Influence of H2S on the pitting corrosion of 316L stainless steel in oilfield brine.

Coupon immersion tests were performed on 316L stainless steel in a simulated oilfield environment to evaluate the effect of H2S partial pressure on pit depth and density. Pitting was most significant at intermediate partial pressures of H2S, for which free H2S in the pit solution is maximised. Inhibition of pitting at higher partial pressures is attributed to blocking of the pit surface by metal sulphide phases. The key role of pH in the pit solution is to determine the solubility of metal sulphides and the availability of free H2S to adsorb on the reacting pit surface and sustain activity.

Forces generated during stretch in the heart of the lobster Homarus americanus are anisotropic and are altered by neuromodulators.

Mechanical and neurophysiological anisotropies mediate three-dimensional responses of the heart of ITALIC! Homarus americanus Although hearts ITALIC! in vivoare loaded multi-axially by pressure, studies of invertebrate cardiac function typically use uniaxial tests. To generate whole-heart length-tension curves, stretch pyramids at constant lengthening and shortening rates were imposed uniaxially and biaxially along longitudinal and transverse axes of the beating whole heart. To determine whether neuropeptides that are known to modulate cardiac activity in ITALIC! H. americanusaffect the active or passive components of these length-tension curves, we also performed these tests in the presence of SGRNFLRFamide (SGRN) and GYSNRNYLRFamide (GYS). In uniaxial and biaxial tests, both passive and active forces increased with stretch along both measurement axes. The increase in passive forces was anisotropic, with greater increases along the longitudinal axis. Passive forces showed hysteresis and active forces were higher during lengthening than shortening phases of the stretch pyramid. Active forces at a given length were increased by both neuropeptides. To exert these effects, neuropeptides might have acted indirectly on the muscle via their effects on the cardiac ganglion, directly on the neuromuscular junction, or directly on the muscles. Because increases in response to stretch were also seen in stimulated motor nerve-muscle preparations, at least some of the effects of the peptides are likely peripheral. Taken together, these findings suggest that flexibility in rhythmic cardiac contractions results from the amplified effects of neuropeptides interacting with the length-tension characteristics of the heart.

Induction of pulmonary edema and emphysema in cattle and goats with 3-methylindole.

Microorganisms from rumen converted L-tryptophan and indoleacetic acid to 3-methylindole in vitro. Oral doses of 3-methylindole caused interstitial pulmonary edema and emphysema in cattle and goats. Intravenous infusion of this metabolite also induced pulmonary disease in cattle. These results demonstrate than an end product of ruminal fermentation of tryptophan can induce acute pulmonary disease in cattle and goats.

Delayed involution of the mammary epithelium in BALB/c-p53null mice.

In mammals, weaning of neonates and subsequent milk stasis initiates removal of the secretory epithelium of the mammary gland by apoptosis. The p53 tumor suppressor gene is induced rapidly following weaning of neonates, but its role in the process of involution has not been defined. Therefore, experiments were performed to identify the cell types in which the p53 gene is expressed during involution and determine the consequences of its absence in BALB/c-p53null mice. Both p53 mRNA and protein were detected in the mammary epithelium within 48 h following weaning and resulted in an eightfold increase in levels of p21WAF1 mRNA. Induction of p21WAF1 mRNA was absent in BALB/c-p53null mice, and therefore, was shown to be p53-dependent. The BALB/c-p53null mice exhibited delayed involution of the mammary epithelium, as measured by 60% greater epithelial area compared to BALB/c-p53(wt) mice through 5 days post-weaning. The delay was transient with no differences being apparent at 7 days post-weaning. Expression of the stromal protease stromelysin-1 was unaffected by the absence of p53 suggesting that stromal responses were intact. These data demonstrate that p53 participates in the first stage of involution initiated by the epithelium itself, but does not affect the second phase during which stromal proteases are induced.

A mammary-specific model demonstrates the role of the p53 tumor suppressor gene in tumor development.

Although alterations in the p53 tumor suppressor gene are detected frequently in human breast cancers, mammary tumors are observed infrequently in p53(null) mice. This has led to the suggestion that absence of p53 alone is not sufficient for induction of mammary tumors. However, early death of p53(null) mice from thymic lymphomas may obscure tumor phenotypes that would develop later. Therefore, p53(null) mammary epithelium was transplanted into cleared mammary fat pads of wild type p53 BALB/c hosts to allow long-term analysis of mammary tumor phenotypes. Five treatments were compared for their effects on tumor incidence in hosts bearing transplants of p53(null) and p53wt mammary epithelium. The treatment groups were: (1) untreated; (2) continuous hormone stimulation with pituitary isografts; (3) multiple pregnancies; (4) DMBA alone; and (5) DMBA+pituitary isografts. The tumor incidences in p53(null) vs p53wt mammary transplants for each treatment group were 62% vs 0%, 100% vs 0%, 68% vs 0%, 60% vs 4% and 91% vs 14%, respectively. The mammary tumors that developed in the p53(null) mammary epithelium were all adenocarcinomas and were frequently aneuploid. These data demonstrate that the absence of p53 is sufficient to cause development of mammary tumors and that hormonal stimulation enhances the tumorigenicity of p53(null) mammary epithelium to a greater extent than DMBA exposure alone. This model provides an in situ approach to examine the molecular basis for the role of p53 in the regulation of mammary tumorigenesis.

The epidemiology of HIV transmission among paid plasma donors, Mexico City, Mexico.

Screening of blood product donations for antibody to HIV began in Mexico in May 1986. From June to October 1986, the HIV cumulative seroprevalence increased from 6.3 to 9.2% in a commercial plasma collection center. Of the 281 people who donated the antibody-positive units, 62 (22.1%) had documented seroconversion during these 5 months. An epidemiologic study of 54 seropositive and 58 seronegative donors was carried out. The HIV serologic status did not change in any of these donors after repeat testing. Only 13.0% of the seropositives and 15.5% of the seronegatives had any of the known risk factors for AIDS. There was a direct relationship between frequency of plasma donation and the risk of being seropositive. A survey of employees disclosed the frequent re-use of disposable blood collection equipment. We conclude that HIV transmission had probably occurred in this plasma collection center.

PIP: This report provides the results of a study of plasma donor clients from records abstracted between June-October 1986. The purpose was to identify risk factors for HIV infection among donors at the National Center for Blood Transfusions. Screening for HIV among donors began in May 1986. 54 Seropositive donors were identified and located from 281 and 58 seronegative donors were randomly selected. 16 employees of the plasma collection center were locatable and also included in the study. The results were that seroprevalence increased between June-October from 6.3% to 9.2%. The total donations were 3201 of which 294 were seropositive. Of 281 seropositive clients, 62 (22%) had seroconversion (a prior seronegative donation). Seroconversions increased from 1.6% in July to 50% in October. On retesting of the 112 study participants, no change in status was found. The groups were similar and both groups had relatively low risk factors for (13% for HIV seropositive and 15.5% for HIV seronegative donors). The rate of seropositivity increased with the frequency of plasma donations from 19.6% for those donating 1-3 times/month to 88.9% for those donating 10 times/month. Of the 16 employees, 1 died who was HIV seropositive; 5 were directly involved in plasma collection and reported reuse of saline solution and intravenous tubing. The results lead the authors to suggest that HIV was transmitted in the collection process. Support for this suggestion comes from the number of seroconversions; the risk factors among the seropositive donors had no known risk factors. Although not statistically significant, male seropositive donors had greater contract with prostitutes in Mexico City, but prostitutes had shown in the past 2 years a seropositivity rate of 1%. More demonstrative evidence comes from the increased rate of seropositivity with frequency of donation, and the employee reports of reutilization of blood collection materials. Other studies have postulated plasma donor site risk. Regardless of the expense of intravenous equipment, it is suggested that the risk of HIV transmission precludes reuse of materials. At present, all blood is collected from volunteer donors with disposable equipment. Other countries need to assess the safety of blood donor centers, particularly with paid donors.

Immunoglobulin A supplementation abrogates bacterial translocation and preserves the architecture of the intestinal epithelium.

BACKGROUND: Breast milk has been shown to prevent gut-origin infections in neonates through undefined mechanisms. Putative protective factors in breast milk include immunoglobulin (Ig)A, IgG, and lactoferrin. We examined their role in bacterial translocation in neonatal rabbits. METHODS: IgA, IgG, and lactoferrin were isolated from rabbit breast milk through gel filtration and ion-exchange chromatography. Neonates were randomized to receive breast milk, formula alone, or formula supplemented with IgA, IgG, or lactoferrin. Quantitative cultures were performed on day 7 for bacterial translocation. Hematoxylin-eosin-stained sections of distal ileum were examined by light microscopy. Transmucosal bacterial passage was determined in vitro, and the ileal mucosal membranes were examined by confocal microscopy. RESULTS: IgA supplementation abrogated bacterial translocation. IgG and lactoferrin had no significant effect. Neonates that received IgA or breast milk gained more weight than those in the other groups. IgA reduced transmucosal bacterial passage in vitro. In contrast to the normal-appearing distal ileum of neonates fed breast milk, intestinal epithelium from neonates that received formula or formula with IgG or IgA demonstrated prominent vacuoles by light microscopy. Those fed formula alone or formula with lactoferrin had slightly shortened villi. CONCLUSIONS: IgA supplementation prevents bacterial translocation by enhancing gut mucosal barrier function.

Optical chip immunoassay for hCG in human whole blood.

We report on the development of an integrated optic chip sensor for performing rapid and sensitive immunoassays with human whole blood using human chorionic gonadotropin (hCG) as the model system. The optical chip is based on the Hartman interferometer, which uses a single planar lightbeam to address multiple interferometers, each comprising a signal/reference pair of sensing regions. The binding of antigen to specific capture antibodies on the signal sensing region causes a change in the refractive index of the surface layer, which is detectable by its effect on the evanescent field of the guided lightbeam. The reference-sensing region is coated with an irrelevant antibody, which optically cancels a large fraction of the non-specific adsorption that occurs on the specific-sensing region when the sensor is tested with clinical specimens. This work extends previous experiments with buffer and human serum to measurements in undiluted whole human blood. Optical chips were stored dry after surface functionalization, and rehydrated with blood. Colloidal gold nanoparticles conjugated to a second anti-hCG monoclonal antibody were used to provide signal amplification, thereby enhancing assay sensitivity, in a one-step procedure with the gold conjugate added to the test sample immediately prior to measurement. Background signals due to non-specific binding (NSB) in blood were found to be higher than those previously reported with human serum. In addition, a high level of background signal was found with the gold conjugate, which had not been observed in experiments with either buffer or serum. Nevertheless, hCG could be detected at 0.5 ng/ml within 10 min of sample application. The sensor response was linear over the concentration range 0.5-5 ng/ml hCG, as compared with the clinically-relevant range 0.3-1.5 ng/ml. Detection at higher concentrations was affected by scattering from large amounts of bound gold nanoparticles. However, initial binding rate measurements could be used to maintain assay quantitation.

Highly sensitive optical chip immunoassays in human serum.

Over the past decade the ability of refractometric optical sensors to quantitatively measure a wide range of biomolecules has been demonstrated. These include proteins, nucleic acids, microorganisms, and in competitive formats small molecules such as drugs and pesticides. Furthermore, by using high refractive index nanoparticles to amplify the biomolecular binding signal, sensitivities approaching those of well established diagnostic assays have been achieved. However, to date it has not been possible to show rapid detection of analytes in complex bodily fluids such as serum, in a one-step procedure, due to the interference resulting from non-specific binding (NSB) to the sensor surface. We have carried out preliminary work on the control of interference due to NSB using an optical chip based on the Hartman interferometer. This interferometer configuration employs a reference sensing region that can be functionalized separately from the specific sensing region. Optical chips were stored dry after surface functionalization, and rehydrated in serum. The observed level of background drift in serum was reduced by an order of magnitude when an exposed reference was used, compared to a reference which was blind to the sample. An additional 70% reduction in signal drift in serum was achieved by controlling the surface chemistry of the optical chip using a biotin-poly(ethylene glycol) (PEG) blocking agent. This functionalization procedure was combined with a sandwich assay using gold nanoparticles to develop a one-step assay for human chorionic gonadotropin (hCG) in human serum with a detection limit of 0.1 ng/ml for a 35 min assay.

Evaluation of specialists' outreach clinics in general practice in England: process and acceptability to patients, specialists, and general practitioners.

OBJECTIVES: The wider study aimed to evaluate specialists' outreach clinics in relation to their costs, processes, and effectiveness, including patients' and professionals' attitudes. The data on processes and attitudes are presented here. DESIGN: Self administered questionnaires were drawn up for patients, their general practitioners (GPs) and specialists, and managers in the practice. Information was sought from hospital trusts. The study formed a pilot phase prior to a wider evaluation. SETTING: Nine outreach clinics in general practices in England, each with a hospital outpatient department as a control clinic were studied. SUBJECTS: The specialties included were ear, nose, and throat surgery; rheumatology; and gynaecology. The subjects were the patients who attended either the outreach clinics or hospital outpatients clinics during the study period, the outreach patients' GPs, the outreach patients' and outpatients' specialists, the managers in the practices, and the NHS trusts which employed the specialists. MAIN OUTCOME MEASURES: Process items included waiting lists, waiting times in clinics, number of follow up visits, investigations and procedures performed, treatment, health status, patients' and specialists' travelling times, and patients' and doctors' attitudes to, and satisfaction with, the clinic. RESULTS: There was no difference in the health status of patients in relation to the clinic site (ie, outreach and hospital outpatients' clinics) at baseline, and all but one of the specialists said there were no differences in casemix between their outreach and outpatients' clinics. Patients preferred, and were more satisfied with, care in specialists' outreach clinics in general practice, in comparison with outpatients' clinics. The outreach clinics were rated as more convenient than outpatients' clinics in relation to journey times; those outreach patients in work lost less time away from work than outpatients' clinic patients due to the clinic attendance. Length of time on the waiting list was significantly reduced for gynaecology patients; waiting times in clinics were lower for outreach patients than outpatients across all specialties. In addition, outreach patients were more likely to be first rather than follow up attenders; rheumatology outreach patients were more likely than hospital outpatients to receive therapy. GPs' referrals to hospital outpatients' clinics were greatly reduced by the availability of outreach clinics. Both specialists and GPs saw the main advantages of outreach clinics in relation to the greater convenience and better access to care for patients. Few of the specialists and GPs in the outreach practices held formal training and education sessions in the outreach clinic, although over half of the GPs felt that their skills/expertise had broadened as a result of the outreach clinic. CONCLUSIONS: The processes of care (waiting times, patient satisfaction, convenience to patients, follow up attendances) were better in outreach than in outpatients' clinics. However, waiting lists were only significantly reduced for gynaecology patients, despite both GPs and consultants reporting reduced waiting lists for patients as one of the main advantages of outreach. Whether these improvements merit the increased cost to the specialists (in terms of their increased travelling times and time spent away from their hospital base) and whether the development of what is, in effect, two standards of care between practices with and without outreach can be stemmed and the standard of care raised in all practices (eg, by sharing outreach clinics between GPs in an area) remain the subject of debate. As the data were based on the pilot study, the results should be viewed with some caution, although statistical power was adequate for comparisons of sites if not specialties.

Look After Your Heart programme: impact on health status, exercise knowledge, attitudes, and behaviour of retired women in England.

OBJECTIVES: To evaluate the impact of the Health Education Authority's 20 hour Look After Your Heart health promotion course on a large group of retired women. DESIGN: Three groups of retired women were compared: group 1 women, drawn from 12 retirement groups, participated in the programme; group 2, drawn randomly from the same groups, declined; group 3, selected randomly from 12 different retirement groups matched for geographical area, were not offered the course. SETTING: Twenty four retirement groups established by a major national retail company in England. SUBJECTS: A total of 739 women with a mean age of 66 years participated. Altogether 200 women were in group 1, 192 in group 2, and 347 in group 3. MAIN OUTCOME MEASURE: The Nottingham Health Profile was administered and exercise knowledge, attitudes, and behaviour of the three groups were assessed using a validated, reliable questionnaire. RESULTS: Group 1 had significantly better self-perceived health, indicated by lower Nottingham Health Profile scores, more exercise knowledge, and positive exercise attitudes and they did more exercise than the other two groups. The responses of groups 2 and 3 were similar. Time since completion of the programme did not have any effect on Nottingham Health Profile scores, exercise knowledge, and behaviour. CONCLUSION: The Look After Your Heart programme is associated with beneficial and persistent effects in retired women. Detailed studies are needed to confirm whether these associations are due to the programme or reflect the selection of fitter, healthier subjects.

Evaluation of outreach clinics held by specialists in general practice in England.

OBJECTIVES: To measure the processes of care, health benefits and costs of outreach clinics held by hospital specialists in primary care settings. DESIGN: The study was designed as a case-referent (comparative) study in which the features of 19 outreach clinics (cases) were compared with matched outpatient clinics (controls). The measuring instruments were self administered questionnaires. Patients were followed up at six months to reassess health status. The specialties included in the study were cardiology, ENT, general medicine, general surgery, gynaecology and rheumatology. SETTING: Specialist outreach clinics in general practice in England, with matched outpatient clinic controls. SUBJECTS: Consecutive patient attenders in the outreach and outpatient clinics, their specialists, the outreach patients' general practitioners, practice managers and trust accountants. Patients' response rate at baseline: 78% (1420). MAIN OUTCOME MEASURES: Patient satisfaction, doctors' attitudes, processes and health outcomes, costs. RESULTS: Outreach patients were more satisfied with the processes of their care than outpatients, their access to specialist care was better than that for outpatients and they were more likely to be discharged. Doctors reported that the main advantages of the outreach clinic were improved patient access to specialists and convenience for patients, in comparison with outpatients, and most GPs and specialists felt the outreach clinic was "worthwhile". At six month follow up, the health status of the outreach sample had significantly improved more than that of the outpatients on all eight sub-scales of the HSQ-12, but this was probably because of their better starting point at baseline. The impact of outreach on health outcomes was small. The NHS costs of outreach were significantly higher than outpatients. An increase in outreach clinic size would reduce cost per patient, but would lead to the loss of most of the clinics' benefits. CONCLUSIONS: While the process of care was of higher quality in outreach than in outpatients, and the efficiency of care was also greater in the latter, the effect on patients' health outcomes was small. Responsiveness to patients' views and preferences is an essential component of good quality service provision. However, the greater cost of outreach raises the issue of whether improvements in the quality and efficiency of health care, without a substantial impact on health outcomes, is money well spent in a publicly funded health service. On the other hand, the real costs of outreach in comparison with outpatients clinics can probably only be truly estimated in a longitudinal study with a resource based costing model derived from documented patient attendances and treatment costs over time in relation to longer term outcome (for example, at a two year end point).

Nitric oxide and intestinal barrier failure.

The systemic inflammatory response syndrome (SIRS) is a leading cause of morbidity and mortality in adults and children. Various proinflammatory mediators have been implicated in the pathogenesis of SIRS; however, their mechanisms of action are poorly defined. Recent evidence suggests that nitric oxide (NO) plays a regulatory role in gut barrier function. Sustained upregulation of NO production in the intestine can lead to intestinal epithelial injury through the formation of peroxynitrite. Peroxynitrite can nitrate mitochondrial proteins and inhibit cellular respiration. The resultant changes in mitochondrial function lead to activation of the caspase cascade, subsequent DNA fragmentation, and enterocyte apoptosis. Enterocyte apoptosis results in a transient "bare area" in the intestinal epithelium where bacteria can attach and then penetrate the lamina propria. Bacteria that successfully escape the immune system may in turn incite a systemic inflammatory response.

Short-term outcome of seizure patients who refuse transport after out-of-hospital evaluation.

OBJECTIVE: To determine the short-term outcome of patients with a known seizure disorder who have a seizure, are evaluated by out-of-hospital care providers, and refuse transport. METHODS: This was a prospective study conducted over a 15-month period. Philadelphia Fire Department paramedics contacted a medical command physician whenever they encountered a patient with a known seizure disorder who had had another seizure and was refusing transport. After confirming that the patient had the mental capacity to refuse care and understood the associated risks, the physician recorded the patient's name, address, and telephone number. Beginning three days later, a registered nurse attempted to reach the patient by telephone and administer a brief questionnaire about his or her medical outcome. Patients not reached by telephone were sent a certified letter. The names of patients lost to follow-up were compared with medical examiner records to confirm that they had not died during the follow-up period. RESULTS: Of 63 patients enrolled in the study, 52 (82.5%) were reached in follow-up. Of these, three (5.8%) had another seizure within 72 hours and recontacted 911. One of these patients (1.9%) was hospitalized. Twenty (38.5%) patients contacted their primary care physicians. There were no deaths, including patients lost to follow-up. CONCLUSIONS: Most patients (94.2%) who were evaluated by out-of-hospital care providers for a seizure and refused transport had no further seizure activity in the subsequent 72 hours. However, because there is a risk of recurrence, out-of-hospital care providers and medical command physicians should ensure that patients understand the risks of refusal.

Missed opportunities for the prevention of cardiovascular disease among British hypertensives in primary care.

BACKGROUND: High-risk strategies for the prevention of cardiovascular disease (CVD) among hypertensive patients require knowledge of the prevalence and interaction of modifiable risk factors to ensure effective targeting of interventions. Comparatively little is known of risk-factor profiles and their modification among hypertensives in primary care. AIM: The present study was designed to explore relationships between patients' knowledge of CVD risk factors, their perception of personal risk and health behaviours, and their use of lifestyle interventions. METHOD: A cross-sectional survey of 2676 men and women with mild to moderate hypertension (diastolic blood pressure 95-115 mmHg), and their general practitioners, recruited from 1044 general practices throughout the UK, was conducted. RESULTS: Levels of modifiable risk factors were high, although there was considerable variation by age and sex; most (98.5%) patients had at least one additional CVD risk factor. A lower standard of living was associated with a higher prevalence of 'unhealthy' behaviours. Out of those with a current lifestyle problem, 85% of obese patients, 59% of smokers, 47% of excess drinkers, 49% of those with dietary risk factors and 32% of inactive patients claimed to have adopted healthier behaviours within the past 3 months. Older subjects and those with a lower standard of living were less likely to acknowledge risks, and those who did were less likely to report improving their lifestyles. While 71% of patients recalled receiving lifestyle advice, the coverage and targeting of specific interventions was generally poor. Overall, 60% of the sample had received advice on weight control, 47% on diet, 38% on exercise, 38% on smoking and 36% on alcohol. Women and older people were less likely to be given relevant counseling, and there was no evidence of targeting with respect to subjects' social class, level of hypertension or duration of diagnosis. CONCLUSION: Lifestyle interventions are welcomed and are viewed as helpful by patients receiving them. Potential health gains among high-risk hypertensives are being lost because of poor targeting and coverage of those at greatest risk.

Influence of competitive adsorption on flocculation and rheology of high-pressure-treated milk protein-stabilized emulsions.

The effect of high-pressure treatment (HPT) on the droplet-size distribution and small-deformation rheology of oil-in-water emulsions containing beta-lactoglobulin and a nonionic surfactant or sodium caseinate has been investigated at neutral pH. Addition of Tween 20 (polyoxyethylenesorbitan monolaurate) to a beta-lactoglobulin-stabilized emulsion results in competitive displacement of the adsorbed globular protein film and, following HPT, the formation of a less flocculated emulsion. The age of the beta-lactoglobulin-stabilized emulsion prior to addition of sodium caseinate influences the competitive adsorption behavior. The strengthening of the beta-lactoglobulin layer with time makes it more resistant to disruption by sodium caseinate. The level of pressure-induced flocculation of beta-lactoglobulin-coated oil droplets depends on the intensity of processing conditions and on the degree of interfacial displacement. In contrast, beta-lactoglobulin added after emulsification appears to show little evidence of competitive adsorption behavior at the caseinate oil-water interface. Changes in the rheological properties of these latter systems following HPT can be attributed to pressure-induced denaturation and gelation of beta-lactoglobulin in the continuous phase of the emulsion.

Interfacial shear rheology of aged and heat-treated beta-lactoglobulin films: displacement by nonionic surfactant.

Interfacial shear rheology of adsorbed beta-lactoglobulin films (bulk protein concentration 10(-)(3) wt %) has been studied over the temperature range 20-90 degrees C using a two-dimensional Couette-type viscometer. Effects of the type of interface (air-water, triolein-water, and n-dodecane-water), the pH (2.0, 5.6, 6.0, 7.0, and 9.0), and the extent of the heat treatment have been assessed via measurements of changes in the apparent interfacial shear viscosity and elasticity before and after the addition of increasing amounts of nonionic surfactant Tween 20 (polyoxyethylene sorbitan monolaurate). The highest interfacial viscosities were obtained at the n-dodecane-water interface and the lowest at the air-water interface. Competitive displacement of protein from the interface by Tween 20 was easier at the air-water and n-dodecane-water interfaces as compared to the triolein-water interface. The surface shear viscosity was higher and the displacement by Tween 20 more difficult as the isoelectric point of the protein was approached, which is in agreement with the presence of a more strongly cross-linked protein network at the interface. The effect of heat treatment was dependent on the pH of the aqueous solution. No simple relationship between the surface rheological characteristics and the ease of displacement by Tween 20 could be inferred.

Time-dependent polymerization of beta-lactoglobulin through disulphide bonds at the oil-water interface in emulsions.

Time-dependent intermolecular sulphydryl-disulphide interchange involving beta-lactoglobulin adsorbed at the oil-water interface in n-tetradecane-in-water emulsions (10 wt% oil, 0.5 wt% protein, pH 7.0) has been investigated using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). While only monomers are detected in the adsorbed protein immediately after emulsion formation with pure beta-lactoglobulin, on storing the emulsion the amount of polymerized beta-lactoglobulin and the sizes of the oligomers are found to increase with time. There is no polymerization of adsorbed protein in emulsions made with pure alpha-lactalbumin after 72 h, or in emulsions made with beta-lactoglobulin in the presence of a reagent (N-ethylmaleimide) for modifying sulphydryl groups. Analysis by two-dimensional SDS-PAGE of adsorbed protein from aged emulsions made with a mixture of alpha-lactalbumin + beta-lactoglobulin shows some linking by disulphide bonds between alpha-lactalbumin and beta-lactoglobulin at the interface. Taken together with earlier time-dependent surface viscosity measurements, the results indicate the important role of free sulphydryl groups in the development of the high surface viscoelasticity of adsorbed globular proteins at the oil-water interface.

Surface shear viscometry as a probe of protein-protein interactions in mixed milk protein films adsorbed at the oil-water interface.

Time-dependent surface viscosities are reported for films adsorbed from binary mixtures of the proteins alpha-lactalbumin, beta-lactoglobulin and beta-casein. The measurements were made at a planar interface between n-tetradecane and various protein solutions (10(-3) wt% of each protein, pH 7, 25 degrees C) using a Couette-type torsion-wire surface viscometer operating at very low shear-rate. Differences in behaviour between simultaneous and sequential exposure of the pairs of proteins to the interface were investigated. Some experiments were performed with chemically modified beta-lactoglobulin samples whose disulphide bonds had been cleaved and blocked. Displacement of one protein by another (e.g. alpha-lactalbumin by beta-casein) is indicated by a sudden drop in surface viscosity immediately after addition of the second protein. In systems containing beta-lactoglobulin, the long-time surface viscosity is very sensitive to the adsorption time of beta-lactoglobulin prior to addition of the second protein. Blocking the disulphide bonds in beta-lactoglobulin leads to a much faster approach to a steady-state surface viscosity. This is interpreted in terms of a much more rapid unfolding of the disordered molecules of modified beta-lactoglobulin at the oil-water interface. We conclude that surface viscosity experiments give useful and sensitive information about competitive adsorption and cooperative interactions in mixed protein films.

Recombinant human interleukin-11 prevents mucosal atrophy and bowel shortening in the defunctionalized intestine.

BACKGROUND: Mucosal atrophy and bowel shortening are the hallmark of proximal intestinal diversion for extensive necrotizing enterocolitis (NEC) or Thiry-Vella fistulas (TVF), in which the ends of a defunctionalized loop of intestine are exteriorized as stomas. Recombinant human interleukin-11 (rhIL-11) is a pleiotropic cytokine that promotes epithelial regeneration and enhances adaptation after bowel resection. The authors hypothesized that rhIL-11 may prevent mucosal atrophy and bowel shortening in rats with TVF METHODS: After creation of ileal TVF, Sprague-Dawley rats were selected randomly to receive either rhIL-11 or equal volume of 0.1% bovine serum albumin (BSA) subcutaneously daily. On day 14, the TVF were excised and examined morphologically. Enterocyte apoptosis was measured using the TUNEL assay. Mucosal DNA and protein content were measured. RESULTS: Administration of rhIL-11 resulted in a significantly greater weight gain and less shortening of TVF than BSA treatment. TVF from the rhIL-11-treated group showed evidence of hyperplasia and hypertrophy and increased crypt to villus ratio. The BSA group had substantial mucosal atrophy. There was a qualitative decrease in the incidence of apoptosis in the rhIL-11 group. CONCLUSIONS: Recombinant human IL-11 prevents mucosal atrophy and shortening of defunctionalized intestinal loops. It may help reduce the incidence of short gut syndrome in infants with extensive NEC.