Plasma homocysteine concentration is a sensitive marker for cobalamin and folate deficiency. The previously reported high incidence of increased plasma homocysteine in psychogeriatric patients and the association between reduced concentrations of cobalamin, folate and neuropsychiatric symptoms led to the present study on 741 consecutive psychogeriatric patients. The concentrations of plasma homocysteine correlated significantly with blood folate, serum cobalamin and serum creatinine both in demented (n = 295) and in non-demented patients with other psychiatric disorders (n = 215). Plasma homocysteine concentrations were significantly increased in both the demented and the non-demented patients, whereas only the demented patients had lower blood folate and serum creatinine concentrations than 163 control subjects. Almost all of the different diagnostic groups of demented and non-demented patients exhibited significantly increased plasma homocysteine concentrations compared with control subjects. Significantly decreased blood folate concentrations were mainly found in the different diagnosis groups of demented patients. Plasma homocysteine concentrations in both demented and non-demented patients with serum cobalamin and blood folate above the lower 20th percentile of these vitamins in the control subjects were also studied. Despite these vitamin concentrations, both groups of patients still exhibited significantly higher plasma homocysteine concentrations than the control subjects, which may indicate an increased frequency of impaired genetic capacity to metabolize homocysteine in these patients. Patients with either dementia of vascular cause or a history of other occlusive arterial disease had a significantly higher plasma homocysteine concentration than those without a history of vascular disease.

Abstract. Plasma homocysteine, serum cobalamin and blood folate were analysed in 296

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Regional cerebral blood flow was measured in 21 normotensive subjects during supine rest and during head-up tilt to 70 degrees. The results showed significant and consistent regional cerebral blood flow changes in the frontal areas with lower relative flow distribution values (percentage of mean flow) during head-up tilt than during supine rest. The lower frontal flow distribution values during tilt were not related to habituation, to repeated measurements, or to the estimated level of arterial CO2 which was derived from expired end-tidal CO2 levels. None of the subjects had orthostatic hypotension and there was no significant difference in mean hemispheric blood flow between lying down and standing up. There was no significant gender difference in regional cerebral blood flow, although female subjects tended to have higher mean hemispheric flow than males in both postures. It remains to be established whether the flow decreases in the frontal cortex are caused by cerebral functional factors or by haemodynamic mechanisms.

Regional cerebral blood flow was measured with the 133-Xenon inhalation method in seven healthy subjects with orthostatic hypotension not due to autonomic failure (i.e. non-neurogenic clinical disorder). Measurements were performed during supine rest and during head-up tilt (70 degrees). All subjects had a consistent drop in systolic blood pressure and the typical symptomatology of orthostatic hypotension. The results showed lower mean hemispheric blood flow during head-up tilt than during supine rest. In addition, a consistent and significant redistribution of the regional flow values was seen, with a reduction in frontal and an increase in postcentral areas. The frontal flow decrease during tilt was more marked than in subjects without orthostatic hypotension and was not related to variations in the level of PCO2 or to respiration. In contrast to the clinical symptoms of orthostatic hypotension (dizziness, nausea, visual disturbances, and in some cases syncope), the cortical blood flow reduction was, however, relatively moderate.

The effect of granulocytes on human platelet aggregation was investigated in vitro. Platelet function was assayed by photometric technique. Incubation of platelets with latex-stimulated granulocytes for 1 h at room temperature resulted in total inhibition of arachidonic acid-induced platelet aggregation. ADP-induced platelet aggregation was suppressed, lacked secondary wave and was pursued by swift disaggregation. Platelet aggregates induced by collagen dispersed faster under the influence of stimulated granulocytes. The present results indicate that granulocytes may play a role in the hemostatic mechanism in man.

Sera of eight unselected adult patients with acute myelogenous leukemia obtained before and after chemotherapy were repeatedly tested for specific complement-dependent cytotoxicity against autochthonous peripheral white blood cells from the acute leukemia stage and from the remission stage, respectively. Complement-dependent cytotas demonstrated in all of the eight patients, while none of three patients' sera were reactive against white blood cells from the remission stage tested in parallel. The cytotoxicity was increased after chemotherapy, also in those patients in whom remission was not achieved.

This study demonstrates that a cytotoxic serum reactivity not requiring the presence of complement appears in the sera of patients with acute myelogenous leukemia. The reaction is detected upon short-term incubation of sera in vitro with autochthonous mononuclear white blood cells from peripheral venous blood of patients at the acute stage of the disease. This reactivity was demonstrated in 18/18 patients. Generally, the cytotoxicity was low in patients at the acute stage of the disease, but increased after chemotherapy and reached the highest level at the onset of clinical remission or just before. No cytotoxicity could be demonstrated against autochthonous remission white blood cells. The serum activity could be absorbed and eluted from protein A-sepharose CL-4B and was recovered in the 7S-fraction of the sera after gel filtration on Sephadex G-200 and ion exchange chromatography. This indicates that the demonstrated cytotoxicity is due to immunoglobulins of IgG-class. It is believed that Fc-receptor-bearing cells present in the target cell preparations function as effector cells. The reaction is designated antibody-associated cellular cytotoxicity (AACC).