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Biomedical subjects

G Davis

Publications and source records attributed to G Davis.

At least 181 records · Page 10Linked to original sources
PubMed1985

Use of DNA immobilized on plastic and agarose supports to detect DNA by sandwich hybridization.

Cloned Salmonella DNA, which has been immobilized irreversibly on plastic and agarose solid supports, can form hybrids in both single-layer and "sandwich" hybridization protocols. In single-layer hybridization, 3 micrograms of immobilized DNA bound at least 30 fmol of a specific 800-base DNA sequence (equivalent to 8.5 ng, or the amount of that sequence present in 4 X 10(10) organisms). In a 4-h sandwich hybridization protocol, as little as 14 amol (equivalent to 8 pg, or the amount of that sequence present in 1 X 10(7) organisms) of a 1600-base sequence of DNA could be detected. The methods described should be applicable to use with any set of probes--not just from Salmonella--that fulfill the criteria specified. The ability to perform DNA hybridizations on solid-phase matrices such as those used for immunoassay should bring DNA hybridization into the realm of routine clinical laboratory procedures.

DNA↗
PubMed1984

Response of protein C and protein C inhibitor to warfarin therapy in patient with combined deficiency of Factors V and VIII.

The role of Protein C in combined factor V/VIII deficiency was examined by reducing the Protein C concentration using warfarin therapy in a patient with the combined deficiency. The factor VIII deficiency was like Hemophilia-A, with deficiency of VIII:C and VIII:C(Ag), but normal VIIIR:Ag and VIIIR:cof. The factor V deficiency was due to loss of the V antigen. During warfarin therapy the Protein C level was reduced, but concentrations of factors V and VIII did not change. Protein C Inhibitor was normal throughout. Thus combined factor V/VIII deficiency is not related to Protein C levels.

Adult↗
PubMed1984

Infections caused by herpes simplex virus in the immunocompromised host: natural history and topical acyclovir therapy.

Sixty-three immunocompromised patients with infections caused by herpes simplex virus were evaluated in a double-blind, placebo-controlled study of topical acyclovir therapy; 33 patients received acyclovir and 30 received the placebo. The two populations of patients were balanced in terms of age, race, sex, underlying disease, preceding chemotherapy, and site, size, and duration of lesions. Acyclovir recipients experienced an acceleration in the clearance of virus (P = .0006), the resolution of pain (P = .004), and the total healing of lesions (P = .038); median temporal differences between populations averaged six days for each of these three parameters. The surface area of herpetic lesions continued to enlarge in placebo recipients after entry into the trial; in contrast, lesion surface area decreased progressively during therapy in drug recipients. The speed of healing was influenced by lesion size. Patients with lesions of greater than or equal to 50 mm2 benefited most from therapy, particularly in terms of pain resolution and time to total healing (median differences between groups, eight days). Irrespective of underlying disease, sex, preceding chemotherapy, or age, acyclovir therapy was of clinical benefit. No adverse clinical or laboratory reactions were encountered.

Acyclovir↗
PubMed1984

Gallium-67 imaging in pulmonary eosinophilic granuloma.

Gallium-67 citrate has been known to localize in the lungs in a variety of pulmonary diseases. Abnormal lung activity implies active underlying disease. Serial Ga-67 lung scans may be helpful when steroids are used as therapeutic agents. A case of pulmonary eosinophic granuloma is reported here with diffuse bilateral Ga-67 pulmonary activity.

Adult↗
PubMed1983

Structure of human erythrocyte spectrin. I. Isolation of the alpha-I domain and its cyanogen bromide peptides.

The alpha-I domain of human erythrocyte spectrin was produced by a mild tryptic digestion of the intact molecule and purified by a single step affinity chromatography procedure using a monoclonal antibody. A tryptic peptide representing the alpha-I domain, which migrated on polyacrylamide gels as an 80,000-dalton peptide, was subjected to automated Edman-Begg degradation. Products from automated sequencing were identified by reverse-phase high performance liquid chromatography. Two smaller proteolytic products of the alpha-I domain (T74 and T50) were also subjected to automated sequence analysis. CNBr cleavage of the alpha-I domain produced nine unique peptides which were separated by gel filtration on a high performance liquid chromatograph. Peptides were further purified by reverse-phase chromatography and characterized by amino acid analysis. Partial sequences were determined by automated NH2-terminal sequence analysis. A single aspartate-proline bond, which was partially hydrolyzed during the cyanogen bromide cleavage reaction, was also identified. These sequence data include the first 86 residues of the alpha-I domain, and the spectrin oligomer binding site has been tentatively localized within the first 39 residues. The sequence of 293 residues of a total 633 residues in the alpha-I domain is presented and represents the first structural information for this protein.

Amino Acid Sequence↗
PubMed1983

Structure of human erythrocyte spectrin. II. The sequence of the alpha-I domain.

The complete sequence of 595 amino acids of the alpha-I domain of human erythrocyte spectrin has been determined. Peptides derived from three different protease cleavages were purified using high performance liquid chromatography and subjected to automated amino acid sequence analysis. These data along with sequences of the cyanogen bromide and large tryptic peptides (Speicher, D.W., Davis, G., Yurchenco, P.D., and Marchesi, V.T. (1983) J. Biol. Chem. 258, 14931-14937) represent most or all of the sequence of spectrin alpha-I. The single remaining ambiguity is the precise termination of the COOH terminus of the alpha-I domain. The sequence data suggest that the 595 residues presented here represent the complete sequence of the alpha-I domain, but the apparent size of the COOH-terminal CNBr fragment suggests the existence of an additional 38 residues at the end of the domain. The sequence of the alpha-I domain contains a single type of internal homology composed of multiple 106-amino acid repeats consistent with the occurrence of multiple gene duplications during the course of spectrin evolution. The only portion of the alpha-I sequence which does not appear to contain this sequence repeat is the segment containing the NH2-terminal 17 residues. This unique segment may be part of the oligomer binding site. No disulfide bonds appear to be involved in the structure of alpha-I and cysteine is not highly conserved. Calculations of secondary structure suggest the presence of short helices which fold into triple helical segments approximately 50 A in length. There is little beta sheet structure. A model of spectrin structure incorporating the repeat unit and proposed secondary structure is presented. A computer search of alpha-I sequence with the National Biomedical Research Foundation database of 2145 protein sequences did not detect any significant relationships. Spectrin is apparently the first member of a new class of proteins to be structurally characterized.

Amino Acid Sequence↗
PubMed1983

Free radical production from the aerobic oxidation of reduced pyridine nucleotides catalysed by phenazine derivatives.

Free radical production from the reaction of reduced pyridine nucleotides with phenazine derivatives in aerobic media at pH 7.5 has been studied by ESR spectroscopy and the ESR technique of spin trapping. With the spin trapping agent, 5,5-dimethyl-1-pyrroline N-oxide (DMPO), the oxidation of NADH and NADPH catalysed by phenazine methosulphate, phenazine ethosulphate and 1-methoxyphenazine methosulphate gave exclusively the hydroxyl radical spin adduct of DMPO, 2-hydroxy-5,5-dimethylpyrrolidino-1-oxyl (DMPO-OH). DMPO-OH production was inhibited from these systems by catalase and sodium benzoate whereas superoxide dismutase gave a small increase in the rate of DMPO-OH production. NADH gives a higher rate of DMPO-OH production than NADPH with initial rates of DMPO-OH production in the order 1-methoxyphenazine methosulphate greater than phenazine ethosulphate greater than phenazine methosulphate. However, for an oxygen-limited system, the maximum DMPO-OH concentration attained varied in the order 1-methoxyphenazine methosulphate greater than phenazine methosulphate greater than phenazine ethosulphate. DMPO-OH production occurred in both the aerobic and anaerobic phases of the reaction with these phenazine derivatives. A similar system with pyocyanine gave DMPO-OH and the superoxide spin adduct of DMPO, 2-hydroperoxy-5,5-dimethylpyrrolidino-l-oxyl (DMPO-OOH). Addition of superoxide dismutase to this system stimulated the rate of DMPO-OH production and inhibited DMPO-OOH production. Addition of catalase and sodium benzoate decreased the production of DMPO-OH only. No DMPO-OH production was observed in the anaerobic phase of the reaction. The auto-oxidation of fully reduced phenazine methosulphate, 5,10-methylhydrophenazine methosulphate, produced the phenazine methosulphate radical cation PMSH+ and DMPO-OH in the presence of DMPO. A mechanism for the auto-oxidation of reduced phenazine derivatives is proposed where superoxide production occurs in discrete steps in the auto-oxidation of fully reduced pyocyanine whereas for the auto-oxidation of fully reduced phenazine methosulphate, phenazine ethosulphate and 1-methyoxyphenazine methosulphate, the production of superoxide appears masked by the rapid further reduction to hydrogen peroxide.

Aerobiosis↗
PubMed1983

Pulmonary emboli from a platelet-rich thrombus attached to a pacemaker electrode.

A patient with recurrent, fatal pulmonary emboli originating from thrombus attached to a permanently-implanted pacemaker electrode is described. While most thromboemboli are composed predominantly of fibrin and erythrocytes, histologic and immunologic studies showed this thrombus to be rich in platelets. A possible therapeutic approach to this rare situation is discussed.

Atrial Fibrillation↗
PubMed1983

Deficiencies of copper and a compound with ion-exchange characteristics of pyridinoline in skin from patients with abdominal aortic aneurysms.

A spontaneously aneurysm-prone mouse has a mutation on the X chromosome, which results in an abnormality of copper metabolism. A deficiency of the copper metalloenzyme, lysyl oxidase, results in a deficiency of lysyl-derived cross-linkages in collagen and elastin. Homology of the X chromosome suggests that this model may be relevant to the human abdominal aortic aneurysm (AAA). The present studies on skin from eight AAA patients suggest that copper deficiency occurs in humans, by comparison to skin of paired control subjects with atherosclerotic occlusive disease of the aorta. The lysyl-derived cross-linkage pyridinoline (or some compound with similar ion exchange elution characteristics) is also deficient in patients with AAA; while there is an excess of one of the cross-linkage precursors, hydroxylysine. In addition, the fluorescent properties of hydrolysates of skin from the patients with AAA differ from those of the controls, suggesting that simple biochemical markers might be defined on the basis of these differences in the future. These experiments support the hypothesis that the mouse model is relevant to the disease as it occurs in humans.

Amino Acids↗
PubMed1982

Patient-initiated therapy for recurrent genital herpetic infections.

Therapy for recurrent genital herpes is difficult to evaluate because of the short duration of lesions and viral shedding. Very early treatment, however, can be begun by patients who experience prodromes before onset of lesions. We have found prodromes to occur in 73 percent of male and 84 percent of female patients; 57 percent of the men and 68 percent of the women experienced prodromes in at least three out of every four recurrent episodes. Variables that might affect results of such a patient-initiated study evaluating topical acyclovir included: application of the ointment (drug or placebo) without prodrome (10 percent); the possibility of a false prodrome (less than or equal to 10 percent); long intervals between experiencing a prodrome and ointment application (15 percent greater than 24 hours); the inability to sense a prodrome during sleep; lack of ointment application to the involved areas with initial or later lesions (approximately 15 percent); noncompliance of enrollees in returning for study evaluations (greater than or equal to 10 percent). Such variables will need to be considered when the code is broken in this multicenter study, as well as for patient-initiated studies with other formulations of acyclovir or with other drugs. Earlier negative studies with other agents given within two to three days of appearance of lesions might also require reevaluation with similar patient-initiated studies.

Acyclovir↗
PubMed1982

A report of five patients with large-volume secretory diarrhea but no evidence of endocrine tumor or laxative abuse.

The purpose of this paper is to report five patients with chronic secretory diarrhea (maximum stool volume greater than 1 liter per day, duration 6 weeks to 8 years) in whom we could find no evidence of an endocrine tumor or of surreptitious laxative ingestion. All except one had severe hypokalemia. There was apparent improvement after treatment with prednisone in two patients and loperamide in one. The diarrhea resolved spontaneously in three patients and has undergone several temporary remissions in one patient. The last patient died after a severe unremitting illness. Extensive investigations failed to establish the etiology, but intestinal perfusion (carried out in four of the five patients) revealed secretion or abnormally low absorption of water and electrolytes in the jejunum and abnormally low absorption in the colon. The management of patients with chronic watery diarrhea is discussed.

Adult↗