bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of temperature on tyrosinase activity in Himalayan mouse skin
Authors: Kidson S. H. , Fabian B. C.
Published: June 2005

The tyrosinase activity of Himalayan mouse skin homogenates was measured over a range of temperatures using two sensitive radiometric assays—namely, (1) the measurement of 14C‐tyrosine incorporation into melanin, and (2) the measurement of 3HOH released as a by‐product of 3H‐tyrosine hydroxylation. Results show that Himalayan tyrosinase is maximally active at temperatures well below normal body temperature (15°C to 25°C). These results are in support of Danneel's visual observations ('41) that “ferment” activity of Himalayan rabbit skin is absent at temperatures above 25°C.

Further results suggest the presence of a tyrosinase inhibitor in Himalayan mouse skin. First, removal of a low molecular weight fraction from Himalayan skin homogenates resulted in an increase in tyrosinase activity. Second, recombination of the low molecular weight fraction to the homogenate from which it was originally separated resulted in a decrease in tyrosinase activity when assayed at 37°C, but no decrease when assayed at 25°C. It is proposed that at the normal body temperature of 37°C, tyrosinase from Himalayan skin is strongly bound to an inhibitor. At lower body temperatures, the affinity of the enzyme for the inhibitor decreases, thus allowing the synthesis of melanin to increase. This change in affinity of the enzyme for the inhibitor could be regulated by temperature‐induced conformational changes in either the enzyme or the inhibitor or both.
Two types of tonic fibers in lobster muscle based on enzyme histochemistry
Authors: Kent Karla S. , Govind C. K.
Published: June 2005

Tonic fibers are differentiated into two types based on enzyme histochemistry in the claw opener and closer muscle of the lobster Homarus americanus. Some of the fibers have a much lower myofibrillar ATPase activity and much higher oxidative capacity (indicated by NADH diaphorase) than the remainder. These slower‐contracting, more fatigue‐resistant fibers are regionally distributed in the claw muscles. The occurrence of two types of tonic fibers particularly in the opener muscle, which is innervated by a single slow excitor axon, shows that the oxidative properties of these fibers are not controlled simply by the presence of this motoneuron as previously proposed.
Poly (A)·oligo (dT)‐stimulated DNA polymerase activity in preimplantation mouse embryos
Authors: Kiessling Ann A. , Weitlauf Harry M.
Published: June 2005

DNA polymerase activity with Poly (A)·oligo(dT) as a template‐primer has been found in preimplantation mouse embryos. A sharp increase in enzyme activity was observed at the time of formation of inner cell mass (ICM) and trophoblast cells. Differential inhibition of enzyme activity before and after ICM formation raised the possibility that more than one Poly(A)·oligo(dT)‐directed DNA polymerase was detected.
Differentiation of melanomas occurring in platyfish‐swordtail hybrids of different ages: An ultrastructural study
Authors: Esaka Takashi , Asada Mari , Wakamatsu Yuko , Ozato Kenjiro
Published: June 2005

The degree of differentiation of two types of hereditary melanomas of interspecific hybrids between the spotted variety of the platyfish (Xiphophorus maculatus) and the swordtail (Xiphophorus helleri) was examined electron microscopically. Melanomas of the fry consisted mainly of pigmented cells containing intermediately matured melanosomes and few other cytoplasmic structures. Melanomas of the adult consisted of lightly pigmented cells having a small number of immature melanosomes; numerous polysomes; well‐developed, rough‐surfaced endoplasmic reticulum (RER) and Golgi systems; and irregularly shaped nuclei. Thus the fry and adult melanomas appear to represent relatively well‐ and poorly differentiated states of fish melanophores, respectively. Amela‐notic melanomas in the adult melanotic F1 generation were also characterized. Virus‐like particles were often found in the nuclei of both melanotic and amelanotic melanoma cells in the adult fish.
Preamputation and postamputation histology of the neonatal opossum hindlimb: Implications for regeneration experiments
Authors: Fleming Michael W. , Tassava Roy A.
Published: June 2005

Mammalian limbs generally do not regenerate, regardless of added hormonal or nervous stimulation, whether amputation occurs during fetal life or post‐partum. The one exception, the newborn opossum, has been reported to regenerate the incompletely developed hindlimb (Mizell, '68). In an attempt to repeat and extend these earlier findings, we have examined the histology of the neonatal opossum hindlimb. After amputation on day 4 post‐partum, we correlated the histology of the amputated segment with the histology of the remaining stump after a “regeneration time” of several weeks. Amputations through the middle of the hindlimb on day 4 did not transect the tibia and fibula because the rudiments of these bones are still almost completely inside the body wall. Midlimb amputations transected instead the tarsal rudiments or even phalangeal rudiments. Limb stumps were therefore left with distal skeletal rudiments which subsequently underwent further embryonic development and growth giving the erroneous impression of regeneration. Of 30 amputated hindlimbs, none showed regeneration.
Development of swimming behavior in sea urchin embryos. I.
Authors: Maruyama Yoshihiko K.
Published: June 2005

Development of behavior in sea urchin embryos and larvae was studied with special attention to rotation on the animal‐vegetal axis. Within the fertilization membrane, each embryo rotated either clockwise or counterclockwise on the animal‐vegetal axis and the direction of rotation (= spin) sometimes reversed in the same embryo. However, the symmetric pattern of spinning motion in prehatching embryos was lost liberation of embryos from the fertilization membrane. Embryos hatching out with counterclockwise spin (as viewed from the vegetal region) maintained the same direction of spin even after hatching, whereas embryos with clockwise spin reversed the direction of spin through a characteristic transient swimming pattern. Eventually, all embryos swam with the animal pole forward and rotated counterclockwise on the animal‐vegetal axis. A developmental change of swimming behavior, first appearing at the pluteus stage, is a transient reversal of swimming direction. The direction of rotation during this backward swimming was invariably “counterclockwise” as in the case of forward swimming, if the larva was viewed from the rear with respect to the swimming direction.
Responses of denervated adult newt limb stumps to reinnervation and reinjury
Authors: Salley Judith D. , Tassava Roy A.
Published: June 2005

It is well known that denervated adult newt limbs do not regenerate. Not understood is why denervated newt limb stumps fail to initiate regeneration upon reinnervation. In an effort to define the regeneration limiting factors, we examined the histology of long‐term denervated newt limb stumps and tested the effects of various kinds of reinjury. In 5‐week denervated limb stumps there were present dedifferentiated cells, differentiated cartilage, and densely packed layered cells. The epidermis covering the limb tip resembled skin epidermis rather than wound epidermis. The kinds of reinjury that were successful in restoring the regeneration capabilities to 5‐week denervated limb stumps included: reamputation (100%), a single razor incision (60%), and removal of the healed tissues from the distal limb tip (70%). The results of this study emphasize the importance of both injury and wound epidermis in initiating regeneration.
Biochemical studies of mammalian oogenesis: Kinetics of accumulation of total and poly(A)‐containing RNA during growth of the mouse oocyte
Authors: Sternlicht Andrew L. , Schultz Richard M.
Published: June 2005

Kinetics of accumulation of total and poly(A)‐containing RNA have been measured during growth of the mouse oocyte. Total RNA from oocytes isolated at discrete stages of growth was determined by two independent micro‐assays. The fully‐grown oocyte contained about 0.60 ng of RNA. Kinetics of accumulation of total RNA with respect to oocyte volume were biphasic. Small, growing oocytes (about 30 pi) contained about 0.20 ng of RNA/oocyte. The amount of RNA increased in a quasi‐linear fashion until oocyte volume was about 160 pl, at which point there was about 0.57 ng of RNA/oocyte. Thus oocytes about 65% of their final volume had accumulated about 95% of the total amount of RNA present in the fully‐grown oocyte. The relative amount of poly(A)‐containing RNA in oocytes of various size was determined by in situ hybridization of [3H]poly(U) to ovarian sections from juvenile mice of known age, followed by autoradiography. The kinetics of accumulation of poly(A)‐containing RNA were similar to those of total RNA; oocytes about 70% of their final volume had accumulated about 95% of the amount of poly(A)‐containing RNA present in the fully‐grown oocyte. The poly(A)‐containing RNA resided predominantly in the cytoplasm and no obvious cytoplasmic localization was observed.

Kinetics of accumulation of total RNA, which is mainly ribosomal, and poly(A)‐containing RNA were consistent with levels of RNA polymerases I and II measured by others during oocyte growth (Moore and Lintern‐Moore, '78). The number of ribosomes that could be made from the amount of rRNA present at various stages of growth was compared to the actual number of ribosomes calculated from a published morphometric study (Garcia et al., '79). Kinetic differences in accumulation between the theoretical and actual number of ribosomes suggested oocyte ribosomes are recruited into cytoplasmic lattice structures. These structures accumulate during oocyte growth and have been postulated to be a ribosomal storage form. In addition, the results from this study are compared to results derived from lower species.
Analysis of perinotochordal materials. I. Studies on proteoglycans synthesis
Authors: Vasan Nagaswamisri
Published: June 2005

Perinotochordal proteoglycans have been shown to influence somite chondrogenic differentiation. However, information concerning the composition of the proteoglycan molecules synthesized by the notochord, or the exact type of molecule necessary for the induction of somite chondrogenesis is not known. The results of the present study indicate that the proteoglycan extracted from the 8 day old notochord culture consists of predominantly small proteoglycans, while the large aggregates form less than 30% of the total. The chondroitin sulfate composition also shows a cartilage type of proteoglycan molecules synthesized by the notochord.
State of water and electrolytes in mammalian cells during maturation and differentiation
Authors: Hempling H. G. , Cicoria A. D. , Dupre A. M. , Thompson S.
Published: June 2005

The state of water and electrolytes was examined (1) in the rat erythroblastic leukemic cell, as a model of a maturing erythrocyte; (2) in the mouse Ehrlich ascites tumor cell during the cell cycle as a model of the uninhibited proliferating cell; and (3) in a clonal population of proliferating and differentiating precursor cells cultured from the bone marrow of the rat. Methods used were phenomenological and included assessments of the volumes of osmotically active water, content of K+, Na+, and Cl−, volumes of distribution for Na+, urea, and ethylene glycol, and the thermodynamics of transport of water and solutes into and out of the cell. The erythroblastic leukemic cell provided evidence for compartments of osmotically active and inactive water and solute. The synchronized ascites tumor cell indicated that these compartments varied during the cell cycle. Membrane function as defined by its permeability to water also varied during the cell cycle. When proliferating cells matured, changes in membrane permeability to water and to nonelectrolytes also correlated with successive stages of differentiation.
Amino acid cycling in ribbed mussel tissues subjected to hyperosmotic shock
Authors: Bishop Stephen H. , Greenwalt Dale E. , Burcham James M.
Published: June 2005

Variations in the high concentrations of intracellular amino acids in the tissues of osmoconforming, euryhaline animals such as the ribbed mussel (Modiolus demissus) appear to have a major role in adjusting intracellular osmotic pressure in response to extracellular osmotic change. The experiments discussed here on the metabolic origins and fates of these amino acids are part of a continuing study on the physiological mechanisms regulating the concentrations of these amino acids. Tissues isolated from ribbed mussels adapted at 12 o/oo were incubated for 8 hrs. in artificial seawater media at 12 o/oo or 32 o/oo. The total marked increase in total intracellular amino acid levels at 32 o/oo vs. 12 o/oo was not blocked by addition of 1 mM amino oxyacetic acid (AOA). However, with AOA the usual increase in alanine and proline concentrations was offset by increases in a variety of amino acids including ornithine. AOA inhibited transaminases associated with ornithine, alanine, and glutamate metabolism (I50s:10−8 to 10−5 M) but did not inhibit the L‐amino acid oxidase. 14C‐tracer experiments with isolated gill tissue indicated no synthesis of proline from glutamate and enhanced synthesis of proline, alanine, and glutamate from ornithine and arginine at 32 o/oo vs. 12 o/oo. L‐amino acid oxidase, proline oxidase, glutamate dehydrogenase, and enzymes in the metabolic pathway between arginine and proline were found in cell‐free extracts of gill tissue. During hyperosmotic stress, proline was apparently derived from the phosphoarginine‐arginine pool, whereas alanine and the other accumlating amino acids have multiple metabolic origins including the amino acids released during protein turnover, the metabolites of the phosphoarginine pool, and possibly endogenous carbohydrate.
Volume regulation in aquatic invertebrates
Authors: Oglesby Larry C.
Published: June 2005

Volume regulation in marine and estuarine invertebrates is usually assessed by the extent of restoration of original weight following a salinity transfer. However, volume regulation also includes the limitation of osmotic water movements. Mechanisms of volume regulation include (1) reduction of permeability of the body wall to water, reducing the rate of osmotic water movement; euryhaline species are less permeable to water than stenohaline species, and may show further adaptive reduction when in low salinities; (2) expulsion of excess water following osmotic influx, primarily as bulk elimination in the urine; and (3) changes in the numbers of extracellular osmolytes, also reducing the osmotic gradient, the major route being loss of solutes to the medium across the body wall and through the urine. Two theoretical approaches to analysis of volume regulation are discussed (Machin, '75; Oglesby, '75) and it is concluded that while both are somewhat imprecise, the approach of Oglesby ('75) has more versatility and resolving power in dealing with both osmoregulators and osmoconformers.
The role of amino acids in anaerobiosis and osmoregulation in bivalves
Authors: Zurburg Wouter , De Zwaan Albertus
Published: June 2005

The role of free amino acids as solutes for cell volume regulation in marine molluscs under salinity stress is well established. Under hypoosmotic stress the intracellular concentrations of amino acids decrease by extrusion from the cells, followed by deamination and/or excretion. However, no uncontroversial evidence is available about mechanisms involved in the enlargement of the free amino acid pool during hyperosmotic stress.

Since anaerobic metabolism in bivalves can result in the accumulation of the amino acids alanine and glutamate, a possible contribution of the anaerobic metabolic pathways to the osmotic adjustment of the cell during hyperosmotic stress has been considered. The net gain of amino acids implies the fixation of ammonia to 2‐oxo acids. The low activity of glutamate dehydrogenase found in bivalves does not exclude its role in osmoregulation and anaerobiosis. Another ammonia‐fixating enzyme may be alanine dehydrogenase, but so far evidence for its presence in bivalves is lacking. In bivalves the source of ammonia for these enzymes may be found in part in uric acid or other amino compounds that are present in reasonable amounts.
A spider fibroin and its synthesis
Authors: Candelas Graciela C. , Cintron José
Published: June 2005

The tissue‐specific fibroin product of the large ampullate glands of the spider Nephila clavipes was isolated and analyzed with respect to homogeneity and size. The solubilized luminar contents of the glands migrate as a homogeneous band in SDS electrophoresis. Its molecular mass has been estimated to be approximately 323,600 daltons. Excised glands have been manintained metabolically active under rather simple culture conditions. Protein synthesis, monitored by incorporation of labeled alanine and glycine, has been elicited through exposure to a cholinergic agent in the culture medium as well as by depleting the animals of their store of silks.
Distribution of polyamines and ornithine decarboxylase activity in the tissues of the lizard, Calotes versicolor
Authors: Baby T. G. , Reddy S. Raghupathi Rami
Published: June 2005

The distribution of polyamines, putrescine, spermidine, and spermine is reported in the tissues of the lizard, Calotes versicolor. The levels of spermidine and spermine are higher than those of putrescine in all tissues and most tissues have more spermine than spermidine. Enzymatic decarboxylation of L‐ornithine is also demonstrated in the lizard tissues. Liver orthinine decarboxylase has optimal activity at about pH 6.8 and apparent Km (Michaelis constant) of 1.23 to 1.73 mM for L‐ornithine.
Cortical vesicle breakdown in fertilized eggs of Fundulus heteroclitus
Authors: Brummett Anna Ruth , Dumont James N.
Published: June 2005

A scanning and transmission electron microscope study has been made of the cortical alveoli of the egg of Fundulus heteroclitus. The study includes both unactivated eggs and fertilized eggs fixed at intervals of 1 second to 10 minutes after insemination.

The alveoli appear to vary considerably in size, in contents, and in morphological aspects of their breakdown. As it undergoes dehiscence, each vesicle may form one or several openings in the egg surface; dense granules and particulate, fibrous, or membranous material, apparently in any combination, are liberated to the nascent perivitelline space. It appears that much of the excess membrane externalized during the reaction is strung out in threads and probably lost to the perivitelline space. The evidence does not suggest that the excess membrane either “dissolves” or is retrieved by the egg cytoplasm. That part of the cortical vesicle membrane which remains continuous with the oolemma gradually becomes microvillous and loses its morphological identity.

Granules and particulate matter, presumably liberated from the cortical alveoli, are seen adhering to the inner surface of chorions removed from activated eggs. The micropyle appears to be sealed with similar material. Supernumerary sperm are observed inside the chorion in some instances.

The cortical reaction appears to play a secondary role in the prevention of polyspermy and to be somehow related to the subsequent formation of a normal embryonic blastodisc.
Active immunization of rats with cumulus‐free mouse ova: Induction of infertility and antibody titers
Authors: Aitken R. J. , Richardson D. W.
Published: June 2005

Active immunization of rats with cross‐reacting zona pellucida antigens derived from cumulus‐free mouse ova resulted in the induction of infertility without adverse side effects. Half of the immunized animals never regained their fertility despite repeated matings with fertile males. Two of the remaining animals conceived when antibody titers fell to basal levels and gave birth to litters of normal healthy young. Post mortem examination of immunized animals 24 hours after finding sperm in the vaginal smears resulted in the recovery of tubal ova exhibiting the presence of a precipitate on the outer surface of the zona pellucida. Some of these ova appeared to have been fertilized, suggesting that anti‐zona antibodies may also inhibit fertility through a post‐fertilization mechanism of action.
Cyclic AMP in mammalian follicle cells and oocytes during maturation
Authors: Moor R. M. , Heslop J. P.
Published: June 2005

Intact ovarian follicles and isolated oocytes were cultured for 30 sec to 18 hr in the presence of gonadotrophins, and the cyclic AMP content in the follicle and oocyte was measured. The basal content of cyclic AMP in ovine oocytes before gonadotrophic stimulation was 6.3 ± 0.7 fmol/oocyte or 8 μM. There was no fall in oocyte cyclic AMP concentration as an immediate response to the gonadotrophins, but at 1, and 12–18 hr after stimulation, the concentration in both the oocytes and follicle cells was considerably elevated. There was no comparable increase in intracellular cyclic AMP in oocytes denuded of follicle cells before culture, even when both gonadotrophins and phosphodiesterase inhibitors were included in the medium. We conclude that the signal which initiates oocyte maturation in mammals differs from that of amphibia, where an early fall in intracellular cyclic AMP is essential for the resumption of meiosis. Moreover, cellular interactions within the mammalian follicle are necessary for the characteristic periods of increased cyclic AMP in oocytes during maturation.
Altered acetylcholinesterase isozyme patterns in mice with hereditary muscular dystrophy
Authors: Kuhn D. E. , Logan D. M. , Rathbone M. P.
Published: June 2005

Normal and dystrophic mouse muscles were separated into a predominantly white muscle fraction (gastrocnemius, extensor digitorum longus) and a predominantly red muscle fraction (diaphragm). Acetylcholinesterase (AChE) was extracted from each muscle fraction using a Triton X‐100/NaCl buffer. Six forms of AChE were separated from each muscle homogenate by velocity sedimentation on linear sucrose gradients. Their apparent sedimentation coefficients in each case were 19.7S, 16.0S, 13.3S, 10.4S, 7.6S, and 3.9S. Gel electrophoresis of crude muscle homogenates under nondenaturing conditions (native gels) and of each separate isozyme fraction gave one band of AChE activity with a consistent Rf (relative mobility) value. Reelectrophoresis of native gel bands on SDS/acrylamide slab gels revealed a similar monomeric subunit protein from either crude muscle homogenates or isozyme fractions with an apparent molecular weight of approximately 69,000 daltons.

Our results indicate that the AChE distribution and activity are severely affected in dystrophic “white” muscles (anaerobic) but much less so in “red” muscles (aerobic). Dystrophic predominantly white muscles weigh less, contain less protein, and have a decreased total AChE activity in comparison with their normal counterparts. Furthermore, the relative proportions of AChE activity in each isozyme fraction is altered between normal white and dystrophic white muscle fractions: i.e., dystrophic white muscle contains a decreased proportion of a low molecular weight form (7.6S) and increased proportions of higher molecular weight forms (16.0S, 19.7S). In contrast, no significant differences occur in AChE activity or distribution between normal and dystrophic predominantly red muscle.

The changes in white muscle AChE are toward a pattern common to red muscle. This suggests that the effect of muscular dystrophy and its related stress on mouse white muscle is at least in part a shift from a predominantly anaerobic, fatigable metabolism to an aerobic, fatigue‐resistant metabolism.
Newt forelimb regeneration blastemas in vitro: Cellular response to explantation and effects of various growth‐promoting substances
Authors: Mescher Anthony L. , Loh Jee‐Joon
Published: June 2005

Macromolecular synthesis was studied in cultured newt forelimb blastemas. Late bud stage blastemas were explanted into organ culture and thus denervated. When the response of the blastemas to explantation was examined, it was found that a peak in 3H‐leucine incorporation occurred at 2 hr of incubation, and a similar peak in 3H‐thymidine incorporation occurred at 3–4 hr. After these initial increases, both parameters declined to levels lower than those determined at the time of explantation. The peaks in macromolecular synthesis reported here in vitro are similar to those observed in blastemas in vivo after denervation (Singer, '74). In the second part of the study, the ability of various growth‐promoting substances to stimulate DNA synthesis in cultured blastemas was investigated. Increasing concentrations of fetal bovine serum caused increased levels of 3H‐thymidine incorporation, with maximal stimulation at 30% serum. Newt brain extract (NBE) was as effective as additional serum, with optimal stimulation at 100 μg total NBE protein per ml culture medium. Fibroblast growth factor (FGF), derived from brain tissue, at a concentration of 10 ng/ml was as effective as both 30% serum and the optimal concentration of NBE. Epidermal growth factor (EGF) produced a maximal effect at 1 ng/ml. Neither nerve growth factor nor the platelet‐derived growth factor were stimulatory. Bovine insulin was highly active in stimulating DNA synthesis at concentrations from 1–10 μg/ml. The requirement of nerves for blastemal development, as well as the possible roles of the various growth‐promoting substances in this process, are discussed.
Oxidative metabolism of spermatozoa from inbred and random bred mice
Authors: Carey Joan E. , Olds‐Clarke Patricia , Storey Bayard T.
Published: June 2005

Epididymal spermatozoa from the random‐bred CFW and from the inbred C57BL/6 strains of mice were treated either hypotonically or with the antibiotic filipin in order to study the mitochondrial oxidative activities of the two strains in the absence of permeability barriers imposed by the plasma membrane. The percentage of motile spermatozoa from C57BL/6 mice was consistently higher than that from CFW mice, but sperm from the latter fertilized a higher percentage of eggs in vitro. In vivo, there was no apparent difference in fertilizing capacity in vivo: no significant difference between strains was observed. There is a strategy of oxidative metabolism in mouse spermatozoa which is common to the two genetic strains of the species tested, but which differs from that of rabbit and bull spermatozoa. The mitochondria of mouse spermatozoa oxidize L‐3‐glycerolphosphate but not glutamate in the presence of malate; both activities are present in bull spermatozoa but neither are present in rabbit spermatozoa. In common with those of the mammalian species thus far studied, the mitochondria of mouse spermatozoa readily oxidize lactate and pyruvate in the presence of malate. They also oxidize acetyl CoA, acetyl carnitine, and long‐chain acyl CoA esters directly, without the intermediacy of the carnitine esters. Mouse spermatozoa, therefore, have access to endogenous acyl CoA esters as a source of metabolic energy, which is consistent with their ability to maintain motility for 4–6 hours in the absence of added energy sources. Mouse spermatozoa are self‐sufficient with regard to oxidative metabolism, which suggests that energy sources are not readily available to them in the mouse female reproductive tract.
Photoperiodic control of seasonal reproduction in tropical weaver bird
Authors: (Nee Pavgi) Sushama Singh , Chandola Asha
Published: June 2005

Experiments were performed in order to provide information on the extent of involvement of daylength, if any, in the control of seasonal breeding in the tropical weaver bird. The reproductive cycle was completely abolished in both short and long photoperiods. The cycle was suppressed in short photoperiods, and in long photoperiods gonads were maintained in a stimulated state indefinitely. These results indicated a definite photoperiodic requirement for gonadal development in the weaver bird. the photoperiodic response threshold was found to be 11 hours daily. Gonads in a period of 12L/12D exhibited cyclicity, though at a low level, indicating that a light period of 12 hours daily allows gonadal regression which is abolished in longer photoperiods. On correlating these laboratory observations with the natural reproductive cycle, it seems that the annual timing of reproduction in the weaver bird may coincide with the time in the spring when the increasing day length reaches the photoperiodic response threshold.
Induced locomotion by midbrain stimulation in restrained skipjack tuna, Katsuwonus pelamis, L.
Authors: Kashin S. M. , Brill R. W. , Ikehara W. N. , Dizon A. E.
Published: June 2005

We show that electrical stimulation of the midbrain of restrained and sedated skipjack tuna (Katsuwonus pelamis) produces coordinated locomotory activity. Therefore, our preparation is a viable alternative for creating normal swimming movements which can be closely controlled by the experimentalist, and demonstrates that a midbrain “locomotory center” is present in skipjack tuna, as in other teleosts.
Microvascular pressures in gill filaments of lingcod (Ophiodon elongatus)
Authors: Farrell A. P. , Smith D. G.
Published: June 2005

Dynamic intravascular pressures were measured in the afferent and efferent filament arteries of Ophiodon elongatus using micropipettes. Measurements from anesthetized fish and from isolated, saline‐perfused preparations indicated that the major site of gill resistance was located in the lamellar complex (secondary lamella and associated arterioles). The presence of a postlamellar cholinergic constrictor site was also supported by efferent arterial pressure measurements during acetylcholine administration.
Site of calcium uptake in the fresh water trout gill
Authors: Payan Patrick , Mayer‐Gostan Nicole , Pang Peter K. T.
Published: June 2005

Using the perfused head preparation, it is shown that in fresh‐water‐adapted animals, the uptake of calcium takes place in the chloride cells.
A possible stress‐warning marker in Ambystomatid salamanders
Authors: Hedberg Thomas G.
Published: June 2005

When placed under thermal and mechanical stress, individuals of Ambystoma tigrinum may produce a chemical substance which elicits aversive movements, increases negative phototaxis, and inhibits swimming coordination in conspecifics in an aquatic environment. Introduction of water in which three individuals were kept under stress elicited these responses in conspecifics kept in another container. Under natural conditions, the proposed substance may serve as a stress‐warning marker during the spring migrations of this species.
Effect of seasonal variations on the immune system of the snake, Psammophis schokari
Authors: Ridi R. El , Badir N. , Rouby S. El
Published: June 2005

In spring and autumn, the lymphoid complex of the colubrid snake, Psammophis schokari is well developed and the humoral response to intraperitoneally administered rat erythrocytes (RRBC), human serum albumin (HSA), or polyvinyl pyrrolidone (PVP) is quick and vigorous. In contrast, in summer and winter, lymphoid elements of the thymus, spleen, and part of the gut‐associated lymphoid tissue are highly depleted. Humoral reactivity to RRBC and HSA is poor in summer presumably due to the deleterious effect of seasonal factors on the thymus and thymus‐derived helper lymphocytes. This assumption is supported by the fact that, in summer, P. schokari responds powerfully to the T‐independent antigen PVP. Humoral response to RRBC, HSA, and PVP is, however, weak in winter suggesting that a further mechanism of immunosuppression is involved.
Cortical control of macronuclear positioning in the ciliate Stentor
Authors: De Terra Noël
Published: June 2005

In the ciliate Stentor, the chain macronucleus has a fixed position within the cell; it is located just beneath the region of narrow cortical striping to the right of the gullet (nuclear site). Stentor therefore lends itself well to experiments on control of nuclear positioning. I have studied this problem by microsurgically producing various abnormalities of nuclear positioning and determining how these are corrected. Breaks in the nuclear chain were repaired by segregation of broken parts into the two daughter cells at division. When a second nucleus was transplanted into a stentor, the abnormality was eventually corrected because the two parallel chains tended to move during oral development (regeneration or division) so that one was anterior to the other. The two nuclei were then segregated into the anterior and posterior daughter cells at division. When a doublet stentor, which has two nuclear sites and two macronuclei, was deprived of one nucleus, it acquired a second one because the remaining nucleus was attracted to both nuclear sites when it elongated during oral development. This phenomenon first produced doublets with a single nuclear chain sharing the two nuclear sites at opposite ends of the cell, a break in the chain then presumably created two nuclei. These latter observations indicate that one mechanism by which the nucleus is positioned involves its attraction toward the nuclear site, a differentiated region of cell cortex, during oral development. Other experiments have shown that the nuclear site also holds the nucleus firmly in place.
Rapid nasal pit formation in mouse embryos stimulated by ATP‐containing medium
Authors: Smuts Marybeth S.
Published: June 2005

The primary palate in the mouse is composed of epithelium and mesenchyme. Most studies on primary palate formation have concentrated on the role of the mesenchyme based upon the hypothesis that mesenchymal accumulation elevated the sides of the nasal placodes, thereby creating the depressed nasal pits.

This study demonstrates that the epithelium is actively participating in formation of the nasal pits. Mouse heads from embryos of 14 to 24 pairs of body somites were placed in medium 199 and photographed. The medium was replaced with medium containing 1.0 mM ATP and 0.05% Triton‐X. Within 5 minutes, the placodes either thickened or invaginated. Control heads exposed to medium 199 containing only Triton‐X or ATP did not show any invaginations.

The rapid thickening and invagination stimulated by ATP‐containing medium demonstrates that the epithelium is the dominant tissue in nasal pit formation. Although mesenchymal accumulation certainly contributes to the formation of the primary palate, it is the placodal epithelial invagination that appears to shape the nasal pits.
Histone synthesis in preimplantation mouse embryos
Authors: Kaye Peter L. , Wales Raymond G.
Published: June 2005

The synthesis of histones by preimplantation mouse embryos was examined by electrophoresis of [3H]‐lysine‐labeled acid extracts of cleavage stage embryos. Histones were synthesized by fertilized zygotes, two‐cell, eight‐cell, and morula stage embryos. Their identity was confirmed by coextraction and coelectrophoresis in a number of systems and differential labeling with [3H]‐tryptophan. There was evidence of post‐translational modifications of the embryonic histones. The estimated histone synthetic rate was sufficient to provide the chromatin requirements of cleavage division as related to DNA synthesis. The results are discussed in relation to coordination of histone and DNA synthesis in the preimplantation embryo.
An intrabursal injection procedure for the in vivo study of ovulation in hamsters
Authors: Martin Gary G. , Talbot Prudence , Pendergrass Paula
Published: June 2005

A new procedure for studying the effect of various drugs on ovulation in vivo is described. In golden hamsters (Mesocricetus auratus), each ovary is enclosed within a complete bursa that is continuous with the oviduct. Drugs can be applied topically to ovaries by injection of a solution into a bursal cavity of an anesthetized hamster several hours before ovulation: the contralateral ovary serves as an in vivo control and receives no treatment. After ovulation, the number of ruptured follicles on experimental and control ovaries are compared. Data presented show that: (1) the operation and injection procedure per se do not affect ovulation; (2) normal saline is a suitable vehicle for administration of drugs by this route; (3) compounds with molecular weights of less than 1,000 daltons rapidly penetrate all layers of the follicle wall; (4) solutions injected into the bursal cavity 6 hours before ovulation remain there until ovulation. The advantages and limitations of this technique are discussed.
The role of follicular smooth muscle cells in hamster ovulation
Authors: Martin Gary G. , Talbot Prudence
Published: June 2005

The role of contractile cells in mammalian ovulation is uncertain. In this study, we examined the morphology and distribution of cells within the theca externa of hamster follicles at various times during ovulation. Cells with all the ultrastructural features of smooth muscle (SMC) were found only in the basal hemisphere of the follicle. In contrast, the theca externa in the top half of the follicle was composed of fibroblasts. We next examined living hamster follicles during in vitro ovulation for morphological evidence of follicular contraction. The following changes in follicle shape were observed: (1) The base of the follicle moved apically; (2) follicles, which were initially spherical, became taller and thinner; and (3) after rupture, the apical follicle wall collapsed onto the surface of the ovary. To analyze the cause of these changes, sections of fixed follicles were examined by light and electron microscopy. During the final minutes before rupture, a V‐shaped constriction formed in the base of the follicle. This constriction continued to narrow and by the time of rupture, it obliterated the basal part of the antrum. We concluded that the apical movement of the base of the follicle seen in living ovaries corresponds to the formation of the basal constriction seen in fixed sections. To determine if follicular SMC were involved in formation of the constriction, the ultrastructure of SMC was examined before, during, and after the constriction formed. The morphology of the SMC changed from the characteristic of relaxed or stretched SMC to that of contracted SMC when the constriction began to form. No other type of cell in the follicle wall showed these changes in morphology. We conclude that the formation of this constriction, and possibly the increase in height of preovulatory follicles and the collapse of the follicle wall after rupture, are due to contraction of SMC in the theca externa in the basal hemisphere of the follicle. This is the first morphological demonstration that follicular SMC contract prior to rupture of the follicle. The significance of these observations in mammalian ovulation is discussed.
Mouse alcohol dehydrogenase isozymes: Products of closely localized duplicated genes exhibiting divergent kinetic properties
Authors: Holmes Roger S. , Albanese Rico , Whitehead Faye D. , Duley John A.
Published: June 2005

Electrophoretic variants for the stomach isozyme (ADH‐C2) and liver isozyme (ADH‐A2) of alcohol dehydrogenase in strains of Mus musculus have been used in genetic analyses to demonstrate close linkage between the structural genes (Ahd‐3 and Adh‐1, respectively) encoding these enzymes. No recombinants were observed between these loci among 126 backcross animals, which places them less than 0.8 centimorgans apart. Previous studies have positioned Adh‐3, and a temporal locus (Adh‐3t), on chromosome 3 (Holmes, '79; Holmes et al., '80). Kinetic analyses on partially purified preparations of these isozymes have demonstrated widely divergent catalytic properties and inhibitor specificities. The liver isozyme exhibited Michaelis constants that were nearly 3 orders of magnitude lower than the stomach isozyme for various alcohol and aldehyde substrates. Moreover, aminopropyl pyrazole strongly inhibited ADH‐A2 (Ki = 1.2 M), whereas ADH‐C2 was insensitive to inhibition under the conditions used. It is proposed that Adh‐1 and Adh‐3 are products of a recent gene duplication event during mammalian evolution and that considerable divergence in the active sites of these enzymes and the “temporal” genes controlling loci expression in differentiated tissues has subsequently occurred.
Effect of day length and reproductive state on diel rhythms of luteinizing hormone levels in the plasma of white‐crowned sparrows, Zonotrichia leucophrys gambelii
Authors: Wingfield John C. , Vleck Carol M. , Farner Donald S.
Published: June 2005

Plasma levels of LH were measured through the course of 24 hours in photosensitive and photorefractory, adult male white‐crowned sparrows, Zonotrichia leucophrys gambelii, exposed to both long (20L, 4D) and short (8L, 16D) days. In photorefractory birds held on both long and short days there is an increase in plasma levels of LH late in the subjective day or soon after the onset of the scotophase. These levels remain high for most of the night and decline to low levels just after the onset of the photophase. In addition there is a second increase in circulating LH, 3–5 hours after the onset of the photophase, with a second minimum about 10 hours later.

A similar rhythm occurs in photosensitive birds held on short days. Plasma levels of LH increase late in the day and remain high throughout most of the night. Lowest levels were measured just after onset of photophase. In contrast, circulating LH in photosensitive birds exposed to long days showed no discernable diel rhythm. During the night, plasma levels of LH of photorefractory birds, and also photosensitive birds on short days, are as high as those of photosensitive birds on long days.
Mouse sperm motility affected by factors in the T/t complex
Authors: Tessler Steven , Carey Joan E. , Olds‐Clarke Patricia
Published: June 2005

Motility characteristics of epididymal sperm from tw32/+ and T/+ males of several strains were compared to those of sperm from the congenic, wild‐type mice. Epididymal sperm from C57BL/6‐tw32/+ (B6‐tw32/+) males showed a significant decline in vigorous motility and a significant increase in adhesivity to glass during 7.5 hours in vitro, while sperm from B6‐+/+ males showed no changes in these characteristics. The apparent mean velocities of epididymal sperm were: B6‐tw32/+, 32 μ/sec; C3H‐tw32/+, 60; B6XC3H hybrids (F1*‐tw32/+), 44; and C3HXB6 hybrids (F1‐tw32/+), 58. Each of these values was significantly lower than that of sperm from their congenic wild‐type strains: B6‐+/+, 115; C3H‐+/+, 177; F1*‐+/+, 168 and F1‐+/+, 195 μ/sec. B6‐T2J/+ sperm had velocities intermediate to the congenic +/+ and tw32/+ genotypes, whereas C3H‐T/+ sperm velocity was not significantly different from C3H‐+/+. These differences in measured sperm velocity may not reflect real differences in swimming speed, but rather may indicate a difference in the shape of swimming trajectories. Erratic and convoluted swimming trajectories were observed for the majority of sperm from tw32/+ males of all genotypes. Differences in motility patterns of sperm from tw32/+ males could play a role in the abnormally high transmission of tw32 through the male.
A comparison of cell proliferation patterns in the digestive tract of ascidians
Authors: Ermak Thomas H.
Published: June 2005

Cell proliferation patterns in the postbranchial digestive tract of a variety of ascidian species were investigated with autoradiography and tritiated thymidine. Based upon the distribution of radioactive nuclei, gut cell populations were classified as either static, expanding, or renewing. In most ascidians, renewing populations occur in the esophagus and stomach, but expanding populations sometimes occur in all or part of the intestine. From species to species, the number of cell renewal units (pairs of germinal and mature zones) in each portion of the digestive tract increases with increasing organ size, and this multiplication of renewal units follows the folding patterns in the gut. Cell turnover is fastest and the size of a cell renewal unit smallest at the anterior end of the gut. The smallest colonial ascidians have a single renewal unit per cell population in the esophagus and stomach and an expanding population in the intestine. Epithelial folding and multiplication of cell renewal units occurs in solitary species of increasing body size. One cell population occurs on the stomach folds of more primitive solitary ascidians, two of those of advanced species. The digestive diverticulum, which only occurs in two families, is renewed much the same as the stomach, and probably evolved from that organ. In the intestine of primitive solitary ascidians, renewing populations only occur at the anterior end; with evolutionary advancement, renewing populations line the entire intestine.
The male factor in fertilization of rat eggs in vitro
Authors: Shalgi Ruth , Kaplan Ruth , Nebel L. , Kraicer P. F.
Published: June 2005

Both epididymal and ejaculated spermatozoa give usable rates of fertilization of superovulated oocytes in vitro. The epididymal sperm gave higher rates, but ejaculated sperm were preferred because intra‐donor variation was lower than inter‐donor variation. A selected population of 14 male donors had normally distributed fertilizing capacity with a mean and standard deviation of 77 ± 14% (2,823 eggs). Successive ejaculates usually gave similar rates of fertilization. An attempt was made to eliminate dead and agglutinated cells from the ejaculated sperm by filtration through a column of glass beads. Despite the expected marked improvement in the average motility, the eluted spermatozoa were incapable of fertilizing. We concluded that the preferred source of spermatozoa for fertilization in vitro is ejaculated sperm. In the rat, motility and cell morphology are not adequate criteria for fertilizing capacity of treated spermatozoa.
Sperm capacitation in the fallopian tube of the hamster and its suppression by endocrine factors
Authors: Viriyapanich P. , Bedford J. M.
Published: June 2005

Evidence obtained in the rabbit, an induced ovulator, has created a general view that the sperm capacitation ability of the oviduct cannot be modified significantly by ovarian steroids. The possibility that this may not be so in the reproductive tract of cyclic species has been investigated by timed transfer of eggs and spermatozoa into female hamsters maintained in different endocrine states. In estrous females, few native eggs were penetrated by 5 hours, but a majority were penetrated 6–6.5 hours after insemination of fresh epididymal spermatozoa directly into the ovarian bursa. This indicates that a time of approximately 5–6 hours is required for capacitation in the hamster oviduct alone. Up to 2 hours were needed for most eggs to be penetrated after their transfer to oviducts containing fully capacitated spermatozoa. Subsequent experiments using these criteria showed that the ability of the oviduct to support fertilization was affected significantly by the endocrine state of the female. It was not influenced noticeably by ovariectomy. However, whereas maximal levels were seen on days 1,3, and 4, fertilization was reduced significantly (P < 0.001) on day 2 of the estrous cycle when progesterone levels had been elevated for approximately 48 hours. Fertilization of eggs transferred to inseminated oviducts was also reduced comparably in ovariectomized hamsters injected with 3 mg of progesterone twice per day for 9–12 days, and in those that were 8–10 days pregnant. The prospects for complete suppression of capacitation in species with more prolonged cycles and the relevance of this for contraception and analysis of the factors responsible for capacition are discussed.