Micelle stability: kappa-casein structure and function

The stability of the casein micelle is dependent on the presence of kappa-casein (CN) on the surface of the micelle where it functions as an interface between the hydrophobic caseins of the micelle interior and the aqueous environment. kappa-Casein is also involved in thiol-catalyzed disulfide interchange reactions with the whey proteins during heat treatments and, after rennet cleavage, in the facilitation of micelle coagulation. These functions of kappa-CN are regulated by the three-dimensional structure of the protein on the micelle surface. The usual means of determining structure are not available for kappa-CN because this protein is strongly self-associating and has never been crystallized. Instead, algorithms were used to predict selected secondary structures and circular dichroism spectroscopy on kappa-CN and the macropeptide released by chymosin. Three peptides were synthesized to cover the chymosin-sensitive site (His98-Lys111), the region in the macropeptide that could be helical (Pro130-Ile153), and the region between. Nuclear magnetic resonance spectroscopy showed that the peptide His98-Lys111 was probably a beta-strand with tight turns at each end. This hypothesis was confirmed by a study of the molecular dynamics showing that the C variant of kappa-CN interacted less strongly with chymosin; consequently, the slow renneting time of milk that contains this protein was explainable. Both circular dichroism and nuclear magnetic resonance indicated that the peptide Pro130-Ile153 was probably helical under normal physiological conditions. A preliminary study using nuclear magnetic resonance showed that the intervening peptide had no discernible secondary structure. Consequently, most of the beta-sheet structure of kappa-CN is likely in the para-kappa-CN region.

Bank voles in linear habitats show restricted gene flow as revealed by mitochondrial DNA (mtDNA)

Genetic structure of bank vole populations in linear river bank habitat in southeast Norway was determined from analyses of DNA sequences for the mitochondrial D-loop. Animals were sampled at sites separated by 1 km, along two forested river banks separated by approximately 100 m of open water. Twenty-six distinct haplotypes were found among 120 voles. The voles showed significant deviation from panmixis on both sides of the river. Animals from the same site or from sites 1 km apart were more likely to share haplotypes than animals 2 km apart or more. Common haplotypes were widespread on both river banks, and had a wider distribution than relatively rare haplotypes. Some rare haplotypes were found on both banks, but most were restricted to a single bank. The results suggest that short-term gene flow may be restricted for female bank voles in linear habitats. Female territorial behaviour may vary with habitat geometry. In the linear habitat described here, females defend only two territorial borders and may effectively limit female dispersal. Results were compared to a previous study of bank voles from this region in a two-dimensional habitat. Gene flow in the linear habitat was much more restricted than gene flow in the two-dimensional habitat. Probable mechanisms underlying this difference are discussed.

A randomized, controlled, molecular study of condylomata acuminata clearance during treatment with imiquimod

Imiquimod, an immune response modifier, has been demonstrated to be safe and effective in the treatment of external genital and perianal warts caused by human papillomavirus (HPV). To identify the molecular mechanism(s) by which condylomata acuminata clear during topical treatment with imiquimod, wart skin biopsies were taken from patients before treatment, at treatment week 6, and at the end of treatment. Tissues were analyzed for HPV DNA and for mRNA of several cytokines and HPV gene products. Wart clearance was associated with evidence of tissue production of interferon-alpha, -beta, and -gamma and tumor necrosis factor-alpha. Regression of warts was strongly associated with a decrease in HPV DNA and in mRNA expression for both early and late viral proteins. Thus, topical imiquimod treatment of anogenital warts led to significant increases in local production of multiple interferon mRNAs and a significant reduction in virus load as measured by decreases in HPV DNA and mRNA for early HPV proteins.

Oxygen Saturation Measurements of Blood in Retinal Vessels during Blood Loss

We describe a noninvasive technique and instrumentation for measuring the oxygen saturation of blood in retinal arteries and veins. The measurements are made by shining low-power lasers into the eye, and scanning the beams across a retinal blood vessel. The light reflected and scattered back out of the eye is collected and measured. The oxygen saturation of blood within the vessel is determined by analyzing the vessel absorption profiles at two wavelengths. A complete saturation measurement can be made in less than 1 s, allowing real-time measurement during physiologic changes. The sensitivity of this measurement technique to changes in retinal saturation has been demonstrated through a series of pilot studies in anesthetized swine. We present data indicating that retinal venous oxygen saturation decreases during ongoing blood loss, demonstrating a potential application of an eye oximeter to noninvasively monitor blood loss. © 1998 Society of Photo-Optical Instrumentation Engineers.

Retinal venous oxygen saturation correlates with blood volume

OBJECTIVES

To evaluate the sensitivity of retinal venous O2 saturation (SrvO2) for early blood loss and reinfusion. A secondary objective was to measure the correlation between SrvO2 and mixed venous O2 saturation (SvO2) during blood loss and reinfusion.

METHODS

Seven anesthetized swine were bled at 0.8 mL/kg/min to 16 mL/kg. Shed blood was re-infused at the same rate and the swine were allowed to equilibrate. After equilibration, repeat hemorrhages were performed at 1.6 mL/kg/min and 2.4 mL/kg/min. SrvO2 was measured using an eye oximeter (EOX) and SvO2 was measured using a fiber-optic catheter.

RESULTS

During blood loss, SrvO2 correlated with blood removed (r = -0.88, -0.97, -0.96) and SvO2 (r = 0.87, 0.98, 0.92). During reinfusion, SrvO2 correlated with blood re-infused (r = 0.63, 0.76, 0.82) and SvO2 (r = 0.80, 0.93, 0.96). SrvO2 decreased 1.22 +/- 0.60%/mL/kg of blood removed. The rate of decrease in SrvO2 per minute (deltaSrvO2) when blood was removed at 2.4 mL/kg/min was significantly greater than deltaSrvO2 when blood was removed at 0.8 mL/kg/min (p < 0.007). The rates of change in blood pressure (BP) and pulse were not significantly different at any rate of blood removal.

CONCLUSIONS

In this model, retinal venous O2 saturation correlated with blood volume and central venous O2 saturation. Unlike the rate of change in BP and heart rate, deltaSrvO2 values were significantly different at different rates of blood removal. Use of an EOX to monitor for blood loss, estimate the rate of hemorrhage, and evaluate the response to therapy during resuscitation warrants further study.

Community-based epidemiology: community involvement in defining social risk

In traditional epidemiologic research, the concept of risk emerges from a biomedical paradigm which draws heavily upon Cartesian-Newtonian ontological assumptions. Rational assessment of individual risk is based on a culturally conditioned metatheoretical framework that seeks specific causes for specific disease conditions. This leads to the identification of "risk factors" that can be individually modified. Research within this orientation tends to produce interpretations of data which further condition and mold cultural understanding of individual and social risks and the available choices that can be made to modify these risks. Community-based eco-epidemiology balances reductionist tendencies of individual risk-factor analysis against social context and local knowledge gained through community involvement in the research process. The community-based partnership model can contribute to a greater understanding of the interrelatedness of social problems and individual risks on the part of community participants and researchers alike.

Retinal large vessel oxygen saturations correlate with early blood loss and hypoxia in anesthetized swine

BACKGROUND

Noninvasive monitoring would likely improve trauma care. Using laser technology, we monitored the oxygen saturation in retinal vessels during exsanguination and hypoxia.

METHODS

Seven anesthetized swine were bled at 0.4 mL/kg/min for 40 minutes. During exsanguination, retinal venous saturation (SrvO2) was measured using an eye oximeter, and central venous saturation (SvO2) was measured using a fiber-optic catheter. After the shed blood was reinfused, the FiO2 was progressively decreased from 0.97 to 0.07. Femoral artery oxygen saturation (SaO2) and retinal artery oxygen saturation (SraO2) were measured at each increment.

RESULTS

During exsanguination, SrvO2 correlated with blood loss (r = -0.93) and SvO2 (r = 0.94). SraO2 correlated with SaO2 during incremental hypoxia (R2 = 0.93 +/- 0.15).

CONCLUSIONS

In this model of exsanguination, retinal venous oxygen saturation correlates with blood volume and with central venous oxygen saturation. The SraO2 correlates with SaO2 during graded hypoxia. Use of an eye oximeter to noninvasively monitor trauma patients appears promising and warrants further study.

Proteinuria in mild to moderate hypertension: results of the VA cooperative study of six antihypertensive agents and placebo. Department of Veterans Affairs Cooperative Study Group on Antihypertensive Agents

The prevalence and natural history of severe proteinuria in mild to moderate hypertension are not completely defined. We screened 1635 men with a history of hypertension and randomized 1292 with untreated diastolic blood pressure (DBP) 95-109 mmHg to single-drug treatment with either hydrochlorothiazide, atenolol, captopril, clonidine, diltiazem-SR, prazosin, or placebo in a double-blind prospective trial. Twenty-seven of 1635 patients (1.7%) satisfying clinical criteria for primary hypertension were found to have developed proteinuria > 1000 mg/24 hours and were removed from the study. Follow-up data were obtained on 19 of these 27 patients. One patient was found to have focal segmental sclerosis and progressed to end-stage renal disease. Three other patients developed severe (serum creatinine > 3.5 mg/dl) chronic renal failure (one with diabetic nephropathy), one progressed from serum creatinine 1.4 to 2.2 mg/dl, but 14 of the 19 remained with stable serum creatinine < 2.0 mg/dl on follow-up for 6-9 years. Data were available for 1076 of 1155 (93%) treated study patients at end titration, 522/600 (87%) at one year and 322/444 (73%) at two years. There were significant associations for proteinuria with obesity and higher systolic blood pressure. There was a trend toward significant difference in mean 24-hour protein excretion rates at baseline between black (127 mg) and white (139 mg) patients (p = 0.07). There were no statistically significant changes in urinary protein excretion/24 hours between or within the different treatment groups (including placebo). Eighteen patients were removed from the study during the active treatment phase for proteinuria > 1000 mg/24 hours: hydrochlorothiazide 4, placebo 3, diltiazem 3, prazosin 3, atenolol 2, clonidine 2, and captopril 1. We conclude: (1) the prevalence of severe (> 1 g/24 hours) proteinuria in the hypertensive population is significant but does not necessarily imply a poor prognosis; (2) mean 24-hour urinary protein excretion rates did not vary in response to the different classes of antihypertensive drugs; and (3) there was no drug-specific increase in proteinuria detected in this study.

A pragmatic approach to estimating total analytical error of immunoassays

Several groups have recently commented on the need for more realistic information on analytical performance of laboratory tests. The term "total analytical error" is sometimes used in this context. However, differing opinions have been expressed on how best to obtain estimates of clinical assay error, as it would be perceived by clinicians. We suggest a pragmatic definition of total analytical error for immunoassays and describe our attempts to estimate it by simple designs in the internal quality-control process. We use results over 29 months from a total serum thyroxine RIA. The most important error sources were those related to calibration materials and operator effects, errors not usually captured by short-term or snapshot experiments.

Perceptions of Species Abundance, Distribution, and Diversity:Lessons from Four Decades of Sampling on a Government-Managed Reserve

/ We examined data relative to species abundance, distribution, anddiversity patterns of reptiles and amphibians to determine how perceptionschange over time and with level of sampling effort. Location data werecompiled on more than one million individual captures or observations of 98species during a 44-year study period on the US Department of Energy's(DOE) Savannah River Site National Environmental Research Park (SRS-NERP) inSouth Carolina. We suggest that perceptions of herpetofaunal speciesdiversity are strongly dependent on level of effort and that land managementdecisions based on short-term data bases for some faunal groups could resultin serious errors in environmental management. We provide evidence thatacquiring information on biodiversity distribution patterns is compatiblewith multiyear spatially extensive research programs and also provide aperspective of what might be achieved if long-term, coordinated researchefforts were instituted nationwide.To conduct biotic surveys on government-managed lands, we recommend revisionsin the methods used by government agencies to acquire and report biodiversitydata. We suggest that government and industry employees engaged inbiodiversity survey efforts develop proficiency in field identification forone or more major taxonomic groups and be encouraged to measure the status ofpopulations quantitatively with consistent and reliable methodologies. Wealso suggest that widespread academic cooperation in the dissemination ofinformation on regional patterns of biodiversity could result byestablishment of a peer-reviewed, scientifically rigorous journal concernedwith status and trends of the biota of the United States. KEY WORDS: Abundance; Amphibian; Biodiversity; Distribution; Landmanagement; Reptile

Statistical methods for the blood beryllium lymphocyte proliferation test

The blood beryllium lymphocyte proliferation test (BeLPT) is a modification of the standard lymphocyte proliferation test that is used to identify persons who may have chronic beryllium disease. A major problem in the interpretation of BeLPT test results is outlying data values among the replicate well counts (approximately 7%). A long-linear regression model is used to describe the expected well counts for each set of Be exposure conditions, and the variance of the well counts is proportional to the square of the expected count. Two outlier-resistant regression methods are used to estimate stimulation indices (SIs) and the coefficient of variation. The first approach uses least absolute values (LAV) on the log of the well counts as a method for estimation; the second approach uses a resistant regression version of maximum quasi-likelihood estimation. A major advantage of these resistant methods is that they make it unnecessary to identify and delete outliers. These two new methods for the statistical analysis of the BeLPT data and the current outlier rejection method are applied to 173 BeLPT assays. We strongly recommend the LAV method for routine analysis of the BeLPT. Outliers are important when trying to identify individuals with beryllium hypersensitivity, since these individuals typically have large positive SI values. A new method for identifying large Sls using combined data from the nonexposed group and the beryllium workers is proposed. The log(SI)s are described with a Gaussian distribution with location and scale parameters estimated using resistant methods. This approach is applied to the test data and results are compared with those obtained from the current method.

Effect of varying intravenous patient-controlled analgesia dose and lockout interval while maintaining a constant hourly maximum dose

STUDY OBJECTIVE

To investigate the effect on the use of intravenous patient-controlled analgesia (PCA) of varying the dose (D) and lockout interval (LI) while keeping the hourly maximum dose constant.

DESIGN

Randomized, prospective study.

SETTING

Teaching hospital.

PATIENTS

75 patients scheduled to receive PCA morphine following abdominal surgery.

INTERVENTIONS

Postoperatively, patients were randomly assigned to receive PCA morphine with the following parameters: D = 1 mg, LI = 6 min (Group 1-6), D = 1.5 mg, LI = 9 min (Group 1.5-9), or D = 2 mg, LI = 12 min (Group 2-12), so that each group could receive a maximum hourly dose or 10 mg. Inadequate analgesia was managed by increasing the dose and lockout interval, while excessive sedation or respiratory rate less than 10 breaths/min resulted in decreasing the dose and lockout interval.

MEASUREMENTS AND MAIN RESULTS

Patients were assessed for pain [visual analog scale (VAS), verbal rating scale (VRS)] and side effects at 1, 2, 4, and 24 hours. The number of doses administered, missed attempts, and morphine used for the first 24 hours was recorded by automatic printout from the PCA machine. There was no difference in the total 24-hour morphine consumption, analgesia, or incidence of side effects among the three groups at any of the measurement times. Two patients, one each in the 1.5-9 and 2-12 groups, required naloxone for respiratory depression. The number of PCA injections, attempts, missed attempts, and the incidence of dosage adjustment were all significantly higher for the 1-6 group (p < 0.05).

CONCLUSION

The use of 1.0 mg with a 6-minute lockout may represent appropriate dose titration because this group obtained equivalent analgesia, morphine use, and side effects as the two larger dose and lockout groups. However, the increased number of PCA attempts and missed attempts may reflect lower satisfaction with PCA therapy.

Doses to workers in the United States nuclear weapons program due to external irradiation at the dawn of the atomic era (1940-1960)

Radiation doses to workers at the Manhattan Engineer District (MED) and Atomic Energy Commission (AEC) sites due to external irradiation during 1940-1960 are reviewed. Categorized radiation dose data were available from AEC annual reports for some years. Annual individual radiation dose data for nine MED/AEC sites for all years were available from the U.S. Department of Energy's Comprehensive Epidemiologic Data Resource. These data are combined to produce an estimate of external collective dose equivalent to 1,720 person-Sv for 1940-1960. During this period there were 19 criticality incidents; 41 persons in a workforce of several hundred thousand were accidentally overexposed in these and other incidents, including three men who died due to acute radiation syndrome.

High levels of genetic change in rodents of Chernobyl

Base-pair substitution rates for the mitochondrial cytochrome beta gene of free-living, native populations of voles collected next to reactor 4 at Chernobyl, Ukraine, were estimated by two independent methods to be in excess of 10(-4) nucleotides per site per generation. These estimates are hundreds of times greater than those typically found in mitochondria of vertebrates, suggesting that the environment resulting from this nuclear power plant disaster is having a measurable genetic impact on the organisms of that region. Despite these DNA changes, vole populations thrive and reproduce in the radioactive regions around the Chernobyl reactor.

A molecular and serologic study of the envelope gene of the British isolate: HIV-1 GB8

The entire envelope gene of a British HIV-1 isolate, GB8, was cloned, sequenced and aligned with those of the reference strains MN, SF2 and IIIB/LAI. Three of the viruses (MN, IIIB/LAI, GB8) and their recombinant gp120s, were then characterised using an extensive panel of human HIV-1 positive sera and mapped neutralising monoclonal antibodies (MAbs). Overall, the GB8 env-gene translation product shares 84% homology with those of the reference strains. Across the V3 region homology was greater between GB8 and SF2/MN (74.3-88.6%) than IIIB/LAI (63.9-66.7%). Accordingly, GB8 was sensitive to V3-specific MAbs which neutralise MN/SF2 and resistant to those that neutralize IIIB/LAI. In the CD4 binding region the central MWQEVGKAMYAPPI was conserved in all viruses but homology in the N-terminus was greater between GB8 and SF2 and IIIB/LAI than MN. GB8 and IIIB/LAI were sensitive to all MAbs raised against the CD4 binding site whereas MN was resistant to 3 of 4 tested. Human sera obtained from a London-based cohort did not differentiate between GB8 and MN in neutralisation assays, whereas IIIB/LAI titres were significantly lower at all stages of disease. These results show that GB8 carries a consensus-like V3 loop and is as representative as MN of HIV-1 viruses circulating in the UK. To our knowledge, GB8 is the only British HIV-1 isolate which has been characterised to date.

Legal obligations to human immunodeficiency virus--seropositive patients and health care providers

Balancing the interest of patients against the interest of health care providers with regard to potential or actual human immunodeficiency virus (HIV) has created many legal issues for health care providers. Some health care providers are reluctant to care for patients with HIV and have occasionally refused to treat HIV-seropositive patients. HIV-seropositive health care providers may be the target of widespread discrimination resulting in both personal and professional losses. Many health care facilities are concerned about the public's response to knowing that HIV-seropositive health care providers are on their staff. An even greater concern is the liability that may result if an HIV-seropositive health care provider transmitted the disease to a patient. Health care providers must keep current on the laws related to HIV/acquired immune deficiency syndrome (AIDS) as well as new developments in the treatment process that will impact on the law.

Peptide sequences binding to MHC class I proteins

Motifs for peptides which bind specifically to the human class I major histocompatibility complex molecules HLA-A2 and B7 were determined by sequence analysis of class I-bound peptides selected from a random synthetic library of nonamers. Thirteen individual peptides were sequenced for HLA-A2, twelve individual and nine pooled peptides were sequenced for HLA-B7. Analysis of sequence alignment implicated four peptide positions in potential contact with the class I HLA-A2 molecule and three positions for the HLA-B7 molecule. The results demonstrate that a synthetic peptide library can be used to identify allele-specific motifs for class I molecules, providing information comparable to the results obtained from sequencing endogenous peptides. This method utilizes denatured class I heavy chains, and similar results were obtained using a class I protein purified from mammalian cells or by expression in Escherichia coli. This method has the potential to detect peptides which may not be generated physiologically, but due to their binding properties, may be valuable to predict or engineer immunomodulatory T cell epitopes.

Regiospecificity of Chlorophenol Reductive Dechlorination by Vitamin B 12s

Vitamin B 12 , reduced by titanium (III) citrate to vitamin B 12s , catalyzes the reductive dechlorination of chlorophenols. Reductive dechlorination of pentachlorophenol and of all tetrachlorophenol and trichlorophenol isomers was observed. Reaction of various chlorophenols with vitamin B 12 favored reductive dechlorination at positions adjacent to another chlorinated carbon, but chlorines ortho to the hydroxyl group of a phenol were particularly resistant to reductive dechlorination, even if they were also ortho to a chlorine. This resulted in a reductive dechlorination pattern favoring removal of para and meta chlorines, which differs substantially from the pattern exhibited by anaerobic microbial consortia.

Comparison of Reactors for Oxygen-Sensitive Reactions: Reductive Dechlorination of Chlorophenols by Vitamin B 12s

Serum bottles are frequently used for studies of reductive dechlorination by vitamin B 12 , but reducing conditions can be maintained only for several days. This time period is inadequate for evaluating the reductive dechlorination of some slow-reacting aromatic compounds. Sealed glass ampoules maintain reducing conditions for many months, but this method has the disadvantage of disallowing subsampling of the reaction mixture. A glass serum tube was modified for these experiments which not only maintained anoxic conditions for several days but also allowed subsamples to be removed during experiments. The modification was a restriction placed in the middle of the tube by heating in a flame, creating two chambers separated by a narrow neck. The lower chamber contained the oxygen-sensitive reaction mixture. The upper chamber, sealed with a septum and screw cap, was purged with purified nitrogen or argon introduced and vented through fused silica capillaries. Reductive dechlorination of chlorophenols by vitamin B 12 reduced with Ti(III) citrate was monitored in all three reactor types. Sealed ampoules maintained reducing conditions for up to 12 months. The two-chambered reactor maintained reducing conditions longer than the serum vials when frequent samples were taken.

Sources of error associated with sample collection and preparation of nucleated blood cells for flow cytometric analysis

Analysis of cellular DNA content by flow cytometry has been used to detect genetic changes associated with exposure to environmental contaminants. In lower vertebrates, nucleated red blood cells can be collected for analysis without harm to the animal. Because erythrocytes sampled from an individual should have identical amounts of DNA, the coefficient of variation (CV) around the G0/G1 peak should be small. Increases in CV can indicate genetic aberrations, but may also be caused by sample handling and preparation or problems with instrumentation. To increase confidence in associating increases in CV with external causes, artifactual changes in CV due to sample treatment and instrument parameters should be identified and minimized. We assessed the effects of various sampling and handling protocols on the CV of nucleated blood cells collected from largemouth bass (Micropterus salmoides). We also compared the distribution of cells among the G0/G1, S, and G2/M phases of the cell cycle to see whether these were affected by sampling or treatment protocols. Groups of 7 fish were bled on 7 consecutive days, and blood from each fish was analyzed by flow cytometry when freshly collected, and after freezing for 1 hour or 10 days. The same fish were bled again over a consecutive 7-day period, and the experiment was repeated. CV and cell cycle distribution were not affected by our freezing protocol. Repeat sampling from the same individual did not affect CV, but altered the distribution of cells in the cell cycle, suggesting increased hemopoiesis in response to blood sampling.(ABSTRACT TRUNCATED AT 250 WORDS)