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Biomedical subjects

M de Mari

Publications and source records attributed to M de Mari.

12 recordsLinked to original sources
PubMed2000

Isinglass/collagen: denaturation and functionality.

Isinglass is widely used commercially to clarify alcoholic beverages by aggregation of the yeast and other insoluble particles. It is derived from swim bladders of tropical fish by solubilisation in organic acids and consists predominantly of the protein collagen. The low content of intermolecular cross-links allows ready dissolution of swim bladder compared to bovine hide which is cross-linked by a high proportion of stable bonds and requires enzymic digestion to solubilise. Isinglass is no longer effective as a clarifying agent if thermally denatured hence the collagenous triple helical structure must be maintained. Thermal denaturation of isinglass occurs at 29 degrees C, compared to 40-41 degrees C for mammalian collagens, primarily due to the lower hydroxyproline content. The hydroxyproline is essential for the formation of H-bonded water-bridges through the hydroxyl group and the peptide chain thereby stabilising the triple helix. Based on the lower enthalpy determined by differential scanning calorimetry we have calculated that the thermally labile domain of the isinglass molecule was 41 residues compared to 66 for mammalian collagen. The fining efficiency was unaffected by pH, chelating agents, detergents and removal of surface proteins from yeast cells. Studies on the mechanism of action of isinglass have shown that higher molecular weight aggregates that increase the length of the collagen molecules (trimers, tetramers, etc.) increase efficiency and that their surface charge are important in the clarification process. By chemical modification, we have shown that blocking positively charged groups had no effect on the fining process, whilst negative charges are clearly essential and that increasing the negative charge by succinylation increases its efficacy. Solutions of bovine hide collagen were shown to be equally effective in refining beers and standard yeast preparations. The higher thermal denaturation temperature, ready availability and reproducibility of bovine collagen preparations gives it considerable advantages over isinglass.

Air Sacs↗
PubMed2000

Parkinsonism in a patient with AIDS and cerebral opportunistic granulomatous lesions.

The localization of opportunistic infections in the basal ganglia in patients with acquired immunodeficiency syndrome (AIDS) can cause movement disorders, such as choreoathetosis, dystonia, hemiballism and, more rarely, parkinsonism. We describe the case of an AIDS patient who developed cerebral opportunistic granulomatous lesions and, subsequently, a parkinsonian akinetic-rigid syndrome. In agreement with cases reported in the literature, the parkinsonian syndrome developed only when the lesions bilaterally involved basal ganglia. The critical localization of the opportunistic lesions in the direct and indirect strio-pallidal pathways possibly associated with the HIV-related neurotoxicity might have contributed to determine this clinical picture.

AIDS-Related Opportunistic Infections↗
PubMed1999

Usefulness of proton magnetic resonance spectroscopy in differentiating parkinsonian syndromes.

Proton magnetic resonance spectroscopy ((1)H-MRS) was performed in patients with a clinical diagnosis of idiopathic Parkinson's disease (IPD), multiple system atrophy (MSA) or progressive supranuclear palsy (PSP) in order to assess metabolic differences between the three groups of patients. Single-volume (1)H-MRS, localized to the lentiform nucleus, was carried out in 19 IPD patients, 14 MSA patients, 11 PSP patients and 12 age-matched healthy subjects. The signals of N-acetylaspartate (NAA), choline-containing compounds (Cho) and creatine-phosphocreatine (Cr) were evaluated as peak area ratios. The NAA/Cho peak ratio was significantly reduced in MSA and in PSP patients compared to IPD patients and to controls. The NAA/Cr peak ratio was significantly reduced in MSA, in PSP and in IPD patients compared to controls, but only in MSA compared to IPD patients. The NAA reduction in the basal ganglia of MSA and PSP patients may reflect a neuronal loss or damage. Single-volume (1)H-MRS may be a useful tool in differentiating MSA and PSP from IPD patients.

Adult↗
PubMed1997

Freezing gait in Parkinson's disease.

Freezing is a well-known problem in Parkinson's disease (PD) and is characterized by an abrupt difficulty in starting or continuing rhythmic and repetitive movements. We utilized a questionnaire in order to assess the occurrence of the freezing gait phenomenon (FG) in a population of 100 consecutive PD patients. Our PD population included 70 males and 30 females, with a mean age of 61.1 +/- 9.1 years. Mean duration of PD was 6.5 +/- 4.0 years. 92/100 patients were under L-Dopa treatment. The FG phenomenon occurred in 60% of patients. It appeared on average 4.8 years after the beginning of PD; in 16% of the cases it was evident before starting L-Dopa treatment. FG was more frequent among female patients. There was no significant correlation between the occurrence of FG and the age of the patients; on the other hand, a significant correlation was found with the duration of the disease (p < 0.001). FG occurred more frequently in the subgroup of patients with the akinetic form (odds ratio: 3.05); whilst an opposite tendency was evident in the subgroup with the tremor predominant form (odds ratio: 0.29).

Adult↗
PubMed1996

Choreoathetosis in acquired immune deficiency syndrome patients with cerebral toxoplasmosis.

The aim of our study was to evaluate both the incidence and the pathologic and clinical features of extrapyramidal disorders in a population of acquired immune deficiency syndrome (AIDS) patients with cerebral toxoplasmosis. Of 240 AIDS patients evaluated in the 1985-1994 period, 50 of them were diagnosed to have cerebral toxoplasmosis on the basis of the following criteria: occurrence of specific antibodies, computed tomography and/or magnetic resonance imaging (MRI), and regression of the symptoms after specific therapy. Three of 50 (6%) had hemichoreoathetosis. In the first case, the disorder began as a dyskinesia of the left hand that subsequently spread to the whole ipsilateral arm and assumed the features of choreic athetotic movements. The other two cases were characterized by left hemisomatic distal choreic movements. Therapy with pyrimethamine and sulfadiazine led to a complete recovery of the extrapyramidal signs in two cases and to improvement in the third. According to our observations, the onset of these movement disorders could not be related to the dimension of the lesion or to the edema, but to a specific localization in subthalamic nucleus, in subthalamic/pallidal, and pallidal/thalamic pathways. MRI seems the elective tool to perform a more accurate study of the anatomic areas involved in this pathway and to verify their integrity. Cerebral toxoplasmosis in AIDS can be considered as a new etiopathogenic cause of choreoathetosis.

AIDS Dementia Complex↗
PubMed1995

Changes in the amplitude of the N30 frontal component of SEPs during apomorphine test in parkinsonian patients.

Somatosensory evoked potentials (SEPs) to median nerve stimulation have been performed before and after apomorphine-test in 10 parkinsonian patients. Latency and amplitude of the P14-N20 parietal complex and of the P20-N30 frontal complex were evaluated. The N30 amplitude was significantly reduced before apomorphine administration (p < 0.001) with a consequent increase of the N20/N30 amplitude ratio (p < 0.001). Eight patients clinically improved after Apomorphine. Following Apomorphine there was no change in the amplitude of the parietal complex P14-N20. On the other hand the frontal complex P20-N30 showed a significant amplitude potentiation (p < 0.005), with a reduction of the N20/ N30 amplitude ratio (ns). This finding was almost constant among the 8 responder patients. These results suggest the utility of combining clinical and neurophysiological data to assess the responsiveness to dopaminergic treatment.

Adult↗
PubMedDate not supplied

Intravenous administration of lisuride in the treatment of neuroleptic malignant syndrome.

The neuroleptic malignant syndrome (NMS) is a very rare but life-threatening complication of neuroleptic treatment. The mortality of NMS has been estimated at 8-30% and the most common cause of death is respiratory failure. Signs and symptoms of NMS are attributed to impairment of dopaminergic neurotransmission in the central nervous system. We describe two cases of NMS successfully treated with intravenous lisuride in combination with oral L-Dopa.

Adult↗
PubMedDate not supplied

Short-latency median nerve somatosensory evoked potentials in three cases of parkinsonism and dopa responsive dystonia.

We studied somatosensory evoked potentials after median nerve stimulation in a sporadic case of dopa responsive dystonia and in two brothers with different combinations of dystonia and parkinsonism. The latencies of all potentials were normal. The amplitude of the P20-N30 frontal complex showed a significant reduction in all cases. Our results suggest a common neurophysiopathological pattern underlying these two conditions.

Adult↗