bluuebunny/crossref_metadata_2025_split huggingface dataset:
A survey of reduced silver techniques for demonstrating neuronal degeneration in insects
Authors: Lund R. D. , Collett T. S. 
Published: June 2005

AbstractDegeneration reactions in locust and moth brains have been studied using a number of techniques commonly applied to the vertebrate nervous system after a variety of central and peripheral lesions. The degeneration reaction is stainable by Nauta rather than “neurofibrillar” methods. A survival time of 2–3 days is desirable to produce staining of the part of the axon separated from its cell body. Three techniques are reliable and generally consistent one with another: the methods of Nauta and Gygax ('51) and of Fink and Heimer ('67) after formaldehyde fixation on frozen sections or with modification on paraffin sections, and the method of Nauta and Gygax ('54), with or without some of the pretreatment stages omitted, on material fixed in formol‐dichromate solution.Material stained by the last method and studied under the electron microscope shows stain granules in axons and terminals partly associated with dense bodies (possibly degenerating mitochondria) and partly more widely scattered.The reliability of the methods has been tested by examining degeneration patterns after lesions in the optic lobe restricted to the retina, lamina and medulla. The resulting distribution of degeneration granules can in part be predicted with some confidence from the descriptions of Cajal and Sanchez ('15), and Zawarzin ('13).It is hoped that the methods in association with fine structural correlative studies may be useful in elucidating anatomical interrelations within the insect nervous system.
Attempts to induce polyspermy in the rabbit by delayed insemination and treatment with progesterone
Authors: Chang M. C. , Hunt Dorothy M. 
Published: June 2005

AbstractRabbits were injected with progesterone at various times before ovulation and inseminated at the time of ovulation (delayed insemination). When their eggs were examined 11–13 hours after ovulation, it was found that 15, 63, 73, and 61% of the eggs were penetrated following the injection of 4 mg progesterone at 24, 12, 6, and 0 hours, respectively, before ovulation as against 51% for control animals. Of the 213 penetrated eggs, 84% had two pronounclei with two polar bodies, 9% had three pronuclei without the second polar body, 3% had three pronuclei with the second polar body, 3% were unevenly cleaved, and 1% had two fertilizing sperm tails. These abnormalities were not correlated with the time of progesterone treatment. The formation of one or two pronuclei was frequently observed when aged, unfertilized eggs were cultured for 3–4 hours. It was concluded that the presence of three pronuclei following delayed mating in the rabbit is due to the formation of a pronucleus from the second polar body or to the fragmentation of the female pronucleus, rather than to polyspermy.
The differentiation of crayfish muscle fibers during development
Authors: Bittner George D. 
Published: June 2005

AbstractAs the length (x, mm) of the propodite segment of a crayfish cheliped doubles, the average diameter of the opener muscle fibers also doubles, whereas average fiber length (y, mm) is given by y = 0.16 × + 0.5. Fiber length is increased by the continuous addition of new sarcomeres in propodites 6–22 mm long; in propodites of less than 6 mm, about half the linear growth can be accounted for by increases in sarcomere length. Cable properties of opener muscle fibers differ from those of vertebrate fibers. In a claw of any given size, length constant is not correlated with fiber diameter, muscle input resistance is not proportional to the two‐thirds power of the diameter, and mjp amplitude is independent of input resistance. Electrical properties of opener fibers change during growth, but the extent of the change is not predictable from classical cable equations.
Correlated physiological and ultrastructural studies on specialised muscles. Ib. Ultrastructure of white and pink fibers of the levator of the eyestalk of Podophthalmus vigil (Weber)
Authors: Hoyle Graham , McNeill Patricia Ann 
Published: June 2005

AbstractThe ultrastructure of the different kinds of muscle fiber found in the specialised eyestalk levator muscle of Podophthalmus vigil was determined by electron microscopy. Pink fibers have wide, 13 μ sarcomeres, an extensive cleft system, branching Z tubules and a thick layer of mitochondria. Their ratio of thin to thick filaments is 4–5:1. Two distinct kinds of white fiber were found, with sarcomere lengths of 7.9 μ and 9.8 μ. The former have a very well‐developed SR, few mitochondria, a thin: thick filament ratio of 3–5:1 and numerous diads. The second kind have a 7:1 ratio, the thin filaments not being in orbits around thick ones. Their SR is quite well developed, but the cleft system only moderately so. There are more mitochondria in them than in the other white fibers.
Reciprocal insemination and egg transfer between ferrets and mink
Authors: Chang M. C. 
Published: June 2005

AbstractEpididymal mink sperm were injected into the uteri of 12 ferrets. On various days after insemination, 80 fertilized eggs and implantation sites including three living embryos in 11 ferrets were observed. No embryos, however, survived beyond 26 days. Ferret sperm were injected into the uteri or ovarian capsules of 22 mink; none of 165 eggs were fertilized. Ferret and mink eggs recovered at different times and from different parts of the genital tract were measured and recorded. When 77 ferret eggs were transferred into the uteri of nine mink, the majority of them developed at a slower rate than normal for a few days and then degenerated, but none implanted. Most of the 67 mink eggs transferred to the uteri of nine ferrets developed and implanted, but all degenerated after implantation. Fifty‐one ferret eggs were transferred to the uteri of eight ferrets; 13 living fetuses and four young were obtained. Eleven mink eggs were transferred into the uteri of two mink; only one implantation site was observed.It is concluded that a high proportion of ferret eggs can be fertilized if a large number of mink sperm are injected, but mink eggs cannot be fertilized by ferret sperm. Ferret blastocysts can develop for a few days in the uterus of mink, but implantation fails. Although mink blastocysts can develop and implant in the uterus of ferrets, they degenerate after implantation.
Enzymatic estimation of glycogen in the cleaving mouse embryo
Authors: Stern Samuel , Biggers J. D. 
Published: June 2005

AbstractRecently developed enzymatic techniques for the ultramicro determination of glycogen (Bueding and Hawkins, '64; Passonneau et al., '67) were used to estimate the glycogen content of preimplantation mouse embryos. From an initial value of 0.14 mμg glycogen/embryo in the 1‐cell fertilized egg. the amount of glycogen increased to 2.24 mμg/embryo at the 8‐cell stage. During the next 48 hours of development, the level fell to 1.81 mμg/embryo.A comparison with previous histochemical findings (Thomson and Brinster, '66) and the possible relationship of glycogen concentration and metabolic capabilities of the embryos is discussed.
Selective affinity as a working force in neurulation movements
Authors: Jacobson Carl‐Olof 
Published: June 2005

AbstractThe appearance of selectivity in the mutual adhesiveness of cells in the vertebrate embryo has been mentioned previously as one of the forces which may be responsible for neurulation. We report here observations made in vivo and on sections of fixed amphibian larvae, on which lateral and medial parts of the neural plate (after transplantation) have been brought into contact with each other at various stages. Our results showed that selective affinities are not released until a stage when neurulation is almost completed. The role of adhesive selectivity and other forces in neural tube formation are discussed.
The development and effect of genetic background on expressivity and penetrance of the Brachyury mutation in the mouse: A study in developmental genetics
Authors: Wittman Karl S. , Hamburgh Max 
Published: June 2005

AbstractThe development of the posterior axial structure of the heterozygous Brachy (T/+) mutant was studied and the expressivity and penetrance of this gene on several genetic backgrounds was analyzed.The Brachy mutant in heterozygous conditions is a dominant non‐lethal and interferes with the normal development of the caudal axis, leading to blunting, shortening and bending of the tail.Study of the developmental changes encountered in T/+ mice from the sixteenth day of gestation until the tenth day of postnatal age revealed that three different processes contribute to the tail abnormalities, these are: (1) reduction in number of tail vertebrae, (2) fragmentation of vertebral processes, (3) fusion of vertebrae or vertebral fragments.The expressivity and penetrance of the T gene in heterozygous condition was tested on four different genetic backgrounds provided by the Black Spot strain, the C57B1/6 strain, the DBA/2 strain and the Swiss Albino strain.On the DBA/2 strain, the effect of the T gene on reduction of caudal vertebrae was considerably modified when the DBA background was provided by the female parent. In reciprocal crosses of ♀T/ × ♂DBA ±, the expression of the T gene on that aspect of development was not changed. The penetrance of the T gene was, however, changed to a 2:1 ratio instead of the expected 1:1 ratio in both reciprocal crosses between T/+ heterozygotes with DBA mice.These results are interpreted as suggesting that the genetic background consists of several “factors,” each controlling independently the expression of some distinct aspect of the T gene, probably by stimulating some kind of correcting processes. The results are further interpreted to mean that some of the modifiers of T gene expressivity are probably non‐nuclear or cytoplasmic in origin, whereas the factors changing penentrance of the T gene are probably provided by more orthodox nuclear genetic loci that operate to inhibit its total activity.
Mitosis in normal and regenerating planarians
Authors: Best Jay Boyd , Hand Sharon , Rosenvold Robert 
Published: June 2005

AbstractThe rate of mitosis in planarians was measured by two methods. First, by tabulating the proportion of nuclei displaying metaphase mitotic figures after varying lengths of time in colchicine. Second, by measuring the total DNA in a colony of planarians as a function of time. The first method gave a rate of mitosis by non‐regenerating Dugesia dorotocephala of 1.4 × 10−4 divisions/cell hour. This rate remains constant for the first 24 hours following decapitation but increases to 2.7 × 10−4 divisions/cell hour by 54 hours. The rate of mitosis in the blastema was no larger than that of the mesenchymal tissues of the older portions. Measurements of the total DNA versus time gave an estimate of the average rate of cell division for spontaneously fissioning planarians of 5.8 × 10−4 divisions/cell hour which, in view of the tendency of the colchicine method to underestimate the true rate, is in satisfactory agreement. The implications of these results for mechanisms of regeneration are discussed.
An analysis of cytokinesis in cultured newt cells
Authors: Rappaport R. , Rappaport B. N. 
Published: June 2005

AbstractCells from the kidneys of the newt Diemictylus (Triturus) viridescens were cultured and used in experiments designed to yield information on cytokinesis. Observations and experiments were restricted to cells that were spread and flattened on the substratum. Flattened cells were capable of initiating and completing division without rounding up or disrupting their marginal attachments to the substratum. They can initiate division from a variety of geometric forms. At interphase and during division, flattened cells are under appreciable self‐induced tensile stress. Division continues when the cell is stretched between needles shortly after furrow establishment. Movement of needles between the cell and the substratum disturbed cells only when the tips of a marginal process were detached. No other connections between cell and substratum could be demonstrated. Objects stuck to the furrow surface and the stretching of attached marginal processes revealed that new surface in the furrow area is created by the stretching of pre‐existing surface. Massive cytoplasmic flow induced by micromanipulation immediately after the beginning of division and maintained throughout the process did not hamper furrowing. Division does not appear to depend upon any specific subsurface cytoplasmic arrangement in the equatorial plane and is unaffected by redistribution of the cytoplasm after the furrow is established.
The feeding biology of the gymnoblastic hydroid, Pennaria tiarella
Authors: Pardy Rosevelt L. , Lenhoff Howard M. 
Published: June 2005

AbstractThe role in food capture of the nematocysts on the filiform and capitate tentacles of Pennaria tiarella is discussed. The feeding response of Pennaria tiarella to Artemia extracts consists of cone bending and mouth opening. A similar feeding response has been demonstrated to be induced by proline at concentration as low as 10−6M. Pipecolic acid, a proline analog, also elicits a feeding response. Proline causes the head of the capitate tentacles to shrink, thereby causing the cnidocils of the large stenoteles to be prominent.
Evidence of circadian rhythms in a cave crayfish
Authors: Jegla Thomas C. , Poulson Thomas L. 
Published: June 2005

AbstractEvidence of a circadiam clock mechanism was found in the cave crayfish, Orconectes pellucidus, even though it is blind and has been isolated from daily cycles for at least 25,000 generations. Five of seven crayfish tested under cave conditions of continuous darkness and 13°C showed apparent rhythms of activity and/or oxygen consumption. These rhythms were statistically significant, as judged by autocorrelation, for three individuals with average periods of 26, 27, and 34 hours. All three crayfish exposed to light:dark cycles with a 24 hour period showed more regular rhythmicity than in continuous darkness but only one showed clear evidence of entrainment, i.e., synchrony of activity or oxygen consumption with the light: dark cycle. Another crayfish tested apparently conformed to Aschoff's circadian rule.
In vitro studies on the mechanical evocation of adventitious cartilage in the chick
Authors: Hall B. K. 
Published: June 2005

AbstractThe quadratojugal‐quadrate articulation from 9–12 day chick embryos was cultivated in vitro and subjected to artificial mechanical stimulation by moving the quadratojugal against the quadrate. Under the influence of this artificial application of intermittent pressure and tension it was found that the germinal cells of the membrane bone were switched from osteogenesis to adventitious chondrogenesis. The quadratojugal‐jugal articulation was treated in a similar manner but no formation of cartilage was seen. Quadratojugal‐quadrate articulations were also cultivated between “rib‐cultures” under constant pressure and it was found that no switch to cartilage formation occurred. It was postulated that the adventitous cartilage which develops on the membrane bones of the embryonic chick arises in response to intermittent pressure and tension accompained by movement.
Patterns of soluble proteins and multiple forms of dehydrogenases in amphibian development
Authors: Chen P. S. 
Published: June 2005

AbstractIn the three amphibian species Bombina variegata, Rana temporaria and Triturus alpestris there is a two‐ to threefold increase in the total content of saline‐soluble proteins during development (prior to feeding). Analyses by polyacrylamide gel electrophoresis revealed the appearance of one or two new protein fractions at gastrulation. Protein bands of transitional occurrence were also observed at various developmental stages. In general, during early embryogenesis protein components with relatively low migrating rates in the anodal direction predominate, whereas in the late larvae fractions of higher mobilities are more abundant.The isozymic patterns of four dehydrogenases in both embryonic and adult tissues of the three amphibians have been analysed. Three molecular forms of lactate dehydrogenase (LDH) are present in Bombina and Triturus, and two in Rana. Triturus and Rana have only a single malate dehydrogenase (MDH), whereas Bombina has two with, however, a clear difference in the mobility of the minor band between embryonic and adult stages. The total number of molecular forms of glucose‐6‐phosphate dehydrogenase (GDH) varies from four in Bombina to two in Rana and Triturus. There are probably four to five isozymes of alcohol dehydrogenase (ADH) of very low activity.Morphogenetic changes of the isozymic patterns include the appearance of one MDH in Bombina and the gradual increases in activities of LDH, GDH and MDH in Rana at gastrulation. After hatching further appearance of ADH isozymes occurs. The new synthesis of one GDH in the late Bombina larvae seems largely associated with the differentiation of heart and fat body. The formation of one MDH in this amphibian is probably delayed until after metamorphosis. A shift in the relative synthesis of isozymes during Bombina development is indicated by the temporary loss of one LDH band at tail‐bud formation and after hatching.
Thyroxine induced tail resorption in vitro as affected by anterior pituitary hormones
Authors: Derby A. , Etkin W. 
Published: June 2005

AbstractIt has been previously shown that discs prepared from the tail fins of tadpoles, (R. pipiens), survive in vitro for several weeks and respond to thyroxine by undergoing resorption. Discs cut from animals during metamorphic climax, demonstrate rapid resorption without addition of exogenous thyroxine.Discs were cut from tadpoles in early prometamorphosis and in climax and were implanted with either whole pituitary glands or the separate lobes. Controls were either implanted with cerebrum or sham‐operated. These discs were maintained in solutions of thyroxine in Hanks medium, (3 ppb or 6 ppb), or in control, Hanks medium. In addition, discs from animals in early prometamorphosis were injected with either prolactin, GH, or control medium and discs from animals at climax were immersed in solutions of prolactin, GH, FSH and control medium.The results of these experiments demonstrates that the anterior pituitary, of the tadpole releases a factor that interferes with the action of thyroxine on tail discs in vitro. Prolactin and GH demonstrate similar activity but are less effective than the graft pituitaries. The results are interpreted to indicate that antagonism exists with respect to tail resorption between a pituitary growth factor, (possibly a prolactin‐like, or GH‐like molecule) and thyroid hormone.
RNA composition of the planarian, Dugesia dorotocephala
Authors: Stewart Kathleen , Goodman Alan B. , Best Jay B. 
Published: June 2005

AbstractThe RNA of anterior and posterior regions of normal and regenerating planarians was extracted by means of a modification of the phenol procedure, and further purified. The nucleotide composition of this RNA was determined by subjecting it to alkaline hydrolysis and resolving the constituent nucleotides by thin layer electrophoresis. Contrary to older reports there was no difference in either amount or base composition of the total RNA from anterior and posterior regions or between regenerate and control worms. Resolution of the various molecular weight species of the planarian RNA by sucrose density centrifugation and gel filtration revealed a typical distribution between ribosomal and transfer RNA as well as the explanation of the negative result. Constancy of base composition of the predominate ribosomal RNA would mask any anticipated changes in base composition.
Experiments and observations on the histology and mechanism of autotomy and regeneration in Gena varia (Prosobranchia, Trochidae)
Authors: Fishelson Lev , Kidron Guliette 
Published: June 2005

AbstractThis investigation describes the autotomy and regeneration of the metapodium in the mollusc, G. varia, a species inhabiting infratidal habitats along the Red Sea littoral. It was shown that in this species there is a histologically prominent autotomy line that separates the metapodium from the propodium and enables autotomy. The animals can regenerate the dropped‐off part of the foot and at new irritation, they can reautotomize and re‐regenerate new metapodia.The histological development of the regenerate is described in detail, especially the development of the neural net and the musculature.
The influence of temperature on steroidogenesis in the rat testis
Authors: LeVier Robert R. , Spaziani Eugene 
Published: June 2005

AbstractThe normal temperature of the rat testis in a scrotal position is approximately 32°C. In vitro incubation of normal testicular tissue at various temperatures has demonstrated a 32°C optimum for the incorporation of lysine and glucose into protein. A thermal optimum of 32°C was also found for the conversion of cholesterol to components of both the Δ4‐ and Δ5‐ steroidogenic pathways except for pregnenolone synthesis which has a positive temperature co‐efficient between 28°C and 36°C. The Δ5‐pathway may be more sensitive than the Δ4‐pathway. In vivo inhibition of protein synthesis with cycloheximide simulated a temperature effect. Compared to saline injected control, tissue from inhibitor treated animals converted less cholesterol to steroids when incubated at 32°C, except for pregnenolone. In vitro cycloheximide treatment was less selective than inhibition of protein synthesis in vivo in that the synthesis of all steroid intermediates was suppressed below control levels. In addition, the hexose monophosphate shunt is less active at 36°C than at 32°C based on the in vitro yields of 14CO2 from glucose‐1‐14C and glucose‐6‐14C.On the basic of these experiments, a hypothesis was proposed which can serve as a foundation for further study concerning the mode of action of temperature in regulating testicular function. The hypothesis is that a thermal environment above or below 32°C in the rat interferes with some aspect of protein synthesis, thus reducing the level of one or more enzyme related to the steroidogenic pathways beyond pregnenolone.
The developmental genetics of polymorphism in the rotiferAsplanchna. I. Dietary vitamin E control of mitosis and morphogenesis in embryos
Authors: Birky C. W. 
Published: June 2005

AbstractCultures ofAsplanchna sieboldifedParamecium aureliaconsist exclusively of parthenogenetically‐reproducing females whose body form is saccate. When such females are fed algae or α‐tocopherol, their offspring developin uterointo humped females with regular outgrowths of the syncytial body wall (hypodermis and cuticle). The hypodermal nuclei are constant in number and position, and can be mapped; such nuclear maps show that saccate and humped females have the same number and arrangement of hypodermal nuclei. The level of dietary vitamin E thus controls differential growth of the hypodermis, without affecting mitosis. Electron micrographs indicate that the hypodermal outgrowths are produced after cell membranes break down in the embryo; the regions of enhanced growth within the hypodermis are therefore not delimited by cell membranes. In contrast, the offspring ofA. sieboldiorA. brightwellifed vitamin E show an increased mean number of nuclei in the vitellarium and gastric glands, organs which are partially freed from the usual rigid control of nuclear number in rotifer tissues. Variations in nuclear number in a tissue might reflect variations in either the number of cells determined to form that tissue or the number of mitotic divisions in the determined primordium. In the former case, reciprocal variations in nuclear number should be found in another tissue. The vitellarium and oocytes are the sole derivatives of a single blastomere; however, counts of oocytes fail to show reciprocal variations. Dietary vitamin E therefore controls, directly or indirectly, the number of mitoses in the vitellarium, and presumably also in the gastric glands.