Stable expression of mammalian beta 1,4-galactosyltransferase extends the N-glycosylation pathway in insect cells

An established lepidopteran insect cell line (Sf9) was cotransfected with expression plasmids encoding neomycin phosphotransferase and bovine beta 1,4-galactosyltransferase. Neomycin-resistant transformants were selected, assayed for beta 1,4-galactosyltransferase activity, and the transformant with the highest level of enzymatic activity was characterized. Southern blots indicated that this transformed Sf9 cell derivative contained multiple copies of the galactosyltransferase- encoding expression plasmid integrated at a single site in its genome. One-step growth curves showed that these cells supported normal levels of baculovirus replication. Baculovirus infection of the transformed cells stimulated beta 1,4-galactosyltransferase activity almost 5-fold by 12 h postinfection. This was followed by a gradual decline in activity, but the infected cells still had about as much activity as uninfected controls as late as 48 h after infection and they were able to produce a beta 1,4-galactosylated virion glycoprotein during infection. Infection of the transformed cells with a conventional recombinant baculovirus expression vector encoding human tissue plasminogen activator also resulted in the production of a galactosylated end-product. These results demonstrate that stable transformation can be used to add a functional mammalian glycosyltransferase to lepidopteran insect cells and extend their N- glycosylation pathway. Furthermore, stably-transformed insect cells can be used as modified hosts for conventional baculovirus expression vectors to produce foreign glycoproteins with "mammalianized" glycans which more closely resemble those produced by higher eucaryotes.      

Negative regulation of CD4 lineage development and responses by CD5

CD5 deficiency results in a hyper-responsive phenotype to Ag receptor stimulation. Here we show that the development and responses of CD4 lineage T cells are regulated by the function of CD5. Thymocytes expressing the I-Ad-restricted DO11.10 TCR undergo abnormal selection without CD5. In H-2d mice, the absence of CD5 causes deletion of double-positive thymocytes, but allows for efficient selection of cells expressing high levels of the DO11.10 clonotype. By contrast, there is enhanced negative selection against the DO11.10 clonotype in the presence of I-Ab. T cell hybridomas and DO11.10 T cells are more responsive to TCR stimulation in the absence of CD5. Such hypersensitivity can be eliminated by expression of wild-type CD5, but not by a form of CD5 that lacks the cytoplasmic tail. Finally, CD5 deficiency partially suppresses the block of CD4 lineage development in CD4-deficient mice. Taken together, the data support a general role for CD5 as a negative regulator of Ag receptor signaling in the development and immune responses of CD4 lineage T cells.     

The t complex polypeptide 1 (TCP-1) is associated with the cytoplasmic aspect of Golgi membranes

The t complex polypeptide 1 (TCP-1) is a protein of unknown function expressed in large amounts during spermatogenesis. Rat monoclonal antibodies recognizing TCP-1 have been prepared and used to immunoprecipitate and Western blot a 57 kd protein from germ cell and tissue culture cell extracts. In tissue culture cells, indirect immunofluorescent localization of antigen indicated a perinuclear distribution similar to that of the Golgi apparatus. Analysis of the TCP-1 distribution in tissue culture cells showed that the polypeptide was associated with the cytoplasmic aspect of membranes of the trans-Golgi network (TGN). The distribution in spermatids suggested that TCP-1 was localized to structures often associated with the developing acrosome. The TCP-1 antigenic epitopes are highly conserved, allowing the protein to be identified in cells across a wide variety of vertebrate species and tissues. These experiments suggest that TCP-1 may be essential for transport of proteins through the exocytic pathway in all cells and required in large amounts for acrosome formation in developing spermatids.     

Mouse mesangial cells produce colony-stimulating factor-1 (CSF-1) and express the CSF-1 receptor

CSF-1 stimulates the survival, proliferation, and differentiation of mononuclear phagocytes and may also play a role in placental development. The expression of CSF-1 and the CSF-1 receptor (CSF-1R) and their regulation were examined in cultures of mouse mesangial cells (MC). The concentration of CSF-1 in the medium of cultured MC increased linearly with time over 24 h. IFN-gamma stimulated and dibutyryl cyclic AMP inhibited CSF-1 production in a dose-dependent manner. MC expression of CSF-1 mRNA was shown by Northern blot analysis, and CSF-1 mRNA levels were increased within 4 h of IFN-gamma addition and inhibited within 4 h of dibutyryl cyclic AMP addition. Indirect immunofluorescence indicated that 90% of the untreated cultured MC expressed CSF-1. In addition, CSF-1R expression by MC was demonstrated by immunofluorescence with anti-receptor antibody, specific binding of [125I] CSF-1, and expression of the CSF-1R mRNA by Northern blot analysis. Thus, mouse MC, specialized pericytes of non-bone marrow origin, not only produce CSF-1 but also express receptors for CSF-1. The effects of CSF-1 on MC may be important in the control of immune function in the glomerulus.     

Low Resting and Sleeping Energy Expenditure and Fat Use Do Not Contribute to Obesity in Women

Objective: Determine whether sleeping and resting energy expenditure and sleeping, resting, and 24‐hour fuel use distinguish obesity‐prone from obesity‐resistant women and whether these metabolic factors explain long‐term weight gain. Research Methods and Procedures: Forty‐nine previously overweight but currently normal‐weight women were compared with 49 never‐overweight controls. To date, 87% of the 98 women have been re‐evaluated after 1 year of follow‐up, without intervention, and 38% after 2 years. Subjects were studied at a General Clinical Research Center after 4 weeks of tightly controlled conditions of energy balance and macronutrient intake. Forty‐nine obesity‐prone weight‐reduced women were group‐matched with 49 never‐overweight obesity‐resistant controls. All were premenopausal, sedentary, and normoglycemic. Energy expenditure and fuel use were assessed using chamber calorimetry. Body composition was assessed using DXA. Results: At baseline, percent body fat was not different between the obesity‐prone and control women (33 ± 4% vs. 32 ± 5%, respectively; p = 0.22). Analysis of covariance results show that after adjusting for lean and fat mass, sleeping and resting energy expenditure of obesity‐prone women was within 2% of controls. Neither sleeping nor resting energy expenditure nor sleeping, resting, or 24‐hour fuel use was significantly different between the groups (p > 0.25). None of the metabolic variables contributed significantly to patterns of weight gain at 1 or 2 years of follow‐up. Discussion: The results suggest that when resting and sleeping energy expenditure and fuel use are assessed under tightly controlled conditions, these metabolic factors do not distinguish obesity‐prone from obesity‐resistant women or explain long‐term weight changes.     

长春市儿童医院1998～2001年婴幼儿杯状病毒腹泻流行病学研究

人类杯状病毒(human calicivirus,HuCV)是引起儿童和成人非菌性胃肠炎的主要病原之一.为了掌握HuCV在我国的流行情况,1998年7月至2001年6月,从长春市儿童医院2343例5岁以下腹泻患儿中共收集粪便标本1264份,其中1056份来自2135例住院患儿.对轮状病毒检测为阴性的588份标本,经多价酶免疫试验(EIA)和两组引物反转录-聚合酶链反应(RT-PCR)检测HuCV,202份为阳性,其中住院患儿标本178份,HuCV检出率为16.9%.HuCV腹泻以2岁以下儿童为主(占96%),流行高峰季节为11月至次年3月.选择17株HuCV进行分子鉴定,15株属GⅡ-4群,1株属GⅡ-3群,另1株属GⅠ-2群,表明GⅡ-4群HuCV是我国流行的优势株.根据HuCV住院患儿的监测资料初步估计,HuCV腹泻住院率约为0.5‰～2.4‰.讨论了长春地区HuCV的流行趋势和疾病负担.以上结果为我国HuCV腹泻的预防和控制提供了科学依据.     

Ubiquitin/proteasome-dependent degradation of D-type cyclins is linked to tumor necrosis factor-induced cell cycle arrest

Tumor necrosis factor-alpha (TNF) is well known for its cytotoxic effect on malignant cells. Its role in cell cycle control is relatively less known. In this study, we found that TNF induced G(1) arrest of TF-1 and MV4-11 cells while simultaneously causing apoptosis. Treatment of the cells with TNF for 48 h caused cell cycle arrest, accompanied by dephosphorylation of pRb and reduction in D-type cyclin expression. The down-regulation of the D-type cyclins resulted in approximately 50-80% decrease of the cyclin-dependent kinase activities. Cells treated with calpain-dependent inhibitor ALLN and apoptosis inhibitor zVAD-FMK suppressed degradation of IkappaBalpha and activation of caspase 3, respectively. However, treatment of cells with these two inhibitors was not able to prevent TNF-induced down-regulation of the D-type cyclins. In contrast, proteasome inhibitor MG-132 and lactacystin blocked both TNF-induced degradation of IkappaBalpha and down-regulation of D-type cyclins. These data suggest that down-regulation of D-type cyclins by TNF may be proteasome-proteolysis dependent. Additional support for this conclusion was obtained from experiments showing an increase of proteasome activity in TNF-treated cells and in vitro degradation of cyclin D3 by 26 S proteasome.