Validity of cycloheximide chylomicron flow blocking method for the evaluation of lymphatic transport of drugs

BACKGROUND AND PURPOSE

Lymphatic transport of drugs after oral administration is an important mechanism for absorption of highly lipophilic compounds. Direct measurement in lymph duct cannulated animals is the gold standard method, but non-invasive cycloheximide chylomicron flow blocking method has gained popularity recently. However, concerns about its reliability have been raised. The aim of this work was to investigate the validity of cycloheximide chylomicron flow blocking method for the evaluation of lymphatic transport using model compounds with high to very high lipophilicity, that is, abiraterone and cinacalcet.

EXPERIMENTAL APPROACH

Series of pharmacokinetic studies were conducted with abiraterone acetate and cinacalcet hydrochloride after enteral/intravenous administration to intact, lymph duct cannulated and/or cycloheximide pre-treated rats.

KEY RESULTS

Mean total absolute oral bioavailability of abiraterone and cinacalcet was 7.0% and 28.7%, respectively. There was a large and significant overestimation of the lymphatic transport extent by the cycloheximide method. Mean relative lymphatic bioavailability of abiraterone and cinacalcet in cycloheximide method was 28-fold and 3-fold higher than in cannulation method, respectively.

CONCLUSION AND IMPLICATIONS

Cycloheximide chylomicron flow blocking method did not provide reliable results on lymphatic absorption and substantially overestimated lymphatic transport for both molecules, that is, abiraterone and cinacalcet. This non-invasive method should not be used for the assessment of lymphatic transport and previously obtained data should be critically revised.

Vancomycin-releasing cross-linked collagen sponges as wound dressings

The study presents a novel vancomycin-releasing collagen wound dressing derived from Cyprinus carpio collagen type I cross-linked with carbodiimide which retarded the degradation rate and increased the stability of the sponge. Following lyophilization, the dressings were subjected to gamma sterilization. The structure was evaluated via scanning electron microscopy images, micro-computed tomography, and infrared spectrometry. The structural stability and vancomycin release properties were evaluated in phosphate buffered saline. Microbiological testing and a rat model of a wound infected with methicillin-resistant Staphylococcus aureus (MRSA) were then employed to test the efficacy of the treatment of the infected wound. Following an initial mass loss due to the release of vancomycin, the sponges remained stable. After 7 days of exposure in phosphate buffered saline (37°C), 60% of the material remained with a preserved collagen secondary structure together with a high degree of open porosity (over 80%). The analysis of the release of vancomycin revealed homogeneous distribution of the antibiotic both across and between the sponges. The release of vancomycin was retarded as proved by in vitro testing and further confirmed by the animal model from which measurable concentrations were observed in blood samples 24 hours after the subcutaneous implantation of the sponge, which was more than observed following intraperitoneal administration. The sponge was also highly effective in terms of reducing the number of colony-forming units in biopsies extracted from the infected wounds 4 days following the inoculation of the wounds with the MRSA solution. The presented sponges have ideal properties to serve as wound dressing for prevention of surgical site infection or treatment of already infected wounds.

A novel gentamicin-releasing wound dressing prepared from freshwater fish Cyprinus carpio collagen cross-linked with carbodiimide

Our study presents a novel collagen wound dressing prepared from freshwater fish skin ( Cyprinus Carpio) collagen type I. Half of the sponges were cross-linked with carbodiimide. The cross-linked and non-cross-linked collagen sponges were subsequently impregnated with gentamicin and lyophilized thus allowing for the attainment of the appropriate gentamicin content without the removal thereof during the cross-linking stage. The structure was evaluated via micro-CT and infrared spectrometry and the structural stability and gentamicin release properties were evaluated in phosphate buffer solution. The sponges were further tested via a rat model of an infected wound with Pseudomonas aeruginosa inoculation and compared with a reference commercial product. The sponges thus prepared provided a degree of open porosity that was comparable to or higher than that of the reference commercial product. Spectrometry analysis revealed that the cross-linked collagen sponge and reference commercial product sponge preserved their secondary collagen structure after 168 h while early accelerated degradation was observed with respect to the non-cross-linked collagen sponge. Gentamicin was released rapidly from all the sponges. Compared to those animals with gentamicin-containing sponges or gentamicin administered intramuscularly, the animals with the cross-linked collagen sponge without gentamicin exhibited marked clinical and laboratory infection signs. Both the administration routes (intramuscular and via gentamicin-containing sponges) provided similar gentamicin plasma levels. The resulting highly homogeneous product which was characterized by excellent structural and clinical properties proved effective in terms of the treatment of a surgical wound infection in a rat model. We demonstrated that all the gentamicin was released from the sponge and was absorbed in the systemic circulation. This is the first time that Cyprinus Carpio collagen has been used in the preparation of wound dressings. Thus, gentamicin-containing sponges provide a promising tool for the treatment and prevention of surgical site infections.

Branched pedal bypass in the treatment of critical limb ischemia - a single center experience

INTRODUCTION

Pedal bypass is a therapeutic option for limb salvage in critical limb ischemia.

METHOD

Retrospective analysis of 20 patients who underwent either simple (14 patients) or branched (6 patients) pedal bypass in a single center and had at least one postoperative follow-up. In patients with branched pedal bypass, the main trunk was connected to the pedal artery of better quality and the side branch to an artery on the opposite side of the foot. The main trunk was constructed as a reverse saphenous bypass in all patients with branched bypass. From patients with simple bypass, nine had reverse saphenous graft, three had an allograft, one patient had in situ saphenous graft, and one PTFE prosthesis.

RESULTS

The difference in the operation time was not significant. One patient with simple bypass required reoperation for wound bleeding and there was one case of perioperative mortality in the same group. The difference between the groups in the primary or secondary patency rates, limb salvage and overall survival was not significant.

CONCLUSIONS

We did not find any significant difference in patency rates, limb salvage, or perioperative complications between patients with simple and branched pedal bypass in our cohort. We believe that the anticipated benefits of constructing an additional branch are masked by the disadvantageous presence of an additional anastomosis. Adoption of a branched pedal bypass may therefore require further improvements - perhaps the utilization of a branched saphenous graft. Key words:  critical limb ischemia - peripheral arterial disease - bypass - revascularization - amputation.

[Fetal magnetocardiography: a promising way to diagnose fetal arrhytmia and to study fetal heart rate variability?]

OBJECTIVE

An overwiev of the new diagnostic method of fetal wellbeing - fetal magnetocardiography (fMCG).

DESIGN

A review article.

SETTING

Department of Gynecology and Obstetrics, Jessenius Faculty of Medicine in Martin, Comenius University in Bratislava, Slovak Republic.

METHODS

An analysis of the literature using database search engines PubMed, and SCOPE in field of fMCG.

RESULTS

Fetal magnetocardiography is a non-invasive technique able to monitor the spontaneous electrophysiological activity of the fetal heart. Compared to cardiotocography and fetal electrocardiography, this is a more effective method with a higher resolution. The signal obtained from the fetal heart is sufficiently precise and the quality allows an assessment of PQRST complex alterations, and to detect fetal arrhythmia. Thanks to early diagnosis of fetal arrhythmia, there is the possibility for appropriate therapeutic intervention and the reduction of unexplained fetal death in late gestation. fMCG with high temporal resolution also increases the level of clinical trials which record fetal heart rate (FHR) variability. According to the latest theories, FHR variability is a possible indicator of fetal status and enables the study of the fetal autonomic nervous system indirectly. fMCG is an experimental method that requires expensive equipment. It is yet to be shown in the future, if this method will get any application in clinical practice.

[Genetic aspects of pelvic floor defects and stress urinary incontinence in women]

OBJECTIVE

An overwiev of the genetic aspects of pelvic floor defects and stress urinary incontinence in women.

DESIGN

A review article.

SETTING

Department of Gynecology and Obstetrics, Jessenius Faculty of Medicine in Martin, Comenius University in Bratislava, Slovak Republic.

METHODS

An analysis of the literature using database search engines PubMed, BLAST and Ensembl in field of POP and SUI.

RESULTS

Pelvic organ prolapse (POP) and stress urinary incontinence (SUI) affect a large number of women and often requires surgical correction. Moreover, these diseases are not only individual health but also social and economic burden on patients and society. It is possible to prevent or at least timely intervene these pathologies by screening of risk patients. The incidence of these disorders leads to find possible genetic factors. In ethiopathogenetic studies of pelvic floor defects and stress urinary incontinence it is looking for genes associated with these diseases and optimization of molecular biology methods is necessary to determine the possible gene mutations or polymorphism site. Selection of relevant genetic factors tend to clarify the pathomechanism of SUI and POP that can greatly affect their current diagnostics and therapeutics.

KEYWORDS

prolapse, stress urinary incontinence, polymorphism, gene expression.

[Principles and limits of clinical methods in the diagnosis of fetal hypoxia]

OBJECTIVE

An overview of electronic fetal monitoring methods (EFM), and an analysis of their physical and technical limits.

DESIGN

A review article.

SETTING

Department of Gynecology and Obstetrics Jessenius Faculty of Medicine in Martin, Comenius University in Bratislava, Slovak Republic.

METHODS

An analysis of the literature using database search engines PubMed, and SCOPE in the years 2000 - 2013 in field of diagnostic methods of fetal status in utero.

RESULTS

The essential aim of modern perinatology is the birth of a live and healthy newborn. This aim is strongly related to the abilities of the diagnostic methods to evaluate the intrauterine fetal status and with the professional skills of obstetricians to analyze these methods accurately. Nowadays, EFM is exposed to criticism, in spite of its widespread use. It is associated with some degree of failure in terms of an over-evaluation and under-evaluation. An over-evaluation of results can lead to unnecessary, often surgical, intervention. An under-evaluation of results can lead to an adverse fetal outcome with a neurologic handicap or intrauterine death. The long-term efforts currently underway to improve the reliability of EFM still remain to show any great progress.

KEYWORDS

cardiotocography, intermittent auscultation, pulse oximetry, ST analysis, fetal electrocardiography.