Showing papers by "University of Maryland, Baltimore published in 1971"
TL;DR: From the Laboratories of Infectious Diseases and Clinical Investigation, National Institute of Allergy and Infectious diseases, National Institutes of Health, Bethesda, Maryland; the University of Maryland School of Medicine, Baltimore, Maryland ; and the Walter Reed Army Institute of Medical Research, Washington, D.C.
Abstract: Raphael Dolin, NeU R. Blacklow, Herbert DuPont, Samuel Formal, Robert F. Buscho, Julius A. Kasel, Robert P. Chames, Richard Hornick, and Robert M. Chanock From the Laboratories of Infectious Diseases and Clinical Investigation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland; the University of Maryland School of Medicine, Baltimore, Maryland; and the Walter Reed Army Institute of Medical Research, Washington, D.C.
194 citations
TL;DR: Results suggested that B. subtilis 168 thy − ind − was capable of repair replication of ultraviolet-damaged DNA and that this process, unlike semi-conservative replication, was refractory to HPUra treatment.
117 citations
TL;DR: The patterns in the ovarian secretion rates of progesterone and 20α-hydroxypregn-4-en-3-one have been studied at various time periods during the 4-day rat estrous cycle and these patterns have been compared to the changes which occur in peripheral plasma concentrations of LH and the progestins in the same animal.
Abstract: The patterns in the ovarian secretion rates of progesterone and 20α-hydroxypregn-4-en-3-one (20α-OHP) have been studied at various time periods during the 4-day rat estrous cycle. These patterns have been compared to the changes which occur in peripheral plasma concentrations of LH and the progestins in the same animal. At proestrus, peak plasma LH concentrations were observed between 1400 and 1600 hr and had decreased to base line values of 10 μg/ml by approximately 1800 hr. No significant increase in ovarian secretion rates of progesterone occurred prior to LH release, although the 20α-OHP was significantly elevated by 1400 hr. Following adenohypophyseal LH release, progesterone secretion rates increased significantly and reached the highest values obtained in this study at 2400 hr. The 20α-OHP did not show a comparable increase at 1700 hr, but thereafter it was elevated above the earlier time periods (1000, 1400, 1700 hr). While similar changes in peripheral plasma progesterone concentrations occurred ...
97 citations
TL;DR: Hypoxemia, as judged by the relative structural integrity of mitochondria, does not seem to be the most important pathogenetic factor in the development of cerebral ischemic necrosis.
Abstract: Structural evaluation of cerebral infarction in twelve squirrel monkeys was conducted for the purpose of elucidating some aspects of the pathogenesis of regional cerebral ischemia.
93 citations
TL;DR: The view is advanced that increases in alpha density during feedback training arise from a diminution of those factors which block this rhythm, and some implications of such a view are discussed.
Abstract: The recent attention given to the feedback control of human brain-wave activity and the implications of such control prompts a careful analysis of this phenomenon. Particular emphasis is placed on the learned control of the alpha rhythm. A review of possible factors that might influence the density of alpha rhythms led to the differentiation of three general sources of influence: constitutional, physiological, and cognitive-attentional factors. Each of these factors is discussed as a possible mediator of the learned control of the alpha rhythm. The view is advanced that increases in alpha density during feedback training arise from a diminution of those factors that block this rhythm, and some implications of such a view arc discussed. Several of the issues raised appear generalizable to the whole question of the operant control of autonomic activity.
89 citations
TL;DR: Sleep data from chronic alcoholics have indicated that sleep disturbance represents an important aspect of alcoholic detoxification, and previous studies have been complicated by problems of poor diet, uncertain time for onset of withdrawal, or a limited time schedule for controlled withdrawal.
Abstract: Sleep data from chronic alcoholics have indicated that sleep disturbance represents an important aspect of alcoholic detoxification. Previous studies have been complicated by problems of poor diet, uncertain time for onset of withdrawal, or a limited time schedule for controlled withdrawal. This stu
71 citations
TL;DR: The early increase in the activity of β-glucosidase indicates that lysosomal enzymes may an important role in the etiology of disuse atrophy.
60 citations
TL;DR: An essential step in the pathogenesis of bacillary dysentery is the penetration of the intestinal epithelial cell by the pathogen, and this was concluded using a virulent Shigella flexneri 2a strain and an avirulent mutant derived from it.
Abstract: The knowledge gained from experiments in laboratory models has been very useful in helping us to reach our present understanding of the pathogenesis of some diarrheal diseases of human beings. This is especially true of bacillary dysentery. Dysentery may be defined as a syndrome in which blood, inflammatory cells, and mucus are present in the watery stool. A cardinal feature of classical shigellosis is an ulcerative lesion of the colonic mucosa, for it is through this defect in the epithelial barrier that the red blood cells reach the intestinal lumen. Thus, in order to gain some insight into at least one aspect of the pathogenesis of classical bacillary dysentery, one must understand how the ulcerative lesion evolves. The previous concept of the evolution of the colonic ulcer envisioned consecutive waves of absorption and excretion of heat-stable toxin across the intestinal wall, resulting in hypoxia and death of the epithe1ium.l For a variety of reasons2 we rejected this hypothesis and sought an alternate explanation. We started by using a virulent Shigella flexneri 2a strain and an avirulent mutant derived from it. As far as could be ascertained, the two strains were identical, with the exception that the parent strain caused disease when fed to starved, opiated guinea pigs or to rhesus monkeys, while the mutant failed to do so. When animals infected with either of the strains were studied using the fluorescent antibody technique, a distinctly different pattern of distribution of the organisms in the intestine was observed. The avirulent mutant was seen only in the lumen of the bowel. On the other hand the virulent bacteria were present in the epithelial cells of the intestine, and also both free and within phagocytic cells in the lamina propria. Rarely were the organisms viewed in the submucosa or in the mesenteric lymph nodes.2 From the results of these experiments we concluded that an essential step in the pathogenesis of bacillary dysentery is the penetration of the intestinal epithelial cell by the pathogen. If the organism is unable to enter the epithelium for one reason or another, few, if any, signs of disease are observed. Similar observations have been made independently by Voino-Yasenetsky and Khavkin and confirmed in extensive studies by Ogawa and colleague^.^ Other procedures are available to test for the ability of dysentery bacilli to
59 citations
TL;DR: It is concluded that hyperactivity is an ill-defined and inconstant phenomenon commonly associated with organic and/or developmental defects coupled with unfavorable environmental influences.
52 citations
50 citations
TL;DR: After a 20 min initial washout, the rate of loss of radioactively labeled sodium ions from sodium-enriched muscle cells is sensitive to the external sodium and potassium ion concentrations.
Abstract: After a 20 min initial washout, the rate of loss of radioactively labeled sodium ions from sodium-enriched muscle cells is sensitive to the external sodium and potassium ion concentrations. In the absence of external potassium ions, the presence of external sodium ions increases the sodium efflux. In the presence of external potassium ions, the presence of external sodium ions decreases the sodium efflux. In the absence of external potassium ions about one-third of the Na+ efflux that depends upon the external sodium ion concentration can be abolished by 10-5 M glycoside. The glycoside-insensitive but external sodium-dependent Na+ efflux is uninfluenced by external potassium ions. In the absence of both external sodium and potassium ions the sodium efflux is relatively insensitive to the presence of 10-5 M glycoside. The maximal external sodium-dependent sodium efflux in the absence of external potassium ions is about 20% of the magnitude of the maximal potassium-dependent sodium efflux. The magnitude of the glycoside-sensitive sodium efflux in K-free Ringer solution is less than 10% of that observed when sodium efflux is maximally activated by potassium ions. The inhibition of the potassium-activated sodium efflux by external sodium ions is of the competitive type. Reducing the external sodium ion concentration displaces the plots of sodium extrusion rate vs. [K]o to the left and upwards.
TL;DR: The mRNA's coding for ribosomal proteins were found to have an average half life of about 2.5–3 h which is similar to the average for the bulk of the mRNA population, but significantly greater than that of the histone mRNA's.
TL;DR: Data indicate that the metabolism of ketone bodies by the brain during early development proceeds through the activation of acetoacetate as catalyzed by CoA transferase, which is demonstrated to be 3–4 fold higher at 12 to 20 days of life than at birth or throughout adult life.
01 Jan 1971
TL;DR: Freeze-etch preparations of phiX174 adsorbed to intact bacteria showed that the virions were submerged to one half their diameter into the host cell wall, and the fivefold axis of symmetry was normal to the cell surface.
Abstract: Bacteriophage phiX174 is an icosahedral phage which attaches to host cells without the aid of a complex tail assembly. When phiX174 was mixed with cell walls isolated from the bacterial host, the virions attached to the wall fragments and the phage deoxyribonucleic acid (DNA) was released. Attachment was prevented if the cell walls were treated with chloroform. Release of phage DNA, but not viral attachment, was prevented if the cell walls were incubated with lysozyme or if the virions were inactivated with formaldehyde. Treatment of the cell walls with lysozyme released structures which were of uniform size (6.5 by 25 nm). These structures attached phiX174 at the tip of one of its 12 vertices, but the viral DNA was not released. The virions attached to these structures were oriented with their fivefold axis of symmetry normal to the long axis of the structure. No virions were attached to these structures by more than one vertex. Freeze-etch preparations of phiX174 adsorbed to intact bacteria showed that the virions were submerged to one half their diameter into the host cell wall, and the fivefold axis of symmetry was normal to the cell surface. A second cell could not be attached to the outwardly facing vertex of the adsorbed phage and thus the phage could not cross-link two cells. When the virions were labeled with (3)H-leucine, purified, and adsorbed to Escherichia coli cells, about 15% of the radioactivity was recovered as low-molecular-weight material from spheroplasts formed by lysozyme-ethylenediaminetetraacetic acid. Other experiments revealed that about 7% of the total parental virus protein label could be recovered in newly formed progeny virus.
TL;DR: An error in copying a DNA template with RNA polymerase confirms earlier observations with RNA templates, and suggests that alkylation of cytosine in DNA may be a mutagenic event.
TL;DR: Lysine racemase is inadequate to permit growth on L-lysine after a block in the L-pathway, but is sufficient to permit cross induction of D-lysines-related enzymes.
TL;DR: In the normal proestrous rat, while the time of initial increase in Plasma LH concentration varied from rat to rat, the majority of animals studied exhibited peak concentration in plasma LH between 1500 and 1600, and it reached approximately basal levels by 1900.
Abstract: The present studies have measured, by radioimmunoassay, the changes which occur in plasma LH concentration in individual unanesthetized rats during various hours on the day of proestrus. These patterns have been compared with those which occur in proestrous rats treated with an ovulation blocking dosage of Nembutal (sodium pentobarbital) and in Nembutal- blocked rats in which “ovulation inducing” electrical stimuli were delivered either unilaterally or bilaterally to the medial preoptic area (POA). The “critical period” for hypothalamic activation of the adenohypophysis was established as occurring between 1300 and 1500 in these animals. In the normal proestrous rat, while the time of initial increase in plasma LH concentration varied from rat to rat, the majority of animals studied exhibited peak concentration in plasma LH between 1500 and 1600. Thereafter, plasma LH declined rapidly, and it reached approximately basal levels by 1900. Injection of Nembutal at 1245 prevented any increase in plasma LH duri...
TL;DR: The failure to cyclize in vivo suggests the cohesive ends are damaged and the intracellular circularization of λ DNA is the first step in phage development altered by nuclease damage.
TL;DR: 4,17α-Dimethyl-4-aza-5α-androstan-17β-ol acetate exhibited significant activity and was compared with acetate esters synthesized and compared for antimicrobial activity.
TL;DR: Tests of proteolytic activity of collagenase as a means of explaining the results revealed that all commercial preparations contain some activity under the conditions used for dissociation.
TL;DR: There appears to be minimal utility in referring children with learning and/or behavioral problems to a diagnostic and evaluation clinic because of suspected “minimal brain dysfunction”, and the final diagnosis is more contigent upon symptomatology and psychological findings than upon any specific medical, neurologic, or electroencephalographic findings.
TL;DR: The metal-binding agent penicillamine increases the urinary excretion of copper and a number of other heavy metals in patients with Wilson's disease and some of its analogous compounds are reviewed.
Abstract: The metal-binding agent penicillamine increases the urinary excretion of copper and a number of other heavy metals. I t is effective when administered orally. I would like to review the biochemical and pharmacological properties of penicillamine and some of its analogous compounds. The work that I shall discuss was performed between 1954 and 1959 at Vanderbilt University School of Medicine.'.' I t was a group effort, which a t that time included two young medical students, a postdoctoral fellow and Mary Aposhian. One of these medical students is at present the Clinical Director of the National Institute of Allergy and Infectious Diseases, Dr. Sheldon Wolff. Another, Dr. Myron Morris, is in practice in Boston. The postdoctoral, Dr. Laurance Bradham, is now a t the University of Arkansas School of Medicine. The formulas of these compounds are shown in FIGURE 1. Penicillamine is the @,@-dimethyl analogue of cysteine. One of the hydrogen atoms on the @-carbon atom of cysteine may be replaced by a methyl group to give P-methyl cysteine. In the case of @-methyl-ðyl cysteine, both of the @-hydrogens of cysteine have been replaced. Acetylation of the amino group produces N -acet ylDL-penicillamine. In 1956, Walsheg reported that the oral administration of penicillamine increases the urinary excretion of copper in patients with Wilson's disease. This disease, also called hepatolenticular degeneration, is an inherited metabolic disorder characterized by the accumulation of excessive amounts of copper in the tissues, Kyser-Fleischer rings in the eye, and a number of neurological symptoms. The nature of the defective gene product in this disease is not known, although a number of theories related to ceruloplasmin deficiency have been proposed.10s11 Walshe's use of peni~illamine~ in the therapy of Wilson's disease was based on a number of observations. While studying by paper chromatography the urinary excretion of amino acids, he found that the urine of four of such patients gave a spot that was indicative of a new amino acid.'* A check of the clinical history of these four patients showed that they had been receiving penicillin. The new urinary amino acid was soon identified as the sulfhydryl amino acid penicillamine. It was surprising that an amino acid with a supposedly highly reactive sulfhydryl group was being excreted unchanged. Walsheg then reasoned that such a metabolically inert amino acid might be used to bind the excessive copper in patients with Wilson's disease. He was correct. In our own laboratory, we had been studying the antimetabolic properties of cysteine analogues.4s687 We expanded these studies to include the metabolism of these sulfhydryl compounds and to look for an effective oral antidote to mercuric ion into~ication.'-~.'.~ The influence of penicillamine analogues on urinary excretion of copper and on the protection of rats against the lethal effects of mercuric chloride is summarized in TABLE 1. Is there any explanation for the difference in the effect of penicillamine
TL;DR: Chrysaora venom was antigenic to rabbits with complement fixing antibodies and protective factors against the lethal, hemolytic and dermonecrotic factors being formed, but actively immunized animals did not develop an eruption after stinging.
TL;DR: Gutta-percha points of five brands which had been labeled with standardized sizes were evaluated with respect to size availability, size accuracy, size consistency, and rigidity and only two brands were judged to have satisfactory rigidity without excessive brittleness.
TL;DR: The development of thiolase in various rat tissues from 7 days before birth to adulthood was studied and enzyme activities in brain, liver, and kidney during the perinatal period reflect the nutritional environment, whereas those in the adult tissues do not.
Abstract: The development of thiolase in various rat tissues from 7 days before birth to adulthood was studied. Enzyme activities in brain, liver, and kidney during the perinatal period reflect the nutritional environment, whereas those in the adult tissues do not.
TL;DR: Clinical studies, laboratory data, and metabolic studies on tissues obtained at postmortem examination excluded methylmalonic acidemia and ketotic glycinemia as the cause of the ketoacidosis.