Low-ultraviolet circular dichroism spectroscopy of sequential peptides 1-63, 64-95, 96-128, and 129-168 derived from myelin basic protein of rabbit

Four sequential peptides (sequences 1-63, 64-95, 96-128, and 129-168) derived from rabbit myelin basic protein by thrombic cleavage were examined by low-ultraviolet circular dichroism spectroscopy in 0.5 mM tris(hydroxymethyl)aminomethane hydrochloride (pH approximately 7.2) containing 0-92% trifluoroethanol (TFE). In the absence of the alcohol, all of the peptides contained a significant amount (17-29%) of beta-structure. In the presence of relatively low concentrations (up to 30%) of TFE, all of the peptides except 96-128 adopted considerable alpha-helix (16-33%). This involved a transition from the beta-structure in peptide 1-63 and transitions from the nonordered structure in peptides 1-63, 64-95, and 129-168. Furthermore, additional alpha-helix formed in peptide 1-63 between 30% and 92% TFE at the expense of nonordered structure, whereas the alpha-helix formation above 50% TFE in peptide 129-168 resulted largely from a beta-structure----alpha-helix transition. With the exception of the 129-168 peptide, approximately 65-100% of the maximum level of beta-structure persisted throughout the entire range of TFE concentration. In the case of peptide 129-168, however, most of the beta-structure was converted to alpha-helix and nonordered structure at 75% TFE. While the present results support our previous assignments of beta-structure- and alpha-helix-forming regions to specific amino acid sequences of the basic protein, they also demonstrate that the beta-structure----alpha-helix transitions evidenced at various concentrations of TFE were influenced to a considerable degree by the length of the peptide, presumably due to the presence or absence of interactions between noncontiguous portions of the myelin basic protein polypeptide chain.

Low-ultraviolet circular dichroism spectroscopy of oligopeptides 1-95 and 96-168 derived from myelin basic protein of rabbit

Myelin basic protein (MBP) is a major protein constituent of the myelin sheath of the central nervous system, where it is believed to have functional alpha-helical segments. One element of the function of the protein might be "conformational adaptability" of specific regions of its amino acid sequence, since the purified protein appears to be largely devoid of ordered structure. To pursue this question, low-ultraviolet circular dichroism (CD) spectroscopy was conducted on the sequential thrombic peptides 1-95 and 96-168 of the protein in the presence of 0-92% trifluoroethanol (TFE), a solvent known to promote stable secondary structures in polypeptides. The series of CD spectra of the oligopeptides were subjected to a computerized best-fit analysis of four peptide conformations, the alpha-helix, beta-structure, beta-turn, and nonordered form. Agreement between experimental and best-fit composite spectra was achieved when standard CD curves of peptide conformations were derived from known theoretical spectra and experimental spectra of polypeptides. In dilute buffer alone, oligopeptides 1-95 and 96-168 evidence no alpha-helix but significant beta-structure (18% and 23%, respectively), as well as a predominant, extended nonordered conformation. However, the two parts of the protein differed in conformational adaptability. From 0% to 30% TFE, 96-168 exhibited concomitant transitions to 10% helix and 32% beta-structure from the nonordered form. In contrast, in 10-30% TFE, 1-95 underwent a transition to approximately 21% helix with partial loss of beta-structure as well as nonordered form; higher concentrations of TFE (40-75%) promoted additional transitions to both helix and beta-structure (totaling 33% and 25%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Physical model approach to gastrointestinal absorption of prostaglandins II: In situ rat intestinal absorption of dinoprost

In situ absorption studies with dinoprost in the rat jejunum were carried out using a modified Doluisio technique. The absorption rate was first order. There was a sigmoidal decrease in the rate with increasing buffer pH (from 3.5 to 9.5), which strongly indicated the partitioning of weak acid species into the lipoidal membrane. An asymptotic minimum rate was attained from buffer pH 7.5 to 9.5, operationally indicative of transport of anions across aqueous pores. The importance of the aqueous diffusion layer on the mucosal side of the membrane was evident; rates at pH 3.5 and 4.5 were faster at high agitation hydrodynamics in the lumen solution. Preliminary studies showed that there was no metabolism in the lumenal solution and that metabolism occurred within the membrane. The transport mechanism involved simultaneous passive diffusion and bioconversion in the membrane because (a) a 1.5 X 10(4)-fold range in dinoprost concentration (0.014-210 microM) showed no saturable carrier-mediated tendency on the rate, (b) iodoacetic acid and indomethacin did not inhibit the absorption rate, and (c) the shape of the absorption-pH profiles was suggestive of passive diffusion. The prostaglandin did not have apparent adverse membrane and vascular effects under the conditions employed. The quantification and factorization of the physically meaningful transport parameters were accomplished using the physical model previously described. The permeability coefficients of the aqueous diffusion layer for the oscillation and static hydrodynamic situations were 0.8 X 10(-4) and 1.7 X 10(-4) cm/s, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

The flushing response to alcohol use among Koreans and Taiwanese

Alcohol use, the existence of a flushing response to alcohol and the amount of alcohol required to evoke flushing were studied by questionnaire in 87 homeland Korean and 101 Taiwan Chinese families. SFs (slow flushers--flush after two or more drinks) and FFs (fast flushers--flush after one drink or less) were compared. Despite the similarity in the proportions of subjects who reported flushing, Koreans reported very heavy and Taiwanese very light alcohol use. The two groups differed substantially in the proportions of SFs and FFs. Five ethnic groups in Hawaii were compared with the Koreans and Taiwanese. It appears that fast flushing, but not slow flushing, leads to substantial decreases in alcohol use among all seven groups. The association of flushing type with the extent and duration of flushing and with the frequency of other alcohol-related symptoms may be dose-dependent. For both Koreans and Taiwanese, family resemblances in flushing are substantial but not supportive of the belief that flushing is dominant and results from the influence of a single autosomal gene pair. Of the large groups of subjects from whom data were obtained (Caucasians, Chinese, Filipinos, Hawaiians or part Hawaiians, and Japanese in Hawaii; homeland Koreans; and Taiwan Chinese), the Koreans and Taiwanese differ the most from one another in alcohol consumption. In summary, there is substantial diversity among groups frequently lumped together as "Mongoloid."

Topical vaginal drug delivery I: effect of the estrous cycle on vaginal membrane permeability and diffusivity of vidarabine in mice

Preliminary studies showed that the vaginal membrane permeability coefficients for vidarabine (9-beta-D-arabinofuranosyladenine) varied widely within a group of mice of the same species and age. This finding prompted an investigation of the influence of the female mouse sexual cycle on the vidarabine permeability. By means of a vaginal smear technique, the sexual cycle, which was approximately 5 days in duration, was divided into five phases. The vaginal membrane permeability of vidarabine was determined during each phase. The results revealed that the permeability coefficients for vidarabine during the diestrus phase (3 X 10(-6)-4 X 10(-5) cm/sec) were 10-100 times higher than those obtained at the early estrus or estrus phases (1-3 X 10(-7) cm/sec). Further permeation studies on membranes at early estrus and estrus were performed by separating the cornified layer from the noncornified portion of the membrane. The low permeability coefficient of vidarabine across the cornified layer (4 X 10(-7) cm/sec) suggests that this layer may be the major diffusion barrier for vidarabine when the drug is topically applied. Collectively, the data also suggest that during estrus a three-layer diffusion model is appropriate, that during early diestrus a single-layer diffusion model may apply, and that during proestrus and postestrus the situations are intermediate and more complicated.

High-performance liquid chromatographic analysis of egg yolk phospholipids

A rapid and efficient method for the separation of egg yolk phospholipids by normal-phase high-performance liquid chromatography has been developed. The separation is accomplished on an Ultrasil-NH2 column using hexane, isopropanol, methanol and water mixtures with direct ultraviolet detection at 206 nm. Phospholipids from a methanol extract of fresh lyophilized egg yolks were analyzed providing complete separation of (in order of elution) neutral lipids, phosphatidylcholine, sphingomyelin, lysophosphatidylcholine and phosphatidylethanolamine. Identification of eluting species was accomplished by comparative retention times of standard samples by thin-layer chromatographic analyses of collected fractions. Furthermore, a mixture of naturally occurring phospholipid standards from bovine and egg sources has been separated by this method. In addition to separating the individual classes of phospholipids, in some instances, separation of molecular species within a class was achieved as in the case of cerebrosides, sphingomyelin and partially with phosphatidylethanolamine.

Reported lactose tolerance of members of various racial/ethnic groups in Hawaii and Asia

Subjects from various racial/ethnic groups in Hawaii and homeland Chinese, Japanese, and Koreans reported on their milk drinking in childhood and adulthood, as well as on whether or not milk drinking produced symptoms of intolerance. Intolerance was comparatively infrequent in all groups, although significant differences existed between groups in the frequency with which they manifested symptoms and in discomfort scores. Differences between Hawaiian subjects of Asian ancestry and homeland Asians in the frequency of reported symptoms, in mean discomfort scores, and in amount of milk needed to produce symptoms, as well as the high proportion of symptomatology among Hapa-Haoles (persons of Caucasian and Oriental ancestry) and other data reported herein, are not supportive of the usual genetic explanation of lactose tolerance and are supportive of the belief that dietary practice influences tolerance.

Micellar distribution equilibria: ultracentrifugal study of apparent partition coefficients

Ultracentrifugation was used for the partial isolation of polysorbate 80 micelles in aqueous media to determine the apparent partition coefficients of various drug species between water and the micellar pseudophase. The ratio of solute concentration in the micelles to that in water was measured for procaine, salicylic acid, sulfapyridine, sulfisoxazole, and sodium 2-naphthalensulfonate over ranges of pH, surfactant concentration, drug concentration, and micelle sedimentation. Apparent partition coefficients for the systems investigated were independent of both drug concentration and surfactant concentration, indicating that the mode(s) of surfactant-drug interaction are essentially invariant over the ranges of systematic variables studied. The method provides a relatively simple and rapid means of quantitatively evaluating drug-surfactant interactions above the CMC, when surfactant and solute can be assayed in mixtures without interference.

Comparison of three isotopic assays of cell-mediated cytotoxicity against mouse tumor cells. I. Basic parameters: baseline controls, target cells, and methods of calculation

We compared three ddifferent isotopic assays of cell-mediated cytotoxicity under identical test conditions: 51Cr, 125iododeoxyuridine, and [3H]proline release assays. We made these comparisons both in a syngeneic mouse tumor system and an allogeneic system. It was found that several parameters could affect considerably the results obtained with these tests, such as: baseline controls, preparation of target cells, and methods of calculation. In comparison of three different baseline controls, the normal control gave the most consistent results, whereas the other two controls (autologous and medium controls) gave varying results depending upon the condition of the target cells. For use as target cells, established tissue culture cells were usually superior because of a much lower spontaneous release of the isotope, when compared to fresh ascites tumor cells or short-term tissue culture cells. The advantage of established culture cells was particularly noted in isotopic assays with prolonged incubation (20-40 hr). In addition, the methods used for calculation were also shown to affect the apparent outcome of the results.

Comparison of three isotopic assays of cell-mediated cytotoxicity against mouse tumor cells. II. Sensitivity and specificity of the assays and characteristics of effector and sensitizing cells

Three assays of cell-mediated cytotoxicity in mice, involving release of either 51Cr (CRA), 125iododeoxyuridine (IRA), or [3H]proline (PRA), were compared under identical test conditions. Experiments were performed with effector cells from mice immunized with FBL-3 tumor cells, a syngeneic Friend virus-induced leukemia, or with allogeneic normal spleen cells. With established tissue culture cells as targets, similar results were obtained in all three assays. The cytotoxicity produced by cells from in vivo-immunized mice and the induction of cytotoxicity in vitro were T-cell-dependent. When short-term culture target cells were used, the IRA gave a more selective pattern of cytotoxicity than did the other two assays. However, when remaining target cells at the end of the assay were treated with trypsin, higher levels of 125iododeoxyuridine (125IUDR) release were seen, and the results were then comparable to those in the CRA and PRA. These results indicated that 125IUDR, a nuclear label, could only be released after lysis of cells. In contrast, 51Cr or [3H]proline, which are cytoplasmic labels, could also be released from damaged but unlysed cells. These fundamental differences could give different results in these assays, which could determine their correlation with in vivo transplantation immunity.

Systems approach to vaginal delivery of drugs III: Simulation studies interfacing steroid release from silicone matrix and vaginal absorption in rabbits

A composite physical model involving the simultaneous receding boundary release of drug from a drug suspension-silicone polymer matrix system, diffusion across the aqueous layer, and passive transport across the vaginal membrane consisting of parallel lipoidal and aqueous pore pathways is described. Simulation studies with progesterone and hydrocortisone illustrate matrix release-limiting, membrane absorption, and aqueous diffusion layer-limiting cases when the cylindrical silicone delivery device is interfaced with the vaginal membrane of the rabbit.

Antifungal effect of an ectotrophic mycorrhizal fungus, Lactarius sp., associated with basswood seedlings

An ectotrophic mycorrhizal fungus associated with basswood, Lactarius sp., produces a potent antifungal compound. The compound's strength was assessed by determining the percentage spore germination of Penicillium implication in Lactarius sp. culture filtrates. Antifungal properties were evaluated by pairing Lactarius sp. with 23 known pathogenic fungi on Hagem agar plate cultures. Greenhouse tests revealed a strong inhibitory effect of Lactarius sp. against fungi that frequently cause damping-off of pine seedlings.