The reduction of dose in paediatric panoramic radiography: the impact of collimator height and programme selection.

OBJECTIVES: The aim of this work was to estimate the doses to radiosensitive organs in the head of a young child undergoing panoramic radiography and to establish the effectiveness of a short collimator in reducing dose. METHODS: Thermoluminescent dosemeters were used in a paediatric head phantom to simulate an examination on a 5-year-old child. The panoramic system used was an Instrumentarium OP200 D (Instrumentarium Dental, Tuusula, Finland). The collimator height options were 110 and 140 mm. Organ doses were measured using exposure programmes intended for use with adult and child size heads. The performance of the automatic exposure control (AEC) system was also assessed. RESULTS: The short collimator reduced the dose to the brain and the eyes by 57% and 41%, respectively. The dose to the submandibular and sublingual glands increased by 32% and 20%, respectively, when using a programme with a narrower focal trough intended for a small jaw. The effective dose measured with the short collimator and paediatric programme was 7.7 µSv. The dose to the lens of the eye was 17 µGy. When used, the AEC system produced some asymmetry in the dose distribution across the head. CONCLUSIONS: Panoramic systems when used to frequently image children should have programmes specifically designed for imaging small heads. There should be a shorter collimator available and programmes that deliver a reduced exposure time and allow reduction of tube current. Programme selection should also provide flexibility for focal trough size, shape and position to match the smaller head size.

Rapid competitive enzyme-linked immunosorbent assay using a monoclonal antibody reacting with a 15-kilodalton tegumental antigen of Schistosoma mansoni for serodiagnosis of schistosomiasis.

A competitive enzyme-linked immunosorbent assay (CELISA) for antibody detection was developed by using a monoclonal antibody which reacts with a 15-kDa tegumental antigen of the adult worm of Schistosoma mansoni. This monoclonal antibody was not able to react with antigens of Schistosoma japonicum or Schistosoma haematobium in enzyme-linked immunoelectrotransfer blot (EITB) and indirect immunofluorescence tests. The assay was performed in a period of 1 h using an adult worm crude extract antigen. To evaluate the CELISA, a total of 73 serum samples was analyzed: 35 were from S. mansoni-infected patients, 23 were from individuals with parasitic infections other than schistosomiasis, and 14 were from healthy individuals. All serum samples from healthy individuals and from patients infected with other parasites were negative, as were two (6%) samples from patients infected with S. mansoni. EITB analysis showed that 32 of 33 CELISA-positive samples were positive in the EITB but with different patterns of reactivity. A 15-kDa protein reacted with 60% of serum samples, and a 60-kDa protein showed the highest level of reactivity (85%). The two samples from patients infected with S. mansoni that were negative in the CELISA reacted with 70-, 60-, 50-, 47-, and 38-kDa proteins. One sample, positive in CELISA, did not react with proteins of the antigenic extract.

Isotypic analysis of humoral immune responses in rhesus monkeys to an adult microsomal antigen of Schistosoma mansoni: an indicator of successful treatment.

A study was undertaken to examine the potential role of immunodiagnostic methods in determining successful chemotherapy in schistosomiasis. Fifteen rhesus monkeys were infected with 1,500 Schistosoma mansoni (Puerto Rico strain) cercariae, and 10 of the monkeys were then treated with a curative dose of praziquantel 13 weeks after infection. Five monkeys remained untreated. One monkey was not successfully cured, as confirmed by the presence of both male and female worms at the time of perfusion. Serum samples were longitudinally collected and specific Ig isotypes were quantified with an adult microsomal antigen of S. mansoni using the FAST-ELISA. Specific isotypes were detected with monoclonal antibodies specific for each human Ig isotype, followed by a peroxidase-conjugated anti-mouse Ig. Longitudinally, all monkeys showed similar isotype patterns. Isotypes increased for the first nine weeks following infection, and then began to decrease. Ten to 14 days following treatment, all isotypes increased. The Ig isotype responses of all monkeys followed classic patterns of isotype expression. A ratio of pretreatment (week 13) IgG1 absorbance values to post-treatment IgG1 absorbance values was generated for each monkey. All successfully treated monkeys, determined to be worm-free by perfusion, had IgG1 ratios at week 53 greater than 2.4 (range 2.4-181). The untreated monkeys and the single monkey that was a treatment failure had IgG1 ratios less than 2.1 (range 0.09-2.05) for the same time period.

Serodiagnosis of parasitic diseases.

In this review on serodiagnosis of parasitic diseases, antibody detection, antigen detection, use of monoclonal antibodies in parasitic serodiagnosis, molecular biological technology, and skin tests are discussed. The focus at the Centers for Disease Control on developing improved antigens, a truly quantitative FAST-enzyme-linked immunosorbent assay, and the very specific immunoblot assays for antibody detection is highlighted. The last two assays are suitable for field studies. Identification of patient response in terms of immunoglobulin class or immunoglobulin G subclass isotypes or both is discussed. Immunoglobulin isotypes may asist in defining the stage of some diseases. In other instances, use of a particular anti-isotype conjugate may increase the specificity of the assay. Monoclonal antibodies have played important roles in antigen purification and identification, in competitive antibody assays with increased sensitivity and specificity, and in assays for antigen detection in serum, body fluids, or excreta. Molecular biological technology has allowed significant advances in the production of defined parasitic serodiagnostic antigens.

A specific diagnostic antigen of Echinococcus granulosus with an apparent molecular weight of 8 kDA.

An echinococcus antigen with an apparent molecular weight of 8 kDa was identified as diagnostically important. An immunoblot assay using this antigen was 91% sensitive for surgically confirmed Echinococcus granulosus hydatid disease of the liver. Specificity was 100% for echinococcosis. Marked cross-reactivity was observed with serum specimens from patients with E. multilocularis and E. vogeli infections. The 8 kDa component was not related to the widely recognized echinococcus antigen 5.

Diagnosis of paragonimiasis by immunoblot.

A sensitive and specific immunoblot assay was used to rapidly and accurately diagnose paragonimiasis. The immunoreactivity of a complex Paragonimus westermani Chaffee antigen was evaluated by SDS-PAGE and Western blot analysis. Initial probing with pooled human serum from proven Paragonimus infections revealed many bands, including a significant antibody response to an approximately 8,000 molecular weight (8 kDa) protein. Forty-three of 45 proven paragonimiasis serum specimens had antibodies to this diagnostic band. Of 29 normal serum specimens and 210 serum specimens from patients with other parasitic and nonparasitic infections, only 1 serum, from a schistosomiasis haematobium patient, reacted positively. These results indicate that our immunoblot for paragonimiasis, which uses a comparatively crude antigen, is highly sensitive (96%) and specific (99%).

The present status of serodiagnosis and seroepidemiology of schistosomiasis.

The literature of the past 4-5 yr on serodiagnosis and seroepidemiology of schistosomiasis is reviewed. A variety of assays with different antigens are being used for serodiagnosis. Several purified antigens appear to be sensitive and specific, but have little if any capability of indicating duration of infection, parasite burden, or effect of chemotherapy. The results of long-term posttherapy field studies indicate that serology has a role in monitoring control programs. Standardized serologic assays and the need for International Standard Reference Sera are emphasized. A standardized enzyme-linked immunosorbent assay based on the Falcon Assay Screening Test system (FAST-ELISA), and involving a standard reference serum pool, is suitable for both serodiagnosis and field studies. Measurement of circulating antigens as a parameter of active infection is considered to have increased potential, compared with antibody measurement, in management of clinical disease and in control programs. Recombinant DNA technology may be useful for producing standard antigens for use in assays measuring antibody or circulating antigen. Time-resolved immunofluorescence involving europium-labeled conjugates may provide the increased assay sensitivity needed for measurement of circulating antigen.

Serodiagnosis of Schistosoma mansoni with microsomal adult worm antigen in an enzyme-linked immunosorbent assay using a standard curve developed with a reference serum pool.

A standardized microtest plate enzyme-linked immunosorbent assay was developed using the microsomal fraction of adult worms of Schistosoma mansoni (MAMA) as antigen. The standard reference serum pool was prepared from acutely and chronically infected rhesus monkeys and was shown to be appropriate as a standard for measuring the levels of reactivity of the unknowns. The standard serum pool was arbitrarily designated as having 100 activity units per microliter. The levels of reactivity of the unknowns were expressed as activity units per microliter. Serum specimens were obtained from 190 patients infected with S. mansoni in the Caribbean, South America, and Africa. Serum was obtained from small numbers of patients infected with S. haematobium, S. japonicum, or S. mekongi. Controls were 136 patients with other helminthic infections, 142 patients with protozoal or other diseases with liver involvement, and 81 healthy serum donors. The J index (or predictability) of the assay was calculated to determine the significant level of reactivity. The assay has a predictability of 95% for both patients with S. mansoni infections and those with other infections. The sensitivity of the assay for S. mansoni infections was 96%, and the specificity (in terms of cross-reactions with infections with other parasite genera or with other liver diseases) was 99%. The heterologous Schistosoma species showed a markedly lower level of reactivity, with an overall sensitivity of 55%. This is in accord with the species-specificity previously recognized in MAMA, and emphasizes the need for standard reference pools of human sera prepared from patients infected with single species of each of the Schistosoma. Use of these pools in assays with antigens of the respective schistosome species would allow optimum serologic evaluation.

Standardization of serological assays for parasitic diseases with schistosomiasis and toxocariasis as prototypes.

A standardized microtest plate enzyme-linked immunosorbent assay (ELISA) was developed using the microsomal fraction of adult worms of Schistosoma mansoni (MAMA) as antigen. A standard reference serum pool was prepared and arbitrarily designated as having 100 activity units per microliter. The precision of the test, the suitability as a standard of the reference serum pool, and the J index as a method of determining the significant level of reactivity were evaluated. The predictability of the assay for patients with S. mansoni infections and for non-schistosomiasis patients was 95%. Preliminary studies with the truly quantitative microtest plate kinetic ELISA indicate that this assay is suitable for standardization for schistosomiasis and toxoplasmosis. The need for WHO International Reference Sera with designated International Units and for well-defined batteries of sera for evaluating the specificity and sensitivity of assays was emphasized.

Quantitative capacities of glutaraldehyde and sodium m-periodate coupled peroxidase-anti-human IgG conjugates in enzyme-linked immunoassays.

Covalently linked peroxidase-anti-human IgG conjugates were prepared by either glutaraldehyde or NaIO4 coupling techniques. Sodium dodecyl sulfate polyacrylamide gel electrophoresis shows that the glutaraldehyde coupled conjugate is composed of generally lower molecular weight components than the NaIO4 coupled product. The NaIO4 conjugate, when used to quantitate human immunoglobulin (Ig) in enzyme-linked immunoassays, appears to be highly sensitive in that small amounts of Ig elicited relatively high reactivities. The quantitative range of this type of conjugates, where reactivities are linearly proportional to the amount of human Ig present, is, however, extremely narrow (0.01-0.10 micrograms/ml of human IgG). Conversely, the glutaraldehyde coupled type conjugate is capable of sustaining a much wider range of linearity (0.01-0.6 micrograms/ml), but with a more gradual rise of reactivity which corresponds well to the amount of human Ig present. Conjugates prepared with glutaraldehyde are thus more useful in quantitative assays where wide quantitative ranges are desirable. NaIO4 conjugates on the other hand, are more suited to qualitative assays where sensitivity is more important.

Demonstration of species-specific and cross-reactive components of the adult microsomal antigens from Schistosoma mansoni and S. japonicum (MAMA and JAMA).

Analysis of human serum reactivities to the Schistosoma mansoni adult microsomal antigens (MAMA) showed that S. japonicum and S. haematobium infection sera, as a rule, did not react as well to MAMA as did the homologous S. mansoni infection sera. The degree of species specificity, although not absolute, was quite pronounced. Purification of the corresponding microsomal antigens from S. japonicum adults (JAMA) and subsequent assays with both homologous and heterologous infection sera show a distinct and reciprocating species specificity between S. mansoni and S. japonicum microsomal antigens. The specificities of these antigens were quantitated by k-ELISA. Qualitative analysis of active antigenic components for both JAMA and MAMA involved assay by the "Western blot" or enzyme-linked immunoelectrotransfer blot (EITB). The EITB patterns of both antigens, after resolution by SDS-PAGE, show species-specific reactive bands at the 16,000 to 35,000 m.w. region. S. japonicum-specific antigens are located at the 18,000 to 35,000 m.w. region whereas S. mansoni-specific antigens were associated with m.w. components of 16,000 to 29,000. High m.w. antigen components (greater than 40,000) of both JAMA and MAMA are recognized by both heterologous and homologous infection sera and are thus not species specific. The demonstration of the clear separation of species-specific antigen bands of JAMA and MAMA by physical size offers a unique opportunity to isolate and characterize the species specificities of antibody-antigen reactions in these parasitic infections.

Evaluation of serologic tests for Pneumocystis carinii antibody and antigenemia in patients with acquired immunodeficiency syndrome.

Sera from 68 patients with acquired immunodeficiency syndrome and 135 controls were used to evaluate the indirect immunofluorescence and enzyme-linked immunosorbent assays for detection of antibodies to Pneumocystis carinii and a counterimmunoelectrophoresis assay for detection of circulating Pneumocystis antigen. None of these assays was helpful in the diagnosis of P. carinii pneumonia. An improved assay for antigenemia is needed to differentiate between clinical and subclinical infection.

Diencephalic neuronal activity during acquisition and ingestion of food in sheep.

Single unit recordings were made in the lateral hypothalamic region and ventrobasal thalamus in conscious sheep during presentation of food and feeding. Unit responses to all aspects of testing were observed between the two areas. However, analysis of the data revealed a functional division of unit types between the two regions. Unit responses specific to the sight of food, to the approach of food to the mouth, and during ingestion of food were observed in the lateral hypothalamic area, but not the ventrobasal thalamus. These responses were not associated with specific or generalized movements, non-specific arousal, with olfactory stimulation, or with other oral stimuli. Units responding in association with specific mouth movements or somatosensory stimulation of the face or mouth-parts were observed in the ventrobasal thalamus but not in the lateral hypothalamic area. In the case of movement-related activity, the response was independent of the stimulus inducing the movement, food and non-food stimuli being equally effective. This was also true of the somatosensory responses observed. Two possibilities in relation to this functional division are discussed. Firstly, that the ventrobasal thalamus receives oral sensory afferents which may be associated with the thalamic area for taste. Secondly, that the activity of hypothalamic cells recorded in the sheep is consistent with a role for this area of the brain in the guidance and control of ingestive behaviour in ruminant as well as non-ruminant species.