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Biomedical subjects

L Fontana

Publications and source records attributed to L Fontana.

At least 73 records · Page 4Linked to original sources
PubMed1998

In vivo morphometry of the lamina cribrosa and its relation to visual field loss in glaucoma.

PURPOSE: The lamina cribrosa has been proposed as a site of origin of the optic nerve damage in glaucoma. The purpose of this study was to investigate, in vivo, the clinical features of the lamina cribrosa pores of glaucomatous patients and to relate their morphometric characteristics to the extent of their visual field loss. METHODS: Images of the internal lamina cribrosa surface of 60 glaucomatous patients and 15 normal subjects were acquired, in vivo, using a scanning laser ophthalmoscope (SLO). A purposely developed technique of image processing was employed to objectively evaluate pore morphometry, with particular regard to their geometrical characteristics (circularity and elongation). Visual function was assessed by automated perimetry (Humphrey Field Analyser). RESULTS: Normal subjects showed approximately round lamina pores. In glaucomatous patients, pores become more elongated and less circular with increasing field loss (p = 0.009 and p < 0.001, respectively). CONCLUSIONS: Scanning laser ophthalmoscopy and a new technique of image processing were employed, for the first time, to the investigation in vivo of the lamina cribrosa of glaucomatous patients, in relation to the extent of visual field loss. The results indicated differences in the lamina cribrosa pore morphometry associated with increasing severity of the disease. These changes may represent the result of compressing and shearing forces applied to the laminar plates.

Adult↗
PubMed1998

Pulsatile ocular blood flow investigation in asymmetric normal tension glaucoma and normal subjects.

AIMS: This study was designed to investigate pulsatile ocular blood flow (POBF) in normal tension glaucoma (NTG) patients and in normal controls. NTG patients with unilateral field loss were evaluated to compare POBF values between eyes with and without field loss. METHODS: POBF measurements from more than 1500 subjects were collected during a period of 6 months from six optometric centres. Subjects with systemic vascular diseases (such as systemic hypertension and diabetes), ophthalmic diseases, a positive family history of glaucoma, and those individuals receiving treatment with systemic beta blockers were excluded on the basis of a questionnaire. For comparison, 95 NTG patients with unilateral field loss, selected from 403 consecutive patients with NTG, underwent POBF testing. For each individual age, sex, intraocular pressure, refraction, and pulse rate were entered into a database. RESULTS: Data from 777 subjects were included in the analysis. POBF measurements of patients and subjects were compared allowing for differences in age, sex, intraocular pressure, refraction, and pulse rate. POBF was significantly lower in eyes of NTG patients with and without field loss (p < 0.001 and p = 0.01 respectively). Eyes of NTG patients with field loss showed significantly lower POBF than the contralateral eyes with normal field (p < 0.001). CONCLUSIONS: POBF was significantly lower in eyes of NTG patients with and without field loss than in normal subjects, suggesting that differences in ocular blood perfusion are relevant to the development of NTG and are detectable from the early stage of the disease. Furthermore, the finding of lower POBF in NTG eyes with field loss than in the contralateral eyes with normal field suggests that haemodynamic differences between fellow eyes contribute to determine the side of onset of the disease.

Adolescent↗
PubMed1997

Ethanol induces the expression of alpha 1(I) procollagen mRNA in a co-culture system containing a liver stellate cell-line and freshly isolated hepatocytes.

To study the fibrogenic action of ethanol in vitro we used a co-culture system of freshly isolated hepatocytes and a liver stellate cell line (CFSC-2G) developed in our laboratory. Our results show that in this co-culture system ethanol induces the expression of alpha 1(I) procollagen mRNA in a dose- and time-dependent manner. This effect of ethanol was due to its metabolism by alcohol dehydrogenase since 4-methylpyrazole prevented the ethanol-mediated increase in alpha 1(I) procollagen mRNA. Ethanol was more efficient than acetaldehyde in inducing alpha 1(I) procollagen mRNA expression and its effect was protein synthesis-independent. Transfection of either hepatocytes or liver stellate cells with a reporter gene, chloramphenicol acetyl transferase (CAT), driven by 3700 bp of the mouse alpha 1(I) procollagen promoter demonstrated that only LSC expressed significant CAT activity and that this activity was enhanced by ethanol. Overall, our results suggest that this co-culture system is a useful model to study alcohol-induced fibrogenesis in vitro and that mechanisms other than acetaldehyde formation may also play an important role in alcohol-induced fibrogenesis.

Acetaldehyde↗
PubMed1997

Quantitative analysis of the lamina cribrosa in vivo using a scanning laser opthalmoscope.

PURPOSE: Structural changes in the lamina cribrosa have been implicated in the pathogenesis of glaucomatous optic nerve atrophy. The purpose of this study was to develop a method for morphometric analysis of the lamina cribrosa pores in vivo, using a scanning laser ophthalmoscope. METHODS: A prototype Zeiss confocal laser scanning ophthalmoscope was used to acquire images of the lamina cribrosa. The images were digitised and aligned to compensate for eye movements. Thirty-two consecutive images were averaged to reduce noise. The images were processed to adjust for luminance gradients prior to segmentation and analysis. Details of the image processing are described. RESULTS: The end result of processing the images was a binary (black and white) image that can be used for automated computer assisted measurements. The pores of the lamina cribrosa are well represented and retain their overall shape in the binary image, as judged by superimposing the binary image on the unprocessed image. We also established the repeatability, reproducibility and intercession variability of this technique. Repeated images of the internal lamina cribrosa of 10 patients were acquired by two observers in two separate visits, and the images were processed before automated computer measurements. The parameters evaluated were number of pores, area covered by the pores and area covered by the visible lamina cribrosa. The coefficient of variation for number of pores, pore area and lamina area was 6.9%, 2.1% and 4.3% for observer A and 5.5%, 2.1% and 5.8% for observer B. Pearson product moment correlation coefficient between the two observers was 0.94, 0.99 and 0.97 for the above parameters respectively. There was no significant difference between the measurements on visit 1 and 2 for both observers. CONCLUSIONS: The technique described allows, for the first time, in vivo morphometry of the internal lamina cribrosa surface. This method has good reproducibility, suggesting future clinical applications.

Aged↗
PubMed1997

HERG- and IRK-like inward rectifier currents are sequentially expressed during neuronal development of neural crest cells and their derivatives.

Quail neural crest cells were cultured in a differentiative medium to study the inward K+ channel profile in neuronal precursors at various stages of maturation. Between 12 and 24 h of culture, neural crest-derived neurons displayed, in addition to the previously described outward depolarization-activated K+ currents, an inward current enhanced in high K+ medium. A biophysical and pharmacological analysis led us to conclude that this inward K+ current is identical to that previously demonstrated in mouse and human neuroblastoma cell lines (I[IR]). This current (quail I[IR] or ql[IR]), which is active at membrane potentials positive to -35 mV, was blocked by Cs+ and by class III antiarrhythmic drugs, thus resembling the K+ current encoded by the human ether-a-gò-gò-related gene (HERG). At later stages of incubation (>48 h), neural crest-derived neurons underwent morphological and biochemical differentiation and expressed fast Na+ currents. At this stage the cells lost qI[IR], displaying instead a classical inward rectifier K+ (IRK) current (quail I[IRK] = qI[IRK]). This substitution was reflected in the resting potential (VREST), which became hyperpolarized by >20 mV compared with the 24 h cells. Neurons were also harvested from peripheral ganglia and other derivatives originating from the migration of neural crest cells, viz. ciliary ganglia, dorsal root ganglia, adrenal medulla and sympathetic chain ganglia. After brief culture following harvesting from young embryos, ganglionic neurons always expressed qI(IR). On the other hand, when ganglia were explanted from older embryos (7-12 days), briefly cultured neurons displayed the IRK-like current. Again, in all the above derivatives the qI(IR) substitution by qI(IRK) was accompanied by a 20 mV hyperpolarization of VREST. Together, these data indicate that the VREST of normal neuronal precursors is sequentially regulated by HERG- and IRK-like currents, suggesting that HERG-like channels mark an immature and transient stage of neuronal differentiation, probably the same stage frozen in neuroblastomas by neoplastic transformation.

Animals↗
PubMed1997

Variation of nerve fibre layer thickness measurements with age and ethnicity by scanning laser polarimetry.

AIMS: Scanning laser polarimetry is a new technique allowing quantitative analysis of the retinal nerve fibre layer in vivo. This technique was employed to investigate the variation of the retinal nerve fibre layer thickness in a group of normal subjects of different ages and ethnic groups. METHODS: 150 normal volunteers of different ages and ethnic groups were recruited for this study. Three consecutive 15-degree polarimetric maps were acquired for each subjects. Nerve fibre layer thickness measurements were obtained at 1.5 disc diameters from the optic nerve. Four 90-degree quadrants were identified. RESULTS: The mean nerve fibre layer thickness varied from a minimum of 55.4 microns to a maximum of 105.3 microns, with a mean thickness value of 78.2 (SD 10.6) microns. Superior and inferior quadrants showed a comparatively thicker nerve fibre layer than nasal and temporal quadrants. Retinal nerve fibre layer thickness is inversely correlated with age (p < 0.001). White people showed thicker nerve fibre layers than Afro-Caribbeans (p = 0.002). CONCLUSION: The results indicate a progressive reduction of the nerve fibre layer thickness with increasing age. This may be due to a progressive loss of ganglion axons with age as suggested in postmortem studies. A racial difference in nerve fibre layer thickness is present between whites and Afro-Caribbeans.

Adolescent↗
PubMed1997

Upper abdominal surgery: does a lung function test exist to predict early severe postoperative respiratory complications?

We evaluated the capacity to predict severe respiratory complications (SRCs) following upper abdominal surgery (UAS) by using the results of a respiratory questionnaire and preoperative pulmonary function tests. Lung volumes, flows and transfer factor of the lung for carbon monoxide (TL,CO,sb) were assessed in 361 consecutive adult patients (248 males and 113 females). SRCs were diagnosed 24 h after UAS by clinical examination and chest radiography. Univariate and stepwise multiple logistic regression analyses were performed to estimate the odds ratio (OR) and 95% confidence interval (95% CI) of each single input variable, and to determine which indices best predicted outcome. These patients had a 1% mortality rate and 14% incidence of SRCs, with a male:female ratio of 0.86. The best predictors for SRCs by multiple analysis were: preoperative current hypersecretion of mucus (OR=133; p<0.0001); an increase in residual volume (RV) (OR=3.11; p=0.01); and, to a lesser extent, low percentage of predicted values both of forced expiratory volume in one second (FEV1 % pred) and TL,CO,sb. The algorithm thus obtained (logit theta) was extremely sensitive (84%), specific (99%), and accurate (95%) for preoperative prediction of SRCs. We have found that preoperative current hypersecretion of mucus and pulmonary hyperinflation, and to a lesser extent percentage predicted values both of forced expiratory volume in one second and transfer factor of the lung for carbon monoxide, have a significant predictive capacity for severe respiratory complications following upper abdominal surgery.

Abdomen↗
PubMed1996

[Seroprevalence of markers of viral hepatitis A, B and C in hospital personnel at the Clermont-Ferrand University Hospital Center].

OBJECTIVES: Evaluate risk of hepatitis A, B and C infection and anti HBV vaccination policy in hospital personnel. METHODS: A sample of 440 health care workers (7.5% of the personnel at the Clermont-Ferrand University Hospital) representing 74.5% people directly involved in health care and 25.5% other workers were selected at random and stratified by work classification and age. A questionnaire was used to establish personal data on viral hepatitis status and blood samples were drawn for serological tests. RESULTS: Seroprevalence for hepatitis A was 52% with no significant difference between health care and other workers. For hepatitis B, 88.3% of the population had been vaccinated and anti-HBs titre was > or = 10 mIU/ml for 91.6% and > or = 50 mIU/ml for 86.1%. Seroprevalence for anti-HBc was 7% and none of the subjects were positive for HBs antigen. Anti-hepatic C antibodies were found in 2 health care workers (0.7%). CONCLUSION: These findings emphasize the need to persue further preventive actions against hepatitis A, B and C and the requirement for continued efforts in elementary hygiene.

Adult↗
PubMed1996

Serum amino acid changes in rats with thioacetamide-induced liver cirrhosis.

To date, no attempt has been made to study alterations occurring in the amino acid profile in chronic models of thioacetamide-induced liver cirrhosis. In this work, changes in serum amino acids and proteins in rats with thioacetamide-induced liver cirrhosis are reported, together with changes in enzyme activities in the liver and serum. Seventeen female Wistar rats were used. Eight rats were given 300 mg thioacetamide/l in drinking water for 4 months and nine rats were given water ad libitum during the same time-period. Significant increases in glycine, alanine, serine, methionine, glutamate, ornithine, phenylalanine, tyrosine, histidine and proline were observed in rats with the resulting experimental liver cirrhosis. Threonine, taurine, glutamine, lysine and citrulline tended to increase while isoleucine, leucine, aspartate, arginine and tryptophan tended to decrease. Total and nonessential amino acids increased significantly in cirrhotic animals. Total essential and aromatic amino acids tended to increase in the thioacetamide-treated group, whereas branched chain amino acids tended to decrease in the same group. Regarding serum proteins, a decrease in albumin concentration in the thioacetamide-treated animals was the only change detected. The liver enzyme activities under observation (aspartate and alanine aminotransferases, glutamate dehydrogenase and threonine deaminase) were lower in the thioacetamide group. Decreases were significant for both transaminases and threonine deaminase. Results for serum activities showed that transaminases did not change in thioacetamide-treated rats in comparison with controls. In contrast, alkaline phosphatase rose dramatically in cirrhotic rats. We conclude that the serum amino acid pattern in this chronic model of liver cirrhosis resembles in part that of the corresponding human disease.

Administration, Oral↗
PubMed1996

JAR human placental choriocarcinoma cells actively synthesize, take up and release polyamines.

Uptake of polyamines has been investigated extensively in many cells, but not in placenta, where the polyamine-polyamine oxidase system is supposed to have an immunoregulatory function in pregnancy. Due to the importance of the transfer in this tissue, we have started this study. JAR human placental choriocarcinoma cells in monolayer at confluency were used as a model for measuring the key enzymes of polyamine synthesis and interconversion, rate of uptake and efflux, and the polyamine content. Polyamines were taken up by JAR cells and released by an independent mechanism. Ornithine decarboxylase and spermidine acetyltransferase activities and the rate of transport in and out of the cell were much higher than in other cells, such as L1210 cells. However the systems used for uptake and release appear in many respects to be similar to those observed in L1210 cells, but different from others. The uptake appears to be regulated by an inhibitory protein. Moreover, protein kinase C appears to be involved in the process. The efflux also is regulated as in L1210 cells, through control of H+ and Ca2+ concentration. In conclusion, this study shows that, in JAR cells, ornithine decarboxylase and spermidine acetyltransferase activities were much higher than in other cells, and so was the rate of transport in and out of the cells. As a result, a much higher polyamine content was observed.

Animals↗
PubMed1996

Influence of administration of long-chain polyunsaturated fatty acids on process of histological recovery in liver cirrhosis produced by oral intake of thioacetamide.

Patients with liver cirrhosis frequently show some degree of protein-energy malnutrition and obviously require nutritional support. In this study, the treatment of rats consisted of the ad libitum oral intake of a 300 mg/liter thioacetamide solution, used as drinking water for four months. Thioacetamide treatment produced a severe alteration in the plasma fatty acid profile with significant decreases of these, which mimicked changes described in human cirrhosis. This hepatotoxic agent causes nodular cirrhosis, with loss of the normal architecture of the liver and disruption of the vascular pattern. The goal of the study was to evaluate the influence of n-3 and n-6 series long-chain polyunsaturated fatty acid dietary supplementation in experimental animals and to assess the effects of those dietary components on structural recovery in the liver. Significant increases of saturated and monounsaturated fatty acids as well as n-6 polyunsaturated fatty acids were seen only in the animals given the n-6 polyunsaturated fatty acid supplemented diet. However, only rats given the standard diet exhibited some degree of histological regeneration.

Animals↗
PubMed1996

In vitro study of the anti-aggregating activity of two nitroderivatives of acetylsalicylic acid.

The antiplatelet activity of two new nitrocompounds, chemically related to acetylsalicylic acid (NCX 4215 and NCX 4016), was studied in vitro to verify the hypothetical dual action of these drugs. Both drugs, in a dose-dependent way, inhibited arachidonic acid-induced platelet aggregation and thromboxane A2 production, measured as thromboxane B2 concentration in whole blood. These effects are likely to be related to cyclo-oxygenase inhibition. NCX 4215 and NCX 4016 in a dose-dependent way inhibited also thrombin-induced aggregation of platelets pretreated with acetylsalicylic acid. These inhibitory effects are related to nitric oxide release and cGMP increase and significantly reversed by oxyhaemoglobin and methylene blue. Either as a cyclo-oxygenase inhibitor or as a nitric oxide donor, NCX 4016 proved to be significantly more potent than NCX 4215.

Arachidonic Acid↗
PubMed1996

Study of platelet adhesion in patients with uncomplicated hypertension.

OBJECTIVE: To evaluate platelet function in patients with essential hypertension by sensitive methods investigating platelet adhesion and expression of some platelet glycoproteins (GP), namely GPIIb/IIIa (CD41/alpha 2 beta 3) and GMP-140 (CD62/P-selectin/PADGEM). Other markers of platelet (beta-thromboglobulin) and endothelium activation (von Willebrand factor) were also measured. METHODS: We studied 21 uncomplicated essential hypertensive patients and 20 healthy normotensive control subjects, non-smokers, matched for age and sex. Resting and stimulated platelet adhesion was performed with a colorimetric method using the activity of platelet acid phosphatase for the determination of the number of platelets adhering to human plasma- or fibrinogen-coated microwells. Platelet activation was characterized by flow cytometric measurement of GPIIb/IIIa and GMP-140 in whole blood and washed platelets suspensions, with antihuman fluorescent monoclonal antibodies. RESULTS: Thrombin-stimulated platelet adhesion to human plasma-coated microwells was significantly higher in hypertensive patients than in control subjects (0.05 U/ml thrombin: 13.4 +/- 1.0 versus 7.7 +/- 0.6% adhesion; 0.1 U/ml thrombin: 19.4 +/- 2.3 versus 12.6 +/- 1.8%; means +/- SEM), whereas platelet adhesion to fibrinogen-coated wells did not differ in the two groups. Flow-cytometry analysis of whole blood demonstrated a significantly increased expression of GMP-140 in hypertensive patients compared with normal subjects (percentage of CD62+ platelets: 7.3 +/- 1.2 versus 3.7 +/- 1; means +/- SEM), whereas the expression of GPIIb/IIIa did not differ in the two groups (percentage of CD41a+ platelets: 72.5 +/- 4.5 versus 70.4 +/- 3.9). Moreover, flow cytometry showed an increased size of platelets in hypertensive patients compared with that in control subjects (forwards scattering: 46.5 +/- 1.5 versus 38.9 +/- 1.1; means +/- SEM). Flow-cytometric evaluation of washed platelet suspensions showed no statistically significant differences between the expression of GMP-140 and GPIIb/IIIa in the two groups. beta-Thrombo-globulin plasma levels were higher in hypertensive patients than they were in normal subjects (36.3 +/- 2.0 versus 28.2 +/- 1.3 ng/ml; means +/- SEM). Von Willebrand factor plasma levels were not significantly different in the two groups (101.2 +/- 10.3 versus 86.3 +/- 5.6 U/dl). CONCLUSIONS: These findings provide further evidence that there is a significant, albeit weak, platelet activation in hypertensive patients compared with normal subjects.

Adult↗
PubMed1996

Influence of dietary nucleotides on liver structural recovery and hepatocyte binuclearity in cirrhosis induced by thioacetamide.

Intake of thioacetamide in drinking water causes liver cirrhosis in rats, which exhibit many changes similar to human disease. Nucleotides play an important part in major cellular functions, and recent studies suggest that dietary nucleotides may be considered 'semi-essential' nutrients in situations when an inadequate dietary supply may affect the growth of tissues with a rapid turnover rate. The aim of this study was to assess the effect of dietary nucleotides on lesions in thioacetamide-cirrhotic rats, and to calculate the proportion of mono and binucleated hepatocytes in different experimental groups. Rats were given cirrhosis by oral intake of thioacetamide in the drinking water (300 mg/l) for four months. One group was treated with a standard nucleotide free diet, and another group was treated with the same diet supplemented with 250 mg of nucleotides per 100 g of diet for one and two weeks. A striking reduction (mean (SEM)) in the proportion of binucleated cells was seen in thioacetamide-cirrhotic rats (4.8 (1.3) v 21.4 (1.0)), showing a change in the mitotic mechanism in focal lesions. Cirrhotic rats that consumed a semipurified diet supplemented with nucleotides during two weeks showed considerable histological regeneration of the injured liver. These animals had significantly higher proportion of binucleated cells than did animals at the beginning of the recovery period (8.2 (1.2) v 4.8 (1.3)). In the second week of recovery, both types of diet (F = 5.54, p < 0.05) and the previous administration of thioacetamide (F = 142.82, p < 0.001) had significant effects on the percentage of binucleated hepatocytes.

Animals↗