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Biomedical subjects

J Cheng

Publications and source records attributed to J Cheng.

At least 487 records · Page 27Linked to original sources
PubMed1989

Endoscopic placement of expandable metal stents for biliary strictures--a preliminary report on experience with 33 patients.

The main problem with palliative treatment of extrahepatic cholestasis with an endoscopic biliary endoprosthesis is clogging. One of the factors thought to be of importance is the diameter of the stent. In order to avoid being limited by the size of the instrumentation channel of the endoscope, expandable stents have been developed. In this article we report on our preliminary clinical experience with an endoscopically placed expandable metal stent ("Wallstent") in 33 patients with extrahepatic bile duct stenoses. When fully expanded, the stent has a diameter of 30 F and a length of 6.7 cm. It was possible to successfully place a stent in every patient. Clinical improvement was achieved in all patients except one. Two patients underwent elective surgery, while one died of renal failure. Another died of septic shock after 5 weeks, but no autopsy was performed. In conclusion, our initial experience with this stent shows that at least in the short term biliary drainage was excellent, with no complications of pancreatitis or hemorrhage. Longer follow-up than our 4 weeks is necessary to establish the position of this stent in comparison with the conventional endoprosthesis in the management of obstructive jaundice.

Aged↗
PubMed1989

Vagal stimulation decreases rate of left ventricular relaxation.

We determined the effects of vagal stimulation on the time constant (tau) of left ventricular isovolumic pressure decay and on the maximum rates of left ventricular pressure change (dP/dt) during contraction and relaxation in anesthetized dogs. In each dog, the atria were paced at a constant rate of 150 beats/min. We recorded left ventricular pressure waveforms in the absence (control) and in the presence of vagal stimulation at frequencies of 1, 2, and 3 Hz. During the control periods and during vagal stimulation at each frequency, we determined tau, the maximal rate of contraction, and the maximal rate of relaxation from left ventricular pressure waveforms recorded at medium (100 mmHg), high (130 mmHg), and low (73 mmHg) afterloads. Vagal stimulation at a frequency of 3 Hz increased tau by 23%. This effect of vagal stimulation on tau was most pronounced at the high afterload. Vagal stimulation at 3 Hz decreased the maximal rate of relaxation by 19%, but it decreased the maximal rate of contraction by only 8%. Thus vagal stimulation significantly decreased the rate of left ventricular relaxation and had a greater depressant effect on ventricular relaxation than on contraction.

Animals↗
PubMed1989

Analysis of submandibular gland sialograms in Sjögren's syndrome.

We report here the sialographic appearances of the submandibular gland in both primary and secondary Sjögren's syndrome (SS). In order to compare these with those of the parotid gland, we defined new criteria for the staging for SS based on the degree of depiction of the peripheral ducts. In 24 out of 74 cases the submandibular sialogram showed more advanced, destructive disease compared with the parotid. This study suggests that although SS involves the parotid gland first, it progresses in the submandibular gland more rapidly.

Adult↗
PubMed1989

Heat stroke: a clinical review of 27 cases.

Heat stroke is the most serious entity amongst the heat disorders. Whilst potentially fatal, it is preventable and salvageable. A retrospective study involving 27 patients admitted for exertional heat stroke to the Medical Unit, Toa Payoh Hospital, Singapore from January, 1984 to January, 1987 was carried out. These patients presented with a rectal temperature of greater than 40 degrees C and central nervous system disturbances. All were males and, except for three, were local born. All except two were below thirty years old. The patients were treated with a standard regime of IV fluids and sponging in the ICU. 19 patients (70.4%) presented in coma whilst abnormal behaviour, e.g. aggression and mental confusion was seen in the remainder. Fits were seen in only 5 patients (18.5%). Metabolic acidosis was seen in 93.3%. Hypokalaemia was present in 3 patients (11.1%). Of the enzymes, creatinine phosphokinase was elevated in all except 1 patient (mean: 4868.8, range: 146-28850). There were no deaths recorded in this series. Complications include reversible DIVC (3 instances), oliguric renal failure (4 instances) and residual neurological deficit (2 instances). 9 patients (39.1%) took more than 4 hours for the rectal temperature to attain 37.5 degrees C. All the above complications except for 1 instance of DIVC occurred in this group with delayed cooling. Heat stroke is a serious condition with serious complications and require prompt treatment.

Adolescent↗
PubMed1988

Brain neurotransmitters in glycine encephalopathy.

We measured neurotransmitter markers in autopsied brain of infants with glycine encephalopathy (GE). Because patients with GE develop intractable seizures, special attention was devoted to those neurotransmitter systems implicated in human epilepsy. Mean levels of glycine in the frontal cortex of GE patients were three times higher than control values. No abnormalities were observed for concentrations of gamma-aminobutyric acid (and related receptors), other major neurotransmitter amino compounds, or activities of cholineacetyltransferase and aspartate aminotransferase. Mean acetylcholinesterase activity was significantly elevated by 46%. As experimental data suggest, glycine markedly potentiates the action of the excitatory neurotransmitter glutamic acid. To the extent that the brain seizures in patients with GE can be explained by this mechanism, pharmacotherapy with excitatory amino acid antagonists may represent a new approach to the treatment of GE.

Amino Acid Metabolism, Inborn Errors↗
PubMed1988

In situ correlative immuno-identification of mononuclear infiltrates and invasive bacteria in diseased gingiva.

The purpose of this study was to identify and quantify mononuclear cells and invasive bacteria in consecutive histological sections in diseased gingiva. Gingival biopsies were obtained from sites displaying evidences of severe periodontitis (pocket depth greater than 5 mm, bleeding on probing) in six patients. Specimens were frozen and serially sectioned at 8 micron in a cryostat. Monoclonal antibodies (mAb) directed against membrane markers of mononuclear infiltrate cells and rabbit polyclonal sera against specific bacteria shown to be invasive in association with an immunoperoxidase technique and specific point quantification were used. The mAb panel included Leu 1 (Pan T), Leu 2a (T suppressor/cytotoxic), Leu 3a (T helper/inducer), Leu 6 (Langerhans/dendritic), Leu 7 (NK/K), Leu M3 (monocyte/macrophage), and B7 (B cell). This methodology allows for in situ per cent quantification of mononuclear cell subsets along with identification and quantification of invasive bacteria in the same gingival tissue site. This may be a practical approach to establish the relationship between bacterial invasion and cellular immune response by the host. This technique enabled the characterization of the mononuclear infiltrate in relationship to specifically identified invasive bacteria in diseased gingiva.

Actinobacillus↗
PubMed1988

[Histamine and lung cancer. II. Human lung cancer cell line and histamine].

Using tissue culture and biochemical technique, the effects of autacoid-histamine and histamine H-2 receptor's antagonist-cimetidine on human lung cancer cell line were studied. It was shown that histamine at the concentration of 1.8 x 10(-7) M stimulated proliferation of the lung cancer cells, but histamine at the concentration of 1.8 x 10(-4) M or cimetidine at 1.76 x 10(-7) M inhibited growth of the lung cancer cells. Relation between histamine, histidine decarboxylase, histamine formation capacity and tumor proliferation is discussed.

Adenocarcinoma↗
PubMed1987

Growth of myoblasts in lipoprotein-supplemented, serum-free medium: regulation of proliferation by acidic and basic fibroblast growth factor.

BC3Hl myoblast cells seeded at low density on gelatin-coated dishes and exposed to a 1:1 (vol/vol) mixture of Dulbecco's modified Eagle's medium and Ham's F12 medium, proliferate actively when exposed to high density lipoproteins (HDL), transferrin, insulin, and basic or acidic fibroblast growth factor (FGF). This serum-free medium combination supported cell multiplication at a rate equal to that of serum-supplemented medium, and at low cell input (10(3) cells/35-mm dish). It also allowed serial transfer of the cultures under serum-free conditions. HDL seems to promote cell survival and to act as progression factor allowing cells to divide when exposed to either basic or acidic FGF. When the potency of basic and acidic FGF were compared, acidic FGF was 20-fold less potent than basic FGF.

Animals↗
PubMed1987

Effect of a course in cancer prevention on students' attitudes and clinical behavior.

The long-term effects of a first-year medical school course in disease prevention focusing on cancer were studied. The authors hypothesized that students' increased knowledge of disease prevention principles would result in more positive attitudes toward aggressive treatment and prevention of cancer and a more frequent use of disease prevention techniques in clinical settings. On two occasions one to three years after the course, groups of students who took the course and groups that did not take the course responded to a test of knowledge of cancer, a cancer attitude survey, a clinical practice survey, and an evaluation of the course's relevance. Also, their clinical behavior was observed and coded during videotaped interviews of patients. While the students who took the course were more knowledgeable about cancer than their peers who did not, they did not have significantly more positive attitudes; nor were they significantly more likely to use prevention techniques in clinical settings. However, the more knowledgeable students--both those who took the course and the control students--had more positive attitudes than the less knowledgeable students. Those students who considered the course relevant to their training were more knowledgeable and had more positive attitudes toward cancer prevention than those who did not consider it relevant.

Attitude of Health Personnel↗
PubMed1987

Increased heart rate accelerates norepinephrine washout from normal myocardium.

We determined whether a change in heart rate affected the decay of the ventricular inotropic response to sympathetic stimulation in an experimental group and in a control group of anesthetized dogs. We induced complete heart block in each animal and paced the ventricles at rates of 90, 120, and 150 min-1 during two observation periods. In the experimental group, desipramine hydrochloride was given during the second period to block the neuronal uptake mechanism. The control animals did not receive desipramine during either period. The time required for the ventricular inotropic response to decay by 50% after cessation of a 2-min train of sympathetic stimulation was used as an index of the rate of norepinephrine washout from the myocardial interstitium. As we increased the pacing rate over the range of 90-150 min-1 in the experimental group, the mean decay half times (+/- SE) decreased by 36 +/- 4% (P less than 0.001) before desipramine and by 26 +/- 6% (P less than 0.001) in the presence of desipramine. These decrements in the decay half times were not significantly different from each other. The mean decay half times decreased by 36 +/- 4% (P less than 0.001) in the control dogs; the effects did not change appreciably from the first to the second observation period. We conclude that an increase in pacing frequency facilitates the washout of norepinephrine from the ventricular myocardium; this facilitation is equally pronounced regardless of whether the neuronal uptake mechanism is intact or suppressed.

Animals↗
PubMed1987

Surgery for neglected congenital torticollis.

Nineteen patients were operated on for congenital muscular torticollis after the age of 1 year. Tenotomy gave good results below 5 years of age and resection of the sternocleidomastoid muscle was satisfactory in most of the older children.

Adolescent↗
PubMed1986

Inhibition of excitatory neurotransmission with kynurenate reduces brain edema in neonatal anoxia.

Excitatory amino acid neurotransmitters have been implicated in fostering brain edema and neuronal death in ischemia. As both of these processes are involved in nervous system damage during neonatal anoxia, the effect of blockade of cell excitation with kynurenate upon brain water was studied following anoxic-ischemic brain injury in neonatal rats. Such treatment attenuated brain edema immediately after, and 24 h following anoxia-ischemia.

Animals↗
PubMed1986

Effect of fibroblast growth factor and lipoproteins on the proliferation of endothelial cells derived from bovine adrenal cortex, brain cortex, and corpus luteum capillaries.

Bovine adrenal and brain cortex and corpus luteum-derived capillary endothelial cells have been established in culture, taking advantage of their ability to proliferate at clonal density when maintained on extracellular matrix (ECM) coated dishes in the presence of serum supplemented medium. All three cell types formed at confluency a monolayer of small, tightly packed, contact inhibited cells that express factor VIII related antigen. Their proliferative response to basic and acidic FGF when cells were maintained on plastic and exposed to serum supplemented medium was similar to that previously reported for endothelial cells derived from large vessels, with acidic FGF being 30-fold less potent than basic FGF. Their requirement for high density lipoproteins and transferrin in order to proliferate actively when maintained on ECM-coated dishes and exposed to serum-free conditions was also similar to that previously reported for endothelial cells derived from large vessels. Heparin strongly reduced the proliferative response of capillary endothelial cells to either basic or acidic FGF, as well as their response to serum alone, regardless of whether cells were maintained on plastic or on ECM-coated dishes. The present data indicate that bovine endothelial cells derived from large or small vessels are indistinguishable in so far as their response to growth factors, plasma factors, and substrata are concerned.

Adrenal Cortex↗
PubMed1986

Heparin protects basic and acidic FGF from inactivation.

The ability of heparin or that of hexuronyl hexosaminoglycan sulfate (HHS-4) to protect basic or acidic fibroblast growth factor (FGF) from acid or heat inactivation has been analyzed. Both freshly prepared basic and acidic FGF stimulate the growth of baby hamster kidney (BHK-21) cells exposed to medium supplemented with transferrin and insulin. Freshly prepared basic FGF was 10 fold more potent than acidic FGF. The addition of heparin to the medium decreased the potency of basic FGF while it potentiated that of acidic FGF. Upon storage of FGF at -80 degrees C, a decline in potency of both basic and acidic FGF was observed. Heparin, when added to the medium, potentiated their activities, which became similar to that of freshly prepared basic FGF. In order to test whether heparin could protect basic or acidic FGF from inactivation, both mitogens were exposed to acid conditions (1% trifluoroacetic acid, pH 1.08, 2 h) or heat (65 degrees C, 5 min) which inactivate basic or acidic FGF. When exposed to such treatment in the presence of heparin or HHS-4, basic and acidic FGF retained their potency. The effect of heparin and HHS-4 on the bioactivity of basic and acidic FGF is truly of a protective nature, since they had no effect when added after inactivation of the mitogens. Potentiation of the bioactivity of the protected mitogens or of the inactivated one could only be observed when cells were exposed to high heparin or HHS-4 concentrations. This indicates that heparin and HHS-4, in addition to protecting FGF from inactivation, also acts at another locus, as yet unidentified.

Animals↗
PubMed1986

Effect of retina-derived basic and acidic fibroblast growth factor and lipoproteins on the proliferation of retina-derived capillary endothelial cells.

Retina-derived capillary endothelial (RCE) cells have been established in culture, taking advantage of their ability to proliferate at clonal density when maintained on extracellular matrix (ECM)-coated dishes in the presence of serum-supplemented medium. This cell type formed at confluence a monolayer of small, tightly packed, contact inhibited cells which expressed Factor VIII-related antigen. Both retina-derived basic and acidic fibroblast growth factors (FGF) were mitogenic when RCE cells were maintained on gelatin-coated dishes and exposed to serum-supplemented medium. Half-maximal stimulation of cell proliferation was observed with concentrations of 13 pg ml-1 for basic FGF and 2.5 ng ml-1 for acidic FGF. Maintaining RCE cells on extracellular matrix (ECM)-coated dishes greatly reduced their requirement for EGF in order to proliferate actively. Heparin strongly reduced the proliferative response of RCE cells to either basic or acidic FGF, as well as their response to serum alone, regardless of whether cells were maintained on gelatin or on ECM-coated dishes. When RCE cells maintained on ECM-coated dishes were exposed to defined medium, high density lipoproteins, transferrin, and FGF were required in order for these cells to proliferate actively.

Animals↗