Interactions and DNA transfer between Agrobacterium tumefaciens, the Ti-plasmid and the plant host

Agrobacterium tumefaciens is a gram-negative bacterium with the unique capacity to induce neoplasmic transformations in dicotyledonous plants. Recently, both the mechanism and the biological significance of this transformation have been elucidated. Agrobacterium tumefaciens strains contain a large extrachromosomal DNA plasmid (the Ti-plasmid). This Ti-plasmid is responsible for the oncogenic properties of Agrobacterium strains. A particular segment of the Ti-plasmid, containing information determining the tumorous growth pattern and the synthesis of so-called 'opines', e.g. octopine (N-alpha-(D-1-carboxyethyl)-L-arginine) and nopaline (N-alpha-(1,3-dicarboxypropyl)-L-argine), is transferred and stably maintained and expressed in the transformed plant cells. This phenomenon can be understood as a 'genetic colonization' of the plant cells by bacterial plasmid DNA so that the transformed plant cells will produce and secrete into the medium amino acid derivatives (the opines) that Ti-plasmid carrying agrobacteria can selectively use as carbon and nitrogen sources.

Capillary Rise in Granitic Rocks: Interpretation of Kinetics on the Basis of Pore Structure

The capillary transport of water into granitic rocks has been interpreted on the basis of the structure of its porous network. An effective pore radius has been calculated from a three-sized single-pore model proposed by F. A. L. Dullien, El-Sayed, and V. K. Batra (J. Colloid Interface Sci. 60, 497, 1977) Considering the porous network of granites as consisting of fissures grouped in two size types, macro- and microfissures, an effective radius was found from the characteristic radii for each type and the average of these two values. Good agreement between the effective radius calculated and the radius estimated using a capillary rate value measured experimentally provides a suitable basis for identifying interrelationships between the pore structure and moisture capillary rise. In fact, it is possible to predict the process rate from only two characteristic pore sizes, corresponding to the radii of macrofissures and microfissures. The abnormally low rate of capillary rise observed in one of the granites studied could be easily interpreted as due to the involvement exclusively of the macrofissures of its porous network in capillary transport. Copyright 2000 Academic Press.

Field diagnosis of Echinococcus granulosus infection among intermediate and definitive hosts in an endemic focus of human cystic echinococcosis

Human, canine and ovine echinococcosis prevalence was determined in a highland community located in the central Peruvian Andes during 1997 and 1998. Human echinococcosis was determined using portable ultrasonography, chest X-ray examination, and an enzyme-linked immunoelectrotransfer blot (EITB) assay. Canine echinococcosis was determined using microscopy stool examinations and a coproantigen detection enzyme-immunoassay (EIA) for Echinococcus granulosus. Ovine echinococcosis was determined by an EITB assay for sheep echinococcosis and necropsy examination of viscera from domestic slaughtered animals. An abdominal ultrasound, a chest X-ray examination and an EITB for echinococcosis were performed on 214 subjects (45% of the village population). The frequency of presumptive liver/abdominal, lung and liver-lung hydatid cysts was 5.1% (11/214), 3.7% (8/214) and 0.5% (1/214), respectively. The overall prevalence of human cystic echinococcosis was 9.3% (20/214). The frequency of canine echinococcosis was 46% (23/50) and 32% (16/50) by the coproantigen EIA test and arecoline purging, respectively. The frequency of sheep echinococcosis was 65% (22/34) by the EITB and 38% (13/34) by necropsy. We demonstrated a high prevalence of human and animal echinococcosis in this Peruvian village. In remote areas where echinococcosis is endemic, both the coproantigen EIA and arecoline purging may be used for the study of canine echinococcosis; the EITB is useful in establishing the diagnosis of echinococcosis in sheep prior to necropsy.

Color measurements as a reliable method for estimating chlorophyll degradation to phaeopigments

The application of biocides is a traditional method of controlling biodecay of outdoor cultural heritage. Chlorophyll degradation to phaeopigments is used to test the biocidal efficacy of the antimicrobial agents. In the present study, the usefulness of color measurements in estimating chlorophyll degradation was investigated. An aeroterrestrial stone biofilm-forming cyanobacterium of the genus Nostoc was chosen as test organism, comparing its different behaviour in both planktonic and biofilm mode of growth against the isothiazoline biocide Biotin T®. Changes in A(435 nm)/A(415 nm) and A(665 nm)/A(665a nm) and in the chlorophyll a and adenosine triphosphate (ATP) cell content were compared with the variations in the CIELAB color parameters (L*, a*, b*, C*(ab) and h(ab)). Our findings showed that both the phaeophytination indexes are useful in describing degradation of chlorophyl a to phaeopigments. Moreover, the CIELAB color parameters represented an effective tool in describing chlorophyll degradation. L* CIELAB parameter appeared to be the most informative parameter in describing the biocidal activity of Biotin T® against Nostoc sp. in both planktonic and biofilm mode of growth.

Vitamin K in colostrum and mature human milk over the lactation period--a cross-sectional study

Vitamin K was quantitated in the milk of four groups of 15 mothers from 1 d to 6 mo postpartum in a cross-sectional study. Concentrations were 7.52 +/- 5.90 and 6.36 +/- 5.32 nmol/L (3.39 +/- 2.66 and 2.87 +/- 2.40 micrograms/L) in colostrum and mature milk, respectively. Differences between colostrum and mature milk or among samples of mature milk collected at 1, 3, and 6 mo were not statistically significant. Because of significantly increased volumes of milk over the lactation period, approximately twice as much vitamin K was delivered in mature milk as in colostrum. Within normal ranges, concentrations of vitamin K in milk were not predicted by dietary intake of vegetables or fat. Vitamin K was correlated with fat in colostrum and was localized in the lipid core of the milk fat globule but was not associated with membranes. Vitamin K in human milk is insufficient to meet recommended intakes for infants aged less than 6 mo. Population and clinical studies are needed to assess the vitamin K status of exclusively breast-fed infants and to evaluate current recommendations.

Treatment of chromium(VI) solutions in a pilot-scale bioreactor through a biofilm of Arthrobacter viscosus supported on GAC

The aim of this work is to evaluate the applicability of a biofilm to the removal of chromium in solution, at a pilot scale. The effect of the initial concentration of metal on the biosorption behavior of an Arthrobacter viscosus biofilm supported on granular activated carbon, in batch and column essays was also analyzed. Six isotherm equations have been tested in the present study. The best fit was obtained with the Freundlich model. It was observed that as the initial chromium concentration increases, the uptake increases too, but the removal percentage decreases, with values between 95.20% (C(0)=5mg/l) and 38.28% (C(0)=1000 mg/l). The batch adsorption studies were used to develop a pilot bioreactor able to remove chromium from aqueous solutions. Data obtained in a pilot-scale reactor showed an average removal percentage of 99.9%, during the first 30 days, for the initial concentration of 10mg/l and an average removal percentage of 72%, for the same period and for the initial concentration of 100mg/l. Uptake values of 11.35 mg/g and 14.55 mg/g were obtained, respectively, for the initial concentration of 10 and 100mg/l. The results obtained are very promising and encourage the utilization of this biofilm in environmental applications.

In vivo transfer of the ti-plasmid of Agrobacterium tumefaciens to Escherichia coli

The Ti-plasmids are naturally self-transmissible from their normal host Agrobacterium to E. coli. They are however unable to stably establish themselves as a replicon in E. coli. It is nevertheless possible to study the Ti-plasmids in E. coli with the help of Ti::RP4 cointegrate plasmids that transfer and maintain themselves very efficiently in E. coli. An E. coli harbouring such a Ti::RP4 plasmid is unable to catabolize octopine and unable to induce crown-gall tumours on plants.

Biodeterioration of granite monuments by Ochrolechia parella (L.) mass: an FT Raman spectroscopic study

Ochrolechia parella is one of the most abundant lichens colonizing granite monuments in the region of Galicia (N.W. Spain). Its interaction with granite used in the construction of four ancient monuments was studied using FT Raman spectroscopy to evaluate the production of calcium oxalate by this lichen and the relationship of this production with different environmental conditions, particularly humidity. The results obtained showed that Ochrolechia parella is an aggressive colonizer, causing chemical disturbances to the granite through the formation of both calcium oxalate monohydrate and dihydrate. Apothecial development appears to be related to the production of calcium oxalate, and humidity determines the state of hydration of the calcium oxalate in the thallus.

Gallstone disease in Peruvian coastal natives and highland migrants

BACKGROUND

In a previous study, we found that gallstones were a common occurrence in the high altitude villages of the Peruvian Andes.

AIMS

To determine if high altitude (> or = 1500 m) is a contributing risk factor for gallstone disease.

METHODS

We conducted a cross sectional study in a periurban community in Lima, Peru, and compared the prevalence of gallstone disease between coastal natives, highland (Sierra) natives and Sierra natives who had migrated to the coast. We also compared the prevalence rates from this study with those from a previous study conducted at high altitude. We examined 1534 subjects >15 years of age for gallstone disease. Subjects were interviewed for the presence or absence of risk factors.

RESULTS

Gallstone disease was more common in females (16.1 cases per 100, 95% CI 13.8-18.2) than in males (10.7 per 100, 95% CI 8.0-13.4). Females had a greater risk of gallstone disease, especially if they had used oral contraception and/or had four or more children. The age adjusted prevalence was not significantly different between coastal natives, Sierra migrants, and Andean villagers. The prevalence of gallstone disease was not associated with time since migration or with having native Sierra parents. After adjusting for other risk factors, Sierra natives who migrated to the coast had a lower prevalence of gallstone disease than coastal natives (odds ratio 0.74, 95% CI 0.58-0.94).

CONCLUSIONS

This study indicates that high altitude is not a positive risk factor for gallstone disease and confirms that this disease is common in Peruvians, which may be attributable to Peruvian-Indian ethnicity.

Direct repetition of a 1.2 Md DNA sequence is involved in site-specific recombination by the P1 plasmid R68

R68.45, a mutant R68 plasmid, carries a 1.5 Md DNA insertion near its kanamycin-resistance region. This DNA consists of a 1.2 Md DNA repetition of neighbouring R68-DNA and a 0.3 Md "foreign" DNA fragment that is flanked by this direct DNA repeat. This fragment seems to be involved in the formation of R'68.45 plasmids. Duplication of the 1.2 Md DNA sequence is also involved in site-specific recombination events of RP4. This 1.2 Md DNA fragment has the properties of an IS sequence and is denoted IS8.

Human hydatidosis in the central Andes of Peru: evolution of the disease over 3 years

To document the natural history of Echinococcus granulosus infection and response to treatment of human hydatidosis, we reexamined 28 of 37 subjects with E. granulosus infection diagnosed in an epidemiological study conducted in 1994. Twenty-six (70%) of those 37 subjects underwent abdominal ultrasonography, chest radiography, and enzyme-linked immunoelectrotransfer blot assay in 1997. Medical records from two additional individuals were reviewed. Eight patients had their cysts surgically removed during the 3-year follow-up interval; no surgical complications or recurrences occurred. Among eight patients with cystic disease not treated by surgery, four had cyst-growth ranging from 0.4 to 1.4 cm during the 3-year interval. One patient developed a new cyst and another's simple cyst became septate; two developed new calcifications. Of 12 seropositive subjects with no cysts present in 1994, 10 reverted to seronegative, a finding that suggests a significant proportion of seropositive subjects in echinococcus-endemic regions may have only transient infection without disease. When cysts do develop, their growth rates and time courses are highly variable; over the 3-year period, we observed growth, septation, degeneration, and calcification of cysts.

Biofilm quantification on stone surfaces: comparison of various methods

In the present study, the efficacy of three different methods of estimating biofilm biomass on stone (amount of chlorophyll a, fluorescein diacetate hydrolysis and changes in colour) is discussed. Stone samples were sprayed with solutions of cyanobacteria and the actual microbial biomass--determined by cell culture--was compared with the biomass estimated using the different methods. Statistically significant differences between actual biomass and that estimated from the fluorescein diacetate hydrolysis method invalidate its use. However, although the results indicated the amount of chlorophyll to be a good estimator of biofilm biomass, problems in the total extraction of chlorophyll from the stone cannot be overlooked. Determination of changes in colour was found to be a good method of quantifying biofilms growing on stone.

Gallstone disease in high-altitude Peruvian rural populations

OBJECTIVE

Cholelithiasis is a common problem in hospitals of the Peruvian Andes; however, its prevalence in Andean communities is unknown. To estimate the prevalence of gallstone disease in this locale, we conducted a cross-sectional community study in three high-altitude Peruvian rural villages (i.e., > 3000 m above sea level).

METHODS

We examined 911 volunteers > 15 yr of age from three villages for gallstone disease by history and ultrasonography. Risk factors for gallstone disease were examined in 382 volunteers from one village.

RESULTS

The age-adjusted prevalence of gallstone disease ranged from 4-10% in men and from 18-20% in women. Women had significantly higher age-adjusted prevalence rates than did men. The prevalence of gallstone disease increased significantly with age and decreased significantly with alcohol consumption. Although not statistically significant, we found a positive association between gallstone disease and body mass index.

CONCLUSION

The results of this study indicate that gallstone disease, commonly perceived as a disease of the developed world, is also a common problem in high-altitude Peruvian communities.

Development of low- and high-serum culture conditions for use of human oral fibroblasts in toxicity testing of dental materials

With the aim of establishing conditions applicable to the testing of dental materials in human target cells, fibroblastic cell lines have been derived and grown from explants of human oral mucosa. Both a high-serum medium (termed "HSM") (CMRL 1066 supplemented with 10% fetal bovine serum) and a low-serum medium (termed "LSM") (a 1:1 mixture of M 199:MCDB 153 supplemented with 1.25% serum) supported radial outgrowths of cells from oral explants, as well as the subsequent transfer and growth of the cells in mass culture and at clonal density. Cells were typically fibroblastic in that they expressed vimentin uniformly, but did not express immunocytochemical markers of epithelial or endothelial cells. Cells derived in either LSM or HSM showed significantly higher colony-forming efficiency and clonal growth rate when transferred in LSM, as compared with HSM. Because cell migration occurred to a lesser extent in LSM, microscopic scoring of colony formation was also markedly facilitated. In both LSM and HSM, cellular low-molecular-weight thiols constituted about 30% of the total amount of sulfhydryls. Glutathione was present in about six- to seven-fold-higher amounts than cysteine--glutathione primarily in its reduced form and cysteine primarily in its oxidized form. A corrosion product of dental amalgam, i.e., Hg2+, decreased cell survival measured as colony-forming efficiency in a dose-dependent manner following either an acute (one h) exposure or continuous exposure (seven days). These studies demonstrated that human oral fibroblasts could be cultured at about one-tenth of the serum content that is commonly used.(ABSTRACT TRUNCATED AT 250 WORDS)

Spectrophotometric color measurement for early detection and monitoring of greening on granite buildings

This paper addresses the detection and monitoring of the development of epilithic phototrophic biofilms on the granite façade of an institutional building in Santiago de Compostela (NW Spain), and reports a case study of preventive conservation. The results provide a basis for establishing criteria for the early detection of phototrophic colonization (greening) and for monitoring its development on granite buildings by the use of color changes recorded with a portable spectrophotometer and represented in the CIELAB color space. The results show that parameter b* (associated with changes of yellowness-blueness) provides the earliest indication of colonization and varies most over time, so that it is most important in determining the total color change. The limit of perception of the greening on a granite surface was also established in a psycho-physical experiment, as Δb*: +0.59 CIELAB units that correspond, in the present study, to 6.3 μg of biomass dry weight cm(-2) and (8.43 ± 0.24) × 10(-3) μg of extracted chlorophyll a cm(-2).

The colored Hanbury Brown-Twiss effect

The Hanbury Brown-Twiss effect is one of the celebrated phenomenologies of modern physics that accommodates equally well classical (interferences of waves) and quantum (correlations between indistinguishable particles) interpretations. The effect was discovered in the late thirties with a basic observation of Hanbury Brown that radio-pulses from two distinct antennas generate signals on the oscilloscope that wiggle similarly to the naked eye. When Hanbury Brown and his mathematician colleague Twiss took the obvious step to propose bringing the effect in the optical range, they met with considerable opposition as single-photon interferences were deemed impossible. The Hanbury Brown-Twiss effect is nowadays universally accepted and, being so fundamental, embodies many subtleties of our understanding of the wave/particle dual nature of light. Thanks to a novel experimental technique, we report here a generalized version of the Hanbury Brown-Twiss effect to include the frequency of the detected light, or, from the particle point of view, the energy of the detected photons. Our source of light is a polariton condensate, that allows high-resolution filtering of a spectrally broad source with a high degree of coherence. In addition to the known tendencies of indistinguishable photons to arrive together on the detector, we find that photons of different colors present the opposite characteristic of avoiding each others. We postulate that fermions can be similarly brought to exhibit positive (boson-like) correlations by frequency filtering.

Relationship between color and pigment production in two stone biofilm-forming cyanobacteria (Nostoc sp. PCC 9104 and Nostoc sp. PCC 9025)

Previous studies have provided evidence that color measurements enable on site quantification of superficial biofilms, thereby avoiding the need for sampling. In the present study, the efficiency of color measurements to evaluate to what extent pigment production is affected by environmental parameters such as light intensity, combined nitrogen and nutrient availability, was tested with two cyanobacteria, Nostoc sp. strains PCC 9104 and PCC 9025, which form biofilms on stone. Both strains were acclimated, in aerated batch cultures for 2 weeks, to three different culture media: BG-11, BG-11(0), and BG-11(0)/10 at either high or low light intensity. The content of chlorophyll a, carotenoids, and phycocyanins was measured throughout the experiment, together with variations in the color of the cyanobacteria, which were represented in the CIELAB color space. The results confirmed that the CIELAB color parameters are correlated with pigment content in such a way that variations in the latter are reflected as variations in color.

Hypercaloric Diet Establishes Erectile Dysfunction in Rat: Mechanisms Underlying the Endothelial Damage

Obesity is characterized by an excessive increase in body mass, leading to endothelial damage that may favor the development of erectile dysfunction (ED). ED is defined as the inability to achieve or maintain a penile erection long enough to have a sexual intercourse. In this context, different ED models were developed, however the high price of special animals or the long period to establish the disease has limited studies in this field. Therefore, this study proposed to establish and characterize a novel model of ED in rats associated to a hypercaloric diet consumption. Animals were randomly divided into control group (CG), which received a standard diet, and obese group (OG), fed with a hypercaloric diet during 8 weeks. Rat's erectile function was evaluated in vivo and in vitro. Food and caloric intake of OG were reduced compared to CG, due to an increased diet energy efficiency. However, OG presented an increased body mass, inguinal, retroperitoneal and epididymal adipose tissues, as well as body adiposity index at the end of experimental protocol. In erectile function analysis, there was a decrease in the number and the latency of penile erections in OG. Additionally, the contractile reactivity of corpus cavernosum was increased in OG, favoring penile detumescence and related to a reduced nitric oxide bioavailability and an increased in contractile prostaglandins levels as a consequence of endothelial damage. Moreover, the endothelium-relaxation reactivity of corpus cavernosum was attenuated in OG associated to the oxidative stress. Thus, it was provided a model for advances in sexual dysfunction field and drug discovery for ED treatment.

Seasonal variations of 226Ra and 222Rn in mineral spring waters of Aguas de Prata, Brazil

In this paper the activity concentrations of 226Ra and 222Rn were assayed in the mineral spring waters of Aguas da Prata in order to evaluate the seasonal variations of such radionuclides. The results obtained were related to the chemical composition of the water as well as to the lithology of the aquifer and temperature. Higher activity concentrations up to 1.8 x 10(3) mBq L-1 for 226Ra and 1.2 x 10(2) Bq L-1 for 222Rn have been observed in waters with low levels of soluble salts. Waters which present high levels of carbonate and sulphate salts showed maximum values of 2.5 x 10(2) mBq L-1 for 226Ra and 2.7 x 10(1) Bq L-1 for 222Rn. This behaviour is mainly due to the physico-chemical properties of these radionuclides in water as well as to the lithologic structure of the aquifers.

Reutilization of Cr-Y zeolite obtained by biosorption in the catalytic oxidation of volatile organic compounds

This work aims at the reutilization of a Cr-loaded NaY zeolite obtained by biorecovery of chromium from water as catalyst in the oxidation of volatile organic compounds (VOC). Cr-NaY catalysts were obtained after biosorption of Cr(VI) using a bacterium, Arthrobacter viscosus, supported on the zeolite. The biosorption experiments were conducted at different pH values in the range 1-4. The catalysts were characterized by several techniques, namely ICP-AES, SEM-EDS, XRD, XPS, Raman, H(2)-TPR and N(2) adsorption. The zeolite obtained at pH 4 has the highest content of chromium, 0.9%, and was selected as the best catalyst for the oxidation of different VOC, namely ethyl acetate, ethanol and toluene. For all VOC tested, the catalyst with chromium showed higher activity and selectivity to CO(2), in comparison with the starting zeolite NaY. The presence of chromium shifted also the reaction pathways. In terms of selectivity to CO(2), the following sequence was observed: ethyl acetate>toluene>ethanol.

Taenia solium infection in a rural community in the Peruvian Andes

An epidemiological study was conducted in a highland, rural community in Peru, to determine the seroprevalences of human and porcine infection with Taenia solium and the risk factors associated with human infection. The seroprevalences, determined using an assay based on enzyme-linked-immuno-electrotransfer blots (EITB), were 21% (66/316) in the humans and 65% (32/49) in the pigs. The human subjects aged <30 years were more likely to be positive for anti-T. solium antibodies than the older subjects (P < 0.001). The risk factors associated with human seropositivity were lack of education beyond the elementary level [odds ratio (OR)=2.69; 95% confidence interval (CI)=1.09-6.65] and pig-raising (OR=1.68; CI=0.96-2.92). Curiously, sheep-raising was inversely associated with human T. solium infection (OR=0.50; CI=0.28-0.90). The study site appears to be a new endemic focus for T. solium in the central Peruvian Andes. Although, in earlier studies, the seroprevalence of T. solium infection has generally been found to increase with age, the opposite trend was observed in the present study. The results of follow-up studies should help determine if the relatively high seroprevalence in the young subjects of the present study is the result of a transient antibody response.