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At least 1,189 records · Page 66Linked to original sources
PubMed1983

Sodium and potassium transport in ferret red cells.

Potassium movements into ferret red cells were measured with the tracer 86Rb. Equilibration of 86Rb between medium and cells could be resolved into two components. 70-90% occurred rapidly with a rate constant of between 3.5-5.5 h-1. The remaining 10-30% occurred slowly. The slow movement was equivalent to a potassium influx of about 1.2-2.76 mmol l-1 cell h-1. Potassium influx was inhibited by 80-90% by 0.1 mM-bumetanide (a high-ceiling, loop diuretic). This suggests that the sodium-potassium co-transport system has a high capacity for carrying potassium (estimated at about 17-35 mmol l-1 cell h-1). After bumetanide (0.1 mM) remaining potassium movements (approximately 0.5 mmol l-1 cell h-1) are at a similar level to that found in red cells from other animals. The sodium pump makes a very small contribution to potassium flux into ferret red cells. Much of this pump activity may be attributed to reticulocytes present in cell samples. Sodium movements across the red cell membrane were measured with 22Na. Sodium equilibrated more slowly than potassium. 60-70% of the sodium influx was inhibited by 0.1 mM-bumetanide, indicating that most sodium influx in ferret red cells is also through the co-transport system. The co-transport system can transport up to 49 mmol sodium l-1 cell h-1 and is half maximally activated by 0.38 mM-potassium in the external medium. In the presence of bumetanide, sodium influx (about 18 mmol l-1 cell h-1) is similar to that of other carnivore red cells. This is about five times greater than that of red cells from non-carnivores. The possibility that there are two populations of ferret red cells with different potassium transport characteristics is discussed.

Animals↗
PubMed1984

Colicin V-treated Escherichia coli does not generate membrane potential.

Colicin V-treated Escherichia coli was inhibited in its capacity to carry out active transport of proline and was unable to generate a membrane potential. Colicin V also prevented membrane potential formation by isolated cytoplasmic membrane vesicles. We conclude that a primary effect of this colicin involves the cytoplasmic membrane as a target.

Biological Transport, Active↗
PubMed2001

Activity of the Kluyveromyces lactis Pdr5 multidrug transporter is modulated by the Sit4 protein phosphatase.

A possible role for posttranslational modifications in regulating the activity of ATP-binding cassette (ABC) transporters has not been well established. In this study, the drug efflux ABC transporter gene KlPDR5 was isolated from the budding yeast Kluyveromyces lactis, and it was found that the encoded KlPdr5 drug pump is posttranslationally regulated by the type 2A-related Ser/Thr protein phosphatase, Sit4p. The KlPdr5 transporter is a protein of 1,525 amino acids sharing 63.8% sequence identity with its Saccharomyces cerevisiae counterpart, ScPdr5p. Overexpression of the KlPDR5 gene confers resistance to oligomycin, antimycin, econazole, and ketoconazole, whereas cells with a disrupted allele of KlPDR5 are hypersensitive to the drugs and have a decreased capacity to carry out efflux of the anionic fluorescent dye rhodamine 123. It was found that a chromosomal disruption of KlPDR5 abolishes the drug-resistant phenotype associated with sit4 mutations and that a synergistic hyperresistance to the drugs can be created by overexpressing KlPDR5 in sit4 mutants. These data strongly indicate that the multidrug-resistant phenotype of sit4 mutants is mediated by negatively modulating the activity of KlPdr5p. As the transcriptional level of KlPDR5 and the steady-state level of KlPdr5p are not significantly affected by mutations in SIT4, the regulation by Sit4p appears to be a posttranslational process.

ATP-Binding Cassette Transporters↗
PubMed1982

Protein synthesis in lysates of Aedes albopictus cells infected with vesicular stomatitis virus.

Aedes albopictus cells (clone LT-C7) showed a marked cytopathic effect and inhibition of protein synthesis (both host and viral) after infection with vesicular stomatitis virus (VSV), but only if (i) cultures were incubated at 34 degrees C rather than 28 degrees C and (ii) serum was present in the medium (S. Gillies and V. Stollar, Mol. Cell. Biol. 2:66-75, 1982). To learn more about how protein synthesis is shut off in VSV-infected A. albopictus cells, we have compared cell-free protein synthesis in extracts prepared from VSV-infected cells and control cells. Extracts prepared 6 h after infection from VSV-infected cells maintained at 34 degrees C in the presence of serum reflected what was observed with intact cells in at least two respects: (i) they showed a markedly diminished capacity to carry out protein synthesis (whether directed by endogenous or exogenously added mRNA), and (ii) there was decreased phosphorylation in vitro by [gamma-32P]ATP of a specific ribosomal protein (Gillies and Stollar, Mol. Cell. Biol. 2:66-75, 1982). In addition, and consistent with a block at the level of initiation, the formation of 80S initiation complexes, as measured by binding of VSV 12 to 18S mRNA, was reduced in the inactive extracts. Addition of an S-100 fraction from uninfected cells to the inactive extract reversed each of the aforementioned changes; i.e., it restored protein synthetic activity, it stimulated the formation of 80S initiation complexes, and it increased phosphorylation of the specific ribosomal protein referred to above. The active component in the S-100 fraction was heat labile and non-dialyzable and, upon ammonium sulfate fractionation of the S-100 fraction, was found in the 40 to 70% saturation fraction. Our findings suggest that VSV infection of A. albopictus cells inhibits protein synthesis by inactivating a macromolecular component, probably a protein, in the S-100 fraction which may be involved in the initiation of protein synthesis. More specifically, we suggest that this component is involved in the joining of the ribosomal subunits to form 80S initiation complexes.

Aedes↗
PubMed1994

Cairo conference.

Explore the source record for details and available documents.

Environment↗
PubMed1996

Averting a world food shortage: tighten your belts for CAIRO II.

We are going to have to eat what the world will produce with all its failings, not what it could produce without them. Trends in global food production are therefore all important. These are now giving cause for anxiety, in that the rate of increase of global grain yields has been slowing seriously. Locally, the food security of some demographically trapped communities is so dire that, like China, they need one child families. The 1994 Cairo population conference (Cairo I) took future food supplies for granted and took no account of demographic entrapment: the conference should be recalled urgently as CAIRO II.

Edible Grain↗
PubMed1993

Population growth and natural resource use: do we need to despair of Africa?.

The authors make the case that population growth can lead to increases in agricultural output per head on a sustainable basis. This argument, originally developed by E. Boserup, is "illustrated by a study of Machakos District, Kenya during 1930-1960, which shows that, if policies are supportive, agricultural and non-farm incomes grow faster than even the rapid population growth rate experienced in Africa. Land use capability is not fixed, but can be transformed by investment, new technologies and good management. Lack of investment and consequent degradation are most likely at low population densities. While the study cannot foretell the future, Java illustrates a similar theme at even higher densities."

Africa↗
PubMed1993

Impacts of emigration on mountain watersheds: the upper Pokhara Valley, Nepal.

"Confronted with adverse physical conditions, marginal landholdings and scarce non-farming employment opportunities, farmers in the Upper Pokhara Valley had opted for temporary emigration as an alternative strategy for fulfilling their subsistence requirements. This had caused somewhat malign effects on watershed due to dwindling farm management practices and increasing dependency on common resources.... Findings of this study are envisaged to be conducive to the formulation of a comprehensive watershed management strategy, including population planning....[It is suggested] that both overpopulation and depopulation could be instrumental in watershed degradation, especially in mountainous areas where labor is a critical factor in the use and management of farmlands."

Agriculture↗
PubMed1986

Towards better nutrition: lip service or a realistic fight?

Progress towards the objective of the World Food Conference of 1974 that "no child should go to bed hungry" is reviewed. The low market price of primary products keeps developing countries poor. Yet in these countries industry rather than agriculture has been supported by governments. All regions are increasing total food production but population growth threatens to offset this increase. In some areas there is decrease in food production per head of population. In many countries the social situation of women affects the nutrition of families. Other causes of malnutrition are discussed and future policies are recommended.

Africa↗
PubMed2001

Preferential and persistent depletion of CCR5+ T-helper lymphocytes with nonlymphoid homing potential despite early treatment of primary HIV infection.

Strains of human immunodeficiency virus (HIV) transmitted between individuals use the CCR5 coreceptor, but no preferential depletion of particular Th-lymphocyte subpopulations has been reported during primary HIV infection (PHI). In contrast, gut-associated Th lymphocytes are preferentially depleted in macaques recently infected by simian immunodeficiency virus. The expression of CCR5 and the intestinal homing receptor integrin alpha4beta7 on subpopulations of Th lymphocytes was studied in 12 patients with PHI. There was a profound decrease of circulating alpha4beta7+ Th lymphocytes and CCR5+ memory Th lymphocytes with nonlymphoid homing potential (CD62L-CD45RO+). Unlike other Th lymphocytes, this cell population remained depleted despite early control of viral replication under antiretroviral treatment. Therefore, HIV preferentially targets a specific CCR5+ subpopulation of Th lymphocytes early during infection, inducing its persistent depletion despite treatment. Protective immunity in vivo depends on Th lymphocytes carrying homing capacity to nonlymphoid tissue, and therefore these data may explain the persistent abnormalities of immune functions in patients infected with HIV.

Anti-HIV Agents↗
PubMed1998

Proton magnetic resonance spectroscopy: an emerging technology in pediatric neurology research.

Proton magnetic resonance spectroscopy (MRS) is an emerging technology that allows for the quantitative noninvasive assessment of regional brain biochemistry. The capacity to carry out MRS studies requires existing magnetic resonance imaging (MRI) technology platforms and the purchase of commercially available software modifications. In this review, the physical basis for MRS will be presented leading to an understanding of its potential applications and limitations within the clinical research milieu. Thus far, within pediatric neurology, proton MRS studies have been used to assist in the prediction of outcome in a variety of settings of acquired brain injuries (perinatal asphyxia, near drowning). In addition, proton MRS has been used to document disturbances in oxidative metabolism in neurometabolic disorders, assisting in defining phenotype and the response to therapeutic interventions. In epilepsy, spectroscopic studies have been useful in localizing the epileptogenic zone in intractable focal epilepsies. Future applications of proton MRS will also be highlighted. These include its use as a means of observing the transport and metabolism of various compounds in the brain, its concurrent application with other nuclear magnetic resonance techniques such as MRI and functional MRI, and finally its potential as a means of assessing the short-term effects of any CNS targeted pharmacologic interventions.

Brain↗
PubMed1994

Reflections on change in science and religion.

Science and the Catholic church are both conservative, slow-to-change institutions. However, science has institutionalized procedures that ensure that ample amounts of criticism of currently accepted theories and methodologies will always be present. This arrangement of continuous conjectures and refutation in science ensures often slow but steady change. Because supporters often think of religions as trafficking in timeless truths, criticism of church beliefs and practices (even when intended to stimulate reflection and improvement) is frequently seen as being disloyal to the institution. Because of the growing crises caused by world overpopulation, I argue that the Catholic church's opposition to all artificial methods of birth control now lacks whatever moral force it might have had when originally promulgated. By highlighting theological perspectives that might be appropriate for the ecological realities of the 21st century, I hope the church will see the wisdom of reevaluating many of its positions in the light of rapidly approaching ecological imperatives.

Catholicism↗