Tools of groundwater protection below the city of Caracas, Venezuela.

Caracas city obtains drinking water from neighbouring catchment areas. Since these water resources are limited in quantity, groundwaters under the city are also considered for drinking water supply. Hydrochemical and isotope investigations show that the active recharge zone which may readily be contaminated reaches to about 50 m below floor. At greater depths the passive recharge zone extends to a maximum of 300 m and is by far less susceptible to groundwater pollution than the active recharge zone. The water balance indicates recharge to the Caracas aquifer of 2.1 m3/s from losses of the distribution and collector systems of waters as well as from subsurface lateral groundwater inflow into the Caracas valley. The active recharge zone of the aquifer beneath Caracas actually acts as an important microbiological reactor. It was proposed that exploitation of 20% of the total amount of groundwater re-charge from depths below 100 m would be sustainable and provide unpolluted water. Abstraction from the active recharge zone would require protection measures in the city area, which are not feasible.

E and P selectins are not required for resistance to severe murine lyme arthritis.

Borrelia burgdorferi-induced arthritis in mice is characterized by tendonitis, synovitis, and inflammatory-cell infiltrate, predominantly of neutrophils. Because genetic deficiency in E and P selectins results in delayed recruitment of neutrophils to sites of inflammation, mice with this deficiency were tested for their response to infection with B. burgdorferi. E and P selectins were not required for the control of B. burgdorferi numbers, nor did deficiency in E and P selectins result in alteration of arthritis severity.

Distinct characteristics of resistance to Borrelia burgdorferi-induced arthritis in C57BL/6N mice.

Studies of mice infected with Borrelia burgdorferi have indicated that the severity of arthritis is influenced by the genetic composition of the host: the C3H mouse develops severe arthritis while BALB/c and C57BL/6 mice develop mild arthritis. In this study, the effects of increasing infectious dose on the severity of arthritis were determined in these three mouse strains. C3H/He mice developed severe arthritis at all infectious doses, with 100% infection requiring 200 spirochetes. In BALB/cAnN mice, arthritis severity was dependent on infectious dose; symptoms were mild with infection by 200 B. burgdorferi and progressively more severe with increasing infectious dose. Infection of BALB/cAnN mice with 2 x 10(4) B. burgdorferi resulted in arthritis with severity identical to that in C3H/He mice. Spirochete levels in rear ankle joints of C3H/HeJ and C3H/HeN mice were relatively high, as detected by PCR, and did not increase with infectious dose. Spirochete levels in joints from BALB/cAnN mice increased with increasing infectious dose to levels found in severely arthritic C3H/He mice. Thus, resistance to severe arthritis in BALB/cAnN mice was conditional: it could be overcome by high infectious dose and the arthritis became severe when high levels of B. burgdorferi were present in joints. A unique response to increasing infectious dose was seen in C57BL/6N mice, which displayed mild to moderate arthritis at all doses of B. burgdorferi tested, up to 2 x 10(5). At all infectious doses, the levels of spirochetes in ankle joints of C57BL/6N mice were high, equivalent to those found in the severely arthritic C3H/He mice. The arthritis observed in infected (C57BL/6N x C3H/HeN)F1 mice was of severity intermediate between those of the two parental strains. The finding that resistance to severe arthritis in C57BL/6N mice could not be overcome by high infectious doses and was independent of spirochete levels in joints suggested that it was mediated by a distinct mechanism from that operating in BALB/cAnN mice.

Pathological manifestations in murine Lyme disease: association with tissue invasion and spirochete persistence.

The clinical manifestations of human Lyme disease present with a spectrum of tissue or organ involvement and severity of symptoms. The murine model of Lyme disease has proved to be an accurate reflection of many of the human symptoms of disease and has been particularly useful for studying development of subacute arthritis and tendonitis. Direct tissue invasion by Borrelia burgdorferi and persistence of high levels of spirochetes in tissues are important components of arthritis development. The outer-surface lipoproteins contain a biologically active lipid-modified moiety with potent ability to stimulate inflammatory cytokine production and other inflammatory mediators such as nitric oxide. Localized inflammation stimulated by these lipoproteins may be the trigger for neutrophil infiltration, synovial proliferation, and other events associated with this arthritis. Invasion of maternal uterine tissue, but not direct invasion of fetal tissue, is associated with low levels of pregnancy loss in mice infected during gestation, consistent with the detrimental effect of inflammatory cytokines on pregnancy.

Immunity to Lyme disease: protection, pathology and persistence.

Persistence of the Lyme disease spirochete, Borrelia burgdorferi, in the presence of an active immune response has been well documented. Evidence from the past year indicates that modulation of surface antigens by the spirochete may be a major mechanism for evading the immune response.

Nitric oxide production during murine Lyme disease: lack of involvement in host resistance or pathology.

The murine model of Lyme disease was used to determine the role of inflammatory induced nitric oxide (NO) during infection by the spirochete Borrelia burgdorferi. The outer surface lipoproteins of B. burgdorferi are potent stimulators of inflammatory cytokines and NO production by cultured macrophages in vitro. The addition of NO to cultures of B. burgdorferi prevents growth, suggesting a protective role of NO for the infected host. NO is also a crucial effector in some models of arthritis. Therefore, the involvement of NO in controlling B. burgdorferi infection and its participation in pathological development of arthritis were investigated. Both mildly arthritic (BALB/c) and severely arthritic (C3H/HeJ) strains of mice systemically produced high levels of NO 1 week after infection with B. burgdorferi, as determined by urinary nitrate. NO production remained high throughout the infection in BALB/c mice, while in C3H/HeJ mice NO production returned rapidly to uninfected levels. The in vivo inhibitor of the NO synthase enzyme NG-L-monomethyl arginine (LMMA) was given to mice to investigate whether decreasing NO production would alter the course of disease. LMMA effectively blocked NO production in infected mice; however, there was no significant difference in arthritis development, spirochete infection of tissues, or production of specific antibody in LMMA-treated mice. These results indicate that B. burgdorferi is able to persist in the host even in the presence of high levels of NO. Furthermore, NO is not involved in the control of spirochete infection of tissues, nor is it involved in the development of arthritis. The potent activity of NO against intracellular pathogens and the in vivo resistance of B. burgdorferi to NO suggest that this organism is not located in an intracellular compartment during an essential portion of its infection of the mammalian host.

Outer surface lipoproteins of Borrelia burgdorferi stimulate nitric oxide production by the cytokine-inducible pathway.

The outer surface lipoproteins of Borrelia burgdorferi, OspA and OspB, stimulate the production of nitric oxide (NO) by murine bone marrow-derived macrophages from BALB/c, C3H/HeN, and C3H/HeJ mice. Gamma interferon (IFN-gamma) caused a three- to fivefold enhancement of this production of NO, and the L-arginine analog N-guanidino-monomethyl L-arginine inhibited it. Activation of transcription of the inducible NO synthase gene in stimulated macrophages was demonstrated by reverse transcriptase rapid PCR. Although IFN-gamma increased the amount of NO produced in macrophage cultures, it did not cause transcription of the inducible NO synthase gene greater than that seen with the Borrelia proteins. OspA and OspB also induced the production of high levels (40 to 150 ng/ml) of IFN-gamma in cultures of macrophages incubated with interleukin-2 (IL-2)-elicited cells from normal (T and NK cells) and scid (NK cells) mice but not in macrophages or IL-2-elicited cells cultured individually. This suggests that OspA stimulated macrophage production of cytokines, which, in turn, stimulated the production of IFN-gamma by NK and T cells. Reverse transcriptase rapid PCR demonstrated that OspA and sonicated B. burgdorferi stimulated production of several inflammatory cytokines in macrophage cultures, including IL-1, IL-6, IL-12, IFN-beta, and tumor necrosis factor alpha. As tumor necrosis factor alpha, IFN-beta, and IL-12 are potent activators of IFN-gamma production by T and NK cells, their presence in these cocultures could be responsible for the IFN-gamma production. Lymphocytes from infected C3H mice also produced IFN-gamma when stimulated with B. burgdorferi; thus, immune cells may also modulate NO responses. The generation of NO during infection with B. burgdorferi may be important, as NO has potent antimicrobial properties. NO can also be involved in pathological inflammatory processes in which its generation is detrimental to the host. Thus, the colocalization of B. burgdorferi lipoproteins, NO-producing cells, and regulatory cytokines may determine the outcome of infection.