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R Calafiore

Publications and source records attributed to R Calafiore.

At least 37 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

Culture maintenance of isolated adult porcine pancreatic islets in three-dimensional gel matrices: morphologic and functional results.

Adult porcine pancreatic islets are attractive for morphological and functional investigations but are difficult to obtain and use. In particular, the islet isolation and purification process is hampered by the lack of an outer capsule membrane, with predisposition to fragmentation. Attempts to culture maintain pig islets and preserve viability and functional competence have also been difficult. We found that placement of isolated porcine islets in biocompatible three-dimensional hydrogel matrices, made of calcium alginate and poly-L-ornithine, would improve morphology, as well as secretory responses to rapid glucose concentration changes.

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↗
PubMed1995

Method for mass retrieval, morphologic, and functional characterization of adult porcine islets of Langerhans: a potential nonhuman pancreatic tissue resource for xenotransplantation in insulin-dependent diabetes mellitus.

BACKGROUND: We aimed to implement and expand an original technique for mass procurement, maintenance, and study of adult porcine pancreatic islets (PPIs), which had been previously developed in our laboratory. METHODS: By screening through specific criteria for pig donor strain selection, we acquired new leads for separation of large, intact islets from the whole pancreas. Accomplishment of this goal also was permitted by adjusting, and or replacing physical/chemical parameters of the pancreatic digestion process. RESULTS: High yield isolation and purification of large and intact PPIs was thoroughly associated with full retention of islet morphologic integrity, as proven by accurate assessment of islet cell structure and ultra-structure, as well as viability and functional competence, in vitro and in vivo. In particular, we observed that isolated PPIs may retain capability of synthesizing insulin "de novo," and regulate this property on glucose stimulation. We also began to explore new approaches for in vitro, long-term PPI culture maintenance. CONCLUSION: We found that a graft of PPI containing algin/polyaminoacidic microcapsules, in nonimmunosuppressed diabetic rodents, was associated preliminary with remission of hyperglycemia, providing further insight into the physiologic competence of these islets.

Alginates↗
PubMed1993

Preventive effects of azathioprine (AZA) on the onset of diabetes mellitus in NOD mice.

We have studied the effects of long-term treatment with azathioprine (AZA) vs cyclosporin A (CSA) vs placebo (PL), in three groups of 10 week old, prediabetic NOD mice. One of 8 AZA, none of 8 CSA and 7 of 11 PL treated mice developed overt diabetes (IDDM). Quantitative morphometric analysis conducted on mouse pancreatic histologic sections documented that extent and degree of islet beta-cell damage were incomparably less severe in the mice that received AZA or CSA compared to those treated with PL. Since early and prolonged treatment with AZA seems to prevent the onset of DM in NOD mice as nearly effectively as CSA, AZA, which is significantly safer than CSA, could replace the latter as a potential approach for the immunotherapy of IDDM.

Animals↗
PubMed1993

Pancreatic beta-cell destruction in non-obese diabetic mice.

We determined the natural history of the widespread pancreatic islet beta-cell destruction that precedes the onset of spontaneous putative autoimmune diabetes mellitus in NOD mice. For this purpose, we performed both histological and immunocytochemical examinations of pancreata retrieved from mice at 2 through 30 weeks of age. An overexpression of la antigens was identified on islet beta cells at 4 weeks of age, without evidence of mononuclear cell infiltration. The abnormal expression of la antigens was age-related and was associated with hyperexpression of class I antigens and progressive islet cell histologic damage after 17 weeks of age. Immunocytochemical examination of islet cell infiltrate showed that the number of macrophages did not increase during the early phase of islet cell damage in these mice. The L3T4/Lyt-2 ratio increased after 7 weeks of age, but was 1:1 in the late stage of insulitis. These findings suggest that widespread islet beta-cell destruction is a process that begins primarily with derangements of the pancreatic beta-cell immune pattern, which may trigger a mononuclear cell reaction.

Animals↗
PubMed1991

Xenotransplantation of microencapsulated pancreatic islets contained in a vascular prosthesis: preliminary results.

Porcine and human pancreatic islets were microencapsulated in an alginate-polylysine biomembrane and put in a chamber of a new vascular prosthesis composed of an inner tubing of Dacron mesh and an outer tubing of expanded polytetrafluorethylene material. The vascular prosthesis was anastomized between the iliac artery and the contralateral vein of diabetic dogs. The recipients did not receive any immunosuppressive therapy. Function of porcine and human islets was monitored by measuring serum glucose levels and human C-peptide concentrations. After transplantation, serum glucose levels were maintained at values lower than 200 mg/dl, and C-peptide concentrations were between 0.8 and 3.2 ng/ml. Injected insulin requirements decreased by 50%-60%. Four to 8 weeks after transplantation, histologic examination showed well-preserved and functioning islets in the majority of intact microcapsules. Fibrin and inflammatory cells were not observed in the chamber. These data suggest long-term survival and function of microencapsulated pancreatic islets in the vascular prosthesis.

Adolescent↗
PubMed1991

A simple method for the DNA content assay of culture maintained pancreatic islets of Langerhans.

A simple method for assaying DNA content of in vitro culture maintained pancreatic islets is described. By employing lyophilization of the islets and subsequent fluorometric analysis, we have been able to measure DNA from relatively small cell samples. The method may result advantageous, over others, previously reported, since it is less subject to experiment-related interfering conditions. This procedure, which is easy and reliable, even for very low DNA concentrations, seems to be very useful for culture maintained pancreatic islets, since in vitro work conducted with this endocrine tissue is usually associated with small size cell samples. The method may help for a simple assessment of the viable islet cell mass in in vitro studies.

Ammonium Hydroxide↗
PubMed1991

Immunoprotection of pancreatic islet grafts within artificial microcapsules.

To circumvent pancreatic islet graft-directed immune destruction we enveloped porcine islets within highly biocompatible and selectively permeable algin/polyaminoacid microcapsules. These special microspheres were deposited between the inner (permeable) and the outer (impermeable) layers of an artificial, coaxial vascular prosthesis, directly anastomized to blood vessels. Five dogs with spontaneous, insulin-dependent diabetes received microencapsulated porcine islets in arterio-vein iliac prosthesis by-passes. One showed complete and the remainder partial, sustained reversal of hyperglycemia. Microencapsulation may be a potential solution to immunological problems related to islet transplantation.

Animals↗
PubMed1990

A method for the massive separation of highly purified, adult porcine islets of Langerhans.

A method for the massive and reproducible isolation of highly purified, adult porcine islets of Langerhans is described. The successful combination of donor animal-strain selection with original procedures for pancreas retrieval and enzymatic digestion permitted us to separate uniquely massive concentrations of pure porcine islets with no need for mechanical disruption of the pancreatic tissue. Following our procedure, porcine islets, which fully retain viability and function, can be harvested easily and rapidly. Xenotransplantation of such islets, immunoprotected within algin/polyaminoacidic microcapsules, was associated with complete reversal of hyperglycemia in rodents with either spontaneous or streptozotocin-induced diabetes mellitus.

Animals↗
PubMed1990

[Islands of Langerhans transplant in the treatment of diabetes mellitus: current status, indications, future perspectives].

Islet cell transplantation is a potential and attractive alternative to exogenous insulin administration for the therapy of IDDM. Large scale clinical applicability of this approach has been hampered, so far, by technical problems such as separation of massive islet concentrations and immune rejection. Microencapsulation within algin/polyaminoacids has provided islets with selective permeable biomembranes thus allowing prevention of the host's immune response and circumvention of general immunosuppression of the recipient. This progress could offer new opportunities for islet cell transplantation in patients with IDDM.

Diabetes Mellitus, Type 1↗
PubMed1989

Insulin resistance in porphyria cutanea tarda.

It has been reported that patients with porphyria cutanea tarda (PCT) develop carbohydrate (CHO) intolerance and manifest diabetes melitus (DM) more frequently than the normal population. In order to verify whether this is due to insulin resistance we studied 5 patients with PCT and 5 normal subjects matched for age, sex and weight. In all the patients an evaluation consisted of the glycemic curve and insulin response to an iv glucose tolerance test (IVGTT: 0.33 g/kg) as well as of an evaluation of the circulating monocyte insulin receptors. Blood samples were drawn in the basal state to measure plasma levels of NEFA, glycerol, and intermediate metabolites. The patients with PCT showed normal glucose tolerance which was obtained, however, at the expense of the elevated insulin levels: therefore a condition of insulin resistance was demonstrated in these subjects. An involvement of the lipid metabolism, observed by the raised levels of plasma NEFA and glycerol, was also evident. The insulin binding to circulating monocytes was reduced but not enough to justify the degree of insulin resistance observed. Therefore, it could be hypothesized, in agreement with similar studies, that a postreceptor defect is responsible for the insulin-resistance observed in patients with PCT and that the reduction of insulin receptors is determined by the down regulation in response to elevated insulinemic levels. An alteration of the porphyrin metabolism might be responsible for this disorder.

Adult↗