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.

Heavy cosmic-ray exposure of Apollo astronauts.

A comprehensive study of the heavy-particle cosmic-ray exposure received by the individual astronauts during the nine lunar Apollo missions reveals a significant variation in the exposure as a function of shielding and the phase of the solar cycle. The data are useful in planning for future long-range missions and in estimating the expected biological damage.

Light flashes observed by astronauts on skylab 4.

Two dedicated light flash observing sessions were conducted by one of the crewmen during the Skylab 4 mission. Analyses of his observations reveal a strong correlation between flash frequency and primary cosmic-ray flux, and an even stronger correlation between flash frequency and the South Atlantic Anomaly (SAA) region of the inner belt trapped radiation. Calculations indicate that an all-proton inner belt probably cannot produce the observed SAA flash rate, and they suggest that there may exist a previously unobserved inner belt flux of multiply charged nuclei.

Light Flashes Observed by Astronauts on Apollo 11 through Apollo 17.

The crew members on the last seven Apollo flights observed light flashes that are tentatively attributed to cosmic ray nuclei (atomic number >/= 6) penetrating the head and eyes of the observers. Analyses of the event rates for all missions has revealed an anomalously low rate for transearth coast observations with respect to translunar coast observations.

Experimental precipitation of apatite pseudofossils resembling fossil embryos.

Certain phosphatic grains preserved in the rock record are interpreted as microfossils representing a diversity of microorganisms from bacteria to fossil embryos. In addition to bona fide primary biological features, phosphatic microfossils and fossil embryos commonly exhibit features that result from abiotic precipitation or diagenetic alteration. Distinguishing between abiotic and primary biological features can be difficult, and some features thought to represent biological tissue could instead be artifacts that are unrelated to the original morphology of a preserved organism. Here, we present experimentally generated, abiotically produced mineral precipitates that morphologically resemble biologically produced features, some of which may be observed in the rock record or noted in extant organisms, including embryos. These findings extend the diversity of biomorphic features known to result from abiotic precipitation.

Abrupt burial imparts persistent changes to the bacterial diversity of turbidite-associated sediment profiles.

The emplacement of subaqueous gravity-driven sediment flows imposes a significant physical and geochemical impact on underlying sediment and microbial communities. Although previous studies have established lasting mineralogical and biological signatures of turbidite deposition, the response of bacteria and archaea within and beneath debris flows remains poorly constrained. Both bacterial cells associated with the underlying sediment and those attached to allochthonous material must respond to substantially altered environmental conditions and selective pressures. As a consequence, turbidites and underlying sediments provide an exceptional opportunity to examine (i) the microbial community response to rapid sedimentation and (ii) the preservation and identification of displaced micro-organisms. We collected Illumina MiSeq sequence libraries across turbidite boundaries at ~26 cm sediment depth in La Jolla Canyon off the coast of California, and at ~50 cm depth in meromictic Twin Lake, Hennepin County, MN. 16S rRNA gene signatures of relict and active bacterial populations exhibit persistent differences attributable to turbidite deposition. In particular, both the marine and lacustrine turbidite boundaries are sharply demarcated by the abundance and diversity of Chloroflexi, suggesting a characteristic sensitivity to sediment disturbance history or to differences in organic substrates across turbidite profiles. Variations in the abundance of putative dissimilatory sulfate-reducing Deltaproteobacteria across the buried La Jolla Canyon sediment-water interface reflect turbidite-induced changes to the geochemical environment. Species-level distinctions within the Deltaproteobacteria clearly conform to the sedimentological boundary, suggesting a continuing impact of genetic inheritance distinguishable from broader trends attributable to selective pressure. Abrupt, <1-cm scale changes in bacterial diversity across the Twin Lake turbidite contact are consistent with previous studies showing that relict DNA signatures attributable to sediment transport may be more easily preserved in low-energy, anoxic environments. This work raises the possibility that deep subsurface microbial communities may inherit variations in microbial diversity from sediment flow and deformation events.

Challenges and opportunities in evaluating a digital sexual health intervention in a clinic setting: Staff and patient views.

OBJECTIVES: The aim of the study was to gather the views of sexual health clinic staff and male clinic users regarding digital sexual health promotion and online trial procedures. METHODS: The Men's Safer Sex website was offered on tablet computers to men in the waiting rooms of three sexual health clinics, in a feasibility online randomised controlled trial (RCT). Interviews were conducted with 11 men who had participated in the trial and with nine clinic staff, to explore their views of the website and views of the online trial. Interviews were audio-recorded and transcribed, and we conducted a thematic analysis of interviews and of 281 free text comments from the online RCT outcome questionnaires. RESULTS: Clinic users and staff felt that digital interventions such as the Men's Safer Sex website are useful, especially if NHS endorsed. Pre-appointment waiting time presents a good opportunity for intervention but clinic users and staff felt that a website should supplement rather than replace face-to-face healthcare. The RCT procedures fitted well around clinical activities, but men did not self-direct to the tablet computers. Staff were more concerned about consent and confidentiality than clinic users, and staff and patients were frustrated by multiple technical problems. The trial outcome questionnaire was thought-provoking and could constitute an intervention in itself. Participants felt that clinics would need to promote a digital intervention and/or offer the site routinely to promote engagement. CONCLUSION: Digital interventions could usefully supplement in-person sexual health care, but there are important obstacles in terms of IT access in NHS settings, and in promoting engagement.

Increasing condom use in heterosexual men: development of a theory-based interactive digital intervention.

Increasing condom use to prevent sexually transmitted infections is a key public health goal. Interventions are more likely to be effective if they are theory- and evidence-based. The Behaviour Change Wheel (BCW) provides a framework for intervention development. To provide an example of how the BCW was used to develop an intervention to increase condom use in heterosexual men (the MenSS website), the steps of the BCW intervention development process were followed, incorporating evidence from the research literature and views of experts and the target population. Capability (e.g. knowledge) and motivation (e.g. beliefs about pleasure) were identified as important targets of the intervention. We devised ways to address each intervention target, including selecting interactive features and behaviour change techniques. The BCW provides a useful framework for integrating sources of evidence to inform intervention content and deciding which influences on behaviour to target.

Barite encrustation of benthic sulfur-oxidizing bacteria at a marine cold seep.

Crusts and chimneys composed of authigenic barite are found at methane seeps and hydrothermal vents that expel fluids rich in barium. Microbial processes have not previously been associated with barite precipitation in marine cold seep settings. Here, we report on the precipitation of barite on filaments of sulfide-oxidizing bacteria at a brine seep in the Gulf of Mexico. Barite-mineralized bacterial filaments in the interiors of authigenic barite crusts resemble filamentous sulfide-oxidizing bacteria of the genus Beggiatoa. Clone library and iTag amplicon sequencing of the 16S rRNA gene show that the barite crusts that host these filaments also preserve DNA of Candidatus Maribeggiatoa, as well as sulfate-reducing bacteria. Isotopic analyses show that the sulfur and oxygen isotope compositions of barite have lower δ(34)S and δ(18)O values than many other marine barite crusts, which is consistent with barite precipitation in an environment in which sulfide oxidation was occurring. Laboratory experiments employing isolates of sulfide-oxidizing bacteria from Gulf of Mexico seep sediments showed that under low sulfate conditions, such as those encountered in brine fluids, sulfate generated by sulfide-oxidizing bacteria fosters rapid barite precipitation localized on cell biomass, leading to the encrustation of bacteria in a manner reminiscent of our observations of barite-mineralized Beggiatoa in the Gulf of Mexico. The precipitation of barite directly on filaments of sulfide-oxidizing bacteria, and not on other benthic substrates, suggests that sulfide oxidation plays a role in barite formation at certain marine brine seeps where sulfide is oxidized to sulfate in contact with barium-rich fluids, either prior to, or during, the mixing of those fluids with sulfate-containing seawater in the vicinity of the sediment/water interface. As with many other geochemical interfaces that foster mineral precipitation, both biological and abiological processes likely contribute to the precipitation of barite at marine brine seeps such as the one studied here.

Lesbians and cervical screening.

Confusion exists in clinical practice about whether lesbians should be offered routine cervical smears. We found cervical smear abnormalities in a sample of 624 lesbians, including those who had never been sexually active with men. These findings suggest that lesbians should be routinely offered cervical cytology as part of the national screening programme. Evidence of human papilloma virus (HPV) infection in the 'exclusively lesbian' group indicates that sexual transmission of HPV may occur between women. The belief by some lesbians that they have less need for cervical smears, coupled with poor uptake of cervical screening by a significant proportion, demonstrates a need for education of lesbians and health service providers.

An examination of the occurrence of surgical wound infection following equine orthopaedic surgery (1981-1990).

Post operative surgical wound infection rates were determined 452 cases of equine orthopaedic surgery performed at the Western College of Veterinary Medicine, Saskatoon, Saskatchewan, between January 1, 1981 and December 31, 1990. Only surgical procedures classified as clean or clean-contaminated by the National Research Council were included in this study. The overall post operative infection rate was 10.0% (45 of 452). Clean surgeries (n = 433) had an 8.1% infection rate while clean-contaminated surgeries (n = 19) had a 52.6% infection rate. Information collected from the medical records was used in univariate and multivariate logistic regression models to evaluate significant determinates of post operative infection. Significant determinates of post operative infection were: surgical classification, orthopaedic involvement, duration of surgery, administration of preoperative antibiotics and gender. Clean-contaminated surgeries had an increased risk of infection compared to clean surgeries (odds ratio (OR) = 24.3), procedures involving long bones had an increased risk of infection compared to procedures involving articular surfaces (OR = 5.1), surgeries lasting 90 minutes or longer had an increased risk of infection compared to those less than 90 minutes (OR = 3.6), administration of preoperative antibiotics was associated with an increased risk of infection (OR = 4.6) and female patients were 2.6 times more likely to develop post operative infection than male patients.

Age-related changes to the molecular and cellular components of equine flexor tendons.

Specific tendons show a high incidence of partial central core rupture which is preceded by degeneration. In the performance horse, the superficial digital flexor tendon (SDFT) is most often affected. We have described previously the molecular changes that are associated with degeneration in the central core region of the equine SDFT. The pathophysiological mechanism leading to change in synthetic activity of central zone cells in degenerated tendons is not known. In this study, we test the hypothesis that ageing results in matrix composition changes within the central zone of the SDFT. Extracellular matrix composition and cellularity were analysed in equine SDFTs collected from Thoroughbred horses and compared with a flexor tendon which rarely shows degenerative change and subsequent injury (deep digital flexor tendon, DDFT). Data were examined for age-related changes to central and peripheral zone tissue of the SDFT and DDFT. Ageing in both tendons (SDFT and DDFT) resulted in a significant increase in collagen-linked fluorescence and a decrease in cellularity in the DDFT but not the SDFT. The central zone tissue from the SDFT had a significantly higher proportion of type III collagen than the peripheral zone of the tendon. The highest level of type III collagen was found in the central zone tissue of the SDFT from the older group of horses and this may represent the early stages of a degenerative change. Collagen content did not differ between the 2 flexor tendons; however, there were differences in collagen type and organisation. The SDFT had a higher type III collagen content, higher levels of the mature trifunctional collagen crosslink hydroxylysylpyridinoline, lower total chondroitin sulphate equivalent glycosaminoglycan content, smaller diameter collagen fibrils and a higher cellularity than the DDFT. In conclusion, differences in macromolecular composition exist between the flexor tendons and ageing contributes to a tendon specific change in composition.

Tropical pasture hay utilization with slaframine and cottonseed meal: ruminal characteristics and digesta passage in wethers.

Sixteen mature, ruminally cannulated wethers (average BW = 41 +/- 1 kg) were fed a low-quality hay diet with or without a cottonseed meal (CSM) supplement and the parasympathomimetic agonist slaframine (SF). Treatments were basal diet (Mitchell grass hay, 4.8% CP, 46.8% ADF) available on an ad libitum basis, basal diet plus SF (8 micrograms/kg BW, 2 x daily i.m. injection), basal diet plus CSM (41.0% CP; 100 g/d), or basal diet plus SF and CSM. Treatments were arranged as a 2 x 2 factorial within a replicated 4 x 4 Latin square with 20-d periods followed by a 10-d adjustment during which only the basal diet was fed. All measurements were performed within the final 10 d of each period. Slaframine increased salivary flow by 10 to 35% (P < .07), ruminal fluid dilution rate by 8 to 11% (P < .10), and pH by 3 to 4% (P < .001). A twofold increase (P < .05) in ruminal cellulolytic bacteria numbers occurred in SF-treated wethers. Despite these SF-induced changes in the ruminal environment, whole-tract apparent nutrient digestibility, N and mineral balance, and ruminal VFA concentrations were not changed. Cottonseed meal increased forage intake by 34 to 54% (P < .001) and DM digestibility by 30% (P < .001). Cottonseed meal supplementation of a Mitchell grass hay diet improved nutritional status and attenuated live weight loss.

A comparison of systolic blood pressure measurement obtained using a pulse oximeter, and direct systolic pressure measurement in anesthetized sows.

Systolic blood pressure measurement obtained with a pulse oximeter has been compared to values obtained by other indirect methods in man. Direct pressure measurement is subject to less error than indirect techniques. This study was designed to compare systolic pressure values obtained using a pulse oximeter, with values obtained by direct arterial pressure measurement. The pulse oximeter waveform was used as an indication of perfusion. A blood pressure cuff was applied proximal to the pulse oximeter probe. The cuff was inflated until the oximeter waveform disappeared, this value was recorded as the systolic pressure at the disappearance of the waveform (SPD). The cuff was inflated to a pressure > 200 mmHg, then gradually deflated until the waveform reappeared, this value was recorded as the systolic pressure at reappearance of the waveform (SPR). The average of the two values, SPD and SPR, was calculated and recorded as SPA. The study was performed in sows (n = 21) undergoing cesarean section under epidural anesthesia and IV sedation. A total of 280 measurements were made of SPD, SPR and SPA. Regression analysis of SPA and direct measurement revealed a correlation coefficient (r) of 0.81. Calculation of mean difference (bias) and standard deviation of the bias (precision) for direct pressure--SPA revealed a value of 1.3 +/- 12.1. When compared with direct measurement, the correlation of this technique was similar to that recorded for other indirect techniques used in small animals. This indicates that this technique would be useful for following systolic pressure trends.(ABSTRACT TRUNCATED AT 250 WORDS)

An evaluation of chemical arthrodesis of the proximal interphalangeal joint in the horse by using monoiodoacetate.

The use of monoiodoacetate (MIA) for arthrodesis of the proximal interphalangeal joint (PIJ) and the effect of exercise on the degree of fusion were investigated. Eight horses received 3 injections (Weeks 0, 3, 6) of MIA (2 mL; 60 mg/mL) into the right or left front PIJ. Peri-operatively, the horses received phenylbutazone, butorphanol, and abaxial sesamoidean nerve blocks to relieve pain. During the study, the horses were monitored for general health, lameness, and swelling around the injection area. Radiographs were taken biweekly to evaluate bony fusion. Horses were randomly divided into non-exercised and exercised groups. Exercise consisted of 20 minutes of trotting on a treadmill (4 m/s), 3 days per week for 13 weeks. The horses were euthanized at 24 weeks. Slab sections of the PIJ were evaluated grossly and radiographically for bony fusion. Histologic examinations were performed to evaluate articular cartilage. Three horses were excluded from the study after developing soft tissue necrosis around the injection site, septic arthritis, and necrotic tendinitis. The remaining horses remained healthy, developed a grade 1 to 4 lameness with minimal to severe swelling in the PIJ region. All 5 horses showed radiographic evidence of bony fusion, however, no fusion was present when injected joints were examined on postmortem examination. Histologic examination revealed thinning of the cartilage, diffuse necrosis of chondrocytes, with the calcified zone intact. Subjectively, exercise did not influence the degree of cartilage destruction. Based on this study, chemical arthrodesis cannot be advocated in clinical cases because of the high complication rate and lack of bony fusion.

Bovine peritoneum: fibrinolytic activity and adhesion formation.

The fibrinolytic activity of peritoneum was evaluated in 4-month-old calves before and after peritoneal trauma. In each calf, a peritoneal resection, abrasion, sutured incision, and nonsutured incision were performed. These 4 trauma sites were evaluated for fibrinolytic activity and adhesion formation at 1 of 6 posttrauma intervals (1, 2, 3, 5, 8, or 14 days). Peritoneal plasminogen activator and fibrinolytic inhibitor activities from pre- and posttrauma samples were evaluated, using a fibrin-slide incubation technique. Calf peritoneal specimens consistently had fibrinolytic inhibitor activity, but did not have plasminogen activator activity. Significant differences were not found between fibrinolytic activity before or after trauma and a significant correlation was not found between fibrinolytic activity and the presence of or severity of adhesions.

Comparison of media and sera used for in vitro culture of equine superficial digital flexor tendon explants.

OBJECTIVE: To compare the effects of different commercial nutrient media and sera on protein synthesis and maintenance of cellular density in cultures of the equine superficial digital flexor tendon (SDFT). ANIMALS: 8 healthy 2- to 4-year-old horses. PROCEDURE: First Dulbecco's modified Eagle's medium, Ham's F12 nutrient mixture, RPMI 1640 medium, minimum essential medium with Earle's salts, minimum essential medium with Hanks' salts, and a Dulbecco's modified Eagle's medium/Ham's F12 nutrient mixture with 10% fetal bovine serum (FBS) were compared. Then FBS, fetal equine serum, and donor horse serum, each at 5, 10, and 15% in RPMI 1640 medium, were compared. Explants were cultured in roller bottles at 37 C and aerated (50% O2/45% N2/5% CO2) daily. Rates of [3H]-proline incorporation were used as a measure of the rates of total protein and collagen synthesis on days 13 and 28. Matrix cellular density of explants at days 14 and 28 was measured by computerized image analysis. RESULTS: Equine SDFT explants were cultured in all media for up to 4 weeks. Proline incorporation was greatest in Ham's F12 nutrient mixture and in RPMI 1640 medium, with the concentration of proline in medium correlating to the in vitro response. Total proline incorporation was greater in 15% FBS than in 5 or 10% FBS. Other differences among sera were not detected. Matrix cell density in 15% donor horse serum was equivalent to that in uncultured controls and higher than that in most other sera at week 2. CONCLUSION: The in vitro SDFT culture system described may be used in future studies to enhance knowledge of the biological and biochemical characteristics of intrinsic tendon healing.

Effect of feed rate and drill speed on temperatures in equine cortical bone.

OBJECTIVE: To examine the amount of heat generated in equine cortical bone by a 6.2-mm drill, using low- and high-speed and controlled feed rate drilling. SAMPLE POPULATION: 10 metacarpal bones harvested from five 2-year-old draft-type horses. PROCEDURE: Drilling on metacarpal bones was done using a machine shop mill with which the feed rate and drill speed could be precisely controlled. Bones were drilled, using 6 combinations of feed rate (1, 2, and 3 mm advance/s) and drill speed (317 and 1,242 revolutions/min [rpm], with maximal temperatures recorded by thermocouples placed 1, 1.5, and 2 mm from the drill. Maximal temperatures were evaluated for the effect of feed rate, drill speed, cortical thickness, and distance from the drill, using linear regression analysis. RESULTS: Increasing feed rate from 1 to 2 and from 2 to 3 mm/s significantly decreased mean maximal temperature. Increasing drill speed from 317 to 1242 rpm significantly increased mean maximal temperature. Increasing cortical thickness significantly increased mean maximal temperature, and increasing the distance from the drill hole significantly decreased mean maximal temperatures. CONCLUSIONS: On the basis of our results, we recommend using low drill speeds while applying sufficient axial force to advance the drill as rapidly as possible through the bone. CLINICAL RELEVANCE: Results of using this in vitro model suggest that temperatures at the drill-bone interface may be sufficiently high to result in significant thermal necrosis when drilling equine cortical bone.

Management of limb fractures in wapiti (Cervus elaphus): 22 cases (1993-1997).

OBJECTIVE: To determine treatment and outcome of a series of wapiti (elk) with fractures of the limbs. DESIGN: Retrospective study. ANIMALS: 22 wapiti. PROCEDURE: Medical records were reviewed to determine affected limb and bone, fracture configuration, method of treatment, outcome, and complications. RESULTS: 2 animals had fractures of the humerus; 8 had fractures of the radius, ulna, or both; 5 had fractures of the third metacarpal bone; 3 had fractures of the tibia; 2 had fractures of the femur; and 2 had fractures of the tarsal bones. Most fractures (n = 11) were closed, displaced, nonarticular fractures; 6 fractures were open. Four animals died or were euthanatized prior to fracture treatment, 2 were not treated because fractures had already healed, and 14 underwent fracture repair. In the remaining 2 animals, the affected limb was amputated. Five animals developed nonfatal complications (wound dehiscence, osteomyelitis [2 animals], delayed union, and malunion) and 2 developed fatal complications (gastrocnemius rupture and femoral fracture during recovery). Overall, 16 animals were discharged from the hospital, and all were doing well at follow-up, 2 months to 4 years after discharge. CLINICAL IMPLICATIONS: In wapiti, limb fractures can be successfully treated by means of internal or external fixation. The high rate of fracture healing, even among wapiti with open fractures, should encourage veterinarians to repair limb fractures in wapiti.

Periorbital skull fractures in five horses.

Periorbital skull fractures were diagnosed in 5 horses, and were associated with ophthalmic complications including corneal ulceration, uveitis, and entrapment of the eye by retrobulbar bone fragments. Physical examination was of greater diagnostic use than radiography. Surgical repair was performed on all horses and was associated with a more favorable postoperative appearance in horses treated acutely; however, the cosmetic results were considered acceptable in all horses. Major postoperative complications were not observed.