Characterization of 19 disease-associated missense mutations in the regulatory domain of the cystic fibrosis transmembrane conductance regulator

In order to gain a better insight into the structure and function of the regulatory domain (RD) of the cystic fibrosis transmembrane conductance regulator (CFTR) protein, 19 RD missense mutations that had been identified in patients were functionally characterized. Nine of these (I601F, L610S, A613T, D614G, I618T, L619S, H620P, G628R and L633P) resulted in aberrant processing. No or a very small number of functional CFTR proteins will therefore appear at the cell membrane in cells expressing these mutants. These mutations were clustered in the N- terminal part of the RD, suggesting that this subdomain has a folding pattern that is very sensitive to amino acid changes. Mutations that caused no aberrant processing were further characterized at the electrophysiological level. First, they were studied at the whole cell level in Xenopus laevis oocytes. Mutants that induced a whole cell current that was significantly different from wild-type CFTR were subsequently analysed at the single channel level in COS1 cells transiently expressing the different mutant and wild-type proteins. Three mutant chloride channels, G622D, R792G and E822K CFTR, were characterized by significantly lower intrinsic chloride channel activities compared with wild-type CFTR. Two mutations, H620Q and A800G, resulted in increased intrinsic chloride transport activities. Finally, T665S and E826K CFTR had single channel properties not significantly different from wild-type CFTR.      

Peripheral neuropathy in the Twitcher mutant. A new experimental model of endoneurial edema

The Twitcher mouse (Twi/Twi) is a recently identified mutant experimental model for human globoid leukodystrophy. Affected mice develop neurologic abnormalities with demyelination of white matter and peripheral nerve due to an inherited enzyme deficiency. The neuropathy has unusual pathologic features:severe interstitial edema and infiltration by eosinophils. To investigate its pathogenesis and to identify the mechanism of demyelination, we studied vascular permeability and measured endoneurial fluid pressure. Significantly increased endoneurial fluid pressure was detected in clinically affected animals (average, 6.4 cm H2O) versus controls (1.7 cm H2O), and these data are the first measurements of EFP to be reported in mice. Increased vascular permeability to horseradish peroxidase was visualized by electron microscopy with leakage of horseradish peroxidase between endothelial cells and flooding of the endoneurial interstitium. Numerous eosinophils were present in the interstitium, as well as some polymorphonuclear cells, occasional erythrocytes, and degranulating mast cells. Abnormalities of nerve fibers included swelling of Schwann cells with intracytoplasmic inclusions, demyelination, and remyelination. As well as being a model for globoid leukodystrophy, the Twitcher is the first spontaneously occurring experimental model for endoneurial edema and increased endoneurial fluid pressure.     

Peripheral blood mononuclear cell proliferative responses to soluble and particulate heat shock protein 65 in health and inflammatory bowel disease

Objectives: The aims of this study were to determine, in peripheral blood mononuclear cells (PBMC), whether particulate antigen triggers (i) an amplified cell proliferative response compared to soluble antigen and (ii) a dysfunctional response in cells derived from patients with chronic inflammation and specifically in those with inflammatory bowel disease (IBD). Subjects: Healthy volunteers (n = 17), inflammatory controls (n = 8) and patients with IBD (n = 17) were recruited from St Thomas’ and Guys’ Hospital, London, UK. Methods: Following optimisation of experimental conditions (0.1–10.0 μg/ml antigen), PBMC were stimulated with (i) 10.0 μg/ml recombinant soluble heat shock protein 65 (hsp 65) and (ii) 1.0 and 10.0 μg/ml hsp 65 conjugated to microparticles (0.5 μm diameter). PBMC proliferative responses were measured by ³H-Thymidine incorporation at day 5 and results compared between groups using unpaired t-test. Results: Conjugation to microparticles of low dose hsp 65 significantly increased overall proliferative responses by 2–11 fold compared to soluble antigen alone (p < 0.05). However, no specific PBMC proliferative dysregulation was noted in cells from subjects with IBD. Conclusions: Low dose antigen, in microparticulate form, leads to amplified cell proliferation in primary human cells, as showed previously in cell lines and animal studies. However there is no abnormal proliferative response in cells from subjects with IBD. Received 8 February 2006; returned for revision 7 March 2006; accepted by G. Wallace 25 October 2006     

A `house doctor' scheme for primary health care for the single homeless in Edinburgh

The single homeless are a heterogeneous population with health care needs greater than those of the general population. The Edinburgh primary health care scheme for single homeless hostel dwellers is an attempt to provide an easily accessible service for this population. Having continued for eight years it is one of the longest established of such schemes. The original aim was for house doctors to take services to the residents in the hostels but the scheme has developed to include a primary health care team operating from a central clinic.

The scheme was evaluated by a study of the use of the service and by interviews with recipients of the service, hostel managers and others. The study confirmed the high health care burden from chronic handicapping conditions for this population. It was also found that the nature and level of primary health care provided by the scheme was acceptable to the hostel residents and the majority of hostel managements and to accident and emergency department staff. The female hostel dwellers expressed a need for a female practitioner in the scheme. Alternatives for primary health care provision for the single homeless are discussed in the light of the findings, and recommendations are made for the future of the scheme.

     

Observations on the process of degeneration of the afferent connections to the sensori-motor cortex of the monkey.

The ultrastructural features of degeneration of the afferent connections to the sensorimotor cortex of the primate have been studied with the electron microscope. Thalamo-cortical terminals show cytoplasmic darkening and swelling of vesicles, and neurofilaments and glycogen are often prominent in the larger terminals, although true neurofilamentous hypertrophy is rare. The terminals of the commissural and association projections similarly show darkening and some swelling of vesicles but are usually smaller and neurofilaments and glycogen are rarely seen. Ethanolic-phosphotungstic acid specifically stains degenerating axons and axon terminals. Degeneration occurs more rapidly in the terminals of the association projections than in those of the longer commissural projection although terminals at different stages of degeneration are present simultaneously in both instances. Micropinocytosis of degenerating terminals has been found and both glial and neuronal profiles are involved in this. Exposed post-synaptic thickenings have been seen and these induce subsurface cisternae in the neuronal structures to which they become apposed, including axon initial segments and unmyelinated axons.Damage to a part of the central nervous system thus causes consequential changes in other regions, and these changes are relevant to the interpretation of experimental studies and to the possibility of reorganization of connections following injury.     

Inactivation of the E-cadherin gene in sporadic diffuse-type gastric cancer.

Loss of the cell adhesion molecule E-cadherin has been observed in a variety of human carcinomas, and germline E-cadherin mutations have been found in several familial cases of diffuse gastric cancer. We sought to determine the prevalence and nature of E-cadherin alterations in "sporadic" gastric carcinomas. We performed comprehensive sequencing of the coding region, loss of heterozygosity (LOH) analysis, and immunohistochemical protein expression determination on 40 sporadic gastric adenocarcinomas. In total, 7 of 25 diffuse-type cancers harbored genetic alterations in the E-cadherin gene. Novel mutations predicted to significantly compromise protein function were found within 4 of these cancers, 2 of which harbored alterations resulting in biallelic inactivation of the gene product. Three diffuse cancers failed to amplify Exon 8 of E-cadherin, suggesting the presence of a homozygous abnormality. Notably, one germline E-cadherin mutation was also identified within these "sporadic" diffuse cancers. Significant gene mutations were not found in the 14 intestinal-type or histologically mixed cancer. Immunohistochemistry revealed aberrant or negative protein expression in seven diffuse-type tumors, four of which correlated with the genetic alterations. Both diffuse and intestinal-type tumors exhibited low rates of LOH, suggesting that allelic loss at the locus is not a common mechanism for E-cadherin inactivation during gastric tumorigenesis. Our observations suggest that inactivation of the E-cadherin gene occurs only in a subset of diffuse-type gastric cancers, as the majority of cases did not contain genetic alterations or identifiable protein abnormalities. Germline E-cadherin alterations, although rare, may underlie some diffuse gastric cancer cases that have important biologic and practical implications