Agonistic autoantibodies to the α(1) -adrenergic receptor and the ß(2) -adrenergic receptor in Alzheimer's and vascular dementia.

Although primary causes of Alzheimer's and vascular dementia are unknown, the importance of preceding vascular lesions is widely accepted. Furthermore, there is strong evidence for the involvement of autoimmune mechanisms. Here, we report the presence of agonistic autoantibodies directed at adrenergic receptors in the circulation of patients with mild to moderate Alzheimer's and vascular dementia. In 59% of these patients, agonistic autoantibodies against the α(1) -adrenergic receptor and the ß(2) -adrenergic receptor were identified. The majority of positive patients (66%) contained both types of autoantibodies in combination. In a control group of patients with neurological impairments others than Alzheimer's and vascular dementia, only 17% were found to harbour these autoantibodies. The autoantibodies to the α(1) -adrenergic receptor interacted preferably with the extracellular loop1 of the receptor. They were further studied in IgG preparations from the column regenerate of a patient who underwent immunoadsorption. The α(1) -adrenergic receptor autoantibodies specifically bound to the extracellular loop1 peptide of the receptor with an apparent EC(50) value of 30 nm. They mobilized intracellular calcium in a clonal cell line expressing the human form of the α(1) -adrenergic receptor. Our data support the notion that autoimmune mechanisms play a significant role in the pathogenesis of Alzheimer's and vascular dementia. We suggest that agonistic autoantibodies to the α(1) -adrenergic and the ß(2) -adrenergic receptor may contribute to vascular lesions and increased plaque formation.

Ultrastructure of the liver after hypoxia in the postnatal period.

Repeated phases of hypoxia (8 h daily for 2 to 5 days at pO2 11.33 kPa = 5.000 m in altitude) were induced to Sprague-Dawley rats in the postnatal period as well as up to the 64th day of age, and after different recovery phases the ultrastructure of hepatocytes was qualitatively and quantitatively analysed. Major results were as follows: 1. Increases in body and liver weights were delayed but were balanced off after 64 days. 2. Qualitative alterations are reversible spherical transformations of mitochondria, a degradation of lipids and a slight increase in autophagocytosis. 3. The quantitative mitochondrial parameters (volume density, number per unit area, average volume) were not even adjusted to control values after 64 days. Granular endoplasmic reticulum and ribosomes/polysomes were insignificantly reduced in comparison to control animals, structure and arrangement are regular. Lipids and glycogen were differently altered. 4. The findings of the hepatocytes after postnatal hypoxia were reversible, though the majority of parameters had not yet returned to normal after 2 months. An adaptation to repetitive hypoxic conditions is not provable.

Discrepancy between biochemical normalization and morphological recovery of jejunal mucosa during postischemic reperfusion in presence of the xanthine oxidase inhibitor oxypurinol.

An increased formation of oxygen free radicals in the reperfused rat small intestine is concluded from accumulations of oxidized glutathione, of thiobarbituric acid-reactive substances and of 4-hydroxynonenal. Xanthine oxidase inhibition prevented these biochemical changes. The histological and electronmicroscopic studies of intestinal sucosa showed significant structural deteriorations already at the end of the ischemic period obviously due to disturbances of cellular energy metabolism. The extent of dosage was increased during the reperfusion without qualitative changes of the pattern of structural dosage. The beneficial effects of oxypurinol on biochemical criteria which occurred already in the early phase of reperfusion were not reflected in significant morphological differences within the first hour of reperfusion. Differences of morphological findings between oxypurinol-treated and untreated animals could be observed after longer periods of reperfusion--during the regeneration of the tissue.

Binding of ions to nuclear chromatin.

Ion concentrations in isolated lymphocyte nuclei subjected to KCl or MgCl2 media of varying ionic strength were measured by X-ray microanalysis. Values were corrected for the contribution of free ions by estimating the volume fraction of the water space morphometrically. The amount of bound cations and Cl was constant and independent of the widely varying free ion concentration. It is concluded that the mechanism of binding is counterion condensation but with limited cooperativity. In contrast to classical counterion condensation theory, the binding of ions occurs at oppositely charged clusters at the surface of the chromatin. Therefore, both cations and anions are bound and binding cannot be completely delocalized. The bound ions stabilize the basic chromatin fibre but are not involved in the regulation of the transition between the condensed and decondensed state. Using earlier data, we estimated the concentration of free cations in rat liver nuclei under in-vivo conditions to be in the order of about 80 mM.

Human platelet electrorotation change induced by activation: inducer specificity and correlation to serotonin release.

Electrorotation of single platelets was compared with [14C]serotonin release, aggregation and electron microscopy. Activation of washed and degranulated platelets was induced by thrombin, arachidonic acid, collagen, adrenaline, platelet activation factor (PAF), ADP and A23187. A strong correlation between electrorotation decrease and serotonin release was found. Electrorotation did not correlate with aggregation. It was concluded that an increase of the specific conductivity of the platelet membrane by three orders of magnitude (approx. 1.0.10(-7) S.m-1 to 1.0.10(-4) S.m-1) upon activation was responsible for the observed decrease of anti-field rotation and the shift of the first characteristic frequency towards higher values. Electrorotation allowed for time-dependent measurements of activation. Characteristic activation times in the order of minutes were found. There was the following sequence of activators classified by increasing activation time constants: A23187 was the fastest followed by thrombin, collagen, PAF, arachidonic acid, adrenaline, and ADP.

Estimation of organelle water fractions from frozen-dried cryosections.

Local dry mass or water fractions can be measured on frozen-dried cryosections assuming constant section thickness in the hydrated state and no net water movements and no differential shrinkage during freezing and drying. These assumptions have been tested on a model consisting of isolated rat liver mitochondria in an albumin matrix with a concentration similar to the dry mass concentration of the cytoplasm. The dry mass concentrations of mitochondria before freezing as measured by interference microscopy and after freezing and freeze-drying of the sections as measured by X-ray microanalysis and scanning microdensitometry are shown to be equal as long as the ice crystals in the medium are smaller than about 100 nm. It is concluded, therefore, that the above-mentioned assumptions could also hold for the cryopreparation of cells and tissues.

The intracellular distribution of ions and water in rat liver and heart muscle.

Local dry mass concentrations of intracellular compartments in rat heart muscle and liver cells were estimated by quantitative electron microscopy and X-ray microanalysis of ultrathin frozen-dried cryosections. The results were used to calculate elemental concentrations per litre of compartment water from the X-ray microanalytical data. Water fractions were between 80.3 +/- 1.3% of wet weight in the decondensed chromatin and only 45.1 +/- 1.7% in mitochondria of liver cells. The lowest water fraction in heart muscle cells was also found in mitochondria. The ionic concentrations found in the cytoplasm of liver cells and in the myofibrils are in accord with the electroneutrality rule and in osmotic equilibrium with the extracellular concentrations. The concentrations of Na, K, Cl and P both in the cytoplasm and in the regions of decondensed chromatin within the nuclei were found to be equal. However, in regions of condensed chromatin K+ concentrations were found to be much higher than expected for a Donnan distribution of ions free in solution. Most probably the activity coefficient for K+ is lower in the condensed chromatin than in the decondensed or in the cytoplasm. The same holds true for the A-band as compared to the I-band in heart muscle cells. A sequestration of K+ was measured also in the rough endoplasmic reticulum (RER) of hepatocytes. The Cl- concentration in mitochondria both in heart muscle and liver cells has been measured far in excess of what might be expected from a Nernstian distribution. A coupled inward Cl- transport in mitochondria must, therefore, be assumed.

Intracellular water and ionic shifts during growth and ageing of rats.

As measured by X-ray microanalysis of frozen-dried cryosections, physiological concentrations of phosphorus, Na+, K+ and Mg2+ show a biphasic age dependence in some compartments of rat hepatocytes, especially in the regions of condensed chromatin associated with the actively transcribed genes. This could be consistent with a reactivation of the protein synthesizing apparatus in old livers. The decrease in intracellular water concentrations in hepatocytes and myocytes during ageing is shown to be solely due to a preferential decrease in the water concentration in mitochondria. As a consequence, ionic strength in mitochondria increases with age. This result could provide a rationale for a better understanding of functional declines found in mitochondria from old donors.

Postnatal development of hepatocytes following oxygen deficiency in utero.

Pregnant rats were exposed to altitude hypoxia (5,000 m = pO2 11.33 kPa) 8 h daily, from the 16th through 21st d of pregnancy. The livers of the newborn male rats were morphometrically examined by electron microscopy for both qualitative and quantitative parameters, on the 2nd, 5th, 11th and 22nd d of age and were compared with those of controls during the same periods of postnatal development. Substantive changes were exhibited by the mitochondria. Processes of autophagocytic decomposition were recorded (focal vacuolisation, formation of myelin structures). Volume densities on the 2nd (0.2041), 11th (0.2048), and 22nd (0.2495) d of age were clearly higher than in control animals and were all on a rising trend. Numerical density, on the other hand, trebled in the controls (0.0738 on the 2nd d and 0.2261 on the 22nd) and almost doubled in the hypoxia animals (0.0849 on the 2nd d and 0.1471 on the 22nd). In other words, the volume of the average mitochondrion was larger in hypoxia animals, whereas surface densities were lower. Hepatocytes differed from cardiomyocytes, in that increased autophagocytosis of mitochondria and glycogen was recordable from the former only on the 5th d. Glycogen levels of hepatocytes went up considerably, with the rise recorded from controls (0.0181 on the 2nd d and 0.1911 on the 22nd) being somewhat stronger than that observed from hypoxia animals (0.0276 on the 2nd d and 0.1742 on the 22nd). The changes postnatally recorded from liver cells in the wake of prenatal hypoxia are believed to be processes of adaptation which do not cause any irreversible damage.