Human deltex is a conserved regulator of Notch signalling

A fundamental cell-fate control mechanism regulating multicellular development is defined by the Notch-signalling pathway. Developmental and genetic studies of wild type and activated Notch-receptor expression in diverse organisms suggest that Notch plays a general role in development by governing the ability of undifferentiated precursor cells to respond to specific signals. Notch signalling has been conserved throughout evolution and controls the differentiation of a broad spectrum of cell types during development. Genetic studies in Drosophila have led to the identification of several components of the Notch pathway. Two of the positive regulators of the pathway are encoded by the suppressor of hairless [Su(H)] and deltex (dx) genes. Drosophila dx encodes a ubiquitous, novel cytoplasmic protein of unknown biochemical function. We have cloned a human deltex homologue and characterized it in parallel with its Drosophila counterpart in biochemical assays to assess deltex function. Both human and Drosophila deltex bind to Notch across species and carry putative SH3-binding domains. Using the yeast interaction trap system, we find that Drosophila and human deltex bind to the human SH3-domain containing protein Grb2 (ref. 10). Results from two different reporter assays allow us for the first time to associate deltex with Notch-dependent transcriptional events. We present evidence linking deltex to the modulation of basic helix-loop-helix (bHLH) transcription factor activity.

"Above-under" exposure of the first rib: a modified approach for the treatment of thoracic outlet syndrome

To provide both adequate exposure of the structures of the thoracic inlet and make removal of the antero-medial portion of the first rib easier, the authors recommend that the customarily used anterior supraclavicular approach for the treatment of thoracic outlet syndromes should be modified by performing through the same incision an additional transmuscular exposure of the first rib below the clavicle to facilitate its removal.

ADP-ribosylation by the extracellular fibrils of Myxococcus xanthus

The isolated, extracellular fibrils of the myxobacterium, Myxococcus xanthus, are capable of carrying out ADP-ribosylation. The substrate for the ADP-ribosylation is reactive with monoclonal antibody 2105, which has been shown to be directed specifically against the integral fibril proteins. The extracellular fibrils thus contain both the ADP-ribosyl transferase and the substrate for the ribosylation. This process may play a role in the contact-mediated cell-cell interactions that are an important part of the social behaviour of M. xanthus.

Development of a single-shot subunit vaccine for HIV-1. 3. Effect of adjuvant and immunization schedule on the duration of the humoral immune response to recombinant MN gp120

HIV-1 prophylaxis may require "sterilizing immunity" (i.e., the prevention of infection), and this is likely to demand a vaccine that gives high, long-lasting antibody titers. Although it is known that vaccine adjuvants and immunization schedule affect the magnitude of the immune response, there are few reports on antibody decay rates and persistence. Guinea pigs were immunized with recombinant gp120 using different adjuvants and immunization schedules, and the anti-gp120 and HIV-1 neutralization titers were determined over time following the last booster immunization. As observed previously in the literature, a longer time between boosting gave higher titers, with a slight increase in the decay half-life as the booster was spaced farther out from the primary immunization. The decay rate of the antibody titers showed surprisingly little effect of adjuvant, except for sustained-release polymer-based formulations. Adjuvants that gave high titers initially after boosting showed the greatest persistence of antibody titers (persistence defined as the residual titers at long times). These data show that high, long-lasting titers may be achieved by using sustained-release formulations, and these are likely the prime vaccine candidates for prophylaxis requiring prolonged sterilizing immunity.

Characterization of the MN gp120 HIV-1 vaccine: antigen binding to alum

PURPOSE

The characterization of recombinant MN gp120/alum vaccine requires the study of the gp120-alum interaction for the successful formulation of an alum-based HIV-1 vaccine.

METHODS

Several observations suggest that the gp120-alum interaction is weak, wherein buffer counterions such as phosphate, sulfate, bicarbonate may cause the desorption of gp120 from alum. Comparison of gp120 with other proteins using particle mobility measurements shows that the weak binding of gp120 to alum is not an anomaly. Serum and plasma also cause desorption of gp120 from alum with a half-life of only a few minutes, wherein this half-life may be faster than the in-vivo recruitment of antigen presenting cells to the site of immunization.

RESULTS

Immunization of guinea pigs, rabbits and baboons with gp120 formulated in alum or saline demonstrated that alum provides adjuvant activity for gp120, particularly after early immunizations, but the adjuvant effect is attenuated after several boosts.

CONCLUSIONS

These observations indicate that both the antigen and the adjuvant require optimization together.

Endogenous ADP-ribosylation during development of the prokaryote Myxococcus xanthus

We examined endogenous ADP-ribosylation of proteins during the development of the prokaryote Myxococcus xanthus. In vivo and in vitro endogenous ADP-ribosylation of M. xanthus proteins was detected and the profile of modified proteins changed during development. Adenosine and nicotinamide inhibited ADP-ribosylation. Nicotinamide stimulated cells at low density to develop, in a manner similar to that previously observed with adenosine. Higher concentrations of nicotinamide inhibited aggregation. The in vivo effects of nicotinamide on developing M. xanthus cells correlate with its in vitro effects on ADP-ribosylation and the developmental profile of putative ADP-ribosylation substrates. These results suggest that ADP-ribosylation may regulate developmental proteins in M. xanthus.

A region of tissue plasminogen activator that affects plasminogen activation differentially with various fibrin(ogen)-related stimulators

The dissolution of blood clots by plasmin is normally initiated in vivo by the activation of plasminogen to plasmin through the activity of tissue plasminogen activator (t-PA). The rate of plasminogen activation can be stimulated several orders of magnitude by the presence of fibrin-related proteins. Here we describe the kinetic analysis of both recombinant human t-PA (wild-type) and a t-PA variant produced by site-directed mutagenesis in which the original sequence from amino acids 296 to 299, KHRR, has been altered to AAAA. This tetra-alanine variant form of t-PA, K296A/H297A/R298A/R299A t-PA, we refer to as "KHRR" t-PA here. The plasminogen activating kinetics of wild-type t-PA (Activase alteplase) showed a catalytic efficiency which changed over 100-fold dependent on the stimulator in the assay. The lowest rate was in the absence of a stimulator. The following stimulators showed increasing ability to accelerate the catalytic efficiency of the reaction: fibrinogen, fragments of fibrinogen obtained by digestion with plasmin, fibrin, and slightly degraded fibrin. This increase in efficiency was driven primarily by decreases in the Michaelis constant (KM) of the reaction, whereas the catalytic rate constant (kcat) of the reaction did not change significantly. The "KHRR" variant of t-PA displayed novel kinetics with all stimulators tested. In the absence of a stimulator or with the poorer stimulators (fibrinogen and fibrinogen fragments), the KM values of the reaction with Activase alteplase and "KHRR" t-PA were similar. The kcat however, was lower with "KHRR" t-PA than with wild-type t-PA.(ABSTRACT TRUNCATED AT 250 WORDS)

Dive-induced modifications in platelet kinetics in rats

The effect of a simulated dive to 8 ATA on platelet kinetics was studied in normal and splenectomized male and normal female rats. Platelet production and consumption was measured in vivo 1 h and 1 day postdive using 35S and 3H isotopes. An increased release of new platelets from the bone marrow and the spleen into the circulation was found 1 h postdive. Data from splenectomized males show that the consumption of new platelets was also increased, resulting in normal platelet counts. The delayed decrease in platelet levels one day postdive has been shown to be caused by a return of new platelet production to normal and an increase in old platelet consumption and/or splenic resorption. No evidence of lung trapping of platelets was found. It appears that decompression stimulates platelet production in the bone marrow and may serve as an adaptive, protective mechanism against severe thrombocytopenia that would otherwise develop in professional divers.

X-ray microscopy of biological objects with carbon kappa and with synchrotron radiation

X-ray micrographs of biological objects have been obtained with a resolution better than 1000 angstroms by using poly(methyl methacrylate) x-ray resist and carbon Kalpha or synchrotron radiation. Synchrotron radiation allows short exposure times; storage rings especially designed as radiation sources and improved x-ray resists would make exposure times under 1 second possible.