In situ variation of cervical mucus pH during exposure to atmospheric air

The objective of the present study was to determine if exposure of cervical mucus to air during specular examination could modify mucus pH. Detection of changes is justified because of their possible interference with sperm-mucus interaction, since an acidic pH is unfavorable to sperm penetration and is associated with infertility due to the cervical factor. Twenty women with good quality mucus were evaluated. pH measurements of ecto- and endocervical mucus were made in situ using a glass electrode after 0-, 5- and 10-min exposure to air. There was a progressive alkalinization of mucus pH. Mean values of ectocervical mucus pH were 6.91, 7.16 and 7.27, while mean values of endocervical mucus pH were 7.09, 7.34 and 7.46 at 0, 5 and 10 min, respectively. Significant differences were found between the mean values obtained at 0 and 5 min, and at 0 and 10 min (P<0.05), whereas the differences in mean values at 5 and 10 min were not significant at either site. We conclude that 5 to 10 min of exposure to atmospheric air affects cervical mucus pH in a significant way. Since tests used to evaluate sperm-mucus interaction generally have not considered this possibility, we suggest that they should be performed immediately after mucus collection in order to avoid misinterpretation of the results.

Detection of amastigote-like forms in the valve of Phlebotomus papatasi infected with Leishmania major

A massive and homogeneous amount of amastigote-like forms was detected in the stomodeal valve (SV) and the thoracic mid-gut (TMG) of Leishmania major-infected Phlebotomus papatasi, which received a second blood meal 13 to 21 days post-infection on healthy anaesthetized hamsters. After re-feeding, the infected sand flies were dissected out to examine the morphology of the parasite in SV, TMG and the abdominal mid-gut (AMG). Different promastigote forms were seen in the infected flies. Among these included typical promastigotes (nectomonads and haptomonads), paramastigotes, metacyclic promastigotes and, in some samples, the here-reported amastigote-like forms. The Leishmania amastigote-like forms were detected in the SV of sand flies with 14, 18 and 21 days of infection as well as in the TMG at 13 and 18 days post-infection. However, the amastigote-like forms were not detected in the AMG. Factors such as the acidic pH predominating the TMG and the SV, as well as the temperature of the ingested blood, among others, are suggested as contributing to the transformation of the typical promastigotes into the amastigote-like forms. The significance of this finding is discussed and the possible biological advantage for transmission of Leishmania is considered.

Molecular mechanisms of Trypanosoma cruzi infection by oral route

Frequent reports on outbreaks of acute Chagas' disease by ingestion of food contaminated with parasites from triatomine insects illustrate the importance of this mode of transmission. Studies on oral Trypanosoma cruzi infection in mice have indicated that metacyclic trypomastigotes invade the gastric mucosal epithelium. A key molecule in this process is gp82, a stage-specific surface glycoprotein that binds to both gastric mucin and to target epithelial cells. By triggering Ca2+ signalling, gp82 promotes parasite internalisation. Gp82 is relatively resistant to peptic digestion at acidic pH, thus preserving the properties critical for oral infection. The infection process is also influenced by gp90, a metacyclic stage-specific molecule that negatively regulates the invasion process. T. cruzi strains expressing high gp90 levels invade cells poorly in vitro. However, their infectivity by oral route varies considerably due to varying susceptibilities of different gp90 isoforms to peptic digestion. Parasites expressing pepsin-susceptible gp90 become highly invasive against target cells upon contact with gastric juice. Such is the case of a T. cruzi isolate from an acute case of orally acquired Chagas' disease; the gp90 from this strain is extensively degraded upon short period of parasite permanence in the gastric milieu. If such an exacerbation of infectivity occurs in humans, it may be responsible for the severity of Chagas' disease reported in outbreaks of oral infection.

Characterization of TcSTI-1, a homologue of stress-induced protein-1, in Trypanosoma cruzi

The life cycle of the protozoan Trypanosoma cruzi exposes it to several environmental stresses in its invertebrate and vertebrate hosts. Stress conditions are involved in parasite differentiation, but little is known about the stress response proteins involved. We report here the first characterization of stress-induced protein-1 (STI-1) in T. cruzi (TcSTI-1). This co-chaperone is produced in response to stress and mediates the formation of a complex between the stress proteins HSP70 and HSP90 in other organisms. Despite the similarity of TcSTI-1 to STI-1 proteins in other organisms, its expression profile in response to various stress conditions, such as heat shock, acidic pH or nutrient starvation, is quite different. Neither polysomal mRNA nor protein levels changed in exponentially growing epimastigotes cultured under any of the stress conditions studied. Increased levels of TcSTI-1 were observed in epimastigotes subjected to nutritional stress in the late growth phase. Co-immunoprecipitation assays revealed an association between TcSTI-1 and TcHSP70 in T. cruzi epimastigotes. Immunolocalization demonstrated that TcSTI-1 was distributed throughout the cytoplasm and there was some colocalization of TcSTI-1 and TcHSP70 around the nucleus. Thus, TcSTI-1 associates with TcHSP70 and TcSTI-1 expression is induced when the parasites are subjected to stress conditions during specific growth phase.

Determinação de carbaril utilizando testes ELISA (Enzyme-linked immunosorbent assay) e CLAE com detecção por arranjo de diodos

ELISAs have been applied to pesticide residue analysis due to their high sensitivity and selectivity. However, some ELISAs performance may be affected by matrix components. In this work, ELISA for carbaryl in water samples was checked for interference by naturally occurring fulvic acids. The results suggested that the high fulvic acid concentration (ž³30 mg L-1) and acidic pH conditions (pH 4.0) interfere with the signal detection decreasing the method sensitivity. A dilution of the samples and adjust to pH 8.0 are appropriate to minimize the matrix interferences in the ELISA method. Good correlation between ELISA and HPLC-DAD results was observed.

Influence of seed size and ecological factors on the germination and emergence of field bindweed (Convolvulus arvensis)

An understanding of seed germination ecology of weeds can assist in predicting their potential distribution and developing effective management strategies. Influence of environmental factors and seed size on germination and seedling emergence of Convolvulus arvensis (field bindweed) was studied in laboratory and greenhouse conditions. Germination occurred over a wide range of constant temperatures, between 15 and 40 ºC, with optimum germination between 20 and 25 ºC. Time to start germination, time to 50% germination and mean germination time increased while germination percentage and germination index decreased with an increase in temperature from 20 ºC, salinity and osmotic stress. However, germination was tolerant to low salt (25 mM) or osmotic stress (0.2 MPa), but as salinity and osmotic stress increased, germination percentage and germination index decreased. Seeds of C. arvensis placed at soil surface showed maximum emergence and decreased as seeding depth increased. Seeds of C. arvensis germinated over a wide range of pH (4 to 9) but optimum germination occurred at pH 6 to 8. Under highly alkaline and acidic pH, time to start germination, time to 50% germination and mean germination time increased while germination percentage and germination index decreased. Increase in field capacity caused decreased time to start germination, time to 50% germination and mean germination time but increased germination percentage and germination index. Bigger seeds had low time to start germination, time to 50% germination and mean germination time but high germination percentage and germination index. Smaller seeds were more sensitive to environmental factors as compared to larger or medium seeds. It can be concluded that except for pH, all environmental factors and seed sizes adversely affect C. arvensis as regards seed germination or emergence and germination or emergence traits, and larger seeds result in improved stand establishment and faster germination than small seeds, regardless of moisture stress or deeper seeding depth.

Some physico-chemical parameters that influence proteinase K resistance and the infectivity of PrP Sc after high pressure treatment

Crude brain homogenates of terminally diseased hamsters infected with the 263 K strain of scrapie (PrP Sc) were heated and/or pressurized at 800 MPa at 60ºC for different times (a few seconds or 5, 30, 120 min) in phosphate-buffered saline (PBS) of different pH and concentration. Prion proteins were analyzed on immunoblots for their proteinase K (PK) resistance, and in hamster bioassays for their infectivity. Samples pressurized under initially neutral conditions and containing native PrP Sc were negative on immunoblots after PK treatment, and a 6-7 log reduction of infectious units per gram was found when the samples were pressurized in PBS of pH 7.4 for 2 h. A pressure-induced change in the protein conformation of native PrP Sc may lead to less PK resistant and less infectious prions. However, opposite results were obtained after pressurizing native infectious prions at slightly acidic pH and in PBS of higher concentration. In this case an extensive fraction of native PrP Sc remained PK resistant after pressure treatment, indicating a protective effect possibly due to induced aggregation of prion proteins in such buffers.

Cloning, purification and comparative characterization of two digestive lysozymes from Musca domestica larvae

cDNA coding for two digestive lysozymes (MdL1 and MdL2) of the Musca domestica housefly was cloned and sequenced. MdL2 is a novel minor lysozyme, whereas MdL1 is the major lysozyme thus far purified from M. domestica midgut. MdL1 and MdL2 were expressed as recombinant proteins in Pichia pastoris, purified and characterized. The lytic activities of MdL1 and MdL2 upon Micrococcus lysodeikticus have an acidic pH optimum (4.8) at low ionic strength (μ = 0.02), which shifts towards an even more acidic value, pH 3.8, at a high ionic strength (μ = 0.2). However, the pH optimum of their activities upon 4-methylumbelliferyl N-acetylchitotrioside (4.9) is not affected by ionic strength. These results suggest that the acidic pH optimum is an intrinsic property of MdL1 and MdL2, whereas pH optimum shifts are an effect of the ionic strength on the negatively charged bacterial wall. MdL2 affinity for bacterial cell wall is lower than that of MdL1. Differences in isoelectric point (pI) indicate that MdL2 (pI = 6.7) is less positively charged than MdL1 (pI = 7.7) at their pH optima, which suggests that electrostatic interactions might be involved in substrate binding. In agreement with that finding, MdL1 and MdL2 affinities for bacterial cell wall decrease as ionic strength increases.

Physiological implications of the regulation of vacuolar H+-ATPase by chloride ions

Vacuolar H+-ATPase is a large multi-subunit protein that mediates ATP-driven vectorial H+ transport across the membranes. It is widely distributed and present in virtually all eukaryotic cells in intracellular membranes or in the plasma membrane of specialized cells. In subcellular organelles, ATPase is responsible for the acidification of the vesicular interior, which requires an intraorganellar acidic pH to maintain optimal enzyme activity. Control of vacuolar H+-ATPase depends on the potential difference across the membrane in which the proton ATPase is inserted. Since the transport performed by H+-ATPase is electrogenic, translocation of H+-ions across the membranes by the pump creates a lumen-positive voltage in the absence of a neutralizing current, generating an electrochemical potential gradient that limits the activity of H+-ATPase. In many intracellular organelles and cell plasma membranes, this potential difference established by the ATPase gradient is normally dissipated by a parallel and passive Cl- movement, which provides an electric shunt compensating for the positive charge transferred by the pump. The underlying mechanisms for the differences in the requirement for chloride by different tissues have not yet been adequately identified, and there is still some controversy as to the molecular identity of the associated Cl--conducting proteins. Several candidates have been identified: the ClC family members, which may or may not mediate nCl-/H+ exchange, and the cystic fibrosis transmembrane conductance regulator. In this review, we discuss some tissues where the association between H+-ATPase and chloride channels has been demonstrated and plays a relevant physiologic role.

Soymilk plain beverages: correlation between acceptability and physical and chemical characteristics

The objective of the research was to relate the physical and chemical characteristics of soymilk plain beverages to its sensory acceptance. Five commercial products and a new product formulated based on the less accepted sample were used. The overall acceptance was evaluated by 102 assessors using a 10-point hybrid hedonic scale. The hedonic scores ranged from 3.8 (sample E) to 7.0 (A). Most assessors (55%) preferred sample A, which was viscous (26.6 cp), dark (L* = 77.7), and slightly acidic (pH = 6.6). Sample C, which had lower solid content and higher acidity, was preferred by 29% of the assessors. These two beverages showed the greatest commercial potential of the products analyzed. The least-accepted sample (E), preferred by 8% of the assessors, had a lighter color (L* = 96.8), lower viscosity (13.5 cp), higher lipid content (2.2 g/100 g), and less protein (1.68 g/100 g) than the other products evaluated. A reformulation of the least preferred product (E) with the addition of maltodextrin and also vanilla and milk flavors increased its acceptance, yielding an average score of 7.2. Overall, it was observed that a soymilk plain beverage with higher viscosity, darker color, and higher protein content best meets consumer expectations.

Nutrient leaching potential following application of papermill lime-sludge to an acidic clay soil

This experiment was carried out under greenhouse conditions with soil pots during 210 days, to evaluate the effect of calcitic papermill lime-sludge application (at the rates 0, 773, 1.547, and 2.320 mg kg-1 or respective equivalents to control, 2, 4, and 6 t ha-1), on chemical composition of soil leachate and its effects on eucalypt growth and yield. Highest soil leachate pH, SO4, and Na concentrations occurred in the 4 and 6 t ha-1 treatments. Soil leachate nitrate concentrations decreased with increasing lime-sludge rate. Soil leachate phosphate remained low (below the detection limit) in all treatments until 120 days, while the concentration increased in the lime-sludge treatments at 210 days (last sampling) in about 600 mg L-1. Lime-sludge decreased leachate Mg concentration, but had no significant effect among rates. Soil leachate Ca, K, B, Cu, Fe, and Zn did not change significantly for any lime-sludge application rates. The maximum NO3, Ca, Mg, K, and Na concentrations in the soil leachate occurred at 60 days after lime-sludge application (leaching equivalent to 1 pore volume), but for pH and SO4, the maximum occurred at 210 days (leaching equivalent to 4 pore volumes). Lime-sludge application decreased the concentration of exchangeable Al in the soil. Plant diameter growth and dry matter yield were increased with increasing lime-sludge rate. Beneficial effects on mineral nutrition (P, K, Ca, B, and Zn) of eucalypts were also obtained by the application of 4 and 6 t ha-1 of lime-sludge.

Determinação da 2,5-hexanodiona em amostras de urina submetidas à hidrólise ácida: importância da coluna cromatográfica e do pH do meio

Acidic hydrolysis of samples is frequent in urinary 2,5-hexanodione determination. This hydrolysis should be performed under proper conditions, in order to avoid interference, such as the presence of 2,5-dimethylfurane and 2-acetylfurane. The results of the present work, as well as data from the literature, show that the use of non-polar or slightly polar chromatographic columns of 30 m length is an essential condition for 2,5-HD determination in an acid hydrolysed urine sample. In the same way the pH should be kept between 0.3 and 0.5. The mean concentrations of 2,5-HD in samples submitted to hydrolysis (0.50 ± 0.28 mg/g of creatinine) was about 3 times higher than those found in the samples without acid hydrolysis (0.19 ± 0.3 mg/g of creatinine).

Recovery of manganese and zinc from spent Zn-C and alkaline batteries in acidic medium

The anode and the internal paste of spent Zn-C and alkaline batteries were leached with 2 mol L-1 H2SO4 at 80 ºC for 2 h. Solid/liquid ratio was 1/10 (g mL-1). The leachate was treated with Na2S in order to precipitate Hg, Cd and Pb. Zn was quantitatively isolated at pH 1,5-2 by adding Na2S. Mn can be precipitated at pH close to 7. Na2S may be replaced by oxalic acid. Zn precipitated at pH around 0, whereas Mn was quantitatively recovered at pH > 4. Acidity control is a critical parameter. Na2SO4 and carbon are the end products.

Estudo comparativo do pH e do volume salivar em indivíduos com laringofaringite crônica por doença do refluxo gastroesofágica antes e após o tratamento

INTRODUÇÃO: A Doença do Refluxo Gastroesofágico (DRGE) é a doença digestiva mais prevalente da atualidade e, recentemente, tem sido implicada em uma gama de alterações do seguimento laringofaríngeo (RLF). No entanto, pouco se sabe dos mecanismos fisiopatológicos destas manifestações supraesofágicas da DRGE. Os achados clínicos contraditórios e recentes pesquisas sugerem haver deficiências na capacidade de defesa deste seguimento. Uma das principais responsáveis pela homeostase da mucosa oral e do trato digestivo é a saliva com seu conteúdo orgânico e inorgânico. Tanto alterações do pH quanto do volume salivar já foram correlacionados com os sintomas e sinais sugestivos da DRGE e RLF. Estudo recente de nossa autoria demonstra diminuição estatisticamente significante do pH salivar de indivíduos com RLF quando comparado a controles sem a doença. Outro estudo constatou correlação entre a redução do volume X pH da saliva em indivíduos com DRGE, estando esta redução diretamente relacionada aos níveis de pH esofágico constatados durante pH-metria esofágica de 24 horas. OBJETIVOS: Avaliar como se comportam o pH e volume da saliva em um mesmo indivíduo com DRGE e RLF antes e após o tratamento clínico. MATERIAL E MÉTODO: Vinte e três pacientes com RLF tiveram o pH e volume da saliva total testados antes e após receberem tratamento com droga bloqueadora de bomba de prótons durante 12 semanas. RESULTADOS: Houve uma diferença estatisticamente significante (p<0,001) entre o pH da saliva antes e após o tratamento, estando este maior após o controle clínico da doença. O volume de saliva no paciente tratado foi significativamente maior do que no paciente pré-tratamento (p=0.009). DISCUSSÃO: Os achados sugerem que o pH salivar é influenciado pela presença de refluxo gastroduodenal à região laringofaríngea. Caso estudos futuros com populações maiores realmente comprovem esta correlação, poderemos cogitar a possibilidade de usar a mensuração do pH salivar, que é feita de forma rápida e não invasiva, como um meio de diagnosticar e avaliar o comportamento e controle do Refluxo Laringofaríngeo.

Immune response in mice immunized with acidic antigenic fractions from Trypanosoma cruzi cytosol

The humoral and cellular immune responses as well as the resistance to infection with bloodstream forms of T. cruzi were studied in mice immunized with acidic antigenic fractions from parasite cytosol, F III and F IV, plus Bordetella pertussis as adjuvant. The immunization with F III induced positive ITH and DTH responses to homologous antigens. In mice immunized with F IV, the ITH was negative and four out of six animals presented positive DTH reactions. In both groups of mice the analysis of IgG aginst T. cruzi showed that the major isotype elicited was IgG1. Specific IgE was also detected in sera from F III immunized mice, thus confirming the presence of homocytothropic antibodies. The parasitemias reached by F III and F IV immunized mice after challenge were lower than those of the controls showing in this way a partial protection against the acute infection. The histological studies of heart and skeletal muscle performed two months after the infection revealed variable mononuclear infiltration in all infected mice despite immunization.