bluuebunny/crossref_metadata_2025 huggingface dataset:
Spermatogenesis in the mexican axolotl, Ambystoma mexicanum
Authors: Miltner Mary Jane , Armstrong John B.
Published: June 2005

Tritiated‐thymidine autoradiography was used to follow the progress of cells through spermatogenesis in the axolotl, Ambystoma mexicanum. Results indicate that, at 18°C, the most rapidly maturing germ cells spend 5 days in leptotene, 5 days in zygotene, 22 days in pachytene, 1 day in diplotene, 6 days completing meiosis I, 10 days as secondary spermatocytes, and about 12 days in spermiogenesis. In these laboratory bred and raised urodeles, mature sperm spend an additional 60 days in the testes before the first label appears in spermatophores. The data suggest that, at least for some animals, there is minimal storage of mature sperm in the vas deferens. Cyst counts on longitudinal sections through the testes revealed large differences in the proportion of cells at different stages in animals examined during the same season. The results show that spermatogenesis passes through the testes of each animal in a wave that, however, is not coordinated with that of other animals in the colony. The overall timing of spermatogenesis is consistent with the results of mutagenesis studies with the alkylating agent, EMS. EMS reacts preferentially with late spermatids and a dominant lethal effect is seen about 60 days after the mutagen treatment, corresponding to the time interval between late spermatids and mature sperm ready to be laid in spermatophores.
Hydrostatic pressure inhibition of hormone‐induced resumption of meiotic maturation in isolated oocytes
Authors: Cloud J. G.
Published: June 2005

Prior to ovulation, fully grown oocytes of both the amphibian (Rana pipiens) and the starfish (Piaster ochraceus), like those of many other organisms, are arrested in late prophase I of meiosis. Reinitiation of meiotic maturation in oocytes from either of these organisms is hormonally induced. Although the meiosis‐inducing substance (MIS) for each organism is chemically dissimilar (a steroid in the frog and a purine in the starfish) induction of oocyte maturation in both biological systems appears to be initiated by the interaction of the MIS with the plasma membrane of the oocyte. The objective of this investigation was to determine if elevated hydrostatic pressure affected hormonal induction of oocyte maturation and to compare the effect of pressure on oocytes stimulated with different meiosis‐inducing substances. In isolated oocytes from either the frog or the starfish, increasing ambient pressure reduced the percentage of oocytes which matured, and a stepwise increase in pressure resulted in a corresponding shift in the dose response curves of hormone‐induced, oocyte maturation to the right. In experiments using only starfish oocytes, this inhibitory effect of pressure was found to be reversible and limited to the initial period of the maturation event. Taken together, these data suggest that elevated ambient pressure inhibits an early cellular event in the hormonal induction of meiotic maturation which is common to both amphibian and starfish oocytes.
The extent of intracellular acidification during anoxia in the catch muscles of two bivalve molluscs
Authors: Ellington W. Ross
Published: June 2005

Intracellular pH (pHi) changes during anoxia in in vitro preparations of the posterior adductor muscle of the blue mussel Mytilus edulis and the byssus retractor muscle of the ribbed mussel Geukensia demissa were observed using phosphorus nuclear magnetic resonance spectrometry. During 12 h of experimental anoxia, the pHi in M. edulis muscles fell from 6.96 to 6.70. Over the same time period, the pHi in G. demissa muscle fell from 6.95 to 6.56. The relatively small degree of intracellular acidification probably reflects low rates of anaerobic energy metabolism in these muscles. However, the degree of pHi change may be sufficient to have important regulatory effects on energy metabolism in catch muscle.
Protrusive activity, mode and rate of locomotion, and pattern of adhesion of Fundulus deep cells during gastrulation
Authors: Trinkaus J. P. , Erickson C. A.
Published: June 2005

The mechanism of locomotion of deep cells of Fundulus heteroclitus was studied in vivo during gastrulation with the aid of time‐lapse cinemicrography (Nomarski differential interference contrast optics), scanning electron microscopy of cells known to be moving at the time of fixation, and cell culture. These are our findings: (1) Deep cells usually move rapidly, at about 10–15 μm/min, regardless of whether they move by blebbing or spreading. Evidence suggests that this high speed is associated with weak adhesion of the trailing edge: it remains rounded, without large retraction fibers, and it advances continuously with advance of the leading edge, not sporadically, as it would if it adhered strongly. (2) In contrast, when stationary cells in close contact separate, they remain connected at first by large retraction fibers, suggesting strong punctate adhesions. (3) Fundulus deep cells appear to move in two ways: a) protrusion of blebs, followed by much cytoplasmic flow; b) spreading of lamellipodia, preceded by filopodia and frequent cell shortening. Locomotion by shortening of a long lobopodium is really a form of spreading movement, since the tip of a lobopodium always spreads. (4) Filopodia were not found except at the leading edge of a spreading lamellipodium and often spread themselves; perhaps filopodia and lamellipodia are interconvertible. (5) A lamellipodial margin may form undulations in vivo that move backward like ruffles in vitro. (6) At all times, whether stationary or moving, the surface of any given deep cell is smooth, raising unanswered questions concerning the source of surface for their rapid protrusive activity.
Prostaglandins and preovulatory follicular maturation in mice
Authors: Downs Stephen M. , Longo Frank J.
Published: June 2005

Experiments have been carried out in an effort to reverse the indomethacin‐induced inhibition of preovulatory follicular development in immature superovulated mice utilizing prostaglandins E2 and F2α. All mice were primed with 5 IU pregnant mare's serum gonadotropin followed 40 h later by 80 IU luteinizing hormone (LH). Animals were sacrificed 10½ or 11½–12 h post‐LH, at which time ovaries were fixed and prepared for microscopic observation. Control mice receiving both indomethacin and prostaglandin (PG) vehicles averaged 92% germinal vesicle breakdown, and 82% of maturing oocytes were surrounded by an expanded cumulus oophorus. Ovarian weight increased by 29% and the apical walls of preovulatory follicles demonstrated appreciable thinning following LH administration. In mice receiving indomethacin plus PG vehicle, follicular maturation was suppressed in a dose dependent manner; in mice receiving 10 mg/kg, less than 50% of the oocytes resumed meiosis and, of these, only 9% were accompanied by cumulus expansion. Ovarian weight gain was also inhibited, and the apical follicle wall exhibited few signs of preovulatory thinning. PGE2 and PGF2α both reversed the inhibition of cumulus and oocyte maturation induced by indomethacin, though PGE2 was more effective. Only PGF2α promoted apical follicullar thinning, and neither PG had a significant effect on ovarian weight. We conclude that, in mice, PGs may play an integral role during preovulatory maturation of the oocyte and cumulus, as well as thinning of the apical wall.
Transport of spermatozoa in the sheep oviduct: Preovulatory sequestering of cells in the caudal isthmus
Authors: Hunter R. H. F. , Nichol R.
Published: June 2005

Progression of ram spermatozoa within the sheep oviduct has been studied in relation to the time of ovulation. Ewes were mated at the onset of estrus and, at increasing intervals thereafter, the oviduct isthmus was transected 1.5–2.0 cm proximal to the utero‐tubal junction. The incidence of fertilization and number of accessory spermatozoa were examined in eggs recovered 1 to 3 days after surgery.

Ovulation occurred 24–26 hours after the onset of estrus. None of 52 eggs recovered from 48 oviducts transected up to 21 hours after mating was fertilized, nor were spermatozoa associated with the zona pellucida. Two of 33 eggs (6.1%) from 29 oviducts transected between 22 and 24 hours after mating were fertilized, while 3 of 14 eggs (21.4%) and 13 of 16 eggs (81.3%) were fertilized with transection at 25 and 26 hours, respectively. The mean numbers of accessory spermatozoa on eggs in the latter two groups were 0.7 (range 0–2) and 7.9 (range 0–26). Results from transection at 27–30 hours after mating indicated a progressive release and adovarian movement of spermatozoa.

Viable spermatozoa are apparently sequestered in the caudal isthmus for as long as 17–18 hours, until shortly before ovulation, when a local transfer of ovarian follicular hormones is thought to facilitate their redistribution. The adrenergic stimulation of powerful adovarian waves of contraction in the isthmus at this time may also act to provoke the capacitation and hyperactivation of ram spermatozoa.
Intersegmental coordination in the crayfish swimmeret system reconsidered
Authors: Macmillan D. L. , Altman J. S. , Kien J.
Published: June 2005

Stein ('71, '74) demonstrated that lesions in areas 78 and 81 of the nerve cord of the crayfish Procambarus affected intersegmental coordination. In these areas he found neurons which appeared to be local interneurons and whose discharge was correlated with motor discharge in the swimmeret roots. He suggested that these neurons might be responsible for intersegmental coordination and termed them coordinating fibres. We reexamined the same areas of the ventral nerve cord in the crayfish Cherax by recording extracellularly from small bundles of axons during rhythmic activity in the swimmeret motor nerves. All the units we located that exhibited correlated discharge appeared to be plurisegmental. Physiological examination revealed that such units may be sensory, motor, or interneurons. We confirmed this finding morphologically by staining some of the units intracellularly with cobalt. Deafferentation experiments and the effects of stimulating units showing correlated discharge suggest that all three types of neurons may be involved in intersegmental coordination. We conclude that the that the present coordinating fibre model should be abandoned.
Preimplantation development of the primate embryo after in vitro fertilization
Authors: Dukelow W. Richard , Chan P. J. , Hutz R. J. , Demayo F. J. , Dooley V. D. , Rawlins R. G. , Ridha M. T.
Published: June 2005

The developing use of in vitro fertilization (IVF) as a human clinical procedure has prompted the exploitation of nonhuman primates to assess the chromosomal and biochemical normality of embryos produced by IVF. Of 1995 oocytes recovered from squirrel monkeys, 628 (31.5%) matured and 339 (54.0%) fertilized. Fertility can be significantly enhanced by the addition of 1 or 10 μM dbcAMP to the culture medium. Chromosome analysis of oocytes and embryos used in these studies revealed an incidence of abnormality between 7 and 25%, comparable with that found for both in vivo and in vitro fertilized embryos from other laboratory species. There is no evidence that the IVF technique increases chromosomal abnormality. There was a decrease in protein synthesis of oocytes at maturation and during the early embryonic development stages, but an increase in the rate of RNA synthesis as development progressed. There was steroid uptake in early preimplantation embryos. The temporal relationships of early embryonic developmental events in the squirrel monkey have been determined.
Developmental aspects of X chromosome inactivation in eutherian and metatherian mammals
Authors: VandeBerg John L.
Published: June 2005

The single active X principle has served for two decades as a focal point for research on the cyclic activation and inactivation of gene loci. Differences in X chromosome inactivation patterns of eutherian and marsupial mammals provide probes for investigating the mechanisms of the X inactivation process.

In eutherian mammals, the X chromosome is inactivated early in meiotic prophase in males and remains inactive throughout the rest of spermatogenesis. During meiosis in females, the inactive X chromosome is activated so that both X chromosomes are active in oocytes. During the early cleavage divisions of female embryos, the paternally derived X is activated. It and the maternally derived X remain active until differentiation begins in early embryogenesis. At that time, the paternally derived X is inactivated in cells that give rise to extraembryonic membranes, whereas a random process determines which X chromosome is inactivated in cells that give rise to the embryo itself.

Although less is known about developmental aspects of X inactivation in female marsupials, it is clear that the paternal X is preferentially inactive in postembryonic somatic cells. Furthermore, the paternal X is partially active at some loci in some cell types, indicating that it is not regulated as a single unit. The successful adaptation of a small (80–150 g), fecund marsupial to simple laboratory conditions now enables extensive experimentation on the large number of marsupials at various developmental stages. This capability, coupled with the application of newly developed cellular and molecular techniques to questions about X chromosome inactivation, shows great promise for advancing our understanding of the mechanisms that control the cyclic behavior of X chromosome activity.
DNA modification, differentiation, and transformation
Authors: Jones Peter A. , Taylor Shirley M. , Wilson Vincent
Published: June 2005

Substantial evidence has accumulated over the last 5 years that the methylation of cytosine residues in vertebrate DNA is implicated in the control of gene expression. We have used analogs of cytidine, modified in the 5 position, as specific inhibitors of DNA methylation to probe the relationship between this process and cellular differentiation. 5‐Azacytidine effected marked changes in the differentiated state of cultured cells and induced the formation of biochemically differentiated state of cultured cells and induced the formation of biochemically differentiated muscle, fat, and chondrocytes from mouse fibroblast cell lines. Since the analog is a powerful inhibitor of DNA methylation, we suggest that this inhibition is causally related to the mechanism of phenotypic conversion. DNA extracted from cells treated with 5‐azacytidine was hemimethylated and was used as an efficient acceptor of methyl groups in an in vitro reaction in the presence of eukaryotic methylases. In vitro methylation was inhibited if the subtrate DNA was preincubated with a diverse range of chemical carcinogens including benzo(a)pyrene diolepoxide. Thus, chemical carcinogens may induce changes in gene expression by alteration of cellular methylation patterns.

Recent experiments have also demonstrated that freshly explanted diploid fibroblasts from mice, hamsters, and humans lose substantial quantities of 5‐methylcytosine during cell division and aging in culture. Taken together, these experiments suggest that the genomic distribution of 5‐methylcytosine might have importance in normal differentiation and also in the aberrant gene expression found in cancer and senescence in culture.
The recovery from anaerobic metabolism in invertebrates
Authors: Ellington W. Ross
Published: June 2005

The duration and completeness of recovery from anaerobic metabolism is of important functional consequence in invertebrates. Two basic processes occur during recovery: (1) recharging of the phosphagen and ATP pools and (2) disposal of end products by excretion, oxidation, or conversion back to anaerobic substrates. The recovery process in invertebrates is largely aerobic, as is evidenced by the near universality of the oxygen debt phenomenon. However, there is often a lack of correlation between end product accumulation and the magnitude of the oxygen debt. Typically, ATP and phosphagen levels are recharged very rapidly during recovery–ATP (0.25 to 1.0 hr) and phosphagens (0.5 to 4 hr). Excretion of propionate, acetate, and, occasionally succinate, is relatively common in annelids and has also been observed in a number of bivalve molluscs. Nitrogen‐containing end products do not appear to be excreted. Cephalopods and large arthropods show elevated hemolymph end product levels following anoxia/hypoxia. In arthropods, these end products display a protracted return to control levels during recovery. In cephalopods, some octopine may be rapidly taken up and metabolized by the heart, brain, and gill. The sites of lactate metabolism in arthropods are unclear. In contrast to the situation in cephalopods and arthropods, most end products in the adductor muscles of bivalve molluscs do not appear to be exported, but are metabolized within the tissue itself. End ducts such as octopine, succinate, and alanine thus appear to be metabolized at the site of their production. Octopine and lactate appear to be gluconeogenic substrates in cephalopods and arthropods, respectively. Although many of the enzymes involved in gluconeogenesis are present in bivalve molluscs, this process has not been demonstrated in this group. Recovery from anaerobic metabolism remains a fruitful area for future research. Of special interest is the identification of sites of gluconeogenesis in the larger, more active species.
Growth and reproduction of two species of Akodon and their hybrids
Authors: Merani María Susana , Vercellini O. , Acuña Ana maría , Horgan C. , Roldan E. R. S.
Published: June 2005

Growth and reproduction of Akodon molinae (A.m.), A. dolores (A.d.) (Rodentia: Cricetidae), and their hybrids are described. A.d. showed less fertility under animal room conditions, fewer “successful” matings, similar litter sizes, and an altered sex proportion as compared to A.m.; A.d. ovulatory index is supposed to be higher than mean litter size. X‐linked lethal gene(s) and chromosome polymorphisms are possible causes of these variations. Interspecific crosses showed a marked seasonal (summer) tendency in parturitions. Intraspecific matings also produced young during winter. F1 hybrids showed a reversed tendency, while F2 matings returned to the parental pattern. A.d. ♀ × A.m. ♂ and F1 crosses presented larger litter sizes than the other pairings.

A.m. exhibited sexual differences in weight after 60 days of age. A.d. and F1 hybrids did not show significant differences in weight of both sexes at any age. A.m. males and females were heavier than A.d. individuals except 12 months after birth. F1 hybrids born to A.m. ♀ were heavier at birth than the A.d. ♀ s interspecific offspring, and may be interpreted as a maternal influence of the A.m. females. Hybrids were heavier than their parents at birth and some of them were also heavier at 21 days, and probably is due to pseudoheterosis. The comparison of body measurements between sexes of both species did not give conclusive results. A.m. females were larger than females of A.d. Males of both species showed similar total lengths; A.m. males had larger body lengths and shorter tails. Body measurements were not related to weight variations. However, differences in weight and measurements between sexes appeared simultaneously at 2–6 months. This probably reflected the attainment of maturity.
Genetic similarity between species of Akodon (Rodentia, Cricetidae)
Authors: Apfelbaum Liliana I. , Blanco Antonio
Published: June 2005

Genetic similarity between species of rodents of the Akodon genus (A. dolores, A. molinae, and A. azarae) has been estimated by analysis of electrophoretic zymograms corresponding to 23 loci. Nei's coefficient between A. dolores and A. molinae was within the range usually found in conspecific populations. This evidence plus the successful production of “hybrids” (Merani et al., J. Exp. Zool., 206:343–346, '78) suggests that A. dolores and A. molinae may represent geographic races of the same species.
Negative correlation of age and the levels of pineal melatonin, pineal N‐acetylserotonin, and serum melatonin in male rats
Authors: Pang S. F. , Tang F. , Tang P. L.
Published: June 2005

Pineal concentrations of N‐acetylserotonin and melatonin and serum levels of melatonin were studied in 3‐wk‐old (prepubertal), 8‐wk‐old (adult), and 17‐mo‐old (senile) male rats. They were adapted to a photoperiod of 12 h light/12 h darkness for a minimum of 1 wk and killed at mild‐light and mid‐dark. Melatonin and N‐acetylserotonin were determined by radioimmunoassay. The concentrations of pineal N‐acetylserotonin and melatonin were high in the dark period and low in the light period. Statistical analysis indicated that pineal N‐acetylserotonin and melatonin levels per 100 gm body weight declined with age. Similarly, serum melatonin demonstrated diurnal changes in all the age groups studied. In addition, there was a significant reduction in the levels of serum melatonin with age. The parallel patterns of decrease in pineal and serum melatonin levels with age suggest a decline in pineal secretion of melatonin in the older animals.
Preparation and some respiratory properties of coupled mitochondria from ribbed mussel (Modiolus demissus) gill tissue
Authors: Burcham James M. , Ritchie Al , Bishop Stephen H.
Published: June 2005

Preliminary experiments with 2,4‐dinitrophenol (DNP), 2,4,6‐trinitrophenol (TNP), and sodium azide (NaN3) indicated that most of the oxygen consumption by ribbed mussel gill tissue is the result of mitochondrial respiration. A procedure utilizing isoosmotic sucrose, EGTA, defatted serum albumin, and HEPES as the isolation medium was devised for the preparation of fully coupled ribbed mussel gill mitochondria. Optimal rates of respiration and respiratory coupling required substrate, ADP, inorganic phosphate, and a fairly high KCl concentration (90 mM) in the assay medium. Glutamate, proline, malate, and succinate stimulated oxygen consumption with high respiratory control indices and P/O of 3, 3, 3 and 2, respectively. Pyruvate was a weak stimulator of mitochondrial respiration and showed a low respiratory control index with a low P/O. Preparation of gill mitochondria in isoosmotic solutions containing high KCl concentrations (150 mM) yielded mitochondria showing state 2 respiration, slow partially uncoupled ATP synthesis during state 3 respiration and no state 4 respiration. D‐mannitol was not used in the mitochondrial isolation or assay medium because of the probable presence of a D‐mannitol oxidase in these gill mitochondria.
Autoradiographic demonstration of adrenergic innervation to scale melanophores of a teleost fish, Oryzias latipes
Authors: Yamada Koji , Miyata Seiji , Katayama Heizaburo
Published: June 2005

The possibility of adrenergic innervation to melanophores in scales of Oryzias latipes was investigated using 3H‐norepinephrine (3H‐NE) by light microscopic autoradiography. When isolated scales were incubated in 3H‐NE, there was observed plexus of varicose fibers labeled with 3H‐NE which intimately enclosed the stellate processes and cell bodies of melanophores. These labeled fibers could not be detected in cocaine‐treated or denervated scales. Potassium ions caused a considerable reduction in the labeling of varicose fibers, which was accompanied with aggregation of melanosomes within melanophores. These findings suggest that the labeled fibers observed are compatible with adrenergic nerve fibers that control the melanosome movements within melanophores.
Monoclonal antibodies developed against Botryllus blood cell antigens bind to cells of distinct lineages during embryonic development
Authors: Schlumpberger J. M. , Weissman I. L. , Scofield V. L.
Published: June 2005

Monoclonal antibodies that bind to adult Botryllus blood cell surface antigens were used to detect and localize identical or cross‐reacting antigenic determinants on Botryllus embryonic cells. These anti‐Botryllus monoclonal reagents could be divided into three categories: 1) those that bound to most embryonic cell types, including all very early embryonic cells; 2) those that bound only to embryonic blood cells and a few other embryonic cell types; and 3) those that did not bind detectably to any embryonic cells.
Timing of early morphogenetic events in tetraploid starfish embryos
Authors: Mita I. , Obata C.
Published: June 2005

When starfish eggs were treated with caffeine, they developed parthenogenetically as tetraploid embryos. The timing of cleavages and gastrulation was compared between these tetraploid embryos and control diploid embryos. The following results were obtained: 1) The number of synchronous cleavages was ten in controls but nine in tetraploid embryos; 2) tetraploid embryos began to gastrulate at almost the same time after first cleavage as did control embryos; 3) the average number of constituent cells of tetraploid gastrulae was about 2,300, whereas that of control gastrulae was about 4,000. These results indicate that 1) the initiation of asynchronous cleavages is closely associated with the nucleocytoplasmic ratio; and 2) the timing of gastrulation is not determined by the number of cell divisions. These conclusions are in good accord with the results of a previous study on timing of early morphogenetic events in half eggs whose cytoplasm was decreased to half that of normal eggs (Mita, '83).
Determination of the plane of bilateral symmetry in the teleost fish, Oryzias latipes
Authors: Long Wilbur L. , Speck Nancy A.
Published: June 2005

Gravitational factors appear to influence the establishment of bilateral symmetry in amphibia, birds, elasmobranchs, chondrostean fishes, and teleostean fishes. Correlations between the plane of symmetry and the planes of the first or second cleavage have similarly been noted. Evidence is presented indicating that neither the direction of gravity nor the first or second cleavage planes can be correlated with the orientation of bilateral symmetry in the Japanese ricefish, Oryzias latipes. An alternative explanation for the previous data supporting a gravitational influence in teleostean fishes is offered.
The modifications of cortical endoplasmic reticulum during in vitro maturation of Xenopus laevis oocytes and its involvement in cortical granule exocytosis
Authors: Campanella C. , Andreuccetti P. , Taddei C. , Talevi R.
Published: June 2005

In Xenopus laevis eggs, cisternae shells which surround cortical granules (CG) are part of a cortical endoplasmic reticulum (ER) network. In this paper the origin of such ER shells has been studied in full‐grown, progesterone‐exposed Xenopus oocytes. Furthermore, the possible role of the cortical ER in the activation process has been investigated by pricking maturing oocytes. It has been shown that in full‐grown ovarian oocytes ER CG shells are absent and ER cisternae are extensively and randomly distributed throughout the peripheral cytoplasm, where they appear to be continuous with annulate lamellae (AL). Following hormone treatment, the AL completely disaggregate and the ER cisternae gradually migrate to the cortex where they surround the CG constituting the typical cortical network described in uterine eggs. Furthermore, it has been found that 8 h after progesterone treatment (before the first polar body extrusion) the response to pricking (CG exocytosis) occurs only at the animal half; there is no observable response in the vegetal half. At this time ER shells surround CG only in the animal hemisphere. A complete CG exocytosis occurs following the first polar body emission, when the cortical ER is well organized in the whole oocyte cortex. The correlation between the differentiation of the cortical ER and the arousal in the oocyte of the ability to respond to a pricking stimulus is discussed in the light of an involvement of the cortical ER in the propagation of CG exocytosis.
Calcium ultrastructural localization in Xenopus laevis eggs following activation by pricking or by calcium ionophore A 23187
Authors: Andreuccetti P. , Denis‐Donini S. , Burrini A. G. , Campanella C.
Published: June 2005

In the egg of Xenopus laevis a cortical network of smooth endoplasmic reticulum (SER) surrounds and interconnects each cortical granule (CG) (Campanella and Andreuccetti, '77). This network is a possible intracellular site of calcium storage to be called into action for CG exocytosis. In our experiments, Xenopus eggs, unfertilized or activated by pricking or by calcium ionophore A 23187, have been fixed in osmium‐pyroantimonate for calcium localization.

Our data show that deposits can be detected only in activated egs. The calcium chelator edetate (EGTA) and x‐ray microprobe analysis demonstrate that they contain calcium. Deposits are found on liposomes and on all intraovular cytomembranes, which therefore appear to be possible sites of calcium sequestration. In the case of ionophore‐activated eggs, deposits are detectable independently of the presence of extracellular calcium. These data show that in Xenopus at activation an intracellular liberation of calcium occurs similar to that described in other species.

Furthermore, the fact that antimony deposits are observed only after activation makes Xenopus eggs appropriate material in which to follow the temporal and spatial sequence of appearance of the deposits during the early stages of activation. Our results show that antimony deposits appear first in SER vesicles between the plasma membrane and CGs and then spread to the rest of the egg cytomembranes. These data corroborate our hypothesis that in Xenopus the cortical SER network is the first intracellular site where calcium is released at activation. The possible mechanism of calcium release and propagation along the egg cortex is discussed.
Effects of hypophysectomy on some osmoregulatory parameters of the catfish, Heteropneustes fossilis (Bloch)
Authors: Parwez Iqbal , Goswami Shashi V. , Sundararaj Bangalore I.
Published: June 2005

The catfish, H. fossilis, survives for long periods after hypophysectomy, although with impaired osmoregulatory mechanisms. Plasma osmolarity and cortisol levels decline significantly within 2 hr after hypophysectomy and attain the lowest values by about 27 hr. Hypophysectomy also results in a marked decrease in urine flow rate principally due to reduced glomerular filtration. The reduction in the ability of the kidney of hypophysectomized catfish to eliminate water results in hyperhydration of blood and muscle. Urine osmolarity and sodium concentration increase due to reduced tubular reabsorption of sodium. There is, however, no net change in the total urinary sodium loss. The catfish survives in fresh water after hypophysectomy presumably because its tissues can tolerate significant dilution of the body fluids.
Neuroendocrine changes in male hamsters following photostimulation
Authors: Steger R. W. , Bartke A. , Matt K. S. , Soares M. J. , Talamantes Frank
Published: June 2005

Transfer of gonadally regressed male golden hamsters from a short (5 L:19 D) to a stimulatory (14 L:10 D) photoperiod elicits, within 24 hr, significant changes in hypothalamic dopamine, serotonin, and possibly norepinephrine metabolism. Hypothalamic LHRH content was significantly elevated in short‐photoperiod animals, but within 24 hr of transfer to a 14:10 photoperiod, LHRH declined to levels not different from those in hamsters maintained continuously in a long photoperiod. Plasma FSH levels were also significantly elevated within 24 hr of transfer, but increases in plasma LH were somewhat slower. Chronic treatment with the tyrosine hydroxylase inhibitor, α‐methyl tyrosine (αMPT), which inhibits catecholamine synthesis, blocked the effect of a stimulatory photoperiod on plasma FSH levels, while treatment of 5:19 hamsters with the catecholamine precursor, L‐dopa, mimicked the effects of photostimulation on plasma FSH levels. Testicular weights were not affected by αMPT or L‐dopa treatment for 1 week. From these data, it appears that endocrine events associated with photoperiod‐induced testicular recrudescence are under the control of hypothalamic neurotransmitters.
Effects of house fly oostatic hormone on egg development neurosecretory hormone action in Aedes atropalpus
Authors: Kelly Thomas J. , Birnbaum Mark J. , Woods Charles W. , Borkovec Alexej B.
Published: June 2005

Oostatic hormone, prepared from mature female house flies, Musca domestica, was examined for its effect on processes mediated by egg development neurosecretory hormone (EDNH). When injected into newly emerged adult female mosquitoes, Aedes atropalpus, oostatic extracts inhibited vitellogenic growth of the ovaries. Comparison of oostatic activities in heads, thoraces, and abdomens of house flies showed that the major portion was present in the abdomens, apparently associated with the ovaries. In contrast to untreated vitellogenic females, no ecdysone or 20‐hydroxyecdysone could be detected in female mosquitoes injected with the oostatic extract. Vitellogenic growth and ecdysteroid levels were suppressed in decapitated females injected with a mixture of extracts containing EDNH and oostatic activities. Since the normal vitellogenic and steroidogenic responses to EDNH can be suppressed by simultaneous injection of EDNH and oostatic material, it is suggested that oostatic hormone acts at a level subsequent to EDNH release. However, we cannot rule out at this time that EDNH release, itself, is also affected.
Abdominal positioning interneurons in crayfish: Projections to and synaptic activation by higher CNS centers
Authors: Larimer James L. , Moore Darrell
Published: June 2005

Intracellular recording, stimulation, and Lucifer dye injections were used to characterize abdominal positioning interneurons from the neuropile of the second through sixth abdominal ganglia of the crayfish, Procambarus clarkii. Motor outputs of these cells were recorded with extracellular electrodes placed on various flexion and extension roots along the nerve cord. In an effort to assess the functional relationships between the postural interneurons in the abdomen and those known to exist in the circumesophageal connectives (CECs), a stimulus pulse train was delivered to each of the CECs while monitoring the intracellular responses of the impaled interneurons. Abdominal positioning interneurons were grouped into four general categories based on their responses to CEC stimulation: 1) those that projected their axons directly through the CECs; 2) those that were remotely activated to spiking; 3) those locally activated to produce EPSPs or IPSPs; and 4) those that were not affected by CEC stimulation.

The majority of abdominal positioning interneurons encountered in this study evoked flexion (N = 82), with relatively fewer evoking extension (N = 29). A major difference appeared between the two classes. Whereas 39% of the flexion interneurons had axons coursing to the brain, only 7% of the axons of extension interneurons coursed rostrally beyond the thoracic level. Finally, the large majority of those flexion and extension interneurons that lacked processes in the CEC received synaptic inputs at various levels along the lower CNS from other CEC neurons. Thus, control of abdominal positioning involves neurons at all levels in the CNS—some sequentially organized, others forming “through” pathways, but all with multiple input sites.
Demonstration of H‐2 antigens on preimplantation mouse embryos using conventional antisera and monoclonal antibody
Authors: Warner Carol M. , Spannaus Donna J.
Published: June 2005

Mouse embryos at the 2‐cell, 8‐cell, and blastocyst stages of development were examined for the presence of H‐2 antigens by immunoperoxidase labeling and transmission electron microscopy. Conventional antisera made in congenic mouse strains were used to study embryos of four different haplotypes: b, a, k, and d. Blastocysts showed uniform heavy labeling of all cells of the trophectoderm, 8‐cell embryos showed lighter labeling of only some of the cells, and 2‐cell embryos showed no labeling. Similar results were found for all four haplotypes studied. In addition, monoclonal antibody 11–4.1 (anti‐Kk) was reacted with homologous (H‐2k) and heterologous (H‐2b) blastocysts. Positive results with the monoclonal antibody corroborates the concept that H‐2 antigens are expressed on early mouse embryos.
In vitro development of the embryonic mouse inner ear following exposure to trypsin
Authors: Saver Jeffrey L. , Van De Water Thomas R.
Published: June 2005

Trypsin has been shown to disrupt normal in vitro morphogenesis of embryonic organ rudiments. Otic tissues derived from 11‐, 12‐, and 13‐day‐old mouse embryos were exposed to either Ca++‐ and Mg++‐free PBS or 0.25% trypsin dissolved in Ca++‐ and Mg++‐free PBS prior to explantation into organ culture. Trypsin treatment of otic explants disrupted the expression of the normal pattern of inner‐ear development in vitro. There was a direct correlation between the embryonic age at time of exposure to trypsin and the severity of dysmorphogenesis of the inner ear. The younger explants showed abnormalities of both vestibular and auditory structures, whereas with increasing embryonic age, abnormalities were confined more to the auditory portion of the inner ear. The results suggest that integrity of the otocyst basal lamina and epitheliomesenchymal tissue interactions are important factors in early otic development. It is postulated that the major effect of trypsin on inner‐ear morphogenesis is through disruption of these factors, which may act to regulate the progressive expression of early otic development.
Long‐term effects of hypothalamic lesions on the pituitary and its target organs in the killifish Fundulus heteroclitus: II. Darkening
Authors: Pickford Grace E. , Knight W. Rea , Knight Janet N. , Baker Bridget I.
Published: June 2005

Presumed lesions in the area of the nucleus preopticus (NPO) of male Fundulus heteroclitus resulted in chronic darkening in 12 fish. Sections revealed that all dark fish were severely injured in the nucleus opticus hypothalami (NOH) (Repérant et al., '82); in 11 cases there was injury to the optic tracts but in one the tracts were uninjured. Seven dark fish were tested on a white background: four were unable to assume pallor but three gradually paled. A caudal band remained dark in the four fish that did not fade but paled in the three that became slowly paler. It is concluded that the pathway to the thalamic paling center was destroyed but that low levels in melanophore‐concentrating hormone (MCH) persisted in the three fish whose denervated caudal bands faded. Darkening was not due to proliferation of new melanocytes or to the synthesis of new melanin, but solely to a chronic state of melanophore dispersion. Pituitary melanocytes appeared mainly normal, and secretion of the melanophore‐dispersing hormone was probably not excessive.
Hormonal regulation of the annual pelage color cycle in the Djungarian hamster, Phodopus sungorus. II. Role of prolactin
Authors: Duncan Marilyn J. , Goldman Bruce D.
Published: June 2005

This study investigated whether photoperiod‐induced changes in circulating prolactin levels, which have been observed in the Djungarian hamster (Yellon and Goldman, '83; Duncan and Goldman, '83a), might be involved in seasonal pelage color changes in this species. Injection of ovine prolactin (100 μg/day) inhibited the short photoperiod‐induced winter molt. This finding indicated that the suppression of endogenous prolactin levels normally occuring in short photoperiod‐housed hamsters (Duncan and Goldman, '83a) may induce the winter molt. Suppression of prolactin secretion with bromoergocryptine (200 μg/day) strongly inhibited the spring molt, while concomitant treatment with ovine prolactin (100 μg/day) overcame this effect of bromoergocryptine. Injection of bromoergocryptine (200 μg/day) stimulated the winter molt in castrated hamsters housed in long photoperiod; concomitant injection of prolactin (100 μg/day) reversed this effect as well. These findings strongly suggested that an increase in endogenous prolactin levels may be necessary for the development and maintenance of the summer pelage.
In vitro induction of sperm nucleus decondensation by cytosol from mature toad eggs
Authors: Iwao Yasuhiro , Katagiri Chiaki
Published: June 2005

An in vitro assay was performed on the cytosol from oocytes of the toad, Bufo bufo japonicus, to examine the cytoplasmic activity that induces sperm nucleus decondensation (SND). When the sperm, pretreated for 15 min with 0.05% Triton X‐100, were incubated in cytosol obtained from mature eggs (18 h post‐hormone treatment: PHT) 30–60 min after activation, their nuclei elongated and swelled markedly to take a spherical shape between 1 and 2 h after incubation. The treatment of such detergent‐treated sperm nuclei with dilute HC1 significantly enhanced this process of nuclear decondensation. The SND activity was retained in the pellet after centrifugation at 105,000g for 1 h. It was completely inhibited by EGTA (1 mM) and serine protease inhibitor (1 mM), though not at all by soybean trypsin inhibitor (1 mg/ml). The cytosol from unactivated eggs at 18 h PHT had hardly any SND activity, but was induced to exhibit a strong activity when 10 mM Ca2+ was added to the extraction medium. No SND activity was observed in the cytosol from full‐grown ovarian oocytes (0 h PHT), oocytes at the first meiotic metaphase (11 h PHT), or activated oocytes at 18 h PHT from which the germinal vesicle had been removed before the hormone treatment. Electron‐microscopic observations revealed that detergent‐ and acid‐treated sperm had completely lost their nuclear envelopes, but, after exposure to active egg cytosol, the decondensed nuclei were surrounded by continuous membranous envelopes. These results point to the importance for the formation of swollen nuclei in fertilized eggs of the membrane system in mature egg cytoplasm that may be activated by Ca2+ at the time of egg activation.
Mitochondria from the hepatopancreas of the marine clam Mercenaria mercenaria: Substrate preferences and salt and pH effects on the oxidation of palmitoyl‐L‐carnitine and succinate
Authors: Ballantyne J. S. , Storey K. B.
Published: June 2005

A method is presented for the isolation of mitochondria with good respiratory control from the hepatopancreas of the marine clam Mercenaria mercenaria. Palmitoyl‐L‐carnitine is the preferred substrate of the mitochondria of the hepatopancreas based on state 3 rates of oxidation (in the presence of ADP). Rates of oxidation of pyruvate and glutamate were about one‐half that of the lipid substrate in state 3. α‐Glycerophosphate was oxidized at a rate about one‐third that of palmitoyl‐L‐carnitine. All Krebs cycle intermediates were oxidized to some extent. Proline was not oxidized at detectable levels. The optimal range of KCI concentrations for the oxidation of palmitoyl‐L‐carnitine is between 250 and 500 mM whereas the optimal range of KCI concentration for the oxidation of succinate is between 200 and 350 mM. The optimal range of pH for the oxidation of succinate and for the oxidation of palmitoyl‐L‐carnitine lies between pH 6.5 and 7.5 based on the respiratory control ratio.
Fish liver protein synthesis during cold acclimatization: Seasonal changes of the ultrastructure of the carp hepatocyte
Authors: Sáez Lino , Zuvić Tatiana , Amthauer Rodolfo , Rodríguez Esteban , Krauskopf Manuel
Published: June 2005

A cell‐free system, active in protein synthesis, was constructed using ribosomes and supernatant factors isolated from the livers of winteracclimatized carps. Upon seasonal adaptation, the hepatocytes of these fishes exhibited distinctive morphological features that were not sex dependent. The cytoarchitecture of the liver cell from summer carps is consistent with the cellular arrangements found when the rate of gene expression is high. During winter, several morphological features reveal that macromolecular synthetic activity may be clearly diminished.
Inhibitory effect of acetylcholine on muscular tonus of the small intestine of a lizard
Authors: Wacyk Jurij , Guerrero Sergio , Morello Antonio
Published: June 2005

The present report concerns the effects of cholinergic agonists on the isometric tension of “in vitro” preparations of the esophagus and distal part of the small intestine of the lizard Liolaemus gravenhorsti.

Acetylcholine (Ach) and carbachol elicited a dose‐related increase of isometric tension in the esophagus, whereas the small intestine was slowly relaxed by these drugs. Eserine induced a synergistic action on the cholinergic responses of both organs, and atropine completely antagonized the respective effects.

The esophagus and the intestine showed different thresholds for the cholinergic evoked responses, the former being about 30 times more sensitive than the intestine. Assessment of cholinesterase activity revealed that Ach is hydrolyzed at a significant lesser speed in the intestine than in the esophagus.

The results do not provide information about the nature of the chemical mediator causing the inhibitory effect observed in the intestine. The eventual role of an adrenergic mechanism mediated by muscarinic receptors is under study in our laboratory.
Juvenile hormone production, juvenile hormone esterase, and juvenile hormone acid methyltransferase in corpora allata of Manduca sexta
Authors: Sparagana Steven P. , Bhaskaran Govindan , Dahm Karl H. , Riddle Vicki
Published: June 2005

Juvenile hormone (JH) secretion by corpora allata (CA) of last instar larvae of Manduca sexta was studied by measuring the rate of JH synthesis in vitro with a radiochemical assay and by analyzing JH esterase and JH acid methyltransferase (JHAMT) activities in CA. CA of 0‐day (0–12 hr after ecdysis), 4‐day (early wandering larvae), and 7‐day (prepupae) animals were used in this study.

CA of 0‐day larvae showed high rates of JH synthesis, whereas CA of both 4‐and 7‐day animals did not produce detectable amounts of radiolabeled JH. JH esterase activity was absent in 0‐day CA, but high activity was present in both 4‐ and 7‐day CA. However, incubation of older CA in medium containing a potent JH esterase inhibitor did not yield radiolabeled JH, indicating that these glands are unable to methylate JH acids. This conclusion is supported by the observations that JHAMT activity was high in 0‐day CA, but absent from older CA. In view of the reported peak of JH in the hemolymph on day 7, an alternative means for producing JH is postulated.
Noninvasive pulsed doppler determination of cardiac output in an unanesthetized neotenic salamander, Ambystoma tigrinum
Authors: Hoyt Reed W. , Eldridge Marlowe , Wood Stephen C.
Published: June 2005

A pulsed Doppler was used to determine cardiac output noninvasively in partially restrained unanesthetized neotenic tiger salamanders, Ambystoma tigrinum (mean wt. 105.0 gm ± 13.7 SD, N = 5). Although mean heart rates were similar, mean stroke volume (0.18 ml ± 0.06) and cardiac output (11.0 ml · min−1 ± 3.6) were greater than those previously reported for other amphibia. This dissimilarity is most likely due to species differences and/or the effects of anesthesia and surgical disruption of the thoracic cavity.
Exocytotic and cytolytic release of histamine from mast cells treated with Portuguese man‐of‐war (Physalia physalis) venom
Authors: Cormier Susan M.
Published: June 2005

Electron microscopic observations suggest that venom from isolated nematocysts of the stinging tentacles of the Portuguese man‐of‐war, Physalia physalis, causes histamine release via a rapid, short‐duration exocytosis of granules and a slower, long‐duration lysis of mast cells. Fine structural changes in mast cells are concurrent with histamine release and are independent of the presence of leukocytes. Vesiculation of the plasma membrane and release of granules nearest the cell surface occur within 10 sec after exposure to 100 μg venom/105 cells. Released granules and granules retained in plasma membrane inaginations are fibrous and less electron opaque than more centrally located granules. Complex channels to the external medium continue to form, and within 1 min, characteristics of both degranulation and cytolysis are well advanced. Mitochondria are swollen or disrupted. Microridges are absent. Intracellular granules are significantly fewer in venom‐treated mast cells, but are more widely separated than in controls. This suggests that degranulation occurs at early stages but is halted as cytolysis proceeds.