Major histocompatibility complex variation associated with juvenile survival and parasite resistance in a large unmanaged ungulate population

Antagonistic coevolution between hosts and parasites has been proposed as a mechanism maintaining genetic diversity in both host and parasite populations. In particular, the high levels of genetic diversity widely observed at the major histocompatibility complex (MHC) of vertebrate hosts are consistent with the hypothesis of parasite-driven balancing selection acting to maintain MHC genetic diversity. To date, however, empirical evidence in support of this hypothesis, especially from natural populations, has been lacking. A large unmanaged population of Soay sheep (Ovis aries L.) is used to investigate associations between MHC variation, juvenile survival, and parasite resistance. We show in an unmanaged, nonhuman population that allelic variation within the MHC is significantly associated with differences in both juvenile survival and resistance to intestinal nematodes. Certain MHC alleles are associated with low survivorship probabilities and high levels of parasitism or vice versa. We conclude that parasites are likely to play a major role in the maintenance of MHC diversity in this population.

Inhibition of lipid peroxidation by the iron-binding protein lactoferrin

Lactoferrin containing physiological amounts of iron is an inhibitor of lipid peroxidation induced by iron(III) salts and ascorbic acid. It might therefore help to protect neutrophils, inflammatory foci and secretions from metal-ion-dependent oxidative damage.

Comorbidity of substance misuse and mental illness in community mental health and substance misuse services

BACKGROUND

Improved management of mental illness and substance misuse comorbidity is a National Health Service priority, but little is known about its prevalence and current management.

AIMS

To measure the prevalence of comorbidity among patients of community mental health teams (CMHTs) and substance misuse services, and to assess the potential for joint management.

METHOD

Cross-sectional prevalence survey in four urban UK centres.

RESULTS

Of CMHT patients, 44% (95% CI 38.1-49.9) reported past-year problem drug use and/or harmful alcohol use; 75% (95% CI 68.2-80.2) of drug service and 85% of alcohol service patients (95% CI 74.2-93.1) had a past-year psychiatric disorder. Most comorbidity patients appear ineligible for cross-referral between services. Large proportions are not identified by services and receive no specialist intervention.

CONCLUSIONS

Comorbidity is highly prevalent in CMHT, drug and alcohol treatment populations, but may be difficult to manage by cross-referral psychiatric and substance misuse services as currently configured and resourced.

No evidence for major histocompatibility complex-dependent mating patterns in a free-living ruminant population

Conventionally, the extraordinary diversity of the vertebrate major histocompatibility complex (MHC is thought to have evolved in response to parasites and pathogens affecting fitness. More recently, reproductive mechanisms such as disassortative mating have been suggested as alternative mechanisms maintaining MHC diversity. A large unmanaged population of Soay sheep (Ovis aries L.) was used to investigate reproductive mechanisms in the maintenance of MHC diversity. Animals were sampled as new-born lambs and between 887 and 1209 individuals were typed at each of five microsatellite markers located either within or flanking the ovine MHC. All loci were in Hardy-Weinberg proportions. A novel likelihood-based approach was developed to analyse mating patterns using paternity data. No evidence for non-random mating with respect to MHC markers was found using this technique. We conclude that MHC diversity in the St Kildan Soay sheep population is unlikely to be maintained by mating preferences and that, in contrast with evidence from experimental mice populations, MHC variation plays no role in the mating structure of this population.

Host immune responses are necessary for density dependence in nematode infections

Nematode infections are subject to density-dependent effects on their establishment, survivorship and fecundity within a host. These effects act to regulate and stabilize the size of nematode populations. Understanding how these density-dependent effects occur is important to guide the development of control strategies against parasitic nematodes and the diseases that they cause. These density-dependent effects have been hypothesized to result from intraspecific competition between parasites for limited resources or from the action of host immune responses. However, no specific evidence exists to distinguish between these two hypotheses. We find that in nematode (Strongyloides ratti) infections, density-dependent effects on parasite establishment, survivorship and fecundity are mediated by the host immune response. These density-dependent effects are only observed late in primary infections and no density-dependent effects are observed in infections in immuno-compromised animals. We find no evidence for intraspecific competition between parasites in experimental infections over a range of doses that encompasses all that is observed in natural infections. We conclude that density-dependent effects due to the immune response will act to regulate S. ratti infections before competition for space or nutrients within the host gut ever occurs.

Evidence for balancing selection at the major histocompatibility complex in a free-living ruminant

Evidence for selective maintenance of genetic diversity at the major histocompatibility complex (MHC) was investigated in an unmanaged population of Soay sheep on the island of Hirta, St. Kilda, Scotland. Animals were sampled as newborn lambs and between 887 and 1209 individuals were typed at each of five microsatellite markers located either within or flanking the ovine MHC. Markers located within the MHC showed high levels of linkage disequilibrium with each other but not with flanking markers. Hardy-Weinberg proportions were found for all loci; however, two of the three markers within the MHC showed relatively even allele frequency distributions that were unlikely to have resulted from neutrality and suggest the action of recent balancing selection. Sequence polymorphism was examined within DRB, a class II gene immediately adjacent to one of the microsatellite markers, and high correlation of sequence polymorphism with microsatellite length variation was found. An excess of nonsynonymous substitution compared to synonymous substitution was found, indicating the action of balancing selection favoring novel MHC variants and hence increased diversity over a longer time period.

Metorphamide: isolation, structure, and biologic activity of an amidated opioid octapeptide from bovine brain

Acid acetone extracts of caudate nucleus from bovine brain were found to contain an amidated opioid octapeptide with the following structure: Tyr-Gly-Gly-Phe-Met-Arg-Arg-Val-NH2. The peptide has been named metorphamide. Bovine metorphamide appears to be derived by proteolytic cleavage from proenkephalin, the common precursor to [Met5]enkephalin and [Leu5]enkephalin. The cleavage within the precursor giving rise to the carboxyl terminus of metorphamide occurs at a single arginine residue and is followed by transformation of a carboxyl-terminal glycine into an amide group. Metorphamide was detected in bovine caudate nucleus extracts by radioimmunoassay, and it was purified to homogeneity by gel filtration and reversed-phase high performance liquid chromatography. Amino acid composition analysis and automated Edman degradation in the gas-phase sequencer confirmed the postulated amino acid sequence. Carboxyl-terminal amidation of bovine metorphamide was shown by stability to carboxypeptidase A digestion and full crossreactivity in a radioimmunoassay that required the carboxyl-terminal amide as part of the recognition site. A synthetic replicate of metorphamide as well as several synthetic analogs were tested for opioid activity in several bioassays and binding assays, and metorphamide was found to have a high mu-binding activity. Metorphamide is the only known naturally occurring opioid peptide that has a high mu-binding activity. The kappa-binding activity is approximately equal to 50% that of the mu-binding activity, but delta-binding activity is negligible.

Network inefficiencies in autism spectrum disorder at 24 months

Autism spectrum disorder (ASD) is a developmental disorder defined by behavioral symptoms that emerge during the first years of life. Associated with these symptoms are differences in the structure of a wide array of brain regions, and in the connectivity between these regions. However, the use of cohorts with large age variability and participants past the generally recognized age of onset of the defining behaviors means that many of the reported abnormalities may be a result of cascade effects of developmentally earlier deviations. This study assessed differences in connectivity in ASD at the age at which the defining behaviors first become clear. There were 113 24-month-old participants at high risk for ASD, 31 of whom were classified as ASD, and 23 typically developing 24-month-old participants at low risk for ASD. Utilizing diffusion data to obtain measures of the length and strength of connections between anatomical regions, we performed an analysis of network efficiency. Our results showed significantly decreased local and global efficiency over temporal, parietal and occipital lobes in high-risk infants classified as ASD, relative to both low- and high-risk infants not classified as ASD. The frontal lobes showed only a reduction in global efficiency in Broca's area. In addition, these same regions showed an inverse relation between efficiency and symptom severity across the high-risk infants. The results suggest delay or deficits in infants with ASD in the optimization of both local and global aspects of network structure in regions involved in processing auditory and visual stimuli, language and nonlinguistic social stimuli.

The maintenance of genetic polymorphism in small island populations: large mammals in the Hebrides

Conventionally, small populations living on islands are expected to lose genetic variation by drift. Fluctuations in population size, combined with polygynous mating systems, are expected to contribute to the process by increasing sampling effects on genetic variation. However, in individually monitored populations of Red deer on Rum and Soay sheep on St. Kilda, which experience fluctuations in population size, two processes have been identified which mitigate loss of genetic variation. First, in a number of examples, population reductions are associated with selection. Selection may be in favour of heterozygotes, or, as we have documented in several cases, it may fluctuate in direction temporally. Second, in Soay sheep, in which mortality over population crashes is male-biased, ostensibly leading to low effective numbers of males, molecular studies show that there are systematic changes in the reproductive success of young males, and in variance in male success, that broaden genetic representation compared with expectation.

Food hypersensitivity in 20 dogs with skin and gastrointestinal signs

Canine food allergy can be defined as a nonseasonal, pruritic skin disorder of dogs that is associated with the ingestion of a substance found in the dog's diet. This study records the use of a proprietary dried fish, corn and soya-based diet for the investigation and maintenance of food allergic dogs when fed initially as a restricted allergen diet and then as a maintenance diet after challenge. All the dogs showed evidence of pruritic skin disease and in addition demonstrated gastrointestinal signs. These included the presence of faecal mucus and blood, tenesmus and increased faecal frequency; all the signs associated with colitis. Both cutaneous and gastrointestinal signs resolved when an elimination diet was fed and could be reproduced when the animal was appropriately challenged. Ten dogs were trialled on a home cooked diet of fish and potato and 10 dogs on the proprietary complete food. All the dogs were challenged to identify their food allergies. Nineteen of the dogs have subsequently been successfully maintained on the proprietary food.

The effect of the host immune response on the parasitic nematode Strongyloides ratti

The host immune response has profound effects on parasitic nematode infections. Here we have investigated how a range of infection parameters are affected by host immune responses and by their suppression and enhancement. The infection parameters considered were the number of parasitic females, their size, per capita fecundity and intestinal position. We found that in immunosuppressive treatments worms persist in the gut, sometimes with a greater per capita fecundity, maintain their size and have a more anterior gut position, compared with worms from control animals. In immunization treatments there are fewer worms in the gut, sometimes with a lower per capita fecundity and they are shorter and have a more posterior gut position, compared with worms from control animals. Worms from animals immunosuppressed by corticosteroid treatment reverse their changes in size and gut position. This description of these phenomena pave the way for a molecular biological analysis of how these changes in infection parameters are brought about by the host immune response.

Qualitative screening for drugs of abuse in hair using GC-MS

A previously described method for the analysis of hair has been modified to include analysis for amphetamines, benzodiazepines, cocaine and its metabolites, methadone and its metabolite, and phencyclidine in addition to opiates on a sample of hair. The samples of hair were washed twice with dichloromethane and cut into 1-mm segments prior to extraction with methanol at 45 degrees C for 18 h. The extracts were split into two parts; both were evaporated to dryness. One half of the extract was derivatized using MBTFA for analysis of amphetamines, and the other half was derivatized using MTBSTFA for analysis of the remaining drugs. The extracts were analyzed using electron impact gas chromatography-mass spectrometry operating in selected ion monitoring mode. In total, 18 drugs of abuse/metabolites could be detected. The method was used to screen 20 hair samples from patients attending a methadone-maintenance clinic.

Intravesicular pH and iron uptake by immature erythroid cells

The intravesicular pH of intact rabbit reticulocytes was measured by two methods; one based on the intracellular:extracellular distribution of DMO (5, 5, dimethyl + oxazolidin-2,4-dione), methylamine, and chloroquine and the other by quantitative fluorescence microscopy of cell-bound transferrin. The latter method was also applied to nucleated erythroid cells from the fetal rat liver. A pH value of approximately 5.4 was obtained with both methods and in both types of cells. Treatment of the cells with lysosomotrophic agents, metabolic inhibitors, and ionophores elevated the intravesicular pH and inhibited iron uptake from transferrin. When varying concentrations of NH4Cl were used, a close correlation was observed between the inhibition of iron uptake and elevation of the intravesicular pH. At pH 5.4 iron release from rabbit iron-bicarbonate transferrin in vitro was much more rapid than from iron-oxalate transferrin. The bicarbonate complex donates its iron to rabbit reticulocytes approximately twice as quickly as the oxalate complex. It is concluded that the acidic conditions within the vesicles provide the mechanism for iron release from the transferrin molecule after its endocytosis and that the low vesicular pH is dependent on cellular metabolism.

Effect of Deception of Distance on Prolonged Cycling Performance

This study examined the effect of deception of distance end-point on prolonged cycling performance. 21 subjects were randomly allocated to three groups ( n = 7 per group). Each group completed three self-paced time-trials separated by one day. Subjects were told that each trial was a 30-km time-trial and were required to complete the distance in the fastest time possible. Following the initial trial of 30 km, one group completed Trial 2 with a longer distance (long distance group; 36 km), another group with a shorter distance (24 km; short distance group), and the third group as control (30 km; control). Each group then completed a third time-trial of 30 km. At no time was the deception of distance in Trial 2 disclosed to the subjects, and all sources of physiological and mechanical feedback were withheld during the trials. Data from Trials 1 and 3 were analysed by repeated-measures analysis of covariance. Time to complete Trial 1 was similar among groups (–65 min.). Following the deception in Trial 2 the time to complete the 30 km in Trial 3 was increased for the short distance group, decreased for the long distance group, whilst the time for the control group remained unchanged. The times to complete the 30 km on Trials 1 and 3 were matched by changes in power output throughout the trials. It is concluded that subjects deceived of the actual distance completed will complete the subsequent performance trial based on perceived effort rather than on actual distance.

The immune response during a Strongyloides ratti infection of rats

A range of immune parameters was measured during a primary infection of Strongyloides ratti in its natural rat host. The immune parameters measured were interleukin-4 (IL-4) and interferon-gamma from both the spleen and mesenteric lymph node (MLN) cells; parasite-specific immunoglobulin G(1)(IgG(1)), IgG(2a) and IgG(2b) in serum and in intestinal tissue; parasite-specific IgG and total IgE in serum; parasite-specific and total IgA in intestinal tissue and rat mast cell protease II in intestinal tissue. Parasite-specific IgG(1), IgG(2a) and total IgE in serum and parasite-specific IgA and rat mast cell protease II in intestinal tissue all occurred at significantly greater concentrations in infected animals, compared with non-infected animals. Similarly, the production of IL-4 by MLN cells stimulated with parasitic female antigen or concanavalin A occurred at significantly greater concentrations in infected animals, compared with non-infected animals. In all, this suggests that there is a T-helper 2-type immune response during a primary S. ratti infection. These data also show the temporal changes in these components of the host immune response during a primary S. ratti infection.

Solution-based nanosensors for in-field detection with the naked eye

Nanomaterials are revolutionising analytical applications with low-cost tests that enable detecting a target molecule in a few steps and with the naked eye.

Analysis of urine for drugs of abuse using mixed-mode solid-phase extraction and gas chromatography-mass spectrometry

A method for the simultaneous analysis of urine for the major drugs of abuse is described. The analytical procedure uses solid-phase extraction (SPE), gas chromatography-mass spectrometry (GC-MS) and a semi-automated identification process. It allows simultaneous extraction, derivatization and analysis of acidic, neutral and basic drugs from urine. Urine samples were subjected to enzymatic hydrolysis followed by SPE using Bakerbond narc-2 columns. The eluant was selectively derivatized with N-methyl-bis-trifluoroacetamide (MBTFA) and N-methyl-N-trimethylsilyltrifluoroacetamide + 1% trimethylchlorosilane. Analysis was performed using a GC-MS system operating in full scan mode. A simple macro programme was written to enhance the mass spectra identification capabilities of the MS software by producing extracted ion chromatograms (EIC) for the drugs of interest. Once a suspect compound was indicated by EIC, the mass spectrum of the compound was searched manually against reference libraries for positive identification and the retention time checked against that of the standard. This procedure has increased both the amount and the reliability of information given to clinicians without increasing the cost per sample. The system has been in routine operation for 24 months, processing up to 40 urine samples per day, with a usual turn-around time of 48 h.

Detecting genes for variation in parasite burden and immunological traits in a wild population: testing the candidate gene approach

Identifying the genes underlying phenotypic variation in natural populations can provide novel insight into the evolutionary process. The candidate gene approach has been applied to studies of a number of traits in various species, in an attempt to elucidate their genetic basis. Here, we test the application of the candidate gene approach to identify the loci involved in variation in gastrointestinal parasite burden, a complex trait likely to be controlled by many loci, in a wild population of Soay sheep. A comprehensive literature review, Gene Ontology databases, and comparative genomics resources between cattle and sheep were used to generate a list of candidate genes. In a pilot study, these candidates, along with 50 random genes, were then sequenced in two pools of Soay sheep; one with low gastrointestinal nematode burden and the other high, using a NimbleGen sequence capture experiment. Further candidates were identified from single nucleotide polymorphisms (SNPs) that were highly differentiated between high- and low-resistance sheep breeds. A panel of 192 candidate and control SNPs were then typed in 960 individual Soay sheep to examine whether they individually explained variation in parasite burden, as measured as faecal egg count, as well as two immune measures (Teladorsagia circumcincta-specific antibodies and antinuclear antibodies). The cumulative effect of the candidate and control SNPs were estimated by fitting genetic relationship matrices (GRMs) as random effects in animal models of the three traits. No more significant SNPs were identified in the pilot sequencing experiment and association study than expected by chance. Furthermore, no significant difference was found between the proportions of candidate or control SNPs that were found to be significantly associated with parasite burden/immune measures. No significant effect of the candidate or control gene GRMs was found. There is thus little support for the candidate gene approach to the identification of loci explaining variation in parasitological and immunological traits in this population. However, a number of SNPs explained significant variation in multiple traits and significant correlations were found between the proportions of variance explained by individual SNPs across multiple traits. The significant SNPs identified in this study may still, therefore, merit further investigation.