Transplantation at the nexus of behavioral economics and health care delivery

The transplant surgeon's decision to accept and utilize an organ typically is made within a constrained time window, explicitly cognizant of numerous health-related risks and under the potential influence of considerable regulatory and institutional pressures. This decision affects the health of two distinct populations, those patients receiving organ transplants and those waiting to receive a transplant; it also influences the physician's life and their institute's productivity. The numerous, at times nonaligned, incentives established by the complex clinical and regulatory environment, have been derived specifically to influence physicians' behaviors, and though well intended, may lead to responses that are nonoptimal when considering the myriad stakeholders being influenced. This may compromise the quality of care provided to the population at risk, and has potential to influence the physician-patient relationship. A synergistic collaboration between transplant physicians and economists that is focused on this decision environment may help to alleviate these strains. This viewpoint discusses behavioral economic principles and how they might be applied to transplantation. Specifically, the previous medical decision-making literature on transplantation will be reviewed and a discussion on how a behavioral model of physician decision making can be utilized will be explored. To date this approach has not been integrated into transplantation decision making.

Antibody responses to HPV6b E polyproteins and production of monoclonal antibodies

A range of fusion constructs (expressed in Escherichia coli) were produced that contained two or more HPV6b E proteins, producing a single continuous amino acid sequence corresponding to the sequences of the individual E proteins. The constructs also included a C-terminal hexahistidine tag fused in-frame to aid purification. The fusion proteins (polyproteins) were semipurified by Ni(++) metal affinity chromatography under denaturing conditions. Immunization of BALB/c mice with these polyproteins resulted in the production of specific E protein antibodies. The draining lymph nodes from these mice were used to produce monoclonal antibodies (MAbs). The specificity of the polyclonal and MAbs was confirmed by immunoblotting and by screening for reaction with a series of synthetic peptides of E proteins. HPV E polyproteins were found to be immunogenic and immunization with the polyproteins resulted in specific antibody responses to the component E proteins.

Automated selection of anti-protein aptamers

The in vitro selection of nucleic acid binding species (aptamers) is frequently repetitive, time-consuming, and poorly adapted to high-throughput applications. We have adapted automated workstations to select anti-protein aptamers; as an example, we demonstrated the selection of anti-lysozyme aptamers that function as efficient inhibitors of cell lysis. The increases in throughput brought about by automation should potentiate the application of aptamer technology to the rapidly growing field of proteomics.

Cytotoxic T cell polyepitope vaccines delivered by ISCOMs

CD8 alphabeta cytotoxic T lymphocyte (CTL) polyepitope or polytope vaccines have traditionally been delivered using recombinant vector or DNA based delivery modalities. Here we show the delivery of polytope vaccines in the form of either synthetic polypeptides or recombinant polytope proteins by ImmunoStimulatory COMplexes (ISCOMs(R)). Induction of multiple protective CTL responses by these polytope-ISCOM formulations were comparable to viral vector or DNA based delivery modalities as assessed by IFNgamma ELISpot, chromium release and viral challenge assays. Measurement of CTL responses specific for the different epitopes revealed immunodominance patterns, which were largely independent of the vaccine vector or the order of the epitopes in the polytope. ISCOMs thus emerge as a viable human delivery modality for protein-based polytope vaccines.

Toward automated nucleic acid enzyme selection

Methods for automation of nucleic acid selections are being developed. The selection of aptamers has been successfully automated using a Biomek 2000 workstation. Several binding species with nanomolar affinities were isolated from diverse populations. Automation of a deoxyribozyme ligase selection is in progress. The process requires eleven times more robotic manipulations than an aptamer selection. The random sequence pool contained a 5' iodine residue and the ligation substrate contained a 3' phosphorothioate. Initially, a manual deoxyribozyme ligase selection was performed. Thirteen rounds of selection yielded ligators with a 400-fold increase in activity over the initial pool. Several difficulties were encountered during the automation of DNA catalyst selection, including effectively washing bead-bound DNA, pipetting 50% glycerol solutions, purifying single strand DNA, and monitoring the progress of the selection as it is performed. Nonetheless, automated selection experiments for deoxyribozyme ligases were carried out starting from either a naive pool or round eight of the manually selected pool. In both instances, the first round of selection revealed an increase in ligase activity. However, this activity was lost in subsequent rounds. A possible cause could be mispriming during the unmonitored PCR reactions. Potential solutions include pool redesign, fewer PCR cycles, and integration of a fluorescence microtiter plate reader to allow robotic 'observation' of the selections as they progress.

Paying doctors more: use of musculoskeletal specialists and increased physician pay to decrease workers' compensation costs

Previous studies evaluating workers' compensation care systems used retrospective controls. We performed a concurrent effectiveness study comparing a WC system that used visiting musculoskeletal specialists to assist primary care physicians with a typical discounted-fee, WC, managed-care system. In the new specialist-direct system, physicians could not profit from self-referral, but were paid 35% to 69% more per patient visit than doctors in the discounted-fee clinics. All claims filed by all employees of two hotels for 2 years were examined. Patients had self-selected either a specialist-direct or a discounted-fee clinic, and the entire cost of the claim was assigned to either system of care. Claim costs were 63% lower in the specialist-direct system (P < 0.001). Medical costs were 45% less (P < 0.014), and indemnity 85% less (P < 0.001), in this system. Claims were closed nearly 6 months faster in the specialist-direct system (P < 0.0001). Indemnity claims were more common in the discounted-fee system (P < 0.0001). Claimant and injury characteristics were not significantly different between the systems. This new care model is a cost-effective alternative to discounted WC managed care. Discounting the services of the primary treating physician may result only in cost-shifting, not cost-saving.

The complexities of DNA computation

Over the past few years, a handful of insightful researchers have bridged the gap between biological computing theory and actual DNA-based computation. By using ingenious encoding techniques and clever molecular-biological manipulations, simple versions of computationally complex problems have been experimentally approached or resolved. However, the technical problems revealed during the execution of these scientific set pieces make it unlikely that DNA will ever rival silicon for the solution of any real-world problem.

Uptake and adjuvant activity of orally delivered saponin and ISCOM vaccines

Saponins are a highly heterogenous group of glycosides which are common in plants and have been known to have adjuvant properties since the 1920s. The immunostimulating complex or ISCOM is a particulate adjuvant/antigen delivery system. ISCOMs are open cage-like complexes typically with a diameter of about 40 nm which are built up by cholesterol, lipid, immunogen and saponins from the bark of Quillaia saponaria Molina (soap bark tree). ISCOMs and saponins are used as adjuvants in some commercial veterinary vaccines and have been examined as adjuvants in a large number of human experimental vaccines. This review describes the current status and potential of saponin and ISCOMs as adjuvants for orally-administered vaccines with special reference to the induction of local and systemic immune responses and interactions with the intestinal epithelium. The structure and composition of saponins and ISCOMs will also be reviewed.

ISCOMs: an adjuvant with multiple functions

Aluminum salts are currently the only widely used adjuvant for human vaccines. Over the past 10-15 years, a large research effort has attempted to find novel adjuvants with ability to induce a broad range of immune responses, including cell-mediated immunity. The immunostimulating complex or ISCOM is one adjuvant with multiple adjuvant properties. ISCOMs are open cage-like complexes typically with a diameter of about 40 nm that are built up by cholesterol, lipid, immunogen, and saponins from the bark of the tree Quillaia saponaria Molina. ISCOMs have been demonstrated to promote antibody responses and induce T helper cell as well as cytotoxic T lymphocyte responses in a variety of experimental animal models, and have now progressed to phase I and II human trials. This review describes recent developments in the understanding of the structure, composition, and preparation of ISCOMs and will cover important aspects of the understanding of the adjuvant functions of ISCOMs and how they act on the immune system.

Automated RNA selection

In vitro selection can be used to generate nucleic acid ligands (aptamers) to target molecules ranging in size and structure from cations to cells. However, the selection process is repetitive and time-consuming. We have automated a protocol for in vitro selection using an augmented Beckman Biomek 2000 pipetting robot. The automated selection procedure requires the integration of four devices and the optimization of four molecular biology methods, and is one of the most complex automated protocols attempted to date. Initial attempts at selection yielded robust replication parasites, but optimization of the automated selection procedure suppressed the emergence of these parasites and led to the selection of true nucleic acid ligands. Automated selection can now be used to generate nucleic acid aptamers in days rather than weeks or months.

The gain of three mitochondrial introns identifies liverworts as the earliest land plants

The first evidence for the emergence of land plants (embryophytes) consists of mid-Ordovician spore tetrads (approximately 476 Myr old). The identity of the early plants that produced these spores is unclear; they are sometimes claimed to be liverworts, but there are no associated megafossils, and similar spores can be produced by a diversity of plants. Indeed, the earliest unequivocal megafossils of land plants consist of early vascular plants and various plants of uncertain affinity. Different phylogenetic analyses have identified liverworts, hornworts and bryophytes as each being the first lineage of land plants; the consensus of these conflicting topologies yields an unresolved polychotomy at the base of land plants. Here we survey 352 diverse land plants and find that three mitochondrial group II introns are present, with occasional losses, in mosses, hornworts and all major lineages of vascular plants, but are entirely absent from liverworts, green algae and all other eukaryotes. These results indicate that liverworts are the earliest land plants, with the three introns having been acquired in a common ancestor of all other land plants, and have important implications concerning the early stages of plant evolution.

Adjuvants--a classification and review of their modes of action

Since early this century, various substances have been added to vaccines and certain formulations have been devised in an attempt to render vaccines more effective. Despite a plethora of options, only aluminium salts have gained acceptance as human vaccine adjuvants and even veterinary vaccines are largely dependent upon the use of aluminium salts. Currently, many new vaccines are under development and there is a desire to simplify vaccination schedules both by increasing the number of components per vaccine and decreasing the number of doses required for a vaccine course. New, more effective adjuvants will be required to achieve this.

Snake envenomation in cats and its detection by rapid immunoassay

OBJECTIVE

To determine the usefulness of a snake venom detection kit (SVDK) in the management of envenomed cats.

DESIGN

A clinical study.

ANIMALS

Twenty-two cats were investigated.

PROCEDURE

Cats injected subcutaneously with approximately 0.25 or 1.0 lethal dose (LD) of tiger snake venom or 1 or 4 LD of brown snake venom were observed for clinical symptoms of envenomation at intervals over the ensuring 24 to 48 hours(h). Blood and urine samples were taken at regular intervals and assayed in a quantitative laboratory assay for snake venoms. Selected samples were assayed in parallel in a rapid, semi-quantitative SVDK.

RESULTS

The studies showed that it was important to estimate the elapsed time from envenomation to presentation. If this time was less than 8 h, blood was the most appropriate sample and a negative result should exclude serious envenomation. If the elapsed time exceeded 8 h, it was essential that urine be sampled. Venom levels in urine were high at 8 h and approached the level of test sensitivity over 24 to 48 h; however by this time clinical signs were obvious in endangered cats.

CONCLUSIONS

Careful use of the SVDK is a valuable aid in the management of a potentially envenomed cat.

Evaluation of a novel diagnostic test for canine parvovirus

The CPV ELISA detection kit (CSL Ltd., Melbourne Australia) was developed as a rapid field test for the detection of canine parvovirus (CPV) antigen in canine faecal samples. The kit utilises a novel concept in enzyme immunoassay (ELISA) where the conjugate is lyophilised along with the solid-phase capture antibody in the test well. The CPV ELISA was compared to the haemagglutination assay (HA) test using electron microscopy (EM) and/or virus isolation (VI) to confirm infection. The CPV ELISA had a sensitivity of 87% and a specificity of 100% compared to 87% and 63% respectively for the HA. The poor specificity of the HA results in a low positive predictive value of 51% compared to 100% for the CPV ELISA. The CPV ELISA requires no specialised equipment, is simple to perform and provides a visible result in less than 15 minutes.

Removal of false-positive reactions from plasma in an enzyme immunoassay for bovine interferon-gamma

A monoclonal antibody-based sandwich enzyme immunoassay (EIA) for bovine interferon-gamma (IFN-gamma) has been developed and can be used in conjunction with a whole blood culture system to diagnose tuberculosis in cattle. During its development, normal bovine plasma samples were tested to establish background levels of circulatory IFN-gamma. Of 191 samples tested, 81 (42.4%) were positive (OD > 0.1) when tested undiluted in intact monoclonal antibody (IgG1)-coated wells compared to only 8 (4.2%) in F(ab')2-coated wells, which suggested non-specific interference in the EIA rather than circulatory IFN-gamma. Reactivity of all remaining samples was removed by diluting plasmas 1/2 with 1% casein-PBS-0.05% Tween 20 supplemented with an optimum amount (5%) of normal mouse serum (NMS). Serum pools derived from BALB/c, DBA/2, C3H/HeJ, CBA/CaH and Swiss, but not C57BL/6J, mice were found to inhibit equally the reactions of five strong false-positive bovine plasma samples but had no effect on the titre of IFN-gamma in the sample. Sera from other species tested were less effective. This suggests that the interfering factors possess a high degree of specificity, since the immunoglobulin heavy chain of IgG1 produced by all these five strains of mice are allotypically identical and different to IgG1 produced by C57BL/6J mice. The use of F(ab')2 antibody fragments to coat plate wells and sample diluent containing 5% NMS has resulted in an EIA for bovine IFN-gamma that is virtually free from false-positive reactions, has a high degree of reproducibility and a sample detection limit equivalent to approximately 80 pg/ml recombinant bovine IFN-gamma.

A novel format for a rapid sandwich EIA and its application to the identification of snake venoms

A rapid sandwich enzyme immunoassay format is described where conjugate is lyophilised within the well in which the test reaction will occur. The format is straight forward to manufacture, has a prolonged shelf life, and eliminates one incubation and wash step from the usual test procedure. The technology has been applied to the development of a rapid assay for the identification of snake venom in clinical specimens. The resultant assay was specific and sensitive, provided rapid results and was appropriate for field use.

The gamma-interferon assay for diagnosis of bovine tuberculosis in cattle: conditions affecting the production of gamma-interferon in whole blood culture

The recently developed gamma-interferon (IFN-gamma) assay system for the diagnosis of bovine tuberculosis in cattle has been accredited by the Standing Committee on Agriculture for use in Australia. In this test system, whole blood is incubated with tuberculin purified protein derivative (PPD) antigens for 16 to 24 h. The plasma is then collected and assayed for IFN-gamma production using an enzyme immunoassay (EIA). The assay system has proven to be a rapid, sensitive and inexpensive method for measuring antigen specific cell-mediated reactivity when compared with the more traditional lymphocyte proliferation assay. The IFN-gamma assay is the first in-vitro cellular assay to be used as a routine diagnostic test in veterinary medicine. While the IFN-gamma EIA has been optimised, several conditions affecting the production of IFN-gamma in whole blood culture needed investigation. We determined that optimal IFN-gamma production required the use of heparinised blood, cultured with 20 micrograms/ml of PPD within 8 h of collection. The use of blood collected post mortem resulted in reduced sensitivity for the assay. The kinetics of IFN-gamma release were established as were the effects of intradermal tuberculin testing on the IFN-gamma assay.

Immunisation against ovine caseous lymphadenitis: correlation between Corynebacterium pseudotuberculosis toxoid content and protective efficacy in combined clostridial-corynebacterial vaccines

Groups of sheep were dosed with vaccines containing Corynebacterium pseudotuberculosis toxoid combined in varying amounts with 5 clostridial antigens. Resistance of the sheep to infection with C pseudotuberculosis was tested at 1, 6 and 12 months after vaccination by infection with pus from ovine lymph glands actively infected with C pseudotuberculosis. The outcome was assessed 3 months after challenge by slaughter and inspection of the sheep for caseous lymphadenitis lesions. Protection was demonstrated by a significant reduction in the proportion of immunised sheep exhibiting lesions compared with control sheep, and by fewer abscesses in affected immunised sheep than in affected control sheep. A positive correlation was found between amount of C pseudotuberculosis toxoid administered and degree of protection obtained. Chromatographically-purified toxoid induced essentially the same protection, suggesting that anti-toxic immunity is the major factor in protection.

A comparison of the sensitivity and specificity of enzyme immunoassays and time-resolved fluoroimmunoassay

Time-resolved fluoroimmunoassay (TR-FIA) and various enzyme immunoassays (EIA) were compared in order to determine the detection system which showed the greatest degree of sensitivity without sacrificing specificity. The system chosen for the evaluation of these assays was the detection of antibodies to human immunodeficiency virus (HIV). For EIA, horseradish peroxidase (HRP) and alkaline phosphatase (AP) were investigated, each with a number of different substrates. HRP with its fluorogenic substrate, 3-(p-hydroxyphenyl)propionic acid (HPPA) was 1.6 times (p less than 0.01) more sensitive than with 3,3',5,5'-tetramethylbenzidine (TMB) and four times (p less than 0.001) more sensitive than with 2,2'-azino-di(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS). AP with its fluorogenic substrate, 4-methylumbelliferyl phosphate (4MeUP), was 6-7 times (p less than 0.001) more sensitive than with phenolphthalein monophosphate (PMP) and 8-13 times (p less than 0.001) more sensitive than with p-nitrophenyl phosphate (pNPP). TR-FIA with Eu3(+)-labelled anti-human IgG was equivalent in sensitivity to HRP with TMB and AP with 4MeUP.

Development and evaluation of a rapid absorbed enzyme immunoassay test for the diagnosis of Johne's disease in cattle

An absorbed enzyme immunoassay (EIA) test for Johne's disease in cattle was developed in which absorption of cross-reacting antibodies occurred as a rapid reaction in solution rather than overnight with whole organisms and a subsequent centrifugation step. Total test time was reduced to less than 2 h with a minimum of manipulations. The test was evaluated in cattle herds from Johne's disease-endemic and Johne's disease-free regions of Australia. Specificity was 99.8%. Calculations of sensitivity were affected by the history of the herd under test. However, the EIA detected in excess of 80% of animals before onset of clinical disease and 65% of faecal shedders were EIA positive on, or before, first detection of Mycobacterium paratuberculosis in their faeces. The test should aid epidemiological studies and be a useful tool in the management and control of Johne's disease.

Evaluation of a commercial enzyme-linked immunosorbent assay for Johne's disease

A new commercial kit for diagnosis of bovine paratuberculosis (Johne's disease), called the Johne's Absorbed EIA (enzyme immunoassay; Commonwealth Serum Laboratories, Parkville, Victoria, Australia), was evaluated by using serum specimens from the National Repository for Paratuberculosis Specimens. The evaluation was specifically designed to measure test sensitivity and specificity for detection of dairy cattle with subclinical paratuberculosis. The case definition of subclinical bovine paratuberculosis was isolation of Mycobacterium paratuberculosis from fecal samples or internal organs of cattle without diarrhea or chronic weight loss. Animals designed as free of the disease originated exclusively from four herds in Wisconsin that were certified to be free of disease. The kit had a sensitivity of 47.3% for serum specimens from 150 infected cattle. The test detected 59.7% of animals that shed M. paratuberculosis in their feces, as defined by conventional fecal culture, at the time of serum collection. Testing of 196 serum specimens from cattle without paratuberculosis yielded two false-positive results; the test specificity was thus 99.0%. Decision analysis procedures on the economics of using the kit in a test-and-cull disease control program indicated it would be cost-effective in any herd with a true paratuberculosis prevalence of greater than or equal to 3%. Comparison of the sensitivity and specificity of the Johne's Absorbed EIA with those of other tests for detection of subclinical paratuberculosis indicated that it may be the most accurate commercially available test at present and better than standard complement fixation test used in the United States.

Characterization of an Escherichia coli mutant pleiotropically altered in membrane-bound oxidoreductase activities

An Escherichia coli mutant pleiotropically altered in membrane-bound oxidoreductase activities was isolated following nitrosoguanidine treatment. Mutant R23 was able to grow on glucose, but was unable to grow on succinate or other oxidizable substrates as a sole energy source. Isolated membranes prepared from R23 failed to oxidize succinate and formate; while NADH was oxidized at a reduced rate by membranes. The mutant also exhibited markedly reduced cytochrome content, but normal DL-lactate PMS reductase and H(+)-translocating ATPase activities relative to the parent strain. Bacteriophage Plkc was used to transduce R23 to growth on glycerol, DL-lactate or succinate; regardless of the selection procedure, each of the 179 transductants had gained the ability to grow on all three substrates. The suc- mutation in R23 appeared to be responsible for the loss of growth on oxidizable substrates, altered membrane-bound oxidoreductase activities, resistance to neomycin, and reduced levels of cytochrome components. The suc- mutation was localized in the 6 to 6.5 min region of the E. coli chromosome map utilizing episomal transfers.

Increased monoclonal antibody ascites production in mice primed with Freund's incomplete adjuvant

The production of monoclonal antibodies is conveniently achieved by propagation of antibody-secreting hybridoma cells as ascites tumours in mice. With a view to improve production and minimise animal usage, the choice of primer (pristane or Freund's incomplete adjuvant (FIA] and the effect of sex of mouse (female vs. uncastrated male) upon antibody yields were compared. The volume of ascitic fluid harvested from 134 FIA-primed mice was 697 ml, which was significantly (P less than 0.02) greater than the 343 ml collected from 116 pristane-primed mice. Moreover, FIA-primed mice required tapping for only 11 days (90% in 7 days) compared to the 17 days needed for pristane-primed mice. While there was little difference between the mean IgG1 concentration (as determined by enzyme immunoassay) of both ascites pools (4.9 mg/ml compared to 4.6 mg/ml), the volume differences equated to yields of 25.5 mg/mouse and 13.5 mg/mouse respectively. The FIA-primed mice were also shown to produce on average more (P less than 0.02) ascites per day. There was no significant difference found between the yield of monoclonal antibodies obtained from either uncastrated males (22.1 mg/mouse) or females (23.1 mg/mouse). The use of FIA to prime mice for the in vivo production of monoclonal antibodies should improve the yield to over 20 mg/mouse, thereby reducing the number of mice required.

A sandwich enzyme immunoassay for bovine interferon-gamma and its use for the detection of tuberculosis in cattle

An in vitro cellular assay for bovine tuberculosis has recently been developed. This assay detects gamma-interferon released in response to specific antigen in a whole blood culture system. The bio-assay previously described for the detection of bovine gamma-interferon (IFN-gamma) has now been replaced with a sandwich enzyme immunoassay (EIA) which utilises two monoclonal antibodies to bovine IFN-gamma. The EIA detects less than 25pg/ml of recombinant bovine IFN-gamma and is specific for biologically active bovine IFN-gamma; and does not detect bovine alpha or beta interferon. IFN-gamma from sheep, goat and buffalo, but not from pig, deer or man, are also recognised by the EIA. The bovine IFN-gamma EIA when used in conjunction with the whole blood culture system has resulted in a simple, rapid and sensitive in vitro assay for specific cell mediated immune responsiveness to M. bovis infection in cattle.

An Escherichia coli mutant conditionally altered in respiratory chain components

Nitrosoguanidine mutagenesis was employed to isolate an Escherichia coli mutant conditionally altered in respiratory chain components. Mutant R25 was able to grow on glucose, fructose, and glycerol but failed to grow on succinate and acetate (suc-). Also, R25 exhibited leaky growth on DL-lactate, fumarate, and malate (lct*). The lct* mutation pleiotropically affected a number of respiratory chain components and its expression was conditional with the growth substrate. Glucose-grown R25 resting cell suspensions oxidized DL-lactate and formate; however, these two substrates were not oxidized by fructose- or glycerol-grown cell suspensions. The same conditional pattern was observed for the concentration of cytochrome components, the membrane-associated oxidation of NADH and formate, and formate phenazine methosulfate (PMS) reductase activity; succinate oxidase and PMS reductase activities were not exhibited by membranes under any growth condition due to the suc- mutation. R25 membrane-associated H(+)-translocating ATPase activity was not conditional with the growth substrate. R25PC, a spontaneous lct+ suc- partial revertant of R25, did not exhibit the conditional pattern of R25. The lct* mutation was found to map in the 27-30-min region and the suc- mutation in the 15-17-min region of the E. coli genome. Two distinct classes of R25 P1kc transductants were isolated that differed in both their growth response on succinate and DL-lactate and their oxidase activities.

Expression of foreign DNA in Chlamydomonas reinhardtii

A chimeric octopine synthase-neomycin phosphotransferase (ocs-nptII) gene was used to transform Chlamydomonas reinhardiii to kanamycin resistance. Southern hybridization using DNA isolated from one transformant, T6.1, indicated that the entire ocs-nptII gene and at least part of the plasmid were integrated into nuclear DNA. Neomycin phosphotransferase II activity has been detected in T6.1 cell extracts. Northern hybridizations, employing a radiolabeled ocs-nptII sequence, revealed a T6.1 transcript of approximately the same size as a homologous transcript isolated from E. coli carrying the nptII gene. Although T6.1 is an extremely rare example of a stable C. reinhardtii transformant, its occurrence nevertheless indicates that bacterial genes can be expressed in the nucleus of the alga.

Escherichia coli formate dehydrogenase mutants with altered selenopolymer profiles

Four classes of Escherichia coli mutants deficient in either or both of their anaerobic selenium-containing formate dehydrogenases (FDH) were isolated. A class I mutant devoid of FDHH activity specifically linked to benzyl viologen (BV) produced a small amount of the FDHH 80,000 dalton selenopeptide. Three class II mutants were deficient in FDHN activity specifically linked to phenazine methosulfate (PMS) and exhibited a selenopeptide "doublet" rather than the FDHN 110,000 dalton selenosubunit. Three class III mutants were selenium incorporation deficient and did not exhibit either FDH activity or 75Se-labeled selenopolymers. A class IV mutant was devoid of PMS-linked FDHN activity; neither its FDHN 110,000 dalton selenosubunit nor its BV-linked FDHH activity was fully regulated by nitrate.

An enzyme immunoassay for isotyping mouse monoclonal antibodies

A rapid, simply performed and relatively inexpensive enzyme immunoassay for isotyping mouse monoclonal antibodies is described, based on the urease/urea system. Because of the high sensitivity (less than 0.1 microgram/ml of immunoglobulin can be detected in cell culture medium) no treatment of the hybridoma supernatant sample is required prior to assay, and the isotype of a mouse immunoglobulin can be determined in about thirty minutes.

Immunogenicity of specific Bordetella pertussis surface antigens in diphtheria-tetanus-pertussis (DTP) vaccines

The predominant causative organism of whooping cough in Australia is of a serotype which has normally been associated overseas with unvaccinated communities. Australian DTP vaccines pass the statutory mouse test for Bordetella pertussis potency but this test is now believed to be relatively insensitive to certain factors, especially the major type-specific agglutinogens, which are presumably also important in the human host-parasite relationship. Because endemic B. bronchiseptica infections make some laboratory animals unsatisfactory for testing B. pertussis agglutinin responses, we have developed a test in which young farm sheep were immunized with vaccines. Type-specific agglutinins in their sera were assayed after absorption of non-specific agglutinins by suspensions of selected bordetella strains. Three well-reputed European DTP vaccines and two recent batches of Australian DTP vaccine were tested and compared thus. All evoked significant agglutinin responses to the main agglutinogens.

Hospital renovation projects: phased construction requires planning at its best

Building a new hospital facility is a difficult task, but adding onto and renovating an existing structure while normal activity continues is even more difficult. Project planners, designers, contractors, and hospital managers must carefully program the joint effort of construction and hospital operation. Several factors in the construction process and potential problems for hospital operations are described to help hospital managers better anticipate difficulties before plans are finalized and construction commences.

Storage of pathogenic leptospires in liquid nitrogen

The virulence and viability of various serovars of Leptospira interrogans were successfully preserved by storage in liquid nitrogen. Dimethyl sulphoxide at a final concentration of 2.5% (v/v) was added as cryoprotectant to a culture of leptospires grown in Ellinghausen-McCullough-Johnson-Harris medium. Ampoules were cooled at a controlled rate of 1 degree-3 degrees C/min to -70 degrees C, then transferred to the liquid phase of a liquid nitrogen storage unit. Glycerol was discounted as a cryoprotectant as it was found to be approximately 10 times more toxic than dimethyl sulphoxide to four of five serovars used in this study. The viability of nine strains has so far been observed over a period of 8-22 months storage in liquid nitrogen and full viability of all strains has been preserved over this period. Virulence of strains of serovars pomona and hardjo was well preserved, as demonstrated by challenge tests in guinea pigs and domestic pigs.

Inactivation of poliovirus with beta-propiolactone

The recovery of poliovirus D-antigen after virus inactivation was studied for two inactivating agents (beta-propiolactone and formalin) using the three poliovirus types (Sabin types 1, 2 and 3). With beta-propiolactone (BPL), D-antigen recoveries were high (88, 88 and 60%, respectively) but were significantly less when formalin was used (22, 15 and 25%). beta-Propiolactone inactivated virus was purified, combined with Freund's adjuvant and used to hyperimmunize rabbits. High titres (50 000-200 000) of specific neutralizing antibody were obtained.

The infectivity of Encephalitozoon cuniculi in vivo and in vitro

The infectivity of Encephalitozoon cuniculi grown in cell cultures was determined in cultured cells and in wild and domestic rabbits. The ratio of the total to tissue culture viable count was 1,300 (median of seven determinations). The mean ratio of intact spore count to total count, as determined by electron microscopy was 0.12. Although variation between infectivity experiments was large, the median animal infective dose contained 51 FFU (cell culture focus-forming units) for wild rabbits (Oryctolagus cuniculus) and 40 FFU for domestic rabbits. These two infectivities were not statistically different.

An evaluation of the use of a pH indicator for the detection of beta-lactamase in enzyme immunoassay

The use of a mixed pH indicator containing bromocresol purple and bromothymol blue was evaluated for the detection of beta-lactamase activity in enzyme immunoassays (EIA) based on this enzyme. The EIA was found to correlate well with a bioassay for antibodies to tetanus toxoid in sheep sera. Results could be read spectrophotometrically at 450 nm or visually as a colour change from dark blue to yellow. The mixed pH indicator was found to have a number of desirable features including good stability, ease of preparation and a sharp colour change which makes the system suitable for visual determination of titration end points.

Immune response and reactions to various dose regimens for raising hyperimmune antisera in sheep

To determine the optimum procedure for raising hyperimmune sera to tetanus toxin, three adjuvants, four antigen preparations and two routes of administration in various combinations were investigated in sheep. Oil-in-water adjuvants alone or in combination with aluminum gels were superior to aluminium gels on their own. This disadvantage of aluminium gels was partially but not completely abrogated when the frequency of doses was increased to three per week. Intensity of local reaction was strongly correlated with immune response; the more immunogenic a dose, the more reactive. Reactivity of oily adjuvants could be lessened by use of a more suitable route of administration, thus oily adjuvants appeared suitable for use when administered by the intraperitoneal route even though moderate to severe reactions resulted from subcutaneous injections. Of other variables investigated, toxin did not confer any advantage over toxoid as an immunogen, purified toxoid was a significantly better immunogen than unpurified toxoid and two large bleeds (30% of total blood volume each) every six weeks rather than 20 ml test bleeds did not affect the titre of the hyperimmune serum produced.

Enzyme immunoassay for antibodies to membrane associated antigen of varicella zoster virus

An in situ enzyme immunoassay to viral membrane antigen was developed to enable the specific estimation of antibodies to varicella zoster (VZ) virus. The technique was compared with a modified fluorescent antibody to membrane antigen (FAMA) procedure and with the complement fixation (CF) test by parallel assay of 352 plasma samples. The enzyme immunoassay (EIA) procedure showed very good correlation with the modified FAMA procedure, and both were far more specific than the CF test. This specificity was achieved by the use, in the EIA, of VZ virus-infected cells grown and fixed in situ with glutaraldehyde. Thus the only virus antigens accessible to antibody were the VZ-specific antigens expressed at the cell membrane, cross-reactions with herpes simplex virus antibodies thereby being avoided.

A rapid semi quantitative capillary enzyme immunoassay for digoxin

A rapid and sensitive enzyme immunoassay (EIA) which does not require highly trained personnel or specialised instrumentation is described for the estimation of digoxin in serum, plasma or whole blood samples. The method is based on the ability of digoxin in a clinical sample to inhibit the binding of urease-conjugated sheep-antidigoxin immunoglobulin to a glass capillary tube coated internally with a human serum albumin-digoxin conjugate. The bound enzyme activity can then be measured using a substrate solution containing urea and a pH indicator, most suitably bromocresol purple. The enzymic hydrolysis of urea produces ammonia which causes a vivid yellow to purple colour change in the pH indicator. Plasma samples from 92 patients receiving digoxin were screened in parallel with reference plasma containing 1.3 or 3.8 nmol/l digoxin. The results were available within a total test time of 30 min, and showed excellent correlation with those obtained by radioimmunoassay.

A comparison of enzyme immunoassay and bioassay for the quantitative determination of antibodies to tetanus toxin

Antibodies to tetanus toxin were induced in sheep by hyperimmunization over 24 weeks. Bleeds taken at weeks 4, 8, 20 and 30 were assayed for antibody titre by both an enzyme immunoassay (EIA) using a newly-described urease enzyme/substrate system and by bioassay in mice. There was a very good correlation between the two assay systems and, with the exception of the week 4 Bleeds, the relationship was the same at all stages of hyperimmunization regardless of titre, adjuvant, or whether toxin or toxoid was used as immunogen or for coating the plates. The results establish that the EIA can replace the bioassay for the determination of tetanus antitoxin in ovine sera.

An investigation of the use of urease-antibody conjugates in enzyme immunoassays

The development of urease (E.C.3.5.1.5) as a label for enzyme immunoassay (EIA) procedures is described and the use of such conjugates illustrated with examples. Urease catalyzes the hydrolysis of urea to carbon dioxide and ammonia. The production of ammonia may be detected readily by a pH shift which we have found best indicated by the vivid colour change (yellow to purple) of bromocresol purple incorporated in the substrate solution. This enzyme-substrate system offers a number of important advantages. The substrate in aqueous solution is stable, titration end points are sharp and readily visible and the enzyme is not inhibited by sodium azide. Thus, test reagents may be prepared with this preservative and stored ready to use. Urease of high specific activity is commercially available and because it does not occur in mammalian tissues, it is suitable for use in EIA tests to detect cell-associated antigens and their antibodies. Finally, the enzyme reaction may be stopped by the addition of organomercurial preservatives, thus allowing storage of developed tests for later examination.

Photopigments in Rhodopseudomonas capsulata cells grown anaerobically in darkness

The phototrophic bacterium Rhodopseudomonas capsulata can obtain energy for dark anaerobic growth from sugar fermentations dependent on accessory oxidants such as trimethylamine-N-oxide or dimethyl sulfoxide. Cells grown for one to two subcultures in this fashion, with fructose as the energy source, showed approximately a twofold increase in bacteriochlorophyll content (per milligram of cell protein) and developed extensive intracytoplasmic membranes in comparison with cells grown photosynthetically at saturating light intensity. Cells harvested from successive anaerobic dark subcultures, however, showed progressively lower pigment contents. After ca. 20 transfers, bacteriochlorophyll and carotenoids were barely detectable, and the amount of intracytoplasmic membrane diminished considerably. Spontaneous mutants incapable of producing normal levels of photosynthetic pigments arose during prolonged anaerobic dark growth. Certain mutants of this kind appear to have a selective advantage over wild-type cells under fermentative growth conditions. Of four pigment mutants characterized (two being completely unable to produce bacteriochlorophyll), only one retained the capacity to grow photosynthetically.

Toxoplasmosis and the wild rabbit Oryctolagus cuniculus in Victoria, Australia with suggested mechanisms for dissemination of oocysts

Sera or serum eluates from 1697 wild rabbits [Oryctolagus cuniculus (L)], collected over the past 10 years from 24 sites in 5 geographic regions of Victoria, were examined for antibodies to Toxoplasma gondii. Sera generally were classified into three broad groups, negative (titre less than 10), weakly reactive (titre 10 to 100) and strongly positive (titre greater than 1000). Strongly positive sera came from rabbits collected in a small number of localized areas, most significantly the Melbourne and Metropolitan Board of Works (MMBW) Sewerage Farm at Werribee and Mud Island in Port Phillip Bay.

Resolution of distinct selenium-containing formate dehydrogenases from Escherichia coli

Formate dehydrogenase, a component activity of two alternative electron transport pathways in anaerobic Escherichia coli, has been resolved as two distinguishable enzymes. One, which was induced with nitrate reductase as a component of the formate-nitrate reductase pathway, utilized phenazine methosulfate (PMS) in preference to benzyl viologen (BV) as an artificial electron acceptor and appeared to be exclusively membrane-bound. A second formate dehydrogenase, which was induced as a component of the formate hydrogenlyase pathway, appeared to exist both as a membrane-bound form and as a cytoplasmic enzyme; the cytoplasmic activity was resolved completely from the PMS-linked activity on a sucrose gradient. When E. coli was grown in the presence of 75Se-selenite, a 110,000-dalton selenopeptide, previously shown to be a component of the PMS-linked enzyme, was induced and repressed with this activity. In contrast, an 80,000-dalton selenopeptide was induced and repressed with the BV-linked activity and exhibited a distribution similar to the BV-linked formate dehydrogenase in cell fractions and in sucrose gradients. The results indicate that the two formate dehydrogenases are distinguishable on the basis of their artificial electron acceptor specificity, their cellular localization, and the size of their respective selenoprotein components.

Simple diagnostic test for antibodies to Encephalitozoon cuniculi based on enzyme immunoassay

Rabbit antibodies against Encephalitozoon cuniculi were detected in an enzyme immunoassay procedure in which antigen was grown and used in situ. The test appeared to be more sensitive than the indirect immunofluorescence test with which it was compared, but gave essentially the same results for the 64 sera evaluated. This procedure will allow any laboratory with cell-culture facilities to produce a diagnostic antigen without the need for antigen processing. It is simple and reliable, and does not require specialized equipment or microscopic assessment.

An immunofluorescence study of influenza virus filament formation

A study is described in which filamentous forms of influenza virus were observed budding from host cell surfaces. Cell cultures infected with influenza virus were stained by indirect immunofluorescence using an antiserum to purified haemagglutinin. Filaments greater than 100 micrometers in length, with several branch points along their length were observed; the number and length of filaments varied according to the virus strain and the time after infection. Examination of infected cells by electron microscopy confirmed the presence of branched structures with an ultrastructure typical of filamentous forms of influenza virus. The immunofluorescence technique was quicker than thin section electron microscopy and was a more sensitive procedure for the detection of filamentous forms of influenza virus than electron microscopy using negative stain. It also enabled the antigenic composition of the filaments to be observed.

Physiology of dark fermentative growth of Rhodopseudomonas capsulata

The photosynthetic bacterium Rhodopseudomonas capsulata can grow under anaerobic conditions with light as the energy source or, alternatively, in darkness with D-fructose or certain other sugars as the sole source of carbon and energy. Growth in the latter mode requires an "accessory oxidant" such as trimethylamine-N-oxide, and the resulting cells contain the photosynthetic pigments characteristic of R. capsulata (associated with intracytoplasmic membranes) and substantial deposits of poly-beta-hydroxybutyrate. In dark anaerobic batch cultures in fructose plus trimethylamine-N-oxide medium, trimethylamine formation parallels growth, and typical fermentation products accumulate, namely, CO2 and formic, acetic, and lactic acids. These products are also found in dark anaerobic continuous cultures of R. capsulata; acetic acid and CO2 predominate when fructose is limiting, whereas formic and lactic acids are observed at elevated concentrations when trimethylamine-N-oxide is the limiting nutrient. Evidence is presented to support the conclusions that ATP generation during anaerobic dark growth of R. capsulata on fructose plus trimethylamine-N-oxide occurs by substrate level phosphorylations associated with classical glycolysis and pyruvate dissimilation, and that the required accessory oxidant functions as an electron sink to permit the management of fermentative redox balance, rather than as a terminal electron acceptor necessary for electron transport-driven phosphorylation.

A serological survey of Encephalitozoon cuniculi infection in the wild rabbit in England and Scotland

Sera from 175 wild rabbits trapped in England or Scotland over the past two years were tested for antibodies to Encephalitozoon cuniculi. No sera were positive, suggesting that this common laboratory rabbit pathogen is rare in wild rabbits in these areas.