Biomedical subjects

G Oliva

Publications and source records attributed to G Oliva.

At least 55 records · Page 3Linked to original sources

PubMed1998

The structure and function of antiamoebin I, a proline-rich membrane-active polypeptide.

BACKGROUND: Antiamoebin is a member of the peptaibol family of polypeptides and has a unique antibiotic activity: it acts as an antiamoebic agent, but does not effectively haemolyze erythrocytes even though it does exhibit membrane-modifying activity. RESULTS: The structure of antiamoebin I has been determined by X-ray crystallography at 1.4 A resolution. The molecule forms a helical structure, which, as a result of the presence of a number of proline and hydroxyproline residues, has a deep bend in the middle. Circular dichroism spectroscopy, single-channel conductance studies and fluorescence diffusion studies suggest a mode of ion transport that is entirely different from that of the other two members of the peptaibol family (alamethicin and zervamicin) whose structures and functions have been examined in detail. CONCLUSIONS: The structure of the polypeptide has been determined and a functional model for its mode of action in membranes is presented. Although under some conditions antiamoebin may form ion channels, unlike the closely related alamethicin and zervamicin polypeptides, its major membrane-modifying activity appears to be as an ion carrier.

Alamethicin↗

PubMed1998

Trypanosoma cruzi glycosomal glyceraldehyde-3-phosphate dehydrogenase: structure, catalytic mechanism and targeted inhibitor design.

The structure of the enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from glycosomes of the parasite Trypanosoma cruzi, causative agent of Chagas' disease, is reported. The final model at 2.8 A includes the bound cofactor NAD+ and 90 water molecules per monomer and resulted in an Rfactor of 20.1%, Rfree = 22.3%, with good geometry indicators. The structure has no ions bound at the active site resulting in a large change in the side chain conformation of Arg249 which as a consequence forms a salt bridge to Asp210 in the present structure. We propose that this conformational change could be important for the reaction mechanism and possibly a common feature of many GAPDH structures. Comparison with the human enzyme indicates that interfering with this salt bridge could be a new approach to specific inhibitor design, as the equivalent to Asp210 is a leucine in the mammalian enzymes.

Animals↗

PubMed1998

Crystallographic and spectroscopic characterization of a molecular hinge: conformational changes in bothropstoxin I, a dimeric Lys49-phospholipase A2 homologue.

Bothropstoxin I (BthTX-I) from the venom of Bothrops jararacussu is a myotoxic phospholipase A2 (PLA2) homologue which, although catalytically inactive due to an Asp49-->Lys substitution, disrupts the integrity of lipid membranes by a Ca2+-independent mechanism. The crystal structures of two dimeric forms of BthTX-I which diffract X-rays to resolutions of 3.1 and 2.1 angstroms have been determined. The monomers in both structures are related by an almost perfect twofold axis of rotation and the dimer interfaces are defined by contacts between the N-terminal alpha-helical regions and the tips of the beta-wings of partner monomers. Significant differences in the relative orientation of the monomers in the two crystal forms results in "open" and "closed" dimer conformations. Spectroscopic investigations of BthTX-I in solution have correlated these conformational differences with changes in the intrinsic fluorescence emission of the single tryptophan residues located at the dimer interface. The possible relevance of this structural transition in the Ca2+-independent membrane damaging activity is discussed.

Animals↗

PubMed1998

Set-up and experimental parameters of the protein crystallography beamline at the Brazilian National Synchrotron Laboratory.

The Brazilian National Synchrotron Light Laboratory (LNLS) has a dedicated protein crystallography beamline. The optical elements of the beamline include an elastically bent cylindrical mirror and a triangular bent-crystal monochromator, which focus synchrotron radiation at the position of the sample in the vertical and horizontal planes, respectively. The monochromatic radiation is tunable between 2.0 and 1.2 A with the optimum wavelengths from 1.3 to 1.6 A, chosen to maximize the photon flux from the bending magnets of the storage ring (1.37 GeV). Diffraction images are recorded on a 345 mm-diameter MarResearch image-plate detector system with on-line readout. The experimental parameters of the beamline, such as the integral monochromatic flux and focus size, have been measured. The size of the beam at the position of the focal point is 0.5 x 0.5 mm(2). The flux density is between 4.4 x 10(10) and 8 x 10(10) photons s(-1) mm(-2) for wavelengths from 1.28 to 1.6 A. The energy resolution is sufficient to measure absorption edges of elements between 1.28 and 2 A. The facility, intended to serve the national and international community, has been commissioned and is available for users.

Journal Article↗

PubMed1998

The use of molecular modelling in the understanding of configurational specificity (R or S) in asymmetric reactions catalyzed by Saccharomyces cerevisiae or isolated dehydrogenases.

This method gives a general ideal how to use crystallographic information of enzymes to understand reactions catalyzed by these biocatalysts, commonly used by biochemists to produce chiral products. The interactions of three acetoacetic esters with the enzymes L-lactate dehydrogenase and alcohol dehydrogenase were studied through molecular modelling computer program. These artificial substrates have been widely used to produce chiral synthons. Through this methodology it was possible to understand the conformational specificity of these enzymes with respect to the products and how these enzymes can be inhibited by modifying the structures of the artificial substrates. Also, it was possible to predict whether some type of artificial substrate will suffer reduction by cells that contain these dehydrogenases and what kind of configuration (R or S) the final product will have.

Catalysis↗

PubMed1998

Comparative efficacy of meglumine antimoniate and aminosidine sulphate, alone or in combination, in canine leishmaniasis.

Thirty-two domestic dogs naturally infected with Leishmania infantum and showing viscero-cutaneous signs of canine leishmaniasis were treated with aminosidine sulphate (11 dogs) meglumine antimoniate (10 dogs) or with a combination of the two drugs (11 dogs) for 21 consecutive days. Clinical and laboratory assessments, made on day 21 and at 2, 4 and 6 months after initiation of treatment, showed that the drug combination gave the best score in terms of clinical efficacy, incidences of early clinical relapse, any clinical relapse or apparent parasitological cure, and reduction in parasite densities in bone-marrow and lymphnode aspirates (even though a lower dose of antimonial was used in the combination than for antimonial monotherapy). For each of the above parameters, however, the higher efficacy of the drug combination was not statistically significant, probably because of the large variations caused by using naturally infected animals of various ages and breeds.

Animals↗

PubMed1998

Ultrastructural and freeze fracture cilia morphology of trachea epithelium in apparently healthy small ruminants.

Specimens of tracheal mucosa were obtained from ten adult apparently healthy small ruminants (five goats and five sheep) both by a fibre optic endoscope and in a slaughterhouse. Ultrastructurally, a total of 50,000 cilia were examined. Pathological cilia were found in all examined subjects. The prevalence of compound cilia showed a range of 0.3% to 3%. Intracytoplasmic and swollen cilia ranged from 0.2% to 0.5%. The microtubular pattern was examined in 4,000 cross-sectioned cilia and an abnormal pattern was found in 5-7%. Microtubular defects involved both peripheral and central doublets, being peripheral abnormalities the prevailing ones. A central plug of electron dense material was observed in 2-3% of the examined basal bodies. Rare basal bodies characterized by an abnormal spatial configuration were also shown. Freeze fracture studies revealed a ciliary necklace composed of 4 to 5 rows of intramembrane particles.

Animals↗

PubMed1998

[Short bowel syndrome].

In the last year at the Department of Surgery of the University of Siena two patients presenting a clinical feature of intestinal infarct have been operated. In these patients a wide intestinal resection has been performed. After this surgical operation, a patient had a residual tract of 40 cm of bowel and the other 50 cm. It was not possible during operation to preserve the Bauin valve in a case; in the other, this valve has been sacrificed during a previous operation for cecal neoplasm. In the postoperative period, patients were transferred temporarily in the intensive care unit, and after some days they returned to the department where total parenteral nutrition with progressive decreasing mixture in calories over time was administered. Enteral nutrition was also started and the quantity of water, calories and azote was slavly increased. In a second time an oral diet was started up to completely weaning from parenteral and then enteral nutrition. At present, these patients are enlisted in quarterly follow-up and are completely stabilized. They are independent from artificial nutrition and they have a good quality of life.

Aged↗

PubMed1998

[Total gastrectomy and malnutrition].

BACKGROUND: The operation more frequently performed for gastric malignancy is total gastrectomy. METHODS: Our reconstructive technique is Roux en Y esophago-jejunostomy, jejunal interposition after gastrectomy. In the next weeks after operation there is always an important, sometimes pathologic, slimming in gastrectomized patients. But is this slimming due to malnutrition or malabsorption? This is the real question. In our Institute a quarterly perspective clinical and instrumental follow-up for these patients has been prepared. RESULTS: We started with 41 patients, but we conducted the complete study only on 23. Of these patients, 56% have lost 10 kg weight, 25% 5 kg and 18% have not lost weight after 2 weeks from discharge dimission. But after 5 weeks, all patients had stabilized their own weight, and 18 months later the first two groups regained weight again, 1-2 kg. With our follow-up, we had educated patients to a correct personal natural diet necessary to normal social and working life. With our program in 3-4 weeks the weight of each patient was stable and we were able to control the malabsorption. CONCLUSIONS: Moreover, according to personal experience, it is important to plan a follow-up to rehabilitate patients to usual social life. This program allows to evaluate malnutrition and the possible iron or vit. B12 deficiency.

Aged↗

PubMed1997

An immunodiffusion assay for the detection of canine leishmaniasis due to infection with Leishmania infantum.

An immunodiffusion assay (IDA) with polyethylene glycol (PEG) was tested for usefulness as diagnostic test for canine leishmaniasis (CL). A comparative analysis of dog sera was made using IDA with PEG, immunofluorescence assay (IFA) and enzyme immunosorbent assay (ELISA) techniques. Fourty-four dogs from Italy with CL (endemic dogs) and eight Dutch dogs with CL contracted in South Europe (expatriate dogs) were tested together with 40 endemic and 35 expatriate controls. Specificity did not differ substantially among the serotests, ELISA in endemic dogs being the least specific (mean specificity given in IFA, IDA and ELISA, 100%, 98% and 93.5%, respectively). Sensitivity in expatriate dogs was 100% for all serotests but was highly variable in endemic dogs. In parasite-negative dogs, IFA had the most sensitivity, i.e., 80.5% compared to 69% for both ELISA and IDA. In contrast, ELISA in parasite-positive endemic dogs had a sensitivity of 100% whereas both IFA and IDA gave a sensitivity of 93%. Despite its slightly lesser sensitivity than IFA or ELISA (2-6% and 5% respectively) in endemically infected dogs, IDA with PEG method may help to bring the diagnosis of CL within reach of the veterinary practitioner.

Animals↗

PubMed1997

A retrospective clinical study of canine leishmaniasis in 150 dogs naturally infected by Leishmania infantum.

The clinical and laboratory findings observed in 150 dogs naturally infected by Leishmania infantum, from a large endemic area of southern Italy, are described. There was a gradual onset of clinical signs and the course of the disease was progressive in almost all the cases. The majority of the dogs were mongrels (43.3 per cent), male (64.7 per cent), of medium size (50.6 per cent), three to seven years old (64.7 per cent), and living outdoors (60 per cent). They showed generalised (56.7 per cent) or symmetrical (32 per cent) lymphadenomegaly; the mucous membranes of 87 of the dogs (58 per cent) were pale and moderate or severe splenomegaly was diagnosed in 80 dogs (53.3 per cent); weight loss was observed in 32 per cent of the animals. Skin abnormalities were very common, and included dry exfoliative dermatitis (56 per cent), ulcers (40 per cent) periorbital alopecia ('lunettes') (18 per cent), diffuse alopecia (14 per cent) and onychogryphosis (24 per cent). Ocular signs were observed in 24 dogs (16 per cent) including 16 cases of keratoconjunctivitis (three with keratoconjunctivitis sicca), six cases of moderate uveitis and two cases of panophthalmitis. The acute form of the disease was diagnosed in only six dogs and was characterised by fever and generalised lymphadenomegaly, and by the absence of skin lesions. Another six dogs had severe renal failure without systemic clinical signs of leishmaniasis. The most important laboratory findings were a severe or moderate increase in gammaglobulins, hypoalbuminaemia, hyperproteinemia and anaemia. Cultures or cytology tests for L infantum parasites were positive in 134 of the dogs. Following the standard procedures developed for human lymph node and bone marrow cytology tests, the leishmania density in the dogs varied from 1+ to 2+. Leishmania antibody titres were high (> 1:160) in almost all the dogs. Immunological tests for autoantibodies were positive in 25 of 53 dogs tested in the antinuclear antibody (ANA) test, in 15 of 43 dogs tested in the latex test and in five of 24 dogs tested in the Coombs test.

Animals↗

PubMed1997

The ultimate wavelength for protein crystallography?

This paper describes an analysis of the optimum choice of the X-ray wavelength for macromolecular diffraction data collection. It is shown that there is no ultimate X-ray wavelength for protein crystallography and that the optimum wavelength depends to a large extent on the size of the protein crystal. It also depends on instrumental factors, such as efficiency of the detector for a particular wavelength and spectral density of the synchrotron radiation. Estimates of the optimum wavelength as a function of crystal size are given.

Journal Article↗

PubMed1997

Crystallization and preliminary crystallographic studies of calgranulin C, an S100-like calcium-binding protein from pig granulocytes.

Calgranulin C (CAGC) from pig granulocytes has been crystallized and X-ray diffraction data have been collected to 2.6 A resolution. The crystals belong to the trigonal system, space group P3(1)21 or P3(2)21, cell parameters a = b = 54.35 (2), c = 141.32 (5) A and probably contain two molecules in the asymmetric unit. CAGC is amongst the first reported typical S100-1ike calcium-binding protein to be crystallized and studied by X-ray crystallography.

Journal Article↗

PubMed1997

Crystallization and preliminary crystallographic data of a neutrophil migration-inducing lectin (KM+) extracted from the seed of Artocarpus integrifolia.

The tetrameric KM+ lectin from the seeds of Artocarpus integrifolia has, when compared to other plant lectins, the singular property of directly inducing neutrophil migration into the peritoneal cavity or into the air pouch of rats. This protein crystals have been grown and they belong to the orthorhombic system with space group C222(1). The unit cell parameters are a = 54.4 A, b = 127.9 A and c = 99.8 A. A native diffraction dataset to 2.8 A was collected and an analysis of the self-rotation function has shown the presence of only one independent non-crystallographic 2-fold axis orthogonal to the crystal b-axis, compatible with a dimer in the asymmetric unit.

Animals↗

PubMed1997

Hyperprolactinaemia and galactorrhoea associated with primary hypothyroidism in a bitch.

An endocrinopathy characterised by hyperprolactinaemia and galactorrhoea was found to be associated with primary hypothyroidism in an entire bitch. Clinical diagnosis was confirmed by lowered baseline T4 blood levels, reduced response to the thyroid stimulating hormone (TSH) test, elevated prolactin and TSH values, and echographic and scintigraphic examinations. Levothyroxine treatment resulted in a clinical improvement (especially of the galactorrhoea), and levels of prolactin, thyroxine, TSH, triglycerides and total cholesterol plasma returned to normal.

Animals↗

PubMed1997

[Further comment on central venous catheter infections].

Many reports from the surgical literature document the incidence of catheter related sepsis varies between 1 and 10 per cent. In many instances sepsis is secondary to contamination from normal saprophyte cutaneous bacteria. In our Institute we set down a standardized methodology to reduce the contamination of venous central access from cutaneous bacteria. Of 31 patients studied, none had bacteria in the last 5 cm of central venous catheter, 2 had streptococcus alpha haemolytic colonies and coagulase negative staphylococcus colonies at the same time on skin over the region of venepuncture. With our paper we had attained one's awareness that it is very difficult to obtain zero per cent in contamination of central venous catheter, mainly in immunodepressed or critical patients, but with careful dressing and with new technology it is possible to reduce the contamination and following sepsis.

Aged↗

PubMed1996

Crystallization and preliminary crystallographic studies of alpha-amylase inhibitor from wheat (Triticum aestivum).

Crystals of the human salivary alpha-amylase inhibitor from wheat have been obtained. A native data set was collected to 2.1 A resolution with 90% completeness at laboratory sources. The crystals belong to the trigonal system, space group P3(1) (or enantiomer) with a = b = 79.31, c = 60.56 A. Crystal density analysis and self-rotation function studies suggest the presence of four subunits in the asymmetric unit.

Journal Article↗

PubMed1996

Crystallization and preliminary X-ray studies on the lectin from the seeds of Cratylia mollis.

The lectin from the seeds of Cratvlia mollis shows strong binding to human malignant cancerous tissues, particularly those from many glands, uterus, rectum and brain. The C. mollis lectin has been crystallized using the hanging-drop method with polyethylene glycol 6000 as a precipitant. Two different crystal forms were grown from the same drops and they belong to space groups I222 and P2(1)2(1)2(1), respectively. The cell parameters obtained were a = 63.26 (4), b = 77.45 (8) and c = 105.22 (8) A, for the I222 form, and a = 88.83 (5), b = 183.24 (9) and c = 61.70 (2) A for the P2(1)2(1)2(1) crystals. The solution of both structures is currently being attempted by means of molecular replacement techniques.

Journal Article↗