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Biomedical subjects

G Luca

Publications and source records attributed to G Luca.

16 recordsLinked to original sources
PubMed2001

Microbiological and densitometric TLC analyses for peptides in liposomes.

Quantitative determination of Leucinostatins and/or of similar peptides, such as Peptaibols, is sometimes quite difficult to perform especially when they are entrapped in vectors, i.e. liposomes, whose components display UV absorbances that may obscure those of the active principle. Therefore, in these cases, it is useful to find alternative ways, especially when high pressure liquid chromatography (HPLC) is difficult to perform or needs long procedure times. In the present paper, the use of microbiological and densitometric methods for quantitative analysis of Leucinostatin A (Leu-A) are described and the results compared with those from HPLC analyses. The use of microbiological and densitometric assays, furnished results comparable with those obtained by HPLC. Of the two methods used, the microbiological procedure appeared to be less accurate and precise.

Chromatography, Thin Layer↗
PubMed2001

Cellular support systems for alginate microcapsules containing islets, as composite bioartificial pancreas.

To improve the functional performance of microencapsulated islets, we examined the effects of putative cellular support systems, consisting of rat purified Sertoli cells (SC) and astrocytes (AA), on coenveloped allogeneic islets. Coincubation of islets with SC but not AA, resulted in significant stimulation of beta cell mitogenesis, coupled with a significant increase in in vitro glucose-stimulated insulin release. Preliminarily, the xenotransplantation of coencapsulated rat islets and homologous SC significantly prolonged remission of hyperglycemia in diabetic mice.

Alginates↗
PubMed2001

Pectin-based microspheres: a preformulatory study.

This paper reports on (a) the production of pectin microspheres and (b) the influence of different experimental parameters and ionic crosslinking on morphological and dimensional characteristics of pectin microspheres. Morphological and dimensional characteristics of pectin were analyzed as a function of the type of pectin, the dispersing phase, the stirring speed, and the emulsifying agent. Crosslinking by calcium chloride and the encapsulation of antibiotics (i.e., metronidazol and tetracycline) gave particles morphologically similar to empty particles but with slower swelling kinetic.

Chemistry, Pharmaceutical↗
PubMed2000

Sertoli cell-induced reversal of adult rat pancreatic islet beta-cells into fetal-like status: potential implications for islet transplantation in type I diabetes mellitus.

BACKGROUND: Clinical success of pancreatic islet allograft (TX) for the therapy of diabetes mellitus is hampered by several pitfalls, primarily including the restricted availability of donor tissue and the immune- and/or non-immune-related TX's early loss, with the latter not necessarily being prevented by the host's general immunosuppression. Finally, adult islet beta-cells normally exhibit minimal proliferation capacity, which would not permit restoration of an eventually declining TX mass. METHODS: To address the limited beta-cell growth capacity, we have examined whether in vitro co-culturing adult rat islets (I) with prepubertal homologous Sertoli cells (SC) would stimulate I beta-cell expansion. SC-derived effects on the islets were studied in vitro, both morphologically (confocal laser microscopy) and functionally (glucose-stimulated insulin release). We have also preliminarily examined the in vivo impact of microencapsulated SC + I co-cultures on TX in diabetic mice. RESULTS: In vitro, we observed that SCs promoted significant beta-cell replication, as I beta-cell mitotic activity increased from 1% to greater than 8%, which coincided with the adult elements reversing into fetal-like status. This finding was coupled with significantly greater insulin release either in basal or in response to glucose, as compared with controls. CONCLUSIONS: Addition of SC to islets promotes reversal of the adult beta-cell elements into fetal-like conditions, thereby providing a new, potentially powerful tool that could significantly enhance the functional performance of islet TX in diabetic recipients.

Animals↗
PubMed2000

Effects of anti-oxidizing vitamins on in vitro cultured porcine neonatal pancreatic islet cells.

Oxidative stress may cause severe cellular damage to both allo- and xeno-transplanted islets, additional to islet graft-directed immunity, in diabetic patients. We thus aimed to examine the effects of antioxidants on in vitro culture-maintained, neonatal porcine cell clusters (NPCCs). NPCCs were treated with antioxidants (vitamins D3 and E) by a certain time of their maturation and differentiation process. Insulin recovery showed that both vitamins D3 and E, unlike untreated controls, resulted in preservation of the islet function for significantly long periods of time. Such effects were also confirmed during NPCCs in vitro static incubation with high glucose. Furthermore, morphologic examination of NPCCs demonstrated that at 16 days of cell culture beta-cell clusters were significantly larger and more intact when exposed to the vitamins as compared to controls. According to these preliminary results, because the employed vitamins, known to retain anti-oxidizing properties, seemed to clearly improve NPCCs morphology and function, they may represent a potentially useful tool for islet culture maintenance in the pre-transplant time period.

Animals↗
PubMed1999

Transplantation of pancreatic islets contained in minimal volume microcapsules in diabetic high mammalians.

To minimize technical problems relating to excessive size (600-800 mu in diameter) of standard alginate microcapsules (CSM) for pancreatic islet graft immunoisolation, we have developed two novel minimal volume, chemically identical, capsule prototypes (MVC): 1) coherent microcapsules (CM), and 2) medium-size microcapsules (300-400 mu, MSM). CM, which envelop each individual islet within a thin alginate hydrogel cast, are prepared by emulsification, whereas MSM are made by atomizing the islet-alginate suspension through a special microdroplet generator. Upon graft into diabetic rodents, CM have shown to immunoprotect both allo- and xenogeneic nondiscordant islets, and restored normoglycemia. In higher mammals, at subtherapeutic doses, CM fully immunoprotected islet allografts (pig-->pig), but only temporarily xenografts (dog-->pig). We then used MSM to immunoisolate canine islet allografts in the peritoneal cavity of dogs with spontaneous insulin-dependent diabetes. Of three grafted dogs, two showed full remission of hyperglycemia with insulin withdrawal. MSM could represent an intermediate solution between CSM and CM for peritoneal immunoisolated islet transplants.

Animals↗
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

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↗