Search PubMed⌕ Search

Biomedical subjects

M Farina

Publications and source records attributed to M Farina.

At least 19 recordsLinked to original sources
PubMed1999

Thrombospondin-1 is a mediator of the neurotypic differentiation induced by EGF in thymic epithelial cells.

Thymic epithelial cell component originates from cranial neural crest as well as from endoderm and ectoderm of the third pharyngeal pouch and branchial cleft. Epidermal growth factor (EGF) has been previously shown to play a crucial role in directing thymic epithelial cells toward a neural-oriented cell fate. To identify genes that are involved in the EGF-induced neurotypic differentiation of the thymic stroma-derived TC-1S cell line, we studied EGF-treated and untreated cells by RNA fingerprinting PCR-based differential screening. We obtained 23 distinct sequences including 18 known genes and 5 sequences previously unreported, which are currently under characterization. Here, we describe the involvement of one of the isolated genes, the thrombospondin-1, as a mediator of the neurotypic differentiation induced by EGF in TC-1S cells. We show that thrombospondin-1 mRNA and protein levels are increased by EGF. Moreover, exogenous thrombospondin-1 is able to enhance the outgrowth of neurite-like processes as well as the expression of neurofilaments and neural cell adhesion molecule in TC-1S cells. These observations suggest that the up-regulation of thrombospondin-1 synthesis induced by EGF contributes to the differentiation choice of thymic epithelial cells toward a neural fate, reminiscent of their neural crest origin.

Animals↗
PubMed1999

Atomic force microscopy study of tooth surfaces.

Atomic force microscopy (AFM) was used to study tooth surfaces in order to compare the pattern of particle distribution in the outermost layer of the tooth surfaces. Human teeth and teeth from a rodent (Golden hamster), from a fish (piranha), and from a grazing mollusk (chiton) with distinct feeding habits were analyzed in terms of particle arrangement, packing, and size distribution. Scanning electron microscopy and transmission electron microscopy were used for comparison. It was found that AFM gives high-contrast, high-resolution images and is an important tool as a source of complementary and/or new structural information. All teeth were cleaned and some were etched with acidic solutions before analysis. It was observed that human enamel (permanent teeth) presents particles tightly packed in the outer surface, whereas enamel from the hamster (continuously growing teeth) shows particles of less dense packing. The piranha teeth have a thin cuticle covering the long apatite crystals of the underlying enameloid. This cuticle has a rough surface of particles that have a globular appearance after the brief acidic treatment. The similar appearance of the in vivo naturally etched tooth surface suggests that the pattern of globule distribution may be due to the presence of an organic material. Elemental analysis of this cuticle indicated that calcium, phosphorus, and iron are the main components of the structure while electron microdiffraction of pulverized cuticle particles showed a pattern consistent with hydroxyapatite. The chiton mineralized tooth cusp had a smooth surface in an unabraded region and a very rough structure with the magnetite crystals (already known to make part of the structure) protruding from the surface. It was concluded that the structures analyzed are optimized for efficiency in feeding mechanism and life span of the teeth.

Acids↗
PubMed1999

Structural basis for mechanical transduction in the frog vestibular sensory apparatus: III. The organization of the otoconial mass.

The saccule and the utricle of the vestibular system detect linear acceleration and gravity. Sensory transduction in these organs depends on myriads of calcium carbonate crystals of high specific gravity, called otoconia, embedded in a filament matrix that overlies the sensory epithelium. The coexistence of hard crystals and slender filaments in this complex extracellular matrix makes it difficult to analyze by conventional electron microscopy. We have now examined this structure in the bullfrog saccule using the quick-freeze, deep-etch replica technique. The otoconia in their typical aragonite polymorph shape exhibit smooth surfaces and are embedded in a loose matrix made of two types of filaments. The regular surface of the otoconia forms a natural smooth background against which we could observe with unprecedented detail the network organization and substructure of the filaments. One type of filament is 8 nm in diameter, while the other, which has a characteristic beaded appearance, is 15 nm in diameter. Both types of filaments either make lateral connections with or end directly on the surface of the otoconia. A consistent observation was the presence of short filaments that directly cross-link adjacent otoconia. Very few otoconia were fractured in an orientation that would allow the study of their internal architecture. These otoconia presented a typical conchoidal cleavage of aragonite. Although crystallites were not clearly apparent, thin lamellar microstructures appeared oriented both perpendicularly and longitudinally to the major otoconial axis. This structural study establishes a framework for the identification of the molecular components present in this unique extracellular matrix and may also help elucidate their role in mechanical transduction.

Animals↗
PubMed1998

Magnetosome size distribution in uncultured rod-shaped bacteria as determined by electron microscopy and electron spectroscopic imaging.

We report uncultured rod-shaped magnetotactic bacteria from natural waters that biomineralize magnetic crystals in two different size ranges. Electron spectroscopic imaging of whole bacteria deposited over formvar-coated grids permitted a better visualization and measurement of the magnetosomes. All magnetosomes of individual bacteria could be observed by this technique. The magnetosomes formed one large chain, composed of three to four columns of crystals, disposed in parallel to the main axis of the bacteria. The magnetosomes ranged from 19 to 136 nm in length and 14 to 112 nm width. Smaller magnetosomes (less than 80 nm in length) localized mostly in extremities of the bacterial body while larger preferentially localized in the middle part of the cell. Electron spectroscopic diffraction and X-ray microanalysis indicate that both types of magnetosomes contain magnetite (Fe3O4). In projection, most magnetosomes seem to present pseudo-hexagonal morphologies described for magnetite. As the aspect ratios for smaller and larger magnetosomes are different, we suggest that different levels of control on biomineralization of magnetosomes may exist.

Bacteria↗
PubMed1998

Phylogenetic affiliation and ultrastructure of uncultured magnetic bacteria with unusually large magnetosomes.

Natural enrichments of magnetic bacteria from the Itaipu lagoon near Rio de Janeiro were dominated by coccoid-to-ovoid morphotypes that produced unusually large magnetosomes. To determine the phylogenetic position of these unusual microorganisms, 16S rRNA genes were retrieved from bacteria magnetically separated from sediment of the Itaipu lagoon by in vitro amplification and cloning of PCR products into a plasmid vector. Partial sequencing of the obtained clones revealed two clusters of closely related sequences affiliated to a distinct lineage consisting exclusively of magnetic bacteria within the alpha-subclass of Proteobacteria. For a detailed phylogenetic analysis, several almost complete sequences of the 16S rRNA genes were determined. One representative clone of each cluster provided a PCR template for the in vitro transcription of group-specific polynucleotide probes complementary to a variable region of the 16S rRNA molecule. At least three different morphotypes of magnetic bacteria were reliably identified by post-embedding hybridization of ultra-thin sections. Electron microscopic analyses of hybridized cells enabled for the first time a detailed description of the morphological variety and ultrastructure of phylogenetically identified, uncultured magnetic bacteria. Two distinct coccoid bacteria were identified by the transcript probe complementary to the 16S rRNA sequence mabrj12, whereas the probe complementary to the sequence mabrj58 allowed the identification of an ovoid morphotype that displayed magnetosomes with the largest volumes observed to date.

Bacteria↗
PubMed1998

The effect of tamoxifen and transdermal 17beta-estradiol on cerebral arterial vessels: a randomized controlled study.

OBJECTIVES: Our objective was to study the effects of tamoxifen on cerebral arterial reactivity. STUDY DESIGN: We studied the reactivity of both the internal carotid artery and the middle cerebral artery during a 12-month period of administration of either oral tamoxifen or transdermal estradiol or no treatment. A total of 45 healthy postmenopausal women who had undergone hysterectomy were followed up. Patients were randomly allocated to treatment with either oral tamoxifen 20 mg/day or transdermal estradiol 50 microg/day or nothing (15 patients in each group). They all underwent Doppler examinations of the internal carotid artery and middle cerebral artery at the beginning of the study and after 2, 6, and 12 months of treatment. The pulsatility index was measured. RESULTS: In the women given transdermal estradiol the pulsatility index of both the internal carotid artery and the middle cerebral artery was significantly reduced compared with that in the controls. Tamoxifen did not induce variations of pulsatility index in either artery during all the study period. The difference between the effect of the two drugs on the pulsatility index of both arteries was highly significant. CONCLUSIONS: Our findings demonstrate that tamoxifen does not cause any variation in the pulsatility index of cerebral arteries. The action of transdermal estradiol on the pulsatility index of cerebral arteries in postmenopausal women is the expression of a generalized action of estrogens on arterial vessels, and if this expression plays a role in the protective effect of hormone replacement therapy on risk of cardiovascular disease, tamoxifen treatment in healthy postmenopausal women should be considered with renewed caution.

Administration, Cutaneous↗
PubMed1998

Distribution of F-actin, alpha-actinin, tropomyosin, tubulin and organelles in Euglena gracilis by immunofluorescence microscopy.

Euglena gracilis, a unicellular flagellated alga, can display numerous shape changes. These changes are most probably caused by a pellicle and an internal cytoskeleton. In this paper we studied the distribution of the cytoskeletal proteins actin, alpha-actinin, tropomyosin and tubulin in dark-adapted Euglena, using immunofluorescence microscopy. We found that F-actin, alpha-actinin, tropomyosin and tubulin have a distribution that is coincident in the plasma membrane and, in addition, alpha-actinin and tropomyosin are seen in small patches in the cytoplasm, and tubulin in the flagella. We have also studied the distribution of the endoplasmic reticulum, nucleus, and Golgi apparatus of these cells, using fluorescent probes. Both the endoplasmic reticulum and the Golgi apparatus have a meshwork pattern distributed throughout the cytoplasm, and the nucleus has a chromatin evenly distributed in the nucleoplasm.

Actinin↗
PubMed1998

Effect of IL-1alpha on prostaglandin synthesis of oestrogenized rat uterus is mediated by nitric oxide.

We examined the possible relationship between cytokines, nitric oxide (NO) and prostaglandins in the oestrogenized rat uterus. Results indicate that: IL-1alpha but not IL-2 enhances the synthesis of prostaglandins in oestrogenized rat uteri; IL-1alpha but not IL-2 induced an augmention of NO production in this tissue; the effect of IL-1alpha on prostaglandin synthesis is abolished by NMMA, an NO antagonist; NS-398, a COX-2 inhibitor, prevents the augmention of prostaglandins produced by IL-1alpha. These results suggest that there is an interaction between IL-1alpha, NO and prostaglandins and that this interrelationship involves COX-2. This mechanism might be important during implantation and labor.

Animals↗
PubMed1998

Hepatitis C virus infection and acute or chronic glomerulonephritis: an epidemiological and clinical appraisal.

BACKGROUND: The relationship between hepatitis C virus (HCV) infection and acute or chronic glomerulonephritis (GN) is not well understood. METHODS: Two hundred and eighty-four patients with biopsy-proven GN and other renal diseases were studied in a multicentre survey performed during the period 1992-1995. Several clinical parameters were collected for each patient at the time of renal biopsy. We made a multivariate analysis by logistic regression model to evaluate the independent association of clinical and histological patient characteristics with HCV infection, as detected by anti-HCV antibody testing. In addition, three patients with HCV-related liver disease, membranous nephropathy, and proteinuria in the nephrotic range received therapy with interferon-alpha in standard doses. RESULTS: The prevalence of anti-HCV positivity was 13% (38/284). The frequency of anti-HCV positivity ranged between 0 and 100% in the different types of renal diseases, the difference was statistically significant (P = 0.0001). The anti-HCV rate was significantly higher in patients with cryoglobulinaemic membranoproliferative and mesangioproliferative GN than among the other individuals (14/14 (100%) vs 24/270 (9%), P = 0.0002). Our multivariate analysis by logistic regression model showed that age (P = 0.0017) and type of renal diseases (P = 0.0007) were independently and significantly associated with anti-HCV antibody. At the completion of treatment with interferon-alpha, 67% (2/3) of patients with membranous nephropathy had lowering of hepatic enzyme levels into the normal range whereas 100% (3/3) of these did not show significant reduction of proteinuria. CONCLUSIONS: We observed strong association between HCV infection and cryoglobulinaemic GN. Age and type of renal disease were important independent predictors of anti-HCV positivity in our cohort of patients. Three anti-HCV-positive patients with membranous nephropathy did not show significant remission of nephrotic proteinuria after treatment with interferon-alpha. Our data do not appear to support an association between HCV and non-cryoglobulinaemic GN. Further epidemiological surveys, experimental studies and clinical trials are warranted to fully elucidate the role of HCV in non-cryoglobulinaemic GN.

Acute Disease↗
PubMed1998

Doctorline: a private toll-free telephone medical information service. Five years of activity: old problems and new perspectives.

UNLABELLED: Introduction; Healthcare professionals need to continually update their knowledge to provide care based on scientific evidence. In some cases it can be difficult to gain access to the different sources of medical information. In an attempt to overcome these problems, a toll-free telephone medical information service (Doctorline) was established. OBJECTIVE: To describe the development, aims, organization, and activities of this private service. METHODS: Doctorline is an independent, unbiased, toll-free medical information service that provides information on clinical, pharmacologic, and toxicologic issues; bibliographic searches; full-text articles; public and private clinics; details of forthcoming congresses; and legislative documentation. The service is available Monday through Friday, 1000 to 2000. Staff members are physicians trained in communication techniques, literature evaluation methodologies, and computerized database use. The main on-line facilities are MEDLINE, Micromedex-CCIS, and the Italian Formulary on CD-ROM. Books, bulletins, national and international drug formularies, and property files (i.e., directory of Italian public and private clinics) are also available. RESULTS: In 5 years, Doctorline has received 65 258 calls. Nearly 34% of the calls were made by general practitioners, followed by cardiologists (22%), orthopedists (15%), pharmacists (14%), gastroenterologists (13%), and urologists (10%). From 1991 to 1996, nearly 20% of the calls concerned pharmacologic issues, 43% nonpharmacologic issues, while the rest of the calls were for nonclinical requests. Approximately 21% of all questions received an answer during the same phone call (on-line answers); for the other answers (off-line answers) the mean +/- SD waiting time was 7.8 +/- 10.4 days. Although the nature of the questions has been recorded since 1991, data about the exact number of physicians who used the service are available only from 1994. Data from 1994 indicate that of the 52,181 physicians who could access the service, only 8817 (16.9%) called at least once, with a mean number of calls per physician of 3.9 (range 3.0-5.6). CONCLUSIONS: The future of Doctorline will depend on the quality and validity of the information provided (i.e., based exclusively on scientific evidence, independent of the source of funds), the promotion of the aims, organization, and clinical utility of the service (especially among physicians who made little or no use of the service), and differentiation of the service activities in relation to the physician's specific needs.

Databases as Topic↗
PubMed1998

A randomized study comparing methylprednisolone plus chlorambucil versus methylprednisolone plus cyclophosphamide in idiopathic membranous nephropathy.

To assess whether chlorambucil or cyclophosphamide may have a better therapeutic index in patients with idiopathic membranous nephropathy, we compared two regimens based on a 6-mo treatment, alternating every other month methylprednisolone with chlorambucil or methylprednisolone with cyclophosphamide. Patients with biopsy-proven membranous nephropathy and with a nephrotic syndrome were randomized to be given methylprednisolone (1 g intravenously for 3 consecutive days followed by oral methylprednisolone, 0.4 mg/kg per d for 27 d) alternated every other month either with chlorambucil (0.2 mg/kg per d for 30 d) or cyclophosphamide (2.5 mg/kg per d for 30 d). The whole treatment lasted 6 mo; 3 mo with corticosteroids and 3 mo with one cytotoxic drug. Among 87 patients followed for at least 1 yr, 36 of 44 (82%; 95% confidence interval [CI], 67.3 to 91.8%) assigned to methylprednisolone and chlorambucil entered complete or partial remission of the nephrotic syndrome, versus 40 of 43 (93%; 95% CI, 80.9 to 98.5%) assigned to methylprednisolone and cyclophosphamide (P = 0.116). Of patients who attained remission of the nephrotic syndrome, 11 of 36 in the chlorambucil group (30.5%) and 10 of 40 in the cyclophosphamide group (25%) had a relapse of the nephrotic syndrome between 6 and 30 mo. The reciprocal of plasma creatinine improved in the cohort groups followed for 1 yr for both treatment groups (P < 0.01) and remained unchanged when compared with basal values in the cohort groups followed for 2 and 3 yr. Six patients in the chlorambucil group and two in the cyclophosphamide group did not complete the treatment because of side effects. Four patients in the chlorambucil group but none in the cyclophosphamide group suffered from herpes zoster. One patient per group developed cancer. It is concluded that in nephrotic patients with idiopathic membranous nephropathy both treatments may be effective in favoring remission and in preserving renal function for at least 3 yr.

Adolescent↗
PubMed1997

Modulation of cytokine gene expression by thymic lympho-stromal cell to cell interaction: effect of retinoic acid.

We have examined the expression of a panel of cytokines in thymic epithelial cells and CD4-CD8- (DN) thymocytes following cell to cell lymphostromal interaction, in an experimental model which enhances in vitro thymocyte maturation. Since retinoic acid (RA) has been previously shown to be an inhibitor of thymocyte maturation process in this model, we wanted to analyse cytokine expression in DN thymocytes and thymic epithelial cells following the RA-induced impairment of in vitro thymocyte maturation. Cell to cell lymphostromal interaction results in increased IL2 and decreased IL7 expression in thymocytes while the expression of IL1 beta and IL7 increased and decreased, respectively, in thymic epithelial cells. Addition of RA to lympho-stromal cell co-culture results in the enhancement of IL4 and IL7 expression in thymocytes while in thymic epithelial cells IL1 alpha decreased and IL6 and IL7 increased. These data indicate that discrete patterns of cytokine expression are present in thymocyte precursors and in thymic epithelial cells during in vitro T-cell development. They furthermore suggest that specific cytokine modulation might contribute to the RA-induced impairment of thymocyte differentiation.

Animals↗
PubMed1997

Intrahepatic expression of c-fos, c-myb and c-myc oncogenes: correlation with virus-induced chronic liver disease and response to interferon.

BACKGROUND & AIMS: Oncogenes were activated in experimental models of hepatocyte regeneration. We studied the intrahepatic expression of c-fos, c-myb and c-myc protooncogenes in 117 patients with chronic liver disease: 12 with hepatitis B, 15 HBsAg carriers, 73 with hepatitis C and 17 with non-viral liver damage. METHODS: Oncoproteins were detected by indirect immunofluorescence using high affinity and monoclonal antibodies. Grade and stage of liver damage were measured by numerical score. RESULTS: Nuclear c-fos and/or c-myb were found in 7 (58.3%) hepatitis B patients, in 38 (52%) hepatitis C patients, in 1 (6.6%) HBsAg carrier (p < 0.004) and in none of the non-viral disease patients (p < 0.0001). In no case was c-myc detected. Oncoproteins were correlated with the histological activity index (p < 0.0001) and its components: lobular degeneration and periportal necrosis (p < 0.0001), fibrosis (p < 0.005) and portal inflammation (p < 0.03). Thirty-one chronic hepatitis C patients were treated with alpha-IFN: 9 out of 14 oncoprotein-positive patients (64%) were non-responders, 5 (36%) relapsed and none was a sustained responder. Conversely 9 out of 17 (53%) oncoprotein-negative patients, including 3 patients with histologically active cirrhosis, showed long-term response (p < 0.005). CONCLUSIONS: Intrahepatic c-fos and c-myb were detected in chronic viral hepatitis patients, but not in non-viral liver diseases. Their expression correlated with the grade and stage of liver disease and with poor response to alpha-IFN.

Adult↗
PubMed1996

Free movement of Tritrichomonas foetus in a liquid medium: a video-microscopy study.

The present paper describes in detail the complex movement of the protozoon Tritrichomonas foetus. By the use of analogue and digital video techniques, we were able to analyze frame by frame the beatings of the anterior flagella and discuss their role in the movement of the cell. We also measured the productive displacement of the cell during one flagellar beating cycle. The obtained data were digitally improved and compared to analogue quantifications. It is shown that during 1 s of recorded movement, T. foetus performs 4 complete anterior flagella beating cycles (with active-like and recovery-like beatings). In each cycle the cell swims +/- 6.5 microns forwards, after the recovery of +/- 1.5 microns of receded movement. These observations led us to conclude that the estimated average speed of T. foetus is 25 microns/s, and that all flagella participate in the cell movement. The recurrent flagellum continuously contribute to the forward movement of the protozoon. The cell also performs rotational movements. The obtained results led us to suggest a model for the movement of T.foetus.

Animals↗
PubMed1996

Cerebral artery blood flow in relation to age and menopausal status.

OBJECTIVE: To investigate vascular reactivity in women's cerebral arteries from reproductive age to postmenopause. METHODS: The pulsatility index (PI) was measured cross-sectionally in the internal carotid and middle cerebral arteries of 120 women, using a Doppler ultrasound system. Fifteen women were enrolled in each of eight 5-year intervals, spanning ages 20-59 years. RESULTS: In the population as a whole, there was a slight but statistically significant correlation between age and the PI in both arteries, but not after excluding postmenopausal subjects. A significant correlation was found between PI and months since menopause (but not chronologic age) in the postmenopausal women. There was also a statistically significant difference in the PI values for both arteries between pre- and postmenopausal women of similar age. CONCLUSION: Menopause causes a significant increase in the PI of women's cerebral arteries. In postmenopausal women, there is a significant correlation between the PI of the internal carotid and middle cerebral arteries and menopausal but not chronologic age. This effect may be one of the mechanisms by which menopause is associated with the known higher risk for coronary heart disease observed in women.

Adult↗