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Biomedical subjects

M Radice

Publications and source records attributed to M Radice.

At least 19 recordsLinked to original sources
PubMed2003

Extended-spectrum beta-lactamases in enterobacteriaceae in Buenos Aires, Argentina, public hospitals.

Resistance to extended-spectrum cephalosporins is often associated with plasmid encoded extended spectrum beta-lactamases (ESBL). In order to evaluate the prevalence and diversity of ESBLs in enterobacteria in our city, a 1-month-period survey was carried out from April to May 2000. Extended-spectrum-cephalosporin-resistant strains, isolated from inpatient clinical specimens other than stools, were collected among 17 participating hospitals. From a total of 427 enterobacterial strains that were collected during this period, 39 were extended-spectrum cephalosporin resistant. The National Committee for Clinical Laboratory Standards' Screening and Confirmatory Tests for ESBL production were performed using cefotaxime and ceftazidime; cefepime and cefepime-clavulanic acid-containing disks were included. beta-Lactamases were characterized by isoelectric focusing and PCR amplification using specific primers. Three different ESBLs were detected: SHV-related (4 isolates), PER-2-type (9 isolates), and CTX-M-2-related (26 isolates). Sequencing of the corresponding genes confirmed CTX-M-2 in 19 of 21 and CTX-M-31 (an allelic variant) in the remaining 2 of 21. CTX-M-2 (or its variant) was detected in all Escherichia coli, Enterobacter aerogenes, Serratia marcescens, Proteus mirabilis, and Providencia stuartii strains, while PER-2 was detected in Enterobacter cloacae, E. aerogenes, and Klebsiella pneumoniae; SHV-related ESBL were found only in K. pneumoniae. These results clearly show that CTX-M-2 is the most prevalent ESBL produced by enterobacterial species isolated from public hospitals in Buenos Aires.

Argentina↗
PubMed2000

Hyaluronan-based biopolymers as delivery vehicles for bone-marrow-derived mesenchymal progenitors.

The tolerability and safety of hyaluronan-based three-dimensional scaffolds as a culture vehicle for mesenchymal progenitor cells was investigated in this pilot study. The proliferation patterns and extracellular matrix production of rabbit and human mesenchymal, bone-marrow-derived progenitors first were characterized in vitro. Subsequently rabbit autologous cells were cultured in this hyaluronan-based scaffold and implanted in a full-thickness osteochondral lesion. In vitro histologic findings showed that mesenchymal progenitor cells adhered and proliferated onto the hyaluronan-derived scaffold. Human stem cells were shown to produce the main extracellular matrix molecules, accompanied by an occasional synthesis of mature type II collagen. In vivo data demonstrated that the biomaterial, with or without mesenchymal progenitors, did not elicit any inflammatory response and was completely degraded within 4 months after implantation. With regard to the efficacy of this cell therapy, even among the small number of animals tested there was histologic evidence that lesions filled with the biomaterial, either seeded or unseeded with cells, achieved a faster and better healing compared to empty controls. The present data suggest that the hyaluronan-based scaffolds are well tolerated and safe and may be a valuable delivery vehicle for tissue engineering in the repair of articular cartilage defects.

Animals↗
PubMed2000

In vitro reconstructed dermis implanted in human wounds: degradation studies of the HA-based supporting scaffold.

The objective of the present study was to demonstrate the safety and efficacy of a dermal replacement for cutaneous wounds of diverse origin. Autologous fibroblasts were cultured in fleece scaffolds made from benzyl esters of hyaluronic acid and applied onto cutaneous lesions. The cases presented are (1) skin removal for multiple epithelioma and (2) chronic deep decubitus ulcer. Dermal-like tissue applied by the surgeon elicited no adverse reactions, and was fully integrated and well-vascularized by 1-3 weeks. In Case 1, the material was fully integrated after 1 week, and after 3 weeks an epidermal autograft was overlaid which showed good take with excellent integration observed after 4 weeks. At 12 months, skin demonstrated visual normo-elastic properties and no signs of excessive scarring. In Case 2, 2-3 weeks after the dermal implant was applied, the wound was invaded with granulation tissue and healing occurred by secondary intention. The ulcer was healed by 8 weeks, with the biomaterial completely resorbed and a complete re-epithelialization over the dermal-like tissue. These results suggest that autologous fibroblast culture in hyaluronan-derived scaffolds may be successfully grafted in diverse cutaneous pathologies and constitute a suitable bed for further epidermal implantation.

Absorbable Implants↗
PubMed2000

Use of a hyaluronan-based biomembrane in the treatment of chronic cholesteatomatous otitis media.

OBJECTIVE: To test the efficacy and safety of a hyaluronan-based biomembrane in stimulating the healing process in patients undergoing tympanomastoid surgery. STUDY DESIGN: The trial was an open, two-arm, controlled, randomized, prospective, multicenter study conducted at two different hospitals. PATIENTS: Sixty subjects (18-65 years of age, both sexes) with chronic cholesteatomatous otitis media were enrolled and treated by the "one-stage open technique." Efficacy and safety parameters were assessed at 3, 5, 7, 9, 11, 13, 17, 21, and 25 weeks after surgery. Three sets of composite criteria were considered: patient's assessment of quality of healing, otomicroscopy, and audiometry. RESULTS: Of the 60 patients, 50 completed the study. Subjects treated with the biomembrane had statistically significant better scores than controls (no treatment) for all variables considered, excluding audiometry (no significant differences). No adverse events occurred in treated patients. CONCLUSION: Data demonstrate that the application of a hyaluronan-based biomembrane improves the healing of the mastoid cavity following "open" tympanoplasty. In particular, re-epithelialization was significantly faster after the application of the biomembrane. Moreover, the device neither caused any adverse events nor showed signs of ototoxicity. Re-epithelialization of open cavities and tympanic grafts still represents for surgeons an unpredictable step in the healing process. Hyaluronian-derivates may effectively contribute to the reduction of such variability.

Adjuvants, Immunologic↗
PubMed2000

Use of dermal-like tissue in the management of chronic and acute full-thickness cutaneous wounds.

This paper presents a dermal replacement technique for cutaneous wounds of diverse origin. An autologous tissue-engineered dermal-like structure was implanted in one patient with an acute surgical excision of a nevus and in another patient with a chronic post-traumatic ulcer. The dermal constructs were well integrated with the wound area, and, at 3 weeks, an epidermal covering was implanted. In both cases, 3 to 8 weeks after autografting, good integration of the transplanted epidermis with the surrounding native skin and a good take over the dermal-like tissue occurred. The use of this technology, despite its high cost, is increasing. Clinicians choose it because it helps heal critical wounds for which current therapies have failed.

Acute Disease↗
PubMed1999

Chondrocyte aggregation and reorganization into three-dimensional scaffolds.

Articular cartilage has a very limited self-repairing capacity; thus, chondral lesions normally result in chronic degeneration and, eventually, osteoarthritis development. Currently, tissue engineering offers a new tool for the clinical treatment of osteochondral defects. The present investigation aimed to develop an in vitro engineered cartilage using a new class of semisynthetic scaffolds. Two nonwoven meshes of hyaluronan esters (Hyaff(R) derivatives) were seeded with sternal chick embryo chondrocytes cultured for up to 21 days, after which time they were assessed for both the cellular growth profile and histological features. Avian chondrocytes easily adhered and proliferated onto hyaluronan-based scaffolds, demonstrating a significant preference for the fully esterified benzylic form. Histochemical staining revealed the presence of a neosynthesized glycosaminoglycan-rich extracellular matrix, and immunohistochemistry confirmed the deposition of collagen type II. Moreover, ultrastructural observations supported evidence that chondrocytes grown onto a hyaluronan-derived three-dimensional scaffold maintained their unique phenotype and organization in a cartilage-like extracellular matrix. These findings support the further pursuit of a transplantable engineered cartilage using human chondrocytes for the regeneration of chondral lesions.

Animals↗
PubMed1999

Histamine effects on conjunctival fibroblasts from patients with vernal conjunctivitis.

Histamine, an important mast cell mediator in allergic disorders, may affect extracellular matrix production and cell growth in vernal keratoconjunctivitis (VKC). In the present study, the histamine reactivity of conjunctival fibroblasts derived from VKC patients was investigated in vitro. Conjunctival fibroblast cultures were derived from biopses of 8 tarsal VKC patients and 5 normal subjects. These cells were maintained in vitro and stimulated with different concentrations of histamine with and without H1 (clorpheniramine) and H2 (cimetidine) receptor antagonists. Comparisons were made to fibroblasts grown in the same media without histamine and to fibroblasts stimulated with just antihistamine. The effects of histamine were evaluated by: (1) the MTT test to assess cell proliferation; (2) an in vitro wound model for cell migration and (3) the measurement of procollagen I (PIP) and procollagen III (PIIIP) in supernatants for collagen production. Results showed: (1) While VKC-derived fibroblasts proliferated at a faster rate than normal cells in unstimulated media, after histamine stimulation, VKC and normal cells grew at a similar rate. Both H1 and H2 antagonists significantly inhibited (P<0.05) histamine-induced cell proliferation. (2) Histamine enhanced cell migration after wounding; this effect was inhibited only by H2 antagonism. (3) When stimulated with histamine, VKC fibroblasts produced significantly more PIP than those in control media. Furthermore, VKC-derived fibroblasts were more sensitive to histamine challenge, producing significantly more PIP than normal fibroblasts. H1 and H2 antagonists did not modify histamine-stimulated PIP production. The enhanced proliferative and productive capacity of VKC fibroblasts may be the result of a selective overgrowth of one or more fibroblast subpopulations in a chronically inflamed tissue. Histamine increased proliferation, migration and collagen production in both normal and VKC fibroblasts. Since H2 antagonism modulated both cell growth and migration, but not histamine-induced collagen production, the latter may be mediated by a different receptor. These results showed that histamine is at least partially responsible for fibroblast stimulation.

Cell Culture Techniques↗
PubMed1999

Cefotaxime-hydrolysing beta lactamases in Morganella morganii.

The frequency of enterobacterial isolates with high resistance to expanded-spectrum beta-lactam antibiotics (mainly cefotaxime or ceftriaxone) has increased notoriously in Argentina, mainly because of the spread of extended-spectrum beta-lactamases. The aim of this work was the study of extended-spectrum beta-lactamases in several Morganella morganii isolates with unusually high resistance to ceftriaxone. These strains produced at least two beta-lactamases, of apparent pIs of 5.4 and 8.2, molecular weight 23 000, well inhibited by clavulanate, compatible with a broad-spectrum beta-lactamase - perhaps TEM-1 - and an extended-spectrum beta-lactamase, respectively. The extended-spectrum beta-lactamase was identified as a CTX-M-type beta-lactamase - probably CTX-M-2 - by polymerase chain reaction, restriction profile analysis and DNA-DNA hybridisation. The remaining isolates studied produced either the broad-spectrum beta-lactamase plus the ubiquitous AmpC beta-lactamase (13 strains), or the AmpC beta-lactamase only (10 strains).

Anti-Bacterial Agents↗
PubMed1998

In vitro engineering of human skin-like tissue.

Coverage of large, full-thickness burns presents a challenge for the surgeon due to the lack of availability of the patient's own skin. Currently, tissue engineering offers the possibility of performing a suitable therapeutic wound coverage after early burn excision by using cultured keratinocyte sheets supported by a dermal layer. The aim of this study was to develop and characterize a skin substitute composed of both epidermal and dermal elements. For this purpose we grew keratinocytes and fibroblasts separately for 15 days within two different types of biomaterials. Cells then were co-cultured for an additional period of 15 days, after which samples were taken and processed with either classic or immunohistochemical stainings. Results showed that (1) human fibroblasts and keratinocytes can be cultured on hyaluronic acid-derived biomaterials and that (2) the pattern of expression of particular dermal-epidermal molecules is similar to that found in normal skin. The data from this study suggest that our skin equivalent might be useful in the treatment of both burns and chronic wounds.

Biocompatible Materials↗
PubMed1998

Semisynthetic resorbable materials from hyaluronan esterification.

In recent years, research on new, biocompatible, degradable materials has seen the development of a series of modified natural polymers. Among these, a new class of materials consisting of different hyaluronan derivatives promises to be useful in a whole range of clinical applications thanks to their varied biological properties. These new materials are obtained by chemical modification of purified hyaluronan consisting of the partial or total esterification of the carboxyl groups of this natural polymer. This review on the properties of the new materials reports some of their biocompatibility and characterization aspects based on findings from studies conducted on the ethyl and benzyl hyaluronan esters, two representative members of this new class of compounds, and is intended to arouse interest in the potential of other, as yet unexplored derivatives. From the results of a number of investigations, the various derivatives appear to possess different physico-chemical properties, especially as far as the degree of hydration and polymer stability are concerned. In addition, the type of esterification and extent of chemical esterification of hyaluronan considerably affects the biological properties of these materials, offering a range of polymers either favouring or, conversely, inhibiting the adhesion of certain types of cell.

Absorbable Implants↗
PubMed1996

Different effects of acute administration of aminophylline and nitroglycerin on exercise capacity in patients with syndrome X.

To investigate the effects of the acute administration of aminophylline and nitroglycerin on effort ischemia, 20 patients with syndrome X underwent 3 bicycle exercise tests after sublingual nitroglycerin (0.3 mg) and after 90 minutes of oral administration of aminophylline (400 mg). Compared with the basal test, only aminophylline induced a significant increase in the time to ischemic threshold and to angina; these findings support the potential therapeutic role of this adenosine receptor blocking agents and suggest a possible role of "steal phenomenon" in the pathogenesis of effort angina in patients with syndrome X.

Aminophylline↗
PubMed1996

Abnormal response to exercise in middle-aged NIDDM patients with and without autonomic neuropathy.

The cardiovascular response to exercise in middle-aged non-insulin-dependent diabetes mellitus (NIDDM) patients and the potential role of clinical characteristics and autonomic function were evaluated. One hundred and eight NIDDM patients, aged 40-65 years, were compared with a control group of 112 subjects, matched by age, sex, physical fitness, and presence of hypertension. All subjects performed a maximal exercise test. The diabetic patients completed cardiovascular autonomic neuropathy (CAN) tests: deep breathing, postural hypotension and lying to standing. There were no significant differences in total work capacity, heart rate, and blood pressure, either at rest or at peak exercise between the two groups. Diabetic patients showed significantly lower values of systolic and diastolic blood pressure during exercise, significantly slower recovery of heart rate (at 5th minute the average values were 102.7 +/- 14.1 beats min-1 vs 91.9 +/- 11.1, p < 0.001); and significantly higher proportion of blunted increase of heart rate (9.2% vs 0.9%, p < 0.001) and systolic blood pressure (9.2% vs 0.7%, p < 0.001) during exercise. No correlation between the exercise results and the main clinical characteristic (presence of hypertension, BMI, duration of diabetes, treatment, microalbuminuria, total score of CAN) was observed. These findings suggest that the cardiovascular response to exercise could be impaired also in the absence of signs of CAN. This impairment was higher in patients showing a dysfunction of orthosympathetic activity.

Adult↗
PubMed1996

Antioxidant effects of hyaluronan and its alpha-methyl-prednisolone derivative in chondrocyte and cartilage cultures.

OBJECTIVE: To compare hyaluronan and its alpha-methyl prednisolone derivative (HYC-141) with respect to their potential to directly cause tissue damage and to protect tissues from attack by reactive oxygen species. METHODS: Cartilage samples and chondrocytes were isolated from 15-day chick embryos and were exposed to enzyme-based and activated inflammatory cell-free radical generating systems in the presence of varying concentrations of alpha-methyl prednisolone, hyaluronan, and HYC-141. Tissue and cell vitality was measured by determining the incorporation of radioactive sulphate into newly synthesized glycosaminoglycans. RESULTS: Only alpha-methyl prednisolone caused a significant decrease in biosynthetic activity. All the tested substances were capable, to some extent, of protecting tissues and cells from damage by reactive oxygen species; HYC-141 demonstrated the greatest protective effect. CONCLUSION: These data suggest that HYC-141 may possess certain advantages over the individual component molecules in the local treatment of arthropathies.

Animals↗
PubMed1995

Non-typhoid Salmonella spp. resistant to cefotaxime.

beta-Lactamases with pIs of 5.4 and 8.1 were detected by hydrolysis of ampicillin and ceftriaxone respectively among cefotaxime resistant serovars of Salmonella spp. suggesting TEM-1 and an unidentified extended spectrum beta-lactamase have spread throughout these strains in Argentina.

Ampicillin↗