bluuebunny/crossref_metadata_2025_split huggingface dataset:
Translational competition as a possible basis of modulation in retinal pigment cell cultures
Authors: Whittaker J. R. 
Published: June 2005

AbstractA 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

AbstractLymphocystis, 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

AbstractMouse 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

AbstractAmpullae 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

AbstractThe 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

AbstractNeuromuscular 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

AbstractPostnatal 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

AbstractPolyploidy 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

AbstractThe 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

AbstractThe 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

AbstractWhen 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

AbstractAdults 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

AbstractExamination 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

AbstractThe 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

AbstractPreferred 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

AbstractThe 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

AbstractEach 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

AbstractSeventy‐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

AbstractThe 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.