The incorporation of acetate by the chemoautotroph Thiobacillus neapolitanus strain C

Summary Cultures of Thiobacillus neapolitanus strain C assimilate ¹⁴C-labelled acetate and aspartate. Both carbon atoms of acetate are incorporated, and 25% of the cell carbon can arise from acetate. Aspartate-¹⁴C contributes 4–5% of the cell carbon, and is found in pyrimidines and in protein as aspartate and its related amino acids. Acetate-¹⁴C contributes to lipid, glutamate, arginine, proline and leucine, but not to aspartate. Acetate assimilation by washed organisms requires carbon dioxide and energy from thiosulphate oxidation. Degradation of ¹⁴C-glutamic acid from acetate-¹⁴C-labelled bacteria; the accumulation of ¹⁴C-citrate in the presence of fluoroacetate and [¹⁴C] acetate; short-term kinetic experiments on acetate-¹⁴C turnover; and the demonstration of citrate synthesis by cell-free extracts all indicate glutamate synthesis from -ketoglutarate formed by reactions of the tricarboxylic acid cycle. The cycle is believed to be incomplete, probably not proceeding further than -ketoglutarate, and functions as a glutamate-synthesising system, using oxaloacetate derived solely from carbon dioxide fixation. Malate synthase (and the glyoxylate cycle) appear to be insignificant in the metabolism, but extracts did form citramalate from acetate and pyruvate.     

Serological reactions associated with the clumping factor of Staphylococcus aureus

Rotter, Joan (University of Oklahoma Medical Center, Oklahoma City), and Florene C. Kelly. Serological reactions associated with the clumping factor of Staphylococcus aureus. J. Bacteriol. 91:588-594. 1966.-Evidence that the substance which causes staphylococci to clump in the presence of fibrinogen (clumping factor) is antigenically similar in strains which are serologically diverse according to agglutination reactions has been obtained from fibrinogen-cell clumping inhibition tests. Antisera for clumping factor (CF)-positive strains inhibited the clumping reaction of all strains tested. After adsorption with homologous cells or with cells of other CF-positive strains, the antisera no longer inhibited clumping. When antisera were adsorbed with trypsin-treated, CF-positive cells, or with cells of CF-negative mutants, the ability to inhibit the clumping reaction persisted. Antibody to CF activity was not associated with coagulase. Latex coated with extracts derived from the cells of five CF-positive and six CF-negative strains was, in each instance, agglutinated by sera from rabbits immunized with CF-positive cells. After adsorption with trypsinized, CF-positive cells, antisera still agglutinated latex which had been treated with the CF-positive extracts, but not with the CF-negative extracts. Similar results were obtained after antisera were adsorbed with the cells of CF-negative mutants. Cell agglutination titers of sera from rabbits immunized with CF-negative staphylococci were significantly lower than those produced in response to CF-positive cells, regardless of their coagulase activity. If the CF-inhibiting antibody also functions as an agglutinin, it apparently is not solely responsible for this difference.     

Beta-adrenergic relaxation of dog trachealis: contractile agonist-specific interaction

The phenomenon of contractile agonist-dependent relaxation by isoproterenol (ISO) of active tension elicited by acetylcholine (ACh), histamine (HIS), serotonin (5-HT), and potassium chloride-substituted Krebs-Henseleit solution (KCl) was studied in 210 tracheal smooth muscle (TSM) strips from 28 mongrel dogs in vitro. All TSM strips were contracted to similar active tensions [target tension (TT) = 50% of the maximal active tension elicited by 127 mM KCl] with ACh, HIS, 5-HT, or KCl and relaxed with either ISO, forskolin (FSK), N6,2'-O-dibutyryladenosine 3',5'-cyclic monophosphate (db-cAMP), or 3-isobutyl-1-methylxanthine (IMX). The concentrations of ISO causing 50% relaxation from TT (RC50) were ACh (2.9 +/- 1.1 x 10(-6) M) greater than 5-HT (8.4 +/- 1.5 x 10(-8) M) approximately KCl (8.1 +/- 2.1 x 10(-8) M) greater than HIS (1.6 +/- 0.2 x 10(-8) M). FSK and IMX relaxed TSM in the same rank order of potency as ISO. In contrast to the contractile agonist-dependent relaxation elicited by ISO, FSK, and IMX, db-cAMP was nearly equipotent in relaxing similarly contracted strips. These results are consistent with contractile agonist-specific interaction with cAMP production by ISO and FSK. These data demonstrate that the phenomenon of contractile agonist-dependent relaxation by ISO is not related specifically to the beta-adrenoceptor.     

Pressure-diameter relationships of the upper airway in awake supine subjects

In awake supine normal subjects, dimensional changes of the oropharyngeal airway were measured during exposure to negative intraluminal pressures. The pressure was generated 1) "actively" by subjects inspiring against an externally occluded airway or 2) "passively" by external suction at the mouth during voluntary glottic closure with no inspiratory effort. Airway dimensions were imaged with X-ray fluoroscopy and anteroposterior diameters measured at levels corresponding to cervical vertebra 3 and 4 (C3 and C4). Cephalad axial displacement of the hyoid bone (CDHY) was also measured. During the "active" maneuver, airway diameters and position were maintained at resting levels despite airway pressure up to -15 cmH2O. In contrast, during the passive maneuver at -15 cmH2O, C3 was only 15 +/- 9% and C4 only 47 +/- 8% of control; CDHY was 5.6 +/- 1.8 mm. In three subjects airway wall apposition occurred and persisted until an active inspiratory effort. We conclude that, in the absence of inspiratory effort, negative oropharyngeal airway pressures result in marked narrowing and cephalad displacement of the upper airway, even during wakefulness. Therefore, our data suggest that the complex interaction of upper airway and thoracic muscle activity is critical in determining the effective compliance and patency of the upper airway, which is readily collapsible even in normal subjects.     

Extracellular Ca2+ mobilization in potential-dependent contraction of trachealis of maturing swine.

We studied the effect of maturation on potassium-induced parasympathetic activation and Ca2+ entry in tracheal smooth muscle (TSM) from fifteen 2-wk-old (2ws) and sixteen 10-wk-old (10ws) male domestic farm swine. Atropine (10(-7) M) caused inhibition of the maximal contraction elicited by potassium to 50.3 +/- 2.6% maximum of control response (P less than 0.001) in TSM from 2ws but had no significant effect in TSM from 10ws (94.6 +/- 4.2% maximum; P = NS vs. control). Verapamil (10(-7) M) plus 10(-7) M atropine reduced contraction elicited by potassium in both 2ws (23.7 +/- 5.8% maximum; P less than 0.001 vs. control) and 10ws (50.6 +/- 6.3% maximum; P less than 0.001 vs. control, P less than 0.05 vs. 2ws); 10(-6)M verapamil caused greater than 95% blockade of contraction caused by potassium in both 2ws and 10ws. In separate studies, atropine-treated strips were equilibrated with extracellular Ca2+ concentrations ([Ca2+]o) ranging from normal (1X [Ca2+]o) to four times normal (4x [Ca2+]o). Increasing [Ca2+]o increased maximal contractile response in atropine-treated TSM strips from 68.7 +/- 3.8% maximum for 1x [Ca2+]o to 100.8 +/- 4.8% maximum for 4x [Ca2+]o (P less than 0.001) in 2ws. Neither atropine nor [Ca2+]o affected maximal responses of TSM in 10ws (103.5 +/- 3.0% maximum for 1x [Ca2+]o; P = NS vs. control). However, in the presence of atropine and verapamil, 4x [Ca2+]o augmented KCl-elicited contraction of TSM from both 2ws (46.9 +/- 6.3% maximum; P less than 0.01 vs. control) and 10ws (78.6 +/- 2.3% maximum; P less than 0.005 vs. control).(ABSTRACT TRUNCATED AT 250 WORDS)