammalian glucagon. These metabolic variations were evaluated by measuring total CO2 and by using either [1‐14C]glucose or [6‐14C]glucose molecules as substrates. The kinetics of 14CO2 production and the dose‐response curves of hormones were determined.

The total expired CO2 increases significantly (17–26%) during treatment with all of the hormones studied.

Modifications to the kinetics of the specific radioactivity and the cumulative yields of 14CO2 derived from [1‐14C]glucose and [6‐14C]glucose under the influence of each of the hormones were recorded. CC extracts and AKH I rapidly (15 min) diverted glucose from pentose cycle (−45%); glucose oxidation was increased (+ 26%), this effect appearing later (75 min). Mammalian glucagon rapidly and durably increased glucose catabolism both via the pentose cycle (+35%) and by the glycolytic pathway (+ 200%).
Association of pigmentary organelles, carotenoid droplets, with endoplasmic reticulum in goldfish xanthophores and swordtail fish erythrophores
Authors: Kimler Victoria A. , Tchen T. T. , Taylor John D.
Published: September 2005

A modified procedure for whole mount transmission electron microscopy (WMTEM) was utilized, for electron microscopes with accelerating voltages of 80 to 100 kV, to view the outer 40% of goldfish (Carassius auratus [Linneaus]) xanthophores and swordtail fish (Xiphophorus hellerii [Heckel]) erythrophores. This viewing region covers most of the lamellae and all of the filopodia and cellular processes. In this region one can observe three of the four physiological states: pigment dispersing, pigment fully dispersed, and pigment aggregating. The pigment in the fourth state, fully aggregated, cannot be viewed because of thickness of the cell body and is not addressed in this report. In goldfish xanthophores and swordtail fish erythrophores, the primary pigmentary organelle, the carotenoid droplet, is not a discrete organelle but is either associated with or attached to an extended tubulovesicular structure. Carotenoid droplet translocations appear to be dependent upon external cues which result in the elongation or retraction of these tubulovesicular structures. Tubulovesicular structures are continous with membranous sacs, which we termed carotenoid bodies. Based upon DiOC6(3) staining for the endoplasmic reticulum, we propose that the tubulovesicular structure and the endoplasmic reticulum are the same organelles. By using inhibitors of microfilaments (cytochalasin B or D) and microtubules (nocodazole), we report results which suggest cytoskeletal involvement in the elongation or retraction of endoplasmic reticular cisternae. Results with the intermediate filament inhibitor, cycloheximide, demonstrated that intermediate filaments were eliminated from the cells. We believe that the results are inconclusive because cycloheximide primarily inhibits protein synthesis and any interpretation must be made with care. © 1993 wiley‐Liss, Inc.
Effect of melatonin on pituitary secretion of prolactin in vitro during delayed implantation and the periimplantation period in the spotted skunk
Authors: Rozell Marcia D. , Mead Rodney A.
Published: September 2005

The pars tuberalis of the western spotted skunk is the only region of the brain known to bind 2‐[125I]iodomelatonin, thus suggesting that this region of the pituitary might be essential in mediating the effects of melatonin in this species. Female skunks were killed during short‐and long‐day photoperiods. Hemisections of the adenohypophysis, with and without the pars tuberalis were cultured in the presence and absence of 10 nM melatonin to determine whether the pars tuberalis mediates the previously observed suppressive effects of melatonin on the seasonal increase in plasma prolactin leves in this species. Pituitaries obtained during long‐day photoperiods secreted significantly more prolactin than those obtained during the short‐day photoperiod. Melatonin had no effect on pituitary response to gonadotropin releasing hormone and failed to inhibit prolactin secretion during the 48 h culture period. However, melatonin significantly reduced the inhibitory effects of dopamine on prolactin secretion. The latter response was observed in both photoperiods and in the presence and absence of the pars tuberalis. These results suggest that the pars tuberalis does not mediate the inhibitory effect of melatonin on prolactin secretion in the absence of the hypothalamus. © 1993 wiley‐Liss, Inc.
Development of collared lemmings, Dicrostonyx groenlandicus, is influenced by pre‐ and postweaning photoperiods
Authors: Nagy Tim R. , Gower Barbara A. , Stetson Milton H.
Published: September 2005

We examined the role of pre‐ and postweaning photoperiod on postweaning development of collared lemmings. Lemmings were gestated and reared to weaning (19 days of age) in one of three photoperiods: 22L:2D (22 hr of light:2 hr of dark), 16L:8D, and 8L:16D. At weaning, lemmings were either maintained in their natal photoperiod or transferred to one of the other two photoperiods. At the termination of the experiment (10 weeks postweaning) data were collected on somatic characters (body weight, bifid claw width, pelage stage, and guard hair length), serum prolactin (PRL), and reproductive parameters (testes, seminal vesicle, and uterine weights). Somatic characters were predominately influenced by postweaning photoperiod, when that photoperiod was either long (22L:2D) or short (8L:16D). When lemmings were exposed to an intermediate postweaning photoperiod (16L:8D), development of somatic characters was significantly influenced by the preweaning photoperiod; animals reared in 8L:16D regarded 16L:8D as a long day, whereas those reared in 22L:2D regarded 16L:8D as a short day. Serum PRL responded to photoperiod changes, often reflecting either the increase or decrease in day length, rather than simply the absolute number of light hours per day. Whereas reproductive indices in both sexes were stimulated by transfer from short to long photoperiod, chronic exposure to long photoperiod inhibited male development. No other photoperiod manipulations significantly influenced reproductive parameters. These observations suggest that, in the collared lemming, the neural and/or humoral factors regulating somatic and reproductive characters differ in their response to photoperiod. These results also suggest that the postweaning responses to photoperiod are programmed by earlier (gestational and/or neonatal) photoperiod exposure of the mother and/or the neonates. © 1993 wiley‐Liss, Inc.
Acquisition of maturational competence in in vitro grown mouse oocytes
Authors: Hirao Yuji , Miyano Takashi , Kato Seishiro
Published: September 2005

The maturational competence of the in vitro grown mouse oocytes of various sizes was examined, and was compared to that of oocytes of equivalent chronological age which grew in vivo. Oocyte‐granulosa cell complexes isolated from 10‐day‐old female mice were cultured for 10 days in vitro in the presence of 2 mM hypoxanthine to maintain the meiotic arrest. When the in vitro grown oocytes were denuded and cultured for further 24 h in the hypoxanthine‐free medium, 9, 37, and 100% of oocytes of 60–64.5, 65–69.5, and over 70 μm in diameter underwent germinal vesicle breakdown (GVBD), respectively. Of those oocytes which underwent GVBD, 19, 37 and 68% of oocytes larger than 60, 65, and 70 μm progressed to metaphase II, respectively. No oocyte less than 60 μm resumed meiosis. The parallelism found in the oocyte size and maturational competence was similar to that of their in vivo counterparts collected from 20‐day‐old mice. A significant proportion of the in vitro grown oocytes, however, formed a pronucleus‐like structure(s) after maturation culture, indicating that they could not maintain a normal arrest at metaphase II. © 1993 wiley‐Liss, Inc.
Hemocyte differentiation in the shore crab (Carcinus maenas) could be accompanied by a loss of glycogenosynthesis capability
Authors: Loret Suzanne M.
Published: September 2005

Hemocytes of the shore crab (C. maenas) were tested for their capability to store glucose, by measurements of the glucose phosphorylating activity. The properties of this hexokinase did not reflect any hepatic role of blood cells for carbohydrate storage, since this kinase seemed not to act as a glucose sensor. Moreover, these cells did not release their glycogen in vitro, even in the presence of CHH (crustacean hyperglycemic hormone). These observations led us to reject the hypothesis considering crustacean blood cells as “circulating hepatocytes.”

A study on separated hemocyte populations for their glycogen content and their ability to synthesize the polysaccharide in vitro provided preliminary results arguing for the connection of the three types of blood cells in a unique cell line. © 1993 wiley‐Liss, Inc.
Horseshoe crab sperm contain a unique isoform of arginine kinase that is present in midpiece and flagellum
Authors: Strong S. J. , Ellington W. R.
Published: September 2005

Spermatozoa of the horseshoe crab, Limulus polyphemus, contained high activities of arginine kinase (AK), the bulk of which was completely solubilized in buffer lacking detergent. Sperm AK, along with the fast isoform of muscle AK, were purified to homogeneity. Sperm AK had similar electrophoretic mobility on cellulose acetate to that of muscle AK. In contrast, sperm AK ran somewhat slower than muscle AK on SDS‐PAGE, indicating that this protein has a higher relative molecular mass (44 kD vs. 41 kD). These two forms also showed different chromatographic behavior on a reverse‐phase HPLC column. Peptide maps of cyanogen bromide cleavage fragments of sperm and muscle AK showed distinct differences. Collectively, these data suggest that the sperm of L. polyphemus contain a unique AK isoform. Polyclonal anti‐muscle AK antibodies, which showed strong reactivity against sperm AK, were used to localize AK in sperm. Both indirect immunofluorescence and immunogold transmission electron microscopy showed that AK was present in the midpiece in the vicinity of the mitochondria and also along the length of the flagellum. Given the polarized geometry of these cells, it appears that the AK reaction may play a role in high energy phosphate transport to dynein ATPases in the flagellum. © 1993 Wiley‐Liss, Inc.
Different distribution of epidermal basal cells in the anuran larval skin correlates with the skin's region‐specific fate at metamorphosis
Authors: Izutsu Yumi , Kaiho Masayoshi , Yoshizato Katsutoshi
Published: September 2005

The epidermis of the body skin in anurans undergoes a metamorphic fate different from that of the tail skin. The former survives metamorphosis and is transformed into the adult type, while the latter is subject to apoptosis. In a search for an explanation for this regional specificity at the cellular level, the epidermis of tadpoles of the bullfrog, Rana catesbeiana, was characterized histologically and immunohistochemically during metamorphosis and was compared between the body and the tail. No histological difference in the epidermis was apparent between the two tissues at stages I and II defined by Taylor and Kollros (Anatomical Record94:7–23, 1946). A clear difference was first noticed at late stage III with respect to basal cells, which are thought to be the progenitor cells of the germinative basal cells of the adult‐type epidermis: basal cells appeared at this stage in the body but not in the tail. At stage X, about 22% of epidermal cells were basal cells in the body, whereas there were still no basal cells in the tail. However, we present histological evidence for the presence of adult‐type cells in the tail at the late stages of climax. Weak but consistent expression of adult antigens in the tail skin was also demonstrated immunohistochemically with antibodies against human blood group A antigen, which cross‐react with an epitope present in adult‐type epidermal cells. We conclude that even the tail epidermis, a larva‐specific tissue, contains a population of cells that can differentiate into adult‐type cells. The different distribution of basal cells between the body and the tail epidermis closely correlates with the difference in metamorphic fate between the two tissues. © 1993 Wiley‐Liss, Inc.
In vitro spontaneous cytotoxic activity against mammalian target cells by the hemocytes of the solitary ascidian, Ciona intestinalis
Authors: Peddie Clare M. , Smith Valerie J.
Published: September 2005

Blood cell‐mediated cytotoxic activity against mammalian target cells by the hemocytes of the solitary ascidian Ciona intestinalis was investigated in vitro by fluorochromasia. Salt‐conditioned target cells were labeled with carboxyfluorescein diacetate and challenged with mixed and separated hemocytes. The assay provided optimal conditions for the functioning of the effector hemocytes while maintaining low background leakage from the target cells. Comparison of different hemocyte populations, separated by density gradient centrifugation, revealed that only cell bands containing the phagocytic and nonphagocytic amoebocytes exhibited cytotoxicity. Experiments to characterize cytolysis demonstrated that activity increased with the effector to target cell ratio, occurred within 15 min, and was maximal at an incubation temperature of 20°C. Both human (K562) and mouse [YAC‐1, P815, WEHI (3B) and L929] target cell lines were killed by the ascidian effector hemocytes. This paper demonstrates a population of nonspecific cytotoxic effector cells in the blood of C. intestinalis that are able to spontaneously kill a range of mammalian targets in vitro. © 1993 Wiley‐Liss, Inc.
Deficiency indices and spectral theory of third order differential operators on the half line
Authors: Behncke Horst , Hinton Don
Published: September 2005

We investigate the spectral theory of a general third order formally symmetric differential expression of the form

acting in the Hilbert space ℒ︁2w (a ,∞). A Kummer–Liouville transformation is introduced which produces a differential operator unitarily equivalent to L . By means of the Kummer–Liouville transformation and asymptotic integration, the asymptotic solutions of L [y ] = zy are found. From the asymptotic integration, the deficiency indices are found for the minimal operator associated with L . For a class of operators with deficiency index (2, 2), it is further proved that almost all selfadjoint extensions of the minimal operator have a discrete spectrum which is necessarily unbounded below. There are however also operators with continuous spectrum. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sturm–Liouville problems with singular non‐selfadjoint boundary conditions
Authors: Eberhard Walter , Freiling Gerhard , Zettl Anton
Published: September 2005

Singular boundary conditions are formulated for non‐selfadjoint Sturm–Liouville problems which are limitcircle in a very general sense. The characteristic determinant is constructed and it is shown that it can be used to extend the Birkhoff theory for so called “Birkhoff regular boundary conditions” to the singular case. This is illustrated for a class of singular Birkhoff‐regular problems; in particular we prove for this class an asymptotic formula for the eigenvalues and an expansion theorem. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A glimpse into the life and times of F. V. Atkinson
Authors: Mingarelli Angelo B.
Published: September 2005

We review the life and scientific work of F. V. Atkinson, mathematician. The article consists of a brief overview of his academic and professional life followed by an extensive compilation of his life's work, some unpublished. He is best remembered for his contributions to Number Theory (mean value theorems for the Riemann zetafunction on the critical line), his work in operator theory (index theorems for abstract Fredholm operators), and his seminal work in many areas of differential equations (multiparameter spectral theory, Sturm–Liouville theory, asymptotics, etc.). (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Best Sobolev constants and quasi‐linear elliptic equations with critical growth on spheres
Authors: Bandle C. , Peletier L. A. , Stingelin S.
Published: September 2005

Sharp existence and nonexistence results for positive solutions of quasilinear elliptic equations with critical growth in geodesic balls on spheres are established. The arguments are based on Pohozaev type identities and asymptotic estimates for Emden–Fowler type equations. By means of spherical symmetrization and the concentration‐compactness principle existence and nonexistence results for general domains on spheres are obtained. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Counting eigenvalues of biharmonic operators with magnetic fields
Authors: Evans W. D. , Lewis R. T.
Published: September 2005

An analysis is given of the spectral properties of perturbations of the magnetic bi‐harmonic operator Δ2A in L 2(Rn ), n = 2, 3, 4, where A is a magnetic vector potential of Aharonov–Bohm type, and bounds for the number of negative eigenvalues are established. Key elements of the proofs are newly derived Rellich inequalities for Δ2A which are shown to have a bearing on the limiting cases of embedding theorems for Sobolev spaces H 2(Rn ). (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Additional spectral properties of the fourth‐order Bessel‐type differential equation
Authors: Everitt W. N. , Kalf H. , Littlejohn L. L. , Markett C.
Published: September 2005

This paper discusses the spectral properties of the self‐adjoint differential operator generated by the fourth‐order Bessel‐type differential expression, as defined by Everitt and Markett in 1994, in a Lebesgue–Stieltjes Hilbert function space. This space involves functions defined on the real line; the Lebesgue–Stieltjes measure is locally absolutely continuous on the real line, with the origin removed; the origin itself has strictly positive measure. It is shown that there is a unique such self‐adjoint operator; this operator has no eigenvalues but has a continuous spectrum on the positive half‐line of the spectral plane. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A non‐standard multiparameter eigenvalue problem in ordinary differential equations
Authors: Faierman M. , Mennicken R.
Published: September 2005

We consider two simultaneous Sturm–Liouville systems involving three spectral parameters. However unlike the standard multiparameter problem, we now suppose that the principal part of each of the differential operators involved is multiplied by a different parameter. For such a non‐standard system we establish the oscillation theory and discuss the associated eigenfunction expansion. Some open problems concerning the eigenfunction expansion are also presented. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Inverse problems for differential operators with singular boundary conditions
Authors: Freiling Gerhard , Yurko Vjacheslav
Published: September 2005

Singular boundary conditions are formulated for Sturm–Liouville operators having singularities and turning points at the end‐points of the interval. For boundary‐value problems with singular boundary conditions, inverse problems of spectral analysis are studied. We give formulations of the inverse problems both for the case of separated and non‐separated singular boundary conditions. For each class of inverse problems we prove a uniqueness theorem and give a procedure for constructing the solution of the inverse problem. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Limits of zeros of orthogonal polynomials on the circle
Authors: Simon Barry , Totik Vilmos
Published: September 2005

We prove that there is a universal measure on the unit circle such that any probability measure on the unit disk is the limit distribution of some subsequence of the corresponding orthogonal polynomials. This follows from an extension of a result of Alfaro and Vigil (which answered a question of P. Turán): namely, for n < N , one can freely prescribe the n ‐th polynomial and N – n zeros of the N ‐th one. We shall also describe all possible limit sets of zeros within the unit disk. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Two perspectives on reduction of ordinary differential equations
Authors: Zagaris Antonios , Kaper Hans G. , Kaper Tasso J.
Published: September 2005

This article is concerned with general nonlinear evolution equations x ′ = g (x ) in RN involving multiple time scales, where fast dynamics take the orbits close to an invariant low‐dimensional manifold and slow dynamics take over as the state approaches the manifold. Reduction techniques offer a systematic way to identify the slow manifold and reduce the original equation to an autonomous equation on the slow manifold. The focus in this article is on two particular reduction techniques, namely, computational singular perturbation (CSP) proposed by Lam and Goussis [Twenty‐Second Symposium (International) on Combustion, The University of Washington, Seattle, Washington, August 14–19, 1988 (The Combustion Institute, Pittsburgh, 1988), pp. 931–941] and the zero‐derivative principle (ZDP) proposed recently by Gear and Kevrekidis [Constraint‐defined manifolds: A legacy‐code approach to low‐dimensional computation, SIAM J. Sci. Comput., to appear]. It is shown that the tangent bundle to the state space offers a unifying framework for CSP and ZDP. Both techniques generate coordinate systems in the tangent bundle that are natural for the approximation of the slow manifold. Viewed from this more general perspective, both CSP and ZDP generate, at each iteration, approximate normal forms for the system under examination. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Friedrichs extension and essential spectrum of systems of differential operators of mixed order
Authors: Kusche Tobias , Mennicken Reinhard , Möller Manfred
Published: September 2005

A general construction for the Friedrichs extension of symmetric semi‐bounded block operators

with not necessarily bounded entries, acting in the product of Hilbert spaces has been given by Konstantinov and Mennicken via the form

There the entry A was assumed to be essentially self‐adjoint. Here it will be shown that the result remains true if A is only symmetric and that the closability of γμ follows from the semiboundedness of L 0. This will be applied to a 2 × 2 system of singular mixed‐order differential equations satisfying the quasi‐regularity condition, thus enabling us to give a much simpler calculation for the essential spectrum than in papers by Hardt, Mennicken, Naboko and Faierman, Mennicken, Möller, respectively, for a related 3 × 3‐system. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Proton Conducting Polysulfone Ionomers Carrying Sulfoaryloxybenzoyl Side Chains
Authors: Lafitte Benoît , Puchner Mario , Jannasch Patric
Published: September 2005

Summary: Novel proton conducting ionomers have been prepared by attaching pendant sulfonated aromatic side chains to polysulfone. Lithiated polysulfone was first reacted with 4‐fluorobenzoic acid chloride to introduce 4‐fluorobenzoyl side chains to the polymer main chain. Next, the activated fluoro groups were replaced by 4‐sulfophenoxy or 7‐sulfo‐2‐naphthoxy in a potassium carbonate‐mediated nucleophilic substitution reaction. This reaction proceeded under full conversion and the degree of substitution was easily controlled by the degree of lithiation in the first step. Membranes based on ionomers carrying one sulfophenoxybenzoyl unit per polymer repeat unit reached a proton conductivity exceeding 30 mS · cm−1 at 120 °C under immersed conditions.

Structures of sulfophenoxybenzoyl polysulfone and sulfonaphthoxybenzoyl polysulfone.

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Structures of sulfophenoxybenzoyl polysulfone and sulfonaphthoxybenzoyl polysulfone.
Thermal Properties of Aromatic Polycarbonates Copolymers Based on Bisphenol A and Tetramethyl Bisphenol A
Authors: Penco Maurizio , Sartore Luciana , Della Sciucca Stefania , Di Ladro Luca , Grassia Luigi , D'Amore Alberto
Published: September 2005

Statistical copolycarbonates containing different bisphenol A/tetramethyl bisphenol A (BPA/TMBPA) molar ratios were synthesized by polycondensation reaction between a mixture of the two bisphenols and phosgene. The reaction conditions were selected for producing polymers having comparable molecular weights (M̄n≈9000 g/mol) but different composition, and the same composition but different molecular weights.

The calorimetric properties of the products were investigated by differential scanning calorimetry (DSC) and dynamical‐mechanical thermal analysis (DMTA). In particular, the effect of the copolymers molecular characteristics on the glass transition temperature (Tg) and the related relaxation processes were studied.

DMTA was employed for evaluating the effect of macromolecular structure on the γ low temperature relaxation peak.
Single Drop Dynamics under Shearing Flow in Systems with a Viscoelastic Phase
Authors: Sibillo Vincenzo , Guido Stefano , Greco Francesco , Maffettone Pier Luca
Published: September 2005

In this article, we discuss the dynamics of a single drop immersed in an immiscible liquid, under an imposed shear flow. The two situations of a viscoelastic matrix with a Newtonian drop and of a viscoelastic drop in a Newtonian matrix are considered, both systems being characterized by a viscosity ratio equal to one, and by the same elasticity parameter. Experimental data are taken with a rheo‐optical computer‐assisted shearing device, allowing for drop observation from the vorticity direction of the shear flow. Data favourably compare with predictions of the recently proposed Maffettone‐Greco model, where the drop is described as a deforming ellipsoid.