David T. Yew

Terminal dUTP nick end labeling (TUNEL) positive cells in the different regions of the brain in normal aging and alzheimer patients

This study investigated terminal dUTP nick-end labeling (TUNEL)-positive cells in the frontal, occipital, and hippocampal cortices of seven normal aging and four Alzheimer’s patients. Significant increase in TUNEL-positive cells was observed in the frontal and hippocampal cortices of Alzheimer’s patients when compared with controls. In the hippocampal cortex, only area CA4 demonstrated a significant increase of TUNEL-positive cells. Double staining of TUNEL-positive cells for glial fibrillary acidic protein revealed that <13% of the TUNEL-positive nuclei belonged to astrocytes. The results of this study illustrated a differential pattern of cortical degeneration between normal aging and Alzheimer patients.

Effects of hypoxia on the proliferation and differentiation of NSCs

Oxygen is vital to nearly all forms of life on Earth via its role in energy homeostasis and other cell functions. Until recently, the effects of oxygen on the proliferation and differentiation of neural stem cells (NSCs) have been largely ignored. Some studies have been carried out on the basis of the fact that NSCs exists within a “physiological hypoxic” environment at 1 to 5% O2 in both embryonic and adult brains. The results showed that hypoxia could promote the growth of NSCs and maintain its survival in vitro. In vivo studies also showed that ischemia/hypoxia increased the number of endogenous NSCs in the subventricular zone and dentate gyrus. In addition, hypoxia could influence the differentiation of NSCs. More neurons, especially more doparminergic neurons, were produced under hypoxic condition. The effects of hypoxia on the other kind of stem cell were briefly introduced as additional evidence. The mechanism of these responses might be primarily involved in the hypoxic inducible factor-1 (HIF-1) signal pathway. The present review summarizes recent works on the role of hypoxia in the proliferation and differentiation of NSCs both in vitro and in vivo, and the mechanism involved in HIF-1 signaling pathway behind this response was also discussed.

Comparative proteomic analysis of mesenchymal stem cells derived from human bone marrow, umbilical cord, and placenta: Implication in the migration

Umbilical cord (UC) and placenta (P) have been suggested as alternatives to bone marrow (BM) as sources of mesenchymal stem cells (MSC) for cell therapy, with both UC‐ and P‐MSC possess immunophenotypic and functional characteristics similar to BM‐MSC. However, their migration capacity, which is indispensable during tissue regeneration process, is unclear. Under defined conditions, the migration capacity of BM‐ and P‐MSC was found 5.9‐ and 3.2‐folds higher than that of UC‐MSC, respectively. By the use of 2‐DE and combined MS and MS/MS analysis, six differentially expressed proteins were identified among these MSC samples, with five of them known to be involved in cell migration as migration enhancing or inhibiting proteins. Consistent with their migration capacity, the levels of migration enhancing proteins including cathepsin B, cathepsin D and prohibitin,were significantly lower in UC‐MSC when compared with those in BM‐ and P‐MSC. For the migration inhibiting proteins such as plasminogen activator inhibitor‐1 (PAI‐1) and manganese superoxide dismutase, higher expression was found in the UC‐MSC. We also showed that the overexpression of the PAI‐1 impaired the migration capacity of BM‐ and P‐MSC while silencing of PAI‐1 enhanced the migration capacity of UC‐MSC. Our study indicates that PAI‐1 and other migration‐related proteins are pivotal in governing the migration capacity of MSC.

Proliferation and apoptosis in the developing human neocortex

The cell kinetics of the developing central nervous system (CNS) is determined by both proliferation and apoptosis. In the human neocortex at week 6 of gestation, proliferation is confined to the ventricular zone, where mitotic figures and nuclear immunoreactivity for proliferating cell nuclear antigen (PCNA) are detectable. Cell division is symmetric, with both daughter cells reentering mitosis. At week 7, the subventricular zone, a secondary proliferative zone, appears. It mainly gives rise to local circuit neurons and glial cells. Around week 12, the ventricular and subventricular zones are thickest, and the nuclear PCNA label is strongest, indicating that proliferation peaks at this stage. Thereafter, asymmetric division becomes the predominant mode of proliferation, with one daughter cell reentering mitosis and the other one migrating out. Towards late gestation, the ventricular and subventricular zones almost completely disappear and proliferation shifts towards the intermediate and subplate zones, where mainly glial cells are generated. A remnant of the subventricular zone with proliferative activity persists into adulthood. In general, proliferation follows a latero‐medial gradient in the neocortex lasting longer in its lateral parts. Apoptotic nuclei have been detected around week 5, occurring in low numbers in the ventricular zone at this stage. Apoptotic cell death increases around midgestation and then spreads throughout all cortical layers, with most dying cells located in the ventricular and subventricular zones. This spatial distribution of apoptosis extends into late gestation. During the early postnatal period, most apoptotic cells are still located in the subcortical layers. During early embryonic development, proliferation and apoptosis are closely related, and are probably regulated by common regulators. In the late fetal and early postnatal periods, when proliferation has considerably declined in all cortical layers, apoptosis may occur in neurons whose sprouting axons do not find their targets. Anat Rec 267:261–276, 2002.

Protective effects of Ginkgo biloba extract (EGb761) and its constituents quercetin and ginkgolide B against β-amyloid peptide-induced toxicity in SH-SY5Y cells

Ginkgo biloba extract EGb761 has been shown to protect against beta-amyloid peptide (Abeta)-induced neurotoxicity but the specific mechanisms remain unclear. In the present study, effects of EGb761 and two of its constituents, quercetin and ginkgolide B, on the cytotoxic action of Abeta (1-42) were tested with human neuroblastoma SH-SY5Y cells. We found that EGb761 was able to block Abeta (1-42)-induced cell apoptosis, reactive oxygen species (ROS) accumulation, mitochondrial dysfunction and activation of c-jun N-terminal kinase (JNK), extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt signaling pathways. Both quercetin and ginkgolide B may be involved in the inhibitory effects of EGb761 on JNK, ERK1/2 and Akt signaling pathways. Ginkgolide B also helped to improve mitochondrial functions but quercetin failed to show this effect. Additional experiments suggest that, protective effects of EGb761 against Abeta toxicity may be associated with its antioxidant and platelet activating factor (PAF) antagonist activities. Quercetin but not ginkgolide B is one of the constituents responsible for the antioxidant action of EGb761. Both quercetin and ginkgolide B may be involved in the PAF antagonist activity of EGb761. Overall, actions of individual EGb761 components provide further insights into direct mechanisms underlying the neuroprotective effects of EGb761.

Age related changes of various markers of astrocytes in senescence-accelerated mice hippocampus.

Astrocytes play a critical role in maintaining normal brain physiology during development and in adulthood, while to date the changes of astrocytes during aging and their effects on age-related functional decline have not been well understood. This study used immunohistochemistry, western blot, and reverse transcriptase polymerase chain reaction techniques to investigate the expression of glial fibrillary acidic protein (GFAP), glutamine synthetase (GS), and S100 beta proteins and mRNAs in the hippocampi of 3 months old and 16 months old senescence-accelerated-prone mice (SAMP8) and senescence-accelerated-resistant mice (SAMR1). The results showed significant age-related increases in both protein and mRNA levels of GFAP in the hippocampi of aged SAMP8 and SAMR1. As well, the GFAP of aged SAMP8 was significantly greater than that of aged SAMR1. However, no such increase was observed for either GS or S100 beta. These results suggested that GFAP, rather than GS or S100 beta, played a more important role in the age related deficits in learning and memory.

Serotonin 5-HT2A and 5-HT6 receptors in the prefrontal cortex of Alzheimer and normal aging patients

BackgroundIt has been hypothesized that alterations of the serotonergic system contribute to neuropsychiatric symptoms in Alzheimer disease (AD). Cellular expressions of the two serotonergic receptors 5-HT2A and 5-HT6 have therefore been determined by immunohistochemistry in the prefrontal cortex of patients with AD (n=6) and normal age-matched controls (n = 7).ResultsIn normal aging patients, 5-HT2A label was mainly observed in large pyramidal cells, but to a lesser extent also in small pyramidal cells and in stellate cells of cortical layers II-VI. In AD, a similar distribution was observed, but density of positive cells was significantly reduced by 33%. In aging control patients, the 5-HT6 receptor was expressed by pyramidal cells and occasional stellate cells, not only of layers II-V, but also of layer I, where a distinct label was observed in neurons and surrounding fibers. 5-HT6 receptor expression in AD patients had the same pattern, but was significantly decreased by 40%.ConclusionOur results indicate that a decline in neurons expressing 5-HT2A, but also 5-HT6 receptors may play a role in the etiopathology of neuropsychiatric symptoms in AD.

Ginkgo biloba extract in Alzheimer's disease: from action mechanisms to medical practice.

Standardized extract from the leaves of the Ginkgo biloba tree, labeled EGb761, is one of the most popular herbal supplements. Numerous preclinical studies have shown the neuroprotective effects of EGb761 and support the notion that it may be effective in the treatment and prevention of neurodegenerative disorders such as Alzheimer’s disease (AD). Despite the preclinical promise, the clinical efficacy of this drug remains elusive. In this review, possible mechanisms underlying neuroprotective actions of EGb761 are described in detail, together with a brief discussion of the problem of studying this herb clinically to verify its efficacy in the treatment and prevention of AD. Moreover, various parameters e.g., the dosage and the permeability of the blood brain barrier (BBB), impacting the outcome of the clinical effectiveness of the extract are also discussed. Overall, the findings summarized in this review suggest that, a better understanding of the neuroprotective mechanisms of EGb761 may contribute to better understanding of the effectiveness and complexity of this herb and may also be helpful for design of therapeutic strategies in future clinical practice. Therefore, in future clinical studies, different factors that could interfere with the effect of EGb761 should be considered.

Changes of the expression of 5-HT receptor subtype mRNAs in rat dorsal root ganglion by complete Freund's adjuvant-induced inflammation.

By using the reverse transcriptase polymerase chain reaction technique, the expression of 5-hydroxytryptamine (5-HT) receptor subtype mRNAs in the rat lumbar dorsal root ganglion (DRG) was investigated following unilateral injection of complete Freunds adjuvant (CFA) into the rat hind paw. The results showed that 5-HT(1A), 5-HT(1B), 5-HT(1D), 5-HT(1F), 5-HT(2A), 5-HT(3), 5-HT(4), 5-HT(5A) and 5-HT(7) receptor subtypes were present in the rat lumbar DRG. CFA injection resulted in a significant increase in mRNA level of 5-HT(1A), 5-HT(1B), 5-HT(1F), 5-HT(2A), 5-HT(3), 5-HT(4) and 5-HT(7) receptor subtypes and a marked induction of 5-HT(2C) subtype mRNA in the DRG. The present results suggest the important roles for these 5-HT receptor subtypes in generating peripheral nociceptive signaling and provide evidence to elucidate the mechanism of 5-HT in nociception.

Mice are prone to kidney pathology after prolonged ketamine addiction.

ICR mice were injected with ketamine for 1, 3 and 6 months and the kidneys and urinary bladders were excised and processed for histology. Starting from 1 month, all addicted mice showed invasion of mononuclear white cells, either surrounding the glomerulus or the other tubules in the kidney. The aggregation of these cells extended all the way to the pelvis and ureter. As well, in the urinary bladder, the epithelium became thin and there was submucosal infiltration of mononuclear inflammatory cells. Silver staining revealed a loss of nerve fibers amongst the muscles of the urinary bladder of the treated. Immunohistochemistry on choline acetyltransferase which is a marker for cholinergic neurons also demonstrated a decrease of those cells. We hypothesized that prolonged ketamine addiction resulted in the animals prone to urinary infection.