Biphasic ordered induction of heme synthesis in differentiating murine erythroleukemia cells: role of erythroid 5-aminolevulinate synthase

During dimethyl sulfoxide (DMSO)-stimulated differentiation of murine erythroleukemia (MEL) cells, one of the early events is the induction of the heme biosynthetic pathway. While recent reports have clearly demonstrated that GATA-1 is involved in the induction of erythroid cell-specific forms of 5-aminolevulinate synthase (ALAS-2) and porphobilinogen (PBG) deaminase and that cellular iron status plays a regulatory role for ALAS-2, little is known about regulation of the remainder of the pathway. In the current study, we have made use of a stable MEL cell mutant (MEAN-1) in which ALAS-2 enzyme activity is not induced by DMSO, hexamethylene bisacetamide (HMBA), or butyric acid. In this cell line, addition of 2% DMSO to growing cultures results in the normal induction of PBG deaminase and coproporphyrinogen oxidase but not in the induction of the terminal two enzymes, protoporphyrinogen oxidase and ferrochelatase. These DMSO-treated cells did not produce mRNA for beta-globin and do not terminally differentiate. In addition, the cellular level of ALAS activity declines rapidly after addition of DMSO, indicating that ALAS-1 must turn over rapidly at this time. Addition of 75 microM hemin alone to the cultures did not induce cells to terminally differentiate or induce any of the pathway enzymes. However, the simultaneous addition of 2% DMSO and 75 microM hemin caused the cells to carry out a normal program of terminal erythroid differentiation, including the induction of ferrochelatase and beta-globin. These data suggest that induction of the entire heme biosynthetic pathway is biphasic in nature and that induction of the terminal enzymes may be mediated by the end product of the pathway, heme. We have introduced mouse ALAS-2 cDNA into the ALAS-2 mutant cell line (MEAN-1) under the control of the mouse metallothionein promoter (MEAN-RA). When Cd and Zn are added to cultures of MEAN-RA in the absence of DMSO, ALAS-2 is induced but erythroid differentiation does not occur and cells continue to grow normally. In the presence of metallothionein inducers and DMSO, the MEAN-RA cells induce in a fashion similar to that found with the wild-type 270 MEL cells. Induction of the activities of ALAS, PBG deaminase, coproporphyrinogen oxidase, and ferrochelatase occurs. In cultures of MEAN-RA where ALAS-2 had been induced with Cd plus Zn 24 h prior to DMSO addition, onset of heme synthesis occurs more rapidly than when DMSO and Cd plus Zn are added simultaneously. This study reveals that induction of ALAS-2 alone is not sufficient to induce terminal differentiation of the MEAN-RA cells, and it does not appear that ALAS-2 alone is the rate-limiting enzyme of the heme biosynthetic pathway during MEL cell differentiation.     

Residual cognitive dysfunctioning at 6 months following coronary artery bypass graft surgery

Neuropsychological testing is a sensitive method for quantitative assessment of cognitive dysfunctioning following cardiopulmonary bypass (CPB). However, the methodological problems associated with this method, such as learning effects due to repeated testing and the effects of distress on test performance, have often been underestimated. In this study, these confounding effects were controlled for by including the spouses of patients, exposed to the same potential stress effects associated with the operation, as a nonsurgical control group. The experimental group consisted of 63 patients (40-75 years) undergoing elective coronary artery bypass graft (CABG) surgery. A battery of standardized neuropsychological tests was administered to both groups 2 weeks preoperatively and 1 week, 1 month, and 6 months postoperatively. Statistical testing of inter-group differences in preoperative to postoperative changes in test performance revealed the following results: (1) For immediate memory and learning, in general test scores showed the same time course for both groups. (2) For recent memory, patients' scores showed a significant deterioration at 1 month after CABG surgery compared with the scores of spouses. This effect had not completely disappeared at 6 months postoperatively. (3) For attention and psychomotor speed as well as verbal fluency, patients' scores had deteriorated significantly at 1 week after surgery, with incomplete recovery at 6 months. These negative cognitive effects were not related to the patients' ages or CPB parameters (duration of CPB, aortic cross-clamp time, mean flow and arterial pressure during CPB and aortic cross-clamping, and minimum nasopharyngeal temperature). No differences in self-ratings of mood over time were found between the patients and spouses. The results indicate that, when adequately controlling for the effects of learning and distress, some cognitive functions are still impaired at 6 months after CABG surgery.     

A precompetitive consortium on wide-band all-optical networks

The technical core of a precompetitive consortium formed by AT&T, DEC, and MIT to study the technology, architecture and applications of wideband all-optical networks of local to national (or international) extent is described. A general introduction to all-optical networks is given, and some proposed applications are discussed. The architecture, technology and testbed portions of this effort are described     

Current role of extracorporeal shockwave therapy in surgery

In urology the introduction of extracorporeal shockwave therapy brought a revolutionary change to the management of urinary calculi. This inspired the introduction of shockwave therapy in several fields of surgery; it has been applied as a potential alternative to several operative procedures but is still experimental. So far, the major application of shockwave therapy has been lithotripsy of stones in the gallbladder, common bile duct, pancreatic duct and salivary gland ducts. Other applications are in the non-operative management of bone healing disturbances and in the inhibition of tumour growth. Steps towards selective thrombus ablation and pretreatment of heavily calcified arteries have also been made. In this review, the applications of extracorporeal shockwave therapy in several areas of surgery are discussed. It is concluded that, for selected patients, shockwave treatment may serve as a useful addition to the surgical armamentarium.     

Mapping of the interleukin 5 receptor gene to human chromosome 3 p25-p26 and to mouse chromosome 6 close to the Raf-1 locus with polymorphic tandem repeat sequences

Simple-sequence tandem repeat sequences in the 3' UTR of interleukin 5 (IL5)-receptor gene of human and mouse are polymorphic in their length among humans and different strains of mice. In 20 different human Epstein-Barr virus (EBV)-transformed cell lines, six alleles of IL5R could be distinguished. In the mouse, three different alleles are found. With the human-specific IL5R tandem repeat marker in human-rodent somatic cell hybrids, the IL5R gene was mapped to human Chromosome (Chr) 3 p25-p26. With the mouse-specific IL5R tandem repeat sequence in recombinant inbred strains of mice, the Il5r gene was mapped to the distal part of mouse Chr 6 close to the Raf-1 locus.