Where the rubber meets the road: Emerging environmental impacts of tire wear particles and their chemical cocktails

About 3 billion new tires are produced each year and about 800 million tires become waste annually. Global dependence upon tires produced from natural rubber and petroleum-based compounds represents a persistent and complex environmental problem with only partial and often-times, ineffective solutions. Tire emissions may be in the form of whole tires, tire particles, and chemical compounds, each of which is transported through various atmospheric, terrestrial, and aquatic routes in the natural and built environments. Production and use of tires generates multiple heavy metals, plastics, PAH's, and other compounds that can be toxic alone or as chemical cocktails. Used tires require storage space, are energy intensive to recycle, and generally have few post-wear uses that are not also potential sources of pollutants (e.g., crumb rubber, pavements, burning). Tire particles emitted during use are a major component of microplastics in urban runoff and a source of unique and highly potent toxic substances. Thus, tires represent a ubiquitous and complex pollutant that requires a comprehensive examination to develop effective management and remediation. We approach the issue of tire pollution holistically by examining the life cycle of tires across production, emissions, recycling, and disposal. In this paper, we synthesize recent research and data about the environmental and human health risks associated with the production, use, and disposal of tires and discuss gaps in our knowledge about fate and transport, as well as the toxicology of tire particles and chemical leachates. We examine potential management and remediation approaches for addressing exposure risks across the life cycle of tires. We consider tires as pollutants across three levels: tires in their whole state, as particulates, and as a mixture of chemical cocktails. Finally, we discuss information gaps in our understanding of tires as a pollutant and outline key questions to improve our knowledge and ability to manage and remediate tire pollution.

Framework for nontargeted investigation of contaminants released by wildfires into stormwater runoff: Case study in the northern San Francisco Bay area

Wildfires can be extremely destructive to communities and ecosystems. However, the full scope of the ecological damage is often hard to assess, in part due to limited information on the types of chemicals introduced to affected landscapes and waterways. The objective of this study was to establish a sampling, analytical, and interpretive framework to effectively identify and monitor contaminants of emerging concern in environmental water samples impacted by wildfire runoff. A nontargeted analysis consisting of comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC × GC/TOF-MS) was conducted on stormwater samples from watersheds in the City of Santa Rosa and Sonoma and Napa Counties, USA, after the three most destructive fires during the October 2017 Northern California firestorm. Chemicals potentially related to wildfires were selected from the thousands of chromatographic features detected through a screening method that compared samples from fire-impacted sites versus unburned reference sites. This screening led to high confidence identifications of 76 potentially fire-related compounds. Authentic standards were available for 48 of these analytes, and 46 were confirmed by matching mass spectra and GC × GC retention times. Of these 46 compounds, 37 had known commercial and industrial uses as intermediates or ingredients in plastics, personal care products, pesticides, and as food additives. Nine compounds had no known uses or sources and may be oxidation products resulting from burning of natural or anthropogenic materials. Preliminary examination of potential toxicity associated with the 46 compounds, conducted via online databases and literature review, indicated limited data availability. Regional comparison suggested that more structural damage may yield a greater number of unique, potentially wildfire-related compounds. We recommend further study of post-wildfire runoff using the framework described here, which includes hypothesis-driven site selection and nontargeted analysis, to uncover potentially significant stormwater contaminants not routinely monitored after wildfires and inform risk assessment. Integr Environ Assess Manag 2021;17:1179-1193. © 2021 SETAC.

The effect of hybrid transgression on environmental tolerance in experimental yeast crosses

Evidence is rapidly accumulating that hybridization generates adaptive variation. Transgressive segregation in hybrids could promote the colonization of new environments. Here, we use an assay to select hybrid genotypes that can proliferate in environmental conditions beyond the conditions tolerated by their parents, and we directly compete them against parental genotypes in habitats across environmental clines. We made 45 different hybrid swarms by crossing yeast strains (both Saccharomyces cerevisiae and S. paradoxus) with different genetic and phenotypic divergence. We compared the ability of hybrids and parents to colonize seven types of increasingly extreme environmental clines, representing both natural and novel challenges (mimicking pollution events). We found that a significant majority of hybrids had greater environmental ranges compared to the average of both their parents' ranges (mid-parent transgression), but only a minority of hybrids had ranges exceeding their best parent (best-parent transgression). Transgression was affected by the specific strains involved in the cross and by the test environment. Genetic and phenotypic crossing distance predicted the extent of transgression in only two of the seven environments. We isolated a set of potentially transgressive hybrids selected at the extreme ends of the clines and found that many could directly outcompete their parents across whole clines and were between 1.5- and 3-fold fitter on average. Saccharomyces yeast is a good model for quantitative and replicable experimental speciation studies, which may be useful in a world where hybridization is becoming increasingly common due to the relocation of plants and animals by humans.

Protein variation in Adh and Adh-related in Drosophila pseudoobscura. Linkage disequilibrium between single nucleotide polymorphisms and protein alleles

A 3.5-kb segment of the alcohol dehydrogenase (Adh) region that includes the Adh and Adh-related genes was sequenced in 139 Drosophila pseudoobscura strains collected from 13 populations. The Adh gene encodes four protein alleles and rejects a neutral model of protein evolution with the McDonald-Kreitman test, although the number of segregating synonymous sites is too high to conclude that adaptive selection has operated. The Adh-related gene encodes 18 protein haplotypes and fails to reject an equilibrium neutral model. The populations fail to show significant geographic differentiation of the Adh-related haplotypes. Eight of 404 single nucleotide polymorphisms (SNPs) in the Adh region were in significant linkage disequilibrium with three ADHR protein alleles. Coalescent simulations with and without recombination were used to derive the expected levels of significant linkage disequilibrium between SNPs and 18 protein haplotypes. Maximum levels of linkage disequilibrium are expected for protein alleles at moderate frequencies. In coalescent models without recombination, linkage disequilibrium decays between SNPs and high frequency haplotypes because common alleles mutate to haplotypes that are rare or that reach moderate frequency. The implication of this study is that linkage disequilibrium mapping has the highest probability of success with disease-causing alleles at frequencies of 10%.

An efficient region of interest acquisition method for dynamic magnetic resonance imaging

Motivated by work in the area of dynamic magnetic resonance imaging (MRI), we develop a new approach to the problem of reduced-order MRI acquisition. Efforts in this field have concentrated on the use of Fourier and singular value decomposition (SVD) methods to obtain low-order representations of an entire image plane. We augment this work to the case of imaging an arbitrarily-shaped region of interest (ROI) embedded within the full image. After developing a natural error metric for this problem, we show that determining the minimal order required to meet a prescribed error level is in general intractable, but can be solved under certain assumptions. We then develop an optimization approach to the related problem of minimizing the error for a given order. Finally, we demonstrate the utility of this approach and its advantages over existing Fourier and SVD methods on a number of MRI images.

A comparison study of linear reconstruction techniques for diffuse optical tomographic imaging of absorption coefficient

We compare, through simulations, the performance of four linear algorithms for diffuse optical tomographic reconstruction of the three-dimensional distribution of absorption coefficient within a highly scattering medium using the diffuse photon density wave approximation. The simulation geometry consisted of a coplanar array of sources and detectors at the boundary of a half-space medium. The forward solution matrix is both underdetermined, because we estimate many more absorption coefficient voxels than we have measurements, and ill-conditioned, due to the ill-posedness of the inverse problem. We compare two algebraic techniques, ART and SIRT, and two subspace techniques, the truncated SVD and CG algorithms. We compare three-dimensional reconstructions with two-dimensional reconstructions which assume all inhomogeneities are confined to a known horizontal slab, and we consider two 'object-based' error metrics in addition to mean square reconstruction error. We include a comparison using simulated data generated using a different FDFD method with the same inversion algorithms to indicate how our conclusions are affected in a somewhat more realistic scenario. Our results show that the subspace techniques are superior to the algebraic techniques in localization of inhomogeneities and estimation of their amplitude, that two-dimensional reconstructions are sensitive to underestimation of the object depth, and that an error measure based on a location parameter can be a useful complement to mean squared error.

Linkage analysis of 150 high-risk prostate cancer families at 1q24-25

Confirmation of linkage and estimation of the proportion of families who are linked in large independent datasets is essential to understanding the significance of cancer susceptibility genes. We report here on an analysis of 150 high-risk prostate cancer families (2,176 individuals) for potential linkage to the HPC1 prostate cancer susceptibility locus at 1q24-25. This dataset includes 640 affected men with an average age at prostate cancer diagnosis of 66. 8 years (range, 39-94), representing the largest collection of high-risk families analyzed for linkage in this region to date. Linkage to multiple 1q24-25 markers was strongly rejected for the sample as a whole (lod scores at theta = 0 ranged from -30.83 to -18. 42). Assuming heterogeneity, the estimated proportion of families linked (alpha) at HPC1 in the entire dataset was 2.6%, using multipoint analysis. Because locus heterogeneity may lead to false rejection of linkage, data were stratified based on homogeneous subsets. When restricted to 21 Caucasian families with five or more affected family members and mean age at diagnosis < = 65 years, the lod scores at theta = 0 remained less than -4.0. These results indicate that the overall portion of hereditary prostate cancer families whose disease is due to inherited variation in HPC1 may be less than originally estimated.

Wavelet domain image restoration with adaptive edge-preserving regularization

In this paper, we consider a wavelet based edge-preserving regularization scheme for use in linear image restoration problems. Our efforts build on a collection of mathematical results indicating that wavelets are especially useful for representing functions that contain discontinuities (i.e., edges in two dimensions or jumps in one dimension). We interpret the resulting theory in a statistical signal processing framework and obtain a highly flexible framework for adapting the degree of regularization to the local structure of the underlying image. In particular, we are able to adapt quite easily to scale-varying and orientation-varying features in the image while simultaneously retaining the edge preservation properties of the regularizer. We demonstrate a half-quadratic algorithm for obtaining the restorations from observed data.

Major histocompatibility complex variation in the endangered Przewalski's horse

The major histocompatibility complex (MHC) is a fundamental part of the vertebrate immune system, and the high variability in many MHC genes is thought to play an essential role in recognition of parasites. The Przewalski's horse is extinct in the wild and all the living individuals descend from 13 founders, most of whom were captured around the turn of the century. One of the primary genetic concerns in endangered species is whether they have ample adaptive variation to respond to novel selective factors. In examining 14 Przewalski's horses that are broadly representative of the living animals, we found six different class II DRB major histocompatibility sequences. The sequences showed extensive nonsynonymous variation, concentrated in the putative antigen-binding sites, and little synonymous variation. Individuals had from two to four sequences as determined by single-stranded conformation polymorphism (SSCP) analysis. On the basis of the SSCP data, phylogenetic analysis of the nucleotide sequences, and segregation in a family group, we conclude that four of these sequences are from one gene (although one sequence codes for a nonfunctional allele because it contains a stop codon) and two other sequences are from another gene. The position of the stop codon is at the same amino-acid position as in a closely related sequence from the domestic horse. Because other organisms have extensive variation at homologous loci, the Przewalski's horse may have quite low variation in this important adaptive region.

Effect of supplementing a fibre basal diet with different nitrogen forms on ruminal fermentation and microbial growth in an in vitro semi-continuous culture system (RUSITEC)

Incubation trials were carried out with the rumen simulation technique (RUSITEC) to study the effects of four forms of N on the growth of ruminal micro-organisms and the fermentation variables when an all-fibre basal diet was incubated. The basal diet consisted of 10 g neutral-detergent fibre (NDF) from grass hay plus 2 g NDF from sugarbeet pulp. N forms were isolated soyabean protein, soyabean peptides, amino acids blended to profile soyabean protein and NH3 as NH4Cl. Half of the daily N supply was infused as NH4Cl and the other half was infused as each of the four treatments described. Non-NH3 N (NAN) forms increased NDF (P = 0.006), acid-detergent fibre (P = 0.003) and cellulose (P = 0.015) disappearance after 48 h incubation, CO2 (P < 0.001), CH4 (P = 0.002) and total volatile fatty acids production (P < 0.001), as well as the molar percentages of isobutyrate, isovalerate and valerate, which reflected the fermentation of amino acid C skeletons. NAN treatments also increased microbial N flow (P < 0.001) compared with NH3, with peptides and protein supporting more (P = 0.036) than amino acids. The proportion of microbial N derived from NH3 decreased successively (P < 0.05) with NH3 > amino acids > peptides > protein treatments, indicating preferential uptake of peptides without passage through the NH3 pool. Microbial efficiency (g microbial N/kg organic matter apparent disappearance) was greater (P = 0.002) for the NAN forms than for the NH3 treatment, with peptides and protein treatments supporting higher (P = 0.009) values than amino acid treatment. These results indicate that N forms other than NH3 are required for optimal fibre digestion and microbial growth.

Evidence for a rare prostate cancer-susceptibility locus at chromosome 1p36

Combining data from a genomic screen in 70 families with a high risk for prostate cancer (PC) with data from candidate-region mapping in these families and an additional 71 families, we have localized a potential hereditary PC-susceptibility locus to chromosome 1p36. Because an excess of cases of primary brain cancer (BC) have been observed in some studies of families with a high risk for PC, and because loss of heterozygosity at 1p36 is frequently observed in BC, we further evaluated 12 families with both a history of PC and a blood relative with primary BC. The overall LOD score in these 12 families was 3.22 at a recombination fraction (theta) of .06, with marker D1S507. On the basis of an a priori hypothesis, this group was stratified by age at diagnosis of PC. In the younger age group (mean age at diagnosis <66 years), a maximum two-point LOD score of 3.65 at straight theta = .0 was observed, with D1S407. This linkage was rejected in both early- and late-onset families without a history of BC (LOD scores -7.12 and -6.03, respectively, at straight theta = .0). After exclusion of 3 of the 12 families that had better evidence of linkage to previously described PC-susceptibility loci, linkage to the 1p36 region was suggested by a two-point LOD score of 4.74 at straight theta = .0, with marker D1S407. We conclude that a significant proportion of these families with both a high risk for PC and a family member with BC show linkage to the 1p36 region.

Statistically based methods for anomaly characterization in images from observations of scattered radiation

In this paper, we present an algorithm for the detection, localization, and characterization of anomalous structures in an overall region of interest given observations of scattered electromagnetic fields obtained along the boundary of the region. Such anomaly detection problems are encountered in applications including medical imaging, radar signal processing, and geophysical exploration. The techniques developed in this work are based on a nonlinear scattering model relating the anomalous structures to the observed data. A sequence of M-ary hypothesis tests are employed first to localize anomalous behavior to large areas and then to refine these initial estimates to better characterize the true target structures. We introduce a method for the incorporation of prior information into the processing which reflects constraints relevant directly to the anomaly detection problem such as the number, shapes, and sizes of anomalies present in the region. The algorithm is demonstrated using a low-frequency, inverse conductivity problem found in geophysical applications.

Outcomes of treatment of socially rehabilitated methadone maintenance patients in physicians' offices (medical maintenance): follow-up at three and a half to nine and a fourth years

OBJECTIVE

To determine whether selected socially rehabilitated former heroin addicts maintained on methadone can continue successful rehabilitation while maintained on methadone by primary care physicians rather than licensed clinics. This procedure has been termed "medical maintenance."

DESIGN

Cohort study with 42-111 months of follow-up.

SETTING

Offices of hospital staff physicians (internists or family practitioners).

PATIENTS

The 100 patients met extensive entry criteria, including five or more years in conventional methadone maintenance treatment; stable employment or other productive activity; verifiable financial support; and no criminal involvement, use of illegal drugs, or excessive alcohol use within three or more years.

MEASUREMENTS AND MAIN RESULTS

Outcome measures used were retention in treatment, discharge for one of several reasons, lost medication incidents, and substance abuse. At one, two, and three years of treatment, 98, 95, and 85 patients, respectively, remained in medical maintenance. Cumulative proportional survival in treatment was 0.735 +/- 0.048 at five years and 0.562 +/- 0.084 at nine years. After 42-111 months, 72 patients remained in good standing; 15 patients had unfavorable discharges (11 for cocaine use, three for misuse of medication, and one for administrative violations); seven voluntarily withdrew from methadone in good standing (after receiving it for 9.1-24.4 years); four died; one transferred to a chronic care facility; and one voluntarily left the program.

CONCLUSIONS

Carefully selected methadone maintenance patients in medical maintenance have a high retention rate and a low incidence of substance abuse and lost medication. Voluntary withdrawal from methadone maintenance after one or two decades is possible. The authors believe that medical maintenance should be made available to appropriate patients in other localities.

Nonphysician placement of arterial catheters. Experience with 500 insertions

To improve availability of arterial line placement, we developed a nonphysician protocol for respiratory therapists to insert arterial catheters. In our experience with more than 500 catheter insertions, in which placement lasted from 1 to 20 days, superficial infection occurred in 5 percent of patients and a major complication occurred in only 1 patient. These results show that specially trained nonphysician personnel can insert arterial catheters safely when following a protocol. Similar reallocation of existing resources should increase patient care while decreasing patient care cost in most settings.

Estimates of linkage disequilibrium and the recombination parameter determined from segregating nucleotide sites in the alcohol dehydrogenase region of Drosophila pseudoobscura

The alcohol dehydrogenase (Adh) region of Drosophila pseudoobscura, which includes the two genes Adh and Adh-Dup, was used to examine the pattern and organization of linkage disequilibrium among pairs of segregating nucleotide sites. A collection of 99 strains from the geographic range of D. pseudoobscura were nucleotide-sequenced with polymerase chain reaction-mediated techniques. All pairs of the 359 polymorphic sites in the 3.5-kb Adh region were tested for significant linkage disequilibrium with Fisher's exact test. Of the 74,278 pairwise comparisons of segregating sites, 127 were in significant linkage disequilibrium at the 5% level. The distribution of five linkage disequilibrium estimators D(ij), D2, r(ij), r2 and D(ij) were compared to theoretical distributions. The observed distributions of D(ij), D2, r(ij) and r2 were consistent with the theoretical distribution given an infinite sites model. The observed distribution of D(ij) differed from the theoretical distribution because of an excess of values at -1 and 1. No spatial pattern was observed in the linkage disequilibrium pattern in the Adh region except for two clusters of sites nonrandomly associated in the adult intron and intron 2 of Adh. The magnitude of linkage disequilibrium decreases significantly as nucleotide distance increases, or a distance effect. Adh-Dup had a larger estimate of the recombination parameter, 4Nc, than Adh, where N is the effective population size and c is the recombination rate. A comparison of the mutation and recombination parameters shows that 7-17 recombination events occur for each mutation event. The heterogeneous estimates of the recombination parameter and the inverse relationship between linkage disequilibrium and nucleotide distance are no longer significant when the two clusters of Adh intron sites are excluded from analyses. The most likely explanation for the two clusters of linkage disequilibria is epistatic selection between sites in the cluster to maintain pre-mRNA secondary structure.

Estimates of gene flow in Drosophila pseudoobscura determined from nucleotide sequence analysis of the alcohol dehydrogenase region

The genetic structure of Drosophila pseudoobscura populations was inferred from a nucleotide sequence analysis of a 3.4-kb segment of the alcohol dehydrogenase (Adh) region. A total of 99 isochromosomal strains collected from 13 populations in North and South America were used to determine if any population departed from a neutral model and to estimate levels of gene flow between populations. This study also included the nucleotide sequences from two sibling species, D. persimilis and D. miranda. We estimated the neutral mutation parameter, 4N mu, in synonymous and noncoding sites for 17 subregions of Adh in each of nine populations with sample sizes greater than three. The nucleotide diversity data in the nine populations was tested for departures from an equilibrium neutral model with two statistical tests. The Tajima and the Hudson, Kreitman, Aguade tests showed that each population fails to reject a neutral model. Tests for genetic differentiation between populations fail to show any population substructure among the North American populations of D. pseudoobscura. The nucleotide diversity data is consistent with direct and indirect measures of gene flow that show extensive dispersal between populations of D. pseudoobscura.

Molecular population genetics of an electrophoretically monomorphic protein in the alcohol dehydrogenase region of Drosophila pseudoobscura

Nucleotide sequence data from the alcohol dehydrogenase (Adh) region of 18 isochromosomal strains of Drosophila pseudoobscura were used to determine whether the lack of amino acid polymorphism in ADH results from a low neutral mutation rate or a recent directional selection event. We estimated the neutral mutation parameter, 4Nmu, in synonymous sites for 17 subregions of Adh. The nucleotide diversity data were tested for departures from an equilibrium neutral model with two statistical tests. The Tajima test and the Hudson, Kreitman and Aguade test each failed to reject a neutral model. These results suggest that the ADH enzyme of D. pseudoobscura lacks amino acid polymorphisms because the neutral mutation rate of nonsynonymous sites is low. The neutral mutation parameter for synonymous sites is heterogeneous between domains of the Adh region. These data indicate that selective constrains on synonymous sites can vary between functional domains.

Nucleotide sequence analysis of Adh genes estimates the time of geographic isolation of the Bogota population of Drosophila pseudoobscura

The population of Drosophila pseudoobscura at Bogota, Columbia, is geographically and partially reproductively isolated from populations in the main body of the species in North America. The degree of genetic differentiation and time of divergence between populations at Bogota and Apple Hill, CA, were estimated by comparison of 3388 nucleotides in the alcohol dehydrogenase region (Adh and Adh-Dup genes) of 18 strains. Of the 146 polymorphic nucleotide sites detected, 68 and 31 were unique to the Apple Hill and Bogota samples, respectively, and 53 were shared. On the basis of an observed net divergence per nucleotide site of 0.264% between the two samples, the Bogota and North American populations were estimated to have been separated for at least 155,000 years. This divergence time suggests that D. pseudoobscura extended its range from North America to South America in a period of Pleistocene glaciation, when habitat suitable for the species presumably existed in lowland Central America.

Personal care attendants and severely disabled adults: attributions for relationship outcomes

Although the personal care attendant (PCA) is identified as the single most important factor in maintaining the independence, health, and well-being of severely disabled adults (SDA), little research about the nature of the interpersonal relationship has been conducted. This study investigated the mutual perceptions of the SDAs and their PCAs of the outcome of their relationship and factors that promoted the outcome. Attribution theory was used to shape the study and guide analysis of the data. The majority of subjects reported mutually successful and satisfying relationships, and most attributed the outcome to their mutual ability, effort, or personal characteristics.

Pronounced increases in the concentration of an ovarian tumor marker, CA-125, in serum of a healthy subject during menstruation

CA-125 is a glycoprotein associated with various ovarian tumors. A commercial radioimmunoassay involving a monoclonal antibody is available for it. In our laboratory, a normal-value study was conducted as part of a routine evaluation of this assay. One healthy subject had a serum CA-125 concentration greater than 300 kU/L, more than eightfold the upper limit of normal (35 kU/L). This increase, which coincided with the onset of the menstrual period, subsided to within the normal range by the end of the menstrual cycle. The half-life of CA-125, calculated from this decrease, was 6.4 days. Similar observations were made in the same subject over several menstrual cycles. Results of clinical and ultrasound examinations of the subject for ovarian tumors were negative. No clinical evidence of malignancy was present eight months after the initial discovery of an increased CA-125. None of the other 39 healthy subjects had a CA-125 value greater than 51 kU/L. Five of these subjects had CA-125 determined several times during their menstrual cycles; none exhibited pronounced variations in CA-125 concentrations. Evidently CA-125 can be extremely increased in a healthy woman, and possible effects of the menstrual period on serum CA-125 concentrations should be considered in pre-menopausal patients.

Pronounced increases in the concentration of an ovarian tumor marker, CA-125, in serum of a healthy subject during menstruation

CA-125 is a glycoprotein associated with various ovarian tumors. A commercial radioimmunoassay involving a monoclonal antibody is available for it. In our laboratory, a normal-value study was conducted as part of a routine evaluation of this assay. One healthy subject had a serum CA-125 concentration greater than 300 kU/L, more than eightfold the upper limit of normal (35 kU/L). This increase, which coincided with the onset of the menstrual period, subsided to within the normal range by the end of the menstrual cycle. The half-life of CA-125, calculated from this decrease, was 6.4 days. Similar observations were made in the same subject over several menstrual cycles. Results of clinical and ultrasound examinations of the subject for ovarian tumors were negative. No clinical evidence of malignancy was present eight months after the initial discovery of an increased CA-125. None of the other 39 healthy subjects had a CA-125 value greater than 51 kU/L. Five of these subjects had CA-125 determined several times during their menstrual cycles; none exhibited pronounced variations in CA-125 concentrations. Evidently CA-125 can be extremely increased in a healthy woman, and possible effects of the menstrual period on serum CA-125 concentrations should be considered in pre-menopausal patients.

Effect of diet and infusion of volatile fatty acids into the rumen on the concentration of plasma free amino acids in sheep

The effect of supplementing barley diets with urea (U), extracted decorticated groundnut meal (GNM) or Peruvian fish meal (PFM) on plasma free amino acid concentrations in sheep have been examined and the first limiting amino acid has been indicated by measuring the changes in the concentration of the plasma essential amino acids (PEAA) during a rumen infusions of a volatile fatty acid (VFA) mixture. 2. Three wethers fitted rumen and re-entrant duodenal cannulas were given isonitrogenous, isoenergetic diets containing (g/kg dry matter (DM) U 20, GNM 106 and PFM 78, the crude protein (nitrogen x 6.25) contents being 139, 145 and 148 respectively. The sheep were fed hourly, the mean daily DM intake being 0.634 kg. 3. Plasma concentrations of valine, threonine, lysine, isoleucine and leucine were linearly related to their concentrations in duodenal digesta. 4. A VFA mixture was infused into the rumen for 6 h to supply (mmol/min) acetate 1.47, propionate 0.22 and n-butyrate 0.27. Blood samples were taken 6 h before, during and 12 h after the end of the infusion. 5. The concentration of all PEAA decreased relative to the pre-infusion and post-infusion controls but there were no significant differences between diets. 6. The mean decrease in concentration averaged over all three diets showed that the decrease in concentration of methionine (41.5%) was far greater than for any other essential amino acid suggesting that under these conditions methionine was the first limiting amino acid.

Imaging with rotating slit apertures and rotating collimators

The statistical quality of conventional nuclear medical imagery is limited by the small signal collected through low-efficiency conventional apertures. Coded-aperture imaging overcomes this by employing a two-step process in which the object is first efficiently detected as an "encoded" form which does not resemble the object, and then filtered (or "decoded") to form an image. We present here the imaging properties of a class of time-modulated coded apertures which, unlike most coded apertures, encode projections of the object rather than the object itself. These coded apertures can reconstruct a volume object nontomographically, tomographically (one plane focused), or three-dimensionally. We describe a new decoding algorithm that reconstructs the object from its planar projections. Results of noise calculations are given, and the noise performance of these coded-aperture systems is compared to that of conventional counterparts. A hybrid slit-pinhole system which combines the imaging advantages of a rotating slit and a pinhole is described. A new scintillation detector which accurately measures the position of an event in one dimension only is presented, and its use in our coded-aperture system is outlined. Finally, results of imaging test objects and animals are given.

Quantitative studies of food protein degradation and the energetic efficiency of microbial protein synthesis in the rumen of sheep given chopped lucerne and rolled barley

1. In a randomized block design, four sheep were given 800 g daily of diets containing: chopped lucerne (L), chopped lucerne-rolled barley (2:1; LB), rolled barley-chopped lucerne (2:1; BL), rolled barley (B); each diet was supplemented with minerals, vitamins and urea as considered necessary. Chronic oxide was included in the diets as a flow marker. 2. Flows of organic matter (OM) and non-ammonia-nitrogen (NAN) to the small intestine (SI) were measured and microbial protein was identified by a 35S-incorporation procedure. 3. OM disappearance in the rumen increased linearly with increasing inclusion of barley in the diet but there was no significant change in microbial NAN flow to the SI so that the yield of microbial NAN (g)/kg fermented OM (FOM) decreased from 29.6 (diet L) to 22.7 (diet B). Changes in the energetic efficiency of microbial protein synthesis appeared to be unrelated to alterations in rumen fluid volatile fatty acid (VFA) proportions or in rumen fluid dilution rate (D). 4. The degradability of dietary protein (non-urea-N), estimated using the 35S procedure, was 0.72, 0.76, 0.86 and 0.86 for diets L, LB, BL and B respectively. Similar values were obtained from concurrent polyester-bag experiments when the fractional outflow rate of undegraded protein from the rumen (k) was assumed to be 0.046.

Coded aperture imaging of gamma-ray sources with an off-axis rotating slit

The rotating slit is a time-varying coded aperture that can be used advantageously with a scintillation camera in imaging of static radioactive objects. The coded image obtained from an on-axis slit conveys no tomographic information, but when the slit is displaced away from the axis of rotation, tomographic information can be obtained. From one set of coded images, each plane of a 3-D object can be brought in focus by shift operations and a computed-tomography algorithm. Inverse filtering is necessary to remove the side lobes of the point spread function. The intrinsic resolution of the camera, the slit width, the filter function, and the display all affect the lateral resolution, while the object distance, the off-axis distance of the slit, and the lateral resolution determine the longitudinal resolution of the system.

A simple procedure using 35S incorporation of the measurement of microbial and undegraded food protein in ruminant digesta

1. A simple procedure using 35S incorporation for the measurement of microbial protein in absomasal or duodenal digesta of ruminants was developed and tested. 2. Microbial protein synthesized in the rumen was labelled with 35S by intraruminal infusion of 35SO4 and a microbial fraction was isolated by differential centrifugation. 3. 35S not bound by micro-organisms and present as inorganic 35S in whole digesta and in microbial fractions was oxidized to 35SO4 and the samples were brought into solution by acid-hydrolysis. 35SO4 was precipitated as Ba35SO4. 4. The proportion of microbial non-ammonia-nitrogen (NAN) in digesta NAN was determined as 35S: NAN (digesta) divided by 35S: NAN (microbial). 5. In sheep offered grass nuts at maintenance level of feeding, 48% of NAN flowing through the abomasum was of microbial origin. NAN flow to the small intestine was estimated using chronic oxide as a marker and it was calculated that 49% of the grass N was degraded in the rumen.

Rumen bacterial protein synthesis and the proportion of dietary protein escaping degradation in the rumen of sheep

1. The effect of supplementing barley diets with urea (U), extracted, decorticated groundnut meal (GNM) or Peruvian fish meal (PFM) on rumen bacterial protein synthesis and the proportion of undegraded food protein passing to the duodenum of sheep has been examined. 2. Three wethers were given isonitrogenous, isoenergetic diets containing (g/kg dry matter (DM)): U 20, GNM 106 or PFM 78, the crude protein (nitrogen x 6.25) contents being 139, 145 and 148 respectively. The sheep were fed hourly, the mean daily intake of DM being 0.634 kg. 3. Rumen bacterial protein synthesis was determined using 35S and diaminopimelic acid (DAPA) as bacterial markers and polyethylene glycol (PEG) and chromic oxide as markers of digesta flow. Rumen volatile fatty acid (VFA) production rate was determined by a continuous infusion of [1-14C]acetate. 4. 35S and DAPA gave similar estimates of the proportion of bacterial N in the trichloroacetic acid-precipitable nitrogen of the rumen digesta, the mean value being 0.86. The VFA production rate did not vary significantly between diets, the mean being 5.8 mol/24 h. The flow of bacterial N from the rumen was calculated from the PEG and CR2O3 estimates of flow and the 35S and DAPA estimates of the proportion of bacterial N in the rumen. 35S and DAPA gave similar values (mean 12.5 g/24 h) and Cr2O3 gave a slightly lower value (11.5 g/24 h) than PEG (13.5 g/24 h). Dietary effects, averaged over the four methods, were not significant; the values were 13.0, 13.4 and 11.0 g/24 h for the U, GNM and PFM diets respectively. 5. Duodenal samples were taken from two 12 h continuous collections from re-entrant cannulas and the DM flow adjusted to total recovery of Cr2O3. The mean recovery Cr2O3 at the duodenum was 0.798. The rates of flow of DM were 0.296, 0.311 and 0.334 kg/24 h and of non-ammonia-N (NAN) 13.5, 15.2 and 15.4 g/24 h on the U, GNM and PFM diets respectively. 6. The concentrations of the essential amino acids in duodenal digesta were generally higher with the PFM diet than with either of the other two diets. The flow of most amino acids through the duodenum was generally higher on the PFM and GNM diets than on the U diet. 7. The energetic efficiency of bacterial protein synthesis was calculated to be 2.1 g bacterial N/mol VFA or 28 g bacterial N/kg organic matter fermented in the rumen. 8. From the estimates of bacterial N flow the rumen and NAN flow through the duodenum it was calculated that 0.22 and 0.69 of the supplemental N from GNM and PFM respectively passed through the rumen undegraded.

Prediction of the protein requirements of farm ruminants and implications of these predictions for diet formulation

Methods of determining protein requirements are reviewed and recent proposals of the Agricultural Research Council working party on nutrient requirements of ruminants outlined. Needs of the rumen microorganisms for degradable nitrogen to achieve optimum rumen digestion of feed are predicted. The extent to which milk production and live-weight gain can be sustained by microbial protein alone is estimated. Higher milk yields and rates of growth require dietary protein that escapes degradation in the rumen but is digested in the small intestine. Small changes in degradability of dietary protein are predicted to have a large effect on the dietary crude protein requirement. Although there is still inadequate data for precise prediction, the concepts of the metabolic approach have been valuable in understanding those physiological situations where protein is most likely to be limiting, where use of protected proteins and urea might be most appropriate, in the planning of critical experiments and in the design of new methods of feeding or management of ruminants.

A study of the relationship of the dental midline to the facial median line

This report presents the results of an original investigation designed to determine (1) the prevalence in the natural dentition of a maxillary midline located in the exact middle of the mouth using the philtrum as the most reliable guide and (2) the percentage of people in whom the maxillary and mandibular midlines precisely coincide with each other. Results indicate that the midline is situated in the exact middle of the mouth in approximately 70% of people and that the maxillary and mandibular midlines fail to coincide in almost three fourths of the population.

Determination of nitrogen requirement for microbial growth from the effect of urea supplementation of a low N diet on abomasal N flow and N recycling in wethers and lambs

1. Plasma urea entry rate, urinary area excretion and, by difference, urea recycling in the body, together with the flow of non-ammonia N through the abomasum and digestion of dry matter (DM) before the abomasum were determined in both wethers and lambs receiving cereal-starch diets supplemented with urea to give 60-120 g crude protein (N X 6-25)/kg DM. 2. Lambs excreted less urea in urine than wethers given the same diet. 3. Relationships between plasma urea entry rate or urine urea excretion rate and plasma urea concentration were different for lambs compared to wethers suggesting greater conservation of body N by renal control in lambs. 4. Recycling of urea was not related to plasma urea concentration in wethers but was related exponentially in lambs, suggesting recycling is controlled rather than the result of simple diffusion from the blood to the gastro-intestinal tract. 5. Abomasal non-ammonia-N flow was similar for wethers and lambs and increased linearly with urea supplementation. 6. DM digestion prior to the abomasum was not significantly altered, although there was a tendency for decreased digestion of the basal diet given to lambs. 7. Maximum microbial N flow to the abomasum was estimated as 30 g N/kg organic matter (OM) fermented in the rumen. 8. This work and the literature reviewed suggested maximum net microbial production can be obtained when the diet supplies an amount of fermentable N equal to the microbial N output. It is calculated the diet should supply approximately 26 g fermentable N/kg digestible OM or 1-8 g fermentable N/MJ metabolizable energy. This corresponds to a fermentable crude protein supply varying from 65 to 130 g/kg DM as digestible OM content increases from 400 to 800 g/kg DM.