Circulating 1,25-Dihydroxycholecalciferol After Intravenous Injections of l{alpha}-Hydroxycholecalciferol in Patients on Regular Haemodialysis

The formation of 1.25-dihydroxycholecalciferol (1.25-(OH)₂D₃after single intravenous injections of 1-hydroxycholecalciferol(1-OHD₃) was examined in four patients with chronic renal failureon regular haemodialysis. Following 1–3µg 1-OHD₃administered at weekly intervals, 1.25-(OH)₂D₃ appeared in thecirculation within 1 h, and peak concentrations were reachedbetween 2 h and 5 h. By 8 h serum 1.25-(OH)₂D₃ concentrationshad started declining and by 44 h they had returned to baselineafter 1µg 1-OHD₃ but they were still above basal after2 and 3 µg by an average of 30 pmol/l. One week afterinjections, concentrations were back to basal in all patientsstudied. The serum 1,25-(OH)₂D₃ dose response to injected la-OHDwas linear, indicating ample capacity of the liver 25-hydroxylaseto further hydroxylate 1-OHD. However, examination of the individualresponses revealed lower increments in serum 1.25-(OH)₃ concentrationsin the patients with the highest basal serum 25-hydroxyvitaminD concen trations. Intravenous 1-OHD₃ may be useful in the furtherstudy of the interactions between 1.25-(OH)₂₃ calcium and PTHin chronic renal failure, as well as of the hepatic metabolismof vitamin D.     

Pattern electroretinogram can be more than the sum of local luminance responses

It is generally accepted that the pattern electroretinogram for very large spatial elements is the result of local luminance stimulation. Responses due to the luminance differences between elements may be assumed to be relatively unimportant because in the case of large elements only few retinal units are stimulated by gradients. With decreasing pattern element size one wonders to what extent the electroretinogram continues to be based on the local luminance stimulation. We investigated this question using 8 Hz checkerboard reversal and compared the pattern recordings with the recordings resulting from the same stimulus field modulated homogeneously (focal electroretinogram). A 100% modulated checkerboard at retinal level may be considerably less modulated because of imperfect optics of the eye. So the pattern electroretinogram should be compared with homogeneous field stimulation of correspondingly lower modulation depth. On the basis of the optical transfer properties of the eye we compared by subtracting the proper focal electroretinogram from the pattern electroretinogram. The difference response was virtually zero for check sizes larger than 120. For checks from 60 down the difference response was of the same order of magnitude as the adjusted focal recording. This difference response for eyes with normal optics is largest around 30; its wave form was found to be rather invariant with check size.     

Etiology of the fear of dentistry

In the present study, 192 extremely anxious dental patients were asked for the factors which may have influenced their dental anxiety. The results showed that a traumatic dental experience, personality and professional behaviour of the dentist, persons in the direct environment, and psychological background all played an important role. Almost all extremely anxious dental patients had more than one negative experience with the dental treatment. Most patients acquired their anxiety at an early age.     

The effect of low sulfate concentrations on the glycosaminoglycan synthesis in anatomically intact articular cartilage of the mouse

We have studied the effect of environmental sulfate concentration on the glycosaminoglycan synthesis of anatomically intact patellar cartilage of the mouse in vitro. Incubation of mouse patellae in medium with sulfate concentrations below 0.5 mM resulted in a diminished incorporation of sulfate but in unaltered incorporation of glucosamine. This suggested the synthesis of undersulfated glycosaminoglycans under these conditions. We characterized glycosaminoglycans synthesized at three different sulfate concentrations: a sulfate concentration physiological for the mouse (1.0 mM), a sulfate concentration in the range where sulfate incorporation was strongly diminished (0.1 mM), and an extremely low sulfate concentration (10 nM). Analysis of glycosaminoglycan disaccharides and DEAE anion chromatography of the glycosaminoglycans could not confirm the synthesis of undersulfated glycosaminoglycans at 0.1 mM. The chromatogram of glycosaminoglycans synthesized in medium containing 10 nM showed the presence of a very low sulfated glycosaminoglycan pool not observed at higher medium sulfate concentrations. Intermediately sulfated glycosaminoglycans were also synthesized during incubation with 10 nM sulfate. So, our data indicate that only very low sulfate concentrations in the medium lead to the synthesis of undersulfated glycosaminoglycans and that the sulfation mechanism of murine patellar cartilage chondrocytes does not seem to fit completely in an "all-or-nothing" pattern.     

Identification of Potential Diagnostic and Vaccine Candidates of Helicobacter pylori by Two-Dimensional Gel Electrophoresis, Sequence Analysis, and Serum Profiling

There is great interest in characterizing the proteins of the gastric pathogen Helicobacter pylori, especially those to which humans respond immunologically, because of the potential importance of such proteins in diagnosis and vaccine development. Two-dimensional gel electrophoresis was used to separate and identify potential antigens of H. pylori ATCC 43504. Over 30 proteins were reactive in Western blots with pooled sera from 14 infected patients. These proteins were analyzed by N-terminal sequence analysis. Fourteen proteins were determined to be distinct from any proteins previously described from H. pylori; the others were previously isolated and characterized proteins. Analysis of eight distinct H. pylori strains showed that most of these antigens were produced by all of the strains. We propose that collection of new antigens such as those recognized here will be useful in serologic tests for detecting and monitoring H. pylori infection and may also serve as potential targets for antimicrobial agent or vaccine development.     

Mitochondrial Antibodies in Primary Biliary Cirrhosis: II. The Complement Fixing Antigen as a Component of Mitochondrial Inner Membranes

The autoantibodies found in the sera of patients with primary biliary cirrhosis have been shown to react with a component of the mitochondrial inner membranes. Outer membranes were inactive. The purity of the inner and outer membrane fractions obtained by 2 different methods was assessed by electron microscopy and marker enzyme tests. Using negative-staining it was possible to visualize antibody binding to mitochondrial membranes. At high resolution it could be seen that the 90° particles on the cristal membranes were not involved in the reaction with antibody, but it was not possible to establish in the present studies the precise antigenic site upon the mitochondrial inner membranes.     

Human smooth pursuit during transient perturbations of predictable and unpredictable target movement

Summary The predictive component of human smooth pursuit was studied by perturbing sinusoidal target motion at unpredictable instants. The disturbances consisted of either a brief period of stabilization of the target on the fovea or a replacement of the sine by a ramp displacement for half a period. To minimize the effects of a possible change of the tracking strategy by the subject the transitions were masked and only the initial part of the response to the disturbance was analyzed. After stabilization on the fovea the eye oscillation continued at the frequency of the preceding target movement for about one half-cycle, whereupon the oscillation was rapidly damped. The mean unidirectional smooth eye acceleration was 70% of the mean unidirectional target acceleration prior to the stabilization. This suggests that during pursuit of a sinusoidal target movement about 75% of the oculomotor response is generated by predictive processes. When the sine was replaced by a ramp, starting at the velocity zero-crossing, the eye accelerated away from the target for ca. 180 ms irrespective of the frequency of prior tracking. In contrast, when the ramp started at the peak velocity of the sinusoidal target motion the eye accelerated away from the target for more than a quarter period. After foveal stabilization during pursuit of a pseudorandom stimulus, the eye continued to oscillate for less than one period at approximately the highest frequency present in the stimulus. The frequency characteristics of human smooth pursuit of predictable as well as unpredictable target motion were correctly simulated by a model, which derived its predictive properties from a lead element, tuned to the current frequency of the target motion.