Dissection of functional domains by expression of point-mutated profilins in Dictyostelium mutants

Profilin is a ubiquitous cytoskeletal protein whose function is fundamental to the maintenance of normal cell physiology. By site-directed mutagenesis of profilin II from Dictyostelium discoideum the point mutations K114E and W3N were generated by PCR thus changing actin and poly-(L)-proline-binding activity respectively. W3N profilin is no longer able to bind to poly-(L)-proline concomitant with a slight reduction in actin binding. The K114E profilin exhibited a profound decrease in its ability to interact with actin, whereas binding to poly-(L)-proline was essentially unchanged. Binding to phospholipids was indistinguishable from the wild-type profilin. The in vivo properties of the point-mutated profilins were studied by expressing either W3N or K114E in profilin-minus D. discoideum mutants which have defects in the F-actin content, cytokinesis and development (Haugwitz et al., Cell 79, 303-314, 1994). Expression of K114E or W3N displayed a reduction in the F-actin content, normal cell morphology, and the transformants were capable of undergoing complete development. Interestingly, only cells that drastically overexpressed W3N could restore the aberrant phenotype, whereas the mutant protein K114E with its fully functional poly-(L)-proline binding and its strongly reduced actin-binding activities rescued the phenotype at low concentrations. Wild-type and both mutated profilins are enriched in phagocytic cups during uptake of yeast particles. These data suggest a) that a functional poly-(L)-proline-binding activity is more important for suppression of the mutant phenotype than the G-actin binding activity of profilin, and b) that the enrichment of profilin in highly active phagocytic cups might be independent of either poly-(L)-proline or actin-binding activities.

Divergent effect of cyclosporine on Th1/Th2 type cytokines in patients with severe, refractory rheumatoid arthritis

OBJECTIVE

To investigate the effect of cyclosporine on cytokine production, especially on T helper 1 (Th1) and T helper 2 (Th2) type cytokines, in patients with rheumatoid arthritis (RA).

METHODS

A 16 week randomized, double blind, placebo controlled study of cyclosporine (2.5 to 4 mg/kg/day) was conducted in 40 patients with severe, refractory RA who had residual inflammation and disability despite partial responses to prior maximal tolerated dose of methotrexate (MTX; < 15 mg/week) and low dose prednisone (< 10 mg/day). Clinical and laboratory variables, and circulating levels of interleukin 2 (IL-2), IL-4, IL-10, IL-12, tumor necrosis factor-alpha (TNF-alpha), and interferon-gamma (IFN-gamma) measured by ELISA were compared between patients (cyclosporine group) treated with cyclosporine plus MTX and those (placebo group) treated with placebo plus MTX at entry and at 16 weeks.

RESULTS

At 16 weeks, the cyclosporine group (n = 17), compared with the placebo group (n = 17), had greater decreases in tender joints, swollen joints, patient global assessment, patient self-assessed disability, and C-reactive protein, as well as having more patients with > 20% improvement. Comparison of circulating cytokines at entry and at 16 weeks showed significant decreases of IL-2 (median -61 vs 7 pg/ml; p = 0.004) ("+" denotes increase, "-" denotes decrease), IL-12 (median -313 vs -14 pg/ml; p = 0.002), TNF-alpha (median -55 vs 5 pg/ml; p < 0.001), and IFN-gamma (median -21 vs 5 pg/ml; p = 0.003), and a significant increase of IL-10 (median 55 vs -12 pg/ml; p < 0.001) in the cyclosporine group compared with the placebo group. The degree of IL-10 increases correlated strongly with the degree of IL-12 decreases in the cyclosporine group (r = 0.572, p = 0.016). However, there was no change in circulating IL-4 between the 2 groups. Within the cyclosporine group, the improved patients (n = 10) compared to the non-improved patients (n = 7) had a greater increase in circulating IL-10 (median 172.0 vs 85.2%; p = 0.01). The rate of increase of IL-10 strongly correlated with the rate of improvement of joint scores (r = 0.718, p = 0.001) after administration of cyclosporine.

CONCLUSION

Our results suggest that the therapeutic effect of cyclosporine is achieved by correcting a Th1/Th2 imbalance (a shift of Th1 type to Th2 type), which may be involved in the pathogenesis of RA; and that circulating IL-10 is useful to assess the clinical improvements in patients with RA after administration of cyclosporine.

Inhibitory effects of curcumin and capsaicin on phorbol ester-induced activation of eukaryotic transcription factors, NF-kappaB and AP-1

Recently, considerable attention has been focused on identifying dietary and medicinal phytochemicals that can inhibit, retard or reverse the multi-stage carcinogenesis. Spices and herbs contain phenolic substances with potent antioxidative and chemopreventive properties. Curcumin, a yellow colouring agent from turmeric and capsaicin, a pungent principle of red pepper exhibit profound anticarcinogenic and antimutagenic activities. Two well-defined eukaryotic transcription factors, nuclear factor-kappa B (NF-kappaB) and activator protein 1 (AP-1) have been implicated in pathogenesis of many human diseases including cancer. These transcription factors are known to be activated by a wide array of external stimuli, such as tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), tumor necrosis factor, reactive oxygen species, bacterial lipopolysaccharide, and ultraviolet. In the present study, we found that topical application of TPA onto dorsal skin of female ICR mice resulted in marked activation of epidermal NF-kappaB and AP-1. Curcumin and capsaicin, when topically applied prior to TPA, significantly attenuated TPA-induced activation of each transcription factor in mouse skin. Likewise, both compounds inhibited NF-kappaB and AP-1 activation in cultured human promyelocytic leukemia (HL-60) cells stimulated with TPA. Based on these findings, it is likely that curcumin and capsaicin exert anti-tumor promotional effects through suppression of the tumor promoter-induced activation of transcription factors, NF-kappaB and AP-1.

Effect of microstructure of low carbon steels on ultrasonic attenuation

The ultrasonic attenuation in low carbon steel with 0.04 wt% C to 0.80 wt% C was measured over a frequency range of 5 to 15 MHz, and the effects of the carbon content and normalizing temperature were analyzed. In pure iron, the attenuation is determined from the average grain size, which increases as the normalizing temperature increases; there is a noticeable effect caused by a few large grains. In the case of the hypoeutectoid steels, the proeutectoid ferrite grain, the size of which depends on prior austenite grain size, acts as the main scatterer. The prior austenite grain size increases as the carbon content decreases and the normalizing temperature increases. The colony is responsible for scattering in the eutectoid steel; scattering by pearlite is greater than that by ferrite.

Hyperalgesia caused by nerve transection: long-lasting block prevents early hyperalgesia in the receptive field of the surviving nerve

The aim of our study was to test the hypothesis that a long-lasting N-butyl tetracaine nerve block (>2 wk) would be much more effective in the prevention of hyperalgesia caused by nerve transection than the short-lasting lidocaine block. The study was performed with the use of the saphenous nerve section model in rats. The saphenous nerve was exposed and injected with saline, lidocaine (37 mM), or N-butyl tetracaine (37 mM). Ten minutes later, the nerve was transected in some of the rats. The development of mechanical hyperalgesia (pressure threshold) of the hindpaw was assessed during a 5-wk period. In rats with saphenous nerve transection without nerve block (saline injection), 3 h after the transection, the pressure threshold decreased by approximately 30% (from 175+/-11 g to 122+/-23 g, P < 0.0001); the threshold increased somewhat the next day, then it remained stable for 2 wk, with a slow process of recovery afterward. N-butyl tetracaine block without nerve transection caused a slow-developing decrease in the pressure threshold with the first statistically significant change at the sixth day. The comparison of the preventive effects of lidocaine and N-butyl tetracaine blocks on early hyperalgesia caused by nerve transection demonstrated that both lidocaine and N-butyl tetracaine prevented hyperalgesia 3 h after the transection. However, the protective effect of lidocaine disappeared the next day. In contrast, N-butyl tetracaine prevented early hyperalgesia for almost a week. The slow-developing late hyperalgesia caused by long-lasting nerve block makes it impossible to study the protective effect of such a block on late hyperalgesia caused by axotomy. As far as early hyperalgesia is concerned, the preventive effect of the N-butyl tetracaine was much longer than that of lidocaine and continued for approximately 1 wk.

IMPLICATIONS

A long-lasting nerve block can prevent early hyperalgesia caused by nerve transection.

Testosterone 5 alpha-reductase inhibitors, menaquinone 7 produced by a Bacillus and phenazine methosulfate

Menaquinone 7 (MW: 649, C46H64O2), a natural electron acceptor for steroid ring A dehydrogenations, produced by Bacillus sp. SNU-299, was isolated as a rat prostate testosterone 5 alpha-reductase inhibitor with an IC50 value of 4.0 x 10(-5) M from the cultured broth. Phylloquinone was as active as the purified microbial metabolite with an IC50 value of 6.6 x 10(-4) M. On the basis of this evidence, the inhibitory activities of electron carriers, menadione, phenazine methosulfate, and 2,6-dichlorophenolindophenol, for rat prostate testosterone 5 alpha-reductase were tested, and the IC50 values were 3.1 x 10(-6) M, 4.9 x 10(-8) M, 8.9 x 10(-5) M, respectively. A product of the 5 alpha-reductase enzyme reaction and an electron and proton carrier, NADP+, inhibited the 5 alpha-reduction by rat prostate testosterone 5 alpha-reductase with an IC50 value of 9.2 x 10(-5) M. However, the inhibition effect of a proton carrier, carbonylcyanide-m-chlorophenylhydrazone, for rat prostate testosterone 5 alpha-reductase was substantially inactive.

Rare epithelial sheets with "cancer-like" nuclei presenting against a background of cytologically normal-appearing endometrial epithelium in endometrial brush samplings: establishing a differential diagnosis

Liquid-fixed Tao brush samples showing small quantities (less than 10%) of endometrial epithelial sheets with cancer-like nuclei that are admixed with benign endometrium raise a concern about false-positive cytology interpretations. This paper details 7 cases along with the outcomes of three prior papers that touch on the differential diagnosis of "small amounts of atypical epithelium with cancer-like nuclei." Liquid-fixed, cytocentrifuge-processed Tao brush endometrial samples from 7 women showing "small amounts of atypical epithelium with cancer-like nuclei" were followed up by hysterectomy. Clinical presentations, diagnostic tests, surgical procedures, and tissue outcomes are detailed. Four women had hyperplastic polyps (three with focal atypical complex hyperplasia, and one with focal atypical simple hyperplasia). One had endometrial microcarcinoma. One had p53-positive endometrial intraepithelial carcinoma (EIC). One had endometrial intraepithelial neoplasia (EIN). The differential diagnosis of the index cytological finding, "small quantities of endometrial epithelial sheets with cancer-like nuclei admixed with benign endometrium," includes hyperplastic polyp, EIC, microcarcinoma/EIN, and carcinoma metastatic to the endometrium. Combining endometrial brushing, endovaginal sonography/sonohysterography, and selective immunostaining may be useful for both detecting and sorting out these lesions. Diagn. Cytopathol. 1999;21:378-386.

Work-related assault injuries among nurses

Work-related violence is a major public health problem; however, there is a serious deficiency in the knowledge of risk factors for this problem. The purpose of this case-control study was to identify risk factors for work-related assault injuries among nurses. We used unconditional logistic regression to model the dependence of work-related assault injuries on each exposure of interest and the respective confounders. We found a decreased rate for the presence of security personnel (RR = 0.40; 95% CI = 0.19-0.82). We found increased rates for the following factors: the perception that administrators considered assault to be part of the job (RR = 8.14; 95% CI = 3.76-17.60); having received assault prevention training in the current workplace (RR = 4.64; 95% CI = 2.33-9.23); a high (>5) vs. low (<2) patient/personnel ratio (RR = 2.54; 95% CI = 1.13-5.70); working predominantly with patients with mental illness (RR = 3.5; 95% CI = 1.41-8.85); and working with patients who had more than 1- to 4-week and more than 4-week lengths of stay in the institution vs. <1 day (RR = 8.85; 95% CI = 1.58-49.52 and 4.25; 95% CI = 1.17-15.39, respectively).

Diagnostic imaging of pigmented villonodular synovitis of the temporomandibular joint associated with condylar expansion

Pigmented villonodular synovitis (PVNS) is a rare lesion of the temporomandibular joint. We report a case which was initially misdiagnosed as a parotid tumor. CT revealed a well-defined mass demonstrating higher attenuation than the adjacent soft tissue with marked expansion of the mandibular condyle. MRI clearly delineated the extent of the lesion which had very low signal intensity on both T1W and T2W sequences due to the effect of hemosiderin. The usefulness of these imaging procedures in diagnosis of PVNS is discussed.

Flow-cytometric measurement of cellular changes in urine: a simple and rapid method for perioperatively monitoring patients after kidney transplantation

OBJECTIVE

In renal transplant patients having graft dysfunction, it is usually difficult to obtain the accurate diagnosis, such as acute rejection, acute tubular necrosis, infection, or cyclosporin nephrotoxicity. An accurate diagnosis can provide the proper treatment of these patients, thereby lessening the chance of kidney loss.

METHODS

A total of 42 patients were enrolled. By using the flow-cytometric technique, the white cell populations of urine in these patients were analyzed and linked to their clinical course. All patients underwent sonography-guided biopsy of the transplanted kidney with a definitive diagnosis.

RESULTS

When 10% lymphocytes and 15% granulocytes in urine were set as the cutoff point of a normal ratio threshold, the flow-cytometric analysis presented the highest sensitivity and the highest negative predictive rate for acute tubular necrosis. However, a lower sensitivity and positive predictive rate was found in acute rejection cases.

CONCLUSIONS

Our results suggest that flow-cytometric analysis of the urinary cell population can be used as an adjunct in patient follow-up after kidney transplantation.

The ability of an herbal mouthrinse to reduce gingival bleeding

Forty healthy adult volunteers from the Junior Comprehensive Care Clinics at New York University College of Dentistry were accepted as subjects for this three-month, examiner-blinded, parallel-group clinical trial. To be eligible for a baseline clinical examination, subjects had to first indicate that during the previous six months they habitually brushed their teeth two or more times per day and had noticed "bleeding gums" or "blood in the toothpaste" after brushing or after flossing their teeth. At the baseline examination, subjects were enrolled in the study if they were found to have at least five Löe-Silness gingival bleeding sites and 20 natural teeth, including four molars. Subjects were assigned to one of the two following treatment groups: 1) Herbal Mouth and Gum Therapy; or 2) Control (distilled water and dye). Subjects were instructed to clean their teeth in their usual manner, not to use any other mouthrinses or oral irrigation products for the duration of the study. Subjects were to return for clinical examinations after three months of product use. At these examinations, gingivitis and gingival bleeding scores were recorded. An independent t-test before treatment indicated that there were no significant differences between the baseline evaluations of the two groups in the study. A one-way analysis of variance (ANOVA), comparing gingivitis and bleeding scores from baseline and three months with the baseline scores as a covariate, indicated that Herbal Mouth and Gum Therapy produced a statistically significant effect (p < 0.01) on both parameters relative to the control mouthrinse. The results of this study support the clinical efficacy of Herbal Mouth and Gum Therapy in reducing gingivitis and gingival bleeding.

Dictyostelium as model system for studies of the actin cytoskeleton by molecular genetics

The actin cytoskeleton is an essential structure for most movements at the cellular and intracellular level. Whereas for contraction a muscle cell requires a rather static organisation of cytoskeletal proteins, cell motility of amoeboid cells relies on a tremendously dynamic turnover of filamentous networks in a matter of seconds and at distinct regions inside the cell. The best model system for studying cell motility is Dictyostelium discoideum. The cells live as single amoebae but can also start a developmental program that leads to multicellular stages and differentiation into simple types of tissues. Thus, cell motility can be studied on single cells and on cells in a tissue-like aggregate. The ability to combine protein purification and biochemistry with fairly easy molecular genetics is a unique feature for investigation of the cytoskeleton and cell motility. The actin cytoskeleton in Dictyostelium harbours essentially all classes of actin-binding proteins that have been found throughout eukaryotes. By conventional mutagenesis, gene disruption, antisense approaches, or gene replacements many genes that code for cytoskeletal proteins have been disrupted, and altered phenotypes in transformants that lacked one or more of those cytoskeletal proteins allowed solid conclusions about their in vivo function. In addition, tagging the proteins or selected domains with green fluorescent protein allows the monitoring of protein redistribution during cell movement. Gene tagging by restriction enzyme mediated integration of vectors and the ongoing international genome and cDNA sequencing projects offer the chance to understand the dynamics of the cytoskeleton by identification and functional characterisation of all proteins involved.

Longiberine and O-methyllongiberine, dimeric protoberberine-benzyl tetrahydroisoquinoline alkaloids from Thalictrum longistylum(1)

Two benzyltetrahydroisoquinoline-protoberberine dimers, longiberine (1) and O-methyllongiberine (2), were isolated from the roots of Thalictrum longistylum and represent a new class of dimeric alkaloids. The structure of longiberine (1) was established by spectral and chemical methods. Reductive cleavage of O-ethyllongiberine (4) with Na/liquid NH(3) yielded (+)-(S)-N-methylcoclaurine (5), which determined one-half of the dimer, and 1D and 2D NMR studies arranged the substituents on the protoberberine nucleus. Chemical conversion of thalidezine (6) to 1 via the O-acetyl N,N-didemethyl derivative 9, which was methylenated in the Mannich reaction and N-methylated by the Eschweiler-Clarke procedure, established the second asymmetric center as S and confirmed the ring size and the order of the substituents for 1. Methylation of 1 with diazomethane formed the O-methyl derivative 2, identical with the natural product.

Clinicopathological analysis of 501 non-Hodgkin's lymphomas in Korea according to the revised European-American classification of lymphoid neoplasms

AIMS

The clinical relevance of the Revised European-American Classification of Lymphoid Neoplasms (REAL) is still debated. To test the clinical validity of the REAL classification in Korea, where the incidence of T-cell lymphoma is higher, we investigated the clinicopathological features of non-Hodgkin's lymphoma (NHL) from Korea Cancer Center Hospital.

METHODS AND RESULTS

Five hundred and one patients with NHL were reclassified according to the REAL classification and clinicopathologically analysed. Immunophenotypically, B-cell lymphoma accounted for 67.9% and T- and NK-cell type for 30.5%. Approximately 48.5% of cases were forms of diffuse large B-cell lymphoma (DLBCL), while only 5.4% were follicular lymphoma. Peripheral T-cell lymphoma unspecified (PTCL-U; 10.8%) and angiocentric lymphomas (11.8%) comprised the majority of T-cell lymphomas. Most of the angiocentric lymphomas presented with localized nasal/nasopharyngeal or tonsillar primaries. All peripheral T-cell lymphomas (PTCL) showed a significantly low overall survival compared to DLBCL (P = 0.02, log rank). Overall survival rates for DLBCL and PTCL-U were also significantly different (P = 0.0043, log rank), though for DLBCL and angiocentric lymphoma there was no significant difference (P = 0.2142, log rank). Angiocentric lymphoma, however, was characterized by a shorter median survival time than DLBCL (54 months vs. 96 months). Among DLBCL patients according to the REAL classification, overall survival was significantly better in nonimmunoblastic type (intermediate-grade, WF-F,G) as compared to large cell immunoblastic type (high-grade, WF-H) (log rank, P < 0.001). The morphological distinction of the immunoblastic and nonimmunoblastic among DLBCL of the REAL classification bears significant prognostic relevance worthy of further consideration.

CONCLUSION

We conclude that lineage assignment (T vs. B) in the REAL classification is a clinically important distinction, but that it is necessary to subdivide the broad category of DLBCL.

Hyperbaric oxygen therapy mitigates the adverse effect of cigarette smoking on the bone healing of tibial lengthening: an experimental study on rabbits

OBJECT

We investigated whether -intermittent hyperbaric oxygen (HBO) therapy can mitigate the adverse effects of cigarette smoking on the bone healing of tibial lengthening by using a previously validated rabbit model.

METHODS

Eighteen male rabbits were randomly divided into three groups of six animals each. Group 1 (smoking plus HBO) went through intermittent cigarette smoke inhalation and hyperbaric oxygen therapy, group 2 (control) did not go through intermittent cigarette smoke inhalation or hyperbaric oxygen therapy and group 3 (smoking) went through intermittent cigarette smoke inhalation. Each animal's right tibia was lengthened 5 mm by using an uniplanar lengthening device. Bone mineral density (BMD) study was performed for all the animals at 1 day before operation and 3, 4, 5, and 6 weeks after operation. All of the animals were killed at 6 weeks postoperatively for biomechanical testing.

RESULTS

By using the preoperative BMD as an internal control, we found that the BMD of group 1 (smoking plus HBO)and group 2 (control) was superior to that of group 3 (smoking). The mean %BMD at 3, 4, 5, and 6 weeks were 58.6%, 66.6%, 73.7%, and 83.8%, respectively, in group 1, whereas the mean %BMD were 52.0%, 64.3%, 70.1%, and 76.2%, respectively, in group 2, and the mean %BMD were 46.2%, 54.0%, 64.9%, and 69.4%, respectively, in group 3 (two-tailed t test, p > 0.05, p > 0.05, p > 0.05, and p < 0.05 at 3, 4, 5, and 6 week respectively between group 1 and group 2, p < 0.01,p < 0.01,p < 0.01, and p < 0.01 at 3, 4, 5, and 6 week, respectively, between group 1 and group 3 and p < 0.05, p < 0.05, p < 0.05, and p < 0.05 at 3, 4, 5, and 6 week respectively between group 2 and group 3). By using the contralateral nonoperated tibia as an internal control, we found that the torsional strength of group 1 (smoking plus HBO) and group 2 (control) was superior to that of group 3 (smoking). The mean percentage of maximum torque was 80.9% in group 1 (smoking plus HBO) and was 78.0% in group 2 (control), whereas the mean percentage of maximum torque was 59.6 % in group 3 (smoking) (two-tailed t test, p < 0.05 between groups land 3 and between groups 2 and 3, whereas p > 0.05 between groups 1 and 2).

CONCLUSION

This study suggests that smoke inhalation delays the bone healing in tibial lengthening; however, HBO mitigates the delayed healing effect of smoke inhalation and, thus, helps the smoking animal in achieving an expeditious bone healing in tibial lengthening.

Aortic regurgitation detected with Doppler echocardiography in apparently healthy adolescents

In this study, we sought to determine the prevalence and characteristics of aortic regurgitation (AR) in apparently healthy adolescent students. A total of 315 healthy junior high school students underwent echocardiographic examination. There were 158 boys and 157 girls, with a mean +/- standard deviation age of 13.3 +/- 0.9 years (range, 13-15 yr). AR was found in six (2%) students. Five of the six (83%) with AR had minimally thickened aortic valves: three (50%) had a thickened right coronary cusp and four (67%) had a thickened noncoronary cusp, but none had a thickened left coronary cusp. The AR was mild in five (83%) students and moderate in one (17%). Two of the six students had aortic valve prolapse, both of whom had minimal thickening. One student with AR did not have any abnormal structural changes, and one had aortic root dilatation. No cardiac chamber dilatation was noted in students with AR. These findings indicate a relatively high prevalence of AR in apparently healthy adolescents.

Allelic exclusion in anamniotic vertebrates

Clonal selection, a central principle in immunology, is predicated on one lymphocyte making one kind of antibody or T cell receptor. At loci encoding antigen receptors only one allele is used, and this has been shown in normal lymphocytes from frogs to humans. Fish antibody chains, however, are encoded by multiple loci, and at some of these loci the gene segments are already rearranged in the germline. The differences in germline organization and the uncoupling of rearrangement and expression raise questions as to whether some of the early vertebrates might be an exception to the clonal selection theory.

A latex slide agglutination test for rapid detection of antimyeloperoxidase antibody

AIM

To develop and test a new latex slide agglutination test (MPO-LSAT) to detect antimyeloperoxidase (anti-MPO) antibody in serum.

METHODS

Latex bead coating was adjusted to give maximum sensitivity by attending to latex size, MPO to latex ratio for coupling, ratio of diluted serum to MPO-latex, reaction time and temperature for coupling, and reaction time for agglutination. Inhibition studies were performed using MPO, proteinase 3, bactericidal/permeability increasing protein, and lactoferrin.

RESULTS

There was very good correlation between this test and the conventional anti-MPO enzyme linked immunosorbent assay (ELISA): 81% of sera positive in the ELISA were positive by MPO-LSAT. MPO-LSAT results correlated better with IgM anti-MPO than with IgG anti-MPO.

CONCLUSIONS

MPO-LSAT is a simple diagnostic test that is potentially useful in the clinical laboratory as a rapid screening tool for vasculitic diseases.

Oncogenic human papillomavirus E6 proteins target the discs large tumour suppressor for proteasome-mediated degradation

Previous studies have shown that the oncogenic HPV E6 proteins form a complex with the human homologue of the Drosophila tumour suppressor protein, discs large (Dlg). This is mediated by the carboxy terminus of the E6 proteins and involves recognition of at least one PDZ domain of Dlg. This region of E6 is not conserved amongst E6 proteins from the low risk papillomavirus types and, hence, binding of HPV E6 proteins to Dlg correlates with the oncogenic potential of these viruses. We have performed studies to investigate the consequences of the interaction between E6 and Dlg. Mutational analysis of both the HPV18 E6 and Dlg proteins has further defined the regions of E6 and Dlg necessary for complex formation. Strikingly, co-expression of wild type HPV18 E6 with Dlg in vitro or in vivo results in a dramatic decrease in the amount of Dlg protein, whereas mutants of E6 which fail to complex with Dlg have minimal effect on Dlg protein levels. The oncogenic HPV16 E6 also decreased the Dlg levels, but this was not observed with the low risk HPV11 E6 protein. Moreover, a region within the first 544 amino acids of Dlg containing the three PDZ domains confers susceptibility to E6 mediated degradation. Finally, treatment of cells with a proteasome inhibitor overrides the capacity of E6 to degrade Dlg. These results demonstrate that Dlg is targeted by high risk HPV E6 proteins for proteasome mediated degradation.

A metal complex that binds alpha-amino acids with high and predictable stereospecificity

Molecular recognition is the key step in a wide range of controlled separation and chemical transformation processes, with enzymes performing this task with an unsurpassed degree of selectivity. Enzymes contain only 20 simple amino acids, yet it remains difficult to rationalize or even predict these stereospecific recognition events. Nonetheless, the rational design of receptors able to recognize amino acids stereospecifically is attracting considerable interest because therapeutic drugs, that may be developed from chiral amino acid intermediates, are increasingly required in enantiomerically pure form. Early work has stimulated the development of efficient receptors based on small molecules, but binding of amino acids with high and predictable stereospecificity remains difficult to achieve. Directed molecular evolution, on the other hand, does select for RNA sequences or antibodies that bind amino acids with high specificity, but typically without providing insights into the molecular recognition mechanisms involved. Here we show that a rationally designed metal complex formed from a trivalent cobalt ion and a tetradentate ligand binds natural amino acids, including the simple yet challenging amino acid alanine, with high and predictable regio- and stereospecificity. We expect that our approach will allow the binding as well as separation and stereospecific catalytic formation of its target amino acids.

Osteosynthesis of carpal scaphoid nonunion with interpositional bone graft and Kirschner wires: a 3- to 6-year follow-up

BACKGROUND

Malreduced or neglected unstable carpal scaphoid fractures may lead to nonunion, which is often difficult to treat and carries the risk of carpal instability and degenerative arthrosis. Here, we describe a new "sandwich" method, which takes advantage of minimal dissection and has promising results.

METHODS

From 1989 through 1992, we treated 39 patients with scaphoid nonunion by using the sandwich method that consisted of a wedge corticocancellous strut graft and numerous cancellous bone chips. Divergent Kirschner wires were used for fixation of reduction. We retrospectively review 26 scaphoids with follow-up periods of 3 to 6 years. The functional outcome was evaluated with modification of the Mayo Wrist Scoring Chart. The radiographs were analyzed, and tomographs were used for confirmation of osseous union.

RESULTS

All 26 scaphoids united within 4 months. The carpal instability and humpback deformity were corrected. In all cases, the functional results were either good or excellent.

CONCLUSION

Interpositional bone grafts corrected scaphoid angulation and length. Divergent multiple pinning rather than screws avoids unwanted shearing and rotational force during application and provides stable fixation with minimal dissection. Most of scaphoid nonunions in our series were the oblique type in which the lag screw never created perfect compression because of a shearing force.

Z-curve: a computer program calculating DNA helical axis coordinates for three-dimensional graphic presentation of curvature

In order to predict curvature of DNA fragments, we previously developed a computer program for simply calculating a vectorial sum of all individual roll, tilt and twist wedge angles between the nearest base pairs for a given DNA fragment [Lee et al., (1991)]. Now, a new program, called Z-curve, was developed to calculate three-dimensional coordinates of the helical center of each base pair along the DNA, using helical axis deviations from B-form DNA by wedge angles. The output file of the new program was designed to become an input file for a graphics program, Insight II. Thus, we were able to obtain three-dimensional graphic presentations of DNA helical axis curvatures of any length. It visualized spatial details of the DNA curvature, where and how much it curves, and to which direction. It also allowed calculation of the three-dimensional distance between two ends of a DNA fragment, which could provide a measure of its curvature. Here, three DNA fragments, both curved and straight, were subjected to the Z-curve and Insight II programs. The results showed that their curvature details could be visualized to the level of the base pair, whether the DNA fragments contained an oligo(A) track or not. Their estimated curvatures were consistent with the experimental results of permutation gel mobility assay.

Roles of phosphatidylinositol 3-kinase and Rac in the nuclear signaling by tumor necrosis factor-alpha in rat-2 fibroblasts

We investigated the extent to which phosphatidylinositol 3-kinase (PI 3-kinase) and Rac, a member of the Rho family of small GTPases, are involved in the signaling cascade triggered by tumor necrosis factor (TNF)-alpha leading to activation of c-fos serum response element (SRE) and c-Jun amino-terminal kinase (JNK) in Rat-2 fibroblasts. Inhibition of PI 3-kinase by LY294002 or wortmannin, two specific PI 3-kinase antagonists, or co-transfection with a dominant negative mutant of PI 3-kinase dose-dependently blocked stimulation of c-fos SRE by TNF-alpha. Similarly, LY294002 significantly diminished TNF-alpha-induced activation of JNK, suggesting that nuclear signaling triggered by TNF-alpha is dependent on PI 3-kinase-mediated activation of both c-fos SRE and JNK. We also found nuclear signaling by TNF-alpha to be Rac-dependent, as demonstrated by the inhibitory effect of transient co-transfection with a dominant negative Rac mutant, RacN17. Our findings suggest that Rac is situated downstream of PI 3-kinase in the TNF-alpha signaling pathway to the nucleus, and we conclude that PI 3-kinase and Rac each plays a pivotal role in the nuclear signaling cascade triggered by TNF-alpha.