Human breast cancer invasion and aggression correlates with ECM stiffening and immune cell infiltration

Tumors are stiff and data suggest that the extracellular matrix stiffening that correlates with experimental mammary malignancy drives tumor invasion and metastasis. Nevertheless, the relationship between tissue and extracellular matrix stiffness and human breast cancer progression and aggression remains unclear. We undertook a biophysical and biochemical assessment of stromal-epithelial interactions in noninvasive, invasive and normal adjacent human breast tissue and in breast cancers of increasingly aggressive subtype. Our analysis revealed that human breast cancer transformation is accompanied by an incremental increase in collagen deposition and a progressive linearization and thickening of interstitial collagen. The linearization of collagen was visualized as an overall increase in tissue birefringence and was most striking at the invasive front of the tumor where the stiffness of the stroma and cellular mechanosignaling were the highest. Amongst breast cancer subtypes we found that the stroma at the invasive region of the more aggressive Basal-like and Her2 tumor subtypes was the most heterogeneous and the stiffest when compared to the less aggressive luminal A and B subtypes. Intriguingly, we quantified the greatest number of infiltrating macrophages and the highest level of TGF beta signaling within the cells at the invasive front. We also established that stroma stiffness and the level of cellular TGF beta signaling positively correlated with each other and with the number of infiltrating tumor-activated macrophages, which was highest in the more aggressive tumor subtypes. These findings indicate that human breast cancer progression and aggression, collagen linearization and stromal stiffening are linked and implicate tissue inflammation and TGF beta.

Validation and reproducibility of food frequency questionnaire for Korean genome epidemiologic study

OBJECTIVE

To evaluate validity and reliability of the food-frequency questionnaire (FFQ) developed for the Korean Genome Epidemiologic Study (KoGES).

METHODS

FFQ was administered twice at 1-year interval (first FFQ (FFQ1) at the beginning and second FFQ (FFQ2) at the end of the study) and diet records (DRs) were collected for 3 days during each of the four seasons from December 2002 to May 2004 for those who attended the health examination center. At the end of the study period, we collected the 12-day DRs of 124 participants. The nutrient intakes from the DRs were compared with both FFQ1 and FFQ2.

RESULTS

The intakes of energy and some nutrients estimated from FFQ1 and FFQ2 were different from those assessed by the DRs. Especially, the consumption of carbohydrates was higher in FFQ1 and FFQ2 than in the DRs. The de-attenuated, age, sex and energy intake adjusted correlation coefficients between the FFQ2 and the 12-day DRs in Korean population ranged between 0.23 (Vitamin A) and 0.64 (carbohydrate). The median for all nutrients was 0.39. The correlations were similar when we compared nutrient densities of both methods. Joint classification of calorie-adjusted nutrient intakes assessed by FFQ2 and 12-day DRs by quartile ranged from 25.8% (vitamin A) to 39.5% (carbohydrate, iron) for exact concordance. Except vitamin A, the proportion of subjects classified into distant quartile was less than 7% in all nutrients. The median of correlations between the two FFQs 1 year apart were 0.45 for all nutrient intakes and 0.39 for nutrient densities.

CONCLUSIONS

We conclude that the FFQ we have developed appears to be an acceptable tool for assessing the nutrient intakes in this population. Further studies for calibration of the FFQ collected from multicenters participating in the KoGES are needed.

SPONSORSHIP

This study was supported by the budget of the National Genome Research Institute, Korea National Institute of Health (2002-347-6111-221).

Modulation of polyketide synthase activity by accessory proteins during lovastatin biosynthesis

Polyketides, the ubiquitous products of secondary metabolism in microorganisms, are made by a process resembling fatty acid biosynthesis that allows the suppression of reduction or dehydration reactions at specific biosynthetic steps, giving rise to a wide range of often medically useful products. The lovastatin biosynthesis cluster contains two type I polyketide synthase genes. Synthesis of the main nonaketide-derived skeleton was found to require the previously known iterative lovastatin nonaketide synthase (LNKS), plus at least one additional protein (LovC) that interacts with LNKS and is necessary for the correct processing of the growing polyketide chain and production of dihydromonacolin L. The noniterative lovastatin diketide synthase (LDKS) enzyme specifies formation of 2-methylbutyrate and interacts closely with an additional transesterase (LovD) responsible for assembling lovastatin from this polyketide and monacolin J.

erbB-2 and response to doxorubicin in patients with axillary lymph node-positive, hormone receptor-negative breast cancer

BACKGROUND

Overexpression of the erbB-2 protein by breast cancer cells has been suggested to be a predictor of response to doxorubicin. A retrospective study was designed to test this hypothesis.

METHODS

In National Surgical Adjuvant Breast and Bowel Project protocol B-11, patients with axillary lymph node-positive, hormone receptor-negative breast cancer were randomly assigned to receive either L-phenylalanine mustard plus 5-fluorouracil (PF) or a combination of L-phenylalanine mustard, 5-fluorouracil, and doxorubicin (PAF). Tumor cell expression of erbB-2 was determined by immunohistochemistry for 638 of 682 eligible patients. Statistical analyses were performed to test for interaction between treatment and erbB-2 status (positive versus negative) with respect to disease-free survival (DFS), survival, recurrence-free survival (RFS), and distant disease-free survival (DDFS). Reported P values are two-sided.

RESULTS

Overexpression of erbB-2 (i.e., positive immunohistochemical staining) was observed in 239 (37.5%) of the 638 tumors studied. Overexpression was associated with tumor size (P=.02), lack of estrogen receptors (P=.008), and the number of positive lymph nodes (P=.0001). After a mean time on study of 13.5 years, the clinical benefit from doxorubicin (PAF versus PF) was statistically significant for patients with erbB-2-positive tumors--DFS: relative risk of failure (RR)=0.60 (95% confidence interval [CI]=0.44-0.83), P=.001; survival: RR=0.66 (95% CI=0.47-0.92), P =.01; RFS: RR=0.58 (95% CI=0.42-0.82), P=.002; DDFS: RR=0.61 (95% CI=0.44-0.85), P=.003. However, it was not significant for patients with erbB-2-negative tumors-DFS: RR=0.96 (95% CI=0.75-1.23), P=.74; survival: RR =0.90 (95% CI=0.69-1.19), P=.47; RFS: RR=0.88 (95% CI=0.67-1.16), P=.37; DDFS: RR=1.03 (95% CI=0.79-1.35), P=.84. Interaction between doxorubicin treatment and erbB-2 overexpression was statistically significant for DFS (P=.02) and DDFS (P=.02) but not for survival (P= .15) or RFS (P=.06).

CONCLUSIONS

These data support the hypothesis of a preferential benefit from doxorubicin in patients with erbB-2-positive breast cancer.

ABT-378, a highly potent inhibitor of the human immunodeficiency virus protease

The valine at position 82 (Val 82) in the active site of the human immunodeficiency virus (HIV) protease mutates in response to therapy with the protease inhibitor ritonavir. By using the X-ray crystal structure of the complex of HIV protease and ritonavir, the potent protease inhibitor ABT-378, which has a diminished interaction with Val 82, was designed. ABT-378 potently inhibited wild-type and mutant HIV protease (Ki = 1.3 to 3.6 pM), blocked the replication of laboratory and clinical strains of HIV type 1 (50% effective concentration [EC50], 0.006 to 0.017 microM), and maintained high potency against mutant HIV selected by ritonavir in vivo (EC50, 50-fold after 8 h. In healthy human volunteers, coadministration of a single 400-mg dose of ABT-378 with 50 mg of ritonavir enhanced the area under the concentration curve of ABT-378 in plasma by 77-fold over that observed after dosing with ABT-378 alone, and mean concentrations of ABT-378 exceeded the EC50 for >24 h. These results demonstrate the potential utility of ABT-378 as a therapeutic intervention against AIDS.

Immune response in Stat2 knockout mice

Type I IFNs induce gene expression through Stat1 and Stat2, which can in turn associate either to form Stat1 homodimers or the transcription factor ISGF-3. Stat1 homodimers also transduce signals for IFN-gamma. To explore the unique properties of Stat2 and ISGF-3 in type I IFN signaling, its gene was targeted for deletion. Stat2 null mice exhibit a number of defects in immune response. This includes an increased susceptibility to viral infection and the loss of a type I IFN autocrine/ paracrine loop, which in turn regulates several aspects of immune response. Intriguingly, Stat2-deficient fibroblasts exhibit a more significant defect in their response to type I IFNs than macrophages, highlighting tissue-specific differences in the response to this family of ligands.

Selective targeting of trabecular meshwork cells: in vitro studies of pulsed and CW laser interactions

The purpose of the present study was to selectively target pigmented trabecular meshwork cells without producing collateral damage to adjacent non-pigmented cells or structures. The ability to selectively target trabecular meshwork cells without coagulation, while preserving the structural integrity of the meshwork, could be a useful approach to study whether the biological response of non-coagulative damage to the trabecular meshwork and trabecular meshwork cells is similar to that seen with coagulative damage to the trabecular meshwork which occurs with argon laser trabeculoplasty. This approach also may be useful to non-invasively deplete trabecular meshwork cells while preserving the structural integrity of the trabecular meshwork in an animal model. A mixed cell culture of pigmented and non-pigmented trabecular meshwork cells were irradiated with Q-switched Nd-YAG and frequency-doubled Nd-YAG lasers, microsound pulsed dye-lasers, and an argon ion laser in order to define a regime where laser absorption would be confined to pigmented trabecular meshwork cells, thereby permitting selective targeting of these cells without producing collateral thermal damage to adjacent non-pigmented cells. Pulse durations ranged from 10 nsec to 0.1 sec. A fluorescent viability/cytotoxicity assay was used to evaluate laser effects and threshold energies, and cells were examined morphologically by light and TEM. Selective targeting of pigmented trabecular meshwork cells was achieved with pulse durations between 10 nsec and 1 microsec and 1 microsec without producing collateral thermal or structural damage to adjacent non-pigmented trabecular meshworks cells when examined by light and transmission electron microscopy. Pulse durations greater than 1 microsec resulted in non-selective killing of non-pigmented trabecular meshwork cells. Threshold radiant exposures were as low as 18 mJ cm-2, and increased at longer wavelengths, longer pulse durations and lower melanin contents within the cells. It is concluded that selective targeting of pigmented trabecular meshwork cells can be achieved using pulsed lasers with low threshold radiant exposures avoiding collateral thermal damage to adjacent non-pigmented trabecular meshwork cells. This approach can be readily applied in vivo.

Modulation of flagellar expression in Escherichia coli by acetyl phosphate and the osmoregulator OmpR

During the search for unknown factors involved in motility, we have found that expression of the flagellar master operon flhDC is affected by mutations of the pta and ackA genes, encoding phosphotransacetylase and acetate kinase, respectively (S. Shin, J. Sheen, and C. Park, Korean J. Microbiol. 31:504-511, 1993). Here we describe results showing that this effect is modulated by externally added acetate, except when both pta and ackA are mutated, suggesting the role of acetyl phosphate, an intermediate of acetate metabolism, as a regulatory effector. Furthermore, the following evidence indicates that the phosphorylation of OmpR, a trans factor for osmoregulation, regulates flagellar expression. First, in a strain lacking ompR, the expression of flhDC is no longer responsive to a change in the level of acetyl phosphate. Second, an increase in medium osmolarity does not decrease flhDC expression in an ompR mutant. It is known that such an increase normally enhances OmpR phosphorylation. Third, OmpR protein binds to the DNA fragment containing the flhDC promoter, and its affinity is increased with phosphorylation by acetyl phosphate. DNase I footprinting revealed the regions of the flhDC promoter protected by OmpR in the presence or absence of phosphorylation. Therefore, we propose that the phosphorylated OmpR, generated by either osmolarity change or the internal level of acetyl phosphate, negatively regulates the expression of flagella.

Association of clinical factors and recent anticancer therapy with COVID-19 severity among patients with cancer: a report from the COVID-19 and Cancer Consortium

BACKGROUND

Patients with cancer may be at high risk of adverse outcomes from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We analyzed a cohort of patients with cancer and coronavirus 2019 (COVID-19) reported to the COVID-19 and Cancer Consortium (CCC19) to identify prognostic clinical factors, including laboratory measurements and anticancer therapies.

PATIENTS AND METHODS

Patients with active or historical cancer and a laboratory-confirmed SARS-CoV-2 diagnosis recorded between 17 March and 18 November 2020 were included. The primary outcome was COVID-19 severity measured on an ordinal scale (uncomplicated, hospitalized, admitted to intensive care unit, mechanically ventilated, died within 30 days). Multivariable regression models included demographics, cancer status, anticancer therapy and timing, COVID-19-directed therapies, and laboratory measurements (among hospitalized patients).

RESULTS

A total of 4966 patients were included (median age 66 years, 51% female, 50% non-Hispanic white); 2872 (58%) were hospitalized and 695 (14%) died; 61% had cancer that was present, diagnosed, or treated within the year prior to COVID-19 diagnosis. Older age, male sex, obesity, cardiovascular and pulmonary comorbidities, renal disease, diabetes mellitus, non-Hispanic black race, Hispanic ethnicity, worse Eastern Cooperative Oncology Group performance status, recent cytotoxic chemotherapy, and hematologic malignancy were associated with higher COVID-19 severity. Among hospitalized patients, low or high absolute lymphocyte count; high absolute neutrophil count; low platelet count; abnormal creatinine; troponin; lactate dehydrogenase; and C-reactive protein were associated with higher COVID-19 severity. Patients diagnosed early in the COVID-19 pandemic (January-April 2020) had worse outcomes than those diagnosed later. Specific anticancer therapies (e.g. R-CHOP, platinum combined with etoposide, and DNA methyltransferase inhibitors) were associated with high 30-day all-cause mortality.

CONCLUSIONS

Clinical factors (e.g. older age, hematological malignancy, recent chemotherapy) and laboratory measurements were associated with poor outcomes among patients with cancer and COVID-19. Although further studies are needed, caution may be required in utilizing particular anticancer therapies.

CLINICAL TRIAL IDENTIFIER

NCT04354701.

HER2 and choice of adjuvant chemotherapy for invasive breast cancer: National Surgical Adjuvant Breast and Bowel Project Protocol B-15

BACKGROUND

Recent retrospective analyses have suggested that breast cancer patients whose tumors overexpress HER2 derive preferential benefit from treatment with anthracyclines such as doxorubicin. This has led some clinicians to propose that HER2 should be used as a predictive marker in choosing between anthracycline-based regimens and combination chemotherapy with cyclophosphamide, methotrexate, and 5-fluorouracil (CMF). We evaluated this recommendation in a retrospective study of National Surgical Adjuvant Breast and Bowel Project Protocol B-15, in which patients received a combination of doxorubicin and cyclophosphamide (AC), CMF, or AC followed by CMF. We hypothesized that AC would be superior to CMF only in the HER2-positive patients.

METHODS

Immunohistochemical detection of HER2 was performed on tumor sections from 2034 of 2295 eligible patients. We used statistical analysis to evaluate the interaction between the efficacy of the assigned treatments and HER2 overexpression. All statistical tests were two-sided.

RESULTS

Tumor sections from 599 patients (29%) stained positive for HER2. AC was superior to CMF in HER2-positive patients only, although differences in outcomes did not reach statistical significance. In the HER2-positive cohort, relative risks of failure (i.e., after AC treatment as compared with CMF treatment) were 0.84 for disease-free survival (DFS) (95% confidence interval [CI] = 0.65--1.07; P =.15), 0.82 for survival (95% CI = 0.63--1.06; P =.14), and 0.80 for recurrence-free survival (RFS) (95% CI = 0.62--1.04; P =.10). Tests for interaction between treatment and HER2 status were suggestive but not statistically significant (P =.19 for DFS, P =.11 for survival, and P =.08 for RFS).

CONCLUSIONS

These results, together with overview results indicating minor overall superiority for anthracycline-based regimens relative to CMF, indicate a preference for the AC regimen in patients with HER2-positive tumors. Both AC and CMF regimens may be considered for patients with HER2-negative tumors.

Increased expression of vascular endothelial growth factor and angiogenesis in the early stage of multistep hepatocarcinogenesis

BACKGROUND

Hepatocellular carcinoma (HCC) is known to receive its blood supply principally from the hepatic arteries. Recent studies have reported differences in the vascular supply, especially arterial supply among low- and high-grade dysplastic nodules (DNs) (also referred to as adenomatous hyperplasia and macroregenerative nodules) and HCCs. Increased expression of vascular endothelial growth factor (VEGF) has been reported in HCC. In addition, VEGF may play an important role in the early phases of hepatocarcinogenesis.

METHODS

We immunohistochemically stained 7 low-grade DNs, 8 high-grade DNs, 11 early HCCs, 17 small HCCs, and 21 advanced HCCs with antibodies against VEGF, alpha-smooth muscle actin (to identify unpaired arteries, ie, arteries not accompanied by bile ducts, indicative of angiogenesis), CD34 (as a marker of sinusoidal capillarization), and proliferation cell nuclear antigen.

RESULTS

Expression of VEGF was found in the hepatocytes and HCC cells. The degree of VEGF expression increased gradually according to the stepwise development of hepatocarcinogenesis. It was higher in high-grade DNs and early HCCs than in low-grade DNs. The hepatocytes and HCC cells adjacent to peliosis and fibrous septa showed stronger VEGF expression. Angiogenesis, unpaired arteries, and sinusoidal capillarization developed from low-grade DNs and gradually increased. It was highest in HCCs. The proliferation cell nuclear antigen labeling indexes of hepatocytes and HCC cells also increased gradually as hepatocarcinogenesis progressed. Small HCCs showed a higher status of neoangiogenesis and cell proliferation activity than advanced HCCs. The degree of VEGF expression was correlated with angiogenesis and cell proliferation activity.

CONCLUSION

We conclude that VEGF plays a significant role in angiogenesis, growth, and development of HCC.

The Efficacy of Platelet-Rich Plasma on Tendon and Ligament Healing: A Systematic Review and Meta-analysis With Bias Assessment

BACKGROUND

There has been a surge in high-level studies investigating platelet-rich plasma (PRP) for tendon and ligament injuries. A number of meta-analyses have been published, but few studies have focused exclusively on tendon and ligament injuries.

PURPOSE

To perform a meta-analysis assessing the ability of PRP to reduce pain in patients with tendon and ligament injuries.

STUDY DESIGN

Systematic review and meta-analysis.

METHODS

This study followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. A comprehensive search of the literature was carried out in April 2017 using electronic databases PubMed, MEDLINE, and the Cochrane Library. Only level 1 studies were included. Platelet and leukocyte count, injection volume, kit used, participant age/sex, comparator, and activating agent used were recorded. The short-term and long-term efficacy of PRP was assessed using the visual analog scale (VAS) to measure pain intensity. Injury subgroups (rotator cuff, tendinopathy, anterior cruciate ligament, and lateral epicondylitis) were evaluated. Funnel plots and the Egger test were used to screen for publication bias, and sensitivity analysis was performed to evaluate the effect of potential outliers by removing studies one at a time.

RESULTS

Thirty-seven articles were included in this review, 21 (1031 participants) of which could be included in the quantitative analysis. The majority of studies published investigated rotator cuff injuries (38.1%) or lateral epicondylitis (38.1%). Seventeen studies (844 participants) reported short-term VAS data, and 14 studies (771 participants) reported long-term VAS data. Overall, long-term follow-up results showed significantly less pain in the PRP group compared with the control group (weighted mean difference [WMD], -0.84; 95% CI, -1.23 to -0.44; P < .01). Patients treated with PRP for rotator cuff injuries (WMD, -0.53; 95% CI, -0.98 to -0.09; P = .02) and lateral epicondylitis (WMD, -1.39; 95% CI, -2.49 to -0.29; P = .01) reported significantly less pain in the long term. Substantial heterogeneity was reported at baseline ( I² = 72.0%; P < .01), short-term follow-up ( I² = 72.5%; P < .01), long-term follow-up ( I² = 76.1%; P < .01), and overall ( I² = 75.8%; P < .01). The funnel plot appeared to be asymmetric, with some missingness at the lower right portion of the plot suggesting possible publication bias.

CONCLUSION

This review shows that PRP may reduce pain associated with lateral epicondylitis and rotator cuff injuries.

Normal splenic size in infants and children: sonographic measurements

The purpose of this study was to establish guidelines for normal splenic size at different ages by using a simple and reproducible sonographic method. Two hundred thirty patients, from neonate to 20-year-old, had sonography because of abdominal and/or pelvic problems unrelated to the spleen. Findings on sonograms of the liver and kidneys were normal in all cases. Splenic size was measured by obtaining a coronal view that included the hilum, while the patient was breathing quietly. The greatest longitudinal distance between the dome of the spleen and the tip (splenic length) was measured and correlated with age, height, and weight. The following guidelines are proposed for the upper limit of normal splenic length based on this simple, easy to use, one-measurement technique: splenic length no greater than 6.0 cm at 3 months, 6.5 cm at 6 months, and 7.0 cm at 12 months, 8.0 cm at 2 years, 9.0 at 4 years, 9.5 cm at 6 years, 10.0 cm at 8 years, 11.0 cm at 10 years, 11.5 cm at 12 years, 12.0 cm at 15 years or older for girls, and 13.0 cm at 15 years or older for boys. Twenty-two patients with known abnormalities of the spleen were randomly selected and their splenic lengths compared with the proposed guidelines; in each case, the length of the spleen exceeded the upper limit of normal for that age. Normal values of a single measurement of the greatest longitudinal diameter of the spleen, from the dome to the tip measured at the hilum in the coronal plane, were obtained in patients from newborn to 20 years old.

Can bedside assessment reliably exclude aspiration following acute stroke?

OBJECTIVE

To investigate the ability of a bedside swallowing assessment to reliably exclude aspiration following acute stroke.

SUBJECTS

Consecutive patients admitted within 24 h of stroke onset to two hospitals.

METHODS

A prospective study. Where possible, all patients had their ability to swallow assessed on the day of admission by both a doctor and a speech and language therapist using a standardized proforma. A videofluoroscopy examination was conducted within 3 days of admission.

RESULTS

94 patients underwent videofluoroscopy; 20 (21%) were seen to be aspirating, although this was not detected at the bedside in 10. In 18 (22%) of the patients the speech and language therapist considered the swallow to be unsafe. In the medical assessment, 39 patients (41%) had an unsafe swallow. Bedside assessment by a speech and language therapist gave a sensitivity of 47%, a specificity of 86%, positive predictive value (PPV) of 50% and a negative predictive value (NPV) of 85% for the presence of aspiration. Multiple logistic regression was used to identify the optimum elements of the bedside assessments for predicting the presence of aspiration. A weak voluntary cough and any alteration in conscious level gave a sensitivity of 75%, specificity of 72%, PPV of 41% and NPV of 91% for aspiration.

CONCLUSION

Bedside assessment of swallowing lacks the necessary sensitivity to be used as a screening instrument in acute stroke, but there are concerns about the use of videofluoroscopy as a gold standard. The relative importance of aspiration and bedside assessment in predicting complications and outcome needs to be studied.

Intrinsic religiousness and religious coping as life stress moderators for Catholics versus Protestants

Two prospective studies were conducted to test the stress-moderating effects of intrinsic religiousness and overall religious coping on the depression and trait anxiety of Catholic and Protestant college students. Both studies found a significant cross-sectional interaction between controllable life stress and religious coping in the prediction of Catholics' depression, with religious coping serving a protective function at a high level of controllable negative events. Both studies also found a significant prospective interaction between uncontrollable life stress and intrinsic religiousness in the prediction of Protestants' depression; the relationship between uncontrollable stress and depression was positive for low intrinsic Protestants, flat for medium intrinsic Protestants, but negative for high intrinsic Protestants. The findings are discussed in terms of their implications for the role of religion in life stress adjustment.

Observation and quantification of nanoscale processes in lithium batteries by operando electrochemical (S)TEM

An operando electrochemical stage for the transmission electron microscope has been configured to form a "Li battery" that is used to quantify the electrochemical processes that occur at the anode during charge/discharge cycling. Of particular importance for these observations is the identification of an image contrast reversal that originates from solid Li being less dense than the surrounding liquid electrolyte and electrode surface. This contrast allows Li to be identified from Li-containing compounds that make up the solid-electrolyte interphase (SEI) layer. By correlating images showing the sequence of Li electrodeposition and the evolution of the SEI layer with simultaneously acquired and calibrated cyclic voltammograms, electrodeposition, and electrolyte breakdown processes can be quantified directly on the nanoscale. This approach opens up intriguing new possibilities to rapidly visualize and test the electrochemical performance of a wide range of electrode/electrolyte combinations for next generation battery systems.

Mutations in NADH:ubiquinone oxidoreductase of Escherichia coli affect growth on mixed amino acids

We isolated and characterized mutants defective in nuo, encoding NADH dehydrogenase I, the multisubunit complex homologous to eucaryotic mitochondrial complex I. By Southern hybridization and/or sequence analysis, we characterized three distinct mutations: a polar insertion designated nuoG::Tn10-1, a nonpolar insertion designated nuoF::Km-1, and a large deletion designated delta(nuoFGHIJKL)-1. Cells carrying any of these three mutations exhibited identical phenotypes. Each mutant exhibited reduced NADH oxidase activity, grew poorly on minimal salts medium containing acetate as the sole carbon source, and failed to produce the inner, L-aspartate chemotactic band on tryptone swarm plates. During exponential growth in tryptone broth, nuo mutants grew as rapidly as wild-type cells and excreted similar amounts of acetate into the medium. As they began the transition to stationary phase, in contrast to wild-type cells, the mutant cells abruptly slowed their growth and continued to excrete acetate. The growth defect was entirely suppressed by L-serine or D-pyruvate, partially suppressed by alpha-ketoglutarate or acetate, and not suppressed by L-aspartate or L-glutamate. We extended these studies, analyzing the sequential consumption of amino acids by both wild-type and nuo mutant cells growing in tryptone broth. During the lag and exponential phases, both wild-type and mutant cells consumed, in order, L-serine and L-aspartate. As they began the transition to stationary phase, both cell types consumed L-tryptophan. Whereas wild-type cells then consumed L-glutamate, glycine, L-threonine, and L-alanine, mutant cells utilized these amino acids poorly. We propose that cells defective for NADH dehydrogenase I exhibit all these phenotypes, because large NADH/NAD+ ratios inhibit certain tricarboxylic acid cycle enzymes, e.g., citrate synthase and malate dehydrogenase.

Notch-1 controls the expression of fatty acid-activated transcription factors and is required for adipogenesis

Notch, a transmembrane receptor member of the homeotic epidermal growth factor-like family of proteins, participates in cell-to-cell signaling to control cell fate during development. Activated Notch-1 constructs lacking the extracellular region prevent differentiation of several mammalian cells in vitro. This effect, however, bypasses the normal mechanisms of cell-to-cell interactions in which Notch-1 participates. We investigated the role of Notch-1 in the hormone-induced adipocyte differentiation of 3T3-L1 fibroblasts, a paradigmatic model of adipogenesis that requires cell-to-cell contact. Unlike other differentiation models, Notch-1 expression and function were necessary conditions for adipogenesis. Impaired Notch-1 expression by antisense Notch-1 constructs prevented adipocyte differentiation. Strategies aimed at blocking putative Notch/ligand interactions also blocked adipogenesis, implicating Notch as a critical molecule in cell-to-cell signaling necessary for differentiation. Inhibition of Notch-1 expression or function decreased the expression of peroxisomal proliferator-activated receptors delta and gamma, transcription factors that control adipocyte differentiation and that are up-regulated at cell confluence. These results implicate Notch in the commitment of 3T3-L1 cells to undergo adipogenesis by controlling the expression of the principal regulators of this process.

Organization and regulation of the D-xylose operons in Escherichia coli K-12: XylR acts as a transcriptional activator

The metabolism of D-xylose in Escherichia coli K-12 is known to be mediated by the xylAB gene. However, the nearby xylFGHR genes were found by genome sequencing and predicted to be responsible for transport and regulation for xylose based on their sequence similarities to other functionally related genes. Here, we investigated transcriptional organization and functions of the xyl genes. An analysis with random transposon insertions revealed that the xyl genes are organized into two major transcriptional units, xylAB and xylFGHR, governed by the promoters PA and PF, respectively. However, there is an additional weak promoter, PR, which is specific for xylR. Sites of transcription initiation were determined by primer extension analysis. When studied with operon fusions to lacZ, the PA and PF promoters were activated by D-xylose and repressed by glucose. In contrast, the PR promoter was not regulated by these sugars. A mutation in xylR completely abolished expression from the PA and PF promoters, causing a defect in both growth and transport. Binding of XylR to the xyl promoter was enhanced by the presence of D-xylose, suggesting that transcription was positively regulated by XylR. In vivo footprinting analysis revealed that XylR binds to at least two DNA regions, IA and IF, each with a direct repeat. It is very likely that XylR interacts with IA and IF as a dimer. The presumed binding sites are located just upstream of the promoter consensus sequences (-35), while IA is additionally flanked by a cyclic AMP receptor protein-binding site on the other side. The proposed structure of xyl promoters is consistent with the regulation of xyl gene expression and with phenotypes of transposon insertions obtained in the promoter regions.

Induced premature G2/M-phase transition in pachytene spermatocytes includes events unique to meiosis

Little is known about the control of events ending the lengthy prophase of meiosis I and leading to the G2/M-phase transition in mammalian spermatocytes, primarily because the relevant late pachytene, diplotene, and MI cells are present in low numbers in the testis and it is not possible to isolate them in significant numbers. We have utilized short-term cultures of pachytene spermatocytes from the mouse to study events of the G2/M cell-cycle transition induced by the protein phosphatase inhibitor okadaic acid (OA). Treatment of cultured pachytene spermatocytes with OA induced a rapid and premature onset of events leading to the M phase, visualized cytologically by nuclear envelope breakdown and chromosome condensation. After OA treatment, condensed chromosomes were seen as bivalents, not as univalents. Treatment with OA induced disassembly of synaptonemal complexes and resolution of crossovers as cytologically visible chiasmata. Chiasmata counts were similar in treated cells and control cells. Thus, surprisingly, even though the treated cells were in the pachytene substage of meiotic prophase, events of recombination were apparently completed to the point of chiasma formation in the majority of these cells. The sex chromosomes, forming the sex body of the pachytene spermatocyte, lagged behind the autosomal chromosomes in their condensation and progression toward the M phase. Treatment with OA induced an increase in histone H1 kinase activity, generally used as an indicator of metaphase-promoting factor (MPF) activity; furthermore, the OA-induced cell-cycle transition does not require new protein synthesis. These results suggest that OA treatment overrides a cell-cycle checkpoint control that normally keeps pachytene spermatocytes in a lengthy prophase and that this control may be exerted by regulation of protein phosphorylation status.

Direct evidence that the rifamycin polyketide synthase assembles polyketide chains processively

The assembly of the polyketide backbone of rifamycin B on the type I rifamycin polyketide synthase (PKS), encoded by the rifA-rifE genes, is terminated by the product of the rifF gene, an amide synthase that releases the completed undecaketide as its macrocyclic lactam. Inactivation of rifF gives a rifamycin B nonproducing mutant that still accumulates a series of linear polyketides ranging from the tetra- to a decaketide, also detected in the wild type, demonstrating that the PKS operates in a processive manner. Disruptions of the rifD module 8 and rifE module 9 and module 10 genes also result in accumulation of such linear polyketides as a consequence of premature termination of polyketide assembly. Whereas the tetraketide carries an unmodified aromatic chromophore, the penta- through decaketides have undergone oxidative cyclization to the naphthoquinone, suggesting that this modification occurs during, not after, PKS assembly. The structure of one of the accumulated compounds together with (18)O experiments suggests that this oxidative cyclization produces an 8-hydroxy-7, 8-dihydronaphthoquinone structure that, after the stage of proansamycin X, is dehydrogenated to an 8-hydroxynaphthoquinone.

Two novel flagellar components and H-NS are involved in the motor function of Escherichia coli

A mutation in H-NS results in non-flagellation of Escherichia coli due to a reduced expression of the flhDC master operon. We found that the hns-negative strain restored its flagellation in the presence of flhDC, although the resulting strain was still non-motile. Since the intracelluar levels of motor components MotA, MotB, and FliG in the Deltahns strain were unaltered, the non-motility indicates that H-NS affects flagellar function as well as biogenesis. We obtained an insertion in ycgR, a putative gene encoding a protein of 244 amino acid residues, which suppresses the motility defect of hns-deficient cells. The abnormally low swimming speed of hns mutant cells was fully restored by an insertion in ycgR, as assessed with computer-assisted motion analysis. A similar suppressor phenotype was observed with a multicopy expression of yhjH, a putative gene encoding a polypeptide of 256 amino acid residues. Since the flagella of most hns-deficient cells were not rotating, except a few with reduced speed, the suppression appears to increase the number of rotating flagella as observed with tethered bacteria. The ycgR and yhjH genes contain the consensus sequence found among the class III promoters of the flagellar regulon, and their expression monitored with a lacZ fusion requires FlhDC. These findings suggest that ycgR and yhjH, together with H-NS, are involved in the motor function and constitute new members of the flagellar regulon.

Transmembrane signalling by a hybrid protein: communication from the domain of chemoreceptor Trg that recognizes sugar-binding proteins to the kinase/phosphatase domain of osmosensor EnvZ

Chemoreceptor Trg and osmosensor EnvZ of Escherichia coli share a common transmembrane organization but have essentially unrelated primary structures. We created a hybrid gene coding for a protein in which Trg contributed its periplasmic and transmembrane domains as well as a short cytoplasmic segment and EnvZ contributed its cytoplasmic kinase/phosphatase domain. Trz1 transduced recognition of sugar-occupied, ribose-binding protein by its periplasmic domain into activation of its cytoplasmic kinase/phosphatase domain as assessed in vivo by using an ompC-lacZ fusion gene. Functional coupling of sugar-binding protein recognition to kinase/phosphatase activity indicates shared features of intramolecular signalling in the two parent proteins. In combination with previous documentation of transduction of aspartate recognition by an analogous fusion protein created from chemoreceptor Tar and EnvZ, the data indicate a common mechanism of transmembrane signal transduction by chemoreceptors and EnvZ. Signalling through the fusion proteins implies functional interaction between heterologous domains, but the minimal sequence identity among relevant segments of EnvZ, Tar, and Trg indicates that the link does not require extensive, specific interactions among side chains. The few positions of identity in those three sequences cluster in transmembrane segment 1 and the short chemoreceptor sequence in the cytoplasmic part of the hybrid proteins. These regions may be particularly important in physical and functional coupling. The specific cellular conditions necessary to observe ligand-dependent activation of Trz1 can be understood in the context of the importance of phosphatase control in EnvZ signalling and limitations on maximal receptor occupancy in binding protein-mediated recognition.

Arterial supply of the anterior ear

Twenty cadaver auricles were injected with a latex solution to define the arterial supply of the anteroauricular surface. Two arterial networks exist, the network of the triangular fossa-scapha and the network of the concha. Both eventually communicate on the anthelix. The triangular fossa-scapha network originates from one subbranch of the upper auricular branch of the superficial temporal artery and from branches of the posterior auricular artery that come through the earlobe and triangular fossa and over the helical margin. The conchal network is provided by two to four perforators that come from the posterior auricular artery, piercing the conchal floor. Auricular branches of the superficial temporal artery in the preauricular region and their communications with the posterior auricular artery also were confirmed. We believe that a greater understanding of the detailed arterial anatomy in this area allows one to develop safely a variety of surgical techniques for reconstruction of the ear.