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Biomedical subjects

L A Parker

Publications and source records attributed to L A Parker.

At least 19 recordsLinked to original sources
PubMed1992

Naltrexone-induced aversions: assessment by place conditioning, taste reactivity, and taste avoidance paradigms.

The reinforcing/aversive properties of various doses of naltrexone (0.01, 1, and 10 mg/kg) were assessed in three experiments that employed place conditioning, taste reactivity, and taste avoidance paradigms. Naltrexone produced a place aversion and a taste aversion, but did not produce aversive taste reactivity responses, even at the highest dose (10 mg/kg) tested. This suggests that drugs that produce a place aversion do not necessarily produce a conditional dislike for a flavored solution with which they are paired.

Animals↗
PubMed1992

Place conditioning in a three- or four-choice apparatus: role of stimulus novelty in drug-induced place conditioning.

A series of 4 experiments examined the suggestion (Scoles & Siegel, 1986) that drug-induced place preference conditioning may be due to interference with habituation. In each experiment, rats had the opportunity to select among a drug-paired chamber, a saline-paired chamber, and a novel (or relatively novel) chamber. The drugs included the positively reinforcing drugs amphetamine, apomorphine, morphine, and nicotine and the aversive drug lithium chloride. The rats preferred chambers that were paired with amphetamine, apomorphine, and morphine more than chambers that were novel; however, they also consistently preferred novel chambers to familiar saline-paired chambers. There was no evidence of place conditioning with nicotine. The drug-induced place preference, but not the novelty preference, occurred after a single conditioning trial in a 3-choice apparatus but not a 4-choice apparatus. Lithium chloride established a place aversion after 1-3 conditioning trials. Measures of activity revealed that the rats were least active while in their most preferred chamber and most active while in their least preferred chamber.

Animals↗
PubMed1992

Morphine- and naltrexone-induced modification of palatability: analysis by the taste reactivity test.

We used the taste reactivity (TR) test, a direct measure of the hedonic properties of a tastant, to assess in Sprague-Dawley rats the ability of morphine (an opiate agonist) and naltrexone (an opiate antagonist) to modify the palatability of a bitter quinine solution and a sweet sucrose solution. Morphine reduced the aversive hedonic properties of both novel and familiar quinine solution (0.05% and 0.1%) but did not modify the palatability of 20% sucrose solution. Naltrexone reduced the positive hedonic properties of sucrose solution (2% and 20%) but did not modify the palatability of 0.05% quinine solution. The pattern of results suggests that the modification of feeding produced by opiate agonists and antagonists may be mediated by an hedonic shift in the palatability of the tastant.

Animals↗
PubMed1991

Chronic posttraumatic aortic pseudoaneurysm. Recognition before rupture.

Few patients survive transection of the aorta caused by blunt trauma. However, among those who do are a small number who go on to live with an unrecognized pseudoaneurysm that may rupture at any time. Because these aneurysms may be mistaken for more common disease processes, such as hilar adenopathy, atherosclerotic aneurysm, or neoplasia, the authors describe radiographic findings that suggest the correct diagnosis.

Aorta, Thoracic↗
PubMed1991

Chin rub CRs may reflect conditioned sickness elicited by a lithium-paired sucrose solution.

Rats were given a single conditioning trial in which 20% sucrose solution was paired with an intraperitoneal (IP) injection of lithium chloride (127.2 mg/kg), d-amphetamine (3 mg/kg) or physiological saline. Thirty min before a subsequent 10-min taste reactivity (TR) test and a 1-h conditioned taste avoidance (CTA) test the rats were injected IP with either the antiemetic agent, trimethobenzamide (5 mg/kg) [corrected] or with physiological saline solution. The lithium-paired, but not the amphetamine- or saline-paired, sucrose solution elicited the aversive TR responses of chin rubs, paw pushes and gapes. Trimethobenzamide suppressed the aversive TR response of chin rubs in the lithium-conditioned group, but not in a group given unconditionally aversive quinine solution. The CTA test was not sensitive to the antiemetic properties of trimethobenzamide, although the drug enhanced sucrose preference overall. The results suggest that chin rub responses may measure conditioned sickness.

Animals↗
PubMed1991

Chlordiazepoxide nonspecifically enhances consumption of saccharin solution.

Following the establishment of a saccharin-amphetamine, saccharin-lithium or saccharin-saline association, rats were given a two-bottle test of preference for saccharin and water. Thirty min prior to the test, half of the rats were pretreated with chlordiazepoxide (9 mg/kg) and half of the rats were pretreated with saline. The results revealed that pretreatment with chlordiazepoxide (CDP) nonselectively enhanced saccharin consumption regardless of whether the flavored solution had been paired with amphetamine, lithium or saline. These results provide evidence that CDP enhances the palatability of flavored solutions.

Amphetamine↗
PubMed1991

Taste reactivity responses elicited by reinforcing drugs: a dose-response analysis.

A series of 3 experiments with Sprague-Dawley rats measured taste reactivity (TR) responses elicited by sucrose that was paired on 5 occasions with various doses of d-amphetamine (0, 1, 2, 5, or 10 mg/kg), nicotine (0, 0.4, 0.8, 1.2, or 2.0 mg/kg), or morphine (0, 2, 8, 20, or 80 mg/kg). The TR responses elicited by flavors paired with each of these drugs were compared with those elicited by flavors paired with lithium. The only doses of d-amphetamine and nicotine that effectively conditioned aversive TR responses were high doses that have also been demonstrated to be incapable of producing a place preference. Extremely high doses of morphine were incapable of producing aversive TR responses. It is suggested that aversive TR responses are only produced by doses of agents that are not reinforcing in other paradigms.

Animals↗
PubMed1990

Sensitivity and specificity of computed tomography for the detection of adrenal metastatic lesions among 91 autopsied lung cancer patients.

The ability of computed tomography (CT) to detect metastatic lesions in adrenal glands was evaluated on 91 autopsied lung cancer patients who died in 11 hospitals in the eastern United States and Canada from January 1983 to February 1988. Abdominal CT scans within 90 days of death were reviewed twice by two radiologists blinded to the autopsy diagnosis. The likelihood of metastatic spread in each adrenal gland was scored on a five-level scale. Histopathologic findings at autopsy were used to establish the presence or absence of metastases. The sensitivity of CT was low. Among 53 adrenal glands with proven metastatic lesions, the proportion with positive CT scans varied from 20.0% to 41.1%, according to the positivity threshold. In contrast, the specificity of CT was high, even at relaxed positivity thresholds, from 84.5% to 99.4%. The relatively low sensitivity of CT to detect adrenal metastatic lesions is explained to a large extent by the lack of substantial structural changes in many adrenal glands found to have metastases at autopsy. With a strongly positive CT scan, the probability of an adrenal metastatic lesion is high, and confirmatory adrenal biopsy may not be needed in patients with adenocarcinoma and large cell carcinoma.

Adenocarcinoma↗
PubMed1990

Computed tomography of hepatic venous hypertension: the reticulated-mosaic pattern.

A reticulated-mosaic pattern of the liver was identified on contrast-enhanced computed tomography in 4 of 20 patients with constrictive pericarditis or congestive heart failure. Reflux of contrast into a distended inferior vena cava and the hepatic veins was identified in 3 of the 4 patients. This abnormal enhancement pattern combined with hepatic venous or caval reflux of contrast indicates the presence of hepatic venous hypertension, and should not be mistaken for other abnormalities that may result in inhomogeneous hepatic enhancement.

Adult↗
PubMed1990

Computed tomography in the evaluation of clinical stage IB carcinoma of the cervix.

A retrospective analysis of 47 cases of clinical stage IB cervical carcinoma radiologically staged with computed tomography (CT) was undertaken. There were no cases where CT provided information which altered staging. In 5 cases, CT suggested extension of disease beyond the cervix which was not confirmed surgically or with other staging procedures. In 3 cases, one or more normal-sized obturator or internal iliac nodes with metastatic disease were discovered at surgery, but the high common iliac and periaortic nodes were disease free. We conclude that routine use of CT in patients with clinical stage IB cervical carcinoma is not warranted unless the patient's body habitus precludes accurate physical examination.

Carcinoma↗
PubMed1990

Pimozide enhances the aversiveness of quinine solution.

The taste reactivity test was employed to assess the effect of pimozide pretreatment on rats' hedonic responsiveness to palatable and unpalatable tastants. Pimozide selectively enhanced the aversiveness of unconditionally unpalatable quinine solution (Experiment 1) and produced the greatest enhancement of aversion at the highest concentration of quinine (0.1%) solution tested (Experiment 3). Pimozide also enhanced the aversiveness of a conditionally unpalatable lithium-paired solution, but only when the dose of pimozide was relatively high and the strength of the baseline aversion was relatively low (Experiment 2). These results are discussed in light of the anhedonia and the sensorimotor deficit hypotheses of neuroleptic effects on reinforced responding.

Animals↗
PubMed1990

Apomorphine-induced flavor-drug associations: a dose-response analysis by the taste reactivity test and the conditioned taste avoidance test.

Apomorphine is a positively reinforcing drug at low to moderate doses, but appears to lose its reinforcing properties at higher doses. In Experiment 1, across a range of doses (0.5-15.0 mg/kg, intraperitoneally), apomorphine produced a CTA over 5 conditioning/testing trials which was not dose-dependent by a single bottle test. The rejection taste reactivity responses of chin rubbing and gaping, however, only occurred at the highest dose of apomorphine (15 mg/kg). In Experiment 2, a CTA test which was designed to more effectively discriminate among the different drug dose conditions indicated that the doses of 2.5, 7.5 and 15 mg/kg of apomorphine produce CTAs of equivalent strength. Our results support the contention that CTAs produced by positively reinforcing drugs are not accompanied by a palatability shift.

Animals↗
PubMed1989

Small bore catheter drainage and sclerotherapy for malignant pleural effusions.

The accumulation of large amounts of fluid in the pleural space is a common sequela of disseminated carcinomatosis. Traditional management has included therapeutic thoracentesis or the placement of a large bore chest tube for drainage with the subsequent installation of a sclerosing agent in an attempt to achieve pleural symphysis. An evaluation of all patients treated in this manner during a 4-year period was undertaken to assess the degree of success obtained with a large bore standard chest tube versus a small pigtail catheter. A study group consisting of 20 patients with a total of 24 pleural effusions was treated with drainage and sclerotherapy. In this group, eight of 13 effusions were adequately treated with pigtail catheter drainage and sclerotherapy, compared with four of 11 effusions adequately treated with standard chest tube drainage and sclerotherapy. Although the numbers are small, it appears that pigtail catheter drainage and sclerosis is at least as successful as the more traditional drainage with the standard chest tube.

Adult↗
PubMed1989

Oblique projections in aortography following blunt thoracic trauma.

We report a patient with innominate artery false-aneurysm formation following blunt trauma to the thorax. Aortography in the standard anteroposterior and left anterior oblique (LAO) projections failed to delineate the injury. Its true extent was only demonstrable in the right anterior oblique (RAO) projection. When the clinical history and a chest radiograph suggest a high likelihood of injury to the aorta or great vessels, routine aortography may need to be performed in both the LAO and RAO projections.

Adult↗
PubMed1988

Defensive burying of flavors paired with lithium but not amphetamine.

Although rats demonstrated avoidance of both lithium- and amphetamine-paired flavored solutions, only the lithium-paired flavor elicited a defensive burying response. These data support the contention that lithium-paired flavors become hedonically unpalatable. Additionally, a simplified economical method for measuring defensive burying is described.

Amphetamine↗
PubMed1988

The role of computed tomography in the evaluation of post-mastectomy locally recurrent breast cancer.

The rate of post mastectomy local-regional recurrence of breast cancer has remained in the range of 10-30% for decades. The traditional treatment, external beam radiation therapy, is successful in eradicating local disease in most cases, but re-recurrences are seen in about 50% of patients. Since 1982, 33 patients with such recurrences have undergone evaluation with computed tomography (CT) at our institution as part of their diagnostic work-up. In 22/33 (67%), CT revealed unsuspected disease, and in 10 of these patients the radiation treatment plan had to be altered. These results, similar to three other published series, strongly suggest that CT is a necessary part of the work-up of patients with post-mastectomy local-regional recurrences. The significance of these findings with respect to the cause of post mastectomy local-regional failures is further discussed.

Breast Neoplasms↗