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Biomedical subjects

R C Petersen

Publications and source records attributed to R C Petersen.

At least 127 records · Page 7Linked to original sources
PubMed1988

Selective posterior cerebral artery Amytal test for evaluating memory function before surgery for temporal lobe seizure.

Selective testing for memory function with Amytal (amobarbital) in the posterior cerebral artery (PCA) is a promising modification of that test in the internal carotid artery (ICA). This new technique, performed with a Tracker catheter system, was completed successfully in 17 of 20 patients being examined before planned surgery for refractory temporal lobe seizure. The PCA test overcomes three major problems with the ICA technique. First, with the PCA technique, memory testing is begun immediately after injection, when the drug has its peak effect. Second, when the speech-dominant hemisphere is being tested with the PCA test, patients do not become aphasic. Third, injection into the PCA delivers the drug more effectively to the target, the ipsilateral hippocampal formation.

Adolescent↗
PubMed1987

Transient global amnesia and epilepsy. Electroencephalographic distinction.

Electroencephalographic recordings were obtained during 13 episodes of transient global amnesia in 13 patients. Eight were entirely normal; none showed seizure discharges or other epileptiform activity. Electroencephalographic recordings were also obtained after 103 episodes of amnesia in 96 patients with transient global amnesia (TGA) alone, five patients who had both TGA and epilepsy independently, and three patients with amnesia related to epilepsy. The majority (60.8%) of waking records were normal during or after episodes of TGA. Mild or moderate and nonfocal abnormalities were found in a minority. Genuine epileptiform activity was observed only among patients who had seizure disorders. Amnestic episodes attributable to seizures were more brief and more apt to be repeated than TGA and usually responded to anticonvulsant drugs. Differentiation of TGA from epilepsy is essential for appropriate management.

Amnesia↗
PubMed1987

Comparison of the biological effects of humic materials under acidified conditions.

The acute and chronic effects of three types of humic material were studied using Daphnia magna at pH 5, 6, and 7. At neutral pH humic material had no biological effect. At pH 6 and 5 maximum survival and population growth rate occurred at intermediate levels of humus material (10 mg C/L, 300 mg Pt/L). Lowest survival and population growth rate occurred at pH 5 in either the absence of humus material or at concentrations exceeding 10 mg C/L (300 mg Pt/L). A second order polynomial was used to fit the dose response curve at pH 5 for both Aldrich humic acid and a natural bog water. Aldrich had greater biological activity. It is suggested that the biological behavior of aquatic humus conforms to second order rate phenomena controlled by high levels of free metals ions at low humus concentrations and direct toxic action of the dissolved organics at low pH due to increased lipophilicity.

Daphnia↗
PubMed1987

Treatment of Gilles de la Tourette's syndrome: eight-year, practice-based experience in a predominantly adult population.

Over 86% of 58 patients with Gilles de la Tourette's syndrome achieved effective pharmacologic control of the symptoms for 3 months or longer. Differences in response patterns were common among patients and required individualized tailoring of management. Dopamine-blocking neuroleptics were the mainstay of therapy. However, frequent mid-course alterations were required as previously successful drugs stopped working or as their side effects became intolerable. While haloperidol and now pimozide are most frequently used, trifluoperazine and thiothixene can provide superior relief in individual patients. A combination of neuroleptics or even a rotation from one to another may occasionally become necessary. No tardive dyskinesia was encountered in this population. Clonidine proved inferior to neuroleptics in the treatment of the motor and vocal tics, but may have a role in some patients with prominent obsessive-compulsive symptomatology.

Adolescent↗
PubMed1987

Transient global amnesia: clinical characteristics and prognosis.

We studied the clinical characteristics of transient global amnesia (TGA) in 277 patients with an average follow-up of 80 months. The syndrome occurred most frequently after age 50. There was a history of migraine in 14.1% and cerebrovascular diseases in 11.2% of patients, but these conditions were usually not temporally linked to TGA. Characteristic antecedent events and activity such as exertion existed in 33.4%. The incidence of TGA was 5.2 per 100,000 per year in Rochester, MN. Although 23.8% of the patients had recurrent episodes, they were not at increased risk for subsequent stroke.

Aged↗
PubMed1985

Surgical treatment of idiopathic hydrocephalus in elderly patients.

We studied 45 adult patients with idiopathic hydrocephalus who had undergone a shunting procedure at the Mayo Clinic during a 16-year period. The follow-up period extended up to 157 months. Thirty-four of the 45 patients (75%) improved at some time after the operation, and 19 (42%) experienced continuous improvement. The median duration of improvement was 24 months. Patients who had symptoms for less than 2 years were most likely to improve. CT played an important role in the diagnosis and follow-up, but ventricular size or degree of atrophy did not correlate with response.

Aged↗
PubMed1985

Ketamine: behavioral effects of subanesthetic doses.

Effects of subanesthetic doses of ketamine (0.25 and 0.5 mg/kg) on memory, cognition, psychomotor function, subjective moods, and incidence of adverse reactions were investigated in 34 healthy young volunteers. The drug caused impairment of immediate and delayed recall. Most of the impairment was due to interference with retrieval processes. Recovery was virtually complete 60 minutes after administration. The incidence of adverse reactions was high. Benzodiazepines need to be administered even when ketamine is used in subanesthetic doses.

Adolescent↗
PubMed1984

Nonionizing radiation aspects of optical fiber manufacturing.

Evaluation of the spectral distribution of the electromagnetic emissions from a system composed of a hydrogen-oxygen torch and a glass tube, used in the manufacturing of glass rods from which optical fibers are drawn, indicated levels in the visible and infrared portion of the electromagnetic spectrum that necessitated a specific type of eye protection to be worn by employees operating this equipment. Specific eye wear which provided qualities of both being lightweight and reducing transmission of all three major regions of the electromagnetic spectrum (ultra-violet, visible, infrared) were specified.

Eye↗
PubMed1983

Pulmonary vascular disease in 57 necropsy cases of total anomalous pulmonary venous connection.

In a semi-quantitative necropsy study, total anomalous pulmonary venous connection (TAPVC) was an isolated anomaly in 35 cases and was associated with asplenia and either pulmonary stenosis or pulmonary atresia in 22 cases. A comparison of the two groups showed pulmonary venous obstruction (26% vs. 4%), a small interatrial communication (51% vs. 4%), a patent ductus arteriosus or operative shunt (40% vs. 64%), medial hypertrophy of muscular pulmonary arteries (80 vs. 23%), muscularization of arterioles (80% vs. 23%), capillary engorgement (60% vs. 27%) alveolar wall thickening (29% vs. 0%), interlobular septal oedema (34% vs. 14%), dilated lymphatics (80% vs. 45%), arterialization of pulmonary veins (86% vs. 68%), medial hypertrophy of veins (26% vs. 0%), and venous dilatation (74% vs. 50%). Only one patient, a 5-year-old girl with isolated TAPVC, had severe plexogenic pulmonary arteriopathy. In the remainder, the pulmonary lesions were those generally associated with reversible pulmonary venous hypertension; they were most striking in patients with pulmonary venous obstruction, and were least prominent in patients with pulmonary stenosis or pulmonary atresia.

Adolescent↗
PubMed1982

Anticholinergic activity of imipramine and some analogs at muscarinic receptors of cultured mouse neuroblastoma cells.

Imipramine and some of its analogs (trimipramine, 3-chlorimipramine, desipramine, 3-chloro-2-hydroxyimipramine, 2-hydroxyimipramine, and didesmethylimipramine), were assayed for their potencies as antimuscarinic agents by their abilities to antagonize muscarinic receptor-mediated cyclic guanosine monophosphate (GMP) formation by cultured mouse neuroblastoma cells. Equilibrium dissociation constants for these compounds yielded the following rank order of potency at the muscarinic receptor: imipramine greater than trimipramine greater than 3-chlorimipramine greater than desipramine greater than 3-chloro-2-hydroxyimipramine greater than 2-hydroxyimipramine greater than didesmethylimipramine. These results indicate that didesmethylation of the side chain nitrogen or hydroxylation of the ring at the 2-position lead to marked reductions (30-fold and 12-fold, respectively) in antimuscarinic activity of imipramine.

Animals↗
PubMed1981

Time course of mental and psychomotor effects of 30 per cent nitrous oxide during inhalation and recovery.

Two experiments were conducted testing the duration of action of nitrous oxide on human performance. In the first experiment, 11 subjects inhaled 30 per cent nitrous oxide for two periods of 40 min each, 45 min apart. Their mental and psychomotor skills were measured using free recall, tapping board, arithmetic and flicker fusion tests before and 2, 12, 22 and 32 min after establishing and end-tidal concentration of N2O of 30 per cent. Recovery was tested using the same tests 2, 12, 22 and 32 min after discontinuation of N2O. Eleven additional subjects inhaled oxygen only and served as a control group. In the second experiment, 8 subjects received both 30 per cent N2O and oxygen in cross-over fashion, and their flicker fusion threshold was measured. When compared to baseline or oxygen administration, N2O significantly impaired tapping rate, number of words recalled, and performance in arithmetic tests. The effects of N2O were maximal at 2 min and remained similar throughout the entire administration. In flicker fusion tests, the effects of N2O were similar to those of stimulant drugs; N2O improved the subjects' ability to discriminate the fusion of flickering light. Recovery was complete in 22 min. The effects of, and recovery from the second administration of N2O were similar to those of the first experiment. There was no evidence of development of tolerance to mental and psychomotor effects of the drug.

Adult↗
PubMed1979

Scopolamine state-dependent memory processes in man.

Scopolamine state-dependent learning was investigated in man using four learning and recall tasks. Twenty-eight subjects performed the four tasks on the first day of the 2 day experiment under either the influence of the drug (5 microgram/kg of scopolamine administered IV) or a placebo and tried to recall the material on the second day in either the same or altered drug state. State-dependent learning theory predicts that those subjects in the same drug state on both days should recall more material than those who had their drug condition changed. Results confirmed this prediction for the two recall tasks which did not involve recall cues or prompts but not for the tasks involving memory acids. This implies that the drug state has memory cueing properties of its own and that recall can be enhanced either by restoring the drug state which existed at the time of learning or by providing external prompts.external prompts.

Adolescent↗
PubMed1979

Electromagnetic radiation emitted from video computer terminals.

There has been a developing concern about potential health hazards attributable to electromagnetic radiation from video computer terminals. Since users of these devices typically spend many hours daily in close proximity, they would be subject to chronic long-term exposures to any emitted radiation. Radiation was detected at frequencies ranging from 1.5 kHz to 1,420 MHz in the RF portion of the EM spectrum and from 350 nm to 600 nm in the ultraviolet and visible region. However, the levels were far less than the most restrictive permissible exposure levels established by any agency or government of any nation. There is no experimental or epidemiological evidence presently available to indicate that these levels of RF radiation have any deleterious effects on the human biological system.

Computers↗