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M Lewis

Publications and source records attributed to M Lewis.

At least 145 records · Page 8Linked to original sources
PubMed1997

The self in self-conscious emotions.

The study of self-conscious emotions has only recently begun. The model outlined here offers an opportunity to consider and to define carefully some of the self-conscious emotions. Unless we develop a more accurate taxonomy, we will be unable to proceed in our study of these emotions. Given the renewed interest in emotional life, it is now appropriate to consider these more complex emotions rather than the more "primary" or "basic" ones. Moreover, as others have pointed out, these self-conscious emotions are intimately connected with other emotions, such as anger and sadness (see for example, H.B. Lewis, 1971; Lewis, 1992b; Morrison, 1989). Finally, given the place of self-evaluation in adult life, it seems clear that the self-conscious evaluative emotions are likely to stand in the center of our emotional life (Dweck & Leggett, 1988; Heckhausen, 1984).

Awareness↗
PubMed1997

Steroid recognition and regulation of hormone action: crystal structure of testosterone and NADP+ bound to 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase.

BACKGROUND: Mammalian 3 alpha-hydroxysteroid dehydrogenases (3 alpha-HSDs) modulate the activities of steroid hormones by reversibly reducing their C3 ketone groups. In steroid target tissues, 3 alpha-HSDs act on 5 alpha-dihydrotestosterone, a potent male sex hormone (androgen) implicated in benign prostate hyperplasia and prostate cancer. Rat liver 3 alpha-HSD belongs to the aldo-keto reductase (AKR) superfamily and provides a model for mammalian 3 alpha-, 17 beta- and 20 alpha-HSDs, which share > 65% sequence identity. The determination of the structure of 3 alpha-HSD in complex with NADP+ and testosterone (a competitive inhibitor) will help to further our understanding of steroid recognition and hormone regulation by mammalian HSDs. RESULTS: We have determined the 2.5 A resolution crystal structure of recombinant rat liver 3 alpha-HSD complexed with NADP+ and testosterone. The structure provides the first picture of an HSD ternary complex in the AKR superfamily, and is the only structure to date of testosterone bound to a protein. It reveals that the C3 ketone in testosterone, corresponding to the reactive group in a substrate, is poised above the nicotinamide ring which is involved in hydride transfer. In addition, the C3 ketone forms hydrogen bonds with two active-site residues implicated in catalysis (Tyr55 and His117). CONCLUSIONS: The active-site arrangement observed in the 3 alpha-HSD ternary complex structure suggests that each positional-specific and stereospecific reaction catalyzed by an HSD requires a particular substrate orientation, the general features of which can be predicted. 3 alpha-HSDs are likely to bind substrates in a similar manner to the way in which testosterone is bound in the ternary complex, that is with the A ring of the steroid substrate in the active site and the beta face towards the nicotinamide ring to facilitate hydride transfer. In contrast, we predict that 17 beta-HSDs will bind substrates with the D ring of the steroid in the active site and with the alpha face towards the nicotinamide ring. The ability to bind substrates in only one or a few orientations could determine the positional-specificity and stereospecificity of each HSD. Residues lining the steroid-binding cavities are highly variable and may select these different orientations.

Aldehyde Oxidoreductases↗
PubMed1997

Molecular replacement using genetic algorithms.

A new molecular replacement (MR) strategy is introduced which features a continuous transform and a genetic algorithm (GA) for search optimization. This strategy uses a GA to simultaneously search the rotational and translational parameters of a test model while maximizing the correlation coefficient between the observed and calculated diffraction data. This has distinct advantages over conventional MR strategies which require a cross-rotation signal. An important feature of this method is its capability to simultaneously search the overall rotation/translation of the test model in the unit cell while refining the relative orientation/position of internal subdomains. This identifies molecular replacement solutions which would otherwise be completely missed using just a static model, and greatly improve the signal-to-noise contrast.

Journal Article↗
PubMed1997

Escherichia coli lac repressor-lac operator interaction and the influence of allosteric effectors.

The wild type E. coli lac operator is embedded in a 35 base-pair DNA sequence containing extensive 2-fold symmetry, suggesting a symmetric repressor operator complex. However, deviations from strict 2-fold symmetry occur at the central base-pair and at three additional base-pairs. Using an operator fragment binding analysis we have determined: (a) a relative contribution each pair provides to the lac repressor-lac operator DNA complex, (b) the operator DNA length necessary for maximum binding to lac repressor; and (c) the contribution of the several non-symmetric base in the wild-type operator to the binding affinity. Since lac repressor-lac operator DNA interaction is reduced upon binding of the gratuitous inducer, isopropyl-beta-D-galactoside (IPTG), the same DNA fragment binding analysis was performed with the low affinity form of lac repressor. In the presence of inducer, the affinity for the left half site of the wild-type lac operator is reduced without significant reduction on the right half of the operator. Conversely, the anti-inducer orthonitrophenylfucoside (ONPF) which stabilizes the lac repressor-lac operator complex increases the binding affinity, particularly to the right half of the operator.

Allosteric Regulation↗
PubMed1997

Osteogenic sarcoma of the jaw. A clinicopathologic review of 12 patients.

OBJECTIVE: To review our experience with osteogenic sarcoma of the jaw. DATA SOURCE: The pathology and clinical files of the Mount Sinai Medical Center, New York, NY, were examined. STUDY SELECTION: For the past 6 years, 12 pathologically documented cases were identified. DATA EXTRACTION: Surgical resection margins, histological tumor grade and subtype, and treatment modality were reexamined with regard to effect on outcome. DATA SYNTHESIS: The mean age of occurrence was 32.6 years, ranging from 12 to 60 years. Male predominance was noted in both mandibular and maxillary tumors. Local recurrence occurred in 6 of 12 patients after 3 months to 5 years; 4 of these patients have either persistent disease or died of disease. In this recurrence group, only 2 patients remain disease free 7 and 12 years after initial diagnosis and 6.5 and 8 years after recurrence. CONCLUSIONS: This study is too small to draw statistically significant conclusions. However, the longest survivor in the group (disease free at 12 years) had a histologically low-grade mandibular tumor. We reiterate the findings in the literature, which agree that osteogenic sarcoma of the jaw is an aggressive disease. Patient prognosis may depend on the tumor grade and size on presentation, as well as the completeness of initial surgery as monitored by resection margins.

Adult↗
PubMed1997

First-time use of newer oral contraceptives and the risk of venous thromboembolism.

Recent epidemiologic studies reported that the risk of venous thromboembolism (VTE) was higher with the use of the newer third generation oral contraceptives than with second generation agents. Although the overall findings of these studies are similar, the results, as they relate to patterns and duration of oral contraceptive use particularly among first-time users, are inconsistent. We reanalyzed data from the Transnational case-control study to assess the risk of VTE associated with first-time use of oral contraceptives as a function of its duration of use. Over the period 1993 to 1995, 471 cases of venous thromboembolism were identified in Germany and the United Kingdom. For each case, up to four controls were obtained, for a total of 1772 controls. Data on oral contraceptive use and confounding variables, including data on sociodemographic, lifestyle, medical history, and family history of disease, were obtained by interview. Data analysis was based on the 105 cases and 422 controls who were first-time users of second or third generation agents, or never users of oral contraception. Rate ratios, adjusted for confounders and approximated by odds ratios, were estimated as a continuous function of duration of oral contraceptive use by logistic regression and quadratic spline models. We found, for first-time users, that the adjusted rate ratio of VTE as a function of the duration of oral contraceptive use is essentially identical for second and third generation pills relative to never users. This rate ratio increases to around 10 in the first year of use and decreases to around two after 2 years of use, remaining at this risk level thereafter for both second and third generation agents. We conclude that second and third generation agents are associated with identical risks of venous thromboembolism when they are prescribed to women who are using oral contraceptives for the first time ever.

Adult↗
PubMed1997

Structure and function of 3 alpha-hydroxysteroid dehydrogenase.

Mammalian 3 alpha-hydroxysteroid dehydrogenases (3 alpha-HSDs) inactivate circulating steroid hormones, and in target tissues regulate the occupancy of steroid hormone receptors. Molecular cloning indicates that 3 alpha-HSDs are members of the aldo-keto reductase (AKR) superfamily and display high sequence identity (> 60%). Of these, the most extensively characterized is rat liver 3 alpha-HSD. X-ray crystal structures of the apoenzyme and the E.NADP+ complex have been determined and serve as structural templates for other 3 alpha-HSDs. These structures reveal that rat liver 3 alpha-HSD adopts an (alpha/beta)8-barrel protein fold. NAD(P)(H) lies perpendicular to the barrel axis in an extended conformation, with the nicotinamide ring at the core of the barrel, and the adenine ring at the periphery of the structure. The nicotinamide ring is stabilized by interaction with Y216, S166, D167, and Q190, so that the A-face points into the vacant active site. The 4-pro-(R) hydrogen transferred in the oxidoreduction of steroids is in close proximity to a catalytic tetrad that consists of D50, Y55, K84, and H117. A water molecule is within hydrogen bond distance of H117 and Y55, and its position may mimic the position of the carbonyl of a 3-ketosteroid substrate. The catalytic tetrad is conserved in members of the AKR superfamily and resides at the base of an apolar cleft implicated in binding steroid hormone. The apolar cleft consists of a side of apolar residues (L54, W86, F128, and F129), and opposing this side is a flexible loop that contains W227. These constraints suggest that the alpha-face of the steroid would orient itself along that side of the cleft containing W86. Site-directed mutagenesis of the catalytic tetrad indicates that Y55 and K84 are essential for catalysis. Y55S and Y55F mutants are catalytically inactive, but still form binary (E.NADPH) and ternary (E.NADH.Testosterone) complexes; by contrast K84R and K84M mutants are catalytically inactive, but do not bind steroid hormone. The reliance on a Tyr/Lys pair is reminiscent of catalytic mechanisms proposed for other AKR members as well as for HSDs that belong to the short-chain dehydrogenase/reductase (SDR) family, in which Tyr is the general acid, with its pKa being lowered by Lys. Superimposition of the nicotinamide rings in the structures of 3 alpha-HSD (an AKR) and 3 alpha, 20 beta-HSD (an SDR) show that the Tyr/Lys pairs are positionally conserved, suggesting convergent evolution across protein families to a common mechanism for HSD catalysis. W86Y and W227Y mutants bind testosterone to the E.NADH complex, with effective increases in Kd of 8- and 20-fold. These data provide the first evidence that the side of the apolar cleft containing W86 and the opposing flexible loop containing W227 are parts of the steroid-binding site. Detailed mutagenesis studies of the apolar cleft and elucidation of a ternary complex structure will ultimately provide details of the determinants that govern steroid hormone recognition. These determinants could provide a rational basis for structure-based inhibitor design.

3-Hydroxysteroid Dehydrogenases↗
PubMed1997

Inhaled corticosteroids and beta-agonists inhibit oxidant production by bronchoalveolar lavage cells from normal volunteers in vivo.

To study the anti-inflammatory mechanisms of inhaled corticosteroids and beta-agonist therapies, we evaluated basal and stimulus-induced superoxide production by human airway inflammatory cells obtained by bronchoalveolar lavage from normal volunteers before and after 3 weeks of an inhaled corticosteroid (flunisolide) and beta-agonist (metaproterenol). Assay of superoxide production by the bronchoalveolar lavage cells was performed in the presence of media alone or media containing phorbol ester by optical density determination of reduced ferricytochrome c at 550 nm. Interleukin-1 beta released from unstimulated cells and cells stimulated with lipopolysaccharide was quantitated by enzyme immunoassay. Interestingly, phorbol ester-stimulated superoxide production was strikingly inhibited (P < 0.05) by inhaled therapies, while stimulus induced Interleukin-1 beta production was not significantly affected (P = 0.12). Suppression of oxidant production by airway inflammatory cells may be a major mechanism for the beneficial anti-inflammatory effects of inhaled corticosteroids and beta-agonists.

Administration, Inhalation↗
PubMed1997

Registration bone scan in the evaluation of wrist pain.

We assessed the value of bone scintigraphy combined with X-ray registration for the diagnosis and management of wrist pain in 65 patients. Studies were reported independently by two observers before and after registration. Registration improved localization of scan abnormalities in 53% (observer 1) and 61% (observer 2). In these patients, the bone scan contributed to the diagnosis independently of the X-ray in 37% and the management was altered in 31%. The value of the bone scan in the early diagnosis and management of wrist pain is increased when it is registered with X-rays.

Adult↗
PubMed1997

Multidisciplinary predialysis programs: quantification and limitations of their impact on patient outcomes in two Canadian settings.

A 1993 National Institutes of Health Consensus statement stressed the importance of early medical intervention in predialysis populations. Given the need for evidence-based practice, we report the outcomes of predialysis programs in two major Canadian cities. The purpose of this report was to determine whether the institution of a multidisciplinary predialysis program is of benefit to patients, and to analyze those factors that are important in actualizing those benefits. Data from two different studies is presented: (1) a prospective, nonrandomized cohort study comparing patients who were or were not exposed to an ongoing multidisciplinary predialysis team (St Paul's Hospital) and (2) a retrospective review of outcomes before and after the institution of a predialysis program (The Toronto Hospital). Although created independently in major academic centers in Canada, the programs both aimed to reduce urgent dialysis starts, improve preparedness for dialysis, and improve resource utilization. The Vancouver study was able to demonstrate significantly fewer urgent dialysis starts (13% v 35%; P < 0.05), more outpatient training (76% v 43%; P < 0.05), and less hospital days in the first month of dialysis (6.5 days v 13.5 days; P < 0.05). Cost savings of the program patients in 1993 are conservatively estimated to be $173,000 (Canadian dollars) or over $4,000 per patient. The Toronto study demonstrated success in predialysis access creation (86.3% of patients), but could not realize any benefit in terms of elective dialysis initiation due to well-documented hemodialysis resource constraints. We conclude that an approach to predialysis patients involving a multidisciplinary team can have a positive impact on quantitative outcomes, but essential elements for success include (1) early referral to a nephrology center, (2) adequate resources for dedicated predialysis program staff and infrastructure, and (3) available resources for patients with end-stage renal disease (ESRD) (dialysis stations). In times of economic constraints, objective data are necessary to justify resource-intensive proactive programs for patients with ESRD. Future studies should confirm and extend our observations so that optimum and cost-effective care for patients approaching ESRD is uniformly available.

Canada↗
PubMed1997

Lac repressor-operator complex.

For many years the lac operon of Escherichia coli has been the paradigm for gene regulation. Recently, the structures of the lac repressor core bound to isopropyl-beta-D-1-thiogalactoside (IPTG), the intact apo lac repressor, the intact lac repressor complexes with IPTG and a 21-base-pair symmetric operator, and the refined headpiece of the repressor have been determined. These structures have provided a framework for understanding a wealth of biochemical and genetic information. An analysis of these structures, as well as a description of their function and a comparison to homologous proteins, is now possible.

Allosteric Regulation↗
PubMed1997

Lac repressor genetic map in real space.

Here, we present a graphic display of the phenotypes of more than 4000 single amino acid substitution mutations on the three-dimensional structure of the lac repressor tetramer bound to DNA. The genetic data and the X-ray diffraction studies contribute to define an allosteric mechanism and yield a visual demonstration of the importance of core or buried residues in protein structure.

Allosteric Site↗
PubMed1997

A phase I-II study of high-dose melphalan, mitoxantrone and carboplatin with peripheral blood stem cell support in patients with advanced ovarian or breast carcinoma.

The purpose of this study was to develop a high-dose chemotherapy (HDC) and peripheral blood stem cell (PBSC) regimen for treatment of patients with ovarian carcinoma that could be administered in an outpatient setting. Fourteen patients with advanced ovarian (n = 9) or breast (n = 5) carcinoma, who had failed conventional chemotherapy, were entered into a dose-escalation trial to determine the maximum tolerated dose (MTD) of carboplatin that could be administered with fixed doses of melphalan (160 mg/m2) and mitoxantrone (50 mg/m2). Twenty-five additional patients were included in a phase II trial at the MTD. Two of two patients had grade 4 severe regimen-related toxicities (RRT), one fatal, at a dose level of 1600 mg/m2. Two of 29 patients (6.9%) treated at the MTD (carboplatin, 1400 mg/m2) died of RRT. All three patients who died of toxicity had a calculated AUC for carboplatin >30 mg/ml/min. Thirty-one patients with ovarian cancer who had failed chemotherapy were treated, 24 at the MTD. Fourteen of 20 patients (70%) with ovarian carcinoma with evaluable disease achieved a CR and seven (35%) are alive disease-free a median of 20 months (range, 7-26). Five of seven patients with ovarian cancer who had failed chemotherapy but were rendered clinically disease-free following surgery survive without progression a median of 13 months (range, 9-19). Eight of 16 (50%) platinum-resistant and 4/12 (33%) platinum-sensitive patients with ovarian cancer survive disease-free.

Adult↗