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.      

Outcome of congenital adrenal hyperplasia

In congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency, affected girls are born with ambiguous genitalia due to increased secretion of androgens in utero by the defective adrenal gland. Even though it is generally accepted that there are differences between male and female brain development, determining factors have been difficult to identify. Girls with CAH have frequently been studied to evaluate the impact of prenatal androgen exposure on psychological, psychosocial, and psychosexual development, and impairments in various areas have been identified. However, there is no comprehensive study available regarding the outcome of this chronic disorder in adult life. We studied the quality of life in women with CAH, with particular emphasis on how they cope with genital malformations, genital operations, and chronic disease as well as lifelong medication. The patients filled out questionnaires covering their physical state, psychological well-being, social relationships, and functional capacity, as well as questionnaires on psychosexual identification and psychosocial integration. The results were evaluated using a computerized statistical program for social studies. Out of a total of 94 patients above 18 years of age, 45 agreed to participate and were compared to 46 healthy, age-matched controls. Age at diagnosis was 2.31 ± 1.55 years and 38% suffered from the simple-virilizing, 45% from the salt-wasting, and 17.0% from the late-onset form of CAH. About one-third of patients had Prader stage 3 or 4 genital virilization. While the overall quality of life did not differ significantly, CAH patients were more often single (47.8% vs. 66.7%) and fewer of them had children (22.2% vs. 38.6%) compared to controls. Significant impairments were found in regard to body image and attitudes toward sexuality, but there was no increased homosexual preference. The women were successful in adjusting to illness and receiving social support. It is speculated that improved psychosocial adaptation is part of a coping mechanism that helps to maintain a high level of well-being despite impairment. Coping mechanisms should be identified and strengthened in order to help patients cope with their chronic illness.     

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)     

Aldosterone receptors in different types of primary hyperaldosteronism

The number of mineralocorticoid-binding sites on mononuclear leukocytes and plasma aldosterone (aldo) concentrations were measured in patients with different types of primary hyperaldosteronism. Patients with unilateral adenoma and patients with bilateral adrenal hyperplasia had a significantly lower (P less than 0.001) mean number of binding sites for aldo [144 +/- 36 (+/- SD; n = 6) and 140 +/- 28 sites/cell (n = 4), respectively] compared with normal subjects (292 +/- 110 sites/cell; n = 25). In four patients with dexamethasone-suppressible hyperaldosteronism, mineralocorticoid-binding sites in mononuclear leukocytes were normal (291 +/- 108 sites/cell). In all patients undergoing surgery for unilateral adenoma, the receptors normalized 3 months after the operation. In two patients the reduction in receptors persisted for a short time after surgery even though the plasma aldo level had already normalized. We conclude that mineralocorticoid excess produces down-regulation of mineralocorticoid receptors, which, in turn, might contribute to the genesis of the aldo escape phenomenon.     

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.     

In vivo kinetics and spectra of 5-aminolaevulinic acid-induced fluorescence in an amelanotic melanoma of the hamster.

For successful photodynamic diagnosis (PDD) and effective photodynamic therapy (PDT) with the clinically used ''photosensitiser'' 5-aminolaevulinic acid (ALA), knowledge of the maximal fluorescence intensity and of the maximal tumour-host tissue fluorescence ratio following systemic or local application is required. Therefore, time course and type of porphyrin accumulation were investigated in neoplastic and surrounding host tissue by measuring the kinetics and spectra of ALA-induced fluorescence in vivo. Experiments were performed in the amelanotic melanoma A-Mel-3 grown in the dorsal skinfold chamber preparation of Syrian golden hamsters. The kinetics of fluorescent porphyrins was quantified up to 24 h after i.v. injection of 100 mg kg-1, 500 mg kg-1 or 1,000 mg kg-1 body weight ALA by intravital fluorescence microscopy and digital image analysis (n = 18). In separate experiments fluorescence spectra were obtained for each dose by a simultaneous optical multichannel analysing device (n = 3). A three-compartment model was developed to simulate fluorescence kinetics in tumours. Maximal fluorescence intensity (per cent of reference standard; mean +/- s.e.) in the tumour arose 150 min post injection (p.i.) (1,000 mg kg-1, 109 +/- 34%; 500 mg kg-1, 148 +/- 36%) and 120 min p.i. (100 mg kg-1, 16 +/- 8%). The fluorescence in the surrounding host tissue was far less and reached its maximum at 240 min (100 mg kg-1, 6 +/- 3%) and 360 min p.i. (500 mg kg-1, 50 +/- 8%) and (1,000 mg kg-1, 6 +/- 19%). Maximal tumour-host tissue ratio (90:1) was encountered at 90 min after injection of 500 mg kg-1. The spectra of tissue fluorescence showed maxima at 637 nm and 704 nm respectively. After 300 min (host tissue) and 360 min (tumour tissue) additional emission bands at 618 nm and 678 nm were detected. These bands indicate the presence of protoporphyrin IX (PPIX) and of another porphyrin species in the tumour not identified yet. Tumour selectivity of ALA-induced PPIX accumulation occurs only during a distinct interval depending on the administered dose. Based on the presented data the optimal time for PDD and PDT in this model following intravenous administration of 500 mg kg-1 ALA would be around 90 min and 150 min respectively. The transient selectivity is probably caused by an earlier and higher uptake of ALA in the neoplastic tissue most likely as a result of increased vascular permeability of tumours as supported by the mathematical model.