Calciphylaxis – a topical overview

'Calciphylaxis', a calcification syndrome associated with ischaemic cutaneous necrosis, is acquired naturally in humans in disease states. It is a life and limb-threatening complication, usually observed in patients with renal disease and secondary hyperparathyroidism, but known to occur in the absence of renal or parathyroid disease. The reported mortality rate, which ranges from 60-80%, relates to wound infection, sepsis and organ failure. It is a small-vessel vasculopathy, which is estimated to occur in about 4% of haemodialysis patients. Clinically, violaceous, reticulate areas of cutaneous necrosis and eschar may be evident, particularly in the extremities. In addition to the clinical picture, a raised calcium phosphorous product, an elevated parathyroid hormone level, radiographic evidence of vessel and soft-tissue calcification and the finding of mural calcification affecting small arteries and arterioles on histopathology help to confirm the diagnosis of this entity which generally has a poor prognosis. A high index of suspicion and an active multidisciplinary management approach, with rigorous attention to wound care and prevention of sepsis, are vital in the management of these patients. In this overview, we discuss the pathophysiology, clinical features and associations, risk factors, diagnosis and management issues relating to calciphylaxis.     

Mutations in the retinal guanylate cyclase (RETGC-1) gene in dominant cone-rod dystrophy

The dominant cone-rod dystrophy gene CORD6 has previously been mapped to within an 8 cM interval on chromosome 17p12-p13. The retinal- specific guanylate cyclase gene (RETGC-1), which maps to within this genetic interval and previously was implicated in Leber's congenital amaurosis, was screened for mutations within this family and in a panel of small families and individuals with various cone and cone- rod dystrophy phenotypes. A missense mutation (E837D) was identified in affected members of the CORD6 family, as well as a second missense mutation (R838C) in three other families with dominant cone-rod dystrophy. RETGC-1 is only the fourth gene to be implicated in cone-rod dystrophy and this is the first report of dominant mutations in this gene.      

Comparison between testosterone oenanthate-induced azoospermia and oligozoospermia in a male contraceptive study. IV. Suppression of endogenous testicular and adrenal androgens

Administration of supraphysiological doses of testosterone to normal men causes inhibition of spermatogenesis, but while most become azoospermic, 30-55% maintain a low rate of spermatogenesis. We have investigated whether there are differences in endogenous androgen production, of testicular and adrenal origin, which may be related to the degree of suppression of spermatogenesis. Thirty-three healthy Caucasian men were given weekly i.m. injections of 200 mg testosterone oenanthate (TE), 18 became azoospermic, while 15 remained oligozoospermic. Urinary excretion of epitestosterone, a specific testicular product, was reduced to <10% of pretreatment values, with no differences between the groups. Similar results were obtained for other markers of testicular steroidogenesis. Urinary and plasma adrenal androgens were also reduced during TE treatment: a statistically significant decrease in both (P < 0.001 and P < 0.05 respectively) was seen in the azoospermic but not oligozoospermic responders. These results suggest that testicular steroidogenesis is decreased to <10% by the administration of supraphysiological doses of exogenous testosterone. Differences in the degree of ongoing steroidogenesis in the testis do not appear to account for incomplete suppression of spermatogenesis, thus differences in androgen metabolism may underlie this heterogeneous response. A small but significant reduction in secretion of adrenal androgens was also detectable, the relevance of which is unclear.      

A locus for autosomal dominant anterior polar cataract on chromosome 17p

Inherited cataract is a clinically and genetically heterogeneous disease. Here we report the identification of a new locus for an autosomal dominant anterior polar cataract on the short arm of chromosome 17. To map this new locus we performed genetic linkage analysis with microsatellite markers in a four-generation pedigree. After exclusion of seven candidate loci for cataract, we obtained significant positive LOD scores for markers D17S849 (Z = 4.01 / theta = 0.05) and D17S796 (Z = 4.17 / theta = 0.05). Multipoint analysis gave a maximum LOD score of 5.2 (theta max = 0.06) between these two markers. From haplotype analysis, the cataract locus lies in the 13 cM interval between markers D17S849 and D17S796. This study provides the first genetic mapping of an autosomal dominant anterior polar cataract.      

Measurement of changes in cytochrome oxidase redox state during obstructive sleep apnea using near-infrared spectroscopy

STUDY OBJECTIVES: To use near-infrared spectroscopy to investigate the effect of obstructive sleep apnea on cytochrome oxidase, the terminal enzyme of the mitochondrial respiratory chain. DESIGN: Observational study. SETTING: Teaching hospital sleep unit. PATIENTS: Subjects with diagnosed moderate to severe obstructive sleep apnea were recruited from the sleep clinic. INTERVENTIONS: Subjects were invited to attend 2 daytime sleep-study sessions, which included near-infrared monitoring of cerebral oxygenation and cytochrome-oxidase oxidation state. In addition, in study session 1, full polysomnography was performed (8 subjects, 303 apneas), and in study session 2, arterial oxygen saturation, cerebral blood flow velocity, and blood pressure were monitored (7 subjects, 287 apneas). MEASUREMENTS AND RESULTS: In study session 1, mean (+/- SD) cytochrome-oxidase changes ranged from 0.48 +/- 0.08 microM to 0.13 +/- 0.05 microM. The magnitude of cytochrome-oxidase change correlated significantly with the magnitude of change in the cerebral tissue oxygenation index (P < .001). In study session 2, there were significant correlations between arterial oxygen-saturation changes and cytochrome-oxidase redox changes and between Doppler cerebral blood flow velocity changes and cytochrome-oxidase redox changes (P < .001 and P = .001, respectively). CONCLUSIONS: Changes in directly measured cerebral tissue saturation and changes in arterial saturation and cerebral blood flow velocity (the 2 main factors affecting cerebral oxygenation) are associated with changes in cytochrome-oxidase oxidation state. The reduced cerebral oxygenation that occurs during obstructive sleep apnea is associated with changes in the intracellular redox state.     

Differential expression of FMR1, FXR1 and FXR2 proteins in human brain and testis

Lack of expression of the fragile X mental retardation protein (FMRP) results in mental retardation and macroorchidism, seen as the major pathological symptoms in fragile X patients. FMRP is a cytoplasmic RNA- binding protein which cosediments with the 60S ribosomal subunit. Recently, two proteins homologous to FMRP were discovered: FXR1 and FXR2. These novel proteins interact with FMRP and with each other and they are also associated with the 60S ribosomal subunit. Here, we studied the expression pattern of the three proteins in brain and testis by immunohistochemistry. In adult brain, FMR1, FXR1 and FXR2 proteins are coexpressed in the cytoplasm of specific differentiated neurons only. However, we observed a different expression pattern in fetal brain as well as in adult and fetal testis, suggesting independent functions for the three proteins in those tissues during embryonic development and adult life.      

Development and validation of a sensitive solid-phase extraction and high-performance liquid chromatography assay for the novel antitumour agent CT2584 in human plasma

A HPLC assay and solid-phase extraction technique from human plasma has been developed and validated for the novel anticancer agent CT2584, 1-(11-dodecylamino-10-hydroxyundecyl)-3,7-dimethylxanthine, which has recently completed a phase I trial at the Christie Hospital, Manchester under the auspices of the CRC phase I/II committee. Following addition of CT2576, 1-(11-octylamino-10-hydroxylundecyl)-3,7-dimethylxanthine, as internal standard, a solid-phase extraction cartridge (100 mg cyanopropyl) was used to isolate the drug CT2584 from human plasma. Analysis was performed by reversed-phase chromatography. CT2576 was used as internal standard at a concentration of 4 microg ml(-1) for the quantification of CT2584 from plasma for the duration of this work. The lower limit of quantification for the drug CT2584 in buffer using this assay was found to be 0.0122 microM (0.008 microg ml(-1)) and 0.048 microM (0.027 microg ml(-1)) when extracted from human plasma.     

Developmental toxicity and genotoxicity studies of 1,1,1,3,3,3-hexachloropropane (HCC-230fa) in rats.

The potential developmental toxicity and the in vitro and in vivo genotoxicity of HCC-230fa were assessed. In the developmental toxicity study, groups of 25 mated Crl:CD(R)(SD)BR rats were exposed (whole body) by inhalation to HCC-230fa over days 7-21 of gestation; the day of confirmed mating was designated as gestation day 1 (GD1). Exposures were 6 h per day at concentrations of 0, 0.5, 2.5, or 25 ppm. Body weight, food consumption, and clinical observation data were collected during the study. On day 22 of gestation, the dams were euthanized and examined grossly. The fetuses were removed and subsequently weighed, sexed, and examined for external, visceral, head, and skeletal alterations. Evidence of maternal and developmental toxicity was observed at 25 ppm and was noted as significant, compound-related reductions in mean maternal body weight, weight change, and food consumption. Significant fetal effects also were observed at 25 ppm as compound-related reductions in mean fetal weight and increased fetal malformations (filamentous tail, situs inversus, absent vertebrae) and variations (rudimentary cervical ribs, delayed sternebral ossification). There was no evidence of either maternal or developmental toxicity at 0.5 or 2.5 ppm. The genotoxicity of HCC-230fa was examined in a bacterial reversion assay and in erythrocyte micronucleus studies in two species by different routes of administration. No increases in the number of revertants were observed in the bacterial reversion assay. In one micronucleus study, HCC-230fa was administered by inhalation to rats as part of a 90-day study at doses indicated above. For the second study, ICR mice were given a single ip dose at 0, 166, 330, or 660 mg/kg. In both micronucleus studies, a significant increase in micronucleated erythrocytes was observed. The results of these studies suggest that HCC-230fa affects rapidly dividing cells and may have long-term consequences for occupational exposures.