bluuebunny/crossref_metadata_2025 huggingface dataset:
Aberrent regeneration in carcinogen‐treated earthworms (Eisenia foetida)
Authors: Andrews Edwin J.
Published: June 2005

Groups of earthworms (Eisenia foetida) were injected either with 1% methyleholanthrene (MCA), 0.5% 7–12, Dimethylbenz (a) anthracene (DMBA) or 3 × 10−4 mg of N‐methyl‐N‐nitrosoguanadine (NMNG), After one week, the posterior ten segments were removed from all worms. Twenty‐five days after amputation the mumber of regenerated segments were counted. A statistically significant overgrowth of segments occurred in MCA‐treated worms as compared to controls. DMBA treatment failed to alter the mumber of regenerating segments and worms treated with NMNG had statistically fewer regenerating segments than controls. An overgrowth of segments also occurred in certain groups of vehicle‐injected control worms. The groups receiving oil‐based vehicles had significantly greater growth than Hank's Balanced Salt Solution injected controls. A new theory of the mechanism of regeneration is offered to explain the seemingly paradoxical results.
Effects of sperm concentration on the capacitation of rat spermatozoa
Authors: Niwa K. , Chang M. C.
Published: June 2005

Rat epididymal spermatozoa were preincubated for various times in concentrated (9.6–14.9 × 106 sperm/ml) or diluted form (0.7–1.2 × 106 sperm/ml) and mixed at similar concentrations with eggs recovered from superovulated immature rats. When the eggs were examined at various times after insemination, the penetration rates, the time of sperm penetration, and the fertilizing capacity of sperm were greatly reduced following the preincubation of spermatozoa in a concentrated form for 5–7.5 hours. By preincubation of sperm in diluted form, capacitation of spermatozoa was achieved in 3–5.5 hours, the penetration rates were increased, and the interval between insemination and sperm penetration was progressively reduced as the duration of preincubation increased up to 7.5 hours. It appears that the sperm concentration plays an important role for the capacitation of rat spermatozoa in vitro and the maintenance of their fertilizing capacity.
Intrinsic rhythmic contractions in insect skeletal muscle
Authors: Hoyle Graham , O'Shea Michael
Published: June 2005

A constant slow rhythm of contraction and relaxation has been discovered in the extensor tibiae (jumping muscle) of saltatory orthopterans. The rhythm is present in the intact insect and persist in the isolated leg, but is abolished when the leg is perfused with saline. The amplitudes and durations of contractions and also the intervals between them, are subject to central nervous modulation. The rhythm may serve to exercise muscle fibers and to promote movement.
In vitro secretion of α‐ecdysone by prothoracic glands of a hemimetabolous insect, Leucophaea maderae (Blattaria)
Authors: Borst David W. , Engelmann Franz
Published: June 2005

Prothoracic glands of the cockroach Leucophaea maderae were maintained in organ culture under defined conditions. Examination of the culture medium from mid‐instar glands revealed material which gave a positive response in an ecdysone radioimmune assay and the Musca bioassay. The material was identified as α‐ecdysone on the basis of its co‐chromatography with α‐ecdysone on thin layer chromatography and gas liquid chromatography using the highly selective electrone capture detector. Only very low amounts of secreted material were detected from glands of early last instar nymphs or 1 day adults. No material was secreted from several control tissues.
Growth of crustacean muscle: Asymmetric development of the claw closer muscles in the lobster, Homarus americanus
Authors: Goudey Linda R. , Lang Fred
Published: June 2005

Muscle fiber types were examined in lobsters using sarcomere length measurements. In the adult, the slender cutter claw was comprised of fast and slow fibers, while the broader crusher contained only slow fibers. In the juvenile lobster, both the cutter and crusher contained fast and slow fibers. Lengthening of sarcomeres is postulated for some fibers during growth and development of crustacean muscle.
Cell migration into the “established” lateral motor column in Rana pipiens larvae. II. Lumbosacral spinal cord and comparative aspects
Authors: Pollack Emanuel D. , Kollros Jerry J.
Published: June 2005

Neuronal turnover has been demonstrated during the period of differentiation and maturation of motor neurons in the developing lateral motor columns of Rana pipiens larvae. As determined by thymidine‐3H labeling, cells continued to migrate into the lateral motor column (LMC) while there was a concurrent reduction in LMC cell numbers. Notably, cells in the lumbosacral LMC ceased to be labeled following thymidine‐3H injection at an earlier time than for the brachial LMC. This is consistent with a caudo‐cephalic direction of development among the two pairs of motor columns in the spinal cord.

Since neuronal turnover occurs following the initial formation of the LMC and continues after the maximum number of cells has been attained, it is proposed that neuronal turnover may be a mechanism that allows for neural readjustment and refinement during spinal cord development.
Phosphatase active antigens in sea urchin eggs and embryos. I. Substrate specificity, pH‐optima and inhibitors
Authors: Westin Monica
Published: June 2005

Phosphatase activity in sea urchin embryonic antigens was investigated by histochemical staining of immunoprecipitates separated by two‐dimensional (crossed) immunoelectrophoresis. Unfertilized eggs were homogenized in a hypotonic medium which solubilized cytoplasmic antigens. Antigens integrated in membranes or enclosed in particles were solubilized by detergent treatment of the residual pellet. Two different phosphatase activities were discerned in the unfertilized eggs, nucleoside diphosphatase (EC 3.6.1.6.) and acid phosphatase (EC 3.1.3.2.). Nucleoside diphosphatase activity was obtained in both the water soluble and detergent extracted protein fractions. This activity was confined to one antigen. Acid phosphatase activity on the other hand was almost exclusively obtained in the detergent extracted fraction and about ten distinct antigens displayed this activity. The nucleoside diphosphatase active antigen preferentially hydrolyzed purine nucleoside diphosphates and to a lesser degree triphosphates of these nucleosides. The acid phosphatase active antigens had a broader substrate specificity and hydrolyzed equally well β‐glycerophosphate and nucleotides. Both activities were essentially inactive at neutral or alkaline pH values. The activities were inhibited by p‐choloromercuribenzoate and accordingly stimulated by cysteine. Tartrate and sodium fluoride, however, inhibited the acid phosphatase activity while nucleoside diphosphatase activity was either stimulated or not affected at all by these agents.
Conjugation in Oxytricha bifaria: Cell interaction
Authors: Ricci Nicola , Esposito Fulvio , Nobili Renzo
Published: June 2005

As a model of cell interaction, the mating process of Oxytricha bifaria has been investigated. Mating involves several distinct and stereotyped stages, each lasting a determined time, and ending with the formation of firmly united pairs. A “waiting period” intervenes between the mixture of complementary mating types and the onset of cell interaction. A proper starvation shortens the waiting period (25 min vs 120 min). Treatment of properly starved cells with heterologous cell‐free fluid further reduces the waiting period. Certain enzyme treatments (pronase, trypsin and lipase) dramatically increase the waiting period in both washed enzymetreated cells and in unwashed cells. Trypsin inhibits the first two stages of the mating process, while lipase inhibits membrane fusion between mates.
Irradiation inhibits the regeneration of aneurogenic limbs
Authors: Wallace H. , Maden M.
Published: June 2005

The developing arms of axolotl larvae from the 2‐digit stage onward and the aneurogenic arms of surgically denervated larvae maintained in parabiosis are able to regenerate after amputation. Such regeneration is uniformly inhibited by local irradiation of the arm, whether innervated or not. This demonstration refutes a recent hypothesis that X‐rays interfere with a special activity of nerves required for regeneration, and supports the earlier concept that X‐rays act directly on those cells which must proliferate to form the regenerated tissues.
Phenoloxidase in the periostracum of the marine bivalve Modiolus demissus dillwyn
Authors: Waite J. Herbert , Wilbur Karl M.
Published: June 2005

Phenoloxidase was extracted from Modiolus demissus mantles and periostraca with the detergent sodium dodecyl sulfate. Partial purification of the periostracal enzyme was achieved by gel filtration and polyacrylamide gel electrophoresis. The enzyme, present in the mantle in latent or proenzyme form, can be chymotryptically activated. Molecular weights of the proenzyme and active enzyme as determined by SDS gel electrophoresis were 80,000 and 70,000 daltons, respectively. A considerable portion of phenoloxidase activity in the periostracum is associated with a large macromolecule that cannot be reduced into smaller subunits, suggesting enzyme covalently immobilized by quinones. Optimal pH of 8.0–8.5 was found for the active enzyme (MW 70,000). Activity was diminished by adding copper chelators or by reducing disulfide bonds. In the former case, activity was restored by titrating the inhibitor with divalent copper. A hydrophobic active site on the enzyme is suggested by low Km and high reaction velocities for substrates with high partition coefficients in 2‐octanol:water such as 4‐methylcatechol and 4‐butylcatechol.
The effects of temperature and thermal acclimation upon the osmotic properties and nonelectrolyte permeability of liver and gill mitochondria from rainbow trout (Salmo gairdneri)
Authors: Hazel Jeffrey R. , Schuster Victor L.
Published: June 2005

Thermal acclimation of rainbow trout (Salmo gairdneri) taken from 20°C to 7°C resulted in adaptation of mitochondrial function, as evidenced by increases in the specific activities of NADH‐ and succinate‐cytochrome c reductase of 1.93‐ and 2.7‐fold respectively. Mitochondria from both gill and liver obeyed the Boyle‐van't Hoff relationship in the range from 400 to 60 mosM. Thermal acclimation had no effect on the osmotic properties of liver mitochondria, whereas gill mitochondria from cold‐acclimated trout were more sensitive to osmotic swelling than mitochondria from warm‐acclimated individuals. The non‐electrolyte permeability of liver mitochondria was assessed by optically monitoring mitochondrial swelling rates in isosmotic solutions of urea, glycerol, mannitol and glucose. Two parameters of mitochondrial swelling were determined: (a) initial swelling rates, d(1/A)dt, and (b) swelling constants, ks, derived from the time required to swell a fixed volume. Regardless of the assay temperature or the permeant employed, liver mitochondria from cold‐acclimated trout exhibited greater initial swelling rates than mitochondria from warm‐acclimated trout, indicating properties of temperature‐compensated permeability. The apparent ranking of nonelectrolyte permeabilities was urea > glycerol > mannitol > glucose. ks values for urea and glycerol from cold‐acclimated trout were greater than values typical of warm‐acclimated populations; however ks values for glucose and mannitol were not influenced by thermal acclimation. Regardless of the permeant considered, activation energies for ks values were 3‐ to 5‐fold greater than those for initial swelling rates. The time course of mitochondrial swelling consists of two components, an initial rapid swelling phase characterized by a half life of 3–12 seconds, and a slower swelling phase characterized by a half life of 1–6 minutes. Initial swelling rates, which approximate the rapid swelling component, are considered to be the least ambiguous index of permeability, whereas ks values are more complex and strongly influenced by the slower swelling component.
Intercalary and supernumerary regeneration in regenerating and mature limbs of Notophthalmus viridescens
Authors: Bryant Susan V. , Iten Laurie E.
Published: June 2005

We describe the ability of advanced limb regenerates and mature limbs of Notophthalmus viridescens to undergo intercalary and supernumerary regeneration following grafting operations to confront normally nonadjacent cells. Although both of these types of regeneration are known to be exhibited by regenerating limbs up to the stage of early digits, this is the first investigation of these abilities in mature limbs of Notophthalmus viridescens using similar grafting procedures. The autopodia of mature limbs, or regenerates at the stage of late digits or older from a distal level of amputation (distal third of forearm), were transplanted to other limb sites so as to oppose either anterior and posterior, or dorsal and ventral positions of stump and transplant. Following transplantation of either the regenerate or the mature autopodium, supernumerary limbs were sometimes formed, and their handedness, position and orientation were, in those cases in which they could be accurately determined, similar to what has been found previously in experiments on younger regenerates. Unlike the results of the experiments on regenerating limbs, when mature autopodia were grafted ipsilaterally with 180° rotation, the handedness of the supernumerary limbs could seldom be determined, and their location appeared to be random. An enhancement of the incidence of supernumerary limb formation in mature limb grafts was noted when the grafts were made so as to oppose normally nonadjacent proximal‐distal as well as circumferential positions.

When advanced regenerates were grafted ipsilaterally and without rotation to a more proximal limb level (mid upper arm), good intercalary regeneration of the distal portion of the humerus as well as the radius and/or ulna occurred in most, but not all cases. When similarly grafted mature autopodia were examined, it was found that none of the limbs formed a complete intercalary regenerate, but the majority formed partial intercalary regenerates by completing the humerus. When mature autopodia were grafted so as to oppose normally non‐adjacent circumferential as well as proximal‐distal positions, then the intercalary regenerate was more complete and frequently included a regenerated radius and/or ulna, normally in conjunction with one or more supernumerary limbs. The similarities between these findings and our earlier ones on intercalary and supernumerary regeneration in regenerating newt limbs are discussed in terms of a recently developed model for pattern regulation in epimorphic fields.
Patterns of heart and scaphognathite activity in the crab Cancer magister
Authors: McDonald D. G. , McMahon B. R. , Wood C. M.
Published: June 2005

The respiratory system of the crab Cancer magister has been investigated with long‐term measurements of the activity in the heart and scaphognathites of unrestrained animals settled on a natural, sandy substrate. Although crabs generally remained motionless in the experimental apparatus, except while in the dark, they initially exhibited a high degree of respiratory activity; the rates of forward pumping by the scaphognathites exceeded 90/minute, reversal incidence was less than five reversals/10 minute and heart rate was constant. Subsequently both the heart rate and the forward pumping rates of the scaphognathites declined, incidence of reversals increased and spontaneous pauses by the heart and scaphognathites began to occur. Eventually one scaphognathite ceased pumping for prolonged periods. Possible roles for reversals, pauses and unilateral pumping are discussed.
Photoperiodic and thermoperiodic interaction affecting fat stores and reproductive indexes in the male green anole, Anolis carolinensis
Authors: Noeske Teresa A. , Meier Albert H.
Published: June 2005

Daily fluctuations in warm (30°C) and cold (20°C) temperatures have different effects on fat stores and gonad weights of male Anolis carolinensis than constant warm or cold temperatures; and the effects vary depending on the phase relations of the daily thermoperiod with a daily photoperiod. In addition there is a seasonal change in the thermoperiod‐photoperiod interaction. For example an 8‐hour interval of warm temperature beginning eight hours after the onset of a 6‐hour daily photoperiod during July is more stimulatory for testicular weights than similar intervals of warm temperature beginning at 0 or 16 hours after the onset of light, but it is less stimulatory in October. The results suggest that the interaction of thermoperiodic and photoperiodic cycles may have important roles in regulating the annual cycles of reproduction and lipid metabolism.
Regulation of the bacterial microflora of the vagina in cyclic female rats
Authors: Koiter T. R. , Hazenberg M. P. , Van der Schoot P.
Published: June 2005

The bacterial microflora was examined in the vagina of cyclic female rats kept under normal laboratory conditions. Large variations occurred during the cycle with high numbers of bacteria (105‐108 per vagina) during proestrus and estrus and low numbers (101‐104 per vagina) during the diestrus period. Histological analysis of in situ vaginal tissue and transplanted vaginal tissue revealed an association of high bacterial numbers with the presence of large amounts of cellular debris in the vaginal lumen during the period of epithelial keratinization. Absence of phagocytosis in leucocytes at metestrus suggested that leucocytes did not play an active role in reduction of bacterial numbers between estrus and metestrus. Accurate measurement of the pH in the vaginal lumen failed to reveal differences which could explain the reduction in bacterial numbers between estrus and metestrus. The cyclic changes in the bacterial population–consisting of species which are normally present in the intestinal flora–seem to be controlled by cyclic changes in the amounts of cellular debris in the vaginal lumen.
Oxygen uptake by Nautilus pompilius
Authors: Redmond J. R. , Bourne G. B. , Johansen K.
Published: June 2005

The oxygen uptake of Nautilus pompilius at 17°C was 27 ml O2·kg−1·h−1 for calm species and 52 ml O2·kg−1·h−1 for active specimens. At 25°C the corresponding uptakes were 64 and 109 ml O2·kg−1·h−1. Oxygen con‐sumption dropped as the oxygen content of inhalant water dropped. Uptake ceased at about 20 mm Hg O2. Nautilus appears to have a lower oxygen demand and an oxygen delivery system less well developed than of that the modern cephalopods.
Metabolic and ultrastructural organization in Nautilus muscles
Authors: Hochachka P. W. , French C. J. , Meredith J.
Published: June 2005

Arginine phosphate is the phosphagen in Nautilus muscles. During “burst” work, arginine concentrations rise to high levels in muscles (up to 70 μm/gm), but arginine is not released into the blood circulation in significant amounts. Instead, arginine either is reconverted to arginine phosphate in situ or it condenses with pyruvate to form octopine, a reaction that oxidizes NADH and removes a highly basic metabolite from the cell. Octopine, formed in muscles, may have two possible fates: either it is released into the blood and is reconverted to arginine plus pyruvate elsewhere (e.g., in liver and gills), or it is re‐metabolized in situ. Of the two, the latter seems more important in Nautilus. Muscles of Nautilus also seem to have a vigorous amino acid metabolism, the details of which are not yet well understood. It is evident, however, that substantial pH gradients can develop between the arterial and venous blood apparently as a result of vigorous deamination and amination reactions.
Some aspects of hemodynamics in Nautilus pompilius
Authors: Bourne George B. , Redmond James R. , Johansen Kjell
Published: June 2005

Blood pressure recordings from the ventricle, dorsal aorta, dorsal hemocoel, vena cava, afferent and efferent branchial veins show that the Nautilus pompilius cardiovascular system possesses similar functional characteristics to those of the modern coleoid cephalopods. In free swimming animals at 17° C ± 1° the contraction rate of the systemic ventricle varied between 5 and 18 beats per minute. Systolic blood pressure averaged 35 cm H2O while diastolic pressure averaged 16 cm H2O in the dorsal aorta. Peak and low pressures in the afferent branchial vein were 9 cm H2O and 1 cm H2O respectively while the mean pressure in the efferent branchial vein was 2 cm H2O and in the vena cava it was 2.2 cm H2O.

The contour of the flow pulse recorded from the dorsal aorta indicated a backflow marking the point of aortic valve closure.

Hemodynamics of the Nautilus pompilius cardiovascular system are discussed.
Adaptation of the tree frog, Hyla cinerea, to colored backgrounds, and the rôle of the three chromatophore types
Authors: Nielsen Hans Ingolf , Dyck Jan
Published: June 2005

Measurements have been made of the spectral reflectance of the dorsal skin of living tree frogs, Hyla cinerea.

The colors assumed by the frogs when placed on backgounds of different col‐ors varied with respect to both dominant wavelength (565–580 nm), purity (42–58%) and lightness (2–19%).

A certain adaptation to the lightness of the background took place, whereas adaptation to hue and purity seems almost negligible.

On the basis of reflection measurements of single chromatophores and chro‐matophore associationa, a model is proposed for the color generation in the chromatophores, assuming an absorption of short‐wave light in the xantho‐phores, a reflection of short‐and medium‐wave light (blue, green) from the iridophores, and almost total absorption of all light in the melanophores, and a uniform, but subtotal, reflection of light of all wavelenghts from the connective tissue.

It is suggested that the states of dispersion of the three types of chro‐matophores may be related to simple parameters which can be calculated from the reflectance spectra. Using these parameters it was found that mela‐nophores, xanthophores and iridophores all play an active part in the color change, and an explanation is presented on how the observed frog colors are generated by means of changes in the chromatophores.

The three types of chromatophores probably are able to react independently of each other, thus indicating that the unihumoral theory fails to explain the color changes in Hyla cinerea.
Purification and properties of glutamate dehydrogenase from the mantle muscle of the squid, Loligo pealeii. Role of the enzyme in energy production from amino acids
Authors: Storey Kenneth B. , Fields Jeremy H. A. , Hochachka Peter W.
Published: June 2005

The activity of glutamate dehydrogenase was measured in the tissues of the squid, Loligo pealeii. The enzyme occurs in high activity in digestive pouch, systemic heart, and all muscle tissues.

Glutamate dehydrogenase from mantle muscle is located intra‐mitochondrially, has a molecular weight of 310,000, and is electrophoretically similar to the enzyme, from all other squid tissues.

The enzyme from mantle muscle was purified 40‐fold by elution from DEAE‐cellulose and used for kinetic studies. The enzyme is NAD+‐specific, activated by ADP, AMP, and leucine, and inhibited by GTP, GDP, ATP, and reaction products (in particular NADH).

Squid glutamate dehydrogenase shows an almost absolute dependence on ADP. The purified enzyme is activated over 100‐fold by saturating concentrations of ADP (K)a = 0.75 mM). The pH optima are also altered significantly by ADP.

The enzyme appears to be kinetically adapted to favour glutamate oxidation in comparison to glutamate dehydrogenase from other sources. The evidence indicates that the primary role of glutamate dehydrogenase in squid mantle muscle is in regulating the catabolism of amino acids for energy production.
Electrophysiological responses of Heteronereis stimulated with sex pheromones (Annelida polychaeta)
Authors: Boilly‐Marer Yolande , Lassalle Bernard
Published: June 2005

Chemical stimulations by sex pheromones have been electro‐physiologically recorded on Heteronereis brain. The presence of the transformed parapodial cirri is necessary to the appearance of the intense and prolonged electrical activity of the brain.
Estrogen localization in the brain of the lizard, Anolis carolinensis
Authors: Martinez‐Vargas M. C. , Keefer D. A. , Stumpf W. E.
Published: June 2005

Estrogen induces reproductive behavior in lizards by acting on specific areas of the brain. Neural areas that selectively concentrate radioactivity after 3H‐estradiol administration were mapped using thawmount autoradiography. Major accumulations of hormone‐concentrating cells occur in the medial preoptic area, basal hypothalamus, amygdala (n. ventromedialis telencephali) and in and around the torus semicircularis. Numerous smaller accumulations are also described and the topographical distribution is compared with that of avian and mammalian species.
Oocyte maturation without follicular epithelium alters egg shape in a dipteran insect
Authors: Went Dirk F.
Published: June 2005

Oocytes of the parthenogenetic gall midge Heteropeza pygmaea assume an elongate shape when they mature inside the follicular epithelium. However, when the oocyte‐nurse chamber complexes grow without the regular follicular layer, they form spherical eggs. Such eggs may develop as far as the blastoderm stage. These findings indicate that the follicular epithelium is responsible for the shape of the egg but is not required for oocyte maturation and for initial steps in embryonic development.
Splenic plaque‐forming cells (PFC) and stem cells (CFU‐s) during acute phenylhydrazine‐induced enhanced erythropoiesis
Authors: Kozlov V. A. , Zhuravkin I. N. , Coleman R. M. , Rencricca N. J.
Published: June 2005

The erythroid status and levels of splenic plaque‐forming cells (PFC) to sheep red blood cells (SRBC) were monitored in mice subsequent to acute phenylhydrazine (PHZ)‐induced hemolytic anemia. From ferrokinetic measurements, we noted a shift in erythropoiesis from bone marrow to spleen. The levels of splenic PFC were significantly depressed following PHZ‐induced erythroid differentiation. Although this immune depression may reflect competition at the stem cell levels, whereby pluripotent stem cells (CFU‐s) are preferentially differentiated into the erythroid line at the expense of lymphopoietic pathways, other possibilities cannot be excluded. In this regard, we have shown that loading of the mononuclear phagocyte system (MPS) by PHZ‐damaged erythrocytes effected profound depressions in splenic PFC numbers. Lastly, in addition to the well‐documented increases in CFU‐s migration from marrow to spleen during enhanced erythropoiesis, we noted increased migration of B lymphocytes (as assessed by PFC) in marrow‐shielded lethally‐irradiated mice given PHZ. We also provide data which show that PHZ‐damaged RBC evoke increased migration of CFU‐s in normal mice, indicating a possible involvement of the MPS in stem cell migration.
Renal excretion of urea in the salamander, Ambystoma tigrinum
Authors: Stiffler Daniel F. , Hawk C. Terrance , Fowler Beth C.
Published: June 2005

Renal excretion of urea was assessed in adult and larval Ambystoma tigrinum by comparing simultaneous clearances of urea and inulin. The mean adult urea clearance ratio (Cu/CIn) was 0.70 ± 0.08 indicating net urea absorption. Larvae yielded a mean CU/CIn) of 0.92 ± 0.04. Individual larvae were quite variable however as approximately 30% displayed CU/CIn>1. There was a significant negative correlation between CU/CIn and fractional water reabsorption. Comparisons of larval kidney urea concentration (KU) and plasma urea concentration (PU) revealed a mean KU/PU of 1.43 ± 0.15. Treatment with 2,4‐dinitrophenol decreased larval CU/CIn to 0.80 ± 0.05 and KU/PU to 0.91 ± 0.08. Phloridzin also decreased CU/CIn (0.67 ± 0.06) however para‐aminohippuric acid had no effect. Hypophysectomy combined with cautery of the pituitary stalk resulted in CU/CIn of 1.71 ± 0.33 as compared to 0.84 ± 0.08 in shams. These results are consistent with the possibility of net urea secretion at some point in the A. tigrinum nephron, followed by passive reabsorption in the distal segments under the influence of antidiuretic hormone. Key words: DNP, hypophysectomy, nephrostome, PAH, phloridzin, urea secretion.
Exchange of skin grafts among monozygotic quadruplets in armadillos
Authors: Billingham Rupert E. , Neaves William B.
Published: June 2005

Skin grafting experiments, with long‐term follow‐ups, on three litters of armadillo quadruplets born in our laboratory have confirmed the familiar rule that grafts exchanged between monozygotic littermates are not rejected as a consequence of alloimmune reactions. A possible explanation of the striking discrepancy between the present findings and those of a previous study is uncertainty about the relationships of the previous animals, which were obtained from a commercial dealer at 10 days of age.
Baroreflex sensitivity in an amphibian, Rana catesbeiana, and a reptilian, Pseudemys scripta elegans
Authors: Millard Ronald W. , Moalli Richard
Published: June 2005

An inverse relationship between heart rate and systematic arterial pressure is demonstrated in unanesthetized bullfrogs (Rana catesbeiana) and red‐eared turtles (Pseudemys scripta elegans). Drug‐induced elevation of systemic blood pressure resulted in proportional decreases in heart rate and lengthening of the pulse interval. Conversely, nitroglycerin‐induced decreases in blood pressure produced compensatory increases in heart rate. This relationship in frogs is defined by y = 25.4x + 1684, and in turtles by y = 64.8x + 1686, where y is pulse interval in msec and x is systolic blood pressure in mmHg. Resting and drug‐induced systolic pressure limits were not different in the two species. However, both resting and reflexly altered heart rates were significantly lower in turtles than in frogs (p<.05). The heart rate responses were abolished by atropinization, without effect on the blood pressure responses. While anatomic identification of the baroreceptor site sensing the pressure changes remains to be made, the translation of pressure information via reflex pathways analogous to mammalian baroreceptor reflex arc system is evidenced in these lower vertebrates.
Formation of tetraploid mouse blastocysts following blastomere fusion with polyethylene glycol
Authors: Eglitis Martin A.
Published: June 2005

A rapid method to produce tetraploid embryos by blastomere fusion using polyethylene glycol (PEG) has been developed. Individual four‐cell stage blastomeres were aggregated into pairs with phytohemagglutinin (PHA) and then treated with 45% (w/v) PEG (MW 1,000). 56.8% (804/1,416) of treated blastomere pairs fused. Tetraploid blastomeres were aggregated into quartets or doublets to restore cell number equivalent to that of whole or half diploid embryos, respectively. Best development was obtained with quartets, 72.9% (78/107) of which cavitated. 46.4% (13/28) of doublets and 31.7% (13/41) of singly cultured tetraploid blastomeres formed cavitated structures. Uniform tetraploidy was confirmed by fixing cavitated embryos and analyzing their metaphase plates. The fusion method described here replaces Sendai virus with a chemically defined fusogen and confirms earlier observations (Snow, '73; Graham, '71) that tetraploidy does not prohibit preimplantation development. This fusion method obviates some of the drawbacks of cytochalasin B‐induced tetraploidy, namely the blocking of cleavage and the potential of diploid/tetraploid mosaicism.
Four new proteins of the eumelanosome matrix of the chick pigment epithelium
Authors: Zimmerman Joel
Published: June 2005

A new procedure is presented for the isolation of electron microscopically clean melanosomes. The procedure provides melanosomes which have been stripped of their membrane components so that only matrix elements are examined. Solubilization of these melanosomes is by 8 M urea‐1% Triton X‐100 treatment with reduction and alkylation. The proteins are examined on sodium dodecyl sulfate‐polyacrylamide gels and on acid‐urea polyacrylamide gels. Evidence is presented indicating the presence of four low‐molecular‐weight proteins which have not previously been reported. Data indicate that these proteins are the major components of the melanosome matrix, that they are not histones and that at least one of them is a glycoprotein.
In vitro steroid production in the postovulatory follicles of the amago salmon, Oncorhynchus rhodurus, in response to salmon gonadotropin
Authors: Nagahama Yoshitaka , Kagawa Hirohiko
Published: June 2005

Partially purified chinook salmon gonadotropin (SG‐G100) was used to investigate estradiol‐17β and progesterone production in vitro in the isolated postovulatory follicles of the amago salmon, Oncorhynchus rhodurus, at varying intervals after ovulation. Chinook salmon gonadotropin stimulated progesterone production in vitro in the young postovulatory follicles, but not in the older ones. In contrast, estradiol‐17β production was not stimulated in either young or older postovulatory follicles. Morphological observations indicate that young postovulatory follicles are more glandular than older ones. Thus, it is concluded that the young postovulatory follicles of the amago salmon are steroidogenic.
The effect of limiting light to the pineal on the rate of forelimb regeneration in the newt
Authors: Maier C. Eberhardt , Singer Marcus
Published: June 2005

Newts with bilaterally amputated forelimbs were exposed to either continuous light (LL), total darkness (DD), or continuous light with the dorsal head epithelium painted with an India ink and Nile blue sulfate mixture (LL‐II‐NBS) that limited light penetration through the skull to the pineal. The LL‐II‐NBS animals regenerated their forelimbs more slowly than their counterparts in LL.
Water loss and survival in embryos of the domestic chicken
Authors: Snyder Gregory K. , Birchard Geoffrey F.
Published: June 2005

In this report we show that the amount of water lost during incubation is an important determinant of hatchability in embryos of the domestic chicken. However, when the loss of water is restricted to the first half versus the second half of the total incubation period, it is the loss of water during the first half that affects hatching success. We propose that regulating the permeability of the egg shell may be important in preventing excessive drying of the inner shell membrane during early development along with limiting the total amount of water lost from the embryo during incubation.
Na+ and Cl− transport and intercellular junctions in the isolated skin of a marine teleost (Blennius pholis L.)
Authors: Nonnotte G. , Colin D. A. , Nonnotte L.
Published: June 2005

Electrical parameters were simultaneously measured with unidirectional fluxes of Cl− and Na+ through isolated short‐circuited skin of a marine teleost, the shanny (Blennius pholis L.). The mean transepithelial potential TEP developed across the skin was 10.6 ± 0.4 mV (n = 6) in open‐circuit conditions. When the skin was short circuited, the mean short circuit current Isc was 35.1 ± 2.7 μamp·cm−2, which represented the difference between mean Cl− and Na+ net fluxes (1.2 ± 0.2 μEq·hour−1·cm−2 equivalent to 32.5 ± 5.4 μamp·cm−2). The junctional complexes between the different cells of the epidermis were also studied. Epithelial cells were linked to each other by tight junctions as well as epithelial and accessory cells. In contrast, junctions between chloride and accessory cells were characterized as shallow junctions. The Na+ and Cl− transport through the skin of the shanny is discussed with reference to the implication of the junctional complexes of the epidermis.
Circadian rhythmicity in Bulla gouldiana: Role of the eyes in controlling locomotor behavior
Authors: Block Gene D. , Davenport Philip A.
Published: June 2005

The eyes of Bulla express a circadian rhythm in optic nerve impulse frequency. Bulla also exhibit a circadian rhythm in locomotor behavior. In order to determine what role the ocular oscillators play in controlling rhythmic behavior, the eyes were removed and locomotor activity was recorded during free runs and while entrained to light‐dark cycles. We find that eye removal leads to a disorganization of the free‐running locomotor rhythm, suggesting that the ocular oscillators are involved in timing this behavior. Eyeless Bulla in the presence of light cycles exhibit locomotor rhythmicity but there is a switch from predominantly nocturnal to diurnal activity. While diurnal behavior in eyeless Bulla reveals the presence of extraocular photoreceptors, we presently find no evidence that a circadian pacemaker mediates this diurnal activity.
Differentiation of muscle fiber types in aneurogenic brachial muscles of the chick embryo
Authors: Butler Jane , Cosmos Ethel , Brierley Joyce
Published: June 2005

Cross‐reinnervation studies performed ex ovo with newly hatched chicks demonstrate that peripheral motor neurons control the phenotypic characteristics of avian muscles. The present experiments were designed to determine whether or not nerves play a similar role during the initial expression of muscle fiber types. Previous experiments indicated that differentiation of specific fiber types occurs during the first week of embryogenesis, temporally coincident with the penetration of nerves within muscle masses. These observations suggested that peripheral nerves may be associated with the initial differentiation of fiber types. To test this hypothesis directly, anterior limb buds of the chick embryo were rendered aneurogenic by deletion of the brachial segment of the neural tube. To ensure a completely aneurogenic environment for developing brachial muscles, surgery was performed at day 2 in ovo before the exit of ventral root fibers. Experimental and control embryos from Stage (St) 25 (4.5 d) through St 45 (19d) were analyzed histochemically by a silver‐cholinesterase reaction to detect nerves and by the myosin ATPase reaction, following alkali and acid preincubation, to determine the fiber type composition of the muscles. In addition, the total volume of aneurogenic and control muscles was compared. Results demonstrate that the characteristic myosin ATPase profiles of individual aneurogenic and innervated (control) muscles were identical throughout the entire period analyzed. Therefore, we conclude that these enzymic profiles are endogenously expressed and are not under neuronal control during early embryogenesis. Furthermore, the entire sequence of events from the migration of myogenic cells to the anterior limb bud through the division of the primary muscle masses to form individual brachial muscles proceeded on schedule in the absence of nerves. Since the growth of aneurogenic muscles was impaired, we conclude that during embryogenesis peripheral motor nerves are necessary initially for the proper growth of muscles and ultimately, for their survival. They are not involved, however, with either the initial formation or initial differentiation of individual brachial muscles.
Resumption of DNA synthesis in delayed implanting mouse blastocysts during activation in vitro
Authors: Given Randall L. , Weitlauf Harry M.
Published: June 2005

The resumption of DNA synthesis in delayed implanting mouse embryos undergoing metabolic activation in vitro was examined. Blastocysts were recovered from ovariectomized mice, incubated for various intervals in basal Eagle's medium, exposed to 3H‐ thymidine, and prepared for light microscopic autoradiography. Following incubation the proportion of labeled cells increased from 4% at 1 hr to 30% by 24 hr. This increase in labeling was not uniform in all regions of the blastocyst, i.e., labeling was initially highest over the inner cell mass (ICM) but remained low over the polar and proximal mural trophoblast for 6 and 12 hr, respectively, and then began to increase. This pattern in the resumption of DNA synthesis during activation in vitro is similar to that reported in vivo (Given and Weitlauf, '81) and suggests that the mechanism responsible is intrinsic to the blastocyst rather than being a differential response to the intrauterine milieu. Furthermore, it appears that the ICM may play an essential role in the resumption of synthesis in the surrounding trophoblast.
Extraintestinal calcium uptake in the killifish, Fundulus heteroclitus
Authors: Mayer‐Gostan Nicole , Bornancin Michel , de Renzis Guy , Naon Robert , Yee John A. , Shew Ronald L. , Pang Peter K. T.
Published: June 2005

Extraintestinal calcium influxes were measured in the killifish, Fundulus heteroclitus, in solutions with different calcium concentrations, from distilled water level (near 0) to seawater level (approximately 12 mM). The extraintestinal influx is modified by the concentration of calcium in the medium during the adaptive period. In freshwater‐adapted fish, calcium depletion resulted in an increase in calcium uptake. Such an adaptation was not observed in calcium‐depleted fish in artificial calcium‐deficient seawater. Calcium depletion in either medium seems to increase the calcium permeability. No correlation was found between Ca‐ATPase activity in the gill tissue and calcium uptake.
Cardiovascular events associated with spontaneous apnea in the Australian short‐finned eel, Anguilla australis
Authors: Hipkins Scott F. , Smith David G.
Published: June 2005

Heart output, arterial pressures, and buccal pressure were measured in conscious, unrestrained eels (Anguilla australis). The branchial ventilatory pattern comprised alternating periods of eupnea and apnea. The transition from eupnea to apnea was always associated with significant decreases in ventral aortic blood pressure (−20%), dorsal aortic blood pressure (−16%), ventral aortic blood flow (−39%) and heart rate (−27%), and a significant increase in systemic vascular resistance (+39%). Although there were, significant decreases in cardiac stroke volume in some animals, heart output was primarily determined by heart rate. The rapidity of the transition to apnea and the occasional occurrence of Mayer waves in the circulation of A. australis is considered as evidence in favour of the neural regulation of systemic vascular resistance.
The ionic concentrations in the mitochondria‐rich or chloride cell of Fundulus heteroclitus
Authors: Potts W. T. W. , Oates K.
Published: June 2005

The intracellular concentrations of sodium, potassium, and chloride ions, together with total phosphorous, in the cytoplasm of the chloride cells of the opercular epithelium of Fundulus heteroclitus have been estimated by X‐ray emission analysis of bulk frozen hydrated tissue. The estimated concentrations are Na, 171 ± 12; Cl, 155 ± 6; K, 62 ± 4 mE/kg water, together with 80 ± 6 mM P/kg water. It is shown that these high concentrations are consistent, with the Silva model of chloride secretion in which a sodium‐chloride linked carrier, driven by the inward diffusion of sodium ions, concentrates chloride in the cytoplasm. The intracellular concentration of chloride is such that if the potential across the apical membrane is greater than 34 mV, inside negative, there will be a net efflux of chloride ions out of the cell. If the linkage between sodium and chloride on the carrier is one to one, it is shown that energy dissipation is minimal when the product of the cytoplasmic concentrations of sodium and chloride approaches the product of those in the plasma and it would be energetically disadvantageous to maintain low intracellular concentrations of these ions. In practice, however, optimum concentrations are not attainable because of other intracellular solutes that contribute substantially to the osmotic pressure.
Contractile responses of single fibers in lobster claw closer muscles: Correlation with structure, histochemistry, and innervation
Authors: Costello Walter J. , Govind C. K.
Published: June 2005

This study incorporates contractile, structural (sarcomere length), histochemical (myofibrillar ATPase and NADH diaphorase), and physiological (fast and slow axon innervation) parameters to define fiber types in lobster muscle. Single fibers were examined in the closer muscle of adult cutter and crusher claws and of developing larval claws of the lobster Homarus americanus. Fibers with short sarcomeres ( < 4 μm) had rise times of 50–160 msec for attaining maximum tension which either was maintained for the period of stimulation (fatigue‐resistant) or declined (fatiguable). Fibers with long sarcomeres ( > 6 μm) had rise times of 90–800 msec for reaching maximum tension, which either was subsequently held at this level or continued to increase. The contractile properties and sarcomere length of single fibers were correlated with their enzymatic properties such that fast‐contracting, short‐sarcomere fibers had high myofibrillar ATPase activity and low oxidative capacity compared to their slow‐contracting, long‐sarcomere counterparts. The slow fibers were also further differentiated into subcategories based on contractile and histochemical properties. Fibers with the fastest rise times tended to be innervated primarily by the fast axon, and those with the slowest rise times were supplied solely by the slow axon. The organization of the massive closer muscle into discrete bundles in which fibers have uniform contractile, structural, and physiological properties leads to functional subdivision within the muscle. The contractile properties of developing fibers were similar to the adult except that larval fibers did not possess very slow rise times.
A unilateral cleavage furrow in embryos of S. droebachiensis
Authors: Anstrom John A. , Summers Robert G.
Published: June 2005

Embryos of the sea urchin, Strongylocentrotus droebachiensis, develop normally at temperatures ranging from 8°C to 0°C. An embyro cultured at 8°C cleaves symmetrically about its equator whereas one cultured at 0°C cleaves unilaterally. In embryos cultured at 8°C the mitotic apparatus (MA) occupies the entire cell volume at late anaphase whereas at 0°C the MA at the same stage is 20% smaller (Anstrom and Summers, '83). At 8°C the MA is centered within the zygote whereas at 0°C it is located eccentrically. The cleavage furrow always forms at the cell surface closest to the eccentric MA. We attribute the unilateral cleavage furrow in the 0°C embryo to the small size and eccentric placement of the mitotic apparatus within it. Both symmetrical and unilateral cleavage are apparently normal in this species, suggesting a common mechanism for both types of cleavage.
Proliferation of epidermal melanocytes during the healing of skin wounds in newborn mice
Authors: Hirobe Tomohisa
Published: June 2005

A full‐thickness cut 7 mm long was made on the middorsal skin of C57BL/10J mice using fine iridectomy scissors. Specimens from the wounded skins were fixed at various days after wounding and were subjected to the dopa reaction and to the combined dopa‐premelanin reaction. In the epidermis within 1 mm from the wound edge, the melanocyte population positive to the dopa reaction as well as the melanoblast‐melanocyte population positive to the combined dopa‐premelanin reaction increased dramatically until the third day, then gradually decreased. In contrast, both populations in the regenerating wound epidermis appeared on the third day and increased until the seventh day, then gradually decreased. However, the maximal population density in the regenerating epidermis did not exceed the initial density. The size of the melanocyte population in both the epidermis within 1 mm from the wound edge and the regenerating epidermis did not differ from that of the melanoblast‐melanocyte population in all stages of wound healing. Moreover, pigment‐producing melanocytes in mitosis were found immediately after wounding in the epidermis within 1 mm from the wound edge, but not in the regenerating epidermis and control epidemis. These results indicate that the epidermal melanocytes in neonatal mouse skin can be stimulated to undergo mitosis immediately adjacent to a skin wound and, thèreafter, to migrate into the regenerating epidermis.