Plasma lipid abnormalities in the miniature poodle with progressive rod-cone degeneration.

The miniature poodle with progressive rod-cone degeneration (prcd) is a model for human retinitis pigmentosa (RP). Since previous studies from several laboratories have shown abnormalities in plasma lipids in human RP, we examined the plasma lipids of prcd-affected animals. Fasting blood was drawn on three separate occasions from affected and control miniature poodles and on one occasion from normal Irish setters and those affected with a different inherited retinal degeneration (rod-cone dysplasia). Plasma phospholipids from prcd-affected animals had significantly lower levels of docosahexaenoic acid (22:6 omega 3) and cholesterol, compared to control miniature poodles. No differences were observed in plasma levels of phospholipids, vitamin E, or vitamin A, and no lipid differences were found between control and affected Irish setters. The ratios of 22:5 omega 3 to 22:6 omega 3 and of 22:4 omega 6 to 22:5 omega 6 were significantly elevated in prcd-affected poodles compared to controls. Since the conversion of 22:5 omega 3 to 22:6 omega 3 and of 22:4 omega 6 to 22:5 omega 6 is catalysed by a delta 4-desaturase, these results are consistent with a defect in desaturase activity in the prcd-affected poodle.     

Omental transposition for low pelvic anastomoses.

Surgeons' opinions differ regarding the role of the omentum in low pelvic intestinal anastomoses. This study was undertaken to define the anatomy and surgical technique of omental transposition to the pelvis. We studied 45 cadavers to elucidate surgical aspects of omental mobilization, lengthening, and transposition into the pelvic cavity. In addition, intraoperative studies of omental transposition to the pelvis were performed in 20 patients with chronic ulcerative colitis, familial adenomatous polyposis, and rectal cancer who were undergoing ileal J-pouch anal anastomosis or low anterior resection. The most important anatomic variables for omental transposition are three variants of arterial blood supply: (1) In 56% of patients, there is one right, one (or two) middle, and one left omental artery. (2) In 26% of patients, the middle omental artery is absent. (3) In the remaining 18% of patients, the gastroepiploic artery is continued as a left omental artery but with various smaller connections to the right or middle omental artery. The first stage of omental lengthening is detachment of the omentum from the transverse colon mesentery. This must be performed carefully, as the omentum is closely adherent to the right transverse mesocolon. The second stage is the actual lengthening of the omentum. The third stage is placement of the omental flap into the pelvis. Creation of an omental pedicle is a simple surgical procedure. This procedure can be performed quickly, does not involve significant blood loss, and may reduce the frequency of complications after low pelvic anastomoses.     

Breed relationships facilitate fine-mapping studies: a 7.8-kb deletion cosegregates with Collie eye anomaly across multiple dog breeds

The features of modern dog breeds that increase the ease of mapping common diseases, such as reduced heterogeneity and extensive linkage disequilibrium, may also increase the difficulty associated with fine mapping and identifying causative mutations. One way to address this problem is by combining data from multiple breeds segregating the same trait after initial linkage has been determined. The multibreed approach increases the number of potentially informative recombination events and reduces the size of the critical haplotype by taking advantage of shortened linkage disequilibrium distances found across breeds. In order to identify breeds that likely share a trait inherited from the same ancestral source, we have used cluster analysis to divide 132 breeds of dog into five primary breed groups. We then use the multibreed approach to fine-map Collie eye anomaly (cea), a complex disorder of ocular development that was initially mapped to a 3.9-cM region on canine chromosome 37. Combined genotypes from affected individuals from four breeds of a single breed group significantly narrowed the candidate gene region to a 103-kb interval spanning only four genes. Sequence analysis revealed that all affected dogs share a homozygous deletion of 7.8 kb in the NHEJ1 gene. This intronic deletion spans a highly conserved binding domain to which several developmentally important proteins bind. This work both establishes that the primary cea mutation arose as a single disease allele in a common ancestor of herding breeds as well as highlights the value of comparative population analysis for refining regions of linkage.     

Extended long-term culture reveals a highly quiescent and primitive human hematopoietic progenitor population

Long-term culture-initiating cells (LTC-IC) are hematopoietic progenitors able to generate colony-forming unit-cells (CFU) after 5 to 8 weeks (35 to 60 days) of culture on bone marrow (BM) stroma and represent the most primitive progenitors currently detectable in vitro. We have recently reported that long-term cultures initiated with CD34+CD38- cells from BM or cord blood are able to continue generating CFU for at least 100 days, ie, beyond the standard LTC-IC period. In this report, single-cell cultures from cord blood and retroviral marking of cord blood and BM were used to study whether the subpopulation of CD34+CD38- cells able to generate CFU beyond 60 days ("extended long-term culture-initiating cells" or ELTC-IC) are functionally distinct from LTC-IC in terms of timing of initial clonal proliferation and generative capacity. All cord blood LTC-IC formed clones of greater than 50 cells by day 30. In contrast, cord blood ELTC- IC proliferated later in culture, 50% forming clones after day 30. Although efficient retroviral marking of LTC-IC was seen (25% to 45%), marking of ELTC-IC was inefficient (< 1%), consistent with a more quiescent progenitor population. There was a positive correlation between time of clonal proliferation and generative capacity. ELTC-IC generated threefold to fourfold more progeny than did LTC-IC (P < .002). These studies show that there is a functional hierarchy of progenitors in long-term culture which correlates with their level of quiescence. By extending the LTC-IC assay, a more primitive progenitor may be studied that may be functionally closer to the human long-term repopulation stem cell in vivo.     

The spectrum of MR detectable cortical microinfarcts: a classification study with 7-tesla postmortem MRI and histopathology

Cerebral microinfarcts (CMIs) are common neuropathologic findings in aging and dementia. We explored the spectrum of cortical CMIs that can be visualized with 7T magnetic resonance imaging (MRI). Thirty-three coronal brain slices of 11 individuals with neuropathologically confirmed dementia were subjected to a high-resolution postmortem 7T MRI protocol. First, we identified all visible small (⩽5 mm) intracortical and juxtacortical lesions on postmortem MRI. Lesions were classified as CMI or nonCMI based on histology, and their MR features were recorded. Thirty lesions were identified on the initial MRI evaluation, of which twenty-three could be matched with histology. Histopathology classified 12 lesions as CMIs, all of which were located intracortically. On the basis of their MR features, they could be classified as chronic gliotic CMIs—with or without cavitation or hemorrhagic components—and acute CMIs. Eleven MRI identified lesions were not of ischemic nature and most commonly enlarged or atypically shaped perivascular spaces. Their MRI features were similar to gliotic CMIs with or without cavitation, but these ‘CMI mimics'' were always located juxtacortically. 7T postmortem MRI distinguishes different histopathologic types of cortical CMIs, with distinctive MR characteristics. On the basis of our findings, we propose in vivo rating criteria for the detection of intracortical CMIs.     

The effect of the Fanconi anemia polypeptide, FAC, upon p53 induction and G2 checkpoint regulation

Fanconi anemia (FA) is an autosomal recessive disease marked by developmental defects, bone marrow failure, and cancer susceptibility. FA cells are hypersensitive to DNA cross-linking and alkylating agents and accumulate in the G2 phase of the cell cycle in response to these agents. FA cells also display genomic instability, suggesting a possible defect in the p53 pathway. To test the effect of heterologous expression of FAC cDNA on drug-induced cytotoxicity, G2 accumulation, and p53 induction in FA cells, we compared two isogenic FA cell lines: HSC536N (mock), a FA type C cell line sensitive to mitomycin C (MMC), and the same cell line transfected (corrected) with wild-type FAC cDNA (HSC536N [+FAC]). HSC536N (+FAC) cells showed a 30-fold increase in resistance to MMC concentration. Similarly, increases in resistance were observed following exposure to cisplatin, carboplatin, and cyclophosphamide. In addition, HSC536N (+FAC) cells showed a twofold lower G2 accumulation following MMC treatment. To analyze the possible interaction of FAC with the p53 pathway, we analyzed p53 induction in mock and corrected cell lines following exposure to MMC. HSC536N (mock) cells induced p53 at lower MMC concentrations than HSC536N (corrected). Caffeine, a known G2 checkpoint inhibitor, not only inhibited G2 accumulation seen in both cell lines but also caused the resistant HSC536N (+FAC) to become as sensitive to MMC as HSC536N (mock) cell line. We conclude that the FAC protein has a specific cytoprotective effect and may function as a cell cycle regulator of the G2 phase of the cell cycle.