Showing papers by "University of Virginia published in 1969"

Release of Adenosine by the Normal Myocardium in Dogs and Its Relationship to the Regulation of Coronary Resistance

Abstract: The evidence supporting the hypothesis that adenosine is the mediator of metabolic regulation of coronary blood flow was obtained from experiments characterized by myocardial hypoxia. If adenosine serves the role of physiological regulator of coronary blood flow, it must also be released by the normal heart. Experiments designed to study this question were performed on 15 open-chest dogs in which adenosine was sought in perfusates of the epicardial surface of the well-oxygenated heart. The pericardial space was perfused with warm (37°C) Tyrode's or Krebs-Henseleit solutions (400 to 1200 ml over 1 to 3 hours), and the perfusates were analyzed for adenosine. With a normal myocardial oxygen supply, adenosine was present in the perfusates in a concentration of 3.1 ± 0.5 x 10>-8M. Partial asphyxia, induced by reducing pulmonary ventilation, significantly (P ≤ 0.02) increased the adenosine concentration of the perfusates to 5.4 ± 0.8 x 10-8M. In four dogs the normal pericardial fluid was found to contain adenos...

Interior electron shells in superheavy nuclei

Abstract: The interior electron shells for superheavy nuclei (90≦Z≦250) have been investigated. Their binding energies are tabulated together with the vacuum polarization corrections for the various levels.

Influence of Norepinephrine and Catecholamine-Depleting Agents on the Synthesis and Release of Prolactin and Growth Hormone1

Abstract: The in vitro incorporation of leucine- 4,5-3H into rat pituitary glands and its subsequent release into the incubation medium were studied. Quantitation of prolactin and growth hormone was by measurement of intensity of the bands obtained with the polyacrylamide gel technique without bioassay. Most of this newly synthesized prolactin is released into the medium and not retained within the gland. The addition of norepinephrine (10-6M) caused a 70–85% decrease in the amount of radioactive prolactin released by the gland during a 7-hr incubation. An accumulation of labeled prolactin occurred in the treated glands, indicating the primary action of norepinephrine was to decrease prolactin release. The accumulation, however, was not proportional to the degree of inhibition of release, indicating that prolactin synthesis was secondarily inhibited. An increase in the radioactive prolactin in the gland was detectable 30 min afterthe addition of norepinephrine and was statistically significant 30 min later. Similar...

Effect of ovariectomy on pituitary secretion of ACTH.

Abstract: The effects of prepuberal gonadectomy on pituitary secretion of ACTH were studied in adult female rats. Plasma concentrations of ACTH in unstressed, adrenalectomized rats were decreased following ovariectomy to 76% (95% confidence limits 62–92%) of the control level. A comparable difference was also observed after the stress of ether anesthesia in rats with adrenals intact (57% of control; 95% confidence limits 46-76%). Unstimulated release of ACTH in vitro by whole pituitary glands from ovariectomized donors, with or without estradiol replacement, did not differ from that of control animals. Hypothalamic content of corticotropinrel easing activity (CRA) in intact and gonadectomized female rats was similar but was decreased in estradiol-injected, ovariectomized rats. The response of incubating pituitaries to uniform CRF stimulation was significantly depressed in the ovariectomized group (55% of control; 42–70%) and administration of 100 fig of polyestradiol phosphate partially reversed (81% of control; 65...

Structural proteins of vesicular stomatitis viruses.

Abstract: Three major and three minor structural proteins were identified by polyacrylamide gel electrophoresis of purified infectious virions of the Indiana serotype of vesicular stomatitis (VS) virus disrupted with acetic acid, 0.5 m urea, sodium dodecyl sulfate (SDS), and 2-mercaptoethanol. Molecular weights of the six virion proteins were estimated by comparative electrophoretic migration of known marker proteins in the presence of SDS. The following values were obtained: major proteins P6 congruent with 34,500, P5 congruent with 59,500, and P4 congruent with 81,500; minor proteins P3 congruent with 140,000, P2 congruent with 186,000, and P1 congruent with 275,000. P1 did not disaggregate in 8 m urea, but P2 and P3 did. The possibility that P1 is an uncleaved large polypeptide chain could not be ruled out. Six identical protein components were dissociated from Indiana VS virions grown in chick and mouse cells; no cellular proteins could be detected in purified virions. Of six proteins identified in virions of the New Jersey serotype, only the smallest protein (P6) could be distinguished from any of the six proteins of the Indiana serotype on the basis of migration in SDS gels. The defective T particles of Indiana VS virus contained the same six proteins in essentially the same proportions as those of the infectious B virions. Only P6 and P5 could be cleanly separated by preparative gel electrophoresis.

In Vivo Effect of Sex Hormones on the in Vitro Synthesis of Prolactin and Growth Hormone in Normal and Pituitary Tumor-Bearing Rats

Abstract: The in vivo effects of hormone-secreting pituitary tumors MtTW5, StW5 and 7315a on the in vitro synthesis of prolactin and growth hormone by rat pituitary gland have been studied. The in vitro incorporation of leucine-4,5-3H into these hormones of male and female rats was followed by subjecting homogenates of the pituitary glands and the incubation medium to polyacrylamide gel electrophoresis. Transplantation of 7315a, a prolactin- and ACTH-secreting tumor; MtTW5, a prolactin- and growth hormone-secreting tumor; or StW5, a growth hormone-secreting tumor, into intact female or male rats, caused a decrease in the incorporation of leucine-4,5-3H into prolactin. This decrease in prolactin synthesis was promptly reversed by administration of polyestradiol phosphate to tumor-bearing rats. The labeling of prolactin was also greatly stimulated in intact and castrated nontumor rats by the administration of estrogen and testosterone, while 17α-hydroxyprogesterone caproate injection was without effect. The incorpora...

Ecological genetics and speciation in land snails of the genus Partula

Abstract: Land snails of the genus Partula Ferussac offer several advantages for the study of micro-evolutionary change. They are highly variable both within and between populations. Their mobility is low, so that there are genetic differences between natural populations only short distances apart (20 m or less). They are ovoviviparous, and easy to rear in the laboratory, so that these genetic differences can be investigated experimentally. Finally, they show, at least in some places, a very curious pattern of speciation. Since 1962 we have been studying the population genetics of Partula species on the island of Moorea in French Polynesia. The late Professor H. E. Crampton, in a classic monograph, recorded ten species from the island. Later, he added an eleventh. One of the species (P. dendroica Crampton) is an allopatric replacement of P. suturalis Pfeiffer and probably deserves only the rank of geographical race, since the two forms cross freely in the laboratory. We have evidence that P. tohiveana Crampton, P. olympia Crampton, and P. mooreana Hartman will all, in some localities, hybridize with P. suturalis. We also have evidence of natural hydridization between P. aurantia Crampton and P. suturalis, and between P. exigua Crampton and P. taeniata Morch. There are thus two major-species groups on Moorea (the suturalis complex and the taeniata complex). The status of the other ‘species’ (P. mirabilis Crampton, P. solitaria Crampton and P. diaphana Crampton and Cooke) remains uncertain, although they are probably members of the taeniata complex. Two members of a species-group may behave as distinct species at one locality, but hybridize freely or intergrade at another. Such changes can take place over distances of 200 m or less. Some of the changes seem to be related to geographical barriers, There is, for instance, an apparent ring-species with a diameter of about 5 km. Other changes are more difficult to interpret, since they occur without obvious relation to geographical features. Ecological and genetic studies on P. taeniata have led to the suggestion that striking divergence between adjacent populations can take place even in the absence of geographical barriers. Whether this can continue to the point of speciation is still uncertain, but an explanation in these terms would clarify many of the puzzling phenomena we have observed in populations of Partula.

Protein Composition of the Structural Components of Vesicular Stomatitis Virus

Abstract: Digitonin, a sterol glycoside which complexes with cholesterol, stripped off the envelope of vesicular stomatitis (VS) virions and liberated two viral structural proteins, 83% of P6 and 53% of P4. Deoxycholate also disrupted VS virions but released nucleocapsid cores which could be identified by higher buoyant density, ratio of incorporated 3H-uridine to 14C-protein, and electron microscopy. The major nucleocapsid protein was P5 but varying amounts of the minor protein aggregate P2 were present, depending on the concentration of urea used for extraction. P2 appeared to be a polymer of P5. Two other minor structural proteins, P1 and P3, could not be located in the virion. From these data, we conclude that the three microscopically identifiable structures of VS virions are each composed primarily of a single major protein, as follows: P6 = envelope protein, P4 = protein of underlying “shell,” and P5 = nucleocapsid protein.

Theory of Surface Scattering and Detection of Surface Phonons

Abstract: A formal theory for the investigation of crystal surfaces by the scattering of particles is developed. Expressions satisfying the condition of unitarity are presented for diffraction as well as one-phonon inelastic scattering, including the effects of surface bound states. The possibility of detection of surface phonons by scattering of low-energy He atoms from a cleaved surface is investigated.

The Sorites Paradox

Abstract: Suppose that a movie camera is focused on a tadpole confined in a small bowl of water. The camera runs continuously for three weeks, and at the end of that time there is a frog in the bowl. At 24 frames per second we will have, assuming that the camera works perfectly, 43,545,600 pictures. Let these be arranged in a series S in the order in which they were taken. Then consider this property of numbers: the property of being the number of a picture in series S which is such that the creature shown in the picture is, at the time the picture was made, a tadpole. It seems clear that however doubtful the ascription of this property may be in some cases, it is correctly ascribable to I and not correctly ascribable to 43,545,600. That is, the first picture depicts a tadpole and the last does not. These two apparently unquestionable facts may be expressed symbolically, letting 'P' stand for the property of numbers just described, as follows: A. P (i) B. ~ P (43,545,600). However, from A and B, it is easy to derive, using the classical version of the least number principle,

Urine formation by the malpighian tubules of Calliphora. II. Anions.

Abstract: 1. Rate of urine formation is very sensitive to potassium concentration. 2. Potassium is concentrated in the urine by a mechanism which is independent of other monovalent cations. Rubidium, caesium and sodium are also capable of maintaining a flow of urine. At low external potassium concentrations, sodium stimulates potassium secretion. 3. Rate of urine secretion is stimulated by low osmotic pressures; the osmotic pressure of urine was slightly hypertonic throughout the range of external osmotic pressure employed. Addition of sucrose depresses rate of urine secretion; the potassium concentration of the urine increased by 1 mM/l. for each 2 mM/l. of sucrose added to the bathing medium. 4. Urine formation is insensitive to sulphanilamide, acetazolamide, ouabain and a wide variation of pH. 5. These observations are discussed in relation to the hypothesis that potassium secretion takes place across both surfaces of the cell. The pump on the basal surface may be a coupled sodium-potassium pump, whereas that on the apical surface may be electrogenic. 6. Microvilli at the apical surface or channels formed by a complex infolding of the basal plasma membrane may represent structural devices by which standing osmotic gradients can be established during solute-linked water transport across the cells of Malpighian tubules.

Cellular organization and ferritin uptake in the mid‐gut epithelium of a moth, Ephestia kühniella

Abstract: The fine structure of the mid-gut epithelium and regenerative cells of larvae of a moth (Ephestia kuhniella) is described. Particular attention is paid to the absorptive and goblet cells and their lateral junctions; these features are discussed in terms of the digestive and regulatory functions of the epithelium. One digestive pathway has been investigated with the aid of ingested ferritin; intake of this marker by endocytosis and the evident involvement of Golgi vesicles in the transformation of endocytic vesicles into multivesicular bodies, together with the fate of the latter, are discussed in terms of the digestive function of this part of the alimentary tract and of the lysosome concept.

Embryogenesis of the inferior olivary nucleus in the rat: a radioautographic study and a re-evaluation of the rhombic lip.

Abstract: Interkinetic nuclear migrations studied by redioautography in the medullar neuroepithelium of the 14-day rat embryo are similar to those in other areas of the neuraxis in other species. The cell cycle lasts approximately 12 hours. Olivary neurons are produced along the length of the alar plate on embryonic days 14 and 15, mostly on day 14. Between 36 and 48 hours after injection of thymidine- H3, labeled cells migrate into the mantle layer and are more concentrated in the alar lamina than in the basal lamina. The olivary primordium appears in the ventromedial medulla on day 17 and is almost mature by day 21. Labeled neurons in the alar lamina migrate to the primordium in two bands, the marginal and the submarginal migration strands. From these strands, labeled cells move into the ventrolateral and ventromedial portions of the olivary complex, Newly arrived neurons push the existing cells dorsally. By embryonic day 21, as proliferation of cells in the neuroepithelium ceases, the migration strands disappear, and the olive in fully formed. In the series injected on day 14, heavily labeled neurons become located dorsally in the medial accessory, dorsal accessory and principal nucleus; lightly labeled cells are found in the ventral half of the complex. In the series injected on day 15, labeled cells are found only in the ventral portions of the olive, in the medial accessory nucleus. His described 2 rhombic lips. The first may be an artifact. The second is not seen in the medulla of the rat. If the term is used for any species, it is best viewed as the lateral part of the alar plate.

On the complex bordism of finite complexes

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Bacteriologic Studies of Rifampin, a New Semisynthetic Antibiotic

Abstract: Rifampin is a semisynthetic N-methyl piperizine derivative of the antibiotic rifamycin SV produced by Streptomyces mediterranei. It is of particular interest because of its wide antibacterial spectrum against gram-positive and gramnegative bacteria as well as Mycobacterium tuberculosis [1-4]. It is an orange-red powder with a molecular weight of 822 and has the structure shown in figure 1. Clinical evaluation is now under way. This report will deal with the in vitro activity of this antibiotic against staphylococci, streptococci, and enteric bacteria. Particular emphasis will be placed on the problem of emergence of resistant strains and the effect of inoculum size

The radical of a jordan algebra.

Abstract: In this paper we define a Jacobson radical for Jordan algebras analogous to that for associative algebras and show that it enjoys many of the properties of the associative radical. We then relate the corresponding notion of “semisimplicity” to the previously defined notion of “nondegeneracy” (Jacobson, N., these Proceedings, 55, 243-251 (1966)).

Wall Properties of Veins

Abstract: After a brief review of the venous wall structure, the physical properties of veins are discussed in terms of their stress-strain relationships. In contrast to the high pressure arterial system, the low pressure venous system may exhibit large changes in volume without major pressure changes. Inferences about wall properties and intravascular volume from pressure measurements alone are thus meaningless. Depending upon the interplay between intra- and extravascular forces, the venous cross section may oscillate between complete collapse and a circular shape. The stress-strain relationships are both nonlinear and time dependent. Comparative data are given for representative arteries and veins and the distribution of blood volume within the peripheral vasculature is discussed. Finally, some of the venomotor agents and their effects upon stress-strain relations are reviewed.

Some determinants of preference and aversion in the rat.

Abstract: Of the events that accompany or follow the act of ingestion and that could therefore serve as “satiety” signals in the regulation of intake, two major classes can be distinguished: 1 ) oropharyngeal events, such as taste, smell, and proprioceptive feedback from the consummatory response, and 2) postingestional events, such as distension of the stomach by the material swallowed, and the hydrational and/or metabolic changes that follow its absorption. Both sets of factors are known to influence feeding and drinking, and attempts to assess the relative contribution of each set of factors have received a great deal of experimental attention. For example, in the rat, Adolph (1947) found that food injected directly into the stomach, bypassing the taste receptors, was about as effective as food eaten normally in suppressing further intake. More recently, Epstein (1960) and Epstein and Teitelbaum (1964) have shown that rats can regulate food and water intake in the total absence of mouth factors by pressing a bar to inject water or liquid diet directly into the stomach. On the other hand, oropharyngeal factors can play a powerful role in determining ingestion if they are permitted to operate. Their influence is most apparent in animals whose regulatory systems have been damaged, as by hypothalamic lesions. Such animals frequently are markedly responsive to small differences in taste and texture which the normal rat will ignore (Teitelbaum & Epstein, 1963). But even the intact rat will, for example, select and ingest large quantities of a saccharin solution, whose major physiological effect is on the taste receptors (Sheffield & Roby, 1950). Many more such investigations could be cited, for the influence on ingestion of these two sets of factors has been a subject of continuing interest, and several of the participants in this monograph have concerned themselves with it. The experiments reported here continue the attempt to identify the contributions of oral and postingestional events, and their interactions, to the regulation of intake. In them, both oral and postingestional mechanisms have been allowed to operate as they normally would do, but they have been dissociated and independently varied. This procedure permits direct assessment of the interaction of oral and postingestional events, as well as of the influence on ingestion of each set of factors in isolation. The method by which this dissociation is produced is shown in FIGURE 1 (Mook, 1963). The Figure shows a rat prepared with a chronic esophageal fistula, so that material swallowed escapes through an opening in the throat, and with an intragastric cannula, which permits both nutritional maintenance and the experimental intubation of material directly into the stomach (for details of preparation and maintenance, see Mook, 1963). The animal’s gastric cannula is attached by flexible tubing to a normally closed solenoid valve, whose input in turn is connected to a fluid reservoir suspended above the test cage. One or more drinking cylinders can be attached to the cage itself, permitting the rat to drink. As the animal laps at the drinking spout, he operates a low-voltage “drink-

The ultrastructure of stellate cells in the pars distalis of the salamander pituitary gland

Abstract: The ultrastructure of a distinct cell type, termed the stellate cell, in the pars distalis of the salamander (Triturus [Notophthalus, Diemyctylus] viridescens viridescens) pituitary gland is described. The cell has three primary characteristics which distinguish it from other cell types of the pars distalis: (1) a lack or sparsity of specific secretory granules, (2) several cellular processes which are long and sheet-like and (3) cell body and nucleus which are considerably smaller than the cell bodies and nuclei of the chromophilic cells. The stellate cell often has an angular shaped nucleus, and the cytoplasm is characterized by an abundance of glycogen particles, several lipid droplets, an inconspicuous Golgi complex showing no evidence of forming secretory granules, filaments, microtubules and a sparsity of rough endoplasmic reticulum. The cells occasionally contain unusual mitochondria which exhibit longitudinally oriented cristae. From the electron micrographic evidence obtained in this study, it was suggested that stellate cells probably contact all secretory cells in the pars distalis; thus they are favorably situated to play a sustentacular role in the piuitary gland. In addition, the processes of the stellate cell frequently terminate on the outer basal lamina of the pericapillary space. Consideration was given also to a possible secretory role for the stellate cells, but little morphological evidence was obtained to suggest such a function. It was noted, however, that the cells occasionally contain dense bodies about 250 mμ in diameter which were interpreted as possible secretory granules.

Increase in PNa and PK of Cultured Heart Cells Produced by Veratridine

Abstract: Noninnervated cultured chick embryonic heart cells are depolarized by veratridine (10-5 10-6 g/ml) within a few minutes to membrane potentials of -12 ± 2 mv. Action potentials and beating cease. Before depolarization begins, the repolarizing phase of the action potential is prolonged and leads to a long-lasting depolarizing afterpotential, probably due to a holding open of Na+ channels. There is no direct effect on automaticity. Maximum rate of rise of the action potential decreases as a function of the depolarization. The inexcitability is transiently reversed by repolarizing current pulses and by 5 mM Ba++ (but not Sr++) which increases membrane resistance (Rm) and produces a small transient repolarization. Cocaine does not reverse the depolarization. The depolarization also occurs in Cl--free Ringer and in Na+-free Li+-Ringer, but not in Na+-free sucrose-Ringer. In most cases, Rm, measured in the presence and absence of Cl-, initially decreases but sometimes increases. Some of the decrease or increase in gK may be indirectly produced by anomalous or delayed rectification, respectively. Tetrodotoxin, although having no effect on the action potential magnitude or rate of rise, prevents the depolarizing action of veratridine but not its effect on decreasing Rm. It is concluded that veratridine depolarizes by increasing the resting Na+ permeability (PNa); it also tends to increase PK, but this action may be obscured by anomalous rectification when Em is allowed to change. The equilibrium potential for veratridine action is about halfway between ENa and EK, similar to that of acetylcholine at the vertebrate neuromuscular junction.