The role of leptin and ghrelin in appetite regulation in the Australian Spinifex hopping mouse, Notomys alexis, during long-term water deprivation.

Water deprivation of the Spinifex hopping mouse, Notomys alexis, induced a biphasic pattern of food intake with an initial hypophagia that was followed by an increased, and then sustained food intake. The mice lost approximately 20% of their body mass and there was a loss of white adipose tissue. Stomach ghrelin mRNA was significantly higher at day 2 of water deprivation but then returned to the same levels as water-replete (day 0) mice for the duration of the experiment. Plasma ghrelin was unaffected by water deprivation except at day 10 where it was significantly increased. Plasma leptin levels decreased at day 2 and day 5 of water deprivation, and then increased significantly by the end of the water deprivation period. Water deprivation caused a significant decrease in skeletal muscle leptin mRNA expression at days 2 and 5, but then it returned to day 0 levels by day 29. In the hypothalamus, water deprivation caused a significant up-regulation in both ghrelin and neuropeptide Y mRNA expression, respectively. In contrast, hypothalamic GHSR1a mRNA expression was significantly down-regulated. A significant increase in LepRb mRNA expression was observed at days 17 and 29 of water deprivation. This study demonstrated that the sustained food intake in N. alexis during water deprivation was uncoupled from peripheral appetite-regulating signals, and that the hypothalamus appears to play an important role in regulating food intake; this may contribute to the maintenance of fluid balance in the absence of free water.

MERP1: a mammalian ependymin-related protein gene differentially expressed in hematopoietic cells.

We have utilized differential display polymerase chain reaction to investigate the gene expression of hematopoietic progenitor cells from adult bone marrow and umbilical cord blood. A differentially expressed gene was identified in CD34+ hematopoietic progenitor cells, with low expression in CD34- cells. We have obtained the full coding sequence of this gene which we designated human mammalian ependymin-related protein 1 (MERP1). Expression of MERP1 was found in a variety of normal human tissues, and is 4- and 10-fold higher in adult bone marrow and umbilical cord blood CD34+ cells, respectively, compared to CD34- cells. Additionally, MERP1 expression in a hematopoietic stem cell enriched population was down-regulated with proliferation and differentiation. Conceptual translation of the MERP1 open reading frame reveals significant homology to two families of glycoprotein calcium-dependant cell adhesion molecules: ependymins and protocadherins.

Hereditary hyperferritinemia-cataract syndrome: prevalence, lens morphology, spectrum of mutations, and clinical presentations.

OBJECTIVES: To provide a comprehensive description of the clinical presentations, cataract morphology, and molecular basis of hereditary hyperferritinemia-cataract syndrome (HHCS) in 4 Australian pedigrees and to estimate its prevalence. METHODS: All known cases of HHCS in southeastern Australia were ascertained. Family members provided a medical history and underwent physical examination, lens photography, and venipuncture for measurement of serum ferritin levels and DNA extraction. Sequence analysis of the iron-responsive element of the ferritin light chain on chromosome 19q13.3-qter was performed. RESULTS: We investigated 26 affected individuals from 5 Australian pedigrees. Two pedigrees with HHCS ascertained independently were subsequently found to form 1 large kindred carrying the mutation A40G. The minimum estimated prevalence of HHCS is 1/200000. One pedigree had the mutation G32C. Among 2 smaller pedigrees studied, one carried a novel mutation (C39A), and the other was identified through the 2-year-old propositus with cataract but no positive family history. The latter case was shown to be due to a de novo mutation (G32U). All cataracts were highly distinctive in morphology, consisting of slowly progressive flecks, vacuoles, and distinctive crystalline deposits scattered predominantly in the lens cortex but also in the nucleus. Eight of 18 affected individuals examined have required cataract extraction to date. No other identified clinical manifestations of HHCS were delineated. CONCLUSIONS: Cataract morphology in HHCS is highly distinctive. Longitudinal observation demonstrated slow progression of the cataracts. This study highlights that, although HHCS is an autosomal dominant condition, the diagnosis should be considered even in sporadic cataract of typical morphology. Furthermore, individuals with unexplained hyperferritinemia should be referred for ophthalmological assessment, as the cataract may be asymptomatic but lead to a correct diagnosis of HHCS. Clinical Relevance Progressive cataracts of highly distinctive morphology are an important feature of HHCS. Evaluation for this type of cataract may be of diagnostic value in patients with unexplained hyperferritinemia. Hereditary hyperferritinemia-cataract syndrome can be a cause of cataracts in pediatric patients even in the absence of any positive family history.

Mechanisms of resistance to the cytotoxic effects of oxysterols in human leukemic cells.

We have developed hematopoietic cells resistant to the cytotoxic effects of oxysterols. Oxysterol-resistant HL60 cells were generated by continuous exposure to three different oxysterols-25-hydroxycholesterol (25-OHC), 7-beta-hydroxycholesterol (7beta-OHC) and 7-keto-cholesterol (7kappa-C). We investigated the effects of 25-OHC, 7beta-OHC, 7kappa-C and the apoptotic agent staurosporine on these cells. The effect of the calcium channel blocker nifedipine on oxysterol cytotoxicity was also investigated. Differential display and real-time PCR were used to quantitate gene expression of oxysterol-sensitive and -resistant cells. Our results demonstrate that resistance to the cytotoxic effects of oxysterols is relatively specific to the type of oxysterol, and that the cytotoxicity of 25-OHC but not that of 7beta-OHC and 7kappa-C, appears to occur by a calcium dependent mechanism. Oxysterol-resistant cells demonstrated no significant difference in the expression of several genes previously implicated in oxysterol resistance, but expressed the bcl-2 gene at significantly lower levels than those observed in control cells. We identified three novel genes differentially expressed in resistant cells when compared to HL60 control cells. Taken together, the results of this study reveal potentially novel mechanisms of oxysterol cytotoxicity and resistance, and indicate that cytotoxicity of 25-OHC, 7beta-OHC and 7kappa-C occur by independent, yet overlapping mechanisms.

Mutation spectrum in Australian pedigrees with hereditary hyperferritinaemia-cataract syndrome reveals novel and de novo mutations.

Hereditary hyperferritinaemia-cataract syndrome (HHCS) (OMIM #600886) is a rare autosomal dominant condition identified by high serum ferritin levels with normal iron saturation and distinctive bilateral cataract. It may be misdiagnosed as haemochromatosis and such patients become anaemic as a result of inappropriate venesection. The elevated serum ferritin is due to a mutation in the iron-responsive element (IRE) of the l-ferritin gene, resulting in excessive l-ferritin production. We report the identification of three Australian pedigrees; one with a previously described mutation at position 40, a pedigree with a novel mutation at position 39 and an individual with a de novo mutation at position 32 of the l-ferritin IRE.