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Biomedical subjects

L Zong

Publications and source records attributed to L Zong.

11 recordsLinked to original sources
PubMed2003

A review of microwave-assisted polymer chemistry (MAPC).

As a relatively new source of processing energy, microwave energy offers many compelling advantages in materials processing over conventional heat sources. These advantages include greater flexibility, greater speed and energy savings, improved product quality and properties, and synthesis of new materials that cannot be produced by other heating methods. Studies of microwave processing of polymeric materials in the early 1960s led to a successful industrial application in the rubber industry. Since the mid-1980's, there has been a great deal of interest in microwave processing of polymeric materials worldwide. The discipline can be categorized in two major fields: microwave-assisted polymer physics (MAPP) and microwave assisted polymer chemistry (MAPC). This paper offers an overview of the state-of-the-art research on the field of MAPC, including polymer processing (curing of thermosets, processing of thermoplastics, and joining), polymer synthesis, plasma modification of polymer surfaces, plasma polymerization, polymer degradation, and production of nanomaterials. Most of these studies have focused on laboratory-scale, exploratory efforts. Challenges and possible future directions for the commercialization of microwave processing technologies are discussed.

Biocompatible Materials↗
PubMed2001

P[Switch], a system for spatial and temporal control of gene expression in Drosophila melanogaster.

We have developed a method for turning on and off the expression of transgenes within Drosophila in both time and space. Two different enhancer detector elements carrying an RU486-inducible form of the yeast transcription factor GAL4 were constructed and used to generate enhancer detector lines. These lines were screened for RU486-inducible reporter gene expression in the adult head. We identified lines that exhibit inducible expression in many cell and tissue types, verifying that the elements respond to nearby enhancers. No expression was detected in the absence of the ligand. The P[Switch1] element responded to genomic enhancers less efficiently than P[Switch2] but produced more specific patterns of expression. Two P[Switch] lines were used to ablate fat body tissue in adult females through the induced expression of diphtheria toxin. These females were sterile, which correlates with fat body loss, and they died prematurely.

Animals↗
PubMed2001

[Association of human leukocyte antigen-DQA1 with endometriosis of women in southern China].

OBJECTIVE: To study the genetic susceptibility in patients with endometriosis by genotyping their human leukocyte antigen-DQA1 (HLA-DQA1) alleles. METHODS: The allelic types of HLA-DQA1 were detected by polymerase chain reaction single specific primers (PCR-SSP) technique in 51 patients with endometriosis proven by laparoscopy or histological examination, and 44 control women who had laparoscopic sterilization and without endometriosis. RESULTS: The frequency of HLA-DQA * 0401 allele (12%) in patients with endometriosis group was markedly higher than that in the control group (0%) (P = 0.019). Contrarily, the frequency of HLA-DQA1 * 0301 allele (39%) in control group was higher than that in endometriosis group (14%) (P = 0.005, odds ratio = 0.253). CONCLUSION: Our result indicated that HLA-DQA1 * 0401 may be a susceptible gene in correlation with endometriosis, whereas HLA-DQA1 * 0301 may be a protective gene against endometriosis.

Adult↗
PubMed2001

[Influence of planting density and precipitation on N2O emission from a winter wheat field].

To investigate the impact of plant density on N2O emission from winter wheat field and the cause of seasonal variation in the emission, field experiment with four planting rates of 0, 90, 180 and 270 kg/ha was conducted at the Jiangning County near Nanjing during 1999-2000 winter wheat growing season. Data of the field measurements indicated that the N2O emission rates during the season from planting to overwintering were not influenced by the plant density, while the emission was positively correlated with the planting density during the season from turning green to maturity. The emissions from the field plots with planting rates of 0 and 90 kg/ha were not found to be significantly different. A further analysis suggested that the seasonal variation of N2O emission be mainly influenced by precipitation, which could be quantitatively described by an exponential function of a weighted average precipitation of 6-day period before measurement.

Agriculture↗
PubMed1999

Metabolic fate of gallic acid orally administered to rats.

The metabolic behavior of orally administered gallic acid was investigated by HPLC and 4-O-methyl gallic acid was found to be the main metabolite in rat peripheral blood and urine. After oral administration of gallic acid, maximum concentration in portal vein and inferior vena cava occurred at 15 and 30 min, respectively. In portal vein, gallic acid was preferentially detected relative to 4-O-methyl gallic acid, whereas gallic acid and 4-0-methyl gallic acid were equally detected in inferior vena cava. On the other hand, 4-O-methyl gallic acid but not gallic acid was found in liver. The contents of gallic acid and 4-O-methyl gallic acid in urine were nearly 100 times higher than those in blood. The ratio of 4-O-methyl gallic acid to total gallic acid metabolites in urine was from 0.55 to 0.76, indicating that a considerable amount of gallic acid was excreted without being metabolized. In this study we found that gallic acid administered orally existed in the blood for 6 h at most, and more than half was metabolized to 4-O-methyl gallic acid, followed by excretion into urine.

Administration, Oral↗
PubMed1994

Insulin-like compounds related to the amphioxus insulin-like peptide.

Three insulin-like compounds consisting of two disulfide-linked polypeptide chains have been synthesized. The A-chains of these compounds correspond either to the A- or to the A + D-domain of the putative amphioxus insulin-like peptide (amphioxus ILP), and their B-chains correspond either to the B-chain of insulin or to a slightly modified (i.e., [1-Thr]) B-domain of amphioxus ILP. The biological potency of these compounds was evaluated in mammalian cells or cell fractions containing either human or rat insulin receptors or human or mouse insulin-like growth factor I (IGF-I) receptors, with respect to binding affinity, insulin-like metabolic activity (lipogenesis), and growth factor activity (mitogenesis). Amphioxus ILP A/bovine insulin B and amphioxus ILP A + D/bovine insulin B exhibited potencies ranging from 2.0 to 9.8% relative to natural insulin, and both compounds were full agonists in lipogenesis assays, stimulating lipogenesis to the same maximal extent as seen with natural insulin. Amphioxus ILP A/amphioxus ILP [1-Thr]B stimulated lipogenesis with a potency of 0.01% relative to natural insulin. We consider this compound also likely to be a full agonist. In assays measuring binding to IGF-I receptors and stimulation of mitogenesis, these compounds displayed some activity although the activity was too low for exact quantification. These results suggest that amphioxus ILP has retained an overall structural similarity to mammalian insulin and IGF-I but has also accumulated substantial mutations which markedly reduce its ability to bind and activate their cognate receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

3T3 Cells↗
PubMed1992

The A14 position of insulin tolerates considerable structural alterations with modest effects on the biological behavior of the hormone.

As part of our aim to investigate the contribution of the tyrosine residue found in the 14 position of the A-chain to the biological activity of insulin, we have synthesized six insulin analogues in which the A14 Tyr has been substituted by a variety of amino acid residues. We have selected three hydrophilic and charged residues--glutamic acid, histidine, and lysine--as well as three hydrophobic residues--cycloleucine, cyclohexylalanine, and naphthyl-(1)-alanine--to replace the A14 Tyr. All six analogues exhibit full agonist activity, reaching the same maximum stimulation of lipogenesis as is achieved with porcine insulin. The potency for five of the six analogues, [A14 Glu]-, [A14 His]-, [A14 Lys]-, [A14 cycloleucine]-, and [A14 naphthyl-(1)-alanine]-insulins in receptor binding assays ranges from 40-71% and in stimulation of lipogenesis ranges from 35-120% relative to porcine insulin. In contrast, the potency of the sixth analogue, [A14 cyclohexylalanine]insulin, in both types of assays is less than 1% of the natural hormone. The retention time on reversed-phase high-performance liquid chromatography for the first five analogues is similar to that of bovine insulin, whereas for the sixth analogue, [A14 cyclohexylalanine]insulin, it is approximately 11 min longer than that of the natural hormone. This suggests a profound change in conformation of the latter analogue. Apparently, the A14 position of insulin can tolerate a wide latitude of structural alterations without substantial decrease in potency. This suggests that the A14 position does not participate directly in insulin receptor interaction. Only when a substitution which has the potential to disrupt the conformation of the molecule is made at this position, is the affinity for the receptor, and hence the biological potency, greatly reduced.

Adipose Tissue↗
PubMed1990

Superactive insulins.

The substitution of aspartic acid for the naturally-occurring histidine residue in position B10 in human insulin results in an insulin analogue which displays an in vitro potency 4- to 5-fold greater than the parent compound. This substitution has been introduced into six insulin analogues which, before modification, display potencies ranging from less than 0.01-fold to 3-fold relative to natural insulin. In each case, the resulting aspartic acid-substituted analogue is substantially more potent than the parent compound. Thus, it is now possible to prepare "tailor-made" insulins with enhanced potency.

Aspartic Acid↗
PubMed1990

An insulin-like hybrid consisting of a modified A-domain of human insulin-like growth factor I and the B-chain of insulin.

We have synthesized an insulin-like compound, consisting of the B-chain of bovine insulin and an A-chain corresponding to the A-domain of human insulin-like growth factor-I (IGF-I), in which the isoleucine residue normally present in position 2 of the A-domain of IGF-I has been replaced with glycine. Biological evaluation of the compound indicated that its insulin-like activity (insulin receptor-binding and stimulation of lipogenesis) was 0.2%, and its growth-factor activity (stimulation of thymidine incorporation) was less than 1%, both relative to natural insulin. We conclude that interactions between IleA2 and TyrA19, which are crucial to high biological activity in insulin, are also present in IGF-I, and are equally critical for its biological activity.

Amino Acid Sequence↗
PubMed1988

Determinants of growth-promoting activity reside in the A-domain of insulin-like growth factor I.

A two-chain, disulfide linked, insulin-like compound embodying the A-domain of insulin-like growth factor I (IGF-I) and the B-chain of insulin has been synthesized and characterized with respect to insulin-like biological activity and growth-promoting potency. The compound displays a potency of ca. 41% relative to insulin in assays for insulin-like activity (e.g., lipogenesis) but significantly higher activity than insulin, ca. 730% relative to insulin, in growth factor assays (e.g., thymidine incorporation). The compound is, however, a less potent growth factor than IGF-I itself, ca. 26.5% relative to IGF-I, and is not recognized by IGF carrier proteins. We conclude that structural features contained in the A-domain of IGF-I are primarily responsible for the growth-promoting ability displayed by IGF-I, while features in the B-domain are responsible for recognition by IGF carrier proteins.

Amino Acid Sequence↗