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Biomedical subjects

G Luca

Publications and source records attributed to G Luca.

27 records · Page 2Linked to original sources
PubMed1996

A rapid qualitative method to assess in vitro immunobarrier competence of pancreatic islets containing alginate/polyaminoacidic microcapsules.

A quick method for the qualitative evaluation of immunoisolatory properties associated with islet-containing alginate/poly-L-ornithine (AG/PLO) microcapsules is described. In particular, we examined a new AG/PLO coherent microcapsule (CM) prototype that was recently developed in our laboratory, although the procedure could be applicable to other capsule types as well. We observed no binding of immunoglobulins (Ig) contained in islet cell antibody (ICA)-positive human sera (> 60 Juvenile Diabetes Foundation units, JDT U) to pig islets, enveloped within AG/PLO CM, under indirect immunofluorescence examination. Also, CM were shown to inhibit human lymphocyte proliferative capacity fully, as assessed by the 3H-thymidine incorporation rate, in in vitro mixed xenogeneic pig islet/human lymphocyte co-cultures. These results provided us with a preliminary method to attempt standardization of basic physical/chemical properties which should be associated with an immunoisolatory membrane for islet allo/xenograft immunoprotection.

Analysis of Variance↗
PubMed1996

Ultrastructural examination of pancreatic islet containing alginate/polyaminoacidic coherent microcapsules.

We ultrastructurally examined pancreatic islet containing alginate/poly-L-ornithine (AG/PLO) coherent microcapsules (CM) which we had previously developed in our laboratory. Specific issues, such as extent of CM coherency as well as morphologic integrity, and viability of the encapsulated islet subcellular organelles were addressed. We preliminarily demonstrated, both at scanning (SEM) and transmission (TEM) electron microscopy analysis, that CM seem to provide for structurally intact and functional, artificial microbarriers, enveloping each individual islet. These findings, additional to CM immunobarrier competence and biocompatibility, previously shown by our studies, might foster progress of CM into islet graft immunoisolation experimental and ultimately clinical trials.

Alginates↗
PubMed1990

Presence of functional domains in Limulus polyphemus hemocyanin.

In an attempt to isolate structural domains of arthropod hemocyanins and possibly to investigate their functional properties, we have undertaken proteolytic digestion experiments of isolated subunits from Panulirus interruptus and Limulus polyphemus oxy-hemocyanin. Satisfactory results have been obtained using trypsin at high concentration and short digestion times. Results show that, in the case of Panulirus hemocyanin, only subunit alpha is susceptible to trypsin digestion, but that proteolytic cleavage is associated with the loss of the copper-oxygen band; on the other hand, in the case of Limulus hemocyanin, four subunits (I, II, III and IV) show a significant susceptibility to trypsin, and their fragmentation takes place with preservation of the oxygen-binding capacity. A more detailed study of the digestion products of subunit IV from Limulus hemocyanin reveals that the proteolytic fragments keep together in a single non-covalent complex. Attempts to separate the native fragments result in the precipitation of the digestion products. Subunit IV of Limulus with proteolytic cuts binds O2 and CO with the same affinity as the native subunit, suggesting that the copper site is still preserved structurally and is functionally active in a 37 kDa trypsin-resistant domain.

Animals↗
PubMedDate not supplied

Short-term stimulation studies on neonatal pig pancreatic duct-derived cell monolayers.

Short-term stimulation with insulinotropic factors may induce morphologic and functional changes in primary ductal cell cultures as a potential source of stem cells. We sought to assess the capacity of hepatocyte growth factor (HGF) to induce expression and maturation of proteins--PDX-1 and GLUT-2--and the subsequent beta-cell secretory profiles. HGF, which is involved in pancreatic development, may induce islet beta-cell neogenesis. Primary ductal cell monolayers were cultured in Click's + FBS 10% at 37 degrees C until tissue confluence. The medium was enriched with HGF (10 ng/mL for different periods); controls were treated for similar times with normal culture medium. At the end of the study, three-dimensional islet-like cell aggregates were observed in both conditions. In all conditions immunostaining studies showed positivity for the major endocrine-phenotype cell markers: insulin, PDX-1, glucokinase, and GLUT-2. Furthermore, treatment with HGF for short periods induced the expression of a functionally active, phosphorylated isoform of PDX-1. Finally, we observed that under basal conditions the cells initially and progressively released proinsulin throughout 5 days in all settings. Thereafter proinsulin was gradually replaced by insulin in the culture medium, reflecting a maturation progress. This pattern of insulin maturation and release was more evident when the cells were continuously stimulated with HGF for 12 days. The employed stimuli seemed to differentiate the original ductal cell layers toward endocrine cell phenotypes that synthesize and release proinsulin and subsequently insulin. HGF seems to provide a more efficient differentiation.

Animals↗
PubMedDate not supplied

[Neonatal muscular spinal atrophy: a case report].

Spinal Muscular Atrophy (SMA) is an autosomal recessive disease characterized by diffuse proximal and distal weakness due to deletions of the survival motor neuron (SMN) gene localised on chromosome 5q13. Pathological studies show decreased numbers of motorneurons in spinal cord. SMA was initially sub-classified clinically into three types base on age at onset and clinical course. SMA type 1, Werdnig-Hoffmann disease, has an onset within the first 6 months and death within the first two years. In contrast, SMA type II has an onset after six months of life and the children achieve the ability to sit unaided. Children with SMA type III (Kugelberg-Welander) usually have normal milestones in the first year and achieve the ability to walk but then show evidence of mild weakness. The prognosis is good and the clinical course is not (or very slowly) progressive. Recently, Dubowitz described a new form of SMA called type 0 with a neonatal onset, facial weakness, progressive and fatal clinical course. These infants show generalised hypotonia, the lower limbs are more affected than the upper with marked weakness of all axial muscles. We report a case of SMA, uncommon for the early onset and the respiratory difficulties. The diagnosis has been done by genetic analyses showing a SMN mutation.

Age Factors↗
PubMedDate not supplied

Complete AV heart block during acute silent myocardial infarction detected only by myocardial perfusion scintigraphy.

Seven patients with complete AV heart block and wide QRS complexes, atypical chest pain and no specific serum enzymes modifications for myocardial necrosis are reported. The patients showed no prior complete AV heart block although myocardial perfusion scintigraphy showed localized uptake demonstrating a small area of acute myocardial necrosis. These cases may be described as "true silent" acute myocardial infarction which could not be clinically recognised without Technetium pyrophosphate scintigraphy.

Atrioventricular Node↗