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2.
Mil Med ; 188(3-4): 64-66, 2023 03 20.
Article in English | MEDLINE | ID: mdl-36579568

ABSTRACT

Leading medical teams as a new attending physician can be a challenging task. This case highlights the important role of leaders in fostering a positive learning environment, developing interpersonal relationships, and establishing clear expectations with regular feedback to improve team function to deliver effective health care.


Subject(s)
Delivery of Health Care , Interpersonal Relations , Humans , Health Personnel , Feedback , Patient Care Team
3.
Cureus ; 14(5): e25355, 2022 May.
Article in English | MEDLINE | ID: mdl-35761923

ABSTRACT

Nephrotic syndrome can result in worsening of existing hypothyroidism in patients requiring thyroid hormone supplementation. The urinary loss of thyroxine-binding globulin, as well as increased gut edema, likely lead to reduced absorption and retention of exogenous thyroid hormone. Here, we present a case of a patient with Hashimoto's thyroiditis, previously well-controlled on levothyroxine, who developed symptomatic hypothyroidism as a result of newly diagnosed nephrotic syndrome, whose symptoms improved with transition to an alternative formulation of levothyroxine and treatment of her underlying nephrotic syndrome. It is important to consider nephrotic syndrome as a cause of worsening hypothyroidism in a patient on a fixed dose of levothyroxine given the potential morbidity associated with a missed diagnosis and often need for escalation of dosage. There is no standardized therapy for hypothyroidism exacerbated by nephrotic syndrome, but liquid or gel formulations of levothyroxine may be more effective in patients with absorption problems.

4.
Curr Opin Gastroenterol ; 38(3): 216-220, 2022 05 01.
Article in English | MEDLINE | ID: mdl-35275898

ABSTRACT

PURPOSE OF REVIEW: This article discusses the most recent studies regarding the emerging field of endohepatology - the use of diagnostic and therapeutic endoscopic tools for the management of patients with liver disease and portal hypertension. RECENT FINDINGS: New research has shown that liver biopsy specimens obtained by each Endoscopic ultrasound (EUS)-guidance, the percutaneous approach, and the transjugular approach contained sufficient portal triads to adequately analyzed by experienced pathologists - suggesting that any of these routes of liver biopsy is clinically acceptable; further, all had similar rates of adverse events. An initial prospective study showed that EUS guided portal pressure measurement was safe, effective, and accurate. A recent metanalysis showed that EUS-guided cyanoacrylate injection and coil embolization was statistically more efficacious and with less complications than EUS guided cyanoacrylate injection and EUS guided coil injection alone, suggesting that combination therapy appears to be the preferred approach for gastric varices (GV) bleeding. A prospective study evaluating focal liver lesions showed that the use of artificial intelligence had up to 100% sensitivity and 81% specificity for identifying malignant focal liver lesions. SUMMARY: EUS guided liver biopsy is safe and enables accurate diagnosis of underlying liver disease. EUS guided portal pressure measurement is also safe and is accurate. Combination therapy of EUS guided cyanoacrylate injection and coil embolization is more efficacious and has less complications than injection or coil therapy alone when used for GV bleeding. Artificial intelligence is highly sensitive and specific when used in conjunction with EUS in the diagnosis of malignant focal liver lesions. Endohepatology is a rapidly expanding field with great potential.


Subject(s)
Esophageal and Gastric Varices , Liver Neoplasms , Artificial Intelligence , Cyanoacrylates , Endosonography , Esophageal and Gastric Varices/diagnosis , Esophageal and Gastric Varices/etiology , Esophageal and Gastric Varices/therapy , Gastrointestinal Hemorrhage/therapy , Humans , Liver Neoplasms/drug therapy , Prospective Studies , Treatment Outcome
5.
Stem Cell Res Ther ; 13(1): 31, 2022 01 25.
Article in English | MEDLINE | ID: mdl-35073957

ABSTRACT

OBJECTIVE: To gain insight into the molecular mechanisms underlying the early stages of vocal fold extracellular matrix (ECM) remodeling after a mid-membranous injury resulting from the use of human amniotic epithelial cells (hAEC), as a novel regenerative medicine cell-based therapy. METHODS: Vocal folds of six female, New Zealand White rabbits were bilaterally injured. Three rabbits had immediate bilateral direct injection of 1 × 106 hAEC in 100 µl of saline solution (hAEC) and three with 100 µl of saline solution (controls, CTR). Rabbits were euthanized 6 weeks after injury. Proteomic analyses (in-gel trypsin protein digestion, LC-MS/MS, protein identification using Proteome Discoverer and the Uniprot Oryctolagus cuniculus (Rabbit) proteome) and histological analyses were performed. RESULTS: hAEC treatment significantly increased the expression of ECM proteins, elastin microfibril interface-located protein 1 (EMILIN-1) and myocilin that are primarily involved in elastogenesis of blood vessels and granulation tissue. A reactome pathway analysis showed increased activity of the anchoring fibril formation by collagen I and laminin, providing mechanical stability and activation of cell signaling pathways regulating cell function. hAEC increased the abundance of keratin 1 indicating accelerated induction of the differentiation programming of the basal epithelial cells and, thereby, improved barrier function. Lastly, upregulation of Rab GDP dissociation inhibitor indicates that hAEC activate the vesicle endocytic and exocytic pathways, supporting the exosome-mediated activation of cell-matrix and cell-to-cell interactions. CONCLUSIONS: This pilot study suggests that injection of hAEC into an injured rabbit vocal fold favorably alters ECM composition creating a microenvironment that accelerates differentiation of regenerated epithelium and promotes stabilization of new blood vessels indicative of accelerated and improved repair.


Subject(s)
Cicatrix , Vocal Cords , Animals , Cell Transplantation , Chromatography, Liquid , Cicatrix/pathology , Epithelial Cells/pathology , Female , Humans , Pilot Projects , Proteomics , Rabbits , Tandem Mass Spectrometry
6.
Appetite ; 166: 105429, 2021 11 01.
Article in English | MEDLINE | ID: mdl-34062175

ABSTRACT

African American women, in particular, have learned to navigate through a food consumption landscape that purposefully, and often aggressively, limits their choices and stigmatizes their resulting physical appearance, and renders them collectively unattractive and unworthy. While American women are challenged to subscribe to traditional slim body standards, a faction of Americans have differing opinions. African American (AA) women celebrate larger body types and defy weight stigma. When African Americans make food choices, taste and cost are not the only factors influencing those choices; the cultural role of food is also considered. We conducted semi-structured interviews with 12 African American girls to identify some of the consequences of this consumption practice that challenges what we argue is a hegemonic taste regime surrounding body size. This work further elucidates the ways in which the African American community has operationalized the concept of cultural capital around the issues of body image to create what we suggest is a type of emotional well-being. In addition to uncovering marketing channels promoting anti-obesity campaigns that would be more likely to capture their attention, our findings also reveal that AA girls embrace shapely bodies, despite not necessarily having one themselves, and overall possess a more positive body image than their Caucasian peers. Having shapely bodies was deemed more attractive among romantic interests and acceptable overall in the AA community regardless of the associated health risks associated with consuming unhealthy foods.


Subject(s)
Black or African American , White People , Body Image , Female , Food Preferences , Humans , Obesity
7.
J Fungi (Basel) ; 6(4)2020 Dec 14.
Article in English | MEDLINE | ID: mdl-33327604

ABSTRACT

Laser capture microdissection (LCM) coupled to label-free quantitative mass spectrometry is a viable strategy to identify biomarkers from infected tissues. In this study, LCM was employed to take a "snapshot" of proteins produced in vivo during Coccidiodies spp. infection in human lungs. Proteomic analysis of LCM lung sections revealed hundreds of hosts and Coccidioidal proteins. Twenty-seven highly abundant Coccidioides spp. proteins were identified which do not share significant sequence orthology with human proteins. Three of the 27 Coccidioidal proteins are also potential Coccidoides-specific biomarkers, as they also do not share sequence homology to any other pathogenic fungus or microbe. Gene ontology analysis of the 27 biomarker candidate proteins revealed enriched hydrolase activity and increased purine and carbohydrate metabolism functions. Finally, we provide proteomic evidence that all 27 biomarker candidates are produced by the fungus when grown in vitro in a media- and growth-phase dependent manner.

9.
Glycobiology ; 30(3): 186-197, 2020 02 19.
Article in English | MEDLINE | ID: mdl-31691790

ABSTRACT

Coccidioides spp. are important pneumonia-causing pathogens of the American southwest, but little is known about their glycobiology and how their glycosylations differ from other pneumonia-causing fungi. There is mounting preliminary evidence to suggest genus or even species-specific glycosylations in the fungal kingdom due to the presence of unique carbohydrate-active enzymes (CAZymes) in fungal genomes (Deshpande et al. 2008, Glycobiology, 18(8), 626-637; Karkowska-Kuleta and Kozik 2015, Acta Biochim Pol., 62(3), 339-351). If Coccidioides spp.-specific glycans can be identified, it may be possible to exploit these differences to develop more specific diagnostic approaches and more effective therapeutics. Herein, we i) mined Coccidioides spp. and other pathogenic fungal genomes to identify CAZymes specific for Coccidioides spp., ii) proteomically determined the Coccidioides spp. "CAZome" produced in vivo and in vitro, and iii) utilized glycomics to differentiate Coccidioides genus-specific N-glycans from other pathogenic fungi. As far as we are aware, this is the first proteomic and glycomic comparison of the N-glycomes and CAZomes of different fungal genera during infection in human hosts.


Subject(s)
Coccidioides/enzymology , Coccidioidomycosis/diagnosis , Fungal Proteins/analysis , Polysaccharides/analysis , Coccidioides/isolation & purification , Coccidioides/metabolism , Coccidioidomycosis/metabolism , Coccidioidomycosis/microbiology , Fungal Proteins/biosynthesis , Fungal Proteins/genetics , Glycomics , Glycosylation , Humans , Polysaccharides/metabolism , Proteomics
10.
J Proteome Res ; 18(7): 2791-2802, 2019 07 05.
Article in English | MEDLINE | ID: mdl-31244214

ABSTRACT

Coccidioidomycosis, also known as Valley fever (VF), is a potentially lethal fungal infection that results in more than 200 deaths per year in the United States. Despite the important role of metabolic processes in the molecular pathogenesis of VF, robust metabolic markers to enable effective screening, rapid diagnosis, accurate surveillance, and therapeutic monitoring of VF are still lacking. We present a targeted liquid chromatography-tandem mass spectrometry-based metabolic profiling approach for identifying metabolic marker candidates that could enable rapid, highly sensitive, and specific VF detection. Using this targeted approach, 207 plasma metabolites and 231 urinary metabolites from many metabolic pathways of potential biological significance were reliably detected and monitored in 147 samples taken from two groups of subjects (48 VF patients and 99 non-VF controls). The results of our univariate significance testing and multivariate model development informed the construction of a three-metabolite panel of potential plasma biomarkers and a nine-metabolite panel of potential urinary biomarkers. Receiver operating characteristic curves generated based on orthogonal partial least-squares-discriminant analysis models showed excellent classification performance, with 94.4% sensitivity and 97.6% specificity for plasma metabolites. Urine metabolites were less accurate, demonstrating 89.7% sensitivity and 88.1% specificity. Enrichment, pathway, and network analyses revealed significant disturbances in glycine and serine metabolism, in both plasma and urine samples. To the best of our knowledge, this is the first study aiming to discover novel metabolite markers of VF, which could achieve accurate diagnosis within 24 h. The results expand the basic knowledge of the metabolome related to VF and potentially reveal pathways or markers that could be therapeutically targeted. This study also provides a promising basis for the development of larger multisite projects to validate our findings across population groups and further advance the development of better clinical care for VF patients.


Subject(s)
Coccidioidomycosis/diagnosis , Metabolomics/methods , Biomarkers/blood , Biomarkers/urine , Case-Control Studies , Chromatography, Liquid , Discriminant Analysis , Humans , Metabolic Networks and Pathways , Metabolome , ROC Curve , Sensitivity and Specificity , Tandem Mass Spectrometry
11.
Appl Biosaf ; 24(1): 30-33, 2019 Mar.
Article in English | MEDLINE | ID: mdl-30962770

ABSTRACT

To date, limited published data exists regarding the efficacy of commonly used disinfectants in inactivating the Risk Group 3 dimorphic fungal pathogens, Coccidioides immitis and Coccidioides posadasii. Newer generation quaternary ammonium compounds, like Virex® II 256 and Virex® Tb, have not been previously evaluated. Herein, these disinfectants are evaluated against 10% bleach and 70% ethanol, for their ability to inactivate 5×107 arthroconidial spores of C. immitis RS or C. posadasii strain Silveira within 2, 5, 10 or 20 minutes contact time in aqueous solution. Evidence is provided that both Virex® II 256 and Virex® Tb are highly effective alternatives to 10% bleach or 70% ethanol for the disinfection of 5×107 arthroconidia of Coccidioides spp. within 2 minutes of contact time. 70% ethanol was seen as less effective in killing C.immitis RS arthroconidia and both 70% ethanol and 10% bleach were seen as less effective than the other disinfectants in killing C. posadasii strain Silveira, as longer contact times were required to completely inactivate the same number of arthroconidia.

12.
Sex Reprod Healthc ; 19: 42-49, 2019 Mar.
Article in English | MEDLINE | ID: mdl-30928134

ABSTRACT

OBJECTIVES: To investigate: (1) whether women self-report an ability to choose their preferred termination of pregnancy (TOP) procedure, (2) what factors influence this choice, and (3) what effect this choice has on emotional responses and satisfaction with care. STUDY DESIGN: A mixed-method prospective comparative study in which women requesting a TOP between five and eighteen weeks gestation for social reasons (as opposed to medical indications), were invited to complete a semi-structured pre-TOP interview and questionnaire, and a post-TOP questionnaire four weeks after the procedure. MAIN OUTCOME MEASURES: Quantitative data was collected using the Patient Health Questionnaire, Generalised Anxiety Disorder Scale, Positive and Negative Affect Scale, Impact of Event Scale - Revised, and Client Satisfaction Questionnaire. RESULTS: Pre-TOP emotion-based factors did not differ between groups. Most women felt that they were able to choose their preferred method of TOP. Their decisions were based on factors categorised as procedure-related, lifestyle or social circumstance-related, emotional, or other factors. When no choice was perceived, common reasons reported were that: (1) gestation was too far along for there to be another option, or (2) an appointment was not available within the required timeframe. When women felt that the method of TOP performed was not their choice they found the procedure more stressful. All women reported high satisfaction with care. CONCLUSION: A better understanding of the patient experience can inform service development, enabling staff to ensure that the services provided meet women's needs. The perception that one is able to choose their preferred TOP procedure is important for reducing procedure-related stress and ensuring high satisfaction with care.


Subject(s)
Abortion, Legal/psychology , Emotions , Patient Preference , Abortion, Legal/methods , Adult , Choice Behavior , Female , Humans , Middle Aged , Pregnancy , Pregnancy Trimester, First , Pregnancy Trimester, Second , Prospective Studies , Surveys and Questionnaires , Young Adult
13.
ACG Case Rep J ; 6(11): e00273, 2019 Nov.
Article in English | MEDLINE | ID: mdl-32309473

ABSTRACT

Drug-induced liver injury is a common cause of acute liver failure. ß-blockers are a widely prescribed class of medications; however, hepatotoxicity is a rare adverse effect of this medication of which clinicians must be aware. This case suggests that hepatotoxicity may be a class effect of ß-blockers.

14.
mBio ; 9(6)2018 11 27.
Article in English | MEDLINE | ID: mdl-30482833

ABSTRACT

Scytonemin is a dimeric indole-phenol sunscreen synthesized by some cyanobacteria under conditions of exposure to UVA radiation. While its biosynthetic pathway has been elucidated only partially, comparative genomics reveals that the scytonemin operon often contains a cluster of five highly conserved genes (ebo cluster) of unknown function that is widespread and conserved among several bacterial and algal phyla. We sought to elucidate the function of the ebo cluster in the cyanobacterium Nostoc punctiforme by constructing and analyzing in-frame deletion mutants (one for each ebo gene and one for the entire cluster). Under conditions of UVA induction, all ebo mutants were scytoneminless, and all accumulated a single compound, the scytonemin monomer, clearly implicating all ebo genes in scytonemin production. We showed that the scytonemin monomer also accumulated in an induced deletion mutant of scyE, a non-ebo scytonemin gene whose product is demonstrably targeted to the periplasm. Confocal autofluorescence microscopy revealed that the accumulation was confined to the cytoplasm in all ebo mutants but that that was not the case in the scyE deletion, with an intact ebo cluster, where the scytonemin monomer was also excreted to the periplasm. The results implicate the ebo cluster in the export of the scytonemin monomer to the periplasm for final oxidative dimerization by ScyE. By extension, the ebo gene cluster may play similar roles in metabolite translocation across many bacterial phyla. We discuss potential mechanisms for such a role on the basis of structural and phylogenetic considerations of the ebo proteins.IMPORTANCE Elucidating the biochemical and genetic basis of scytonemin constitutes an interesting challenge because of its unique structure and the unusual fact that it is partially synthesized in the periplasmic space. Our work points to the ebo gene cluster, associated with the scytonemin operon of cyanobacteria, as being responsible for the excretion of scytonemin intermediates from the cytoplasm into the periplasm during biosynthesis. Few conserved systems have been described that facilitate the membrane translocation of small molecules. Because the ebo cluster is well conserved among a large diversity of bacteria and algae and yet insights into its potential function are lacking, our findings suggest that translocation of small molecules across the plasma membrane may be its generic role across microbes.


Subject(s)
Indoles/metabolism , Nostoc/metabolism , Periplasm/metabolism , Phenols/metabolism , Pigments, Biological/metabolism , Biological Transport , Biosynthetic Pathways/genetics , Gene Deletion , Microscopy, Confocal , Microscopy, Fluorescence , Multigene Family , Nostoc/genetics , Nostoc/radiation effects , Ultraviolet Rays
15.
BMJ Case Rep ; 20182018 Sep 08.
Article in English | MEDLINE | ID: mdl-30196255

ABSTRACT

We report the case of a patient with remote orthotopic liver transplant who was ultimately diagnosed with Merkel cell carcinoma following admission for initial venous thromboembolism. Additionally, we review pertinent literature related to the risk of skin cancer in solid organ transplant recipients and discuss the importance of yearly skin exams in this patient population.


Subject(s)
Carcinoma, Merkel Cell/diagnosis , Liver Transplantation/adverse effects , Skin Neoplasms/diagnosis , Venous Thromboembolism/etiology , Carcinoma, Merkel Cell/complications , Carcinoma, Merkel Cell/etiology , Diagnosis, Differential , Humans , Male , Middle Aged , Skin/pathology , Skin Neoplasms/complications , Skin Neoplasms/etiology , Transplant Recipients , Ventilation-Perfusion Scan
16.
Inflamm Bowel Dis ; 24(11): 2322-2326, 2018 10 12.
Article in English | MEDLINE | ID: mdl-29788235

ABSTRACT

There is a well-established association between chronic inflammation and an elevated risk of heart disease among patients with systemic autoimmune conditions. This review aims to summarize existing literature on the relationship between inflammatory bowel disease and ischemic heart disease, heart failure, arrhythmia, and pericarditis, with particular attention to approaches to management and treatment.


Subject(s)
Heart Diseases/etiology , Inflammatory Bowel Diseases/complications , Heart Diseases/pathology , Humans , Prognosis
17.
Proteomics ; 18(1)2018 01.
Article in English | MEDLINE | ID: mdl-29130603

ABSTRACT

The aims of this study are to provide protein-based evidence upon which to reannotate the genome of Coccidiodes posadasii, one of two closely related species of Coccidioides, a dimorphic fungal pathogen that causes coccidioidomycosis, also called Valley fever. Proteins present in lysates and filtrates of in vitro grown mycelia and parasitic phase spherules from C. posadasii strain Silveira are analyzed using a GeLC-MS/MS method. Acquired spectra are processed with a proteogenomics workflow comprising a Silveira proteome database, a six-frame translation of the Silveira genome and an ab initio gene prediction tool prior to validation against published ESTs. This study provides evidence for 837 genes expressed at the protein level, of which 169 proteins (20.2%) are putative proteins and 103 (12.3%) are not annotated in the Silveira genome. Additionally, 275 novel peptides are derived from intragenic regions of the genome and 13 from intergenic regions, resulting in 172 gene refinements. Additionally, we are the first group to report translationally active retrotransposon elements in a Coccidioides spp. Our study reveals that the currently annotated genome of C. posadasii str. Silveira needs refinement, which is likely to be the case for many nonmodel organisms.


Subject(s)
Coccidioides/genetics , Coccidioides/metabolism , Molecular Sequence Annotation , Peptide Fragments/analysis , Peptide Fragments/genetics , Proteogenomics/methods , Proteome/metabolism , Coccidioidomycosis/microbiology , Computational Biology , Peptide Fragments/chemistry , Tandem Mass Spectrometry
18.
BMJ Case Rep ; 20172017 Oct 20.
Article in English | MEDLINE | ID: mdl-29054895

ABSTRACT

Infectious suppurative thrombophlebitis of the portal venous system, referred to as pylephlebitis, is a rare complication of intra-abdominal inflammatory processes. Advances in diagnostics and antibiotics have improved survival, but mortality remains remarkably high even in the most recent literature. The majority of patients have concomitant bacteraemia on presentation most commonly with typical gastrointestinal (GI) organisms. On rare occasion, patients have culture positive Fusobacterium, which has recently been associated with occult GI and genitourinary malignancies. Here, we describe a patient presenting with pylephlebitis and Fusobacterium bacteraemia who responded well to medical therapy, review pertinent literature and discuss the benefits of screening endoscopy in this patient population.


Subject(s)
Anti-Bacterial Agents/therapeutic use , Fusobacterium Infections/microbiology , Fusobacterium necrophorum/isolation & purification , Lemierre Syndrome/microbiology , Phlebitis/microbiology , Abdominal Pain/microbiology , Anticoagulants/therapeutic use , Endoscopy, Gastrointestinal , Ertapenem , Fever/microbiology , Fusobacterium Infections/drug therapy , Fusobacterium Infections/physiopathology , Heparin/therapeutic use , Humans , Lemierre Syndrome/drug therapy , Lemierre Syndrome/physiopathology , Male , Penicillanic Acid/analogs & derivatives , Penicillanic Acid/therapeutic use , Piperacillin/therapeutic use , Piperacillin, Tazobactam Drug Combination , Portal Vein , Treatment Outcome , beta-Lactams/therapeutic use
19.
J Proteome Res ; 15(10): 3463-3472, 2016 10 07.
Article in English | MEDLINE | ID: mdl-27546806

ABSTRACT

Coccidioides is a virulent dimorphic fungus that causes coccidioidomycosis (valley fever) in mammals, including humans. Although the genome has been sequenced, a proteomic analysis does not exist. To address this gap in proteomic knowledge, we generated the proteome of spherulin (a well-studied lysate of fungal spherules) and identified 1390 proteins. Some of the proteins included glycosylation enzymes, which led us to hypothesize that fungal glycosylation patterns may be different from those of mammals and could be exploited to detect Coccidioides in tissues. We performed lectin-based immunohistochemistry on formalin-fixed paraffin-embedded human patients' lung tissues. GSL-II (Griffonia simplificonia lectin II) and sWGA (succinylated wheat germ agglutinin) lectins bound specifically to endospores and spherules in infected lungs. To identify lectin-binding glycoproteins in spherulin, we performed lectin-affinity chromatography, followed by LC-MS/MS. A total of 195 glycoproteins from spherulin bound to GSL-II, 224 glycoproteins bound to sWGA, and 145 glycoproteins bound to both lectins. This is the first report of the specific reactivity of GSL-II and sWGA lectins to Coccidioides endospores and spherules in infected human tissues and the first listing of the Coccidioidal proteome from spherulin using sequences present in three Coccidioides databases: RefSeq, SwissProt, and The Broad Institute's Coccidioides Genome project.


Subject(s)
Coccidioides/chemistry , Coccidioidin/chemistry , Fungal Proteins/analysis , Lectins/metabolism , Proteome/metabolism , Chromatography, Affinity , Coccidioidomycosis/diagnosis , Coccidioidomycosis/pathology , Glycoproteins/analysis , Glycoproteins/metabolism , Glycosylation , Humans , Immunohistochemistry , Lung/pathology , Protein Binding
20.
Biochim Biophys Acta ; 1858(5): 988-94, 2016 May.
Article in English | MEDLINE | ID: mdl-26514602

ABSTRACT

Iso- and anteiso-branched lipids are abundant in the cytoplasmic membranes of bacteria. Their function is assumed to be similar to that of unsaturated lipids in other organisms - to maintain the membrane in a fluid state. However, the presence of terminally branched membrane lipids is likely to impact other membrane properties as well. For instance, lipid acyl chain structure has been shown to influence the activity of antimicrobial peptides. Moreover, the development of resistance to antimicrobial agents in Staphylococcus aureus is accompanied by a shift in the fatty acid composition toward a higher fraction of anteiso-branched lipids. Little is known about how branched lipids and the location of the branch point affect the activity of membrane-active peptides. We hypothesized that bilayers containing lipids with low phase transition temperatures would tend to exclude peptides and be less susceptible to peptide-induced perturbation than those made from higher temperature melting lipids. To test this hypothesis, we synthesized a series of asymmetric phospholipids that only differ in the type of fatty acid esterified at the sn-2 position of the lipid glycerol backbone. We tested the influence of acyl chain structure on peptide activity by measuring the kinetics of release from dye-encapsulated lipid vesicles made from these synthetic lipids. The results were compared to those obtained using vesicles made from S. aureus and Staphylococcus sciuri membrane lipid extracts. Anteiso-branched phospholipids, which melt at very low temperatures, produced lipid vesicles that were only slightly less susceptible to peptide-induced dye release than those made from the iso-branched isomer. However, liposomes made from bacterial phospholipid extracts were generally much more resistant to peptide-induced perturbation than those made from any of the synthetic lipids. The results suggest that the increase in the fraction of anteiso-branched fatty acids in antibiotic-resistant strains of S. aureus is unlikely to be the sole factor responsible for the observed increased antibiotic resistance. This article is part of a Special Issue entitled: Antimicrobial peptides edited by Karl Lohner and Kai Hilpert.


Subject(s)
Anti-Bacterial Agents/pharmacology , Antimicrobial Cationic Peptides/pharmacology , Cell Membrane/drug effects , Lipid Bilayers/chemistry , Liposomes/chemistry , Anti-Bacterial Agents/chemistry , Antimicrobial Cationic Peptides/chemistry , Bacterial Proteins/chemistry , Bacterial Proteins/metabolism , Cell Membrane/chemistry , Drug Compounding , Drug Liberation , Drug Resistance, Bacterial , Fluoresceins/metabolism , Fluorescent Dyes/metabolism , Hemolysin Proteins/chemistry , Hemolysin Proteins/metabolism , Kinetics , Lipid Bilayers/metabolism , Liposomes/metabolism , Lysophosphatidylcholines/chemistry , Lysophosphatidylcholines/metabolism , Myristic Acids/chemistry , Myristic Acids/metabolism , Phase Transition , Phosphatidylcholines/chemistry , Phosphatidylcholines/metabolism , Phosphatidylglycerols/chemistry , Phosphatidylglycerols/metabolism , Staphylococcus/chemistry , Staphylococcus aureus/chemistry
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