bluuebunny/crossref_metadata_2025 huggingface dataset:
Uptake and incorporation of amino acids in minute mutants of Drosophila
Authors: Farnsworth M. W.
Published: June 2005

Uptake into blood and incorporation into tissue protein of cystine‐35S were assayed in larvae of controls and of five heterozygous Minute mutants of Drosophila melanogaster. The mutants studied were M(2)S‐10, M(2)12, M(2)z, M(3)y and M(3)w. In all mutants, the level of cystine in the blood was significantly higher than in controls and differences in concentration between these mutants were evident. All mutants incorporated cystine into protein, although the specific activities obtained were dependent on genotype. The fraction of the cystine in the blood pool which was incorporated into protein was directly correlated with viability and rate of growth. In contrast, the radioactivity of leucine‐1‐14C, both in blood and in tissue proteins, was not different in M(2)12 and M(3)w heterozygotes as compared to controls, although in M(2)12 the fraction of leucine in the blood pool incorporated into protein was lowered. It was concluded that these mutants possessed a common inability to withdraw cystine (or other sulfur‐containing compounds) from the blood into various metabolic pathways. Feeding activity, digestion and absorption of nutrients appeared normal in these mutants.
Mammalian lung development: Interactions in primordium formation and bronchial morphogenesis
Authors: Spooner Brian S. , Wessells Norman K.
Published: June 2005

The manner in which mouse lung primordia form has been analyzed by observation of trypsin‐isolated gut endoderm from nine‐day embryos. The tissue interactions involved in initial formation of lung primordia and those involved in subsequent morphogenesis of the primordia have been investigated by various organ culture procedures. Mouse lungs form in a manner different from that generally described for amniote embryos. Thus, two lung buds appear first and form the primary bronchi, whereas the trachea appears secondarily.

The initial lung buds form at the 25–27 somite stage. Whole‐guts from embryos as young as the two‐somite stage form lung buds in culture. Such buds do not undergo branching morphogenesis if the guts are taken from embryos younger than the 25‐somite stage, but undergo characteristic dichotomous branching if combined with older bronchial mesoderm. If 20–25 somite‐stage endoderm is isolated and cultured in direct combination with gut, older salivary or older bronchial mesoderms, lung buds form. However, such buds only branch in combinations containing bronchial mesoderm. Our results reveal two levels of mesodermal control of lung development. Interactions between nonspecific mesoderm and gut endoderm result in lung bud formation, while those between specific bronchial mesoderm and bud endoderm are required for branching morphogenesis.
Mammalian lung development: Interactions in formation and morphogenesis of tracheal buds
Authors: Wessells Norman K.
Published: June 2005

Mesoderm present in early developing lung is of two sorts: bronchial, which can evoke formation of bronchial buds from tracheal epithelium; and tracheal, which inhibits bronchial morphogenesis. The latter process correlates with the presence of highly ordered sheaths of collagen and mesoderm cells near the epithelial surface. In contrast, bronchial mesoderm lacks such regularly arrayed components. Initial formation of supernumerary buds on the trachea can be evoked by nonspecific mesoderms, but such buds never branch. Bronchial mesoderm is required if the latter morphogenetic process is to occur.

Thymidine labeling experiments fail to provide evidence that differential mitotic activity leads to initial bud formation.
Polar granules of Drosophila. III. The continuity of polar granules during the life cycle of Drosophila
Authors: Mahowald Anthony P.
Published: June 2005

Polar granules of Drosophila embryos fragment into fibrous bodies which become associated with the nuclear envelope of pole cells prior to the formation of the embryonic gonad. Similar fibrous structures are found attached to the outer nuclear membrane of primordial germ cells and oogonia throughout the life cycle of the fly. These structures have not been found in any other cell type except the germ cell of the testis. During oogenesis, the oocyte nucleus loses the fibrous bodies associated with the nuclear membrane, but the 15 sister nurse cells retain these structures until the end of vitellogenesis. At this time the cytoplasm and fibrous bodies of the nurse cells are contributed to the ooplasm. Occasionally, polar granules are found in previtellogenic stages of oogenesis, but they only accumulate at the posterior tip of the egg during the latter portion of vitellogenesis. After polar granules have formed, they attach to mitochondria in three species studies, but fail to form this association in D. hydei. Fibrous structures in the egg, believed to be the fibrous bodies attached to the nuclear envelope of nurse cells, are found throughout the mature egg, and have the same species‐specific property of associating or not with mitochondria as was found for polar granules. These fibrous bodies are no longer found following fertilization. A possible role of these fibrous bodies in the egg is discussed.
Culture stability of morphogenetic properties of chick limb‐bud mesoderm
Authors: Finch Robert A. , Zwilling Edgar
Published: June 2005

Stability of morphogenetic properties of leg bud cells (stage 20+) after two culture procedures was tested with a technique described by Zwilling ('64). This technique involves the placing of the cells to be tested into ectodermal jackets obtained from stage 20–21 limb buds and then grafting the composites either to the dorsum of the wing bud or over the somites of a host embryo. There is a decline in the limb properties between 12 and 18 hours of either shaking flask or plate culture. This decline parallels that observed in the limb bud in vivo. The distal area of the wing dorsum as a graft site partially overcomes the decline of the limb properties. Plating at high cell density retards the decline in morphogenetic properties.

It is concluded that the culture conditions used in the present experiments have little, if any, effect on the stability of the morphogenetic properties of leg bud cells. Loss of these properties appears to be time dependent. This situation has possible implications for future in vitro studies of the molecular basis for the properties of the morphogenetic phase of chick limb development.
Effects of diabetes on intestinal growth in the rat
Authors: Schedl Harold P. , Wilson Helen D.
Published: June 2005

Diabetes mellitus in rats was induced with alloxan and streptozotocin. Growing rats, six to seven weeks of age, were studied. Growth of the small intestine was compared in diabetic and matched control animals at 5, 8, 44, 55, 70 and 140 days. After five days the total intestinal wet weight was significantly greater in diabetic animals. Intestinal weight of diabetic animals increased progressively in comparison with controls. By 140 days after induction of diabetes, intestinal wet weight was doubled and dry weight was increased by 50% in comparison with controls. Tissue water content was significantly higher in diabetic rats. Body weight of diabetic animals at 140 days was half that of controls. Thus, the ratio of wet weight of intestine to body weight was four times greater in diabetic than control animals. Intestinal length and circumference were significantly increased at 44 days of diabetes. Growth of full thickness gut wall (by the criterion of significantly increased dry weight in g/cm of length) was primarily in the proximal small intestine. The dry weight of mucosal scrapings (g/cm length) was significantly greater in diabetic animals at eight days. The weight of underlying tissue remaining after scraping off mucosa was not significantly different, localizing the growth to the mucosa.
The stress response in the abundance of circulating leucocytes in the killifish, Fundulus heteroclitus I. The cold‐shock sequence and the effects of hypophysectomy
Authors: Pickford Grace E. , Srivastava Anil K. , Slicher Anna M. , Pang Peter K. T.
Published: June 2005

When intact male Fundulus heteroclitus, adapted to 20°C in sea water, are subjected to three minute immersion at ca. 1°C they pass into a state of transitory coma from which they recover when returned to warm temperature. Hematological studies at recovery time intervals revealed an alternating sequence of leucopenia and leucocytosis that was not accompanied by corresponding changes in the abundance of erythrocytes, in serum chloride or total osmolality. The typical sequence was as follows: leucopenia at three minutes, leucocytosis at 15 minutes, leucopenia at 30 to 60 minutes, and leucocytosis at two hours. This was followed by a gradual return to normal. The major leucocytic cell type resembles a lymphocyte; the cycle was not accompanied by corresponding changes in the abundance of small or large lymphocytes, or in the abundance of eosinophils. Hypophysectomy abolished, or minimized, the second leucocytic phase, but the earlier phases of the cycle were unaffected. Serum glucose increased significantly in the second leucocytic phase.
The stress response in the abundance of circulating leucocytes in the killifish, Fundulus heteroclitus II. The role of catecholamines
Authors: Pickford Grace E. , Srivastava Anil K. , Slicher Anna M. , Pang Peter K. T.
Published: June 2005

Intraperitoneal injections of distilled water at 5 μ1/g, but not at 1 μ1/g, elicit transitory leucopenia at three minutes post‐injection in intact Fundulus heteroclitus. Later phases of the stress sequence (Pickford et al., '71) are not elicited. Intraperitoneal injections of epinephrine (0.025 μg/g in 5 μ1/g H2O) completely simulate the cold‐shock leucocyte sequence. Hypophysectomy abolishes the two hour leucocytic phase, as in the cold‐shock response. Norepinephrine is ineffective at 0.1 μg/g but simulates the epinephrine response at a high dose (1.0 μg/g). Isoprenaline (1.0 or 0.1 μg/g) elicits the leucopenic but not the leucocytic phases.

Pretreatment with phenoxybenzamine (2.5 mg/liter aquarium water) abolishes both three minute and 45–60 minute cold‐shock leucopenia; two hour leucocytosis is unimpaired but the 15 minute response is reversed. Pretreatment with propranolol (1 μg/liter aquarium water) has no effect on the two leucopenic phases; two hour leucocytosis is delayed or, at higher doses, abolished; 15 minute leucocytosis is either unaffected, or reversed.

It is not possible to interpret these results in terms of classical mammalian alpha‐ and beta‐adrenergic mechanisms.
Cytoplasmic control of nuclear behavior during meiotic maturation of frog oocytes
Authors: Masui Yoshio , Markert Clement L.
Published: June 2005

Fully grown oocytes of the frog (Rana pipiens) undergo cytoplasmic and nuclear maturation when treated with progesterone after the follicular envelopes have been removed. The mechanism of this maturation was investigated by injection of cytoplasm from progesterone‐treated oocytes at various stages of maturation into fully grown but immature oocytes. The injected cytoplasm becomes effective in inducing maturation by 12 hours after progesterone administration, reaches a maximum effectiveness around 20 hours, and then declines after the donor oocytes complete maturation. However, even cytoplasm from early embryos retains some capacity to induce oocyte maturation. The frequency with which maturation is induced is proportional to the volume of the injected cytoplasm. Progesterone itself is not directly responsible for the maturation‐producing effect of injected cytoplasm since injected progesterone does not promote maturation. However, externally applied progesterone does induce the completion of the first meiotic division, presumably by releasing a cytoplasmic “maturation promoting factor.” The production of this cytoplasmic factor was not affected by removal of the nucleus.

After completion of the first meiotic division, oocytes cease further development at the metaphase of the second meiotic division, where they remain until fertilized or activated to develop. Cytoplasm from such secondary oocytes when injected into one of the blastomeres at the two‐cell stage of development suppresses mitosis as well as cleavage. Mitosis is usually arrested at metaphase. No such inhibition was brought about by injection of cytoplasm from cleaving blastomeres. Thus, the arrest of mitosis and cleavage can be attributed to a specific “cytostatic factor” in the cytoplasm of the secondary oocyte. Activation of donor secondary oocytes by insemination or pricking with a glass needle soon destroys the cytostatic factor. Likewise, addition of cortical cytoplasm to endoplasm from the secondary oocyte rapidly destroys the cytostatic capacity. This result implies that cortical material is involved in the process of removing the cytostatic factor at the time of normal activation or fertilization. Enucleation of oocytes demonstrated that production and removal of the cytostatic factor is independent of the nucleus.
Further observations on tail regeneration in Anolis carolinensis (Iguanidae, lacertilia)
Authors: Maderson P. F. A. , Salthe S. N.
Published: June 2005

The rate and extent of tail replacement was followed during two consecutive post‐amputation periods in adult and juvenile male Anolis carolinensis, maintained under three different experimental regimes. Great variation, as indicated by the coefficient of variability, was observed in all experimental groups. These data confirm previous studies and demonstrate that variability is not associated with population or individual genetic make‐up, age, or environment. The general and specific implications of variability in tail regenerative capacity are discussed.
Caste determination in honey bees. I. The significance of moisture in larval food
Authors: Dietz Alfred , Haydak Mykola H.
Published: June 2005

Honey bee larval growth is markedly influenced by the moisture content of the larval food. A gradual increase in the moisture content of the larval food (royal jelly) resulted in a large percentage of queens. An apparent linear relationship of royal jelly moisture content to time of larval development was used in the feeding trials. Since the larval food tested was one and one‐half or two and one‐half years old, it is probable that a highly labile queen determining substance, or substances, if present in larval food, is not responsible for caste determination. Results of this study suggest that nurse bees may initiate the mechanism of queen differentiation simply by increasing the moisture content of the food of growing larvae and, thereby, controlling the intake of essential nutrients. The secretions of the mandibular glands are presumably responsible for the change in consistency of the food of either queen or worker larvae.
Superprecipitation of actomyosin extracted from crayfish skeletal muscle: The effect of heavy metal cations, EDTA and drugs
Authors: Huddart Henry
Published: June 2005

Actomyosin from crayfish skeletal muscle will superprecipitate in the presence of ATP without added Ca++ or Mg++. EDTA totally inhibits Ca++‐induced superprecipitation of actomyosin, but in some cases Mg++ will reverse this effect. It is suggested that Mg++ and not Ca++ is a prerequisite for superprecipitation with ATP alone. EDTA only partly inhibits heavy metal‐induced actomyosin superprecipitation.

Heavy metal cations induce far greater actomyosin superprecipitation than Ca++, and they can even enhance previously formed Ca++‐induced precipitates. It is suggested that heavy metal cations may be more strongly bound to crayfish actomyosin than Ca++, and that they may displace Ca++ from existing actomyosin binding sites. Heavy metal potentiation of muscular contraction may thus involve direct action at myofibril binding sites.

Caffeine and quinine are without effect either on the rate or extent of development of actomyosin precipitates in the presence of ATP, ATP plus Ca++, and ATP plus Zn++. These observations rule out any direct effect of these drugs at the myofibril level during drug‐induced potentiation of muscular contraction.
Endocrinology of amphibian ultimobranchial glands
Authors: Robertson Douglas R.
Published: June 2005

The historical observations of the amphibian ultimobranchial gland are reviewed and interpreted in light of recent evidence which demonstrates the relationship of this organ to the hypocalcemic hormone, calcitonin. Its discrete anatomical location and separation from other endocrine tissues has made extirpation feasible and has revealed the importance of this gland in preventing excessive mobilization of calcium from the paravertebral lime sacs in larval and adult forms. These glands also appear to prevent hypercalcemia during periods of high dietary calcium ingestion. In view of its phylogenetic development and relationship to the parathyroids, two major functions of the ultimobranchial glands can be ascribed. First, amphibian calcitonin sequesters calcium in storage depots, in pre‐metamorphic and post‐metamorphic forms to insure maximal ossification of adult bone. Such protection in an aquatic environment deficient in calcium ions would be of extreme importance. Second, amphibian calcitonin prevents the rapid influx of calcium across gut epithelium during feeding to protect against acute periods of hypercalcemia. The diversity of aquatic and terrestrial amphibian types provides a broad spectrum of forms in which to develop model systems for calcium homeostasis.
The structure and function of the lateral line system in larval Xenopus laevis
Authors: Shelton Peter M. J.
Published: June 2005

Each lateral line organ in Xenopus laevis larvae contains about two dozen receptor cells. These are divided into two classes on the basis of the orientation of the cilia in their sensory‐hair‐bundles. The fine structure of the lateral line organs is similar to the adult pattern and that found in other species of amphibia and fish. However apparently degenerating receptor cells are found in normal tadpoles. Two types of nerve ending, considered to be afferent and efferent, contact the bases of receptor cells. Each organ has two physiologically distinct sensory units which are sensitive to mechanical deflection of the organ's sensory hairs. The organs have a plane of maximum sensitivity to stimulation and respond in a phasic‐tonic manner to vibrational stimuli and water currents. Efferent activity in unmyelinated fibres in the larval lateral line nerves is associated with tadpole movement; heavy efferent activity occurs throughout locomotory tail flexions and periodic bursting activity coincides with branchial respiratory movement. These patterns of activity are modified at metamorphosis when the mode of locomotion and breathing change. The larvae can detect differential stimulation of the system by small jets of water and turn to face the source although the lateral line system is not essential for the orientation of tadpoles in a flowing water mass. Adult toads subjected to a similar stimulus exhibit feeding behaviour.
Origin of calcified tissue in regenerating spines of the sea urchin, Strongylocentrotus purpuratus (Stimpson): A quantitative radioautographic study with tritiated thymidine
Authors: Heatfield Barry M.
Published: June 2005

Cellular proliferation in the calcified dermis during regeneration of fractured spines of the sea urchin, Strongylocentrotus purpuratus (Stimpson), was studied quantitatively in radioautograms of tissues labeled with tritiated thymidine in vivo or in vitro to establish the origin of regenerated calcified tissue. Non‐fractured, whole spines were included for comparison. In short term experiments, incorporation of tritiated thymidine occurred throughout the length of regenerating and non‐fractured spines, with a peak in the number and proportion of labeled cells in the shaft occurring near the milled ring, declining to low levels in the the base and tip. A localized apical growth zone was absent in these spines. In pulse‐labeling experiments, there was a marked distal shift in the distribution of labeled cells during regeneration of fractured spines and in whole spines presumably due to migration. Significantly, labeled cells appeared in increasing numbers throughout the regenerate during growth. Few migratory coelomocytes within the calcified dermis were observed to incorporate detectable quantities of tritiated thymidine. The results of this study are consistent with the hypothesis that regenerated connective tissue of the calcified dermis originates by distal migration of cells, primarily from proximal regions of relatively high mitotic activity within the shaft near the level of the milled ring.
A study of the intrinsic factors which control the initiation of asexual reproduction in the tunicate Amaroucium constellatum
Authors: Freeman G.
Published: June 2005

The first part of this study describes the normal pattern in terms of which budding takes place as a colony composed of a large number of zooids is generated from an oozooid. During the time interval which elapses from the formation of a zooid until it reproduces asexually by strobilating, size increase is logarithmic. The length of time which elapses until a given zooid strobilates is correlated with the size of its thoracic region and its prior history.

The role of zooid size increase in bringing about the conditions which lead to the initiation of strobilization was examined by irradiating small zooids which had been growing for a short period of time with different dosages of gamma radiation. The dosages of irradiation used slowed down the rate of growth or stopped growth; however, these animals strobilated at the same time that the unirradiated controls strobilated, demonstrating that the initiation of strobilization is not tied to the growth cycle of the zooid.

The possible role that organ systems situated in different regions of these animals might have in initiating strobilization was studied by removing parts of zooids at different times during their growth cycle. These experiments demonstrated that a population of cells in the dorsal half of the thorax normally function to inhibit strobilization. Studies in which parts of animals were made to regenerate thereby creating a condition in which different regions of the same zooid were of two different chronological ages demonstrated that the activities of cells in the thoracic region of these animals also regulate the time interval which will elapse until strobilization. These experiments were done by compounding “Siamese twin” zooids with two thoracic regions and showing that the youngest thoracic region controls the timing of strobilization.

This work is discussed in relation to experimental work which has been done on other ascidian species and to the suggestions that have been made for the purpose of explaining how asexual reproduction is regulated in tunicates.
An evaluation of myotypic respecification in axolotls
Authors: Grimm Leslie M.
Published: June 2005

Nerves supplying forearm flexor muscles were exchanged (crossed) with those supplying forearm extensors. After complete recovery, the movements of the forelimb were the same as those of normal limbs. Dissections showed that the nerves remained crossed, and electrical stimulation of the crossed nerves close to the muscles they supplied showed that the nerves were functionally connected to the foreign muscles. On the basis of these criteria, it appeared that axolotl nerves could respecify themselves.

Stimulation of the crossed nerves further from the muscles they innervated, however, yielded contractions in the muscles that the nerves had originally supplied. Therefore, one of the two crossed nerves was severed at the shoulder and allowed to degenerate so that any movements elicited by subsequent electrical stimulation could be ascribed unambiguously to the remaining, non‐degenerated nerve. Electrical stimulation now showed clearly that the nerve which had originally innervated forearm flexors continued to produce flexion responses after it was crossed, and the nerve which had formerly innervated extensors continued to produce extension. Thus the fibers had somehow recrossed to reinnervate their original muscles.

It therefore appears from the present investigation that axolotl nerves do not respecify themselves. Instead, a few fibers find their way back to their original muscles, and this is enough to produce normal movement.
Localization of primordia within the dorsal mesothoracic disc of Drosophila
Authors: Murphy Collin
Published: June 2005

Distal regions or “marginal ridge” areas of the dorsal mesothoracic disc of mature Drosophila larvae, not previously included in fate maps, were marked by microcauterization in situ. Structures assumed to have primordia in the distal half of the disc (mesopleura, pteropleura, arch, ventral scutellum, ventral wing hinge and wing proper) are either missing, deficient, or damaged among adults surviving the operation. In contrast, neither the dorsal wing hinge nor mesonotum, which are known to have primordia in the proximal half of the disc, are similarly affected.

The pattern of distribution of deformities in surviving adults indicates that (a) the anlage of the mesopleural sclerite is located in the distal edge portion or “marginal ridge” of the disc, (b) anlagen of pteropleura, arch and ventral scutellum may also be tentatively assigned to this location, (c) there are significantly high associations between deformities affecting the pteropleura and the ventral wing hinge, and (d) the anlage of the deep phragma of the postnotum may be more closely related to the first abdominal tergite than to the dorsal mesothoracic disc.

The distal localization of pleural, arch, and ventral scutellar anlagen corresponds to the physical separation from mesonotal anlagen predicted from an earlier statistical analysis of genetic mosaics; i.e., these presumptive sclerites are separated from the mesonotal anlagen by the anlagen of the wing in the “pouch” area of the disc.

The new information has been incorporated into a hypothetical fate map of the disc, which includes anlagen plans suggested by previous authors.
Growth and differentiation in hydra. II. The effect of temperature on budding in Hydra littoralis
Authors: Park Helen D. , Ortmeyer Anne B.
Published: June 2005

Hydra littoralis acclimates to 5°, 10°, 15° and 21° C. After acclimation, animals actively initiate and drop buds. The relationship between budding rate of acclimated hydras and temperature in the 5° to 21° range is direct but non‐linear. The temperature coefficient for bud development is much greater than for bud initiation at low temperature. The size (dry weight) of individual buds and adults increases with decreasing temperature; animals acclimated to 5° are more than twice as large as animals acclimated to 21°. Hydras subjected to an abrupt temperature rise show a temporary overshoot in budding rate as compared to controls already acclimated to the higher temperature. The budding rate of hydras subjected to an abrupt temperature drop is temporarily depressed severely as compared to the rate of controls already acclimated to the lower temperature.
The mechanism of puparium formation in flies
Authors: Zdarek Jan , Fraenkel G.
Published: June 2005

The mechanism of puparium formation in the fleshfly Sarcophaga bullata Parker was studied. Several distinct morphological events take place during the hour prior to the completion of the white puparium. 1. The anterior three larval segments are irreversibly retracted. 2. The body contracts by muscular action to about two‐thirds of its original length. 3. Simultaneously a longitudinal shrinkage occurs in the cuticle, giving it a smooth surface. 4. Finally the cuticle becomes stabilized in the sense that it can no longer be stretched, and no longer collapses upon release of internal pressure by bleeding. 5. Tanning starts almost as soon as the smooth barrel shape of the puparium is completed. The following observations demonstrate the largely independent nature of these processes: 1. Paralyzing the musculature, by ligation, tetrodotoxin, or bee venom, leads to tanned puparia in the shape of the larva. 2. Disabling the shrinkage system (e.g., by ryanodine or eserine) leads to puparia with a deeply folded surface. 3. Injecting smaller doses of tetrodotoxin or bee venom leads to elongated puparia with a shrunken (smooth) surface. 4. Injecting a certain ecdysone analogue leads to a puparium which is normal except for the failure of the anterior end to retract. 5. Release of internal pressure by bleeding leads to puparia which are supercontracted and folded. 6. Injection of a tanning inhibitor (α‐MDH) leads to a white puparium of normal shape which fails to tan. The transformation of the larval cuticle into the tanned puparium is accompanied by a spectacular water loss in the cuticle which is particularly rapid during the brief period between completion of the white puparium and start of tanning. This water loss is almost certainly correlated with the above mentioned stabilization of the puparium.
Fine structure of muscles controlling the strike of the mantis shrimp, Hemisquilla
Authors: McNeill Patricia , Burrows Malcolm , Hoyle Graham
Published: June 2005

The ultrastructure of some muscle fibers of the five physiologically different motor units operating the strike of the mantis shrimp were studied by electron microscopy. The distal portion of the lateral flexor was found to have the shortest sarcomere length (4.3 μm), the densest, most complex sarcoplasmic reticulum, the largest number of dyads per unit cross‐sectional area and the smallest filament cluster (“fibril”) size. The proximal portion of the same muscle differs from it mainly in having a less well‐developed reticulum and a large filament cluster size.

The remaining muscles have longer sarcomere lengths: 5.3 μm for the medial flexor, 7.8 μm for the lateral extensor, and 6.0–10.2 μm for the medial extensor, as well as a weakly‐developed sarcoplasmic reticulum and fewer dyads per unit cross‐sectional area.

These data were compared with contraction and relaxation times of the units and showed that the rates of both contraction and relaxation are lower the greater the A band or true relaxed sarcomere length. For fibers of equal A band length, faster rates were found to be associated with a more extensive sarcoplasmic reticulum, giving reduced filament cluster size, as well as with a larger number of dyads.
The development of avian red cell shape
Authors: Barrett Lucy A. , Scheinberg S. L.
Published: June 2005

Immature erythrocytes of pigeons and chickens change from a spherical to a flat form following the final mitotic division during development. In vitro studies provide evidence that initial changes in shape are influenced by conditions that affect availability of oxygen. Transformation to a flat form occurred most rapidly at 37°C, a temperature that results in deoxygenation of hemoglobin in erythrocytes of the bone marrow. The maximum rate of transformation occurred at pH 6.5, a pH which favors deoxygenated hemoglobin. Oxygen inhibited the transformation in shape at 37 °C and resulted in a reversion of shape, from flat to spherical. Flattening and deoxygenation of hemoglobin are highly correlated. Precursor erythrocytes in plasma clot culture were observed microscopically. The cell stages identified in sequence were: (1) the “n‐2” dark cells, apparently lacking hemoglobin. These cells divided to form “n‐1” cells which synthesized hemoglobin as they matured. The “n‐1” cells divided, forming spherical daughter “n” cells which flattened within 60 minutes after mitosis.
Comparative studies on creatine kinase isozymes from skeletal‐muscle and stomach of trout
Authors: Perriard Jean‐Claude , Scholl Adolf , Eppenberger Hans M.
Published: June 2005

Tissue‐specific heterogeneity of creatine kinase (CPK) isozymes is particularly pronounced in various trout species. Several of the isozymes expressed in stomach and in skeletal muscle appeared to be identical as judged by their electrophoretic behavior, but reversible dissociation studies on single, electrophoretically pure, CPK‐isozymes isolated from these two tissues revealed significant differences between isozymes of similar electrophoretic mobility. Moreover, in contrast to trout skeletal muscle, the native and reassociated stomach CPK isozyme patterns could be accounted for by the association of the polypeptide products of two gene loci into homodimers and heterodimers, providing further evidence that the isozymes of stomach and skeletal muscle are non‐identical and thus presumably the products of distinct genes.
The developmental biology of annual fishes. II. Naturally occurring dispersion and reaggregation of blastomeres during the development of annual fish eggs
Authors: Wourms John P.
Published: June 2005

Complete dispersion and subsequent reaggregation of pre‐embryonic blastomeres, features characteristic of annual fish development, are analyzed in Austrofundulus myersi Dahl. Cleavage produces a typical teleost blastoderm. During the mid‐blastula stages, blastomeres segregate into two populations; deep blastomeres which disperse, and outer blastomeres which form the enveloping cell layer. When epiboly of the enveloping cell layer and periblast commences, the deep blastomeres come together as a consolidated mass and then migrate outward as amoeboid cells. When epiboly has concluded, the deep blastomeres are completely dispersed. After a few days, these cells come together to form a definitive aggregate within which embryogenesis occurs. The reaggregation process was quantified in vivo by determining “coefficients of dispersion.” Amoeboid blastomeres were found to be: uniformly distributed when epiboly is completed (day 2); randomly distributed on day 3; and aggregated on day 4.

The origin of the annual fish developmental pattern has involved the spatial and temporal dissociation of the processes of epiboly and embryogenesis. This has been accomplished by the interposition of the dispersion‐reaggregation phases. They may represent an exaggeration of the phases of incipient dispersion and localized aggregation which occur in most teleosts. The dispersion‐reaggregation process is considered to be a control mechanism operating on the principle of a requirement for “critical cell mass” as a necessary prelude to the primary events of embryogenesis. The survival value of the dispersed phase is discussed.

Comparative studies of 43 closely related species have shown that the dispersion‐reaggregation pattern is present only in those cyprinodont fishes with annual life cycles. This group includes members of the following genera: Aphyosemion (annual species only); Austrofundulus; Cynolebias (including Cynopoecilus); Nothobranchius; Pterolebias; Rachovia; and Roloffia. Non‐annual cyprinodonts develop as do other fishes. Some Aphyosemion species have transitional developmental patterns.
Chloride and the generation of amniotic fluid in the early embryo
Authors: Faber J. Job , Gault Charles F. , Green Thomas J. , Long Lawrence R. , Thornburg Kent L.
Published: June 2005

The concentrations of chloride in the amniotic fluid of the four and one‐half day chick embryo exceed those in the blood plasma and in the sero‐amniotic fluid. The electrical potential of the amniotic fluid is negative compared to the electrical potentials of the plasma and sero‐amniotic fluid. Nevertheless, the amniotic fluid volume continues to grow without a sensible diminution of its chloride concentration. There is evidence, therefore, of non diffusional influx of chloride into the amniotic fluid.

Radioactive chloride injected into the blood stream of the embryo also indicates
that chloride is transferred into the amniotic fluid partly by an active process.
Similar experiments with sodium ion fail to unequivocally demonstrate the
existence of a sodium pump.

From these measurements the rate of transfer of chloride by a chloride pump
and the rate of efflux of chloride under the influence of the electrochemical
gradient were calculated. The calculated net influx of chloride agrees with
the net influx calculated from the observed growth rate of the amniotic fluid,
and the same is true for sodium. It is postulated that a metabolically driven
transfer of chloride into the amniotic cavity is an early step in the generation
of the amniotic fluid.
The function of the middle ear in lizards: Divergent types
Authors: Wever Ernest Glen
Published: June 2005

The anatomy of the middle ear and auditory sensitivity in terms of the cochlear potentials have been studied in 12 lizard species whose conductive mechanisms show various forms of divergence from normal. In addition, results are given for two normal species for purposes of comparison.

Three forms of defect are found that impair the reception of sounds and reduce the effectiveness of their action on the sensory cells of the cochlea. These are the absence of the tympanic membrane, the interposition of a muscle mass barring direct access of the ear to the exterior, and the absence or encumbrance of the round window.

Certain structural developments, found in several of these species, seem to be secondary in nature, and compensate in some degree for the primary changes. Therefore the sensitivity of these ears, though below average for lizards in general, is not as seriously handicapped as it might otherwise have been. These developments include: (1) an extension of the pars inferior of the extra‐columella to make effective contact with skin and muscle layers, (2) the strategic location of air spaces to increase the mobility of these tissue layers, and (3) the use of reëntrant fluid pathways to replace the round window in the mobilization of cochlear fluids.

Despite the changes in the middle ear mechanism in these lizards, there is evidence that their cochlear structures remain fully functional, and that the ear as a whole, although handicapped, continues as a serviceable instrument in the perception of sounds.
Glutamine synthetase in the avian diencephalon
Authors: Piddington Ronald
Published: June 2005

Glutamine synthetase (GS) activities are high in the nucleus rotundus of the avian diencephalon in late embryos and hatched chicks. The nucleus rotundus is known to be one component of a visual pathway in birds involving also the neural retina, the optic tectum and the cerebral ectostriatum. Since previous studies have shown that the retina, tectum and ectostriatum have high GS activities as well, the enzyme is considered to be clearly associated in some measure, although not exclusively, with processes subserving vision. Some of the possible normal functions for GS at specific neural sites are discussed.

Hydrocortisone promotes GS levels in vitro in the embryonic diencephalon, just as GS activities are increased with this steroid in cultures of embryonic retina, tectum and cerebrum. The effects of steroid on GS in the diencephalon appear to be general and not restricted to the nucleus rotundus or the visual pathway.
Estrogen and brood pouch formation in the marsupial frog, Gastrotheca riobambae
Authors: Jones Richard E. , Gerrard Althea M. , Roth Jan J.
Published: June 2005

Immature female Gastrotheca riobambae were treated with either 1 μg or 10 μg estradiol daily for 24 days. Both estrogen dosages elicited formation of the brood pouch, a dorsal integumentary structure which contains eggs or larvae during the breeding season. A decrease or loss of epidermal keratin, dermal chromatophore units and dermal poison glands occurred during both normal and estrogen‐induced pouch formation. Also, pouch skin exhibited dermal hypervascularity and connective tissue hyperplasia. The epidermis lining the pouch lumen possessed crypts. The importance of these changes is discussed in relation to pouch function.
Squid nidamental gland extract: Isolation of a factor inhibiting ciliary activity
Authors: Atkinson Burr G.
Published: June 2005

A component of the egg string jelly of Loligo pealei inhibits ciliary activity in ciliated cells, thereby immobilizing a variety of swimming ciliated organisms. This report establishes the nidamental gland as a source of both the egg jelly sheath and the ciliary immobilizing factor. Methods are described for preparing crude and purified fractions of the immobilizing factor from the nidamental gland.
Response of tail fin of Proteus anguinus to thyroxine
Authors: Švob M. , Musafija A. , Frank F. , Durovic N. , Švob T. , Čuˇković S. , Hlaˇa D.
Published: June 2005

Discs prepared from dorsal tail fins of Proteus anguinus Laur. were immersed in a solution of thyroxine in Hank's medium. The tail tissues did not regress under the influence of thyroxine although the concentration of hormone was 100 ppb. Thyroid hormones synthesis was investigated in Proteus through the use of I125 injected intraperitoneally as sodium iodine. Chromatographically separated fractions of Proteus tissues, compared with known standards, indicate synthesis of thyroxine, triiodothyronine, and their precursors mono‐ and diiodotyrosone. It is concluded that the permanent neoteny of Proteus is due to loss of tissue sensitivity to thyroxine.
Glucosamine HCl, hydroxyproline and developmental homeostasis in Drosophila melanogaster
Authors: Rapport Ellen W.
Published: June 2005

A new cryptocephal (crc) phenocopy agent is described for Drosophila melanogaster. The morphogenetic action of this agent, hydroxyproline (OHP) is compared to that of another crc phenocopy agent, glucosamine HCI (GA). The sensitive period for OHP lasts somewhat longer than that of GA. A comparison of the effect of GA and OHP on two strains of Drosophila showed that a relatively high strain sensitivity to one agent could be accompanied by a low response to the other. It is concluded that the developmental buffering of the agents is controlled by different genes.
Non‐budding strains of hydra: Isolation from sexual crosses and developmental regulation of form
Authors: Moore Linda B. , Campbell Richard D.
Published: June 2005

New strains of hydra were obtained from sexual crosses; 15% of these strains exhibited impaired or no budding. Altered tentacle number, regeneration, size and form almost always accompanied this non‐budding trait. Strains selected for deficient budding activities were also more variable in morphology than are normal hydra.

Two developmental traits were studied in the non‐budding animals; regenerative ability and the formation and control of supernumerary tentacles. The regeneration patterns of non‐budding hydra vary with the size of the piece of regenerating tissue. Column segments greater than 3 mm in length regenerate hydranths at all cut surfaces, whereas pieces less than 1 mm long usually regenerate bases at proximal surfaces, as do normal animals. When polyps grow abnormally long, they form supernumerary tentacles. Formation of these tentacles seems to be normally suppressed by a nearby hydranth. Supernumerary tentacle formation can be suppressed even in long, non‐budding hydra, by implants of hypostomal or subhypostomal tissue.

The non‐budding hydra phenotype appears to result from developmental lesions spread throughout the polyp body. Budding is one of the primary aspects of development which is affected, and a lack of budding leads to increased animal size. This in turn results in many pleiotropic effects including supernumerary tentacle formation and altered regeneration patterns.
The effects of anoxia on isozyme patterns and ultrastructure of cultured human fibroblasts
Authors: Henderson Nanine S.
Published: June 2005

Numerous studies with lower eukaryotes such as yeast and Neurospora have shown that mitochondrial morphology and enzyme levels change markedly in response to changes in oxygen tension. Several studies with mammalian cells in culture have indicated that these cells also respond to low oxygen with changes in the levels of certain enzymes. In this study gel electrophoretic analysis of enzymes and electron microscopic analysis of cell organelle morphology were used to study the effects of anaerobic conditions on cultured human embryo fibroblasts. Lactate dehydrogenase showed a marked shift from LDH‐1 toward LDH‐5 as has been previously described. Isocitrate dehydrogenase, NAD‐malate dehydrogenase, and NADP‐malate dehydrogenase all have been shown to exist as separate supernatant and mitochondrial isozymes. However, none of these enzymes showed extensive changes in isozyme patterns in response to anaerobiosis. Electron microscopic examination of cell cultures revealed striking changes in mitochondrial structure. Aerobically grown cells have well‐developed, elongated mitochondria with numerous well‐defined cristae and an electron‐dense matrix. In cells cultured anaerobically the mitochondria show degenerative changes. They are more rounded, have few and poorly defined cristae, and the matrix is more electronlucent. These studies indicate that, as in lower eukaryotes, the mitochondria of cultured human cells also respond morphologically and biochemically to changes in oxygen tension.
Factors influencing molting in the crayfish Procambarus clarki
Authors: Bittner George D. , Kopanda Richard
Published: June 2005

Molting frequency is increased and intermolt period is decreased by autotomizing the chelipeds and/or walking legs of crayfish (Procambarus clarki) kept under constant environmental conditions. The increase in molting frequency cannot be explained by a loss of body mass since other operations which produced specific tissue damage to nerve or muscle fibers resulted in little or no loss of body mass yet these operations significantly increased molting frequency. Other factors associated with autotomy or nerve and muscle damage such as exoskeletal damage or loss of hemolymph have much less effect on molting frequency and immobilization actually decreases molting frequency. The molting responses to autotomy, muscle or nerve damage, immobilization, and overcrowding appear to be adaptively advantageous.
Analysis of the crowding effect in Rana pipiens tadpoles
Authors: Gromko Mark H. , Mason Francene S. , Smith‐Gill Sandra J.
Published: June 2005

Rana pipiens tadpoles were grown at four densities in each of three series. Retardation due to crowding was seen despite the presence or absence of feces. Statistical analysis shows retardation due to crowding to be a function of effective density, possibly mediated by behavioral or social factors, more importantly than by diffusible products of the tadpoles. Although previous work has assumed the growth‐inhibiting factors of “conditioned water” (water occupied by a population of tadpoles) to be identical with the cause of the crowding effect, we have found that the crowding effect operates relatively independently of these growth‐inhibiting factors.