Gene conversion is a likely cause of mutation in PKD1

Approximately 70% of the gene responsible for the most common form of autosomal dominant polycystic kidney disease ( PKD1 ) is replicated in several highly homologous copies located more proximally on chromosome 16. We recently have described a novel technique for mutation detection in the duplicated region of PKD1 that circumvents the difficulties posed by these homologs. We have used this method to identify two patients with a nearly identical cluster of base pair substitutions in exon 23. Since pseudogenes are known to be reservoirs for mutation via gene conversion events for a number of other diseases, we decided to test whether these sequence differences in PKD1 could have arisen as a result of this mechanism. Using changes in restriction digest patterns, we were able to show that these sequence substitutions are also present in N23HA, a rodent-human somatic cell hybrid that contains only the PKD1 homologs. Moreover, these changes were also detected in total DNA from several affected and unaffected individuals that did not harbor this mutation in their PKD1 gene copy. This is the first example of gene conversion in PKD1 , and our findings highlight the importance of using gene-specific reagents in defining PKD1 mutations.      

Psychotropic drug use by women: demographic, lifestyle, and personality correlates

From initial telephone interviews with a random population of 1187 francophone women, 179 women participated in a further three-hour person-to-person interview focusing on the use of psychotropic medications. Psychotrope users typically were older, in poorer health, and had a lower level of education than abstainers. They showed an increased prevalence of nervousness, anxiety, depression, and restlessness. Initial contact with psychotrope use was through their general practitioners after presentation of vague and ill-defined symptoms. Psychotropic drug use was found among housewives, especially those with children, and among those unemployed but desiring work. Personality profiles of psychotrope users showed that they think of themselves as failures and are more distressed, with significantly greater life changes. Users scored higher on "femininity" subscales, apparently reflecting dependent and nondefensive personality types. In addition, personality measures defined psychotrope users as precise, methodical, cautious, serious, unassertive, and modest. The incompleteness of present unidirectional models of psychotropic drug use are discussed. Suggestions for future research include encompassing the cognitive organization of the psychotrope user within the context of social, affective, and physician influences on this form of coping style.     

Shwachman syndrome: Exocrine pancreatic dysfunction and variable phenotypic expression

BACKGROUND & AIMS: Shwachman syndrome is an inherited condition with multisystemic abnormalities, including exocrine pancreatic dysfunction. The aim of this study was to evaluate the occurrence and progression of features in a large cohort of patients. METHODS: Clinical records of 25 patients with Shwachman syndrome were reviewed. RESULTS: Mean birth weight (2.92 +/- 0.51 kg) was at the 25th percentile. However, by 6 months of age, mean heights and weights were less than the 5th percentile. After 6 months of age, growth velocity was normal. Severe fat maldigestion due to pancreatic insufficiency was present in early life (fecal fat, 26% +/- 17% of fat intake; age, < 2 years). Serial assessment of exocrine pancreatic function showed persistent deficits of enzyme secretion, but 45% of patients showed moderate age-related improvements leading to pancreatic sufficiency. Neutropenia was the most common hematologic abnormality (88%), but leukopenia, thrombocytopenia, and anemia were also frequently encountered. Patients with hypoplasia of all three bone marrow cellular lines (n = 11) had the worst prognosis; 5 patients died, 2 of sepsis and 3 of acute myelogenous leukemia. Other findings included hepatomegaly and/or abnormal liver function test results and skeletal abnormalities. CONCLUSIONS: A wide and varied spectrum of phenotypic abnormalities among patients with Shwachman syndrome is described. Pancreatic acinar dysfunction is an invariable abnormality. Patients with severe bone marrow involvement may have a guarded prognosis. (Gastroenterology 1996 Dec;111(6):1593-602)     

Prostaglandin E2 potentiates platelet aggregation by priming protein kinase C

Prostaglandin E2 (PGE2) is produced by activated platelets and by several other cells, including capillary endothelial cells. PGE2 exerts a dual effect on platelet aggregation: inhibitory, at high, supraphysiologic concentrations, and potentiating, at low concentrations. No information exists on the biochemical mechanisms through which PGE2 exerts its proaggregatory effect on human platelets. We have evaluated the activity of PGE2 on human platelets and have analyzed the second messenger pathways involved. PGE2 (5 to 500 nmol/L) significantly enhanced aggregation induced by subthreshold concentrations of U46619, thrombin, adenosine diphosphate (ADP), and phorbol 12-myristate 13-acetate (PMA) without simultaneously increasing calcium transients. At a high concentration (50 mumol/L), PGE2 inhibited both aggregation and calcium movements. PGE2 (5 to 500 nmol/L) significantly enhanced secretion of beta-thromboglobulin (beta TG) and adenosine triphosphate from U46619- and ADP-stimulated platelets, but it did not affect platelet shape change. PGE2 also increased the binding of radiolabeled fibrinogen to the platelet surface and increased the phosphorylation of the 47-kD protein in 32P- labeled platelets stimulated with subthreshold doses of U46619. Finally, the amplification of U46619-induced aggregation by PGE2 (500 nmol/L) was abolished by four different protein kinase C (PKC) inhibitors (calphostin C, staurosporine, H7, and TMB8). Our results suggest that PGE2 exerts its facilitating activity on agonist-induced platelet activation by priming PKC to activation by other agonists. PGE2 potentiates platelet activation at concentrations produced by activated platelets and may thus be of pathophysiologic relevance.     

Autologous bone marrow transplantation in acute myelogenous leukemia: in vitro treatment with myeloid cell-specific monoclonal antibodies

Second or third chemotherapy-induced remissions in acute myelogenous leukemia (AML) are limited by early relapse of the leukemia. We developed monoclonal antibodies (MoAbs) that are cytotoxic to myeloid leukemia cells to treat bone marrow from these patients ex vivo for autologous transplantation. In this pilot study, bone marrow was harvested from ten patients with AML in remission, treated with one or two complement-fixing MoAbs, PM-81 and AML-2-23, which react with myeloid differentiation antigens, incubated with rabbit complement, and cryopreserved. These MoAbs were chosen because they have broad reactivity with AML cells but not with pluripotent progenitor cells. At the time of transplant, 6 patients were in second complete remission, 1 each was in third complete or partial remission, and 2 were in early first relapse. The patients were treated with cyclophosphamide (60 mg/kg a day for 2 days) and total body irradiation (200 cGy twice a day for 3 days) and given infusions of MoAb-treated bone marrow. Full bone marrow reconstitution was observed in eight patients; two patients did not recover platelets. Seven of the ten patients are surviving and disease-free at 21.0, 15.0, 13.0, 10.0, 6.0, 3.0, and 2.0 months posttransplant. Treating bone marrow with MoAbs to myeloid differentiation antigens does not interfere with pluripotential stem cell engraftment. Longer follow-up and a controlled study are necessary to prove that the apparent efficacy of this therapeutic approach in some patients is attributable to MoAb-mediated killing of leukemia cells.     

Interleukin-6 enhances growth factor-dependent proliferation of the blast cells of acute myeloblastic leukemia

The effects of recombinant interleukin-6 (IL-6) on the proliferation of blast precursors present in the peripheral blood of patients with acute myeloblastic leukemia (AML) was investigated. IL-6 had little effect by itself; however, it synergized with granulocyte macrophage colony- stimulating factor (GM-CSF) and interleukin-3 (IL-3) in the stimulation of AML blast colony formation. Responsiveness of blast progenitors to IL-6 was heterogeneous. On normal bone marrow cells the same synergy was observed on granulocyte and monocyte precursors (GM-CFC), while there was no significant effect on erythroid and multipotential precursors.     

Intraperitoneal protein injection in the axolotl: the amphibian kidney as a novel model to study tubulointerstitial activation

BACKGROUND: A substantial body of experimental evidence suggests that protein loading causes activation of proximal tubular epithelial cells with consecutive interstitial fibrosis. These studies have mostly been performed using mammalian in vivo models of glomerular damage or tissue cultures of mammalian tubulointerstitial cells. The kidney of the axolotl contains not only closed nephrons, but also nephrons with ciliated peritoneal funnels called nephrostomes that have access to the peritoneal fluid. Injection of protein into the peritoneal cavity fails to expose closed nephrons to a protein load, but causes selective uptake and transient storage of proteins in tubular epithelial cells of nephrons with nephrostomes. The purpose of the present study was to determine whether (a) the axolotl kidney can be used as a model to assess protein uptake by tubular cells in vivo in the absence of glomerular damage, and (b) this is accompanied by any evidence of tubular epithelial cell activation and interstitial fibrosis. METHODS: Male and female axolotl (80 to 120 g of weight) were given a daily intraperitoneal injection of 1.5 mL endotoxin-free calf serum or saline as control. Kidneys were harvested after 4 or 10 days using perfusion fixation for light microscopy (fibrous tissue stain) and saline perfusion for immunohistochemistry (fibronectin, TGF-beta and collagen I). RESULTS: The findings document selective storage of protein and lipids, progressive with time, in proximal tubular epithelial cells of nephrons draining the coelomic cavity. In addition, progressive focal accumulation of fibrous tissue was noted around protein-storing tubules. Immunohistochemical staining demonstrated the presence of fibronectin and TGF-beta in the tubular epithelial cells and interstitial cells. CONCLUSION: The axolotl kidney provides a novel in vivo model to study tubulointerstitial activation and induction of interstitial fibrosis by protein loading. The findings are independent of alterations of glomerular function that may have potential confounding effects on peritubular hemodynamics, pO2, cell traffic, etc.