Search PubMed⌕ Search

Biomedical subjects

M Cohn

Publications and source records attributed to M Cohn.

At least 289 records · Page 16Linked to original sources
PubMedDate not supplied

A theory of the ontogeny of the chicken humoral immune system: the consequences of diversification by gene hyperconversion and its extension to rabbit.

The immune system's repertoire is generated in two stages: Stage I results in a small size high copy number repertoire that is diversified by "mutation" to result in a large size low copy number repertoire referred to as Stage II. The Stage I or high copy number repertoire is derived from information stored directly in the genome by two mechanisms. (a) The copy-cassette mechanism: the Ig-locus has one rearrangeable V gene segment which acts as recipient for controlled gene conversion in cis from a set of donor V gene segments that results in a family of subunits, L and H. This is illustrated by the avian systems. (b) The cassette-exchange mechanism: the Ig-locus has many rearrangeable V gene segments which are fused into transcription units, the products of which are a family of L and H subunits identical in function to those resulting from the copy-cassette mechanism. This is illustrated by the murine or human systems. It is possible for a species to use both mechanisms, copy-cassette at one Ig locus and cassette-exchange at the other Ig locus. This seems to obtain in the rabbit system. Further, it is possible to encode the high copy number repertoire directly in the genome as tandemly repeated rearranged transcription units as one sees in shark (a genomic analogue of the cassette-exchange mechanism). We have discussed here and elsewhere (Cohn and Langman, 1990) the consequences of these mechanisms for haplotype exclusion and functional responsiveness to antigen. The Stage I or high copy number repertoire generated by any of the above mechanisms is now a substrate for "mutation" which generates the low copy number or Stage II repertoire. These three species are compared in table V. The high copy number repertoire is small but the response to any antigen that it recognizes is rapid. The low copy number repertoire is large but responsiveness to any antigen it recognizes is slow. Cooperativity between the two repertoires optimizes the overall responsiveness with respect to rapidity of response and range of responsiveness. The use of a copy-cassette mechanism requires that the phi B cell undergoing gene conversion have a single rearranged L- and H-chain haplotype (L+/oH+/o). The reason is that conversion can correct an aberrantly rearranged transcription unit and generate an unacceptable level of doubles. In order to have one chromosome functionally rearranged and the homologue in the germline configuration, a selection mechanism is required.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMedDate not supplied

Intravenous anesthesia with propofol for painful procedures in children with cancer.

OBJECTIVE: To study the safety and efficacy of propofol-based intravenous anesthesia in children with cancer undergoing painful procedures. METHODS: This study is a retrospective analysis of data collected from 52 consecutive children who underwent 335 procedures using propofol anesthesia. These data were routinely collected in all patients: time to induction, duration of the procedure, time to recover, and the doses of the drugs used. Monitoring with electrocardiography and pulse oximetry was continuous during the procedure; blood pressures were recorded before and after the procedure and every 5 to 10 minutes during the procedure. The patients received one of these four propofol-based intravenous regimens according to the anesthesiologist's preference: propofol only; propofol plus fentanyl; propofol plus midazolam; or propofol, fentanyl, and midazolam. The efficacy of sedation was rated by this scoring system: 3 = no movement during procedure; 2 = minimal movement that did not interfere with the procedure; 1 = moderate movement requiring physical restraint to complete the procedure. RESULTS: There were six episodes of mild hypoxia (oxygen saturation 85%-94%) and one episode of laryngospasm. None required intubation. Two patients had agitation and one patient had emesis during the postrecovery phase. There was no difference in the efficacy of sedation between the four regimens. Patients receiving the combination of propofol, fentanyl, and midazolam received the least amount of propofol and required the least time to recover. There were no life-threatening complications. CONCLUSIONS: Propofol-based anesthesia, when administered by an anesthesiologist in a controlled setting, is safe and effective for performing painful procedures in children with cancer.

Ambulatory Care↗
PubMedDate not supplied

If the "adaptive" immune system can recognize a significant portion of the pathogenic universe to which the "innate" immune system is blind, then...

The "adaptive" immune repertoire functionally recognizes pathogens (and their toxic products) that the "innate" defense system misses. This requires that the self-nonself discrimination and the regulation of effector output be dependent primarily on somatic learning mechanisms (i.e. on the somatically generated, large, random "adaptive" immune paratopes repertoire).

Humans↗
PubMedDate not supplied

Relationship between renal mass and atrial natriuretic peptide release. 1. Paradoxical effect of unilateral nephrectomy on serum atrial natriuretic peptide in rats.

Serial serum atrial natriuretic peptide (ANP) determinations were performed in 15 uninephrectomized Charles River rats and in 15 sham-operated control animals during the 60 days following surgery. In a second group of 7 control and 7 uninephrectomized animals, housed in metabolism cages, serum ANP, body weight, 24-hour urine volume, osmolality and sodium excretion were serially measured. In a third group of uninephrectomized and control rats the effect of acute salt loading 24 h, 6 and 60 days after surgery on serum ANP was studied. No significant changes in ANP levels were observed during the 60 days following surgery in control animals. In the uninephrectomized animals a sharp drop in basal ANP levels was evident 24 and 48 h after surgery, but increased levels of serum ANP were seen from day 6 to 28. Thereafter ANP returned to baseline levels for the rest of the study period. Urinary sodium excretion decreased in the nephrectomized animals on days 1 and 2 following surgery. No such change was seen in the control animals during the same period. Body weight, 24-hour urine volume and urine osmolality were not statistically different in the nephrectomized vs. control rats at any time and remained constant in each group throughout the experimental period. Central venous pressure (CVP) did not change significantly in both groups 24 h and 6 days following surgery. CVP rose similarly in both groups immediately following saline loading and returned to preload levels 1 h later.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗