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Biomedical subjects

R J Stuart

Publications and source records attributed to R J Stuart.

12 recordsLinked to original sources
PubMed2003

Abundance of Diaprepes abbreviatus (L.) (Coleoptera: Curculionidae) neonates falling to the soil under tree canopies in Florida citrus groves.

The purpose of these experiments was to estimate the number and distribution of Diaprepes abbreviatus (L.) neonate larvae dropping from the canopy of infested citrus trees. The number of neonates was monitored in the field using passive funnel traps in two simultaneous experiments and a separate experiment for an additional year. In one experiment, traps were placed from trunk to dripline in the cardinal directions under each of five trees (132 traps total). In a second experiment, eight traps were placed under each tree in the cardinal directions, one trap 30 cm from the trunk and one trap 30 cm from the dripline/direction for 25 trees (200 traps total). Larvae were collected weekly for 50 wk in conical tubes containing ethylene glycol as a preservative. Traps closer to the tree trunk captured more larvae than traps nearer the dripline. The area under the tree canopy was positively correlated with the total estimated number of larvae captured per tree. The estimated number of total larvae/tree over the course of our experiments ranged from 955 to 7,290. The highest number of neonate larvae observed in 1 wk was 67 +/- 6/m2. There was an inverse relationship between the number of traps beneath a tree and the number of trees that needed to be sampled to estimate mean population density with a given precision. However, there was a direct relationship between number of traps/tree and the total number of traps needed for a given precision. This passive technique could be used to quantify the destructive larval stage and to assess D. abbreviatus management strategies.

Aging↗
PubMed1997

Differential susceptibility of Dysmicoccus vaccinii (Homoptera: Pseudococcidae) to entomopathogenic nematodes (Rhabditida: Heterorhabditidae and Steinernematidae).

The susceptibility of the mealy bug, Dysmicoccus vaccinii Miller & Polavarapu, to infection by various species and strains of entomopathogenic nematodes was investigated in laboratory sand-dish and sand-column assays. Steinernemo carpocapsae (Weiser) (All strain), S. feltiae (Filipjev) (AB [Australia] strain), and S. glaseri (Steiner) (NC strain) were ineffective against individual mealybugs in sand-dish assays conducted in small petri dishes (1 cm high by 3.5 cm diameter) at 25 degrees C with doses of infective juvenile nematodes ranging up to 500 or 1,000 infective juveniles and exposure periods up to 5 d. However, Heterorhabditis bacteriophora Poinar (HP88 strain and 2 New Jersey isolates). H. hawaiiensis Gardner, Stock & Kaya (MG-13 strain), and H. indicus Poinar, Karunakar & David (EMS-13 strain) induced significant mortality (65.0-90.0%) at doses as low as 100 infective juveniles and an exposure of 5 d. H. bacteriophora (HBNJ strain) was effective at doses of 500 and 1,000 infective juveniles but, together with H. zealandica Poinar (V16 strain) and 4 other H. bacteriophora isolates from New Jersey, was ineffective at doses of 100 infective juveniles. Removal of the waxy coating from the mealybugs did not influence susceptibility to H. bacteriophora (HP88 strain). In the sand-column assay (5.5 cm high by 5 cm diameter, 5-d exposure, 25 degrees C), which more closely resembles host-finding in the field, H. bacteriophora (HP88 strain) induced no significant mortality against individual mealybugs at doses of 100 infective juveniles but produced 93.8% mortality at 500 infective juveniles, whereas H. indicus (EMS-13 strain) induced 56.3 and 100% mortality at 100 and 500 infective juveniles, respectively. H. bacteriophora (HP88 strain and some New Jersey isolates), H. hawaiiensis (MG-13 strain), and H. indicus (EMS-13 strain) successfully reproduced in and emerged from mealybug cadavers. This study demonstrates strong variability in the susceptibility of D. vaccinii to different species and strains of entomopathogenic nematodes, and implicates certain heterorhabditids as promising candidates for the biological control of this insect.

Animals↗
PubMed1988

Collective cues as a basis for nestmate recognition in polygynous leptothoracine ants.

Three alternative hypotheses have been advanced to explain the dynamics of individually produced nestmate-recognition cues in colonies of social insects: (i) that there is no effective transfer of cues among nestmates (individual hypothesis); (ii) that cues are shared reciprocally among nestmates (collective hypothesis); and (iii) that cues derived from the queen are transferred to all colony members and dominate all other cues in nestmate recognition (queen hypothesis). In the present study, a bioassay based on aggression by laboratory colonies toward workers introduced into their nests was used in conjunction with isolation and interspecific-adoption experiments to test these hypotheses for colonies of two closely related, polygynous, and polydomous ant species, Leptothorax ambiguus and Leptothorax longispinosus. The results provide strong evidence for the collective hypothesis. A collective system has long been postulated as one of the primary modes of nestmate discrimination among social insects but to my knowledge has never before been clearly demonstrated.

Journal Article↗
PubMed1985

Does exercise alter anaerobic threshold in coronary artery disease during beta blockade?

The effect of propranolol on cardiac patients undergoing exercise training is reported to increase exercise tolerance and maximum oxygen uptake (VO2 max) but its effect on anaerobic threshold (AT) is unknown. It was the purpose of this study to determine the role of exercise training with propranolol on AT in patients with coronary artery disease (CAD). Eight men and one woman with significant (CAD) were selected for this study. Each patient completed a maximum treadmill stress test (MTST) following the Bruce protocol on propranolol 40-160 mg/day as a control study. Cardiorespiratory variables were measured at rest and at each stage of the treadmill test. These patients underwent an exercise training programme for 12-16 weeks on the same dose of propranolol. Training sessions were for a minimum of 30-40 minutes, 3 times a week, with training heart rate of 75%-85% of the pretraining peak heart rate. Training heart rate ranged from 98 to 128 beats/min. They were retested with a MTST after the training programme, on the same dose of propranolol. AT was calculated noninvasively by measuring respiratory variables every 30 seconds in relation to work increment. AT was identified by measuring the time course of VE, VCO2, VE/VO2, etc. in relation to incremental work. The mean values of VO2, O2P and % VO2 max at AT before and after training on propanolol were as follows: VO2 = 1.43 L/min +/- .25 and 1.86 L/min +/- .44, O2P = 14.35 +/- 2.40 and 18.73 +/- 4.00 ml/beat, % of VO2 max = 68.20 +/- 6.31 and 73.59 +/- 5.84. The mean changes of VO2 O2P, and % of VO2 max were + 0.43 L/min +/- 0.20 (P < .003), + 4.38 +/- 2.55 (P < .003) and +/- 5.07% +/- 4.84 (P < .001). After exercise training on propanolol, the mean peak exercise tolerance time and absolute VO2 max increased by 2.8 min (from 9.0 to 11.8 min) (P < .001) and 22.7% (P < .007), respectively. We conclude that the increase in anaerobic threshold in patients with coronary artery disease may be due to improvement in VO2 max, increased stroke volume, and peripheral O2 extraction.

Body Weight↗
PubMed1980

National survey of exercise stress testing facilities.

This report surveys the method, volume, protocol, criteria for a positive test, and complications of 518,448 exercise stress tests at 1,375 centers. Exercise test capacity was estimated at 2,147,450. An even distribution of bicycle, Master and treadmill testing was seen by regions within the country. The majority were using the Bruce protocol. The S-T segment depression of .5 mm was considered positive by 4.6 percent; 1.0 mm by 75.4 percent; 1.5 mm by 14.0 percent, and 2.0 mm or greater by 11.9 percent of the centers. Complications were 3.58 infarctions, 4.78 serious arrhythmias, and 0.5 deaths per 10,000 tests. Total of all complications was 8.86 per 10,000 tests. We conclude that exercise stress testing has increased with office-based testing undergoing the greatest expansion. This has been associated with few complications and greater safety.

Exercise Test↗
PubMed1976

Upsloping S-T segments in exercise stress testing. Six year follow-up study of 438 patients and correlation with 248 angiograms.

A 6 year follow-up study of 438 patients who underwent maximal treadmill stress testing revealed the following annual incidence rate of coronary events (death, myocardial infarction or onset or progression of angina pectoris): 13 percent in 84 subjects whose stress test produced 2 mm downsloping S-T segment depression, 9 percent in 230 subjects with 2 mm horizontal S-T depression and 9 percent in 124 subjects who had an upsloping S-T segment with 2 mm S-T depression measured 0.08 second from the J point. Coronary angiograms were obtained in another group of 248 subjects who underwent maximal treadmill stress testing. They revealed major (greater than 50 percent) obstruction of two or three vessels in 67 percent of 62 subjects with a downsloping S-T pattern on the stress test, in 60 percent of 116 subjects with horizontal S-T depression and in 57 percent of 70 subjects with upsloping S-T depression. Patients with an upsloping pattern of S-T depression during stress testing had the same incidence of coronary events as those with a horizontal pattern of S-T depression. Upsloping S-T depression should not be confused with isolated J point depression. Subjects with an upsloping segment also had the same incidence of major two or three vessel disease as those with horizontal depression. Subjects with a downsloping pattern has a slightly greater incidence of coronary events and major two or three vessel disease.

Angina Pectoris↗