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The 3-dimensional structure of the pheromone Er-1 isolated from the ciliated protozoan Euplotes raikovi has been determined in aqueous solution by 1H NMR spectroscopy. The structure of this 40-residue protein was calculated with the distance geometry program DIANA on the basis of 503 upper distance constraints derived from nuclear Overhauser effects and 77 dihedral angle constraints derived from spin-spin coupling constants, and refined by restrained energy minimization with the program OPAL. The Er-1 solution structure is represented by a group of 20 conformers with an average RMS deviation relative to the mean structure of 0.55 A for the backbone atoms N, C alpha, and C', and 0.93 A for all heavy atoms of the complete polypeptide chain, residues 1-40. The molecular architecture is dominated by an up-down-up bundle of 3 alpha-helices formed by residues 2-9, 12-19, and 24-33. Although this core part coincides closely with the previously determined structure of the homologous pheromone Er-10, the C-terminal peptide segment adopts a novel conformation. This is of interest in view of previous suggestions, based on sequence comparisons, that this molecular region may be important for the different specificity of receptor recognition by different pheromones.

We retrospectively reviewed the radiographic findings of fibrosing mediastinitis (FM) in 33 patients. Imaging studies included chest radiographs, computed tomographic scans, magnetic resonance imaging examinations, esophograms, ventilation perfusion scans, angiograms, and venograms. Findings include bronchial narrowing in 11 patients (33 percent), pulmonary artery obstruction/narrowing in 6 patients (18 percent), esophageal narrowing in 3 patients (9 percent), and superior vena cava obstruction/narrowing in 13 patients (39 percent). Two distinctly different radiographic patterns were identified: a localized pattern seen in 27 patients (82 percent) that frequently contained calcification and a diffuse pattern seen in 6 patients (18 percent) that did not contain calcification. The localized pattern is most likely due to histoplasmosis and does not show radiographic evidence of improvement with steroid therapy. The diffuse pattern may more likely be truly idiopathic or of a noninfectious etiology. Several patients with the diffuse pattern showed radiographic evidence of improvement with steroid therapy.

Thymomas and thymic carcinomas are thymic epithelial tumors that constitute approximately 15% of all mediastinal masses. From 28 to 66% of thymomas cause chest symptoms as the initial manifestation; the rest are discovered on routine chest roentgenograms or during investigations prompted by the presence of a paraneoplastic syndrome. Forty percent of patients with thymoma have one or more paraneoplastic syndromes, including myasthenia gravis, pure red cell aplasia, and hypogammaglobulinemia. Extrathymic malignant lesions develop in up to 20% of patients. Traditional histologic classifications have not accurately predicted tumor behavior; a recently developed classification based on cellular differentiation toward thymic medullary or cortical epithelium may correlate better with prognosis. Nevertheless, the prognosis is best predicted by stage of the tumor determined intraoperatively and is poorer in patients with incomplete resection than in those with complete resection of the thymoma. In addition to surgical intervention, irradiation and chemotherapy have important roles in the management of thymomas, particularly in advanced stages. In this article, the clinical manifestations, diagnosis, pathologic features, staging, and treatment of thymomas are reviewed, and the prognosis of affected patients is discussed.

Primary mediastinal neoplasms encompass a long list of histologically diverse lesions that can arise from a wide variety of mediastinal structures. Recent advances in diagnostic techniques have considerably enhanced the evaluation of the mediastinum with use of noninvasive or minimally invasive procedures. In adults, most primary mediastinal neoplasms can be classified in one of four categories: thymus-derived neoplasms, neurogenic tumors, lymphomas, or germ cell neoplasms. In children, neurogenic tumors (especially neuroblastomas) and lymphomas are most frequently encountered. Because of the presence of many vital structures in the confined thoracic cavity, even benign mediastinal neoplasms can cause severe symptoms from the mass effect and therefore warrant a carefully planned management strategy. With modern therapeutic and surgical interventions, associated morbidity and mortality can often be substantially decreased.

The three-dimensional structure in solution of the pheromone Er-10 from the ciliated protozoan Euplotes raikovi has been determined by nuclear magnetic resonance spectroscopy. The structure of this 38-residue protein was obtained from 384 nuclear Overhauser enhancement distance constraints and 78 dihedral angle constraints using the distance geometry program DIANA for the structure calculation and the program AMBER for energy minimization. For a group of 20 conformers used to characterize the solution conformation, the average root-mean-square distance calculated for the backbone heavy atoms relative to the mean structure was 0.33 A. The structure includes three short helices of residues 2 to 8, 12 to 19 and 24 to 33, and a turn in the carboxy-terminal region of residues 34 to 38. These structural elements are held together by three disulfide bridges. The structure is quite stable relative to heat denaturation, since at both pH 4.6 and pH 6.0 only minor changes in the circular dichroism and nuclear magnetic resonance spectra were observed over the temperature range 20 to 80 degrees C. The surface of the Er-10 structure shows an asymmetric charge distribution that results in a predominantly apolar surface on one side of the molecule. There is also a deep cleft in the structure with an asymmetric distribution of charged and apolar residues on the two walls. These surface features may be important for the homologous (autocrine) and heterologous binding of the pheromone to receptors.

Human lymphoblastoid cells transiently expressing the hemagglutinin (HA) glycoprotein of influenza virus are rapidly and efficiently recognized by CD4+ HA-specific T lymphocytes. This endogenous presentation pathway is sensitive to chloroquine and is therefore likely related to the classical class II major histocompatibility complex (MHC) exogenous pathway of antigen presentation. In this study we have examined a series of transport-defective HA mutants. We correlate the intracellular fate of the native antigen with its presentation characteristics. We have found that the native antigen must enter the secretory pathway since a cytosolic form is not presented. However, surface expression and normal trafficking through the Golgi apparatus are not required for efficient presentation. Instead, escape of native antigen from the endoplasmic reticulum appears to be both necessary and sufficient for gaining access to a compartment where antigen is processed and binds class II MHC molecules.

Objective: A new asymmetric screen-film combination for conventional chest radiography was evaluated by four thoracic radiologists., Materials and Methods: Fifty chest radiographs obtained with a new asymmetric screen-film combination were compared with radiographs obtained in the same patients during the same breath-hold with a conventional system. Patients referred from the oncology service were studied because of the increased prevalence of abnormal findings on chest radiographs in this population. The differences in the quality of the images were assessed by four chest radiologists who used a direct-comparison technique. Eleven anatomic shadows that are normal on chest radiographs were assessed. Fifty abnormal findings also were compared., Results: The image quality of the new asymmetric screen-film combination was judged to be superior to that of the conventional system for normal anatomy and abnormal findings (p < or = .003)., Conclusion: The new asymmetric film consistently showed more clinically useful detail in the mediastinum and in the lung projected over the diaphragm and heart. The radiation dose was about 30% less with the new screen-film system.

The three-dimensional structure in solution of the alpha-neurotoxin from the black mamba (Dendroaspis polylepis polylepis) has been determined by nuclear magnetic resonance spectroscopy. A high quality structure for this 60-residue protein was obtained from 656 NOE distance constraints and 143 dihedral angle constraints, using the distance geometry program DIANA for the structure calculation and AMBER for restrained energy minimization. For a group of 20 conformers used to represent the solution structure, the average root-mean-square deviation value calculated for the polypeptide backbone heavy atoms relative to the mean structure was 0.45 A. The protein consists of a core region from which three finger-like loops extend outwards. It includes a short, two-stranded antiparallel beta-sheet of residues 1-5 and 13-17, a three-stranded antiparallel beta-sheet involving residues 23-31, 34-42 and 51-55, and four disulfide bridges in the core region. There is also extensive non-regular hydrogen bonding between the carboxy-terminal tail of the polypeptide chain and the rest of the core region. Comparison with the crystal structure of erabutoxin-b indicates that the structure of alpha-neurotoxin is quite similar to other neurotoxin structures, but that local structural differences are seen in regions thought to be important for binding of neurotoxins to the acetylcholine receptor. For two regions of the alpha-neurotoxin structure there is evidence for an equilibrium between multiple conformations, which might be related to conformational rearrangements upon binding to the receptor. Overall, the alpha-neurotoxin presents itself as a protein with a stable core and flexible surface areas that interact with the acetylcholine receptor in such a way that high affinity binding is achieved by conformational rearrangements of the deformable regions of the neurotoxin structure.

The authors hypothesized that the degree of contrast material enhancement of a pulmonary nodule, measured with computed tomography (CT), may indicate the likelihood of malignancy. Fifty-two patients with uncalcified solitary pulmonary nodules (diameter, 6-30 mm) were studied. Five single serial thin-section CT scans were obtained at 1-minute intervals after injection of 100 mL of nonionic contrast material. Twenty-two patients were excluded because the diagnosis was not clearly established: The observation period was less than 2 years, or the examination was technically inadequate. Malignant nodules were identified in 23 of the 30 remaining patients, and benign nodules were identified in seven. Within the first 2 minutes after the injection, all the malignant nodules had enhanced by 20 HU or greater (only one benign nodule had that degree of enhancement). The authors conclude that the degree of contrast material enhancement of pulmonary nodules as measured with CT may indicate the likelihood of malignancy.

Tumors that metastasize are considered "malignant" by definition. However, benign giant-cell tumor of bone is an exception because of the potential for histologically benign pulmonary metastases, a fact seldom emphasized in the radiologic literature. We therefore report our experience with 13 cases of pulmonary metastasis among 475 patients (prevalence, 3%) in whom benign giant-cell tumor of bone was diagnosed before 1990 at our institution. Five (38%) of the 13 primary bone tumors were located in the distal radius. Local recurrence at the site of the primary bone tumor tumor occurred in seven patients (54%) before pulmonary metastases developed. The mean interval from the diagnosis of the primary bone tumor to the onset of pulmonary metastasis was 3.8 years, with a maximum of 10.7 years. Fifty-four percent of the patients (7/13) had pulmonary metastases 3 years after diagnosis of the primary bone lesion, and 92% (12/13) had pulmonary metastases 7.5 years after diagnosis. Overall mortality rate directly due to giant-cell tumor and its metastases was 23%. On chest radiographs and CT scans, pulmonary metastases appeared as rounded, nodular opacities of homogeneous density, ranging from 0.5 cm to 8.0 cm in diameter. Peripheral regions of the lungs were involved in 85% of the cases and basilar regions in 62%. Our study shows that benign giant-cell tumor of bone can produce pulmonary metastases, that metastases most often occurred with recurrent local disease and distal radial lesions, that the prognosis was relatively favorable, and that such metastases had no distinguishing radiologic features.

CT and MR imaging allow earlier diagnosis and more specific characterization of anterior mediastinal masses than is possible with plain film radiographs. This review describes state-of-the-art CT and MR imaging of the anterior mediastinum. After a discussion of CT and MR imaging and indications for their use, normal and abnormal CT and MR findings in the anterior mediastinum are reviewed. Abnormalities include benign and malignant neoplasms, cysts, and mediastinal thyroid. Several masses such as thymolipomas, goiters, cysts, and lymphangiomas often do not require removal and now can be diagnosed with reasonable accuracy when imaging results are combined with clinical history. Detection, diagnosis, staging, and follow-up of malignant anterior mediastinal masses are important and have been improved with CT and MR imaging.

We have identified the site encompassing residues 126-145 on the A/Japan/57 influenza hemagglutinin molecule that is recognized in association with HLA-DRw11 by a clonal population of human, influenza specific, CD4+ cytolytic T lymphocytes. The critical core sequence of the T cell determinant spans hemagglutinin residues 129-140 and overlaps a putative antibody binding site. Hemagglutinins of influenza field strains that are not recognized by the T cell clones contain sequence alterations within the 129-140 target site of the CD4+ T cells. Functional analyses, with synthetic peptides, of the contribution of each of the residues within the sequence toward the capacity of the antigenic fragment to associate with both the restriction element and the TCR revealed a continuous linear array of residues necessary for MHC binding and/or Ag receptor engagement. At least one residue, the lysine at position 134, was shown to be critical for both DRw11 association and TCR recognition. The significance of these findings for recognition of glycoproteins by human CD4+ T cells is discussed.

The stoichiometry of dodecylphosphocholine/palmitoyllysophosphatidic acid/myelin basic protein complexes and the location of the protein in the micelles have been investigated by electron paramagnetic resonance, ultracentrifugation, small-angle X-ray scattering, 31P, 13C, and 1H nuclear magnetic resonance spectroscopy, and electron microscopy. Ultracentrifugation measurements indicated that well-defined complexes are formed by association of one protein molecule with approximately 133 detergent molecules. The spin-labels 5-, 12-, and 16-doxylstearate have been incorporated into detergent/protein aggregates. Electron paramagnetic resonance spectral parameters and 13C and 1H nuclear magnetic resonance relaxation times showed that the addition of myelin basic protein does not affect the environment and location of the labels or the organization of the micelles. Previous results suggesting that the protein lies primarily near the surface of the micelles have been confirmed by comparing 13C spectra of the detergents with and without protein with spectra of detergent/protein aggregates containing the spin labels. Electron micrographs of the complexes taken by using the freeze-fracture technique revealed the presence of particles with an estimated radius about three times the radius of the micelles measured by small-angle X-ray scattering. The structural integrity of the complexes appears to be based on intramolecular protein interactions as well as protein-detergent interactions.

The A/Japan/57 influenza hemagglutin (HA) peptide HA 128-145, when bound by human histocompatibility leukocyte antigen-DRw11 cells, is recognized by the human CD4+ T cell clone V1. A rabbit antiserum has been raised against HA 128-145 which recognizes not only the free peptide, but also the HA 128-145/DRw11 complex on a solid matrix, in solution, or on the surface of viable cells. The detection of these complexes on viable cells was shown to be class II specific, DRw11 restricted, and commensurate with the level of DRw11 expression. The identity of DRw11 as the cell surface molecule binding HA 128-145 was confirmed by immunoprecipitation, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and tryptic peptide mapping. Using this antiserum HA 128-145/DRw11 complexes could be detected on the cell surface as soon as 30 min after the peptide was added, and increased up to 24 h. Dissociation kinetics showed these complexes were long-lived, with a half-life of approximately 14 h. This anti-HA peptide antiserum represents the first direct means of studying antigenic peptide-human leukocyte antigen class II complexes on the surface of living cells without the addition of a non-amino acid moiety to the peptide. The properties of this antiserum thus provide the potential to study naturally processed antigenic peptides as well as the mechanism of processing itself in a physiologically relevant system.

In 35 cases of pulmonary blastomycosis, the roentgenologic features were as follows: consolidation 26%, mass 31%, intermediate-sized nodules 6%, miliary pattern 11%, solitary cavity 9%, fibrotic and cavitary changes 6%, interstitial pattern 6%, diffuse alveolar involvement 3%, and mixed alveolar and interstitial infiltrate 3%. All symptomatic cases of consolidation were acute (symptoms for less than 1 month), and most were in young patients (mean age, 34 years). Consolidation constituted 58% of the acute cases in this series. Two of the nine cases of consolidation were asymptomatic epidemic cases detected by screening. A pulmonary mass was the most common initial manifestation in this series; it tended to occur in patients with chronic symptoms (more than 1 month). The mass was considered suggestive enough of bronchogenic carcinoma to necessitate resection in 55% of cases. The military form of pulmonary blastomycosis occurred in older patients with disseminated disease. Fibrotic and cavitary disease was chronic in nature. The presence of intermediate-sized nodules elsewhere in the lung proved to be a helpful diagnostic finding in several patients with consolidation, mass, or cavitary disease. Hilar adenopathy, postinfectious calcification, chest wall invasion, and pleural effusion occurred infrequently or not at all in this series.

Knowledge of normal and abnormal hilar and mediastinal anatomy as depicted by chest radiography is important for the practicing radiologist. This article is an illustrated review of some of the alterations of normal anatomy that can indicate signs of metastatic spread of bronchogenic carcinoma. Thorough analysis of conventional radiographs with recognition of normal variants and detection of abnormal alterations will expedite or obviate certain therapeutic options in patients with bronchogenic carcinoma.

The interactions of myelin basic protein and peptides derived from it with detergent micelles of lysophosphatidylglycerol, lysophosphatidylserine, palmitoyllysophosphatidic acid, and sodium lauryl sulfate, and with mixed micelles of the neutral detergent dodecylphosphocholine and the negatively charged detergent palmitoyllysophosphatidic acid, were investigated by 1H NMR spectroscopy and circular dichroic spectropolarimetry. The results with single detergents suggested that there are discrete interaction sites in the protein molecule for neutral and anionic detergent micelles and that at least some of these sites are different for each type of detergent. The data on the binding of the protein and peptides to mixed detergent micelles suggested that intramolecular interactions in the intact protein and in one of the longer peptides limited the formation of helices and also that a balance between hydrophobic and ionic forces is achieved in the interactions of the peptides with the detergents. At high detergent/protein molar ratios, hydrophobic interactions appeared to be favored.

The release of fluoride from glass ionomer materials is one of the most important features of this newly implemented material, and the remineralization effects of this phenomenon have been documented (Hicks and Silverstone 1986). This paper examines the effects of glass ionomer/silver cermet restorations on the plaque levels of interproximal mutans streptococci. Fifteen patients with Class II lesions in primary molars were selected for study. Interproximal plaque samples were obtained from each of the lesion sites and from one caries-free site approximal to a primary molar. One lesion was restored with composite resin to serve as a treated control to the glass ionomer/silver cermet (Ketac Silver, ESPE/Premier Sales Corp., Norristown, Pennsylvania) test site. A sound (unaltered) interproximal site served as the untreated control site. Plaque samples were collected before and at one week, one month, and three months post-treatment. Samples were serially diluted to enable colony counts of mutans streptococci. One week post-treatment counts showed that the glass ionomer/silver cermet restorations significantly reduced (P less than 0.05) the approximal plaque levels of mutans streptococci. Conversely, the untreated and treated control sites did not exhibit reductions in approximal plaque levels of mutans streptococci. These results indicate that glass ionomer restorations may be inhibitory to the growth of mutans streptococci in dental plaque approximal to this restorative material in the primary dentition.

Effects of different dietary lipids and excess vitamin E on plasma and hepatic concentrations of beta-carotene were evaluated in rats fed diets containing a large excess (0.2%) of beta-carotene. Male weanling Wistar Kyoto rats were fed beta-carotene-supplemented diets containing various dietary lipids as follows: Group I, a saturated fat (coconut oil); Group II, a monounsaturated fat (olive oil); Group III, a polyunsaturated fat rich in omega-6 fatty acids (safflower oil); Group IV, same as Group III plus vitamin E; and Group V, a polyunsaturated fat rich in omega-3 fatty acids (menhaden oil). All diets contained 2% safflower oil to provide sufficient amounts of linoleic acid (an essential fatty acid). Rats were killed after six weeks of feeding the various diets, and the concentrations of beta-carotene and vitamin A were determined in plasma and liver. Plasma vitamin A levels were not altered by any of the dietary lipids or by an excess of vitamin E. The concentrations of beta-carotene in plasma were the lowest in rats fed the diet containing menhaden oil. The feeding of the diet containing an excess of vitamin E also resulted in a significant decrease in plasma beta-carotene concentration. Similarly, the hepatic beta-carotene concentration was also reduced to about one-half in rats fed the diet containing an excess of vitamin E. Liver beta-carotene concentration was higher in Groups II and III than in the other three dietary groups. Hepatic vitamin A concentrations were also affected by the type of dietary fat.(ABSTRACT TRUNCATED AT 250 WORDS)

A study of 15 cases of carcinoid tumor of the thymus, diagnosed and treated at the Mayo Clinic, revealed histopathologic features of the neoplasm that might cause it to be confused with other mediastinal tumors, both primary and secondary. The tumor was associated with ectopic ACTH production in six patients, of whom five had Cushing's syndrome. Metastasis, which occurred in 11 patients (73%), was delayed for as long as 8 years after initial diagnosis. Eleven patients underwent surgical resection of their primary thymic neoplasms, and nine of these received postoperative radiotherapy or chemotherapy or both. One patient was treated with chemotherapy alone, and three had no treatment for their neoplasms, which were discovered at autopsy. Eight patients are still alive. Of these, five have developed metastases, and only one is free of metastatic disease more than 5 years after diagnosis. In the two remaining cases, the discovery of the thymic tumor was recent and follow-up is not yet meaningful. Overall, four of the seven patients who died had proven metastatic disease. The mean survival after the appearance of extrathymic tumor in this group was 3 years. Of the five patients who are still alive with metastasis, all have survived at least 2 years since that spread of their disease.

The latest edition of the AFGL atmospheric absorption line parameters compilation for the seven most active infrared terrestrial absorbers is described. Major modifications to the atlas for this edition include updating of water-vapor parameters from 0 to 4300 cm(-1), improvements to line positions for carbon dioxide, substantial modifications to the ozone bands in the middle to far infrared, and improvements to the 7- and 2.3-microm bands of methane. The atlas now contains approximately 181,000 rotation and vibration-rotation transitions between 0 and 17,900 cm(-1). The sources of the absorption parameters are summarized.

The relative rates of RNA polymerase biosynthesis in Bacillus subtilis has been examined under steady-state growth conditions. The synthesis of RNA polymerase subunits (alpha, beta, beta', omega) has been followed by subunit fractionation of immunoprecipitated [3H]-labelled samples on SDS-polyacrylamide gels. The stoichiometries of alpha:beta:beta':omega subunits have been determined from cultures pulse-labelled during steady-state growth. The results suggest that an unassembled pool of the alpha-subunit exists from which the holoenzyme is formed. Upon shift-up from acetate to glycerol containing medium, a rapid rise in the differential rate of core enzyme synthesis was observed, while the rate of synthesis of the alpha-subunit was not stimulated. During shift-down, a concomitant reduction in the rate of synthesis of all subunits occurred for the first 20 min after the shift; thereafter, a rate of synthesis characteristic of the new growth rate was established. As cultures enter sporulation, an immediate reduction in the rate of beta beta'-subunit synthesis was demonstrated.

Interactions of myelin basic protein (MBP) and peptides derived from it with micelles of dodecylphosphocholine (DPC) and perdeuterated DPC have been studied by proton nuclear magnetic resonance (NMR) at 400 MHz and by circular dichroism (CD). When MBP binds to DPC micelles, it acquires about 18% alpha-helicity. The CD spectra of various peptides derived by cleavage of MBP indicate that a major alpha-helical region occurs in residues 85-99 just before the sequence of three prolyl residues 100-102. From line broadenings by fatty acid spin-labels in the micelles and from changes in chemical shifts, the NMR data identify specific residues in MBP that participate in lipid binding. One such sequence is an alpha-helical region from residues 85 to 95, and others occur around methionine-21 and between residues 117 and 135. The different effects of C5, C12, and C16 spin-labels suggest that some segments of the protein may penetrate beyond the dipolar interfacial region of the micelles into the hydrophobic interior, but no part of the protein is protected by the micelles against rapid exchange of its amide groups with the aqueous environment. Even at a lipid to protein molar ratio of 200/1, most NMR resonances from side chains of amino acid residues are not appreciably broadened, suggesting that much of the polypeptide remains highly mobile.

The effect of orthodontic banding on the prevalence of Streptococcus mutans in plaque was evaluated by comparisons between patients wearing bands and patients just prior to banding on the basis of treatment and/or dental caries history. Banded patients had significantly higher levels of S. mutans in plaque and greater numbers of S. mutans-infected sites than did caries-free patients. Caries-free banded patients had more S. mutans-infected sample sites than did the caries-free non-banded group.

Using a modified silver stain of Merril et al. [(1981) Science 211, 1437-1438] for staining polypeptides in sodium dodecyl sulfate-polyacrylamide gels, protein bands reproducibly stain different shades of blue, yellow, red, and gray. The procedure is highly temperature dependent, with optimal color formation at 42 degrees C. The procedure may be completed within 2 h. Color formation is due to silver ion complexes with charged amino acid side chains. The color of the silver-protein complex can be predicted if the amino acid sequence is known, although some exceptions are discussed. This provides another dimension to the characterization of proteins by gel electrophoresis.

A description and summary of the latest edition of the AFGL HITRAN molecular absorption parameters database are presented. This new database combines the information for the seven principal atmospheric absorbers and twenty-one additional molecular species previously contained on the AFGL atmospheric absorption line parameter compilation and on the trace gas compilation. In addition to updating the parameters on earlier editions of the compilation, new parameters have been added to this edition such as the self-broadened halfwidth, the temperature dependence of the air-broadened halfwidth, and the transition probability. The database contains 348043 entries between 0 and 17,900 cm(-1). A FORTRAN program is now furnished to allow rapid access to the molecular transitions and for the creation of customized output. A separate file of molecular cross sections of eleven heavy molecular species, applicable for qualitative simulation of transmission and emission in the atmosphere, has also been provided.

A novel sequence-specific endonuclease has been isolated from Streptococcus cremoris F. ScrFI recognises the sequence: (formula; see text) and cleaves as indicated by the arrow ( ). It is the first enzyme to recognise this sequence and the first endonuclease reported from the lactic streptococci used in dairy fermentations.

The positions and strengths of ~1900 absorption lines of methane between 3700 and 4136 cm(-1) were measured experimentally to provide a reference line list for the identification of weak CH(4) features in planetary spectra. The line parameters were obtained at room temperature with accuracies of 0.0002-0.003 cm(-1) for positions and +/-3-40% for strengths using spectra recorded at 0.011-cm(-1) resolution (unapodized) with a Fourier transform spectrometer at Kitt Peak National Observatory/National Solar Observatory. Individual line strengths range from 2 x 10(-5) to 1.3 x 10(-2) cm(-2) atm(-1) at room temperature, and the sum of the observed strengths is 1.42 cm(-2) atm(-1) at 297 K. All measurements are reported in natural isotopic abundance.

A new compilation of methane line parameters for the 4136-4666-cm(-1) region has been obtained using experimental positions and intensities combined with known quantum assignments from the literature. Positions and intensities measured directly from the observed spectrum by computer are reported with accuracies of +/-0.0005 cm(-1) and 2%, respectively, for single unblended absorptions.

A fluoride-sensitive (FS) strain of Streptococcus mutans and a laboratory-induced fluoride-resistant (FR) offspring were compared for the effects of sodium fluoride on viability and growth. There was a significant fluoride-related loss of viability in resting cell suspensions of the FS strain during a 47-hour exposure to fluoride levels above 75 ppm that was not encountered with the FR strain. The addition of 300 ppmF to actively growing six-hour broth cultures almost totally arrested the growth of the FS strain, while only slightly reducing that of the FR culture. The addition of 600 ppmF immediately terminated FS growth, and greatly reduced the rate and maximum growth of FR cultures.

A prospective study was done involving 822 women who had both film screen mammography and a breast transillumination light scan examination. The study population was not randomized; a modified phase-2 study was done. Mammography was superior for detecting malignancy: of the 67 pathologically proved breast cancers, 64 (95.5%) were detected by mammography and 45 (67.2%) were detected by transillumination. Biopsy revealed that 74 patients had benign lesions. In this group of patients, the false-positive rate was 12.2% for light scanning and 79.7% for mammography; however, 117 other patients had false-positive light scans.

Complexes of melittin with detergents and phospholipids have been characterized by fluorescence, circular dichroism, ultracentrifugation, quasi-elastic light scattering and 1H nuclear magnetic resonance (NMR) experiments. By ultracentrifugation and quasi-elastic light-scattering measurements it is shown that melittin forms stoichiometrically well-defined complexes with dodecylphosphocholine micelles consisting of one melittin molecule and approximately forty detergent molecules. Evidence from fluorescence, circular dichroism and 1H nuclear magnetic resonance experiments indicates that the conformation of melittin bound to micelles of various detergents or of diheptanoyl phosphatidylcholine is largely independent of the type of lipid and furthermore appears to be quite closely related to the conformation of melittin bound to phosphatidylcholine bilayers. 1H NMR is used to investigate the conformation of micelle-bound melittin in more detail and to compare certain aspects of the melittin conformation in the micelles with the spatial structures of monomeric and self-aggregated tetrameric melittin in aqueous solution. The experience gained with this system demonstrates that high resolution NMR of complexes of membrane proteins with micelles provides a viable method for conformational studies of membrane proteins.

4 mM melittin solution in 0.05 M sodium phosphate buffer at p2H 7.0 and 30 degrees C was shown by ultracentrifugation to contain tetrameric melittin. Using the spectra of this species and the previously characterized monomeric melittin as references, high-resolution 1H-NMR at 360 MHz was used to investigate self-aggregation of melittin at variable temperatures, pH and ionic strength. The NMR parameters show that the spatial structure of aggregated melittin is different from monomeric mellitin in aqueous solution but resembles closely the conformation adopted by melittin bound to detergent micelles. Comparison of melittin bound to different detergent micelles and self-aggregated melittin in different aqueous media indicates that the mellitin monomers adopt similar conformations in all these systems. The present data suggest that melittin assumes an amphiphilic spatial structure which is stabilized both by the formation of mixed micelles with detergents or by self-aggregation.

The ability of computed tomography of the lungs to detect pulmonary nodules was compared with that of conventional chest roentgenography and whole-lung tomography. Computed tomography detected more pulmonary nodules in 10 of 29 patients studied with both computed tomography and whole-lung tomography. Computed tomography of the lungs is the most accurate noninvasive method available for detecting pulmonary nodules.

A study was undertaken of five patients with Cushing syndrome due to adrenocorticotropin (ACTH) production by thymic carcinoid tumor (primary mediastinal APUDomas), including two recent patients examined by computed tomography (CT) of the chest. Plain roentgenography of the chest initially failed to detect tumor in four of the five patients, while CT of the chest yielded definitive diagnostic information in both patients in whom it was employed. For one of these patients, a mediastinal tumor could be seen retrospectively on plain roentgenograms of the chest, although it had been missed on the first examination. One of the tumors appeared to be partially calcified on CT scan, a finding not previously reported. Blastic osseous metastasis, which is common when malignant carcinoid tumors spread to bone, was seen in one patient. Our data suggest that in patients with suspected ectopic ACTH production, CT scanning of the mediastinum should be performed early in order to avoid delay in diagnosis of an ACTH-secreting carcinoid tumor of the mediastinum.

The amino groups of ribonuclease A (RNase-A) have been methylated with formaldehyde and borohydride to provide observable resonances for proton magnetic resonance (PMR) studies. Although enzymatic activity is lost, PMR difference spectroscopy and PMR studies of thermal denaturation show native conformation is largely preserved in methylated RNase-A. Resonances corresponding to the NH2-terminal alpha-amino and 10 xi-amino N-methyl groups are titrated at 220 MHz to obtain pK values. After correction for the effects of methylation, using values previously derived from model compound studies, a pK of 6.6 is found for the alpha-amino group, a pK of 8.6 for the xi-amino group of lysine-41 and pK values ranging from 10.6 to 11.2 for the other lysine xi-amino groups. Interactions between lysine-7 and lysine-41 or between the alpha-amino and xi-amino groups of lysine-1 have been proposed to account for deviations from simple titration behaviour. The correct continuities for the titration curves of the histidine H-2 proton resonances have been confirmed by selective deuteration of the H-2 protons. Titration curves for the H-2 proton resonances of histidine-12 and histidine-119 of methylated RNase-A show deviations from the titration curves for the native enzyme, indicating some alteration of the active-site conformation. In the presence of phosphate, titration curves for the H-2 proton resonances of histidine-12 and histidine-119 of methylated RNase-A indicate binding of phosphate at the active site, but these curves continue to show deviations from the titration behaviour of native RNase-A. The titration curve for the N-methyl resonance of lysine-41 is perturbed considerably by the presence of phosphate, which indicates a possible catalytic role for lysine-41.