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Biomedical subjects

B Schwartz

Publications and source records attributed to B Schwartz.

At least 379 records · Page 21Linked to original sources
PubMed1978

[The idiopathic paroxysmal myoglobinuric myopathy (Meyer-Betz) (author's transl)].

The idiopathic paroxysmal myoglobinuric myopathy (IPMM) as a genuine disease can be differentiated from other myoglobinurias by clinical criterias. Concerning the course of the disease two different types of IPMM are to be seen, sporadic cases are observed as well as familiar, autosomal recessive inherited ones. Regarding the pathogeny of IPMM several metabolic disorders are discussed: Provocation of the disease by physical exertion and glucose deficiency point to a disturbance of carbohydrate metabolism. Disorders of lipid metabolism are reported, too. So we tried to analyse the results of a case study in relation to the presently discussed - still hypothetical - pathogenetic ideas. Our laboratory, histological and electromyographic findings suggest a primary myopathy, which might be based on a peripheral glucose utilisation disorder (ATP-deficiency). Under the condition of exertion this disorder leads to a decompensation of the muscular functional and structural metabolism manifested by an excessive efflux of myoglobin and enzymes.

Adenosine Triphosphate↗
PubMed1978

Inflammatory response of guinea pig to injected limbal tissue.

This study examined the possibility that homologous limbal tissue, including trabecular meshwork, serving as an antigen, could elicit inflammatory cells responsible for both aqueous obstruction and inflammation; the possible role of this response in ocular disease was also studied. Four sets of guinea pigs were sensitized with complete Freund's adjuvant. One set received just adjuvant and saline, one set received adjuvant plus uvea, and two sets received adjuvant plus limbal tissue. The animal injected with only adjuvant and saline all showed normal ocular histology. Sensitizing guinea pigs with limbus and adjuvant produced mononuclear infiltration of the uvea, trabeculum, and episclera. Lymphocytes and plasma cells predominated. The response induced by the limbus seemed to consist of two components: a uveal and a specific limbal component. The lymphoid infiltration of the uvea was identical to the response induced by uveal antigen in our uvea control group. The limbal component was characterized by clusters of lymphocytes and plasma cells in the trabecular and episcleral regions. This study showed that limbal tissue antigen induces an inflammatory response in both uvea and limbus, and that the inflammatory response in the trabeculum is greater with limbal than uveal antigen.

Animals↗
PubMed1977

Fluorescein angiographic defects of the optic disc in glaucoma.

An improved technique for high-contast, high-resolution fluorescein angiography of the optic disc has been developed that almost eliminates pseudofluorescence. Fluorescein angiography of the optic disc was performed on normal, ocular hypertensive, and glaucomatous patients. Rapid-sequence angiograms in the early arterial phases have demonstrated localized areas of hypofluorescence or filling defects of the optic disc. Two types of fluorescein filling defects were observed-absolute and relative. The number of absolute filling defects, which increased with degree of visual field loss, was greater in glaucomatous than in ocular hypertensive or normal eyes. Similarly, ocular hypertensive eyes showed a larger number of discs with filling defects than normal eyes. It is postulated that relative defects progress to absolute filling defects, which may be an indication of impending loss of visual field.

Adult↗
PubMed1977

Optic disc in glaucoma: Topography and extent of fluorescein filling defects.

The topography and extent of localized areas of hypofluorescence or absolute filling defects of the optic discs of glaucomatous patients correlated positively with the loss of visual field. Filling defects tended to cluster at the inferior and superior poles of the optic disc and were closer to the disc margin than to the center. The location of the defects corresponded with the expected site of visual field loss. There was a positive correlation between the percent area of the filling defects and the degree of visual field loss. These observations support the concept that fluorescein filling defects of the optic disc in glaucoma represent areas of ischemia that are highly correlated with loss of visual field.

Adult↗
PubMed1977

Fluorescein angiographic defects of the optic disc in ocular hypertension.

Fluorescein angiograms of the optic disc were studied in 23 normal and 29 ocular hypertensive eyes. Significant differences in the frequency distributions of areas of defects were obtained between normal and ocular hypertensive eyes. Increased areas of filling defects were noted in ocular hypertensive eyes as compared to normals. There were also significant correlations of the areas of filling defects with age and systolic blood pressure in the ocular hypertensive eyes that were not present in the normals. These observations support the concept that fluorescein angiography of the optic disc demonstrates localized areas of impaired circulation that increase with ocular pressure, age, and systolic blood pressure. This technique may be useful in separating normal from the ocular hypertensive patient who shows changes in the circulation of the optic disc with increased ocular pressure.

Adolescent↗
PubMed1977

Scanning microdensitometry of optic disc pallor in glaucoma.

A scanning microdensitometric technique has been developed for measuring the optical density of black and white photographs of the optic disc. From the frequency distribution curve of all the densities of the whole area of the optic disc, a separate peak was identified as corresponding to the area of pallor of the optic disc. Areas of pallor were measured as percentage of areas of the total disc for normal, ocular hypertensive, open-angle glaucoma patients, and those with suspect discs. Median values of percent area of pallor showed correspondence with the clinical diagnosis, the glaucoma patients having significantly larger areas than the normal subjects. The microdensitometric technique provides an objective means of measuring the amount of optic dis pallor. It has potential usefulness for screening and for following up suspect and confirmed glaucomas to determine progression of the disease.

Densitometry↗
PubMed1977

Specificity of fluorescein angiographic defects of the optic disc in glaucoma.

Fluorescein angiography of the optic disc was performed on normal subjects, patients with nonmyopic open-angle glaucoma dna myopic open-angle glaucoma, normal myopes, patients with optic atrophy due to chiasmal pituitary tumors, and patients with sectorial ischemic optic neuropathy due to vascular hypotension. The normal myopes, those with optic atrophy secondary to pituitary tumor, and the ischemic optic neuropathy group had optic discs similar in appearance to those with open-angle glaucoma. Absolute fluorescein filling defects occurred only in patients with open-angle glaucoma and sectorial ischemic optic neuropathy. The filling defects in open-angle glaucoma appear to be specific, indicating that the blood supply to the anterior portion of the optic nerve is involved, as in ischemic optic neuropathy. Fluorescein angiography of the optic disc may be useful to differentiate open-angle glaucoma from other entities that have similar optic discs.

Adult↗
PubMed1977

Dermal patch urethroplasty: experimental and clinical experience.

Our experience with a dermal patch graft urethroplasty is presented in 10 Pitman-Moore minipigs. Histologic review at various post-urethroplasty intervals showed epithelialization of the graft. In addition, several cases in which this technique was used are presented with early followup. The advantages of dermal patch urethroplasty as well as the application of dermal grafts in other areas of the urinary tract are discussed.

Animals↗
PubMed1977

Studies of operant and reflexive key pecks in the pigeon.

The duration of pigeons' key pecks was studied in three experiments. Experiment I revealed that key pecks early in exposure to continuous reinforcement were of short duration, as were key pecks observed on an omission procedure in which pecks prevented food delivery. Key pecks later in exposure to continuous reinforcement, and those that occurred on positive automaintenance procedures, were of long duration. In Experiment II, pigeons were exposed to fixed-interval and fixed-ratio reinforcement schedules, and durations were recorded separately for each quarter of each interval or ratio. On fixed interval, durations were shorter in the first quarter of each interval than in subsequent quarters; on fixed ratio, durations were longer in the first quarter of the ratio than in subsequent quarters. These data parallel observations of concurrent operant responding and salivation in dogs. In Experiment III, pigeons were exposed to a discrete trial, differential-reinforcement-of-low-rate 6-sec schedule. Durations of responses in the first 2 sec of the trial were substantially shorter than those of responses that occurred later. The data from all three experiments support the view that the pigeon's "key peck" actually consists of two subclasses of peck, one reflexive and one operant.

Journal Article↗
PubMed1977

Two types of pigeon key pecking: suppression of long- but not short-duration key pecks by duration-dependent shock.

The key pecking of eight pigeons was maintained on a variable-interval 1-minute schedule of food reinforcement. Sometimes, all responses between 35 and 50 milliseconds in duration produced a shock; sometimes, all responses between 10 and 25 milliseconds produced a shock; sometimes, shocks were produced by pecks without regard to duration (nondifferential punishment), and sometimes shocks were delivered independently of responding. Punishment of 35- to 50-millisecond responses selectively suppressed those responses, while punishment of 10- to 25-millisecond responses and nondifferential punishment suppressed responding overall but did not suppress responses of particular duration. Punishment of 35- to 50-millisecond responses suppressed key pecking slightly less than did nondifferential punishment. Punishment of 10- to 25-millisecond responses and response-independent shock produced roughly equal amounts of suppression, substantially less than the other punishment procedures. The data support the view that there are at least two kinds of key peck, identifiable on the basis of duration, one of which (short duration) is insensitive to its consequences.

Journal Article↗
PubMed1977

Cold agglutinins in infectious mononucleosis and heterophil-antibody-negative mononucleosis-like syndromes.

Cold agglutinins (CA) were evaluated prospectively in patients with various mononucleosis syndromes and in a large control group. Cold agglutinins with anti-i specificity were seen mainly in heterophil-positive or -negative Epstein-Barr virus (EBV)-induced infectious mononucleosis (31.8% of cases). Unclassified CA with equal reactivity against cord and adult erythrocytes were seen in 56 of 150 (37.3%) cases of heterophil-antibody-positive infectious mononucleosis (IM), in 1 of 7 (14.3%) cases of heterophil-negative EBV-induced IM, and in 12 of 31 (38.7%) cases of the heterophil-negative mononucleosis-like syndrome due to cytomegalovirus or other unspecified agents. One patient with heterophil-positive IM had a persistent, partially papain sensitive CA with anti-Pr-like activity. Anti-i CA were seen in less than 1.0% of healthy young adults (500) or patients without mononucleosis (500) submitted for heterophil studies. Unclassified CA were noted in 3.2% of the latter 1000 samples.

Agglutinins↗
PubMed1975

Discriminative stimulus location as a determinant of positive and negative behavioral contrast in the pigeon.

Four pigeons were exposed to a series of two-component multiple schedules of reinforcement that ordinarily yield positive and negative behavioral contrast. The stimuli that signalled the component schedules were sometimes located on the response key and sometimes off. Positive behavioral contrast was observed only when the stimuli were on the key. Negative contrast was observed independent of stimulus location. These data suggest that positive and negative contrast may be causally unrelated, and support an account of contrast in terms of the summation of key pecks that are separately controlled by response-reinforcer and stimulus-reinforcer dependencies.

Journal Article↗
PubMed1975

Behavioral contrast in the pigeon: a study of the duration of key pecking maintained on multiple schedules of reinforcement.

Pecks on an operant key were reinforced on either multiple variable-interval variable-interval or multiple variable-interval extinction schedules of reinforcement. The stimuli that signalled the multiple-schedule components were located on a second key (signal key), and a changeover delay prevented reinforcement of signal key-peck-operant key-peck sequences. No behavioral contrast was observed on the operant key, and appreciable responding to the signal key occurred during the variable-interval component of the multiple variable-interval extinction procedure. Peck durations on the signal key were markedly shorter than peck durations on the operant key. Moreover, most responses on the signal key occurred just after the multiple-schedule components changed. These data support an account of behavioral contrast in terms of the summation of pecks that are separately controlled by stimulus-reinforcer and response-reinforcer dependencies, and suggest that the stimulus-reinforcer dependency is responsible primarily for local contrast. In addition, the data suggest that pecks that are controlled by these two dependencies may belong to topographically different classes.

Journal Article↗