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Biomedical subjects

Z X Lu

Publications and source records attributed to Z X Lu.

At least 37 records · Page 2Linked to original sources
PubMed1994

[Staged surgery in the treatment of Budd-Chiari's syndrome of mixed type].

9 patients with Budd-Chiari's syndrome of mixed type were operated upon. Among them 3 cases were treated by percutaneous transluminal angioplasty using balloon catheters, and 1 to 2 weeks after followed by Hassab's procedure and Linton's procedure. Two cases were treated by incision and plasty of IVC, and 1 month after followed by Hassab's procedure and Linton's procedure. The remaining 4 were treated by prehepatic cavoatrial shunt, succeeded by Hassab's procedure and Linton's procedure one month after. 6 to 24 months' follow up of the 9 cases revealed satisfactory results.

Adult↗
PubMed1994

[Anastomotic coarctation in the treatment of serious encephalopathy following splenosystemic shunt].

In this study, 11 cases of serious encephalopathy following splenorenal or splenocaval shunt were treated by anastomotic coarctation, in 4 of the 11 cases, portoazygos disconnection was added. All symptoms and signs disappeared soon after the procedure. The portal hepatopetal blood flow increased. Liver function improved. Blood ammonia concentration decreased. Follow-up of 6 to 48 months found, no recurrent encephalopathy or variceal bleeding. Anastomotic coarctation is effective method to treat serious post-splenosystemic shunt encephalopathy.

Adult↗
PubMed1993

Nucleotide sequence of a flower-specific MADS box cDNA clone from orchid.

An orchid (Aranda deborah) mature flower cDNA library was screened with an agamous cDNA probe from Arabidopsis. One positive clone for agamous gene was isolated, cloned and sequenced. This cDNA clone (om1) has a full length open reading frame of 750 bp corresponding to 250 amino acid residues. Comparison of om1 MADS box with that of its counterparts in tomato and Arabidopisis reveals significantly high homology (> 95%). Northern analysis indicated this gene is expressed in mature flowers and not in young developing inflorescences or young floral buds. In the mature flowers, it is only expressed in petals and weakly in sepals but not in the column (gynostemium).

Amino Acid Sequence↗
PubMed1992

Mutations at the dimer, hexamer, and receptor-binding surfaces of insulin independently affect insulin-insulin and insulin-receptor interactions.

Mutagenesis of the dimer- and hexamer-forming surfaces of insulin yields analogues with reduced tendencies to aggregate and dramatically altered pharmacokinetic properties. We recently showed that one such analogue, HisB10----Asp, ProB28----Lys, LysB29----Pro human insulin (DKP-insulin), has enhanced affinity for the insulin receptor and is useful for studying the structure of the insulin monomer under physiologic solvent conditions [Weiss, M. A., Hua, Q. X., Lynch, C. S., Frank, B. H., & Shoelson, S. E. (1991) Biochemistry 30, 7373-7389]. DKP-insulin retains native secondary and tertiary structure in solution and may therefore provide an appropriate baseline for further studies of related analogues containing additional substitutions within the receptor-binding surface of insulin. To test this, we prepared a family of DKP analogues having potency-altering substitutions at the B24 and B25 positions using a streamlined approach to enzymatic semisynthesis which negates the need for amino-group protection. For comparison, similar analogues of native human insulin were prepared by standard semisynthetic methods. The DKP analogues show a reduced tendency to self-associate, as indicated by 1H-NMR resonance line widths. In addition, CD spectra indicate that (with one exception) the native insulin fold is retained in each analogue; the exception, PheB24----Gly, induces similar perturbations in both native insulin and DKP-insulin backgrounds. Notably, analogous substitutions exhibit parallel trends in receptor-binding potency over a wide range of affinities: D-PheB24 greater than unsubstituted greater than GlyB24 greater than SerB24 greater than AlaB25 greater than LeuB25 greater than SerB25, whether the substitution was in a native human or DKP-insulin background. Such "template independence" reflects an absence of functional interactions between the B24 and B25 sites and additional substitutions in DKP-insulin and demonstrates that mutations in discrete surfaces of insulin have independent effects on protein structure and function. In particular, the respective receptor-recognition (PheB24, PheB25), hexamer-forming (HisB10), and dimer-forming (ProB28, LysB29) surfaces of insulin may be regarded as independent targets for protein design. DKP-insulin provides an appropriate biophysical model for defining structure-function relationships in a monomeric template.

Amino Acid Sequence↗
PubMed1989

Crystal structure determination of desheptapeptide (B24--B30)-insulin.

Desheptapeptide (B24--B30)-insulin (DHPI), an essentially inactive insulin analog, is crystallized in space group P212121 with two molecules in an asymmetric unit. The orientations of the molecules in the crystal cell have been determined by using Patterson search method at 6 A resolution and the positions of the molecules are deduced from translation function calculation and R search at 3 A resolution. After using the rigid body refinement (CORELS) further to refine the orientational and positional parameters as well as the initial energy restrained refinement (EREF) for the model, the crystallographic R value is reduced to 0.384 at 3 A resolution. The initial Fourier map shows that the B-chain N-terminal (B1-B8) and C-terminal (B20-B22) segments, compared with the native 2 zinc insulin, exhibit drastic conformational changes, but the three helices of B- and A-chains and their relative arrangement are essentially kept in DHPI.

Crystallography↗
PubMed1988

Properties of NAD glycohydrolase purified from five-pace snake (Agkistrodon acutus) venom.

NAD glycohydrolase (NADase) (E.C. 3.2.2.5) from five-pace snake (Agkistrodon acutus) venom was purified to electrophoretic homogeneity through a 4-step isolation procedure, including column chromatography using DEAE-Sephadex A-50, Sephadex G-75, CM Sephadex C-50 and Sephadex G-100. The final product was 11.8-fold purified with a 3.9% yield. The pure enzyme showed maximal activity at about 40 degrees C with optimal pH at 7.5. It was a glycoprotein with a pI of 7.6. Its mol. wt was respectively 98,000 as measured by gel filtration and 50,000, by SDS-PAGE. There was only one N-terminal residue, proline. NADase is thus composed of two identical subunits in each molecule. The enzyme contained copper ions. NADase activity was lost when the copper enzyme complex was treated with EDTA. The Km of the enzyme for beta-NAD, NADP and beta-NGP were 0.50 mM, 0.13 mM and 0.16 mM respectively.

Animals↗
PubMed1988

Transforming genes in duck hepatic carcinoma--mht(raf) and Ha-ras.

The transfection of NIH 3T3 cells was performed with DNAs from 2 duck primary hepatic carcinomas (DHC 40K, 9K) and 1 tumor-adjacent liver tissue (TAL, 9N). Transfectants were found from 40K, 9K and 9N DNAs. The secondary transfectants were obtained after transfection of RAT-1 cells with DNAs from primary transfectants. After hybridization with Ha-ras, Ki-ras, N-ras and mht oncogenes, it was found that duck mht (5.2 and 3.2 kb EcoRI fragments) and duck Ha-ras (3.4 kb EcoRI fragments) were present in all these transformants. This is the first report on transforming genes in duck primary hepatic cancer as well as tumor-adjacent liver tissue.

Animals↗
PubMed1986

Effect of amitraz on heart rate and aortic blood pressure in conscious dogs: influence of atropine, prazosin, tolazoline, and yohimbine.

The effect of amitraz on heart rate (HR) and mean aortic blood pressure (MAP) were studied in five conscious male dogs. An iv injection of amitraz (1 mg/kg) caused a decrease in HR, which was accompanied by sinus arrhythmia for at least 60 min. Administration of amitraz also caused an increase in MAP for 20 min. Atropine sulfate (0.045 mg/kg, iv) increased HR and prevented amitraz-induced bradycardia. In addition, atropine potentiated amitraz-induced hypertension for 45 min. Yohimbine, an alpha 2-adrenoreceptor antagonist, given iv at 0.1 mg/kg, prevented hypertension, bradycardia, and sinus arrhythmia induced by amitraz. Tolazoline, a nonselective alpha-adrenoreceptor antagonist, given iv at 5 mg/kg, reduced the bradycardia and sinus arrhythmia caused by amitraz administration but did not change amitraz-induced hypertension. Tolazoline alone also increased both HR and MAP. Prazosin, an alpha 1-adrenoreceptor antagonist, given iv at 1 mg/kg, did not affect the cardiovascular actions of amitraz. The results suggest that (1) alpha 2-adrenoreceptors mediate amitraz-induced bradycardia and hypertension, and (2) yohimbine, but not atropine, can be used to control the untoward reactions of amitraz.

Animals↗
PubMed1985

Effect of xylazine on heart rate and arterial blood pressure in conscious dogs, as influenced by atropine, 4-aminopyridine, doxapram, and yohimbine.

The effects of xylazine on heart rate (HR) and mean arterial blood pressure (ABP) were studied in 5 conscious male dogs. An IV injection of xylazine (1 mg/kg) caused a decrease in HR, which was accompanied by sinus arrhythmia. Xylazine administration also caused an initial increase in ABP, which was followed by a decrease. Atropine sulfate (0.045 mg/kg, IM) increased both the ABP and HR, but prevented xylazine-induced bradycardia only in 3 of 5 dogs. The other 2 dogs had to be given a supplemental dose of atropine sulfate (0.01 mg/kg, IV) before xylazine-induced bradycardia was antagonized. In addition, atropine sulfate potentiated xylazine-induced hypertension for 60 minutes. Yohimbine, an alpha 2-adrenoreceptor blocking agent, given IV at a dosage of 0.1 mg/kg, antagonized hypertension, hypotension, and bradycardia induced by xylazine. In addition, doxapram HCl, given IV at a dosage of 5.5 mg/kg, antagonized bradycardia but potentiated xylazine-induced hypertension, and an IV injection of 4-aminopyridine at a dosage of 0.5 mg/kg did not affect the cardiovascular actions of xylazine. It was concluded that atropine sulfate at the IM dosage of 0.045 mg/kg may be insufficient to antagonize xylazine-induced bradycardia but may potentiate xylazine-induced hypertension, and yohimbine may be useful in antagonizing these untoward reactions associated with xylazine administration. Doxapram and 4-aminopyridine were not found to be beneficial.

4-Aminopyridine↗
PubMed1985

Studies on the chemical modification of hemorrhagic toxin I from five pace snake (Agkistrodon acutus) venom.

The chemical modification of hemorrhagic toxin I (AaHI) from Agkistrodon acutus has been studied. Inactivation was observed upon modification of 3 out of 7 histidine residues with diethyl pyrocarbonate. The His residues are deblocked, accompanied by a return of activity, upon treatment with neutral hydroxylamine. The circular dichroism and fluorescence spectra of diethyl pyrocarbonate inactivated toxin and the native toxin are the same, indicating that modification with diethyl pyrocarbonate does not cause any gross change in the structure of the protein. At least one His residue may thus play an essential role in the enzyme activity. Reaction of the toxin with N-bromosuccimide abolished the enzyme activity, with modification of Trp, Tyr and His residues. The loss of Trp did not parallel the inactivation. Hydrogen peroxide, dioxane and 2-hydroxy-5-nitrobenzyl-bromide treatment damaged the Trp residues, but did not affect the activity. Therefore, the modified tryptophan side chains are not essential for activity. Modification of 2.5-3.0 Tyr residues out of 9 with acetylimidazole did not affect the enzyme activity, nor did nitration of the toxin with tetranitromethane. The reactive tyrosines are apparently not essential.

Amino Acids↗
PubMed1984

Effect of yohimbine on xylazine-ketamine anesthesia in cats.

Xylazine and ketamine are an anesthetic combination used in feline practice for routine surgical procedures. In a controlled study, we evaluated the effects of yohimbine, an antagonist of xylazine, on the anesthesia induced by this anesthetic combination in cats. Two intramuscular doses of xylazine and ketamine (2.2 mg of xylazine/kg plus 6.6 mg of ketamine/kg and 4.4 mg of xylazine/kg plus 6.6 mg of ketamine/kg) caused approximately 60 and 100 minutes of anesthesia, respectively, in control cats. When yohimbine (0.1 mg/kg) was given intravenously 45 minutes after ketamine administration, the cats regained consciousness within 3 minutes. They were ambulatory 1 to 2 minutes after regaining consciousness. Yohimbine also reversed the bradycardia and respiratory depression elicited by xylazine-ketamine. The results indicated that yohimbine may be useful for controlling the duration of xylazine-ketamine anesthesia in cats.

Anesthesia↗
PubMed1984

Conformational analysis of COOH-terminal segments of human C3a. Evidence of ordered conformation in an active 21-residue peptide.

Human C3a, a 77-residue fragment released during activation of the serum complement system, is a potent spasmogen that contracts a variety of smooth muscle tissues and enhances vascular permeability. Previous studies have suggested that a 5-residue, COOH-terminal segment of C3a constitutes the essential active site of this molecule; however, the pentapeptide is 1000-fold less active than C3a. Human C3a 57-77, a synthetic segment containing the 21 COOH-terminal residues of C3a, exhibits potencies nearly equivalent to those of natural C3a in several biologic assay systems. The circular dichroism spectra of synthetic peptides corresponding to sequences 57-77, 65-77, and 73-77 in human C3a were measured in water and trifluoroethanol. The CD spectra in the far-UV region indicate that each C3a peptide assumes a random coil conformation in aqueous solution with little evidence of alpha-helical structure. However, C3a peptide 57-77 assumes predominantly an alpha-helical conformation (47%) in 25% trifluoroethanol, while the shorter tridecapeptide 65-77 and pentapeptide 73-77 appear by CD to contain beta-turn conformations only Crystallographic analysis of human C3a indicated that the NH2-terminal portion of peptide 57-77 adopts an alpha-helical structure and that the COOH-terminal portion, including residues 73-77, contains an irregular fold much like a beta-turn. Since C3a peptide 57-77 exhibits activities qualitatively and quantitatively similar to natural C3a, we propose that this synthetic peptide adopts a helical conformation when bound to its cellular receptor which corresponds to that in the intact C3a molecule. Consequently, the NH2-terminal portion (residues 1-21) and the disulfide-linked core region (residues 22-57) in intact C3a serve primarily to stabilize ordered conformation in the COOH-terminal region (residues 58-77) and thereby orient side chains at the essential active site for optimal receptor interaction.

Amino Acid Sequence↗
PubMed1983

Conformation of Asn-Ala-Gly-Ala-Asn and its derivatives in solution--a CD spectra analysis.

The CD method has been used to study the conformation of the pentapeptide Asn-Ala-Gly-Ala-Asn (NAGAN) and the tetrapeptides Asn-Ala-Gly-Ala (NAGA) and Asn-D-Ala-Gly-Ala-NH2 (NDAGA) in solution. At low pH the far UV CD spectra of aqueous solutions of NAGAN show a positive extremum at 215 nm and a negative extremum at 232.5 nm. Under this condition, the molecule of NAGAN may assume a beta-turn structure. In the solution of 90% ethanol or tri-fluoroethanol at pH 5.8, NAGAN reveals CD spectra with a negative 218 nm extremum. The[theta]218 values are independent of the concentration of NAGAN. Au intramolecular beta-pleated sheet-like structure is suggested to explain the negative peak. The CD spectra of NAGA show a single positive band at around 215 nm. The possibility of forming a beta-turn by NAGA has been discussed. Only the 196 nm negative extremum can be seen in the spectra of NDAGA. It seems as if NDAGA is in the form of a random coil. According to the report made by Pan et al. all these peptides possess analgesic activity. Therefore, it seems that the analgesic activity is not related to the special conformation of the peptides.

Analgesics↗
PubMed1982

Purification and partial characterization of hyaluronidase from five pace snake (Agkistrodon acutus) venom.

A hyaluronidase (EC 3.2.1. 35) was isolated and purified from Agkistrodon acutus venom. The purification procedure included CM-Sephadex C-50 chromatography, gel-filtration on Sephadex G-75 and CM-Sephadex C-25 chromatography. The purified preparation of the enzyme was homogeneous on polyacrylamide gel electrophoresis at pH 4.3, a 45-fold purification being obtained. The hyaluronidase was a glycoprotein (positive PAS staining) with a molecular weight of 33,000 and a pI of 10.3. No hemorrhagic activity was found. The hyaluronidase had an optimum pH of 3.5-5.0 and an optimum temperature of 37 degrees C. It was heat sensitive, was more stable in the acidic than in the neutral region, and lost its activity in the alkaline region. Fe2+, Cu2+ and heparin inhibited the venom hyaluronidase. The Km value for hyaluronic acid was 6.2 X 10(-3) mg/ml.

Animals↗