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Biomedical subjects

P Jenkins

Publications and source records attributed to P Jenkins.

At least 73 records · Page 4Linked to original sources
PubMed1990

Regulation of macrophage-mediated larvicidal activity in Echinococcus granulosus and Mesocestoides corti (Cestoda) infection in mice.

Killing of metacestodes by normal or post-infection macrophages and the regulation of this activity by cytokines were studied in vitro. The protoscolecidal activity of normal macrophages against Echinococcus granulosus was inhibited by a product of naive T-enriched lymphocytes co-cultured with protoscoleces (PSC). By contrast, supernates from co-cultures of Mesocestoides corti tetrathyridia (MCT) and T-enriched or B-enriched normal lymphocytes increased killing of MCT by normal macrophages. Larvicidal activity (against both PSC and MCT) was enhanced by high concentrations of macrophage-activating factors produced by Con A-stimulated rat lymphocytes (Con A-LK), but was reduced by low concentrations of these factors. Activation by synergism between Con A-LK and recombinant interferon-gamma(r. IFN-gamma) was demonstrated in macrophage-mediated killing of MCT at high effector to target ratio. Cytokine-activation of normal or post-MCT infection macrophages was compared. Macrophages from both 8 and 20 week post-infection mice were refractory to lymphokines from lymphocyte-MCT cultures and displayed greatly reduced killing of MCT. Macrophage activation by Con A-LK and r.IFN-gamma was also impaired, implying a general defect in the ability of these post-infection macrophages to respond to macrophage activating signals. The data indicate that two different mechanisms may exist by which metacestodes regulate potentially larvicidal effector mechanisms. E. granulosus can elicit the production of lymphokines suppressive for PSC killing, whereas M. corti appears directly to induce a refractory state in effector macrophages.

Animals↗
PubMed1990

When is it safe to stop patching?

Prior reports indicate that about half of amblyopia patients successfully treated with occlusion subsequently require maintenance patching. This retrospective study was designed to discover what clinical characteristics might be associated with a stable outcome following primary occlusion. Included were 188 patients who: (1) had amblyopia related to strabismus, anisometropia or media opacity; and (2) were followed up for at least one year after successful primary occlusion. Patients who did not comply with treatment or who did not achieve equal vision were excluded. Their ages ranged from 2 to 119 months (mean 29 months). Eighty-eight patients (47%) who required no further occlusion were designated the clinically stable group (CSG). The remaining 100 (53%), who subsequently needed patching because of unequal acuities, constituted the maintenance patching group (MPG). CSG patients were older at the beginning (mean 33 months) and at the end (mean 40 months) of primary occlusion than were MPG patients (means 26 and 31 months). Primary occlusion was more likely to have been discontinued because of equal recognition acuities in CSG patients, while equal fixation behaviour or preferential looking was more likely in MPG patients. Distribution of diagnoses, severity of amblyopia at presentation, and length of follow-up were similar in the two groups. Visual outcomes at last follow-up were slightly better in the CSG (p = 0.002). We conclude that, in general, patching can be safely discontinued after the third birthday. Although follow-up after primary occlusion is important to ensure stable results in all patients, preverbal children are more likely to require maintenance patching.

Age Factors↗
PubMed1989

Potassium restoration in hypertensive patients made hypokalemic by hydrochlorothiazide.

Among 447 hypertensive patients, most with a history of diuretic-induced hypokalemia, 252 developed diuretic-induced hypokalemia while receiving hydrochlorothiazide, 50 mg/d. In a randomized study we evaluated the efficacy of three drug regimens in restoring potassium levels while maintaining blood pressure control: hydrochlorothiazide (50 mg/d) plus potassium supplement (20 mmol/d); hydrochlorothiazide (50 mg/d) plus potassium supplement (40 mmol/d); or hydrochlorothiazide (50 mg/d) with triamterene (75 mg/d) in one combination tablet. In all groups, mean serum levels of potassium rose within 1 week and showed no further change thereafter. However, the hydrochlorothiazide/triamterene and hydrochlorothiazide plus 40 mmol of potassium regimens were significantly more effective in restoring serum potassium levels than was the hydrochlorothiazide plus 20 mmol of potassium regimen. A significant increase in magnesium levels was observed only in the group treated with the hydrochlorothiazide/triamterene combination. Each regimen provided continued control of mild to moderate hypertension.

Adult↗
PubMed1989

Comparison of the antihypertensive effects of betaxolol and chlorthalidone as monotherapy and in combination.

In this multicenter, double-blind, parallel study, the antihypertensive effects of betaxolol (20 mg once daily) and/or chlorthalidone (25 mg once daily) were analyzed in 186 patients with essential hypertension. Following a 2- to 4-week placebo baseline period, patients were randomized to one of two treatment groups (betaxolol or chlorthalidone) and studied for 6 weeks while receiving single therapy and an additional 6 weeks with a combination of the two agents. Significant decreases from baseline supine diastolic blood pressure (SDBP) were observed in both groups at the end of the single-therapy phase (11 mm Hg in SDBP for betaxolol and 12 mm Hg in SDBP for chlorthalidone); a further significant decrease (7 mm Hg for betaxolol and 8 mm Hg for chlorthalidone in SDBP) was observed from the end of the single-therapy phase to the end of the combination-therapy phase. Changes in supine systolic blood pressure (SSBP) from baseline to the end of the single-therapy phase were 10 mm Hg for the betaxolol and 16 mm Hg for the chlorthalidone group. In all cases, within-group changes were statistically significant. From the end of single therapy to end of combination therapy there was an additional 14-mm Hg and 13-mm Hg reduction in SSBP in the betaxolol and chlorthalidone groups, respectively. Overall, 89% of the randomized patients completed the single-treatment phase (phase I), and 89% of those patients completed the combined therapy phase (phase II). There was no significant difference between treatment groups in the clinical response rate (SDBP at or below 90 mm Hg or a decrease from baseline of at least 10 mm Hg). A substantial percentage of patients completing phase I responded to either single agent (58% for betaxolol and 65% for chlorthalidone). Among patients completing phase II therapy, the combination of the two agents produced a greater response rate (83% for the betaxolol-first group and 85% for the chlorthalidone-first group). In conclusion, both agents were effective and well tolerated. The most frequent adverse events in the single-therapy phase were headache, arthralgia, and dizziness, while bradycardia, rhinitis, arthralgia, and dizziness were most frequent in the combination-therapy phase. The combination of betaxolol (20 mg) and chlorthalidone (25 mg) once daily produced an additive antihypertensive effect regardless of which drug was administered first.

Betaxolol↗
PubMed1987

Beta blockers in combination with class I antiarrhythmic agents.

The hemodynamic and antiarrhythmic interactions between nadolol and a commonly used class I antiarrhythmic agent, quinidine or procainamide, were evaluated in 18 patients with ventricular arrhythmias in a double-blind, parallel study. Patients qualified for entry into the study if their ventricular arrhythmias remained poorly controlled (greater than or equal to 10 ventricular premature complexes/hr) with the class I agent alone and they had a left ventricular ejection fraction greater than 30%. Patients received their usual therapeutic doses of quinidine or procainamide throughout the study, which consisted of 3 treatment periods; a 2-week placebo treatment period, a 2-week open-label oral nadolol dose titration period, during which the dosages of nadolol were gradually increased from 40 mg daily to a maximum tolerated dose up to 120 mg daily, and a 4-week randomized, parallel comparison period during which patients were treated with either a class I agent alone or a combination of a class I agent and nadolol. Left ventricular ejection fractions by radionuclide ventriculography and 24-hour ambulatory electrocardiographic (Holter) recordings were obtained at the end of each treatment period. A positive treatment response was defined as greater than or equal to 75% reduction in ventricular premature complex frequency. During the dose titration phase, combination therapy with nadolol (mean dose 94 mg daily) and class I agents produced a mean decrease in ventricular premature complexes of 79% (p less than 0.01), and a mean decrease in ventricular couplets of 95% (p less than 0.01). A positive response was observed in 57% of patients treated with nadolol plus a class I agent.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1987

Study of written communication between general practitioners and departments of child psychiatry.

Previous studies have pointed to the general dissatisfaction with written communication between general practitioners and medical specialists, in terms of quality and usefulness to both groups. This study examined the letters of referral from general practitioners to two child psychiatry departments and the replies of the psychiatric staff, and looked at the information exchanged in the light of the needs of both groups. It was concluded that the requirements of both psychiatric staff and general practitioners were being met to a limited extent, but that there was room for improvementon both sides.

Child Psychiatry↗
PubMed1986

Echinococcus granulosus infection in mice: host responses during primary and secondary infection.

The reaction of Balb/c mice to primary and secondary subcutaneous infection with Echinococcus granulosus protoscoleces (PSC) is described. From 3 to 14 days following primary exposure to PSC, draining lymph nodes increase in weight and there is expansion of T and B lymphocyte populations, enhancement of in vitro lymphocyte transformational responses and production of PSC-specific IgM and IgE antibodies. Despite the persistence of viable PSC in host tissues, lymphocyte responses decline to pre-infection values over the period 3-8 weeks post-infection. Secondary exposure to PSC immediately induces lymphoproliferation, enhancement of transformational responses, production of IgE antibody and encapsulation of PSC by inflammatory cells. Although specific antibody levels remain high until at least 8 weeks after challenge infection, lymphocyte activity begins to decline after 4 days and is profoundly suppressed by 10 days. Parasite viability appears to be significantly reduced in secondary, as opposed to primary, infection and is associated with the accumulation of large numbers of eosinophils, mast cells and macrophages in infected tissues.

Animals↗
PubMed1986

Echinococcus granulosus: changes in the transformational behaviour of murine lymph node cells during early infection.

Subcutaneous inoculation of living Echinococcus granulosus protoscolices (PSC) caused blastic transformation in local lymph node cells (LNC). The effect was maximal seven days post-infection (p.i.), had declined by day 21, and was prevented by killing the PSC prior to inoculation. LNC from inoculated mice also showed marked enhancement of blastogenesis in response to a secondary stimulation by live PSC in vitro. This secondary reaction occurred after exposure to living or killed PSC. There was generally enhanced reactivity to T- and B-cell mitogens at day 7. Phytohaemagglutinin was exceptional in that the killed parasite caused early changes in reactivity as above, but the live parasite induced a rise at 56 days p.i. It is concluded that E. granulosus may cause a determinate change in T-cell function.

Animals↗
PubMed1985

The effects of visual feedback on hemispheric alpha asymmetries and reported processing strategies: a single-subject experimental design.

A double reversal single-subject experimental design was used to study the effects of visual feedback on the hemispheric alpha asymmetries of a male subject during a linguistic task. Results indicated that the subject demonstrated flexibility in hemispheric alpha and corresponding processing strategies employed when an alpha biofeedback procedure was used. These results provide further support for the notion that right and left hemispheric activation is associated with different, yet compatible, cognitive strategies and that both can be manipulated under conditions of feedback.

Adult↗