Noradrenaline use is not associated with extubation failure in septic patients.

Standard clinical practice recommends minimal doses of vasoactive drugs during weaning of patients from mechanical ventilation. However there are currently no clinical data to inform clinicians about whether the use of noradrenaline during weaning predisposes to weaning failure. The objective of this study was to evaluate whether the necessity of the vasopressor noradrenaline in mechanically ventilated patients recovering from septic shock changed the extubation outcome. A total of 656 patients recovering from septic shock on mechanical ventilation were selected from intensive care units in two university hospitals. Patients receiving noradrenaline at the time of weaning and case-controls not taking noradrenaline were matched for age, gender, haemodynamic and ventilatory parameters, aetiology of respiratory failure and APACHE II score. One hundred and forty-five patients who successfully tolerated a spontaneous breathing trial were extubated while on noradrenaline therapy and the reintubation rate was measured. In the noradrenaline group, the mean dose of noradrenaline during initial shock treatment was 0.52+/-0.29 microg/kg/min and 0.12+/-0.10 microg/kg/min during weaning. The reintubation rate was 12/63 (19%) in the noradrenaline group and 15/82 (18.3%) in the control group (P=1.00). Intensive care unit mortality was also similar in both groups (10/63, 15.9%) for noradrenaline patients and (11/82, 13.4%) for control patients (P=0.81). Arterial blood gases and ventilatory and haemodynamic parameters were similar in all patients regardless of weaning success. We did not find that the use of noradrenaline at the time of weaning was associated with extubation failure. Low doses of noradrenaline may not preclude weaning from mechanical ventilation.

Antibody raised against soluble CD4-rgp120 complex recognizes the CD4 moiety and blocks membrane fusion without inhibiting CD4-gp120 binding.

We studied the humoral response of mice immunized with soluble CD4-rgp120 complex, testing polyclonal and monoclonal antibodies (mAbs) with the aim of identifying molecular changes that take place after the first interaction between human immunodeficiency virus and the cell surface. The antisera had a paradoxically high syncytia-blocking titer associated with anti-CD4 specificity, while their capacity to inhibit CD4-gp120 binding was relatively modest. One of the mAbs produced from these responders blocks syncytia formation but does not inhibit CD4 interaction with gp120. Apparently, this mAb interacts with the CD4 moiety of CD4-gp120 complex and prevents a post-binding event necessary for membrane fusion and viral infection.

Regulation of Thy-1 gene expression in transgenic mice.

Genomic DNA fragments encompassing the human Thy-1 or mouse Thy-1.1 gene have been microinjected into pronuclei of mouse embryos homozygous for the Thy-1.2 allele. In the resulting transgenic mice, the human gene is expressed in a pattern characteristic of normal human tissues, and is not influenced by the pattern of endogenous mouse Thy-1 expression. The mouse Thy-1.1 gene fragment is expressed in a pattern typical of mouse Thy-1, although it is more limited in its distribution. The results indicate the presence of multiple cis-acting regulators of Thy-1 gene expression that have changed in both their character and arrangement over the course of Thy-1 gene evolution.

Polymorphism of HLA-DR beta chains in DR4, -7, and -9 haplotypes: implications for the mechanisms of allelic variation.

We have isolated and sequenced cDNA clones corresponding to the DR beta 1 and DR beta 2 loci from two homozygous B-cell lines typed as DR7 (Burkhart) and DR9 (ISK). These nucleotide sequences were compared to beta 1 and beta 2 chains of other DR haplotypes. The first-domain sequences of beta 2 chains are identical in DR4 and DR7 haplotypes. In addition, there is strong sequence homology within the 3' untranslated regions of beta 1 genes from DR4, -7, and -9 haplotypes, thus confirming the close evolutionary relationship among these three haplotypes. In contrast, the first-domain sequences of beta 1 molecules from these haplotypes are very different from each other and do not reflect the DR4, -7, -9 family relationship. Two explanations for the differences in degree of diversity between beta 1 and beta 2 chains are suggested. The differences may be a consequence of selection pressures; this implies functional differences for products of the beta 1 and beta 2 loci. Alternatively, closely linked segments of the human class II region may differ in their underlying rates of variation, independent of selection pressures, and this may in part account for the extraordinary diversity found in the beta 1 first domain.

Analysis of DR beta and DQ beta chain cDNA clones from a DR7 haplotype.

A cDNA library was constructed from a DR7, DRw53, DQw2 homozygous cell line, cDNA clones corresponding to DR beta and DQ beta chains were isolated, and the nucleotide sequences of the polymorphic first domains of these chains were determined. A novel screening strategy allowed rapid and simple identification of cDNA clones corresponding to both DR beta chains (DR7 beta1 and DR7 beta2): DR7 beta2 clones have a recognition site for the enzyme BssHII, whereas DR7 beta1 clones do not. The DR7 beta 1 sequence differs significantly from all previously described DR beta chains. As predicted by the presence of the BssHII site in DR7 beta 2 clones, the DR7 beta 2 sequence differs from the DR7 beta 1 sequence. The sequence of the DRw53-associated DR7 beta 2 chain is identical to the reported sequence of the DRw53-associated DR4 beta 2 chain. In addition, the sequence of the DQ beta chain from the DR7, DQw2 cell line is identical to the reported sequence of a DQ beta chain from a DR3, DQw2 cell. These findings raise interesting questions about the evolution of the DR3, DR4, and DR7 haplotypes.

Molecular diversity of HLA-DR4 haplotypes.

Complementary DNA (cDNA) clones encoding beta chains of the DR and DQ regions and alpha chains of the DQ region were isolated and sequenced from four homozygous DR4 cell lines of different HLA-D types: GM3103(Dw4), FS(Dw10), BIN(Dw14), and KT3(Dw15). When compared with each other and with a previously published sequence from a DR4 (Dw13 cell line), the variability of DR beta 1 gene products is generally restricted to the region around amino acid position 70, with an additional polymorphism at position 86. Many of these differences, including an unusual amino acid substitution at position 57 in the Japanese cell line KT3(Dw15), may be due to gene conversion events from the DR beta 2 or DX beta genes. In contrast, DR beta 2 molecules are identical in Dw15, Dw10, and Dw4 cell lines. DQ beta chains isolated from GM3103(Dw4), FS(Dw10), and BIN40(Dw14) are also identical. However, the DQ beta sequence from cell line KT3(Dw15) differs substantially from all other previously reported DQ beta alleles, consistent with its serological designation, DQ "blank." The first domain sequences of DQ alpha chains were identical in all four cell lines. The data suggest that relatively circumscribed amino acid changes in the DR beta 1 molecule are responsible for the HLA-D typing differences between some haplotypes.