Physiological effects of long term exposure to low concentrations of SO2 and NH3 on poplar leaves

Shoots of poplar (Populus euramericana L. cv. Flevo) were exposed to filtered air, SO₂, NH₃ or a mixture of SO₂ and NH₃ for 7 weeks in fumigation chambers. After this exposure gas exchange measurements were carried out using a leaf chamber. As compared to leaves exposed to filtered air, leaves pretreated with 112 μg m^?3 SO₂ showed a small reduction in maximum CO₂ assimilation rate (P_max) and stomatal conductance (g_s). They also showed a slightly higher quantum yield and dark respiration. In addition, the fluorescence measurements indicated that the Calvin cycle of the leaves pretreated with 112 μg m^?3 SO₂ was more rapidly activated after transition from dark to light. An exposure to 64 μg m^?3 NH₃ had a positive effect on P_max, stomatal conductance and NH₃ uptake of the leaves. This positive effect was counteracted by an SO₂ concentration of 45 μg m^?3. The exposure treatments appeared to have no effect on the relationship between net CO₂-assimilation and g_s. Also, no injury of the leaf cuticle or of epidermal cells was observed. Resistance analysis showed that NH₃ transfer into the leaf can be estimated from data on the boundary layer and stomatal resistance for H₂O transfer and NH₃ concentration at the leaf surface, irrespective of whether the leaves are exposed for a short or long time to NH₃ or to a mixture of NH₃ and SO₂. In contrast SO₂ uptake into the leaves was only partly correlated to the stomatal resistance. The results suggest a large additional uptake of this gas by the leaves. The possibility of a difference in path length between SO₂ and H₂O molecules is proposed.     

Dimeric and trimeric proanthocyanidins possessing a doubly linked structure from Pavetta owariensis

Pavetannin A-2, a new A-type proanthocyanidin, along with the trimers cinnamtannin B-1, pavetannin B-1, B-2, B-3, B-5 and B-6 have been isolated in their free phenolic form from the stem bark of Pavetta owariensis. Spectral data and partial acid-catalysed degradation established their structures as ent-epicatechin-(4→8,2→O→7)-catechin, epicatechin-(4β→8,2β→O→7)-epicatechin-(4→8)-epicatechin, epicatechin-(4β→8,2β→O→7)-epicatechin-(4β→8)-ent-epicatechin, epicatechin-(4β→8,2β→O→7)-epicatechin-(4β→8)-epicatechin, epicatechin-(4β→6,2β→O→7)-epicatechin-(4β→8)-epicatechin, epicatechin-(4β→6,2β→O→7)-catechin-(4β→8)-epicatechin, epicatechin-(4β→8,2β→O→7)-epicatechin-(4→8)-catechin, respectively.     

Relationship between secretion of the Anton blood group antigen in saliva and adherence of Haemophilus influenzae to oropharynx epithelial cells

Abstract Inhibition of adherence of bacteria to epithelial cells contributes to a reduction of infections by these bacteria. We have shown that the Anton blood group antigen, the erythrocyte receptor for Haemophilus influenzae (van Alphen et al. 1986, FEMS Microbiol. Lett. 37, 69–71), occurs in saliva, that the occurrence is not related to the secretor state of the donor of the saliva and that saliva containing Anton antigen could not inhibit the adherence of H. influenzae to oropharynx epithelial cells.
Anton antigen was detected in saliva samples of 14 donors by immunoblotting with two different anti-Anton sera. The amount of Anton antigen correlated with the ability of H. influenzae to adhere to the epithelial cells of the donor of the saliva: 4.1 ± 0.1 Anton antigen units for donors with more than 50 H. influenzae per cell and 1.6 ± 0.5 units for donors with less adhering epithelial cells. No correlation between the amount of Anton antigen in saliva and secretor status of the donor was observed. Adherence of H. influenzae to epithelial cells was not inhibited by saliva of secretors ( N = 11) or non-secretors ( N = 3). The same saliva did not inhibit the interaction of the bacteria with Anton antigen bearing erythrocytes as measured by haemagglutination inhibition. This indicates that the amount of Anton antigen in saliva is probably too low to interfere with the interaction of H. influenzae with oropharynx epithelial cells and erythrocytes.     

Cigarette smoking and human papillomavirus in patients with reported cervical cytological abnormality.

OBJECTIVE--To assess the relation between two risk factors for cervical neoplasia: smoking and infection with oncogenic human papillomavirus. It has been suggested that smoking causes a local immunological defect, which could facilitate the infection and persistence of human papillomavirus. DESIGN--Cross sectional epidemiological study. Completion of a structured questionnaire by the patients, analysis of cervical scrapes for human papillomavirus, and morphological examination of biopsy specimens. SETTING--Outpatient gynaecological clinic. SUBJECTS--181 women with a report of cervical cytological abnormality. MAIN OUTCOME MEASURES--Prevalence of infection with oncogenic human papillomavirus and smoking habits. RESULTS--Oncogenic human papillomavirus was found in the cervix of 26 (41%) of the 63 women who did not smoke, 22 (58%) of the 38 who smoked 1-10 cigarettes a day, 28 (61%) of the 46 who smoked 11-20 cigarettes a day, and 26 (76%) of the 34 who smoked > or = 21 cigarettes a day. The prevalence of the virus thus increased in accordance with the number of cigarettes smoked (p = 0.001). This relation remained after adjustment for age at first intercourse and lifetime number of sexual partners. Of the 63 non-smokers, 23 had previously smoked at least 10 cigarettes a day at some time. Of these 23 women, 14 (61%) had oncogenic human papillomavirus in their cervix. Of the 40 women who had never smoked at least 10 cigarettes a day, 12 (30%) had the virus. The prevalence of oncogenic human papillomavirus in non-smokers therefore depended on previous smoking habits (p = 0.03). CONCLUSION--The dose dependent effect of cigarette smoking on the occurrence of oncogenic human papillomavirus favours a causal relation between these risk factors for cervical neoplasia.     

Immunity against extracellular pathogens

Summary Eukaryotic cells live in a relatively comfortable equilibrium with a wide variety of microbes. However, while many of the cohabiting microorganisms are harmless or even beneficial to the eukaryotic host, a number of prokaryotes have evolved the capacity to invade and replicate within host cells, thereby becoming potentially pathogenic. To be able to cope with potential pathogens, most organisms have developed several host defense mechanisms. First, microbes can be internalized and destroyed by a number of cell types of an innate immune system in a rather aspecific manner. Second, more complex organisms possess additionally an adaptive immune system that is capable of eliminating hazardous microbes in a highly specific manner. This review describes recent progress in our understanding of how pathogens interact with cells of the immune system, resulting in activation of the immune system or, for certain microorganisms, in the evasion of host defense reactions.     

Quality control of roots of Eleutherococcus senticosus by HPLC

An HPLC method based on several known methods for the determination of eleutherosides B and E was developed, optimised and validated in terms of linearity, precision (repeatability and intermediate precision on different days and at different concentration levels) and accuracy (recovery). The extraction procedure, the extraction solvent and the extraction yield were evaluated and optimised. A reversed-phase RP-18 column gradient eluted with a two-phase system consisting of phosphoric acid:water (0.5:99.5) and acetonitrile was used to evaluate the samples; detection was at 220 nm. Although eleutherosides B and E are commercially available, they are very costly, and therefore ferulic acid was chosen as external standard. The correction factors for the response of ferulic acid against both eleutherosides were determined and validated. This method, accepted by the European Pharmacopoeia Commission, will be included in the monograph on Eleutherococcus senticosus roots to assay the content of eleutherosides B and E.     

The Trojan horse: survival tactics of pathogenic mycobacteria in macrophages

Mycobacterium tuberculosis, the causative agent of tuberculosis, has infected billions of people worldwide. A key to the success of M. tuberculosis and related pathogenic mycobacteria lies in their ability to persist within the hostile environment of the host macrophage. After internalization by macrophages, most microbes are rapidly transported to lysosomes in which they are destroyed. By contrast, pathogenic mycobacteria prevent fusion of phagosomes with lysosomes, thereby surviving intracellularly. Recent progress in understanding the molecular biology of host-mycobacteria interactions is providing insights into these survival tactics.     

In vitro inhibition of beta-haematin formation, DNA interactions, antiplasmodial activity, and cytotoxicity of synthetic neocryptolepine derivatives

Neocryptolepine, a minor alkaloid of Cryptolepis sanguinolenta, was investigated as a lead for new antiplasmodial agents, because of its lower cytotoxicity than cryptolepine, the major alkaloid. Synthetic 2- or 3-substituted neocryptolepine derivatives were evaluated for their biological activity. In addition to the antiplasmodial activity (Plasmodium falciparum chloroquine-sensitive and -resistant) also the cytotoxicity (MRC-5 cells) was determined. Several compounds such as 2-bromoneocryptolepine showing higher and more selective antiplasmodial activity than neocryptolepine were obtained. Several functional assays and in vitro tests were used to obtain additional information on the mechanism of action, i.e., the beta-haematin formation inhibitory assay (detoxification of haem) and the DNA-methylgreen displacement assay (interaction with DNA). It could be demonstrated that the 2- or 3-substituted neocryptolepine derivatives investigated here have about the same potency to inhibit the beta-haematin formation as chloroquine, indicating that inhibition of haemozoin formation makes at least an important contribution to their antiplasmodial activity, although their in vitro antiplasmodial activity is still less than chloroquine.