bluuebunny/crossref_metadata_2025 huggingface dataset:
The developmental genetics of polymorphism in the rotifer Asplanchna. III. Quantitative modification of developmental responses to vitamin E, by the genome, physiological state, and population density of responding females
Authors: Birky C. W.
Published: June 2005

An increase in the level of vitamin E in the diet of amictic female Asplanchna fed paramecia and reproducing by parthenogenesis elicits three responses: (1) the mixis response: a proportion of their offspring develop into mictic females, which reproduce bisexually; (2) the BWO response: the offspring develop regular body‐wall outgrowths and (3) a reduction in fecundity of amictic females. The quantitative control of these responses has been studied. Genotypic modification of the BWO response has been demonstrated by showing consistent quantitative differences in the response of different clones from the same or different natural populations. Variation in the BWO response has also been demonstrated among the progeny of different females from a clone, and among the individual progeny of single females. The age of a female proved to be a significant physiological factor affecting both the BWO and mixis responses as measured in her offspring. The composition of the culture fluid may also modify the BWO response. An environmental variable of special interest is population density. The BWO, mixis and fecundity responses are all enhanced at high densities, and this effect is seen at natural population levels. It is suggested that this effect may help explain the observation that mixis generally coincides with peaks of population density in nature; this variable, rather than levels of dietary vitamin E per se, may be the most significant factor controlling polymorphism in nature. The density effect has been shown to be due to one or more conditioning factors, possibly pheromones, liberated by the female rotifers.
Testis growth and regression in starlings (Sturnus vulgaris) as a function of the presence of females
Authors: Schwab Robert G. , Lott Dale F.
Published: June 2005

Four groups of male starlings were exposed to stimulatory photoperiods. Two groups had 14 hours of light per day, the other two groups, 12 hours. One of the two groups treated with each photoperiod was in a cage including both male and female starlings; the other group was in a cage including only male starlings. Testis widths were measured via laporotomy every 15 days through a growth and regression cycle.

Neither the rate of testis development, nor the maximum size reached, was significantly changed by the presence of the females in either photoperiod. Likewise, the chronology of testis involution in those treated with a 14 hour light per day photoperiod was not changed by the presence of females. But maintenance of spermatogenesis in birds treated with 12 hours of light daily was significantly longer in the group caged with females.
Modification of excitation‐contraction coupling in locust skeletal muscle induced by caffeine
Authors: Huddart Henry , Abram Roland G.
Published: June 2005

Potassium contractures were recorded isometrically in locust extensor tibialis muscles. The graphs relating contracture tension to external potassium, and contractute tension to depolarization were of sigmoid shape. In normal circumstances, peak contracture tension was obtained with 100 mM/1 potassium saline at a depolarization level of about −10 mV. At a concentration of 2 mM/1, caffeine considerably lowered the mechanical threshold of the muscle fibres such that peak contracture tension was obtained with 40 mM/1 potassium saline, at a depolarization level of only −30 mV. Withdrawal of calcium ions from caffeine containing salines resulted in a loss of the contractile response to depolarization, and the lowering of the mechanical threshold was abolished. These results are consistent with the view that caffeine may activate muscle in vivo by accelerating calcium release from the sarcoplasmic reticulum and by suppressing active calcium binding by the reticular calcium pump. Since caffeine can activate depolarized muscle it is suggested that caffeine short‐circuits the normal excitation‐contraction coupling channels to initiate a direct release of calcium ions from the sarcoplasmic reticulum without transient depolarization.
Lactate dehydrogenase isozymes of the flatfish, Pleuronectiformes: Kinetic, molecular and immunochemical analysis
Authors: Markert Clement L. , Holmes Roger S.
Published: June 2005

At least two genes are responsible for lactate dehydrogenase (LDH) synthesis in the tissues of eighteen species of flatfish (Pleuronectiformes). The relative activity of these genes is markedly skewed with LDH‐A4 being present in much larger amounts and in a wider variety of tissues than LDH‐B4. Certain flatfish exhibit a single LDH‐A4 while others have five forms of this tetramer. Molecular hybridization experiments demonstrate that these five tetramers have two distinguishable subunits. These subunits were purified and subjected to amino acid analysis, peptide mapping, kinetic and immunochemical analysis and shown to be very similar, perhaps identical, in primary structure. Treatment with reducing reagents failed to interconvert them. LDH‐B4 was partially purified and shown to be kinetically and immunochemically distinct from LDH‐A4. As is true for many other fish, additional LDH isozymes are obseved in eye and brian tissues. These results show that the flatfish genetic information for LDH synthesis is similar to that of other fish, and flatfish LDH A and B subunits are homologous to those of other vertebrates.
The effect of teratogenic doses of trypan blue on the yolk sac placenta of the mouse. A histological and histochemical study
Authors: Greenhouse Gerald , Pesetsky Irwin , Hamburgh Max
Published: June 2005

Injection of teratogenic doses of trypan blue into pregnant mice resulted in depression of acid phosphatase activity in embryonic visceral yolk sac endoderm. In addition, the apical localization of this enzyme was lost, and enzyme active loci were dispersed throughout the cytoplasm. Perinuclear Golgi structures were prominent in yolk sac cells of control mice incubated for thiamine pyrophosphatase activity. In trypan blue treated animals the Golgi apparatus was attenuated and disrupted. Whereas yolk sacs of most trypan blue treated embryos showed depression of acid phosphatase activity and morphological alteration in Golgi, only 25% of such embryos exhibited gross malformations. Trypan blue treatment may cause malformations by altering nutritive and transport functions of the yolk sac placenta or the dye may exert a direct effect upon the cells of the embryo.
Hormone‐stimulated amino acid incorporation by Rana catesbeiana tadpole hindleg muscle in vitro
Authors: Hosick Howard L. , Strohman Richard C. , Bern Howard A.
Published: June 2005

Treatment of isolated tadpole (Rana catesbeiana) gastrocnemius muscles with either insulin or thyroxine, in a rich nutritive medium, results in an approximate doubling of incorporation of 3H‐leucine into perchloric acid‐precipitable material. We have not observed parallel increases in the amount of acid‐soluble label appearing in hormone‐treated muscles. Various combinations of insulin and/or thyroxine with growth hormone give responses similar to those occurring with insulin or thyroxine alone. The greatest rates of incorporation, relative to control muscles receiving no hormone treatment, were observed in muscles exposed briefly to thyroxine, insulin and growth hormone simultaneously. The interaction of prolactin with thyroxine in this quasi‐adult system remains equivocal.
Survival and limb regeneration of hypophysectomized newts with pituitary xenografts from larval axolotls, Ambystoma mexicanum
Authors: Tassava Roy A.
Published: June 2005

Ten of 15 hypophysectomized newts with pituitary xenografts from larval axolotls, Ambystoma mexicanum, survived for over 140 days, regenerated amputated limbs and underwent occasional molts. Newts from which the larval pituitary graft was removed underwent typical hypophysectomy symptoms: sluggishness, lack of molting and death within 30 days. The results suggest that the pituitary of the larval axolotl, when implanted into the adult newt, secretes the hormones which are essential for survival and limb regeneration of the adult newt. Furthermore, pituitary xenografts to newts survive as long as pituitary homografts.
A histological study of the regenerative response in a lizard, Anolis carolinensis
Authors: Zika Jocelyn M.
Published: June 2005

Amputated hyperinnervated Anolis carolinensis limbs were studied histologically at various times from early stages of post‐amputational wound healing to formation of mature mounds. Comparable stages of normally innervated amputated limbs were also studied. The sequence of events involved in tissue repair was found to be similar in both groups. The mounded adigital outgrowths which were produced on the hyperinnervated limbs were composed, in 80% of the cases, of large amounts of connective tissue or bone, whereas the other 20% contained primarily nerve fascicles and adipose tissue. The mounds were formed as the result of extensive regeneration of individual tissues without the interposition of a mesenchymatous cell blastema. It was concluded that the regenerative response shown by the hyperinnervated Anolis limb differs from the de novo regeneration seen in urodele amphibians. Whether this hyperinnervation procedure accurately tests the influence of nerve tissue on reptilian limb regeneration is discussed.
Cytological aspects of fertilization in the lamellibranch, Mytilus edulis I. Polar body formation and development of the female pronucleus
Authors: Longo Frank J. , Anderson Everett
Published: June 2005

Aspects of fertilization encompassing the meiotic events of the maternal chromatin, the formation of the polar bodies, and the development of the female pronucleus have been investigated in the lamellibranch, Mytilus edulis.

The cromosomes of the mature egg of Mytilus edulis at the time of fertilization are organized on the first metaphase plate of meiosis. The first meiotic metaphase figure, oriented normal to the egg's cortex, consists of two asters, each of which contains paired centrioles, microtubules, and some smooth endoplasmic reticulum. Subsequent to sperm incorporation, the first polar body is produced by a process akin to cytokinesis following the movement of the chromosomes at anaphase. Later, the metaphase plate of the second meiotic apparatus is formed. Morphologically, the second metaphase figure is similar to the first; however, each aster appears to contain only one centriole. The second polar body, produced in the same manner as the first, remains associated with the zygote via a cytoplasmic bridge which persists up to the time of the first cleavage. Both polar bodies contain the same cellular inclusions as the zygote; however, only the second polar body has its chromatin delimited by a perforated nuclear envelope. After the formation of the second polar body, the maternal chromatin is organized into chromosomal vesicles. The chromosomal vesicles later fuse to form the female pronucleus.
The relationship between the intensity of light pulses and the extent of phase shifts of the circadian rhythm in the eclosion rate of Drosophila pseudoobscura
Authors: Chandrashekaran M. K. , Loher Werner
Published: June 2005

The advance as well as the dealy phases of the circadian system of Drosophila pseudoobscura respond in a similar manner to exposure to light signals of 15‐minute duration and different intensities. The response, measured by the extent of phase shifts four to five days after the signals, is complete at an intensity of 10 lux; light signals of higher intensities such as 3000 and 10000 lux effect phase shifts of similar time course and magnitude as light signals of 10 lux. Light pulses of intensities below 10 but above 1 lux induce phase shifts of a lesser degree. The response of the system to light signals in this range appears to be a graded one. Low light intensity signals of 0.1, 0.3 and 1.0 lux induce “reversing transients,” i.e., transients having a direction opposite to that seen in the subsequent steady state, whereas light pulses of higher intensities do not induce reversing transients.
Clonal distribution of melanocytes in piebald‐spotted and variegated mice
Authors: Schaible Robert H.
Published: June 2005

Experimental observations of mice support the hypothesis that the complete pigmentation of most normal mammals and birds develops by the expansion and merger of clones of pigment cells from the same centers that appear as pigmented spots against a white background in piebald‐spotted mutants. Specific piebald‐spotted mutants, bt and s, having nearly normal pigment coverge in certain parts of their bodies were selected for progressive restriction of those areas until the center of each area was located. Repeated reversion of the same pigment areas in variegated Miwh, Wa, and Va heterozygotes indicated that each of the areas was a clone of cells derived from a single primordial melanoblast that migrated from the neural crest to the location of the center during embryogenesis. White regions completely separated cells of different clones into differently pigmented spots when piebald‐spotting mutants, bt or s, were combined with variegated Miwh/+. Because the separation of clones was so complete, it appears that no pigment cells exist in the intervening white regions at any stage of development. Additional evidence also indicates that restricted proliferation of pigment cells is a common end effect in all piebald‐spotting mutants, even though more direct effects may be on the pigment cell, the neural crest or the tissue environment of the skin.
Studies on the relationship between uterine fluid components and the diapausing state of blastocysts from mammals having delayed implantation
Authors: Daniel Joseph C. , Krishnan R. S.
Published: June 2005

In the uterine secretions of certain mammals, gross qualitative and quantitative differences in their protein content were observed depending on whether or not the animals exhibited delayed implantation. Diapause blastocysts of the animals representative of those with obligate delayed implantation were stimulated to grow (as measured by total expansion and increased mitotic index) when maintained in vitro in medium containing rabbit “blastokinin” but not in serum‐containing medium. Diapause rat blastocysts taken from animals where a facultative delayed implantation has been produced by heavy lactation, expanded in F10 medium alone or containing serum or the macromolecular components of uterine secretions taken from a 5‐day pregnant animal, but not in rabbit “blastokinin.” The mitotic index, however, was the same under all three conditions and higher than in uncultured controls. Growth of active 5‐day rat blastocysts was stimulated by medium containing the proper concentration of uterine macromolecular components; mitotic activity increased three to four‐fold.

We conclude that delayed implantation results from the failure of the mother to provide sufficient protein and/or certain specific proteins as needed for active growth of the blastocysts. In facultative delayed implantation, as exemplified by the lactating rat, there is evidence that, in addition to the protein deficiency, some substance or condition exists in the uterus which inhibits growth of the blastocysts.
Physiological studies on supercooled killifish (Fundulus heteroclitus) II. Serum organic constituents and the problem of supercooling
Authors: Umminger Bruce L.
Published: June 2005

To gain insight into the mechanism permitting Fundulus heteroclitus to survive subzero temperatures in a supercooled state, previously published data on inorganic components of the serum were complemented by studies on serum organic constituents in parallel groups of adult male killifish acclimated to various temperatures (30°C, 20°C, 10°C, 4°C, 2°C, −1°C and −1.5°C) in salt water under otherwise constant laboratory conditions. When the acclimation temperature was lowered from 20°C to −1.5°C, there was little or no change in levels of serum total non‐protein nitrogen, total amino acids, urea and non‐glucose free carbohydrates. Total serum protein levels were usually unaffected by the cold, but occasionally showed a decrease. Serum total cholesterol levels increased by 69% in the subzero cold, presumably due to an increased lipid metabolism. Whereas most serum constituents (organic and inorganic) showed only minor changes in supercooled F. heteroclitus, serum glucose levels increased from three‐ to sixfold. Serum glucose levels of 68 mg% in fish at 20°C increased to 460 mg% in sexually regressed fish at −1.5°C but to only 280 mg% in supercooled mature fish. It was suggested that the elevation of serum glucose in the subzero cold permitted survival in a supercooled state, presumably by retarding ice crystal growth on any ice nuclei that might form spontaneously in the blood.
Deletion‐transplantation experiments on embryos of Fundulus heteroclitus. II. The anterior embryonic shield
Authors: Brummett Anna Ruth
Published: June 2005

Experiments are described in which the differentiative capacity of the anterior embryonic shield of the teleost. Fundulus heteroclitus, was investigated by means of deletion‐transplantation techniques.

The anterior embryonic shield, deleted from gastrula stages and transplanted into the pericardial chamber of an older embryo, exhibits growth and differentiates structures appropriate only to anterior head. All germ layers are involved in both the operation and subsequent differentiation. The donor embryos, in general, develop normally except for striking deficiencies in forebrain and eyes. Both donors and grafts indicate increasing specificity of determination in the cells of the anterior shield as development proceeds from early to late gastrula.

The experiments are discussed from the standpoint of their elucidation of localization of developmental potencies in the anterior embryonic shield.

Two unexpected effects of graft on host are described and briefly discussed: (1) the differentiation of glandular cells in the host pericardial epithelium in the immediate vicinity of the graft, tentatively labeled an “induction,” and (2) a deleterious systemic effect of the graft on the host embryo. Both of these effects occurred in a significant number of cases but appear to be unrelated to each other and are, as yet, unexplained.
Ultrastructure of the germinal epithelium during oogenesis in the rabbit
Authors: Gondos Bernard
Published: June 2005

Electron microscopic examination of newborn New Zealand white rabbit ovaries revealed numerous germ cells within the germinal epithelium during the early stages of oogenesis. The germ cells were found at all levels of the germinal epithelium, as well as in bridges connecting with the underlying sex cords. Germ cell nuclei were large and round with smooth, regular double membranes, reticular nucleoli and evenly distributed chromatin. Mitochondria were characteristically spherical with slightly eccentric cristae. The number of germ cells within the germinal epithelium gradually diminished until they were completely absent by the time oogenesis was complete.

The germinal epithelial cells were characterized by irregular, elongated nuclei with eccentric nucleoli and peripherally marginated chromatin. Cytoplasm was rich in ribosomes, rough‐surfaced endoplasmic reticulum and elongated mitochondria. Junctional complexes, cytoplasmic projections and occasional cilia were present on the cell surfaces. At the junctions of germ cells and germinal epithelial cells, cell membranes were closely apposed and small interdigitating cytoplasmic projections were present.

During the early stages of oogenesis, the germinal epithelium was multilayered and connected to the cortical sex cords in many places. Bridges joining the germinal epithelium to the sex cords contained both germ cells and germinal epithelial cells. Occasionally, germinal epithelial cells could be seen extending partially into the sex cords. With increase in the thickness and extent of the tunica albuginea, contact between the germinal epithelium and the sex cords was gradually diminished. As oogenesis reached completion, the germinal epithelium was reduced to a single layer of epithelial cells separated from the developing follicles below by a dense band of fibroblasts, collagen and capillaries.
The control of DNA synthesis in macronuclei and micronuclei of a hypotrich ciliate: A comparison of normal and regenerating cells
Authors: Jerka‐Dziadosz Maria , Frankel Joseph
Published: June 2005

Urostyla weissei, a hypotrichous ciliate possessing two macronuclei and four or more micronuclei, has an inter‐division interval of about 12 hours. Macronuclear DNA replication occurs between five and ten hours after cell division, while micronuclear DNA replication takes place a short time prior to mitosis. Synchronous populations of dividing cells were isolated, provided with H3‐thymidine labelled Tetrahymena, and then were equatorially transected during either G1 or macronuclear S. Regeneration was completed, with attendant micronuclear and macronuclear division, four to five hours after transection. No macronuclear DNA synthesis took place during the regeneration interval. In cells transected during macronuclear S, the replication band generally disappeared and DNA synthesis was arrested. The macronucleus then divided without mixing of replicated and un‐replicated portions, so that the replicated material generally passed to only one of the macronuclear division products, which was larger than the other. Following the completion of regeneration, a new wave of DNA synthesis commenced immediately in macronuclei of cells transected during G1, and with some delay in cells transected during S. The completion of this replication wave was not followed by cell division; instead a second replication was initiated a few hours later, and then the cells divided.

Micronuclei initiated DNA synthesis prior to mitosis, which occurred whenever regeneration was completed, and regardless of the time of transection or the concurrent state of the macronucleus. Thus, in cells transected during G1, micronuclei replicated considerably earlier than in the unoperated controls.

In cells subjected to repeated transection at four to five hour intervals, macronuclei became progressively smaller while micronuclei remained the same size, which is expected if macronuclear replication is suppressed due to the regeneration‐stimulus, while micronuclear replication occurs automatically prior to every mitosis.
Target discrimination by the echolocating bat Vampyrum spectrum
Authors: Bradbury Jack W.
Published: June 2005

Five specimens of Vampyrum spectrum were trained to discriminate between solid targets differing in shape or size using echolocation alone. A pair of lucite targets, one a sphere, the other a prolate spheroid, were then designed so as to produce echoes of approximately equal overall amplitude at the distance of choice by the bats, but of different frequency composition. This discrimination was successfully performed by four of the animals and the two best performers were studied in detail by photographic analysis to ascertain whether frequency or amplitude cues were actually being utilized. By manipulating the degree of frequency dependence in the echoes, it was shown that one animal seemed to rely on the availability of frequency‐dependent cues for successful discrimination while the other did not. Examination of the structure of the pulses used on these flights indicated a consistent pattern of changes as the targets were approached. Some of these changes could be correlated with the kinds of cues the two bats seemed to be using in making the discriminations.
Factors influencing sperm penetration of rabbit eggs in vivo
Authors: Harper M. J. K.
Published: June 2005

Unfertilized eggs recovered from donor rabbits at known times after injection of HCG were transferred to the oviducts of mated recipients (prevented from ovulating by having their ovaries covered with nail polish) at specific times after mating. When newly ovulated eggs (11.25–13.5 hours after HCG injection) were left in the oviducts of the recipients for 1, 1.5, 2, 2.5 and 3 hours, 15, 30, 44, 59 and 75% respectively were penetrated by spermatozoa. If the unfertilized eggs were allowed to age in the oviducts of the donor before transfer then fertilizability decreased: only 41 and 25% of eggs 15–15.5 hours and 17–17.5 hours old at time of transfer respectively were penetrated during 2.5 hours in the recipients' oviducts compared to 59% of 13–13.5 hour eggs. No beneficial effect from maturation in the donor of the unfertilized egg and its membranes was observed. When eggs with cumulus cells removed were transferred to recipients at 9–9.5 hours after mating, then a decrease in the percentage of eggs penetrated during 2.5 hours in the recipients' oviducts was found. Removal of both cumulus and corona cells had no greater effect than removal of cumulus alone. However, when eggs similarly treated were transferred to recipients at 14 hours after mating, neither removal of cumulus nor of cumulus and corona cells had any effect on the percentage of eggs penetrated during 2.5 hours. It is concluded that when conditions for fertilization are not optimal the cumulus is important for ensuring meeting of sperm and egg, but that when conditions are optimal then presence of these cellular layers is not important. Whether the products of ovulation play a role in the final stages of capacitation of sperm was tested by transferring eggs into the oviducts of rabbits unilaterally ovariectomized (more than 3 weeks previously) at 13.5–14.75 hours after mating. No difference in percentage of eggs penetrated was observed between oviducts on the ovariectomized and intact sides. The contact of the sperm with the products of ovulation in the one oviduct did not give them an advantage over the sperm in the other oviduct without such contact. It was found that although only 30% of newly ovulated eggs were penetrated in 1.5 hours following transfer to recipients at 9–9.5 hours after mating, 57 and 66% were penetrated during the same period if the transfers of similar eggs were delayed until 13.75–14.0 hours and 19.5–20.0 hours after mating of recipients respectively. It is suggested that these increases in percentages of eggs penetrated are a reflection of the presence of more sperm or of more fully capacitated sperm in the oviduct at these later times.
The synchronization of oral development without cell division in Tetrahymena pyriformis GL‐C
Authors: Frankel Joseph
Published: June 2005

Cells of T. pyriformis strain GL‐C synchronized in an amino‐acid‐free medium underwent synchronous oral replacement in place of cell division. This involved development of an oral primordium at the anterior end of the cell, with a concomitant rounding of the cell. The timing of this development was very similar to that of primordium development during synchronous division. In some experiments a second synchronous oral replacement was observed about 90 minutes after the first.

Synchronization of oral replacement was similar to that of cell division. Prior to the heat shocks cells maintained in amino‐acid‐free medium were undergoing oral replacement asynchronously (with no concurrent macronuclear DNA synthesis). During the synchronizing treatment, development was initiated in the inter‐shock intervals but was arrested by the 34° heat shocks. As a result, cells became progressively accumulated in the earliest stage of oral replacement development. This accumulation did not take place if a single continuous heat treatment was given, or if cells were maintained in 2,4‐dinitrophenol, actinomycin D, or cycloheximide during the periodic heat shock treatment.

The synchronous oral replacement which took place after the end of the synchronizing treatment (EST) could be blocked completely by actinomycin D, cycloheximide, and puromycin, and partially by p‐fluorophenylalanine. Exposure to cycloheximide (1 μg/ml) during stage 1 of stomatogenesis (10–30 minutes after EST) resulted in arrest of development, exposure during stages 3 and 4 (45 minutes) brought about primordium resorption, while exposure in stage 5 (60 minutes) permitted completion of development, with subsequent partial resorption. These responses were identical to those of synchronized dividing cells treated at comparable stages.
Congenital eye defects in the mouse. III. Lens opacity in NAW‐wa‐2+ − +/Sp
Authors: Pierro Louis J. , Spiggle Jean
Published: June 2005

A pin‐point lens opacity can be detected at a frequency of 90% in weanling mice from inbred strain NAW‐wa‐2+ − +/Sp. Defective lenses show abnormal thickening of the anterior epithelium localized over a region of persistent contact between the primary lens fiber mass and the epithelium.

A morphological study of lens development indicates that the mutant strain clearly differs from normal as early as the twelfth day of embryonic life. In a lens sector associated with the naso‐ventral quadrant of the optic cup, cells undergoing the elongation characteristic of primary lens fibers are separated from the normal boundary of the anterior epithelium by a peculiar group of cells. These cells can still be detected on the following day; they do not differentiate into primary fibers. They contribute to the anterior epithelium instead, and the zone of elongation is asymmetrically displaced from the equator. Secondary fibers formed in this sector before birth do not completely displace the primary fibers from contact with the anterior epithelium. If secondary fibers formed during the neonatal period do not accomplish separation, abnormal thickening of the anterior epithelium begins around the end of the second week of postnatal life. The epithelial thickening and capsule‐like material deposited within it apparently provide the structural basis for the opacity detected upon gross examination.
Responses of perfused isolated leg preparations of the cockroach, Gromphadorhina portentosa, to L‐Glutamate, GABA, picrotoxin, strychnine and chlorpromazine
Authors: Faeder Isabelle R. , O'Brien Richard D.
Published: June 2005

A perfused leg preparation of Gromphadorhina portentosa (Orthoptera) was developed for use in pharmacological studies and bioassay procedures. Study of tibial flexion with increasing stimulation intensity at low frequency revealed five fast motor units. Chlorpromazine (2.5 × 10−4 M) progressively blocked these motor units. GABA generally failed to affect fast system responses, even at high concentration (2.5 × 10−4 M). A high concentration (2.5 × 10−4 M), picrotoxin produced effects consistent with the interpretation that motor axon excitability was affected. Strychnine (2.5 × 10−4 M) produced no effect on isolated leg preparations. L‐Gultamate (pH 7.2) produced contractures; the threshold for this response was 2.5 × 10−4 M. Contractures were produced after application to resting muscle, and were also observed in preparations receiving low frequency indirect stimulation. The response to glutamate under the latter condition closely resembled incomplete tetanus. L‐Glutamate (2.5 × 10−4 M) produced a reversible depression of kick force in locusts. These responses are compatible with the hypothesis that L‐glutamate is an excitatory neuromuscular transmitter in insects.
Digestion in Haliotis rufescens Swainson (Gastropoda: Prosobranchia)
Authors: McLean Norman
Published: June 2005

Digestion was studied in the marine archaeogastropod Haliotis rufescens, with emphasis on identification of absorptive regions in the gut. Extracellular enzymes were found in the digestive fluid. Absorption in the digestive gland was demonstrated by autoradiography of tissue sections after feeding animals on 14C‐labeled algae. After absorption, food was retained apically in the absorptive cells of the digestive gland in an insoluble form. Possible mechanisms of uptake are discussed. It was shown chromatographically that small compounds derived from the food were present in both the crop fluid and blood early in digestion. Studies in vitro showed that the crop epithelium was permeable to small organic materials. Glucose and phenylalanine were found to have been taken up by the crop epithelium in considerable quantities; smaller amounts were passed through the epithelium, and would in life be transferred to the blood. The surface area of the food mass was seen to be increased in an intestinal sorting area at the beginning of the intestine. The intestinal epithelium was shown in vitro to be permeable to glucose. It is concluded that the large crop is an important region of absorption, and that digestion and absorption continue to occur as food passes along the intestine.
Bioelectric interactions between cultured fetal rodent spinal cord and skeletal muscle after innervation in vitro
Authors: Crain Stanley M.
Published: June 2005

Electrophysiologic analyses of cultures of various combinations of spinal cord and skeletal muscle tissues demonstrate that characteristic neuromuscular transmission can develop and be maintained for months in vitro. The studies include: (1) cultures of mouse embryo spinal cord with attached myotomes, explanted prior to formation of neuromuscular junctions, and (2) in vitro‐coupled fetal rodent cord and muscle explants, in which one tissue is grown in isolation before presentation of the other explant (0.5–1 mm apart).

After innervation occurs during the first few weeks in vitro, selective stimulation of spinal cord evokes widespread synchronized twitches in the muscle tissue. Simultaneous microelectrode recordings of cord and muscle responses to local cord stimuli show that muscle action potentials generally occur with latencies of several msec after onset of cord discharges. Rhythmic spontaneous bursts of muscle potentials (and contractions) occur, at times, in close correlation with periodic cord discharges.

d‐Tubocurarine (1–10 μg/ml) selectively blocks neurally evoked muscle contractions while electric stimuli applied directly to the muscle fibers are still effective. Many apparently non‐innervated fibers, on the other hand, show sporadic, asynchronous fibrillations which are not altered by cord stimuli nor blocked by curare.

Eserine and strychnine produce characteristic increases in repetitive muscle activities related to the primary site of action of these pharmacologic agents.

Cultured neuromuscular tissues can, then, provide a valuable model system for correlative physiologic and cytologic studies of nerve and muscle cells during critical stages of maturation and formation of intercellular relationships under isolated conditions in vitro.
Does differential adhesion govern self‐assembly processes in histogenesis? Equilibrium configurations and the emergence of a hierarchy among populations of embryonic cells
Authors: Steinberg Malcolm S.
Published: June 2005

The differential adhesion hypothesis attributes sorting‐out behavior of embryonic cells to differences in the strengths of their intercellular adhesions. It suggests that cells in mixed populations rearrange themselves to minimize their total adhesive free energy. The final configuration adopted is viewed as approaching a moststable or equilibrium configuration, with the less cohesive cell/population tending to envelop the more cohesive one.

The hypothesis enables two predictions to be made. First, if the final configuration adopted by a mixed cell population indeed approximates an equilibrium configuration, the same final configuration should be approached irrespective of the starting configuration. Second, comparison of the equilibrium configurations for all possible pair‐combinations of a series of cell populations of different types should reveal a hierarchy of “preference” for the internal position, reflecting a hierarchy of cellular cohesiveness.

These predictions have been tested and confirmed. First, any particular pair of tissues approaches the same final configuration, irrepective of whether the cells are initially randomly intermixed or tissue fragments are laterally joined. Second, the predicted hierarchy of preference for the internal position has been found, consistent with a hierarchy of cellular cohesiveness.

An effort has been made to clarify confusions that have arisen concerning the differential adhesion hypothesis. It is particularly stressed that the hypothesis offers an explanation for cell population behavior in terms of relative strengths of cell adhesions and makes no proposals concernnig the chemistry of adhesion. However, the value of equilibrium configurations in guiding biochemical investigations of cell surface adhesives is pointed out, as is the relevance of the present observations to natural morphogenetic events.
Fusion of unfertilized mouse eggs with somatic cells
Authors: Baranska Wanda , Koprowski Hilary
Published: June 2005

The purpose of these investigations was to study optimal conditions for the maintenance and stimulation of division of unfertilized mouse eggs in culture after fusion with somatic cells of various species origin.

When unfertilized eggs obtained from superovulated C57B1/6 virgin mice were maintained in culture in Brinster's medium for 72 hours, less than 6% of the eggs divided. Following fusion in the presence of inactivated Sendai virus with somatic cells of mouse, hamster, monkey or human origin, 10 to 60% of the eggs divided, often developing to the early morula stage (3–10 cells).

Blastomeres observed at this stage of development did not differ morphologically from embryo cells dividing after fertilization. Examination of autoradiograms obtained after fusion of eggs with labeled somatic cells support the belief that fusion may be a factor which initiates egg cell division. Ultimately, nuclei of the somatic cells inside the cytoplasm undergo karyorrhexis.

Mouse fibroblasts infected with Moloney sarcoma virus fused better with egg cells than did non‐infected fibroblasts.
The influence of early extirpation of the otocysts on development of behavior of the chick
Authors: Decker John D.
Published: June 2005

Previous investigations have shown that through day 15 of incubation behavior of the chick was not influenced by sensory input. Behavior of chick embryos after this period has been reported to be controlled by integration of stimuli at centers located in different regions of the central nervous system. In this investigation experiments were designed to determine when sensory input of the vestibular system demonstrates an overt influence on the development of behavior and to determine how integration of stimuli at different levels of the CNS was affected by early extirpation of the otocysts.

Unilateral and bilateral extirpations of the chick otocysts were made on day 3 or 4 of the incubation period. Embryonic motility was qualitatively and quantitatively monitored through 15 weeks post‐hatching. (Behavior of embryos was compared with unoperated controls and the ablated regions of the nervous system of experimentals were histologically compared with each other as well as with controls.)

Primary losses of peripheral vestibular (inner ear) receptors and ganglia with little secondary degeneration of vestibular motor nuclei showed no influence on embryonic behavior until hatching. However, gross secondary degenerative changes of vestibular nuclei due to removal of the otocysts influenced behavior of the chick embryos around day 17. Presumably, the early acquisition of sensory capacity by the vestibular system does not influence the development of behavior until the end of the incubation period, but loss of interrelations between vestibular motor centers and other centers of the CNS influences behavior around day 17.
The electrophysiology of muscle fibers in the hearts of Decapod Crustaceans
Authors: Van Der Kloot William
Published: June 2005

Intracellular recordings from the muscle fibers in contracting hearts of the crayfish and the lobster show a sequence of potential changes superficially resembling the vertebrate cardiac action potential. In the Crustaceans, however, the plateau part of the depolarization is produced by fused junctional potentials, elicited by the firing of motor neurons whose cell bodies lie in the cardiac ganglion. The first or second JP elicits an active membrane response that probably is produced by Ca2+ influx, since it is blocked by Mn2+. Local currents can flow between the individual muscle fibers, presumably by way of gap junctions. Simultaneous records were made extracellularly from one of the efferent nerves coming from the lobster cardiac ganglion and intracellularly from a muscle fiber. Four motor axons were identified in the efferent nerve and the firing of each of these sets up a JP at each point on the muscle membrane. A fifth motor neuron may also run to each muscle fiber. In the isolated heart the motor outflow from the cardiac ganglion is quite variable. Nevertheless, the system is such that the potential changes on the muscle membrane are almost indistinguishable from beat to beat. The hermit crab cardiac muscle usually has only two JPs per beat; the first JP sets up an overshooting spike.
Function of the pericardial sacs during the molt cycle in the land crab Gecarcinus lateralis
Authors: Mason Carol Ann
Published: June 2005

The hypothesis that the pericardial sacs of the land crab Gecarcinus lateralis directly take up and store proecdysial water has been investigated. At all stages of the molt cycle, the convoluted surface of the pericardial sacs apposed to the carapace forms a system of channels for capillary transfer of ground water to the gills. When exposed to an osmotic gradient in vitro, isolated intact pericardial sacs from normal or dehydrated intermolt, premolt, and postmolt crabs show no hydrosmotic response. Permeability to 3H2O (THO), expressed as hourly water exchange, is low for sacs under such conditions. If the separated old cuticle has been removed from sacs of late premolt crabs, up to 40 μl of water are gained in the first 15 minutes of exposure to an osmotic gradient, and the hourly exchange rate of THO is increased 30‐fold. These findings indicate that the pericardial sacs may allow osmotic entry of proecdysial water as detachment of the old cuticle takes place. From analyses of osmotic pressure, cations, and 14C‐insulin space of both hemolymph and pericardial sac fluid, it appears that the pericardial sacs do not store water per se but expand to accommodate an increasing hemolymph volume as proecdysial water enters the whole animal. Although water uptake occurs over a longer period in G. lateralis, the pattern of preparation for ecdysis is similar to that of all other brachyurans.
Environmental influence on experimental teratocarcinogenesis in testes of mice
Authors: Stevens Leroy C.
Published: June 2005

Testicular teratomas were experimentally produced in mice of strains 129, A/He, and their F1 hybrids. When male genital ridges from 12‐ or 13‐day fetuses were grafted to various sites in adults, they developed into testes and some of them had teratomas. When male genital ridges were grafted into sites which descend into the scrotum, (the testis, the epididymis, or the epididymal fat pad of intact or castrate males), they developed into testes most of which contained teratomas. When genital ridges were grafted into sites which do not descend into the scrotum (the kidney, spleen, liver, cryptorchid testis, and ovarian fat pad) they developed into testes and most of them did not have teratomas. When genital ridges were grafted into intact females or into castrate females injected daily with peanut oil or with a physiological dose of testosterone proprionate, the incidence of teratomas was very low. These results are in accord with the hypothesis that the lower temperature in the scrotum promotes teratocarcinogenesis in grafted genital ridges. None of our results suggest that testicular or ovarian hormones of host origin are involved.
Hemocytes of saturniid silkworms: Their behavior in vivo and in vitro in response to diapause, development, and injury
Authors: Walters David R.
Published: June 2005

The blood of the wild silkworms Antheraea polyphemus, Samia cynthia, and Hyalophora cecropia (Lepidoptera; Saturniidae) contains two predominant classes of hemocytes, plasmatocytes and granulocytes, which are markedly different in their behavior. In diapausing pupae or developing adults, both types occur in nearly equal numbers. Following surgical injury there is a dramatic increase in the population of plasmatocytes. The behavior of the cells in vitro is not related to their origin but depends on the conditions of culture. In hanging drops the plasmatocytes clump together. On glass or plastic surfaces they become flattened and, like vertebrate fibroblasts, migrate apart to cover the surface with a sheet of cells. Identical cellular membranes from in vivo at wound sites. When dissociated fat‐body cells or tiny beads of resin are cultured in blood, the plasmatocytes adhere to them and draw them into large, heterogeneous aggregates. The granulocytes are completely passive in vitro under all conditions.
Division delays and abnormal oral development produced by colchicine in Tetrahymena
Authors: Nelsen E. Marlo
Published: June 2005

The effects of continuous colchicine treatment on cell division and oral morphogenesis were studied in synchronized Tetrahymena pyriformis GL‐C. The colchicine concentration used for most of this study, 4.0 mg/ml, was shown to have no effect on protein synthesis, as assayed by incorporation of C14‐leucine into hot TCA insoluble material. It was demonstrated that colchicine treatment produced agedependent division delays in Tetrahymena until a “transition point” was reached at about EST + 50−55 minutes, after which treatment produced a very little delay of division. Colchicine treatment prior to the transition point produced arrest or reversal of oral differentiation, followed by redifferentiation of abnormal structures in association with the delayed division. Treatment with colchicine after the transition point blocked oral development even though the cells continued to divide, which resulted in daughter cell with non‐functional oral strures. Under the assumption that colchicine specifically binds microtubule protein, it is suggested that assembly of microtubules prior to the transition point is required for both division and oral differentiation. After the transition point, microtubule formations is required for oral morphogenesis but not for cell cleavage.
The distribution of glycosaminoglycans in the axial region of the developing chick embryo. I. Histochemical analysis
Authors: Kvist Tage N. , Finnegan Cyril V.
Published: June 2005

Histochemical analysis of the developing chick axial region indicated very little sulphated glycosaminoglycan present in early embryonic stages (stage 17) and this appeared to be confined extra‐cellularly to the region of the notochordal sheath. Strongly acidic material was observed in the cytoplasm of cells in all examined axial areas, viz., dermatome, myotome, sclerotome, neural tube and notochord. Weakly acidic anionic glycosaminoglycans were present in the extracellular portion of all axial areas and increased in concentration during development, particularly in the neural tube and the sclerotome. At the same time the concentration of sulphated anionic glycosaminoglycans also increased in the extracellular matrix of all axial areas. By stage 25 the extracellular matrix of the perichordal scleratome appeared to be mostly sulphated polyanions, but elsewhere in the axial tissues the staining for sulphated glycosaminoglycans never approached that intensity demonstrated by the weakly acidic anionic glycosaminoglycans. Testicular hyaluronidase digestion suggested that most of the stainable material was either hyaluronic acid or chondroitin‐4‐sulphate and/or chondroitin‐6‐sulphate (chondroitin sulphate A and C). There was a small amount of strongly acidic (polysulphated) glycosaminoglycan present in the scleratome, neural tube and notochord.