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Biomedical subjects

R Porter

Publications and source records attributed to R Porter.

At least 73 records · Page 4Linked to original sources
PubMed1992

A comparison of alexithymia in American and Japanese dialysis patients.

A comparison of alexithymia in American and Japanese dialysis patients was performed using the Beth Israel Hospital Questionnaire (BIQ) and the MMPI Alexithymia Scale (MMPI-AS) including structured interviews. No significant differences between the USA and Japan were observed in all dialysis patients with both BIQ and MMPI-AS. However, the alexithymia score in US hemodialysis (HD) patients was significantly lower than that in Japanese HD patients, whereas the alexithymia score in American continuous ambulatory peritoneal dialysis (CAPD) patients was significantly higher than that in Japanese CAPD patients. These results may suggest the possibility that the differences in dialysis policy between USA and Japan have secondary effects on alexithymia, which is one of the psychosomatic factors reflecting self-control ability in dialysis patients.

Adult↗
PubMed1991

A fractal analysis of pyramidal neurons in mammalian motor cortex.

Pyramidal neurons in the mammalian cerebral cortex can be described by a fractal dimension (Mandelbrot, 1982), which is an objective, quantitative measure of the complexity of their soma/dendritic borders. In the cat, the fractal dimensions of lamina V cells, which include pyramidal tract neurons (PTN), indicate that these cells are more complex than other pyramidal neurons (PN) in the same region of motor cortex. The lamina V cells of the cat are also more complex than those in motor cortex of the monkey. Moreover, lamina III neurons in the monkey are more complex than monkey lamina V neurons. The fractal dimension of the intracortical axon collateral arborizations of the same pyramidal neurons indicated, in all cases, that the branching of these terminals is less complex than the branching of the dendrites of the same cells. In line with the observation that the fractal dimensions of some homologous cellular populations are different in different species, it is suggested that the fractal dimension and the degree of morphological complexity may relate to the requirement for the number of separable functions to be accommodated within one neuron. For example, as the size of the cortex and the number of neurons in a region increase, the opportunity exists within a given cortical zone, for individual functions to be segregated and for functional specialization to be accommodated with less morphological complexity of the individual neurons performing each of these functions.

Animals↗
PubMed1991

Antibodies to the N-terminal sequence of GVPa bind to the ends of gas vesicles.

Antibodies were raised against intact gas vesicles of Anabaena flos-aquae, and against a synthetic peptide (GVPaNT) whose sequence is identical to the N-terminal region of the main gas vesicle protein, GVPa. A two-stage centrifugation procedure is described for separating gold-labelled antibodies bound to gas vesicles from unbound antibodies. The GVPaNT antibody bound to gas vesicles that had been previously rinsed with SDS to remove the outer gas vesicle protein, GVPc. Treatment with this antibody caused the gas vesicles to aggregate together end-to-end rather than side-by-side. The binding of the anti-GVPaNT-immunogold particles to the gas vesicle was restricted to the conical ends of the structure. These observations indicate that the sequence to which the GVPaNT antibodies were raised, residues 1 to 13 of the GVPa molecule, is exposed only at the outer surface of the cones and that it is normally obscured by GVPc. As GVPa forms both the conical ends and the cylindrical midsection of the gas vesicle, exposure of the N-terminal sequence only in the cones must be due to differences in the contact between adjacent GVPa molecules in the central cylinders and end-cones.

Amino Acid Sequence↗
PubMed1991

The role of hysteroscopy in patients having failed IVF/GIFT transfer cycles.

Fifty patients who had undergone 2 or more failed in vitro fertilization (IVF) embryo transfer (ET) cycles or failed GIFT cycles where fertilization had been demonstrated, underwent hysteroscopy; 28% were found to have intrauterine abnormalities which may have been responsible for the failure of the IVF-ET or GIFT. Patients with an abnormality found at hysteroscopy had undergone a significantly higher mean number of transfer cycles. These results suggest that intrauterine abnormalities may be a cause for failure of IVF-ET or GIFT and therefore hysteroscopy should be part of the infertility work-up of all patients prior to undergoing IVF treatment.

Abortion, Spontaneous↗
PubMed1991

Mental health consumers as case management aides.

Mental health consumers with chronic mental illness were trained for employment as case management aides in a psychiatric rehabilitation project in Denver. The project incorporated cooperative arrangements between the mental health system and vocational rehabilitation and occupational education agencies. The process used to recruit, select, train, and employ the consumer case management aides is described. Eighteen of the 25 trainees who began the training completed the program, and 17 moved on to employment as case management aides. At two-year follow-up, the 15 trainees who were still employed as case management aides had required a total of only two bed-days of psychiatric hospitalization since the training ended.

Adult↗
PubMed1990

The Kugelberg lecture. Brain mechanisms of voluntary motor commands--a review.

At a time when both electrical and magnetic stimulation of the human brain are being used to assess cortical motor outflow in man, it is important to re-examine the organization of the motor areas of the cerebral cortex, the evidence which exists about the structures that are activated by epicortical stimulation, the nature of the projections from the cerebral cortex to lower motor centers, the physiological influences that are exerted on motoneurons and interneurons by these descending pathways and the relevance of all of these for the control of voluntary movement. This review examines the relationships of neuronal activities in some motor regions of the cerebral cortex to movement performance as revealed by recording of neuronal discharges during self-paced movements performed by conscious monkeys, and the relevance of these observations to the understanding of mechanisms of voluntary control of skilled movement performance in man. It documents detailed information about the precise connections made by descending cortico-motoneuronal fibers in the monkey and proposes a relationship between the analogous structural arrangements in man and the voluntary control of skilled movement. Comparison of some of the general propositions which derive from studies of cortico-motoneuronal commands in the monkey with the EMG results from magnetic stimulation in man leads to the suggestion that direct monosynaptic excitatory effects may be relevant to the control of both proximal and distal muscles in man. Electrical recordings of the neuronal activities of individual cells in strategic cytoarchitectonic areas of the monkey's cerebral cortex also provide a neurophysiological correlate of observations on regional cerebral blood flow and regional metabolism as these are studied in human subjects performing movement tasks. Hence it is possible to explain the involvement of supplementary motor areas of both hemispheres in the organization of the time-ordered commands for manual tasks. A deficit in bimanual coordination is evident in monkeys with a unilateral lesion of the supplementary motor area and this deficit mimics the disorder of voluntary control of bimanual manipulation reported in man.

Animals↗
PubMed1990

Responses of monkey precentral neurones to passive movements and phasic muscle stretch: relevance to man.

Single cell recordings were made from movement-related neurones from the precentral cortex of two monkeys, trained to perform a simple lever-pulling task. They were also trained to remain relaxed while the arm was explored with passive movements at different joints, cutaneous stimuli and during the application of two types of phasic muscle stretch: percutaneous vibration and percussion of muscle tendons. Recordings were made of the responses of cortical neurones both to the 'natural' stimuli and to vibration of specific muscle tendons or percussion of the triceps tendon. Both tendon percussion and vibration excited neurones within area 4 with an average latency for tendon percussion of 21.0 msec. There was a high degree of consistency in the effects on single neurones of tendon percussion and vibration at the same site. Although long-term facilitation was not seen. vibration-induced discharge in the motor cortex should be considered as a potential mechanism of its effects in intact man. In contrast to the similarity of the effect of the two forms of phasic stretch, the relationship between a single neurone's response to either tendon percussion or vibration and to passive movement was complex. The dissociation seen between the effects of phasic muscle stretch and that of passive movement may underlie the failure, in man, to find uniformly increased long-latency stretch reflexes in clinical states of extrapyramidal rigidity.

Action Potentials↗
PubMed1989

The treatment of somatization: evaluation of a teaching package with general practice trainees.

A teaching package is described which aims to improve the management of somatization by general practice trainees. The package comprises a training videotape in which a model (described in the preceding paper) is demonstrated, together with material for paired role-play of new skills and small group videofeedback of consultations. Evaluation of the teaching package reveals that the skills can be effectively learned.

Education, Medical, Continuing↗
PubMed1989

Myosin dephosphorylation during rapid relaxation of hog carotid artery smooth muscle.

Changes in myosin light chain phosphorylation were measured during histamine-induced rhythmic contractions of hog carotid artery smooth muscle strips. Histamine made the muscle strips contract spontaneously every 1-5 min, and this allowed measurement of the time course of phosphorylation in relation to force development under conditions where diffusion of the agonist through tissue would not complicate the interpretation of the data. In the absence of histamine, phosphorylation was low [0.12 +/- 0.04 mol P/mol of the 20,000-Da light chain (LC 20)]. Phosphorylation was slightly (but not significantly) higher in the presence of 10 microM histamine in the relaxed state between contractions (0.20 +/- 0.03 mol P/mol LC 20). In muscle strips frozen during force development, when force had reached half of its peak value, phosphorylation was 0.38 +/- 0.06 mol P/mol LC 20. The highest levels of phosphorylation (0.49 +/- 0.04 mol P/mol LC 20) were found in strips frozen at the peak of the rhythmic contractions. Strips frozen when force had declined to half of the peak force showed low levels of phosphorylation (0.17 +/- 0.07 mol P/mol LC 20), indicating that the myosin light chain phosphatase activity was quite high. Mathematical modeling of the kinase and phosphatase reactions suggested that the apparent first-order phosphatase rate constant was at least 0.08 s-1 under these conditions. To obtain a better estimate of this rate constant, a second series of phosphorylation measurements were made early in the relaxation phase of the rhythmic contractions. The highest phosphatase rate constant obtained from these measurements was 0.23 s-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Morphology of neurons in area 4 gamma of the cat's cortex studied with intracellular injection of HRP [corrected and issued with original paging in J Comp Neurol 1988 Nov 8;277(2)].

Neurons in laminae II, III, V, and VI of area 4 gamma of the cat motor cortex were studied following intracellular penetration with an HRP-filled micro-electrode. Antidromic and synaptic responses produced by stimulation of the cerebral peduncles and/or of the ventrolateral nucleus of the thalamus were investigated. Horseradish peroxidase was then iontophoresed into the same neurons to allow examination of their detailed morphology. The morphology of pyramidal neurons whose somata were located in a particular lamina was similar but differed from that of pyramidal neurons in other laminae. The modified pyramidal neurons of lamina II had a truncated apical dendrite or did not possess an obvious apical dendrite, even though the ascending dendritic branches were longer and more extensive than the "basal" branches. As was the case for the pyramidal cells in other laminae, the axons of these lamina II modified pyramidal cells descended toward the white matter; their somata were generally pyramidal in shape, and their dendrites were spiny. All pyramidal neurons except some of lamina VI had ascending dendrites which terminated in a tuft in lamina I, subpially. No intracortical collaterals were seen originating from the axons of lamina II or of lamina VI pyramidal neurons. Lamina III pyramidal neurons had extensive short and long axon collaterals which contributed synaptic boutons to all laminae of the cortex. Pyramidal neurons of lamina V had fewer axon collaterals whose synaptic boutons were restricted to laminae V and VI. All somata of pyramidal tract neurons (PRNs), identified by antidromic responses from peduncular stimulation, were located in lamina V, except for one which was located in lamina VI. Recurrent collaterals of pyramidal neurons were activated by peduncular stimulation. Recurrent excitatory postsynaptic potentials (epsps) could be evoked in fast PTNs, slow PTNs, other pyramidal neurons of lamina V, and pyramidal neurons of lamina VI at latencies between 1.3 and 6.25 msec. In some slow PTNs, a recurrent inhibitory postsynaptic potential of long duration was the predominant response. Stimulation of the ventrolateral nucleus of the thalamus resulted in epsps in pyramidal neurons of lamina III, V, and VI at latencies between 1.0 and 5.0 msec.

Animals↗
PubMed1988

Morphology of pyramidal neurones in monkey motor cortex and the synaptic actions of their intracortical axon collaterals.

1. Pyramidal neurones in the precentral motor area of the monkey were studied using intracellular techniques. Pyramidal tract neurones (PTNs) were identified by antidromic activation from the cerebral peduncles or medullary pyramids. Orthodromic responses were recorded in PTNs and in other pyramidal neurones when antidromic volleys were set up by stimulation of the peduncles or pyramids. The neurones were then labelled by intracellular ionophoresis of horseradish peroxidase and their morphology examined. All neurones studied were identified as pyramidal cells according to their morphology. 2. Six pyramidal neurones located in lamina V were well stained; they included two fast PTNs and two slow PTNs. The morphology of all pyramidal neurones in this lamina (fast PTNs, slow PTNs and those pyramidal cells that were not antidromically characterized) was essentially similar. A single apical dendrite branched as it ascended and its terminals arborized subpially. Numerous lateral and oblique dendrites branched from the apical dendrites in lamina V and near its border with lamina III: short basal dendrites arborized in the vicinity of the soma in lamina V. Long basal dendrites had a wider field of arborization in lamina V and sometimes extended into lamina VI. 3. Three to five collaterals arose from the axon of lamina V cells in the cortex and arborized in laminae V and VI. Short collateral branches arborized in the vicinity of the soma in the region of the basal and lateral dendrites. Long collateral branches could be traced over long distances (often more than 1 mm). One pyramidal neurone in this lamina (a fast PTN) lacked short collateral branches from the axon. 4. Four pyramidal neurones in lamina III were stained well. The dendritic morphology of all these neurones was similar. Apical dendrites branched as they ascended and terminated subpially. Lateral and basal dendrites formed a column of dendritic branches around the soma. No long basal dendrites were seen. 5. The number and arborization of intracortical collaterals from the axon of lamina III cells varied widely; from three to twelve collaterals arose from the axon. The biggest arbor of collateral branches involved all the cortical laminae and was about 3 mm wide mediolaterally, while the smallest arbor was restricted mainly to lamina III in the vicinity of the soma. One neurone in this lamina also lacked short collateral branches from the axon. 6. Antidromic volleys from the pyramidal tract evoked excitatory responses in fast PTNs, predominantly inhibitory responses in slow PTNs and either excitatory or inhibitory responses in other pyramidal neurones in lamina V.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗