Identification of yeast artificial chromosomes containing the inversion 16 p-arm breakpoint associated with acute myelomonocytic leukemia

We report the cloning of the chromosome 16 p-arm breakpoint involved in inversion 16(p13;q22) associated with subtype of acute myelomonocytic leukemia (AMML) M4Eo. Inter-Alu polymerase chain reaction (PCR) products from a series of interspecific somatic cell hybrids that contain only small portions of the human chromosome 16 p-arm were generated for use as fluorescent in-situ hybridization (FISH) probes. When applied to patient cells, rapid and unambiguous identification of the inversion resulted. Using FISH analysis, cosmid clones associated with the hybrids were identified that bracketed the p-arm breakpoint. A repeat-free fragment of one of these cosmids (35B11) when used as probe on Southern blots from pulsed-field gels identified rearranged macrorestriction fragments in patient DNA. Yeast artificial chromosomes (YACs) were isolated using sequences derived from cosmids flanking 35B11 in a cosmid contig. Of 4 YACs so identified, 3 were shown by FISH to cross the inversion-16 p-arm breakpoint. Therefore, the breakpoint has been molecularly cloned, and identified as being within these 3 YACs. These clones will facilitate the unraveling of the genetic events associated with inversion-16 and are available tools with immediate clinical application.     

Nonrandom inactivation of the X chromosome in early lineage hematopoietic cells in carriers of Wiskott-Aldrich syndrome

The Wiskott-Aldrich syndrome (WAS) is an X-linked (Xp11.22) recessive immunodeficiency syndrome characterized by susceptibility to opportunistic and pyogenic infections, thrombocytopenia, and eczema. Previous studies of obligate carriers of WAS documented that nonrandom inactivation of the X chromosome carrying the defective gene is observed in all peripheral blood cells. The existence of both abnormal platelets and lymphocytes is consistent with a defect that affects early hematopoietic precursors. We isolated CD34+ hematopoietic progenitor cells collected from obligate carriers of WAS by apheresis and used polymerase chain reaction analysis of a polymorphic variable number of repeats (VNTR) within the X-linked androgen receptor to document nonrandom inactivation. These data show that nonrandom inactivation of the X-chromosome in WAS-obligate carriers occurs early during hematopoietic differentiation.     

Sizing of the human T cell receptor alpha locus and detection of a large deletion in the Molt-4 cell line

The human T cell receptor alpha (TCR-alpha) chain gene consists of discontinuous DNA segments encoding multiple variable (V), multiple joining (J), and one constant (C) region. Unlike other immunoglobulin or TCR genes, however, the TCR-alpha locus exhibits an unusual dispersal of J segments that occupy a region of greater than 50 kilobases (kb) upstream of the C region, with the exact size still unknown. We report here the study of the TCR-alpha genetic locus by using pulsed-field gel electrophoresis (PFGE), which permits the separation of large DNA fragments. Analysis of DNA prepared from normal peripheral blood mononuclear cells, human endothelial cells, and a B cell line demonstrates that both V and C sequences are contained within a single 400-kb SfiI restriction fragment. PFGE analysis of the T cell line Molt 4 suggests a greater than 600-kb deletion involving the TCR- alpha gene.     

Adverse events associated with somatostatin analogs in acromegaly

Introduction: In patients with acromegaly, somatostatin analogs (SSA) represent the first choice medical treatment. The long-acting SSA have been found to be effective in controlling growth hormone and IGF-I levels in a high percentage of patients, resulting in an improvement in the quality of life; moreover, these peptide analogs have a proven safety record and are generally well tolerated.

Areas covered: The most commonly reported adverse events include injection-site discomfort and erythema, gastrointestinal (GI) disturbances such as diarrhea, abdominal pain, nausea and vomiting, biliary sludge or gallstones, and abnormal glucose metabolism. Most SSA-related adverse events are transient and of mild-to-moderate intensity, and the prevalence of such effects markedly and progressively decreases during treatment, so that treatment discontinuations due to adverse events are rare and commonly related to GI disturbances. Cholelithiasis represents the most serious complication of SSA, but is generally asymptomatic, and has been reported in 3 – 56% of patients. Whereas the effect of SSA on glucose metabolism is still controversial, several pieces of evidence have confirmed a modest and transient negative impact on glucose homeostasis. Also the novel SSA pasireotide has shown a safety profile as expected for a SSA, except for the degree of hyperglycemia.

Expert opinion: On the basis of these findings, a close and careful monitoring of gallbladder ultrasound and glucose levels is recommended in patients receiving SSA for medical treatment of acromegaly.     

硒谷胱甘肽过氧化物酶保护心肌作用机制

通过人工半合成及天然低成饲料喂养豚鼠，在出现组织硒水平及谷胱甘肽过氧化物酶（ＧＰ）活性明显降低同时，动物红细胞、心肌细胞等的膜结构出现异常，膜脂组成中的磷脂减少．代表细胞膜老化指数的胆固醇／磷脂的分子比增加，作为心肌线粒体内膜必需界面脂的心磷脂明显减少，线粒体能量转换的关键呼吸酶．细胞色素氧化酶（ＣＣＯ）活性明显降低，同时代表其二级结构的园二色谱异常，２０８ｎｍ峰及２２４ｎ峰明显降低．各型脂质过氧化产物，如代表膜磷脂自由基氧化损伤初级产物的脂氢过氧化物、续发产物的丙二醛、呼气烷烃和脂过氧化物聚集产物的荧光色脂均明显增加。这可能正是３０多年前Ｎｅｕｂｅｒｔ等（１９６２）提出ＧＰ对细胞膜的保护作用，尤其所谓线粒体“收缩因子”（“Ｃｏｎｔｒａｃｔｉｏｎ　ｆａｃｔｏｒ”）作用的机制所在。     

Calcium-dependent proteolysis of actin during storage of platelet concentrates

In an ongoing study of the changes that occur in platelet concentrates during storage, we investigated two 28-26-Kd proteins designated SP-1 and SP-2, respectively, which increase markedly during blood-bank storage of platelet concentrates at room temperature. Formation of SP-1 and SP-2 was inhibited by storage at 4 degrees C as well as by treatment of the concentrates with leupeptin, N-ethylmaleimide, and EDTA; DFP and PPACK had no effect. The calcium ionophore A23187 markedly stimulated production of SP-1 and SP-2. After partial purification, the two proteins were found to be associated with platelet cytoskeletal protein. Two-dimensional peptide mapping and amino acid sequencing identified SP-1 and SP-2 as fragments of actin formed by cleavage on the N-terminal side of residues Thr-106 and Ala- 114, respectively. Generation of SP-1 and SP-2 during storage of platelet concentrate is likely attributable to calcium-dependent neutral protease degradation of actin and may have implications for development of the platelet storage lesion.     

The deletion in both common types of hereditary persistence of fetal hemoglobin is approximately 105 kilobases

The most common forms of hereditary persistence of fetal hemoglobin (HPFH) involve large deletions that remove the adult delta and beta genes but leave the paired fetal genes (G gamma and A gamma) intact. The size of these deletions has previously eluded exact definition. Using pulsed-field gel electrophoresis and the enzyme SfiI, which cuts only rarely in genomic DNA, we have constructed a large-scale restriction map of the beta-globin cluster in normal and HPFH DNA. The deletions in HPFH-1, which occurs in American blacks, and in HPFH-2, which occurs in Ghanaian blacks, are found to be approximately 105 kilobases (kb) in length, though the endpoints are staggered by approximately 5 kb. The fact that two previously reported gamma delta beta-thalassemia deletions to the 5' side of the beta-globin cluster are also about 100 kb suggests a common mechanism, possibly involving the loss of a complete chromatin loop.     

The Apple 1 and Apple 4 domains of factor XI act synergistically to promote the surface-mediated activation of factor XI by factor XIIa

Binding sites for high molecular weight kininogen (HK) and for factor XIIa are present in the Apple 1 (A1) and the A4 domains of factor XI, respectively. To define the roles of these two sites in surface- mediated factor-XI activation we prepared conformationally constrained synthetic peptides and recombinant A1 domain (rA1) and determined their effects on the activation of factor XI by factor XIIa in the presence of HK and either kaolin or dextran sulfate. Surface-mediated factor-XI activation by factor XIIa was inhibited by a conformationally constrained A4 peptide (Ala317-Gly350), by an A1 peptide (Phe56-Ser86), and by rA1 (Glu1-Ser90). When used in combination at equimolar concentrations, rA1 and A4 peptide were 10-fold more effective than either one alone in inhibiting surface-mediated activation of factor XI by factor XIIa. The A4 peptide was a competitive inhibitor of factor XIIa amidolytic activity and a noncompetitive inhibitor of factor-XI activation by factor XIIa, whereas rA1 and the A1 peptide did not inhibit factor XIIa. The rA1 domain inhibited factor XI binding to HK, whereas the A4 peptide did not. We conclude that specific sequences exposed on the surfaces of the A1 (Val59-Lys83) and A4 (Ala317-Gly350) domains of factor XI act synergistically to promote surface-mediated factor-XI activation by factor XIIa in the presence of HK by binding factor XI to surface-bound HK (A1 domain) and by binding factor XIIa near the cleavage site (Arg369-Ile370) of factor XI (A4 domain).