Foundational and Clinical Science Integration in a Team-Based Learning Module Modeling Care of a Patient With Dyslipidemia

Introduction

Foundational and clinical science integration, a long-standing goal of undergraduate medical education, benefits learners by promoting retention of critical knowledge and skills as well as their transfer to the clinical setting. We implemented a team-based learning (TBL) module in which foundational knowledge and skills from the disciplines of biochemistry, nutrition, and genetics were leveraged in a simulated patient encounter for diagnosis and management of a patient with dyslipidemia.

Methods

The TBL was deployed in a first-year medical student cardiovascular system course with 125 students over three academic years. Following individual and team readiness assurance tests (iRAT and tRAT, respectively), teams participated in an initial application exercise requiring consideration of clinical and laboratory data and other risk factors to engage the patient in a shared decision-making process. Using dietary and family history narratives in subsequent application exercises, teams completed recommendations for an individualized diet plan and an assessment of potential disease inheritance patterns to formulate appropriate patient care management strategies.

Results

Student engagement with prelearning materials and session team activities was high as judged by RAT performance and application exercise outcomes: iRAT question performance ranged from 89% to 99% for individual items, and tRAT performance was routinely 100%. Learners reported that the exercises were impactful and believed the learned foundational knowledge and skills were transferable to future patient care.

Discussion

The dyslipidemia TBL module provides an illustration for early clinical learners of how foundational knowledge and skills can be operationalized and transferred for optimal patient care.

Rapid Conversion to a Completely Virtual Multidisciplinary ALS Clinic in Response to the COVID-19 Pandemic: Implications for Future Care Delivery

OBJECTIVES

The goals of this study were to assess the feasibility of maintaining multidisciplinary remote care, patient preferences, and outcomes of this transition because of COVID-19.

METHODS

From March 18, 2020 to June 3, 2020, 127 patients with amyotrophic lateral sclerosis (ALS) who were scheduled to be seen in our ALS clinic were contacted and scheduled according their preference for a telemedicine visit, telephone visit, or postponement until the next available in-person visit. Age, time from disease onset, ALS Functional Rating Scale-Revised, patient choices, and outcomes were recorded.

RESULTS

Patient visit preferences were 69% telemedicine, 21% telephone, and 10% postpone for a later in-clinic visit. Patients with higher ALS Functional Rating Scale-Revised were more likely to choose the next in-person opening (P = 0.04). Age and time from disease onset were not related to visit type preference. There were 118 virtual encounters, of which 91 (77%) began as telemedicine and 27 (23%) as telephone visits. Most telemedicine visits were conducted successfully, but 10 were converted to a telephone visit. The clinic maintained 88.6% of patient volume compared with the prior year, during which most visits were in-person.

CONCLUSIONS

Telemedicine care using synchronous videoconferencing is preferable and feasible for most patients on short notice, with telephone as back-up. Clinic volumes can be maintained. These findings support the conversion of a multidisciplinary ALS clinic to 1 with exclusively virtual visits when future events again disrupt in-person care.

Using What's at Hand: The Creation of an Online Microbiology Outreach Program

Outreach programs lead to increased student interest to pursue careers in science fields. However, hosting existing programs during a pandemic has proven difficult. We used "The Seven Principles of Good Practice," which emphasizes interactions between the instructor and students, feedback, and peer interactions, to design an online microbiology program for high school students. Moreover, we incorporated diverse learning techniques to reach learners at disparate levels. While our program was primarily asynchronous, to accommodate for the schedules of our student population, synchronous sessions were held each morning to answer questions, ensure clarity of instructions, and encourage students to benefit from the content expertise of the multidisciplinary faculty. Student and faculty assessment indicated that the program was a success. Our online microbiology precollege outreach program demonstrated an effective way to expose students to infectious disease concepts and information literacy. In this paper, we describe some tips and tools from lessons learned in our outreach program for high school students that was offered online on the topic of microbiology and antimicrobial resistance.

Nutritional neuropathies

Neuropathies associated with nutritional deficiencies are routinely encountered by the practicing neurologist. Although these neuropathies assume different patterns, most are length-dependent, sensory axonopathies. Cobalamin deficiency neuropathy is the exception, often presenting with a non-length-dependent sensory neuropathy. Patients with cobalamin and copper deficiency neuropathy characteristically have concomitant myelopathy, whereas vitamin E deficiency is uniquely associated with a spinocerebellar syndrome. In contrast to those nutrients for which deficiencies produce neuropathies, pyridoxine toxicity results in a non-length-dependent sensory neuronopathy. Deficiencies occur in the context of malnutrition, malabsorption, increased nutrient loss (such as with dialysis), autoimmune conditions such as pernicious anemia, and with certain drugs that inhibit nutrient absorption. When promptly identified, therapeutic nutrient supplementation may result in stabilization or improvement of these neuropathies.

The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project

The PREDICTS project-Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)-has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.

The PREDICTS database: a global database of how local terrestrial biodiversity responds to human impacts

Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habitat destruction, exploitation, pollution and introduction of alien species. Existing global databases of species’ threat status or population time series are dominated by charismatic species. The collation of datasets with broad taxonomic and biogeographic extents, and that support computation of a range of biodiversity indicators, is necessary to enable better understanding of historical declines and to project – and avert – future declines. We describe and assess a new database of more than 1.6 million samples from 78 countries representing over 28,000 species, collated from existing spatial comparisons of local-scale biodiversity exposed to different intensities and types of anthropogenic pressures, from terrestrial sites around the world. The database contains measurements taken in 208 (of 814) ecoregions, 13 (of 14) biomes, 25 (of 35) biodiversity hotspots and 16 (of 17) megadiverse countries. The database contains more than 1% of the total number of all species described, and more than 1% of the described species within many taxonomic groups – including flowering plants, gymnosperms, birds, mammals, reptiles, amphibians, beetles, lepidopterans and hymenopterans. The dataset, which is still being added to, is therefore already considerably larger and more representative than those used by previous quantitative models of biodiversity trends and responses. The database is being assembled as part of the PREDICTS project (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems – http://www.predicts.org.uk). We make site-level summary data available alongside this article. The full database will be publicly available in 2015.

Flowering phenology and its implications for management of big-leaf mahogany Swietenia macrophylla in Brazilian Amazonia

PREMISE OF THE STUDY

Flowering phenology is a crucial determinant of reproductive success and offspring genetic diversity in plants. We measure the flowering phenology of big-leaf mahogany (Swietenia macrophylla, Meliaceae), a widely distributed neotropical tree, and explore how disturbance from logging impacts its reproductive biology.

METHODS

We use a crown scoring system to estimate the timing and duration of population-level flowering at three forest sites in the Brazilian Amazon over a five-year period. We combine this information with data on population structure and spatial distribution to consider the implications of logging for population flowering patterns and reproductive success.

KEY RESULTS

Mahogany trees as small as 14 cm diam flowered, but only trees > 30 cm diam flowered annually or supra-annually. Mean observed flowering periods by focal trees ranged from 18-34 d, and trees flowered sequentially during 3-4 mo beginning in the dry season. Focal trees demonstrated significant interannual correlation in flowering order. Estimated population-level flowering schedules resembled that of the focal trees, with temporal isolation between early and late flowering trees. At the principal study site, conventional logging practices eliminated 87% of mahogany trees > 30 cm diam and an estimated 94% of annual pre-logging floral effort.

CONCLUSIONS

Consistent interannual patterns of sequential flowering among trees create incompletely isolated subpopulations, constraining pollen flow. After harvests, surviving subcommercial trees will have fewer, more distant, and smaller potential partners, with probable consequences for post-logging regeneration. These results have important implications for the sustainability of harvesting systems for tropical timber species.

The importance of tree size and fecundity for wind dispersal of big-leaf mahogany

Seed dispersal by wind is a critical yet poorly understood process in tropical forest trees. How tree size and fecundity affect this process at the population level remains largely unknown because of insufficient replication across adults. We measured seed dispersal by the endangered neotropical timber species big-leaf mahogany (Swietenia macrophylla King, Meliaceae) in the Brazilian Amazon at 25 relatively isolated trees using multiple 1-m wide belt transects extended 100 m downwind. Tree diameter and fecundity correlated positively with increased seed shadow extent; but in combination large, high fecundity trees contributed disproportionately to longer-distance dispersal events (>60 m). Among three empirical models fitted to seed density vs. distance in one dimension, the Student-t (2Dt) generally fit best (compared to the negative exponential and inverse power). When seedfall downwind was modelled in two dimensions using a normalised sample, it peaked furthest downwind (c. 25 m) for large, high-fecundity trees; with the inverse Gaussian and Weibull functions providing comparable fits that were slightly better than the lognormal. Although most seeds fell within 30 m of parent trees, relatively few juveniles were found within this distance, resulting in juvenile-to-seed ratios peaking at c. 35–45 m. Using the 2Dt model fits to predict seed densities downwind, coupled with known fecundity data for 2000–2009, we evaluated potential Swietenia regeneration near adults (≤30 m dispersal) and beyond 30 m. Mean seed arrival into canopy gaps >30 m downwind was more than 3× greater for large, high fecundity trees than small, high-fecundity trees. Tree seed production did not necessarily scale up proportionately with diameter, and was not consistent across years, and this resulting intraspecific variation can have important consequences for local patterns of dispersal in forests. Our results have important implications for management and conservation of big-leaf mahogany populations, and may apply to other threatened wind-dispersed Meliaceae trees.

Pertussis outbreak in northwest Ireland, January – June 2010

We report a community pertussis outbreak that occurred in a small town located in the northwest of Ireland. Epidemiological investigations suggest that waning immunity and the absence of a booster dose during the second year of life could have contributed to the outbreak. The report also highlights the need to reinforce the surveillance of pertussis in Ireland and especially to improve the clinical and laboratory diagnosis of cases.

Pertussis outbreak in northwest Ireland, January - June 2010

We report a community pertussis outbreak that occurred in a small town located in the northwest of Ireland. Epidemiological investigations suggest that waning immunity and the absence of a booster dose during the second year of life could have contributed to the outbreak. The report also highlights the need to reinforce the surveillance of pertussis in Ireland and especially to improve the clinical and laboratory diagnosis of cases.

Multi-component adsorption model for pellicle formation: The influence of salivary proteins and non-salivary phospho proteins on the binding of histatin 5 onto hydroxyapatite

The acquired enamel pellicle formed by selective adsorption of proteins in whole saliva is a protective integument on the tooth surface. The purpose of the present study was to investigate the formation of human acquired enamel pellicle using an in vitro hydroxyapatite (HA) model and 3H-histatin 5 to allow accurate measurement of histatin 5 binding in a multi-component experimental system. A binary system was employed by mixing 3H-histatin 5 with one unlabeled protein prior to incubation with HA or by first incubating 3H-histatin 5 with the HA which had been pre-coated with one of a panel of unlabeled proteins (human albumin, salivary amylase, lysozyme, acidic PIFs, statherin, the N-terminal fragment of statherin, and egg yolk phosvitin). A ternary system was employed by mixing 3H-histatin 5 with HA sequentially pre-coated with two different unlabeled proteins, including recombinant histatin 1. The results showed that only salivary statherin and egg yolk phosvitin promote histatin 5 adsorption significantly. The amount of histatin 5 adsorbed was also found to increase as a function of the amount of phosvitin and statherin used to pre-coat HA up to a maximum level that was two- to four-fold greater than that observed on untreated HA. These data suggest that specific protein-protein interactions may play important roles in pellicle formation in vivo.

Prospective comparison of methods of closure of the coronal flap after craniofacial surgery in children

The coronal flap in children may be closed with clips or sutures. The results of closure with clips in patients treated during 1 year at the paediatric craniofacial unit, Liverpool, UK, were audited. Eight of 43 required a further general anaesthetic for removal of clips. A prospective audit the following year of patients whose wounds were closed with a rapidly-absorbed polyglactin suture (Vicryl rapide) showed that 3 out of 39 required re-suture of the wound in theatre (two following trauma from falls). There was one infection in each group. Neither of these patients required formal debridement of the wound in theatre. Rapidly-absorbed polyglactin is a safe alternative to clips for wound closure after craniofacial surgery in children and the morbidity is less because fewer patients have to return to theatre than closure with surgical clips.

Physical parameters of hydroxyapatite adsorption and effect on candidacidal activity of histatins

Histatins 1, 3 and 5 are the major members of a histidine-rich protein family present in human salivary secretions. These proteins are distinct from many salivary proteins in their high positive charge density at neutral pH, and their antibacterial and antifungal properties. In this study, the hydroxyapatite adsorption characteristics of histatin 1, containing a single phosphoserine residue, recombinantly expressed histatin 1, native histatin 3, synthetic histatin 5 and an internal 12-residue sequence of histatin 5 were investigated. A Langmuir-type model was used to analyse the adsorption. A comparison of the affinities and binding sites of phosphorylated and recombinant histatin 1 provided an estimate of the positive influence of the single phosphoseryl group on mineral adsorption. Furthermore, an apparent correlation was shown to exist between peptide chain length and the number of binding sites. The influence of histatin 5 adsorption on its anticandidal activity was also investigated by performing Candida albicans killing assays with histatin 5 and histatin 5/hydroxyapatite suspensions. A decrease in killing activity was observed with the increase of hydroxyapatite present. The results suggest that the anticandidal properties of histatin 5 could be impaired by the conformations resulting from mineral adsorption, or that putative cellular receptors necessary for candidacidal activity are inaccessible when histatin 5 is adsorbed on hydroxyapatite.

Tandem mass spectrometry for structural characterization of proline-rich proteins: application to salivary PRP-3

Proline-rich proteins (PRPs), including collagens, complement 1q, and salivary PRPs, are unusually difficult to sequence by mass spectrometry, due to the high efficiency of cleavage at the amide bond on the N-terminal of proline residues and the consequently low relative abundance of fragment arising from cleavages at other amide bonds. To fully characterize these proteins by mass spectrometry, specialized approaches to fragmentation are needed for the peptides with high proline content. Our work reported herein focused on the analysis of the set of peptides derived by tryptic cleavage of the salivary protein PRP-3. Two methods of fragmentation were compared: Collision-induced dissociation (CID) and electron capture dissociation (ECD). The data obtained demonstrated that ECD spectra of peptides containing more than 30% proline residues are simpler and easier to interpret than are CID spectra of those peptides. Factors that limit the two methods of fragmentation include the complexity of information contained in the CID spectra and the low efficiency of ECD processes. A complementary approach using both decomposition methods provides more complete and interpretable sequence information and yielded >93% sequence coverage for the 11-kDa PRP-3 isolated from human saliva.

Compositional analysis of human acquired enamel pellicle by mass spectrometry

Relatively little is known about the formation of the acquired enamel pellicle other than that it involves the selective adsorption of specific proteins from oral fluids. Previous studies on the identification of pellicle components have relied largely on immunological or enzymatic detection and have been hampered by the fact that only minute quantities of pellicle can be removed from tooth surfaces. The present work describes an improved method of harvesting pellicle that combines mechanical and chemical removal; this approach was used to investigate systematically the desorption of in vitro pellicle components with different solutions. Eleven major in vitro pellicle proteins were identified by using a combination of electrophoretic separation and matrix-assisted laser desorption/ionization-reflectron time-of-flight mass spectrometry. A similar analysis of in vivo-formed pellicle revealed the presence of intact statherin, lysozyme, albumin and amylase. Further analysis of in vivo pellicle by liquid chromatography-electrospray ionization mass spectrometry suggested the presence of numerous low molecular-weight fragments of precursor proteins. The protein composition of in vitro whole-salivary pellicle adsorbed to hydroxyapatite and that of in vivo enamel pellicle differed for proline, the result of a reduction in the content of acidic proline-rich proteins in the in vivo samples. Unique features of the oral environment such as enzymatic activities or mineral surface properties may account for these differences between in vivo and in vitro pellicle formation.

Zinc and copper bind to unique sites of histatin 5

Metal binding has been suggested to be relevant in the antifungal and antibacterial mechanism of histatin 5, a human salivary protein. Proton nuclear magnetic resonance (NMR) spectra were obtained to investigate the specificity of metal binding to the seven histidyl, one aspartyl and one glutamyl amino acid side-chains of histatin 5 in aqueous solutions. Three C(epsilon1)-H histidyl and the C(gamma)-H glutamyl resonances of histatin 5 were selectively altered in spectra of solutions containing three equivalents of zinc. Copper binding to histatin 5 resulted in a reduced intensity of C(beta)-H aspartyl resonances, while no evidence for calcium binding was found. These results indicate that zinc binding to histatin 5 involves His-15 present within the -H-E-X-X-H- zinc binding motif, and copper binding occurs within the N-terminal D-S-H-, ATCUN motif.

Is salivary histatin 5 a metallopeptide?

Histatins are small histidine-rich salivary polypeptides which exhibit antimicrobial activity against Candida albicans. This antimicrobial activity has been ascribed in part to a high content of basic amino acids. However, unlike most other antimicrobial proteins histatins have a high content of histidine, tyrosine and acidic amino acids known to participate in metal ion coordination. This study was conducted to test whether histatin 5 could bind zinc and copper which are metals present in salivary secretions and whole saliva. Physical binding parameters and spectral properties of zinc- and copper-histatin complexes were investigated in order to obtain direct evidence of these interactions. A spectrophotometric competition assay using the metallochromic indicator murexide showed that histatin 5 dissociates metal indicator complexes containing zinc or copper ions. Absorption spectra of histatin 5 at increasing copper chloride concentrations resulted in higher absorbance in the 230-280 nm wavelength range and this spectral change was saturated at a peptide:metal molar ratio of approx. 1:1. A corresponding band was observed in the visible range of the spectrum with a maximum and molar extinction coefficient corresponding to that of copper binding to an ATCUN motif. Quantitative assessment of zinc and copper binding to histatin 5 using isothermal titration calorimetry revealed at least one high affinity site for each metal, with binding constants of 1.2x10(5) and 2.6x10(7) M(-1), respectively. These results indicate that histatin 5 exhibits metallopeptide-like properties. The precise biological significance of this has not yet been established but histatins may contribute significantly to salivary metal binding capacity.

Salivary histatin 5 is a potent competitive inhibitor of the cysteine proteinase clostripain

Histatin 5 is a low molecular weight salivary protein which is known to exhibit inhibitory activity against several proteinases, including the cysteine proteinases gingipains. The purpose of this study was to characterize the effect of salivary histatin on the proteolytic activity of the cysteine proteinase clostripain derived from the pathogen Clostridium histolyticum. Using a synthetic nitroanilide substrate, we studied in detail the inhibition of clostripain by histatin 5 and compared the effect of this peptide to that of leupeptin, a known competitive inhibitor of clostripain. It was found that the concentration of histatin 5 required to inhibit 50% of clostripain activity was 23.6+/-1.6 nM. Kinetic analysis revealed that histatin 5 is a competitive inhibitor of clostripain with an inhibition constant (K(i)) of 10 nM. The K(i) for the inhibition of clostripain activity against nitroanilide substrate by leupeptin was found to be 60 nM, significantly higher than that of histatin 5. Thus, histatin 5 inhibits clostripain more effectively than leupeptin and other cysteine protease inhibitors studied here. No significant proteolysis of histatin 5 was observed when histatin 5 was incubated at physiologic concentrations with clostripain. The potent inhibition of clostripain by histatin 5 points towards the possibility that this protein may prevent establishment of clostridial infections and therefore may have significant potential for the treatment of diseases associated with this enzyme.

Saliva and dental pellicle--a review

The acquired enamel pellicle is an organic film covering the surfaces of teeth. When this film was first discovered, it was thought to be of embryologic origin. Only in the middle of this century did it become clear that it was acquired after tooth eruption. Initially, the small amounts of material that could be obtained have virtually limited the investigation of pellicle proteins to amino acid analysis. Nevertheless, this technique revealed that the pellicle is mainly proteinaceous and is formed by selective adsorption of salivary proteins on tooth enamel. Later, immunologic techniques allowed for the identification of many salivary and fewer non-salivary proteins as constituents of pellicle. However, to this date, isolation and direct biochemical characterization of in vivo pellicle protein have not been possible, because only a few micrograms can be obtained from a single donor. Therefore, the composition and structure of the acquired enamel pellicle are still essentially unknown. Information on the functions of pellicle has been obtained mainly from in vitro experiments carried out with saliva-coated hydroxyapatite and enamel discs. It was found that pellicle protects enamel by reducing demineralization upon acid challenge. Improved pellicle harvesting procedures and analysis by state-of-the-art proteomics with mass spectroscopy approaches promise to make major inroads into the characterization of enamel pellicle.

Extended-spectrum beta-lactamase-producing Klebsiella pneumoniae in a Dublin paediatric hospital

Klebsiella pneumoniae resistant to third-generation cephalosporins and gentamicin was isolated from two patients in a paediatric intensive care unit within a two-week period. The double-disc diffusion test indicated the presence of an extended-spectrum beta-lactamase (ESBL). The unit was closed to admissions, and stringent infection control procedures were implemented. Environmental screening and screening of staff and patients on the unit were commenced. Two weeks later, K. pneumoniae with an identical antibiogram was isolated from the urine of a patient in a different ward. Blood-culture isolates possessed the K16 antigen, while the urine isolate was non-typeable. The isolates were shown to be similar when banding patterns of XbaI chromosomal DNA digests were compared. The resistance to the extended-spectrum cephalosporins was shown to be transferable in association with a large plasmid > 98 mDa. Resistance to gentamicin always co-transferred with beta-lactamase resistance and appeared to be encoded by the same plasmid.

Lumbar facet joint tropism does not accelerate degeneration of the facet joints

PURPOSE

To study the relationship of lumbar facet joint tropism to degeneration of the cartilage and subcortical bone in the facet joints and the effect of tropism in intervertebral disk degeneration.

METHODS

The orientation of 104 cadaveric lumbar facet joints with respect to sagittal plane was measured on CT scans, and the joints were classified as having no tropism, mild tropism, or severe tropism. On MR images, the severity of cartilage degeneration and bony sclerosis was measured. The correlation between tropism and degeneration was calculated, as was the relationship among age, spinal level, and degeneration.

RESULTS

We identified four spinal levels with severe tropism, six with moderate tropism, and 94 without tropism. Cartilage degeneration was not significantly more severe in the joints with tropism than in the joints without. Sclerosis was slightly greater in the joints with tropism than in the joints without it. Sclerosis and cartilage degeneration were significantly related to age and spinal level.

CONCLUSION

Age, spinal level, and overall facet joint angle are more important factors in facet joint degeneration than is tropism.

New Races of Phytophthora sojae with Rps1-d Virulence

Hypocotyl inoculations of differential soybean (Glycine max) cultivars were used to identify seven new physiologic races of Phytophthora sojae (syn. P. megasperma f. sp. glycinea). Five of the new races were virulent on soybeans with the Rps1-d allele, while four of the new races were virulent on soybeans with the Rps1-k allele. The Rps1-k and Rps1-d alleles provide resistance to a majority of the previously described races that cause Phytophthora root and stem rot. The seven new races were assigned race numbers 33, 34, 41, 42, 43, 44, and 45 since race numbers 35 through 40 were assigned to other new races recently identified in Ohio, California, Arkansas, and Iowa. The new races identified in this study constituted 14% of the 1993 isolates evaluated from 27 counties in central and northern Indiana. Races 1 and 3 were the most prevalent, representing 31 and 26% of the P. sojae isolates identified in 1993. Races 4, 6, 7, 8, 9, 13, 28, and 29 each constituted 2 to 6% of the 1993 isolates. Other races identified among the 1993 isolates included races 19, 21, 25, and 30.

Recognition of Schistosoma mansoni cathepsins B and L by human IgG1 and IgG4 antibodies

Human schistosome infections are chronic in nature and elevated IgG4 levels are associated with length of exposure. To examine how structure, localization and dynamics of exposure of a protein to the immune system can affect antibody isotype expression, specific antibody levels against two Schistosoma mansoni recombinant cathepsin molecules were determined in S. mansoni-infected individuals. Cathepsin B (rCatB, secreted in the gut) and cathepsin L (rCatL, localized in the reproductive structures) were used to determine IgG1 reactivity, as a measure of the stimulation of the immune response, and the switch to IgG4 as an indicator of the dynamics and rate of presentation to the immune system. Sera from three groups of S. mansoni-infected patients were used: individuals with life-long exposure in an endemic area in Burundi, a group from a recent endemic focus in Senegal, and of acutely infected European travellers. We report for the first time the ability of rCatL to trigger an immune response and show distinct antibody isotype reactivity between rCatB versus rCatL. Patients harbouring long-term chronic infections had elevated levels of IgG4 to both antigen, whereas individuals infected for less than four years had high IgG4 to rCatB but not to rCatL. Acutely infected travellers developed IgG1 to rCatB only. Our results demonstrate that an immune response is mounted more rapidly against a cathepsin molecule secreted in the gut of the worm than against an internally localized cathepsin.

Reactions of phenoxyl radicals with NADPH-cytochrome P-450 oxidoreductase and NADPH: reduction of the radicals and inhibition of the enzyme

Phenoxyl radicals are intermediates of one-electron oxidation of phenolic compounds by various peroxidases. This report describes reactions of phenoxyl radicals with human NADPH-cytochrome P-450 oxidoreductase (OR) and NADPH. Purified truncated OR catalyzed quenching of EPR signal of the phenoxyl radical of a vitamin E homolog, 2,2,5,7,8-pentamethyl-6-hydroxychromane. The quenching required both reductase and NADPH and was not supported by NADH. NADPH quenched directly the EPR signal of phenoxyl radical of a phenolic antitumor drug, etoposide, in the absence of the OR. Quenching of the EPR signal was accompanied by increased rate of NADPH oxidation and decreased rate of etoposide oxidation. Phenoxyl radicals of etoposide did not inactivate the OR. In the absence of NADPH, OR was inhibited irreversibly when exposed to phenoxyl radicals of phenol. The activity of the flavoprotein could not be recovered by dithiothreitol (DTT) but the inhibition was prevented by saturation of OR with NADP+ prior to the exposure to phenoxyl radicals. The OR was also inhibited by 5,5'-dithionitrobenzoic acid (DTNB). The inhibition was reversible by subsequent addition of DTT. OR pretreated with DTNB was protected from inhibition by phenoxyl radicals of phenol. The results indicate that phenoxyl radical of 2,2,5,7,8-pentamethyl-6-hydroxychromane is likely reduced enzymatically by transfer of electrons from NADPH via the FAD/FMN of the OR. Phenoxyl radicals with higher redox potential, e.g., phenoxyl radicals of etoposide, oxidize NADPH directly. Phenoxyl radicals of phenol can also inactivate OR likely by oxidation of cysteine 565 in the NADPH binding region of the enzyme.

Specificity of cDNA-expressed human and rodent cytochrome P450s in the oxidative metabolism of the potent carcinogen 7,12-dimethylbenz[a]anthracene

7,12-Dimethylbenz[a]anthracene (DMBA), a potent carcinogen, requires metabolic activation by cytochrome P450s (P450s) to electrophilic metabolites that result in DNA modification, mutagenicity, and carcinogenicity. In this study, we used eight human forms, four rodent forms, and one rabbit form of P450 expressed from recombinant vaccinia or baculovirus vectors to define their specificity for metabolizing DMBA. Of the eight human P450s, 1A1 was the most active (specific activity = 14.7 nmol/min/nmol of P450) in total metabolism of DMBA and showed approximately 6- to 33-fold more activity than other P450s, 2B6, 2C9, and 1A2 were also capable of metabolizing DMBA (2.0-2.5 nmol/min/nmol of P450), whereas 2C8, 2E1, 3A4, and 3A5 exhibited relatively low activities. Among animal P450s, mouse 1A1 exhibited activity similar to that of human 1A1 and had 5.0- to 37-fold more activity than other rodent and rabbit P450s. In regard to enzyme regioselectivity, most human and rodent P450s predominantly formed the 8,9-diol, but human 2B6 and rat 2B1 preferentially formed the 5,6-diol. In the production of monohydroxymethyl metabolites, all the enzymes yielded more 7-hydroxymethyl-12-methylbenz[a]anthracene (7HOM12MBA) than 12-hydroxymethyl-7-methylbenz[a]anthracene (7M12HOMBA), except for human 1A1, which presented the reverse selectivity. Human liver microsomes from 10 organ donors were shown to metabolize DMBA and in most circumstances generated the metabolic profile DMBA trans-8,9-dihydrodiol > 7HOM12MBA > or = DMBA trans-5,6-dihydrodiol > or = 7,12-dihydroxymethylbenz[a]anthracene > 7M12HOMBA > DMBA trans-3,4-dihydrodiol. Thus, the combined activity of hepatic microsomal 2C9, 1A2, and 2B6 may contribute to the metabolic activation and the metabolism of DMBA in normal human liver.

Inhibitory and noninhibitory monoclonal antibodies to human cytochrome P450 2E1

A panel of 17 hybridomas producing (MAbs) against human cytochrome P450 2E1 (h2E1) was generated by immunizing mice with baculovirus-expressed h2E1. All 17 hybridoma clones gave positive ELISA or immunoblots with either baculovirus-or vaccinia virus-expressed h2E1. Two of the latter were further developed due to their desirable characteristics. MAb 1-73-18 was found to be a powerful inhibitor of P450 h2E1; however, it did not yield a positive immunoblot. MAb 2-106-12 was found to be noninhibitory but formed a strong positive immunoblot with P450 h2E1. These MAbs to h2E1 were highly specific and did not recognize six other human P450s as tested with ELISA or immunoblot analyses. The MAbs to baculovirus-expressed h2E1 also reacted with h2E1 expressed from a vaccinia virus vector system as well as with microsomal fractions of human and acetone-treated rat liver. MAb 1-73-18 inhibited h2E1 enzyme activity catalyzing the metabolism of phenanthrene by 85%, p-nitroanisole by 90%, 4-methylanisole by 60-80%, toluene by 90%, and chlorzoxazone by 90%. The inhibitory MAb 1-73-18 is uniquely useful for determining the contribution of h2E1 to the metabolism of h2E1 substrates in human liver containing multiple P450s. The quantitatively determined contribution of h2E1 to the metabolism of the above substrates ranged from 25% to 75%. Thus, h2E1 was responsible for the following percentages of the total metabolism in human liver: p-nitroanisole (35%), phenanthrene (23%), methylanisole to cresol (25%), methylanisole to methoxybenzyl alcohol (12%), toluene (40%), and chlorzoxazone (72%). The MAb 2-106-12 forming a strong immunoblot is useful for determining the amount of h2E1 protein in a tissue. Thus the utility of the inhibitory and immunoblot positive MAbs is complementary and can determine both the contribution of h2E1 to the metabolism of specific substrates and the amount of h2E1 protein in human tissue. The analyses of metabolism with the inhibitory MAb 1-73-18 can be generalized and applicable to all h2E1 substrates.

Substrate probe for the mechanism of aromatic hydroxylation catalyzed by cytochrome P450

The effect of branch pathways on the observed intramolecular isotope effect and deuterium retention associated with 6- and 7-hydroxylation of selectively monodeuterated (R)- and (S)-warfarin with cytochrome P450 (CYP) 2C9 and CYP1A2 were studied. cDNA-expressed CYP2C9 was incubated with enantiomerically pure (S)-7d1- and (S)-6d1-warfarin, and expressed CYP1A2 was incubated with enantiomerically pure (R)-7d1- and (R)-6d1-warfarin. A high degree of deuterium retention was observed in all metabolites, independent of the stereochemistry of the substrate or CYP isoform. No deuterium kinetic isotope effect was observed for the formation of 6-hydroxy- or 7-hydroxywarfarin in the case of the (S)-6d1-warfarin metabolism by CYP2C9, or for the formation of 6-hydroxy-, 7-hydroxy-, and 8-hydroxywarfarin in the case of the (R)-6d1-warfarin metabolism by CYP1A2. Deuterium isotope effects of 1.17 and 1.23 accompanied formation of 7-hydroxywarfarin from (S)-7d1-warfarin by CYP2C9 and from (R)-7d1-warfarin by CYP1A2, respectively. These observations are consistent with the addition-rearrangement pathway for aromatic hydroxylation, in which a triplet-like active oxygen species initially adds to the pi system, resulting in a tetrahedral intermediate. The intermediate subsequently rearranges to generate the phenol, the final product of the reaction.

Cytochrome P450 2A1, 2E1, and 2C9 cDNA-expression by insect cells and partial purification using hydrophobic chromatography

High-level expression of three cloned cytochrome P450 enzymes was accomplished using the baculovirus-insect cell expression system. The amount of enzyme expression was enhanced by cell infections in the presence of medium-supplements containing hemin and by growth in suspension cultures. Human cytochromes P450 2E1 and 2C9 and rat cytochrome P450 2A1 were partially purified from cell extracts using hydrophobic interaction and hydroxyapatite chromatography. The resulting enzymes were of estimated molecular masses similar to those reported previously and analyzed by PAGE. Reconstitution of enzyme activity resulted when the enzymes were incubated together with NADPH-cytochrome P450 reductase, phospholipid, NADPH, and appropriate substrates. The cytochrome P450 activity of the partially purified enzymes was comparable to that of the corresponding enzymes expressed in the vaccinia virus-Hep G2 system. These results provide evidence for a general means of obtaining cytochrome P450 enzymes for mechanistic, immunochemical, and biophysical investigations.

Cefotaxime twice daily versus ceftriaxone once daily. A randomized controlled study in patients with serious infections

We randomized 365 patients with serious infections to treatment with either 2 g intravenously (IV) cefotaxime every 12 h or 2 g IV ceftriaxone once daily. Clinical response rates were similar in both treatment groups, with success defined as satisfactory or improved response in 107 of 124 (86.3%) evaluable patients in the cefotaxime group compared with 103 of 114 (90.4%) evaluable patients in the ceftriaxone group. Bacteriologic cure rates were also similar in the two groups (86.4%) in the cefotaxime group compared with 87.0% in the ceftriaxone group). There was no statistically significant difference in the incidence of drug-related adverse events in the two groups. These results indicate that 2 g cefotaxime twice daily is as effective, both clinically and bacteriologically, as 2 g ceftriaxone once daily in serious infections caused by susceptible pathogens.

Selective biotransformation of taxol to 6 alpha-hydroxytaxol by human cytochrome P450 2C8

The principal taxol biotransformation reaction of humans and of human hepatic in vitro preparations is 6 alpha-hydroxylation of the taxane ring, but a separate, minor hydroxylation pathway (metabolite B formation) also exists. Taxol metabolism was studied using membrane fractions from Hep G2 cells infected with recombinant vaccinia viruses that contain complementary DNAs encoding several human cytochrome P450 enzymes. Only P450 2C8 formed detectable 6 alpha-hydroxytaxol. Metabolite B formation was catalyzed by complementary DNA-expressed 3A3 and 3A4, but not by 3A5. Each P450 3A preparation catalyzed felodipine oxidation. The apparent Km and Vmax values for taxol 6 alpha-hydroxylation were 5.4 +/- 1.0 microM and 30 +/- 1.5 nmol/min/nmol P450, respectively, for complementary DNA-expressed P450 2C8; the values were 4.0 +/- 1.0 microM and 0.87 +/- 0.06 nmol/min/mg protein, respectively, for human hepatic microsomes. The inhibition of 6 alpha-hydroxytaxol formation by quercetin was competitive with an apparent Ki of 1.3 or 1.1 microM with 2C8 or hepatic microsomes, respectively; retinoic acid was inhibitory, showing an apparent Ki of 27 microM with hepatic microsomes; inhibition by tolbutamide was complex, weak, and unlikely to be clinically relevant. The correlation between hepatic 2C8 protein content and 6 alpha-hydroxytaxol formation was high (r2 = 0.82), while the correlation with 2C9 content was low (r2 = 0.38). These data show that human biotransformation routes of taxol result from catalysis by specific enzymes of two P450 families and that taxol 6 alpha-hydroxylation is a useful indicator of P450 2C8 activity in human hepatic microsomes.