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Biomedical subjects

L J Allen

Publications and source records attributed to L J Allen.

45 records · Page 3Linked to original sources
PubMed1987

Persistence, extinction, and critical patch number for island populations.

Sufficient conditions are derived for persistence and extinction of a population inhabiting several islands. Discrete reaction-diffusion population models are analyzed which describe growth and diffusion of a population on a group of islands or a patch environment. A critical patch number is defined as the number of islands below which the population goes extinct on that group of islands. It is shown that population persistence on one island leads to population persistence for the entire archipelago. Both single-species and multi-species models are discussed.

Animals↗
PubMed1986

A neuroendocrine tumor of the small intestine with a karyotype of 46,XY,t(11;22).

Direct preparations of cells from a neuroendocrine carcinoma of the small intestine reveal a karyotype of 46,XY,t(11;22)(q25;q12). Though only 13 cells could be analyzed from both direct and 24 hour preparations, all revealed the translocation; no normal cell line was seen. The patient had not been treated at the time of biopsy. A similar translocation recently has been reported in a number of cases of Ewing's sarcoma and in peripheral neuroepithelioma. This common occurrence, along with the observation that a rearranged chromosome #22 with breakpoints at q11 or q12 are observed in other neoplasias including leukemia, suggests a possible causative role for these phenomena.

Carcinoma↗
PubMed1982

Translocation(X;Y)(p22.33;p11.2) in XX males: etiology of male phenotype.

Analysis of G-banded prometaphase chromosomes from three XX males revealed extra bands on the distal end of one X short arm. These bands were similar both in size and staining properties to the distal Y short arm of their fathers (in the two cases examined) and also to other chromosomally normal males. The extra material on the abnormal X chromosomes was not C- or G-11 positive in the two cases examined, suggesting that the proximal Y long arm was not present. Previous karyotype-phenotype correlations with structurally altered Y chromosomes provided evidence for localization of male determinants on the Y short arm. The present findings in XX males provide support for more precise localization, to bands p11.2 leads to pter of Y short arm.

Adult↗