Comparison of a radioallergosorbent (RAST) inhibition method and a monoclonal enzyme linked immunosorbent assay (ELISA) for aeroallergen measurement

BACKGROUND: Mouse and rat urinary proteins are potent occupational allergens for exposed personnel. Methods of measuring airborne allergens differ greatly, and reported levels of allergens vary considerably between laboratories. OBJECTIVES: To compare the values obtained using two different methods of allergen detection. METHODS: Air samples were collected in rat rooms in Sweden and the United Kingdom at 2 L/min on to polytetrafluoroethylene (PTFE) filters and extracted in buffer containing 0.5% v/v Tween 20. Airborne rat urinary allergen (RUA) was measured in all samples by both RAST inhibition using a polyclonal human serum pool (UK) and a two monoclonal antibody sandwich ELISA employing antibodies specific for Rat n 1.02 (alpha2u-globulin) (Sweden). RESULTS: The two methods gave values which were correlated (r2 log values = 0.72, P<0.0001), but differed by several orders of magnitude (median [range] ratio of RAST inhibition/ELISA = 316 [7-26(80)]. There was a systematic bias: as the absolute values increased, the difference in the measurements increased. The rat urine standards used were antigenically similar. CONCLUSIONS: A large contrast in RUA values obtained from the two assays was observed in this study. This may be primarily due to methodological differences, but variations in antibody specificities or composition of allergenic epitopes in the air samples may contribute. The results demonstrate that standardization of methods and antibodies is necessary before interlaboratory comparisons can be made.     

Variability in blood flow and pO2 in tumors in response to carbogen breathing

PURPOSE: There is speculation that the CO2 in carbogen (95% O2, 5% CO2) can block the vasoconstrictive effects of oxygen. However, it has recently been shown that blood flow in human tumors is variable while patients breathe carbogen. Furthermore, we have shown a consistent decrease in tumor blood flow (TBF) with carbogen breathing in the rat window chamber model. Also, we have previously shown that there is no significant difference in tumor growth time after radiation with air vs. carbogen breathing. This study was designed to investigate the effects of carbogen breathing on blood flow and oxygen levels in a solid tumor. METHODS: Measurements were made in Fischer-344 rats with 8-10 mm diameter R3230Ac tumors transplanted either within the quadriceps muscle (n = 16) or subcutis (n = 14). Nontumor-bearing quadriceps muscle was studied in six other rats. After a 20-minute air-breathing baseline, rats breathed carbogen for an additional 40 minutes. Partial pressure of oxygen (pO2) was continuously monitored at one position for 60 minutes using 9-12 microm diameter oxygen microelectrodes. Blood flow was simultaneously monitored in all animals using laser Doppler flowmetry (1-2 probes/tumor). RESULTS: Blood flow changes during carbogen breathing were variable in all tissues and intratumoral heterogeneity was observed. Despite variability in blood flow, pO2 consistently increased in normal muscle but varied in both tumor sites. During carbogen breathing, the percent pO2 measurements greater than the baseline average were 99.5% +/- 0.4% (mean +/- SEM), 42.7% +/- 13.8%, and 79.8% +/- 11.0% in normal muscle, subcutaneous tumor, and muscle tumor, respectively. To show the magnitude of change, average pO2 values during air and carbogen breathing were calculated for each site. Normal muscle increased from 14.9 +/- 2.3 to 39.0 +/- 6.4 mm Hg (paired t-test; p = 0.009). Muscle tumors showed a rise from 14.6 +/- 3.2 to 34.5 +/- 8.2 mm Hg (p = 0.019). However, pO2 in subcutaneous tumors remained unchanged, with a pO2 of 7.3 +/- 2.0 mm Hg on air and 7.3 +/- 4.1 mm Hg (p = 0.995) during carbogen breathing. CONCLUSIONS: Carbogen had no consistent effect on blood flow and was ineffective at increasing tumor pO2. These results may partially explain why carbogen breathing failed to improve the efficacy of radiation in this tumor model when transplanted subcutaneously.     

Is endoluminal abdominal aortic aneurysm repair using an aortoaortic (tube) device a durable procedure?

BACKGROUND: Controversies over the frequency and intensity of the follow-up care of breast cancer patients exist. Some physicians have adopted an intensive approach to follow-up care that consists of frequent laboratory tests and routine imaging studies, including chest radiographs, bone scans, and CT scans, whereas others have established a minimalist approach consisting of only history, physical examinations, and mammograms. OBJECTIVES: Our objective was to evaluate the role of intensive follow-up on detection of breast cancer recurrence and to examine the impact of follow-up on overall survival. METHODS: During a 10-year period (1986-1996), 129 patients with recurrent disease were identified from a prospective database of 1898 breast cancer patients. The patients with recurrent disease were divided into minimalist or intensive groups according to method of detection. RESULTS: Twenty-seven of 126 (21%) patients were assigned to the intensive method of detection group (LFT, CEA, CA 15-3, chest radiograph, CT scan, and bone scan); 99 of 126 (79%) patients were assigned to the minimal detection group (history, physical examination, and mammography). Distant disease to the bone was the most common initial tumor recurrence, at 27%. History, physical examination, and mammography detected recurrent cancer in approximately the same amount of time as LFTs, tumor markers, CT scans, and chest radiographs (P = .960). When the recurrent patients were divided into intensive and minimalist groups and analyzed by time to detection of recurrence, there was no significant difference between the time to detection in those recurrences detected by intensive methods and those recurrences detected by minimalist methods (P = .95). The independent variables age, tumor size, type of surgery, number of positive nodes, time to recurrence, method of detection, and site of recurrence (regional or distant) were subject to univariate and multivariate analysis by the Cox proportional hazards model. Only two variables had an impact on survival by multivariate analysis: early timing of the recurrence (P = .0011) and the site of the recurrence (P = .02). Timing was defined as early (< or =365 days from the time of diagnosis to recurrence) or late (> or =365 days from the time of diagnosis to recurrence). Early recurrence was the first variable found to be significant on stepwise forward regression analysis. The primary site of recurrence was significant at step two. The method of detection--intensive or minimal--did not significantly affect survival (P = .18). CONCLUSIONS: There is no survival benefit to routine intensive follow-up regimens in detecting recurrent breast cancer. Expensive diagnostic tests such as bone scans, CT scans, and serial tumor markers are best used for detection of metastasis in symptomatic patients.     

Morphological changes associated with long-term potentiation

Long-term potentiation (LTP) is a long-lasting form of synaptic plasticity induced by brief repetitive afferent stimulation that is thought to be associated with learning and memory. It is most commonly studied in the hippocampus where it may last for several weeks, and involves the synthesis of new proteins that might play a structural role. In this review we summarize the evidence in favor of modifications of neuronal architecture during LTP. We focus our attention on changes occurring at the level of single synapses, including components of postsynaptic dendrites (dendritic spines, the postsynaptic density, and synaptic curvature), of presynaptic terminals, and the formation of new synapses. We conclude that although many morphological changes at various sites have been observed during LTP, there is no definitive proof in favor of structural changes associated with LTP. However, morphological modifications remain a valid candidate for mechanisms of learning and memory.     

Vaccination with glutaraldehyde-fixed bovine respiratory syncytial virus (BRSV)-infected cells stimulates a better immune response in lambs than vaccination with heat-inactivated cell-free BRSV

The lamb model was used to investigate the possible protective effects of vaccination with inactivated viral antigens against experimental infection with bovine respiratory syncytial virus. Two groups of eight lambs were vaccinated with either glutaraldehyde-inactivated cell-associated virus or heat-inactivated cell-free virus and subsequently challenged with live virus, along with a group of naive lambs. The virus was shed for significantly longer periods, and the virus titres in nasal secretions were significantly higher in the group of naive lambs than in the two groups of vaccinated lambs. The period of virus-shedding in nasal secretions and virus titres was significantly lower (p < 0.01) in the group of lambs immunized with the cell-associated preparation. The same antigen stimulated better cellular immune responses as measured by virus-specific cytotoxicity or by virus-specific lymphocyte proliferation. However, priming with inactivated vaccines had no significant effect on lymphocyte responses to phytohaemagglutinin, which was found to be significantly reduced (p < 0.01) following challenge with live virus.     

Liquid chromatographic determination of methylxanthines and catechins in herbal preparations containing guaraná

Herbal preparations derived from the dried seeds of guaraná (Paullinia cupana) have become a popular nutritional supplement used for stimulatory purposes. Once considered a drug substance in the United States, guaraná currently is classified as a food additive and dietary supplement. The pharmacological activity of guaraná-containing products is primarily due to methylxanthine alkaloids. For guaraná preparations, methylxanthine levels and, more significantly, the presence of several polyphenol compounds (i.e., catechins) provide phytochemical markers of authenticity. Methylxanthines and polyphenols are extracted from sample matrix with a heated phosphate buffer-methanol solution, the cooled extract is filtered, and the extract is injected into the liquid chromatographic (LC) system. A Nova-Pak C18 column eluted with phosphate buffer-methanol mobile phase (pH = 3.50) and monitored at 272 nm gave satisfactory resolution for the methylxanthines theobromine, theophylline, caffeine and the polyphenols (+)-catechin and (-)-epicatechin. Twenty-four products including dried seeds, dried paste, seed powders, tablets, and capsule formulations were assayed and conclusions were drawn about their authenticity. The LC system responded linearly to methylxanthines over the 100-fold range in concentration from 0.043 to 4.30 micrograms/mL for theobromine and caffeine and from 0.041 to 4.10 micrograms/mL for theophylline. Precision data for the 3 methylxanthines obtained from 10 different products (n = 5) gave relative standard deviation (RSD) values of 1.18-15.52% within a concentration range of 0.01-52.28 mg/g. Recoveries of methylxanthines from fortified products varied from 87.5 to 120.0%. The response for catechins was linear over a 200-fold range in concentration of 0.05-10.0 micrograms/mL. Precision data from 5 products (n = 5) gave RSD values of 1.08-5.54% within a concentration range of 0.34-32.65 mg/g. Recoveries from these products ranged from 87.7 to 109.7%. Results and chromatographic profiles for 14 commercial products in solid dosage form indicate that a number of these products may not contain authentic guaraná as an active ingredient or contain less than the declared quantity of guaraná. The proposed procedure also was applied to 2 carbonated soft drinks and a sample of maté.     

Acute cyanide toxicity caused by apricot kernel ingestion

A 41-year-old woman ingested apricot kernels purchased at a health food store and became weak and dyspneic within 20 minutes. The patient was comatose and hypothermic on presentation but responded promptly to antidotal therapy for cyanide poisoning. She was later treated with a continuous thiosulfate infusion for persistent metabolic acidosis. This is the first reported case of cyanide toxicity from apricot kernel ingestion in the United States since 1979.     

Characterization of microdialysis acidification for capillary isoelectric focusing-microelectrospray ionization mass spectrometry

A microdialysis junction, based on a microdialysis membrane connecting a separation capillary and a short, sharply tapered microelectrospray emitter capillary, is demonstrated for on-line combination of capillary isoelectric focusing (CIEF) with electrospray ionization mass spectrometry (ESI-MS). The microdialysis junction provides the necessary electrical connection across the dialysis membrane for defining the electric fields needed for the CIEF separation and the electrospray process. Additionally, postseparation acidification of focused protein zones eluted from the CIEF capillary is achieved using the microdialysis junction while separation efficiency and resolution is maintained. A microelectrospray emitter produces a stable electrospray of protein analytes without the need for a makeup liquid flow and eliminates any subsequent sample dilution and reduction in MS sensitivity. The microdialysis junction is advantageous over the coaxial liquid sheath interface as evidenced by the simplicity in operation procedures, the enhancement in detection sensitivity, and the linear correlation between protein migration time and isoelectric point in CIEF-ESI-MS.