bluuebunny/crossref_metadata_2025 huggingface dataset:
Loss of laminin and type IV collagen in uterine luminal epithelial basement membranes during blastocyst lmplantation in the mouse
Authors: Blankenship Thomas N. , Given Randall L.
Published: February 2005

Background: Removal of the uterine luminal epithelium and its basement membrane is necessary for successful implantation of invasive blastocysts. Few reports, however, have specifically addressed the penetration and loss of the uterine luminal epithelial basement membrane (UEBM). We investigated the loss of UEBM by examining the distribution of laminin and type IV collagen.

Methods: Blastocyst implantation sites were collected from mice on days 5,6, and 7 of pregnancy. Paraffin sections were prepared from these tissues and processed with standard immunoperoxidase techniques to reveal the distribution of laminin and type IV collagen.

Results: On day 5 of pregnancy blastocysts were adherent to the uterine epithelium. The epithelium and UEBM were complete and uninterrupted. On day 6 the juxtaembryonic uterine epithelium was lost and focal discontinuities were seen along the UEBM. By 1200 hr the UEBM had receded to the region near the ectoplacental cone, but staining was reduced for both antigens over the entire region surrounded by decidual cells. This decreased staining of the UEBM occurred in areas not yet occupied by trophoblast cells. On day 7 the UEBM was lost over the entire embryonic half of the uterine lining, corresponding to the distribution of decidual cells.

Conclusions: Progressive loss of the UEBM occurred in a consistent spatiotemporal pattern following the onset of blastocyst implantation. Diminished immunoreactivity of laminin and type IV collagen in the UEBM was closely correlated with the area occupied by decidualized endometrial stroma and occurred in areas not yet in contact with trophoblast cells. We conclude that decidual cells are instrumental in the removal of UEBM during early pregnancy. © 1995 Wiley‐Liss, Inc.
In normal development pulmonary veins are connected to the sinus venosus segment in the left atrium
Authors: DeRuiter M. C. , Gittenberger‐De Groot A. C. , Wenink A. C. G. , Poelmann R. E. , Mentink M. M. T.
Published: February 2005

Background: Classic theories descibe that the common pulmonary vein develops as an outgrowth from either the sinus venosus or atrial segment. Recent studies show that the pulmonary veins are connected to the sinu‐atrial region before its differentiation into a sinus venosus and atrial segment.

Methods: The development of the sinu‐atrial region with regard to the developing common pulmonary vein and the growth of the atrial septum was investigated in avian embryos, using both scanning electron microscopy and immunohistochemistry. Embryos ranging between stage HH12 and HH28 were incubated with QH‐1 that recognizes quail endothelial cells and precursors, HNK‐1, that appears in this study to detect the myocardium of the sinus venosus, or with HHF‐35, being specific for muscle actins. Also vascular casts of the heart were produced by injecting prepolymerized Mercox into the vascular system.

Results: In preseptation stages the common pulmonary vein drains into the left part of the sinus venosus, that is clearly demarcated by the sinuatrial fold and HNK‐1 expression. During atrial septation the left part of the sinus venosus, in contrast to the right part, loses its HNK‐1 antigen from stage HH23 onwards, while at the same time the sinu‐atrial fold in the left atrial dorsal wall flattens and disappears. From stage HH25 onwards HNK‐1 expression is restricted to the right part of the sinus venosus, which contributes to the right atrium. The myocardial atrial septum never expresses the HNK‐1 antigen, suggesting that the septum is of atrial origin.

Discussion: It appeared that the sinus venosus does not only contribute to the sinus venarum of the right atrium, but also to the left atrium. © 1995 Wiley‐Liss, Inc.
Ultrastructural quantitative analysis of the innervation of axillary lymph nodes of the rat after antigenic stimulation
Authors: Novotny G. E. K. , Heuer T. , Schötelndreier A. , Fleisgarten C.
Published: February 2005

Background: In a previous study at the LM level we have found an increase in the density of innervation of axillary lymph nodes of the rat 4 months after antigenic stimulation.

Methods: To reduce the variability of the results, animals reared under sterile conditions, and stimulated by subcutaneous application of bovine albumin, were used. The control group of animals was compared with three experimental groups surviving the application of antigen for varying periods, so that the ascending phase, the peak, and the descending phase of production of antibodies were represented. The present publication presents the results of the same experiment, but with an ultrastructural analysis of axonal profiles and their spatial relationship to the cells of the lymph node.

Results: The present study indicates that, at the ultrastructural level, significant changes occur also during the early phase of the immune response, 10 days after application of antigen. In the short‐term response these changes take the form of an increase in the proportion of unensheathed axonal profiles (open areas) that contain vesicles, a more frequent association of open areas containing vesicles with cells, and an increase in the size of the open areas. In the long‐term reaction there is a general increase in the number of all open areas, but a reduction in the proportion that contains vesicles.

Conclusions: Our results demonstrate functional plasticity of the autonomic nervous system in response to normal physiological stimuli, and interaction between the nervous and immune systems during the immune response. © 1995 Wiley‐Liss, Inc.
Special relationship between mitochondria and hypolemmal nerve terminals in salivary glands of some bats
Authors: Tandler Bernard , Phillips Carleton J.
Published: February 2005

Background: Hypolemmal nerve terminals, which are abundant in many types of salivary glands, are naked axons that have penetrated the basement membrane to take up a position between adjacent parenchymal cells. Although they may form vesicle‐filled varicosities, there usually are no obvious morphological indications as to which cell actually is being innervated.

Methods: Specimens of over 200 species of bats were live‐trapped and their major salivary glands extirpated and prepared for electron microscopic examination.

Results: In 13 species of bats out of the more than 200, mitochondria‐hypolemmal nerve terminal complexes were observed in different sites in different salivary glands. In these 13 species, mitochondria in epithelial cells that abut nerve varicosities are closely applied to the plasma membranes of their cells to follow the contours of these nerve elements. The complexes so formed often consist of a varicosity flanked by two mitochondria in separate cells. In intensely innervated glandular segments, mitochondria may be apposed not only to varicosities, but to the axonal portions of these nervous elements as well.

Conclusions: The physiological significance of such complexes is unknown; it is conceivable that the mitochondria facilitate signal transmission or play a role in local calcium homeostasis related to nerve function. © 1995 Wiley‐Liss, Inc.
Complex structure of the common carotid artery of sheep
Authors: Gabella Giorgio
Published: February 2005

Background: Mechanical properties of blood vessels are dictated by the vessel wall structure. In many large conduit vessels the tunica media is a sheath of circular musculature and the tunica adventitia a layer of fibrous connective tissue with limited longitudinal extensibility. In contrast, the carotid artery of the sheep displays in each tunica a more complex architecture of muscle and connective tissue.

Methods: Vessels collected from ewes were measured and processed for light microscopy and for transmission electron microscopy.

Results: Layers of histologically different materials are found within the tunica intima, media and adventitia. (1) The tunica media is made of circumferentially arranged muscle cells markedly different at different depths. In the innermost third of the media. muscle cells are small and with irregular profiles, the cells are widely separated, and the extracellular material is abundant and composed mainly of elastic fibres. In the outermost third, muscle cells are larger and with more regular profiles, the cells are relatively close to each other and the extracellular material is sparse and consists mainly of collagen fibrils. (2) A small number of fibroblasts is found in all parts of the media amongst the preponderant muscle cells. (3) The intima contains fibroblast‐like cells and longitudinally arranged muscle cells. (4) The adventitia contains a thick layer of collagen and elastic fibres; external to this, it displays a conspicuous musculature, made of large bundles of longitudinal muscle.

Conclusions: The carotid artery of the sheep presents in all three coats of its wall features which are at variance from those in the better known vessels of small laboratory animals. The presence of many layers of material within the wall, the heterogeneity of the tissues found, and the occurrence of an extensive longitudinal musculature, have important effects on the mechanical properties of the vessel. © 1995 Wiley‐Liss, Inc.
Studies on the fetal development of the gubernaculum in cetacea
Authors: van der Schoot P.
Published: February 2005

Background. Adult cetacean males, like non‐mammalian vertebrates and other testicond mammals, have intra‐abdominal testes. There is no evidence of a processus vaginalis in them. Testicondia in cetaceans is considered secondary as they are judged, evolutionarily, the descendants of terrestrial mammals (ungulates) with testis descent. A possible argument in support of the latter contention would be that cetacean fetuses develop gubernacula which are the primordia of the processus vaginalis and other structures associated with testis descent in other placental mammals. the present study intended to analyse cetacean fetuses in this respect.

Methods. Serial sections of 25 fetuses (total body length between 39.5 and 160 mm) of 4 cetacean species (Delphinus delphis, Phocoena phocoena, Eschrichtius robustus, Physeter catodon) were examined with special attention to the presence or absence of structures homologous to the gubernaculum of other placental mammals (rats and humans).

Results. Gubernacular primordia were observed in fetuses from about the time of onset of sexual differentiation. Their shape and anatomical relationship with the surrounding structures were similar as those in mammals with testis descent. The gubernaculum in males developed into a large mass of dense connective tissue in the ventral‐caudal abdominal region at the site of the insertion of the mesonephric inguinal ligament and associated to the tip of the internal abdominal oblique muscle. No (or only very little) development of a processus vaginalis was noticed.

Conclusions. The results demonstrate initial emergence of mammalianlike gubernacular primordia in cetacean fetuses without their further development to elaborate structures required for testis descent. The findings support the view that cetaceans are secondarily testicond. It is suggested that (1) absence of the pelvic girdle together with (2) the development of structures in and beyond the caudal abdominal region, particularly the caudal hypaxial musculature, precludes the outgrowth, into caudal direction, of hollow organs (such as the processus vaginalis) from the abdominal cavity. © 1995 Wiley‐Liss, Inc.
Combined vascular‐bronchoalveolar casting using formalin‐fixed canine lungs and a low viscosity silicone rubber
Authors: Nettum John A.
Published: February 2005

Background: Previous work using unfixed or fixed tissues has shown that casts can be made that demonstrate the three‐dimensional structure of tissues such as the bronchoalveolar tree or the vasculature. In this report, a new method for creating a vascular‐bronchoalveolar cast is described.

Method: Canine lungs were taken from storage in formalin. Silastic 734 RTV (room temperature vulcanizing) with added red or blue pigments was injected into the pulmonary arteries and veins, respectively, using compressed air. This was followed by filling the airway with clear (translucent) Silastic 734 RTV. The lung tissue was then corroded with potassium hydroxide.

Results: Vascular‐bronchoalveolar casts were recovered giving fine detail as shown using stereo light microscopy or scanning electron microscopy.

Conclusions: This method may be useful for not only microvascular anatomy studies of lungs, but also for studying the microvasculature of other normal and diseased tissues. © 1995 Wiley‐Liss, Inc.
Electrochemical probe for on‐chip type flow immunoassay: Immunoglobulin G labeled with ferrocenecarboaldehyde
Authors: Okochi Mina , Ohta Hiroko , Tanaka Tsuyoshi , Matsunaga Tadashi
Published: February 2005

Labeling of ferrocenecarboaldehyde (Fc‐CHO) to immunoglobulin G (IgG) via formation of Schiff‐base and its reduction was investigated for construction of an electrochemical probe for miniaturized amperometric flow immunoassay. Approximately eight molecules of Fc‐CHO were labeled to IgG and the reversible redox property of ferrocene was observed. Labeling efficiency improved by over three times as compared to the conventional method using ferrocenemonocarboxylic acid (Fc‐COOH). Also, binding affinity of IgG labeled with Fc‐CHO to its antigen, IgE, was investigated by enzyme‐linked immunosorbent assay (ELISA) and surface plasmon resonance assay. IgG labeled with Fc‐CHO that retained eight ferrocene moiety showed sufficient binding affinity to its antigen and the current response obtained in the flow electrochemical detection system increased by 14‐fold as compared with IgG labeled with Fc‐COOH when applying the potential of 390 mV vs. Ag/AgCl. The minimum detectable concentration of IgG labeled with Fc‐CHO was 0.06 μM. IgG labeled with Fc‐CHO demonstrate biochemical and electrochemical properties that are useful for electrochemical immunosensors. © 2005 Wiley Periodicals, Inc.
Studies on synchronously dividing cultures of Euglena gracilis Klebs (strain Z). III. Circadian Components Of Cell Division
Authors: Edmunds Leland N.
Published: February 2005

Euglena gracilis Klebs (Z) was grown axenically and autotrophically in four‐liter serum bottles at 25°C on an aerated, continuously stirred, inorganic salt medium. Four fluorescent illumination regimes were employed: (1) continuous bright light of 3500 lux (LLb); (2) continuous dim light of 800 lux (LLd); (3) a LbD: 14, 10 (3500 lux) light‐dark cycle; and (4) a LdD: 14, 10 (800 lux) light‐dark cycle. Cell number was automatically monitored throughout all experiments.

In LLb the generation time (G.T.) of the population was about 12 hours, whereas in LLd following LLb it was approximately five days; exponential growth occurred in either case. In LbD: 14, 10 synchronous growth occurred with a doubling of cell number every cycle of 24 hours. In LdD: 14, 10, however, although rhythmic cell division took place every 24 hours, the average increase in cell number during the division burst which occurred in each dark period was only 13.4%, so that the G.T. of the culture was about five days, as was the case for LLd. In the constant conditions of temperature and continuous dim light (LLd), following synchronous growth in LbD: 14, 10, small (17.0%) rhythmic division bursts lasting 14.5 hours continued to occur for at least ten days, with a period of 24.2 hours. The overall G.T. of the culture was about five days. These data demonstrating the circadian, endogenous nature of rhythmic cell division under certain conditions of continuous dim illumination were discussed in relation to the synchronous division observed in temperature and light‐dark cycles.
Acid‐base, fluid and electrolyte metabolism in the elasmobranch. III. oxygen, CO2, bicarbonate and lactate exchange across the gill
Authors: Robin Eugene D. , Murdaugh Herschel V. , Millen J. Eugene
Published: February 2005

Methods have been developed which permit measurements of cardiac output and sampling of mixed venous and arterial blood in the elasmobrach, Squalus acanthias. These methods have been utilized to characterize some of the parameters involved in gill gas exchange. A total of 17 animals have been studied with the following results. Cardiac output: 1.49±0.57 1/kg/hr.; V̇o2: 38.3±22.1 ml/kg/hr.; V̇co2: 32.1±19.0 ml/kg/hr.; RER: 0.92±0.17; PaO2: 104±27 mmHg; Pv̄o2: 18±8.8 mmHg; PaCO2: 2.9±0.75 mmHg; Pv̄co2: 4.6±1.1 mmHg; CaO2: 3.8±0.75 vol. %; Cv̄o2: 1.26±0.59 vol. %; pHa: 7.52±0.10 units; Pv̄: 7.42±0.11 units; [HCO3−]a: 3.92± 1.14 meq/1; [HCO3−]v̄: 4.80±1.15 meq/1; [dissolved CO2]a: 0.17± 0.04 mM/1; [dissolved CO2]v̄: 0.24±0.04 mM/1; [lactate−]a: 13.47±7.17 meq/1; [Lactate−]v̄: 13.01±8.18 meq/1. Some of the mechanisms involved in gill gas exchange have been characterized.
Respiration and glycolysis in the human diploid cell strain wi‐38
Authors: Cristofalo V. J. , Kritchevsky David
Published: February 2005

Assessment of the respiratory and glycolytic capacity of non‐growing WI‐38 cells shows that, in the absence and presence of added glucose, the mean rates of oxygen consumption were 247 (QO2 = 5.61) and 208 (QO2 = 4.73) mμmoles/mg dry wt/hr., respectively. Mean glucose consumption was 225 mμmoles/mg dry wt/ hr. With uniformly labeled 14C glucose as substrate, 36 mμg atoms of carbon dioxide were produced, corresponding to 15–20% of the total cellular respiration. Mean values for lactate production in the presence and absence of glucose were 345 (QLO2 = 7.85) and 196 (QLO2 = 4.45) mμmoles/mg dry wt/hr., respectively.

Human diploid cells in culture age, in the sense that their ability to proliferate decreases with time during serial subcultivation. Studies of their respiratory and glycolytic capacity as a function of the aging process showed that total respiration, glucose respiration and glycolytic capacity were relatively constant for cells in the middle and late passages and indicate that aging in this sense is not directly related to the respiratory and glycolytic capacity of the cell.
Hemolysis of elasmobranch erythrocytes in urea solutions: Effect Of Temperature
Authors: Rabinowitz Lawrence
Published: February 2005

Skate and stingray cells were shown to hemolyze in isosmotic solutions containing urea as the sole solute. The rate of urea penetration into these cells as determined by the rate of hemolysis is highly temperature dependent with a Q10 of 2.50–2.75. A reduced rate of methylurea penetration in the presence of urea was reconfirmed. The present results are consonant with the hypothesis of carrier mediated transport of urea in elasmobranch erythrocytes previously proposed by Murdaugh, Robin and Hearn.
The influence of temperature on the water exchange in amphibian eggs and embryos
Authors: Haglund Birgit , Løvtrup Søren
Published: February 2005

The water exchange has been measured in oocytes of siredon mexicanum and rana temporaria, and in unfertilized eggs and early gastrulae of the former species, by recording the D2OH2O exchange with the cartesian diver balance.

In oocytes, where no diffusion barrier to water is demonstrable, the temperature coefficient Q10 for the exchange of water is about 1.3–1.4, corresponding to that of free diffusion. in unfertilized eggs, and in early gastrulae the exchange is considerably slowed down, indicating that a surface membrane to some extent limits the rate of exchange. at the same time the Q10 value is increased, lying in the range 2.3–3.8. since it is most likely that the exchange even in this case occurs by diffusion, but through membrane pores, it is concluded that the area available for diffusion (pore size or number, or both) increases with temperature.
Reversed potentials in isolated frog skin. II. Active transport of chloride
Authors: Martin Duncan W. , Curran Peter F.
Published: February 2005

Net inward transport of Cl in the absence of an electrochemical potential difference was demonstrated in the skin of two species of frog, R. pipiens and R. esculenta under conditions of low (2 mM) Cl concentration in the bathing solutions. The electrical potential profile of skins of R. pipiens was examined with microelectrodes under conditions in which the inside solution was negative relative to the outside solution. This reversal of the normal potential difference was found to arise as a result of potential changes across the outward facing electrical barriers in the skin. The reversed potential difference appears to arise, at least in part, as a result of the inward Cl transport. The effect may be due either to electrogenic Cl transfer or to variations in internal composition of the epithelial cells arising as a result of Cl transport.
The hibernation cycle and related changes in the brown fat tissue of Citellus lateralis
Authors: Grodums E. I. , Spencer W. A. , Dempster G.
Published: February 2005

The hibernating habits of Citellus lateralis under standard laboratory conditions are described. It has been shown that it is possible to use a biopsy technique to investigate the brown fat tissues without serious disturbance to the hibernation pattern. This technique was used to sample brown and white fat tissues in the same animal at various seasons of the year. Histological studies did not reveal any changes in morphology or lipid composition which could be related purely to the hibernating season, however, during the short periods of arousal a large proportion of the brown fat cells appeared to be partially depleted of neutral fat. At this time a large increase in Luxol fast blue staining was always observed, which may be due to unmasking of tissue phosphatides.
Experimental coxsackie B‐3 virus infection in Citellus lateralis
Authors: Dempster G. , Grodums E. I. , Spencer W. A.
Published: February 2005

Coxsackie B‐3 virus produces a mild infection which passes unnoticed in the non‐hibernating Citellus lateralis. A severe infection occurs in the hibernating animal. The progress of infection in the hiberating animal is related to the number of arousal hours and quite independent of the number of infected days. Nevertheless, it has been shown that the low‐temperature hibernation phase has a potentiating effect upon subsequent viral production. Infective virus has not been found in the inoculated brown fat pads during the hibernation phase but very high virus titers are recorded 48 hours after arousal. This results in an earlier viraemia and earlier and higher titers in other organs of the body. A similar effect is noted when virus is inoculated at the very beginning of the arousal phase. While most animals recover with subsequent antibody development, a few succumb. Antibody development is slow and related only to the number of arousal hours experienced.

Particular note is made of the fact that an animal may successfully resume hibernation despite complete loss of the axillary brown fat pads.
Response of cultured chick heart cells to changes in ionic environment
Authors: Levinson Charles , Green James W.
Published: February 2005

Ventricles from 11‐day‐old chick embryonic heart were disaggregated by elastase and the component cells cultured on glass in maintenance medium containing 10 μc of P32. After 48 hours incubation at 37°C the medium was removed, the cells rinsed and exposed to a phosphate‐free test solution for two hours. During this period samples of the test medium were removed for counting and spectrophotometric analysis. Cells incubated in solutions lacking amino acids or vitamins or serum components lost phosphate at essentially the same rate as in the complete culture medium; furthermore such cells lost very small amounts of nucleotide materials. Cells incubated in 0.16 M NaCl lost phosphate and nucleotides rapidly; the addition of either K+ or Ca+2 or Mg+2 reduced phosphate and nucleotide loss and cells in balanced saline media containing all four cations, retained phosphate and nucleotides at essentially the same level as in the complete medium. These results show that primary isolated chick heart cells can be maintained for short periods in physiological saline solutions without injury and that saline balance in short term studies is a primary factor in maintaining these cells in an uninjured state.
Effect of thermal conductance on water economy in the antelope jack rabbit, Lepus alleni
Authors: Dawson Terence , Schmidt‐Nielsen Knut
Published: February 2005

The heat and water balance of the antelope jack rabbit, Lepus alleni, was studied at various ambient temperatures. At high ambient temperature the animal primarily depends on evaporation for dissipation of the heat load. The use of water was, however, less than could be expected if only body size is considered.

It was shown that, when the ambient temperature is below body temperature, there is a two‐ to three‐fold increase in the conductance of the animal as ambient approaches body temperature. This facilitates dry heat loss and contributes to water economy. At ambient temperatures above body temperature the direction of heat flow is reversed, now being from the environment to the body. In this situation the heat flow inwards is impeded by a decrease in conductance to minimal values, thus achieving a considerable saving in the use of water for evaporation.
Differential effects of strychnine on crustacean slow, fast, and inhibitory neuromuscular systems
Authors: Parnas I. , Atwood H. L.
Published: February 2005

The effect of strychnine was studied on the slow, fast, and inhibitory systems in the abdominal extensor muscles of the crayfish. Strychnine nitrate (0.1 mg/ml and up) caused rapid block of the fast responses of the deep abdominal extensor muscles. The nerve and muscle remained directly excitable, and the blocked preparation contracted with added glutamate. It is concluded that strychnine acts mainly presynaptically or to neutralize the transmitter substance. No marked effect was observed on the purely slow superficial extensor muscles or on inhibitory systems. Essentially the same results were obtained in other slow and fast systems of Pachygrapsus and Panulirus. The possibility of a common transmitter substance for the slow and fast neuromuscular systems is discussed.
Contraction of protoplasm. I. Cinematographic analysis of the anodally stimulated contraction of spirostomum ambiguum
Authors: Jones Alick R. , Jahn Theodore L. , Fonseca James R.
Published: February 2005

Electrically stimulated contraction of Spirostomum ambiguum was investigated by high speed cinematography (up to 6,000 pps). Contraction is completed in about 4 msec following a latent period of up to 30 msec. Reduction in length during contraction followed a sigmoid curve, and final length was about 50% of the original length. Contraction always started at the end of the animal directed towards the anode. When the length of each half was measured separately, it was found that the cathodal end lagged about 1 msec in all cases observed. Rate of contraction was increased when the external calcium contraction was increased, and was decreased in Ca‐free and K‐free solutions, but was unchanged in K‐rich solutions. These results are interpreted in terms of contraction being associated with a relative increase of calcium bound to the contractile protein. The differential migration of potassium and calcium ions in an electric current would result in a temporary lowering of K+ at the anodal end of the animal, hence a relative rise would take place in the Ca++ available for binding. The results of experiments using changed calcium and potassium concentrations can be explained by this hypothesis which is in general agreement with modern work on muscle contraction and relaxation.
Influence of ions and tonicity of RNA metabolism in Tetrahymena pyriformis
Authors: Cline Sylvia G.
Published: February 2005

Net RNA degradation occurs in Tetrahymem pyrifmmis when this ciliate is suspended in a non‐nutrient medium. The quantity and quality of the excretion products is at least partially under the control of the ionic content and the tonicity of the cellular environment. The excretion of ultraviolet‐absorbing materials was found to be elevated by sodium ions in a medium isotonic to the culture fluid, or by a hypertonic environment. Magnesium counteracted these effects.

In isotonic suspension, sodium and magnesium ions lowered orthophosphate excretion; however, sodium altered the nature of the phosphate products so that acidlabile phosphates were also excreted rather than solely orthophosphate. Similar results were obtained in a hypertonic environment with or without sodium.

The degree of purine and pyrimidine loss from the cells in all conditions of suspension was reflected in the amount of RNA degraded. The ion and tonicity effects apparently reflect events which alter the stability of the RNA and the properties of the membrane system, resulting in changes in both the rate of RNA degradation and the nature of the excreted products. The rates of orthophosphate excretion appear to be affected by changes in the acid‐base balance within the cell which may be governed by the cation levels. The manipulation of the ionic content and tonicity of the medium offers a convenient method for obtaining cells reduced in RNA content.
Delayed inhibition of DNA synthesis in mouse jejunum by low doses of Actinomycin D
Authors: Baserga Renato , Estensen Richard D. , Petersen Robert O.
Published: February 2005

Actinomycin D (0.008 μg/gm of body weight) injected intraperitoneally every two hours, produced a prompt 50% inhibition of RNA synthesis in the jejunum of mice, and a delayed inhibition of DNA synthesis, that reached its maximum inhibition (68% of control values) 4.5 hours after the first injection of actinomycin D. Autoradiographic studies indicated that this low level of actinomycin D inhibited a step in the G1 phase of the cell cycle, preventing the initiation, but not affecting the continuation, of DNA biosynthesis. The activity of DNA polymerase was not affected under these conditions. The results are substantially similar to those previously obtained with Ehrlich ascites cells growing in the peritoneal cavity of mice and can be interpreted as indicating that in the G1 phase of dividing cells there is an actinomycin sensitive step whose inhibition prevents the entrance of cells into the DNA‐synthesis phase.
Extraction of an actin‐like protein from the plasmodium of a myxomycete and its interaction with myosin a from rabbit striated muscle
Authors: Hatano Sadashi , Oosawa Fumio
Published: February 2005

An actin‐like protein was obtained from the plasmodia of a myxomycete, Physarum polycephalum. It forms a complex with muscle myosin A which behaves similarly to the actomyosin from rabbit striated muscle. On the addition of ATP the complex of this protein with myosin A shows a viscosity drop at high concentrations of KCl (∼0.5 M). At low concentrations of KCl (∼0.05 M) this complex superprecipitates from solutions containing 1 mM MgCl2 and shows Mg‐activated ATPase activity. That is, the actin‐like protein converts the ATPase of myosin A to the actomyosin type.
The conversion of ATP to IMP by muscle surface enzymes
Authors: Dunkley C. R. , Manery J. F. , Dryden E. E.
Published: February 2005

These experiments showed that an isolated muscle bundle could be used to study, simultaneously, ion transport and the activity of surface enzymes. Frog muscles were carefully dissected and incubated for four hours in Ringer's solution containing a tris buffer and 3 mM ATP; at various times samples of the medium were chromatographed and analysed spectrophotometrically for nucleotide content. Samples of the final medium were analysed for inorganic phoshpate and for ammonia. The results demonstrated the conversion of adenosine triphosphate to inosine monophosphate, via adenosine diphosphate and adenosine monophosphate. Under the conditions of the experiment IMP was detected on chromatograms within 20 minutes of incubation; at the end of four hours the media had concentrations of 2.3 mM IMP, 4.4 mM inorganic phosphate and 2.6 mM ammonia, showing a stoichiometric relation among the products formed. There was convincing evidence that the enzymes involved (ATPase, adenylate kinase and AMP deaminase) must be situated close to or on the muscle surface. No effect of ouabain (1 μM) on the activity of the ATPase, adenylate kinase or deaminase could be found in these experiments, but the drug inhibited Na and K recovery from a Na‐loaded, K‐depleted state.
Amino acid incorporation by cleaving nucleate and non‐nucleate egg‐fragments of Arbacia punctulata
Authors: Rinaldi Robert A.
Published: February 2005

Tritium labeled alanine and leucine are incorporated into activated non‐nucleate and nucleate egg‐fragments of Arbacia. Labeling is similar in both non‐nucleate and nucleate fragments, and the pattern is network‐like. There may be slight amino acid incorporation by asters, prespindles, or mitotic apparatus in early cleavages of the activated fragment, but it is not above incorporation by the cytoplasm. In some samples it is not significantly above “background.” It is concluded that these organelles do not necessarily depend on new synthesis of proteins during early cleavage stages. The role of those proteins synthesized during the first precleavage stage is unknown.
Erythrocyte membrane sulfhydryl groups and cation permeability
Authors: Sutherland Robert M. , Rothstein Aser , Weed Robert I.
Published: February 2005

Reaction of the slowly penetrating organic mercurial compound parachloromercuribenzene sulfonate (PCMBS) with intact erythrocytes has been characterized. Addition of concentrations of PCMBS which result in binding within the interior of the membrane of more than 1.9 × 10−18 moles/cell produces alterations in Na+ and K+ permeability, but does not affect choline permeability. However, the increased cation permeability is observed only after a lag period of over two hours. After ten hours, a spontaneous slow “recovery” to normal rates of K+ leakage occurs at 25°C but not at 2°C. Subsequent to the effects on cation balance, increasing degrees of hemolysis occur, interpreted as colloid osmotic lysis. The relationships between the binding of the agent and its effects are as follows: a small, rapid initial uptake does not affect cation permeability; the subsequent slower uptake is associated with increased leakage of K+ and Na+; and the recovery at 25°C is associated with desorption of about half of the PCMBS due to competition by soluble thiol substances released into the medium from the cells. Desorption and “recovery” can be mimicked at any time by addition of small amounts of protein in the medium. The half of the PCMBS that cannot be desorbed is assumed to be bound by the hemoglobin inside the cell. The sulfhydryl groups involved in control of cation permeability constitute only a fraction of the total within the membrane (4–18%). They are located within the interior of the membrane separated from the medium and from the interior of the cell by diffusion barriers to PCMBS.
Regeneration of sialic acid on the surface of chinese hamster cells in culture. II. Incorporation of radioactivity from glucosamine‐l‐14C
Authors: Kraemer Paul M.
Published: February 2005

Cultured Chinese hamster cells incorporated radioactivity from glucosamine‐1‐14C into surface sialic acid and into trypsin‐removable material distinct from the surface sialoglycans. Cells prelabeled with glucosamine‐1‐14C and then transferred to medium containing unlabeled glucosamine progressively lost counts to the medium for many hours. Such chase experiments suggested a more rapid turnover of trypsinremovable material than of surface‐bound sialic acid. Further studies of the regeneration of surface sialic acid showed that the actinomycin D‐resistant portion of the process involved emergence of an intracellular precursor onto the cell surface. An earlier portion of the process was inhibited by actinomycin D, and at least three steps were inhibited by puromycin or cycloheximide.
Comparison of the requirements for ribonucleic acid synthesis with the requirements for deoxyribonucleic acid synthesis in animal tissues
Authors: Furth J. J. , Rosenberg Martin , Ho Patricia L.
Published: February 2005

Ribonucleic acid polymerase and deoxyribonucleic acid polymerase have been partially purified from bovine lymphosarcoma, lymph node, and thymus. An examination of the deoxyribonucleic acid requirements of the two enzymes indicates that “native” deoxyribonucleic acid is the preferred template for ribonucleic acid synthesis; heat‐denatured deoxyribonucleic acid is considerably less active. The primer requirements for deoxyribonucleic acid synthesis differ: “native” deoxyribonucleic acid is usually inactive, while denatured deoxyribonucleic acid is active. The two enzymes also differ in pH optima and in their requirements for metal cofactors.
Effects of inhibitors of RNA and protein synthesis on activation of glyconeogenesis in Tetrahymena
Authors: Levy Michael R.
Published: February 2005

The effects of actinomycin D, puromycin, and p‐fluorophenylalanine on the activation of glyconeogenesis in Tetrahymena were studied.

The extent of activation of glyconeogenesis in cultures containing inhibitor was as great as or greater than in the controls, as was the uptake of tracer levels of acetate into glycogen. These increases occurred despite a partial or complete inhibition of synthesis of isocitrate lyase, a glyconeogenic enzyme in Tetrahymena. Washed cells from these cultures could convert tracer or substrate levels of acetate to glycogen at enhanced rates. When glyconeogenesis was activated in starved cells in the presence of inhibitor, there was a negligible increase in the amount of isocitrate lyase, but a significant increase in the rate of glyconeogenesis. The data indicate that glyconeogenesis in Tetrahymena can be activated in the absence of enzyme synthesis.
Growth of the L‐cell in galactose medium
Authors: Baugh Clarence L. , Fitzgerald Joan M. , Tytell Alfred A.
Published: February 2005

The failure of the L‐cell to grow in a medium containing galactose as the sole carbohydrate was found to be directly related to the initial pH of the medium. Excellent growth of L‐M cultures in Eagle's minimum essential medium containing galactose instead of glucose was obtained by adjusting the medium to pH 6.2–6.8.
Ribonucleic acid within the cellular peripheral zone and the binding of calcium to ionogenic sites
Authors: Weiss L. , Mayhew E.
Published: February 2005

Ribonuclease was shown to reduce the electrophoretic mobility of a line of cultured mammalian cells (RPMI no. 41), and Ehrlich ascites tumour cells. No reduction was detected in the case of human, mouse or embryonic chick erythrocytes. These data, taken with the various controls, support the hypothesis that RNA is a structural component of the peripheries of two types of cells, but not of erythrocytes from three species.

Calcium‐binding was studied in RPMI no. 41 cells, Ehrlich ascites tumour cells, and human and mouse eryhrocytes, by measurement of reduction in cellular electrophoretic mobility in suspending solutions containing various concentrations of calcium chloride. The effect of treating cells with neuraminidase and/or ribonuclease on calcium‐binding was also studied. The results suggest that less calcium binds to the carboxyl groups of peripheral sialic acids than to the phosphates of peripheral, structural RNA. However, calcium apparently binds most avidly to as yet unidentified anionic sites.
Clonal repopulation in reticular tissues of x‐irradiated mice: Effect of dose and of limb‐shielding
Authors: Nowell Peter C. , Cole Leonard J.
Published: February 2005

Chromosome studies in irradiated mice have indicated that following high sublethal whole‐body exposure regeneration of the reticular tissues occurs in a clonal fashion. With increasing doses, from 100 to 700 rads, these organs appeared to be repopulated from fewer and fewer surviving stem cells. In a few instances at the highest dose, the progeny of the same cell apparently differentiated to marrow cells at one site and to lymphoid cells in others, suggestive evidence of a totipotent hematopoietic stem cell in the adult mouse.

Chromosome studies in mice receiving 900 rads with one limb shielded have indicated repopulation of the thymus and other reticular tissues by undamaged cells from the shielded marrow. Such marrow‐derived cells, perhaps by restoring immunological competence or by non‐immunological contact inhibition, could account for the known effect or limb shielding in reducing the incidence of radiation‐induced thymic lymphomas.
Distribution in tissue homogenates, and the nature of the linkage of injected proteins to subcellular particles
Authors: Bertini Francisco , Mego John L. , McQueen J. Donald
Published: February 2005

Intravenously injected labeled proteins were recovered mostly in particulate fractions of rat liver homogenate. Distribution showed changes depending on the time elapsed from the injection. 131I‐albumin undergoes an intraparticulate hydrolysis which shows the highest activity in the gradient fractions associated with the highest level of acid phosphatase. The labeled albumin‐bearing particles separated at 27,000 g × 10 minutes released their radioactive protein at the same rate as acid phosphatase appeared in the medium, under the effect of such agents as distilled water, salts, homogenization, sonication and pH changes. The substitution of sucrose for distilled water or salts showed that the particles behave as an osmotic system as do lysosomes. These experiments prove that secondary lysosomes involved in the hydrolysis of foreign proteins, whose existence was shown by other authors only at the histochemical level, may survive the distrupting action of conventional homogenization and maintain many properties characteristic of primary lysosomes in addition to the ability of hydrolysing “in vitro” the engulfed material.
Cyclic changes in the alcohol‐soluble carbohydrates in synchronized Tetrahymena. I. Fractionation
Authors: Whitson G. L. , Green J. G. , Francis A. A. , Willis D. D.
Published: February 2005

Fifteen alcohol‐soluble carbohydrates have been isolated from logphase cultures of Tetrahymena. Preliminary results obtained by parallel chromatography of impure extracts indicate that some of the soluble components were 2‐D‐deoxyribose, ribose, mannose, fructose, arabinose, xylose, and glucose. Another elution gradient with extracts from cells washed several times, indicates that maltose and glucose were the only identifiable components as compared with 18 known standards. Differences were observed in the alcohol‐soluble carbohydrate content in log‐phase versus stationary‐phase cells. For example, it is clearly indicated that component 13 is missing in stationary‐phase cells while component 15 is missing in log‐phase cells. Fifteen alcohol‐soluble carbohydrates have been chromatographed from synchronized cells. All of these compounds show cyclic variation in relation to cell division. Component 13 accumulates in cells blocked in morphogenesis and decreases as oral development proceeds in synchronized cells.
Control of polytenic replication in dipteran larvae. I. Increased number of cycles in a mutant strain of Drosophila melanogaster
Authors: Rodman Toby C.
Published: February 2005

Previous studies have demonstrated that a consistent maximum number of polytenic replication cycles occurs in the salivary gland nuclei of a wild‐type strain of D. melanogaster. Since that number is achieved within the larval period, the DNA synthesis of the prepupal period is believed to be that of propagation of the final cycle. Photometric determinations have been made, in this study, of the salivary gland nuclei of larvae and prepupae of the tu‐h strain in which the larval period has been extended as a consequence of delay or failure of pupation. The DNA values indicate that a higher maximum number of polytenic replications is achieved in such nuclei. It is inferred, thereby, that initiation of polytenic replication is a function of the larval state and, since it is terminated by the intervention of metamorphosis, a hormonal dependence is suggested.
Control of polytenic replication in dipteran larvae. II. Effect of growth temperature
Authors: Rodman Toby C.
Published: February 2005

A comparison has been made, by Feulgen photometry, of the polytene nuclei of the salivary glands of a wild‐type strain of Drosophila melanogaster grown at 17°C and 25°C, respectively. Despite the fact that the time period of the larval stage was more than doubled at the lower temperature, the DNA values were the same in magnitude and similar in distribution of replication classes at each of the stages studied. The data have been interpreted as indicating that, so long as the larval state prevails, initiation of polytenic replication occurs upon completion of the previous cycle.
Orthophosphate flux across the membrane of Tetrahymena pyriformis W
Authors: Pruett Patricia O. , Conner Robert L. , Pruett John R.
Published: February 2005

Tetrahymena pyriformis W suspended in a buffered glucose solution accumulated orthophosphate [32P] from the external solution at a measurable rate. The uptake of orthophosphate by the organisms was linear with respect to time when corrections were made to account for a constant efflux observed during the one hour time course of the experiments. Such corrections were based on the measured lowering of the relative specific activity of the suspension medium and led to the derivation of the expressions for the influx and efflux coefficients. The derived expressions for the coefficients are based solely upon the isotopic measurements and by means of these equations it is possible to describe the observed net inward flux of orthophosphate in quantitative terms. The dependence of the uptake of orthophosphate on the external concentration of orthophosphate followed Michaelis‐Menten kinetics, and the temperature coefficient (18–28°) of 1.7 for the process fell into the range normally associated with a chemical reaction. The kinetic pattern, per se, does not distinguish a membrane transport mechanism from metabolic incorporation of Pi. Deviations from the expected pattern of uptake were observed at low temperatures.
The effect of pH on the propagation of the diploid cell WI‐38 in galactose medium
Authors: Baugh Clarence L. , Lecher Robert W. , Tytell Alfred A.
Published: February 2005

The pH range for optimal growth of WI‐38 in Eagle's minimum essential medium varies with the carbohydrate utilized. Growth with glucose occurred only in the pH range 6.8–7.4. Glucose‐free galactose supported growth only if the pH of the medium was adjusted to 6.4–6.8. Supplementing the galactose medium with pyruvate extended the pH range for growth to 7.4. The addition of 0.01% glucose to the galactose medium increased growth at pH 7.0–7.4, reduced growth at pH 6.8, and completely inhibited growth at pH 6.6. This toxic effect of glucose under conditions impairing glycolysis was considered to be a contributing factor to the post‐confluent growth rate decline associated with “contact inhibition.”