Development of an Internally Quenched Fluorescent Substrate and a Continuous Fluorimetric Assay for Streptococcus pneumoniae Signal Peptidase I

Signal peptidase (SPase) I is responsible for the cleavage of signal peptides of many secreted proteins in bacteria and serves as a potential target for the development of novel antibacterial agents due to its unique physiological and biochemical properties. In this paper, we describe a novel fluorogenic substrate, KLTFGTVK(Abz)PVQAIAGY(NO2)EWL, in which 2-aminobenzoic acid (Abz) and 3-nitrotyrosine (Y(NO2)) were used as the fluorescent donor and acceptor, respectively. The substrate can be cleaved by both Streptococcus pneumoniae and Escherichia coli SPase I. Upon cleavage of the fluorogenic substrate by SPase I, the fluorescent intensity increases and can be monitored continuously by spectrofluorometer. Kinetic analysis with S. pneumoniae SPase I demonstrated that the K(m) value for the substrate is 118.1 microM, and the k(cat) value is 0.032 s(-1). Mass spectrometric analysis and peptide sequencing of the two cleaved products confirmed that the cleavage occurs specifically at the predicted site. More interestingly, the positively charged lysine in the N-terminus of the substrate was demonstrated to be important for effective cleavage. Phospholipids were found to stimulate the cleavage reaction. This stimulation by phospholipids is dependent upon the N-terminal charge of the substrate, indicating that the interaction of the positively charged substrate with anionic phospholipids is important for maintaining the substrate in certain conformation for cleavage. The substrate and assay described here can be readily automated and utilized for the identification of potential antibacterial agents.

A diffusion of innovations model of physician order entry

OBJECTIVE

To interpret the results of a cross-site study of physician order entry (POE) in hospitals using a diffusion of innovations theory framework.

METHODS

Qualitative study using observation, focus groups, and interviews. Data were analyzed by an interdisciplinary team of researchers using a grounded approach to identify themes. Themes were then interpreted using classical Diffusion of Innovations (DOI) theory as described by Rogers [1].

RESULTS

Four high level themes were identified: organizational issues; clinical and professional issues; technology implementation issues; and issues related to the organization of information and knowledge. Further analysis using the DOI framework indicated that POE is an especially complex information technology innovation when one considers communication, time, and social system issues in addition to attributes of the innovation itself.

CONCLUSION

Implementation strategies for POE should be designed to account for its complex nature. The ideal would be a system that is both customizable and integrated with other parts of the information system, is implemented with maximum involvement of users and high levels of support, and is surrounded by an atmosphere of trust and collaboration.

Brachial artery catheterization to facilitate endovascular grafting of abdominal aortic aneurysm: safety and rationale

PURPOSE

Endovascular treatment of abdominal aortic aneurysms (AAAs) is a technically demanding procedure that is based on the complexity and multiplicity of steps and the guidewire and catheter manipulations required. Brachial artery catheterization is an adjunctive technique that can facilitate the placement of an endoluminal prosthesis.

METHODS

Brachial access was used during endoluminal AAA repair in 79 of 103 consecutive patients with a modular-design stent-graft prosthesis at two institutions.

RESULTS

Left brachial access facilitated (1) angiography to guide juxtarenal device deployment, (2) antegrade contralateral limb access, (3) device delivery through disadvantaged iliac arteries by means of a brachial femoral wire, (4) access to renal arteries when necessary, and (5) catheter exchanges and a reduction in fluoroscopic positional changes. Complications included one puncture-site pseudoaneurysm, seven hematomas, and 29 patients with extensive ecchymosis. The length of stay was not prolonged in any case. There were no embolic, oculocerebral, or ischemic upper extremity events.

CONCLUSIONS

Brachial artery catheterization, as an adjunctive technique to endoluminal AAA repair, offers noteworthy technical advantages with few, but self-limiting complications.

Bootstrap confidence intervals: when, which, what? A practical guide for medical statisticians

Since the early 1980s, a bewildering array of methods for constructing bootstrap confidence intervals have been proposed. In this article, we address the following questions. First, when should bootstrap confidence intervals be used. Secondly, which method should be chosen, and thirdly, how should it be implemented. In order to do this, we review the common algorithms for resampling and methods for constructing bootstrap confidence intervals, together with some less well known ones, highlighting their strengths and weaknesses. We then present a simulation study, a flow chart for choosing an appropriate method and a survival analysis example.

Evaluation of the performance enhancement of silicone biofouling-release coatings by oil incorporation

In response to increased evidence of ecosystem damage by toxic antifouling paints, many researchers have developed nontoxic silicone fouling release coatings. The fouling release capability of these Systems may be improved by adding nonbonding silicone oils to the coating matrix. This idea has been tested by comparing the adhesion strength of hard- and soft-fouling organisms on a cured polydimethylsilicone (PDMS) network to that of the same network containing free polydi-methyldiphenylsilicone (PDMDPS) oil at five exposure sites in North America and Hawaii. Fouling coverage is discussed, together with the bioadhesion data, to emphasize that although these coatings foul the fouling is easily removed. The partitioning of the incorporated oil upon exposure of the coatings to a simulated marine environment containing sediment was determined. Less than 1.1 wt% of the incorporated oil was lost from the coating over one year, and the toxicity of these coatings was shown to be minimal to shrimp and fish. Brush abrasion wear was greater for coatings containing free oil, but the modulus of elasticity was not appreciably decreased by the addition of 10wt% free oil.

Operation and organisation of services for people with severe mental illness in the UK. A survey of the Care Programme Approach

BACKGROUND

Since 1991, English mental health policy guidelines have been explicit in recommending inter-professional working, involvement of patients and carers, harmonisation between health and social services and targeting at people with severe mental illness.

AIMS

To explore the structure and operation of mental health services in practice and relate them to measurable data.

METHOD

A survey of mental health trusts was conducted in 1997-1998. Responses were compared with a concurrent survey of social services departments. Some qualitative data were collected. Harmonisation and targeting scores were devised and tested for association.

RESULTS

The response rate was 79%. The frequency with which different professionals, patients and carers were involved in the care process is described. Reasons for this are discussed briefly. Levels of harmonisation and targeting were found to vary widely and to be positively associated.

CONCLUSIONS

This survey portrays mental health services' practice in relation to Government policy. However, adherence to guidelines cannot be taken as a guarantee of service quality or efficiency.

Barriers to complaints: a survey of mental health service users

Reports on a survey of 222 mental health service users in two health service trusts, which provides evidence to support and elaborate Wood's analysis of barriers to effective complaints procedures. Identifies key confounding factors such as: lack of awareness of the existence of procedures, the fears of service users about making a complaint, and the lack of awareness of rights and expectations of services. Notes key implications for managers including: the provision of accurate, comprehensive information to service users about complaints procedures, the need to recognize the many factors which inhibit service users from using procedures and the need to inform service users about their rights and services.

A massive epidemic of multidrug-resistant typhoid fever in Tajikistan associated with consumption of municipal water

From 1 January through 30 June 1997, 8901 cases of typhoid fever and 95 associated deaths were reported in Dushanbe, Tajikistan. Of 29 Salmonella serotype Typhi isolates tested, 27 (93%) were resistant to ampicillin, chloramphenicol, nalidixic acid, streptomycin, sulfisoxazole, tetracycline, and trimethoprim-sulfamethoxazole. In a case-control study of 45 patients and 123 controls, Salmonella Typhi infection was associated with drinking unboiled water (matched odds ratio, 7; 95% confidence interval, 3-24; P<.001). Of tap water samples, 97% showed fecal coliform contamination (mean level, 175 cfu/100 mL). Samples taken from water treatment plants revealed that fecal coliform contamination occurred both before and after treatment. Lack of chlorination, equipment failure, and back-siphonage in the water distribution system led to contamination of drinking water. After chlorination and coagulation were begun at the treatment plants and a water conservation campaign was initiated to improve water pressure, the incidence of typhoid fever declined dramatically.

Stable antisense RNA expression neutralizes the activity of low-density lipoprotein receptor-related protein and promotes urokinase accumulation in the medium of an astrocytic tumor cell line

Low-density lipoprotein receptor-related protein (LRP) binds and internalizes multiple ligands that are structurally and functionally diverse. However, the effects of LRP on cellular phenotype remain unclear. To study LRP in human astrocytic tumor cells, we designed LRP antisense RNA expression constructs in which the antisense cDNA fragment was expressed under the control of the cytomegalovirus (CMV) promoter. U-1242 MG astrocytic tumor cells were transfected with the antisense constructs and cloned from single cells to yield multiple cell lines with decreased LRP expression. Further studies were performed with two cell lines in which LRP antigen was completely eliminated (L(alpha)42) or substantially decreased (Lalpha47), as determined by Western blot analysis. Untransfected U-1242 MG cells and cells that were stably transfected with empty vector (pBK-CMV) bound activated alpha2-macroglobulin (alpha2M) in a specific and saturable manner. The Bmax was about 5000 receptors/cell. Lalpha42 cells did not bind alpha2M, and binding was decreased by >60% in Lalpha47 cells. Lalpha42 and Lalpha47 cells also demonstrated reduced susceptibility to the cytotoxin, Pseudomonas exotoxin A, and accumulated greatly increased levels of urokinase-type plasminogen activator (uPA) in conditioned medium. The accumulation of uPA demonstrates a major role for LRP in the catabolism of this protein in astrocytic tumor cells. The LRP-deficient cell lines, developed using antisense technology, represent a new model system for studying LRP function in astrocytes.

The calibration and validation of a phase-modulated near-infrared cerebral oximeter

OBJECTIVE

This study was undertaken to compare the cerebral oxygenation measured by an experimental phase-modulated near-infrared (NIR) spectroscopy system with capillary saturation estimated from jugular venous oxygen saturation.

METHODS

Jugular venous catheters were placed in 30 patients undergoing carotid endarterectomy and 194 measurements of venous oxygen saturation were obtained intra operatively. Simultaneous measurement of optical path length at 754, 785, and 816 nm was performed using a phase-modulated near-infrared spectroscopy system. Optical calibration was performed using both an optical bench and a scattering mold. Hemoglobin saturation was calculated from NIR measurements using equations derived from diffusion theory. Capillary saturation was calculated from the arterial and venous saturations.

RESULTS

Jugular venous saturations ranged from 41 to 92%. When calibrated using the optical bench, the NIR estimates of hemoglobin saturation deviated from estimated capillary values by an average of 2.6% bias and 4.3% deviation. No systematic bias was noted. NIR values derived from mold calibration were less accurate and precise (4.6% bias and 6.9% deviation.) Use of the initial venous sample as an in vivo calibration improved the accuracy of the mold calibration but did not alter the performance of the bench calibration.

CONCLUSIONS

Under the conditions tested, an experimental phase-modulated near-infrared spectroscopy system calibrated using an optical bench agreed with capillary saturation estimated from jugular venous samples. Further work is necessary to demonstrate valid performance of the system under other conditions.

Epidermal growth factor differentially regulates low density lipoprotein receptor-related protein gene expression in neoplastic and fetal human astrocytes

Low density lipoprotein receptor-related protein (LRP) is a multifunctional endocytotic receptor that may modify the biological activity of reactive astrocytes in neuroplasticity and neurodegeneration and of malignant astrocytes in brain invasion. In this study, the regulation of LRP by epidermal growth factor receptor (EGFR) ligands in both cultured human fetal astrocytes and astrocytic tumor cell lines (U-251 MG and U-1242 MG) was investigated. All astrocytic cell types expressed LRP, as determined by the binding of activated alpha2-macroglobulin (alpha2M*) on intact cells and by Western and Northern blot analyses of cell extracts. Primary cultured astrocytes expressed the highest levels of alpha2M*-binding capacity (Bmax = 30 fmol/mg protein). This was twofold higher than for the U-1242 MG astrocytoma cells (Bmax = 15 fmol/mg protein) and fourfold greater than for the glioblastoma U-251 MG cells (7.0 fmol/mg protein). Receptor affinity (K(D)) ranged from 0.25 to 0.6 nM in all the astroglial cell types. Functional LRP at the surface was down-regulated by EGF, compared with controls, as indicated by a reduction of both Bmax and LRP-mediated endocytosis by approximately 50% and 60%, respectively. In comparison, EGF treatment of primary astrocytes did not down-regulate LRP expression or LRP-mediated endocytosis. Treatment of the tumor cells with EGF or TGFalpha (25 ng/ml) significantly down-regulated total cellular LRP. Receptor-associated protein (RAP) mRNA expression was not affected by EGF in either tumor cells or primary astrocytes. The reduction of LRP in the tumor cells resulted from a specific decrease in LRP mRNA transcription, as determined by Northern blot and nuclear run-on experiments. These data suggest that EGF mediates a functional down-regulation of LRP endocytotic activity in astrocytic tumor cells and that LRP expression is differentially regulated in neoplastic and non-neoplastic astrocytes.

Endorsement of DSM-IV dependence criteria among caffeine users

The purpose of this article is to determine whether some caffeine users endorse clinical indicators of dependence and abuse. We asked 162 randomly-selected caffeine users generic DSM-IV criteria for dependence, abuse, intoxication and withdrawal pertaining to their caffeine use in the last year via a structured telephone interview. The prevalence of endorsement of dependence items was 56% for strong desire or unsuccessful attempt to stop use, 50% for spending a great deal of time with the drug, 28% for using more than intended, 18% for withdrawal, 14% for using despite knowledge of harm, 8% for tolerance and 1% for foregoing activities to use. Seven percent of users met DSM-IV criteria for caffeine intoxication and, among those who had tried to stop caffeine permanently, 24% met DSM-IV research criteria for caffeine withdrawal. Test-retest interviews for dependency agreed in 29/30 cases (97%). Eight expert substance abuse clinicians agreed with self-endorsed caffeine dependence 91% of the time. Our results replicate earlier work and suggest that a substantial proportion of caffeine users exhibit dependence-like behaviors. Further studies are needed to determine whether such users exhibit a clinically significant syndrome of drug dependence.

Decreased dihydropyrimidine dehydrogenase activity in a population of patients with breast cancer: implication for 5-fluorouracil-based chemotherapy

Dihydropyrimidine dehydrogenase (DPD) is the initial, rate-limiting enzyme in the catabolism of 5-fluorouracil (5-FU), one of the most widely used chemotherapeutic agents in the treatment of breast cancer. The objective of this study was to determine the population characteristics of DPD activity in patients with breast cancer as well as the frequency of DPD deficiency in this population. DPD activity in peripheral blood mononuclear cells (PBM-DPD) was determined in 360 patients with breast cancer, with the mean PBM-DPD (0.26 +/- 0.01 nmol/min/mg protein) being significantly lower than that observed in female controls (0.44 +/- 0.02 nmol/min/mg protein; P < 0.01). ANOVA analysis examining the significance of differences in DPD activity among various groups indicated that only disease difference (breast cancer versus normal subjects) was significant after adjustments for race and age. In the present study, 21 (5.8%) patients were considered to be DPD deficient, indicating that this pharmacogenetic syndrome may be more common than anticipated (no DPD-deficient individual was found in the controls). Significantly lower DPD activity in patients with breast cancer may predispose to 5-FU-associated toxicity. These results provide further rationale for individualizing the 5-FU dose, thus reducing the risk of toxicity and/or improving therapeutic efficacy in patients with breast cancer.

Pheochromocytoma in von Hippel-Lindau disease: clinical presentation and mutation analysis in a large, multigenerational kindred

The clinical presentation and characterization of the mutation in members of a large kindred with von Hippel-Lindau disease (VHLD) and pheochromocytoma were examined. Twenty-five proven cases of VHLD occurring in four generations of a large kindred have been followed since 1964, and pheochromocytoma has occurred in 17. Symptoms of pheochromocytoma developed at an early age, on average at 12.5 +/- 1.3 yr, and definitive diagnosis and treatment of pheochromocytoma occurred at 19.9 +/- 2.6 yr. Significantly higher urine catecholamine concentrations were observed in younger patients than in older ones. Mutation analysis was performed in 14 family members, and a new mutation in the VHLD gene was identified in 11; this mutation is a G to T change at nucleotide 658 that results in the substitution of a serine for an alanine residue at position 149 of the polypeptide chain. Seven of the 11 patients with the mutation have VHLD; four, all 10 yr old or less, are asymptomatic and have no evidence of disease, but are at high risk for developing VHLD. These children are being followed closely for clinical and biochemical manifestations. The characterization of this new mutation has permitted identification of family members who are likely to develop VHLD.