[Modification of form, material and modularity of threaded acetabulum cups]. / Modifikationen von Form, Material und Modularität der Schraubpfannen.

The fixation principle of threaded cups ensures high primary stability. Inadequate results with first-generation threaded cups led to modifications of surface machining. 10 threaded cups of the first generation, and 27 of the second and third generations were systematically analysed and their shapes measured using a no-touch light section technique. In addition, measurements of surface roughness were performed. Implants of the first generation made of polyethylene, ceramic or cobalt-chrome have an average surface roughness (Ra) of 1.5 microns. Approximately one-half of these implants have a conical shape, and one-third a height that is greater than the radius. Threaded cups of the second generation are made either of CP-titanium or titanium alloy. The average corundum-blasted surface roughness is 4.5 microns. Hydroxyapatite-coated (HA) implants have a surface roughness of 5.0 microns. Approximately 45% of the implants have a conical, biconical or flattened-conical shape, while one-third are of hemispherical shape. Approximately 90% of the cups have a height that is up to 23% smaller than the radius. A few cups have a height that approximates the radius. Implants of the third generation with identical surface structure can be supplied with crosslinked-polyethylene inlays or, optionally, with metal/metal or ceramic/ceramic contact surfaces. Primary stability, biocompatible materials and a structured surface are essential for ensuring osseointegration over the long-term. Corundum-blasted pure titanium or titanium alloys with corundum-blasted or HA-coated implants can be considered standard for these cups.

Occurrence of Bacillus thuringiensis on cured tobacco leaves.

A worldwide survey was conducted to evaluate the frequency and distribution of Bacillus thuringiensis populations on cured tobacco leaves during post-harvest storage. In total, 133 tobacco samples of different types and origins were analyzed. Nine percent of the samples showed the presence of B. thuringiensis, and 24 B. thuringiensis strains were isolated and characterized. The majority of the isolates produced bipyramidal crystals, and three fourths of them showed a second type of crystal protein (cuboidal or heterogeneous crystals). Only three isolates showed the rhomboidal crystal morphology characteristic of the anti-coleopteran B. thuringiensis subsp. tenebrionis. PCR analysis with primers specific for cry1 and cry3 genes revealed eight distinct cry gene profiles. The results of this study indicate that B. thuringiensis is naturally present at low frequency on the phylloplane of cured tobacco leaves and that its distribution is worldwide.

Isolation of Bacillus thuringiensis from Stored Tobacco and Lasioderma serricorne (F.).

Bacillus thuringiensis was isolated from dried tobacco residues and dead tobacco beetles (Lasioderma serricorne (F.); Coleoptera: Anobiidae) collected in a large number of locations worldwide. Eighty-eight samples of stored tobacco were analyzed and yielded 78 B. thuringiensis strains which were characterized on the basis of parasporal crystal morphology, sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles, and the results of an immunoblot analysis of the insecticidal crystal proteins. Flagellar antigen identification was used to differentiate selected isolates. Strains that produced rhomboidal crystals associated with the Coleoptera-specific pathotype (Cry III group) were the most abundant strains (59% of the isolates). Preliminary toxicity assays were performed with L. serricorne larvae, and the results suggested that activity is not restricted to isolates related to the Coleoptera-specific group. The results of our survey indicate that B. thuringiensis is part of the natural microflora in the stored-tobacco environment and that this special habitat represents a source of B. thuringiensis isolates that may be used to control stored-product pests.

MR imaging of the brainstem: normal postnatal development.

Magnetic resonance imaging (MRI) of the mesencephalon during the first four years of life allowed normal maturational processes of the various midbrain structures in vivo to be followed. Using T2-weighted SE sequences, we found 5 characteristic age dependent patterns on axial tomograms taken at the level of the superior colliculi, that let us derive a grading system for normal development of the quadrigeminal plate, the cerebral peduncles, the reticular substantia nigra and the red nuclei. A subsequent statistical analysis of these age dependent changing patterns on T2-weighted MRI of 60 neonates, infants and small children yielded normal age ranges for each of the 5 maturational stages of the midbrain. Grading the changing pattern of midbrain structures during early postnatal life into 5 distinct maturational stages allowed not only monitoring of normal differentiation, e.g. myelination of the brainstem in vivo, but may also help to distinguish between normal, delayed and abnormal development of the mesencephalon on routine MRI.

MR imaging of brain maturation in normal and developmentally handicapped children.

White matter myelination was assessed in the frontal, temporal, and occipital lobes and in the internal capsule in 91 neurodevelopmentally handicapped infants on T2-weighted images (spin echo 3,000/120 ms) and compared with myelination scores from 53 normal control subjects. Clinical diagnosis was birth asphyxia (34), seizures with delays of various causes (33), congenital infections (15), and intracerebral hemorrhages (9). Myelination in the total group of patients was generally delayed. However, we found distinct differences in myelin deposition between groups. Myelination of handicapped children with seizures or with intrauterine infections was retarded most severely at all ages. Children with intracerebral hemorrhages were almost never significantly different from normals in any part of the brain, whereas children with birth asphyxia had myelination scores in between. We conclude that magnetic resonance staging of developmental processes, such as myelination, in the infants' brain helps to recognize delays at an early age.

Non-invasive 31P magnetic resonance spectroscopy revealed McArdle disease in an asymptomatic child.

A Turkish couple suffering from McArdle disease (myophosphorylase deficiency) and their two sons aged 5 and 9 years, respectively, were studied using 31phosphorus magnetic resonance spectroscopy (31P MRS). During exercise both sons showed the same pathological pattern as their parents. In contrast to healthy volunteers, intracellular pH (pHi) as measured by 31P MRS every 10 s during exercise, never fell below the lower 95% confidence limit (6.94) of pHi at rest (7.06), but tended to be raised. It is of special interest that the 5-year-old boy was completely asymptomatic, although the enzyme defect seems to be fully expressed at the cellular level.

Developmental stages of human brain: an MR study.

The differentiation of the telencephalon (TC) gyri and the myelination of TC and diencephalon were analyzed quantitatively in 50 children, 32-240 weeks' postconceptional age (PCA). For this purpose, a four-stage grading system was developed by correlating magnetic resonance images from age-matched postmortem brains with subsequently prepared myelin-stained macroslices. Gyration and myelination progressed in a occipito-rostral direction. Stages 3 and 4 myelination were recognized earlier on T1-weighted images [spin echo (SE) 500/30] than on T2-weighted images (SE 3,000/120). However, long repetition time/echo time sequences yielded better contrast and allowed finer differentiation between myelinated and nonmyelinated structures. At term, the posterior limb of the internal capsule was generally myelinated (stage 2), whereas in 50% of the children, myelin appeared in the TC between 55 and 65 weeks' PCA, e.g., between 3 and 6 months postnatally. The morphological differentiation of the brain surface preceded the biochemical maturation (myelination) by an average of 12 months. Applying such a grading system to a larger population will help establish normal standards for brain maturation and a "brain age" scale during the first 4 years of life.