Biomedical subjects

R Serra

Publications and source records attributed to R Serra.

At least 37 records · Page 2Linked to original sources

PubMed2001

The perichondrium plays an important role in mediating the effects of TGF-beta1 on endochondral bone formation.

Endochondral bone formation is complex and requires the coordination of signals from several factors and multiple cell types. Thus, chondrocyte differentiation is regulated by factors synthesized by both chondrocytes and cells in the perichondrium. Previously, we showed that expression of a dominant-negative form of the transforming growth factor beta (TGF-beta) type II receptor in perichondrium/periosteum resulted in increased hypertrophic differentiation in growth plate chondrocytes, suggesting a role for TGF-beta signaling to the perichondrium in limiting terminal differentiation in vivo. Using an organ culture model, we later demonstrated that TGF-beta1 inhibits chondrocyte proliferation and hypertrophic differentiation by two separate mechanisms. Inhibition of hypertrophic differentiation was shown to be dependent on Parathyroid hormone-related peptide (PTHrP) and expression of PTHrP mRNA was stimulated in the perichondrium after treatment with TGF-beta1. In this report, the hypothesis that the perichondrium is required for the effects of TGF-beta1 on growth and/or hypertrophic differentiation in mouse metatarsal organ cultures is tested. Treatment with TGF-beta1 inhibited expression of type X collagen mRNA in metatarsal cultures with the perichondrium intact. In contrast, hypertrophic differentiation as measured by expression of Type X collagen was not inhibited by TGF-beta1 in perichondrium-free cultures. TGF-beta1 added to intact cultures inhibited BrdU incorporation in chondrocytes and increased incorporation in the perichondrium; however, TGF-beta1 treatment stimulated chondrocyte proliferation in metatarsals from which the perichondrium had been enzymatically removed. These results suggest that the TGF-beta1-mediated regulation of both chondrocyte proliferation and hypertrophic differentiation is dependent upon the perichondrium. Thus, one or several factors from the perichondrium might mediate the way chondrocytes respond to TGF-beta1.

Animals↗

PubMed2001

Signaling to the epithelium is not sufficient to mediate all of the effects of transforming growth factor beta and bone morphogenetic protein 4 on murine embryonic lung development.

Many studies have suggested that transforming growth factor beta (TGF-beta) and bone morphogenetic protein 4 (Bmp4) regulate early development of the lung. In this study, administration of growth factors directly into the lumen of lungs grown in organ culture was used to limit their activity to the epithelium and test the hypothesis that signaling to the epithelium is sufficient to mediate the known effects of TGF-beta and BMP-4 on early lung development. Addition of TGF-beta1, beta2, or beta3 to the medium surrounding lungs grown in organ culture resulted in decreased branching, reduced cell proliferation, accumulation of alpha-smooth muscle actin protein (alpha-SMA) in the mesenchyme, and decreased expression of a marker for respiratory epithelium, surfactant protein-C (Sp-C). When TGF-beta1 was restricted to the epithelium, accumulation of alpha-SMA and inhibition of Sp-C expression were not observed but branching and proliferation were inhibited. In contrast, branching was not inhibited in lungs where TGF-beta2 or TGF-beta3 were restricted to the epithelium suggesting differences in the mechanism of signaling by TGF-beta1, TGF-beta2 or TGF -beta3 in lung. Addition of Bmp4 to the medium surrounding lungs grown in organ culture stimulated cell proliferation and branching morphogenesis; however, direct injection of Bmp4 into the lung lumen had no effect on proliferation or branching. Based on these data and data from mesenchyme-free cultures, we propose that the mesenchyme influences growth factor signaling in the lung.

Animals↗

PubMed2001

Preferential channeling of energy fuels toward fat rather than muscle during high free fatty acid availability in rats.

The preferential channeling of different fuels to fat and changes in the transcription profile of adipose tissue and skeletal muscle are poorly understood processes involved in the pathogenesis of obesity and insulin resistance. Carbohydrate and lipid metabolism may play relevant roles in this context. Freely moving lean Zucker rats received 3- and 24-h infusions of Intralipid (Pharmacia and Upjohn, Milan, Italy) plus heparin, or saline plus heparin, to evaluate how an increase in free fatty acids (nonesterified fatty acid [NEFA]) modulates fat tissue and skeletal muscle gene expression and thus influences fuel partitioning. Glucose uptake was determined in various tissues at the end of the infusion period by means of the 2-deoxy-[1-3H]-D-glucose technique after a euglycemic-hyperinsulinemic clamp: high NEFA levels markedly decreased insulin-mediated glucose uptake in red fiber-type muscles but enhanced glucose utilization in visceral fat. Using reverse transcriptase-polymerase chain reaction and Northern blotting analyses, the mRNA expression of fatty acid translocase (FAT)/CD36, GLUT4, tumor necrosis factor (TNF)-alpha, peroxisome proliferator-activated receptor (PPAR)-gamma, leptin, uncoupling protein (UCP)-2, and UCP-3 was investigated in different fat depots and skeletal muscles before and after the study infusions. GLUT4 mRNA levels significantly decreased (by approximately 25%) in red fiber-type muscle (soleus) and increased (by approximately 45%) in visceral adipose tissue. Furthermore, there were marked increases in FAT/CD36, TNF-alpha, PPAR-gamma, leptin, UCP2, and UCP3 mRNA levels in the visceral fat and muscle of the treated animals in comparison with those measured in the saline-treated animals. These data suggest that the in vivo gene expression of FAT/CD36, GLUT4, TNF-alpha, PPAR-gamma, leptin, UCP2, and UCP3 in visceral fat and red fiber-type muscle are differently regulated by circulating lipids and that selective insulin resistance seems to favor, at least in part, a prevention of fat accumulation in tissues not primarily destined for fat storage, thus contributing to increased adiposity and the development of a prediabetic syndrome.

Adipose Tissue↗

PubMed2001

An improved metabolic calibrator for stress test equipment: protocol for its clinical utilization.

In previous articles, the technical specifications, validation and clinical applicability of a new metabolic calibrator for stress test apparatuses were described. However no indication was given of a basic protocol for the current clinical practice. Here we present an organised check system to satisfy this aim. A method for the exhaustive evaluation of the technical reliability of the metabolic instruments is presented together with the proposal of a uniform simulation approach to organise checks on-line of the apparatuses' ability to follow correctly the various test phases (protocol). Examples of recordings of checks using the standardised approach are shown. The method seems to be very effective. Every operation is computer directed.

Calibration↗

PubMed2000

[Refractory angina treated by spinal cord stimulation. The results of a long-term follow-up].

INTRODUCTION AND OBJECTIVES: The quality of life in patients with refractory angina has been shown to improve dramatically with spinal cord stimulation because of its beneficial results. The aim of this study was to assess the long-term morbimortality of this technique of spinal cord stimulation in the long term. PATIENTS AND METHODS: 41 patients with refractory angina and treated with spinal cord stimulation were included. Median follow-up was 31.0 [12.0-42.5] months, and total follow-up was 1,236 months. RESULTS: Annual number of admissions per patient year were dramatically reduced after spinal cord stimulation (2.31 vs. 0.28). Patients that died during follow-up had a 3-fold increase rate of admissions than patients that survived (0.37 vs. 0.19). However, patients that died during follow-up also had a lower admission rate after spinal cord stimulation (2.03 vs. 0.37). Overall mortality was 9.7%/year; cardiac mortality was 7.7%/year. Both figures are not different from those of other groups of patients with similar anatomical characteristics of coronary artery disease severity without spinal cord stimulation. Complications of this treatment were minimal (we only observed an early post implantation infection and a battery extrusion, without any complications with electrodes). The outcome was similar in patients with subacute unstable refractory angina or stable angina. CONCLUSIONS: Spinal cord stimulation can be considered a safe and effective alternative treatment of refractory angina. Long-term morbidity is low, and mortality is not higher than the expected in this group of patients.

Aged↗

PubMed2000

Substrate competition and insulin action in animal models.

Increased basal plasma FFA and lactate concentrations are often present in obesity and may deeply affect insulin action. The inhibition of glucose transport or phosphorylation is thought to be involved in this phenomenon, but the molecular mechanisms on the basis are still unknown. In our laboratory we observed that a chronic infusion of Intralipid plus heparin in rats significantly decreased the insulin dependent-glucose uptake, as well as GLUT4 gene expression in muscular tissue. On the other hand it has been shown that an enhanced plasma lactate concentration may increase insulin secretion and hepatic insulin clearance. Moreover we observed that chronic hyperlactatemia in rats is able to decrease glucose uptake in muscles, while reducing GLUT4 mRNA and protein in the same tissues. In obesity, lactate and FFA overproduction from visceral fat may therefore play a synergic role in reducing insulin sensitivity.

Adipose Tissue↗

PubMed1999

Parathyroid hormone-related peptide (PTHrP)-dependent and -independent effects of transforming growth factor beta (TGF-beta) on endochondral bone formation.

Previously, we showed that expression of a dominant-negative form of the transforming growth factor beta (TGF-beta) type II receptor in skeletal tissue resulted in increased hypertrophic differentiation in growth plate and articular chondrocytes, suggesting a role for TGF-beta in limiting terminal differentiation in vivo. Parathyroid hormone-related peptide (PTHrP) has also been demonstrated to regulate chondrocyte differentiation in vivo. Mice with targeted deletion of the PTHrP gene demonstrate increased endochondral bone formation, and misexpression of PTHrP in cartilage results in delayed bone formation due to slowed conversion of proliferative chondrocytes into hypertrophic chondrocytes. Since the development of skeletal elements requires the coordination of signals from several sources, this report tests the hypothesis that TGF-beta and PTHrP act in a common signal cascade to regulate endochondral bone formation. Mouse embryonic metatarsal bone rudiments grown in organ culture were used to demonstrate that TGF-beta inhibits several stages of endochondral bone formation, including chondrocyte proliferation, hypertrophic differentiation, and matrix mineralization. Treatment with TGF-beta1 also stimulated the expression of PTHrP mRNA. PTHrP added to cultures inhibited hypertrophic differentiation and matrix mineralization but did not affect cell proliferation. Furthermore, terminal differentiation was not inhibited by TGF-beta in metatarsal rudiments from PTHrP-null embryos; however, growth and matrix mineralization were still inhibited. The data support the model that TGF-beta acts upstream of PTHrP to regulate the rate of hypertrophic differentiation and suggest that TGF-beta has both PTHrP-dependent and PTHrP-independent effects on endochondral bone formation.

Activin Receptors, Type I↗

PubMed1999

Seasonal changes of zinc, copper, and iron in gilthead sea bream (Sparus aurata) fed fortified diets.

Four groups of gilthead sea bream (Sparus aurata) were fed diets with additional metal contents: a basal diet (diet A) contained Zn at 60.9 +/- 1.9 mg/kg diet, Cu at 3.9 +/- 0.9 mg/kg diet, and Fe at 138.3 +/- 6.8 mg/kg diet; the other diets were supplemented with copper (20 mg/kg, diet B), iron (100 mg/kg, diet C), or zinc (300 mg/kg, diet D). Two consecutive year-classes (0+ and 1+ age fish) from the same parent stock were examined. Several fish tissues were analyzed for metal contents in five different periods of each year in order to determine (1) the sensitivity of certain tissues as indicators of trace element metabolism and (2) possible seasonal variations. Growth data were similar for gilthead sea bream fed the basal diet and the metal-fortified diets. Mineral concentrations in tissues were found to be little affected by the dietary supplementation of trace elements, suggesting an efficient homeostatic control of these three metal concentrations. Tissues involved in metal metabolism (e.g., liver, kidney, gills) presented greater variations between minimum and maximum values with respect to other tissues (e.g., brain, muscle, eye). Seasonal variations were observed during the 2 yr of this study and were especially evident for zinc and copper concentrations in the liver. The overall pattern of metal variations showed a decreasing trend during the 2 yr. Results from this study indicate that (1) trace element concentrations in fish tissues vary with age and life cycle and (2) trace element requirements may vary in function of age and life cycle.

Analysis of Variance↗

PubMed1999

Seasonal dependence of cadmium accumulation and Cd-binding proteins in Mytilus galloprovincialis exposed to cadmium.

At different periods of the year specimens of Mytilus galloprovincialis were exposed to 0.5 microg Cd/ml seawater for 7 days. Concentrations of trace elements (Cd, Zn, Cu and Fe) and Cd-binding proteins in gills, viscera, muscle and mantle were determined after 1 weeks exposure. Cadmium accumulation was higher in May and June and was tissue dependent; it was highest in the gills and decreased in the order: gills > viscera > mantle and adductor muscle. Significant seasonal variations of zinc, copper and iron, were also found, in both exposed and control molluscs. The percentage of Cd distribution between cytosol and pellet changed during the year; a clear shift from the particulate fractions to the cytosolic fractions was measured during May and June, especially in the gills. Metallothionein (MT) was the main ligand responsible for Cd accumulation, and this protein reached a maximum between May and June. Inclusion of mercaptoethanol during the purification procedure was found to improve MT isolation by gel chromatography. In the absence of mercaptoethanol, MT showed polymerization patterns which were season dependent and temperature independent, whereas its concentration was increased in mussels kept at higher temperature.

Animals↗

PubMed1999

Overexpression of a kinase-deficient transforming growth factor-beta type II receptor in mouse mammary stroma results in increased epithelial branching.

Members of the transforming growth factor-beta (TGF-beta) superfamily signal through heteromeric type I and type II serine/threonine kinase receptors. Transgenic mice that overexpress a dominant-negative mutation of the TGF-beta type II receptor (DNIIR) under the control of a metallothionein-derived promoter (MT-DNIIR) were used to determine the role of endogenous TGF-betas in the developing mammary gland. The expression of the dominant-negative receptor was induced with zinc and was primarily localized to the stroma underlying the ductal epithelium in the mammary glands of virgin transgenic mice from two separate mouse lines. In MT-DNIIR virgin females treated with zinc, there was an increase in lateral branching of the ductal epithelium. We tested the hypothesis that expression of the dominant-negative receptor may alter expression of genes that are expressed in the stroma and regulated by TGF-betas, potentially resulting in the increased lateral branching seen in the MT-DNIIR mammary glands. The expression of hepatocyte growth factor mRNA was increased in mammary glands from transgenic animals relative to the wild-type controls, suggesting that this factor may play a role in TGF-beta-mediated regulation of lateral branching. Loss of responsiveness to TGF-betas in the mammary stroma resulted in increased branching in mammary epithelium, suggesting that TGF-betas play an important role in the stromal-epithelial interactions required for branching morphogenesis.

Animals↗

PubMed1999

Hyperlactatemia reduces muscle glucose uptake and GLUT-4 mRNA while increasing (E1alpha)PDH gene expression in rat.

An increased basal plasma lactate concentration is present in many physiological and pathological conditions, including obesity and diabetes. We previously demonstrated that acute lactate infusion in rats produced a decrease in overall glucose uptake. The present study was carried out to further investigate the effect of lactate on glucose transport and utilization in skeletal muscle. In chronically catheterized rats, a 24-h sodium lactate or bicarbonate infusion was performed. To study glucose uptake in muscle, a bolus of 2-deoxy-[3H]glucose was injected in basal condition and during euglycemic-hyperinsulinemic clamp. Our results show that hyperlactatemia decreased glucose uptake in muscles (i.e., red quadriceps; P < 0.05). Moreover in red muscles, both GLUT-4 mRNA (-30% in red quadriceps and -60% in soleus; P < 0.025) and protein (-40% in red quadriceps; P < 0.05) were decreased, whereas the (E1alpha)pyruvate dehydrogenase (PDH) mRNA was increased (+40% in red quadriceps; P < 0.001) in lactate-infused animals. PDH protein was also increased (4-fold in red gastrocnemius and 2-fold in red quadriceps). These results indicate that chronic hyperlactatemia reduces glucose uptake by affecting the expression of genes involved in glucose metabolism in muscle, suggesting a role for lactate in the development of insulin resistance.

Animals↗

PubMed1998

Interactions between cellular actin and human respiratory syncytial virus (HRSV).

Actin the main component of the cellular microfilament network, is present in human respiratory syncytial virus (HRSV) purified virions, as an internal component. This fact and the results of immunoprecipitation studies indicate that during HRSV infection in HEp-2 cells there are interactions between cellular actin and viral components, that can promote a transitory increase in the polymerization of synthetized actin, mainly of the beta isotype. This increased actin polymerization can be related with the formation of cytoplasmic extensions, that contain beta actin and viral particles observed in the HRSV infected HEp-2 cells. The formation of these structures may indicate that HRSV has developed an actin-based motility system similar to that described for other viral and bacterial systems.

Actins↗

PubMed1998

Dominant-negative interference of the transforming growth factor beta type II receptor in mammary gland epithelium results in alveolar hyperplasia and differentiation in virgin mice.

Transforming growth factor (TGF)-beta1 and TGF-beta3 are normally expressed at high levels in the mammary gland during quiescence and at all stages of development, except lactation. Exogenously added TGF-beta1, -beta2, and -beta3 have been shown to regulate growth and differentiation of mammary epithelial cells in vitro and in vivo. TGF-betas signal through a heteromeric complex of type I and type II serine/threonine kinases. The type II receptor is necessary for ligand binding and growth suppression by TGF-betas. Deletions of the cytoplasmic domains of several kinase receptors known to function in multimeric complexes have been shown to act as dominant-negative mutations. To evaluate the role of endogenous TGF-betas in the growth and differentiation of the mammary gland in vivo, we have targeted expression of a truncated, kinase-defective TGF-beta type II receptor to mammary epithelial cells in transgenic mice using the mouse mammary tumor virus promoter/enhancer. Transgene expression was localized to the epithelial cells of terminal ducts and alveolar buds. At approximately 20 weeks of age, virgin female transgenic mice demonstrated varying degrees of mammary epithelial hyperplasia. Mammary glands from transgenic, virgin animals exhibited alveolar development and expression of the milk protein, beta-casein. The data suggest that impaired responsiveness in the epithelium to endogenous TGF-betas results in inappropriate alveolar development and differentiation in the mammary gland. We conclude that endogenous TGF-betas signal to the epithelium to maintain quiescence in the mammary glands of virgin animals.

Animals↗

PubMed1998

Improved simulation system for routine cardiopulmonary exercise test equipment. Part III: A new cycle ergometer check system. ECSC Working Group on Standardization of Stress Test Methods.

A new check system for cycle ergometers is described. The system consists of a device with a calibrated reference moment which connects to the crank axle of the ergometer to be controlled and exerts a known amount of force. It is equipped with a balance system that indicates whether the force applied corresponds to the preset resistance of the ergometer. The power actually produced by the ergometer is calculated by a mathematical formula. A mechanical and an electronic version are described. The accuracy of the calibrator was tested: mean error during constant pedal revolutions per minute (rpm) conditions was < 0.59% (SD < 0.31); in variable rpm conditions it was < 0.645% (SD < 0.378). An isoline diagram for rapid clinical use is also illustrated.

Calibration↗

PubMed1997

Modelling Bacterial Degradation of Organic Compounds with Genetic Networks

The bacterial degradation of organic compounds plays a crucial role in the biogeochemical cycles of the earth and in the clean-up of contaminated soils. The processes are carried out by bacterial consortia, rather than isolated strains, which are usually modelled by phenomenological kinetic equations which describe a fictitious, homogeneous bacterial species which mimics the behaviour of the consortium. An alternative modelling framework is presented here, where the bacterial consortia are considered as networks of genes interacting with other genes as well as with chemicals, which may be either introduced from outside or produced by bacterial metabolism. The model is based on an extension of the random Boolean network model of genetic networks, which makes use of continuous dynamical variables. Three different models are introduced, which differ in the way how they account for the existence of different species: (i) a single supercell model, where all the genes can interact strongly with each other; (ii) a graded interaction model, where genes interact strongly within a species, and weakly among different species; and (iii) a separate subsets model, where genes interact only within species. It is shown how this modelling framework is sound, as it is able to reproduce some of the generic behaviours of bacterial consortia, describing experimentally observed phenomena like population changes induced by contamination, and prey-predator dynamics.Copyright 1997 Academic Press Limited Copyright 1997 Academic Press Limited

Journal Article↗

PubMed1997

Expression of a truncated, kinase-defective TGF-beta type II receptor in mouse skeletal tissue promotes terminal chondrocyte differentiation and osteoarthritis.

Members of the TGF-beta superfamily are important regulators of skeletal development. TGF-betas signal through heteromeric type I and type II receptor serine/threonine kinases. When over-expressed, a cytoplasmically truncated type II receptor can compete with the endogenous receptors for complex formation, thereby acting as a dominant-negative mutant (DNIIR). To determine the role of TGF-betas in the development and maintenance of the skeleton, we have generated transgenic mice (MT-DNIIR-4 and -27) that express the DNIIR in skeletal tissue. DNIIR mRNA expression was localized to the periosteum/perichondrium, syno-vium, and articular cartilage. Lower levels of DNIIR mRNA were detected in growth plate cartilage. Transgenic mice frequently showed bifurcation of the xiphoid process and sternum. They also developed progressive skeletal degeneration, resulting by 4 to 8 mo of age in kyphoscoliosis and stiff and torqued joints. The histology of affected joints strongly resembled human osteo-arthritis. The articular surface was replaced by bone or hypertrophic cartilage as judged by the expression of type X collagen, a marker of hypertrophic cartilage normally absent from articular cartilage. The synovium was hyperplastic, and cartilaginous metaplasia was observed in the joint space. We then tested the hypothesis that TGF-beta is required for normal differentiation of cartilage in vivo. By 4 and 8 wk of age, the level of type X collagen was increased in growth plate cartilage of transgenic mice relative to wild-type controls. Less proteoglycan staining was detected in the growth plate and articular cartilage matrix of transgenic mice. Mice that express DNIIR in skeletal tissue also demonstrated increased Indian hedgehog (IHH) expression. IHH is a secreted protein that is expressed in chondrocytes that are committed to becoming hypertrophic. It is thought to be involved in a feedback loop that signals through the periosteum/ perichondrium to inhibit cartilage differentiation. The data suggest that TGF-beta may be critical for multifaceted maintenance of synovial joints. Loss of responsiveness to TGF-beta promotes chondrocyte terminal differentiation and results in development of degenerative joint disease resembling osteoarthritis in humans.

Animals↗

PubMed1997

Lactate infusion to normal rats during hyperglycemia enhances in vivo muscle glycogen synthesis.

Both hyperglycemia and hyperinsulinemia stimulate whole body and muscle glucose disposal. To define the impact of increased lactate concentration (4-5 mM) on muscle glucose disposal during hyperglycemia, we studied anesthetized normal rats infused with either sodium lactate or sodium bicarbonate as control. Animals were studied under hyperglycemic clamp (13 mM) using [3-3H]glucose (study 1) and 2-deoxy-[1-3H]glucose (study 2) to assess glucose rate of disappearance (Rd), glycolytic flux (GF), glycogen synthesis, and glucose utilization index by different tissues. Moreover, in study 3, the effect of lactate on the pattern of plasma insulin response to hyperglycemia was evaluated. In study 1, lactate infusion resulted in an increased Rd (38.7 +/- 1.7 vs. 32.3 +/- 1.3 mg.min-1.kg-1; P < 0.01), which was explained by an enhanced rate of glycogen synthesis (23.0 +/- 1.7 vs. 14.7 +/- 1.2 mg.min-1.kg-1; P < 0.001), whereas GF was unchanged. In study 2, lactate-infused animals showed an increased 2-deoxy-glucose disposal and a stimulated glycogen synthase activity as well as an increased glycogen accumulation at the end of the study in several skeletal muscles. In study 3, lactate did not induce any change in either early or late insulin response to hyperglycemia. In conclusion, our results show that muscle glycogen deposition may be enhanced by elevated lactate levels under hyperglycemic conditions and support a role for lactate in the regulation of glucose homeostasis.

Animals↗

PubMed1997

Improved simulation system for routine cardiopulmonary exercise test equipment: introductory remarks. ECSC Working Group on Standardization Stress Test Methods.

The instruments used in the evaluation of cardiorespiratory function employ extraordinarily fast and complex techniques: instantaneous ventilatory flow-volume transducer operate together with rapid CO2-O2 analysers, and are coupled to on-line cardiocirculatory monitors working in real time under the control of advanced software. It is clear that, with such powerful equipment, the calibrations currently made at rest before exercise are insufficient and must be accompanied by, or replaced with, methods capable of continuous (breath-to-breath) monitoring of the instrument's activity throughout the exercise period. Two new simulation and check systems were developed for the calibration and the continuous monitoring of exercise equipment. The former applies to metabolic determinations, the latter to the cycle ergometers employed to impose varying workloads in the implementation of specific protocols.

Calibration↗