bluuebunny/crossref_metadata_2025 huggingface dataset:
Resting tension, “negative” contraction and “break” contraction in specialised crustacean muscle fibers
Authors: Hoyle Graham
Published: June 2005

A few tinted fibers (color grey‐brown‐pink) occur in certain crustacean muscles of diverse species. Many of these were found to have relatively low resting membrane potentials and to be developing tension continually in the normal resting state, i.e., in the absence of extrinsic stimulation. This tension is rapidly relaxed if polarizing current is passed across the membrane. The relaxation in response to a brief polarizing pulse follows a time‐course resembling that of a twitch, but is, of course, the inverse. Fibers which were similar in color but which did not show resting tension often gave a strong contraction when a polarizing current was turned off. These “break contractions” had a slower time‐course than normal twitches. The relaxation rate was accelerated by polarizing pulses. Possible explanations of the phenomena are offered in terms of modern views on excitation‐contraction coupling.
Maturation of ovarian frog eggs without ovulation
Authors: Subtelny Stephen , Smith L. Dennis , Ecker R. E.
Published: June 2005

The dissociation of the processes of ovulation and maturation of full grown Rana pipiens ovarian oocytes has been demonstrated by the in vitro exposure of ovarian fragments to amphibian pituitaries or to the mammalian steroids, progesterone, and deoxycorticosterone acetate. With optimal concentrations of these substances, and under controlled conditions, all of the full grown oocytes can be stimulated to undergo germinal vesicle breakdown and maturation to the second meiotic metaphase while still in the ovarian fragment. Such oocytes are physiologically mature as shown by their positive response to an activation stimulus. That ovulation and maturation are not interdependent processes is further demonstrated by the liberation from the ovary of occasional oocytes which do not possess any follicular investments, but do possess an intact germinal vesicle. Such oocytes do not respond to an activation stimulus. The responses of ovaries to the action of pituitary extracts and steroid suspensions indicate that steroids are more efficient inducers of oocyte maturation while pituitary factors are better inducers of ovulation. These data, discussed with other findings, suggest the possible roles played by pituitary gonadotropins and steroid hormones in ovulation and physiological maturation of the anuran egg.
Degeneration in the nucleus of origin of the preganglionic fibers to the chick ciliary ganglion following early removal of the optic vesicle
Authors: Cowan W. M. , Wenger Eleanor
Published: June 2005

Extirpation of the optic vesicle in chick embryos towards the end of the second day of incubation leads to a progressive hypoplasia in the ciliary ganglion and to a secondary, or retrograde transneuronal degeneration, in the accessory oculomotor nucleus from which the preganglionic fibers to the ciliary ganglion are derived. The primary changes in the ciliary ganglion are first observed at about the eighth day of incubation and the resulting cell loss proceeds over the next three or four days to include almost all of the ganglion cells. At the tenth day of incubation (when the volume of the ciliary ganglion is reduced by just over 70%) early signs of cell degeneration can be recognized in both the medial and lateral divisions of the accessory oculomotor nucleus in the form of cell shrinkage, loss of Nissl material and some cell loss. By the fourteenth day of incubation (Stage 40) the nucleus is virtually depleted of neurons with only an occasional shrunken cell persisting in the medial accessory nucleus. After even longer survival periods complete cell loss may occur in the nucleus, but in many of the experiments a small number of cells survive: these are probably related to ciliary ganglion cells which have established aberrant peripheral connections, or in those cases in which the lesion of the optic vesicle was incomplete, to the cells which innervate the surviving ocular tissue.
An in vitro quantitative analysis of the response of tadpole tissue to thyroxine
Authors: Derby A.
Published: June 2005

Dorsal tail fins of tadpoles, (Rana pipiens) at various stages of metamorphosis, were cut into pieces or discs and then cultured either in Hanks balanced salt solution or Hanks containing L‐thyroxine (T4). Six concentrations of T4 were tested: 3, 9, 27, 81, 250, and 750 parts per billion (ppb). In addition, early prometamorphic discs were cultured in medium containing 3 ppb of T4 for different periods of time: 1, 3, 5, and 7 days and then placed into control medium for the remainder of the experimental period. Controls for this experiment were maintained continuously in either 3 ppb of T4 or in control medium. To test the specificity of response to T4 early prometamorphic discs were cultured in medium containing KI, DL‐thyronine or DL‐diiodothyronine. Discs respond to treatment with thyroxine by shrinkage. The degree of shrinkage was determined quantitatively by measurement of area.

The results show that a direct quantitative relationship exists between concentration of thyroxine and resorption. Resorption is dependent upon the continuous presence of T4. It was also demonstrated that tail discs change in their sensitivity to thyroxine at progressive stages of metamorphosis. It is proposed that the increased sensitivity of tail tissues to T4 during metamorphosis results from their previous exposure to a low but rising level of thyroid hormone that increases sharply in the donor tissues one to two days before the emergence of the forelegs. Finally, it was demonstrated that these results represent the specific action of thyroid hormone.
Isozyme patterns of salmonid fishes: Evidence for multiple cistrons for lactate dehydrogenase polypeptides
Authors: Massaro Edward J. , Markert Clement L.
Published: June 2005

Starch gel electrophoretic and molecular hybridization studies indicate that the genomes of rainbow (Salmo gairdneri) and brown (S. trutta) trouts may code for eight electrophoretically distinct types of lactate dehydrogenase (LDH) subunits. The interactions of these subunits in vivo produce eighteen isozymes. These isozymes are naturally arranged into four groups, designated a, b, d, and e, on the basis of physico‐chemical properties. Groups a, b, and d each consist of five isozymes while group e is composed of three isozymes. An obvious tissue specific distribution of the isozyme groups is observed.

Like the rainbow and brown trouts, other salmonids such as the Atlantic salmon (S. salar), sockeye (Onchorynchus nerka), and bloater (Coregonus hoyi) possess numerous LDH isozymes. Also, we and others have detected an unusual multiplicity of molecular forms of other proteins in Salmonidae. Representatives of the Osmeridae, Clupeidae, Engraulidae, Argentidae, and Esocidae, which are closely related families, possess no more than five LDH isozymes. Moreover, salmonids contain twice as much DNA per cell and have karyotypes which show about twice as many chromosome arms as certain closely related forms. From these observations, it has been concluded that salmonids are tetraploids. In our view, it seems most likely that they arose through allotetraploidization of a primitive hybrid ancestor.
Ontogeny of vocalization in duck and chick embryos
Authors: Gottlieb Gilbert , Vandenbergh John G.
Published: June 2005

Vocalizations can be elicited from some duck embryos five and one‐half days before hatching and from some chick embryos three days before hatching. All duck embryos can vocalize three and one‐quarter days before hatching (at 88% of incubation period) and all chick embryos are able to vocalize one day before hatching (95% of the incubation perod). Thus, the vocal apparatus of the duck embryo achieves a functional stage of development sooner that that of the chick embryo, indicating that the syringeal structures of the duck embryo begin development sooner or develop at a faster rate than those of the chick embryo. According to audiospectrographic analysis, both species are capable of uttering at least three different kinds of vocalizations prior to hatching, and these three calls are similar to the ones emitted most frequently after hatching (“distress,” “contentment,” and brooding‐lke calls). These vocalizations can be objectively defined by reference to the contexts in which they are emitted and the physical structure of the call notes. It was verified in situ that the constriction and vibration of the tympaniform membranes during exhalation is the basic or primary source of sound production in birds. The clavicular sac is not essential to sound production, and the syrinx, trachea, and syringeal muscles are important only for modulating and/or resonating the sounds produced by the tympaniform membranes. Based on this knowledge, a technique was devised to de‐vocalize duck embryos 3 days before hatching. The technique involves immobilizing the tympaniform membranes by applying a nontoxic substance (“Collodion”) to them. Collodion forms a glue‐like sheath over the membranes, and when the tympaniform membranes are thus rigidified, the embryo can not vocalize. Eighty‐five percent of the embryos treated were completely mute after hatching. The long‐term effectiveness of the de‐vocalization procedure is not reliably known. It was possible to keep only one bird for observation beyond the first four days after hatching and she was still mute at five months of age.
The neuromuscular basis of lobster swimmeret beating
Authors: Davis William J.
Published: June 2005

The anatomy and innervation of the swimmeret muscles of the lobster Homarus americanus were studied using histological and intracellular recording techniques. Each swimmeret is controlled by 12 muscles, each of which comprises from one to five anatomically‐distinguishable bundles of muscle fibers. The bundles which make up each muscle are usually merged along part of their lengths. Sometimes, however, bundles which share efferent innervation and which are therefore part of a single functional muscle are separate along their entire lengths. Thus, the concept of a muscle as a discrete anatomical unit is of limited use in the swimmeret system.

The pattern of neuromuscular activity underlying swimmeret beating was determined by recording the rhythmic movements of a swimmeret simultaneously with the electrical activity of its muscles. Each muscle is active for a fixed fraction of every movement cycle, during which it discharges several muscle potentials. The 12 muscles of each swimmeret are recruited in the same temporal sequence during each cycle of swimmeret beating.
Inductive interactions in the development of the mouse metanephros
Authors: Erickson Robert A.
Published: June 2005

Embryonic mouse kidney mesenchymes of various ages were tested for their abilities to initiate and supportureteric bud morphogenesis in vitro.

Nephrogenic cord mesenchyme taken from animals before metanephros initiation (10 days) was combined with ureteric buds. The buds showed no morphogenesis. This was true for presumptive metanephric mesenchyme and for mesenchymes (pronephric and mesonephric) already undergoing nephrogenesis. These results indicate basic physiological differences between pronephric, mesonephric and metanephric regions of the cord. When entire nephric systems were cultured alone no metanephros developed. This, and the fact that presumptive metanephric mesenchyme had no influence on ureteric buds, indicates that metanephros initiation (both bud and mesenchyme) results from some activity originating outside the nephrogenic cord.

When combined with metanephric mesenchyme at various stages of tubulogenesis (loose, condensed, or tubular), ureteric buds branched only in the presence of the loose mesenchyme. Branching occurred in loose mesenchyme taken from 11 to 15 day kidneys. Apparently once a given group of cells begins tubulogenesis they lose their ability to induce ureteric bud morphogenesis.

As tubulogenesis proceeds, the amount of loose mesenchymes per kidney decreases sharply. Ultimate size of the metanephros may be established by depletion of loose mesenchyme resulting in its ureteric bud‐inducing potential falling below some critical level.
Translational competition as a possible basis of modulation in retinal pigment cell cultures
Authors: Whittaker J. R.
Published: June 2005

A theory is suggested that new messenger RNA produced by rapidly growing primary monolayer cultures of chick retinal pigment cells competes for translation with existing tyrosinase messenger RNA and dilutes out tyrosinase synthesis. A correlation between the rapid loss of tyrosinase synthesis and an early increase in the rate of new RNA synthesis is consistent with thsi theory. Protein synthesis increases at a lower rate than RNA synthesis, and rapid DNA synthesis occurs later. When monolayer cultures become crowded, the cells begin synthesizing melanin at a more rapid rate; there is also a decrease in the rates of both RNA and protein synthesis. A persistent low level of melanin synthesis in older cultures suggests that tyrosinase genes may remain continually active and that some tyrosinase synthesis leaks through the competition barrier. Two additional observations support a translational competition theory. If new RNA synthesis in cultured cells is blocked by the inhibitor actinomycin D, then tyrosinase synthesis continues instead of almost disappearing by 12 hours of culture. Secondly, an estimate of tyrosinase messenger RNA stability, using actinomycin D, illustrates that it is more stable than is indicated by the early decrease in tyrosinase synthesis. For this reason some mechanism other than tyrosinase gene inactivation seems to be a necessary cause of the decrease in tyrosinase synthesis observed early in culture. The possibility is discussed that translational competition may occur in other examples of cellular dedifferentiation.
A cytochemical study of lymphocystis tumor cells in vivo
Authors: Pritchard Hayden N. , Malsberger Richard G.
Published: June 2005

Lymphocystis, a virus caused, tumor producing disease of marine and fresh water fish was studied using various cytochemical methods for general proteins, histones, both classes of nucleic acids (DNA and RNA), and polysaccharides including mucopolysaccharides and acid mucopolysaccharides. Special interest is afforded the Feulgen‐positive cytoplasmic inclusions which accompany the virus infection of the cells, and concomitant increases in RNA and protein. Particular attention is given the chemistry and formation of the acid mucopolysaccharide capsule which develops around individual cells following viral infection. Possible significance of the capsule is discussed.
Development of zygotes in cultured mouse oviducts. I. The effect of varying oviductal conditions
Authors: Whittingham D. G.
Published: June 2005

Mouse zygotes developed to the blastocyst stage within the explanted ampullar region of the oviduct maintained on a chemically defined medium. No differences were found in the ability of the explanted ampullae to maintain development of native or transferred ova. Ampullae explanted from either mated or unmated mice, 20–24 hours after the injection of HCG, were equally successful in maintaining development of zygotes. The removal of the cumulus cells did not affect the subsequent development of the zygote within the explanted ampulla. No differeces were found between the development of zygotes with and without the zona pellucida. Only the explanted ampullar region of the oviduct was able to support development. Zygotes degenerated when cultured within the explanted isthmus or anterior portion of the uterine horn.
Development of zygotes in cultured mouse oviducts. II. The influence of the estrous cycle and ovarian hormones upon the development of the zygote
Authors: Whittingham D. G.
Published: June 2005

Ampullae explanted from mice at different stages of the estrous cycle were able to maintain the development of zygotes transferred to them in organ culture. A cyclical variation was observed; the maxium number of zygotes developed into blastocysts within ampullae explanted at metestrus 1, and the least number of zygotes developed within ampullae explanted from mice in diestrus. Such evidence indicates that there are cyclical functional changes in the mouse oviduct during the estrous cycle.

Ampullae explanted from spayed mice previously treated with estradiol were able to maintain zygote development to a significantly greater extent than those removed from untreated spayed controls. Pre‐treatment of spayed mice with progesterone did not increase the number of zygotes developing within the explanted ampulla. Also, progesterone had no effect when given in combination with estradiol.
Statolith differentiation in Aurelia aurita
Authors: Spangenberg Dorothy Breslin
Published: June 2005

The discovery that Aurelia polyps metamorphosing in sulfate‐free ASW failed to synthesize statoliths led to extensive investigations of statolith differentiation in these organisms. Radioautographic studies revealed that the sulfate and at least some of the calcium for statolith synthesis is incorporated into statoliths from the environmental medium early in the metamorphosis of each segment. Dissection procedures indicate that statolith synthesis is an in situ event. Sulfate‐deprivation also causes an inhibition of nematocyst differentiation and abnormal pulsing and swimming in ephyrae.

The presence of sulfated acid mucopolysaccharides and of collagenous material at the site of statolith formation implies that these materials may be involved in calcium concentration in these organisms and that similar mechanisms may be involved in statolith synthesis in Aurelia as in bone and tooth development in higher animals.
The development of neuromuscular junctions in cultures of chick embryo tissues
Authors: Nakai J.
Published: June 2005

Neuromuscular junctions formed in vitro have been obtained previously only in cultures of cross‐sections of embryos. These have represented simply the further development in vitro of the anlage of neuromuscular junctions previously formed in vivo. The present experiments were designed to determine whether such junctions could form de novo in tissue culture and in organ culture from spatially separated spinal cord and skeletal muscle. Cultures of dissociated spinal cord and muscle cells could not be maintained sufficiently long to lead to differentiated neuromuscular junctions. However, when fragments of spinal cord and muscle from chick embryos of varying developmental stages were cultivated for several weeks neuromuscular junctions could be identified by phase contrast microscopy, silver impregnation, and AChE staining. The neuromuscular junctions were similar histologically and histochemically to those developing in vivo.
Oxygen consumption, body temperature, and brown adipose tissue in the postnatal golden hamster (Mesocricetus auratus)
Authors: Rink R. D.
Published: June 2005

Postnatal hamsters were examined for a metabolic response to cold by measuring oxygen consumption at ambient temperatures of 25°, 30°, 33°, and 36°C. In conjunction with this, colonic temperatures were recorded, and the animals were examined for brown adipose tissue development.

During the first ten days of postnatal development hamsters increased their O2 consumption linearly as ambient temperature was raised from 25° to 36°C. Thus, they are initially poikilothermic. Body temperatures were directly dependent on environmental temperature, and no mature brown fat deposits had yet developed.

On days 11 and 12, O2 consumption curves began to vary from a linear relation with ambient temperature, and small inflexions developed at 30° and 33°C. By postnatal days 14 and 15 maximal values were recorded at 25°C. Simultaneously, brown fat deposits developed definitive characteristics and body temperatures came to range only slightly below adult temperatures during exposure at 25°C.

During the latter stage of maturation studied in these experiments, days 17 to 21, the animals achieved homeothermic stability between 25° and 36°C. Only 25°C prompted a metabolic increase, 30° to 36°C became a zone of thermal neutrality, and body temperatures came to equal or exceed adult temperatures. The animals had gained significant weight, thereby increasing thermal insulation, and brown fat deposits had accumulated additional lipid.
Development of polyploidy in silk glands of Melipona quadrifasciata anthidioides Lep. (Hym. apoidea) during the larval stage
Authors: Da Cruz‐Landim Carminda , Mello Maria Luiza Silveira
Published: June 2005

Polyploidy was verified in silk glands of Melipona quadrifasciata anthidioides Lep. Glands in five larval instars and in the beginning of the prepupal stage were studied karyometrically and cytophotometrically: The DNA content increases until the third instar, undergoing two replications in the first instar, one in the second and another in the third instar. After this, the DNA values stabilize but the nuclear volume increases until the fifth instar and decreases in prepupae. The relationship between DNA content and nuclear volumes and probable reasons for discrepancies are discussed.
Epithelial metaplasia induced on extraembryonic membranes. I. Induction of epidermis from chick chorionic epithelium
Authors: Kato Yoshihiro
Published: June 2005

The induction of typical epidermis from the chick chorionic epithelium (CE) was studied with the following methods: (a) Grafting of 15‐day scale dermis (tarsometatarsal dermis) directly onto 9‐day host‐chorioallantoic membrane (CAM). (b) Grafting of a recombinant composed of 9‐day CE and 15‐day scale dermis onto 9‐day host‐CAM. (c) Grafting of a recombinant composed of 9‐day CE and 15‐day scale dermis inside a Millipore filter chamber placed on top of host‐CAM and (d) Organ culture of 9‐day CE in contact with 15‐day scale dermis on a liquid culture medium.

Examination of the explants resulting from the four different explantation methods mentioned above has shown that the CE is highly plastic and is readily transformed into typical scale epidermis. There is no epidermal induction when a non‐dermal tissue (muscle) is placed in contact with 9‐day CE. These observations together with other results obtained in the control series, support the idea that a specific dermal influence is involved in the metaplasia of the CE to epidermis.

Metaplastic changes of the CE leading to epidermal differentiation are described. Evidence is presented indicating that the sole origin of the induced epidermis is from the homogeneous cell population belonging to the inner, basal cells of 9‐day CE. Environmental conditions in which CE metaplasia proceeds influence the degree of normality of the induced epidermis. The limitations and the advantages of each transplantation method and its possible application to a more general problem concerning epithelial metaplasia and tissue interactions in skin development are discussed.
Cattanach's translocation as a tool for studying the action of the shaker‐1 gene in the mouse
Authors: Deol M. S. , Green Margaret C.
Published: June 2005

The effects of the mutant gene shaker‐1 (sh‐1) in the mouse include degeneration of the neural epithelium in the inner ear, which in places is so constructed that degeneration of minute areas, even single cells, can be identified. In Cattanach's translocation the piece of autosome 1 that is translocated onto the X‐chromosome bears the normal allele of sh‐1, and so this gene would be expected to acquire the charateristics of sex‐linked genes in mammals. It was thought that a study of sh‐1/‐; Dp/X animals might illuminate some aspect of the development of the inner ear in normal and sh‐1/sh‐1 animals. Normal and affected regions were found to coexist in the organ of Corti but not in the macula of the saccule. The degree of abnormality of the macula differed from ear to ear but was quite uniform within each ear. This points to a radical difference in early development in the relationship between the otic epithelium and its innervation in the cochlea and the saccule. It also appears highly unlikely that abnormalities of the stria vascularis are responsible for the degeneration of the organ of Corti.
Photoperiodic control of antler cycles in deer. I. Phase shift and frequency changes
Authors: Goss Richard J.
Published: June 2005

When subjected to reversed light cycles, deer antlers are shed and regenerated six months out of phase with respect to the outdoor environment. They respond solely to the lighting conditions, not to temperature changes. Deer exposed to accelerated years grow antlers more frequently than normal, but in no cases do they produce them more often than every three months. When the annual light cycle is prolonged to 24 months, deer tend to grow antlers every other year in accordance with the artificial cycle. In general, deer forced to grow antlers more frequently than normal produce stunted outgrowths owing to the abbreviated years. Those maintained on extra long light cycles, however, do not grow extra large antlers.

Analysis of these data suggests that the onset of antler growth is entrained by increasing day lengths in deer previously sensitized by decreasing days. However, older animals can sometimes express an endogenous yearly antler growth cycle irrespective of certain prevailing artificial lighting conditions.
Re‐establishment of forelimb regeneration in adult hypophysectomized Diemictylus (Triturus) viridescens given frog anterior pituitary extract
Authors: Liversage Richard A. , Scadding Steven R.
Published: June 2005

Adults of Diemictylus (Triturus) viridescens were included in this work which was designed to test to what extent a limb of an hypophysectomized animal can regenerate when given frog anterior pituitary extract. The results are based on 123 animals which comprise six experimental, three experimental control, one sham control and one normal control series.

Consideration was given to the essential relationship between the anterior pituitary gland and forelimb regeneration and whether or not daily injections of adenohypophysis extracts of adult Rana pipiens, frogs (which do not regenerate limbs) could promote normal limb regeneration and also long‐term survival in adult hypophysectomized Diemictylus. In this approach, hypophysectomy was followed by a period of five days (to minimize remaining circulatory levels of hormones) before the right forelimb was amputated. From the time of amputation daily replacement therapy of frog pituitary extract was administered until the day of fixation. In 26 out of 28 cases, from series 2 to 5, normal regeneration ensued. In one series (no. 6), forelimb amputation was performed five days post‐hypophysectomy, however, injections of extracts were delayed for ten days after amputation (15 days post‐hypophysectomy) in order to determine whether or not limb regeneration could be re‐established in an essentially stumping forelimb of a dying animal. Retarded and somewhat abnormal regeneration occurred in ten out of the fifteen cases of series 6; the five non‐regenerating cases displayed precocious dermal wound healing.

These results demonstrate that the normal, advanced, forelimb regeneration, as well as the long‐term survival, of our adult, hypophysectomized Diemictylus was due, directly or indirectly, to the presence of a continuous, hormonal background provided by the adenohypophyseal hormones of frog.
The mesoglea of hydra. II. Possible role in morphogenesis
Authors: Burnett Allison L. , Hausman Robert E.
Published: June 2005

Examination of histological sections and isolated mesogleas in Hydra pseudoligactis reveals that the mesoglea is not a uniform structure but changes in form in different body regions and during asexual reproduction. At the extremities of the body column, the rim of the mouth and aboral pore, the fiber system of the mesoglea is strongly developed and appears to occlude the cementing matrix which usually surrounds the fibers. Cells, on reaching these extremities, pass over the fiber mass and slough off the body column.

The mesoglea of the gastric region is well‐developed but the fibers here are thinner than those in the peduncle. During budding the fiber system breaks down throughout the gastric and budding region while the fiber system in the peduncle persists. It is suggested that cells moving down the gastric column, because their basal processs can no longer attach to the fiber system, cannot readily enter the peduncle where attachment sites are already occupied. These cells will pass out into the budding tissue. It is suggested that the spindle orientation of dividing cells is probably perpendicular to the oral‐aboral axis of the parents in the area of the bud.

The adhesiveness of the two cell layers in various body regions is discussed.
Correlation of structure, speed of contraction, and total tension in fast and slow abdominal muscle fibers of the lobster (Homarus americanus)
Authors: Jahromi S. S. , Atwood H. L.
Published: June 2005

The fibers in the deep and superficial extensor muscles of the lobster abdomen differ in structural and physiological characteristics. The superficial extensor muscle fibers have relatively long (> 6 μ) sarcomeres, in which thin and thick myofilaments overlap for about 3 μ per half‐sarcomere at rest length. The deep extensor muscle fibers have relatively short (< 4 μ) sarcomeres, in which the region of overlap is about 1.5 μ per half‐sarcomere at rest length. The ratio of thin to thick filaments is 6:1 in the superficial muscle fibers and 3:1 in the deep muscle fibers. Contraction and relaxation are much more rapid in the deep muscle fibers. The superficial muscle fibers develop substantially more tension than the deep muscle fibers in high K+, in caffeine, in high K+ plus caffeine, and during prolonged spikes in solutions containing tetraethylammonium chloride. The results are consistent with the predictions of the sliding filament hypothesis of muscle contraction.
The effect of photoperiod acclimation on the thermoregulation of the lizard, Sceloporus undulatus
Authors: Ballinger Royce E. , Hawker Jon , Sexton Owen J.
Published: June 2005

Preferred temperatures of Sceloporus undulatus, which were acclimated to 20°C under 12 hour and 6 hour photoperiods, were determined in a thigmothermal gradient. The longer photoperiod (12 hours light) increased the preferred temperature in lizards collected in May while the shorter photoperiod (6 hours light) decreased the preferred temperature in lizards collected in July. Response in the preferred temperature to photoperiod is suggested to be a physiological adaptation which facilitates the use of the mechanism of acclimation of the thermal tolerance to seasonal changes in environmental temperatures. Photoperiod differences did not alter the criitcal maximum or lethal maximum temperatures.
Effect of several hormones on the tolerance to glucose in the non diabetic stage of KK mice
Authors: Penhos J. C. , Wu C. H. , Camerini‐Davalos R. A.
Published: June 2005

The effect of several hormones on the oral glucose tolerance test was studied in genetically diabetic KK mice at the stage of “prediabetes” (less than two months of age), and compared with Swiss albino mice. No significant difference in the oral glucose tolerance test, or in the blood glucose fall after insulin, was found between the two strains at that stage. The KK mice maintained higher blood glucose values up to three hours after glucagon injection and after pretreatment with growth hormone and triamcinolone. The response to epinephrine in the KK strain was delayed, when compared with the Swiss albino control mice.

The exact mechanism by which the hormones studied produced these changes in the tolerance to glucose and their site of action remains unknown, but the data seems to suggest the presence of a congenital condition in the KK mice, by which the response to exogenously administered hormones is in some way modified.
An ultrastructural and cytological study of preimplantation development of the mouse
Authors: Calarco Patricia G. , Brown Edward H.
Published: June 2005

Each stage of preimplantation development in the mouse from the fertilized egg to the blastocyst stage (including the unfertilized egg) was studied cytologically and ultrastructurally. Observations were made on the appearance and elaboration of several cellular organelles, inclusions and cell surface specilizations. The fertilized egg exhibits many intranuclear annulate lamellae, an increase in cytoplasmic vesicle number when compared to the unfertilized egg, and small amounts of crystalloids; mitochondria are vacuolated and small. The 2‐cell stage is very similar to the fertilized egg but shows an increase in the number of cytoplasmic vesicles. The 4‐cell stage is characterized by many changes: functional nucleoli appear, vacuolated mitochondria enlarge, cytoplasmic vesicles continue to increase in number, rough endoplasmic reticulum appears (as mitochondria‐associated sacs), and some ribosomes are localized near the plasma membrane. At the 8‐cell stage, large numbers of free ribosomes are observed in the cytoplasm, but clusters (polysomes) predominate at the 16‐cell stage (morula). Morulae develop junctional complexes and exhibit differences in cytoplasmic basophilia between cells, which may be a prelude to differentiation. At the blastocyst stage, nucleoli change to an elongate form and differences in cytoplasmic background density can be observed ultrastructurally. Observations suggest that the contents of the blastocoel may be derived from the cytoplasmic vesicles, which increase in number and size subsequent to fertilization and discharge their contents into the intercellular spaces; the blastocoel arises as these fluid‐filled spaces become confluent and enlarge.
Cyclic fluctuations in sexual responsiveness in the male rat
Authors: Lisk Robert D.
Published: June 2005

Seventy‐five per cent of a population of active copulators among Sprague‐Dawley male rats showed cyclic mating activity. This group of 84 animals had 6% 5‐day cyclers, 27% 4‐day cyclers, 45% 3‐day cyclers and 22% 2‐day cyclers. Observed copulatory sequences show that 82% of the time the copulation plug is dislodged from the female's vagina during the first three intromissions of a succeeding copulation. Most copulatory activity occurs between 3.5 and 5.5 hours after the start of the dark phase of the light cycle. Over 79% of the animals are sexually active for only one hour per day.
Cytological aspects of fertilization in the lamellibranch, Mytilus edulis II. Development of the male pronucleus and the association of the maternally and paternally derived chromosomes
Authors: Longo Frank J. , Anderson Everett
Published: June 2005

The events of fertilization involving the modifications of the incorporated spermatozoon and the association of the paternally and maternally derived pronuclei have been studied by techniques of light and electron microscopy in the lamellibranch, Mytilus edulis. At the site of gamete plasma membrane fusion a small fertilization cone is produced. As the spermatozoon moves through the fertilization cone, its nuclear envelope degenerates. The degeneration of the nuclear envelope is followed by the dispersion of the sperm chromatin and the formation of the pronuclear envelope. The sperm aster, produced during the formation of the male pronucleus, consists of fasicles of microtubules and endoplasmic reticulum which radiate from a centrosphere region containing two centrioles.

When the pronuclei complete their migration toward each other they are structurally similar and contain a fibro‐granular nucleoplasm. Eventually, the pronuclei become closely apposed, their proximal surfaces flatten, and produce an array of interdigitating nucleoplasmic projections. Concomitantly, the chromatin condenses and forms large reticular aggregations. Association of the parentally derived chromosomes is effected when the two pronuclear envelopes are dismantled. Microtubules that comprise a portion of the mitotic spindle become associated with the chromosomes as they move together in preparation for the first cleavage division. Hence, like many vertebrates, but unlike sea urchins, no zygotic nucleus is produced.
Degeneration and regeneration in abdominal flexor motor neurons in the crayfish
Authors: Hoy Ronald R.
Published: June 2005

Electrophysiological studies of sectioned crayfish motor axons of the abdominal flexor muscle have demonstrated that the distal stumps, isolated from their central connections for up to several months, are remarkably resistant to degeneration, as previously shown in the crayfish claw opener preparation. These distal stumps remained electrically excitable and intracellular recording showed that their neuromuscular junctional properties were indistinguishable from normal ones in such properties as waveform and amplitudes of the evoked junctional potentials. Furthermore, repetitive stimulation of the distal stumps evoked jp's which showed facilitation as in normal preparations. When degeneration finally occurred, electrical stimulation of the nerve no longer evoked jp's, and no progressive deterioration of junctional properties was observed.

Regeneration ultimately occurred in these nerves but required at least three weeks or more. The electrical properties of these regenerated junctions were not different from normal ones.

The evidence from time‐course and correlated histological studies of degeneration and regeneration suggest that regeneration of these crayfish nerves occurs by axonal fusion rather than by outgrowth of an entirely new distal apparatus from centrally located cell bodies, as is the mechanism in vertebrates and some invertebrates.
Physiological studies on supercooled killifish (Fundulus heteroclitus) I. Serum inorganic constituents in relation to osmotic and ionic regulation at subzero temperatures
Authors: Umminger Bruce L.
Published: June 2005

Physiochemical properties (serum osmolality and blood pH), serum inorganic ions (sodium, potassium, calcium, magnesium, chloride, phosphate and bicarbonate) and tissue water were studied in parallel groups of adult male Fundulus heteroclitus 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, serum osmolality increased by 20%. This increase was not indicative of osmoregulatory failure, however, since the proportion of total serum osmolality accounted for by inorganic electrolytes dropped from 98% at 20°C to 93% at −1.5°C. Serum electrolytes such as sodium, chloride, calcium, magnesium and bicarbonate increased in the subzero cold by 12%, 17%, 30%, 33% and 11% respectively whereas serum potassium and inorganic phosphate levels were unchanged. Blood pH was significantly higher at 10°C than at any other temperature. The water content of liver, testes and muscle decreased by 8% in the subzero cold. These changes in serum electrolytes and tissue water did not indicate osmoregulatory failure, however, since the new levels, once established, were maintained as long as the fish were alive. Although osmotic and ionic regulation were not as effective in the cold, they were by no means so poor as to cause death by osmotic imbalance.
Environmental control of annual testicular cycles in the lizard Anolis carolinensis. III. Temperature thresholds for photoperiodism
Authors: Licht Paul
Published: June 2005

Photo‐sexual responses in Anolis carolinensis during the fall are highly temperature dependent and show distinct thermal thresholds. If body temperatures are maintained at 32°C (the species' preferred temperature), day lengths of 13 hours or more stimulate testicular growth, whereas day lengths of 12 hours or less inhibit recrudescence. The testis develops slowly and independently of day length at 25°C or below. With fluctuating body temperatures, photoperiodism depends on both the duration of daily heating to 32°C (the thermoperiod) and the level of nocturnal cooling. Photo‐sexual responses occur with thermoperiods of eight hours or more when the nocturnal temperature is 20°C, but longer thermoperiods are required if nocturnal temperatures are reduced. There may be some equivalence between heat and light with regard to photo‐sexual responses; the critical day length for photostimulation varies with temperature.

Field observations of behavioral thermoregulation and climatic data for the lizards' habitat (around New Orleans, Louisiana) indicate that body temperatures are high enough to allow photoperiodism in September. Since the effective day length is 12 hours or less, testicular growth may be photoperiodically inhibited in September and early October. The natural onset of testicular growth in mid‐October may be due to a reduction of thermoperiod and nocturnal temperatures which abolishes the photo‐periodic responsiveness and to an inherent reduction in photosensitivity.

Studies begun in January confirm that the completion of testicular recrudescence in the spring is determined largely by the elevation of body temperatures and is independent of day length. Testicular development is rapidly completed with only a few hours of daily heating to preferred levels (32°C) even if nights are cold (e.g., 12°C).
Effects of estrogen, SU‐9055, and cyproterone acetate on the hypersecretory activity in the seminal vesicles of the castrate catfish, Heteropneustes fossilis (Bloch)
Authors: Sundararaj Bangalore I. , Nayyar S. K.
Published: June 2005

The effect of estradiol benzoate (EB), SU‐9055, and cyproterone acetate (CA) on the hypersecretory seminal vesicles of the castrate catfish has been studied. EB to a marked extent, SU‐9055 and CA to a lesser extent inhibit castration induced hypersecretion in the seminal vesicles. This implies that while EB inhibits the gonadotrophin production, SU‐9055 and CA act at the level of the interrenal glands and the seminal vesicles respectively. The data indicate that following castration the high level of circulating gonadotrophin induces the interrenals to produce androgens which in turn bring about hypersecretion in the seminal vesicles.
The mesoglea of hydra. III. Fiber system changes in morphogenesis
Authors: Hausman Robert E. , Burnett Allison L.
Published: June 2005

Examination of isolated mesogleas of Hydra pseudoligactis demonstrates that the organization of the collagen‐elastin‐like fiber system is dependent on the morphogenic state of the animal. There is a fiber system change associated with each of the three morphogenic capabilities of the animal: budding regeneration, and body column growth.

Non‐budding animals maintain a complete oral‐aboral fiber system throughout the body column. Hydra in the early stages of budding exhibit an organized fiber system in the peduncle only. Hydra maintained as continuously budding do not reorganize the mesogleal fiber pattern. The molecular or macromolecular changes in the fiber system are not, as yet, known.

Fiber system changes experimentally induced by feeding or hypostome excision appear the same as the breakdown associated with budding but differ in their extent through the animal. The observed changes are related to the different morphogenic capabilities of Hydra through a theory of cell migration and cell adhesion.
Chloride‐cell and mucus cell response to chloride and sulphate‐enriched media in the gills of Gambusia affinis affinis (Barid and Girard) and Catla catla (Hamilton)
Authors: Ahuja Surender K.
Published: June 2005

Comparative response of “chloride‐cell” and mucus cell to chloride‐and sulphate‐enriched media in the gill of Gambusia and Catla was studied. The presence of a large number of “chloride‐secretory cells” and their significant hypertrophy are correlated with the high tolerance of Gambusia to chloride media. The functional difference of phospholipids and mitochondria in the “chloride‐cells” between active and dying Gambusia is described. Mucus cells normally present in freshwater Gambusia, are not observed in the gills of active, salt‐adapting fishes beyond 2.7% salinity. Reappearance of these cells in a small number in the gills of non‐adapting and dying Gambusia at high chloride salinities may represent stages of “chloride‐cell” transformation into the mucus type. At high sulphate salinities the “chloride‐cells” become functional as is evidenced by increase in cell‐size under conditions of extreme kidney degeneration. Results suggest that “chloride‐cells” may not excrete bivalent ions in Gambusia adapting to comparatively low concentrations (0.57–1.81%) of sulphate media. Mucus cells are observed at all concentrations of sulphate media containing no chlorides.

Absence of “chloride‐secretory cells” in the gill of Catla is correlated with their low tolerance to chloride media. Mucus cells normally present in a large number in freshwater Catla are completely absent in fishes acclimatized to 1.1 to 1.5% chloride media. These cells show a partial atrophy in sulphate media containing a proportionately small quantity of chlorides. The physiological significance of the presence or absence of “chloride‐secretory cells” is discussed in relation to the tolerance of euryhaline and stenohaline teleostean species to univalent and bivalent ions.
Thymidine kinase activity during regeneration in the planarian Dugesia dorotocephala
Authors: Coward S. J. , Hirsh F. M. , Taylor J. H.
Published: June 2005

Thymidine kinase (TdR kinase) activity has been measured at various stages of regeneration in the planarian Dugesia dorotocephala. It is argued that TdR kinase activity is a valid, indirect measurement of cell proliferation in this organism. The earliest measured responses to wounding and the initiation of regeneration show maximal TdR kinase activities in non‐blastema regions. Later phases of regeneration show a shift of maxima to the blastemata with the general relations: prospective head blastemata have higher activity than prospective tail balstemata and posterior blastemata lag behind more anterior blastemata of the same developmental fate. It is concluded that the earliest proliferative response to wounding is in non‐blastema regions with secondary waves of proliferation in the blastemata proceding differentiation. The data are consistent both with models invoking long‐range cell migration and with models of local origin of the blastemata. Hydroxyurea treatment increases the level of TdR kinase activity and at low concentrations causes a modest acceleration in the rate of regeneration. Hydroxyurea treatment also produces bipolar (hetermorphic) regenerants from posteriorly‐derived sections. The possible role of cell number is invoked in relation to bipolar forms and as a regulator of normal differentiation.
Androgenic and male‐inducing effects of 11‐ketotestosterone on a teleost, the medaka (Oryzias latipes)
Authors: Hishida Tomi‐O , Kawamoto Noriko
Published: June 2005

The androgenic and the male‐inducing (androtermonic) activities of 11‐ketotestosterone were evaluated respectively by its abilities to stimulate a secondary sex character and to reverse gonadal sex differentiation in a teleost, the medaka (Oryzias latipes). The median effective dose (ED 50) of this steriod necessary to induce the formation of papillar process on the anal fin was 37 μg/g of food. The androgen is therefore about 8 times potent than testosterone propionate and 17 times more potent than pure testosterone in the same test. The ED 50 for androtermonic activity (reversal of genetic females to phenotypic males) was found to be about 110 μg/g of food. Compared with testosterone propionate the 11‐keto compound is about five times more potent. Thus, in teleosts, 11‐ketotestosterone appears to be the most potent androgen of vertebrate origin for both androgenic and androtermonic potencies. The ratio of androtermonic to androgenic potencies (ED 50s) for 11‐ketotestosterone is 3.0.