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Biomedical subjects

S Y Liu

Publications and source records attributed to S Y Liu.

At least 19 recordsLinked to original sources
PubMed1992

Antitumor agents. 134. New shiraiachrome-A- and calphostin-C-related perylene derivatives as cytotoxic and antiviral agents and inhibitors of protein kinase C.

Shiraiachrome-A and -B have been isolated from the mycelium of the Chinese bamboo fungus Shiraia bambusicola as the cytotoxic principles. A series of new perylene derivatives (7-27) related to Shiraiachrome-A and -B as well as Calphostin-C have been synthesized and evaluated for their cytotoxicity, antiviral activity, and inhibitory activity against protein kinase C. The results indicated that 11 and 12 are potent cytotoxic agents against HCT-8, RPMI-7951, and TE-671 solid tumor cells, whereas 24 and 26 demonstrated strong antiviral activity against HSV-1 and HSV-2. Compound 10 is an inhibitor of protein kinase C.

Animals↗
PubMed1992

Antitumor agents. 123. Synthesis and human DNA topoisomerase II inhibitory activity of 2'-chloro derivatives of etoposide and 4 beta-(arylamino)-4'-O-demethylpodophyllotoxins.

The 2'-chloro derivatives of etoposide and 4 beta-(arylamino)-4'-O-demethylpodophyllotoxins have been synthesized and evaluated for their inhibitory activity against the human DNA topoisomerase II as well as for their activity in causing cellular protein-linked DNA breakage. The results showed that none of the compounds are active as a result of the C-2' chloro substitution on ring E. This would suggest that the free rotation of ring E is essential for the aforementioned enzyme inhibitory activity. In addition, these 2'-chloro derivatives showed no significant cytotoxicity (KB).

Antineoplastic Agents↗
PubMed1992

Effects of body position and age on membrane diffusing capacity and pulmonary capillary blood volume.

The effects of body position and age on the membrane diffusing capacity (Dm), pulmonary capillary blood volume (Vc), and the single breath carbon monoxide diffusing capacity (Dco) were evaluated in the erect (sitting) and supine positions in 16 normal young men (under 40 years old, younger group) and in 13 older men (over 40 years old, older group). Dm and Vc were estimated by several measurements of the Dco at increasing alveolar oxygen tension (PAO2). The results showed that Dco, Dm, Vc, and Kco (Dco corrected by alveolar volume) decreased with age in both positions. The differences in Dco, VC, and Kco between the two positions (supine minus the erect position) also decreased with age. The mechanisms of the increases in Dco in the supine position remain to be explained but may be due to a change in pulmonary capillary shape from an elliptical (erect position) to a circular configuration (supine position) since Vc increased more than Dm on assuming the supine position. The findings may be of clinical importance since many physicians have attempted to utilize a reduction in the positional change in Dco as a potential marker of disease.

Adult↗
PubMed1992

Accuracy of capnography in nonintubated surgical patients.

Previous studies have reported mixed results when correlating etCO2 and PaCO2 in mechanically ventilated patients with underlying respiratory disease. However, the utility and accuracy of capnography in nonintubated patients, without chronic pulmonary disease, has received little attention. We studied 25 nonintubated surgical patients to (1) examine the correlation between PaCO2 and etCO2 and (2) describe the relationship between dead space (VD/VT), venous admixture and P(a-et)CO2. End tidal CO2 was lower than PaCO2 by an average of 3.6 mm Hg. Regression analysis found a close correlation between dead space and the P(a-et)CO2 gradient (r = 0.77, p < 0.001), while venous admixture was of lesser importance (r = 0.47). Capnographic estimates of PaCO2 can be useful for continuously monitoring the respiratory status of nonintubated spontaneously breathing patients weaned from mechanical ventilation. This may be of particular value in trauma victims and in selected surgical patients without underlying respiratory disease in whom other injuries require continued critical care.

Adolescent↗
PubMed1992

Relationship between cardiovascular functions and ionic hypocalcemia induced by citrate infusion in anhepatic swines: CaCl2 therapy in severe ionic hypocalcemia.

Baseline and serial values of serum [Ca++], [K+], [Na+], arterial blood gas tensions, acid-base status, temperature and hemodynamic functions were measured during infusion of citrate-phosphate-dextrose (CPD) solution (0.35 ml.kg-1 x min-1) in anhepatic pigs of three randomized groups. Thirteen pigs (group I) continued to receive intravenous infusion of CPD solution until cardiac arrest. When mean arterial pressure (MAP) decreased to about 50 mmHg (group II, n = 7), or 40 mmHg (group III, n = 7) infusion of CPD solution was discontinued, and pigs received CaCl2 (20 mg/kg) intravenously. Serial (1, 4, 8, and 12 min after CaCl2 administration) values of all the above variables and serum citrate at baseline and lowest [Ca++] were measured. After hepatectomy and venovenous bypass, cardiac output (CO) decreased 30%. When ionic hypocalcemia was above 0.7 mM, there was no significant change of cardiovascular functions. When [Ca++] was between 0.34-0.7 mM, there were linear relationships between [Ca++] and CO, systemic vascular resistance (SVR) and MAP, respectively. When [Ca++] was below 0.34 mM, cardiovascular functions decreased abruptly, and the pigs died at [Ca++] of 0.26 +/- 0.06 mM. When [Ca++] decreased to 0.36 +/- 0.06 mM and MAP to 50 +/- 4 mmHg, most hemodynamic functions could be reversed by calcium therapy. However, when [Ca++] decreased to 0.33 +/- 0.05 mM and MAP to 40 +/- 2 mmHg, hemodynamic functions could not be reversed by calcium therapy alone.

Animals↗
PubMed1992

[Isolation and identification of yibeissine].

A new steroidal alkaloid, yibeissine (II), with a know alkaloid (I) was isolated from the bulb of Fritillaria pallioiflora Schrenk by column chromatographic techniques. Their structures have been determined based on spectral and chemical data.

Alkaloids↗
PubMed1992

Effectors of hypercarbia during experimental pneumoperitoneum.

Hypercarbia occurs during laparoscopy with carbon dioxide (CO2) insufflation. This may be due to increased ventilatory dead space after expansion of the peritoneal cavity with impairment of diaphragmatic excursion, or to increased absorption of CO2 from the peritoneum. To separate these effects, the authors examined the consequences of different insufflating gases and of diminished tissue perfusion on hypercarbia and dead space during pneumoperitoneum. Helium was chosen as an alternate insufflating gas because it is both inert and minimally absorbed. Eight swine (18 to 20 kg) were anesthetized, paralyzed, and mechanically ventilated at constant minute volume. Pneumoperitoneum with helium was maintained at 15 mm Hg for 45 minutes. After desufflation and stabilization for 1 hour, pneumoperitoneum was repeated with CO2. The sequence was again repeated after hemorrhagic shock to constant mean arterial pressure of 50 mm Hg. Data was analyzed by analysis of variance; significance levels are P < 0.01 unless otherwise listed. Arterial PCO2 increased significantly with CO2 insufflation within 15 minutes in normotensive animals and within 30 minutes during hypotension. Arterial pH decrease with CO2 pneumoperitoneum was significant in both groups at 30 minutes. Mixed venous PCO2 also increased with CO2 pneumoperitoneum within 30 minutes. Hypotension did not alter these changes. No significant changes were seen with helium pneumoperitoneum. Neither helium nor CO2 pneumoperitoneum significantly altered dead space. The authors make the following conclusions: 1) Absorption of CO2 from the abdomen during CO2 pneumoperitoneum produces respiratory acidosis, which is not seen with helium insufflation; 2) Pneumoperitoneum does not significantly increase dead space with either gas; 3) Transperitoneal absorption of CO2 is only partly related to perfusion because significant hypercarbia occurs during hemorrhagic shock.

Absorption↗
PubMed1991

Effect of 4 beta-arylamino derivatives of 4'-O-demethylepipodophyllotoxin on human DNA topoisomerase II, tubulin polymerization, KB cells, and their resistant variants.

Six 4 beta-arylamino derivatives of 4'-O-demethylepipodophyllotoxin were examined for inhibitory activity against human DNA topoisomerase II and tubulin polymerization, their ability to generate protein-linked DNA breaks in cells, and their cytotoxicity toward the KB cell line and its VP-16- and vincristine-resistant variants. Five of these derivatives were 5- to 10-fold more potent than VP-16 as inhibitors of DNA topoisomerase II in vitro, and all of these derivatives could generate the same amount of or more protein-linked DNA breaks in cells than VP-16 at 1-20 microMs. Tubulin polymerization was inhibited by these compounds to different degrees in the order: podophyllotoxin greater than W73 greater than W87 greater than NPF greater than NPC greater than W68 greater than W38 greater than VP-16. These analogues were cytotoxic not only to KB cells but also to their VP-16-resistant and vincristine-resistant variants which showed decreased cellular uptake of VP-16 and a decrease in DNA topoisomerase II content or overexpression of MDR1 phenotype. These characteristics may cause these derivatives to have different spectrums of antitumor activity.

DNA Damage↗
PubMed1991

A new method for the study of the formation and transformation of calcium phosphate precipitates: effects of several chemical agents and Chinese folk medicines.

A simple method of assaying the formation of amorphous calcium phosphate and its transformation to hydroxyapatite using a conventional pH meter and recorder is described. Its validity was confirmed by direct assay of calcium consumption with atomic absorption spectrophotometry. The method was used to study substances which influence the formation of amorphous calcium phosphate and its transformation to hydroxyapatite, such as albumin, casein, chondroitin sulphate, phospholipid, ATP, Mg2+, Sr2+, pyrophosphate and several Chinese folk medicines.

Adenosine Triphosphate↗
PubMed1991

Amino acid sequence of a phospholipase A2 from the venom of Trimeresurus gramineus (green habu snake).

Two phospholipases A2, named phospholipases A2-I and A2-II, were purified to homogeneity from the venom of Trimeresurus gramineus (green habu snake). The complete amino acid sequence of phospholipase A2-I was determined by sequencing the native protein and the peptides produced by enzymatic (Achromobacter protease I, clostripain, and chymotrypsin) and chemical (hydroxylamine) cleavages of the S-pyridylethylated derivative of the protein. The protein consisted of 122 amino acid residues and was similar in sequence to phospholipases A2 from the venoms of crotalid snakes which belong to the category of Group II. A most striking feature of this protein is that tyrosine at the 28th position which is common in phospholipases A2 and is assumed to be a part of the Ca2(+)-binding loop is replaced by phenylalanine. Such replacement is the first finding in Group II phospholipases A2. Secondary structure compositions of phospholipase A2-I are similar to those of Crotalus atrox phospholipase A2. No appreciable Ca2(+)-induced difference spectrum was observed, due probably to the absence of the effective chromophoric groups in the neighborhood of the Ca2+ binding site although Ca2+ is bound with affinity similar to that for T. flavoviridis phospholipase A2.

Amino Acid Sequence↗
PubMed1991

Evaluation of root quality of Bupleurum species by TLC scanner and the liver protective effects of "xiao-chai-hu-tang" prepared using three different Bupleurum species.

A simple and quick quantitative analysis of saikosaponins a, c and d, the major bioactive principles contained in Bupleurum species, by TLC scanner is described. Results with Bupleurum kaoi, the species native to Taiwan, showed that the roots, rhizomes and aerial parts (leaves and stem) have greater quantities of saikosaponins than cultivated B. falcatum var. komarowi and imported B. chinense. The liver protective effects of water extracts of "Xiao-Chai-Hu-Tang" (XCHT), a mixture of seven crude drugs, prepared using roots of the three different Bupleurum species and aerial parts of B. kaoi and B. falcatum var. komarowi, were evaluated using CCl4-induced toxicity in rats. The acute increase of serum transaminase (SGOT and SGPT) levels caused by CCl4 administration (3.0 ml/kg, s.c.) was dramatically reduced when treated with XCHT prepared with the roots of B. kaoi. The histological metamorphoses such as fatty changes, ballooning degeneration, cell necrosis and lymphocyte and Kupffer cell increases around the central vein, were clearly decreased by XCHT prepared with B. kaoi. Furthermore, water extracts of aerial parts of both B. kaoi and cultivated B. falcatum var. komarowi decreased SGOT and SGPT levels and moderately reduced the pathological changes.

Animals↗
PubMed1991

Effect of pH buffer molecules on the light-induced currents from oriented purple membrane.

The effect of pH buffers on the microsecond photocurrent component, B2, of oriented purple membranes has been studied. We found that under low salt conditions (less than 10 mM monovalent cationic salt) pH buffers can dramatically alter the waveform of the B2 component. The effect is induced by the protonation process of the buffer molecules by protons expelled from the membrane. These effects can be classified according to the charge transition upon protonation of the buffer. Buffers that carry two positive charges in their protonated form add a negative current component (N component) to B2. Almost all of the other buffers add a positive current component (P component) to B2, which is essentially a mirror image of the N component. Buffers with a pK less than 5.5 have only a small positive buffer component. The pH dependence of the buffer effect is closely related to the pK of the buffer; it requires that the buffer be in its unprotonated form. The rise time of the buffer component increases with the concentration of the buffer molecules. All the buffer effects can be inhibited by the addition of 5 mM of a divalent cation such as Ca2+. Reducing the surface potential slows down the N component but accelerates the P component without affecting the amplitude of the buffer effect significantly. Many of the buffer effects can be explained if we assume that upon protonation of the buffer by a proton expelled from the membrane by light, the buffer molecules move toward the membrane. This backward movement of buffer molecules forms a counter current very similar to that due to cations discussed in Liu, S. Y., R. Govindjee, and T. G. Ebrey. (1990. Biophys. J. 57:951-963).

Bacteriorhodopsins↗
PubMed1991

Prospective analysis of cardiopulmonary responses to laparoscopic cholecystectomy.

This prospective study evaluates the extent and temporal course of the cardiorespiratory effects of CO2 during laparoscopic cholecystectomy in otherwise healthy patients. Sixteen patients (M:F = 3:13, average age = 40.2 +/- 14.1 years) were monitored with capnography, transesophageal cardiac output, continuous blood pressure, heart rate, and pulse oximetry. Arterial blood gases were obtained immediately before insufflation of the abdomen with CO2 and before desufflation. Average operative time was 137 +/- 13 minutes. Patients were paralyzed and mechanically ventilated. Minute ventilation was increased if EtCO2 exceeded 45 mmHg or rose by more than 12 mmHg from baseline. End tidal (EtCO2) and arterial CO2 (PaCO2) increased from 31.4 +/- 0.7 mmHg to 42.1 +/- 1.6 mmHg and 33.3 +/- 0.7 mmHg to 43.7 +/- 1.2 mmHg, respectively, during the course of the procedure. Arterial pH decreased from 7.43 +/- 0.01 to 7.34 +/- 0.01, while bicarbonate concentration remained unchanged. Thirteen of the 16 patients required increased minute ventilation due to hypercarbia detected by capnography. Blood pressure increased from 78 +/- 2 mmHg (mean) at the start to 98 +/- 2 mmHg. This increase was coincidental with the maximal PaCO2. Good agreement was observed between paired EtCO2 and PaCO2 measurements. Laparoscopic cholecystectomy with carbon dioxide insufflation causes significant respiratory acidosis and associated cardiovascular changes in otherwise healthy patients. Careful monitoring and cautious application of this technique in patients with pre-existing cardiopulmonary disorders will be required to prevent acute decompensation.

Acidosis, Respiratory↗
PubMed1991

Cucurbitacin contents in Hemsleya dolichocarpa.

Hemsleya dolichocarpa was studied for its cucurbitacin contents during growing period. A colorimetric method was used to determine the total cucurbitacin levels, and a TLC densitometric assay was employed for estimating dihydrocucurbitacin F and its acetate, two active principles in Hemsleya plants. Cucurbitacin contents rise progressively from May to November; the month of November is thus the most desirable time for harvesting plant materials for medicinal uses. It was noticed that the spoiled plant samples gave an intense color reaction while dihydrocucurbitacin F and its acetate levels were not significantly altered. The accuracy of the assays is discussed.

Antineoplastic Agents, Phytogenic↗