Clinical review: Renal tubular acidosis – a physicochemical approach

The Canadian physiologist PA Stewart advanced the theory that the proton concentration, and hence pH, in any compartment is dependent on the charges of fully ionized and partly ionized species, and on the prevailing CO₂ tension, all of which he dubbed independent variables. Because the kidneys regulate the concentrations of the most important fully ionized species ([K⁺], [Na⁺], and [Cl^-]) but neither CO₂ nor weak acids, the implication is that it should be possible to ascertain the renal contribution to acid–base homeostasis based on the excretion of these ions. One further corollary of Stewart's theory is that, because pH is solely dependent on the named independent variables, transport of protons to and from a compartment by itself will not influence pH. This is apparently in great contrast to models of proton pumps and bicarbonate transporters currently being examined in great molecular detail. Failure of these pumps and cotransporters is at the root of disorders called renal tubular acidoses. The unquestionable relation between malfunction of proton transporters and renal tubular acidosis represents a problem for Stewart theory. This review shows that the dilemma for Stewart theory is only apparent because transport of acid–base equivalents is accompanied by electrolytes. We suggest that Stewart theory may lead to new questions that must be investigated experimentally. Also, recent evidence from physiology that pH may not regulate acid–base transport is in accordance with the concepts presented by Stewart.     

Image quality in mammography with special reference to anti-scatter grids and the magnification technique

Some of the parameters determining image quality in mammography are analyzed: the effects of primary photon spectra, focal spot size and screen-film systems on spatial resolution are discussed as are scattered radiation, development temperature and absorbed dose. The parameters limiting spatial resolution and contrast are evaluated for the standard and magnification techniques. Methods of reducing scattered radiation to improve contrast are evaluated. Scatter to primary ratios for different scatter reducing methods are compared, using the physical quantity energy imparted. For the standard technique the spatial resolution has been found to be limited by the fluorescent screen. With magnification technique the focal spot is the weakest link for the spatial resolution. The contrast is mainly set by the amount of scatter using the standard technique considering the use of a low tube potential (approximately 25 kVp). Using the magnification technique the amount of scatter is so small, that the tube potential is the limiting factor. We have found the optimized standard mammographic technique to be achieved under the following conditions: 25 kVp, 0.3 to 0.6 mm focal spot, film-focus distance 500 mm, anti-scatter grid, developing temperature 36 to 38 degrees C and 4 minutes total processing time with the screen-film system we have used. In magnification technique an air gap of at least 20 mm is desired. With an FFD of about 500 mm this will give a magnification ratio of 1.8 to 2.0 and a 0.1 mm X 0.1 mm focus spot is mandatory. With this technique, it is necessary to use a faster screen-film system than that used in standard mammography.     

四膜虫对8-MOP处理的生长反应—真核原生生物四膜虫DNA损伤修复机理的研究(Ⅰ)

本文研究了四膜虫在8—MOP和紫外线(波长为365nm)照射联合处理以后细胞的生长反应。我们观察到被处理的细胞或暂时性受抑(<1μg—8MOP/ml细胞悬液)或永久性受抑(>1μg 8—MOP/1ml)细胞悬液)。暂时性受抑的细胞,在经过一定的迁延期以后可恢复其生长能力,其迁延期长短与8—MOP的剂量有关。     

Bone mass, bone structure and vertebral fractures in osteoporotic patients

The clinical severity of bone disease was studied in 44 post-menopausal osteoporotic women. Spinal x-rays were assessed and compared to objective measurements of bone mass and bone structure; forearm bone mineral content (BMCarm) by single photon absorptiometry, total body bone mineral content (TBBM), and spinal bone mineral content (BMCspine) by dual photon absorptiometry, and corrected cortical width (C Cor W), trabecular bone volume (TBV), and indices of trabecular microstructure by iliac crest biopsy. For comparison data of BMCarm, TBBM and BMCspine in 25 post-menopausal normals are shown. The results showed a reduction in amount of both cortical and trabecular bone in the fracture patients compared to normals. A subdivision of the fracture patients into two groups constituting 26 patients with wedge fractures alone and 18 patients with compression (+wedge) fractures showed that the latter group had a further predominantly trabecular bone loss and a further deteriorated trabecular microstructure. On an individual basis no agreement between clinical severity of bone disease and amount and structure of bone could be demonstrated.     

Rapid estimation of serum myoglobin concentration during rhabdomyolysis with a latex-agglutination test (Rapi-Tex)

A latex-agglutination test (Rapi-Tex) was used for semiquantitative estimation of myoglobin concentration in 89 serum samples obtained from ten patients undergoing lower-limb arterial embolectomy. Each serum sample was tested with Rapi-Tex both undiluted and after 1:50 dilution with saline. The myoglobin concentration was additionally measured with enzyme-immunoassay. In the undiluted samples there were five 'false negative' Rapi-Tex results--two in the myoglobin concentration interval 0-300 micrograms and three in the samples with myoglobin exceeding 25,000 micrograms/l--and four 'false positive' results. None of the diluted samples gave rise to false classification. Using 1:50 diluted serum, the negative predictive value of the Rapi-Tex test for identification of a myoglobin concentration greater than 5,000 micrograms/l was 0.99 (95% confidence limits 0.94-1.00), and the positive predictive value was 1.00 (0.61-1.00). Rapi-tex is concluded to be a useful emergency test for severe hypermyoglobinemia.     

Meningococcal disease in congenital absence of the fifth component of complement

We describe a family in which 2 brothers had meningococcal infection, 1 of them twice. Their parents were first degree cousins. The brothers showed a complete, isolated deficiency of C5, both antigenic and functional. The parents had half-normal values, and the data are compatible with an inherited C5 deficiency where the defect is transmitted as an autosomal codominant trait.     

A double‐blind,randomized trial of 0.05% betamethasone vs. topical catalase/dismutase superoxide in vitiligo

Background Among all the topical immunomodulators, vitiligo's mainstay therapy includes topical corticosteroids. Many other non‐immune theories have also been suggested for vitiligo's pathogenesis, but the role of oxidative stress has gained more importance in recent years. Objective To compare the effect of topical 0.05% betamethasone vs. catalase/dismutase superoxide (C/DSO). Study design Randomized, matched‐paired, double‐blind trial. Setting Dermatology Section, University of Antioquia, Medellín, Colombia. Subjects Patients (aged > 18 years or between 12 and 18 years) with parent's informed consent, with stable or active bilateral vitiligo. Intervention Topical 0.05% betamethasone or C/DSO. Methods Two lesions similar to each other in size were chosen. All assessments were made by two blinded investigators, and photographs were subjected to morphometry analysis. Main outcome Skin repigmentation by digital morphometry. Results Twenty‐five patients were enrolled in the study (21 women and 4 men). Mean age of participants was 40 years (range: 12–74 years). One patient on C/DSO experienced a mild local erythematous papular rash that self‐resolved. At 4 months of therapy, there was no statistical difference on the percentage of repigmentation between betamethasone and C/DSO (5.63% ± 27.9 vs. 3.22% ± 25.8, respectively, P = 0.758). After 10 months of therapy, the percentage of skin repigmentation increased to 18.5 ± 93.14% with betamethasone and to 12.4 ± 59% with C/DSO, but again, we found no statistical differences (P = 0.79). Discussion and conclusions Few studies have described objective methods to evaluate repigmentation among vitiligo patients. Digital morphometry provides an objective assessment of repigmentation in vitiligo. Objective vitiligo repigmentation with topical C/DSO at 10 months is similar to topical 0.05% betamethasone. Although a mild adverse effect was related to the use of C/DSO, such finding was not severe enough to discontinue treatment.     

Employability and workability among Danish employees.

The study is based on a cross-sectional study of 5575 employees interviewed by telephone in 1995. The response rate was 80%. The purpose of the study was to examine the association between employability, workability, and age. The findings of this study support the hypothesis of a correlation between employability and workability. Furthermore, it shows a strong association between employability, age, and gender.