Thiamine uptake in human intestinal biopsy specimens, including observations from a patient with acute thiamine deficiency

Mucosal biopsy specimens obtained by routine endoscopy from 108 human subjects, including one patient with thiamine deficiency, were incubated at 37 degrees C in oxygenated calcium-free Krebs-Ringer solution (pH 7.5) containing tritiated thiamine and [14C]dextran as a marker of adherent mucosal water. The amount of labeled thiamine taken up was measured radiometrically. In subjects with no clinical evidence of thiamine deficiency, 1) thiamine uptake by duodenal mucosa had a hyperbolic time course, reaching equilibrium at 10 min; 2) thiamine concentrations < 2.5 mumol/L were taken up predominantly by a saturable mechanism displaying Michaelis-Menten kinetics (K(m) 4.4 mumol/L and Jmax 2.3 pmol.mg wet tissue-1.6 min-1), whereas higher concentrations were taken up by passive diffusion; 3) thiamine transport had different capacities along the gastrointestinal tract (duodenum >> colon > stomach); and 4) thiamine uptake was competitively inhibited in the duodenum by thiamine analogs, albeit with a different order of potency compared with rats, and was blocked by 2,4-dinitrophenol. In the thiamine-deficient patient, the duodenal saturable uptake was increased, with higher K(m) and Jmax values. In conclusion, physiologic concentrations of thiamine were transported in human small intestine by a specific mechanism dependent on cellular metabolism, whose transporters appear to be down-regulated.

Alzheimer's disease and senile brains: an immunofluorescence study

The results obtained with direct immunofluorescence techniques on normal, senile and Alzheimer's disease brains are reported. The antisera used were directed against C3c, IgG (gamma chain), IgG Fc., kappa and lambda light chains and anti-Ig (total). The brain samples were prepared in different ways: formalin-fixed and paraffin embedded; fresh frozen samples and alcohol fixed, paraffin-embedded samples. The images obtained with the different processing methods did not coincide. In order to obtain a more complete picture, we suggest the use of different methods on the same samples. In Alzheimer's disease brains, abundant but probably not monoclonal Ig antigenic determinants were found. Ig were found diffusely in the tissue, connected to amyloid (both in senile plaques and blood vessel walls), in glial cells and neurons. The significance of such data in relation to the genesis of brain amyloid are discussed.

[Anatomo-clinical study of 4 cases of Jakob-Creutzfeldt disease (spongiform encephalopathy)]

Four anatomo-clinical cases of Creutzfeldt-Jakob disease (spongiform encephalopathy) are described. In 3 cases the correct diagnosis was made while the patients were living. The most important diagnostic elements are the following: rapid evolution of a presenile or senile dementia, with neurological symptoms unusual in the Alzheimer's disease. The importance of EEG for the diagnosis of Creutzfeldt-Jakob disease is confirmed: however the onset of the typical EEG abnormalities was very late in its manifestation, the CT alterations are in general absent or very limited. The pathological alterations are aspecific. The spongiform process was sometimes scarce or limited to specific cerebral areas.

Electroencephalographic and histopathological correlations on Jakob-Creutzfeldt disease

Three patients with Jakob-Creutzfeldt disease were studied. The clinical evolution was followed and several EEG controls were made. In all patients characteristic EEG abnormalities were present. Histopathological features in the cortical, subcortical grey matter and in the white matter were examined. Subcortical and cortical grey matter were involved while the white matter appeared intact. The results were compared with previous studies of other Authors and the correlation between the characteristic EEG alterations and the histopathological features was studied in order to explain the appearance of the paroxysmal EEG findings. In agreement with other studies, the Authors emphasized the cortical and subcortical grey matter involvement in the genesis of EEGraphic paroxysmal aspects. The intervention of other factors, possibly of histochemical nature, was postulated.