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Biomedical subjects

L Geng

Publications and source records attributed to L Geng.

At least 73 records · Page 4Linked to original sources
PubMed1995

Amperometric thin film biosensors based on glucose dehydrogenase and Toluidine Blue O as catalyst for NADH electrooxidation.

Amperometric glucose sensors were constructed based on solid graphite electrodes, surface-modified with NAD+ dependent glucose dehydrogenase (GDH), Toluidine Blue O (TBO), and protective ionic polymers. The electrocatalytic oxidation of NADH was evaluated from cyclic voltammetry with TBO dissolved, adsorbed, and electrostatically or covalently bound to polymers. The NADH and glucose sensors constructed were investigated and operated at 0 mV vs. Ag/AgCl using single potential step chronoamperometry. The operational stability of the glucose sensors was limited by leakage of NAD+. A glucose sensitivity much higher than carbon paste electrode was found. A sensitivity as high as 25 microA cm-2 mM-1 was achieved.

Biosensing Techniques↗
PubMed1995

Determination of HLA class II alleles by genotyping in a Manchu population in the northern part of China and its relationship with Han and Japanese populations.

The genetic polymorphism of the HLA class II loci was investigated in a Manchu population resident in the northern part of China and compared with those of other Asian populations including Japanese and Han. In 8 DQA1 alleles, the most frequent allele was DQA1*03 with the gene frequency of 25.5%. Of 15 DQB1 alleles tested, 11 were observed and the most common allele was DQB1*0301 with the gene frequency of 24.5%. Among 19 DPB1 alleles, 11 were detected and DPB1*0501 (43.8%) was the most frequent allele as observed in other Asian populations such as Japanese, Chinese and Korean. Of 43 DRB1 alleles tested, 21 were detected and DRB1*0901 (14.0%), *1501 (11.0%), *1201 (11.0%), *07 (9.0%) and *1401 (9.0%) were highly predominant and account for the high frequencies of DR9, DR2, DR5, DR7 and DR6. In the DRB3 gene (DR52), DRB3*0202 (18.0%) was the most frequent. With respect to the DRB4 gene (DR53), the gene frequency of DRB4*0101 was 35.0%. Of 3 DRB5 alleles detected, DRB5*0101 (11.0%) was highly predominant. Comparison of HLA class II allele frequencies in Manchu with those in Japanese and Han Chinese populations (South & North) detected some significant differences and genetic divergence between these Oriental populations. The dendrogram constructed by the neighbor-joining (NJ) method based on the allele frequencies of DQA1, DQB1, DPB1 and DRB1 of 10 representative populations over the world suggested that Manchu is the closest, but at the same genetic distance to both Northern and Southern Han Chinese.

Alleles↗
PubMed1995

Comparative distribution of the alpha 1(IV), alpha 5(IV), and alpha 6(IV) collagen chains in normal human adult and fetal tissues and in kidneys from X-linked Alport syndrome patients.

We have shown previously that the 5' ends of the genes for the alpha 5(IV) and alpha 6(IV) collagen chains lie head-to-head on Xq22 and are deleted in patients with Alport syndrome (AS)-associated diffuse leiomyomatosis. In this study, we raised a rabbit anti-human alpha 6(IV)chain antibody, demonstrated its specificity by the analysis of recombinant NC1 domains af all six type IV chains, and studied the distribution of the alpha 6(IV) chain in relation to the alpha 1(IV) and alpha 5(IV) chains in human adult and fetal tissues involved in AS and diffuse leiomyomatosis. The alpha 6(IV) chain colocalizes with the alpha 5(IV) chain in basement membranes (BMs) of many tissues, but not in glomerular BM. These data exclude the alpha 6(IV) chain as a site for AS mutations. The head-to-head genomic pairing of the alpha 5(IV) and alpha 6 (IV) genes implies coordinate transcription of the two genes. Differential localization of the alpha 5(IV) and alpha 6(IV) chains shows that the two chains are not always coordinately regulated. The alpha 6(IV) chain, together with the alpha 3(IV)-alpha 5(IV) chains, was absent from all renal BMs in eight patients with X-linked AS while the alpha 1(IV) and alpha 2(IV) chains were increased. The data support the existence of two independent collagen networks, one for the alpha 3(IV)-alpha 6(IV) chains and one for the alpha 1(IV) and alpha 2(IV) chains.

Adult↗
PubMed1995

[Reports on two species of Pegohylemyia tibetana group in Xiling snow mountain of Dayi county, Sichuan, China (Anthomyiidae, Diptera)].

Male:Body 7mm. in length. Having a pair of bristles on the distal part of cercal plate, a blunt round angle of postgonite, the new species being less related to Pegohylemyia macrospini gera Deng, 1990, but having 4 pairs of large spines on the 5th sternite, a spherical point of postgonite and biconcave surstyli at apex, thus differing from the relative species. Holotype male, paratypes 18 male male, Xiling snow mountain of Dayi county, Sichuan, 17, July 1993, coll. Geng Lin, Deng Anxiao. Male:Body 7mm. in length. Having 4 pairs of spines on the 5th sternite being similar to Pegohylemyia nigribella above, but having legs with yellow color and round apex of surstyli resembling Pegohylemyia setisilva Jin, 1983; however, broadening postgonite and slender surstyli may be distinguished from all yellow leg species in this group. Holotype male:paratypes 63 male male, date and place of collection being the same as the first species above, coll Geng Lin, Li Ling, Deng Anxiao. Holotype and paratypes are kept in author's laboratory.

Animals↗
PubMed1995

The prostaglandin E1 analog, misoprostol, a normal tissue protector, does not protect four murine tumors in vivo from radiation injury.

The clinical development of radioprotectors, such as misoprostol, to protect normal tissue during cancer treatment must proceed with the assurance that tumors are not protected similarly or significantly. To provide data on this critical question, radiation-induced growth delay with or without the presence of misoprostol was measured in four murine tumors grown in the flanks of mice: the Lewis lung carcinoma, M-5076 ovarian sarcoma, FSA and NFSA. The effect of misoprostol on the tumor control dose (TCD50) of radiation was measured in FSA-bearing mice with or without prior treatment with the nonsteroidal anti-inflammatory agent, indomethacin. Misoprostol did not influence the in vivo growth of any of the four tumors, nor did it protect any of the tumors from radiation-induced growth delay. Likewise, there was no increase in the radiation TCD50 to treat the FSA in vivo in control or indomethacin-treated tumor-bearing mice. To measure any possible influence of tumor burden on the protective effect of misoprostol on normal tissue in mice, the protective effect of misoprostol on the survival of intestinal clonogenic cells was measured in M-5076-bearing mice and found to be the same as in non-tumor-bearing mice. These data suggest that misoprostol protects normal tissue in mice without protecting at least four experimental murine tumors. The data support the contention that misoprostol can achieve therapeutic gain by protecting normal tissues without protecting tumors.

Animals↗
PubMed1994

Immunopharmacology and toxicology of the plant flavonoid baohuoside-1 in mice.

The plant flavonoid baohuoside-1 (B-1), isolated from Epimedium davidii, was shown to suppress antibody and delayed-type hypersensitivity responses in mice in a dose-dependent fashion. By contrast, similar dosage schedules of B-1 did not significantly prolong survival of cardiac grafts. Furthermore, B-1 did not potentiate the effects of the standard anti-rejection drug cyclosporine. Assessment of the mice for appearance, behaviour, biochemistry, haematology and histology revealed no toxic effects at the dosages used in the experiments. These results indicate that the immunosuppressive properties of B-1 are confined to the antibody-mediated system, and suggest that B-1 may be of value in the treatment of chronic inflammatory and autoimmune diseases in which autoantibodies have a major role in pathogenesis.

Animals↗
PubMed1994

[Treatment of endometriosis with domestic luteinizing hormone--releasing hormone analogue].

Sixty patients with endometriosis, stage I-IV, diagnosed by laparoscopy or laparotomy, were treated with 200 micrograms of domestic luteinizing hormone-releasing hormone analogue (LHRH-A) subcutaneously twice daily, starting from the early follicular phase for 6-10 months. Serum FSH and LH levels elevated at first declined significantly thereafter, and remained low after the sixth day of treatment. Serum E2 concentrations were suppressed below that of the early follicular phase or to the castrated levels after one month of therapy. Symptoms and signs of endometriosis improved markedly during the treatment and patients became anovulatory and amenorrheic. At the end of treatment, resolution of endometriotic implants and softening of adhesions were shown under the second laparoscopy. Endometrial biopsies revealed inactive endometrium. After discontinuation of the treatment, ovulatory menses returned within 34-72 days, more than half of the patients complicated with infertility for 2-10 years became pregnant within 1-8 months. The recurrence rate was 37% after 0.5-5 year follow-up. Side effects were only related to hypooestrogenism. These data indicated that LHRH-A therapy had the effect of temporary reversible medical oophorectomy, and was therefore an effective approach for the treatment of endometriosis.

Adult↗
PubMed1993

Prostaglandins protect against murine hair injury produced by ionizing radiation or doxorubicin.

Several years ago we showed that prostaglandins (PGs) are potent radioprotective agents. To investigate further the potential use of these compounds we employed quantitative measures of murine hair loss and regrowth to assess the effects of PG administration before multi-dose fractionated radiation exposures. We compared these results with findings utilizing the thiol compounds WR-2721 or WR-1065, the "gold standard" laboratory radioprotectors. Three weeks after systemic administration of 16-16 dm PGE2 (Upjohn Company) or WR-2721, given 1 h before each dose of 2-4.5 Gy per fraction for 10-15 fractions, regrowing hair counts increased up to 100% compared to irradiated-only skin sites. The thiol compound effects were slightly superior to the PG effects in these studies. Local applications of 16-16 dm PGE2 or WR-1065 given 15 min before each radiation fraction also enhanced post-radiation hair regrowth, although systemic administration of either agent was more effective than the topical route. We also evaluated possible protective effects of PGs given before doxorubicin, measuring murine hair loss 1 week after parenteral injections of the drug. Five daily doses of doxorubicin, 0.1 mg/25 g animal, reduced the number of hairs in a 4.42 mm2 area of skin from 241 +/- 5 (controls) to 144 +/- 3. Misoprostol (G.D. Searle & Co.), 25 micrograms/mouse, applied locally 2 h before each dose of doxorubicin, resulted in 213 +/- 8 residual hairs. We conclude that clinical use of these compounds may provide significant protection of hair follicles and possibly other normal tissues (skin; oral, rectal, and bladder mucosa) lying within a radiation field or in patients treated with chemotherapeutic agents. Further assessment of possible tumor protection effects are needed, however.

Administration, Oral↗
PubMed1992

Topical or systemic 16, 16 dm prostaglandin E2 or WR-2721 (WR-1065) protects mice from alopecia after fractionated irradiation.

Our previous studies in mice demonstrated that systemic or topical 16,16 dm PGE2 protected against single dose radiation-induced hair loss. We have now investigated prostaglandin, or WR-2721, protection against murine alopecia produced by varying doses and schedules of fractionated radiation. On days one to eight after hair was plucked from the thighs of B6D2F1 mice, groups of 6 animals each were given daily exposures of 4.0 or 4.5 Gy for 5 days; 2.5, 3.5, 4.5 or 5.5 Gy for 10 days; or 2 Gy for 15 days. One hour before irradiation each mouse received 10 microgram 16,16 dm PGE2, either by subcutaneous injection into the neck or topical application, 8 mg WR-2721 by injection, or 0.3 mg WR-1065 by topical application. Three weeks later counts of regrowing hairs were recorded from excised skin samples. For the radioprotectors used, hair regrowth was increased 25-100% in the various radiation groups in comparison to irradiated-only control sites. In some studies with the radioprotector given systemically, WR-2721 afforded slightly greater radioprotection than 16,16 dm PGE2. The two compounds were essentially equally radioprotective in the topical application studies. Since both systemic and topical applications of the agents tested enhanced hair regrowth following radiation, we conclude that clinical use of these compounds may provide some protection of hair follicles, and perhaps other tissues, lying within a radiation therapy field.

16,16-Dimethylprostaglandin E2↗
PubMed1991

Retina-specific expression from the IRBP promoter in transgenic mice is conferred by 212 bp of the 5'-flanking region.

IRBP is a photoreceptor-specific glycoprotein that has been suggested as a retinoid carrier in the visual process. Previous research has shown that 1.3 kb of 5'-flanking sequence from the human IRBP gene is sufficient to promote photoreceptor-specific expression of reporter genes in transgenic mice. To define more narrowly the sequences that promote tissue-specific expression, chimeric constructs with shorter promoters were used to generate transgenic mice. The bacterial CAT gene was fused to fragments of 706 bp or 212 bp from the 5' end of the human IRBP gene. Analysis of the three transgenic families bearing the 706 bp IRBP promoter revealed that CAT expression was confined to the neuro-retina and the pineal gland. Analysis of the four transgenic families bearing the 212 bp IRBP promoter revealed the same tissue-specific CAT expression in three families. These results establish that tissue-specific expression of IRBP can be regulated by a short 212 bp promoter which has been conserved between humans and mice.

Amino Acid Sequence↗
PubMed1991

Interphotoreceptor retinoid-binding protein: biochemistry and molecular biology.

Interphotoreceptor retinoid-binding protein (IRBP) is a recent and still somewhat enigmatic newcomer in the family of photoreceptor-specific proteins involved in vision. It has been isolated, characterized, cloned and sequenced from several species in less than a decade. Its extracellular localization and the increased amount of bound all-trans retinol following illumination are consistent with the proposed function of IRBP in extracellular transport or buffering of retinol and retinal isomers in the IPM. Its capacity to bind a great many other hydrophobic ligands, however, may indicate a multi-purpose function. Many questions concerning biosynthesis and processing, secretion, tertiary structure and ligand binding remain to be answered. Perhaps most interesting, from a molecular biology point of view, will be the regulation of transcription and tissue-specific expression of this photoreceptor protein, and possible involvement of its gene in human retinal degenerations. Constructs consisting of IRBP regulatory sequences and foreign antigens incorporated into the germ line of transgenic mice will help in the characterization of promoters and enhancer elements, while suppression of IRBP gene expression and its consequences may give us a more precise answer about IRBP function.

Amino Acid Sequence↗
PubMed1990

Tissue-specific expression in transgenic mice directed by the 5'-flanking sequences of the human gene encoding interphotoreceptor retinoid-binding protein.

Interphotoreceptor retinoid-binding protein (IRBP) is an extracellular protein that has been suggested to participate in the visual process as a carrier for visual retinoids. A chimeric gene composed of the human IRBP promoter fused to the bacterial reporter gene chloramphenicol acetyltransferase (CAT) was used to generate transgenic mice. Analysis of six transgenic families revealed that the CAT gene, concomitant with the endogenous IRBP gene, was expressed primarily in the retina and, to a lesser extent, in the pineal gland. These results establish that a 1.3-kilobase fragment from the 5' end of the human IRBP gene is sufficient to direct transgene expression to a visual subdivision of the central nervous system.

Animals↗
PubMed1990

Hair medullary cell counts: a simple and sensitive indicator of radiation exposure.

The medulla in the lower regions of a growing mouse hair contains a very regularly spaced column of cell nuclei. The total number of nuclei 3 days after irradiation in this column (from its lower recognition point to the point of terminal differentiation and nuclear degradation) proves to be a sensitive indicator of the level of radiation exposure.

Animals↗
PubMed1990

[Glomerulonephropathy associated with hepatitis B virus (HBV) infection].

Forty-seven renal biopsies of glomerulonephropathy with persistent Australian antigenaemia (HBsAg is mostly positive) were studied with light microscope, electron microscope and direct immunofluorescence. Immunohistochemical method (ABC method) was used to examine HBsAg, HBeAg and HBcAg deposits in renal tissue. In addition 20 cases of idiopathic membranous nephropathy (MN) were studied for comparison. These 47 cases included 19 children and 28 adults. The results indicated that Australian antigens diffusely deposited in glomeruli in 14 cases (29.7%), with HBsAg in 7 cases (50.0%), HBeAg in 13 cases (92.8%) and HBcAg in 2 cases (14.3%). The 14 positive cases included 11 children and 3 adults. The pathologic types were membranous nephropathy in 12 and membranoproliferative glomerulonephritis in 2 cases. The membranous type was characterized by irregular thickening of capillary wall and double contour, bubble-like appearance and spike formation of glomerular basement membrane (GBM); immune complexes and electron dense deposits may be present in different sites of glomeruli. Coarse granular deposits of IgG and C3 along GBM were the principal pattern, but IgA, IgM and C1q were often present. Among the 20 idiopathic MN, 2 were found to have HBeAg deposition along GBM, one was a child and the other an adult IgG, IgA, IgM, C3 and C1q with HBeAg deposits were present in glomeruli.

Adult↗
PubMed1990

Changes after irradiation in the number of mitotic cells and apoptotic fragments in growing mouse hair follicles and in the width of their hairs.

The hair follicle or its differentiated product, the hair, which represents the linear historical record of the follicular proliferative activity, could provide a biological dosimeter of value for dose distribution determinations after accidental exposure. Here we present some further studies on irradiated mouse hair follicles and hair, and discuss the difficulties in obtaining similar data for humans. The incidence of cell death in the follicles has been shown elsewhere to be maximum 12 h after irradiation, and it increases with dose. Here we confirm that doses of 0.2-0.4 Gy can be readily detected. We show here that there is only a little more cell death in the larger follicles even though they contain many more cells and mitotic figures. About one-third of all the dead cell fragments in a follicle can be seen in a good longitudinal follicle section. Mitotic activity declines progressively with dose in the large follicles, which start with more mitotic cells, showing the dose-dependent changes most readily. The dead cells are morphologically identical to apoptotic cells at the level of the light microscope, and they fragment into several bodies, the number of which increases with dose. The total number of apoptotic bodies or fragments in whole large follicles increases almost 100-fold over a range of 1.3 Gy (from 0.2 to 1.5 Gy) and about tenfold over the range 0.2-0.5 Gy. The estimated number of dead (apoptotic) cells increases about sevenfold over the same 1.3-Gy range. The width of the middle portion of the broadest, awl, hairs measured 12 days after irradiation decreases with increasing dose. About 80% of the hairs show an obvious reduction in width after 2 Gy and the effects of a dose of about 1 Gy can be detected. The width of the hair is reduced by 10-14% per Gy. A comparison has been made between BDF1 (black) and BALB-c (albino) mice. The large follicles contain similar numbers of mitotic cells, but the BALB-c mice are more sensitive both in terms of the radiation-induced apoptosis and in terms of a reduction in awl hair width.

Animals↗
PubMed1989

Human interstitial retinoid-binding protein. Gene structure and primary structure.

Interstitial retinoid-binding protein (IRBP) is synthesized and secreted by rod photoreceptor cells into the interphotoreceptor matrix and is known to bind retinoids and fatty acids. We have used cDNA clones encoding human IRBP to isolate a 15-kilobase genomic fragment that encompasses the complete human IRBP gene. The IRBP gene spans more than 11 kilobases and is interrupted by three introns, all of which are positioned near the 3'-end of the coding sequence. The 3741-base pair coding region of IRBP appears to have been generated by quadruplication of an approximately 900 base pair long ancestral gene. The deduced amino acid sequence predicts a mature protein of 1,230 residues (calculated molecular weight 133,000). The protein sequence can be aligned into four homologous segments, each consisting of about 300 residues. Sequence similarity between segments is as high as 60% when conservative substitutions are taken into account. Two putative N-linked glycosylation sites are located in highly conserved domains in the center of the first and second segment of IRBP. A domain consisting of 41 residues at the COOH-terminal end of the third segment has 15 matching residues (38%) with an intradiscal loop of rhodopsin, a retinal-binding protein in rod photoreceptors.

Amino Acid Sequence↗