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Biomedical subjects

S Piro

Publications and source records attributed to S Piro.

At least 19 recordsLinked to original sources
PubMed2006

Cellular and molecular effects of protons: apoptosis induction and potential implications for cancer therapy.

Due to their ballistic precision, apoptosis induction by protons could be a strategy to specifically eliminate neoplastic cells. To characterize the cellular and molecular effects of these hadrons, we performed dose-response and time-course experiments by exposing different cell lines (PC3, Ca301D, MCF7) to increasing doses of protons and examining them with FACS, RT-PCR, and electron spin resonance (ESR). Irradiation with a dose of 10 Gy of a 26,7 Mev proton beam altered cell structures such as membranes, caused DNA double strand breaks, and significantly increased intracellular levels of hydroxyl ions, are active oxygen species (ROS). This modified the transcriptome of irradiated cells, activated the mitochondrial (intrinsic) pathway of apoptosis, and resulted in cycle arrest at the G2/M boundary. The number of necrotic cells within the irradiated cell population did not significantly increase with respect to the controls. The effects of irradiation with 20 Gy were qualitatively as well as quantitatively similar, but exposure to 40 Gy caused massive necrosis. Similar experiments with photons demonstrated that they induce apoptosis in a significantly lower number of cells and in a temporally delayed manner. These data advance our knowledge on the cellular and molecular effects of proton irradiation and could be useful for improving current hadrontherapy protocols.

Apoptosis↗
PubMed2005

Functional and morphological alterations of mitochondria in pancreatic beta cells from type 2 diabetic patients.

AIMS/HYPOTHESIS: Little information is available on the insulin release properties of pancreatic islets isolated from type 2 diabetic subjects. Since mitochondria represent the site where important metabolites that regulate insulin secretion are generated, we studied insulin release as well as mitochondrial function and morphology directly in pancreatic islets isolated from type 2 diabetic patients. METHODS: Islets were prepared by collagenase digestion and density gradient purification, and insulin secretion in response to glucose and arginine was assessed by the batch incubation method. Adenine nucleotides, mitochondrial membrane potential, the expression of UCP-2, complex I and complex V of the respiratory chain, and nitrotyrosine levels were evaluated and correlated with insulin secretion. RESULTS: Compared to control islets, diabetic islets showed reduced insulin secretion in response to glucose, and this defect was associated with lower ATP levels, a lower ATP/ADP ratio and impaired hyperpolarization of the mitochondrial membrane. Increased protein expression of UCP-2, complex I and complex V of the respiratory chain, and a higher level of nitrotyrosine were also found in type 2 diabetic islets. Morphology studies showed that control and diabetic beta cells had a similar number of mitochondria; however, mitochondrial density volume was significantly higher in type 2 diabetic beta cells. CONCLUSIONS/INTERPRETATION: In pancreatic beta cells from type 2 diabetic subjects, the impaired secretory response to glucose is associated with a marked alteration of mitochondrial function and morphology. In particular, UCP-2 expression is increased (probably due to a condition of fuel overload), which leads to lower ATP, decreased ATP/ADP ratio, with consequent reduction of insulin release.

Adenine Nucleotides↗
PubMed2001

Bovine islets are less susceptible than human islets to damage by human cytokines.

BACKGROUND: The potential benefits of islet xenografting in type 1 diabetes include the intriguing, but still unanswered, possibility that the grafted xenoislets may be less subjected to human autoimmune attack. Cytokines may play a major role in the pathogenesis of autoimmune diabetes by causing impairment of insulin release and pancreatic islet cell toxicity. METHODS: We compared insulin secretion, islet cell death and survival, inducible nitric oxide synthase (iNOS) mRNA expression, nitrite production, and Bcl-2 and Bax mRNA expression in isolated human and large mammal (bovine) islets exposed to 50 U/ml recombinant human interleukin-1, 1,000 U/ml recombinant human tumor necrosis factor-alpha and 1,000 U/ml recombinant human interferon-gamma. RESULTS: After 24-hr exposure, a marked decrease of glucose-stimulated insulin secretion was observed with human, but not with bovine islets. After 48-hr exposure, human, but not bovine, pancreatic islets showed a significantly higher percentage of apoptotic cells compared to controls. Treatment of human islets with human cytokines induced up-regulation of iNOS mRNA, increased levels of nitrites, and down-regulation of Bcl-2 mRNA, with unchanged levels of Bax mRNA. These parameters were not affected by cytokines in bovine islets. CONCLUSIONS: Bovine islets are less susceptible than human islets to the effects of human cytokines, which may be a potential advantage of xenotransplantation.

Animals↗
PubMed2001

Melanosynthesis, differentiation, and apoptosis in Kupffer cells from Rana esculenta.

It is well known that amphibian Kupffer cells (KCs) contain eumelanins. In this paper, we demonstrate through a molecular analysis that Rana esculenta KCs synthesize high levels of mRNA for tyrosinase and through cytochemistry that they possess dopa oxidase activity: both these data prove that frog KCs are capable of autonomously synthesizing eumelanins. On the other hand, by using a highly sensitive reverse transcription-polymerase chain reaction assay we clearly show that in mammalian KCs the tyrosinase gene is not expressed. Quite unexpectedly, we have detected tyrosinase mRNA in Rana esculenta spleen, lung, and heart; to explain this finding, we suggest that it could be due to the presence of pigmented macrophages within the spleen, that probably behave as KCs, and of melanophores in lung and heart. It also may be hypothesized that the Rana esculenta tyrosinase gene, as opposed to its mammalian counterpart, is expressed in many cell types because its promoter contains sequences that are recognized by widely synthesized transcription factors. Our experiments also demonstrate that there is an inverse correlation between the amount of tyrosinase mRNA and melanin content, and that populations of terminally differentiated KCs are characterized by a high degree of apoptosis. Based on these data, we propose that differentiating KCs start accumulating eumelanins, as a result of previous expression of high levels of tyrosinase and of dopa oxidase activity, acquire the full KC phenotype (characterized by both phagocytic and melanosynthetic ability), and then undergo apoptosis. Accordingly, we propose that these cells could represent an interesting model to study, at the molecular level, the relationship between differentiation, specific gene expression, and programmed cell death in higher eukaryotes.

Animals↗
PubMed2001

Hospital-acquired malaria transmitted by contaminated gloves.

We describe two cases of malaria occurring in a malaria-free zone in two in-patients, two weeks after a case of Plasmodium falciparum malaria, acquired in Burkina Faso, had been admitted to the same ward. After reviewing the techniques used by nursing staff, we conclude that transmission probably occurred via gloves contaminated following manipulation of venous cannulae and drip lines of the patient with Burkina Faso-acquired malaria and which had not been discarded before manipulating the intravenous lines of the other two patients. Nosocomial transmission of unusual and potentially life-threatening infections should be taken into consideration in those settings where compliance with universal precautions is not rigorous.

Adult↗
PubMed2001

Chronic exposure to high leucine impairs glucose-induced insulin release by lowering the ATP-to-ADP ratio.

Exposure of rat pancreatic islets to 20 mM leucine for 24 h reduced insulin release in response to glucose (16.7 and 22.2 mM). Insulin release was normal when the same islets were stimulated with leucine (40 mM) or glyburide (1 microM). To investigate the mechanisms responsible for the different effect of these secretagogues, we studied several steps of glucose-induced insulin secretion. Glucose utilization and oxidation rates in leucine-precultured islets were similar to those of control islets. Also, the ATP-sensitive K(+) channel-independent pathway of glucose-stimulated insulin release, studied in the presence of 30 mM K(+) and 250 microM diazoxide, was normal. In contrast, the ATP-to-ADP ratio after stimulation with 22.2 mM glucose was reduced in leucine-exposed islets with respect to control islets. The decrease of the ATP-to-ADP ratio was due to an increase of ADP levels. In conclusion, prolonged exposure of pancreatic islets to high leucine levels selectively impairs glucose-induced insulin release. This secretory abnormality is associated with (and might be due to) a reduced ATP-to-ADP ratio. The abnormal plasma amino acid levels often present in obesity and diabetes may, therefore, affect pancreatic islet insulin secretion in these patients.

Adenosine Diphosphate↗
PubMed2001

Th2 cytokines have a partial, direct protective effect on the function and survival of isolated human islets exposed to combined proinflammatory and Th1 cytokines.

Studies in rodents have suggested that Th2 and Th3 cytokines can be effective in reducing proinflammatory and Th1 cytokine-induced islet damage. Whether this is the case with human islets and might be due to a direct action of Th2 and Th3 cytokines is not known. In the present study, we evaluated whether Th2 (500 U/ml IL-4 plus 100 U/ml IL-10) or Th3 (5 ng/ml TGF-1beta) cytokines may prevent the derangements induced on isolated human islets by prolonged (12 or 72 h) exposure to combined proinflammatory (50 U/ml IL-1beta, 1000 U/ml TNF alpha) and Th1 (1000 U/ml interferon gamma) cytokines. Compared with control islets, cells preincubated for 12 or 72 h with proinflammatory and Th1 cytokines showed a significant decrease of glucose-stimulated insulin secretion and a significant increase of nitrites production. The addition of IL-4 plus IL-10 or TGF-1beta in the medium prevented these cytostatic effects in the 12-h incubation experiments, but not after the 72-h exposure period. IL-1beta, interferon gamma, and TNF alpha caused no major change in either islet cell survival or Bcl-2 and Bax mRNA expression after a 12-h incubation; however, a marked increase in the amount of dead cells, with a major decrease of Bcl-2 mRNA expression, was observed after 72 h. The presence of Th2, but not of Th3, cytokines significantly reduced beta-cell death, without any major effect on Bcl-2 and Bax mRNA expression. These results suggest that Th2 and (at lower extent) Th3 cytokines may have a partial, direct protective effect on isolated human islets exposed to the cytostatic and cytotoxic action of proinflammatory and Th1 cytokines.

Glucose↗
PubMed2000

Exposure to glibenclamide increases rat beta cells sensitivity to glucose.

An increased sensitivity to glucose was observed in islets pre-exposed for 1 h to glibenclamide (0.1 micromol 1(-1)), but not to tolbutamide (100 micromol l(-1)), as indicated by a shift to the left of the dose-response curve (EC(50) at 5.8+/-0.3 mmol l(-1) glucose vs 10.6+/-0.8 in control islets; n=11, P<0.005). According to this secretory pattern also glucose utilization at 2.5 and 5.0 mmol l(-1) glucose was higher in islets exposed to glibenclamide. Since binding to mitochondria results in an increased enzyme activity, we measured hexokinase (HK) and glucokinase (GK) activity both in a cytosolic and in a mitochondrion-enriched fractions. Cytosolic hexokinase activity was similar in islets exposed to glibenclamide and in control islets but mitochondrial hexokinase activity was significantly increased after exposure to glibenclamide (124+/-7 vs 51+/-9 nmol microgram prot(-1) 90 min(-1), P<0.01), with no change in the enzyme protein content. In contrast, glucokinase activity in the two groups of islets was similar. When in islets < exposed to glibenclamide hexokinase binding to mitochondria was inhibited by the addition of 20 nmol l(-1) dicyclohexylcarbodiimide (DCC), no increase of glucose sensitivity was observed (EC(50) 10.9+/-1.3 mmol l(-1) glucose, n=3, similar to that of control islets). These data indicate that a 1 h exposure to glibenclamide causes the beta cell to become more sensitive to glucose. This increased sensitivity is associated with (and may be due to) an increased hexokinase activity, in particular the mitochondrial-bound, more active, form. This mechanism may contribute to the hypoglycemic action of this drug.

Animals↗
PubMed2000

Metformin restores insulin secretion altered by chronic exposure to free fatty acids or high glucose: a direct metformin effect on pancreatic beta-cells.

Because metformin affects glucose and free fatty acid (FFA) metabolism in peripheral insulin target tissues, we investigated the effect of this drug in restoring a normal secretory pattern in rat pancreatic islets whose function has been impaired by chronic exposure to elevated FFA or glucose concentrations. We cultured rat pancreatic islets with or without FFA (2 mmol/l oleate/palmitate 2:1) or high glucose (16.7 mmol/l) concentrations in the presence or absence of metformin (0.25-12.5 microg/ml) and then measured insulin release, glucose utilization, glucose, and FFA oxidation. When compared with control islets, islets exposed to high FFA or glucose concentrations showed an increased basal and a decreased glucose-induced insulin release. In islets cultured for an additional 24 h with FFA or glucose in the presence of metformin (2.5 microg/ml), both basal and glucose-induced insulin secretions were restored. Both glucose utilization and glucose oxidation were altered in islets pre-exposed to high FFA or glucose concentrations. In particular, regarding control islets, glucose utilization was increased at 2.8 mmol/l glucose and decreased at 16.7 mmol/l glucose; glucose oxidation was similar to control islets at 2.8 mmol/l glucose but decreased at 16.7 mmol/l glucose. In contrast, oleate oxidation was increased in islets pre-exposed to FFA. All of these abnormalities were reversed in islets cultured for an additional 24 h with high FFA or glucose concentrations in the presence of metformin (2.5 microg/ml). In conclusion, our data show that metformin is able to restore the intracellular abnormalities of glucose and FFA metabolism and to restore a normal secretory pattern in rat pancreatic islets whose secretory function has been impaired by chronic exposure to elevated FFA or glucose levels. These data raise the possibility that, in diabetic patients, metformin (in addition to its peripheral effects) may have a direct beneficial effect on the beta-cell secretory function.

Animals↗
PubMed1998

Validation of automated sleep analysis in normal children.

With the aim of determining normal reference values for our sleep laboratory and evaluating the reliability of automated analysis for scoring polysomnographic studies in children, we recorded polysomnograms in 16 healthy boarding-school children. Sleep recordings were obtained with a computer system (Medilog SAC, Oxford Instruments). Polysomnographic variables were monitored continuously on a 16-channel recorder equipped with a video. Data were acquired on optical disk for computer-assisted data interpretation. Sleep stages and respiratory events were also scored visually by operator. Comparison with visual scores showed that the computer system significantly overscored wakefulness (W) (p<0.02) and stage IV (p<0.001) and underscored stage II (p<0.001) and rapid eye movement (REM) sleep (p<0.001). It also assigned respiratory events a higher score than did visual scoring, as shown by the higher apnoea index (AI) and hypopnoea index (HI) (AI p<0.03; HI p<0.001). Regression analysis showed a significant correlation between visual and automated scores for central (r=0.679; p<0.004) and obstructive apnoea (r=0.631; p<0.008). Computer apnoea scores did not correlate with visual scores. Much remains to be done before computer-based scoring systems can be relied upon, without visual scoring, for polysomnographic sleep studies in children. Their main advantage at present is that they offer a convenient means of saving paper, space and time.

Apnea↗
PubMed1997

Bi-level positive airway pressure (BiPAP) ventilation in an infant with central hypoventilation syndrome.

A 4-month-old baby girl, after a period of apparent good health, began to have aphonia, dyspnea, difficulties with swallowing, cyanosis, apnea, and hypopnea during sleep that resulted in admission to an intensive care unit for intubation and mechanical ventilation. At the age of 9 months she was admitted to our hospital with a possible diagnosis of central hypoventilation syndrome. A polysomnographic study showed apnea and hypopnea (apnea + hypopnea index = 47.1), hypercapnia (mean end-tidal PCO2 89 +/- 15.0 mmHg), and arterial desaturation (mean SaO2 91 +/- 1.7%; lowest SaO2 < 50%; 68% of total sleep time at SaO2 below 93%); the study also showed an absent ventilatory response to CO2, absent cardiac responses to apnea during sleep, and right ventricular hypertrophy. Nocturnal nasal bi-level positive airway pressure (BIPAP), applied initially at 6 cmH2O and gradually increased to 16 cmH2O, caused the sleep-related abnormal respiratory events to disappear. End-tidal PCO2 decreased to 39 mmHg, and SaO2 increased to 94%. After 6 months of nocturnal BiPAP ventricular right hypertrophy reversed and arrested growth and hypotonia normalized. The child has tolerated and has remained on BiPAP support up to her current age of 3 years and continues to use this form of ventilatory assistance without difficulties.

Female↗
PubMed1997

Hexokinase shift to mitochondria is associated with an increased sensitivity to glucose in rat pancreatic islets.

When rat pancreatic islets are incubated in 5.5 or 16.7 mmol/l glucose for 3 h, an increased sensitivity is observed in islets pre-exposed to high glucose, as indicated by a shift to the left of the glucose dose-response curve (EC50 7.1 +/- 0.9 and 11.5 +/- 1.2 in high- and low-glucose-exposed islets, respectively; n = 5, P < 0.05). To investigate the mechanism(s) responsible for this effect, we measured hexokinase and glucokinase activity both in the cytosolic fraction and in a mitochondrion-enriched fraction, since binding to the outer mitochondrial membrane has been reported to result in an increased enzyme activity. In islets cultured at 16.7 mmol/l glucose, the cytosolic hexokinase activity was similar to control islets, but mitochondrial enzyme activity was significantly increased (124 +/- 7 vs. 51 +/- 9 nmol x microg(-1) x 90 min(-1), P < 0.01). As a consequence, the cytosolic:mitochondrial fraction ratio was altered in comparison with control islets. In contrast, glucokinase activity in the two groups of islets was similar in the cytosolic fraction and undetectable in the mitochondrial fraction. Hexokinase I quantitation by Western blot confirmed the enzyme translocation from the free cytosolic to the mitochondria-bound form in islets cultured at 16.7 mmol/l glucose. Glucose-induced alterations were reversible after 1 h exposure to 5.5 mmol/l glucose. Moreover, in islets exposed to 16.7 mmol/l glucose, inhibition of hexokinase binding to mitochondria by the addition of 20 nmol/l dicyclohexylcarbodiimide resulted in no increase of glucose sensitivity (EC50 10.9 +/- 0.4, n = 3, similar to that of control islets). These data indicate that after chronic exposure to high glucose, the beta-cell becomes more sensitive to glucose before eventually getting desensitized. This increased sensitivity is associated with (and may be due to) an increased hexokinase activity secondary to a subcellular shift of the enzyme from the free cytosolic to the mitochondria-bound, more active form.

Animals↗
PubMed1995

A comparison of the antiemetic efficacy and safety of intramuscular and intravenous formulations of granisetron in patients receiving moderately emetogenic chemotherapy.

A total of 120 patients were treated with granisetron either intramuscular (i.m.) or intravenous (i.v.) in a crossover design, over two successive cycles of moderately emetogenic chemotherapy. Of the 117 patients evaluable for efficacy, 74.4% receiving i.m. and 76.9% receiving i.v. treatment experienced a complete response (no vomiting, no more than mild nausea, no need for rescue medication and no study withdrawal in the 24 h following the onset of chemotherapy). Only a small proportion of the patients experienced any vomiting, either during the first 24 h or in the follow-up period of 4-10 days. There were no statistically significant differences in any of the efficacy parameters between the two routes administration of granisetron. Both formulations of granisetron were also equally well tolerated. The main treatment-related adverse effects were headache and constipation (experienced by 13-15% of patients); local reactions to i.m. injection of granisetron were experienced by 2.6% of patients.

Adult↗
PubMed1986

[Pneumocystis carinii in male drug addicts: morphologic study of the parasite].

This work describes the first case of Acquired Immuno-Deficiency Syndrome (AIDS) to be found in Sardinia. The patient was an adult male drug-addict who died following a respiratory inadequacy due to bronchial pneumonia resulting from Pneumocystis carinii (PCP). For diagnostic purposes the emphasis is laid on the importance of morphological research into the parasite, considering the lack of specific evidence regarding serological investigation. Therefore, the various techniques of coloration are examined here. That which stands out for its simplicity of performance and its thoroughness of investigation is the May-Grünwald-Giemsa coloration which also points out other micro-organisms frequently associated with this type of pathology. In conclusion, then, this work indicates the advisability, on behalf of the Services of Anatomy and Pathological Histology to adopt, as routine practice the specific colorations for Pneumocystis carinii (PC), taking into account the considerable diffusion of this parasite in patients with immuno-deficiency.

Acquired Immunodeficiency Syndrome↗
PubMed1983

[Botulism caused by preserved mushrooms].

We describe two cases of botulism caused by home-prepared under olive oil mushrooms. We stress the importance of an accurate anamnestic study and of the recovery of the toxic material for the diagnosis and therapy. The serological test on patient's blood, the isolation and the identification of botulinic toxin give the possibility to confer a specific character to the serotherapy The prevention of these toxic infections require a wide education on the preparation and storage of foods.

Adult↗