The current understanding of mammalian kidney development is largely based on mouse models. Recent landmark studies revealed pervasive differences in renal embryogenesis between mouse and human. The scarcity of detailed gene expression data in humans therefore hampers a thorough understanding of human kidney development and the possible developmental origin of kidney diseases. In this paper, we present a single-cell transcriptomics study of the human fetal kidney. We identified 22 cell types and a host of marker genes. Comparison of samples from different developmental ages revealed continuous gene expression changes in podocytes. To demonstrate the usefulness of our data set, we explored the heterogeneity of the nephrogenic niche, localized podocyte precursors, and confirmed disease-associated marker genes. With close to 18,000 renal cells from five different developmental ages, this study provides a rich resource for the elucidation of human kidney development, easily accessible through an interactive web application.

Pure and active oxygen-evolving PS II core particles containing 35 Chl per reaction center were isolated with 75% yield from spinach PS II membrane fragments by incubation with n-dodecyl-β-D-maltoside and a rapid one step anion-exchange separation. By Triton X-100 treatment on the column these particles could be converted with 55% yield to pure and active PS II reaction center particles, which contained 6 Chl per reaction center.

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Many fish species adapt to hypoxia by reducing their metabolic rate and increasing hemoglobin-oxygen (Hb-O2) affinity. Pilot studies with young broods of cichlids showed that the young could survive severe hypoxia in contrast with the adults. It was therefore hypothesized that early exposure results in improved oxygen transport. This hypothesis was tested using split brood experiments. Broods of Astatoreochromis alluaudi, Haplochromis ishmaeli, and a tilapia hybrid ( Oreochromis) were raised either under normoxia (NR; 80–90% air saturation) or hypoxia (HR; 10% air saturation). The activity of the mitochondrial citrate synthase was not different between NR and HR tilapia, but was significantly decreased in HR A. alluaudi and H. ishmaeli, indicating lowered maximum aerobic capacities. On the other hand, hemoglobin and hematocrit levels were significantly higher in all HR fish of the three species, reflecting a physiological adaptation to safeguard oxygen transport capacity. In HR tilapia, intraerythrocytic GTP levels were decreased, suggesting an adaptive increase of blood-O2 affinity. Similar changes were not found in HR H. ishmaeli. In this species, however, all HR specimens exhibited a distinctly different iso-Hb pattern compared with their NR siblings, which correlated with a higher intrinsic Hb-O2 affinity in the former. All HR cichlids thus reveal left-shifted Hb-O2 equilibrium curves, mediated by either decreased allosteric interaction or, in H. ishmaeli, by the production of new hemoglobins. It is concluded that the adaptation to lifelong hypoxia is mainly due to improved oxygen transport.

The effect of polychlorinated biphenyls (PCBs) on the energy consum ption of fasting silver European eel (Anguilla anguilla L.) was studied over a 27-day period during w hich the anim als w ere at rest or were sw im m ing 800 km in Blazka sw im tunnels. Three-year-old female hatchery eels (silver stage) betw een 73 and 80 cm long weighing around 1 kg w ere dosed intraperitoneally w ith PCBs at a nom inal dosage of 10x the consum ption standard as a m ixture representative for planar (7 ^gPCB126/kgeel), non-planar (5 m g PCB153/kg eel) and m etabolizable PCBs (50 ^g PCB77/kg eel) found in wild eel, or only w ith the vehicle (corn oil, 10 m l/kg eel). Four m ajor observations were m ade: (1) PCB-exposed anim als lose less w eight com pared to their unexposed controls; (2) PCB-concentrations on a lipid basis are 2.8-14 tim es higher in sw im m ing com pared to resting anim als; (3) the standard m etabolic rate is significantly lower in the PCB-exposed anim als than in unexposed controls. In addition, PCB-exposure significantly reduces oxygen consum ption during swim m ing, and starting at 4 0 0 k m (18 days) this effect increases w ith tim e; (4) the relative spleen and liver w eight significantly increased in the PCB-swim anim als but not in the PCB-rest animals. The sw im m ing anim als lost about 75% m ore w eight com pared to resting anim als and had about 50% lower plasm a fat content. Hematocrit, haem oglobin, plasm a pH, ion levels (sodium and potassium ), and plasm a lactate w ere not affected by PCB-exposure or swim m ing. Apparently, the current levels of PCBs and other dioxin-like com pounds m ay seriously im pair the reproduction of the European eel.