Search PubMed⌕ Search

Biomedical subjects

R L Warren

Publications and source records attributed to R L Warren.

At least 73 records · Page 4Linked to original sources
PubMed1981

Dichotic ear preference for C-V-C words in Wernicke's and Broca's aphasias.

A dichotic listening task was administered to subjects with a relatively distinct Broca's aphasia, subjects with a relatively distinct Wernicke's aphasia, and normal subjects. The dichotic stimuli consisted of C-V-C words differing in initial consonant only. Subjects were instructed to respond only to the stimulus of which they were most sure by pointing to a picture representing the dichotic stimuli or foils. while normal subjects demonstrated the usual right ear effect, both the Broca's and Wernicke's aphasia groups demonstrated left ear effects. One salient explanation for these results was that any severe defect in the language systems of the left hemisphere affects the way that the left hemisphere processes linguistic information. It was postulated that left ear stimuli, which arrive at the left hemisphere later, disrupt the processing of right ear stimuli in subjects with aphasia. However, a more definitive explanation requires further research.

Adult↗
PubMed1981

Restriction endonuclease map of phage group 2 Staphylococcus aureus exfoliative toxin plasmid.

A restriction endonuclease map of the phage group 2 Staphylococcus aureus exfoliative toxin plasmid pRW001 was constructed. The orientation of the restriction endonuclease fragments was determined by a series of single and double enzyme digestions. The location of the deletions found in pRW002, a naturally occurring deletion mutant of the exfoliative toxin plasmid, was determined by comparing the restriction endonuclease fingerprints of the two plasmids. This physical map provided a means for comparing other insertion or deletion mutants of the exfoliative toxin plasmid.

Bacterial Toxins↗
PubMed1980

Exfoliative toxin plasmids of bacteriophage group 2 Staphylococcus aureus: sequence homology.

The plasmid contents of seven exfoliative toxin-producing strains of phage group 2 Staphylococcus aureus were analyzed by agarose gel electrophoresis and deoxyribonucleic acid-deoxyribonucleic acid hybridization. All strains were found to contain a large plasmid with a molecular weight of 27 X 10(6) except for strain RW1005. A comparison of the restriction endonuclease cleavage products by agarose gel electrophoresis showed that the number and size distribution of the fragments of all these Tox plasmids were similar, except for pRW002, which appeared to contain two deletions. Deoxyribonucleic acid-deoxyribonucleic acid hybridization studies confirmed that these plasmids were related to a plasmid which carried the genes for exfoliative toxin B and bacteriocin R1 biosynthesis and that they shared some sequence homology with the penicillinase plasmid pI258 isolated from a phage group 3 S. aureus.

Bacterial Toxins↗
PubMed1978

Replication of plasmid DNA in Proteus mirabilis in limiting concentrations of thymine.

Replicating forms of the R plasmid pRR12 and the colicin E1 plasmid RSF2124 were isolated from Proteus mirabilis after growth in medium containing a limiting concentration of thymine. Both plasmids were replicated as partially supercoiled intermediates, which have densities between the values of covalently closed circular and nicked circular plasmid DNA in ethidium bromide-cesium chloride gradients. In addition, both plasmids had replication intermediates, which have densities lower than that of linear P. mirabilis chromosomal DNA. Some structural features of these replication intermediates were examined.

DNA Replication↗
PubMed1978

Investigations into the role of calcium ions in the control of steroid production by isolated adrenal zona glomerulosa cells of the rat.

An increase in the concentration of extracellular potassium from 3.6 to 8.4 mmol/1 had only a small delayed effect on the uptake of radioactive calcium by isolated adrenal glomerulosa cells. However, the same stimulus had a rapid and highly significant effect on the efflux of radioactive calcium from glomerulosa cells preloaded with 45Ca2+. Cells incubated in medium containing 8.4 mmol potassium/1 had retained approximately 15% more radioactivity than conrol cells after 2.5 min and this difference was maintained for up to 90 min. There was an increase in the production of steroids by the glomerulosa cells in the presence of 8.4 mM-potassium. No effect on calcium efflux was observed in similar experiments with isolated fasciculata cells; it has been established that this concentration of potassium does not affect steroidogenesis in fasciculata cells, indicating that the effect on glomerulosa cells may be causally linked to steroidogenesis. There was no significant change in the total calcium content of glomerulosa cells in the presence of 8.4 mM-potassium. Exchangeable calcium in these cells was found to be 60% of the total calcium content.

Adrenal Cortex↗
PubMed1977

Short-term memory scan in normal individuals and individuals with aphasia.

Ten matched pairs of normal adults and adults with aphasia participated in a short-term memory, visual recognition paradigm wherein each determined whether or not a probe digit appeared in a subset of digits previously presented. Reaction times, measured in milliseconds from onset of probe digits until completion of visual-motor responses, were analyzed as a function of increasing subset size (two, four, and six digits) and the positive versus the negative response condition. Reaction times were significantly slower for the subjects with aphasia. Both groups of subjects demonstrated linear increases in reaction time across levels of subset size. For both groups, increases in reaction time were similar in the positive vs the negative-response conditions. Resulting parallel slopes suggested that both groups of subjects used a serial exhaustive scan of short-time memory. Results from this study did not support results obtained by others in previous studies which may have been confounded by group differences in visual retention spans.

Adult↗
PubMed1975

Micromethods for the simultaneous measurement of intracellular potassium and corticosterone output of isolated adrenal cortical cells.

1. A technique is described for the measurement of potassium and water spaces in less than 1 mul of packed cells. 2. The total potassium content of cell pellets is measured in a perchloric and nitric acid extract by flame spectrophotometry. The potassium in trapped medium is estimated from the distribution space of hydroxy[-14C]methylinulin and subtracted from the total potassium content to give intracellular potassium content. Corticosterone output was measured by radioimmunoassay. 3. The simultaneous measurement of total water from the [-3H]water space allows calculation of the intracellular water space. 4. Values obtained for intracellular potassium content, intracellular water space and calculated intracellular potassium concentration are presented for different preparations of isolated adrenal cortical cells.

Adrenal Cortex↗
PubMed1973

The distribution of sodium and potassium in amphibian embryos during early development.

1. Intracellular and intercellular concentrations of sodium and potassium have been measured in pregastrular embryos of Xenopus laevis and Amblystoma mexicanum. Calcium and magnesium contents have also been determined.2. Between egg and gastrula stages of development the potassium concentration is near to 60 m-mole/l. embryo. Up to the blastula stage the sodium concentration is near to 50 m-mole/l. embryo; the amount of sodium in the embryo begins to fall just before gastrulation.3. Embryo calcium and magnesium concentrations show no significant variations prior to gastrulation. Average calcium concentrations for the different stages range from 5 to 8 m-mole/l. embryo; magnesium concentrations lie between 12.4 and 17 m-mole/l. embryo.4. The intercellular fluid contains 100 mM sodium and 1 mM potassium; the majority of the sodium is ionically active. As no net uptake of sodium or potassium occurs before gastrulation these cations must have been transferred from the cells to the cavity.5. At all developmental stages studied, the intracellular potassium concentration is close to 100 m-mole/l. cell water. Intracellular sodium falls steadily from 80 m-mole/l. cell water in eggs to 30 m-mole/l. cell water at the beginning of gastrulation.6. The intracellular sodium activity, measured with sodium sensitive intracellular micro-electrodes, is relatively constant between egg and blastula stages at about 14 mM. During each cell division cycle the intracellular sodium activity rises transiently by 2-3 mM.

Amphibians↗
PubMed1971

A study of the electrochemistry and osmotic relationships of the cochlear fluids in the neonatal rat at the time of the development of the endocochlear potential.

1. Changes in the endocochlear potential between the 8th and 18th days after birth were investigated in the rat. Initially the potential was low but its magnitude increased rapidly between the 11th and 16th day. During the 13th and 14th days the rate of increase was approximately 1 mV/hr.2. The rapid potential increase arose virtually simultaneously in all three turns of the cochlea.3. Histological examination revealed the cochlea, including the hair cells of Corti's organ and the stria vascularis, to be fully mature before the period of rapid change in the endocochlear potential, apart from the cells of Claudius, whose final development coincided with the latter part of this phase.4. The endolymphatic sodium concentration (average 1.0 m-equiv/l.) had attained the very low adult level in the earliest period studied. The potassium and chloride concentrations were slightly below the normal adult levels, the result of some degree of general hypo-osmolality present at this time.5. The endolymphatic ionic concentrations remained unchanged during the phase of rapid increase in the endocochlear potential.6. The findings thus indicate that the distinctive endolymphatic ionic composition and the endocochlear potential arise largely independently and in succession during cochlear maturation.7. No differences in osmotic pressure were demonstrated between endolymph, perilymph and serum. The problems concerning the homoeostasis of the inner ear fluids do not consequently seem to be complicated by unusual hydrodynamic aspects.8. Alterations in body fluid osmolality, produced by intraperitoneal injection of water or hypertonic glycerol, were accompanied by simultaneous changes in the osmotic pressures of the inner ear fluids. Some portion of the membranes bounding the endolymphatic space is therefore considered to be freely permeable to water.9. The investigations provide no further information about the nature of the endocochlear potential, although an increase in the electrical resistance of the cochlear duct membranes is thought responsible for its appearance. The time relationships of this period support the concept that the potential is an essential feature of the mechano-electric transduction process.

Animals↗