Biomedical subjects

R M Bauer

Publications and source records attributed to R M Bauer.

48 records · Page 3Linked to original sources

PubMed1988

A GABAergic mechanism in the posterior hypothalamus modulates baroreflex bradycardia.

Several laboratories have shown that electrical stimulation in the posterior hypothalamus inhibits the baroreceptor reflex. However, the results of these studies are difficult to interpret since it is not known if the attenuation of the baroreflex results from activation of axons of passage or from stimulation of hypothalamic cell bodies. The purpose of this study was to determine the effects of chemical stimulation of posterior hypothalamic neurons upon the baroreflex. Arterial baroreceptors were activated by increasing the pressure in an isolated carotid sinus in anesthetized cats and by an increased arterial pressure following intravenous injection of phenylephrine in both anesthetized cats and rats. The baroreceptor reflex was evaluated before and after a GABA antagonist (picrotoxin) was microinjected into the posterior hypothalamus. The bradycardia, but not the depressor response, elicited by increasing carotid sinus pressure was attenuated after unilateral microinjections of picrotoxin into the posterior hypothalamus. In addition, the heart rate response to a phenylephrine-evoked rise in arterial pressure was reduced after picrotoxin was microinjected in both the cats and the rats. Microinjection of a GABA agonist (muscimol) into the same hypothalamic site returned resting heart rate and arterial pressure to levels seen prior to picrotoxin. These results show that the depression of the bradycardia produced by hypothalamic stimulation results from activation of cell bodies in the posterior hypothalamus. This hypothalamic effect upon the baroreflex bradycardia may involve a GABAergic mechanism.

Animals↗

PubMed1988

Expression, release, and characterization of soluble human T-lymphotropic virus-I (HTLV-I) antigens from an infected cell line.

The Human T-lymphotropic virus type I (HTLV-I) infected cell line MT-2 was studied to obtain HTLV-I or related proteins for the purpose of producing an effective vaccine for HTLV-I infection. The cells were characterized as to HTLV-I antigen expression during the cell cycle and antigens released into the culture fluids. MT-2 cell grown in fetal calf supplemented media produced more HTLV-I related antigens during the G2/M phase of the cell cycle. To determine the conditions for maximal release and harvest of HTLV-I associated proteins, the MT-2 cells were grown in RPMI 1640 medium supplemented with serum-free medium. Cell- and virus-free supernatants were collected on day 4, lyophilized, and concentrated 50-fold. The proteins in these supernatants were characterized using SDS-PAGE and western blot using rabbit anti-HTLV-I sera and human adult T-cell leukemia sera. The western-blot analysis indicated that the supernatants obtained from the MT-2 cells grown in serum-free supplemented medium contained detectable amounts of proteins which reacted with human ATL and rabbit anti-HTLV-I sera. The molecular weights of these proteins observed are 68kd, 46kd, 28kd, 24kd, 19kd, and 15kd indicating that gag, env, and pX gene products are present.

Blotting, Western↗

PubMed1987

Comprehension of emotional prosody following unilateral hemispheric lesions: processing defect versus distraction defect.

Two studies were conducted in order to determine whether the poor performance of RHD patients on emotional prosody tasks could be attributed to a defect in perceiving/categorizing emotional prosody (processing defect) or to a problem in being distracted by the semantic content of affectively intoned sentences (distraction defect). In one study, patients with RHD, LHD or NHD listened to affectively intoned sentences in which the semantic content was congruent or incongruent with the emotional prosody. In a second study, the patients listened to affectively intoned sentences that had been speech filtered or unfiltered. Findings from these studies indicate that both processing and distraction defects are present in RHD patients.

Attention↗

PubMed1987

Chronic fatal disease in gorillas seropositive for simian T-lymphotropic virus I antibodies.

Sera from 10 gorillas were tested by indirect immunofluorescent antibody assay, Western blotting and ELISA to Human T-lymphotropic viruses for cross-reacting with antibodies to Simian T-lymphotropic virus I (STLV-I). Four were antibody positive. Of the 4 seropositive gorillas, one has remained healthy, while 3 have died with similar disease problems as reconstructed from clinical records. It is not known whether a causal relationship exists between these diseases and STLV-I retrovirus infection.

Animals↗

PubMed1986

Nocturnal hypoxia and neuropsychological variables.

Hypoxia is a well known cause of brain dysfunction. Neuropsychological impairments have been observed in normal subjects experiencing hypoxia iatrogenically as well as in patients with chronic lung disease. Recent investigations have demonstrated significant nocturnal hypoxia in subjects with sleep-disordered breathing. In the present study, heavy-snoring males, a group known to experience frequent episodes of sleep-disordered breathing received neuropsychological testing and a night of continuous monitoring of respiratory parameters. Partial correlations, controlling for age, weight, and education, indicated reliable relationships between nocturnal hypoxia and measures of general intelligence, verbal and nonverbal memory, and expressive verbal fluency. It is proposed that heavy-snoring males may potentially serve as a population in which to model the neurobehavioral effects of hypoxia. Further research in subjects with sleep-disordered breathing may help clarify the extent of the possible cognitive deficits as well as point out possible ameliorative treatments.

Brain Damage, Chronic↗

PubMed1985

Processing of faces by patients with unilateral hemisphere lesions. I. Dissociation between judgments of facial affect and facial identity.

In this study, right-hemisphere-damaged (RHD) subjects performed significantly worse than LHD and NHD controls across a series of seven facial identity and facial affect tasks. Even when the patient groups were statistically equated on a measure of visuoperceptual ability, the RHD group remained impaired on three emotional tasks--naming, picking, and discriminating emotional faces. These findings suggest that the defects shown by RHD patients on facial affect tasks cannot be solely attributed to defects in visuoperceptual processing and that the right-hemisphere superiority for processing facial affect exists above and beyond its superiority for processing facial identity.

Affect↗

PubMed1984

Autonomic recognition of names and faces in prosopagnosia: a neuropsychological application of the Guilty Knowledge Test.

A prosopagnosic was shown two sets of faces, one comprised of famous personalities, the other of family members. After he was allowed to visually inspect each face, he was given five names, one of which was correct. Skin conductance was continuously recorded. He could not identify any of the faces spontaneously, and performed at chance level when given multiple choice names. However, electrodermal responses indicated far more accurate discrimination between correct and incorrect names, suggesting that the patient "recognized" facial identity at the psychophysiological level. Neuropsychological mechanisms for this phenomenon, which in this case involve multiple visual-limbic interrelationships, are postulated. The method appears useful for studying islands of spared recognition ability in associative agnosia.

Adult↗

PubMed1984

Visual memory and perceptual impairments in prosopagnosia.

A patient who suffered traumatic hematomas of both occipitotemporal regions, but who had normal visual acuity, language, and cognitive functions, could not recognize faces of family members, celebrities , or recent acquaintances (prosopagnosia). He could distinguish same from different faces when they were presented simultaneously, but could not recognize faces that had been presented to him 90 seconds earlier. He could read and name objects correctly, but could not recognize any previously viewed object if it was reexamined later with other objects of the same semantic class. He had no difficulty copying complex figures, but synthesized incomplete visual information poorly and pursued an abnormal visual search strategy. We suggest that prosopagnosia is part of a more general inability to distinguish among objects within a visual semantic class. It results from impaired visual memory and perception caused by visual association cortex damage and interruption of the inferior longitudinal fasciculus connecting visual association cortex and temporal lobe.

Adult↗

PubMed1982

Visual hypoemotionality as a symptom of visual-limbic disconnection in man.

In a patient with bilateral occipitotemporal hematomas secondary to head trauma, profound prosopagnosia, topographical memory disturbance, and a modality-specific inability to become emotionally aroused by visual cues developed. Data from neurological, neuropsychological, and psychophysiological assessment of the patient's deficits were interpreted as indicating a visual-limbic disconnection syndrome. The patient's symptoms were related to findings of emotional changes and visual impairment in macaques with bitemporal ablations and/or complete visual-temporal disconnection.

Acoustic Stimulation↗

PubMedDate not supplied

Effect of 1,1-dimethylhydrazine on lymphoproliferation and interleukin 2 immunoregulatory function.

The studies reported here suggest that the immunomodulatory effects of 1,1-dimethylhydrazine (UDMH) are associated, in part, with interference with interleukin 2 (IL-2) regulatory action. Concanavalin A (Con A)-stimulated DNA synthesis in murine splenocytes was inhibited from 18.6 to 44.1% at sub-toxic concentrations of UDMH (10 to 50 micrograms/ml) and IL-2-dependent DNA synthesis in CTLL-20 cells was inhibited from 11.3 to 41.58% at sub-toxic concentrations of UDMH (10 to 50 micrograms/ml). In addition, UDMH suppressed phorbol myristic acetate (PMA)-stimulated IL-2 production in EL-4 cells by up to 30% and slightly suppressed IL-2 production by Con A-stimulated murine splenocytes. In all cases, inhibition was evident at sub-toxic UDMH concentrations and was demonstrated to be independent of inactivation of IL-2 or interference with IL-2 absorption. It is suggested that UDMH has the potential to modify immune function through interference with IL-2 production and especially the lymphoproliferative response to IL-2.

Animals↗

PubMedDate not supplied

Seeing but not recognizing.

Visual recognition disturbances are caused by lesions that affect visual cortex as well as white matter connections between visual cortex and temporal and parietal cortex. Homonymous visual field defects are often present but do not explain the recognition difficulty. In "alexia without agraphia" (pure alexia), the intact right visual cortex is disconnected from the left parietal language center by a lesion in the splenium. In "prosopagnosia," visual cortex is disconnected bilaterally from temporal cortex. In simultanagnosia, visual association cortex is damaged. The first condition is most commonly caused by left posterior cerebral artery occlusion, the second by bilateral posterior cerebral artery occlusion or head trauma, and the third by watershed infarction, tumors, abscesses, head trauma, leukoencephalopathies and Alzheimer's disease. When such disorders are suspected, the examiner should supplement the routine visual examination with suggested screening maneuvers.

Adult↗

PubMedDate not supplied

Recall of three words after five minutes: its relationship to performance on neuropsychological memory tests.

This paper examines the statistical relationship between a memory screening test (recall of three words after 5 minutes, 3W5M) and an extensive battery of neuropsychological memory tests. Subjects were 142 consecutive referrals for neuropsychological examination and were given 3W5M in addition to measures of memory, language, and intelligence. Performance on 3W5M was categorized as either "impaired" or "unimpaired" in a manner consistent with judgement used in clinical settings. Linear discriminant function analysis was used to predict 3W5M performance from neuropsychological test scores. Results indicated that 3W5M was a relatively good screening measure, but that its sensitivity and utility as a measure of memory was significantly influenced by the nature of the neurological disorder. Significantly higher diagnostic accuracy rates were obtained in patient groups with clinically obvious memory impairment (e.g., dementia, pure amnesia) than in groups with less obvious memory impairment (e.g., closed head injury, psychiatric disorders). Implications for clinical memory testing, and for the relationship between screening and battery approaches to assessment, are discussed.

Journal Article↗