The chain composition of tetanus toxin.

Although tetanus toxins from cell and culture filtrate appear indistinguishable by several criteria, only the filtrate toxin can be cleaved into two chains by disulfide scission. These chains approximate molecular weights of 95,000 and 55,000. Determinations of sulfhydryl groups and total half-cystine residues for both the cell and filtrate toxins gave values of approximately six and nine, respectively and in filtrate toxin the half-cystine residues are found evenly distributed between the two chains.

Tuberculosis due to Mycobacterium bovis in the Australian population: cases recorded during 1970-1994.

OBJECTIVE: To determine the contribution of Mycobacterium bovis to active tuberculosis in the Australian population during 1970-1994, and to collate and analyse demographic data from bacteriologically proven cases. DESIGN: Summary data for tuberculosis cases notified by Australian public health agencies during 1970-1985 and 1991-1994 were obtained from the database of notifiable diseases maintained by the Department of Health and Family Services. More detailed demographic data for cases confirmed by bacteriology during 1970-1994 were supplied by the Australian Mycobacterium Reference Laboratory Network. RESULTS: At least 236 cases of bovine tuberculosis (TB) occurred in the Australian population during 1970-1994 (mean 9.4 cases; range 3-22 cases annually). The bovine strain has accounted for around 1% of Australian cases of TB during this period. Laboratory sources provided demographic data for 150 cases with positive bacteriology. For this group, the mean age was 54 years (range 22-86), and the male:female ratio was 2.4:1. The majority of cases (74%) involved pulmonary disease. Australian-born persons accounted for 68% of the total cases and typically had histories of employment in meat and/or livestock industries. CONCLUSION: M. bovis was responsible for less than 1.5% of cases of TB in the Australian population during 1970-1994. Most cases were apparently due to reactivation of infection acquired through occupational exposure. Thus, although virtual eradication of M. bovis from Australia's cattle herds has now reduced the risk of exposure, it can be expected that human cases of bovine TB will continue to be detected for years to come. The bovine strain should be considered as the possible agent of TB in foreign-born Australians.

Tuberculosis due to Mycobacterium bovis in the Australian population: DNA typing of isolates, 1970-1994.

SETTING: Bacteriologically confirmed cases of Mycobacterium bovis in the Australian population. OBJECTIVE: To evaluate the DNA fingerprinting techniques commonly used for M. bovis on isolates from humans and determine whether they were useful for determining the origin of human infection. DESIGN: M. bovis strains isolated between 1970 and 1994 were obtained from five Australian Reference Laboratories. Four DNA fingerprinting techniques, comprising Southern hybridisation with three different probes (the insertion sequence [IS]6110, the polymorphic guanine-cytosine-rich sequence [PGRS] and the direct repeat [DR]) and a PCR-based method (spoligotyping) were used. RESULTS: The PGRS, DR and IS6110 RFLP methods identified 32, 22 and 14 different types respectively from the 45 isolates available. Spoligotyping identified 18 different types. When all methods were combined 41 different strains were identified. Clear differences were found between many isolates from Australian-born patients and those from patients born overseas. CONCLUSIONS: The PGRS RFLP method was the most effective method for typing the human strains, but a combination of methods is recommended for maximum sensitivity. Most Australian-born patients that had worked in the meat and livestock industries were infected with strains similar to those that are commonly found in Australian cattle, confirming the occupational risk in these industries. Patients born overseas were typically infected with strains genetically different from those of patients born in Australia. This suggests that patients born overseas identified with M. bovis were presenting with reactivation of infection acquired outside Australia.

Elongation effects on the Therac 6 linear accelerator.

The effects of field elongation on the central-axis output at dmax and on the depth-dose curves for the 6-MV x rays from the Therac 6 linear accelerator are considered. These parameters are independent of the collimator angle for both square and elongated fields. The exchange of collimator pairs results in significant output differences but has a negligible effect on the depth-dose curves. Both the central-axis output at dmax and the depth-dose curves agree satisfactorily with the predictions of the equivalent-square technique. An alternative method of greater accuracy is also indicated for the prediction of central-axis outputs at dmax for elongated fields.

Tissue-maximum ratios for high-energy x rays.

The tissue-maximum ratios for high-energy betatron x rays, measured at target-axis distances of 90, 110, and 130 cm, exhibit a strong dependence on the target-axis distance in the buildup region as well as a significant dependence in the exponential region. This dependence and the field-size dependence of the tissue-maximum ratios at a fixed target-axis distance are studied with the use of phantom and collimator scatter factors. The depth and field-size dependence of these scatter factors are determined experimentally. The measurements indicate that the collimator scatter factor is dependent on both the collimator opening and the targetaxis distance. These components are quantitated separately and are associated primarily with high-energy electron scatter from the collimating system. An equation involving these components of the collimator scatter factor is derived for the conversion of tissue-maximum ratios from one target-axis distance to another. With the use of this equation, the tissue-maximum ratios measured for one target-axis distance can be used to calculate within 1% those at other target-axis distances.

Analysis of utilization-related parameters on a 6-MV linear accelerator.

An analysis of unscheduled downtime and of patient treatment data for a 6-MV linear accelerator is presented for a 7-yr period. Following the initial year of clinical use, the unscheduled downtime has averaged 2.4%, with a corresponding loss of 1.3% in patient treatments. The quality assurance, preventive maintenance, and repairs are handled in-house, with an investment of approximately 500 man-hours annually.

Characteristics of cobalt-60 penumbral regions.

Ionization chambers with wall materials of various electron densities have been employed to investigate the penumbral region of a cobalt-60 beam of side length 10 cm. Measurements were made in air with chambers of various inside diameters. The homogeneous walls of the ionization chambers were 0.5 g/cm2 in thickness. Extrapolation techniques to zero inside diameter and to infinite density were used, respectively, to eliminate the effect of the inside diameter of the chamber and to determine the penumbral photon-fluence distribution. The method also quantitates both the penumbral primary-dose profiles in water-equivalent media and the degradation of these profiles in media of low electron density.

A statistical analysis of ionometrically measured 6-MV x-ray beam parameters.

A statistical analysis has been made of ionometrically measured parameters related to the central-axis output, the beam symmetry, the beam flatness, and the depth dose for the 6-MV x-ray beam from the Therac-6 linear accelerator. The means and coefficients of variation of the measurements are determined on a monthly basis for each parameter. Mean coefficients of variation less than +/- 1% have been determined and are useful in establishing the optimal limits of acceptance of these parameters. The results of this study indicate that the long-term stability of the radiation parameters associated with this unit can be maintained within acceptable limits with a consistent quality-assurance program.

Analysis of physical parameters associated with the measurement of high-energy x-ray penumbra.

The effect of dosemeter type and configuration on the measured penumbral distribution for Co-60, 6-MV, and 31-MV x rays has been determined in air using equilibrium buildup caps for three commercial detection systems including a silicon diode and two ionization chambers. The diode is shown to be measuring a different parameter in the penumbral region than the ionization chambers. This fact in combination with the lateral spread of the secondary electrons and the difference in the inside diameters of the ionization chambers results in significant differences between the measured beam penumbra. The latter effect is studied in more detail with a series of specially designed ionization chambers of varying inside diameter from 0.3 to 1.4 cm. A theoretical model is described which resolves these differences, indicates a method to determine the true penumbral primary-dose distribution and introduces the concept of an effective diameter for the ionometric measurement of high-energy x-ray penumbra. Recommendations are made concerning the dosemeters of choice for penumbral measurements over this range of photon energies.

A doorless entry system for high-energy radiation therapy rooms.

A doorless entry system has been designed for use in high-energy radiation therapy rooms. The doorless entry improves patient access, safety and throughput, increases the physical safety for the radiation therapists, and avoids the significant cost of heavy shielding doors. The design meets concerns relating to radiation safety, operational ease, and authorized entry. The new system is currently operating in one room housing a cobalt-60 unit and is to be employed in five additional rooms housing dual-energy accelerators (maximum energies of 10 and 18 MV). The doorless entry has received wide approval from the radiation therapists and no concerns have been expressed with respect to unauthorized entry or radiation safety.

Penumbral measurements in water for high-energy x rays.

Ionization chambers of varying inside diameter have been used to investigate the penumbral region of 60Co, 6-MV, and 31-MV x-ray beams. Measurements were made in water at varying depths up to 25 cm for a square field of side length 10 cm. The dependence of the penumbral widths on both the inside diameter of the ionization chamber and the depth in water is established along with the asymmetry of the penumbral distributions about the 50% level. A standard correction is indicated to eliminate the dependence of the measured penumbral widths on the inside diameter of the ionization chamber.

Atypical mycobacteria causing non-pulmonary disease in Queensland.

During the period 1971--7, the Tuberculosis Reference Laboratory in Queensland dealt with 52 isolates of atypical mycobacteria made from non-pulmonary sites under circumstances suggesting complicity in disease. Twenty-four isolates belonging to the MAIS complex were associated with lymph node infections in children. Twelve isolates belonged to the M. fortuitum-chelonei complex; most were from superficial abscesses. Five cases of M. marinum infection and 8 of M. ulcerans disease were detected.

Mycobacteria of the intracellulare-scrofulaceum group in soils from the Adelaide area.

Soil samples from the Adelaide area--where organisms belonging to the Mycobacterium intracellulare-scrofulaceum (MIS) group are rarely encountered in sputum of persons under investigation of pulmonary mycobacterial disease--were examined for the MIS group. Thirty-one per cent were positive for MIS organisms and 17% were positive for MIS serotypes known to be disease-associated. Comparison with an earlier study of soils from the Brisbane area--where this group of organisms is frequently isolated from sputum of persons under investigation for pulmonary mycobacterial disease--suggests that the disease-associated MIS serotypes are significantly more common in the environment of the Brisbane area. This implies a positive correlation, and consolidates existing evidence that the environment is the reservoir of, and a source of infection with, organisms of the MIS group.

Mycobacterium avium associated with chronic pulmonary disease in a Queensland resident.

Bacteriological investigation over an 11-year period has implicated Mycobacterium avium ser I as the most probable cause of chronic pulmonary disease in a resident of south-eastern Queensland. Although the patient had contact with domestic fowls and a pet budgerigar, the source of the organism is uncertain.

Unusual mycobacteria in 5 cases of opportunistic infections.

Five cases of infection due to an unusual mycobacterium are recorded, and the growth requirements and histological findings are discussed. On initial culture, these mycobacteria could be grown only on Lowenstein-Jensen medium containing ferric ammonium citrate, and the histology of the skin lesions was not always typical of mycobacterial disease.

Percentage depth doses for high energy x-rays.

Percentage depth doses for 34 MV betatron X-rays were measured ionometrically for a number of square fields of side 5-20 cm. Significant differences in the depth doses for different field sizes were found in the build-up region and in the depth of maximum dose. A systematic change with depth was also indicated in the exponential region of these curves. These differences are discussed in terms of the changes in the contributions of primary radiation and of scattered radiation from both the collimator and the phantom.

Technetium 99m-labelled-sucralphate isotope scanning in the detection of peptic ulceration.

An isotope scan using sucralphate labelled with technetium-99m has been compared with barium meal in the detection of peptic ulceration in 18 patients with endoscopically proven upper gastrointestinal lesions and eight controls. Gastric (75%) and duodenal (67%) ulcers were detected with identical frequency by isotope scan and barium meal but both were inferior to endoscopy. Structural, non-ulcerated lesions, were not identified by isotope scanning. The scan has potential value in duodenal ulcer disease, the serial assessment of ulcer healing and in paediatric gastroenterology.

Characterization by restriction endonuclease analysis and seroagglutination of strains of Mycobacterium avium and Mycobacterium intracellulare obtained from farmed deer.

Restriction endonuclease analysis and seroagglutination were used to characterize strains of Mycobacterium avium and Mycobacterium intracellulare (collectively, MAI) recovered from 1 local herd and 2 imported shipments of red deer (Cervus elaphus) that developed sensitization to bovine tuberculin during skin testing. A total of 31 MAI strains were isolated from lymph node pools (head, thorax, abdomen, and peripheral regions) of 21 of 29 local deer. Similarly, 15 MAI strains were isolated from the lymph node pools of 12 deer from the 2 imported shipments. Mycobacterial strains were isolated from more than 1 of the lymph node pools of 9 local and 2 imported deer. Most of the strains (59% from local deer, 46% from imported deer) were recovered from the lymph nodes of the head region. After restriction endonuclease analysis of these isolates using the enzymes Bcl I, BstEII, and Pvu II, 26 of the strains from the local herd were separated into 3 groups, each consisting of strains with indistinguishable or closely related patterns. Seroagglutination results indicated that the first of these groups contained strains belonging to serotype 1, the second group contained strains belonging to serotype 8; and the third group of strains belonged to serotype 3 and 9. The 5 remaining strains from the local herd had unrelated restriction patterns. One of these belonged to serotype 3, whereas the remaining 4 could not be serotyped. Restriction analysis of the 15 strains from the imported deer identified 2 groups. Seroagglutination results indicated that 1 group contained strains belonging to serotype 2 and the other group contained strains belonging to serotype 8.(ABSTRACT TRUNCATED AT 250 WORDS)

Subcutaneous granuloma caused by Mycobacterium avium complex infection in a cat.

A localised subcutaneous swelling developed on the nasal bridge of a cat receiving chemotherapy for alimentary tract lymphosarcoma. Cytological and histological examination of representative samples of the lesion demonstrated pyogranulomatous inflammation and abundant acid-fast bacilli. A Mycobacterium sp was cultured from tissue excised from the lesion. Extensive testing at three reference laboratories indicated the strain was a member of the Mycobacterium avium complex. The infection was treated successfully by cytoreductive surgery and a 6 weeks course of orally administered clofazimine.