Evaluation of Normothermic Machine Perfusion of Porcine Livers as a Novel Preclinical Model to Predict Biliary Clearance and Transporter-Mediated Drug-Drug Interactions Using Statins

There is a lack of translational preclinical models that can predict hepatic handling of drugs. In this study, we aimed to evaluate the applicability of normothermic machine perfusion (NMP) of porcine livers as a novel ex vivo model to predict hepatic clearance, biliary excretion, and plasma exposure of drugs. For this evaluation, we dosed atorvastatin, pitavastatin, and rosuvastatin as model drugs to porcine livers and studied the effect of common drug-drug interactions (DDIs) on these processes. After 120 minutes of perfusion, 0.104 mg atorvastatin (n = 3), 0.140 mg pitavastatin (n = 5), or 1.4 mg rosuvastatin (n = 4) was administered to the portal vein, which was followed 120 minutes later by a second bolus of the statin coadministered with OATP perpetrator drug rifampicin (67.7 mg). After the first dose, all statins were rapidly cleared from the circulation (hepatic extraction ratio > 0.7) and excreted into the bile. Presence of human-specific atorvastatin metabolites confirmed the metabolic capacity of porcine livers. The predicted biliary clearance of rosuvastatin was found to be closer to the observed biliary clearance. A rank order of the DDI between the various systems upon coadministration with rifampicin could be observed: atorvastatin (AUC ratio 7.2) > rosuvastatin (AUC ratio 3.1) > pitavastatin (AUC ratio 2.6), which is in good agreement with the clinical DDI data. The results from this study demonstrated the applicability of using NMP of porcine livers as a novel preclinical model to study OATP-mediated DDI and its effect on hepatic clearance, biliary excretion, and plasma profile of drugs. SIGNIFICANCE STATEMENT: This study evaluated the use of normothermic machine perfusion (NMP) of porcine livers as a novel preclinical model to study hepatic clearance, biliary excretion, plasma (metabolite) profile of statins, and OATP-mediated DDI. Results showed that NMP of porcine livers is a reliable model to study OATP-mediated DDI. Overall, the rank order of DDI severity indicated in these experiments is in good agreement with clinical data, indicating the potential importance of this new ex vivo model in early drug discovery.

Sulfasalazine in ionic liquid form with improved solubility and exposure

An ionic liquid form of sulfasalazine demonstrates improved solubility (4000×), bioavailability (2.5×), andin vivoexposure over the neutral drug.

Karyotype heterogeneity and unclassified chromosomal abnormalities

In a departure from traditional gene-centric thinking with regard to cytogenetics and cytogenomics, the recently introduced genome theory calls upon a re-focusing of our attention on karyotype analyses of disease conditions. Karyotype heterogeneity has been demonstrated to be directly involved in the somatic cell evolution process which is the basis of many common and complex diseases such as cancer. To correctly use karyotype heterogeneity and apply it to monitor system instability, we need to include many seemingly unimportant non-specific chromosomal aberrations into our analysis. Traditionally, cytogenetic analysis has been focused on identifying recurrent types of abnormalities, particularly those that have been linked to specific diseases. In this perspective, drawing on the new framework of 4D-genomics, we will briefly review the importance of studying karyotype heterogeneity. We have also listed a number of overlooked chromosomal aberrations including defective mitotic figures, chromosome fragmentation as well as genome chaos. Finally, we call for the systematic discovery/characterization and classification of karyotype abnormalities in human diseases, as karyotype heterogeneity is the common factor that is essential for somatic cell evolution.

The spatial distribution of leprosy cases during 15 years of a leprosy control program in Bangladesh: an observational study

BACKGROUND

An uneven spatial distribution of leprosy can be caused by the influence of geography on the distribution of risk factors over the area, or by population characteristics that are heterogeneously distributed over the area. We studied the distribution of leprosy cases detected by a control program to identify spatial and spatio-temporal patterns of occurrence and to search for environmental risk factors for leprosy.

METHODS

The houses of 11,060 leprosy cases registered in the control area during a 15-year period (1989-2003) were traced back, added to a geographic database (GIS), and plotted on digital maps. We looked for clusters of cases in space and time. Furthermore, relationships with the proximity to geographic features, such as town center, roads, rivers, and clinics, were studied.

RESULTS

Several spatio-temporal clusters were observed for voluntarily reported cases. The cases within and outside clusters did not differ in age at detection, percentage with multibacillary leprosy, or sex ratio. There was no indication of the spread from one point to other parts of the district, indicating a spatially stable endemic situation during the study period. The overall risk of leprosy in the district was not associated with roads, rivers, and leprosy clinics. The risk was highest within 1 kilometer of town centers and decreased with distance from town centers.

CONCLUSION

The association of a risk of leprosy with the proximity to towns indicates that rural towns may play an important role in the epidemiology of leprosy in this district. Further research on the role of towns, particularly in rural areas, is warranted.

Identification of human liver cytochrome P450 enzymes involved in the metabolism of SCH 351125, a CCR5 antagonist

The identification and relative contribution of human cytochrome P450 enzyme(s) involved in the metabolism of SCH 351125 were investigated. In human liver microsomes, O-deethylation was the major metabolic pathway, whereas aromatization of a piperidine ring to pyridine and the reduction of the N-oxide moiety were minor routes. Recombinant human CYP3A4 and CYP2C9 both exhibited catalytic activity with respect to the formation of rotameric O-deethylated metabolites (M12, M13), the metabolites resulting from aromatization (M22/M24) and N-oxide reduction (M31). Using the relative activity factor (RAF) approach, the relative contributions of CYP3A4 and CYP2C9 to M13 formation were estimated to be 76 and 24%, respectively. There was a high correlation (r>0.96) between the rate of formation of M12 and M13 and 6 beta-hydroxylation of testosterone catalysed by CYP3A4/5. Ketoconazole (2microM) and CYP3A4/5-specific inhibitory monoclonal antibody inhibited the formation of M12 and M13 from human liver microsomes by approximately 60 and 71%, respectively. The results demonstrate that the in vitro metabolism of SCH 351125 is mediated primarily via CYP3A4 and that CYP2C9 plays a minor role. Clinical study designs should encompass these enzymology data to address any potential drug interactions.

Disposition of loratadine in healthy volunteers

The absorption, metabolism and excretion of carbon-14-labeled loratadine (LOR, SCH 29851, Claritin) administered orally to healthy male volunteers were evaluated. Following a single oral 10-mg dose of [(14)C]LOR ( approximately 102 microCi), concentrations of LOR and desloratadine (DL; a pharmacologically active descarboethoxy metabolite of LOR) were determined in plasma. Metabolites in plasma, urine and feces were characterized using a liquid chromatography-mass spectrometry system (LC-MS) connected in line with a flow scintillation analyzer (FSA). Maximum plasma LOR and DL concentrations were achieved at 1.5 h and 1.6 h, respectively; thus, LOR was rapidly absorbed but also rapidly metabolized as indicated by these similar t(max) values. Metabolite profiles of plasma showed that LOR was extensively metabolized via descarboethoxylation, oxidation and glucuronidation. Major circulating metabolites included 3-hydroxy-desloratadine glucuonide (3-OH-DL-Glu), dihydroxy-DL-glucuronides, and several metabolites resulting from descarboethoxylation and oxidation of the piperidine ring. LOR was completely metabolized by 6 h post-dose. LOR-derived radiocarbon was excreted almost equally in the urine (41%) and feces (43%). About 13% of the dose was eliminated in the urine as 3-OH-DL-Glu. DL accounted for less than 2% of the dose recovered in the urine and only trace amounts of LOR were detected. 3-OH-DL was the major fecal metabolite ( approximately 17% of the dose). The combined amount of 5- and 6-hydroxy-DL contributed to an additional 10.7% of the dose in feces. Approximately 5.4% and 2.7% of the dose were excreted in the feces as unchanged drug and DL, respectively.

Disposition of desloratadine in healthy volunteers

The absorption, metabolism and excretion of desloratadine (DL, Clarinex) were characterized in six healthy male volunteers. Subjects received a single oral 10-mg dose of [(14)C]DL ( approximately 104 microCi). Blood, urine and feces were collected over 240 h. DL was well absorbed; drug-derived radioactivity was excreted in both urine (41%) and feces (47%). With the exception of a single subject, DL was extensively metabolized; the major biotransformation pathway consisted of hydroxylation at the 3 position of the pyridine ring and subsequent glucuronidation (3-OH-DL-glucuronide or M13). In five of the six subjects, DL was slowly eliminated (mean t((1/2)) = 19.5 h) and persisted in the plasma for 48-120 h post-dose. This is in contrast to a t((1/2)) of approximately 110 h and quantifiable plasma DL concentrations for the entire 240-h sampling period in one subject, who was identified phenotypically as a poor metabolizer of DL. This subject also exhibited correspondingly lower amounts of M13 in urine and 3-OH-DL (M40) in feces. Disposition of DL in this subject was characterized by slow absorption, slow metabolism and prolonged elimination. Further clinical studies confirmed the lack of safety issues associated with polymorphism of DL metabolism (Prenner et al. 2006, Expert Opinion on Drug Safety, 5: 211-223).

Congenital hearing impairment associated with rubella: lessons from Bangladesh

Infection with rubella virus during pregnancy may cause fetal death or the multiple congenital fetal abnormalities that are known as congenital rubella syndrome (CRS). Studies have demonstrated that congenital hearing impairment is the most frequent abnormality associated with intrauterine rubella infection. In the present study, the first of its kind in Bangladesh, we investigated the presence of rubella antibody in hearing-impaired children in order to understand the possible role of rubella infection in the development of hearing impairment. A total of 198 hearing-impaired children and 200 children without hearing problems were studied. After taking a detailed history from the parents, blood samples were collected from both mothers and children; sera were subjected to enzyme-linked immunosorbent assay (ELISA) for anti-rubella IgG. Rubella antibody was detected in 74% of the hearing-impaired children and in 18% of those with normal hearing: this finding correlated with the presence of rubella antibody in the mothers (67%) of rubella seropositive hearing-impaired children. In contrast, we observed rubella antibody in only 14% of the mothers of the children without hearing problems. Consistent with the presence of antibody, 41% of the seropositive mothers who had hearing-impaired children gave a history of fever and rash during early pregnancy. Our study indicates a strong association between rubella infection and hearing impairment in Bangladeshi children. In addition, it also indicates that infection by rubella virus is common in Bangladesh: this suggests that priority should be given to implementing appropriate measures for the control of rubella.

Intestinal nematode infection ameliorates experimental colitis in mice

Epidemiological studies suggest that inflammatory bowel disease (IBD) is common in developed countries and rare in countries where intestinal nematode infections are common. T cells are critical in many immune responses, including those associated with IBD and nematode infection. Among the distinct T helper (Th) cell subsets, Th1-type immune response is predominantly associated with Crohn's disease, while many nematode infections generate a strong Th2 response. The reciprocal cross regulation between Th1 and Th2 cells suggests that generation of a Th2 response by nematodes could prevent or reduce the effects of Th1-mediated diseases. In the present study, we investigated the effect of polarizing the immune response toward the Th2 type, using intestinal nematode infection, on subsequent experimental colitis. Mice were infected with the intestinal nematode Trichinella spiralis and allowed to recover before colitis was induced with dinitrobenzene sulfonic acid. The mice were sacrificed postcolitis to assess colonic damage macroscopically, histologically, and by myeloperoxidase (MPO) activity and Th cytokines. Prior nematode infection reduced the severity of colitis both macroscopically and histologically together with a decreased mortality and was correlated with a down-regulation of MPO activity, Th1-type cytokine expression in colonic tissue, and emergence of a Th2-type immune response. These results indicate a protective role of nematode infection in Th1 cell-driven inflammation and prompt consideration of a novel therapeutic strategy in IBD based on immunological distraction.

Fragmentation of N-oxides (deoxygenation) in atmospheric pressure ionization: investigation of the activation process

The diagnostic fragmentation of N-oxides resulting from loss of the oxygen atom (MH+ --> MH+-O) in electrospray and atmospheric pressure chemical ionization (APCI) mass spectra was investigated. When the temperature of the heated capillary tube was elevated, the ratio of the intensity of the [MH+ -16] fragment to the precursor ion (MH+) increased. This 'deoxygenation' process was associated with thermal activation and did not result from collisional activation in the desolvation region of the API source. Although the extent of 'deoxygenation' is compound-dependent, it can provide evidence for the presence of an N-oxide in a sample and can be used to distinguish N-oxides from hydroxylated metabolites (Ramanathan et al. Anal. Chem. 2000; 72: 1352). To demonstrate the practical application of thermal fragmentation of N-oxides, liquid chromatography (LC)/APCI-MS was used to distinguish an N-oxide drug from its hydroxylated metabolite in an unprocessed rat urine sample, despite the fact that the drug and its metabolite were not fully resolved by HPLC.

Activities of mitochondrial oxidative phosphorylation enzymes in cultured amniocytes

Amniocytes represent a population of foetal cells that can be used for prenatal diagnosis in families with suspected mitochondrial oxidative phosphorylation (OXPHOS) defects. In this paper, we present a complex protocol for evaluation of the function of mitochondrial OXPHOS enzymes in cultured amniocytes using three independent and complementary methods: (a) spectrophotometry as a tool for determination of the capacities of mitochondrial respiratory-chain enzymes (NADH ubiquinone oxidoreductase, succinate- and glycerophosphate cytochrome c reductase, cytochrome c oxidase and citrate synthase); (b) polarography as a tool for the evaluation of mitochondrial OXPHOS enzyme functions in situ using digitonin-permeabilised amniocytes (rotenone-sensitive oxidation of pyruvate+malate, antimycin A-sensitive oxidation of succinate, KCN-sensitive oxidation of cytochrome c, ADP-activated substrate oxidation) and (c) cytofluorometric determination of tetramethyl rhodamine methyl ester (TMRM) fluorescence in digitonin-permeabilised amniocytes as a sensitive way to determine the mitochondrial membrane potential under steady-state conditions (state 4 with succinate). These protocols are presented together with reference control values using 9-22 independent cultures of amniocytes.

Negative fast atom bombardment ionization of aromatic sulfonic acids: unusual sample-matrix interaction

The most intense ion(s) in negative ion fast atom bombardment (FAB) mass spectra of 2- and 4-benzaldehyde sulfonic acid (BSA) in glycerol or 3-nitrobenzyl alcohol matrix corresponds to a covalent association of the analyte with one or two matrix molecules accompanied by the elimination of a molecule of water. The molecular ion [M - H](-), however, is of low abundance. The identity of the resulting ions [M + nA - H(2)O - H](-) (where M is the analyte and A is the matrix) was confirmed by exact mass measurement using the peak matching technique. These covalent matrix-analyte complexes were not observed when the sulfonic acid functionality in BSA was substituted with COOH, NO(2), and OH or when the sulfonic acid was in salt form. These observations indicate that the free sulfonic acid group in BSA is responsible for the covalent adduct formation. To our knowledge, analyte-matrix covalent association in negative ion FAB spectra of BSA has not been reported previously.

A novel deficiency of mitochondrial ATPase of nuclear origin

We report a new type of fatal mitochondrial disorder caused by selective deficiency of mitochondrial ATP synthase (ATPase). A hypotrophic newborn from a consanguineous marriage presented severe lactic acidosis, cardiomegaly and hepatomegaly and died from heart failure after 2 days. The activity of oligomycin-sensitive ATPase was only 31-34% of the control, both in muscle and heart, but the activities of cytochrome c oxidase, citrate synthase and pyruvate dehydrogenase were normal. Electrophoretic and western blot analysis revealed selective reduction of ATPase complex but normal levels of the respiratory chain complexes I, III and IV. The same selective deficiency of ATPase was found in cultured skin fibroblasts which showed similar decreases in ATPase content, ATPase hydrolytic activity and level of substrate-dependent ATP synthesis (20-25, 18 and 29-33% of the control, respectively). Pulse-chase labelling of patient fibroblasts revealed low incorporation of [(35)S]methionine into assembled ATPase complexes, but increased incorporation into immunoprecipitated ATPase subunit beta, which had a very short half-life. In contrast, no difference was found in the size and subunit composition of the assembled and newly produced ATPase complex. Transmitochondrial cybrids prepared from enucleated fibroblasts of the patient and rho degrees cells derived from 143B. TK(-)human osteosarcoma cells fully restored the ATPase activity, ATP synthesis and ATPase content, when compared with control cybrids. Likewise, the pattern of [(35)S]methionine labelling of ATPase was found to be normal in patient cybrids. We conclude that the generalized deficiency of mitochondrial ATPase described is of nuclear origin and is caused by altered biosynthesis of the enzyme.

Immunosuppression in hamsters with progressive visceral leishmaniasis: an evaluation of the role of nitric oxide toward impairment of the lymphoproliferative response

The progressive visceral infection caused in golden hamsters by Leishmania donovani amastigotes led to gradual impairment of the proliferative response of their splenic (SPMC) or peripheral blood (PBMC) mononuclear cells to in vitro stimulation with leishmanial antigen, with mitogen (concanavalin A), and even with a combination of phorbol myristate acetate (PMA) and ionomycin (Io). Removal of macrophage-like adherent cells from SPMC or PBMC of infected animals, however, almost completely restored their proliferative response to PMA + Io, thus ruling out the possibility of any intrinsic defect in the signal-transduction pathways of lymphocyte activation and proliferation. Subsequent studies demonstrated that the generation of soluble mediators such as nitric oxide by these adherent cells is responsible, albeit partially, for the down-regulation of the lymphoproliferative response in hamsters with visceral leishmaniasis.

An LC/MS/MS method for the quantitation of MTIC (5-(3-N-methyltriazen-1-yl)-imidazole-4-carboxamide), a bioconversion product of temozolomide, in rat and dog plasma

A sensitive and selective HPLC/electrospray ionization tandem mass spectrometric (LC/ESI/MS/MS) method for the quantitative determination of MTIC (5-(3-N-methyltriazen-1-yl)-imidazole-4-carboxamide), a pharmacologically active hydrolysis product of temozolomide, was developed and validated over a linear range from 10 to 400 ng ml(-1) in dog plasma and from 10 to 500 ng ml(-1) in rat plasma. This HPLC method utilized small plasma volumes (70 microl), rapid sample processing, and isocratic elusion conditions to achieve sensitive and selective MS/MS detection. Samples were processed and analyzed one at a time every 4.5 min in order to compensate for the inherent instability of MTIC. Both MTIC and the internal standard DTIC [5-(3,3'-N,N'-dimethyltriazen-1-yl)-imidazole-4-carboxamide] were quantitated in the positive ion, selected reaction monitoring (SRM) mode. The lower limit of quantitation (LLOQ) was 10 ng ml(-1) in the plasma from both species. Inter-assay accuracy and precision of all calibration standards and quality control (QC) samples were within +/- 11 and 12%, respectively, with the exception of the LLOQ in rat plasma (17%). The validated method was used to determine the time dependent plasma concentration of MTIC in rats and dogs following a single oral dose of temozolomide. The standard curve and the quality control data indicate that the method performed acceptably throughout the sample analysis period.

Identification of new autolytic sites of recombinant truncated mature human fibroblast stromelysin by mass spectrometry

Stromelysin has been proposed to play a major role in the pathologic degradation of diseased cartilage of osteoarthritis and rheumatoid arthritis patients. A truncated, recombinant form of this enzyme, with the sequence Phe83 to Thr260 (mSL-t), has been expressed and purified from E. coli to investigate its biochemical and biophysical properties, and to develop inhibitors for arthritis treatment. LC/ESI-MS technique was utilized for the characterization of mSL-t. The mass spectra of mSL-t showed the presence of a number of different protein components in addition to the full-length mSL-t form. We have demonstrated that protein degradation arose from autolysis. Molecular weights determined by LC/ESI-MS of these autolysis products allowed for the identification of new autolytic sites in mSL-t. Furthermore, two strategies were undertaken to prepare mSL-t free of degradation products. These include preparation of a mutant form of the enzyme in which Arg163 was substituted for Leu163 and purification of mSL-t using affinity chromatography. The LC/ESI-MS data of the mutant protein confirmed the Leu to Arg mutation. The affinity-purified material showed only one LC peak in the LC/MS chromatograms, and the mass spectrum of the peak identified only the intact protein, demonstrating that the full-length protein has been successfully separated from the autodegradation products and further autolysis of the enzyme has been prevented.

Fingerprinting proteins coupled with polymers by mass spectrometry: Investigation of polyethylene glycol-conjugated superoxide dismutase

Matrix-assisted laser desorption-ionization (MALDI) mass spectrometry was investigated as a method for the rapid determination of the extent of polymer coupling in polyethylene glycol- (PEG) conjugated superoxide dismutase (SOD). PEG-conjugated SOD, an antioxidant with an extended in vivo circulation lifetime compared to that of superoxide dismutase, is being evaluated as an effective therapeutic agent for the treatment of injuries and arthritis. The mass spectra of a standard batch of PEG-conjugated bovine SOD showed the presence of identifiable and well resolved peaks that correspond to 0-7 PEG molecules attached to bovine SOD. The area of each of the peaks provides a determination of the amount of PEG-conjugated SOD with a given number of bound PEG groups. SOD is a noncovalent dimer of two identical subunits that dissociates in MALDI. The information obtained in the mass spectra thus corresponds to a monomer of SOD. Each SOD monomer contains 10 lysines, which are the sites of PEG-conjugation. Multiple MALDI determinations of two batches of samples indicated good reproducibility for routine determination of the extent of polymer content. The amount of PEG-conjugated SOD that contained a given number of PEG molecules, determined by MALDI, was compared with the value deduced from the amount of PEG-conjugation at each attachment site measured by a peptide mapping method. Agreement between the data obtained in the two techniques (MALDI and peptide mapping) indicates that MALDI may be used to obtain quantitative information on PEG-conjugated SOD to determine the amounts of PEG-conjugated protein each with a different number of PEG groups attached. Measurement of several batches of samples stored at a higher temperature showed a lower extent of PEG-conjugation in PEG-conjugated SOD. This reduction in the PEG content resulted from the PEG-deconjugation of PEG-conjugated SOD at a higher temperature. Thus, MALDI can be used to examine the stability of PEG-conjugated SOD. The high sensitivity, relatively straightforward data interpretation, speed of analyses, and good reproducibility in measurements make this technique a useful analytical tool for fingerprinting PEG-conjugated SOD as well as potentially other polymer-conjugated proteins.

Production of selenomethionine-labeled recombinant human neutrophil collagenase in Escherichia coli

Molecular analogs of amino acids can be incorporated into proteins. The amino acid analog selenomethionine (SeMet) has been shown to be efficiently incorporated into the proteins of growing Escherichia coli. SeMet-containing proteins are known to produce sufficiently strong anomalous scatter permitting the solution of the selenomethionyl crystal structure by multiwavelength anomalous diffraction (MAD) techniques. The recombinant protein chosen for these studies is mature, truncated neutrophil collagenase (rmNC-t). The rmNC-t protein is a monomer of 163 amino acid residues featuring one active site and two Met residues. We developed a T7 polymerase expression system allowing incorporation of SeMet into rmNC-t protein produced in E. coli. Substitution of Met with SeMet was accomplished by culturing E. coli DL41(DE3), a SeMet-tolerant strain with metA lesion, in a defined medium containing SeMet as the sole source of Met. The SeMet-labeled rmNC-t was isolated from inclusion bodies by solubilizing in urea, purified by anion column chromatography, and then refolded in the presence of Ca2+ and Zn2+. Analysis of SeMet-labeled rmNC-t demonstrated that Met replacement was 100%. Enzymatic characterization revealed no obvious differences in activity or inhibitor binding between rmNC-t and the SeMet-labeled product. We have produced pure, active SeMet-labeled rmNC-t in sufficient quantities for macromolecular crystallography studies.

Mass spectrometric identification of amino acid transformations during oxidation of peptides and proteins: modifications of methionine and tyrosine

Liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS), tandem mass spectrometry with on-line liquid chromatography (LC/ESI-MS/MS) and high-resolution mass spectrometry with liquid secondary ionization (LSI-MS) were utilized to identify the modified amino acids in peptides and proteins formed during oxidation with performic acid. The procedure of protein oxidation was chosen to assist in protein unfolding by oxidizing the cystines to cysteic acids to allow for more complete proteolytic digestion and to create additional cleavage sites for endoproteinase Asp-N. Investigation of the Asp-N peptide map of oxidized superoxide dismutase (SOD) by LC/ESI-MS revealed that an expected proteolytic fragment of the protein was missing. In its place, two peptides with molecular weights 66 and 100 higher than that calculated for the missing peptide were observed. To identify the modified amino acids in the unexpected peptides, a model peptide with some amino acid similarities (tyrosine, arginine, methionine, lysine) to the missing peptide was chosen and was subjected to similar oxidation and enzymatic digestion steps, conditions, and reactions. After oxidation and digestion, the model peptide (TAP; sequence, Ac-MDKVLNRY) showed three major peaks in LC/MS. The peptides in the three peaks were identified as the unmodified peptide and two peptides whose molecular weights were 66 and 100 higher than that of TAP.(ABSTRACT TRUNCATED AT 250 WORDS)

Examination of recombinant truncated mature human fibroblast collagenase by mass spectrometry: identification of differences with the published sequence and determination of stable isotope incorporation

Human fibroblast collagenase belongs to a family of matrix metalloproteinases which have been implicated in a number of connective tissue disorders ranging from rheumatoid arthritis to tumor invasion. To examine the active site of this enzyme by biophysical studies, a 19 kDa recombinant truncated mature collagenase (mCL-t) was prepared. Electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry have been utilized for the characterization of mCL-t. The molecular weights measured by these techniques identified the presence of two closely related protein components separated by approximately 100 Da. Edman sequence analysis demonstrated that the two protein components differ from each other by an amino terminal valine, consistent with the mass spectrometric data. In addition, the molecular weight of mCL-t determined by mass spectrometry did not agree with that calculated from the reported sequence. To identify the origin of this discrepancy, the DNA sequence of the mCL-t clone was examined. Several differences were noted between the DNA sequence of mCL-t and the published collagenase gene sequence. When these differences were taken into account, the measured molecular weights were found to be in good agreement with that calculated for the modified sequence. In separate experiments, both ESI and MALDI mass spectrometry have been used to determine molecular weights of mCL-t samples enriched with stable isotopes 15N and (15N + 13C). The measured molecular weights demonstrated a 97% (15N) and 99% (15N + 13C) incorporation of labeled isotopes in the two samples.

Mass closure versus layer closure of abdominal wound: a prospective clinical study

The results of a controlled clinical trial of two currently recommended methods of abdominal closure have been reported here. OUt of 160 patients, 80 cases were randomised to have their abdominal wall closed in single layer mass closure with monofilament nylon and 80 cases in layer closure with chromic catgut. Eighteen patients (22.5%) in the former and 38 (47.5%) in the latter had wound infection (p < 0.001). Sinus formation occurred in 2 patients (2.5%) in the mass and 20 (25%) in the layered group (p < 0.001). Three cases (3.75%) of burst abdomen occurred in layer closure and none in mass closure. Wound infection was the most important denominator next to suture material influencing wound healing. There was a significant association between the rate of infection and sinus formation. Minimal complication and good patient compliance seem to justify the use of mass closure in place of layer closure in all types of abdominal operations.

Primary structure of Euplotes raikovi pheromones: comparison of five sequences of pheromones from cells with variable mating interactions

The amino acid sequences of five pheromones, Er-2, Er-3, Er-9, Er-11, and Er-20, secreted by cells of different mating types of the ciliated protozoa Euplotes raikovi, have been determined by automated Edman analyses of the whole proteins and germane fragments. In each case, the molecular mass was determined by plasma desorption or laser desorption mass spectrometry and was in excellent agreement with the calculated values. Where available, the determined sequences were also in accord with the corresponding segments of the precursor molecules predicted from relevant nucleic acid sequences. Of the five, two were found to be identical (Er-2 and Er-9) and one (Er-3) was identical to a pheromone previously sequenced (Er-1), even though mating pair formation was found to take place (although to a limited extent) when cells secreting those pheromones were combined in a mixture. Comparison of the five unique sequences suggested a closer relationship between Er-1 (Er-3) and Er-10 and between Er-11 and Er-20 (44% and 56% identity, respectively) than was generally observed among the other members. This pairing was also supported by hydrophobicity analyses. Interestingly, Er-20 cannot, as a rule, induce cell union in any of the other cell types, including cells secreting Er-11, despite the fact that Er-20 and Er-11 are the most similar of the five unique sequences. Thus sequence identity and secondary structure profiles are not a good indicator of biological relatedness as manifested in heterologous receptor interaction.

Use of a single-quadrupole mass spectrometer for collision-induced dissociation studies of multiply charged peptide ions produced by electrospray ionization

The feasibility of obtaining the collision-induced dissociation (CID) spectra of multiply charged peptide ions produced by electrospray ionization in a simple and inexpensive single-quadrupole mass spectrometer is demonstrated. Collisional activation was carried out in the high-pressure region between the capillary exit and the skimmer entrance to the mass analyzer. The CID of multiply charged peptide ions is very efficient, and the observed fragment ion intensities are typically 1-5% of the parent ion intensity prior to CID. About 70 pmol of the peptide is consumed in obtaining each CID spectrum. Spectra obtained by CID of multiply charged ions from bradykinin, angiotensin II, two peptides with features similar to tryptic peptides, and a synthetic analogue of a component of TGF-alpha containing two disulfide bonds are shown. The influence of the primary structure of the peptide on the observed fragmentation pathways is discussed. Although the present single-quadrupole configuration is simple and effective, the inability to choose a particular parent ion for collisional activation makes it less powerful than the triple-quadrupole configuration for mixtures of peptides and peptide samples that yield more than one charge state in the normal mass spectrum. However, it has the potential for inexpensively obtaining sequence information of proteins at high sensitivity by analyzing the pure tryptic peptides obtained by on-line or off-line chromatographic separation of tryptic digests.

Analysis of mixtures of closely related forms of bovine trypsin by electrospray ionization mass spectrometry: use of charge state distributions to resolve ions of the different forms

Electrospray ionization mass spectrometry has been utilized for the analysis of bovine trypsin. Commercial active bovine trypsin is comprised of a mixture of three closely related different forms: beta-, alpha-, and psi-trypsin with similar molecular masses (23293, 23311, and 23329 mass units respectively). Peak broadening caused by the natural isotopic abundance of atoms in the protein molecules results in overlap of the ion peaks from the different trypsin forms. Therefore, accurate determination of the molecular masses of these trypsins in a mixture is not straightforward. However, because the trypsin isoforms have different number of basic groups and different higher order structures, the different forms acquire different numbers of charges. Therefore, ions from the different trypsins appear in different parts of the mass spectrum allowing accurate determination of their molecular masses.

Origin and removal of adducts (molecular mass = 98 u) attached to peptide and protein ions in electrospray ionization mass spectra

Electrospray ionization of peptides and proteins often produces intense adduct ions resulting from the attachment of a moeity with mass 98 u. The formation of these adduct ions results in a substantial reduction in the mass spectrometric sensitivity and an undesirable increase in the complexity of the mass spectra. In the present study it was shown that the removal of the attached adducts from peptide and protein ions can be affected by collisional activation and that the adducts arise from the attachment of sulfuric acid or phosphoric acid to peptide and protein ions. When sulfate and phosphate ions are removed from the samples by chemical means, adduct free ions are obtained from proteins yielding spectra with improved quality and sensitivity.

Electrospray ionization mass spectrometric peptide mapping: a rapid, sensitive technique for protein structure analysis

Electrospray ionization mass spectrometric peptide mapping is demonstrated to be a useful new technique for protein structure analysis. The procedure involves the digestion of the protein with trypsin and subsequent analysis of the total unfractionated digest by electrospray ionization mass spectrometry. The utility of the technique for investigating protein structure is illustrated by a peptide mapping analysis of human apolipoprotein AI (Mr = 28 kDa). The technique is rapid, sensitive, and requires no prior separation of the peptides. The discrimination effects observed in other mass spectrometric methods are less important in the present procedure.

A mass spectrometric technique for detecting and identifying by-products in the synthesis of peptides

The utility of a new mass spectrometric technique for detecting and identifying peptide by-products produced in the synthesis of peptides is demonstrated. The technique involves three sequential steps: (1) practically nondestructive 252Cf plasma desorption mass spectrometric analysis of monolayer amounts of the peptide(s) of interest bound to a thin layer of nitrocellulose; (2) enzyme-catalyzed microscale chemical reaction of the surface-bound peptide(s) to produce structurally informative hydrolysis products; (3) plasma desorption mass spectrometric analysis of these hydrolysis products. The first step determines the presence and the molecular weights of unwanted by-products resulting from errors or incomplete reactions during synthesis. The subsequent two steps provide information on the precise location in the peptides where errors have occurred. In the present paper, the technique is applied to an investigation of unwanted peptide by-products associated with the use of tryptophan during stepwise solid-phase peptide synthesis. Synthetic preparations of melittin and [Bpa-8]dynorphin A (1-17) were each found to contain a major impurity with molecular weight 28 Da higher than that of the desired product. The impurity in the melittin preparation, in which the final deprotection step involved the high-low HF procedure, was shown to result from incomplete removal of the formyl group from Trp-19. On the other hand, the impurity in the [Bpa-8]dynorphin A (1-17) preparation, where the removal of the formyl group from Trp-14 was carried out using piperidine, was shown to result from migration of the formyl group to Lys-11 or Lys-13.(ABSTRACT TRUNCATED AT 250 WORDS)

Frequency analysis of adventitious lung sounds

Adventitious lung sounds from twenty patients with respiratory diseases have been recorded and analysed by analogue methods. The results obtained are compared with those from five normal subjects. The difference in the frequency components of lung sounds from patients with pulmonary obstruction in the airways and those from normal subjects are pointed out. This technique may well prove to be an objective method of diagnosis in pulmonary medicine.

Interrelationship of tryptophan pyrrolase with tyrosinase in melanogenesis of Bufo melanostictus

Tryptophan pyrrolase, a microsomal enzyme responsible for the break-down of tryptophan, has been detected in Bufo melanostictus. The enzyme has been found to be deactivated under influence of antivitiligo drug psoralene and activated by hydroquinone, an inhibitor of tyrosinase. Tryptophan pyrrolase has been found to have an antagonistic relationship with tyrosinase in Bufo melanostictus. The implication of the results has been discussed in relation to melanogenesis in vitiligo.