Do Toxocara canis larval antigens used in enzyme-linked immunosorbent assay for visceral larva migrans cross-react with AB isohemagglutinins and give false positive results?

A variety of helminth parasites have A and B blood group antigens on their surface. These antigens may cross-react with elevated concentrations of A and B isohemagglutinins in some patients and give false-positive results in the serologic diagnosis of visceral larva migrans caused by T. canis. To clarify this point, serum from patients with visceral larva migrans and elevated T. canis antibody titers as determined by ELISA were absorbed with AB blood cells and retested by ELISA without a demonstrable decline in T. canis antibody titers. Similarly, absorption with T. canis embryonated egg antigens of serum containing elevated levels of anti-A or anti-B isohemagglutinins failed to decrease the isohemagglutinin titer. This indicates that the ELISA using T. canis embryonated egg antigen does not give false positive results with sera containing high concentrations of anti-A or anti-B isohemagglutinins.     

Cold habituation does not improve manual dexterity during rest and exercise in 5 °C

When exposed to a cold environment, a barehanded person experiences pain, cold sensation, and reduced manual dexterity. Both acute (e.g. exercise) and chronic (e.g. cold acclimatization or habituation) processes might lessen these negative effects. The purpose of this experiment was to determine the effect of cold habituation on physiology, perception, and manual dexterity during rest, exercise, and recovery in 5 °C. Six cold weather athletes (CWA) and eight non habituated men (NON) volunteered to participate in a repeated measures cross-over design. The protocol was conducted in 5 °C and was 90 min of resting cold exposure, 30 min of cycle ergometry exercise (50 % VO_{2 peak}), and 60 min of seated recovery. Core and finger skin temperature, metabolic rate, Purdue Pegboard dexterity performance, hand pain, thermal sensation, and mood were quantified. Exercise-induced finger rewarming (EIFRW) was calculated for each hand. During 90 min of resting exposure to 5 °C, the CWA had a smaller reduction in finger temperature, a lower metabolic rate, less hand pain, and less negative mood. Despite this cold habituation, dexterity performance was not different between groups. In response to cycle ergometry, EIFRW was greater in CWA (~12 versus 7 °C) and occurred at lower core temperatures (37.02 versus 37.31 °C) relative to NON but dexterity was not greater during post-exercise recovery. The current data indicate that cold habituated men (i.e., CWA) do not perform better on the Purdue Pegboard during acute cold exposure. Furthermore, despite augmented EIFRW in CWA, dexterity during post-exercise recovery was similar between groups.     

An M13 vector library for cloning DNA with four nucleotide 3' overhangs

A flexible M13 vector library incorporating the BstXI site has been developed. DNA cut by any currently commercially available restriction endonuclease that generates a 4-nucleotide (nt) 3' overhang can be ligated into a specific clone of the library. The BstXI enzyme recognizes a 6-bp bipartite palindromic sequence. The central nucleotides are not specified, and form a 4-base, 3' overhang when cut by BstXI. 5' CCANNNNN NTGG GGTN NNNNNACC 5' Since the 4-base overhang formed is not part of the BstXI recognition sequence, it is possible to generate a library of 256 different clones by introducing the BstXI site, 151 of the possible 256-member library have been isolated, including all 13 M13BF clones in which the overhang formed by BstXI digestion is complementary to those formed by currently available restriction endonucleases. Of these 13 vectors, BstXI digestion of six clones results in nonpalindromic cohesive ends and should facilitate in vitro tandem gene amplification. The BstXI site is adjacent to the four codons corresponding to the factor Xa recognition sequence. Hence the vector library could facilitate the expression of a fusion protein that could be proteolytically cleaved by factor Xa.