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Biomedical subjects

G Wu

Publications and source records attributed to G Wu.

At least 415 records · Page 23Linked to original sources
PubMed1997

[Injury effects of nicotine on isolated rat common carotid artery].

OBJECTIVES: To investigate the injured effects of nicotine on isolated rat common carotid artery and to supply experimental proofs for vascular vessel and organ transplantation. METHODS: Asins relaxing and contractile functional test of isolated vascular vessel and scanning electron microscopy techniques, we observed the influence of nicotine on the contractile and the relaxing function of isolated artery and the intact of the intima. RESULTS: Lower concentrations of nicotine (6 x-10 mol/L-6 x 10(-6) mol/L) produced a concentration-dependent constrictor response of 18%-41% relative to those induced by norepinephrine (NE, 10(-7) mol/L), whereas removal of endothelium reduced nicotine-induced constrictions to 5%-21%. Higher concentrations of nicotine (6 x 10(-5) mol/L-6 x 10(-3) mol/L) not only injured contractile function of vascular smooth muscle but also caused severe damage to the intima. Various concentrations of nicotine all inhibited acetylcholine-induced relaxation response. CONCLUSIONS: Nicotine not only has cytotoxicity to vascular vessel but also results in vasoconstrictor effects which depend upon endothelium intact, probably by inhibiting the release of endothelium-derived relaxing factor.

Animals↗
PubMed1997

[Follow-up study on children with obesity and hypertension].

OBJECTIVE: To study obesity development and its relationship between obesity and hypertension of children in China. METHOD: A 8-year follow-up study was conducted in 468 children aged 6 years by the criteria of hight, weight, thickness of skin fat and blood pressure. RESULTS: Obesity morbidity rose from 6 years (4.9%) to 13 years (16.2%), with the peak at 9 to 11 years. Both sexes developed obesity, which dominated in males. Children with obesity developed hypertension at age 13, the morbidity increased 3.5 times than that of those without obesity. CONCLUSION: Prevention of malnutrition is important in China but interventions to children with obesity in China are in urgent need.

Adolescent↗
PubMed1997

[Relation between fetal intrauterine growth retardation and anticardiolipin antibodies].

OBJECTIVE: To investigate the relationship between fetal intrauterine growth retardation and anticardiolipin antibodies. METHODS: Serum anticardiolipin antibodies were detected with ELISA method in 5,330 cases of normal gravidas. Meanwhile, the observation of immunocomplex depositions in placentas in cases of positive anticardiolipin antibodies (ACA) were observed by immunofluorescence examination. RESULTS: The positive ACA rate in normal gravidas was 2.70%. The incidence of intrauterine growth retardation (IUGR) was 15.28% in cases of positive ACA, whereas was 1.77% in cases of negative ACA. There were significant differences between two groups (P < 0.001). Among children born in mothers with positive ACA, there were 5 cases of positive ACA. Immunocomplex depositions (Immunoglobulins & Complements) were all found in placenta of IUGR. CONCLUSIONS: ACA could be one of causes of IUGR. Determination of serum ACA would offer a new clue to diagnosis and treatment of IUGR.

Adult↗
PubMed1997

[The study of DSX-I type microcomputer autometic control injector system].

This paper studies the propulsive force of injector system controlled by 8031 single-chip microcomputer for Medical use By using one 8031 single-chip microcomputer as a microprocessor, the minimal autometic control system is constructed, which turns real-time control into reality. This product is a modern appliance used in diagnostic imaging medicine, in design of which the advanced instrument and electrical machinery are integrated into a unified structure. The clinic data demonstrate that the contrast medium can be injected to patients with rapidly and evenly. Dynamic CT Scanning can be intensified at any site of the body. x-ray dose exposed and lobour intensity to the operator can be decreased greatly, raise working efficiency.

Automation↗
PubMed1997

[Spectral analysis of R-R intervals in adolesent persons during mental stress].

In this study, power spectrum analysis of the autoregressive model was used to quantitatively estimate the power spectrum of R-R intervals in adolesent during the state of the mental stress. The power spectrum density of the lower frequency (HF: 0.05-0.15 Hz) and the high frequency (HF: 0.15-0.5 Hz) component were acquired. The results showed that during the mental stress the HF component decreased significantly (P < 0.001) while the LF component increased relatively and the center frequency of the HF increased remarkably (P < 0.001). This suggests that the spectral analysis of heart rate variability (R-R interval) offers an efficient non-invasive method to assess the autonomic nerve activity of cardiovascular system during the stress condition.

Adult↗
PubMed1996

An important role for pentose cycle in the synthesis of citrulline and proline from glutamine in porcine enterocytes.

This study was designed to determine a role of pentose cycle in the provision of NADPH for the synthesis of citrulline and proline from glutamine in porcine enterocytes. Enterocytes from 4-day-old pigs were incubated at 37 degrees C for 0 to 30 min in Krebs-Henseleit bicarbonate buffer (pH 7.4) containing 2 mM glutamine and 5 mM glucose in the presence of 0, 0.1, or 0.25 mM dehydroepiandrosterone (DHEA), a potent inhibitor of glucose-6-phosphate dehydrogenase which is the key regulatory enzyme of pentose cycle. The activity of this cycle was estimated with the use of [1-14C]glucose and [6-14C]glucose. In some experiments, the medium included 2 mM ornithine and 2 mM NH4Cl (no glutamine). About 14% of glucose taken up by enterocytes was metabolized via pentose cycle. The flux from glucose into this cycle was decreased by 70 and 86%, respectively, in the presence of 0.1 and 0.25 mM DHEA compared with its absence. DHEA inhibited the synthesis of ornithine, citrulline, arginine, and proline from glutamine in a concentration-dependent manner, but had no effect on the formation of citrulline and arginine from ornithine. However, DHEA decreased the synthesis of proline from ornithine by 79%. DHEA had no effect on cellular ATP concentrations. These results provide the first line of evidence suggesting that glucose metabolism via pentose cycle plays an important role in providing NADPH for the conversion of glutamine into pyrroline-5-carboxylate in porcine enterocytes, which may explain the glucose-dependent synthesis of citrulline and proline from glutamine in these cells.

Adenosine Triphosphate↗
PubMed1996

Multiple action potential waveforms of single units in man as signs of variability in conductivity of their myelinated fibres.

Percutaneous microneurography was performed with concentric needle electrodes to record neural activity from myelinated fibres in human peripheral nerves. Template matching techniques were used together with interspike interval analysis and studies on functional class, receptive field characteristics, conduction velocities and other single fibre properties to classify single units. Sometimes the same fibres exhibited different action potentials at the same time. The potentials had some common features, but differed either in their waveform types or only in duration. There was a correlation between the occurrence of the different potential shapes and firing frequency of the studied unit. The outcome of the studies suggested that there was a common denominator which could explain the observations. Most likely, momentary fluctuations in excitability of the myelinated fibres occurring during the relative refractory period or the supernormal period were responsible for the variations in complexity of the studied units due to a partial block of fibre propagation probably caused by the recording electrode. Thus, action potentials deriving from the same axon may not always have the same shapes. Methods for unit classification, such as template matching, are discussed in the light of our findings.

Action Potentials↗
PubMed1996

Demonstration of a fibre afferents with overlapping receptive fields in humans.

According to previous data peripheral nerves may lack a detailed microanatomical organization. Nevertheless, stimuli within restricted skin areas might excite more than one afferent of the same modality. Since, as recently demonstrated, peripheral myelinated afferents are at least partially organized by both modality and somatotopy it might be possible to demonstrate such a phenomenon electrophysiologically provided that adequate procedures are used. To address this issue we recorded activity in single myelinated afferents supplying the hand with concentric needle electrodes. A combination of electrical and/or natural stimuli applied to the area where rapidly adapting (RA) or slowly adapting type I (SAI) fibres ended demonstrated that fibres of the same functional class may exhibit overlapping receptive fields in the skin.

Action Potentials↗
PubMed1996

Maturation of a central glutamatergic synapse.

Whole-cell recordings from optic tectal neurons in Xenopus tadpoles were used to study the maturation of a glutamatergic synapse. The first glutamatergic transmission is mediated only by N-methyl-D-aspartate (NMDA) receptors and is silent at resting potentials. More mature synapses acquire transmission by alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors. This maturational program is mimicked by postsynaptic expression of constitutively active calcium-calmodulin-dependent protein kinase II (CaMKII). Newly formed synapses may be silent unless sufficient depolarization is provided by coincident activity that could activate postsynaptic CaMKII, resulting in the appearance of AMPA responses.

Animals↗
PubMed1996

A survey of FRAXE allele sizes in three populations.

FRAXE is a fragile site located at Xq27-8, which contains polymorphic triplet GCC repeats associated with a CpG island. Similar to FRAXA, expansion of the GCC repeats results in an abnormal methylation of the CpG island and is associated with a mild mental retardation syndrome (FRAXE-MR). We surveyed the GCC repeat alleles of FRAXE from 3 populations. A total of 665 X chromosomes including 416 from a New York Euro-American sample (259 normal and 157 with FRAXA mutations), 157 from a Chinese sample (144 normal and 13 FRAXA), and 92 from a Finnish sample (56 normal and 36 FRAXA) were analyzed by polymerase chain reaction. Twenty-seven alleles, ranging from 4 to 39 GCC repeats, were observed. The modal repeat number was 16 in the New York and Finnish samples and accounted for 24% of all the chromosomes tested (162/665). The modal repeat number in the Chinese sample was 18. A founder effect for FRAXA was suggested among the Finnish FRAXA samples in that 75% had the FRAXE 16 repeat allele versus only 30% of controls. Sequencing of the FRAXE region showed no imperfections within the GCC repeat region, such as those commonly seen in FRAXA. The smaller size and limited range of repeats and the lack of imperfections suggests the molecular mechanisms underlying FRAXE triplet mutations may be different from those underlying FRAXA.

Alleles↗
PubMed1996

PKD2, a gene for polycystic kidney disease that encodes an integral membrane protein.

A second gene for autosomal dominant polycystic kidney disease was identified by positional cloning. Nonsense mutations in this gene (PKD2) segregated with the disease in three PKD2 families. The predicted 968-amino acid sequence of the PKD2 gene product has six transmembrane spans with intracellular amino- and carboxyl-termini. The PKD2 protein has amino acid similarity with PKD1, the Caenorhabditis elegans homolog of PKD1, and the family of voltage-activated calcium (and sodium) channels, and it contains a potential calcium-binding domain.

Amino Acid Sequence↗
PubMed1996

Trophic effect of cholera toxin B subunit in cultured cerebellar granule neurons: modulation of intracellular calcium by GM1 ganglioside.

Survival of cerebellar granule cells (CGC) in culture was significantly improved in the presence of cholera toxin B subunit (Ctx B), a ligand which binds to GM1 with specificity and high affinity. This trophic effect was linked to elevation of intracellular calcium ([Ca2+]i), and was additive to that of high K+. Survival was optimized when Ctx B was present for several days during the early culture period. 45Ca2+ and cell survival studies indicated the mechanism to involve enhanced influx of Ca2+ through L-type voltage-sensitive channels, since the trophic effect was blocked by antagonists specific for that channel type. Inhibitors of N-methyl-D-aspartate receptor/channels were without effect. During the early stage of culture Ctx B, together with 25 mM K+, caused [Ca2+]i to rise to 0.2-0.7 microM in a higher proportion of cells than 25 mM K+ alone. A significant change in the nature of GM1 modulation of Ca2+ flux occurred after 7 days in culture, at which time Ctx B ceased to elevate and instead reduced [Ca2+]i below the level attained with 25 mM K+. GM1 thus appears to serve as intrinsic inhibitor of one or more L-type Ca2+ channels during the first 7 days in vitro, and then as intrinsic activator of (possibly other) L-type channels after that period. This is the first demonstration of a modulatory role for GM1 ganglioside affecting Ca2+ homeostasis in cultured neurons of the CNS.

Animals↗
PubMed1996

The role of 5HT3 in nociceptive processing in the rat spinal cord: results from behavioural and electrophysiological studies.

Recent studies have suggested that activity at different 5HT receptor subtypes in the spinal cord either inhibits or facilitates nociceptive processing in the spinal cord. The present study has examined the role of 5HT3 receptors in nociceptive processing in the dorsal horn of the rat spinal cord. Using both behavioural and electrophysiological studies, 5HT3 ligands have been applied by a common route (i.e. intrathecal microinjection). In addition, only noxious heat has been used as a form of stimulation. Intrathecal injection of mCPBG (0.02-0.2 nmol) increased the responsiveness of dorsal horn neurones to noxious stimulation. In contrast, two 5HT3 antagonists (ICS 205-930 (0.015-0.15 nmol) and GR 380032F (ondansetron 34 nmol)) reduced nociceptive responses. Using doses which influenced nociceptive neuronal responses no significant change in TFL was recorded. These findings suggest that activation at 5HT3 receptor facilitates nociceptive responses of some dorsal horn neurones; these results are discussed in relation to earlier reports concerning alternative effects.

Animals↗
PubMed1996

In vitro transcription of the rat insulin-like growth factor-I gene.

Although the liver is the major source of circulating insulin-like growth factor-I (IGF-I), relatively little is known about the regulation of IGF-I gene transcription in this tissue. Since transcripts are initiated largely in exon 1, we established an in vitro transcription system to evaluate activation of transcription via the major exon 1 initiation site. Transcription of a G-free cassette reporter was directed by rat IGF-I genomic fragments, and the adenovirus major late promoter was used as an internal control. Tissue specificity was demonstrated by a 60-90% decrease in transcripts with spleen extracts as compared with liver. 54 base pairs (bp) of upstream sequence were sufficient to direct IGF-I gene transcription, and activity increased 5-fold with 300 bp of upstream sequence. DNase I footprinting revealed four protected regions between -300 and -60 bp; binding was confirmed by gel shift analysis, and tissue specificity was demonstrated by reduced shifts with spleen extracts. The necessity of transcription factor binding to such sites was established by competition analysis, which revealed a specific decrease in IGF-I transcription in the presence of a competing fragment. Use of this in vitro transcription system should permit analysis of the function of individual transcription factors involved in regulation of IGF-I gene expression.

Animals↗
PubMed1996

Platelet glycoprotein (Gp) IX associates with GpIb alpha in the platelet membrane GpIb complex.

The platelet membrane glycoprotein (Gp) Ib complex consists of four polypeptides: the disulfide-linked GpIb alpha and GpIb beta subunits; GpIX, tightly, but noncovalently associated with GpIb alpha-beta; and the more weakly associated GpV. It is not certain whether the association of GpIX to Gplb alpha-beta is via GpIB alpha, GpIb beta, or both subunits, although recently published evidence implicates an interaction with GpIb beta. We have investigated the interaction of GpIX with GpIb alpha-beta using polyclonal rabbit antibodies to GpIb alpha and GpIb beta raised by immunization with purified glycocalicin and with synthetic peptide sequences from GpIb beta, respectively, as well as monoclonal antibodies directed against GpIX (FMC-25) and against GpIb alpha (AP-1). We performed two types of experiments, using either purified GpIb complex or platelets. (1) When wells were coated with nonreduced GpIb complex, the binding of FMC-25 was inhibited 73% by GpIb alpha antibody, but only 30% by the GpIb beta antibody; when wells were coated with reduced complex, FMC-25 binding was inhibited by the same two antibodies by 86% and 13%, respectively. When wells were coated with polyclonal GpIb alpha or GpIb beta antibodies and then incubated with reduced GpIb complex, only wells coated with GpIb alpha antibodies captured GpIX reactivity. When wells were coated with FMC-25 and then incubated with nonreduced GpIb complex, both the GpIb alpha and GpIb beta polyclonal antibodies reacted strongly; in contrast, only GpIb alpha reactivity was retained when wells coated with FMC-25 were incubated with reduced GpIb complex. In the reciprocal experiment, AP-1-coated wells incubated with either nonreduced or reduced GpIb complex bound radiolabeled FMC-25. (2) The ability of polyclonal GpIb alpha and GpIb beta antibodies to inhibit binding of FMC-25 to platelets was studied by ELISA and by flow cytometry. In both systems, FMC-25 binding was inhibited by the GpIb alpha antibody, but not significantly by the GpIb beta antibody. We conclude that GpIX is strongly associated with GpIb alpha in the purified platelet GpIb complex and in the platelet membrane.

Blood Platelets↗
PubMed1996

Single unit discrimination among discharges from neighboring myelinated fibers in human peripheral nerves: improved unit identification by interspike interval analysis of nerve responses evoked by tactile stimuli.

Clustered rapidly adapting (RA) or slowly adapting type I (SA I) units recorded with concentric needle electrodes from median nerves of healthy human volunteers may exhibit overlapping receptive fields in the skin as also Paccini afferents (PC units) and slowly adapting type II unitary elements (SA II units) with their much larger innervation areas. Fundamental for the discrimination of such pairs of neighboring units in the nerve with overlapping peripheral fields was the refractory period of the studied fibers, which was assumed to be normal, i.e., of the order of 1-2 ms. When a unit belonging to one of the categories mentioned was found, it was activated by different tactile stimuli in the palm or fingers. Simultaneously, interspike interval analysis of the evoked responses was performed. In situations when the minimal interspike intervals were longer than the absolute refractory period of a single fiber the response derived from one single unit. Responses from at least two units were considered to contribute to the recorded sequences when computer analysis showed that the durations of the minimal intervals were shorter. In this way, the reported procedure facilitated the discrimination of both pairs of RA and SAI units and, in particular, pairs of neighboring PC or SA II units with overlapping receptive fields in human palmar skin.

Adolescent↗
PubMed1996

Fit fluctuating blood drug concentration: a beginner's first note.

In linear pharmacokinetics a blood drug concentration can be described and fitted using the equation of a sum of exponential functions, but this equation cannot exactly describe and fit a fluctuating (oscillating) blood drug concentration, which is a common phenomenon in clinical pharmacokinetic settings. Although a number of hypotheses have been provided for the phenomenon of a fluctuating blood drug concentration, a possible mathematical analysis has yet to be fully explored. In the present study we proposed several equations from other research fields to be used in pharmacokinetics. These equations contain decaying exponential sinusoidal functions and can theoretically fit a fluctuating curve. We used these equations to produce fluctuating curves. The results suggested that these equations might be suitable for use in pharmacokinetics. Furthermore, we demonstrated that the analytical solution of the differential equation system for a compartmental model can contain decaying exponential sinusoidal functions. We conclude that the analytical solution of the differential equation system for a compartmental model in pharmacokinetics is a sum of decaying exponential and sinusoidal functions rather than a sum of exponential functions, the latter one being only an approximate analytical solution of the differential equation system for a compartmental model.

Animals↗