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Biomedical subjects

M Hernandez

Publications and source records attributed to M Hernandez.

At least 37 records · Page 2Linked to original sources
PubMed2001

ApoE(-/-) mice develop atherosclerosis in the absence of complement component C5.

Previous studies have suggested that the terminal complex of complement may contribute to the pathogenesis of atherosclerosis. C5b-9 complexes colocalize with the extracellular lipid in the aortic intima of hypercholesterolemic rabbits, and C6-deficient rabbits develop less atherosclerosis than controls. To test the role of complement in atherosclerosis in a different animal model, C5 deficient (C5def) mice were cross-bred with atherosclerosis susceptible apoE(-/-) mice, generating mice deficient in both apoE and C5 and control apoE(-/-) mice. Progeny were typed for C5 titer and serum cholesterol levels. Both male and female mice were fed a high fat diet from weaning until 22 weeks of age. At that time there were no significant differences in plasma cholesterol or triglycerides between apoE(-/-) control and apoE(-/-)/C5def groups. Morphometric analysis of the aortic root lesions gave mean (+/-SEM) lesion areas for male apoE(-/-) and apoE(-/-)/C5def mice of 468,176 +/- 21,982 and 375,182 +/- 53,089 microm(2), respectively (n = 10 each, P value = 0.123). In female apoE(-/-) mice (n = 5), the mean lesion area was 591,981 +/- 53,242 microm(2), compared to 618,578 +/- 83,457 microm(2) for female apoE(-/-)/C5def mice (n = 10) (P value = 0.835). Thus neither male nor female mice showed a significant change in lesion area when C5 was not present. In contrast to the case in the hypercholesterolemic rabbit, activation of the terminal complex of complement does not play a major role in the development of atherosclerosis in apoE(-/-) mice.

Animals↗
PubMed2001

The use of extracellular enzymes from Streptomyces albus ATCC 3005 for the bleaching of eucalyptus kraft pulp.

The suitability of culture supernatant from Streptomyces albus ATCC 3005 for use in the biobleaching of eucalyptus kraft pulp was investigated. S. albus was found to grow on a minimal salts medium containing oat spelts xylan and yeast extract as the main carbon and nitrogen sources, respectively. Maximal extracellular xylanase and peroxidase production was detected after 120 h (11.97 U ml(-1)) and 72 h (0.58 U ml(-1)), respectively. Importantly, no cellulase activity could be detected. When the effect of pH on enzyme activity was examined, maximal xylanase and peroxidase activity was obtained at pH 6.5 and pH 9.9, respectively. The optimum hydrogen peroxide (H2O2) concentration for peroxidase activity was found to occur at 20 mM, with peroxidase remaining active at 100 mM H2O2 after 1 h incubation at 53 degrees C; the half-life of the enzyme at that temperature was estimated to be 33 min. Short-term (1 h) biobleaching of eucalyptus kraft pulp with culture supernatant from S. albus in the presence of H2O2 resulted in a significant reduction of kappa number (2.85 units) with no change in viscosity. These results suggest a potential application of cellulase-free culture supernatants from S. albus in biobleaching.

Biotechnology↗
PubMed2001

Rapid protein-based assays for the diagnosis of T-B+ severe combined immunodeficiency.

The severe combined immunodeficiencies (SCID) are a heterogeneous group of conditions arising from a variety of molecular defects. The X-linked form of SCID (X-SCID) is caused by defects in the common gamma chain (gammac), and is characterized by a T-B+NK- immunophenotype. This lymphocyte profile is seen in an autosomal recessive form of SCID caused by mutations in the JAK3 molecule. Thus, X-SCID and JAK3-deficient SCID are clinically and immunologically indistinguishable. Knowledge of the precise molecular defect is essential for antenatal diagnosis, carrier testing and for treatment using somatic gene therapy. To identify the molecular defect in children presenting with a T-B+NK- form of SCID, we have developed rapid assays based on flow cytometric analysis of gammac, immunoblotting for JAK3 and gammac, and detection of interleukin-2 (IL-2)-induced tyrosine phosphorylation of JAK3. Sixteen T-B+NK- SCID patients from 15 families were examined. Nine had no detectable gammac, four had abnormal gammac expression and no IL-2-induced JAK3 tyrosine phosphorylation, and one had normal gammac expression but no IL-2-induced JAK3 tyrosine phosphorylation, although JAK3 was present. All these patients had mutations identified in their gammac gene. Two patients exhibited normal gammac expression, but JAK3 was not detected by immunoblotting and these patients were confirmed as having JAK3 gene mutations. Thus, these protein-based assays have led to rapid molecular diagnoses in T-B+ SCID that have subsequently been confirmed by genetic analysis.

B-Lymphocytes↗
PubMed2001

Photoreactivation in airborne Mycobacterium parafortuitum.

Photoreactivation was observed in airborne Mycobacterium parafortuitum exposed concurrently to UV radiation (254 nm) and visible light. Photoreactivation rates of airborne cells increased with increasing relative humidity (RH) and decreased with increasing UV dose. Under a constant UV dose with visible light absent, the UV inactivation rate of airborne M. parafortuitum cells decreased by a factor of 4 as RH increased from 40 to 95%; however, under identical conditions with visible light present, the UV inactivation rate of airborne cells decreased only by a factor of 2. When irradiated in the absence of visible light, cellular cyclobutane thymine dimer content of UV-irradiated airborne M. parafortuitum and Serratia marcescens increased in response to RH increases. Results suggest that, unlike in waterborne bacteria, cyclobutane thymine dimers are not the most significant form of UV-induced DNA damage incurred by airborne bacteria and that the distribution of DNA photoproducts incorporated into UV-irradiated airborne cells is a function of RH.

Air Microbiology↗
PubMed2001

Simvastatin has anti-inflammatory and antiatherosclerotic activities independent of plasma cholesterol lowering.

Inhibitors of 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase, such as simvastatin, lower circulating cholesterol levels and prevent myocardial infarction. Several studies have shown an unexpected effect of HMG-CoA reductase inhibitors on inflammation. Here, we confirm that simvastatin is anti-inflammatory by using a classic model of inflammation: carrageenan-induced foot pad edema. Simvastatin administered orally to mice 1 hour before carrageenan injection significantly reduced the extent of edema. Simvastatin was comparable to indomethacin in this model. To determine whether the anti-inflammatory activity of simvastatin might affect atherogenesis, simvastatin was tested in mice deficient in apoE. Mice were dosed daily for 6 weeks with simvastatin (100 mg/kg body wt). Simvastatin did not alter plasma lipids. Atherosclerosis was quantified through the measurement of aortic cholesterol content. Aortas from control mice (n=20) contained 56+/-4 nmol total cholesterol/mg wet wt tissue, 38+/-2 nmol free cholesterol/mg, and 17+/-2 nmol cholesteryl ester/mg. Simvastatin (n=22) significantly (P<0.02) decreased these 3 parameters by 23%, 19%, and 34%, respectively. Histology of the atherosclerotic lesions showed that simvastatin did not dramatically alter lesion morphology. These data support the hypothesis that simvastatin has antiatherosclerotic activity beyond its plasma cholesterol-lowering activity.

Administration, Oral↗
PubMed2001

Familial CD8 deficiency due to a mutation in the CD8 alpha gene.

CD8 glycoproteins play an important role in both the maturation and function of MHC class I-restricted T lymphocytes. A 25-year-old man, from a consanguineous family, with recurrent bacterial infections and total absence of CD8(+) cells, was studied. Ab deficiencies and ZAP-70 and TAP defects were ruled out. A missense mutation (gly90-->ser) in both alleles of the immunoglobulin domain of the CD8 alpha gene was shown to correlate with the absence of CD8 expression found in the patient and two sisters. Conversely, high percentages of CD4(-)CD8(-)TCR alpha beta(+) T cells were found in the three siblings. A novel autosomal recessive immunologic defect characterized by absence of CD8(+) cells is described. These findings may help to further understanding of the role of CD8 molecules in human immune response.

Adult↗
PubMed2001

Using fault tree analysis to identify causes of non-compliance: enhancing violation outcome data for the purposes of education and prevention.

An enhanced coding system for the characterization of notices of violation (NOV's) issued to radiation permit holders in the State of Texas was developed based on a series of fault tree analyses serving to identify a set of common causes. The coding system enhancement was retroactively applied to a representative sample (n = 185) of NOV's issued to specific licensees of radioactive materials in Texas during calendar year 1999. The results obtained were then compared to the currently available summary NOV information for the same year. In addition to identifying the most common NOV's, the enhanced coding system revealed that approximately 70% of the sampled NOV's were issued for non-compliance with a specific regulation as opposed to a permit condition. Furthermore, an underlying cause of 94% of the NOV's was the failure on the part of the licensee to execute a specific task. The findings suggest that opportunities exist to improve permit holder compliance through various means, including the creation of summaries which detail specific tasks to be completed, and revising training programs with more focus on the identification and scheduling of permit-related requirements. Broad application of these results is cautioned due to the bias associated with the restricted scope of the project.

Health Physics↗
PubMed2000

Deficiency in inducible nitric oxide synthase results in reduced atherosclerosis in apolipoprotein E-deficient mice.

Inducible NO synthase (iNOS) present in human atherosclerotic plaques could contribute to the inflammatory process of plaque development. The role of iNOS in atherosclerosis was tested directly by evaluating the development of lesions in atherosclerosis-susceptible apolipoprotein E (apoE)-/- mice that were also deficient in iNOS. ApoE-/- and iNOS-/- mice were cross-bred to produce apoE-/-/iNOS-/- mice and apoE-/-/iNOS+/+ controls. Males and females were placed on a high fat diet at the time of weaning, and atherosclerosis was evaluated at two time points by different methods. The deficiency in iNOS had no effect on plasma cholesterol, triglyceride, or nitrate levels. Morphometric measurement of lesion area in the aortic root at 16 wk showed a 30-50% reduction in apoE-/-/iNOS-/- mice compared with apoE-/-/iNOS+/+ mice. Although the size of the lesions in apoE-/-/iNOS-/- mice was reduced, the lesions maintained a ratio of fibrotic:foam cell-rich:necrotic areas that was similar to controls. Biochemical measurements of aortic cholesterol in additional groups of mice at 22 wk revealed significant 45-70% reductions in both male and female apoE-/-/iNOS-/- mice compared with control mice. The results indicate that iNOS contributes to the size of atherosclerotic lesions in apoE-deficient mice, perhaps through a direct effect at the site of the lesion.

Animals↗
PubMed2000

Intestinal absorption of cholesterol is mediated by a saturable, inhibitable transporter.

Although the mechanism by which dietary cholesterol is absorbed from the intestine is poorly understood, it is generally accepted that cholesterol is absorbed from bile acid micelles in the jejunum. Once inside the enterocytes, cholesterol is esterified by the action of acyl-coenzyme A:cholesterol acyltransferase (ACAT), assembled into chylomicrons, and secreted into the lymph. In this work, mechanistic aspects of cholesterol absorption were probed using compounds that block cholesterol absorption in hamsters. Sterol glycoside cholesterol absorption inhibitors, exemplified by L-166,143, (3 beta, 5 alpha,25R)-3-[(4", 6"-bis[2-fluoro-phenylcarbamoyl]-B-D-cellobiosyl)oxy]-spirostan -11-on e, potently blocked absorption of radioactive cholesterol, and the potencies of several analogs correlated with their ability to lower plasma cholesterol. Each molecule of L-166,143 blocked the uptake of 500 molecules of cholesterol, rendering it unlikely that the inhibitor interacts directly with the cholesterol or bile acid. Radiolabeled L-166,143 bound to the mucosa and binding was blocked by active, but not inactive, cholesterol absorption inhibitors. Subtle changes in the structure of sterol glycosides yielded large changes in their ability to block both cholesterol absorption and binding of radiolabeled L-166,143. Large species-to-species variation in potency was also observed. These lines of evidence support the interpretation that dietary cholesterol is absorbed via a specific transporter found in the intestinal mucosa.

Animals↗
PubMed2000

A target for cholesterol absorption inhibitors in the enterocyte brush border membrane.

Uptake of cholesterol by the intestinal absorptive epithelium can be selectively blocked by specific small molecules, like the sterol glycoside, L-166,143. Furthermore, (3)H-labeled L-166,143 administered orally to hamsters binds specifically to the intestinal mucosa, suggesting the existence of a cholesterol transporter. Using autoradiography, the binding site of (3)H-L-166,143 in the hamster small intestine was localized to the very apical aspect of the absorptive epithelial cells. Label was competed by non-radioactive L-166,143 and two structurally distinct cholesterol absorption inhibitors, suggesting a common site of action for these compounds. L-166,143 blocked uptake of (3)H-cholesterol into enterocytes in vivo, as demonstrated by autoradiography, suggesting that it inhibits a very early step of cholesterol absorption, incorporation into the brush border membrane. This conclusion was confirmed by studies in which intestinal brush borders were isolated from hamsters dosed with (3)H-cholesterol in the presence or absence of L-166,143. Uptake of (3)H-cholesterol into the membranes was substantially inhibited by the compound. In contrast, an inhibitor of acyl CoA:cholesterol acyltransferase, did not affect uptake of (3)H-cholesterol into the brush border membranes. These results strongly support the existence of a specific transporter that facilitates the movement of cholesterol from bile acid micelles into the brush border membranes of enterocytes.

Animals↗
PubMed2000

Infectious agents are not necessary for murine atherogenesis.

Recent work has revealed correlations between bacterial or viral infections and atherosclerotic disease. One particular bacterium, Chlamydia pneumoniae, has been observed at high frequency in human atherosclerotic lesions, prompting the hypothesis that infectious agents may be necessary for the initiation or progression of atherosclerosis. To determine if responses to gram-negative bacteria are necessary for atherogenesis, we first bred atherosclerosis-prone apolipoprotein (apo) E(-/)- (deficient) mice with animals incapable of responding to bacterial lipopolysaccharide. Atherogenesis was unaffected in doubly deficient animals. We further tested the role of infectious agents by creating a colony of germ-free apo E(-/)- mice. These animals are free of all microbial agents (bacterial, viral, and fungal). Atherosclerosis in germ-free animals was not measurably different from that in animals raised with ambient levels of microbial challenge. These studies show that infection is not necessary for murine atherosclerosis and that, unlike peptic ulcer, Koch's postulates cannot be fulfilled for any infectious agent in atherosclerosis.

Animals↗
PubMed2000

Health status and risk behavior of adolescents in the north of Madrid, Spain.

PURPOSE: To study the health status and risk behavior in an adolescent population of Madrid, Spain. METHODS: An anonymous self-administered questionnaire was completed by 2831 pupils aged 14-20 years from urban, suburban, and rural populations in the north of Madrid. A large number of questions were from the Minnesota Adolescent Health Survey questionnaire, which included sociodemographics, health status, drug use, sexual practices, suicidal thoughts, emotional problems, and injury risk. Student's t-test, analysis of variance, and Chi-square statistics are used for analyzing associations between the different variables. RESULTS: A majority (80%) of students thought they are in good or very good health (better for males than females); 18.3% had had intercourse, the average age of the first intercourse was 15.4 years +/- 1.68 SD for males and 16.1 years +/- 1.46 SD for females. Most (73%) had used some kind of contraception. Eighty-five percent had tried alcohol, and regular use (frequently or every day) was as high as 24%. Males drank more than females (28% vs. 20%); 58.2% of the population drink only during weekends, the percentage increasing with age. Seventy percent of the sample had smoked at least once; 34. 5% reported regular tobacco use and this increased with age. Males smoked less than females (27% vs. 42%); 3.2% smoked more than 20 cigarettes/day. The consumption of illegal drugs was very low (20% had tasted cannabis and use by males was higher). Cocaine, heroin, etc. were used by less than 5%. CONCLUSION: In general, our adolescents are in good health with most problems being preventable. Sexual activity was lower than in other European and American countries. The consumption of tobacco and alcohol started early and in general was high. Our study confirms the relationship among different health-compromising behaviors. There is a need to implement health promotion and preventive programs for adolescents.

Adolescent↗
PubMed2000

Kinase mutant Btk results in atypical X-linked agammaglobulinaemia phenotype.

X-linked agammaglobulinaemia (XLA) is a B cell humoral abnormality arising from mutations in the gene encoding Bruton's tyrosine kinase (Btk). The phenotype of XLA can be variable, with some individuals having a less severe immunophenotype, although in most cases this cannot be correlated with the Btk mutation or expression of Btk protein. In this study we describe clinical and immunological heterogeneity within the same pedigree. Analysis of the genetic defect identified a missense mutation in the kinase domain of Btk which, unusually, preserved Btk protein expression but at reduced levels, and also considerably diminished autophosphorylation activity. Structural analysis of the effect of this mutation on the kinase domain suggests that this mutation is not an integral part of the ATP or substrate binding domains but may affect the interaction of the kinase domain with its own kinase domain and other substrates. Together, these data may provide an explanation for the variable XLA phenotype.

Adult↗
PubMed2000

Induction of transforming growth factor-beta 1 production in human cells by herpes simplex virus.

Transforming growth factor-beta (TGF-beta) is a cytokine of particular interest in human retrovirus infections because it can abrogate antigen-specific cellular activation. Although TGF-beta production has been observed in HIV infections, there is no evidence that herpes simplex virus (HSV)-stimulated human cells produce this cytokine. Here we present evidence, for the first time, that in vitro infection of human mononuclear cells with HSV type 1 (HSV-1) induced the release of TGF-beta1 protein. The production of this cytokine was time dependent and was found highly significant (p < 0.001) after 48 h. In addition, we observed that the secretion of TGF-beta1 was dependent on the concentration of human cells. It was found that virus needs to replicate in human cells for the production of TGF-beta1, as UV-inactivated virus did not induce significant production of cytokine protein. Interestingly, increased HSV-1-induced TGF-beta1 production in cultures containing antiinterleukin (IL)-12 or antiinterferon (IFN)-gamma antibodies was observed, whereas an irrelevant antibody had no effect on the production of this cytokine. Taken together, these findings indicate that human cells synthetize TGF-beta1 in response to HSV-1 and at the same time suggest that HSV-1-induced TGF-beta1 production may be one of the mechanisms by which HSV can at least partly evade activation of the host immune system.

Adjuvants, Immunologic↗
PubMed2000

Prevalence and correlates of herpes simplex virus type 2 infection in a population-based survey of young women in low-income neighborhoods of Northern California. The Young Women's Survey Team.

BACKGROUND: Herpes simplex virus type 2 (HSV-2) is one of the most common sexually transmitted infections and may enhance transmission of HIV. However, population-based estimates of HSV-2 prevalence and correlates of infection are rare. GOALS: To obtain population-based estimates of HSV-2 prevalence and to identify demographic and sexual behavioral correlates of infection among women in low-income communities of Northern California. STUDY DESIGN: A randomized, single-stage, cluster sample, cross-sectional survey of women age 18 to 29 years who reside in 1990 US Census block groups at the lowest tenth percentile for household income. RESULTS: The survey-weighted prevalence of HSV-2 infection was 34.8% (95% CI, 30.4-39.2). Factors independently associated with HSV-2 seropositivity were black race, older age, lower income, parity, greater number of lifetime male sexual partners, earlier onset of sexual intercourse, sex work, history of sexually transmitted disease (STD), and cocaine use. CONCLUSION: The high prevalence of HSV-2 and the strong correlation with sexual risk underscores the potential for further spread of STD, including HIV, in this young population.

Adolescent↗
PubMed2000

Development and application of small-subunit rRNA probes for assessment of selected Thiobacillus species and members of the genus Acidiphilium.

Culture-dependent studies have implicated sulfur-oxidizing bacteria as the causative agents of acid mine drainage and concrete corrosion in sewers. Thiobacillus species are considered the major representatives of the acid-producing bacteria in these environments. Small-subunit rRNA genes from all of the Thiobacillus and Acidiphilium species catalogued by the Ribosomal Database Project were identified and used to design oligonucleotide DNA probes. Two oligonucleotide probes were synthesized to complement variable regions of 16S rRNA in the following acidophilic bacteria: Thiobacillus ferrooxidans and T. thiooxidans (probe Thio820) and members of the genus Acidiphilium (probe Acdp821). Using (32)P radiolabels, probe specificity was characterized by hybridization dissociation temperature (T(d)) with membrane-immobilized RNA extracted from a suite of 21 strains representing three groups of bacteria. Fluorochrome-conjugated probes were evaluated for use with fluorescent in situ hybridization (FISH) at the experimentally determined T(d)s. FISH was used to identify and enumerate bacteria in laboratory reactors and environmental samples. Probing of laboratory reactors inoculated with a mixed culture of acidophilic bacteria validated the ability of the oligonucleotide probes to track specific cell numbers with time. Additionally, probing of sediments from an active acid mine drainage site in Colorado demonstrated the ability to identify numbers of active bacteria in natural environments that contain high concentrations of metals, associated precipitates, and other mineral debris.

Acetobacteraceae↗