Why should obesity be managed? The obese individual's perspective

Weight loss can be achieved using a variety of different methods, alone or in combination, including energy restricted diets, drug treatment and surgical intervention. The difficulty is maintaining weight loss over a prolonged period. Physicians, dietitians and nurses are often pessimistic about their ability to manage obesity. Such negative attitudes, combined with the erroneous belief that obesity is not a serious medical condition, have adversely affected the level of care received by obese patients. Despite this, the family doctor is often approached for help with weight control. Obese patients are generally well informed about diet and weight issues, and are in a good position to critically assess the weight loss advice given by their doctor. The perception of such advice formed part of a questionnaire completed by obese people (346 female/24 male) who successfully reduced their weight while attending a weight loss group. Eighty per cent had previously been advised by their doctor to lose weight, but guidance on how to do this was generally judged to be poor. Only 22% of subjects received positive advice, although 23% of subjects reported that their doctor's advice was indirectly responsible for their weight loss. Patients derived evident health benefits from their weight loss and were generally given a positive response on returning to their doctor. To help patients lose weight, doctors must realise that obesity is a serious chronic medical condition. Ongoing help and support from doctors and other healthcare professionals is a key element in successful long-term weight management.

Strength of a weak bond connecting flexible polymer chains

Bond dissociation under steadily rising force occurs most frequently at a time governed by the rate of loading (Evans and Ritchie, 1997 Biophys. J. 72:1541-1555). Multiplied by the loading rate, the breakage time specifies the force for most frequent failure (called bond strength) that obeys the same dependence on loading rate. The spectrum of bond strength versus log(loading rate) provides an image of the energy landscape traversed in the course of unbonding. However, when a weak bond is connected to very compliant elements like long polymers, the load applied to the bond does not rise steadily under constant pulling speed. Because of nonsteady loading, the most frequent breakage force can differ significantly from that of a bond loaded at constant rate through stiff linkages. Using generic models for wormlike and freely jointed chains, we have analyzed the kinetic process of failure for a bond loaded by pulling the polymer linkages at constant speed. We find that when linked by either type of polymer chain, a bond is likely to fail at lower force under steady separation than through stiff linkages. Quite unexpectedly, a discontinuous jump can occur in bond strength at slow separation speed in the case of long polymer linkages. We demonstrate that the predictions of strength versus log(loading rate) can rationalize conflicting results obtained recently for unfolding Ig domains along muscle titin with different force techniques.

Spinal clonidine prolongs labor analgesia from spinal sufentanil and bupivacaine

We sought to determine whether spinal clonidine 50 microg prolongs the analgesia from the spinal administration of sufentanil 7.5 microg and bupivacaine 2.5 mg early in the first stage of labor. Thirty patients were randomized to receive a 2-mL spinal injection of sufentanil 7.5 microg + bupivacaine 2.5 mg with or without clonidine 50 microg using a combined spinal-epidural (CSE) technique. Pain, nausea, pruritus, sedation, motor block, blood pressure, and heart rate were assessed until the patient requested additional analgesia. Analgesia was significantly prolonged in patients who received spinal sufentanil + bupivacaine + clonidine (197 +/- 70 vs 132 +/- 39 min; P = 0.004). Pain scores and side effects, including motor block, sedation, and hypotension, were similar between groups. Spinal clonidine significantly prolongs labor analgesia from spinal sufentanil and bupivacaine without producing serious adverse side effects.

IMPLICATIONS

We studied the effects of spinal clonidine administered with spinal sufentanil and bupivacaine on labor analgesia using a combined spinal-epidural technique and conclude that spinal clonidine significantly prolongs labor analgesia from spinal sufentanil and bupivacaine without producing serious adverse effects.

Indwelling catheter care: dispelling the misconceptions

Long-term indwelling catheters often are incorrectly used and managed. Nurses insert and manage catheters, yet studies have shown that most nurses have limited scientific knowledge in the area of catheters and their care. This article will review the Agency for Health Care Policy and Research guidelines for recommended catheter use and suggest troubleshooting tips for catheter-related problems. The problems of infection, catheter selection and size, urinary leakage, encrustation, catheter blockage, and inadvertent catheter removal will be addressed. Patient and caregiver education tips also will be listed.

Conserved residues of human XPG protein important for nuclease activity and function in nucleotide excision repair

The human XPG endonuclease cuts on the 3' side of a DNA lesion during nucleotide excision repair. Mutations in XPG can lead to the disorders xeroderma pigmentosum (XP) and Cockayne syndrome. XPG shares sequence similarities in two regions with a family of structure-specific nucleases and exonucleases. To begin defining its catalytic mechanism, we changed highly conserved residues and determined the effects on the endonuclease activity of isolated XPG, its function in open complex formation and dual incision reconstituted with purified proteins, and its ability to restore cellular resistance to UV light. The substitution A792V present in two XP complementation group G (XP-G) individuals reduced but did not abolish endonuclease activity, explaining their mild clinical phenotype. Isolated XPG proteins with Asp-77 or Glu-791 substitutions did not cleave DNA. In the reconstituted repair system, alanine substitutions at these positions permitted open complex formation but were inactive for 3' cleavage, whereas D77E and E791D proteins retained considerable activity. The function of each mutant protein in the reconstituted system was mirrored by its ability to restore UV resistance to XP-G cell lines. Hydrodynamic measurements indicated that XPG exists as a monomer in high salt conditions, but immunoprecipitation of intact and truncated XPG proteins showed that XPG polypeptides can interact with each other, suggesting dimerization as an element of XPG function. The mutation results define critical residues in the catalytic center of XPG and strongly suggest that key features of the strand cleavage mechanism and active site structure are shared by members of the nuclease family.

Energy landscapes of receptor-ligand bonds explored with dynamic force spectroscopy

Atomic force microscopy (AFM) has been used to measure the strength of bonds between biological receptor molecules and their ligands. But for weak noncovalent bonds, a dynamic spectrum of bond strengths is predicted as the loading rate is altered, with the measured strength being governed by the prominent barriers traversed in the energy landscape along the force-driven bond-dissociation pathway. In other words, the pioneering early AFM measurements represent only a single point in a continuous spectrum of bond strengths, because theory predicts that these will depend on the rate at which the load is applied. Here we report the strength spectra for the bonds between streptavidin (or avidin) and biotins-the prototype of receptor-ligand interactions used in earlier AFM studies, and which have been modelled by molecular dynamics. We have probed bond formation over six orders of magnitude in loading rate, and find that the bond survival time diminished from about 1 min to 0.001 s with increasing loading rate over this range. The bond strength, meanwhile, increased from about 5 pN to 170 pN. Thus, although they are among the strongest noncovalent linkages in biology (affinity of 10(13) to 10(15) M(-1)), these bonds in fact appear strong or weak depending on how fast they are loaded. We are also able to relate the activation barriers derived from our strength spectra to the shape of the energy landscape derived from simulations of the biotin-avidin complex.

Surface-catalysed disinfection of thick Pseudomonas aeruginosa biofilms

Transition metal catalysts were incorporated into polymers which formed the surface for bacterial attachment and biofilm formation in a constant depth film fermenter (100 microns thickness), flow chamber (about 30 microns thickness) and in batch culture (< 30 microns thickness). The catalysts drive the breakdown of persulphates to reactive oxygen species. When Pseudomonas aeruginosa biofilms were exposed to dilute solutions of potassium monopersulphate (20 micrograms ml-1-1 mg ml-1), significant enhancement of killing was notable for catalyst-containing surfaces over that of controls. The degree of enhancement was greatest for thin films, but was nevertheless significant for the 100 microns thick biofilms. Fluorescence probes and viability staining, in conjunction with laser confocal microscopy, showed that reactive species were generated at the biofilm-substratum interface and killed the biofilm from the inside. Reaction-diffusion limitation now concentrates the active species within the biofilm rather than protecting it, and a diffusion bump is established whereby further treatment agent is drawn to the substratum enabling relatively thick biofilms to be disinfected.

Newly arising fibroadenomas in women aged 35 and over

BACKGROUND

Fifty-one cases of de novo fibroadenoma in women aged 35 years and older were found during an analysis of 117,729 visits to the Wesley Breast Clinic from 1990 to 1996.

METHODS

The clinical, mammographic and ultrasound diagnosis of fibroadenoma was confirmed by either fine needle aspiration cytology or histology of an open biopsy specimen. In all cases there was a well-documented previous visit available for review, at which there was no clinical or radiological evidence of the fibroadenoma.

RESULTS

Thirty-seven of the de novo fibroadenomas were palpable, the remainder satisfying strict mammographic and/or ultrasound criteria. Four of the new fibroadenomas were in women aged 50-52.

CONCLUSIONS

This study provides information about the natural history of fibroadenomas, confirming that they can appear for the first time in middle-aged women. This has important clinical implications, since new lesions appearing in women over 35 have tended to be automatically categorized as suspicious of carcinoma. However, a multidisciplinary approach involving clinical examination, mammography, ultrasound, and fine needle aspiration cytology or core biopsy can result in a confident diagnosis of fibroadenoma. This will allow some women with new lesions to be managed conservatively rather than by open biopsy.

The vaccinia virus I1 protein is essential for the assembly of mature virions

The product of the vaccinia virus I1 gene was characterized biochemically and genetically. This 35-kDa protein is conserved in diverse members of the poxvirus family but shows no homology to nonviral proteins. We show that recombinant I1 binds to both single-stranded and double-stranded DNA in a sequence-nonspecific manner in an electrophoretic mobility shift assay. The protein is expressed at late times during infection, and approximately 700 copies are encapsidated within the virion core. To determine the role of the I1 protein during the viral life cycle, a inducible viral recombinant in which the I1 gene was placed under the regulation of the Escherichia coli lac operator/repressor was constructed. In the absence of isopropyl-beta-D-thiogalactopyranoside, plaque formation was abolished and yields of infectious, intracellular virus were dramatically reduced. Although all phases of gene expression and DNA replication proceeded normally during nonpermissive infections, no mature virions were produced. Electron microscopic analysis confirmed the absence of mature virion assembly but revealed that apparently normal immature virions accumulated. Thus, I1 is an encapsidated DNA-binding protein required for the latest stages of vaccinia virion morphogenesis.

Mechanism of open complex and dual incision formation by human nucleotide excision repair factors

During nucleotide excision repair in human cells, a damaged DNA strand is cleaved by two endonucleases, XPG on the 3' side of the lesion and ERCC1-XPF on the 5' side. These structure-specific enzymes act at junctions between duplex and single-stranded DNA. ATP-dependent formation of an open DNA structure of approximately 25 nt around the adduct precedes this dual incision. We investigated the mechanism of open complex formation and find that mutations in XPB or XPD, the DNA helicase subunits of the transcription and repair factor TFIIH, can completely prevent opening and dual incision in cell-free extracts. A deficiency in XPC protein also prevents opening. The absence of RPA, XPA or XPG activities leads to an intermediate level of strand separation. In contrast, XPF or ERCC1-defective extracts open normally and generate a 3' incision, but fail to form the 5' incision. This same repair defect was observed in extracts from human xeroderma pigmentosum cells with an alteration in the C-terminal domain of XPB, suggesting that XPB has an additional role in facilitating 5' incision by ERCC1-XPF nuclease. These data support a mechanism in which TFIIH-associated helicase activity and XPC protein catalyze initial formation of the key open intermediate, with full extension to the cleavage sites promoted by the other core nucleotide excision repair factors. Opening is followed by dual incision, with the 3' cleavage made first.

Dynamic strength of molecular adhesion bonds

In biology, molecular linkages at, within, and beneath cell interfaces arise mainly from weak noncovalent interactions. These bonds will fail under any level of pulling force if held for sufficient time. Thus, when tested with ultrasensitive force probes, we expect cohesive material strength and strength of adhesion at interfaces to be time- and loading rate-dependent properties. To examine what can be learned from measurements of bond strength, we have extended Kramers' theory for reaction kinetics in liquids to bond dissociation under force and tested the predictions by smart Monte Carlo (Brownian dynamics) simulations of bond rupture. By definition, bond strength is the force that produces the most frequent failure in repeated tests of breakage, i.e., the peak in the distribution of rupture forces. As verified by the simulations, theory shows that bond strength progresses through three dynamic regimes of loading rate. First, bond strength emerges at a critical rate of loading (> or = 0) at which spontaneous dissociation is just frequent enough to keep the distribution peak at zero force. In the slow-loading regime immediately above the critical rate, strength grows as a weak power of loading rate and reflects initial coupling of force to the bonding potential. At higher rates, there is crossover to a fast regime in which strength continues to increase as the logarithm of the loading rate over many decades independent of the type of attraction. Finally, at ultrafast loading rates approaching the domain of molecular dynamics simulations, the bonding potential is quickly overwhelmed by the rapidly increasing force, so that only naked frictional drag on the structure remains to retard separation. Hence, to expose the energy landscape that governs bond strength, molecular adhesion forces must be examined over an enormous span of time scales. However, a significant gap exists between the time domain of force measurements in the laboratory and the extremely fast scale of molecular motions. Using results from a simulation of biotin-avidin bonds (Izrailev, S., S. Stepaniants, M. Balsera, Y. Oono, and K. Schulten. 1997. Molecular dynamics study of unbinding of the avidin-biotin complex. Biophys. J., this issue), we describe how Brownian dynamics can help bridge the gap between molecular dynamics and probe tests.

Open complex formation around a lesion during nucleotide excision repair provides a structure for cleavage by human XPG protein

Human XPG nuclease makes the 3' incision during nucleotide excision repair of DNA. The enzyme cleaves model DNA bubble structures specifically near the junction of unpaired DNA with a duplex region. It is not yet known, however, whether an unpaired structure is an intermediate during actual DNA repair. We find here that XPG requires opening of >5 bp for efficient cleavage. To seek direct evidence for formation of an open structure around a lesion in DNA during a nucleotide excision repair reaction in vitro, KMnO4 footprinting experiments were performed on a damaged DNA molecule bearing a uniquely placed cisplatin adduct. An unwound open complex spanning approximately 25 nucleotides was observed that extended to the positions of 5' and 3' incision sites and was dependent on XPA protein and on ATP. Opening during repair occurred prior to strand incision by XPG.

Xeroderma pigmentosum group F caused by a defect in a structure-specific DNA repair endonuclease

Nucleotide excision repair, which is defective in xeroderma pigmentosum (XP), involves incision of a DNA strand on each side of a lesion. We isolated a human gene homologous to yeast Rad1 and found that it corrects the repair defects of XP group F as well as rodent groups 4 and 11. Causative mutations and strongly reduced levels of encoded protein were identified in XP-F patients. The XPF protein was purified from mammalian cells in a tight complex with ERCC1. This complex is a structure-specific endonuclease responsible for the 5' incision during repair. These results demonstrate that the XPF, ERCC4, and ERCC11 genes are equivalent, complete the isolation of the XP genes that form the core nucleotide excision repair system, and solve the catalytic function of the XPF-containing complex.

Biomembrane templates for nanoscale conduits and networks

Long nanotubes of fluid-lipid bilayers can be used to create templates for photochemical polymerization into solid-phase conduits and networks. Each nanotube is pulled from a micropipette-held feeder vesicle by mechanical retraction of the vesicle after molecular bonding to a rigid substrate. The caliber of the tube is controlled precisely in a range from 20 to 200 nanometers merely by setting the suction pressure in the micropipette. Branched conduits can be formed by coalescing separate nanotubes drawn serially from the feeder vesicle surface. Single nanotubes and nanotube junctions can be linked together between bonding sites on a surface to create a functionalized network. After assembly, the templates can be stabilized by photoinitiated radical cross-linking of macromonomers contained in the aqueous solution confined by the lipid bilayer boundary.

The vaccinia virus D5 protein, which is required for DNA replication, is a nucleic acid-independent nucleoside triphosphatase

The vaccinia virus D5 gene encodes a 90-kDa protein that is transiently expressed at early times after infection. Temperature-sensitive mutants with lesions in the D5 gene exhibit a fast-stop DNA- phenotype and are also impaired in homologous recombination. Here we report the overexpression of the D5 protein within the context of a vaccinia virus infection and its purification to apparent homogeneity. The purified protein has an intrinsic nucleoside triphosphatase activity which is independent of, and not stimulated by, any common nucleic acid cofactors. All eight common ribo- and deoxyribonucleoside triphosphates are hydrolyzed to the diphosphate form in the presence of a divalent cation. Implications for the role of D5 in viral DNA replication are addressed.

Characterization and chromosomal localization of ELANH2, the gene encoding human monocyte/neutrophil elastase inhibitor

Human monocyte/neutrophil elastase inhibitor (HEI) is a protease inhibitor of the serpin superfamily that rapidly inactivates neutrophil elastase, proteinase-3, and possibly cathepsin-G in vitro and, by regulating these potent proteases, is thought to prevent tissue damage at inflammatory sites. The HEI gene (ELANH2) was characterized by amplifying intron regions using cDNA-specific primers. Intron positions of ELANH2 were found to be homologous to intron positions in the genes for the serpin molecules chicken ovalbumin and human plasminogen activator inhibitor-2 (PLANH2). Because serpin superfamily genes in general have widely different organizational patterns, the shared organization of these genes strengthens the evidence that they form a subgroup or family, the "ovalbumin-related serpin" ("Ov-serpin") family. By amplifying DNA of a somatic cell hybrid panel, ELANH2 was unambiguously localized to chromosome 6. The use of a panel of radiation and somatic cell hybrids specific for chromosome 6 refined the localization of ELANH2 to the short arm telomeric of D6S89, F13A, and D6S202 at 6p24-pter. Another Ov-serpin gene PI6 (placental thrombin inhibitor) was colocalized to the same region, thus defining an Ov-serpin locus on chromosome 6 in addition to the previously defined PLANH2-containing Ov-serpin locus on chromosome 18.

Sensitive force technique to probe molecular adhesion and structural linkages at biological interfaces

Adhesion and cytoskeletal structure are intimately related in biological cell function. Even with the vast amount of biological and biochemical data that exist, little is known at the molecular level about physical mechanisms involved in attachments between cells or about consequences of adhesion on the material structure. To expose physical actions at soft biological interfaces, we have combined an ultrasensitive transducer and reflection interference microscopy to image submicroscopic displacements of probe contact with a test surface under minuscule forces. The transducer is a cell-size membrane capsule pressurized by micropipette suction where displacement normal to the membrane under tension is proportional to the applied force. Pressure control of the tension tunes the sensitivity in operation over four orders of magnitude through a range of force from 0.01 pN up to the strength of covalent bonds (approximately 1000 pN)! As the surface probe, a microscopic bead is biochemically glued to the transducer with a densely-bound ligand that is indifferent to the test surface. Movements of the probe under applied force are resolved down to an accuracy of approximately 5 nm from the interference fringe pattern created by light reflected from the bead. With this arrangement, we show that local mechanical compliance of a cell surface can be measured at a displacement resolution set by structural fluctuations. When desired, a second ligand is bound sparsely to the probe for focal adhesion to specific receptors in the test surface. We demonstrate that monitoring fluctuations in probe position at low transducer stiffness enhances detection of molecular adhesion and activation of cytoskeletal structure. Subsequent loading of an attachment tests mechanical response of the receptor-substrate linkage throughout the force-driven process of detachment.

Integrating nursing research and practice: Part II-A Delphi study of nursing practice priorities for research-based solutions

Reading formal research reports and developing the art of critical analysis and evaluation are essential skills for nurses in practice. Here is an opportunity to begin developing these skills as Catherine Cooney, Susan Stebbings, Margaret Roxburgh, Janice Mayo, Niqui Keen, Ellen Evans and Therese Meehan report a survey done by nurses in Northland. Feedback through letters to the editor would be welcomed.

Biofilm-related infections in ophthalmology

A biofilm is a functional consortium of microorganisms organised within an extensive exopolymer matrix. Organisms within a biofilm are difficult to eradicate by conventional antimicrobial therapy and can cause indolent infections. This paper reviews the pathophysiology of biofilms and their application of ophthalmology. Under certain environmental conditions such as nutrient limitation, some bacteria may secrete and reside in an exopolysaccharide glycocalyx polymer. This confers relative protection from humoral and cellular immunity, antibiotics and surfactants. Biofilms occur in natural aquatic ecosystems, on ship hulls, in pipelines and on the surface of biomaterials. They cause clinical infections of prosthetic hip joints, heart valves and catheters. Biofilm formation may occur rapidly on contact lenses and their cases and hence contribute to the pathogenesis of keratitis. Formation of biofilms is also implicated in delayed post-operative endophthalmitis and crystalline keratopathy. Bacteria within biofilms are 20-1000 times less sensitive to antibiotic than free-living planktonic organisms. Existing experimental methods for modifying biofilm include the use of macrolide antibiotics that specifically impair biofilm production, and the use of enzymes to digest it. These may have clinical applications, as potential adjunctive therapies to antibiotic treatment, for these resistant infections. In conclusion, biofilm is an important cause of infections associated with biomaterials. Novel strategies are needed to deal with these.

Comparison of weight-based dosages of enteric-coated microtablet enzyme preparations in patients with cystic fibrosis

Twenty-one stable hospitalized cystic fibrosis patients with malabsorption syndrome participated in an open-label crossover clinical trial to evaluate the efficacy of two-period dosing regimens of a pancreatic microtablet enzyme preparation in the treatment of steatorrhea. Standard dosing consisted of 500 U lipase/kg body weight/meal, 250 U lipase/kg body weight/snack; high dosing consisted of 1,500 U lipase/kg body weight/meal, 750 U lipase/kg body weight/snack. Doses were determined by units of lipase/kg body weight to provide dosing consistency among patients of varying size. Each patient was on a regular diet of approximately 100 g of fat per day. Two separate, 72-h stool collections were performed between markers. A significant difference in mean percentage fat absorbed between the standard dose and the high dose was found (86% versus 91%, p < 0.05). Subjects were then stratified into two groups, based on the grams of fecal fat eliminated (GFFE) as follows: Group 1 with < or = 7 GFFE/24 h on both dosages (n = 7) and Group 2 with > 7 GFFE/24 h on either dose (n = 14). A significant difference (p < 0.05) between Group 1 (96%) and Group 2 (88%) was noted in the percentage fat absorbed while on the high dose. Fat absorption improved from 81% to 88%, (p < 0.05) in Group 2. During the study period, the adverse reactions of constipation or elevated serum uric acid levels were not observed. The increased doses of pancreatic enzymes resulted in improved correction of steatorrhea.