Differences in fish communities on natural versus artificial temperate reefs, groundfish conservation applications in British Columbia.

Human-made marine habitats such as artificial reefs are used to mitigate marine habitat degradation and aid conservation of species at risk. We used ROV and sonar to survey threatened rockfish (Sebastes spp.) and other groundfish species associated with 18 artificial and natural reefs along the south coast of BC, Canada. Using an information-theoretic approach, we found that community composition significantly differed between natural and artificial reefs. Artificial reefs had high variability in rockfish abundance, some supporting very high or low relative abundance. Natural reefs consistently supported intermediate rockfish abundances. Groundfish diversity was significantly greater on natural reefs than artificial reefs. Depth and relief were significant predictors for both abundance and species richness. Interestingly, rockfish abundance was negatively associated with proximity to nearest rockfish conservation area. This research is a first step in understanding causal mechanisms leading to differences between fish communities on artificial reefs in our study system, and which reef attributes may facilitate successful contributions to conservation. Though artificial reefs show promise in the conservation of some threatened species, the maintenance of diverse fish communities depends on protection of heterogenous natural reef communities.

Fish processing facilities: new challenge to marine biosecurity in Canada.

The transmission of pathogens is a common consequence of animal food production. Marine salmon farms and their processing facilities can serve as sources of virulent fish pathogens; our study is the first to confirm the broadcast of a live fish pathogen from a farmed salmon processing facility into the marine waters of Canada's Pacific coast. We found live salmon lice Lepeophtheirus salmonis, mucus, and fish tissue in effluent from the processing facility. Sea lice transmitted from this source may pose a threat to wild salmon populations, and the release of untreated offal, including blood water, is of considerable concern. Further research is needed to quantify the extent to which processing facilities release sea lice and to determine whether more virulent fish pathogens are present in effluent. These data underscore the need for fish farming nations to develop mandatory biosecurity programs to ensure that farmed salmon processing facilities will prevent the broadcast of infectious fish pathogens into wild fish habitat.

Increased ultraviolet sensitivity and chromosomal instability related to P53 function in the xeroderma pigmentosum variant.

The xeroderma pigmentosum (XP) variant (XPV) is a form of XP that has normal excision repair but shows defective DNA replication after UV irradiation. In developing various transformed fibroblast cell lines from these patients, we have found that there are significant phenotypic changes in transformed cells that seem to correlate with inactivation of p53. After transformation with SV40, XPV cell lines are only slightly UV sensitive, like their primary counterparts, but their sensitization with caffeine and the induction of sister chromatid exchanges (SCEs) by UV irradiation are greatly enhanced. After transformation by HPV16 E7, which targets the retinoblastoma cell cycle regulatory gene, there is no change in the UV sensitivity of XPV cells; but, when transformed by HPV16 E6 or E6 and E7 combined, there is a large increase in UV sensitivity and in the induction of SCEs. These changes are not associated with any detectable changes in the reactivation of an externally irradiated luciferase expression vector, the excision of cyclobutane pyrimidine dimers from bulk DNA, or unscheduled DNA synthesis and, therefore, do not involve excision repair. We suggest that if SCEs represent homologous recombination between sister chromatids, then in the absence of p53 function, the DNA chain arrest typical of UV-damaged XPV cells initiates strand exchange during recovery. In untransformed cells with normal p53, the preferred mode of recovery would then be replication bypass. The symptoms of elevated solar carcinogenesis in XPV patients may, therefore, be associated with increased genomic instability in cells of the skin in which p53 is inactivated by UV-induced mutations.

Radiation risk estimation in human populations: lessons from the radiological accident in Brazil.

The development of radiological and nuclear technologies and the deployment of nuclear weapons have made ionizing radiation one of the most studied human mutagens. Exposure to ionizing radiation produces DNA damage which can result in mutation and cancer, making the risk associated with human exposure a critical issue. In this paper we estimate the risk associated with radiation exposure for individuals exposed to 137Cs during the 1987 Goiânia radiological accident. Using combined regression slopes from both the in vivo hprt mutant frequency and micronucleus frequency data we estimated a doubling dose of 173 (+/-47) cGy for these two endpoints. This is in close agreement with the published estimates for low dose rate and chronic exposure to low-LET radiation. We obtained risk estimates of about 24-fold increase in dominant disorders in the post-exposure generation of the directly exposed population. No detectable increase was found in the population at large. The risk of carcinogenesis in the directly exposed population was found to be increased by a factor in the range of 1.4 to 1.5. The small sample size in this study requires a large element of caution with respect to risk estimates interpretation. Moreover, the doubling dose estimates prepared here are derived from lymphocytes. This somatic data may require additional considerations for both cancer and certainly germ-line events. Nevertheless, the risk of carcinogenesis and genetic harm for this population are good indicators of the potential genetic damage imposed by ionizing radiation to the Goiânia population.

Molecular genetic examination of the polymorphic Arctic charr Salvelinus alpinus of Thingvallavatn, Iceland.

Thingvallavatn, Iceland contains two sympatric morphotypes (benthic and limnetic) of Arctic charr Salvelinus alpinus. Each morphotype is composed of two morphs and these differ markedly in ecology, behaviour and life history. We used molecular genetic approaches to test whether (i) genetic heterogeneity exists among morphs and (ii) if morphs arose in allopatry and came into secondary contact or arose sympatrically within the lake through genetic segregation and/or phenotypic plasticity. Direct sequencing of 275 bp of the mitochondrial DNA (mtDNA) control region, mtDNA restriction fragment length polymorphisms and single locus minisatellite analyses detected insufficient variation to test our hypotheses. Analysis of multilocus minisatellite band sharing detected no significant differences between morphs within the same morphotype. However, significant differences among morphs belonging to different morphotypes suggest some genetic heterogeneity in Thingvallavatn charr. Limnetic charr from Thingvallavatn were more similar to sympatric benthic charr than to allopatric limnetics from two other Icelandic lakes. This suggests that the Thingvallavatn morphs arose sympatrically within the lake rather than in allopatry followed by secondary contact.

Characterization of mutant HA-ras gene expression in transformed murine keratinocyte lines grown under in vitro and in vivo conditions.

We investigated the Ha-ras and Ki-ras gene status, tumorigenicity, pathology, line derivation, and intercellular communication of 7,12-dimethylbenz[a]anthracene-initiated papilloma-, carcinoma-, and hyperplastic skin-producing cell lines to further characterize them. Six of nine tumor cell lines grown in vitro expressed both mutant and normal Ha-ras proteins, and three lines expressed only normal Ha-ras. However, when grown subcutaneously in nude mice, seven of the nine lines expressed both mutant and normal Ha-ras, one line expressed normal Ha-ras, and one line did not grow subcutaneously. One papilloma line, P2/15, appeared to have an inducible mutant Ha-ras gene, as it was expressed only in vivo. These findings suggest that mutant Ha-ras genes may be lost in only a minor population of tumor lines during growth in culture. Finally, we found that mutant Ha-ras gene expression was strongly correlated with tumorigenicity in nude mice and that intercellular communication was strongly correlated with the derivation of the lines.

Artifacts in chest radiographs with a third-generation computed radiography system.

Photostimulable phosphor computed radiography (CR) is a developing and increasingly widespread technology. The purpose of this pictorial essay is to familiarize readers with the appearance and cause of image artifacts that can occur in a third-generation computed radiographic system. Artifacts are described that relate to imaging plates, image readers, image processing, and film processing.

Xeroderma pigmentosum variant cells are resistant to immortalization.

Xeroderma pigmentosum (XP) is a human repair-deficient disorder that is caused by mutations in any of eight genes (A-G, V). The genes for complementation groups A-G have been cloned fully or in part, but the gene for the XP variant (XPV) has yet to be cloned. The lack of progress with XPV is in large part due to the rarity of stably transformed cell lines. We have attempted to immortalize fibroblasts from several XPV patients to obtain cell lines with which to characterize this disease and clone the appropriate gene. We have found, as have other investigators, that this XP group is very difficult to immortalize. We used a variety of approaches, including transfection with pSV ori- (a plasmid containing the simian virus (SV) 40 large T antigen) followed by spontaneous transformation, which provided stable immortal lines from Cockayne syndrome A and B, but not from XPV; transfection with pSV ori- and exposure to 3 Gy of X-rays; transfection with pSV ori-, exposure to 2 Gy of X-rays, and treatment with 1 mM ethyl methanesulfonate; transfection with human papilloma virus-16; and infection with SV40. Even though we used as many as 2 x 10(8) cells in some experiments, we were able to immortalize only one of our lines, XP30RO. Because the biochemical defect in XPV cell lines involves the capacity to replicate damaged DNA templates, perhaps the XPV gene product could be a replication factor that interacts with SV40 T antigen, and whose absence from XPV cell lines presents difficulties for the immortalization process to proceed.

Sister chromatid exchanges in cells defective in mismatch, post-replication and excision repair.

Three processes associated with DNA damage and genomic instability have been defined experimentally as operating during or soon after DNA replication: mismatch repair, post-replication repair and sister chromatid exchange. All these processes appear to operate on damage and/or errors in newly replicated DNA. Both mismatch repair and post-replication repair involve resynthesis of up to 1 kb of newly synthesized DNA: mismatch repair operates on single-base or slippage errors; post-replication repair operates on persistent gaps in newly synthesized DNA caused by damage on parental strands. Using colon cancer cells with different mismatch repair capacity, together with normal cells and excision-repair-defective and post-replication-repair-defective xeroderma pigmentosum (XP) cells, we analysed possible interactions between these processes. No evidence for overlap of mismatch repair with excision or post-replication repair was found. However, post-replication-repair-defective XP variant cells that were SV40 transformed showed higher UV-induced sister chromatid exchange frequencies than did untransformed cells. This suggests that sister chromatid exchanges in the XP variant are closely involved with UV-induced replication errors that are enhanced by transformation.

Peripheral bronchopleural fistula: CT evaluation in 20 patients with pneumonia, empyema, or postoperative air leak.

PURPOSE: To assess the usefulness of standard and thin-section computed tomography (CT) in the examination of patients with possible bronchopleural fistulas (BPFs). MATERIALS AND METHODS: Twenty patients with known or suspected BPFs underwent CT. Twelve had pleural air and fluid collections; eight had air leaks. Fourteen patients also underwent thin-section CT. RESULTS: The BPF or its probable cause was visualized in all patients with air and fluid collections and in two of the patients with air leaks. BPFs due to bronchiectasis, necrotizing pneumonia, or alveolar cell carcinoma were identified in 10 patients. In four others, bronchiectasis was seen but the actual communication was not. In seven patients with postoperative air leaks, standard or thin-section CT demonstrated the air-leak source in only one. Thin-section CT was superior to standard CT in six of eight patients in whom the BPF or its probable cause was visible. CONCLUSION: Standard and thin-section CT are useful in the diagnosis and management of peripheral BPFs.

Nucleotide excision repair: variations associated with cancer development and speciation.

Nucleotide excision repair requires the action of multiple interacting proteins that locate damage in DNA, remove it as a short oligonucleotide and synthesize a replacement patch. Mutations in genes coding for these proteins give rise to a wide range of diseases involving skin carcinogenesis, neuronal decline and developmental disorders of bone and central nervous system. Complex clinical symptoms of more than one clinical disorder may occur because of mutations that influence protein-protein interactions. Significant differences in repair occur between individuals and species for which the molecular basis and phenotypic consequences have yet to be explained.

Prenatal diagnosis of xeroderma pigmentosum and Cockayne syndrome.

In a study of fetal cells from a series of 12 pregnancies in ten families at risk for the ultraviolet light-sensitive, DNA repair-deficient diseases xeroderma pigmentosum (XP) and Cockayne syndrome (CS), we detected one XP and two CS homozygote fetuses. The diagnoses were confirmed by analysis of fetal skin fibroblasts or second amniotic samples after termination of the pregnancies. The measurement of ultraviolet light sensitivity and DNA repair depended on properties common to the seven excision repair-deficient XP complementation groups (A-G) and the two CS complementation groups (A, B). No XP variant families were included in the study, because the variant requires different testing techniques. Reliable and rapid diagnosis proved possible in all but one of the 12 pregnancies, supporting the use of these methods until the spectrum of mutations in the various XP and CS genes of the U.S. population is fully characterized and a DNA sequence-based diagnostic procedure becomes available.

Can a non-tumorigenic dose of carcinogen cause two or more errors in a cell?

Cancer is believed to be the result of a multistep process, beginning with a single alteration in a cell's genome. Here the hypothesis that a few cells may receive two or more hits after the application of a non-tumorigenic or higher dose of carcinogen is proposed. Preneoplastic lesions that arise from such doubly-hit cells may be few in number, but may more easily undergo tumor formation and tumor progression. This hypothesis augments the multihit model of carcinogenesis and explains much data that the single, first-hit assumption cannot.

The use of quantitative genetics for estimating the non-inherited and inherited contributions to metastasis formation.

The contribution of both non-inherited (stochastic, random, environmental, and other non-inherited influences) and inherited factors (genetic and inherited epigenetic factors) to the variability of spontaneous lung metastasis formation in over 100 metastatic lines from each of three murine tumors was measured. The contribution of inherited and genetic sources of variability to metastasis formation was significantly greater than 0 in all cases, but only in the lines of sarcoma SANH was it the major influence on metastatic variability. In the sarcoma SA4020 and hepatocarcinoma HCA-1 lines, non-inherited factors accounted for the majority of the variation in spontaneous lung metastasis formation. A similar situation was also observed in the variability of the tumors with respect to the diameter doubling time. In conclusion, both non-inherited and genetic/inherited factors significantly influenced the formation of spontaneous metastases in the tumors examined. The significance of this finding for the cloning of metastatic genes is discussed.

Influence of tumor transplantation methods on tumor growth rate and metastatic potential of solitary tumors derived from metastases.

This study was performed to determine whether the growth rate and metastatic potential of tumors generated by spontaneous lung metastases is influenced by transplantation methods. Three different tumors syngeneic to C3Hf/Kam mice were studied: the SA-NH and SA-4020 sarcomas and the hepatocarcinoma HCA-I. Solitary tumors in the legs of mice were generated by a single metastatic nodule taken at random from lung metastases, by a single metastatic nodule taken from each mouse with the highest number of metastases, by a mixture of cells from lung metastases taken randomly, or by a mixture of cells from primary leg tumors. These transplantation procedures were repeated for two to four isotransplant generations. Repeated isotransplants of primary tumors showed little if any change in the growth rate and metastatic spread. In contrast, primary tumors derived from spontaneous metastases frequently exhibited a decrease in their growth rate and an increase in metastatic potential. This was particularly frequent when tumors were established from single metastatic nodules taken randomly from the lung, or taken from lungs that contained the largest number of metastatic nodules. The magnitude of this change varied greatly among the three tumors studied. Increased metastatic formation in the lung was also frequently associated with slower growth of the primary tumors. Thus, transplantation methods used for establishing primary tumors have an important influence on the metastatic potential of tumor transplants.

Metastatic abilities of murine sarcomas and carcinomas. II. Relationship to cell volume and DNA index.

The cell volume and DNA content were determined in 12 murine tumors and correlated with the ability of these tumors to metastasize spontaneously or to form lung nodules when injected i.v. The cell volume significantly correlated with spontaneous metastatic potential of investigated tumors (r = 0.683; 0.02 less than P less than 0.05) but not with the ability of tumor cells to form artificial metastasis. The DNA index significantly correlated with both spontaneous metastasis (r = 0.594; 0.02 less than P less than 0.05), and lung colonization (r = 0.631; 0.02 less than P less than 0.05). The DNA index barely correlated with the cell volume (r = 0.564; P = 0.10).

The radiologic evaluation of renal metastases.

Renal metastases can arise from practically any primary neoplasm and should no longer be considered rare. Such lesions are usually detected during surveillance US or CT examinations. Appearances favoring metastases over an additional renal carcinoma are multiplicity, bilaterality, metastatic disease elsewhere, and perinephric disease. Since not all renal metastases behave predictably and may even appear as single, exophytic lesions, guided fine-needle aspiration may be required when such information will alter patient management.

Genetic instability of cancer. Why a metastatic tumor is unstable and a benign tumor is stable.

It is theorized that tumors may be initiated by two methods: by an error affecting one or several oncogenes, or by an error affecting one or several of the genes controlling the stability of the genome. The majority of cells that misexpress an oncogene(s) and that later form a tumor probably form nonevolving benign tumors. A minority of these cells with an activated oncogene(s) (or one of the descendant cells) may also come to misexpress a stability gene(s). A normal cell that misexpresses only a stability gene(s) may form an evolving and genetically unstable cell line that may later misexpress an oncogene(s). A cell or cell line that misexpresses both an oncogene(s) and a stability gene(s) may form a genetically unstable tumor that creates diverse variants, allowing for extensive tumor cell evolution and the acquisition of malignant and metastatic properties.