Modelling hepatitis C transmission over a social network of injecting drug users.

Hepatitis C virus (HCV) is a blood-borne virus that disproportionately affects people who inject drugs (PWIDs). Based on extensive interview and blood test data from a longitudinal study in Melbourne, Australia, we describe an individual-based transmission model for HCV spread amongst PWID. We use this model to simulate the transmission of HCV on an empirical social network of PWID. A feature of our model is that sources of infection can be both network neighbours and non-neighbours via "importing". Data-driven estimates of sharing frequency and rate of importing are provided. Compared to an appropriately calibrated fully connected network, the empirical network provides some protective effect on the time to primary infection. We also illustrate heterogeneities in incidence rate of infection, both across and within node degrees (i.e., number of network partners). We explore the reduced risk of infection from spontaneously clearing cutpoint nodes whose infection status oscillates, both in theory and in simulation. Further, we show our model-based estimate of per-event transmission probability largely agrees with previous estimates at the lower end of the range 1-3% commonly cited.

Determination of thermal histories of archeological cereal grains with electron spin resonance spectroscopy.

The thermal histories of archeological cereal grains were examined by electron spin resonance spectroscopy. Studies with modern samples of heated cereal grain showed that the parameters of the electron spin resonance signal characterize the maximum temperature to which the sample had previously been heated. This technique has applicability in archeology and other disciplines.

Improving network approaches to the study of complex social-ecological interdependencies.

Achieving effective, sustainable environmental governance requires a better understanding of the causes and consequences of the complex patterns of interdependencies connecting people and ecosystems within and across scales. Network approaches for conceptualizing and analyzing these interdependencies offer one promising solution. Here, we present two advances we argue are needed to further this area of research: (i) a typology of causal assumptions explicating the causal aims of any given network-centric study of social-ecological interdependencies; (ii) unifying research design considerations that facilitate conceptualizing exactly what is interdependent, through what types of relationships, and in relation to what kinds of environmental problems. The latter builds on the appreciation that many environmental problems draw from a set of core challenges that re-occur across contexts. We demonstrate how these advances combine into a comparative heuristic that facilitates leveraging case-specific findings of social-ecological interdependencies to generalizable, yet context-sensitive, theories based on explicit assumptions of causal relationships.

International variation in Helicobacter pylori infection and rates of oesophageal cancer.

AIM: To examine the association between gastric atrophy, Helicobacter pylori and CagA status, and ratio of oesophageal squamous cell carcinoma to oesophageal adenocarcinoma (OSCC:OAC) amongst international heterogeneous populations. METHODS: Standardised protocols were used to collect and process questionnaire data and serum samples for PgA and PgC levels and H. pylori and CagA serology. The OSCC:OAC were used to construct appropriate models. RESULTS: There were significant correlations between the OSCC:OAC and both rates of low PgA:PgC ratios and serological markers of H. pylori infection, in males, but not females. A significant correlation between OSCC:OAC and overall CagA-seropositivity was seen in males, but not females, but this was not independently associated with increasing OSCC:OAC. CONCLUSIONS: In males, populations with higher rates of gastric atrophy or H. pylori infection have a higher OSCC:OAC. CagA seropositivity rates seem to have no additional effect.

Evaluation of the need for endoscopy to identify low-risk patients presenting with an acute upper gastrointestinal bleed suitable for early discharge.

AIMS: To audit the safety of differing protocol-driven early-discharge policies, from two sites, for low-risk acute upper gastrointestinal (GI) bleeding and determine if default early (<24 h) in-patient endoscopy is necessary. METHODS: All patients with low-risk acute upper GI bleeding presenting to two separate hospital sites in Leeds from August 2002 to March 2005 were identified. Both hospitals operate nurse-led process-driven protocols for discharge within 24 h, but only one includes default endoscopy. Relevant information was obtained from patients' notes, patient administration systems, discharge letters and endoscopy records. RESULTS: 120 patients were admitted to site A and 74 to site B. Median length of stay on the clinical decisions unit was 12.6 h at site A and 9.4 h at site B (p = 0.045). Oesophagogastroduodenoscopy was performed on 89/120 (74%) patients at site A compared with only 7/74 (9%) at site B (p<0.001). Six of 120 (5%) patients from site A were admitted to hospital for further observation compared with 6/74 (8%) from site B (p = 0.38). Of the remaining patients, all were discharged within 24 h, and 8/114 (7%) at site A vs 17/68 (25%) at site B were given hospital clinic follow-up (p<0.001). None of the 194 patients had further bleeding or complications within 30 days. CONCLUSIONS: Patients admitted with a low-risk acute upper GI bleeding can be managed safely by a nurse-led process-driven protocol, based on readily available clinical and laboratory variables, with early discharge <24 h. Avoiding in-patient endoscopy appears to be safe but at the price of greater clinic follow-up.

Evaluation of the triple tibial osteotomy. A new technique for the management of the canine cruciate-deficient stifle.

The triple tibial osteotomy (TTO) is a technique which combines the features of tibial tuberosity advancement and wedge osteotomy for the treatment of complete and partial cruciate ligament injuries in dogs. In this paper, the technique is described and the results of a prospective study of 64 consecutive cases are presented. TTO provided a satisfactory clinical outcome in a very high percentage of cases. The technique is relatively easy to learn and has a low post-operative complication rate.

Time is of the essence: an application of a relational event model for animal social networks.

Understanding how animal social relationships are created, maintained and severed has ecological and evolutionary significance. Animal social relationships are inferred from observations of interactions between animals; the pattern of interaction over time indicates the existence (or absence) of a social relationship. Autonomous behavioural recording technologies are increasingly being used to collect continuous interaction data on animal associations. However, continuous data sequences are typically aggregated to represent a relationship as part of one (or several) pictures of the network of relations among animals, in a way that parallels human social networks. This transformation entails loss of information about interaction timing and sequence, which are particularly important to understand the formation of relationships or their disruption. Here, we describe a new statistical model, termed the relational event model, that enables the analysis of fine-grained animal association data as a continuous time sequence without requiring aggregation of the data. We apply the model to a unique data set of interaction between familiar and unfamiliar steers during a series of 36 experiments to investigate the process of social disruption and relationship formation. We show how the model provides key insights into animal behaviour in terms of relationship building, the integration process of unfamiliar animals and group building dynamics. The relational event model is well suited to data structures that are common to animal behavioural studies and can therefore be applied to a range of social interaction data to understand animal social dynamics.

Resorbable and non-resorbable augmentation devices for tenorrhaphy of xenografts in extensor tendon deficits: 12 week study.

Resorbable (poly-L-lactide) and non-resorbable (polyethylene terephathalate) tendon augmentation devices (TAD) in conjunction with a pericardial adhesion barrier, were designed to strengthen tenorrhaphies and were evaluated in an ovine extensor tendon deficit model in a short term study. Fifteen centimetres of tendon were resected and replaced with kangaroo tail tendon xenografts that had been cross-linked with 0.075% glutaraldehyde (GA) at 4 degrees C for one or seven days. Compared with tenorrhaphies performed with Kessler sutures alone, both types of TAD were more effective at preventing tenorrhaphy dehiscence, and thus maintaining tendon function. Furthermore, tensile strength of TAD tenorrhaphies increased significantly between zero and twelve weeks. For xenografts cross-linked in GA for one day, the tensile strength of tenorrhaphies with the resorbable TAD rose from 38 +/- 9 N at time zero, to 116 +/- 46 N at twelve weeks, while non-resorbable TAD tenorrhaphy strength at time zero was 42 +/- 16 N and 99 +/- 27 N at twelve weeks. For xenografts cross-linked with GA for seven days, similar increases in tensile strength of tenorrhaphies, with the two types of TAD were found. As there was no significant difference in mechanical performance or tissue response between the two TAD types in the first 12 weeks, use of the resorbable poly-L-lactide device may be advantageous clinically. Tensile strengths of midsections of the tendon xenograft cross-linked for 7 days was not significantly diminished 12 weeks after implantation and these xenografts were partially remodelled around the periphery. However, the tensile strength of xenografts cross-linked for one day declined significantly between time zero (319 +/- 80 N) and twelve weeks (239 +/- 92 N), suggesting that this degree of cross-linking was inadequate for maintenance of mechanical strength. Evaluation of the performance of tenorrhaphy augmentation devices with xenografts, over a longer implantation period, is required to further understand their usefulness for reconstruction of traumatic tendon injuries.

Kainic acid rapidly induces cyclooxygenase (COX)-2 in piglet cerebral cortex.

Ischemia/reperfusion (I/R) results in a robust induction of cyclooxygenase (COX)-2 in the newborn brain via unknown mechanisms, but glutamate release and activation of KA receptors may be involved. We examined effects of local KA (3-300 micromol/l for 10 min) treatment on cortical COX-2 expression in anesthetized piglets using a closed cranial window. Treated and corresponding control tissue samples were collected 0.5-10 h after treatment. COX-2 mRNA and protein levels were assessed using RNase protection assay and immunohistochemistry, respectively. KA elicited reproducible dose-dependent increases in cortical COX-2 mRNA unaffected by indomethacin or N(G)-nitro-L-arginine methyl ester pretreatment. COX-2 mRNA levels were elevated at 30 min, peaked at 2 h, but remained enhanced for up to 10 h after KA. Neuronal COX-2 immunoreactivity was also enhanced compared with the control side in all cortical layers 8h after KA. In summary, activation of KA receptors may be involved in the neuronal induction of COX-2 after I/R in the newborn.

Temporomandibular joint dysplasia and open-mouth jaw locking in the dog.

In 2 Basset Hounds, the condyloid processes of the mandible became subluxated when the mouth was opened widely, resulting in repeated episodes of locking of the coronoid process lateral to the zygomatic arch. Locking was prevented by osteotomy of a ventral portion of the zygomatic arch.

Disseminated opportunistic fungal disease in dogs: 10 cases (1982-1990).

Medical records of 10 dogs in which fungal infection was diagnosed between 1982 and 1990 were reviewed. In each dog, infection was determined to be caused by a single species of fungus, either Aspergillus terreus, Penicillium sp, Paecilomyces sp, Chrysosporium sp, or Pseudallescheria boydii. Nine dogs were German Shepherd Dogs; 1 was a German Shepherd Dog cross, and 9 were females. The most common clinical signs were signs of neck or back pain (9 dogs), weight loss (7 dogs), anorexia (6 dogs), pyrexia (6 dogs), paresis (3 dogs), and paralysis (3 dogs). All 10 dogs had evidence of multiple sites of diskospondylitis. Urine sediment was examined in 6 dogs, and all 6 had fungal hyphae. Urine samples from these dogs produced a medium to heavy pure growth of fungi when placed on Sabaraud's medium. Predisposing causes were not identified in any of the dogs. Four dogs were euthanatized immediately after diagnosis because of paralysis or paresis. The other 6 dogs were treated, and 4 of the 6 received itraconazole. One dog was euthanatized for an unrelated problem after 21 months of treatment; 1 dog was still alive after 4 years of continuous treatment with itraconazole. The other 4 dogs were euthanatized because of eventual paralysis or paresis. Our results suggest that German Shepherd Dogs are predisposed to infection with opportunistic fungi, possibly because of a specific inability to mount an effective response. This predisposition needs to be further studied.

Deformity of the proximal tibia in dogs.

A condition has been recognised in five young dogs in which the proximal tibia exhibited cranial bowing. This altered conformation, sometimes accompanied by bow legs (genu varum), occurs bilaterally, but to differing degrees. The deformity apparently altered the biomechanics of the stifle joint so that degenerative joint disease and rupture of the cranial cruciate ligament followed in four of the five dogs. The aetiology is unknown, but the most likely cause appears to be retardation of growth in the caudal aspect of the proximal tibial physis. Treatment involving surgical techniques to correct the joint instability was only moderately successful.

Surgical remodelling of the femoral trochlea: an experimental study.

Surgical deepening of the groove in the femoral trochlea is a technique commonly employed in the correction of patellar dislocation in dogs. In order to discover how this deep articular defect repairs the operation was studied experimentally in young goats. Observations were made on the appearance of the trochlea and the histologic changes that had taken place after approximately six, 12, and 40 weeks. The abraded groove became filled with fibrocartilage with a relatively smooth surface and it articulated freely with the patella. The majority of the replacement tissues arose by differentiation of the granulation tissue which initially filled the groove, but there appeared to have been some contribution made by the hyaline cartilage at the margins of the groove.

Hemivertebra in the dog: clinical and pathological observations.

The clinical and radiographic findings associated with the presence of hemivertebra ("wedge-shaped"vertebra) in small and brachycephalic breeds of dogs are reported together with the results of post mortem examination in the availabel cases. The condition is characterised clinically by progressive hind-leg weakness, spinal pain, abnormalities of the nervous system and evidence of muscle atrophy or other abnormalities of conformation. Confirmation of the clinical diagnosis is by radiography. It is suggested that the condition is congenital in origin. Breed incidences are reported. The occurrence of the disorder in certain families of dogs suggests also that it may be hereditary. Other congenital abnormalities are seen in some dogs affected by hemivertebrae.

Osteochondritis dissecans in the dog.

The diagnosis, aetiology, pathogenesis and treatment of osteochondritis dissecans in the shoulder, elbow, stifle and hock joints of the dog is reviewed. A technique of surgically exploring the shoulder joint with minimal exposure is described. Recommendations for preventing the development of osteochondritis dissecans are made.

Osteochondrosis of the elbow: a review of the pathogenesis and a new approach to treatment.

To test the hypothesis that joint incongruity contributes to the pathogenesis of elbow osteochondrosis, the left and right radius and ulna of 20 young large breed dogs were measured to determine any variation in length and to observe any incongruity of the elbow joint. Both lame and normal dogs were included in the study. Nine of the 20 dogs had marked disparity in radial and ulnar lengths yet only one had obvious elbow joint incongruity. The use of a sliding osteotomy for the treatment of fragmented coronoid process and a lengthening osteotomy for the treatment of an ununited anconeal process is also discussed. All four dogs treated with a sliding osteotomy showed a marked clinical improvement, and two of the three dogs treated with a lengthening osteotomy showed radiographic fusion of the anconeal process.

Spinal cord compression caused by a metastatic lesion from an aortic body tumour.

An aortic body tumour in a 7-year-old wire-haired fox terrier with hind limb ataxia is described. A metastatic lesion in the dorsal arch of the eighth thoracic vertebra caused compression of the spinal cord. Radiographic techniques are discussed that enabled the position and extent of the primary tumour and its metastasis to be defined and allowed a provisional diagnosis of chemodectoma.

Effect of terbutaline tocolysis on infant birthweight.

BACKGROUND: Previous research has suggested that terbutaline sulfate increases serum glucose in pregnant women. Increases in serum glucose in women who have gestational diabetes mellitus often lead to the birth of larger infants. This study examines the effect on infant birthweight of terbutaline used as a tocolytic agent in otherwise normal term pregnancies. METHODS: An historical cohort study was conducted of all births in a 12-month period at a US Army community hospital. There were 1376 deliveries of all types; 481 of the patients were excluded for variables that influence gestational duration or fetal weight, and 5 patients' records were lost. Birthweights relative to gestational age were compared. RESULTS: The two groups (women who were treated with terbutaline, n = 94; control group, n = 796) differed with respect to age (terbutaline group, 1.6 years younger, P = .002); pregravid weight (terbutaline group, 10.3 lb lighter, P < .001); and total weight gain (terbutaline group, 3.2 lb less, P = .001). The groups were comparable in all other variables studied (P > .05). Women receiving terbutaline therapy (average length of therapy, 4.7 weeks) gave birth an average of 1 week earlier than those not treated with terbutaline (39.09 weeks and 40.09 weeks, respectively, P < .001). The mean absolute birthweight of infants exposed to terbutaline in utero was less than that of infants from the control group (P < .001), but this difference (191.6 g) can be accounted for by the difference in average gestational age between the terbutaline group and the control group. There was no difference in birthweight (P > .05) when birthweight relative to gestational age was compared between the two groups. CONCLUSIONS: Women in this study who were treated with terbutaline did not give birth to larger infants. The previously noted hyperglycemia in women receiving terbutaline may not have been present in this study population or may not have been significant enough to affect birthweight.

Modification through modeling and reinforcement in leaderless groups.

This study compared the effects of modeling plus reinforcement (MR), reinforcement alone (R), and demand characteristics (D) on individual verbal output in a leaderless group discussion. Seventy-two male and female volunteers from undergraduate psychology courses (mean age 20.7 years) were assigned to three-person groups in the three conditions and participated in two 10 minute discussions. Ss who spoke the least in the first discussion were chosen as target persons (TPs). TPs in the R condition were reinforced for talking and punished for silence. TPs in the MR condition received the same treatment but were also exposed to a leadership modeling film. TPs in the D condition received no reinforcement, but were encouraged to become the group's leader. All conditions showed increases in verbral output, but the MR was superior to both the R (p less than .05) and D (p less than .01) conditions. The results were interpreted as consistent with Bandura's mediational theory of modeling.

Rapid stimulation of human renal ENaC by cAMP in Xenopus laevis oocytes.

Among the compensatory mechanisms restoring circulating blood volume after severe haemorrhage, increased vasopressin secretion enhances water permeability of distal nephron segments and stimulates Na(+) reabsorption in cortical collecting tubules via epithelial sodium channels (ENaC). The ability of vasopressin to upregulate ENaC via a cAMP-dependent mechanism in the medium to long term is well established. This study addressed the acute regulatory effect of cAMP on human ENaC (hENaC) and thus the potential role of vasopressin in the initial compensatory responses to haemorrhagic shock. The effects of raising intracellular cAMP (using 5 mmol/L isobutylmethylxanthine (IBMX) and 50 µmol/L forskolin) on wild-type and Liddle-mutated hENaC activity expressed in Xenopus oocytes and hENaC localisation in oocyte membranes were evaluated by dual-electrode voltage clamping and immunohistochemistry, respectively. After 30 min, IBMX + forskolin had stimulated amiloride-sensitive Na(+) current by 52% and increased the membrane density of Na(+) channels in oocytes expressing wild-type hENaC. These responses were prevented by 5 µmol/L brefeldin A, which blocks antegrade vesicular transport. By contrast, IBMX + forskolin had no effects in oocytes expressing Liddle-mutated hENaC. cAMP stimulated rapid, exocytotic recruitment of wild-type hENaC into Xenopus oocyte membranes, but had no effect on constitutively over-expressed Liddle-mutated hENaC. Extrapolating these findings to the early cAMP-mediated effect of vasopressin on cortical collecting tubule cells, they suggest that vasopressin rapidly mobilises ENaC to the apical membrane of cortical collecting tubule cells, but does not enhance ENaC activity once inserted into the membrane. We speculate that this stimulatory effect on Na(+) reabsorption (and hence water absorption) may contribute to the early restoration of extracellular fluid volume following severe haemorrhage.