Enhanced Hydrogen Bonding by Urea Functionalization Tunes the Stability and Biological Properties of Peptide Amphiphiles

Self-assembled nanostructures such as those formed by peptide amphiphiles (PAs) are of great interest in biological and pharmacological applications. Herein, a simple and widely applicable chemical modification, a urea motif, was included in the PA's molecular structure to stabilize the nanostructures by virtue of intermolecular hydrogen bonds. Since the amino acid residue nearest to the lipid tail is the most relevant for stability, we decided to include the urea modification at that position. We prepared four groups of molecules (13 PAs in all), with varying levels of intermolecular cohesion, using amino acids with distinct β-sheet promoting potential and/or containing hydrophobic tails of distinct lengths. Each subset contained one urea-modified PA and nonmodified PAs, all with the same peptide sequence. The varied responses of these PAs to variations in pH, temperature, counterions, and biologically related proteins were examined using microscopic, X-ray, spectrometric techniques, and molecular simulations. We found that the urea group contributes to the stabilization of the morphology and internal arrangement of the assemblies against environmental stimuli for all peptide sequences. In addition, microbiological and biological studies were performed with the cationic PAs. These assays reveal that the addition of urea linkages affects the PA-cell membrane interaction, showing the potential to increase the selectivity toward bacteria. Our data indicate that the urea motif can be used to tune the stability of a wide range of PA nanostructures, allowing flexibility on the biomaterial's design and opening a myriad of options for clinical therapies.

Structure-Activity Relationship Study to Develop Peptide Amphiphiles as Species-Specific Antimicrobials

Antimicrobial peptide amphiphiles (PAs) are a promising class of molecules that can disrupt the bacterial membrane or act as drug nanocarriers. In this study, we prepared 33 PAs to establish supramolecular structure-activity relationships. We studied the morphology and activity of the nanostructures against different Gram-positive and Gram-negative bacterial strains (such as Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Acinetobacter baumannii). Next, we used principal component analysis (PCA) to determine the key contributors to activity. We found that for S. aureus, the zeta potential was the major contributor to the activity while Gram-negative bacteria were more influenced by the partition coefficient (LogP) with the following order P. aeruginosa>E. coli>A. baumannii. We also performed a study of the mechanism of action of selected PAs on the bacterial membrane assessing the membrane permeability and depolarization, changes in zeta potential and overall integrity. We studied the toxicity of the nanostructures against mammalian cells. Finally, we performed an in vivo study using the wax moth larvae to determine the therapeutic efficacy of the active PAs. This study shows cationic PA nanostructures can be an intriguing platform for the development of nanoantibacterials.

Patient-level costs in intensive care: a case report of a standardized and scalable approach

Background

Intensive care units (ICU) costs account to up to 30% of hospital budgets. Nevertheless, determination of their costs is complex and without agreed methodology, specially when considering patient-level costs (Value-Based Healthcare).

Methods

Case report of a costing methodology implementation, in a 15-bed ICU, in a public, teaching hospital at Teresina/Piauí-Brazil (as part of a broader initiative, with 10 hospitals from all Brazilian regions). All costs incurred during ICU stay were measured from the hospital perspective, applying absorption costing method, by using a standardized approach and a specific central IT system. The study was carried out from Oct/19-Sep/20, including 613 patients, and a team of 10 researchers working with 4 teams of the local hospital (costs, IT, ICU and managers).

Results

ICU fixed costs (personnel, overheads, energy/water, depreciation, non-tracked drugs/medical materials), were divided by service capacity (total bed-hours) for calculation of the costs/minute. Costs were then allocated in the patient level multiplying costs/minute by the ICU length of stay. Variable costs (lab/image tests, transfusions, hemodialysis, and traceable medical materials/drugs) were directly allocated, multiplying the unit cost by the volume consumed per patient. A mini-survey applied 1-year after showed that both cost researchers and hospital staff agreed on the main challenges in measuring patient-level costs (fragmented process; fixed costs available only at the hospital level; lack of control on cost-drivers; indirect costs not considered; any reference for lab/image costs) and that the approach was sufficient to overcome them. The local team also reported increased awareness about the importance of patient-level costs after the experience.

Conclusions

The proposed costing approach allowed the assessment of estimated total costs of each ICU admission. We believe this model can be easily and quickly replicated in other similar scenarios.

Key messages

ICU costs account to up to 30% of hospital budgets. Nevertheless, determination of their costs is complex and without agreed methodology, specially when considering patient-level costs. The proposed costing approach allowed the assessment of estimated total costs of each ICU admission. We believe this model can be easily and quickly replicated in other similar scenarios.

Legionnaires' disease: when an 'outbreak' is not an outbreak

During August 2006, there was a large increase in non-travel related legionella cases throughout England and in the Netherlands.

Differential esterase expression in leaves of Manihot esculenta Crantz infected with Xanthomonas axonopodis pv. manihotis

The polyacrylamide gel electrophoresis system (PAGE) and inhibition tests for biochemical characterization of alpha- and beta-esterases were used to obtain a functional classification of esterases in plants and to show a differential expression of esterases as markers of pathogenesis in cassava plants (Manihot esculenta Crantz). The characterization of alpha- and beta-esterases from leaves of M. esculenta by the PAGE system was possible using an extraction solution containing two phenol-complexing agents (PVP-40 and sodium metabisulfite), three antioxidant agents (EDTA, beta-mercaptoethanol, and DTT), and one quinone reducer (ascorbic acid). Fourteen esterase isozymes were detected in young unexpanded leaves of M. esculenta cultivars. The inhibition pattern of alpha- and beta-esterases of M. esculenta showed that Est-9 is an arylesterase, and in the unexpanded leaves of the M. esculenta plants infected with Xanthomonas axonopodis pv. manihotis, the Est-7 beta-esterase showed the characteristic staining of an alpha/beta-esterase. This diffrential expression of Est-7 isozyme in young unexpanded leaves of cassava plants can be used as a marker of pathogenesis after infection with X. axonopodis pv. manihotis.

Maxillary lateral incisor with two root canals: fusion, gemination or dens invaginatus?

Endodontic retreatment of a maxillary right lateral incisor with two root canals is described. The diagnosis of fusion, gemination or dens invaginatus could not be made, due to conflicting findings, and to previous root canal treatment that erased the original configuration of the pulp chamber.

[Cryptococcus neoformans isolated from patients with AIDS]

Cryptococcosis is considered the most frequent fungal systemic opportunist infection in patients with AIDS. C. neoformans var. neoformans infects the patients with AIDS more often than C. neoformans var. gattii which has been rarely isolated from patients with AIDS. Even in endemic regions of C. neoformans var. gattii, the variety of neoformans is still the most common agent diagnosed in cryptococcosis of patients with AIDS. Cerebrospinal fluid (CSF) from fifty patients with neurocryptococcosis associated with AIDS were studied. The fungi were isolated in agar Sabouraud medium, and were identified by microscopic and macroscopic examination by agar Sabouraud, agar niger and Christensen's urea medium. The variety was determined based on a color characteristic reaction on glycine-L-canavanina-bromothymol blue agar. From all of the fifty patients' cerebrospinal fluid (CSF) we were able to recover C. neoformans. The isolates were identified as C. neoformans var. neoformans in 47 patients and as C. neoformans var. gattii. in the 3 remaining patients. These findings suggest that both varieties, gattii and neoformans, are agents of neurocryptococcosis in patients with AIDS.

Intercomparison of calibration procedures for 192Ir HDR sources in Brazil

The lack of well established dosimetry protocols for HDR sources is a point of great concern regarding the uniformity of procedures within a particular country and worldwide. The main objective of this paper is to report the results from ten institutions of an intercomparison of calibration procedures for 192Ir HDR sources currently in use in Brazil. The treatment irradiator of one institution was calibrated by a reference system and used by all participants with their own measuring electrometers and ionization chambers under the same experimental conditions. Two methods were used: the calibration jig and the well-type ionization chamber. Each participant was allowed to use their own method and formalism. The results of this exercise were very positive since this was the first time in Brazil that a group of users gathered to share their experience and openly discuss the physical concepts behind the calibration procedures. The results were all within +/-3.0%, except one case where -4.6% was observed and later identified as a problem with the Nk value for x-rays. Though the magnitude of the deviations found was generally acceptable considering the diversity of formalisms currently in use, a proposal is now being prepared to be adopted as a national protocol. The identification of the institutions was left out for the sake of confidentiality.

Mitochondrial association of a plus end-directed microtubule motor expressed during mitosis in Drosophila

The kinesin superfamily is a large group of proteins (kinesin-like proteins [KLPs]) that share sequence similarity with the microtubule (MT) motor kinesin. Several members of this superfamily have been implicated in various stages of mitosis and meiosis. Here we report our studies on KLP67A of Drosophila. DNA sequence analysis of KLP67A predicts an MT motor protein with an amino-terminal motor domain. To prove this directly, KLP67A expressed in Escherichia coli was shown in an in vitro motility assay to move MTs in the plus direction. We also report expression analyses at both the mRNA and protein level, which implicate KLP67A in the localization of mitochondria in undifferentiated cell types. In situ hybridization studies of the KLP67A mRNA during embryogenesis and larval central nervous system development indicate a proliferation-specific expression pattern. Furthermore, when affinity-purified anti-KLP67A antisera are used to stain blastoderm embryos, mitochondria in the region of the spindle asters are labeled. These data suggest that KLP67A is a mitotic motor of Drosophila that may have the unique role of positioning mitochondria near the spindle.

Motor activity and mitotic spindle localization of the Drosophila kinesin-like protein KLP61F

The KLP61F gene product is essential for Drosophila development. Mutations in KLP61F display a mitotic arrest phenotype caused by a failure in the proper separation of duplicated centrosomes (Heck et al., 1993). Sequence analysis of KLP61F identified it as a member of the bimC family of kinesin-like microtubule motor proteins. Here we report that KLP61F is distinct from KRP130, a kinesin-like protein recently purified from Drosophila embryos and suggested to be the product of the KLP61F gene (Cole et al., 1994). We also characterized recombinant KLP61F and found that it possesses microtubule-stimulated ATPase and microtubule translocation activities in vitro. In addition, we have used an affinity-purified, KLP61F-specific antiserum to localize native KLP61F and an epitope-tagged KLP61F fusion protein during various stages of mitosis in Drosophila syncytial blastoderm embryos. From early prophase through anaphase, KLP61F is coincident with the distribution of tubulin. Together these results confirm the existence of multiple bimC-like kinesins in Drosophila and suggest that KLP61F function is intrinsic to the mitotic spindle.

An inverse PCR screen for the detection of P element insertions in cloned genomic intervals in Drosophila melanogaster

We developed a screening approach that utilizes an inverse polymerase chain reaction (PCR) to detect P element insertions in or near previously cloned genes in Drosophila melanogaster. We used this approach in a large scale genetic screen in which P elements were mobilized from sites on the X chromosome to new autosomal locations. Mutagenized flies were combined in pools, and our screening approach was used to generate probes corresponding to the sequences flanking each site of insertion. These probes then were used for hybridization to cloned genomic intervals, allowing individuals carrying insertions in them to be detected. We used the same approach to perform repeated rounds of sib-selection to generate stable insertion lines. We screened 16,100 insert bearing individuals and recovered 11 insertions in five intervals containing genes encoding members of the kinesin superfamily in Drosophila melanogaster. In addition, we recovered an insertion in the region including the Larval Serum Protein-2 gene. Examination by Southern hybridization confirms that the lines we recovered represent genuine insertions in the corresponding genomic intervals. Our data indicates that this approach will be very efficient both for P element mutagenesis of new genomic regions and for detection and recovery of "local" P element transposition events. In addition, our data constitutes a survey of preferred P element insertion sites in the Drosophila genome and suggests that insertion sites that are mutable at a rate of approximately 10(-4) are distributed every 40-50 kb.

[Visualization of thrombi in the left auricular appendix using transesophageal echocardiography. Apropos of a clinical case]

A case of Transesophageal Echocardiography (T.E.E.) Assessment of "Rheumatic Mitral Stenosis" is presented. T.E.E. has been recently referred as having superior resolution than transthoracic Echocardiography on the detection of thrombi. In the presented case a thrombi was detected in the left atrial appendage. This fact has allowed a better planning of surgery.

[Surgery for infectious endocarditis]

OBJECTIVE

to assess the experience of both departments in the surgical therapy of infective endocarditis--indications and results.

DESIGN

retrospective analysis on clinical data, surgery and follow up.

SETTING

patients (pts) studied in the Cardiology Department and Cardiothoracic Surgery Department of the Santa Marta Hospital in Lisbon.

PATIENTS AND INTERVENTIONS

sequential sample of 28 patients (11 females, 17 males, mean age 39 years) submitted to surgery between 1978 and 1987 for infective endocarditis.

MEASUREMENTS AND RESULTS

the indications for surgery were: heart failure (15 pts), "resistant" infection (8 pts), emboli (4 pts) and "large" vegetations shown by echocardiography (2 pts). Surgical mortality -27.5%. Four patients developed periprosthetic leaks. There was an improvement in functional class of the survivals.

CONCLUSION

the indications for surgery were heart failure, "resistant" infection, emboli and "large" vegetations. There was a high surgical mortality, namely in the patients with resistant infection, severe heart failure and periprosthetic leaks. In the follow up there was a net improvement of functional class. The morbidity is due to the periprosthetic leaks, which induced most of the reoperations.

[Infective endocarditis of pulmonary valve. Considerations apropos of a case associated with interventricular communication and aortic insufficiency ]

We report the case of a 23 year old patient in whom heart disease was detected in childhood. He began to have suddenly fever and symptoms of right side heart failure. There were signs of aortic regurgitation, a systodiastolic murmur in the left parasternal region and a diastolic murmur in the left 4th intercostal space. The bidimensional and Doppler Echocardiogram showed a saccular dilatation in the right ventricular outflow tract. He was submitted to catheterisation which confirmed aortic regurgitation and detected ventricular septal defect and pulmonary hypertension. During surgery, a subaortic ventricular septal defect was seen as well as a dilatation of the right coronary aortic cusp which prolapsed through the defect to the right ventricular outflow tract. Vegetations were seen in the pulmonary valve. The aortic valve and a pulmonary cusp were excised and a Björk Shiley aortic prosthetic valve was inserted. The septal defect was closed. The patient is still alive, symptomless, with 40 months of follow up. We discuss some problems related to this case, particularly the surgical indication and the rarity of the morphology discovered.

[Isolated hypoplasia of the right ventricle--apropos of a case]

OBJECTIVE

To report one case of a rare heart disease (Isolated Hypoplasia of the Right Ventricle) and discuss the methodology used to propose surgery with goal. Good follow up results.

DESIGN

To report a case.

SETTING

One patient studied in the Cardiology Department of the Santa Marta Hospital, Lisbon, and submitted to surgery in the Cardiothoracic Surgery Department of the same Hospital.

PATIENT

A 22 years old woman, who had cyanosis since birth, normal cardiac auscultatory findings, pulmonary oligohemia in the chest Roentgenogram and right atrial strain on the Electrocardiogram.

INTERVENTIONS

She had an echocardiogram (M1 Mode and 2D) and catheterised, with pressure and oximetry measurements. During the latter procedure, the atrial septal defect was occluded for 20 minutes with a Fogarty catheter and pressure and oximetries were reevaluated. She was later operated.

MEASUREMENTS AND RESULTS

The Echocardiogram showed right ventricular hypoplasia, with a normally inserted tricuspid valve and a dilated right atrium. The hemodynamic study confirmed the presence of an atrial septal defect with right to left shunt, normal pulmonary artery pressure, no gradients and giant "a" wave in the right auriculogram. The right ventriculography showed right ventricular inflow hypoplasia. The occlusion of the atrial septal defect with the balloon catheter decreased the peripheral insaturation, without a significant increase in the right ventricular pressure. With this information, surgery was proposed (closure of the atrial septal defect), with good results (4 years of follow-up).

CONCLUSION

The interruption of the shunt with a balloon allows us to see if the right ventricle can handle properly the volume load. With this information surgery can be suggested. It may be rather simple as in this case.