Presentation of viral antigen controlled by a gene in the major histocompatibility complex

We describe a mutant human cell line (LBL 721.174) that has lost a function required for presentation of intracellular viral antigens with class I molecules of the major histocompatibility complex (MHC), but retains the capacity to present defined epitopes as extracellular peptides. The cell also has a defect in the assembly and expression of class I MHC molecules, which we show can be restored by exposure of the cells to a peptide epitope. This phenotype suggests a defect in the association of intracellular antigen with class I molecules similar to that described for the murine mutant RMA-S (ref. 5), but in the present case the genetic defect can be mapped within the MHC locus on human chromosome 6.     

Localization of VP4 neutralization sites in rotavirus by three-dimensional cryo-electron microscopy

Three-dimensional structures of several spherical viruses have been determined by electron microscopy and X-ray crystallography. We report here the first three-dimensional structure of the complex between an intact virus and Fab fragments of a neutralizing monoclonal antibody. The antibody is against VP4, one of the two outer capsid proteins of rotaviruses. These large icosahedral viruses cause gastroenteritis in children and young animals and account for over a million human deaths annually. VP4 in these viruses has been implicated in several important functions such as cell penetration, haemagglutination, neutralization and virulence. Here we demonstrate that the surface spikes on rotavirus particles are made up of VP4. Antigenic sites are located near the distal ends of the spikes and two Fab fragments bind to each of the sixty spikes. The mass of the spike indicates that it is a dimer of VP4. The bilobed structure at the distal end of the spike may be involved in both the attachment to the cell and in viral penetration. A novel feature in the virus-Fab complex is the structural difference between the two chemically equivalent Fab fragments on each spike, which could be indicative of variations in the Fab elbow angles.     

二阶卷积的构造

文中给出了二阶卷积算子的定义和性质并举例说明。     

一类周期拟环的结构

本文得到了拟环满足条件ｘｙ＝ｘｙ￣（ｎ（ｘ，ｙ）ｘ或ｘｙ＝ｙｘ￣（ｎ（ｘ，ｙ）ｙ的分解定理。     

Incubation periods for paediatric AIDS patients

A recent seroprevalence study of newborns indicates that one in 62 children born in New York City has antibodies to the human immunodeficiency virus (HIV). The distribution of incubation periods for paediatric patients is needed to estimate future AIDS case loads from these seroprevalence data. Current estimates of incubation periods for paediatric patients are based on limited data. We use parametric and non-parametric methods to analyse incubation periods for 215 paediatric patients with AIDS whose only known route of infection is maternal. We conclude that incubation periods are longer than previously reported; that there is a distinct knee in the incubation period distribution at seven months which suggests two risk populations; and that there is an increase in incidence which is consistent with exponential growth.     

Identification of a new class of steroid hormone receptors

The gonads and adrenal glands produce steroids classified into five major groups which include the oestrogens, progestins, androgens, glucocorticoids and mineralocorticoids. Gonadal steroids control the differentiation and growth of the reproductive system, induce and maintain sexual characteristics and modulate reproductive behaviour. Adrenal steroids also influence differentiation as well as being metabolic regulators. The effects of each steroid depend primarily on its specific receptors, the nature of which could therefore provide a basis for classification of steroid hormone action. The successful cloning, sequencing and expression of the human glucocorticoid (hGR) (ref. 1), oestrogen (hER), progesterone (hPR), and mineralocorticoid (hMR) receptors, complementary DNA, plus homologues from various species, provides the first opportunity to study receptor structure and its influence on gene expression. Sequence comparison and mutational analysis show structural features common to all groups of steroid hormone receptors. The receptors share a highly conserved cysteine-rich region which functions as the DNA-binding domain. This common segment allows the genome to be scanned for related gene products: hMR cDNA for example, was isolated using an hGR hybridization probe. In this study, using the DNA-binding domain of the human oestrogen receptor cDNA as a hybridization probe, we have isolated two cDNA clones encoding polypeptides with structural features suggestive of cryptic steroid hormone receptors which could participate in a new hormone response system.     

Effect of intralipid infusion on serum high- and low-density lipoprotein cholesterol,lecithin: Cholesterol acyltransferase,and lipoprotein lipase in tumor-bearing rats

We compared the effects of 0.45% normal saline (NS), 5% Intralipid^® (IL), and 16.7% glucose (Glu) infusions on total serum triglycerides and cholesterol, serum high-(HDL-c) and low-density lipoprotein cholesterol (LDL-c), and activity of serum lecithin: cholesterol acyltransferase (LCAT), and serum lipoprotein lipase (LPL) in rats implanted with a fibrosarcoma. In tumor-bearing rats given NS, a two-fold increase in total serum cholesterol, a four-fold increase in LDL-c, and a five-fold decrease in the HDL-c/LDL-c ratio were observed compared to tumor-free rats. In tumor-bearing rats administered IL, a two-fold increase in total serum triglyceride and cholesterol, a three-fold increase in HDL-c and HDL-c/LDL-c ratio, and a two-fold increase in LPL activity were observed compared to tumor-bearing rats administered NS. In tumor-bearing rats administered Glu, a two-fold decrease in total serum cholesterol, a two-fold decrease in HDL-c, and a three-fold decrease in LDL-c were observed compared to tumor-bearing rats administered NS. Tumor weights and LCAT activity did not differ significantly between treatment groups. Previous results have demonstrated that lipophilic compounds that interact with plasma lipoproteins have altered pharmacological effects when administered with IL. Therefore, this study suggests that IL infusions alter the HDL-c/LDL-c ratio and could affect the pharmacological behavior of anticancer compounds that predominantly distribute into the LDL fraction upon entrance into the bloodstream.