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Biomedical subjects

L A Sechi

Publications and source records attributed to L A Sechi.

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

Molecular epidemiology by ribotyping and PCR-ribotyping of Enterococcus faecium strains isolated from intercontinental areas.

In this study classical ribotyping based on hybridization of an enteroccocal ribosomal operon previously cloned from Enterococcus hirae (Sechi and Daneo-Moore, 1993) with XbaI cut chromosomal DNA and PCR-ribotyping were used to characterize the molecular epidemiology of 131 Enterococcus faecium, with high-level resistance to gentamicin, isolated from different hospitals in Italy and the United States. The ribotyping was able to differentiate all 131 clinical isolates into 96 family patterns. These family patterns appeared to be useful in establishing epidemiological spread. The results obtained were in agreement with those previously published, suggesting the presence of five to six operons in the Enterococcus genus (Sechi et al., 1994). We performed PCR-ribotyping, based on conserved sequences at the 3' end of the enterococcal 16S rrn and the 5' end of the 23S rrn, on 131 clinical isolates as well as on several enterococcal ATCC strains tested. The results were then compared with those obtained with the classical ribotyping method. The results suggest the presence of at least four classes of intergenic spacers among enterococci, but these classes are not helpful in differentiating between Enterococci or among Enterococcal isolates.

DNA, Bacterial↗
PubMed1997

Association of serum lipoprotein(a) levels and apolipoprotein(a) size polymorphism with target-organ damage in arterial hypertension.

OBJECTIVE: To investigate the association between lipoprotein(a) [Lp(a)] and other plasma lipids and apolipoproteins and target-organ damage (TOD) in patients with arterial hypertension. DESIGN: Cross-sectional study of a case series. SETTING: University medical center. PARTICIPANTS: Lipoprotein(a) and apolipoproteins were analyzed in 277 untreated patients with mild to moderate essential hypertension and in 102 healthy controls. Apolipoprotein(a) [apo(a)] phenotypes were additionally analyzed in an independent sample set of 106 hypertensive and 105 control subjects. MAIN OUTCOME MEASURES: Staging of TOD obtained according to World Health Organization guidelines by clinical evaluation, and laboratory tests including measurments of creatinine clearance, proteinuria, ophthalmoscopy, electrocardiography, echocardiography, and ultrasound examination of major arteries; levels of lipids, apolipoproteins, Lp(a), fibrinogen, and apo(a) phenotypes. RESULTS: Blood pressure, duration of hypertension, and levels of total cholesterol, low-density lipoprotein cholesterol, apolipoprotein B, Lp(a), and fibrinogen were significantly related to the presence and severity of TOD in univariate analysis. Stepwise multivariate analysis showed Lp(a) levels (P<.001) to be the best discriminator of the presence of TOD, followed by systolic blood pressure (P<.001), duration of hypertension (P=.01), and low-density lipoprotein cholesterol (P=.04). The Lp(a) levels were related to TOD independent of the level of blood pressure. We confirmed this association between Lp(a) concentrations and severity of TOD in a second independent sample set and observed a significantly higher frequency of low-molecular-weight apo(a) isoforms with increasing severity of TOD (P=.02). CONCLUSIONS: Lipoprotein(a) and apo(a) phenotype are sensitive indicators of the severity of TOD in patients with essential hypertension, and their evaluation might permit identification of hypertensive subjects liable to the development of organ damage. The higher frequency of low-molecular-weight apo(a) isoforms in patients with TOD demonstrates a genetically determined risk for the development of TOD in hypertensive patients.

Adult↗
PubMed1997

Detection of Mycobacterium tuberculosis by PCR analysis of urine and other clinical samples from AIDS and non-HIV-infected patients.

A number of different clinical specimens, such as sputum, cerebrospinal fluid and blood, have been reported to be good substrates for the detection of Mycobacterium tuberculosis by PCR assay. We wanted to search for the presence of mycobacteria in other body fluids, such as urine. Urine samples and other samples obtained from AIDS patients and non HIV-infected patients were analysed by PCR. The results were compared with those obtained using conventional methods (Bactec 460 TB and AFB (acid fast bacilli strain)). We analysed 412 urine samples and 210 different other samples (sputum and cerebrospinal fluid) obtained from AIDS patients by PCR; almost identical levels of PCR-positive (14-17%) results were observed in all samples analysed. The results were then compared with those obtained with the Bactec 460 TB and AFB. PCR, Bactec 460 TB and acid fast stain were also used to analyse 190 urine samples and 230 other samples from non-HIV infected patients in the consumption ward of Sassari Hospital. The number of urine samples positive by PCR (6.3%) and Bactec 460 TB (2.1%) was half that obtained from samples taken from the AIDS patients. As expected, an increase in the number of positive sputum samples was observed with all methods. The results indicate that PCR analysis of urine samples represents a valid alternative for fast and sensitive detection of M. tuberculosis. This method can be routinely used in the clinical laboratory, especially in HIV-infected patients.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Renal antioxidant enzyme mRNA levels are increased in rats with experimental diabetes mellitus.

Exposure to high glucose concentrations increases the mRNA levels of oxygen radical scavenging enzymes in cultured endothelial cells, suggesting a compensatory response to increased free radical production. To test the hypothesis that this response also occurs in vivo, Cu.Zn-superoxide dismutase (Cu.Zn-SOD) and catalase mRNA levels, were measured in the kidneys of Sprague-Dawley rats 17 days after intravenous injection of streptozotocin (60 mg/kg body weight) and compared with those of control rats. Diabetic rats were either left untreated or given differing insulin regimens (2. 3-8, 6-10 IU/day) in two different experiments that were designed to achieve varying degrees of metabolic control. Cu,Zn-SOD and catalase mRNA levels were measured by Northern blot hybridization and standardized by 28S ribosomal RNA determination. Renal Cu,Zn-SOD and catalase mRNA levels were significantly greater in untreated diabetic and in low-dose (2 IU/day) insulin-treated rats than in controls. Treatment with a moderate dose (3-8 IU/day) of insulin normalized catalase but not Cu,Zn-SOD mRNA levels. The highest insulin regimen (6-10 IU/day), in addition to achieving complete metabolic control as evidenced by normal growth and plasma glucose levels, normalized both catalase and Cu,Zn-SOD mRNA levels. Thus, in rats with streptozotocin-induced diabetes Cu,Zn-SOD and catalase renal mRNA levels are greater than in normal rats. This difference is prevented by sufficient insulin dosage to normalize plasma glucose and might be due to an increased production of free radicals.

Animals↗
PubMed1997

Effects of angiotensin II on insulin receptor binding and mRNA levels in normal and diabetic rats.

Both the density and level of mRNA encoding insulin receptors in the kidney are inversely related to the dietary sodium content, suggesting a feedback mechanism that limits the insulin-induced sodium retention when extracellular fluid volume is expanded. Because angiotensin II affects tissue sensitivity to insulin in humans, we investigated whether angiotensin II affects insulin receptor binding and mRNA levels in the kidney, liver, and renal arteries of normal rats and rats with streptozotocin-induced diabetes mellitus. Non-diabetic and diabetic rats were infused for 7 days with either vehicle or angiotensin II at a rate of 200 ng. kg-1. min-1. In a separate experiment, normal rats were treated with an angiotensin converting enzyme inhibitor (captopril, 100 mg/dl in the drinking water) or vehicle for 7 days. Regional analysis of insulin receptor binding in the kidney and renal arteries was performed by an in situ technique using computerized microdensitometry and emulsion autoradiography. Insulin receptor mRNA levels were determined in renal and hepatic tissue by Northern blot hybridization and normalized with 28S rRNA. No differences in blood pressure were observed among diabetic and non-diabetic rats infused with either vehicle or angiotensin II, whereas captopril-treated rats had significantly lower blood pressure levels than their respective controls. Angiotensin II significantly decreased plasma renin concentration in both non-diabetic and diabetic rats. Insulin receptor number was significantly greater in the renal cortex of diabetic rats than in non-diabetics, whereas no significant differences were found in the outer medulla, inner medulla, or renal arteries. Angiotensin II infusion did not affect either the number or affinity of insulin receptors in any of the renal regions studied. Insulin receptor mRNA levels were significantly greater in the kidney and liver of diabetic rats than in non-diabetics and were not affected by angiotensin II infusion. Similar to angiotensin II infusion, captopril treatment did not affect either renal insulin receptor binding or mRNA levels. Thus, diabetic rats have increased insulin receptor binding and mRNA levels in comparison to non-diabetic rats. Angiotensin II infusion and captopril treatment do not affect insulin receptor binding and mRNA levels in the kidney, arguing against a role for this peptide in the modulation of renal sensitivity to insulin.

Angiotensin II↗
PubMed1997

Hypertension and abnormalities of carbohydrate metabolism possible role of the sympathetic nervous system.

To investigate the relationships between the sympathetic nervous system (SNS) and parameters of glucose metabolism in arterial hypertension, daily urinary excretion of catecholamines and plasma glucose, insulin, and C-peptide response to an oral glucose load (OGL) have been evaluated in 77 untreated patients with mild-to-moderate essential hypertension and in 31 normotensive controls. Urinary excretion of norepinephrine (UNE) was positively correlated with body mass index and with plasma glucose levels both at fast and after OGL. No correlations were found between urinary excretion of catecholamines and plasma insulin and C-peptide levels both at fast and in response to OGL. Because the frequency distribution of UNE was bimodal, hypertensive subjects were separated into two subgroups using an arbitrary cutoff, and the parameters of glucose metabolism were compared. Subjects with UNE > 205 microg/day had greater levels of fasting glucose and greater glycemic response to OGL than subjects with UNE < 205 microg/day, whereas no significant differences between the groups were found in fasting and stimulated plasma insulin and C-peptide. Thus, activation of SNS is related to glucose tolerance but not hyperinsulinemia and insulin hypersecretion in essential hypertension. Plasma glucose levels, independent of insulin, may contribute to the relationship between SNS activity and blood pressure in essential hypertension.

Carbohydrate Metabolism↗
PubMed1997

Glucose metabolism and insulin receptor binding and mRNA levels in tissues of Dahl hypertensive rats.

Increased insulinemic response to an oral glucose load has been demonstrated in Dahl salt-sensitive hypertensive rats. To determine whether this abnormality is mediated at the level of the insulin receptor, we compared insulin receptor binding and mRNA levels in tissues of Dahl salt-sensitive rats (DS) and in their normotensive controls, Dahl salt-resistant rats (DR). To evaluate possible influences of dietary sodium intake, rats were fed either low (0.07% NaCl) or high salt (7.5% NaCl) chow until the DS became hypertensive, and then were killed by decapitation. Fasting plasma glucose and plasma insulin levels did not differ between DR and DS rats and were not affected by salt intake. In response to an oral glucose load, plasma glucose had a similar increase in DR and DS rats, but the increase in plasma insulin was significantly greater in DS rats. Scatchard analysis of binding was obtained from in situ autoradiographic studies performed in frozen skeletal muscle and kidney sections, and insulin receptor mRNA levels were measured by slot-blot hybridization. Number and affinity of insulin receptors were comparable in skeletal muscle and kidney of DR and DS rats and, in both groups, binding parameters were not affected by dietary sodium chloride. Hepatic and renal insulin receptor mRNA levels were also comparable in DR and DS rats fed either low or high salt chow. Thus, increased plasma insulin response to oral glucose load is associated with normal insulin receptor binding and gene expression in peripheral tissues in rats with Dahl hypertension. A postreceptor defect is likely responsible for the decreased sensitivity to insulin in this model of genetic hypertension.

Animals↗
PubMed1997

Ontogenic expression of renal and hepatic angiotensin II receptor genes in the rat.

In addition to its well-characterized renal hemodynamic effects, angiotensin II (Ang II) promotes growth of cultured glomerular and tubular cells, suggesting a possible role in renal development. To better define potential developmental effects of Ang II, we examined the expression of Ang II receptors in embryonic (E19) and postnatal (1, 2, 3, 10 days, 6 weeks, 3 and 9 months) rat kidneys, using in situ autoradiography and the nonpeptide antagonists losartan and PD-123177 to identify receptor subtypes. At E19, 125I-[Sar1, Ile8]Ang II binding was equally reduced by losartan and PD-123177, indicating the presence of both AT1 and AT2 receptors. A progressive increase in Ang II receptor density occurred after birth, reaching a plateau at day 10. At that time, the AT1 subtype predominated and was virtually the sole subtype present thereafter. Ang II receptor density and AT1 mRNA levels decreased in aging rats. Total AT1 receptor mRNA levels in both kidney and liver were determined by Northern hybridization analysis using a radiolabeled AT1 anti-sense cRNA probe. In both tissues, AT1 mRNA levels increased rapidly following birth, reached a maximum on day 10 and decreased thereafter. To further characterize the ontogenic effects on AT1 gene expression, renal AT1A and AT1B receptor mRNA isoforms were determined by reverse transcription and the polymerase chain reaction. No significant differences were observed during maturation between the relative levels of AT1A and AT1B mRNAs, with the AT1A isoform accounting for approximately 78% at any time point. Thus, renal AT1 receptor density increases rapidly after birth, in association with an increase in both AT1A and AT1B receptor gene expression. As the predominant receptor isoform in the adult kidney, the AT1A receptor may account for the majority of the effects of Ang II on glomerular and tubular function.

1-Sarcosine-8-Isoleucine Angiotensin II↗
PubMed1997

The renin-angiotensin system and compensatory renal hypertrophy in the rat.

Angiotensin II (Ang II) may act as an angiogenic and growth promoting factor in different tissues. To assess the role of Ang II in compensatory renal growth following unilateral nephrectomy (UNX), we measured renin, angiotensinogen, and Ang II type 1 (AT1) receptor mRNA levels, as well as Ang II receptor density, in two groups of Sprague-Dawley rats 7 days after either sham operation or UNX. Half of each group received either no treatment or an angiotensin-converting enzyme inhibitor (100 mg/dL captopril in the drinking water, initiated at the time of the intervention). Following UNX, the ratio of kidney weight to body weight (KW/BW) in untreated animals was greater than in rats undergoing sham UNX (0.46 +/- 0.01 v 0.37 +/- 0.01%, P < .01). Neither renal renin, nor renal or hepatic angiotensinogen mRNA levels, determined by slot blot hybridization, changed significantly after UNX. Ang II receptor density in glomeruli, determined using an 125I-Sar1-Ile8 Ang II in situ receptor binding assay on frozen kidney sections, did not change significantly after UNX, nor did renal AT1 receptor mRNA. In captopril-treated rats, KW/BW was greater in UNX than in sham operated rats (0.44 +/- 0.01 v 0.37 +/- 0.01%, P < .01), similar to results in untreated animals. Renal and hepatic angiotensinogen mRNA levels were not affected by captopril treatment and did not change further in response to UNX. Captopril treatment increased renin mRNA in both sham operated and UNX rats as compared with untreated controls, but had no significant effect on Ang II receptor density and AT1 receptor mRNA; and no change was observed in either variable as a consequence of UNX. Thus, compensatory renal hypertrophy following UNX occurred in the absence of measurable changes in components of the renin-angiotensin system, and despite functionally significant inhibition of this system by captopril. These data do not support a critical role for Ang II in compensatory renal hypertrophy.

Animals↗
PubMed1996

Benign familial macrocytosis.

We have identified a 52-year-old woman and her 27-year-old daughter with macrocytosis, normal haemoglobin and mean corpuscular haemoglobin concentration. Macrocytosis could be demonstrated from the age of 40 and 25 respectively. All blood tests were normal including vitamin B12 and folic acid. Bone marrow investigation showed rare macroblasts without other abnormalities. Endoscopy of the upper gastrointestinal tract and ultrasonography of the abdomen were normal. Thus, persistent macrocytosis was present without evidence of diseases that might account for it. In these subjects, macrocytosis is likely to be related to the presence of a genetic defect.

Adult↗
PubMed1996

Molecular epidemiology of Mycobacterium tuberculosis strains isolated from different regions of Italy and Pakistan.

The use of the (GTG)5 oligonucleotide, a repetitive marker in the Mycobacterium tuberculosis chromosome, as a primer in association with an IS6110 outlooking primer has been successfully applied to a PCR-based fingerprinting method. This method classified 62 strains of M. tuberculosis, isolated from human immunodeficiency virus-seropositive and -seronegative patients in different regions of Italy and Pakistan, as having 53 different patterns. The results were compared with traditional IS6110 fingerprinting, by which 47 distinct patterns were observed.

AIDS-Related Opportunistic Infections↗
PubMed1996

Abnormalities of insulin receptors in spontaneously hypertensive rats.

Insulin resistance is present in some strains of rats with genetic hypertension. To determine whether this abnormality is present at the level of the insulin receptor, we compared insulin sensitivity, insulin receptor binding, and mRNA levels in tissues of 10-week-old spontaneously hypertensive rats (SHR) and their normotensive Wistar-Kyoto (WKY) controls. Because we have previously demonstrated an inverse relationship between dietary sodium intake and renal insulin receptor density and mRNA levels in normal Sprague-Dawley rats, the two rat strains in the current experiment were fed either low salt (0.07% NaCl) or high salt (7.5% NaCl) chow until the SHR became hypertensive. Fasting plasma glucose and plasma insulin levels did not differ between SHR and WKY and were not affected by salt intake. When the rats were maintained on the low salt diet, the rate of glucose infusion required to main euglycemia during a hyperinsulinemic clamp was significantly lower in SHR than WKY. High salt diet decreased the rate of glucose utilization during the hyperinsulinemic clamp in WKY but not SHR. During the low salt diet, insulin infusion decreased sodium excretion in both WKY and SHR. When the rats were maintained on the high salt diet, the antinatriuretic response to insulin was blunted in WKY but not SHR. Both the density and mRNA levels of insulin receptor were comparable in the kidney of WKY and SHR, but only WKY had the previously demonstrated decrease in receptor number and mRNA levels when fed the high salt chow. Hepatic insulin receptor mRNA levels were significantly lower in SHR than WKY fed the low salt diet. High salt diet decreased significantly insulin receptor mRNA levels in the liver of WKY but not of SHR. Thus, SHR appear to have lost the feedback mechanism that normally limits insulin-induced sodium retention when extracellular volume is expanded. A decreased expression of insulin receptor in the liver of SHR provides a possible explanation for the insulin resistance and decreased insulin clearance present in this strain.

Animals↗
PubMed1996

Tissue-specific regulation of type 1 angiotensin II receptor mRNA levels in the rat.

Most of the biological effects of the renin-angiotensin system are mediated by the binding of angiotensin II (Ang II) to the type 1 Ang II (AT1) receptor, the predominant receptor subtype present after fetal life. To study tissue-specific regulation of the expression of the AT1 receptor in the rat, we altered activity of the renin-angiotensin system by feeding rats a low (0.07% NaCl), normal (0.3% NaCl), or high (7.5% NaCl) salt chow for 14 days; infusing Ang II (200 ng/kg per minute IP) or vehicle for 7 days; and administering an angiotensin-converting enzyme inhibitor (captopril, 100 mg/dL in the drinking water) or vehicle for 7 days. Renin, angiotensinogen, and total AT1 receptor mRNA levels were measured by slot-blot hybridization with cRNA probes, and AT1 receptor subtypes (A and B) were measured by reverse transcription-polymerase chain reaction in the presence of a cRNA internal standard. Plasma renin concentration and renal renin, renal and hepatic angiotensinogen, and hepatic AT1 receptor mRNA levels were all inversely related to salt intake; in contrast, renal AT1 receptor mRNA levels were significantly lower in rats fed low salt, a difference that was exclusively due to a decrease in the AT1A subtype. This difference did not appear to be mediated by a change in the circulating levels of Ang II, because Ang II infusion reduced plasma renin concentration and renal renin mRNA with no effect on either angiotensinogen or AT1 receptor mRNA levels in kidney or liver, renal Ang II receptor density (determined by in situ autoradiography) decreased, presumably via a posttranscriptional mechanism. Similarly, inhibition of Ang II generation with captopril increased plasma renin concentration and renal renin mRNA levels without altering renal or hepatic angiotensinogen mRNA or renal AT1 receptor mRNA levels. Thus, AT1 receptor gene expression is regulated in a tissue-specific manner that is distinct from other components of systemic and local renin-angiotensin systems and that appears to be mediated by a mechanism other than through changes in the circulating levels of Ang II.

Angiotensin II↗