Microbial strengthening of loose sand.

AIMS: To test whether the addition of Flavobacterium johnsoniae could increase the strength of saturated Ottawa 30 sand. METHODS AND RESULTS: A box model was built that simulates groundwater-like flow through a main sand compartment. Strength tests were performed at seven locations and at two depths, 10.8 and 20.3 cm below the top of the tank, using a vane shear device before and after the addition of bacteria. After the addition of Fl. johnsoniae, sand samples were obtained from multiple sampling ports on the vertical sides of the box model. The presence of a bacterial biofilm was confirmed by staining these sand samples with SYTO-9 and Alexa Fluor 633 and viewing with a confocal microscope. The average shear strength increases after the addition of Fl. johnsoniae were 15.2-87.5%, depending on the experimental conditions. CONCLUSIONS: Flavobacterium johnsoniae caused a statistically significant increase in the strength of saturated Ottawa 30 sand. SIGNIFICANCE AND IMPACT OF THE STUDY: Biofilm-forming bacteria can increase the shear strength of saturated sand. The addition of biofilm-forming bacteria to a building site may be an alternate method to mitigate the effects of liquefaction.

Risk factors for oesophageal squamous dysplasia in adult inhabitants of a high risk region of China.

BACKGROUND: Oesophageal squamous cell carcinoma (OSCC) is a common cancer worldwide and has a very high mortality rate. Squamous dysplasia is the precursor lesion for OSCC and it can be seen during routine endoscopy with Lugol's iodine staining. We aimed to examine the risk factors for squamous dysplasia and determine if a risk model could be constructed which would be useful in selecting apparently healthy subjects for endoscopic screening in a high risk population in Linzhou, People's Republic of China. SUBJECTS AND METHODS: In this cross sectional study, 724 adult volunteers aged 40-65 years were enrolled. All subjects completed a questionnaire regarding potential environmental exposures, received physical and dental examinations, and underwent upper endoscopy with Lugol's iodine staining and biopsy. Subjects were categorised as having or not having histologically proven squamous dysplasia/early cancer. Risk factors for dysplasia were examined using univariate and multivariate logistic regression. The utility of the final multivariate model as a screening tool was assessed using a receiver operating characteristics curve. RESULTS: We found that 230 of 720 subjects (32%) with complete data had prevalent squamous dysplasia. In the final multivariate model, more household members (odds ratio (OR) 1.12/member (95% confidence interval (CI) 0.99, 1.25)), a family history of cancer (OR 1.57 (95% CI 1.13-2.18)), higher systolic blood pressure OR 1.11/10 mm Hg (95% CI 1.03-1.19)), heating the home without a chimney (OR 2.22 (95% CI 1.27-3.86)), and having lost more but not all of your teeth (OR 1.91 for 12-31 teeth lost (95% CI 1.17-3.15)) were associated with higher odds of having dysplasia. Higher household income (OR 0.96/100 RMB (95% CI 0.91-1.00)) was associated with a lower odds of having dysplasia. Although we found several statistically significant associations, the final model had little ability to accurately predict dysplasia status, with maximum simultaneous sensitivity and specificity values of 57% and 54%, respectively. CONCLUSIONS: We found that risk factors for dysplasia were similar to those previously identified as risk factors for OSCC in this population. The final model did a poor job of identifying subjects who had squamous dysplasia. Other methods will need to be developed to triage individuals to endoscopy in this high risk population.

Histological precursors of oesophageal squamous cell carcinoma: results from a 13 year prospective follow up study in a high risk population.

BACKGROUND: Oesophageal squamous cell carcinoma (OSCC) has a very poor prognosis, which is largely due to late diagnosis. Successful early detection strategies will require identification of clinically relevant precursor lesions that can be targets for screening and treatment. AIMS: To identify the clinically relevant histological precursors of OSCC. SUBJECTS: A cohort of 682 endoscoped patients from a high risk rural population in Linxian, China. METHODS: Subjects were endoscoped and biopsied at baseline and followed for 13.5 years. We estimated the relative risk of developing OSCC for each of the initial histological diagnoses using Cox proportional hazards regression models. RESULTS: A total of 114 (16.7%) patients developed OSCC during the follow up period. After adjusting for potential confounding factors, relative risks (95% confidence intervals) for incidence of this tumour, by initial histological diagnosis, were: normal 1.0 (reference), oesophagitis 0.8 (0.2-3.2), basal cell hyperplasia 1.9 (0.8-4.5), mild dysplasia 2.9 (1.6-5.2), moderate dysplasia 9.8 (5.3-18.3), severe dysplasia 28.3 (15.3-52.3), and carcinoma in situ 34.4 (16.6-71.4). CONCLUSIONS: In this study, squamous dysplasia and carcinoma in situ were the only histological lesions associated with a significantly increased risk of developing OSCC within 13.5 years after endoscopy. There was no evidence that oesophagitis predisposed to this tumour. Increasing grades of dysplasia were strongly associated with increasing risk, indicating that the histological grading was clinically meaningful. The follow up experience of severe dysplasia and carcinoma in situ was equivalent, suggesting that this distinction is not clinically relevant. Documenting these precursor lesions of OSCC should assist in the development of effective prevention, early detection, and treatment strategies for this disease.

Common genetic variants of TP53 and BRCA2 in esophageal cancer patients and healthy individuals from low and high risk areas of northern China.

TP53 and BRCA2 are frequently mutated in cancer and polymorphisms of these genes may modify cancer risk. We used SSCP and DNA sequencing to assess and compare frequencies of R72P (TP53) and 5'UTR203G>A, N372H, and K1132K (BRCA2) polymorphisms in healthy Chinese subjects at varying risk for esophageal squamous cell carcinoma (ESCC) and in ESCC patients. Suggestive overall differences in the distributions of genotypes by risk groups were seen for all genotypes except K1132K. Differences in R72P and N372H were most likely a reflection of lack of Hardy-Weinberg equilibrium (HWE), however, the difference in 203G>A was due to low prevalence of GG in ESCC patients (0.22 versus 0.36 in high risk group (P=0.047), and 0.22 versus 0.40 in low risk group (P=0.010)), consistent with a disease association. These data suggest that the 203G>A polymorphism in BRCA2 may be associated with risk of ESCC.

Development of a urinary biomarker of human exposure to deoxynivalenol.

Deoxynivalenol (DON) is a mycotoxin frequently found as a contaminant of cereal crops and may be etiologically associated with adverse health effects in developing countries where considerable quantities of contaminated crops are consumed. We investigated the metabolism of DON in rats as a basis to establish methodology for a candidate biomarker of human exposure to this toxin and tested this methodology on urine samples from a potentially highly exposed population. Sprague-Dawley rats received a single dose of [14C]DON (5.0+/-0.1 mg/kg body weight, 5.5+/-0.1 microCi/kg) and the distribution of DON in body fluids was investigated over 72 h. DON and its metabolites were detectable in the plasma of rats with the highest levels at 8 h, at which time approximately 9% was bound to plasma protein. A total of 37% of the administered DON was excreted in the urine and DON-glucuronide was implicated as the major urinary metabolite based on reverse-phase HPLC analysis of beta-glucuronidase- and sulphatase-treated samples. An immunoaffinity column (IAC)-HPLC method was subsequently developed to measure urinary metabolites, with a view to establishing a urine-based human biomarker. Urine samples were collected from female inhabitants of Linxian County, China, a high risk region for oesophageal cancer (OC) and an area of potentially high DON exposure, and Gejiu, a low risk region in China. DON was detected in all 15 samples following beta-glucuronidase treatment and IAC enrichment with the identity of DON being confirmed by mass spectrometry. The mean levels of DON from the suspected high and low exposure regions of China were 37 ng/ml (range 14-94 ng/ml) and 12 ng/ml (range 4-18 ng/ml), respectively. This is estimated to correspond to daily exposures of 1.1-7.4 microg/kg/day and 0.3-1.4 microg/kg/day, respectively. This is the first reported measurement of a urinary biomarker for DON in both animals and humans and should facilitate epidemiological studies of disease associations with this mycotoxin.

Assembly and catalysis of concerted two-end integration events by Moloney murine leukemia virus integrase.

Retroviral integration results in the stable and coordinated insertion of the two termini of the linear viral DNA into the host genome. An in vitro concerted two-end integration reaction catalyzed by the Moloney murine leukemia virus (M-MuLV) integrase (IN) was used to investigate the binding and coordination of the two viral DNA ends. Comparison of the two-end integration and strand transfer assays indicates that zinc is required for efficient concerted integration utilizing plasmid DNA as target. Complementation assays using a pair of nonoverlapping integrase domains, consisting of the HHCC domain and the core/C-terminal region, yielded products containing the correct 4-base target site duplication. The efficiency of the coordinated two-end integration varied depending on the order of addition of the individual protein and DNA components in the complementation assay. Two-end integration was most efficient when the long terminal repeat (LTR) was premixed with either the target DNA or the HHCC domain. The preference for two-end integration through preincubation of the HHCC finger with the viral DNA supports the role of this domain in the recognition and/or positioning of the LTR.

Allelic loss on chromosome bands 13q11-q13 in esophageal squamous cell carcinoma.

Allelic loss on chromosome 13 occurs frequently in esophageal squamous cell carcinoma. However, studies of the two known tumor suppressor genes located on 13q, RB1 and BRCA2, have shown few mutations, suggesting that other genes are likely to be involved in the development of this tumor type. To identify a minimal deletion interval, we first analyzed 42 microsatellite markers spanning chromosome bands 13q11-q13 in 56 esophageal squamous cell carcinoma patients, including 34 with a family history of upper gastrointestinal cancer and 22 without a family history of cancer. Lifestyle risk factors and clinical/pathologic characteristics were also collected. Two commonly deleted regions were identified: one was located on band 13q12.11, between markers D13S787 and D13S221; the other was located on bands 13q12.3-q13.1 from markers D13S267 to D13S219. We observed higher allelic loss frequencies for eight of the microsatellite markers in those patients with a family history of upper gastrointestinal cancer compared to patients without such a history. This study suggests that one or more unidentified tumor suppressor genes are located on chromosome arm 13q that play a role in the development of esophageal squamous cell carcinoma.

Polycyclic aromatic hydrocarbons identified in soot extracts from domestic coal-burning stoves of Henan Province, China.

Using high-pressure liquid chromatography with ultraviolet-visible diode-array detection, we have analyzed polycyclic aromatic hydrocarbons (PAH) in the dichloromethane extracts of soot deposits from coal-burning stoves in several homes of Henan Province, China--including Linxian County, where esophageal cancer rates are some of the highest in the world. Thirty-two individual polycyclic aromatic compounds, ranging in size from three to eight fused aromatic rings, have been unequivocally identified among the soot extract components--including 20 benzenoid PAH, 6 fluoranthene benzologues, 1 cyclopentafused PAH, 1 indene benzologue, 3 oxygenated PAH, and 1 ring-sulfur-containing aromatic. Most of the identified compounds have been observed before among the products of laboratory coal pyrolysis experiments, but two of the components, the six-ring C24H14 napthol[1,2-b]fluoranthene and the eight-ring C30H16 tribenzo[e,ghi,k]perylene, have never before been documented as products of coal in any system. All of the Henan coal soot extracts are remarkably similar qualitatively in that they contain the same set of identified PAH, but absolute levels of individual species vary by up to 5 orders of magnitude, from sample to sample. The bulk of the identified component mass in all of these soot extracts lies in the five- and six-ring PAH--the largest single class being the family of five-ring C20H12 isomers, to which the samples' most abundant components, benzo[b]fluoranthene and benzo[e]pyrene, belong. The five- and six-ring PAH also account for the majority of the samples' known mutagens. The three strong mutagens identified in these soot samples are the C20H12 benzo[a]-pyrene and two C24H14 PAH, dibenzo[a,e]pyrene and naphtho-[2,1-a]pyrene. Seven moderate mutagens are found among the C20H12, C22H12, C22H14, and C24H14 PAH. A major class of mutagens, the cyclopenta-fused PAH, appears to be absent from these samples, but our detection of an oxidation product of the major mutagen cyclopenta[cd]- pyrene--itself mutagenic--suggests that these soot deposits may contain additional mutagenic cyclopentafused PAH oxidation products as well.

Genetic progression and heterogeneity associated with the development of esophageal squamous cell carcinoma.

Esophageal squamous cell carcinoma is a common fatal cancer, and Shanxi province, a region in north-central China, has some of the highest esophageal cancer rates in the world. Chromosomal regions with frequent allelic loss may point to major susceptibility genes that will assist us in understanding the molecular events involved in esophageal carcinogenesis and may serve as the basis for the development of markers for genetic susceptibility and screening for early detection of this cancer. This study was designed to identify events in the molecular progression of precursor and invasive lesions of squamous esophageal cancer. Twelve marker loci identified during our previous studies as having some of the highest rates of loss of heterozygosity (LOH) in invasive esophageal cancer were evaluated in laser-microdissected DNA obtained from low- and high-grade dysplastic lesions and invasive tumor foci from 10 fully embedded esophageal resection specimens. Each resection specimen contained a spectrum of disease, from epithelium that appeared histologically normal to invasive cancer, including a single dominant tumor surrounded by a region of precursor lesions (low- and high-grade dysplasia) and occasional "remote," nonadjacent precancerous foci. Using the 12 polymorphic markers, LOH was found in all of the three stages of disease. The frequency of LOH for all of the markers together increased with increasing disease severity. Among the informative low-grade dysplasia samples, LOH was detected with markers D3S1766 (3p), D4S2632 (4p), D9S910 (9q), and D13S1493 (13q), suggesting that LOH at these loci may be associated with early stages of tumor initiation and/or progression. LOH was detected among the informative high-grade (but not low-grade) dysplasia samples for the other eight markers tested, suggesting that LOH at these loci may occur later in the neoplastic process. In addition to the association between disease progression and these genetic changes, considerable genetic heterogeneity was found in each fully embedded resection specimen both between and within geographically separate neoplastic lesions.

Reverse phase protein microarrays which capture disease progression show activation of pro-survival pathways at the cancer invasion front.

Protein arrays are described for screening of molecular markers and pathway targets in patient matched human tissue during disease progression. In contrast to previous protein arrays that immobilize the probe, our reverse phase protein array immobilizes the whole repertoire of patient proteins that represent the state of individual tissue cell populations undergoing disease transitions. A high degree of sensitivity, precision and linearity was achieved, making it possible to quantify the phosphorylated status of signal proteins in human tissue cell subpopulations. Using this novel protein microarray we have longitudinally analysed the state of pro-survival checkpoint proteins at the microscopic transition stage from patient matched histologically normal prostate epithelium to prostate intraepithelial neoplasia (PIN) and then to invasive prostate cancer. Cancer progression was associated with increased phosphorylation of Akt (P<0.04), suppression of apoptosis pathways (P<0.03), as well as decreased phosphorylation of ERK (P<0.01). At the transition from histologically normal epithelium to PIN we observed a statistically significant surge in phosphorylated Akt (P<0.03) and a concomitant suppression of downstream apoptosis pathways which proceeds the transition into invasive carcinoma.

Functional characterization of the N termini of murine leukemia virus envelope proteins.

The function of the N terminus of the murine leukemia virus (MuLV) surface (SU) protein was examined. A series of five chimeric envelope proteins (Env) were generated in which the N terminus of amphotropic 4070A was replaced by equivalent sequences from ecotropic Moloney MuLV (M-MuLV). Viral titers of these chimeras indicate that exchange with homologous sequences could be tolerated, up to V17eco/T15ampho (crossover III). Constructs encoding the first 28 amino acids (aa) of ecotropic M-MuLV resulted in Env expression and binding to the receptor; however, the virus titer was reduced 5- to 45-fold, indicating a postbinding block. Additional exchange beyond the first 28 aa of ecotropic MuLV Env resulted in defective protein expression. These N-terminal chimeras were also introduced into the AE4 chimeric Env backbone containing the amphotropic receptor binding domain joined at the hinge region to the ecotropic SU C terminus. In this backbone, introduction of the first 17 aa of the ecotropic Env protein significantly increased the titer compared to that of its parental chimera AE4, implying a functional coordination between the N terminus of SU and the C terminus of the SU and/or transmembrane proteins. These data functionally dissect the N-terminal sequence of the MuLV Env protein and identify differential effects on receptor-mediated entry.

Frequent inactivation of the TP53 gene in esophageal squamous cell carcinoma from a high-risk population in China.

Esophageal squamous cell carcinoma (ESCC) is one of the most common fatal cancers worldwide, and north central China has some of the highest rates in the world. Previous studies from tumors in this area of China have shown high frequencies of allelic loss on chromosome 17p13-11, which includes the region where the TP53 gene is found. We examined 56 ESCC patients using single-strand conformation polymorphism and DNA sequencing to assess the frequency and spectrum of TP53 mutation and the association between allelic loss at microsatellite marker TP53 and TP53 mutations. Ninety-six % of cases were found to have at least one genetic alteration, including TP53 mutation (77%), allelic loss within the TP53 gene (73%), and/or loss of heterozygosity at the TP53 microsatellite marker (80%); 75% had two or more such alterations, including 59% with both a point mutation and an intragenic allelic loss ("two hits"). The majority of mutations observed were in exon 5, where the most common type of nucleotide substitution was a G:C-->A:T or C:G-->T:A transition, including half that occurred at CpG sites. Allelic loss was most commonly found in exon 4 but was very common in exon 5 as well. Taken together, the multiple genetic alterations of TP53 in this population at high risk for ESCC indicate that there is a very high degree of genetic instability in these tumors, that TP53 is a primary target for inactivation, and that this tumor suppressor gene plays a critical role in the carcinogenesis process for ESCC.

Mutational analysis of the N-terminus of Moloney murine leukemia virus integrase.

The retroviral integrase (IN) carries out the integration of viral DNA into the host genome. The IN protein consists of three domains: the N-terminal HHCC motif, the catalytic core region, and the C-terminus. The Moloney murine leukemia virus (M-MuLV) IN encodes a unique 45-amino-acid domain N-terminal to the HHCC motif. The function of the N-terminus of M-MuLV IN was studied through deletional and mutational analyses. The IN 1-105 domain was dissected into two halves expressing either the unique N-terminus or the HHCC domain. Although the parental IN 1-105 could functionally complement the core-C-terminus for integration reactions, neither half of the N-terminus was sufficient. Partial complementation of strand transfer, but not 3prime prime or minute processing, could be obtained through mixing the two halves. The dimerization of the M-MuLV N-terminus was dependent on the expression of the intact 1-105. Critical basic amino acids within the HHCC domain which are required for 3' processing and strand transfer reactions were identified through alanine mutagenesis. Loss of in vitro strand transfer activity correlated with loss of viral titer in vivo for this cluster of basic amino acids within the HHCC domain.

Substitution of Asp114 or Arg116 in the fingers domain of moloney murine leukemia virus reverse transcriptase affects interactions with the template-primer resulting in decreased processivity.

Reverse transcriptase, an essential retroviral DNA polymerase, replicates the single-stranded RNA genome of the retrovirus, producing a double-stranded DNA copy, which is subsequently integrated into the host's genome. Substitution of Ala for either Asp114 or Arg116, two highly conserved residues in the fingers domain of Moloney murine leukemia virus reverse transcriptase, results in enzymes (D114A or R116A) with significant defects in their abilities to processively synthesize DNA using RNA or DNA as a template. D114A and R116A enzymes also bind more weakly to template-primer in the presence of added deoxyribonucleotides, as seen by gel-shift analysis, but retain the ability to strand transfer and accumulate smaller RNase H cleavage products when compared to the wild-type enzyme. In addition, mutant proviruses, including D114A and R116A substitutions in Moloney murine leukemia virus reverse transcriptase, are not viable despite the presence of processed reverse transcriptase in the viral particles. A potential mechanistic role in processive synthesis for D114 and R116 is discussed in the context of our results, related studies on HIV-1 reverse transcriptase, and previous structural studies.

Loss of annexin 1 correlates with early onset of tumorigenesis in esophageal and prostate carcinoma.

Annexin I protein expression was evaluated in patient-matched longitudinal study sets of laser capture microdissected normal, premalignant, and invasive epithelium from human esophageal squamous cell cancer and prostatic adenocarcinoma. In 25 esophageal cases (20 by Western blot and 5 by immunohistochemistry) and 17 prostate cases (3 by Western blot and 14 by immunohistochemistry), both tumor types showed either complete loss or a dramatic reduction in the level of annexin I protein expression compared with patient-matched normal epithelium (P < or = 0.05). Moreover, by using Western blot analysis of laser capture microdissected, patient-matched longitudinal study sets of both tumor types, the loss of protein expression occurred in premalignant lesions. Concordance of this result with immunohistochemical analysis suggests that annexin I may be an essential component for maintenance of the normal epithelial phenotype. Additional studies investigating the mechanism(s) and functional consequences of annexin I protein loss in tumor cells are warranted.

High frequency allelic loss on chromosome 17p13.3-p11.1 in esophageal squamous cell carcinomas from a high incidence area in northern China.

Allelic loss on chromosome 17p has been reported frequently in esophageal squamous cell carcinoma (ESCC) and generally encompasses the p53 locus at 17p13.1. However, a good correlation between allelic loss on 17p and mutation of p53 has not been found. This suggests the possibility that unknown tumor suppressor genes near p53 may be involved in the development of ESCC. To evaluate this possibility, we analyzed 30 microsatellite markers covering the entire short arm of chromosome 17 in 56 ESCC patients from a high risk population in northern China, including 34 with a family history of upper gastrointestinal (UGI) cancer and 22 without a family history of any cancer. Cancer lifestyle risk factors and clinical/pathological characteristics were also collected. We found frequent allelic loss (>/=65%) at 28 of the 30 markers evaluated in these ESCC patients. The highest frequencies of allelic loss (> or =80%) were found in three smaller regions: deletion region I located at 17p13.3-p13.2 (between D17S849 and D17S1828); deletion region II located at 17p13.2-p13.1 (between D13S938 and TP53); deletion region III located at 17p13.1-p12 (between D17S804 and D17S799). A number of genes have already been identified in these deleted regions, including: OVCA1, OVCA2 and HIC-1 in deletion region I; p53 in deletion region II; ZNF18, ZNF29, ALDH3 and ALDH10 in deletion region III. These results will help us direct future testing of candidate genes and narrow the search region for major new tumor suppressor genes that may play a role in the pathogenesis of ESCC.

Comparison of second-strand transfer requirements and RNase H cleavages catalyzed by human immunodeficiency virus type 1 reverse transcriptase (RT) and E478Q RT.

Truncated tRNA-DNA mimics were examined in an in vitro assay for second-strand transfer during human immunodeficiency virus type 1 (HIV-1) reverse transcription. Strand transfer in this system requires the progressive degradation of the RNA within the 18-mer tRNA-DNA (plus-strand strong stop DNA) intermediate to products approximately 8 nucleotides in length. The ability of the truncated substrates to substitute for directional processing by RNase H or reverse transcriptase (RT) was examined. Using wild-type HIV-1 RT, substrates which truncated the 5' end of the tRNA primer by 6, 9, and 12 nucleotides (Delta6, Delta9, and Delta12, respectively) were recognized by RNase H and resulted in strand transfer. An overlap of 5 nucleotides between the acceptor and newly synthesized DNA template was sufficient for strand transfer. The mutant RT, E478Q correctly catalyzed the initial cleavage of the 18-mer tRNA-DNA mimic in the presence of Mn(2+); however, no directional processing was observed. In contrast, no RNase H activity was observed with the Delta6, Delta9, and Delta12 substrates with E478Q RT in this strand transfer assay. However, when complemented with Escherichia coli RNase H, E478Q RT supported strand transfer with the truncated substrates. E478Q RT did cleave the truncated forms of the substrates, Delta6, Delta9, and Delta12, in a polymerase-independent assay. The size requirements of the substrates which were cleaved by the polymerase-independent RNase H activity of E478Q RT are defined.

Differential effects of C-terminal molecular tagged integrase on replication competent moloney murine leukemia virus.

Moloney murine leukemia virus (M-MuLV) proviruses carrying integrase (IN) protein tagged either with a simian virus 40 (SV40) nuclear localization signal (NLS) or various antigenic epitopes were generated. Hexahistidine (His(6)), hemagluttinin (HA), or two consecutive HA sequences (2XHA) were fused to the C-terminus of IN as antigenic markers. These epitope-tagged IN proteins were stably expressed through multiple rounds of infection. The IN-His(6), IN-HA, and IN-2XHA proteins, purified from virus, could be immunoprecipitated with antibodies against His(6) and HA, respectively. An M-MuLV provirus encoding the SV40 large T antigen NLS fused to IN at the same position as the epitope tags was also passaged through cells. In contrast to the stability of the epitope tags, the SV40 NLS sequence was rapidly mutated by a frameshift mutation that introduced negatively charged amino acids into the basic NLS. The instability of the NLS suggests that the strong nuclear localization of the IN-SV40 NLS may have detrimental effects on virus assembly. These observations have implications for studying nuclear transport properties of M-MuLV and for engineering a murine-based retroviral vector for gene therapy.

Changes to the quantity and processing of starchy foods in a western diet can increase polysaccharides escaping digestion and improve in vitro fermentation variables.

This study investigated how readily achievable changes to the quantity and processing of starchy foods in a typical Western diet: (1) were reflected in levels of resistant starch (RS) and NSP excreted from the small intestine; and (2) more favourable profiles of butyrate, NH3 and phenol production. Two diets, a low-starch diet (LSD) and a high-starch, low-fat diet (HSLFD) were compared. The LSD with 20% total energy (%E) from starch was based on a 'typical' Australian diet, while the HSLFD (40%E as starch) was the same Australian diet modified by an increased content of legumes, starchy foods and coarsely-ground cereals and by a reduced fat content. Four subjects with iliostomies consumed each diet for 2 d, with ileal effluent collection on the second day. On the HSLFD compared with the LSD, RS in ileal effluent increased from from 0.49 to 1.7 g/MJ per d (P < 0.005) while ileal NSP excretion increased from 2.0 to 3.3 g/MJ per d (P < 0.05). Ileal effluents obtained after each diet were incubated for 24 h in vitro with a human faecal innoculum. After fermentation, ileal effluent from the HSLFD produced more butyrate relative to other short-chain fatty acids (17.5 v. 15.8 molar %, P < 0.005) and less phenol (2.3 v. 5.7 mg/l, P < 0.05) and NH3 (20.3 v. 23.1 mmol/l, P < 0.005) than the LSD diet. The HSLFD also generated a lower pH (6.15 v. 6.27, P < 0.05). On a wt/wt basis, RS was 2.3-fold higher in the HSLFD effluent while NSP did not increase, suggesting that the change in RS largely contributed to the fermentation effects. Changes in in vitro variables when the HSLFD ileal effluent was ground before fermentation indicated the importance of physical structure in determining ileal excretion of RS. We conclude that: (1) readily achievable modifications to the amount and processing of starchy foods in an Australian diet would produce potential benefits for in vitro fermentation variables; and (2) the physical structure of grains and cereals is important in determining access by colonic bacteria to a carbohydrate substrate.