Probing the alignment-dependent mechanical behaviors and time-evolutional aligning process of collagen scaffolds

Efficiently manipulating and reproducing collagen (COL) alignment in vitro remains challenging because many of the fundamental mechanisms underlying and guiding the alignment process are not known. We reconcile experiments and coarse-grained molecular dynamics simulations to investigate the mechanical behaviors of a growing COL scaffold and assay how changes in fiber alignment and various cross-linking densities impact their alignment dynamics under shear flow. We find higher cross-link densities and alignment levels significantly enhance the apparent tensile/shear moduli and strength of a bulk COL system, suggesting potential measures to facilitate the design of stronger COL based materials. Since fibril alignment plays a key factor in scaffold mechanics, we next investigate the molecular mechanism behind fibril alignment with Couette flow by computationally investigating the effects of COL's structural properties such as chain lengths, number of chains, tethering conditions, and initial COL conformations on the COL's final alignment level. Our computations suggest that longer chain lengths, more chains, greater amounts of tethering, and initial anisotropic COL conformations benefit the final alignment, but the effect of chain lengths may be more dominant over other factors. These results provide important parameters for consideration in manufacturing COL-based scaffolds where alignment and cross-linking are necessary for regulating performance.

GcSTUA, an APSES transcription factor, is required for generation of appressorial turgor pressure and full pathogenicity of Glomerella cingulata

Glomerella cingulata, which infects a number of different hosts, gains entry to the plant tissue by means of an appressorium. Turgor pressure generated within the appressorium forces a penetration peg through the plant cuticle. A visible lesion forms as the fungus continues to grow within the host. A G. cingulata homolog (GcSTUA) of the genes encoding Asm1, Phd1, Sok2, Efg1, and StuA transcription factors in Magnaporthe grisea and other fungi was cloned and shown to be required for infection of intact apple fruit and penetration of onion epidermal cells. Mobilization of glycogen and triacylglycerol during formation of appressoria by the GcSTUA deletion mutant appeared normal and melanization of the maturing appressoria was also indistinguishable from that of the wild type. However, GcSTUA was essential for the generation of normal turgor pressure within the appressorium. As is the case for its homologs in other fungi, GcSTUA also was required for the formation of aerial hyphae, efficient conidiation, and the formation of perithecia (sexual reproductive structures).

Purification of an isoflavonoid 7-O-beta-apiosyl-glucoside beta-glycosidase and its substrates from Dalbergia nigrescens Kurz

A beta-glycosidase was purified from the seeds of Dalbergia nigescens Kurz based on its ability to hydrolyse p-nitrophenyl beta-glucoside and beta-fucoside. This enzyme did not hydrolyze various glycosidic substrates efficiently, so it was used to identify its own natural substrates. Two substrates were identified, isolated and their structures determined as: compound 1, dalpatein 7-O-beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranoside and compound 2, 6,2',4',5'-tetramethoxy-7-hydroxy-7-O-beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranoside (dalnigrein7-O-beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranoside). The beta-glycosidase removes the sugar from these glycosides as a disaccharide, despite its initial identification as a beta-glucosidase and beta-fucosidase.

Deletion of the Candida albicans G-protein-coupled receptor, encoded by orf19.1944 and its allele orf19.9499, produces mutants defective in filamentous growth

Filamentous growth of Candida albicans occurs in response to a variety of environmental signals. The C. albicans gene orf19.1944 and its allele orf19.9499 are identical and are predicted to encode an 823-residue, 7-transmembrane-domain protein that has all the expected features of a G-protein-coupled receptor. The protein is 20.9% identical to the Saccharomyces cerevisiae Gpr1p receptor that signals both glucose availability and nitrogen limitation. Deletion of both copies of the gene in C. albicans abolished filamentation by colonies embedded in rich media (YPS, YPGal, and YPGlu), whereas mutants carrying a single copy of the gene were indistinguishable from the parental strain under these conditions. On medium containing low concentrations of ammonia (SLAD and SLAM media), surface colonies of both the homozygous deletion mutants and the mutants carrying a single copy of the gene were defective in filamentation. Serum-induced germ tube formation was unaffected by deletion of this gene, as was filamentation of the mutants growing on the surface of solid Spider medium at 37 degrees C or embedded in solid Spider medium at 25 degrees C. The protein encoded by orf19.1944 and orf19.9499 has a role in filamentation by both surface and embedded colonies, presumably as a sensor of environmental cues.

Identification of the dialysable serum inducer of germ-tube formation in Candida albicans

Yeast cells of Candida albicans are induced by serum at 37 degrees C to produce germ tubes, the first step in a transition from yeast to hyphal growth. Previously, it has been shown that the active component is not serum albumin but is present in the dialysable fraction of serum. In this study, serum induction of germ-tube formation is shown to occur even in the presence of added exogenous nitrogen sources and is therefore not signalled by nitrogen derepression. The active component in serum was purified by ion-exchange, reverse-phase and size-exclusion chromatography from the dialysable fraction of serum and was identified by NMR to be d-glucose. Enzymic destruction of glucose, using glucose oxidase, demonstrated that d-glucose was the only active component in these fractions. Induction of germ-tube formation by d-glucose required a temperature of 37 degrees C and the pH optimum was between pH 7.0 and 8.0. d-Glucose induced germ-tube formation in a panel of clinical isolates of C. albicans. Although d-glucose is the major inducer in serum, a second non-dialysable, trichloroacetic acid precipitable inducer is also present. However, whereas either 1.4 % (v/v) serum or an equivalent concentration of d-glucose induced 50 % germ-tube formation, the non-dialysable component required a 10-fold higher concentration to induce 50 % germ-tube formation. Serum is, therefore, the most effective induction medium for germ-tube formation because it is buffered at about pH 8.5 and contains two distinct inducers (glucose and a non-dialysable component), both active at this pH.

Analysis of the interaction between the aspartic peptidase inhibitor SQAPI and aspartic peptidases using surface plasmon resonance

Aspartic peptidase inhibitors, which are themselves proteins, are strong inhibitors (small inhibition constants) of some aspartic peptidases but not others. However, there have been no studies of the kinetics of the interaction between a proteinaceous aspartic peptidase inhibitor and aspartic peptidases. This paper describes an analysis of rate constants for the interaction between recombinant squash aspartic peptidase inhibitor (rSQAPI) and a panel of aspartic peptidases that have a range of inhibition constants for SQAPI. Purified rSQAPI completely inhibits pepsin at a 1:1 molar ratio of pepsin to rSQAPI monomer (inhibition constant 1 nM). The interaction of pepsin with immobilized rSQAPI, at pH values between 3.0 and 6.0, was monitored using surface plasmon resonance. Binding of pepsin to rSQAPI was slow (association rate constants ca 10(4)M (-1)s(-1)), but rSQAPI was an effective pepsin inhibitor because dissociation of the rSQAPI-pepsin complex was much slower (dissociation rate constants ca 10(-4)s(-1)), especially at low pH values. Similar results were obtained with a His-tagged rSQAPI. Strong inhibition (inhibition constant 3 nM) of one isoform (rSap4) of the family of Candida albicans-secreted aspartic peptidases was, as with pepsin, characterized by slow binding of rSap4 and slower dissociation of the rSap4-inhibitor complex. In contrast, weaker inhibition of the Glomerella cingulata-secreted aspartic peptidase (inhibition constant 7 nM) and the C. albicans rSap1 and Sap2 isoenzymes (inhibition constants 25 and 400 nM, respectively) was, in each case, characterized by a larger dissociation rate constant.

Peptide inhibitors of appressorium development in Glomerella cingulata

The phytopathogen Glomerella cingulata (anamorph: Colletotrichum gloeosporioides) infects host tissue by means of a specialised infection structure, the appressorium. The Saccharomyces cerevisiae alpha-mating factor pheromone, the Saccharomyces kluyveri alpha-mating factor pheromone and a hendecapeptide produced by G. cingulata inhibit appressorium development. The amino acid sequence of the G. cingulata peptide, GYFSYPHGNLF, is different from that of the mature pheromone peptides of other filamentous fungi. The peptide has sequence similarity with the Saccharomyces alpha-mating factor pheromones, but is unable to elicit growth arrest in S. cerevisiae.

Aspartyl proteinases of Candida albicans and their role in pathogenicity

Among the putative virulence factors of Candida albicans, secreted aspartic proteinases (Sap, encoded by a family of at least nine genes) continue to attract the attention of many investigators studying the pathogenesis of candidiasis. Several early studies documented a correlation between the levels of Sap secretion and the virulence of different strains, but much stronger support for this role has been provided by more recent data on differential SAP gene(s) expression in ex vivo and in vivo models, the outcome of infections with SAP-deleted mutants, and use of Sap immunogens. In particular, some SAP-deleted strains suffered a substantial loss of virulence, and, more interestingly, this was specifically associated with selected gene products and selected experimental pathologies. Moreover, anti-Sap antibodies have been shown to mediate a degree of protection in an experimental, mucosal candidiasis model. There is now initial evidence that distinct Saps are differentially produced in various Candida illnesses or stages of them. The exact mechanisms of each Sap involvement in any particular Candida disease, with special regard to human infections, and how the immune system deals with Sap, are critical issues for future research. An answer to these questions will possibly facilitate the generation of Sap-based anticandidal drugs or immunotherapeutics.

A DNA polymorphism specific to Candida albicans strains exceptionally successful as human pathogens

A large proportion of infection-causing isolates of the yeast Candida albicans belong to a general-purpose genotype, identifiable by fingerprinting with the moderately repetitive sequence Ca3. The high prevalence of this group -- up to 70% in some patient categories -- suggests that its members possess genetic determinants, which enhance their success as pathogens compared to other strains. To find such determinants we are comparing the genomes of representatives of the general-purpose genotype cluster with the genomes of other strains. In this paper we describe the identification of a 985 bp HpaII fragment (MU13-4) specific to general-purpose genotype strains. The fragment was present in 90% of these strains, but only in 10% of other strains. The fragment did not hybridize with probe Ca3, used to define the general-purpose cluster. It contains elevated levels of repetitive DNA. Sequences homologous to MU13-4 are dispersed throughout the chromosomes of general-purpose strains but are rarer or absent in other strains, as judged by Southern hybridization. Using the Stanford C. albicans genome database, we have placed the MU13-4 fragment next to a CARE-1 element. We also found 79 significant homologies between parts of MU13-4 and 19 other contigs. Attempts to amplify the region surrounding the polymorphic fragment in non-general-purpose genotype strains suggest, as do the hybridization data, that the polymorphism is created by a deletion in non-cluster strains. These results show that it is possible to identify polymorphisms specific to general-purpose genotype strains. Primers against the fragment will allow PCR-based discrimination between general-purpose genotype strains and other strains, facilitating investigations aimed at determining morbidity and mortality caused by general-purpose genotype strains compared to other strains.

How should dysphagia care of older adults differ? Establishing optimal practice patterns

An unprecedented demographic transformation is occurring as our population ages. Those older than age 65 represent the fastest growing segment of the population. Within this older group, approximately 10% to 30% of adults are estimated to have dysphagia, but true incidence and prevalence are unknown. They make up a heterogeneous mix of both healthy and disabled individuals that reside across a spectrum of living settings. As clinicians approach older adults with dysphagia, general geriatric principles should be followed to optimize care for this diverse group. Likewise, practitioners need to appreciate the physiology that distinguishes a healthy old swallow from dysphagia and acknowledge the wide array of causes that contribute to dysphagia in older people. Clinicians need to recognize the heterogeneity in health, functional abilities, social supports, and resources among the elderly and understand how these factors may influence approaches to dysphagia in different care settings. Standard outcome measures of pneumonia, malnutrition, and mortality must be blended with other quality of life indices. Advanced directives are essential in caring for elderly patients with dysphagia irrespective of their health acuity or care setting. Ultimately, patient and family preferences should dictate the swallowing and feeding interventions offered.

Varying influence of the autolysin, N-acetyl muramidase, and the cell envelope proteinase on the rate of autolysis of six commercial Lactococcus lactis cheese starter bacteria grown in milk

The autolysin, N-acetyl muramidase (AcmA), of six commercial Lactococcus lactis subsp. cremoris starter strains and eight Lc. lactis subsp. cremoris derivatives or plasmid-free strains was shown by renaturing SDS-PAGE (zymogram analysis) to be degraded by the cell envelope proteinase (lactocepin; EC 3.4.21.96) after growth of strains in milk at 30 degrees C for 72 h. Degradation of AcmA was less in starter strains and derivatives producing lactocepin I/III (intermediate specificity) than in strains producing lactocepin I. This supports previous observations on AcmA degradation in derivatives of the laboratory strain Lc. lactis subsp. cremoris MG1363 (Buist et al. Journal of Bacteriology 180 5947-5953 1998). In contrast to the MG1363 derivatives, however, the extent of autolysis in milk of the commercial Lc. lactis subsp. cremoris starter strains in this study did not always correlate with lactocepin specificity and AcmA degradation. The distribution of autolysins within the cell envelope of Lc. lactis subsp. cremoris starter strains and derivatives harvested during growth in milk was compared by zymogram analysis. AcmA was found associated with cell membranes as well as cell walls and some cleavage of AcmA occurred independently of lactocepin activity. An AcmA product intermediate in size between precursor (46 kDa) and mature (41 kDa) forms of AcmA was clearly visible on zymograms, even in the absence of lactocepin I activity. These results show that autolysis of commercial Lc. lactis subsp. cremoris starter strains is not primarily determined by AcmA activity in relation to lactocepin specificity and that proteolytic cleavage of AcmA in vivo is not fully defined.

Minor structural consequences of alternative CUG codon usage (Ser for Leu) in Candida albicans exoglucanase

In some species of Candida the CUG codon is encoded as serine and not leucine. In the case of the exo-beta-1,3-glucanase from the pathogenic fungus C. albicans there are two such translational events, one in the prepro-leader sequence and the other at residue 64. Overexpression of active mature enzyme in a yeast host indicated that these two positions are tolerant to substitution. By comparing the crystal structure of the recombinant protein with that of the native (presented here), it is seen how either serine or leucine can be accommodated at position 64. Examination of the relatively few solved protein structures from C. albicans indicates that other CUG encoded serines are also found at non-essential surface sites. However such codon usage is rare in C. albicans, in contrast to C. rugosa, with direct implications for respective recombinant protein production.

Relationship between aerodynamic measures of glottal efficiency and stroboscopic findings in asymptomatic singing students

Singing requires exquisite coordination between the respiratory and phonatory systems to efficiently control glottal airflow. Asymptomatic singing students underwent pulmonary function testing (PFT), videostrobolaryngoscopic examination, and measures of glottal efficiency (maximum phonation time [MPT], glottal flow rate [GFR], and phonation quotient [PQ]) performed in both a sung and spoken tone. Pulmonary function and glottal efficiency values were within reported normative data for professional singers. However, sung tones were made with significantly higher GFR and PQ and lower PQ than spoken tones. The mean GFR was not related to the degree of glottal closure (by videostrobolaryngoscopy) or underlying pulmonary support.

Effects of anion substitution on hydration behavior and water uptake of the red-spotted toad, Bufo punctatus: is there an anion paradox in amphibian skin?

Amphibians absorb water osmotically across their skins and rely on chemosensory information from the skin to assess the suitability of hydration sources. The time spent with skin in contact with a moist surface provides a quantitative measure of their ability to perceive the ionic and osmotic properties of aqueous solutions. Dehydrated toads given hyperosmotic (250 mM) solutions of NaCl or Na-gluconate showed significantly longer periods of hydration behavior on the gluconate solution, but they lost water osmotically when immersed in either solution. Similarly, dehydrated toads given 250 mM solutions of NaCl, Na-acetate, Na-phosphate or Na-gluconate showed a progressively greater length of hydration time on solutions with the larger mol. wt anions. These results are consistent with the chemosensory phenomenon previously described in mammalian tongue as 'anion paradox'. On dilute (50 mM) solutions of NaCl or Na-gluconate, the hydration time was not different between anions, despite toads gaining water more rapidly when immersed in dilute NaCl than in Na-gluconate solutions. The differing behavioral results with hyperosmotic and hypoosmotic salt solutions suggest that chemosensory transduction through toad skin involves both transcellular and paracellular pathways.

The structure of the exo-beta-(1,3)-glucanase from Candida albicans in native and bound forms: relationship between a pocket and groove in family 5 glycosyl hydrolases

A group of fungal exo-beta-(1,3)-glucanases, including that from the human pathogen Candida albicans (Exg), belong to glycosyl hydrolase family 5 that also includes many bacterial cellulases (endo-beta-1, 4-glucanases). Family members, despite wide sequence variations, share a common mechanism and are characterised by possessing eight invariant residues making up the active site. These include two glutamate residues acting as nucleophile and acid/base, respectively. Exg is an abundant secreted enzyme possessing both hydrolase and transferase activity consistent with a role in cell wall glucan metabolism and possibly morphogenesis. The structures of Exg in both free and inhibited forms have been determined to 1.9 A resolution. A distorted (beta/alpha)8 barrel structure accommodates an active site which is located within a deep pocket, formed when extended loop regions close off a cellulase-like groove. Structural analysis of a covalently bound mechanism-based inhibitor (2-fluoroglucosylpyranoside) and of a transition-state analogue (castanospermine) has identified the binding interactions at the -1 glucose binding site. In particular the carboxylate of Glu27 serves a dominant hydrogen-bonding role. Access by a 1,3-glucan chain to the pocket in Exg can be understood in terms of a change in conformation of the terminal glucose residue from chair to twisted boat. The geometry of the pocket is not, however, well suited for cleavage of 1,4-glycosidic linkages. A second glucose site was identified at the entrance to the pocket, sandwiched between two antiparallel phenylalanine side-chains. This aromatic entrance-way must not only direct substrate into the pocket but also may act as a clamp for an acceptor molecule participating in the transfer reaction.

Hydrolase and transferase activities of the beta-1,3-exoglucanase of Candida albicans

The exo-beta-1,3-glucanase of Candida albicans (Exg) has a marked specificity for beta-1,3-glucosidic linkages as judged by the kinetic constants for p-nitophenyl beta-glucoside, beta-linked disaccharides of glucose (laminaribiose, gentiobiose, and cellobiose), oligosaccharides of the laminari series, laminarin and pustulan. The kcat/Km ratios for a series of laminari oligosaccharides from -biose to -heptaose showed that Exg has an extended substrate-binding site which contains at least five binding sites for sugar residues. Binding at position +2 (the third sugar residue) increases the kcat twofold while positions +3 and +4 lower the Km value further and thereby increase the catalytic efficiency. Exg catalyses an efficient transglucosylation reaction with high concentrations of laminari-oligosaccharides which specifically form beta-1,3 linkages and with yields up to 50%. The rate of the transglucosylation is concentration-dependent and can be more than 10 times faster than the hydrolytic reaction with excess donor substrates such as laminaritriose and laminarihexaose. The kinetics of Exg and the predicted substrate-binding site for up to five sugar residues are consistent with a recent structural analysis of the enzyme-binding site.

Inhibition of growth and secreted aspartyl proteinase production in Candida albicans by lysozyme

Lysozyme (muramidase) is a non-specific, antimicrobial protein ubiquitous in human mucosal secretions such as saliva. Although its antibacterial and antifungal activities are well recognised, there are no data on the specific concentrations necessary to affect the growth of Candida albicans or about the effect of lysozyme on the production of secreted aspartyl proteinase (Sap), a putative virulence factor of C. albicans. Five Sap-producing isolates of C. albicans were cultured in YCB-BSA medium with various concentrations of lysozyme to examine its effect on yeast cell growth, ultrastructural cellular topography and extracellular and intracellular Sap concentration and activity. Lysozyme was candidacidal at high concentrations and decreased significantly the extracellular Sap concentration at sublethal doses, accompanied by intracellular accumulation of the enzyme. At low concentrations of lysozyme (c. 10 microg/ml), Sap activity decreased more than two-fold and Sap concentration decreased five-fold without any appreciable effect on cell growth or viability. Ultrastructural investigations showed ballooned cells and cells with invaginations (especially present near bud scars), indicating that cell-wall components may be possible targets for this enzyme. All concentrations of lysozyme tested were well within physiologically attainable levels. These data suggest that lysozyme has, at least, a bimodal action on C. albicans, killing the organism at higher concentrations and modulating Sap metabolism at lower concentrations.

Incidence of abnormal laryngeal findings in asymptomatic singing students

OBJECTIVE

Abnormalities in the mucosal lining of the vocal folds may interfere with the normal vibratory patterns and result in vocal limitations, especially for singers whose demands are great. A prospective, longitudinal study was undertaken to investigate the incidence of laryngeal abnormalities in asymptomatic singing students.

METHODS

Sixty-five singing students at the school of music underwent videostroboscopic evaluation and completed a comprehensive questionnaire. Videos were rated by 3 experienced clinicians, and interrater reliability was calculated. Results were correlated with demographic factors, background medical history, and singing history.

RESULTS

Five students (8.3%) exhibited early signs of benign vocal fold lesions (2 with nodules and 3 with cysts). A high incidence of posterior erythema (n = 44; 73.4%), suggesting possible reflux, was found.

CONCLUSIONS

A surprisingly high number of otherwise asymptomatic singing students demonstrated abnormal laryngeal findings. Their relationship with vocal performance will be addressed as well as implications for preventative measures.

Aspiration: cause and implications

The purpose of this investigation was to determine the overall prevalence of aspiration in dysphagic individuals referred for a modified barium swallow and the underlying anatomic and/or physiologic causes. A total of 166 patients were seen during a 1-month period at 5 participating institutions. Aspiration was detected in 51.2% of the patients. The most common causes were decreased laryngeal elevation and delayed triggering of the pharyngeal motor response. A history of aspiration pneumonia was significantly associated with the presence of aspiration on modified barium swallow study. The presence of a protective cough was present in only 53% of patients who aspirated, reinforcing the need for appropriate radiologic assessment in patients with suspected dysphagia.

The Rhizopus oryzae secreted aspartic proteinase gene family: an analysis of gene expression

Rhizopus oryzae was shown to possess a secreted aspartic proteinase gene family (sap) of at least four members (sap1-sap4). Within the family there was 77-87% identity at the nucleotide level and 76-92% identity at the amino acid level. Transcription of three members of this gene family (sap1-sap3) required an acidic medium (pH < 4.5) and either nitrogen or sulphur depression. Regulation was co-ordinate and hierarchical, with pH occupying the higher position in the hierarchy. Exogenous protein increased transcript levels, probably via the provision of metabolic intermediates rather than by direct induction of gene expression. sap4 was not expressed under these conditions. SAP1-SAP4 are predicted to have almost identical substrate-binding sites and therefore substrate specificity. It is proposed that sap1-sap3 exist to provide amplified expression of the secreted aspartic proteinase because protein, an important secondary nitrogen source for this fungus, requires extensive degradation to make its nitrogen available to the cell.

Mortality studies of metalworking fluid exposure in the automobile industry: VI. A case-control study of esophageal cancer

BACKGROUND

Results are reported from a nested case-control study of 60 esophageal cancer deaths among 46,384 automobile manufacturing workers potentially exposed to metalworking fluids (MWF) in machining and grinding operations.

METHODS

By using incidence-density sampling, controls were selected with a sampling ratio of 20:1 from among co-workers who remained at risk by the age of death of the case, matched on race, gender, plant, and year of birth. Conditional logistic regression was used to evaluate the risk associated with cumulative exposure (mg/m3-years) to each of three types of metalworking fluid (straight, soluble, and synthetic MWF), as well as with years of exposure to selected components of MWF, including nitrosamines, sulfur, biocides, and several metals.

RESULTS

Esophageal cancer was found to be significantly associated with exposure to both soluble and synthetic MWF in grinding operations. The odds ratios (ORs) for grinding with soluble MWF were elevated at 2.5 or greater in all categories of cumulative exposure, although the exposure-response trend was statistically significant only when exposure was measured as duration. Those with 12 or more years exposure to soluble MWF in grinding operations experienced a 9.3-fold relative risk of esophageal cancer mortality (95% CI = 2.1-42.1). The OR for ever grinding with synthetic MWF was 4.1 (95% CI = 1.1-15.0). Elevated risk was also associated with two agents found in both synthetic and soluble fluids, nitrosamines, and biocides. For exposure to nitrosamines, the OR was 5.4 (95% CI = 1.5-19.9); for biocides the OR was 3.8 (95% CI = 0.8-18.9). However, because the same workers were exposed to grinding with synthetics, nitrosamines and biocides, it was not possible to separate the specific risks associated with these components.

Purification, characterization and cloning of an aspartic proteinase inhibitor from squash phloem exudate

Phloem exudate from squash fruit contains heat-inactivated material which inhibits pepsin activity. This inhibitory activity was purified by mild acid treatment, chromatography on trypsin-agarose, Sephadex G-75 and reverse-phase HPLC, resulting in the elution of three peaks with pepsin-inhibitory activity. N-terminal sequencing indicated a common sequence of MGPGPAIGEVIG and the presence of minor species with seven- or two-amino-acid N-terminal extensions beyond this point. Microheterogeneity in this end sequence was exhibited within and between two preparations. Internal sequencing of a major peak after a trypsin digestion gave the sequence FYNVVVLEK. The common N-terminal sequence was used to design a degenerate primer for 3' rapid amplification of cDNA ends and cDNA clones encoding two isoforms of the inhibitor were obtained. The open reading frames of both cDNAs encoded proteins (96% identical) which contained the experimentally determined internal sequence. The amino acid content calculated from the predicted amino acid sequence was very similar to that measured by amino acid analysis of the purified inhibitor. The two predicted amino acid sequences (96 residues) had neither similarity to any other aspartic proteinase inhibitor nor similarity to any other protein. The inhibitors have a molecular mass of 10,552 Da, measured by matrix-assisted laser-desorption ionisation time-of-flight mass spectrometry and approximately 10,000 Da by SDS/PAGE, and behave as dimers of approximately 21,000 Da during chromatography on Superdex G-75 gel-filtration medium. The calculated molecular masses from the predicted amino acid sequences were 10,551 Da and 10,527 Da. The inhibitor was capable of inhibiting pepsin (Ki = 2 nM) and a secreted aspartic proteinase from the fungus Glomerella cingulata (Ki = 20 nM). The inhibitor, which is stable over acid and neutral pH, has been named squash aspartic proteinase inhibitor (SQAPI).

A secreted aspartic proteinase from Glomerella cingulata: purification of the enzyme and molecular cloning of the cDNA

A secreted aspartic proteinase from Glomerella cingulata (GcSAP) was purified to homogeneity by ion exchange chromatography. The enzyme has an M, of 36000 as estimated by SDS-PAGE, optimal activity from pH 3.5 to pH 4.0 and is inhibited by pepstatin. The N-terminal sequence, 23 residues long, was used to design a gene-specific primer. This was used in 3' RACE (rapid amplification of cDNA ends) PCR to amplify a 1.2 kb fragment of the gcsap cDNA. A second gene-specific primer was designed and used in 5' RACE PCR to clone the 5' region. This yielded a 600 bp DNA fragment and completed the open reading frame. The gcsap open reading frame encodes a protein with a 78 residue prepro-sequence typical of other fungal secreted aspartic proteinases. Based on the deduced sequence, the mature enzyme contains 329 amino acids and shows approximately 40% identity to other fungal aspartic proteinases. Subsequent cloning and sequencing of gcsap fragments obtained from PCR with genomic DNA revealed a 73 bp intron beginning at nt 728. Southern analyses at medium and high stringency indicated that G. cingulata possesses one gene for the secreted aspartic proteinase, and Northern blots indicated that gene expression was induced by exogenous protein and repressed by ammonium salts. GcSAP is a putative pathogenicity factor of G. cingulata, and it will now be possible to create SAP-mutants and assess the role GcSAP plays in pathogenicity.

Identification of Glu-330 as the catalytic nucleophile of Candida albicans exo-beta-(1,3)-glucanase

The exo-beta-(1,3)-glucanase from Candida albicans hydrolyzes cell wall beta-glucans via a double-displacement mechanism involving a glycosyl enzyme intermediate. Reaction of the enzyme with 2',4'-dinitrophenyl-2-deoxy-2-fluoro-beta-D-glucopyranoside resulted in the time-dependent inactivation of this enzyme via the accumulation of a 2-deoxy-2-fluoro-glycosyl-enzyme intermediate as monitored also by electrospray mass spectrometry. The catalytic competence of this intermediate is demonstrated by its reactivation through hydrolysis (kreact = 0.0019 min-1) and by transglycosylation to benzyl thio-beta-D-glucopyranoside (kreact = 0.024 min-1; Kreact = 56 mM). Peptic digestion of the labeled enzyme followed by tandem mass spectrometric analysis in the neutral loss mode allowed detection of two glycosylated active site peptides, the sequences of which were identified as NVAGEW and NVAGEWSAA. A crucial role for Glu-330 is confirmed by site-directed mutagenesis at this site and kinetic analysis of the resultant mutant. The activity of the Glu-330 --> Gln mutant is reduced over 50,000-fold compared to the wild type enzyme. The glutamic acid, identified in the exoglucanase as Glu-330, is completely conserved in this family of enzymes and is hereby identified as the catalytic nucleophile.

Identification of salivary basic proline-rich proteins as receptors for Candida albicans adhesion

The adherence of Candida albicans cells to oral surfaces is believed to be an important step in the development of oral candidosis. Electrophoretically separated parotid salivary proteins were transferred to nitrocellulose membranes and incubated with [35S]methionine-radiolabelled C. albicans cells in a cell overlay adherence assay. A subset of four proteins with apparent molecular masses of 17, 20, 24 and 27 kDa (designated bands A-D) acted as receptors for cells of C. albicans ATCC 10261 and four clinical C. albicans isolates, in overlay assays. The N-terminal amino acid sequence of bands A-D indicated that these proteins were members of the basic proline-rich protein (bPRP) family. Digestion of protein A with endoproteinase Glu-C resulted in a single band (designated Ap) detected by Coomassie blue staining after SDS-PAGE. This band was not bound by C. albicans cells in overlay assays and comprised two fragments, designated ApN and ApC. These fragments had N-terminal sequences corresponding to the N-terminal and post endoproteinase Glu-C cleavage site sequences of bPRP IB-6 and had molecular masses of 6189 and 4261 Da as determined by mass spectrometry. Thus intact bPRP IB-6, and other bPRPs, may act as receptors for C. albicans adhesion.

Analysis of secreted aspartic proteinases from Candida albicans: purification and characterization of individual Sap1, Sap2 and Sap3 isoenzymes

The recently discovered secreted aspartic proteinase multi-gene (SAP) family in Candida albicans has complicated assessment of proteolytic activity as a factor in the onset and development of Candida infections. Differential expression of the SAP genes under various conditions, as well as possible variation in the properties of the individual isoenzymes, have consequences for immunological detection, for targeted drug design and possibly for pathogenicity. It is therefore important to be able to monitor Sap isoenzyme profiles in different strains of C. albicans cultures, and to know the biochemical properties of each isoenzyme. We have employed a simple purification protocol based on strong anion exchange chromatography for the direct analysis of C. albicans Sap isoenzymes from culture filtrates, as well as recovery of individual Sap1, Sap2 and Sap3 products. In the case of Sap1, this involved development of an overexpression system using the pEMBLyex4 vector transformed into Saccharomyces cerevisiae. The C. albicans strains ATCC 10231 and 10261 were shown to produce different ratios of Sap2 and Sap3 under the same conditions. Analysis of all three purified proteins by gel electrophoresis, immunoblotting and proteinase assays which were designed to evaluate pH dependence, thermal stability and substrate specificity revealed similar but distinct properties for each isoenzyme. Although Sap3 was shown to be antigenically more similar to Sap2 than was Sap1, it was less similar in terms of thermal stability and activity at low pH, being more stable and more active.

Blood pressure and heart rate dynamics during and after exercise in an unselected population

It has been suggested that the systolic blood pressure (SBP) response to exercise may be useful in predicting future hypertension. However, controversy exists as to whether the SBP response to exercise in borderline hypertensives is actually greater than normotensives or merely increases equally but from a higher resting value. Our aim was to determine the influence of resting SBP, age and sex on changes of SSP during exercise for both healthy subjects and untreated mild hypertensives. Three hundred and eighteen (230 males) underwent a self limited exercise protocol. SBP was measured at baseline and between the 2nd and 3rd minutes of each exercise stage. Age was positively related to SBP at rest and during exercise. The magnitude of SBP change induced by exercise was similar irrespective of the level of resting SBP. The relationship between resting SBP and the absolute SBP change which occurred during exercise was independent of sex. Our findings indicate that (i) age is positively related to SBP at rest and during exercise, (ii) SBP rises equally during exercise irrespective of its resting level and (iii) males and females have a similar pattern of BP response to exercise.

Defect formation on surfaces bombarded by energetic multiply charged proteins: Implications for the conformation of gas-phase electrosprayed ions

Indirect information on the conformation of highly charged molecular ions may be obtained by monitoring their collisional cross sections and the course of simple gas-phase reactions such as hydrogen-deuterium exchange. In this work, another indirect but more visually oriented approach is explored: electrosprayed protein ions are accelerated toward a highly oriented pyrolytic graphite surface and the resulting single-ion defects are imaged by scanning force and tunneling microscopy. All protein impacts generated shallow hillocks: the shapes depended on the identity and charge state of the incident protein. Lysozyme and myoglobin, both compact, globular proteins in the native state, produced compact, almost circular hillocks. However, hillocks generated by myoglobin that had been denatured in the solution phase were elongated, and the elongation was positively correlated with the charge state of the ion. It appears that structural information about gas-phase multiply charged proteins can be derived from imprints generated by energetic protein impacts on surfaces.

Elevated aspartic proteinase secretion and experimental pathogenicity of Candida albicans isolates from oral cavities of subjects infected with human immunodeficiency virus

Isolates of Candida albicans from the oral cavities of subjects at different stages of human immunodeficiency virus (HIV) infection or uninfected controls were examined for (i) production of aspartic proteinase(s), a putative virulence-associated factor(s); (ii) the presence in the fungal genome of two major genes (SAP1 and SAP2) of the aspartic proteinase family; and (iii) experimental pathogenicity in a murine model of systemic infection. It was found that the fungal isolates from symptomatic patients secreted, on average, up to eightfold more proteinase than the isolates from uninfected or HIV-infected but asymptomatic subjects. This differential property was stably expressed by the strains even after years of maintenance in stock cultures. Moreover, representative high-proteinase isolates were significantly more pathogenic for mice than low-proteinase isolates of C. albicans. The characters high proteinase and increased virulence were not associated with a single molecular type or category identifiable through DNA fingerprinting or pulsed-field electrophoretic karyotype, and both SAP1 and SAP2 genes were present in both categories of isolates, on the same respective chromosomes. In conclusion, our data suggest that during HIV infection more-virulent strains or biotypes of C. albicans which are identifiable by direct analysis of virulence determinants are selected. It also appears that the biotype switch to increased aspartic proteinase and virulence properties occurs before the HIV-infected subject enters the symptomatic stage and overt AIDS.

The crystal structure of a major secreted aspartic proteinase from Candida albicans in complexes with two inhibitors

BACKGROUND

Infections caused by Candida albicans, a common fungal pathogen of humans, are increasing in incidence, necessitating development of new therapeutic drugs. Secreted aspartic proteinase (SAP) activity is considered an important virulence factor in these infections and might offer a suitable target for drug design. Amongst the various SAP isozymes, the SAP2 gene product is the major form expressed in a number of C. albicans strains.

RESULTS

The three-dimensional structures of SAP2 complexed with the tight-binding inhibitor A70450 (a synthetic hexapeptide analogue) and with the general aspartic proteinase inhibitor pepstatin A (a microbial natural product) have been determined to 2.1 A and 3.0 A resolution, respectively. Although the protein structure retains the main features of a typical aspartic proteinase, it also shows some significant differences, due mainly to several sequence insertions and deletions (as revealed by homology modelling), that alter the shape of the binding cleft. There is also considerable variation in the C-terminal structural domain.

CONCLUSIONS

The differences in side chains, and in the conformations adopted by the two inhibitors, particularly at their P4, P3 and P'2 positions (using standard notation for protease-inhibitor residues), allows the A70450 structure to complement, more accurately, that of the substrate-binding site of SAP2. Some differences in the binding clefts of other SAP isoenzymes may be deduced from the SAP2 structure.

Differential extraction of N-acetylglucosaminidase and trehalase from the cell envelope of Candida albicans

Dithiothreitol (DTT) extraction of N-acetylglucosaminidase and trehalase from intact Candida albicans ATCC 10261 cells was monitored as an index of cell envelope porosity during N-acetylglucosamine-induced morphogenesis. Trehalase, which is secreted into the cell envelope during starvation and bud-formation, displayed similar extraction kinetics in starved, germ tube-forming, and bud-forming cells, indicating that the mother cell wall remains largely unchanged during morphogenic outgrowth and that the porosity of bud and mother cell walls is similar. N-acetylglucosaminidase, which is secreted specifically during morphogenesis, was released eightfold more rapidly from germ tube-forming than bud-forming cells, reflecting major differences in porosity between bud and germ tube. In addition, by assaying DTT extracts and extracted cell residues, it was found that the total extracellular N-acetylglucosaminidase activity increased 2- to 2.5-fold during DTT treatment. Thus, DTT unmasks a cryptic form of N-acetylglucosaminidase. The cryptic activity was associated with the cell wall fraction.

Respiratory disease risks in the construction industry

This chapter focuses on the primary identified respiratory hazards in construction, including respiratory tract cancers, pulmonary and pleural fibrosis, airway diseases, inhalation injuries, and respiratory infection. An extensive table identifies the exposure limits specified by NIOSH, OSHA, and ACGIH for more than 30 substances.

Measurement of wall deformation and flow limitation in a mechanical trachea

A mechanical model of the human trachea is investigated experimentally. A modified version of an earlier model, it consists of a square sectioned rigid tube in which part of one wall is removed, and replaced by a prestretched flat latex membrane. Air is drawn from atmosphere through an inlet into the rigid upstream tube; it then flows through the flexible section and finally through a rigid section into a plenum chamber where suction is applied. As the membrane collapses in response to flow, the transmural pressure and deflection are measured at the mid-point. These values are used in conjunction with a finite deformation membrane wall theory to determine the elastic constant in a nonlinear material constitutive equation. This equation is used to predict the tube law. Results show that the flow limits at the long wave speed predicted by this law. Thus it behaves as a conventional collapsible tube while having the advantage of a rational wall model.

Kinetics of beta-1,3 glucan interaction at the donor and acceptor sites of the fungal glucosyltransferase encoded by the BGL2 gene

Formation of branched glucan, glucan-glucan cross links, and glucan-chitin cross links most likely involves the action of fungal wall glucanases and transglycosylases. We developed an HPLC assay using radiolabeled substrates in order to study the kinetics of interaction of donor and acceptor molecules with a glucosyltransferase present in the cell walls of both Saccharomyces cerevisiae and Candida albicans. Purified transferase first forms an activated intermediate from a donor beta-1,3 glucan, releasing free disaccharide. The activated intermediate is transferred, in the presence of an appropriate acceptor beta-1,3 glucan, yielding a linear glucan containing a beta-1,6 linkage at the transfer site [Yu, L., Goldman, R., Sullivan, P., Walker, G. & Fesik, S. W. (1993) J. Biomol. NMR 3, 429-441]. An apparent Km of 0.41 mM for the acceptor site was determined using laminaritetraose as the acceptor. An apparent Km of 31 mM for the donor site was determined using increasing concentrations of laminaripentaose, and monitoring formation of laminaribiose. The enzyme functioned as a glucanase at low concentrations of acceptor molecules, with excess H2O competing for reaction at the activated donor site, thus resulting in hydrolysis. However, as the concentration of acceptor increased, the reaction shifted from hydrolysis to glucosyltransfer. The reaction appeared specific for beta-1,3 glucan as acceptor, in as much as no transfer was detected when either hexa-N-acetyl-chitohexaose or maltooligosaccharides were used as acceptors. The roles of such an enzymic activity in cell wall metabolism is discussed in terms of repair, cross linking and incorporation of newly synthesized chains of beta-1,3 glucan into the previously existing cell wall structure.

Purification and characterization of two forms of N-acetylglucosaminidase from Candida albicans showing widely different outer chain glycosylation

Two forms of N-acetylglucosaminidase were purified to homogeneity by ion exchange (TSK DEAE-3SW, Aquapore CX-300) and gel filtration (TSK G4000 SW) HPLC of Candida albicans ATCC 10261 culture filtrates. Synthesis and secretion of N-acetylglucosaminidase were induced by incubating starved yeast cells at 37 degrees C in medium containing N-acetylglucosamine (GlcNAc). The form of the enzyme depended on the cell growth and starvation conditions before GlcNAc induction. N-Acetylglucosaminidase A (32% total carbohydrate, M(r) 85,000 subunit) was isolated from cells grown in glucose/salts/biotin medium, and N-acetylglucosaminidase B (56% carbohydrate, M(r) 132,000 subunit) was isolated from cells grown in yeast extract/peptone/dextrose. The estimated relative molecular masses of the native enzymes, based on Sephacryl S-300 gel filtration were: A form, 350,000; B form, 600,000; A and B forms after endoglycosidase H (endo H) treatment, 180,000. The purified enzymes migrated on SDS polyacrylamide gels as heterogeneous glycoproteins of M(r) centred at approximately 100,000 (A) and approximately 150,000 (B) but were reduced to a single 58,000 band after denaturation with SDS and cleavage of asparagine-linked sidechains by endo H. When the native glycoproteins were treated with endo H, both enzyme forms had three oligosaccharide sidechains of M(r) approximately 3000 that were endo H resistant. Therefore the difference in the size of N-acetylglucosaminidase A and B was due to variations in outer chain glycosylation of endo H-sensitive inner core structures. N-Acetylglucosaminidase was active and stable over a broad pH range with maximum activity against both p-nitrophenylGlcNAc (pNPGlcNAc) and pNPGalNAc at pH 4.0. The kinetic parameters kcat (s-1) and Km (mM) of N-acetylglucosaminidase A using the following substrates were, respectively: pNPGlcNAc, 740, 0.77; pNPGalNAc, 910, 1.26; N,N'-diacetylchitobiose 620, 0.20; and N,N',N"-triacetylchitotriose, 170, 0.044. The enzyme showed substrate inhibition with all substrates above 0.5 mM except for pNPGalNAc.

A measure of growth. A system's corporate ethics committee assesses its accomplishments and future direction

In 1992 the Sisters of Mercy Health System (SMHS) Corporate Ethics Committee (CEC) developed a three-step evaluative process of the system's ethics programs. The evaluation consisted of a retrospective review of the minutes of CEC meetings since the committee's inception, an oral evaluation with current CEC members, and a written assessment of the committee's performance by current and former members. In the open discussion, 86 percent of participants indicated that the system needs the CEC because it facilitates in-depth examination of ethical issues and provides important research and consulting services to the system executive. Respondents completing the written evaluation indicated that the CEC's dominant strength is the diversity of its membership, which includes trustees, physicians, ethicists, nurses, administrators, managers, and chaplains. More than 57 percent of respondents reported the CEC has achieved all six of its goals, which included education, articulation, decision making, policy development, program development, and evaluation. A review of the CEC evaluation suggests that the committee has moved beyond the development stage and entered a period of active growth. CEC members have made great strides in educating themselves, and the committee must now consider whether to broaden its focus by developing its knowledge base and skills for bioethical education and policy recommendations. The CEC is currently testing an ethical decision-making model it recently developed.

Cassette mutagenesis of Aspergillus awamori glucoamylase near its general acid residue to probe its catalytic and pH properties

Nine single amino acid mutations in the active site of Aspergillus awamori glucoamylase were made by cassette mutagenesis to alter the pH dependence of the enzyme and to determine possible functions of the mutated residues. The Glu179-->Asp mutation expressed in yeast led to a very large decrease in kcat but to no change in Km, verifying this residue's catalytic function. Asp176-->Glu and Glu180-->Asp mutations affected Km more than kcat, implying that Asp176 and Glu180 are involved in substrate binding or structural integrity. The Leu177-->Asp mutation decreased kcat only moderately, probably by changing the position of the general acid catalytic group, and did not affect Km. The Trp178-->Asp mutation greatly decreased kcat while increasing Km, showing the importance of Trp178 in the active site. Val181-->Asp and Asn182-->Asp mutations changed kinetic values little, suggesting that Val181 and Asn182 are of minor catalytic and structural importance. Finally, insertions of Asp or Gly between residues 176 and 177 resulted in almost complete loss of activity, probably caused by destruction of the active site structure. No large changes in pH dependence occurred in those mutations where kinetic values could be determined, in spite of the increase in most cases of the total negative charge. Increases in activation energy of maltoheptaose hydrolysis in most of the mutant glucoamylases suggested cleavage of individual hydrogen bonds in enzyme-substrate complexes.

The cell wall of the oleaginous yeast Trichosporon cutaneum

The cell wall of Trichosporon cutaneum consists of 11% protein, 63% neutral carbohydrate, 9% glucosamine and 13% glucuronic acid. The sugars include glucose (32%), mannose (6%) and traces of xylose and galactose. The cell wall was fractionated with alkali to yield a mixture of alkali-soluble matrix components, and an alkali-insoluble glucan associated with chitin. The alkali-insoluble glucan contained a mixture of (1-3) and (1-6) glycosidic linkages. It was only partly susceptible to digestion by the beta(1-3) glucanase, Zymolyase. The alkali-soluble fraction contained glucan, mannan and acidic polymers. The glucan was (1-3)-linked with no (1-6) linkages and only trace amounts of (1-3-6)-linked glucose. It was resistant to digestion by Zymolyase. Extensive hydrolysis of this fraction with trifluoroacetic acid released a high-molecular-mass glucuronan which had 1H- and 13C-NMR profiles matching those of the beta(1-4) glucuronan, mucoric acid. Xylomannan was purified from isolated cell walls and from whole cells. It contained glucose, mannose, xylose, and D-glucuronic acid. It was very similar in composition and structure to the capsular polysaccharides of Cryptococcus neoformans, and to an extracellular polysaccharide produced by another yeast described as T. cutaneum. Electron microscopy showed that the cell wall of T. cutaneum has a lamellar structure characteristic of a basidiomycetous yeast rather than the electron-dense 'fuzzy coat' seen in Candida albicans.

Identification of a putative active site residue in the exo-beta-(1,3)-glucanase of Candida albicans

Recombinant exo-beta-(1,3)-glucanase from Candida albicans was expressed in Saccharomyces cerevisiae and purified. The enzyme contains a number of short blocks of sequence homology with several genes for cellulases of the family A glucanases including the conserved sequence motif NEP which has previously been shown to be important in the catalytic function of several cellulases. Site directed mutagenesis of this glutamic acid residue in the 1,3 glucanase (E230D, E230Q) decreased the enzymatic activity 15,000- and 400-fold, respectively. This suggests that the E of the NEP participates in catalysis of the exoglucanase and other related glucanases.

Expression of the exoglucanase gene in yeast and hyphal forms of Candida albicans

The gene for the beta-(1,3) exoglucanase of Candida albicans was used as a probe to detect transcripts of related genes in C. albicans and in several other Candida species. A single homologous transcript was detected in all of the species tested. Expression of the exoglucanase gene in C. albicans was found to be coincident with the onset of growth and the levels of the transcript were proportional to the growth rate. Comparable levels of the transcript were produced during yeast and hyphal forms of growth.

An exo-beta-(1,3)-glucanase of Candida albicans: purification of the enzyme and molecular cloning of the gene

A nucleotide sequence encoding an exo-beta-(1,3)-glucanase was cloned from a library of genomic DNA of Candida albicans ATCC 10261. The sequenced gene encodes a protein of 438 amino acid residues. The amino terminal and an internal peptide sequence of the enzyme matched with deduced sequences within the cloned gene. Analysis of the sequence indicated that the nascent protein is processed during secretion by the signal peptidase and a Kex2-like proteinase, yielding a predicted mature enzyme of 400 residues. There is 58% identity and 85% similarity between the amino acid sequences of this exoglucanase and the homologous enzyme of Saccharomyces cerevisiae. An antiserum to the purified exoglucanase cross-reacted with the S. cerevisiae exoglucanase and a similar protein secreted by other C. albicans strains and Candida species. There are no sites for N-linked glycosylation in the sequence and this is consistent with the carbohydrate content of the secreted enzyme. Putative upstream promoter elements are associated with the gene. Southern analysis of the gene indicated that it was present at one copy per genome and that the diploid genome of C. albicans ATCC 10261 is heterozygous at this locus for a BglII RFLP. A 2.5 kb mRNA transcript was detected by Northern analysis and gene expression, as monitored by Northern and Western blots, reflected the growth rates of the cultures.

Short-term strenuous exercise training: effects on blood pressure and hormonal levels in mild hypertension

The effect of a six-week strenuous exercise training programme (modified Bruce protocol, treadmill, three times per week) on resting and exercising blood pressure, heart rate, plasma catecholamines, chromogranin A, renin activity and aldosterone levels was investigated in 15 patients with mild hypertension. An identical exercise test was conducted at baseline and study close (six weeks). At follow-up, seven to ten days after study close, patients completed an exercise test of equivalent intensity to that at baseline, achieving comparable heart rate levels at maximal exercise. On each occasion, blood pressure, heart rate and hormonal variables were measured at rest (supine), maximal exercise and ten minutes after stopping exercise. Resting and exercising blood pressure and heart rate were reduced by the six-week exercise regimen. There was a trend, although not statistically significant, for resting plasma noradrenaline levels to be lower at study close. The reduction in blood pressure and heart rate at maximal exercise was associated with a significant attenuation of the plasma renin response to exercise. Plasma catecholamines also appeared to be lower after exercise training, although this effect was not statistically significant. Plasma levels of chromogranin A and aldosterone measured at rest and maximal exercise were not influenced by the exercise regimen. Further controlled studies are required to corroborate the results of this preliminary study.

A second gene for a secreted aspartate proteinase in Candida albicans

The gene (PRA11) encoding a secreted aspartate proteinase of Candida albicans has been cloned and sequenced. The nucleotide and deduced amino acid sequences of PRA11 are 77 and 73% identical, respectively, with the reported sequences of PRA10 also cloned from C. albicans. Southern analyses indicated that the genome of each strain examined (ATCC 10231 and ATCC 10261) contains PRA10 and PRA11. Northern (RNA) analyses showed that PRA11 was expressed at a much higher level than was PRA10 when secretion of the proteinase by strain ATCC 10261 was induced with albumin.

Enalapril versus combined enalapril and nadolol treatment: effects on blood pressure, heart rate, humoral variables, and plasma potassium at rest and during exercise in hypertensive patients

The effect of enalapril alone and in combination with nadolol on resting and exercising blood pressure, heart rate, plasma renin activity, aldosterone, noradrenaline, and potassium levels was studied in 10 hypertensive patients (diastolic blood pressure between 95 and 114 mmHg). Patients received placebo for 4 weeks, enalapril (mean daily dose 24.5 mg) for 8 weeks, and nadolol, 40 mg once daily, was added for the remaining 8 weeks of the study. Exercise testing (modified Bruce, treadmill) was conducted at the end of the placebo run-in phase and at the end of each treatment period. Enalapril reduced resting and exercising blood pressure independent of any change in heart rate: This effect was increased with combination treatment. Plasma renin activity at rest and during exercise was increased by enalapril. Combination treatment attenuated this response and significantly reduced plasma aldosterone. Neither treatment had any effect on plasma noradrenaline levels. Resting plasma potassium levels were increased with combination treatment, whereas both treatment regimens increased plasma potassium levels during exercise. There were no clinically relevant episodes of hyperkalemia. Further investigation is required to qualify the nature of the blood pressure and plasma potassium response with combination treatment.