Biomedical subjects

R Sandbrink

Publications and source records attributed to R Sandbrink.

23 records · Page 2Linked to original sources

PubMed1993

Expression of L-APP mRNA in brain cells.

Several reports addressed the issue of how the alternative splicing of exon 7 and 8 in the APP pre-mRNA is regulated in different tissues. Of special interest here was the potential involvement of exon 7 containing APP splice isoforms, since this exon codes for a serine protease inhibitor and is therefore of putative relevance for amyloidogenic catabolism of the precursor protein. The recent identification of a third alternative splice site in close proximity to the beta A4-amyloid portion in the APP gene which may also increase APP amyloidogenicity, allowed us to investigate its regulation in cells of the central nervous system. With our assay, we were able to resolve six different APP isoforms of the eight potential isoforms which can be generated from the three alternatively spliced exons 7, 8, and 15. We demonstrate here that, in addition to rat brain microglia cells, astrocyte-enriched cultures also skip the novel alternative 3'-splice site in front of exon 15, generating L-APP mRNA. Neurons are the only cells in the central nervous system which seem to use the 3'-splice site of intron 14 nearly 100%. Interestingly, this very 3'-splice site is the only one present in the APP gene that completely matches the consensus sequence for the branchpoint sequence proposed for introns. We would therefore suggest that neurons lack a specific splicing factor which inhibits the use of the rather strong 3'-splice site in front of exon 15. It remains to be shown whether this is also the case for neurons in Alzheimer's disease.

Alternative Splicing↗

PubMed1991

Photoaffinity labeling of leukotriene binding sites in hepatocytes and hepatoma cells.

The method of direct photoaffinity labeling in the frozen state using the leukotrienes as suitable photolabile compounds may serve to identify and characterize polypeptides which interact with these eicosanoids during their hepatobiliary transport and metabolism. Furthermore, it will be a helpful technique to evaluate changes in the cell-specific protein pattern during neoplastic dedifferentiation of hepatocytes.

Affinity Labels↗

PubMedDate not supplied

Cerebral changes and cerebrospinal fluid beta-amyloid in Alzheimer's disease: a study with quantitative magnetic resonance imaging.

Pathological and biochemical studies indicate that beta-amyloid (betaA4) deposition is a hallmark in the pathogenesis of Alzheimer's disease (AD). Neuroimaging studies demonstrate that the respective cerebral changes primarily strike the temporal lobe and the amygdala-hippocampus complex and may be reliably assessed using quantitative magnetic resonance imaging (MRI). Therefore one may expect that reduced betaA4-levels are significantly correlated with measures of the temporal lobe rather than global cerebral atrophy in AD patients. To test this hypothesis in a clinical study, cerebrospinal fluid concentrations of total betaA4 and its major C-terminal variations betaA4 1-40 and betaA4 1-42 were compared with cerebral changes as assessed by quantitative magnetic resonance imaging (MRI). Significantly (P< 0.05) reduced betaA4 1-40 and betaA4 1-42 levels were found in the AD patients (17 female; six male; AD/NINCDS-ADRDA-criteria) in comparison to the patients with major depression (seven female; two male; DSM-III-R). Within the AD group, betaA4 and betaA4 1-42 levels were significantly correlated with the volume of the temporal lobes (r= 0.46 and r= 0.48, respectively) but none of the other volumetric measures. These findings indicate that changes in cerebral betaA4 levels contribute to temporal lobe atrophy in AD and support the possibility that betaA4 is central to the etiology of AD.

Aged↗

PubMedDate not supplied

APP expression in primary neuronal cell cultures from P6 mice during in vitro differentiation.

Primary neuronal cell cultures from P6 mice were investigated in order to study amyloid protein precursor (APP) gene expression in differentiating neurons. Cerebellar granule cells which strongly express APP 695 allowed the identification of three distinct isoforms of neuronal APP 695. The high-molecular-weight form of APP 695 is sialylated. The expression pattern of neuronal APP 695 changes during in vitro differentiation. Sialylated forms become more abundant upon longer cultivation time. The secreted forms of sialylated, neuronal APP 695 are shown to comigrate with APP isolated from cerebrospinal fluid. We suggest that the different sialylation states of APP 695 may reflect the modulation of cell-cell and cell-substrate interactions during in vitro differentiation and regeneration.

Amyloid beta-Protein Precursor↗

PubMedDate not supplied

APP with Kunitz type protease inhibitor domain (KPI) correlates with neuritic plaque density but not with cortical synaptophysin immunoreactivity in Alzheimer's disease and non-demented aged subjects: a multifactorial analysis.

The formation of beta A4 amyloid protein in neuritic plaques in Alzheimer's disease (AD) and advanced age is a complex process that involves a number of both cellular and molecular mechanisms, the interrelations of which are not yet completely understood. We have examined quantitatively, in AD and aged controls an extended spectrum of amyloid plaque-related cellular and molecular factors and the cortical synaptophysin immunoreactivity (synaptic density) in order to check for interrelations between them by multifactorial analysis. In 3 cases of senile dementia of the Alzheimer type (SDAT) aged 72, 80 and 82 years, and 9 controls aged 43-88 (mean age 65) years, the cortical synaptophysin immunoreactivity was assessed, together with the numbers of neurons, astrocytes and microglial cells, senile plaques, of tangle-bearing neurons, and the amount of beta A4 amyloid precursor protein (APP) with and without the Kunitz type serine protease inhibitor (KPI) domain. The main results were: APP including the KPI domain (KPI-APP) correlated with the number of neuritic plaques, regardless of whether they occurred in SDAT or non-demented controls. There was no significant difference in the amount of KPI-APP between SDAT and controls. Conversely, APP695 (without KPI) was significantly reduced in SDAT. KPI-APP did not correlate with the synaptophysin immunoreactivity (RGVA), while APP695 showed a significant correlation with the latter in all evaluations. It also correlated with the neuron counts, which was not true for KPI-APP. These results support previous findings indicating that KPI-APP is an important local factor for amyloid deposition in the neuritic plaques, both in AD and in non-demented aged people. On the contrary, KPI-APP does not seem to be significantly involved in the mechanisms of synaptic change outside of the plaques.

Adult↗