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Biomedical subjects

E Kaplan

Publications and source records attributed to E Kaplan.

At least 127 records · Page 7Linked to original sources
PubMed1989

The neuropsychology of schizophrenic speech.

Recent interest in the biological basis of schizophrenia has led to a reexamination of many symptomatic aspects of the disorder in terms of brain-behavioral models. Schizophrenic speech disturbances have traditionally been described in terms of a model of acquired aphasia. We review some of the limitations of this model and provide an alternative model for the study of some characteristics of schizophrenic speech based on neuropsychological theories of frontal lobe dysfunction in schizophrenia. The emphasis is placed on the study of productive errors noted in schizophrenic speech, most notably verbal perseverations. In a study of errors observed during a sample of 15 schizophrenics performance on a confrontation naming test, we were able to reliably identify and classify hierarchic categories of verbal perseverations occurring at both semantic and phonemic levels. These perseverations constituted 20% of the total errors. We argue that these perseverations represent a special case of executive dysfunction resulting from a disturbance of language monitoring mechanisms. We examine the implications of these findings for a hypothesis of schizophrenic speech disturbances in terms of frontal lobe dysfunction and the developmental neuropathological processes involved in the illness.

Adult↗
PubMed1989

Linguistic and nonlinguistic impairments in writing: a comparison of patients with focal and multifocal CNS disorders.

The hypothesis that the language disorder in Alzheimer's disease (AD) depends on degenerative brain changes in classical left-hemisphere language zones was tested by comparing the written language performances of a group of AD patients with mild-moderate dementia and left-hemisphere stroke patients with equally severe naming and auditory comprehension deficits who were in varying stages of recovery from Wernicke's aphasia. The results indicated significant qualitative group differences in performances between tasks and in errors within tasks. The findings are consistent with hypothesized disruption of more diffusely organized neurolinguistic systems in AD. The hypothesis that the language disorder in AD represents an exaggeration of the pattern of language change in normal aging was also examined by comparing the performances of AD patients to the changes that occur with very advanced normal aging. The data indicate convergence between AD and very elderly healthy subjects in some aspects of written language production.

Aged↗
PubMed1989

Age-related changes in lipid peroxidation and protective enzymes in the central nervous system.

Brain homogenates were used to measure in vitro formation of thiobarbituric acid reactive substances (TBARS) in 5 CNS regions of 3, 12 and 22 month old male Fischer 344 rats. Glutathione peroxidase, catalase and superoxide dismutase activity in 105,000 x g supernatants of these homogenates was also measured. Results indicated that in vitro TBARS formation declined with age in all 5 areas studied. Glutathione peroxidase, catalase and superoxide dismutase activity did not change with age. Regional differences in the activity of glutathione peroxidase and catalase were noted.

Age Factors↗
PubMed1988

Variations in aphasic language behaviors.

This study reports intraindividual variations in the semantic and syntactic complexity of language and in the linguistic errors produced by mildly and moderately impaired aphasic and nonneurologically impaired control subjects in different communication contexts. Aphasic patients, compared to control subjects, evidenced as many, if not more, linguistic variations in response to changing communication requirements. In conditions that restricted visual contact between speaker and listener, aphasic patients produced fewer communicative gestures and more complex verbalizations. Verbal complexity and language errors also varied significantly with different contents of communication. Measures of verbal complexity and errors in verbal communications were found to vary independently across different communication contexts, contents, and tasks. These findings demonstrate that despite their linguistic impairments, aphasic patients show appropriate and predictable linguistic changes in response to nonlinguistic social contextual variables.

Adult↗
PubMed1988

Background light and the contrast gain of primate P and M retinal ganglion cells.

Retinal ganglion cells projecting to the monkey lateral geniculate nucleus fall into two classes: those projecting to the magnocellular layers of the nucleus (M cells) have a higher contrast gain to luminance patterns at photopic levels of retinal illumination than those projecting to the parvocellular layers (P cells). We report here that this difference in luminance contrast gain between M and P cells is maintained at low levels of mean retinal illumination. In fact, our results suggest that in the mesopic and scotopic ranges of mean illumination, the M-cell/magnocellular pathway is the predominant conveyor of information about spatial contrast to the visual cortex.

Animals↗
PubMed1988

Ten-year-replicated circadian profiles for 36 physiological, serological and urinary variables in healthy men.

At 3-hr intervals over a 24-hr span, 36 systemic, serologic and urinary variables were examined in 7 men in their mid 20's in the Spring of 1969, and again in the same 7 men in the Spring of 1979 under a similar chronobiologic protocol, using the same chemical and numerical analytical procedures. The variables examined for rhythms by cosinor were: vital signs--blood pressure (systolic, diastolic, pulse pressure and mean arterial pressure), heart rate, intraocular pressure (left and right), oral temperature; serum components--albumin, albumin/globulin ratio, total bilirubin, calcium, carbon dioxide, chlorides, bilirubin, cholesterol, globulin, glucose, potassium, sodium, sodium/potassium ratio, transaminase, triglycerides, total protein, urea nitrogen; and urine components--calcium, calcium/magnesium ratio, creatinine, magnesium, pH, potassium, sodium, sodium/potassium ratio, urea clearance, urea nitrogen, volume and zinc. Although all subjects appeared clinically healthy in 1969 and in 1979, certain inter-study differences were observed in a number of rhythm parameters of different variables. Statistically significant increases in mesor for the group as a whole were observed for serum Ca, cholesterol, Cl, CO2, K, Na, and while statistically significant mesor decreases for a group as a whole were noted in serum glucose and transaminase. Statistically significant increases in amplitude for the group as a whole were observed in serum chloride and urinary Na/K ratio, while statistically significant decreases were observed in amplitude for blood pressure, heart rate, serum albumin, A/G ratio, globulin, glucose, protein, sodium and transaminase.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Comparison of the effects of dopamine and fenoldopam, a selective dopamine-1 agonist, on parathyroid hormone release in man.

Dopamine has been reported to transiently increase parathyroid hormone (PTH) secretion in man; however, the mechanism is unclear. To test the hypothesis that selective dopamine-1 receptor (DA1) stimulation increases PTH secretion, we compared the effects of fenoldopam, a novel selective DA1 receptor agonist, as well as dopamine on serum PTH secretion and total serum calcium concentration in seven normal human subjects. Dopamine was infused at 1 and 3 micrograms/kg/min, each for 10 minutes, and 5 micrograms/kg/min for 25 min. Fenoldopam was infused at 0.1 and 0.3 micrograms/kg/min, each for 10 min. and thereafter at 0.5 micrograms/kg/min for 25 min. The infusions were given at least 1 week apart. Blood samples for PTH, calcium and dopamine or fenoldopam concentrations were drawn prior to and at the 25th minute of each drug infusion. PTH concentrations increased in all subjects at the 25th minute of dopamine but not fenoldopam infusion. Serum calcium was not significantly affected. The plasma concentrations of both dopamine (83.6 +/- 7.1 ng/ml) and fenoldopam (13.0 +/- 3.4 ng/ml) were in the range known to cause equivalent DA1 receptor stimulation. Since dopamine but not fenoldopam increased PTH secretion in man, we conclude that selective DA1 receptor stimulation alone does not increase PTH release and the effects of dopamine must be mediated through some other mechanism.

Adolescent↗
PubMed1988

Magnetic resonance imaging with gadolinium-DTPA for detecting cardiac transplant rejection in rats.

To date, no noninvasive tool has gained widespread acceptance as an adequate substitute for endomyocardial biopsy for the diagnosis and grading of cardiac transplant rejection. We examined the potential role of magnetic resonance imaging with gadolinium (Gd)-diethylenetriamine penta-acetic acid (DTPA) image enhancement for the diagnosis of cardiac graft rejection. We studied 15 rats with heterotopic cardiac transplants, nine of which received no immunosuppression, and six of which received cyclosporine, azathioprine, and methylprednisolone. The animals underwent magnetic resonance imaging, which was immediately followed by sacrifice (2-12 days after transplant). Myocardial image enhancement was assessed on T1-weighted images performed before and after administration of Gd-DTPA, 0.5 mmol/kg. Histological specimens were graded I, II, or III to indicate increasing severity of rejection. In the absence of rejection, Gd-DTPA induced mild homogeneous myocardial enhancement. Ten of 11 cases with Grade II or III rejection manifested one or more areas of intense myocardial enhancement. The extent and distribution of intense myocardial enhancement corresponded to the severity and distribution of histological rejection. Quantitative myocardial enhancement, expressed as the ratio of maximal signal intensity after Gd-DTPA to signal intensity before Gd-DTPA administration, separated Grade I animals (1.61 +/- 0.27; mean +/- SD) from Grades II (2.89 +/- 0.58) and III (3.10 +/- 0.77; p less than 0.01) animals. In conclusion, cardiac transplant rejection is characterized by intense T1-weighted image enhancement after administration of Gd-DTPA. Magnetic resonance imaging with Gd-DTPA thus has potential application in the clinical diagnosis of cardiac transplant rejection.

Animals↗
PubMed1988

Abnormal orientation bias of LGN neurons in strabismic cats.

The reduced visual sensitivity of strabismic amblyopes is often accentuated when they view vertical as opposed to horizontal gratings ("vertical effect"). Earlier attempts to show neurophysiological correlates of the vertical effect in strabismic cats have yielded controversial findings. We now report the results of experiments in the lateral geniculate nucleus (LGN) that clearly demonstrate the reduced sensitivity of X-cells in strabismic cats to vertical gratings as compared to horizontal ones. We conclude that the neural basis for the vertical effect is present at least at the level of the LGN.

Animals↗
PubMed1987

A randomized study of methotrexate, bleomycin, hydroxyurea with versus without cisplatin in patients with previously untreated and recurrent squamous cell carcinoma of the head and neck.

The value of a combination of methotrexate, bleomycin and hydroxyurea with vs. without cisplatin was randomly examined in 62 evaluable patients with previously untreated (44 patients) and recurrent (18 patients) squamous cell carcinoma of the head and neck. Methotrexate (30 mg/m2) and bleomycin (15 mg) were given intravenously weekly, hydroxyurea (1000 mg/m2) per os 3 times per week for 4 weeks. Cisplatin (60 mg/m2) was added on Day 1 every month. A higher overall response rate was observed with the cisplatin-containing regimen (66%, included 17% complete) as compared with 27% (3% complete) with the 3-drug combination (P value 0.0025). The cisplatin-containing regimen was more active in both previously untreated patient group and in the group recurrent patients. Toxicity was more pronounced in the cisplatin regimen and necessitated frequently reduced drug dosages. No survival difference was observed between the treatment groups. Median survival in previously untreated patients was 16.2 months and 7.2 months in patients who failed conventional local treatment. It is concluded that a cisplatin-containing regimen is more effective in advanced head and neck carcinoma than the same combination without cisplatin.

Adult↗
PubMed1987

Time-based multiple organ functional images.

Computer generation of functional images has gained recognition as a valuable method of analyzing physiologic data. However, most mathematical models used to produce these images are frequency-based, which requires that the entire function be examined. Because frequency-based characteristics are only indirectly related to physiologic characteristics, this technique has inherent deficiencies that may be minimized through various manipulations. Our technique is to base such images on time-related features, rather than frequency-based. This technique deals directly with regional count rate behavior, which in turn reflects function. Benefits from such an approach include the ability to generate images from isolated portions of an event and the removal of sinusoidal models that may or may not accurately represent function. Our experience with such an approach to the generation of functional images of the heart, lungs, and liver has been highly successful.

Adult↗
PubMed1987

Circadian rhythms in Limulus photoreceptors. I. Intracellular studies.

The sensitivity of the lateral eye of the horseshoe crab, Limulus polyphemus, is modulated by efferent optic nerve impulses transmitted from a circadian clock located in the brain (Barlow, R. B., Jr., S. J. Bolanowski, and M. L. Brachman. 1977. Science. 197:86-89). At night, the efferent impulses invade the retinular, eccentric, and pigment cells of every ommatidium, inducing multiple anatomical and physiological changes that combine to increase retinal sensitivity as much as 100,000 times. We developed techniques for recording transmembrane potentials from a single cell in situ for several days to determine what circadian changes in retinal sensitivity originate in the primary phototransducing cell, the retinular cell. We found that the direct efferent input to the photoreceptor cell decreases its noise and increases its response. Noise is decreased by reducing the rate of spontaneous bumps by up to 100%. The response is increased by elevating photon catch (photons absorbed per flash) as much as 30 times, and increasing gain (response per absorbed photon) as much as 40%. The cellular mechanism for reducing the rate of spontaneous quantum bumps is not known. The mechanism for increasing gain appears to be the modulation of ionic conductances in the photoreceptor cell membrane. The mechanism for increasing photon catch is multiple changes in the anatomy of retinal cells. We combine these cellular events in a proposed scheme for the circadian rhythm in the intensity coding of single photoreceptors.

Animals↗