The envelope glycoprotein ectodomains determine the efficiency of CD4+ T lymphocyte depletion in simian-human immunodeficiency virus-infected macaques

CD4+ T lymphocyte depletion in human immunodeficiency virus type 1 (HIV-1)-infected humans underlies the development of acquired immune deficiency syndrome. Using a model in which rhesus macaques were infected with chimeric simian-human immunodeficiency viruses (SHIVs), we show that both the level of viremia and the structure of the HIV-1 envelope glycoprotein ectodomains individually contributed to the efficiency with which CD4(+) T lymphocytes were depleted. The envelope glycoproteins of recombinant SHIVs that efficiently caused loss of CD4(+) T lymphocytes exhibited increased chemokine receptor binding and membrane-fusing capacity compared with those of less pathogenic viruses. These studies identify the HIV-1 envelope glycoprotein ectodomains as determinants of CD4(+) T lymphocyte loss in vivo and provide a foundation for studying pathogenic mechanisms.     

Atypical acute dystonia

Acute dystonia is a common adverse effect following anti-psychotic medication, which mainly appears shortly after beginning treatment or increasing the dosage. Laryngeal dysfunction may carely occur as part of the picture of acute dystonia and, if so, usually with dyspnoea. We describe a case of acute dystonia with atypical onset without relation to changes in dosage and with laryngeal involvement with aphonia, but without dyspnoea.     

The role of N-glycosylation for functional expression of the human platelet-activating factor receptor. Glycosylation is required for efficient membrane trafficking

Streptococcus pneumoniae has been shown to utilize the platelet activating factor receptor for binding and invasion of host cells (Cundell, D. R., Gerard, N. P., Gerard, C., Idanpaan-Heikkila, I., and Tuomanen, E. I. (1995) Nature, in press). Because bacterial binding is in part carbohydrate dependent, and the human platelet-activating factor (PAF) receptor bears a single N-linked glycosylation sequence in the second extracellular loop, we undertook studies to determine the role of this epitope in PAF receptor function. Binding of pneumococci to COS cells transfected with the human PAF receptor is greatly reduced for a receptor mutant that bears no N-linked glycosylation site. Immunohistochemical and binding analyses show decreased expression of the non-glycosylated molecule on the cell membrane relative to the wild type receptor; however, metabolic labeling and immunopurification indicate it is synthesized intracellularly at a level similar to the native molecule. A mutant receptor encoding a functional glycosylation site at the NH2 terminus is better expressed at the cell surface compared with the non-glycosylated form, indicating that trafficking to the cell surface is facilitated by glycosylation, but its location is relatively unimportant. The binding affinity for PAF is not significantly effected by the presence or location of the carbohydrate, and variations in cell surface expression have little influence on signal transduction, as the non-glycosylated PAF receptor is equally effective for activation of phospholipase C as the native molecule. These data are supportive of pneumococcal binding on protein moiety(ies) of the PAF receptor and indicate that N-glycosylation facilitates expression of the protein on the cell membrane.     

Three distinct D-amino acid substitutions confer potent antiangiogenic activity on an inactive peptide derived from a thrombospondin-1 type 1 repeat

Mal II, a 19-residue peptide derived from the second type 1 properdin-like repeat of the antiangiogenic protein thrombospondin-1 (TSP-1), was inactive in angiogenesis assays. Yet the substitution of any one of three L-amino acids by their D-enantiomers conferred on this peptide a potent antiangiogenic activity approaching that of the intact 450-kDa TSP-1. Substituted peptides inhibited the migration of capillary endothelial cells with an ED50 of 8.5 nM for the D-Ile-15 substitution, 10 nM for the D-Ser-4 substitution, and 0.75 nM for the D-Ser-5 substitution. A peptide with D-Ile at position 15 could be shortened to its last seven amino acids with little loss in activity. Like whole TSP-1, the Mal II D-Ile derivative inhibited a broad range of angiogenic inducers, was selective for endothelial cells, and required CD36 receptor binding for activity. A variety of end modifications further improved peptide potency. An ethylamide-capped heptapeptide was also active systemically in that when injected i.p. it rendered mice unable to mount a corneal angiogenic response, suggesting the potential usefulness of such peptides as antiangiogenic therapeutics.     

A combined approach of conventional and molecular cytogenetics for detailed karyotypic analysis of the small cell lung carcinoma cell line U2020

Until recently the ability to analyze complex karyotypic rearrangements was totally dependent upon light microscopy of G-banded chromosomes. Developments in the area of molecular cytogenetics have revolutionized such analysis, making it possible to determine the nature of complex rearrangements. An extensive analysis has been made of the small cell lung carcinoma (SCLC) cell line U2020, using a combined approach of conventional and molecular cytogenetics, enabling a highly detailed karyotype to be constructed revealing rearrangements previously undetected by G-banding alone. This approach offers the opportunity to reassess other tumor karyotypes, particularly those of high complexity found in solid tumors, for tumor-specific consistent rearrangements indecipherable by conventional karyotyping.     

Effects of temperature and volatile anesthetics on GABA(A) receptors

BACKGROUND: Potentiation of the activity of the gamma-aminobutyric acid type A (GABA(A)) receptor channel by volatile anesthetic agents is usually studied in vitro at room temperature. Systematic variation of temperature can be used to assess the relevance of this receptor to general anesthesia and to characterize the modulation of its behavior by volatile agents at normal body temperature. METHODS: Potentiation of the GABA(A) receptor by halothane, sevoflurane, isoflurane, and methoxyflurane was studied at six temperatures in the range 10-37 degrees C using the whole-cell patch-clamp technique and mouse fibroblast cells stably transfected with defined GABA(A) receptor subunits. RESULTS: Control GABA concentration-response plots showed small and physically reasonable changes in the GABA concentration required for a half-maximal effect, the Hill coefficient, and maximal response over the range 10-30 degrees C. Potentiations of GABA (1 microM) responses by aqueous minimum alveolar concentrations of the volatile anesthetic agents decreased with increasing temperature from 10-37 degrees C in an agent-specific manner (methoxyflurane > isoflurane > sevoflurane > halothane) but tended to equalize at normal body temperature (37 degrees C). These findings are in line with published results on the temperature dependence of anesthetic potencies in animals. CONCLUSIONS: These results are consistent with direct binding of volatile anesthetic agents to the GABA(A) receptor channel playing an important role in general anesthesia. The finding that the degree of anesthetic potentiation was agent-specific at low temperatures but not at 37 degrees C emphasizes the importance of doing in vitro experiments at normal body temperature.     

The material basis for reduced mechanical properties in oim mice bones

Osteogenesis imperfecta (OI), a heritable disease caused by molecular defects in type I collagen, is characterized by skeletal deformities and brittle bones. The heterozygous and homozygous oim mice (oim/+ and oim/oim) exhibit mild and severe OI phenotypes, respectively, serving as controlled animal models of this disease. In the current study, bone geometry, mechanics, and material properties of 1-year-old mice were evaluated to determine factors that influence the severity of phenotype in OI. The oim/oim mice exhibited significantly smaller body size, femur length, and moment of area compared with oim/+ and wild-type (+/+) controls. The oim/oim femur mechanical properties of failure torque and stiffness were 40% and 30%, respectively, of the +/+ values, and 53% and 36% of the oim/+ values. Collagen content was reduced by 20% in the oim/oim compared with +/+ bone and tended to be intermediate to these values for the oim/+. Mineral content was not significantly different between the oim/oim and +/+ bones. However, the oim/oim ash content was significantly reduced compared with that of the oim/+. Mineral carbonate content was reduced by 23% in the oim/oim bone compared with controls. Mineral crystallinity was reduced in the oim/oim and oim/+ bone compared with controls. Overall, for the majority of parameters examined (geometrical, mechanical, and material), the oim/+ values were intermediate to those of the oim/oim and +/+, a finding that parallels the phenotypes of the mice. This provides evidence that specific material properties, such as mineral crystallinity and collagen content, are indicative and possibly predictive of bone fragility in this mouse model, and by analogy in human OI.