Mean Optical Density Values Research Articles

Comparison of latex hypersensitivity among patients with neurologic defects

Background: Latex hypersensitivity has been described in discrete populations including health care workers and children with spina bifida (SB). Objective: This study was designed to determine whether the SB population is a unique neuroimmunologic group manifesting this sensitivity. Methods: Four groups of subjects were studied. These included: 36 patients with SB with or without clinical evidence of latex hypersensitivity, 50 patients with spinal cord injury (SCI), and 10 patients with cerebrovascular accidents (CVAs), all of whom were questioned regarding contact with and possible clinical allergic reactions to latex. Ten healthy control subjects were also studied. We used a latex sap extract, previously shown to react with latex-specific IgE in a biotin-avidin ELISA, to determine latex-specific IgE antibody titers and to compare the groups. Results: Responses to questionnaires indicated that neither the patients with SCI nor the patients with CVA had histories suggestive of latex hypersensitivity. In contrast, 72% of the SB population had histories of clinical latex allergy. Comparisons of latex contact among the SB, SCI, CVA, and control groups revealed that the SB and SCI groups had similar latex exposure, whereas the other groups had less exposure. Both the SB and SCI groups had an average of two surgical procedures per year, which was greater than the average for the other groups. Comparisons of IgE latex antibody titers among the groups indicated that only the SB group had significant levels. The mean optical density values for each group were: 0.299 ± 0.177 for patients with SB and positive skin prick test results, 0.072 ± 0.066 for patients with SB and negative skin prick test results, 0.098 ± 0.005 in patients with SCI, 0.073 ± 0.038 in patients with CVA, and 0.053 ± 0.034 in control subjects. The percentages of positive latex IgE antibody detection were 72% for SB, 4% for SCI, 0% for CVA, and 0% for control groups. Conclusions: The results suggest that the SB population is unique in demonstrating IgE responses to latex contact, which may be due to increased latex exposure or altered neuroimmunologic interactions. (J A LLERGY C LIN I MMUNOL 1995;95:950-4.)

Immune response to sulfamethoxazole in patients with AIDS.

Antibody- and cell-mediated responses to sulfamethoxazole (SMX) were analyzed in AIDS patients with or without a history of hypersensitivity and in negative controls. In 20 of 20 (P < 0.01) human immunodeficiency virus (HIV)-seropositive patients with skin reactions to cotrimoxazole, we found SMX-specific antibodies, while only 9 of 20 and 17 of 20 HIV-seropositive patients without a history of hypersensitivity to cotrimoxazole had SMX-specific immunoglobulin M (IgM) and IgG, respectively. The levels of specific IgM and IgG were higher in patients with skin reactions than in patients without reactions (IgM, 1.0 +/- 0.19 versus 0.47 +/- 0.23 [P < 0.001]; IgG, 0.68 +/- 0.15 versus 0.47 +/- 0.14 [P < 0.001] [mean optical density values +/- standard deviations]). Seronegative controls with no history of exposure to sulfa compounds did not have SMX-specific IgG or IgM antibodies, and controls with a history of intake of SMX with or without reactions had low levels of IgG and IgM. The SMX-specific IgG subclasses were exclusively IgG1 and IgG3. None of the patients had detectable SMX-specific IgE or IgA antibodies nor did they exhibit a cell-mediated response as measured by a lymphocyte proliferation assay. Antibodies to SMX recognized N-acetyl-sulfonamide, N-(2-thiazolyl)-sulfanilamide, sulfadiazine, and sulfisoxazole but did not recognize sulfanilamide or 3-amino-5-methyl isoxazole in an inhibition assay. It is not known whether the SMX-specific antibodies associated with hypersensitivity reactions to SMX in HIV-seropositive patients have a pathogenic role in these reactions. Sulfanilamide or 3-amino-5-methyl isoxazole, on the other hand, could be potential alternative therapies in HIV-seropositive patients with a history of skin reactions to SMX.

6-Bit and 8-bit digital radiography for detecting simulated periodontal lesions

The purpose of this study was to compare the diagnostic performance of a digital radiography system that uses 6-and 8-bit displays with conventional D-speed film for the detection of simulated periodontal bone lesions. Eleven human hemimandibles were used as specimens. Simulated lesions were created at the buccal cortical plate in the marginal bone area with the use of a round bur 1.4 mm in diameter. Lesions were created in a defined sequence to preclude visual cues as to the depth of the lesions. Lesion size progressed in 0.5 mm increments. At each stage the mandibles were imaged with a Sens-A-Ray system (REGAM Medical Systems AB, Sundsvall, Sweden) and D-speed film. Exposure parameters for each specimen/receptor combination were standardized by either the mean optical density or mean gray value at the approximal crestal bone area. Film images and digital images displayed with 64 and 256 gray levels were presented to six observers for evaluation. Observers were ask to rate their confidence as to the presence or absence of a lesion using a 5-point confidence scale. A total of 96 lesion sites and 96 control sites were presented to the observers. Receiver operating characteristic curves were generated for each system. The area under the curve was used as the index of diagnostic accuracy. The mean receiver operating characteristic areas for 6-bit and 8-bit displays and D-speed film were 0.746 ± 0.043, 0.717 ± 0.056 and 0.742 ± 0.059, respectively. Analysis of variance was used to compare the means. No statistical difference was found between any of the three image displays ( p > 0.05). These findings are consistent with an analytic analysis of the viewing conditions and indicate that 6-bit (64 gray levels) are sufficient for the diagnosis of these simulated periodontal lesions.

The serological differentiation of acute and chronic Schistosoma japonicum infection by ELISA using keyhole limpet haemocyanin as antigen

Antibodies (immunoglobulin (Ig) G and IgM) that recognize keyhole limpet haemocyanin (KLH), which shares a well defined carbohydrate epitope with the surface of larval schistosomes, were determined by enzyme-linked immunosorbent assay in patients with acute or chronic schistosomiasis japonica. Marked differences in IgG and IgM responses were evident between acute and chronically infected patients at a serum dilution of up to 1:2000. The acute sera had mean (±standard deviation) optical density values at 405 nm for IgG and IgM of 0.64±0.18 and 0.30±0.19 respectively; the chronic sera had mean readings for IgG and IgM of 0.14 ± 0.08 and 0.04 ± 0.03 respectively. Setting the lowest positive limit at 2 standard deviations above the mean value for chronic sera, 41 (98%) of the 42 patients previously diagnosed as having acute schistosomiasis were correctly identified by anti-KLH IgG and 35 (83%) of the 42 patients were correctly identified by anti-KLH IgM detection. Of 17 patients studied longitudinally, IgG optical density values dropped 45% and those of 5 patients fell below the established cut-off level 6 months after treatment. This study supports the use of KLH for rapidly and easily identifying individuals with acute Schistosoma japonicum infection.

Localization of oxytocin receptor mRNA in the ovine uterus during the oestrous cycle and early pregnancy

A synthetic 45-mer oligonucleotide corresponding to part of the ovine endometrial oxytocin receptor cDNA was hybridized to sections of ovine uterus collected from 40 ewes at different stages during the oestrous cycle, the first 3 weeks of pregnancy and seasonal anoestrus. The quantity of oxytocin receptor mRNA was measured as the optical density (OD) value on autoradiographs using image analysis. Message first appeared in the luminal epithelium on days 14-15 of the cycle, increasing to a peak OD of 0.48 at oestrus and decreasing again between days 2 and 5. Oxytocin receptor mRNA in the superficial glands, deep glands and caruncular stroma increased between day 15 and oestrous to peak OD values of 0.17, 0.11 and 0.11 respectively, declining again by day 2 and reaching basal values (OD < 0.015) by day 5. Hybridization to the myometrium tended to rise from a mean OD value of 0.01 on days 2-15 to a peak of 0.03 +/- 0.01 (mean +/- S.E.M.) on days 0-1, but the change was not significant. In pregnant ewes there was no detectable oxytocin receptor mRNA on days 14-15 in any region, but hybridization to the luminal epithelium was present in two of three ewes on day 21. In anoestrous ewes oxytocin receptor mRNA concentrations in all areas of the endometrium were approximately half those measured at oestrus. Optical density readings for oxytocin receptor mRNA in the various uterine compartments were compared with measurements of oxytocin receptors in the same regions as assessed by binding studies using the 125I-labelled oxytocin antagonist d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH2(9)]-vasotocin (125I-labelled OTA). In the endometrium, receptor mRNA and 125I-labelled OTA binding patterns changed in parallel, and both sets of measurements were significantly correlated (P < 0.01). In the myometrium, a significant increase in 125I-labelled OTA binding occurred at oestrus; this was not accompanied by a similar increase in oxytocin receptor mRNA hybridization. This study helps to confirm that the previously identified cDNA clone is derived from the ovine oxytocin receptor, as patterns of oxytocin receptor mRNA expression in the endometrium closely resembled those of oxytocin binding. Maximum expression and binding both occurred at oestrus, suggesting that regulation of the oxytocin receptor gene in the uterus occurs principally at the transcriptional, rather than at the translational, level. Failure to detect a significant increase in myometrial mRNA expression at oestrus may indicate that the endometrial and myometrial oxytocin receptors are of different isoforms.

Determination of Listeria in Dairy and Environmental Samples: Comparison of a Cultural Method and a Colorimetric Nucleic Acid Hybridization Assay

The efficiency of the International Dairy Federation (IDF) Listeria detection method (IDF Standard 143:1990) was compared to that of a colorimetric nucleic acid hybridization assay. Out of 250 naturally contaminated cheese and environmental samples tested, the IDF method revealed 153 and the Gene-Trak assay 144 positive samples, respectively. Hence, the Gene-Trak assay gave a false-negative rate of 5.9%. False-positive samples could not be detected. When Oxford and LPM agar were compared for suitability as the streaking medium for the Gene-Trak assay, more satisfactory results were obtained with the Oxford agar. Both the overall number of positive samples and the mean optical density values of the Gene-Trak-positive samples were higher with Oxford than with LPM agar. The extension of sample enrichment time from 1 d (Gene-Trak-assay), and 2 d (IDF method), respectively, to 7 d resulted in a small increase in the number IDF method-positive samples but led to a drastic decrease in the number of Gene-Trak-positive samples.

Interpretation of an enzyme-linked immunosorbent test using different cut-offs between positive and negative samples for diagnosis of paratuberculosis

The purpose of this study was to compare the serologic responses of cows infected and non-infected with Mycobacterium paratuberculosis in infected and non-infected herds using different cut-offs between positive and negative samples. Infection status of cattle was determined by fecal culture. The serological test was an enzyme-linked immunosorbent assay (ELISA) using an affinity-purified antigen. Cows differed in their level of exposure (high- vs. low-prevalence and negative herds) and disease manifestation (clinical vs. subclinical infection). The ELISA optical density (OD) for cow samples from fecal culture-positive herds (no clinical cases) was higher than that for samples from the fecal culture-negative herd (0.49 vs. 0.26, respectively). The mean OD value (0.61) for clinically-affected cows was not different from that of fecal culture-positive, clinically-normal cows (0.49), nor were differences found between the OD values from fecal culture-negative cows from the herd with no history of paratuberculosis (0.21) and cattle with negative cultures from paratuberculosis-infected herds (0.26). The likelihood-ratio method was used to calculate the optimum ELISA discrimination value between test-positives and -negatives at a given prevalence in a herd, a d a receiver-operator characteristic (ROC) curve was constructed.

Persistence of rinderpest maternal antibodies in lambs

Rinderpest antibodies in 166 lambs of different ages, born to vaccinated ewes were studied with avidin-biotin enzyme-linked immunosorbent assay. The mean serum background optical density (OD) value in 20 colostrum deprived lambs and 50 unvaccinated adult sheep was 0.12. The OD values of 166 one to six month-old colostrum-fed lambs ranged from 0.08 to 0.64 and the pooled rinderpest positive serum was 1.44. A peak value of 0.64 was obtained in the first week which gradually declined to become negative for the presence of rinderpest maternal antibodies at around six months of age (OD=< 0.24). Primary vaccination of lambs of vaccinated ewes is therefore considered appropriate at six months of age for effective immunisation with least interference of maternally-derived antibodies.

Comparison of Freund's and Ribi adjuvants for inducing antibodies to the synthetic antigen (TG)-AL in rabbits

Antibody responses and health parameters were compared in rabbits immunized with a synthetic polypeptide antigen, [ l- Tyr, l- Glu, DL- Ala]- poly- L- lysine , in Freund's (FA) or RIbi (RA) adjuvants, Rabbits, 12 weeks old, of both sexes, were inoculated with 0.5 ml divided between two intramuscular (i.m.) sites. Eight received FA and antigen (50 μg); eight RA and antigen, eight PBS and antigen; four FA and PBS; four RA and PBS, and four PBS. Identical booster inoculations were made 21 days later, except that incomplete FA was substituted for complete FA. Rabbits were monitored until euthanasia and necropsy 7 weeks after the primary inoculation. Sera, obtained weekly, were analyzed for immunoglobulins using an enzyme immunoassay. Only rabbits given antigen with adjuvant produced high titered antibodies. Mean optical density values for immunoblobulin (Ig)M were greater the week after the booster in the group given FA. IgG values were similar for both adjuvant/antigen groups the week after the booster, but thereafter decreased in rabbits given RA. Antisera from rabbits given antigen with FA had greater avidity for the antigen than that from rabbits given antigen with RA, however, the difference was not significant ( p>0.05). Rabbits inoculated with FA and antigen had high serum creatinine kinase levels the day after inoculation, showed evidence of discomfort, and extensive granulomatous inflammation at the inoculation sites. Lesions were minimal to mild in rabbits given antigen with RA and PBS with either adjuvant. While RA did not result in adverse side effects, the IgG response to (TG)-AL with RA was transient compared to FA.

Relationships between trypanosome infection measured by antigen detection enzyme immunoassays, anaemia and growth in trypanotolerant N'Dama cattle

Relationsips were evaluated between trypanosome infection as measured by antigen detection enzyme immunoassays (antigen ELISA), anaemia as determined by average packed red cell volume (PCV), and animal performance as assessed by daily weight gain in 99 N'Dama cattle in Gabon exposed to natural tsetse challenge at 11.5 months of age and recorded 14 times over a 13 week period. Approximately half the animals were found to be infected for an average of five of the 14 times that they were examined: 38% with Trypanosoma congolense, 13% with Trypanosoma vivax and 49% with a mixed infection. Trypanosoma congolense infections had significant deleterious effects on animal growth, while T. vivax infections did not. Animals found on several occasions to be infected with T. congolense had significantly lower PCV values than those demonstrated to be infected on fewer occasions. No relationship was found between mean optical density (OD) values in antigen ELISA and PCV values. Animals capable of maintaining PCV values, even when antigen ELISA positive on a high number of occasions, grew at the same rate as uninfected animals. Animals that could not maintain PCV values when infected had poorer growth. Antigen ELISA has the potential to increase the efficiency of selection of trypanotolerant N'Dama cattle under tsetse challenge in the field, in three main ways. (1) Accurate identification of trypanosome species, especially in mixed species infections, clarifies relations between infection, anaemia and animal performance. (2) Detection of animals antigenaemic without patent parasitaemia could allow individuals with superior ability to control trypanosome infection to be identified. (3) More accurate measurement of the proportion of time an animal is infected allows more accurate evaluation of its anaemia control capability.

The serodiagnosis of tuberculosis in children: an evaluation of an ELISA test using IgG antibodies toM. tuberculosis, strain H37 RV

An enzyme-linked immunosorbent assay (ELISA) for detecting serum IgG antibodies to an autoclaved suspension of Mycobacterium tuberculosis H37 RV was evaluated as a diagnostic tool in 132 clinical cases of childhood tuberculosis. The mean (SD) optical density value in these patients was 0.115 (0.122) compared with 0.022 (0.017) in the control group of patients who had non-tuberculous acute respiratory tract infections. Using as a cut-off level the mean of the control plus 2 standard deviations, the test sensitivity was 62% and the specificity was 98% in all the patients with a clinical diagnosis of tuberculosis. In the culture-positive group (n = 35), the sensitivity was 69%. A positive correlation was shown between the optical density levels and increasing age and chronicity of infection but not with respect to tuberculin skin reactivity, nutritional status and the duration of prior therapy. In addition, BCG vaccination (presence of a scar) did not affect the ELISA result. We conclude that this ELISA test is a useful diagnostic test in children.

Survey of trichinosis in breeding and cull swine, using an enzyme-linked immunosorbent assay

Summary Serum samples obtained from 40,927 swine at various locations in North Carolina between Aug 1, 1987 and July 31, 1988, were tested for antibodies to Trichinella spiralis, using an elisa based on a larval T spiralis excretory-secretory antigen. In the elisa, samples were considered to have positive results if the optical density (OD) reading was equal to or 5 times greater than the mean OD value of 4 negative-control sera from trichina-free swine. Of the 40,927 serum samples tested, 154 (0.38%) were positive by elisa; the rate for breeding swine was 0.35% (105/30,162), and the rate for cull swine was 0.45% (49/10,765). Of the 49 seropositive samples from cull swine, 11 were from out of the state, 22 had no identification, and 16 were known to originate from North Carolina. Seropositivity had a bimodally seasonal distribution, with peaks in March and September. There was no difference between the mean age of seropositive and seronegative swine, but males were at greater risk for seropositivity than were females. Pigs from lots with &lt; 100 sera tested were at increased risk for seropositivity, as were pigs from the central coastal region of North Carolina.

68 DIAGNOSIS OF CAMPYLOBACTER PYLORI GASTRITIS BY IgG ELISA

11 patients age range 8-15, median 13 years, presenting with abdominal pain were investigated for Campylobacter pylori (C pylori) associated gastritis by upper GI endoscopy and serum IgG antibodies to C pylori. Control sera were obtained from 9 patients aged 9-15, median 12 years, undergoing orthopaedic procedures. Antral biopsies were examined for chronic gastritis and stained for C pylori using a modified Giemsa stain. C pylori specific IgG antibodies were assayed by an indirect ELISA technique, using a soluble bacterial antigen preparation as antigen and the results expressed as optical density measurement. 4 patients with chronic gastritis were colonised with C pylori. Serum IgG mean optical density value was 172±35 for C pylori +ve patients and 30±16 for C pylori -ve patients. Control patients had a mean optical density value of 22.9±4, similar to C pylori -ve patients.

An epidemiologic study of anti-ATLA (antibody to adult T-cell leukemia-associated antigen) in Nichinan district of southern Kyushu by enzyme immunoassay

Kyushu is known as area in which adult T-cell leukemia (ATL) is endemic.In order to determine the distribution of antibody to ATL-associated antigen (anti-ATLA) in the Nichinan district of southern Kyushu, determination of anti-ATLA status of inpatients in a general hospital in Nichinan City, Miyazaki prefecture was carried out from August to December, 1983. Sera from 914 inpatients were tested for presence of anti-ATLA by Enzymeimmunoassay (EIA) prepared by Eisai Co., Ltd., Tokyo, Japan.Results obtained are as follows1) Overall prevalence of anti-ATLA was 18.9 per cent (173 of 914 individuals).Prevalence of anti-ATLA increased with age, reaching a maximum of 37.1 per cent for people 70 years old or over.2) Prevalence of anti-ATLA was 18.1 per cent (73 of 403) in males and 19.6 per cent (100 fof 511) in females.Significant difference by sex was not recognized.3) Anti-ATLA was most prevalent in patients with neoplasms (36.7%).Patients with following pathological conditions were included in this category (anti-ATLA prevalencies are given in parenthesis): malignant lymphoma (100%), leukemia (0%), stomach cancer (41.7%), and miscellaneous cancer (26.8%).After neoplasms, anti-ATLA was most prevalent in patients with diseases of the musculoskeletal system and connective tissue (33.3%) and diseases of the circulatory system (27.9%).4) Mean optical density (OD) values by EIA were 1.034±1.035 for the 173 anti-ATLA-positive individuals and 0.038±0.023 for the 741 negative individuals;The difference between the values for the positive and negative sera was large.Furthermore, the mean OD value was significantly higher for anti-ATLA-positive males (1.142±0.888) than for anti-ATLA-positive females (0.955±1.180) (p<0.001).

The Incidence of Tuberculosis in a Herd in Northern Rhodesia

The strategic use of the gamma-interferon (IFN-γ) assay (Bovigam®) can provide a means for the early identification of Mycobacterium bovis infected cattle, thus ensuring their removal from an infected herd. It has been reported that performance of the test can be influenced by various factors including a recent tuberculin skin test and the length of delay between collection and processing of blood samples. In this study, single intradermal comparative tuberculin test (SICTT) reactor and non-reactor cattle were recruited from herds infected with M. bovis and grouped according to their SICTT responses. Group 1 comprised reactor cattle selected on the basis of their SICTT response to PPD-bovine (purified protein derivative of tuberculin) exceeding that of PPD-avian by at least 12 mm. Group 2 animals were selected from herds undergoing routine surveillance for bovine tuberculosis and contained standard SICTT reactor cattle (PPD-bovine exceeding that of PPD-avian by at least 4 mm) and non-reactors. We investigated the effects of the SICTT on the assay results by measuring the in vitro IFN-γ responses of Group 1 reactor cattle at time intervals pre- and post-skin test. No significant differences were measured in the IFN-γ responses of the reactor animals to PPD-bovine and PPD-avian for up to 65 days. To investigate if a delay in processing of blood affected the performance of the assay, we compared results using duplicate blood samples from Group 1 and Group 2 cattle stimulated with PPD antigen at 8 h and at 24 h after collection. In both groups of animals the mean optical density (OD) values of the assay at 24 h post-collection were significantly lower than those at 8 h. Our results demonstrated that a delay in processing of the blood samples from cattle subjected to routine surveillance could significantly impact on the outcome of the IFN-γ assay resulting in a change of the IFN-γ status of the animals.