Partial antagonism of propofol anaesthesia by physostigmine in rats is associated with potentiation of fast (80-200 Hz) oscillations in the thalamus.

BACKGROUND: Positron emission tomography studies in human subjects show that propofol-induced unconsciousness in humans is associated with a reduction in thalamic blood flow, suggesting that anaesthesia is associated with impairment of thalamic function. A recent study showed that antagonism of propofol-induced unconsciousness by the anticholinesterase physostigmine is associated with a marked increase in thalamic blood flow, supporting the implication of the thalamus. The aim of the present study was to assess the role of the thalamus in the antagonistic effects of physostigmine during propofol anaesthesia using electrophysiological recordings in a rat model. METHODS: Local field potentials were recorded from the barrel cortex and ventroposteromedial thalamic nucleus in 10 chronically instrumented rats to measure spectral power in the gamma/high-gamma range (50-200 Hz). Propofol was given i.v. by target-controlled infusion at the lowest concentration required to abolish righting attempts. Physostigmine was given during anaesthesia to produce behavioural arousal without changing anaesthetic concentration. RESULTS: Compared with baseline, gamma/high-gamma power during anaesthesia was reduced by 31% in the cortex (P=0.006) and by 65% in the thalamus (P=0.006). Physostigmine given during anaesthesia increased gamma/high-gamma power in the thalamus by 60% (P=0.048) and caused behavioural arousal that correlated (P=0.0087) with the increase in power. Physostigmine caused no significant power change in the cortex. CONCLUSIONS: We conclude that partial antagonism of propofol anaesthesia by physostigmine is associated with an increase in thalamic activity reflected in gamma/high-gamma (50-200 Hz) power. These findings are consistent with the view that anaesthetic-induced unconsciousness is associated with impairment of thalamic function.

Design of a survey to inform state health decision making: a collaborative effort.

BACKGROUND: The North Carolina Health Profile (NCHP), a statewide telephone survey, was introduced as part of the state's Health Policy Information Project aimed at enhancing the use of health data for state policy decision making and program management. A key factor in the creation of the NCHP was a collaboration between the State Center for Health Statistics and the Survey Research Unit at the University of North Carolina at Chapel Hill. The purpose of this article is to describe our partnership, the development of the survey design, and the dissemination of survey results. METHODS: Three designs were considered during the planning and development of the survey. The final design consisted of a random digit dialing sample of 2,400 households in the state's noninstitutionalized population. The questionnaire was comprised of an adult module (addressing adult health care use and insurance coverage), a child module (addressing health care use and insurance coverage of children ages 0-17 years), and a young child module (addressing child development and safety for children ages 0-5 years). RESULTS: Several statistical briefs, a report, a public dataset, and accompanying public use documentation were prepared for a variety of audiences, including state legislative committees and commissions, state agencies, and advocacy groups. DISCUSSION: We learned several lessons in our research and practice partnership including the need for collaboration between data creators and users, for addressing obstacles in soliciting policy information needs, and for prioritization in meeting information needs.

Turbidimetric assay for virginiamycin in feeds and premixes.

A turbidimetric assay method applicable to virginiamycin at level ranging from 5 g/ton in feeds to 50% in a premix is described. Incubation period is 4 h. Test organism is Streptococcus faecium ATCC 8043. On 6 levels of feed-grade material, the overall mean recovery was 6.75% Standard recovery studies resulted in RSD values ranging from 2.01 to 3.88% and a mean standard recovery of 100%.

Turbidimetric microbiological determination of oxytetracycline hydrochloride in finished feeds and a feed premix: collaborative study.

New automated and manual turbidimetric microbiological assay methods for oxytetracycline (OTC) in finished feeds and a feed premix were submitted to 17 collaborating laboratories for comparison with the official AOAC method. Six finished feeds of 50 and 100 g/ton levels and one premix containing 20 g OTC/lb were sent to the collaborators. Results were received from 12 laboratories. Six laboratories provided results derived from the Autoturb System and 7 laboratories poerformed the turbidimetric analyses manually. All 12 laboratories assayed the samples by the AOAC cylinder-plate method. Ranges of recoveraies expressed as percent were 89.5-102.0, 91.2-97.0, and 91.4-96.0 for the AOAC, Autoturb turbidimetric, and manual turbidimetric methods, respectively. Average recoveries were 96.3, 93.4, and 93.6%, respectively. The mean relative standard deviation values were 5.7, 6.3, and 7.2, respectively. There was little significant difference between the turbidimetric methods and the AOAC method; however, the turbidimetric methods were faster.

Rapid automated turbidimetric assay for chlortetracycline hydrochloride, using Leuconostoc mesenteroides as the test organism.

A rapid turbidimetric assay has been developed for chlortetracycline hydrochloride (CTC-HCl) in finished animal feeds and feed supplements, using Leuconostoc mesenteroides as the test organism. Two modifications are presented: The incubation period of modification 1 is 2.5 hr and the sensitivity of the assay is 0.03 microgram CTC-HCl/assay tube. Modification 2 has a sensitivty of 0.01 microgram CTC-HCl/assay tube and requires an incubation period of 3.5 hr. For 21 feed formulations, the turbidimetric method recovered 95.7% of label claim. Recoveries of CTC-HCl standards from the same feeds ranged from 93.4 to 134% with a mean of 103%. The relative standard deviation among day-to-day duplicates is 3.50% for the faster modification and 1.63% for the more sensitive modification.

Temperature-sensitive mutants of a Chinese hamster cell line. I. Selection of clones with defective macromolecular biosynthesis.

Temperature-sensitive clones have been selected from a mutagenized culture of Chinese hamster lung cells by a procedure involving bromodeoxyuridine (BrdU) incorporation and irradiation with black light. The selection procedure used in these studies was adapted from methods developed by others to yield mutants that cease DNA replication within a short time after they are transferred to nonpermissive temperature. After mutagenesis with ethyl methanosulfonate ten clones survived the selection procedure. Three of the clones (mutants) were temperature-sensitive as measured by growth properties. Two mutants ceased DNA synthesis within six hours of being shifted to 39degrees and the third mutant continued to synthesize DNA at nonpermissive temperature at a reduced rate for at least 24 hours. Thus, all three mutants survived the selection procedure for understandable reasons, since each was unable to incorporate sufficient BrdU at 39degrees to lethally protosensitize its DNA during the standard exposure period. The two mutants that cease DNA synthesis at high temperature (clones 115-47 and 115-53) also stop incorporating radioactive amino acids and uridine within six hours at 39degrees. Their complex phenotype, i.e. defective DNA, RNA and protein biosynthesis, is reversible. When these mutants were returned to 33 degrees after 8 hours at 39 degrees, both resumed DNA synthesis immediately (less than 1 hour). Reversal of defective DNA synthesis in both mutants were sensitive to drugs that inhibit protein biosynthesis specifically. Those same drugs, as well as toxic amino acids analogs, also effected a striking mutant phenocopy in wild-type cells. The phenocopy produced by amino acid analogs that are incorporated into mammalian proteins suggested that one or more proteins must be synthesized continuously to support mammalian cells engaged in programmed DNA replication.