[Retrospective analysis of 35 burn patients in different stages of pregnancy].

Objective: To summarize the clinical outcomes of burn patients in different stages of pregnancy and explore a rational therapeutic scheme for burns during pregnancy. Methods: A retrospective observational study was conducted. From June 2010 to June 2020, 21 patients who met the inclusion criteria were admitted to the Department of Burns of Wuhan Third Hospital and 14 patients who met the inclusion criteria were admitted to the Department of Burns of the First Affiliated Hospital of Nanchang University. Based on the pregnancy period when patients suffered burns, the 35 patients were divided into early pregnancy group with 18 patients (aged (26±4) years, with 8 (4, 11) weeks of gestation), middle pregnancy group with 10 patients (aged (26±3) years, with 21 (14, 27) weeks of gestation), and late pregnancy group with 7 patients (aged (30±5) years, with 32 (29, 35) weeks of gestation). All the patients received treatment including fluid resuscitation, anti-infection, wound treatment, and multidisciplinary comprehensive managements. The burn-related complications during the treatment, maternal outcomes, fetal outcomes, fetal delivery mode, gestational weeks at delivery, and newborn weight of patients in the 3 groups were recorded. Data were statistically analyzed with one-way analysis of variance, Kruskal-Wallis test, and Fisher's exact probability test. Results: During the treatment, there were 4, 4, and 2 patients who suffered wound infections and 1, 3, and 2 patients who developed shock symptoms, respectively, in early pregnancy group, middle pregnancy group, and late pregnancy group. There were no statistically significant differences in them among the 3 groups (P>0.05). One patient in late pregnancy group developed into multiple organ dysfunction syndrome after debridement. At last, all the pregnant women survived, and no statistically significant difference existed among the 3 groups (P>0.05). In early pregnancy group, middle pregnancy group, and late pregnancy group, the survived fetus cases were 9, 8, and 6, respectively, and the differences between them were not statistically significant (P>0.05). Variables including stillbirth and full-term birth were close in patients in the 3 groups (P>0.05), while the preterm birth and miscarriage in patients in the 3 groups were statistically different (P<0.05 or P<0.01), with the early pregnancy group having the most miscarriage cases and the fewest preterm birth cases. There were no statistically significant differences in fetal delivery mode, gestational weeks at delivery, and newborn weight among the patients with survived fetus in 3 groups (P>0.05). Conclusions: For patients suffering burns during early, middle, and late pregnancy, superior rates of maternal and fetal survival can be achieved after timely and adequate treatments including fluid resuscitation, anti-infection, wound treatment, and multidisciplinary comprehensive managements.

LncRNA PAPAS aggravates the progression of gastric cancer through regulating miRNA-188-5p.

Since this paper presents several inaccuracies and mistakes, the article "LncRNA PAPAS aggravates the progression of gastric cancer through regulating miRNA-188-5p, by X. Shi, X. You, W.-C. Zeng, Y.-J. Deng, H.-L. Hong, O.-X. Huang, M.-F. Wang, published in Eur Rev Med Pharmacol Sci 2019; 23 (24): 10761-10768-DOI: 10.26355/eurrev_201912_19778-PMID: 31858543" has been withdrawn. The Publisher apologizes for any inconvenience this may cause. https://www.europeanreview.org/article/19778.

LncRNA PAPAS aggravates the progression of gastric cancer through regulating miRNA-188-5p.

OBJECTIVE: To uncover the biological effect of long non-coding RNA (lncRNA) PAPAS on the progression of gastric cancer (GC) by mediating microRNA-188-5p (miRNA-188-5p) level. PATIENTS AND METHODS: The relative level of PAPAS was determined in GC tissues and cell lines by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). The Kaplan-Meier method was introduced to assess the prognostic potential of PAPAS in the overall survival of GC patients. Regulatory effects of PAPAS on proliferative, migratory, and invasive abilities of HGC-27 and AGS cells were detected by cell counting kit-8 (CCK-8), transwell, and wound closure assay, respectively. Subsequently, the binding relation between PAPAS and miRNA-188-5p was verified by the Dual-luciferase reporter gene assay. Correlation between expression levels of PAPAS and miRNA-188-5p in GC tissues was explored. Finally, rescue experiments were conducted to uncover the role of PAPAS/miRNA-188-5p axis in the progression of GC. RESULTS: PAPAS was upregulated in GC tissues and cell lines compared to controls. GC patients expressing a high level of PAPAS suffered worse prognosis relative to those with low level. The silence of PAPAS remarkably attenuated proliferative, migratory, and invasive abilities of HGC-27 cells. Overexpression of PAPAS in AGS cells obtained the opposite trends. MiRNA-188-5p was the direct target of PAPAS, which was negatively regulated by PAPAS. MiRNA-188-5p was able to reverse the regulatory effects of PA-PAS on proliferative, migratory, and invasive abilities of GC cells. CONCLUSIONS: LncRNA PAPAS is upregulated in GC and closely related to lymphatic metastasis, distant metastasis, and poor prognosis of GC patients. PAPAS aggravate the malignant progression of GC by negatively regulating the miRNA-188-5p level.

Knockdown of LINC00461 inhibits cell proliferation and induces apoptosis in gastric cancer by targeting LSD1.

OBJECTIVE: To uncover the function of LINC00461 in regulating cellular behaviors of gastric cancer (GC) via targeting LSD1. PATIENTS AND METHODS: LINC00461 level in GC tissues with different tumor node metastasis (TNM) staging and lymphatic metastasis statues was determined by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). In vitro influences of LINC00461 on proliferative and apoptotic rates were evaluated in AGS and SGC-7901 cells. The interaction between LINC00461 and LSD1 was explored by RNA immunoprecipitation (RIP) assay and qRT-PCR. Finally, the potential role of LSD1 in the proliferative ability of GC cells mediated by LINC00461 was assessed. RESULTS: LINC00461 level was higher in GC tissues relative to matched control ones. It was positively correlated to TNM staging and lymphatic metastasis of GC. Knockdown of LINC00461 markedly attenuated viability and the proliferative ability of AGS and SGC-7901 cells, but induced apoptosis. RIP assay demonstrated the interaction between LINC00461 and LSD1. Moreover, LSD1 could reverse the regulatory effect of LINC00461 on the proliferative ability of GC cells. CONCLUSIONS: LINC00461 is upregulated in GC, which is positively related to TNM staging and lymphatic metastasis. LINC00461 mediates proliferation and apoptosis of GC cells, thereafter aggravating the progression of GC.

Carcinogenic activity of pentabrominated diphenyl ether mixture (DE-71) in rats and mice.

Pentabrominated diphenyl ether (PBDE) flame retardants have been phased out in Europe and in the United States, but these lipid soluble chemicals persist in the environment and are found human and animal tissues. PBDEs have limited genotoxic activity. However, in a 2-year cancer study of a PBDE mixture (DE-71) (0, 3, 15, or 50 mg/kg (rats); 0, 3, 30, or 100 mg/kg (mice)) there were treatment-related liver tumors in male and female Wistar Han rats [Crl:WI(Han) after in utero/postnatal/adult exposure, and in male and female B6C3F1 mice, after adult exposure. In addition, there was evidence for a treatment-related carcinogenic effect in the thyroid and pituitary gland tumor in male rats, and in the uterus (stromal polyps/stromal sarcomas) in female rats. The treatment-related liver tumors in female rats were unrelated to the AhR genotype status, and occurred in animals with wild, mutant, or heterozygous Ah receptor. The liver tumors in rats and mice had treatment-related Hras and Ctnnb mutations, respectively. The PBDE carcinogenic activity could be related to oxidative damage, disruption of hormone homeostasis, and molecular and epigenetic changes in target tissue. Further work is needed to compare the PBDE toxic effects in rodents and humans.

Ganciclovir and Foscarnet Therapy of Cytomegalovirus-Associated Meningoencephalitis in a Hemodialysis Patient With Liver Transplantation: Case Report.

Cytomegalovirus (CMV) infection in patients with liver transplantation (LT) remains a highly prevalent complication with a significant increase in morbidity and mortality. However, CMV-associated meningoencephalitis is rarely diagnosed, and treatment is very difficult. The aim of the present report is to review the experience of successful treatment with combined ganciclovir and foscarnet of CMV-associated meningoencephalitis refractory to ganciclovir alone in a hemodialysis (HD) patient after LT. A 54-year-old woman with end-stage renal disease on HD developed a seizure with loss of consciousness. She had received a liver transplant 4 months before. Blood CMV polymerase chain reaction was positive, and cerebrospinal fluid (CSF) analysis was compatible with viral meningitis. Brain magnetic resonance imaging (MRI) showed extensive dural thickening with enhancement and a round ring-like enhancement in the left centrum semiovale. She was diagnosed with CMV-associated meningoencephalitis. At that time, ganciclovir was started intravenously. After that, there were no improvements in mental state, CSF analysis, or brain MRI. Intravenous foscarnet at reduced dose was added to ganciclovir therapy. With combined ganciclovir and foscarnet, there was a slight improvement in her mental state and brain MRI.

Understanding the Cu-Zn brass alloys using a short-range-order cluster model: significance of specific compositions of industrial alloys.

Metallic alloys show complex chemistries that are not yet understood so far. It has been widely accepted that behind the composition selection lies a short-range-order mechanism for solid solutions. The present paper addresses this fundamental question by examining the face-centered-cubic Cu-Zn α-brasses. A new structural approach, the cluster-plus-glue-atom model, is introduced, which suits specifically for the description of short-range-order structures in disordered systems. Two types of formulas are pointed out, [Zn-Cu12]Zn(1~6) and [Zn-Cu12](Zn,Cu)6, which explain the α-brasses listed in the American Society for Testing and Materials (ASTM) specifications. In these formulas, the bracketed parts represent the 1(st)-neighbor cluster, and each cluster is matched with one to six 2nd-neighbor Zn atoms or with six mixed (Zn,Cu) atoms. Such a cluster-based formulism describes the 1st- and 2nd-neighbor local atomic units where the solute and solvent interactions are ideally satisfied. The Cu-Ni industrial alloys are also explained, thus proving the universality of the cluster-formula approach in understanding the alloy selections. The revelation of the composition formulas for the Cu-(Zn,Ni) industrial alloys points to the common existence of simple composition rules behind seemingly complex chemistries of industrial alloys, thus offering a fundamental and practical method towards composition interpretations of all kinds of alloys.

Cytomegalovirus infection after acute rejection therapy in seropositive kidney transplant recipients.

BACKGROUND: Acute rejection (AR) after solid organ transplantation has been known to be a risk factor for cytomegalovirus (CMV) infection. However, data regarding the risk for CMV infection during and after anti-rejection therapy are limited. This study investigated whether the risk of CMV infection and disease within 6 months of kidney transplantation (KT) increases in CMV-seropositive KT recipients who develop AR. METHODS: A total of 992 seropositive KT recipients, including 75 patients (8%) who developed AR within 6 months after KT and 917 patients (92%) who did not, were recruited between May 2007 and April 2012. RESULTS: No significant difference was found in the incidence of CMV infection between the groups (AR group, 13% [10/75] vs. non-AR group, 10% [92/917], P = 0.37). The number of KT recipients in each group receiving preemptive therapy for CMV was similar (5% [4/75] vs. 6% [53/917], P > 0.99). While the incidence of CMV syndrome was comparable (0% [0/75] vs. 1% [12/917], P > 0.99), the incidence of tissue-invasive CMV disease (8% [6/75] vs. 3% [27/917], P = 0.04), particularly gastrointestinal CMV disease, was significantly greater in patients who experienced AR. No CMV-related mortality occurred in either group. AR (odds ratio, 2.81; 95% confidence interval, 1.08-7.29; P = 0.03) was an independent risk factor for tissue-invasive CMV disease within 6 months of KT. CONCLUSIONS: A high index of suspicion and active evaluation for tissue-invasive CMV disease in KT recipients suffering AR may be necessary to ensure appropriate treatment.

Emerging fluoroquinolone resistance in Streptococcus agalactiae in South Korea.

The goal of this study was to determine the prevalence of fluoroquinolone resistance in Streptococcus agalactiae and the serotype distribution of this resistant bacterium. S. agalactiae strains collected from 221 asymptomatic pregnant women (35-37 weeks of gestation) and 838 patients with S. agalactiae infection in Korea, from 2006 to 2008, were tested for susceptibility to four fluoroquinolones. Rates of resistance of S. agalactiae to ciprofloxacin, levofloxacin, and moxifloxacin were 9.3 %, 9.5 %, and 0.8 %, respectively; greater than 94 % of S. agalactiae strains were resistant to norfloxacin. Resistance to ciprofloxacin and levofloxacin increased between 2006 and 2008. All strains were susceptible to penicillin. Resistance to ciprofloxacin and levofloxacin was higher in the clinical strains of S. agalactiae isolated from infections than in colonizing strains isolated from pregnant women. Mutations in the quinolone resistance-determining regions of gyrase and topoisomerase genes were detected in strains resistant to ciprofloxacin, levofloxacin, and moxifloxacin; no such mutations were found in strains resistant only to norfloxacin. There was a strong correlation between the minimum inhibitory concentrations and the presence of mutations in gyrase and topoisomerase genes. In conclusion, the prevalence of fluoroquinolone resistance was unexpectedly high. Strain serotypes were not associated with susceptibility to fluoroquinolones.

o-Nitrotoluene-induced large intestinal tumors in B6C3F1 mice model human colon cancer in their molecular pathogenesis.

In the previous 500 2-year chemical bioassays within the National Toxicology Program, large intestinal tumors (cecal carcinomas) related to chemical exposure have not been observed in B6C3F1 mice. The recently completed o-nitrotoluene study provided the first cecal tumor response and an opportunity to evaluate the morphology and molecular profile of oncogenes and tumor suppressor genes that are relevant to humans. Morphologically, the carcinomas were gland-forming tumors lined by tall columnar epithelial cells that were positive for cytokeratin 20 and negative for cytokeratin 7. Using immunohistochemistry beta-catenin (encoded by Catnb) protein accumulation was detected in 80% (8/10) of the cecal carcinomas, while increased cyclin D1 and p53 protein expression was detected in 73% (8/11), respectively. There was no difference in adenomatous polyposis protein expression between normal colon and cecal carcinomas. All tumors examined exhibited mutations in exon 2 (corresponds to exon 3 in humans) in the Catnb gene. Mutations in p53 were identified in nine of 11 carcinomas, and all were in exon 7. Analysis of the K-ras gene revealed mutations in 82% (9/11) of carcinomas; all had specific G --> T transversions (Gly --> Val) at codons 10 or 12. The alterations in cancer genes and proteins found in the mouse large intestinal tumors included mutations that activate signal transduction pathways (K-ras and Catnb) and changes that disrupt the cell-cycle and bypass G(1) arrest (p53, cyclin D1). These alterations, which are hallmarks of human colon cancer, probably contributed to the pathogenesis of the large intestinal carcinomas in mice following o-nitrotoluene exposure.

Chemical-specific alterations in ras, p53, and beta-catenin genes in hemangiosarcomas from B6C3F1 mice exposed to o-nitrotoluene or riddelliine for 2 years.

The most prominent neoplastic lesions in mice in the 2-year studies of o-nitrotoluene and riddelliine were hemangiosarcomas. Fifteen o-nitrotoluene-induced hemangiosarcomas of the skeletal muscle, subcutaneous tissue, and mesentery; 12 riddelliine-induced hemangiosarcomas of the liver; and 15 spontaneous subcutaneous hemangiosarcomas were examined for genetic alterations in ras, p53, and beta-catenin genes. Mutations in at least one of these genes were identified in 13 of 15 (87%) of the o-nitrotoluene-induced hemangiosarcomas with missense mutations in p53 exons 5-8 detected in 11 of 15 (73%) of these neoplasms. Seven of 15 (47%) hemangiosarcomas from mice exposed to o-nitrotoluene had deletions at exon 2 splice sites or smaller deletions in the beta-catenin gene. K-ras mutation was detected in only 1 of the 15 (7%) o-nitrotoluene-induced hemangiosarcomas. In contrast to the o-nitrotoluene study, 7/12 (58%) riddelliine-induced hemangiosarcomas had K-ras codon 12 GTT mutations and, when screened by immunohistochemistry, 9/12 (75%) had strong staining for the p53 protein in malignant endothelial cells, the cells of origin of hemangiosarcomas. Riddelliine-induced hemangiosarcomas were negative for the beta-catenin protein. Spontaneous hemangiosarcomas from control mice lacked both p53 and beta-catenin protein expression and ras mutations. Our data indicated that p53 and beta-catenin mutations in the o-nitrotoluene-induced hemangiosarcomas and K-ras mutations and p53 protein expression in riddelliine-induced hemangiosarcomas most likely occurred as a result of the genotoxic effects of these chemicals. It also suggests that these mutations play a role in the pathogenesis of the respective hemangiosarcomas in B6C3F1(1) mice.

Wildtype Kras2 can inhibit lung carcinogenesis in mice.

Although the ras genes have long been established as proto-oncogenes, the dominant role of activated ras in cell transformation has been questioned. Previous studies have shown frequent loss of the wildtype Kras2 allele in both mouse and human lung adenocarcinomas. To address the possible tumor suppressor role of wildtype Kras2 in lung tumorigenesis, we have carried out a lung tumor bioassay in heterozygous Kras2-deficient mice. Mice with a heterozygous Kras2 deficiency were highly susceptible to the chemical induction of lung tumors when compared to wildtype mice. Activating Kras2 mutations were detected in all chemically induced lung tumors obtained from both wildtype and heterozygous Kras2-deficient mice. Furthermore, wildtype Kras2 inhibited colony formation and tumor development by transformed NIH/3T3 cells and a mouse lung tumor cell line containing an activated Kras2 allele. Allelic loss of wildtype Kras2 was found in 67% to 100% of chemically induced mouse lung adenocarcinomas that harbor a mutant Kras2 allele. Finally, an inverse correlation between the level of wildtype Kras2 expression and extracellular signal-regulated kinase (ERK) activity was observed in these cells. These data strongly suggest that wildtype Kras2 has tumor suppressor activity and is frequently lost during lung tumor progression.

Point mutations of K-ras and H-ras genes in forestomach neoplasms from control B6C3F1 mice and following exposure to 1,3-butadiene, isoprene or chloroprene for up to 2-years.

1,3 Butadiene (BD), isoprene (IP) and chloroprene (CP) are structural analogs. There were significantly increased incidences of forestomach neoplasms in B6C3F1 mice exposed to BD, IP or CP by inhalation for up to 2-years. The present study was designed to characterize genetic alterations in K- and H-ras proto-oncogenes in a total of 52 spontaneous and chemically induced forestomach neoplasms. ras mutations were identified by restriction fragment length polymorphism, single strand conformational polymorphism analysis, and cycle sequencing of PCR-amplified DNA isolated from paraffin-embedded forestomach neoplasms. A higher frequency of K- and H-ras mutations was identified in BD-, IP- and CP-induced forestomach neoplasms (83, 70 and 57%, respectively, or combined 31/41, 76%) when compared to spontaneous forestomach neoplasms (4/11, 36%). Also a high frequency of H-ras codon 61 CAA-->CTA transversions (10/41, 24%) was detected in chemically induced forestomach neoplasms, but none were present in the spontaneous forestomach neoplasms examined. Furthermore, an increased frequency (treated 13/41, 32% versus untreated 1/11, 9%) of GGC-->CGC transversion at K-ras codon 13 was seen in BD-, and IP-induced forestomach neoplasms, similar to the predominant K-ras mutation pattern observed in BD-induced mouse lung neoplasms. These data suggest that the epoxide intermediates of the structurally related chemicals (BD, IP, and CP) may cause DNA damage in K-ras and H-ras proto-oncogenes of B6C3F1 mice following inhalation exposure and that mutational activation of these genes may be critical events in the pathogenesis of forestomach neoplasms induced in the B6C3F1 mouse.

Microbial keratitis--a late complication of penetrating keratoplasty.

A retrospective review of 323 penetrating keratoplasties performed in Taiwan between January 1993 and December 1997 revealed that late microbial keratitis developed in 39 eyes of 36 patients (12.1%). All patients were operated on by the same surgeon, and all were followed for at least 1 year. The mean interval between the corneal transplantation and the onset of graft infection was 8.6 +/- 8.8 months (range 3 weeks-47 months). Predisposing risk factors for keratitis included chronic blepharitis with poor lid hygiene (43.6%), suture-related problems (38.5%), dry eyes (28.2%), epithelial defects (25.6%), and use of contact lenses (5.1%). Infectious keratitis was diagnosed within 6 months after keratoplasty in 59% of cases. Positive cultures were obtained in 100% of the ulcers; Pseudomonas aeruginosa and Staphylococcus aureus were the most common pathogens. In the final visual outcome assessment, 30.8% of cases had clear grafts, 20.5% had graft failures, and 10.3% had corneal perforations.

Caveolin-1 expression in Schwann cells.

Caveolae are non-clathrin-coated invaginations of the plasma membrane, which are present in most cell types. An integral component of caveolae is the caveolin family of related proteins, which not only forms the structural framework of caveolae, but also likely subserves its functional roles, including regulation of signal transduction and cellular transport, in particular, cholesterol trafficking. Although caveolae have been identified ultrastructurally in the peripheral nervous system (PNS), caveolin expression has not previously been studied. To date, three caveolin genes have been reported. Here, we show for the first time that caveolin-1 is expressed by Schwann cells (SC) as well as several SC-derived cell lines. Caveolin-1 is enriched in the buoyant, detergent-insoluble membranes of rat sciatic nerve (SN) and SC, a hallmark of the caveolar compartment. Caveolin-1 exists as both soluble and insoluble forms in rat SN and SC, and localizes to SC cytoplasm and abaxonal myelin. SC caveolin-1 decreases after axotomy, when SC revert to a premyelinating phenotype. We speculate that caveolin-1 may regulate signal transduction and/or cholesterol transport in myelinating SC.

Mutations in ras genes in experimental tumours of rodents.

Studies of carcinogenesis in rodents are valuable for examining mutagenesis in vivo. An advantage of evaluating the frequency and spectra of ras mutations in chemically induced neoplasms is that the additional data at the molecular level indicate whether the carcinogenic effect is due to the chemical and is not a spontaneous event, as illustrated by the numerous examples in Appendices 1 and 2. In addition, data on the frequency and spectra of ras mutations in spontaneous and chemically induced neoplasms clearly expand the toxicological database by providing information helpful for understanding the pathogenesis of carcinogenesis. For example: (1) ozone-induced lung neoplasms had two unique mutations, one (codon 61 K-ras CTA mutation) consistent with a direct genotoxic event and a second (codon 12 K-ras G --> T transversion) consistent with an indirect genotoxic effect; (2) isoprene-induced Harderian gland neoplasms had a unique K-ras A --> T transversion at codon 61 which provided evidence that formation of an epoxide intermediate was involved; (3) 1,3-butadiene-induced neoplasms had a characteristic K-ras G --> C transversion mutation at codon 13 which was also consistent with a chemical-specific effect; (4) methylene chloride-induced liver neoplasms had an H-ras mutation profile at codon 61 similar to that of spontaneous tumours, suggesting that methylene chloride promotes cells with 'spontaneously initiated' ras mutations and (5) oxazepam-induced liver neoplasms had a low frequency of ras mutations, suggesting a nonmutagenic pathway of carcinogenesis. By extending the evaluation of rodent tumours to include molecular studies on ras mutation spectra and abnormalities in other cancer genes with human homologues, a number of hypotheses can be tested, allowing the most complete understanding of carcinogenesis in rodents and in potential extrapolation to the human risk situation.

High frequency of codon 61 K-ras A-->T transversions in lung and Harderian gland neoplasms of B6C3F1 mice exposed to chloroprene (2-chloro-1,3-butadiene) for 2 years, and comparisons with the structurally related chemicals isoprene and 1,3-butadiene.

Chloroprene is the 2-chloro analog of 1,3-butadiene, a potent carcinogen in laboratory animals. Following 2 years of inhalation exposure to 12.8, 32 or 80 p.p.m. chloroprene, increased incidences of lung and Harderian gland (HG) neoplasms were observed in B6C3F1 mice at all exposure concentrations. The present study was designed to characterize genetic alterations in the K- and H-ras proto-oncogenes in chloroprene-induced lung and HG neoplasms. K-ras mutations were detected in 80% of chloroprene-induced lung neoplasms (37/46) compared with only 30% in spontaneous lung neoplasms (25/82). Both K- and H-ras codon 61 A-->T transversions were identified in 100% of HG neoplasms (27/27) compared with a frequency of 56% (15/27) in spontaneous HG neoplasms. The predominant mutation in chloroprene-induced lung and HG neoplasms was an A-->T transversion at K-ras codon 61. This mutation has not been detected in spontaneous lung tumors of B6C3F1 mice and was identified in only 7% of spontaneous HG neoplasms. In lung neoplasms, greater percentages (80 and 71%) of A-->T transversions were observed at the lower exposures (12.8 and 32 p.p.m.), respectively, compared with 18% at the high exposure. In HG neoplasms, the percentage of A-->T transversions was the same at all exposure concentrations. The chloroprene-induced ras mutation spectra was similar to that seen with isoprene, where the predominant base change was an A-->T transversion at K-ras codon 61. This differed from 1,3-butadiene, where K-ras codon 13 G-->C transitions and H-ras codon 61 A-->G transitions were the predominant mutations. The major finding of K-ras A-->T transversions in lung and Harderian gland neoplasms suggests that this mutation may be important for tumor induction by this class of carcinogens.

Both K-ras and H-ras protooncogene mutations are associated with Harderian gland tumorigenesis in B6C3F1 mice exposed to isoprene for 26 weeks.

Isoprene is the 2-methyl analog of 1,3-butadiene, a genotoxic and carcinogenic compound in rats and mice. Male B6C3F1 mice were exposed to 0, 2200 or 7000 ppm isoprene by inhalation (6 h/day; 5 days/week) for 26 weeks. Following a 26-week recovery period, an increased incidence of Harderian gland (HG) neoplasms was observed at both concentrations. The present study was designed to characterize genetic alterations in the K-ras and H-ras protooncogenes in HG neoplasms. Mutations in K-ras and H-ras were identified by single-strand conformational analysis and direct sequencing of polymerase chain reaction (PCR) amplified DNA, isolated from paraffin-embedded sections of HG neoplasms. A higher frequency of ras mutations, in particular K-ras mutations, was detected in isoprene-induced neoplasms than in 1,3-butadiene-induced or control HG neoplasms. All of the isoprene-induced HG neoplasms exhibited activated K-ras (60%) or H-ras (40%) mutations. In contrast, ras mutations were detected in 69% of HG neoplasms from 1,3-butadiene exposed mice (14% K-ras and 55% H-ras) and in 56% of HG neoplasms obtained from control B6C3F1 mice (8% K-ras and 48% H-ras). The predominant mutations in isoprene-induced HG neoplasms, but not in previously or newly analysed 1,3-butadiene-induced HG neoplasms, consisted of A-->T transversions (CAA-->CTA) at K-ras codon 61 (15/30) and C-->A transversions (CAA-->AAA) at H-ras codon 61 (8/30). Two-thirds of the K-ras CTA mutations were detected in HG neoplasms from the 2200 ppm exposure group while one-third was present in the 7000 ppm group. Isoprene-induced HG neoplasms with K-ras or H-ras mutations had an elevated proliferating cell nuclear antigen (PCNA) index, compared to spontaneous HG neoplasms without ras mutations. The high frequency and specificity of the ras mutation profile suggest that ras protooncogene activation contributes to isoprene-induced HG tumorigenesis.

Increased frequency of K-ras mutations in lung neoplasms from female B6C3F1 mice exposed to ozone for 24 or 30 months.

The National Toxicology Program recently completed long-term ozone inhalation studies in B6C3F1 mice and F344/N rats. Mice and rats were exposed to 0, 0.5 or 1.0 p.p.m. ozone by inhalation for 24 or 30 months. There was an increased incidence of lung neoplasms in B6C3F1 mice. However, there was no evidence of carcinogenicity in F344/N rats. The objectives of this study were to (i) evaluate benign and malignant lung neoplasms from B6C3F1 mice for mutations in the K-ras gene at codons 12, 13 and 61, (ii) determine if the frequency and spectra of K-ras mutations were unique for ozone-induced lung neoplasms, (iii) determine if specific K-ras mutations were associated with the size and morphological patterns of lung neoplasms or ozone exposure concentrations and (iv) screen lung neoplasms by immunohistochemical methods for the p53 protein. K-ras mutations were detected by single-strand conformation analysis and identified by direct sequencing of polymerase chain reaction-amplified DNA isolated from formalin-fixed, paraffin-embedded neoplasms. K-ras mutations were detected in 73% of ozone-induced neoplasms, as compared with 33% of lung neoplasms from controls. The predominant mutations consisted of A-->T transversions at codon 61 (8/19) and G-->T transversions at codon 12 (7/19). Specific K-ras mutations in lung neoplasms were not associated with various morphological patterns. Our data suggests that ozone may cause direct and/or indirect DNA damage in the K-ras proto-oncogene of B6C3F1 mice.

Toxicokinetics of pentachlorophenol in the F344 rat. Gavage and dosed feed studies.

1. The toxicokinetics of pentachlorophenol (PCP) were studied in the Fischer 344 rat using i.v. and oral (gavage, dosed feed) routes of exposure. 2. Only minor sex differences were observed in the elimination kinetics of PCP after i.v. administration at 5 mg/kg. 3. Absorption of PCP from the gastrointestinal tract after gavage doses of 9.5 and 38 mg/kg in aqueous methylcellulose vehicles was first order with an absorption half-life of about 1.3 h. 4. The absorption rate constant of PCP from doses feed was comparable with that obtained from aqueous methylcellulose gavage formulations. 5. Bioavailability of PCP administered in dosed feed was significantly lower than the bioavailability of PCP administered by gavage. 6. Dose proportionality was established to a dosage of at least 38 mg/kg. 7. Daily fluctuation of PCP plasma concentrations was observed during the dosed feed study with peak and trough concentrations occurring in early morning and late afternoon, respectively. 8. The time course of PCP plasma concentrations during the dosed feed study were simulated using a computer model based on linear theory. The simulations were comparable with the experimentally determined concentrations.