Ingested mineral fibers: elimination in human urine.

Sediment in human urine examined by transmission electron microscopy contains amphibole fibers which originate from the ingestion of drinking water contaminated with these mineral fibers. The ingestion of filtered water results in the eventual disappearance of amphibole fibers from urine. These observations provide the first direct evidence for the passage of mineral fibers through the human gastro-intestinal mucosa under normal conditions of the alimentary canal.

Asbestiform amphibole minerals: detection and measurement of high concentrations in municipal water supplies.

Ashestiform amphibole minerals, which have been demonstrated to be associated with human health problems, have been detected in substantial quantities in municipal water supplies taken from western Lake Superior Water. The total concentrationl of amphibole minerals in the Duluth, Minnesota, water supply, as measured by x-ray diffraction for daily samples of suspended solids averages 0.19 milligram per liter with large fluctuations due to seasonal and climatological effects on lake circulation. Electron microscopic examination of these water samples confirms the presence of asbestiform amphibole fibers. A conservatiue estimate of the fiber count for 1973 Duluth water supply samples is (1 to 30) x 10(6) amphibole fibers identifiable by electron diffraction per liter of water with a mass concentration of 1 to 30 micrograms per liter.

Variability and evolution of Kaposi's sarcoma-associated herpesvirus in Europe and Africa. International Collaborative Group.

OBJECTIVE: To study the evolution of Kaposi's sarcoma-associated herpesvirus (KSHV) or human herpesvirus type 8 in Europe and Africa. DESIGN AND METHODS: PCR and sequence analysis of the variable viral membrane glycoprotein gene K1 in 58 tumour and peripheral blood samples from patients with AIDS-related Kaposi's sarcoma (KS), 'classic' (HIV-negative) KS, transplant KS, Multicentric Castleman's Disease, other lymphoproliferative disorders, and healthy KSHV-infected individuals from the UK, Denmark, Sweden, Italy, Spain, Iceland, The Faroe Islands, Greece, The Gambia and Uganda. RESULTS: Three major groups of K1 sequences were found: A, B and C, as defined previously. The K1 gene has evolved, both within and between these three groups, under positive selection. KSHV group B strains predominate in Africa and are more distant from groups A and C, found in Europe, than A and C are from each other. Within group C two subgroups, C' and C", can be identified. Subgroup C" is more closely related to group A in a region of the K1 protein and appears to be phylogenetically close to the branchpoint between A and C. Group A and C strains are currently found in both HIV-1-infected and -uninfected Europeans, and were already present in Europe before the start of the AIDS epidemic. We found some examples of closely related K1 sequences in Italy and Denmark, but in general KSHV strains in Europe did not cluster geographically. CONCLUSION: KSHV strains in East and West Africa are closely related but phylogenetically distant from those in Europe. The two major KSHV groups in Europe are more closely related, with some strains adopting an intermediate phylogenetic position. In Europe, KSHV strains may have been disseminated at least several decades ago. Variability in the K1 region is driven by selection and does not correlate with different KSHV-related pathologies or geographic regions where clinically more aggressive HIV-negative KS ('endemic' KS) is more common.

Review of published studies on gut penetration by ingested asbestos fibers.

During the 1970s, potential health risks associated with exposure to asbestos in drinking water became a national concern. One of the key questions that arose from debate over whether ingestion of mineral fibers could result in increased gastrointestinal cancer risk was whether fibers can penetrate the gastrointestinal mucosa and thus have some chance of residing in tissue. It is likely that such movement of a large number of fibers is a necessary precursor for carcinogenesis following ingestion of asbestos. Studies of the potential for fiber accumulation in tissues and body fluids following introduction of asbestos to the alimentary canal have provided seemingly contradictory observations. This review, which places particular emphasis on the impact of experimental and analytical limitations on the evidential strengths of each study, indicates the likelihood that a very small fraction of ingested microscopic asbestos fibers penetrates the gastrointestinal mucosa. A reliable estimate of the magnitude of long-term fiber retention in tissues as a consequence of chronic human ingestion of asbestos cannot be made at this time.

In vitro effects of mineral fibers.

In vivo tests available to determine the toxicity of mineral fibers are too expensive and time-consuming to be regularly employed in the evaluation of the potential health hazard posed by natural and man-made fibers. In vitro procedures, while economical, convenient and capable of ranking "relative toxicity," are uncertain predictors of specific lesions. Thus, it is of interest to compare the results of various standard in vitro tests with the results of in vivo tests. Data are available for intratracheal and intrapleural exposures of animals to amphibole mineral fibers from UICC amosite and a fibrous form of ferroactinolite. This paper presents data from parallel in vitro studies employing these minerals. The methods used were mammalian erythrocyte lysis, Chinese hamster ovary cell clonal cytotoxicity assay, and rabbit alveolar macrophage cytotoxicity assay. The experiments were conducted in triplicate to determine dose effect by mass and by number of fibers with aspect ratios greater than 3. A comparison of relative toxicity was made between the ferroactinolite and amosite. In the erythrocyte system, there was a greater lytic effect per unit of fibers for ferroactinolite than for the UICC amosite.

Correlation of in vitro and in vivo methods by means of mass dose and fiber distribution for amosite and fibrous ferroactinolite.

Oncogenesis and in vitro data (reported elsewhere in detail) are compared on the basis of relative activity by mass and by dimensional fiber parameters. When tumor induction is compared to the number of fibers of various lengths and aspect ratios in the dose in rats to the degree of tumor induction, a degree of difference with the long thin fiber concept of tumorigenesis by mineral fibers is noted. Consistency is re-established, however, when cognizance is taken of the change in the length and aspect ratio that took place during residence in the lung. This change resulted in a severalfold excess for ferroactinolite of all fiber lengths with high aspect ratios, produced as a result of longitudinal splitting of the introduced fibers. The response by mass in the in vitro procedures did not mimic oncogenesis. When mass was so adjusted that there were an equal number of mineral fibers, aspect ratio greater than 3, for dose for the two minerals, agreement was closer in both the rabbit alveolar macrophage toxicity test and the clonal cytotoxicity assay in Chinese hamster ovary cells. When activity was related to the number of mineral fibers, the same aspect ratio computed to have been contained in the mass dose, agreement with the relative induction of lung tumors was closer. In all cases, erythrocyte lysis was more active in reflecting the number of mineral fibers.

Tumorigenesis by a ferroactinolite mineral.

In lifetime exposure of male Fischer-344 rats to ferroactinolite fibers and to UICC amosite asbestos fibers by means of intratracheal and intrapleural treatments, oncogenesis was greater in the lung for the ferroactinolite and in the pleura for the amosite. The lack of correlation between the effects of the two methods of exposure suggests that in this instance intrapleural inoculation was not a good predictor of pulmonary response on the basis of mass dose. Another feature of the ferroactinolite was that pleural tumors resulted from intratracheal instillations. Conversely, lung tumors or tumorlike lesions were also induced by intrapleural inoculations of ferroactinolite. These facts suggest a greater in vivo transport for the ferroactinolite than for the amosite. Since there are far fewer mineral fibers per mass unit in the ferroactinolite the tumor yield per unit of mineral fibers was strikingly greater by both routes of administration for ferroactinolite than for amosite.

Interpretation of the carcinogenicity of amosite asbestos and ferroactinolite on the basis of retained fiber dose and characteristics in vivo.

Rats were exposed to amosite asbestos and ferroactinolite fibers by intrapleural inoculation and intratracheal instillation. The ferroactinolite sample was found to be more carcinogenic in both exposures than the amosite sample on the basis of total fiber dose or fiber dose expressed for any size category of hypothetical greatest carcinogenic potency. Quantitative transmission electron microscope analysis of low-temperature ashed whole lung samples collected at different times following intratracheal instillation of fibers demonstrated that concentrations and sizes of fibers retained in rat lungs were greatly influenced by the relative ability of each mineral to undergo longitudinal splitting as a consequence of dissolution in vivo. Ferroactinolite fibers rapidly split to produce many thin fibers so that the number of ferroactinolite fibers retained in the lung 2 years after intratracheal instillation was four times greater than the number of fibers originally instilled. The number of short, thin ferroactinolite fibers retained (10-fold more than amosite) after in vivo splitting best explains the greater lung carcinogenicity of ferroactinolite compared to amosite.

The role of spontaneous retinal activity before eye opening in the maturation of form and function in the retinogeniculate pathway of the ferret.

During early mammalian development, inputs from the two retinas intermix within the lateral geniculate nucleus (LGN), then segregate during the first postnatal week into layers that receive input from a single retina. Functionally, the LGN also changes markedly during the first postnatal month; early geniculate responses to retinal input are mainly excitatory, then inhibitory circuits mature within the LGN. These remarkable changes in form and function of the retinogeniculate pathway occur at a time when patterned visual activity is not present, but retinal ganglion cells already manifest spontaneous action potential activity. To examine the role of early retinal activity in these critical developmental processes, we placed the slow release polymer Elvax embedded with tetrodotoxin (TTX) into the vitreous chamber of one or both eyes of neonatal ferrets. Animals receiving monocular injection of TTX had the other eye treated with Elvax containing control citrate buffer. Intraocular injection of horseradish peroxidase was made at the end of the period of TTX treatment to reveal the retinal terminals in the LGN. Chronic monocular or binocular blockade of retinal activity during the first postnatal week did not prevent eye-specific segregation, although it made the boundaries between layers less distinct. Retinal terminals ended preferentially in the appropriate layer, but a large number of terminals were also present in the inappropriate layer. Further segregation was achieved during the second postnatal week of activity blockade, when most retinal terminals ended preferentially in the appropriate geniculate layer and sharper layer boundaries were present. However, a small but significant number of terminals still extended into the inappropriate layer. Together, these findings indicate that monocular as well as binocular blockade of retinal activity resulted in some anomalous retinogeniculate projections and delayed eye-specific patterning, but segregation was largely intact at the end of the second postnatal week. We also report here that intraocular tetrodotoxin had a marked effect on the maturation of intrinsic geniculate circuits prior to eye opening. Whole-cell patch-clamp recordings in the LGN slice preparation revealed that activity blockade prevented the maturation of the slow, but not the fast, hyperpolarizing potential of LGN neurons during the first postnatal month and up to P38, the oldest age studied. In conclusion, these results indicate that spontaneous retinal activity modulates the time course of binocular segregation but does not alone account for the segregation of retinogeniculate terminals. However, early retinal activity plays an important role in developing the intrinsic circuitry of the LGN.

Pathogenesis of pneumovirus infections in mice: detection of pneumonia virus of mice and human respiratory syncytial virus mRNA in lungs of infected mice by in situ hybridization.

The pathogenesis of pneumonia virus of mice (PVM) and human respiratory syncytial virus (HRSV) in BALB/c mice were investigated by using in situ hybridization to detect virus mRNA in fixed lung sections. Following intranasal inoculation with 120 p.f.u. PVM the pattern of hybridization showed that virus mRNA was initially detected within 2 days in alveolar cells. As the infection progressed the number of hybridizing alveolar cells increased and signal was also detected in cells lining the terminal bronchioles. By days 4 to 5 post-infection areas of morphological abnormality could be seen, particularly in the strongly hybridizing regions of the lung, and this correlated with the appearance of clinical signs of infection. In animals which survived the infection virus-specific mRNA could not be detected 10 days post-infection. Mice infected with 1500 p.f.u. HRSV showed significant differences in the distribution of virus-specific mRNA when compared to the pattern seen with PVM. HRSV mRNA was detected over large areas, but predominantly in peribronchiolar and perivascular regions of the lungs 5 days post-infection. The yield of PVM from infected mouse lungs was considerably higher than that of HRSV. The possible implications of these results for the use of the mouse model for pneumovirus infections are discussed.

Human herpesvirus 8 infection occurs following adolescence in the United States.

Most recent evidence suggests that human herpesvirus 8 (HHV-8) infection is restricted to persons with Kaposi's sarcoma (KS) or to persons who may subsequently develop KS. To accurately determine the prevalence of infection in the United States, children and adults with AIDS were examined for evidence of HHV-8 infection to see whether HHV-8 (like other herpesviruses) would be readily detected in immunosuppressed persons. By use of nested polymerase chain reaction, DNA specific for HHV-8, Epstein-Barr virus, and cytomegalovirus was detected in blood leukocytes from 0, 26 (51%), and 9 (18%), respectively, of 51 children. Similarly, HHV-8-specific antibodies were not detected in analyses of sera from the children. By contrast, HHV-8 DNA was detected in 9 (27%) of 33 adult AIDS patients without KS. These findings suggest that the pattern of transmission of HHV-8 in the United States differs from that of other herpesviruses in that primary infection occurs predominantly in adults.

Potency of a complex mixture of polychlorinated dibenzo-p-dioxin, dibenzofuran, and biphenyl congeners compared to 2,3,7,8-tetrachlorodibenzo-p-dioxin in causing fish early life stage mortality.

Use of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxicity equivalents concentration (TEC) assumes that polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs) act additively and via a common mechanism to cause toxicity. To test these assumptions, 11 TCDD-like congeners and three non-TCDD-like congeners were combined at ratios typically found in Lake Michigan lake trout. The potency of the mixture, expressed as TEC based on fish-specific toxic equivalency factors, was compared to TCDD for producing lake trout and rainbow trout early life stage mortality. Signs of toxicity following exposure of newly fertilized eggs to the mixture or to TCDD were indistinguishable; sac fry mortality associated with blue-sac disease, and slopes of the dose-response curves for percentage sac fry mortality versus egg TEC or versus egg TCDD were parallel. However, the mixture dose-response curves were significantly shifted to the right of the TCDD dose-response curves by 1.3- and 1.8-fold as illustrated by LD50 values. Following exposure to the mixture or TCDD, LD50S for lake trout early life stage mortality were 97 (89-110) pg TE/g egg and 74 (70-80) pg TCDD/g (LD50, 95% fiducial limits) and for rainbow trout were 362 (312-406) pg TE/g egg and 200 (148-237) pg TCDD/g egg. These data suggest that TCDD-like congeners act via a common mechanism to cause toxicity during trout early development, but may not act strictly additively when combined in a mixture of TCDD- and non-TCDD-like congeners at ratios found in Great Lakes fish. The deviation from additivity, however, is less than current safety factors of 10-fold commonly applied in ecological risk assessments, providing support for the continued use of a TE additivity model for assessing risk posed by complex mixtures of PCDDs, PCDFs, and PCBs to fish.

Risk factors for Kaposi's-sarcoma-associated herpesvirus (KSHV/HHV-8) seropositivity in a cohort of homosexual men, 1981-1996.

A newly identified herpesvirus has been associated with Kaposi's sarcoma. We determined risk factors for Kaposi's-sarcoma-associated herpesvirus/human herpesvirus 8 (KSHV/HHV-8) seropositivity and incidence of infection over time in a cohort of Danish homosexual men followed from 1981 to 1996. Antibodies to a latent nuclear (LANA) and a structural (orf65) antigen of KSHV/HHV-8 were measured by immunofluorescence and ELISA/WB respectively. Through linkage with the national AIDS registry, all cohort members diagnosed with AIDS as of September 1996 were identified and their hospital records were scrutinized to record all diagnoses of KS. Overall, 21.1% (52/246) of the men were KSHV/HHV-8-seropositive in 1981. Among the initially seronegative, the rate of KSHV/HHV-8 seroconversion was highest between 1981 and 1982 and declined steadily thereafter. In a multivariate analysis of the status at enrollment in 1981, KSHV/HHV-8 seropositivity was not associated with age but was independently associated both with number of receptive anal intercourses (OR = 2.83; p = 0.03) and with sex with US men (OR = 2.27; p < 0.05). In a multivariate analysis of follow-up data, risk of KSHV/HHV-8 seroconversion was independently associated with having visited homosexual communities in the United States, and current HIV-positive status. More than 5 years' homosexual experience was associated with an insignificantly increased risk (RR = 2.68). KS occurred only in HIV-positive men who were KSHV/HHV-8-positive at or prior to their KS diagnosis. In conclusion, KSHV/HHV-8 appears to be sexually transmitted, probably by receptive anal intercourse, and may have been introduced to Danish homosexual men via sex with US men. The epidemic of KSHV/HHV-8 is now declining. These findings are concordant with the view that KSHV/HHV-8 may have been actively spread simultaneously with and by the same activities that lead to the spread of HIV.

Integrated assessment of contaminated sediments in the lower Fox River and Green Bay, Wisconsin.

Samples of sediment and biota were collected from sites in the lower Fox River and southern Green Bay to determine existing or potential impacts of sediment-associated contaminants on different ecosystem components of this Great Lakes area of concern. Evaluation of benthos revealed a relatively depauperate community, particularly at the lower Fox River sites. Sediment pore water and bulk sediments from several lower Fox River sites were toxic to a number of test species including Pimephales promelas, Ceriodaphnia dubia, Hexagenia limbata, Selenastrum capricornutum, and Photobacterium phosphorum. An important component of the observed toxicity appeared to be due to ammonia. Evaluation of three bullhead (Ictalurus) species from the lower Fox River revealed an absence of preneoplastic or neoplastic liver lesions, and the Salmonella typhimurium bioassay indicated relatively little mutagenicity in sediment extracts. Apparent adverse reproductive effects were noted in two species of birds nesting along the lower Fox River and on a confined disposal facility for sediments near the mouth of the river, and there were measurable concentrations of potentially toxic 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), and planar polychlorinated biphenyls (PCBs) both in the birds and in sediments from several of the study sites. Based on toxic equivalency factors and the results of an in vitro bioassay with H4IIE rat hepatoma cells, it appeared that the majority of potential toxicity of the PCB/PCDF/PCDD mixture in biota from the lower Fox River/Green Bay system was due to the planar PCBs. The results of these studies are discussed in terms of an integrated assessment focused on providing data for remedial action planning.

Prevalence of Kaposi's sarcoma associated herpesvirus infection measured by antibodies to recombinant capsid protein and latent immunofluorescence antigen.

BACKGROUND: Kaposi's sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus 8, may be the infectious cause of KS. Its prevalence in the general population, on the basis of detection of the virus genome, is controversial. To investigate the seroprevalence, we measured antibodies to a recombinant capsid-related (lytic cycle) KSHV antigen and a latent antigen complex. METHODS: We selected potentially immunoreactive capsid-related proteins of KSHV by expressing them as recombinant proteins and testing them in western blot assays. We used a truncated recombinant protein encoded by KSHV open reading frame 65 (orf 65) to develop a diagnostic enzyme-linked immunosorbent assay (ELISA) and tested sera from HIV-infected individuals with KS, HIV-uninfected patients with "classic" KS, other HIV risk groups, and blood donors. We also compared the antibody response to this capsid-related protein to the response to latent antigen(s) in an immunofluorescence assay. FINDINGS: 77/92 (84%) sera from KS patients reacted with the KSHV orf 65 protein and 84/103 (81.5%) reacted with KSHV latent antigen(s). The dominant immunogenic region of orf 65 is within the carboxyterminal 80 aminoacids, a region with little sequence similarity to the related Epstein-Barr virus, suggesting that orf 65 is a KSHV specific antigen. Only three sera from patients with haemophilia (1/84) or from intravenous drug users (2/63) had KSHV specific antibodies in the orf 65 assay whereas none of these sera reacted with latent antigen. Antibodies to KSHV were also infrequently found in UK and US blood donors by either assay (UK, 3/174 with orf 65 and 4/150 with latent antigen; US, 6/117 with orf 65 and 0/117 with latent antigen). They were more common among HIV-infected gay men without KS (5/16 by orf 65 ELISA, 10/33 by IFA), HIV-uninfected STD clinic attenders (14/166 by IFA), and Ugandan HIV-uninfected controls (6/17 by orf 65 ELISA, 9/17 by IFA). Antibody reactivity to the orf 65 protein (ELISA) and to latent antigen(s) (IFA) was concordant in 89% of 462 sera tested but reactive blood donor sera were discordant in both assays. Four AIDS-KS sera were unreactive in both assays. INTERPRETATION: The distribution of antibodies to both a capsid-related recombinant protein and latent antigen(s) of KSHV strongly supports the view that infection with this virus is largely confined to individuals with, or at increased risk for, KS. However, infection with KSHV does occur, rarely, in the general UK and US population and is more common in Uganda. Antibodies to latent antigen(s) or to orf 65 encoded capsid protein will not detect all cases of KSHV infection, and a combination of several antigens will probably be required for accurate screening and confirmatory assays.