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Results for “Barrier Methods”

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At least 595 records · Page 33Linked to original sources
PubMed1999

Squamometry: an evaluation method for a barrier protectant (tannic acid).

Squamometry for evaluating skin barrier substances is described. Forearms of 8 volunteers were dosed with 0, 0.25, 0.5, and 1% sodium lauryl sulfate (SLS) in distilled water (semi-open method) for 24 h, to skin pretreated with distilled water and 5% tannic acid, a model barrier protectant. Squamometric evaluation indicated the skin damage increased with SLS concentration in a dose-dependent manner, and that tannic acid reduced the damage (p<0.01). The results suggest that squamometry may be a useful method for determining efficacy of skin barrier substances.

Aged↗
PubMed1994

A method to determine the ability of drugs to diffuse through the blood-brain barrier.

A method has been devised for predicting the ability of drugs to cross the blood-brain barrier. The criteria depend on the amphiphilic properties of a drug as reflected in its surface activity. The assessment was made with various drugs that either penetrate or do not penetrate the blood-brain barrier. The surface activity of these drugs was quantified by their Gibbs adsorption isotherms in terms of three parameters: (i) the onset of surface activity, (ii) the critical micelle concentration, and (iii) the surface area requirement of the drug at the air/water interface. A calibration diagram is proposed in which the critical micelle concentration is plotted against the concentration required for the onset of surface activity. Three different regions are easily distinguished in this diagram: a region of very hydrophobic drugs which fail to enter the central nervous system because they remain adsorbed to the membrane, a central area of less hydrophobic drugs which can cross the blood-brain barrier, and a region of relatively hydrophilic drugs which do not cross the blood-brain barrier unless applied at high concentrations. This diagram can be used to predict reliably the central nervous system permeability of an unknown compound from a simple measurement of its Gibbs adsorption isotherm.

Blood-Brain Barrier↗
PubMed1988

The cervical cap.

Explore the source record for details and available documents.

Cervix Uteri↗
PubMed2005

Large-scale rodent production methods make vendor barrier rooms unlikely to have persistent low-prevalence parvoviral infections.

A recent article in Contemporary Topics in Laboratory Animal Science by Pullium and colleagues expressed the opinion that because no other source could be found for a parvoviral contamination detected in sentinel mice prior to deployment, the infection apparently came from the unspecified vendor, even though no antibodies were ever detected in mice within 3 weeks of arrival. As this opinion may be shared by others and expresses some of the deep frustration in trying to detect the source of parvoviral infection in facilities using cage-level bioexclusion housing, Charles River Laboratories (CRL) feels it important to contribute to scientific dialogue by claiming to be the unnamed vendor in the Pullium article and discussing why a parvoviral contamination in a CRL barrier room would be detected rapidly. We show that viral infections in CRL barrier rooms rapidly reach high prevalence and that such contaminations historically have been detected quickly, and we describe why we feel enhancements in current monitoring methods provide for even more rapid detection of parvoviruses. Furthermore, we present substantial evidence that the barrier rooms that served as the source of the customer-suspect sentinel mice remain free of all parvoviruses, in light of monitoring of hundreds of mice by all available techniques. Therefore, although an initial list of all possible sources of contamination prudently should include vendors, the evidence is overwhelming that this vendor was not the source of the parvoviral contamination discussed in the Pullium paper.

Animals↗
PubMed2003

[Study on the microdischarge in dielectric barrier discharge by optical method].

The global light emission of dielectric barrier discharge with pattern mode in air was measured and compared with the global current obtained with a small resistor. The results show that the moments and the amplitudes of the pulses in light emission correspond to those in the global current, respectively. So the discharge current can be measured by optical methods. Further more, the temporal aspect of the microdischarges in dielectric barrier discharge was obtained by using this method. It is believed that the results are of great importance to the study of spatiotemporal dynamics in dielectric barrier discharge, and are valuable to the study of gas discharge as well.

English Abstract↗
PubMed2003

Reassessment of methyl rotation barriers and conformations by correlated quantum chemistry methods.

Internal rotations of the methyl group in ortho-substituted and 2,6-disubstituted toluenes in their ground state have been investigated by means of various ab initio quantum chemistry methods. Computed barriers at the Hartree-Fock (HF) level using medium sized basis sets agreed reasonably with experimental results in the case of the studied ortho-substituted toluenes. However, this agreement worsens when using very large basis sets. Furthermore, the determination of the conformation and barriers of more weakly hindered methyl groups, that is, for 2,6-dihalogenotoluenes or toluene itself, necessitates high level correlated computations, because of a possible failure of HF calculations in this case. Density functional theory (DFT) techniques required, in several cases, much more extended basis sets than the post-HF Møller-Plesset perturbation (MP2, MP4) ones, to insure the convergence of the computed barriers. Non-negligible variations of the computed barriers when using different DFT functionals are observed for some systems.

Journal Article↗
PubMed1992

Porcine model for studying the passage of non-depolarizing neuromuscular blockers through the blood-brain barrier.

A method has been developed for blood-brain barrier disruption to provide reproducible access to the cerebrospinal fluid of the cerebello-medullary cistern. The technique was used successfully to investigate transfer of pancuronium to the cerebral CSF compartment in pigs. After osmotic disruption of the blood-brain barrier, pancuronium concentrations increased significantly in the cerebrospinal fluid.

Animals↗
PubMed2002

The role of qualitative methods for investigating barriers to adult immunization.

In 1999, the Agency for Healthcare Research and Quality funded a study of barriers to immunization, which included a short-term qualitative data collection to assess the organizational and cultural features of selected primary care practices and to explore their impact on adult immunization rates. The authors describe the short-term qualitative data collection system and the contributions made by the qualitative study to the parent project. They address previously held concerns about qualitative research and provide a system that can be replicated or modified for use for projects designed to assess complex attitudes and behaviors that affect health outcomes.

Adult↗
PubMed1991

The cervical cap.

The cervical cap is a barrier contraceptive method with an efficacy similar to that of the diaphragm. It has several advantages over other barrier contraceptives. In particular, it can be left in place for up to 48 hours, and repeated applications of spermicide are not necessary, even if sexual intercourse occurs more than once. In addition, the side effects seen with other barrier methods do not occur with the cervical cap. In some women, Papanicolaou tests may become abnormal, especially during the first three months of cap use. Therefore, careful monitoring of cervical cap users is essential.

Contraceptive Devices, Female↗