Biomedical subjects

H Duan

Publications and source records attributed to H Duan.

81 records · Page 5Linked to original sources

PubMed1995

Crop and midgut filling and emptying in a female Phormia regina (Diptera: Calliphoridae) fed a liver diet.

To study the role of the crop in protein storage, crop and midgut filling in female Phormia regina (Meigen) was measured volumetrically and the soluble protein content determined. During a 4-h feeding period on homogenized liver, nonligated females consumed and stored enough protein in the crop and midgut to develop a normal compliment of eggs. Within 26 h from the onset of feeding, 75% of the protein content of the crop and a similar amount from the midgut were emptied. Neck ligation or sham neck ligation 7 h after females fed to repletion slowed but still allowed delivery of sufficient protein for egg development.

Animals↗

PubMed1995

Tumor necrosis factor-alpha modulates monocyte/macrophage apoprotein E gene expression.

apo E has been shown to modulate cholesterol balance in arterial wall cells. Production of apo E by macrophages in atherosclerotic plaques could thereby influence the development of the plaque lesion. Cytokines, including TNF alpha, have been identified in human lesions, therefore, we undertook a series of studies to evaluate the effect of TNF alpha on monocyte/macrophage apo E production. The addition of TNF alpha to freshly isolated human monocytes led to a four- to fivefold increase of apo E mRNA abundance. The addition of TNF alpha to fully differentiated macrophages either had no effect or modestly inhibited apo E mRNA expression. THP1 human monocytic cells also responded to TNF alpha in a phenotype-specific manner. Treatment of these cells with TNF alpha produced a dose- and time-dependent increase in apo E mRNA. This increase was reflected in apo E synthesis and was associated with inhibition of DNA synthesis, and with induction of c-fos and ICAM-1 gene expression. Cell-permanent analogues of ceramide did not reproduce TNF alpha effect on apo E, but antagonists of protein kinase C did inhibit its effect. TNF alpha induction of apo E mRNA abundance was associated with stimulation of apo E promoter-dependent gene transcription. In summary, TNF alpha stimulates apo E gene transcription, mRNA abundance, and protein synthesis in the monocyte/macrophage in a phenotype-specific manner. Such regulation could significantly modify the amount of apo E present in vessel wall lesions.

Apolipoproteins E↗

PubMed1994

Age-related alterations of proteoglycan in mouse tracheal cartilage matrix: an electron histochemical analysis with the cationic dye of polyethyleneimine.

Age-related alterations of the proteoglycans (PGs) contents and size were observed in the tracheal cartilage matrix of ddY mice at various ages with the cationic dye of polyethyleneimine (PEI). In young animals (aged 1 day to 1 month after birth), the PGs content and size increased, resulting in the formation of the territorial matrix (TM) and the decrease of the space between the PEI aggregates and the collagen fibers. In 1 month old mice, the TM could be distinguished from the interterritorial matrix (ITM). In adult mice (from 2 to 6 months), the PGs content and size kept stable, but the rearrangement of the PGs and collagen fibers was observed. From 6 months of age on, the decrease of PGs content and size occurred mainly in the ITM. The developing stopping sign was recognized in 1 month and the senile sign from 6 months in the ddY mice as for the complete formation of the TM in 1 month and the decrease of the PGs content and size from 6 months. These results demonstrated the age-related alteration of PGs in the ultrastructural level first and could contribute to the aging study of the tracheal cartilage.

Aging↗

PubMed1993

Postnatal development and aging of esophageal epithelium in mouse: a light and electron microscopic radioautographic study.

DNA synthesis and fine structure of the esophageal epithelium of ddY mouse in different age groups, from neonatal to senescent, were investigated by light and electron microscopic radioautography after 3H-thymidine labeling in vitro. At 1-3 days after birth, the esophagus was lined with two cell types, ciliated and nonciliated cells. From 1 week on, ciliated cells could not be found. At 2 weeks, the superficial cells still possessed nuclei and short microvilli on the apical plasma membranes. From 1 month, the superficial cells became keratinized and the microvilli on the apical plasma membrane disappeared. With aging of the mice, the epithelia became markedly thick. These results show that disappearance of ciliated cells, keratinization of superficial cells and increase of the thickness are the main changes in structure of mouse esophageal epithelium from neonatal to senescent ages. By light microscopic radioautography, labelled cells were almost confined in the basal layer, regardless of the aging stages. The highest labeling index was recorded at 1 day after birth, then decreased with age. By electron microscopic radioautography, silver grains indicating DNA synthesis were observed in nuclei. As compared with those of unlabelled cells in the basal layer, the nuclei and nucleoli of labelled cells were larger, with fewer cell organelles. The present study provides, for the first time, the basic quantitative data regarding cell proliferation of mouse esophageal epithelium from neonatal to senescent stage.

Aging↗

PubMedDate not supplied

Association between metabolic gene polymorphisms and susceptibility to peripheral nerve damage in workers exposed to n-hexane: a preliminary study.

Chronic exposure to n-hexane may result in peripheral neuropathy. 2,5-Hexanedione (2,5-HD) has been identified as a toxic metabolite of n-hexane. The CYP2E1, CYP1A1 and GST genes are involved in the formation of 2,5-hexanedione from n-hexane as well as the elimination of 2,5-HD-formed electrophile, and these genes are highly polymorphic in the general population. A nested case-control study in an industrial cohort was conducted to evaluate the associations between polymorphisms in these metabolic genes and n-hexane-induced peripheral nerve damage. The study subjects included 22 cases, who worked in a printing factory with symptoms of peripheral nerve damage, and 163 controls, who came from the same factory of cases. DNA was extracted from blood samples and genotyping was conducted for CYP2E1 Pst, CYP2E1 Dra, CYP2E1 Ins96, CYP1A1 Msp, GSTT1 null, GSTM1 null and GSTP1 105V. Unconditional logistic regression was applied to estimate the odds ratio and 95% confidence intervals. There were no significant differences between the two groups regarding age, sex, smoking and alcohol status. A significant association between Dra polymorphism and peripheral nerve damage was found. The frequency of CYP2E1 Dra homozygous mutation in the case group (18.2%) was higher than that in the control group (3.7%, p=0.015). Individuals with homozygote genotype (CC) of CYP2E1 Dra had a significantly higher risk of peripheral nerve damage compared with those with DD genotype (adjusted OR=?.58, 95% CI=1.32-23.65) after n-hexane exposure duration, sex, age, smoking and alcohol status were adjusted. No significant association was found that CYP2E1 Pst, CYP2E1 Ins96, CYP1A1 Msp, GSTT1, GSTM1, GSTP gene polymorphisms associated with the susceptibility of peripheral nerve damage. These findings suggested that CYP2E1 gene might increase the susceptibility to n-hexane-induced peripheral damage.

Adult↗

PubMedDate not supplied

Immunohistochemical detection of interferon-gamma-producing cells in dermatophytosis.

Skin lesions of dermatophytosis are thought to be a result of a T cell-dependent inflammatory response that is mediated by various cytokines. We examined whether IFN-gamma-positive cells (as expression of Th1 response) were present in the skin lesions of dermatophytosis in situ by immunohistochemical techniques. Mixtures of CD4-positive T cells and CD8-positive T cells were found to be present in the dermal infiltrates of the lesions. Considerable numbers of CD1a-positive cells were detected in the upper dermis and epidermis. A marked accumulation of CD68-positive cells was found in the upper dermis. IFN-gamma-positive cells were present in the upper dermis of the lesions. The pattern of IFN-gamma staining appeared to be intracellular in mononuclear lymphoid cells. The staining was considered to be highly specific because it could be completely blocked by preabsorption with recombinant IFN-gamma. Our data support the hypothesis that the skin lesions of dermatophytosis may be associated with a Th1 response. Th1 response, which is characterized by IFN-gamma release, is thought to be involved in the host defense against dermatophytes and to reflect cutaneous reaction in dermatophytosis.

Animals↗

PubMedDate not supplied

Immunohistochemical localization of activated and mature CD83+ dendritic cells in granulomas of sporotrichosis.

Dendritic cells (DC) are considered to be the most potent antigen-presenting cells (APC) and CD83 is expressed at a high level on immune-competent, activated and mature DC. In order to obtain insight into the immune response in sporotrichosis, we searched immunohistochemically for CD83+ DC in the granulomatous skin lesions of patients. A small but significant subpopulation of CD83+ DC (approximately 0.2 to 0.8% of inflammatory cells) was found. The most common distribution pattern of CD83+ DC was as clusters with mononuclear lymphoid cells within the granulomas. In addition, CD83+ DC were occasionally scattered around the granulomas. High-intensity staining of CD83 antigens was detected not only on the surface, but also in the cytoplasm of DC. No CD83+ DC were observed in the epidermis. A considerable amount of CD1a+ cells were detected in the epidermis, papillary dermis and around the granulomas, but CD1a+ cells were rarely found within the granulomas. There were large numbers of CD68+ monocytes and macrophages in the granulomas. These results indicate that activated and mature DC may play a role in the immune response to sporotrichosis.

Antigens, CD↗

PubMedDate not supplied

Growth hormone receptor antagonist administration inhibits growth of human colorectal carcinoma in nude mice.

Increasing evidence has accumulated in support of the hypothesis that growth hormone (GH) and insulin-like growth factors (IGFs) play a role in carcinogenesis. In order to test this hypothesis, female nude mice were xenografted with two different human colorectal cancer cell lines (COLO 205 and HT-29) and randomized to receive placebo or a GH receptor antagonist (GHRA) (B2036-PEG) every second day for 16 days. The tumour volume was measured in each animal throughout the study and by the end of the experiment the tumour weights were recorded. After 16 days of therapy in nude mice with the COLO 205 colorectal cancer, GHRA treatment caused a 39% reduction in tumour volume (p < 0.02) and a 44% reduction in tumour weight (p < 0.01). GHRA treatment equally reduced circulating IGF-I and IGFBP-3 levels, while apoptosis was increased in the treatment group. Expression of IGF-I, IGF-II and the corresponding receptors in COLO 205 tumours was also decreased by the treatment. GHRA had no effect on the growth of the HT-29 colorectal cancer despite pronounced reduction in serum IGF-I. The present study thereby demonstrates a central role for the GH/IGF system in the pathogenesis of some colorectal cancers and suggests that specific GHR blockade may present a new concept in the treatment of colorectal cancer.

Adenocarcinoma↗

PubMedDate not supplied

Calorimetric monitoring of lyophilization.

This paper describes an apparatus and method for monitoring the lyophilization of a formulation by using calorimetric measurements. From calorimetric measurements, the energy transferred during each phase of the process can be determined. A brief review of the existing monitoring methods shows that they possess no direct relationship to the thermal energy that represents the real driving force for the lyophilization process. A general description of the apparatus is presented with special emphasis made on the sensor construction and calibration. The means for determining the heat transfer rate (Qm) and total energy (Hm) for each step of the process are described. The use of calorimetric measurements are demonstrated by showing actual thermographs of freezing, primary drying and secondary drying processes for several formulations. Some key advantages of calorimetric monitoring of the lyophilization process are demonstrated by accurately determining the completion of the primary drying and detection of exothermic reactions during the secondary drying.

Calibration↗