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Biomedical subjects

Z Ding

Publications and source records attributed to Z Ding.

126 records · Page 7Linked to original sources
PubMed1991

Cystic echinococcosis in the Xinjiang/Uygur Autonomous Region, People's Republic of China. II. Comparison of three levels of a local preventive and control program.

A project to compare different levels of a hydatid disease control program was instigated and evaluated in 16 randomly selected villages in the Xinjiang/Uygur Autonomous Region, PRC (China). Factors tested included the effect of: 1) the role of a village hydatid disease control officer, 2) the use of praziquantel-medicated "bait" tablets for treatment of Echinococcus granulosus tapeworms in dogs, and 3) the use of educational materials for children and adults. Evaluation of contrasting treatment levels was done by determining infection rates of E. granulosus in about 25 dogs examined from each of the 16 villages before and after the trial period, and by use of pre- and post-treatment questionnaires distributed to 40 randomly selected households in each village. Optimum results were obtained in those villages which received medicated tablets and support visits from a control officer on a monthly basis (so-called "moderate intervention level").

Adolescent↗
PubMed1990

[Detection and significance of anti-pre S2 in patients with hepatitis B and HBsAg carriers].

We studied anti-Pre S2 by ELISA incorporating a synthetic peptide corresponding to the pre S2 (120-150) sequence and a monoclonal anti-human IgG, conjugated with peroxidase in 139 patients with hepatitis B and HBsAg carriers. The positive rate was 90% inpatients with acute-hepatitis 6.7% in chronic active hepatitis and 2.5% in persistent hepatitis. No positive case was seen in the HBsAg carriers. These findings indicate that anti-pre S2 may contribute to virus clearance and early diagnosis. The coexistence of anti-pre S2 with pre-S2 antigen was found only in patients with acute hepatitis, and anti-pre S2 may be coexistent with HBeAg in acute hepatitis, whereas all HBeAg positive patients with chronic hepatitis and HBsAg carriers lacked anti-pre S2. Comparing with anti-HBc IgM, anti-HBs and anti-HBe, anti-pre S2 is an earlier antibody in humoral immune response to HBV infection during the acute phase of hepatitis.

Adult↗
PubMed1990

Studies on medicamentous inhibitory therapy for esophageal precancerous lesions--3- and 5-year inhibitory effects of antitumor-B, retinamide and riboflavin.

Since 1983, we have been conducting inhibitory therapy for precancerous lesions of the esophagus in two regions of Henan Province considered high-risk areas of esophageal carcinoma. Our goal was to effect a 50% reduction in the canceration rate of marked esophageal dysplasia. By means of a cytological survey, 2531 cases of marked esophageal dysplasia and 3393 cases of mild esophageal dysplasia were selected. The former were randomly divided into 3 groups for antitumor-B (ATB, a mixture of Chinese herbs), retinamide (4-ethoxycarbophenylretinamide) and placebo treatment respectively, and the latter into 2 groups treated with riboflavin and placebo respectively. Treatment was continued for 3 or 5 years (administration rate greater than 90% in all groups) and esophageal cytology reexamined (reexamination rates were 94.1% and 92.5% respectively). Our results were as follows: 1) ATB 3- and 5-year subjects saw the canceration rate of marked esophageal dysplasia drop by 52.2% and 47.3% respectively as compared to control (P less than 0.01). 2) Retinamide lowered the canceration rate by 37.3% after a 3-year treatment period, with this reduction reaching 43.2% after an additional 2 years of treatment with increased dosages (P less than 0.05, P less than 0.01). 3) In the riboflavin group, the canceration rate of mild esophageal dysplasia was reduced by 22.2% and 34.8% after 3 and 5 years of treatment respectively, but these differences were not statistically significant. The above results verify the efficacy of medicamentous inhibitory therapy for esophageal precancerous lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[A pharmacognostical study on the fruits of Cnidium monnieri (L.) Cuss].

The fruits of three species are used as the Chinese drug "Shechuangzi", namely Cnidium monnieri, C. monnieri var. formosana and C. japonicum, among which only C. monnieri is the real sort. The authors have distinguished them by macroscopic and microscopic structures and TLC. The total coumarin, trace element and amino acid contents are reported.

Coumarins↗
PubMed1990

Cystic echinococcosis in the Xinjiang/Uygur Autonomous Region, People's Republic of China. I. Demographic and epidemiologic data.

Demographic and epidemiologic data on those factors potentially related to the prevalence and transmission of hydatid disease caused by Echinococcus granulosus were collected in 1987 from each household in 85 villages in the two communities of Yuanhucun and Ershilidian within Hutubi County in the Xinjiang/Uygur Autonomous Region, PRC, with additional questionnaire data collected from approximately 40 households randomly selected from each of 16 villages within those communities. Yuanhucun and Ershilidian represent a combined area of 522.7 square km, and have 4,853 households with 25,684 inhabitants. Of those households, 69.9% are of the Han ethnic group, 22.1% Hui, 5.3% Uygur, and 2.7% Kazak. The total number of animals censused included 4,169 dogs, 41,369 sheep, 3,673 goats, 2,639 cattle, 5,400 pigs, 1,472 horses, and 59 donkeys. Levels of infection of the causative organism of cystic hydatid disease in various hosts were: dogs harboring Echinococcus granulosus tapeworms - 63 (16.2%) positive of 390 examined in 16 villages; domestic animals with hydatid cysts - 1,593 (88.6%) sheep of 1,797 examined, 69 (56.1%) of 123 goats, and 47 (94.0%) of 50 cattle; and 15 surgeries in inhabitants from 85 villages during the last 16 months prior to completion of the survey (annual case rate of 43.8/100,000). Questionnaire data collected from inhabitants in 16 villages showed that about 82% of the families owned at least one dog and 78% owned sheep. Of those families with sheep, most (84%) killed sheep for meat at least periodically, 76% had seen hydatid cysts in liver or lungs of butchered animals, and 77% routinely gave raw offal to their dog.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Mechanistic investigation of smart polymer-protein conjugates.

Many affinity separation and diagnostic applications rely upon both capture and release steps. There is thus a need for methods to enhance the reversibility of biomolecular interactions. We have previously demonstrated that stimuli-responsive polymers can be used to gate biomolecular reactions when conjugated near the active site of proteins. Here we have used a new smart polymer, N,N-dimethyl acrylamide-co-4-phenylazophenylacrylate that has allowed a mechanistic investigation of the smart polymer switches. This polymer was conjugated via a vinyl sulfone terminus to cysteine residues of genetically engineered streptavidin mutant E116C, where the polymer is conjugated close to the biotin-binding site, and streptavidin mutant S139C, where the conjugation site is distant. The biotin binding switching activity was strongly dependent on conjugation position, as the E116C conjugate displayed a large thermal response while the S139C conjugate displayed only small effects. Kinetic measurements of biotin release demonstrated that the off-rate of biotin was unperturbed and that the thermally triggered release of biotin with the E116C conjugate was due to the blocking the reassociation of biotin. The addition of free polymer to purified E116C conjugates was also shown to increase the blocking and release properties of the switch. This effect was site dependent, suggesting that the conjugated polymers were directing a physical aggregation near the binding site that effectively enhanced the switching activity. These investigations provide mechanistic insight that can be utilized to design better molecular switches for a variety of stimuli-responsive polymer-protein conjugates.

Acrylates↗
PubMedDate not supplied

Synthesis and purification of thermally sensitive oligomer-enzyme conjugates of poly(N-isopropylacrylamide)-trypsin.

Using chain-transfer polymerization, we have synthesized oligomers of poly(N-isopropylacrylamide) [poly(NIPAAm)] with one carboxyl group at the end of each oligomer chain. The lower critical solution temperature (LCST) of the oligomers is very close to that of homo-poly(NIPAAm) lacking the end carboxyl group. The carboxyl groups were activated in methylene chloride using N,N'-dicyclohexyl-carbodiimide (DCC) and N-hydroxysuccinimide (NHS). A conjugate of trypsin with the preactivated oligomer has been prepared. We studied the effect of oligomer to enzyme (O/E) ratio in the feed on the O/E ratio of the conjugate (the average number of oligomer chains conjugated to one trypsin molecule), assuming that only the primary amino groups of lysine residues and the amino terminal of trypsin would react. The O/E ratio of the conjugate was estimated by determination of the remaining primary amine groups on the trypsin molecule. More than 95% of the conjugate can be recovered by thermally induced precipitation.

Acrylic Resins↗
PubMedDate not supplied

Temperature control of biotin binding and release with A streptavidin-poly(N-isopropylacrylamide) site-specific conjugate.

The many laboratory and diagnostic applications utilizing streptavidin as a molecular adaptor rely on its high affinity and essentially irreversible interaction with biotin. However, there are many situations where recovery of the biotinylated molecules is desirable. We have previously shown that poly(N-isopropylacrylamide) (PNIPAAm), a temperature-sensitive polymer, can reversibly block biotin association as the polymer's conformation changes at its lower critical solution temperature (LCST). Here, we have constructed a streptavidin-PNIPAAm conjugate which is able to bind biotin at room temperature or lower and release bound biotin at 37 degrees C. The conjugate can repeatedly bind and release biotin as temperature is cycled through the LCST. A genetically engineered streptavidin mutant, E116C, which has only one cysteine residue, was conjugated site specifically via the sulfhydryl groups with a PNIPAAm that has pendent sulfhydryl-reactive vinyl sulfone groups. The conjugation site is near the tryptophan 120 residue, which forms a van der Waals contact with biotin that is important in generating the large binding free energy. The temperature-induced conformational change of the polymer at position 116 may lead to structural changes in the region of tryptophan 120 that are responsible for the reversible binding between biotin and the conjugated streptavidin.

Acrylamides↗
PubMedDate not supplied

Thermoprecipitation of streptavidin via oligonucleotide-mediated self-assembly with poly(N-isopropylacrylamide).

A versatile strategy has been developed for selectively and sequentially isolating targets in a liquid-phase affinity separation environment. The strategy uses a recently developed approach for joining together molecules in linkages that are defined by the complementary pairing of oligonucleotides conjugated to the different molecules [Niemeyer, C. M., Sano, T., Smith, C. L., and Cantor, C. R. (1994) Nucleic Acids Res. 22, 5530-9]. In the work presented here, streptavidin was noncovalently coupled with the temperature-responsive poly(N-isopropylacrylamide) [poly(NIPAAM)] through the sequence-specific hybridization of oligonucleotides conjugated to the protein and polymer. A 20-mer oligonucleotide was covalently linked through a heterobifunctional linker to a genetically engineered streptavidin variant that contained a unique cysteine residue at the solvent-accessible site Glu 116. The complementary DNA sequence was conjugated to the end of a linear ester-activated poly(NIPAAM). The two conjugates were allowed to self-assemble in solution via hybridization of their complementary DNA sequences. The streptavidin-poly(NIPAAM) complex could be used to affinity-precipitate radiolabeled biotin or biotinylated alkaline phosphatase above 32 degrees C through the thermally induced phase separation activity of the poly(NIPAAM). The streptavidin-oligo species could then be reversibly separated from the precipitated polymer-oligo conjugate and recycled by lowering the salt concentration, which results in denaturation of the short double-stranded DNA connection. The use of oligonucleotides to couple polymer to streptavidin allows for selective precipitation of different polymers and streptavidin complexes based on the sequence-specific hybridization of their oligonucleotide appendages.

Acrylamides↗
PubMedDate not supplied

Site-specific polymer-streptavidin bioconjugate for pH-controlled binding and triggered release of biotin.

Low molecular weight copolymers of acrylic acid (AAc) and N-isopropylacrylamide (NIPAAm) have been synthesized with reactive OH groups at one end, using a chain transfer polymerization technique. The copolymer displays both pH and temperature sensitivity over a wide and useful range of pHs and temperatures, which permits both pH and temperature control of polymer conformation. This copolymer has been conjugated to a specific cysteine thiol site inserted by genetic engineering near the recognition site of streptavidin (SAv). In this paper, we demonstrate that this bioconjugate can provide pH control of biotin binding to and triggered release from the mutant SAv. These actions are relevant to affinity separations, biosensors, diagnostics, enzyme processes, and targeted delivery of drugs or chemical agents, labels, and other signals.

Acrylamides↗
PubMedDate not supplied

A rapid simplified purification of bovine thrombin.

A rapid simplified method was developed to obtain highly pure bovine thrombin. Prothrombin was directly activated when it was enriched from bovine plasma without prior purification. The activated thrombin was isolated by a single Heparin-Sepharose affinity chromatography step. About 87% of activated thrombin was recovered and the yield was 25.1 mg of thrombin per liter of starting plasma. Specific activity of the final preparation was 4018 NIH units/mg, representing a 402 fold purification over the starting material. Comparative experiments showed that the simplified method was about six times as effective as previous two-step methods.

Animals↗
PubMedDate not supplied

Orthotopic hepatic transplantation in the dog.

Orthotopic hepatic transplantation has become a well-established treatment modality for end-stage liver disease, and research in this field is constantly evolving. Of the 34 canine liver transplants performed in this study, 17 (50%) survived more than 3 days (mean survival time 15 days). Causes of perioperative death included hemorrhage (4), anesthetic complications (3), systemic anaphylaxis (3), portal vein thrombosis (3), hepatic venous outflow block (2), and hepatic artery thrombosis (2). Gentle handling with minimal dissection of the donor liver in situ resulted in a decreased incidence of hepatic venous outflow block. The incidence of biliary leak was similar irrespective of the method of biliary reconstruction, although the incidence of acute cholangitis was 56% in the cholecystoduodenostomy group compared with 0% in the choledochocholedochostomy cohort. Using celiac to common hepatic end-to-side arterial anastomosis with preservation of the gastroduodenal artery, thrombosis of the hepatic artery was encountered in four instances, an incidence similar to previously reported studies where end-to-end hepaticohepatic arterial anastomosis or donor aortic conduit was utilized. The incidence of postoperative intestinal intussusception was reduced from 40 to 0% in those who underwent transmesenteric intestinal plication following implantation of the liver. Among short-term survivors, sepsis was the most frequent noted complication (10), followed by intestinal intussusception (6), rejection (6), and gastrointestinal bleeding (1). Among recipient dogs that survived more than 3 days, rejection was the most common cause of graft loss (5), followed by biliary leak (4) and hepatic artery thrombosis (2).

Animals↗