Search PubMed⌕ Search

Biomedical subjects

G Valenti

Publications and source records attributed to G Valenti.

At least 91 records · Page 5Linked to original sources
PubMed1994

A 28 kDa sarcolemmal antigen in kidney principal cell basolateral membranes: relationship to orthogonal arrays and MIP26.

Two recently cloned water channels, CHIP28 and WCH-CD, are homologous to MIP26, an integral membrane channel-forming protein found in lens fiber plasma membranes. CHIP28 is found in basolateral and apical plasma membranes of kidney proximal tubules and thin descending limbs of Henle, whereas WCH-CD is apically located in collecting duct principal cells. So far, the putative water channel that may be responsible for the high constitutive permeability of principal cell basolateral membranes has not been identified. Interestingly, freeze-fracture electron microscopy has shown that characteristic orthogonal arrays of intramembrane particles (OAPs) are found on the basolateral plasma membranes of collecting duct principal cells, and that morphologically identical OAPs present in lens fiber cell plasma membranes contain the protein MIP26. Similar OAPs have also been detected on plasma membranes of other cell types including gastric parietal cells, astroglial cells and skeletal muscle fibers. By indirect immunofluorescence, western blotting and northern blotting, MIP26 was found only in lens fibers. In addition, functional studies on reconstituted and oocyte-expressed MIP26 excluded the possibility that MIP26 might be a basolateral water channel in the kidney. However, a polyclonal antibody raised against skeletal muscle sarcolemmal vesicles, which are enriched in OAPs, produced an intense staining of principal cell basolateral plasma membranes in kidney collecting duct and immunoprecipitated a 28 kDa protein from kidney papilla. The immunoprecipitated protein from papilla was not recognized by anti-CHIP28 or anti-MIP26 antibodies, indicating that principal cell basolateral membranes contain a novel member of the CHIP/MIP family. Because this antibody also stained brain astrocyte end feet, which are enriched in OAPs, it is possible that the 28 kDa protein is related to these structures. We conclude that OAPs probably contain related but distinct proteins that may have different membrane channel functions in different cell types.

Animals↗
PubMed1994

Calcitriol and calcium carbonate therapy in early chronic renal failure.

The aim of this study was to evaluate the effects of a combined low-dose therapy of calcitriol and calcium carbonate on bone metabolism in the early phases of chronic renal failure. A 30-month study involving 17 patients with ECRF was made: 6 months of observation were followed by 24 months of therapy (calcitriol 0.25 microgram/day plus calcium carbonate 1 g/day). The most important results were that renal function was stable throughout the study and there was an increase in calcaemia and a decrease in plasma alkaline phosphatase, plasma osteocalcin, plasma PTH and urinary hydroxyproline. We observed a progressive slowing of the rate of loss of appendicular bone density as well as a decrease of osteoblastic and osteoclastic activity and an improvement of bone mineralization. In conclusion, low doses of calcitriol plus calcium carbonate seem to improve the biochemical and bone derangements in early renal failure.

Adult↗
PubMed1994

[A rare case of accessory choledochus associated with diverticulum of the common bile duct].

The Authors report on a rare congenital anomaly of the biliary tract characterized by an accessory choledochus, which drained the inferior paramedian segments of the liver. Such anomalous duct emerged from the hepatic hilum right behind the cystic artery, the cystic duct and the gallbladder to join the primary choledochus few millimeters from the papilla of Vater. At the point of junction, in the posterior aspect of the II duodenal portion, a choledochal diverticulum containing cholesterin and bilirubin stones was also present. Surgery was indicated by the onset of a pseudo-obstructive syndrome followed by jaundice. At laparotomy the exact diagnosis was possible. The intervention consisted in a choledochotomy and duodenotomy with tube drainage and exeresis of the choledochal cyst containing the stones.

Adult↗
PubMed1993

[Subclavian steal syndrome. Clinical aspects and therapeutic problems].

Cerebrovascular disease is a leading cause of morbidity and mortality in Italy. Although atherosclerotic involvement of the carotid artery is more prevalent, some patients suffer from stenosis of the subclavian artery, usually proximal to the origin of the vertebral artery. Neurological symptoms result from reversed flow in the vertebral artery, so-called "subclavian-steal". This collateral pathway may rob the posterior circulation of perfusion to the degree of producing episodes of vertebrobasilar insufficiency. The authors have therefore reviewed their experience with this disease and present their findings, therapeutic procedures and short-term results. During 1990 four patients affected by "subclavian-steal syndrome" were observed at the Surgical Department of Montecchio Maggiore Hospital (VI). Two patients were operated on and axillo-axillary bypass operations were performed (with a 5 mm Gore-tex graft). The goal of surgical treatment is to alleviate cerebrovascular symptomatology by restoring flow to the subclavian artery distal to the occlusion. Axillo-axillary bypass offers distinct advantages over the alternative methods such as transthoracic procedures or carotid-subclavian bypass. Axillo-axillary bypass is a technically simple procedure with very good results and minimal complications. It avoids sternotomy, thoracotomy and clavicular resections: the carotid artery is not involved in the procedure. The authors conclude that axillo-axillary bypass is a cheap, safe and effective treatment for symptomatic subclavian artery insufficiency.

Aged↗
PubMed1993

Tetrameric assembly of CHIP28 water channels in liposomes and cell membranes: a freeze-fracture study.

Channel forming integral protein of 28 kD (CHIP28) functions as a water channel in erythrocytes, kidney proximal tubule and thin descending limb of Henle. CHIP28 morphology was examined by freeze-fracture EM in proteoliposomes reconstituted with purified CHIP28, CHO cells stably transfected with CHIP28k cDNA, and rat kidney tubules. Liposomes reconstituted with HPLC-purified CHIP28 from human erythrocytes had a high osmotic water permeability (Pf0.04 cm/s) that was inhibited by HgCl2. Freeze-fracture replicas showed a fairly uniform set of intramembrane particles (IMPs); no IMPs were observed in liposomes without incorporated protein. By rotary shadowing, the IMPs had a diameter of 8.5 +/- 1.3 nm (mean +/- SD); many IMPs consisted of a distinct arrangement of four smaller subunits surrounding a central depression. IMPs of similar size and appearance were seen on the P-face of plasma membranes from CHIP28k-transfected (but not mock-transfected) CHO cells, rat thin descending limb (TDL) of Henle, and S3 segment of proximal straight tubules. A distinctive network of complementary IMP imprints was observed on the E-face of CHIP28-containing plasma membranes. The densities of IMPs in the size range of CHIP28 IMPs, determined by non-linear regression, were (in IMPs/microns 2): 2,494 in CHO cells, 5,785 in TDL, and 1,928 in proximal straight tubules; predicted Pf, based on the CHIP28 single channel water permeability of 3.6 x 10(-14) cm3/S (10 degrees C), was in good agreement with measured Pf of 0.027 cm/S, 0.075 cm/S, and 0.031 cm/S, respectively, in these cell types. Assuming that each CHIP28 monomer is a right cylindrical pore of length 5 nm and density 1.3 g/cm3, the monomer diameter would be 3.2 nm; a symmetrical arrangement of four cylinders would have a greatest diameter of 7.2 nm, which after correction for the thickness of platinum deposit, is similar to the measured IMP diameter of approximately 8.5 nm. These results provide a morphological signature for CHIP28 water channels and evidence for a tetrameric assembly of CHIP28 monomers in reconstituted proteoliposomes and cell membranes.

Animals↗
PubMed1993

Unilateral nephrectomy and progression of renal failure.

Extensive ablation of renal mass in experimental animals leads to progressive glomerulosclerosis and chronic renal failure (CRF). Clinical studies are far from answering the question whether patients with reduced renal mass are at risk of developing progressive CRF. The aim of our study was to examine the morphological and functional aspects of the remnant kidney in a group of patients who underwent unilateral nephrectomy for renal tuberculosis: 313 patients (161 M, 152 F) mean age 57.2 +/- 10.7, were examined after a period ranging from 13.56 to 591.2 months. All patients were on ad libitum diet. Hypertension was found in 34.19% of the patients; SBP was 155.29 +/- 19.9 mmHg and DBP was 92.74 +/- 13.07 mmHg. Estimation of renal size performed by ultrasound scanner gave the following results: length 116.78 +/- 8.99 mm; width 58.24 +/- 7.21 mm; thickness 17.88 +/- 1.96 mm. Kidney function assessed by serum creatinine levels showed a mean level of 1.28 +/- 0.53 mg%. Forty-two patients (13.41%) had serum levels > 1.5 mg% but 18 of them had nonconcomitant systemic or renal involvement. Microalbuminuria determined by RIA assay was found in 50.5% of the patients. In our group of patients renal functional impairment was low and hyperfiltration expressed as microalbuminuria does not appear to be a primary factor in the progression of renal failure.

Creatinine↗
PubMed1993

Localization of the CHIP28 water channel in reabsorptive segments of the rat male reproductive tract.

The water channel protein CHIP28 is responsible for the high constitutive plasma membrane permeability to water of erythrocytes, renal proximal tubule, and thin descending limb of Henle. The male reproductive tract is embryologically related to kidney and some segments, particularly the efferent ducts, exhibit a high rate of solute flux-dependent reabsorption of luminal fluid. To determine whether this could occur through water channels in the plasma membrane of reproductive tract epithelial cells, we used anti-CHIP28 antibodies to localize this protein by Western blotting and immunocytochemistry. Western blotting of proteins from efferent duct homogenate indicated the presence of CHIP28 in the efferent duct cells. By indirect immunofluorescence and protein A-gold immunolabeling, CHIP28 was localized to the brush-border and basolateral membranes of nonciliated cells. Ciliated cells in the same epithelium showed no plasma membrane staining for CHIP28. In accord with immunocytochemical findings, freeze-fracture of nonciliated efferent duct cells revealed a plasma membrane organization resembling that of renal proximal tubule cells that are rich in CHIP28. The anti-CHIP28 antibodies also stained plasma membranes of epithelial cells in the ampulla of the vas deferens, seminal vesicles, and prostate, but not the cells in seminiferous tubules, epididymis, and proximal parts of the vas deferens. Therefore, CHIP28 may be a principal mediator of the transmembrane water transport in absorptive epithelial cells of efferent ducts, as well as in epithelial of several other segments of the male reproductive tract that show both secretory and reabsorptive functions.

Absorption↗
PubMed1993

[Laparoscopic appendectomy in clinical practice. Aesthetic and functional advantages].

The mortality rate following traditional (open) surgical appendectomy has declined over the past 60 years to almost zero. Many surgeons question the utility of laparoscopic surgery for appendicitis as the appendix can often be removed through a small incision and the degree of trauma to the patient may be minimal. However, some patients suffer wound infection, prolonged hospitalization and delay in returning to full normal activity. Moreover, postoperative adhesions have been recorded in as many as 63 per cent of cases. Although recent studies have shown that laparoscopic appendectomy is safe and feasible, controversies still exist concerning indications and limits of the procedure. The aim of the present study is to clarify the advantages of the laparoscopic technique in performing appendectomy for both acute and chronic appendicitis. The Authors report on their experience of laparoscopic appendectomy performed at the Surgical Department of Montecchio Maggiore Hospital (VI) from July 1992 to December 1992. Ten laparoscopic appendectomies were performed in 8 female and 2 male patients with a mean age of 19 years (range 14-31). There were no conversions to laparotomy; mean operative time was 57 minutes (range 28-92). As far as the position of trocars is concerned, the Authors utilize a particular technique which presents an aesthetic advantage but requires the use of an endolaparoscopic stapler (Multifire Endo GIA 30 Autosuture). There was no mortality; the postoperative course was uneventful in all cases. Patients were discharged from the hospital the day after laparoscopic intervention. Follow up showed no postoperative pain, short bed stay at home and fast return to full activity; functional and aesthetic results were most satisfactory.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

The nature of Cl- secretion, induced by carbaryl, across the isolated skin of Rana esculenta.

1. The pesticide carbaryl induces Cl- secretion through the isolated frog skin. 2. This effect is due to the activation of both processes responsible for this phenomenon: (a) Na+/K+/2Cl- cotransport on the serosal membrane; (b) Cl- selective channels on the external membrane. 3. Cl- outflux is inhibited by bumetanide (10(-5) M) on the serosal side and by diphenylamine-2-carboxylic acid (DPC) (10(-3) M) on the external side. 4. The DPC action is not mimicked by Naproxen, a specific inhibitor of cyclooxygenase. 5. A comparison with isoprenaline, demonstrates that the carbaryl action is, paradoxically, more selective than that of isoprenaline. 6. This selectivity of carbaryl action on Cl- permeability is confirmed by the fact that, unlike isoprenaline, carbaryl does not affect the permeability of Na+ and thiourea.

Animals↗
PubMed1992

alpha-Glycerylphosphorylcholine administration increases the GH responses to GHRH of young and elderly subjects.

Growth hormone (GH) secretion is decreased during aging in humans and in rodents. This decrease may be due to increased hypothalamic somatostatin release, which is inhibited by cholinergic agonists, or to decreased secretion of GHRH. Alpha-glyceryl-phosphorylcholine (alpha-GFC) is a putative acetylcholine precursor used in the treatment of cognitive disorders in the elderly. In order to learn what effect alpha-GFC had on GH secretion, GH-release hormone (GHRH) was given to young and old human volunteers, with or without the addition of alpha-GFC. GH secretion was greater in the younger subjects than in the old individuals, and both groups had a greater GH response to the GHRH+alpha-GFC than to GHRH alone. The potentiating effect of alpha-GFC on GH secretion was more pronounced in the elderly subjects. These findings confirm the observation that aged individuals respond less well to GHRH than younger subjects, and provides further evidence that increased cholinergic tone enhances GH release.

Adult↗
PubMed1992

Localization of the CHIP28 water channel in rat kidney.

CHIP28 is an integral membrane protein that has been identified as the erythrocyte water channel and that is also expressed in the kidney. Antibodies against erythrocyte CHIP28 were used to localize this protein along the rat urinary tubule. By Western blotting, CHIP28 was detected in kidney plasma membrane and endosome fractions. With the use of immunocytochemistry, CHIP28 was located in brush-border and basolateral plasma membranes of the proximal tubule. The initial S1 segment was weakly stained, but the S2 and S3 segments were heavily labeled. Subapical vesicles were also positive. Apical and basolateral membranes of the long thin descending limb were strongly labeled, but ascending thin and thick limbs of Henle and distal convoluted tubules were negative. Some vasa recta profiles in the medulla were positive. CHIP28 is, therefore, present in membranes with a high constitutive water permeability, where it probably acts as a transmembrane water-conducting channel. Finally, a weak staining of apical and basolateral membranes of cortical collecting duct principal cells was detectable, suggesting a potential relationship of CHIP28 to the vasopressin-sensitive water channel.

Animals↗
PubMed1992

Selected polyclonal antibodies and ADH challenge in frog urinary bladder: a label-fracture study.

It is clearly established that the changes induced by antidiuretic hormone (ADH) in its target epithelial cells result from the insertion in the apical membrane of new components that contain channels for water. We have already undertaken an initial study of these channels by raising polyclonal antibodies against Triton X-100 apical extracts from ADH-treated bladders and approached their purification by different adsorption steps. In the present study, we used the label-fracture technique to investigate the localization of the binding sites of the obtained polyclonal antibodies on the apical membrane of ADH-stimulated frog urinary bladder. The results obtained clearly demonstrated a preferential labeling by the selected antibodies of morphological structures such as the groove arrays and the fusion images that are generally accepted as being involved in ADH-induced changes in water permeability of the apical membrane.

Adsorption↗
PubMed1991

EGF in breast cyst fluid: relationships with intracystic androgens, estradiol and progesterone.

The relationship between intracystic levels of epidermal growth factor (EGF) and those of dehydroepiandrosterone sulphate (DHEA-S), delta-4-androstenedione (delta-4-A), 17-beta-estradiol (17-beta-E) and progesterone (PROG) have been studied in 77 breast cyst fluid (BCF) samples. EGF and all tested hormones appeared to be inversely correlated with the intracystic Na+/K+ ratio (p less than 0.001). Consequently, when the BCFs were subdivided according to the Na+/K+ ratio, significantly higher levels of EGF, DHEA-S, delta-4-A, 17-beta-E and PROG were found in Na+/K+ less than 3 BCFs compared with Na+/K+ greater than 3 BCFs (p less than 0.001 in all cases). Strong direct relationships were found among all steroid hormones when they were correlated to one another (p less than 0.001). Intracystic EGF concentration was directly and significantly correlated with each tested hormone (p less than 0.001). However, the relationship between EGF and steroid hormones appeared to be different in the 2 BCF types (Na+/K+ less than 3 or greater than 3).

Adult↗
PubMed1991

The effects of aging on the secretion of the common alpha-subunit of the glycoprotein hormones in men.

To investigate the effects of aging on the secretion of the common alpha-subunit of the glycoprotein hormones, we measured basal levels of luteinizing hormone (LH), testosterone (T) and alpha-subunit in 176 normal men aged 19 to 89 years. In addition, in two groups of young (less than 65 years; n = 25) and old (greater than 65 years; n = 15) subjects, the effects of luteinizing hormone-releasing hormone (LHRH) on LH and alpha-subunit secretion were determined. Age-related increases in serum alpha-subunit and LH were noted only in the oldest men while T levels decreased progressively with advancing age. LHRH stimulation resulted in significantly greater secretion of alpha-subunit in the old subjects while no difference in LH release between young and old men was observed. Moreover, there was a delay to peak LH and alpha-subunit levels after LHRH in the old subjects. These data suggest that the aging process in males involves deficits in both testicular and gonadotroph functions as demonstrated by (1) the relative hypogonadotropic hypogonadism seen until the ninth decade; (2) the hypergonadotropic hypogonadism apparent in men greater than 80 years; (3) the delay in the timing of peak responses of LH and alpha-subunit after LHRH administration; and (4) the disproportionate increase in the secretion of alpha subunit relative to intact LH.

Adult↗
PubMed1991

Polyclonal antibodies in study of ADH-induced water channels in frog urinary bladder.

It is now generally accepted that changes in water permeability in anti-diuretic hormone (ADH)-responsive target epithelial cells result from the insertion in the plasma apical membrane of new components that contain channels for water. The specificity of these channels suggests that they are formed by intrinsic proteins having access to both facies and spanning the whole membrane. We have previously shown that Triton X-100 apical extracts from ADH-stimulated frog urinary bladder contain some proteins inserted under hormonal stimulation. In the present study we have developed polyclonal antibodies using Triton X-100 extract as an immunogen. After considering the inhibitory effect exerted by the whole immune serum on the osmotic water flow, we used different adsorption steps to select, from the immune serum, antibodies to apical membrane proteins inserted in response to the hormone. Immunoblot analysis of these selected antibodies shows that they recognize seven to eight proteins, of which 55-, 35-, 26-, and 17-kDa proteins are always present. Antibodies to these four proteins, affinity purified on nitrocellulose sheets, inhibited ADH-induced osmotic water flow. Altogether these results strongly suggest that proteins of 55, 35, 26, and 17 kDa (or at least one of them) are likely to be involved in the mechanism of water transport.

Animals↗