bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and function of tarsal sensilla in the spider Araneus diadematus
Authors: Foelix Rainer F. 
Published: June 2005

AbstractThe tarsal hairs of the spider Araneus diadematus (Clerck) were examined by light and electron microscopy and for surface structures with a scanning electron microscope. Three different types of hairs could be found: (1) straight, sharp‐pointed hairs, (2) serrated bristles, (3) curved, blunt‐tipped hairs. The third type of hair shows all typical features of chemosensitive hairs, such as multiple innervation and an open tip, and was not included in the present study. The firs two types share the same histological characteristics of having the dendrite of one bipolar neuron attached proximally to the hair base. Also, most of the fine structural details, such as the presence of an extracellular space, a scolopale and a tubular body, correspond to tactile hairs as described in insects. However, in Araneus diadematus the nerve terminal has a three‐lobed structure and seems to be fastened to the socket cuticle which is not known from other arthropods. The five or six serrated bristles at the tip of the tarsus, together with the middle hook, grasp the thread. This relationship was suggested by Nielsen ('31) and was verified by means of the scanning electron microscope. The importance of this mechanism for grasping the thread was demonstrated in ablation experiments with quantitative evaluation of changes in web geometry.
Focal recording of responses evoked by light in the lamina ganglionaris of the fly Sarcophaga bullata
Authors: Mote Michael I. 
Published: June 2005

AbstractThe responses of the lamina ganglionaris in the compound eye of the fly Sarcophaga bullata to light stimulation were investigated. Measurements made at known depths from the corneal surface and upon visual placement of extracellular electrodes in the lamina of decapitated animals showed that the response to back‐ground illumination consisted of slow potentials which were mainly monophasic, 10–15 mv positive, and arose from a negative DC bias of 30–90 mv existing between the lamina and a neutral electrode placed in the thorax. These responses and DC characteristics differed markedly from those observed in adjacent regions of the visual system and allowed accurate placement of microelectrodes in the lamina from the rear in intact animals. The amplitude of the monophasic positive portion of the laminar response was used as a guide to adjust the position and angle of incidence of a focused light beam to yield a maximum response. Following a 10 to 15 minute period in the dark, flashes of light evoked responses of up to 65 mv, with usual values of 30 to 45 mv. These dark‐adapted responses were characterized by an initial dynamic phase followed by a post dynamic repolarization and finally a static phase that was maintained for the duration of the stimulus. The static phase was attained within 50 ms of the onset of stimulation. The latency of the rising limb of the dynamic phase had a minimum value of 4.5 ms. The laminar action potential is nearly identical to the receptor potential (described by others) in form, latency, and dependence on light intensity. It is concluded that the laminar response is dominated by activity in a DC, low resistance, electronic pathway between retinular units and a site or sites in the lamina ganglionaris.
Acid hydrolases and their relationship to lysosomes in the mesonephros of the chick embryo
Authors: Patel Virginia Broaddus 
Published: June 2005

AbstractThe activities of three acid hydrolases (cathepsin, acid phenylphosphate, and acid β‐glycerophosphatase) appear to be involved in the regression of embryonic chick mesonephroi and to be associated with cellular particles (lysosomes). Although total activities of these enzymes decrease during mesonephric involution, their importance to this process is indicated by their enhanced specific activities. There is approximately a two‐fold increase in the specific activity of acid phenylphosphatase from 12 to 19 days of incubation, a three‐fold increase in that of acid β‐glycerophosphatase from 9 to 19 days of incubation, and almost a two‐fold increase in that of cathepsin from 12 to 19 days of incubation. During the early period of regression from 14 to 17 days of incubation, there is approximately a 31% decrease in the wet weight and a 33% decrease in the total protein per mesonephric pair. Centrifugation of mesonephric homogenates into residue and supernatant fractions at 10 days, 14 days, and 17 days of incubation indicates that at the earliest stages of regression, a release of acid hydrolases does not seem to occur. It is suggested that the cellular particles with which these acid hydrolytic activities are associated act like cytolysomes.
Mitochondria and early development of the mouse
Authors: Stern Samuel , Biggers John D. , Anderson Everett 
Published: June 2005

AbstractThe mitochondrial morphology during oogenesis and early cleavage in the mouse have been explored by techniques of electron microscopy. The mitochondria of 1‐ and 2‐cell stages has an electron dense matrix and peripherally located cristae. At the 4‐ and 8‐cell stages the mitochondria are more diverse in form and contain vacuole‐like inclusions. The majority of the mitochondria in the morula and blastocyst stages contain transverse cristae. We have related these changes in structure to certain physiological alterations known to occur during embryogenesis in the mouse.
Dual functional and structural properties of the interhyoideus muscle of the bullfrog tadpole (Rana catesbeiana)
Authors: Gradwell Norman , Walcott Benjamin 
Published: June 2005

AbstractEvidence is presented for the existence of two different types of striated muscle fiber in discrete contiguous bundles in the interhyoideus muscle of the bullfrog tadpole. These tow types of muscle fiber share certain properties with conventional slow and fast contracting muscle of other vertebrates. The continuous, rhythmic activity of the pink fibers drives the buccal force pump, whereas sporadic twitches of the white fibers expel detritus from the irrigation system. Light microscopy shows that the pink fibers have a greater proportion of sarcoplasm to myofibrils than the white fibers and there is also a greater vascularization of the pink fiber than of the white fibers. Electron microscopy shows differences in the mitochondrial size and density and in the M‐bands, H‐zones, Z‐lines and motor endings of the two parts of the muscle. The white fibers have shorter sarcomeres and A‐bands than the pink fibers. Differences in the concentrations of lactic dehydrogenase isozymes suggests a concomitant dichotomy in the energy dynamics of the two parts of the muscle.
Echolocation: Discrimination of targets by the bat, Eptesicus fuscus
Authors: Simmons James A. , Vernon Jack A. 
Published: June 2005

AbstractBats of the species Eptesicus fuscus learned to discriminate differences in the size of targets, the shape of targets, and the distance to targets by means of sonar. Eptesicus can detect differences of as little as 17% in the surface area of triangular targets. Measurements of the echo properties of the targets suggest that the bats used differences in the overall intensity of the echoes to differentiate the larger triangle from the smaller. If so, the smallest detectable echo intensity difference for Eptesicus would be between 1.5 and 3.0 dB. In discriminating a tall, narrow triangle from a short, wide triangle the bats may have scanned the target shapes with the directional beam of their sonar to produce discriminable intensity differences between echoes.Eptesicus can discriminate between targets differing by as little as 12 to 13 mm in distance. If echo travel time is providing the bat with target range information, then the bat evidently can detect echo arrival‐time differences of as little as 70 to 75 μsec.The ability of the bat to discriminate between targets which produce echoes that arrive at the bat's ears overlapping each other for 90 to 100% of their total duration demonstrates the effectiveness of the mechanisms in the bat's sonar for rejecting interference caused by multiple‐target clutter.
Neuroendocrine control of photoperiodically induced fat deposition in white‐crowned sparrows
Authors: Stetson Milton H. 
Published: June 2005

AbstractElectrolytic lesions in the ventral hypothalamus of 28 adult male white‐crowned sparrows interrupted photoperiodically induced hyperphagia and fat deposition. Lesions in posterior regions of the infundibular nuclear complex or median eminence (22 birds) eliminated both the fattening response and testicular recrudescence. Lesions restricted to the anterior division of the median eminence or the tractus hypophyseus (6 birds) eliminated the fattening response only.
Structure and neuromuscular physiology of a newly discovered muscle in the walking legs of the lobster Homarus americanus
Authors: Sherman R. G. , Atwood H. L. 
Published: June 2005

AbstractThe structure and neuromuscular physiology of a newly discovered muscle (Wales et al., '70) in the walking legs of Homarus americanus was investigated. This muscle is quite small and is located at the posterior surface of the carpopodite near the distal end of the stretcher muscle.The new muscle is innervated by one excitatory and one inhibitory axon. The excitor appears to be separate from all other axons in the leg, while the inhibitor is shared with the stretcher and closer muscles.The new muscle can be considered to be of the slow or tonic type of crustacean muscle from both a structural and functional standpoint. Structural features determined for the new muscle are: long sarcomeres, thick, uneven Z lines, poorly defined H zones, and a high thin to thick filament ratio. Contractions of the new muscle are graded in nature and the rate and magnitude of tension development depends on the frequency of nerve stimulation.Upon stimulation of its excitatory axon the new muscle produces first slight rotation and then weak bending of the leg at the carpo‐propodite joint.Similarities between the new muscle and the rotator muscle found in decapod Natantia and Stomatopoda are discussed. Thus far Homarus is the only genus of the decapod Reptantia known to possess the new muscle.
Chromosomes at prometaphase and metaphase of the first cleavage in mouse and hamster eggs
Authors: McGaughey R. W. , Chang M. C. 
Published: June 2005

AbstractThe chromosome behavior from the late pronucleus to the first cleavage was examined in air‐dry preparations of mouse and hamster eggs. At recovery 88% of 327 eggs from 28 mice and 93% of 185 eggs from 13 hamsters were showing various stages during fertilization. The presence of fuchsin positive, intertwining and condensing chromatin fibers was first seen in the late pronuclei and later the fibers contracted into individual elements. In some pronuclei the number of chromatin fibers was greater than the haploid number for the species. The degree of contraction of the fibers was different in the male and female pronucleus of some eggs. Of 22 mouse and 12 hamster eggs at these stages, 18 (82%) and 6 (50%) respectively exhibited asynchronously contracted fibers. In eggs at the stage of “syngamy” the two groups of chromosomes were closely associated and intermingled. Of eight mouse and nine hamster eggs at “syngamy,” only one (13%) and O respectively were asynchronous in the degree of chromosomal contraction. The chromosomes at metaphase were in a single group and individual chromosomes with two chromatids were seen. At metaphase, 4 of 33 mouse eggs (12%) and 1 of 20 hamster eggs (5%) were asynchronous. Forty‐seven, 55 and 58% of mouse eggs were at “syngamy” or at later stages when recovered 22.5–23, 23.5, and 24–24.5 hours and 3, 26 and 34% of hamster eggs were at these stages when recovered 14–14.5, 15–15.5 and 16–17 hours after ovulation respectively. The results indicate that prometaphase of the first cleavage occurs over a longer range of time in mice than in hamsters.
Sperm lytic activity and its relation to fertilization in the frog Rana pipiens
Authors: Elinson Richard P. 
Published: June 2005

AbstractFully jellied frog oocytes lost their fertilizability with time after being placed in 10% Ringer's, the normal medium for fertilization. One stage in the loss of fertilizability was the appearance of blebs on the surface of the unfertilized oocytes. The blebs resulted from the weakening or lysis of the vitelline coat surrounding the oocyte by the sperm and the subsequent failure of sperm penetration into the oocyte.Both blebbing and fertilization were inhibited by soybean trypsin inhibitor. The inhibitor did not harm the sperm or the oocyte, or prevent the sperm from travelling through the jelly. The lytic activity was therefore necessary but not sufficient for fertilization. The lytic activity appeared to be induced by the jelly surrounding the frog oocyte.Sperm of the toad Bufo americanus did not fertilize oocytes of Rana pipiens but did cause blebbing. The blebbing was inhibited by soybean trypsin inhibitor.
Neural lateralization of vocal control in a passerine bird. I. Song
Authors: Nottebohm Fernando 
Published: June 2005

AbstractThe right and left hypoglossal nerves provide the motor innervation to the syrinx. The mechanism of song production in the chaffinch, Fringilla coelebs, is inferred from losses of song components following unilateral denervation of the syrinx. Greenwalt ('68) and Stein's ('68) “two‐voice” theory of song production is supported. An independent sound source in each bronchus is under the control of the hypoglossal innervation to that side of the syrinx. Since a bird can silence a denervated bronchus, this is probably done by reducing air flow through its bore.Bilateral denervation of the syrinx renders a chaffinch virtually aphonic. The effect of unilateral denervation depends on the stage of vocal development when this operation is conducted, and on whether the right or left hypoglossus is cut. In adult birds section of the left hypoglossus results in the loss of most of the song's components. Section of the right hypoglossus results in the loss of few, if any, components. These losses are irreversible. The same operation in birds in the plastic song stage results in partly reversible changes, so that some of the lost song components can be redeveloped by the intact nerve. When either the right or the left hypoglossus is cut before the bird has started developing its song, normal song will develop under the control of the intact side. These observations are interpreted in terms of neural lateralization of vocal control and loss of motor plasticity. Loss of motor plasticity probably determines the end of the critical period for song learning.It is known that in the chaffinch song develops to match an acquired auditory model or template. The availability of this template is evaluated in the light of song recovery after unilateral hypoglossectomy during the plastic song stage. It is suggested that as song development proceeds, the template is recalled with greater and greater precision. Motor disruption of vocal development may render this template inaccessible.
Regeneration in the sea cucumber Leptosynapta. I. The process of regeneration
Authors: Smith Gerald N. 
Published: June 2005

AbstractThe process of regeneration of a lost posterior by an anterior piece of the sea cucumber Leptosynapta crassipatina (Apoda) is described.The methods used were histological study and direct observation of regenerating animals. Vital stains were used to define growth patterns.The regeneration process is morphallaxis; the residual tissues are remodeled to produce a smaller but functionally complete animal. The process can be seen by sing the divisions of the gut as linear markers.Leptosynapta has a straight, unlooped digestive tract consisting of three externally visible division: the esophagus, the stomach and the intestine. The esophagus and stomach are suspended in the dorsal mesentery; the intestine is suspended in the ventral mesentery.Near the middle of the animal, the mesenteric attachment of the gut to the body wall changes from dorsal to ventral and the digestive tract crosses the coelomic cavity. This is the crossover point.In anterior pieces, produced by sectioning animals just anterior to the crossover point the posterior end of the stomach crosses the coelom creating a new crossover point near the amputation surface. This crossover point then moves anteriad to restore the normal location of a crossover. crossing over is accompanied by redifferentiation, so that normal gut proportions and structure are attained.Crossover is faster at more posterior levels of transection. The vital stain technique showed a region of elongation just anterior to the amputation surface. No elongation was ever shown within, or just posterior to, the oral complex. Histological study revealed low mitotic activity in all parts of the oral complex.
Growth and renewal studies of the choanocyte population in Hymeniacidon sinapium (Porifera: Demospongiae) using colcemid and 3‐H thymidine
Authors: Shore Richard E. 
Published: June 2005

AbstractThe choanocyte population of a marine sponge was studied determining the time course of Colcemid arrest and of tritiated thymidine uptake. Cells arrested by Colcemid accumulate at the rate of about 5.1 per 100 cells per hour. Cells labeled with tritiated thymidine accumulate at the rate of 5.5 cells per 100 per hour. The entire choanocyte population appears to be actively dividing with a mean cell cycle time of about 20 hours.
Prelethal effects of killing action by stock 7 of Paramecium aurelia
Authors: Jurand A. , Rudman B. M. , Preer J. R. 
Published: June 2005

AbstractWhen stock 16 sensitives are exposed to kappa particles of stock 7, the kappa particles enter food vacuoles in large numbers. The kappa quickly break down, R bodies unroll and penetrate the cytoplasm, food vacuole membranes show a general breakdown, and the formation of new food vacuoles is suppressed. The observations suggest that R body unrolling is important in the toxic activity and that the food vacuole membranes may be a major site of action of the toxin.
The mesoglea of Hydra. IV. A qualitative radioautographic study of the protein component
Authors: Hausman Robert E. , Burnett Allison L. 
Published: June 2005

AbstractThe synthesis of the collagen‐elastin‐like protein of the mesoglea of Hydra pseudoligactis was studied using tritiated proline. Radioproline was incorporated by direct incubation in “hot” hydra culture medium and by feeding Hydra labeled Artemia nauplii.Hydra cells are permeable to proline in the culture medium and exhibit radioproline incorporation within two hours in regenerating animals. Non‐regenerating Hydra exhibit incorporation only after a longer time. Isolated mesoglea of Hydra also exhibits incorporation of radioproline subsequent to its appearance in the cells.Epithelio‐muscular cells and digestive cells appear to be responsible for mesoglea synthesis. The distribution of radioproline label in Hydra mesoglea can be explained on the basis of the theory of directed cell movement previously presented by the authors and the observed synthesis of mesoglea protein.
Plasma adrenocorticosteroid levels in adult Fundulus heteroclitus (killifish) following hypophysectomy and pectoral fin amputation
Authors: Liversage Richard A. , Price Brian W. , Clarke W. Craig , Butler David G. 
Published: June 2005

AbstractAdult male and female Fundulus heteroclitus (killifish) were used in experiments designed to measure the plasma corticosteroid levels in control regenerate, sham hypophysectomized, hypophysectomized and intact fish ten days after pectoral fin amputation.Our data provide evidence for an anterior pituitary—adrenocortical axis in this fish since hypophysectomy was followed by a significant decrease in the plasma adrenocorticosteroid levels. The data also indicate that plasma adrenocorticosteroids are not abolished ten days after hypophysectomy. Cortisol is the major adrenocorticosteroid in this species although lesser amounts of corticosterone were also detected. The use of metopirone failed to reduce adrenocorticosteroid levels further in the hypophysectomised fish.In the presence of only low titres of adrenocorticosteroids our hypophysectomized fish survived and fin regeneration ensued for the ten days duration of the experiments.
The teratogenic action of the nicotinamide analogs 3‐acetylpyridine and 6‐aminonicotinamide on developing chick embryos
Authors: Caplan Arnold I. 
Published: June 2005

AbstractThe nicotinamide analogs 3‐acetylpyridine (3AP) and 6‐amino‐nicotinamide (6AN) have been reported to produce muscle and bone malformations respectively. Previous reports showed that 3AP is effective if introduced into the developing egg between the fourth and eighth day of incubation. 6AN is effective if introduced on the fourth to sixth day of incubation. In all cases, co‐treatment with nicotinamide completely relieves the teratogenic action of 6AN or 3AP. Observations are reported here which show that upon using appropriate doses, embryos are sensitive to 3AP until about day 14.5 and sensitive to 6AN until day 11.5 of embryonic development. These extended periods of teratogen sensitivity more closely correspond to the period of expression for the myogenic and chondrogenic phenotypes from mesodermal cells. Results are also presented which show that the 3AP analogs 2‐acetylpyridine and 4‐acetylpyridine do not produce significant teratogenic effects even though they marginally mimic 3AP in limb mesoderm cell cultures. These observations are discussed in light of nicotinamide's suggested role in controlling myogenic and chondrogenic phenotypic expression.
An in vitro study of programmed death in rat placental giant cells
Authors: Dorgan W. J. , Schultz R. L. 
Published: June 2005

AbstractPlacental giant cells were removed from rats at day 13 of pregnancy and maintained in vitro. The giant cells demonstrated a fixed age limit or programmed cell death in culture that corresponded to their life span in vivo. They began to decrease in number by the equivalent of day 17 of pregnancy and completely disappeared from the cultures by the equivalent of day 23 of pregnancy.Radioactive tracers were used to determine the synthesis of DNA, RNA and protein throughout the life span in vitro of giant cells. The cells were not observed to divide on or after the equivalent of day 13 of pregnancy but DNA synthesis was continuous up to the equivalent of day 16 of pregnancy. The DNA synthesis on or after the equivalent of day 13 was thought to be a result of endoreplication of DNA. RNA synthesis was observed to occur throughout the life span in vitro of the giant cell with a possible reduction after the equivalent of day 19 of pregnancy. In cell cultures RNA synthesis was observed first in the non‐nucleolar portion of the nucleus and then in the nucleoli. The labeled RNA (both nucleolar and non‐nucleolar) then appeared to migrate to the cytoplasm. Time lapse cinematography studies also demonstrated the apparent movement of nucleolar material from the nucleus to the cytoplasm. Protein synthesis was observed to occur throughout the life span in vitro of the giant cells.