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Biomedical subjects

S Giunta

Publications and source records attributed to S Giunta.

At least 19 recordsLinked to original sources
PubMed1992

New in vitro findings on the "free" form of apolipoprotein A-1.

Clinical and experimental gerontologists are extremely interested in lipoproteins as well as in new methods for investigating and probing the apolipoprotein pattern. Using immunofixation electrophoresis, we separated free apolipoprotein A-1 from the apo A-1 associated with high-density lipoproteins. Free apolipoprotein A-1 is a low-molecular-mass form of apo A-1 that seems to contain an extremely low quantity of lipids. The use of IFE as a tool for probing free apo A-1 has revealed new and interesting findings, such as its "artificial" increase during serum conservation at temperatures between 0-4 degrees C. From the clinical point of view, we demonstrated a decrease to the point of disappearance of free apo A-1 in some patients with liver cirrhosis. Moreover, one of the main findings here reported is the failure of anti-human apo A-1 murine monoclonal antibody and monoclonal antibody mixture to precipitate free apo A-1 in agarose systems. This discovery has important implications both for basic knowledge on apolipoproteins and for practical reasons concerning variability in those immunoassays (radial immunodiffusion) utilizing monoclonal antibody mixtures.

Antibodies, Monoclonal↗
PubMed1991

An in vitro bacterial model of cytotoxicity to living cells caused by dopamine and 6-hydroxydopamine oxidation at physiological pH.

The cytotoxicity of dopamine (DA) and 6-hydroxydopamine (6-OHDA) on living cells, in vitro, has been previously deeply investigated in neuroblastoma cells. This study was designed to explore the possibility to use bacteria as targets for studying DA and 6-HODA cytotoxicity. Both DA and 6-HODA oxidize when added to bacteriological media. The rate of autoxidation of 6-HODA was greater than DA within the first hours. The oxidation-dependent cytotoxicity caused bacterial growth-inhibition and killing at concentration of 10(-4)M. All the bacterial strains tested were slightly more susceptible to DA than to 6-HODA. Antioxidants (sodium metabisulfite, cysteine) prevented the oxidation and abolished the growth-inhibitory activity. The addition of exogenous catalase protected the cells against the effect of the oxidation of both the catecholamines up to the concentration of 5 mM, while the addition of exogenous superoxide dismutase protected the cells only at the minimal inhibitory concentrations. Taking into account that some of the results obtained are similar to those previously reported using neuroblastoma cells as targets, the use of bacteria for studying oxygen toxicity from these catecholamines seems to be a potentially useful model system.

Bacteria↗
PubMed1990

CT demonstration of peritoneal metastases after intraperitoneal injection of contrast media.

Thirty-three patients with ovarian carcinoma who had no evidence of metastases or ascites demonstrated on computed tomography (CT) with and without contrast agent were examined with CT after injection of approximately 3000 cc of a 2.4% solution of nonionic contrast media into the peritoneum. After intraperitoneal injection with CT (IPC CT), 22 were diagnosed as having intraperitoneal metastases. Of these, 19 were found to be true positives and 3 false negatives. Three other patients diagnosed as normal were found to have metastases. In all patients the peritoneum was well outlined and generally any metastases smaller than 1 cm were demonstrated. It was possible to identify compartmentalization of the peritoneum and to determine the location of the lesion to be in the peritoneum or the extraperitoneal space. This information is necessary in the planning of chemotherapy, particularly endoperitoneal chemotherapy. Tiny metastases to the omentum or adherent loops of small bowel could not be seen well.

Female↗
PubMed1990

Mueller-Hinton broth undergoes visible oxidative color changes in the presence of peroxidase and hydrogen peroxide.

In the presence of peroxidase and hydrogen peroxide, Mueller-Hinton broth undergoes a slow but clearly detectable color change from pale yellow to dark yellow or brown. An investigation of this phenomenon led to the conclusion that it is the result of the oxidation of tyrosine, a major component of the broth. Indeed, tyrosine has long been known to oxidize upon treatment with peroxidase and hydrogen peroxide. The observations reported here, besides being curious for the clinical microbiologist, might deserve attention for the possible implications in the medium color darkening which sometimes happens during microbial growth.

Bacteriological Techniques↗
PubMed1988

Streptococcus faecalis susceptibility to amiloride depends on medium pH.

Amiloride is one of the major molecular probes in basic and applied investigations on the physiology of cation transport in animal cells. In these cells the drug also exerts growth inhibitory activity. Recently, we discovered that amiloride causes growth inhibition also on bacterial cells. In this paper we report that medium pH influences amiloride activity on Streptococcus faecalis. The lowering of external pH causes a drop in the susceptibility of this bacterium to amiloride up to an almost complete resistance. This finding, constitutes a novel aspect of the in vitro experimental pharmacology of this diuretic potentially useful also in clinical pharmacology and in animal cell investigations.

Amiloride↗
PubMed1985

In vitro antistreptococcal activity of the potassium-sparing diuretics amiloride and triamterene.

The ionophore antimicrobial agents provide evidence that perturbations of the electrolyte balance of bacterial cells exert a growth-inhibitory activity. Several drugs acting on animal cell membranes have also been shown to be active on bacterial cells. In this paper, we report preliminary susceptibility studies showing that the class of potassium-sparing diuretics acting directly on monovalent cation fluxes on animal cells possesses a selective growth-inhibitory activity on hemolytic streptococci.

Amiloride↗
PubMed1985

Acebutolol-induced decrease of mononuclear leukocyte beta-adrenoceptors in hypertension.

The regulatory action exerted on receptors by acebutolol, a cardioselective beta-blocker containing intrinsic sympathomimetic activity, has been investigated. beta-Adrenoceptor affinity and density of human mononuclear leukocytes were assayed in hypertensive patients before and after treatment with 400 mg/day acebutolol. While receptor affinity showed no changes between pre- and post-treatment values, a statistically significant decrease has been demonstrated in receptor density following treatment. Blood pressure and heart rate were also measured in order to test the efficacy of the administered drug. All these parameters showed a fall in the post-treatment values. It is concluded that the partial agonist acebutolol, in spite of the fact that it acts clinically as a beta-blocker, has the regulatory mechanism characteristic of agonists.

Acebutolol↗
PubMed1984

Amiloride, a diuretic with in vitro antimicrobial activity.

The effect of amiloride, an inhibitor of passive sodium influx in animal cells, was investigated on the in vitro bacterial growth. Amiloride blocked the growth of different bacterial strains at concentrations ranging from 25 to 1,300 micrograms/ml. While generally the block was bacteriostatic and bacteria, on amiloride removal, recovered their ability to growth, the drug showed a killing activity on hemolytic streptococci. Gram-positive bacteria revealed a greater susceptibility to amiloride than gram-negative ones. Although an hitherto unknown effect of amiloride cannot be excluded, from the known mechanism of action of amiloride on animal cells it might be suggested that sodium permeability plays a critical role on bacterial multiplication.

Amiloride↗
PubMed1984

Atenolol-induced regulation of leukocyte beta 2-adrenoceptors in hypertension.

beta 2-Adrenoceptor characteristics of human mononuclear leukocytes were assayed in hypertensive patients before and after treatment with 100 mg/day atenolol. While no changes have been observed in receptor affinity, a statistically significant increase (36%) has been demonstrated in receptor density following treatment. Blood pressure and heart rate were also measured in order to test the efficacy of the administered drug. All these parameters showed a fall in the post-treatment values. It is concluded that at therapeutic concentration, beta 2-adrenoceptors undergo up-regulation by atenolol in spite of its cardioselectivity. Such a regulation, which may represent a fundamental step in the mechanism leading to withdrawal syndrome, may, therefore, be suggested being quite widespread.

Adult↗
PubMed1983

Decline of thymus-cell potential in diabetic and aged men.

Human peripheral blood thymus lymphocytes are capable of forming, when stimulated by phytohemagglutinin, single-cell-derived colonies in an in vitro soft-agar system. Blood samples were obtained from 33 healthy men ranging in age from 20 to 96 years of age and from 11 diabetic men ranging in age from 42 to 60 years and 11 age-matched controls. With increasing age a reduction in the number of single-cell-derived colonies and a decrease in their residual in vitro proliferation potential was observed. Such a defect appeared at an earlier age in diabetic men. The defect in proliferative potential of cells of either old or diabetic men did not depend on factors present in their blood plasma.

Adult↗
PubMed1983

New method for detecting Epstein-Barr virus association in nonproducer lymphoblastoid cell lines.

Epstein-Barr virus association in nonproducer human lymphoblastoid cell lines can be demonstrated by the presence of the virus genome (nucleic acid hybridization studies) or by the detection of the virus-coded complement-fixing antigen (complement fixation and/or anti-complement immunofluorescent test). This paper describes an enzyme immunoassay for the detection of Epstein-Barr virus complement-fixing antigen and its application to the demonstration of Epstein-Barr virus association in nonproducer lymphoblastoid cell lines. The assay is based on competition for complement between Epstein-Barr complement-fixing antigen and its specific antibody and a probe complex composed of Escherichia coli beta-galactosidase and specific anti-beta-galactosidase antibody. This competitive enzyme immunoassay is a specific and sensitive procedure for detecting Epstein-Barr virus association in nonproducer cell lines, allowing also quantitative estimation of the amount of antigen produced.

Antigens, Viral↗
PubMed1975

Lymphoid cells in infectious mononucleosis classified according to T and B cell markers.

It has been demonstrated that peripheral blood lymphocytes, particularly the "atypical" ones, are predominantly of the T type in infectious mononucleosis (IM). This is based on membrane marker studies (E rosettes, receptor for complement, receptor for Fc fragment of immunoglobulins (Ig), and membrane Ig) and by anti-T lymphocyte serum. On the other hand, lymphoblastoid cell lines derived from IM patients show the characteristics of B lymphocytes. This permits the suppostion that EBV infects B lymphocytes and stimulates them to proliferate. The cell proliferation is unlimited in vitro and is probably controlled in vivo by T cells. The reduction of cellular immunity in vivo, which contrasts with the high number of T cells in peripheral blood, could be explained by the fact that T cells are engaged in the regulation of B cell proliferation.

Animals↗
PubMedDate not supplied

Whole-cell bacterial peroxidase test with isoproterenol as the hydrogen donor.

The beta-adrenergic compound isoproterenol was used as oxidizable reagent in a whole-cell assay for the detection of bacterial peroxidase activities. Isoproterenol has been shown to constitute a useful reagent for detecting peroxidase activities in enzymatic tests, utilizing standard purified enzymes, and in the microbiological application proposed. The procedure developed is simple and rapid to perform. In contrast to currently used whole-cell tests for bacterial peroxidases, the assay described here does not need preliminary permeabilization; moreover, the compound utilized does not have related toxicological problems. Therefore, the isoproterenol assay may represent a low-cost safe additional peroxidase test in clinical bacteriology.

Bacteria↗