Biomedical subjects

B Rossi

Publications and source records attributed to B Rossi.

At least 91 records · Page 5Linked to original sources

PubMed1998

Usefulness of ultrasound in Sudeck's atrophy of the foot.

Quantitative ultrasound (QUS) of bone has been proposed as an inexpensive and radiation-free device method of assessing skeletal status. QUS has been widely used in the assessment of osteoporosis. Until now only few data are available on the usefulness of QUS in different disorders, such as Sudeck's atrophy. To evaluate the ability of QUS in the diagnosis and monitoring of regional osteoporosis, we investigated 19 patients (12 women and 7 men, age range 30-65 years) with osteoporosis of the foot (Sudeck's atrophy), as evidenced by X-ray study and Technetium-99 bone scan. In all patients we measured speed of sound (SOS), broadband ultrasound attenuation (BUA), and stiffness of the calcaneus using Lunar Achilles Ultrasound, both in the affected and unaffected foot. Bone mineral density at the lumbar spine, by DXA (Hologic QDR 1000), was also performed. QUS was repeated after 3 and 6 months of treatment with salmon calcitonin (100 IU I.M. every second day). At baseline, SOS, BUA, and stiffness, expressed as T-score, were -1.9, -2.4, and -2.4 in unaffected feet and -2.9, -5.1, and -4.3, respectively, in affected feet. The difference between the unaffected and affected foot was significant for SOS, BUA, and stiffness (P < 0.001). No significant difference was found in QUS parameters in the unaffected foot during the study period. After 3 and 6 months of treatment, SOS increased in the affected foot by 0.2% and 0.3%, BUA increased by 6. 2% and 8.2%, and stiffness by 7.5% and 11.1%, respectively. In conclusion, BUA and stiffness seem to be influenced more than SOS by Sudeck's atrophy; QUS, namely, BUA and stiffness, significantly increase with calcitonin treatment. In conclusion, QUS is a sensitive tool in the diagnosis of Sudeck's atrophy of the foot and is adequate for measuring improvement in bone status following treatment.

Adult↗

PubMed1998

Comparison between plasma concentrations of testosterone, nitric oxide and endothelin 1-2 in penile and brachial venous blood: preliminary results in men with psychogenic impotence.

In the present study venous plasma concentrations of testosterone (T), nitric oxide (NO) and endothelin 1-2 (ET1-2) in the flaccid penis and brachial blood were measured in men with psychogenic impotence. T and NO were significantly lower in the penile venous blood, while ET1-2 showed no statistical difference. These data support the hypothesis of testosterone dependence of penile nitric oxide synthesis (NOS).

Adult↗

PubMed1998

Escherichia coli cytotoxic necrotizing factor 1 effaces microvilli and decreases transmigration of polymorphonuclear leukocytes in intestinal T84 epithelial cell monolayers.

Cytotoxic necrotizing factor type 1 (CNF1), a 110-kDa toxin-like protein from pathogenic Escherichia coli strains, induces an actin cytoskeleton reorganization consisting of the formation of prominent stress fibers by permanent activation of the small GTP-binding protein Rho. Since p21Rho regulates tight-junction permeability and perijunctional actin reorganization in epithelial intestinal cells (A. Nusrat, M. Giry, J. R. Turner, S. P. Colgan, C. A. Parkos, E. Lemichez, P. Boquet, and J. L. Madara, Proc. Natl. Acad. Sci. USA 92:10629-10633, 1995), we used polarized T84 epithelial intestinal cell monolayers to examine whether CNF1 could affect microvillus structure, transepithelial resistance, and polymorphonuclear leukocyte (PMN) transmigration. Incubation of T84 cells with CNF1 did not influence transepithelial resistance, suggesting that barrier function and surface polarity were not affected by the toxin. However, CNF1 effaced intestinal cell microvilli and induced a strong decrease of PMN transepithelial migration in either the luminal-to-basolateral or the basolateral-to-luminal direction. CNF1 could thus be a virulence factor exhibiting a new type of combined activity consisting of effacing of microvilli and occlusion of the epithelial barrier to PMNs. Attenuated transepithelial migration of PMNs could result in the enhanced growth and protection of luminal bacteria.

Bacterial Toxins↗

PubMed1998

Abnormal increase of creatine kinase plasma levels following muscle exercise in nephrotic patients.

Nephrotic syndrome is a protein-wasting disorder affecting total body protein metabolism, often leading to reduction of lean body mass and changes of muscle cell composition. The aim of this study was to investigate the susceptibility to muscle cell damage in nephrotic patients following submaximal physical exercise, by detection of the creatine kinase (CK) plasma level changes. Fourteen patients affected by primary nephrotic syndrome, without chronic renal failure, underwent an exercise test on a cycle ergometer for 20 min at a constant speed (60 rpm). In each subject, the work rate (expressed as watts) was established as 70% of the maximum power theoretically calculated on a sex, age, weight and height basis. CK plasma levels (U/l) were determined before and 1, 3, 6 and 24 h after the exercise. Following exercise, CK plasma levels became higher in nephrotics than in normal controls. That is, the amount of CK increments was greater in nephrotics than in controls from the first hour after the end of exertion. These changes, both as absolute values and as percentage of the basal values, correlate positively to daily urinary protein losses; moreover, an inverse relationship was detected with albumin serum levels. However, no correlation was observed between the amount of plasma CK increases and age, body weight, plasma creatinine, plasma cholesterol or hemoglobin levels. These results demonstrate that a greater than normal increase of CK plasma levels occurs in nephrotics following physical exercise, and that this increment correlates with the severity of urinary protein wasting. This suggests an increased susceptibility to muscle injury in nephrotic patients probably related to protein depletion and/or to modifications of muscle cell metabolism. Further studies are needed to define the pathogenesis of our findings.

Adult↗

PubMed1998

Arg777 plays a major role in the conformation of the colony-stimulating factor-1 receptor intracellular kinase domain.

A point mutation substituting Arg777 by Gln was obtained in a highly conserved region of the human colony-stimulating factor-1 receptor (CSF-1R) sequence. Constitutive expression of wild-type receptors in CHO cells confers susceptibility to CSF-1 for proliferation whereas the mutated receptors exhibited a 90% reduced efficiency in proliferation. We sought to determine the alterations intervening in the CSF-1 signal transduction of the Arg777Gln mutated receptor. We found that ligand binding and ligand-induced CSF-1R internalization were unaffected. CSF-1-induced receptor dimerization and autophosphorylation were impaired to the same extent as mitogen-activated protein kinase activation (90%). However, only phosphatidylinositol 3-kinase activation and ligand-induced receptor ubiquitination were abrogated by the mutation. These features probably reflect the inability of the mutated CSF-1R kinase domain to fold properly and hence to autophosphorylate and/or to associate correctly with transduction proteins. These data may indicate a role for the conserved regions of the RTK kinase domains in the stabilization of the intracellular domain conformation.

Amino Acid Substitution↗

PubMed1998

[Esophageal perforations. Diagnosis and treatment].

Perforation of the esophagus was retrospectively analysed in six patients. The age span was 30 years to 81 years, and the male to female ratio was 2 to 1. Each case was studied with regard to presentation, etiology, treatment and complications. The diagnosis was made at postmortem examination only in 1 patient. The perforation was iatrogenic in 1 of the patients and spontaneous in 5. Management was nonoperative in 3 cases and primary repair with drainage was performed in 2 patients. Overall mortality rate for the series was 33%. This series accumulated from a review of the literature emphasizes the importance of the influence of different methods of treatment and time lapsed between occurrence and therapy.

Adult↗

PubMed1997

Extracellular ATP and UTP control the generation of reactive oxygen intermediates in human macrophages through the opening of a charybdotoxin-sensitive Ca2+-dependent K+ channel.

Human monocyte-derived macrophages possess a NADPH oxidase that catalyzes superoxide formation upon phagocytosis. Extracellular ATP per se does not activate NADPH oxidase but potentiates superoxide generation triggered by opsonized zymosan. UTP can substitute for ATP with the same efficiency, suggesting that ATP mediates its effects specifically through P2U receptors. Extracellular UTP stimulates a rapid increase in cytoplasmic Ca2+ concentration in monocytic cells, which results from a release of intracellular Ca2+ stores. Moreover, UTP-induced calcium increase is sufficient to activate a charybdotoxin-sensitive Ca2+-dependent outward K+ channel (K(Ca)). The activity of this channel develops between 0.1 and 1.0 microM free cytoplasmic Ca2+ concentration; it is half-blocked by 10 nM charybdotoxin but insensitive to iberiotoxin. Under asymmetrical K+ conditions, this K(Ca) channel does not depend on membrane potential and is characterized by a linear single-current voltage relationship in the voltage range of -100 to +50 mV, giving a unitary conductance of 10 pico-Siemens. Interestingly, ATP/UTP-induced oxygen radicals release was inhibited by charybdotoxin in the same range of concentration as the UTP-induced K(Ca) channel. Furthermore, we show that ATP or UTP fail to enhance oxygen radicals production before K(Ca) channel is expressed (3 days). The electrogenic nature of the NADPH oxidase, i.e., its level of activation, being dependent on the plasmic membrane potential, might provide the causal link between the reactive oxygen intermediates generation and the opening of the K(Ca) channel.

Adenosine Triphosphate↗

PubMed1997

Chronic administration of suramin induces neurotoxicity in rats.

In the present study, the ability of suramin 18 mg/kg i.p. twice a week to induce chronic neurotoxicity in rats was investigated. After 20 weeks of suramin treatment, morphological analysis of nerve fibers demonstrated that 57.7+/-3.2% of them presented vesicular disruption of myelin sheaths; their thickness was 0.23+/-0.07 microm in suramin-treated rats with respect to 0.43+/-0.07 microm of controls (P<0.05). To investigate the interaction between suramin and nerve tissue, the binding of the drug to partially purified myelin P0 protein obtained from sciatic nerves was analysed. The percentage of suramin bound to rat myelin P0 protein was 94.0+/-9.5%; this value was decreased to 55.0+/-7.6% when heparan sulfate was added to the myelin protein suspension before suramin. The analysis of tissue drug concentrations at 5, 10 and 20 weeks of treatment showed that suramin accumulated into the sciatic nerve in a time-dependent fashion (130.8+/-18.1, 219.7+/-17.1 and 449.3+/-15.6 microg/g of tissue, respectively). In conclusion, suramin induces a chronic peripheral neurotoxicity in rats characterized by myelin damage and high tissue levels of the drug. The high affinity of suramin for partially purified myelin P0 protein suggests a possible mechanism for drug-induced toxicity.

Action Potentials↗

PubMed1997

The multiple endocrine neoplasia type 2B point mutation switches the specificity of the Ret tyrosine kinase towards cellular substrates that are susceptible to interact with Crk and Nck.

The RET proto-oncogene encodes a Tyrosine Kinase Receptor (RTK) which plays an important function in the proliferation and/or differentiation of neuroectodermic cells. Germline mutation of a methionine to a threonine within the RET TK domain predisposes to the Multiple Endocrine Neoplasia type 2B (MEN 2B). It has been demonstrated that, unlike c-Ret, the MEN 2B mutated Ret displays constitutive TK activity, tyrosine autophosphorylation and transforms fibroblasts. However, this oncoprotein is more than a fully activated wild-type (WT) Ret TK since it also displays modified substrate specificity. Change in substrate specificity leads to the tyrosine autophosphorylation of MEN 2B Ret on new sites as well as the phosphorylation of several novel downstream targets. But, none of these substrates have been identified and the ability of MEN 2B Ret phosphoprotein to interact with Src Homology 2 (SH2) domain containing molecules has been poorly investigated. In this report, using a constitutively activated Ret TK form, Ret-ptc 2, we demonstrate that the MEN 2B as the activated WT Ret TK binds to several SH2 signalling proteins such as Shc, Grb-2, Phospholipase Cgamma, Crk and Nck. However, in contrast to the activated WT form, expression of the MEN 2B mutated Ret-ptc 2 results in the tyrosine phosphorylation of a panel of proteins which interestingly interact with Crk and Nck. We identified Paxillin, a cytoskeletal protein as one of the Crk associated proteins that is dramatically phosphorylated in MEN 2B but not in WT Ret expressing cells. These data suggest that MEN 2B mutated Ret triggers distinct signalling pathways that might be related to its transforming power.

Adaptor Proteins, Signal Transducing↗

PubMed1997

Differential SP220K expression in renal carcinoma and oncocytoma cells.

SP220K is a newly described serine proteinase which displays guanidinobenzoatase activity in its inactive form and gelatinolytic activity in its active form. SP220K expression was studied in 20 renal clear-cell carcinomas and in a series of renal oncocytomas, a rare benign tumor derived from the kidney tubule epithelium. We provide evidence that SP220K expression, as assessed by guanidinobenzoatase activity, gelatin zymography and Western blot immunodetection, was increased markedly in cancer basolateral membranes compared to kidney cortex controls, whereas no signal was detectable in basolateral membranes from the 5 renal oncocytomas studied. Cytoplasms of carcinoma cells were immunodetected consistently, whereas no expression was seen in oncocytic cells from any of the oncocytomas studied (12/12). Endothelial cells were immunodetected in all 3 tissue types. Our data favor a potential mechanistic relationship between expression of the matrix proteinase SP220K and invasive phenotype in kidney epithelium proliferative processes.

Adenoma, Oxyphilic↗

PubMed1997

CSF-1 stimulation induces the formation of a multiprotein complex including CSF-1 receptor, c-Cbl, PI 3-kinase, Crk-II and Grb2.

Recently c-Cbl has been reported to be phosphorylated upon CSF-1 stimulation. The product of the c-cbl proto-oncogene (c-Cbl) is a 120 kDa protein harboring several docking sites for Src homology 2 (SH2) domain containing proteins and proline-rich regions that have been shown to allow its constitutive association with the SH3 domains of Grb2. We demonstrate here that CSF-1 exposure of stable transfectant CHO cells expressing the CSF-1 receptor induced the sustained tyrosine phosphorylation of c-Cbl and its subsequent association with Crk-II and the p85 kDa subunit of the PI 3-kinase, while it constitutively associates with Grb2. We demonstrate by in vitro experiments that these associations require the SH2 domain of Crk-II and both the C- and N-terminal SH2 domains of the p85 subunit of the PI 3-kinase. cCbl is the major PI 3-kinase-containing protein in c-Fms expressing CHO cells upon CSF-1 stimulation. Thus c-Cbl behaves as a core protein, allowing the formation of a quaternary complex including, Crk-II, PI 3-kinase and Grb2. We provide evidence that this multiprotein complex can interact with the tyrosine phosphorylated CSF-1 receptor through the unoccupied SH2 domain of Grb2.

Adaptor Proteins, Signal Transducing↗

PubMed1997

Cleavage site mutants of the subtype B insulin receptor are uncleaved and fully functional.

The insulin receptor (IR) is a membrane-bound glycoprotein composed of alpha and beta subunits derived from a common precursor. This processing is observed for both subtypes A and B of the IR and its physiological importance is poorly understood. In order to investigate the functional consequences of the absence of IR precursor cleavage, using site-directed mutagenesis of the hIRB cDNA, we have produced two mutants replacing the sequence Arg-Lys-Arg-Arg by either His-Lys-His-Arg or Arg-Lys-Arg-Ser. These two mutants, stably expressed in CHO, were structurally and functionally characterized in comparison to the wild-type human IR. These mutations result in the production of uncleaved receptors which are expressed normally at the cell surface. These receptors bind insulin with a normal affinity and activate the tyrosine-kinase resulting in normal phosphorylation of the receptors. These uncleaved receptors can mediate both the metabolic and mitogenic effects of insulin. These results provide evidence for a fully functional uncleaved insulin receptor of the B subtype (exon 11 + ) in contrast to the uncleaved A subtype (exon 11 -) described in the literature, which shows a reduced affinity for insulin and cannot therefore correctly transduce the insulin signal.

Amino Acid Sequence↗

PubMed1997

CD10 (endopeptidase 24.11) is a thymic peptide-degrading enzyme possibly involved in the regulation of thymocyte functions.

Human immature thymocytes express significant levels of the CD10 (endopeptidase 24.11) cell surface antigen. We report here that IOB5, an anti-CD10 mAb, as well as the phorbol ester PMA down-regulate CD10 activity at the surface of human thymocytes. The kinetics of CD10 modulation were drastically different for both effectors, indicating different regulatory mechanisms. We also demonstrated that intact human thymocytes hydrolyze thymopentin and that CD10 significantly participates in this process. Finally, we found that thymopentin and to a lesser extent phosphoramidon, a specific endopeptidase 24.11 inhibitor, induced up-regulation of CD4 and CD8 molecules at the thymocyte cell surface. In view of these results, we suggest that down-regulation of endopeptidase 24.11 at the thymocyte cell surface might reduce its activity toward thymic factors possibly involved in the regulation of thymocyte functions.

Antibodies, Monoclonal↗

PubMed1997

Interleukin 6 stimulates a tyrosine kinase activity potentially involved in mouse hybridoma cell growth.

In this report the authors describe the characterization of a cytosolic tyrosine kinase activity (IL-6PTK) stimulated by interleukin 6 (IL-6). IL-6PTK appears 6 h after IL-6 addition and is inhibited by tyrphostin but not genistein. It is active under its phosphorylated form although it is not immunoprecipitated by antiphosphotyrosine antibodies, suggesting that autophosphorylation occurs on residues other than tyrosine. Using the ATP-binding site covalent label, 5'-p-fluorosulfonylbenzoyladenosine (FSBA), two phosphoproteins have been identified of 52 and 59 kDa respectively, that could potentially harbour IL-6PTK activity. The intracellular elevation of cAMP, which inhibits 7TD1 cell proliferation, decreases as the same time IL-6PTK activity suggesting that the cAMP-dependent kinase could act as a negative regulator of this tyrosine kinase species. Taken together the results strongly suggest that a tyrosine kinase (IL-6PTK) might be involved in the cascade of events leading to the proliferation of 7TD1 cells under IL-6 stimulation.

Adenosine↗

PubMed1997

Potential use of iodine-123 metaiodobenzylguanidine radioaerosol as a marker of pulmonary neuroadrenergic function.

Iodine-123 metaiodobenzylguanidine (123I-MIBG) radioaerosol is of potential use in the investigation of the neuroadrenergic function of the lungs; however, before the method can be successfully employed the following issues need to be clarified: (1) Does the nebulization affect the radiochemical purity of 123I-MIBG? (2) Is the pulmonary distribution of inhaled 123I-MIBG homogeneous in normal subjects? (3) Does the pulmonary clearance of inhaled 123I-MIBG reflect the functional status of the neuroadrenergic system of the lungs? In this study we performed: (1) a chromatographic study of nebulized 123I-MIBG; (2) a quantitative evaluation of the lung distribution of 123I-MIBG radioaerosol in normal subjects as compared with that of technetium-99m diethylene triamine penta-acetic acid (99mTc-DTPA) and (3) an assessment of 123I-MIBG lung clearance both under control conditions and after pharmacologically induced beta-blockade, again compared with 99mTc-DTPA. For these purposes, eight normal subjects were divided randomly into an "MIBG group" and a "DTPA group" (four subjects each) and submitted to three scintigraphic studies each: a baseline study, and studies after the administration of a low (80 mg) and a high (160 mg) dose of propranolol. Radiochemical purity of nebulized 123I-MIBG ranged between 97.18% and 98.70%. The lung distribution of 123I-MIBG, as judged by the aerosol penetration index, was identical to that of 99mTc-DTPA under all study conditions. The 123I-MIBG clearance rate was slower than that of 99mTc-DTPA under baseline conditions (135+/-32 min vs 69+/-27 min, P<0.01) and increased significantly after propranolol administrations, while the 99mTc-DTPA clearance did not change. The following conclusions were drawn: (1) the nebulization does not affect the radiochemical purity of 123I-MIBG; (2) the lung distribution of 123I-MIBG is homogeneous in normal subjects; (3) the pulmonary clearance of 123I-MIBG reflects the functional status of the neuroadrenergic system of the lungs. Thus this scintigraphic method is suitable for research and perhaps for future clinical use.

3-Iodobenzylguanidine↗

PubMed1997

Platelet monoamine oxidase molecular activity in demented patients.

Blood platelet monoamine oxidase activity, as well as other platelet enzyme activities, have been studied in several neuropsychiatric disorders in an attempt to identify biochemical markers of altered brain function. In this study, we determined both total and molecular monoamine oxidase activity in platelets derived from demented patients, which showed significantly greater enzyme activity than those of the controls. It therefore seems that the high degree of monoamine oxidase activity depends on the increased intrinsic activity of individual enzyme molecules. A significant positive correlation was found between monoamine oxidase activity and the severity of illness, which suggests that monoamine oxidase activity may be a state-dependent marker of neurodegeneration. These findings are discussed with reference to the central nervous system biochemical abnormalities of demented subjects: it may be that Alzheimer-type dementia involves some central biochemical changes that are reflected in certain peripheral tissues (e.g. platelets), or a systemic derangement that also affects the brain.

Aged↗

PubMed1997

Electrically-elicited surface mechanomyogram in myotonic dystrophy.

The surface oscillation of the muscle during electrical stimulation is detectable by an accelerometer as a surface mechanomyogram (MMG). The aim of this study was to evaluate whether MMG properties reflect the mechanical muscle changes induced by myotonic dystrophy (MyD). To this end, the tibialis anterior of seven MyD patients and seven age- and sex-matched controls (C) was supramaximally stimulated at 1 (single twitches), 5, 10, 15, 20 Hz for 3 s at the most proximal motor point. RESULTS SINGLE TWITCHES: The MMG amplitude was 67% less, the duration 37% longer, the electromechanical delay 64% longer, and the spectrum mean frequency, 44% lower in the MyD patients than in controls. REPETITIVE STIMULATION: At each stimulation frequency, the average MMG peak-to-peak was less in the MyD patients than in C. CONCLUSION: The differences between the MMGs of MyD patients and C support the hypothesis that, together with the well-known changes in sarcolemmal excitability, an alteration in electromechanical coupling and a failure in contractile machinery may coexist in MyD.

Biomechanical Phenomena↗

PubMed1997

Endopeptidase 24.11 (CD10/NEP) is required for phorbol ester-induced growth arrest in Jurkat T cells.

Jurkat T cells express a functional endopeptidase 24.11 that is involved in the regulation of T cell activation. We have analyzed the effect of ectopic CD10 expression in mutant Jurkat cell clones that fail to express CD10 and, unlike wild-type cells, are resistant to the growth-inhibitory effects of the protein kinase C activator, PMA. No differences in the expression of the mRNA encoding the alpha, beta, gamma, delta, epsilon, and zeta isoforms of PKC were found in parental vs. PMA-resistant Jurkat cells, ruling out the possibility that the defect could be accounted for by an altered expression of one of these isoforms. Phorbol ester-induced growth arrest was not due to apoptosis since PMA failed to trigger DNA fragmentation in parental and mutant Jurkat T cells. CD10 mRNA expression and activity were abrogated in four independent PMA-resistant Jurkat T cell clones compared to parental cells, whereas the activities of several other peptidases were unaffected. Transfection of one mutant clone with a functional endopeptidase 24.11 restored in a significant manner PMA-induced growth arrest in all the clones selected and tested, whereas transfection of an inactive form of endopeptidase 24.11 had no effect, demonstrating that the enzymatic activity of CD10 is critical in the mediation of the PMA growth arrest. The data presented here demonstrate that a functional CD10 is required for PMA-induced growth arrest in Jurkat cells and provide further evidence for a role of endopeptidase 24.11 in the regulation of tumor cell proliferation.

Apoptosis↗