AB0602 Temporal artery biopsy positivity rates vary more between similar hospitals than by length, with particular variation between geographic regions

Background

Clinical practice surrounding giant cell arteritis (GCA) diagnosis, including the use of temporal artery biopsy (TAB) where appropriate, needs to be consistently accurate to minimise both GCA-related end-organ damage and unnecessary glucocorticosteroid toxicity in all patients. Despite this imperative, the delivery of such clinical care, which can be measured by diagnostic investigation performance characteristics such as TAB positivity rates, varies substantially between different hospitals as it is traditionally reliant on unstructured clinical intuition. While clinical care practices plausibly might be more consistent between neighbouring hospitals given they frequently exchange medical staff and use common teaching sources, these factors are less likely to be applicable when comparing hospitals in different geographical regions within a country, even though educational standards, online information resources, and access to clinical care should be consistent. It therefore stands to reason that variation of diagnostic practice might be greater between geographically distant hospitals.

Objectives

To compare clinical practice surrounding GCA diagnosis, using TAB positivity rates, between similar hospitals in the same city and a geographically distant city in a different region, to understand the contribution of geographic separation to variance in practice.

Methods

TAB histopathological reports were reviewed at three tertiary referral hospital centres: two with neighbouring catchments in the same city, and one in a different city in a neighbouring geographical region in the same country. All three had similar resourcing and catchment demographics during the study period, and none used formal clinical risk stratification scores for GCA pre-test probability. Characteristics including age, sex, biopsy laterality, biopsy length, and hospital were captured, in addition to key histopathological features. Multivariable logistic regression with site-varying intercept was performed, using cubic splines for biopsy length to account for the non-linearity observed.

Results

TAB reports from 708 patients were captured between the three hospitals in two geographical regions. All three sites had a median age of 74 years, had 67-69% of patients being female, and reported median biopsy length between 1.7-2.0cm (Table 1). Despite these similarities, they reported positivity rates varying widely (16% and 24% in Region 1, 29% in Region 2). Apart from age, hospital site was the strongest contributing factor to TAB positivity, with length having little effect outside the very extreme high end and 90% of patients had a biopsy length <4.8cm (Figure 1). For these patients, hospital site differentiated TAB positivity across all biopsy lengths, with Region 2 reporting the highest TAB positivity odds ratio of 2.39 (95%CI: 1.37-4.19).

Table 1.CharacteristicSite1Region1 N = 218Site2Region1 N = 361Site1Region2 N = 129Bilateral laterality (%)66 (30%)105 (29%)1 (0.8%)Biopsy length (cm, median (IQR))2.0 (1.4, 3.0)1.7 (1.2, 3.5)1.7 (1.4, 2.2)Female sex (%)149 (68%)249 (69%)86 (67%)Age (y, median (IQR))74 (65, 81)74 (65, 80)74 (68, 81)TAB positivity (%)34 (16%)88 (24%)38 (29%)Figure 1.

Marginal probabilities of positive TAB obtained from the multivariable logistic regression model (A) across biopsy lengths, with 80% of observed lengths falling between the two vertical red lines (10% and 90% deciles); (B) across hospital sites; (C) across patient age.

Conclusion

Hospital site contributes more greatly to variation in GCA diagnosis clinical practice than demographics or other clinical features do, with particular variation between geographic regions. As part of clinical care standards, using a replicable pre-test GCA probability score1 to select patients is likely to be as important to diagnosis as the diagnostic tool characteristics themselves.

References

[1]Laskou F, et al. A probability score to aid the diagnosis of suspected giant cell arteritis. Clin Exp Rheumatol. 2019 Jan 1;37(Suppl 117):104-8.

Disclosure of Interests

None declared

AB0371 PATIENTS WITH PROLONGED SYMPTOMS BEFORE GCA DIAGNOSIS DO NOT INCUR HIGHER RATES OF VISUAL LOSS

Background:

Giant cell arteritis (GCA), if left untreated, confers the threat of serious cranial ischaemic complications including permanent visual loss. Although achieving a prompt and accurate diagnosis remains challenging, early diagnosis is viewed as being paramount in preventing significant morbidity.1 This raises the question of whether GCA patients are at greater risk of developing visual sequelae if there is a longer window between symptom onset and presentation.

Objectives:

To compare the frequency of lasting visual loss in patients diagnosed with GCA undergoing temporal artery biopsy (TAB) within three months and after three months of symptom onset.

Methods:

Patients who underwent TAB from January 2011 to November 2020 were identified from the pathology database of an Australian rheumatology referral centre. The diagnosis of GCA was established for each patient based on either positive TAB or, in the setting of negative TAB, clinical diagnosis by a rheumatologist. Baseline demographics, symptoms and major confounders – including age, sex, history of polymyalgia rheumatica or inflammatory arthritis, headache, jaw pain, fatigue, temporal artery tenderness or diminished pulse, and number of 1990 American College of Rheumatology (ACR) classification criteria for GCA2 fulfilled – were manually extracted from electronic medical records, as was the duration between onset of GCA symptoms and TAB, and the presence of visual loss before and after TAB. Logistic regression log-likelihood tests were used to examine the two cohorts presenting before and after three months.

Results:

There were 167 patients who underwent TAB during the study period with accessible clinical information. Of these, 31 (19%) had a delayed presentation of greater than three months from symptom onset. There were no statistical differences in patient demographics between the two groups (Table 1). No patients with delayed presentation experienced lasting, objective visual loss. In contrast, there were three cases in the cohort of patients who presented more promptly; these included two patients who developed permanent unilateral blindness, and one who experienced unilateral vision loss with some improvement at three months of follow-up.

Table 1.

Patient characteristics by time from symptom onset to TAB.

Presentation <3 monthsPresentation ≥3 monthsp-valueAge (years)73.45±10.0669.84±10.750.080Female92 (67.65%)20 (64.52%)0.738History of polymyalgia rheumatica23 (16.91%)4 (12.90%)0.586History of inflammatory arthritis6 (4.41%)2 (6.45%)0.633Headache110 (80.88%)23 (74.19%)0.406Jaw pain37 (27.21%)5 (16.13%)0.206Fatigue28 (20.59%)6 (19.35%)0.878Temporal artery tenderness or diminished pulse46 (33.82%)11 (35.48%)0.860ACR classification criteria2.83±0.992.58±0.890.199

Conclusion:

GCA patients with a lengthier course of symptoms before diagnosis did not experience any enduring visual loss. This may reflect a pattern of more aggressive disease leading to earlier presentation, but further study should explore whether longer symptom duration before diagnosis necessitates a higher degree of clinical concern.

References:

[1]Font C, Cid MC, Coll-Vinent B, López-Soto A, Grau JM. Clinical features in patients with permanent visual loss due to biopsy-proven giant cell arteritis. Br J Rheumatol. 1997 Feb;36(2):251-4. doi: 10.1093/rheumatology/36.2.251. PMID: 9133940.

[2]Hunder GG, Bloch DA, Michel BA, Stevens MB, Arend WP, Calabrese LH, Edworthy SM, Fauci AS, Leavitt RY, Lie JT, et al. The American College of Rheumatology 1990 criteria for the classification of giant cell arteritis. Arthritis Rheum. 1990 Aug;33(8):1122-8. doi: 10.1002/art.1780330810. PMID: 2202311.

Disclosure of Interests:

None declared

Monitoring silver diamine fluoride application with optical coherence tomography

The objective of this study was to investigate the use of optical coherence tomography (OCT) for monitoring changes in the structure of caries lesions overtime after treatment with silver diamine fluoride (SDF). Artificial caries lesions were formed on dentin bovine blocks. Each block was partitioned into 5 windows: one lesion was covered by nail varnish as control (LC), one sound window was covered with nail varnish (SC), one sound window was exposed to SDF (SCT), one lesion received 2 applications of SDF (L2), while the other lesion received one application of SDF (L1). Each window was scanned using OCT before SDF application, and every week subsequently, for 12 weeks after initial SDF treatment. Parameters such as mean intensity and the width of the peak of increased reflectivity located at the sample surface and the intensity at a depth of 180-μm were monitored. High-resolution microscopy was also used to for the analysis of selected samples. Changes in the parameters measured showed significant changes on dentin lesions after SDF application. OCT resolved structural changes after SDF application as well as changes overtime. High resolution microscopy images confirm penetration of SDF into the samples. Such changes can potentially be monitored to determine if and when re-application of SDF is needed.

Thermal Imaging of Root Caries In Vivo

Improved methods are needed to assess the structure and activity of lesions on root surfaces in order to improve clinical decision making. Conventional visual and tactile methods for assessing lesion activity are not reliable, and the clinician is often unable to evaluate if the lesion is progressing or has remineralized. An important marker of an arrested lesion is a highly mineralized surface zone that forms when mineral is deposited in the outer layer of the lesion. In vitro studies have shown that a mineralized surface zone influences the kinetics of water evaporation and the surface temperature while drying. Temperature changes can be monitored by measuring the thermal emission with thermal imaging. Studies have also shown that the depth and severity of demineralization and the thickness of the highly mineralized transparent surface zone on arrested lesions can be measured nondestructively with optical coherence tomography (OCT). Thermal imaging at 8-µm to 13-µm wavelengths was completed on 30 test subjects with a suspected active root caries lesion by monitoring thermal emission from the tooth surfaces during 30 s of air drying. Lesions were also evaluated using cross-polarization OCT (CP-OCT) during lesion dehydration to identify transparent surface zones indicative of arrested lesions and determine if shrinkage occurred during drying. The overall thermal emission recorded during drying was significantly different (P < 0.001) when comparing sound tooth surfaces, lesion areas identified as arrested, and lesion areas identified as active, demonstrating that thermal imaging is a promising approach for the clinical assessment of lesion activity on root surfaces. Ten of the lesions in this study had distinct areas with transparent surface zones that were visible in CP-OCT images. Shrinkage was detected with CP-OCT during drying for 12 lesions. This study confirms that these novel approaches for assessing lesion activity on root surfaces can be implemented in vivo.

SAT0279 FACTORS PREDICTIVE OF POSITIVE TEMPORAL ARTERY BIOPSY IN TWO AUSTRALIAN COHORTS

Background:

Temporal artery biopsy (TAB) is widely recognised as the diagnostic gold standard for GCA despite having a poor sensitivity due to the presence of ‘skip’ lesions. There is, however, a lack of consensus guiding TAB practice, particularly in relation to optimal length, need for bilateral specimens, and number of segments examined.

Objectives:

To investigate the impact of factors such as total biopsied length, laterality, segment number, and referral centre on histopathological outcomes in an Australian setting.

Methods:

Reports for all available biopsy specimens labelled “temporal artery” were extracted from the pathology service records of two rheumatology referral centres with adjacent geographic catchments. Each histopathology report was manually reviewed to establish length of biopsied artery, laterality, and number of segments, along with patient demographics such as age, sex, and referral centre. Key histopathological findings including intimal hyperplasia, disruption of the internal elastic lamina, presence of giant cells, and adventitial inflammation were recorded. Multivariable logistic regression with site-varying intercept was performed.

Results:

TAB reports from a total of 577 patients were captured, with results available from the two centres from 1999-2019 and 2010-2019 respectively. The mean age in this group was 73, and 69% were female (Table 1). A bilateral TAB was performed in 29%, and the mean total biopsy length was 2.5cm. Of these patients, 122 had positive biopsies (21%), with intimal hyperplasia reported in 100 (17%), giant cells in 83 (14%), and adventitial findings in 68 (12%). Positive biopsy weakly correlated with increased total length of biopsy in centimetres (OR 1.25 [1.06-1.47]) (Figure 1) and increased age in years (OR 1.02 [1.00-1.05]) but not laterality or sex (Table 2). There was a substantial difference between the two centres, which was incompletely accounted for once corrected for total biopsy length and calendar year of biopsy, suggesting either unmeasured differences in patient demographics or a difference in clinical practice. This change was preserved across analysis of different histopathological subtypes.

Table 1.

Patient characteristics by biopsy result.

Negative(n = 455)Positive(n = 122)Total(n = 577)Age (years) Mean (SD)72 (± 11)75 (± 8.9)73 (± 10)Sex Female310 (68%)88 (72%)398 (69%) Male145 (32%)34 (28%)179 (31%)Maximum biopsy length (cm) Mean (SD)1.8 (± 0.86)2.0 (± 1.10)1.9 (± 0.92)Total biopsy length (cm) Mean (SD)2.4 (± 1.6)2.8 (± 2.1)2.5 (± 1.7)Mean biopsy length (cm) Mean (SD)1.7 (± 0.78)1.9 (± 0.97)1.7 (± 0.83)Laterality Bilateral130 (29%)39 (32%)169 (29%) Unilateral325 (71%)83 (68%)408 (71%)Table 2.

Associations with positive TAB on multivariable logistic regression.

Overall positive findingIntimal hyperplasiaGiant cellsAdventitial inflammationTotal biopsy length (cm)1.25(1.06-1.47)1.18(0.98-1.40)1.21(1.00-1.46)1.07(0.87-1.31)Unilateral (vs. bilateral)1.56(0.82-3.07)1.12(0.56-2.30)1.28(0.61-2.77)0.82(0.38-1.82)Age (years)1.02(1.00-1.05)1.02(1.00-1.04)1.03(1.00-1.05)1.00(0.98-1.03)Male (vs. female)0.83(0.52-1.29)0.63(0.37-1.05)0.59(0.32-0.92)0.75(0.41-1.31)Centre 2 (vs. centre 1)0.54(0.34-0.84)0.41(0.24-0.68)0.55(0.32-0.92)0.46(0.25-0.82)Figure 1.

The effect of total biopsy length on result, stratified by laterality.

Conclusion:

Total biopsy length was weakly associated with a positive TAB result, but differences in results between referral centres independent of biopsy length suggest other selection factors may be important in determining TAB yield. Examination of differences in results between a greater number of referral centres would assist in determining the extent of this variability.

Disclosure of Interests:

None declared

Estimation methods for flow imaging with high frequency ultrasound

This article proposes to estimate slow blood flow with high frequency ultrasound imaging. The proposed technique combines 2 methods. First, a statistical method, called Speckle Flow Imaging (SFI) based on the analysis of changes in the speckle pattern along time, gives an index directly related to the total velocity vector. Secondly, a block matching approach estimates the in-plane velocity components. Results on calibrated flow sequences of blood mimicking fluid have shown good agreement with the statistical model. The quantification of flow is achieved with pulsed flow and is also angle independent when the flow is perpendicular to the ultrasound beam. Speckle Tracking has been evaluated on the same data and has shown good estimation of the in-plane velocity vector when the component of velocity perpendicular to the imaging plane is inferior to 1mm/s. The results of these two methods permit the evaluation of the total 3D velocity field and the orthogonal velocity component relative to the imaging plane. This allows the quantification of blood flow (volumetric per time unit across the sequence).

Krüppel-like factor 4 exhibits antiapoptotic activity following gamma-radiation-induced DNA damage

In response to gamma-radiation-induced DNA damage, organisms either activate cell cycle checkpoint and repair machinery or undergo apoptosis to eliminate damaged cells. Although previous studies indicated that the tumor suppressor p53 is critically involved in mediating both responses, how a cell decides which pathway to take is not well established. The zinc-finger-containing transcription factor, Krüppel-like factor 4 (KLF4), is a crucial mediator for the checkpoint functions of p53 after gamma-irradiation and does so by inhibiting the transition from the G(1) to S and G(2) to M phases of the cell cycle. Here, we determined the role of KLF4 in modulating the apoptotic response following gamma-irradiation. In three independent cell systems including colorectal cancer cells and mouse embryo fibroblasts in which expression of KLF4 could be manipulated, we observed that gamma-irradiated cells underwent apoptosis if KLF4 was absent. In the presence of KLF4, the degree of apoptosis was significantly reduced and cells resorted to checkpoint arrest. The mechanism by which KLF4 accomplished this antiapoptotic effect is by activating expression of the cell cycle arrest gene, p21(WAF1/CIP1), and by inhibiting the ability of p53 to transactivate expression of the proapoptotic gene, BAX. Results of our study illustrate an unexpected antiapoptotic function of KLF4, heretofore considered a tumor suppressor in colorectal cancer, and suggest that KLF4 may be an important determinant of cell fate following gamma-radiation-induced DNA damage.

Reliability and dimensionality of judgments of visually textured materials

We extended perceptual studies of the Brodatz set of textured materials. In the experiments, texture perception for different texture sets, viewing distances, or lighting intensities was examined. Subjects compared one pair of textures at a time. The main task was to rapidly rate all of the texture pairs on a number scale for their overall dissimilarities first and then for their dissimilarities according to six specified attributes (e.g., texture contrast). The implied dimensionality of perceptual texture space was usually at least four, rather than three. All six attributes proved to be useful predictors of overall dissimilarity, especially coarseness and regularity. The novel attribute texture lightness, an assessment of mean surface reflectance, was important when viewing conditions were wide-ranging. We were impressed by the general validity of texture judgments across subject, texture set, and comfortable viewing distances or lighting intensities. The attributes are nonorthogonal directions in four-dimensional perceptual space and are probably not narrow linear axes. In a supplementary experiment, we studied a completely different task: identifying textures from a distance. The dimensionality for this more refined task is similar to that for rating judgments, so our findings may have general application.

Transactivation and growth suppression by the gut-enriched Krüppel-like factor (Krüppel-like factor 4) are dependent on acidic amino acid residues and protein-protein interaction

Gut-enriched Krüppel-like factor (GKLF or KLF4) is a pleiotropic (activating and repressive) transcription factor. This study characterizes the mechanisms of transactivation by GKLF. Using a GAL4 fusion assay, the activating domain of murine GKLF was localized to the 109 amino acid residues in the N-terminus. Site-directed mutagenesis showed that two adjacent clusters of acidic residues within this region are responsible for the activating effect. Transactivation by GKLF involves intermolecular interactions as demonstrated by the ability of wild-type, but not mutated, GKLF to compete with the N-terminal activation domain. In addition, wild-type adenovirus E1A, but not a mutated E1A that failed to bind p300/CBP, inhibited transactivation by the N-terminal 109 amino acids of GKLF, suggesting that p300/CBP are GKLF's interacting partners. A physical interaction between GKLF and CBP was demonstrated by glutathione- S -transferase pull-down and by in vivo co-immuno-precipitation experiments. We also showed that the two acidic amino acid clusters are essential for this interaction, since GKLF with mutations in these residues failed to co-immunoprecipitate with CBP. Importantly, the same mutations abrogated the ability of GKLF to suppress cell growth as determined by a colony suppression assay. These studies therefore provide plausible evidence for a structural and functional correlation between the transactivating and growth-suppressing effects of GKLF.

Tissue prostanoids as biomarkers for chemoprevention of colorectal neoplasia: correlation between prostanoid synthesis and clinical response in familial adenomatous polyposis

Recent studies indicate that sulindac, a nonsteroidal anti-inflammatory drug (NSAID), lowers mucosal prostanoid levels and regresses colorectal adenomas in patients with familial adenomatous polyposis (FAP). To determine whether they are biomarkers for sulindac-mediated chemoprevention of colorectal adenomas, levels of 5 prostanoids [prostaglandin (PG) D2, PGE2, PGF2alpha, thromboxane B2, and 6-keto-PGF1alpha] in the normal-appearing rectal mucosa from 7 FAP patients with a history of subtotal colectomy and ileorectal anastomosis and 4 FAP patients without surgery, were measured in the absence or presence of exogenously added arachidonic acid before the initiation and at the end of 3 months of sulindac treatment. The addition of arachidonic acid resulted in a uniform increase in the levels of all 5 prostanoids although this increase was selectively attenuated in patients with ileorectal anastomosis who took sulindac. In the latter patients, arachidonic acid also augmented the inhibition of prostanoid synthesis by sulindac. In contrast, sulindac failed to attenuate the increase in prostanoid levels resulting from arachidonic acid in patients without previous surgery. Importantly, when measured in the presence of arachidonic acid, the reduction in the levels of all 5 prostanoids due to sulindac was statistically correlated with a reduction in the size and number of adenomas in the two groups of patients combined. These results suggest that tissue prostanoids measured in the presence of arachidonic acid may serve as sensitive and reliable biomarkers in monitoring the clinical responsiveness of FAP patients undergoing chemoprevention for colorectal neoplasia with NSAIDs.

Characterization of the structure and regulation of the murine gene encoding gut-enriched Krüppel-like factor (Krüppel-like factor 4)

Gut-enriched Krüppel-like factor (GKLF, KLF4) is an epithelial-specific transcription factor whose expression is associated with growth arrest. In order to understand the mechanisms regulating expression of the gene encoding GKLF, we isolated a genomic clone containing murine GKLF. The gene spans 5.3 kb and contains four exons. A major start site of transcription was mapped to an adenine residue 601 nt 5' of the translation initiation codon. An additional 1 kb of the 5'-flanking region was sequenced and found to contain multiple cis -elements homologous to the binding sites of several established transcription factors including Sp1, AP-1, Cdx, GATA, and USF. In particular, three closely spaced GC-boxes 5' of the TATA box resemble the established binding site for GKLF. DNase I protection and electrophoretic mobility shift assays verified that recombinant GKLF bound to each of the three GC-boxes. In co-transfection experiments, GKLF transactivated a reporter gene linked to the GKLF 1 kb 5'-flanking region, as did Sp1, Sp3 and Cdx-2. Mutations of one or both of the first and second GC-boxes in the promoter resulted in diminished transactivation by GKLF. These results demonstrate that the 5'-flanking sequence of the mouse GKLF gene functions as a promoter and is subject to autoregulation by its own gene product.

The molecular genetics of colorectal cancer

Colorectal cancer is a major cause of morbidity and mortality among types of cancer in the United States. Significant progress has been made in understanding the molecular mechanisms that lead to it. Much knowledge was obtained through study of genetic changes that occur in individuals with a familial predisposition to colorectal cancer, including familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC) syndromes. The gene with mutations that result in FAP has been identified as adenomatous polyposis coli (APC). Similarly, mutations in several genes that normally function in DNA mismatch repair result in HNPCC. Colorectal cancer is the result of accumulated mutations in several additional oncogenes or tumor suppressor genes, and this information leads to the formulation of a genetic model for the disease. Recent studies have also identified a relatively prevalent polymorphism in the APC gene in Ashkenazi Jews that is associated with an increased risk for colorectal cancer. These studies present a paradigm based on the APC mutation (APC I1307K) for the screening of cancer susceptibility genes in the population at large. Currently available techniques for genetic testing of colorectal cancer are also discussed in this review, along with their ethical implications.

Trench-shaped binding sites promote multiple classes of interactions between collagen and the adherence receptors, alpha(1)beta(1) integrin and Staphylococcus aureus cna MSCRAMM

Most mammalian cells and some pathogenic bacteria are capable of adhering to collagenous substrates in processes mediated by specific cell surface adherence molecules. Crystal structures of collagen-binding regions of the human integrin alpha(2)beta(1) and a Staphylococcus aureus adhesin reveal a "trench" on the surface of both of these proteins. This trench can accommodate a collagen triple-helical structure and presumably represents the ligand-binding site (Emsley, J., King, S. L., Bergelson, J. M., and Liddington, R. C. (1997) J. Biol. Chem. 272, 28512-28517; Symersky, J., Patti, J. M., Carson, M., House-Pompeo, K., Teale, M., Moore, D., Jin, L., Schneider, A., DeLucas, L. J., Höök, M., and Narayana, S. V. L. (1997) Nat. Struct. Biol. 4, 833-838). We report here the crystal structure of the alpha subunit I domain from the alpha(1)beta(1) integrin. This collagen-binding protein also contains a trench on one face in which the collagen triple helix may be docked. Furthermore, we compare the collagen-binding mechanisms of the human alpha(1) integrin I domain and the A domain from the S. aureus collagen adhesin, Cna. Although the S. aureus and human proteins have unrelated amino acid sequences, secondary structure composition, and cation requirements for effective ligand binding, both proteins bind at multiple sites within one collagen molecule, with the sites in collagen varying in their affinity for the adherence molecule. We propose that (i) these evolutionarily dissimilar adherence proteins recognize collagen via similar mechanisms, (ii) the multisite, multiclass protein/ligand interactions observed in these two systems result from a binding-site trench, and (iii) this unusual binding mechanism may be thematic for proteins binding extended, rigid ligands that contain repeating structural motifs.

Decorin is a Zn2+ metalloprotein

Decorin is ubiquitously distributed in the extracellular matrix of mammals and a member of the proteoglycan family characterized by a core protein dominated by leucine-rich repeat motifs. We show here that decorin extracted from bovine tissues under denaturing conditions or produced in recombinant "native" form by cultured mammalian cells has a high affinity for Zn2+ as demonstrated by equilibrium dialyses. The Zn2+-binding sites are localized to the N-terminal domain of the core protein that contains 4 Cys residues in a spacing reminiscent of a zinc finger. A recombinant 41-amino acid long peptide representing the N-terminal domain of decorin has full Zn2+ binding activity and binds two Zn2+ ions with an average KD of 3 x 10(-7) M. Binding of Zn2+ to this peptide results in a change in secondary structure as shown by circular dichroism spectroscopy. Biglycan, a proteoglycan that is structurally closely related to decorin contains a similar high affinity Zn2+-binding segment, whereas the structurally more distantly related proteoglycans, epiphycan and osteoglycin, do not bind Zn2+ with high affinity.

Size-dependent increase in prostanoid levels in adenomas of patients with familial adenomatous polyposis

Recent studies indicate that nonsteroidal anti-inflammatory drugs have a chemopreventive effect against colorectal neoplasia. Nonsteroidal anti-inflammatory drugs inhibit cyclooxygenases, principal enzymes that mediate the formation of prostanoids. To determine whether prostanoids are involved in the pathogenesis of colorectal adenomas, we compared the levels of five major stable metabolic products of the cyclooxygenase pathway in the normal-appearing mucosa and in adenomas of patients with familial adenomatosis polyposis. Of 12 patients tested, 6 had elevated levels of at least one prostanoid in the adenomas. More importantly, the relative levels of three prostanoids [prostaglandin (PG)D2, PGE2, and 6-keto-PGF1alpha] were elevated in adenomas compared to normal-appearing mucosa from the same patients, and the resulting ratios were correlated with the size of the adenoma. These results suggest a role for prostanoids in progression of colorectal polyposis in familial adenomatosis polyposis patients.

Prostaglandin levels in human colorectal mucosa: effects of sulindac in patients with familial adenomatous polyposis

Recent evidence suggests that nonsteroidal antiinflammatory drugs (NSAIDs) may prevent colorectal cancer. The mechanism of action of NSAIDs in chemoprevention is unknown but may be linked to their effect on mucosal prostaglandin levels. Levels of five major prostaglandin metabolites were measured by gas chromatography-mass spectrometry in biopsy specimens of flat rectal mucosa from four patients with familial adenomatous polyposis (FAP) before and after sulindac therapy and from five healthy individuals. The prostaglandin present at highest concentration in rectal mucosa from FAP and control subjects was prostaglandin E2. The concentration of thromboxane B2 alone was significantly elevated in FAP patients compared to controls (P = 0.016). In FAP patients treated with sulindac, all prostaglandin metabolite levels were significantly reduced compared to pretreatment levels (P < 0.05) except prostaglandin D2 (P = 0.07). Prostaglandins D2, E2, F2alpha, and 6-keto-F1alpha levels also were significantly reduced in FAP patients on sulindac compared to healthy controls (P < 0.05). However, interpatient heterogeneity of response to sulindac was evident with changes ranging from +19% to -89%, and the patient with the greatest reductions after sulindac developed colorectal cancer after 35 months of therapy. Sulindac treatment, at drug doses shown to regress colorectal adenomas in FAP patients, has heterogeneous effects on the level of major prostaglandins in their rectal mucosa and may not prevent colorectal cancer due to uncoupling of prostaglandin levels and carcinogenesis.

Identification of the DNA sequence that interacts with the gut-enriched Krüppel-like factor

The gut-enriched Krüppel-like factor (GKLF) is a recently identified eukaryotic transcription factor that contains three C2H2zinc fingers. The amino acid sequence of the zinc finger portion of GKLF is closely related to several Krüppel proteins, including the lung Krüppel-like factor (LKLF), the erythroid Krüppel-like factor (EKLF) and the basic transcription element binding protein 2 (BTEB2). The DNA sequence to which GKLF binds has not been definitively established. In the present study we determined the DNA binding sequence of GKLF using highly purified recombinant GKLF in a target detection assay of an oligonucleotide library consisting of random sequences. Upon repeated rounds of selection and subsequent characterization of the selected sequences by base-specific mutagenesis a DNA with the sequence 5'-G/AG/AGGC/TGC/T-3' was found to contain the minimal essential binding site for GKLF. This sequence is present in the promoters of two previously characterized genes: the CACCC element of the beta-globin gene, which interacts with EKLF, and the basic transcription element (BTE) of the CYP1A1 gene, which interacts with Sp1 and several Sp1-like transcription factors. Moreover, the selected GKLF binding sequence was capable of mediating transactivation of a linked reporter gene by GKLF in co-transfection experiments. Our results establish GKLF as a sequence-specific transcription factor likely involved in regulation of expression of endogenous genes.

Regulation of phosphotransferases in glucose- and xylose-fermenting yeasts

This research examined the titers of hexokinase (HK), phosphofructokinase (PFK), and xylulokinase (XUK) in Saccharomyces cerevisiae and two xylose fermenting yeasts, Pachysolen tannophilus and Candida shehatae, following shifts in carbon source and aeration. Xylose-grown C. shehatae, glucose-grown P. tannophilus, and glucose-grown S. cerevisiae, had the highest specific activities of XUK, HK, and PFK, respectively. XUK was induced by xylose to moderate levels in both P. tannophilus and C. shehatae, but was present only in trace levels in S. cerevisiae. HK activities in P. tannophilus were two to three fold higher when cells were grown on glucose than when grown on xylose, but HK levels were less inducible in C. shehatae. The PFK activities in S. cerevisiae were 1.5 to 2 times higher than in the two xylose-fermenting yeasts. Transfer from glucose to xylose rapidly inactivated HK in P. tannophilus, and transfer from xylose to glucose inactivated XUK in C. shehatae. The patterns of induction and inactivation indicate that the basic regulatory mechanisms differ in the two xylose fermenting yeasts.

Colonic epithelium-enriched protein A4 is a proteolipid that exhibits ion channel characteristics

Expression of the human gene A4 is enriched in the colonic epithelium and is transcriptionally activated on differentiation of colonic epithelial cells in vitro (M. M. Oliva, T. C. Wu, and V. W. Yang. Arch. Biochem. Biophys. 302: 183-192, 1993). A4 cDNA contains an open reading frame that predicts a polypeptide of 17 kDa. To determine the function of the A4 protein, we characterized its biochemical and physiological properties. Hydropathy analysis of deduced A4 amino acid sequence revealed four putative membrane-spanning alpha-helices. The hydrophobic nature of A4 was confirmed by its being extractable with organic solvents. Immunocytochemical studies of cells expressing A4 localized it to the endoplasmic reticulum. Moreover, A4 multimerized in vivo as determined by coimmunoprecipitation experiments. The four-transmembrane topology and biophysical characteristics of A4 suggest that it belongs to a family of integral membrane proteins called proteolipids, some of which multimerize to form ion channels. Subsequent electrophysiological studies of nuclei isolated from microinjected Xenopus laevis oocytes transiently expressing A4 showed the appearance of a 28-pS channel. Thus our studies indicate that A4 is a colonic epithelium-enriched protein localized to the endoplasmic reticulum and that, similar to other proteolipids, A4 multimerizes and exhibits characteristics of an ion channel.

Ornithine decarboxylase and polyamines in familial adenomatous polyposis

Familial adenomatous polyposis (FAP), due to germ-line mutation of the adenomatous polyposis coli (APC) gene, is characterized by development of colorectal adenomas and ultimately colorectal cancer. The usefulness of ornithine decarboxylase (ODC) activity and polyamine levels in normal-appearing colorectal mucosa to stratify risk for colorectal neoplasia by discriminating presymptomatic individuals with germ-line APC mutation (genotype-positive) from genotype-negative family controls was evaluated in 36 at-risk subjects undergoing endoscopic and genetic screening for FAP. ODC activity and levels of putrescine, spermidine, and spermine were significantly higher in presymptomatic genotype-positive patients compared to genotype-negative persons (P = 0.029, <0.001, 0.002, and <0.001, respectively). Moreover, a putrescine level with a cutoff point of 1.5 nmol/mg protein was the most accurate single discriminator of risk status. ODC activity and polyamine levels are significantly elevated in gene carriers of FAP before the development of polyposis, suggesting a role for these compounds in tumorigenesis of FAP. These assays may be useful in evaluating at-risk members of FAP families in which mutation of the APC gene cannot be found.

Eicosanoids and inflammatory bowel disease

IBD is a disease of unknown cause that involves an amplification of the inflammatory response in the intestinal mucosa. Although not the only offending agents leading to the disease, eicosanoids, the collective group of AA metabolites, may a significant role in the pathogenesis of IBD. This article reviewed the biochemical pathways of eicosanoid formation and the clinical relevance of eicosanoids to IBD. Potential strategies designed to interfere with various aspects of AA metabolism were also outlined. Further clinical trials of newer compounds may soon prove them effective in the management of IBD.

The class I alcohol dehydrogenase gene is glucocorticoid-responsive in the rat hepatoma microcell hybrid cell line, 11-3

Expression of the class I alcohol dehydrogenase (ADH) gene in the rat hepatoma microcell hybrid cell line, 11-3, was examined. The steady-state level of ADH mRNA in 11-3 was approximately 2-fold higher than that or rat liver and Fao, the parental cell line of 11-3. Removal of steroid hormones by activated charcoal from the serum in which 11-3 cells were maintained resulted in a significant decrease in the level of ADH transcript. Dexamethasone at a concentration of 1 muM increased the ADH mRNA content in 11-3 in a time-dependent fashion, up to 48 hr after its addition to cells that had first been deprived of steroid hormones. In addition, levels of ADH transcript in cells treated with dexamethasone increased in a dose-dependent manner, and the concentration of dexamethasone required to achieve half-maximal activation was 5 nM. By using the techniques of reverse transcription and polymerase chain reaction, and by taking advantage of a restriction polymorphism present between the rat and mouse ADH cDNA, we found that 11-3 contained both the rat and mouse class I ADH transcripts, although the rat sequence accounted for the great majority. Moreover, levels of both rat and mouse class I ADH transcripts increased in a similarly time-dependent manner in cells treated with dexamethasone. These results indicate that expression of class I ADH gene in 11-3 is high and is regulated by glucocorticoids, making the cell line an excellent model for the in vitro study of ADH expression.

Promoter regulation of a differentially expressed gene in the human colonic epithelial cell lines HT29-18 and HT29-18-C1

Gene A4 is transcriptionally activated upon enterocyte differentiation of the human colonic epithelial cell line HT29-18 and its highly differentiated subclone HT29-18-C1 [Oliva et al., Arch. Biochem. Biophys. 302 (1993) 183-192]. To characterize the mechanisms regulating the differential transcription of A4, we analyzed its immediate 5'-flanking region for regulatory elements. Promoter-linked transfection experiments of progressively deleted A4 5'-flanking sequences fused to the bacterial cat reporter gene suggest the presence of one negative and two positive DNA elements within the first 371 bp of the A4 promoter (pA4). DNase I footprint and electrophoretic mobility shift assays demonstrate that one positive element which contains the core binding sequence for the transcription factor, Sp1, mediates an equal level of transcription in the two cell types. The second positive element, localized between nucleotide positions--169 and -152, contains a sequence previously unrecognized as a transcription factor-binding site. This element mediates a twofold increase in the activity of pA4 in HT29-18-C1, as compared to HT29-18. Furthermore, nuclear extracts obtained from HT29-18-C1 contain a higher binding activity for this element than those from HT29-18. Southwestern blot analysis suggests that the protein interacting with this element has an estimated molecular mass of 50 kDa. We conclude that this protein may be involved in the differential regulation of A4 in these intestinal cell lines.

The 5-lipoxygenase pathway in cultured human intestinal epithelial cells

Leukotrienes (LTs), the 5-lipoxygenase (5-LOX) metabolites of arachidonic acid, have roles in many biological processes relevant to the gastrointestinal tract, including intestinal inflammation. We screened two well-known human intestinal epithelial cell lines, HT29 and Caco-2, for evidence of LT-associated enzyme transcripts and LT synthesis. Northern blot analysis of total RNA from both intestinal lines demonstrated high levels of transcripts for LTA4 hydrolase, a multisubstrate enzyme that converts the 5-LOX metabolite, LTA4, to LTB4. With total RNA, the 5-LOX transcript was detected only in HT29. Caco-2 failed to show 5-LOX message even with poly A-containing RNA, although the transcript could be amplified with the polymerase chain reaction. Messenger RNA for FLAP, the 5-lipoxygenase-activating protein, was detectable in both cell lines, but only with poly A-containing RNA. In a sonicated cell preparation, HT29, but not Caco-2, revealed detectable levels of 5-HETE and LTB4. These results suggest that certain intestinal epithelial cells possess a limited capacity to synthesize LTs.

High-efficiency transformation of Pichia stipitis based on its URA3 gene and a homologous autonomous replication sequence, ARS2

This paper describes the first high-efficiency transformation system for the xylose-fermenting yeast Pichia stipitis. The system includes integrating and autonomously replicating plasmids based on the gene for orotidine-5'-phosphate decarboxylase (URA3) and an autonomous replicating sequence (ARS) element (ARS2) isolated from P. stipitis CBS 6054. Ura- auxotrophs were obtained by selecting for resistance to 5-fluoroorotic acid and were identified as ura3 mutants by transformation with P. stipitis URA3. P. stipitis URA3 was cloned by its homology to Saccharomyces cerevisiae URA3, with which it is 69% identical in the coding region. P. stipitis ARS elements were cloned functionally through plasmid rescue. These sequences confer autonomous replication when cloned into vectors bearing the P. stipitis URA3 gene. P. stipitis ARS2 has features similar to those of the consensus ARS of S. cerevisiae and other ARS elements. Circular plasmids bearing the P. stipitis URA3 gene with various amounts of flanking sequences produced 600 to 8,600 Ura+ transformants per micrograms of DNA by electroporation. Most transformants obtained with circular vectors arose without integration of vector sequences. One vector yielded 5,200 to 12,500 Ura+ transformants per micrograms of DNA after it was linearized at various restriction enzyme sites within the P. stipitis URA3 insert. Transformants arising from linearized vectors produced stable integrants, and integration events were site specific for the genomic ura3 in 20% of the transformants examined. Plasmids bearing the P. stipitis URA3 gene and ARS2 element produced more than 30,000 transformants per micrograms of plasmid DNA. Autonomously replicating plasmids were stable for at least 50 generations in selection medium and were present at an average of 10 copies per nucleus.

The adult enhancer factor-1, a Drosophila melanogaster transcriptional repressor, modulates the promoter activity of the rat class-I alcohol dehydrogenase-encoding gene

Expression of the Drosophila melanogaster alcohol dehydrogenase-encoding gene (ADH) in the adult fat body is controlled by the ADH adult enhancer site (AAE). The D. melanogaster transcription repressor, adult enhancer factor-1 (AEF-1), binds to AAE at a site which overlaps with a sequence recognized by the mammalian transcription factor, CCAAT/enhancer-binding protein alpha [C/EBP alpha; Falb and Maniatis, Genes Dev. 6 (1992a) 454-465]. C/EBP alpha also activates the promoter of the rat class-I ADH gene in a sequence-specific manner [Potter et al., Arch. Biochem. Biophys. 285 (1991a) 246-251]. In this study, we explored the possibility that D. melanogaster AEF-1 influences transcription of the rat class-I ADH. By DNase I footprint analysis, bacterially produced AEF-1 protects a region of DNA between nucleotides (nt) -22 and -36 of the rat class-I ADH promoter (pADH), just 5' to the binding site of C/EBP alpha, a result confirmed by the electrophoretic mobility shift assay (EMSA). Co-transfection of a rat pADH-CAT reporter construct with expression vectors containing C/EBP alpha, AEF-1, or both, indicates that AEF-1 inhibits induction of the rat pADH by C/EBP alpha. Moreover, rat liver nuclear extracts appear to contain AEF-1-like-binding activities to AAE by EMSA. These experiments suggest an evolutionarily conserved mechanism by which AEF-1 modulates expression of the D. melanogaster and rat ADH genes.

Characterization of the 5'-flanking sequence of rat class I alcohol dehydrogenase gene

Expression of the rat class I alcohol dehydrogenase (ADH) gene is highest in the liver and regions of the intestine. We characterized over 3 kilobases of the gene's 5'-flanking region by sequencing and transient transfection. Alignment of the flanking sequence of the rat gene with those of the mouse and human class I genes revealed a cis-acting element, known to be a functional glucocorticoid response element in the human gene and conserved in the mouse, is interrupted in the rat promoter by a 490-base pair processed retropseudogene of the ribosomal protein S25. Southern analysis indicated that this inserted element is present in the class I ADH promoters of multiple strains of rat. Transfection analysis of the rat and mouse promoters showed that the mouse, but not the rat promoter, is inducible by dexamethasone. Electrophoretic mobility shift assays using nuclear extracts from dexamethasone-treated cells confirmed that the mouse's element interacts with the glucocorticoid receptor. Transient transfection of the 5'-flanking region of the rat gene linked to a human growth hormone reporter demonstrated the liver and intestinal specificity of the rat promoter. Two positive elements, one from nucleotides -1,327 to -977 and the other from -241 to -12, were shown to support high levels of reporter activity. In addition, a suppressive element was localized between nucleotides -403 and -241, a region of DNA situated within the domain of the S25 ribosomal protein pseudogene.

Expression of the class I alcohol dehydrogenase gene in developing rat fetuses

Class I alcohol dehydrogenase (ADH) is the principal enzyme responsible for ethanol oxidation in mammals. Although primarily regarded as an enzyme that functions in the adult, Class I ADH has been reported to be present in fetal tissues. By in situ hybridization, we demonstrated the tissue localization of the Class I ADH transcript in developing rat fetuses between Days 15 (E15) and 18 (E18) of gestation. Abundant transcripts were present in epidermis, lung, and urinary bladder. In these tissues, the messages were localized primarily to the superficial layer of the epithelium and increased with development. The liver exhibited significant signals only in the E18 fetus, when parenchymal hepatocytes first appeared. The E15 and E16 small intestines, with their epithelium arranged in a stratified fashion, displayed signals in the submucosal mesenchymal layer. By E17, a rearrangement of the intestinal epithelium into an almost monolayer configuration was observed. This change was associated with a redistribution of the ADH transcript to the surface of the epithelium. Further relocation of the messages was noted in the adult small intestine, in which they became concentrated in the base of the crypt. These findings indicate that expression of the rat class I ADH gene follows a dynamic course in specific epithelial tissues during fetal development. In addition, the apparent superficial localization of the ADH message in most of these tissues suggests that ADH functions in metabolizing either endogenously or exogenously derived alcohol substrates present in the fetal environment.

Cellular localization of the class I alcohol dehydrogenase transcript in adult rat tissues

The mammalian class I alcohol dehydrogenase is the principal enzyme responsible for ethanol metabolism. While it is regarded primarily as a liver-specific enzyme, class I alcohol dehydrogenase is known to be present in a number of extrahepatic tissues. The purpose of the current study is to define the tissue and cellular distribution of the dehydrogenase transcript in four rat tissues previously shown to contain high levels of mRNA: the liver, the proximal small intestine, the colon and the testis. Localization of the transcript was examined in formalin-fixed, paraffin-embedded rat tissues by in situ hybridization using radioactively labelled antisense rat alcohol dehydrogenase RNA probe. In the liver, the dehydrogenase message is localized primarily to the perivenous hepatocytes. In the proximal small intestine and the colon, the message follows a vertical gradient of distribution along the crypt-villus and the crypt-surface epithelium axes, respectively, with the base of the crypt exhibiting the greatest concentration. In the testis, the message is localized primarily to cells in the interstitium. These findings illustrate a highly compartmentalized nature of distribution of the class I alcohol dehydrogenase transcript in the tissues studied and may help to elucidate the metabolic functions of this enzyme in these tissues.

Isolation and characterization of a differentiation-dependent gene in the human colonic cell line HT29-18

The human colonic epithelial cell line HT29, and its clonal derivatives HT29-18 and HT-29-18-C1, differentiate in vitro. Differential screening of a subtraction cDNA library enriched for sequences unique to HT29-18-C1, a highly differentiated subclone of HT29-18, resulted in the isolation of a differentiation-dependent cDNA clone, A4. A full-length clone encoding A4 was obtained and sequenced to its entirety. It is 945 bp in length and contains an open reading frame (ORF) of 456 bp. The amino acid sequence deduced from the ORF reveals a polypeptide of 152 amino acids with a predicted molecular mass of 17,000 Da, a size confirmed by coupled in vitro transcription and translation directed by the full-length A4 cDNA. This polypeptide contains four potential membrane-spanning domains and consensus sequences for N-linked glycosylation as well as phosphorylation sites for protein kinase C and casein kinase II. Comparison of A4 to published DNA and protein sequences revealed no significant homology. Genomic Southern blot analysis suggests that the gene is present in a single copy within the human genome and is conserved in the rat. Northern blot analysis of RNA obtained from various rat tissues shows that the expression of the A4 gene is tissue-selective and is enriched in colonic mucosa. In situ hybridization using human intestinal tissues indicates that the expression of A4 follows a gradient along the crypt-to-villus axis with the most abundant message occurring in the lower half of the crypt. Furthermore, nuclear run-on assays suggest that the induction of the A4 gene during differentiation of HT29-18 is regulated at a transcriptional level. A clone was isolated from a human genomic library and found to contain all five exons of A4. S1 nuclease analysis localized the start site of transcription to an adenosine residue 91 nucleotides upstream from the ATG translation initiation codon. Examination of the immediate sequence 5' to the mRNA start site reveals no TATA box and multiple known enhancer sequences. A4 is also noted to share certain features with the gene encoding the cystic fibrosis transmembrane conductance regulator protein. They include a similar vertical distribution of expression along the intestinal epithelium, enhanced transcription upon differentiation of HT29-18, and multiple shared putative regulatory sequences in the promoter regions. Further characterization of the mechanisms regulating expression of the A4 gene could contribute to the understanding of mammalian intestinal differentiation.

Regulation of the rat class I alcohol dehydrogenase gene by growth hormone

Growth hormone (GH) increases the transcription of the rat class I alcohol dehydrogenase (ADH) gene. Two transcription factors, the CCAAT/enhancer binding protein (C/EBP) and the liver activator protein (LAP), were previously shown to bind to the ADH promoter at nucleotide positions -11 to -22 relative to the start-site of transcription and to activate the ADH promoter in co-transfection experiments. In this study, exposure of cultured rat hepatocytes to GH (1 micrograms/ml) for 4 days increased LAP mRNA, but not C/EBP mRNA, in conjunction with an increase in ADH mRNA. GH, in transient transfection experiments of primary rat hepatocyte cultures, activated an ADH promoter-reporter gene construct containing the C/EBP binding site, but failed to activate a construct containing a 4-bp mutation at this site. These results suggest that the effect of GH in enhancing ADH promoter activity is mediated by LAP binding to the C/EBP site.

Enhancer-site downstream binding protein activity is enriched in rat tissues that express the class I alcohol dehydrogenase gene

The activity of the rat class I alcohol dehydrogenase (ADH) is enriched in certain tissues including the liver, intestine and testis. The tissue-specific expression of the gene encoding ADH in the rat was studied and found to closely correlate with tissue isozymic activity. A factor designated enhancer-site downstream binding protein (EDBP) was recently identified in the rat liver and found to interact with the proximal promoter of the class I ADH gene. The distribution of EDBP in nuclear extracts obtained from various tissues was examined based on its sequence-specific DNA binding property and found to correlate with tissue ADH expression. These findings suggest that EDBP is potentially a positive regulatory factor which is involved in controlling the tissue-specific expression of the ADH gene.

Regulation of cystic fibrosis transmembrane conductance regulator (CFTR) gene transcription and alternative RNA splicing in a model of developing intestinal epithelium

Transcriptional and post-transcriptional regulation of CFTR (cystic fibrosis transmembrane conductance regulator) gene expression was studied in HT29 cells. It is known that the abundance of CFTR mRNA increases during differentiation of pluripotent HT29-18 cells and is maintained at high levels in the stably differentiated HT29-18-C1 subclone. Nuclear run-on assays suggest that increased transcription of the CFTR gene explains the increased abundance of total CFTR mRNA in differentiated HT29 cells. The increased transcription cannot be ascribed to cell cycle-dependent expression of the CFTR gene or to changes in CFTR gene copy number between subcloned cells. Similar to native tissue cells, differentiated HT29 cells contain low copy numbers of CFTR transcripts (1-5/cell), and a portion of the CFTR transcripts are alternatively spliced to remove exon 9 (and make 9-mRNA). During differentiation of HT29-18 cells, the absolute amount of full-length CFTR mRNA increases 8-fold, whereas the amount of 9- mRNA increases 18-fold. The fraction of 9- mRNA in the CFTR mRNA pool is increased in differentiated HT29 cells. The results show that gene transcription regulates the abundance of CFTR transcripts and that regulatory control of alternative RNA splicing may also be a cellular mechanism to modulate CFTR function.

The first 22 base pairs of the proximal promoter of the rat class I alcohol dehydrogenase gene is bipartite and interacts with multiple DNA-binding proteins

The rat class I alcohol dehydrogenase (ADH) gene is primarily expressed in the liver. We previously showed that the liver-enriched transcription factor, the CCAAT/enhancer binding protein (C/EBP), binds to the proximal promoter of the rat class I ADH gene between positions -11 and -22 relative to the start site of transcription. We now demonstrate that another transcription factor, the liver activator protein (LAP), also interacts with the same region of the promoter based on the following observations: (1) LAP synthesized by in vitro transcription and translation of cloned cDNA sequence forms complexes with an oligonucleotide containing the C/EBP-binding sequence within the ADH promoter as determined by the electrophoretic mobility shift assay (EMSA), (2) purified LAP interacts with the proximal ADH promoter when analyzed by the DNase I protection assay, and (3) an ADH promoter-reporter gene construct containing the C/EBP-binding site is transactivated by an eukaryotic expression vector containing the LAP sequence. EMSA of an oligonucleotide containing the first 22 base pairs (between positions -1 and -22) of the ADH promoter with rat liver nuclear extracts (RLNE) resulted in the formation of two major complexes. Complex 1 was competed away by a heterologous oligonucleotide containing a C/EBP-binding site within the promoter of the adipocyte 422 (aP2) gene, while complex 2 was not. Additional competition experiments with the ADH or 422 (aP2) oligonucleotide using either RLNE or extracts from 3T3-L1 adipocytes demonstrated that complex 1 contains either C/EBP or LAP, while complex 2 contains a DNA-binding protein that binds to a novel sequence 5'-TGGCCCAGTT-3' between positions -1 and -10 of the ADH promoter. Ultraviolet cross-linking between RLNE and a labeled oligonucleotide containing the above sequence indicates that this protein, designated EDBP (for enhancer-site downstream binding protein), has an estimated molecular weight of 47 kDa, which is larger than that reported for either C/EBP (42 kDa) or LAP (36 kDa).

Genetic transformation of Aureobasidium pullulans

Aureobasidium pullulans strain Y117 was transformed to hygromycin resistance using plasmid pDH33, which contains the bacterial hygromycin B phosphotransferase gene (hph) fused to promoter elements of the Aspergillus niger glucoamylase gene (glaA). Southern hybridizations of transformants revealed multiple, integrated copies of the vector. The glaA promoter was not induced by starch in A. pullulans as it is in A. niger; however, the transcriptional start points were the same in both species.

The upstream stimulatory factor binds to and activates the promoter of the rat class I alcohol dehydrogenase gene

The gene encoding rat class I alcohol dehydrogenase (ADH) is expressed primarily in the liver. Recent studies in our laboratories indicate that multiple cellular factors present in the rat liver interact with various regions of the promoter of this gene. One of the regions contains the sequence 5'-CACATG-3' that has an "E box" homology to which a number of transcription factors containing the basic helix-loop-helix motif bind. We now demonstrate that the human transcription factor, upstream stimulatory factor (USF), a basic helix-loop-helix-containing protein, binds to and activates the promoter of the rat class I ADH gene. Electrophoretic mobility shift assays of labeled oligonucleotide containing the 5'-CACATG-3' sequence within the ADH promoter revealed the formation of multiple DNA-protein complexes when nuclear extracts obtained from adult rat liver were used. The binding of proteins to the DNA could be competed away with an oligonucleotide specifying a sequence within the adenovirus major late promoter (MLP) that had previously been shown to bind USF. Similar complexes were observed when electrophoretic mobility shift assays of labeled MLP oligonucleotide were performed with rat liver nuclear extracts. Conversely, nuclear extracts isolated from HeLa cells, cells known to have abundant USF, contain factors that interact with the sequence present in the ADH promoter. This interaction could be competed efficiently by the MLP oligonucleotide. USF synthesized in an in vitro transcription and translation system also binds to the ADH promoter as well as to the MLP. In addition, antiserum directed against USF recognizes factors present in the rat liver nuclear extracts that interact with the ADH promoter. Furthermore, transcription directed from both the ADH and the adenovirus major late promoters was inhibited by an oligonucleotide representing the USF-binding site within the ADH promoter in a cell-free in vitro transcription system. Lastly, an ADH promoter-reporter gene construct was transactivated by an eukaryotic expression vector containing USF in HepG2 cells co-transfected with the two constructs. These experiments demonstrate that USF is present in the rat liver and that it binds to and activates the promoter of the rat class I ADH gene in a sequence-specific manner.

Molecular cloning and expression of a cDNA encoding the rabbit ileal villus cell basolateral membrane Na+/H+ exchanger

A cDNA clone encoding a rabbit ileal villus cell Na+/H+ exchanger was isolated and its complete nucleotide sequence was determined. The cDNA is 4 kb long and contains 322 bp of 5'-untranslated region, 2451 bp of open reading frame and 1163 bp of 3'-untranslated area, with 70%, 91% and 40% identity to the human sequence, respectively. Amino acid sequence deduced from the longest open reading frame indicated a protein of 816 residues (predicted Mr 90,716) which exhibits 95% amino acid identity to the human Na+/H+ exchanger. The two putative glycosylation sites in the human Na+/H+ exchanger are conserved in this protein, suggesting that it is a glycoprotein. Stable transfection of the cDNA into an Na+/H+ exchanger deficient fibroblast cell line, established Na+/H+ exchange. The Na+/H+ exchanger was stimulated by serum and a phorbol ester but not by 8-Br-cAMP. In Northern blot analysis, the cDNA hybridized to a 4.8 kb message in rabbit ileal villus cells, kidney cortex, kidney medulla, adrenal gland, brain and descending colon and to a 5.2 kb message in cultured human colonic cancer cell lines, HT29-18 and Caco-2. In immunoblotting, a polyclonal antibody raised against a fusion protein of beta-galactosidase and the C-terminal 158 amino acids of the human Na+/H+ exchanger identified a rabbit ileal basolateral membrane protein of 94 kd and only weakly interacted with the ileal brush border membrane. In immunocytochemical studies using ileal villus and crypt epithelial cells, the same antibody identified basolateral and not brush border epitopes. Restriction analysis of genomic DNA with a 462 bp PstI-AccI fragment of the rabbit Na+/H+ exchanger strongly suggests the existence of closely related Na+/H+ exchanger genes. The near identity of the basolateral Na+/H+ exchanger and the human Na+/H+ exchanger plus the ubiquitous expression of this message suggests that the ileal basolateral Na+/H+ exchanger is the 'housekeeping' Na+/H+ exchanger.

Neuropsychological performance in medicated and unmedicated patients with Tourette's disorder

OBJECTIVE

To date, there have been no formal investigations of neuropsychological performance in patients with Tourette's disorder who are taking psychotropic medications. The authors conducted this study to provide such information.

METHOD

They examined the neuropsychological performance of 96 patients 6-18 years old who met DSM-III-R criteria for Tourette's disorder; 51 of these patients were taking neuroleptic medications and 45 were not. The groups were well matched with regard to age, sex, education, and duration of symptoms. Each group was given a complete neuropsychological test battery as well as instruments rating symptoms of Tourette's disorder, obsessive-compulsive characteristics, and other behavioral disturbances.

RESULTS

The patients taking medications did not differ from those not taking medications on any of the neuropsychological, intellectual, or educational measures. In addition, the groups did not differ with regard to level of Tourette's disorder symptoms.

CONCLUSIONS

The results of this investigation suggest that patients with Tourette's disorder who do not experience intolerable side effects from neuroleptic medications are able to perform on educational, intellectual, and neuropsychological tests at a level comparable to that of unmedicated patients. These results have positive implications for patients with Tourette's disorder who respond to neuroleptic medications.