New method for determination of fecal sterols in urine using non-chlorinated solvents

A new method has been developed to determine a number of sterols in urine using non-chlorinated solvents, namely methyl tert.-butyl ether and methanol (the MTB method). The method involves liquid–liquid extraction, saponification, reextraction, silylation and final identification and quantification by GC–FID. The sterols determined were coprostanol, epicoprostanol, cholesterol and dihydrocholesterol. 5α-Cholestane was used as internal standard. The limit of detection for the sterols in this experiment was 2 μg l⁻¹ urine. Recovery of coprostanol over the range 5–100 μg l⁻¹ urine by this method was between 80 and 92%.     

Adenovirus early gene products may control viral mRNA accumulation and translation in vivo

The mechanisms controlling early adenovirus gene expression in vivo have been studied using inhibitors of protein synthesis. When inhibitors were added shortly before or at the onset of infection, viral mRNA from all early regions was transcribed, spliced and accumulated over a 7 hr period. After longer pretreatment, accumulation of several early mRNAs were suppressed. Addition of inhibitors 1 hr after infection enhanced the accumulation of viral mRNA in the cytoplasm. Translation of early mRNA selected on adenovirus DNA in a cell-free system reflected the amount of viral mRNA present. A viral coded product may therefore control accumulation of viral mRNA.A different pattern emerged when inhibitors of protein synthesis were removed at 5 hr postinfection and cells were pulse-labeled in vivo. If inhibitors were introduced at or before infection, early viral proteins were synthesized only after a lag of 1–3 hr. However, if treatment was introduced 1 hr post-infection, reversion of the protein synthesis block was instantaneous. It appears that protein synthesis inhibitors reveal an in vivo translational block for viral mRNA. This block could be overcome by preinfection with a related virus. Furthermore, no block was observed in a virus-transformed human embryonic kidney cell line (293) which expresses early region 1 of the viral genome. Viral gene product(s) encoded in early region 1 may control translation of early adenovirus messenger RNA in vivo.     

In situ generation of iminodiacetic acid groups on nanoporous alumina for the reversible immobilization of enzymes and other biomolecules

Nanoporous alumina membranes were silanized with aminopropylsilane and iminodiacetic acid (IDA) groups were generated in situ by reaction with iodoacetate. The membranes were mounted in standard filter holders, connected to a HPLC system and saturated with selected metal ions. Cu(II) allowed the capture of chicken muscle lactate dehydrogenase with such stability, repeatability and reproducibility that Michaelis–Menten kinetics could be studied. The IDA surface was stable for months and could be depleted and regenerated with metal ions multiple times without appreciable loss of capacity. The binding of lactate dehydrogenase influenced the backpressure to the extent that could be expected for a monolayer according to Poiseuilles law.     

No Diagnostic Value of Plasma Clusterin in Alzheimer's Disease

There is an urgent need for biomarkers to enable early diagnosis of Alzheimer''s disease (AD). It has recently been shown that a variant within the clusterin gene is associated with increased risk of AD and plasma levels of clusterin have been found to be associated with the risk of AD. We, therefore, investigated the diagnostic value of clusterin by quantifying clusterin using an ELISA in plasma from 171 controls, 127 patients with AD, 82 patients with other dementias and 30 patients with depression. We observed similar plasma clusterin levels in controls, AD patients and patients with other dementias, suggesting that plasma clusterin levels have no diagnostic value for AD. There was a slight, but significant, increase in plasma clusterin in patients with depression compared to all other groups tested, which may warrant further investigation.     

Population growth and habitat distribution in cyclic small rodents: to expand or to change?

Habitat selection determined by intraspecific interactions (social behaviour), being either free or despotic, should result in the largest densities in the most favourable habitat at least in late increase and decline phases of cyclic populations. Habitat distribution determined by interspecific effects such as herbivore-plant or predator-prey interactions may result in higher densities in inferior habitats at late peaks and/or declines due to overgrazing of preferred habitats, or invasion of such habitats by specialist predators. An examination of the distributions of the rodent species Clethrionomys glareolus and Microtus agrestis during a population cycle on forest clearcuts at Grimsö, south-central Sweden, demonstrated clear changes towards less preferred habitats during the decline phase, particularly in M. agrestis. Intraspecific competition could be excluded as a cause since the numbers of both species declined simultaneously. There was no sign of overgrazing, while weasels, Mustela nivalis, invaded the preferred M. agrestis habitat during peak–decline. Predation thus appears more important for the local occurrence at early decline, rather than territoriality or other social behaviour. It is concluded that distributions in various habitats do not always reveal any primary habitat selection but, rather, habitat-dependent survival.