Search PubMed⌕ Search

Biomedical subjects

C Edwards

Publications and source records attributed to C Edwards.

At least 307 records · Page 17Linked to original sources
PubMed1977

Permeability of the endplate membrane activated by acetylcholine to some organic cations.

The ability of various organic cations to depolarize the ACh-activated endplate membrane in the absence of Na ions was examined on frog sartorius muscle by measuring the endplate potential on the muscle surface with the moving electrode technique. The ACh-activated endplate membrane was very permeable to ammonium and its methyl and hydroxy derivatives, and moderately permeable to guanidine derivatives and Tris (hydroxymethyl) aminomethane. The permeability of alkylol derivatives of ammonium diminished progressively with increase in molecular size. The present results suggested that the endplate ionic channels can be represented by a pore of about 6.4 A in diameter.

Acetylcholine↗
PubMed1977

Effect of increased potassium concentrations on particle motion within a neurosecretory structure.

Intensity fluctuation spectroscopy was used to detect particle motion within the pericardial organ of the crab Carcinus while it was perfused with media with increased potassium concentrations. Replacement of some or all of the sodium ions of the normal medium with potassium ions caused a graded increase in motion. Evidence is presented which indicates that this effect is not a consequence of membrane depolarization or calcium ion influx, but is due to the flux of potassium chloride and water into the cytoplasm of the cells.

Animals↗
PubMed1977

Subcellular fractionation by differential and zonal centrifugation of the trypanosomatid Crithidia fasciculata.

Homogenates of Crithidia fasciculata were fractionated by differential centrifugation. Mitochondria were sedimented quantitatively at 10(4) g-min and accounted for approximately 10% of the total recovered protein. Catalase was found exclusively in the supernatant fraction whilst NADH:cytochrome c oxidoreductase and p-nitrophenylphosphatase were found in all the fractions. Zonal centrifugation confirmed that catalase was non-sedimentable. Clean separation of mitochondria was obtained in both high-speed and rate zonal experiments, but no NADH:cytochrome c oxidoreductase activity could be detected in these organelles. Separation of large lysosomal vacuoles which contained p-nitrophenylphosphatase activity was obtained and these were clearly resolved from mitochondria by both high-speed and rate zonal centrifugation.

Cell Fractionation↗
PubMed1976

Congenital absence of the vagina. The Mayer-Rokitansky-Kuster-Hauser syndrome.

We describe 14 patients with congenital absence of the vagina associated with a variable abnormality of the uterus and review the literature. Associated developmental anomalies of the urinary tract and skeleton are common. As a result of the analysis of two affected families, we believe that the disorder may represent the variable manifestation of a single underlying genetic defect that can be expressed alone or in any combination of vertebral, renal, and genital abnormalities. Some affected persons may have lethal manifestations such as absence of both kidneys, and some cases may result from multifactoral causes rather than a single gene defect. Whatever the cause, the defect involves mesodermal development and the mesonephric kidney, the latter resulting in abnormalities in the paramesonephros (uterus and vagina) and in the metanephric kidney. Both nonoperative and surgical treatments are generally successful in repairing the vaginal abnormality.

Adolescent↗
PubMed1975

Donnan potential of rabbit skeletal muscle myofibrils I: electrofluorochromometric detection of potential.

The fluorescence of the dye CC-6 [(3-hexyl-2-(3-hexyl-2-benzoxazolinylidene)-1-propenyl)-benzoxazolium iodide] has been shown to indicate Donnan potentials in rabbit skeletal muscle myofibrils. These results are in agreement with previously published work in which the potentials were measured with microelectrodes on glycerol-extraced muscle fibers. The magnitude of the Donnan potential of the myofibrils has been shown to be dependent on the state (rigor or relaxed) of the system.

Adenosine Triphosphate↗
PubMed1975

The preparation of large-scale synchronous cultures of the trypanosomatid, Crithidia fasciculata,by cell-size selection: changes in respiration and adenylate charge through the cell-cycle.

Large-scale synchronous cultures of Crithidia fasciculata were prepared by a sedimentation-velocity-size-election method using a non-somotic gradient in a zonal rotor. Synchrony indices of up to 0-68 were obtained (average length of cell-cycle, 5-1h). Dry weight, protein and RNA increased continuously so as to double in one cell-cycle. Rates of oxygen uptake/ml culture increased overall so as to double over a cell-cycle, but rose to maxima at five periods in the cell-cycle. KCN gave a similar degree of inhibition throughout, and so did not alter the periodicity or amplitude of the oscillations. Total adenylates doubled over a cycle, and complex changes in pool sizes of ATP, ADP and AMP were temporally interrelated and were correlated with changes of oxygen uptake rates rather than with changes in biosynthetic requirements. Adenylate charge varied between 0-47 and 0-66 Discontinuous respiratory activity of mitochondria through the cell-cycle and possible mechanisms for its control are discussed with reference to previous data.

Adenine Nucleotides↗
PubMed1975

Synchronous cultures of micro-organisms: large-scale preparation by continuous-flow size selection.

The separation of the smallest cells from an exponentially growing culture by passage through a continuous flow centrifuge rotor under controlled conditions of rotor speed and flow rate, provides a simple method for the rapid production of large-scale synchronous cultures. The effluent from the rotor, containing the smallest-sized class of organisms, still suspended in their growth medium and still growing undisturbed throughout this rapid procedure, provides a culture which goes on to exhibit synchronous cell division. Successfully applied to budding and fission yeasts and to amoeboid and ciliated protozoa, this procedure ti potentially applicable to any non-filamentous, non-aggregating, unicellular organism or to cells of higher plants or animals growing in liquid tissue-cultures.

Animals↗
PubMed1975

The pathology of the lung in byssinotics.

A report of the gross and microscopic appearances in the lungs and the weights of the cardiac ventricles in 43 subjects receiving industrial benefit for byssinosis is presented. In 27 (63%) there was no significant emphysema, in 10 (23%) there were varying amounts of centrilobular emphysema, and panacinar emphysema was found in six (14%). Other changes were of non-specific nature, but most cases showed heavy black dust pigmentation, often associated with centrilobular dilatation of distal air spaces.

Aged↗
PubMed1974

Differences in the charge distribution of glycerol-extracted muscle fibers in rigor, relaxation, and contraction.

Glycerol-extracted rabbit psoas muscle fibers were impaled with KCl-filled glass microelectrodes. For fibers at rest-length, the potentials were significantly more negative in solutions producing relaxation than in solutions producing either rigor or contraction; further the potentials in the latter two cases were not significantly different. For stretched fibers, with no overlap between thick and thin filaments, the potentials did not differ in the rigor, the relaxation, or the contraction solutions. The potentials measured from fibers in rigor did not vary significantly with the sarcomere length. For relaxed fibers, however, the potential magnitude decreased with increasing sarcomere length. The difference between the potentials measured for rigor and relaxed fibers exhibited a nonlinear relationship with sarcomere length. The potentials from calcium-insensitive fibers were less negative in both the rigor and the relaxation solutions than those from normal fibers. When calcium-insensitive fibers had been incubated in Hasselbach and Schneider's solution plus MgCl(2) or Guba-Straub's solution plus MgATP the potentials recorded upon impalement were similar in the rigor and the relaxation solution to those obtained from normal fibers in the relaxed state. It is concluded that the increase in the negative potential as the glycerinated fiber goes from rigor to relaxation may be due to an alteration in the conformation of the contractile proteins in the relaxed state.

Animals↗