Planktonic marine iron oxidizers drive iron mineralization under low-oxygen conditions

Observations of modern microbes have led to several hypotheses on how microbes precipitated the extensive iron formations in the geologic record, but we have yet to resolve the exact microbial contributions. An initial hypothesis was that cyanobacteria produced oxygen which oxidized iron abiotically; however, in modern environments such as microbial mats, where Fe(II) and O2 coexist, we commonly find microaerophilic chemolithotrophic iron-oxidizing bacteria producing Fe(III) oxyhydroxides. This suggests that such iron oxidizers could have inhabited niches in ancient coastal oceans where Fe(II) and O2 coexisted, and therefore contributed to banded iron formations (BIFs) and other ferruginous deposits. However, there is currently little evidence for planktonic marine iron oxidizers in modern analogs. Here, we demonstrate successful cultivation of planktonic microaerophilic iron-oxidizing Zetaproteobacteria from the Chesapeake Bay during seasonal stratification. Iron oxidizers were associated with low oxygen concentrations and active iron redox cycling in the oxic-anoxic transition zone (<3 μm O2 , <0.2 μm H2 S). While cyanobacteria were also detected in this transition zone, oxygen concentrations were too low to support significant rates of abiotic iron oxidation. Cyanobacteria may be providing oxygen for microaerophilic iron oxidation through a symbiotic relationship; at high Fe(II) levels, cyanobacteria would gain protection against Fe(II) toxicity. A Zetaproteobacteria isolate from this site oxidized iron at rates sufficient to account for deposition of geologic iron formations. In sum, our results suggest that once oxygenic photosynthesis evolved, microaerophilic chemolithotrophic iron oxidizers were likely important drivers of iron mineralization in ancient oceans.

Cognitive status is a determinant of health resource utilization among individuals with a history of falls: a 12-month prospective cohort study

SUMMARY

Falls are a costly public health problem worldwide. The literature is devoid of prospective data that identifies factors among fallers that significantly drive health care resource utilization. We found that cognitive function--specifically, executive functions--and cognitive status are significant determinants of health resource utilization among older fallers.

INTRODUCTION

Although falls are costly, there are no prospective data examining factors among fallers that drive health care resource utilization. We identified key determinants of health resource utilization (HRU) at 6 and 12 months among older adults with a history of falls. Specifically, with the increasing recognition that cognitive impairment is associated with increased falls risk, we investigated cognition as a potential driver of health resource utilization.

METHODS

This 12-month prospective cohort study at the Vancouver Falls Prevention Clinic (n = 319) included participants with a history of at least one fall in the previous 12 months. Based on their cognitive status, participants were divided into two groups: (1) no mild cognitive impairment (MCI) and (2) MCI. We constructed two linear regression models with HRU at 6 and 12 months as the dependent variables for each model, respectively. Predictors relating to mobility, global cognition, executive functions, and cognitive status (MCI versus no MCI) were examined. Age, sex, comorbidities, depression status, and activities of daily living were included regardless of statistical significance.

RESULTS

Global cognition, comorbidities, working memory, and cognitive status (MCI versus no MCI ascertained using the Montreal Cognitive Assessment (MoCA)) were significant determinants of total HRU at 6 months. The number of medical comorbidities and global cognition were significant determinants of total HRU at 12 months.

CONCLUSION

MCI status was a determinant of HRU at 6 months among older adults with a history of falls. As such, efforts to minimize health care resource use related to falls, it is important to tailor future interventions to be effective for people with MCI who fall.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01022866.

Aortic dissection in giant-cell arteritis

Twenty-three cases of aortic dissection in patients with giant-cell arteritis are reviewed and an additional case is reported. Forty-six percent presented catastrophically with aortic dissection and no prior history of giant cell arteritis. Eighty percent died within 2 weeks of the event; four patients had successful surgical grafts. There was diffuse involvement of the aorta with giant cells in 89%, but dissecting tears occurred primarily in the proximal aorta in 85% of cases. The majority of cases with a preceding history of giant cell arteritis were on low doses of steroid or on no treatment at the time of dissection, and the median erythrocyte sedimentation rate of these patients was 62 mm/h (range 21-98). Evidence of some form of hypertension, whether acute or chronic, mild or severe, was found in 77% of patients. Inadequate treatment of giant-cell arteritis and underlying hypertension (treated or untreated) are potential factors leading to aortic dissection in these patients.

Hypoplasia and immaturity of the terminal lung unit (acinus) in congenital diaphragmatic hernia

We assessed the maturity of the lungs and the radial count in 10 infants with congenital diaphragmatic hernia who died in the immediate perinatal period. The lungs were all immature, with a histologic appearance of less than stated gestational age. The ipsilateral lungs were less mature in appearance than were the contralateral ones. The radial count, an assessment of acinar complexity, was reduced in all cases, and once again the ipsilateral lung was more affected. We present evidence that, in 4 of 6 lungs, volumes were more reduced than predicted from the radial count, and this may be due to loss of (airway) units. We have discussed the controversy about the appearance of the acinus in diaphragmatic hernia and present reasons to explain this. Hyaline membrane disease often occurs in diaphragmatic hernia, even at full term. Intra-alveolar hemorrhage is a common complication of diaphragmatic hernia.

Small bowel malignant lymphoma complicating celiac sprue and the mesenteric lymph node cavitation syndrome

Malignant small intestinal lymphoma may complicate or antedate clinical recognition of celiac sprue. However, histologic diagnosis of lymphoma is made especially difficult in the presence of small bowel ulceration. A 70-yr-old man with celiac sprue and a history of dermatitis herpetiformis was initially seen for recurrent diarrhea; panmalabsorption with steatorrhea and protein-losing enteropathy were documented. Subsequent studies showed ectopic gastric mucosa in the small bowel, hyposplenism with mesenteric lymph node cavitation, and small bowel erosions and ulceration. Despite strong clinical suspicion for more than 2 yr, only 1 of 88 small bowel biopsy specimens was positive for lymphoma. At autopsy, shortly after histologic diagnosis of lymphoma, extensive small bowel involvement and infiltration were observed. This is the first report of lymphoma complicating the recently described nonneoplastic lymphoreticular syndrome associated with celiac sprue characterized by splenic atrophy and mesenteric lymph node cavitation.

Multifocal small bowel lymphoma and latent celiac sprue

Malignant small intestinal lymphoma may complicate or antedate clinical recognition of celiac sprue, a disorder becoming increasingly diagnosed as a subclinical or occult disease. A 73-yr-old woman with previously resected jejunoileal lymphoma and normal proximal small bowel biopsy specimens was given a high-gluten diet containing 40 g of added gluten daily for 4 wk. This caused small intestinal biopsy abnormalities typical of celiac sprue; the abnormalities resolved 6 wk later with a gluten-free diet. This indicates that latent celiac sprue may be present in some patients with lymphoma and suggests that the association of celiac sprue and lymphoma may be more frequent than is currently appreciated.

Subacute splenic abscess. Appearance on indium-111 leukocyte, gallium-67, and technetium-99m sulfur colloid imaging

A case of a 23-year-old man with an encapsulated, anaerobic splenic abscess is reported. Both the In-111 leukocyte and Tc-99m sulfur colloid scans demonstrated an intrasplenic defect. The Ga-67 citrate scan revealed uptake in the rim of the abscess only where the abscess cavity was relatively photon-deficient. The combined Tc-99m sulfur colloid/In-111 leukocyte/Ga-67 scan appearance of a subacute splenic abscess has not been described previously. In cases suspected to be splenic abscesses the combined In-111 leukocyte/Tc-99m sulfur colloid imaging is the most useful.