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Biomedical subjects

S Horenstein

Publications and source records attributed to S Horenstein.

At least 19 recordsLinked to original sources
PubMed1992

Cerebral lateralization and color perception: a transcranial Doppler study.

Eight normal subjects were examined in dark, light and color conditions. Mean cerebral blood flow velocity (MBFV) were recorded almost simultaneously from their posterior cerebral arteries (PCA) using transcranial Doppler (TCD) ultrasound. The side-to-side difference was significant during the dark (p = 0.0159) and color stimulation (p = 0.0001) but not in light condition. This side-to-side difference in MBFV was used to characterize lateralization of color perception. This showed that the right PCA was always greater than the left during the presentation of color stimuli. Primary psychological colors (blue, yellow, red and green) induced greater lateralization as compared with color resulting from a mixed blue-green wavelength. This suggests that the right visual cortex is selectively sensitive to wavelengths.

Adolescent↗
PubMed1991

Fourier analysis of the cerebrovascular system.

We performed Fourier analysis of the middle cerebral artery blood flow velocity waveform envelope in 14 normal subjects (group A) and 15 patients, of whom five had arteriovenous malformations (group B), five had cerebral vasospasm (group C), and five had arterial hypertension (group D). Measurements were obtained under conditions of normocapnia, hypercapnia, and hypocapnia. The Fourier coefficients measured in the first five harmonics of the Doppler waveforms of group A were used as the reference baseline and were compared with the coefficients found in the other three groups. Group B showed significantly lower Fourier coefficients, while groups C and D showed higher coefficients (p less than 0.05). The elevation of the Fourier coefficients occurred in an alternating pattern in group C and a decremental pattern in group D. This distinction was attributed to possible differences in the underlying pathophysiological processes. The degree of vascular distensibility of the cerebral arterioles, inferred from the shape of the Fourier analysis curves, was compared in all four groups. Vascular distensibility was characterized as abnormal in arteriovenous malformations, vasospasm, and arterial hypertension. Fourier coefficients may be better indicators of cerebrovascular abnormalities than mean blood flow velocity in hypertension and pulsatility index in arteriovenous malformations, vasospasm, and hypertension.

Adult↗
PubMed1989

Microvasculopathy may precede idiopathic cerebral calcifications--case report.

Cerebral and cerebellar calcifications were discovered by computerized tomography (CT) in a man who presented with a dementing illness characterized by progressive memory loss, irritability, and dystonia. He had no known family. Magnetic resonance imaging showed areas of absent signal corresponding to the calcifications and areas of high-intensity signal on the T2-weighted images without counterpart on the CT. These are postulated to be static liquid pools secondary to endothelial membrane incompetence and leakage of plasma-derived fluid.

Basal Ganglia Diseases↗
PubMed1989

Chronic low back pain and the failed low back syndrome.

Disorders associated with back pain usually have two components. One pertains to the spinal disorder and the other to symptoms and signs that result from compromise of individual nerve roots, the cauda equina, or, in some cases, the conus medullaris. In this article, those spinal structures capable of giving rise to pain, its approximate distribution, the nature of the discomfort and disturbance of spinal and neural function consequent upon disease of the vertebral column, and the evaluation and management of the individual patient will be considered.

Back Pain↗
PubMed1986

AB variant GM2 gangliosidosis: cerebrospinal fluid and neuropathologic characteristics.

A child with AB variant GM2 gangliosidosis who had progressive intellectual deterioration and seizures commencing at the age of 12 months is described. Neuronal loss, and neuronal and astrocytic inclusions characteristic of the gangliosidoses, were seen on cortical biopsy. GM2 ganglioside was detected in the CSF. As CNS ganglioside accumulation in this condition occurs in the presence of normal leukocyte hexosaminidase A and B levels, spinal fluid assay for GM2 ganglioside may serve as a valuable aid in diagnosis.

Cerebral Cortex↗
PubMed1984

Somatosensory-evoked potentials in spinal cord injuries.

Short-latency somatosensory-evoked potentials after peroneal nerve stimulation were recorded in 25 patients with long-standing incomplete spinal cord injuries. The results were correlated with the patient's ability to walk. Nine patients had normal latencies, and four of these patients had no useful function in their lower limbs. Sixteen patients had prolonged latencies, and eight of these had useful ambulation. It is concluded that the scalp-recorded somatosensory-evoked potentials from peroneal nerve stimulation does not reliably predict function after spinal cord trauma.

Adult↗
PubMed1981

Auditory evoked potentials in bacterial meningitis.

Auditory evoked potentials obtained on infants and children recovering from bacterial meningitis are effective in early and reliable detection of sensorineural deafness, particularly in those who demonstrate absence of wave I.

Child, Preschool↗
PubMed1978

Primary leptomeningeal melanoma: an ultrastructural study.

A primary leptomeningeal melanoma in a 19-year-old white women has been shown by electron microscopy to contain light and dark cells. The light cells fill the subarachnoid space, contain mature melanosomes and exhibit intracytoplasmic fine fibrils. The dark cells are found within the collagen network of pia-arachnoid. They possess a small rim of ribosomal-rich cytoplasms, occasional premelanosomes and no intracytoplasmic fibrils. The tumor cells appear to arise from these dark activated melanoblasts in the pia-arachnoid and proliferate into more differentiated light cells. A similar pattern of two types of cells has not been described in primary CNS melanomas. The possibility of differentiation from cutaneous melanoma is discussed.

Adult↗
PubMed1978

The effect of epinephrine on phenylethanolamine N-methyltransferase in cultured explants of adrenal medulla.

The investigation reported here was designed to gain further insight into the mechanisms by which phenylethanolamine N-methyltransferase (PNMT) is regulated. Explants of adrenal medullae were cultured in defined media for up to 48 h, during which time the tissue remained histologically intact. Addition of epinephrine to the medium led to a diminution in the activity of PNMT, measurable in the dialyzed homogenates of the cultured tissue. The enzyme activity was inversely proportional to the concentration of epinephrine present in the culture medium. A diminution in the amount of PNMT protein also resulted from incubation of the explants in the presence of epinephrine. The extent of loss of PNMT, measured by immunochemical titration, corresponded to the degree of loss in PNMT activity under the same conditions. None of the metabolites of epinephrine, including 3,4-dihydroxy- or 3-methoxy-4-hydroxymandelate, or metanephrine, had an effect on PNMT. Tyrosine hydroxylase and catechol O-methyltransferase activities were also diminished, whereas tyrosine transaminase, acid phosphatase, and monoamine oxidase activities were not affected by addition of epinephrine to the medium. Ascorbic acid added to the medium prolonged the lifetime of epinephrine but did not alter the degree of diminution of PNMT. The results obtained are consistent with the view that epinephrine is rapidly assimilated into the cytoplasm of medullary cells and plays an important role in regulating the concentration of PNMT in the adrenal gland.

Adrenal Medulla↗