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.      

Abnormal tricarboxylic acid cycle metabolites in isovaleric acidaemia

Summary Background  Although a number of abnormal diagnostic metabolites have previously been described in the urine of patients with isovaleric acidaemia (IVA), they do not fully explain the clinical symptoms associated with this disease. Methods  On the basis of our current understanding of the TCA cycle and IVA, we predicted a number of abnormal methylated TCA cycle metabolites, initiated by methylsuccinic acid. We subsequently obtained characteristic gas chromatography–mass spectrometry elution times and mass spectra of the chemically synthesized predicted compounds and screened the urine of 6 IVA patients and 24 age-matched controls. Further proof for our findings was generated from a series of in vitro enzyme reactions using the chemically synthesized standards as substrates to their respective TCA cycle enzymes. Results  Apart from the previously described methylsuccinic and methylfumaric acid, 3-methylmalic acid, (2R,3S)- and (2R,3R)-methylcitric acid and 2-methyl-cis-aconitic acid were detected in the urine of all 6 IVA patients in increased amounts. Additionally, although not directly determined, the in vitro enzyme reaction using of 3-methylmalic acid and malate dehydrogenase, in conjunction with the detection of 2-ketobutyric acid in the urine of all 6 IVA patients, strongly suggests an additional synthesis of 3-methyloxaloacetic acid by the same cycle. Conclusion  Not only do these newly identified metabolites serve as additional diagnostic markers to those previously identified in IVA, but due to the structural arrangements of the (2R,3R)-methylcitric acid and 2-methyl-cis-aconitinic acid-derived 2-methylisocitric acid, inhibition of normal TCA cycle metabolism results at citrate synthase and isocitrate dehydrogenase, respectively. Synopsis  Methylsuccinic acid acts as the initiating substrate to a series of abnormal, potentially harmful, methylated tricarboxylic acid cycle metabolites in isovaleric acidaemia. Competing interests: None declared References to electronic databases: Isovaleric acidaemia: OMIM #243500. Isovaleryl-CoA dehydrogenase: EC 1.3.99.10.     

Chronic leg ulcer caused by Mycobacterium immunogenum

Rare tropical skin diseases are seen more frequently in Western countries because of the increased popularity of visiting tropical regions. A 55-year-old white man developed a painless leg ulcer after traveling in Guatemala and Belize. A mycobacterium was cultured from a biopsy specimen and was identified as Mycobacterium immunogenum by 16S recombinant deoxyribonucleic acid sequence analysis. The leg ulcer healed after 6 months of compression therapy and hydrocolloids; a hypopigmented depressed scar remained.     

Child abuse study among Swedish physicians and medical students

Background: The purpose of the present paper was to examine the attitudes and experiences of reporting child abuse and neglect among primary care and hospital‐based physicians and to study the responses of physicians and medical students to case vignettes suggestive of possible physical abuse or neglect. Methods: Physicians at the child health centers in Göteborg primary care (n= 44) and the general pediatricians at the pediatric hospital (n= 21) in Göteborg answered a questionnaire regarding their attitude and experiences reporting child abuse and neglect. The physicians and medical students (n= 34) responded to three case vignettes in which child abuse and neglect could be suspected. Results: A majority of the physicians had reported child abuse and neglect to the social services (80%). No differences were found between primary care and hospital‐based physicians in terms of reporting or attitudes. Two‐thirds of the physicians had suspected child abuse and neglect and decided not to report, and the major reason for not reporting was a lack of confidence in social services organization. Twenty‐one percent had never reported a child for abuse or neglect during their working career. Medical students were more likely to report hypothetical cases than physicians. Conclusion: Many physicians have reported child abuse to social services but also have neglected to do so even when suspecting abuse. It is important that medical students’ willingness to report is continued when starting to work clinically and that all physicians should be continuously educated.     

Parathyroid adenomas evaluated by Tl-201/Tc-99m pertechnetate subtraction scintigraphy and high-resolution ultrasonography

Thallium-201/technetium-99m pertechnetate subtraction scintigraphy of the parathyroid glands was performed in a prospective study of 33 patients who had undergone bilateral neck exploration for elevated serum calcium and serum parathyroid hormone levels. In 31 cases, the Tl-201/Tc-99m subtraction technique yielded an overall sensitivity of 81%, specificity of 99%, and accuracy of 94% for identifying solitary parathyroid adenomas. Tl-201/Tc-99m subtraction scintigraphy correctly identified 73% of parathyroid adenomas weighing less than 499 mg, 79% of those weighing 500-1,499 mg, and 100% of adenomas weighing more than 1,500 mg. In a subgroup of 24 patients with solitary parathyroid adenomas who underwent both scintigraphy and high-resolution sonography, the sensitivity, specificity, and accuracy of both procedures were similar.     

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.     

Effect of exercise on met-enkephalin in unfit and superfit individuals

Summary Twenty-four unfit volunteers and twenty-three superfit athletes were subjected to a progressive intensity treadmill exercise to total exhaustion in order to study the plasma met-enkephalin response to exercise. Blood samples were collected before and 5 min post-exercise.The basal met-enkephalin levels were significantly higher in the superfit individuals (180 fmol·ml^–1) than in the unfit individuals (126 fmol·ml^–1). Post-exercise the increase from basal levels of plasma met-enkephalin was significantly higher in the superfit athletes (180–278 fmol·ml^–1) than in the unfit individuals (126–157 fmol·ml^–1).The magnitude of the met-enkephalin responses to exercise therefore appears to be dependent on the amount of work performed and the degree of previous physical training. Peripherally circulating opioid peptides may, therefore, possibly play a role in the body's adaptation to exercise training.