Search PubMed⌕ Search

Biomedical subjects

F Schwartz

Publications and source records attributed to F Schwartz.

At least 55 records · Page 3Linked to original sources
PubMed1987

Accurate modification of a chromosomal plasmid by homologous recombination in human cells.

We have examined the consequences of modifying mammalian cellular DNA sequences by homologous recombination. A plasmid carrying a 248-base-pair deletion in the neomycin phosphotransferase (neo) gene was introduced into hamster and human cells. The integrated, defective neo gene was used as a target for modification by a second round of transfection with a plasmid carrying a different (283-base-pair) deletion in the neo gene. Recombinants resulting in an intact neo gene were selected by their G418 resistance phenotype. The best ratio of homologous to nonhomologous recombination events was about 1:80. Analyses of the functional neo genes in various independent cell lines establish that simple crossovers (single and double) generated the wild-type neo genes.

Animals↗
PubMed1986

Suppression behavior analyzed as a function of monovision addition power.

Monovision, the use of a monocular addition for near viewing, is a clinical technique sometimes used to correct presbyopia. This technique attempts to maintain binocular function while requiring a degree of central suppression. We examined suppression behavior in spectacle monovision as a function of addition power. Suppression behavior was determined by measuring the length and frequency of periods of suppression for a range of monocular addition powers. Testing was conducted at viewing distances of 6 m and 40 cm. The most striking result is the existence of a near/distance differential: the monocular addition power required to stabilize suppression at near is greater than at distance. It was also found that suppression behavior may be stable even in the presence of a relatively high level of stereoscopic acuity. The relation between the contradictory needs for suppression and binocular functioning under monovision conditions is discussed.

Adult↗
PubMed1985

Homologous recombination between autonomously replicating plasmids in mammalian cells.

The ability of autonomously replicating plasmids to recombine in mammalian cells was investigated. Two deletion plasmids of the eukaryotic-prokaryotic shuttle vector pSV2neo were cotransfected into transformed monkey COS cells. Examination of the low molecular weight DNA isolated after 48 hr of incubation revealed that recombination between the plasmids had occurred. The DNA was also used to transform recA- E. coli. Yield of neoR colonies signified homologous recombination. Examination of the plasmid DNA from these colonies confirmed this view. Double-strand breaks in one or both of the input plasmids at the sites of deletion resulted in an enhancement of recombination frequency. The recombination process yielded monomeric and dimeric molecules. Examination of these molecules revealed that reciprocal recombination as well as gene conversion events were involved in the generation of plasmids bearing an intact neo gene. The COS cell system we describe is analogous to study of bacteriophage recombination and yeast random-spore analysis.

Animals↗
PubMed1984

Differences in keratin synthesis between normal epithelial cells and squamous cell carcinomas are mediated by vitamin A.

A number of recent studies have indicated that the expression of keratins is altered upon malignant transformation of human epithelial cells. We have shown that the altered expression of 67-kDa and 40-kDa keratins in established squamous cell carcinoma lines from tongue and epidermis stems largely from a difference in their sensitivity to vitamin A apparently acquired during tumorigenesis. When the vitamin A concentration in the medium is raised, the 40-kDa keratin is produced at increased levels. Conversely, when the amount of vitamin is reduced, the 67-kDa keratin is synthesized and the cells undergo stratification and terminal differentiation. However, even when vitamin A is quantitatively removed from the medium, the maximal degree of differentiation attained by each squamous cell carcinoma cell as judged by the synthesis of 67-kDa keratin was still less than that of the normal keratinocytes. These findings suggest that the altered patterns of keratins observed for some tissues upon malignant transformation arise from a complex mixture of intracellular changes in the differentiative pathway in addition to changes in the responsiveness of cells to extracellular regulators of keratin gene expression.

Animals↗
PubMed1982

The contaminated Rorschach response: formal features.

Collected 100 contaminated Rorschach responses and scored for location, form level, presence of human content, populars, color use, movement, and confabulation in an effort to delineate the most salient characteristics of this rarely occurring psychotic and thought-disordered response. The unexpected finding of extremely high form level and much human and popular content, along with relatively little confabulation, points to preserved reality contact in tandem with grossly disordered thought. The relatively high incidence of both color and movement in these responses raises questions about the context in which contaminations are likely to occur. There appears to be a need for further clarification of the contamination response process.

Adolescent↗
PubMed1981

Psychic structure.

An attempt has been made to define psychic structure in strictly psychological terms. The concept of psychic structure refers to enduring aspects of the personality and to means-end functions that do not have to be created de novo each time one is faced with a similar situation. A psychic structure is a functional organization that generates a range of meaningful contents. Structures are categorical in nature and display relative functional equivalence. The above formulation provides a place for meaning in the theory and distinguishes structured functions from structured contents. The latter are the end product of a behavioural sequence and not centres of action. In this analysis, percepts, thoughts, images, wishes, fantasies, affects and internal objects are contents, not dynamic systems that make things happen. Only people make things happen, employing operational systems as tools of adaptation. Structure formation transform temporal sequences into the units of experience and action. The spatialization of temporal order fosters the treatment of mental processes as if they occupied space in the mind as a place. This error accounts for the ready confounding of structure and content. The present analysis accepts the traditional definition of psychic structure in terms of function and organization, but without recourse to a physicalistic theory of energy and force. The above analysis was applied to a number of special problems in the theory of structure. Consideration was also given to the concept's range of application, systemic relevance and heuristic value.

Humans↗
PubMed1979

The scientific status of the Rorschach.

Demonstrated that the interpretation of projective test data is semantic, not probabilistic. The clinician does not employ the model of statistical inference in evaluating the meaning of test responses, although he may employ probabilistic rules as guides to interpreation. Procedural rules for interpreting meaning, the nature of clinical diagnosis from psychological tests, and the meaning of prediction as a clinical activity are discussed. It was concluded that clinicians do not make inferences, in the mathematical sense of this term.

Association↗
PubMed1978

Pictorial depth and related constancy effects as a function of recognition.

It is argued that while pictorial cues must be fundamental in the perception of an extended ground plane in daily life (and, by definition, in the perception of depth in pictures), the traditional pictorial cues such as perspective or texture gradients are neither a necessary nor a sufficient basis for it. That they are not necessary was shown by experiments in which such cues were eliminated from pictures representing a scene in depth. Illusory size perception based on localization of objects in depth in such pictures nonetheless occurred. That they are not sufficient was shown by experiments in which photographs of grassy fields did not yield impressions of depth or related size illusions when conditions were such that the scene was not recognized. Once recognized, however, these same pictures did yield such perceptions. It is suggested that a critical step in perceiving depth based on pictorial information is recognition of the scene.

Art↗
PubMed1977

Effects of nitroglycerin, postextrasystolic potentiation, and pacing-induced ischaemia on wall motion in patients with ischaemic heart disease.

The influence of nitroglycerin, postextrasystolic potentiation, and rapid ventricular pacing on total and regional ventricular function was studied in 32 patients with normal ventricular function and in 44 patients with left ventricular asynergy caused by obstructive coronary artery disease. Total ventricular function was assessed by ventriculography and regional ventricular function was analysed by use of 7 hemiaxes. Nitroglycerin increased ejection fraction and decreased left ventricular systolic and end-diastolic pressures in the normally functioning ventricles; apical wall motion increased, while basal wall motion remained unchanged after nitroglycerin in these ventricles. Pressures fell significantly in ventricles with asynergy after nitroglycerin; ejection fraction decreased while wall motion in asynergic areas was inconsistently influenced. Postextrasystolic potentiation augmented ejection fraction by a powerful and homogeneous increase of wall motion in normally functioning ventricles. Asynergic areas and normal areas in diseased ventricles showed identical augmentation of wall motion after a premature beat. Rapid venticular pacing produced a significant increase in end-diastolic pressure and a fall in ejection fraction in patients with obstructive coronary artery disease. Wall motion in normal areas perfused by arteries with critical stenoses was dramatically depressed after pacing, while asynergic areas and normal areas perfused by normal arteries remained unchanged. The results show that normal contractile behaviour can be detected by postextrasystolic potentiation in asynergic areas, suggesting that some normally perfused muscle exists in these areas. Pacing stress does not further deteriorate function in asynergic areas, which suggests the presence of viable and well perfused muscle (within scar tissue) whose function may not profit from revascularization. Pacing-induced asynergy identifies the functional significance of coronary stenoses and suggests that bypass surgery might be beneficial.

Cardiac Volume↗
PubMed1975

[Labile repolarization changes in the ECG of patients without heart disease (author's transl)].

Nine patients with suspicious repolarization (ST-T segment) changes in the ECG were further investigated. Each had ten different additional ECG tests (after various degrees of exercise, and orciprenaline, amylnitrite, glucose, potassium chloride, and propranolol injections). The ECG changes became normal in all patients, orciprenaline and propranolol injection providing optimal results. Clinical investigation, left-heart angiocardiography and coronary angiography were normal in all. The questionably abnormal repolarization distrubances were, therefore, judged to be benign. As both beta-stimulation and beta-blockade normalized the ECG it can be safely assumed that the ECG changes were induced by autonomic nervous system factors. Cardiac catheterization appears, therefore, not indicated in each case and a potential iatrogenic heart disease can be avoided by relatively simple means.

Adolescent↗
PubMed1975

Response of uremic patients to nandrolone decanoate.

The effect of anabolic steroid therapy on anemia in 13 women with and without kidneys undergoing chronic hemodialysis for renal failure was investigated. All but one of the six patients with kidneys demonstrated a noticeable increase in hematocrit level (6.4% to 14.6%). Of the anephric women, four of the seven also showed hematocrit level elevations, but these were less remarkable (3.1% to 6.4%). A majority of patients demonstrated increments in weight and serum creatinine measurements but no definitive alteration in serum blood urea nitrogen levels. The androgenic effects of nandrolone decanoate were minimal and well tolerated. We conclude that anabolic steroid therapy is effective in ameliorating the anemia of women undergoing hemodialysis, if given in a dose that produces minimal and tolerable untoward effects.

Adult↗