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Biomedical subjects

E M Roberts

Publications and source records attributed to E M Roberts.

At least 19 recordsLinked to original sources
PubMed1990

Effect of chronic selenite supplementation on selenium excretion and organ accumulation in rats.

We examined the effect of chronic selenite supplementation on whole body and selected organ selenium (Se) accumulation, urine excretion of total Se and trimethylselenonium ion, and Se balance in adult male rats. Animals were housed in metabolic cages and given either deionized water or water containing 4 micrograms of Se/mL as selenite for 30 d. Absorption of selenite was nearly complete, with only approximately 10% of ingested Se appearing in feces. There was a rapid rise in urinary Se that reached a plateau within a few days and accounted for 54 +/- 2% of the intake. Excretion of trimethylselenonium ion (TMSe) in urine increased rapidly, representing 35-40% of urinary Se in the supplemented animals compared with only 2% for the control group. In one experiment, rats were killed at 30 d and total carcass Se was measured using isotope dilution analysis. Supplemented rats had only a modest increase in whole body Se (94 +/- 4 micrograms Se vs. 66 +/- 3 in controls). Calculation of Se balance in the supplemented rats showed that approximately 35% of ingested Se could not be accounted for by urine plus fecal losses combined with the portion retained in the carcass. The results from this study demonstrate that under the condition of supplementation at 4 micrograms of Se/mL of drinking water, pathways other than urinary and fecal excretion may account for a substantial portion of Se loss.

Absorption↗
PubMed1989

Non-ocular cancer in relatives of retinoblastoma patients.

A series of 1,438 parents and 2,663 other relatives of retinoblastoma patients have been followed up to ascertain the incidence among them of non-ocular cancer. Among 117 of these relatives who were known carriers of the mutation of the retinoblastoma gene 23 cases of non-ocular cancer developed during the follow-up period of the study. This compares with an expected number of 2.3, a relative risk of 9.9. A total of 25 deaths among these carriers included 21 from non-ocular cancer; the expected number was 1.8, a relative risk of 11.6. Relatives who are carriers are about 15 times more likely to die from lung cancer than the general population. Previous findings of an association of melanoma and bladder cancer with retinoblastoma are borne out in this study. The incidence of non-ocular cancer among relatives of hereditary cases who are not definitely known to be carriers shows an excess risk of 1.6: it is concluded that a proportion of these relatives are in fact carriers of the mutated retinoblastoma gene. For relatives who are not gene carriers there appears to be no excess risk of developing cancer. Carriers relatives who are not themselves affected with retinoblastoma may be inherently less liable than affected carriers to the further genetic changes which lead to the development of both retinoblastoma and subsequent non-ocular cancer.

Adult↗
PubMed1988

Fibrinolytic and haemostatic responses to desamino-D-arginine vasopressin (DDAVP) administered by intravenous and subcutaneous routes in healthy subjects.

DDAVP was administered at 0.4 microgram kg-1 intravenous (i.v.) and subcutaneous (s.c.) routes to 6 healthy subjects in a double blind crossover study. Both study treatments were well tolerated. Flushing occurred after both treatments but was more prominent after i.v. than after s.c. DDAVP. Mild transient local discomfort at the s.c. injection site occurred in 5 of 6 subjects. The mean peak factor VIII (FVIII) response was 369% and 247% of baseline after i.v. and s.c. DDAVP respectively and the maximum increase in FVIII occurred earlier with the i.v. route. Changes in FVIII antigen (FVIII:Ag) and von Willebrand factor antigen (vWF:Ag) were also monitored. Tissue-type plasminogen activator (t-PA) activity measured by a chromogenic assay employing soluble fibrin had a median peak value of 2.9 IU ml-1 at 20 min after i.v. and of 1.9 IU ml-1 at 60 min after s.c. DDAVP. t-PA antigen was also measured so that the specific activity of circulating t-PA could be determined. Preinjection median values of 14,650 and 13,700 IU mg-1 increased to peak median values of 236,200 IU mg-1 at 20 min after i.v. and 202,400 IU mg-1 at 60 min after s.c. DDAVP. Plasminogen activator inhibitor (PAI) activity fell following DDAVP and became undetectable in some subjects during the sampling period. The ratio of maximum fibrinolytic response was similar to the ratio of maximum haemostatic responses obtained by two routes of injection. Our results indicate that s.c. DDAVP might successfully replace i.v. DDAVP in several applications such as confirmation of haemostatic or fibrinolytic responsiveness in patient groups; for obtaining FVIII enriched plasma; as well as its obvious potential usefulness in home treatment of haemophilia A and von Willebrand's disease.

Adult↗
PubMed1988

Effect of anti-oestradiol-17B antibodies on the reproductive response of ewes superovulated with PMSG.

A field experiment was conducted to examine the effect of anti-oestradiol-17B antibody titre on the oestrous and ovulatory responses of ewes to low (600 i.u.) or high (1200 i.u.) doses of pregnant mare's serum gonadotrophin (PMSG). Merino ewes were treated with intravaginal sponges and were subsequently used as vehicle-treated controls or were immunized to produce reciprocal anti-oestradiol-17B antibody titres less than 1000 or greater than 1000. Ewes were then treated with PMSG and the incidence of oestrus and ovulation, ovulation rate, and yield of embryos recorded. Treatment of immune ewes with 1200 i.u. PMSG resulted in both a higher proportion of ewes ovulating and a higher ovulation rate than in immune ewes treated with 600 i.u. (86% v. 67% and 13.4 v. 6.0 respectively). As anti-oestradiol-17B titres increased there was a reduction in the proportion of ewes exhibiting oestrus. The proportion of ewes ovulating decreased as antibody increased in ewes treated with 600 i.u. PMSG but not in those treated with 1200 i.u., suggesting an increased positive feedback of oestradiol with high PMSG doses. Fertilization rates were highest at the lower PMSG dose (68% v. 42%) and increased with increasing titre. Overall, there was no increase in ovulation rate or in yield of embryos over control values from either low (less than 1000) or high (greater than 1000) antibody titres.

Animals↗
PubMed1983

Quantification of intersegmental reactions during rapid swing motion.

A simple mathematical model was developed to quantify the non-muscular reactions between two adjacent segments undergoing rapid free-segment motion. Newtonian equations of motion were used to simulate the trajectories of the two segments using the input parameters of linear acceleration and muscular moment acting only about the proximal end of the proximal link. The intersegmental muscular force and moment were mathematically considered to be zero, and no constraints were placed on the motion of the two segments. The motion of the thigh and shank during the swing phase of running was simulated by the model and compared to the real motion obtained from cinematographic records. The simulation demonstrated that proximal thigh motion has a significant effect on the distal shank motion. Depending on the initial conditions, intersegmental reactions alone can produce large increases in distal segment speed. The role of the knee musculature in preventing these reactions during the swing phase of running was inferred.

Biomechanical Phenomena↗
PubMed1983

Spline solution to terminal zero acceleration problems in biomechanical data.

An augmented cubic spline function was evaluated as an alternative solution to the end-point problem which frequently arises in the smoothing and differentiation of biomechanical position-time data. The usual procedures of natural cubic spline functions and digital filtering have the undesirable effect of forcing the accelerations to zero at the ends of the data set. The proposed augmented cubic spline procedure does not have this characteristic but rather requires the curve to pass through a single extra point at each end of the data set. Using two different criteria with large acceleration magnitudes near the end of the data set, we have compared the effectiveness of all three methods in terms of the total curve (root mean square error) and in terms of the last few points (percent and algebraic error). In both experiments the augumented cubic spline procedure was found to be superior to both digital filtering and natural cubic spline functions. It was concluded that this technique could be used for smoothing and differentiating biomechanical data in instances where the underlying function is unknown and the accelerations at the end points of the data set are suspected of being non-zero.

Biomechanical Phenomena↗
PubMed1981

Pseudomonas maltophilia bacteremia in children undergoing open heart surgery.

Pseudomonas maltophilia was isolated from intraoperative blood cultures in eight of 13 children undergoing open heart surgery during a five-week period. Antibiograms were identical and included resistance to prophylactic antibiotics. The source of the outbreak was traced to contamination of both the calibration device used on the pressure monitoring system and the sensor surface of transducers used in this system. In a mock system, calibration with a contaminated device resulted in recovery of the organism from transducer dome fluid. Dye studies confirmed the integrity of the transducer membrane but demonstrated reflux of dome fluid into the monitoring line fluid. A case-control study revealed no patient- or surgery-related factors predisposing to P maltophilia bacteremia and no excess of morbidity or mortality in patients as a result of bacteremia. The outbreak was confined to patients undergoing open heart surgery and was terminated abruptly by sterilization of transducers and revision of the calibration device.

Cardiac Surgical Procedures↗
PubMed1978

Effect of thymine concentration on cell shape in Thy- Escherichia coli B/r.

Cells of a thymineless mutant of Escherichia coli B/r are shown to change their shape when the concentration of thymine in the growth medium is reduced. Electron micrographs of whole cells and isolated sacculi were used to make quantitative measurements of the changes in cell length and width which occur as a result of such a change in thymine concentration. The results showed that there is an increase in cell volume, which is due to an increase in cell width accompanied by a decrease in cell length. These changes were compared with the predictions of models which assume that cell shape is influenced by the chromosome replication cycle.

DNA, Bacterial↗
PubMed1978

Lower extremity forces and torques during systematic variation of non-weight bearing motion.

Component and resultant external forces and torques at ankle, knee, and hip joints of unrestrained lower extremity motion were computed as resultant limb velocities were systematically changed. Cinematographic and modeling techniques were used to analyze 45 trials of five skilled soccer players who performed slow, medium and fast velocity kicks. A model of the lower extremity was incorporated, with kinematic data and segment mass estimates, into computer programs to quantify the mechanical variables. Monotonic increases in magnitudes of all kinetic elements occurred as the velocity of kicking was increased. Significant differences were also observed in the maximum values of the net parallel and perpendicular external force actions, and resultant torques at the joints with changes in limb velocity.

Ankle↗
PubMed1976

Tissue inactivation of slow reacting substance of anaphylaxis.

The release of slow reacting substance of anaphylaxis (SRS-A) from sensitized guinea-pig lung challenged with antigen was followed by a fall in the activity of this mediator in the diffusate when the incubations were continued for 3 h. The inactivating principle was also present in normal lung in addition to other normal guinea-pig tissues such as the liver, kidney, spleen, ileum and skin. No acitivity was found in muscle. Evidence is provided that some of this SRS-A-inactivating activity was due to tissue arylsulphatases. These were measured by hydrolysis of p-nitrophenyl sulphate (p-NPS) and p-nitrocatechol sulphate (p-NCS), which reflect activities of arylsulphatase II A and II B respectively. Hydrolytic activity for p-NCS was present in all tissues with SRS-A-inactivating properties, whereas only lung, liver and skin tissue hydrolysed p-NCS and p-NPS. Following passage of a cell-free lung homogenate through a column of Sephadex G-200 the p-NCS hydrolysing and SRS-Z-inactivating activities eluted together, with molecules having a molecular size of approximately 150,000 Daltons, p-NPS hydrolysing activity being destroyed during the preparation of the homogenate. The release of arylsulphatase from sensitized tissue was not dependent on the presence of specific antigen. These experiments suggest that inactivation of SRS-A is related to tissue arylsulphatase and that these enzymes may play a role in the expression of the effective levels of this mediator within the tissues.

Animals↗