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Biomedical subjects

L Galeazzi

Publications and source records attributed to L Galeazzi.

At least 19 recordsLinked to original sources
PubMed1999

In vitro peroxidase oxidation induces stable dimers of beta-amyloid (1-42) through dityrosine bridge formation.

beta-amyloid (A beta) is a normal soluble peptide found in the cerebrospinal fluid (CSF) and other biological fluids. A beta fibrils are associated with Alzheimer's disease (AD) senile plaques. We have used purified soluble A beta (1-42) and A beta (12-28) peptides in order to determine the oxidative modification induced in these peptides by exposure to peroxidase and hydrogen peroxide. We have demonstrated that under these in vitro conditions, dimeric forms of A beta (1-42) can be detected by high-resolution polyacrylamide SDS-PAGE electrophoresis. Further experiments performed by reverse-phase high performance liquid chromatography (RP-HPLC), and monitored by fluorescence detection, showed that the dimeric A beta (1-42) forms induced by the peroxidase reaction are the outcomes of dityrosine bridge formation. This cross-link results from the enzyme catalyzed oxidation. During this reaction, phenolic coupling of tyrosine residues of two A beta (1-42) peptides occurs. No detectable peroxidative modifications were observed with the A beta (12-28) peptide which lacks a tyrosine residue. Since oxidative stress is thought to be associated with AD, the experimental model described here can help in understanding the early events leading to chemical, structural and conformational modifications before the conversion of sA beta to amyloid fibrils and eventually the formation of senile plaques in AD.

Amino Acid Sequence↗
PubMed1999

Quantitation of intraplatelet Ca++ deposits as a potential marker of senility.

OBJECTIVE: To perform a morphometric evaluation of calcium deposits in human platelets as a quantitative procedure to seek a potential marker of senility in a peripheral cellular model. STUDY DESIGN: In human blood samples from middle-aged, healthy volunteers, the intraplatelet calcium content was cytochemically evidenced by the oxalatepyroantimonate (OPA) reaction. The number and area of OPA aggregates per square micrometer of total sampled area, the area of the deposits per square micrometer of platelet surface and the percentage of positive platelets were the ultrastructural features calculated by computer-assisted image analysis. RESULTS: OPA precipitates were easily identified in all the samples evaluated. The area of OPA deposits per square micrometer of platelet surface was rather constant not only among the measurements performed on the same sample but also comparing the different subjects analyzed. Other OPA deposit features showed higher variabilities; thus, to obtain a representative sample from each patient, several measurements had to be carried out. CONCLUSION: Quantitation of calcium deposits may be of help in evidencing increased Ca++ sequestering activity by platelets, supposedly due to altered calcium homeostasis. The OPA cytochemical procedure visualizes millimolar quantities of Ca++ ions; thus, only high calcium concentration sites (granules) can be detected by morphometric methods.

Aging↗
PubMed1996

Synaptic structural dynamics and aging.

Synaptic junctional areas are not immutable structures, on the contrary, they are remodelled throughout the individual's lifespan as a consequence of environmental stimulations. This adaptive capacity of the synapses is discussed from a morphological standpoint with reference to aging. In old subjects, the number of contacts and the total surface area of synaptic appositions per unit volume of tissue decrease significantly, while the average synaptic size increases at a different extent according to the CNS area taken into account. This increase in synaptic average area is due to a higher percent of a subpopulation of enlarged contacts supposed to represent either the degenerating junctional zones or a compensatory phenomenon counteracting the synaptic reduction in number. Recent studies on perforated synapses support that the enlarged junctions are possible intermediates in synaptic physiological restructuring, thus the higher percentage of this type of contacts in the old CNS may witness unaccomplished synaptic turnover cycles. Taking into account the high metabolic rate of nerve cells, an age-related impairment in energy provision at synaptic terminal regions may constitute an early and subtle alteration affecting synaptic dynamic morphology in aging.

Aging↗
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

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↗
PubMed1983

Inhibition of nonspecific streptococcal coagglutination reactions.

The reliability of latex coagglutination testing for the serological grouping of hemolytic streptococci is limited by the relatively high incidence of false-positive reactions. Pretreatment of streptococcal suspensions with antisera for the various groups that show clumping gives a specific inhibition of the latex agglutination with the true group, whereas the other groups continue to agglutinate aspecifically. The method is rapid and easy to perform, allows the exact grouping of those streptococci giving aspecific reactions, and is also a useful confirmatory test with monoreactive strains.

Antibodies, Bacterial↗
PubMed1975

[ABO blood-group phenotypes and pathogenesis of cardiovascular diseases. Congenital, rheumatic and coronaric heart disease and arterial hypertension (author's transl)].

Many cases of cardiovascular diseases have been examined in reference to the distribution of ABO blood-groups, in order to calculate the relative risk of disease and the hemogroupal distributive significance in our samples as related to those of other authors, using combined calculation. The analysis concerned the following cases: 746 with arterial hypertension, 3258 with congenital heart disease, 4503 with articular rheumatism, 1047 with acquired valvulopathia, and respective controls. It was found that blood-group phenotypes represent an important biophysiopathological action in regard to articular rheumatism and its cardiac consequences, in myocardial infarction and in hypertension, males only. On the contrary, no action in regard to congenital heart disease was found, with the exception of some single anomalies which have yet to be confirmed. This hemogroupal action greatly exceeds the one limited to the immunitary analogy and is a noticeable part of family heredity. It shows itself in: -- a significant negative association with group O and positive association with group A in the myocardial infarction; -- a significant negative association with group O and positive for the others in the valvulopathic (rheumatic) diseases; -- a positive association with A phenotype and negative with B in arterial hypertension, males only; -- no association with ABO blood-groups and congenital heart disease.

ABO Blood-Group System↗