Agar-Gel Precipitin Technique in Anthrax Antibody Determinations

A modification of the agar-gel precipitation inhibition technique of Thorne and Belton for detecting anthrax antibodies reduces inconsistency of visually determined end points on the same sera observed by different technicians. Determination of the minimal reacting concentrations of the anthrax antigen and antibody reagents, modifications of the visualization apparatus, methods for combining reagents, and length of incubation periods contribute to the ease of the end-point determinations and the uniformity of results. When compared with the previous technique, the modified procedure is less time-consuming while retaining satisfactory reproducibility, simplicity, specificity, and sensitivity.     

Agar-Gel Precipitin-Inhibition Technique for C-Reactive Protein Determinations

An application of the agargel precipitin-inhibition technique of Ray and Kadull detects the C-reactive protein present in the acute-phase human sera. The sensitivity of this procedure is compared with the capillary tube-precipitin method of Selman and Halpern.     

Agar-Gel Precipitin-Inhibition Technique for C-Reactive Protein Determinations: III. Quantitation of C-Reactive Protein in Serum Specimens

A quantitative C-reactive protein serological procedure has been developed. By use of this method, which is performed in agar-gel plates, from 2 to 654 μg of C-reactive protein per ml of titrated human serum can be detected. The method is based on the inhibition of a specific C-reactive protein antigen-antibody precipitate formed in agar-gel by the minimal reactive dilutions of each reagent in 48 hr. It is simple, sensitive, and readily reproducible.     

Tachykinins mediate bronchoconstriction elicited by isocapnic hyperpnea in guinea pigs

We tested the hypothesis that tachykinins mediate hyperpnea-induced bronchoconstriction (HIB) in 28 guinea pigs. Stimulus-response curves to increasing minute ventilation with dry gas were generated in animals depleted of tachykinins by capsaicin pretreatment and in animals pretreated with phosphoramidon, a neutral metalloendopeptidase inhibitor. Sixteen anesthetized guinea pigs received capsaicin (50 mg/kg sc) after aminophylline (10 mg/kg ip) and terbutaline (0.1 mg/kg sc). An additional 12 animals received saline (1 ml sc) instead of capsaicin. One week later, all animals were anesthetized, given propranolol (1 mg/kg iv), and mechanically ventilated (6 ml/kg, 60 breaths/min, 50% O2 in air fully water saturated). Phosphoramidon (0.5 mg iv) was administered to five of the noncapsaicin-treated guinea pigs. Eucapnic dry gas (95% O2-5% CO2) hyperpnea "challenges" were performed by increasing the tidal volume (2-6 ml) and frequency (150 breaths/min) for 5 min. Capsaicin-pretreated animals showed marked attenuation in HIB, with a rightward shift of the stimulus-response curve compared with controls; the estimated tidal volume required to elicit a twofold increase in respiratory system resistance (ES200) was 5.0 ml for capsaicin-pretreated animals vs. 3.7 ml for controls (P less than 0.03). Phosphoramidon-treated animals were more reactive to dry gas hyperpnea compared with control (ES200 = 2.6 ml; P less than 0.0001). Methacholine dose-response curves (10(-11) to 10(-7) mol iv) obtained at the conclusion of the experiments were similar among capsaicin, phosphoramidon, and control groups. These findings implicate tachykinin release as an important mechanism of HIB in guinea pigs.