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Biomedical subjects

G A Robinson

Publications and source records attributed to G A Robinson.

At least 37 records · Page 2Linked to original sources
PubMed1989

Linearity of the accumulation of various dosages of uranium in the major organs of mature male Japanese quail. Effect of various doses of estradiol-17 beta.

1. Male Japanese quail were given 2.20 x 10(-4)-14.53 mg uranium/kg intravenously as uranyl ion (235U label). 2. The relationship between dosage and the 18-hr accumulation of U in leg bones, liver, kidneys and testes was linear. 3. Increases in U deposition with increased dosage were approximately 1:1, except for kidneys where 10-fold increases in dosage resulted in 25-fold increases in deposition. 4. Estradiol-17 beta increased U deposition in bones by 15-fold thereby providing some protection for the kidneys as now the ratio of dosage to accumulation was 1:1.

Animals↗
PubMed1989

Warfarin and cataract extraction.

Ten cataract extractions were performed on eight patients for whom warfarin was not discontinued prior to surgery. Three were complicated by hyphaema. No retrobulbar haemorrhages occurred in the four cases given a local anaesthetic. Cataract surgery can be performed successfully without discontinuing warfarin.

Aged↗
PubMed1989

Task and fatigue effects on low-threshold motor units in human hand muscle.

1. The activity of single motor units was recorded in the first dorsal interosseus muscle of human subjects while they performed an isometric ramp-and-hold maneuver. Motor-unit activity was characterized before and after fatigue by the use of a branched bipolar electrode that was positioned subcutaneously over the test muscle. Activity was characterized in terms of the forces of recruitment and derecruitment and the discharge pattern. The purpose was to determine, before and after fatigue, whether motor-unit activity was affected by the direction in which the force was exerted. 2. Regardless of the task during prefatigue trials, interimpulse intervals were 1) more variable during increases or decreases in force than when force was held constant at the target value (4-6% above the recruitment force), and 2) more clustered around an arbitrary central value than would be expected with a normal (Gaussian) distribution. Both effects were seen during the flexion and abduction tasks. The behavior of low-threshold motor units in first dorsal interosseus is thus largely unaffected by the direction of the force exerted by the index finger. The absence of a task (i.e., a direction of force) effect suggests that the resultant force vector about the metacarpophalangeal joint of the index finger is not coded in terms of discrete populations of motor units, but, rather, it is based on the net muscle activity about the joint. 3. Motor-unit behavior during and after fatigue showed that the relatively homogeneous behavior seen before fatigue could be severely disrupted. The fatiguing protocol involved the continuous repetition, to the endurance limit, of a 15-s ramp-and-hold maneuver in which the abduction target force was 50% of maximum and was held for 10-s epochs (ramps up and down were approximately 2 s each). Motor-unit threshold was assessed by the forces of recruitment and derecruitment associated with each cycle of the fatigue test. Changes in recruitment force during the protocol were either minimal or, when present, not systematic. In contrast, the derecruitment force of all units exhibited a marked and progressive increase over the course of the test. 4. After the fatigue test, when the initial threshold tasks were repeated, the behavior of most motor units changed. These changes included the derecruitment of previously active motor units, the recruitment of additional motor units, and an increased discharge variability of units that remained recruited. The variation in recruitment order seemed to be much greater than that reported previously for nonfatiguing conditions.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1988

A stable, selective electrode for recording single motor-unit potentials in humans.

A new application of electrode technology has enabled recording of single motor-unit potentials in human first dorsal interosseus muscle with more versatility than has been traditionally associated with this paradigm. The design, manufacture, and application are detailed for an electrode which has been used to discriminate potentials during efforts up to maximal voluntary contraction. The electrode comprises a branched, bipolar configuration which is positioned subcutaneously over the belly of the muscle. This extramuscular location maximizes stability and, with appropriate orientation of the electrode relative to the architecture of the muscle, ensures adequate selectivity of single motor-unit potentials.

Action Potentials↗
PubMed1988

Distribution of nanomole quantities of 235U in young and adult Japanese quail and in the F1 generation. Comparison with 153Gd.

Enriched uranium, 93.16% for 235U, served as a tracer of uranium deposition in an avian species, the Japanese quail. A second label, 153Gd, provided for monitoring of procedures and for estimation of the 235U content of live eggs. Depositions of 235U were greater than for 153Gd in all tissues except the yolk sac and the liver. Skeletal levels for 235U were age- and sex-dependent. Feathers contained only 0.11% of the 235U tracer in contrast to 50% of the endogenous uranium. The results show that 235U provides for tracing uranium metabolism in small animals, since in quail the tracer increased the uranium burden of the body by only 1-8%.

Animals↗
PubMed1986

The development and recovery of motor function in spinal cats. I. The infant lesion effect.

Normal development of motor function was compared to that of cats with spinal transections at birth (newborn operates) or at approximately two weeks after birth (two week operates). Newborn operates expressed motor behavior not seen until sometime later in normal newborn cats, suggesting that this behavior is normally suppressed by descending systems in newborn cats. After reaching adulthood, the motor performance of newborn operates surpassed that of both two week operates and chronic adult operates (cats with spinal cord transection in adulthood), suggesting that the earlier transection occurs, the greater the recovery of motor function. Transection at birth may alter the course of spinal cord development, accounting for the differences in motor performance among the three age groups.

Aging↗
PubMed1986

The development and recovery of motor function in spinal cats. II. Pharmacological enhancement of recovery.

The effects of the gamma-aminobutyric acid (GABA) antagonist bicuculline (BCC) on hindlimb motor performance was examined in mature spinal cats with spinal cord transections made either on the day of birth or at approximately two weeks postpartum and in chronic adult cats with spinal transections made in adulthood. In those adult operates, whose pre-drug performance was poor compared to neonatal operates, treadmill locomotion and weight support were improved dramatically by BCC administration. In neonatal operates (examined as adults), BCC administration increased the force of extension to abnormal levels and this increase appeared to disrupt locomotion. Immunocytochemical localization of GABA's synthetic enzyme, glutamic acid decarboxylase (GAD) within the spinal cords of these animals revealed an abnormal distribution of GAD reaction product only in newborn operates. The behavioral results indicate that the full extent of recovery in adult operates is prevented by inhibitory influences and this may contribute to the comparatively superior performance of neonatal operates i.e., the infant lesion effect. The anatomical results suggest that one requirement for the normal development of some intrinsic spinal circuitry is transneuronal regulation mediated by the maturation of descending systems.

Aging↗
PubMed1986

Bioelectrochemical immunoassay for human chorionic gonadotrophin in serum using an electrode-immobilised capture antibody.

An amperometric technique for the quantification of an enzyme immunoassay which utilises a capture antibody covalently attached to a carbon electrode is described. The electrode is used both to separate the assay and to monitor the activity of the bound enzyme label. A 'two-site' immunometric assay with monoclonal antibodies directed against human chorionic gonadotrophin (HCG) was used as the model system. The activity of the enzyme bound to the electrode is determined electrochemically by the use of an electron transfer mediator (dimethylaminomethyl ferrocene) permitting rapid quantification of the analyte without the need for a separate incubation step to measure enzyme activity. The sensitivity of the assay is 9mIU HCG ml-1 in serum (1st International Reference Preparation). The correlation between the amperometric measurement of serum HCG and data for an immunoradiometric assay was r = 0.988. The assay is rapid requiring a total assay time of 20 min per sample, which includes 15 min for antibody-antigen binding.

Antibodies, Monoclonal↗
PubMed1986

A homogeneous bioelectrochemical immunoassay for thyroxine.

Thyroxine has been modified with a ferrocene derivative to produce an immunologically reactive conjugate which remains capable of functioning as an electron transfer mediator, shuttling electrons between an oxido-reductase enzyme and an electrode. On binding with an anti-thyroxine antibody the conjugate's ability to function as a mediator is impaired. The conjugate has been used as a tracer in an homogeneous competitive assay to quantify the total thyroxine concentration in serum, the assay being measured electrochemically after the addition of a suitable oxidoreductase enzyme (glucose oxidase) and its substrate (glucose) on completion of antibody/antigen binding. This results in a simple and sensitive assay for thyroxine.

Electrochemistry↗
PubMed1986

Increased deposition of uranium in the bones of vitellogenic male Japanese quail. Effect of estradiol-17 beta on the distribution of uranium (VI), thorium (IV), gadolinium (III), and calcium (II).

Japanese quail were given, intramuscularly, either 16-mumol estradiol-17 beta (E2) in .25-ml ethanol solution/100 g body weight or .25 ml ethanol/100 g. Four days later, these quail were given, intravenously, 1.5-mumol UO2(NO3)2, Th(NO3)4, GdCl3 (153Gd-labeled) or CaCl2 (47Ca-labeled)/.15 ml .03 N HCl solution/100 g. The distribution of uranium among selected tissues was markedly different than for thorium or gadolinium and was approximately the same as for calcium. For example, 18 hr after giving the metal ions to the quail, the mean uranium content of the femora + tibiotarsi of E2-treated males was 15.4 +/- 1.3% (SE; n = 12) vs. 3.07 +/- .59% (12; P less than .001) for the control males. Similarly, 18 hr after giving calcium, the femora + tibiotarsi of E2-treated males had accumulated 20.8 +/- 1.5% (4) of the label vs. 9.94 +/- .46% (4; P less than .001) for controls. The livers of E2-treated males had 41.9 +/- 8.5% (4) of the thorium by 18 hr vs. 90.9 +/- 7.1% (4; P less than .01) for the controls, or 34.3 +/- 3.1% (8) of the gadolinium vs. 68.9 +/- 3.4% (8; P less than .001) for controls. The 18-hr accumulation of calcium in the femora + tibiotarsi of the E2-treated females was 18.0 +/- 1.1% (4) vs. 10.7 +/- 1.9% (4; P less than .05) for the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Interfering with inhibition may improve motor function.

Motor behavior not seen in newborn cats can be revealed by spinal transection and is therefore normally suppressed. Motor performance of these spinal kittens after reaching adulthood surpasses that of chronic adult-operated spinal cats but the latter display a significant improvement when GABAergic inhibition is blocked pharmacologically. Thus, inhibitory processes influence normal motor development as well as recovery of function after neurological damage.

Age Factors↗
PubMed1985

Dispersal of estradiol-17 beta from the site of injection in the pectoral muscles of Japanese quail.

Exogenous estrogens, if given in sufficient quantity, stimulate vitellogenesis in the males of vitellogenic species. In the present study, ethanolic solutions of estradiol-17 beta (E2), labeled with 16-alpha-[125I]iodoestradiol ([125I]E2) or sodium iodide (Na125I), were injected into the pectoral muscles of male Japanese quail. The rate of dispersal of the estradiol from the site of injection was measured in vivo during 4 days. The curves of radioactivity appeared to be diphasic. The dose percentages forming the second phase of these curves and the half-time for the second phase were: for 16 mumol E2 ([125I]E2 label)/100 g body weight, 84.6% and 27.6 hr; for 6 pmol [125I]E2/100 g, 20.0% and 17.2 hr; for 16 mumol E2 (Na125I label)/100 g, 6.7% and 99.0 hr, and for Na125I, 6.1% and 83.1 hr. Thus, in male quail the estradiol-induced stimulation of vitellogenesis apparently resulted from a continuing hormonal pressure on the liver during the period of study and not from a rapid flow of E2 to the liver shortly after injection.

Animals↗
PubMed1985

Increased clearance rate of plasma thyroxine accompanies estradiol-induced vitellogenesis in male Japanese quail.

Four days after giving 16 mumol estradiol-17 beta (E2) per 100 g body weight to male Japanese quail, the thyroids of these quail accumulated twice as much 125I as did the thyroids of control quail. Plasma thyroxine concentrations were 7.38 +/- 45 (SE) ng/ml (n = 16) for the E2-treated quail and 3.38 +/- .53 ng/ml (n = 16) for the controls. Clearance rates of plasma thyroxine were 534 ng thyroxine/100 g/day for the E2-treated quail and 234 ng/100 g/day for the control quail. The E2 may have increased the metabolism of thyroxine in these male quail and, by inference, stimulated a twofold increase in the rate of synthesis and secretion of thyroxine.

Animals↗
PubMed1985

Bioelectrochemical enzyme immunoassay of human choriogonadotropin with magnetic electrodes.

We describe an amperometric technique for quantification of an enzyme immunoassay in which we use a magnetic working electrode, both to separate bound and free analyte and to monitor the electrochemical response. We used a "two-site" immunometric assay with monoclonal antibodies for human choriogonadotropin (hCG) as a model system in which magnetic particles were used as the solid phase. Separation of bound and free label is readily achieved by localizing the particles at the electrode. Activity of the bound enzyme in the environment of the electrode is determined electrochemically, permitting rapid quantification of the analyte without the need for a separate incubation step to measure enzyme activity. The sensitivity of the system is 150 int. units of hCG per litre (1st Int. Ref. Preparation). Correlation between the amperometric measurement of urinary hCG and data for an immunoradiometric assay was r = 0.9. The assay is rapid, requiring a total assay time for each sample of 20 min, which includes 15 min for antibody/antigen binding.

Antibodies, Monoclonal↗
PubMed1984

A comparison of the distributions of the actinides uranium and thorium with the lanthanide gadolinium in the tissues and eggs of Japanese quail: concentrations of uranium in feeds and foods.

Japanese quail were given UCl3 , UO2 (NO3)2, Th(NO3)4, or GdCl3 ( 153Gd -labeled) intravenously in aqueous solution. Distribution of Th among the tissues was as for Gd; distributions of U(III) and U(VI) were markedly different. For example, 18 hr after a 1.5 mumol/100 g dose, accumulations in females were: growing oocytes, U(III) 2.0%, U(VI) 2.4%, Th 27.7%, Gd 44.7%; leg bones, U(III) 12.5%, U(VI) 14.1%, Th 1.2%, Gd 1.4%; liver, U(III) 1.1%, U(VI) 1.1%, Th 44.0%, Gd 40.2%. Whole body losses by 18 hr were: females, U 24%, Th 14%, Gd 4%; males, U 72%, Th 23%, Gd 1%. Cumulative depositions in yolks of eggs laid over 8 days were: U(III) 1.9%, U(VI) 1.7%, Th 57.3%, Gd 46.8%. The distribution of U in quail may be atypical of actinides . Concentrations of U in various feeds, foods, and mineral supplements ranged from 169 micrograms/g in a phosphate fertilizer for farm use to below the lower detectable limit of .01 microgram/g in many foods intended for human use. Two batches of the game bird laying ration supplied to the quail colony contained 3.05 and 4.42 micrograms U/g. Body burdens of 3.5 micrograms U/bird for noninjected quail were attributed to the U content of this feed.

Animal Feed↗
PubMed1984

Induction of vitellogenesis in Japanese quail as a sensitive indicator of the estrogen-mimetic effect of a variety of environmental contaminants.

Vitellogenesis was induced in mature male Japanese quail following intramuscular injections of 16 mumol/100 g body weight of any one of four estrogen analogues or 160 mumol/100 g of the nonsteroid zearalenone. Six hours after the injections, microgram levels of vitellogenin were detected and quantitated by rocket immunoelectrophoresis. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of plasma from estrogen-treated birds and from 160 mumol zearalenone-treated birds showed, 4 days after the injections, the three subunits of vitellogenin normally seen in the plasma of egg-laying female quail. As evidenced by increased concentrations of plasma protein-bound phosphorus, total plasma calcium, and total plasma protein, mole-for-mole diethylstilbestrol dipropionate was 114%, ethynyl estradiol 75%, moxestrol 108%, and zearalenone 5.6% as effective as estradiol-17 beta in inducing vitellogenesis over a 4-day period. The responses to 160 mumol zearalenone/100 g over 8 days were approximately .6 the responses for estradiol. The responses to ethynyl estradiol were about equal to those for estradiol for days 1 and 2, then faded to .3 the estradiol response by day 8. Doses of 16 or 160 mumol/100 g of cholecalciferol, chlordecone, corticosterone, o,p1-DDT [1,1,1-trichlor-2-(p-chlorphenyl)-2-(o-chlorphenyl)eth ane], methoxychlor, progesterone, or testosterone, or 16 mumol/100 g of zearalenone did not induce vitellogenesis. Induction of vitellogenesis in male Japanese quail can thus provide a sensitive test of the estrogen-mimicking activity of some possible environmental contaminants.

Animals↗
PubMed1982

Comparative study of the physiology of vitellogenesis in Japanese quail.

1. During a study of vitellogenesis in the Japanese quail, male or female quail were given, intramuscularly, one to three doses of estradiol-17 beta (16 mumol/100 g body weight). 2. In treated males, the plasma concentrations of protein-bound P (PBP, a measure of the phosphate groups in vitellogenin), Ca, and total protein fluctuated in unison. 3. Packed cell volume (PCV) values varied approx, inversely as the PBP concentrations. 4. Maxima of approx. 0.85 mg PBP/ml occurred six, five, and four days after the primary, secondary, and tertiary injections. Following each maximum, the PBP concentrations declined rapidly to the 0.004 mg/ml level found in the plasma of untreated male quail. 5. During periods of elevated PBP levels, Ca and PBP were present in equimolar quantities. 6. When laying female quail were given a single injection of estradiol, the PBP concentration rose from 0.12 to 0.97 mg/ml. 7. PCV values for both male and female estrogen-treated quail decreased from approx. 0.50 to 0.30. The decreases in PCV values were attributed to increases in plasma volume as measured using 125I-labelled serum albumin. No marked change in total erythrocyte mass was measured using 51CrO2-(4) as the cell label. 8. Perhaps the decrease in plasma serum albumin concentrations reported by some investigators for estrogen-treated animals is due to dilution rather than to repression of serum albumin synthesis.

Animals↗