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Biomedical subjects

S Alvarez

Publications and source records attributed to S Alvarez.

At least 163 records · Page 9Linked to original sources
PubMedDate not supplied

Prolactin, estriol and progesterone levels in frequent blood samples throughout normal pregnancy (lack of prolactin pulsatile secretion).

The aim of this paper was to study the episodic fluctuations of circulating prolactin (PRL), estriol (E3) and progesterone (P4) concentrations throughout pregnancy. We examined 24 pregnant women; 21 were between the 28th and 40th week of gestation, and the other 3 in the 12th, 16th and 20th week of gestation. Blood samples were drawn every 5 min for half an hour, and every 15 min for one and a half hour. Blood samples were taken in two and three different weeks of gestation in 11 and 2 of the cases, respectively. Two normal non-pregnant women were also studied and used as controls. PRL, E3 and P4 were determined by radioimmunoassay in all the samples. The coefficients of variation of PRL values were 40 and 22.6%, respectively, in the two control women, 8, 12 and 9.8% in the pregnant women studied at the 12th, 16th and 20th week of gestation, respectively, while in the 21 cases studied during the third trimester the coefficient of variation was 8 +/- 3% (mean +/- SD). The coefficients of variation of the values obtained for E3 and P4 in women studied in he third trimester were 26 +/- 15 and 16 +/- 6% (Mean +/- SD), respectively. There was an increase in the average concentration of the three hormones in all the cases at two or three different weeks. We can conclude that E3 and P4 have a pulsatile secretion pattern throughout pregnancy, and that PRL looses its pulsatile secretion as from an early gestational age. Our results suggested that central mechanisms regulating PRL episodic fluctuations were altered during pregnancy.

Estriol↗
PubMedDate not supplied

Antioxidant adaptive response of human mononuclear cells to UV-B: effect of lipoic acid.

Supplementation of human mononuclear cells with 3 and 6 mM of lipoic acid produces an inhibition of the antioxidant adaptive response triggered by treatment with UV-B light (0.30 W/m2 for 15 min). Supplementation with 1.5 mM of lipoic acid gives no conclusive results. The adaptive response is characterized by an increase in the activities of superoxide dismutase, catalase, glutathione peroxidase and DT-diaphorase. Catalase (5.5 +/- 0.6 pmol/mg prot) increases its activity by up to 22 +/- 3 pmol/mg prot, after irradiation with UV-B. Supplementation with 3 and 6 mM of lipoic acid completely inhibits the adaptive response. The activities of the membrane-bound mitochondrial enzymes succinate dehydrogenase and cytochrome oxidase do not increase after UV-B exposure. Moreover, their activities are found to decrease and the addition of lipoic acid does not prevent this effect. The inhibition of the antioxidant response by lipoic acid in human cells appears as indirect evidence of the existence of oxidative stress in the development of this response. As lipoic acid behaves as an effective antioxidant, it seems that its action decreases the intracellular oxidative signals necessary to develop the adaptive response in human mononuclear cells.

Adult↗
PubMedDate not supplied

Interactions of rifampin and trimethoprim in vitro.

Combination of rifampin and trimethoprim (TMP) has been suggested as a means of preventing the emergence of bacterial resistance to the individual agents and of achieving synergistic antimicrobial activity. By means of standard techniques of antimicrobial susceptibility testing, combinations of rifampin and TMP were tested against clinical isolates of a variety of aerobic bacteria. Synergism was defined as a fourfold or greater decrease in the minimal inhibitory concentration (MIC) of the more active agent in the combination. Antagonism was defined as a fourfold or greater increase in the MIC of the more active agent. No change or, at most, a twofold change was considered to represent indifference. Combinations of rifampin and TMP in ratios of 7:1, 7:2, and 1:1 demonstrated synergistic activity against 12%, 13%, and 28% of 440 isolates, respectively. Antagonism was observed in 10%, 9%, and 8% of strains tested against the above ratios. Killing curves determined with selected organisms failed to demonstrate synergistic antibacterial activity. Combinations of rifampin and TMP failed to prevent the emergence of resistance to both drugs when selected strains of various bacteria were exposed to serial, subinhibitory concentrations. Thus, synergism of rifampin and TMP was observed in only a minority of strains tested, and combination of the two agents failed to prevent the emergence of drug resistance in vitro.

Bacteria↗
PubMedDate not supplied

Dysgonic fermenter 2 septicemia.

Dysgonic fermenter 2 (DF-2) is a slow-growing gram-negative bacillus causing a zoonotic infection that is acquired through dog bites or other contact with dogs. Splenectomized patients and those with alcoholic liver disease are most susceptible to DF-2 infection. The clinical picture can be one of fulminant septicemia and disseminated intravascular coagulation in the splenectomized patient; the presentation is milder in the alcoholic patient. The overall mortality from DF-2 septicemia among the 41 cases reported in the literature is 27%. The organism is sensitive to penicillin, resistant to aminoglycosides, and not easily grown on common media. It appears to be serum-sensitive in tests with normal human serum. Penicillin prophylaxis of dog bite wounds is especially important in high-risk patients. DF-2 infection should be considered when any splenectomized patient develops fulminant septicemia, disseminated intravascular coagulation, and peripheral gangrene. Examination of a gram stain of the peripheral blood or buffy coat is of value in such cases.

Aged↗
PubMedDate not supplied

Branhamella catarrhalis respiratory infections.

Branhamella catarrhalis, a normal commensal of the oropharynx, is increasingly recognized as an important cause of bronchitis and bacterial pneumonia. Six patients with B. catarrhalis pneumonia documented by transtracheal aspirate or blood culture were studied, and 429 previously reported cases of B. catarrhalis bronchitis and pneumonia were reviewed. The mean age of patients with B. catarrhalis infection was 64.8 years, and preexisting chronic obstructive pulmonary disease was common. The typical clinical picture was that of purulent tracheobronchitis; patients with pneumonia were not severely ill and differed from those with bronchitis mainly by the presence of patchy lower-lobe infiltrates on chest roentgenogram. Fifty-three percent of reported strains produced beta-lactamase. Thirty-nine percent of the cultures were mixed, predominantly with Haemophilus influenzae and Streptococcus pneumoniae. The microbiologic, immunologic, and clinical features of B. catarrhalis infection, as well as the antimicrobial susceptibilities of this organism, were reviewed. The reasons for the lack of recognition of this common pathogen and possible solutions were considered.

Antibodies, Bacterial↗
PubMedDate not supplied

Cholera in the United States.

Cholera remains a threat to human health in many parts of the world, including the United States. The epidemiology of cholera is reviewed to prepare for identification and prevention of the disease in appropriate clinical settings. The clinical manifestations of cholera and the pathophysiology of the toxin-induced diarrhea are reviewed to introduce and to clarify appropriate therapeutic and preventive interventions.

Cholera↗
PubMedDate not supplied

Intestinal microflora and the interaction with immunocompetent cells.

The intestinal mucosal surface is colonised by the comensal microflora that attains very high numbers of bacterial cells in the distal intestine, more specifically in the colon. At the same time these extensive areas are the interface with the external environment, through which most pathogens initiate infectious processes in mammals. Intestinal mechanisms of defense need to discriminate accurately between comensal, symbiotic microflora, and exogenous pathogens. Today we do not fully understand the essence of the mechanism of discrimination but, probably, innate as well as adaptive immune responses participate in this process. We have explored, in in vitro models, the capacity of mucosal immunocompetent cells to discriminate amongst signals delivered by different types of bacteria. We have found at least two different patterns of innate response to gram-negative and gram-positive bacteria, and within this last group big differences are observed between species. We have only worked with non-pathogenic bacteria in what may represent the modulation of the physiological host status. The understanding of these modulatory functions could render a unique possibility for the use of food-borne bacteria to prevent or correct intestinal problems associated with food allergy, inflammatory bowel disease, and autoimmunity.

Animals↗
PubMedDate not supplied

Tumor necrosis factor-alpha and nitric oxide in vertically HIV-1-infected children: implications for pathogenesis.

We performed a cross-sectional study to investigate the plasma TNF-alpha and nitric oxide (NO) production in 44 vertically HIV-1-infected children, and the relationship with immunological status and viral replication. As a control group, 36 healthy, uninfected children were studied. Plasma TNF-alpha and NO levels were determined by ELISA. Viral load was quantified using standard assays. Cell proliferation, apoptosis and viral replication were evaluated in vitro by incorporation of (3H)-thymidine, flow cytometry and p24 antigen, respectively. Higher plasma TNF-alpha and NO levels were observed in HIV-1-infected children compared with healthy controls. We found a very strong correlation between plasma TNF-alpha and NO levels in HIV-1-infected children (r = 0.98; p < 0.001). Moreover, HIV-1-infected children with higher viral load (> 4.7 log10) showed higher TNF-alpha and NO levels than those with viral load below this threshold. Interestingly, we detected inducible nitric oxide synthase (iNOS) mRNA in T-lymphocytes from HIV-1-infected children. To address their possible patho-physiological significance, we tested the in vitro effects of NO and TNF-alpha in HIV-1 replication. Addition of TNF-alpha and NO donors to mitogen-activated, HIV-1-infected PBMC cultures produced a significant increase in viral replication. Moreover, HIV-1 replication in mitogen-stimulated, PBMC cultures was partially inhibited by iNOS specific inhibitors, and a neutralising, anti-TNF-alpha monoclonal antibody. Our results indicate that TNF-alpha and NO correlated with high viral load in HIV-1-infected children and favoured HIV-1 in vitro replication. These data suggest a detrimental role of NO in HIV-1 infection, and that NOS inhibitors may have some therapeutic benefit in HIV-1-infection.

Cells, Cultured↗
PubMedDate not supplied

Influence of the oral administration of lactic acid bacteria on iga producing cells associated to bronchus.

Intestinal, respiratory and genitourinary mucosal surfaces are the most important routes of entry for microbial pathogens. The stimulus of the mucosal immunity is not easy because the trigger keys for the activation do not follow the ones of the systemic immune response. In previous works we have demonstrated that some Lactic Acid Bacteria (LAB), when orally administered, can induce an enhance of the gut immune response. Taking into account the concept of a common mucosal response, we studied the effect of orally administered mice with Lactobacillus casei, L. acidophilus, L. rhamnosus, L. delbrueckii subsp. bulgaricus, Streptococcus salivarius subsp. thermophilus and Lactococcus lactis on the IgA secreting cells associated to bronchus. As shown before, oral immunostimulation with LAB induced an increase of the IgA* cells at intestinal level by a dose depending effect. In this study it is also showed that the LAB assayed, with exception of L. acidophilus, were able to enhance IgA+ cells at bronchial level, being also this effect dose dependent. The increment induced by some LAB in the number of IgA+ cells on the mucosa surface of the lower respiratory tract may be very important to prevent bronchus diseases.

Journal Article↗
PubMedDate not supplied

[Adjuvant activity of lactic bacteria: perspectives for its use in oral vaccines].

The effect of the oral and subcutaneous administration of Lactobacillus casei, Lactobacillus acidophilus, Lactobacillus bulgaricus and Streptococcus thermophilus on humoral antibody production and delayed type hypersensitivity response against sheep red blood cells (SRBC) was studied. The species of the genus Lactobacillus proved to be more effective in both cases, effects being stronger when working with viable bacteria than with non-viable cells. The stimulation of primary cellular and humoral immune responses reached optimal activity with a dose of 6 x 10(9) cells. The plaque-forming cells (PFC) and the circulating antibody titers to the SRBC antigen obtained in the groups treated with lactobacilli were 2 to 3 times higher than those of the non-treated control group. In mice fed with the different lactic acid bacteria circulating antibody against these microorganisms failed to be detected, but when they were administered by subcutaneous route a strong response to antilactic acid bacteria was stimulated. S. thermophilus was not effective in increasing the immune response. These results suggest that the lactobacilli by oral route, exert a strong adjuvant activity which is responsible for the enhanced host immune responses obtained. In this respect, lactobacilli could be considered as the most promising oral adjuvant.

Adjuvants, Immunologic↗