bluuebunny/crossref_metadata_2025_split huggingface dataset:
The function of the middle ear in lizards: Gekko gecko and Eublepharis macularius (Gekkonoidea)
Authors: Werner Yehudah L. , Wever Ernest Glen 
Published: June 2005

AbstractThe structure and function of the middle ear is considered in Gekko gecko (Gekkonidae) and Eublepharis macularius (Eublepharidae). Middle ear anatomy is described in detail for Gekko, and minor points of difference in Eublepharis are indicated. By use of the alternating potentials of the cochlea the peripheral sensitivity function was determined, and then the contribution of the middle ear to this function was assessed by cutting the columellar shaft and removing the more peripheral structures. The sensitivity was then determined by presenting the sounds through a tube sealed over the oval window. This method provides known sound pressures at the columellar footplate and avoids simultaneous stimulation of the cochlea by way of the round window, which other forms of aerial stimulation would produce. This procedure reveals the performance of the middle ear as a mechanical transformer without complicating side effects. The transformer action was indicated as improving peak sensitivity by about 35 db in Gekko gecko and by about 53 db in Eublepharis macularius.The operation of the middle ear was further analyzed by the use of mechanical vibrations first applied to the surface of the tympanic membrane just over the pars inferior with the ear intact, and then to the stump of the columella after this ossicle was separated. The basic form of the sensitivity function persists in these vibratory types of stimulation, which is taken to mean that this form depends in large measure on the cochlea itself.Two processes are considered as achieving the force amplification required for impedance transformation, which is the principal function of a middle ear. One is a lever action of the columellar system, and the other is the hydraulic action arising from the difference in areas between the surfaces of the tympanic membrane and the columellar footplate. No specific evidence for lever action was obtained in this study. Measurements of areas of the tympanic membrane and columellar footplate indicated fairly large hydraulic ratios in these gekkonoid species. The evidence shows that the efficient transmission of sounds by the middle ear contributes in a significant way to the high degree of auditory sensitivity of these lizards.
The ear and hearing in Amphisbaenia (Reptilia)
Authors: Gans Carl , Wever Ernest Glen 
Published: June 2005

AbstractThe burrowing squamates of the order Amphisbaenia lack external ears. The middle ear involves an extremely large stapes with the head of its shaft (columellar portion) projecting just posterior to and as far laterally as the quadrate. In most species a cartilaginous extracolumella articulates with the distal tip of the shaft and then stretches along the lower jaw and is attached to the skin in the region of the second infralabial. Records of the electrical potentials of the cochlea in some nine species show sensitivity curves whose maxima are approximately −20dB for a standard output of 0.1 μv. The zone of greatest sensitivity lies in the low frequencies, usually between 300 and 700 Hz. The sensitivity of amphisbaenians differs from that of snakes in being fairly good above levels of 700 Hz, where the latter drops off sharply. Interruption of the extracolumella causes a 20 to 30 dB loss in sensitivity. Sound waves applied asymmetrically produce different electrical responses in the two ears, suggesting an explanation for behavioral observations on the utilization of the system.
Neural lateralization of vocal control in a passerine bird. II. Subsong, calls, and a theory of vocal learning
Authors: Nottebohm Fernando 
Published: June 2005

AbstractMale chaffinches deafened at three months of age produce as adults abnormal calls and subsong. These vocalizations develop as part of a plastic vocal ontogeny which culminates in song learning. In the adult bird, calls and subsong are under the dominant control of the left hypoglossus nerve. Section of this nerve after song crystallization leads to drastic changes in all vocalizations tested. Section of the right hypoglossus results in lesser modifications. These changes are not corrected with practice. When the left hypoglossus is sectioned in young birds before the onset of Spring subsong, the right hypoglossus assumes the dominant vocal role. The food‐begging call of nestlings provides the first evidence in ontogeny for the asymmetrical vocal roles of both halves of the syrinx. This asymmetry of roles is further developed during the vocal stages leading to full song. It is theorized that these vocal stages are of the nature of sequential building blocks, and as such necessary prerequisites for normal song development. The observed ontogeny of hypoglossal dominance can be explained by three assumptions: (1) The left hypoglossus innervates its syringeal musculature before the right one does. (2) This primacy of innervation leads to greater vocal control at the onset of vocal ontogeny. (3) This initial bias is confirmed and further developed as a result of vocal learning.
An analysis of feather germ formation in the embryo and in vitro, in normal development and in skin treated with hydrocortisone
Authors: Stuart E. S. , Garber B. , Moscona A. A. 
Published: June 2005

AbstractThe initial phases of feather development in the saddle tract of embryonic chick skin were examined in situ and in vitro, under normal and various experimental conditions. A birefringent, fibrous lattice was found in the dermis; it has a strikingly grid‐like organization and is probably collagenous. The development of dermal papillae coincided with a characteristic distribution pattern of dermal cells in relation to this fibrous lattice: elongated cells were aligned along the tracts of the lattice; rounded cells formed clusters at the intersections of the lattice which represented the sites of the future dermal papillae. Evidence is presented that the cell clusters at the lattice intersections are the precursors of the dermal papillae and arise by aggregation of cells that migrate along the fibrous tracts. The results of this study point to a close involvement of the lattice in the formation of the individual condensations of prospective papilla cells and in the patterned distribution of dermal papillae in the dorsal feather field. Experiments with collagenase have shown that the integrity of this lattice is essential for feather morphogenesis. Skin treated with hydrocortisone at the appropriate stages of embryonic development lacks the organized fibrous grid and does not form feathers. The generation of these integumental structures is discussed in the context of epidermal‐dermal interactions.
Cell migration into the “established” lateral motor column in Rana pipiens larvae: I. Brachial spinal cord
Authors: Pollack Emanuel D. 
Published: June 2005

AbstractIt has previously been assumed that once the lateral motor columns are set aside as a definitive region of the spinal cord in Rana pipiens larvae (about stage V of Taylor and Kollros, '46), no further movement of cells into the column occurs. Since the cells of the lateral motor column (LMC) arise from cells dividing in the ventricular zone of the spinal cord, it is possible to label some of the nuclei of cells destined for the LMC with thymidine‐H3. It was, thus, shown directly that cells enter the brachial LMC at stages after its initial formation. Larvae of R. pipiens were injected with thymidine‐H3 at various stages of development, and subsequent autoradiographs were made of serially sectioned spinal cords. Animals injected through stage VII exhibited a greater frequency of labeled LMC cells at later stages than did those injected after stage VII. By the onset of metamorphic climax, stage XIX, no further production of cells for the LMC could be detected.It is suggested that cell turnover in the developing LMC may have a role in the formation of the proper neuro‐muscular and neuro‐neuronal connections.
Isozyme patterns of coregonine fishes: Evidence for multiple cistrons for lactate and malate dehydrogenases and achromatic bands in the tissues of Prosobium cylindraceum (Pallas) and P. coulteri (Eigenmann and Eigenmann)
Authors: Massaro Edward J. 
Published: June 2005

AbstractStarch gel electrophoresis reveals the presence of 22 LDH isozymes in the round whitefish (Prosobium cylindraceum). Immunoprecipitation and molecular hybridization experiments demonstrate that the genome of this species codes for ten types of LDH subunits designated A, A′, B, B′, D, D′, E, E′, F, and F′. These subunits comprise the parental homotetramers of five distinct groups of isozymes designated a, b, d, e, and f. The group f isozymes are found exclusively in skeletal muscle and the e group isozymes are found exclusively in the eye. The a, b, d, and e group isozymes are immunologically related. The group f isozymes do not cross‐react with antibodies prepared against either the A4 or B4 homotetramers of weakfish, Cynoscion regalis.Six types of LDH subunits; designated B, B′, D, D′, E, and E′, are coded for by the genome of the pygmy whitefish (P. coulteri). They comprise the parental homotetramers of three distinct, but immunologically related, groups of isozymes designated b, d, and e.As in the rainbow trout (Salmo gairdneri), no in vivo intergroup molecular hydridization of LDH isozymes has been observed nor can it be induced in vitro in either P. cylindraceum or P. coulteri. The isozymes of analogous groups from P. cylindraceum, P. coulteri, and S. gairdneri can be hybridized in vitro.Two distinct MDH phenotypes were observed in P. cylindraceum; a simpler (S) pattern composed of four isozymes and a more complex (C) pattern composed of six‐seven isozymes. A pattern of six‐seven MDH isozymes similar to the C pattern of P. cylindraceum is found in P. coulteri.The ovarian LDH and MDH isozymes of P. cylindraceum are unique in that they migrate more slowly toward the anode than analogous isozymes in other tissues.The achromatic bands which are observed on starch gels stained for LDH or MDH activity are described.
Preferential inhibition of allelic isozyme synthesis in an interspecific sunfish hybrid
Authors: Whitt Gregory S. , Cho Paula L. , Childers William F. 
Published: June 2005

AbstractInterspecific hybrids were produced in the laboratory by crossing male redear sunfish (Lepomis microlophus) with female warmouth (Lepomis gulosus). Approximately three‐fourths of the F1 hybrids were morphologically normal, whereas the remainder possessed a deformity of the lower jaw. This deformity may have been due to a failure of nucleocytoplasmic interactions during development. The reciprocal cross of male warmouth × female redear was subject to complete mortality at the free‐swimming stage.Enzymes, the parental allelic isozymes of which are electrophoretically distinguishable, were chosen as genetic markers. Both of the parentally derived allelic isozymes for malate dehydrogenase and tetrazolium oxidase were synthesized in the adult F1 hybrid. Heteropolymers containing both types of subunits were formed for these two enzymes. Thus, both parental alleles were functional in the hybrid.An esterase isozyme observed only in the redear was absent in the adult F1 hybrid. This result suggests that the synthesis of this paternal isozyme may have been repressed because the egg cytoplasm was incompatible with the paternally derived allele. Maternal allelic repression was apparently observed at the lactate dehydrogenase E locus. The warmouth E locus functioned in the heart tissue so that the two heteropolymers B3E1 and A3E1 were synthesized, but these two heteropolymers were not detected in the redear cardiac tissue or in the heart tissue of the adult F1 hybrid. These results suggest the repression of this maternally derived gene function in the F1 hybrid. The morphologically normal and abnormal F1 hybrids possessed identical isozyme patterns for all four enzyme systems.
Chick embryo development: Chemical variations of cartilage
Authors: Vittur Franco , Pugliarello Maria Chiara , Rovis Lorenzo , de Bernard Benedetto 
Published: June 2005

AbstractThe chemical composition of cartilage from vertebrae and long bones of chick embryos 8 to 18 days old has been established. Collagen, muco‐polysaccharides, and non‐collagenous protein show similar patterns of distribution in the two types of cartilage; the maximum variation in these components has been found between the fourteenth and the sixteenth day of the prehatching period. The modifications that we have measured seem to be related more to a general biochemical feature of embryo development than to the preparation of the cartilage matrix for calcification.
The effect of thyroidectomy on testicular size and on the photorefractory period in the starling (Sturnus vulgaris L.)
Authors: Wieselthier Arthur S. , Van Tienhoven A. 
Published: June 2005

AbstractThyroidectomy of Starlings prior to exposure to long photo‐periods (17L:7D) resulted in a failure of testes to regress after an initial size increase. Thyroidectomy after four weeks of such exposure resulted in testicular regression followed by a second period of size increase. Testicular size was correlated with androgen secretion as indicated by yellowing of the bill. The effect of thyroidectomy was not due to increased gonadal sensitivity to gonadotrophins and not due to the requirement of the presence of the thyroid for regression per se. Presumably thyroidectomy results in higher gonadotrophin secretion.Thyroidectomy did not affect the termination of the photorefractory period in the fall.Thyroidectomized Starlings had higher body weights than controls.
Neuromuscular physiology of the strike mechanism of the mantis shrimp, Hemisquilla
Authors: Burrows Malcolm , Hoyle Graham 
Published: June 2005

AbstractThis study was planned to determine the neuromuscular basis of the very rapid strike movement, lasting only 5–10 ms, used by mantis shrimps to capture prey or defend themselves. The raptorial second thoracic append‐ages which are responsible for the strike action are unfurled by four muscles in the merus, two extensors and two flexors. All were found to be specialized for slow not fast contraction. The largest extensor muscle has a twitch time of 400 ms, reaches peak tetanic tension in 700 ms and takes one second to relax completely from this. It receives two “slow” and one “fast” motor axons distributed uniformly throughout the muscle. An overshooting spike occurs in each muscle fiber from the first activation of a train in the fast axon, but many seconds must elapse before the first muscle fiber will again respond with a spike. The smaller, medial extensor receives one fast axon which may give rise to overshooting spikes and an inhibitor whose effects appear to be minor; its muscle fibers are only weakly electrically excitable. The contraction and relaxation rates are slow, as are those of the medial flexor which receives two slow axons. The lateral flexor is divisible into two parts; a proximal region comprised of electrically passive fibers innervated solely by a slow axon and a distal region of spiking fibers innervated by a fast axon. The rapid strike action is explained not in terms of the rapid contraction of these muscles but in their operation of a mechanical device in the form of a “click‐joint,” described previously.
A comparison of the fine structure of late mouse blastocysts developed in vivo and in vitro
Authors: McReynolds Hal D. , Hadek Robert 
Published: June 2005

AbstractThe utrastructure of the in vivo developed late preimplantation mouse blastocyst has been compared with the fine structure of mouse blastocysts developed in vitro for 72 and 92 hours from the late two‐cell stage, as well as those grown in vitro for 26 hours from the late morula or early blastocyst stage. Very little difference was observed between the in vivo developed blastocysts and those cultured 26 hours in vitro. The differences between 72 and 92 hour‐embryos and the in vivo grown ones were significant. The in vivo specimen and those grown 26 hours in vitro had differentiated a layer of endoderm cells while the ones cultured in vitro from the two‐cell stage did not. Nuclear and cytoplasmic structures in the in vivo developed blastocysts are well‐differentiated while those of the embryos grown in vitro from the two‐cell stage were less advanced. Possible reasons for the apparently less differentiated stage of blastocysts developed in vitro from the two‐cell stage are discussed.
Photoperiodic control of fur growth and reproduction in the mink (Mustela vison)
Authors: Duby R. T. , Travis H. F. 
Published: June 2005

AbstractThe influence of light on fur growth and reproduction in the mink has been investigated. Exposure of kits and adults to 4L/20D (4 light hours/20 dark hours) after completion of the summer furring cycle accelerated the development of the winter pelage. Gradually increasing the length of the daily photoperiod after growth of the winter pelage had been completed also hastened the onset of the breeding season. An abrupt change from 4L/20D to 16L/8D either inhibited gonadal development or initiated gonadal atrophy. It was also noted that mink changed from a 4L/20D schedule to a 16L/8D schedule immediately after completion of the winter furring cycle failed to begin development of the summer pelage for 10 to 12 weeks. This observation suggests that a refractory period exists in the initiation of growth of the summer pelage. However, a similar experiment conducted after completion of the summer pelage showed that the animals responded immediately to decreased light by molting into the winter pelage. It was also noted that changes leading to the development of the summer pelage occurred concomitant with or slightly after the initiation of testicular regression, while gonadal recrudescence occurred after completion of the winter furring cycle. The significance of these observations in relation to possible hypophyseal mechanisms for their control is discussed.
Hemoglobin transitions in the bullfrog, Rana catesbeiana, during spontaneous and induced metamorphosis
Authors: Just John J. , Atkinson Burr G. 
Published: June 2005

AbstractElectrophoretic separation of hemoglobins (Hb) during normal metamorphosis reveals larval Hb starting to disappear and adult Hb appearing during tail regression (Taylor and Kollros stage XXII). This transition is nearly complete by stage XXIV. Labeled amino acid incorporation studies demonstrate selective production of adult Hb at stage XXII, complete suppression of larval Hb by stage XXIII, and continued high levels of adult Hb production in one‐week‐old froglets. In circulating blood cells DNA synthesis begins to increase after forelimb emergence (stage XX), attains its height at stage XXII, and then declines. These results indicate that after the increase in thyroid hormone during normal metamorphosis, the first event in new blood cells is DNA synthesis. One week later these same new blood cells demonstrate a marked increase in adult Hb production.In triiodothyronine (T3)‐induced metamorphosis there is measurable adult Hb production beginning 12 days after hormone treatment, indicating that thyroid hormone treatment can partially mimic the Hb transition of normal metamorphosis. This mimicry is not total because larval Hb continues to be produced and does not disappear, suggesting that other factors besides thyroid hormone may be involved in causing Hb transition during normal metamorphosis.
Morphogenetic movements in Salmo gairdneri Richardson
Authors: Ballard William W. 
Published: June 2005

AbstractUncoordinated movements of individual internal blastomeres of the pregastrular blastodisc are distinguished from true morphogenetic movements which later segregate the germ layers and establish the embryonic axis and its organs. These coordinated movements are described in detail for stages 7 through 10 on the basis of recorded drift of chalk dust implanted among the blastomeres, and of vital dye spots printed on the blastodisc. The movements of the chalk and of the living colored cells follow the same pattern but the chalk gives more precise information over a longer time span. There is no evidence of invagination, or in‐wheeling, or centripetal convergence. Most of the movements combine epiboly and convergence, but in different proportions varying with the depth of the cells and their distance from the blastodisc center. A line of chalk dust, implanted by needle thrust down the full depth of the blastodisc often divides into a superficial, chiefly epibolic, cloud of granules and a deeper one, convergent toward the axis. Particles from a single implantation site may become incorporated into a variety of organs and tissues, indicating that a fate map for Salmo must be three‐dimensional. The forebrain receives secondary contributions from the center of the blastodisc. Movements directly comparable to closure of neural folds are described during formation of the brain. The role of the germ ring is examined in detail. It does contribute to the mesoderm of the tail. Migration along it toward the axis involves only the hypoblast, through which cells move at very different rates.
Site of gene action in steel mice: Analysis of the pigment defect by mesoderm‐ectoderm recombinations
Authors: Mayer Thomas C. 
Published: June 2005

AbstractMice homozygous for the gene steel (S1) are black‐eyed white, anemic and sterile. Previous studies have shown that the pigment defect in the skin and hair results from a failure of the tissue environment to support pigment cell development. In an attempt to analyse more critically this block of pigmentation by the skin, recombinations were made between dermal mesoderm and epidermal ectoderm from normal and mutant 13 day mouse embryos. The re‐combined skin pieces were then grown for 14 days in the chick coelom and subsequently examined for melanocytes in the dermis and epidermis. The results demonstrated that both the mesodermal and ectodermal components of steel skin are adversely affected by the mutant gene. Steel dermis combined with normal epidermis failed to receive or support the development of melanoblasts from the normal component. Steel epidermis combined with normal dermis likewise remained free of melanocytes. No effect of the steel components on the development of pigmentation in the normal associated component was observed. These results are discussed in relation to the general inhibition of pigment in tissues other than skin of steel mice, and in relation to the interesting pleiotropic effects of the gene steel.