Lipoprotein receptors and atherogenic receptor-mediated mechanisms

The liver plays a decisive role in the regulation of the plasma levels of atherogenic lipoproteins. The primary liver interaction site of chylomicron remnants and VLDL remnants (beta-VLDL) is still unidentified, whereas the subsequent cellular uptake is likely to be mediated in concert by the LDL receptor-related protein and the LDL receptor. The nature of the primary interaction site of remnants (remnant receptor) might be a liver-specific proteoglycan or a liver-specific protein. Atherogenic modified LDL can be recognized by a family of scavenger receptors. A newly identified 95 kDa protein forms the most likely candidate for mediating the in-vivo uptake of oxidized LDL from the circulation and may, therefore, protect the body against the presence of oxidized LDL in the blood compartment.     

Effects of unilateral upper incisor extraction on facial growth of young rats

The effects of unilateral extraction of the upper incisor (one tooth) on facial growth of young rats were studied. The remaining upper incisor showed deviation towards the opposite side, and there was regular dental wear of all the incisors. The effects were evident only in the mid-facial area. Cephalometric measurements showed significant shortening with deviation of the incisor bone on the extraction side. There was no significant disturbance of the growth of the rest of the maxilla and mandible. These results indicate that upper incisor extractions have a localized influence, leading to impairment of incisor bone growth.     

Characterisation of immune responses in pancreatic carcinoma patients after mutant p21 ras peptide vaccination

This is a study of immune responses generated by mutant ras peptide vaccination of patients with pancreatic adenocarcinoma. Responding T cells from one patient were cloned and two CD4+ T-lymphocyte clones (TLC) specific for the 12 Val peptide and restricted by HLA-DR6 or DQ2 were obtained. These class II molecules have not previously been found to bind or present mutant ras peptides to T cells. The DR6-restricted TLC showed marked cytotoxicity against autologous target cells pulsed with the 12 Val peptide. Target cells pulsed with the control peptide were not killed. Responding T cells from another patient showed cross-reactivity towards the homologous ras peptides. Investigation by limiting dilution analysis (LDA) revealed different T-cell precursor frequencies for the immunising, mutant ras peptide (1:28000), compared with the normal ras peptide (1:110000).     

On the distribution of cholecystokinin B receptors in monkey brain

In view of recent evidence for a role for the B subtype of cholecystokinin (CCKB) receptor in panic and anxiety, the distribution of CCKB receptors in the forebrain of a Rhesus macaca monkey was examined by receptor autoradiography employing [125I]D-Tyr25(Nleu28,31)-CCK25-33S. CCKB receptors were widely and topographically distributed in cortex. Other structures with notable labelling included the basal ganglia, presubiculum, amygdala, mamillary bodies, cerebellar cortex and pineal gland. The distribution of CCKB receptors further supports roles for this peptide in behavioural processes.     

Efficient allocation of patients to treatment cells in clinical trials with more than two treatment conditions

OBJECTIVE: Clinical trials generally allocate patients to equal-sized treatment groups. The authors propose that it may be more efficient to allocate unequal proportions of the total sample size to treatments when more than two treatments are being compared. METHOD: This proposal is illustrated with two examples. One involved a comparison of three treatments and used a dichotomous categorical outcome. The other involved comparison of three treatments and used a continuous measure. RESULTS: In both examples, a considerable increase in efficiency was realized by reducing the number of patients assigned to the placebo cell. CONCLUSIONS: Unequal allocation of patients to treatments should be considered when more than two groups are compared.     

Use of the exercise treadmill to measure baseline functional status and surgical outcome in patients with severe lumbar spinal stenosis

Glanzmann thrombasthenia (GT) is caused by a defect in either glycoprotein (GP)IIb (alphaIIb) or GPIIIa (beta3) genes and therefore screening of both genes is required for mutation identification. The beta subunit of the GPIIb/IIIa complex (beta3) forms a complex with another alpha subunit (alpha(v)) yielding the alpha(v)beta3 vitronectin receptor (VnR). GT patients with mutations in the GPIIIa gene that cause diminished synthesis of GPIIIa are deficient in both GPIIb/IIIa and VnR, whereas patients with mutations in the GPIIb gene are deficient in GPIIb/IIIa, yet express normal or increased VnR in their platelets. The presence or absence of VnR in platelet membranes of GT patients has therefore been used for distinguishing between mutations in the GPIIb gene and mutations in the GPIIIa gene. However, the method of assessing VnR in platelets is cumbersome and use of fresh platelets is indispensible. In the present work we devised a procedure for detection of the VnR in B-lymphocytes transformed by Epstein-Bar virus (EBV). The transformed lymphocytes transcribed GPIIIa mRNA but not GPIIb mRNA and expressed VnR on their surface. Using flow cytometry analysis or immuno-precipitation and western blotting VnR was found in B-lymphocytes of GT patients bearing a well characterized mutation in the GPIIb gene. In contrast, in B-lymphocytes of GT patients bearing 2 different mutations in the GPIIIa gene no VnR was detectable. Thus, for determining which gene is mutated in a GT patient, EBV-transformed B-lymphocytes are useful and can as well be used for analyses of GPIIIa mRNA and genomic DNA. Ten ml of blood are sufficient for the procedure.     

Characterization of a novel cis-syn and trans-syn-II pyrimidine dimer glycosylase/AP lyase from a eukaryotic algal virus, Paramecium bursaria chlorella virus-1

Endonuclease V from bacteriophage T4, is a cis-syn pyrimidine dimer-specific glycosylase. Recently, the first sequence homolog of T4 endonuclease V was identified from chlorella virus Paramecium bursaria chlorella virus-1 (PBCV-1). Here we present the biochemical characterization of the chlorella virus pyrimidine dimer glycosylase, cv-PDG. Interestingly, cv-PDG is specific not only for the cis-syn cyclobutane pyrimidine dimer, but also for the trans-syn-II isomer. This is the first trans-syn-II-specific glycosylase identified to date. Kinetic analysis demonstrates that DNAs containing both types of pyrimidine dimers are cleaved by the enzyme with similar catalytic efficiencies. Cleavage analysis and covalent trapping experiments demonstrate that the enzyme mechanism is consistent with the model proposed for glycosylase/AP lyase enzymes in which the glycosylase action is mediated via an imino intermediate between the C1' of the sugar and an amino group in the enzyme, followed by a beta-elimination reaction resulting in cleavage of the phosphodiester bond. cv-PDG exhibits processive cleavage kinetics which are diminished at salt concentrations greater than those determined for T4 endonuclease V, indicating a possibly stronger electrostatic attraction between enzyme and DNA. The identification of this new enzyme with broader pyrimidine dimer specificity raises the intriguing possibility that there may be other T4 endonuclease V-like enzymes with specificity toward other DNA photoproducts.     

Chlorinated hydrocarbon contaminants in polar bears from eastern Russia, North America, Greenland, and Svalbard: biomonitoring of Arctic pollution

Adipose tissue samples from polar bears (Ursus maritimus) were obtained by necropsy or biopsy between the spring of 1989 to the spring of 1993 from Wrangel Island in Russia, most of the range of the bear in North America, eastern Greenland, and Svalbard. Samples were divided into 16 regions corresponding as much as possible to known stocks or management zones. Concentrations of dieldrin (DIEL), 4,4'-DDE (DDE), sum of 16 polychlorinated biphenyl congeners (sigma PCB), and sum of 11 chlordane-related compounds and metabolites (sigma CHL) were determined. In order to minimize the effect of age, only data for adults (320 bears age 5 years and older) was used to compare concentrations among regions. Concentrations of sigma PCB were 46% higher in adult males than females, and there was no significant trend with age. Concentrations of sigma CHL were 30% lower in adult males than females. Concentrations of sigma PCB, sigma CHL, and DDE in individual adult female bears were standardized to adult males using factors derived from the least-square means of each sex category, and geometric means of the standardized concentrations on a lipid weight basis were compared among regions. Median geometric mean standardized concentrations (lipid weight basis) and ranges among regions were as follows: sigma PCB, 5,942 (2,763-24,316) micrograms/kg; sigma CHL, 1,952 (727-4,632) micrograms/kg; DDE, 219 (52-560) micrograms/kg; DIEL, 157 (31-335) micrograms/kg. Geometric mean sigma PCB concentrations in bears from Svalbard, East Greenland, and the Arctic Ocean near Prince Patrick Island in Canada were similar (20,256-24,316 micrograms/kg) and significantly higher than most other areas. Atmospheric, oceanic, and ice transport, as well as ecological factors may contribute to these high concentrations of sigma PCB. sigma CHL was more uniformly distributed among regions than the other CHCs. Highest sigma CHL concentrations were found in southeastern Hudson Bay, which also had the highest DDE and DIEL concentrations. In general, concentrations of sigma CHL, DDE, and DIEL were higher in eastern than western regions, suggesting an influence of North American sources. Average sigma PCB concentrations in bears from the Canadian Arctic were similar to those in 1982-84, while average sigma CHL and DDE concentrations were 35-44% lower and DIEL was 90% lower. However, the significance of these temporal trends during the 1980s is not conclusive because of the problems of comparability of data.