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Biomedical subjects

G Cheng

Publications and source records attributed to G Cheng.

At least 199 records · Page 11Linked to original sources
PubMed1995

Determination of DLCO and cardiac output from expired gas slopes with cardiogenic oscillations.

Effects of 'cardiogenic oscillations' on alveolar plateau gas concentration slope measurements, constant expiratory pulmonary capillary blood flow, and DLCO determination have not been previously described. We examined cardiogenic oscillations during constant expiratory maneuvers to assess factors influencing magnitude of oscillations as well as effect of oscillatory phase at the start and end of exhalation measurement period on alveolar gas slope. Five normal volunteers performed repeated single breath constant exhalation vital capacity maneuvers using test gas containing 2 physiologically 'inert' gases: Helium (He Mw 4) and argon (Ar Mw 40). The mixture contained 3 absorbable gases, acetylene (C2H2 Mw 26), carbon monoxide (C18O Mw 30), and oxygen. Alveolar plateau slope, magnitude of cardiogenic oscillations, relative signal to noise ratios, and effect of cardiogenic oscillation phase on measured slope were determined for each gas. Cardiogenic oscillations were present for all inert gases. Oscillations were less evident for CO. However, the effects on calculated Qc and DLCO were negligible. Cardiac oscillations of considerable magnitude are seen during single breath constant exhalation maneuvers and affect constant expiratory gas slope calculations. Cardiogenic oscillation phase does not have a significant effect on measured Qc and DLCO using constant expiratory techniques.

Adult↗
PubMed1995

The effect of Roux-en-Y diversion on gastric and Roux-limb emptying in a rodent model.

BACKGROUND: The "Roux stasis syndrome" is characterized by symptoms of upper gut stasis following Roux-en-Y gastrojejunostomy (RG). Whether symptoms result from delayed gastric emptying, altered Roux-limb transit, or both has never been settled, partly because of the difficulty of measuring Roux-limb transit. The aim of this study was to develop a model to simultaneously quantitate Roux-limb transit and gastric emptying. METHODS: Rats underwent vagotomy and antrectomy with RG or Billroth II reconstruction (B-II). Gastrointestinal transit of a solid meal (Technetium-99m sulfur colloid-labelled egg white) was assessed 0.5, 1, and 1.5 hours postprandial (pp). Transit of a liquid marker (Na51-CrO4 injected through an efferent-limb catheter) was measured at 25 minutes pp. RESULTS: Solid gastric emptying was slower in RG than in B-II rats at 60 and 90 minutes pp. More of the solid meal and of the liquid marker was retained in the Roux limb than the efferent limb of the B-II at all time points (P < 0.05). CONCLUSIONS: In a rodent model, Roux-en-Y gastrojejunostomy is associated with delayed gastric emptying and slowed efferent-limb transit of solids and liquids.

Analysis of Variance↗
PubMed1995

Effect of axial ligation and delivery system on the tumour-localising and -photosensitising properties of Ge(IV)-octabutoxy-phthalocyanines.

Four Ge(IV)-octabutoxy-phthalocyanines (GePcs) bearing two alkyl-type axial ligands were assayed for their pharmacokinetic properties and phototherapeutic efficiency in Balb/c mice bearing an intramuscularly transplanted MS-2 fibrosarcoma. The GePcs were i.v. injected at a dose of 0.35 mumol kg-1 body weight after incorporation into either Cremophor emulsions or small unilamellar liposomes of dipalmitoyl-phosphatidylcholine (DPPC). Both the nature of the delivery system and the chemical structure of the phthalocyanine were found to affect the behaviour of the GePcs in vivo. Thus, Cremophor-administered GePcs invariably yielded a more prolonged serum retention and a larger association with low-density lipoproteins (LDLs) as compared with the corresponding liposome-delivered phthalocyanines. This led to a greater efficiency and selectivity of tumour targeting. These effects were more pronounced for those GePcs having relatively long alkyl chains (hexyl to decyl) in the axial ligands. Maximal tumour accumulation (0.67 nmol per g of tissue) was found for Ge-Pc(hexyl)2 at 24 h after injection. Consistently, the Ge-Pc(hexyl)2, administered via Cremophor, showed the highest phototherapeutic activity towards MS-2 fibrosarcoma.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1995

Divergent human papillomavirus type 16 variants are serologically cross-reactive.

It is not known whether DNA sequence variants of human papillomavirus type 16 (HPV-16) are distinct serotypes. To examine this question, the reactivities of women's sera from Zaire (n = 97) and Denmark (n = 123) were compared in IgG-specific ELISAs based on virus-like particles (VLPs) composed of the L1 major capsid protein derived from an HPV-16 variant common in central Africa (Z-1194) or one common in northern Europe (114K). These L1s differ in seven amino acids. There was a strong correlation between reactivity in the two assays for both sets of sera (correlation coefficients, 0.73 and 0.85 for Zairian and Danish sera, respectively). In only 1 serum was there evidence for a specific reaction to one but not the other VLP variant. The results support the conclusion that the virions of strains Z-1194 and 114K are serologically cross-reactive.

Cross Reactions↗
PubMed1995

Evaluation of the gel test for antibody screening in a tertiary hospital in Hong Kong; insensitivity for some cold antibodies that are reactive at 37 degrees C by conventional indirect antiglobulin tests.

The antiglobulin gel test (DiaMed) was compared with conventional IAT methods in pretransfusion antibody screening in a tertiary hospital in Hong Kong. Antibody titrations showed that the gel system was more sensitive than the tube IAT method in detecting anti-D, anti-S, anti-s, but slightly less sensitive with anti-E. The gel tests detected all clinically significant warm reacting allo-antibodies detected by conventional IAT methods except one case of weak anti-E. It detected a case of anti-C missed in conventional screening. The number of serological investigations due to false positive screens, non-specific antibodies and clinically insignificant cold antibodies (anti-P, and anti-Lewis) were reduced. The gel system was fast and easy to use. It would reduce delays and inconvenience caused to patients due to false positive screens and non-specific antibodies without compromising detection of clinically significant antibodies. However, of concern was the failure to detect several cases of anti-Le(a) and anti-P1 that were reactive at 37 degrees C by conventional IAT and one case of anti-H in a patient with Parabombay A.

Blood Grouping and Crossmatching↗
PubMed1995

Alpha-subunit of calcium/calmodulin-dependent protein kinase II enhances gamma-aminobutyric acid and inhibitory synaptic responses of rat neurons in vitro.

1. Here we report that in acutely isolated rat spinal dorsal horn neurons, the gamma-aminobutyric acid-A (GABAA) receptor can be regulated by calcium/calmodulin-dependent protein kinase II (CaM-KII). Intracellularly applied, the alpha-subunit of CaM-KII enhanced GABAA-receptor-activated current recorded with the use of the whole cell patch-clamp technique. This effect was associated with reduced desensitization of GABA responses. 2. GABA-induced currents are also potentiated by calyculin A, an inhibitor of protein phosphatases 1 and 2A. 3. Conventional intracellular recordings were made from hippocampal CA1 neurons in slices to determine the effect of intracellular application of CaM-KII on inhibitory synaptic potentials evoked by electrical stimulation of the stratum oriens/alveus. The inhibitory synaptic potential was enhanced by CaM-KII; this mechanism may contribute to long-term enhancement of inhibitory synaptic transmission and may also play a role in other forms of plasticity in the mammalian brain.

Animals↗
PubMed1995

The first example of anti-Gya detected in Hong Kong.

The incidence of anti-Gya is known to be extremely rare, and only a few examples have been reported in Japanese persons and in Caucasians. This case history reports the first example of anti-Gya detected in a Chinese person. The propositus is an 83-year-old male patient whose anti-Gya was revealed because of incompatibility of all units of blood tested by a saline indirect antiglobulin test (SIAT). Although the antibody had a titer of 512 by SIAT, 10 units of Gy(a+) red cells were transfused without any adverse effect.

Journal Article↗
PubMed1995

kappa-opioid receptor agonists modulate excitatory transmission in substantia gelatinosa neurons of the rat spinal cord.

This study examined the effects of selective activation of kappa 1-opioid receptors on excitatory transmission in substantia gelatinosa (SG) using intracellular recordings from SG neurons in transverse slices of the young rat lumbar spinal cord. Monosynaptic and polysynaptic excitatory postsynaptic potentials (EPSPs) were evoked by orthodromic electrical stimulation of A delta or C primary afferent fibers in the dorsal root after blocking inhibitory inputs with bicuculline and strychnine, NMDA receptors with D-2-amino-5-phosphonovaleric acid and mu- and delta-opioid receptors with CTAP and ICI 174,864, respectively. Bath application of dynorphin A1-17 or U-69, 593 caused dual modulation of the peak amplitude of presumed monosynaptic AMPA receptor-mediated EPSPs, decreasing synaptic potentials at nanomolar concentrations in a majority of SG cells examined (dynorphin, 63%; U-69,593, 91%), and increasing EPSPs at micromolar concentrations. Only the inhibitory action of dynorphin A1-17 was consistently and completely blocked by norbinaltorphimine (nor-BNI). Since U-69,593 and nor-BNI are selective for the kappa 1-opioid receptors, the depression of EPSPs is likely to be mediated by the kappa1-opioid receptors. Under conditions of blockade of synaptic transmission with TTX and mu-and delta-opioid receptors, dynorphin A1-17 and U-69,593 hyperpolarize most of SG neurons and decrease their membrane input resistance, the finding suggesting that direct interaction of kappa-agonists with a postsynaptic receptor is likely explanation for the inhibition of EPSPs. However, in some SG cells, the inhibition of EPSPs appears to be of presynaptic origin since dynorphin A1-17 and U-69,593 did depress the EPSPs in the absence of changes in passive membrane properties. Rp-cAMPS, a membrane permeant potent competitive inhibitor of cAMP-activated protein kinase, prevented the depressant effect of dynorphin A 1-17. This finding suggested a possibility that dynorphin A1-17, acting through a decrease in intracellular cyclic AMP levels, can reduce the synaptic responses of SG neurons. These results provide the first electrophysiological demonstration that the activation of kappa 1-opioid receptors inhibits AMPA receptor-mediated primary afferent neurotransmission in the substantia gelatinosa of the young rat spinal cord. This effect may mediate the ability of kappa-receptor agonists to produce antinociception.

Animals↗
PubMed1995

Photodynamic therapy of ocular melanoma with bis silicon 2,3-naphthalocyanine in a rabbit model.

PURPOSE: To investigate bis (tri-n-hexylsiloxy) silicon 2,3-naphthalocyanine (SINc; 0.5 mg/kg) for photodynamic therapy of an experimental ocular melanoma in pigmented rabbits. METHODS: SINc was dissolved in canola oil by heating, emulsified with Tween 80, and administered by ear vein. Pharmacokinetics were studied in frozen tumor sections by fluorescence microscopy using a charge coupled device, camera-based, low-light detection system with digital image processing at 1 and 24 hours. A Ti:sapphire laser and a microlens were used to deliver the light (770 nm; 40 mW/cm2; 20 J/cm2). A control rabbit received light without SINc. RESULTS: Localization studies of SINc showed intravascular distribution shifting to a tumor stromal and perivascular distribution 24 hours after treatment. Tissue thermal damage after irradiation was minimal in the control. Exudative retinal detachments were not observed. Tumor destruction was observed, with sharp demarcation to a depth of 3.5 mm. CONCLUSIONS: Tumor light penetration was good at 770 nm, and thermal effects from the exciting light alone were minimal. Photodynamic therapy with SINc resulted in localized tumor destruction reflecting the light beam path without damage to adjacent tissue or intraocular complications.

Animals↗
PubMed1995

[Micellar solubilized spectrophotometric determination of trace Mn2+ in rhizoma Zedoariae, fruit Amomi and herba Epimedii].

A green quaternary complex of manganese with o-phenanthroline (Phen), cetyltrimethylammoniun bromide (CTMAB) and chromazurol S (CAS) has been studied in the pH range of 10.10-10.80, with maximum absorption at 612nm and molar absorptivity being 8.79 x 10(4) L.mol-1.cm-1. Beer's law is obeyed in the range of 0-16 micrograms/25ml for manganese. The molar ratio for Mn-Phen-CTMAB-CAS in the complex is established to be 1:1:4:2. The influence of foreign ions and their elimination have also been studied.

Drugs, Chinese Herbal↗
PubMed1995

[Copper needle puncturing for the treatment of cavernous hemangioma].

From the beginning of 1990 to Oct. 1993, we have treated 31 patients with cavernous hemangioma using copper needle puncturing. Three months' to one and half years' follow-up showed positive effects in all cases. The paper describes general and local reaction of the treatment, the changes in blood copper concentration and echocardiography and complications.

Adolescent↗
PubMed1995

[Serum hepatitis B antigen-antibody system in patients with hepatocellular carcinoma].

Serum hepatitis B antigen-antibody system was detected by ELISA method in 150 patients suffering from hepatocellular carcinoma (HCC) with positive AFP. The overall infection rate of hepatitis B virus (HBV) was 86.0% (129/150). According to the antigens and antibodies to HBV, two major types of seven models could be demonstrated. In type I (including models 1 to 4) HBV infection was present in 81.9%, 74.6% among whom were considered to be of weak infectivity and 7.3% of strong one. In type II (including models 5 to 7) 18.0% (27/150) had no antigen and antibody to HBV was detected, indicating the absence of HBV infection. This study suggests that chronic infection with HBV is the major etiologic agent for human HCC and the patients with HCC often accompanied by active HBV replication.

Adult↗
PubMed1995

[Isolation and reassociation of acetogen and methanogen in a syntrophobic coculture degrading butyrate anaerobically].

Anaerobic coculture BF2 which degraded butyrate into acetate and produced methane was isolated from granular methanogenic sludge. The coculture is associated syntrophically the Syntrophomonas subsp. saponavida strain CF2 with Methanobacterium formicicum strain MF2 and appeared to degraded C4 approximately C18 fatty acids including isobutyrate. The optimal temperature and pH for growth was 37 degrees C and 7.7 respectively. The strain CF2 was obtained in pure culture with crotonate as substrate and produces acetate and butyrate. The doubling time of strain CF2 in crotonate media was about 20 hours. Strain CF2 is Gram negative, slightly curved 0.2 approximately 0.3 x 2.0 approximately 3.0 micron with round ends, motile by lateral flagellation at the concave side, non sporeforming. With a hydrogen scavenging organism, such as Methanospillum hungatei JF1, Methanobacterium formicicum 1535, Methanobrevibacterium bryantii 1125 and Desulfovibrio sp. B11, the strain CF2 paired up and the defined coculture degraded butyrate to acetate. When the strain CF2 associated with the original accompanist, Methanobacterium formicius strain MF2, the reassociated couculture degraded butyrate to acetate and produced methane again.

Butyrates↗
PubMed1994

Binding of Bruton's tyrosine kinase to Fyn, Lyn, or Hck through a Src homology 3 domain-mediated interaction.

Bruton's tyrosine kinase (Btk) is a recently described B-cell-specific tyrosine kinase. Mutations in this gene lead to human X chromosome-linked agammaglobulinemia and murine X-linked immunodeficiency. Although genetic evidence strongly suggests that Btk plays a crucial role in B-lymphocyte differentiation and activation, its precise mechanism of action remains unknown, primarily because the proteins that it interacts with have not yet been identified. Here, we show that Btk interacts with Src homology 3 domains of Fyn, Lyn, and Hck, protein-tyrosine kinases that get activated upon stimulation of B- and T-cell receptors. These interactions are mediated by two 10-aa motifs in Btk. An analogous site with the same specificity is also present in Itk, the T-cell-specific homologue of Btk. Our data extend the range of interactions mediated by Src homology 3 domains and provide an indication of a link between Btk and established signaling pathways in B lymphocytes.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1994

Block of induction and maintenance of calcium-induced LTP by inhibition of protein kinase C in postsynaptic neuron in hippocampal CA1 region.

Calcium-induced LTP (Ca-LTP) refers to the long-lasting potentiation of synaptic transmission in hippocampal synapses that can be induced by a transient (7-10 min) and small increase (from 2 mM to 4 mM) in extracellular calcium concentration. In this paper the effects of protein kinase C (PKC) inhibitors, polymyxin B (PMB) and PKC(19-31), given intracellularly to the postsynaptic neuron in the CA1 region, on the induction and maintenance of Ca-LTP were studied and compared with those found in a similar study earlier made in this laboratory on tetanic stimulation-induced LTP (TS-LTP) [18]. When the intracellular delivery of the inhibitor(s) was made to begin 30 min before the exposure to increased [Ca2+]0, the development of Ca-LTP was completely blocked, leaving only a brief enhancement of EPSPs directly attributable to the brief increase in [Ca2+]0. When the intracellular delivery of either PKC(19-31) alone or PMB+PKC(19-31) was made to begin after the full establishment of Ca-LTP, it soon made the maintained potentiation begin to decline, the EPSP amplitude gradually returning to the control value before the exposure to increased calcium. Thus postsynaptic PKC inhibition blocks both the induction and the maintenance of Ca-LTP, just as it has been shown to do to TS-LTP. But quantitative differences exist: both the induction and the maintenance of Ca-LTP appeared to be more susceptible to block by postsynaptic PKC inhibition than those of TS-LTP.

Animals↗
PubMed1994

Identifying the measurement noise in glaucomatous testing: an artificial neural network approach.

Diagnosis of visual function losses in glaucomatous patients depends to a large extent on the analysis of the data collected from corresponding psychophysical tests. One of the main difficulties in obtaining reliable data from patients in these tests is the measurement noise caused by the learning effect, inattention, failure of fixation, fatigue etc. Using Kohonen's self-organising feature map, we have developed a computational method to distinguish between the noise and true measurement and to provide an instant assessment of reliability of the computer-based visual function test. In particular we have experimented with 270 test records from glaucoma patients and glaucoma suspects and found that this method provides a satisfactory way of locating and rejecting noise in the test data, an improvement over conventional statistical methods. This method can also provide doctors with a clear view of the patient's behaviour during the test, thus assisting in their diagnostic decision making process.

Electricity↗