皮肤组织模型中吸收和散射系数对单线态氧发光特性的影响

构建由脂肪乳剂和墨水组成的皮肤组织模型,定量研究皮肤组织模型的吸收系数μa和散射系数μs对光敏化单线态氧(singlet oxygen,~1O_2)发光特性的影响。利用~1O_2发光检测系统测量含光敏剂四硫磺基酞菁氯化铝的皮肤组织模型分别在中心波长为1 230,1 270和1 310 nm处的时间分辨发光光谱,对扣除背景信号后的时间分辨~1O_2发光光谱进行积分和拟合,获得~1O_2发光积分强度以及激发三重态寿命τ_T和~1O_2寿命τ_D。结果表明在皮肤组织模型中,~1O_2发光积分强度随着μ_a和μ_s的增大而减小,μ_a对τ_T和τ_D没有影响。τ_T随着μs的增加而增加,τ_D随μ_s的增加先骤降而后缓慢上升。当μ_a1.5 mm~(-1)和μ_s32 cm~(-1)时,~1O_2发光积分强度和τ_T、τ_D均趋于稳定,其中τ_T和τ_D分别为3.4±0.6μs和3.3±0.7μs。     

TAK1 regulates SCF expression to modulate PKBα activity that protects keratinocytes from ROS-induced apoptosis

Dysregulated reactive oxygen species (ROS) generation contributes to many human pathologies, including cancer and diabetes. During normal wound repair, inflammation-induced ROS production must be tightly controlled, but the mechanisms reining their generation remain unclear. Herein, we show that transforming growth factor β-activated kinase 1 (TAK1) directly regulates stem cell factor (SCF) expression, which activates the protein kinase B (PKB)α pro-survival pathway in a cell-autonomous manner to protect keratinocytes from ROS-mediated cell death. TAK1 is a pivotal inflammatory mediator whose expression was transiently elevated during wound healing, paralleling the ROS production profile. TAK1 deficiency in keratinocytes led to increased apoptosis in response to anoikis and TNF-α treatment and was associated with elevated ROS level as analyzed by FACS. Using organotypic skin co-culture and comparative growth factor array analysis, we revealed a cell-autonomous mechanism that involved the SCF/c-Kit/PKBα signaling cascade. Ectopic expression of TAK1 or treatment with exogenous recombinant SCF restored the increased ROS production and apoptotic cell death in TAK1-deficient keratinocytes. Conversely, normal keratinocytes treated with various inhibitors targeting the SCF/c-Kit/PKBα pathway exhibited increased ROS production and TNF-α- or anoikis-induced apoptosis. Our study reveals a novel anti-apoptotic role for SCF in keratinocytes and identifies TAK1 as a novel player uniting inflammation and ROS regulation in skin redox biology.     

Photosynthetic response of Nereocystis luetkeana (Phaeophyta) to high light

Photosynthetic response to high light was determined for Bull kelp, Nereocystis luetkeana (K. Mertens) Postels and Ruprecht in order to understand how this species is affected by short‐term fluctuations in irradiance. Exposure of N. luetkeana blades to high intensity photosynthetically active radiation (1000 µmol photons m^?2 s^–1) caused increased non‐photochemical quenching of fluorescence and higher de‐epoxidation ratios for xanthophyll pigments indicating that energy‐quenching xanthophylls were used to protect blades against photoinhibition. Despite initiation of these photoprotective mechanisms, maximum photochemical efficiency of photosystem II (F_v/F_m) decreased 40% in response to a 60 min exposure to 1000 µmol photons m^?2 s^–1 photosynthetically active radiation indicating that photoinhibition had occurred. Light‐saturated rates of oxygen evolution were not changed significantly by the high light treatment. Recovery of maximum photochemical efficiency of photosystem II to within 8% of initial values occurred after a 300‐min dim light period. Younger sections of the blades were slightly more susceptible to high light damage than older sections. Middle sections of the blades were more prone to light‐induced damage at water temperatures of 7°C or 18°C, as compared to 13°C. Exposure to biologically effective ultraviolet‐B radiation (UV‐B_be) (up to 4.5 kJ m^–2 day^–1) in photoinhibitory light conditions did not significantly affect light‐induced damage to photosystem II.     

Basal superoxide as a sex-specific immune constraint

There is increasing evidence that reactive oxygen species (ROS), a group of unstable and highly reactive chemical molecules, play a key role in regulating and maintaining life-history trade-offs. Upregulation of ROS in association with immune activation is costly because it may result in an imbalance between pro- and antioxidants and, hence, oxidative damage. Previous research aimed at quantifying this cost has mostly focused on changes in the pro-/antioxidant balance subsequent to an immune response. Here, we test the hypothesis that systemic ROS may constrain immune activation. We show that systemic, pre-challenge superoxide (SO) levels are negatively related to the strength of the subsequent immune response towards the mitogen phytohaemagglutinin in male, but not female painted dragon lizards (Ctenophorus pictus). We therefore suggest that systemic SO constrains immune activation in painted dragon males. We speculate that this may be due to sex-specific selection pressures on immune investment.     

Real-time measurement of pheromone release from individual female moths and synthetic dispensers in a wind tunnel by recording of single receptor-neurone responses

Measurements of single neurone activity in the peripheral pheromone receptors of male Agrotis segetum (Denis & Schiffermüller) (Lepidoptera: Noctuidae) were performed in a wind tunnel using a portable electrophysiological recording unit. Filter paper and rubber septa loaded with synthetic sex pheromone, as well as individual conspecific female glands, were used as pheromone sources. Recordings, up to 3 h long, were analysed for temporal variation in spiking activity. The recordings were performed 2 m downwind of the source, where the pheromone plume had a width of approximately 12 cm, as could be measured with the single cell preparations. The system allowed reliable measurements of relative pheromone concentration with a 20-s time resolution. The release rate from rubber septa loaded with pheromone was more or less constant over time, whereas the release rate from filter paper loaded with pheromone decreased to one tenth of the initial value within 6 min from the application of the pheromone. The release of pheromone from female pheromone glands was pulsed with an interval of 2–10 min between bursts. This pulsing was not caused by retraction of the gland, as the glands were forcibly extruded during the entire experiment, but should reflect variation in transport of pheromone to the gland surface and subsequent release. The demonstrated stability of the preparations using tungsten electrodes, the reliable monitoring of female-produced pheromone plumes at several metres distance, and the time resolution obtained are important steps towards field monitoring of natural pheromone plumes, as well as pheromone concentration and distribution in applications for mating disruption.     

Protein Kinase FA/Glycogen Synthase Kinase-3α After Heparin Potentiation Phosphorylates τ on Sites Abnormally Phosphorylated in Alzheimer''s Disease Brain

In this work, we tested the effect of ion channel blockers and of phorbol ester treatments on [³H]dopamine ([³H]DA) release and neurotensin (NT)-induced facilitation of [³H]DA release from cultures of rat fetal mesencephalic cells. The potassium channel blockers tetraethylammonium and 4-aminopyridine increased basal [³H]DA release and decreased K⁺-evoked [³H]DA release, whereas apamin was without effect. K⁺-evoked [³H]DA release was decreased by ω-conotoxin and nifedipine, totally suppressed by cadmium, and unaffected by amiloride. These results show the differential sensitivity of [³H]DA release to blockade of various ion channels and suggest the involvement of N-type, L-type, and non-L-non-N-type, but not T-type, voltage-sensitive calcium channels in K⁺-evoked release. Phorbol 12-myristate 13-acetate increased both spontaneous and K⁺-evoked [³H]DA release, suggesting a modulatory action of protein kinase C on DA release in this system. Unexpectedly, however, the effects of the phorbol ester were not counteracted by the protein kinase C inhibitors H7, staurosporine, or polymyxin B. NT-induced facilitation of K⁺-evoked [³H]DA release was insensitive to most of the ion channel blockers, except cadmium (64% decrease in NT effect), suggesting that the corresponding potassium' and calcium channels were not involved in the effect of NT on [³H]DA release in this system. The NT effect was totally suppressed by phorbol ester treatments, indicating a possible desensitization of the corresponding transduction mechanisms after protein kinase C activation.     

A continuous-flow method of organ culture

Summary A method of perfusion organ culture is described in which explants cultured at the airmedium interface are bathed by a continuous flow of nutrient medium. Morphological studies on the fetal rat lung indicate that explant development in this system is comparable to that obtained using standard organ-culture dishes. Medium supply is easily manipulated and continuous sampling of the effluent stream is possible without disturbing the immediate explant environment. The basic design facilitates secretory-response studies on cultured organ explants as demonstrated by a study of glucose-stimulated insulin release by the neonatal rat pancreas. This work was supported by U. S. Public Health Service Training Grant No. GM 00114.