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Biomedical subjects

M R Diaz

Publications and source records attributed to M R Diaz.

11 recordsLinked to original sources
PubMed2005

Microcoding: the second step in DNA barcoding.

After the process of DNA barcoding has become well advanced in a group of organisms, as it has in the economically important fungi, the question then arises as to whether shorter and literally more barcode-like DNA segments should be utilized to facilitate rapid identification and, where applicable, detection. Through appropriate software analysis of typical full-length barcodes (generally over 500 base pairs long), uniquely distinctive oligonucleotide 'microcodes' of less than 25 bp can be found that allow rapid identification of circa 100-200 species on various array-like platforms. Microarrays can in principle fulfill the function of microcode-based species identification but, because of their high cost and low level of reusability, they tend to be less cost-effective. Two alternative platforms in current use in fungal identification are reusable nylon-based macroarrays and the Luminex system of specific, colour-coded DNA detection beads analysed by means of a flow cytometer. When the most efficient means of rapid barcode-based species identification is sought, a choice can be made either for one of these methodologies or for basic high-throughput sequencing, depending on the strategic outlook of the investigator and on current costs. Arrays and functionally similar platforms may have a particular advantage when a biologically complex material such as soil or a human respiratory secretion sample is analysed to give a census of relevant species present.

Biodiversity↗
PubMed2000

Molecular sequence analyses of the intergenic spacer (IGS) associated with rDNA of the two varieties of the pathogenic yeast, Cryptococcus neoformans.

The pathogen Crytococcus neoformans has been traditionally grouped in two varieties, C. neoforrmans var. neoformans (serotypes A, D and AD) and C. neoformans var. gattii (serotypes B and C). A recent taxonomic evaluation of C. neoformans var. neoformans described C. neoformans var. grubii as a new variety represented by serotype A isolates. Despite immunological, biochemical, ecological and molecular differences the three varieties are classified within one species. We examined the genetic variability of one hundred and five clinical and environmental isolates that included all varieties and serotypes. Sequence analysis of the intergenic spacer (IGS) associated with rDNA revealed significant differences in nucleotide composition between and within the varieties. Parsimony analysis showed five different genotypes representing distinct genetic lineages. Although there was a high degree of relatedness between serotype and genotype this relatedness was not exclusive as serotypes were not restricted to one particular genotypic group. Serotyping and sequence analyses indicate that C. neoformans var. grubii (serotype A) should not be recognized as a separate variety. Based on this study we propose to accept two separate species, C. neoformans (serotypes A, D and AD) and C. bacillisporus (serotypes B and C synonymous with C. neoformans var. gattii).

Cryptococcosis↗
PubMed2000

Molecular analyses of the IGS & ITS regions of rDNA of the psychrophilic yeasts in the genus Mrakia.

Species of the genus Mrakia are currently classified as synonyms based on molecular sequence analyses of the large sub-unit ribosomal DNA (LrDNA). Physiological and protein electrophoretic studies, however, reveal possible species differences. To clarify this discrepancy, we undertook molecular sequence analyses of the internal transcribed spacer (ITS) and intergenic spacer (IGS) regions of rDNA from the four psychrophilic Mrakia species and the psychrophilic yeast, Cryptococcus curiosus. Identical ITS sequences were found between C. curiosus, M. nivalis and M. frigida. Although, M. stokesii and M. gelida displayed identical ITS and IGS sequences, their sequences differed from the other three species by 2.3% and 38%, respectively. The results suggest that M. stokesii is a synonym of M. gelida, whereas M. nivalis is a synonym of M. frigida. Sequence differences (1.9%) observed in the IGS region indicates that C. curiosus is a distinct strain of M. frigida.

Base Sequence↗
PubMed1997

Organic osmolytes in aerobic bacteria from mono lake, an alkaline, moderately hypersaline environment.

The identity and concentrations of intracellular organic solutes were determined by nuclear magnetic resonance spectroscopy for two strains of aerobic, gram-negative bacteria isolated from Mono Lake, Calif., an alkaline, moderately hypersaline lake. Ectoine (1,4,5,6-tetrahydro-2-methyl-4-pyrimidinecarboxylic acid) was the major endogenous solute in both organisms. Concentrations of ectoine varied with external NaCl levels in strain ML-D but not in strain ML-G, where the level was high but invariant from 1.5 to 3.0 M NaCl. Hydroxyectoine also occurred in strain ML-D, especially at elevated NaCl concentrations (2.5 and 3.0 M), but at levels lower than those of ectoine. Exogenous organic solutes that might occur in Mono Lake were examined for their effects on the de novo synthesis of ectoine. Dimethylsulfoniopropionate (DMSP) (0.1 or 1 mM) did not significantly lower ectoine levels in either isolate, and only strain ML-G showed any capacity for DMSP accumulation. With nitrogen limitation, however, DMSP (0.1 mM) substituted for ectoine in strain ML-G and became the main organic solute. Glycine betaine (GB) was more effective than DMSP in affecting ectoine levels, principally in strain ML-D. Strain ML-D accumulated GB to 50 or 67% of its organic solute pool at 2.5 M NaCl, at an external level of 0.1 or 1 mM GB, respectively. Strain ML-D also accumulated arsenobetaine. The methylated zwitterionic compounds, probably metabolic products of phytoplankton (DMSP and GB) or brine shrimps (arsenobetaine) in Mono Lake, may function as osmolytes for indigenous bacteria when present at high concentrations or under conditions of nitrogen limitation or salt stress.

Journal Article↗
PubMed1993

Amniotic band syndrome: a nursing perspective.

Amniotic band syndrome is a disease process that is unfamiliar to many neonatal nurses. It's presentation is variable in both type and severity, and pathophysiology and etiology still mystify those who have studied it in depth. Although better understood today, there remain many unanswered questions. A review of the current literature revealed an abundant supply of medically-based information and also a lack of resources focused on nursing-oriented information. This paper addresses the nursing implications of caring for an infant with amniotic band syndrome. A knowledgeable nurse will be able to assist in the diagnosis of amniotic band syndrome and have a better understanding of how to care for both the infant and his family. Both nursing and medical research needs to continue in this area to gain more knowledge about this complex disease process.

Abnormalities, Multiple↗
PubMed1992

Heparin resistance after intraoperative platelet-rich plasma harvesting.

Records of anticoagulation for cardiopulmonary bypass from 58 patients who underwent elective coronary artery revascularization were analyzed to determine whether the harvesting of autologous platelet-rich plasma produces heparin resistance. The effect of preoperative heparin therapy on anticoagulation for cardiopulmonary bypass after harvesting of platelet-rich plasma was also evaluated. Patients were grouped by presence of preoperative heparin therapy and type of blood component harvested before cardiopulmonary bypass, including platelet-rich plasma, autologous whole blood, both, or neither. The dose of heparin required to initiate and to maintain anticoagulation for cardiopulmonary bypass was determined for each patient, and the groups were compared by two-way analysis of variance. Significantly more heparin was required to maintain anticoagulation for cardiopulmonary bypass in the platelet-rich plasma group than in the groups receiving autologous whole blood or no blood products. More heparin was also required to initiate and to maintain anticoagulation for cardiopulmonary bypass after preoperative heparin therapy. These results reinforce the concept that anticoagulation during cardiopulmonary bypass must be carefully monitored, and increased vigilance may be warranted in patients after harvesting of platelet-rich plasma.

Analysis of Variance↗