bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some critical points in the metamorphosis of the halichondrine sponge larva
Authors: Wilson H. V. 
Published: February 2005

AbstractThe larval epithelium cells of Mycale syrinx (O. Schm.) unite syncytially with one another. The stratum so formed is continuous with the syncytial interior of the larva and into this interior the epithelial nuclei are drawn. Many of them degenerate and are digested by the syncytium or, eventually, by nucleolate cells. The syncytial cytoplasm breaks up into cell bodies, some surrounding epithelial nuclei and thus forming choanocytes, others surrounding nucleolate and non‐nucleolate mesenchyme nuclei. The larval epithelial cells do not then become the choanocytes. Only their nuclei are specifically determined. The bodies of the choanocytes are picked out of the general syncytium in accordance with the location which the nuclei may occupy at the time. Non‐nucleolate cells of the interior break through to the surface and form epidermis. Or non‐nucleolate nuclei, usually not in special cell bodies but in the general syncytium, are drawn to the surface, the surface layer there condensing to form epidermis.There is a provisional formation of limiting membranes by the reticular syncytium around spaces of the interior and at the surface. The definitive cellular membranes, epidermis and canal epithelia, are only completed later. Some mesenchyme cells may be digested by the general syncytium. Such cells lie in vacuoles, as in a digesting protozoan.
The phenomena of anuran metamorphosis. III. The development of the thyroid gland
Authors: Etkin William 
Published: February 2005

AbstractThis paper presents a study of the growth and histological development of the thyroid in three species of frogs, the small Pseudacris triseriata, the large Rana catesbeiana and the intermediate Rana palustris. It was found that the history of the gland in relation to metamorphosis is essentially the same in all. Previous to metamorphosis the gland is small, and the cells very poor in cytoplasm. At the beginning of metamorphosis (i.e., rapid hind leg growth) the thyroid shows a marked acceleration of growth and activity, which continues and reaches a peak at the time of the emergence of the front legs. Late in metamorphosis a regression occurs.The conclusion is drawn that there is a rising concentration of thyroid hormone during the course of metamorphosis. The author has previously shown that such a rising concentration will induce the normal pattern as to sequence and time spacing of metamorphic events.The beginning of metamorphosis is conceived as dependent upon the time of stimulation of the thyroid and the pattern of its subsequent continuance as dependent upon the pattern of response of this gland.
The interkinetic migration of embryonic epithelial nuclei
Authors: Sauer F. C. 
Published: February 2005

AbstractNuclei of columnar epithelia of vertebrate embryos move to the free epithelial surface before a division, the movement of the nucleus accompanying a shortening of the columnar cell. After division at the free surface the daughter cells elongate, the nuclei passing away from the free surface. This is illustrated by drawings and measurements of cells of the fore‐gut it of the garter snake embryo. The elongation of these cells after mitosis is associated with an elongation of the spindle fibers to produce a prominent cytoplasmic fiber which persists through the interkinetic stage and into the next mitosis. The appearance of nests of nuclei in mitosis is accounted for by the fact that descendants of an earlier cell have kept approximately in step in their divisions.
The gularis muscle in Urodela
Authors: Eaton Theodore H. 
Published: February 2005

AbstractThe last muscle in the transverse superficial throat series in all genera of salamanders is here called ‘gularis.’ This eliminates a long list of synonyms. A description of its metamorphic changes in Dicamptodon (Ambystomidae) and comparison of the larval and adult conditions in this genus with those in other known genera clears up the homologies of the muscle throughout the series. The study is based on dissections and a survey of the literature covering all important groups except the Hynobiidae.
The adrenal‐autonomic complex in Alligator mississippiensis
Authors: Lawton Florence Emily 
Published: February 2005

AbstractThe adrenal‐autonomic systems were studied in embryonic and juvenile alligators. In the class Reptilia virtually no previous work has been done on the adrenal‐autonomic systems.The adrenals are definite bodies, distinct from the kidney. In young forms they are in close proximity to the gonads and in both the embryonic and young forms the adrenals lie against the wall of the inferior vena cava.Cortical cells predominate. In embryonic forms the medullary tissue is not dispersed as in older forms. The medullary tissue lies in close proximity to the blood sinuses or may completely surround them.The arterial supply is scanty there being only a few small arteries to the adrenal while the blood supply from the inferior vena cava is profuse.The innervation is segmental in nature with four or five consecutive sympathetic ganglia giving off sympathetic nerves to the adrenal. Parasympathetic innervation was not observed in the forms studied. The innervation suggests a transition from lower forms with their segmental diffuse medullary material to the higher forms that display concentration of nerve supply and adrenal tissue.
The relation of germ cell degeneration to modifications of the testicular structure of Plethodontid salamanders
Authors: Burger J. Wendell 
Published: February 2005

AbstractA study of the male sexual cycles of five species of Plethodontid salamanders indicated that annually occurring non‐functional regions at the anterior and posterior ends of the testis are associated with the two types of germ cell degeneration: (1) extensive degeneration of secondary spermatogonia in the anterior region; (2) complete degeneration in the posterior region, beginning with the young spermatocytes, of all germ cells except the primary spermatogonia. The improbability of the posterior degenerations being caused by a suggested climatic action is discussed. The presence only in urodeles of a caudo‐cephalic polarity of spermatogenesis over the length of the testis and of these degenerations seem more than a coincidence. The abortive spermatogenetic cycle of immature males shows a caudo‐cephalic sequence and the stages of degeneration that are identical with the adult. Inanition experiments indicate that the formation of secondary spermatogonia and the ability to form sperm are not synonomous. It is suggested, therefore, that normally more of the testis is activated than can be brought to a successful spermatogenesis. Since spermatogenesis moves caudo‐cephalically, the posterior end will be left outside the functional zone, and consequently the cells degenerate. The anterior degenerations and the failure of anterior end of the testis to be involved in spermatogenesis, mark the anterior regulation of the spermatogenetic process. Degenerations can be regarded as the by‐product of the regulation of overactivation.
The continuity of the germ cells in the urodele, Plethodon cinereus (Green)
Authors: Burger J. Wendell 
Published: February 2005

AbstractPlethodon cinereus is favorable for a study of the history of the germ line. The germ cells are large, while the gonads are small and show an almost diagrammatic structure. Germ cell degeneration is not extensive during ontogeny. As long as all the germ cells contain yolk during development, these cells are derived solely from germ cells. In Plethodon, yolk lasts in all germ celis through sex differentiation. A comparison of the number of mitoses necessary for the primordial germ cells to produce the numbers of germ cells in gonads where every germ cell contains yolk, with the mitoses necessary for the primordial cells to produce the adult complements of germ cells, shows that at least 72% of the increase of germ cells can be followed by yolk. A cytological study from the embryo through the adult sexual cycle gave no evidence that somiatic cells ever transform into germ cells. Mitoses are abundant in the testes of salamanders starved 4 months. This fact together with a statistical study on the adult male sexual cycle indicates that the germ cells present in the testis do not need to be augmented by transformed somatic cells. It is concluded that in Plethodon germ cells alone give rise to germ cells, and that the germ line is continuous.
The effect of ultracentrifuging on Paramecium, with special reference to recovery and macronuclear reorganization
Authors: King R. L. , Beams H. W. 
Published: February 2005

AbstractParamecium caudatum becomes much elongated upon centrifuging at 21,000 times gravity. The chromatin is sometimes forced from the achromatic matrix of the macronucleus. The materials in the cell are redistributed according to their relative specific gravities as follows: At the centrifugal end of the cell, crystals, layer of fluid, micronucleus and macronuclear chromatin, food vacuoles and neutral red inclusions, achromatic matrix of the macronucleus, endoplasm with large clear alveoli, and fat, at the centripetal end of the cell. The contracting vacuole is displaced sometimes but not the feeding canals or pore. In some cases the crystals, micronucleus and macronuclear chromatin may be extruded from the cell. Animals which survive centrifuging regain their usual shape and the disturbed materials return to their usual distribution rapidly. Sometimes the crystals remain in large compact masses and are so passed to the daughter cells upon fission. The two components of the macronucleus do not fuse the macronuclear chromatin regenerates an achromatic matrix, and division is somewhat delayed. The old macronuclear matrix persists over a long time and sometimes interferes with division. Animals which have no micronucleus may survive and divide, but no amicronucleate races have been established. Apparently macronuclear chromatin is necessary for the survival and division of P. caudatum; in the absence of the macronuclear chromatin no replacement occurs from the micronucleus. The membrane of the contracting vacuole is temporary.
The dimensions of the renal tubules of Necturus maculosus
Authors: Kempton Rudolf Theodore 
Published: February 2005

AbstractThe method of micro‐injection was used in the study of a large number of tubules. The limits of the several parts of the tubule were determined with a high degree of accuracy without sectioning; the error of the measurements was small. Of 137 tubules studied the measurements of forty‐nine comprised the entire length from renal corpuscle to collecting duct or ureter.The proximal tubule was found to be about twice as long as the distal. While the longest proximal tubule was nearly six times the length of the shortest, the great majority of tubules fell within a much shorter range. There was little or no correlation between proximal tubule length and weight of the animal.The proximal tubule is larger in diameter than the distal tubule. Calculations indicate that the area of exposed cell surface in the proximal tubule is nearly four times as great as in the distal; however, compared to tubule volume, a relatively greater cell surface is exposed in the distal tubule.
Studies on the amphibian digestive system II. Comparative histology of the pancreas, following early larval development, in certain species of anura
Authors: Janes R. G. 
Published: February 2005

AbstractAnatomically, the structure of the pancreas in four species of anura studied, is very similar during various stages of development. The gland is greatly reduced in size during both artificially induced and natural metamorphosis. When metamorphosis is artificially induced, the regression of the pancreas occurs somewhat earlier and is a little more rapid than in the case of natural metamorphosis, but the condition exhibited at the end of the phenomenon is similar in each case. Correlated with the anatomical regression during metamorphosis, many of the acinous cells, small collecting ducts and sinusoidal capillaries, undergo degeneration. This histolysis occurs somewhat earlier in animals that undergo artificially induced metamorphosis, but regeneration occurs about the same time in both metamorphic types. Most of the degenerated elements are autolyzed in situ; some are sloughed into sinusoidal capillaries; while a small number are eliminated through pancreatic ducts. It is doubtful whether these elements are ingested by phagocytes. The pancreas, in certain cases during later stages of metamorphosis, appears to take on a temporary hematopoietic function leading to the differentiation of red blood cells. Zymogen granules, lipoid granules, and X‐granules are demonstrated in the anuran pancreas. X‐granules, found in the larvae, are indeterminate in nature and are quite probably remnants of vitelline material found in the early embryo.
A study of the nucleoli of certain insects and the crayfish
Authors: Johnson Mychyle W. 
Published: February 2005

AbstractNucleoli in the germ cells of certain Orthoptera, Hemiptera and the crayfish have been studied. In Ceuthophilus (camel cricket) these bodies are found to be definitely connected with chromatin threads and are believed to be products of chromatin.The large structure in the ova of Nemobius (cricket) is interpreted as a nucleolus because of its very irregular behavior and apparent complete disappearance.It is found that some of the nucleoli of Gelastocoris (toad bug) arise within the chromatin threads.Observations on Cambarus (crayfish) fail to show nucleolar extrusion, a phenomenon which has formerly been reported for this form.The unique behavior and fate of the nucleolar material in Pselliopus (true bug) is described. In this species the nucleolar material is added to and becomes part of the general oxychromatin network of the nucleus.This study fully supports the opinion that nucleoli have a chromatin origin.
The segmental excretory glands of Artemia salina linn., var. principalis simon. (the brine shrimp)
Authors: Warren Herbert Stetson 
Published: February 2005

AbstractArtemia salina, a very widely distributed species in North America, Europe and Asia, breeds freely and rapidly under laboratory conditions, living in all salinities from fresh water to almost saturated brine. Its soft exoskeleton permits of easy sectioning.The morphology and embryology of the segmentally arranged excretory glands—the antennal, mandibular and maxillary glands, are described. The antennal gland, consisting of extracellular end sac and intracellular excretory duct, is located in the second antenna and opens to the exterior on the lateroposterior face of the protopodite. It attains its maximum development by the sixth instar, degenerating by the tenth. The vestigial mandibular gland consists only of an end sac surrounding a schizocoele, and a rudimentary duct. The large maxillary gland in the adult consists of an end sac, an excretory duct of three circular coils, and a terminal duct opening to the exterior. The maxillary gland develops from a mass of mesenchyme cells in the maxillary segment of the nauplius, becoming fully differentiated by the sixth instar.The vestigial second maxilla has two bristles. It serves only as a terminus for the maxillary gland. A pair of small ganglia are accepted as internal evidence for the presence of a maxillular segment.The presence of three pair of schizocoeles in three consecutive segments is interpreted as evidence of homology with the Annelid coelome, with the possibility of further homologizing the excretory ducts with the segmental nephridia.
A cytological study of the ovaries of the bats Myotis lucifugus lucifugus and Myotis grisescens
Authors: Guthrie Mary J. , Jeffers Katharine R. 
Published: February 2005

AbstractOvaries of bats, Myotis lucifugus lucifugus and M. grisescens, have been studied in all phases, except gestation, of the annual reproductive cycle. Oocytes arise in the germinal epithelium and grow with an orderly differentiation of the storage products of metabolism—chondriosomes, fat drops, and yolk vesicles. The evidence indicates that the zona pellucida is derived from the oocyte. Squamous cells of the primary follicle become cuboidal and then columnar as follicular growth begins (unilaminar secondary stage). The secondary follicle becomes multilaminar and in a very few cases gives rise to a tertiary follicle by antrum formation. Most growing follicles undergo retrogression by one of two methods. Degeneration of type I is common in multilaminar follicles and begins in the granulosa which is almost completely obliterated before the oocyte is affected. Spindles occur in some of these oocytes and fragmentation is common; phagocytes eliminate the contents of the zona. In type II, which is rare and has been found only in unilaminar secondary follicles, the oocyte degenerates, leaving an uninjured granulosa. Medullary cords are common embryonic vestiges in these ovaries; epithelial nodules are less frequent. Interstitial cells are very numerous in newborn bats, arise throughout life from the hypertrophied thecae internae of retrogressing follicles of type I, are phagocytized and, also, undergo hyaline degeneration, are hypertrophied in late pregnancy, and continue so during lactation.
The chromosomes in the maturation of the germ cells of two species of triclad Turbellarians
Authors: Pennypacker Miriam I. 
Published: February 2005

AbstractThe maturation of the germ cells of the two hermaphroditic species, Curtisia foremanii (Girard) and Bdelloura candida (Girard) has supplied the material for this chromosome study.Both species of flatworms are believed by the author to possess a diploid number of twelve chromosomes and a haploid number of six, although Curtisia foremanii has previously been reported as having a smaller and variable number of chromosomes.A tendency of the chromatids comprising individual chromosomes to separate from one another at certain times was noted in both species. This action results in giving the appearance of a larger number of chromosomes than the germ cells actually possess. A further source of apparent increase in chromosome number in the Curtisia oocytes, after treatment with the usual Allen's B3 and B15 and Heidenhain's iron haematoxylin, is the presence of some deeply staining, non‐chromatin material.No significant differences in number, form and behavior of chromosomes of male and female complexes were noted, with the possible exception of the tendency of the chromatids to separate from one another, to be greater in the female than in male germ cells.
Gynandromorph spiders
Authors: Exline Harriet 
Published: February 2005

AbstractFour cases of gynandry in American spiders present the following morphologic deviations: The specimen belonging to Neoantistea agilis (Keyserling) externally is a bilateral gynandromorph with distortion of the single male palp, with half of the epigynum nearly normal; internally both testes and ovaries are present. The Drassodes neglectus (Keyserling) is not a completely developed bilateral gynandromorph. One side has a normal male palp, a larger chelicera and longer legs than the other, the epigynum is complete and normal; internally only degenerate ovaries are present. The Linyphiid, near Bathyphantes, is three‐quarters female, the only male organ being an imperfectly developed male palp. Ovaries are well developed but immature, whereas the epigynum is complete. In the Pardosa sternalis (Thorell) the anterior part of the body is male, as indicated by the swollen palps and the length of the legs; the epigynum is completely developed, but internal reproductive organs are missing except for a very much aborted ovary. The bisexuality in all cases has caused degeneration or abnormalities in the reproductive structures.Included is a tabulation of all recorded instances of gynandry in spiders, arranged according to the type of abnormality. The term ‘leg‐index’ is introduced to express ratio between length of the leg and length of cephalothorax.
Morphogenesis of the cranial muscles of Amblystoma punctatum
Authors: Piatt Jean 
Published: February 2005

AbstractThe development of the cranial musculature of Amblystoma punctatum is described in detail, for both larva and adult. In addition, a brief account of the innervation of each muscle is given. The study of normal development is supplemented by extirpation experiments performed on embryos in early stages of development. These extirpations include the mesodermal head segments, mesoderm of mandibular, hyoid, second branchial, third branchial arches, and somites 1, 2 and 3. The eye muscles are found to develop from the mesodermal head segments in precisely the same manner as in other classes of vertebrates; head segmentation of Amphibia, though less accentuated, is shown to be homologous with that of other classes. The remaining extirpation experiments corroborate, in general, the finding from normal development studies. An attempt is made to summarize in tabular form the prospective fate of the prechordal plate and parachordal mesoderm, the two earliest divisions of the head mesoderm, with regard to their complete muscle derivatives.
Winning business: business development issues and priorities
Authors: Coulson‐Thomas Colin 
Published: February 2005

Abstract

Training and development activities are largely overlooking the attitudes, knowledge and skills required for relationship and account management and winning business in competitive bid situations.
There is considerable scope for using E‐business to develop new markets and change how business is done and for packaging and exploiting knowledge and understanding to generate additional income.
Many organizations devote too little emphasis to defining and communicating their corporate strengths and core competencies.
More proactive and differentiated approaches to business development are required. Greater selectivity and automating the more routine aspects of proposal preparation can release the resources needed to improve and tailor individual responses.
Prioritization, focus and learning from experience are vital. Proposals should be structured around the main requirements of the prospective customer and the key influencing and deciding factors that have been identified.

Copyright © 2001 John Wiley & Sons, Ltd.
Acceleration of onset of oocyte maturation in vitro by luteinizing hormone
Authors: Kaplan R. , Dekel N. , Kraicer P. F. 
Published: February 2005

AbstractThe purpose of this study was to analyze the effect of luteinizing hormone (LH) on the earliest stage of oocyte maturation ‐ the stage of breakdown of the dictyate nucleus. Oocytes were isolated from the preovulatory follicles of adult, cyclic rats. They were incubated in culture medium with or without 10 μg/ml LH. The cultures were observed continuously for up to 3 hours. Analysis of the rate of disappearance of the germinal vesicle nucleolus revealed that LH accelerated the breakdown process. The median times of disappearance were 91.3 minutes without LH and 62.3 minutes with LH. This is in accord with earlier reports on enhancement of fertilizability of oocytes matured in vitro with LH. Thus, although oocytes mature spontaneously in culture, the maturation remains LH sensitive.