Showing papers by "University of Virginia published in 1971"
TL;DR: Comparison of the Triton-soluble and TritOn-insoluble proteins from the cell wall and cytoplasmic membrane fractions by polyacrylamide gel electrophoresis and gel filtration in acidified dimethyl formamide indicated that the detergent specifically solubilized proteins of the cy toplasmi membrane.
Abstract: Treatment of a partially purified preparation of cell walls of Escherichia coli with Triton X-100 at 23 C resulted in a solubilization of 15 to 25% of the protein. Examination of the Triton-insoluble material by electron microscopy indicated that the characteristic morphology of the cell wall was not affected by the Triton extraction. Contaminating fragments of the cytoplasmic membrane were removed by Triton X-100, including the fragments of the cytoplasmic membrane which were normally observed attached to the cell wall. Treatment of a partially purified cytoplasmic membrane fraction with Triton X-100 resulted in the solubilization of 60 to 80% of the protein of this fraction. Comparison of the Triton-soluble and Triton-insoluble proteins from the cell wall and cytoplasmic membrane fractions by polyacrylamide gel electrophoresis after removal of the Triton by gel filtration in acidified dimethyl formamide indicated that the detergent specifically solubilized proteins of the cytoplasmic membrane. The proteins solubilized from the cell wall fraction were qualitatively identical to those solubilized from the cytoplasmic membrane fraction, but were present in different proportions, suggesting that the fragments of cytoplasmic membrane which are attached to the cell wall are different in composition from the remainder of the cytoplasmic membrane of the cell. Treatment of unfractionated envelope preparations with Triton X-100 resulted in the solubilization of 40% of the protein, and only proteins of the cytoplasmic membrane were solubilized. Extraction with Triton thus provides a rapid and specific means of separating the proteins of the cell wall and cytoplasmic membrane of E. coli.
506 citations
TL;DR: The results are interpreted in terms of the types of noncovalent bonds involved in maintaining the organized structure of the cell wall and suggest that the main forces involved are hydrophobic protein-protein interactions between thecell wall proteins and to a lesser degree a stabilization of protein- protein and protein-lipopolysaccharide interactions by divalent cations.
Abstract: Extraction of a partially purified preparation of cell walls from Escherichia coli with the nonionic detergent Triton X-100 removed all cytoplasmic membrane contamination but did not affect the normal morphology of the cell wall. This Triton-treated preparation, termed the "Triton-insoluble cell wall," contained all of the protein of the cell wall but only about half of the lipopolysaccharide and one-third of the phospholipid of the cell wall. This Triton-insoluble cell wall preparation was used as a starting material in an investigation of several further treatments. Reextraction of the Triton-insoluble cell wall with either Triton X-100 or ethylenediaminetetraacetic acid (EDTA) caused no further solubilization of protein. However, when the Triton-insoluble cell wall was extracted with a combination of Triton X-100 and EDTA, about half of the protein and all of the remaining lipopolysaccharide and phospholipid were solubilized. The material which remained insoluble after this combined Triton and EDTA extraction still retained some of the morphological features of the intact cell wall. Treatment of the Triton-insoluble cell wall with lysozyme resulted in a destruction of the peptidoglycan layer as seen in the electron microscope and in a release of diaminopimelic acid from the cell wall but did not solubilize any cell wall protein. Extraction of this lysozyme-treated preparation with a combination of Triton X-100 and EDTA again solubilized about half of the cell wall protein but resulted in a drastic change in the morphology of the Triton-EDTA-insoluble material. After this treatment, the insoluble material formed lamellar structures. These results are interpreted in terms of the types of noncovalent bonds involved in maintaining the organized structure of the cell wall and suggest that the main forces involved are hydrophobic protein-protein interactions between the cell wall proteins and to a lesser degree a stabilization of protein-protein and protein-lipopolysaccharide interactions by divalent cations. A model for the structure of the E. coli cell wall is presented.
305 citations
TL;DR: Whenever fusion is experimentally delayed proliferation continues, at an undiminished rate, for a longer period of time generating a larger cell population, thus, although close proximity is a necessary condition for fusion it is not a sufficient condition.
274 citations
TL;DR: It is suggested that adenosine may play a role in the metabolic regulation of skeletal muscle blood flow, whereas ATP, ADP, AMP, and P1 may not.
Abstract: Experiments were performed on isolated frog sartorius muscle and in situ dog skeletal muscle to determine whether adenine nucleotides and their degradation products are released during contraction in concentrations capable of producing arteriolar dilation ATP was not detectable (>10 -8 M) in the bathing solution of the resting or contracting frog sartorius muscle. Inorganic phosphate (P 1 ) in the muscle bath increased from 9 x 10 -5 M to 28 x 10 -5 M with 30 minutes of contraction (2 Hz) or with rest. With the dog hindlirnb preparation, ATP, ADP, and AMP were not detectable (>5 x 10 ⊟8 M in the venous blood collected after 5 minutes of ischemic contraction whereas P 1 was present at a concentration of 3.7 x 10 x8 M. Arterial blood levels required to elicit detectable vasodilation for ATP, ADP, AMP, and P 1 were 28.7 x 10 -8 M, 27.1 x 10 -8 M 31.4 x 10 -8 M and 7.2 ⊠ 10 -4 M respectively. The adenosine concentration in dog muscle increased from 0.7 to 1.5 nmole/g with ischemic contraction, and hypoxanthine and inosine increased from 4.5 to 8.5 nmole/g and 2.0 to 5.5 nmole/g, respectively. The adenosine concentration in venous plasma collected from the hiodlimb immediately after termination of the irchemic contraction period was 2.2 x 10 -7 MM as compared to 0.4 x 10 -7 M in control venous and arterial blood samples. Hypoxanthine and inosine concentrations in venous blood increased 22- and 270-fold, respectively, foflowing ischemic contraction. The calculated interstitial fluid adenosine concentration was twice the arterial concentration of adenosine required to elicit maximal arteriolar dilation. These findings suggest that adenosine may play a role in the metabolic regulation of skeletal muscle blood flow, whereas ATP, ADP, AMP, and P 1 may not.
202 citations
TL;DR: The partial specific volume of phospholipid vesicles was determined by the sedimentation velocity method in various concentrations of hydrogen and deuterium oxide mixture and the apparent isodensity point in the KCl solution was found to be approximately equal to that obtaining in NaCl solution but smaller than that obtained in D2O-H2O medium.
185 citations
TL;DR: In this paper, an exact solution to diffusion equations governing the motion of parallel steps on a crystal surface was obtained, and the expression for the rate of growth versus supersaturation was reduced to a simple relation valid under most experimental conditions.
184 citations
TL;DR: In this article, the authors discuss the characteristics of glycogen synthase and its control mechanisms, and show that insulin has both an effect to increase total phosphatase activity and to stimulate conversion of an inactive form of the enzyme to an active form.
Abstract: Publisher Summary This chapter discusses the characteristics of glycogen synthase and its control mechanisms. Glycogenic steroids in mammalian liver appear to act via insulin, as do puromycin and thyroxine in tadpole liver. Testosterone has been shown to increase weight and glycogen content of rat perineal muscle of castrate animals. The rat levator ani muscle present only in the male is a completely white muscle, which is part of the male reproductive system that is trophically dependent on androgens. The action of injected estrogen has been studied in the rat levator ani of the castrate rat. The covalent conversions act to interchange the allosteric control mechanisms of the two forms of the enzyme. In liver, insulin has both an effect to increase total phosphatase activity and to stimulate conversion of an inactive form of phosphatase to an active form. Glycogen synthase has no pyridoxal phosphate and has much more phosphate than phosphorylase.
167 citations
TL;DR: MOUSE neuroblastoma C-1300 has a large number of electrical, biochemical and morphological properties characteristic of differentiated neurones1–9 and is particularly useful as a model in which neuronal functions can be studied in a clonal propagating system in vitro.
Abstract: MOUSE neuroblastoma C-1300 has a large number of electrical, biochemical and morphological properties characteristic of differentiated neurones1–9. The cell line is thus particularly useful as a model in which neuronal functions can be studied in a clonal propagating system in vitro.
158 citations
TL;DR: Three female patients are presented with a syndrome of low birth weight, dwarfism, aplastic alae nasi, midline ectodermal scalp defects, microcephaly, deafness, thyroid dysfunction, rectourogenital abnormalities, motor-mental retardation, and absent permanent tooth buds.
157 citations
TL;DR: The data obtained are consistent with two hypotheses: (i) the lipid composition of VS viruses primarily reflects their membrane site of maturation, and (ii) the newly synthesized viral proteins inserted into cell membranes influence the proportions of phospholipids and neutral lipids selected for incorporation into the viral membrane.
Abstract: Methods are described for the production of vesicular stomatitis (VS) virus of sufficient purity for reliable chemical analysis VS virions released from infected cells were concentrated and purified at least 150-fold by sequential steps of precipitation with polyethylene glycol, column chromatography, rate zonal centrifugation, and equilibrium centrifugation The Indiana serotype (VSInd virus) propagated in L-cells was found to contain 3% ribonucleic acid, 64% protein, 13% carbohydrate, and 20% lipid; the molar ratio of cholesterol to phospholipid was 06 or greater Thin-layer chromatography revealed no unusual neutral lipids or phospholipids and gas-liquid chromatography revealed no unusual fatty acids incorporated into VS virions The antigenically distinct New Jersey serotype (VSNJ virus) grown in L-cells showed a similar lipid profile except that the proportion of neutral lipids was larger than in VSInd virus also grown in L-cells This differences was less pronounced when the lipid composition of VSInd and VSNJ viruses grown in chick embryo cells was compared, but VSNJ virus grown in either cell type always contained larger amounts of neutral lipids other than cholesterol than did VSInd virus The lipid composition of both VSInd and VSNJ viruses grown in L-cells or chick embryo cells more closely resembled that of plasma membrane than of whole cells A consistent finding was the relatively large amounts of phosphatidylethanolamine and sphingomyelin and the relatively small amounts of phosphatidylcholine in both VS viruses compared with uninfected whole L-cells and chick embryo cells or their plasma membranes The methods available for isolation of plasma membranes were inadequate for conclusive comparison of the lipids of VS virions with the lipids of the plasma membranes of their host cells Nevertheless, the data obtained are consistent with two hypotheses: (i) the lipid composition of VS viruses primarily reflects their membrane site of maturation, and (ii) the newly synthesized viral proteins inserted into cell membranes influence the proportions of phospholipids and neutral lipids selected for incorporation into the viral membrane
144 citations
TL;DR: The synthesis of rRNA precursors, and by implication RNA accumulation and cellular growth, may be regulated through a mechanism which controls the time taken for transcription of these molecules.
Abstract: The synthesis of rRNA precursors, and by implication RNA accumulation and cellular growth, may be regulated through a mechanism which controls the time taken for transcription of these molecules.
TL;DR: The origin of large neurons of the substantia nigra, ventral tegmental area of Tsai and interpeduncular nucleus was determined in three‐week‐old rats receiving a single injection of thymidine‐H3 during gestation.
Abstract: The origin of large neurons of the substantia nigra, ventral tegmental area of Tsai and interpeduncular nucleus was determined in three-week-old rats receiving a single injection of thymidine-H3 during gestation. These neurons underwent final mitotic division on embryonic days 11 through 15 with maximal production on days 14 and 15. Glia and the smallest type of granular neurons were produced from day 11 through 22. Cells in the ventral angle of the neuroepithelium were not labeled one hour after injection of thymidine-H3 in any of the series.
Study of animals receiving a single injection of thymidine-H3 during gestation and killed at serial intervals thereafter showed that neurons forming the substantia nigra migrated from the middle third of the basal neuroepithelium and moved between existing cells in radial patterns. Production of neurons specifically for each division of the substantia nigra was not observed either in cross-section or rostrocaudally, nor was the destination of neurons related to their time of origin. The ventral tegmental area of Tsai and interpeduncular nucleus formed from neurons originating in the medial third of the basal plate and migrating almost to the ventral surface of the mesencephalon. The neurons then divided into two streams to create a pattern of an inverted fountain comparable to the distribution of neurons containing catecholamines. Some of these neurons may have contributed to the substantia nigra. The primordia in all three nuclear areas were first seen on embryonic day 18.
TL;DR: In this paper, a treatment of onephonon inelastic scattering of particles which do not penetrate appreciably into the crystal is presented, and a full quantum-mechanical treatment of the lattice vibrations is used throughout.
TL;DR: The distribution of the enzymes of phospholipid synthesis in cell wall and membrane subfractions of the cell envelope of Escherichia coli, isolated by a procedure involving particle electrophoresis and sucrose gradient density centrifugation, has been studied.
TL;DR: The experiments were designed to differentiate among several alternative hypotheses; the results indicating a failure to edit the responses at the time of recall, and in terms of a core and extra-core dichotomy due to organizational processes.
TL;DR: The results of this study indicate that the dorsal column system, generally considered to be a phylogenetically new direct pathway to the thalamus, contains other components comparable to some of the spinal efferent connections with the brainstem, even in this intermediate form.
Abstract: The aim of this study was to compare the projections of the dorsal column nuclei and spinal pathways to the brainstem and thalamus in Tupaia glis. Animals with unilateral lesions in the dorsal column nuclei or with lateral hemisections were perfused after 5 to 14 days survival time and sections were treated with Nauta or Fink/Heimer silver impregnation methods. The findings indicate that efferent fibers of dorsal column nuclei terminate not only in the thalamus but also in the dorsal accessory nucleus of the inferior olive and bilaterally in the external nucleus of the inferior colliculus. Some fibers terminate in periaqueductal gray and a few in pontine nuclei. In the diencephalon, efferents of the dorsal column nuclei were found to terminate in the posterior group (PO), ventroposterior nucleus (VP) and zona incerta. Spinal efferents were traced to the medial and dorsal accessory nuclei of the inferior olive, medullary and mesencephalic reticular formation, facial and vestibular nuclei, cuneiform nucleus, locus caeruleus, parabrachial nuclei and periaqueductal gray, and also to the external nucleus of the inferior colliculus. Evidence was found of more limited additional spinal projections to PO intralaminar nuclei and VP. The results of this study indicate that the dorsal column system, generally considered to be a phylogenetically new direct pathway to the thalamus, contains other components comparable to some of the spinal efferent connections with the brainstem. Moreover, even in this intermediate form, whose exact taxonomic position is unsettled, the dorsal column-medial lemniscus system to the thalamus appears to be of greater volume than the anterolateral spinothalamic connection.
TL;DR: Preparations of both D and I forms of glycogen synthase (UDPG:glycogen α-4-glucosyltransferase, EC 2.4.1.11) have been demonstrated to be virtually homogeneous by gel electrophoresis in sodium lauryl sulfate.
TL;DR: In this paper, scaling laws in terms of the invariant exchange coupling are derived for the Kondo effect, and the effective energy dependent coupling strength goes to unity at small energies, which is the likely origin of the difficulties in working out the low temperature Kondo scattering.
TL;DR: The impressively heavy termination of dorsal column fibers in PO, when contrasted with the meager projection of the rest of the cord, suggests that the VP-PO complex developed under the influence of the dorsal columns.
TL;DR: In this paper, a coherent picture of scattering of gas atoms by solid surfaces is beginning to emerge, and some of the more important theoretical ideas which we have about gas-surface interactions (including, for example, the idea that different types of theory are applicable to different physical regimes).
TL;DR: In this paper, the long and short term correlates of first and second grade retention are examined in relation to the variables of achievement and intelligence over a six year period, and the data led the authors to conclude that retention is an unjustifiable, discriminatory, and noxious educational policy.
TL;DR: A pure phosphatidyl choline containing branched-chain, saturated acyl substituents has been prepared by a novel synthesis and membranes formed from this non-autoxidizable, pure phospholipid are very stable and have an interfacial tension of 1.5 ± 0.1 dyne/cm at 24°.
TL;DR: The cross-tachyphylaxis and DMAE studies suggest that several of the analogues and angiotensin II are interacting with a common adrenal medullary receptor.
Abstract: A structure-activity relationship study was attempted to determine the structural specificity of the no. 8 amino acid residue of [1-asp,5-ileu]-angiotensin II for adrenal medullary stimulation. Isolated cat adrenal glands were perfused retrograde at a flow rate of 1 ml/min with phosphate-buffered Locke's solution at 23 to 25 C. Continuous catecholamine analysis was performed using an automated trihydroxyindole procedure. All drugs were administered either by single injection (0.05 to 0.1 ml) or by perfusion. Angiotensin analogues studied were: [8-(OMe)tyr]-angiotensin II; [8-tyr]-angiotensin II; [8-ala]-angiotensin II; [5-ileu,8-(3-amino-4-phenylbutyric acid)]-angiotensin II (referred to as [8-APB]-angiotensin II); [5-ileu,8-(DL-3-amino-3'-phenylisobutyric acid)]-angiotensin II (referred to as [8-APIB]-angiotensin II); [1-asp(NH2),5-val]-angiotensin II; [1-asp,5-ileu]-angiotensin I; tetradecapeptide.
Three peptides (angiotensin II, [8-tyr]-angiotensin II, and [8-ala]-angiotensin II) were studied in vivo for stimulation of adrenal catecholamine secretion. For maximum pressor activity, angiotensin must be an octapeptide with an aromatic amino acid and free COOH group in the no. 8 position. None of these three are structural requirements in adrenal chromaffin tissue. There was cross-tachyphylaxis between angiotensin II and all the analogues studied except two ([8-APB]- and [8-APIB]-angiotensin II).
In vitro studies with 10-leu-C14-angiotensin I and angiotensin II antibody indicated that angiotensin I has a marked, direct stimulatory effect on the adrenal medulla. Adrenal medullary catecholamine secretion induced by angiotensin I and II was greatly potentiated by DMAE perfusions. Responses to nicotine were blocked by DMAE and bradykinin-induced catecholamine release was unchanged. The cross-tachyphylaxis and DMAE studies suggest that several of the analogues and angiotensin II are interacting with a common adrenal medullary receptor.
TL;DR: In this article, the existence and stability of equilibrium strategies for many player nonzero-sum linear games with quadratic cost functionals is studied and the results are applied to differential games and a feedback synthesis of the equilibrium strategies is developed.
TL;DR: Embryonic chick hearts younger than 5 days old are electrically and mechanically insensitive to tetrodotoxin, and the action potentials of myocardial cells from older embryonic hearts in monolayer culture, and thereby denervated, are also insensitive, suggesting that the cell membranes of non-innervated muscles do not possess receptor sites for tetrodOToxin even though there is Na + channel activation.
TL;DR: In this article, the authors used a capture model to investigate the importance of capture in the formation of stream networks, through the use of a simulation model involving capture within rectangular stream networks on a square matrix.
Abstract: Because the importance of the process of capture, or piracy, in the formation of stream networks is difficult to evaluate by field or map studies, an indirect approach is used in this paper to investigate capture, through the use of a simulation model involving capture within rectangular stream networks on a square matrix. The simulation rules make the probability of capture of a stream by a lower adjacent stream proportional to the advantage in gradient of the potential path of capture between the streams compared to the present gradient of the higher stream. Stream elevations are assumed to be defined by the same type of pattern observed in natural stream networks, that is, a linear relationship between the logarithms of gradient and drainage area. The slope of this relationship, Z, is variable in nature and is the main adjustable parameter in the simulation model. Simulation of capture must start from assigned initial network patterns; random walk networks and parallel drainage are among those used for initial networks. For a given value of Z, the statistical properties of networks (for example, stream numbers, length and area ratios, and shape factors) formed after repeated captures are nearly the same for a wide range of assigned initial networks. However, when the value of Z changes during capture, the statistical properties of the resultant networks may depend upon the type of change, so that properties may be partially inherited from earlier stages of basin evolution. Both the networks simulated by capture and natural networks have similar slight deviations from topological randomness. The capture simulations more closely predict many properties of natural networks than do completely random methods of simulation, such as the random walk. In addition, several parameters in the capture-simulated networks exhibit a consistent trend with respect to the parameter Z that appears to occur also in natural networks. These correspondences between the capture model and natural networks suggest that capture may be an important natural process. However, capture should have its greatest relative importance in early stages of drainage basin evolution.
TL;DR: In this article, a critical review of the present quantum theory of inelastic gas-surface interactions, due to Lennard-Jones, Devonshire and Strachan, is given.
TL;DR: An autoradiographic study of the nutrition of articular cartilage in rabbits using intravenous 35S provided additional evidence that the route of nutrients for the articular Cartilage is affected by skeletal maturity.
Abstract: An autoradiographic study of the nutrition of articular cartilage in rabbits using intravenous 35S described. In immature rabbits (open epiphyses) the isotope appeared to enter the cartilage from both the synovial fluid and the subchondral bone, while in the mature animals (closed epiphyses) the isotope appeared to enter articular cartilage only from the synovial fluid. The experiment provides additional evidence that the route of nutrients for the articular cartilage is affected by skeletal maturity.