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During the past two decades, accelerator mass spectrometry (AMS) has allowed major developments in many areas of geosciences and archaeology. In the near future, AMS should realize a similar potential in the field of biomedical research, leading ultimately to clinical applications. For such applications, the required instrument differs significantly from that presently used in the field of 14C dating. Whereas the needed accuracy and sensitivity is more than an order of magnitude less demanding than that for present state-of-the-art 14C instrumentation, the widespread acceptance of 14C AMS in biomedical research will require AMS spectrometers that are small, simple to operate and capable of handling CO2 samples. In order to satisfy these demands, HVEE has developed a compact 14C AMS spectrometer dedicated to biomedical research. The instrument consists of a compact accelerator with a footprint of 2.25 × 1.25 m and an ion source that features direct CO2 acceptance and optimal user friendliness. Having previously described the layout and design of the accelerator, we here discuss progress on the accelerator and present the design and first results of the CO2 ion source.
We have developed and demonstrated a practical methodology for dating specific compounds (and octade-canoic or stearic acid—C18:0—in particular) from the lipid material surviving in archaeological cooking pots. Such compounds may be extracted from about 10 g of cooking potsherd, and, after derivatization, can be purified by gas chromatography. To obtain sufficient material for precise dating repetitive, accumulating, GC separation is necessary. Throughout the 6000-year period studied, and over a variety of site environments within England, dates on C18:0 show no apparent systematic error, but do have a greater variability than can be explained by the errors due to the separation chemistry and measurement process alone. This variability is as yet unexplained. Dates on C16:0 show greater variability and a systematic error of approximately 100-150 years too young, and it is possible that this is due to contamination from the burial environment. Further work should clarify this.
Reliable radiocarbon dating depends upon well-defined samples. We have been investigating whether or not reliable 14C dates can be obtained directly from sub-fossil insect cuticle or biochemical fractions derived from it. Initial carbon and nitrogen stable isotope measurements on sub-fossil insect chitin from species with known feeding behaviors found within a single site (St Bees, Cumbria) clustered in a manner reminiscent of trophic level effects seen in terrestrial ecosystems. Although this finding implied some chemical stability, the measurement of CN ratios from the same samples indicated compositional variability. In addition, 14C dates obtained from these same samples were different from dates obtained from plant macrofossils found at the same depth. We have experimented with protocols designed to biochemically reduce chitin to its principle carbohydrate component glucosamine with the aim of using this compound to generate reliable 14C dates. Solvent extractions of sub-fossil chitin were carried out to remove both endogenous and exogenous lipid-soluble materials. Base hydrolysis reactions designed to extract polypeptides retained surprisingly high levels of contaminating amino acids. Proteinase K enzyme treatment had little affect on the level of amino acid contamination. Strong acid hydrolysis reactions designed to depolymerize chitin to glucosamine yielded only 5% glucosamine. Clearly alternative methods of chitin depolymerization must be identified before the purification and 14C dating of glucosamine from sub-fossil chitin becomes practical.
Preliminary experiments were carried out on archaeological wood to investigate methods of cellulose hydrolysis and carbohydrate monomer purification for the purpose of compound-specific radiocarbon dating. The Chelford log, a known 14C dead source of wood cellulose, was selected for study in order to investigate the levels of contamination introduced during sample purification. Two methods of hydrolysis were examined, mineral acid hydrolysis and enzyme hydrolysis using cellulase from Penicillium funiculosum. Under the conditions described, enzymolysis was far superior to acid hydrolysis in terms of the glucose monomer yield. Glucose monomer purification was accomplished using high pH anion exchange chromatography with pulsed amperometric detection. This high performance liquid chromatography (HPLC) method does not require sample derivatization and the chromatography products can be collected in water. These characteristics make it potentially well suited to carbon dating applications. 14C dating of chromatographically purified glucose fractions revealed significant levels of contamination had accumulated during both protocols. Glucose contamination from the cellulase enzyme preparation was a major source of contamination within the enzymatically hydrolyzed samples. Ultrafiltration of the enzyme removed some but not all of this contamination. The contamination must be reduced 10-fold before the methodology could be viable for dating. This hydrolysis/HPLC method is also being investigated for 14C dating of other carbohydrate polymers such as chitin.
Since the aminoglycoside antibiotic apramycin was licensed for veterinary use in 1980, all isolates of Escherichia coli and salmonellas received at the Central Veterinary Laboratory have been monitored for resistance to apramycin and the related antibiotic gentamicin. During the period 1982–4, the incidence of resistance in E. coli to apramycin increased from 0·6% in 1982 to 2·6% in 1984. In salmonellas the incidence of resistance to apramycin increased from 0·1% in 1982 to 1·4% in 1984. Resistance to both apramycin and gentamicin was detected in six different salmonella serotypes, although an isolate of Salmonella thompsonfrom poultry was resistant to gentamicin but not apramycin. Most of the cultures were isolated from pigs, although the incidence of apramycin resistance in S. typhimurium (DT 204C) from calves has shown a recent dramatic increase. All the isolates with one exception produced the enzyme aminoglycoside 3-N-acetyltransferase IV (ACC(3)IV). The resistance was transferable by conjugation in most of the strains examined, and the plasmids specifying the resistance have been found to belong to a number of different incompatibility groups. Plasmids from three E. coli strains were compatible with all the reference plasmids and belonged to a previously undescribed group which was investigated further.
It is suggested that bacteria from humans should be examined for resistance to apramycin and gentamicin to determine the possibility of the antibiotic-resistance bacteria, and their genes, spreading from animals to humans.
Host ranges of members of four groups of male-specific RNA coliphages were determined by plating on hosts carrying various derepressed plasmids. An RNA phage originally isolated on Pseudomonas aeruginosa failed to form plaques on any of the strains of Escherichia coli.
A bacteriophage was isolated from a strain of Salmonella manilla. This phage, υ15, was found to have adsorption and conversion properties similar to phage ε15. The two phages show similar transduction efficiencies but phage υ15 lysogenizes more efficiently. Phage υ15 is not subject to repression by ε15 type prophage. The densities of the two phages are indistinguishable.
Phage υ15 can ‘cure’ ε15 type prophages and recombination is possible between genomes of the two phages. It seems probable that they are heteroimmune representatives of a single bacteriophage family.
Chain-termination suppressors which are almost certainly amber suppressors have been isolated in Salmonella anatum by a technique involving the use of amber mutants of bacteriophage 01. The same technique could be used in any species of Salmonella (and many strains of Arizona) and analogous techniques are suggested for use in other genera of bacteria and in higher plants.
Thymineless strains of Escherichia coli C600 were constructred harbouring both an R factor of the N incompatibility group (R46 or R447b) and a compatible plasmid (Plac- of the A-C group or the Iα plasmid R62), which contained a segment of N group DNA. Selection was made for the transferred plasmid and dislodgement phenomena were manifest either as loss of an entire plasmid or as deletions of a region of plasmid DNA. Even after the two R factors had become established as separate replicons, the N group R factor but not the other plasmid exhibited instability.
Thymine starvation of strain C600 thy (R447b/R62) increased the elimination rate of the N group plasmid R447b but no elimination of R62 was observed. However, thymine starvation of strain C600 thy (R46/Plac-) not only increased the rate of elimination of R46 but also increased the rate of loss of Plac-. There was no detectable increase in nuclease activity in unstarved R46/Plac- strains and it is concluded that dislodgement of R46 from these strains is not due to induction of the nuclease that has been proposed to be responsible for the elimination of N group plasmids during thymine starvation.
Two variants of Plac- were isolated. These did not dislodge R46 from unstarved R46/Plac- strains and were not lost during thymine starvation even though thymineless elimination of R46 occurred at normal frequency.
Bacteriophage εγ is capable of transduction both by replacement of a genetic segment of the recipient by the homologous genetic material from the donor strain and by the formation of defective transducing particles capable of lysogenizing the recipient strain of S. anatum.
The isolation of strains carrying such prophages, which have incorporated the lactose or arabinose operons, is reported. Lysogenic strains, carrying both normal and defective transducing prophage, form high-frequency transducing lysates. Other strains, carrying only defective prophage, show evidence that the association of prophage genes and transduced materials is stable since the loss of one frequently entails loss of the other.
Paramedics accurately estimate the closest trauma hospital for ground transport.
Ground ambulance scene transports of trauma system patients to six participating trauma hospitals in Multnomah County, Oregon from 1 January 1986 to 1 January 1987 were studied. Transports involving multiple patients or pediatric patients were excluded.
A retrospective analysis was performed on consecutive patient transports to be taken to the closest trauma hospital as required by protocol. The availability of each hospital to receive trauma patients was monitored continuously by a central communications facility. Paramedics were provided hospital availability data at the time of patient system entry. When several hospitals were available, the paramedics were required by protocol to select the “closest” hospital. Subsequently, the vector distance from the trauma site to each of the available hospitals was measured using a grid map. This method was validated by odometer measurement (r2 = 0.924). Chisquare analysis was used to analyze hospital bypasses to specific hospitals.
Of the 1193 eligible patients entered into the trauma system, 160 (13%; 95% CI = 11–15%) transports bypassed the closest available hospital for a receiving hospital ≥1 mile more distant. There were 11 (1%; 0–2%) patients transported to a hospital more than five miles more distant. Of the 132 patients with a trauma score (TS) <12, 15 (11%; 6–18%) were taken to a hospital one mile or further beyond the closest hospital. None (0%; 0–2%) were transported more than five miles past the closest hospital. Of the six hospitals, three were bypassed more than one mile significantly more often then they received bypass patients. One hospital received such patients four times more than it was bypassed (p <.001).
While paramedics generally can identify the closest hospital for trauma patient transport, some systematic hospital bypass errors occur. If a community wants assurance of an equitable patient distribution among participating trauma hospitals and assignment of the closest geographic hospital for injured patients, then map vector distance determination to identify the closest available hospital should supplement paramedic dispatching.
Patients initially refusing care (PIRC) place their health in jeopardy and consume paramedic and base-station physician time. This study quantifies the time spent on-scene related to PIRC cases.
A retrospective analysis of 128 PIRC cases was performed in the Multomah County EMS system.
The PIRC cases had a significantly longer mean on-scene time than did non-refusal cases (30.3 vs 14.6 min; p<.001). Medication administration by paramedics (14% of patients) significantly increased the on-scene time. Overall, the mean time on-scene was not affected by age, gender, vital signs (pulse, blood pressure, respiratory rate), police involvement, and whether the patient was transported. The type of call had limited influence on on-scene time, although mean on-scene time was significantly longer for altered mental status cases than for trauma related cases (35.6 vs 22.4 min; p<.03).
PIRC cases create a burden on the EMS system by consuming paramedic and base-station physician time and by preventing these personnel from responding to other calls.
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