Biomedical subjects

D J O'Brien

Publications and source records attributed to D J O'Brien.

At least 19 recordsLinked to original sources

PubMed1997

Association between blood pressure and dietary factors in the dietary and nutritional survey of British adults.

OBJECTIVES: To measure the associations among blood pressure, hypertension, and recorded dietary factors. METHODS: Data were analyzed from the computer file of the Dietary and Nutritional Survey of British Adults, in which persons of both sexes aged 16 to 64 years living in private households (excluding pregnant women) had been randomly selected from the United Kingdom Electoral Register. Main outcome measures were systolic blood pressure, diastolic blood pressure, and hypertension (defined as systolic blood pressure of > or = 140 mm Hg, diastolic blood pressure of > or = 90 mm Hg, or both, or receiving antihypertensive medication). RESULTS: After controlling for 24-hour urinary potassium excretion, age, obesity, alcohol intake, and season of interview, a single measure of 24-hour urinary sodium excretion was significantly associated with systolic blood pressure (P < or = .001), diastolic blood pressure (P < .05), and hypertension (P = .009). These associations persisted after controlling for many variables of blood chemistry and dietary intake. CONCLUSIONS: Sodium is positively associated with blood pressure over a range of sodium excretion rates from 70 to 400 mmol/d. This finding supports the international consensus that the risk of hypertension is lower when salt intake is lower and suggests that a proportion of the British population has a sodium excretion rate that is habitually low enough to have some preventive effect.

Adult↗

PubMed1996

Treatment and control of psoroptic mange (sheep scab) with moxidectin.

In an investigation into alternative methods for the treatment and control of sheep scab, the efficacy of moxidectin, a second generation milbemycin, was evaluated in a series of laboratory and field studies in Ireland. Initial laboratory trials demonstrated that moxidectin, given as a subcutaneous injection at 200 micrograms/kg bodyweight was effective in the treatment of clinical psoroptic mange. Subsequent work showed that a single injection of clean sheep with moxidectin at the same dose rate provided protection against natural and experimental sheep scab infection for up to 35 days. This residual protective efficacy was tested in a large scale field trial in County Offaly, Ireland, in which more than 6500 sheep on 50 farms received a single prophylactic injection with moxidectin in the autumn and remained free from scab throughout the winter. This was comparable to the preventive effect of the annual compulsory dipping programme applied at that time. In a parallel series of field trials conducted across several counties in Ireland, two injections, 10 days apart, were effective in the treatment of outbreaks of scab. It is concluded that moxidectin is suitable for the treatment and control of sheep scab and has advantages over some existing methods because of its ease of use, safety for the user, the sheep and the environment, and because it also provides worm control owing to its efficacy against the major nematodes of sheep.

Administration, Topical↗

PubMed1995

Analysis of intact hopanoids and other lipids from the bacterium Zymomonas mobilis by high-performance liquid chromatography.

Hopanoids and other lipids were extracted from Zymomonas mobilis and quantitatively analyzed by high-performance liquid chromatography. Previous methods for hopanoid analysis required derivatization of the hopanoids via periodate oxidation or acetylation. The current method employs a normal-phase silica gel column, a ternary gradient of hexane-isopropanol-water-triethylamine, and detection with a flame ionization detector. Three major hopanoid classes were separated and quantified by this new method, and together they comprised 30 to 40% of the total lipid in these cells. Mass spectrometry confirmed that chemical structures of these hopanoids were consistent with those previously proposed. In addition, several other common lipid classes (free fatty acids and six classes of common phospholipids), comprising the remaining 60 to 70% of the total lipids, were also separated and quantified. This new chromatographic method represents the first technique for the analysis and purification of intact hopanoids. This method should be useful for the analysis and purification of hopanoids from other bacterial species.

Chromatography, High Pressure Liquid↗

PubMed1995

Semipreparative separation of intact hopanoids from Zymomonas mobilis.

Hopanoids are an important class of molecules that play a structural and physiological role in the membrane processes of prokaryotic and plant cells. Studies on the function of hopanoids require milligram quantities but have been limited by current procedures for isolation and characterization: most separations have isolated only derivatized compounds of hopane in microgram quantities. Our method employs aminopropyl bonded-phase solid-phase extraction columns with sequential elution and silica semipreparative HPLC with isocratic elution. When applied to freeze-dried cells of Zymomonas mobilis, the procedure separated the three major hopanoids present (bacteriohopanetetrol, bacteriohopanetetrol-glucosamine, and bacteriohopanetetrol-ether) from the other lipid classes. Using the solid-phase extraction column, a fraction containing an average of 3.3 mg of bacteriohopanetetrol per gram dry weight of cells was recovered without any detectable impurities along with a fraction that contained a mixture of the other two hopanoids. After this mixture was subsequently purified by semipreparative HPLC, approximately 4.7 mg of bacteriohopanetetrol-glucosamine and 3.6 mg of bacteriohopanetetrol-ether per gram dry weight of cells could be separated and recovered.

Chromatography, High Pressure Liquid↗

PubMed1995

Haematology and blood biochemistry during the course of psoroptic scabies in sheep.

Haematology and blood biochemistry were monitored during the development and regression of psoroptic scabies in sheep. There were rises in numbers of neutrophils and eosinophils and in the fibrinogen concentrations, with lowered haemoglobin concentrations any lymphocyte numbers. The only biochemical parameters that were affected were the estimated serum globulin concentration, which rose during the disease process, and the serum albumin concentration, which fell. All of these changes reverted to normal soon after treatment.

Animals↗

PubMed1994

Examination of possible transmission of sheep scab mite Psoroptes ovis between host species.

Examination of possible transmission of the Irish strain of the sheep scab mite (Psoroptes ovis) of ovine origin between host species involved calves and goats being placed with infected sheep and also directly challenged with live mites. Although mites remained on recipient species for up to a week, they failed to produce disease in either of these species. Calves and goats that had live mites placed on them likewise failed to infect sheep with which they were housed.

Animals↗

PubMed1994

Survival and retention of infectivity of the mite Psoroptes ovis off the host.

Psoroptes ovis mites were removed from infected sheep and placed in positions where wool and mites normally accumulate during sheep scab outbreaks. The ambient temperature and humidity were monitored over a 3-week period and the survival and infectivity times were examined. The procedure was carried out during each of the seasons. The hatchability of mite eggs was also examined. It was found that little variation occurred between seasons, with mites regularly retaining viability and infectivity for 15 days during all seasons. Mites that survived for more than 16 days failed to infect sheep. Mite eggs retained hatchability for up to 7 days.

Animals↗

PubMed1994

The changing strategies in operation for transposition of the great vessels.

Between July 3, 1985, and February 24, 1994, a total of 55 infants underwent arterial switch procedures for the repair of transposition of the great vessels. Thirty-five infants had an intact ventricular septum and 20 had ventricular septal defects. To date, there have been three late deaths, one in the group with an intact ventricular septum and two in the group with a ventricular septal defect. Early postoperative complications included atrial dysrhythmias, prolonged ventilation, inability to close the sternum, and tension on the coronary arteries. Follow-up echocardiographic data for 44 patients indicate that pulmonary artery gradients are a worrisome postoperative problem, especially in infants who have ventricular septal defects.

Child, Preschool↗

PubMed1994

The use of moxidectin 1% injectable for the control of psoroptic mange in sheep.

Three groups, each consisting of ten sheep of mixed breeds, naturally infected with Psoroptes ovis, were injected with 200 mcg kg-1 moxidectin 1% solution. Two groups were injected twice with an interval of 10 days between the injections, the other group was injected once. Two groups of five animals, one group infected, the other uninfected, acted respectively as positive and negative controls. Parasitological examinations, by direct examination of the sheep using a hand lens and microscopically of wool and scab samples were performed on Days 5, 8, 10, 12, 14 and 21 post-treatment and thereafter weekly for 4 months. Clinical examinations were also carried out. Moxidectin 1% injectable was completely effective in eliminating the mite from each of the treatment groups, including the group which was injected once only.

Animals↗

PubMed1994

End-tidal carbon dioxide during extremely low cardiac output.

STUDY OBJECTIVE: A number of studies have shown that expired CO2 concentration is closely related to cardiac output, but that cardiac output was not controlled as an independent variable. In addition, the partial pressure of end-tidal CO2 (PETCO2) during extremely low cardiac output has not been reported. The objective of the present study was to measure PETCO2 during well-controlled, very low blood flow rates under conditions of constant minute ventilation. DESIGN: Ten anesthetized, intubated, and mechanically ventilated swine (weight, 43 to 102 kg) were placed on two ventricular assist devices in order to control cardiac output. Minute ventilation was measured and kept constant. Ventricular assist device output (measured with an ultrasonic flow probe); PETCO2; and aortic, pulmonary artery, and central venous pressures were recorded continuously. INTERVENTIONS: After electrical induction of ventricular fibrillation, pump output was decreased in steps. MEASUREMENTS AND MAIN RESULTS: Cardiac index ranged from 0 to 5,371 mL/min/m2; 59% of PETCO2 measurements were made at cardiac indexes of less than 1,313 mL/min/m2 (30 mL/min/kg). The relationship of PETCO2 levels to cardiac index was determined with linear regression analysis; P < .05 was statistically significant. PETCO2 correlated significantly with cardiac index (P < .0001). The best-fit line by least-squares analysis produced the equation: PETCO2 = 4.98 + 0.012 [cardiac index] (r2 = .82). CONCLUSION: Under conditions of constant minute ventilation, PETCO2 correlated closely with cardiac index over a large range of blood flow rates, including extremely low rates.

Animals↗

PubMed1994

Effect of ventilation on acid-base balance and oxygenation in low blood-flow states.

OBJECTIVES: To investigate how minute ventilation affects the partial pressure of end-tidal CO2 and arterial and mixed venous pH, PCO2, PO2, and the concentration of bicarbonate during low blood-flow states. We tested the null hypothesis that acid-base conditions during low rates of blood flow are not significantly different when minute ventilation is doubled or halved. DESIGN: Prospective, experimental, animal study. SETTING: University hospital laboratory. SUBJECTS: Domestic swine. INTERVENTIONS: We studied ten anesthetized and mechanically ventilated swine (weight, 43 to 102 kg) in a new model of controlled systemic and pulmonary blood flow in which each animal was maintained on ventricular assist devices. After electrical induction of ventricular fibrillation, ventricular assist device blood flow was decreased in steps. At each decrease, control minute ventilation, two times the control minute ventilation (hyperventilation), and one-half the control minute ventilation (hypoventilation) were administered; each ventilatory change was maintained for 6 mins. MEASUREMENTS AND MAIN RESULTS: Aortic, pulmonary arterial and central venous pressures, ventricular assist device blood flow, and end-tidal CO2 were recorded continuously. Acid-base conditions were studied at three different mean blood flow rates: 49%, 30%, and 12% of baseline prearrest cardiac index. Arterial pH and PaO2 and mixed venous pH varied directly (p < .003) with minute ventilation, while PaCO2 and mixed venous PCO2, and end-tidal CO2 varied inversely (p < .0001) with minute ventilation. Mixed venous PO2 was not significantly related to minute ventilation (p = .6). PaCO2 and arterial bicarbonate; mixed venous pH, mixed venous PO2, and mixed venous bicarbonate, and end-tidal CO2 varied directly (p < .001) with blood flow, while mixed venous PCO2 varied inversely with blood flow (p < .05). Arterial pH was not significantly related to blood flow (p = .3). When minute ventilation changed from hyperventilation to hypoventilation at a mean blood flow rate of 49%, mean arterial pH decreased 0.22 +/- 0.06 (p < .05), mean PaCO2 increased 28 +/- 6 torr (3.7 +/- 0.8 kPa) (p < .05), and mean PaO2 decreased 99 +/- 77 torr (13.2 +/- 10 kPa); mean mixed venous pH decreased 0.11 +/- 0.02, mean mixed venous PCO2 increased 16 +/- 2.2 torr (2.1 +/- 0.3 kPa) (p < .05), and mean mixed venous PO2 did not change; mean end-tidal CO2 increased 18 +/- 2 torr (2.4 +/- 0.3 kPa) (p < .05). The effect of changes in minute ventilation on blood gases and end-tidal CO2 was similar for mean blood flow rates of 30% and 12% of baseline cardiac index. CONCLUSIONS: During low rates of blood flow similar to those rates found in shock and cardiopulmonary resuscitation, alterations in minute ventilation significantly influenced end-tidal CO2 and both arterial and mixed venous pH and PCO2. These findings may have clinical importance in improving the treatment of shock and cardiac arrest.

Acid-Base Equilibrium↗

PubMed1993

Identifying Blalock-Taussig shunts using a Silastic band.

Placement of an encircling Silastic band around Blalock-Taussig shunts facilitates identification and ligation of the shunt at the time of corrective operation. This technique of "shunt banding" is particularly useful for left-sided shunts, both native and modified. We have noted no complications, specifically shunt constriction. Placement of the band adds minimal operative time during shunt placement and substantially lessens the time and amount of dissection required during subsequent procedures.

Anastomosis, Surgical↗

PubMed1993

The use of mammals as sentinels for human exposure to toxic contaminants in the environment.

The use of sentinel species shows the potential to bridge the gap between animal-based and human-based environmental health research. With regard to the assessment of environmental contamination, the use of the terms "indicator," "monitor," and "sentinel" has often been confusing and ambiguous. A set of definitions is proposed as a standard to rectify this situation. The advantages of the use of sentinel species are provided, as well as criteria for sentinel selection, based on species characteristics. The recent use of mammals as sentinels for human exposure to toxic environmental contaminants is reviewed. A tabulated review of mammals proposed as indicators or monitors is included, as these may act as a database for the selection of sentinel species for future research efforts. The complexity and subtlety of factors interacting between an organism and its environment make it imperative that one provide a focused definition of what one wants the sentinel to assess and for what particular aspect of human health. Some examples of how sentinels might be selected for particular research questions are provided. While the potential for sentinel use in the field of environmental health is enormous, future investigators need to choose sentinels carefully, based on well-defined research questions, and confine conclusions drawn to the particular problem the sentinel was chosen to assess.

Animals↗

PubMed1992

Familial cardiac myxoma.

The majority of cardiac myxomas occur sporadically as isolated lesions in the left atrium of middle-aged women. However, a "familial" form and a "syndrome" form of this lesion have been identified. The syndrome myxoma can present with pigmented skin lesions and peripheral or endocrine neoplasms. The familial and syndrome forms of cardiac myxomas can usually be distinguished from the sporadic form by the presentation at a younger age, the unusual location and multicentricity of the lesions, and the presence of rare pathological conditions. In addition, a higher rate of recurrent lesions is usually associated with the familial and syndrome forms of this disease. To date, 15 families with cardiac myxomas have been reported in the world's literature. Here we present 2 additional case reports.

Adolescent↗

PubMed1992

Patient memory before and after cardiac operations.

The memories of 20 patients undergoing elective operations on the heart were assessed by a comprehensive battery of standardized psychometric tests. Testing was conducted 1 to 2 days before, 7 to 10 days after, and 1 month after each operation. Twenty age-matched, healthy control subjects were given the same battery of tests at comparable times. Compared with healthy subjects, the patient group had significantly lower scores on 3 of 19 tests before, 10 of 19 tests 1 week after, and 5 of 19 tests 1 month after surgical intervention. The patient group had similar test performances before and 1 week after the operations and improved on 3 of 19 measures 1 month after the operations. Degrees of illness and cardiopulmonary bypass variables were significantly related to only a small subset of memory measures. Results of this study are consistent with previous reports that underscore the contribution of nonspecific aspects of surgical intervention to neuropsychologic dysfunction in the immediate postoperative period. We conclude that neither the illness nor the surgical variables are directly related to substantial variance in cognitive function after operations on the heart.

Adult↗

PubMed1991

Control of fly strike in sheep by means of a pour-on formulation of cyromazine.

Cyromazine, a triazine insecticide, was used as a pour-on preparation to prevent blowfly myiasis in sheep kept in pairs of neighbouring farms in two locations. In 1987 one of the farms in each location used conventional dipping with a diazinon dip while the other used the pour-on treatment. The results achieved with the pour-on preparation compared favourably with the results of conventional dipping and the incidence of blowfly strike was substantially lower than the proportion affected among the untreated groups on the same farms. The 1988 trial results confirmed the efficacy of the pour-on treatment for up to 13 weeks and that retreatments at eight-weekly intervals could reduce the incidence of fly strike to zero.

Administration, Topical↗

PubMed1991

Electronic weaponry--a question of safety.

Electronic weapons represent a new class of weapon available to law enforcement and the lay public. Although these weapons have been available for several years, there is inadequate research to document their safety or efficacy. Two of the most common, the TASER and the stun gun, are reviewed. The electronic weapon was initially and still is approved by the US Consumer Product Safety Commission; its approval was based on theoretical calculations of the physical effects of damped sinusoidal pulses, not on the basis of animal or human studies. These devices are widely available and heavily promoted, despite limited research into their safety or efficiency and despite recent animal studies documenting their potential for lethality.

Animals↗

PubMed1990

Feasibility of reversible pulmonary artery banding: early results and intermediate-term follow-up.

Development of a reversible pulmonary artery band might obviate the need for a second cardiac surgical procedure in children with some forms of congenital heart disease. We evaluated a segmented Silastic-coated Dacron mesh band 2 to 4 mm wide sewn together with absorbable 2-0 polydioxanone suture for use as a reversible pulmonary artery band. Nine puppies 6 to 8 weeks old (mean weight, 5.8 kg) underwent placement of this pulmonary artery band. All survived the operation with a mean initial systolic gradient of 6.5 +/- 1.6 mm Hg and underwent cardiac catheterization at monthly intervals for 3 months. Two puppies died of right ventricular failure. The remaining puppies underwent balloon angioplasty with balloons 20 to 25 mm in diameter. No complications resulted from balloon angioplasty, but 1 puppy died 24 hours later of unidentified causes. Balloon angioplasty decreased the mean gradient from 46.7 +/- 6.8 mm Hg to 6.7 +/- 2.6 mm Hg. Angiography showed an increase in mean diameter of the site of the pulmonary artery band from 5.2 +/- 1.0 to 10.8 +/- 1.7 mm Hg. There was no evidence of vessel injury on angiograms. Fourteen months after balloon angioplasty, the mean gradient was 22.3 +/- 17.0 mm Hg. Our data demonstrate that a functionally reversible pulmonary artery band constructed of segmented Silastic-coated Dacron mesh and 2-0 polydioxanone suture is feasible.

Angioplasty, Balloon↗