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Biomedical subjects

D J Weber

Publications and source records attributed to D J Weber.

At least 37 records · Page 2Linked to original sources
PubMed2000

Structural and functional differences of two toxins from the scorpion Pandinus imperator.

The Pandinotoxins, PiTX-K alpha and PiTX-K beta, are members of the Charybdotoxin family of scorpion toxins that can be used to characterize K+ channels. PiTX-K alpha differs from PiTX-K beta, another peptide from Pandinus imperator, by one residue (P10E). When the two toxins are compared in a physiological assay, the affinity of PiTX-K beta for voltage-gated, rapidly inactivating K+ channels in dorsal root ganglia (DRG) neurons is 800-fold lower than that of PiTX-K alpha (K alpha-IC50 = 8.0 nM versus K beta-IC50 = 6,500 nM). To understand this difference, the three-dimensional structure of PiTX-K beta was determined by nuclear magnetic resonance (NMR) spectroscopy and compared to that of PiTX-K alpha. This comparison shows that structural differences between the two toxins occur at a residue that is critical for blocking K+ channels (K27) as well as at the site of the natural mutation (P10E). In PiTX-K beta, the negatively charged carboxylate oxygen of E10 can approach the positive charge of K27 and presumably reduces the net positive charge in this region of the toxin. This is likely the reason why PiTX-K beta binds K+ channels from DRG neurons with a much lower affinity than does PiTX-K alpha.

Amino Acid Sequence↗
PubMed2000

A Bayesian statistical method for the detection and quantification of rotational diffusion anisotropy from NMR relaxation data.

It has recently become more widely appreciated that the presence of rotational diffusional anisotropy in proteins and other macromolecules can have a significant affect on the interpretation of NMR relaxation data in terms of molecular motion. In this paper, we show how commonly used NMR relaxation data (R(1), R(2), and NOE) obtained at two spectrometer frequencies can be analyzed using a Bayesian statistical approach to reliably detect and quantify the degree of rotational diffusion anisotropy. Our approach differs from previous methods in that it does not make assumptions concerning the internal motions experienced by the residues which are used to quantify the diffusion anisotropy, but rather averages the results over all internal motions consistent with the data. We demonstrate our method using synthetic data corresponding to isotropic, axially symmetric anisotropic, and fully asymmetric anisotropic rotational diffusion, as well as experimental NMR data. We compare the Bayesian statistical approach with a widely used method for extracting tumbling parameters using both synthetic and experimental data. While it can be difficult to separate the effects of chemical exchange from rotational anisotropy using this "standard" method, these effects are readily separated using Bayesian statistics. In addition, we find that the Bayesian statistical approach requires considerably less CPU time than an equivalent standard analysis.

Algorithms↗
PubMed2000

Structure of the negative regulatory domain of p53 bound to S100B(betabeta).

A Ca2+ dependent conformational change in dimeric S100B(betabeta) is required for it to bind p53 and inhibit phosphorylation of this tumor suppressor in its C-terminal negative regulatory domain. A peptide derived from this region of p53 (residues 367-388) was found to have no regular structure in its native form by NMR spectroscopy, but becomes helical when bound to Ca2+ loaded S100B(betabeta). The three-dimensional structure of this complex reveals several favorable hydrophobic and electrostatic interactions between S100B(betabeta) and the p53 peptide in the binding pocket, where S100B(betabeta) sterically blocks sites of phosphorylation and acetylation on p53 that are important for transcription activation.

Acetylation↗
PubMed2000

Utility of obtaining blood cultures in febrile neutropenic patients undergoing bone marrow transplantation.

Infection remains an important cause of morbidity and mortality after bone marrow or stem cell transplantation. To evaluate the role of obtaining blood cultures for intermittent or persistent fever in neutropenic patients on antibiotic therapy, we performed a retrospective chart review of 196 consecutive patients admitted to the Bone Marrow Transplant Unit at the University of North Carolina Hospitals from 1995 to 1998. From the cohort of 196 patients, 154 patients developed neutropenic fever. The initial blood culture was positive in 16 of 145 patients during the first fever episode giving a prevalence of 11%. From the total of 109 patients that had blood cultures drawn after day 1 of fever, five patients had blood cultures positive for a pathogen, a prevalence of 4.6%. In only one patient, did blood cultures drawn after day 1 identify an organism not present on day 1 (prevalence 0.9%). After reviewing the results in the first 105 patients, we changed our timing of collection of blood cultures. Forty-nine patients were treated in this manner and we found that the mean number of blood cultures decreased from 9.2 to 4.7 per patient without a change in the frequency of infectious complications or length of hospitalization.

Adolescent↗
PubMed2000

Antimicrobial activity of home disinfectants and natural products against potential human pathogens.

OBJECTIVE: To assess the efficacy of both natural products (vinegar, baking soda) and common commercial disinfectants (Vesphene IIse, TBQ, Clorox, Lysol Disinfectant Spray, Lysol Antibacterial Kitchen Cleaner, Mr. Clean Ultra, ethanol) designed for home or institutional use against potential human pathogens, including selected antibiotic-resistant bacteria. DESIGN: A quantitative suspension test was used to assess the efficacy of selected disinfectants following exposure times of 30 seconds and 5 minutes. Activity was assessed against Staphylococcus aureus, Salmonella choleraesuis, Escherichia coli O157:H7, and Pseudomonas aeruginosa. Selected disinfectants were also tested against poliovirus, vancomycin-susceptible and -resistant Enterococcus species, and methicillin-susceptible and -resistant S. aureus. RESULTS: The following compounds demonstrated excellent antimicrobial activity (>5.6-8.2 log10 reduction) at both exposure times: TBQ, Vesphene, Clorox, ethanol, and Lysol Antibacterial Kitchen Cleaner. Mr. Clean eliminated 4 to >6 logs10 and Lysol Disinfectant approximately 4 logs10 of pathogenic microorganisms at both exposure times. Vinegar eliminated <3 logs10 of S. aureus and E. coli, and baking soda <3 logs10 of all test pathogens. All tested chemical disinfectants completely inactivated both antibiotic-resistant and -susceptible bacteria at both exposure times. Only two disinfectants, Clorox and Lysol, demonstrated excellent activity (>3 log10 reduction) against poliovirus. CONCLUSIONS: A variety of commercial household disinfectants were highly effective against potential bacterial pathogens. The natural products were less effective than commercial household disinfectants. Only Clorox and Lysol disinfectant were effective against poliovirus.

Disinfectants↗
PubMed2000

Clinical infection control in gene therapy: a multidisciplinary conference.

Gene therapy is being studied for the treatment of a variety of acquired and inherited disorders. Retroviruses, adenoviruses, poxviruses, adeno-associated viruses, herpesviruses, and others are being engineered to transfer genes into humans. Treatment protocols using recombinant viruses are being introduced into clinical settings. Infection control professionals will be involved in reviewing the safety of these agents in their clinics and hospitals. To date, only a limited number of articles have been written on infection control in gene therapy, and no widely available recommendations exist from federal or private organizations to guide infection control professionals. The goals of the conference were to provide a forum where gene therapy experts could share their perspectives and experience with infection control in gene therapy and to provide an opportunity for newcomers to the field to learn about issues specific to infection control in gene therapy. Recommendations for infection control in gene therapy were proposed.

Congresses as Topic↗
PubMed2000

Efficacy of a washer-pasteurizer for disinfection of respiratory-care equipment.

We evaluated the efficacy of a commercial washer-pasteurizer. Carriers were inoculated with 10(4) to 10(6) test organisms and pasteurized at 170 degrees F for 30 minutes. Pasteurization eliminated all test organisms with the exception of Bacillus subtilis spores. Pasteurization appears efficacious for the disinfection of respiratory-care equipment and could result in a cost savings of approximately $30,000 per year.

Bacillus subtilis↗
PubMed2000

Work toward real-time control of a cortical neural prothesis.

Implantable devices that interact directly with the human nervous system have been gaining acceptance in the field of medicine since the 1960's. More recently, as is noted by the FDA approval of a deep brain stimulator for movement disorders, interest has shifted toward direct communication with the central nervous system (CNS). Deep brain stimulation (DBS) can have a remarkable effect on the lives of those with certain types of disabilities such as Parkinson's disease, Essential Tremor, and dystonia. To correct for many of the motor impairments not treatable by DBS (e.g. quadriplegia), it would be desirable to extract from the CNS a control signal for movement. A direct interface with motor cortical neurons could provide an optimal signal for restoring movement. In order to accomplish this, a real-time conversion of simultaneously recorded neural activity to an online command for movement is required. A system has been established to isolate the cellular activity of a group of motor neurons and interpret their movement-related information with a minimal delay. The real-time interpretation of cortical activity on a millisecond time scale provides an integral first step in the development of a direct brain-computer interface (BCI).

Animals↗
PubMed1999

Role of the C-terminal extension in the interaction of S100A1 with GFAP, tubulin, the S100A1- and S100B-inhibitory peptide, TRTK-12, and a peptide derived from p53, and the S100A1 inhibitory effect on GFAP polymerization.

Whereas native and recombinant S100A1 inhibited GFAP assembly, a truncated S100A1 lacking the last six C-terminal residues (Phe88-Ser93) (S100A1Delta88-93) proved unable to do so. The inhibitory effects of native and recombinant S100A1 on GFAP assembly were blocked by both TRTK-12, a synthetic peptide derived from the alpha-subunit of the actin capping protein, CapZ, and a synthetic peptide derived from the tumor-suppressor protein, p53, in a dose-dependent manner. By fluorescent spectroscopy, TRTK-12 and the p53 peptide, like GFAP and tubulin, caused a dose- and Ca2+-dependent blue-shift of the fluorescence maximum of acrylodan-S100A1. In contrast, GFAP, tubulin, TRTK-12, or the p53 peptide caused no significant changes in the fluorescence spectrum of acrylodan-S100A1Delta88-93. By chemical crosslinking, both TRTK-12 and the p53 peptide strongly reduced or blocked the formation of GFAP-S100A1 or tubulin-S100A1 complexes, respectively, and S100A1Delta88-93 was unable to complex with tubulin, whereas a remarkably reduced complexation of GFAP with the truncated protein was observed. All the above observations show that the C-terminal extension of S100A1 is an essential part of the S100A1 site implicated in the recognition of GFAP, tubulin, p53, and the alpha-subunit of CapZ.

Animals↗
PubMed1999

Solution structure and mechanism of the MutT pyrophosphohydrolase.

The MutT enzyme prevents errors in DNA replication by hydrolyzing mutagenic nucleotide substrates such as 8-oxo-dGTP. It does so by catalyzing nucleophilic attack at the electron rich P beta of nucleoside triphosphates. Members of this small mechanistic class of enzymes require two divalent cations per active site for activity--one coordinated by the enzyme and the other by the enzyme-bound NTP--and show low catalytic powers of 10(7)- to 10(9)-fold. The first structure of an enzyme of this class, obtained by NMR methods in solution, shows MutT to be a compact globular protein with an alpha + beta-fold. The binding of the essential divalent cation activator Mg2+ and the substrate analog Mg(2+)-AMPCPP to the MutT enzyme to form the quaternary E-Mg(2+)-AMPCPP-Mg2+ complex does not alter the global fold of the enzyme but produces localized small conformational changes at or near the metal and substrate binding sites. The adenine-ribose moiety binds in a hydrophobic cleft near 3-strands of a mixed beta-sheet, with the 6-NH2 group of the purine ring approaching the -NH2 side chain of Asn-119. With a 6-keto group, GTP would interact more favorably with Asn-119, consistent with the substrate preference of MutT for guanine over adenine nucleotides. The enzyme-bound metal is coordinated by three conserved Glu residues (Glu-56, Glu-57, and Glu-98), the backbone carbonyl of a conserved Gly residue (Gly-38), and by two water ligands. The metal-triphosphate moiety of the metal-AMPCPP complex binds in the second coordination sphere of the enzyme-bound divalent cation. One of the water ligands of the enzyme-bound metal ion is well positioned to attack P beta with inversion and to be deprotonated or oriented by Glu-53, which in turn may be oriented by Arg-52. Lys-39 is positioned to interact electrostatically with the alpha-phosphoryl group and thereby to facilitate the departure of the NMP-leaving group. Quantitatively, the 10(9)-fold rate acceleration produced by the MutT enzyme may be ascribed to catalysis by approximation and polarization of the attacking water by the enzyme-bound metal ion (> or = 10(5)-fold), activation of the NMP leaving group by Lys-39 (10-fold), charge neutralization at P beta by the nucleotide-bound divalent cation (> or = 10-fold), and orientation and/or deprotonation of the attacking water by Glu-53 (> or = 10(2)-fold). This reaction mechanism, derived from the solution structure of the quaternary MutT complex, is both qualitatively and quantitatively consistent with the results of mutagenesis studies and may well be applicable to other enzymes that catalyze nucleophilic substitution at the electron-rich P beta of NTP substrates.

Bacterial Proteins↗
PubMed1999

Inactivation of Cryptosporidium parvum oocyst infectivity by disinfection and sterilization processes.

BACKGROUND: Cryptosporidium parvum is a common cause of self-limited gastroenteritis in the normal host but may cause severe disease in immunocompromised persons. Person-to-person transmission has been well documented in households, child care centers, and hospitals. Because contaminated environmental surfaces and medical devices such as endoscopes may play a role in disease transmission, we studied the susceptibility of C parvum to chemical agents commonly used for disinfection and evaluated the efficacy of sterilization processes. METHODS: Seven disinfectants were studied at their use dilution using a suspension test. Antimicrobial activity was assessed with the use of a cell infectivity assay. RESULTS: All sterilization processes tested (steam, ethylene oxide, Sterrad 100) inactivated 3 logs or greater of C parvum. The only liquid disinfectant/sterilant able to inactivate greater than 3 logs of C parvum was 6% and 7.5% hydrogen peroxide. Agents that did not completely inactivate C parvum included hydrogen peroxide at lower concentrations or exposure times, peracetic acid, sodium hypochlorite, a phenolic, a quaternary ammonium compound, 2% glutaraldehyde, and ortho-phthalaldehyde. CONCLUSIONS: Most high-level disinfectants used on endoscopes have limited efficacy against C parvum. However, the infectivity of C parvum on dry surfaces decreases rapidly. Therefore, current cleaning and high-level disinfection guidelines are adequate to prevent nosocomial transmission of C parvum by means of endoscopes.

Animals↗
PubMed1999

Infection control: the role of disinfection and sterilization.

Many articles that document infections after improper decontamination of patient-care items have emphasized the necessity for appropriate disinfection and sterilization procedures. This paper provides recommendations on the preferred method for disinfection and sterilization of patient-care items based on the intended use of the item (i.e., critical, semicritical, noncritical). The chemical disinfectants recommended for patient-care items and instruments include glutaraldehyde, hydrogen peroxide, peracetic acid, sodium hypochlorite, alcohol, iodophors, phenolics, and quaternary ammonium compounds. The choice of disinfectant, concentration, and exposure time is based on the risk of infection associated with the use of the item. The sterilization methods briefly discussed include steam sterilization, ethylene oxide, new low-temperature sterilization technologies and dry heat. When properly used, these disinfection and sterilization processes can ensure the safe use of invasive and noninvasive medical devices. However, this requires strict adherence to current cleaning, disinfection, and sterilization guidelines.

Cold Temperature↗
PubMed1999

Faucet aerators: A source of patient colonization with Stenotrophomonas maltophilia.

BACKGROUND: Multiple nosocomial outbreaks have been linked to contaminated water sources within the hospital. We report in this article a cluster of patients in a surgical intensive care unit who were colonized or infected with Stenotrophomonas maltophilia. METHODS: This study was conducted at an acute care academic hospital. Patients colonized or infected with S maltophilia were identified by prospective surveillance. Environmental isolates were obtained by culturing multiple water sources by using standard techniques. Patient and environmental isolates were examined by pulsed-field gel electrophoresis. RESULTS: Patients were colonized with 2 isolates of S maltophilia, which were found by pulsed-field gel electrophoresis to be identical to strains isolated from the faucet aerators present in sinks in the patients' rooms. Multiple different strains, as defined by pulsed-field gel electrophoresis, were isolated from patients during this outbreak. CONCLUSIONS: We believe that low level contamination of our potable water led to contamination of the faucet aerators with subsequent bacterial amplification on the aerator, which led to contamination of water after aeration. Cultures should be performed on faucet aerators when water sources are suspected as the reservoir for a nosocomial outbreak. If additional clusters of infected or colonized patients are linked to contaminated aerators, consideration should be given to routine disinfection or removal of the aerators.

Cross Infection↗
PubMed1999

Disinfection of endoscopes: review of new chemical sterilants used for high-level disinfection.

Chemical sterilants are used to high-level disinfect heat-sensitive semicritical items such as endoscopes. Most endoscopes have been reprocessed between each patient use with glutaraldehyde (>2%) or the Steris System 1. Several new chemical sterilants have been developed recently, including 7.5% hydrogen peroxide, 0.08% peracetic acid plus 1.0% hydrogen peroxide, and 0.55% orthophthalaldehyde. In order to aid the infection control professional in choosing the appropriate disinfection methodology, this article reviews the characteristics, advantages, and disadvantages of high-level disinfectants intended for reprocessing endoscopes.

Anti-Infective Agents, Local↗
PubMed1999

The effect of blood on the antiviral activity of sodium hypochlorite, a phenolic, and a quaternary ammonium compound.

OBJECTIVE: To assess the virucidal activity of three disinfectants (sodium hypochlorite, a phenolic, and a quaternary ammonium compound) in the presence and absence of blood. METHODS: Disinfectants at varying concentrations (hypochlorite: 5,000, 500, or 50 ppm; phenolic: 1:10 or 1:128 dilution; quaternary ammonium compound: 1:10 or 1:128 dilution) were added to either saline or whole blood (final concentration, 80% or 20% blood) and mixed. Test organisms included an attenuated vaccine strain of poliovirus type 1 (prototype for relatively resistant hydrophilic viruses) and herpes simplex virus (HSV) type 1 (prototype for relatively susceptible lipophilic viruses). Virus was added to create a viral-blood suspension. Viral survival was tested at room temperature at the following times: 0, 15 seconds, 30 seconds, 1 minute, 2 minutes, 5 minutes, and 10 minutes. A neutralizer stopped the reaction, and virus was assayed using a plaque technique. RESULTS: In the absence of blood, complete inactivation of HSV was achieved within 30 seconds with 5,000 (1:10 dilution of bleach) and 500 (1:100 dilution of bleach) ppm chlorine, 1:10 and 1:128 diluted phenolic (use dilution), and 1:10 and 1:128 diluted quaternary ammonium compound (use dilution). In the presence of 80% blood, only 5,000 ppm hypochlorite, 1:10 phenolic, and 1:10 or 1:128 quaternary ammonium compound were effective. In the absence of blood, complete inactivation of polio was achieved within 30 seconds by 5,000 and 500 ppm chlorine and 1:10 quaternary ammonium compound. In the presence of 80% blood, no solution tested was capable of completely inactivating poliovirus within 10 minutes. CONCLUSIONS: Our data suggest that, in the absence of visible blood, environmental surfaces may be disinfected with a diluted hypochlorite solution (1:10 or 1:100), a phenolic, or a quaternary ammonium compound. Based on our studies using HSV, which has similar susceptibilities to disinfectants as human immunodeficiency virus (HIV), phenolics at their use dilution and 1:100 diluted hypochlorite are unlikely to inactivate HIV or hepatitis B virus reliably in the presence of blood. Hypochlorite at a final concentration of 5,000 ppm (1:10 dilution) should be used to decontaminate blood spills, but, even after decontamination, care should be used to avoid sharps injuries.

Blood↗