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Biomedical subjects

J L Valentine

Publications and source records attributed to J L Valentine.

At least 19 recordsLinked to original sources
PubMed1992

Health response by questionnaire in arsenic-exposed populations.

The health status of populations exposed to arsenic through drinking water was determined by a mailed questionnaire. Participants were selected from three communities located in Nevada with 1977 tap water arsenic levels of approximately 0.1 mg/l and one California community with 1977 levels around 0.39 mg/l. The questionnaire responses were obtained in 1979 from the four exposed communities and compared to those of a Wyoming community whose tap water levels of arsenic were less than 0.001 mg/l in 1979. No difference in health status for gastrointestinal, neurological, musculoskeletal, circulatory and skin disorders was found. The average number of years of consumption given by length of residence was 6-16 years. We conclude that the health status of these arsenic-exposed populations has not been adversely affected.

Adolescent↗
PubMed1991

Detection of Helicobacter pylori by using the polymerase chain reaction.

A 1.9-kb cloned fragment of chromosomal DNA randomly selected from a Helicobacter pylori cloned library was evaluated as a potential probe. The probe detected 19 of 19 H. pylori strains and yielded a specificity of 98.7% when tested against 306 other bacterial strains representing 32 different species. False-positive results with non-H. pylori strains were due to the presence of contaminating vector sequences. A polymerase chain reaction (PCR) assay was developed by using 20-base oligonucleotide primers homologous to a portion of the 1.9-kb fragment. The PCR assay amplified a 203-nucleotide-pair product which was analyzed by agarose gel electrophoresis and Southern hybridization by using a third 20-base 32P-labeled oligonucleotide complementary to a region of DNA between the primers. The PCR assay was 100% sensitive, detecting all 35 H. pylori strains tested, and did not amplify sequences in several closely related species. The assay was sensitive for as little as one copy of the cloned plasmid DNA or 100 H. pylori bacterial cells. To evaluate the PCR assay for clinical samples, gastric biopsy and aspirate specimens were tested by PCR, and the results were compared with those of microbiologic culture and histologic examination. In fresh biopsy specimens, H. pylori sequences were detected by PCR in 13 of 14 (93%) positive tissues and 0 of 19 negative tissues. In gastric aspirate specimens, 11 of 13 (85%) positive tissues were positive by PCR. H. pylori DNA was detected in 1 of 14 aspirate specimens negative by culture, histology, and PCR of the accompanying biopsy tissue. PCR is a rapid, accurate, and sensitive method for the detection of H. pylori.

Base Sequence↗
PubMed1991

Intervascular occlusion of canine renal, splenic, and vertebral arteries using electromagnetic field focusing (EFF) probe.

Electromagnetic field-focusing (EFF) probe is a precision surgical and interventional tool. Use of the device produces maximum temperature in excess of 1800 degrees C by convergence of radio-frequency (RF) induced eddy currents in biological tissues. Applications of the EFF probe in angioplasty, aneurysm thrombosis, and neurosurgery have been previously reported. In the present work, the EFF probe was guided under fluoroscopic control and used to occlude renal, splenic, and vertebral arteries in dogs. The occlusion was typically accomplished with about one minute of RF power application. Histology of the treated vessel three to six weeks posttreatment showed total occlusion consisting of intimal and subintimal changes and organized thrombus in the lumen. This suggests that the EFF probe in comparison with other procedures is an inexpensive, relatively safe precision interventional tool for performing an occlusion for experimental and therapeutic purposes.

Animals↗
PubMed1991

Effects of cocaine on canines' coronary arteries.

Nine canines were anesthetized with pentobarbital and studied by both selective and semiselective coronary artery angiography following intravenous bolus doses of 1,3,5,8, or 10 mg/kg of cocaine. Catheterization was accomplished with a 5 Fr catheter over a 0.035 inch guidewire under fluoroscopic control, and angiograms were obtained by injection of a diatrizoate solution. Digital subtraction angiography (DSA) was performed prior to cocaine administration and at minutes 0.5, 1, 1.5, 3, 5, and, in some cases, minutes 10 and 15 after cocaine administration. The 1 and 3 mg/kg doses of cocaine had no effect on the coronary arteries. The 5 mg/kg dose significantly dilated the coronary arteries. The 8 mg/kg dose produced significant dilation at 30 seconds after cocaine but nonsignificant dilation of the coronary arteries at all other times. The 10 mg/kg dose produced significant dilation at 30 seconds, nonsignificant dilation at 60 seconds followed by significant constriction at 90 seconds after cocaine, which led to immediate death in most animals. The coronary dilation and constriction produced by 10 mg/kg of cocaine could be prevented by either preadministration or postadministration of naloxone, but this did not prevent subsequent death.

Angiography, Digital Subtraction↗
PubMed1990

Toxic effects of cocaine to the cardiovascular system in conscious and anesthetized rats and rabbits: evidence for a direct effect on the myocardium.

The cardiovascular toxicity of cocaine is complex because it has local anesthetic properties, central nervous system stimulatory effects, as well as cardiac effects. Recreational use of this drug has increased recently, but the precise mechanism of sudden cardiac death induced by cocaine is not known. The primary objective of this work was to test for a direct cardiovascular toxicity of cocaine. Rats and rabbits were anesthetized, and the femoral vein and artery were cannulated for drug infusion and blood pressure monitoring. Different doses of cocaine (0.3, 1, 3, 10 mg/kg) were infused. For conscious animal experiments, the animals were allowed to recover from the anesthesia and then were subjected to cocaine. Low doses of cocaine (0.3 and 1 mg/kg) increased systolic as well as diastolic pressure in conscious rats and rabbits. In anesthetized rats and rabbits, the same dose of cocaine increased blood pressure with a decrease in heart rate. With the high doses of cocaine (3 and 10 mg/kg), all cardiac parameters were reduced in both rats and rabbits. In isolated rabbit hearts, cocaine decreased all cardiac parameters. Based on the fact that high doses of cocaine severely depressed all cardiac parameters and its effect on the isolated heart, cocaine-induced sudden cardiac death appears to be due to a primary effect on the myocardium.

Animals↗
PubMed1989

Precocious retinal adhesion is affected by furosemide and ouabain.

A "precocious" adhesive force develops between the neurosensory retina (NSR) and the retinal pigment epithelium (RPE) 15-30 minutes after eyes are removed from day 15 embryonic chickens and incubated at 37 degrees C. Precocious adhesion has been reported to be blocked by exposure to cold but to be unaffected by exposure to furosemide and ouabain. Since RPE transport is thought to play a major role in the adhesion between the RPE and NSR of adult mammals, and since ouabain and furosemide block RPE transport in embryonic chickens, it has been thought that precocious adhesion in embryonic chickens is not a good model for studying adhesion between the RPE and the NSR of adult mammals. We have found, however, that when steps are taken to ensure that ouabain and furosemide reach the transport sites on RPE apical membrane before precocious adhesion develops, that ouabain and furosemide do affect precocious adhesion.

Animals↗
PubMed1989

The plasma endorphin, prostaglandin and catecholamine profile of patients with fibrositis treated with cyclobenzaprine and placebo: a 5-month study.

During a 5 month, double blind crossover study of the clinical effect of cyclobenzaprine on 7 patients with fibrositis, weekly measurements were done of plasma beta-endorphin (endorphin, prostaglandin E (PGE) and catecholamines). Endorphin levels were normal but varied with tender point tenderness. Mean plasma dopamine and PGE were elevated. Norepinephrine was normal to very high while epinephrine levels were continuously low to normal. We conclude that patients with fibrositis have a neurotransmitter plasma profile like other chronic pain states having stress and increased vasomotor activity with the possible exception of having low circulating epinephrine. This disparity may mark a failure of central nervous system pain modulation in fibrositis.

Adult↗
PubMed1989

Furosemide-sensitive Cl transport in bovine retinal pigment epithelium.

Bovine retinal pigment epithelium (RPE)-choroid explants were sealed in an Ussing chamber. Typical preparations produced a transepithelial voltage (Ve) of 12 mV (retina side positive) and had an electrical resistance (R) of 300 ohm-cm2. These values can be attributed to the RPE. Furosemide and ouabain reduced the Ve without affecting R when applied to the apical side of the RPE, but had no effect upon Ve and R when applied to the choroidal side. Acetazolamide had no effect upon Ve and R when applied to either side of the tissue. In Cl-free medium, ouabain reduced Ve without affecting R, while furosemide had no effect upon Ve and R. In Na-free medium, ouabain and furosemide had no effect upon Ve and R. Unidirectional isotope flux studies performed under open circuit conditions showed a net retina-to-choroid Cl flux that was abolished by furosemide. These results indicate that bovine RPE possesses a furosemide-sensitive Cl transport system.

Animals↗
PubMed1989

Topical phenylephrine for mydriasis affects rabbit retinal pigment epithelial transport.

Rabbit retinal pigment epithelium (RPE) has an alpha-1 adrenoreceptor that substantially reduces RPE short circuit current (Isc) when stimulated. Since phenylephrine is a potent alpha adrenergic agonist frequently used to obtain pupil dilation, we examined the effect of topically applied phenylephrine for pupil dilation on RPE transport. Naive black dutch-belted rabbits received either one drop of 10% phenylephrine applied at t = 0 and t = 30 min or one drop of 1% cyclopentolate applied at t = 30 min. At t = 50 min, RPE-choroid-sclera explants from these animals were sealed in an Ussing chamber. At t = 60-70 min, 1.4 X 10(-4) M epinephrine was introduced into both sides of the Ussing chamber. The change in Isc produced by epinephrine was measured. The Isc reduction in rabbits receiving phenylephrine was 26% (+/- 5% SD, n = 6). The Isc reduction in rabbits receiving cyclopentolate was 39% (+/- 6% SD, n = 5). These values are significantly different (P less than 0.02, student two-tail t-test). These results indicate that topical phenylephrine reached the RPE in vivo and prestimulated the alpha-1 adrenoreceptors.

Administration, Topical↗
PubMed1988

Human glutathione peroxidase activity in cases of high selenium exposures.

Four communities with water supplies having selenium concentrations of less than 3.1, 1.7, 189, and 496 micrograms/liter were selected for study. Samples of blood, urine, and tap water were obtained from participants in each community and analyzed for selenium content. Blood samples were also analyzed for glutathione peroxidase activity. Results showed an increase in selenium concentration in the urine as the water selenium increased. Selenium concentrations in blood did not reflect the increased selenium exposure. Glutathione peroxidase activity in whole blood decreased in highly exposed participants compared to those with low exposure. We conclude that glutathione peroxidase activity in cases of possible environmental toxic exposures will not show the increased activity seen in supplementation of selenium to deficient subjects.

Adolescent↗
PubMed1988

Effects of extended feeding of decocainized erythroxylon coca leaves on growth and selected organs in rats and rabbits.

Erythroxylon coca leaves from the Trujillo area of Peru were extracted with methylene chloride to remove most cocaine-like alkaloids. The decocainized leaves were formulated in a honey-water vehicle and fed on a chronic basis to female rats for 32 weeks and female rabbits for 13 weeks. Rabbits fed decocainized leaves at doses of 21 or 210 mg demonstrated no significant change in growth (weight gain) when compared with those receiving vehicle. Histological findings were unremarkable except for fatty islands in the myocardium. Rats fed the decocainized leaves at doses of 1.5 and 15 mg demonstrated no significant changes in weight, whereas those receiving 150 mg had a significant decrease in weight gain when compared with control animals receiving vehicle. Necropsy findings in rats demonstrated pyometra in all groups receiving decocainized leaves as well as in some of the controls. Those rats with pyometra often exhibited endometrial metaplasia. Renal tubular calcification and proteinaceous material were consistently noted at all dose levels. Portal triaditis was also found in the livers of most rats.

Alkaloids↗
PubMed1988

Electromagnetic field focusing system in the treatment of brain tumors.

The electromagnetic field focusing (EFF) probe, which is based on the principle of eddy current convergence, produces intense pinpoint heat at its point of contact with tissue. This allows cutting and vaporization of tissue and coagulation of vessels. The present experiments were conducted to study heat distribution to the surrounding tissue in brain and phantom and the effect on the brain of vaporization of intracerebral tumors in 19 rabbits. The follow-up period was as long as 47 days. The heating pattern showed a rise of temperature up to 250 degrees C at the probe tip, with minimal or no temperature increase at 2 mm and beyond. Minimal or no change was noted in the surrounding brain after tumor vaporization, indicating that this system would be safe in the vaporization of brain tumors in clinical neurosurgery.

Animals↗
PubMed1988

Initial observations of rabbit retinal pigment epithelium-choroid-sclera preparations.

Retinal pigment epithelium (RPE)-choroid-sclera preparations from black dutch-belted rabbits were sealed in an Ussing chamber maintained at 37-39 degrees C. Typical preparations produced a spontaneous voltage (Ve) of 12.5 mV (retina side positive) and possessed an electrical resistance (R) of 350 ohm-cm2. Both of these values can be attributed to the RPE. Ouabain and amiloride diminished the Ve without affecting R. Ouabain was effective when applied to the apical but not to the basolateral side of the preparation, suggesting the presence of a Na-K ATPase on rabbit RPE apical membrane similar to that found in bullfrogs, embryonic chickens, cats and dogs. Dinitrophenol also reduced Ve. Digoxin, furosemide, bumetanide, ethacrynic acid and chlorothiazide had no apparent effect upon Ve and R. The lack of response to furosemide, bumetanide and ethacrynic acid strongly suggests that, unlike RPE from other species, rabbit RPE does not possess Na-dependent Cl transport and/or does not possess furosemide receptors on its apical membrane.

Amiloride↗
PubMed1988

Alpha-1 adrenergic receptors on rabbit retinal pigment epithelium.

Retinal pigment epithelium (RPE)-choroid-sclera preparations from black, dutch-belted rabbits were sealed in an Ussing chamber. The RPE-generated trans-RPE voltage (Ve) and electrical resistance (R) were monitored. Epinephrine (an alpha and beta adrenergic agonist) reduced Ve by as much as 39% without affecting R. A response to epinephrine was noted at concentrations as low as 1.4 X 10(-7) M. Phenylephrine (an alpha adrenergic agonist) had essentially the same effect as epinephrine at identical concentrations. Clonidine (an alpha-2 adrenergic agonist) had a very slight effect but only at 10(-4) M. Isoproterenol (a beta adrenergic agonist) had no apparent effect upon Ve or R. The RPE response to epinephrine and phenylephrine was blocked by the alpha adrenergic antagonist phentolamine and by the alpha-1 adrenergic antagonist prazosin but not by the alpha-2 adrenergic antagonist yohimbine or by the beta adrenergic antagonist propranolol. Dibutyryl cyclic AMP (in the presence and absence of IBMX) and cyclic GMP (as cGMP and in the dibutyryl form) had no apparent effect upon Ve or R. These results indicate that rabbit RPE possesses an alpha-1 adrenoreceptor which, when stimulated, substantially reduces the RPE generated trans-RPE electrical current.

Animals↗
PubMed1988

Precision surgery with an electromagnetically induced current convergence probe application in aneurysm treatment, angioplasty, and brain tumor resection in in vivo and in vitro models.

A hand-held probe, or one introduced through a catheter, rapidly produces an extremely high, tissue-vaporizing temperature in a precisely defined manner enabling surgeons or interventional radiologists to perform angioplasty, thrombose aneurysms, and vaporize tumors. The probe is operated in a near field of an inductive coil, and the current induced in the biologic tissue is converged maximally at the tip of the probe at the resonance frequency of both the inductor and the probe, producing a maximum temperature in excess of 1400 degrees C. Radio-frequency power controls the probe-tip temperature. The operation of the probe is comparable to that of a CO2 or YAG laser and is complementary to laser-surgical techniques. The low cost relative to lasers and simplicity of the device including its disposable components make the prospect of commercialization of this device promising.

Aneurysm↗
PubMed1988

Digoxin cannot account for the reported association of EKG abnormalities and rhegmatogenous retinal detachment.

The prevalence of cardiovascular disease (by EKG criteria) in patients with rhegmatogenous retinal detachments has been reported to be more than four times that found in age-matched controls. Adhesion between the retinal pigment epithelium (RPE) and the photoreceptors is facilitated by RPE transport. Because RPE transport is driven by a Na-K ATPase, it has been suggested that the correlation of EKG abnormalities and retinal detachment may be due to clinical use of digoxin, a Na-K ATPase inhibitor frequently given to patients with cardiovascular disease. The prevalence of EKG abnormalities in 299 consecutive patients with primary retinal detachment is about the same as that reported previously. However, 92% of these patients with EKG abnormalities did not take digoxin. Therefore, clinical use of digoxin cannot account for the reported association of EKG abnormalities and rhegmatogenous retinal detachment.

Cardiovascular Diseases↗
PubMed1987

Electromagnetic field focusing (EFF) probe--a new neurosurgical tool.

The electromagnetic field focusing (EFF) probe is capable of producing well circumscribed, intense heat at the point of contact with the tissue. Experimental studies were carried out to assess this probe as a neurosurgical tool using 38 rats and 4 mice with mammary carcinoma. The study on the rats included study of the cutting, coagulating and vaporizing effect on brain tissue including study of blood brain barrier disruption and heat dissipation. The study on the mice included the study of vaporizing property of the probe on solid tumours. The probe proved to be an excellent tool for cutting, coagulating and vaporizing purposes with very minimal disruption of blood brain barrier and demonstrated well circumscribed heating pattern. The study indicates that this tool combines the beneficial effect of both the YAG and CO2 laser.

Animals↗