Primitive neuroectodermal tumors of the brainstem: investigation of seven cases

OBJECTIVE

We discuss the clinical aspects, pathology, and molecular genetics of 7 patients with primitive neuroectodermal tumors (PNETs) arising in the brainstem that were treated at our institution from 1986 through 1995. Most neuro-oncologists avoid performing biopsies in children with pontine tumors. This article raises the question as to whether biopsies should be performed, because treatment recommendations might differ if a PNET was diagnosed rather than a pontine glioma.

PATIENTS AND METHODS

We reviewed the clinical neuro-oncology database and the files of the Division of Neuropathology at New York University Medical Center from 1986 through 1995 and identified 7 histologically confirmed PNETs arising in the brainstem among 146 pediatric brainstem tumors. The clinical, neuroradiological, and neuropathological data were reviewed. Postmortem examinations were performed in 2 cases. Formalin-fixed, paraffin-embedded tumor tissues were also available in 6 of 7 patients that were tested for p53 gene mutations using single-strand conformation polymorphism analysis. We also tested 9 cerebellar PNETs, 9 brainstem gliomas, and 3 normal brains for p53 gene mutations as controls.

RESULTS

All 7 patients presented with focal cranial nerve deficits, and 2 were also hemiparetic. The median age at diagnosis was 2.7 (1-8 years). Magnetic resonance imaging (MRI) characteristics included a focal intrinsic exophytic nonenhancing brainstem lesion that had low T1-weighted and high T2-weighted signals. Hydrocephalus was present in 5 patients at diagnosis, 3 of whom had leptomeningeal dissemination. Meningeal dissemination occurred later in the course of the disease in 3 other patients. Five children required shunts at diagnosis and another 2 at recurrence. Despite therapy, all 7 PNET patients died within 17 months of diagnosis with a mean survival of 8 (4-17) months. No mutation in the p53 gene was detected.

CONCLUSIONS

Brainstem PNETs tend to arise at a younger age than brainstem gliomas and medulloblastomas. The MRI pattern suggests a localized rather than a diffuse intrinsic nonenhancing brainstem tumor. Like other PNETs, brainstem PNETs have a high predilection to disseminate within the central nervous system. The absence of p53 mutations is similar to other PNETs. Despite their origin close to the cerebellum, brainstem PNETs exhibit a more aggressive behavior and result in worse clinical outcomes than do cerebellar PNETs.

Intracranial fibrosarcoma arising 5 years after chemotherapy alone for glioblastoma multiforme in a child

We present a child diagnosed with glioblastoma multiforme during infancy and successfully treated with the 'eight-in-one' chemotherapy regimen, who developed an intracranial fibrosarcoma 5 years later. After resection of the fibrosarcoma, she received cranial radiation therapy and high dose chemotherapy with bone marrow transplant. She remains alive and recurrence-free 7 years following the diagnosis of her second intracranial malignancy.

An alpha-particle emitting antibody ([213Bi]J591) for radioimmunotherapy of prostate cancer

A novel alpha-particle emitting monoclonal antibody construct targeting the external domain of prostate-specific membrane antigen (PSMA) was prepared and evaluated in vitro and in vivo. The chelating agent, N-[2-amino-3-(p-isothiocyanatophen-yl)propyl]-trans-cyclohexane-1, 2-diamine-N,N',N',N'',N''-pentaacetic acid, was appended to J591 monoclonal antibody to stably bind the 213Bi radiometal ion. Bismuth-213 is a short-lived (t 1/2 = 46 min) radionuclide that emits high energy alpha-particles with an effective range of 0.07-0.10 mm that are ideally suited to treating single-celled neoplasms and micrometastatic carcinomas. The LNCaP prostate cancer cell line had an estimated 180,000 molecules of PSMA per cell; J591 bound to PSMA with a 3-nM affinity. After binding, the radiolabeled construct-antigen complex was rapidly internalized into the cell, carrying the radiometal inside. [213Bi]J591 was specifically cytotoxic to LNCaP. The LD50 value of [213Bi]J591 was 220 nCi/ml at a specific activity of 6.4 Ci/g. The potency and specificity of [213Bi]J591 directed against LNCaP spheroids, an in vitro model for micrometastatic cancer, also was investigated. [213Bi]J591 effectively stopped growth of LNCaP spheroids relative to an equivalent dose of the irrelevant control [213Bi]HuM195 or unlabeled J591. Cytotoxicity experiments in vivo were carried out in an athymic nude mouse model with an i.m. xenograft of LNCaP cells. [213Bi]J591 was able to significantly improve (P < 0.0031) median tumor-free survival (54 days) in these experiments relative to treatment with irrelevant control [213Bi]HuM195 (33 days), or no treatment (31 days). Prostate-specific antigen (PSA) was also specifically reduced in treated animals. At day 51, mean PSA values were 104 ng/ml +/- 54 ng/ml (n = 4, untreated animals), 66 ng/ml +/- 16 ng/ml (n = 6, animals treated with [213Bi]HuM195), and 28 ng/ml +/- 22 ng/ml (n = 6, animals treated with [213Bi]J591). The reduction of PSA levels in mice treated with [213Bi]J591 relative to mice treated with [213Bi]HuM195 and untreated control animals was significant with P < 0.007 and P < 0.0136, respectively. In conclusion, a novel [213Bi]-radiolabeled J591 has been constructed that selectively delivers alpha-particles to prostate cancer cells for potent and specific killing in vitro and in vivo.

Measuring compliance with preventive care guidelines: standardized patients, clinical vignettes, and the medical record

OBJECTIVE

To determine how accurately preventive care reported in the medical record reflects actual physician practice or competence.

DESIGN

Scoring criteria based on national guidelines were developed for 7 separate items of preventive care. The preventive care provided by randomly selected physicians was measured prospectively for each of the 7 items. Three measurement methods were used for comparison: (1) the abstracted medical record from a standardized patient (SP) visit; (2) explicit reports of physician practice during those visits from the SPs, who were actors trained to present undetected as patients; and (3) physician responses to written case scenarios (vignettes) identical to the SP presentations.

SETTING

The general medicine primary care clinics of two university-afflliated VA medical centers.

PARTICIPANTS

Twenty randomly selected physicians (10 at each site) from among eligible second- and third-year general internal medicine residents and attending physicians.

MEASUREMENTS AND MAIN RESULTS

Physicians saw 160 SPs (8 cases x 20 physicians). We calculated the percentage of visits in which each prevention item was recorded in the chart, determined the marginal percentage improvement of SP checklists and vignettes over chart abstraction alone, and compared the three methods using an analysis-of-variance model. We found that chart abstraction underestimated overall prevention compliance by 16% (P < .01) compared with SP checklists. Chart abstraction scores were lower than SP checklists for all seven items and lower than vignettes for four items. The marginal percentage improvement of SP checklists and vignettes to performance as measured by chart abstraction was significant for all seven prevention items and raised the overall prevention scores from 46% to 72% (P < .0001).

CONCLUSIONS

These data indicate that physicians perform more preventive care than they report in the medical record. Thus, benchmarks of preventive care by individual physicians and institutions that rely solely on the medical record may be misleading, at best.

N1-(Benzenesulfonyl)tryptamines as novel 5-HT6 antagonists

N-Benzenesulfonyl-5-methoxy-N,N-dimethyltryptamine (BS/5-OMe DMT; 5) was shown to bind at human 5-HT6 serotonin receptors with high affinity (Ki = 2.3 nM) relative to serotonin (Ki = 78 nM). Structural variation failed to result in significantly enhanced affinity. BS/5-OMe DMT acts as an antagonist of 5-HT-stimulated adenylate cyclase (pA2 = 8.88 nM) and may represent the first member of a novel class of 5-HT6 antagonists.

Age-related changes in gastric mucosal repair and proliferative activities in rats exposed acutely to aspirin

The present study was designed to determine whether there are any age-related changes in the repair of acute gastric mucosal injury induced by aspirin in Fischer 344 rats. We have also examined the influence of aging on gastric mucosal proliferative activities, a major component of gastric mucosal defense and repair mechanisms. Our data demonstrated that aging was associated with significant delays in both resolution of gross mucosal injury and regeneration of the injured gastric mucosa. However, there were no correlations between the regeneration of the injured gastric mucosa and gastric mucosal expression of proliferating cell nuclear antigen and transforming growth factor-alpha immunoreactivities.

Regulation of the Pcl7-Pho85 cyclin-cdk complex by Pho81

Saccharomyces cerevisiae strains lacking a functional Pho85 cyclin-dependent kinase (cdk) exhibit a complex phenotype, including deregulation of phosphatase genes controlled by the transcription factor Pho4, slow growth on rich media, failure to grow using galactose, lactate or glycerol as a carbon source and hyperaccumulation of glycogen. The ability of Pho85 to regulate the transcription factor Pho4 is mediated by its association the Pho80 cyclin. Some other regulatory functions of the Pho85 cdk have been shown to be mediated via its interaction with a recently identified family of Pho80-related cyclins (Pcls). Here, we show that the poorly characterized Pho80-like protein Pcl7 forms a functional kinase complex with the Pho85 cdk, and that the activity of this complex is inhibited in response to phosphate starvation. Additionally, we show that Pcl7 interacts with the phosphate-regulated cyclin-cdk inhibitor Pho81, and that the regulation of the Pcl7-Pho85 complex in response to changes in phosphate levels is dependent on Pho81. Thus, we demonstrate for the first time that the Pho81 regulator is not dedicated to regulating Pho80, but may act to co-ordinate the activity of both the Pho80-Pho85 and Pcl7-Pho85 cyclin-cdk complexes in response to phosphate levels. We also demonstrate that expression of Pcl7 is cell cycle regulated, with maximal activity occurring in mid to late S-phase, perhaps suggesting a role for Pcl7 in cell cycle progression. Finally, we describe the phenotype of pcl7Delta and pcl6Delta yeast strains that have defects in carbon source utilization.

Induction of osteopontin gene expression during mammary gland involution and effects of glucocorticoid on its expression in mammary epithelial cells

To understand the molecular mechanisms of mammary gland involution, an involution-induced clone was identified from a cDNA library of mouse mammary gland by differential screening. Characterization of a clone by sequencing and northern analysis showed that expression of the osteopontin gene was induced during involution of mouse mammary gland. But induction of the osteopontin gene was not observed in apoptotic HC11 mammary epithelial cells under serum starvation. In HC11 cells, dexamethasone treatment from the seeding stage showed five-fold induction of osteopontin gene expression, but the expression was not changed when dexamethasone was added to confluent cells.

Assessment of physical activity with a single global question in a large, multiethnic sample of midlife women

This study compared responses from 13,621 African-American, Chinese, Hispanic, Japanese, and White women to a single, global physical activity question. Respondents aged 40-55 years were randomly selected from seven geographic locations in the United States for the 1996-1997 cross-sectional survey of the Study of Women's Health Across the Nation, a longitudinal, observational study of the menopause transition. Respondents rated their activity level as much less, less, the same as, more, or much more than other women their age. Physical activity rating varied minimally by race/ethnicity. The proportions of women who rated themselves much less active and much more active ranged from 3.1% for Whites to 4.8% for Japanese and from 13.6% for Japanese to 16.4% for African Americans, respectively. Multiple logistic regression models, stratified by race/ethnicity, showed independent associations between a low level of activity and higher body mass index, poor health, functional impairment, perceived stress, difficulty sleeping, and not being employed. A high level of activity was associated with excellent health, single marital status, higher education, lower body mass index, and older age. These findings suggest that a comparative rating of physical activity may rank women by activity level within a specific racial/ethnic group but may not capture differences across racial/ethnic groups.

Accuracy of cyclosporin measurements made in capillary blood samples obtained by skin puncture

International consensus guidelines suggest that cyclosporin should be measured in whole blood. In some instances it may be advantageous to collect capillary blood, by a finger or ear prick method. However, drug concentrations in skin-puncture blood may not necessarily correlate with those measured in venous blood. This study compared cyclosporin concentrations in blood collected from the fingertip or earlobe with blood collected by standard venipuncture. Patient preference for each of the blood collection methods was also assessed. Specimens were obtained from organ transplant patients receiving cyclosporin, using each of the three methods: venipuncture, finger prick, and earlobe prick. The samples were assayed using a specific radioimmunoassay and the results were compared. In the 102 sets of samples collected, the mean difference (+/- standard deviation) in cyclosporin concentration between finger prick and venipuncture and ear prick and venipuncture was 2.6% (+/- 9.5%) and 2.7% (+/- 12.1%), respectively, while the comparable median (IQR) differences were 1.9% (-3.4% to +6.6%) and -1.1% (-2.8% to +7.2%), respectively. A high degree of correlation was observed between finger prick and venipuncture or ear prick and venipuncture or ear prick and finger prick (r2 > 0.86). Of the three methods of blood collection, finger prick was the patients' preferred method (P < 0.01). These data suggest that capillary blood collected by skin puncture is suitable for use in cyclosporin blood monitoring and acceptable to patients.

Interrelationship of apoptosis, mutation, and cell proliferation in N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced medaka carcinogenesis model

The present study examined the interrelationship of GSH depletion, apoptosis, mutation, and cell proliferation following carcinogen exposure. Medaka (Oryzias latipes) were investigated following a 28 day, three times/week pulse exposure to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Fish (5 weeks old) were exposed to MNNG at concentrations of 0, 0.5, and 1 mg l(-1) and reared for 3, 5 and 7 more months after the last day of exposure. GSH levels were decreased in the higher concentration groups and longer-reared groups. Flow cytometric analysis revealed that fish from the groups reared 3 and 5 months showed active apoptotic changes in the dose- and time-dependent manner, but the group reared 7 months had fewer apoptotic, rather showed more necrotic and carcinogenic alterations. Mutational responses were detected by an arbitrarily primed polymerase chain reaction (AP-PCR) fingerprinting method using whole body DNA samples as templates and pBR primer. A mutational change was expressed by a loss or gain of a band. There was a time-dependent mutational change, but no distinctive concentration-dependent one. A band from normal fish sample that disappeared after treatment of MNNG was excised and sequenced. The band had an 869 base pair-long sequence, however, there was no putative protein-coding region based on an analysis by DNAsis. Spindle cell sarcomas invading muscle were detected on the whole body sections from three of ten fish examined, and immunohistochemical analysis with PCNA showed that tumor cells were actively proliferating. However, terminal deoxynucleotidyl transferase (TdT) assay showed that tumored fish still had active apoptotic cell changes in the tissues without tumor. This study shows not only the interrelationship of GSH depletion, apoptosis, mutation and cell proliferation, but also indicates that medaka is appropriate as a fish model for research on the passage of carcinogenesis.

[(3)H]Nicotine binding in peripheral blood cells of smokers is correlated with the number of cigarettes smoked per day

The principal sites for biological action of tobacco products are thought to be the nicotinic acetylcholine receptors (nAChR). Nicotinic receptor subunit genes, therefore, represent an important gene family for study in nicotine addiction. They are localized in both brain and in the periphery. In brain these receptors appear to function as modulators of synaptic transmission; the function of peripheral receptors is not known. Nicotinic receptor levels in human brain are regulated by smoking in a dose-dependent manner. In peripheral blood, nicotinic receptors are present on both lymphocytes and polymorphonuclear cells (PMN). We have compared [(3)H]nicotine binding in PMN isolated from smokers and non-smokers. [(3)H]nicotine binding was increased in smokers and was correlated, as in brain, with tobacco use. Expression of both mRNA and protein in lymphocytes and PMN, for a subset of nicotinic receptor subunits, suggests that these cell types contain both alpha4beta2 and alpha3beta4 receptors.

Impact of baseline symptom severity on future risk of benign prostatic hyperplasia-related outcomes and long-term response to finasteride. The Pless Study Group

OBJECTIVES

To evaluate the long-term effects of finasteride on symptoms, acute urinary retention (AUR), and the need for benign prostatic hyperplasia (BPH)-related surgery in relationship to baseline symptom severity.

METHODS

A total of 3040 men with BPH were treated for 4 years with finasteride or placebo. The changes from baseline in symptoms and the incidence of BPH-related surgery and AUR were determined in men with mild (less than 8), low-moderate (8 to 12), high-moderate (13 to 19), and severe (greater than 19) baseline quasi-American Urological Association symptoms for all patients and for the subgroup with a baseline prostate-specific antigen (PSA) level of 1.4 ng/mL or greater.

RESULTS

In patients who completed the 4-year study, the change in symptom score, stratified by baseline symptom severity, was +1.4 +/- 0.5 (mild), -0.8 +/- 0.3 (low-moderate), -3.6 +/- 0.3 (high-moderate), and -7.7 +/- 0.5 (severe) in finasteride-treated patients and, respectively, +3.4 +/- 0.5, +0.7 +/- 0.3, -1.4 +/- 0.3, and -5.3 +/- 0.6 in placebo-treated patients (between-group P <0.01). The between-group differences were greater in the subgroup of patients with a baseline PSA of 1.4 ng/mL or greater. The risk of BPH-related surgery increased among placebo patients with increasing baseline symptom severity to a greater extent than the risk of AUR. Finasteride reduced the risk of AUR or the need for BPH-related surgery in all subgroups (P <0.001), especially in men with a baseline PSA of 1.4 ng/mL or greater.

CONCLUSIONS

Compared with placebo, finasteride had a beneficial effect on symptoms, AUR, and BPH-related surgery in all symptom categories. BPH-related surgery, but not AUR, occurred more commonly in placebo-treated men with more severe baseline symptoms. The greatest absolute benefit of finasteride on symptoms and the reduction in risk of AUR and surgery was in men with higher baseline symptom scores and a baseline PSA level of 1.4 ng/mL or greater.

Surgical management of intractable epilepsy in children with hemophilia

Intracranial hemorrhage occurs in 2-8% of patients with hemophilia and can result in neurologic sequelae including seizure disorders. There is a paucity of data concerning the surgical treatment of epilepsy in children with hemophilia. We review our experience with 2 children who developed medically refractory seizure disorders. Both children underwent hemispherotomy, at 18 months (case 1) and 13 years of age (case 2), respectively. Perioperative management included continuous factor replacement. Both children tolerated surgical intervention without complications or increased neurologic deficit. Case 2 showed a 90% reduction in seizure frequency, and case 1 is seizure free. Surgical management of intractable epilepsy in children with hemophilia is safe and effective.

Characterization of a nuclear factor that binds to AP1-like element in the rat p53 promoter during liver regeneration

The transcription level of the rat p53 gene increases at 5-12 h in the regenerating liver after partial hepatectomy. It was previously reported that an activator protein 1 (AP1)-like element (-264--284) mediated the induced transcription of the rat p53 gene during liver regeneration. In this study, we characterize the protein binding to the AP1-like element by various methods. Oligonucleotide competition assays showed that the binding protein did not require AP1 consensus sequence. Therefore, the binding protein is not an AP1 family protein. Zn(2+) was required for maximum DNA-binding activity of the protein, suggesting that the binding protein contains zinc fingers. The binding protein was highly resistant to denaturant. Even 1.8 M urea did not eliminate the protein-DNA complexes. In addition, the binding protein was stable up to 55 degrees C. The protein-DNA complexes were abolished in the presence of 0.6 M NaCl and higher. Protease clipping assay showed that the protein had a protease-resistant core DNA binding domain. These results provided new insights into the structure of the protein that binds to the AP1-like element of the p53 promoter during liver regeneration.

Angle-multiplexed hologram storage in LiNbO(3):Tb, Fe

We have performed hologram multiplexing with a cw laser at lambda=532 nm in a near-stoichiometric LiNbO(3) :Tb, Fe crystal that exhibits a visible absorption band induced by UV light. When 50 plane-wave holograms were angle multiplexed from the UV preexposed state, the recording sensitivity gradually decreased, owing to bleaching of the induced absorption. However, a conventional recording schedule of multiplexing many holograms of equal diffraction efficiency can be used in this photochromic material. The gradual decrease in recording sensitivity throughout multiplexing can be compensated for by the increased erasure-time constants of later-written holograms. An M/# of 1.73 was obtained in a crystal of 3.3-mm thickness.

Formulation and in vivo evaluation of omeprazole buccal adhesive tablet

For the development of omeprazole buccal adhesive tablets, we studied the release and bioavailability of omeprazole delivered by buccal adhesive tablets composed of sodium alginate, hydroxypropylmethylcellulose (HPMC), magnesium oxide and croscarmellose sodium. Croscarmellose sodium enhanced the release of omeprazole from the tablets. The analysis of the release mechanism showed that croscarmellose sodium changed the release profile of omeprazole from first- to zero-order release kinetics by forming porous channels in the tablet matrix. However, it decreased the bioadhesive forces and stability of omeprazole tablets in human saliva. The tablet is composed of omeprazole-sodium alginate-HPMC-magnesium oxide-croscarmellose sodium (20:24:6:50:10 mg). It may be attached to the human cheek without collapse and it enhanced the stability of omeprazole in human saliva for at least 4 h, giving a fast release of omeprazole. The plasma concentration of omeprazole in hamsters increased to reach a maximum of 370 ng/ml at 45 min after buccal administration and remained at the high level of 146-366 ng/ml for 6 h. The buccal bioavailability of omeprazole in hamsters was 13.7+/-3.2%. These results demonstrate that the omeprazole buccal adhesive tablet would be useful to deliver omeprazole which degrades very rapidly in acidic aqueous medium and undergoes hepatic first-pass metabolism after oral administration.

Are prior head injuries or diagnostic X-rays associated with glioma in adults? The effects of control selection bias

The causes of glioma, the most common type of primary malignant brain tumors, are poorly understood. This study compares personal histories of head injury and diagnostic radiation procedures of the head and neck among 476 adults newly diagnosed with glioma in the San Francisco Bay Area between August of 1991 and April of 1994 (82% of all those diagnosed during that time period) with 462 age-, gender-, and ethnicity-frequency-matched controls (63% of those eligible from random digit dialing). In addition, limited information was obtained from 101 controls during a brief telephone interview conducted with controls who declined participation in the lengthy in-person interview. Controls who participated in the full interview were much more likely than controls who only completed the telephone interview to report head injury [odds ratios (OR) and 95% confidence intervals (CI) were 2.3 (1.0-4.9) and 3.0 (1.6-5.8) for women and men, respectively]. The OR for any head injury in cases versus controls who completed the full interview was 0.9. However, OR for any head injury in cases versus both control groups was 1.3, 95% CI (1.0-1.7), and the OR for head injury for which the subject sought medical attention was 1.1, 95% CI (0.8-1.4). Among subjects completing the full interview, cases who responded by self-report were less likely than controls to report prior non-dental head and neck X-rays (OR = 0.7; 95% CI: 0.5-1.0). However, stratification by respondents' history of head injury indicated no difference in history of head and neck X-ray among those without prior head injury; OR 0.9; 95% CI (0.6-1.2). Cases and controls shared a very similar history of dental procedures and frequency of dental visits. These results suggest that head injury requiring medical attention, dental visits, or non-dental diagnostic X-rays to the head and neck are not important contributors to the risk of adult glioma and reveal some of the methodological obstacles encountered in forming convincing conclusions about these risk factors for brain tumors.

Prognostic value of c-erbB2 and other markers in patients treated with chemotherapy for recurrent head and neck cancer

BACKGROUND

Chemotherapy is widely used in patients with recurrent head and neck cancer, but no clear markers are available that can predict response to treatment or survival in these patients.

METHODS

Twenty-nine patients evaluated in this study had recurrent head and neck squamous carcinomas, previously treated with surgery and/or radiotherapy. Patients received either cisplatin and 5-fluorouracil (5-FU) (n = 15) or cisplatin and paclitaxel (Taxol) (n = 14). Expression of c-erbB2, p53, glutathione S-transferase pi, multidrug resistance-associated protein, thymidylate synthase, and glutathione synthetase were evaluated in biopsy tissues.

RESULTS

Response to chemotherapy was significantly correlated with improved survival (progression-free survival, p =.0005; overall survival, p =. 007). Of the factors examined, expression of c-erbB2 was associated with significantly decreased progression-free survival (p =.023) and overall survival (p =.029). This was seen in patients treated with cisplatin/taxol but not in patients treated with cisplatin/5-FU.

CONCLUSION

Expression of c-erbB2 may be a clinically useful predictor of survival in this group of patients.

Mechanisms of chloride secretion induced by thermostable direct haemolysin of Vibrio parahaemolyticus in human colonic tissue and a human intestinal epithelial cell line

Thermostable direct haemolysin (TDH) produced by Vibrio parahaemolyticus is thought to play an important role in the severe diarrhoea caused by this organism. This study investigated the enterotoxicity of TDH for human intestinal cells. Addition of TDH to the mucosal side of human colonic tissue in Ussing chambers caused increased short circuit currents (Isc), a process that was inhibited by 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS), an inhibitor of Ca2+ -activated chloride (Cl-) channels. With human colonic epithelial (Caco-2) cells, high Isc and intracellular Ca2+ concentrations ([Ca2+]in) were detected after the addition of TDH to the apical side of the cell monolayer. The Isc decreased with the addition of DIDS, but not with glybenclamide, 5-nitro-2-(3-phenylpropylamino) benzoic acid, or gadolinium chloride. No Isc increase with TDH was observed when the Cl- in the medium was replaced by gluconate or when Ca2+ was depleted. Similarly, TDH did not raise [Ca2+]in after depletion of extracellular Ca2+. R7, a mutant form of TDH, reduced the effects of TDH on Isc and [Ca2+]in, as did protein kinase C (PKC) inhibitors. Thus, TDH increases Cl- secretion in human colonic epithelial cells, apparently through mechanisms involving cell binding and Ca2+ influx, followed by elevation of [Ca2+]in associated with PKC phosphorylation.

Alteration in the choice of DNA repair pathway with increasing sequence selective DNA alkylation in the minor groove

BACKGROUND

Many conventional DNA alkylating anticancer drugs form adducts in the major groove of DNA. These are known to be chiefly repaired by both nucleotide (NER) and base (BER) excision repair in eukaryotic cells. Much less is known about the repair pathways acting on sequence specific minor groove purine adducts, which result from a promising new class of anti-tumour agents.

RESULTS

Benzoic acid mustards (BAMs) tethering 1-3 pyrrole units (compounds 1, 2 and 3) show increasing DNA sequence selectivity for alkylation from BAM and 1, alkylating primarily at guanine-N7 in the major groove, to 3 which is selective for alkylation in the minor groove at purine-N3 in the sequence 5'-TTTTGPu (Pu=guanine or adenine). This increasing sequence selectivity is reflected in increased toxicity in human cells. In the yeast Saccharomyces cerevisiae, the repair of untargeted DNA adducts produced by BAM, 1 and 2 depends upon both the NER and BER pathways. In contrast, the repair of the sequence specific minor groove adducts of 3 does not involve known BER or NER activities. In addition, neither recombination nor mismatch repair are involved. Two disruptants from the RAD6 mutagenesis defective epistasis group (rad6 and rad18), however, showed increased sensitivity to 3. In particular, the rad18 mutant was over three orders of magnitude more sensitive to 3 compared to its isogenic parent, and 3 was highly mutagenic in the absence of RAD18. Elimination of the sequence specific DNA adducts formed by 3 was observed in the wild type strain, but these lesions persisted in the rad18 mutant.

CONCLUSIONS

We have demonstrated that the repair of DNA adducts produced by the highly sequence specific minor groove alkylating agent 3 involves an error free adduct elimination pathway dependent on the Rad18 protein. This represents the first systematic analysis of the cellular pathways which modulate sensitivity to this new class of DNA sequence specific drugs, and indicates that the enhanced cytotoxicity of certain sequence specific minor groove adducts in DNA is the result of evasion of the common excision repair pathways.

In vitro inhibitory effect of some flavonoids on rotavirus infectivity

The inhibitory effects of some flavonoids on the infectivity of rotavirus, which predominantly causes sporadic diarrhea in infants and young children, were investigated. Among tested flavonoids, diosmin and hesperidin had the most potent inhibitory activity on rotavirus infection. The fifty percent inhibitory concentration of both compounds was 10 microM. However, their aglycones did not have the inhibitory activity. The rutinose moiety of flavonoids should protect against the invasion of rotavirus into cells.

2-Amino-3-methylimidazo[4,5-f]quinoline inhibits nitric oxide production in lipopolysaccharide-stimulated RAW 264.7 cells by blocking p38 kinase activation

We show that 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), a heterocyclic amine, significantly inhibits nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated macrophages. The decrease in NO production was found to correlate well with a decrease in inducible NO synthase (iNOS) mRNA expression as demonstrated by Northern blot analysis. Treatment of RAW 264.7 cells with IQ selectively inhibited the activation of NF-kappaB/Rel, an important transcription factor of iNOS gene expression, while neither AP-1 nor Oct was affected by IQ. Since iNOS transcription has been shown recently to be under the control of the p38 kinase signaling cascade, we assessed the effect of IQ on p38 kinase activation. Treatment of RAW 264.7 with IQ inhibited LPS-stimulated p38 kinase phosphorylation in a dose-related manner. IQ also inhibited the p38 kinase activity. Collectively, this series of experiments indicates that IQ inhibits LPS-induced expression of iNOS gene in RAW 264.7 cells. Based on our findings, the most likely mechanism that can account for this biological effect involves the negative regulation of NF-kappaB/Rel and p38 kinase pathway.

Radicicol suppresses expression of inducible nitric-oxide synthase by blocking p38 kinase and nuclear factor-kappaB/Rel in lipopolysaccharide-stimulated macrophages

We show that radicicol, a fungal antibiotic, produces a marked inhibition of p38 kinase, nuclear factor-kappaB/Rel (NF-kappaB/Rel), and inducible nitric-oxide synthase (iNOS) transcription by the macrophage line RAW 264.7 in response to lipopolysaccharide (LPS). Treatment of RAW 264.7 with radicicol inhibited LPS-stimulated p38 kinase phosphorylation in a dose-related manner. iNOS transcription, which is regulated in part by the NF-kappaB/Rel family of transcription factors, has been shown to be under the control of the p38 kinase signaling cascade. Our data also show that the p38 kinase pathway is specifically involved in LPS-induced NF-kappaB/Rel activation and iNOS expression because NF-kappaB/Rel DNA binding and iNOS mRNA production in the presence of a specific inhibitor of p38 kinase, SB203580, were dramatically diminished. In contrast, PD98059, a specific inhibitor of mitogen-activated protein kinase/extracellular signal-regulated protein kinase kinase 1 had no effect on NF-kappaB/Rel activation and iNOS expression. LPS-induced loss of inhibitory proteins IkappaB-alpha and IkappaB-beta and translocation of p65, c-Rel, and p50 was inhibited by radicicol. Collectively, this series of experiments indicates that radicicol inhibits iNOS gene expression by blocking p38 kinase signaling. Due to the critical role that NO release plays in mediating inflammatory responses, the inhibitory effects of radicicol on iNOS suggest that this potent antifungal agent may represent a useful anti-inflammatory agent.