bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of choline and related compounds on the growth and development of Drosophila melanogaster
Authors: Geer B. W. , Vovis G. F.
Published: June 2005

Twenty‐three structurally related compounds were tested as choline substitutes in the diet of D. melanogaster to determine the specificity of different structural groups in the growth action of the choline molecule. None of the substitutes completely replaced choline in the diet, indicating that the intact choline molecule is essential for maximal growth action. The single most important group is the hydroxyl group. It must be located terminally and on the 2‐carbon for the maximal growth effect. Three methyl groups are essential for maximal growth action, but they are not employed in transmethylation. The sulfur analogue is effective at low concentrations but is toxic at higher concentrations, indicating the importance of the nitrogen atom.

A comparison of dietary requirements indicated that the choline requirements for the growth of Drosophila, the growth of Neurospora choline‐requiring mutants, perosis‐prevention in the chick, and fatty liver prevention in the rat have a basic similarity. It is suggested that choline is required as a phospholipid entity by all of these organisms.

The insects differ in their abilities to utilize quaternary ammonium compounds which have carbon groups associated with the 2‐carbon. D. melanogaster can use carnitine, deoxycarnitine, and β‐methylcholine in place of choline, apparently converting deoxycarnitine to carnitine and carnitine in turn to β‐methylcholine. This contrasts with the specific carnitine requirement of the beetles of the family Tenebrionidae.

D. melanogaster can also convert betaine aldehyde to choline.
An autoradiographic investigation of tooth renewal in the purple sea urchin (Strongylocentrotus purpuratus)
Authors: Holland Nicholas D.
Published: June 2005

The DNA‐synthesizing cells in the tooth of the purple sea urchin were labeled with tritiated thymidine and detected with autoradiography. After one hour many cells were labeled in the abaxial peripheral layer of the soft, aboral end of the tooth. These cells were the chief source of new cells for tooth renewal. With time, the cells labeled in the abaxial peripheral layer (and several generations of their progeny) migrated as a zone of labeled cells. The zone migrated in an oral direction toward the hard, biting end of the tooth. The labeled cells in the leading part of the migrating zone occupied lateral positions in the tooth, and the labeled cells in the trailing part of the migrating zone occupied a median position. The time of tooth renewal in young adult specimens of the purple sea urchin maintained in the laboratory is approximately 75 days.
Acoustic orientation by fish‐catching bats
Authors: Suthers Roderick A.
Published: June 2005

Captive Noctilio leporinus were unable to detect pieces of fish tissue or small air‐filled balloons mounted a few millimeters below the surface of the water. An up‐welling of water and small wires projecting vertically above the water surface were readily detected and dipped at, however. Single wires 0.21 mm in diameter extending 5 mm out of the water were regularly detected and 1 mm lengths of this same diameter wire were dipped at well above chance levels. One or 2 cm2 cubes of fish muscle mounted above the water surface were detected at average distances of 148 and 132 cm as judged by the distances at which pulse duration and interval, respectively, first began to decrease. The average distance of detection of 5 mm lengths of 0.21 mm diameter wire was 59 cm as estimated by decreases in pulse interval. Several bats learned to distinguish between a single wire 1.3 mm in diameter extending 5 mm above the surface and a pair of wires 0.9 mm in diameter extending 5 mm above the surface and spaced 2 cm apart. Experienced bats made about 80% of their dips at whichever of these two targets marked the position of the submerged food. A pair of identical wires sloping in opposite directions were not distinguished. Detection and discrimination are independent of vision and olfaction, being accomplished entirely by echolocation. Two well defined pulse types are emitted: an almost constant frequency one at 60 kc/s and one with an initial portion of constant frequency followed by a downward frequency sweep of about one octave. Entirely frequency followed by a downward frequency sweep of about one octave. Entirely frequency modulated pulses are emitted only during difficult maneuvers which require high pulse repetition rates, such as when catching food or landing. When bats flying low over the water approach each other on a collision course, the downward frequency sweep is lengthened to cover about tow octaves. This serves as a warning allowing the bats to swerve off their collision course.
A stable mitochondrial DNA in Tetrahymena pyriformis
Authors: Stone G. E. , Miller O. L.
Published: June 2005

Autoradiographs of Tetrahymena cells labeled with 3H‐thymidine for long periods of time indicate incorporation into acid‐insoluble, DNase sensitive material in the cytoplasm. Results of electron microscope autoradiography show that 73% of the cytoplasmic silver grains occurred over mitochondria profiles, 92% of the grains were located over or within 0.5 μ of mitochondria while 97% of the silver grains were over or within 1.0 μ of mitochondria.

Tests to determine loss or gain of radioactivity during cell growth and division show that approximately one‐half of the label in each cell is transmitted to each daughter cell during division.

The results demonstrate that mitochondria of Tetrahymena pyriformis contain a stable DNA‐like material.
Juvenile phase in weaver finch (Ploceus philippinus)
Authors: Thapliyal J. P. , Chatterji S.
Published: June 2005

The photosensitive weaver bird (Ploceus philippinus) has a long juvenile phase when, while the bird is insensitive to photostimulation, the gonads respond to injected gonadotrophins. It is suggested that the immature status of the hypothalamo/hypophyseal complex may be responsible for the presence of a long pre‐photoresponsive phase in this bird.
Inhibition of regeneration of the gonopodium of the guppy by treatment with thiouracil
Authors: Hopper Arthur F.
Published: June 2005

It has been shown previously that the gonopodium of Lebistes develops and regenerates under the influence of testicular hormone. Since it has also been demonstrated that hypothyroidism inhibits gonopodial differentiation in the young fish, the relation between the hypothyroid state and gonopodial regeneration deserves investigation.

Adult male guppies kept in 0.03% thiouracil fail to regenerate normal gonopodia and the longer the exposure, the greater the inhibition. However, thiouracil has no effect on the regeneration of the female and fin. Thiouracil treatment results in thyroid follicular hyperplasia and vacuolization of and fat deposit in the liver. However, it is postulated that inhibition of anal fin regeneration in the male following thiouracil treatment is not the result of disturbance in protein or fat metabolism, but is due to a hormonal imbalance.
Fertilization in tunicates: Loss of the paternal mitochondrion prior to sperm entry
Authors: Ursprung Heinrich , Schabtach Eric
Published: June 2005

The spermatozoa of Ascidia nigra contain only one mitochondrion. Phase contrast and electron microscopical evidence is presented showing that the spermatozoon loses its mitochondrion before it enters the perivitelline space. Thus, in these organisms, the paternal mitochondrion plays no role in the development of the zygote and cannot contribute mitochondrial DNA to the genetic repertory of the zygote.
Some effects of bleeding on the iron metabolism of normal and of starved turtles (Pseudemys scripta elegans)
Authors: Hirschfeld William J. , Gordon Albert S.
Published: June 2005

The effects of bleeding on the short and long‐term iron metabolism of the turtle, Pseudemys scripta elegans, have been determined. Values are given for the plasma radioiron clearance and the clearance constant (K) in normal, bled‐normal and in unbled‐starved turtles. Clearance rates were increased by bleeding but were unaffected by starvation. The rate of the long‐term plasma radioiron clearance (normally slow) was augmented by bleeding in both normal and starved animals. Bleeding increased both the rate and magnitude of erythrocyte radioiron incorporation in normal but not in starved turtles. The distribution of injected 59Fe in plasma, erythrocytes, spleen, liver and duodenum is described for normal turtles. The time of availability of injected radioiron for splenic erythropoiesis was about two days, beginning on the second day after administration of the isotope. Storage of iron in the spleen appeared unlikely because of the decrease in spleen radioactivity noted from the fourth day on. This decrease was followed after two days by a similar decrease in circulating erythrocyte radioactivity. From the sixth to the fourteenth days after injection, radioiron moved to the liver and duodenum. It remains to be determined whether this migration represented storage or excretion of the iron.
The plant estrogen, coumestrol, as an agent affecting hypophysial gonadotropic function
Authors: Leavitt Wendell W. , Wright Paul A.
Published: June 2005

Mice bearing intrasplenic ovarian autografts were treated with coumestrol (500 μg/gm diet) and estradiol‐17 β (0.5 μg/day) for 14 days. The splenic grafts of all controls were in various stages of follicular development, whereas some of those receiving estradiol and coumestrol became luteinized. The gonadotropes in the pars distalis of controls were abundant and degranulated. Few PAS‐positive gonadotropes were left after estradiol treatment, showing that the dose used was capable of inhibiting production of gonadotropin. Coumestrol was thought to block release of gonadotropin rather than production since gonadotropes were plentiful and filled with PAS‐positive material.

Dietary coumestrol for 10 days at several lower levels produced estrogenic effects on the vagina and uterus of immature mice. However, none of the diets depressed ovarian growth, and it was concluded that no significant inhibition of gonadotropin occurred under these conditions.

In general, the results of this study indicate that coumestrol has physiological effects on hypophysial function, relatively large doses are required for antigonadotropic effects, and its primary effect on gonadotropes is to inhibit release.
Growth and cytochrome c oxidase activity in minute mutants of Drosophila
Authors: Farnsworth M. W.
Published: June 2005

Total soluble protein present in 48‐, 60‐ and 72‐hour larval stages of Drosophila melanogaster was determined for controls and for heterozygotes of the following Minute mutants: M(2)1, M(2)173, M(2)z, M(2)S‐10, M(3)w, M(3)124, M(3)B2, M(3)y and M(3)1. Cytochrome c oxidase activity was also assayed at these stages of development in mitochondria isolated from whole larvae of each genotype. The results indicate that all of these mutants possess a common retardation in the rate of growth throughout the larval period. The different Minutes, however, each had distinctive growth patterns, often characterized by particular lags occurring at specific stages. The concentration of cytochrome c oxidase was not necessarily lowered in conjunction with periods of especially retarded growth, but instead, activity higher than that of the control was frequently found. Only one mutant of those tested, M(2)z, showed a significantly lower concentration of this enzyme.
Developmental temperature tolerance of certain anuran species
Authors: Ballinger Royce E. , McKinney Charles O.
Published: June 2005

Eggs of Bufo punctatus, B. cognatus, B. valliceps, B. luetkeni, a hybrid combination (male B. valliceps X female B. luetkeni), Scaphiopus couchi, Microhyla olivacea, Acris crepitans, Pseudacris clarki, and Hyla cinerea were exposed to a range of temperatures to determine the developmental temperature tolerance of each species.

When comparing closely related species, the species with the most northern distribution has the lowest lethal minimum temperature, while the species with the most southern distribution has the highest lethal maximum temperature.

Temperatures of water in which anurans breed are found to be within the temperature tolerance range of the particular species, and usually near that temperature most favorable for optimum development.
Assay of a proteinaceous growth factor required for maturation of the free‐living nematode, Caenorhabditis briggsae
Authors: Lower William R. , Hansen Eder , Yarwood Evangeline A.
Published: June 2005

The time to maturation of a free‐living, protandrous, self‐fertilizing nematode, Caenorhabditis briggsae, was used to assay preparations of a proteinaceous growth factor and the effects of different treatments. Development was measured as time of the production of F1 offspring against concentration of growth factor. The data were transformed to the reciprocal of F1 time against logarithm of the dose and analyzed by regression analysis. Estimates were made of the dose of growth factor required for maturation in seven days, and relative potencies were determined for assays whose regression coefficients did not significantly differ from one another. The dose of growth factor required for maturation in seven days fell within the range from 8 μg/ml to 28 μg/ml. The methods of treatment for activation of growth factor studied were freezing overnight at —23°C, dialysis to low phosphate, and addition of the sucrose polymer, FICOLL. Reproducibility of results was shown for controls made for each experiment and for assays repeated at different times. Inocula of various numbers of larvae per tube, 1 through 30, were compared; significant increase in maturation time occurred when inocula were larger than 8.
Histochemical localization of neurohumors in a sponge
Authors: Lentz Thomas L.
Published: June 2005

The histochemical localizations of acetylcholinesterase, monoamine oxidase, epinephrine, norepinephrine, 5‐hydroxytryptamine, and neurosecretory substance were investigated in Sycon. All reactions that were most intense and sensitive to inhibitors were localized in spindle‐shaped bipolar cells and multipolar cells situated in the mesenchyme. Some spindle‐shaped cells formed a ring around the osculum and others contained branching and interconnecting processes. Multipolar cells were situated singly and possessed up to ten short processes. Activity was most commonly localized to small granules, vesicles, or large droplets within the cells and their processes. These results demonstrate the presence of cells specialized for the secretion of neurohumors and neurosecretory substance in sponges.
Anomalous cardioregulator innervation in certain individuals of the crayfish Pacifastacus leniusculus
Authors: Florey Ernst
Published: June 2005

Several individuals within a population of crayfish (Pacifastacus leniusculus) were found to have within their cardio‐accelerator nerves not one but two accelerator axons and one inhibitory axon. The effects of stimulation of the new inhibitory axons are identical with those of the regular inhibitory axon present in the inhibitory nerves. Their action is blocked by picrotoxin. The new inhibitory axons are not branches of the regular cardio‐inhibitor neurons, but represent processes of separate nerve cells.
Breakdown and reformation of somatic muscle during the molt cycle of the land crab, Gecarcinus lateralis
Authors: Skinner Dorothy M.
Published: June 2005

For intermolt (nongrowing) specimens of the land crab G. lateralis the amount of recoverable muscle per claw equals 0.095 ± 0.013 (propus length × propus width)3/2 gm/cm2. During the premolt period (approximately 50 days in large specimens of this animal) the quantity of muscle per chela decreases to approximately 60% the amount found in intermolt animals; during this time the fraction of protein per unit of wet weight of muscle remains constant. Therefore the decrease in wet weight represents extensive degradation of the tissue, not merely water loss.

Immediately after ecdysis water moves into the tissue. Approximately two weeks later, muscle proteins are rapidly synthesized, and the animal enters a new intermolt period with both the amount of muscle per chela and the dimensions of the chela greater than in the previous intermolt period.
Tissue transplantation immunity in the adult newt, Diemictylus viridescens. II. The rejection phase: First‐ and second‐set allograft reactions and lack of sexual dimorphism
Authors: Cohen Nicholas
Published: June 2005

Rejection of first‐set allografts in field collected Diemictylus viridescens is manifested by: (1) secondary vessel dilation (about 17 days), (2) hemostasis (about 20 days), (3) hemorrhage (about 23 days), and (4) eventual melanophore death (from 28 to 40 days). All these events were somewhat variable with respect to the time of onset, intensity, and duration. Histologically, these changes that distinguished allografts from autografts were paralleled by: (1) an increasing infiltration of small lymphocytes without graft destruction (secondary vasodilation), and (2) a stronger infiltration of lymphocytes concomitant with glandular death (hemostasis, hemorrhaging, and melanophore death). Although this pattern of rejection was the norm, several examples of long‐term graft survival were encountered.

When 28 days separated the transplantation of single first‐ and second‐set grafts, a clear anamnestic response was elicited although circulation was re‐established in 58% of the secondary transplants. Specificity of the second‐set response was demonstrated.

Single second‐set transplants grafted ten days after single first‐set grafts were not rejected in an accelerated fashion; rather such grafts often survived for a few days longer than the first‐set grafts transplanted to the same host.

The rejection of allografts from donors of different sexes transplanted to hosts of both sexes did not reveal any sexual dimorphic response. The site of transplantation (flank or throat) did not alter the timing or sequence of the rejection pattern.
Cell proliferation, migration, and specialization in the epithelium of the mouse tongue
Authors: Cameron Ivan L.
Published: June 2005

The three dimensional structure of the filiform papilla of the mouse tongue is presented.

Two distinctly different keratinized cell products are found in the region of the filiform papilla. Evidence for the existence of the two cell types is based on a series of histological, cytological, micro‐manipulative and cell migration studies.

A study of the tongues of embryonic and adult mice shows no morphological evidence of heterogeneity in the cells of the basal layer of epithelium which supports the concept that the two different keratinized cell products derive from a homogeneous cell population.

Tritiated thymidine autoradiographic studies reveal that the proliferative pool of epithelial cells is limited to the basal cell layer. The avergae cell renewal rate of this layer is presented for the various parts of the tongue. The progenitor cell cycle is also described.

The studies indicate that the movement of a cell from the basal layer to the spinous layer is a random event in time and that the movement of a cell out of the basal layer precludes further cell proliferation by that cell.

The results indicate that it is positional chance at the time of cell birth which determines whether a cell will specialize into one of two different alternate fates. The fate of the cell in this particular case is based on the particular micro‐environment the cell is forced to occupy. The force is provided by the growth of cellular mass and the subsequent crowding out of those cells not able to remain attached to the basement membrane.
Capacitation of rabbit spermatozoa delayed in vivo by double ligation of uterine horn
Authors: Soupart Pierre , Orgebin‐Crist Marie‐Claire
Published: June 2005

An in vivo experimental design is described for the study of capacitation that permits simultaneous testing of both sperm capacitation and viability in two series of recipient does. In this system, superimposed capacitation is prevented in one of the series by performing tubal insemination 13 hours after HCG injection.

Using this system it is possible to demonstrate that: the timing of tubal insemination is critical for the study of capacitation; there is no difference in terms of time required for capacitation between spermatozoa from the distal cauda epididymidis and from the ejaculate; in vitro capacitation does not result from sperm incubation with endometrium strips; ten hours incubation of sperm suspension in vivo in a double ligated and distended uterine horn delays capacitation without altering sperm fertilizing ability.
Separation and characterization of the lens proteins of the amphibian, Rana pipiens
Authors: McDevitt David S.
Published: June 2005

The soluble lens proteins (α, β, and γ crystallins) of the adult American grass frog, R. pipiens, were investigated, using DEAE‐cellulose ion‐exchange chromatography and disc electrophoresis on polyacrylamide gels. Column chromatography of whole adult lens proteins, with a NaH2PO4‐Na2HPO4‐NaCl buffer elution program, revealed six fractions. The first to be eluted was identified as γ crystallin, the predominant lens protein of this organism; the second and third as β crystallins; and the fourth, fifth, and sixth as a crystallins. Disc electrophoresis of these fractions on polyacrylamide gels of appropriate porosity confirmed the identity of these proteins as separated by ion‐exchange chromatography. Rechromatography of the isolated γ crystallin fraction of whole lens protein, employing a tris‐HCl buffer elution system, resolved the γ crystallin into four distinct components. These individual γ crystallins exhibited different electrophoretic mobilities, as judged by their behavior in disc electrophoresis. This precludes the possibility that the fractions obtained are artifacts of the elution process, and confirms the existence of four γ crystallins in the lens of adult R. pipiens, as has been reported for mammalian (bovine) embryonic and adult γ crystallins. The phylogenetic and development implications of these findings are discussed.
Metabolic and endocrine differences between the mutation whirler and normal female mice
Authors: Sackler A. M. , Weltman A. S.
Published: June 2005

This study reports metabolic, body and endocrine organ weight differences between a recessive mutation whirler, and its normal heterozygote. The whirlers, a waltzing mice mutation, are extremely restless, nervous, and excitable. They show syndromes of rapid circling locomotor activity, head‐shaking and deafness. O2 consumption and metabolic rates of female mice were studied at ages up to 14 months. The two groups of homozygous and heterozygous whirlers were autopsied at three and one‐half, ten and eighteen months of age for body and organ weight analyses. At all age levels, either significant or marked decreases were noted in the body weights of the whirler mice compared to the normal heterozygotes. Significant increases were observed in the adrenal weights accompanied by significant decreases in the thymic weights. O2 consumption and metabolic rate analyses demonstrated significant or marked increases in whirler metabolic rates at all age periods. The whirler ovarian and uterine weight changes suggest delayed gonadal function. The data indicate consistently increased metabolic and adrenocortical activities during the life span of the whirlers. The thyroidal and gonadal weight alterations at the various time periods suggest age‐related changes which may also be a function of acute and chronic states of heightened adrenocortical activity.
Adipose tissue of Drosophila melanogaster. II. The effect of the adult internal environment on growth, protein deposition, and histolysis in the larval fat body
Authors: Butterworth F. M. , Bodenstein D.
Published: June 2005

Transplantation experiments show that growth, protein deposition, and histolysis in the larval fat body of Drosophila melanogaster are controlled by a secretion of the larval ring gland. The internal environment of the normal adult female generally mimics the effect of the ring gland. However, the female environment induces more growth but less histolysis than the ring gland. The internal environment of the adult male stimulates only growth in the fat body. Transplantation studies with normal, castrated, and mutant adults indicate that the ovary is important in the stimulation of growth, protein deposition, and histolysis. The corpus allatum‐corpus cardiacum complex of adult D. virilis females will induce growth, protein deposition, and histolysis in the larval fat body of D. melanogaster.
Nature of induced persistent vaginal cornification in mice. I. Effect of neonatal treatment with various doses of steroids
Authors: Kimura T. , Basu S. L. , Nandi S.
Published: June 2005

Various doses of estradiol, testosterone, progesterone, or cholesterol were injected daily for five days, beginning within 24 hours after birth, into female RIII and BALB/c mice. Daily examination of vaginal smears of these animals revealed that neonatal administration of estradiol or testosterone, but not of progesterone or cholesterol, was effective in inducing persistent vaginal cornification. Mice of the RIII strain appeared to be more sensitive than BALB/c animals to the induction of persistent vaginal estrus by steroids. The existence of both ovary‐dependent and ovary‐independent types of persistent vaginal cornification was demonstrated. Ovariectomy completely eliminated vaginal estrus in most animals which had been treated neonatally with low doses of steroids. In contrast, neither ovariectomy nor combined ovariectomy + adrenalectomy + hypophysectomy had this effect in the majority of mice which had received higher dose levels of the same steroids neonatally. A single high dose of estradiol did not restore ovary‐dependent vaginal cornification in ovariectomized mice, and the administration of a high dose of progesterone for 15 days failed to block completely ovary‐independent vaginal cornification in mice of the BALB/c strain.
Embryological development of the A2cl‐antigen of pigeon erythrocytes
Authors: Hierholzer J. C. , Scheinberg S. L. , Hansen P. A.
Published: June 2005

The “A” antigen of pigeon erythrocytes detectable by Phaseolus lunatus lectin was given the nomenclature “A2cl” to designate it as the agglutinogen of Columba livia which is apparently identical to the A2 of man.

This antigen appeared at day 10 in ovo and increased linearly to day 17. (The average incubation time of pigeon embryos was 17.4 days.) At the time of hatching 2% of the expected, parental titer was reached. After another linear increase from one to seven days post‐hatching, the titer of the squab bloods exceeded the parental titer, arriving at a maximum of 160% at one month post‐hatching. The level then slowly decreased to 110% of the average parental titer at three months post‐hatching and remained stable thereafter.

The ratio of human cells to pigeon cells involved in mixed agglutination was used to show that high‐titer bloods (older eggs) contain an abundance of cells with multiple active sites and a few cells lacking active sites, whereas low‐titer bloods (younger eggs) contain mostly inactive cells or cells with proportionately fewer sites.

Hemagglutination inhibition tests performed on plasma from eggs and neonatal squabs failed to detect the presence of a soluble A2cl antigen. These results, together with the in ovo development of the antigen and the detection of the antigen in embryonic bone marrow cells, indicate that the agglutinogen may develop in the early stem cells and then be carried over onto the maturing red cells.
Proprioceptor distribution and properties in Limulus walking legs
Authors: Hayes Wilbur F. , Barber Saul B.
Published: June 2005

The third walking leg of Limulus has approximately 350 proprioceptor neurons found in 12 distinct organs. They are categorized as articular membrane receptors (9 organs), nerve receptors (2 organs) and tendon receptors (one organ). The articular membrane organs are present in one or more of the soft articular membranes of each walking leg joint except the tarsoclaw joint. These proprioceptors, as exemplified by the coxotrochanteral units, are large multipolar neurons with long, multiple branching dendrites ending among epidermal cells. The nerve proprioceptors are located near the femoropatellar and tarsoclaw articular membranes and appear as cell bodies in ganglion‐like swellings of branches of the small leg nerve. The cells resemble the articular‐membrane type in size and shape, but they may be bipolar and their peripheral endings are unknown. The tendon receptor organ is composed of a group of multipolar neurons embedded in a tendon with fixed ends. In addition the organ has two accessory muscles connected to the tendon close to the region where the sensory cells are located. This organ monitors movements and position of the trochanter and femur segments by means of unidirectional extension movement units and position units which differ by predominance of phasic or tonic response. Flexion inhibits the tonic response and is followed by recovery of the response at a lower frequency. All of these responses are probably mediated by the effects of the joint movements on tension changes in the accessory muscles. The presence of efferent innervation to the accessory muscles implies its function for efferent control of the receptor response.
The central nervous organization underlying control of antagonistic muscles in the crayfish. I. types of command fibers
Authors: Evoy William H. , Kennedy Donald
Published: June 2005

1. A limited number of “command” interneurons mediate the release of coordinated ganglionic output to antagonistic postural muscles in the crayfish abdomen. Graded contractions of these muscles are regulated by the frequency of discharge in several motoneurons, whose own discharge is in turn controlled by the level of activity in command fibers.

2. Different command fibers having a similar effect (i.e., flexion or extension) vary in the relative effectiveness with which they excite specific motoneurons. This selectivity is responsible for different rates of tension development.

3. Command fibers connect with the postural motor system in each segment in a bilaterally symmetrical fashion. Many of the same command elements also have unilateral or reciprocal effects on other motor systems, especially on those which control the swimmerets and uropods.

4. The reciprocity between flexors and extensors is inherent in the ganglionic organization. Activation or modulation of this ganglionic center is accomplished by the command interneurons, which in turn are activated by appropriate combinations of sensory inputs. A wide variety of postural adjustments may thus be controlled by a limited number of central neurons that make complex but specific output connections.
Electrophysiological observations on hearing and sound production in the fish, Porichthys notatus
Authors: Cohen Melvin J. , Winn Howard E.
Published: June 2005

Males of the northern midshipman, Porichthys notatus emit sounds that can be characterized as irregular grunts, trains of regularly spaced grunts and buzzes. The grunts contain their maximum amplitude in a band from 85‐600 cps with a possible fundamental just below 85 cps. The buzzes contain frequencies from 85 cps to 1 kc. Some buzzes have a well defined fundamental at approximately 85 cps. In others, the fundamental varies between 150 and 250 cps. Microphonics were recorded from the sacculus and appear to originate primarily from the posterior region of the saccular macula. Two microphonic potentials are produced for each cycle of sound. A hearing frequency curve based on a 20 microvolt microphonic response indicates that the ear can detect sounds from 30 to at least 210 cps. There is a low threshold at 30 and at 150 cps. Electromyograms from the pair of muscles attached to the air bladder indicate that they contract simultaneously at frequencies from 93‐227 per second during sound production. Each contraction is associated with a pulse of sound. The variety of sounds produced in any given behavioral situation indicates that there is no clear association between a given type of activity and the sound produced. The low threshold of the ear at 150 cps corresponds to a fundamental frequency commonly found in the sounds produced by the fish. This indicates that the fish could use these sounds for communication between individuals.
The effect of 5‐fluorouracil on the development of the adult eye in Ephestia kühniella
Authors: Imberski Richard B.
Published: June 2005

The effects of the nucleic acid base analog, 5‐fluorouracil (5FU), on the development of the imaginal eye of the moth, Ephestia kühniella, were studied. Crystals of 5FU were implanted into the abdomina of pupae of known ages, and the extent of ommatidial differentiation occurring after this treatment was observed.

In the study of normal development, it is observed that several early differentiation processes occur in a spreading fashion, i.e., a specific differentiation begins in the dorsoposterior region of the eye and spreads across the eye disc in a ventroanterior direction. All spreading processes are completed by 126–132 hours following pupation and all further differentiation occurs in all parts of the eye simultaneously. By 246–252 hours, all differentiation processes are essentially completed.

Differentiation processes can be characterized by critical periods during which their occurrence can be completely inhibited by 5FU treatment. Those differentiations which are spreading processes can be further characterized by a period when 5FU treatment inhibits the progress of their spreading. Treatment at 78–84 hours no longer affects any spreading processes and, at 150–156 hours, it is no longer inhibitory toward complete ommatidial differntiation.
Effects of duct ligation on the fertilzing ability of spermatozoa from different regions of the rabbit epididymis
Authors: Bedford J. M.
Published: June 2005

In the normal rabbit, fertile spermatozoa first appear in the lower half of the corpus epididymidis. If sperm passage is impeded in the low corpus region, the capacity to fertilize and initiate normal ovum development can ultimately arise in sperm withheld in any part of the ductus epididymidis, distal to the caput flexure. Sperm released from the initial part of the epididymis proximal to the caput flexure did not fertilize, even though many showed apparently normal progressive motility twelve and one‐half to fifteen days after low corporeal ligation. Since these infertile, motile sperm did not show the normal head–head agglutination reaction of mature rabbit sperm in a medium containing serum, it appears that the dichotomy between motility and fertilizing ability may have been at least partly due to the persistence in an immature state of the sperm plasma membrane.

Many caput sperm which displayed normal sustained motility had retained the cytoplasmic droplet in the neck region, whereas, in others showing comparable motility, the droplet had moved along the midpiece or had been lost. It, therefore, seems unlikely that movement and loss of the droplet can be of importance in development of the capacity for motility in maturing spermatozoa.
Studies of the melanogenic response of regenerating feathers in the weaver bird: Comparison of two species in response to two gonadotrophins
Authors: Ralph C. L. , Grinwich Daniel L. , Hall Peter F.
Published: June 2005

The gonadotrophic hormones, interstitial cell‐stimulating hormone (ICSH, also known as luteinizing hormone) and pregnant mare serum (PMS), stimulate melanogenesis in regenerating feathers of weaver birds. In experiments designed to explore the mechanism by which these hormones stimulate melanogenesis, a method was devised for examining feathers microscopically, soon after injection of the gonadotrophic hormone. The two hormones were compared and two species of weaver bird, namely Euplectes after and Steganura paradisaea, were used for this comparison. In response to both hormones, melanocytes began to appear in the feathers of Steganura 12–24 hours after injection, but it was not until about 30–54 hours that they could be seen in feathers of Euplectes. ICSH induced a transient proliferation of melanocytes, higher doses causing responses of longer duration but generally not lasting more than 24 hours. In contrast, the responses to PMS continued for at least 72 hours in Steganura and for at least 96 hours in Euplectes. The possible significance of these observations is discussed in relation to the mechanism by which the hormones stimulate melanogenesis in feathers.
Hormonal regulation of feather pigmentation in African weaver birds: The exclusion of certain possible mechanisms
Authors: Ralph C. L. , Grinwich Daniel L. , Hall Peter F.
Published: June 2005

An earlier paper (Hall et al., '65) presented evidence to show that in producing pigmented feathers in the weaver bird, interstitial cell‐stimulating hormone (ICSH or LH) does not act locally upon the feathers. The present paper describes our further search for the site of action of the hormone. It is concluded as the result of these experiments that ICSH is unlikely to act via the hypothalamus, the adrenal, the thyroid or the pineal. Evidence is also presented to suggest that synthetic α‐MSH does not produce black feathers and that extensive damage to the pituitary (short of total destruction) by means of electrocautery does not alter the response to ICSH. The site of action of ICSH in producing pigmented feathers remains unknown but the possibilities are now reduced.
In vitro fertilizaton and the sperm acrosome reaction in the hamster
Authors: Barros C. , Austin C. R.
Published: June 2005

The feasibility of procuring fertilization of ovulated hamster eggs in vitro with epididymal spermatozoa has been confirmed, and additional evidence is brought forward to show that a period of just under four hours is needed for sperm capacitation in vitro.

It has also been found that follicular eggs can be fertilized in vitro with epididymal spermatozoa, and at a higher incidence than ovulated eggs. Female tract secretion in the hamster therefore play no unique role in sperm capacitation or sperm penetration into eggs.

A close correlation, both in time and the nature of effective media, existed between the acquisition of fertilizing capacity by spermatozoa and the occurrence of the sperm acrosome reaction. The highest incidence of spermatozoa showing the acrosome reaction was seen when the cells were incubated in the contents of mature follicles; the incidence was lower with the contents of part‐grown follicles and with the secretions of the Fallopian tube. Neither the egg nor its investments appear to be the source of significant amounts of the agent or agents responsible. Induction of the acrosome reaction by follicular contents showed partial species specificity. No reactions were seen with homologous aqueous humor and fluid hen egg‐white.

From observations on the frequency of polyspermy and numbers of supplementary spermatozoa it is inferred that the efficiency of both the zona reaction and the block to polyspermy increases during preovulatory follicular enlargement to reach a peak during the first 2 or 3 hours after ovulation.
Regional influences on development of the single comb primordium
Authors: Lawrence Irvin E.
Published: June 2005

In an effort to resolve some of the developmental controls in single comb morphogenesis, comb primordia from New Hampshire Red and White Leghorn chick embryos were excised and grafted in atypical positions. The grafts were allowed to develop and recognizable structural details were later recorded and analyzed.

Four different experimental series were made: (1) defect, i.e., the comb primordium was excised and the embryo developed with deficiency; (2) orthotopic, i.e., donor primordium grafted to frontonasal process of host; (3) heterotopic, i.e., donor primordium grafted to neck region of host; and (4) chorioallantoic, i.e., entire primordium grafted to chorioallantoic membrane of host chick. The promordia ranged in developmental age from stage 9 to stage 29.

The results showed that the comb primordium can self‐differentiate. Single comb primordia of the White Leghorn breed are determined for comb by stage 15. The primary source of comb tissue appears to be local in origin. Regional influence of growing structures seems to affect comb form. When grafted in most regions and positions, the developing comb did not grow in length. Neck grafts which included some beak tissue developed elongate and typical comb. Rostral extension of the nasal and interorbital septum around seven days of development is thought to be important in normal elongation. Complex clusters of points developed in neck grafts that did not elongate. The normal distribution of comb components was not seen in such grafts. Form of blade and points appears to be predetermined.

The conclusion is made that the capacity to differentiate comb form, e.g., ridge, axes, and regional divisions with or without serrations is fixed within the cell population that will form comb by stage 15; distribution of the structural components and typical elongation can be modified through tissue interactions in later stages.
Histological and ultrastructural study of the muscular and nervous systems in Hydra. II. Nervous system
Authors: Davis Lowell E. , Burnett Allison L. , Haynes Julian F. , Osborne Dallas G. , Spear Mary Lou
Published: June 2005

Nerve cells in hydra have been studied with the light and electron microscopes. Techniques for observing bi‐polar, tri‐polar, multi‐polar and sensory cells are described. Evidence is presented that these cells form a major part of the nervous system in hydra.

The ultrastructural studies indicate the following: (1) There are three types of nerve cells: ganglionic, sensory and neurosecretory. (2) Nerve cells are concentrated at the base of tentacles, hypostome and basal regions. (3) Nerve cells are situated adjacent to the muscle fibers of the epithelio‐muscular cells. Criteria for identification of nerve cells at the ultrastructural level are presented. The nerve cells in hydra appear to be structurally different from similar cells in higher invertebrates and vertebrates. An important distinction is the lack of specialized synaptic vesicles in hydra.

The appearance, dimensions, and location of secretory droplets in cells identified as neurosecretory cells are discussed. The droplets resemble closely neurosecretory droplets in nerve cells of higher invertebrates and vertebrates. The mechanism for the release of neurosecretory material in hydra appears to be similar to that suggested for higher organisms.

It is suggested that one type of secretory droplet in hydra nerve cells may represent a growth stimulating principle that is believed to control growth and differentiation (Burnett, '66). The relationship of nerve cells to muscle processes is discussed.
The dynamics of stolon elongation in the hydroid, Campanularia flexuosa
Authors: Wyttenbach Charles R.
Published: June 2005

Stolon elongation in Campanularia has been shown to occur in cycles, each consisting of the following phases: (a) extended and resting, (b) retraction, (c) retracted and resting, (d) re‐extension to the length in phase (a), (e) resting, and (f) extension. Three features of this cycle — cycle duration, magnitude of extension and magnitude of retraction — have been evaluated to determine their inherent constancy and their modification by environmental and other factors.

In the strain studied, cycle duration was a highly reproducible 6.15 ± 0.05 minutes at 20° C, consistent both from cycle to cycle in a given stolon, and among different stolons. This time is most markedly affected by temperature but is also genetically regulated within moderate limits and is affected to a small degree by the organic content of the sea water.

Extension per cycle averages 20 μ (about 5.0 mm daily) in most older stolons, though individual cycles vary randomly from this mean by ± 20%. This average varies considerably among different genetic stocks, is less in newly‐initiated than in older, establised, stolons and is markedly reduced at temperatures exceeding 22° C. It is remarkably resistent in established stolons to all but severe starvation.

The magnitude of retraction is highly variable (1 to 28 μ) from cycle to cycle, though this variation occurs in a predictable fashion. Evidence is presented that the extent of retraction is determined by the degree of internal hydroplasmic pressure behind the tip.

Isolated stolon tips 300–500 μ long (diameter about 200 μ) display all essential features of the normal growth cycle. Such rhythmic activity is therefore intrinsic to the cells at or within 0.3 mm of the tip. Effects exerted by more distant regions may modify but do not basically change this pattern.

Synchronized with this elongation cycle is a cycle of thinning and thickening of the epidermal layer at the stolon tip. Thinning is interpreted as a passive response to the forward thrust of the gastrodermis.
Effect of low nutrition on size of striated muscle fibres in the mouse
Authors: Rowe R. W. D.
Published: June 2005

Inbred, male 129/Re mice were maintained on a low plane of nutrition for a period of 21 days. After this time they were sacrificed and the following five muscles were examined for total fibre number and fibre diameter distributions, anterior tibialis, biceps brachii, extensor digitorum longus, soleus and sternomastoideus. Changes in body weight and muscle weight were also recorded.

The low plane of nutrition resulted in a significant body weight loss (30%) and variously decreased muscle weights. The ratios, muscle weight: body weight, however, were higher in the experimental mice. The total fibre numbers of the muscles were not affected by the plane of nutrition. The mean fibre diameters of all the muscles, except the soleus, were lower in the experimental mice. These lower values were brought about by a decrease in the proportions of fibres of large diameter and not by the reduction in diameter of all the fibres.

It was concluded that a low plane of nutrition caused fat deposits to be depleted, thereby reducing the body weight and the work‐load of the phasic muscles, i.e., muscles bringing about body movements. This enabled the muscles to be effective at a smaller size. The level of muscle growth was adjusted at the individual fibre level.