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Biomedical subjects

R Morris

Publications and source records attributed to R Morris.

At least 361 records · Page 20Linked to original sources
PubMed1984

Developments of a water-maze procedure for studying spatial learning in the rat.

Developments of an open-field water-maze procedure in which rats learn to escape from opaque water onto a hidden platform are described. These include a procedure (A) for automatically tracking the spatial location of a hooded rat without the use of attached light-emitting diodes; (B) for studying different aspects of spatial memory (e.g. working memory); and (C) for studying non-spatial discrimination learning. The speed with which rats learn these tasks suggests that they may lend themselves to a variety of behavioural investigations, including pharmacological work and studies of cerebral function.

Animals↗
PubMed1984

Central cyanosis following coronary artery bypass graft surgery.

A case of central cyanosis occurring after coronary artery bypass graft surgery is described. This was due to the development of a right ventricular infarction which facilitated shunting from right to left through a previously undiagnosed patent foramen ovale or small atrial septal defect.

Coronary Artery Bypass↗
PubMed1984

Reduction of naturally occurring enteroviruses by wastewater treatment processes.

The levels of cytopathic enteroviruses at two wastewater-treatment works were monitored over a period of 9 months. The maximum level of virus at works 1 was 72500 p.f.u. l-1 and at works 2, 57500 p.f.u. l-1. Examination of process efficiency showed an overall reduction of 63% for works 1 and 26% for works 2 when used without lagooning. When lagooning was employed at the second works, virus reduction was 97%. Individual treatment processes showed poor reduction of virus levels. Sedimentation and rapid sand filtration had no significant effect on levels whilst both percolating filtration and activated sludge showed some reduction. Only lagooning resulted in substantial reductions of virus levels.

Enterovirus↗
PubMed1984

Kinetic studies on IgG transport by the jejunum of the neonatal rat.

A 0.2-ml dose containing 500 micrograms labelled rat IgG saturated the receptor-mediated transport system of the enterocytes of the jejunum of the small intestine. At subsaturation dose levels very little intracellular digestion of IgG occurred--the intact transport system was primarily employed. The uptake of IgG by enterocytes, at doses above saturation, was assessed over periods up to 6 h. There was an initial phase of rapid intracellular digestion by the enterocytes, followed by a much longer period during which the receptor-mediated transport system discharged intact IgG into the vascular compartment. The observations are discussed in the light of recent evidence relating to the numbers of IgG receptors on jejunal enterocytes.

Animals↗
PubMed1984

Peripheral autoregulation of thyroxine to triiodothyronine conversion in man.

This study describes the existence of a peripheral tissue mechanism for maintaining serum T3 concentrations in states of T4 deficiency or excess in man. Serum T3 and T4 levels were determined in 242 primary hypothyroid subjects who had been maintained on varying doses of oral T4 therapy. Subjects treated with sub-maintenance T4 doses were supplemented by additional oral T3 therapy to maintain eumetabolic status as assessed by suppression of serum TSH values. This T3 supplementation was withdrawn 4-5 days prior to study in order to obviate any influence on serum T3 indices. Serum total T3/T4 ratio values in this study population were observed to progressively decline fivefold in a curvilinear manner as serum T4 concentrations rose from less than 0.5 to 20 micrograms/dl (total serum T3/T4 ratio fell from approximately 50 to 10, ng T3/ng T4 X 10(3)). This phenomenon is presumably the result of an altered T4 to T3 conversion by peripheral tissue 5'-deiodinase systems. A similar alteration of T4 to rT3 conversion with changing serum T4 levels does not appear to occur since serum rT3/T4 ratios did not vary in a separate study population over a serum T4 concentration span from 4-16 micrograms/dl. The mechanism by which this autoregulatory control of T4 to T3 conversion occurs is unknown. However, it would appear physiologically to complement the pituitary-thyroid autoregulatory system by acting to defend and maintain serum T3 concentrations in states of T4 deficiency and excess.

Female↗
PubMed1983

Distribution of substance P-responsive and nociceptive neurones in relation to substance P-immunoreactivity within the caudal trigeminal nucleus of the rat.

Substance P is a peptide which is found in small diameter primary afferent fibres and may have a function in nociceptive afferent transmission. In order to study the role of substance P in sensory processes in depth, we have compared the distributions of nociceptive neurones and substance P-responsive neurones with the distribution of substance P in the caudal trigeminal nucleus of the rat. It was found that substance P-like immunoreactivity was located primarily in the superficial layers of nucleus caudalis (equivalent to laminae I and II of the dorsal horn) and in more ventromedially located areas (equivalent to laminae V and VI). The distribution was found to be in good agreement with the distribution of nociceptive neurones. Iontophoretically applied substance P had predominantly excitatory actions on both nociceptive and non-nociceptive nucleus caudalis neurones, although the peptide did appear to be slightly more likely to excite nociceptive neurones. Similarly, the peptide appeared slightly more likely to be excitatory in areas of nucleus caudalis showing substance P staining, but excitations were also predominantly seen in areas containing little or no apparent substance P staining. These results are consistent with the proposed role for substance P as a nociceptive afferent neurotransmitter. However, it is also possible that the peptide performs other functions in the processing of sensory information.

Animals↗
PubMed1983

Protein binding to brush borders of enterocytes from the jejunum of the neonatal rat.

The specific binding of IgG to jejunal brush borders was greatest at acidic pH, at neutral pH no specific binding occurred. Specific binding declined with age-no specific binding occurred in borders from 20-and 24-day-old animals. There was no specific binding of IgG to borders from ileal enterocytes. Human transferrin and bovine serum albumin did not bind specifically to borders. The affinity of binding (-Ka) and the receptors site numbers per border estimated for rat IgG were 18.64 X 10(6) M-1 to 3.53 X 10(6) sites; for human IgG, 25.06 X 10(6) M-1 to 3.30 X 10(6) sites; for bovine IgG, 10.48 X 10(6) M-1 to 2.11 X 10(6) sites and for sheep IgG, 7.26 X 10(6) M-1 to 2.34 X 10(6) sites.

Animals↗
PubMed1983

The development of handedness and dichotic ear listening asymmetries in relation to school achievement: a longitudinal study.

To assess the development of dichotic ear asymmetries and handedness, 208 male school children were evaluated in kindergarten and at Grades 2 and 5 (ages 66, 92, and 130 months of age, respectively) with a dichotic listening task and a hand preference test. The Wide Range Achievement Test (WRAT) also was administered at each of the three grade levels. There was significant variability in handedness scores over time only for those subjects whose scores at initial testing, that is, in kindergarten, identified them as non-right-handers. Both right and left handers had a significant increase in dichotic listening scores over time; however, only right handers had a significant right ear advantage at each evaluation. Regression analyses showed that combined hand preference scores and ear recall scores at each probe when combined accounted for almost 44% of the variance in WRAT achievement scores at Grade 5. Ear asymmetry scores, however, were not predictive of school achievement.

Achievement↗
PubMed1983

Clinical and electrophysiologic recovery in Arnold-Chiari malformation.

The case of a 16-year-old boy with occipital headache, diplopia, ataxia, and weakness in the lower extremities of 1-month duration is reported. Slowness of mentation, speech, and motor action was also present. Massive chronic hydrocephalus was indicated by an enlarged head. The prominent clinical features suggested involvement of the brainstem, and contrast studies showed compression of the brainstem and a filling defect posteriorly at C1-2. Brainstem auditory evoked potential latency suggested bilateral lesions of the brainstem. Posterior fossa decompression confirmed the presence of an Arnold-Chiari malformation, with the cerebellar tonsils as low as C-3. The fourth ventricle was microdissected and opened. Remarkable clinical and evoked potential recovery ensued over several months. Clinical-anatomic and anatomic-physiologic correlations in Arnold-Chiari malformation are discussed.

Adolescent↗
PubMed1983

Naloxone reversible inhibition of reticular neurones in the rat caudal medulla produced by electrical stimulation of the periaqueductal grey matter.

Chronic dorsal periaqueductal grey matter electrodes were implanted into adult rats under pentobarbitone anaesthesia. Stimulating these electrodes (25-300 microA) produced behavioural analgesia in 23 of 44 rats tested. In rats given the opiate antagonist naloxone attenuation of this analgesia was seen. In 14 rats displaying behavioural analgesia to periaqueductal grey matter stimulation acute electrophysiological experiments were performed under urethane anaesthesia. Microelectrode recordings were made from neurones, excited by noxious heat or pinch applied to the limbs and tail, and located in the reticular formation of the caudal medulla. Stimulation of the periaqueductal grey matter at an intensity sufficient to produce analgesia in the conscious animal produced direct inhibition of the firing of 62% of neurones tested, excited 23%, had no effect on 14% and attenuated the nociceptive responses of 66%. The inhibitions were characteristically long. Local application of naloxone by microiontophoresis attenuated these long inhibitions in 11 out of 16 neurons tested. Immunohistochemical localization of beta-endorphin containing structures in the vicinity of stimulating and recording sites suggested that the naloxone sensitive inhibition of nociceptive neuronal responses in caudal medulla reticular formation may be due to activation of beta-endorphin fibres descending through the periaqueductal area to the caudal medulla.

Action Potentials↗
PubMed1983

A study of the natural history of low-back pain. Part II: development of guidelines for trials of treatment in primary care.

In a prospective study of 230 episodes of low-back pain presenting in primary care, the natural history of the symptom of low-back pain has been described. Clinical features predictive of outcome have been identified in order to define groups of patients who were relatively homogeneous with respect to the outcome of the episode. A Disability Questionnaire performed more satisfactorily as an outcome measure than either absence from work or a simple pain-rating scale. Guidelines for future trials of treatment of back pain in primary care are described.

Adolescent↗
PubMed1983

Effects of excitatory amino acids and their antagonists on membrane and action potentials of cat caudate neurones.

The electrical activity of caudate neurones was recorded with intracellular electrodes in halothane anaesthetized cats. Agonists and antagonists of excitatory amino acid receptors were applied by micro-ionophoresis and their effects on membrane- and action potentials and on cortically evoked synaptic potentials evaluated. The agonists, L-aspartate (asp), L-glutamate (glu), N-methyl-DL-aspartate (NMA), quinolinate and quisqualate all depolarized the membrane, caused repetitive firing, reduced the apparent amplitude of the cortically evoked excitatory post-synaptic potentials (e.p.s.p.s) and increased the amplitude of the associated inhibitory post-synaptic potential. Two of the agonists, NMA and quinolinate, additionally caused the appearance of up to 500 ms long depolarizations (plateaus) on the falling phase of action potentials. These plateaus were seen in about two-thirds of the cells in this sample while in the other third the excitatory effects of NMA and quinolinate were indistinguishable from those of glu and quisqualate. The N-methyl-D-aspartate (NMDA) receptor antagonist D-alpha-aminoadipate (DAA) reversibly inhibited the effects of NMA and quinolinate but only on those cells where these two agents evoked action potential plateaus while on the same cells the effects of asp, glu and quisqualate were either only weakly antagonized or not affected. On cells not displaying plateaus to NMA or quinolinate none of the effects of the agonists could be antagonized by DAA. DAA applications that completely antagonized the effects of NMA never reduced the amplitudes of cortically evoked e.p.s.p.s. Cis-2,3-piperidine dicarboxylate also blocked the effects of NMA and asp at low application currents while at higher currents it enhanced the effects of glu or asp although still retaining its NMA antagonistic activity. High-frequency stimulation of the cortico-caudate pathway resulted in long-lasting depolarizations and repetitive firing, but plateaus of the type caused by NMA or quinolinate were not seen.

2-Aminoadipic Acid↗
PubMed1983

The binding of proteins to isolated enterocytes from the small intestine of the neonatal rat.

IgG binds specifically to isolated jejunal enterocytes but not to ileal enterocytes; maximum binding occurred at pH 6. The ability of jejunal enterocytes to bind IgG was reduced to low levels at 20 days of age and was lost at 24 days. Human and rat IgG were bound specifically in similar amounts; human IgG displaced rat IgG with identical efficiency to rat IgG (ED50 = 50 nM). Much less bovine and sheep IgG were bound to enterocytes and the ED50s for these proteins were 150 nM and 2.5 microM, respectively. Rat IgG bound to jejunal enterocytes with high affinity (13.21 x 10(6)M-1) and to 4.83 x 10(6) sites per cell. Receptor protein was estimated to represent 0.18% of total cell protein. These observations are discussed in relation to the results of in vivo IgG transmission studies. It is estimated that the IgG transport mechanism, operating at maximum efficiency, requires that available IgG receptors would come into use once to twice per hour.

Aging↗