bluuebunny/crossref_metadata_2025_split huggingface dataset:
Production of genetically identical sets of mammals: Cloning?
Authors: Seidel George E. 
Published: June 2005

AbstractIn the past few years, there has been phenomenal progress in producing genetically identical mammalian multiplets by asexual means. The simplest method is to divide embryos into two, three, or four parts, and transfer the parts to surrogate mothers for gestation to term. Another approach is to inject nuclei from totipotent embryonic cells into fertilized one‐cell embryos and to remove both male and female pronuclei. When these embryos reach the blastocyst stage, nuclei from their totipotent cells can be removed and injected into one‐cell embryos, thus amplifying the process ad infinitum. Subsets of these embryos can be stored in liquid nitrogen to make genetic material for additional copies available indefinitely. Some of these techniques are fairly efficacious, others are not.No reliable techniques are available for making genetic copies of nonhomozygous adult mammals (or other vertebrates) unless samples of embryonic cells were cryopreserved when the individuals were embryos. However, injection of nuclei of spermatogonia into enucleated one‐cell embryos is a promising strategy. The genetic totipotency of these nuclei is obvious since they become gamete nuclei. Moreover, the birth of mice from the diploidized genetic material of a single X‐bearing spermatozoan after removal of the female pronucleus from a one‐cell fertilized embryo suggests that we should eventually be able to make genetic copies of adult male mammals. This approach would not work for adult females because their oogonia have all become oocytes, and the DNA configuration in oocytes is not identical to somatic cells due to meiotic crossing over.
Measuring aerobic and anaerobic metabolism of benthic infauna under natural conditions
Authors: Pamatmat Mario M. 
Published: June 2005

AbstractSome species of invertebrates, particularly benthic infauna, show extreme metabolic fluctuations, from a truly basal metabolic rate while quiescent in anaerobic mode to higher rates as a result of physical activity whether they are anaerobic or aerobic. The fluctuations may be random or cyclic, endogenous, induced by experimental conditions, or by natural changes in environmental conditions; they are readily seen and quantified by direct calorimetry.Biochemists studying anaerobic metabolism sometimes find large quantitative variations in metabolite concentration between individual test organisms. One source of variability may be the variability in the metabolic activity of the control and experimental animals. Information contained in heat flow recordings could be useful in normalizing data and making more precise correlations between actual metabolic rates and chemical measures of metabolism.Theoretical enthalpy changes from known anaerobic end products and results of direct calorimetry do not agree at present. Continual comparisons, leading to consistent agreement or satisfactory explanation of their discrepancy, are necessary to demonstrate full understanding of anaerobic metabolism.
A steady efflux of ionic current predicts hind limb development in the axolotl
Authors: Borgens Richard B. , Rouleau Marie F. , DeLanney Louis E. 
Published: June 2005

AbstractFor more than a week prior to the emergence of a hind limb, a steady electric current is driven out of the ventrolateral flank in the immature axolotl, returning through the integument in adjacent regions of the body. A marked peak in the density of this outcurrent could be observed over the exact area of hind limb formation 4 to 6 days prior to its appearance. After a bud projected from the flank, current densities were observed to decrease in magnitude yet localize about the early limb. In about one‐half of the animals observed, current reversed its polarity and entered the apex of large buds, 0.4 to 0.5 mm in length. We discuss the possible role such endogenous currents and their associated fields may play in limb development and compare it to similar current flow associated with the regeneration of amphibian limbs.
Presence and localization of chitinase in Hydra and Podocoryne (Cnidaria, Hydrozoa)
Authors: Klug Marianne , Tardent Pierre , Smid Iris , Holstein Thomas 
Published: June 2005

AbstractThe presence of chitinase was checked in three species of Hydrozoa by incubating γ‐chitin‐red (Hackmann and Goldberg, '64) with crude extracts of entire polyps or parts of them. When the substrate is lytically degraded it releases its soluble red dye the quantities of which were spectrophotometrically (λ = 510 nm) determined. Crude extracts of entire polyps of Hydra attenuata Pall., H. circumcincta M. Sch., and Podocoryne carnea M. Sars all contained active chitinase. A more detailed localization which was studied in H. attenuata revealed that the enzyme is confined to the endoderm of the body column and that it is absent in the ectoderm and in the tentacles which contain the stenotele nematocysts. Therefore, it is very unlikely that enzymatic action of chitinase aids the nematocyst in boring holes in the cuticule of the prey.
Neural crest cell behavior in white and dark larvae of Ambystoma mexicanum: Time‐lapse cinemicrographic analysis of pigment cell movement in vivo and in culture
Authors: Keller R. E. , Spieth John 
Published: June 2005

AbstractThe pattern of migration and motile activity of developing pigment cells of the Mexican axolotl, Ambystoma mexicanum, were analyzed by time‐lapse cinemicrography in vivo and in culture. In vivo, melanocytes of dark (D/–) larvae migrate from dorsal to ventral in a highly directional manner. They are elongated and aligned parallel to the direction of migration. Nearly all protrusive activity occurs at their ventral, leading edges. Translocation occurs at a mean rate of 0.7 μm/min and involves alternate or simultaneous advance of the leading and trailing edges of the cell. Indirect evidence suggests that cytoplasmic flow is common. Directional migration occurs in apparent absence of contact between melanocytes. In white (d/d) larvae, protrusive activity is infrequent and the melanocytes move slowly or not at all. Explanted neural crest cells of dark and white larvae attach, spread, and differentiate into melanophores and xanthophores in culture. Individual cultured cells are unbiased in direction of protrusive activity and path of migration. Centrifugal spreading occurs by contacting inhibition of movement. Distribution of protrusive activity, polarity, and contact behavior changes with developmental age in vivo and in culture in ways that may be important in establishing the pigment pattern.
Cell cycle and histological effects of reinnervation in denervated forelimb stumps of larval Ambystoma
Authors: Olsen Cherie L. , Tassava Roy A. 
Published: June 2005

AbstractAlthough nerves are a requirement for regeneration of a salamander limb, denervation of an amputated larval Ambystoma forelimb does not permanently prevent the limb from regenerating. When nerves grow back into the distal stump in sufficient numbers, regeneration occurs. In this study we examined histological and cell cycle events in denervated limb stumps of Ambystoma as they became reinnervated and began to regenerate. Prior to reinnervation and regeneration, dedifferentiated cells are present in the distal stump but are rarely synthesizing DNA or undergoing mitosis and are densely packed. About 2 days after the distal tip of the stump becomes reinnervated, the limb tip appears to “expand” as cells become less densely packed, and cell cycle activity begins. Mitotic index (MI) and labeling index (LI) increase slowly compared to MI and LI in control amputated limbs. Evidence for the localization of cycling activity is presented. In reinnervated stumps, the increase in LI precedes the increase in MI, suggesting that most of the cells are initiating cycling from the G1 phase.
The tissue‐specific patterns of lactate dehydrogenase (LDH), alcohol dehydrogenase (ADH), and G‐6‐phosphate dehydrogenase (G‐6‐PD) in adults and their occurrence during ontogeny of the guppy, Poecilia reticulata Peters (pisces: Poeciliidae)
Authors: Chingjiang Wu , Schröder Johannes Horst 
Published: June 2005

AbstractUsing polyacrylamide gel electrophoresis, the tissue‐specific and ontogenetic patterns of three dehydrogenase enzymes (LDH, ADH, and G‐6‐PD) of the guppy were investigated. Only one band of G‐6‐PD was detected in extracts of the liver. Isozyme LDH‐B4 was ubiquitous; isozyme LDH‐A4 was detected predominantly in extracts of muscle, and isozyme LDH‐C was only observed in extracts of the eye. Isozyme ADH‐A was detected in all tissues except the heart, while isozymes ADH‐B and ADH‐C were only detected in extracts of the eye. Isozymes LDH‐C and its heteromers with LDH‐B first appear following complete differentiation of the retinal cells. The appearance of isozyme LDH‐A coincided with the onset of contractile movements of muscle. Isozymes ADH‐B and ADH‐C are not detected until fry are 16 mm long after the onset of the complete differentiation of the retinal cells and visional function. Isozymes ADH‐D and G‐6‐PD are enzymes found only in embryonic stages and suddenly disappear after hatching. They may be regulative enzymes of cell differentiation.
The synchronisation of hatching in quail embryos: Aspects of development affected by a retarding stimulus
Authors: Vince M. A. , Ockleford E. , Reader M. 
Published: June 2005

AbstractOne hundred twenty‐eight quail embryos were tested in 33 groups. In each group one egg was stimulated with sounds at a rate known to delay hatching (0.9 clicks/second). In groups of bobwhite quail, stimulation began three days or two days before hatching, and three days before hatching in groups of Japanese quail. All eggs were incubated separately and respiration was monitored to indicate 1) the onset of lung ventilation, 2) the time when the egg began to click, and 3) the hatching time. In one set of bobwhite quail heart rate was also monitored.Stimulated bobwhite quail hatched later than controls, but only when stimulated from three days before hatching. In the Japanese quail fewer embryos were retarded. In retarded bobwhites the duration of breathing, but not the duration of clicking, was lengthened. Respiration rates in stimulated bobwhites were higher throughout stimulation than those of controls. One factor contributing to this increase appeared to be the pacing of breathing in stimulated embryos: breathing tended to stabilise at the level of the stimulation rate. The heart rate of stimulated embryos was higher than that of controls, significantly so around the time of the onset of breathing.In bobwhite, but not in Japanese quail, the increase in respiration rate was found to be associated with retardation and not with stimulation alone; it did not occur in those embryos which were stimulated but not retarded.
Hyaluronidase dissolves a component in the hamster zona pellucida
Authors: Talbot Prudence 
Published: June 2005

AbstractMammalian sperm must pass between cumulus cells and corona radiata cells before reaching the surface of the zona pellucida which surrounds the oocyte. The cumulus and corona radiata cells are separated from each other by an extracellular matrix (ECM) containing hyaluronic acid. The structure of this ECM and of the zona pellucida was investigated in the hamster oocyte‐cumulus complex (OCC) using transmission electron micros copy (TEM) following processing in ruthenium red. When fixed in the presence of ruthenium red, the ECM of the OCC and the zona pellucida were well preserved and highly structured. The ECM between corona radiata cells was comprised of a network of granules and filaments which resembled hyaluronic acid containing matrices described in other systems. The outer one‐third to one‐half of the zona pellucida was porous; the ECM of the corona radiata extended into these pores. Bovine testicular hyaluronidase, Streptomyces hyaluronidase, and hamster sperm extracts containing hyaluronidase each dispersed the cumulus cells and most of the corona radiata cells. TEM examination revealed that brief (5–10 min) hyaluronidase treatment of OCCs removed the matrix filaments and caused clumping of the granules in both the corona radiata and zona pellucida. Longer hyaluronidase treatments (15–30 min) removed both filaments and granules. Our observations are consistent with the ideas that: 1) the ECM between corona radiata cells contains hyaluronic acid, and 2) hyaluronic acid is present in the outer one‐third to one‐half of the zona pellucida. The function of sperm hyaluronidase in penetration of the OCC has not yet been established with certainty. Our data show that the substrate for sperm hyaluronidase is present in the zona pellucida as well as in the corona radiata and cumulus layer and suggest that the function of this enzyme in fertilization should be examined further.
Electron microscopic studies of planarian regeneration. III. Degeneration and differentiation of muscles
Authors: Morita Michio , Best Jay Boyd 
Published: June 2005

AbstractPlanarians were surgically decapitated, and morphological changes in their muscles during regeneration were studied with the electron microscope. Many damaged muscles were found in the vicinity of the wound surface immediately following decapitation. These stain darker than normal muscle and show degenerative changes in organelles as early as 1 hour. Some damaged muscles were observed to fall of f the cut surface into the external medium during the first 16 hours, but most were phagocytized by reticular cells mobilized to the wound area during this period. These were the only fates observed for damaged muscle in the vicinity of the wound. Detailed searches of large areas of wound region, at various times from 1 to 72 hours following decapitation, revealed no evidence of de‐ and redifferentiation of preexisting muscle cells. Newly differentiating muscle cells, identifiable by small nascent myofibril bundles in the cytoplasm close to the nuclear envelope or rough endoplasmic reticulum, are first discernible in the cellular aggregate of the new regeneration blastema on the third day. Vestiges of nuclear satellite material in the perinuclear cytoplasm of such cells indicate their derivation from neoblasts. Further histogenesis involved migration of these newly formed muscle cells to the apical perimeter of the blastema 4 to 6 days after decapitation. Neuromuscular junctions were observed to form during these later stages.
Pattern regulation along the proximodistal axis of the developing chick limb
Authors: Gay Steven W. , MacCabe Jeffrey A. 
Published: June 2005

AbstractTransplants creating presumptively excess or deficient proximodistal segments were performed to investigate pattern regulation in stage 21 and stage 23 chick limb buds. Excess skeletal elements were not removed by regulation. Deficiencies appeared to be regulated by host tissue. The ability of the host tissue to participate in regulation declined in more proximal tissue and with increased age. These results suggest that there are two requirements for pattern regulation. First, the tissue in question must be sufficiently uncommitted in terms of pattern formation. Second, this tissue must be sufficiently close to the ectodermal ridge before it can respond. Results of previous work and implications for pattern formation are discussed with these requirements in mind.
Ectopic testes in the Norway rat
Authors: Gumbreck Laurence G. , Stanley Allan J. , Allison John E. , Peeples E. Edward 
Published: June 2005

AbstractAnimals with ectopic testes, some unilateral (on either the right or left side) and some bilateral, have appeared in a colony of King‐Holtzman rats. This heritable defect has been given the genetic symbol “ect.” Females carrying the gene are unaffected by it. When such females are bred to apparently normal males, they produce no ect offspring. Since 25% of their F2 generation carry the gene, it is assumed it is autosomal recessive. Studies involving selective breeding for males with ectopic testes indicate that some males have genomes resistant to the expression of the ect gene and that the apparent thresholds essential to left side, right side, and bilateral expression appear to be a secondary control of the multifactorial type.
The use of cell surface antigens to characterize and select for fragments of human chromosomes retained by interspecies hybrids
Authors: Kamarck Michael E. , Macyko Catherine A. , Jones Carol , Ruddle Frank H. 
Published: June 2005

AbstractWe have used a mouse cell transformant generated by human chromosome‐mediated gene transfer (CMGT) to explore the use of cell surface antigens in the identification of fragments of human chromosomes retained by somatic cell hybrids. The transformed line, 21–30b, contained an intact rearranged human chromosome, and could be shown by isozyme analysis to contain genetic material from chromosomes 9 and X. By using the transformant as an immunogen in mice, it was also possible to produce antiserum to human‐specific surface antigens. Using genetically characterized human × rodent hybrid lines, the genes controlling expression of these antigens could be localized to 11pter → 11p13, segregating concordantly with surface antigen S3. These conclusions were possible despite the fact that the presence of chromosome 11 in the transformant was not detectable by the presence of chromosome specific isozyme LDH‐A or surface antigens W6/34 and 4F2. Finally, the fluorescence‐activated cell sorter (FACS) was used to fractionate the transformant cells into antigen positive and negative subpopulations. This resulted in the isolation and characterization of four additional chromosome rearrangements involving interspecies chromosome translocations. This work demonstrates the value of chromosome‐specific surface antigens and the FACS in the evaluation of human chromosome fragments retained by interspecies hybrids.
Heat shock proteins in Aurelia (cnidaria, scyphozoa)
Authors: Black Robert E. , Bloom Laird 
Published: June 2005

AbstractHeat shock proteins (hsp) in Aurelia identified by one‐dimensional SDS‐PAGE are of sizes 93,83,70,68,45, and 39 kD, the most rapidly labeled being hsp 70 in all developmental stages. Labeled hsp in the polyp are found mostly in the epidermis; gastrodermal nuclei are also labeled. The minimum temperature for induction of the proteins is about the same (27° to 28°C), regardless of whether polyps have been cultured at 15° or 24°C. Adults and planulae taken from natural water at 28°C do not show accumulation of hsp 70. Induction of strobilation by raising polyps from 15° to 25°C is not associated with appreciable labeling of hsp. Polyps transferred to higher or lower salinity have decreased protein synthesis but do not synthesize stress proteins.
The effect of trifluoperazine on maturation of Xenopus laevis oocytes
Authors: Hollinger T. G. , Alvarez I. M. 
Published: June 2005

AbstractFull grown Xenopus oocytes were incubated with trifluoperazine (TFP) or injected with TFP. Incubation of oocytes in TFP resulted in normal‐appearing meiotic maturation, as judged by the presence of the white spot and the absence of the germinal vesicle. Cortical granule breakdown in TFP‐incubated oocytes was not normal. Abnormal cortical granule breakdown was also observed when progesterone‐matured oocytes were activated in the presence of TFP. Oocytes microinjected with TFP and incubated with progesterone appeared to mature in a normal manner, as judged by the absence of the germinal vesicle; these underwent cortical granule breakdown following activation, but frequently lacked the white spot. Oocytes microinjected with TFP did not mature in the absence of progesterone. We conclude that incubation, although not microinjection, of oocytes with TFP induces essentially normal resumption of meiotic maturation.
Two‐dimensional gel analysis of zymogen‐activating factors in small intestine of the mouse
Authors: Isobe Masaharu , Ogita Zen‐Ichi 
Published: June 2005

AbstractZymogen‐activating factors in the mouse were investigated by two‐dimensional electrophoresis. Mouse pancreatic zymogens—trypsinogen‐I group (Try G‐I group), trypsinogen‐II (Try G‐II), and chymotrypsinogen (Chy G)—were purified using DEAE‐cellulose column chromatography. Analysis by two‐dimensional electrophoresis, using the purified zymogens as substrates, revealed enterokinase isozymes and chymotrypsinogen‐activating factors in both the intestinal extract and luminal fluid. Mouse enterokinase was separated into at least two bands in the first‐dimensional gel, each able to activate both trypsinogens Try G‐I group and Try G‐II. Chymotrypsinogen‐activating factors were separated into several bands in the first‐dimensional gel. Some activating factors showed mobilities similar to those of mouse enterokinase isozymes. Moreover, other activating factors that can activate chymotrypsinogen were present only in the more anodal area of the first‐dimensional gel. These findings indicate that at least two enterokinases and several chymotrypsinogen‐activating factors play an important role in the process of activating digestive enzymes.
Cardioregulatory nerves in the spider Eurypelma marxi Simon
Authors: Gonzalez‐Fernandez Federico , Sherman R. G. 
Published: June 2005

AbstractThe objective of this study was to locate nerves arising from the CNS that have a cardioregulatory function in the tarantula, Eurypelma marxi Simon. Ramifications of the paired abdominal nerve VIIIb merge with the cardiac ganglion within the first heart segment. Electrical stimulation of the branches of nerve VIIIb that connect with the cardiac ganglion produce changes in heartbeat rate and amplitude. Nerve cutting experiments indicate that no other cardioregulatory nerves are present.Both increases and decreases in heart activity can be produced upon electrical stimulation of nerve VIIIb on each side of the heart. Only one action potential associated with the response of each type could be recorded in each member of the nerve pair. Therefore, we conclude that there are two inhibitory and two acceleratory neurons that arise in the central nervous system to modulate heartbeat activity.The inhibitory effect becomes maximal at a stimulation frequency of 20–30 Hz and the accelerator effect at 30–40 Hz. The aftereffect of acceleratory nerve activity exceeds that of inhibitory nerve activity. When the inhibitor and accelerator are activated simultaneously, the inhibitor dominates.The regulatory nerves interact with neurons in the cardiac ganglion. During inhibition, the number of externally recorded spikes in each ganglionic burst is decreased. The rate and magnitude of the heartbeat are decreased concomitantly. Stimulation of the accelerator enhances electrical activity in the cardiac ganglion at the same time that the heartbeat rate and amplitude are increased.
Functional study of the Caenorhabditis elegans secretory‐excretory system using laser microsurgery
Authors: Nelson F. Kenneth , Riddle Donald L. 
Published: June 2005

AbstractIndividual cells of the Caenorhabditis elegans secretory‐excretory system were ablated by laser microbeam in various larval stages. Effects on growth, molting, osmoregulation, fertility, longevity, and dauer larva formation were tested. Single‐cell ablations did not prevent subsequent molting, but ablation of the pore cell or the duct cell resulted in the absence of the normal cuticular lining of the excretory duct following a molt. When the pore cell, duct cell, or excretory cell was ablated, the animals filled with fluid within 12–24 hr and died within a few days, producing very few progeny. Ablation of the excretory gland cell, on the other hand, had no obvious developmental or behavioral effects. Excretory activity was monitored in dauer larvae by observing pulsation of the excretory duct in conditions of differing osmolarity. The rate of pulsation was quite variable over time in conditions of low osmotic strength, but averaged five‐ to six‐fold higher than that observed in buffered saline. These observations, combined with the effects of laser ablation, lead to the conclusion that one function of the excretory system is osmoregulation.