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Biomedical subjects

G Kempermann

Publications and source records attributed to G Kempermann.

29 records · Page 2Linked to original sources
PubMed1998

An essential role for retinoid receptors RARbeta and RXRgamma in long-term potentiation and depression.

Hippocampal long-term potentiation (LTP) and long-term depression (LTD) are the most widely studied forms of synaptic plasticity thought to underlie spatial learning and memory. We report here that RARbeta deficiency in mice virtually eliminates hippocampal CA1 LTP and LTD. It also results in substantial performance deficits in spatial learning and memory tasks. Surprisingly, RXRgamma null mice exhibit a distinct phenotype in which LTD is lost whereas LTP is normal. Thus, while retinoid receptors contribute to both LTP and LTD, they do so in different ways. These findings not only genetically uncouple LTP and LTD but also reveal a novel and unexpected role for vitamin A in higher cognitive functions.

Animals↗
PubMed1998

Endolymphatic sac tumours.

This review article surveys clinical and pathological literature on endolymphatic sac tumours (ELST) and summarizes characteristics that describe the entity. ELST are rare neuroectodermal neoplasms in the petrous bone, originating from inner ear structures. They can be encountered sporadically or in von Hippel-Lindau disease. The most prominent symptom is sensorineural deafness. Historically, nomenclature of invasive adenoid tumours in the petrous bone has been divergent, the term papillary adenocarcinoma used most frequently. Histologically, they have a follicular or papillary and adenoid pattern that can be easily confused with various other neoplastic conditions including metastatic carcinoma. It remains to be verified whether similar tumours (papillary adenocarcinomas) can originate from the middle ear. Middle ear adenomas have a similar appearance but probably originate from neural crest cells in the middle ear. ELST can express a variety of epitopes (including cytokeratin and neuroectodermal markers) which can be detected immunohistochemically. In cases in von Hippel-Lindau disease the cerebello-pontine angle should be included in routine radiological examinations to detect ELST before the tumours lead to deafness. In apparently sporadic cases of ELST, genetic testing for von Hippel-Lindau disease should be considered. Correct distinction of ELST from metastatic carcinoma prevents futile searches for unknown primary tumours.

Diagnosis, Differential↗
PubMed1997

Genetic influence on neurogenesis in the dentate gyrus of adult mice.

To address genetic influences on hippocampal neurogenesis in adult mice, we compared C57BL/6, BALB/c, CD1(ICR), and 129Sv/J mice to examine proliferation, survival, and differentiation of newborn cells in the dentate gyrus. Proliferation was highest in C57BL/6; the survival rate of newborn cells was highest in CD1. In all strains approximately 60% of surviving newborn cells had a neuronal phenotype, but 129/SvJ produced more astrocytes. Over 6 days C57BL/6 produced 0.36% of their total granule cell number of 239,000 as new neurons, BALB/c 0.30% of 242,000, CD1 (ICR) 0.32% of 351,000, and 129/SvJ 0.16% of 280,000. These results show that different aspects of adult hippocampal neurogenesis are differentially influenced by the genetic background.

Animals↗
PubMed1997

Epidermal growth factor and fibroblast growth factor-2 have different effects on neural progenitors in the adult rat brain.

Neurons and glia are generated throughout adulthood from proliferating cells in two regions of the rat brain, the subventricular zone (SVZ) and the hippocampus. This study shows that exogenous basic fibroblast growth factor (FGF-2) and epidermal growth factor (EGF) have differential and site-specific effects on progenitor cells in vivo. Both growth factors expanded the SVZ progenitor population after 2 weeks of intracerebroventricular administration, but only FGF-2 induced an increase in the number of newborn cells, most prominently neurons, in the olfactory bulb, the normal destination for neuronal progenitors migrating from the SVZ. EGF, on the other hand, reduced the total number of newborn neurons reaching the olfactory bulb and substantially enhanced the generation of astrocytes in the olfactory bulb. Moreover, EGF increased the number of newborn cells in the striatum either by migration of SVZ cells or by stimulation of local progenitor cells. No evidence of neuronal differentiation of newborn striatal cells was found by three-dimensional confocal analysis, although many of these newborn cells were associated closely with striatal neurons. The proliferation of hippocampal progenitors was not affected by either growth factor. However, EGF increased the number of newborn glia and reduced the number of newborn neurons, similar to the effects seen in the olfactory bulb. These findings may be useful for elucidating the in vivo role of growth factors in neurogenesis in the adult CNS and may aid development of neuronal replacement strategies after brain damage.

Animals↗
PubMed1997

More hippocampal neurons in adult mice living in an enriched environment.

Neurogenesis occurs in the dentate gyrus of the hippocampus throughout the life of a rodent, but the function of these new neurons and the mechanisms that regulate their birth are unknown. Here we show that significantly more new neurons exist in the dentate gyrus of mice exposed to an enriched environment compared with littermates housed in standard cages. We also show, using unbiased stereology, that the enriched mice have a larger hippocampal granule cell layer and 15 per cent more granule cell neurons in the dentate gyrus.

Animals↗
PubMed1996

Deafness due to bilateral endolymphatic sac tumours in a case of von Hippel-Lindau syndrome.

A case of bilateral endolymphatic sac tumours is reported. In a patient with von Hippel-Lindau syndrome, tumour growth in the right cerebellopontine angle caused deafness. The tumour was removed and classified as a metastasis from a thyroid carcinoma. However, on thyroidectomy no primary neoplasm could be found. Eight years later a similar tumour was operated on in the left petrosal bone. Histological appearance, immunocytochemical findings, and the clinical context gave evidence that the tumours had to be reclassified as endolymphatic sac tumours--extremely rare entities. The report supports the hypothesis, suggested by the few earlier case reports, that endolymphatic sac tumours could be one of the inherent tumour manifestations in von Hippel-Lindau syndrome.

Carcinoma↗
PubMed1995

Phenytoin inhibits expression of microtubule-associated protein 2 and influences cell-viability and neurite growth of cultured cerebellar granule cells.

The objective of this study was to show whether an in vitro model for Phenytoin-related cytoskeletal impairment could be helpful to investigate cerebellar side effects of Phenytoin (DPH). DPH dose-and time-dependently resulted in decreasing numbers of vital cells. Cells formed only a rarefied intercellular neuritic network. This effect was already evident 24 h after plating. Western-blot analysis revealed that the expression of the dendritic marker microtubule-associated protein 2 (MAP2) was dramatically decreased in DPH-treated cultures.

Animals↗
PubMed1995

[A case of gustatory sweating and facial pain].

We report a case of a patient with gustatory sweating, a unilateral hyperhidrosis following a gustatory stimulus and an accompanying thermoregulatory hypohidrosis in the same area. Unusual features in this case are a possible association with a face pain and that the causing lesion can be localized in the brain-stem by neurological-topical reasoning. Most cases of gustatory sweating are caused by damage to the parotid gland.

Aged↗
PubMed1994

Cytochrome P450 in rat astrocytes in vivo and in vitro: intracellular localization and induction by phenytoin.

Cytochrome P450IIB1,2 (nomenclature according to Nelson et al., DNA Cell Biol 12:1-51, 1993 and Volk et al., Neuroscience 42:215-235, 1991) immunoreactivity (P450-IR) is associated with astrocytes both in vivo and in vitro. Although they are unevenly distributed throughout the brain with a preference for phylogenetically elder parts, no significant differences between astrocytes prepared from different brain regions were observed in astrocyte cultures. The percentage of strongly immunoreactive astrocytes decreased from 40% after 7 days in culture to 15% after 21 days. Essentially all astrocytes have a low but significant P450-IR within this interval. Preembedding immunoelectron microscopy revealed peroxidase reaction products on the endoplasmic reticulum and on the outer membranes of mitochondrial and nuclear envelopes. Phenytoin (1 microM) added to the medium for 7 days significantly (1.22-fold) increased the amount of total P450 in astrocyte homogenates as measured by spectrophotometry. Considerably more immunoreactive cells (1.5-fold) were found in treated cultures than in controls.

Animals↗
PubMedDate not supplied

Environmental stimulation of 129/SvJ mice causes increased cell proliferation and neurogenesis in the adult dentate gyrus.

New neurons are continuously born in the dentate gyrus of the adult mouse hippocampus, and regulation of adult neurogenesis is influenced by both genetic and environmental determinants. Mice of the 129/SvJ strain have significantly less hippocampal neurogenesis than other inbred mouse strains [1] and do not perform well in learning tasks. Here, the impact of environmental stimuli on brain plasticity during adulthood of 129/SvJ mice was studied using 'enriched environments' where mice receive complex inanimate and social stimulation [2,3]. In contrast to our earlier reports on mice of the C57BL/6 strain - which are competent in learning tasks and in which environmental stimulation did not influence cell proliferation [4,5] - environmentally stimulated 129/SvJ mice were found to have twice as many proliferating cells in the dentate gyrus compared with mice in standard housing. Environmental stimulation fostered the survival of newborn cells in 129/SvJ mice; this effect had also been seen in C57BL/6 mice. Phenotypic analysis of the surviving cells revealed that environmental stimulation resulted in 67% more new neurons. In combination with our earlier results, these data indicate a differential impact of inheritable traits on the environmental regulation of adult hippocampal neurogenesis. In addition, we observed behavioral changes in environmentally stimulated 129/SvJ mice.

Animals↗