Inhibition of protein glycosylation causes renal dysplasia in the chick embryo

Computational and experimental analysis identified 6-diazo-5-oxonorleucine as a potential agent for treating infection by Plasmodium falciparum

Plasmodium falciparum (PF) is the most severe malaria parasite. It is developing resistance quickly to existing drugs making it indispensable to discover new drugs. Effective drugs have been discovered targeting metabolic enzymes of the parasite. In order to predict new drug targets, computational methods can be used employing database information of metabolism. Using this data, we performed recently a computational network analysis of metabolism of PF. We analyzed the topology of the network to find reactions which are sensitive against perturbations, i.e., when a single enzyme is blocked by drugs. We now used a refined network comprising also the host enzymes which led to a refined set of the five targets glutamyl-tRNA (gln) amidotransferase, hydroxyethylthiazole kinase, deoxyribose-phophate aldolase, pseudouridylate synthase, and deoxyhypusine synthase. It was shown elsewhere that glutamyl-tRNA (gln) amidotransferase of other microorganisms can be inhibited by 6-diazo-5-oxonorleucine. Performing a half maximal inhibitory concentration (IC50) assay, we showed, that 6-diazo-5-oxonorleucine is also severely affecting viability of PF in blood plasma of the human host. We confirmed this by an in vivo study observing Plasmodium berghei infected mice.

Dysplastic kidneys in children - do they grow?

OBJECTIVES

Dysplastic kidneys (DK) are a common cause of chronic kidney disease (CKD). Little is known about their growth or how their sonographic appearance changes. This study aimed to test the hypothesis that DK gain little length, and to identify radiologic trends predictive of CKD.

METHODS

Ultrasound scans of children with DK born in 1980-2005 and referred to a single tertiary centre were analysed by a pediatric radiologist. Renal lengths were plotted on standard nomograms and the degree of dysplastic appearance noted. Factors related to DK - bladder outlet obstruction, vesico-ureteric reflux and renal impairment - were noted.

RESULTS

Fifty-three children were studied (83 kidneys), of whom 41 were boys; 289 scans were analysed. In 33 children there was associated bladder outlet obstruction or vesico-ureteric reflux. Forty-four DK were noted to fall off their renal length 'centile'. This correlated well with the development of CKD and is statistically significant. Deterioration occurred in 53% of DK; primarily progressive reduction in corticomedullary differentiation. This also correlated well with development of CKD.

CONCLUSION

More than half of the DK showed poor growth velocity. This, together with the degree of sonographic abnormality, carries a high predictive value for development of CKD. We recommend diligent serial sonography to follow renal growth and dysplastic appearance in children with DK.

Histomorphology of renal dysplasia--an autopsy study

A retrospective analysis of pediatric autopsies in the past 18 years was done with the aim of studying the histomorphology of renal dysplasia. Renal dysplasia comprised 150 (3.66%) of the 4,099 pediatric autopsies from 20 weeks of gestation to 1 year of life. Primitive ducts with the fibromuscular collar, the sine qua non of renal dysplasia, was seen in all cases. Lobar disorganization and cysts were seen in all cases except for the 7 cases of hypodysplasia. Other elements were seen in varying proportions: cartilage in 33.7%, bone in 1.08%, thickening of basement membrane of the primitive ducts in 64.13%, extramedullary hematopoiesis in 98.9%, nerve twigs in 72.8%, and nodular renal blastema in 2.17% cases. In unilateral multicystic dysplasia/renal agenesis, the contralateral kidney showed abnormalities in 44.45% and 47.37% of cases, respectively.

Expression of laminin and fibronectin in renal dysplasia

The pathogenesis of renal dysplasia is a matter of debate. Recent theories have conceptualized the role of extracellular matrix proteins in the genesis of renal dysplasia. During normal nephrogenesis, collagen type I and III and fibronectins are lost and laminin and syndecan appear once proper induction has occurred. Any deviation from the normal pattern is said to lead to dysplasia. In this study, the expressions of adhesive glycoproteins, laminin, and fibronectin were studied immunohistochemically in 25 autopsy cases of renal dysplasia and normal age-matched control cases. These cases of renal dysplasia were categorized into 3 groups based on the period of gestation: 20 to 26 weeks, 27 to 33 weeks, and 34 to 40 weeks. The immunohistochemical findings were graded from 0 to 4+ based on the visual intensity. Chi-square analysis was used to calculate the difference in expressions of laminin and fibronectin in cases and controls as a whole and within and between age groups. Immunostaining for laminin in all age groups showed a significant difference in expression between dysplastic kidneys (less expression) and normal controls (greater expression). In the case of fibronectin expression, all but 1 group showed a significant difference, with dysplastic kidneys showing more and normal controls showing less expression. The inference derived is that laminin expression decreases and fibronectin expression increases in renal dysplasia compared with normal nephrogenesis.

Development of an in vitro model for the disruption of extracellular matrix components in the study of congenital renal parenchymal dysmorphism

We attempted to refine a model system for the study of renal parenchymal malformations and demonstrate its use with a preliminary study of the induction of congenital renal dysmorphism. A technique is described whereby 3-day chick embryos are explanted from their shells and cultured in vitro in specially constructed polyethylene chambers. At 8 days of development, the time of ureteral induction of the metanephric mesenchyme, 6-diazo-5-oxo-norleucine, an inhibitor of proteoglycan biosynthesis, is administered as a single microinjection into the posterolateral body wall. Histological examination of fixed metanephric tissue revealed a gross deficiency in the number of differentiated tubules in norleucine-treated animals. A morphometric analysis was made of the actual area occupied by differentiated tubules in the norleucine-treated and control kidneys between 10 and 15 days of development. This analysis revealed a total tubule surface area of control kidneys of more than 2 times greater than that of embryos injected with norleucine at ureteral induction.

Induced renal dysplasia in the young pouch opossum

Using the North American opossum, Didelphis virginiana, we have developed a new model for studying the effects of early fetal urinary obstruction on subsequent renal development. We have successfully induced renal dysplasia in the marsupial that has a typically mammalian kidney.