A hexagon in Saturn's northern stratosphere surrounding the emerging summertime polar vortex.

Saturn's polar stratosphere exhibits the seasonal growth and dissipation of broad, warm vortices poleward of ~75° latitude, which are strongest in the summer and absent in winter. The longevity of the exploration of the Saturn system by Cassini allows the use of infrared spectroscopy to trace the formation of the North Polar Stratospheric Vortex (NPSV), a region of enhanced temperatures and elevated hydrocarbon abundances at millibar pressures. We constrain the timescales of stratospheric vortex formation and dissipation in both hemispheres. Although the NPSV formed during late northern spring, by the end of Cassini's reconnaissance (shortly after northern summer solstice), it still did not display the contrasts in temperature and composition that were evident at the south pole during southern summer. The newly formed NPSV was bounded by a strengthening stratospheric thermal gradient near 78°N. The emergent boundary was hexagonal, suggesting that the Rossby wave responsible for Saturn's long-lived polar hexagon-which was previously expected to be trapped in the troposphere-can influence the stratospheric temperatures some 300 km above Saturn's clouds.

The effectiveness of parallel gamma-interferon testing in New Zealand's bovine tuberculosis eradication programme.

In bovine tuberculosis (bTB) eradication programmes, especially where prevalence is low, sensitivity of testing in infected herds must be maximised to reduce the possibility of recrudescence of prior infection and the risk to other herds via animal movement. The gamma-interferon (γ-IFN) assay applied in parallel with intradermal tuberculin testing has been shown to increase test sensitivity. The aim of this work was to substantiate this effect in the field. A retrospective observational study was conducted on 239 New Zealand cattle breeding and dairy herds with bTB infection between 1 July 2011 and 1 September 2015 to evaluate the outcomes of new policy introduced in 2011. The investigation defined the number and proportion of reactors (animals testing positive and slaughtered) found with lesions of bTB in intradermal caudal fold testing (CFT) and parallel γ-IFN testing, at the breakdown test or first whole herd test after breakdown, WHT(1), and at the final or projected final whole herd test, WHT(F). Parallel γ-IFN testing was used in 26.8% of the 239 herds at WHT(1), and 430 animals in 49 herds were deemed reactors. One hundred and sixty (37.2%) of these reactors from 32 herds were found to have bTB lesions, despite having been negative to caudal fold testing. These 160 infected animals accounted for 29.6% of all infection found at WHT(1). At WHT(F), parallel γ-IFN testing was conducted on 93 herds and detected a total of 122 reactors in 49 herds, in addition to those found by CFT. Twenty-one of these reactors, from 13 herds, had bTB lesions at slaughter, accounting for 67.7% of all reactors found with bTB at WHT(F). Eleven of these 13 herds would have had their movement restrictions revoked based on a negative herd CFT alone, and could potentially have caused outward transmission of bTB to other herds, as well as experiencing recrudescent breakdowns. We conclude that γ-IFN testing in infected herds, in parallel with intradermal tuberculin testing, is a valuable tool in a bTB eradication programme, as it enables higher test sensitivity at both herd and animal level. The use of the γ-IFN test over a risk cohort early in a breakdown assists in removal of early infection and some cases of anergy to intradermal tuberculin testing. Parallel γ-IFN with compulsory slaughter of reactors should be considered in breeding and dairy herds in conjunction with tuberculin testing before movement control is revoked, and will assist in achieving TB freedom on a herd level and nationally.

Recurrent bovine tuberculosis in New Zealand cattle and deer herds, 2006-2010.

A retrospective cohort study was conducted to identify risk factors for bovine tuberculosis (bTB) recurrence in New Zealand cattle and deer herds identified as bTB-infected from 1 June 2006 to 1 November 2010. A Cox proportional hazards model identified a positive relationship between the daily hazard of bTB recurrence and: (1) the number of prior bTB episodes for two episodes [hazard ratio (HR) 3·22, 95% confidence interval (CI) 1·21-8·60], and for five episodes (HR 89·5, 95% CI 13·8-580), (2) more than one positive bTB case animal at the index episode (HR 2·25, 95% CI 1·19-4·25) and (3) the presence of cleared test-positives at the final test of the index episode. The proportional hazards assumption was violated for the latter variable so a time-dependent covariate was introduced. Up to 2 years post-clearance, the daily hazard of bTB recurrence was greater in herds with test-positives at the final test (HR 2·59, 95% CI 1·30-5·13), but this effect was not observed more than 2 years' post-clearance (HR 1·05, 95% CI 0·28-3·91). We conclude that unresolved infection contributes to further bTB episodes in the first 2 years after herd clearance.

The influence of the choice of digestion enzyme used to prepare rat hepatocytes on xenobiotic uptake and efflux.

Isolated rat hepatocytes are widely used to assess the metabolism and toxicity of xenobiotics. The choice of digestion enzyme used to prepare the cells has been shown previously to influence their metabolic capability. This study investigates the effect of the digestion enzyme (collagenase II, collagenase A/trypsin inhibitor, or collagenase plus dispase) on the uptake of xenobiotics into, and efflux from, hepatocytes. The choice of digestion enzymes used in this study does not affect uptake of either pravastatin (an organic anion probe substrate for Oatp transporter) or metformin (an organic cation probe substrate for Oct transporter). With regard to efflux transporters, hepatocyte differentiation was better maintained when cells were isolated using collagenase II alone.

The extent of phase I and phase II reactions is affected by the choice of enzyme used to prepare rat hepatocytes.

The preparation of hepatocytes using the two-stage perfusion technique usually involves the use of collagenase (CII) alone or in combination with dispase (C/D) or trypsin inhibitor (CA/TI) as digestion enzymes. The effect of CII, C/D and CA/TI on cell viability, yield, cytochrome P450 mediated oxidation of testosterone, glucuronidation and sulfation of 7-hydroxycoumarin, glutathione content, glutathione-S-transferase activity and glutathione-conjugation capacity of hepatocytes has been assessed. Cytochrome P450 mediated oxidation of testosterone was significantly (p < 0.05) decreased with CII isolated hepatocytes (81.7 +/- 3.3 nmol/10(6) cells, mean +/- S.E.M., n = 3), compared with those isolated using CA/TI (96.6 +/- 1.9 nmol/10(6) cells) or C/D (95.1 +/- 2.1 nmol/10(6) cells). In contrast, glutathione conjugation of the non-specific substrate 1-chloro-2,4-dinitrobenzene was significantly (p < 0.05) increased with CII isolated hepatocytes (56.9 +/- 5.9 nmol/10(6) cells, mean +/- S.E.M., n = 3), compared with those isolated using CA/TI (36.0 +/- 3.7 nmol/10(6) cells) or C/D (31.6 +/- 3.7 nmol/10(6) cells). These findings have significant implications for the interpretation of metabolism data derived from hepatocytes in suspension, particularly in terms of glutathione conjugation of potentially toxic reactive intermediates of xenobiotic metabolism. Indeed, data presented show that the presence of trypsin inhibitor in the preparation of isolated rat hepatocytes significantly affects the formation of glutathione conjugates of reactive intermediate products of troglitazone metabolism.

Results of a UK survey on methods for compensating for unscheduled treatment interruptions and errors in treatment delivery.

In order to obtain a preliminary overview of the current national status regarding the management of both unintentional interruptions to radiotherapy treatments and inadvertent errors in treatment delivery, a short questionnaire was sent to 60 UK radiotherapy departments, of which 35 (58%) responded. The study was initiated by the authors and was not commissioned by any professional body. Amongst the centres which responded the majority (86%) currently have standardized protocols in place for dealing with treatment interruptions and many have extended the enactment of compensation methods to cover a wider range of tumour types than are encompassed within the Royal College of Radiologists (RCR)-defined Categories 1 and 2. Fewer of the respondents (60%) have standardized methods for dealing with treatment errors. Given that 42% of centres did not respond it is difficult to assess the fuller national picture. Some smaller departments may seek protocols or advice from larger adjacent centres, but the overall percentage of centres with systems in place may be lower than indicated from the survey results. The desirability of providing training in the radiobiological methods pertaining to treatment compensation was raised by a number of respondents.

Practical methods for compensating for missed treatment days in radiotherapy, with particular reference to head and neck schedules.

Unscheduled interruption of a radiotherapy treatment can lead to significant loss in local tumour control, particularly in tumours that repopulate rapidly. General guidelines for dealing with such treatment gaps have been issued by the Royal College of Radiologists and more specific advice on the use of compensation methods has been published previously [Hendry et al., Clin Oncol 1996;8:297-307; Slevin et al., Radiother Oncol 1992;24:215-220]. This article further elaborates on the practical application of these methods. It sets out the main considerations arising in the especially critical case of head and neck treatments and simple calculations are used to illustrate the approaches which may be adapted for particular situations. Radiobiological parameter values are suggested for use in the calculations, but these may require modification in the light of further research in this important area.

Dose equivalents of tumour repopulation during radiotherapy: the potential for confusion.

When employing linear quadratic equations to calculate compensation for changes in overall treatment time, a potential confusion exists regarding use of the parameter commonly described as the dose equivalent of tumour repopulation. The more correct term for this factor is the biologically effective dose equivalent of tumour repopulation. The distinction between the two concepts is discussed and the potential errors arising from their confusion are illustrated by means of an example.

Lhermitte's sign following head and neck radiotherapy.

Lhermitte's sign is an uncommon sequel of radiotherapy to the cervical spinal cord. Although the exact mechanism underlying its occurrence remains unclear; it is felt to be the result of a temporary interference with the turnover and synthesis of myelin, leading to focal demyelination. We have undertaken a detailed analysis of the radiation delivered to four patients who developed the sign after irradiation for malignancies of the head and neck. Our data support the view that radiation dose is crucial to its development, but calculations using the linear-quadratic radiobiological model raise interesting questions regarding the dose-response relationship. In particular, we find that calculations of biologically effective doses are predictive of a late rather than an early normal tissue response. The onset of symptoms after irradiation was apparent in all four patients within 4 months, with resolution in all being complete within a further 6 months. The recognition of this benign transient form of radiation-induced paraesthesia and its differentiation from the later onset, progressive and unremitting symptoms associated with radiation myelopathy is essential in reassuring patients undergoing head and neck irradiation.

Sensitivity of a standard host resistance assay using Streptococcus agalactiae for assessing exposure to immunotoxicants in wild cotton rats (Sigmodon hispidus).

Resident small mammals have been used for in situ biomonitoring of contaminated waste sites containing suspected immunotoxicants. Host resistance assays, which involve challenging animals with an actual pathogen, allow for testing of overall immune system function in animals. Because such assays have not been evaluated for use with wild rodent species, it was our objective to assess the efficacy of Streptococcus agalactiae as a pathogenic model for use in a host resistance assay for detecting alterations in immune system function in wild cotton rats (Sigmodon hispidus). The ability of the assay to detect immunosuppression was evaluated by inducing immunosuppression chemically (cyclophosphamide or dexamethasone) and by protein malnutrition. The estimated lethal dose of S. agalactiae that killed 50% of challenged animals (LD50) was 5.76x10(7) colony-forming units (CFUs). Although bacterial agglutination titers indicated that animals developed an antibody response when immunized, immunization was not sufficient to adequately protect animals from a subsequent pathogenic challenge. Sensitivity of the host resistance assay was only suitable for detecting substantial immunosuppression, such as that induced by protein malnutrition or dexamethasone administration.

BED-time charts and their application to the problems of interruptions in external beam radiotherapy treatments.

PURPOSE: The use of radiobiological modelling to examine the likely consequences of interruptions to radiotherapy schedules and to assess various compensatory measures. METHODS AND MATERIALS: An effect-time graphical display, the BED-time chart, has been developed using the linear-quadratic (LQ) model. This is used to examine the effects on tumour and normal tissues of treatment interruption scenarios representative of clinical situations. The mathematical criteria governing successful salvage have also been drafted and applied to typical situations. RESULTS: The successful salvage of an interrupted treatment is dependent on a number of interacting factors and the method presented here can be used to examine the trade-offs that exist. Although the mathematics may be complex, it is shown that the dilemmas posed by an interrupted treatment may be more easily appreciated with reference to BED-time charts. These may therefore have a useful role as a teaching aid for portraying a wider variety of radiotherapy problems and also in the documentation of interruptions to treatment and the measures taken to compensate for them. CONCLUSIONS: Interruptions to radiotherapy regimes are undesirable and compensatory measures need to be initiated as soon as possible after the gap, with a view to completing the amended treatment within the originally prescribed treatment time. Adequate compensation is particularly difficult for long gaps and gaps which occur towards the end of the scheduled treatment. Modelling exercises can help establish guidelines on the available windows of opportunity.

Tumoricidal activity of lymphokine-activated killer cells during acute protein restriction in the cotton rat (Sigmodon hispidus).

Habitat-induced alterations of immune system function have been implicated in the regulation of survival rates in wild herbivore populations. Protein availability in the diet has been shown to fluctuate with density and influence immunity in hispid cotton rats (Sigmodon hispidus), a common herbivorous rodent of the southeastern United States. In this study, we examined the impact of short-term, moderate restrictions in dietary protein on the tumoricidal activity of lymphokine-activated killer (LAK) cells in the spleen of subadult male cotton rats in captivity. Animals were fed complete, isocaloric diets containing either 20% casein (high quality diet), or one of three moderate levels of protein (10, 8, or 5% casein) for two weeks prior to assessing LAK cell activity in vitro in the presence of YAC-1 tumor cells. Moderate restrictions in protein resulted in depressed body growth, although all animals gained mass during the second week of the trial, without significant increases in food intake. Immune organ development and cellularity were suppressed in moderately restricted cotton rats when compared to those on a high quality diet. Tumoricidal activity of LAK cells against YAC-1 targets were significantly altered by diet treatments, being elevated in the group fed a diet containing 10% casein. There was a general tendency for increased LAK cell activity among those fed one of the three moderate quality diets, but observed suppressions in splenic cellularity tended to result in a slight decline in total lytic capacity of spleens.

Sensitivity of wild cotton rats (Sigmodon hispidus) to the immunotoxic effects of low-level arsenic exposure.

Arsenic is a ubiquitous contaminant of many toxic waste sites around the country and experimental animal trials have indicated that arsenic may be immunotoxic to laboratory rodents. Because wild rodents such as the herbivorous cotton rat (Sigmodon hispidus) reside on many of these toxic waste sites, we explored the sensitivity of their immune systems to oral exposures of environmentally relevant concentrations of inorganic arsenic. We exposed adult male cotton rats (n = 36) to either 0 (controls), 5 (low dose), or 10 (high dose) ppm sodium arsenite in drinking water for 6 weeks. Daily food intake decreased in a dose-dependent manner, ranging from an average of 10.03 +/- 0.45 in the high-dose group to 11.27 +/- 0.42 (SE) g/animal/day in the control group. Mass of testes in the low-dose group increased significantly compared to controls, but there was no difference between the high-dose and control groups. Masses of liver, kidney, adrenals, popliteal lymph nodes, spleen, epididymides, and seminal vesicles and selected hematological parameters were unaffected by arsenic exposure. In vivo cell-mediated immunity, as measured by a phytohemagglutinin-hypersensitivity response to an intradermal challenge, was suppressed 30% in the low-dose group compared to controls; however, responses of those receiving a high dose of arsenic were similar to controls. Arsenic treatment did not have a measurable impact on lymphoproliferative responses of cultured splenocytes to the mitogens Concanavalin A and Pokeweed mitogen, or to the lymphokine interleukin-2. We also observed no impact of low-level arsenic exposure on macrophage phagocytic activity and tumoricidal activity of lymphokine-activated killer cells in vitro. It is possible that malnutrition caused by decreased food intake may eventually lead to atrophy of lymphoid organs and render animals more susceptible to environmental pathogens. However, direct effects of low-level arsenic exposure on immune function of cotton rats was minimal (a moderate depression in the in vivo cell-mediated immunity assay) and may not be clinically relevant with regard to susceptibility to disease in the wild.

A proposed figure of merit for the assessment of unscheduled treatment interruptions.

There are, as yet, no standard radiobiological methods for devising compensation for unscheduled interruptions to fractionated radiotherapy. For the foreseeable future it is likely that the concept of biologically effective dose (BED) will play an important role in the intercomparison of treatment regimes, and in the examination of the options available for dealing with unscheduled treatment interruptions. However, comparison of the BEDs associated with different treatment options does not provide an intuitively obvious indication of the magnitude of any associated differences in biological effect--an important consideration in the case of those treatments which are designed to deliver near-tolerance doses. This article reviews the implications which derive from this complication, and discusses the desirable properties of possible "one-number" treatment scoring systems which could utilize the BEDs of both the tumour and the critical normal tissue. One possible form of such a scoring parameter is suggested, and applied to some clinical examples. No special "robustness" is claimed for the proposed scoring system, but the method nevertheless allows the ranking of treatment options such that the least satisfactory may be identified and rejected.

Production and characterization of monoclonal antibodies to cervine herpesvirus-1.

Fourteen hybridoma cell lines secreting monoclonal antibodies (Mab) to cervine herpesvirus-1 (CerHV-1) produced following the fusion of NSO myeloma cells with splenocytes of BALB/c mice previously immunized with gradient purified CerHV-1 were selected using an indirect enzyme-linked immunosorbent assay (ELISA) employing CerHV-1 antigen and tested by the ELISA against four other ruminant alphaherpesviruses from cattle (bovine herpesvirus type 1.1 and 1.2) goat (caprine herpesvirus-2) and reindeer (rangiferine herpesvirus-1). Comparison of all five ruminant alphaherpesviruses with these Mabs confirmed their close antigenic relationships, with two Mabs reacting against all viruses. Ten Mabs which were able to differentiate between the viruses reacted with a 64 kDa polypeptide in a western blot. Four Mabs including two specific only for CerHV-1 with neutralizing activity against the virus used for immunization were directed against a 74 kDa viral protein.

The production and survival of lambs persistently infected with border disease virus.

From 1985 to 1989 lambs persistently infected with border disease virus (BDV) were produced for comparative immunological studies by infecting 57 susceptible pregnant ewes between 50 and 60 days' gestation with Moredun or Oban strains of BDV. Ewes were infected either by injection with virus grown in cell culture or by housing with lambs excreting BDV. There was no significant difference in the outcomes of these different methods of infection. There was a significant difference in the number of viable lambs born to ewes receiving the two viruses. Of 41 ewes infected with Moredun virus 21 produced 32 live lambs of which 17 were reared to 1 month old (53% viability). Of 16 ewes receiving Oban virus 10 gave birth to 17 live lambs of which 15 were reared to 1 month old (88% viability). All the lambs born to ewes infected with Moredun BDV had varying signs of tremor and increased hairiness ("hairy-shakers") while those born to ewes infected with the Oban virus had no obvious clinical signs. Survival of the lambs was poor. Up until February 1991, 14 Moredun and 10 Oban sheep between the ages of 4 months and 5.5 yr had died from a variety of causes. The two commonest causes were a chronic wasting syndrome and a mucosal disease-like syndrome which was associated with the recovery of cytopathic BDV. Mating of unrelated persistently infected sheep was largely unproductive although 2 lambs were reared.

A monoclonal antibody capture ELISA to detect antibody to border disease virus in sheep serum.

An enzyme-linked immunosorbent assay (ELISA) has been developed to detect antibody to border disease virus (BDV) in sheep serum. A monoclonal antibody bound to 96-well microplates was used to capture antigen from detergent-solubilised BDV-infected cells. Single dilutions of test sera were then added to wells containing bound BDV antigen and control wells containing uninfected cell lysates. Specific antibody to BDV was detected by an anti-ovine IgG antiserum conjugated with horseradish peroxidase and the results expressed as ELISA units with reference to a standard curve. Sequential sera from 16 experimentally infected sheep and single sera from 103 sheep involved in a field outbreak were tested in the ELISA and for neutralising antibody. There was good qualitative correlation between the two tests.

Uroporphyria produced in mice by 20-methylcholanthrene and 5-aminolaevulinic acid.

Iron-loaded male C57BL/6 mice allowed free access to an aqueous solution of 5-aminolaevulinic acid (ALA) (2 mg/ml) as their only drink, develop severe uroporphyria within 9 days of a single intraperitoneal dose of 20-methylcholanthrene (MC) (125 mg/kg). At 21 days, uroporphyrinogen decarboxylase (EC 4.1.1.37) activities are less than 10% of control activities. The porphyria is not dependent on pretreatment with iron and persists for at least 21 days after withdrawal of ALA. The same intraperitoneal dose of MC does not produce porphyria within 21 days when given without ALA. Continuous administration of ALA markedly accelerates the onset of porphyria in iron-loaded male C57BL/6 mice after a single intraperitoneal dose of hexachlorobenzene (200 mg/kg); mice given phenobarbitone and ALA do not become porphyric. MC with ALA does not produce porphyria in iron-loaded male DBA/2 mice. At least two separate events are needed to produce uroporphyria in mammals: induction of a specific form of cytochrome P-450 and stimulation of the formation of intermediates of haem biosynthesis in the liver. These results show that severe, persistent porphyria can be produced in mammals by compounds other than polyhalogenated aromatic hydrocarbons and suggest that a similar mechanism underlies the porphyrogenic action of halogenated and non-halogenated compounds.

Prevalence of antibodies to bovine virus diarrhoea-mucosal disease virus in Tanzanian cattle.

A serological survey to determine the prevalence of antibodies to bovine virus diarrhoea-mucosal disease (BVD-MD) virus was conducted on 419 bovine serum samples originating from 18 of 20 regions (except Mwanza and Shinyanga) of the Tanzania mainland. The sera were a small proportion of samples collected for the appraisal of immune response to rinderpest vaccination. The survey indicated that the virus is prevalent in cattle populations and approximately 12% of sera tested contained demonstrable neutralising antibodies against BVD-MD virus.