Effects of hypoxia on the pulmonary microvascular permeability in adult rabbit lung

Within the last 30 years, researchers have explored what role hypoxia might play in causing permeability changes in the pulmonary microvasculature. Since the data accumulated thus far are unclear, the effects of hypoxia on microvascular transport in the isolated, Ringer's perfused adult rabbit lung was observed and the following parameters were measured or computed for both oxygenated and hypoxic perfusates: pulmonary arterial (r_a) and pulmonary venous (r_v) resistances, pulmonary capillary filtration coefficients (K_f), and pulmonary capillary endothelial reflection coefficients () for NaCl and inulin. Separate reservoir bottles were used to create the desired oxygenated (aeration of solution with 95% O₂-5% CO₂) gas mixture or hypoxic (aeration of solution with 95% N₂-5% CO₂) gas mixture. A higher, but not significant, resistance value was found during the oxygenated state. A significant increase in the pulmonary capillary filtration coefficient during hypoxia (10.72 × 10^–4±0.446 × 10^–4 cm³/s cm H₂O for the hypoxic perfusate and 8.80 × 10^–4±0.384 × 10^–4 cm³/s cm H₂O for the oxygenated perfusate) was found and a significant difference between oxygenated and hypoxic pulmonary capillary reflection coefficients for inulin was computed (oxygenated solution revealed a finding of 0.120±0.003 and the hypoxic solution revealed 0.105±0.002). These findings imply a change in the microvascular permeability during hypoxia. According to the pore theory, a change in pore number, pore size, or both could have occurred. However, from the reflection coefficient data, a change in pore radius seems most likely.     

Investigation of the mechanisms for wireless nerve stimulation without active electrodes

Electric-field stimulation of neuronal activity can be used to improve the speed of regeneration for severed and damaged nerves. Most techniques, however, require invasive electronic circuitry which can be uncomfortable for the patient and can damage surrounding tissue. A recently suggested technique uses a graft-antenna—a metal ring wrapped around the damaged nerve—powered by an external magnetic stimulation device. This technique requires no electrodes and internal circuitry with leads across the skin boundary or internal power, since all power is provided wirelessly. This paper examines the microscopic basic mechanisms that allow the magnetic stimulation device to cause neural activation via the graft-antenna. A computational model of the system was created and used to find that under magnetic stimulation, diverging electric fields appear at the metal ring's edges. If the magnetic stimulation is sufficient, the gradients of these fields can trigger neural activation in the nerve. In-vivo measurements were also performed on rat sciatic nerves to support the modeling finding that direct contact between the antenna and the nerve ensures neural activation given sufficient magnetic stimulation. Simulations also showed that the presence of a thin gap between the graft-antenna and the nerve does not preclude neural activation but does reduce its efficacy.     

Ethical issues raised by uterus transplantation: A report from the People's Republic of China

The recent advances in assisted reproductive technology, such as hormonal stimulation, IVF, and intracytoplasmic sperm injection (ICSI), have made it possible to circumvent many causes of male and female factor infertility. However, uterine infertility is still considered an ‘‘unconditionally infertile’’ condition. Owing to the continued advances in organ transplantation, microvascular anastomosis techniques, and immunosuppressive medicine, the transplantation of organs is no longer restricted to the ones necessary for continued life. Quality-of-life enhancing types of transplantation, such as uterine transplantation, in recent years, have also entered the clinical arena. This undoubtedly brings new hope to such women, but also creates ethical challenges. Selection of the donor, the impact on the recipient and offspring, as well as challenges to moral and social norms are issues that cannot be ignored. In the present review, the ethical issues of transplantation of the uterus will be discussed in light of recent progress in the procedure.     

Photoselection in polarized photolysis experiments on heme proteins.

Polarized photolysis experiments have been performed on the carbon monoxide complex of myoglobin to assess the effects of photoselection on the kinetics of ligand rebinding and to investigate the reorientational dynamics of the heme plane. The results are analyzed in terms of the optical theory developed in the preceding paper by Ansari and Szabo. Changes in optical density arising from rotational diffusion of the photoselected population produce large deviations from the true geminate ligand rebinding curves if measurements are made with only a single polarization. The apparent ligand rebinding curves are significantly distorted even at photolysis levels greater than 90%. These deviations are eliminated by obtaining isotropically-averaged optical densities from measurements using both parallel and perpendicular polarizations of the probe pulse. These experiments also yield the optical anisotropy, which gives a novel method for accurately determining the degree of photolysis, as well as important information on the reorientational dynamics of the heme plane. The correlation time for the overall rotational diffusion of the molecule is obtained from the decay of the anisotropy. The anisotropy prior to rotational diffusion is lower than that predicted for a rigidly attached, perfectly circular absorber, corresponding to an apparent order parameter of S = 0.95 +/- 0.02. Polarized absorption data on single crystals suggest that the decreased anisotropy results more from internal motions of the heme plane which take place on time scales shorter than the duration of the laser pulse (10 ns) than from out-of-plane polarized transitions.     

Seasonal fluctuations in cannabinoid content of Kansas Marijuana

Marijuana (Cannabis sativa L.) was sampled at nine progressive growth stages in Riley County, Kansas, and analyzed for four major cannabinoids: cannabidiol (CBD), della-8-tetrahydrocannabinol (delta-8-THC), delta-9-tetrahydrocannabinol (delta-9-THC), and cannabinol (CBN). Seasonal fluctuation in cannabinoids were related to stage of plant development. Cannabinoids were lowest in seedlings, highest prior to flowering and at an intermediate level thereafter until physiological maturity. Cannabinoids were highest in flowers and progressively lower in leaves, petioles, stems, seeds, and roots. Cannabinoid content of male and female flowers was not significantly different. Cannabidiol occurred in the highest concentrations (0.01 to 0.94% of dry matter) in all plant parts; delta-9-THC, the next highest (0.0001 to 0.06%) in the study over time. Cannabidiol content of leaf tissue of plants sampled from ten locations at flowering, ranged from 0.12 to 1.7%; delta-9-THC, from 0.01 to 0.49%. Some variation was attributed to environmental factors. Results indicate transformation of CBD to delta-9-THC to CBN. Environmental stress apparently increased delta-9-THC concentration, and bivalent ions: Mg, Mn, and Fe of leaf tissue could have regulated enzyme systems responsible for cannabinoid synthesis.     

Brain uptake and metabolism of estradiol benzoate and estrous behavior in ovariectomized guinea pigs

Groups of spayed guinea pigs were injected sc with tritiated estradiol benzoate in oil and killed at intervals varying from 12 to 120 hr later. The quantities of radioactivity with the mobility of estrone (E₁), estradiol-17β (E₂), and estriol (E₃) were estimated in plasma, hypothalamus, cortex, and cerebellum. Radiometabolites extracted from the hypothalamus and the cortex were identified by derivative formation and by isotope dilution techniques. The hypothalamus contained larger quantities of E₂ than any of the other tissues studied. The same pattern of uptake and decay of radioactivity was observed in all tissues. Concentration of total radioactivity was greatest 12 hr after injection and declined fairly regularly to minimal value at 120 hr. Unlike the hypothalamus and the cerebellum, in the cortex a large proportion of the radioactivity was present as E₁. ³H-estradiol benzoate was metabolized to ³H-estradiol by blood in vitro suggesting that the esterified form of the hormone is long lasting because of its slow release from the site of injection rather than its long half-life in the blood.Additional groups of spayed guinea pigs were tested for lordosis in response to fingering after injection of estradiol benzoate followed by progesterone at intervals varying from 12 to 120 hr. The expression of lordosis varied in a complex manner as a function of the interval between the injection of estradiol benzoate and progesterone. Maximum measures of lordosis were obtained when the interval between injections was 36 hr. The relation between behavior and the neural uptake of estrogens suggests that both the duration of estrogen action and the concentration of estrogens at the time the behavior is being displayed determine the character of the response.