Additive Effects of Sevoflurane and Propofol on γ-Aminobutyric Acid Receptor Function

Background: Previous studies have shown that propofol and sevoflurane enhance the function of [gamma]-aminobutyric acid type A (GABAA) receptors. However, it is not known whether these two drugs modulate the same molecular pathways. In addition, little is known about receptor function in the presence of both propofol and sevoflurane. The aim of this study was to better understand the interactions of propofol and sevoflurane with the GABAA receptor.

Methods: Wild-type [alpha]1, [beta]2, [gamma]2s GABAA receptor subunit complementary DNAs were transfected into human embryonic kidney cells grown on glass coverslips using a calcium phosphate transfection method. After transfection (36-72 h), cells were whole cell patch clamped and exposed to combinations of the following: 0.3-1,000 [mu]m [gamma]-aminobutyric acid (GABA), 0-10 [mu]m propofol, and 0-1,650 [mu]m sevoflurane. Chemicals were delivered to the cells using two 10-channel infusion pumps and a rapid solution exchanger.

Results: Both propofol and sevoflurane alone enhanced the amplitude of GABAA receptor responses to submaximal concentrations of GABA in a dose-dependent manner. The enhancement was underpinned by an increase in the apparent affinity of the receptor for GABA. Coapplication of both anesthetics further enhanced the apparent affinity of the receptor for GABA.     

Patient readiness for return to home: Discord between expectations and reality

This study examined the interface between acute hospital care and return to home in relation to elderly patients' perceived ability and preparedness to cope at home. Seventy-six (n = 76) elderly patients aged 60 years and over were randomly recruited from a large Queensland hospital and interviewed prior to discharge about their perceived health, functional status and their ‘readiness’ to cope at home. They were followed up at home 7–10 days post-discharge. Comparisons were made between a number of measures at discharge and post-discharge. Although the majority of patients indicated that they would cope very well upon discharge, a large number of patients reported experiencing considerable difficulty with activities of daily living, particularly instrumental activities of daily living prior to and especially after discharge. The self-reported health status of patients similarly deteriorated between discharge and follow-up. Despite a large number of patients experiencing functional limitations, few were referred to hospital or community-based therapy services. Some policy implications are explored.     

Evaluation of the influence of the aqueous phase bioconstituent environment on the F-19 T1 of perfluorocarbon blood substitute emulsions

Oxygen-sensitive F-19 magnetic resonance imaging of perfluorocarbon compounds requires that fluorocarbon T1 changes correlate with the local Po₂ and not with the composition of the surrounding aqueous phase. The influence of various bioconstituents and paramagnetic ions within the aqueous phase on the F-19 fluorocarbon phase T1 for PFC emulsions was evaluated at 0.14 and 0.66 T. T1 was measured for FC-43, perflubron, and a fluorinated surfactant. Controlled variables introduced in the aqueous phase included annex solution constituents, blood, pH changes, and Gd-DTPA. For a constant Po₂, the F-19 T1s were independent of the emulsion constituents, blood concentration, and pH. For FC-43 and perflubron, F-19 T1 was independent of the Gd-DTPA concentration, while the aqueous phase T1 decreased by more than an order of magnitude. XMO-10 (smallest emulsion particle size) showed a slight decrease in F-19 T1 with increasing Gd-DTPA concentration at 0.66 T.     

The binding of blood-borne estrogens in normal vegetarian and omnivorous women and the risk of breast cancer

Serial blood samples were taken at two-hour intervals over a 24-hour period from 25 premenopausal vegetarians (12 vegans and 13 ovolactovegetarians) and from 21 omnivorous controls. All members of the former group had been on a vegetarian diet for a minimum of three years. The mean proportion of estradiol unbound to blood proteins was similar in both vegetarians (1.26%) and meat eaters (1.16%). However, the amount bound to albumin was significantly raised in vegetarians (50.1% vs. 43.1%, p less than 0.009), whereas that bound to sex hormone-binding globulin (SHBG) was correspondingly lower (48.7% vs. 55.8%, p = 0.01). Mean levels of SHBG were similar in vegetarians (59.9 nmole/l) and omnivores (62.0 nmole/l), as was the total amount of free fatty acid (0.42 mmole/l for both). Within the vegetarian group, no differences were detected between vegans and ovolactovegetarians.     

Activation of human B cells mediated through two distinct cell surface differentiation antigens, Bp35 and Bp50.

Two human B-cell differentiation antigens, Bp35 and Bp50, apparently play distinct roles as signal receptors in B-cell activation. Monoclonal antibodies (mAbs) to either Bp35 or Bp50 deliver positive signals to B cells that stimulate their transition through the cell cycle. mAb to Bp35, like anti-immunoglobulin antibodies, functions principally to activate resting B cells to become competent to enter the G1 phase of the cell cycle. In contrast, mAb to Bp50, a 50-kDa polypeptide expressed on all B cells, functions to stimulate activated B cells to traverse the cell cycle. mAb to Bp35, like anti-immunoglobulin antibodies, activates tonsillar B cells and induces low levels of B-cell proliferation. In contrast, anti-Bp50 mAb alone neither activates B cells nor induces B cells to proliferate but, together with anti-Bp35 or anti-immunoglobulin, augments B-cell proliferation. In this respect the action of anti-Bp50 antibody resembles the activity of B-cell growth factor(s) (BCGF). As little as 0.05 microgram of anti-Bp50 per ml is needed to augment proliferation and, like BCGF, anti-Bp50 is effective even when added 12-24 hr after B cells are activated with anti-immunoglobulin or anti-Bp35. Without additional exogenous signals, anti-Bp35 and anti-Bp50 together induce strong proliferation of purified resting B cells. These results suggest that the Bp35 and Bp50 surface molecules function in the regulatory control of B-cell activation and progression through the cell cycle.     

Cerebral hemorrhagic risk of aspirin or heparin therapy with thrombolytic treatment in rabbits

We studied the incidence of cerebral hemorrhage in an animal model of embolic stroke to determine the safety of aspirin, heparin, and tissue plasminogen activator therapies. We occluded the middle cerebral arteries of rabbits with labeled blood clots and administered either tissue plasminogen activator, heparin, aspirin, tissue plasminogen activator plus aspirin, tissue plasminogen activator plus heparin, or saline at various times after stroke. Compared to saline controls, both the aspirin-only and the tissue plasminogen activator-plus-aspirin groups had a significantly higher incidence of cerebral hemorrhage, whereas the heparin and tissue plasminogen activator combination groups did not. We conclude that aspirin antiplatelet therapy alone may increase the risk of hemorrhagic infarction, whereas heparin or tissue plasminogen activator therapy appears to be relatively safe.     

Intramuscular hypoperfusion, adrenergic receptors, and chronic muscle pain.

Despite a high prevalence of chronic muscle pain disorders such as fibromyalgia and regional myofascial pain, there is still limited knowledge about the factors that initiate and perpetuate these pain states. Although there are also likely to be downstream neuropathic changes in the central nervous system and spinal cord that sustain and exacerbate the pain states known as fibromyalgia, the focus of this critical review is on studies that examined the connection between both fibromyalgia and regional myofascial pain and sympathetic function. Specifically, we looked at studies that described Raynaud-like symptoms, cardiovascular dysfunction and altered intramuscular perfusion in chronic muscle pain. Our analysis showed that although the first 2 phenomena were intermittently present, a prominent and consistent feature for regional myofascial pain and to a lesser degree for fibromyalgia was intramuscular hypoperfusion. Several hypotheses can be offered why this hypoperfusion exists, and additional studies comparing and contrasting these theories are needed. This review focuses on one of these theories, namely, agonist-induced beta-adrenergic receptor desensitization as an explanatory model for hypoperfusion. What cannot be done at this time and is needed in the future is to compare and contrast to what degree the regional muscle pain disorder (myofascial) is similar or different from the more generalized disorder (fibromyalgia).