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  • Key words Hydrothermal system  (1)
  • LYMPHOCYTE SUBSETS  (1)
  • 1
    ISSN: 1432-0819
    Keywords: Key words Hydrothermal system ; Fluid geochemistry ; Stable isotopes ; Geochemical monitoring ; Taal Volcano
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  The hydrologic structure of Taal Volcano has favored development of an extensive hydrothermal system whose prominent feature is the acidic Main Crater Lake (pH〈3) lying in the center of an active vent complex, which is surrounded by a slightly alkaline caldera lake (Lake Taal). This peculiar situation makes Taal prone to frequent, and sometimes catastrophic, hydrovolcanic eruptions. Fumaroles, hot springs, and lake waters were sampled in 1991, 1992, and 1995 in order to develop a geochemical model for the hydrothermal system. The low-temperature fumarole compositions indicate strong interaction of magmatic vapors with the hydrothermal system under relatively oxidizing conditions. The thermal waters consist of highly, moderately, and weakly mineralized solutions, but none of them corresponds to either water–rock equilibrium or rock dissolution. The concentrated discharges have high Na contents (〉3500 mg/kg) and low SO4/Cl ratios (〈0.3). The Br/Cl ratio of most samples suggests incorporation of seawater into the hydrothermal system. Water and dissolved sulfate isotopic compositions reveal that the Main Crater Lake and spring discharges are derived from a deep parent fluid (T≈300  °C), which is a mixture of seawater, volcanic water, and Lake Taal water. The volcanic end member is probably produced in the magmatic-hydrothermal environment during absorption of high-temperature gases into groundwater. Boiling and mixing of the parent water give rise to the range of chemical and isotopic characteristics observed in the thermal discharges. Incursion of seawater from the coastal region to the central part of the volcano is supported by the low water levels of the lakes and by the fact that Lake Taal was directly connected to the China sea until the sixteenth century. The depth to the seawater-meteoric water interface is calculated to be 80 and 160 m for the Main Crater Lake and Lake Taal, respectively. Additional data are required to infer the hydrologic structure of Taal. Geochemical surveillance of the Main Crater Lake using the SO4/Cl, Na/K, or Mg/Cl ratio cannot be applied straightforwardly due to the presence of seawater in the hydrothermal system.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-2568
    Keywords: LYMPHOCYTE SUBSETS ; FLOW CYTOMETRY ; HEPATITIS C VIRUS ; VIRUS REPLICATION ; KNODELL SCORE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The host immune responses have been suggested toplay a role in liver injury occurring in patients withchronic hepatitis C. In order to explore therelationship between the relative proportions ofintrahepatic and peripheral blood lymphocytes (IHL, PBL),the levels of viremia, and the histological hepatitisactivity score, three-color fluorescence-activatedcytometric analysis was performed for 36 patients with chronic hepatitis C and six control subjectswithout chronic hepatitis. The liver biopsy wasperformed before any antiviral therapy. Each liverspecimen was divided into two parts: one forhistological examination and one for immunological analysis.Tricolor CD45 was used to improve“lymphogating.” Fluorescein isothiocyanate-or phycoerythrin-conjugated monoclonal antibodies withspecificity for CD3, CD4, CD8, and CD20 (lymphocyte subpopulations),for CD69 (activated lymphocytes), and for CD16/56(natural killer cells) were used. The livers of patientswith chronic hepatitis C contained a greater proportion of CD4+ lymphocytes that exhibitedmarked expression of CD69 than in control subjects (20.7± 7.3% vs 10.2 ± 4.6%, P = 0.027).Moreover, in patients with chronic hepatitis C, theproportion of CD4+ IHL correlated with the histological hepatitisactivity evaluated by the Knodell score (r = 0.48, P =0.004). No correlation was found between the percentageof CD4+ IHL and the level of viremia ortransaminase activities. Our findings clearly indicate thata cellular immune response does take place inHCV-infected livers and could thus contribute to theoutcome of hepatitis C virus infection.
    Type of Medium: Electronic Resource
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