scholarly journals Activity of an Antimicrobial Hydrocephalus Shunt Catheter against Propionibacterium acnes

2010 ◽  
Vol 54 (12) ◽  
pp. 5082-5085 ◽  
Author(s):  
Roger Bayston ◽  
Litza Vera ◽  
Waheed Ashraf
Keyword(s):  
Propionibacterium Acnes ◽  
Major Complication ◽  
Shunt Infection ◽  
Constant Flow ◽  
Flow Conditions ◽  
Attached Bacteria ◽  
Methods Of Evaluation ◽  
Fluid Penetration ◽  
Emergence Of Resistance ◽  
Skin Bacterium

ABSTRACT Shunt infection is a major complication affecting approximately 10% of procedures. Propionibacterium acnes, an anaerobic skin bacterium, is increasingly recognized as a shunt pathogen, causing up to 14% of infections. Though susceptible to penicillin and cephalosporins, P. acnes shunt infections are not preventable by means of perioperative prophylaxis, due to poor cerebrospinal fluid penetration. Antimicrobial shunts with activity against staphylococci are available, but their activity against P. acnes is unknown, and the study was designed to determine this. Three methods of evaluation were used in order to determine the emergence of resistance when exposure is to high inocula for long periods, the time taken to kill 100% of the bacteria attached to the shunt, and the duration of activity under constant flow conditions with repeated bacterial challenge. Despite repeated exposure to high bacterial inocula over 70 days, no resistance was seen. The time taken to kill all attached bacteria, 96 h, was twice that taken to kill attached staphylococci. Nevertheless, under constant flow conditions with repeated challenges, the antimicrobial catheters resisted colonization by P. acnes for 56 days. Using tests that were designed to be clinically predictive when done together, the results suggest that the antimicrobial catheters will be able to prevent colonization of hydrocephalus shunts by P. acnes.

scholarly journals Fabrication of a Urea Biosensor for Real-Time Dynamic Fluid Measurement

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2607 ◽  
Author(s):  
Kyunghee Kim ◽  
Jeongeun Lee ◽  
Bo Moon ◽  
Ye Seo ◽  
Chan Park ◽  
...  
Keyword(s):  
Real Time ◽  
Urea Concentration ◽  
Electrochemical Sensing ◽  
Constant Flow ◽  
Flow Conditions ◽  
Time Dynamic ◽  
Constant Flow Rate ◽  
Linear Current ◽  
Clinically Significant ◽  
Significant Concentration

In this study, a portable urea sensor that monitors the urea concentration in flow conditions was fabricated. We propose an electrochemical sensor that continually measures the urea concentration of samples flowing through it at a constant flow rate in real time. For the electrochemical sensing, a porous silk fibroin membrane with immobilized urease was mounted in a polydimethylsiloxane (PDMS) sensor housing. The fabricated urea sensor elicited linear current–concentration characteristics in the clinically significant concentration range (0.1–20 mM) based on peritoneal dialysis. The sensor maintained the linear current–concentration characteristics during operation in flow conditions.

Role of oxygen in autoregulation of blood flow in isolated vessels

1964 ◽  
Vol 206 (5) ◽  
pp. 951-954 ◽  
Author(s):  
Oliver Carrier ◽  
James R. Walker ◽  
Arthur C. Guyton
Keyword(s):  
Blood Flow ◽  
Normal Level ◽  
Constant Pressure ◽  
Constant Flow ◽  
Average Increase ◽  
Flow Conditions ◽  
Low Oxygen ◽  
Local Blood Flow ◽  
Initial Flow

The role of oxygen in control of local blood flow was investigated in isolated arterial segments 1 cm in length and 0.5–1.0 mm in diameter by perfusion with blood of various Po2 levels. A decrease in vascular resistance always occurred when the Po2 was lowered and an increase occurred when it was raised. In 20 vessels, using constant-pressure perfusion, an average increase in conductance of 2.38 times normal level was obtained when the Po2 was lowered from 100 to 30 mm Hg. When this datum was plotted according to initial flow, the smaller vessels gave the greatest response to low oxygen (2.73 times normal; sem ± 0.15), whereas the largest gave the least (1.76 times normal; sem ± 0.10). Forty-three vessels perfused under constant-flow conditions gave results which were consistent with and confirmed the constant-pressure results. In all of these experiments pH, Pco2, and temperature were monitored and kept at physiological levels. The results indicate that oxygen could well be a factor in the autoregulation of blood flow.

N omega-nitro-L-arginine selectively inhibits vasodilator responses to acetylcholine and bradykinin in cats

1991 ◽  
Vol 260 (3) ◽  
pp. H1025-H1029 ◽  
Author(s):  
J. A. Bellan ◽  
R. K. Minkes ◽  
D. B. McNamara ◽  
P. J. Kadowitz
Keyword(s):  
Receptor Agonist ◽  
Vascular Tone ◽  
Nitroso Compound ◽  
Constant Flow ◽  
Flow Conditions ◽  
Relaxing Factor ◽  
Thromboxane Receptor ◽  
Vascular Bed ◽  
Resistance Vessels ◽  
Regulation Of Vascular Tone

The effects of N omega-nitro-L-arginine (nitroarginine), an inhibitor of endothelium-dependent relaxing factor (EDRF) production, on vascular tone and responses to vasodilator and vasoconstrictor agents were investigated in the hindquarters vascular bed of the cat. Under constant flow conditions, infusion of nitroarginine into the hindquarters vascular bed caused a significant increase in systemic arterial and hindquarters perfusion pressures. During infusion of nitroarginine, hindquarters vasodilator responses to acetylcholine and bradykinin were reduced significantly whereas vasodilator responses to isoproterenol, PGE1, nitroprusside, and 8-bromoguanosine 3',5'-cyclic monophosphate were not altered. Infusion of nitroarginine significantly enhanced vasoconstrictor responses to the thromboxane receptor agonist U 46619 and to phenylephrine. The results of these studies are consistent with the hypotheses that EDRF production may involve the formation of nitric oxide or a nitroso compound from L-arginine, and that EDRF production may play a role in the regulation of vascular tone and in the mediation of responses to the endothelium-dependent vasodilators, acetylcholine and bradykinin, in resistance vessels in the hindquarters. These data support the concept that EDRF is very likely an endogenous nitrovasodilator derived from L-arginine in the hindquarters vascular bed of the cat.

Comparison of responses to sarafotoxins 6a and 6c in pulmonary and systemic vascular beds

1992 ◽  
Vol 262 (3) ◽  
pp. H852-H861
Author(s):  
R. K. Minkes ◽  
J. A. Bellan ◽  
T. R. Higuera ◽  
P. J. Kadowitz
Keyword(s):  
Arterial Pressure ◽  
Vascular Resistance ◽  
Perfusion Pressure ◽  
Venous Pressure ◽  
Constant Flow ◽  
Flow Conditions ◽  
Arterial Perfusion ◽  
Intravenous Injections ◽  
Autonomic Reflexes ◽  
Pressure Changes

Cardiovascular and pulmonary responses to sarafotoxin (S) 6a and S6c were investigated in the anesthetized cat. Intravenous injections of the peptides in doses of 0.1-1.0 nmol/kg caused decreases or biphasic changes in arterial pressure (AP) and increases in central venous pressure, pulmonary arterial pressure (PAP), and cardiac output (CO). Secondary decreases in CO were observed in response to higher doses, and biphasic changes in systemic (SVR) and pulmonary (PVR) vascular resistances were observed. Under constant-flow conditions, the peptides only increased pulmonary lobar arterial perfusion pressure and lobar vascular resistance. AP responses to S6a, S6c, endothelin (ET)-1, ET-2, vasoactive intestinal contractor (VIC), and Lys7-ET-1 were similar, whereas AP responses to S6b and ET-3 were similar. S6a, S6b, S6c, ET-1, ET-2, ET-3, VIC, Lys7-ET-1, and big ET-1 increased PAP. S6a and S6c increased distal aortic and superior mesenteric arterial (SMA) blood flow and caused biphasic changes at the highest doses. Under constant-flow conditions, S6a and S6c produced dose-dependent biphasic changes in hindquarters perfusion pressure. Changes in SVR and PVR in response to the peptide were not affected by hexamethonium, glyburide, or meclofenamate, indicating that responses are independent of autonomic reflexes, activation of ATP-regulated K+ channels, or release of cyclooxygenase products. In contrast, N-nitro-L-arginine methyl ester decreased hindquarters vasodilator response to S6a and S6c. The present data show that S6a and S6c produce both vasodilation and vasoconstriction in the systemic vascular bed and increase lobar vascular resistance and that hindquarters vasodilator responses are mediated, in part, by the release of endothelium-derived relaxing factor.

Comparative responses to endothelin-2 and sarafotoxin 6b in the pulmonary vascular bed of the cat

1991 ◽  
Vol 69 (2) ◽  
pp. 211-214 ◽  
Author(s):  
R. K. Minkes ◽  
B. D. Nossaman ◽  
P. Kvamme ◽  
P. J. Kadowitz
Keyword(s):  
Arterial Pressure ◽  
Systemic Arterial Pressure ◽  
Significant Activity ◽  
Constant Flow ◽  
Carboxy Terminus ◽  
Flow Conditions ◽  
Vascular Bed ◽  
Natural Flow ◽  
Pulmonary Arterial ◽  
Pulmonary Vascular Bed

Pulmonary vascular responses to endothelin-2 and sarafotoxin 6b were investigated in the feline pulmonary vascular bed under natural flow and constant flow conditions. Injections of endothelin-2 and sarafotoxin 6b in a dose of 0.3 nmol/kg iv increased pulmonary arterial and left atrial pressures and cardiac output, and caused a biphasic change in calculated pulmonary vascular resistance. Endothelin-2 caused a biphasic change in systemic arterial pressure, while sarafotoxin 6b only decreased arterial pressure. Under constant flow conditions in the intact-chest cat, injections of endothelin-2 and sarafotoxin 6b in doses of 0.1–1 nmol into the perfused lobar artery increased lobar arterial pressure in a dose-related manner but were less potent than the thromboxane A2 mimic, U46619. An ET analog with only the Cys1–Cys15 disulfide bond and an amidated carboxy terminus had no significant activity in the pulmonary vascular bed. The present data show that endothelin-2 and sarafotoxin 6b have significant vasoconstrictor activity in the pulmonary vascular bed of the cat.Key words: pulmonary circulation, endothelin-2, sarafotoxin 6b.

Analysis of responses to kallidin, DABK, and DAK in feline hindlimb vascular bed

1995 ◽  
Vol 269 (6) ◽  
pp. H2057-H2064
Author(s):  
J. A. Santiago ◽  
E. A. Garrison ◽  
H. C. Champion ◽  
R. E. Smith ◽  
O. Del Rio ◽  
...  
Keyword(s):  
Time Course ◽  
Blocking Agent ◽  
Constant Flow ◽  
Flow Conditions ◽  
B1 Receptor ◽  
Vascular Bed ◽  
Channel Blocking ◽  
Kinin B1 Receptor ◽  
B2 Receptors ◽  
Dose Dependent

Responses to kallidin, des-Arg9-bradykinin (DABK), and des-Arg10-kallidin (DAK) were investigated in the hindlimb vascular bed of the cat under constant-flow conditions. Injections of kallidin, DABK, and DAK into the hindlimb perfusion circuit produced dose-dependent vasodilator responses in the hindlimb vascular bed. Vasodilator responses to kallidin and bradykinin (BK) were similar in magnitude and time course, and both peptides were approximately 100-fold more potent than DABK or DAK. Responses to kallidin were decreased by the kinin B2 antagonist, HOE 140, whereas responses to DABK and DAK were reduced by des-Arg9[Leu8]BK, a kinin B1-receptor antagonist. N omega-nitro-L-arginine methyl ester (L-NAME) reduced vasodilator responses to kallidin, DABK, and DAK, whereas meclofenamate, atropine, and U-37883A, a vascular selective ATP-sensitive K+ (K+ATP) channel-blocking agent, did not alter responses to the three peptides. These data suggest that both kinin B1 and B2 receptors are normally present in the hindlimb vascular bed. These data also suggest that kinin B1 and B2 receptor-mediated vasodilator responses are mediated by the release of nitric oxide and that the activation of K+ATP channels or muscarinic receptors, or the release of vasodilator prostaglandins play little if any role in mediating responses to kallidin, DABK, or DAK in the hindlimb vascular bed of the cat.

scholarly journals In VitroActivities of Dermaseptins K4S4and K4K20S4against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa Planktonic Growth and Biofilm Formation

2014 ◽  
Vol 58 (4) ◽  
pp. 2221-2228 ◽  
Author(s):  
Amira Zaïri ◽  
Lionel Ferrières ◽  
Patricia Latour-Lambert ◽  
Christophe Beloin ◽  
Frédéric Tangy ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Alternative Therapies ◽  
Bacterial Biofilm ◽  
Flow Conditions ◽  
Dynamic Flow ◽  
Gram Negative ◽  
Cytotoxicity Assays ◽  
Attached Bacteria ◽  
Antibiofilm Agents ◽  
Intensive Search

ABSTRACTThe rising number of infections caused by biofilm formation and the difficulties associated with their treatment by conventional antimicrobial therapies have led to an intensive search for novel antibiofilm agents. Dermaseptins are antimicrobial peptides with a number of attractive properties that might offer alternative therapies against resistant microorganisms. In this study, we synthesized a set of dermaseptin-derived peptides and evaluated their activities against Gram-positive and Gram-negative bacterial biofilm formation. All dermaseptin-derived peptides demonstrated concentration-dependent antibiofilm activities at microgram concentrations, and their activities were dependent on the nature of the peptides, with the highest levels of activity being exhibited by highly charged molecules. Fluorescent binding and confocal microscopy demonstrated that dermaseptin K4S4, a substituted derivative of the native molecule S4, significantly decreased the viability of planktonic and surface-attached bacteria and stopped biofilm formation under dynamic flow conditions. Cytotoxicity assays with HeLa cells showed that some of the tested peptides were less cytotoxic than current antibiotics. Overall, these findings indicate that dermaseptin derivatives might constitute new lead structures for the development of potent antibiofilm agents.

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