Arrangement of pili in colonies of Neisseria gonorrhoeae.

The morphology and arrangement of pili in the P++ colony phenotype of Neisseria gonorrhoeae were examined by a variety of electron microscopic techniques. The apparent structure and organization of gonococcal pili varied depending upon the method of specimen preparation. Pili as thin, individual, unbranched structures were demonstrated by negative staining and in sections of epoxy-embedded specimens. Pili forming thick structures which branch, subdivide, and rejoin to form an irregular lattice were demonstrated in specimens processed by the critical-point drying method and by rapid freezing and low temperature sublimination. We propose that in gonococcal colonies of the P++ phenotype, pili exist as individual threadlike structures only on the bacterial surfaces; as the pili leave the bacterial surfaces, they form thick bundles which branch, subdivide, and rejoin to form a supporting framework interconnecting the colony members. This arrangement of pili is usually disrupted by the commonly used method of negative staining and cannot be clearly detected within epoxy-embedded specimens. These data are summarized in a model depicting the organization of pili in the P++ colony phenotype of N. gonorrhoeae.     

IgE immune complexes induce immediate and prolonged release of leukotriene C4 (LTC4) from rat alveolar macrophages

Alveolar macrophages obtained by lung lavage from rats were incubated with monoclonal mouse anti-DNP IgE and specific antigen (DNP-HSA) and were found to release a slow reacting substance (SRS), which was characterized by high performance liquid chromatography as leukotriene C4 (LTC)4. Alveolar macrophages incubated with 1 microM A23187 (calcium ionophore) released similar amounts of SRS (6.0 +/- 2.2 and 5.7 +/- 3.7 X 10(-10) mol of LTC4 per 5 X 10(6) alveolar macrophages, respectively). The optimal conditions and mechanism of LTC release by IgE and antigen were examined. LTC4 release was maximal when freshly retrieved alveolar macrophages were incubated for 20 min with 10 micrograms/ml IgE and then for 20 min with 100 ng/ml antigen or for 20 min with IgE and antigen that had been preincubated together for 30 min at room temperature. In addition, LTC4 release was maximal when cells were challenged with IgE and antigen in a protein-free balanced salt solution and when the cells were tumbled to prevent adherence. Dose response experiments revealed that macrophages released LTC4 when stimulated with as little as 10 ng IgE and 100 ng DNP-HSA. Alveolar macrophages did not release LTC when challenged with IgE or DNP-HSA alone. Activation of LTC4 release by IgE and antigen was rapid in onset (2.5 to 5 min), and washing to remove fluid phase IgE and antigen revealed that once activated, alveolar macrophages were capable of prolonged and continuous release of LTC4. Peritoneal lavage cells stimulated with IgE and antigen did not release SRS but could release SRS when incubated with A23187 (5.7 +/- 1.3 X 10(-10) mol LTC4/5 X 10(6) macrophages). A large variability existed between individual rats in the ability of their alveolar macrophages to be activated by IgE and antigen to release LTC4. DNP-HSA labeled with 125I was used to show formation of immune complexes of IgE and antigen when IgE and antigen were incubated together before macrophage challenge. IgE immune complexes containing as little as 2 ng of antigen elicited the release of LTC4 from alveolar macrophages. These data indicate that rat alveolar macrophages release primarily LTC4 when challenged with IgE immune complexes, and that the alveolar macrophage may differ in this respect from peritoneal macrophages that do not release detectable quantities of LTC4 when challenged under identical conditions.     

The lipid composition and permeability to the triazole antifungal antibiotic ICI 153066 of serum-grown mycelial cultures of Candida albicans

The total lipid content of Candida albicans (serotype A: NCPF 3153) exponential-phase mycelial cultures grown in tissue-culture medium 199 (containing 10%, v/v, foetal calf serum) was 29.8 +/- 8 mg (g dry weight)-1 (mean +/- SD). The weight ratios of phospholipid to neutral lipid and phospholipid to non-esterified sterol were 2.6 +/- 0.4 and 24.9 +/- 0.5, respectively. The major phospholipid was phosphatidylcholine with smaller amounts of phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylglycerol and diphosphatidylglycerol; the most abundant fatty acids were palmitic, palmitoleic, oleic and linoleic acids. The major neutral lipids comprised esterified sterol, triacylglycerol and non-esterified fatty acid with a smaller amount of non-esterified sterol. The fatty acid compositions of the three fatty-acid-containing neutral lipids were distinct from each other and the phospholipids. Comparison with previous data on yeast cultures of C. albicans A grown in glucose broth shows that mycelial cultures have a larger lipid content, lower phospholipid to neutral lipid ratio and higher phospholipid to non-esterified sterol ratio. We now show that mycelial cultures were more permeable to a [14C]triazole antifungal antibiotic compared with exponentially growing yeast cultures of several azole-sensitive strains. Taken together these data are consistent with there being a relationship between the phospholipid/non-esterified sterol ratio of a culture and its ability to accumulate a triazole.     

The Value of a hoard: not just energy

We present a stochastic dynamic programming model of the contributionof stored food to winter survival. Using the acorn woodpecker(Melanerpes formtcivorus) as a model organism, we demonstratethat a hoard of small energetic value can impart considerableimprovement in the probability of surviving the winter and soimprove fitness. With this model we hope to resolve Koenig andMumme's paradox, that acorn woodpeckers expend much time andeffort to create and maintain hoards of acorns which provideno more that 16% of their energetic needs over the period inwhich they are used. We further demonstrate that the contributionof hoarded acorns to survival depends on the variability inforaging outcome, independently of the energetic value of thehoard in absolute terms. We point out that the results applyin principle to all hoarding animals and suggest a number offurther elaborations of the model.     

Separation and partial characterization of fractions derived from frog lung homogenates. A possible marker system for amphibian pulmonary surfactant.

The purpose of this study is to determine if inframammalian vertebrate (amphibian) lung contains certain nonspecific esterases that have been identified as enzyme markers for mammalian (rat and mouse) pulmonary surfactant. Density gradient centrifugation procedures were utilized to concentrate any surface-active material in frog lung homogenates. Lipid and protein analyses of one of the derived fractions and of pulmonary lavage fluid were consistent with other techniques indicating that these preparations were surface active. A comparison of the nonspecific esterases in the derived fractions and the pulmonary lavage fluid allowed the identification of a nonspecific esterase that has an electrophoretic mobility comparable to one of the nonspecific esterases already identified as an enzyme marker for mammalian (rat and mouse) pulmonary surfactant. These results indicate that these enzyme markers may be useful in the further investigation of the surfactant systems of other inframammalian vertebrates.     

Reduction in basal adenylate cyclase activity during the immunologic release of histamine from guinea pig lung.

Cyclic AMP has been implicated in the regulation of the immunologic release of histamine from lung and other tissues and cell types. The mechanism whereby intracellular levels of cAMP are altered during mediator release was investigated. Measurements of histamine, adenylate cyclase, and cAMP phosphodiesterase activities were made in actively and passively sensitized guinea pig lung after challenge with antigen. A transient decrease in basal adenylate cyclase activity occurred which returned to control levels after histamine release. There was no change in cAMP phosphodiesterase activity determined at substrate concentrations of 1 mM and 0.01 mM. The adenylate cyclase response did not occur under the following conditions: 1) incubation of nonsensitized lung with antigen, 2) incubation of sensitized lung with antigen in the absence of extracellular calcium, and 3) incubation of nonsensitized lung with compound 48/80. These observations indicate 1) the adenylate cyclase response and the immunologic release of histamine are intimately related, and 2) the reduction in intracellular levels of cAMP which have been reported to occur during immunologic histamine release are mediated via adenylate cyclase.     

Study of the structure of troponin-T by measuring the relative reactivities of lysines with acetic anhydride

The structure of troponin-T has been studied by measuring the relative reactivity of lysines with acetic anhydride using a competitive labeling method. Troponin-T was acetylated free and complexed with -I and -C in the native state with [³H]acetic anhydride, purified, and then combined with ¹⁴[C]troponin-T that had been acetylated in 6 m-guanidine · HCl. Peptides containing labeled lysines were isolated following chymotryptic and tryptic digestion and identified in the published sequence. The ${}^3\text{H}{}^{14}\text{C}$ ratio of these peptides was used as a measure of relative accessibility of the lysines. Troponin-T contains 39 lysines; we have identified 35 of these in 22 different peptides. The region of troponin-T influenced by binding to the other troponin components is extensive and includes the C-terminal half of the molecule as well as some residues in the N-terminal half. The lysines showing the greatest change in reactivity are concentrated between residues 114 to 223. The reactivities of the troponin-T lysines labeled in native troponin were not significantly influenced by the binding of calcium to the calcium-specific binding sites of troponin-C. A model for the structure of troponin-T is proposed based on the present and previous studies.     

Regulation of lysine- and lysine-plus-threonine-inhibitable aspartokinases in Bacillus brevis.

Further studies on the expression of the two aspartokinase activities in Bacillus bovis are presented. Aspartokinase I (previously shown to be inhibited and repressed by lysine) was found to be repressed by diaminopimelate in the wild-type strain. However, in a mutant unable to convert diaminopimelate to lysine, starvation for lysine resulted in an increase in aspartokinase I activity. Thus, lysine itself or an immediate metabolite was the true effector of repression. Aspartokinase II (previously shown to be inhibited by lysine plus threonine) was repressed by threonine. Studies with the parent strain and auxotrophs inidicated that only threonine or an immediate metabolite of threonine was involved in this repression. Methionine and isoleucine were not effectors of any of the detected aspartokinase activities. Apart from inhibition and repression controls, a third as yet undefined regulatory mechanism operated to decrease the levels of both aspartokinases as growth declined, even in mutants in which repression control was absent. In thiosine-resistant, lysine-excreting mutants with elevated levels of aspartokinase, the increase in activity could always be attributed to one enzyme or the other, never both. The existence of separate structural genes for each aspartokinase is therefore suggested.     

Actin deoxyroboncuclease I interaction. Depolymerization and nucleotide exchange

Deoxyribonuclease I (DNase I) forms a 1:1 complex with globular actin (G-actin) and also will depolymerize filamentous actin (F-actin) to form a 1:1 complex. The effect of DNase I on the exchange of the actin nucleotide has been investigated. When DNase I is added to G-actin, the rate of nucleotide exchange is decreased from 1.16 +/- 0.25 X 10(-4) s-1 to 0.28 +/- 0.09 X 10(-4) s-1 (0 degrees C). The presence of ATP or ADP in the actin has little effect on the rate of exchange of the nucleotide for ATP. This suggests that the weaker affinity of ADP than ATP for actin is due to a slower association rate of ADP. The rate of the nucleotide exchange in the actinDNase I complex is increased by the addition of NaCl or MgCl2. When DNase I is added to F-actin, the rate of nucleotide exchange (6.2 +/- 1.6 X 10(-4) x-1, 0 degrees C) is similar to the rate of depolymerization as measured by loss of viscosity. The actinDNase I complex formed by depolymerization of F-actin exchanges nucleotide at a 4-fold faster rate than the G-actinDNase I complex in the same ionic conditions. This and other experiments suggest that DNase I binds first to F-actin before dissociating the monomer from the filament. These results are discussed in terms of possible mechanisms of action depolymerization.     

Regulation of muscle contraction: bindings of troponin and its components to actin and tropomyosin.

The bindings of troponin components to actin and tropomyosin has been studied by cosedimentation with actin and affinity chromatography. It is shown that troponin binds to actin and tropomyosin in the presence and absence of calcium but the binding to actin is sensitive to ionic strength. Troponin-I + C binds to actin-tropomyosin in the absence of calcium but not to actin or tropomyosin alone. Troponin-I binds to actin and the binding is improved in the presence of tropomyosin even though troponin-I does not bind to tropomyosin alone. Troponin-C does not bind to actin or tropomyosin. The results suggest that the binding of troponin by actin is influenced by tropomyosin. A model of regulation by troponin is proposed.