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Biomedical subjects

J C Hart

Publications and source records attributed to J C Hart.

At least 19 recordsLinked to original sources
PubMed1999

Cardiopulmonary bypass on a patient with malaria.

There are special considerations when performing cardiopulmonary bypass (CPB) on a patient with malaria. A 70-year-old female with a recent history of severe aortic stenosis was scheduled to undergo elective aortic valve replacement. One week prior to surgery, the patient developed shaking chills and fever, with a positive malaria smear. An extensive literature search was undertaken to determine the effect of CPB on a patient with active malaria, but no prior reference was found. One major concern was the lysis of red blood cells while on bypass. The surgery was performed uneventfully, following 2 weeks of treatment with primaquine phosphate.

Aged↗
PubMed1999

Radiographic trends of dental offices and dental schools.

BACKGROUND: A survey of private practice facilities in the United States that perform dental radiography was conducted in 1993 and repeated in dental schools in 1995-1996. METHODS: Both surveys were conducted as part of the Nationwide Evaluation of X-ray Trends, or NEXT, survey program. A representative sample of dental facilities from each participating state were surveyed, and data on patient radiation exposure, radiographic technique, film-image quality, film-processing quality and darkroom fog were collected. RESULTS: The authors found that dental schools use E-speed film more frequently than do private practice facilities. The use of E-speed film and better film processing by dental schools resulted in lower patient radiation exposures without sacrificing image quality. The authors also found that dental school darkrooms had lower ambient fog levels than did those of private practice facilities. CONCLUSIONS: The distribution for the 1993 NEXT survey facilities was greater than that observed for dental schools for radiation exposure, film-processing quality and darkroom fog. Dental schools, in general, had better film quality and lower radiation exposures than did private practice facilities. PRACTICE IMPLICATIONS: Facilities need to emphasize better quality processing and the use of E-speed film to reduce patient exposure and improve image quality.

Absorptiometry, Photon↗
PubMed1999

Muscarinic receptor agonists, like dopamine receptor antagonist antipsychotics, inhibit conditioned avoidance response in rats.

The purpose of our studies was to determine the effects of muscarinic receptor agonists on conditioned avoidance responding in the rat. Rats were trained to avoid or escape an electric shock delivered to the feet in a discrete trial procedure. The muscarinic receptor agonists pilocarpine and [2-ethyl-8-methyl-2,8-diazaspiro(4. 5)decane-1,3-dione] hydrochloride (RS86) and the cholinesterase inhibitor physostigmine all decreased the percentage of avoidance responses at doses that produced less than approximately 30% response failures. Similar results were obtained with the antipsychotic drugs haloperidol, trifluoperazine, chlorpromazine, and clozapine. However, the benzodiazepine anxiolytic diazepam did not decrease avoidance responding up to doses that produced ataxia. On the other hand, oxotremorine and arecoline decreased avoidance responding only by producing response failures, whereas aceclidine produced intermediate changes. The muscarinic receptor antagonists scopolamine, trihexyphenidyl, and benztropine were without effect when administered alone but antagonized the decreases in avoidance responding produced by pilocarpine and RS86. Scopolamine had little effect on the decreases in avoidance responding produced by haloperidol. The newer muscarinic receptor partial agonists or agonist/antagonists [R-(Z)-(+)-alpha-(methoxyimino)-1-azabicyclo[2.2. 2]octane-3-acetonitrile] hydrochloride, talsaclidine, milameline, and xanomeline also produced dose-related decreases in avoidance responding. Our results demonstrate that muscarinic receptor agonists can decrease avoidance responding in a manner similar to dopamine-receptor antipsychotic drugs, suggesting that muscarinic receptor agonists may provide an alternative approach to the treatment of psychosis.

Animals↗
PubMed1996

The scotopic electroretinogram to blue flashes and pattern reversal visual evoked potentials in insulin dependent diabetes.

Pattern reversal visual evoked responses (PR-VEPs), the electroretinogram (ERG) to blue flashes of light in dark adaptation, the steady state ERG to 40 Hz flicker, and alterations in pupil diameter following dark adaptation were studied in 56 juvenile onset diabetics, 34 of whom had no ophthalmoscopic or photographic evidence of diabetic retinopathy (DR-group). The remaining 22 had mild background retinopathy (DR+group). Normal data was obtained from 24 subjects matched for age and sex with diabetics. Skin electrodes were used for all recordings. The scotopic 'b' wave of the ERG was significantly lower in amplitude in the DR- diabetics and it was even more reduced in the DR+group. The PR-VEP was significantly delayed in diabetics but there was no difference between the two groups. The steady state ERG was not significantly different between normals and diabetics. These findings indicate that retinal and more central abnormalities develop early in diabetics. Detection of objective electrophysiological abnormalities may be used to identify persons at risk of developing retinopathy and to monitor the effects of treatment.

Adolescent↗
PubMed1994

Electrodiagnostic evaluation of the visual system: the role of the clinician.

Visual electrodiagnosis is a new discipline with a long history. The foundations include the disciplines of psychophysics, neurophysiology, electronics, computer science, statistics and medicine. However, with such a complex heritage, visual electrodiagnosis has taken a considerable time to evolve to its present form. Today visual electrodiagnostic assessment is relevant, not only for conditions primarily affecting the visual system, but also in more generalised pathological states in which eye changes may be a manifestation. Pressures for more refined and accurate diagnoses stem both from a continuing improvement in knowledge of disease processes by the medical profession and greater expectations on the part of patients seeking advice. Specialised investigative services such as electrodiagnosis, if these are appropriately funded and maintained, provide data to clinicians which is repeatable and objective, without resorting to invasive technology.

Adult↗
PubMed1990

Assessment of working memory in rats using spatial alternation behavior with variable retention intervals: effects of fixed-ratio size and scopolamine.

The effects of fixed-ratio (FR) size, scopolamine, and the interactions between FR size and scopolamine were investigated in male F344 rats on working memory as assessed by spatial alternation behavior maintained under FR schedules of food presentation where the interval between trials was varied among values of 2, 4, 8, 16, and 32 s within each session. The magnitude of the FR size on the correct and incorrect levers was varied systematically from 1 response to 2, 4, 8, or 16 responses in order to determine whether the FR size influenced either the percentage of correct responding, rates of responding, or both. Under the primary baseline condition, that is when the FR size on both the correct and incorrect levers was one response (designated FR1 FR1), the percentage of correct responses decreased with increasing retention interval duration. Increasing the FR size on the correct lever produced FR-dependent increases in the percentage of correct responding as well as in rates of responding. Increasing the FR size on the incorrect lever produced FR-dependent decreases in correct responding, but had little effect on rates of responding. Dose-effect curves for scopolamine were determined on performance maintained under FR values on the correct and incorrect levers, respectively, of FR1 FR1, FR1 FR10, FR10 FR1, and FR10 FR10. In general, scopolamine produced dose-related decreases in the percentage of correct responding, although the magnitude of the effects of scopolamine varied not only with dose, but also with the length of the retention interval and with changes in FR size.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

A comparison of the wound integrity produced by various suture patterns in penetrating keratoplasty: a cadaver eye model.

We tested the watertightness of wound closure in penetrating keratoplasty as a function of suture pattern by performing a 7.5-mm penetrating keratoplasty on 12 human cadaver eyes using a variety of suture patterns. We then tested wound integrity by hydrostatically raising the intraocular pressure. In this cadaver eye model, we demonstrated that running sutures produced better wound closure than interrupted sutures using the same number of bites. A 16-bite running or a combined running-interrupted pattern produced more than ample watertightness in penetrating keratoplasty wound closure.

Cadaver↗
PubMed1990

Suture patterns and corneal graft rotation in the cadaver eye.

Torque and antitorque running sutures as described by Eisner are commonly used in penetrating keratoplasty. We tested the rotational effect of three different 16-bite running suture patterns on eight cadaver eyes, with the following results: (1) the torque pattern rotates the corneal graft counterclockwise by 0.7 +/- 0.1 mm at the wound or 11 degrees; (2) the antitorque pattern rotates the corneal graft clockwise by 0.7 +/- 0.1 mm at the wound or 11 degrees; (3) an intermediate "no torque" pattern, the bites of which form an isosceles triangle, produces no rotational effect. We recommend the use of a "no torque" pattern to minimize corneal graft rotation.

Cadaver↗
PubMed1987

Kappa agonist-induced diuresis: evidence for stereoselectivity, strain differences, independence of hydration variables and a result of decreased plasma vasopressin levels.

Marked diuresis has previously been reported after administration of kappa opioid agonists. The present study shows that this effect is stereospecific; MR-2034 markedly increased urinary output over the dose range 0.08 to 1.25 mg/kg, whereas the opposite isomer, MR-2035, was markedly less potent. Bremazocine increased urinary output in Long-Evans hooded and Sprague-Dawley albino rats as well as lean and fatty Zucker rats. In the lean Zucker and the albino rats, bremazocine produced an inverted U-shaped diuretic dose-effect curve, an effect characteristic of kappa agonists with mu agonist activity. This pattern was not seen with the fatty Zucker rats or the Long-Evans hooded rats. The full kappa agonists bremazocine, ethylketazocine and U-50,488 increased urinary output under three different conditions of hydration: water loaded, normal hydration and water deprived. In contrast, the partial kappa agonists reliably only increase urinary output under the normal hydration condition. The diuretic effects of full and partial kappa agonists correlated with plasma vasopressin levels in water-deprived rats. The full kappa agonists (ethylketazocine, U-50,488, tifluadom and MR-2034) suppressed plasma vasopressin levels below the threshold of detectability of the radioimmunoassay, whereas the partial kappa agonists (nalorphine and butorphanol) suppressed vasopressin levels compared with control values but did not have the efficacy of the full kappa agonists. All these results support the hypothesis that kappa agonists produce their diuretic effect by suppression of plasma vasopressin levels.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1985

Screening of diabetics for retinopathy by ophthalmic opticians.

Diabetes mellitus is a major cause of blindness in England and Wales in those aged between 30 and 64. Photocoagulation can frequently prevent blindness provided the retinopathy is detected at an appropriate stage but unfortunately the benefits are small if the changes are advanced. Early detection of diabetic retinopathy by regular examination is needed. We have shown that ophthalmic opticians have the skill to detect retinal changes at a treatable stage. Out of 844 eye checks, 80 were reported by ophthalmic opticians to justify referral to an ophthalmologist and 20 of these required photocoagulation treatment. Of a sample of 197 patients rechecked by an ophthalmologist reported by ophthalmic opticians not to justify referral, only one needed treatment. With local agreement this system of detecting retinopathy could be easily applied anywhere in the United Kingdom. No extra personnel or facilities are needed.

Blindness↗
PubMed1985

Diuresis and suppression of vasopressin by kappa opioids: comparison with mu and delta opioids and clonidine.

The effects of agonists at kappa, mu and delta opioid receptors were determined on vasopressin levels in water-deprived rats. Bremazocine and U-50, 488 (kappa agonists) markedly suppressed vasopressin levels, whereas morphine and methadone (mu agonists) and metkephamid (a mixed mu and delta agonist) did not suppress vasopressin levels. Likewise, clonidine, a potent diuretic in normally hydrated rats, did not clearly suppress vasopressin levels. Metkephamid was shown to have a modest diuretic effect in normally hydrated rats but not in water-deprived rats. The diuretic effects of bremazocine were blocked completely by simultaneous treatment with desmopressin, a synthetic vasopressin-like analog. Desmopressin also blocked the diuretic effect of a waterload, but only partially attenuated the diuretic effect of clonidine. These results support the hypothesis that kappa opioid agonists produce a diuretic effect by suppressing plasma levels of vasopressin, and at higher doses produce a pattern of urination similar to animals lacking vasopressin. By comparison, mu and delta opioid agonists have little effect on vasopressin levels in water-deprived rats.

Animals↗
PubMed1983

Metastatic periosteal osteosarcoma causing cardiac and renal failure.

The case of a 25-year-old man who had periosteal osteogenic sarcoma with intravascular metastases in unusual locations is reported. The patient presented with acute renal failure, unilateral pulmonary edema, functional mitral stenosis, and low cardiac output. After successful surgical removal of a left atrial metastasis with subsequent improvement in cardiac output, renal function improved only transiently and urinary output varied markedly. At autopsy, metastatic osteogenic sarcoma was discovered within the lumen of the abdominal aorta obstructing both renal arteries. The case is the first report of a neoplasm metastatic to the aorta causing intermittent bilateral renal arterial obstruction; it illustrates the diagnostic difficulties presented by intravascular metastatic disease.

Acute Kidney Injury↗
PubMed1983

Reversed subclavian flap angioplasty for arch coarctation of the aorta.

Subclavian flap repair in infants with coarctation of the aorta has been shown to be superior to end-to-end reconstruction. Aortic arch coarctations in 2 infants were repaired utilizing reversed subclavian flaps with good results. The effectiveness of flap reconstruction in less common forms of aortic coarctation in infants is demonstrated.

Aorta, Thoracic↗
PubMed1983

Subclavian catheterization for the placement of a ventriculovenous shunt.

Repeated nonfunction of the distal end of a ventriculoperitoneal shunt led to an unsuccessful attempt to introduce the distal catheter into the vena cava through the jugular vein. Subclavian catheterization utilizing a cardiac pacemaker introducer set proved to be a simple and effective means of establishing a ventriculovenous shunt.

Catheterization↗
PubMed1982

Novel phenylpiperidine opioid antagonists and partial agonists: effects on fluid consumption.

The effects of five opioid antagonists, a racemate partial agonist and its agonist and antagonist optical isomers were studied on deprivation-induced drinking. All compounds had a phenylpiperidine nucleus. The antagonists produced dose-related decreases in drinking, and the potencies for decreasing drinking correlated with morphine-antagonist doses. The racemic partial agonist and its agonist isomer decreased drinking at doses higher than those which produced marked analgesia. Within the class of phenylpiperidine drugs studied, some had less specificity than naloxone for the mu-receptors as compared to the delta-receptor, but the suppression of drinking was not related to changes in mu-to-delta ratios.

Animals↗
PubMed1981

Accessory diaphragm in an infant.

Accessory diaphragm is a rare congenital abnormality that almost always occurs on the right side and is often associated with cardiovascular anomalies. This paper describes the clinical presentation, radiologic diagnosis, and surgical treatment of the condition. Early recognition and prompt surgical treatment will prevent the chronic pulmonary complications reported in the literature.

Diaphragm↗