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Biomedical subjects

J R Harvey

Publications and source records attributed to J R Harvey.

36 records · Page 2Linked to original sources
PubMed1992

Sphincter of Oddi regulates flow by acting as a variable resistor to flow.

Two models of transsphincteric flow and a model evaluating pumping activity were established in the anesthetized Australian brush-tailed possum to determine whether the sphincter of Oddi (SO) acts as a resistor or as a pump. A simple model of transsphincteric flow (inflow only) demonstrated that at physiological common bile duct (CBD) pressure, 9.5 +/- 0.3 cmH2O (n = 7), transsphincteric flow occurred between SO pressure waves (n = 10). A second more complex transsphincteric flow model was established that permitted simultaneous measurements of inflow, outflow, CBD pressure, SO basal pressure, SO contraction frequency, and amplitude. At physiological CBD pressure, inflow always equaled outflow (157.0 +/- 11.2 and 156.4 +/- 11.4 microliters/min, respectively; n = 7). The SO displayed regular contractions superimposed on a basal pressure of 1.1 +/- 0.4 mmHg. Contraction amplitude was 12.6 +/- 3.0 mmHg and the frequency was 3.6 +/- 0.4 contractions/min (n = 7). Pressure waves recorded in the CBD corresponded to the SO contractions and reflected SO activity. Transsphincteric flow occurred between SO contractions and was obstructed by these contractions. Stimulation of SO activity (basal pressure and contraction frequency) with intra-arterial injections of motilin (200 ng/kg) or erythromycin (200 micrograms/kg) abolished transsphincteric flow. Reduction in SO contraction frequency to 72.7 +/- 7.2% (P < 0.01, paired t test) after administration of Cisapride (2 mg/kg iv) increased transsphincteric flow to 147.6 +/- 12.3% (n = 7, P < 0.05, paired t test). In six possums, possible SO pumping action was evaluated. A manometer was connected to the CBD, and a second manometer was connected to the duodenum surrounding the papilla.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

The effect of weight loss on change in waist-to-hip ratio in patients with type II diabetes.

This study sought to determine whether weight loss would alter body fat distribution in obese men and women with type II diabetes. Subjects were 60 women and 33 men who participated in a year-long weight loss program. Weight losses of women and men, respectively, averaged 13.4 kg and 16.8 kg at six months and 11.2 kg and 13.1 kg at one year. WHR decreased significantly in both genders: for women, WHR decreased from 0.95 at baseline to 0.93 at six months and 0.94 at one year; for men WHR decreased from 0.99 at baseline to 0.96 at six months and 0.96 at one year. Subjects with greater upper body obesity at baseline did not lose more weight than subjects with less upper body obesity, but they did have greater reductions in WHR at six months in both genders and at one year in men. The magnitude of WHR reduction was strongly related to the amount of weight lost in men, but was not related to weight loss in women. Improvements in fasting glucose, fasting insulin, and HbA1 were significantly related to weight loss, but not to reductions in WHR. Thus, participation in a weight loss program had beneficial effects on body fat distribution in patients with type II diabetes, but these changes in WHR were not independently associated with improvements in glycemic control.

Adipose Tissue↗
PubMed1989

Benefit of the perfusion catheter for emergency coronary artery grafting after failed percutaneous transluminal coronary angioplasty.

Of 2,102 consecutive patients who underwent percutaneous transluminal coronary angioplasty, 31 (1.5%) had emergency coronary bypass grafting for failed angioplasty. To determine the potential impact of different therapeutic strategies for controlling associated myocardial ischemia, 3 groups were analyzed. Group 1 comprised 11 patients (36%) in whom a "bailout" catheter was used to maintain anterograde coronary perfusion, group 2 included 16 patients (52%) in whom only intraaortic balloon counterpulsation was used and group 3 contained 4 patients (13%) in whom neither bailout catheter nor intraaortic balloon was used. Despite a longer average time to cardiopulmonary bypass, patients managed with the bailout catheter had a significantly lower incidence of Q-wave myocardial infarctions (9 vs 75%, p less than 0.05) compared with patients managed with intraaortic balloon counterpulsation alone. Those managed with the bailout catheter also had more consistent resolution of ST elevation and greater use of internal mammary artery grafts than patients supported by intraaortic balloon counterpulsation alone.

Aged↗
PubMed1988

Use of balloon flotation pacing catheters for prophylactic temporary pacing during diagnostic and therapeutic catheterization procedures.

The use of prophylactic temporary pacemakers during diagnostic catheterization, coronary angioplasty and percutaneous balloon valvuloplasty was investigated retrospectively over an 18-month period. Balloon flotation temporary pacemaker leads were placed in 193 (12%) of 1,609 patients undergoing diagnostic catheterization, 641 (65%) of 993 patients undergoing coronary angioplasty and 199 (100%) of 199 patients undergoing aortic or mitral valvuloplasty. There were no perforations or significant arrhythmic complications related to pacemaker placement in these 1,033 cases, and pacing was initiated promptly when required by withdrawal of the catheter tip into the right ventricle. Significant bradycardia or new conduction defects developed in 17 patients (1%) during diagnostic catheterization, 10 patients (1%) during angioplasty and 20 patients (10%) during valvuloplasty, but were severe enough to require initiation of temporary pacing in only 1 (0.06%), 4 (0.4%) and 5 (2.5%) patients, respectively. No patient undergoing diagnostic catheterization or angioplasty (but 5 patients undergoing valvuloplasty) required immediate pacing support to treat a life-threatening bradycardia. The total cost of prophylactic pacemakers was $103,300, with a cost per actual use of $19,300 for diagnostic cases, $16,025 for angioplasty and $3,980 for balloon valvuloplasty. These data suggest that prophylactic temporary pacing is not indicated during either diagnostic catheterization or coronary angioplasty, but should be used routinely during balloon valvuloplasty.

Angioplasty, Balloon↗
PubMed1986

Clinically silent atrial septal defects with evidence for cerebral embolization.

The cause of stroke in young patients frequently cannot be established. Eleven consecutive patients, age 50 and younger, had clinical evidence of cerebral embolization. Results of physical, radiographic, electrocardiographic, and two-dimensional echocardiographic examinations were normal in all patients. During normal respiration, eight of the patients had right-to-left shunts at the atrial level shown by microcavitation contrast two-dimensional echocardiography. Six of the eight patients with positive contrast studies had cardiac catheterization. Five of six patients had an atrial septal defect, normal right and left heart pressures, and small right-to-left shunts during a Valsalva strain. Four patients had surgical closure of the defect, which ranged in size from 5 to 10 mm. The remaining patients received anticoagulants. Interatrial communications appear to be common in young patients with stroke, suggesting paradoxical embolization as a possible mechanism. Contrast two-dimensional echocardiography should be done in such patients because it is the only noninvasive technique that reliably finds these defects.

Adolescent↗
PubMed1981

The basis of a suggested instrumental approach to the surveying of neutron fields and the measurement of personal dose from neutrons.

The basis of a two-component neutron monitoring system that could be applied to both survey instruments and personal dosemeters is considered. Neutrons with energies below 10 keV are detected by a thermal neutron detector which, in the survey instrument, is located inside a small moderating sphere, whereas in the personal dosemeter it is positioned behind a thermal neutron shield located on an individual's body. Neutrons above 10 keV are detected by counting pulses produced by protons ejected from a thin hydrogenous foil. By judicious choice of the characteristics of the detection elements, it is possible to ensure that the sum of the sensitivities of the elements of both survey instrument and personal dosemeter vary with neutron energy in a way close to that required for radiological protection purposes throughout the range thermal-10 MeV. The realisation of the elements sensitive below 10 keV presents few fundamental problems and appropriate devices have been reported in the literature. Those sensitive above 10 keV have proved to be more difficult to realise in practice.

Fast Neutrons↗
PubMed1979

Thin-layer thermoluminescent dosemeters based on high-temperature self-adhesive tape.

Dosimetric material was fabricated by coating commercially available self-adhesive tape able to withstand temperatures up to 400 degrees C with thermoluminescent lithium fluoride crystals. Tests were made on dosemeters of about one centimetre diameter cut from the coated tape. High loading and reproducibility was further by spreading the crystalline materials onto heated tape. Reproducibility was further improved when sieved and washed ground crystalline material was used. Dosemeters with various loadings were fabricated and representative batches with loadings of 12.2 mg cm-2 and 5.9 mg cm-2 were tested for reproducibility, matching, sensitivity to light and photon energy dependence. The dosemeters show exceptional reproducibility and matching, are simple and inexpensive to make and are ideal for many applications where thin-layer dosemeters with approximate tissue equivalence are required.

Adhesives↗
PubMed1976

A neutron source with an effective energy of 0-5 keV.

Calculations indicate that an assembly consisting of an antimony-beryllium source at the centre of a 4 cm radius water sphere surrounded by a 1 mm thick shell of boron-10 will emit neutrons with a broad spectrum at intermediate energies. A device based on this design was constructed using a water-filled, boron-carbide loaded, plastic shell with an antimony-beryllium source located at the centre. The output spectrum was calculated by Monte Carlo program and the computed total yield agreed well with measurements made with a manganese bath system. The main peak has an effective energy of 0-5 keV and the total yield is 18% of the antimony-beryllium source strength. Experience with this source suggests some possible avenues for future development.

Antimony↗
PubMed1975

An approach to the surveying of radiation environments for radiation protection purposes.

Many of the inadequacies of the system presently used for surveying environments containing penetrating radiation stem from the impossibility of defining a radiation parameter which is additive, measurable and closely related to peak dose equivalent in the body. Many of the present conceptual difficulties would be eliminated if surveys were made in terms of a quantity 'dose equivalent ceiling' defined as the sum of the peak dose equivalents generated by all the components of the field if each were incident normally to the front face of an anthropomorphic phantom. 'Dose equivalent ceiling' is close to the quantity measured by existing instruments, is both additive and measurable, and can be rigorously related to primary radiation field quantities. It is always greater than peak dose equivalent in the body, and would be used to define an exposure period during which a given dose equivalent could not be exceeded. The dose to specific parts of the person's body would then be estimated by personal dosimetry. Fields of low penetrating radiation could continue to be surveyed in terms of dose to specific superficial organs. Dose equivalent ceiling, which corresponds to the instrumental measurement, exceeds dose equivalent index, an indication of peak dose equivalent in the body, by a factor which can be as large as six.

Gamma Rays↗