Mutant presenilins of Alzheimer's disease increase production of 42-residue amyloid beta-protein in both transfected cells and transgenic mice

The mechanism by which mutations in the presenilin (PS) genes cause the most aggressive form of early-onset Alzheimer's disease (AD) is unknown, but fibroblasts from mutation carriers secrete increased levels of the amyloidogenic A beta 42 peptide, the main component of AD plaques. We established transfected cell and transgenic mouse models that coexpress human PS and amyloid beta-protein precursor (APP) genes and analyzed quantitatively the effects of PS expression on APP processing. In both models, expression of wild-type PS genes did not alter APP levels, alpha- and beta-secretase activity and A beta production. In the transfected cells, PS1 and PS2 mutations caused a highly significant increase in A beta 42 secretion in all mutant clones. Likewise, mutant but not wildtype PS1 transgenic mice showed significant overproduction of A beta 42 in the brain, and this effect was detectable as early as 2-4 months of age. Different PS mutations had differential effects on A beta generation. The extent of A beta 42 increase did not correlate with presenilin expression levels. Our data demonstrate that the presenilin mutations cause a dominant gain of function and may induce AD by enhancing A beta 42 production, thus promoting cerebral beta-amyloidosis.

cAMP activates MAP kinase and Elk-1 through a B-Raf- and Rap1-dependent pathway

Cyclic adenosine monophosphate (cAMP) has tissue-specific effects on growth, differentiation, and gene expression. We show here that cAMP can activate the transcription factor Elk-1 and induce neuronal differentiation of PC12 cells via its activation of the MAP kinase cascade. These cell type-specific actions of cAMP require the expression of the serine/threonine kinase B-Raf and activation of the small G protein Rap1. Rap1, activated by mutation or by the cAMP-dependent protein kinase PKA, is a selective activator of B-Raf and an inhibitor of Raf-1. Therefore, in B-Raf-expressing cells, the activation of Rap1 provides a mechanism for tissue-specific regulation of cell growth and differentiation via MAP kinase.

Rap1 mediates sustained MAP kinase activation induced by nerve growth factor

Activation of mitogen-activated protein (MAP) kinase (also known as extracellular-signal-regulated kinase, or ERK) by growth factors can trigger either cell growth or differentiation. The intracellular signals that couple growth factors to MAP kinase may determine the different effects of growth factors: for example, transient activation of MAP kinase by epidermal growth factor stimulates proliferation of PC12 cells, whereas they differentiate in response to nerve growth factor, which acts partly by inducing a sustained activation of MAP kinase. Here we show that activation of MAP kinase by nerve growth factor involves two distinct pathways: the initial activation of MAP kinase requires the small G protein Ras, but its activation is sustained by the small G protein Rap1. Rap1 is activated by CRK adaptor proteins and the guanine-nucleotide-exchange factor C3G, and forms a stable complex with B-Raf, an activator of MAP kinase. Rap1 is required for at least two indices of neuronal differentiation by nerve growth factor: electrical excitability and the induction of neuron-specific genes. We propose that the activation of Rap1 by C3G represents a common mechanism to induce sustained activation of the MAP kinase cascade in cells that express B-Raf.

Identification of a gene encoding a hyperpolarization-activated pacemaker channel of brain

The generation of pacemaker activity in heart and brain is mediated by hyperpolarization-activated cation channels that are directly regulated by cyclic nucleotides. We previously cloned a novel member of the voltage-gated K channel family from mouse brain (mBCNG-1) that contained a carboxy-terminal cyclic nucleotide-binding domain (Santoro et al., 1997) and hence proposed it to be a candidate gene for pacemaker channels. Heterologous expression of mBCNG-1 demonstrates that it does indeed code for a channel with properties indistinguishable from pacemaker channels in brain and similar to those in heart. Three additional mouse genes and two human genes closely related to mBCNG-1 display unique patterns of mRNA expression in different tissues, including brain and heart, demonstrating that these channels constitute a widely expressed gene family.

Rapid and visual detection of 2019 novel coronavirus (SARS-CoV-2) by a reverse transcription loop-mediated isothermal amplification assay

OBJECTIVE

To evaluate a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay for detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and compare it with RT-PCR.

METHODS

We designed primers specific to the orf1ab and S genes of SARS-CoV-2. Total viral RNA was extracted using the QIAamp Viral RNA Mini Kit. We optimized the RT-LAMP assay, and evaluated it for its sensitivity and specificity of detection using real-time turbidity monitoring and visual observation.

RESULTS

The primer sets orf1ab-4 and S-123 amplified the genes in the shortest times, the mean (±SD) times were 18 ± 1.32 min and 20 ± 1.80 min, respectively, and 63°C was the optimum reaction temperature. The sensitivities were 2 × 10¹ copies and 2 × 10² copies per reaction with primer sets orf1ab-4 and S-123, respectively. This assay showed no cross-reactivity with 60 other respiratory pathogens. To describe the availability of this method in clinical diagnosis, we collected 130 specimens from patients with clinically suspected SARS-CoV-2 infection. Among them, 58 were confirmed to be positive and 72 were negative by RT-LAMP. The sensitivity was 100% (95% CI 92.3%-100%), specificity 100% (95% CI 93.7%-100%). This assay detected SARS-CoV-2 in a mean (±SD) time of 26.28 ± 4.48 min and the results can be identified with visual observation.

CONCLUSION

These results demonstrate that we developed a rapid, simple, specific and sensitive RT-LAMP assay for SARS-CoV-2 detection among clinical samples. It will be a powerful tool for SARS-CoV-2 identification, and for monitoring suspected patients, close contacts and high-risk groups.

Mir-30 reduction maintains self-renewal and inhibits apoptosis in breast tumor-initiating cells

Accumulating evidence indicates that a sub-population of cancer cells with stem-like properties, termed tumor-initiating cells (T-ICs), exist in many different kinds of malignancies, which have a pivotal role in tumorigenesis, tumor progression, metastasis and post-treatment relapse. However, how the stem-like properties of T-ICs are regulated remains obscure. Our previous study showed that reduction of let-7 microRNA (miRNA) in breast tumor-initiating cells (BT-ICs) contributes to the maintenance of their self-renewal capacity and undifferentiated status. In this study we show the effect of mir-30 reduction on the stem-like features of BT-ICs. Similar to let-7, mir-30 is reduced in BT-ICs, and the protein level of Ubc9 (ubiquitin-conjugating enzyme 9) and ITGB3 (integrin beta3), the target genes of mir-30, is markedly upregulated. Enforced constitutive expression of mir-30 in BT-ICs inhibits their self-renewal capacity by reducing Ubc9, and induces apoptosis through silencing ITGB3. On the contrary, blocking the miRNA with a specific antisense oligonucleotide (ASO) in differentiated breast cancer cells revived their self-renewal capacity. Furthermore, ectopic expression of mir-30 in BT-IC xenografts reduces tumorigenesis and lung metastasis in nonobese diabetic/severe combined immunodeficient mice, whereas blocking mir-30 expression enhances tumorigenesis and metastasis. Together, our data suggest mir-30 as one of the important miRNAs in regulating the stem-like features of T-ICs.

A novel mitogen-activated protein kinase phosphatase. Structure, expression, and regulation

Mitogen-activated protein (MAP) kinase lies at the convergence of various extracellular ligand-mediated signaling pathways. It is activated by the dual-specificity kinase, MAP kinase kinase or MEK. MAP kinase inactivation is mediated by dephosphorylation via specific MAP kinase phosphatases (MKPs). One MKP (MKP-1 (also known as 3CH134, Erp, or CL100)) has been reported to be expressed in a wide range of tissues and cells. We report the identification of a second widely expressed MKP, termed MKP-2, isolated from PC12 cells. MKP-2 showed significant homology with MKP-1 (58.8% at the amino acid level) and, like MKP-1, displayed vanadate-sensitive phosphatase activity against MAP kinase in vitro. Overexpression of MKP-2 in vivo inhibited MAP kinase-dependent gene transcription in PC12 cells. MKP-2 differed from MKP-1 in its tissue distribution and in its extent of induction by growth factors and agents that induce cellular stress, suggesting that these MKPs may have distinct physiological functions.

Stimulus timing-dependent plasticity in cortical processing of orientation

The relative timing of presynaptic and postsynaptic spikes plays a critical role in activity-induced synaptic modification. Here we examined whether plasticity of orientation selectivity in the visual cortex depends on stimulus timing. Repetitive pairing of visual stimuli at two orientations induced a shift in orientation tuning of cat cortical neurons, with the direction of the shift depending on the temporal order of the pair. Induction of a significant shift required that the interval between the pair fall within +/-40 ms, reminiscent of the temporal window for spike timing-dependent synaptic plasticity. Mirroring the plasticity found in cat visual cortex, similar conditioning also induced a shift in perceived orientation by human subjects, further suggesting functional relevance of this phenomenon. Thus, relative timing of visual stimuli can play a critical role in dynamic modulation of adult cortical function, perhaps through spike timing-dependent synaptic plasticity.

Exosome-mediated shuttling of microRNA-29 regulates HIV Tat and morphine-mediated neuronal dysfunction

Neuronal damage is a hallmark feature of HIV-associated neurological disorders (HANDs). Opiate drug abuse accelerates the incidence and progression of HAND; however, the mechanisms underlying the potentiation of neuropathogenesis by these drugs remain elusive. Opiates such as morphine have been shown to enhance HIV transactivation protein Tat-mediated toxicity in both human neurons and neuroblastoma cells. In the present study, we demonstrate reduced expression of the tropic factor platelet-derived growth factor (PDGF)-B with a concomitant increase in miR-29b in the basal ganglia region of the brains of morphine-dependent simian immunodeficiency virus (SIV)-infected macaques compared with the SIV-infected controls. In vitro relevance of these findings was corroborated in cultures of astrocytes exposed to morphine and HIV Tat that led to increased release of miR-29b in exosomes. Subsequent treatment of neuronal SH-SY5Y cell line with exosomes from treated astrocytes resulted in decreased expression of PDGF-B, with a concomitant decrease in viability of neurons. Furthermore, it was shown that PDGF-B was a target for miR-29b as evidenced by the fact that binding of miR-29 to the 3′-untranslated region of PDGF-B mRNA resulted in its translational repression in SH-SY5Y cells. Understanding the regulation of PDGF-B expression may provide insights into the development of potential therapeutic targets for neuronal loss in HIV-1-infected opiate abusers.

New insight into deformation-dependent hydraulic permeability of gels and cartilage, and dynamic behavior of agarose gels in confined compression

Equilibrium, creep, and dynamic behaviors of agarose gels (2.0-14.8%) in confined compression were investigated in this study. The hydraulic permeabilities of gels were determined by curve-fitting creep data to the biphasic model (J. Biomech. Eng. 102 (1980) 73) and found to be similar in value to those published in the literature (AIChE J. 42 (1996) 1220). A new relationship between intrinsic permeability and volume fraction of water was found for agarose gel, capable of predicting deformation-dependent permeabilities of bovine articular cartilage and 2% agarose gel published in literature. This relationship is accurate for gels and cartilage over a wide range of permeabilities (four orders of magnitude variation). The dynamic stiffness of the gels increases with gel concentration and loading frequency (0.01-1.0Hz). The increase in dynamic stiffness with loading frequency is less pronounced for gels with higher concentrations. The results of this study provide a new insight into deformation-dependent permeability behavior of agarose gel and cartilage, and are important for understanding biological responses of cells to interstitial fluid flow in gel or in cartilage under dynamic mechanical loading.

Calcium and cAMP signals differentially regulate cAMP-responsive element-binding protein function via a Rap1-extracellular signal-regulated kinase pathway

Two major intracellular signals that regulate neuronal function are calcium and cAMP. In many cases, the actions of these two second messengers involve long term changes in gene expression. One well studied target of both calcium and cAMP signaling is the transcription factor cAMP-responsive element-binding protein (CREB). Multiple signaling pathways have been shown to contribute to the regulation of CREB-dependent transcription, including both protein kinase A (PKA)- and mitogen-activated protein (MAP) kinase/extracellular signal-regulated kinase (ERK)-dependent kinase cascades. We have previously described a mechanism by which cAMP and calcium influx may stimulate ERKs in neuronal cells. This pathway involves the PKA-dependent activation of the Ras-related small G-protein, Rap1, and subsequent stimulation of the neuronal Raf isoform, B-Raf. In this study, we examined the contribution of the Rap1-ERK pathway to the control of gene transcription by calcium influx and cAMP. Using the PC12 cell model system, we found that both calcium influx and cAMP stimulated CREB-dependent transcription via a Rap1-ERK pathway, but this regulation occurred through distinct mechanisms. Calcium-mediated phosphorylation of CREB through the PKA-Rap1-ERK pathway. In contrast, cAMP phosphorylated CREB via PKA directly but required a Rap1-ERK pathway to activate a component downstream of CREB phosphorylation and CREB-binding protein recruitment. These data suggest that the Rap1/B-Raf signaling pathway may have an important role in the regulation of CREB-dependent gene expression.

Time-resolved x-ray diffraction and calorimetric studies at low scan rates: I. Fully hydrated dipalmitoylphosphatidylcholine (DPPC) and DPPC/water/ethanol phases

The phase transitions in fully hydrated dipalmitoylphosphatidylcholine (DPPC) and DPPC/water/ethanol phases have been studied by lowangle time-resolved x-ray diffraction under conditions similar to those employed in calorimetry (scan rates 0.05-0.5 degrees C/min and uniform temperature throughout the samples). This approach provides more adequate characterization of the equilibrium transition pathways and allows for close correlations between structural and thermodynamic data. No coexistence of the rippled gel (P(beta')) and liquid-crystalline (L(alpha)) phases was found in the main transition of DPPC; rather, a loss of correlation in the lamellar structure, observed as broadening of the lamellar reflections, takes place in a narrow temperature range of approximately 100 mK at the transition midpoint. Formation of a long-living metastable phase, denoted by P(beta')(mst), differing from the initial P(beta') was observed in cooling direction by both x-ray diffraction and calorimetry. No direct conversion of P(beta')(mst) into P(beta') occurs for over 24 h but only by way of the phase sequence P(beta')(mst) --> L(beta') --> P(beta'). According to differential scanning calorimetry (DSC), the enthalpy of the P(beta')(mst)-L(alpha) transition is by approximately 5% lower than that of the P(beta')-L(alpha) transition. The effects of ethanol (Rowe, E. S. 1983. Biochemistry. 22:3299-3305; Simon, S. A., and T. J. McIntosh. 1984. Biochim. Biophys. Acta 773:169-172) on the mechanism and reversibility of the DPPC main transition were clearly visualized. At ethanol concentrations inducing formation of interdigitated gel phase, the main transition proceeds through a coexistence of the initial and final phases over a finite temperature range. During the subtransition in DPPC recorded at scan rate 0.3 degrees C/min, a smooth monotonic increase of the lamellar spacing from its subgel (L(c)) to its gel (L(beta')) phase value takes place. The width of the lamellar reflections remains unchanged during this transformation. This provides grounds to propose a "sequential" relaxation mechanism for the subgel-gel transition which is not accompanied by growth of domains of the final phase within the initial one.

The cyclic adenosine monophosphate-dependent protein kinase (PKA) is required for the sustained activation of mitogen-activated kinases and gene expression by nerve growth factor

Induction of neuronal differentiation of the rat pheochromocytoma cell line, PC12 cells, by nerve growth factor (NGF) requires activation of the mitogen-activated protein (MAP) kinase or extracellular signal-regulated kinase (ERK). cAMP-dependent protein kinase (protein kinase A (PKA)) also can induce differentiation of these cells. Like NGF, the ability of PKA to differentiate PC12 cells is associated with a sustained activation of ERKs. Here we show that maximal sustained activation of ERK1 by NGF requires PKA. Inhibitors of PKA partially blocked activation of ERK1 by NGF but had no effect on activation of ERK1 by EGF. Inhibition of PKA also reduced the ability of NGF and cAMP, but not EGF, to activate the transcription factor Elk-1, reduced the induction of both immediate early and late genes after NGF treatment, and blocked the nuclear translocation of ERK1 induced by NGF. We propose that PKA is an important contributor to the activation of ERK1 by NGF and is required for maximal induction of gene expression by NGF.

Complete genomic sequence and analysis of the prion protein gene region from three mammalian species

The prion protein (PrP), first identified in scrapie-infected rodents, is encoded by a single exon of a single-copy chromosomal gene. In addition to the protein-coding exon, PrP genes in mammals contain one or two 5'-noncoding exons. To learn more about the genomic organization of regions surrounding the PrP exons, we sequenced 10(5) bp of DNA from clones containing human, sheep, and mouse PrP genes isolated in cosmids or lambda phage. Our findings are as follows: (1) Although the human PrP transcript does not include the untranslated exon 2 found in its mouse and sheep counterparts, the large intron of the human PrP gene contains an exon 2-like sequence flanked by consensus splice acceptor and donor sites. (2) The mouse Prnpa but not the Prnpb allele found in 44 inbred lines contains a 6593 nucleotide retroviral genome inserted into the anticoding strand of intron 2. This intracisternal A-particle element is flanked by duplications of an AAGGCT nucleotide motif. (3) We found that the PrP gene regions contain from 40% to 57% genome-wide repetitive elements that independently increased the size of the locus in all three species by numerous mutations. The unusually long sheep PrP 3'-untranslated region contains a "fossil" 1.2-kb mariner transposable element. (4) We identified sequences in noncoding DNA that are conserved between the three species and may represent biologically functional sites.

Acetylation of adenovirus E1A regulates binding of the transcriptional corepressor CtBP

Adenovirus E1A mediates its effects on cellular transformation and transcription by interacting with critical cellular proteins involved in cell growth and differentiation. The amino terminus of E1A binds to CBP/p300 and associated histone acetyltransferases such as P/CAF. The carboxyl terminus binds to the carboxyl-terminal binding protein (CtBP), which associates with histone deacetylases. We show that 12S E1A can be acetylated by p300 and P/CAF and map one of the acetylation sites to Lys-239. This Lys residue is adjacent to the consensus CtBP binding motif, PXDLS. Mutation of Lys-239 to Gln or Ala blocks CtBP binding in vitro and disrupts the E1A-CtBP interaction in vivo. Peptide competition assays demonstrated that the interaction of E1A with CtBP is also blocked by Lys-239 acetylation. Supporting a functional role for Lys-239 in CtBP binding, mutation of this residue to Ala decreases the ability of E1A to block cAMP-regulated enhancer (CRE)-binding protein (CREB)-stimulated gene expression. Finally, we demonstrate that Lys-239 is acetylated in cells by using an antibody directed against an acetyl-Lys-239 E1A peptide. CtBP interacts with a wide variety of other transcriptional repressors through the PXDLS motif, and, in many instances, this motif is followed by a Lys residue. We suggest that acetylation of this residue by histone acetyltransferases, and the consequent disruption of repressor complexes, might be a general mechanism for gene activation.

The placentas of patients with severe acute respiratory syndrome: a pathophysiological evaluation

Aims

The pathology of the placentas delivered from pregnant women who had severe acute respiratory syndrome (SARS) in Hong Kong was studied.

Methods

The pathology of the placentas was retrospectively studied in detail and compared with control sets. The clinical data of the women and neonates were also reviewed.

Results

A total of seven placentas were studied. The placentas from two women convalescent from SARS in the first trimester were normal. In three placentas delivered in the acute stage of SARS, there were increases in intervillous or subchorionic fibrin which might be related to disturbances in maternal placental blood flow due to the hypoxic respiratory disease. Extensive fetal thrombotic vasculopathy (FTV) with sharply demarcated zones of avascular fibrotic villi was noted in the placentas of two patients convalescent from SARS in the third trimester. Both pregnancies had intrauterine growth retardation, oligohydramnios and newborns small for gestation. The aetiology of the FTV might be related to thrombotic tendency due to SARS or placental hypoxia.

Conclusions

This report highlights placental pathology that was probably the result of pathophysiological alteration of the maternal fetal unit during SARS. Further studies are required to delineate the relationship between severe maternal respiratory disease, placental pathology and pregnancy outcome.

Elevated plasma homocysteine levels and risk of silent brain infarction in elderly people

BACKGROUND AND PURPOSE

Silent brain infarction (SBI) on MRI is common in elderly people, and recent studies have demonstrated that SBI increases the risk of progression to clinically apparent stroke and cognitive decline. Therefore, an early and accurate detection of SBI and a search for potential treatable risk factors may have a significant impact on public health.

METHODS

Community-dwelling elderly people aged >/=66 years who participated in the present study (n=153) underwent brain MRI and standardized physical and neuropsychological examinations as well as blood biochemistry determinations, including total plasma homocysteine (pHcy), renal function, vitamin status, and polymorphisms of the methylenetetrahydrofolate reductase gene.

RESULTS

SBI was found in 24.8% of the participants. In the univariate analysis, the pHcy levels in subjects with SBI (13.6+/-4.1 micromol/L) were significantly higher (P=0.0004) than those in subjects without SBI (11.0+/-3.3 micromol/L). When pHcy levels were stratified into high (>/=15.1 mmol/L), moderate (11.6 to 15.0 mmol/L), and low (</=11.5 mmol/L) groups, age (P<0.0001), male sex (P<0.0001), the habits of cigarette smoking (P<0.0001) and of alcohol consumption (P=0.0002), and folate levels (P=0.01) were significantly associated with an elevation of pHcy levels. The elevated pHcy levels were significantly associated with SBI after individual adjustment for age, sex, hypertension, renal function, and the habits of smoking and alcohol consumption.

CONCLUSIONS

pHcy level is associated with age and nutritional and other lifestyle factors, and it contributes to a risk for SBI.

Ovariectomy exacerbates and estrogen replacement attenuates photothrombotic focal ischemic brain injury in rats

BACKGROUND AND PURPOSE

We previously reported the infarct volumes in female spontaneously hypertensive rats (SHR) to be significantly smaller than those in male SHR. The purpose of the present study was to determine whether estrogen is responsible for the sex difference in ischemic vulnerability in SHR.

METHODS

In experiment 1, 1 week (short-term) or 4 weeks (long-term) after the ovariectomy (OVX), female SHR (5 months old) were randomly subjected to photothrombotic occlusion of the middle cerebral artery, and the infarct volumes were determined. In experiment 2, the rats were randomly assigned to 3 groups (ie, the sham-ovariectomized, ovariectomized, and estrogen replacement groups). In the replacement group, estradiol valerate (200 microgram/kg) was subcutaneously injected once a week after the OVX. Four weeks after the OVX or sham-OVX, all rats were subjected to middle cerebral artery occlusion. Changes in regional cerebral blood flow were determined by laser-Doppler flowmetry.

RESULTS

In experiment 1, the infarct volume produced 1 week after the OVX was not different from that of the sham-ovariectomized group. In contrast, the infarct volume produced 4 weeks after the OVX was significantly larger than that of the sham-ovariectomized group (82.4+/-11.6 versus 54.5+/-16.0 mm(3), P=0.0058). In experiment 2, estradiol replacement after the OVX was observed to attenuate the infarct volume compared with the ovariectomized group (55.6+/-18.8 versus 78.5+/-21.0 mm(3), P=0.0321). The degrees of regional cerebral blood flow reduction did not differ among the sham-ovariectomized, ovariectomized, and estrogen replacement groups.

CONCLUSIONS

Chronic estrogen depletion was thus found to increase the infarct size, which was attenuated by estradiol replacement. These findings indicate that estrogen contributes to the sex difference in ischemic vulnerability and that endogenous estrogen also has a neuroprotective effect against ischemic brain damage.

Cerebral blood flow and oxygen metabolism in patients with vascular dementia of the Binswanger type

We performed clinical and neuroradiologic studies, including positron emission tomography, in five patients with vascular dementia of the Binswanger type. The clinical features of these cases consisted of slowly progressive dementia, together with vascular risk factors such as hypertension and often a history of minor stroke, and characteristic white matter lesions on brain computed tomograms or magnetic resonance images. Digital subtraction angiography of the cervical and intracranial arteries demonstrated no occlusive lesion in any patient. Both cerebral blood flow and the cerebral metabolic rate for oxygen were markedly reduced in the white matter (54-77% of control values), and both were decreased in the parietal (73% of control), frontal (74-80%), and temporal (74-83%) cortices, where no abnormalities were detected by brain computed tomography or magnetic resonance imaging. We conclude that vascular dementia of the Binswanger type may be caused by disconnection between the cerebral cortex and subcortical structures due to ischemic damage in the white matter.

Microbial Biomass and Community Structure in a Sequence of Soils with Increasing Fertility and Changing Land Use

The microbial biomass and community structure of eight Chinese red soils with different fertility and land use history was investigated. Two community based microbiological measurements, namely, community level physiological profiling (CLPP) using Biolog sole C source utilization tests and phospholipid fatty acid (PLFA) profiles, were used to investigate the microbial ecology of these soils and to determine how land use alters microbial community structure. Microbial biomass-C and total PLFAs were closely correlated to organic carbon and total nitrogen, indicating that these soil microbial measures are potentially good indices of soil fertility in these highly weathered soils. Metabolic quotients and C source utilization were not correlated with organic carbon or microbial biomass. Multivariate analysis of sole carbon source utilization patterns and PLFAs demonstrated that land use history and plant cover type had a significant impact on microbial community structure. PLFAs showed these differences more than CLPP methods. Consequently, PLFA analysis was a better method for assessing broad-spectrum community differences and at the same time attempting to correlate changes with soil fertility. Soils from tea orchards were particularly distinctive in their CLPP. A modified CLPP method, using absorbance readings at 405 nm and different culture media at pH values of 4.7 and 7.0, showed that the discrimination obtained can be influenced by the culture conditions. This method was used to show that the distinctive microbial community structure in tea orchard soils was not, however, due to differences in pH alone.

Paracrine signals from mesenchymal cell populations govern the expansion and differentiation of human hepatic stem cells to adult liver fates

The differentiation of embryonic or determined stem cell populations into adult liver fates under known conditions yields cells with some adult-specific genes but not others, aberrant regulation of one or more genes, and variations in the results from experiment to experiment. We tested the hypothesis that sets of signals produced by freshly isolated, lineage-dependent mesenchymal cell populations would yield greater efficiency and reproducibility in driving the differentiation of human hepatic stem cells (hHpSCs) into adult liver fates. The subpopulations of liver-derived mesenchymal cells, purified by immunoselection technologies, included (1) angioblasts, (2) mature endothelia, (3) hepatic stellate cell precursors, (4) mature stellate cells (pericytes), and (5) myofibroblasts. Freshly immunoselected cells of each of these subpopulations were established in primary cultures under wholly defined (serum-free) conditions that we developed for short-term cultures and were used as feeders with hHpSCs. Feeders of angioblasts yielded self-replication, stellate cell precursors caused lineage restriction to hepatoblasts, mature endothelia produced differentiation into hepatocytes, and mature stellate cells and/or myofibroblasts resulted in differentiation into cholangiocytes. Paracrine signals produced by the different feeders were identified by biochemical, immunohistochemical, and quantitative reverse-transcription polymerase chain reaction analyses, and then those signals were used to replace the feeders in monolayer and three-dimensional cultures to elicit the desired biological responses from hHpSCs. The defined paracrine signals were proved to be able to yield reproducible responses from hHpSCs and to permit differentiation into fully mature and functional parenchymal cells.

CONCLUSION

Paracrine signals from defined mesenchymal cell populations are important for the regulation of stem cell populations into specific adult fates; this finding is important for basic and clinical research as well as industrial investigations.

miR-27a regulates endothelial differentiation of breast cancer stem like cells

Recent studies suggested that cancer stem cells (CSCs) are capable of differentiating into endothelial cells and tumor endothelium may be derived from CSCs. But the mechanism remains unclear. We showed that vascular endothelial growth factor (VEGF) induced the expression of endothelial markers in breast cancer stem like cells (BCSLCs). In addition, the VEGF-treated BCSLCs formed capillary structure in matrigel and released vWF upon histamine treatment. The miR-27a expression was significantly increased in VEGF-treated BCSLCs. Antagonizing miR-27a by miR-27a anti-sense oligos (ASOs) in VEGF-treated BCSLCs led to decreased endothelial markers and function, while increasing miR-27a in BCSLCs resulted in enhanced endothelial properties. VEGF enhanced the transcription of miR-27a by increasing RUNX1 binding to miR-27a promoter. Increased miR-27a paralleled the reduced expression of ZBTB10, a known miR-27a target. Both expression of miR-27a and knockdown of ZBTB10 in BCSLCs promoted in vivo angiogenesis and tumor metastasis. Further, we demonstrated that VEGF-treated BCSLCs secreted more endogenous VEGF compared with undifferentiated BCSLCs. Thus, miR-27a promotes angiogenesis by mediating endothelial differentiation of BCSLCs and it may be a new target for anti-angiogenesis cancer therapy.

Intracellular pH regulation of CA1 neurons in Na(+)/H(+) isoform 1 mutant mice

To understand the role of Na(+)/H(+) exchanger 1 (NHE1) in intracellular pH (pH(i)) regulation and neuronal function, we took advantage of natural knockout mice lacking NHE1, the most ubiquitously and densely expressed NHE isoform in the central nervous system (CNS). CA1 neurons from both wild-type (WT) and NHE1 mutant mice were studied by continuous monitoring of pH(i), using the fluorescent indicator carboxy-seminaphthorhodafluor-1 (SNARF-1) and confocal microscopy. In the nominal absence of CO(2)/HCO(3)(-), steady-state pH(i) was higher in WT neurons than in mutant neurons. Using the NH(4)Cl prepulse technique, we also show that H(+) flux in WT neurons was much greater than in mutant neurons. The recovery from acid load was blocked in WT neurons, but not in mutant neurons, by removal of Na(+) from the extracellular solution or by using 100 microM 3-(methylsulfonyl-4-piperidino-benzoyl)-guanidine methanesulfonate (HOE 694) in HEPES buffer. Surprisingly, in the presence of CO(2)/HCO(3)(-), the difference in H(+) flux between WT and mutant mice was even more exaggerated, with a difference of more than 250 microM/s between them at pH 6.6. H(+) flux in CO(2)/HCO(3)(-) was responsive to diisothiocyanato-stilbene-2, 2'-disulfonate (DIDS) in the WT but not in the mutant. We conclude that (a) the absence of NHE1 in the mutant neurons tended to cause lower steady-state pH(i) and, perhaps more importantly, markedly reduced the rate of recovery from an acid load; and (b) this difference in the rate of recovery between mutant and WT neurons was surprisingly larger in the presence, rather than in the absence, of HCO(3)(-), indicating that the presence of NHE1 is essential for the regulation and/or functional expression of both HCO(3)(-)-dependent and -independent transporters in neurons.