Cooperative predation in the social amoebae Dictyostelium discoideum.

The eukaryotic amoeba Dictyostelium discoideum is commonly used to study sociality. The amoebae cooperate during development, exhibiting altruism, cheating, and kin-discrimination, but growth while preying on bacteria has been considered asocial. Here we show that Dictyostelium are cooperative predators. Using mutants that grow poorly on Gram-negative bacteria but grow well on Gram-positive bacteria, we show that growth depends on cell-density and on prey type. We also found synergy, by showing that pairwise mixes of different mutants grow well on live Gram-negative bacteria. Moreover, wild-type amoebae produce diffusible factors that facilitate mutant growth and some mutants exploit the wild type in mixed cultures. Finding cooperative predation in D. discoideum should facilitate studies of this fascinating phenomenon, which has not been amenable to genetic analysis before.

Can salivary activity predict periodontal breakdown in A. actinomycetemcomitans infected adolescents?

OBJECTIVE: While Aggregatibacter actinomycetemcomitans (Aa) is highly associated with localised aggressive periodontitis (LAP) many Aa-carriers do not develop LAP. This study was designed to determine whether specific salivary factors could distinguish between subjects who have Aa initially and remain healthy (H/AA) as compared to those who develop LAP (LAP/AA). DESIGN: H/AA subjects and healthy controls with no Aa (H) were enrolled in a longitudinal cohort study to investigate initiation of bone loss (LAP) over 3 years. After detection of LAP, stored saliva from 10 H, 10 H/AA, and 10 LAP/AA subjects was thawed, processed, and tested for (1) lactoferrin (Lf) concentration and iron levels; (2) agglutination of Aa; (3) killing of Gram-positive bacteria. RESULTS: LAP/AA saliva levels of Lf iron were low prior to and after bone loss (3.6+1.7ngFe/µg) (LAP/AA vs. H and H/AA p≤0.01). Saliva from H/AA subjects caused Aa to agglutinate significantly more than H or LAP/AA saliva (p≤0.01). LAP/AA saliva killed Streptococcus mutans, Streptococcus sanguis and Lactobacillus in vitro by >83%. Saliva from H individuals killed these bacteria by <3.3% (LAP/AA vs. H; p≤0.01). H/AA killing was intermediate. CONCLUSION: LAP/AA saliva showed: low levels of Lf iron, minimal Aa agglutinating activity, and high killing activity against Gram-positive bacteria. Aa-positive healthy saliva (H/AA) showed: higher levels of Lf iron, maximal Aa agglutinating activity, and moderate killing of Gram-positive bacteria. A salivary activity profile can distinguish between subjects who are Aa-positive and remain healthy from those who develop LAP.

Validity of sampling error as a cause of noncorrelation.

BACKGROUND: Sampling error is a common explanation of noncorrelation in women whose Papanicolaou (Pap) tests show high-grade intraepithelial lesions (HSIL) but whose follow-up cervical biopsies show only cervical intraepithelial neoplasia (CIN) 1, koilocytosis, or reactive/inflammatory changes. The purpose of this study was to demonstrate the validity of sampling error in this setting by determining the proportion of negative colposcopic cervical biopsies in women with HSIL who subsequently undergo cone/loop electrode excision procedure (LEEP) biopsies or repeat cervical biopsies that confirm the diagnosis of high-grade CIN (HGCIN). METHODS: In all, 368 cases of HSIL were retrieved from the computerized database from January 1, 2003 to December 31, 2005. Follow-up was obtained as part of routine quality assurance/quality control activities including cytologic-histologic correlation. RESULTS: A total of 368 HSIL Pap diagnoses were retrieved. Of the 254 cases that were followed up by cervical biopsy, 146 showed HGCIN in the biopsy. Of the remaining 108 patients whose cervical biopsies failed to demonstrate HGCIN, 47 had a subsequent procedure, either cone/LEEP, cervical biopsy, or repeat Pap test. Cone biopsy/LEEP was performed in 34 cases (72.3%) with a diagnosis of HGCIN in 19. Repeat cervical biopsy was performed in 9 cases (19.1%) with HGCIN diagnosed in 5. Repeat Pap test was performed in 4 cases (8.5%) with HSIL diagnosed in 2. CONCLUSIONS: In the population of women with HSIL by Pap test followed up by cervical biopsy with or without subsequent cone/LEEP, there was a discordant cervical biopsy rate for HGCIN of 43%. In the subgroup of women with HSIL by Pap test followed up by cervical biopsy and subsequent cone/LEEP or repeat cervical biopsy, the proportion of women with negative colposcopic cervical biopsy and subsequent histology-proven HGCIN was 56%. These figures justify sampling error as a valid cause of noncorrelation in women with HSIL followed up by cervical biopsy alone.

Long-term outcome of surgically treated Crohn's colitis: a prospective study.

PURPOSE: Although bowel-sparing techniques have been published for treatment of Crohn's disease of the small bowel because of its relentless nature, extent of resection in Crohn's colitis is still a topic of debate. This study was designed to prospectively evaluate the long-term outcomes of patients with isolated Crohn's colitis to identify patients that may benefit from initial more aggressive resection. METHODS: We identified 179 patients with Crohn's disease operated on for primary colonic disease. They were divided into segmental colectomy, total abdominal colectomy, and total proctocolectomy groups, based on their initial operation. They were further characterized by extent and location of colonic involvement. Long-term outcome variables evaluated included colonic and small-bowel surgical recurrences, postoperative complications and long-term sequelae, long-term need for medical therapy, and need for permanent fecal diversion. RESULTS: Fifty-five patients underwent segmental colectomy, 49 total abdominal colectomy, and 75 total proctocolectomy. Patients with diffuse colonic involvement were significantly less likely to undergo segmental colectomy than total abdominal colectomy (P < 0.0001) or total proctocolectomy (P < 0.0001). Patients with distal involvement or pancolitis were significantly less likely to undergo segmental colectomy than total abdominal colectomy (P < 0.0001) or total proctocolectomy (P < 0.0001). Overall there were 31 patients (24.4 percent) with surgical Crohn's recurrences during follow-up: 19 (38.8 percent) in the segmental colectomy, 8 (22.9 percent) in the total abdominal colectomy, and 4 (9.3 percent) in the total proctocolectomy group. There was a significant difference in time to recurrence between the three groups by log-rank test (P = 0.017). Segmental colectomy patients had a significantly shorter time to first recurrence than total proctocolectomy patients (P = 0.014). After adjusting for extent of disease, the segmental colectomy group had a significantly greater risk of surgical recurrence than the total proctocolectomy group (P = 0.006). Total proctocolectomy patients were significantly less likely to be still taking medications one year after the index operation than total abdominal colectomy patients (P = 0.003) and segmental colectomy patients (P = 0.0003). During follow-up, patients with isolated distal disease were significantly more likely to require a permanent stoma than patients with isolated proximal disease (P = 0.004). CONCLUSIONS: A more aggressive approach should be considered in patients with diffuse and distal Crohn's colitis. Total proctocolectomy in the properly selected patients is associated with low morbidity, lower risk of recurrence, and longer time to recurrence. Patients after total proctocolectomy are more likely to be weaned off all Crohn's-related medications. Long-term rate of permanent fecal diversion is significantly higher in patients with distal disease.