9:45-10:00. Superimposition of EBCT Determined Coronary Calcium Deposits onto Myocardial PET Perfusion Images by Rubidium-82 and Nitrogen-13 Ammonia for Assessment of Flow Limiting Defects

Calcium localization by Electron Beam CT (EBCT) in the coronary arteries is becoming an important non-invasive method for screening asymptomatic patients for early coronary atherosclerosis. However, the relationship between coronary artery calcium deposits and myocardial perfusion abnormalities has not been established. We have developed software to superimpose location of coronary calcium by EBCT onto PET myocardial perfusion images, so that we can determine the role of location and amount of calcium in the arteries to flow-limiting perfusion defects by PET.EBCT and PET transaxial images are each first converted to three-dimensional arrays of 1 mm voxels. The resulting two image volumes sets are displayed so that a vertical line can be drawn from the clavicle to the spine for proper rotation of the body. The rotated images are then displayed superimposed and are shifted in the vertical, horizontal, and the long axis directions to co-register the EBCT and PET images. The EBCT images are windowed for calcium Houndsfield numbers and calcium location is added to the PET images as a maximum intensity value in the image. The modified PET image volume is then translated back to the PET data format and reprocessed using cardiac analysis software such that the calcium location is superimposed on the PET myocardial perfusion images.Preliminary results of the PET-EBCT superimposition program correlate with location of coronary calcium by EBCT and PET perfusion defects following stress. This technique may be useful for identifying flow-limiting calcium deposits in the coronary arteries.

Identification of a novel nuclear factor-kappaB sequence involved in expression of urokinase-type plasminogen activator receptor

We have previously defined the promoter of human urokinase-type plasminogen activator receptor (uPAR) gene in a 188-bp fragment between bases -141 and +47 relative to the translation start site. Here, we report that a novel nuclear factor-kappaB (NF-kappaB)-like sequence (5'-GGGAGGAGTC-3') at -45 is located in the uPAR promoter and one of the two DNase I-protected regions, region I between bases -51 and -30. This NF-kappaB-like motif differs at positions 7-9 from the decameric consensus sequences of NF-kappaB (5'-GGGRNNYYCC-3' where R indicates A or G, Y indicates C or T, and N indicates any nucleotide) and at positions 1 and 7-9 from the kappaB-like motifs (5'-HGGARNYYCC-3' where H indicates A, C, or T, R indicates A or G, Y indicates C or T, and N indicates any nucleotide). Nuclear extracts from HCT116 cells contain proteins that specifically bind to the NF-kappaB-like site at position -45. Mutation of the NF-kappaB-like motif decreased the binding of transcription factor NF-kappaB and reduced the uPAR promoter activity in comparison with the wild-type sequences. Co-transfection with a dominant negative I-kappaB kinase-2 expression vector reduced uPAR promoter activity by 65-75%. These results demonstrate that a previously uncharacterized NF-kappaB motif is required for uPAR promoter activity.

The ArcB sensor kinase of Escherichia coli: genetic exploration of the transmembrane region

The Arc two-component signal transduction system of Escherichia coli regulates the expression of numerous operons in response to respiratory growth conditions. Cellular redox state or proton motive force (Delta(H(+))) has been proposed to be the signal for the membrane-associated ArcB sensor kinase. This study provided evidence for a short ArcB periplasmic bridge that contains a His47. The dispensability of this amino acid, the only amino acid with a pK in the physiological range, renders the Delta(H(+)) model unlikely. Furthermore, results from substituting membrane segments of ArcB with counterparts of MalF indicate that the region does not play a stereospecific role in signal reception.

A mutant hunt for defects in membrane protein assembly yields mutations affecting the bacterial signal recognition particle and Sec machinery

We describe an Escherichia coli genetic screen that yields mutations affecting two different cellular processes: disulfide bond formation and membrane protein assembly. The mutants defective in disulfide bond formation include additional classes of dsbA and dsbB mutations. The membrane protein assembly defective mutants contain a mutation in the secA operon and three mutations in the ffs gene, which encodes 4.5S RNA. These latter mutations are the only ones to be isolated in a gene encoding a component of the bacterial signal recognition particle by screening in vivo for defects in membrane protein insertion. A sensitive method for examining membrane protein localization shows that the ffs and secA locus mutations affect membrane assembly of the polytopic membrane protein, MalF. The ffs mutations also affect the membrane insertion of the FtsQ and the AcrB proteins. Although both the ffs and the secA locus mutations interfere with membrane protein assembly, only the latter also reduces export of a protein containing a cleavable signal sequence.

Coccidioidomycosis in human immunodeficiency virus-infected persons in Arizona, 1994-1997: incidence, risk factors, and prevention

From 1 January 1995 through 31 June 1997, 153 cases of coccidioidomycosis in human immunodeficiency virus (HIV)-infected persons were identified in Arizona (incidence, 41/1000 persons living with AIDS). A case-control study was conducted to evaluate risk factors for coccidioidomycosis in HIV-infected persons. A case was defined as laboratory-confirmed, incident coccidioidomycosis in a person infected with HIV for > or =3 months, and each case patient had 3 control patients matched by county, age group, sex, HIV/AIDS status, and CD4 lymphocyte count. Multivariable analysis identified black race and a history of oropharyngeal or esophageal candidiasis to be associated with increased risk of coccidioidomycosis; protease inhibitor therapy was associated with a reduced risk. In persons with previous history of oropharyngeal or esophageal candidiasis, having received an azole drug was associated with a reduced risk (odds ratio, 0.4; 95% confidence interval, 0.2-0.9; P=.04). Physicians may need to consider azole chemoprophylaxis for HIV-infected persons who live in areas of endemicity, have CD4 cell counts <200/microL, are black, or have a history of thrush.

Individualized mouth prop for dental professionals and carers

Maintaining a high standard of dental health in children with special needs, particularly those who are unable to control mandibular activity, can prove difficult and time consuming for parents, carers and dental professionals. This article describes the construction of an individually made and relatively unobtrusive finger guard mouth prop, designed to facilitate intraoral examination and oral hygiene care for these children. An initial evaluation by a number of users found these mouth props were simple to fit, stable and provided adequate finger protection. All users planned to continue using their mouth prop after the trial period. It is concluded that similar finger mounted mouth props may help facilitate dental care and oral hygiene for children requiring special care.

Towards single-copy gene expression systems making gene cloning physiologically relevant: lambda InCh, a simple Escherichia coli plasmid-chromosome shuttle system

We describe a simple system for reversible, stable integration of plasmid-borne genes into the Escherichia coli chromosome. Most ordinary E. coli strains and a variety of pBR322-derived ampicillin-resistant plasmids can be used. A single genetic element, a lambda phage, is the only specialized vector required. The resultant strains have a single copy of the plasmid fragment inserted stably at the lambda attachment site on the chromosome, with nearly the entire lambda genome deleted.

Regulation of BAD phosphorylation at serine 112 by the Ras-mitogen-activated protein kinase pathway

The function of the pro-apoptotic molecule BAD is regulated by phosphorylation of two sites, serine-112 (Ser-112) and serine-136 (Ser-136). Phosphorylation at either site results in loss of the ability of BAD to heterodimerize with the survival proteins BCL-XL or BCL-2. Phosphorylated BAD binds to 14-3-3 and is sequestered in the cytoplasm. It has been shown that phosphorylation of BAD at Ser-136 is mediated by the serine/threonine protein kinase Akt-1/PKB which is downstream of phosphatidylinositol 3-kinase (PI3K). The signaling process leading to phophorylation of BAD at Ser-112 has not been identified. In this study, we show that phosphorylation of the two serine residues of BAD is differentially regulated. While Ser-136 phosphorylation is concordant with activation of Akt, Ser-112 phosphorylation does not correlate with Akt activation. Instead, we demonstrate that activated Ras and Raf, which are upstream of mitogen-activated protein kinases (MAPK), stimulate selective phosphorylation of BAD at Ser-112. Furthermore, phosphorylation of Ser-112, but not Ser-136 requires activation of the MAPK pathway as the MEK inhibitor, PD 98059, blocks EGF-, as well as activated Ras- or Raf-mediated phosphorylation of BAD at Ser-112. Therefore, the PI3K-Akt and Ras-MAPK pathways converge at BAD by mediating phosphorylation of distinct serine residues.

Organochlorine contaminant levels in Eskimo harvested bowhead whales of arctic Alaska

Organochlorine (OC) levels in liver and blubber of 20 bowhead whales (Balaena mysticetus) collected during the Eskimo subsistence harvest at Barrow (Alaska, USA) in 1992 and 1993 are presented. Liver sum DDT (lipid weight) was significantly greater in male whales than in females. Most of the organochlorines measured were at higher levels in longer (older) than in shorter (younger) males. For female bowhead whales, hexachlorobenzene and lipid levels decreased and other OC levels did not change significantly with increasing length. Most organochlorine contaminants have low concentrations in tissues of the bowhead whale compared to concentrations in tissues of other cetaceans, especially Odontocetes. Based on allowable daily intakes (ADI) levels established by the Canadian Northern Contaminants Program (Ottawa, Ontario, Canada) "safe" levels of blubber to consume were calculated. Chlordane levels in bowhead whale blubber results in the most restrictive consumption amount (50 g blubber/day). We expect no adverse effects related to these organochlorine contaminants to occur in bowhead whales or in consumers of their tissues. However, investigation of low level chronic exposure effects and a more rigorous assessment of histopathology, biomarkers, and immune status in the bowhead whale would be required to conclude "no effect" with more certainty.

A region between -141 and -61 bp containing a proximal AP-1 is essential for constitutive expression of urokinase-type plasminogen activator receptor

An 8.5-kb 5'-flanking region of the human urokinase-type plasminogen activator receptor (uPAR) gene was cloned and the detailed uPAR promoter region defined in an 188-bp fragment between bases -141 and +47 relative to the transcription-start site. 5'-Deletion to -100 and -60 in the region abolished its promoter activity, indicating that an 81-bp segment between -141 and -61, which contains a proximal AP-1 site at position -70, is required for uPAR promoter activity. Nuclear extracts from HCT116 cells contain proteins that specifically bind to the AP-1 site. Mutation of the AP-1 motif reduced uPAR promoter activity in comparison with the wild-types. Induction of uPAR expression by phorbol ester requires this AP-1 motif in colon cancer cells. Cotransfection with the c-jun and c-fos expression vectors stimulated the uPAR promoter activity four- to fivefold. These results demonstrate that the proximal AP-1 motif is responsible for approximately 50% of the basal expression of the uPAR gene.

Targeted disruption of the K-ras oncogene in an invasive colon cancer cell line down-regulates urokinase receptor expression and plasminogen-dependent proteolysis

The urokinase receptor, overexpressed in invasive colon cancer, promotes tumour cell invasion. Since K-Ras is activated in many colon cancers, we determined if urokinase receptor overexpression is a consequence of this activated oncogene. Accordingly, urokinase receptor expression was compared in HCT 116 colon cancer cells containing either a mutation-activated K-Ras or disrupted for this oncogene (by homologous recombination). HCT 116 cells containing the disrupted K-Ras oncogene expressed between 50 and 85% less urokinase receptor protein compared with the parental HCT 116 cells. Reduced urokinase receptor expression in cells containing the disrupted mutated K-Ras was not due to a physical impairment of the urokinase receptor gene since phorbol ester treatment was inductive for its expression. Constitutive urokinase receptor expression in HCT 116 cells required an intact AP-1 motif in the promoter (at -184) and electrophoretic mobility shifting assays indicated less c-Jun, JunD, c-Fos and Fra-1 bound to this motif in the K-Ras-disrupted cells. Since the urokinase receptor accelerates proteolysis, laminin degradation was compared in cells containing the mutation-activated and disrupted K-Ras oncogene. The latter cells displaying fewer urokinase receptors, degraded 80% less laminin. This is the first study to demonstrate a role for K-Ras as a regulator of the constitutive expression of the urokinase receptor.

PD 098059, an inhibitor of ERK1 activation, attenuates the in vivo invasiveness of head and neck squamous cell carcinoma

Increased mortality of patients with oral cancer largely reflects the local and regional spread of the disease. The invasiveness of these tumours requires hydrolases which are regulated through AP-1-dependent transcriptional mechanisms. Since the amount/activity of transcription factors bound to the AP-1 motif are regulated partly through the extracellular signal-regulated kinases (ERK1/ERK2), we determined the effect of PD 098059, an inhibitor of ERK1/ERK2 activation, on the in vivo invasiveness of a human squamous cell carcinoma cell line (UM-SCC-1) derived from the oral cavity. We utilized the floor of mouth musculature consisting of the mylohyoid, geniohyoid and genioglossus muscle (which are sequentially arranged), as a natural barrier to assess tumour spread in vivo in the nude mouse. Mice were inoculated with tumour cells superficial to the mylohyoid muscle. After 18 days, tumours were injected with either empty liposomes (control) or liposomes containing 5 microM PD 098059 and, after an additional 22 days, the jaws of mice examined histologically. Highly infiltrative tumours, which had penetrated the genioglossus muscle, were evident in 10/12 control mice. In contrast, in 9/12 mice in which the tumours were injected with PD 098059, tumours did not extend beyond the mylohyoid or geniohyoid muscles. Tumours penetrated bone nutrient canals in 7/12 control mice but in only 3/12 PD 098059-treated mice. Neurotropism, characteristic of aggressive oral squamous cell carcinoma, was evident in 6/12 control mice but was completely abolished (0/12 mice) in the PD 098059-treated mice. Using a staging system based on the muscle layer involved, neurotropism, as well as bone involvement, we found the inhibition of invasion to be statistically significant (P < 0.01). The reduced invasiveness of the PD 098059-liposome-treated oral cancers was associated with diminished 92-kDa type IV collagenase and ERK1/ERK2 activities but was not a consequence of a slower tumour growth rate. This is the first study to demonstrate reduced in vivo invasiveness of a malignancy brought about by an inhibitor of ERK1/ERK2 activation. These results raise the exciting possibility that second generation PD 098059 congeners may reduce the spread of the disease in patients afflicted with oral cancers.

Measurement of matrix metalloproteinases and tissue inhibitors of metalloproteinases in blood and tissues. Clinical and experimental applications

The balance between production and activation of MMPs and their inhibition by TIMPs is a crucial aspect of cancer invasion and metastasis. On the basis of the concept that MMPs synthesized in tissues seep into the bloodstream, we have examined MMP levels in the plasma of patients with cancer. In colorectal, breast, prostate, and bladder cancer, most patients with aggressive disease have increased plasma levels of gelatinase B. In patients with advanced colorectal cancer, high levels of either gelatinase B or TIMP complex were associated with shortened survival. We propose that these assays may be clinically useful in characterizing metastatic potential in selected kinds of cancer. In rheumatoid arthritis and systemic lupus erythematosus (SLE), serum and plasma levels of stromelysin-1 were approximately 3-5-fold increased. Fluctuating serum stromelysin-1 levels in SLE did not correspond with change in disease activity. In SLE, stromelysin-1 may be a component of the chronic tissue repair process rather than being responsible for inciting tissue damage. On the basis of these observations, we conclude that measurement of plasma/serum MMP and TIMP levels may provide important data for selecting and following patients considered for treatment with drugs that interfere with MMP activity.

Characterization and proposed nomenclature of epidemic strains of methicillin-resistant Staphylococcus aureus in Canada

We hope that standardized nomenclature for identifying epidemic MRSA strains prevalent in Canadian hospitals will be helpful to physicians and infection control practitioners attempting to understand and control the spread of the organism in health-care facilities. It is anticipated that as MRSA continues to evolve in Canadian health-care facilities other strains may be recognized as "epidemic"; as these strains become better characterized they may be added to those designated above. Laboratory physicians and infection control personnel are invited to submit strains that may warrant characterization and designation as a Canadian epidemic strain to the Laboratory Centre for Disease Control, Health Canada, Winnipeg, Manitoba.

Transactivation of the urokinase-type plasminogen activator receptor gene through a novel promoter motif bound with an activator protein-2alpha-related factor

The urokinase receptor overexpressed in invasive cancers promotes laminin degradation. The current study was undertaken to identify cis elements and trans-acting factors activating urokinase receptor expression through a footprinted (-148/-124) region of the promoter containing putative activator protein-2- and Sp1-binding motifs. Mobility shifting experiments using nuclear extract from a high urokinase receptor-expressing cell line (RKO) indicated that Sp1, Sp3, and a factor similar to, but distinct from, activator protein-2alpha bound to this region. Mutations preventing the binding of the activator protein 2alpha-related factor diminished urokinase receptor promoter activity. In RKO cells, the expression of a negative regulator of activator protein-2 function diminished urokinase receptor promoter activity, protein, and laminin degradation. Conversely, urokinase receptor promoter activity in low urokinase receptor-expressing GEO cells was increased by activator protein-2alphaA expression. Although using GEO nuclear extract, little activator protein-2alpha-related factor bound to the footprinted region, phorbol 12-myristate 13-acetate treatment, which induces urokinase receptor expression, increased complex formation. Mutations preventing the activator protein-2alpha-related factor and Sp1/Sp3 binding reduced urokinase receptor promoter stimulation by this agent. Thus, the constitutive and phorbol 12-myristate 13-acetate-inducible expression of the urokinase receptor is mediated partly through trans-activation of the promoter via a sequence (-152/-135) bound with an activator protein-2alpha-related factor.

A mutational study of the ArcA-P binding sequences in the aldA promoter of Escherichia coli

The aldA gene (encoding aldehyde dehydrogenase) of Escherichia coli is anaerobically repressed by ArcA-P, the phosphorylated response regulator of the ArcB/A two-component signal transduction system. The promoter region of aldA contains two 10-bp sequences (5'-TGTTAATTAA-3') that perfectly match the proposed ArcA-P binding consensus (5'-[A/T]GTTAATTA[A/T]-3'). One consensus sequence is on the coding strand (-13 to -4 from the transcriptional start point), whereas the other is on the template strand (position -2 to -11). In this study we used the aldA promoter to test the validity of the proposed consensus sequence. DNase I protection experiments confirmed the 10-bp sequence to be a strong ArcA-P binding site. Alteration of the wild-type sequence from 5'-TGTTAATTAAC-3' to 5'-TCTTAATTAAG-3' or 5'-TATTAATTAAT-3' by site-directed mutagenesis markedly decreased the in vitro affinity of the promoter region for ArcA-P, and abolished the anaerobic repression of mutant att lambda::phi (aldA'-lacZ) transcriptional reporter constructs. Both the in vitro and in vivo results therefore support the proposed consensus sequence.

Localization of FtsI (PBP3) to the septal ring requires its membrane anchor, the Z ring, FtsA, FtsQ, and FtsL

Assembly of the division septum in bacteria is mediated by several proteins that localize to the division site. One of these, FtsI (also called penicillin-binding protein 3) of Escherichia coli, consists of a short cytoplasmic domain, a single membrane-spanning segment, and a large periplasmic domain that encodes a transpeptidase activity involved in synthesis of septal peptidoglycan. We have constructed a merodiploid strain with a wild-type copy of ftsI at the normal chromosomal locus and a genetic fusion of ftsI to the green fluorescent protein (gfp) at the lambda attachment site. gfp-ftsI was expressed at physiologically appropriate levels under control of a regulatable promoter. Consistent with previous results based on immunofluorescence microscopy GFP-FtsI localized to the division site during the later stages of cell growth and throughout septation. Localization of GFP-FtsI to the cell pole(s) was not observed unless the protein was overproduced about 10-fold. Membrane anchor alterations shown previously to impair division but not membrane insertion or transpeptidase activity were found to interfere with localization of GFP-FtsI to the division site. In contrast, GFP-FtsI localized well in the presence of beta-lactam antibiotics that inhibit the transpeptidase activity of FtsI. Septal localization depended upon every other division protein tested (FtsZ, FtsA, FtsQ, and FtsL). We conclude that FtsI is a late recruit to the division site, and that its localization depends on an intact membrane anchor.

An orthotopic floor-of-mouth cancer model allows quantification of tumor invasion

OBJECTIVES

To establish an orthotopic murine floor-of-mouth cancer model for the analysis of the role of proteases such as urokinase-type plasminogen activator (u-PA) and the matrix metalloprotease MMP-9 (MMP-9) in in vivo invasion.

STUDY DESIGN

Randomized, prospective animal study.

METHODS

Two human squamous cell carcinoma cell lines, UM-SCC-1 and 022, were assayed via zymography for their in vitro secretion levels of u-PA and MMP-9. Both cell lines (5 x 10(6) cells) were injected into the cervical subcutaneous tissues of female athymic nude (nu/nu) mice superficial to the mylohyoid muscle. Mice were sacrificed after 30 days, and tumor invasion characteristics were histologically compared. Additional mice were then inoculated with invasive UM-SCC-1 cells and sacrificed 10, 30, and 40 days after inoculation to identify distinct stages of invasion.

RESULTS

In vitro secretion levels of MMP-9 and activity of u-PA were higher in UM-SCC-1 cells than in 022 cells. In the in vivo studies, tumors formed from 022 cells were found to be noninvasive, whereas tumors derived from UM-SCC-1 cells progressed through distinct and readily identifiable histologic stages of invasion. These stages included invasion of adjacent muscle layers (mylohyoid, geniohyoid, and genioglossus muscles) and of associated structures (blood vessels, bone, nerve, and regional lymph nodes). A staging system was devised accordingly.

CONCLUSION

We developed an in vivo quantitative cancer invasion model that allows determination of the effect of the expression and activity levels of the proteases MMP-9 and u-PA. Tumor invasion occurred in an orderly and stepwise fashion involving muscles and related vascular, nervous, and bony structures of the floor of the mouth and tongue. This orderly invasion allowed the development of a staging system. We anticipate that this model will have wide applicability in the study of in vivo tumor response to a variety of novel therapeutic approaches.

Stimulation of urokinase-type plasminogen activator receptor expression by PMA requires JNK1-dependent and -independent signaling modules

The urokinase-type plasminogen activator receptor (u-PAR) has been implicated in tumor progression, and previous studies have shown that the expression of this gene is strongly up-regulated by PMA. Although the signaling mechanism by which PMA modulates u-PAR expression is not known, the effect of this phorbol ester on the expression of other genes has been ascribed to activation of the c-Raf-1-ERK signaling pathway. However, in the current study we examined an alternate possibility that the inductive effect of PMA on u-PAR expression also required a JNK1-dependent signaling cascade usually associated with stress-inducing stimuli. PMA treatment of the u-PAR-deficient OVCAR-3 ovarian cancer cells, which contain low JNK activities, resulted in a rapid (5 min) increase in JNK activity. Maximal JNK activity (12-fold induction) occurred after 30 min; this preceding the earliest detected rise in u-PAR protein (2 h). Dose-response studies with PMA also indicated that the increased JNK activity was tightly correlated with elevated u-PAR protein levels. The stimulation of u-PAR promoter activity by PMA required an intact upstream AP-1 motif (-184) and in PMA-treated cells this motif was bound with c-Jun as indicated from mobility shift assays. PMA up-regulated the c-Jun trans acting activity as indicated by the higher activity of a GAL4-regulated luciferase reporter in phorbol-ester-treated cells co-transfected with an expression vector encoding the c-Jun transactivation domain fused to the GAL4 DNA-binding domain. The ability of PMA to stimulate u-PAR promoter activity was effectively titrated out by the co-expression of either a kinase-defective JNK1 or a dominant negative MEKK1 the latter being an upstream activator of JNK1. Conversely, u-PAR promoter activity was stimulated by the co-expression of a constitutively active MEKK1 and this induction was antagonized by the inclusion of the kinase-defective JNK1 plasmid. We also determined the biological significance of the JNK1-dependent signaling cascade in regulating u-PAR promoter activity by c-Ha-ras since this oncogene is activated and/or overexpressed in a variety of tumors including ovarian cancer. Transfection of an activated c-Ha-ras into OVCAR-3 cells stimulated u-PAR promoter activity over 20-fold and this could be countered by the individual expression of dominant negative expression constructs to Rac-1, MEKK1 or JNK1. Taken together, these data suggest that the PMA- or c-Ha-Ras-dependent stimulation of u-PAR gene expression requires a JNK1-dependent signaling module and that, at least for PMA, the concurrent stimulation of a JNK1-independent signaling module is also required. Thus, caution should be exercised in invoking linear signaling modules to account for the regulation of inducible gene expression.