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Biomedical subjects

S Penny

Publications and source records attributed to S Penny.

8 recordsLinked to original sources
PubMed2001

The highly reduced genome of an enslaved algal nucleus.

Chromophyte algae differ fundamentally from plants in possessing chloroplasts that contain chlorophyll c and that have a more complex bounding-membrane topology. Although chromophytes are known to be evolutionary chimaeras of a red alga and a non-photosynthetic host, which gave rise to their exceptional membrane complexity, their cell biology is poorly understood. Cryptomonads are the only chromophytes that still retain the enslaved red algal nucleus as a minute nucleomorph. Here we report complete sequences for all three nucleomorph chromosomes from the cryptomonad Guillardia theta. This tiny 551-kilobase eukaryotic genome is the most gene-dense known, with only 17 diminutive spliceosomal introns and 44 overlapping genes. Marked evolutionary compaction hundreds of millions of years ago eliminated nearly all the nucleomorph genes for metabolic functions, but left 30 for chloroplast-located proteins. To allow expression of these proteins, nucleomorphs retain hundreds of genetic-housekeeping genes. Nucleomorph DNA replication and periplastid protein synthesis require the import of many nuclear gene products across endoplasmic reticulum and periplastid membranes. The chromosomes have centromeres, but possibly only one loop domain, offering a means for studying eukaryotic chromosome replication, segregation and evolution.

Base Sequence↗
PubMed2000

Chloroplast protein and centrosomal genes, a tRNA intron, and odd telomeres in an unusually compact eukaryotic genome, the cryptomonad nucleomorph.

Cells of several major algal groups are evolutionary chimeras of two radically different eukaryotic cells. Most of these "cells within cells" lost the nucleus of the former algal endosymbiont. But after hundreds of millions of years cryptomonads still retain the nucleus of their former red algal endosymbiont as a tiny relict organelle, the nucleomorph, which has three minute linear chromosomes, but their function and the nature of their ends have been unclear. We report extensive cryptomonad nucleomorph sequences (68.5 kb), from one end of each of the three chromosomes of Guillardia theta. Telomeres of the nucleomorph chromosomes differ dramatically from those of other eukaryotes, being repeats of the 23-mer sequence (AG)(7)AAG(6)A, not a typical hexamer (commonly TTAGGG). The subterminal regions comprising the rRNA cistrons and one protein-coding gene are exactly repeated at all three chromosome ends. Gene density (one per 0.8 kb) is the highest for any cellular genome. None of the 38 protein-coding genes has spliceosomal introns, in marked contrast to the chlorarachniophyte nucleomorph. Most identified nucleomorph genes are for gene expression or protein degradation; histone, tubulin, and putatively centrosomal ranbpm genes are probably important for chromosome segregation. No genes for primary or secondary metabolism have been found. Two of the three tRNA genes have introns, one in a hitherto undescribed location. Intergenic regions are exceptionally short; three genes transcribed by two different RNA polymerases overlap their neighbors. The reported sequences encode two essential chloroplast proteins, FtsZ and rubredoxin, thus explaining why cryptomonad nucleomorphs persist.

Algal Proteins↗
PubMed2000

Training initiatives for essential obstetric care in developing countries: a 'state of the art' review.

Increased international awareness of the need to provide accessible essential or emergency obstetric and newborn care in developing countries has resulted in the recognition of new training needs and in a number of new initiatives to meet those needs. This paper reviews experience in this area so far. The first section deals with some of the different educational approaches and teaching methods that have now been employed, ranging from the traditional untheorized 'chalk and talk', to competency-based training, to theories of adult learning, problem solving and transferable skills. The second section describes a range of different types of indicators and data sources (learner assessments, user and community assessments, trainer assessments and institutional data) that have been used in the assessment of the effectiveness of such training. The final section of the paper draws together some of the lessons. It considers evaluation design issues such as the inclusion of medium and long term evaluation, the importance of methods that allow for the detection of iatrogenic effects of training, and the roles of community randomized trials and 'before, during and after' studies. Issues identified for the future include comparative work, how to keep training affordable, and where training ought to lie on the continuum between straightforward technical skills acquisition and the more complex learning processes required for demanding professional work.

Clinical Competence↗
PubMed2000

A nucleomorph-encoded CbbX and the phylogeny of RuBisCo regulators.

Chloroplasts contain proteins that are encoded by different genetic systems, the plastid genome and the nuclear chromosomes. By comparing the gene content of plastid genomes of different taxa, some predictions about nuclear-encoded genes for plastid proteins are possible. However, early in evolution, many genes were transferred from the plastid to the cell nucleus and are therefore missing from all known plastid genomes and escape such predictions. By sequencing the miniaturized chromosomes of the nucleomorph of the cryptophyte Guillardia theta, as well as the plastid genome, we uncovered two genes encoding CbbX which are predicted to be involved in plastid function. Our findings suggest that (1) red-type plastid rbcLS genes evolved together with cbbX, which is related to cbbX genes of purple bacteria; (2) early in rhodoplast evolution, the cbbX gene was duplicated and transferred into the nucleus; (3) the plastid-encoded LysR transcriptional activator gene, rbcR, is homologous to rbcR and cbbR transcriptional activator genes of purple bacteria and cyanobacteria; and (4) the ancestral plastid probably harbored both types of form I RuBisCo.

Amino Acid Sequence↗
PubMedDate not supplied

Creative use of microcomputer software by graduate nursing students.

Educating nurses to use computer technology involves complex strategies. As adult students, many are eager to learn uses of computers for nursing education, nursing research, nursing practice, and nursing administration. It is the role of the faculty member to make the computer laboratory experiences meaningful and pragmatic for these 'first time' computer users. This article describes a method that promotes learning by requiring students to solve a nursing problem relevant to their practice using available microcomputer software.

Computer User Training↗