Rate and mechanism of enamel demineralization in situ.

In this paper, data are presented on the in situ demineralization of human enamel as a function of the demineralization period. To quantify the mineral loss parameters versus time, it is important to obtain information on the kinetics, and thus on the mechanism of dental caries. The results show that for in situ enamel demineralization, the lesion depth as well as the mineral loss parameter both vary linearly with the demineralization time. This is in contrast to in vitro lesion formation where the third power, or the square power of the lesion depth is linearly related to the demineralization time. In in situ demineralization, the rate-determining step of the demineralization process is the inhibitor-controlled dissolution process at the enamel crystallite surfaces, while the inhibitor content (F-, proteins etc.) in the lesion originating from the plaque, saliva and enamel is high. Furthermore, the study indicates that in in situ demineralization, interprismatic mineral loss is very important.     

Presence of pulmonary intravascular macrophages in the equine lung: some structuro-functional properties.

The pulmonary intravascular macrophages (PIMs) have been described in several species of animals. This study demonstrates for the first time that the equine lung has PIMs as resident phagocytes in its microvasculature. Their salient features such as globular surface coat, structures of the endocytic pathway, and related cell organelles closely resemble those of the calf, goat, and sheep. The exquisite organization of the coat globules in the form of a linear chain was structurally similar to the lipolytic lipase and the heparin-sensitive globular coat from PIMs of calf, goat, and sheep. Monastral blue (MB) when employed as a tracer to assess the phagocytic properties of equine PIMs induced similar modification of the globules of the coat into lipid droplets, reminiscent of neutral lipids. Lipids droplets (modified coat globules) were delivered into acid phosphatase-positive endosomes and lysosomes. Concurrently, the unaltered globules of the coat, probably internalized via fluid-phase constitutive pinocytoses, followed a different endocytic pathway. Large-scale platelet uptake by the PIMs was observed with thrombocytopenia in MB-treated ponies. The possible significance of hypothetical LDL-coat and the endocytic organelles as equivalents of synthetic apparatus of vasoactive lipids in the PIMs of horse needs to be assessed in future studies.     

Difficult supracondylar elbow fractures in children: analysis of percutaneous pinning technique.

After treatment with two lateral percutaneous pins, 80 children with grade II-III supracondylar elbow fractures were reviewed. The result was good in 55 patients (68%) and was the same for extension- and flexion-type injuries. These patients had less than 10 degrees change in carrying angle and less than 20 degrees total change in range of motion. This method eliminates risk of iatrogenic injury to the ulnar nerve but is technically very demanding. Redisplacement, joint penetration, and damage to the capitellar side of growth plate can be avoided only by positioning the pins divergently.     

Anatomy of the posterior urethra]

The short section of the urethra that passes through the urogenital diaphragm is termed the membranous urethra. It is accompanied by several vessels and nerve fibers. In surgery on the membranous urethra the perineal body is of crucial importance, and precise knowledge of the course of the urethra through the pelvic floor is essential. Furthermore, the relationship between the membranous urethra and its accompanying structures is of great importance. These include the branches of the internal pudendal artery, the prostatic venous plexus and the cavernous nerves coursing ventrally from the pelvic plexus. The nerves supplying the membranous urethra were studied in fetuses with the help of a magnifying lens. The results of the dissections are documented by histological sections, photographs and paintings.     

Utilisation des implants biodégradables dans le traitement chirurgical des fractures et au cours des ostéotomies

Résumé L'utilisation de matériaux d'ostéosynthèse biodégradables a l'avantage d'éviter la réintervention pour extraire le matériel. Les biomatériaux de polymères polyglycolides ont été expérimentés sur plus de 3 600 animaux de laboratoire avant leur introduction en pratique clinique. Depuis 1984 nous les avons utilisés comme matériau d'ostéosynthèse dans près de 1 700 cas parmi lesquels 880 cas de fracture malléolaire, 226 cas d'ostéotomie en chevron pour hallux valgus, 65 cas de fracture de la tête radiale et 54 cas de fracture de l'olécrane. Parmi les 800 premiers cas traités par broches biodégradables nous avons obtenu des résultats favorables et sans incidents dans 91 pour cent des cas. Il y eut 7 cas de fixation défaillante nécessitant une réintervention. Il y a eu 7 cas d'infection superficielle et 3 cas d'infection profonde. Nous avons observé la formation d'une collection séreuse sous-cutanée sans influence sur le résultat radiologique ou clinique dans 52 cas (6,5 %). Au vue de ces résultats et compte tenu des avantages économiques et psychologiques des matériaux biodégradables (pas de réintervention), on peut penser que l'usage de biomatériaux rivalise favorablement avec l'usage de matériaux conventionnels dans certains types d'ostéosynthèse.

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Utilization of biodegradable implants in the surgical treatment of fractures and osteotomies

Summary The utilization of biodegradable implants instead of metals in orthopaedic surgery abolishes the need to remove the fixation material. For this study biodegradable rods and screws of self-reinforced polyglycolide, polylactide and lactide-glycolide copolymer were developed and manufactured. The clinical introduction of these implants was preceded by thorough experimental studies with 3 600 animals. From November 1984 the developed biodegradable method of osteofixation was used in 1 700 operations. These included 880 displaced malleolar fractures, 226 chevron-osteotomy for hallux valgus, 65 displaced fracture of the radial head, 54 displaced frature of the olecranon and other fresh fractures or orthopaedic operations. In the first 800 cases operated on using self-reinforced polyglycolide rods the postoperative course was uneventful (91%). Because of failure in the fixation reoperation was needed in 7 cases. A superficial wound infection was observed in 7 cases, deep infection in 3 and transient fluid accumulation in 52 cases (6,5%). Fluid accumulation did not influence the radiological or clinical end-result. The advantages of biodegradable fixation are many-sided. There is a costbenefit and clinical capacity is free for other use, and psychological advantages must be emphasised because removal of implants is not needed. The over all results of this study were considered favourable.

     

The Effect of High-Dose Ascorbate Supplementation on Plasma Lipoprotein(a) Levels in Patients With Premature Coronary Heart Disease

Study Objective . To determine the efficacy of high-dose ascorbate supplementation in lowering lipoprotein(a) [Lp(a)] levels in patients with premature coronary heart disease (CHD). Design . Randomized, double-blind, placebo-controlled trial. Setting . Outpatient clinic. Patients . Forty-four patients with documented premature CHD. defined as confirmed myocardial infarction and/or angiographically determined stenosis of 50% or greater in at least one major coronary artery before age 60 years. Interventions . Patients were block randomized on the basis of age, gender, and screening Lp(a) concentrations to receive ascorbate 4.5 g/day or placebo for 12 weeks. Measurements and Main Results . High-dose ascorbate was well tolerated and produced a marked elevation in mean plasma ascorbate levels (+1.2 mg/dl; p<0.001). Multiple linear regression analysis revealed no significant effect of supplementation on postintervention Lp(a) levels (p=0.39) in a model that included treatment group assignment, and baseline Lp(a) levels. Conclusions . Our findings do not support a clinically important lowering effect of high-dose ascorbate on plasma Lp(a) in patients with premature CHD.     

Tuberculosis and Leprosy: Attempts to Identify T-Cell Antigens of Potential Value for Vaccine Design

Tuberculosis and leprosy are chronic bacterial infectious diseases which represent major health problems worldwide. It is generally accepted that, on the one hand, effective vaccination strategies are required for satisfactory control of these diseases and, on the other hand, that currently available vaccination measures are insufficient for this purpose. Ideally, a subunit vaccine should be designed which is composed of one or a few protective antigens. In this brief treatise our approach towards the identification of antigens with potential value for vaccine design is described. It comprises high resolution fractionation by two-dimensional gel electrophoresis, transfer of separated fractions by electroelution and testing of separated fractions with viable T cells and accessory cells. Using this approach we find: (1) multiple antigens are recognized by T cells from leprosy and tuberculosis patients as well as healthy contacts; (2) apparently, suppressive antigens exist in leprosy; (3) an antigen cluster which is apparently indicative for immunity against M. tuberculosis is present among secreted proteins. We hope that further improvement of this methodology will help in the rational design of subunit vaccines against tuberculosis and leprosy.