While macro-and microscopic kidney development appear to proceed normally in mice that lack Foxi1, electron microscopy reveals an altered ultrastructure of cells lining the distal nephron. Northern blot analyses, cRNA in situ hybridizations, and immunohistochemistry demonstrate a complete loss of expression of several anion transporters, proton pumps, and anion exchange proteins expressed by intercalated cells of the collecting ducts, many of which have been implicated in hereditary forms of distal renal tubular acidosis (dRTA). In Foxi1-null mutants the normal epithelium with its two major cell types -principal and intercalated cells -has been replaced by a single cell type positive for both principal and intercalated cell markers. To test the functional consequences of these alterations, Foxi1 -/-mice were compared with WT littermates in their response to an acidic load. This revealed an inability to acidify the urine as well as a lowered systemic buffer capacity and overt acidosis in null mutants. Thus, Foxi1 -/-mice seem to develop dRTA due to altered cellular composition of the distal nephron epithelium, thereby denying this epithelium the proper gene expression pattern needed for maintaining adequate acid-base homeostasis.

The invariant active site residue Glu 441 in protein R1 of ribonucleotide reductase from Escherichia coli has been engineered to alanine, aspartic acid, and glutamic acid. Each mutant protein was structurally and enzymatically characterized. Glu 441 contributes to substrate binding, and a carboxylate side chain at position 441 is essential for catalysis. The most intriguing results are the suicidal mechanism-based reaction intermediates observed when R1 E441Q is incubated with protein R2 and natural substrates (CDP and GDP). In a consecutive reaction sequence, we observe at least three clearly discernible steps: (i) a rapid decay (k 1 > 1. Ribonucleotide reductase is an essential enzyme of all living cells and catalyzes the reduction of ribonucleotides to the corresponding deoxyribonucleotides. Several classes of ribonucleotide reductases with different subunit composition and cofactor requirements are known, but they all share a radical-based reaction mechanism (1).The aerobic class Ia ribonucleotide reductase from Escherichia coli is the best characterized enzyme. It consists of two components denoted protein R1 and protein R2, each of which is a homodimer. Protein R1 contains redox-active cysteines essential for catalysis. Cysteines 225, 439, and 462 are located at the active site, where all four physiological substrates (CDP, UDP, GDP, or ADP) can bind. R1 also contains two different allosteric sites that bind nucleoside triphosphate effector molecules. One site regulates the overall enzyme activity, and the other site determines the substrate specificity (2, 3). Protein R2 contains a stable tyrosyl free radical at position 122 and an adjacent dinuclear iron center (4 -6). The tyrosyl radical is essential for catalysis.The separate three-dimensional structures of protein R1 and of protein R2 are known (6 -9). A model-built holoenzyme complex of the R1 and R2 structures indicates that the distance between the active site in R1 and Tyr 122 in R2 is about 30 -40 Å (8). Chains of conserved hydrogen-bonded residues leading from the active site of R1 in the direction of Tyr 122 in R2, and vice versa, have been identified and are believed to be part of a radical transfer pathway between the two sites (1, 6 -9). Mutational analysis of the residues postulated to be involved in radical transfer between R1 and R2 during catalysis supports this hypothesis (4, 10 -14).

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These results demonstrate the existence of a cross-talk between the nitrate-nitrite-NO pathway and the NOS-dependent pathway in control of vascular NO homeostasis.

Cyanobacteria are unique prokaryotes since they in addition to outer and plasma membranes contain the photosynthetic membranes (thylakoids). The plasma membranes of Synechocystis 6803, which can be completely purified by density centrifugation and polymer two-phase partitioning, have been found to be more complex than previously anticipated, i.e. they appear to be essential for assembly of the two photosystems. A proteomic approach for the characterization of cyanobacterial plasma membranes using two-dimensional gel electrophoresis and mass spectrometry analysis revealed a total of 57 different membrane proteins of which 17 are integral membrane spanning proteins. Among the 40 peripheral proteins 20 are located on the periplasmic side of the membrane, while 20 are on the cytoplasmic side. Among the proteins identified are subunits of the two photosystems as well as Vipp1, which has been suggested to be involved in vesicular transport between plasma and thylakoid membranes and is thus relevant to the possibility that plasma membranes are the initial site for photosystem biogenesis. Four subunits of the Pilus complex responsible for cell motility were also identified as well as several subunits of the TolC and TonB transport systems. Several periplasmic and ATP-binding proteins of ATPbinding cassette transporters were also identified as were two subunits of the F 0 membrane part of the ATP synthase.

Following challenge with virulent Mycobacterium tuberculosis, mice of the I/St inbred strain exhibit shorter survival time, more rapid body weight loss, higher mycobacterial loads in organs, and more severe lung histopathology than mice of the A/Sn strain. We previously performed a genome-wide scan for quantitative trait loci (QTLs) that control the severity of M. tuberculosis-triggered disease in [(A/Sn ؋ I/St) F1 ؋ I/St] backcross-1 (BC1) mice and described several QTLs that are significantly or suggestively linked to body weight loss. In the present study we expanded our analysis by including the survival time phenotype and by genotyping 406 (A/Sn ؋ I/St) F2 mice for the previously identified chromosomal regions of interest. The previously identified 12-cM-wide QTL on distal mouse chromosome 3 was designated tbs1 (tuberculosis severity 1); the location of the QTL on proximal chromosome 9 was narrowed to a 9-cM interval, and this QTL was designated tbs2. Allelic variants of the tbs2 locus appeared to be involved in control of both body weight loss and survival time. Also, the data strongly suggested that a QTL located in the vicinity of the H-2 complex on chromosome 17 is involved in control of tuberculosis in mice of both genders, whereas the tbs1 locus seemed to have an effect on postinfection body weight loss in female mice. Interestingly, these loci appeared to interact with each other, which suggests that there might be a basic genetic network for the control of intracellular parasites. Overall, linkage data reported here for F2 mice are in agreement with, and add to, our previous findings concerning the control of M. tuberculosis-triggered disease in the BC1 segregation.Identification of genes and their alleles that confer resistance and/or susceptibility to tuberculosis (TB) provides deep insight into basic mechanisms of immunity and pathology. Variations in NRAMP1 (5) and/or NRAMP1-linked loci on human chromosome 2q35 (8), VDR (3, 27), and class II HLA genes (6, 7) were shown to be linked to or associated with susceptibility to TB in humans. However, linkage and association results vary between studies, which may be due to the genetic control being polygenic and ethnicity dependent and to the absence of clearly delineated phenotypes (4, 24).Mouse models of TB have proved to be valuable for studies of antimycobacterial immunity and of the genetic control of susceptibility and resistance (16). For example, the Nramp1 gene, which has provided great insight in our understanding of macrophage-mycobacterium relationships, was first discovered in a mouse model of susceptibility to Mycobacterium bovis BCG (9, 28). Numerous inbred mouse strains have been tested to determine their survival times after challenge with virulent Mycobacterium tuberculosis (1,17,20). Among these strains, I/StSnEgYCit (I/St) mice display the shortest survival time, while A/SnYCit (A/Sn) mice survive significantly longer. In addition, I/St mice display more severe and rapid disease progression than A/Sn mice in terms of body weight los...

The megencephaly mouse, mceph/mceph, displays dramatically increased brain volume and hypertrophic brain cells. Despite overall enlargement, the mceph/mceph brain appears structurally normal, without oedema, hydrocephaly or leukodystrophy, and with only minor astrocytosis. Furthermore, it presents striking disturbances in expression of trophic and neuromodulating factors within the hippocampus and cortex. Using a positional cloning approach we have identified the mceph mutation. We show that mceph/mceph mice carry an 11-base-pair deletion in the gene encoding the Shaker-like voltage-gated potassium channel subtype 1, Kcna1. The mutation leads to a frame shift and the predicted MCEPH protein is truncated at amino acid 230 (out of 495), terminating with six aberrant amino acids. The expression of Kcna1 mRNA is increased in the mceph/mceph brain. However, the C-terminal domains of the corresponding Kv1.1 protein are absent. The putative MCEPH protein retains only the N-terminal domains for channel assembly and may congregate nonfunctional complexes of multiple Shaker-like subunits. Indeed, whereas Kcna2 and Kcna3 mRNA expression is normal, the mceph/mceph hippocampus displays decreased amounts of Kv1.2 and Kv1.3 proteins, suggesting interactions at the protein level. We show that mceph/mceph mice have disturbed brain electrophysiology and experience recurrent behavioural seizures, in agreement with the abnormal electrical brain activity found in Shaker mutants. However, in contrast to the commonly demonstrated epilepsy-induced neurodegeneration, we find that the mceph mutation leads to seizures with a concomitant increase in brain size, without overt neural atrophy.

Driver sleepiness is a contributing factor in many road fatalities. A long-standing goal in driver state research has therefore been to develop a robust sleepiness detection system. It has been suggested that various heart rate variability (HRV) metrics can be used for driver sleepiness classification. However, since heart rate is modulated not only by sleepiness but also by several other time-varying intra-individual factors such as posture, distress, boredom and relaxation, it is relevant to highlight not only the possibilities but also the difficulties involved in HRV-based driver sleepiness classification. This paper investigates the reliability of HRV as a standalone feature for driver sleepiness detection in a realistic setting. Data from three real-road driving studies were used, including 86 drivers in both alert and sleep-deprived conditions. Subjective ratings based on the Karolinska sleepiness scale (KSS) were used as ground truth when training four binary classifiers (k-nearest neighbours, support vector machine, AdaBoost, and random forest). The best performance was achieved with the random forest classifier with an accuracy of 85%. However, the accuracy dropped to 64% for three-class classification and to 44% for subject-independent, leave-one-participant-out classification. The worst results were obtained in the severely sleepy class. The results show that in realistic driving conditions, subject-independent sleepiness classification based on HRV is poor. The conclusion is that more work is needed to control for the many confounding factors that also influence HRV before it can be used as input to a driver sleepiness detection system.