Biomedical subjects

U Gonzalez

Publications and source records attributed to U Gonzalez.

4 recordsLinked to original sources

PubMed2006

Interventions for vitiligo.

BACKGROUND: Around 1% of the world's population has vitiligo, which causes a loss of skin colour in patches. The methods currently available to treat vitiligo are largely unsatisfactory and vary widely between cultures and within health systems. OBJECTIVES: To assess the effects of interventions used to manage vitiligo. SEARCH STRATEGY: We searched the Cochrane Skin Group Specialised Register, the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, AMED and other databases (last searched September 2004). Reference lists of articles and conference proceedings were searched. Authors of reviews were contacted. SELECTION CRITERIA: Randomised controlled trials (RCTs). DATA COLLECTION AND ANALYSIS: At least two reviewers independently assessed study eligibility and methodological quality and carried out data extraction. The included studies compared different interventions and used different outcome measures so we considered it inappropriate to combine their results. MAIN RESULTS: Nineteen trials with a total of 1350 participants were included. The RCTs generally had low numbers of participants and only RCTs of repigmentation and not other methods of managing vitiligo were able to be included. In one study, potent topical steroids resulted in better repigmentation than placebo and they were also better than oral psoralens plus sunlight in another study (RR 4.70 95% CI 1.14 to 19.39) although their long-term use is limited by adverse effects. Two studies suggested that topical calcipotriol enhanced repigmentation rates from PUVAsol and PUVA when compared with placebo. Another two studies showed higher repigmentation rates with oral PUVAsol versus placebo plus sunlight (RR 19.20 95% CI 1.21 to 304.50 in 79 adults and RR 2.29 95% CI 1.14 to 4.58 in a study of 50 children). The safety of these interventions was poorly described and none of the studies was able to demonstrate long term benefits. Very few studies were carried out on children or included segmental vitiligo. No trials evaluating micropigmentation, melanocyte transplantation, depigmentation or cosmetic camouflage could be found. Despite the fact that the main impact of vitiligo is psychosocial only one study on psychological therapy was found and it is awaiting assessment. AUTHORS' CONCLUSIONS: This review has found some evidence to support existing therapies for vitiligo, but the different designs and outcome measurements, lack of quality of life measures and adverse effect reporting in the studies limit the usefulness of their findings. There is a pressing need for high quality randomised trials using standardised measures of repigmentation and which address relevant clinical outcomes including quality of life.

Humans↗

PubMed1993

Oxidative metabolism and body weight: inactive, active, and mitochondrial volumes.

In homeotherms, the standardized (basal) metabolic rate should not be expressed per kilogram of body weight (specific metabolic rate), nor per unit of body surface (square meters of body-ambient interface), since both mitochondrial thermogenesis and heat-loss mechanisms (radiation, conduction, convection, evaporation) are not uniform processes. On the contrary, each organism is an heterogeneous bioreactor, which is composed at least of two compartments: 1) a metabolically active volume (aV), where oxidative phosphorylation takes place; and 2) a metabolically inactive volume (iV), where oxygen consumption is negligible. The ratio (aV/iV) is not invariant, since iV increases disproportionately with the scaling up of body size, and as shown by us, when the three main components of iV, i.e., skeleton, fat deposits, and blood volume, are added together, a similar disproportionality is found. The aV was determined by subtracting the iV from the total volume (V) of an organism, or by estimating the volume occupied by all mitochondria, or mitochondrial volume (mtV). For this purpose two procedures are discussed: 1) the stereological or morphometric method; and 2) the oxygen consumption per unit time or physiometric method. The latter procedure is based on the equivalence between an VO2 = 3 ml O2.min-1 and a mtV of 1 ml, whose oxidative phosphorylation yields an approximate power output of 1 watt. The correspondence between oxygen consumption, heat production, and electron flux at the respiratory chain of the mitochondrial cristae, is discussed. From a physical point of view, the metabolic rate is a "power" function (P = M L2T-3), where M = mass, L = length, and T = time. The dimensional analysis and the statistical treatment of the corresponding numerical values of more than 200 allometric equations yields the 3/4 power, law established by Kleiber (1961), for the relationship between basal metabolism and body weight. Instead of expressing the metabolic rate per unit body weight (kg-1) or per unit body surface (m-2) structural and functional criteria should be taken into account as, for instance, the distinction between iV and aV, and particularly by emphasizing the paramount importance of the mtV where oxidative phosphorylation takes place. An allometric equation relating mtV and body weight (W) could be tentatively established for interspecies comparisons.

Adenosine Triphosphate↗

PubMed1992

Biological similarity theories: a comparison with the empirical allometric equations.

Twelve biological variables were submitted to dimensional analysis in accordance with the MLT-system of physics (M, mass; L, length; T, time). Each of these variables has a characteristic numerical value for the exponents alpha for mass, beta for length, and gamma for time. By means of Newton's reduction coefficient (chi), the three dimensions (MLT) can be expressed as power functions of body mass (Mb); the exponent (b) is the result of the combination of the three dimensional exponents (alpha, beta, gamma). By linear regression analysis of 203 allometric exponents (betaE) obtained from the literature, the following equation was found for the regression exponent (bR) (equation: see text). The estimated numerical coefficients (ki) for the three exponents (alpha, beta, gamma) of the basic dimensions (MLT) do not agree with those of the prevailing theories of biological similarity.

Animals↗

PubMed1988

Clinical relevance of the substitution of different brands of sustained-release theophylline.

In order to assess whether clinically important changes in serum theophylline concentrations occur when patients switch their brand of slow-release (SR) theophylline, 10 subjects with asthma were administered the same dose of four different SR theophylline formulations for 2-week periods in a random, double-blinded, crossover manner. Analysis of the data revealed significant differences in mean peak-to-trough fluctuations of serum theophylline concentrations between the formulations of SR theophylline, which varied from 60% to 106% of trough concentration (p less than 0.0001, analysis of variance). On at least one occasion in every subject, switching between brands of SR theophylline was responsible for raising the serum theophylline concentrations outside the accepted therapeutic range, and this was associated with symptoms of toxicity in five of the subjects. Worsening pulmonary functions were observed in two of the subjects whose switching resulted in lowered theophylline concentrations. Many of the formulation-related changes in theophylline concentrations appeared to be idiosyncratic and could not be predicted by the overall bioavailability differences between the drugs. These results argue against the open substitution of these formulations and suggest that if patients are switched between different brands of SR theophylline, their serum theophylline concentrations need to be closely monitored.

Adult↗