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Biomedical subjects

R T Ross

Publications and source records attributed to R T Ross.

At least 37 records · Page 2Linked to original sources
PubMed1991

Dissociated loss of vibration, joint position and discriminatory tactile senses in disease of spinal cord and brain.

The clinical functions of the posterior columns of the spinal cord and the signs of disease of these structures have been debated for years. Todd in 1847 and Schiff in 1858 knew the functions of the posterior columns and 10 years later Brown-Séquard knew as well. Reynolds, Romberg, and Duchenne, each described a posterior column syndrome based on a disease in which the primary lesion was not in the posterior columns. In the last 150 years almost every white matter structure of the cord has been credited with serving the sensations that we now know are a function of the posterior columns. Vibration, joint position and movement as well as discriminatory touch each seem to be served by separate fibres of the posterior columns and medial lemniscus. There is evidence of this in cat and man. These sensations may be lost individually, totally, or in certain stereotyped combinations. Vibration or joint sense is commonly lost alone. When a discriminatory touch sensation is lost with one other sense, it is almost inevitably joint position sense. Absent discriminatory touch and vibration sense with normal joint position sense appears to be unknown. This functional separation continues into the thalamus. At the highest level there is no evidence that vibration sense has any conscious somatosensory cortical affiliation, while joint position and discriminatory touch senses definitely do.

Brain↗
PubMed1990

Factor analysis of the near-ultraviolet absorption spectrum of plastocyanin using bilinear, trilinear, and quadrilinear models.

Factor analysis was used to resolve the spectral components in the near-uv absorption spectrum of plastocyanin. The data set was absorption as a function of four variables: wavelength, species of plastocyanin, oxidation state of the copper center, and environmental pH. The data were fit with the traditional bilinear model, as well as with trilinear and quadrilinear models. Trilinear and quadrilinear models have the advantage that they uniquely define the components, avoiding the indeterminacy of bilinear models. Bilinear analysis using the absorption spectra of tyrosine and copper metallothionein as targets resulted in a two-component solution which was nearly identical to that obtained using trilinear and quadrilinear models, for which no targets are required. The two-component models separate the absorption into tyrosine and copper center components. The absorption of tyrosine is found to be pH dependent in reduced plastocyanin, and the absorption magnitude of the reduced copper center is the same in the four different plastocyanin species. Further resolution is provided by a three-component quadrilinear model. The results indicate that there are at least two different electronic transitions which cause the absorption of the reduced copper center and that one of them couples to a tyrosine residue. It is the absorption of this coupled tyrosine residue which is pH dependent. Correlation of the results with previous studies indicates that it is Tyr 83 which is the perturbed residue. The separation of the absorption of the copper center and Tyr 83 provides spectroscopic probes for the conformations of the north pole and east face reaction sites on the plastocyanin protein.

Binding Sites↗
PubMed1990

Drug-induced parkinsonism and other movement disorders.

This is a review of reserpine, haloperidol, and various phenothiazines that produce parkinsonism and other movement disorders. The by-products of illicit meperidine synthesis, MPTP and its more sinister companion, MPP, are also discussed. Movement disorders, transient or fixed, frank parkinsonism and/or dyskinesia, due to a variety of other medications and toxic agents are included. These are methanol, lithium, methyldopa, antimetabolites, antidepressants, sympathomimetic anorexiants, some types of antihistamines, and various combinations of agricultural chemicals.

Haloperidol↗
PubMed1990

Retraction of Ross and LoLordo findings concerning blocking in serial feature-positive discriminations.

Findings concerning the effectiveness of stimuli from various conditioning procedures in blocking conditioned excitation and occasion-setting functions of an added stimulus in a serial feature-postive discrimination training procedure (LoLordo & Ross, 1987; Ross & LoLordo, 1986, 1987) are retracted. Videotapes on which the published data were based were rescored by 2-5 people, most of whom were uninformed about group memberships of the subjects. In no case did the rescoring confirm any of the orginal findings of blocking. Possible factors contributing to the discrepancies are discussed. The experiments should be repeated with feature stimuli that are less similar to each other and with several scorers, at least one of whom is unaware of the group assignment of the subjects.

Retraction Notice↗
PubMed1988

The relationship of brachiocephalic vessel atheroma to transient ischemia of the brain and retina.

The relationships between transient cerebral and retinal ischemic symptoms and brachiocephalic angiographic findings were studied in 464 patients. The arterial abnormalities were more often bilateral than the symptoms suggested. Normal angiographic appearances were common, although abnormal arteries in patients without related symptoms were also common. When stenosis of the carotid system was 75 per cent or more, there was a strong correlation with symptoms.

Adult↗
PubMed1987

Evaluation of the relation between Pavlovian occasion-setting and instrumental discriminative stimuli: a blocking analysis.

Experiments with rat subjects used a blocking design (A+, then AB+) to assess the relation between Pavlovian occasion-setting and instrumental discriminative stimuli. Prior conditioning of both associative and occasion-setting functions of A in a serial feature-positive procedure blocked acquisition of an instrumental discriminative function by a novel stimulus (B) trained in compound with A. However, neither prior conditioning of only an A-US (unconditioned stimulus) association nor prior conditioning of Stimulus A using a Pavlovian simultaneous feature-positive procedure, which does not endow A with an occasion-setting function, blocked acquisition of an instrumental discriminative function by B. Prior acquisition of an instrumental discriminative function by A blocked acquisition of a Pavlovian occasion-setting function by a novel stimulus (B) trained in compound with A, but did not block acquisition of an association between B and the US. These outcomes indicate that Pavlovian occasion-setting and instrumental discriminative properties of a stimulus are functionally equivalent and that both Pavlovian occasion-setting and instrumental discriminative properties of a stimulus are functionally independent of simple associative relations between that stimulus and other events.

Animals↗
PubMed1986

Malignant intracranial fibrous histiocytomas. Histologic, ultrastructural and immunohistochemical studies of two cases.

Two cases of malignant intracranial fibrous histiocytoma are presented. In Case 1 the tumour arose from the meninges and showed a disseminated spread throughout the neuroaxis. In the second case the tumour appeared to arise from within the brain substance. In this case surgical intervention and radiotherapy appeared to have achieved a cure, since no residual tumour was found at autopsy. The tumours were examined using ultrastructural and immunohistochemical techniques, which appeared advantageous in delineating this rare tumour from other intracranial neoplasms.

Aged↗
PubMed1986

Pavlovian second-order conditioned analgesia.

Three experiments with rat subjects assessed conditioned analgesia in a Pavlovian second-order conditioning procedure by using inhibition of responding to thermal stimulation as an index of pain sensitivity. In Experiment 1, rats receiving second-order conditioning showed longer response latencies during a test of pain sensitivity in the presence of the second-order conditioned stimulus (CS) than rats receiving appropriate control procedures. Experiment 2 found that extinction of the first-order CS had no effect on established second-order conditioned analgesia. Experiment 3 evaluated the effects of post second-order conditioning pairings of morphine and the shock unconditioned stimulus (US). Rats receiving paired morphine-shock presentations showed significantly shorter response latencies during a hot-plate test of pain sensitivity in the presence of the second-order CS than did groups of rats receiving various control procedures; second-order analgesia was attenuated. These data extend the associative account of conditioned analgesia to second-order conditioning situations and are discussed in terms of the mediation of both first- and second-order analgesia by an association between the CS and a representation or expectancy of the US, which may directly activate endogenous pain inhibition systems.

Analgesia↗
PubMed1986

Casualty and surgical services in Perthshire general practitioner hospitals 1954-84.

The results are reported of a study of casualty and surgical services in five general practitioner hospitals in Perthshire - Aberfeldy, Auchterarder, Blairgowrie, Crieff and Pitlochry. Details of the total workload, the nature of the conditions treated and the referral rate to major hospitals are given. Figures for the Royal Infirmary, Perth, the main referral hospital for the county, are also given for comparison. The surgical service at one of the rural hospitals is described.Experience has demonstrated the usefulness of these hospitals in providing casualty and surgical services to both the local population and to visitors, and their superiority in providing these services over health centres because staff and beds are available 24 hours a day.Rural general practitioner hospitals merit a continuing share of resources and bed allocation as they spare major hospitals surgical and medical work. The general practitioners serving the hospitals studied here undertook almost 40% of the total accident and emergency workload in the Perth and Kinross area of Scotland.

Adolescent↗
PubMed1985

Spinal cord infarction in disease and surgery of the aorta.

Diseases of the aorta and surgery of the aorta can produce spinal cord damage. There are major variations in blood supply to the spinal cord between individuals. The spinal cord may be tamponaded by increased spinal fluid pressure subsequent to clamping the aorta. Both of these factors may contribute to spinal cord infarction. The available methods and procedures to protect the spinal cord during surgery are discussed.

Aortic Dissection↗
PubMed1984

Ocular and cerebral ischemic mechanisms in disease of the internal carotid artery.

Stenosis of the internal carotid artery reduces the flow velocity in the ophthalmic artery. Lowered velocity permits increased red cell aggregation and decreased red cell deformability which increases viscosity. Contrary to the theory of remotely originating emboli, this is an alternate hypothesis regarding transient attacks of ocular and cerebral ischemia. The ophthalmic artery circulation time was measured in two groups of patients. The circulation time was defined as the interval between the appearance of contrast media in the siphon of the internal carotid artery and in the ocular choroid. The measurement was made on 151 angiograms of 108 subjects. These vessels were normal. An additional 76 patients had 108 angiograms which showed various amounts of internal carotid artery stenosis. These 76 patients had transient ischemic attacks; retinal, cerebral, or both. There is a significant difference in the ophthalmic artery circulation time in the two groups. The slowing in the ophthalmic artery is related to the degree of internal carotid artery narrowing. The circulation time in a cerebral branch of the internal carotid was not measured. It is presumed that stenosis of the internal carotid artery would have the same effect on a cerebral artery as on the ophthalmic artery.

Blood Circulation Time↗