Taxonomic studies of the genus Hypoxis in East Africa

East African material of the genus Hypoxis L. has preliminarily been divided into the heterogenous, probably apomictic H. obtusa Burch- complex (2n = 40–50, ca. 75, 76, ca. 85, >86, ca. 92, ca. 98, ca. 108, 130–135, 160–200) and 5 rather homogenous species: H. angustifolia Lam. (2n = 14, 28), H. goetzei Harms (2n = ca. 62), H. kilimanjarica Bak., H. malosana Bak. (2n = 14) and H. macrocarpa Holt & Staubo sp. nov. H. kilimanjarica is divided into ssp. kilimanjarica and ssp. prostrata Holt & Staubo ssp. nov.     

Involvement of the cytoplasmic membrane in nitrogen fixation by Rhizobium leguminosarum bacteroids

1. The nitrogen-fixing efficiency of freshly prepared suspensions of Rhizobium leguminosarum bacteroids from pea root nodules was considerably enhanced by addition of bovine serum albumin. Evidence was found that during preparation of bacteroids the cell membrane is exposed to the uncoupling effect of free fatty acids and to plant phospholipase D activity. Both effects could be counteracted by bovine serum albumin. 2. A technique was developed by which concentrations of free O2 and nitrogenase activity could be measured simultaneously under conditions of steady-state respiration. By means of this system it could be shown that in contrast to previous claims, high ATP/ADP ratios can be achieved in bacteroids even with a high concentration of O2 in the medium. 3. Nitrogen fixation was found to be controlled by the ATP/ADP ratio, the generation of reducing equivalents and the switch-off phenomenon. It was demonstrated that the generation of reducing equivalents for nitrogenase is regulated by the energized state and the integrity of the bacteroid cell membrane. The data indicate that the process of aerobic nitrogen fixation in R. leguminosarum bacteroids resembles that of Azotobacter vinelandii.     

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 In addition, they share another feature, that of joining neighbor cells via membrane junctions (12, 26, and Fletcher, unpublished observation).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.     

Antioxidant activities of carotenoids: quantitative relationships between theoretical calculations and experimental literature data

Quantitative structure activity relationships (QSARs) are described for the antioxidant activity of series of all-trans carotenoids. The antioxidant activity of the carotenoids is characterised by literature data for (i) their relative ability to scavenge the ABTS^·+ radical cation, reflected by the so-called trolox equivalent antioxidant capacity (TEAC) value, (ii) their relative rate of oxidation by a range of free radicals, or (iii) their capacity to inhibit lipid peroxidation in multilamellar liposomes, leading to a decrease in formation of thiobarbituric acid reactive substances (TBARS). All these antioxidant values for radical scavenging action correlate quantitatively with computer-calculated ionisation potentials of the carotenoids. These correlations are observed both when the ionisation potential is calculated as the negative of the energy of the highest occupied molecular orbital (-E(HOMO)) of the molecule, or as the relative change in heat of formation (ΔΔHF) upon the one-electron oxidation of the carotenoids.

The calculations provide a theoretical assay able to characterise the intrinsic electron donating capacity of an antioxidant, in hydrophilic, hydrophobic or artificial membrane environment.     

Combining optical and electrical impedance techniques for quantitative measurement of confluence in MDCK-I cell cultures

A new method combining optical and electrical impedance measurements is described that enables submicroscopic cell movements to be monitored. The cells are grown on small gold electrodes that are transparent to light. This modified electrical cell-substrate impedance sensor (ECIS) allows simultaneous microscopic recording of both growth and motility, thus enabling cell confluence on the electrodes to be systematically correlated to the impedance in regular time intervals of seconds and for extended periods of time. Furthermore, the technique provides an independent measure of monolayer cell densities that we compare to calculated values from a theoretical model. We have followed the attachment and spreading behavior of epithelial Madin-Darby canine kidney strain I (MDCK-I) cell cultures on microelectrodes for up to 40 h. The studies reveal a high degree of correlation between the measured resistance at 4 kHz and the corresponding cell confluence in 4- to 6-h intervals with typical linear cross-correlation factors of r equaling approximately 0.9. In summary, the impedance measured with the ECIS technique provides a good quantitative measure of cell confluence.     

Horseradish peroxidase-catalyzed oligomerization of ferulic acid on a template of a tyrosine-containing tripeptide

Ferulic acid (FA) is an abundantly present phenolic constituent of plant cell walls. Kinetically controlled incubation of FA and the tripeptide Gly-Tyr-Gly (GYG) with horseradish peroxidase and H2O2 yielded a range of new cross-linked products. Two predominant series of hetero-oligomers of FA linked by dehydrogenation to the peptidyl tyrosine were characterized by electrospray ionization (tandem) mass spectrometry. One series comprises GYG coupled with 4-7 FA moieties linked by dehydrogenation, of which one is decarboxylated. In the second series 4-9 FA moieties linked by dehydrogenation, of which two are decarboxylated, are coupled to the tripeptide. A third series comprises three hetero-oligomers in which the peptidyl tyrosine is linked to 1-3 FA moieties of which none is decarboxylated. Two mechanisms for the formation of the FA-Tyr oligomers that result from the dualistic, concentration-dependent chemistry of FA and their possible role in the regulation of plant cell wall tissue growth are presented.     

Monitoring viral-induced cell death using electric cell-substrate impedance sensing

Using an electrical measurement known as electric cell-substrate impedance sensing (ECIS), we have recorded the dynamics of viral infections in cell culture. With this technique, cells are cultured on small gold electrodes where the measured impedance mirrors changes in attachment and morphology of cultured cells. As the cells attach and spread on the electrode, the measured impedance increases until the electrode is completely covered. Viral infection inducing cytopathic effect results in dramatic impedance changes, which are mainly due to cell death. In the current study, two different fish cell lines have been used: chinook salmonid embryonic (CHSE-214) cells infected with infectious pancreatic necrosis virus (IPNV) and epithelioma papulosum cyprini (EPC) carp cells infected with infectious hematopoeitic necrosis virus (IHNV). The impedance changes caused by cell response to virus are easily measured and converted to resistance and capacitance. An approximate linear correlation between log of viral titer and time of cell death was determined.     

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.