Determination of the critical micelle concentration of surfactants using the fluorescent probe N-phenyl-1-naphthylamine

The fluorescence quantum yield of N-phenyl-1-naphthylamine (NPN) increases about 10-fold and the wavelength of maximum fluorescence emission is blue-shifted when this molecule partitions into the apolar core of micellar structures from the aqueous phase. This property allowed the utilization of NPN as a fluorescent indicator of micelle formation by 14 different surfactants belonging to the families of alkyltrimethylammonium halides, alkylsulfates, alkylbetaines, alkylglucosides, and bile salts. The critical micelle concentrations (CMCs) determined with NPN agreed well with literature values. In this work NPN was used at a concentration of 10(-6) M which allowed determination of CMCs in the range between approximately 10(-5) and greater than 10(-2) M. With high-sensitivity instrumentation considerably lower NPN concentrations can be used and consequently considerably lower CMCs can be rapidly and accurately determined.     

Pathology of the human pulmonary paracoccidioidomycosis

Lungs of twelve patients with chronic paracoccidioidomycosis (Pb) were studied in an attempt to understand the pathogenesis of the pulmonary disease. Ribbons of the lung parenchyma including the hilar region and directed towards apical, basal and lateral regions were subdivided into sections from the hilar, intermediate and peripheral segments. The following histopathological reactions directly or indirectly related to P. brasiliensis were described and analysed in relation to the number of slides studied and the pulmonary region involved: (1) pneumonic reaction; (2) early granulomatous formation; (3) mature and healed granulomata; (4) mixed pattern (early and mature granuloma in the same pulmonary area visualized in the slide); (5) pulmonary fibrosis.It was concluded that chronic pulmonary Pb is a recurrent disease affecting equally both lungs. Fibrosis was connected mainly with the progressive evolution of the granulomata towards cicatrization and to a lesser degree probably to a direct induction by the fungi. Based chiefly on the tendency of the fibrosis to run around bronchi and to make up septa interconnecting bronchi and vessels it was hipothesized that these findings were the result of a previous chronic specific lymphangitis by the fungi. Hilar fibrosis would be the result of this lymphangitis and/or of the progression of the specific granulomatous reaction seen in the hilar lymph nodes.Non specific forms of arteritis and areas of destructive emphysema related to granulomatous inflammation and fibrosis were described. Three cases developed pulmonary hypertension.     

Polypeptide composition of rat sperm outer dense fibers. A simple procedure to isolate the fibrillar complex

Treatment of caput or cauda epididymal rat sperm with a low concentration (0.05%) of the cationic detergent cetyltrimethylammonium bromide and 30 mM 2-mercaptoethanol solubilized most of the sperm structures except for the sperm head and the outer dense fiber-connecting piece complex. The latter were purified, and about 10% of these complexes are formed by nine fibers attached to the connecting piece. Of these fibers, two are shorter than the other seven and presumably correspond to fibers 3 and 8 (Fawcett, D.W. (1975) Dev. Biol. 44, 394-436). Electron microscopy confirmed the purity of the isolated outer dense fibers and revealed their characteristic irregular cross-sectional shape. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate showed six major polypeptides (Mr = 87,000, 30,400, 26,000, 18,400, 13,000, and 11,500) with a high content of serine, aspartic and glutamic acids, proline, cysteine, leucine, and tyrosine. Furthermore, several lines of evidence indicate a close structural relationship between the components of 30,400 and 26,000 Da. The six major components of the fibers are phosphorylated at serine residues. These results indicate that the major components of rat sperm outer dense fibers are a unique family of phosphoproteins.     

Comparative NMR studies on cardiac troponin C and a mutant incapable of binding calcium at site II

One- and two-dimensional NMR techniques were used to study both the influence of mutations on the structure of recombinant normal cardiac troponin C (cTnC3) and the conformational changes induced by Ca2+ binding to site II, the site responsible for triggering muscle contraction. Spin systems of the nine Phe and three Tyr residues were elucidated from DQF-COSY and NOESY spectra. Comparison of the pattern of NOE connectivities obtained from a NOESY spectrum of cTnC3 with a model of cTnC based on the crystal structure of skeletal TnC permitted sequence-specific assignment of all three Tyr residues, as well as Phe-101 and Phe-153. NOESY spectra and calcium titrations of cTnC3 monitoring the aromatic region of the 1H NMR spectrum permitted localization of six of the nine Phe residues to either the N- or C-terminal domain of cTnC3. Analysis of the downfield-shifted C alpha H resonances permitted sequence-specific assignment of those residues involved in the beta-strand structures which are part of the Ca(2+)-binding loops in both the N- and C-terminal domains of cTnC3. The short beta-strands in the N-terminal domain of cTnC3 were found to be present and in close proximity even in the absence of Ca2+ bound at site II. Using these assignments, we have examined the effects of mutating Asp-65 to Ala, CBM-IIA, a functionally inactive mutant which is incapable of binding Ca2+ at site II [Putkey, J.A., Sweeney, H. L., & Campbell, S. T. (1989) J. Biol. Chem. 264, 12370]. Comparison of the apo, Mg(2+)-, and Ca(2+)-bound forms of cTnC3 and CBM-IIA demonstrates that the inability of CBM-IIA to trigger muscle contraction is not due to global structural changes in the mutant protein but is a consequence of the inability of CBM-IIA to bind Ca2+ at site II. The pattern of NOEs between aromatic residues in the C-terminal domain is nearly identical in cTnC3 and CBM-IIA. Similar interresidue NOEs were also observed between Phe residues assigned to the N-terminal domain in the Ca(2+)-saturated forms of both cTnC3 and CBM-IIA. However, chemical shift changes were observed for the N-terminal Phe residues in CBM-IIA. This suggests that binding of Ca2+ to site II alters the chemical environment of the residues in the N-terminal hydrophobic cluster without disrupting the spatial relationship between the Phe residues located in helices A and D.     

Studies on the yield and gel strength of agar from Gracilaria domingensis Sonder ex Kuetzing (Gracilariales,Rhodophyta) following the addition of calcium

Studies were carried out on the seasonal variation in yield and gel strength of agar from Gacilaria domingensis with and without the addition of calcium chloride. Extraction was done with and without treatment with 1% hydrochloric acid. The results showed an increase in yield and gel strength when an alkaline solution of calcium was used, but the gel strength was low. For commercial use, Gracilaria domingensis should be mixed with better quality Gracilaria species because of its low gel strength.     

REPRODUCTIVE BIOLOGY OF A TROPICAL PALM SWAMP COMMUNITY IN THE VENEZUELAN LLANOS

The reproductive biology of a tropical palm swamp community, called morichal in the Venezuelan Central Llanos, was studied. Of the 128 woody and herbaceous species of plants recorded, 99 (77.34%) were hermaphrodites, 25 (19.53%) were monoecious, and four (3.13%) were dioecious. The morichal is characterized by a low number of species with obligate cross-fertilization. The frequencies of species with different breeding systems in a subsample of 26 species showed that eight (30.77%) were self-incompatible, 14 (53.85%) were self-compatible, and four (15.38%) were agamospermous. Ten of 14 self-compatible species were autogamous. Regardless of the self-incompatibility level estimated, seed and fruit set were greater in self-fertilized flowers than in hand-pollinated flowers in three of the nine self-incompatible species. These results are related to the facts that: 1) the relative isolation of the plant population limits the gene flow among similar communities and enforces the intrapopulation pollen flow; 2) the overlapping flowering patterns and infrequent and unspecialized pollinators may be enforcing self-compatibility and agamospermy; 3) self-compatibility is the rule among short-lived species in the morichal; and 4) three out of four agamospermous species are of the Melastomataceae family.