The first formal qualification of safety biomarkers for regulatory decision making marks a milestone in the application of biomarkers to drug development. Following submission of drug toxicity studies and analyses of biomarker performance to the Food and Drug Administration (FDA) and European Medicines Agency (EMEA) by the Predictive Safety Testing Consortium's (PSTC) Nephrotoxicity Working Group, seven renal safety biomarkers have been qualified for limited use in nonclinical and clinical drug development to help guide safety assessments. This was a pilot process, and the experience gained will both facilitate better understanding of how the qualification process will probably evolve and clarify the minimal requirements necessary to evaluate the performance of biomarkers of organ injury within specific contexts.

Kinesin is a heterotetramer composed of two 115-kD heavy chains and two 58-kD light chains. The microtubule motor activity of kinesin is performed by the heavy chains, but the functions of the light chains are poorly understood. Mutations were generated in the Drosophila gene Kinesin light chain (Klc), and the phenotypic consequences of loss of Klc function were analyzed at the behavioral and cellular levels. Loss of Klc function results in progressive lethargy, crawling defects, and paralysis followed by death at the end of the second larval instar. Klc mutant axons contain large aggregates of membranous organelles in segmental nerve axons. These aggregates, or organelle jams (Hurd, D.D., and W.M. Saxton. 1996. Genetics. 144: 1075–1085), contain synaptic vesicle precursors as well as organelles that may be transported by kinesin, kinesin-like protein 68D, and cytoplasmic dynein, thus providing evidence that the loss of Klc function blocks multiple pathways of axonal transport. The similarity of the Klc and Khc (Saxton et al. 1991. Cell 64:1093–1102; Hurd, D.D., and W.M. Saxton. 1996. Genetics 144: 1075–1085) mutant phenotypes indicates that KLC is essential for kinesin function, perhaps by tethering KHC to intracellular cargos or by activating the kinesin motor.

This study reports the evaluation of four urinary biomarkers of renal toxicity, α-glutathione-S-transferase (α-GST), μ-GST, clusterin, and renal papillary antigen-1 (RPA-1), in male Sprague-Dawley and Han-Wistar rats given cisplatin, gentamicin, or N-phenylanthranilic acid (NPAA). Kidney injury was diagnosed histopathologically, according to site/nature of renal injury, and graded for severity. The area under the receiver operating characteristic (ROC) curve was used to compare the diagnostic accuracy of each exploratory renal biomarker with traditional indicators of renal function and injury (blood urea nitrogen [BUN], serum creatinine [sCr] as well as urinary N-acetyl-β-D-glucosaminidase [NAG] and protein). These analyses showed that increased urinary α-GST was superior to BUN, sCr, and NAG for diagnosis of proximal tubular (PT) degeneration/necrosis. Paradoxically, urinary α-GST was decreased in the presence of collecting duct (CD) injury without PT injury (NPAA administration). RPA-1 demonstrated high specificity for CD injury, superior to all of the reference biomarkers. The clusterin response correlated well with tubular injury, whatever the location, particularly when regeneration was present (superior to all of the reference markers for cortical tubular regeneration). There was no conclusive evidence for the diagnostic utility of μ-GST. The data were submitted for qualification review by the European Medicines Agency and the US Food and Drug Administration. Both agencies concluded that the data justified the qualification of RPA-1 and increased the level of evidence for, and clarified the context of use of, the previously qualified clusterin for use in male rats. These biomarkers can be used in conjunction with traditional clinical chemistry markers and histopathology in Good Laboratory Practice rodent toxicology studies used to support renal safety studies in clinical trials. Qualification of α-GST must await further explanation of the differences in response to PT and CD injury.

The coronaviruses, ubiquitous in mammals, including man, manifest serotype-related predeliction for different tissues. This presentation deals with specificity of the murine viscerotropic MHV3 and neurotropic JHMV for explanted cells from the CNS of newborn, inbred, Wistar-Furth rats. An unambiguous tropism of MHV3 for astrocytes and JHMV for oligodendrocytes is demonstrated. With the latter cell-virus interaction, relatively small differences in spatial density of oligodendrocytes influence profoundly the duration of persistence and virus yield. The in vitro temporal program of oligodendrocyte differentiation, monitored by induction of a myelin-related enzyme, 2':3'-cyclic nucleotide-3'-phosphohydrolase, corresponds to that occurring in vivo (F. A. McMorris, J. Neurochem. 41, 506-515, 1983). It is complete within 15-21 days and is coincident with the onset of insusceptibility to disease caused by JHMV. Experimental elevation of intracellular cyclic-AMP levels, presumed to reflect oligodendrocyte differentiation, likewise suppresses JHMV replication without affecting that of MHV3 in astrocytes. On the basis of these data it is concluded that in vitro interaction of JHMV with oligodendrocytes reflects accurately the in vivo host control over the tropism and expression of this virus, thereby effecting the progressive, demyelinative disease, process.

We isolated cDNA clones from an Aplysia sensory-cell library encoding two isoforms of protein kinase C (PKC). Several isozyme-specific regions are conserved in the Aplysia kinases, notably the variable regions V5 in the Ca(2+)-dependent PKC (Apl I) and V1 in the Ca(2+)- independent PKC (Apl II). Neuronal proteins with the properties expected of these two isoforms can be identified with antibodies raised against peptides synthesized from the amino acid sequences deduced from the clones. Sacktor and Schwartz (1990) measured the proportion of kinase activity that can be translocated to membrane in Aplysia sensory neurons and ganglia by stimuli that produce the presynaptic facilitation underlying behavioral sensitization. Much less Apl I and Apl II are translocated, suggesting that still other isoforms of PKC exist in these cells.