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Biomedical subjects

P S Eriksson

Publications and source records attributed to P S Eriksson.

At least 19 recordsLinked to original sources
PubMed2006

Reactive astrogliosis induces astrocytic differentiation of adult neural stem/progenitor cells in vitro.

Neural stem cells reside in defined areas of the adult mammalian brain, including the dentate gyrus of the hippocampus. Rat neural stem/progenitor cells (NSPCs) isolated from this region retain their multipotency in vitro and in vivo after grafting into the adult brain. Recent studies have shown that endogenous or grafted NSPCs are activated after an injury and migrate toward lesioned areas. In these areas, reactive astrocytes are present and secrete numerous molecules and growth factors; however, it is not currently known whether reactive astrocytes can influence the lineage selection of NSPCs. We investigated whether reactive astrocytes could affect the differentiation, proliferation, and survival of adult NSPCs by modelling astrogliosis in vitro, using mechanical lesion of primary astrocytes. Initially, it was found that conditioned medium from lesioned astrocytes induced astrocytic differentiation of NSPCs without affecting neuronal or oligodendrocytic differentiation. In addition, NSPCs in coculture with lesioned astrocytes also displayed increased astrocytic differentiation and some of these NSPC-derived astrocytes participated in glial scar formation in vitro. When proliferation and survival of NSPCs were analyzed, no differential effects were observed between lesioned and nonlesioned astrocytes. To investigate the molecular mechanisms of the astrocyte-inducing activity, the expression of two potent inducers of astroglial differentiation, ciliary neurotrophic factor and leukemia inhibitory factor, was analyzed by Western blot and shown to be up-regulated in conditioned medium from lesioned astrocytes. These results demonstrate that lesioned astrocytes can induce astroglial differentiation of NSPCs and provide a mechanism for astroglial differentiation of these cells following brain injury.

Analysis of Variance↗
PubMed2006

Apoptosis-inducing factor is a major contributor to neuronal loss induced by neonatal cerebral hypoxia-ischemia.

Nine-day-old harlequin (Hq) mice carrying the hypomorphic apoptosis-inducing factor (AIF)(Hq) mutation expressed 60% less AIF, 18% less respiratory chain complex I and 30% less catalase than their wild-type (Wt) littermates. Compared with Wt, the infarct volume after hypoxia-ischemia (HI) was reduced by 53 and 43% in male (YX(Hq)) and female (X(Hq)X(Hq)) mice, respectively (P<0.001). The Hq mutation did not inhibit HI-induced mitochondrial release of cytochrome c or activation of calpain and caspase-3. The broad-spectrum caspase inhibitor quinoline-Val-Asp(OMe)-CH(2)-PH (Q-VD-OPh) decreased the activation of all detectable caspases after HI, both in Wt and Hq mice. Q-VD-OPh reduced the infarct volume equally in Hq and in Wt mice, and the combination of Hq mutation and Q-VD-OPh treatment showed an additive neuroprotective effect. Oxidative stress leading to nitrosylation and lipid peroxidation was more pronounced in ischemic brain areas from Hq than Wt mice. The antioxidant edaravone decreased oxidative stress in damaged brains, more pronounced in the Hq mice, and further reduced brain injury in Hq but not in Wt mice. Thus, two distinct strategies can enhance the neuroprotection conferred by the Hq mutation, antioxidants, presumably compensating for a defect in AIF-dependent redox detoxification, and caspase inhibitors, presumably interrupting a parallel pathway leading to cellular demise.

Amino Acid Chloromethyl Ketones↗
PubMed2006

Efficient non-viral transfection of adult neural stem/progenitor cells, without affecting viability, proliferation or differentiation.

BACKGROUND: Neurogenesis occurs in defined areas of the adult mammalian brain, including the dentate gyrus of the hippocampus. Rat neural stem/progenitor cells isolated from this region retain their multipotency in vitro and in vivo after grafting into the adult brain. Molecular signalling and lineage selection in these cells may be examined using genetic manipulation. However, valid analysis requires that this manipulation should not affect cellular viability, proliferation or differentiation. METHODS: We screened several transfection protocols to develop a method which met these criteria. We then tested the effects of transfection on viability, proliferation and differentiation into the three neural lineages: neurons, astrocytes and oligodendrocytes. RESULTS: In initial testing, ExGen500 and FuGene6 efficiently transfected adult neural stem/progenitor cells, in vitro. After optimisation, these agents transfected 16% and 11% of cells, respectively. FuGene6-treated cells did not differ from untransfected cells in their viability or rate of proliferation, whereas these characteristics were significantly reduced following ExGen500 transfection. Importantly, neither agent affected the pattern of differentiation following transfection. Both agents could be used to genetically label cells, and track their differentiation into the three neural lineages, after grafting onto ex vivo organotypic hippocampal slice cultures. CONCLUSIONS: These data demonstrate that non-viral transfection may be used to genetically manipulate neural stem/progenitor cells, without adversely affecting their growth or perturbing lineage selection. Such a method is valuable for examining the molecular mechanisms of cell fate determination in vitro. Furthermore, this protocol may be exploited in the development of cell-based gene therapy strategies.

Animals↗
PubMed2004

Demonstration of multiple novel glycoforms of the stem cell survival factor CCg.

We have investigated the presence of different glycoforms of cystatin C secreted by adult hippocampal rat-derived stem/progenitor cells (AHPs) into conditioned medium. A glycosylated form of cystatin C (CCg) has been identified previously in conditioned medium from AHPs as an autocrine/paracrine cofactor. Fibroblast growth factor-2 (FGF2) requires cooperation with CCg to support AHP survival at low density in vitro. The purpose of the present study was to investigate further if cystatin C consists of one glycoform or if several different glycoforms are secreted by AHPs in vitro. The presence of the glycoforms was studied using enzymatic deglycosylation in conjunction with gel electrophoresis and Western blotting. The glycoforms of cystatin C were isolated with a combination of gel electrophoresis and electroelution, yielding the intact glycoforms in liquid phase before enzymatic deglycosylation. Our results revealed several novel glycoforms, in contrast to previous publication. The results suggest that N- and O-linked glycans with sialic acid are attached to cystatin C. Furthermore, we have demonstrated that all glycoforms are present in conditioned medium after only 48 hr of culturing and that all nestin-positive AHPs are immunopositive against cystatin C. These findings suggest secretion of the glycoforms by cultured AHPs.

Animals↗
PubMed2004

Functional consequences of stress-related suppression of adult hippocampal neurogenesis - a novel hypothesis on the neurobiology of burnout.

BACKGROUND: Burnout is generally recognized as a work-related stress-induced condition associated with memory problems, fatigue, a sense of inadequacy, and depressed mood. Neurogenesis, the formation of new neurons in the human adult brain, provides a newly discovered dimension of brain plasticity. OBJECTIVES: In a novel theory, we propose that the failure of adult hippocampal neurogenesis may provide the biological and cellular basis for altered brain plasticity in stress-related syndromes like burnout. METHODS: A number of recent animal studies have shown that the rate of neurogenesis in the adult hippocampus may provide an important neurobiological correlate to the symptoms of stress. RESULTS: As of yet, the normal physiological function of new neurons in the adult hippocampus remains unresolved although a number of studies and reviews indicate the importance of neurogenesis for memory and learning. CONCLUSION: In line with this hypothesis, we propose burnout to be an exponent of stress-mediated decrease in adult neurogenesis leading to a decreased ability to cope with stress through decreased hippocampal function possibly involving a disturbed hippocampal regulation of the hypothalamo-pituitary-adrenal axis (HPA axis).

Adult↗
PubMed2003

Astrocytes and stroke: networking for survival?

Astrocytes are now known to be involved in the most integrated functions of the central nervous system. These functions are not only necessary for the normally working brain but are also critically involved in many pathological conditions, including stroke. Astrocytes may contribute to damage by propagating spreading depression or by sending proapoptotic signals to otherwise healthy tissue via gap junction channels. Astrocytes may also inhibit regeneration by participating in formation of the glial scar. On the other hand, astrocytes are important in neuronal antioxidant defense and secrete growth factors, which probably provide neuroprotection in the acute phase, as well as promoting neurogenesis and regeneration in the chronic phase after injury. A detailed understanding of the astrocytic response, as well as the timing and location of the changes, is necessary to develop effective treatment strategies for stroke patients.

Astrocytes↗
PubMed2001

Measurement of the dynamics of exocytosis and vesicle retrieval at cell populations using a quartz crystal microbalance.

The quartz crystal microbalance-dissipation technique (QCM-D) is used in two different measurement strategies to monitor the mass change and rigidity of populations of excitable cells during exocytosis and subsequent retrieval of dense-core vesicles. Two cell lines, NG 108-15 and PC 12, were grown to confluence on piezoelectric quartz crystals and were examined separately to demonstrate differences in release and retrieval with cells of different morphology, size, and number of dense-core vesicles. Stimulating the cells to exocytosis with media containing an elevated potassium concentration resulted in an increase in the frequency response corresponding to loss of mass from the cells owing to release of vesicles. In Ca2+-free media, the response was completely abolished. The amplitude and peak area in the frequency response corresponding to mass change with stimulated release was larger for PC 12 cells than for NG 108-15 cells, whereas the initial rate constants for the frequency responses were similar. The data suggest (1) that a greater number and larger size of vesicles in PC 12 cells results in a greater amount of release from these cells vs NG 108-15 cells, (2) the recycling of vesicles utilizes similar fusion/retrieval mechanisms in both cell types, (3) that the control of excess retrieval might be related to the number and size of released vesicles, and (4) that measured retrieval has a rapid onset, masking exocytosis and implying a rapid retrieval mechanism in the early stages of release. These results demonstrate that measurements of complex dynamic processes relating to dense-core vesicle release and retrieval can be simultaneously accomplished using the QCM-D technique.

Animals↗
PubMed2001

Electroporation of single cells and tissues with an electrolyte-filled capillary.

We show how an electrolyte-filled capillary (EFC) coupled to a high-voltage power supply can be used as a versatile electroporation tool for the delivery of dyes, drugs, and biomolecules to the cytoplasm of single cells and cells in tissues. A large-voltage pulse applied across the EFC (fused silica, 30 cm long, 375-microm o.d., 30-microm i.d.) gives rise to a small electric field outside the terminus of the EFC, which causes pore formation in cell membranes and induces an electroosmotic flow of electrolyte. When the EFC contains cell-loading agents, then the electroosmotic flow delivers the agents at the site of pore formation. The combination of pore formation and delivery enables loading of materials into the cytoplasm. By patch-clamp and fluorescence microscopy, formation of pores was observed at estimated transmembrane voltages of <85 mV with half-maximum values around 206 mV. The electroporation protocol was demonstrated by introduction of fluorogenic dyes into single NG108-15 cells, cellular processes, and small populations of cells in organotypic hippocampal cultures. Preliminary results are shown in which this protocol was employed for in vivo electroporation of ventral mesencephalon in rat brains. The technique was also used to access organelle-based detection systems inside cells. As a demonstration, 1,4,5-inositoltriphosphate was added to the electrolyte and detected by intracellular organelles in electroporated cells.

Animals↗
PubMed2001

Selective introduction of antisense oligonucleotides into single adult CNS progenitor cells using electroporation demonstrates the requirement of STAT3 activation for CNTF-induced gliogenesis.

We have developed a novel method in which antisense DNA is selectively electroporated into individual adult neural progenitor cells. By electroporation of antisense oligonucleotides against signal transducer and activator of transcription 3 (STAT3) we demonstrate that ciliary neurotrophic factor (CNTF) is an instructive signal for astroglial type 2 cell fate specifically mediated via activation of STAT3. Activation of the mitogen-activated protein kinase (MAPK) signaling pathway induced only a transient increase in glial fibrillary acidic protein (GFAP) expression, and inhibition of this signaling pathway did not block the induction by CNTF of glial differentiation in progenitor cells. In addition we show that microelectroporation is a new powerful method for introducing antisense agents into single cells in complex cellular networks.

Age Factors↗
PubMed2001

Gender and strain influence on neurogenesis in dentate gyrus of young rats.

To investigate whether rat hippocampal neurogenesis varies with strain and gender, the authors examined proliferating progenitor cells and their progeny in young male and female Sprague-Dawley (SD) and spontaneously hypertensive rats (SHR) using the thymidine analog bromodeoxyuridine (BrdU) combined with immunohistochemistry for the neuronal marker Calbindin D28k and glial fibrillary acidic protein. Rats were given 7 consecutive daily BrdU injections and were killed 1 day or 4 weeks later to allow for discrimination between proliferation and cell survival. Stereologic analysis of the numbers of BrdU-immunoreactive cells in the dentate gyrus revealed both a strain difference with significantly higher cell proliferation and net neurogenesis in SHR than in SD and a gender difference with males from both strains producing significantly more cells than their female counterparts. Whereas the number of progenitors four weeks after BrdU injections was still significantly greater in male than in female SHRs, resulting in a greater net neurogenesis in the male, the number of BrdU-immunoreactive cells did not differ between male and female SD rats, suggesting a greater survival of newly generated cells in the dentate gyrus in female than in male SD rats. No sex or strain difference was observed in the relative ratio of neurogenesis and gliogenesis.

Animals↗
PubMed2001

Endothelin-1 decreases glutamate uptake in primary cultured rat astrocytes.

Endothelin-1 (ET-1) is a potent vasoconstrictor peptide that is also known to induce a wide spectrum of biological responses in nonvascular tissue. In this study, we found that ET-1 (100 nM) inhibited the glutamate uptake in cultured astrocytes expressing the glutamate/aspartate transporter (GLAST); astrocytes did not express the glutamate transporter-1 (GLT-1). The V(max) and the K(m) of the glutamate uptake were reduced by 57% and 47%, respectively. Application of the ET(A) and ET(B) receptor antagonists BQ-123 and BQ-788 partly inhibited the ET-1-evoked decrease in the glutamate uptake, whereas the nonspecific ET receptor antagonist bosentan completely inhibited this decrease. Incubation of the cultures with pertussis toxin abolished the effect of ET-1 on the uptake. The ET-1-induced decrease in the glutamate uptake was independent of extracellular free Ca(2+) concentration, whereas the intracellular Ca(2+) antagonists thapsigargin and 3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester abolished the effect of ET-1 on the glutamate uptake. Incubation with the protein kinase C (PKC) antagonist staurosporine, but not with the fatty acid-binding protein bovine serum albumin, prevented the ET-1-induced decrease in the glutamate uptake. These results suggest that ET-1 impairs the high-affinity glutamate uptake in cultured astrocytes through a G protein-coupled mechanism, involving PKC and changes in intracellular Ca(2+).

Amino Acid Sequence↗
PubMed2000

Differential expression of delta opioid receptors and mRNA in proliferating astrocytes during the cell cycle.

Previous immunohistochemical and radioligand binding studies have shown a cell cycle-dependent regulation of the delta opioid receptor (DOR). The relationship between DOR expression and mitosis in primary astroglial cultures of rat cerebral cortex was investigated in this study. The cultures were arrested during the G(1)/S transition or during mitosis. The DOR protein level increased twofold (P = 0.009) during mitosis and DOR mRNA level increased threefold (P = 0.002) during the G(1)/S transition compared to nonsynchronized cultures. DOR mRNA was also elevated (1.6-fold, P = 0.008) during the G(1)/S transition compared with mitotic cells. A premitotic increase in DOR mRNA suggests that elevated DOR protein levels during mitosis might be regulated during transcription.

Animals↗
PubMed2000

Astrocyte beta1-adrenergic receptor immunoreactivity and agonist induced increases in [Ca2+]i: differential results indicative of a modified membrane receptor.

Antibodies against the C-terminus of the beta1-adrenergic receptor were used for staining cultured astrocytes from the rat cerebral cortex. Immunoreactivity was found to be localized exclusively to an intracellular organelle structure similar to the Golgi complex, with no staining of the plasma membrane. The astrocytes stained positive with BODIPY CGP 12177, a FITC-conjugated beta-adrenergic receptor agonist, and this staining was blocked by the beta1-adrenergic antagonist atenolol, indicating that these receptors are expressed on the surface of the astrocytes. The presence of functional plasma membrane beta1-adrenergic receptors was further verified using microspectrofluorometry for measurements of intracellular calcium changes upon beta-adrenergic agonist stimulation. Intracellular immunoreactivity confined to the organelles was also found in astrocytes from mixed astroglial-neuronal cultures. In contrast, the neurons in these cultures showed a strong labeling of the cell bodies by the beta1-adrenergic receptor antibodies. Thus, the beta1-adrenergic receptor antibody, which stains the cell bodies of the neurons, recognizes the astroglial receptors only intracellularly, although functional beta1-adrenergic receptors are present on the astroglial surface. Taken together, these data suggest that the beta1-adrenergic receptors observed intracellularly might be processed on their passage to the surface to a modified form of the final plasma membrane receptor, which is not recognized by the antibodies.

Adrenergic alpha-Agonists↗
PubMed2000

Peripheral infusion of IGF-I selectively induces neurogenesis in the adult rat hippocampus.

In several species, including humans, the dentate granule cell layer (GCL) of the hippocampus exhibits neurogenesis throughout adult life. The ability to regulate adult neurogenesis pharmacologically may be of therapeutic value as a mechanism for replacing lost neurons. Insulin-like growth factor-I (IGF-I) is a growth-promoting peptide hormone that has been shown to have neurotrophic properties. The relationship between IGF-I and adult hippocampal neurogenesis is to date unknown. The aim of this study was to investigate the effect of the peripheral administration of IGF-I on cellular proliferation in the dentate subgranular proliferative zone, which contains neuronal progenitor cells, and on the subsequent migration and differentiation of progenitor cells within the GCL. Using bromodeoxyuridine (BrdU) labeling, we found a significant increase of BrdU-immunoreactive progenitors in the GCL after 6 d of peripheral IGF-I administration. To determine the cell fate in progenitor progeny, we characterized the colocalization of BrdU-immunolabeled cells with cell-specific markers. In animals treated with IGF-I for 20 d, BrdU-positive cells increased significantly. Furthermore, the fraction of newly generated neurons in the GCL increased, as evaluated by the neuronal markers Calbindin D(28K), microtubule-associated protein-2, and NeuN. There was no difference in the fraction of newly generated astrocytes. Thus, our results show that peripheral infusion of IGF-I increases progenitor cell proliferation and selectively induces neurogenesis in the progeny of adult neural progenitor cells. This corresponds to a 78 +/- 17% (p < 0.001) increase in the number of new neurons in IGF-I-treated animals compared with controls.

Animals↗
PubMed2000

Manipulating the genetic identity and biochemical surface properties of individual cells with electric-field-induced fusion.

A method for cell-cell and cell-liposome fusion at the single-cell level is described. Individual cells or liposomes were first selected and manipulated either by optical trapping or by adhesion to a micromanipulator-controlled ultramicroelectrode. Spatially selective fusion of the cell-cell or cell-liposome pair was achieved by the application of a highly focused electric field through a pair of 5-micrometer o.d. carbon-fiber ultramicroelectrodes. The ability to fuse together single cells opens new possibilities in the manipulation of the genetic and cellular makeup of individual cells in a controlled manner. In the study of cellular networks, for example, the alteration of the biochemical identity of a selected cell can have a profound effect on the behavior of the entire network. Fusion of a single liposome with a target cell allows the introduction of the liposomal content into the cell interior as well as the addition of lipids and membrane proteins onto the cell surface. This cell-liposome fusion represents an approach to the manipulation of the cytoplasmic contents and surface properties of single cells. As an example, we have introduced a membrane protein (gamma-glutamyltransferase) reconstituted in liposomes into the cell plasma membrane.

Animals↗
PubMed2000

Growth hormone increases connexin-43 expression in the cerebral cortex and hypothalamus.

Several studies indicate that systemic GH influences various brain functions. Connexin-43 forms gap junctions that mediate intercellular communication and establish the astroglial syncytium. We investigated the effects of peripheral administration of bovine GH (bGH) and recombinant human insulin-like growth factor I (rhIGF-I) on the expression of connexin-43 in the rat brain. Hypophysectomized female Sprague Dawley rats were substituted with cortisol (400 microg/kg x day) and L-T4 (10 microg/kg x day) and treated with either bGH (1 mg/kg x day) or rhIGF-I (0.85 mg/kg x day) for 19 days. The abundance of connexin-43 messenger RNA (mRNA) and protein in the brainstem, cerebral cortex, hippocampus, and hypothalamus was quantified by means of ribonuclease protection assays and Western blots. Treatment with bGH increased the amounts of connexin-43 mRNA and protein in the cerebral cortex and hypothalamus. No changes were found in the brainstem or hippocampus. Infusion of rhIGF-I did not affect connexin-43 mRNA or protein levels in any of the brain regions studied. These results show that administration of bGH increases the abundance of cx43 in specific brain regions, suggesting that GH may influence gap junction formation and thereby intercellular communication in the brain.

Animals↗
PubMed1999

Enriched environment increases neurogenesis in the adult rat dentate gyrus and improves spatial memory.

The fetal and even the young brain possesses a considerable degree of plasticity. The plasticity and rate of neurogenesis in the adult brain is much less pronounced. The present study was conducted to investigate whether housing conditions affect neurogenesis, learning, and memory in adult rats. Three-month-old rats housed either in isolation or in an enriched environment were injected intraperitoneally with bromodeoxyuridine (BrdU) to detect proliferation among progenitor cells and to follow their fate in the dentate gyrus. The rats were sacrificed either 1 day or 4 weeks after BrdU injections. This experimental paradigm allows for discrimination between proliferative effects and survival effects on the newborn progenitors elicited by different housing conditions. The number of newborn cells in the dentate gyrus was not altered 1 day after BrdU injections. In contrast, the number of surviving progenitors 1 month after BrdU injections was markedly increased in animals housed in an enriched environment. The relative ratio of neurogenesis and gliogenesis was not affected by environmental conditions, as estimated by double-labeling immunofluorescence staining with antibodies against BrdU and either the neuronal marker calbindin D28k or the glial marker GFAp, resulting in a net increase in neurogenesis in animals housed in an enriched environment. Furthermore, we show that adult rats housed in an enriched environment show improved performance in a spatial learning test. The results suggest that environmental cues can enhance neurogenesis in the adult hippocampal region, which is associated with improved spatial memory.

Aging↗