Orientation dependence of trinucleotide CAG repeat instability in Saccharomyces cerevisiae.

To examine the chromosomal stability of repetitions of the trinucleotide CAG, we have cloned CAG repeat tracts onto the 3' end of the Saccharomyces cerevisiae ADE2 gene and placed the appended gene into the ARO2 locus of chromosome VII. Examination of chromosomal DNA from sibling colonies arising from clonal expansion of strains harboring repeat tracts showed that repeat tracts often change in length. Most changes in tract length are decreases, but rare increases also occur. Longer tracts are more unstable than smaller tracts. The most unstable tracts, of 80 to 90 repeats, undergo changes at rates as high as 3 x 10(-2) changes per cell per generation. To examine whether repeat orientation or adjacent sequences alter repeat stability, we constructed strains with repeat tracts in both orientations, either with or without sequences 5' to ADE2 harboring an autonomously replicating sequence (ARS; replication origin). When CAG is in the ADE2 coding strand of strains harboring the ARS, the repeat tract is relatively stable regardless of the orientation of ADE2. When CTG is in the ADE2 coding strand of strains harboring the ARS, the repeat tract is relatively unstable regardless of the orientation of ADE2. Removal of the ARS as well as other sequences adjacent to the 5' end of ADE2 alters the orientation dependence such that stability now depends on the orientation of ADE2 in the chromosome. These results suggest that the proximity of an ARS or another sequence has a profound effect on repeat stability.

Mapping the polarity of changes that occur in interrupted CAG repeat tracts in yeast.

To explore the mechanisms by which CAG trinucleotide repeat tracts undergo length changes in yeast cells, we examined the polarity of alterations with respect to an interrupting CAT trinucleotide near the center of the tract. In wild-type cells, in which most tract changes are large contractions, the changes that retain the interruption are biased toward the 3' end of the repeat tract (in reference to the direction of lagging-strand synthesis). In rth1/rad27 mutant cells that are defective in Okazaki fragment maturation, the tract expansions are biased to the 5' end of the repeat tract, while the tract contractions that do not remove the interruption occur randomly on either side of the interruption. In msh2 mutant cells that are defective in the mismatch repair machinery, neither the small changes of one or two repeat units nor the larger contractions attributable to this mutation are biased to either side of the interruption. The results of this study are discussed in terms of the molecular paths leading to expansions and contractions of repeat tracts.

Medical graduates of the National University of Ireland in 1978: who and where are they?

To inform debate on medical manpower planning and aspects of medical education, we gathered data on graduates of three Irish medical schools in 1978. Twenty six years later, four of the 236 graduates had died and seven were untraceable. All but one of the remainder were in clinical practice and in a wide range of disciplines. A third were overseas. The implications of these findings are briefly discussed.

Characterization of a satellite DNA from Antilocapra americana.

The nucleotide sequence of a cloned satellite DNA from Antilocapra americana (American pronghorn antelope) is presented. The 1477-bp satellite is composed of degenerate 31-bp sub-repeats which are very similar in sequence to those of the major satellite DNAs from cattle and sheep. The sub-repeat sequence is more degenerate and variable in pronghorn than it is in cattle or sheep. The sequence is organized in the pronghorn genome in multicopy tandem arrays.

Asymptomatic grotesque deformities of the cervical spine. An occupational hazard in railway porters.

STUDY DESIGN: A case report. OBJECTIVE: To illustrate an extremely rare occurrence of chronic, occupational, low-grade trauma leading to asymptomatic grotesque cervical spine deformities in railroad station porters. SUMMARY OF BACKGROUND DATA: Occupational trauma causing spinal deformities has been described in relation to thoracic and lumbar spines in miners. To the authors' knowledge, this is the first reported case of asymptomatic cervical spinal deformity in railway porters as a result of chronic occupational trauma. METHODS: A magnetic resonance imaging study was performed on both patients. RESULTS: The magnetic resonance images showed advanced degenerative changes in the cervical spine causing obvious deformities, along with apparently normal cord signal intensity. CONCLUSIONS: Chronic, occupational, low-grade trauma of the cervical vertebral region is extremely unusual in industrialized countries. Nevertheless, in view of the increasing mobility of people in general and of the labor force in particular, this complication of an occupational exposure deserves attention as an unusual cause of cervical spinal deformity.

Gamekeeper's thumb. Ligament localisation by echography.

Twenty-one patients presenting clinically with a lesion of the ulnar collateral ligament complex of the metacarpo-phalangeal joint of the thumb underwent prospective diagnostic echography, in order to recognize the possible dislocation of the ligament over the adductor aponeurosis (Stener's lesion). Seven patients were treated surgically, the others conservatively. The accuracy of the echography was controlled by surgery and by the follow-up. We determined 15 true negatives, 4 true positives, 2 false positives, there was no false negative. Ultrasound imaging is a non-invasive, cost-effective diagnostic aid in differentiating the ruptured non-displaced ligament from the true Stener's lesion, solely requiring surgical repartir.

[Hemorrhagic shock due to splenic rupture in non-severe acute pancreatitis]. / Choc hémorragique sur rupture splénique au cours d'une pancréatite aiguë non sévère.

A 54-year old man was hospitalized for a non severe acute pancreatitis of alcoholic aetiology. Four days after his admission, whilst symptoms and laboratory findings were on the mend, he suddenly presented with acute shock. A CT-scan demonstrated a massive haemoperitoneum due to splenic rupture which necessitated an emergency splenectomy. The causes of shock in acute pancreatitis and the factors that may lead to splenic rupture are discussed. In this patient, a possible role of the non-steroidal anti-inflammatory treatment remains undetermined.

Gamekeeper thumb: identification of the Stener lesion with US.

PURPOSE: To determine the value of ultrasound (US) in recognizing the ligamentary dislocation occasionally associated with gamekeeper thumb (Stener lesion). Detecting such dislocations is important because they require surgical repair, whereas nondisplaced ruptured ligaments respond to conservative treatment. This dislocation cannot be reliably diagnosed with standard methods, leading to unnecessary surgical procedures. MATERIALS AND METHODS: Forty-eight hyperabduction injuries of the thumb were included. The thumbs were either unstable or unexaminable because of tenderness. No fractures were seen on standard radiographs. RESULTS: Sonograms were positive in 13 patients, who then underwent surgery. A Stener lesion was found in 10 patients and a partial Stener lesion in three. Three patients with negative sonograms also underwent surgery, and no dislocation was found. The other 32 patients with negative US findings were treated conservatively, and none developed subsequent instability. CONCLUSION: US proved to be a reliable, simple, and easily reproducible tool for recognition of the Stener lesion.

Characterization of aminopeptidase N from Torpedo marmorata kidney.

A major antigen of the brush border membrane of Torpedo marmorata kidney was identified and purified by immunoprecipitation. The sequence of its 18 N terminal amino acids was determined and found to be very similar to that of mammalian amino-peptidase N (EC 3.4.11.2). Indeed aminopeptidase N activity was efficiently immunoprecipitated by monoclonal antibody 180K1. The purified antigen gives a broad band at 180 kDa after SDS-gel electrophoresis, which, after treatment by endoglycosidase F, is converted to a thinner band at 140 kDa. This antigen is therefore heavily glycosylated. Depending on solubilization conditions, both the antigen and peptidase activity were recovered either as a broad peak with a sedimentation coefficient of 18S (2% CHAPS) or as a single peak of 7.8S (1% CHAPS plus 0.2% C12E9), showing that Torpedo aminopeptidase N behaves as an oligomer stabilized by hydrophobic interactions, easily converted into a 160 kDa monomer. The antigen is highly concentrated in the apical membrane of proximal tubule epithelial cells (600 gold particles/microns2 of brush border membrane) whereas no labeling could be detected in other cell types or in other membranes of the same cells (basolateral membranes, vacuoles or vesicles). Monoclonal antibodies prepared here will be useful tools for further functional and structural studies of Torpedo kidney aminopeptidase N.

Immunological effects of competitive versus recreational sports in cross-country skiing.

For a period of two months during the competitive season the effects of endurance training in cross-country skiers were evaluated in order to compare the adaptive and innate immune systems between 10 competitive athletes, 10 moderately trained athletes and 10 untrained healthy controls. The main results were as follows: the peripheral T-lymphocyte count of the competitive athletes was decreased. In contrast the number of peripheral blood NK cells was increased in this group. These data imply a diminution of the adaptive immune system due to repeated bouts of intense exercise and contemporaneous reinforcement of the innate immune response. Moreover the inducible IL-12-expression following monocyte stimulation was significantly decreased in competitive athletes. Compared with the other two groups, the moderately trained athletes showed a significantly increased production of IFN-gamma upon T-cell stimulation. These data suggest that the immune system may profit from moderate endurance training by an increased capacity to generate IFN-gamma while the immune situation following repeated exhausting exercise of competitive athletes tends to deteriorate through downregulation of IFN-gamma and IL-12.

Glucose regulation of the acetyl-CoA carboxylase promoter PI in rat hepatocytes.

The rat acetyl-CoA carboxylase (ACC) alpha gene is transcribed from two promoters, denoted PI and PII, that direct regulated expression in a tissue-specific manner. Induction of ACC, the rate-controlling enzyme of fatty acid biosynthesis, occurs in the liver in response to feeding of a high carbohydrate, low fat diet, conditions that favor enhanced lipogenesis. This induction is mainly due to increases in PI promoter activity. We have used primary cultured hepatocytes from the rat to investigate glucose regulation of ACC expression. Glucose and insulin synergistically activated expression of ACC mRNAs transcribed from the PI promoter with little or no effect on PII mRNAs. Glucose treatment stimulated PI promoter activity in transfection assays and a glucose-regulated element was identified (-126/-102), homologous to those previously described in other responsive genes, including l-type pyruvate kinase, S(14) and fatty acid synthase. Mutation of this element eliminated the response to glucose. This region of the ACC PI promoter was able to bind a liver nuclear factor designated ChoRF that interacts with other conserved glucose-regulated elements. This ACC PI element is also capable of conferring a strong response to glucose when linked to a heterologous promoter. We conclude that induction of ACC gene expression under lipogenic conditions in hepatocytes is mediated in part by the activation of a glucose-regulated transcription factor, ChoRF, which stimulates transcription from the PI promoter. Similar mechanisms operate on related genes permitting the coordinate induction of the lipogenic pathway.