Showing papers by "University of Maryland, Baltimore published in 1969"
TL;DR: In the United States, epidemic shigellosis has been a particularly important problem in confined groups such as the military, institutions for the mentally retarded, and Indian reservations, it is in such confined populations that an effective Shigella vaccine would be most beneficial.
Abstract: In the United States, epidemic shigellosis has been a particularly important problem in confined groups such as the military, institutions for the mentally retarded, and Indian reservations. It is in such confined populations that an effective Shigella vaccine would be most beneficial. Shigella flexneri 2a is an important cause of both sporadic and epidemic shigellosis in the United States. Between the years 1963 and 1966 this pathogen accounted for approximately one-fourth of all Shigella isolates reported to the National Communicable Disease Center [1]. In 1967 this center recorded 11,405 isolations of all Shigella [2]. In order to test the effectiveness of oral attenuated living S. flexneri 2a vaccines, an experimental model has been developed in man. The response of volunteers to oral challenge by virulent S. flexneri 2a was determined at doses of 104 -108 viable organisms.
152 citations
TL;DR: The time courses and magnitudes of the intermediate and very slow sodium conductance restorations induced by long hyperpolarizing pulses are in agreement with those predicted from the calculated rates and magnitude of [K+] depletion in the space between the axolemma and the Schwann layer.
Abstract: Giant axons were voltage-clamped in solutions of constant sodium concentration (230 mM) and variable potassium concentrations (from 0 to 210 mM). The values of the peak initial transient current, Ip, were measured as a function of conditioning prepulse duration over the range from less than 1 msec to over 3 min. Prepulse amplitudes were varied from Em = -20 mv to Em = -160 mv. The attenuation of the Ip values in high [Ko] was found to vary as a function of time when long duration conditioning potentials were applied. In both high and low [Ko], Ip values which had reached a quasi-steady—state level within a few milliseconds following a few milliseconds of hyperpolarization were found to increase following longer hyperpolarization. A second plateau was reached with a time constant of about 100–500 msec and a third with a time constant in the range of 30 to 200 sec. The intermediate quasi-steady—state level was absent in K-free ASW solutions. Sodium inactivation curves, normalized to Ipmax values obtained at either the first or second plateaus, were significantly different in different [Ko]. The inactivation curves, however, tended to superpose after about 1 min of hyperpolarizing conditioning. The time courses and magnitudes of the intermediate and very slow sodium conductance restorations induced by long hyperpolarizing pulses are in agreement with those predicted from the calculated rates and magnitudes of [K+] depletion in the space between the axolemma and the Schwann layer.
152 citations
TL;DR: Comparative reactivity of mature albino rabbits and of healthy man to the pyrogenic activity of purified S. typhosa, E. coli, and Pseudomonas endotoxins is presented to provide a more definitive base line for interpreting studies with bacterial endotoxin that involve extrapolation of rabbit febrile responses to man.
Abstract: SummaryComparative reactivity of mature albino rabbits (1.8–2.2 kg) and of healthy man to the pyrogenic activity of purified S. typhosa, E. coli, and Pseudomonas endotoxins is presented. On a per kilogram basis, rabbit and man are approximately equally reactive to threshold pyrogenic quantities of endotoxin. When larger doses of endotoxin are employed, the dose-response relationships become considerably steeper for man. On a total dose basis, rabbits require smaller quantities of endotoxin to elicit threshold febrile responses, but as total toxin dose is increased, febrile responses of man rapidly exceed those of the rabbit. Subjective toxic responses of man parallel the pyrogenic responses. These data provide a more definitive base line for interpreting studies with bacterial endotoxin that involve extrapolation of rabbit febrile responses to man.
144 citations
TL;DR: Tyrosinase in hamster skin, measured by the production of 3HOH from L-tyrosine-3,5-3H, increases about sevenfold in specific activity from the 14-day fetus to day 6 of life.
Abstract: Tyrosinase in hamster skin, measured by the production of 3HOH from L-tyrosine-3,5-3H, increases about sevenfold in specific activity from the 14-day fetus to day 6 of life. Albino hamsters exhibit no activity, but enzyme is present in the ventral (white) areas of the Syrian hamster. 3,4-Dihydroxy-L-phenylalanine is required as a cosubstrate.
104 citations
TL;DR: Self-report measures indicated that following final exams there was a significant reduction of daily anxiety for treatment groups as compared to the controls, and a strong trend favoring the Therapist-Present group was noted for improved G.P.A. following treatment.
99 citations
TL;DR: Wild-type Escherichia coli B grew poorly on glutamate as the sole carbon source, except at very high concentrations of the amino acid, except in the presence of an energy source, chloramphenicol, and arsenite, which retarded glutamate degradation.
Abstract: Wild-type Escherichia coli B grew poorly on glutamate as the sole carbon source, except at very high concentrations of the amino acid. The addition of sodium ion markedly stimulated the growth. It had the same effect in a mutant of E. coli B selected for the ability to grow at low glutamate concentrations. Sodium ion also potentiated growth inhibition by analogues of glutamate. The uptake of glutamate by nongrowing cells of the mutant was markedly stimulated by sodium ion in the presence of an energy source, chloramphenicol, and arsenite, which retarded glutamate degradation.
84 citations
TL;DR: The varying potential clamp replaces the constant command potentials of the standard voltage clamp with potentials which vary with time, which enables rapid and accurateENa andEK determinations and enables simple and accurate determination of Cm.
Abstract: A new mode of voltage clamping in the squid giant axon is introduced and its advantages are analyzed, tested, and utilized to investigate membrane conductances and capacity. This method replaces the constant command potentials of the standard voltage clamp with potentials which vary with time. Some of the advantages in using the varying potential clamp are: (1) slowly varying potentials generate practically pureIK; (2) rapidly varying potentials generate practically pureINa; (3) triangular waves generate, under proper conditions, pure capacity currents and easy-to-analyze leakage currents; (4) the method gives direct, on-line display of sodium or potassium I–V characteristics within milliseconds; (5) it enables rapid and accurateENa andEK determinations; and (6) it enables simple and accurate determination ofCm. The method was utilized to study the effects of various ions on membrane conductances and the effects of ionic composition, ionic strength, and temperature on membrane capacity. Membrane capacity was found to be practically independent of frequency in the 200 to 2,000 Hz range. Replacement of external sodium by Ca++, by impermeable Tris+, or even by dextrose or sucrose (low ionic-strength solutions) had negligible effects onCm.Cm showed a small, positive temperature coefficient of 1.39% per °C in the 3 to 21°C range, and little change with temperature in the 20 to 40°C range. Above 40°C, bothCm andgL increased considerably with temperature.
80 citations
TL;DR: The general biological properties of a temperature-sensitive morphological mutant of Bacillus subtilis (168ts-200B) are described and growth curves, deoxyribonucleic acid replication kinetics, and the morphology of mutant 168ts- 200B are described.
Abstract: The general biological properties of a temperature-sensitive morphological mutant of Bacillus subtilis (168ts–200B) are described. At the restrictive temperature (45 C), cells grow as spheres which divide irregularly to form grapelike clusters. At the permissive temperature (30 C), the mutant grows as typical B. subtilis rods in short chains. A log-phase culture of rods (30 C) may be converted to spheres by transfer to 45 C. Reversion of spheres to rods occurs when the alternate temperature shift is made. Growth curves, deoxyribonucleic acid replication kinetics, and the morphology of mutant 168ts–200B are described.
77 citations
TL;DR: Single units were isolated in the orbito-insular cortex of cats and the animals were presented with visual and auditory stimuli whose temporal relationship was varied in a systematic manner, revealing multimodal, unimodal and unresponsive cells.
75 citations
TL;DR: It is concluded that external potassium ions have an inactivating effect on the initial transient membrane conductance which cannot be explained solely on the basis of potassium membrane depolarization.
Abstract: Isolated giant axons were voltage-clamped in seawater solutions having constant sodium concentrations of 230 mM and variable potassium concentrations of from zero to 210 mM. The inactivation of the initial transient membrane current normally carried by Na+ was studied by measuring the Hodgkin-Huxley h parameter as a function of time. It was found that h reaches a steady-state value within 30 msec in all solutions. The values of h∞, τh, αh,and βh as functions of membrane potential were determined for various [Ko]. The steady-state values of the h parameter were found to be inversely related, while the time constant, τh, was directly related to external K+ concentration. While the absolute magnitude as well as the slopes of the h∞ vs. membrane potential curves were altered by varying external K+, only the magnitude and not the shape of the corresponding τh curves was altered. Values of the two rate constants, αh and βh, were calculated from h∞ and τh values. αh is inversely related to [Ko] while βh is directly related to [Ko] for hyperpolarizing membrane potentials and is independent of [Ko] for depolarizing membrane potentials. Hodgkin-Huxley equations relating αh and βh to Em were rewritten so as to account for the observed effects of [Ko]. It is concluded that external potassium ions have an inactivating effect on the initial transient membrane conductance which cannot be explained solely on the basis of potassium membrane depolarization.
69 citations
TL;DR: An action spectrum was measured for photoinduction of colored carotenoids in dark-grown, early stationary-phase cells of Myxococcus xanthus, which had been shown to have an action spectrum resembling the absorption spectrum of protoporphyrin IX.
Abstract: An action spectrum was measured for photoinduction of colored carotenoids in dark-grown, early stationary-phase cells of Myxococcus xanthus. Maximum activity was observed at 405 to 410 nm with subsidiary maxima at 512, 533, 548, 585, and 635 nm. These maxima correspond closely in position and magnitude with absorption maxima of protoporphyrin IX, which had previously been isolated from M. xanthus cells and had been shown to increase during the stationary phase of the culture. Late stationary-phase, dark-grown cells undergo photolysis which had been shown to have an action spectrum resembling the absorption spectrum of protoporphyrin IX. The similarity of the action spectra of photolysis and photoinduced carotenogenesis in M. xanthus and of other photoinduced biological phenomena is discussed.
TL;DR: The pyridoxal phosphate contents of several enzymes have been compared both by fluorometry and by absorption spectrophotometry of the phenylhydrazone, and give results in good agreement.
TL;DR: Compressible starch gives results comparable to USP starch in terms of disintegration time and dissolution rate when used at equivalent levels and the high moisture content of compressible starch does not affect the stability of aspirin when compressed together.
TL;DR: Alanine racemase, induced in Pseudomonas putida by growth on DL -alanine, was purified about 1000-fold to homogeneity and contains approximately one molar equivalent of pyridoxal phosphate.
TL;DR: Tetrodotoxin blocks the action potential and both the inward and outward transient current, but has no effect on either the resting membrane potential or the steady-state current, taken as an indication that this current component is probably carried by Na.
Abstract: A new dissection procedure for preparing Myxicola giant axons for observation under voltage clamp is described. Preparation time is generally 40–45 min. 65–70% of the preparations attempted may be brought through the entire procedure, including insertion of the long internal electrode, and support an initial action potential amplitude of 100 mv or greater. Mean values for axon diameter, resting membrane potential, action potential amplitude, maximum peak inward transient current, and resting membrane resistance are 560 µ, —66.5 mv, 112 mv, 0.87 ma/cm2 and 1.22 KΩ cm 2 respectively. Cut branches do not seem to be a problem in this preparation. Behavior under voltage clamp is reasonably stable over several hours. Reductions in maximum inward transient current of 10% and in steady-state current of 5–10% are expected in the absence of any particular treatment. Tetrodotoxin blocks the action potential and both the inward and outward transient current, but has no effect on either the resting membrane potential or the steady-state current. This selective action of tetrodotoxin on the transient current is taken as an indication that this current component is probably carried by Na.
TL;DR: In addition to inducing the degradative enzymes, the two hydroxyproline epimers were also found to induce an uptake system that concentrates hydroxy Proline intracellularly and either amino acid induced the uptake system for its epimer as well as for itself.
Abstract: Studies in Pseudomonas putida of the inducible degradation of hydroxyproline to α-ketoglutarate have indicated that either of the two epimers, hydroxy-l-proline or allohydroxy-d-proline, acts as an inducer of all the pathway enzymes. In a mutant lacking the first enzyme of the sequence, hydroxyproline-2-epimerase, which interconverts these two hydroxyproline epimers, either epimer is still equally active as an inducer of the remaining three enzymes, suggesting that each epimer has intrinsic inducer activity. The second and third enzymes of the sequence were induced coordinately. The induction process appeared to be insensitive to catabolite repression under a number of experimental conditions. The induced enzymes were stable even under conditions of nitrogen starvation and other conditions designed to increase protein turnover. In addition to inducing the degradative enzymes, the two hydroxyproline epimers were also found to induce an uptake system that concentrates hydroxyproline intracellularly. Either amino acid induced the uptake system for its epimer as well as for itself.
TL;DR: TFE was not oxidized by alcohol dehydrogenase and NAD in vitro ; however, TFE was a competitive inhibitor of ethanol oxidation, and was as toxic as hydrochloric acid.
TL;DR: Blood glucose, plasma insulin, FFA and β‐hydroxybutyrate values during intravenous glucose tolerance were reported in 20 small for gestational age (SGA) and 15 appropriate for gestations age (AGA) low birthweight infants.
Abstract: Summary
Blood glucose, plasma insulin, FFA and β-hydroxybutyrate values during intravenous glucose tolerance were reported in 20 small for gestational age (SGA) and 15 appropriate for gestational age (AGA) low birthweight infants. The babies were divided into three groups according to their age when tested; 48 hours.
Both the SGA and AGA infants cleared glucose more rapidly with increasing age. The change was more marked in the SGA babies. The clearance rates were similar to those reported in normal full-sized infants.
The insulin values before the glucose load were similar in all groups and comparable to those reported in normal newborn infants.
The insulin response to glucose was variable. There were no significant differences with increasing age or between the two groups of infants. The insulin curve of the individual infant followed one of three patterns. Most commonly seen was a double-peak curve. The infants who showed a single-peak insulin response had a better but not significantly different glucose tolerance than that of the other babies. Infants with no appreciable insulin response still removed glucose from plasma at a rate similar to those with a double-peak insulin curve. It is concluded that insulin as measured in peripheral plasma could not explain the rate of removal of glucose from the plasma of the newborn low birthweight infant.
Infants of low birthweight had higher plasma FFA values as compared to that reported in normal full term infants. The FFA values in SGA infants were higher than those in AGA babies. In both groups of infants, the jS-hydroxybutyrate values were comparable to those reported in normal full-term babies. Thus there was an unexpected discrepancy between the high FFA and relatively low β-hydroxybutyrate levels in plasma. The fall in plasma FFA and β-hydroxybutyrate after glucose was minimal but similar in both groups of infants.
The findings are compatible with a decreased sensitivity to insulin in the infants studied.
TL;DR: Rickettsia quintana grew readily on blood-agar base when the following conditions and supplements were supplied: aerobic conditions; increased CO(2) tension; crystalline hemoglobin or hemin, but not protoporphyrin; and a colloidal "detoxifying agent," such as starch or charcoal.
Abstract: Rickettsia quintana grew readily on blood-agar base when the following conditions and supplements were supplied: (i) aerobic conditions; (ii) increased CO(2) tension; (iii) crystalline hemoglobin or hemin, but not protoporphyrin; and (iv) a colloidal "detoxifying agent," such as starch or charcoal. Serum was not required nor did it enhance growth when all of the aforementioned components were supplied.
TL;DR: This finding provides further evidence that MHPG is the major metabolite formed within these tumours, and the assay of urinary MHPG, especially after enzymatic hydrolysis of the glucuronide and sulfate conjugates, should be of value in the diagnosis of tumors of neural crest origin.
TL;DR: Results support the premise that the nettle's sting, which clinically injures human skin, might affect other tissues if an adequate dosage were administered.
Abstract: SummarySea nettle (Chrysaora quinquecirrha) tentacles inflict cutaneous damage on many animals, including man. The cardiovascular action of the nettle toxin was investigated to determine whether this agent was capable of injuring tissues other than skin. Cardiac conduction abnormalities and ischemic electrocardiographic changes occurred in rats shortly after intravenous injections of the nettle toxin. Large doses of toxin produced a prompt increase in arterial blood pressure. These results support the premise that the nettle's sting, which clinically injures human skin, might affect other tissues if an adequate dosage were administered.This study was supported in part by grants-in-aid from the U. S. Bureau of Commercial Fisheries and Maryland Department of Chesapeake Bay Affairs, Grant 14-17-007-959 and the U. S. Department of Health, Education and Welfare, Grant 1 R01 UI 00642-01. The authors gratefully acknowledge the assistance of Mrs. Patricia Fannin, Mr. Michael P. Zimring, Mr. John C. Lee, Dr. John ...
Journal Article•
TL;DR: The polarity of the lesion and the absence of mature virus particles below the Malpighian layer support the hypothesis that molluscum infections are transmitted by external contact.
TL;DR: Sea nettle (Chrysaora quinquecirrha) fishing tentacles were studied with thick and thin sections of Epon or Araldite embedded material to define the different types of threads, nematocysts, and nematocytes present.
TL;DR: The chromosome complements of the following 15 species of culicine mosquitoes were studied and illustrated; the subgenera Christophersiomyia and Lutzia were examined for the first time and new karyotypes for 3 species were described.
Abstract: The chromosome complements of the following 15 species of culicine mosquitoes were studied and illustrated: Aedes (Christophersiomyia) thomsoni (Theobald), Aedes (Stegomyia) albopictus (Skuse), Aedes (Stegomyia) aegypti (Linnaeus), Armigeres (Armigeres) subalbatus (Coquillett), Culex (Lutzia) fuscanus Wiedemann, Culex (Lutzia) raptor (Edwards), Culex (Culex) fuscocephala Theobald, Culex (Culex) pipiens fatigans Wiedemann, Culex (Culex) annulus Theobald, Culex (Culex) pseudovishnui Colless, Culex (Culex) tritaeniorhynchus Giles, Culex (Culex) sitiens Wiedemann, Culex (Culex) neolitoralis Bram, Culex (Culex) bitaeniorhynchus Giles, and Culex (Culex) gelidus Theobald.
The chromosomes of 11 of these species had not previously been studied, and the subgenera Christophersiomyia and Lutzia were examined for the first time. The diploid chromosome number for all species examined was 6. No heteromorphic chromosomes were found in tissues from testis or ovary. While the karyotypes of 12 of these species were in conformity to previous work, i.e., chromosome 1 being considerably shorter than chromosome 2 and 3 with chromosome 2 approximating chromosome 3, new karyotypes for 3 species, C. (L.) fuscanus, C. (L.) raptor and C. (C.) gelidus , were described in which chromosome 2 is considerably shorter and approximates chromosome 1.
TL;DR: It is concluded that potassium or cesium ions do not compete with these drugs for a particular site on the ion transport complex in frog muscle as are required for inhibition of ion transport in other tissues, inhibition of sodium-potassium-stimulated ATPases, and toxicity to animals.
Abstract: Cesium uptake by sodium-loaded frog sartorius muscles was inhibited 100% by 10-6 M ouabain and 10-6 M cymarin. The doses for 50% inhibition of cesium uptake by five cardiotonic aglycones were 1.5 x 10-6 M for strophanthidin, 2 x 10-7 M for telocinobufagin, 1.6 x 10-6 for digitoxigenin, 2.4 x 10-6 M for periplogenin, and 6.3 x 10-6 M for uzarigenin. Because of the limited solubility of sarmentogenin the maximum concentration studied was 2 x 10-6 M which inhibited cesium uptake about 36%. Inhibition of cesium uptake by cymarin was not reversed during a 3.5 hr incubation in fresh solution while the muscles treated with ouabain and strophanthidin recovered partly during this time. Cymarin was a more potent inhibitor of sodium efflux than strophanthidin and periplogenin was less potent. Increased cesium ion concentration in the external solution decreased the strophanthidin inhibition of cesium uptake but 25 mM cesium did not overcome the inhibition by 10-8-10-6 M strophanthidin. Increased potassium ion concentration in the external solution decreased but did not completely overcome inhibition of sodium efflux by strophanthidin. It is concluded that potassium or cesium ions do not compete with these drugs for a particular site on the ion transport complex. The same structural features of the drugs are necessary for inhibition of ion transport in frog muscle as are required for inhibition of ion transport in other tissues, inhibition of sodium-potassium-stimulated ATPases, and toxicity to animals.
TL;DR: Tests in volunteers showed that vaccination with strain LVS by the oral route is useful and practical for the immunization of man against tularemia.
Abstract: SummaryStudies on the immunogenicity of live tularemia vaccine for animals and man vaccinated dermally or aerogenically were sufficiently encouraging to warrant an evaluation of vaccination of the monkey via the oral route. A preliminary investigation of the oral infectivity and virulence of P. tularensis SCHU S4, fatal for the monkey infected dermally or by the respiratory route with 10-25 organisms, revealed that 104 viable cells swallowed with milk did not result in infection but that 106 organisms infected two of eight animals, both of which died. An oral dose of 108 or 1010 cells infected all monkeys tested and the majority died; severe inflammation and ulceration of the gastrointestinal tract were found at necropsy. The course and outcome of the disease were comparable when animals were compelled to swallow intact a gelatin capsule containing 1010 organisms.In a study on the reactivity and immunogenicity of live vaccine strains LVS and of strain 425, highly infectious but seldom lethal for the monke...
TL;DR: Plasma tryptophan can be extracted from spots on filter paper with dilute ethanol and estimated directly by spectrofluorometry in alkaline medium by using an inert support and results obtained are in agreement with previously published values.