Identification of single nucleotide polymorphisms in human DNA repair genes

Variation in gene coding sequence represents a significant factor in predisposition to disease, including cancer. Variants of some DNA repair genes (e.g. MLH1, MSH2 and MSH6) are known to predispose to cancer. We identified single nucleotide polymorphisms (SNPs) in five DNA repair genes in 142 healthy individuals using a DNA sequencing protocol optimized for the direct detection of single nucleotide polymorphisms. This approach, called the heterozygote sequencing protocol (HSP), enables moderate-scale population surveys of SNPs. HSP uses fluorescently tagged primers and exploits the large dynamic range and low background of automated fluorescent sequencing. HSP may be used for any sequence that can be amplified by PCR. A total of 12 SNP variants in MGMT, ERCC1, CDK7, CCNH and XRCC4 were identified, 11 at polymorphic frequencies, with an average frequency of 0.22 (95% confidence interval 0.20-0.24). Among the 82 individuals for whom complete SNP profiles were available, no one person carried the GenBank reference sequence for all five genes. The extensive heterogeneity observed in these five genes is intriguing. All variants are in Hardy-Weinberg equilibrium, although the meaning of this equilibrium is unclear. Using this approach, possible associations of sequence variation, and hence of variation in DNA repair, with disease risk can be assessed.     

Cytopathic effects of Actinobacillus actinomycetemcomitans on monkey blood leukocytes

The suitability of cynomolgus monkeys (Macaca fascicularis) for studies concerned with the biologic properties of Actinobacillus actinomycetemcomitans is the subject of the present investigation. We found that normal monkeys harbored leukotoxic strains of A. actinomycetemcomitans in subgingival plaque samples. Monkey peripheral blood PMNs and monocytes were killed following in vitro exposure to sonic extracts of leukotoxic strains of A. actinomycetemcomitans . Monkey sera were capable of inhibiting the leukotoxic properties of A. actinomycetemcomitans sonic extracts due to the presence of IgG antibodies which neutralized the leukotoxin. Similarly, sera from patients with juvenile periodontitis (but not normal human sera) abolished leukotoxin-mediated killing of monkey PMNs. Monkey peripheral blood lymphoid cells were not killed by A. actinomycetemcomitans but demonstrated depressed responses to mitogens following pre-incubation with A. actinomycetemcomitans sonicates prepared from either leukotoxic or "non-leukotoxic" human strains. These studies suggest that cynomolgus monkeys may serve as a suitable in vitro and in vivo model for delineating more about host- A. actinomycetemcomitans interrelationships in the etiology of human periodontal disease.     

Elicitation of water ingestion in the Mongolian gerbil (Meriones unguiculatus) by intracranial injections of angiotensin II and 1-norepinephrine

Intracranial injections of Angiotensin II (AII) through permanent brain chemodes aimed for the lateral hypothalamic, lateral preoptic, or septal region evoked drinking of tap water from Mongolian gerbils in normal water balance. When lettuce was the only available free water source, AII injections elicited prolonged lettuce-eating responses. l-Norepinephrine injections did not elicit eating of food pellets but, like AII, proved to be a reliable and potent dipsogenic agent. Carbachol, a cholinergic agonist, failed to elicit any ingestive behaviors over a wide dose range. The species-typical foot-thumping behavior of the gerbil was seen during some tests with all drugs utilized. It is suggested that the dipsogenic property of AII across a wide variety of species reflects the nature of a primitive, i.e., phylogenetically old, brain mechanism shared by most mammals to deal with problems of water economy, while the organization and utilization of other central neurochemicals in thirst-related substrates may vary among species.     

A space-time cluster of adverse events associated with canine rabies vaccine

Electronic medical records of a large veterinary practice were used for surveillance of potential space-time clustering of adverse events associated with rabies vaccination in dogs. The study population was 257,564 dogs vaccinated in 169 hospitals in 13 US metropolitan areas during a 24-month period. Using a scan statistic for population rate data, significant space-time clusters were identified involving the Atlanta and Tampa/St. Petersburg areas during a 4-month period. Separate spatial-temporal analyses of these cities using coordinates for individual address coordinates identified one significant patient cluster (P=0.002), associated with a 23.26 km-radius area in Atlanta (20 adverse events in 702 dogs; 2.85%) from November 2002 through February 2003. This percentage of adverse events was significantly increased after adjustment for host-related factors and the number of concurrent vaccinations.