Improved envelope function selected by long-term cultivation of a translation-impaired HIV-1 mutant

The untranslated leader region of the human immunodeficiency virus (HIV) RNA genome contains multiple regulatory elements that fold into stable hairpin structures. Because extensive secondary structure can block the scanning of ribosomes, an alternative mechanism for HIV translation seems feasible. To study the mechanism of HIV-1 mRNA translation, a start codon was introduced in the leader region that will usurp scanning ribosomes. This upstream AUG mutation (uAUG) inhibited HIV gene expression, indicating that HIV-1 mRNA translation occurs via the regular scanning mechanism. Revertant viruses with increased replication capacity were obtained upon prolonged culturing of the mutant virus. To our surprise, the introduced start codon had not been inactivated in these phenotypic revertants. Instead, these revertants contain additional mutations in the envelope (Env) protein that stimulated HIV-1 replication. These second-site Env mutations did not specifically overcome the gene expression defect of the uAUG mutant, as the replication capacity of other HIV-1 mutants with an unrelated defect could also be improved. The uAUG construct appears to be a unique tool in forced HIV-1 adaptation studies because the deleterious uAUG mutation is stably maintained in the progeny, yielding phenotypic revertants with second-site mutations elsewhere in the viral genome.     

Differential effect of thyroid-stimulating hormone (TSH) on intracellular free calcium and cAMP in cells transfected with the human TSH receptor

The major part of research dealing with the biophysical and biochemical properties of airway smooth muscle is based on the assumption that the cells constituting the tissue are homogenous. For striated muscle this has been shown untenable. In recent years almost every property of vascular smooth muscle has been also demonstrated to be heterogeneous. This realization has been late in arriving on the airway smooth muscle research scene. Our own studies have shown that mechanical properties are, in quantitative terms, heterogeneously distributed down the airways and that contractility, for example, in extrapulmonary and intrapulmonary airways differs markedly. Another indication of heterogeneity is derived from studies of the biochemical properties of airway smooth muscle cells (ASMCs) in culture. Dramatic changes in phenotype expression were found with days in culture. Just after isolation from the tissue, the cells were of contractile type and contained mature isoforms of contractile, regulatory and cytoskeletal proteins. After the fourth day in culture the cellular phenotype changed such that contractile filaments diminished rapidly with smooth muscle isoforms being replaced by non-muscle isoforms. The cell assumed secretory or synthetic properties and commenced proliferating rapidly. It is possible that similar changes in phenotype could occur in vivo in cells undergoing hypertrophy or hyperplasia. Thus, a thickened medial layer of the type seen in the walls of airways from asthmatic airways is not necessarily one endowed with increased contractility and, in fact, the latter may be subnormal. Finally, using the so-called motility assay, we studied the velocity of translation of actin filaments by myosin molecules obtained from antigen-sensitized and control airway smooth muscle. We found no change in maximum velocity of actin translation. This was under conditions where the myosin light chain (MLC) was fully phosphorylated. However, in these tissues we found heterogeneity in myosin light chain kinase (MLCK) content which, we inferred, accounted for the difference in shortening velocity between control and sensitized muscle strips in vitro.     

Diuresis and natriuresis produced by long term administration of a selective Angiotensin-(1-7) antagonist in normotensive and hypertensive rats

Intrarenal arterial infusion of endothelin-1 (1, 3 and 10 ng/kg per min) reduced renal blood flow, urine flow rate and urinary Na+ excretion without affecting fractional Na+ excretion in anesthetized rabbits. An endothelin ET(A) receptor antagonist (R)2-[(R)-2-[(S)-2-[[1-(hexahydro-1H-azepinyl)]carbonyl]amino-4-me thyl-pentanoyl]amino-3-[3-(1-methyl-1H-indolyl)]propionyl]amino-3-(2-pyr idyl)propionic acid (FR139317, 1 microg/kg per min) attenuated the endothelin-1 (1 ng/kg per min)-induced renal responses. An endothelin ET(B) receptor antagonist N-cis 2,6-dimetylpiperidinocarbonyl-L-gamma-metylleucyl-D-1-met hoxycarbonyltryptophanyl-D-norleucine (BQ-788, 1 microg/kg per min) potentiated the endothelin-1-induced changes in renal blood flow, urine flow rate and urinary Na+ excretion. A nitric oxide (NO) synthase inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME, 50 microg/kg per min) also potentiated the endothelin-1-induced reductions in urine flow rate and urinary Na+ excretion but not the reduction in renal blood flow. Endothelin-1 reduced fractional Na+ excretion in the presence of BQ-788 or L-NAME. A spontaneous NO donor 1-hydroxy-2-oxo-3-(N-methyl-3-aminopropyl)-3-methyl-1-triazene (30 ng/kg per min) slightly attenuated the antinatriuresis but not the vasoconstriction induced by endothelin-1. These results suggest that in the rabbit kidney in vivo endothelin ET(A) receptors mediate endothelin-1-evoked vasoconstriction and tubular Na+ reabsorption, that the concomitant stimulation of endothelin ET(B) receptors by endothelin-1 counteracts both the ET(A) receptor-mediated vascular and tubular actions, and that the tubular action, but not the vascular action, of endothelin-1 is also susceptible to changes in renal NO level.     

Idiopathic CSF rhinorrhoea presenting with tension pneumocephalus and hemiparesis

A case of non-traumatic/non-iatrogenic CSF rhinorrhoea, presenting with tension pneumocephalus and hemiparesis is described. The possible pathological processes involved in this rare case are discussed. Cases in the literature of idiopathic CSF rhinorrhoea and also those of spontaneous pneumocephalus are reviewed.     

Application of distal metaphyseal osteotomy for treatment of high intermetatarsal angle bunion deformities

4-1BB is an inducible T cell surface receptor which belongs to the tumor necrosis factor receptor superfamily, a group of cysteine-rich cell-surface molecules. Both human and mouse 4-1BB recently received HLDA nomenclature. Naive T cells lack 4-1BB, which is not only induced upon T cell activation, but also remains on activated T cells. The natural ligand for 4-1BB, 4-1BBL is also induced and is found on activated antigen-presenting cells. Cross-linking of the 4-1BB molecule by agonistic antibody transmits a distinct and potent co-stimulatory signal leading to the activation and differentiation of CD4(+) and CD8(+) cells. 4-1BB transmits signals through the TRAF2-NIK pathway and activates NF-kappaB. Signals relayed through 4-1BB inhibit activation-induced cell death and rescue the immune system during the post-CD28 phase. Antibodies to the 4-1BB molecule can increase GVHD, accelerate the rejection of cardiac allograft and skin transplants, and eradicate established tumors. Interference with the 4-1BB-4-1BBL pathway may be of therapeutic use in the treatment of HIV infection. 4-1BB-deficient mice show dysregulated immune responses and mount elevated Ig responses to T-dependent antigens.     

Bacterial contig map of the 21q11 region associated with Alzheimer's disease and abnormal myelopoiesis in Down syndrome

We present a high-resolution bacterial contig map of 3.4 Mb of genomic DNA in human chromosome 21q11-q21, encompassing the region of elevated disomic homozygosity in Down Syndrome-associated abnormal myelopoiesis and leukemia, as well as the markers, which has shown a strong association with Alzheimer's Disease that has never been explained. The map contains 89 overlapping PACs, BACs, or cosmids in three contigs (850, 850, and 1500 kb) with two gaps (one of 140-210 kb and the second <5 kb). To date, eight transcribed sequences derived by cDNA selection, exon trapping, and/or global EST sequencing have been positioned onto the map, and the only two genes so far mapped to this cytogenetic region, STCH and RIP140 have been precisely localized. This work converts a further 10% of chromosome 21q into a high-resolution bacterial contig map, which will be the physical basis for the long-range sequencing of this region. The map will also enable positional derivation of new transcribed sequences, as well as new polymorphic probes, that will help in elucidation of the role the genes in this region may play in abnormal myelopoiesis and leukemia associated with trisomy 21 and Alzheimer's Disease.     

Excessive fibrinolysis: the coagulopathy following Merrem''s hump-nosed viper (Hypnale hypnale) bites

In 56 patients with proven hump-nosed viper (Hypnale hypnale) bites, 12 (21.4%) developed continued oozing of blood from the site of the bite and a prolonged clotting time. Further investigations showed low fibrinogen levels and increased fibrinogen degradation products in plamsa. The bleeding time, platelet count, prothrombin time, and partial thromboplastin time with kaolin were normal. The bite of this snake can be complicated with a coagulopathy in which excessive fibrinolysis seems to be the main abnormality.     

Use of the Hough transform for image data compression

It is shown here that the Hough transform may be used for encoding of line curves and waveforms that consist of the concatenation of curves from an underlying set of families of curves. Several properties of the transform are given in this context.