A muscle-powered energy delivery system and means for chronic in vivo testing

1999 ◽  
Vol 86 (6) ◽  
pp. 2106-2114 ◽  
Author(s):  
Dennis R. Trumble ◽  
James A. Magovern
Keyword(s):  
In Vitro Tests ◽  
Access Port ◽  
Wide Range ◽  
Piston Displacement ◽  
In Vivo Testing ◽  
Implant Testing

Electrically stimulated skeletal muscle represents a potentially unlimited source of energy for the actuation of motor prostheses. Devices to harvest and deliver contractile power have proven mechanically feasible, but long-term efficacy has not been demonstrated. This report describes recent refinements in muscle energy converter (MEC) design and details the development of an implantable afterload chamber (IAC) designed to facilitate implant testing. The IAC comprises a fluid-filled bladder housed within a titanium cylinder that connects directly to the MEC. A vascular access port allows percutaneous measurement and adjustment of air pressure within the housing and provides a means both to monitor MEC function and to control hydraulic loading conditions. Data from in vitro tests show that IAC pressure mirrors changes in MEC-piston displacement over a wide range of actuation speeds and stroke lengths. Stroke lengths and actuation forces calculated from IAC pressure readings were typically found to be within 5% of measured values. This testing scheme may yield important information in regard to the ability to harness energy from in situ muscle over prolonged periods.

Correlation between magnesium and potassium contents in muscle: role of Na(+)-K+ pump

1993 ◽  
Vol 264 (2) ◽  
pp. C457-C463 ◽  
Author(s):  
I. Dorup ◽  
T. Clausen
Keyword(s):  
Extensor Digitorum Longus ◽  
Extensor Digitorum ◽  
Deficient Diet ◽  
Young Rats ◽  
Wide Range ◽  
86Rb Influx

In young rats fed a Mg(2+)-deficient diet for 3 wk, Mg2+ and K+ contents in soleus and extensor digitorum longus muscles were significantly reduced and closely correlated. In isolated soleus muscles, Mg2+ depletion induced an even more pronounced loss of K+, and Mg2+ and K+ contents were correlated over a wide range (r = 0.95, P < 0.001). Extracellular Mg2+ (0-1.2 mM) caused no change in total or ouabain-suppressible 86Rb influx. After long-term incubation in Ca(2+)-Mg(2+)-free buffer with EDTA and EGTA, cellular Mg2+ and K+ contents were reduced by 35 and 15%, respectively, without any reduction in ATP and total or ouabain-suppressible 86Rb influx. In Mg(2+)-depleted muscles 42K efflux was increased by up to 42%, and repletion with Mg2+ produced a graded decrease. We conclude that Mg2+ and K+ contents are closely correlated in muscles Mg2+ depleted in vivo or in vitro and that neither extracellular nor moderate intracellular Mg2+ depletion affects total or Na(+)-K+ pump-mediated K+ influx. The reduced K+ content may rather be related to increased K+ efflux from the muscles.

Minimum intracellular PO2 for maximum cytochrome turnover in red muscle in situ

1987 ◽  
Vol 252 (5) ◽  
pp. H906-H915 ◽  
Author(s):  
T. E. Gayeski ◽  
R. J. Connett ◽  
C. R. Honig
Keyword(s):  
Energy Demand ◽  
Concentration Ratio ◽  
Probability Distributions ◽  
Michaelis Constant ◽  
Cytochrome Aa3 ◽  
Wide Range ◽  
Red Muscle

Probability distributions of myoglobin (Mb) saturation and intracellular PO2 were determined with subcellular spatial resolution in dog gracilis muscles during steady-state twitch contraction at 5-100% of maximal rate of O2 consumption (VO2). Calculations (Clark, A., and P. A.A. Clark. Biophys. J. 48: 931-938, 1985) and measurements (Gayeski, T. E. J., and C. R. Honig. Adv. Exp. Med. Biol. 200: 487-494, 1986) indicate that the PO2 in equilibrium with Mb is virtually identical to the PO2 at cytochrome aa3. Median intracellular PO2 and PO2 in the lower tails of probability distributions were poorly correlated with VO2. The variability of cell PO2 was greatly diminished when median PO2 was less than the PO2 for half saturation of MB, since Mb acts as a PO2 buffer. The lower tails of PO2 distributions contained almost no anoxic loci even when median PO2 was less than 1 Torr. VO2 was well correlated with the concentration ratio of phosphocreatine to free creatine (PCr/Crf) over a wide range of PO2. PO2 greater than or equal to 0.5 Torr supported maximal VO2 and energy demand. We conclude that 1) the mechanism of action of cytochrome aa3 is the same in red muscle in vivo as in mitochondria in vitro, and 2) an upper bound on the apparent Michaelis constant for maximal VO2 of red muscle is approximately 0.06 Torr.

The Primary Investigation on Biological Effect of Mesoporous Bioactive Glass In Vivo

2013 ◽  
Vol 750-752 ◽  
pp. 1651-1655
Author(s):  
Bai Yan Sui ◽  
Cheng Tie Wu ◽  
Jiao Sun
Keyword(s):  
Bioactive Glass ◽  
Biological Effect ◽  
Degradation Products ◽  
Long Term Effect ◽  
Liver And Kidney ◽  
Mesoporous Bioactive Glass

Mesoporous bioactive glass (MBG) has superior bioactivity and degradation than non-mesoporous bioactive glass (BG) in vitro. But the biological effect of MBG in vivo is still unknown. In this study, MBG powders with 20μm were implanted into the femoral condyles in SD rats. BG powders with 20μm were used as a control. The local degradation and osteogenesis were observed at 1 week and 4 weeks after implantation, and the systemic toxicity of the degradation products were also evaluated simultaneously. The results revealed MBG powders had the faster rate of degradation and better osteogenesis effect than BG powders at 4 weeks, although the most of material still remained in situ. Histopathological analyses indicated the degradation products did not have any damage to major organs such as liver and kidney. In conclusion, this preliminary study demonstrated that MBG powders have more excellent biological effect at 4 weeks than that of BG in vivo. However the long-term effect needs to be confirmed.

In vitro techniques to replace in vivo methods for estimating amino acid supply

1998 ◽  
Vol 22 ◽  
pp. 131-144 ◽  
Author(s):  
T. Hvelplund ◽  
M. R. Weisbjerg
Keyword(s):  
Protein Synthesis ◽  
Alternative Methods ◽  
Microbial Protein ◽  
Microbial Protein Synthesis ◽  
Wide Range ◽  
Intestinal Digestibility ◽  
Protein Degradability

Abstract Expressing the protein value of a food involves measurements of several of its characteristics. Many in vivo studies have shown, that the protein degradability in the rumen varies substantially both between and within foods and therefore estimation of protein degradability in the rumen is an important task in protein evaluation. The most common method used has been the in situ (in sacco, nylon bag) method but many in vitro methods have been introduced and are based on use of either buffer solubility, chemical methods, rumen fluid or enzymes. None of these in vitro methods has proven to be of general use. In further development of in vitro methods as well as the in situ method a major problem is lack of a set of samples with a ‘true’ in vivo degradability which can be used for calibration of alternative methods. Microbial protein synthesis in the rumen has to be related to food characteristics which can be analysed easily. In vitro methods which can predict organic matter digestibility in foods are available and can be used to predict microbial protein synthesis in the rumen. Intestinal digestibility of undegraded dietary protein varies substantially both between and within foods and easy methods to estimate intestinal digestibility are therefore essential. The mobile bag method is easy to use and seems to give reliable results on most foods but requires access to duodenal cannulated animals which prevents this method from being routine. Alternative in vitro methods have been developed but further research is required for validation of these methods on a wide range of foods before they can be accepted for general use.

scholarly journals Survival of and In Situ Gene Expression by Vibrio vulnificus at Varying Salinities in Estuarine Environments

2007 ◽  
Vol 74 (1) ◽  
pp. 182-187 ◽  
Author(s):  
Melissa K. Jones ◽  
Elizabeth Warner ◽  
James D. Oliver
Keyword(s):  
Gene Expression ◽  
Vibrio Vulnificus ◽  
Natural Habitat ◽  
Term Survival ◽  
Long Term Survival ◽  
Wide Range ◽  
Opportunistic Human Pathogen

ABSTRACT The opportunistic human pathogen Vibrio vulnificus survives in a wide range of ecological environments, which demonstrates its ability to adapt to highly variable conditions. Survival and gene expression under various conditions have been extensively studied in vitro; however, little work has been done to evaluate this bacterium in its natural habitat. Therefore, this study monitored the long-term survival of V. vulnificus in situ and simultaneously evaluated the expression of stress (rpoS, relA, hfq, and groEL) and putative virulence (vvpE, smcR, viuB, and trkA) genes at estuarine sites of varying salinity. Additionally, the survival and gene expression of an rpoS and an oxyR mutant were examined under the same conditions. Differences between the sampling sites in the long-term survival of any strain were not seen. However, differences were seen in the expression of viuB, trkA, and relA but our findings differed from what has been previously shown in vitro. These results also routinely demonstrated that genes required for survival under in vitro stress or host conditions are not necessarily required for survival in the water column. Overall, this study highlights the need for further in situ evaluation of this bacterium in order to gain a true understanding of its ecology and how it relates to its natural habitat.

scholarly journals Predicting and Testing Bioavailability of Magnesium Supplements

Nutrients ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1663 ◽  
Author(s):  
Laura Blancquaert ◽  
Chris Vervaet ◽  
Wim Derave
Keyword(s):  
Serum Magnesium ◽  
Area Under The Curve ◽  
In Vitro Tests ◽  
In Vitro Test ◽  
Beneficial Effects ◽  
Dissolution Tests ◽  
Acute Ingestion ◽  
In Vivo Testing

Despite the presumption of the beneficial effects of magnesium supplementation, little is known about the pharmacokinetics of different magnesium formulations. We aimed to investigate the value of two in vitro approaches to predict bioavailability of magnesium and to validate this in subsequent in vivo testing. In vitro assessment of 15 commercially available magnesium formulations was performed by means of a Simulator of the Human Intestinal Microbial Ecosystem (SHIME®) and by dissolution tests. Two magnesium formulations with contrasting bioavailability prediction from both in vitro tests (best vs. worst) were selected for in vivo testing in 30 subjects. In vivo bioavailability was compared following one acute ingestion by monitoring blood magnesium concentrations up to 6 h following intake. The in vitro tests showed a very wide variation in absorption and dissolution of the 15 magnesium products. In the in vivo testing, a significant different serum magnesium absorption profile was found up to 4 h following supplement ingestion for the two supplements with opposing in vitro test results. Moreover, maximal serum magnesium increase and total area under the curve were significantly different for both supplements (+6.2% vs. +4.6% and 6.87 vs. 0.31 mM.min, respectively). Collectively, poor bioaccessibility and bioavailability in the SHIME model clearly translated into poor dissolution and poor bioavailability in vivo. This provides a valid methodology for the prediction of in vivo bioavailability and effectiveness of micronutrients by specific in vitro approaches.

Regulatory Perspective on in Vitro Assays as Predictors of Phototoxicity and Photo Co-Carcinogenicity

1998 ◽  
Vol 17 (5) ◽  
pp. 571-575 ◽  
Author(s):  
Amy L. Ellis
Keyword(s):  
Mammalian Cells ◽  
Hairless Mouse ◽  
In Vitro Assays ◽  
In Vitro Tests ◽  
Drug Products ◽  
Drug Classes ◽  
Wide Range ◽  
Regulatory Perspective

Drugs from a variety of chemical classes used for a wide range of therapeutic indications can be photosensitizers in humans. Several drugs are phototoxic in animal models as well; there are no nonclinical data for many. In vitro tests have been developed as predictors of phototoxicity and although they have been used as screens, none have replaced the in vivo tests done in rodents (usually mice or guinea pigs) since these have been good predictors of clinical phototoxicity. Some phototoxic drug classes are co-carcinogens with ultraviolet radiation (UVA and/or UVB) in hairless mice, specifically psoralens, retinoids, and fluo-roquinolones. Treatment with 8-methoxypsoralen and ultraviolet A radiation for psoriasis is also carcinogenic in humans. It has been suggested that in vitro photogenotoxicity assays using microorganisms or mammalian cells may be predictive of photo co-carcinogenicity. Some attractions of these in vitro assays, compared to the hairless mouse photo co-carcinogenicity assay, are their generally shorter duration and lower cost as well as reducing the number of animals used in research. Currently, personnel at the Food and Drug Administration (FDA) are examining the available data on phototoxicity, photogenotoxicity, and photo co-carcinogenicity to determine how this information can best be used toregulate and label drug products, and considering which assays should be recommended under specific circumstances.

scholarly journals Testing the antimicrobial activity of essential oils

2011 ◽  
pp. 71-74
Author(s):  
Adela Frankova ◽  
Pavel Kloucek ◽  
Jakub Smid ◽  
Lenka Nedorostova
Keyword(s):  
Antimicrobial Activity ◽  
Essential Oils ◽  
Vapor Phase ◽  
Salmonella Enteritidis ◽  
Food Preservatives ◽  
Fast Screening ◽  
Wide Range ◽  
In Vivo Testing

The vapor phase of some essential oils proved to have antimicrobial activity. Utilization of the vapor phase of Eos is presently understood as one of the possible alternatives to synthetic food preservatives which could be used in the future. However, testing the vapor phase of EOs against microorganisms causing food-borne diseases (e.g. Salmonella enteritidis or Staphylococcus aureus) or food spoilage is relatively new. Consequently, due to the large number of known EOs, research on their antimicrobial activity is still largely in the phase of in vitro rather than in vivo testing. Moreover, no standard and reliable method for fast screening of a wide range of samples exists. Thus, the aim of this study is to show results concerning tests of the antimicrobial activity of EOs against S. enteritidis or S. aureus, which were conducted by two modifications of the disc volatilization method we developed. The lately developed method has the potential to become widely used for fast screening of EO antimicrobial activity in the vapor phase.

scholarly journals Long-term evolution of antibiotic persistence in P. aeruginosa lung infections

2021 ◽  
Author(s):  
Melanie Ghoul ◽  
Sandra B Andersen ◽  
Helle Krogh Johansen ◽  
Lars Jelsbak ◽  
Søren Molin ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Resistance Mechanisms ◽  
Term Evolution ◽  
Bacterial Clone ◽  
Evolution Of Resistance ◽  
Lung Infections

Pathogenic bacteria respond to antibiotic pressure with the evolution of resistance but survival can also depend on their ability to tolerate antibiotic treatment, known as persistence. While a variety of resistance mechanisms and underlying genetics are well characterised in vitro and in vivo, the evolution of persistence, and how it interacts with resistance in situ is less well understood. We assayed for persistence and resistance with three clinically relevant antibiotics: meropenem, ciprofloxacin and tobramycin, in isolates of Pseudomonas aeruginosa from chronic cystic fibrosis lung infections spanning up to forty years of evolution. We find evidence that persistence is under positive selection in the lung and that it can particularly act as an evolutionary stepping stone to resistance. However, this pattern is not universal and depends on the bacterial clone type and antibiotic used, indicating an important role for antibiotic mode of action.

scholarly journals Acellular Small-Diameter Tissue-Engineered Vascular Grafts

2019 ◽  
Vol 9 (14) ◽  
pp. 2864 ◽  
Author(s):  
Zhen Li ◽  
Xinda Li ◽  
Tao Xu ◽  
Lei Zhang
Keyword(s):  
Effective Means ◽  
Vascular Grafts ◽  
Small Diameter ◽  
Test Results ◽  
In Vivo Test ◽  
Current State

Tissue-engineered vascular grafts (TEVGs) are considered one of the most effective means of fabricating vascular grafts. However, for small-diameter TEVGs, there are ongoing issues regarding long-term patency and limitations related to long-term in vitro culture and immune reactions. The use of acellular TEVG is a more convincing method, which can achieve in situ blood vessel regeneration and better meet clinical needs. This review focuses on the current state of acellular TEVGs based on scaffolds and gives a summary of the methodologies and in vitro/in vivo test results related to acellular TEVGs obtained in recent years. Various strategies for improving the properties of acellular TEVGs are also discussed.

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