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Biomedical subjects

R T Ross

Publications and source records attributed to R T Ross.

At least 55 records · Page 3Linked to original sources
PubMed1984

Hippocampectomy disrupts acquisition and retention of learned conditional responding.

The effects of bilateral hippocampal and neocortical lesions were examined on acquisition and retention of classically conditioned responses based on (a) simple associations, (b) a nonconditional discrimination, and (c) a conditional discrimination in the same subjects. Results showed that combined hippocampal and neocortical damage permanently prevented (within the limits tested) both acquisition and retention of learned behavior based on the conditional discrimination but had no effect on behaviors based on the nonconditional discrimination or simple associations. Neocortical lesions alone had no effect on either conditional or nonconditional discriminative responding, but they did temporarily disrupt acquisition and retention of behavior dependent on CS-CS (two conditioned stimuli) associations. Neither lesion affected learned behaviors mediated by CS-US (conditioned stimulus and unconditioned stimulus) associations. Thus, results showed that hippocampal damage selectively disrupted learned conditional behaviors and also revealed that central nervous system control of conditional discrimination performance, within-compound associations, and CS-US associations is mediated by different neural mechanisms.

Animals↗
PubMed1984

Unconditioned stress-induced analgesia following exposure to brief footshock.

Four experiments examined the properties of unconditioned analgesia elicited by electric footshock stimuli using unconditioned stimulus (US) parameters typical of aversive conditioning paradigms. In all experiments, analgesia was inferred from the latency to paw lick in response to painful thermal stimulation in the hot-plate assay. In Experiment 1, rats exposed to a 1-s, 2-mA electric shock US showed significantly longer latencies to respond to painful thermal stimulation than nonshocked controls, whereas nonsignificant increases in response latencies were observed with 1-s shock USs of either 0.5 or 1.25 mA. In Experiment 2, rats exposed to a 2-mA electric shock US showed systematic increases in latencies to respond to painful thermal stimulation as the duration of the shock was varied between 0.5 and 2 s. Experiment 3 showed that this form of shock-induced analgesia was of short temporal duration. Specifically, significant increases in latencies to respond to painful thermal stimulation occurred 30 s but not 90 or 300 s following exposure to a 1-s, 2-mA shock US. Experiment 4 demonstrated that this form of analgesia was unaffected by pretreatment with the opiate receptor antagonist naloxone in dosages of 1, 5, 10, or 20 mg/kg. Finally, there was no evidence showing that environmental stimuli paired with shock presentations acquired the capacity to evoke analgesia as a conditioned response. The implications of shock-induced analgesia for the study of aversive conditioning and behavior are discussed.

Animals↗
PubMed1983

Transient tumor attacks.

The presence of an intracranial mass lesion should be considered in any patient experiencing episodes of reversible cerebral deficit. I studied four patients, all with intracranial masses, who had recurrent attacks of hemiparesis, hemisensory disturbance, disorientation, or dysphasia. While the mechanism of these attacks is unknown, there are several possibilities.

Adult↗
PubMed1983

Brain swelling and ventricle size.

Cerebral ventricle size was measured in one hundred normal people, age 10 to 50 years. The measurements were obtained from computed tomographic (CT) scan examinations, using the Huckman (1975) method. Normal ventricles were significantly bigger at age 45 than at age 15. These normals were compared to groups of patients with pseudotumor cerebri, water intoxication and cerebral edema, and cerebral hypoxia and edema due to cardio-respiratory arrest. The relative ventricular size was the same in the normal group and all three disease groups. Measurement of ventricle size from CT scan images is not even a crude index of cerebral edema in these three diseases.

Adolescent↗
PubMed1983

Relationships between the determinants of performance in serial feature-positive discriminations.

Three experiments using an appetitive behavioral observation procedure with rats investigated the effects of various pre- and postdiscrimination treatments on learning and performance in serial feature-positive discriminations. Previous work suggests that performance in this discrimination is based on feature-unconditioned stimulus (US) associations, feature-common element associations, and a conditional occasion-setting relation. Experiment 1 examined the effects of prediscrimination reinforcement of the various components of the discrimination. Experiments 2 and 3 investigated the effects of various postdiscrimination nonreinforcement and reinforcement procedures, respectively, on performance of previously established discriminative responding. The results of the present studies and those of previous work are interpreted to show that the conditional occasion-setting relation may be independent of feature-US associations and may not be dependent on feature-common element associations. The implications of assumming that rats used conditional information independently of simple associations are discussed.

Animals↗
PubMed1982

Sudden infant death syndrome and progesterone.

Some victims of sudden infant death syndrome have evidence of chronically defective ventilation as do some members of the victims family and the subsequent siblings. Furthermore, the death seems to occur when the proportion of more vulnerable non-rapid eye movement sleep is increasing and serum progesterone is low. Both endogenous and exogenous progesterone are effective respiratory stimulants. The relationship of these three features does not appear to have been studied.

Age Factors↗
PubMed1980

Statute and legislative history of the Federal Insecticide, Fungicide, and Rodenticide Act and its impact on agriculture.

This report discusses the responsibilities of government for the legislation of pesticides, and describes the impact of various statutes on the use of pesticides in agriculture. Governmental responsibilities for management of the economy, education, and enactment of laws and regulations are discussed, and the history of U.S. legislation of pesticides and related substances is presented. Finally, the impact of pesticide regulation on international trade is considered.

History, 20th Century↗
PubMed1977

Bounds on rate constants and relative potentials in electron transport chains.

Minimization of free-energy losses requires that the rate constants for reaction in both forward and reverse directions be several times the net rate of a reaction. In an electron transfer between wound molecules, the forward and reverse rate constants contribute separate factors to the free-energy drop across the reaction. If such a reaction has a reverse rate constant which is much greater than the net rate of reaction, then the midpoint potential of the acceptor may economically be more negative than the midpoint potential of the donor.

Computers↗
PubMed1977

Transient monocular blindness.

This paper is a review of the causes of intermittent monocular blindness. The nature of cholesterol and platelet retinal emboli is discussed. Their sources, the frequency with which they may cause transient or fixed blindness and the association between these emboli and pathology of the major cerebral vessels and other organs is discussed. Consideration is given to the equally important abnormalities of platelet behavior and to some of the physiology of retinal blood flow and non-embolic blindness. The current treatment of this symptom may be anticoagulation, surgical correction of a stenotic artery or both. The effect of treatment is unpredictable and in some situations the rationale is suspect. This review may provide a summary on which to base future studies of the effectiveness of various therapeutic agents.

Adult↗
PubMed1977

Pigment variant of neuronal ceroid-lipofuscinosis (Kufs' disease).

A case of pigment variant of Kufs' disease is presented. The nature of the extra-neuronal pigment is discussed. Despite some of the histochemical discrepancies that existed between this pigment and the material that had accumulated in the nerve cells, they seemed to be ultrastructurally related. The hepatocytes contained numerous heterogeneous cytosomes, some of which resembled the storage material of Niemann-Pick's disease. Clinically the syndrome may present with progressive ataxia, spontaneous and reflex, coarse myoclonic jerks and eventual mental deterioration as well as epilepsy and muscle wasting. The pigment variant cannot be distinguished from Kufs' disease except pathologically.

Adult↗
PubMed1975

Cucumber shaped and 35 nm particles in Creutzfeldt-Jakob disease.

A 63 year old female with the ataxic form of Creutzfeldt-Jakob disease (CJD) is presented. In addition to amyloid plaques which were not associated with Alzheimer's neurofibrillary tangles, rare profiles similar to those reported in Scrapie were also seen. To our knowledge, these profiles have never been observed in CJD and their presence in this condition adds a further morphologic similarity between the human and animal forms of subacute spongiform "viral" encephalopathies.

Amyloid↗
PubMed1974

Metastatic medulloblastoma.

The incidence of metastatic medulloblastoma is probably greater than the thirteen documented patients. Case reports of metastatic medulloblastoma must be carefully analysed. We have added two cases which conform to Weiss' criteria for metastatic disease. The direction and factors influencing spread have been discussed.

Adrenal Gland Neoplasms↗