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Biomedical subjects

R Dyer

Publications and source records attributed to R Dyer.

At least 19 recordsLinked to original sources
PubMed2006

Neospora caninum detected in feral rodents.

The role of rodents in the epidemiology of neosporosis was investigated by assaying brain tissue of feral mice (Mus musculus) and rats (Rattus norvegicus) for Neospora caninum. Both mouse and rat brain tissue were extracted for total DNA, and subjected to two different N. caninum-specific nested polymerase chain reaction (PCR) assays. A portion of brain tissue from the mice and rats were also assayed for N. caninum in gerbils or gamma-interferon gene knockout (KO) mice. Of the 105 feral mice tested, 10% were positive in the N. caninum-specific PCR assays. Of the 242 rats tested, 30% were positive in both assays. Although mice and rats had N. caninum by PCR testing, clinical signs of N. caninum infection were not observed nor were N. caninum parasites observed in gerbils or KO mice inoculated with the rodent brain tissue.

Animals↗
PubMed2005

Bladder augmentation using Pelvicol implant for intractable overactive bladder syndrome.

The objective of the study was to evaluate the effectiveness of an implant of porcine dermis to augment the bladder in women with refractory overactive bladder syndrome (OAB). Twelve women underwent a Pelvicol bladder augmentation. A visual analogue score for severity of incontinence and a quality of life questionnaire was carried out pre-operatively and at 12 months post-operatively. Follow up cystoscopy was carried out in three women in addition. Three women were dry and cured; five women were significantly improved; two women were slightly improved and the procedure was unsuccessful in the remaining two women. There were no significant complications and voiding was spontaneous in every case. A bladder augmentation using porcine dermis may have a role in the surgical management of non-neuropathic women with OAB that has failed to respond to conservative therapy.

Adult↗
PubMed2004

Comparison between porcine dermal implant (Permacol) and silicone injection (Macroplastique) for urodynamic stress incontinence.

The objective of this study was to compare the efficacy of porcine dermal implant injection (Permacol) and silicone injection (Macroplastique) in the treatment of female urodynamic stress incontinence (USI) in a prospective randomized trial. Fifty women with urodynamically proven stress incontinence were recruited and randomised to receive either Permacol or Macroplastique injection. Twenty-five patients were enrolled in each case. An International Continence Society (ICS) standard 1-h pad test was carried out prior to the injection and a subjective analysis of incontinence made using a Stamey scoring system. In addition, a Kings College Hospital Quality of Health Questionnaire (KCQ) was completed. The women were followed up at 6 weeks and 6 months and the same methods used to gauge the success or failure of the operation. Preoperatively there were no significant differences in pad losses, Stamey score or King's score between the two groups. The mean age of the women was 61 years (range 28-80 years). At 6 weeks there were significant reductions in the mean and median values in pad losses, Stamey score and King's score in both Permacol and Macroplastique patients but the effects were more pronounced in Permacol patients than Macroplastique patients. Of the Permacol patients, 64% were improved on quantified pad losses out of which 60% were dry whereas 54% of Macroplastique patients were improved on pad losses of which 41.6% were dry. Of the Permacol patients, 64% and 60% had reduction in Stamey and KCQ score, respectively, whereas Macroplastique patients had 46% reduction in one or more grades of Stamey scores and 42% reduction in KCQ scores. At 6 months the results in the Permacol patients appeared to be sustained but not for Macroplastique patients. This study has shown that Permacol injection when used as a urethral bulking agent appears to have a higher cure rate for urodynamic stress incontinence than Macroplastique and these results persist until the follow-up period of 6 months. The use of Permacol injection is an attractive alternative in the treatment of urodynamic stress incontinence.

Adult↗
PubMed2001

Modelling the resilience of Australian savanna systems to grazing impacts.

Savannas occur across all of northern Australia and are extensively used as rangelands. A recent surge in live cattle exports to Southeast Asia has caused excessive grazing impacts in some areas, especially near watering points. An important ecological and management question is "how resilient are savanna ecosystems to grazing disturbances?" Resilience refers to the ability of an ecosystem to remain in its current state (resist change) and return to this state (recover) if disturbed. Resilience responses can be measured using field data. These responses can then be modelled to predict the likely resistance and recovery of savannas to grazing impacts occurring under different climatic conditions. Two approaches were used to model resilience responses. First, a relatively simple mathematical model based on a sigmoid response function was used. This model proved useful for comparing the relative resilience of different savanna ecosystems, but was limited to ecosystems and conditions for which data were available. Second, a complex process model, SAVANNA, was parameterised to simulate the structure and function of Australian savannas. Simulations were run for 50 years at two levels of grazing to evaluate resistance and then for another 50 years with no grazing to evaluate recovery. These runs predicted that savanna grasslands were more resistant to grazing (changed less) than red-loam woodlands, which recovered relatively slowly from grazing impacts. The SAVANNA model also predicted that these woodlands would recover slightly slower under the climate change scenario projected for northern Australia.

Animal Husbandry↗
PubMed2001

Modelling the trade-off between fire and grazing in a tropical savanna landscape, northern Australia.

As savannas are widespread across northern Australia and provide northern rangelands, the sustainable use of this landscape is crucial. Both fire and grazing are known to influence the tree-grass character of tropical savannas. Frequent fires open up the tree layer and change the ground layer from perennials to that dominated by annuals. Annual species in turn produce copious quantities of highly flammable fuel that perpetuates frequent, hot fires. Grazing reduces fuel loads because livestock consumes fuel-forage. This trade-off between fire and grazing was modelled using a spatially explicit, process-orientated model (SAVANNA) and field data from fire experiments performed in the Victoria River District of northern Australia. Results of simulating fire (over 40 years) with minimal or no grazing pressure revealed a reduction in the shrub and woody plants, a reduction in grasses, and no influence on the tree structure given mild fires. While mature trees were resistant to fire, immature trees, which are more likely associated with the shrub layer, were removed by fire. The overall tree density may be reduced with continual burning over longer time periods because of increasing susceptibility of old trees to fire and the lack of recruitment. Increases in stocking rates created additional forage demands until the majority of the fuel load was consumed, thus effectively suppressing fire and reverting to the grazing and suppressed fire scenario where trees and shrubs established.

Animal Husbandry↗
PubMed1999

Function of Rieger syndrome gene in left-right asymmetry and craniofacial development.

Rieger syndrome, an autosomal dominant disorder, includes ocular, craniofacial and umbilical abnormalities. The pitx2 homeobox gene, which is mutated in Rieger syndrome, has been proposed to be the effector molecule interpreting left-right axial information from the early embryonic trunk to each organ. Here we have used gene targeting in mice to generate a loss-of-function allele that would be predicted to result in organ randomization or isomerization. Although pitx2-/- embryos had abnormal cardiac morphogenesis, mutant hearts looped in the normal direction. Pitx2-/- embryos had correctly oriented, but arrested, embryonic rotation and right pulmonary isomerism. They also had defective development of the mandibular and maxillary facial prominences, regression of the stomodeum and arrested tooth development. Fgf8 expression was absent, and Bmp4 expression was expanded in the branchial-arch ectoderm. These data reveal a critical role for pitx2 in left-right asymmetry but indicate that pitx2 may function at an intermediate step in cardiac morphogenesis and embryonic rotation.

Abnormalities, Multiple↗
PubMed1999

Lipid and lipoprotein analysis of cats with lipoprotein lipase deficiency.

BACKGROUND: We have previously described a colony of domestic cats with a naturally occurring mutation in the lipoprotein lipase (LPL) gene. We have now further characterized cats homozygous for LPL deficiency (LPL -/-, homozygotes), and have contrasted these with heterozygotes (LPL +/-) and normal cats (LPL +/+). MATERIALS AND METHODS: Density gradient ultracentrifugation with subsequent lipid analysis, agarose and polyacrylamide gel electrophoresis was used to examine detailed liproprotein differences between the genotypes. Oral fat loading studies and breast milk fatty acid analysis were also performed to further characterize the phenotypic expression of LPL deficiency in this model system. RESULTS: Several lipid abnormalities associated with homozygosity for LPL deficiency were evident. Triglyceride-rich lipoprotein-triglycerides (TRL-TG) and cholesterol (TRL-C) were higher (TRL-TG 2.09 +/- 1.14 vs. 0.15 +/- 0.04 mmol L-1, P < 0.001; TRL-C 0.42 +/- 0.30 vs. 0.11 +/- 0.16 mmol L-1, P < 0.05) in male -/- than in male +/+ cats, as was HDL-cholesterol (HDL-C, 1.75 +/- 0.24 vs. 1.41 +/- 0.14 mmol L-1, P < 0.05). LDL-C levels were lower in homozygous cats than in control cats, similar to what is seen in human LPL deficiency. Oral fat loading studies revealed that homozygous cats have a marked reduced ability to clear plasma TGs in terms of peak time (7 h vs. 3 h), peak height (9.36 vs. 1.1 mmol L-1), area under the TG clearance curve (AUC, 280.3 vs. 2.2 h mmol L-1) and time to return to baseline. Fasting lipid and lipoprotein levels were not significantly different between heterozygous and normal cats. However, oral fat loading in heterozygotes revealed an intermediate phenotype (peak of 2.35 mmol L-1 at 5 h, AUC 13.1 h mmol L-1), highlighting the impaired TG clearance in these animals. CONCLUSION: Thus, LPL deficiency in the cat results in a lipid and lipoprotein phenotype that predominantly parallels human LPL deficiency, further validating the use of these animals in studies on the pathobiology of LPL.

Animals↗
PubMed1998

Matrix metalloproteinases.

Matrix metalloproteinases are a family of highly regulated peptidases that are collectively responsible for the degradation of extracellular matrix during tissue remodeling. Dysregulated activity has long been implicated in the pathologies of cancer and arthritis, and the number of diseases more recently associated with these enzymes has been increasing. In the past year, new transgenic models of matrix metalloproteinase knockouts have been described, allowing the direct assessment of specific enzyme activity in particular disease models. In addition, more selective inhibitors with improved pharmacokinetic profiles have entered clinical trials, allowing the assessment of the safety and efficacy of this strategy.

Animals↗
PubMed1997

Sorption/desorption of radioactive contaminants by sediment from the Kara Sea.

To understand the long term impact of the disposal of radioactive waste on the Kara Sea, partition coefficients (Kd) for several important radionuclides, the mineralogy of the sediment, and the relationship of Kd to liquid-to-solid ratio were quantified. Sediment was obtained from four locations in the Kara Sea area. Slow sorption kinetics were observed for 85Sr, 232U, 125I and 99Tc, whilst sorption was rapid (less than 50 h to steady-state) for 137Cs, 210Pb, and 241Am. Partition coefficients (Kd) were determined using batch type experiments and sorption isotherms which were developed for 85Sr, 99Tc, 125I, U and 137Cs. Partition coefficients for 137Cs were approx. 350 ml/g for sediment from the Trough and 180 ml/g for Stepovogo Fjord. This difference may be caused by the lower fraction of expandable clay in sediment from the fjord. Uptake of 85Sr, 99Tc, 125I, and U were all similar for both locations, with Kd values averaging 4, 3, 17 and 60 ml/g, respectively. The Kd for 137 Cs varied non-linearly from 40 to 3800 ml/g as the liquid-to-solid ratio varied from 3.4 to 6500, but only when the sorption capacity was high compared to the mass of 137Cs in the closed system of the experiment. Under identical conditions, sediment with lower Kd values showed no effect. Oxidation of sediment effectively desorbed 99Tc from the solid phase, whilst it caused increased uptake of 85Sr and U. In sequential rinses with fresh seawater, desorption was limited to 60% of 137Cs and 85Sr, and 35% of uranium.

Absorption↗
PubMed1997

Diet-induced changes in liver and bile but not brain fatty acids can be predicted from differences in plasma phospholipid fatty acids in formula- and milk-fed piglets.

The fatty acid composition of plasma phospholipids differs between infants fed formula and infants fed human milk, but the extent to which this is accompanied by differences in tissue phospholipid fatty acids is unclear. This paper describes analysis of plasma, liver and brain fatty acids from piglets fed one of seven formulas, varying in saturated, monounsaturated, (n-6) and (n-3) fatty acids or sow milk from birth for 18 d. Bile fatty acids were analyzed because they are secreted from liver and may be an important source of fatty acids for intestinal lipoprotein synthesis. The results were used to determine the relation between diet-related differences in plasma phospholipid fatty acids and those in brain, liver and bile. Where significant associations were found, prediction limits were constructed to assess the usefulness of analysis of plasma phospholipid fatty acids to predict diet-induced changes in tissue fatty acids. The proportions (g/100 g fatty acids) of 16:0, 18:0, 18:1, 18:2(n-6) and 20:4(n-6) in plasma phospholipids were significantly associated with the proportions of the same fatty acids in liver and bile, but not brain. The results show a reasonably precise, predictable association between plasma and liver, and plasma and bile fatty acids. Brain 20:4(n-6) and 22:6(n-3), in contrast, were not reliably associated with plasma phospholipid 20:4(n-6) and 22:6(n-3) for piglets fed milk or formula providing about 1.5% energy as 18:3(n-3).

Animal Feed↗
PubMed1997

Dietary triacylglycerols with palmitic acid (16:0) in the 2-position increase 16:0 in the 2-position of plasma and chylomicron triacylglycerols, but reduce phospholipid arachidonic and docosahexaenoic acids, and alter cholesteryl ester metabolism in formula-Fed piglets.

Milk triacylglycerols have an unusual fatty acid distribution, with palmitic acid (16:0) esterified predominately at the center (sn-2) position. Other dietary triacylglycerols contain 16:0 predominantly at the sn-1,3 positions. This study was designed to evaluate the effect of formula triacylglycerol fatty acid distribution on the composition and distribution of plasma lipoprotein fatty acids in piglets fed formula containing synthesized triacylglycerols or palm olein oil with about 32 or 4.2% 16:0, respectively, in fatty acids at the sn-2 position, with comparison to piglets fed sow's milk. Feeding formula with 16:0 at the triglyceride sn-2 position or sow's milk resulted in higher chylomicron triacylglycerol sn-2 16:0 than when palm olein was fed. This suggests that dietary triacylglycerol sn-2 position fatty acids are conserved during digestion, absorption and reassembly to chylomicron triacylglycerols. The increased chylomicron triacylglycerol sn-2 position 16:0 in piglets fed synthesized triacylglycerols was accompanied by lower chylomicron triacylglycerol arachidonic and docosahexaenoic acid than in piglets fed formula with palm olein, suggesting an interaction between dietary triacylglycerol saturated fatty acid distribution and (n-6) and (n-3) fatty acid transport.

Animals↗
PubMed1996

Dietary triacylglycerol structure and saturated fat alter plasma and tissue fatty acids in piglets.

Human and pig milk triacylglycerols contain a large proportion of palmitic acid (16:0) which is predominately esterified in the 2-position. Other dietary fats contain variable amounts of 16:0, with unsaturated fatty acids predominantly esterified in the 2-position. These studies determined if the amount or position of 16:0 in dietary fat influences the composition or distribution of liver, adipose tissue, lung, or plasma fatty acids in developing piglets. Piglets were fed to 18 d with sow milk or formula with saturated fat from medium-chain triglyceride (MCT), coconut or palm oil, or synthesized triacylglycerols (synthesized to specifically direct 16:0 to the 2-position) with, in total fatty acids, 30.7, 4.3, 6.5, 27.0, and 29.6% 16:0, and in 2-position fatty acids, 55.3, 0.4, 1.3, 4.4, and 69.9% 16:0, respectively. The percentage of 16:0 in the 2-position of adipose fat from piglets fed sow milk, palm oil, and synthesized triacylglycerols were similar and higher than in piglets fed MCT or coconut oil. Thus, the amount, not the position, of dietary 16:0 determines piglet adipose tissue 16:0 content. The effects of the diets on the plasma and liver triacylglycerols were similar, with significantly lower 16:0 in total and 2-position fatty acids of the MCT and coconut oil groups, and significantly higher 16:0 in the plasma and liver triacylglycerol 2-position of piglets fed the synthesized triacylglycerols rather than sow milk or palm oil. The lung phospholipid total and 2-position 16:0 was significantly lower in the MCT, coconut, and palm oil groups, but similar in the synthesized triacylglycerol group and sow milk group. The lung phospholipid total and 2-position percentage of arachidonic acid (20:4n-6) was significantly lower in all of the formula-fed piglets than in milk-fed piglets. The physiological significance of this is not known.

Adipose Tissue↗
PubMed1996

False aneurysm--a complication following an inversion ankle sprain: a case report.

Sprains of the lateral ligamentous structures of the ankle joint as a result of inversion are common and frequently result in pain. In most cases, the pain is related to soft-tissue injury and the associated hemorrhage and swelling. This case report describes the complication of posttraumatic false aneurysm of the peroneal artery following an inversion ankle sprain in a 22-year-old athlete, a complication which should be added to the differential diagnosis as a rare, but important possibility. Emphasis of the case report is placed on the rehabilitation of the patient following medical intervention.

Adult↗
PubMed1996

One-session management of cervical intraepithelial neoplasia: a solution for developing countries.

Six hundred thirty-nine patients with CIN on referral Pap were evaluated cytocolposcopically at the first visit and decided whether to be treated the same day or not. One hundred ninety-two patients (30%) were considered negative. Follow-up evidenced later appearance of CIN in five of them. One hundred fifty-three (24%) were candidates for delayed treatment due to conditions contraindicating same-day treatment. Two hundred ninety-four patients (46%) were randomly allocated in LEEP (149) or excisional laser (145) arms, and treated the same day under local anesthesia. Both arms were comparable. There were three microinvasive carcinomas diagnosed in the surgical specimen. LEEP was faster and produced less bleeding than laser, although required a mean of four slices to remove the lesion. Arterial hypertension after anesthetic infiltration was detected in 26% of cases. Two intraoperative and two delayed bleeders required surgery. The size of lesion and surgical defect were larger than those reported in the literature. Margins were involved in 8 patients (2.7%). Only 4.7% (7/149) of patients randomized to LEEP and 3.4% (5/145) with excisional laser had persistent or recurrent CIN on follow-up. Factors predisposing to failure included depth of surgical defect, grade of lesion, and operator's expertise. With this approach, 69% of patients referred for cytology of CIN were adequately managed in the first visit, which contrasts to classical management that reaches the state of treatment in 30% of patients. LEEP appears to be faster, less costly, and requires less expertise. Its use in conjunction with adequate screening is recommended for developing countries.

Conization↗
PubMed1996

One-Session Management of Cervical Intraepithelial Neoplasia: A Solution for Developing Countries. A Prospective, Randomized Trial of LEEP versus Laser Excisional Conization

Six hundred thirty-nine patients with CIN on referral Pap were evaluated cytocolposcopically at the first visit and decided whether to be treated the same day or not. One hundred ninety-two patients (30%) were considered negative. Follow-up evidenced later appearance of CIN in five of them. One hundred fifty-three (24%) were candidates for delayed treatment due to conditions contraindicating same-day treatment. Two hundred ninety-four patients (46%) were randomly allocated in LEEP (149) or excisional laser (145) arms, and treated the same day under local anesthesia. Both arms were comparable. There were three microinvasive carcinomas diagnosed in the surgical specimen. LEEP was faster and produced less bleeding than laser, although required a mean of four slices to remove the lesion. Arterial hypertension after anesthetic infiltration was detected in 26% of cases. Two intraoperative and two delayed bleeders required surgery. The size of lesion and surgical defect were larger than those reported in the literature. Margins were involved in 8 patients (2.7%). Only 4.7% (7/149) of patients randomized to LEEP and 3.4% (5/145) with excisional laser had persistent or recurrent CIN on follow-up. Factors predisposing to failure included depth of surgical defect, grade of lesion, and operator's expertise. With this approach, 69% of patients referred for cytology of CIN were adequately managed in the first visit, which contrasts to classical management that reaches the state of treatment in 30% of patients. LEEP appears to be faster, less costly, and requires less expertise. Its use in conjunction with adequate screening is recommended for developing countries.

Journal Article↗
PubMed1995

Thermocoagulation effect of diode laser radiation in the human prostate: acute and chronic study.

OBJECTIVES: To evaluate the safety and efficacy of low-power slow-heating diode laser-induced photocoagulation of prostatic tissue for treatment of benign prostatic hyperplasia, we conducted a series of acute and chronic studies using a diode laser (810 nm) to irradiate human prostate. METHODS: The study included 6 patients undergoing radical prostatectomy because of malignancy. Laser radiation to the prostate was given transurethrally, in a noncontact mode, at the time of the procedure in 2 patients (acute group): 10 W for 300 seconds on the right side of the prostate and 15 W for 180 seconds on the left. In the remaining 4 patients (chronic group), laser radiation was given at 1, 7, 10, and 12 weeks prior to the prostatectomy. RESULTS: In the acute group the average depth of coagulation was 8.5 and 9.0 mm for the laser regimens of 15 W for 180 seconds and the 10 W for 300 seconds, respectively. In the chronic group, the average depth of coagulation was 8.9 mm for both laser regimens studied. In the acute group, there was an ill-defined hemorrhagic ring at the periphery of the lesion. At 1 week, an intact necrotic coagulum was present. At 7 weeks, some of the coagulated tissue had already sloughed off. Longer follow-up at 10 and 12 weeks demonstrated formation of a well-defined cavity with mostly re-epithelialized surface. CONCLUSIONS: Our findings suggest that noncontact diode laser (810 nm) irradiation can induce in the human prostate significant coagulation necrosis followed by sloughing of tissue and cavitation of the prostatic urethra.

Aged↗