SEARCH · PubMed Health

Results for “Barrier Methods--indications”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources

PubMed2000

Mitochondrial phylogeny of notothenioids: a molecular approach to Antarctic fish evolution and biogeography.

Antarctic waters represent a unique marine environment delimited by an oceanographic barrier, the Polar Front Zone, and characterized by constant subzero temperatures and presence of sea ice. A group of teleost fish, the Notothenioidei, have adapted to these challenging environmental conditions, undergoing a remarkable diversification. In the present study a total of 798 base pairs, generated from partial sequencing of 16S and 12S mitochondrial ribosomal RNA genes, were examined in 33 notothenioid species representative of all families included in the suborder Notothenioidei. Phylogenetic trees, reconstructed on the basis of sequence data by different methods, indicate that traditional hypotheses on notothenioid systematics and biogeography might be in need of reexamination. Molecular evidence suggests that vicariant speciation could be invoked to explain the early divergence of Eleginops maclovinus, a species previously included in the family Nototheniidae, which is now proposed as the closest sister group to all the rest of notothenioids apart from bovichtids. On the other hand, repeated, independent dispersal through the Polar Front is proposed for the divergence of other subantarctic notothenioid species. Likewise, multiple, independent transitions from benthic to pelagic habit are inferred from molecular data, at variance with the more conservative hypothesis based on cladograms reconstructed from morphological data.

Animals↗

PubMed1989

How do serine proteases really work?

Recent advances in genetic engineering have led to a growing acceptance of the fact that enzymes work like other catalysts by reducing the activation barriers of the corresponding reactions. However, the key question about the action of enzymes is not related to the fact that they stabilize transition states but to the question to how they accomplish this task. This work considers the catalytic reaction of serine proteases and demonstrates how one can use a combination of calculations and experimental information to elucidate the key contributions to the catalytic free energy. Recent reports about genetic modifications of the buried aspartic group in serine proteases, which established the large effect of this group (but could not determine its origin), are analyzed. Two independent methods indicate that the buried aspartic group in serine proteases stabilizes the transition state by electrostatic interactions rather than by alternative mechanisms. Simple free energy considerations are used to eliminate the double proton-transfer mechanism (which is depicted in many textbooks as the key catalytic factor in serine proteases). The electrostatic stabilization of the oxyanion side of the transition state is also considered. It is argued that serine proteases and other enzymes work by providing electrostatic complementarity to the changes in charge distribution occurring during the reactions they catalyze.

Kinetics↗

PubMedDate not supplied

Patterns of risk behaviour for patients with sexually transmitted diseases and surveillance for human immunodeficiency virus in Kuala Lumpur, Malaysia.

A study was conducted to determine the feasibility of establishing a sentinel human immunodeficiency virus (HIV) surveillance system involving patients with sexually transmitted diseases attending private clinics and a government sexually transmitted disease clinic in Kuala Lumpur, Malaysia. Information on risk behaviours for HIV infection were also collected. A total of 84 female and 91 male patients were interviewed and tested for HIV infection; 41.7% of the women reported working as prostitutes, other occupations included masseuses, hairdressers, waitresses, salesgirls, receptionists, factory workers, and others. The most common diagnosis was gonorrhoea. Other diagnoses included non-specific genital infection, pelvic inflammatory disease, genital herpes and syphilis. 58.3% of the women had a hundred or more sex partners during the previous month; 99% had 6 or more sex partners. Only 4.8% of female patients had their male partners using condoms most of the time, 11.9% hardly used condoms at all. Of the males, 93.3% were heterosexual, while 6.7% were bisexuals, 41.1% had between 6-20 different partners in the previous year. 78.0% of them had prostitutes as their sex partners most of the time. 41.8% had experiences in Thailand and the Philippines. 73.6% never used condoms, while 19.8% only used condoms rarely. Although all patients were tested negative for HIV antibodies, lot quality assurance sampling methods indicate that the upper limits of prevalences for females and males were 3.5% and 3.3% respectively, at a 5% type I error. The study has shown that it is feasible to carry out a sentinel surveillance programme among STD patients and provided useful baseline data for future comparisons.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1982

Measurement of fluorescein binding in human plasma using fluorescence polarization.

The binding of fluorescein was measured in human plasma using four methods: steady-state dialysis, pressure dialysis, equilibrium dialysis, and fluorescence polarization. All methods indicated that fluorescein is approximately 85% bound throughout a wide range of concentrations. Technical difficulties were encountered with the fluorescence polarization method above fluorescein concentrations of 10(-5) g/mL, but below this concentration, the method gave reproducible and reliable results compared with the three other methods. The number of binding sites available in plasma was estimated to be 4 x 10(-3) M, and the dissociation constant was estimated to be 6 x 10(-4) M. These estimates imply that the bound-free ratio of fluorescein in plasma is almost constant at concentrations below 10(-4) g/mL. Fluorescein binding can affect the fluorescent intensity or the rate at which fluorescein penetrates the blood-ocular barriers.

Blood Chemical Analysis↗

PubMed1980

Failure of allogeneic thymocytes to survive in nude mice.

Athymic nude mice or thymectomized mice, irradiated and reconstituted with T-depleted bone marrow cells ("B mice"), were injected with allogeneic or syngeneic thymocytes bearing caryotypically distinct chromosomes. The fate of the thymocytes was investigated after various periods of time using two methods: (a) frequency of the cells bearing the Thy-1 antigen as detected by immunofluorescence with a heteroantiserum among the recipient spleen cells, (b) presence of chromosomally detectable donor cells in phytohemagglutinin-stimulated spleen cell cultures. These two methods indicate that allogeneic thymocytes disappear after about 7 days, semiallogeneic thymocytes after about 20 days, while syngeneic thymocytes, even when injected in 50 times lower number (10(6) cells), are detectable for months, thanks to the sensitivity of the caryotypic method. Allogeneic thymocytes induce the production of high titers of alloantibodies, which were shown to react specifically against their own H-2, a phenomenon interpreted as a "suicidal" allogeneic collaboration. These experiments demonstrate that the failure of allogeneic thymocytes, in contrast to syngeneic thymocytes, to achieve long-term restoration of the immune responsiveness of T-depleted mice is due to a rejection of the foreign thymocytes, and not to a failure of T and B cells to collaborate across the histocompatibility barrier.

Animals↗

PubMed1984

The effect of chemical intravaginal contraceptives and Betadine on Ureaplasma urealyticum.

The purpose of this study was to find a barrier contraceptive agent capable of controlling infections and sexual transmission of Ureaplasma urealyticum from the female genital tract, especially to help reduce nongonococcal urethritis in males caused by this organism. Therefore, the in vitro antimicrobial activity of six intravaginal contraceptives and BetadineR against the eight serotypes of the organism was investigated. The results indicate that some of these contraceptives produce partial inhibition of the Ureaplasma at low dilutions, while BetadineR produces a ureaplasmacidal effect up to dilutions of 1:64. These effects appear not to be due primarily to the pH of these agents. Thus, some of these agents may have a potential role in controlling transmission of Ureaplasma urealyticum.

Contraceptive Agents, Female↗

PubMed2002

Determination and pharmacokinetic profile of omeprazole in rat blood, brain and bile by microdialysis and high-performance liquid chromatography.

The disposition and biliary excretion of omeprazole was investigated following i.v. administration to rats at 10 mg/kg. We used a microdialysis technique coupled to a validated microbore HPLC system to monitor the levels of protein-unbound omeprazole in rat blood, brain and bile, constructing the relationship of the time course of the presence of omeprazole. Microdialysis probes were simultaneously inserted into the jugular vein toward right atrium, the brain striatum and the bile duct of the male Sprague-Dawley rats for biological fluid sampling after the administration of omeprazole (10 mg/kg) through the femoral vein. The concentration-response relationship from the present method indicated linearity (r2>0.995) over a concentration range of 0.01-50 microg/ml for omeprazole. Intra-assay and inter-assay precision and accuracy of omeprazole fell well within the predefined limits of acceptability. Following omeprazole administration, the blood-to-brain coefficient of distribution was 0.15, which was calculated as the area under the concentration versus time curve (AUC) in the brain divided by the AUC in blood (k=AUCbrain/AUCblood). The blood-to-bile coefficient of distribution (k=AUCbile/AUCblood) was 0.58. The decline of unbound omeprazole in the brain striatum, blood and bile fluid suggests that there was rapid exchange and equilibration between the compartments of the peripheral and central nervous systems. In addition, the results indicated that omeprazole was able to penetrate the blood-brain barrier and undergo hepatobiliary excretion.

Animals↗

PubMed1985

Prescription contraceptives: countering the risks.

Explore the source record for details and available documents.

Contraceptives, Oral, Hormonal↗

PubMed2002

Bioengineering methods employed in the study of wound healing of sulphur mustard burns.

BACKGROUND/PURPOSE: Sulphur mustard (SM) is a potent incapacitating chemical warfare agent that remains a threat to war fighters and civilians worldwide. SM lesions may require weeks or months to heal, depending upon their severity. This study was undertaken to find a treatment regimen that promotes speedier healing of deep cutaneous SM burns in a weanling pig model. The principal objective of the study was to compare four treatment regimens and establish which achieved the shortest healing time. METHODS: Twelve Yorkshire Cross weanling pigs were exposed to SM liquid for 2h, generating six large deep dermal/full thickness burns on the ventrum of each animal. Three additional animals served as sham-exposed controls. Surgical intervention occurred at 48 h postexposure. Treatments included: (i) full-thickness debridement of the burns with a computer controlled, raster scanned continuous wave CO2 laser followed by autologous split-thickness skin grafting; (ii) full-thickness sharp surgical tangential excision followed by skin grafting, the 'Gold Standard' used in human deep dermal/full-thickness thermal burns management; (iii) partial-thickness laser ablation with no grafting; and (iv) partial-thickness sharp surgical excision with no grafting. Several non-invasive bioengineering methods were used to monitor the progress of wound healing throughout a 36-day healing period: reflectance colourimetry, evaporimetry, laser Doppler perfusion imaging and ballistometry. RESULTS: Bioengineering methods indicated that laser debridement followed by autologous split-thickness skin grafting was as efficacious in improving the wound healing of deep SM burns in weanling swine as the 'Gold Standard.' Regardless of the method of debridement, barrier function, skin colour and mechanical properties returned to near-normal levels within 15 days of treatment in the grafted sites. Regardless of surgical approach, blood flux levels remained approximately 50-60% of normal tissue throughout the 36-day postsurgical observation period. Mid-dermal debridement by sharp surgical tangential excision or laser ablation without the use of skin grafts did not produce as good a result as those attained through the use of grafts, but was better than no surgical treatment of the wounds. CONCLUSION: Bioengineering methods were useful in evaluating multiple characteristics during wound healing: (i) reflectance colourimetry for skin colour, (ii) evaporimetry to measure transepidermal water loss as an indicator of barrier function, (iii) laser Doppler perfusion imaging to assess cutaneous blood flow, and (iv) ballistometry to measure the mechanical properties of skin hardness and elasticity. Perhaps the most useful method was evaporimetry, as a restored barrier function was the best indicator of healed wounds. The use of reflectance colourimetry and ballistometry will continue in future wound healing studies for their contributions in judging cosmetic and functional outcomes. While useful, laser Doppler perfusion imaging was found to be rather time consuming. This methodology will be limited in the future to burn depth estimation prior to treatment, and for evaluation of pharmaceuticals specifically designed to improve or sustain blood flow into damaged areas.

Animals↗

PubMedDate not supplied

Herpes simplex virus transmission: condom studies.

The incidence of genital herpes simplex infections has risen at a rapid rate over the past 20 years. Sexually active young adults ask whether condoms will effectively block the transmission of herpes simplex virus from one individual to another. Using a laboratory plunger model to stimulate human coitus, the authors have shown that high concentrations of HSV-2 did not cross the latex or natural membrane condoms that were tested. We have also shown that high concentrations of HSV-2 left in contact with a condom for 8 hr does not penetrate the barrier. This study gives good indirect evidence that condoms block the transmission of herpes simplex virus.

Contraceptive Devices, Male↗

PubMed2001

Biostability and pharmacokinetics of LJP 920, an octameric Gal (alpha1-3) Gal conjugate for the inhibition of xenotransplantation rejection.

Antibodies to an alpha-galactosyl saccharide structure present in human serum are associated with hyperacute rejection and delayed xenograft rejection after pig-to-primate xenotransplantation. To overcome this major barrier to the xenotransplantation, LJP 920, a galactosyl alpha1-3 galactose (Gal (alpha1-3) Gal) coupled to a non-immunogenic platform at a valency of eight Gal (alpha1-3) Gal molecules/platform, was synthesized to clear circulating antibodies and to inhibit their production by B cells that produce these antibodies. Herein we report on the stability of UP 920 in biological media and its pharmacokinetic profile. Incubation of LJP 920 with mouse serum or liver microsomes at 37 degrees C for 2 days showed no indication of degradation of the conjugate as detected by a reversed-phase HPLC method, indicating that the conjugate is not subject to enzymatic metabolism. After intravenous administration of LJP 920 to mice at the doses of 20 and 100 mg kg(-1), UP 920 serum concentration decreased rapidly, showing a biphasic pattern, with a distribution half-life of 3 min and an elimination half-life of more than 30 min, respectively. The serum-to-erythrocyte concentration ratio of UP 920 was 33- and 36-fold excess at 0.5 and 5 min, respectively, after intravenous administration (100 mg kg(-1)). Both Cmax and AUC values increased in a dose-proportional manner. UP 920 displayed a great distribution to well-perfused tissues. It was eliminated mainly through renal excretion in the unchanged form, which accounted for 23% of the total amount within 8 h of dosing.

Animals↗

PubMed1992

Commentary: methods women can use that may prevent sexually transmitted disease, including HIV.

Although sexually transmitted diseases, including human immunodeficiency virus (HIV), are a major concern for women, few prevention messages are targeted specifically to women. Those that are generally stress abstaining, altering the number or selection of partners, and urging partners to use condoms. But these behaviors may be unrealistic for many women, particularly women who are at highest risk for sexually transmitted diseases, because they require significant changes in life-style or depend on male-controlled condom use. Recommendation of contraceptives for prevention of sexually transmitted diseases depends largely on how well specific methods perform under controlled conditions, either in the laboratory or in clinical trials. Observational studies, which better reflect day-to-day use, indicate that condoms, barriers, and spermicides, used properly and consistently, can provide substantial protection against various sexually transmitted diseases. Condoms can similarly help protect against HIV, but studies of barriers and spermicides are scant and currently inconclusive. Finally, those methods that are controlled by women are consistently more effective in preventing sexually transmitted diseases. Thus, although condoms used well are still the best choice, the imperative for female-controlled methods indicates that diaphragms and spermicides should receive greater emphasis in prevention messages.

Condoms↗

PubMed1983

The influence of systemic arterial pressure and intracranial pressure on the development of cerebral vasogenic edema.

The influence of intracranial pressure (ICP), systemic arterial pressure (SAP), and cerebral perfusion pressure (CPP) upon the development of vasogenic cerebral edema is largely unknown. To study their relationship, the authors have produced an osmotic disruption of the blood-brain barrier unilaterally in rabbits by injecting 1 cc/kg of 2M NaCl into the left internal carotid artery. The amount of vasogenic edema produced was assessed by quantitation of the extravasation of Evans blue dye into the area of maximum blood-brain barrier breakdown by means of optical densitometry following formamide extraction. The ICP was measured using a cisterna magna catheter into which mock cerebrospinal fluid could be infused at a predetermined pressure. The SAP was controlled by exsanguination from a femoral artery catheter. In 18 animals in which blood pressure was not controlled, no significant relationship between the ICP and the degree of Evans blue dye extravasation was noted. In these animals, however, a direct relationship between CPP (defined as mean arterial pressure minus mean ICP) and extravasation of Evans blue dye was found (correlation coefficient 0.630; p less than 0.001). When ICP was held constant at 0 to 5 mm Hg in another group of 16 animals and different levels of blood pressure were produced by exsanguination, a significant direct relationship between extravasation of Evans blue dye and the SAP was found (correlation coefficient 0.786; p less than 0.001). In a third group of 20 animals, the blood pressure was held constant at 90 to 100 mm Hg and the ICP was varied between 0 and 75 mm Hg. There was a highly significant result indicating increasing Evans blue dye extravasation with lower levels of ICP (p less than 0.001). Cerebral blood flow determinations by the hydrogen clearance method indicated loss of autoregulation in all animals in the areas of brain injured by intracarotid hypertonic saline. These results indicate that high SAP and low ICP (that is, a large CPP) promote Evans blue dye extravasation in this model of blood-brain barrier disruption. This finding has implications for the management of patients with vasogenic edema.

Animals↗

PubMed1989

Reliability of the Cobb angle index derived by traditional and computer assisted methods.

The reliability of the traditional Cobb angle index, which at present exhibits a wide range of reported values, was determined in this study and amounted to a within subject error of +/-4.3 degrees and a between subject error of +/-4.9 degrees. An attempt to pinpoint the source of this variability by investigating the influence of choice of end vertebrae proved inconclusive. The reliability of a computer assisted Cobb angle index, developed to improve measurement accuracy, was also examined and an estimated within subject error of +/-1.5 degrees and a between subject error of +/-1.6 degrees obtained. A comparison of the traditional and computer assisted methods indicates a high correlation between the Cobb angle derived using the two methods when measuring like curves and an improved reliability obtained by the computer method. Such an improvement is worth implementing clinically but of course the availability of a computer and digitizer and a little extra time for an operator to input the X-ray coordinates may be a barrier to its general use.

Diagnostic Errors↗

PubMed1988