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Biomedical subjects

B Schwartz

Publications and source records attributed to B Schwartz.

At least 343 records · Page 19Linked to original sources
PubMed1982

Failure to produce response variability with reinforcement.

Two experiments attempted to train pigeons to produce variable response sequences. In the first, naive pigeons were exposed to a procedure requiring four pecks on each of two keys in any order, with a reinforcer delivered only if a given sequence was different from the preceding one. In the second experiment, the same pigeons were exposed to this procedure after having been trained successfully to alternate between two specific response sequences. In neither case did any pigeon produce more than a few different sequences or obtain more than 50% of the possible reinforcers. Stereotyped sequences developed even though stereotypy was not reinforced. It is suggested that reinforcers have both hedonic and informative properties and that the hedonic properties are responsible for sterotyped repetition of reinforced responses, even when stereotypy is negatively related to reinforcer delivery.

Journal Article↗
PubMed1982

Interval and ratio reinforcement of a complex sequential operant in pigeons.

Pigeons were required to produce exactly four pecks on each of two keys in any order for reinforcement. Correct response sequences were reinforced on either fixed-interval two-minute or fixed-ratio four schedules, with each correct sequence treated as a single response. Each pigeon developed a particular dominant sequence that accounted for more than 80% of all sequences. Sequence stereotypy was relatively unaffected by the temporal properties of the fixed-interval and fixed-ratio schedules. Response time (time from the first response in each sequence to the last) was also relatively unaffected by the temporal properties of the schedules. In contrast, response latency (time from end of one sequence to the beginning of the next) was markedly affected by the schedules. Latencies were long early in the interreinforcement interval and got shorter as the interreinforcement interval progressed. These data suggest that stereotyped response sequences become functional behavioral units, resistant to disruption or alteration by reinforcement variables that ordinarily influence the temporal spacing of individual responses.

Journal Article↗
PubMed1982

Dog serum albumin as an allergen. IgE, IgG and lymphocyte responses in dog dander-sensitive asthmatic children.

To study the allergenicity of dog serum albumin (DSA) in dog-sensitive subjects, we investigated 203 asthmatic children by means of the skin prick test (SPT), the radioallergosorbent test (RAST) and the in vitro lymphocyte stimulation test. Significant SPT reactions to DSA were observed in only 9 out of 80 subjects with a significantly positive SPT reaction to dog dander and hair (DDH). Analogously, positive DSA RAST results were observed only in a minority of the cases with a positive DDH RAST. Significant SPT reactions to DSA were not observed in subjects with a negative clinical history of dog allergy, or in subjects with a negative reaction to DDH in the SPT or in the provocation test. DSA induced remarkable lymphocyte stimulation in only 1 subject, who also had a significant SPT reaction to DSA. DSA-specific serum IgG antibody titers measured by ELISA were not found to correlate with DSA SPT or DSA RAST.

Adolescent↗
PubMed1982

Increased concentration of glucocorticoid receptors in rabbit iris--ciliary body compared to rabbit liver.

Dexamethasone binding to both rabbit iris-ciliary body and rabbit liver glucocorticoid receptors was compared by means of a batch assay in which the binding components were adsorbed to hydroxylapatite. The results showed that homogenates of both the rabbit iris-ciliary body and the rabbit liver contained a single class of high-affinity receptors. Binding affinity was virtually identical for the two receptors. A comparison of total binding sites in homogenates of the iris-ciliary body and the liver revealed that the iris-ciliary body glucocorticoid receptor was present in nearly twice the concentration of the hepatic receptor.

Adsorption↗
PubMed1981

Episcleral venous pressure. Differences between normal, ocular hypertensive, and primary open angle glaucomas.

The pressures of the episcleral veins of 20 normal patients, 29 patients with ocular hypertension, and 22 patients with treated primary open angle glaucoma were measured by an air pressure chamber device mounted on a slitlamp. The episcleral venous pressures (EVPs) of the patients with ocular hypertension were found to be significantly lower than those of the patients with glaucoma and the normal patients. The EVP was also found to be significantly negatively correlated with the ocular pressure (OP), so that the EVP decreases as the OP increases. A logarithmic model of the form EVP = 19.41 - 3.65 1n OP was found to best fit the data.

Adult↗
PubMed1981

Fluorescein angiography. Demonstration of flow pattern of anterior ciliary arteries.

With fluorescein angiography of the episcleral region at two frames per second, the wide, tortuous vessels perforating the sclera near the limbus were shown to first fill with fluorescein at an average of 19 s after intravenous injection of fluorescein. These perforating vessels should be called the anterior ciliary arteries because they are the first vessels to fill with fluorescein, fill at the same time the iris fills, give out branches, have higher pressure compared with veins, and show pulsations when the pressure is applied to them. In addition in most cases, distinctly different veins that fill laminarly or fully were seen. The first filling with fluorescein occurred at the scleral perforation point and proceeded posteriorly toward the recti muscles. This finding is in contrast to the accepted concept that the anterior ciliary arteries, as the continuation of the muscular arteries, as the continuation of the muscular arteries, fill from the region of the recti muscles. No significant differences were observed in the fluorescein angiographic patterns of the episcleral vessels between normal eyes, ocular hypertensive eyes, and eyes with primary open angle glaucomas.

Adult↗
PubMed1981

Absence of lymphocyte glucocorticoid hypersensitivity in primary open angle glaucoma.

The glucocorticosteroid sensitivity of patients with primary open angle glaucoma and normal patients was determined by the quantity of dexamethasone required to reduce concanavalin A-induced lymphocyte blast transformation to 50% of control values (I50). This was performed under culturing conditions employing both serum-free medium and medium supplemented with 10% autologous serum. A comparison of the I50 between normal subjects and those with primary open angle glaucoma did not show a significant difference in steroid sensitivity under either of the two culturing conditions. It is concluded that persons with primary open angle glaucoma do not have a generalized inherited or acquired cellular hypersensitivity to glucocorticoids.

Adult↗
PubMed1981

Differences of adrenal stress control mechanisms in subjects with glaucoma and normal subjects. Effect of vasopressin and pyrogen.

Various types of glaucomatous and normal subjects were tested for the adequacy of the stress response of their hypothalamic-pituitary-adrenal axis to pyrogen and vasopressin. With pyrogen, a significant response of elevation of plasma cortisol levels was positively correlated with ocular pressure and changes of the optic disc. Those subjects with increased ocular pressure and optic disc cupping and pallor had greater rises of plasma cortisol levels. With vasopressin, a decreased response of plasma cortisol levels was negatively correlated with the degree of elevated ocular pressure. Those subjects with increased ocular pressure and lower tonographic outflow facilities had smaller rises of plasma cortisol levels. Both tests indicated a disturbance of the hypothalamic-pituitary-adrenal axis in subjects with glaucoma.

Female↗
PubMed1981

Increased plasma cortisol levels in ocular hypertension.

Significant differences in plasma cortisol levels were found between patients with elevated ocular pressure and those with normal ocular pressure. The higher levels of plasma cortisol occurred in patients with higher ocular pressures. This significant separation was particularly related to the ocular pressure at the time of the plasma cortisol sampling; it was not related to other ocular factors or to systemic factors other than blood pressure (BP). Associated with the difference in levels of plasma cortisol was a significant difference in both systolic and diastolic BP between these two groups. Significant positive correlations were also found between plasma cortisol values and systolic BP and between ocular pressure and systolic BP. We concluded that an elevated plasma cortisol level is closely related to the pressure in the eye at the time of the cortisol sampling.

Adult↗
PubMed1981

6-hydroxydopamine in the treatment of open-angle glaucoma.

We evaluated the effectiveness of subconjunctival injections of 6-hydroxydopamine in conjunction with epinephrine in lowering ocular tension in 63 eyes of 61 patients with open-angle glaucoma. A single injection caused a peak median reduction in ocular tension of 6 mm Hg four weeks after the injection. Ten eyes (16%) showed no significant decrease in ocular tension. A single injection significantly decreased the ocular tension for 12 weeks in 40 (63%) and for 20 weeks in 21 (33%) of the eyes. The fellow control eyes showed a slight but not significant decrease in ocular tension.

Adult↗
PubMed1981

Vascular accidents in acute angle closure glaucoma.

Four cases of acute angle closure glaucoma with different types of ocular vascular accidents are presented: one case of optic nerve head ischemia; two cases of central retinal vein occlusion, and one case of vitreous hemorrhage. One of the patients had vitreous hemorrhage following the lowering of intraocular pressure in acute angle closure glaucoma. The possible predisposition to ocular vascular accidents of patients with poor hematologic and cardiovascular status is discussed.

Aged↗
PubMed1981

An electron microscopic radioautographic identification of the APUD endocrine cells in the rat gastric pyloric glands.

The rat stomach was shown some years ago to contain numerous endocrine cells with APUD ability--cells that could take up the amino acids L-5-hydroxytryptophan (5-HTP) or L-dihydroxyphenylalanine (L-DOPA) and could decarboxylate them to their respective amines, 5-hydroxytryptamine (5-HT, serotonin) and dopamine, by means of the enzyme DOPA-decarboxylase. In a recent study, most of the APUD endocrine cells in the rat oxyntic mucosa were shown by electron microscopic radioautography to be the enterochromaffinlike cells, while the A-like cells were shown to lack APUD ability. To identify the APUD cells in the pyloric mucosa, pieces of rat pylorus were incubated in organ culture with 3H-5-HTP and were processed for light microscopic and electron microscopic radioautography. Additional specimens were incubated with 3H-5-HTP and carbidopa, an inhibitor of DOPA-decarboxylase, used to block the decarboxylation of 3H-5-HTP to 3H-5-HT, or with 3H-5-HT, used to determine where exogenous 3H-5-HT localizes in the pyloric mucosa. The 3H-5-HTP labeled all three types of endocrine cells identified within the pyloric glands--the G, enterochromaffin, and D cells. As this labeling was inhibited by carbidopa, and as exogenous 3H-5-HT labeled these cells only lightly, the labeling must have resulted from the uptake and intracellular conversion of the 3H-5-HTP of 3H-5-HT. Thus despite their morphologic differences, all rat pyloric endocrine cells possess APUD ability, a property shared by many, but not all, of the peptide- and amine-producing endocrine cells located throughout the body.

5-Hydroxytryptophan↗
PubMed1981

Does helplessness cause depression, or do only depressed people become helpless? Comment on Alloy and Abramson.

Alloy and Abramson reported that depressed people are accurate at assessing response-outcome contingencies, whereas normal people display various distortions. It is argued that such a finding causes problems for a learned helplessness theory of depression, because it suggests that people can only detect some of the conditions necessary for producing helplessness after they are already depressed. The presumed causal relation between helplessness and depression may be strengthened if one assumes that helplessness prevents the development of active hypothesis-testing strategies that would otherwise produced biased assessments of contingency.

Cognition↗
PubMed1981

Helplessness, illusions, and depression: final comment.

Abramson and Alloy's reply to my comment suggests that we are in broad agreement. However, they suggest there is evidence that nondepressed people detect noncontingency accurately. That evidence seems weak at best. They also criticize me for faulting helplessness as being neither necessary nor sufficient for depression when it never actually claimed to be either. My concern was not with necessity or sufficiency, but with relevance.

Cognition↗