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Biomedical subjects

B Schwartz

Publications and source records attributed to B Schwartz.

At least 361 records · Page 20Linked to original sources
PubMed1980

Spontaneous trends in ocular pressure in untreated ocular hypertension.

Sixty ocular hypertensive patients receiving no treatment with ocular pressures of 21 mm Hg or more were followed up for a median time of 42 months for changes in ocular pressure. Three significant patterns were observed--stability, downward trend, or an upward trend. The majority of patients showed relatively stable pressures over the course of time. Cyclic swings of pressure over one- or two-year periods were also observed. A group of 43 normal patients with ocular pressures less than 21 mm Hg showed no trends of pressure with time except for three who had a small increase. For some patients, ocular hypertension appears to be a specific entity that represents either stable pressures with time or an episode of increased pressure that eventually decreases. In patients whose pressures continue to increase, ocular hypertension may become true glaucoma. Evaluation of the course of ocular hypertension in relation to diagnosis and treatment is important, especially in terms of the efficacy of treatment.

Adult↗
PubMed1980

Two-point fluorophotometry in the evaluation of glaucomatous optic disc.

The two-point fluorophotometry technique was used to analyze quantitatively absolute fluorescein filling defects or hypofluorescent areas in glaucomatous optic discs. Significant differences were found between hypofluorescent and normal fluorescent areas. The hypofluorescent areas had slower and lesser filling of fluorescein and a slower disappearance of fluorescein compared with normal fluorescent areas. Also, the hypofluorescent areas showed a slow and persistent accumulation of fluorescein. Age, blood pressure, ocular pressure, and percent area of optic disc pallor were significantly correlated with changes in the circulation in the areas of normal fluorescence and hypofluorescence. This study suggests a decreased blood flow and a smaller vascular bed together with narrower vessels and increased permeability of the vessels in the hypofluorescent areas.

Age Factors↗
PubMed1980

Fluorescein angiography of the optic disc. A longitudinal follow-up study.

A comparison of two or more disc fluorescein angiograms performed on separate occasions was done on 60 eyes of normal subjects and patients with ocular hypertension, primary open-angle glaucoma, and low-tension glaucoma. Clinically stable patients did not show any change in their disc angiographic filling patterns. Eyes that developed new visual-field defects with increased disc cupping and pallor correspondingly showed new absolute filling defects or areas of hypofluorescence. In those with established field defects, however, further changes in the visual field occurred without obvious changes in the disc fluorescein filling defect. Surgical lowering of intraocular pressure with or without decrease in disc cupping and pallor did not result in visible improvement of the disc angiographic pattern. Thus, the development of new visual-field defects is associated with changes of the circulation of the optic disc.

Adult↗
PubMed1980

Increased fluorescein filling defects in the wall of the optic disc cup in glaucoma.

One hundred seventy-one optic disc fluorescein angiograms of glaucomatous, ocular hypertensive, and normal patients were studied for the occurrence of areas of hypofluorescence or absolute filling defects in the rim, wall, and floor of the optic cup using disc stereo photographs compared with the fluorescein angiogram. The frequencies of involvement of the rim, wall, and floor of the cup by filling defects were determined. The wall of the cup has a greater percentage of filling defects in subjects with glaucoma than in ocular hypertensive or in normal subjects. The floor of the cup has more filling defects in normal subjects than in those with glaucoma. The involvement of the wall of the cup increases with the degree of visual-field loss in glaucoma. We suggest that, in glaucoma, the effect of ocular pressure is greater on the wall of the cup than on the floor of the cup.

Fluorescein Angiography↗
PubMed1980

Age, increased ocular and blood pressures, and retinal and disc fluorescein angiogram.

From the densitometric and time curves of fluorescein angiograms of matched groups of normal, ocular hypertensive, and glaucomatous eyes, the time and rate of filling of the retinal arteries and veins, optic disc, and peripapillary choroid were measured. In the whole population of eyes, with increasing age there was a decreased rate of filling of the retinal arteries, optic disc, and the peripapillary choroid. With increased diastolic blood pressure, increased time was needed to fill the peripapillary choroid. Increased ocular pressures and decreased tonographic outflow facility were particularly correlated with the decreased filling of the retinal veins and the disc. Significant differences of circulatory changes in the retinal arteries and veins were obtained between the normal, ocular hypertensive, and glaucomatous eyes. Further evaluation of these circulatory events could be clinically useful, especially in differentiating normal from ocular hypertensive eyes in relation to the effect of ocular pressure on the retinal and disc circulations.

Age Factors↗
PubMed1980

A scleral buckle pressure gauge for continuous monitoring of intraocular pressure.

An implantable variable resistance pressure gauge has been constructed from a conductive elastomere in the form of a scleral buckle which is suitable for recording intraocular pressure in vivo continuously over an indefinite period of time. The similarity of the pressure transducer to the standard scleral buckles used to reduce retinal detachments suggests that it will be tolerated over a period of years without significant effect on intraocular pressure. The electrical output from these pressure gauges appears to be both well defined and of sufficient magnitude to operate a valve to control intraocular pressure.

Animals↗
PubMed1980

Cataract surgery in the United States, 1968--1976. A descriptive epidemiologic study.

Several large United States data sources were examined to determine the trend in cataract surgery for the eight-year period 1968--1976. Age-stratified rates of intracapsular cataract extractions were calculated to control for changes in the age structure of the population. Cataract extractions increased steadily at the rate of 4.2% per year. A number of medical, social, and economic factors appear to be involved in this increase. The relative contribution of some of these factors was determined through examination of data related to hospitalizations for cataracts and the availability of ophthalmic services. Additionally, the increasing demand for better vision among the elderly was estimated by examining the increase of drivers' licenses in force for this period.

Adult↗
PubMed1980

Development of complex, stereotyped behavior in pigeons.

A pigeon's peck on one key moved a light down one position in a 5x5 matrix of lights, while a peck on another key moved the light across one position. Reinforcement depended upon the occurrence of four pecks on each key (moving the matrix light from the top left to the bottom right), and a fifth peck on either key ended a trial without food. Though there were 70 different sequences that led to reinforcement, each of 12 pigeons developed a particular, stereotyped sequence which dominated its behavior (Experiment 1). Extinction produced substantial increases in sequence variability (Experiment 2). Removal of the matrix cues disrupted performance, though it partially recovered with extended training (Experiment 3). The pigeons did not master a contingency which required a different sequence on the current trial than on the previous one (Experiment 4), though they were able to learn to emit sequences which began with either left-left or left-right response patterns (Experiment 5). The experiments suggest that contingencies of reinforcement may contribute to the creation of complex units of behavior, and that stereotypy may be a likely consequence of contingent reinforcement.

Journal Article↗
PubMed1979

Essential fatty acid deficiency in total parenteral nutrition. Detection by changes in intraocular pressure.

Essential fatty acid deficiency (EFAD) has been commonly and readily diagnosed during fat-free total parenteral nutrition (TPN), with only vague awareness of possible functional and clinical derangements secondary to essential fatty acid deficiency. Arachidonic acid is known to be a precursor for prostaglandin (PG) synthesis. Prostaglandins are known to be intermediaries between stimulus and cellular response in a variety of physiologic and pathologic processes; one would suspect therefore that EFAD would result in PG deficiency with resultant multiple derangements in functions regulated by PG. We tested this hypothesis by serially measuring intraocular pressure (IOP) in patients before and during fat-free TPN and after supplementing these patients with fat. In the eye as well as in various other organs PG are believed to act as mediators of adrenergic neurotransmission by a negative feedback mechanism. As catecholamines are potent ocular hypotensive agents, decreased levels of PG due to EFAD will cause increase in catecholamine turnover with a reduction in IOP. Two groups of patients matched as to their age, sex, nutritional status and diseases were studied. One group (control) was receiving a normal diet or fat-containing TPN while the other group was receiving fat-free TPN. IOP in the fat-free TPN group dropped from 13.7 +/- 0.4 mmHg pre-TPN to 9.3 +/- 0.5 mmHg during the first week of fat-free TPN. Within two weeks after supplementation of fat or return to normal oral diet IOP returned to 13.9 +/- 0.3 mmHg. Prostaglandin levels, which were 0.025 +/- 0.004 ng/ml pre-TPN or in control patients decreased to 0.012 +/- 0.002 ng/ml (p < 0.001) during fat-free TPN, to return to normal after fat was added to TPN regime or patients returned to normal oral diet. During fat-free TPN linoleic acid levels decreased to 40% of its initial value with a mild increase upon the addition of fat, while eicosatrienoic acid and the triene:tetraene ratio increased to 6.5 times their initial values. Arachidonic acid levels did not change during fat-free TPN or after repletion with fat. Intraocular pressure determination seem to be a simple, harmless, inexpensive, reliable and sensitive indicator of EFAD. Moreover, IOP determination represent a functional derangement which in a clinical setting lends functional credence to the biochemical changes of EFAD whose entire significance has not yet been determined. Similarly, serial IOP determinations are sensitive in detecting adequate functional repletion of EFAD. As PG are known to act as intermediaries in a variety of physiological processes it seems reasonable to assume that the change in IOP is only one of many different changes and derangements to occur as a result of PG and EFA deficiency.

Adult↗
PubMed1979

Electron microscopic radioautographic identification of the ECL cell as the histamine-synthesizing endocrine cell in the rat stomach.

Rat gastric oxyntic glands contain argyrophil "enterochromaffin-like" endocrine cells that synthesize and store histamine and also have APUD ability--they can take up exogenous L-5-hydroxytryptophan (5-HTP), can decarboxylate it to 5-hydroxytryptamine (5-HT, serotonin) by the enzyme DOPA-decarboxylase, and can store the amine. Previous cytochemical studies suggested that these cells correspond to both the ECL and A-like cells, the two predominant endocrine cells identified by electron microscopy (EM) in rat oxyntic glands. In a recent study, however, we demonstrated that the ECL but not the A-like cell exhibited APUD ability when rat gastric mucosa was incubated with H3-5-HTP and studied by EM radioautography. The purpose of the present study was to identify by EM radioautography the histamine-synthesizing endocrine cells in the rat stomach. Pieces of rat (male Sprague-Dawley) gastric mucosa were incubated in organ culture with L-H3-histidine (50 muCi, 1.8 x 10(-5) M) with and without inhibitors and were processed for LM and EM radioautography. H3-histidine labeled the ECL cells heavily but the A-like and other endocrine cells only lightly. The labeling of ECL cells was only modestly reduced by cycloheximide, an inhibitor of protein synthesis, whereas the labeling of A-like and other endocrine cells was almost abolished. In contrast, the labeling of ECL cells was markedly reduced by 4-bromo-3-hydroxybenzyloxyamine (NSD-1055), an inhibitor of histidine decarboxylase and DOPA decarboxylase, but was not appreciably affected by carbidopa, an inhibitor of only the DOPA decarboxylase. Incubations with H3-histamine (50 muCi, 0.9 x 10(-5) M) failed to label endocrine cells. Thus, this study demonstrates that the ECL but not the A-like cell is the histamine-synthesizing endocrine cell of the rat stomach.

APUD Cells↗
PubMed1979

University center and community hospital: problems in integration.

This study of health care in Chicago and its suburbs deals with a dilemma faced by many university hospitals located in our nation's metropolitan areas. Because of a massive displacement of population from the city to its suburban ring, some of the major medical centers in Chicago's inner zone have experienced a leveling-off of inpatient admissions. In contrast, outer zone and suburban community hospitals are in need of referral sources with specialized personnel and equipment to accommodate growing admissions. This imbalance would be corrected in a regional network based on an exchange of clients and services. A case study of the University of Chicago Medical Center highlights the tensions, strains, and resistances which inhibit the development of such a system and thus raises questions about the role of the research and teaching hospital in regional health care planning.

Chicago↗
PubMed1978

Stimulus-reinforcer contingencies and local behavioral contrast.

Four pigeons were exposed to a series of multiple schedules of variable-interval reinforcement in which pecks were required on one key (operant key) and components were signalled on a second key (signal key). Four additional pigeons experienced identical conditions, except that a yoking procedure delivered food on variable-time schedules, with no key pecks required. One of the components of the multiple schedule was constant throughout the experiment as a variable-interval (or variable-time) 30-second schedule. Operant-key responding during the constant component was uniform throughout the component, uninfluenced by changes in the duration of the variable component, and only slightly influenced by changes in reinforcement frequency correlated with the variable component. By comparison, signal-key response rate during the constant component was highest at the onset of the component, was higher when the variable component was 60-sec long than when it was 1-sec long, and was higher when no reinforcement occurred in the variable component than when reinforcement was scheduled in the variable component. These characteristics of signal-key pecking matched characteristics of local positive behavioral contrast. These data are taken to support the "additivity theory" of behavioral contrast and to suggest that Pavlovian stimulus-reinforcer relations contribute primarily to the phenomenon of local positive contrast.

Journal Article↗