Search PubMed⌕ Search

Biomedical subjects

M Levitt

Publications and source records attributed to M Levitt.

284 records · Page 16Linked to original sources
PubMedDate not supplied

Conformations of immunoglobulin hypervariable regions.

On the basis of comparative studies of known antibody structures and sequences it has been argued that there is a small repertoire of main-chain conformations for at least five of the six hypervariable regions of antibodies, and that the particular conformation adopted is determined by a few key conserved residues. These hypotheses are now supported by reasonably successful predictions of the structures of most hypervariable regions of various antibodies, as revealed by comparison with their subsequently determined structures.

Amino Acid Sequence↗
PubMedDate not supplied

Fistula-in-ano: a prospective study of 107 patients.

BACKGROUND: While the majority of fistulas-in-ano are anatomically simple and easy to treat, a significant number are high or anatomically complex and have the potential to become a major management problem. METHODS: One hundred and seven consecutive patients undergoing surgery for fistula-in-ano were studied prospectively with standardized anatomic diagrams. RESULTS: Fistulas were classified as superficial (15%), intersphincteric (43%), trans-sphincteric (35%) or 'high' (7%). Within each group fistulas were considered either simple or complex (high tracks, extra tracks or other complications). Trans-sphincteric fistulas were more often complex than intersphincteric fistulas (32 vs 6%). A prior history of perianal sepsis and surgery was more frequent among the trans-sphincteric and 'high' groups. An external fistula opening within a narrow are 30 degrees either side of the posterior midline was almost always associated with a simple superficial or intersphincteric fistula (97%). Anterior and especially posterolaterally located external openings were frequently associated with complex fistulas (16 and 47%, respectively) and often had trans-sphincteric or 'high' tracks (58 and 56%). Goodsall's Law was more accurate for posterior (91%) and intersphincteric (93%) fistulas than for anterior (69%) and trans-sphincteric (68%) fistulas. Histopathology of fistula material showed unremarkable fistula-in-ano in 87% of requests. Six patients had unexpected abnormal results, including three new diagnoses of Crohn's disease. CONCLUSIONS: The presence of additional anatomic complexity should always be anticipated in trans-sphincteric fistulas. Trans-sphincteric and 'high' fistulas are more likely to occur in females, and in patients with previous perianal sepsis or surgery for fistula. External openings close to the posterior midline almost always underlie simple fistulas, whereas posterolateral external openings are predictive of complex fistulas.

Adult↗
PubMedDate not supplied

The theory of chronic deafferentation dysesthesias.

The chronic dysesthesias are abnormal disturbing somatic sensations, which are painful or non-painful. Their abnormality is revealed by their null or distorted psychophysical relationships; they occur spontaneously or can be peripherally induced by innocuous or noxious stimuli. Among nonverbal or mentally incompetent humans and also subhumans, these dysesthesias are expressed by patterns of escape or avoidance behaviors. There is no contemporaneous and necessary relationship with peripheral nociception. The basic mechanisms of these abnormalities have been obscure, and conventional modes of therapy have been unsuccessful. The origin of these chronic abnormalities is known to arise from lesions of peripheral or central components of the neural pathway for normal pain and temperature sensibility. The cause of these abnormalities is thought to reside in pathophysiological foci of excitability among deafferented central nocireceptive neurons. The spontaneous dysesthesias can occur after partial or total deafferentation. The peripherally induced dysesthesias occur after partial deafferentations, which include loss of small caliber myelinated afferents in cases of peripheral origin; and they are mediated via remaining afferent pathways. Little is known about the deafferented neurons in the brain, or the pertinent remaining central afferent pathways. More is now known about the pathophysiological effects of deafferentation on nonspecific nocireceptive neurons in the dorsal horn. These include morphological alterations, reduced inhibition, supersensitivity, hyperexcitability, and novel afferent excitation. Additional studies of chronic deafferentation in subhumans are necessary to provide further information and to test hypotheses concerning the chronic deafferentation dysesthesias.

Afferent Pathways↗
PubMedDate not supplied

Physiological disposition and metabolism of N-t-butylarterenol and its di-p-toluate ester (bitolterol) in the rat.

The metabolism and disposition of the bronchodilator, N-t-butylarterenol (tBA) and its di-p-toluate ester (bitolterol) were compared in the rat. Radioactivity was preferentially retained in lungs of rats compared with heart and blood after iv medication with tritium-labeled bitolterol, but was not retained in tissues after iv medication with [3H]tBA. After oral and iv medication with [3H]bitolterol, fecal radioactivity accounted for 24% of the dose and 65 and 79% of the radioactivity, respectively, was excreted in urine (0-72 hr). In comparison, urine radioactivity after oral and iv medication with [3H]tBA was 43 and 83% of the dose, respectively, and fecal radioactivity accounted for 43 or 23% of the dose, respectively (0-72 hr). Bitolterol was hydrolyzed in vitro to tBA by esterases found in various tissues including small intestine, liver, and plasma. Moreover, tBA was a substrate for catecholamine O-methyltransferase but not for monoamine oxidase. Similar metabolites were observed in urine samples of rats given either [3H]tBA or [3H]bitolterol. Urine metabolites were identified as free and conjugated forms of both tBA and 3-O-methyl-tBA.

Animals↗
PubMedDate not supplied

Postnatal persistence of methadone following prenatal exposure in the rat.

Tritiated methadone (3HME) was administered daily by gastric intubation to gravid rats during the last week of gestation. Fostered neonates were sacrificed every 5 days from birth to 30 days of age and brains and livers removed. Tissue 3HME was extracted, isolated on a high pressure liquid chromatograph, and counted. Highest concentrations of 3HME were present on the day of birth; after 5 days, approximately 22% remained. However, small but significant concentrations of 3HME were detected in tissues through 30 days of age. These results are of interest in relation to persistent opiate withdrawal symptoms in rat and human neonates.

Age Factors↗
PubMedDate not supplied

The creative process and the narcissistic personality disorder.

This paper describes the emergence of the creative process during the psychoanalysis of a patient suffering from a narcissistic personality disorder. Infantile history revealed an unending series of failures in the maternal holding environment to which the patient had reacted by withdrawal into fantasy, apathy, and hypochondriasis. The transference material made affective reconstructions of early life possible, and a creative communication was initiated. The newly liberated creative capacity permitted an important sublimatory release for the blocking which had hitherto threatened the patient' emotional health. As infantile fantasies were reexamined and their role as a reaction against threatening experience was understood, the creative arrest was slowly lifted. By creation of artifacts concerned with distorted scoptophiliac derivatives, the patient brought into consciousness material which reflected a broadening of his perceptual field.

Adult↗