Hydrocephalus induced by immunological blockage of the subcommissural organ–Reissner's fiber (RF) complex by maternal transfer of anti-RF antibodies

Stenosis of the cerebral aqueduct seems to be a key event for the development of congenital hydrocephalus. The causes of such a stenosis are not well known. Overholser et al. in 1954 (Anat Rec 120:917-933) proposed the hypothesis that a dysfunction of the subcommissural organ (SCO) leads to aqueductal stenosis and congenital hydrocephalus. The SCO is a brain gland, located at the entrance of the cerebral aqueduct, that secretes glycoproteins into the cerebrospinal fluid that, upon release, assemble into a fibrous structure known as Reissner's fiber (RF). By the permanent addition of new molecules to its rostral end, RF grows and extends along the aqueduct, fourth ventricle, and central canal of the spinal cord. The immunological blockage of the SCO-RF complex has been used to test Overholser's hypothesis. The following was the sequence of events occurring in pregnant rats that had been immunized with RF glycoproteins: the mother produced anti-RF antibodies and transferred them to the fetus through the placenta and to the pup through the milk, and the antibodies reached the brain of the fetus and pup and blocked the SCO-RF complex. This resulted in a permanent absence of RF that was followed by stenosis of the cerebral aqueduct, and then by the appearance of hydrocephalus. The latter was patent until the end of the 6-month observation period. The chronic hydrocephalic state appeared, in turn, to induce new alterations of the SCO. It is concluded that a selective immunological knock out of the SCO-RF complex leads to hydrocephalus.     

The Drosophila projectin mutant,bent D,has reduced stretch activation and altered indirect flight muscle kinetics

Projectin is a ca. 900 kDa protein that is a member of the titin protein superfamily. In skeletal muscle titins are involved in the longitudinal reinforcement of the sarcomere by connecting the Z-band to the M-line. In insect indirect flight muscle (IFM), projectin is believed to form the connecting filaments that link the Z-band to the thick filaments and is responsible for the high relaxed stiffness found in this muscle type. The Drosophila mutant bent ^D (bt ^D ) has been shown to have a breakpoint close to the carboxy-terminal kinase domain of the projectin sequence. Homozygotes for bt ^D are embryonic lethal but heterozygotes (bt ^D /+) are viable. Here we show that bt ^D /+ flies have normal flight ability and a slightly elevated wing beat frequency (bt ^D /+ 223 ± 13 Hz; +/+203 ± 5 Hz, mean ± SD; P < 0.01). Electron microscopy of bt ^D /+ IFM show normal ultrastructure but skinned fiber mechanics show reduced stretch activation and oscillatory work. Although bt ^D /+ IFM power output was at wild-type levels, maximum power was achieved at a higher frequency of applied length perturbation (bt ^D /+ 151 ± 6 Hz; +/+ 102 ± 14 Hz; P < 0.01). Results were interpreted in the context of a viscoelastic model of the sarcomere and indicate altered cross-bridge kinetics of the power-producing step. These results show that the bt ^D mutation reduces oscillatory work in a way consistent with the proposed role of the connecting filaments in the stretch activation response of IFM.     

Using Bayesian networks in the construction of a bi-level multi-classifier. A case study using intensive care unit patients data

Combining the predictions of a set of classifiers has shown to be an effective way to create composite classifiers that are more accurate than any of the component classifiers. There are many methods for combining the predictions given by component classifiers. We introduce a new method that combine a number of component classifiers using a Bayesian network as a classifier system given the component classifiers predictions. Component classifiers are standard machine learning classification algorithms, and the Bayesian network structure is learned using a genetic algorithm that searches for the structure that maximises the classification accuracy given the predictions of the component classifiers. Experimental results have been obtained on a datafile of cases containing information about ICU patients at Canary Islands University Hospital. The accuracy obtained using the presented new approach statistically improve those obtained using standard machine learning methods.     

A voltage-dependent K+ current contributes to membrane potential of acutely isolated canine articular chondrocytes

The electrophysiological properties of acutely isolated canine articular chondrocytes have been characterized using patch-clamp methods. The 'steady-state' current–voltage relationship ( I–V ) of single chondrocytes over the range of potentials from −100 to +40 mV was highly non-linear, showing strong outward rectification positive to the zero-current potential. Currents activated at membrane potentials negative to −50 mV were time independent, and the I–V from −100 to −60 mV was linear, corresponding to an apparent input resistance of 9.3 ± 1.4 GΩ ( n = 23). The outwardly rectifying current was sensitive to the K⁺ channel blocking ion tetraethylammonium (TEA), which had a 50% blocking concentration of 0.66 m m (at +50 mV). The 'TEA-sensitive' component of the outwardly rectifying current had time- and membrane potential-dependent properties, activated near −45 mV and was half-activated at −25 mV. The reversal potential of the 'TEA-sensitive' current with external K⁺ concentration of 5 m m and internal concentration of 145 m m , was −84 mV, indicating that the current was primarily carried by K⁺ ions. The resting membrane potential of isolated chondrocytes (−38.1 ± 1.4 mV; n = 19) was depolarized by 14.8 ± 0.9 mV by 25 m m TEA, which completely blocked the K⁺ current of these cells. These data suggest that this voltage-sensitive K⁺ channel has an important role in regulating the membrane potential of canine articular chondrocytes.     

Diversity of enteric viruses detected in patients with gastroenteritis in a tertiary referral paediatric hospital

The genetic diversity of enteric viruses co-circulating in a cohort of patients with viral gastroenteritis in a large tertiary paediatric hospital in London, UK, was determined. Multiple strains of noroviruses (NV), sapoviruses (SV) and astroviruses (HAsV) were detected in these patients, indicating the likelihood of multiple introductions from different sources, possible sub-clinical infections and simultaneous infection with different viruses in immunocompromised and other patients. Routine screening of immunocompromised patients and infection control procedures are important to prevent nosocomial infection.     

The mammalian testis-specific thioredoxin system

Redox control of cell physiology is one of the most important regulatory mechanisms in all living organisms. The thioredoxin system, composed of thioredoxin and thioredoxin reductase, has emerged as a key player in cellular redox-mediated reactions. For many years, only one thioredoxin system had been described in higher organisms, ubiquitously expressed in the cytoplasm of eukaryotic cells. However, during the last decade, we and others have identified and characterized novel thioredoxin systems with unique properties, such as organelle-specific localization in mitochondria or endoplasmic reticulum, tissue-specific distribution mostly in the testis, and features novel for thioredoxins, such as microtubule-binding properties. In this review, we will focus on the mammalian testis-specific thioredoxin system that comprises three thioredoxins exclusively expressed in spermatids (named Sptrx-1, Sptrx-2, and Sptrx-3) and an additional thioredoxin highly expressed in testis, but also present in lung and other ciliated tissues (Txl-2). The implications of these findings in the context of male fertility and testicular cancer, as well as evolutionary aspects, will be discussed.