bluuebunny/crossref_metadata_2025 huggingface dataset:
Recuperation of regeneration in denervated limbs of Ambystoma larvae
Authors: Thornton Charles S. , Thornton Mary T.
Published: June 2005

The current neurotrophic theory of amphibian limb regeneration allows for a non‐neural tissue contribution of trophic substance (TS) which during ontogeny is suppressed by the production of large amounts of neural TS. A difficulty has been to account for the inability of denervated limbs to initiate regeneration in the absence of neural TS when non‐neural tissue TS synthesis, no longer “quenched,” might be expected to function. This difficulty has now been overcome in the aneurogenic limb system. Aneurogenic forelimbs of A. maculatum larvae were transplanted orthotopically and homoplastically in place of left forelimbs of normally innervated larvae. The brachial nerves of the host larva were allowed to grow into the grafted aneurogenic limb. When tested by subsequent denervation and amputation, the grafted limbs became progressively nerve‐dependent, for regeneration purposes, between 10 and 13 days post‐transplantation, dependence on nerves being complete at 13 days. Grafted, aneurogenic limbs were allowed to become innervated for periods of 2–3 weeks. Then for at least 30 days the limbs were maintained in a nerveless state by denervations, repeated at five day intervals, with histological checks on effectiveness of denervation. Amputation through the forearm was performed at 30 days with continued denervations to prevent reinnervation. Regeneration occurred in 49% of cases (in 16 of 33 limbs) with histological verification of nerveless or sparsely innervated condition. Thus, regeneration‐competent aneurogenic limbs may become nerve‐dependent after transplantation and then, after prolonged denervation, recover ability to regenerate under essentially nerveless conditions.
Regeneration in the African lungfish, Protopterus. I. Gross aspects
Authors: Conant Elizabeth Babbott
Published: June 2005

The regeneration of appendages of Protopterus annectens and P. aethiopicus has been studied. Both limbs and tail demonstrate a notable capacity for self‐replacement. The initial direction of growth in the regenerate depended upon the nature of the amputation plane: straight, pointed, or terminally notched cuts elicited new growth along the primary axis, whereas cuts made at an angle resulted in regenerates whose axis was perpendicular to the plane of cut. In these cases, differential growth ultimately compensated and the final form was consistent with the axis of the original appendage. Lateral notches made in the posterior margin of the pectoral limb may effect the growth of a secondary filament. Such bifidism could not be elicited from pelvic limbs or tails.

Growth curves showed a lag period of up to three and one‐half weeks, a period of rapid growth lasting one or more months, and then a time of decelerating growth. For each individual fish, these phases were undergone simultaneously, regardless of appendage, direction of cut, or amputation level. Limbs cut proximally, however, showed greater and more rapid growth than those with less material removed. Total replacement was found in all but some pelvic limbs.

Regeneration, if in the lag phase, was halted by estivation, but rapid growth commenced shortly after arousal.

Comparisons are made with other vertebrates.
Phototactic orientation by the marine dinoflagellate Gyrodinium dorsum Kofoid. I. A mechanism model
Authors: Hand William G.
Published: June 2005

Phototatic orientation by the marine dinoflagellate Gyrodinium dorsum was examined using closed circuit television methods. Mono‐ and bi‐directional stimuli were used to determine directional discrimination by the cells. Cell orientation time was also measured. From the results obtained, a model is presented which proposes paired photoreceptor sites.
Effects of low environmental pH on blood pH and sodium balance of brook trout
Authors: Packer Randall K. , Dunson William A.
Published: June 2005

Brook trout (Salvelinus fontinales) exposed to a low environmental pH (3.0–3.3) showed a drop in mean blood pH from 7.39 to 6.97. Trout at an environmental pH of 3.5 lost 50% of their total body sodium. Control sodium influx (72.5 μmoles/100 g hours) decreased to zero between pH 3.0 and 4.9 as Na efflux increased markedly over control levels. There was no significant difference in body Na content of wild trout from three streams ranging in pH from 6.05 to 7.10. Trout survived 13.1 to 14.7 hours in a 150 mM Na solution of pH 3.5 as compared to 2.5 to 4.9 hours at 100 μM Na and the same pH. The inability of brook trout to live in waters of pH less than about five, seems to be related to a drop in blood pH caused by the high hydrogen ion concentration of the medium. The loss of body Na appears to be of secondary importance as a cause of death.
The effect of nerve growth factor on limb regeneration in Ambystoma
Authors: Weis Judith S. , Weis Peddrick
Published: June 2005

Young Ambystoma larvae were subjected to forelimb amputation followed by a series of injections of either nerve growth factor (NGF) or saline solution. The animals receiving the NGF injections showed an increase in the length of the regenerate and an acceleration of digit formation at times up to two weeks after amputation. The maximum per cent increase in length occurred at about nine days post‐amputation. By two weeks after amputation, however, the difference between NGF‐treated and control animals had diminished considerably. The nerve growth factor, by increasing the extent of sensory innervation to the stump apparently accelerated blastema formation and early stages of regeneration. The fact that the regenerative rate can be altered by changing the nerve supply implies that there is not an absolute neural threshold for regeneration. Striking differences were noted in the normal regenerative rate of A. opacum as compared with A. maculatum.
Cytological observations on sperm penetration of rabbit eggs
Authors: Harper M. J. K.
Published: June 2005

Photomicrographs of the cytological changes of the sperm head and of the female chromatin in the rabbit egg, from the time of sperm penetration and activation of the second meiotic metaphase up to the formation of pronuclei and syngamy, are presented. During a study on factors affecting sperm penetration of rabbit eggs, some anomalous eggs were observed. One unfertilized egg possessed two second meiotic metaphases and associated first polar bodies, while another similar egg had two first and two second polar bodies, two sets of female chromatin, and one fertilizing sperm. In this latter egg fertilization was apparently proceeding normally. Two eggs within a single zona pellucida were also seen; one of these was a primary oocyte, while the other was a normally penetrated egg. Evidence is also presented which indicates that the incidence of polyspermy (usually dispermy) is increased, if eggs enter the oviduct at 14 hours or later after mating. This is thought to be due to more fully capacitated sperm present at the site of fertilization at these later times, and thus there is a greater chance of two or more sperm entering the vitellus at the same time.
An analysis of the development of conjunctival papillae and scleral ossicles in the eye of the scaleless mutant,
Authors: Palmoski M. J. , Goetinck P. F.
Published: June 2005

An analysis was carried out on the number and location of conjunctival papillae and scleral ossicles in chick embryos homozygous for the recessive gene scaleless. There are, on the average, three conjunctival papillae per eye in the mutant, while normal embryos have 14. The mutant is also deficient in the number of scleral ossicles having an average of one ossicle per eye. The ossicles of scaleless mutants in contrast to normals, are variable in size and irregular in shape. They are found in the same region as the papillae which remain after nine days of incubation. Histological examinations indicate a general retardation of the scaleless conjunctival papillae.
Effect of gonadotropins and testosterone on the initiation of spermatogenesis in the hypophysectomised Indian house lizard, Hemidactylus flaviviridis Ruppell
Authors: Reddy P. R. K. , Prasad M. R. N.
Published: June 2005

The action of gonadotropins (FSH, LH, PMS, and HCG) and testosterone on the initiation of spermatogenesis was studied in the Indian House Lizard Hemidactylus during the non‐breeding season after pituitary ablation. Both ovine FSH and PMS initiated spermatogenesis leading to the formation of mature spermatozoa after 45 days while LH, HCG, or TP had no stimulatory effect on the testis. Synergistic action was not observed when FSH or PMS was injected in combination with LH, TP, or HCG as evidenced by the germ cell counts in the seminiferous tubules.

The androgen‐dependent sexual segment of the kidney was also fully developed in the animals treated with FSH or PMS. These results indicate that the initiation of gametogenic and androgenic functions in the testis of the Indian house lizard are dependent on an FSH‐like protein.
Electromechanical coupling in a molluscan muscle, the radula protractor of Busycon canaliculatum
Authors: Hill Robert B. , Greenberg Michael J. , Irisawa Hiroshi , Nomura Hiromichi
Published: June 2005

The radula protractor can be made to be spontaneously rhythmic, although it is normally a quiescent, phasic muscle, with apparently multi‐unit organization. Acetylcholine and potassium depolarize with contracture. Once a radula muscle has been put into a long‐lasting contracture by acetylcholine, tryptamine can repolarize it with accompanying relaxation. In the continued presence of acetylcholine and tryptamine, the repolarization and relaxation gradually taper off while membrane oscillation accompanied by mechanical rhythmicity develops. Contrariwise, if a radula protractor is in a potassium contracture, tryptamine will potentiate the contracture without affecting the level of membrane depolarization. Potentiation of potassium contracture, without changing potential level, can also be effected by increased calcium concentrations or by caffeine. After a muscle has been soaked in artificial sea water lacking calcium, its twitch tension, tetanic tension, potassium contracture, and acetylcholine contracture become directly dependent on external calcium concentration.
On the measurement of cell adhesiveness
Authors: Gershman Howard
Published: June 2005

Four parameters that might be related to either the cell surface or cell adhesiveness were examined as a function of embryonic age in chick cells, and compared to each other. The four parameters were: (1) size of aggregates formed in shaker culture; (2) rate of aggregation in shaker culture; (3) sorting‐out behavior; (4) surface charge density. Aggregate size and aggregation rate of retinal cells were both found to decrease from 5 to 19 days of embryonic development, but the decreases followed different patterns. Sorting‐out behavior remained constant from as early as four to as late as 19 days of development (liver, heart and retinal cells). Surface charge density of retinal cells at physiological pH's rose from five to seven days, reached a maximum value between 7 and 11 days, and decreased from 11 to 19 days of development. Because of this negative correlation, it was concluded that the four parameters reflect different properties of the cell surface.
Some kinetic aspects of sperm specific lactate dehydrogenase in mice
Authors: Hawtrey Christopher O. , Goldberg Erwin
Published: June 2005

Purified LDH‐X, LDH‐1, and LDH‐5 isozymes from mouse tissues were compared according to several biochemical parameters. The sperm specific LDH‐X is more thermostable than the other isozymes, retaining 100% activity after 30 minutes at 65°C. Activity of LDH‐1 is reduced by 50% under these conditions while LDH‐5 is completely inactivated at this temperature within 18 minutes. The three isozymes had different Km values for both pyruvate and lactate with LDH‐X showing the highest substrate “affinities.” In addition, LDH‐X reacted significantly with both α‐hydroxy‐valerate and ketovalerate substrates. There was little or no catalytic activity of LDH‐X with other substrates, including several steroids, β‐hydroxybutyrate, α‐hydroxyisobutyrate, α‐ketoglutarate, α‐hydroxycaproate, and sorbitol.
Structure and function of tarsal sensilla in the spider Araneus diadematus
Authors: Foelix Rainer F.
Published: June 2005

The 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

The 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

The 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

The 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

Evidence 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

Bats 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

Electrolytic 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

The 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

The 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

Fully 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

The 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

The 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

The 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

When 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

The 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

Adult 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

The 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

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

The 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

The 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

Male 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

The 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

It 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

Starch 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

Interspecific 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

The 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.