Mechanical Behavior and Failure Analysis of Prosthetic Retaining Screws after Long-term Use In Vivo. Part 3: Preload and Tensile Fracture Load Testing

Introduction In a previous paper, the authors investigated the mechanical behavior of several commercial polyurethane peripherally inserted central venous catheters (PICCs) in their ‘brand new’ condition. The present study represents a second step of the research activity and aims to investigate possible modifications of the PICC mechanical response, induced by long-term conservation in in vivo-like conditions, particularly when used to introduce oncologic drugs. Methods Eight 5 Fr single-lumen catheters from as many different vendors, were examined. Several specimens were cut from each of them and kept in a bath at 37°C for 1, 2, 3 and 6 months. Two fluids were used to simulate in vivo-like conditions, i.e. ethanol and Ringer-lactate solutions, the first being chosen in order to reproduce a typical chemical environment of oncologic drugs. The test plan included swelling analyses, uniaxial tensile tests and dynamic mechanical thermal analysis (DMTA). Results and conclusions All tested samples were chemically and mechanically stable in the studied conditions, as no significant weight variation was observed even after six months of immersion in ethanol solution. Uniaxial tensile tests confirmed such a response. For each PICC, very similar curves were obtained from samples tested after different immersion durations in the two fluid solutions, particularly for strains lower than 10%.

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Long term in vivo reactions to PTFE and polyester in the cardiovascular system - what will be the fate of septal defect occlusion devices?

The Thoracic and Cardiovascular Surgeon ◽

10.1055/s-0034-1367355 ◽

2014 ◽

Vol 62 (S 01) ◽

Author(s):

M. Sigler ◽

S. Huell ◽

R. Foth ◽

W. Ruschewski ◽

T. Tirilomis ◽

...

Keyword(s):

Cardiovascular System ◽

Septal Defect

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The depressing (negative) effect of oestradiol benzoate on the in vitro secretion of LH and FSH by the pituitary gland of the LRH-pretreated long-term ovariectomized rat changes into the augmentative (positive) effect after discontinuation of the LRH-pretreatment

Acta Endocrinologica ◽

10.1530/acta.0.1100329 ◽

1985 ◽

Vol 110 (3) ◽

pp. 329-337 ◽

Cited By ~ 2

Author(s):

G. A. Schuiling ◽

H. Moes ◽

T. R. Koiter

Keyword(s):

Depressing Effect ◽

Ovx Rats ◽

Gonadotrophin Secretion ◽

Oestradiol Benzoate ◽

Negative Effect ◽

Positive Effect ◽

Perifusion System

Abstract. The effect of pretreatment in vivo with oestradiol benzoate on in vitro secretion of LH and FSH was studied in long-term ovariectomized (OVX) rats both at the end of a 5-day continuous in vivo pretreatment with LRH and 4-days after cessation of such LRH pretreatment. Rats were on day 0 sc implanted with osmotic minipumps which released LRH at the rate of 250 ng/h. Control rats were implanted with a piece of silicone elastomer with the dimensions of a minipump. On days 2 and 4 the rats were injected with either 3 μg EB or with oil. On day 5 part of the rats were decapitated and the in vitro autonomous (i.e. non-LRH-stimulated) and 'supra-maximally' LRHstimulated release of LH and FSH was studied using a perifusion system. From other rats the minipumps were removed on day 5 and perifusion was performed on day 9. On the 5th day of the in vivo LRH pretreatment the pituitary LH/FSH stores were partially depleted; the pituitaries of the EB-treated rats more so than those of the oil-injected rats. EB alone had no significant effect on the content of the pituitary LH- and FSH stores. On day 9, i.e. 4 days after removal of the minipumps, the pituitary LH and FSH contents had increased in both the oil- and the EB injected rats, but had not yet recovered to control values. In rats not subjected to the 5-days pretreatment with LRH EB had a positive effect on the supra-maximally LRH-stimulated secretion of LH and FSH as well as on the non-stimulated secretion of LH. EB had no effect on the non-stimulated secretion of FSH. After 5 days of in vivo pretreatment with LRH only, the in vitro non-stimulated and supra-maximally LRH-stimulated secretion of both LH and FSH were strongly impaired, the effect correlating well with the LRH-induced depletion of the pituitary LH/FSH stores. In such LRH-pretreated rats EB had on day 5 a negative effect on the (already depressed) LRH-stimulated secretion of LH (not on that of FSH). EB had no effect on the non-stimulated LH/FSH secretion. It could be demonstrated that the negative effect of the combined LRH/EB pretreatment was mainly due to the depressing effect of this treatment on the pituitary LH and FSH stores: the effect of oestradiol on the pituitary LRH-responsiveness (release as related to pituitary gonadotrophin content) remained positive. In LRH-pretreated rats, however, this positive effect of EB was smaller than in rats not pretreated with LRH. Four days after removal of the minipumps there was again a positive effect of EB on the LRH-stimulated secretion of LH and FSH as well as on the non-stimulated secretion of LH. The positive effect of EB on the pituitary LRH-responsiveness was as strong as in rats which had not been exposed to exogenous LRH. The non-stimulated secretion of FSH was again not affected by EB. The results demonstrate that the effect of EB on the oestrogen-sensitive components of gonadotrophin secretion consists of two components: an effect on the pituitary LRH-responsiveness proper, and an effect on the pituitary LH/FSH stores. The magnitude of the effect of EB on the LRH-responsiveness is LRH dependent: it is very weak (almost zero) in LRH-pretreated rats, but strong in rats not exposed to LRH as well as in rats of which the LRH-pretreatment was stopped 4 days previously. Similarly, the effect of EB on the pituitary LH and FSH stores is LRH-dependent: in the absence of LRH, EB has no influence on the contents of these stores, but EB can potentiate the depleting effect of LRH on the LH/FSH-stores. Also this effect disappear after cessation of the LRH-pretreatment.

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Enhanced Stability and Controlled Delivery of MOF Encapsulated Vaccines and Their Immunogenic Response In Vivo

10.26434/chemrxiv.7335122.v1 ◽

2018 ◽

Author(s):

Michael Luzuriaga ◽

Raymond P. Welch ◽

Madushani Dharmawardana ◽

Candace Benjamin ◽

Shaobo Li ◽

...

Keyword(s):

Viral Vector ◽

Controlled Delivery ◽

Conformational Structure ◽

Spectroscopy Analysis ◽

Zeolitic Imidazolate Framework ◽

Structural Conformation ◽

Depth Study ◽

Viral Nanoparticle

<div><div><div><p>Vaccines have an innate tendency to lose their structural conformation upon environmental and chemical stressors. A loss in conformation reduces the therapeutic ability to prevent the spread of a pathogen. Herein, we report an in-depth study of zeolitic imidazolate framework-8 (ZIF-8) and its ability to provide protection for a model viral vector against dena- turing conditions. The immunoassay and spectroscopy analysis together demonstrate enhanced thermal and chemical stability to the conformational structure of the encapsulated viral nanoparticle. The long-term biological activity of this virus-ZIF composite was investigated in animal models to further elucidate the integrity of the encapsulated virus, the bio-safety, and immunogenicity of the overall composite. Additionally, histological analysis found no observable tissue damage in the skin or vital organs in mice, following multiple subcutaneous administrations. This study shows that ZIF-based protein composites are strong candidates for improved preservation of proteinaceous drugs, are biocompatible, and capable of controlling the release and adsorption of drugs in vivo.</p></div></div></div>

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THE ROLE OF POLYETHYLENIMINE IN ENHANCING PERFORMANCE OF GLUTAMATE BIOSENSORS

Journal of Medicine and Pharmacy ◽

10.34071/jmp.2018.3.6 ◽

2018 ◽

Vol 8 (3) ◽

pp. 36-41

Author(s):

Diep Do Thi Hong ◽

Duong Le Phuoc ◽

Hoai Nguyen Thi ◽

Serra Pier Andrea ◽

Rocchitta Gaia

Keyword(s):

First Generation ◽

Good Reproducibility ◽

Complex Matrices ◽

Long Term Stability ◽

In Vitro Characterization ◽

Glutamate Oxidase

Background: The first biosensor was constructed more than fifty years ago. It was composed of the biorecognition element and transducer. The first-generation enzyme biosensors play important role in monitoring neurotransmitter and determine small quantities of substances in complex matrices of the samples Glutamate is important biochemicals involved in energetic metabolism and neurotransmission. Therefore, biosensors requires the development a new approach exhibiting high sensibility, good reproducibility and longterm stability. The first-generation enzyme biosensors play important role in monitoring neurotransmitter and determine small quantities of substances in complex matrices of the samples. The aims of this work: To find out which concentration of polyethylenimine (PEI) exhibiting the most high sensibility, good reproducibility and long-term stability. Methods: We designed and developed glutamate biosensor using different concentration of PEI ranging from 0% to 5% at Day 1 and Day 8. Results: After Glutamate biosensors in-vitro characterization, several PEI concentrations, ranging from 0.5% to 1% seem to be the best in terms of VMAX, the KM; while PEI content ranging from 0.5% to 1% resulted stable, PEI 1% displayed an excellent stability. Conclusions: In the result, PEI 1% perfomed high sensibility, good stability and blocking interference. Furthermore, we expect to develop and characterize an implantable biosensor capable of detecting glutamate, glucose in vivo. Key words: Glutamate biosensors, PEi (Polyethylenimine) enhances glutamate oxidase, glutamate oxidase biosensors

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Faculty Opinions recommendation of Activity-induced long-term potentiation of excitatory synapses in developing zebrafish retina in vivo.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.717956765.793461346 ◽

2012 ◽

Author(s):

David Zenisek ◽

Christina Joselevitch

Keyword(s):

Long Term Potentiation ◽

Excitatory Synapses ◽

Term Potentiation

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Brivaracetam Prevents the Over-expression of Synaptic Vesicle Protein 2A and Rescues the Deficits of Hippocampal Long-term Potentiation In Vivo in Chronic Temporal Lobe Epilepsy Rats

Current Neurovascular Research ◽

10.2174/1567202617666200514114917 ◽

2020 ◽

Vol 17 (4) ◽

pp. 354-360 ◽

Cited By ~ 1

Author(s):

Yu-Xing Ge ◽

Ying-Ying Lin ◽

Qian-Qian Bi ◽

Yu-Juan Chen

Keyword(s):

Synaptic Plasticity ◽

Temporal Lobe Epilepsy ◽

Synaptic Vesicle ◽

Long Term Potentiation ◽

Synaptic Dysfunction ◽

Over Expression ◽

Term Potentiation ◽

Synaptic Vesicle Protein 2A

Background: Patients with temporal lobe epilepsy (TLE) usually suffer from cognitive deficits and recurrent seizures. Brivaracetam (BRV) is a novel anti-epileptic drug (AEDs) recently used for the treatment of partial seizures with or without secondary generalization. Different from other AEDs, BRV has some favorable properties on synaptic plasticity. However, the underlying mechanisms remain elusive. Objective: The aim of this study was to explore the neuroprotective mechanism of BRV on synaptic plasticity in experimental TLE rats. Methods: The effect of chronic treatment with BRV (10 mg/kg) was assessed on Pilocarpine induced TLE model through measurement of the field excitatory postsynaptic potentials (fEPSPs) in vivo. Differentially expressed synaptic vesicle protein 2A (SV2A) were identified with immunoblot. Then, fast phosphorylation of synaptosomal-associated protein 25 (SNAP-25) during long-term potentiation (LTP) induction was performed to investigate the potential roles of BRV on synaptic plasticity in the TLE model. Results: An increased level of SV2A accompanied by a depressed LTP in the hippocampus was shown in epileptic rats. Furthermore, BRV treatment continued for more than 30 days improved the over-expression of SV2A and reversed the synaptic dysfunction in epileptic rats. Additionally, BRV treatment alleviates the abnormal SNAP-25 phosphorylation at Ser187 during LTP induction in epileptic ones, which is relevant to the modulation of synaptic vesicles exocytosis and voltagegated calcium channels. Conclusion: BRV treatment ameliorated the over-expression of SV2A in the hippocampus and rescued the synaptic dysfunction in epileptic rats. These results identify the neuroprotective effect of BRV on TLE model.

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