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M Cohn

Publications and source records attributed to M Cohn.

At least 289 records · Page 16Linked to original sources
PubMed1969

In vitro differentiation of a mouse neuroblastoma.

Mouse tumor C1300 has been established in tissue culture. The cells have a round cell morphology in both the subcutaneous tumor and in suspension culture. However, when given a surface on which to attach, they send out processes up to 3 mm in length and assume the morphology of mature neurons. The attached cells are stained by the Bodian silver procedure for neurons, whereas the cells grown in suspension are not. Electron microscopy reveals that the attached cells contain neurofilaments, neurotubules, and densecore vesicles indicative of nerve fibers. Both free-floating and attached cells have tyrosine hydroxylase activity characteristic of sympathetic nervous tissue. Apparently cell attachment can induce morphological differentiation from an anaplastic round cell to a cell which has many properties of a mature neuron.

Animals↗
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↗