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Biomedical subjects

L Urbani

Publications and source records attributed to L Urbani.

51 records · Page 3Linked to original sources
PubMed1996

Transient evoked otoacoustic emissions in occupational medicine as an auditory screening test for employment.

TEOAEs are considered a valuable test for specific evaluation of the inner ear function and can be used as a screening method for an objective diagnosis of cochlear damage. The aim of this study was the evaluation of TEOAEs as a diagnostic tool for adult male subjects undergoing medical selection for recruitment in the Italian Air Force (IAF). The analysis was performed with ILO88 System on 30 normal and 83 hearing-impaired subjects. Only cochlear hearing losses were considered and categorized in three classes: unilateral (UHL), bilateral (BHL), high frequencies (HFHL: cochlear damage only at 6 and/or 8 kHz). TEOAE intensity, reproducibility and spectrum were the main parameters investigated. A qualitative comparison between the responses obtained in the two ears of the same subject was also performed. Moreover, TEOAE spectra and Pure Tone Audiometry (PTA) data were compared. Significant differences between the normal and the affected ear in UHLs were found, while no variations between the two ears were observed in BHLs and HFHLs. A high correlation between TEOAE spectrum and PTA was reported in normals and UHLs. The global test sensitivity was high in UHLs (94%) and BHLs (83%), while specificity was 85.0% in the normal sample. Although significant limitations reduce their efficiency, TEOAEs can be regarded as a useful complementary test to standard PTA for audiological selective purposes.

Acoustic Stimulation↗
PubMed1996

Effect of acute exposure to hypoxia on electrolytes and water metabolism regulatory hormones.

BACKGROUND: Many studies suggest the hypothesis that the pathology of high altitude could be due to an early alteration of the hormones that regulate sodium homeostasis. HYPOTHESIS: The aim of this study was to evaluate the behavior of these hormones during an acute exposure to hypobaric hypoxia. METHODS: We studied 26 young healthy pilot students (23.1 +/- 2.9 yrs) in a hypobaric chamber, for 3 h (samples collected at time 0, 120, and 180 min), at 5000 m ASL. RESULTS: The results show an early increase of plasma renin activity (PRA) paradoxically associated to a decrease of aldosterone plasma levels. This later returned to the baseline values at 180 min, whereas PRA remained increased throughout the exposure. Both arginine-vasopressin (ADH) and the atrial natriuretic peptide (ANP) significantly increased, while a new putative hormone, the so-called digoxin-like substance (DLS) did not show significant changes. CONCLUSIONS: Our data demonstrate a specific sensitivity of the hormonal systems to hypoxia, which may be influenced by the time of the exposure. The relationship with results previously reported is also addressed.

Acute Disease↗
PubMed1995

Dissociation of nuclear and cytoplasmic cell cycle progression by drugs employed in cell synchronization.

We have studied the effect of the cell synchronization agents compactin, ciclopirox olamine, mimosine, aphidicolin, ALLN, and colcemid on several parameters of cell cycle progression in mitotically synchronized HeLa S3 cells. Using cell size and cyclin A and B levels as markers of cytoplasmic progression and DNA content as a measure of nuclear cell cycle position, we have examined coordination of cytoplasmic and nuclear events during induction synchrony. Each synchronizing agent was unique in its effect on the coordination of the cytoplasmic and nuclear cycle. Mimosine, aphidicolin, ALLN, and colcemid disrupted cell cycle integration while compactin and ciclopirox olamine did not. Continued net cell growth during cell cycle arrest was the most dramatic in aphidicolin-treated cells, which averaged a 60% increase in size. Mimosine, ALLN, and colcemid produced an increase in cell size of approximately 25%, and ciclopyrox olamine and compactin exerted a negligible effect. Cyclin A and B were found at mitotic (high) or G1 (low) levels, or in combination of high and low concentrations not correlated with DNA content in drug-treated cells. For example, treatment with mimosine, which arrests cells in G1 with 2C DNA, resulted in cyclin A accumulating to mitotic levels, whereas cyclin B remained at a low concentration, the first time this phenomenon has been observed. These results demonstrate that populations of synchronized cells obtained by different drug treatments are blocked at biochemically distinct cell cycle points not apparent by cytometric measurement of DNA content. Our results provide conclusive evidence that induced synchrony methods differ with respect to their impact on cell cycle organization and from the pattern seen with nonperturbing cell selection methods.

Aphidicolin↗
PubMed1994

Effects of hypobaric hypoxia on the human auditory brainstem responses.

Auditory brainstem responses (ABRs) were recorded in six volunteers before, during and after 90-min exposure to hypobaric hypoxia (5,184 m; barometric pressure = 405 mmHg) in an altitude chamber. Waves I, III and V absolute and interpeak latencies were analysed. The main result of the experiment was a significant shortening of the brainstem transmission time (I-V interval) in the recovery from hypoxia compared with the basal condition. This finding could be explained with a slow decay of the compensatory mechanisms acting during hypoxia and/or a transient neuronal hyperexcitability at the end of the hypoxic stress.

Acoustic Stimulation↗
PubMed1992

Effects of high altitude exposure on plasma and urinary digoxin-like immunoreactive substance.

Six young healthy subjects underwent a 20 day exposure to altitude, at 4930 m (16,174 ft), to evaluate possible plasma and urine digoxin-like immunoreactive substance (DLIS) changes accompanying the altered water and electrolyte balance induced by hypoxia. We studied DLIS, plasma renin activity (PRA), aldosterone, atrial natriuretic peptide (ANP), and arginine vasopressin (ADH) in serial blood and urine samples. An increase in DLIS in plasma (P less than .005) and urine (P less than .01) was found, while aldosterone was decreased (P less than .02). PRA, ADH, and ANP did not change significantly. A trend to a greater loss of sodium through urinary excretion, correlated with urinary DLIS values (r = 0.47, P less than .01), was observed. Data suggest a possible important role of DLIS in adaptive response of human organism to high altitude.

Adult↗
PubMed1992

[Effects of acute and protracted hypoxia on plasma levels of atrial natriuretic factor].

Acute hypoxia stimulates the release of atrial natriuretic factor (ANF) from isolated rat and rabbit hearts. Increased ANF plasma levels have been found in rats exposed to chronic hypoxia and recently some studies have been conducted on men, with discordant results. The aim of the present study was to verify changes in ANF plasma levels during acute and prolonged hypoxia in young healthy men. We studied 22 subjects (aged 20-28 years, mean 22.7 years) during a simulated exposure to altitude (5000 m) in a hypobaric chamber for 3 hours (A), and 6 subjects (aged 24-51 years, mean 36.5 years) during the scientific expedition to mount Poumori (Nepal 4930 m altitude) with an exposure at maximum altitude for 20 days (B). ANF was measured by the radioimmunoassay method. Results (pg/ml): (A) baseline: 29.4 +/- 18.6; 120 min: 32.0 +/- 17.4 (NS); 180 min: 35.4 +/- 17.1 (p less than 0.05). (B) baseline: 39.6 +/- 13.3; third day: 38.2 +/- 14.1; fifth day: 31.3 +/- 11; seventh day: 29.1 +/- 13.5; tenth day: 32.2 +/- 20.8; fifteenth day: 37.9 +/- 20.2; twentieth day: 34.6 +/- 23.7 (all differences were not significant). In (B) we observed a higher dispersion of values perhaps due to individual variability. The different behaviour of ANF plasma levels in acute and chronic conditions might be due to the adaptive modification of different physiological parameters as loss of plasma volume, natriuresis and attenuation of tissue hypoxia by enhanced erythropoiesis, observed more evidently during prolonged exposure.

Acute Disease↗
PubMed1990

Cholesterol and vesicular stomatitis virus G protein take separate routes from the endoplasmic reticulum to the plasma membrane.

Transport of newly synthesized cholesterol and vesicular stomatitis virus G protein from the endoplasmic reticulum to the plasma membrane is interrupted by incubation at 15 degrees C. Under this condition the newly synthesized molecules accumulate in both the endoplasmic reticulum (ER) and a subcellular vesicle fraction of low density called the lipid-rich vesicle fraction. The material in the lipid-rich vesicle fraction appears to be a post-ER intermediate in the transport process to the plasma membrane (PM). Although both newly synthesized cholesterol and G protein accumulate in this intermediate compartment at 15 degrees C, suggesting cotransport, treatment with Brefeldin A does not affect cholesterol transport to the PM, whereas it strongly inhibits G protein transport. We conclude that cholesterol and G protein leave the ER in separate vesicles, the cholesterol containing vesicles bypass the Golgi apparatus and proceed to the PM, whereas G protein containing vesicles follow the well documented Golgi route to the cell surface.

Animals↗
PubMedDate not supplied

Switch to tacrolimus for cyclosporine-induced gynecomastia in liver transplant recipients.

We report herein on two male liver transplant (LT) recipients who presented with cyclosporine (CsA)-related gynecomastia 6 and 10 months after transplantation. The clinical workup showed increased luteinizing hormone (LH), associated with a slight reduction in testosterone blood levels in one patient and increased prolactin levels in the other. After excluding concomitant primary endocrine and/or malignant disease, conversion to tacrolimus (TAC) was performed resulting in clinical improvement of gynecomastia and return of hormone blood levels to normal range within 3 months. Our report confirms a putative role of CsA in post-LT gynecomastia, reversible however upon conversion to TAC.

Carcinoma, Hepatocellular↗
PubMedDate not supplied

Effects of hypobaric hypoxia on the middle-latency and steady-state auditory evoked potentials.

The aim of the present paper was the investigation of middle-latency responses (MLRs) and steady-state responses (SSRs) during and after a 30-min exposure to hypobaric hypoxia (5182 m above sea level). The test was performed in a hypobaric chamber on 8 male audiologically normal volunteers. The auditory stimulus (500-Hz tone burst), delivered at rates of 10 and 40/s for MLRs and SSRs, respectively, was recalibrated in the hypobaric condition because of the reduced air density. Absolute latencies of waves Na and Pa and their interpeak amplitude were the MLR parameters investigated; for the SSRs, the first positive wave (P1) absolute latency and the interpeak amplitude between P1 and the first negative wave (N1) were considered. The results showed an absence of statistically significant modification of the MLRs. On the contrary, the SSRs showed a significant (p < 0.025) latency increase during hypoxia, with an immediate recovery upon return to ground level. No significant changes of SSR amplitudes were observed. One possible data interpretation is related to the higher stimulation rate adopted for the SSRs; a second possibility could be a different electrogenesis between MLRs and SSRs.

Acoustic Stimulation↗
PubMedDate not supplied

Liver transplantation. A summary of our surgical practice.

At the turn of the new century, liver transplant procedures can finally be considered an efficient treatment option. Technology has helped transplant intervention become a preferred treatment for patients with progressive and irreversible liver failure. New immuno-suppressive drugs have been introduced which reduce the patient's immunological reaction to the implanted organ, entail minimal side effects and improve practical applications of liver transplantation. As a result of these technological advanced and proper disease management, liver transplant procedures are no longer thought of as an elite therapy, reserved for selected patients with end stage liver disease. In our opinion, it is now a sound and valid surgical option with strictly defined characteristics, indications and well-understood limits. Throughout the past decade, we have studied and applied this type of intervention and have come to terms with its rapid expansion at both the theoretical and practical levels. The most significant obstacle remaining today is the discrepancy between the ever increasing demand and limited supply of organs. The future of liver transplant lies in overcoming this obstacle. Liver transplant practice began at our Institute on 23 November 1990 with the first surgical intervention to replace an organ. In the past 10 years, we have exceeded 200 liver transplant procedures.

Adolescent↗