bluuebunny/crossref_metadata_2025 huggingface dataset:
Fine structure of the chorion and site of sperm entry in the egg of Brachydanio
Authors: Hart Nathan H. , Donovan Michael
Published: June 2005

The fine structure of the chorion and the region of the unfertilized egg immediately beneath the micropylar apparatus of the zebra danio, Brachydanio rerio, were studied using Nomarski differential interference optics, and scanning and transmission electron microscopy. The chorion consisted of three distinct zones: an outer, electron‐dense zone containing pore canal plugs (zona radiata externa), a middle fibrillar zone (superficial zona radiata interna), and an inner zone of 16 horizontal electrondense lamellae alternating with 15 interlamellae of lower electron density (deep zona radiata interna). The zona radiata interna was pierced by open pore canals. The single micropylar apparatus was regionalized into a cone‐shaped vestibule and a tapered micropylar canal traversing the entire chorion. The outer diameter of the micropylar canal was 7.5–8.5 μn and the inner diameter about 2.3 μn. Since the diameter of the inner micropylar aperture was slightly larger than the size of the sperm head, the block to polyspermy in eggs of the zebra danio appears to be mechanical and guaranteed by the morphological design of the micropyle. The egg plasmalemma beneath the inner micropylar aperture was differentiated as a circular cluster of 15–20 microvilli‐like projections. The cluster of surface projections, approximately 2.1–2.5 μn in diameter under scanning, electron microscopy, was distinguishable from the microplicae covering the rest of the egg surface and identified as the sperm entry site. The cortical cytoplasm subjacent to the sperm entry site was organized as a compact, electron‐dense, and homogeneous band. The sperm entry site itself was circumscribed by an area of cytoplasm (approximately 100 μn in diameter) in which cortical granules were typically arranged as a single layer immediately beneath the plasmalemma. However, there was a complete absence of cortical granules in the cytoplasm directly below the sperm entry site. The single row arrangement contrasted with the multilayered rows of cortical granules found throughout the remainder of the egg cytoplasm. Based upon Nomarski and ultrastructural analyses, there was a significant polarity in the cortex created by the size distribution and volume density of the cortical granules layered just beneath the plasmalemma. The cortical granules in the vicinity of the sperm entry site were 2.7 to 2.8 μm in diameter and densely packed. From this region to the vegetal pole, the cortical granules appeared to progressively increase in size and become less densely packed. The polarity in granule distribution established a distinct gradient in the structural organization of the egg cortex from the site of sperm entry to the vegetal pole.
The rate of estrone production by mouse blastocysts increases with estradiol‐17β concentration in medium
Authors: Wu Jung‐Tsung , Lin Guey‐Meei
Published: June 2005

Following the finding of 17β‐hydroxysteroid dehydrogenase activity in mouse blastocysts, the present study examined the relation of estrone (E1) production rate to estradiol‐17β (E2) concentration in the medium. When Day 5 blastocysts were cultured in 107–6,860 ng E2/ml medium, the amount of E1 formed during the first 5 hours (y) was found to increase linearly with the logarithm of E2 concentration (x), as represented by the equation y = 2,161x − 3,947. However, there was a sharp decline during the next 5 hours of culture except for the 107 ng E2 culture. The E1 production then remained steady for up to 46–58 hours. There was a tendency for further decline during the 46–70‐hour period. The results indicate that (1) E2 may be metabolized to E1 and, probably, another unknown steroid; (2) E1 production rate is E2 ‐dose dependent; and (3) the blastocyst possesses the enzymatic capability to change the steroid milieu to suit its own needs and/or to cause local effects in the uterus for its proper implantation.
Lipids and the permeability of epidermis from snakes
Authors: Roberts Johnna B. , Lillywhite Harvey B.
Published: June 2005

Evaporative water loss was measured in vitro from shed epidermis of 11 species of snakes from widely ranging habitats. Permeability of epidermis was inversely related to habitat aridity and increased 1.9‐ to 31.3‐ fold when lipids were extracted prior to measurements. The quantity of lipids extracted from epidermis varied severalfold among species, and was significantly greater in xeric‐adapted, terrestrial species than in aquatic species. However, there was no significant correlation between lipid quantity and the increase of permeability produced by extraction of lipids. Both quantity and composition of lipids are likely involved in evolutionary or physiological adjustments to habitat. Lipids were demonstrated histochemically to be located primarily in the mesos layer of the epidermis, with some lipids also present in the alpha and beta keratin. Alteration of keratin without lipid extraction increased permeability only 20% if that produced by lipid extraction in the same species. The data corroborate other recent findings indicating that epidermal lipids play a major role in regulating the permeability of reptilian integument.
Effect of complete tail amputation on the rate of metamorphosis in anuran tadpoles
Authors: Kumar T. Rajendra , Krishanaprasadan T. N. , Kotak V. C.
Published: June 2005

Complete tail amputation enhanced the rate of metamorphosis threefold in the late prometamorphic tadpoles of Microhyla ornata and Rana tigrina. By contrast, premetamorphic tadpoles after tail amputation showed no acceleration of metamorphosis; instead, they regenerated their tails. Both these events could be reflective of the strategies employed in the different stages to enhance survival value.
A new technique for dechorionation and observations on the development of the naked egg in Oryzias latipes
Authors: Iwamatsu Takashi
Published: June 2005

A simple technique for removing the chorion (egg envelope) of Oryzias latipes eggs is described in which the chorion is mechanically cut off with microsurgical scissors before and immediately after insemination. When dechorionated eggs were inseminated, a high incidence of polyspermic fertilization was observed. Fusion was induced among dechorionated eggs that were in contact when they were inseminated with a high concentration of spermatozoa. However, monospermic eggs that were dechorionated immediately after completion of the cortical reaction induced by insemination changed shape periodically during cleavage and developed normally to fry.
Electron microscopic observations during monospermic fertilization process of the brittle‐star Amphipholis kochii Lütken
Authors: Yamashita Masakane
Published: June 2005

This paper describes the process of monospermic fertilization in the brittle‐star, Amphipholis kochii Lütken, as observed by scanning and transmission electron microscopy: The observations concern the penetration of spermatozoon, the male and female pronuclei formation, and the fusion of pronuclei. The acrosomal process of this species is short, about 5 μm long. The thickness of the jelly coat is correspondently thin, confirming the notion that the length of the acrosomal process of the non‐echinoids corresponds to the thickness of the jelly coat. Decondensation of the sperm nucleus, formation of the male pronuclear envelope, and the growth of the male pronucleus occur irrespective of meiosis and the female pronucleus formation. This observation suggests the presence of different substances responsible for the decondensation of paternal and maternal chromosomes and for the formation of the male and female pronuclei. In spite of the different maturation state of eggs at insemination, the fertilization process of the ophiuroid, including the pronucleus formation and the association of pronuclei, is generally similar to that of the echinoid, indicating that Wilson's hypothesis may not apply to ophiuroids.
Inherited sex reversal in mice: Identification of a new primary sex‐determining gene
Authors: Eicher Eva M. , Washburn Linda L.
Published: June 2005

We present evidence that the inbred mouse strain C57BL/6J (B6) differs from Mus domesticus (DOM) at a locus involved in gonad determination and development as well as at the testis‐determining locus on the Y chromosome (Tdy). This newly identified gene is named testis‐determining, autosomal‐1 (tda‐1). Although the inheritance of tda‐1 suggests it is located on an autosome, its location on the X and Y chromosome in their pairing‐recombination region is not excluded. When mice are homozygous for the C57BL/6J‐derived tda‐1 allele (tda‐1B6) and carry the Y chromosome from M. domesticus, they develop as true hermaphrodites or, more rarely, as females. In contrast, when they are homozygous Tda‐1DOM/Tda‐1DOM or heterozygous Tda‐1DOM/tda‐1B6 and carry a B6‐derived or M. domesticus‐derived Y chromosome they develop as normal males.

A simple genetic model is presented that integrates proposed steps in gonad determination and the results from genetic experiments reported here. In addition, arguments are presented for the existence of an ovary‐determining gene.
An attempt to approach the molecular mechanisms of primary sex determination: W‐ and Y‐chromosomal conserved simple repetitive DNA sequences and their differential expression in mRNA
Authors: Epplen Jörg T. , Cellini Alessandra , Romero Sally , Ohno Susumu
Published: June 2005

The biological role of simple repetitive DNA consisting of short, tandemly arrayed sequences, is still enigmatic. Previously we have described how simple quadruplet repeats (sqr)isolated from a sex‐specific snake satellite (Elaphe radiata) are also “sex‐specifically” arranged in mouse and man (Epplen et al, '81, '82a). In the mouse, these sqr are interspersed on all chromosomes, but a substantial part is concentrated in the pericentromeric region of the Y‐chromosome (Epplen et al., '82b). In one of the subcloned snake satellite DNA component (pErs5), the sqr are adjacent to a single‐copy sequence that in turn identifies a male‐specific putative mRNA in the mouse (Epplen et al. '82b). The isolated stretch of sqr themselves cross‐hybridizes with at least two species of poly (A)+ RNA from mice occurring in both sexes (Epplen et al., '82b, '83). By examining one of the non‐sex‐specific transcripts, we demonstrate here substantial open reading frames in the corresponding 2.5‐kilobase (kb)‐long mouse cDNA clone, including some 130 copies of sqr. The results are discussed in the context of mechanisms of primary sex‐determination in vertebrates, in particular the gonadal induction mechanism in heterogametic sex determination.
Studies of foreign genes transmitted through the germ lines of transgenic mice
Authors: Gordon Jon W.
Published: June 2005

A novel gene transfer system has recently been developed in which DNA sequences isolated by molecular cloning can be introduced and permanently integrated into the genomes of developing mice. The procedure entails the microinjection of such cloned sequences into the pronuclei of onecelled embryos followed by reimplantation into pseudopregnant females for continued development. Although data obtained from this system are still few, they indicate it will have broad applicability to problems of mammalian developmental genetics. In order that such experiments be fully exploited, it will be necessary to understand the behavior of foreign genes introduced into the mouse and the relationship of that behavior to endogenous gene structure, function, and regulation. As a step in this direction, we have examined a line of mice into which has been transferred a recombinant plasmid consisting of a human leukocyte interferon genomic fragment cloned into the BamHI site of pBR322. The donor material has been integrated as a large concatameric structure which is inherited as a single Mendelian trait to several generations of progeny. Crossing of heterozygotes has apparently resulted in the production of viable homozygotes. In one animal, the structure of the integrated fragment was altered in spleen DNA but not in germ cells. This finding may reflect a normal processing mechanism whereby the structure of genes is altered during cell differentiation, or it may mean that transferred DNA does not behave as endogenous genes do.
Major histocompatibility complex (MHC)‐linked genes affecting development
Authors: Gill Thomas J. , Siew Shirley , Kunz Heinz W.
Published: June 2005

Genes affecting growth and development which are linked to the major histocompatibility complex have been found in the mouse (t‐complex) and in the rat (growth and reproduction complex, grc), and there is some evidence that they also exist in humans. The genes of the t‐complex have different effects depending upon the specific combinations involved: skeletal and fertility abnormalities, complete or partial embryonic mortality, high transmission ratios (segregation distortion) in males, high level of linkage disequilibrium with H‐2, and suppression of recombination over the adjacent portion of the chromosome. The grc in the homozygous state causes small body size, sterility in the male and reduced fertility in the female, partial embryonic mortality, and a high level of linkage disequilibrium with RT1. It also interacts epistatically with the heterozygous Tal (tail anomaly lethal) gene to cause complete embryonic death. Mice carrying t‐haplotypes and rats carrying the grc have an antigen in the male germ cells whch cross‐reacts very strongly (t‐antigen). Suggestive evidence for such genes in humans comes from (1) studies on the relationship between skeletal defects and HLA haplotypes; (2) the association of specific HLA and complement haplotypes with a high transmission ratio in males, linkage disequilibrium among certain HLA and complement specificities and suppression of recombination in some MHC haplotypes; and (3) the lack of homozygotes in an isolated inbreeding population of desert nomads (Kel Kummer Tuaregs). In addition, immunogenetic studies on couples having chronic spontaneous abortions suggest that there is an unusually high incidence of homozygosity for the HLA‐D/DR and HLA‐A loci in these couples, and this finding is consistent with the presence of linked loci which behave like t or grc.
Production of genetically identical sets of mammals: Cloning?
Authors: Seidel George E.
Published: June 2005

In the past few years, there has been phenomenal progress in producing genetically identical mammalian multiplets by asexual means. The simplest method is to divide embryos into two, three, or four parts, and transfer the parts to surrogate mothers for gestation to term. Another approach is to inject nuclei from totipotent embryonic cells into fertilized one‐cell embryos and to remove both male and female pronuclei. When these embryos reach the blastocyst stage, nuclei from their totipotent cells can be removed and injected into one‐cell embryos, thus amplifying the process ad infinitum. Subsets of these embryos can be stored in liquid nitrogen to make genetic material for additional copies available indefinitely. Some of these techniques are fairly efficacious, others are not.

No reliable techniques are available for making genetic copies of nonhomozygous adult mammals (or other vertebrates) unless samples of embryonic cells were cryopreserved when the individuals were embryos. However, injection of nuclei of spermatogonia into enucleated one‐cell embryos is a promising strategy. The genetic totipotency of these nuclei is obvious since they become gamete nuclei. Moreover, the birth of mice from the diploidized genetic material of a single X‐bearing spermatozoan after removal of the female pronucleus from a one‐cell fertilized embryo suggests that we should eventually be able to make genetic copies of adult male mammals. This approach would not work for adult females because their oogonia have all become oocytes, and the DNA configuration in oocytes is not identical to somatic cells due to meiotic crossing over.
Measuring aerobic and anaerobic metabolism of benthic infauna under natural conditions
Authors: Pamatmat Mario M.
Published: June 2005

Some species of invertebrates, particularly benthic infauna, show extreme metabolic fluctuations, from a truly basal metabolic rate while quiescent in anaerobic mode to higher rates as a result of physical activity whether they are anaerobic or aerobic. The fluctuations may be random or cyclic, endogenous, induced by experimental conditions, or by natural changes in environmental conditions; they are readily seen and quantified by direct calorimetry.

Biochemists studying anaerobic metabolism sometimes find large quantitative variations in metabolite concentration between individual test organisms. One source of variability may be the variability in the metabolic activity of the control and experimental animals. Information contained in heat flow recordings could be useful in normalizing data and making more precise correlations between actual metabolic rates and chemical measures of metabolism.

Theoretical enthalpy changes from known anaerobic end products and results of direct calorimetry do not agree at present. Continual comparisons, leading to consistent agreement or satisfactory explanation of their discrepancy, are necessary to demonstrate full understanding of anaerobic metabolism.
A steady efflux of ionic current predicts hind limb development in the axolotl
Authors: Borgens Richard B. , Rouleau Marie F. , DeLanney Louis E.
Published: June 2005

For more than a week prior to the emergence of a hind limb, a steady electric current is driven out of the ventrolateral flank in the immature axolotl, returning through the integument in adjacent regions of the body. A marked peak in the density of this outcurrent could be observed over the exact area of hind limb formation 4 to 6 days prior to its appearance. After a bud projected from the flank, current densities were observed to decrease in magnitude yet localize about the early limb. In about one‐half of the animals observed, current reversed its polarity and entered the apex of large buds, 0.4 to 0.5 mm in length. We discuss the possible role such endogenous currents and their associated fields may play in limb development and compare it to similar current flow associated with the regeneration of amphibian limbs.
Presence and localization of chitinase in Hydra and Podocoryne (Cnidaria, Hydrozoa)
Authors: Klug Marianne , Tardent Pierre , Smid Iris , Holstein Thomas
Published: June 2005

The presence of chitinase was checked in three species of Hydrozoa by incubating γ‐chitin‐red (Hackmann and Goldberg, '64) with crude extracts of entire polyps or parts of them. When the substrate is lytically degraded it releases its soluble red dye the quantities of which were spectrophotometrically (λ = 510 nm) determined. Crude extracts of entire polyps of Hydra attenuata Pall., H. circumcincta M. Sch., and Podocoryne carnea M. Sars all contained active chitinase. A more detailed localization which was studied in H. attenuata revealed that the enzyme is confined to the endoderm of the body column and that it is absent in the ectoderm and in the tentacles which contain the stenotele nematocysts. Therefore, it is very unlikely that enzymatic action of chitinase aids the nematocyst in boring holes in the cuticule of the prey.
Neural crest cell behavior in white and dark larvae of Ambystoma mexicanum: Time‐lapse cinemicrographic analysis of pigment cell movement in vivo and in culture
Authors: Keller R. E. , Spieth John
Published: June 2005

The pattern of migration and motile activity of developing pigment cells of the Mexican axolotl, Ambystoma mexicanum, were analyzed by time‐lapse cinemicrography in vivo and in culture. In vivo, melanocytes of dark (D/–) larvae migrate from dorsal to ventral in a highly directional manner. They are elongated and aligned parallel to the direction of migration. Nearly all protrusive activity occurs at their ventral, leading edges. Translocation occurs at a mean rate of 0.7 μm/min and involves alternate or simultaneous advance of the leading and trailing edges of the cell. Indirect evidence suggests that cytoplasmic flow is common. Directional migration occurs in apparent absence of contact between melanocytes. In white (d/d) larvae, protrusive activity is infrequent and the melanocytes move slowly or not at all. Explanted neural crest cells of dark and white larvae attach, spread, and differentiate into melanophores and xanthophores in culture. Individual cultured cells are unbiased in direction of protrusive activity and path of migration. Centrifugal spreading occurs by contacting inhibition of movement. Distribution of protrusive activity, polarity, and contact behavior changes with developmental age in vivo and in culture in ways that may be important in establishing the pigment pattern.
Cell cycle and histological effects of reinnervation in denervated forelimb stumps of larval Ambystoma
Authors: Olsen Cherie L. , Tassava Roy A.
Published: June 2005

Although nerves are a requirement for regeneration of a salamander limb, denervation of an amputated larval Ambystoma forelimb does not permanently prevent the limb from regenerating. When nerves grow back into the distal stump in sufficient numbers, regeneration occurs. In this study we examined histological and cell cycle events in denervated limb stumps of Ambystoma as they became reinnervated and began to regenerate. Prior to reinnervation and regeneration, dedifferentiated cells are present in the distal stump but are rarely synthesizing DNA or undergoing mitosis and are densely packed. About 2 days after the distal tip of the stump becomes reinnervated, the limb tip appears to “expand” as cells become less densely packed, and cell cycle activity begins. Mitotic index (MI) and labeling index (LI) increase slowly compared to MI and LI in control amputated limbs. Evidence for the localization of cycling activity is presented. In reinnervated stumps, the increase in LI precedes the increase in MI, suggesting that most of the cells are initiating cycling from the G1 phase.
The tissue‐specific patterns of lactate dehydrogenase (LDH), alcohol dehydrogenase (ADH), and G‐6‐phosphate dehydrogenase (G‐6‐PD) in adults and their occurrence during ontogeny of the guppy, Poecilia reticulata Peters (pisces: Poeciliidae)
Authors: Chingjiang Wu , Schröder Johannes Horst
Published: June 2005

Using polyacrylamide gel electrophoresis, the tissue‐specific and ontogenetic patterns of three dehydrogenase enzymes (LDH, ADH, and G‐6‐PD) of the guppy were investigated. Only one band of G‐6‐PD was detected in extracts of the liver. Isozyme LDH‐B4 was ubiquitous; isozyme LDH‐A4 was detected predominantly in extracts of muscle, and isozyme LDH‐C was only observed in extracts of the eye. Isozyme ADH‐A was detected in all tissues except the heart, while isozymes ADH‐B and ADH‐C were only detected in extracts of the eye. Isozymes LDH‐C and its heteromers with LDH‐B first appear following complete differentiation of the retinal cells. The appearance of isozyme LDH‐A coincided with the onset of contractile movements of muscle. Isozymes ADH‐B and ADH‐C are not detected until fry are 16 mm long after the onset of the complete differentiation of the retinal cells and visional function. Isozymes ADH‐D and G‐6‐PD are enzymes found only in embryonic stages and suddenly disappear after hatching. They may be regulative enzymes of cell differentiation.
The synchronisation of hatching in quail embryos: Aspects of development affected by a retarding stimulus
Authors: Vince M. A. , Ockleford E. , Reader M.
Published: June 2005

One hundred twenty‐eight quail embryos were tested in 33 groups. In each group one egg was stimulated with sounds at a rate known to delay hatching (0.9 clicks/second). In groups of bobwhite quail, stimulation began three days or two days before hatching, and three days before hatching in groups of Japanese quail. All eggs were incubated separately and respiration was monitored to indicate 1) the onset of lung ventilation, 2) the time when the egg began to click, and 3) the hatching time. In one set of bobwhite quail heart rate was also monitored.

Stimulated bobwhite quail hatched later than controls, but only when stimulated from three days before hatching. In the Japanese quail fewer embryos were retarded. In retarded bobwhites the duration of breathing, but not the duration of clicking, was lengthened. Respiration rates in stimulated bobwhites were higher throughout stimulation than those of controls. One factor contributing to this increase appeared to be the pacing of breathing in stimulated embryos: breathing tended to stabilise at the level of the stimulation rate. The heart rate of stimulated embryos was higher than that of controls, significantly so around the time of the onset of breathing.

In bobwhite, but not in Japanese quail, the increase in respiration rate was found to be associated with retardation and not with stimulation alone; it did not occur in those embryos which were stimulated but not retarded.
Hyaluronidase dissolves a component in the hamster zona pellucida
Authors: Talbot Prudence
Published: June 2005

Mammalian sperm must pass between cumulus cells and corona radiata cells before reaching the surface of the zona pellucida which surrounds the oocyte. The cumulus and corona radiata cells are separated from each other by an extracellular matrix (ECM) containing hyaluronic acid. The structure of this ECM and of the zona pellucida was investigated in the hamster oocyte‐cumulus complex (OCC) using transmission electron micros copy (TEM) following processing in ruthenium red. When fixed in the presence of ruthenium red, the ECM of the OCC and the zona pellucida were well preserved and highly structured. The ECM between corona radiata cells was comprised of a network of granules and filaments which resembled hyaluronic acid containing matrices described in other systems. The outer one‐third to one‐half of the zona pellucida was porous; the ECM of the corona radiata extended into these pores. Bovine testicular hyaluronidase, Streptomyces hyaluronidase, and hamster sperm extracts containing hyaluronidase each dispersed the cumulus cells and most of the corona radiata cells. TEM examination revealed that brief (5–10 min) hyaluronidase treatment of OCCs removed the matrix filaments and caused clumping of the granules in both the corona radiata and zona pellucida. Longer hyaluronidase treatments (15–30 min) removed both filaments and granules. Our observations are consistent with the ideas that: 1) the ECM between corona radiata cells contains hyaluronic acid, and 2) hyaluronic acid is present in the outer one‐third to one‐half of the zona pellucida. The function of sperm hyaluronidase in penetration of the OCC has not yet been established with certainty. Our data show that the substrate for sperm hyaluronidase is present in the zona pellucida as well as in the corona radiata and cumulus layer and suggest that the function of this enzyme in fertilization should be examined further.
Electron microscopic studies of planarian regeneration. III. Degeneration and differentiation of muscles
Authors: Morita Michio , Best Jay Boyd
Published: June 2005

Planarians were surgically decapitated, and morphological changes in their muscles during regeneration were studied with the electron microscope. Many damaged muscles were found in the vicinity of the wound surface immediately following decapitation. These stain darker than normal muscle and show degenerative changes in organelles as early as 1 hour. Some damaged muscles were observed to fall of f the cut surface into the external medium during the first 16 hours, but most were phagocytized by reticular cells mobilized to the wound area during this period. These were the only fates observed for damaged muscle in the vicinity of the wound. Detailed searches of large areas of wound region, at various times from 1 to 72 hours following decapitation, revealed no evidence of de‐ and redifferentiation of preexisting muscle cells. Newly differentiating muscle cells, identifiable by small nascent myofibril bundles in the cytoplasm close to the nuclear envelope or rough endoplasmic reticulum, are first discernible in the cellular aggregate of the new regeneration blastema on the third day. Vestiges of nuclear satellite material in the perinuclear cytoplasm of such cells indicate their derivation from neoblasts. Further histogenesis involved migration of these newly formed muscle cells to the apical perimeter of the blastema 4 to 6 days after decapitation. Neuromuscular junctions were observed to form during these later stages.
Pattern regulation along the proximodistal axis of the developing chick limb
Authors: Gay Steven W. , MacCabe Jeffrey A.
Published: June 2005

Transplants creating presumptively excess or deficient proximodistal segments were performed to investigate pattern regulation in stage 21 and stage 23 chick limb buds. Excess skeletal elements were not removed by regulation. Deficiencies appeared to be regulated by host tissue. The ability of the host tissue to participate in regulation declined in more proximal tissue and with increased age. These results suggest that there are two requirements for pattern regulation. First, the tissue in question must be sufficiently uncommitted in terms of pattern formation. Second, this tissue must be sufficiently close to the ectodermal ridge before it can respond. Results of previous work and implications for pattern formation are discussed with these requirements in mind.
Ectopic testes in the Norway rat
Authors: Gumbreck Laurence G. , Stanley Allan J. , Allison John E. , Peeples E. Edward
Published: June 2005

Animals with ectopic testes, some unilateral (on either the right or left side) and some bilateral, have appeared in a colony of King‐Holtzman rats. This heritable defect has been given the genetic symbol “ect.” Females carrying the gene are unaffected by it. When such females are bred to apparently normal males, they produce no ect offspring. Since 25% of their F2 generation carry the gene, it is assumed it is autosomal recessive. Studies involving selective breeding for males with ectopic testes indicate that some males have genomes resistant to the expression of the ect gene and that the apparent thresholds essential to left side, right side, and bilateral expression appear to be a secondary control of the multifactorial type.
The use of cell surface antigens to characterize and select for fragments of human chromosomes retained by interspecies hybrids
Authors: Kamarck Michael E. , Macyko Catherine A. , Jones Carol , Ruddle Frank H.
Published: June 2005

We have used a mouse cell transformant generated by human chromosome‐mediated gene transfer (CMGT) to explore the use of cell surface antigens in the identification of fragments of human chromosomes retained by somatic cell hybrids. The transformed line, 21–30b, contained an intact rearranged human chromosome, and could be shown by isozyme analysis to contain genetic material from chromosomes 9 and X. By using the transformant as an immunogen in mice, it was also possible to produce antiserum to human‐specific surface antigens. Using genetically characterized human × rodent hybrid lines, the genes controlling expression of these antigens could be localized to 11pter → 11p13, segregating concordantly with surface antigen S3. These conclusions were possible despite the fact that the presence of chromosome 11 in the transformant was not detectable by the presence of chromosome specific isozyme LDH‐A or surface antigens W6/34 and 4F2. Finally, the fluorescence‐activated cell sorter (FACS) was used to fractionate the transformant cells into antigen positive and negative subpopulations. This resulted in the isolation and characterization of four additional chromosome rearrangements involving interspecies chromosome translocations. This work demonstrates the value of chromosome‐specific surface antigens and the FACS in the evaluation of human chromosome fragments retained by interspecies hybrids.
Heat shock proteins in Aurelia (cnidaria, scyphozoa)
Authors: Black Robert E. , Bloom Laird
Published: June 2005

Heat shock proteins (hsp) in Aurelia identified by one‐dimensional SDS‐PAGE are of sizes 93,83,70,68,45, and 39 kD, the most rapidly labeled being hsp 70 in all developmental stages. Labeled hsp in the polyp are found mostly in the epidermis; gastrodermal nuclei are also labeled. The minimum temperature for induction of the proteins is about the same (27° to 28°C), regardless of whether polyps have been cultured at 15° or 24°C. Adults and planulae taken from natural water at 28°C do not show accumulation of hsp 70. Induction of strobilation by raising polyps from 15° to 25°C is not associated with appreciable labeling of hsp. Polyps transferred to higher or lower salinity have decreased protein synthesis but do not synthesize stress proteins.
The effect of trifluoperazine on maturation of Xenopus laevis oocytes
Authors: Hollinger T. G. , Alvarez I. M.
Published: June 2005

Full grown Xenopus oocytes were incubated with trifluoperazine (TFP) or injected with TFP. Incubation of oocytes in TFP resulted in normal‐appearing meiotic maturation, as judged by the presence of the white spot and the absence of the germinal vesicle. Cortical granule breakdown in TFP‐incubated oocytes was not normal. Abnormal cortical granule breakdown was also observed when progesterone‐matured oocytes were activated in the presence of TFP. Oocytes microinjected with TFP and incubated with progesterone appeared to mature in a normal manner, as judged by the absence of the germinal vesicle; these underwent cortical granule breakdown following activation, but frequently lacked the white spot. Oocytes microinjected with TFP did not mature in the absence of progesterone. We conclude that incubation, although not microinjection, of oocytes with TFP induces essentially normal resumption of meiotic maturation.
Two‐dimensional gel analysis of zymogen‐activating factors in small intestine of the mouse
Authors: Isobe Masaharu , Ogita Zen‐Ichi
Published: June 2005

Zymogen‐activating factors in the mouse were investigated by two‐dimensional electrophoresis. Mouse pancreatic zymogens—trypsinogen‐I group (Try G‐I group), trypsinogen‐II (Try G‐II), and chymotrypsinogen (Chy G)—were purified using DEAE‐cellulose column chromatography. Analysis by two‐dimensional electrophoresis, using the purified zymogens as substrates, revealed enterokinase isozymes and chymotrypsinogen‐activating factors in both the intestinal extract and luminal fluid. Mouse enterokinase was separated into at least two bands in the first‐dimensional gel, each able to activate both trypsinogens Try G‐I group and Try G‐II. Chymotrypsinogen‐activating factors were separated into several bands in the first‐dimensional gel. Some activating factors showed mobilities similar to those of mouse enterokinase isozymes. Moreover, other activating factors that can activate chymotrypsinogen were present only in the more anodal area of the first‐dimensional gel. These findings indicate that at least two enterokinases and several chymotrypsinogen‐activating factors play an important role in the process of activating digestive enzymes.
Cardioregulatory nerves in the spider Eurypelma marxi Simon
Authors: Gonzalez‐Fernandez Federico , Sherman R. G.
Published: June 2005

The objective of this study was to locate nerves arising from the CNS that have a cardioregulatory function in the tarantula, Eurypelma marxi Simon. Ramifications of the paired abdominal nerve VIIIb merge with the cardiac ganglion within the first heart segment. Electrical stimulation of the branches of nerve VIIIb that connect with the cardiac ganglion produce changes in heartbeat rate and amplitude. Nerve cutting experiments indicate that no other cardioregulatory nerves are present.

Both increases and decreases in heart activity can be produced upon electrical stimulation of nerve VIIIb on each side of the heart. Only one action potential associated with the response of each type could be recorded in each member of the nerve pair. Therefore, we conclude that there are two inhibitory and two acceleratory neurons that arise in the central nervous system to modulate heartbeat activity.

The inhibitory effect becomes maximal at a stimulation frequency of 20–30 Hz and the accelerator effect at 30–40 Hz. The aftereffect of acceleratory nerve activity exceeds that of inhibitory nerve activity. When the inhibitor and accelerator are activated simultaneously, the inhibitor dominates.

The regulatory nerves interact with neurons in the cardiac ganglion. During inhibition, the number of externally recorded spikes in each ganglionic burst is decreased. The rate and magnitude of the heartbeat are decreased concomitantly. Stimulation of the accelerator enhances electrical activity in the cardiac ganglion at the same time that the heartbeat rate and amplitude are increased.
Functional study of the Caenorhabditis elegans secretory‐excretory system using laser microsurgery
Authors: Nelson F. Kenneth , Riddle Donald L.
Published: June 2005

Individual cells of the Caenorhabditis elegans secretory‐excretory system were ablated by laser microbeam in various larval stages. Effects on growth, molting, osmoregulation, fertility, longevity, and dauer larva formation were tested. Single‐cell ablations did not prevent subsequent molting, but ablation of the pore cell or the duct cell resulted in the absence of the normal cuticular lining of the excretory duct following a molt. When the pore cell, duct cell, or excretory cell was ablated, the animals filled with fluid within 12–24 hr and died within a few days, producing very few progeny. Ablation of the excretory gland cell, on the other hand, had no obvious developmental or behavioral effects. Excretory activity was monitored in dauer larvae by observing pulsation of the excretory duct in conditions of differing osmolarity. The rate of pulsation was quite variable over time in conditions of low osmotic strength, but averaged five‐ to six‐fold higher than that observed in buffered saline. These observations, combined with the effects of laser ablation, lead to the conclusion that one function of the excretory system is osmoregulation.
Division of constricted and urethane‐treated sand dollar eggs: A test of the polar stimulation hypothesis
Authors: Rappaport R. , Rappaport Barbara N.
Published: June 2005

In spherical cells with a central mitotic apparatus, the centers of the asters are closer to the poles than to the equator. This circumstance is basic to several hypothetical explanations of the way in which the mitotic apparatus establishes the division mechanism. This investigation was designed to determine whether that geometrical relationship is necessary for division.

Fertilized, mechanically denuded sand dollar eggs were inserted into glass loops, which reduced the diameter in the constriction plane from the normal 142 to 78–80 μm and partly constricted the cell into equal parts. The mitotic apparatus straddled the constriction, and its length was not significantly changed. The manipulation increased the distance from the astral centers to the poles and decreased the distance from the astral centers to the equator to a degree that reversed the normal distance relations. These cells divided normally.

Ethyl urethane (0.06 M) reduces the size of the mitotic apparatus and blocks cleavage in spherical cells. When treated cells are confined in 80‐μm i.d. capillaries, they divide. Treated cells also divide when they are constricted by an 80‐μm i.d. glass loop if the mitotic apparatus straddles the constriction. An equal degree of constriction in the subfurrow and subpolar areas did not reverse the effect of urethane.

The results demonstrate that cleavage does not depend on the normal distance relation between the mitotic apparatus and the poles, and that the urethane effect can be remedied only by reducing the distance between the mitotic apparatus and the equatorial surface. Both findings are inconsistent with the polar stimulation hypothesis.
Compensatory testicular hypertrophy in the lizard Anolis carolinensis
Authors: Summers Cliff H.
Published: June 2005

In reproductively responsive, male Anolis carolinensis undergoing artificially induced testicular recrudescence, unilateral orchidectomy of the left testis produced compensatory hypertrophy of the remaining testis. Testosterone inhibited this compensatory testicular hypertrophy on a weight basis, but did not reduce the rate of spermatogenic development. These results suggest that there is a mechanism of testosterone feedback in Anolis carolinensis that controls gonadotropin secretion during the recrudescent phase. In reproductively thermorefractory lizards, unilateral orchidectomy had no effect on the remaining testis. Administration of exogenous follicle‐stimulating hormone to refractory animals increased testicular weight and stage of spermatogenic development. Sensitivity to gonadotropin, as well as failure of unilateral orchidectomy to produce compensatory hypertrophy in refractory male anoles, suggests that the control of the refractory period in A. carolinensis results from physiological mechanisms in the pituitary gland or brain rather than in the testis.
The development potential of ethanol‐induced monosomic and trisomic conceptuses in the mouse
Authors: Kaufman M. H. , Bain I. M.
Published: June 2005

The development potential of fertilized embryos isolated from female mice previously given a single dose of either a dilute solution of ethanol or distilled water (controls) by mouth was studied. Exposure to ethanol occurred at various times during the cycle leading to ovulation and shortly after fertilization. The chromosome constitution of all preimplantation embryos isolated from these females was determined either at the first cleavage mitosis or at the morula stage. The incidence of aneuploidy in the ethanol‐exposed groups at these times was approximately 19% and 13.5%, respectively, with a similar number of monosomic and trisomic conceptuses observed at these times. In addition, about 2% of all conceptuses examined were triploid. Further females were autopsied on the 10th or 11th day of gestation, though the chromosome constitution of only the morphologically abnormal or developmentally retarded embryos was determined. Eight embryos out of a total of 16 studied in the ethanol‐exposed group were either aneuploid or triploid, whereas in the control group only one out of 11 examined proved to be aneuploid. The triploids and ethanol‐induced aneuploid conceptuses appeared to be capable of surviving to the morula stage but generally failed to survive to the 10th/11th day. No monosomics were in fact observed in the postimplantation series. The present findings are briefly discussed with reference to the possible pathogenesis of spontaneous abortions in man, which often possess similar types of chromosomal anomalies.
Firing patterns of closer motoneurons during reflex activity in the dimorphic claws of the Lobster Homarus americanus
Authors: Costello Walter J. , Hill Russell H. , Lang Fred
Published: June 2005

The in vivo firing patterns of the fast closer excitor (FCE) and slow closer excitor (SCE) motoneurons to the dimorphic claws of the lobster Homarus americanus were analyzed during reflex closure activity by identifying postsynaptic potentials in muscle fibers with known motor innervation. Three types of claw activity were observed: slow closure, rapid closure, and maintained closure. Slow closure and rapid closure in both claws were mediated by SCE and FCE, respectively. In the cutter, maintained closure was mediated only by SCE; in the crusher, both FCE and SCE could maintain closure. The homologous SCEs displayed no significant differences in activity; in both claws, they fired at medium‐to‐high frequency. The homologous FCEs did display different spike frequencies during claw closure. The crusher FCE fired at high frequencies; the cutter FCE fired at much lower frequencies. Such in vivo differences in axon activity between homologous FCEs are correlated with claw dimorphism and with the population of muscle fiber types.
Injury, nerve, and wound epidermis related electrophoretic and fluorographic protein patterns in forelimbs of adult newts
Authors: Garling David J. , Tassava Roy A.
Published: June 2005

Polyacrylamide slab gel electrophoresis and [35S]methionine fluorography were used to examine proteins in regenerating newt limbs, amputated denervated limbs, unamputated denervated limbs, and separated blastema mesodermal core and wound epidermis. A total of 27 protein electrophoretic bands were obtained from amputated limbs and 24 bands from unamputated limbs. Amputation resulted in the appearance of 4 new bands and the loss of 1 band as compared to unamputated limbs. These 5 banding differences were apparent on stained gels 3 days postamputation and were maintained through 10 weeks postamputation (complete regenerate stage).

Only one band in unamputated limbs was always detectable on fluorographs, whereas virtually all of the stainable bands of amputated limbs were visible on fluorographs. Amputation clearly stimulated a marked, generalized increase in the synthesis of limb proteins.

The 5 amputation induced changes were equally evident in stained gels of both innervated and denervated limbs. Amputated denervated limbs possessed a full set of fluorographic bands (including the 5 differences) through 18 days postamputation. However, denervation without amputation was not sufficient to alter the stainable banding pattern.

Wound epidermis and mesodermal core both displayed the 5 banding differences and had identical banding patterns with the exception of one epidermal specific band. This band was also present in whole limb skin but was absent in unamputated mesodermal limb tissue. This was the only band of unamputated limbs that was consistently detectable by fluorography.

It is concluded that amputation induces nerve independent changes in protein synthesis that are common to both mesodermal core and wound epidermis. These changes may represent preparation for cellular proliferation.
Electrophysiology of in vitro insulin‐ and progesterone‐induced reinitiation of oocyte meiosis in Rana pipiens
Authors: Lessman C. A. , Marshall W. S.
Published: June 2005

Induction of meiosis in Rana pipiens oocytes in vitro was studied using intracellular electrophysiological recordings and a morphological count of nuclear dissolution. In type III (i.e., defolliculated theca‐free, with follicle cells) and type IV (i.e., denuded lacking follicle cells) Rana oocytes (Schuetz and Lessman, '82), Na+‐insulin evoked nuclear or germinal vesicle dissolution (GVD), apparent reinitiation of meiosis, and marked reductions in cellular membrane potential and membrane current. Electrophysiological indications of the reinitiation of oocyte meiosis were most strongly apparent in the marked reduction (ca. 98%) of membrane current. The overall GVD activity of insulin was reduced but not totally absent in type IV oocytes compared to type III cells that received similar hormone treatment, confirming previously published findings that the follicle wall enhances insulin‐induced GVD. Results confirm insulin GVD activity in this system and demonstrate that insulin‐induced reinitiation of meiosis is associated with changes in membrane‐associated parameters that are indistinguishable from those induced by progesterone. These results raise interesting questions concerning the cellular mechanism by which two chemically dissimilar hormones (i.e., steroid vs. protein) have similar or even identical effects on a cell such as the oocyte. The findings presented are consistent with the concept that more than one hormone may be involved in meiotic maturation of the oocyte.