Submicroscopic deletions and duplications in individuals with intellectual disability detected by array-CGH.

Intellectual disability (ID) affects about 3% of the population (IQ < 70), and in about 40% of moderate (IQ 35-49) to severe ID (IQ < 34), and 70% of cases of mild ID (IQ 50-70), the etiology of the disease remains unknown. It has long been suspected that chromosomal gains and losses undetectable by routine cytogenetic analysis (i.e., less than 5-10 Mb in size) are implicated in ID of unknown etiology. Array CGH has recently been used to perform a genome-wide screen for submicroscopic gains and losses in individuals with a normal karyotype but with features suggestive of a chromosome abnormality. In two recent studies, the technique has demonstrated a approximately 15% detection rate for de novo copy number changes of individual clones or groups of clones. Here, we describe a study of 22 individuals with mild to moderate ID and nonsyndromic pattern of dysmorphic features suspicious of an underlying chromosome abnormality, using the 3 Mb and 1 Mb commercial arrays (Spectral Genomics). Deletions and duplications of 16 clones, previously described to show copy number variability in normal individuals [Iafrate et al., 2004; Lapierre et al., 2004; Schoumans et al., 2004; Vermeesch et al., 2005] were seen in 21/22 subjects and were considered polymorphisms. In addition, three subjects showed submicroscopic deletions and duplications not previously reported as normal variants. Two of these submicroscopic changes were of de novo origin (microdeletions at 7q36.3 and a microduplication at 11q12.3-13.1) and one was of unknown origin as parental testing of origin could not be performed (microduplication of Xp22.3). The clinical description of the three subjects with submicroscopic chromosomal changes at 7q36.3, 11q12.3-13.1, Xp22.3 is provided.

Cognitive rehabilitation following anterior communicating artery aneurysm bleeding: a case report.

The present case report documents the successful rehabilitation of a severely amnesic anterior communicating artery aneurysm patient. The patient was able to return to his premorbid high-level occupation after significant improvement in executive functioning, moderate improvement in visual memory, modest improvement in immediate verbal memory, and minimal improvement in delayed verbal memory. An interdisciplinary approach to rehabilitation was utilized in conjunction with empirically based intervention strategies. The implications of improved executive functions versus memory functions for successful rehabilitation are discussed.

The non-sliding filaments of the sarcomere.

A model is proposed for the 'gap' or 'third' filaments of muscle, here renamed 'T-filaments'. These consist of single titin molecules, spanning the half sarcomere from M-line to Z-line. Of several possibilities for stoichiometry and arrangement, the one most favoured here consists of six T-filaments lying longitudinally on the surface of the A-filament, one against each peripheral subfilament of myosin. C-protein molecules over-lie the T-filaments in transverse and axial rows, with their long axes following a helix. Each C-protein molecule helps to bind a pair of T-filaments to one A-strand (but not to bind A-strands together), and hinders the immune response of titin in the C-zone. The gap filaments arise from the coalescence of T-filaments in the I-band, and their extreme extensibility from an unravelling of a beaded structure in the titin molecule. A layout is presented for the molecule in zones of configuration and function. Possible arrangements of the T-filaments in the M- and N(2)-zones are discussed.

A comparative study of high molecular weight proteins in various types of muscle across the animal kingdom.

A wide range of phyla have been surveyed by SDS-PAGE for the new large proteins of the myofibril. Connectin (or titin) appears to be widely distributed. It is seen as a band of constant intensity and mobility in vertebrate striated muscle, but is absent from smooth muscle. It appears in more variable amounts, in a form of constant but greater mobility in many invertebrates: worms, molluscs (adductor but not gastropod feet), insects, a myriapod, and even in human blood platelets. Nebulin shares the same distribution in vertebrate muscles except for its notable absence in all heart muscle examined. It too is found in many invertebrates, not always with titin. It has been found in a worm, molluscs (adductor and gastropod feet), insects, crustaceans and an echinoderm. The mobility of nebulin varies within the vertebrates and more so between invertebrates (where, as with titin, it is greater). The isoforms of filamin in skeletal, cardiac, and smooth muscles of vertebrates are recorded. C-protein in rabbit muscles has four isoforms: white, alpha-red (X-protein), beta-red, and cardiac.

The N-lines of skeletal muscle.

The N-lines of skeletal muscle, although known for a century, have remained elusive and neglected structures. Their fortuitous appearance in diverse experiments on beef sternomandibularis muscle, involving stretch, heat denaturation, and myosin extraction, have been collected and related to the literature. Treatments with pyroantimonate and formamide solutions have proved a more reliable way of visualizing N-lines. It is concluded that there are at least seven N-lines: an N1-line always near the Z-line, four N2-lines in the mid-I-band, and two N3-lines at the extremity of the I-filaments or in the "gap." There is evidence for suspension of both N2- and N3-lines on G-filaments.

Tenderisation of meat by pressure-heat involves weakening of the gap filaments in the myofibril.

These results confirm previous Australian experience that pressure-heat (P-H) treatment tenderises rigor meat effectively only after considerable periods at elevated temperatures; that prior ageing abolishes the effect; and that cold shortened meat is effectively tenderised. Yield point is also profoundly affected by P-H, although this effect is not related to tenderness. As predicted by the new G-filament theory of meat tenderness, P-H greatly weakens the G-filaments. These then break on extension by 50% but not if subsequently cooked. However the tensile properties of cooked meat support the weakening of G-filaments. A problem is that mild P-H treatments which are ineffective at tenderising, produce the same histological damage as harsher tenderising treatments. This paper reviews the considerable body of results on the P-H treatment of rigor meat that have now accumulated. The effects of pressure on the various filaments is discussed. The nature of the changes induced in the G-filaments remains obscure.

'Ageing' of cold shortened meat depends on the criterion.

Although cold shortened muscles show little decline in shear force during ageing, they do, like unshortened muscles, undergo a drastic reduction in yield point. The differing responses to the two criteria arise from the involvement of different structural elements. Our previous claim, that yield point is highly sensitive to ageing and reflects changes in tenderness, remains valid for unshortened muscles, but is clearly inappropriate to cold shortened samples.

The fate of the large proteins of the myofibril during tenderising treatments.

Changes in the large structural proteins of the myofibril, during treatments which affect tenderness, have been followed using SDS-PAG electrophoresis. Despite the known decay of gap filaments during ageing, and the identification of connectin as their substance, connectin survives prolonged ageing at 15°C (although it succumbs at temperatures at which it denatures). Cold shortening or stretching of muscle does not affect autolysis, except in the prolonged ageing of stretched samples, where myosin 'heads' are apparently detached due to their greater accessibility to proteases. The only two changes on the same time scale as tenderisation are the disappearance of nebulin and an increase in a protein lying between connectin and nebulin on the gels. The evidence for nebulin as the N(2)-line protein is questionable, and it is proposed that it may instead be a component of the G-filaments, necessary for their stability. In pressure-heat (P-H) treatment at 50 or 55°C, which reduces yield point rather than shear force, connectin survives, while nebulin is partly destroyed. A tenderising P-H treatment at 60°C degrades both. Cooking to various degrees apparently causes a random splitting of connectin, revealed as a smear down the gels. After cooking at 80°C a little of the original band survives, while most of the smear represents material with a molecular weight above half a million, and should therefore still be capable of contributing to structural strength. Prior tenderising treatments have little effect on gels derived from material cooked at 80°C, although what remains of the sharp connectin band in cooked controls disappears in aged or P-H treated samples.

Tensile properties of cooked beef in relation to rigor temperature and tenderness.

A study of the tensile properties of cooked strips from beef sternomandibularis which had gone into rigor at various temperatures showed no clear relationships with earlier observed variations in shear force with rigor temperature. A consistent feature of the load extension curves was a sudden increase in extensibility at a 'change point' of about 1 kg/cm(2). Some curves, particularly those for strips cooked under restraint, showed a third intermediate extensibility. Evidence points to modification of a myofibrillar component as the reason for the sudden changes.

Yield point in raw beef muscle. The effects of ageing, rigor temperature and stretch.

The yield point of raw sternomandibularis muscle of the ox decreased markedly with ageing. This parameter is the most sensitive and selective indicator of ageing since, unlike shear measurements on cooked meat, it is not complicated by heat denaturation or the contribution of the collagen net. Rigor at 2°C with consequent cold shortening has little effect on yield point, but rigor at 37°C diminishes yield values relative to the 15°C controls. Muscles stretched by 40-60% during rigor show higher yield points. Yield was also studied in other muscles. Unaged strips of bull sternomandibularis, or steer psoas and rectus abdominis tended to break rather than yield, but after ageing usually yielded at the same low loads as aged ox sternomandibularis. The histological changes due to yielding varied widely, but stretched, rather than broken, I-bands were the dominant feature. Our interpretation of the electron micrographs is that in rigor muscle, actin filaments fracture while gap filaments stretch, but in aged muscle both sets of filaments fail simultaneously at low loads.

Myofibrils of cooked meat are a continuum of gap filaments.

When cooked meat is subjected to high degrees of stretch it becomes apparent in high magnification electron micrographs that A-filaments have ceased to exist. The A-band is filled with a coagulum of actomyosin. Fragmentation of this coagulum during stretch reveals an array of fine filaments (identified as gap filaments). This result is obtained irrespective of rigor temperature, state of contraction or degree of cooking. If the meat is first aged, the gap filaments surviving in the I-band are too weak to open up the A-band. The results show that myofibrils in cooked meat are entirely dependent on heat-stable gap filaments for structural continuity and tensile strength. Theories of meat tenderness must be revised accordingly.

Meat tenderness and the gap filaments.

A theory is developed relating the myofibrillar component of meat tenderness to a third set of filaments in the sarcomere: the 'gap filaments'. It is prooposed that the gap filaments set the limit to the tensile strength of the raw or heat-denatured myofibril. The basic process of ageing appears to be an attack by 'calcium-activated factor' (CAF) on the integrity of these filaments. An attempt is made to give an integrated picture of the role of both gap filaments and connective tissue in determining the tensile properties of raw, lightly cooked and well cooked meat.