Evidence of oxygenic phototrophy in ancient phosphatic stromatolites from the Paleoproterozoic Vindhyan and Aravalli Supergroups, India.

Fossil microbiotas are rare in the early rock record, limiting the type of ecological information extractable from ancient microbialites. In the absence of body fossils, emphasis may instead be given to microbially derived features, such as microbialite growth patterns, microbial mat morphologies, and the presence of fossilized gas bubbles in lithified mats. The metabolic affinity of micro-organisms associated with phosphatization may reveal important clues to the nature and accretion of apatite-rich microbialites. Stromatolites from the 1.6 Ga Chitrakoot Formation (Semri Group, Vindhyan Supergroup) in central India contain abundant fossilized bubbles interspersed within fine-grained in situ-precipitated apatite mats with average δ13 Corg indicative of carbon fixation by the Calvin cycle. In addition, the mats hold a synsedimentary fossil biota characteristic of cyanobacterial and rhodophyte morphotypes. Phosphatic oncoid cone-like stromatolites from the Paleoproterozoic Aravalli Supergroup (Jhamarkotra Formation) comprise abundant mineralized bubbles enmeshed within tufted filamentous mat fabrics. Construction of these tufts is considered to be the result of filamentous bacteria gliding within microbial mats, and as fossilized bubbles within pristine mat laminae can be used as a proxy for oxygenic phototrophy, this provides a strong indication for cyanobacterial activity in the Aravalli mounds. We suggest that the activity of oxygenic phototrophs may have been significant for the formation of apatite in both Vindhyan and Aravalli stromatolites, mainly by concentrating phosphate and creating steep diurnal redox gradients within mat pore spaces, promoting apatite precipitation. The presence in the Indian stromatolites of alternating apatite-carbonate lamina may result from local variations in pH and oxygen levels caused by photosynthesis-respiration in the mats. Altogether, this study presents new insights into the ecology of ancient phosphatic stromatolites and warrants further exploration into the role of oxygen-producing biotas in the formation of Paleoproterozoic shallow-basin phosphorites.

Biogenicity of an Early Quaternary iron formation, Milos Island, Greece.

A ~2.0-million-year-old shallow-submarine sedimentary deposit on Milos Island, Greece, harbours an unmetamorphosed fossiliferous iron formation (IF) comparable to Precambrian banded iron formations (BIFs). This Milos IF holds the potential to provide clues to the origin of Precambrian BIFs, relative to biotic and abiotic processes. Here, we combine field stratigraphic observations, stable isotopes of C, S and Si, rock petrography and microfossil evidence from a ~5-m-thick outcrop to track potential biogeochemical processes that may have contributed to the formation of the BIF-type rocks and the abrupt transition to an overlying conglomerate-hosted IF (CIF). Bulk δ(13) C isotopic compositions lower than -25‰ provide evidence for biological contribution by the Calvin and reductive acetyl-CoA carbon fixation cycles to the origin of both the BIF-type and CIF strata. Low S levels of ~0.04 wt.% combined with δ(34) S estimates of up to ~18‰ point to a non-sulphidic depository. Positive δ(30) Si records of up to +0.53‰ in the finely laminated BIF-type rocks indicate chemical deposition on the seafloor during weak periods of arc magmatism. Negative δ(30) Si data are consistent with geological observations suggesting a sudden change to intense arc volcanism potentially terminated the deposition of the BIF-type layer. The typical Precambrian rhythmic rocks of alternating Fe- and Si-rich bands are associated with abundant and spatially distinct microbial fossil assemblages. Together with previously proposed anoxygenic photoferrotrophic iron cycling and low sedimentary N and C potentially connected to diagenetic denitrification, the Milos IF is a biogenic submarine volcano-sedimentary IF showing depositional conditions analogous to Archaean Algoma-type BIFs.

Deep-biosphere consortium of fungi and prokaryotes in Eocene subseafloor basalts.

The deep biosphere of the subseafloor crust is believed to contain a significant part of Earth's biomass, but because of the difficulties of directly observing the living organisms, its composition and ecology are poorly known. We report here a consortium of fossilized prokaryotic and eukaryotic micro-organisms, occupying cavities in deep-drilled vesicular basalt from the Emperor Seamounts, Pacific Ocean, 67.5 m below seafloor (mbsf). Fungal hyphae provide the framework on which prokaryote-like organisms are suspended like cobwebs and iron-oxidizing bacteria form microstromatolites (Frutexites). The spatial inter-relationships show that the organisms were living at the same time in an integrated fashion, suggesting symbiotic interdependence. The community is contemporaneous with secondary mineralizations of calcite partly filling the cavities. The fungal hyphae frequently extend into the calcite, indicating that they were able to bore into the substrate through mineral dissolution. A symbiotic relationship with chemoautotrophs, as inferred for the observed consortium, may be a pre-requisite for the eukaryotic colonization of crustal rocks. Fossils thus open a window to the extant as well as the ancient deep biosphere.

Experimental taphonomy of giant sulphur bacteria: implications for the interpretation of the embryo-like Ediacaran Doushantuo fossils.

The Ediacaran Doushantuo biota has yielded fossils interpreted as eukaryotic organisms, either animal embryos or eukaryotes basal or distantly related to Metazoa. However, the fossils have been interpreted alternatively as giant sulphur bacteria similar to the extant Thiomargarita. To test this hypothesis, living and decayed Thiomargarita were compared with Doushantuo fossils and experimental taphonomic pathways were compared with modern embryos. In the fossils, as in eukaryotic cells, subcellular structures are distributed throughout cell volume; in Thiomargarita, a central vacuole encompasses approximately 98 per cent cell volume. Key features of the fossils, including putative lipid vesicles and nuclei, complex envelope ornament, and ornate outer vesicles are incompatible with living and decay morphologies observed in Thiomargarita. Microbial taphonomy of Thiomargarita also differed from that of embryos. Embryo tissues can be consumed and replaced by bacteria, forming a replica composed of a three-dimensional biofilm, a stable fabric for potential fossilization. Vacuolated Thiomargarita cells collapse easily and do not provide an internal substrate for bacteria. The findings do not support the hypothesis that giant sulphur bacteria are an appropriate interpretative model for the embryo-like Doushantuo fossils. However, sulphur bacteria may have mediated fossil mineralization and may provide a potential bacterial analogue for other macroscopic Precambrian remains.

Double-stranded RNA increases kinin B1 receptor expression and function in human airway epithelial cells.

Increased levels of kinins have been detected within the airways during upper respiratory viral infections (URIs). Rhinovirus, the major URI associated with acute exacerbations of asthma, is an ssRNA virus that primarily infects the airway epithelium and produces dsRNA during replication. We asked whether dsRNA could increase the expression of kinin receptors in airway epithelial cells, thereby potentiating the inflammatory consequences of kinin generation. Human airway epithelial cell line BEAS-2B was stimulated with the dsRNA analog Poly I:C and kinin receptor expression detected by quantitative RT-PCR as well as radioligand binding. Poly I:C induced an increase in B1 and B2 receptor mRNA levels in BEAS-2B and primary human normal bronchial epithelial cells. At the cell surface, only B1 receptor expression was increased by Poly I:C. Furthermore, pretreatment of BEAS-2B cells with Poly I:C enhanced the induction of phospho-ERK following B1 receptor ligand stimulation. To investigate whether these finding had potential in vivo relevance, we assessed B1 receptor expression in nasal tissue obtained from 8 normal human subjects with URIs and 3 control subjects. Five of the URI subjects demonstrated increased B1 receptor mRNA compared to the 3 control subjects. We suggest that increased expression of B1 receptor in the human airway following a URI could increase the risk of an exacerbation of asthma by contributing to increased inflammation in the airway.

Prevalence of sparganosis by county of origin in Florida feral swine.

Sparganosis is a parasitic infection in amphibians, reptiles and mammals including feral swine and man. It is caused by migration of the metacestode (spargana) of Spirometra. The primary objective of this study was the determination of the prevalence of gross sparganosis in Florida county of origin in slaughtered feral swine. Tracebacks to county of origin were conducted for Florida feral swine with and without gross sparganosis. Feral swine trapped in Florida and presented for slaughter in a Texas slaughter establishment from May to December 1999 was the sample population. Overall prevalence of sparganosis in Florida feral swine was 6.9%. Because Highlands county had the same prevalence, other counties were compared to it. Sparganosis was detected in 17 Florida counties. Swine originating from Osceola or Hillsborough counties (4.3 and 1.8% prevalence, respectively) had lower prevalence of sparganosis than in Highlands, whereas those from Marion county (21.7% prevalence) had a higher prevalence. Transmission to humans may occur via consumption of infected feral swine, other species of secondary intermediate hosts or the primary intermediate hosts.

Metabolic parameters of Bion 11 monkeys.

Biochemical parameters of protein, carbohydrate, and fluid-electrolyte metabolism were measured in the blood of Bion 11 rhesus monkeys. The 14-day flight induced changes in total protein, BUN, and calcium, which were also seen in humans during long-duration space missions. It was concluded that protein and calcium metabolism changed while carbohydrate metabolism remained unaltered.

Prosthetic osteomyelitis with special reference to the knee: risks, treatment and costs.

The overall incidence of osteomyelitis following primary knee arthroplasty is 1-2%. Major risk factors are large prostheses, rheumatoid arthritis, postoperative wound-healing complications, skin infections, and prior deep infections. The major infecting organism is Staphylococcus aureus. Healing of the infection is to be expected in 20% when systemic antibiotics alone are used, in 24% when soft tissue surgery is used, in 50% when resection arthroplasty is used, in 76% when revision arthroplasty is used, in 90% when arthrodesis is used, and in 100% when amputation is used. The direct medical costs average US$ 62,100 for an infected patient and US$ 8600 for a non-infected patient. Attention should focus on prophylactic measures directed towards the soft tissue problems: by avoiding conflicting skin incisions, by gentle handling of the periarticular soft tissues, by avoiding the use of constrained prostheses and oversized compartmental prostheses, by letting wound healing take priority over motion in knees with compromised soft tissues, and by using prophylactic antibiotic treatment for skin ulcers until these have healed.

Predatorial borings in late precambrian mineralized exoskeletons.

The late Precambrian tube-forming Cloudina, the earliest known animal to produce a mineralized exoskeleton, shows evidence of having been attacked by shell-boring organisms. Of more than 500 tubes from Shaanxi Province, China, 2.7% have rounded holes 40 to 400 micrometers in diameter. The relation between the size of the holes and the width of the bored tubes suggests that the attacking organism was a predator, selecting its prey for size. If true, this would be the oldest case of predation in the fossil record and would support the hypothesis that selection pressures from predation was a significant factor in the evolution of animal skeletons around the Precambrian-Cambrian boundary.

The infected knee arthroplasty. A 6-year follow-up of 357 cases.

The incidence of deep infection after 12,118 primary knee arthroplasties performed in Sweden from October 1, 1975 through 1985 with a median follow-up of 6 years was 1.7 percent for arthrosis and 4.4 percent for rheumatoid arthritis. Risk factors for infection were large prostheses, postoperative wound-healing complications, rheumatoid arthritis, a prior deep infection, and skin infections. We have analyzed the treatment of 357 knee arthroplasties with a deep infection. Systemic antibiotics alone were primarily used in 225 knees, with healing of the infection in 44 knees, 20 of which had a functioning prosthesis at the final follow-up; the treatment did not compromise later revision surgery. Soft-tissue surgery was used in 154 knees--37 healed, 15 of which had a functioning prosthesis. Resection arthroplasty resulted in healing of the infection in 11 of 22 knees. Revision arthroplasty was performed in 107 knees, with eventual healing of the infection in 81 knees, 36 of which had a functioning prosthesis; there were no differences in the outcome of one-stage and two-stage procedures. Arthrodesis was attempted in 135 knees, with eventual healing of the infection in 120 knees and fusion in 105. Twenty-two patients were amputated. Thus, the infection healed in 315 knees (88 percent), but only 71 (20 percent) recovered with a functioning prosthesis, and 8 patients died of the infection. Attention should therefore focus on prophylactic measures directed towards the soft-tissue problems--by avoiding conflicting skin incisions, by gentle handling of the periarticular soft tissues, by avoiding the use of constrained prostheses and oversized compartmental prostheses, by letting wound healing take priority over motion in knees with compromised soft tissues, and by using prophylactic antibiotic treatment for skin ulcers until these have healed.

Acute compartment syndrome from anterior thigh muscle contusion: a report of eight cases.

Eight patients with an anterior thigh muscle contusion or rupture developed an acute anterior compartment syndrome. All patients had an increased pressure in the quadriceps muscle, ranging between 41 and 80 mm Hg. At fasciotomy, three cases had a hematoma in the rectus femoris and four in the vastus intermedius, and in one case only, edema of the anterior compartment was found. Postoperatively, there was immediate pain relief in all cases, and after about 4 weeks, all patients had normal function. We recommend broad indications for fasciotomy and evacuation of hematoma after thigh muscle contusion or rupture.

External fixation of femoral fractures: experience with 15 cases.

We report our experience with external fixation in 15 femoral fractures in 14 patients. Follow-up times ranged from 4 to 56 months. Thirteen patients had multiple injuries. All but two fractures healed. In one patient with a supracondylar fracture, a knee arthrodesis had to be performed. One septic osteomyelitis of the femur led to amputation. The range of active knee joint motion was greater than or equal to 90 degree in 13 knees. Only six knees, however, regained a flexion of greater than or equal to 120 degrees. Pin tract infection occurred in one case and resolved uneventfully after revision and systemic antibiotics. External fixation should not be routinely used for fixation of femoral fractures, but may be considered in multiply injured and critically ill patients or in case of extensive soft tissue injury.

Treatment of the exposed knee prosthesis.

Ten knees with early tissue breakdown after knee arthroplasty resulting in exposed prostheses were treated with different plastic surgical techniques. Six knees were successfully covered: four using a gastrocnemius musculocutaneous flap, one using a fasciocutaneous flap, and one using split-skin grafts. Four knees failed: two using local skin flaps and two using split-skin grafts. A gastrocnemius musculocutaneous flap seems to provide a reliable coverage of the exposed knee joint.

Hematogenous infection after knee arthroplasty.

Twenty-five hematogenously infected knee arthroplasties in 20 patients (17 with rheumatoid arthritis and 3 with arthrosis) were followed for 3 years. Staphylococcus aureus was the major infecting organism. Three patients with four arthroplasties died of sepsis. Two patients had removal of the arthroplasty, one of which resulted in an above-the-knee amputation. Four out of five arthrodeses fused. Two knees healed after early debridement and two healed without surgery. Ten knees had successful revision arthroplasty. Rheumatoid arthritis and constrained prostheses increase the risk of hematogenous infection. Any infection and especially cutaneous lesions in a patient with a knee arthroplasty should be treated vigorously.

Revision of infected knee arthroplasty.

Sixteen infected knee arthroplasties were revised and followed for 5 (1-10) years. There were nine recurrences of infections, but in one of these a second revision was successfully carried out. The remaining seven revisions resulted in only four functioning prostheses. The results were poor for hinged and stabilized prostheses for which arthrodesis, after eradication of the infection, is recommended. Infected compartmental prostheses with good bone stock could be treated with a two-stage procedure using tricompartmental revision prostheses.