Multidisciplinary shock team is associated with improved outcomes in patients undergoing ECPR

OBJECTIVES

Veno-arterial extracorporeal membrane oxygenation (VA ECMO) has been increasingly used in cardiopulmonary resuscitation (ECPR) in select patients. Few centers have published their experience or outcomes with ECPR. The aim of our study was to evaluate outcomes of adult patients in cardiac arrest placed on VA ECMO in the catheterization laboratory.

METHODS

We performed a retrospective analysis of adult patients in refractory cardiac arrest who underwent ECPR at the Minneapolis Heart Institute (MHI) at Abbott Northwestern Hospital from January 2012 to December 2017. Relevant data were obtained from electronic medical records, including arrest to ECMO flow time, total ECMO support time, and outcomes.

RESULTS

Twenty-six adult patients underwent ECPR at the study site during the defined time period. Seven patients (27%) sustained cardiac arrest out of hospital, 19 patients arrested in-hospital with eight of those occurring in the catheterization laboratory. Seventeen (65%) patients had initial rhythm of ventricular fibrillation or tachycardia (VF/VT). All patients underwent mechanical CPR with LUCAS device. Overall 30 day and 6 month survival was 69%. Median time from arrest to ECMO flow was 46 mins (21,68) vs 61 mins (36,71) in survivors and non-survivors, respectively. Sixteen of 18 survivors discharged with a CPC score of 1 or 2.

CONCLUSIONS

We demonstrate that adult patients in cardiac arrest initiated on VA ECMO in the cardiac catheterization laboratory and cared for by a multidisciplinary shock team in the critical care unit have superior long-term survival and functionally favorable neurologic recovery when compared to current literature.

Clinical outcomes associated with sedation and analgesia in patients supported with venoarterial extracorporeal membrane oxygenation

Sedatives and analgesics are frequently used in critically ill adult patients requiring mechanical ventilation in the intensive care unit, but optimal agent selection and dosing in patients supported with venoarterial extracorporeal membrane oxygenation remain poorly defined. This retrospective study evaluated whether sedative and analgesic agent selection and dosing had any impact on clinical outcomes after venoarterial extracorporeal membrane oxygenation decannulation. The primary endpoint of our study was the incidence of delirium within 48 h after venoarterial extracorporeal membrane oxygenation decannulation in patients who received an empiric ⩾50% sedation reduction of benzodiazepines (N = 22, group 2) compared to those who did not (N = 10, group 1) and those who required no sedatives within 24 h prior to venoarterial extracorporeal membrane oxygenation decannulation (N = 21, group 3). Secondary endpoints included time to extubation after decannulation, need for tracheostomy after decannulation, intensive care unit length of stay after decannulation, total hospital length of stay, and in-hospital mortality. Delirium within 48 h after decannulation was observed in 47% of all patients and did not differ between the three groups (50% vs 50% vs 43%, p = 0.9). No differences were observed in the secondary endpoints; though there was a trend toward shorter duration of mechanical ventilation and intensive care unit length of stay in patients who received an empiric ⩾50% sedation reduction. Our study suggests that we may need more than a 50% reduction in sedation but prospective studies with a larger sample size are warranted to evaluate how sedative/analgesic selection and dosing affect important clinical outcomes.

Isolation of sterol mutants inChlamydomonas reinhardi: Chromatographic analyses

Several sterol mutants ofChlamydomonas reinhardi were isolated by selecting for single colonies resistant to the polyene antibiotic, nystatin. The sterol profiles of three isolates-KD7, KD16, and KD21-as well as a wild type strain (137C) were determined by gas liquid chromatography and mass spectrometry. The wild type strain contained ergosterol (C28-5,7,22-triene) as the predominant sterol, with smaller amounts of a C28-5,7-diene, a C28-7-ene, and C-24 ethyl analogs of these three sterols. The three mutants had altered sterol composition, but none required exogenous sterol for growth. KD7 contained a C28-5,7,22,25-tetraene, a C28-5,7,25-triene, a C28-7,25-diene, and three C-24 ethyl analogs. The lesion in KD7 is apparently an inability to reduce the C-25 double bond required for the biosynthesis of ergosterol and an ethyl analog. The predominant sterols accumulated by KD16 and KD21 were a C28-5,7-diene, a C28-7-ene, and C-24 ethyl versions of these two sterols, suggesting that these strains are 22(23)-desaturase mutants.

Diversity of Rhizobia Nodulating Phaseolus vulgaris L. in Two Kenyan Soils with Contrasting pHs

Rhizobia were isolated from two Kenyan soils with pHs of 4.5 and 6.8 and characterized on the basis of their host ranges for nodulation and nitrogen fixation, colony morphologies, restriction fragment fingerprints, and hybridization with a nifH probe. The populations of rhizobia nodulating Phaseolus vulgaris in the two soils were similar in numbers and in effectiveness of N(inf2) fixation but were markedly different in composition. The population in the Naivasha soil (pH 6.8) was dominated by isolates specific in host range for nodulation to P. vulgaris; these all had multiple copies, in most cases four, of the structural nitrogenase gene nifH. Only one of the isolates from this soil formed effective nodules on Leucaena leucocephala, and this isolate had only a single copy of nifH. By contrast, the population in the acid Daka-ini soil (pH 4.5) was composed largely of broad-host-range isolates which had single copies of nifH. The isolates from the Daka-ini soil which were specific to P. vulgaris generally had three copies of nifH, although one isolate had only two copies. These rhizobial isolates are indigenous to Kenyan soils and yet have marked similarities to previously described Rhizobium species from other continents.

Development of polymorphic expressed sequence tag-derived microsatellites for the extension of the genetic linkage map of the black tiger shrimp (Penaeus monodon)

In this study, microsatellite markers were developed for the genetic linkage mapping and breeding program of the black tiger shrimp Penaeus monodon. A total of 997 unique microsatellite-containing expressed sequence tags (ESTs) were identified from 10 100 EST sequences in the P. monodon EST database. AT-rich microsatellite types were predominant in the EST sequences. Homology searching by the blastn and blastx programs revealed that these 997 ESTs represented 8.6% known gene products, 27.8% hypothetical proteins and 63.6% unknown gene products. Characterization of 50 markers on a panel of 35-48 unrelated shrimp indicated an average number of alleles of 12.6 and an average polymorphic information content of 0.723. These EST microsatellite markers along with 208 other markers (185 amplified fragment length polymorphisms, one exon-primed intron-crossing, six single strand conformation polymorphisms, one single nucleotide polymorphism, 13 non-EST-associated microsatellites and two EST-associated microsatellites) were analysed across the international P. monodon mapping family. A total of 144 new markers were added to the P. monodon maps, including 36 of the microsatellite-containing ESTs. The current P. monodon male and female linkage maps have 47 and 36 linkage groups respectively with coverage across half the P. monodon genome.

Predictors for non-adherence to antiretroviral therapy

Objectives: To determine the risk factors for non-adherence to antiretroviral therapy. Methods: Two hundred clients attending the Melbourne Sexual Health Centre completed a questionnaire about lifestyle, self-efficacy, depression, drug or alcohol use, social supports, and attitudes to health care. Self-reported adherence (SRA) was measured by missed doses in the last 4, 7 and 28 days. Routinely collected viral load levels were reviewed. Results: Two hundred (85%) out of 231 eligible clients participated in the study. Viral load was most strongly associated with SRA for the last 28 days (P < 0.001). Non-adherence was defined as <98.2% SRA. Non-adherence was most strongly associated with having regular daily routines [odds ratio and 95% confidence interval = 0.4 (0.2, 0.7], having set times for getting up and going to bed [0.5 (0.3, 1.0)], using marijuana more than 4 times per week [0.4 (0.2, 1.0)] and lower self-efficacy which included; being sure that you will be able to take medications as directed [0.2 (0.1, 0.6)] and being sure that missing doses of HIV medication will result in drug resistance [0.4 (0.2, 0.7)]. When significant questions were combined into a composite score to screen for non-adherence, the sensitivity to predict non-adherence was as high as 71% with a specificity of 59%. Conclusions : This study showed that a 10-min questionnaire was associated with clients past non-adherence to antiretroviral therapy and may be useful for predicting future adherence.

Structure-Based design, synthesis and sAR of a novel series of thiopheneamidine urokinase plasminogen activator inhibitors

The serine protease urokinase plasminogen activator (uPA) is thought to play a central role in tumor metastasis and angiogenesis. Molecular modeling studies suggest that 5-thiomethylthiopheneamidine inhibits uPA by binding at the S1 pocket of the active site. Further structure based elaboration of this residue resulted in a novel class of potent and selective inhibitors of uPA.

Synthesis of thiophene-2-carboxamidines containing 2-aminothiazoles and their biological evaluation as urokinase inhibitors

The serine protease urokinase (uPa) has been implicated in the progression of both breast and prostate cancer. Utilizing structure based design, the synthesis of a series of substituted 4-[2-amino-1,3-thiazolyl]-thiophene-2-carboxamidines is described. Further optimization of this series by substitution of the terminal amine yielded urokinase inhibitors with excellent activities.

Research and development to improve naval shipboard waste management using a compact closed-loop-controlled waste incinerator

Research has been conducted into the application of forced acoustics for enhancing the performance of a pyrolyzed waste afterburner configured as a dump combustor. Subscale studies showed that acoustic forcing of an air jet entering a dump chamber could trigger the formation of coherent vortices generated by entrainment of ambient gases. Subsequent studies showed that combustible gases could be introduced into the coherent vortices, and with additional modulation this configuration would lead to an enhanced combustion rate with low emissions of pollutants. The acoustically forced burner concept was scaled up to practical levels and tested as an afterburner on a commercial waste incinerator operating in pyrolysis mode. Results show that the afterburner can promote both compactness, due to the rapid combustion rate, and low pollutant emissions resulting from enhanced mixing prior to combustion.

Phylogenetic diversity of bacteria associated with the marine sponge Rhopaloeides odorabile

Molecular techniques were employed to document the microbial diversity associated with the marine sponge Rhopaloeides odorabile. The phylogenetic affiliation of sponge-associated bacteria was assessed by 16S rRNA sequencing of cloned DNA fragments. Fluorescence in situ hybridization (FISH) was used to confirm the presence of the predominant groups indicated by 16S rDNA analysis. The community structure was extremely diverse with representatives of the Actinobacteria, low-G+C gram-positive bacteria, the beta- and gamma-subdivisions of the Proteobacteria, Cytophaga/Flavobacterium, green sulfur bacteria, green nonsulfur bacteria, planctomycetes, and other sequence types with no known close relatives. FISH probes revealed the spatial location of these bacteria within the sponge tissue, in some cases suggesting possible symbiotic functions. The high proportion of 16S rRNA sequences derived from novel actinomycetes is good evidence for the presence of an indigenous marine actinomycete assemblage in R. odorabile. High microbial diversity was inferred from low duplication of clones in a library with 70 representatives. Determining the phylogenetic affiliation of sponge-associated microorganisms by 16S rRNA analysis facilitated the rational selection of culture media and isolation conditions to target specific groups of well-represented bacteria for laboratory culture. Novel media incorporating sponge extracts were used to isolate bacteria not previously recovered from this sponge.

Five Crustacean Hyperglycemic Family Hormones of Penaeus monodon: Complementary DNA Sequence and Identification in Single Sinus Glands by Electrospray Ionization-Fourier Transform Mass Spectrometry

Five novel neuropeptides, designated Pm-sgp-I to -V, of the crustacean hyperglycemic hormone (CHH) family have been identified from the giant tiger prawn Penaeus monodon by isolation of the preprohormone genes from an eyestalk complementary DNA library. On the basis of sequence similarity, the encoded peptides have been classified as CHH-like type I hormones, which include all known CHHs and the molt-inhibiting hormone (MIH) of the lobster Homarus americanus. Consistent with CHH type I preprohormones, the Pm-sgp precursors include a signal peptide, a CHH precursor-related peptide (CPRP), and the CHH-like hormone. Analysis by electrospray ionization-Fourier transform mass spectrometry enabled the neuropeptide complement of individual sinus glands to be resolved. It also confirmed the presence of the five Pm-sgp neuropeptides within the sinus gland of an individual animal, in that the masses observed were consistent with those predicted from the gene sequence of the Pm-sgps after posttranslational modification. These modifications included cleavage of the signal peptide and precursor protein, carboxy-terminal amidation, and formation of three disulfide bridges. Analysis of crude extracts of single sinus glands from different animals revealed variation in neuropeptide content and will provide a tool for determining whether the content varies as a function of the physiological state of the animal.

Tissue-Specific Expressed Sequence Tags from the Black Tiger Shrimp Penaeus monodon

: Expressed sequence tag data were generated from complementary DNA libraries created from cephalothorax, eyestalk, and pleopod tissue of the black tiger shrimp (Penaeus monodon). Significant database matches were found for 48 of 83 nuclear genes sequenced from the cephalothorax library, 22 of 55 nuclear genes from the eyestalk library, and 6 of 13 nuclear genes from the pleopod library. The putative identities of these genes reflected the expected tissue specificity. For example, genes for digestive enzymes were identified from the cephalothorax library and genes involved in the visual and neuroendocrine system from the eyestalk library. A few sequences matched anonymous EST or genomic sequences, and others contained mini-satellite or microsatellite repeat sequences. The remainder, 31 from the cephalothorax library, 25 from the eyestalk library, and 5 from the pleopod library, were sequences of high nucleotide complexity with no matches in any database searched and thus may represent novel genes.

Prediction of peptide affinity to HLA DR molecules

A method to quantitatively predict peptide binding to HLA DRB1*0401, B1*0101, and B1*1501 has been developed using a dataset of the relative contributions of each of the naturally occurring amino acids in the context of a simplified peptide backbone. The prediction assumed that the relative role of each of the peptide sidechains could be treated independently and could be measured by assaying each of the twenty naturally occurring amino acids at the central eleven positions of a 13 residue peptide previously shown to contain the minimal requirements for high affinity binding to HLA DR proteins. Three separate databases were generated. They were shown to have predictive value when tested on a set of 13 unrelated peptides known to bind the DR proteins with a wide range of apparent affinity. The DRB1*0401 database was tested further by analyzing myelin basic protein. All 13 amino acid peptides containing a hydrophobic amino acid at the third position were synthesized and assayed for binding purified DRB1*0401. In every case, the measured affinity correlated with the predictive values within the experimental error of the assays. Finally, the ability to predict peptide binding to MHC class II molecules was shown to help in identifying T cell determinants. The specificity of DRB1*0401 restricted T cell hybridomas against human serum albumin corresponded to two peptides, predicted, and shown to bind the class II protein with high affinity.

Down-regulation of poison ivy/oak-induced contact sensitivity by treatment with a class II MHC binding peptide:hapten conjugate

Immune regulation of contact sensitivity to the poison ivy/oak catechol was studied at the level of class II MHC-restricted T cell recognition of hapten:peptide conjugates. In this study we have shown that 1) T cells from C3H/HeN (H-2k) mice, immunized with a synthetic I-Ak binding peptide coupled to 3-pentadecyl-catechol (PDC; a representative catechol in urushiol), recognized peptides derived from syngeneic cells linked to the same catechol; 2) T cells from draining lymph nodes of C3H/HeN mice skin-painted with PDC proliferated in response to a peptide carrier:PDC conjugate only when it was linked at the 7th, but not the 4th or the 10th, position on the peptide carrier; and 3) tolerization studies confirmed down-regulation of PDC-induced delayed-type hypersensitivity following treatment with a single I-Ak binding peptide carrying PDC covalently bound to a lysine residue at the middle (7th) TCR contact position. Tolerization with peptide:PDC conjugate resulted in abrogation of hapten-specific T cell proliferative responses that correlated with diminished IL-2 secretion. On the basis of these data we propose that it may be sufficient to couple the hapten at a single, well-chosen position on a carrier peptide to target a relevant population of T cells involved in contact sensitivity.

Effect of ovariectomy and steroid hormone replacement on the recovery of arterial blood pressure following haemorrhage in anaesthetized Brattleboro rats

There is increasing evidence that ovarian steroids inhibit vascular responsiveness to the neurohypophysial hormone vasopressin. The present study examined the recovery of the arterial blood pressure following a single (2 ml/100 g body weight) haemorrhage in ovariectomized (OVX) Brattleboro rats with hereditary hypothalamic diabetes insipidus (BDI) and rats of the parent Long Evans (LE) strain. Some groups of OVX rats received subcutaneous implants of either 17 beta-oestradiol (E2) or progesterone 7 days prior to haemorrhage. The arterial blood pressure recovery immediately following haemorrhage was significantly impaired in both groups of steroid-treated OVX LE rats compared with the OVX controls (both comparisons P < 0.05). The impairment in blood pressure recovery seen in the steroid-replaced OVX LE rats was similar to that seen in pro-oestrous rats (when ovarian steroid levels are raised) compared with male rats of this strain (P < 0.05). In contrast, ovariectomy with or without steroid replacement in BDI rats had no further effect on the already attenuated recovery of arterial blood pressure after haemorrhage in this strain. Heart rate responses to haemorrhage also showed strain differences, which were dependent on steroid treatment. Pro-oestrous female LE rats showed a small decrease in heart rate after haemorrhage, followed by a recovery process, and this initial bradycardia was markedly enhanced in the OVX steroid-treated animals. In contrast, untreated OVX LE rats showed an initial and sustained increase in heart rate which was significantly higher than in the steroid-treated OVX animals (P < 0.05). All BDI rats, irrespective of treatment, consistently showed an increased heart rate after haemorrhage. In conclusion, ovarian steroid replacement in OVX LE, but not vasopressin-deficient BDI, rats was associated with an attenuated pressor recovery after haemorrhage. This provides further evidence for the existence of an important inhibitory interaction between ovarian steroids and vasopressin. The initial decrease in heart rate observed in pro-oestrous and steroid-treated OVX LE rats after haemorrhage also appears to be related to an ovarian steroid-vasopressin interaction.

Down-regulation of poison ivy/oak-induced contact sensitivity by treatment with a class II MHC binding peptide:hapten conjugate

Immune regulation of contact sensitivity to the poison ivy/oak catechol was studied at the level of class II MHC-restricted T cell recognition of hapten:peptide conjugates. In this study we have shown that 1) T cells from C3H/HeN (H-2k) mice, immunized with a synthetic I-Ak binding peptide coupled to 3-pentadecyl-catechol (PDC; a representative catechol in urushiol), recognized peptides derived from syngeneic cells linked to the same catechol; 2) T cells from draining lymph nodes of C3H/HeN mice skin-painted with PDC proliferated in response to a peptide carrier:PDC conjugate only when it was linked at the 7th, but not the 4th or the 10th, position on the peptide carrier; and 3) tolerization studies confirmed down-regulation of PDC-induced delayed-type hypersensitivity following treatment with a single I-Ak binding peptide carrying PDC covalently bound to a lysine residue at the middle (7th) TCR contact position. Tolerization with peptide:PDC conjugate resulted in abrogation of hapten-specific T cell proliferative responses that correlated with diminished IL-2 secretion. On the basis of these data we propose that it may be sufficient to couple the hapten at a single, well-chosen position on a carrier peptide to target a relevant population of T cells involved in contact sensitivity.

Simultaneous detection of different Rhizobium strains marked with either the Escherichia coli gusA gene or the Pyrococcus furiosus celB gene

A new marker system for gram-negative bacteria was developed on the basis of the celB gene from the hyperthermophilic archaeon Pyrococcus furiosus, which encodes a thermostable beta-glucosidase with a high level of beta-galactosidase activity. The celB gene is highly suitable as a marker for studying plant-bacterium interaction because endogenous background beta-glucosidase and beta-galactosidase enzyme activity can readily be inactivated by heat and because inexpensive substrates for detection are commercially available. Two celB-expressing transposons were constructed for use in ecological studies of a variety of gram-negative bacteria. The combined use of the gusA marker gene and celB allowed the simultaneous detection of several Rhizobium strains on a plant, and multiple-strain occupancy of individual modules also could be easily detected.

Differential stability of HLA-DR alleles independent of endogenous peptides

Purified HLA DRB1*0101 was shown to be inherently more stable to dissociation than DRB1*0401. The residues responsible for the differential stability were defined by constructing hybrid molecules, which contained a small number of residues from DRB1*0101 substituted into the framework of DRB1*0401. One of the hybrid molecules, containing six substituted amino acids, was as stable as DRB1*0101, but exhibited the binding specificity of DRB1*0401. This result indicated that the differential stability between the alleles arose from structural differences, and was not due solely to varying populations of endogenous peptides.

Differential stability of HLA-DR alleles independent of endogenous peptides

Purified HLA DRB1*0101 was shown to be inherently more stable to dissociation than DRB1*0401. The residues responsible for the differential stability were defined by constructing hybrid molecules, which contained a small number of residues from DRB1*0101 substituted into the framework of DRB1*0401. One of the hybrid molecules, containing six substituted amino acids, was as stable as DRB1*0101, but exhibited the binding specificity of DRB1*0401. This result indicated that the differential stability between the alleles arose from structural differences, and was not due solely to varying populations of endogenous peptides.

beta-Glucuronidase (GUS) transposons for ecological and genetic studies of rhizobia and other gram-negative bacteria

A series of transposons are described which contain the gusA gene, encoding beta-glucuronidase (GUS), expressed from a variety of promoters, both regulated and constitutive. The regulated promoters include the tac promoter which can be induced by IPTG, and nifH promoters which are symbiotically activated in legume nodules. One transposon contains gusA with a strong Shine-Dalgarno translation initiation context, but no promoter, and thus acts as a promoter-probe transposon. In addition, a gus operon deletion strain of Escherichia coli, and a transposon designed for use in chromosomal mapping using PFGE, are described. The GUS transposons are constructed in a mini-Tn5 system which can be transferred to Gram-negative bacteria by conjugation, and will form stable genomic insertions. Due to the absence of GUS activity in plants and many bacteria of economic importance, these transposons constitute powerful new tools for studying the ecology and population biology of bacteria in the environment and in association with plants, as well as for studies of the fundamental molecular basis of such interactions. The variety of assays available for GUS enable both quantitative assays and spatial localization of marked bacteria to be carried out.

Prediction of peptide affinity to HLA DRB1*0401

A method to predict quantitatively peptide binding to HLA DRB1*0401 has been developed using a data set of the relative contributions of each of the naturally occurring amino acids in the context of a simplified peptide back-bone. The prediction assumed that the relative role of each of the peptide side chains could be treated independently and could be measured by assaying each of the 20 naturally occurring amino acids at the central 11 positions of a 13-residue peptide previously shown to contain the minimal requirements for high-affinity binding to HLA-DR proteins. The resultant database was shown to have predictive value when tested on a set of 13 unrelated peptides known to bind DRB1*0401 with a wide range of apparent affinity. The database was tested further by analyzing myelin basic protein. All 13 amino acid peptides containing a hydrophobic amino acid at the third position were synthesized and assayed for binding purified DRB1*0401. In every case, the measured affinity correlated with the predictive values within the experimental error of the assays. Finally, the ability to predict peptide binding to MHC class II molecules was shown to help in identifying T cell determinants. The specificity of DRB1*0401-restricted T cell hybridomas against human serum albumin corresponded to two peptides, predicted and shown to bind the class II protein with high affinity.

Prediction of peptide affinity to HLA DRB1*0401

A method to predict quantitatively peptide binding to HLA DRB1*0401 has been developed using a data set of the relative contributions of each of the naturally occurring amino acids in the context of a simplified peptide back-bone. The prediction assumed that the relative role of each of the peptide side chains could be treated independently and could be measured by assaying each of the 20 naturally occurring amino acids at the central 11 positions of a 13-residue peptide previously shown to contain the minimal requirements for high-affinity binding to HLA-DR proteins. The resultant database was shown to have predictive value when tested on a set of 13 unrelated peptides known to bind DRB1*0401 with a wide range of apparent affinity. The database was tested further by analyzing myelin basic protein. All 13 amino acid peptides containing a hydrophobic amino acid at the third position were synthesized and assayed for binding purified DRB1*0401. In every case, the measured affinity correlated with the predictive values within the experimental error of the assays. Finally, the ability to predict peptide binding to MHC class II molecules was shown to help in identifying T cell determinants. The specificity of DRB1*0401-restricted T cell hybridomas against human serum albumin corresponded to two peptides, predicted and shown to bind the class II protein with high affinity.

Specific T cell recognition of minimally homologous peptides: evidence for multiple endogenous ligands

The T cell receptor (TCR) can interact with a spectrum of peptides as part of its ligand, including the immunogenic peptide, variants of this peptide,and apparently unrelated peptides. The basis of this broad specificity for ligand was investigated by substitution analysis of a peptide antigen and functional testing using a B cell apoptosis assay. A peptide containing as few as 1 aa in common with this peptide could stimulate a specific T cell response. Two endogenous ligands, an agonist and a partial agonist, were readily identified from a search of the SwissProt database, indicating that multiple endogenous ligands likely exist for a given T cell. These findings strongly support the concept that one TCR has the ability to interact productively with multiple different ligands, and provide evidence that such ligands exist in the endogenous peptide repertoire.

Characterization of epitopes recognized by hapten-specific CD4+ T cells

Although protein-derived nominal Ags have, in many instances, been precisely determined, the epitopes recognized by hapten-specific CD4+ T cells responsible for contact sensitization have not been defined. To better understand the nature of the precise epitopes generated after hapten interaction with Langerhans cells (LC), we assessed the ability of TNP-modified I-Ak- and I-Au-binding peptides to activate hapten-specific CD4+ T cells obtained respectively from TNCB-primed C3H (H-2k) and PL/j (H-2u) mice. Using LC as APC, I-Ak-restricted TNP-specific CD4+ T cells proliferated in the presence of the synthetic peptide hen egg lysozyme 52-61 derivatized with TNP at position 56, and less so when TNP was coupled at positions 53 or 59. Similarly, I-Au-restricted TNP-specific CD4+ T cells from PL/j mice were triggered by the synthetic I-Au-binding 13 mer poly(A)-Y5-R6 TNP-modified at position 4, and to a limited extent with TNP coupled in positions 7 or 10. Our results indicate that hapten-modified MHC class II binding nonautologous peptides are recognized by hapten-specific CD4+ T cells and that precise positioning of hapten molecules on peptides binding MHC class II molecules is required for optimal CD4+ T cell recognition. These findings provide insight into the manner in which haptens are recognized by T cells involved in contact sensitivity and should facilitate the study and design of specific therapies for the manipulation of hapten-specific CD4+ T cell responses.

Characterization of epitopes recognized by hapten-specific CD4+ T cells

Although protein-derived nominal Ags have, in many instances, been precisely determined, the epitopes recognized by hapten-specific CD4+ T cells responsible for contact sensitization have not been defined. To better understand the nature of the precise epitopes generated after hapten interaction with Langerhans cells (LC), we assessed the ability of TNP-modified I-Ak- and I-Au-binding peptides to activate hapten-specific CD4+ T cells obtained respectively from TNCB-primed C3H (H-2k) and PL/j (H-2u) mice. Using LC as APC, I-Ak-restricted TNP-specific CD4+ T cells proliferated in the presence of the synthetic peptide hen egg lysozyme 52-61 derivatized with TNP at position 56, and less so when TNP was coupled at positions 53 or 59. Similarly, I-Au-restricted TNP-specific CD4+ T cells from PL/j mice were triggered by the synthetic I-Au-binding 13 mer poly(A)-Y5-R6 TNP-modified at position 4, and to a limited extent with TNP coupled in positions 7 or 10. Our results indicate that hapten-modified MHC class II binding nonautologous peptides are recognized by hapten-specific CD4+ T cells and that precise positioning of hapten molecules on peptides binding MHC class II molecules is required for optimal CD4+ T cell recognition. These findings provide insight into the manner in which haptens are recognized by T cells involved in contact sensitivity and should facilitate the study and design of specific therapies for the manipulation of hapten-specific CD4+ T cell responses.

Detergent-enhanced dissociation of endogenous peptides from PI-DRB1*0401

A variety of detergents have been shown to catalyze the dissociation of bound peptides from a soluble from of DRB1*0401. By using a class II molecule lacking the hydrophobic transmembrane region, the need for solubilizing the transmembrane protein was removed and enabled the specific interaction between the class II protein and the amphiphile to be identified. The presence of detergent increased the rate of association of added peptide and the percent occupancy of the receptor, presumably because the dissociation of endogenous peptide was the rate-limiting step in binding. The data help explain the differences reported between peptide binding to class II proteins on the surface of cells and binding to class II proteins solubilized in detergent. The interaction did not correlate with the critical micellar concentration of the detergent nor were all amphiphilic structures equally effective, consistent with a specific interaction between the amphiphile and the MHC class II protein. Of the eight detergents examined, octyl glucoside was the most efficient. These experiments did not distinguish between an allosteric mechanism or direct competition with the peptide for binding.

Prediction of peptide affinity to HLA DRB1*0401

Hydrogen bonding between conserved amino acids in the HLA DR and the peptide backbone of the ligand both provide the majority of free energy of binding and force the peptide ligands to adopt a similar extended conformation. Consequently the corresponding side chains of all peptides interact with similar pockets in the binding site. For peptides of a common length the contribution of the peptide backbone can be treated as a constant and the differential affinity can be viewed as a simple sum of the side chain interactions. These can be quantified by measuring the effects of each of the naturally occurring amino acids in the context of a simplified polyalanine backbone containing an aromatic amino acid to orient the peptide unequivocally in the binding site. The dataset of the relative contributions can be used to predict quantitatively the affinity of any peptide sequence.

Cloning and nucleotide sequence of the Vibrio proteolyticus aminopeptidase gene

The gene encoding the Vibrio proteolyticus aminopeptidase was cloned and sequenced and its amino acid sequence was deduced. The gene encodes a 54 kDa protein, larger than the previously reported size of 30 kDa for the purified aminopeptidase. Sequence alignments revealed a 43-45% homology with two other Vibrio sp. extracellular proteinases.

The time dependent UV resonance Raman spectra, conformation, and biological activity of acetylcholine analogues upon binding to acetylcholine binding proteins

In order to obtain quantitative data on the relation between the conformation of acetylcholine and its interaction with biologically significant proteins, a series of acetylcholine analogues with absorption bands in the region 200-300 nm have been synthesized or obtained commercially. Each of these compounds were assayed to measure its activity as an ion channel activator of the nicotinic acetylcholine receptor protein (AChR). In addition, the suitability of some of these compounds as substrates for hydrolysis by acetylcholine esterase (AChE) was determined. One of these analogues, dimethylthionocarbamylcholine (DMTC-Ch), has the ester carbonyl oxygen replaced by a thionyl sulfur. DMTC-Ch has been found to be quite active as an ion channel activator when bound to AChR and was found to react with the enzyme AChE as a suicide substrate. It forms a thionoester of the serine at the AChE active site by an ester exchange reaction that releases the choline as the first product. However, the second or acid product is not released even at pH 7.5 over a period of days. This acetylcholine analog has an absorption band at about 240 nm and exhibits very strong ultraviolet resonance Raman (UVRR) spectra using 239 nm excitation from a frequency modified Nd:YAG laser. This technique allows observation of both conformational changes of the ligand molecule that result in frequency changes as well as changes in the excited state electronic structure that results in changes in the relative intensity of the Raman bands. The time dependence of the UVRR spectrum of the ligand upon binding to both AChE and AChR has been studied from 0.1 msec to minutes. Some time dependence in the conformation of DMTC-Ch upon binding to AChE has been found for very short (0.1-0.5 msec) times. However, no change in the conformation of this neurotransmitter analog is found in the available time range upon binding to AChR. From these data it is concluded that a previous suggestion that acetylcholine has a conformational change upon binding to AChR may be incorrect since the solution behavior of the carbamyl cholines and acetylcholine are similar. Even if acetylcholine does change conformation upont binding to AChR, it is unlikely that such a conformational change plays a significant role in channel activation. We present strong evidence that acetylcholine and its analogues can be active in a variety of conformations.(ABSTRACT TRUNCATED AT 400 WORDS)

Structural Similarities between Spinach Chloroplast and Cytosolic Class I Fructose 1,6-Bisphosphate Aldolases : Immunochemical and Amino-Terminal Amino Acid Sequence Analysis

Immunochemical studies using polyclonal antisera prepared individually against highly purified cytosolic and chloroplast spinach leaf (Spinacia oleracea) fructose bisphosphate aldolases showed significant cross reaction between both forms of spinach aldolase and their heterologous antisera. The individual cross reactions were estimated to be approximately 50% in both cases under conditions of antibody saturation using a highly sensitive enzyme-linked immunosorbent assay. In contrast, the class I procaryotic aldolase from Mycobacterium smegmatis and the class II aldolase from yeast (Saccharomyces cerevisiae) did not cross-react with either type of antiserum. The 29 residue long amino-terminal amino acid sequences of the procaryotic M. smegmatis and the spinach chloroplast aldolases were determined. Comparisons of these sequences with those of other aldolases showed that the amino-terminal primary structure of the chloroplast aldolase is much more similar to the amino-terminal structures of class I cytosolic eucaryotic aldolases than it is to the corresponding region of the M. smegmatis enzyme, especially in that region which forms the first "beta sheet" in the secondary structure of the eucaryotic aldolases. Moreover, results of a systematic comparison of the amino acid compositions of a number of diverse eucaryotic and procaryotic fructose bisphosphate aldolases further suggest that the chloroplast aldolase belongs to the eucaryotic rather than the procaryotic "family" of class I aldolases.

Micro-level protein and peptide separations

The current major limitation in protein micro-structural and -functional studies is our inability to purify and manipulate microgram or smaller quantities of material. Both high performance liquid chromatography (HPLC) and polyacrylamide gel electrophoresis (PAGE) have been widely used in attempts to address such needs. This review summarizes the current status of preparative and analytical applications for both methods, and suggests which directions the micro-separations field will take within the next few years.

Environmental ultrasound in laboratories and animal houses: a possible cause for concern in the welfare and use of laboratory animals

Many laboratory animals are known to be sensitive to sounds (ultrasounds) beyond the nominal upper limit (20 kHz) of the human hearing range. Sources of sound in laboratories and animal houses were examined to determine the extent of ambient ultrasound. Of 39 sources monitored, 24 were found to emit ultrasonic sounds. Many of these (e.g. cage washers and hoses) also produced sound in the audible range. Running taps, squeaky chairs and rotating glass stoppers created particularly high sound pressure levels and contained frequencies to over 100 kHz. The oscilloscopes and visual display units investigated provided particular cause for concern as they emitted sounds that were entirely ultrasonic and therefore were apparently silent. Ambient ultrasound therefore appears to be common in laboratories and animal houses. It is suggested that its effect on laboratory animals should be investigated and guidelines on acceptable levels be formulated.

Effect of buffer pH and peptide composition on the selectivity of peptide separations by capillary zone electrophoresis

A series of 10 synthetic peptides containing varying degrees of charge and hydrophobicity was used to study the effects of peptide composition and buffer pH on the selectivity of separations by capillary zone electrophoresis (CZE). A simple model is used to explain the effect of buffer pH on the separation. It was found that pH is an important parameter affecting the selectivity of CZE separations. Furthermore, it is shown that the selectivity of the separation is such that peptides differing in neutral amino acid composition can be resolved, and that even differences in a peptide's amino acid sequence can be detected. A protease digest of beta-lactoglobulin A is shown as a practical example of a separation of a complex peptide mixture.

Comparative evaluation of the diffusion of tobramycin and cefotaxime out of antibiotic-impregnated polymethylmethacrylate beads

Both tobramycin and cefotaxime diffuse from antibiotic-impregnated polymethylmethacrylate (PMMA) beads in quantities sufficient to inhibit the growth of bacteria on agar lawns or in broth cultures over a 28-day period. Extraction of antibiotic from tobramycin or cefotaxime-impregnated PMMA beads revealed that substantial amounts of both antibiotics remained within the beads despite 28 days of diffusion. Diffusion of antibiotic from the PMMA beads during the initial 3-5 days is much greater than occurs for the remainder of the 4-week period. The results of the study suggest that perhaps tobramycin of cefotaxime-impregnated PMMA beads would produce local levels of antibiotic high enough to sterilize a given dead space for a period of 28 days.

Applications of tandem microbore liquid chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis/electroblotting in microsequence analysis

Protein isolation by microbore HPLC is compared with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)/electroblotting methods for several major proteins from rabbit muscle. Although single-mode HPLC or SDS-PAGE/electroblotting provides excellent speed and sensitivity for submicrogram-level protein purification, neither one alone has adequate resolution for separating such a complex protein mixture. Tandem procedures, utilizing two different modes of HPLC in separate steps or a combination of single HPLC separation and SDS-PAGE/electroblotting, offer the necessary versatility. One of the major concerns in this investigation was to evaluate electroblotting techniques for microsequencing. The Aebersold et al. procedure (R.H. Aebersold, D.B. Teplow, L.E. Hood, and S.B.H. Kent (1986) J. Biol. Chem. 261, 4229-4238) was substantially modified and improved; the details of this work will be published elsewhere. These changes significantly improve repetitive yields at the low microgram level without producing high backgrounds. At lower levels the recovery of sequenceable protein currently limits our ability to obtain useful results. Starting with 250-750 micrograms of rabbit muscle crude extract, several proteins (15-70 kDa) were isolated by tandem microbore LC and PAGE/electroblotting for amino-terminal sequence analysis. It appears that the combination of electroblotting and microbore LC represents a powerful approach for microsample preparation.

Properties of Single K and Cl Channels in Asclepias tuberosa Protoplasts

Potassium and chloride channels were characterized in Asclepias tuberosa suspension cell derived protoplasts by patch voltage-clamp. Whole-cell currents and single channels in excised patches had linear instantaneous current-voltage relations, reversing at the Nernst potentials for K(+) and Cl(-), respectively. Whole cell K(+) currents activated exponentially during step depolarizations, while voltage-dependent Cl(-) channels were activated by hyperpolarizations. Single K(+) channel conductance was 40 +/- 5 pS with a mean open time of 4.5 milliseconds at 100 millivolts. Potassium channels were blocked by Cs(+) and tetraethylammonium, but were insensitive to 4-aminopyridine. Chloride channels had a single-channel conductance of 100 +/- 17 picosiemens, mean open time of 8.8 milliseconds, and were blocked by Zn(2+) and ethacrynic acid. Whole-cell Cl(-) currents were inhibited by abscisic acid, and were unaffected by indole-3-acetic acid and 2,4-dichlorophenoxyacetic acid. Since internal and external composition can be controlled, patch-clamped protoplasts are ideal systems for studying the role of ion channels in plant physiology and development.

Identification of a long form of cystatin from human saliva by rapid microbore HPLC mapping

Microbore HPLC methodology permits rapid and sensitive mapping of human saliva proteins. Saliva is sampled and processed in less than one hour, greatly reducing the likelihood of artifactual protein degradation. As little as 50 microliters of saliva yields proteins in sufficient quantities and purity to obtain amino terminal sequences directly. By this route we have discovered a 14 kDa protein extremely homologous to Cystatin S, but amino-terminally extended by eight amino acids.

Effects of abscisic acid on K+ channels in Vicia faba guard cell protoplasts

Potassium channels were resolved in Vicia faba guard cell protoplasts by patch voltage-clamp. Whole-cell currents and single K+ channels had linear instantaneous current-voltage relations, reversing at the calculated Nernst potential for K+. Whole cell K+ currents activated exponentially during step depolarizations, with half-activation times of 400-450 msec at +80 mV and 90-110 msec at +150 mV. Single K+ channel conductance was 65 +/- 5 pS with a mean open time of 1.25 +/- 0.30 msec at 150 mV. Potassium channels were blocked by internal Cs+ and by external TEA+, but they were insensitive to external 4-aminopyridine. Application of 10 microM abscisic acid increased mean open time and caused long-lasting bursts of channel openings. Since internal and external composition can be controlled, patch-clamped protoplasts are ideal systems for studying the role of ion channels in plant physiology.

Isolation and characterization of symbiotic mutants of bradyrhizobium sp. (Arachis) strain NC92: mutants with host-specific defects in nodulation and nitrogen fixation

Random transposon Tn5 mutagenesis of Bradyrhizobium sp. (Arachis) strain NC92, a member of the cowpea cross-inoculation group, was carried out, and kanamycin-resistant transconjugants were tested for their symbiotic phenotype on three host plants: groundnut, siratro, and pigeonpea. Two nodulation (Nod- phenotype) mutants were isolated. One is unable to nodulate all three hosts and appears to contain an insertion in one of the common nodulation genes (nodABCD); the other is a host-specific nodulation mutant that fails to nodulate pigeonpea, elicits uninvaded nodules on siratro, and elicits normal, nitrogen-fixing nodules on groundnut. In addition, nine mutants defective in nitrogen fixation (Fix- phenotype) were isolated. Three fail to supply symbiotically fixed nitrogen to all three host plants. Surprisingly, nodules elicited by one of these mutants exhibit high levels of acetylene reduction activity, demonstrating the presence of the enzyme nitrogenase. Three more mutants have partially effective phenotypes (Fix +/-) in symbiosis with all three host plants. The remaining three mutants fail to supply fixed nitrogen to one of the host plants tested while remaining partially or fully effective on the other two hosts; two of these mutants are Fix- in pigeonpea and Fix +/- on groundnut and on siratro, whereas the other one is Fix- on groundnut but Fix+ on siratro and on pigeonpea. These latter mutants also retain significant nodule acetylene reduction activity, even in the ineffective symbioses. Such bacterial host-specific fixation (Hsf) mutants have not previously been reported.

Partial primary structures of human and murine macrophage colony stimulating factor (CSF-1)

Approximately 40 amino-terminal residues and 20 internal residues of CSF-1 purified from the media of cultured human pancreatic carcinoma (MIA PaCa) cells and of cultured murine L cells have been identified. Results indicated that the two subunits in each molecule of biologically active CSF-1 are identical in their amino-terminal portions. The twelve amino-terminal residues of MIA PaCa CSF-1 were found to be identical to those of human-urinary CSF-1, suggesting that the polypeptide portions of the two human proteins may be identical. Approximately 75% of the amino acids identified in both MIA PaCa CSF-1 and murine CSF-1 were found to be common to both. No homology to other proteins was observed. This study suggests a subunit polypeptide Mr nearer to 17K than to 26K predicted from cDNA.

Microbore flow-rates and protein chromatography

Reversed-phase chromatography of proteins on microbore columns can achieve sensitivities that exceed those for standard-bore columns by a factor of 10-20, when operated at the same linear velocities. These gains in sensitivity are accompanied by proportional reductions in peak volume. Sensitivities on standard- (4.6 mm I.D.) and narrow-bore (2.1 mm I.D.) columns have been further improved by reducing the flow-rates to those typical for microbore (1 mm I.D.) columns. We have investigated the role of flow-rate in determining peak volumes for a constant time gradient and found that flow-rate affects peak volume to a much greater extent than column diameter. Column length was not found to have a significant effect on either peak volume or sensitivity. We have found that a four-fold reduction in flow-rate results in at least a two-fold reduction in peak volume over the flow-rate range from 25 to 400 microliters/min. Recovery of proteins in smaller volumes should prove beneficial to subsequent protein characterization methodologies.

Salmonella cytotoxin: a component of the bacterial outer membrane

Salmonella cytotoxin present in cell-free sonic lysates causes rounding and detachment of Chinese hamster ovary (CHO) cells. Although the precise role of this toxin in the pathogenesis of salmonellosis is unclear, cytotoxin production by Salmonella could account for tissue damage or possibly, facilitate invasion. A variety of other bacteria (e.g. Shigella, Escherichia, Legionella) have been shown to form soluble cytotoxins, many of which may be involved in pathogenesis. The data in this report indicate that the Salmonella cytotoxin in cell-free sonic lysates is firmly associated with cell membrane fragments that can be pelleted by ultracentrifugation (270,000 g for 2.4 h). Furthermore, lysozyme treatment of filter-sterilized sonic extracts of Salmonella species followed by isopycnic sucrose gradient ultracentrifugation allowed separation of the outer and inner membrane components. The outer membrane (OM) peak contained the cytotoxic activity when assayed for detachment of CHO cells. The importance of these data resides in the observation that the Salmonella cytotoxin is an outer membrane component. Its mere location places it in a position of direct contact with host cells and suggests a possible role in cell damage and/or invasion. Furthermore, ultracentrifugation provides a method by which much of the Salmonella cytotoxin in sonic extracts can be removed allowing expression of the Salmonella enterotoxin, whose CHO cell elongation effect is usually obscured by the presence of the cytotoxin causing cell rounding and detachment.

Specific proteolytic modification of creatine kinase isoenzymes. Implication of C-terminal involvement in enzymic activity but not in subunit-subunit recognition

We are using the isoenzymes of creatine kinase (CK) to investigate the effect of specific proteolytic modification on the abilities of enzyme subunits to establish precise subunit-subunit recognition in vitro. Previous work by others has shown that treatment of the MM isoenzyme of rabbit CK with Proteinase K results in a specific proteolytic modification and inactivation of the enzyme. In the present work, we show that both the MM and BB isoenzymes of chicken CK are also specifically modified by Proteinase K, resulting in over 98% loss of catalytic activity and approx. 10% decreases in subunit molecular masses of the enzymes. Similar reactions appear to occur when the isoenzymes are treated with Pronase E. Limited amino acid sequence analysis of intact and Proteinase K-modified MM-CK suggests that the proteolytic modification results from a single peptide-bond cleavage occurring between alanine residues 328 and 329, about 50 amino acid residues from the C-terminal end; the active-site cysteine residue was recovered in the large protein fragment of modified M-CK subunits. Proteolytically modified M-CK and B-CK subunits were able to refold and reassociate into dimeric structures after treatment with high concentrations of LiCl and at low pH. Thus the proteolytically modified CK subunits retain their ability to refold and to establish precise subunit-subunit recognition in vitro.

Molecular cloning of a complementary DNA encoding human macrophage-specific colony-stimulating factor (CSF-1)

Complementary DNA (cDNA) clones encoding human macrophage-specific specific colony-stimulating factor (CSF-1) were isolated. One cDNA clone codes for a mature polypeptide of 224 amino acids and a putative leader of 32 amino acids. This cDNA, which was cloned in the Okayama-Berg expression vector, specifies the synthesis of biologically active CSF-1 in COS cells, as determined by a specific radioreceptor assay, macrophage bone marrow colony formation, and antibody neutralization. Most of the cDNA isolates contain part of an intron sequence that changes the reading frame, resulting in an abrupt termination of translation; these cDNA's were inactive in COS cells. The CSF-1 appears to be encoded by a single-copy gene, but its expression results in the synthesis of several messenger RNA species, ranging in size from about 1.5 to 4.5 kilobases.

Characterization of translational inhibitors from Phytolacca americana. Amino-terminal sequence determination and antibody-inhibitor conjugates

Two translational inhibitors (pokeweed antiviral protein and pokeweed antiviral protein II) isolated from the leaves of the pokeweed plant, Phytolacca americana, were characterized as to their behavior during reverse-phase HPLC and their amino-terminal sequences. Alignment of the sequences demonstrated that a substantial degree of homology was present (10 of 29 identical residues). Pokeweed antiviral protein was shown by reverse-phase chromatography to be composed of at least two components, pokeweed antiviral proteina and pokeweed antiviral proteinb, which comigrated on sodium dodecyl sulfate polyacrylamide gel electrophoresis, shared identical N-terminal amino-acid sequences through residue 31, and had similar specific activities in a cell-free translation inhibition assay. Pokeweed antiviral protein II was covalently coupled to a monoclonal antibody that recognizes the transferrin receptor (anti-transferrin receptor). The disulfide-linked conjugate inhibited protein synthesis in the human breast tumor cell line MCF-7, whereas anti-transferrin receptor, pokeweed antiviral protein II, or an immunotoxin composed of an irrelevant antiserum and pokeweed antiviral protein II, were nontoxic. The inhibitory dose 50% of anti-transferrin receptor-pokeweed antiviral protein II for MCF-7 cells was 0.7 nM, whereas the corresponding ricin A chain conjugate (anti-transferrin receptor-ricin A chain) was more potent with a inhibitory dose 50% of 0.1 nM. Pokeweed antiviral protein II can be added to the growing list of translation inhibitors that are effective as components of immunotoxins in vitro. Additional studies will be needed to determine whether pokeweed antiviral protein II immunotoxins provide advantageous properties for in vivo applications.