Presence of pancreatic hormones in islet cells with MHC-class II antigen expression

In the normal rat pancreas, only few islet cells express MHC-class II antigens. Their nature and function has not yet been elucidated. We report a method for the purification of Ia-positive islet cells by fluorescence-activated cell sorting. The isolated mononuclear cells appear of nonendocrine origin but contain vacuoles with partially digested secretory vesicles. Both insulin- and glucagon-immunoreactive granules were identified in these vacuoles of varying size and composition. It is suggested that at least part of the rat islet cells with class II antigen expression can exhibit phagocytotic properties leading to the uptake of fragments from damaged endocrine cells. This functional characteristic may implicate this particular islet cell type in the pathology of the endocrine pancreas in type I diabetes.     

Dual-energy X-ray absorptiometry of lumbar vertebrae: relative contribution of body and posterior elements and accuracy in relation with neutron activation analysis.

The bone mineral content of 34 lumbar vertebrae obtained from ten cadavers (three men, seven women; age 61-88 years) was measured using a pulsed source dual-energy X-ray absorptiometry (DEXA) apparatus. Scanning was performed in the frontal projection and was repeated on the vertebral bodies obtained after removal of the posterior elements of the vertebrae. Subsequently a nondestructive neutron activation analysis (NAA) was performed. The mineral content of the vertebral bodies was found to represent (mean, SEM) 53.0% (1.9%) of the content of the whole vertebrae. The mineral content of the vertebral bodies assessed with NAA (BMC NAA) and with DEXA (BMC DEXA) showed a high correlation: BMC NAAA = (1.016 x BMC DEXA) + 0.990 r = 0.949 (p less than 0.001). We conclude that the mineral content of lumbar vertebral bodies can be accurately measured in vitro in a water environment by DEXA, and that the mean contribution of the posterior elements of the vertebra to the calcium hydroxyapatite content of whole vertebrae measured in the frontal projection is as high as 47.0%.     

Optimization of production yields, radionuclidic purity and hotcell shielding of SPECT and PET radionuclides produced by proton irradiation in variable energy 30 MeV cyclotrons--Part 67Ga.

Optimization of the production parameters (incident and exit proton energy, thickness of the (68)Zn target layer, decay time to start chemical processing of an irradiated target after the end of bombardment) and of the thickness of the lead shield of the processing hotcell for the cyclotron production of (67)Ga by the (68)Zn(p,2n) threshold reaction are accomplished by powerful divide et impera and binary search algorithms with the Pharmacopoeia radionuclidic purity of the (67)Ga-citrate radiopharmaceutical at a reference time and the locally accepted dose rate level for the controlled area as boundary conditions. Two sets of equations are presented (one associated with the maximum production rate, the other with the use of a minimum target layer thickness) that allow the expression of the optimized production parameters, the radionuclide yields satisfying the Pharmacopoeia requirements at the start of distribution and the necessary shielding as a function of the required activity at the start of distribution and of the maximum allowable beam current on target.     

Molecular genetic studies in alpha-thalassemia]

A group of 5,000 patients, suspected of haemolytic anaemia, were investigated with molecular genetic methods for deletion types of alpha-thalassemia. In 776 (15.6%) patients a deletion of one or more alpha-globin genes was found. The same group of patients was also investigated for abnormal haemoglobins and beta-thalassaemia. In about 30% of the patients either an alpha-thalassaemia, an abnormal haemoglobin, a beta-thalassaemia, or a combination was diagnosed. In a group of patients with a haemoglobinopathy, the frequency of alpha-thalassaemia was much higher (i.e. 33%) than in individuals without haemoglobinopathy. Preselection of the patients based on the presence of microcytic erythrocytes and/or a decreased ADW0.5 of the erythrocytes gave a high incidence of false-negative and false-positive results. Therefore, haemoglobin examination should not be restricted to protein chemistry, but should include molecular genetic investigations for deletion types of alpha-thalassaemia.     

The effect of isoluminant and isochromatic stimuli on latency and amplitude of saccades

When two stimuli are presented in different positions successively at short time intervals saccadic eye movements are usually directed at intermediate positions. This phenomenon of "averaging" of saccadic eye movements has been studied in responses to double-step target displacements in different stimulus conditions. In these conditions isoluminant and isochromatic stimuli were used with variable contrast and at different background luminances. Although the critical duration of temporal summation differed considerably in these stimulus conditions the duration of the phenomenon of "averaging" remained the same in all conditions. This indicates that temporal properties of the sensory system are not the prime cause of "averaging". Moreover, the onset time of "averaging" relative to the second target displacement turned out to be highly correlated with the mean latency of saccades in the different conditions. The implications of the results for models of oculomotor control are discussed.     

Significance of skin temperature changes in surface electromyography

Summary Differing results have been reported concerning the direction and quantity of the electromyogram (EMG) amplitude response to changes in tissue temperature. The EMG signals from the soleus muscle of six healthy human subjects were therefore recorded during dynamic exercise (concentric contractions) at ambient temperatures of 30°C and 14°C. The mean skin temperature above the muscle investigated was 32.9° C and 21.7° C, respectively. The core temperature, estimated by rectal temperature, was unchanged. The cooling of the superficial tissues caused approximately a doubling of the EMG amplitude. For the probability level 0.9 in the amplitude probability distribution function, the average signal level increased from 73 V to 135 V (P=0.02). The average mean power frequency of the EMG signal was reduced from 142 Hz to 83 Hz (P=0.004). The amplitude increase was not due to shivering but other possible explanations are presented. As the changes in T _sk investigated were within the range which may occur normally during the working hours, it was concluded that T _sk should be carefully controlled in vocational EMG studies.