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Biomedical subjects

J Parker

Publications and source records attributed to J Parker.

At least 235 records · Page 13Linked to original sources
PubMed1988

Pain in rheumatoid arthritis: relationship to demographic, medical, and psychological factors.

Our purpose was to investigate the relationship among demographic, medical, and psychological factors and self-reported pain in 135 patients with classic or definite rheumatoid arthritis (RA). Patients were examined using the systemic index, articular index, McGill Pain Questionnaire, Symptom Checklist-90-R, and a pain visual analogue scale. Multiple regression analyses found no significant relationships between pain and the medical variables. However, age, income, and selected psychological variables were significantly correlated with pain reports. The greatest pain management challenge occurred in patients who were middle-aged, living on limited incomes, and experiencing major stresses in everyday life. These high risk pain patients were also worry-prone and felt isolated and lacking in social support. Attention to these related psychosocial problems is recommended as an important pain management strategy in RA.

Arthritis, Rheumatoid↗
PubMed1987

Missense misreading of asparagine codons as a function of codon identity and context.

During asparagine starvation the frequency of lysine for asparagine substitutions increases to levels that enable one to isolate and sequence mistranslated protein. We have used site-directed mutagenesis to construct a series of derivatives of the gene encoding the coat protein of the bacteriophage MS2. The mutant set constructed has either AAU or AAC as codon three in the gene with each possible adjoining 3' base. Lysine incorporation in coat protein encoded by these genes shows that AAU is misread from 4- to 9-fold more frequently than AAC with any 3' context. Although in some cases context effects of approximately 2-fold were noted, there seems to be no simple hypothesis to explain them.

Asparagine↗
PubMed1987

Evidence of protein kinase C involvement in phorbol diester-stimulated arachidonic acid release and prostaglandin synthesis.

Many stimulators of prostaglandin production are thought to activate the Ca2+- and phospholipid-dependent protein kinase first described by Nishizuka and his colleagues (Takai, Y., Kishimoto, A., Iwasa, Y., Kawahara, Y., Mori, T., and Nishizuka, Y. (1979) J. Biol. Chem. 254, 3692-3695. In this paper we report evidence that the activation of protein kinase C caused by 12-O-tetradecanoylphorbol-13-acetate (TPA) is involved in the increased prostaglandin production induced by 12-O-tetradecanoylphorbol-13-acetate in Madin-Darby canine kidney (MDCK) cells. We have shown that TPA activates protein kinase C in MDCK cells with similar dose response curve as observed for TPA induction of arachidonic acid release in MDCK cells. Activation of protein kinase C was associated with increased phosphorylation of proteins of 40,000 and 48,000 daltons. We used two compounds (1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine (ET-18-OMe) and 1-(5-isoquinolinesulfonyl)piperazine) known to inhibit protein kinase C by different mechanisms to further examine if activation of protein kinase C was involved in the increased synthesis of prostaglandins in TPA-treated MDCK cells. We found that both compounds inhibited protein kinase C partially purified from MDCK cells and that ET-18-OMe inhibited the phosphorylation of proteins by protein kinase C in the intact cells. Addition of either compound during or after TPA treatment decreased both release of arachidonic acid from phospholipids and prostaglandin synthesis. Release of [3H]arachidonic acid from phosphatidylethanolamine in TPA-treated cells was blocked by ET-18-OMe or 1-(5-isoquinolinesulfonyl)piperazine addition. However, arachidonic acid release stimulated by A23187 is not blocked by Et-18-OMe. When assayed in vitro, treatment of cells with Et-18-OMe did not prevent the enhanced conversion of arachidonic acid into prostaglandins induced by pretreatment of cells with TPA. Our results suggest that the stimulation of phospholipase A2 activity by TPA occurs via activation of protein kinase C by TPA.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1987

Comparison of the optical transmission properties of pulsed and continuous wave light in biological tissue.

The purpose of this study is to compare the optical transmission of the pulsed gold vapor laser (628 nm) to that of the continuous wave argon-pumped dye laser (630 nm) in a homogenous tissue model. Gluteal muscle was taken from a rabbit, and sections of varying thicknesses were made. The tissue samples were positioned at the aperture of an integrating sphere. The laser light was passed through an optical attenuator, coupled to a 600-microns fiber, and then directed onto the surface of the tissue. Transmitted light was collected by the integrating sphere. Light measurements were made with a radiometer. This procedure was repeated for samples of differing thickness using the gold vapor laser as the light source. The identical procedure was performed using the argon-pumped dye laser. No significant difference was found in percent transmission of light using the gold vapor laser as compared to the argon-pumped dye laser.

Animals↗
PubMed1987

Regulation of inactive renin secretion: studies with aprotinin.

The kidney and plasma of many species contain both an active form of renin and an inactive, but activatable, form. The kallikrein inhibitor aprotinin suppressed acid-activation of rabbit plasma inactive renin but not activation of the form of inactive renin released by rabbit kidney cortex slices incubated in vitro. This suggests that inactive renin is structurally modified after secretion. An aprotinin-sensitive step appears to regulate inactive renin secretion. Aprotinin inhibited inactive, but not active, renin secretion by rabbit kidney cortex slices and selectively suppressed the elevated release of inactive renin produced in sheep by the converting enzyme inhibitor enalapril. In anaesthetised rats, aprotinin potentiated the increase in plasma renin produced by captopril.

Animals↗
PubMed1987

Ether lipids inhibit the effects of phorbol diester tumor promoters.

Recent studies have shown that the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) stimulates protein kinase C (PKC), whereas the ether-linked phospholipid 1-O-octadecyl-2-O-methyl-rac-glycerol-3-phosphocholine (ET-18-OCH3) inhibits PKC activity in vitro. Therefore, the antitumor effects of ET-18-OCH3 could be due to its inhibition of PKC activity and the effects of tumor promotion. TPA stimulates arachidonic acid release, prostaglandin synthesis, phosphatidylcholine synthesis and the degradation of phosphatidylcholine by phospholipase C in Madin Darby canine kidney (MDCK) cells. Therefore, we have determined the effects of ET-18-OCH3 on these consequences of TPA stimulation. Preliminary experiments determined that ET-18-OCH3 inhibited PKC partially purified from MDCK cells by ion-exchange chromatography on DEAE-cellulose. In addition, ET-18-OCH3 inhibited the TPA-stimulated phosphorylation of a 40,000-dalton protein in intact MDCK cells. These data indicate that ET-18-OCH3 is an effective inhibitor of PKC activity in MDCK cells. In addition, ET-18-OCH3 was found to inhibit arachidonic acid release and prostaglandin synthesis. The inhibition of prostaglandin synthesis appears to be secondary to inhibition of arachidonic acid release, since ET-18-OCH3 does not inhibit TPA-stimulated synthesis of prostaglandin H synthase or the activity of the enzyme directly (Parker, J., Daniel, L. W., and Waite, M. [1987] J. Biol. Chem. 262, 5385-5393). ET-18-OCH3 also inhibits TPA-stimulated phosphatidylcholine synthesis and phosphatidylcholine degradation by phospholipase C.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Two heat-induced proteins are associated with transformation of Schistosoma mansoni cercariae to schistosomula.

Infection with Schistosoma mansoni, a parasitic fluke, is acquired when cercariae found in freshwater bodies at ambient temperature penetrate human skin. In this study the response of S. mansoni cercariae to change in temperature from ambient to that of mammalian hosts was compared to the response of other stages that do not experience such dramatic temperature shifts. In cercariae, temperature increases from 23 degrees C to either 37 degrees C or 42 degrees C primarily induced the synthesis of two proteins unique to this stage, of Mr 60,000 and 58,000. Neither protein could be induced by similar treatment in the other two stages of the parasite found in mammalian hosts. Instead, these stages predominantly synthesized a Mr 70,000 protein that crossreacted with monoclonal and polyclonal antibodies against the Mr 70,000 heat shock protein of Drosophila and chicken. No crossreactive material was detected in cercariae, suggesting that a protein homologous to the highly conserved heat shock protein of Mr 70,000 is absent or induced to very low levels by temperature increase at this stage. The induction of the Mr 60,000 and 58,000 proteins was confined to the initial 3-hr period during cercarial transformation to the schistosomula stage.

Animals↗
PubMed1987

What resources should be made available for coronary artery bypass surgery in Europe.

In the immediate future it seems correct to aim to provide for between 500 and 700 per million interventions for coronary artery disease per year. There is a continuing need for valve surgery, congenital heart surgery and miscellaneous conditions at a rate of about 150-200 per million per year. It is recommended that centres should be organised with a minimum of 750-1000 open heart procedures resulting in a minimum population requirement of between 1.2 M-1.5 M to support an individual unit. The likely revenue costs of running such a service at 1986 values is approximately 5-7 million pounds and such a unit is likely to have capital equipment of nearly 3 M pounds with an expected life span of seven to ten years. There is a continuing requirement to review the total need for surgery as more information becomes available and new techniques develop.

Adult↗
PubMed1987

Nitrate tolerance. A relevant clinical problem?

Tolerance to nitrates has been shown to develop rapidly during therapy in experimental animals and in man. Although tolerance to the haemodynamic effects was originally considered to be of no clinical significance, it has now been demonstrated to have a major effect on the management of patients with angina. The mechanism of tolerance is not clear, but the hypothesis that it is related to depletion of reduced sulfhydryl groups, with resultant decreased production of S-nitrosothiols and cyclic guanosine monophosphate, is not supported by our investigation. Although the mechanism of action is unknown, dosage strategies providing intermittent therapy with nitrates appear to be effective in preventing nitrate tolerance.

Drug Tolerance↗
PubMed1987

A quantitative immunofluorescence test for detection of serum antibody to Sendai virus in mice.

A simple, semi-automated immunofluorescence assay, (TRACK XI), was developed for the detection and quantitation of circulating antibodies to Sendai virus in mice. The assay was validated by selecting Sendai virus-free and naturally infected mice from six different colonies and testing each serum in both ELISA and quantitative immunofluorescence (QIF) assays. The QIF test utilizes Sendai viral proteins immobilized within a dried colloid gel and permits serum antibody quantitation in 30 minutes. Using a dedicated fluorometer, antibody titers in test sera are calculated automatically from a three-point best fit calibration line. The QIF test gave 92.9% agreement with the ELISA and proved to be a reproducible, accurate and convenient assay for the quantitative measurement of serum antibody to Sendai virus in mice.

Animals↗
PubMed1987

Problem drug users known to Bristol general practitioners.

A 12-month prospective survey was undertaken of all 239 problem drug users known to general practitioners in Bristol and the doctors' attitudes towards them. The drug users were predominantly young, aged 15-35 years, and males outnumbered females by approximately two to one. Seventy-eight per cent had problems associated with opiates, almost invariably heroin, 10% had problems with stimulants (mainly amphetamine powder), and others had problems with hallucinogens, cannabis, barbiturates and solvents. Opiate dependence was the commonest single problem but ill health, hepatitis, psychiatric illnesses, relationship problems, work and financial difficulties were also frequently mentioned.There was a wide variation in the numbers of problem drug users seen by individual practices, which related both to the situation of the practice and the widely varying attitudes of the partners towards drug users and drug problems. General practitioners were aware of the grapevine that transmits news of their treatment to other users, and individual practices had typically evolved a general strategy for all drug users, to minimize arguments. General practitioners were asked their views about specialist services: they thought that services in the area for drug users were inadequate to help them and their patients in 58% of cases. Several suggestions were made for additional services which were needed.

Adolescent↗
PubMed1986

Methylation and restriction endonuclease cleavage of linear Z-DNA in the presence of hexamminecobalt (III) ions.

These studies employed the synthetic linear DNA, poly dGdC, in the B and cobalt hexammine chloride (Co)-induced Z form to determine the effect of conformation on protein-DNA interactions. The rate of the reaction of the restriction endonucleases, Hha I and Cfo I, are reduced with Z DNA as compared to B DNA. The ability of both restriction endonucleases to react with an aggregate form of Z DNA (Z* DNA) is found to depend upon how the Z* DNA is formed. When Z* DNA is induced by low concentrations of Co (50 microM), the endonucleases remain active. In the presence of 100 microM Co, which causes increased aggregation, the endonucleases are inactive. The Hha I DNA methyltransferase reacts at equal rates with the B, Z and low cobalt Z* forms and at a greatly reduced rate with the high cobalt Z* form. These results are significantly different than those observed with Z form dGdC tracts inserted into circular DNA molecules.

Chlorides↗