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Biomedical subjects

K Rodriguez

Publications and source records attributed to K Rodriguez.

14 recordsLinked to original sources
PubMed2001

Surface activity in vitro: role of surfactant proteins.

Pattle, who provided some of the initial direct evidence for the presence of pulmonary surfactant in the lung, was also the first to show surfactant was susceptible to proteases such as trypsin. Pattle concluded surfactant was a lipoprotein. Our group has investigated the roles of the surfactant proteins (SP-) SP-A, SP-B, and SP-C using a captive bubble tensiometer. These studies show that SP-C>SP-B>SP-A in enhancing surfactant lipid adsorption (film formation) to the equilibrium surface tension of approximately 22-25 mN/m from the 70 mN/m of saline at 37 degrees C. In addition to enhancing adsorption, surfactant proteins can stabilize surfactant films so that lateral compression induced through surface area reduction results in the lowering of surface tension (gamma) from approximately 25 mN/m (equilibrium) to values near 0 mN/m. These low tensions, which are required to stabilize alveoli during expiration, are thought to arise through exclusion of fluid phospholipids from the surface monolayer, resulting in an enrichment in the gel phase component dipalmitoylphosphatidylcholine (DPPC). The results are consistent with DPPC enrichment occurring through two mechanisms, selective DPPC adsorption and preferential squeeze-out of fluid components such as unsaturated phosphatidylcholine (PC) and phosphatidylglycerol (PG) from the monolayer. Evidence for selective DPPC adsorption arises from experiments showing that the surface area reductions required to achieve gamma near 0 mN/m with DPPC/PG samples containing SP-B or SP-A plus SP-B films were less than those predicted for a pure squeeze-out mechanism. Surface activity improves during quasi-static or dynamic compression-expansion cycles, indicating the squeeze-out mechanism also occurs. Although SP-C was not as effective as SP-B in promoting selective DPPC adsorption, this protein is more effective in promoting the reinsertion of lipids forced out of the surface monolayer following overcompression at low gamma values. Addition of SP-A to samples containing SP-B but not SP-C limits the increase in gamma(max) during expansion. It is concluded that the surfactant apoproteins possess distinct overlapping functions. SP-B is effective in selective DPPC insertion during monolayer formation and in PG squeeze-out during monolayer compression. SP-A can promote adsorption during film formation, particularly in the presence of SP-B. SP-C appears to have a superior role to SP-B in formation of the surfactant reservoir and in reinsertion of collapse phase lipids.

Animals↗
PubMed1999

Clandestine abortion in Latin America: provider perspectives.

This paper presents the results of in-depth interviews with ten clandestine abortion providers in urban Latin America. Three related issues are addressed: how abortion providers come to this line of work; their major difficulties; and their sources of job satisfaction. A variety of paths bring health professionals to the practice of abortion; common elements are a sense of calling, a desire to help women, personal experience with abortion, and a commitment to political change. Providers describe difficulties that include a lack of medical support, the need for secrecy, and threats of violence, extortion, and prosecution. In spite of difficulties, all providers report a great deal of fulfillment in their work, based on their satisfaction in saving women's lives, maintaining supportive relationships with colleagues, and empowering women.

Abortion, Illegal↗
PubMed1998

Affinity purification and partial characterization of a yeast multiprotein complex for nucleotide excision repair using histidine-tagged Rad14 protein.

The nucleotide excision repair (NER) pathway of eukaryotes involves approximately 30 polypeptides. Reconstitution of this pathway with purified components is consistent with the sequential assembly of NER proteins at the DNA lesion. However, recent studies have suggested that NER proteins may be pre-assembled in a high molecular weight complex in the absence of DNA damage. To examine this model further, we have constructed a histidine-tagged version of the yeast DNA damage recognition protein Rad14. Affinity purification of this protein from yeast nuclear extracts resulted in the co-purification of Rad1, Rad7, Rad10, Rad16, Rad23, RPA, RPB1, and TFIIH proteins, whereas none of these proteins bound to the affinity resin in the absence of recombinant Rad14. Furthermore, many of the co-purifying proteins were present in approximately equimolar amounts. Co-elution of these proteins was also observed when the nuclear extract was fractionated by gel filtration, indicating that the NER proteins were associated in a complex with a molecular mass of >1000 kDa prior to affinity chromatography. The affinity purified NER complex catalyzed the incision of UV-irradiated DNA in an ATP-dependent reaction. We conclude that active high molecular weight complexes of NER proteins exist in undamaged yeast cells.

Chromatography, Affinity↗
PubMed1998

Children's phonological awareness: confusions between phonemes that differ only in voicing.

Given the role of phonemic awareness in learning to read and spell, it is important to examine the linguistic factors that influence children's performance on phonemic awareness tasks. We found that, contrary to some previous claims, children did not perform better with fricative consonants (e.g., /z/) than with stops (e.g., /d/) in a phoneme recognition task. However, preschoolers and kindergartners were more likely to mistakenly judge that a syllable began with a target phoneme when the initial phoneme of the syllable differed from the target only in voicing (e.g., /t/ for the target /d/) than when it differed in place of articulation (e.g., /b/-/d/) or in both place and voicing (e.g., /p/-/d/). These results shed light on the organization of children's phonological systems. They also have implications for the design and interpretation of phonemic awareness tasks.

Analysis of Variance↗
PubMed1998

The foundations of literacy: learning the sounds of letters.

Learning the sounds of letters is an important part of learning to read and spell. To explore the factors that make some letter-sound correspondences easier for children to learn than others, we first analyzed knowledge of letters' sounds (and names) by 660 children between 3 1/2 and 7 1/2 years old. A second study examined pre-schoolers' (M age 4 years, 11 months) ability to learn various sound-letter mappings. Together, the results show that an important determinant of letter-sound knowledge is whether the sound occurs in the name of the letter and, if so, whether it is at the beginning or the end. The properties of the sound itself (consonant versus vowel, sonorant versus obstruent, stop versus continuant) appear to have little or no influence on children's learning of basic letter-sound correspondences. The findings show that children use their knowledge of letters' names when learning the letters' sounds rather than memorizing letter-sound correspondences as arbitrary pairings.

Child↗
PubMed1997

Agreement between peripheral venous and arterial lactate levels.

STUDY OBJECTIVE: To test the hypothesis that measurements of peripheral venous lactate (V-LACT) can be substituted for arterial lactate (A-LACT) in predicting arterial hyperlactacidemia. METHODS: We conducted a prospective comparison of paired A-LACT and V-LACT measurements obtained from a convenience sample of 74 ED patients who presented to an urban, public teaching hospital, 70% of whom had abnormal A-LACT. RESULTS: Mean A-LACT and V-LACT were 2.8 mmol/L and 3.0 mmol/L, respectively. A-LACT and V-LACT were strongly correlated (r2 = .89). Simultaneous multivariate adjustment for tourniquet time and for time elapsed between drawing of A-LACT and V-LACT had no effect on this correlation. Although the mean difference between V-LACT and A-LACT was only .22 mmol/L, the range that included 95% of the disagreement between paired measurements in individual patients was-1.3 mmol/L to 1.7 mmol/L. When A-LACT and V-LACT levels were each divided into normal and abnormal (elevated) groups, V-LACT showed 94% sensitivity (95% confidence interval [CI], 83% to 99%), 57% specificity (95% CI, 34% to 78%), a positive likelihood ratio of 2.2, and a negative likelihood ratio of .1. A-LACT values were used as the criterion standard for these calculations. CONCLUSION: Correlation between A-LACT and V-LACT was high in this cohort of patients, but agreement is imperfect. The odds of arterial hyperlactacidemia appear to be reduced substantially by the finding of a normal V-LACT but are only marginally increased if the V-LACT is increased. Caution should be used in the routine substitution of V-LACT for A-LACT.

Acidosis, Lactic↗
PubMed1996

Identification of functional domains within the RAD1.RAD10 repair and recombination endonuclease of Saccharomyces cerevisiae.

Saccharomyces cerevisiae rad1 and rad10 mutants are unable to carry out nucleotide excision repair and are also defective in a mitotic intrachromosomal recombination pathway. The products of these genes are subunits of an endonuclease which recognizes DNA duplex/single-strand junctions and specifically cleaves the 3' single-strand extension at or near the junction. It has been suggested that such junctions arise as a consequence of DNA lesion processing during nucleotide excision repair and the processing of double-strand breaks during intrachromosomal recombination. In this study we show that the RAD1 RAD10 complex also cleaves a more complex junction structure consisting of a duplex with a protruding 3' single-strand branch that resembles putative recombination intermediates in the RAD1 RAD10-mediated single-strand annealing pathway of mitotic recombination. Using monoclonal antibodies, we have identified two regions of RAD1 that are required for the cleavage of duplex/single-strand junctions. These reagents also inhibit nucleotide excision repair in vitro, confirming the essential role of the RAD1 RAD10 endonuclease in this pathway.

Animals↗
PubMed1985

Efficacy of imipenem/cilastatin in endocarditis.

Imipenem, a potent new beta-lactam antibiotic, which is bactericidal against most pathogenic bacteria, and cilastatin, a dehydropeptidase inhibitor combined with imipenem to prevent the metabolism of imipenem in the kidney, were evaluated in the treatment of bacterial endocarditis. Seventeen patients, including 14 who used intravenous drugs, were treated with imipenem/cilastatin in a dose of 500 mg each infused over 30 minutes every six hours. The mean duration of treatment was 29 days with a range of 21 to 56 days. Causative bacteria were Staphylococcus aureus in 10 patients, S. aureus plus group B Streptococcus in one, viridans group Streptococcus in two, Neisseria subflava, Eikenella corrodens, and group G Streptococcus in one patient, and Staphylococcus epidermidis, Hemophilus aphrophilus, and Enterobacter aerogenes in one patient each. The minimal bactericidal concentration of imipenem against 16 of 18 isolates tested was 0.04 micrograms/ml, 1 microgram/ml against H. aphrophilus, and 0.4 micrograms/ml against E. aerogenes. The site of infection was the right side of the heart in 11 patients, the left side in five, and both sides in one. The mean number of days to defervescence was 9.7. All patients were cured, and none required cardiac surgery. Adverse effects were few and interrupted treatment occurred in only one patient who had acute dyspnea during an infusion on Day 26 of therapy. Imipenem/cilastatin appears to be a relatively safe and highly effective treatment of staphylococcal endocarditis in intravenous drug users; too few patients with endocarditis caused by other bacteria were treated to allow a firm statement about efficacy in non-staphylococcal endocarditis.

Adult↗
PubMed1985

Successful treatment of gram-negative bacillary meningitis with imipenem/cilastatin.

A patient with meningitis caused by a strain of Actinetobacter anitratus that was resistant to all commercially available antibiotics was treated with imipenem/cilastatin administered intravenously in a dose of 1 gm of imipenem every six hours. The minimal inhibitory concentration of imipenem against the isolate was less than or equal to 0.04 micrograms/ml. The patient tolerated the drug well and was cured after 12 days of therapy.

Acinetobacter Infections↗
PubMed1977

Use of hair dyes by patients with breast cancer: a case-control study.

The recent finding that many permanent and semipermanent hair dyes are strongly mutagenic in a laboratory test, together with the fact that single female hair-dressers had higher than expected death rates from breast-cancer in 1959-63, prompted a study into the use of hair dyes by patients with breast cancer and by matched controls. There was no difference between the patients and their controls in their use of hair dyes. There were also no significant differences between the two groups when the analysis was confinedto women who had used dyes over four years and over nine years before diagnosis. The only significant findings were a higher proportion of past or present smokers among women aged over 50 who used hair dyes and an association between hair dyes use and age at first pregnancy. Further epidemiological studies are clearly needed in view of the mutagenicity found in the Ames test, and the fact th & several human carcinogens are also mutagenic according to this test.

Age Factors↗