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Biomedical subjects

M Alberti

Publications and source records attributed to M Alberti.

At least 37 records · Page 2Linked to original sources
PubMed1992

[Complications of disposable extended-wear contact lenses. Apropos of 6 cases].

We report six cases of corneal complications observed in disposable extended-wear contact lens users: two corneal ulcers, one superficial infiltrate, two punctate keratitis with subepithelial infiltrates and one superficial punctate keratitis. In four cases a bacterial etiology was confirmed. Disposable contact lenses are not complication-free. In our series, complications were favoured or provoked by incorrect use in most cases. Other possible risk factors include poor hygiene during lens manipulation, damage to the corneal epithelium during lens exchange or lens wear, use of contaminated lubricant eyedrops, relative corneal hypoxia during overnight wear or in the case of improper fitting. Correct and adequate patient information is therefore essential to ensure that these lenses constitute a safe choice.

Adolescent↗
PubMed1990

Preprocessing of Holter ECGs for analysis of the dynamic interrelations between heart rate and ventricular repolarization duration variabilities.

The use of approved commercial digital Holter systems as equipment for data acquisition in cardiologic research presents several potential advantages. In fact, it may provide a standard data acquisition procedure that allows the scientists to concentrate on the data processing phase. As a consequence, it may contribute to the comparability of results among different laboratories. In general, some steps of preprocessing are needed before performing the final analysis on the data. In case of study on the variabilities of the heart rate and the duration of repolarization, preprocessing consists of beat-by-beat measurement time intervals in the 24-hour electrocardiograms. Further preprocessing steps may be required, depending on the particular analysis technique that will be applied to the data. In particular, the present study introduces an operator-free method of preprocessing Holter electrocardiograms for time series analysis of signals related to heart rate variability and variability in the duration of ventricular repolarization.

Adult↗
PubMed1990

Conserved enzymes mediate the early reactions of carotenoid biosynthesis in nonphotosynthetic and photosynthetic prokaryotes.

Carotenoids comprise one of the most widespread classes of pigments found in nature. The first reactions of C40 carotenoid biosynthesis proceed through common intermediates in all organisms, suggesting the evolutionary conservation of early enzymes from this pathway. We report here the nucleotide sequence of three genes from the carotenoid biosynthesis gene cluster of Erwinia herbicola, a nonphotosynthetic epiphytic bacterium, which encode homologs of the CrtB, CrtE, and CrtI proteins of Rhodobacter capsulatus, a purple nonsulfur photosynthetic bacterium. CrtB (prephytoene pyrophosphate synthase), CrtE (phytoene synthase), and CrtI (phytoene dehydrogenase) are required for the first three reactions specific to the carotenoid branch of general isoprenoid metabolism. The homologous proteins from E. herbicola and R. capsulatus show sequence identities of 41.7% for CrtI, 33.7% for CrtB, and 30.8% for CrtE. E. herbicola and R. capsulatus CrtI also display 27.2% and 27.9% sequence identity, respectively, with R. capsulatus CrtD (methoxyneurosporene dehydrogenase). All three dehydrogenases possess a hydrophobic N-terminal domain containing a putative ADP-binding beta alpha beta fold characteristic of enzymes known to bind FAD or NAD(P) cofactors. In addition, E. herbicola and R. capsulatus CrtB show 25.2% and 23.3% respective sequence identities with the protein product of pTOM5, a tomato cDNA of unknown function that is differentially expressed during fruit ripening. These data indicate the structural conservation of early carotenoid biosynthesis enzymes in evolutionarily diverse organisms.

Amino Acid Sequence↗
PubMed1990

Long QT syndrome. New electrocardiographic characteristics.

The long QT syndrome is electrocardiographically characterized by a prolonged QT interval and by several other, more subtle, ST-T-U wave abnormalities, most of which have not been quantified. To determine the possible usefulness of several new electrocardiographic characteristics in identifying patients with known long QT syndrome, logistic regression models were applied to a data base of seven new, relatively independent, electrocardiographic repolarization variables. These were measured on digitized 12-lead electrocardiograms of 315 normal subjects and 37 patients with the long QT syndrome (members of well-identified long QT syndrome families, QTc greater than 0.44 second, 27% symptomatic), who ranged in age from 17 to 60 years. Electrocardiographic variables that independently differentiated (p less than 0.001) patients with long QT syndrome from normal subjects included quantitative measures of repolarization: early duration, rate, T wave symmetry, late phenomena, and heterogeneity. All selected repolarization variables except the early duration variable were essentially independent of the QTc (r2 less than 0.15), and all contributed significantly to the identification of patients with long QT syndrome. A classification model of five electrocardiographic predictor variables resulted in an estimated sensitivity (95% confidence interval) of 92.6% (81.6-100%) and an estimated specificity (95% confidence interval) of 95.8% (93.6-98.1%). This model performed significantly better than an alternative classification model that was based on the early duration variable as a single predictor variable. The symptomatic status of patients with long QT syndrome could not be predicted by any combination of the electrocardiographic variables in the investigated model.

Adolescent↗
PubMed1989

Nucleotide sequence, organization, and nature of the protein products of the carotenoid biosynthesis gene cluster of Rhodobacter capsulatus.

Carotenoid pigments are essential for the protection of both photosynthetic and non-photosynthetic tissues from photooxidative damage. Although carotenoid biosynthesis has been studied in many organisms from bacteria to higher plants, little is known about carotenoid biosynthetic enzymes, or the nature and regulation of the genes encoding them. We report here the first DNA sequence of carotenoid genes from any organism. We have determined the complete nucleotide sequence (11,039 bp) of a gene cluster encoding seven of the eight previously known carotenoid genes (crtA, B, C, D, E, F, I) and a new gene, designated crtK, from Rhodobacter capsulatus, a purple non-sulfur photosynthetic bacterium. The 5' flanking regions of crtA, I, D and E contain a highly conserved palindromic sequence homologous to the consensus binding site for a variety of prokaryotic DNA-binding regulatory proteins. This putative regulatory palindrome is also found 5' to the puc operon, encoding the light-harvesting II antenna polypeptides. Escherichia coli-like sigma 70 promoter sequences are located 5' to crtI and crtD, suggesting for the first time that such promoters may exist in purple photosynthetic bacteria. The crt genes form a minimum of four distinct operons, crtA, crtIBK, crtDC and crtEF, based on inversions of transcriptional orientation within the gene cluster. Possible rho-independent transcription terminators are located 3' to crtI, B, K, C and F. The 3' end of crtA may overlap transcription initiation signals for a downstream gene required for bacteriochlorophyll biosynthesis. We have also observed two regions of exceptional amino acid homology between CrtI and CrtD, both of which are dehydrogenases.

Amino Acid Sequence↗
PubMed1989

Electrocardiographic quantitation of ventricular repolarization.

Quantification of the electrocardiographic ventricular repolarization involving the T-U wave complex is usually performed with reference to the axis of the T wave and the QT interval duration. A novel quantitative approach to improve the description of ventricular repolarization was applied to the digitized electrocardiograms of 423 normal subjects. Six electrocardiographic repolarization characteristics were identified: duration, rate, area, symmetry, late phenomena, and interlead heterogeneity. A computer algorithm was designed to automatically interpret the electrocardiographic repolarization segment and measure 11 variables that quantified these repolarization characteristics. The application of redundancy-reduction techniques selected a final set of seven variables that were used in the statistical analysis. The QT interval, which was included in the initial group of variables, was replaced by the time interval between S wave offset and T wave maximum. All selected electrocardiographic variables were independent of age (r2 less than 0.11) and body surface area (r2 less than 0.03); all except the early duration variable were heart rate- and QT interval-independent (r2 less than 0.2, r2 less than 0.13, respectively; and most were uncorrelated to each other. A comparison of repolarization characteristics by gender revealed that repolarization duration was significantly more prolonged (p less than 0.0001) in women than in men. This multidimensional quantitative approach conveys a new and more complete description of the repolarization process and provides an electrocardiographic repolarization database in normal subjects as a reference standard for identifying patients with disordered repolarization.

Adult↗
PubMed1988

Automatic assessment of the interaction between respiration and heart rate variability signal.

The present paper introduces an original method of processing heart rate variability (HRV) and respiration signals as detected respectively through chest electrodes and thoracic belt in dogs under different experimental conditions. Signals are processed as time series synchronous with the occurrence of QRS complexes on ECG signal and auto and cross spectra are accordingly calculated. Two particular bands appear mainly of interest on the spectrum of HRV signal: one in correspondence with the respiration rate and another one at a lower frequency value. Values of power at these frequency bands together with coherence and phase between HRV signal and respiration complete the parameters which try to quantify a few aspects of the complex dynamic relationships between the original signals. In particular, controlled respiration in dogs was studied through the connection with an automatic ventilator, as well as the effects of drugs which interact with the neural regulatory systems (i.e. sympathetic and parasympathetic nervous system). Gain and phase relationships between heart rate variability and respiration, obtained with spectral analysis, could be used to provide a better understanding of the neural control mechanisms linking heart rate and respiration in various experimental conditions. The method described in this study is to be used both in physiological and clinical research.

Animals↗
PubMed1987

[Hyperplastic primary vitreous with persistent hyaloid artery in 2 non-twin brothers].

The authors describe the case of two brothers afflicted with persistent anterior hyperplasic primary vitreous and hyaloid artery. The occurrence of combination in two members of the same family is unusual, also moreover one of the patients was affected by macular retinoschisis. The two cases were clinically different; the first was typical, complicated by cataract; the second presented alterations mostly located in the posterior vitreous. In one eye fluorescein angiography showed a very slow and delayed filling of the hyaloid artery. Blood flow was directed from its anterior portion towards the optic disk. Nd: YAG laser photoresection of the hyaloid artery, performed in order to obtain a better visualization of the macula did not lead to remarkable hemorrhages. In an other eye fluorescein angiography could be performed after Nd: YAG laser photoresection of a vitreous membrane located in front of the posterior pole: remnants of the hyaloid vascular system with retrograde blood filling were present also in this case. The mechanisms leading to this reverse filling of the vessels are discussed.

Adult↗
PubMed1986

Oxygen-regulated mRNAs for light-harvesting and reaction center complexes and for bacteriochlorophyll and carotenoid biosynthesis in Rhodobacter capsulatus during the shift from anaerobic to aerobic growth.

The stability and regulation by oxygen of mRNAs for the photosynthetic apparatus in Rhodobacter capsulatus have been studied by using proflavin to inhibit transcription and by shifting cells from anaerobic to aerobic conditions. The results from the inhibition experiments show that the mRNA for the light-harvesting LH-II polypeptides (beta, alpha) is more stable than that for the light-harvesting LH-I polypeptides (beta, alpha) during anaerobic growth, whereas the mRNAs for the reaction center polypeptides L (RC-L), M (RC-M), and H (RC-H) are less stable than both the LH-I and LH-II mRNAs. When photosynthetic cells are shifted from anaerobic to aerobic conditions, an immediate decrease in the levels of mRNA for the LH-I, LH-II, RC-L, RC-M, and RC-H proteins was observed. The level of mRNA for the LH-II proteins, however, is more sensitive to oxygen and is reduced faster than the level of mRNA for the LH-I proteins. These results suggest that oxygen represses the expression of genes coding for the light-harvesting antenna and reaction center complexes and may selectively accelerate the degradation of mRNA for the LH-II proteins. The mRNAs for several enzymes in the bacteriochlorophyll biosynthetic pathway are regulated by oxygen in a similar manner. The mRNAs for carotenoid biosynthetic enzymes, however, are regulated by oxygen in a different way. We have found that the amounts of mRNAs for carotenoid biosynthetic enzyme, relative to the amounts of mRNAs for LH and RC, increased during the shift from anaerobic to aerobic conditions. We have particularly shown that although the expression of most photosynthetic genes in R. capsulatus is repressed by oxygen, the crtA gene, located in the BamHI H fragment of the R' plasmid pRPS404 and responsible for the oxidation of spheroidene to spheroidenone, responds to oxygen in an opposite fashion. This exzymatic oxidation may protect the photosynthetic apparatus from photooxidative damage.

Aerobiosis↗
PubMed1984

Nucleotide and deduced polypeptide sequences of the photosynthetic reaction-center, B870 antenna, and flanking polypeptides from R. capsulata.

The complete nucleotide sequence (8867 bp) and the deduced polypeptide sequence are given for 11 proteins from the photosynthetic gene cluster of R. capsulata (46 kb), including the photosynthetic reaction-center L, M, and H subunits and the B870 alpha and B870 beta polypeptides (light-harvesting I). These polypeptides bind bacteriochlorophyll, bacteriopheophytin, carotenoids, and quinones that are involved in the primary light reactions of photosynthesis. Hydropathy plots indicate that the L and M subunits are transmembrane proteins that may cross the membrane five times, while the H subunit has only one hydrophobic section near the amino terminus, which may be transmembrane. The L and M subunits are homologous over their entire length and have a high degree of homology with the QB protein from photosystem II of higher plants. An additional six genes were identified that may have some unknown role in bioenergetics since only mutations that affect the differentiation of the photosynthetic apparatus are known to map to this gene cluster.

Amino Acid Sequence↗
PubMed1984

Reaction center and light-harvesting I genes from Rhodopseudomonas capsulata.

Five structural genes coding for the reaction center (RC) L, M, and H subunits and the two light-harvesting (LH) I polypeptides, B870alpha and B870beta, have been mapped on two restriction fragments from the R-prime plasmid pRPS404. It has been recently shown that enhanced near-infrared fluorescence mutants of Rhodopseudomonas capsulata typically lack RC or LH I polypeptides and that these lesions are marker-rescued by two restriction fragments from the R-prime plasmid: the 7.5-kilobase-pair EcoRI F fragment and the 4.75-kilobase-pair BamHI C-EcoRI fragment. We have now determined the nucleotide sequence of two restriction fragments and have found that the BamHI C-EcoRI B fragment carries the structural genes for the RC L and M subunits and both LH I polypeptides. Forty kilobase pairs away from this locus, the BamHI F fragment (within the EcoRI F fragment) carries the RC H subunit. The structural genes on the BamHI C-EcoRI B fragment are probably transcribed as part of a polycistronic mRNA. All of the structural genes begin with a consensus Shine-Dalgarno sequence and separate AUG start codons, indicating that the structural polypeptides are not cleaved from larger precursor polypeptides.

Journal Article↗
PubMed1978

Screening coagulation tests and clotting factors in homozygous beta-thalassemia.

In 30 children with homozygous beta-thalassemia the hemostasis screening tests (bleeding time, PT, PTT), platelet count and specific assays of clotting factors were carried out 25 days after their last transfusion. PT, PTT, and bleeding time showed minor variations; considerable thrombocytosis was found in splenectomized patients. Factors IX and XII were decreased in a high proportion of patients, the vitamin K-dependent factors (II, VII, IX, X) were slightly reduced and factors I, V and VIII remained within the normal range in a majority of patients. Hepatic failure resulting in defective protein synthesis does not explain the more marked impairment of factors XI and XII, which might be secondary to activation of the intrinsic coagulation and/or kallikrein systems following intravascular haemolysis and multiple blood transfusions.

Adolescent↗
PubMedDate not supplied

Comparative study of the analgesic efficacy of flurbiprofen and diclofenac in patients following excimer laser photorefractive keratectomy.

This randomized, patient-masked, crossover trial compared the analgesic efficacy of flurbiprofen and diclofenac in 16 patients following excimer laser photorefractive keratectomy. Patients were randomly assigned to receive one study medication after surgery on the first eye and the other medication after surgery on the second eye (approximately 30 days later). After both surgeries, patients instilled one drop of the assigned medication six times daily for the first 3 days postsurgery and one drop four times daily on postsurgery days 4 through 7. Patients assessed the intensity of postsurgical pain beginning at postsurgery hour 5 and pain relief beginning at postsurgery hour 8 and continued to do so daily thereafter. On the last day (day 7), patients rated the global efficacy of the analgesic treatment. All assessments were performed by patients using descriptor and visual ordinal scales and were recorded in diaries. Patients were queried as to the presence, severity, and duration of any adverse events. Flurbiprofen produced significantly greater reductions in pain intensity than did diclofenac at all evaluations through day 4 and significantly greater relief of pain than did diclofenac at all evaluations through day 3. Significantly more patients treated with flurbiprofen reported being pain free on days 3 and 4 (11 [69%] and 16 [100%], respectively) compared with those treated with diclofenac (3 [19%] and 9 [56%], respectively). Based on patient ratings, flurbiprofen had significantly better global analgesic activity than diclofenac. Both treatments were well tolerated. Mild and transient ocular burning after instillation was the only reported adverse event; it was reported by all patients in both study groups at approximately 50% of study visits.

Adult↗
PubMedDate not supplied

[Ergonomic approach to risk control].

The aim of the paper is to emphasise the role and the importance of the ergonomic approach to improve reduction and management of the risk related to repetitive strain injuries. The authors tried to select and to put in evidence the risk factors related to the investigated problem, proposing a critical analysis of them, and to detect some guide lines to design or correct workplaces and tasks. These guidelines are based on ergonomic principles and they aim at reducing the risk related to repetitive strain injuries. The proposed interventions are grouped by a risk-factor criterion.

Arm Injuries↗