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Biomedical subjects

J R Richardson

Publications and source records attributed to J R Richardson.

At least 19 recordsLinked to original sources
PubMed2001

Analysis of the additivity of in vitro inhibition of cholinesterase by mixtures of chlorpyrifos-oxon and azinphos-methyl-oxon.

Organophosphorus (OP) insecticides or their active metabolites act through a common mechanism of toxicity, the inhibition of cholinesterase (ChE). The effects of in vitro exposure of brain (target) and serum (biomarker) ChE to chlorpyrifos-oxon (C horizontal lineO) and azinphos-methyl-oxon (AZM horizontal lineO), the active metabolites of the insecticides chlorpyrifos and azinphos-methyl, respectively, were investigated to determine if simultaneous or sequential exposure to these two OP compounds results in purely additive effects. Additive was defined by the theoretical calculated percent inhibition (dose additivity), which takes into account the fraction of ChE molecules assumed to be available for inhibition by the second compound following inhibition by the first compound, not simple mathematical summation of percent inhibition (response additivity). Brain ChE simultaneously exposed to the two compounds resulted in additive effects, which were less than the simple mathematical summation of percent inhibition. However, serum ChE simultaneously exposed to the two compounds resulted in a nonlinear response, presumably due in part to the presence of detoxifying enzymes in the serum. Sequential exposure of both brain and serum ChE to the two compounds resulted in greater than additive effects at the higher concentrations of each compound. There was no departure from additivity at the lower concentrations of the two compounds. These data suggest that simple mathematical summation of percent inhibitions, i.e., response additivity, is not the appropriate method for describing the combined effects of C horizontal lineO and AZM horizontal lineO on ChE in vitro. In addition, there are other mechanisms involved, such as the presence of detoxication enzymes, that must be taken into account when analyzing the effects of combined exposure of ChE to these two compounds.

Animals↗
PubMed2001

Effects of repeated oral postnatal exposure to chlorpyrifos on open-field behavior in juvenile rats.

Organophosphorus (OP) insecticides have the potential to cause behavioral effects in children. This study was designed to determine if repeated oral exposure of preweanling rats to chlorpyrifos would produce behavioral changes at both pre- and postweanling ages. Treatment occurred every second day beginning on post-natal day (PND) 1, and continued through PND 21. The rats received one of the following regimens: a low-dosage (3 mg/kg) from PND 1-21; a medium dosage (mg/kg from PND 1-5, and then 6 mg/kg from PND 7-21; or a high-dosage schedule of 3 mg/kg on PND 1-5, then 6 mg/kg from PND 7-13, and 12 mg/kg from PND 15-21. There were no differences in body weights among the control-, low-, and medium-dosage groups but the high-dosage group had significantly lower body weights on PND 13-21. An open field was used to measure locomotor activity on PND 10, 12, 14, 16, 18, 20, 25, and 30. There were no differences in locomotor activity levels or treatment effects between males and females. On PND 10, 12, 14, 16, 18, and 20 there was no effect on locomotor activity with any dosage. On days 25 and 30, locomotor activity was significantly decreased with the medium- and high-dosage groups. Brain cholinesterase (ChE) inhibition was about 25-38% on PND 25 and 14-34% on PND 30. On PND 25 but not 30, lung and diaphragm ChE and serum butyrylcholinesterase (BChE), with the high-dosage animals, and heart ChE with the medium- and high-dosage groups were significantly inhibited. There was no significant inhibition of skeletal muscle ChE or serum acetylcholinesterase (AChE) on PND 25 and 30. These data suggest that early postnatal chlorpyrifos exposures will depress locomotor activity in juvenile rats, with the effects most pronounced after brain ChE activity has substantially recovered.

Acetylcholinesterase↗
PubMed2000

Coronary angiography and coronary artery revascularisation rates in public and private hospital patients after acute myocardial infarction.

OBJECTIVE: To determine the rates of coronary angiography or coronary artery revascularisation procedures in patients with acute myocardial infarction (AMI) managed in private versus public hospitals. DESIGN: Case record linkage analysis of data from the Victorian Inpatient Minimum Dataset for admissions for AMI in the 12 months after the index admission. SETTING: Victorian acute care hospitals from July 1995 to December 1997. PATIENTS: Victorian residents aged 15-85 years admitted to hospital with AMI. MAIN OUTCOME MEASURES: Rates of coronary angiography or coronary artery revascularisation procedures after AMI. RESULTS: Compared with public patients in public hospitals, patients with AMI managed in private hospitals were more likely to undergo coronary angiography (rate ratio [RR], 2.17; P< 0.001; 95% CI, 2.06-2.29), coronary angioplasty or stenting (RR, 3.05; P<0.001; 95% CI, 2.82-3.31), and coronary artery bypass grafting (RR, 1.95; P<0.001; 95% CI, 1.79-2.14). Once coronary angiography had been performed, patients in private hospitals were more likely to undergo angioplasty or stenting (RR, 1.94; P<0.001; 95% CI, 1.79-2.11), but were only marginally more likely to undergo coronary artery bypass grafting (RR, 1.17; P<0.001; 95% CI, 1.07-1.28). CONCLUSIONS: In Victoria, management of patients with acute myocardial infarction is influenced by the public or private status of the patient, and by whether management occurs in private or public hospitals. Patients are more likely to undergo coronary angiography and coronary artery revascularisation procedures in private hospitals.

Adolescent↗
PubMed1998

Non-invasive assessment of cardiac output in children.

BACKGROUND: Stroke distance, the systolic velocity integral of aortic blood flow, is a linear analogue of stroke volume; its product with heart rate is minute distance, analogous to cardiac output. OBJECTIVE: To investigate the feasibility of assessing cardiac output in children with a simple non-invasive Doppler ultrasound technique, and to determine the normal range of values. METHODS: Peak aortic blood velocity, stroke distance, and minute distance were measured through the suprasternal window in 166 children (mean age 9.6 years, range 2-14) using a portable non-imaging Doppler ultrasound instrument. RESULTS: The technique was well tolerated by all the children participating. Mean peak aortic blood velocity was 138 cm/s and was independent of age. Mean stroke distance was 31.8 cm and showed a small but significant increase with age; mean minute distance was 2490 cm and fell with age, as did heart rate. CONCLUSIONS: Suprasternal Doppler ultrasound measurement of stroke distance is a convenient, well tolerated, non-invasive technique for the assessment of cardiac output in children. The normal range of values during childhood has been established. The technique has great potential for assessing hypovolaemia in children.

Adolescent↗
PubMed1996

Deflation techniques for faulty Foley catheter balloons: presentation of a cystoscopic technique.

The Foley catheter is used for drainage of the urinary bladder in < or = 15% of hospitalized patients and is self-retained by an inflatable balloon mechanism. Faulty balloon deflation, which leads to a retained catheter, is a condition treated by the urologist. In this article we describe a cystoscopic approach to deflation, evaluation, and recovery of retained fragments; review the techniques for deflation; and provide an algorithm to approach the retained Foley catheter.

Algorithms↗
PubMed1995

Paraphimosis in elderly men.

Paraphimosis occurs when the foreskin of the penis is retracted over the glans and cannot be replaced in its normal position. The tight ring of preputial skin constricts the distal penis causing vascular occlusion, much like a tourniquet. The condition is painful and, if not dealt with quickly, can lead to necrosis of the glans. Simple reduction of the prepuce can be achieved by compressing the edematous fluid out of the glans and repositioning the foreskin. Irreducible paraphimosis is treated by dorsal slit procedure and subsequent circumcision. We present two cases illustrating the treatment techniques and possible complications of paraphimosis in men.

Age Factors↗
PubMed1995

Fatal genitourinary mucormycosis in a patient with undiagnosed diabetes.

We present what we believe is the first report in the world literature of penile necrosis due to mucormycosis, a rare and often fatal fungal infection. This case of rhizopus mucormycosis began with a penile lesion in a 27-year-old patient with undiagnosed diabetes; it led to necrosis of the phallus, lower urinary tract, rectum, and pelvic musculature and finally to death. Despite repeated aggressive surgical debridement in conjunction with medical therapy, we were unable to halt the progression of the fungal and synergistic bacterial infections.

Adult↗
PubMed1994

Diuretic renal scan: is it always reliable?

The differentiation between significant mechanical obstruction and nonobstructive dilation of the kidneys and ureters is fundamental to patient management. The diuretic renal scan is a useful test in this situation because it usually is reliable and reproducible and is noninvasive and objective, providing information about the function of each kidney. However, this study has given variable results in a small number of patients. We report our experience with five such patients and recommend an algorithm for evaluating patients with equivocal scan results. This report emphasizes the importance of continued follow-up and the need for periodic reevaluation of patients with unexplained urinary symptoms or persistent flank pain, even when the initial diuretic renal scan is normal.

Adolescent↗
PubMed1992

Continuous infusion of intrathecal morphine to control acquired immunodeficiency syndrome-associated bladder pain.

A 36-year-old man with acquired immunodeficiency syndrome had incapacitating dysuria and vesical pain secondary to interstitial cystitis. When medical management and suprapubic urinary diversion failed to control the symptoms the patient was started on subarachnoid morphine sulfate. Bupivacaine was added 1 year later via an implanted Therex M-3000 implantable continuous infusion pump, which has continued successfully for more than 18 months. We believe that subarachnoid narcotics and other analgesic agents, such as clonidine, bupivacaine hydrochloride and baclofen, may prove equally valuable in the treatment of bladder spasm and pain. Furthermore, implanted intrathecal ports and pumps may have less associated risk of infection than the percutaneous vascular access catheters presently used for the continuous delivery of medications in immunosuppressed patients.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Angiographic management of retroperitoneal hemorrhage from renal angiomyolipoma in polycystic kidney disease.

Angiographic management of bilateral angiomyolipomas complicated by hemorrhage in autosomal dominant polycystic kidney disease is presented. The patient had mild stigmata of tuberous sclerosis, and a family history of tuberous sclerosis and autosomal dominant polycystic kidney disease. The radiographic features at diagnosis, and those present during and after embolization are described. Radiological criteria for diagnosis and successful control of bleeding with intra-arterial selective embolization are discussed. Radiographic features before, during and after embolization are exhibited.

Adult↗
PubMed1986

Unsuspected intraperitoneal rupture of bladder presenting with abdominal free air.

We present a case of intraperitoneal rupture of the bladder discovered during exploratory laparotomy for abdominal free air associated with an indwelling Foley catheter found in the peritoneal cavity. This report emphasizes the need for systematic and thorough evaluation of the genitourinary tract in the patient with multiple trauma.

Aged↗