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Biomedical subjects

J Roberts

Publications and source records attributed to J Roberts.

At least 487 records · Page 27Linked to original sources
PubMed1987

Measurement of total circulating blood volume following subarachnoid haemorrhage: methodological aspects.

The total circulating blood volume (TCBV) and total body/venous haematocrit ratio (Htb/Hv) was determined by simultaneous measurement of the red cell volume (RCV) and the plasma volume (PV) in 10 subarachnoid haemorrhage (SAH) patients, 10 supine bedresting control patients and 20 ambulant out-patients. The mean Htb/Hv of the SAH patients, 0.866, was found to be significantly lower than that of the supine controls, 0.908, and the ambulant patients, 0.909, (p less than 0.01). Using the ratio 0.866 the total circulating blood volume of the SAH patients was calculated from either their RCV or their PV and compared with their measured TCBV. Expressed as a percentage of measured TCBV the mean errors of these single volume determinations were 2.84% and 1.76% respectively. The significance of these changes in the Htb/Hv ratio of SAH patients is discussed in relation to the circulatory disturbances they suffer.

Adult↗
PubMed1987

Protection of CGS 10078B against ouabain-induced arrhythmia in the cat.

CGS 10078B (CGS; 1-[2,3-dihydro-1,4-(2S)-benzodioxin-2-yl]-5-[2,3-dihydro-1,4-(2R)- benzodioxin-2-yl]-3-(1R,5S)-aza-1,5-pentanediol methane sulfonate) is an agent with alpha- and beta-receptor and calcium channel blocking actions. To study its antiarrhythmic activity, cats were anesthetized with alpha-chloralose, ventilated, and given atropine and gallamine. CGS (10 or 20 mg/kg, i.v.) was infused 15 min prior to ouabain. Bolus injections of ouabain (25 micrograms/kg, i.v.) were given every 15 min until death (D). Some cats were pretreated with reserpine (R; 5 mg/kg, i.p.) 24 h prior to the experiment. In other cats 6-hydroxydopamine (6-OHDA; 20 mg/kg, i.v.) was administered 3 days prior to CGS 20 mg/kg and ouabain. Data were compared with those of Lathers [Eur. J. Pharmacol. 64: 95, 1980], i.e., with 12 cats who received only ouabain and with 11 pretreated with timolol (T; 5 mg/kg, i.v.) prior to ouabain. After CGS (10 or 20 mg/kg, i.v.), but just prior to the first dose of ouabain, the blood pressure (BP) was decreased (p less than 0.05) from control (165 +/- 6 vs. 96 +/- 7, and 136 +/- 5 vs. 90 +/- 10 mm Hg, respectively). Comparable heart rate (HR) values were also decreased (p less than 0.05) from 225 +/- 17 to 166 +/- 14 and from 193 +/- 8 to 152 +/- 6 beats/min. 11 min after T, BP and HR had decreased (p less than 0.05) from 133 +/- 6 to 103 +/- 7 mm Hg and from 134 +/- 4 to 104 +/- 6 beats/min, respectively. Ouabain did not influence these decreases in BP and HR. CGS (10 or 20 mg/kg, i.v.) increased (p less than 0.05) the time to ouabain-induced arrhythmia (AR) and D. The magnitude of the protection appeared to be similar to that afforded by T. R given prior to CGS (20 mg/kg, i.v.) also increased the time to ouabain-induced AR and D while 6-OHDA increased the time to AR. The CGS protection against ouabain-induced AR was still present in animals pretreated with R or 6-OHDA. This indicates that the antiarrhythmic affect is not dependent upon adrenergic neuronal blockade.

Adrenergic alpha-Antagonists↗
PubMed1987

Epitope mapping of the von Willebrand factor subunit distinguishes fragments present in normal and type IIA von Willebrand disease from those generated by plasmin.

A small but consistent proportion of the von Willebrand factor (vWF) in normal plasma is composed of 189, 176, and 140 kD fragments cleaved from the 225 kD subunit. A monoclonal antibody map of vWF, based on the reactivity of individual antibodies with cyanogen bromide and tryptic fragments of known carboxy and/or amino termini, showed that in normal and IIA von Willebrand disease (vWD) plasmas the 140 kD fragment was derived from the amino-terminal region, whereas the 176 kD fragment was derived from the carboxy-terminal region of the subunit. In type IIA vWD, however, the fragments comprised a greater proportion of circulating vWF. In contrast, plasmin cleaved a 176 kD fragment from the amino terminus and a 145 kD fragment from the carboxy terminus of the subunit. Species similar to these plasmin-cleaved fragments were demonstrated in plasmas from four patients treated with fibrinolytic agents, but not in IIA vWD.

Antibodies, Monoclonal↗
PubMed1987

Social support and married agoraphobic women.

This study was conducted to determine if a relationship exists between social support and agoraphobia. Married agoraphobic women from a support group for phobics were compared with married, non-agoraphobic women from Family Practice clinics, and social support factors were examined. The agoraphobic women were found to perceive their husbands as less supportive. As well, there were important reductions in network size and network support in these agoraphobic women.

Adolescent↗
PubMed1987

Does contingent reinforcement strengthen operant behavior?

In Experiment 1, pigeons were trained to peck keys with equal food-reinforcement schedules in components that ended with either noncontingent or contingent transitions to a third component with a five-fold richer schedule. Response rates were higher in the initial component with contingent transitions, but resistance to prefeeding or extinction was not consistently greater. Experiment 2 also included noncontingent or contingent transitions to a signaled period of nonreinforcement. There was no effect of the contingency on transitions to nonreinforcement, but the difference in response rates maintained by contingent versus noncontingent transitions to the richer schedule was replicated. In addition, response rates were higher in components that preceded nonreinforcement than in components that preceded the richer schedule. However, resistance to extinction was greater for noncontingent transitions to the richer schedule than to nonreinforcement, implicating stimulus-reinforcer relations in the determination of resistance to change. Resistance to change was also somewhat greater for noncontingent than for contingent transitions to the richer schedule. The latter result, together with the results of Experiment 1 and related research, suggests that response-contingent reinforcement does not increase resistance to change.

Journal Article↗
PubMed1987

Absence of age-related changes in the binding of the beta adrenergic antagonist 125I-iodohydroxybenzylpindolol in rat heart.

The effect of age on the density and the affinity of beta adrenergic receptors was determined in the hearts of Fischer 344 rats at three ages, 6, 12, and 24 months old. The binding of the beta adrenergic antagonist 125I-iodohydroxybenzylpindolol (IHYP), was used to quantitate and characterize cardiac beta adrenergic receptors. The maximal number of binding sites (Bmax = F moles/mg of protein) were 26.3 +/- 2.5, 25.4 +/- 0.99, and 24.5 +/- 2.4 and the dissociation constants (Kd = nM) were 0.166 +/- 0.014, 0.126 +/- 0.006, and 0.135 +/- 0.015 for 6, 12, and 24 months old animals, respectively. There were no significant differences among the three ages. These results support the contention that neither beta adrenergic receptor density or affinity changes with age in the ventricles of the rat heart.

Adrenergic beta-Antagonists↗
PubMed1987

N-methyl-N-nitrosourea-induced transformation of rat urothelial cells in vitro is not mediated by activation of ras oncogenes.

Adult rat urothelial cells were transformed in vitro following treatment with a single dose of N-methyl-N-nitrosourea (MNU) or MNU treatment followed by promotion with sodium saccharin. This in vitro transformation process involves multiple steps: slow-growing 'pre-neoplastic' epithelial foci are induced 70-100 days after MNU treatment and from such foci rapidly proliferating immortal cell lines were established, some of which became tumorigenic after a further latent period. A series of epithelial cell lines and a single fibroblast cell line established in this way were analysed for the presence of transforming genes by DNA transfection into NIH3T3 cells. None of the epithelial cell lines induced foci in a focus formation assay. The single non-epithelial line induced foci and was found to contain an activated c-Ki-ras gene with a G----A transition in codon 12. To assay for the possible presence of transforming genes which were not active in a focus formation assay, two of the epithelial lines were analysed further by co-transfection with a dominant selectable marker, followed by selection and inoculation into nude mice. No tumours were induced within the latent period for tumour production by control cells transfected with NIH3T3 cell DNA (40-60 days). These results suggest that there is cell type specificity for oncogene activation during in vitro rat bladder transformation initiated by a single carcinogen and that ras gene activation is not a necessary step in urothelial transformation in vitro.

Animals↗
PubMed1987

Total anomalous pulmonary venous return: report of a case diagnosed on ECMO.

After repeated echocardiographic assessment and cardiology consultation, a 2,750-g, 36 weeks' gestation neonate with esophageal atresia, tracheo-esophageal fistula, and pneumonia thought to be complicated by persistent pulmonary hypertension was placed on extracorporeal membrane oxygenation (ECMO). While on ECMO, pre-oxygenator and umbilical artery blood gas patterns suggested the diagnosis of total anomalous pulmonary venous return which was subsequently confirmed by cardiac catheterization.

Diagnosis, Differential↗
PubMed1987

Sudden death following white cell transfusion in a premature infant.

A 1,700-g, 31 weeks' gestational age infant developed early onset Group B streptococcal septicemia associated with shock and respiratory distress. The infant was treated with antibiotics, exchange transfusion, and white cell transfusion. The infant improved, and then acutely deteriorated following the third white cell transfusion. Cause of death was presumed to be pulmonary sequestration of white cells or anaphylaxis.

Anaphylaxis↗
PubMed1987

Influence of transcutaneous oxygen monitoring on the incidence of retinopathy of prematurity.

This study was performed to determine whether the use of continuous transcutaneous oxygen tension (tcPO2) monitoring could reduce the incidence of retinopathy of prematurity in preterm infants receiving oxygen therapy. A total of 296 infants with birth weights less than or equal to 1,300 g were randomly assigned to a continuous monitoring or a standard care group. Infants in the continuous monitoring group had tcPO2 monitored continuously as long as they required supplemental oxygen, and infants in the standard care group had tcPO2 monitored only during the more acute state of their illness. Management of both groups was otherwise identical. Of 148 infants in the continuous monitoring group, 101 survived; of the 148 patients in the standard care group, 113 survived. Mean birth weights and gestational ages were similar for both groups. Duration of mechanical ventilation and oxygen therapy was also similar. The overall incidence of retinopathy of prematurity was 51% in the continuous monitoring group and 59% in the standard care group. As birth weight for infants greater than or equal to 1,000 g increased, a higher risk of retinopathy of prematurity developing was noted in the standard care group. Cicatricial retinopathy of prematurity developed in four infants in the continuous monitoring group and five in the standard care group. These results suggest that continuous tcPO2 monitoring may reduce the incidence of retinopathy of prematurity in infants with birth weights greater than 1,000 g but not in the smaller infants in whom this complication occurs more frequently and is more severe.

Birth Weight↗
PubMed1987

Hypnosis as an intervention for pain control.

The use of formal hypnosis and/or positive, comforting suggestions to patients for control of pain, fear, and anxiety is simple and effective. In addition, it is easy to learn and teach to patients. Spiegel states that hypnosis, a group of techniques long associated with fantasies of loss of control, is ironically very helpful in actually enhancing patients' sense of control. The clinicians daring to become proficient in the use of hypnotic trance must begin with a conscious effort to abandon all negative suggestions such as "Do you have pain?"; "How much do you hurt?"; and "Move your bad leg." Simultaneously, a conscious effort is made to increase the use of the following positive suggestions: "How comfortable are you going to be tonight?" "Your hand feels so soft and warm"; "It is important to move this leg." These communication skills are best learned from clinicians skilled in hypnotherapeutic techniques. Simultaneously, it is important to become familiar with the works of Erikson and Barber. The American Society of Clinical Hypnosis will provide information about the national organizations and state hypnosis societies that offer approved workshops, conferences, and training opportunities. Hypnosis as analgesia surely provides rest, relaxation, and comfort for patients without the negative side effects of other analgesics. In addition, the ultimate benefit of hypnotic analgesia lies in enabling patients to potentiate their inner strength, resulting in improved self-esteem and self-control.

Humans↗
PubMed1986

The effect of age on release of norepinephrine by tyramine from rat heart.

The effect of age on the capacity of tyramine to promote the release of norepinephrine (NE) at the cardiac adrenergic neuroeffector junction was investigated in isolated hearts of rats, 6, 12 and 24 months of age. Hearts were perfused by the method of Langendorff and tyramine was administered in increasing doses as a bolus injection. There was no age-related difference in the effect of tyramine on NE release nor on the relationship between the amount of NE released and chronotropic response induced by the released NE. These findings indicate that there is no difference in the effectiveness of tyramine in promoting the release of NE from the tyramine-sensitive pool as a function of age.

Aging↗
PubMed1986

Comparative red blood cell metabolism in three wallaby species, Macropus eugenii, Macropus parma and Thylogale thetis (Macropodidae: Marsupialia).

Aspects of red blood cell metabolism were compared among three species of small macropodid marsupials from different habitats. Packed cell volume (PCV), erythrocyte reduced glutathione (GSH) concentration and GSH regeneration rates were similar in all three species. The Parma wallaby had very low red cell potassium levels compared to the other species studied. The Tammar wallaby had higher rates of glucose consumption and lactate production in vitro at both pH 7.4 and 8.2 than did the Parma and significantly lower adenosine triphosphate (ATP) levels than the other species. These findings are consistent with preliminary reports published previously. The differences noted cannot be directly related to differences in the habitats of the species.

Adenosine Triphosphate↗
PubMed1986

Phosphorus and fluorine NMR examination of the anesthetized newt (Notopthalamus viridescens).

We have examined newts by 19F-NMR using the anesthetic halothane as a probe and in another set of experiments taken 31P-NMR spectra under similar conditions. The spectra were recorded from the animal's tail. The water soluble 31P-NMR signals point to little difference between anesthetized and unanesthetized newts except for the potential disappearance of two pools of inorganic phosphate in the anesthetized animals. The 19F spectra show two anesthetic populations in the tail which the phosphorus spectra suggest arise from populations of halothane in muscle and in lipid.

Adenosine Triphosphate↗