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N Yu

Publications and source records attributed to N Yu.

At least 73 records · Page 4Linked to original sources
PubMed1995

Different roles for KinA, KinB, and KinC in the initiation of sporulation in Bacillus subtilis.

Activation (phosphorylation) of the transcription factor encoded by spo0A is essential for the initiation of sporulation in Bacillus subtilis. At least three histidine protein kinases are involved in the phosphorylation of Spo0A. Under some growth conditions, KinA was the primary kinase, but under other conditions, KinB had the more critical role. KinC was required for the initial activation of Spo0A, even in the presence of KinA and KinB.

Bacillus subtilis↗
PubMed1995

Tumor necrosis factor-alpha and interleukin-1 alpha enhance glucose utilization by astrocytes: involvement of phospholipase A2.

Cytokines can be produced within the nervous system by various cell types, including astrocytes, which secrete them in response to pathological processes such as viral infections. Astrocytes are known to play an important role in the homeostasis of the nervous system, in particular, by contributing to the regulation of local energy metabolism. We report that tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 alpha (IL-1 alpha) markedly stimulate glucose uptake and phosphorylation in primary cultures of neonatal murine astrocytes, as determined with [3H]-2-deoxyglucose ([3H]2DG). This effect is both concentration dependent, with observed EC50 values of 8 ng/ml for TNF-alpha and 30 pg/ml for IL-1 alpha, and time dependent, with a maximal response observed 24 hr after cytokine application. The effects of TNF-alpha and IL-1 alpha on glucose uptake and phosphorylation appear to be mediated by the phospholipase A2 signal transduction pathway. Evidence in support of this includes (i) inhibition by mepacrine, a phospholipase A2 inhibitor, of [3H]2DG uptake evoked by TNF-alpha and IL-1 alpha, and (ii) stimulation of [3H]arachidonic acid release by TNF-alpha and IL-1 alpha. Protein kinase C activation does not appear to be involved as the specific protein kinase C inhibitor Ro 31-7549 does not abolish TNF-alpha- or IL-1 alpha-induced increase in [3H]2DG uptake and phosphorylation. The additional glucose imported by astrocytes on exposure to TNF-alpha and IL-1 alpha is neither stored as glycogen nor released as glycolytically derived lactate, suggesting that it is processed through the tricarboxylic acid cycle or pentose phosphate pathway. These results demonstrate that TNF-alpha and IL-1 alpha can fundamentally perturb the energy metabolism of astrocytes, possibly impairing their ability to provide adequate energy substrates for neurons.

Animals↗
PubMed1995

[Amylopsin activator in the decoction of fried malt].

From the decoction of fried malt (Fructus Hordei Germinatus) a kind of amylopsin activator was extracted and distinguished as calcium nitrate (with small amount of sodium chloride). The existence of this activator may can be explain properly why the decoction is helpful to digestion.

Calcium Compounds↗
PubMed1995

[Endoscopic sinus surgery for chronic sinusitis in children].

Anatomical features show maxillary sinus to be most commonly involved during childhood chronic sinusitis. Fifty-one cases who failed to respond to medications and irrigation were selected to undergo the middle meatal antrostomy under endoscopy. The majority of them had maxillary sinusitis. 10 cases had middle turbinate edema and polyps. 6 had ethmoiditis. After operations, signs of headache eliminated in 20 cases, nasal obstruction in 43 cases and yellowish discharge in 37 cases. The operative results were satisfactory. It is demonstrated that endoscopic sinus surgery is an ideal therapy for the treatment of childhood chronic maxillary sinusitis at present.

Adolescent↗
PubMed1994

Studies on the extracellular polysaccharide from Agrobacterium radiobacter biovar I S-1231.

A strain S-1231 isolated from specimen of soil around Beijing area is gram-negative, non-sporing, motile by peritrichous flagella. It produces exopolysaccharide succinoglycan from carbohydrates as its carbon source but not starch and cellulose. Acid is produced during fermentation of glucose. Growing for 12-24 hr, the cells are rods 0.7-0.8 x 1.3-1.5 microns, round ended, single or in pairs. Colonies on nutrient agar plate are unpigmented, circular, raised, smooth and moist-glistening, edge entire. The organism produces 3-ketolactose and is unable to invade sunflower tissue. The G+C content of DNA is 62.8-63.4 mol%. The organism is referred to as Agrobacterium radiobacter. Moreover, the strain is oxidase-positive, catalase-positive, H2S-produce and can grow at 35 degrees C and 2% NaCl also. Litmus milk is alkalified. Thus, the organism was renamed Agrobacterium radiobacter biovar I. Component analyses showed that the exopolysaccharide (Agran-S) from A. radiobacter biovar I S-1231 consisted of D-glucose (69.1%), D-galactose (8.6%), pyruvic acid (9.5%) and succinic acid (10.5%). Methylation analyses revealed that the polysaccharide Agran-S contained following main structural units: (1-->3)-linked D-glucose (21.2%), (1-->3)-linked D-galactose (11.4%), (1-->6)-linked D-glucose (10.5%), (1-->4)-linked D-glucose (30.4%), (1-->4, 1-->6)-linked D-glucose (22.2%) and terminal D-glucose (4.3%). The -1H-NMR spectrum of the polysaccharide indicated that the linkages in the polymer are all beta-glycosidic. The IR spectra of the polysaccharide revealed the presence of ester linkage in polysaccharide Agran-S.

Bacterial Typing Techniques↗
PubMed1993

Arachidonic acid stimulates glucose uptake in cerebral cortical astrocytes.

Arachidonic acid (AA) has recently been shown to influence various cellular functions in the central nervous system. Here we report that AA increases, in a time- and concentration-dependent manner, 2-deoxy-D-[1-3H]glucose ([3H]2DG) uptake in primary cultures of astrocytes prepared from the cerebral cortex of neonatal mice. This effect is mimicked by an unsaturated fatty acid such as linolenic acid, while palmitic and arachidic acids, two saturated fatty acids, are inactive. Pharmacological agents that increase the endogenous levels of AA by stimulating AA release (melittin) or by inhibiting its reacylation (thimerosal) also promote [3H]2DG uptake by astrocytes. We also report that norepinephrine (NE) stimulates the release of [3H]AA from membrane phospholipids, with an EC50 of 3 microM; this effect is accompanied, with a temporal delay of approximately 4 min, by the stimulation of [3H]2DG uptake, for which the EC50 of NE is 1 microM. Since the cerebral cortex, the brain region from which astrocytes used in this study were prepared, receives a massive noradrenergic innervation, originating from the locus coeruleus, the effects of NE reported here further stress the notion that certain neurotransmitters may play a role in the regulation of energy metabolism in the cerebral cortex and point at astrocytes as the likely targets of such metabolic effects.

Animals↗
PubMed1993

Neurotransmitters regulate energy metabolism in astrocytes: implications for the metabolic trafficking between neural cells.

In recent years a vast array of experimental evidence has indicated the presence of functional receptors for neurotransmitters on nonneuronal cells, in particular astrocytes. The two neurotransmitters vasoactive intestinal peptide (VIP) and noradrenaline (NA) exert profound, receptor-mediated, metabolic actions on astrocytes. Thus both neurotransmitters stimulate glycogenolysis in primary astrocyte cultures, with EC50s of 3 and 20 nM respectively. Astrocytes display basal glucose utilization rates ranging between 3 and 9 nmol/mg prot/min, a value that is remarkably close to glucose utilization of cerebral cortical grey matter as determined by the 2-deoxyglucose autoradiographic technique. NA markedly enhances glucose uptake and phosphorylation by astrocytes, with an EC50 of 1 microM. The metabolic substrate that is released by astrocytes is predominantly lactate and not glucose. Since lactate can support neuronal activity and synaptic function in vitro, the possibility should be considered that glucose uptake by the brain parenchyma occurs predominantly into astrocytes which subsequently release lactate for the use of neurons.

Animals↗
PubMed1992

The 31S0-33P0 transition in the aluminum isotope ion 26A1+: a potentially superior passive laser frequency standard and spectrum analyzer.

The aluminum 26 isotope ion is proposed here as a possible candidate for a superior atomic clock. For this even isotope, the extraordinarily long lifetime of the 33P0 state offers a potential clock transition (31S0-33P0) linewidth of 300 microHz. The mF = 0 --> 0 transition has only a quadratic Zeeman shift approximately 4 x 10(-18) at 0.1 Gauss magnetic field, compared to approximately 10(-8) for the hydrogen maser. Electronic quadrupole moments vanish for both J and J' states and with them shifts due to electric field gradients. All shifts have been estimated and are orders of magnitude less than for Hg+ and Ba+, which are being studied as atomic clock elements.

Journal Article↗
PubMed1992

VIP receptor subtypes in mouse cerebral cortex: evidence for a differential localization in astrocytes, microvessels and synaptosomal membranes.

The binding characteristics of a monoiodinated form of vasoactive intestinal peptide (M-[125I]VIP) to the membranes of astrocytes, intraparenchymal microvessels and synaptosomes were analyzed in mouse cerebral cortex. Binding to astrocytes, studied in primary cultures, indicates the presence of a single class of high affinity binding sites with a Kd of 3.3 nM and a Bmax of 565 fmol/mg protein. The structurally related peptide secretin does not compete for sites labeled by M-[125I]VIP. In cultured astrocytes, VIP has been previously shown to promote glycogenolysis. Secretin, despite its lack of interaction with sites labeled by M-[125I]VIP, stimulates glycogenolysis with an EC50 of 0.5 nM, thus demonstrating the presence in astrocytes of functional secretin receptors independent from those for VIP. Trypsinization of the primary astrocyte cultures followed by replating as secondary cultures, reveals a second class of low affinity binding sites, with a Kd of 41.3 nM and a Bmax of 881 fmol/mg protein. Secretin does not compete for this class of low affinity binding sites either. Binding of M-[125I]VIP to intraparenchymal microvessels reveals the presence of two classes of binding sites with Kd of 1.4 and 30.3 nM, and Bmax of 7.1 and 73.8 pmol/mg protein, respectively. Similar to what is observed in primary or secondary astrocyte cultures, secretin does not interact with these sites. In this cell type VIP stimulates cAMP formation with an EC50 of 18 nM, while secretin is ineffective. Finally, in agreement with previous reports in rat and guinea pig cerebral cortex, two classes of binding sites are observed in synaptosomal membranes: a high affinity class with a Kd of 4.9 nM and a Bmax of 316 fmol/mg protein, and a low affinity class with a Kd of 42.8 nM and a Bmax of 1578 fmol/mg protein. In contrast to what is observed in non-neuronal membranes, in synaptosomal membranes, secretin effectively competes for sites labeled by M-[125I]VIP with an EC50 of approximately 150 nM. These results indicate that secretin may represent a useful tool to discriminate between neuronal and non-neuronal VIP binding sites, since it competes with M-[125I]VIP exclusively for the neuronal class of binding sites.

Animals↗
PubMed1991

Reduced chloramphenicol acetyltransferase activity observed with vectors containing an upstream SphI recognition sequence.

Chloramphenicol acetyltransferase (CAT) is the most commonly used reporter gene for studying the regulation of mammalian gene transcription. Some of the currently available CAT vectors contain the recognition sequence for the restriction endonuclease SphI within the multiple cloning site. This sequence introduces an ATG triplet that is out of frame with the initiation codon of the CAT gene. Transient expression of CAT fusion genes, constructed using three different cellular promoters, demonstrates that the presence of the upstream AUG triplet in the CAT transcript reduces CAT activity, presumably by interfering with the translation of the coding sequence. Deletion of the SphI site from each of the plasmids increased CAT activity between 4-fold and 5-fold. From these results, we conclude that upstream, out-of-frame ATG triplets must be avoided in order to achieve maximum expression of the reporter gene.

Base Sequence↗
PubMed1990

Reduction of vinblastine neurotoxicity in mice utilizing a collagen matrix carrier.

Vinblastine sulfate (VLB) suspended within a collagen matrix (CM) as a diffusion limiting drug delivery vehicle was examined in vitro, as well as in mouse subcutaneous and brain tumor models. Against RIF-1 and KHT subcutaneous tumors, there was enhancement of antitumor activity with intratumoral (i.t.) delivery of VLB when it was combined with CM and/or epinephrine (epi) provided as a vasoactive agent to limit diffusion of VLB away from the injection site. Furthermore, in pharmacokinetic studies an 3-fold enhancement of tumor exposure to drug (AUC) with the CM-formulation was observed relative to the administration of free VLB i.t. Craniotactic injection of VLB into mouse brain in doses from 0.2 to 2 mg/kg revealed that the CM association markedly reduced the acute toxicity of VLB in normal mouse brain. Furthermore, mice with stereotactically implanted KHT brain tumors treated with 0.2 mg/kg VLB in CM had less tumor present in the brain histologically compared to the free VLB and untreated control groups.

Animals↗
PubMed1990

[A processing study of herba Cistanches].

The synthetic rate of DNA in the liver and spleen and metallic microelements have been determined for the different preparations of Herba Cistanches. The results show that the salted Herba Cistanches in steamed from affects the synthetic rate of DNA in "Yang-Deficiency" animal models, with trace elements Zn, Mn, Cu, and Fe higher in content than other traditional preparations.

Animals↗