Reduced collagen VI causes Bethlem myopathy: a heterozygous COL6A1 nonsense mutation results in mRNA decay and functional haploinsufficiency

We have identified a new pathogenic mechanism for an inherited muscular dystrophy in which functional haploinsufficiency of the extracellular matrix protein collagen VI causes Bethlem myopathy. The heterozygous COL6A1 mutation results in a single base deletion from the mRNA and a premature stop codon. The mutant mRNA is unstable, subject to nonsense- mediated mRNA decay, and is almost completely absent both from patient fibroblasts and skeletal muscle, resulting in haploinsufficiency of the alpha1(VI) subunit and reduced production of structurally normal collagen VI. This is the first example of a muscular dystrophy caused by haploinsufficiency of a structural protein or member of the dystrophin-glycoprotein complex, and identifies collagen VI as a critical contributor to cell-matrix adhesion in skeletal muscle.      

Studies of percutaneous epididymal sperm aspiration (PESA) and intracytoplasmic sperm injection

Four distinct studies were carried out using two data sets ofpercutaneous epididymal sperm aspiration (PESA) and intracytoplasmicsperm injection (ICSI) procedures performed from March 1993to January 1997. In study A, an analysis of 181 ICSI treatmentcycles following PESA revealed a successful epididymal spermretrieval rate of 83%. It confirmed that PESA is an effectivesperm retrieval method and the associated ICSI pregnancy rate(35% per embryo transfer) compared favourably with that of othersperm retrieval methods. In study B, the relevance of a priordiagnostic PESA procedure was ascertained by comparing the spermretrieval rates in two groups of patients having their firstICSI treatment cycle with spermatozoa retrieved through PESA.Group B1 (n=50) had diagnostic PESA prior to the ICSI treatmentcycle PESA procedure, unlike patients in group B2 (n=64) whodid not. The sperm retrieval rate in the treatment cycle procedurewas not different at 90 and 82.8% for groups B1 and B2 respectively.However, the discontinuation of diagnostic PESA is fraught withproblems including liability to medico-legal sanctions. In studyC, analysis of 177 treatment cycles involving PESA and ICSIrevealed a successful sperm retrieval rate by PESA of 82% inthe first cycle, 93% in the second, 96% in the third and 100%in the fourth cycle. The same trend was evident when sperm retrievalwas examined in relation to each of the epididymides. Retrievedspermatozoa were found to be motile in 67-100% of cases andthe frequency of samples containing motile spermatozoa did notdecrease with increase in the number of PESA attempts. Theseresults show that PESA does not jeopardize future epididymalsperm retrieval. In study D, the outcome of treatment with ICSIusing ejaculated spermatozoa (305 cycles) (group D1) was comparedwith that of ICSI using spermatozoa obtained through PESA (54cycles) (group D2). The median age of women in the two groupsof couples was similar (34 years). In group D1, 70% of metaphaseII oocytes were fertilized compared with 61% in group D2 (P<0.01).The cleavage rate and the median numbers of transferred andcryopreserved embryos were similar in both groups. There wasno significant difference between the clinical pregnancy rates(33 and 42% in groups D1 and D2 respectively). Our results showthat the outcome of PESA-ICSI treatment compared favourablywith that of ICSI using ejaculated spermatozoa.     

B7-CD28 interaction is a late acting co-stimulatory signal for human T cell responses

The interaction of CD28 with one of the B7 molecules (CD80 and CD86) on professional antigen-presenting cells (APC) is generally considered as the most important co-stimulatory signal for T cell activation. APC in a resting condition express either no or only low levels of B7 molecules. These are up-regulated as a result of interactions with activated T cells, thus suggesting that B7-CD28 interaction is not required at initiation of T cell activation. To study this issue, we blocked B7-CD28 interaction at various time points after in vitro stimulation of peripheral blood T cells with allogeneic monocytes. Epstein-Barr virus-transformed B cells or soluble antigens. We observed that T cell proliferation and IL-2 production were inhibited by B7- blocking agents (CTLA-4-Ig or anti-B7 mAb) almost to the same degree when added either at initiation of culture or 24 h later. B7-blocking agents still resulted in significant inhibition of allogeneic T cell activation when added after 48 h. Furthermore, when CTLA-4-Ig was added at the start of an allogeneic T cell stimulation, addition of anti-CD28 mAb after 24 h of culture nearly fully restored T cell proliferation to control levels. Finally, we demonstrate that delayed addition of B7- blocking agents together with cyclosporin A 1 day after the onset of culture of T cells with allogeneic B cells is highly efficient to induce energy as evaluated by lack of proliferation, cytotoxic T lymphocyte reactivity and IFN-gamma or IL-5 production upon alloantigen rechallenge. Taken together, our data can explain why B7 expression on APC is not required at the time of initial APC-T cell contact, and suggest that the effect of the CD28 signal indeed consists in prolonging IL-2 production and amplifying T cell responses, rather than in providing a critical co-stimulatory signal at the time of initial TCR triggering.      

Analysis of murine CD22 during B cell development: CD22 is expressed on B cell progenitors prior to IgM

CD22 is a B cell-restricted glycoprotein involved in cell adhesion and signaling. Since CD22 is likely to play an important role in interactions between B cells and other cells, and in regulating signaling thresholds, we characterized the expression of murine CD22 during different stages of B cell development. In contrast to previous reports, we show that CD22 is expressed on B cell progenitors prior to expression of IgM. IL-7-responsive B cell precursors from the fetal liver and early B lineage cells (B220+IgM-) from the bone marrow both express a low density of surface CD22. The majority of the earliest B cell progenitors (B220+IgM-CD43+) in the bone marrow, however, do not express CD22. As B cells mature, the density of CD22 molecules on the cell surface increases. B220brightIgM+ bone marrow cells express high levels of CD22, as do splenic B cells. The correlation of CD22 levels with B cell maturation is replicated in an in vitro culture system, which distinguishes stages of B cell development based on function. Following activation of mature resting splenic B cells with anti-mu mAb or lipopolysaccharide (LPS), levels of CD22 decrease. Finally, we show that the addition of anti-CD22 mAb augments the proliferative response of both anti-mu- and LPS-stimulated B cells, suggesting a role for CD22 in diverse signaling pathways.      

Predicting a low cortisol response to adrenocorticotrophic hormone in the critically ill: a retrospective cohort study

Introduction  

Identification of risk factors for diminished cortisol response to adrenocorticotrophic hormone (ACTH) in the critically ill could facilitate recognition of relative adrenal insufficiency in these patients. Therefore, we studied predictors of a low cortisol response to ACTH.     

Onyx embolisation of cavernous sinus dural arteriovenous fistula via direct percutaneous transorbital puncture

The cavernous sinus dural arteriovenous fistulas of three patients were successfully embolised by using Onyx (Onyx Liquid Embolic System, MTI, Irvine, CA, USA) as the sole embolic agent, through direct percutaneous transorbital punctures of the cavernous sinuses. Our early experience suggests that this direct approach, coupled with the unique physical properties of Onyx, is a safe and effective alternative to treat cavernous sinus dural arteriovenous fistulas when the conventional transvenous routes are inaccessible.