Biomedical subjects

G Dong

Publications and source records attributed to G Dong.

At least 73 records · Page 4Linked to original sources

PubMed1996

Identification of a cis-acting sequence in the human plasminogen activator inhibitor type-1 gene that mediates transforming growth factor-beta1 responsiveness in endothelium in vivo.

The mechanism of regulation of the plasminogen activator inhibitor type-1 (PAI-1) gene by transforming growth factor-beta1 (TGF-beta1) was studied in vitro and in vivo in endothelial cells. We constructed adenovirus vectors containing PAI-1 5'-flanking sequences driving expression of a beta-galactosidase (beta-gal) reporter gene. Cultured bovine endothelial cells were transduced with the vectors and treated with TGF-beta1. beta-Gal expression was up-regulated 10-20-fold by TGF-beta1 when vectors contained 799-base pair (bp) of 5'-flanking sequence, but only minimally (2-3-fold) from a vector containing only 82-bp of 5' PAI-1 flanking sequence. TGF-beta1 up-regulated beta-gal expression at the mRNA level, congruently with TGF-beta1 up-regulation of expression of the endogenous PAI-1 gene. The constructs were transduced into intact rat carotid endothelium, and TGF-beta1 was injected systemically. In vivo, TGF-beta1 up-regulated endothelium-specific expression of beta-gal 3-fold (p < 0.03) from a vector containing the 799-bp sequence, but did not alter expression from a vector containing the 82-bp sequence. The sequence between -799 and -82 mediates up-regulation of reporter gene expression by TGF-beta1 in endothelial cells in vitro and in vivo. This general method permits the elucidation of mechanisms of gene regulation by physiologic stimuli delivered to the endothelium of intact animals.

Adenoviridae↗

PubMed1995

Endothelium-specific in vivo gene transfer.

Targeted expression of genetic material within the vascular endothelium is potentially a powerful tool for the investigation of endothelial cell (EC) biology. We developed, optimized, and characterized an efficient somatic transgenic model of EC-specific gene transfer. Rat carotid arteries were infused with adenovirus expressing a beta-galactosidase (beta-gal) gene. The level and cell-type specificity of recombinant gene expression were measured by assaying beta-gal activity in vessel extracts and by counting transduced cells in histological sections. Toxicity was evaluated by counting total ECs (3 days) and by measuring neointimal formation (14 days). Effects of transduction on the proliferation of vascular cells were measured with bromodeoxyuridine and [3H]thymidine. Maximum recombinant gene expression resulted from infusion of 1 x 10(10) to 1 x 10(11) plaque-forming units (pfu) per milliliter; approximately 35% of luminal ECs were transduced. A high degree of EC specificity (90% to 98% of total transduced cells) was maintained over this range of virus concentrations. More highly concentrated virus resulted in loss of beta-gal expression and a large decrease in luminal EC number (97% decrease, P < .001). Gene transfer at 4 x 10(10) pfu/mL was efficient, preserved EC integrity, and caused minimal neointimal formation. After gene transfer, there were early (3-day) increases in both EC and smooth muscle cell proliferation. At 14 days, only EC proliferation remained elevated (18% versus 1.4% in vehicle-infused arteries, P = .005). This animal model permits efficient highly EC-specific gene transfer. Vascular toxicity is minimal, although the EC proliferative index is elevated. This model will be useful in experiments that elucidate the biological role of EC gene products and define pathways of EC gene regulation and signal transduction in vivo.

Adenoviridae↗

PubMed1995

[Compositive treatment of acute deep vein thrombosis of lower extremity].

Fourteen patients with acute deep vein thrombosis of lower extremity (DVT) were treated with composite methods including thrombectomy (iliofemoral venous thrombectomy and ascending venous thrombectomy), thrombolytic and anticoagulant therapy. Follow-up for 2-27 months (average 11.5 months) showed excellent and good results in 78.6%, and the morbidity of post-thrombotic syndrome only 21.4%. The remarkable results were due to opening of occlusive vein of the lower extremities by thrombectomy, which could make thrombolytics effective and reduce the dose of thrombolytics to prevent bleeding complication. Ascending venous thrombectomy could not only remove the venous thrombi of the lower extremities but also protect the deep venous valves and reduce the morbidity of postthrombotic syndrome. Additionally, to reach a satisfied therapy, lesion in iliac vein, such as anatomical compression, stenosis, occlusion, diaphragm and so on, shall be managed as well. Otherwise, DVT shall be recurrent.

Adult↗

PubMed1995

[Mortality study of cancer among Anshan iron and steel workers].

Cancer mortality in the period between 1971 and 1988 was surveyed among 71,803 male workers at thirty two major plants in Anshan Iron and Steel Corporation. A total of 5,896 deaths was registered. Cancer deaths occurred in 1,830, accounting for 31.04% of all deaths. The five leading cancers were that of lung, liver, stomach, esophagus and intestine. Cancer death rate increased with age and with calender year. The SMR for all cancers and for the cancer of lung, stomach and esophagus indicated significant excess (P < 0.01). 77.49% of all cancer deaths, and 82.82% of deaths with lung cancer occurred in smokers. The findings show that the mortality of cancer amongiron and steel workers in Anshan was the leading cause of death, and the death rate was higher than that of local and large city population such as in Beijing, Shanghai, etc. The excess cancer rate, especially that of lung cancer, may be related to carcinogenic agents in the working environment and smoking habit.

Adult↗

PubMed1995

[Structural changes of extra pulmonary artery and pulmonary arterioles of rats during chronic hypoxia and their significance].

The structural changes of extra pulmonary artery (PA) and pulmonary arterioles and their effects on the pulmonary arterial pressure (PAP) under chronically hypobaric hypoxia (5000 m) were studied. The results showed that (1) The endothelial edema of extra PA and pulmonary arterioles gradually reduced and the endothelial proliferation took place along with the prolongation of hypoxic exposure followed by the recovery of endothelium-dependent relaxation evoked by Ach from depression. This result suggested that the release of E-DRFs from endothelium increased with the structural changes of endothelium in the course of hypoxic exposure, which may be a reason why PAP did not increase any more after 21 to 40 of days exposure. However, the strengthened contraction of PA, the proliferation of cells on the vascular wall, and the muscularity of pulmonary arterioles being related to the hypoxic endothelium may produce a negative effect on decrease of PAP, resulting in persistently higher PAP. (2) The structural changes of pulmonary arteriole endothelium were more severe than those of extra PA endothelium, indicating that pulmonary arterioles might be more sensitive to the stimulation of hypoxia.

Altitude Sickness↗

PubMed1995

Guyin decoction in the treatment of immuno-sterility and its effect on humoral immunity.

60 cases of immuno-sterility (treated group) were treated with Guyin Decoction, and were compared with 25 control cases treated by Western medicine. The results showed that in the treated group 19 cases were cured, 32 improved and 9 failed respond, while in the control group 6 were cured, 8 improved and 11 failed. The decoction had significant effect on serum IgA and IgG.

Adult↗

PubMed1994

Human papillomavirus type 11 E2 proteins repress the homologous E6 promoter by interfering with the binding of host transcription factors to adjacent elements.

The E6 promoter of human papillomaviruses (HPVs) trophic for epithelia for the lower genital tract and the upper respiratory tract is regulated in vitro by homologous and heterologous papillomaviral E2 proteins that bind to a consensus responsive sequence (E2-RS) ACCN6GGT. When HPV type 11 (HPV-11) expression is examined in epithelial cell lines, the HPV-11 E2-C protein, which lacks the amino-terminal transactivating domain of the full-length E2 protein, invariably represses the homologous viral E6 promoter. In contrast, when the novel constitutive enhancer (CE) CE II is deleted, not only is the basal promoter activity much reduced, it is further repressed by the intact HPV-11 E2 protein (M. T. Chin, T. R. Broker, and L. T. Chow, J. Virol. 63:2967-2976, 1989). Here, we demonstrated that, when expressed from a stronger surrogate promoter, the HPV-11 E2 protein represses the E6 promoter effectively, regardless of CE II. By performing systematic mutational analyses of the four highly conserved copies of the HPV-11 E2-RS and of the adjacent enhancer-promoter elements, we show that the furthest upstream, promoter-distal E2-RS copy 1 plays no apparent role in E6 promoter regulation. Repression by the homologous HPV-11 E2 proteins is mediated through each of the three promoter-proximal copies of the E2-RS, but the presence of CE II abrogates the full-length E2 protein repression exerted at E2-RS copy 2. Repression is alleviated when the two (for E2) or three (for E2-C) promoter-proximal copies of E2-RS are mutated. We specifically demonstrate that repression exerted at E2-RS 3 is due to preclusion of binding of the host transcription factor Sp1 or Sp1-like proteins to a nonconsensus sequence AGGAGG located 1 bp upstream of the tandem E2 protein binding sites 3 and 4. A 3-bp insertion between the adjacent Sp1 and E2-RS 3 sites permits both Sp1 and E2 proteins to bind, with a concomitant relief of E2-RS 3-mediated repression. Similar mutational analyses show that proteins that bind to the GT-1 motif near the upstream E2-RS 2 help abrogate repression by the E2 protein in the presence of CE II. The implications of these results with respect to the viral infectious cycle and during viral oncogenesis are discussed.

Base Sequence↗

PubMed1993

Purification of endo-polygalacturonase by affinity precipitation using alginate.

The precipitation of alginate by Ca2+ at pH 3.8 was found to occur concomitantly with the precipitation of endo-polygalacturonase from Aspergillus niger. Under optimum conditions, 92% of the enzyme activity was precipitated. The enzyme could be recovered from the precipitate by washing with 0.5 M NaCl/0.2 M Ca2+. All the precipitated endo-polygalacturonase activity could be recovered in this way. The enzyme thus obtained was purified 10-fold. A comparison of SDS/PAGE gel patterns of the crude preparation and enzyme purified by the affinity precipitation also showed a significant purification of the enzyme.

Alginates↗

PubMed1992

In vitro selection of human immunodeficiency virus type 1 resistant to 3'-azido-3'-deoxythymidine.

3'-Azido-3'-deoxythymidine (AZT)-resistant human immunodeficiency virus type 1 (HIV-1) was obtained by growing HTLV-IIIB in C8166 cell cultures in the presence of inhibitory concentrations of AZT. The AZT-resistant HIV-1 was capable of replicating, as measured by infectious virus yield, and inducing cytopathic effect in the presence of AZT concentrations able to completely suppress the replication of parental HTLV-IIIB. Cloning of the AZT-resistant HIV-1 revealed that a number of different variants of HIV-1 with various degrees of sensitivity to AZT emerged during propagation of HTLV-IIIB in C8166 cells in the presence of the drug. PCR experiments performed on DNA extracted from C8166 cells infected with a resistant strain revealed that viral DNA was produced in the presence of inhibitory concentrations of AZT, while viral DNA in C8166 cells infected with the parental virus was drastically inhibited. Reverse transcriptase isolated from the AZT-resistant HIV-1 variant failed to show resistance to AZT 5'-triphosphate.

Antiviral Agents↗

PubMed1992

Resistance of HIV-1 to AZT might also involve the cellular expression of multidrug resistance P-glycoprotein.

Resistance of tumor cells to the antigrowth activity of several cytotoxic compounds has been associated with the expression of the so-called multidrug resistance protein or P-glycoprotein. This article addresses the question whether the expression of such protein could also affect the sensitivity of HIV to AZT. Our data indicate that this possibility does exist. In fact, multidrug-resistant CEM VBL100 cells, which express high levels of P-glycoprotein, are less sensitive to both the antiproliferative activity and the antiviral action of AZT. Additionally, our data suggest that this phenomenon is specifically mediated by P-glycoprotein since trifluoroperazine, which is known to circumvent multidrug resistance due to the action on P-glycoprotein, increases the intracellular accumulation of AZT and affects the sensitivity of HIV to AZT. Although the biological and clinical significance of these observations has still to be established, this study suggests that cellular factors, other than virus itself, should be taken into account to address the phenomenon of drug resistance of HIV.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1992

Control of human papillomavirus type 11 origin of replication by the E2 family of transcription regulatory proteins.

Replication of human papillomavirus type 11 (HPV-11) DNA requires the full-length viral E1 and E2 proteins (C.-M. Chiang, M. Ustav, A. Stenlund, T. F. Ho, T. R. Broker, and L. T. Chow, Proc. Natl. Acad. Sci. USA 89:5799-5803, 1992). Using transient transfection of subgenomic HPV DNA into hamster CHO and human 293 cells, we have localized an origin of replication (ori) to an 80-bp segment in the upstream regulatory region spanning nucleotide 1. It overlaps the E6 promoter region and contains a short A + T-rich segment and a sequence which is homologous to the binding site of the bovine papillomavirus type 1 (BPV-1) E1 protein in the BPV-1 ori. However, unlike the BPV-1 ori, for which half an E2-responsive sequence (E2-RS) or binding site suffices, an intact binding site is essential for the HPV-11 ori. Replication was more efficient when additional E2-RSs were present. The intact HPV-11 genome also replicated in both cell lines when supplied with E1 and E2 proteins. Expression vectors of transcription repressor proteins that lack the N-terminal domain essential for E2 transcriptional trans activation did not support replication in collaboration with the E1 expression vector. Rather, cotransfection with the repressor expression vectors inhibited ori replication by the E1 and E2 proteins. These results demonstrate the importance of the N-terminal domain of the E2 protein in DNA replication and indicate that the family of E2 proteins positively and negatively regulates both viral DNA replication and E6 promoter transcription.

Animals↗

PubMed1991

Hairless micropig skin. A novel model for studies of cutaneous biology.

Reported here is the structural and immunohistochemical similarities between the Yucatan hairless micropig (HMP) skin and that of humans. Hairless micropig skin surface was composed of complex intersecting furrows that created geometric patterns remarkably similar to human skin surface glyphics. The dermal--epidermal interface consisted of undulant downgrowths that interdigitated with dermal papillae. Hairless micropig epidermis contained two morphologically distinct populations of basal keratinocytes (serrated and nonserrated). Similar heterogeneity has been seen only in human epidermis and primate palmar epidermis. Immunohistochemistry revealed that the HMP epidermis is reactive with monoclonal and polyclonal antisera to keratin proteins. Melanocytes reactive with antisera to S-100 protein, as in human skin, also were observed in HMP epidermis. Organization of dermal extracellular matrix, including collagen and elastic fibers, and the organization and reactivity of the microvasculature with antisera to factor VIII, were consistent with human skin. The costicosteroid-induced atrophy and subsequent rebound phenomenon after withdrawal of steroid observed in HMP skin was similar with that observed in humans. It is concluded that HMP skin approximates human skin significantly more precisely than most existing species and is an excellent model for studies of cutaneous physiology and pharmacology.

Animals↗

PubMed1991

Relative proliferative rates of limbal and corneal epithelia. Implications of corneal epithelial migration, circadian rhythm, and suprabasally located DNA-synthesizing keratinocytes.

An important element of the recently proposed limbal stem cell model is that corneal epithelial cells migrate centripetally. The driving force for this migration is unknown, although it has been suggested that limbal epithelium, proliferates at a higher rate than central corneal epithelium, thus creating a population pressure toward the central cornea. This hypothesis was tested by measuring the relative proliferative rates of limbal and central corneal epithelia using 3H-thymidine autoradiographic techniques. The results indicate that, in both the New Zealand white rabbit and SENCAR mouse, the labeling index (LI) of limbal epithelium is actually lower than that of central corneal epithelium. This difference in LI persists throughout the circadian rhythm cycle. These results suggest that population pressure per se cannot be responsible for the centripetal migration of corneal epithelium and raise the possibility that preferential desquamation of central corneal epithelium may "draw" peripheral cells toward the central cornea. In both epithelia, the LI peak precedes the mitotic index (MI) peak during circadian cycle by 4-6 hr. These data therefore are in close agreement with earlier results on several nonocular stratified epithelia but contradict an earlier suggestion that the LI and MI peaks of corneal epithelium coincide. Finally, although most of the 3H-thymidine incorporating cells in central cornea may appear to be suprabasally located, they are only partially displaced into the suprabasal compartment. In most cases, such cells are still connected with the basement membrane through a thin stalk of cytoplasm. Since corneal epithelium rests on an exceptionally flat and rigid substratum, an increase in cellular volume in DNA-synthesizing cells may not be tolerated well in an already crowded basal layer. This may explain why an unusually large proportion of DNA-synthesizing cells are expelled preferentially into either a "second tier basal layer" or into the suprabasal compartment.

Animals↗

PubMed1990

[Development and preliminary characterization of monoclonal antibodies to 987P adhesin antigen of E. coli].

A panel of 11 monoclonal antibodies (MAbs) to 987P adhesin antigen of E. coli were developed and partially characterized. They only reacted with E. coli strains bearing 987P adhesin but neither with other E. coli (K88+, K99+ and F41+) strains nor other species in family of Enterobacteriaceae in IF or ELISA. The amount of 987P+ bacteria which could be detected by the HRPO-conjugated MAb EPN3 was as small as 2 X 10(3) cells/ml, and the detected rate of fecal or intestinal samples from piglets with artificially induced diarrhoea by IF and/or ELISA was 4/4 and 6/6, respectively. The adhesion of 987P+ E. coli to porcine intestinal epithelial cells could be inhibited by seven of these MAbs in vitro. The binding pattern of MAb EPN2 with 987P fimbriae as shown in immunogold stain under electron microscope was periodic and discrete distribution along the length of each of the fimbriae. ELISA and IF blocking test suggested that there were at least 3 kinds of determinants on 987P adhesion. These MAbs were not only useful in identification of 987P fimbriae of enterotoxigenic E. coli, but also in the studies of its molecular structure and biological function.

Adhesins, Escherichia coli↗

PubMed1990

[Relation of pale tongue, purple tongue and TXA2-PGI2 regulation system].

This paper analysed the relationship between pale tongue, purplish tongue and TXB2, 6-keto-PGF1 alpha levels in plasma of 70 cases with coronary heart disease (CHD) and 45 normal subjects. The results showed the following characteristics: The pale tongue group (217.76 +/- 30.5 pg/ml) showed no significant difference in TXB2 level compared with the normal group (164.49 +/- 10.85 pg/ml, P greater than 0.05), while both showed significant difference compared with the purplish tongue group (360.1 +/- 31.3 pg/ml) and that with purple spots (485.07 +/- 106.1 pg/ml, P less than 0.01). The pale tongue group (179.29 +/- 9.08 pg/ml) showed a significant difference in 6-keto-PGF1 alpha level compared with the normal group (244 +/- 19.31 pg/ml, P less than 0.01), but it showed no significant difference compared with the purplish tongue group (185.08 +/- 17.07 pg/ml) and that with purple spots (229.3 +/- 33.2 pg/ml, P greater than 0.05). The comparison between the groups of purplish tongue and that with purple spots and the normal group showed no significant difference (P greater than 0.05). The pale tongue group (1.33 +/- 0.18) showed a marked difference in TXB2/6-keto-PGF1 alpha ratio compared with the normal group (0.72 +/- 0.04, P less than 0.01), the purplish tongue group (2.12 +/- 0.22, P less than 0.01) and that with purple spots (2.25 +/- 0.55, P less than 0.05). The purplish tongue group and that with purple spots showed significant difference compared with the normal group (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗

PubMed1989

Existence of slow-cycling limbal epithelial basal cells that can be preferentially stimulated to proliferate: implications on epithelial stem cells.

Despite the obvious importance of epithelial stem cells in tissue homeostasis and tumorigenesis, little is known about their specific location or biological characteristics. Using 3H-thymidine labeling, we have identified a subpopulation of corneal epithelial basal cells, located in the peripheral cornea in a region called limbus, that are normally slow cycling, but can be stimulated to proliferate in response to wounding and to a tumor promotor, TPA. No such cells can be detected in the central corneal epithelium, suggesting that corneal epithelial stem cells are located in the limbus. A comparison of various types of epithelial stem cells revealed a common set of features, including their preferred location, pigment protection, and growth properties, which presumably play a crucial role in epithelial stem cell function.

Animals↗

PubMed1989

Walking and cycling tests in neurogenic and intermittent claudication.

The walking and cycling tolerance of 19 patients with neurogenic claudication and 11 with intermittent claudication was assessed, first in the upright and then in 30 degrees of flexion, repeating the tests on a second day. The flexed posture improved the walking and cycling distance, respectively, in 11 and six patients with neurogenic claudication. In two of the 11 patients, this posture significantly improved by more than 100% of both walking and cycling distances. In addition, one patient had claudication pain when he was walking, but could cycle unlimited distance. Only one of the patients with intermittent claudication could walk or cycle further in the flexed position. Although some patients with neurogenic claudication increase their walking distance by flexing forwards, we conclude that posture-related walking and cycling are insufficiently sensitive tests to distinguish between neurogenic and intermittent claudication.

Exercise↗

PubMed1989

Morphology of aged skin.

Despite an overall thinning of the epidermis and focal areas of cytologic atypia, there was no morphologic evidence that the protective function of this tissue was compromised by age. The characteristic morphologic markers associated with the keratinization process were not altered either in appearance or in amounts. A well-formed stratum corneum was present, suggestive that barrier ability is not compromised in senile skin. Whereas alterations in the aged epidermis are slight, the dermal-epidermal changes are marked and have greater physiologic consequences. The major change is a relatively flat dermal-epidermal junction because of retraction of the epidermal papillae as well as the microprojections of basal cells into the dermis. This flattening results in a more fragile tissue that is less resistant to shearing forces. Retraction of the epidermal downgrowths may also explain the loss in proliferative capacity associated with the aged epidermis. The major alterations in the aged dermis concern the architecture of the collagen and elastin networks. Both fibrous components appear more compact because of a decrease in the voids or spaces between the fibers; the spaces resulted from a loss of ground substance. Collagen bundles appear to unravel, and the individual elastic fibers show signs of elastolysis. The net effect of these fibrous rearrangements and alterations is a dermis that is less stretchable, less resilient, more lax, and prone to wrinkling.

Aging↗