Search PubMed⌕ Search

Biomedical subjects

M Rotunno

Publications and source records attributed to M Rotunno.

At least 19 recordsLinked to original sources
PubMed2006

Memory effects in nematics with quenched disorder.

We present a combined experimental and Monte Carlo study of a nematic phase in the presence of quenched disorder. The turbidity of a nematic liquid crystal embedded in a porous polymer membrane is measured under different applied field conditions for field-cooled and zero-field-cooled samples. We find that a significant permanent alignment of the nematic can be induced by fields as low as 0.1 V/microm applied during the isotropic to nematic transition. An analogous effect and dependence on sample history is found by studying the order parameter of a sprinkled disorder Lebwohl-Lasher spin model, indicating that dilute quenched randomness is sufficient to produce memory effects in nematics. The large memory induced by field cooling appears to be written in the system during the transition as a result of the field action on freely oriented nematic nuclei. At lower temperature the nuclei consolidate into permanent nematic textures developed from the interaction with quenched disorder.

Journal Article↗
PubMed2005

Nematics with quenched disorder: pinning out the origin of memory.

Memory effects and glassy behavior have been repeatedly observed in disordered nematic liquid crystals but the connection between these effects and the system topology remained unrevealed. We present an analysis of the local and global topology of the nematic ordering in the presence of quenched disorder and we show that nematics with quenched disorder can be mapped into a system of pinned defect lines and that the memory of the system stems from the pinning of these strings.

Journal Article↗
PubMed1985

In vivo localization of C3 on the brush border of proximal tubules of kidneys from nephrotic patients.

Deposits of C3 but not of C1q and C4 were detected on the proximal tubules of kidneys from nephrotic patients with non-selective proteinuria. The incidence of tubular C3 deposits was significantly higher in patients with membranous glomerulonephritis, focal glomerulosclerosis, membrano-proliferative glomerulonephritis and non-selective proteinuria than in patients with minimal change disease, nephrotic syndrome and selective proteinuria or in patients with glomerular disease, but without nephrotic syndrome. The occurrence of tubular C3 deposits was positively correlated with the amount of urinary C3 excretion. In vitro studies showed that the human normal kidney as well as pathologic specimens negative for in vivo tubular C3 deposits were able to bind C3 on the brush border of proximal tubules when incubated with fresh heterologous serum. In contrast, in patients with non-selective proteinuria and in vivo tubular C3 deposits, the binding of heterologous C3 to the brush border of proximal tubules was markedly reduced. The positive correlation between the occurrence of tubular C3 deposits and the urinary complement excretion, together with the detection of the C3 breakdown products in the urines further supported the hypothesis that complement components, once filtrated through the glomerular barrier, might be activated by the brush border of the proximal tubule.

Adolescent↗
PubMed1982

In vitro alternative pathway activation of complement by the brush border of proximal tubules of normal rat kidney.

The purpose of this study was to investigate which structures of the nephron, if any, are capable of directly activating the complement (C) system. To this end, two sets of experiments were performed. First, activation of C was assessed on sections of frozen kidney tissue, using the indirect immunofluorescence technique for the demonstration of C fixation. Second, glomerular or tubular fractions of kidney were incubated with normal fresh serum, and subsequent C consumption was measured. The data obtained support the interpretation that the brush border of proximal tubules activates the alternative pathway of the C system. This phenomenon may have pathogenic significance in conditions of aselective proteinuria.

Anaphylatoxins↗
PubMed1981

Coagulation and fibrinolysis study in systemic lupus erythematosus: haematological, urinary and tissue parameters.

Haematochemical, urinary and tissue parameters were examined in the elaboration of the coagulation and fibrinolysis profile in 33 cases of systemic lupus erythematosus in different stages of the disease. Coagulation abnormalities varied from hypo- to hyper-coagulability, these being often associated in the same patient, either simultaneously or at different stages of the disease. Activation of coagulation, closely related to the immunological activity of the disease, was present in 80% cases in the acute stage, and 36% of those in the remission stage. The lupus-like anticoagulant was not much involved, and platelets were the prime figures in the haemostatic abnormalities of lupus, those being the preferred target of direct antibody activities, or possibly of immune complexes as well. Activation of the coagulatory cascade is not uncommonly accompanied by a thrombophilic tendency coupled with signs of consumption, this being the expression of a continuously stimulated haemostatic balance.

Autoantibodies↗
PubMed1980

[Hormonal modulation of inflammation].

The tissue damage during the inflammation is determined by the enzymes and the mediators of anaphylaxis released from polymorphonuclear cells (PMN), platelets, basophils and mastocytes. The control of this release involves the cAMP and cGMP. The cyclic nucleotides independently or synergically regulate the polymerisation of the microtubules and the microfilaments. Drugs increasing the intracellular concentration of cAMP or cGMP inhibit or enhance respectively the enzymatic release from PMN, basophils and mastocytes. In the platelets, cAMP plays a very important role, whereas the cGMP function is controversial.

Adenylyl Cyclases↗