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Biomedical subjects

J Wall

Publications and source records attributed to J Wall.

At least 55 records · Page 3Linked to original sources
PubMed1988

Improved solid-phase extraction and liquid chromatography with electrochemical detection of urinary catecholamines and 5-S-L-cysteinyl-L-dopa.

We describe a rapid, precise, accurate liquid chromatographic procedure for determining urinary catecholamines and 5-S-L-cysteinyl-L-dopa. The catecholamines (norepinephrine, epinephrine, and dopamine) and 5-S-L-cysteinyl-L-dopa are extracted from 1.0 ml of urine together with internal standards, by using a Bond-Elut strong cation-exchange (SCX) and an affinity phenylboronic acid (PBA) extraction column in series. The eluate obtained from PBA column is then chromatographed on a reversed-phase C18 column with a mobile phase containing pentane- and heptanesulfonate as ion-pair reagents. The detection is achieved with an amperometric detector set at an oxidation potential of +0.55 V. The chromatography is complete is less than 8 min for catecholamines and less than 5 min for cysteinyldopa. The method can measure less than 2 micrograms/l for catecholamines and 5 micrograms/l for cysteinyldopa. Analytical recoveries of catecholamines and cysteinyldopa added to urine pool ranged from 90-107%. Between run coefficient of variation ranged from 4.7 to 8%. None of the drugs and catecholamines metabolites tested interfered with the assay.

Catecholamines↗
PubMed1986

Concentrations of endogenous free amino acids in rabbit reticulocyte lysates and the effect of incubation.

Amino acid analyses show that while the free amino acids found in the rabbit reticulocyte translation system do not increase during nuclease treatment or during prolonged storage, the endogenous levels of many amino acids are so high that the choice of a radioactive precursor for a translation should be based not only on the abundance of the amino acid in the translation product but also on its concentrations in the lysate preparation. It is shown that the variation of amino acid concentrations reported in this study to calculate the amount of radioactive amino acid necessary for satisfactory incorporation.

Amino Acids↗
PubMed1986

Dominantly inherited craniodiaphyseal dysplasia: a new craniotubular dysplasia.

We describe a mother and her male infant affected with a craniotubular dysplasia characterized by severe craniofacial hyperostosis and sclerosis with obliteration of paranasal sinuses and foramina of the skull base. Subsequent severe bilateral hearing loss and facial diplegia with relative sparing of the optic nerves were noted. The long bones show extreme asymmetric hyperostosis and sclerosis of the diaphyses and evidence of a modelling defect in the metaphyses. The spine, ribs, clavicles, and pelvis all show some degree of sclerosis and defective modelling, but are less severely involved. According to the definition by Gorlin, this disorder would best be classified as craniodiaphyseal dysplasia. Distinguishing features in these two patients as contrasted to previously described cases include a greater degree of hyperostosis and sclerosis than that described for other patients with craniodiaphyseal dysplasia, apparent dominant transmission, and significant metaphyseal involvement.

Adult↗
PubMed1986

RNs may cost less than you think.

The health care environment is in a new era. Hospital and nursing administrators will be faced with tough decisions regarding number and skill level of staff. Productivity of various levels of nursing personnel is one parameter upon which decisions can be made. In this research, productivity is defined as the percentage of time spent in direct care, indirect care, and unit-related activities. The research indicates that the higher the level of personnel, the higher the productivity.

Clinical Competence↗
PubMed1984

Methylenetetrahydrofolate reductase. Evidence for spatially distinct subunit domains obtained by scanning transmission electron microscopy and limited proteolysis.

Scanning transmission electron microscopy of individual unfixed molecules of methylenetetrahydrofolate reductase has been used to determine the molecular mass distribution of the protein. Methylenetetrahydrofolate reductase, which has a subunit molecular mass of 77 kilodaltons, was found to exist predominantly as a dimer with an apparent molecular mass of 136 +/- 29 kilodaltons. The mass distribution of the enzyme molecules was unchanged in the presence of the allosteric inhibitor S-adenosylmethionine. Examination of negatively stained protein molecules suggested that each subunit of the dimer consists of two globular domains of approximately equal size. Limited proteolysis of the enzyme by trypsin gave results which were entirely consistent with the presence of two domains per subunit. In the presence of 1% trypsin, the enzyme was cleaved into two fragments. The masses of these fragments were 39 and 36 kilodaltons as assessed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Tryptic cleavage did not lead to loss of NADPH-menadione or NADPH-methylenetetrahydrofolate oxidoreductase activity, and the flavin prosthetic group remained bound to the protein. However, the cleaved protein was completely desensitized with respect to inhibition by S-adenosylmethionine. These results suggest that each subunit of methylenetetrahydrofolate reductase contains two domains and that allosteric inhibition requires specific interactions between these domains. The region between these two domains appears to be very sensitive to proteolysis, while the domains themselves are relatively resistant to further degradation.

5,10-Methylenetetrahydrofolate Reductase (FADH2)↗
PubMed1984

Thumb reconstruction in the burned hand by advancement pollicization of the second ray remnant.

Reconstruction of 15 thumbs in 14 patients with severe postburn deformity has been carried out by advancement and transferral of the second ray remnant onto the remaining proximal thumb metacarpal stump. This technique combines the advantages of thumb lengthening and pollicization procedures in a single operation and has been a useful method for restoration of single hand prehension in the severely burned mitten hand.

Adolescent↗
PubMed1983

The arrangement of the subunits of the acetylcholine receptor of Torpedo californica.

The monomeric form of the acetylcholine receptor from torpedo is composed of five, membrane-spanning chains with the stoichiometry alpha 2 beta gamma delta. The native receptor is predominantly a dimer cross-linked by a disulfide bridge between delta chains. We reduced native dimer to monomer and generated a different dimer by diamide-induced disulfide formation specifically between beta chains. Purified beta-beta cross-linked dimer, when adsorbed to a carbon film and negatively stained, appears in the electron microscope as two contiguous disks, frequently with central, stain-filled pits; i.e. it looks like native receptor in situ viewed normal to the plane of the membrane. We take the region of closest approach of the disks to mark the portions of the beta chains involved in the cross-link. In addition, we tagged the acetylcholine binding sites (one on each alpha chain) for electron microscopic identification, using a complex of monobiotinylated cobratoxin and avidin. Based on the locations of avidins bound to the beta-beta cross-linked dimer, the two toxin binding sites/monomer appear to be separated on the average by 110 degrees, as measured between lines from the center of the monomer to the centers of the avidins. One toxin binding site appears close to the beta-beta cross-link and the other close to the end of the monomer opposite to the cross-link; these locations are similar to the locations of the toxin binding sites relative to the delta-delta cross-link in native dimer. On the assumptions that the chains are compact units and are arranged in a unique order around the central pit, we interpret these results as indicating that the alpha chains are not contiguous and that neither the beta chain nor the delta chain lies between them. Therefore, the arrangement of the chains most easily reconciled with our assumptions and observations is alpha gamma alpha beta delta.

Animals↗
PubMed1983

Topographic reorganization of somatosensory cortical areas 3b and 1 in adult monkeys following restricted deafferentation.

Two to nine months after the median nerve was transected and ligated in adult owl and squirrel monkeys, the cortical sectors representing it within skin surface representations in Areas 3b and 1 were completely occupied by 'new' and expanded representations of surrounding skin fields. Some occupying representations were 'new' in the sense that (1) there was no evidence that these skin surfaces were represented in this region prior to median nerve transection; and (2) these skin surfaces retained their normal representation elsewhere within these two cortical representations of hand surfaces. Large 'new' representations of the dorsal surfaces of digits 1 and 2 (innervated by the radial nerve) and large 'new' representations of the hypothenar eminence (innervated by the ulnar nerve) were consistently recorded. Some surrounding skin surface representations expanded into the former median nerve zone, so that bordering skin surfaces (the ulnar insular palmar pad, the third digital palmar pad, glabrous ulnar digit 3, radial hand dorsum) were represented over far larger than normal cortical areas. These expanded representations of always-innervated skin sometimes appeared to move in entirety into the former median nerve representational zone (e.g. in the zone of representation of glabrous digit 4) were also consistently recorded. Reorganizational changes following median nerve sections were much more variable in Area 1 than in Area 3b. The topographic order of the reorganized cortical zone was comparable to normal. In at least most cortical sectors, there was a consistent, maintained relationship between receptive field size and magnification, i.e. as representations enlarged, receptive fields were correspondingly reduced in size. These studies indicate that topographic representations of the skin surface in adult monkeys are maintained dynamically. They clearly reveal that this projection system retains a self-organizing capacity in adult monkeys. They suggest that processes perhaps identical to a part of the original developmental organizing processes (by which details of field topographics are established) are operational throughout life in this projection system in primates. Some of the implications of these studies for the neural origins of tactile perception are discussed.

Afferent Pathways↗
PubMed1982

Structure of fibroblastic intermediate filaments: analysis of scanning transmission electron microscopy.

The structure of fibroblastic intermediate filaments from Chinese hamster ovary cells has been investigated by scanning transmission electron microscopy. Freshly extracted (native) filaments were compared with filaments reassembled in vitro from purified decamin. From digital micrographs of unstained specimens, direct measurements of linear mass density were performed on many individual filaments. Native filaments beyond a certain minimal length constitute a homogeneous population, averaging 38 +/- 4 kilodaltons (kDal)/nm. A minor but distinct polymorphic variant (23 +/- 4 kDal/nm) was also present as very short filaments or end-segments; these may represent breakdown products or assembly intermediates. Analysis of reassembled filaments demonstrates that the in vitro assembly reaction is--in the main--faithful, although the distribution of their mass measurements is appreciably broader than that of the native data. In addition to the predominant type at 37 +/- 4 kDal/nm and a minor component at 26 +/- 4 kDal/nm, small amounts of a third, more massive, polymorphic variant at 52 +/- 5 kDal/nm were also present. Micrographs of negatively stained specimens clearly demonstrate that the filaments are composed of bundles of protofilaments--each 2-3 nm in diameter--and also reveal an axial periodicity of about 46 nm. The implications of these findings are discussed for three classes of model previously proposed for the structure of intermediate filaments.

Animals↗
PubMed1982

Electron microscopy of complexes of isolated acetylcholine receptor, biotinyl-toxin, and avidin.

The principal curarimimetic toxin of Naja naja siamensis derivatized with biotinyl groups binds specifically both to acetylcholine receptor, isolated from Torpedo californica electric tissue, and to avidin. Isolated complexes of receptor monomer or dimer, biotinyl-toxin, and avidin were negatively stained and examined in the scanning transmission electron microscope. We measured the angle made by the radius of each avidin bound at the periphery of a monomeric unit in dimer to the axis connecting the centers of the monomers, starting at the crosslink between the monomers. We infer from the distribution of these angles that one toxin binding site is located in the range of 45 degrees to 85 degrees and another at about 100 degrees further from the crosslink between the monomers. Because it is known that there are two toxin binding sites per monomer, associated with the two alpha chains, the bound avidins presumably point to portions of the alpha chains, indicating their positions relative to that portion of the delta chain located at the crosslink between monomers in dimer.

Animals↗
PubMed1981

Relative locations of the beta and delta chains of the acetylcholine receptor determined by electron microscopy of isolated receptor trimer.

The monomeric unit of the acetylcholine receptor of electric tissue of Torpedo californica has previously been shown to have a subunit composition of alpha 2 beta gamma delta. Receptor in membrane isolated from Torpedo electric tissue occurs as both monomer and dimer. In the dimer which is the predominant form, the monomeric units are cross-linked via a disulfide bond between delta chains. The addition of diamide to receptor-rich membrane causes the formation of trimer and higher oligomers in which the monomeric units are linked by disulfide bonds alternately between pairs of delta chains and between pairs of beta chains. We have isolated receptor trimer and determined the relative locations of the monomeric units by scanning transmission electron microscopy of negatively stained preparations. In face view, the trimer appears as three approximately 90 A disks, each with a central, densely staining pit. From the angles of the triangle formed by the lines connecting the centers of the monomers in the trimer, we infer that the beta-beta disulfide bond is separated from the delta-delta disulfide bond by an angle in the range of 50-80 degrees.

Animals↗