bluuebunny/crossref_metadata_2025 huggingface dataset:
Origin of melanosome structures and cytochemical localizations of tyrosinase activity in differentiating epidermal melanocytes of newborn mouse skin
Authors: Hirobe Tomohisa
Published: June 2005

The mode of differentiation of epidermal melanocytes was studied by ultrastructural cytochemistry in the skin of newborn mice of strain C57BL/10J. From observations of epidermal melanoblasts and melanocytes, stage I melanosomes, including both unit membranes and inner matrices, appear to be formed from Golgi vacuoles or rough endoplasmic reticulum (RER). Stage I melanosomes were positive to ammoniacal silver‐nitrate reaction in the melanoblasts of 1‐day‐old mice. All stages of melanosomes were similarly positive in the differentiating melanocytes of 2‐day‐old mice. However, Golgi apparatus, RER, and vesicles were negative. Therefore, it is conceivable that structural proteins, originated from Golgi vacuoles or RER, are developed into specialized proteins and are detected by this reaction in stage I melanosomes. Stage I melanosomes were dopa‐negative in the melanoblasts. Stage I and II melanosomes were similarly negative in the differentiating melanocytes. Thus, the melanoblasts are thought to begin production of stage I melanosomes prior to the onset of tyrosinase activity. In the differentiating melanocytes, dopa‐melanin depositions were observed in stage III and IV melanosomes, trans Golgi saccules, and small vesicles derived from these saccules, but not in RER. These vesicles were in contact with, or fused to, melanosomes. These findings suggest that tyrosinase may be transferred by Golgi vesicles into stage I and II melanosomes originating from Golgi vacuoles or RER.
Biology of the scrotum. IV. Testis location and temperature sensitivity
Authors: Bedford J. M. , Berrios M. , Dryden G. L.
Published: June 2005

Whereas abdominal temperatures have no effect on spermatogenesis in testicondid mammals but inhibit the process completely in scrotal mammals, the inguinal testes of the naturally cryptorchid musk shrew and degu have been found to display an intermediate response. Twelve to 18 weeks after transposition to the abdomen (and so about 1.5°C above its normal inguinal temperature) the weight of the testis was reduced by 27% (musk shrew) and 52% (degu). Nonetheless, spermatogenesis continued in both, though at a lower rate and with a greater proportion of abnormal spermatozoa formed. The ultrastructural anomalies evident in some spermatids of the degu testis transposed to the abdomen were reminiscent of those seen commonly in the germinal epithelium of “normal” men. Natural cryptorchids may thus be useful models in which to discover whether spermatogenesis at a temperature somewhat above the norm for the species compromises the ability of fertilizing spermatozoa to support normal development.

The fact that deep‐body temperature induces only a partial suppression of function in the inguinal testis of natural cryptorchids shows that there is no absolute distinction between the scrotal and ascrotal states among mammals with respect to the temperature sensitivity of the testis. That visible sensitivity seems more likely to reflect the adaptation of the metabolically dynamic germinal epithelium to function optimally at the temperature of the location to which the testis migrates, rather than any fundamental incompatability between spermatogenesis and the temperature imposed by homeothermy. External migration of the testis itself may originally have helped the sperm storage region of the associated epididymis to project from and so attain a cooler environment than that beneath the body surface.
Intrafollicular pressure decreases in hamster preovulatory follicles during smooth muscle cell contraction in vitro
Authors: Schroeder Paul C. , Talbot Prudence
Published: June 2005

Smooth muscle cells in the base of hamster follicles contract minutes prior to ovulation; during this contraction the profile of the follicle changes from low to tall. Our purpose was to measure intrafollicular pressure, independent of an intact circulatory system to the ovary, at the time when follicular smooth muscles are known to be contracting. Hamster ovaries were removed 13 hours after hCG injection and placed in a culture medium which supports in vitro ovulation. Intrafollicular pressure was measured continuously with a WPI Model 900 Micropressure system, while the follicle was being observed and photographed using a dissecting microscope and Zeiss 35 mm camera. Initial intrafollicular pressure was 2.1 ± 1.1 mmHg (n = 47) in the absence of a blood supply. This pressure decreased slowly (0.03 mmHg/min.) until the transition from a low to tall profile occurred at which time the pressure decreased at a rate of 0.09 mmHg/min. At ovulation, the pressure drops precipitously to 0.0 mmHg. The condition of the follicle, in particular the apex, was examined using scanning electron microscopy (SEM). At 13 hours after hCG, rupture sites had started forming in the apices of 94.3% of the unovulated follicles. In some instances, surface epithelial cells were stretched apart and gaps were present between cells. More often portions of the surface epithelium were missing and the underlying cell layers were exposed. Fluid and erythrocytes were observed passing through the developing rupture sites. Taken together these observations demonstrate that intrafollicular pressure in hamster preovulatory follicles decreases gradually at the time follicular smooth muscle cells contract. We suggest that contraction of follicular SMC is a slow, gradual process which causes formation and/or enlargement of holes in the rupture site. An increase in the size or number of these apertures would lead to increased leakiness and could account for the observed acceleration in the rate of pressure decrease during profile transition. Our observations are the first to correlate changes in intrafollicular pressure with the contraction of smooth muscle cells and condition of the apex.
Factors controlling the ovarian cycle in a temperate zone anuran, the toad Bufo bufo: Food uptake, nutritional state, and gonadotropin
Authors: Jørgensen C. Barker
Published: June 2005

The relations between nutritional state and vitellogenic growth of oocytes were studied in 87 sexually mature female toads Bufo bufo during the postbreeding season before initiation of the next annual ovarian cycle. Recruitment of small oocytes to vitellogenic growth was correlated with resumption of food uptake and the restoration of a positive energy balance in the toads that had become depleted of energy reserves during hibernation and breeding. Treatment with exogenous gonadotropin (hCG) immediately initiated vitellogenic growth, independently of the nutritional state. But the hCG‐induced vitellogenic growth was faster in toads that ate more than the maintenance ration than in those that ate less. hCG also maintained rapid vitellogenic growth in toads that starved after an initial period of feeding during which vitellogenic growth had been resumed. The results support the hypothesis that the period of ovarian quiescence, which normally follows breeding in Bufo bufo, and other anurans from the northern range of distribution of the species, results from inactivation of the hypothalamic‐hypophysial gonadotropic system, and that reactivation of the system depends upon reestablishment of a proper nutritional state of the organism.
Intercalary regeneration in legs of crayfish: Central segments
Authors: Mittenthal Jay E. , Trevarrow William W.
Published: June 2005

Each leg of a crayfish embodies two types of morphogenetic fields, a limb field and a sequence of segmental fields. These fields were manifest in grafting operations along the proximodistal axis of legs 3 and 4. The propodite was grafted into more proximal segments—carpopodite, meropodite, or basipodite—in one set of operations. In a second set the propodite was host for a graft from the propodite or carpopodite. After these operations intercalary regeneration yielded complete regenerates, which manifested the limb field, and incomplete regenerates, which showed the segmental field. Complete legs contained all structures present in a normal leg. After some operations complete legs also had supernumerary structures. Several types of incomplete legs regenerated—(1) legs with fusion of the host and graft segments; (2) legs with a joint girdling only part of the leg circumference; and (3) legs with one mosaic segment intercalated to replace two deleted segments. These results show that both limb and segmental fields control intercalation in the tested segments of crayfish legs, as in insect legs. We propose a “mode control hypothesis” to describe the way in which molt cycle phase and healing rate bias the type of field controlling regeneration. Our observations also provide clues about the operation of the fields to generate structures. Homologous parts of the segmental field do not necessarily generate analogous structures in different leg segments. Although intersegmental membrane often develops in conjunction with an apodeme (muscle tendon), in a mosaic joint intersegmental membrane can still develop in the absence of the corresponding apodeme. In a partial joint the length of the segments adjacent to the joint is subnormal, but greater than the length of the segments between which a joint is missing. The jointless region may limit the growth of the jointed region.
Effects of saltwater feeding and reduced food intake on femurs of domestic ducklings
Authors: Wink Carole S. , Armstrong Este , Onge Michele St.
Published: June 2005

Seven‐day‐old domestic ducklings were assigned to groups and fed freshwater and food ad libitum (control), 1% NaCl and food ad libitum (stressed), or freshwater and only as much food as the stressed group ate (starved). Tissues were sampled after 3 and 7 days. Other groups of ducklings were fed freshwater and food ad libitum for 9 days (control), 1% NaCl and food ad libitum for 7 days followed by freshwater for 2 days (de‐stressed), or freshwater and the same amount of food as the de‐stressed group for 7 days followed by food ad libitum for 2 days (de‐starved). Body weights were recorded and the femurs were analyzed. Univariate, multivariate, and allometric analyses clearly demonstrate that stressed and starved regimens influence femoral morphology differently. Stressing for 3 days reduced femoral ash and by 7 days had retarded femoral linear growth. Three days fo starvation produced no apparent effect on the femur, but starvation for 7 days reduced the amount of femoral ash/femoral lenght. Furthermore, major differences between stressed and starved ducks disappeared after de‐stressing for 2 days. Studies of bone growht and metabolism may benefit by using this avian model.
Differentiation of the avian secondary palate
Authors: Greene Robert M. , Shah Ravindra M. , Lloyd Martha R. , Crawford B. J. , Suen Roger , Shanfeld Joseph L. , Davidovitch Z.
Published: June 2005

The avian secondary palate exhibits the unique feature of a midline cleft. Cryostat sections indicated that although extensive contact between homologous shelves was present, chick palatal medial edge epithelium (MEE) failed to fuse. The failure of fusion and subsequent clefting of the avian palate were correlated with continued proliferation of the avian MEE, a failure of selective MEE cell death, and an absence of elevated levels of intracellular cAMP. Moreover, immunohistochemical staining for cAMP and microspectro‐photometric quantitation of staining intensity indicated that staining of chick MEE was significantly (p < .01) less than murine MEE at comparable gestational ages. These data indicate that differentiation of the avian secondary palate is fundamentally different than reported for the mammalian palate in that many developmental events known to be associated with normal mammalian palate formation (cessation of MEE proliferation, MEE cell death, elevated levels of MEE cAMP) fail to occur in the chick. The developing avian secondary palate, with its midline cleft, thus provides an interesting and useful model system with which to compare mammalian palate formation where the palate is normally fused in the midline.
Effects of delaying injections of prolactin and actinomycin D on metamorphic changes in thyroxine‐treated Ambystoma tigrinum
Authors: Platt James E. , Luetkehans Daniel L.
Published: June 2005

As a part of our continuing effort to understand the nature of the inhibition of thyroxine‐induced metamorphosis by prolactin in the tiger salamander, we examined the effects of delaying the initiation of prolactin treatment for progressively longer time intervals following the injection of a metamorphosing dose of thyroxine. Prolactin continued to inhibit gill resorption when given either 2 or 4 days following thyroxine, but the magnitude of the inhibition appeared to diminish. Delay of prolactin treatment until day 6 abolished the inhibition. In contrast, tail fin regression appeared to be inhibited in an undiminished fashion by prolactin given 2, 4, or 6 days following thyroxine. Body weight loss was inhibited in a similar manner. In a second experiment, actinomycin D, a transcription inhibitor, was observed to inhibit metamorphic changes. A delay of 5 days in the administration of this drug relative to thyroxine treatment produced a significant reduction in its inhibition of gill resorption, tail fin regression, and body weight loss. Surprisingly, late (day 5 following thyroxine) treatments with prolactin still produced a significant inhibition of fin regression and weight loss even when the inhibitory dose of actinomycin D was given on day 5 along with the prolactin. These results are discussed with respect to their implications concerning our understanding of the mechanism of prolactin action during amphibian metamorphosis.
Male fertility in Drosophila melanogaster: Genetics of the vermilion region
Authors: Geer Billy W. , Lischwe Timothy D. , Murphy Kevin G.
Published: June 2005

Male sterility is one of three phenotypic effects of mutations at three loci in region 9F4 to 10C2 of the polytene X chromosome of Drosophila melanogaster, female sterility and reduced viability being other mutant effects. The male sterile (ms) alleles at these loci are allelic with lethal mutations. Male sterile mutations are induced at lower frequencies than lethal mutations at these loci by EMS. Because gene products of two of the loci are essential to larval development and the product of the other locus is essential to pupal development, the occurrence of ms mutations is not restricted to loci whose products function solely in developing adult tissue. Mutations at a locus in 10A2‐5 cause male sterility without adversely influencing viability or female fertility. We conclude that many loci whose products function in nonreproductive tissue can mutate to a form for which male sterility is a secondary effect. Another group of loci encode products that function exclusively in reproductive tissue.
Comparative feeding and breeding strategies of a sympatric pair of leopard frogs (Rana pipiens complex)
Authors: Frost John S.
Published: June 2005

Ovary weight and fat body weight relative to total body weight were ascertained from samples of Rana magnaocularis and Rana forreri taken routinely from sympatric populations of the two species. Relative fat body weight reaches a maximum in R. forreri in October and November, about 2 months later than in R. magnaocularis (August and September). Relative ovary weight in R. forreri reaches a maximum in July and August, some 8 to 9 months after the fat body peak. In R. magnaocularis, in contrast, maximum relative ovary weight occurs in November, December, and January, only about 2 to 4 months later than the fat body peak. Both species may capitalize on abundant food in late summer to increase fat storage. Maturation of the ova and the laying of eggs are almost completely asynchronous for the two species, however. These differences are considered from the standpoint that they may represent an example of reproductive character displacement via temporal competitive exclusion.
Quantitative study on the reproduction of two strains of agamic planarians Dugesia gonocephala and Dugesia tigrina
Authors: Zaccanti Francesco , Tognato Giovanni
Published: June 2005

In two asexual planarian strains (Dugesia gonocephala and Dugesia tigrina), reproduction by transverse fission and regeneration is observed under normal conditions and upon decapitation and reserpine treatment. The pattern of asexual reproduction processes in planarians, as it results from our quantitative observations compared with the literature data, indicates that autotomy and regeneration processes have an extremely wide range of possible expressions. In such a heterogeneous situation it is still possible to suppose the existence of a negative cephalic control of fissiparity, similar to the ones involved in general tissue organization and in the regeneration of planarians.
Refractive index gradients subserve optical isolation in a light‐adapted reflecting superposition eye
Authors: Nilsson D.‐E.
Published: June 2005

The freshwater shrimp Macrobrachium rosenbergii (de Man) has reflecting superposition compound eyes. Upon adaptation from dark to light conditions, the eye converts from superposition to apposition optics by screening pigment migration. The clear zone, typical of dark‐adapted superposition eyes, persisted after adaptation to 500 lux, when the eye optically behaved like an apposition eye. In this state, optical isolation is maintained by a proximal refractive‐index gradient in the crystalline cone, which only requires the proximal pigment to be in the light‐adapted position around the junction between the cone and rhabdom. Thus, the distal pigment need not invade the clear zone for the eye to convert to apposition optics. This mechanism probably decreases the time required for light adaptation. Furthermore, as a result of total internal reflections in the cone tip, the proximal gradient increases the acceptance angle.
The effects of pulsed magnetic fields on chick embryo cartilaginous skeletal rudiments in vitro
Authors: Archer C. W. , Ratcliffe N. A.
Published: June 2005

The biological response of cultured 7‐day embryonic chick tibiae to small alternating currents induced by pulsed magnetic fields (PMFs) was investigated. It was found that continuous exposure to PMFs over 7 days did not alter the overall DNA content of rudiments nor the incorporation of 3H‐thymidine when compared with control tibiae. The overall collagen content of explants was slightly reduced by PMF exposure whilst the incorporation of 3H‐proline was significantly suppressed. The synthesis of sulphated glycosaminoglycans was also measured in terms of 35SO4− incorporation, but PMF treatment failed to alter the levels of isotope incorporation.

These results suggest that, whereas noncollagenous, and possibly collagenous, protein synthesis is affected by PMF exposure, glycosaminoglycan synthesis is not. Histological and electron microscopical observations substantiated this interpretation and revealed selective inhibition of matrix secretion in the periphery of the proliferative epiphyseal zones in experimental explants. High‐power electron microscope examination of these zones showed that PMF‐exposed matrix was sparsely invested with fibrous protein while elements of the stellate reticulum had formed large aggregates which were often clumped about the cell membrane. The results are discussed in terms of the possible role of naturally occurring potentials in the development and maintenance of connective tissue systems such as cartilage and bone.
Epigenesis in developing avian scales. II. Cell proliferation in relation to morphogenesis and differentiation in the epidermis
Authors: Tanaka Shoji , Kato Yoshihiro
Published: June 2005

Throughout the early development of chicken scale epidermis, consisting of discrete placode and interplacode cell populations, morphogenesis and differentiation were examined from the standpoints of cell proliferation. From day 9.25 to day 11, active cell proliferation was observed only in the interplacode region, whereas the number of constituent cells increased considerably within the placode. After 26 hr of continuous labeling with [3H]thymidine (3H‐TdR) in ovo, three regions could be recognized: (1) unlabeled placode on the distal edge, (2) labeled placode in both lateral and proximal sites to the unlabeled placode, and (3) extensively labeled interplacode on the most proximal site of the scale.

Examination of the distribution pattern of labeled cells has demonstrated that a fraction of the cells in the interplacode transits and annexes only to the proximal side of the placode. Cells transit after mitosis, accompanied with changes in morphology and proliferation activity. During the period of cell transition, orientation of mitosis paralleled completely along the proximodistal axis of the scale. Cell marking with carbon particles was carried in organ cultures from day 10, and the changes in the position of marked cells were observed. The results confirm those obtained after continuous labeling with 3H‐TdR. Various combinations of pulse‐chase experiments with 3H‐TdR clearly demonstrated the establishment of a cell lineage in which cells were aligned along the axis of the scale according to order of their birth. Along with a sudden resumption of active proliferation after day 11, a new class of cells (suprabasal cells) differentiated upward from the basal cells on the top region of the hump scale. At the first stage of development of suprabasal cells from day 11 to day 11.75, the direction of mitoses became preferentially polarized in the direction of axis vertical to the basal lamina. The important coordination of cell proliferation in relation to morphogenesis and cell differentiation is discussed.
Modulation of melanosome ultrastructure in cultured embryonic pigment cells
Authors: Garcia Raul I. , Szabo George
Published: June 2005

Melanosomes synthesized by embryonic chick retinal pigment cells in vitro are of a different size and shape than those made in ovo and in vivo. Ultrastructurally, the melanosomes made by cultured cells are small, spherical, contain an irregular internal matrix, and appear similar to the pheomelanosomes found in red hair and feathers. This modulation in melanosome ultrastructure in cultured retinal pigment cells does not appear to be caused by an irreversible change in differentiated capability but to a response of cells to the culture environment. Cells grown in embryo extract‐free and serum‐free defined media were found to synthesize melanosomes of normal size and shape in vitro, although at a much reduced number. The predominant melanosome type found was still the smaller, spherical variety. It appears that some still unknown factors in the culture environment have produced a shift to a different type of melanogenesis.
The relationship between age and body size of individuals in isolated clutches of the terrestrial slug, Limax maximus (linnaeus, 1858)
Authors: Prior David J.
Published: June 2005

The variability of the relationship between age and growth rate was analyzed using isolated clutches of eggs from the terrestrial slug, Limax maximus. The slugs that hatched from isolated clutches of eggs were weighed every 30 days until they were 150 days old. The weights of the slugs at every age were highly variable. For example, the range of weights at 150 days was 0.21–8.15 gm, which represents a 39‐fold difference. In addition, there was considerable variation in the age of slugs that weighed the same. The mean weights of slugs in clutch T4 at 90 days and of slugs in clutch T2 at 150 days were the same (2.19 gm). Also the ranges of weights at 30 and 150 days indicate that there were 30‐day‐old slugs that weighed the same as some 150‐day‐old slugs. The large variability of growth rate of Limax indicates that age‐related studies of gastropod molluscs will require knowledge of the hatch dates, as well as developmental or biochemical staging schemes.
Tissue‐specific alanopine dehydrogenase and strombine dehydrogenase from the sea mouse, Aphrodite aculeata (polychaeta)
Authors: Storey Kenneth B.
Published: June 2005

Each tissue of the sea mouse, Aphrodite aculeata, contains a single cytoplasmic dehydrogenase acting at the pyruvate branchpoint: Alanopine dehydrogenase (ADH) occurs in longitudinal muscle, nerve, and elytra, and strombine dehydrogenase (SDH) characterizes pharynx and intestine. Lactate and octopine dehydrogenases were not detected in any tissue. ADH from muscle and SDH from pharynx were partially purified. The two enzymes had the same molecular weight, 44,000 ± 4,000 but differed in isolelectric point. Although similar in keto acid specificity, the enzymes differed strongly in amino acid specificity. Pharynx SDH showed a very high specificity for glycine, all other alternative amino acids showing very high apparent Kms and/or low Vmaxs. Muscle ADH, however, displayed high velocities and relatively low apparent Kms with L‐alanine, L‐serine, L‐threonine, and L‐cysteine. Amino acid analysis of the tissues showed that serine and threonine contents were high enough in muscle to suggest that these amino acids might be alternative substrates to alanine in vivo; only glycine, present at 382 μmol/g in pharynx, is likely to be a physiological substrate for SDH, however. Absolute Kms for L‐alanine, glycine, and pyruvate were 2.75 ± 0.03, 285 ± 6, and 0.2 ± 0.006 for muscle ADH and 130 ± 2.2, 26 ± 1 and 0.15 ± 0.005 for pharynx SDH. In the reverse direction, apparent Kms for meso‐alanopine, D‐strombine, and NAD, at pH 9.5, were 1.68 ± 0.06, 87.0 (n = 1), and 0.75 ± 0.03 for ADH and 6.75 ± 0.20, 7.57 ± 0.07, and 0.54 ± 0.02 for SDH. The enzymes also differed strongly in effects of inhibitors. Meso‐alanopine, L‐lactate, and D‐lactate were strong inhibitors of the forward reaction for muscle ADH. Pharynx SDH, however, was strongly inhibited by meso‐alanopine and iminodiacetic acid but showed only weak inhibition by D‐ or L‐lactate or by its product, D‐strombine.
A histological and dynamic study of the gastric region of Discoglossus pictus larvae, cultured with or without thyroxine
Authors: Pouyet J. C. , Hourdry J. , Mesnard J.
Published: June 2005

The organotypic culture of the gastric region is carried out on premetamorphic Discoglossus pictus larvae. Adding thyroxine to the culture medium provokes various transformations. On the cytological level, the reactions observed, which are variable depending on the cell category concerned, can be divided into two types of phenomena: histolytic and histogenetic. Auto‐phagia linked to lysosome intervention is frequently found among the histolytic processes. Autophagic vacuoles and residual bodies are observed. The gastric lumen is filled with deteriorated cells that probably come from the degeneration of the tadpole epithelium (primary epithelium). The incorporation of tritiated thymidine makes it possible to study the evolution of cell proliferation in the control and in the thyroxinated cultures. After a 1–2 day latency period, possibly due to the adjustment of the tissue to the culture environment, the incorporation of the radioprecursor H3‐thymidine into the epithelium and the tunica muscularis of thyroxine‐treated gut tissue increased on day 3, reached a maximum on day 5, and then dropped slightly on day 7. In the control cultures H3‐thymidine incorporation showed the same pattern but lower levels on the same days. The histolytic phenomena induced by thyroxine in vitro are comparable to those of natural metamorphosis. On the other hand, the histogenetic phenomena are incomplete. Proliferating and transitional phases occur but neoformated (or secondary) epithelium does not replace the degenerated primary epithelium, whatever the culture time.
Studies on the mechanisms of neurulation in the chick: Possible involvement of myosin in elevation of neural folds
Authors: Lee Hsin‐Yi , Kosciuk Mary C. , Nagele Robert G. , Roisen Fred J.
Published: June 2005

The possible involvement of myosin in elevation of neural folds in the chick was studied. Indirect immunofluorescence revealed the presence of myosin in the neuroepithelium as early as the neural‐plate stage and was concentrated in the apical regions of neuroepithelial cells where microfilaments are known to be organized into discrete bundles. This fluorescent pattern persisted until closure of the neural tube. Actin‐specific fluorescence followed a similar distribution pattern as myosin. Diazepam (Valium/Roche), at 400 μg/ml, was found to preferentially inhibit elevation of neural folds in explanted stage 8 embryos within 6 hr of incubation. Affected neuroepithelial cells were often less elongated, contained thinner and less conspicuous microfilament bundles, and had apical surfaces which were smoother and broader than the controls. These morphological changes were accompanied by a considerable reduction in the intensity of myosin‐specific fluorescence, particularly in the cell apices. Results suggest that (1) diazepam inhibits elevation of neural folds through its disruptive effects on the organization and contractility of apical microfilament bundles in developing neuroepithelial cells and (2) myosin may be directly involved in elevation of neural folds.
Developmental arrest of endoparasitoid wasp larvae (Nemeritis canescens grav.) caused by an ectoparasitoid wasp (Bracon hebetor say)
Authors: Petters Robert M. , Stefanelli Joseph
Published: June 2005

The effect of Bracon hebetor‐induced host paralysis on the development of Nemeritis canescens was examined. These two wasp species were found to often coexist at the same location and can utilize the same host species. N. canescens females were allowed to oviposit into Anagasta kuehniella larvae. The parasitized host caterpillars were then exposed to B. hebetor females which paralyzed the caterpillars with a venom. Subsequent to host paralysis and removal of the B. hebetor females, host caterpillars were dissected daily to determine the developmental stage of the endoparasitoid N. canescens larvae. Virtually complete inhibition of development occurred when host paralysis was induced within 12 hours of N. canescens oviposition although larval movement and morphology were normal. Developmental inhibition also took place when host paralysis was induced 1 week after oviposition but it required a few days to become evident. The possible mechanisms of developmental arrest are discussed.
Adhesion of mouse blastocysts to uterine epithelium in culture: A requirement for mutual surface interactions
Authors: Morris John E. , Potter Sandra W. , Rynd Lori S. , Buckley Patricia M.
Published: June 2005

Blastocysts readily adhered to inert materials in culture, but they resisted adhesion to living cells even after several days under conditions which encouraged cell aggregation. As far as could be determined by observing their spreading behavior on polylysine‐ and polyglutamate‐coated dishes, the mechanism of adhesion of blastocysts to inert surfaces was similar to that of freshly dissociated cells and cell lines. However, their adhesion to vesicles of isolated uterine epithelium, which was encouraged by hanging drop culture, was by a different mechanism that involved microvilli on both the embryonic and maternal surfaces. This interactive step, which was similar to that seen during attachment in vivo, was followed by a brief period of close trophoblast‐epithelial contact which led ultimately to phagocytosis of sloughed epithelium. Blastocysts showed a clear preference for adhesion to cultured epithelium in vesicles that had begun to collapse. In this case the cells showed a columnar profile with sharply defined microvillous apexes, unlike the flattened cells in fully expanded vesicles or on culture dishes. We conclude that the preimplantation adhesion of mouse blastocysts requires specific changes on both the embryonic and maternal surfaces to overcome the mutual nonadhesiveness typical of epithelia. The relatively rapid adhesion of blastocysts to a culture dish, on the other hand, is more typical of the well‐known spreading behavior of cells on a highly attractive surface.
Determination of the rate of rRNA synthesis in Xenopus laevis triploid embryos produced by low‐temperature treatment
Authors: Tashiro K. , Misumi Y. , Shiokawa K. , Yamana K.
Published: June 2005

Triploid embryos of Xenopus laevis were obtained by cold‐temperature shocking of the fertilized eggs, and the rate of the ribosonial RNA (rRNA) synthesis was determined for comparison with that in diploid embryos. For this purpose, both triploid and diploid embryos were dissociated into cells at the neu‐rula stage, and then labeled with (3H)uridine for varying lengths of time. The rate of rRNA synthesis, as estimated after determination of (3H)UTP specific radioactivity and the total label incorporation into the purified rRNA, was about 0.1 pg/cell/hr for both diploid and triploid embryo cells.

Nuclei of triploid embryo cells contained three nucleoli of apparently similar sizes—an indication of the functioning of all the three rRNA gene clusters to a more or less similar extent. Also, rates of synthesis of 4S RNA and 5S RNA were determined: Both rates did not change appreciably between triploid and diploid embryo cells. Based on these results, it appears that transcription of these redundant genes occurs at a constant rate on a per cell basis irrespective of the presence of 1.5 times as many genes as the control.
Localization of actin in the sperm head of the plains mouse, Pseudomys australis
Authors: Flaherty Sean P. , Breed William G. , Sarafis V.
Published: June 2005

Actin was localized in the sperm head of the plains mouse, Pseudomys australis, using NBD‐phallacidin, a fluorescent‐labeled phallotoxin. It was found to be present in the two ventral hooks in sperm from the testis, epididymis, and vas deferens. Faint fluorescence was observed in other regions of the sperm head, whereas autofluorescence occurred in the midpiece of the tail in some preparations. The material in the ventral hooks was also found to be birefringent, which is consistent with it showing preferential orientation.
Evidence that the ciliate Euplotes raikovi releases mating inducing factors (gamones)
Authors: Luporini Pierangelo , Miceli Cristina , Ortenzi Claudio
Published: June 2005

Eight mating type complementary strains of E. raikovi were mixed two by two in all the possible combinations. In addition to heterotypic pairs, homotypic pairs of both mixed strains were usually found. Each strain was then suspended with the cell‐free fluid obtained from any other complementary strain. Most strains appeared capable of both producing an active cell‐free fluid and responding to a heterotypic cell‐free fluid by pairing. The induced pairs were usually able to complete conjugation, to survive, and to yield viable offspring. The results indicate that mating inducing factors (gamones) are normally released into the extracellular environment by the E. raikovi cells.
Oxygen consumption and whole body lactate accumulation during progressive hypoxia in the tropical freshwater prawn,Macrobrachium rosenbergii(de Man)
Authors: Spotts Daniel G.
Published: June 2005

Daytime and nighttime rates of oxygen consumption (VO2) were determined for young freshwater prawns during progressive hypoxia. During daytime hypoxia VO2fell slightly, then was maintained at 0.200 ml O2/gm/h to 40 mm Hg partial pressure of oxygen. Below 40 mm Hg VO2fell markedly. At night VO2averaged 0.310 ml O2/gm/h before falling at a critical pressure (Pcr) of 65 mm Hg. Sets of prawns were exposed to progressive hypoxia both day and night at rates simulating conditions during the closed respirometry studies. Prawns were sacrificed at different PO2s and analyzed for whole body lactate concentrations. Concentrations of 0.153 mg lactate/gm body weight were unchanged until the respective Pcrwas reached during either day or night. Below Pcrlactate concentrations increased at a constant rate regardless of the severity of hypoxia. Combined aerobic metabolism and anaerobic glycolysis did not increase as a result of progressive hypoxia, indicating a small energy requirement for oxyregulation. Anaerobic energy production via glycolysis during hypoxia proceeded at only 1–3% of the regulated aerobic metabolism. This is much less than in other crustaceans, underscoring the importance of well‐aerated environments both inMachrobrachium rosenbergii'snatural habitat and under aquaculture conditions.
Increased amino acid oxidation in the gills of blue crabs acclimated to dilute seawater
Authors: Pressley Thomas A. , Graves James S.
Published: June 2005

Substrate oxidation was measured in the gills of blue crabs, Callinectes sapidus, acclimated to different salinities. The oxidation rates for glucose and the four major amino acids of hemolymph were about twice as great in the gills from crabs acclimated to 17%0 seawater relative to the gills from crabs acclimated to full‐strength, 35%0 seawater. Alanine oxidation contributed about 36% to the total CO2 released from amino acid oxidation. Alanine was also deaminated and released into the medium as α‐keto acids. Both alanine oxidation and α‐keto acid formation were concentration dependent and did not appear to reach saturation within physiological concentrations. However, the rates of amino acid oxidation were not sufficient to explain the efflux of NH4+ in excised gills.
Contractions of amphibian Wolffian duct in response to acetylcholine, norepinephrine, and arginine vasotocin
Authors: Zoeller R. Thomas , Lais L. Terry , Moore Frank L.
Published: June 2005

The regulation of sperm transport through the Wolffian duct of male amphibians is poorly understood. These experiments were conducted using rough‐skinned newts (Taricha granulosa) to determine if Wolffian ducts are capable of contracting in vitro and, if so, to characterize the contractile responses to acetylcholine (ACh), norepinephrine (NE), and neurohypophysial hormones. Dose‐response curves for NE and ACh, which were prepared by measuring isometric contractions, are similar to those reported for mammalian vas deferens. For NE, the minimum effective dose and ED50 were found to be 1 × 10−5 M and 4.17 × 10 −5 M, respectively. For ACh, the minimum effective dose was 3.2 × 10−8 M and the ED50 was 1.37 × 10−5 M. Alpha‐adrenorecep‐tors appear to mediate the contractile responses to NE because phentolamine (10 −5 M) blocked or attenuated the response to NE (10−6 M, 10−5 M or 10−4 M). Beta‐adrenoreceptors appear to mediate relaxation because dichloroisoproterenol (10 −5 M) enhanced the response to 10−5 M NE. The contractile response to three neurohypophysial hormones were also investigated. Arginine vasotocin was more effective in eliciting contractions than oxytocin. The effect of lysine vasopressin was intermediate between arginine vasotocin and oxytocin. These experiments demonstrate that amphibian (Taricha) Wolffian ducts contract in vitro in response to neurotransmitters and neurohypophysial hormones. The contractile response to neurotransmitters occurs in a dose‐dependent manner; the response to neurotransmitters and neurohypophysial hormones is hormone specific.
Hatching in the teleost Oryzias latipes: Limited proteolysis causes egg envelope swelling
Authors: Schoots Andréa F. M. , Sackers Ruud J. , Overkamp Perry S. G. , Denucé J. Manuel
Published: June 2005

Homogenates of hatching gland explants were fractionated by means of different electrophoretic techniques, and the fractions analyzed for proteolytic activity and for their capacity to affect the envelope of the eggs. Agar gel electrophoresis resulted in two fractions that were able to digest the zona radiata interna, and a third fraction that caused a significant swelling of the egg envelope. All three fractions were proteolytically active. Agarose gel and polyacrylamide gel electrophoresis gave only two fractions that showed proteolytic activity and were capable of digesting the zona radiata interna. The presence of these two fractions may imply that hatching enzyme is stored as proenzyme in the hatching gland granules. Swelling of egg envelopes was also observed during envelope digestion by thermolysin, pronase, and 0.5–1.0 N NaOH. Moreover, breakdown by hatching enzyme and pepsin under suboptimal conditions showed a slight swelling of the envelope. These results demonstrate that substances capable of solubilizing the zona radiata interna may cause envelope swelling. The swelling of the envelopes probably represents an intermediate phase in the proteolysis of the zona radiata interna. The agar gel electrophoresis fraction of hatching gland homogenates that causes swelling may contain a physicochemically different form of hatching enzyme.
Syntheses of nucleic acids during spermatogenesis in Nereis diversicolor (Annelida Polychaeta): A quantitative autoradiographic study
Authors: Bertout Marc
Published: June 2005

The development of DNA and RNA synthesis in the germ cell population was studied after a 3H‐thymidine or 3H‐uridine pulse at each stage of spermatogenesis. The autoradiographic results show that the first sign (after 3 days in vitro) of cellular changes is an increase in RNA synthesis which reaches a maximum at day 5. DNA replication (premeiotic S phase) occurred at day 7, then cells entered meiotic prophase (day 9). Meiotic divisions and spermiogenesis occurred after 11 days. Silver grain counts permit the conclusion that RNA synthesis is clearly higher during premeiotic interphase (days 3–7) than during spermatogonial proliferation (day 0). It appears therefore that male meiotic differentiation in Nereidae is accompanied by increased RNA synthesis.
Carbonic anhydrase localization in the elasmobranch rectal gland
Authors: Lacy Eric R.
Published: June 2005

Carbonic anhydrase (CA) activity was histochemically localized in the elasmobranch rectal gland at the light and electron microscopic levels. Reaction product in the secretory tubules was localized coincident with that reported for sodium‐potassium activated adenosine triphosphatase (Na‐KATPase): along the highly amplified basolateral plasma membranes of the epithelial cells. Reaction product was also localized along the plasma membrane of adjacent central canal epithelial cells. The results suggest that CA plays a role in modulating the environment of the intercellular space which in the secretory tubule is believed to be the paracellular pathway for sodium. The results also draw attention to the possible role of the central canal epithelium in modification of the secreted fluid.
Thermoperiodic and photoperiodic influences on daily and seasonal changes in the physiology of the male green anole, Anolis carolinensis
Authors: Noeske Teresa A. , Meier Albert H.
Published: June 2005

Male green anole lizards, Anolis carolinensis, were kept for 22 days on one of five temperature regimes: constant 20°C, constant 30°C, or a thermoperiod (8 h at 30°C, 16 h at 20°C) with heat onset at 0, 8, or 16 h after light onset. Groups of animals on each temperature regime were sacrificed at one of six times of day, every 4 h, for 24 h. The experiment was repeated at three different times of year: April (animals were kept on a photoperiod of LD 13:11), August (LD 13.5:10.5), and December (LD 10.5:13.5). Weight gain, testes weights, reproductive stage, and abdominal fat body weights varied with the temperature treatment and with the season. Depending on the time of day lizards received the warm temperature phase of the thermoperiod, increased heat could be stimulatory to weight gain and reproductive indexes in comparison to heat treatment at other times of day. The effect of constant temperatures on testis state and body weight gain was different from that of the thermoperiod regimes and of the natural environment on these processes.

There were also diel variations in both testis DNA synthesis and fat body lipogenesis in the green anole. The photoperiod appeared to set the daily variation of DNA synthesis in the testis, whereas the thermoperiod phased the daily variation of fat body lipogenesis.
Characterization of molluscan phagocyte subpopulations based on lysosomal enzyme markers
Authors: Granath Willard O. , Yoshino Timothy P.
Published: June 2005

This study quantitatively analyzed the distribution and abundance of the lysosomal enzyme markers, acid phosphatase (AP), nonspecific esterase (NE), and peroxidase (PO) within and between the phagocytes (hemocytes) of two strains of the snail, Biomphalaria. Glabrata, vector host for the human blood fluke, Schistosoma mansoni. Discrete subpopulations of AP‐, NE‐, and PO‐staining cells were found in the glass‐adherent hemocyte population of both schistosome‐resistant (10‐R2) and susceptible (PR albino) strains of the snail. Furthermore, there were significant differences in the distribution and abundance of the different enzymes defining the subpopulations within and between the snail strains. Generally, 10‐R2 hemocytes have a higher enzymatic activity than PR albino cells, which, in part, can be attributed to larger NE‐only, AP‐only, and AP + NE‐staining hemocytes in the 10‐R2 strain, and a larger subpopulation of negative cells in PR albino snails. Moreover, these differences in hemocyte enzyme content are further augmented by the fact that the 10‐R2 strain has nearly twice as many circulating, glass‐adherent blood cells when compared to PR albino snails. These findings may be of additional significance, since previous studies have implicated hemocyte lysosomal enzymes in the killing of schistosome larvae in naturally resistant 10‐R2 snails, although accurate measurements of strain‐specific enzyme levels in these cells have not been conducted. The present study provides direct evidence that 10‐R2 snails naturally possess a much greater lysosomal enzyme content than do those of the PR albino strain, which, in turn, may be related to the observed resistance or susceptibility in these two molluscan strains.
Vitellogenic cycles in laboratory‐maintained females of the leopard frog, Rana pipiens
Authors: Smalley Katherine N. , Nace George W.
Published: June 2005

As a part of studies on the reproduction of laboratory maintained frogs, wild‐caught Rana pipiens were ovulated and maintained a t 22–27°C for up to 18 months. Vitellogenic oocytes were periodically staged and counted, and a “maturity index” was calculated to assess the progress of the vitellogenic cycle. The initial cycle was similar to that of wild frogs except that the first oocytes to reach stage 5 (mature eggs) usually began to degenerate before later starting oocytes became mature. In addition, a second cycle began before the first was completed. After more than 1 year at room temperature, abnormal cycles were common. Ovaries of such animals contained very few mature eggs. Many of their oocytes were in early stages of vitellogenesis or, if pigmented, had begun to degenerate. These deficiencies were partially corrected in females placed in 4°C for 4–6 weeks. The average number of mature eggs increased 15‐fold and ovary weights more than doubled. Oviduct weights almost doubled. Although the rates of cooling, photoperiod, and nutritional status could be important influences, the results imply that cold treatment alone increases estrogen secretion. We suggest that low estrogen secretion may account for the reproductive deficiencies seen in R. pipiens cultured at room temperature.
Uncoordinated synthesis of histones and DNA by mouse eggs and preimplantation embryos
Authors: Kaye Peter L. , Church Robert B.
Published: June 2005

The temporal coordination of histone and DNA synthesis in mouse eggs and preimplantation embryos were examined. In unfertilized mouse eggs arrested at metaphase II, histone synthesis was observed, but at lower rates than previously reported for fertilized zygotes. Cytosine arabinoside, an inhibitor of DNA synthesis, was used to study the relationship between DNA and histone synthesis during cleavage stages of mouse development. Cytosine arabinoside (50 μM) inhibited by 90% the incorporation of [3H]thymidine into DNA by two‐cell embryos and blastocysts. At this concentration, cytosine arabinoside inhibited incorporation of [3H] lysine into blastocyst histones by only 30% and had no effect at the two‐cell stage. These results are interpreted to show that DNA synthesis and histone synthesis are not coordinated temporally during early development of the mouse, but may become more so as development proceeds.