Showing papers by "University of Siena published in 1996"

Identification of a c-fos-induced gene that is related to the platelet-derived growth factor/vascular endothelial growth factor family

Abstract: Using a mRNA differential screening of fibroblasts differing for the expression of c-fos we isolated a c-fos-induced growth factor (FIGF). The deduced protein sequence predicts that the cDNA codes for a new member of the platelet-derived growth factor/vascular endothelial growth factor (PDGF/VEGF) family. Northern blot analysis shows that FIGF expression is strongly reduced in c-fos-deficient cells. Transfection of exogenous c-fos driven by a constitutive promoter restores the FIGF expression in these cells. In contrast, both PDGF and VEGF expression is unaffected by c-fos. FIGF is a secreted dimeric protein able to stimulate mitogenic activity in fibroblasts. FIGF overexpression induces morphological alterations in fibroblasts. The cells acquire a spindle-shaped morphology, become more refractive, disorganized, and detach from the plate. These results imply that FIGF is a downstream growth and morphogenic effector of c-fos. These results also suggest that the expression of FIGF in response to c-fos activation induces specific differentiation patterns and its aberrant activation contributes to the malignant phenotype of tumors.

Inhaled PGE2 prevents aspirin-induced bronchoconstriction and urinary LTE4 excretion in aspirin-sensitive asthma.

Abstract: Bronchial overproduction of leukotrienes and inhibition of prostaglandin synthesis are involved in the pathogenesis of aspirin-induced asthma. We investigated whether inhaled prostaglandin E2 (PGE2) attenuates the response to bronchial challenge with lysine acetylsalicylate (LASA) and the associated increase in urinary leukotriene E4 (u-LTE4) in seven aspirin-sensitive subjects with asthma. Each subject performed two challenges with a single dose of LASA that caused a decrease in FEV1 of 20% or more in a preliminary test, immediately after inhaling 100 micrograms PGE2 in 4 ml saline or placebo, according to a randomized double-blind protocol. FEV1 was recorded at 30-min intervals for 4 h. u-LTE4 was measured by combined high-performance liquid chromatography enzyme immunoassay at 2-h intervals. After placebo, LASA caused an obstructive reaction in all patients, with a maximum decrease in FEV1 of 35 +/- 5% with respect to baseline. u-LTE4 rose from 911 +/- 261 picograms (pg)/mg creatinine at baseline to a ...

Periodontal Regeneration of Human Intrabony Defects With Bioresorbable Membranes. A Controlled Clinical Trial

Abstract: The purpose of this controlled clinical trial was to compare the clinical efficacy of 3 treatment modalities in the treatment of deep interproximal intrabony defects. Thirty-six (36) defects in 36 patients were randomly assigned to 1 of 3 treatment groups by blocking to prognostic variables. The test was treated with bioresorbable membranes positioned coronal to the interproximal bone crest; the second group (membrane control) was treated with conventional non-resorbable (ePTFE) barrier membranes applied coronal to the alveolar crest; the third group (flap Control) was treated with an access flap procedure (MWF). No differences were observed in terms of baseline oral hygiene and defect characteristics among the 3 groups, indicating that the blocking approach was effective. A stringent infection control program was enforced for 1 year. The results indicated that: 1) at 1 year all treatment modalities resulted in clinically significant improvements in clinical attachment levels (CAL) and reductions in probing depths; 2) a statistically significant treatment effect (P or = 4 mm were observed in 83.3% of cases in both GTR groups, while CAL gains of this magnitude were not detected in the MWF group. We concluded that clinically significant CAL gains can be obtained with GTR procedures using both bioresorbable and non-resorbable membranes. Patients' morbidity, however, was lower in the group treated with bioresorbable membranes.

Comparison of the antiinflammatory efficacy of chondroitin sulfate and diclofenac sodium in patients with knee osteoarthritis.

Abstract: Objective To assess the clinical efficacy of chondroitin sulfate (CS) in comparison with the non-steroidal antiinflammatory drug (NSAID) diclofenac sodium (DS) in a medium/longterm clinical study in patients with knee osteoarthritis (OA) Methods This was a randomized, multicenter, double blind, double dummy study 146 patients with knee OA were recruited into 2 groups During the first month, patients in the NSAID group were treated with 3 x 50 mg DS tablets/day and 3 x 400 mg placebo (for CS) sachets ; from Month 2 to Month 3, patients were given placebo sachets alone In the CS group, patients were treated with 3 x 50 mg placebo (for diclofenac) tablets/day and 3 x 400 mg CS sachets/day during the first month ; from Month 2 to Month 3, these patients received only CS sachets Both groups were treated with 3 x 400 mg placebo sachets from Month 4 to Month 6 Clinical efficacy was evaluated by assessing the Lequesne Index, spontaneous pain (using the Huskisson visual analog scale), pain on load (using a 4 point ordinal scale), and paracetamol consumption Results Patients treated with the NSAID showed prompt and plain reduction of clinical symptoms, which, however, reappeared after the end of treatment ; in the CS group, the therapeutic response appeared later in time but lasted for up to 3 months after the end of treatment Conclusion CS seems to have slow but gradually increasing clinical activity in OA ; these benefits last for a long period after the end of treatment

Factors affecting the healing response of intrabony defects following guided tissue regeneration and access flap surgery

Abstract: Identification and control of significant factors determining clinical outcomes is of paramount importance to improve expected results of a variety of therapeutic procedures. The aim of this investigation was to identify, with a multivariate approach, factors associated with healing outcomes of 3 periodontal surgical procedures in deep intrabony defects. 45 patients with evidence of deep intrabony defects were randomly assigned to 3 treatment groups: access flap (group C), conventional guided tissue regeneration (GTR) with non-resorbable expanded polytetrafluoroethilene (ePTFE) membranes (group B), and GTR with self supporting membranes combined with the modified papilla preservation technique (group A). In both GTR procedures, membranes were positioned coronal to the interproxymal alveolar crest. Primary outcome variables (i.e., probing attachment level gains at 1 year and the amount of newly formed tissue present at membrane removal) were explained in terms of a series of patient, defect morphology and surgical factors, using a multivariate approach. Highly significant treatment effects were observed, indicating that the 3 tested therapeutic modalities resulted in significant differences in primary outcome variables. Detailed analysis assessing the significance of the tested factors in determining the healing outcomes following each procedure was performed with a stepwise elimination approach of non-significant factors. The results indicated that: (i) the need to create and maintain space should be a key objective of regenerative approaches based upon the principles of guided tissue regeneration; (ii) control of patient's oral hygiene and residual periodontal infection in the oral cavity are strongly associated with clinical outcomes of both regenerative and conventional surgical procedures and should receive proper attention.

Oligomeric and subunit structure of the Helicobacter pylori vacuolating cytotoxin.

Abstract: Disease-associated strains of Helicobacter pylori produce a potent toxin that is believed to play a key role in peptic ulcer disease in man. In vitro the toxin causes severe vacuolar degeneration in target cells and has thus been termed VacA (for vacuolating cytotoxin A). Cytotoxic activity is associated with a > 600-kD protein consisting of several copies of a 95-kD polypeptide that undergoes specific proteolytic cleavage after release from the bacteria to produce 37- and 58-kD fragments. Quick freeze, deep etch electron microscopy has revealed that the native cytotoxin is formed as regular oligomers with either six- or seven-fold radial symmetry. Within each monomer, two domains can clearly be distinguished, suggesting that the 37- and 58-kD fragments derive from proteolytic cleavage between discrete subunits of the monomer. Analysis of preparations of the toxin that had undergone extensive cleavage into the 37- and 58-kD subunits supports this interpretation and reveals that after cleavage the subunits remain associated in the oligomeric structure. The data suggest a structural similarity with AB-type toxins.

Phage antibodies with pan‐species recognition of the oncofoetal angiogenesis marker fibronectin ED‐B domain

Abstract: Fibronectin (FN) exists in several polymorphic forms due to alternative splicing. The B-FN isoform (with ED-B domain inserted by splicing) is present in the stroma of foetal and neoplastic tissues and in adult and neoplastic blood vessels during angiogenesis but is undetectable in mature vessels. This isoform, therefore, represents a promising marker for angiogenesis, as already shown using the mouse monoclonal antibody (MAb) BC-1 directed against an epitope on human B-FN. However, this MAb does not directly recognise the human ED-B domain nor does it recognise B-FN of other species; therefore, it cannot be used as a marker of angiogenesis in animal models. In principle, antibodies directed against the human ED-B domain should provide pan-species markers for angiogenesis as the sequence of this domain is highly conserved in different species (and identical in humans and mice). As it has proved difficult to obtain such antibodies by hybridoma technology, we used phage display technology. Here, we describe the isolation of human antibody fragments against the human ED-B domain that bind to human, mouse and chicken B-FN. As shown by immunohistochemistry, the antibody fragments stain human neoplastic tissues and the human, mouse and chicken neovasculature.

Identification and mapping of human cDNAs homologous to Drosophila mutant genes through EST database searching

Abstract: Cross–species comparison is an effective tool used to identify genes and study their function in both normal and pathological conditions. We have applied the power of Drosophila genetics to the vast resource of human cDNAs represented in the expressed sequence tag (EST) database (dbEST) to identify novel human genes of high biological interest. Sixty–six human cDNAs showing significant homology to genes causing Drosophila mutant phenotypes were identified by screening dbEST using the ‘text string’ option, and their map position was determined using both fluorescence in situ hybridization (FISH) and radiation hybrid mapping. Comparison between these genes and their putative partners in Drosophila may provide important insights into their function in mammals. Furthermore, integration of these genes into the transcription map of the human genome contributes to the positional candidate approach for disease gene identification.

Sequential approximation of feasible parameter sets for identification with set membership uncertainty

Abstract: In this paper the problem of approximating the feasible parameter set for identification of a system in a set membership setting is considered. The system model is linear in the unknown parameters. A recursive procedure providing an approximation of the parameter set of interest through parallelotopes is presented, and an efficient algorithm is proposed. Its computational complexity is similar to that of the commonly used ellipsoidal approximation schemes. Numerical results are also reported on some simulation experiments conducted to assess the performance of the proposed algorithm.

Apoptosis in human ejaculated sperm cells (notulae seminologicae 9).

Abstract: In this work we apply the Hoechst 33258 DNA staining, the TUNEL procedure and conventional electron microscopy to study the ejaculate of fertile and infertile men, in order to detect apoptosis in human sperm cells. We have observed that apoptosis is abnormally frequent in the sperm cells of the ejaculate of sterile men, and that it shows the classical biochemical and ultrastructural pattern in spermatozoa, spermatids and apoptotic bodies. These characteristics, involving the chromatin, the nuclear envelope, the plasma membrane, the presence of cytoplasmic vacuoles and the status of mitochondria, are consistent whatever the pathology of the patient is. What is varying is the percentage of the apoptotic sperm cells, that is about 0.1% in fertile controls, and increases up to about 10% in varicocele, infected (including AIDS), "round headed' patients, to 20% in cryptorchid men, to 25% in immature patients, and to 50% in testicular seminoma carriers. Obviously in each category the frequence of apoptotic cells increases concomitantly with the degree of the affection. The present demonstration not only extends to human spermiogenetic epithelium the natural presence of apoptosis, which starts in the testis and is revealed in the ejaculate, but also explains many abnormal ultrastructural sperum patterns hitherto unexplained in fertile and infertile individuals.

Benign Paroxysmal Positional Vertigo of the Horizontal Canal: A Form of Canalolithiasis with Variable Clinical Features

Abstract: Benign paroxysmal positional vertigo of the horizontal semicircular canal (HC-BPPV) is a well-defined syndrome characterized by direction-changing horizontal positional nystagmus. We report the clinical features of 5 patients who illustrate the possible variables of the syndrome. In most cases, nystagmus is geotropic and more intense when the pathological ear is lowermost; less often the syndrome presents with apogeotropic nystagmus that is more intense when the affected ear is uppermost. The nystagmus pattern may vary in time in the same patient, changing from apogeotropic to geotropic even in observations at short intervals. In some patients, the features indicate involvement of more than one canal, either simultaneously or in succession. It is sustained that the clinical findings can be explained by movement of endolymph caused by displacement of otoconia in the semicircular canals and that variants are due to different positions of the otoconia within the canals.

Sonographic endometrial thickness: a useful test to predict atrophy in patients with postmenopausal bleeding. An Italian multicenter study

Abstract: Eighteen centers took part in this prospective study into which 930 eligible patients were recruited. The selection criteria for admission were atypical bleeding after at least 6 months of postmenopausal amenorrhea, and absence of hormonal therapies for at least 6 months. The sonographic measurement of the maximum bi-endometrial thickness was made in a longitudinal plane. Sonographic measurements were always performed within 3 days prior to histological evaluation. In these patients the mean number of years from menopause (25-75th centile) was 6 (range 2-16). The prevalence of endometrial carcinoma was 11.5% and the prevalence of atrophy was 49.2%. The area under the receiver operator characteristic curves generated by sonographic thickness measurements reached the level of 85%, both for cancer and atrophy. The likelihood ratio for cancer, yielded by an endometrial thickness of 4.0 mm yielded a sensitivity for the detection of cancer of 98% and a negative predictive value of 99%. The overall sensitivity and positive predictive value for atrophy achieved by this cut-off were 57.2% and 87.3%, respectively. A multivariate logistic model showed that age and body mass index were independent variables associated with a significantly higher risk of endometrial cancer. The post-test probabilities for cancer and atrophy were recalculated on the basis of the integration of age, body mass index and endometrial thickness. The estimated reduction of invasive procedures on the basis of this integration was 31%. Transvaginal sonographic measurement of endometrial thickness, integrated with individual risk factors, can help in the management of postmenopausal patients with atypical bleeding, with regard to either the need for histological evaluation in high risk cases, or the choice of possible expectant management. We have shown that an endometrial thickness of < or = 4.0 mm safely predicts endometrial atrophy and justifies expectant management when the patient understands the need for proper follow up. This could be achieved with a reduction in the use of invasive procedures without unwanted delay in cancer diagnosis.

Accumulation Pattern of Butyltin Compounds in Dolphin, Tuna, and Shark Collected from Italian Coastal Waters

Abstract: Tributyltin (TBT) and its breakdown products, mono-(MBT) and dibutyltin (DBT) were determined in bottlenose dolphin (Tursiops truncatus), bluefin tuna (Thunnus thynnus thynnus) and blue shark (Prionace glauca) collected from the Italian coast of the Mediterranean Sea in 1992–1993. Concentrations of total butyltin (BTs) in the liver of dolphin (1,200–2,200 ng/g wet wt) were an order of magnitude higher than in the blubber (48–320 ng/g wet wt). TBT was the predominant butyltin species in the blubber while DBT accounted for an higher proportion in the liver of dolphins. Butyltin concentrations in bluefin tuna were lower than those in dolphins, with TBT highest in the muscle and DBT in the liver. Concentrations of BTs in blue sharks were lower than those in dolphin and tuna, with kidney having the highest concentrations. TBT was the predominant form of butyltin derivatives in all the tissues of shark. Accumulation of butyltin compounds in liver/kidney seems to be associated with the presence of proteins such as glutathione.

Comparison between a cisplatin-containing regimen and a carboplatin-containing regimen for recurrent or metastatic bladder cancer patients. A randomized phase II study.

Abstract: BACKGROUND The aim of this randomized Phase II study was to compare the efficacy and toxicity of a cisplatin-containing regimen with a carboplatin-containing regimen for patients with recurrent or metastatic bladder cancer. METHODS Fifty-seven patients with recurrent or metastatic bladder cancer were randomized to receive M-VEC treatment (methotrexate, vinblastine, epirubicin, and cisplatin) (n = 29) or M-VECa treatment (methotrexate, vinblastine, epirubicin, and carboplatin) (n = 28). The chemotherapy was scheduled at 28-day intervals. Recombinant granulocyte-colony stimulating factors were administered daily when the absolute neutrophil count fell below 1000/mm3. The development of ototoxicity was evaluated by measuring auditory brain stem response. RESULTS Of the 57 entered patients, 55 were evaluable for response and toxicity. The overall clinical response rate was 71% (with 25% complete responses) in the M-VEC group and 41% (with 11% complete responses) in the M-VECa group (P = 0.04). M-VEC chemotherapy was associated with more pronounced side effects. There was a statistically significant difference between M-VEC and M-VECa in terms of gastrointestinal toxicity (P = 0.04), nephrotoxicity (P = 0.03), and neurotoxicity (P = 0.02) during Cycle 3 of chemotherapy. Leukopenia and neutropenia were worse in the M-VECa arm, but not significantly so (P = 0.4). Ototoxicity was only detected in one of seven examined M-VEC patients after two cycles of chemotherapy. CONCLUSIONS M-VECa has a low level of gastrointestinal, renal, neurologic, and otologic toxicity, but is apparently less effective than M-VEC in the treatment of recurrent or metastatic bladder cancer. However, a larger, randomized Phase III trial is needed to confirm these results. Cancer 1996;77:344-51.

Long‐term stability of clinical attachment following guided tissue regeneration and conventional therapy

Abstract: UNLABELLED 44 patients (34% smokers) presenting with severe periodontitis were treated with full mouth root planing (RPL). In each patient, 1 intrabony defect was treated with guided tissue regeneration (GTR). After 1 year of monthly prophylaxis, full mouth plaque (FMPS) and bleeding (FMBS) scores were 8.3 +/- 4.1% and 5.6 +/- 3.8%. At 1 year, the GTR treated sites were matched, in each patient, with 1 RPL site, in terms of probing attachment level (PAL 6.8 +/- 2.4 mm GTR, and 6.5 +/- 2.3 mm RPL). At this point, 24 patients took part in a supportive periodontal care program. 20 patients did not participate, and received only sporadic care by general dentists. At 5 years, all patients were reexamined. FMPS was 10.5 +/- 6.8% and FMBS 7.7 +/- 6.4%. A significant PAL loss was observed in both sites (1.2 +/- 1.4 mm GTR, 1.3 +/- 1.3 mm RPL, p < 0.0001) between 1 and 5 years. Differences in PAL loss between GTR and RPL sites were not statistically significant. Only a minority of sites (34%), however, lost PAL, while 66% remained stable. 75% of the matched sites (GTR and RPL) within the same patients were concordant in terms of PAL stability. The 23 patients in which both sites remained stable, had good oral hygiene, complied with the recall system, and did not smoke. The 10 patients in which both sites lost PAL showed deteriorating oral hygiene, did not comply with the recall system, and smoked. PAL loss in the GTR and/or RPL sites was consistently observed in patients (losers) showing PAL loss in other teeth. Losers had, in general, negative subjects characteristics, and showed a higher prevalence of tooth loss. IN CONCLUSION (i) GTR and RPL sites showed comparable susceptibility to periodontal breakdown; (ii) stability of outcomes was consistently associated with good oral hygiene, compliance with a supportive periodontal care program, and no cigarette smoking.

Types and meaning of pollen carbohydrate reserves

Abstract: During pollen development, soluble carbohydrates of sporophytic origin may be consumed immediately, polymerized to form starch reserves or intine, or transformed into other molecules. Disregarding intine, in mature pollen there are three different types of carbohydrates: (1) polysaccharides such as starch in amyloplasts or polysaccharides in cytoplasmic vesicles, (2) disaccharides such as sucrose and (3) monosaccharides such as glucose and fructose. At dispersal, pollen may be partly or slightly dehydrated, or not dehydrated at all. Partly dehydrated pollen has the capacity to lose or acquire water within limits without detriment to its viability. Slightly and non-dehydrated pollen is vulnerable to water loss and quickly becomes inviable. In partly dehydrated of pollen the carbohydrates consist of cytoplasmic polysacharides and sucrose; in slightly and non-dehydrated pollen these are absent or in low concentrations but there may be reserves of cytoplasmic callose. Starch, glucose and fructose are found in both types. It is postulated that cytoplasmic carbohydrates and sucrose are involved in protecting pollen viability during exposure and dispersal.

Elevated cadmium accumulation in marine organisms from Terra Nova Bay (Antarctica)

Abstract: As a contribution towards identification of the principal environmental factors involved in cadmium accumulation in Antarctic marine organisms and the establishment of a baseline near the Italian Antarctic Station “Baia Terra Nova”, surface sediments, plankton and benthic organisms were studied in coastal waters of Terra Nova Bay (Ross Sea). The cadmium content of sediments was similar to that regarded as background in most marine coastal areas, whereas in surface water, phytoand Zooplankton it was similar to values measured in areas of enhanced upwelling. Algal and animal taxa dominating benthic associations had a higher cadmium content than related species from other seas. Very high concentrations of the metal were found in sponges (10–80 μg/g dw) and in the digestive gland of molluscs (up to 345 μg/g inNeobuccinum eatoni). The rapid regeneration of cadmium and its natural occurrence and bioavailability in highly productive coastal waters seem to be responsible for cadmium accumulation in the tissues of marine organisms near the “Baia Terra Nova” station.

Ozone as a bioregulator. Pharmacology and toxicology of ozonetherapy today.

Abstract: The disinfectant activity of ozone is well recognized and ozone is used worldwide for sterilization of water. The use of ozone as a complementary medical approach is less known, because it has mostly been used in an empirical fashion without a rational basis and appropriate controls. In spite of this drawback, the use of judicious and standardized ozone dosages can elicit the formation of ROS acting as natural physiological activators of several biological functions. There is now a reasonable understanding of a few mechanisms of action and, using classical pharmacological concepts, it appears possible to formulate a rationale for optimizing clinical applications. A further exciting development is that ozone, being an oxidizer, can upregulate the intracellular anti-oxidant enzymes eventually inhibiting the constant, life-long oxidative stress responsible for degenerative diseases and aging. Among various routes for the administration of ozone, the autohemotransfusion procedure, consisting in exposing blood to ozone, i.e. to a calculated and brief oxidative stress, appears safe, simple, inexpensive and amenable to be adjusted to different pathological states It is hoped that this review will help to dispel prejudices, to clarify that ozone toxicity can be tamed, to show that ozone can act as a bioregulator and to encourage controlled clinical investigations to evaluate definitely the validity of ozonetherapy.

Guided tissue regeneration versus mucogingival surgery in the treatment of human buccal recessions. A 4-year follow-up study.

Abstract: The 4-year follow-up results of a clinical trial are reported. The clinical results of the treatment of buccal recession were analyzed comparing the outcomes of a guided tissue regeneration (GTR) procedure with nonresorbable membranes and a 2-step mucogingival procedure consisting of a coronally-positioned free gingival graft in two groups of 25 patients each. The final root coverage was 73.07% in the test group (GTR) and 72.3% in the control group (mucogingival surgery). In the test group, statistically significant recession reduction, probing depth reduction, clinical attachment level gain, and increase of keratinized tissue width were observed. In the control group the results were similar except for probing depth, which did not vary significantly. At the end of the 4-year follow-up period, the average periodontal conditions did not differ between the 2 groups, with the exception of the keratinized tissue width. This was obviously greater in the control group, where a free gingival graft had been carried out. Recessions > or = 5 mm had a greater root coverage after GTR treatment. In both groups, the periodontal parameters remained stable between 18 months and 4 years after surgery, indicating remarkable stability; the only exception was a significant increase in the keratinized tissue width in the test group. When the changes between the baseline and the 4-year follow-up were compared, the average reduction in the recession was similar in the two groups while probing depth reduction and clinical attachment level were greater in the GTR group.

Endothelin-B Receptor Mutations in Patients with Isolated Hirschsprung Disease from a Non-Inbred Population

Abstract: Hirschsprung disease (HSCR), or aganglionic megacolon, is the most common cause of congenital intestinal obstruction. Two different loci have been found to be tightly linked to HSCR on chromosomes 10 and 13, respectively. Recently, mutations in the RET protooncogene on chromosome 10q11.2 were identified in several HSCR patients. In addition, a missense mutation in the endothelin-B receptor (EDNRB) gene on chromosome 13q22 was found in an inbred Mennonite kindred affected by HSCR and associated abnormalities, demonstrating the involvement of EDNRB in HSCR pathogenesis. To test whether mutations in the EDNRB gene could account for Hirschsprung in patients from non-inbred populations, we analysed DNA samples from 17 probands of Italian origin with HSCR. We have identified two novel EDNRB mutations : a missense mutation in a sporadic case, S305N, which leads to a change of a serine to an asparagine, disrupting a putative phosphorylation site ; and a single nucleotide deletion in a familial case, N3781, resulting in a truncated protein. Both mutations were found in one of the healthy parents, and neither of these mutations were found in any of the normal individuals tested. These data confirm the involvement of EDNRB in HSCR pathogenesis and demonstrate that EDNRB mutations could contribute to HSCR disease in non-inbred populations.

Differential distribution of ryanodine receptor type 3 (RyR3) gene product in mammalian skeletal muscles.

Abstract: Activation of intracellular Ca(2+)-release channels/ryanodine receptors (RyRs) is a fundamental step in the regulation of muscle contraction. In mammalian skeletal muscle, Ca(2+)-release channels containing the type 1 isoform of RyR (RyR1) open to release Ca2+ from the sarcoplasmic reticulum (SR) upon stimulation by the voltage-activated dihydropyridine receptor on the T-tubule/plasma membrane. In addition to RyR1, low levels of the mRNA of the RyR3 isoform have been recently detected in mammalian skeletal muscles. Here we report data on the distribution of the RyR3 gene product in mammalian skeletal muscles. Western-blot analysis of SR of individual muscles indicated that, at variance with the even distribution of the RyR1 isoform, the RyR3 content varies among different muscles, with relatively higher amounts being detected in diaphragm and soleus, and lower levels in abdominal muscles and tibialis anterior. In these muscles RyR3 was localized in the terminal cisternae of the SR. No detectable levels of RyR3 were observed in the extensor digitorum longus. Preferential high content of RyR3 in the diaphragm muscle was observed in several mammalian species. In situ hybridization analysis demonstrated that RyR3 transcripts are not restricted to a specific subset of skeletal-muscle fibres. Differential utilization of the RyR3 isoform in skeletal muscle may be relevant to the modulation of Ca2+ release with respect to specific muscle-contraction properties.