Sequential bilateral isolated lung perfusion in the rat: an experimental model

BACKGROUND: A model of isolated single-lung perfusion in the rat has been established in our laboratory to study the chemotherapeutic treatment of pulmonary metastases. A sequential bilateral isolated lung perfusion model was designed to investigate the feasibility of staged perfusions in the rat. METHODS: Twenty-four Fischer rats were randomized into three experimental groups of 8 rats each. All rats underwent left isolated lung perfusion. One, 2, or 3 weeks later, the rats in groups I, II, and III, respectively, underwent contralateral (right) perfusion. Five control animals (group IV) underwent sequential bilateral sham thoracotomies 1 week apart. Arterial blood gas analysis was performed 1 week after the second operation in the rats in groups I and IV. RESULTS: All animals survived the first operation, with 100% (8/8), 75% (6/8), and 100% (8/8) of the animals in perfusion groups I, II, and III, respectively, surviving the second operation. All control animals (group IV) survived the second sham thoracotomy. Arterial blood gas analysis did not show a significant difference in the oxygen or carbon dioxide partial pressure or the pH between group I and IV (p = 0.32, 0.96, and 0.76, respectively). CONCLUSIONS: Our experiments demonstrate that sequential bilateral isolated lung perfusion is safe in and well tolerated by the rat. This model can be used to investigate the safety and efficacy of staged perfusions with chemotherapeutic agents in the treatment of bilateral pulmonary metastases in the rat.     

Changes in the signalling status of the small GTP-binding proteins Rac and Rho do not influence insulin-stimulated hexose transport

Post-receptor signalling molecules that convey the signal from the activated insulin receptor to the actual process of Glut4 translocation and hexose uptake are poorly understood. Various studies have suggested a requirement of the lipid kinase phosphatidylinositol-3 kinase (PI3-kinase) in this process. PI3kinase regulates the activation status of the small GTP-binding protein Rac which, in turn, is able to activate another G-protein Rho. Rac and Rho are known to regulate the structure of the membrane- and cytoplasmic actin-cytoskeleton. We have examined whether Rac and Rho transfer the signals generated by PI3kinase towards insulin-stimulated hexose uptake. For that purpose, we expressed in 3T3-L1 adipocytes the dominant-negative mutant of RacN17 using vaccinia virus-mediated gene transfer. The expression levels of the RacN17 protein were monitored by Western blotting. The abrogation of endogenous Rac signalling by expression of RacN17 was inferred from the observed loss of arachidonic acid release in response to insulin. Basal and insulin-stimulated hexose transport were not affected by expression of the RacN17 mutant. A possible contribution of Rho.GTP to stimulation of hexose uptake was examined by pre-incubation of adipocytes with lysophosphatidic acid (LPA). We observed a profound effect of LPA on the structure of the cytoskeleton and on the phosphorylation of Focal Adhesion Kinase (p125FAK), indicating that 3T3-L1 adipocytes respond to LPA and that Rho was activated by LPA. However, no effect was detected on the basal or on the insulin-stimulated hexose transport. We conclude that Rac and Rho are unlikely to be involved in insulin-stimulated hexose transport, suggesting a possible contribution of other signalling pathways, downstream of PI3kinase to this process.     

Clinical presentation of herpes zoster in a Singapore hospital

The purpose of the study was to give a histological picture of the different skin regions of the mammary gland in mares. Special emphasis on the dark coating in the sulcus intermammarius was given. As a result, the dark pigmented udder skin can be subdivided into the skin of the Corpus mammae, the sulcus intermammarius and the teat skin. In the sulcus intermammarius the whole epidermis was considerably thicker than usual, especially the stratum corneum (up to 70 layers of cornified layers) and the stratum spinosum. In general, the squamous keratinocytes were unusually large. The histological preparations of the coating revealed a stratum corneum instead of a supposed secretion of the sebaceous glands. The dermal papillae ended immediately below the stratum corneum.     

Enzymology of the reduction of the novel fused pyrazine mono-n-oxide bioreductive drug, RB90740 roles for P450 reductase and cytochrome b5 reductase

RB90740 is the lead compound in a series of fused pyrazine mono-N-oxide bioreductive drugs. Theses agents have potential application in cancer therapy, since they are more toxic to hypoxic than to aerobic cells as a consequence of their bioactivation by cellular reductase enzymes within the hypoxic regions of a tumour. In this study, mouse liver microsomes have been used to characterise the enzymology of the reductive activation of RB90740. Under hypoxic conditions, the reduction of RB90740 to its stable 2-electron reduced product RB92815 was supported by both NADH and NADPH, the former supporting a rate approximately 80% of the latter. Combining the two cofactors had no additive effect. Neither carbon monoxide nor metyrapone inhibited reduction of RB90740, indicating that P450 isozymes were not involved in the reduction of this compound. 2' AMP, and inhibitor of P450 reductase, did not inhibit formation of RB92815, whereas DPIC, another inhibitor but with a different mode of action, inhibited both the NADH, and NADPH-dependent reduction of RB90740. Similarly, two selective inhibitors of NADH: cytochrome b5 reductase, pHMB and PTU, completely inhibited both NADH and NADPH-dependent reduction of RB90740. Our findings implicate P450 reductase, cytochrome b5 reductase, and cytochrome b5 in the activation of the compound. However, there is no clear relationship between the intracellular levels of P450 reductase and cytochrome b5 reductase and the hypoxic toxicity of RB90740, which implies that other factors, in addition to drug activation, play a major role in controlling the toxicity of this particular bioreductive drug.     

When is a lifting movement too asymmetric to identify low-back loading by 2-D analysis?

In ergonomics research, two-dimensional (2-D) biomechanical models are often used to study the mechanical loading of the low back in lifting movements. When lifting movements are asymmetric, errors of unknown size may be introduced in a 2-D analysis. In the current study, an estimation of these errors was made by comparing the outcome of a 2-D analysis to the results of a recently developed and validated 3-D model. Four subjects made two repetitions of five lifting movements, differing in the amount of asymmetry. The results showed a significant underestimation of the peak torque by 20, 36 and 61% when the initial position of a box was rotated 30, 60 and 90 degrees with respect to the sagittal plane of the subject. The main cause of this underestimation was a pelvic twist, resulting in an erroneous projection of a pelvic marker on to the sagittal plane due to pelvic twist. It is suggested that from 30 degrees box rotation a 2-D analysis may easily lead to wrong conclusions when it is used to study asymmetric lifting.     

Visual laser ablation of the prostate for patients with acute urinary retention

Examination of the long-term relation of a single fibrinogen determination to initial and recurrent atherosclerotic cardiovascular events over 20 years of follow-up revealed a powerful and comparably independent impact on initial events in both sexes but an influence on recurrent events only in men.     

Prostacyclin analogue (OP-2507) attenuates hepatic microcirculatory derangement, energy depletion, and lipid peroxidation in a rat model of reperfusion injury

Between 1985 and 1994, 1223 patients with malleolar fractures of the ankle were treated by open reduction and internal fixation with absorbable pins and screws, of whom 74 (6.1%) had an obvious inflammatory foreign-body reaction to the implants. Of these 74, ten later developed moderate to severe osteoarthritis of the ankle despite no evidence of incongruity of the articular surface. The implants used in these patients were made from polyglycolide, polylactide or glycolide-lactide copolymer. The joint damage seemed to be due to polymeric debris entering the articular cavity through an osteolytic extension of an implant track. The ten patients had a long clinical course which included a vigorous local foreign-body reaction, synovial irritation and subsequent degeneration. At a follow-up of three to nine years, ankle arthrodesis had been necessary in two patients and is being considered for another two. The incidence of these changes in the whole series was 0.8%, which is not high, but awareness of this possible late complication is essential.     

Ion channels and transporters in the electroreceptive ampullary epithelium from skates

Two ampullary epithelial properties necessary for electroreception were used to identify the types of ion channels and transporters found in apical and basal membranes of ampullary receptor cells of skates and to assess their individual role under voltage-clamp conditions. The two essential properties are (1) a steady-state negative conductance generated in apical membranes and (2) a small, spontaneous current oscillation originating in basal membranes (Lu and Fishman, 1995). The effects of pharmacological agents and ion substitutions on these properties were evaluated from transorgan or transepithelial complex admittance determinations in the frequency range 0.125 to 50 Hz measured in individual, isolated ampullary organs. In apical membranes, L-type Ca channels were found to be responsible for generation of the steady-state negative conductance. In basal membranes, K and Ca-dependent Cl (Cl(Ca)) channels were demonstrated to contribute to a net positive membrane conductance. L-type Ca channels were also evident in basal membranes and are thought to function in synaptic transmission from the electroreceptive epithelium to the primary afferent nerve. In addition to ion channels in basal membranes, two transporters (Na+/K+ pump and Na(+)-Ca+ exchanger) were apparent. Rapid (minutes) cessation of the current oscillation after blockage of any of the basal ion channels (Ca, Cl(Ca), K) suggests critical involvement of each of these channel types in the generation of the oscillation. Suppression of either Na+/K+ transport or Na(+)-Ca2+ exchange also eliminated the oscillation but at a slower rate, indicating an indirect effect.