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Biomedical subjects

J D Fitzgerald

Publications and source records attributed to J D Fitzgerald.

At least 19 recordsLinked to original sources
PubMed2001

Distortion of the spermathecae of phytoseiid mites (Acari: Phytoseiidae) in slide preparation.

The shape and dimensions of the spermathecae are taxonomically important characteristics in phytoseiid mites. In experiments with Neoseiulus californicus (McGregor) and Typhlodromus pyri Scheuten, the shape of the cervix of the spermatheca changed considerably and its diameter was increased by 42-49% when mites were flattened, compared to being mounted with 140 microm spacers underneath the coverslips. Dimensions of the dorsal shield were also affected by flattening. increasing by 3-5%.

Animals↗
PubMed2001

Biological control of strawberry tarsonemid mite Phytonemus pallidus and two-spotted spider mite Tetranychus urticae on strawberry in the UK using species of Neoseiulus (Amblyseius) (Acari: Phytoseiidae).

Two species of Neoseiulus, N. californicus and N. cucumeris, showed potential for biocontrol of phytophagous mites on strawberry. N. californicus controlled Tetranychus urticae on potted strawberry plants in a gauze-sided glasshouse at temperatures comparable to early summer in the UK (8-20 degrees C). Both species of phytoseiid reduced numbers of the tarsonemid Phytonemus pallidus on potted strawberry plants under glasshouse conditions (15-23 degrees C). In several experiments reductions in the range of 71-81% in numbers of tarsonemid active stages and eggs, compared to non-release plants, were obtained. The importance of establishing a suitable predator: prey ratio at an early stage was demonstrated in an experiment where an initial ratio of 1 N. cucumeris: 10 P. pallidus gave a greater degree of control than 1:20 or 1:40.

Animals↗
PubMed2000

Differences in biological characteristics in organophosphorus-resistant strains of the phytoseiid mite Typhlodromus pyri.

Strains of Typhlodromus pyri were collected from orchards in SW England, where populations differed in their response to organophosphorus insecticides compared with strains collected in the SE. Biological characteristics of these strains were compared with those in OP-resistant strains collected from the SE and OP- susceptible strains. There were significant differences in size of eggs and adult mites from the different strains, but these differences did not appear to be related to resistance status of the mites. Female OP-susceptible mites had a longer development time than other strains. Over all strains total development time for female mites was 0.8 day less than for males. There were significant differences between strains for pre-oviposition period, but not oviposition or post-oviposition periods. There were significant differences in total numbers of eggs produced between strains, with a standard OP-resistant strain producing the most and an OP-susceptible strain the fewest eggs. There were significant differences in male longevity between strains, but this did not appear to be related to resistance status. This study highlights the fact that strains may differ in biological characteristics that contribute to fitness regardless of their pesticide resistance status.

Animals↗
PubMed1993

Do partial agonist beta-blockers have improved clinical utility?

Although beta-blockers were introduced into clinical medicine 30 thirty years ago, controversy continues as to the optimal pharmacodynamic profile of such agents. This commentary reviews the development of beta-blockers with partial agonist properties in the context of a recent study on epanolol. The influence of partial agonism on the efficacy and tolerability of beta-blockers is summarized, and it is concluded that, in general, there is little convincing evidence from controlled clinical studies that partial agonism confers significant clinical benefit over full antagonists.

Adrenergic beta-Agonists↗
PubMed1991

The applied pharmacology of beta-adrenoceptor antagonists (beta blockers) in relation to clinical outcomes.

Despite the fact that beta blockers were introduced into clinical practice 25 years ago, new beta blockers with differing kinetic and dynamic profiles continue to be developed and marketed. This overview assesses some of the more extensively studied agents from the point of view of proof of utility and the validity of claims for therapeutic advances. The clinical data suggests that despite the expectations of improvements based on kinetic and dynamic consideration, none of the newer agents have been shown unequivocally, either in terms of efficiency or tolerability, to be an advance over the reference agents, the beta 1 antagonists atenolol and metoprolol. This may be either because such improvements will not occur or because of shortcomings in the design and duration of comparative studies. There are trends to suggest that celiprolol has lesser effects on bronchial function and that it has a lesser impact on lipoprotein profiles. Approaches are suggested that might enable clinicians to appraise for themselves the validity of claims for the improved efficiency of new beta blockers.

Adrenergic beta-Antagonists↗
PubMed1988

Age-related effects of beta-blockers and hypertension.

The literature relating to the effect of age on the blood pressure response to beta-blockade is critically reviewed. It is concluded that although there may be an interaction, the appropriate clinical studies have not, as yet, been performed. There is no evidence of an increase in adverse events with age.

Adrenergic beta-Antagonists↗
PubMed1985

The possible role of the ancillary properties of beta adrenoceptor antagonists in the management of angina pectoris.

Beta adrenoceptor antagonists are effective in the symptomatic management of angina pectoris. This paper examines critically the possible influence of the ancillary properties of beta 1 selectivity, partial agonism and membrane-stabilizing action on the response in anginal patients. The response is categorized according to experimental, pharmacological and clinical endpoints, placing emphasis on the possible errors which may arise from extrapolation from the former to the latter. It is concluded: That selective beta adrenoceptor antagonism confers limited, but tangible advantages over non-selective antagonists in regard to patients with reversible airways obstruction, and also in the metabolic and haemodynamic response to acute hypoglycaemia. Cardioselectivity does not influence the central haemodynamic response to exercise, but lessens adrenaline-mediated hypertensive responses to smoking and hypoglycaemia. Non-selective partial agonists cause less reduction in resting ventricular function, but their effects on cardiac output during exercise are indistinguishable from full antagonists. Membrane stabilizing properties have a marked influence on the tolerability of these agents in terms of unwanted, nonspecific central nervous system symptoms. Unresolved questions relate to the influence of partial agonism on fatigue, metabolic responses, especially blood lipids and glucose, and the possibility of lesser efficacy in angina compared to full antagonists.

Adrenergic alpha-Antagonists↗
PubMed1982

Changes of gap junctions in myometrium of guinea pig at parturition and abortion.

Myometrial tissues from guinea pigs were quantitatively examined for gap junctions in electron micrographs. Small numbers of gap junctions were present between smooth muscle cells in myometria of pregnant guinea pigs at days 50 and 65 of gestation. The junctions increased in number and size at parturition on day 69 and decreased again to control levels 24 h after parturition. A similar increase in junctions occurred when abortion was induced by 16,16-dimethylprostaglandin E2 (PGE2) on day 65. There were no consistent or significant differences in number of gap junctions from myometrium taken over sites of placental attachment and from other sites. These results together with previous studies suggest that an increase in myometrial gap junction area is associated with and may be essential for parturition in guinea pigs, but the control of their development may differ from that in other mammals.

Abortion, Induced↗
PubMed1982

The effect of different classes of beta-antagonists on clinical and experimental hypertension.

The reference beta adrenoceptor antagonist propranolol reduces blood pressure in about 60% of patients with essential hypertension. Pressure is reduced in the supine, and erect positions without postural hypotension as well as during exercise. The average extent of pressure reduction is approximately 26/16 mm.Hg. Though all clinically available beta antagonists reduce blood pressure, the profile may be modified by both adrenotropic and non-adrenotropic ancillary properties. Of the adrenotropic properties, potency influences dose frequency and total body burden of drug. Selective beta 1 antagonism may enhance safety without reducing efficacy in patients with obstructive airways disease. Selective beta 2 blockade does not reduce blood pressure in experimental models or normal subjects, but the response in patients is unknown. Partial agonism may reduce efficacy if the degree of stimulant activity is too great. Of the non-adrenotropic properties, membrane stabilising properties are of relevance only in so far as such agents undergo extensive biotransformation resulting in either reduced efficacy when drugs are used at fixed doses or the formation of biologically active metabolites. The additional properties of either alpha adrenergic blockade or inhibition of vascular smooth muscle tone modify both the speed of onset and the haemodynamic profile. The interaction of these ancillary pharmacological properties is evaluated in this review.

Adrenergic beta-Antagonists↗
PubMed1978

Studies on the pharmacokinetics and pharmacodynamics of atenolol in man.

The non-stimulant cardioselective beta adrenocepter antagonist atenolol has been studied in volunteers in order to define its pharmacokinetic characteristics. Atenolol (100 and 200 mg orally) is rapidly absorbed, reductions in heart rate and systolic pressure being observed in 30 min. The effect persists for up to 8 h. Over 85% of an intravenous dose is excreted in urine within 24 h but only 50% of an oral dose. The bioavailability of approximately 50% is due to reduced absorption. Peak blood levels are observed at 2-4 h and the half life of atenolol given orally is 5-6 h. Atenolol reduces the cardiac response to standing and head-up tilt. It does not reduce circulating levels of renin but slightly impairs the renin response to tilt. Atenolol both orally and intravenously reduces supine diastolic pressure about four hours after administration, the effect persisting for up to 24 h.

Administration, Oral↗
PubMed1978

Aerosol therapy with Sch 1000. Short-term mucociliary clearance in normal and bronchitic subjects and toxicology in normal subjects.

The anticholinergic bronchodilator drug, Sch 1000, was administered as an aerosol by a metered-dose inhaler (200 microgram) to six normal and six bronchitic subjects. The short-term effect on mucociliary clearance was assessed and compared to a placebo (propellant and dispersal agent) in a double-blind crossover study. Mucociliary clearance in the normal group was significantly faster with administration of Sch 1000 than with placebo (P less than 0.01). There was no significant difference between the effects of administration of Sch 1000 and placebo on mucociliary clearance in the bronchitic group. Pulmonary function was significantly increased by therapy with Sch 1000 (as compared to administration of placebo) in the bronchitic group for two hours (P less than 0.05) and in the normal group for one hour (P less than 0.05). In another study, 12 normal subjects inhaled aerosols containing 40 microgram of placebo or 400 microgram of Sch 1000 from metered-dose inhalers on separate days in a randomized double-blind fashion. A significant sustained improvement in pulmonary function (P less than 0.05) and a transient fall in diastolic blood pressure were observed after administration of Sch 1000.

Adult↗
PubMed1977

Oral and intravenous propranolol during exercise.

The intrinsic sinoatrial (SA) rate at rest and during exercise was measured in 5 normal male subjects after prolonged oral and acute intravenous administration of propranolol and atropine. At rest, the intrinsic SA rate was similar after both oral and intravenous propranolol. At the higher levels of power output on a cycle ergometer, cardiac rate was slower after oral than after intravenous propranolol. When the intravenous study was repeated with the use of an additional dose of propranolol, cardiac rate was lower at comparable levels of power output, but not as low as that after oral propanolol. Differences in responses were interpreted as reflecting varying degrees of beta blockade, the most complete being that after prolonged oral propranolol administration of 320 mg daily. The intravenous dose of propranolol usually used to obtain the "pharmacologically isolated heart" at rest is too small to induce full beta blockade in exercise.

Administration, Oral↗
PubMed1977

A comparison of the bronchodilator activity of Sch 1000 and salbutamol.

The effects of the beta 2-adrenergic agonist, salbutamol, 200 mug, and the cholinergic antagonist, Sch 1000, 40 mug, have been compared in 25 asthmatic patients using a single dose, double-blind, crossover trial design. Salbutamol aerosol produces a greater degree of bronchodilatation than Sch 1000 aerosol during the initial three hours following drug administration. There is no significant difference in the bronchodilator effects of the two drugs in the interval four to eight hours after drug administration. Nonatopic patients showed less difference in bronchodilator response to each of the two drugs than atopic patients. Neither drug showed any significant adverse effect on blood pressure, pulse rate, or electrocardiogram. In six asthmatic patients the effect of the combination of salbutamol, 200 mug, and Sch 1000, 40 mug, was evaluated. The combination produced a longer duration of bronchodilatation than either drug alone when compared to placebo.

Adult↗