Quantitative Correlation between Steric Defects and Thermal Behavior in Highly Syndiotactic Polystyrene: A Study Based on DSC and 13C NMR Spectroscopy

Several syndiotactic polystyrene (sPS) samples have been synthesized by using different catalytic systems. Their stereochemistry has been determined by ¹³C NMR spectra in both the aliphatic CH₂ and aromatic C₁ resonance regions. The observed peaks have been unambiguously assigned to specific hexads and heptads, respectively, and their intensities have been used to draw the percent of defects (meso dyads) in the polymer chains. On the hypothesis that chain defects are at the origin of chain folding and thus determine the thickness of crystalline lamellae, we performed differential scanning calorimetry (DSC) analysis on the same samples, and their thermal parameters were measured. A model was developed to determine the amount of steric defects from the DSC melting‐peak profiles, and the results obtained were compared with the NMR results. A satisfactory agreement was found (correlation factor 0.96) in the explored range of defect concentrations (up to 2.5% of meso dyads). The possible influence of the extraction procedure of the amorphous fraction was found to be negligible. Thus, information on stereochemistry can be obtained from DSC experiments starting from as‐prepared (not extracted) samples.

     

Structural investigations of cross-linked hyaluronan.

Structural properties of several cross-linked hyaluronan derivatives, obtained by scanning electron microscopy, monodimensional NMR microscopy and small angle X-ray scattering of synchrotron radiation, are presented and compared with those observed for non-modified hyaluronic acid, used as a reference material. The experimental results, obtained in different media, showed a consistent picture of the synthesized matrices. In particular, the presence of zones of denser polymeric material observed by electron microscopy resulted in a higher transversal relaxation rate of the bulk water protons as well as in a decrease of the diffusion coefficient obtained by NMR microscopy. Moreover, the presence of polymer junction zones gave rise to the appearance of a well-defined correlation peak in the pattern of intensity of the scattered X-radiation.     

Genetic polymorphisms and cerebrospinal fluid levels of tissue inhibitor of metalloproteinases 1 in sporadic Alzheimer's disease

Tissue inhibitor of metalloproteinases 1 (TIMP-1) inhibits several proteinases including a disintegrin and metalloproteinase 10 (ADAM10), a major alpha-secretase that cleaves the beta-amyloid precursor protein within its amyloidogenic Abeta domain. The gene encoding TIMP-1 (TIMP 1) maps to the short arm of the X chromosome, in a region previously suggested as conferring genetic susceptibility for Alzheimer's disease (AD). To determine whether genetic variability of TIMP 1 contributes to the pathogenesis of AD, we analysed one single nucleotide polymorphism within TIMP 1 and one single nucleotide polymorphism in the 5'-untranslated region of TIMP 1 in patients with AD and control subjects from two independent and ethnically different populations. We did not observe any association between TIMP 1 genotypes and the diagnosis of AD in men or women. We also measured TIMP-1 protein levels in the cerebrospinal fluid of patients with AD, healthy control subjects, and patients with other neurological disorders. TIMP-1 levels were similar in all groups. In addition, no significant differences were observed after stratification for TIMP 1 genotypes. Our data show that neither genetic variability nor protein levels of TIMP-1 are associated with AD.     

Early atherosclerotic lesions in infancy: role of parental cigarette smoking

Cigarette smoking is associated with an increased incidence of atherosclerotic diseases. The aim of this study was to examine the progression of the preatherosclerotic lesions previously observed by us in coronary arteries of fetuses of smoker mothers and in infants with smoker parents. We examined the coronary arteries of 34 infants, aged 1–36 months, and the histological and biological [c-fos, proliferating cell nuclear antigen (PCNA), and apoptosis] features of the early atherosclerotic lesions. In 17 infants (50%), at least one parent smoked, generally more than five cigarettes a day. In 18 cases (53%), we observed variable thickening of the coronary walls from preatherosclerotic lesions to juvenile atherosclerotic plaques, related to parental smoking habit. This morphological progression of the lesions was accompanied by a sequence of biological changes in the smooth muscle cells of the tunica media. We suggest that the oxidants present in the gas phase of the parental cigarette smoke pass through the endothelium and induce at first the c-fos gene activation and subsequently the PCNA positivity, that is, a proliferative process.     

The efficacy of enrofloxacin,alone or combined with metronidazole,in the therapy of canine leishmaniasis

We evaluated the efficacy of enrofloxacin, alone or combined with metronidazole, against Leishmania infantum. The in vitro activity of this fluoroquinolone was assessed using two different methods: a direct test aimed at assessing the drug activity on the parasite, and an indirect test aimed at evaluating the drug effect on macrophage killing, lymphomonocyte activation and nitric oxide production. An in vivo test was also performed on 36 dogs with leishmaniasis, subdivided into three groups, one treated with enrofloxacin, another with enrofloxacin plus metronidazole, and a control group with meglumine antimoniate. The direct test did not show any action of enrofloxacin on the parasite, while the indirect testing showed an enhancement of macrophage killing and an increase in nitric oxide production. These findings show that enrofloxacin does not exert a direct anti-leishmanial activity in vitro. However, on the basis of the positive immunostimulation results shown in vitro and the clinical improvement, particularly of the cutaneous lesions, obtained in several dogs in the in vivo trial, the use of enrofloxacin in association with a specific anti-leishmanial drug can be proposed in the therapeutic protocol of canine leishmaniasis.     

Loss of lamin A/C expression revealed by immuno-electron microscopy in dilated cardiomyopathy with atrioventricular block caused by<Emphasis Type="Italic"> LMNA</Emphasis> gene defects

Mutations of the LMNA gene encoding the lamin A and C nuclear envelope proteins cause an autosomal dominant form of dilated cardiomyopathy (DCM) with atrioventricular block (AVB). The aim of this study was to investigate ultrastructural nuclear membrane changes by conventional electron microscopy and protein expression by immuno-electron microscopy in the heart of patients with DCM and AVB due to LMNA gene mutations. Four immunohistochemical techniques were used: pre-embedding and post-embedding in Epon-Araldite resin and London Resin White (LRW), with and without silver enhancement. Parallel light microscopy immunohistochemistry studies were performed. Conventional electron microscopy showed a loss of integrity of the myocyte nuclei with blebs of the nuclear membrane, herniations and delamination of the nuclear lamina and nuclear pore clustering. Post-embedding LRW was the most informative technique for morphology and immuno-labelling. Immuno-labelling was almost absent in the nuclear envelope of patients with LMNA gene mutations, but intensely present in controls. The loss of labelling selectively affected myocyte nuclei; the endothelial cell nuclei were immunostained in patients and controls. Light immunohistochemistry confirmed the results. These findings confirm the hypothesis that LMNA gene defects are associated with a loss of protein expression in the selective compartment of non-cycling myocyte nuclei.     

Anxiolytic effects of intra-amygdaloid injection of the D1 antagonist SCH23390 in the rat

The intercalated islands are intra-amigdaloid clusters of D1 receptor rich GABAergic neurons, which control impulse traffic between the basolateral complex and the central nucleus of the amygdala. As dopaminergic transmission within the amygdala may play a role in anxiety, the effect of the D1 antagonist SCH23390 microinjected mainly close to the rostral intercalated islands in rats was studied, using the White and Black Box test. SCH23390 reduced anxiety by an increase in the latency of the first entry into the black compartment and by an increase in the total time spent in the white compartment of the White and Black Box test, while there was no significant modification of locomotion. It is suggested that blockade of D1 receptors in the rostral intercalated islands may reduce anxiety through a reduction of GABA-mediated dishinibition of the central amygdaloid nucleus.