bluuebunny/crossref_metadata_2025_split huggingface dataset:
Environmental control of annual testicular cycles in the lizard Anolis carolinensis. II. Seasonal variations in the effects of photoperiod and temperature on testicular recrudescence
Authors: Licht Paul 
Published: June 2005

AbstractThe effects of photoperiod and changing body temperature on testicular growth in Anolis carolinensis vary seasonally. Both a photo‐ and thermal‐refractoriness are evident. During September and October, 14‐hour day‐lengths accelerated testicular recrudescence in lizards at 32°C; a more rapid response occurred during October, suggesting a “relative” photorefractoriness. Photoperiod had little influence on the testicular cycle after October, once testis development started. Day‐lengths between 12 and 16 hours had no effect during any month if body temperatures were kept at 20°C.Exposures to high temperatures (32°C) in September delayed testicular recrudescence when day‐lengths were 12 hours or less, but after mid‐October, high temperatures accelerated gonadal development, independent of day‐length. These data suggest a thermal refractoriness during September that might be important in preventing premature testicular hypertrophy.A differential temperature sensitivity was evident among various testicular activities. The testes became abnormally enlarged but spermatogenic development was retarded at 20°C. Spermiation and androgen production appear especially temperature‐sensitive. These temperature sensitivities account for the long (3 month) arrest of spermatogenic development in nature during the winter. The rapid completion of testicular development during the two weeks following emergence from hibernation is probably dependent on elevations in body temperature and not on increased day‐lengths. Temperature, not photoperiod, appears to be the primary factor in controlling testicular recrudescence once it has started. A similar environmental control may explain testicular cycles among other species of lizards.
Relation of resting potential of rat gastrocnemius and soleus muscles to innervation, activity, and the Na‐K pump
Authors: Locke S. , Solomon H. C. 
Published: June 2005

AbstractThe effect of nerve on resting membrane potential of rat muscle was studied. Denervation produces a decline from 83.5 mV in gastrocnemius and from 68.8 mV in soleus to a range of 60 mV. The rate of decline is more rapid with distal than with proximal nerve section. With reinnervation, potential returns to normal. Immobilization, posterior rhizotomy or spinal section produces a decline in gastrocnemius membrane potential to about 70 mV indicating that integrity of ventral root does not prevent a fall. Independence of resting potential and muscle fiber size is indicated by work hypertrophy, by near and distant section of nerve and by variation in resting potential for the same degree of atrophy produced by disuse or denervation.Existence of a plateau below which resting potential does not decline following denervation is compatible with the concept of two fractions of normal resting potential maintained by different mechanisms. The higher and more vulnerable is less in soleus than in gastrocnemius. It responds to diresct and indirect tetanus with a decline, the low point of which is similar to that which follows nerve section. Direct tetanization of denervated gastrocnemius muscle affects only the residual of the upper fraction of membrane potential not yet reduced by denervation.Topical or intravenous administration of ouabain produces a decline of resting potential to the range of 60 mV. Following nerve section only the residual portion of “upper fraction” is vulnerable to ouabain. At no time does administration of ouabain produce a fall of mean resting potential below the level achieved by long term nerve section alone.
The effect of light and light deprivation upon the ultrastructure of the larval mosquito eye. II. The rhabdom
Authors: White Richard H. 
Published: June 2005

AbstractThe surface area of the rhabdom membrane is two to three times greater in mosquito larvae grown in darkness than it is in larvae grown in light. Moreover, light adapted rhabdom microvilli are covered with a surface coat and produce coated vesicles, while the light deprived rhabdom has no coat and does not form coated vesicles. The light adapted microvilli are held together by septate desmosomes; the light deprived microvilli appear to be packed loosely together.When a light deprived rhabdom is first exposed to light, the membranes of adjacent microvilli rapidly fuse so that the intervillous space is lost. During the next several hours the rhabdom reorganizes to the light adapted state. The intervillous space reopens. The area of the rhabdom membrane diminishes. The coat forms, and coated vesicles are produced in large numbers. This light induced transformation is of interest because of the presumed photoreceptive function of the rhabdom.
Anaerobiosis in a frog, Rana pipiens
Authors: Rose Francis Lewis , Drotman Robert Benjamin 
Published: June 2005

AbstractRana pipiens shows an obvious reduction in hepatic, ventricular, and gastrocnemius muscle glycogen concentrations with increasing time in anoxia. Pulmonary repiratory movements drop sharply during the first three minutes of anoxia and virtually cease after 30 minutes. Iodoacetate‐poisoned frogs survive anoxia only 20 minutes; whereas, non‐poisoned animals survive anoxia in excess of two hours. The combined evidence indicates that energy derived from anaerobic processes helps manintain physiological integrity in anurans during conditions of anoxic stress.
Lysosomes in the spleen of the chick embryo. II. Changes during the graft‐versus‐host reaction
Authors: Kimmel Charles B. 
Published: June 2005

AbstractThe graft‐versus‐host reaction (GVHR) was induced in developing chick embryos by inoculation of competent allogeneic cells. The enzyme contents and some properties of lysosomes from the host spleens were examined.Lysosomal enzymes were found to increase markedly during the GVHR. Changes also were found in the distribution of the enzymes within subcellular fractions obtained by differential centrifugation. A higher proportion of the enzymes was not sedimented with the particulate fractions, and in addition, the proportion of nonlatent enzyme activity in homogenates was significantly increased.These results could be correlated with those of a cytochemical analysis of acid phosphatase in the spleen during the GVHR. The activity increased markedly and the reaction product was located in small particles, as well as in large vacuoles and inclusion bodies within giant cells. Both granulocytes and mononuclear cells were found with increased amounts of demonstrable enzyme. Many cells showed diffuse staining within their cytoplasm, which suggests that the lysosomes had broken down in these cells.Similar changes in content and properties of lysosomes have been shown to occur in other systems in which phagocytes are active, or are subjected to stress, as with toxins or antibodies. The present findings are interpreted to reflect an extensive mobilization of host phagocytes in the GVHR, both in terms of their appearance, and of their phagocytic activation.
Adipose tissue of Drosophila melanogaster. III. The effect of the ovary on cell growth and the storage of lipid and glycogen in the adult tissue
Authors: Butterworth F. M. , Bodenstein D. 
Published: June 2005

AbstractCytometric analysis was made on the adult adipose tissue of sectioned abdomens of normal and experimentally treated adult Drosophila melanogaster. The adipose cells of two week old males and females are equal in size. The male cells contain 72% glycogen and 7% lipid, whereas the female cells contain 60% glycogen and 23% lipid. The adipose tissue of males containing a mature, transplanted ovary is similar to the female adipose tissue with regard to the cell size and amounts of lipid and glycogen. The adipose cells of castrated females are about 1.4 times larger than those of normal females, but the amount of lipid and glycogen per cell remains somewhat feminine. The adipose cells of genetically sterile, fes, females are about 1.4 times larger than those of normal females, but the amount of lipid and glycogen per cell remains somewhat feminine. The adipose cells of genetically sterile, fes, females are about 1.5 times larger than normal cells and are similar to normal male cells with regard to the proportions of reserve substances. The adipose cells of fes females containing a transplanted, normal ovary shrink to the same size as those of normal flies; and are similar to those of the normal females with respect to amount of glycogen, but are similar to those of normal males with respect to the amount of lipid. The ovary's stimulatory effect on the growth of the larval and repressive effect on the growth of the adult tissue is discussed.
Neuromuscular synapses of a crab motor axon
Authors: Atwood H. L. , Johnston H. S. 
Published: June 2005

AbstractNeuromuscular transmission of the “fast” motor axon of a crab, Pachygrapsus crassipes, was investigated, using extracellular microeletrodes to record electrical events at individual synaptic regions, and intracellular microelectrodes to record simultaneously the postsynaptic potentials of the muscle fiber. At 1/sec stimulation of the motor axon, the transmitter quantum content per stimulus was estimated at about 2 for many synapses, with relatively slight facilitation at higher frequencies. At some synapses a lower quantum content was measured at 1/sec, and more facilitation was apparent at higher frequencies. Fatigue of transmission with maintained stimulation was rapid.Observations of time course and amplitude of extracellularly recorded potentials suggested heterogeneity of these events.Electron micrographs of synapse‐bearing nerve endings showed them to be in clefts or embedded beneath the surface of the muscle fiber. The presynaptic vesicles were usually present at relatively low density, which could account for the rapid fatigue of transmission. Calculated volume distributions of the vesicles did not correspond to amplitude distributions of extracellularly recorded spontaneous potentials; possible reasons for the lack of agreement are discussed.
Correlated physiological and ultrastructural studies on specialised muscles. Ia. Neuromuscular physiology of the levator of the eyestalk of Podophthalmus vigil (Weber)
Authors: Hoyle Graham 
Published: June 2005

AbstractThe eyestalk levator muscle of the crab Podophthalmus vigil has been found to contain two kinds of fiber, pink and white, in separate bundles. Neuromuscular preparations were made of the whole muscle, as well as of white and pink portions separately, and biophysical properties of individual fibers examined. It was found that in extreme cases the fibers have markedly different properties. Some pink fibers were developing tension at normal levels of membrane potential and this was rapidly relaxed by hyperpolarizing pulses. They contracted slowly, but sustained tetani indefinitely. By contrast, some white fibers had quick contraction times, but fatigued extremely rapidly. Evidence was found for four axons: two “fast” excitatory, one “slow” and one inhibitory. It was concluded that a subtle interplay of different neuromuscular properties and different properties of individual muscle fibers, but especially the latter, are both of significance in determining the functioning of the muscle in relation to its role as an organ for minute, precise length changes.
Resting tension, “negative” contraction and “break” contraction in specialised crustacean muscle fibers
Authors: Hoyle Graham 
Published: June 2005

AbstractA few tinted fibers (color grey‐brown‐pink) occur in certain crustacean muscles of diverse species. Many of these were found to have relatively low resting membrane potentials and to be developing tension continually in the normal resting state, i.e., in the absence of extrinsic stimulation. This tension is rapidly relaxed if polarizing current is passed across the membrane. The relaxation in response to a brief polarizing pulse follows a time‐course resembling that of a twitch, but is, of course, the inverse. Fibers which were similar in color but which did not show resting tension often gave a strong contraction when a polarizing current was turned off. These “break contractions” had a slower time‐course than normal twitches. The relaxation rate was accelerated by polarizing pulses. Possible explanations of the phenomena are offered in terms of modern views on excitation‐contraction coupling.
Maturation of ovarian frog eggs without ovulation
Authors: Subtelny Stephen , Smith L. Dennis , Ecker R. E. 
Published: June 2005

AbstractThe dissociation of the processes of ovulation and maturation of full grown Rana pipiens ovarian oocytes has been demonstrated by the in vitro exposure of ovarian fragments to amphibian pituitaries or to the mammalian steroids, progesterone, and deoxycorticosterone acetate. With optimal concentrations of these substances, and under controlled conditions, all of the full grown oocytes can be stimulated to undergo germinal vesicle breakdown and maturation to the second meiotic metaphase while still in the ovarian fragment. Such oocytes are physiologically mature as shown by their positive response to an activation stimulus. That ovulation and maturation are not interdependent processes is further demonstrated by the liberation from the ovary of occasional oocytes which do not possess any follicular investments, but do possess an intact germinal vesicle. Such oocytes do not respond to an activation stimulus. The responses of ovaries to the action of pituitary extracts and steroid suspensions indicate that steroids are more efficient inducers of oocyte maturation while pituitary factors are better inducers of ovulation. These data, discussed with other findings, suggest the possible roles played by pituitary gonadotropins and steroid hormones in ovulation and physiological maturation of the anuran egg.
Degeneration in the nucleus of origin of the preganglionic fibers to the chick ciliary ganglion following early removal of the optic vesicle
Authors: Cowan W. M. , Wenger Eleanor 
Published: June 2005

AbstractExtirpation of the optic vesicle in chick embryos towards the end of the second day of incubation leads to a progressive hypoplasia in the ciliary ganglion and to a secondary, or retrograde transneuronal degeneration, in the accessory oculomotor nucleus from which the preganglionic fibers to the ciliary ganglion are derived. The primary changes in the ciliary ganglion are first observed at about the eighth day of incubation and the resulting cell loss proceeds over the next three or four days to include almost all of the ganglion cells. At the tenth day of incubation (when the volume of the ciliary ganglion is reduced by just over 70%) early signs of cell degeneration can be recognized in both the medial and lateral divisions of the accessory oculomotor nucleus in the form of cell shrinkage, loss of Nissl material and some cell loss. By the fourteenth day of incubation (Stage 40) the nucleus is virtually depleted of neurons with only an occasional shrunken cell persisting in the medial accessory nucleus. After even longer survival periods complete cell loss may occur in the nucleus, but in many of the experiments a small number of cells survive: these are probably related to ciliary ganglion cells which have established aberrant peripheral connections, or in those cases in which the lesion of the optic vesicle was incomplete, to the cells which innervate the surviving ocular tissue.
An in vitro quantitative analysis of the response of tadpole tissue to thyroxine
Authors: Derby A. 
Published: June 2005

AbstractDorsal tail fins of tadpoles, (Rana pipiens) at various stages of metamorphosis, were cut into pieces or discs and then cultured either in Hanks balanced salt solution or Hanks containing L‐thyroxine (T4). Six concentrations of T4 were tested: 3, 9, 27, 81, 250, and 750 parts per billion (ppb). In addition, early prometamorphic discs were cultured in medium containing 3 ppb of T4 for different periods of time: 1, 3, 5, and 7 days and then placed into control medium for the remainder of the experimental period. Controls for this experiment were maintained continuously in either 3 ppb of T4 or in control medium. To test the specificity of response to T4 early prometamorphic discs were cultured in medium containing KI, DL‐thyronine or DL‐diiodothyronine. Discs respond to treatment with thyroxine by shrinkage. The degree of shrinkage was determined quantitatively by measurement of area.The results show that a direct quantitative relationship exists between concentration of thyroxine and resorption. Resorption is dependent upon the continuous presence of T4. It was also demonstrated that tail discs change in their sensitivity to thyroxine at progressive stages of metamorphosis. It is proposed that the increased sensitivity of tail tissues to T4 during metamorphosis results from their previous exposure to a low but rising level of thyroid hormone that increases sharply in the donor tissues one to two days before the emergence of the forelegs. Finally, it was demonstrated that these results represent the specific action of thyroid hormone.
Isozyme patterns of salmonid fishes: Evidence for multiple cistrons for lactate dehydrogenase polypeptides
Authors: Massaro Edward J. , Markert Clement L. 
Published: June 2005

AbstractStarch gel electrophoretic and molecular hybridization studies indicate that the genomes of rainbow (Salmo gairdneri) and brown (S. trutta) trouts may code for eight electrophoretically distinct types of lactate dehydrogenase (LDH) subunits. The interactions of these subunits in vivo produce eighteen isozymes. These isozymes are naturally arranged into four groups, designated a, b, d, and e, on the basis of physico‐chemical properties. Groups a, b, and d each consist of five isozymes while group e is composed of three isozymes. An obvious tissue specific distribution of the isozyme groups is observed.Like the rainbow and brown trouts, other salmonids such as the Atlantic salmon (S. salar), sockeye (Onchorynchus nerka), and bloater (Coregonus hoyi) possess numerous LDH isozymes. Also, we and others have detected an unusual multiplicity of molecular forms of other proteins in Salmonidae. Representatives of the Osmeridae, Clupeidae, Engraulidae, Argentidae, and Esocidae, which are closely related families, possess no more than five LDH isozymes. Moreover, salmonids contain twice as much DNA per cell and have karyotypes which show about twice as many chromosome arms as certain closely related forms. From these observations, it has been concluded that salmonids are tetraploids. In our view, it seems most likely that they arose through allotetraploidization of a primitive hybrid ancestor.
Ontogeny of vocalization in duck and chick embryos
Authors: Gottlieb Gilbert , Vandenbergh John G. 
Published: June 2005

AbstractVocalizations can be elicited from some duck embryos five and one‐half days before hatching and from some chick embryos three days before hatching. All duck embryos can vocalize three and one‐quarter days before hatching (at 88% of incubation period) and all chick embryos are able to vocalize one day before hatching (95% of the incubation perod). Thus, the vocal apparatus of the duck embryo achieves a functional stage of development sooner that that of the chick embryo, indicating that the syringeal structures of the duck embryo begin development sooner or develop at a faster rate than those of the chick embryo. According to audiospectrographic analysis, both species are capable of uttering at least three different kinds of vocalizations prior to hatching, and these three calls are similar to the ones emitted most frequently after hatching (“distress,” “contentment,” and brooding‐lke calls). These vocalizations can be objectively defined by reference to the contexts in which they are emitted and the physical structure of the call notes. It was verified in situ that the constriction and vibration of the tympaniform membranes during exhalation is the basic or primary source of sound production in birds. The clavicular sac is not essential to sound production, and the syrinx, trachea, and syringeal muscles are important only for modulating and/or resonating the sounds produced by the tympaniform membranes. Based on this knowledge, a technique was devised to de‐vocalize duck embryos 3 days before hatching. The technique involves immobilizing the tympaniform membranes by applying a nontoxic substance (“Collodion”) to them. Collodion forms a glue‐like sheath over the membranes, and when the tympaniform membranes are thus rigidified, the embryo can not vocalize. Eighty‐five percent of the embryos treated were completely mute after hatching. The long‐term effectiveness of the de‐vocalization procedure is not reliably known. It was possible to keep only one bird for observation beyond the first four days after hatching and she was still mute at five months of age.
The neuromuscular basis of lobster swimmeret beating
Authors: Davis William J. 
Published: June 2005

AbstractThe anatomy and innervation of the swimmeret muscles of the lobster Homarus americanus were studied using histological and intracellular recording techniques. Each swimmeret is controlled by 12 muscles, each of which comprises from one to five anatomically‐distinguishable bundles of muscle fibers. The bundles which make up each muscle are usually merged along part of their lengths. Sometimes, however, bundles which share efferent innervation and which are therefore part of a single functional muscle are separate along their entire lengths. Thus, the concept of a muscle as a discrete anatomical unit is of limited use in the swimmeret system.The pattern of neuromuscular activity underlying swimmeret beating was determined by recording the rhythmic movements of a swimmeret simultaneously with the electrical activity of its muscles. Each muscle is active for a fixed fraction of every movement cycle, during which it discharges several muscle potentials. The 12 muscles of each swimmeret are recruited in the same temporal sequence during each cycle of swimmeret beating.
Inductive interactions in the development of the mouse metanephros
Authors: Erickson Robert A. 
Published: June 2005

AbstractEmbryonic mouse kidney mesenchymes of various ages were tested for their abilities to initiate and supportureteric bud morphogenesis in vitro.Nephrogenic cord mesenchyme taken from animals before metanephros initiation (10 days) was combined with ureteric buds. The buds showed no morphogenesis. This was true for presumptive metanephric mesenchyme and for mesenchymes (pronephric and mesonephric) already undergoing nephrogenesis. These results indicate basic physiological differences between pronephric, mesonephric and metanephric regions of the cord. When entire nephric systems were cultured alone no metanephros developed. This, and the fact that presumptive metanephric mesenchyme had no influence on ureteric buds, indicates that metanephros initiation (both bud and mesenchyme) results from some activity originating outside the nephrogenic cord.When combined with metanephric mesenchyme at various stages of tubulogenesis (loose, condensed, or tubular), ureteric buds branched only in the presence of the loose mesenchyme. Branching occurred in loose mesenchyme taken from 11 to 15 day kidneys. Apparently once a given group of cells begins tubulogenesis they lose their ability to induce ureteric bud morphogenesis.As tubulogenesis proceeds, the amount of loose mesenchymes per kidney decreases sharply. Ultimate size of the metanephros may be established by depletion of loose mesenchyme resulting in its ureteric bud‐inducing potential falling below some critical level.