Furosemide-sensitive Na+-K+ cotransport and cellular metabolism in human erythrocytes

Metabolic depletion of human red cells with 2-deoxy-D-glucose in the presence of EGTA decreased ATP to about 4% of the initial value and increased total ouabain- and furosemide-resistant Na+ and K+ effluxes by 20% and 100%, respectively, and furosemide-sensitive Na+ and K+ effluxes by 100% and 60%, respectively. When ATP was restored, all the components of Na+ and K+ fluxes measured returned to baseline levels suggesting a metabolic dependence.     

The Kinetics of Ouabain Inhibition and the Partition of Rubidium Influx in Human Red Blood Cells

In the development of ouabain inhibition of rubidium influx in human red blood cells a time lag can be detected which is a function of at least three variables: the concentrations of external sodium, rubidium, and ouabain. The inhibition is antagonized by rubidium and favored by sodium. Similar considerations could be applied to the binding of ouabain to membrane sites. The total influx of rubidium as a function of external rubidium concentration can be separated into two components: (a) a linear uptake not affected by external sodium or ouabain and not requiring an energy supply, and (b) a saturable component. The latter component, on the basis of the different effects of the aforementioned factors, can be divided into three fractions. The first is ouabain-sensitive, inhibited by external sodium at low rubidium, and requires an energy supply; this represents about 70–80% of the total uptake and is related to the active sodium extrusion mechanism. The second is ouabain-insensitive, activated by external sodium over the entire range of rubidium concentrations studied, and dependent on internal ATP; this represents about 15% of the total influx; it could be coupled to an active sodium extrusion or belong to a rubidium-potassium exchange. The third, which can be called residual influx, is ouabain-insensitive, unaffected by external sodium, and independent of internal ATP; this represents about 10–20% of the total influx.     

Outward sodium and potassium cotransport in human red cells

Summary This paper reports some kinetic properties of Na–K cotransport in human red cells. All fluxes were measured in the presence of 10^–4 M ouabain. We measured Na and K efflux from cells loaded by the PCMBS method to contain different concentrations of these ions into a medium that contained neither Na nor K (MgCl₂-sucrose substitution) in the absence and presence of furosemide. Furosemide inhibited 30–60% of the total efflux depending on the internal ion concentration and the individual subject. We took the furosemide-sensitive fluxes to be a measure of Na–K cotransport. The ratio of Na to K cotransport was 1 over the entire range of internal Na and K concentrations studied. When Na was substituted for K as the only internal cation, cotransport was maximally activated when the Na and K concentrations were between 20 and 90 mmol/liter cells. The concentration of internal Na required to produce half-maximal cotransport was about 13±4 mmol/liter cells (n=4), while the comparable concentration of K was somewhat lower. The activation curve was definitely sigmoid in character, suggesting that at least two Na ions are involved in the transport process. The maximum of Na–K cotransport was about 0.5±0.15 mmol/liter cells × hr (n=5); it had a flat maximum in the medium at about pH 7.0, decreasing in both the acid and alkaline sides. furosemide-resistant effluxes were found to be linear functions of internal Na and K concentrations and to yield rate coefficients of 0.019±0.002 hr^–1 and 0.014±0.002 hr^–1 (n=7), respectively. These values are of the same order of magnitude expected of ions moving across phospholipid bilayers.Charge de Recherches CNRS.     

Intercellular communication in the rat anterior pituitary gland: an in vivo and in vitro study

The concept of "stimulus-secretion coupling" suggested by Douglas and co-workers to explain the events related to monamine discharge by the adrenal medulla (5, 7) may be applied to other endocrine tissues, such as adrenal cortex (36), pancreatic islets (4), and magnocellular hypothalamic neurons (6), which exhibit a similar ion-dependent process of hormone elaboration. In addition, they share another feature, that of joining neighbor cells via membrane junctions (12, 26, and Fletcher, unpublished observation). Given this, and the reports that hormone secretion by the pars distalis also involves a secretagogue-induced decrease in membrane bioelectric potential accompanied by a rise in cellular [Ca++] (27, 34, 41), it was appropriate to test the possibility that cells of the anterior pituitary gland are united by junctions.     

Natural products as starting points for future anti-malarial therapies: going back to our roots?

Background

Population movements along the Thailand-Cambodia border, particularly among highly mobile and hard-to-access migrant groups from Cambodia and Myanmar, are assumed to play a key role in the spread of artemisinin resistance. Data on treatment-seeking behaviours, knowledge and perceptions about malaria, and use of preventive measures is lacking as characteristics of this population prevent them from being represented in routine surveillance and the lack of a sampling frame makes reliable surveys challenging.

Methods

A survey of migrant populations from Cambodia and Myanmar was implemented in five selected rural locations in Thailand along the Thai-Cambodian border using respondent driven sampling (RDS) to determine demographic characteristics of the population, migratory patterns, knowledge about malaria, and health-care -seeking behaviours.

Results

The majority of migrants from Myanmar are long-term residents (98%) with no plans to move back to Myanmar, understand spoken Thai (77%) and can therefore benefit from health messages in Thai, have Thai health insurance (99%) and accessed public health services in Thailand (63%) for their last illness. In comparison, the majority of Cambodian migrants are short-term (72%). Of the short-term Cambodian migrants, 92% work in agriculture, 18% speak Thai, 3.4% have Thai health insurance, and the majority returned to Cambodia for treatment (45%), self-treated (11%), or did not seek treatment for their last illness (27%).

Conclusion

Most highly mobile migrants along the Thai-Cambodia border are not accessing health messages or health treatment in Thailand, increasing their risk of malaria and facilitating the spread of potentially resistant Plasmodium falciparum as they return to Cambodia to seek treatment. Reaching out to highly mobile migrants with health messaging they can understand and malaria diagnosis and treatment services they can access is imperative in the effort to contain the spread of artemisinin-resistant P. falciparum.     

Airway cellularity, lipid laden macrophages and microbiology of gastric juice and airways in children with reflux oesophagitis

Background and methods

Human metapneumovirus (hMPV) is a recently discovered respiratory virus associated with bronchiolitis, pneumonia, croup and exacerbations of asthma. Since respiratory viruses are frequently detected in patients with acute exacerbations of COPD (AE-COPD) it was our aim to investigate the frequency of hMPV detection in a prospective cohort of hospitalized patients with AE-COPD compared to patients with stable COPD and to smokers without by means of quantitative real-time RT-PCR.

Results

We analysed nasal lavage and induced sputum of 130 patients with AE-COPD, 65 patients with stable COPD and 34 smokers without COPD. HMPV was detected in 3/130 (2.3%) AE-COPD patients with a mean of 6.5 × 10⁵ viral copies/ml in nasal lavage and 1.88 × 10⁵ viral copies/ml in induced sputum. It was not found in patients with stable COPD or smokers without COPD.

Conclusion

HMPV is only found in a very small number of patients with AE-COPD. However it should be considered as a further possible viral trigger of AE-COPD because asymptomatic carriage is unlikely.     

植物的遗传转化及其应用(英文)

近年来,植物遗传转化研究有了长足的发展。已经达到能够通过简单的遗传控制手段研究具有新表现型的植物,甚至达到进入商业化的程度。这些手段包括植物生物学的主要研究技术以及植物组织培养和树种改良的一些实用方法。尽管采用农瘤杆菌和鸟枪法等技术的植物遗传转化系统已经得到了广泛的应用,但是在如何开发具有能够得到控制表达的转基因高产植物方面,在如何使所得到的转基因植物远离遗传危害等方面,目前的转化系统遇到了极大的技术挑战。已经提出了各种各样的方法用于将新基因稳定地导入120多种不同植物的核基因组。本文将讨论这些遗传转化系统所需的生物学要求和实际应用方面的需求、基因转化和转基因表达的研究策略、遗传转化植物的鉴定以及转基因植物与大众的认可。本文将分为七个部分加以讨论:一、导言;二 、基因转化到细胞里的方法;三、植物遗传转化策略;四、植物遗传转化的鉴定;五、植物遗传转化的实际应用;六、转基因植物与环境;七、未来植物遗传转化的需求与发展方向。