Decrease in the airways' nonadrenergic noncholinergic inhibitory system in allergen sensitized rabbits.

A decrease in the airways' nonadrenergic noncholinergic inhibitory (NANC-i) system is one of the mechanisms that may contribute to allergen-induced changes in neural control within airways. We measured the airways' neurally mediated contractile and relaxant (NANC-i) responses in tracheal segments and left mainstem bronchus (LMB) from normal (control), immune (ragweed sensitized), and immune challenged rabbits. Immune rabbits were sensitized to mixed ragweed extract through parenteral injections from birth, while the immune challenged group had an additional airway exposure to aerosolized ragweed 48 hours prior to the in vitro studies. Neurally mediated contractile responses to electrical field stimulation (EFS) were increased in the immune challenged group, with the increase most significant in tracheal smooth muscle at a stimulation frequency of 20 Hz. To assess NANC-i responses, airway smooth muscle (ASM) segments from these groups were placed in tissue baths containing atropine (10(-6) M) and propranolol (5 x 10(-6) M). After contraction of the tissue with neurokinin A (NKA, 10(-5) M), the NANC-i response to EFS at 20 Hz was measured and reported as the mean (+/- SEM) percent relaxation. No significant differences were seen in the contractile responses of ASM segments to NKA among the three groups. The tracheal segments showed a significantly different NANC-i relaxation response among all groups: in the control group, 29.1 +/- 3.7; in the immune group 15.8 +/- 2.3%; and in the immune challenged group, 2.1 +/- 4.2%.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of divalent metal ions on the fluorescence and glucose-quenching of yeast hexokinase isozymes.

Titrations of the quenching of the tryptophan fluorescence of yeast hexokinase isozymes P-I and P-II by Mg2+, Mn2+, Ca2+, Cd2+, and Zn2+ ions and by glucose in the presence of each of these ions (10mM) were performed at pH 5.5 and 6.5 at 20 degrees C. At the higher pH there was a reversal of the type of glucose-binding cooperativity for P-II from negative to positive when either Mn2+ or Ca2+ was present in the buffered isozyme solution before the glucose titration, whereas Mg2+ caused the glucose binding to become noncooperative. Zn2+ and Cd2+ decreased the glucose quenching of P-II fluorescence drastically at pH 5.5, from a value of 15% in buffer to only 4%. Thus, only these two ions, of the five studied, cause the conformation change that results in quenching of the glucose-quenchable cleft tryptophan of P-II. Glucose binding to the P-I isozyme exhibited positive cooperativity in the presence of either Ca2+, Mg2+, or Mn2+, as well as in buffer alone, at both pH's. At the lower pH, Ca2+ enhanced the efficiency of glucose quenching of P-I fluorescence several-fold, while Mn2+ increased it only about 40% and Mg2+ not at all. Further, Ca2+ raised the degree of cooperativity (Hill coefficient) of glucose binding to P-I at this pH from the value of 1.42 in buffer and in the presence of Mg2+ and Mn2+ to 1.94, i.e., almost up to the highest possible value, 2, for dimeric hexokinase. However, at pH 6.5 the Ca2+ effect on the cooperativity was negligible, while Mg2+ and Mn2+ decreased the coefficient from 1.6 in buffer to about 1.4. The biological implications of these diverse metal ion effects are discussed.

Latex allergy.

Latex is a natural product obtained from rubber trees. Sensitization and subsequent exposure to latex products can lead to allergic (immediate hypersensitivity) reactions including anaphylaxis. Gloves are the largest source of latex exposure, and the majority of serious latex reactions occur in medical settings. Allergen testing and avoidance in history positive or high risk groups (medical personnel, spina bifida patients and rubber workers) is presently the best treatment option.

Increased acetylcholine release in tracheas from allergen-exposed IgE-immune mice.

Increased release of acetylcholine (ACh) from airway parasympathetic nerve endings is one mechanism that may contribute to increases in airway responsiveness in immunoglobulin E (IgE)-immune allergen-exposed animals. We measured ACh released from murine tracheas following electrical field stimulation in vitro. BALB/c mice were immunized by exposure to an aerosol of 1% ovalbumin in sterile phosphate-buffered saline for 20 min/day for 10 days. At this time, levels of ovalbumin-specific IgE were proportionately higher than ovalbumin-specific IgG. As a control, nonimmune mice were similarly exposed to phosphate-buffered saline alone. Forty-eight hours after the last aerosol, tracheas were removed for assessment of either the contractile responses to electrical field stimulation and a cholinergic agonist (methacholine or ACh) or release of ACh produced by electrical field stimulation. ACh in the bath was measured using high-performance liquid chromatography with electrochemical detection. The stimulation frequencies causing one-half the maximal contractile response to electrical field stimulation were 4.1 +/- 0.2 and 2.8 +/- 0.2 Hz (P = 0.0001) for nonimmune and immune mice, respectively, whereas the molar concentrations of methacholine causing one-half of the maximal contractile response did not significantly differ. In addition, the dose-response curves of immune and nonimmune tracheas to ACh were superimposable. A significant increase in ACh release was demonstrated at both 10 and 20 Hz in tracheas from immune mice. ACh release (pmol.g tissue-1.min-1) from nonimmune and immune murine tracheas, respectively, were 140 +/- 8 and 205 +/- 22 (P = 0.013) at 10 Hz and 147 +/- 13 and 227 +/- 14 (P = 0.008) at 20 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)