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Biomedical subjects

I Brooks

Publications and source records attributed to I Brooks.

15 recordsLinked to original sources
PubMed2000

Medical management of acute bacterial sinusitis. Recommendations of a clinical advisory committee on pediatric and adult sinusitis.

Acute sinusitis is commonly encountered in clinical practice and treated in the primary care setting. The clinician should recognize the subtle clinical presentation of acute bacterial sinusitis and initiate appropriate, aggressive treatment. Other upper respiratory tract disorders can confound the accurate diagnosis and appropriate treatment of sinusitis. Variable patterns of microbial resistance and antibiotic susceptibility and the dissociation between in vitro findings and clinical efficacy are a treatment challenge. This report is a comprehensive review of the pathophysiology and diagnosis of acute sinusitis, infectious agents, treatment methods, antibiotic resistance patterns, and costs associated with the management of sinusitis. Treatment algorithms are presented for adult and pediatric sinusitis.

Acute Disease↗
PubMed1997

The lights are bright? Debating the future of the permanent night shift.

Debates a controversial issue in healthcare management, that is, whether internal rotation (day-night) or permanent night shifts is an appropriate shift system for nursing staff. A multidisciplinary approach draws together international research from the fields of occupational psychology, management, ergonomics and medicine. Explores evidence on sleep, physical and mental health, job satisfaction, performance, absenteeism, and social and domestic disruption, all important factors in considering appropriate shift patterns. Suggests that both nurse choice (or non-choice) of shift and adjustment, or otherwise, of circadian rhythms are important causal factors influencing the debate. As no unequivocal picture emerges, recognizes some of the real and potential limitations of a paper of this kind; however, the balance of argument tends to favour the maintenance of permanent night shift nurses as opposed to the further extension of internal rotation systems. This is especially the case as many nurses will still be given a choice of shift pattern which may, in itself, negate some of the potential ill-effects of night working. Decisions further to extend internal rotation may, in the light of the complex, ambiguous and equivocal evidence, be informed by partial knowledge and influenced by a managerial perspective.

Choice Behavior↗
PubMed1997

Leadership of a cultural change process.

Explores the successful role of leadership in initiating and sustaining a major process of change. The findings build on the work of others who have so ably demonstrated the influence of powerful leaders. Research is based on qualitative data from an ethnographic study which immersed itself in the minutiae of organizational life. Outlines the processes that have unfolded in the wider context of NHS change. Discusses the findings and debates supporting evidence. The resultant model of change indicates that successful leadership of cultural change requires leaders to think culturally, to be guided by a cognitive model of change and to employ the cultural tools of symbolism while actively focusing on the politics of acceptance. Hard systems and structural changes can be implemented in parallel with soft symbolic and political activity. A highly receptive context, either real or created, assists by providing a trigger for change.

Administrative Personnel↗
PubMed1996

Mutational effects on inclusion body formation in the periplasmic expression of the immunoglobulin VL domain REI.

BACKGROUND: Inclusion body (IB) formation in bacteria is an important example of protein misassembly, a phenomenon which also includes folding-dependent aggregation in vitro and amyloid deposition in human disease. Previous studies of mutational effects in other systems implicate the stability of a folding intermediate-rather than the native state-as playing a key role in IB formation. To contribute to an understanding of the comparative biophysics of VL misassembly in different biological settings, we have studied mutation-dependent periplasmic IB formation by the VL domain REI in Escherichia coli. RESULTS: A series of mutants were produced in periplasmic IBs, where, in all cases, the signal peptide was removed. In addition, the intradomain disulfide was clearly formed before deposition into IBs. IB formation in these mutants does not correlate with monomer/dimer equilibrium constants, but does correlate with the thermodynamic stability of the native state. CONCLUSIONS: The results implicate a late, equilibrium folding intermediate in IB formation, in contrast to the apparent involvement of transient folding intermediates in other IB systems described to date. As equilibrium unfolding intermediates have also been implicated in light chain amyloidosis and deposition diseases, IB formation may prove a useful model for these human diseases.

Amino Acid Sequence↗
PubMed1996

Using ritual to reduce barriers between sub-cultures.

Examines the potential for reducing the dysfunctional consequences of demarcation between work groups and professions in the NHS. Suggests that change may be achieved by interpreting and manipulating rituals which preserve the negative aspects of professional and work group autonomy. Discusses a number of rituals observed in a case study hospital during an extensive research exercise and demonstrates how they help maintain potentially dysfunctional culture norms and behaviours which, consciously or not, serve to resist moves to achieve more flexible, team-orientated, patient-centred changes. In addition, explores new rituals which may question current practices, and argues that attention to rituals in the wider change process may facilitate the desired change. Suggests that changes which confront unnecessary demarcation, but which do not undermine professional integrity, can create real benefits for NHS hospitals.

Attitude of Health Personnel↗
PubMed1994

Determination of the monomer-dimer equilibrium of interleukin-8 reveals it is a monomer at physiological concentrations.

Interleukin-8 has been shown by X-ray crystallography and NMR to be a homodimer, suggesting that this is the form which binds to its receptor. Here we measure, for the first time, the monomer-dimer equilibrium of interleukin-8 using analytical ultracentrifugation and titration microcalorimetry and find that it dissociates readily to monomers with an equilibrium dissociation constant of 18 +/- 6 microM at 37 degrees C. The present findings suggest that the monomer is the form which binds to the receptor. Comparison of experimental and structure-based calculated thermodynamics of interleukin-8 dimerization argues for limited subunit conformational changes upon dissociation to monomer.

Calorimetry↗
PubMed1994

The soluble form of E-selectin is an asymmetric monomer. Expression, purification, and characterization of the recombinant protein.

The gene coding for a soluble form of human E-selectin (sE-selectin) has been expressed in Chinese hamster ovary (CHO) cells. Cells seeded into a hollow fiber reactor secreted protein at a level of 160 mg/liter. The protein was purified to > 95% pure and low endotoxin (< 2 ng/mg), using physiological pH and buffers. The amino acid composition and N-terminal sequence were as predicted from the cDNA sequence. HL-60 cells bound to sE-selectin-coated plates in a dose-dependent manner, and this binding could be blocked up to 100% by pretreatment of HL60 cells with sE-selectin. The concentration of sE-selectin required for 50% inhibition was 1 microM. This value puts an upper limit for the affinity of E-selectin for its natural receptor. sE-selectin also inhibited inflammatory migration of neutrophils in a selective fashion. Purified sE-selectin exhibited a broad band of M(r) approximately 75,000 on nonreducing SDS-PAGE. sE-selectin eluted with M(r) approximately 310,000 from size exclusion chromatography at physiological pH and buffers, suggesting an oligomeric state. Matrix-assisted laser-desorption MS gave a molecular weight of 80,000, while the minimum monomer molecular weight from the gene sequence should be 58,571, demonstrating that the monomeric molecule thus expressed had 27% carbohydrate. Equilibrium analytical ultracentrifugation gave an average solution molecular weight of 81,600 (+/- 4,500). Velocity ultracentrifugation gave a sedimentation coefficient of 4.3 S and, from this, an apparent axial ratio of 10.5:1, assuming a prolate ellipsoid of revolution. An analysis of the NMR NOESY spectra of sE-selectin, sialyl-Lewis X, and sE-selectin with sialyl-Lewis X demonstrates that the recombinant protein binds sialyl-Lewis X productively. Hence, in solution, sE-selectin is a functional elongated monomer.

Amino Acid Sequence↗
PubMed1994

Instability of frog virus 3 mRNA in productively infected cells.

Cloned DNA restriction fragments encoding representative frog virus 3 messages were used as probes to assess the stability of viral transcripts in infected fathead minnow cells. Analysis of Northern blot hybridization profiles confirmed earlier findings and revealed that in infected cells the steady-state level of representative frog virus 3 (FV3) messages increased throughout the replication cycle. However, when actinomycin D was added at 4 hr after infection to block the synthesis of new transcripts, viral messages were observed to turn over rapidly, with half-lives of approximately 2 hr. These results indicate that viral transcripts were not preferentially stabilized in FV3-infected cells and suggest that the high steady-state level of viral messages present at late times after infection was due to viral transcription outpacing message degradation. Moreover, the instability of viral messages challenges the suggestion that the terminal dyad symmetry (hairpin structure) observed in all frog virus 3 messages sequenced to date plays a role in transcript stability.

Animals↗
PubMed1994

Kinetic and mutational analysis of human immunodeficiency virus type 1 reverse transcriptase inhibition by inophyllums, a novel class of non-nucleoside inhibitors.

Inophyllums are novel non-nucleoside inhibitors of human immunodeficiency virus (HIV) type 1 reverse transcriptase identified through an enzyme screening program and isolated from the plant Calophyllum inophyllum. The kinetics of reverse transcriptase inhibition by inophyllum B were characterized using recombinant purified enzyme, a heteropolymeric RNA template, and a scintillation proximity assay. Preincubation of inhibitor with the enzyme-template-primer complex for 11 min was required for maximal inhibition of reverse transcriptase to occur, suggesting that inophyllum B had a slow on-rate and that template-primer must bind to reverse transcriptase prior to inhibitor binding. Inhibition of reverse transcriptase by inophyllums was shown to be reversible. When thymidine triphosphate was the variable substrate, inophyllum B inhibited reverse transcriptase noncompetitively with a Ki of 42 nM. Enzyme inhibition with respect to template-primer was uncompetitive with a Ki of 26 nM. Reverse transcriptase enzymes containing point mutations in which tyrosine 181 was changed to either cysteine or isoleucine exhibited marginal resistance to inophyllums but were resistant to (+)-(5S)-4,5,6,7-tetrahydro-9-chloro-5-methyl-6- (3-methyl-2-butenyl)-imidazo[4,5,1-j,k][1,4]benzodiazepin-2-(1H)-t hione (TIBO R82913). A mutant enzyme in which tyrosine 188 was changed to leucine was cross-resistant to both inophyllum B and TIBO R82913, as was HIV type 2 reverse transcriptase. These studies suggest that inophyllum B and TIBO R82913 bind to distinct but overlapping sites. Inhibition of avian myeloblastosis virus reverse transcriptase and Moloney murine leukemia virus reverse transcriptase by inophyllum B was detectible, suggesting that these inhibitors may be more promiscuous than other previously described non-nucleoside inhibitors. Inophyllums were active against HIV type 1 in cell culture with IC50 values of approximately 1.5 microM. These studies imply that the inophyllums have a novel mechanism of interaction with reverse transcriptase and as such could conceivably play a role in combination therapy.

Antiviral Agents↗
PubMed1994

Determining confidence intervals for parameters derived from analysis of equilibrium analytical ultracentrifugation data.

In the above discussion, we have introduced the profiling approach of Bates and Watts. It is an easy to implement, empirical approach to the determination of confidence intervals for parameters in nonlinear models. We have applied the approach to the analysis of equilibrium sedimentation data and have demonstrated that, although models for analyzing such data are formally nonlinear they are functionally linear. As such, linear approximation confidence intervals for the parameters are adequate for these models and data sets. Further, we have been able to examine the effect of implementing a multiple independent variable approach (in this case, using multiple rotor speeds) on the precision of the analysis. We found that the standard errors of the parameters were reduced and that this is accounted for by either the increase in the number of data points or the decreases in parameter correlation. In this case, profiling helped to visualize the effect on the sum of squares surface of reducing parameter correlation, making the effect of the small decreases in the correlation of some parameters more evident. Using profiling, it should be easy to explore other methods for the improvement of the analysis of ultracentrifugation data and to be able to quantitate the improvement. With the above discussion as an example, it is likely that the profiling approach should be quite useful and broadly applicable in the analysis of data in terms of nonlinear models.

Computer Simulation↗
PubMed1993

Determination of rate and equilibrium binding constants for macromolecular interactions using surface plasmon resonance: use of nonlinear least squares analysis methods.

Surface plasmon resonance (SPR) is a label-free, real time, optical detection method which has recently been commercialized as the BIAcore (Pharmacia). The technique relies on the immobilization of one of the interactants, the ligand, onto a dextran-coated gold surface. The second interactant, the ligate, is then injected across the surface and the interaction of the soluble ligate with the immobilized ligand is observed continuously and directly. The process of dissociation of bound ligate may also be observed directly after the sample plug has traversed the layer. Thus, the data generated contain information on the kinetic rate and equilibrium binding constants for the interaction under investigation. Historically, data from this instrument have been analyzed in terms of linear transformations of the primary data and requires that data from several ligate concentrations be analyzed to determine a single value for the association and dissociation rate constants. Here we discuss the analysis of untransformed BIAcore data by nonlinear least squares methods. The primary data are analyzed according to the integrated rate equations which describe the kinetics of the interaction of soluble ligate with immobilized ligand and the dissociation of the formed complex from the surface, respectively. Such analyses allow the direct determination of the association and dissociation rate constants for each binding experiment and, further, allow the analysis of data over a wider concentration range with lower associated errors compared to previously described methods. Through the use of modeling these interactions, we also demonstrate the limitations in determining the dissociation rate constant from the association phase of the interaction, thereby requiring that the dissociation process be analyzed. Indeed, the dissociation phase should be analyzed first to yield a relatively precise and unambiguous value of the dissociation rate constant, kd, which can then be used to constrain the analysis of the association phase to yield a better estimate of the association rate constant, k(a). We further demonstrate that, at least for the interaction investigated, the apparent rate and equilibrium binding constants determined using SPR are concentration independent and can be determined with good reproducibility.

Animals↗
PubMed1992

Proteolysis of an active site peptide of lactate dehydrogenase by human immunodeficiency virus type 1 protease.

The muscle and heart lactate dehydrogenase (LDHs) of rabbit and pig are specifically cleaved at a single position by HIV-1 protease, resulting in the conversion of 36-kDa subunits of the oligomeric enzymes into 21- and 15-kDa protein bands as analyzed by SDS-PAGE. While the proteolysis was observed at neutral pH, it became more pronounced at pH 6.0 and 5.0. The time courses of the cleavage of the 36-kDa subunits were commensurate with the time-dependent loss of both quaternary structure and enzymatic activity. These results demonstrated that deoligomerization of rabbit muscle LDH at acidic pH rendered its subunits more susceptible to proteolysis, suggesting that a partially denatured form of the enzyme was the actual substrate. Proteolytic cleavage of the rabbit muscle enzyme occurred at a decapeptide sequence, His-Gly-Trp-Ile-Leu*Gly-Glu-His-Gly-Asp (scissile bond denoted throughout by an asterisk), which constitutes a "strand-loop" element in the muscle and heart LDH structures and contains the active site histidyl residue His-193. The kinetic parameters Km, Vmax/KmEt, and Vmax/Et for rabbit muscle LDH and the synthetic decapeptide Ac-His-Gly-Trp-Ile-Leu*Gly-Glu-His-Gly-Asp-NH2 were nearly identical, suggesting that the decapeptide within the protein substrate is conformationally mobile, as would be expected for the peptide substrate in solution. Insertion of part of this decapeptide sequence into bacterial galactokinase likewise rendered this protein susceptible to proteolysis by HIV-1 protease, and site-directed mutagenesis of this peptide in galactokinase revealed that the Glu residue at the P2' was important to binding to HIV-1 protease. Crystallographic analysis of HIV-1 protease complexed with a tight-binding peptide analogue inhibitor derived from this decapeptide sequence revealed that the "strand-loop" structure of the protein substrate must adopt a beta-sheet structure upon binding to the protease. The Glu residue in the P2' position of the inhibitor likely forms hydrogen-bonding interactions with both the alpha-amide and gamma-carboxylic groups of Asp-30 in the substrate binding site.

Amino Acid Sequence↗
PubMed1989

Principles of cancer pain management. Use of long-acting oral morphine.

Oral morphine is increasingly recognized as the pharmacologic standard for cancer pain management. Yet for the primary care physician and oncologist alike, misconceptions of the safety and efficacy of oral morphine along with lack of recognized guidelines for use have often resulted in inadequate cancer pain therapy. Use of controlled-release oral morphine sulfate (MSC) requires additional guidelines for optimum analgesia. Proposed are ten principles of dosing oral morphine, especially MSC, which were followed in a clinical trial involving cancer patients. MSC dosed at 8-, 10-, and 12-hour intervals was compared with immediate-release morphine (IRMS) dosed every four hours, and with prestudy analgesics. Patients achieved satisfactory analgesia at daily doses (mean +/- SE) of 118.0 +/- 8.6 mg and 111.4 +/- 12.6 mg (P greater than .05) for IRMS and MSC, respectively. Dosing endpoints were determined by titration with IRMS and MSC to a minimal and equivalent amount of supplemental short-acting analgesic. Side effects were typical for opioids and tolerated except for one dropout on IRMS (nausea and constipation). The ten principles have been incorporated into a dosing scheme as a practical guide for MSC therapy.

Administration, Oral↗
PubMedDate not supplied

Changes in cardiac function following administration of thyroid hormones in thyroidectomised rats: assessment using the isolated working rat heart preparation.

We investigated the changes in cardiac function following alterations in thyroid state of rats, using the isolated working heart preparation. This technique allows heart rate, contractility, and pump function to be studied under controlled conditions. Surgical thyroidectomy resulted in significant impairment of cardiac function. Single doses of 3,5,3'-triiodo-L-thyronine (T3) or L-thyroxine (T4) were given to thyroidectomised rats. Cardiac function was restored to normal within 48 h of administration of 0.5 mg/kg T3 or 2.5 mg/kg T4 without significant changes in heart weight. The dose-response relationships between T3 and T4 and cardiac function showed that significant changes occurred after single doses of T3, 0.02 mg/kg, or T4, 0.5 mg/kg. An increase in contractility was seen within 12 h of administration of T3, before other physiological effects of T3 are reported to occur. This indicates that the change in contractility is the result of a direct effect of thyroid hormones on the heart and is not secondary to changed loading conditions of the heart. Changes in heart rate occurred between 18 and 48 h. The maximum heart rate achieved did not exceed that in hearts from euthyroid rats, although contractility could be increased above euthyroid levels.

Animals↗