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Biomedical subjects

E Kaplan

Publications and source records attributed to E Kaplan.

At least 199 records · Page 11Linked to original sources
PubMed1982

Time--domain analysis in gated cardiac blood pool studies.

A technique is presented for producing functional images derived from equilibrium gated blood pool studies as a means of diagnosing cardiac disease. These functional images are based on characteristics associated with the time variation of the count rate (the time domain) at each point of the image matrix rather than on the Fourier transform of the time-activity curve (the frequency domain) which has gained recent attention. As examples of this method, we present images which display the statistical variance of the time-activity curve at each pixel, corrected for the expected contribution due to random statistical fluctuation, and images which display the time at which each pixel reaches its minimum count value. Variance and time-to-minimum images are comparable to Fourier amplitude and phase images, respectively, and have been found to be useful in facilitating the diagnosis of wall motion abnormalities. A major advantage of time-domain analysis is the wide variety of features of potential clinical significance which may be investigated.

Fourier Analysis↗
PubMed1982

X and Y cells in the lateral geniculate nucleus of macaque monkeys.

1. Cells of the lateral geniculate nucleus (l.g.n.) in macaque monkeys were sorted into two functional groups on the basis of spatial summation of visually evoked neural signals. 2. Cells were called X cells if their responses to contrast reversal of fine sine gratings were at the fundamental temporal modulation frequency with null positions one quarter of a cycle away from positions for peak response. Cells were called Y cells if their responses to such stimuli were at twice the modulation frequency and were approximately independent of spatial phase. 3. Ninety-nine percent of the cells in the four dorsal parvocellular layers of the l.g.n. were X cells; about seventy-five percent of the cells in the two ventral magnocellular layers were also X cells. The remainder were Y cells. 4. We confirmed previous findings that magnocellular cells had a shorter latency of response to electrical stimulation of the optic chiasm. 5. Magnocellular cells had much higher contrast sensitivities than did parvocellular cells. 6. Therefore, two distinct classes of X cells exist in the macaque l.g.n.: parvocellular X cells and magnocellular X cells. The great difference in their properties suggests that they have different functions in vision. The Y cells in the magnocellular layers form a third functional group with spatial properties distinctly different from the X cells. 7. We propose that the magnocellular layers of the macaque monkey's l.g.n. may be homologous to the A and A1 layers of the cat's l.g.n.

Animals↗
PubMed1982

Dynamic imaging of the respiratory cycle with 81mKr.

To define the regional ventilation of the human lung, subjects were monitored with a gamma camera, while breathing air labeled with radioactive 81mKr which is being continuously eluted from a generator. The information observed is displayed as a reiterated multiframe moving picture. This is accomplished by storing the information from multiple breaths, selecting acceptable cycles (determined by the duration of inspiration and expiration and the amplitude to extremes of the cycles), and normalizing the usable information and converting the summed data into sequential frames, which are repeatedly shown on a video screen from computer memory.

Computers↗
PubMed1981

An apparent increase in the incidence of acute nonlymphocytic leukemia in black children.

A community-wide study was conducted to examine time trends in incidence rates of leukemia in children. Cases of acute leukemia, both lymphocytic (ALL) and nonlymphocytic (ANLL), newly diagnosed in children ages 0-19 years in the Baltimore area from 1960 to 1974 were ascertained. Over the 15 years, 286 children with acute leukemia were identified, of whom 77% had ALL. Incidence rates of ALL were two to three times as high in whites as in blacks, and remained virtually unchanged over time. However, the picture was quite different for ANLL. Initially, incidence rates were higher in whites than in blacks, but during the final five years the incidence increased dramatically in blacks so that it actually exceeded the rate among whites. The increase of ANLL in black children occurred primarily in blacks of high socioeconomic status. This suggests that the increase may have resulted from environmental influences associated with upward socioeconomic mobility in the black population in recent years.

Adolescent↗
PubMed1981

The effect of monocular paralysis on the lateral geniculate nucleus of the cat.

The proportions and some of the properties of X and Y cells in lateral geniculate nucleus (LGN) of adult cats were measured 14-16 days after monocular paralysis. The paralysis was produced by sectioning cranial nerves III, IV and VI. No difference from normal was observed in the proportions of X and Y cells either in the A layer driven by the paralyzed eye or in the A1 layer driven by the mobile eye. The distribution of latencies to chiasm stimulation and the average visual spatial resolution were within the normal range in both A and A1 layers. These experiments indicate that monocular paralysis in the adult cat does not affect the numbers of X and Y cells in the LGN. However, the averages of cell body size in layers A and A1 contralateral to the immobilized eye were roughly equal, whereas in the normal cat cells in layer A1 are larger than those in layer A.

Animals↗
PubMed1980

Circadian clock in Limulus brain increases response and decreases noise of retinal photoreceptors.

The sensitivity and structure of ommatidia in the Limulus lateral eye exhibit circadian rhythms. The cyclic changes are mediated by the activity of efferent optic nerve fibres that originate in the brain and terminate in the retina. We report here that the effects of the efferent input to the retina are detectable in single photoreceptor cells. At night the efferent input decreases photoreceptor noise (discrete waves of the membrane potential in darkness) and increases the photoreceptor response to light (amplitude of the receptor potential).

Animals↗
PubMed1980

Lateralized asymmetries in self-perception.

Thirty right-handed males and females, displaying happy and sad expressions, compared left-left and right-right composites of his/her own face. For each pair of composites, depicting one emotional state, subjects chose that composite which (a) looked most like themselves and (b) depicted the more intense emotion. The results for females failed to support the contention that the right hemisphere specializes in the perception of negative affect whereas the left hemisphere is prominent for positive states. Finally, asymmetries were more pronounced in females rather than males.

Brain Mapping↗
PubMed1980

Bicuculline enhances a negative component and diminishes a positive component of the visual evoked cortical potential in the cat.

Visual evoked potentials (VEPs), elicited by modulation of luminance of homogeneous fields of light, were recorded from the scalp and from the surface of the visual cortex of cats before and after topical application of bicuculline to the cortex. The application of this drug drastically altered the VEP: the amplitude of a normally small negative component was increased greatly, and a normally prominent late positive component was diminished. Bicuculline is known to block the action of gamma-aminobutyric acid, which is thought to be the primary inhibitory neurotransmitter in the visual cortex. We suggest, therefore, that the affected negative wave reflects an excitatory process in the visual cortex and that the affected late positive wave reflects an intracortical inhibitory process.

Animals↗
PubMed1980

Effect of pargyline on hepatic glutathione levels in rats treated acutely and chronically with ethanol.

A single dose of pargyline severely depleted hepatic reduced glutathione (GSH) levels in the rat. Ethanol administration, acute or chronic, had no effect on hepatic GSH levels; nor did such administration exacerbate the pargyline mediated GSH depletion. However a single dose of ethanol given one hour after pargyline administration enhanced the rate of recovery of hepatic GSH.

Alcoholism↗