bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyclic AMP derivatives stimulate the chondrogenic differentiation of the mesoderm subjacent to the apical ectodermal ridge of the chick limb bud
Authors: Kosher Robert A. , Savage Mary P. , Chan Sai‐Chung
Published: June 2005

Recent studies indicate that one of the major functions of the apical ectodermal ridge (AER) of the embryonic chick limb bud is to maintain mesenchymal cells directly subjacent to it (i.e., cells extending 0.4–0.5 mm from the AER) in a labile, undifferentiated condition. Furthermore, when mesenchymal cells are freed from the AER's influence, either artifically or as a result of normal polarized proximal‐to‐distal limb outgrowth, they are freed to commence cytodifferentiation. In a preliminary attempt to investigate at a molecular level the mechanism by which the AER exerts its “negative” effect on the cytodifferentiation of subridge mesenchymal cells, we have examined the effect of a variety of agents that elevate cyclic AMP levels on the chondrogenic differentiation of the unspecialized subridge mesoderm of the limb bud in an organ culture system. Dibutyryl‐ and 8‐hydroxy‐cyclic AMP elicit a dose‐dependent increase in the rate and amount of cartilage matrix formation and a corresponding dose‐dependent increase in sulfated glycosaminoglycan accumulation by subridge mesoderm explants. The stimulatory effect of suboptimal concentrations of cyclic AMP derivatives is potentiated by the addition of theophylline. The stimulatory effect is limited to cyclic AMP derivatives, since dibutyryl‐cyclic GMP and 5′‐AMP have no effect. Thus agents that elevate intracellular cyclic AMP levels stimulate the chondrogenic differentiation of the unspecialized subridge mesoderm of the embryonic chick limb bud.
An ultrastructural study of epididymal mouse spermatozoa binding to zonae pellucidae in vitro: Sequential relationship to the acrosome reaction
Authors: Saling Patricia M. , Sowinski Janice , Storey Bayard T.
Published: June 2005

Mouse sperm bind to the zona pellucida of the egg prior to penetration of the zona and entry into the perivitelline space. The question then arises: when does the acrosome reaction occur relative to these processes? An Ultrastructural study of mouse epididymal sperm bound to the surface of the zona and in the privitelline space was undertaken to clarify this point. Cumulus‐free mouse eggs were inseminated in either a complete defined culture medium capable of supporting in vitro fertilization or in Tris/NaCl buffer containing Ca+2. Both media support sperm binding to the zona to the same extent; binding is complete in 15 minutes. Unbound sperm were removed by a step gradient density centrifugation to yield a preparation of eggs with sperm firmly bound. All sperm in the perivitelline space had undergone the acrosome reaction. Sperm bound at the surface of the zonae pellucidae of eggs recovered at ten minutes after insemination all had intact acrosomes. At 40 minutes after insemination, half of the sperm were intact; the other half were in the initial stages of the acrosome reaction. At 90 minutes after insemination, 12% of the sperm had undergone the full acrosome reaction and were starting to penetrate the zona; of the balance, half were in various stages of the acrosome reaction, while half were still intact. These findings support the hypothesis that the sequence of the early reactions leading to fertilization in the mouse is: intact sperm binding to zona; acrosome reaction at the zona surface; penetration of the zona.
Relationships between eye factors and lens‐forming transformations in the cornea and pericorneal epidermis of larval Xenopus laevis
Authors: Bosco Luigi , Filoni Sergio , Cannata Stefano
Published: June 2005

Larval Xenopus laevis at stage 56 (Nieuwkoop and Faber, '56) were subjected to various types of lentectomy:

simple lentectomy, from the pupillary space after incision of outer and inner cornea;

lentectomy from the dorsal region of the eye;

lentectomy from the dorsal region of the eye and simultaneous incision of the outer cornea;

lentectomy from the dorsal region of the eye and simultaneous incision of the outer and inner cornea.

The results obtained show that the outer cornea underwent lens‐forming transformations only when the inner cornea had been incised, thus permitting direct communication between the lentectomized eye environment and the outer cornea (Experiments I‐IV). No lens regeneration occurred when the inner cornea was left intact (Experiments II, III). It was concluded that the factor(s) allowing the lens‐forming transformations of the outer cornea is not an aspecific nutritional factor(s) but a more specific factor(s) that cannot reach the outer cornea when the inner cornea is intact. Therefore, the absence of the lens and sufficient nutrient available to the outer cornea are not enough to allow lens regeneration from the outer cornea.

When lens removal was carried out through the dorsal part of the eye (Experiments III‐IV) the lens regenerated from the pericorneal epidermis of this region in a large number of cases.
Avian feather keratins: Molecular aspects of structural heterogeneity
Authors: Busch Neal E. , Brush Alan H.
Published: June 2005

Solubilized SCM‐Keratins from feathers of a tern (Sterna hirundo) and turkey (Meleagris gallopavo) were fractionated by gel‐filtration and ion‐exchange chromatography. Tryptic peptide maps were prepared and amino‐acid compositions determined. Subsequent comparison indicated that within each species the FKM were closely related, but separate gene products. Interspecific comparison showed species specificity. The data were compared with the homologous FKM of other species and to amino‐acid composition data of the unfractionated SCM‐KM from other tissues.

These results support the proposition that feather keratins represent a family of closely related gene products. The primary function of the multiplicity of structural elements is in the macro‐molecular organization of the tissue. The monomers can self‐associate to form both the filamentous structures and an intermolecular matrix. The FKM also provide tissue specific organizational information. The chemical composition and distribution of the different FKM presumably determines the unique morphological and functional aspects of the feathers.
Acute and chronic hypoxia in rats. 1. Effect on organismic respiration, mitochondrial protein mass in liver and succinic dehydrogenase activity in liver, kidney and heart
Authors: Pickett Cecil B. , Cascarano Joseph , Wilson Margaret A.
Published: June 2005

The objective of this investigation was to characterize organismic, organ and mitochondrial alterations in rats over the course of 27 days at 0.4 atm. In the adjustment phase (day 1 through 5) a significant decrease in systemic oxygen uptake and body weight (23% of pre‐altitude values) occurred. In the acclimating state (day 7 to 27) body weight was regained but oxygen consumption remained depressed. Hematocrit increased hyperbolically from 45% in 0‐day rats to 79% in 27‐day rats. Liver, kidney and heart weights and total organ protein paralleled the changes observed in body weight. Total organ succinic dehydrogenase activity showed a wave‐like oscillation for liver and kidney; activity was decreased in both organs by day 5, showed a transient but significant increase on days 16 through 18 and a return to diminished activity on day 27. Succinic dehydrogenase activity for heart became depressed in the adjustment phase but showed a stable level comparable to pre‐altitude values in the acclimating phase, days 7 through 27. Liver mitochondrial protein mass was unchanged from pre‐altitude values on days 5 and 27 even though succinic dehydrogenase activity was significantly depressed. Therefore, the changes in succinic dehydrogenase activity are not representative of altered mitochondrial mass but suggest that mitochondrial function was altered.
The developmental appearance of hexokinase and alcohol dehydrogenase in Xenopus laevis
Authors: Wesolowski Mary H. , Lyerla Timothy A.
Published: June 2005

The stages of appearance of hexokinase (HK; E.C. 2.7.1.1) and alcohol dehydrogenase (ADH; E.C. 1.1.1.1) in Xenopus laevis were studied using starch gel electrophoresis. The HK activity detected in this investigation is gut‐specific and appears at metamorphic climax (stage 63: Nieuwkoop and Faber, '67). Kinetic studies from crude homogenates tentatively identify this as a low Km HK type. ADH is first detected in larval stage 47 and is primarily liver‐specific. It is postulated that the observed electromorphic variation can be explained by assuming there are at least three ADH loci in this species, but the products of only two can form heterodimers. These enzyme systems, from their tissue specificities and post‐fertilization stages of appearance, should be useful for studies of gene activation in X. laevis development.
Acclimation to successive short term salinity changes by the bivalve Modiolus demissus. II. Nitrogen metabolism
Authors: Strange Kevin B. , Crowe John H.
Published: June 2005

The bivalve Modiolus demissus acclimates rapidly to new salinity regimes when exposed to successive short term osmotic stress. During exposure to hypoosmotic stress ventricular primary amine concentration decreases to an apparent steady‐state level within six hours, while hemolymph primary amine concentration increases. Upon re‐exposure to 100% sea water following a 6‐hour hypoosmotic stress, intracellular primary amines increase rapidly and return to control levels after six hours of exposure. Concomitant with this is an apparent decrease in hemolymph primary amine concentration. The rapidity with which reacclimation to hyperosmotic media proceeds and the pattern of change of individual amino acids suggests that transport of hemolymph FAA may play an important role in cell volume regulation induced by increases in external salinity.
Stimulation of mitosis in cultured limb blastemata of the newt, Notophthalmus viridescens
Authors: Carlone Robert L. , Foret J. E.
Published: June 2005

Experiments were performed in vitro to assess the mitogenic activity of brain homogenates and cyclic nucleotides on adult newt limb blastemal cells. Early cone stage blastemata were explanted into organ culture, and thus denervated. The mitotic index (M.I.) of each was calculated and shown to decline steadily in vitro. The inclusion in the medium of newt brain homogenate (NBH) or dibutyryl cAMP (dbcAMP) delayed the loss of mitotic activity. Cyclic GMP alone or in combination with theophylline was ineffective as a mitogen. Bovine serum albumin and fetal calf serum were also ineffective, thus the mitogenic activity of brain homogenate appears to be distinct from a simple enrichment of the culture medium. Preliminary characterization of the active principles in NBH revealed a mitogenic activity that was both heat labile and trypsin sensitive. In related experiments, control cultures were maintained for 54 hours, roughly equivalent to one urodele blastemal cell cycle. When the decline in M. I. had stabilized, NBH or dbcAMP were added to the medium. A burst of mitotic activity was observed in both cases 8 hours later. Cyclic GMP was again ineffective. Since the G2 phase of the blastemal cell cycle lasts approximately four to eight hours, this result lends support to the hypothesis that blastemal cells are blocked in G2 in the absence of nerves. Cyclic AMP mimics the effect of brain homogenates at a specific phase of the blastemal cell cycle in vitro, and may therefore play some as yet undefined role in this neurotrophic process in vitro.
Western fence lizard (Sceloporus occidentalis) chemical signals. I. Conspecific discriminations and release of a species‐typical visual display
Authors: Duvall David
Published: June 2005

Western fence lizards, Sceloporus occidentalis, were exposed to markings, droppings, and exudates (e.g., femoral and proctodeal gland secretions, and feces) collected from conspecific males and females in a chemicalcue, simultaneous discrimination procedure. Females performed no discrimination between unmarked brick surfaces and those labelled by conspecifics of either sex, as indexed by relative numbers of substrate licks or tongue flicks. Males performed significantly more of these actions to male‐ but not female‐labelled surfaces. Immediately subsequent to licks of labelled surfaces, but never after licks of unlabelled surfaces, both sexes performed push‐ups, a visual display in this genus. These findings suggest that these lizards are capable of discriminating and utilizing chemical signals as a mode of social communication, and that chemical signals alone are capable of releasing a visual display from conspecifics.
Hormonal control of apolysis in barnacle mantle tissue epidermis, in vitro
Authors: Freeman John A. , Costlow John D.
Published: June 2005

Ecdysterone (5–20 μg/ml) stimulated apolysis in inner mantle tissue explants of the barnacle, Balanus amphitrite, maintained under in vitro conditions. Apolysis was noticeable after 12 to 15 hours while complete apolysis was reached by 24 hours. Enlargement of the epidermal cells was also observed in ecdysterone‐stimulated tissues. Ecdysone (10–20 μg/ml) was equally as effective as ecdysterone in stimulating apolysis. In some tissues, which had been cultured with 20 μg/ml ecdysterone for 24 hours, new cuticle formation had occurred following apolysis. The initiation of apolysis by ecdysterone was dependent on RNA and protein synthesis, as indicated by the inhibition of ecdysterone‐promoted apolysis by actinomycin D and cycloheximide. Aqueous extracts of shrimp eyestalks (MIH) (10 es eq/ml), either as a crude extract, or as a low molecular weight fraction from a Sephadex G‐25 column, were active in repressing the apolysis‐stimulating action of ecdysterone. The MIH activity could be overridden by increased levels of ecdysterone. Protease treatment of the MIH from crude and partially purified fractions abolished the inhibitory activity. Molt‐inhibiting hormone did not bind 3H‐ecdysterone. The results demonstrate that the early premolt integumental activities are under the control of ecdysterone and molt‐inhibiting hormone.
Neural regulation of cholinesterase in newt skeletal muscle. I. Distribution and characterization of the enzyme species
Authors: Rathbone Michel P. , Vickers John D. , Ganagarajah Mailvaganam , Brown Judy A. , Logan David M.
Published: June 2005

The molecular forms of acetylcholinesterase (AChE) in triceps muscles of newts (Notophthalmus viridescensiwere identified and their distribution in the muscle determined. Six forms of AChE were separated from crude muscle homogenates using velocity sedimentation on sucrose gradients. Their sedimentation coefficients were 16.5S, 1226, 9.8S, 7S, 5.5S, and 3.7S. They were identified as acetylcholinesterases by their ability to hydrolyze acetyl‐β‐methylcholine, but not butyrylthiocholine. The 7S form, however, has not been as thoroughly characterized as it can only be consistently identified in sucrose gradients of Tris‐Triton X‐100‐NaC1 extracts of muscle previously extracted with Tris‐Triton X‐100. The Tris‐Triton X‐100 extraction removes the 5.55 and 9.8S AChE forms which mask the 7S form in sucrose gradients of unfractionated material. The region of muscle containing the motor endplates was enriched in the 16.5S form, whereas the musculotendinous junction contained a high proportion of the 12.8S form. Contamination by AChE present in blood and nerve, did not account for the distribution of the 12.8S species within the muscle. The 3.7S and 5.5S forms were soluble in Tris buffer and are probably located in the cytoplasm. The 9.8S forms required 1MNaCl for solubilization, indicating that it is associated with an osmotic shock‐resistant intracellular compartment, possibly the sarcotubular system. Triton X‐100 was required to solubilize the 16.5S, 12.8S and 7S forms indicating that they may be membrane bound. Crude muscle homogenates and each of the forms of AChE isolated on sucrose gradients yielded nine bands of AChE activity when subjected to polyacrylamide gel electrophoresis (PAGE). The bands of AChE were apparently monomers and multimers from which the larger forms of AChE were assembled.
Isolation of O‐phosphorylethanolamine from the erythrocytes of an elasmobranch (the Southern Fiddler Ray — Trygonorhina fasciata guanerius)
Authors: Coates Michael , Thompson Judith , Tate M. E.
Published: June 2005

An amphoteric organic phosphate, which represents 20% of erythrocyte acid soluble phosphate components from an elasmobranch (the Southern Fiddler Ray — Trygonorhina fasciata guanerius) has been isolated as a colourless crystalline solid. Its phosphorus content, melting point behaviour, chromatographic, electrophoretic and ion‐exchange properties, together with its infrared and electron impact mass spectra are consistent with its formulation as O‐phosphorylethanolamine.

Assuming minimal degradation in the isolation procedure, the calculated erythrocyte intracellular concentrations of characterised phosphates from the Southern Fiddler Ray are as follows: O‐phosphorylethanolamine (1.89 mM), adenosine triphosphate (1.61 mM), inorganic phosphate (0.26 mM), inosine monophosphate (0.47 mM), guanosine triphosphate (0.34 mM) and adenosine diphosphate (0.11 mM). On a molar basis O‐phosphorylethanolamine is the major acid soluble phosphate of the Southern Fiddler Ray erythrocyte, but examination of the literature suggests its concentration may vary considerably among other elasmobranchs and possible reasons for such variance are considered.
Tissue culture evidence on the control of the switch from contact inhibition of cell movement to overlapping behavior in annual fish embryos of nothobranchius korthausae
Authors: Lesseps Roland J. , Lapeyre Michel V. , Hall Marian V.
Published: June 2005

Deep blastomeres of annual fish embryos exhibit contact inhibition of cell movement during epiboly and early dispersed stages before returning to self‐cohering and overlapping behavior. Deep blastomeres were dissociated from embryos of several different ages and cultured in hanging drops and in sitting drops. In every culture the cells rapidly reaggregated, irrespective of whether the cells were aggregated or dispersed in the living embryo. In sitting‐drop cultures, some cells subsequently flattened onto the plastic surface and assumed a fibroblastic shape. These results indicate that the contact inhibition and the overlapping behavior exhibited by deep blastomeres in vivo depend upon interactions of these cells with their embryonic environment, probably with the cell layers on which they are moving.
A proctolin‐like peptide in crab pericardial organs
Authors: Sullivan Robert Emmett
Published: June 2005

Evidence is presented that one of the cardio‐excitatory peptides known from crab pericardial organs is identical to or a close analog of proctolin, a putative peptide‐transmitter in insects. Acid ethanol extracts of crab pericardial organs contain a cardioexcitatory peptide which is pharmacologically and chromatographically indistinguishable from proctolin. The peptide exhibits an apparent molecular weight of approximately 600 as determined by gel filtration, is not degraded by trypsin but readily inactivated by leucine aminopeptidase. Application of this decapod cardioexcitatory peptide to the cockroach gut effects a dose‐dependent contracture identical to that produced by proctolin. Similarly, proctolin elicits a characteristic inotropic response from crab hearts.
Paternal X chromosome expression in extraembryonic membranes of XO mice
Authors: Frels William I. , Chapman Verne M.
Published: June 2005

The paternally derived allelic form of the X chromosome linked enzyme phosphoglycerate kinase (PGK‐1) is expressed in both the fetus and extraembryonic membranes of 9.5 day post coitum XO (XPO) mouse conceptuses. Previous studies on trophectoderm and primitive endoderm derived extraembryonic membranes in XX conceptuses suggest expression of only the maternally derived X chromosome (Xm). Our results suggest that the observed lack of expression of XP in the trophectoderm and primitive endoderm derivatives of XX embryos is not an intrinsic property of the XP chromosome.
Salt and water balance in the oligohaline clam, Rangia cuneata I. Anisosmotic extracellular regulation
Authors: Henry Raymond P. , Mangum Charlotte P.
Published: June 2005

The euryhaline mollusc Rangia cuneata maintains blood NaCl above that in the ambient medium in the range 0–2 ppt salinity and below ambient in the range 12–24 ppt. A hyperosmotic condition of the blood found at low salinity disappears at 12–16 ppt, and the blood medium‐difference becomes labile at high salinity. Hypersaline regulation of the blood at low salinity is accompanied by increased oxygen uptake, both in intact animals and in isolated gill and mantle tissue. However, only mantle andnot gill oxygen uptake is depressed at low salinity by ouabain, a specific inhibitor of the Na+ + K+ ATPases. These findings, together with other results on enzyme activity and the ionic effects on enzyme inhibition, suggest that hyperosmotic regulation of the blood at low salinity involves the absorption of NaCl from the medium, and that the process requires both oxidative metabolism and unimpaired functioning of the Na+ + K+ ATPases. The excretion of ammonia is also, depressed by ouabain, suggesting an exchange of Na+ and NH4+. The NH4+ may arise during deamination of intracellular free amino acids. The size of the free amino acid pool in gill, mantle and adductor muscle, varies directly with ambient salinity. Although the evidence is less complete, we also suggest that the hyposaline condition of the blood at high salinity results from an active process, and depends upon the uninhibited activity of the Na+ + K+ ATPases.
The effect of anemia on metabolic performance in the frog, Rana pipiens
Authors: Hillman Stanley S.
Published: June 2005

Anemias were induced in Rana pipiens hemolytically and by repetitive bleedings. Maximal rates of oxygen consumption ( max) declined with anemia. The pattern of decline in max with anemia did not closely approximate theoretical predictions of systematic oxygen transport. Anemic frogs accumulated lactate faster than control frogs during exercise. The length of exercise time to fatigue (stamina) was positively correlated with both gastrocnemius and blood lactate concentrations, indicating that fatigue was not dependent on a threshold lactate concentration in muscle or blood. Anemic frogs had the same stamina as control frogs.
Evidence suggesting a role for cyclic nucleotides in acrosome reactions of hamster sperm in vitro
Authors: Mrsny Randall J. , Meizel Stanley
Published: June 2005

There have been conflicting reports concerning the involvement of cyclic nucleotides in sperm capacitation. We have examined the effects of micromolar concentrations of dibutyryl cyclic AMP (Bt2cAMP) and of the phosphodiesterase inhibitors SQ20009 and ICI63,197 on hamster sperm incubated under in vitro capacitating conditions. Washed hamster sperm were incubated in a capacitation media containing bovine serum albumin, and a protein‐free “motilityfactor” from bovine adrenal cortex. Incubation for 3.5 hours was followed by addition of one of the compounds (0.1–10 μM) or control buffer. At the time of addition and after 30–120 minutes further incubation, sperm were examined by phase contrast microscopy. The final motility was similar to the, initial motility (50–70%) and the same in incubation of controls or experimental compounds. Bt2cAMP, SQ20009, and ICI63,197 at these concentrations stimulated acrosome reactions to a statistically significant extent (P <0.005) compared to controls. Activation was stimulated to a varying degree by all three experimental compounds. These results suggest a role for cyclic nucleotides in capacitation and the acrosome reaction of hamster sperm.
Salinity adaption of gill Na, K‐ATPase in the blue crab, Callinectes sapidus
Authors: Neufeld Gaylen J. , Holliday Charles W. , Pritchard John B.
Published: June 2005

Both male and female blue crabs were shown to hyperosmoregulate efficiently at low salinities. The posterior gill pairs, particularly numbers six and seven, exhibited the highest specific activity of Na, K‐ATPase in crabs adapted to full‐strength seawater. When the crabs were acclimated to 200 mOs/kg, Na,K‐ATPase activity increased in all gill pairs, with the most pronounced increase in gills six and seven (∼ 80%). Crabs which had been acclimated to waters of 1000, 800, 500, and 200 mOs/kg showed asequential increase in Na, K‐ATPase activity which matched the decrease in medium osmolality. At the lowest salinity, the increase was somewhat greater in males, approximately 26% higher than in females. In crabs adapted to 100% seawater, the highest enzyme activity was localized in the lateral one‐third of the gill lamellae, near the afferent vessel. Acclimation to low salinities was accompanied by a significant increase in Na,K‐ATPase activity in the middle and medial portions of the gill. Abrupt transfer of crabs from 1000 mOs/kg to 200 mOs/kg, or vice versa, resulted in rapid changes in hemolymph osmolality which stabilized within 24 hours. However, the Na,K‐ATPase activity changed gradually and did not reach equilibrium levels until 12 to 18 days,after transfer. These data suggest that Na,K‐ATPase activity was altered primarily by synthesis and degradation, rather than by modulation of the activity of existing enzyme.
Amino acid metabolism and cell volume regulation in the little skate, Raja erinacea. I. Oxidation
Authors: King Patricia A. , Cha Chung‐Ja , Goldstein Leon
Published: June 2005

The capacity of isolated tissues of the little skate (Raja erinacea) to oxidize β‐alanine, sarcosine, and taurine, and the role of amino acid oxidation in the modulation of intracellular free amino acid concentrations was investigated in vitro. Liver was found to be the primary site of β‐alanine and sarcosine oxidation. Chronic acclimation of skates to half‐strength sea water increased in vitro oxidation of β‐alanine and alanine by liver slices. Taurine oxidation could not be detected in any of the tissues tested. In vivo studies showed that taurine is excreted intact and that excretion increases significantly following acute acclimation of skates to half‐strength sea water.
Age and endocrine effects on fat body metabolite composition in adult male Blaberus discoidalis cockroaches
Authors: Mannix John J. , Keeley Larry L.
Published: June 2005

Endocrine‐and age‐related changes in metabolite contents were used as a measure of fat body development and function in adult male Blaberus discoidalis cockroaches. Fat body dry weight, protein, glycogen, and lipid levels coordinately decreased at days two to three of adult life, increased at day four, then declined to lower stable levels by days six to seven. The metabolite contents remained stable from days seven through ten and were still at this level on day 30. Long‐term endocrine deficiencies resulting from corpora cardiaca‐allata extirpation did not change the amounts of metabolites present at 30 days of age. The fat body DNA content remained constant regardless of age or endocrine balance. Unlike other metabolites, the RNA content increased to twice its original level during the first six days of adult life and was unaffected by either age or endocrine balance thereafter. The findings suggest that the adult fat body changes from a storage function at the time of the nymphal‐adult molt to a biosynthetic function by day six. The transition is independent of endocrine control by the corpora cardiaca‐allata complex.
Effect of DNA inhibitors upon DNA synthesis and development of Drosophila embryos
Authors: Parente Anthony , Arking Robert , Kalata Karen
Published: June 2005

Staged wildtype embryos Drosophila melanogaster were permeabilized and then subjected to a short pulse of either methyl‐3H‐thymidine, one of four different inhibitors of DNA synthesis (mitomycin C, 5‐fluorouracil, nalidixic acid, or 1‐β‐D‐arabino‐furanosylcytosine‐5′‐monophosphate), or a combination of both. The incorporation of methyl‐3H‐thymidine into acid insoluble material was at a maximum during the first half‐hour of embryogenesis, after which the incorporation dropped to half the initial value and remained constant throughout the remainder of development. There was no correlation between the rate of incorporation of methyl‐3H‐thymidine into DNA and the known periods of high mitotic activity. The time course of the estimated specific activity of the DNA newly synthesized in vivo closely paralleled the known changes in the DNA polymerase activity determined in vitro. The known periods of high mitotic activity in the embryo (0–3 hours, 5–12 hours) agree with the periods of maximal sensitivity of the embryo to the inhibitors of DNA synthesis. All four DNA inhibitors affected the incorporation of methyl‐3H‐thymidine into DNA, although they did not affect it in any simplistic manner. Inhibitor treatment during early cleavage resulted in arrested development, and treatment during late cleavage and blastoderm stages resulted in abnormal development, and treatment during late blastoderm and early gastrula resulted in normal development. The major phenotypic abnormality caused by the inhibitors is an abnormal distribution of blastoderm cells. As judged by the ID50 values, the embryos remained very sensitive to the effects of the inhibitors until the stages of head and body segmentation, when they then very rapidly became insensitive.
Relationships between the release of acid, the cortical reaction, and the increase of protein synthesis in sea urchin eggs
Authors: Nishioka David , McGwin Natalie F.
Published: June 2005

Cortical granule discharge has been separated from Na+‐‐dependent acid release and the increase of protein synthesis in sea urchin eggs. When 2% egg suspensions are inseminated or treated with the ionophore A23187 in normal sea water, cortical granule discharge is induced and the pH of the suspensions decrease approximately 0.35 pH units. When a similar suspension is treated with A23187 in Na+‐free sea water, cortical granule discharge is induced, but the pH of the suspension decreases only 0.05 pH units, and the rate of protein synthesis remains at the level of the unfertilized egg. When 0.05 M NaCl is added to this suspension, the pH decreases the remaining 0.30 pH units, and the rate of protein synthesis increases to the level of the fertilized egg. Thus, there appear to be two components of acid release from sea urchin eggs at fertilization: (1) a Na+‐independent component which correlates with cortical granule discharge; and (2) a Na+‐dependent component which correlates with the increase of protein synthesis.
Autonomous development of reciprocally exchanged regeneration blastemas of normal forelimbs and symmetrical hindlimbs
Authors: Stocum David L.
Published: June 2005

Normal upper arm blastemas and blastemas derived from double posterior or double anterior thighs of A. mexicanum were reciprocally exchanged either by autografting or homografting between dark and white animals. Those grafted blastemas which survived always regenerated a morphology and pigmentation characteristics of the donor limb. Thus, upper arm blastemas on double anterior or posterior thigh stumps regenerated normal forelimbs. Double anterior blastemas on normal upper arm stumps failed to regenerate, and double posterior blastemas on normal upper arm stumps regenerated posterior half hindlimbs. These results show that the morphogenetic field of the regenerate is reflected in the composition of the limb stump, and that its pattern is expressed autonomously.

Supernumerary limbs formed where posterior and anterior tissues of graft and host were opposed in 35–43% of cases where normal upper arm blastemas were grafted to symmetrical thighs. The morphology and pigmentation of the supernumeraries suggests that they are probably derived from both graft and stump, although a singular origin from either graft or stump is not ruled out in some cases.
A study of hetero‐specific sperm‐egg interactions in the rat, mouse, and deer mouse using in vitro fertilization and sperm injection
Authors: Thadani Vijay M.
Published: June 2005

Hetero‐Specific fertilization of zona‐free eggs is used in these experiments as a tool to analyze the barriers to hybridization and to gain insight into the mechanisms of normal fertilization. When the zonae of rat eggs, which are a barrier to hetero‐specific fertilization, are removed with pronase, the eggs can be fertilized by mouse sperm and the zygotes start to develop normally. A rat egg fertilized with mouse sperm completes meiosis and forms both male and female pronuclei. Chromosomes from both parents are found on the spindle at the metaphase stage of the first cleavage division. Under present culture conditions, embryos develop only to the two‐cell stage, but this initial development of the hybrid is apparently normal.

The question of whether sperm and egg membrane fusion is requisite for normal development is addressed by injecting sperm directly into the cytoplasm of unfertilized eggs. The injection of mouse sperm into rat eggs frequently leads to activation and formation of male and female pronuclei. The first cleavage division is indistinguishable from that following hetero‐specific fetilization. Capacitated and uncapacitated sperm react alike when injected into eggs. Egg activation, however, is necessary for male pronucleus formation. Sperm from the deer mouse Peromyscus maniculatus bairdii, which are incapable of fertilizing even zona‐free rat eggs, respond like mouse sperm when injected into rat eggs. These data indicate that sperm interactions with the egg cytoplasm are less species‐specific than interactions at the egg surface. Furthermore, the normal surface interactions of sperm and eggs are not essential for the start of development.
Electrophysiological responses of the central nervous system in the presence of homospecific and heterospecific sex pheromones in nereids (Annelida polychaeta)
Authors: Boilly‐Marer Yolande , Lassalle Bernard
Published: June 2005

The influence of sex pheromones on the electrical activity in the brain and the nerve cord was studied in mature and immature nereids. The pheromone of the opposite sex induces an intense electrical activity in the brain and the nerve cord only when the nereid is mature and possesses transformed parapodial cirri (swollen cirri in this work). The integrity of the connections between brain and nerve cord is also required for the stimulation of the electrical activity of the brain but not for the nerve cord. The electrical activity of the brain and the nerve cord is also stimulated by heterospecific pheromones of the opposite sex in the same way as with homospecific sex pheromones. Thus, homospecific and heterospecific sex pheromones are both perceived by mature (epitokous) nereids. The stimulation is received by the transformed parapodial cirri and is transmitted to the brain through the nerve cord.
Histone synthesis in preimplantation rabbit embryos
Authors: Matheson R. Clair , Schultz Gilbert A.
Published: June 2005

Intracellular specific radioactivities of lysine and arginine were measured in preimplantation rabbit embryos. In conjunction with measurements of radioactivity incorporated into total protein and histones and amino acid composition data, absolute rates of synthesis were calculated. Total protein is synthesized at a rate of 0.78 ng/hr/embryo or 0.049 ng/hr/cell for the 2‐day (16‐cell) cleavage embryo and 2,828 ng/hr/embryo or 0.036 ng/hr/cell for the 6‐day (80,000‐cell) blastocyst. Calculated rates of accumulation for histone proteins were 40 pg/hr/embryo for the 2‐day cleavage embryo (5.12% of total protein accumulation) and 96,600 pg/hr/embryo (3.42% of total protein accumulation) for the 6‐day blastocyst. These amounts of histone synthesis are only slightly in excess of that required to package newly synthesized DNA into nucleosomes during the cycle of replication, suggesting that histone and DNA synthesis are quantitatively coordinated. Further, when cytosine arabinoside was used to inhibit DNA synthesis by 97% in cleavage embryos, amino acid incorporation into histone was inhibited by 82%, while total incorporation was reduced by about 20%, indicating that histone and DNA synthesis are also temporally coordinated.
Anaerobic metabolism, gas exchange, and acid‐base balance during hypoxic exposure in the channel catfish, Ictalurus punctatus
Authors: Burggren Warren W. , Cameron James N.
Published: June 2005

Gill ventilation, blood gas and acid‐base values, ṀO2, ṀCO2 and the gas exchange ratio have been measured before, during, and after exposure to hypoxia in the channel catfish, Ictalurus punctatus.

I. punctatus maintains ṀO2 at control levels to a PIO2 as low as 60 mm Hg, through a profound branchial hyperventilation. Concomitantly, however, a lactic acidosis usually develops, indicating a significant anaerobic glycolysis. Both a metabolic acidosis and respiratory alkalosis occur in Ictalurus during hypoxic exposure, with the former usually predominating. ṀCO2 doubles and the gas exchange ratio (RE) increases from 0.8 at control levels to 2.0 at hypoxic levels, indicating that, in addition to anaerobic glycolysis, nonglycolytic pathways producing CO2 also operate during hypoxic exposure.

Analysis reveals that at least half of the increased ṀCO2 during hypoxic exposure is due strictly to lactate acidfication of the tissue HCO3− pool, rather than from metabolic production of molecular CO2. Thus, the actual respiratory quotient (RQ) only rises to 1.5 during hypoxic exposure.

Within one hour of a return to air saturated water, a large lactate “flush” and severe plasma acidosis occur, and control levels for these and other values are not reachieved for 2–6 hours after hypoxic exposure.

Complete analysis of O2 and CO2 exchange in the catfish exposed to short‐term hypoxia thus must consider both the time course of acid‐base disturbance and the evolution of CO2 from the acidified tissue bicarbonate pool.
Segmental innervation of rotated and supernumerary axolotl hindlimbs
Authors: Bennett M. R. , McGrath P. A.
Published: June 2005

The segmental nerve supply to axolotl limbs was misrouted by severing the limbs at the level of the femur, rotating them 180° around their long axis, and then suturing them to the intact proximal stump. Following return of the blood supply to the rotated limb by the cross‐anastomosing of blood vessels, a blastema often formed to the side of the rotation site giving rise to a supernumerary limb. The muscles of both rotated and supernumerary limbs were innervated by the segmental nerves. The percentage of cells innervated by segmental nerves 16 and 17 in each muscle was determined with intracellular electrodes at 14 weeks after the operation. Despite histological evidence that nerves had been misrouted in the rotated limb, the percentage innervation of each muscle by nerves 16 and 17 was similar to that in the unoperated contralateral controls. The same results were obtained for the supernumerary limbs. In some muscles a few synaptic sites were found innervated by segmental nerves which did not innervate that muscle in the contralateral controls. These had synaptic potentials with very low quantal contents if immediately adjacent sites were innervated by the segmental nerve, which did innervate that muscle in the contralateral controls. The results suggest that the selective properties of synaptic sites are alone sufficient to determine the entire segmental innervation pattern of the muscles in a limb.
Respiratory properties of whole blood and hemoglobin from the burrowing reptile, Amphisbaena alba
Authors: Johansen K. , Abe A. S. , Weber R. E.
Published: June 2005

Respiratory properties of whole blood and hemoglobin solutions have been studied in the burrowing reptile, Amphisbaena alba.

Whole blood is distinguished from that of other squamate reptiles by an extraordinary high O2 affinity (P50 = 12 mmHg at pH 7.60 and 25°C). The Bohr factor,ϕ, was large at −0.85 and the n‐value was 1.80. O2 capacity averaged 12.0 vol%. The molar concentration of erythrocyte ATP was high and twice that of hemoglobin.

Stripped Amphisbaena hemoglobin shows an extremely high O2 affinity and reduced pH sensitivity compared to whole blood (P50 = 1 mmHg at pH 7.60 and 25°C, ϕ = −0.35, n‐value = 2.0). The hemoglobin O2 affinity was much more sensitive to ATP than for other poikilotherm vertebrates.

Isoelectric focusing revealed a multicomponent hemoglobin with the major components showing similar O2 affinities and Bohr shifts.

The data obtained are discussed in relation to the burrowing habits of Amphisbaena and found to be adaptive to a fossorial mode of life.
Changes in RNA and protein synthesis in the neural retina during lens regeneration in newts
Authors: Gulati Adarsh K.
Published: June 2005

Since neural retina stimulates regeneration of a lens from the dorsal iris in newts, RNA and protein synthesis in the neural retina was investigated during this process. Incorporation of 3H‐leucine using liquid scintillation counting was employed to compare RNA and protein synthesis in the neural retina from sham‐operated control eyes with that in eyes during lens regeneration. An initial increase in 3H‐uridine uptake was seen one to three days after lentectomy. This was followed by greater incorporation of 3H‐leucine, indicating increased protein synthesis between 5 to 15 days after lens removal. A decrease in 3H‐uridine uptake was also seen at 5 to 12 days after lentectomy. After 20 days both the RNA and protein synthesis returned to the normal level. Since the increase in protein synthesis is preceded by an increase in RNA synthesis, the two processes might be related. The results indicate significant changes in the synthesis of macromolecules by the neural retina following lentectomy. These may be indirectly related to the production of the neural retinal factor with stimulates lens differentiation.
Transport of nitrite across fish gills
Authors: Bath R. N. , Eddy F. B.
Published: June 2005

The results show that rainbow trout (Salmo gairdneri) are able to concentrate NO ions in the blood plasma. After 24 hr in water containing 0.7 mM/l NO, the blood plasma contained about 5mM/l NO suggesting that the gills have the ability to transport NO2 against a concentration gradient.
Histochemical, enzymatic, and contractile properties of skeletal muscle fibers in the lizard Dipsosaurus dorsalis
Authors: Gleeson Todd T. , Putnam Robert W. , Bennett Albert F.
Published: June 2005

Lizard skeletal muscle fiber types were investigated inthe iliofibularis (IF) muscle of the desert iguana (Dipsosaurus dorsalis). Three fiber types were identified based on histochemical staining for myosin ATPase (mATPase), succinic dehydrogenase (SDH), and αglycerophosphate dehydrogenase (αGPDH) activity. The pale region of the IF contains exclusively fast‐twitch‐glycolytic (FG) fibers, which stain dark for mATPase and αGPDH, light for SDH. The red region of the IF contains fast‐twitch‐oxidative‐glycolytic (FOG) fibers, which stain dark for all three enzymes, and tonic fibers, which stain light for mATPase, dark for SDH, and moderate for αGPDH confirm these histochemical interpretations. Lizard FG and FOG fibers possess twitch contraction times and resistance to fatigue comparable to analogous fibers in mammals, but are one‐half as oxidative and several times as glycolytic as analogous fibers in rats. Lizard tonic fibers demonstrate the acetylcholine sensitivity common to other vertebrate tonic fibers.
Localization of smooth‐muscle myosin in branchial pillar cells of snapper (Chrysophys auratus) by immunofluorescence histochemistry
Authors: Smith D. G. , Chamley‐Campbell J.
Published: June 2005

Smooth muscle myosin was localized in pillar cells by immunofluorescence histochemistry of gills from snapper (Chrysophys auratus). The amount of myosin present is comparable to that seen in mammalian vascular smooth muscle. No differences in the distribution of myosin‐containing pillar cells, either within or between different secondary lamellae, were noted. The possibility that contractile proteins in pillar cells could function as autoregulators of blood flow, by responding with changes in active tension to alterations in the rate of change of pressure with each cardiac cycle, is discussed.
Tetrodotoxin‐Sensitive action potentials from the brain of the polyclad flatworm, Notoplana acticola
Authors: Keenan Larry , Koopowitz Harold
Published: June 2005

Action potentials recorded intracellularly from the brain of the polyclad flatworm, Notoplana acticola, show reductions in amplitude in the presence of 3.2 × 10−5 M tetrodotoxin. Vibration responder cells and spontaneously active cells were sensitive to tetrodotoxin. One cell was found that did not respond to the toxin. Most brain cells filled with Lucifer Yellow dye were found to be heteropolar multipolar neurones quite unlike those commonly found in other invertebrate ganglia.
Metabolic consequences of the extent and disposition of the aqueous intracellular environment
Authors: Clegg James S.
Published: June 2005

Attention is focused on the aqueous compartments of eucaryotic cells (nucleoplasm, cytosol, and interior compartments of cytoplasmic membrane‐bound organelles). Previous work on the relationship between cell water content, the physical properties of cell water, and metabolic activity in cysts of the brine shrimp, Artemia is summarized and discussed in that context. A previously proposed general model of the organization of metabolic activity in the aqueous compartments will be summarized.
Verification of an in vitro bioassay for limb bud polarizing activity
Authors: Maccabe Jeffrey A. , Knouse Eunice R. , Richardson Kathryn E. Y.
Published: June 2005

An in vitro bioassay for limb bud polarizing activity in the chick embryo has been verified by two procedures, demonstrating that the culture procedure mimics occurrences in vivo. First, no activity can be detected with the in vitro assay 24 hours after removal of the posterior region of the limb. In addition, after a positive assay for activity, the responding tissue develops into polarized limb structures when transplanted to a host embryo. After a negative assay, the transplanted responding tissue fails to develop into recognizable limb structures. Since polarizing activity is defined by its ability to induce polarized limb structures in vivo we conclude that the in vitro system provides a valid assay for limb polarizing activity.
Aspirin‐induced teratogenesis: A unique pattern of cell death and subsequent polydactyly in the rat
Authors: Klein Kenneth L. , Scott William J. , Wilson James G.
Published: June 2005

Offspring of pregnant rats treated with a high dose of aspirin on day 11 of gestation frequently had predominantly right‐sided polydactyly of the hindlimbs at term. Aspirin‐treated embryos removed on day 12 exhibited a unique pattern of preaxial mesodermal cell death in the hindlimb buds. In addition, these embryos had a delay of the normal episode of cell death in the preaxial apical ectodermal ridge and an absence of cell death in a zone of physiological necrosis in the preaxial mesoderm thought to be instrumental in controlling preaxial digit formation. The role of cell death in the pathogenesis of polydactyly is discussed.