Search PubMed⌕ Search

Biomedical subjects

P Dean

Publications and source records attributed to P Dean.

At least 109 records · Page 6Linked to original sources
PubMed1987

Descending projections from the superior colliculus in rat: a study using orthograde transport of wheatgerm-agglutinin conjugated horseradish peroxidase.

Despite extensive behavioural work on the rat superior colliculus, its descending efferent pathways have not been fully characterised with modern anatomical tract-tracing techniques. To investigate these pathways, wheatgerm-agglutinin conjugated with horseradish peroxidase (1%) was injected at various locations within the superior colliculus of hooded rats. Label judged to be transported orthogradely was plotted on coronal sections modified from the atlas of Paxinos and Watson (1982). Two major descending pathways were identified. (i) The bulk of the fibres in the ipsilateral descending pathway leave the superior colliculus ventrolaterally, and course around the lateral margin of the midbrain reticular formation. Caudally, projecting fibres leave the main bundle to innervate the cuneiform nucleus, and parts of the pontomedullary reticular formation. Terminal fields associated with the major bundle of fibres are found in an area medial to the brachium of the inferior colliculus; the parabigeminal nucleus and adjacent tegmentum; the ventrolateral midbrain reticular formation; and the lateral pontine nuclei. (ii) The fibres of the main contralateral descending pathway leave the superior colliculus ventromedially, to cross midline in the dorsal tegmental decussation. They immediately turn caudally to join the predorsal bundle, in which they run the length of the brainstem to reach the cervical spinal cord. Major terminal fields occur in nucleus reticularis tegmenti pontis; the pedunculopontine/parabrachial area; paramedian pontomedullary reticular formation; and inferior olive. In addition there is lighter labelling in many areas of the pontomedullary reticular formation and in the cervical spinal cord. There was also a much sparser contralateral descending projection that crossed midline in the tectal commissure, and sent terminals to the contralateral cuneiform area and adjoining regions. These results suggest that the distribution of the descending efferent pathways from the superior colliculus in rats is similar to those described in other species. The fact that the two major pathways project to quite different terminal areas, together with previous findings that they have separate cells of origin within the tectum, suggests that they may also be functionally distinct.

Animals↗
PubMed1987

[Hyperparathyroidism in patients having undergone a kidney transplant].

The persistence or onset of hyperparathyroidism following kidney transplant is characterized by an incidence ranging from 2.6 to 70% according to the various statistics available. In a total of 462 kidney transplants performed in our department, hyperparathyroidism was detected in 9 patients. Surgery took the form of parathyroidectomy 8/8 plus autograft in 3 cases, parathyroidectomy 3/4 in 2 cases, 7/8 in 2 cases, and 4/8 in 1 case. Serum calcium values returned to normal in all patients after the operation.

Humans↗
PubMed1987

[Cyclosporin A in immunosuppressive therapy of kidney transplants (clinical results in 55 patients)].

The authors report the results of a clinical study of the use of cyclosporin A plus low-dose steroids in a consecutive series of 55 kidney transplants with follow-up ranging from 6 to 20 months. The clinical results (rejects, immunosuppressant side effects, 12-month survival of transplant and patient) are compared with those of a similar group of patients on "traditional" therapy (azathioprine plus high-dose steroids). The results of the study confirm the efficacy of cyclosporin A in preventing and controlling acute reject crises in the course of allogenic transplant, though many of the problematic issues related its clinico-therapeutic management remain open questions.

Cyclosporins↗
PubMed1987

[Malignant neoplastic pathology in patients given a kidney transplant].

The incidence of malignant neoplasms in patients subjected to pharmacological immunosuppression following kidney transplantation is higher than that observed in the control population at large. In our unit, in a study population of 451 patients undergoing a total of 462 kidney transplants over the period from 1968 to 1986, four malignant neoplasms (0.9%) were observed in 3/369 (0.8%) patients treated with azathioprine (1 ovarian papilliferous cystoadenoma, 1 embryonal carcinoma of the testicle and 1 Kaposi's sarcoma) and in 1/93 (1.1%) patients treated with cyclosporin (1 Kaposi's sarcoma). The neoplasm was successfully controlled only in the first case after bilateral extended adnexectomy.

Azathioprine↗
PubMed1987

[Echographic monitoring of 80 renal transplants. Critical analysis of signs of graft rejection].

In a period of one year and a half, the follow-up of 80 patients after renal transplant has been monitored with echography. Altogether were made 418 echographies, which later were correlated with the clinical conditions of the patients at the moment of each echography. As rejection represents the most important complication, care was particularly given to the possibility of sonographic identification of such pathology. The sensitivity, specificity and diagnostic accuracy of each echographic sign in the diagnosis of rejection were evaluated. The absent or reduced renal sinus (sensitivity 63%) and hyperechogenicity of the cortical parenchyma (sensitivity 50%) resulted the most important signs in the diagnosis of rejection, while the increase of renal volume and the increased hypoechogenic pyramids resulted less reliable. The combination of three or more signs proved to be particularly significant.

Adolescent↗
PubMed1986

Tectal cells of origin of predorsal bundle in rat: location and segregation from ipsilateral descending pathway.

In rats, as in other mammals, one of the principal projections of the superior colliculus (SC) crosses the midline in the dorsal tegmental decussation to join the contralateral predorsal bundle (PDB). The cells of origin of this pathway were studied by injections of retrograde tracers (true blue or wheatgerm agglutinin-conjugated horseradish peroxidase) into the PDB rostral to its major fields of termination. Labelled cells were plotted with respect to fibre layers within the SC. The majority of labelled cells in the contralateral SC were located within the stratum album intermediale (SAI), between the fasciles oriented caudorostrally in that layer. They were of a wide range of sizes, and were much more numerous in lateral SC (where the SAI is broader) than in medial SC. The remaining labelled cells were found mainly in the deep layers. The effects of midline knife-cuts made prior to the injection of tracer suggested that most of the labelled SAI cells, but few of the deep-layer cells, projected across the midline in the dorsal tegmental decussation. Double-labelling procedures were used to investigate whether the cells of origin of the PDB send collaterals in the ipsilateral descending pathway of the SC. Injections of diamidino-yellow into the terminal regions of this pathway labelled very few PDB cells, although large numbers of other tectal cells were labelled. In contrast, extensive double labelling was observed after control injections of diamidino-yellow into the ipsilateral ascending pathway in the ventral diencephalon. These findings suggest that there is anatomical, and therefore perhaps functional, segregation of descending output channels from the superior colliculus in rat. This suggestion receives some support from comparison of the present results with those of tectal stimulation studies. Stimulation in the vicinity of lateral SAI gives contralaterally-directed head and body movements characteristic of orienting and approach, whereas stimulation in other tectal regions that contain predominantly the cells of origin of the ipsilateral descending pathway can give movements resembling avoidance or escape.

Animals↗
PubMed1986

Head and body movements produced by electrical stimulation of superior colliculus in rats: effects of interruption of crossed tectoreticulospinal pathway.

Stimulation of the superior colliculus in rats produces movements of the head and body that resemble either orientation and approach towards a contralateral stimulus, or avoidance of, or escape from, such a stimulus. A variety of evidence indicates that the crossed descending pathway, which runs in the contralateral predorsal bundle to the pontomedullary reticular formation and the spinal cord, is involved in orienting movements. The nature of this involvement was investigated, by assessing the effects on tectally-elicited movements of midbrain knife-cuts intended to section the pathway as it crosses midline in the dorsal tegmental decussation. As expected, ipsilateral movements resembling avoidance or escape were little affected by dorsal tegmental decussation section, whereas contralateral circling movements of the body were almost abolished. However, contralateral movements of the head in response to electrical stimulation were not eliminated, nor were orienting head movements to visual or tactile stimuli. There was some suggestion that section of the dorsal tegmental decussation increased the latency of head movements from electrical stimulation at lateral sites, and decreased the accuracy of orienting movements to sensory stimuli. These results support the view that the crossed tectoreticulospinal system is concerned with approach rather than avoidance movements. However, it appears that other, as yet unidentified, tectal efferent systems are also involved in orienting head movements. It is possible that this division of labour may reflect functional differences between various kinds of apparently similar orienting responses. One suggestion is that the tectoreticulospinal system is concerned less in open-loop orienting responses (that are initiated but not subsequently guided by sensory stimuli), than in following or pursuit movements.

Animals↗
PubMed1986

Ketoconazole: clinical evaluation in severe fungal infections.

Ketoconazole, a new imidazole-derivative antifungal agent, has been studied in sixteen patients with systemic fungal infections. Seven patients had deep localized infections (three cases with pneumonia and one case each with urinary infection, osteomyelitis, endophthalmitis and peritonitis); three patients suffered from granulomatous or acute mucocutaneous infections and six patients had fungal septicemia. All patients suffered from severe underlying diseases and/or predisposing factors such as antibiotic treatment, immunosuppressive therapy or indwelling catheters. Candida albicans was isolated in 13 cases, C. parapsilosis (septicemia), Aspergillus (ophthalmitis) and Mucor (pneumonia) in the other three cases. Ketoconazole was administered orally at daily dosages of 400-800 mg; 5-fluorocytosine was associated in four cases. Out of the ten patients with localized infections, seven were cured and three improved. Two of the six septic patients were cured, one improved who subsequently died from Pseudomonas septic shock and three patients showed no improvement. Two relapses were recorded, both followed by further eradication. The tolerance of the drug was always excellent. Ketoconazole proved a very effective and well-tolerated drug in systemic infections, caused by opportunistic fungi in high-risk patients.

Adolescent↗
PubMed1986

Movements resembling orientation or avoidance elicited by electrical stimulation of the superior colliculus in rats.

Some studies have reported that stimulation of the superior colliculus in rats produces orienting responses, as it does in a number of species. However, other studies have reported movements resembling avoidance and escape, which are not characteristic of collicular stimulation in other mammals. This apparent discrepancy was investigated by systematically recording the effects on head and body movements of electrical stimulation at a large number of sites throughout the superior colliculus (SC) and surrounding structures. It was found that the nature of the movements observed depended on the location of the stimulating electrode. Contralateral head and body movements resembling orienting and approach were obtained from sites in the intermediate and deep layers in rostral colliculus, the intermediate white layer and immediately surrounding tissue in central colliculus, and in all layers except deep white in caudal colliculus. At the remaining responsive sites, movements resembling avoidance and escape were obtained. The most common response was an ipsilateral cringelike movement of the body that developed into ipsilateral locomotion, followed by running and jumping as the current was increased. These movements were obtained from sites in the superficial and intermediate layers rostrally; from the intermediate gray and the medial superficial and deep layers in central colliculus; and from the deep layers and underlying tegmentum caudally. The distributions of sites, together with evidence from other studies, suggested the following conclusions: Within the superficial layers, avoidance responses were obtained from a region of the superior colliculus that appeared to represent the upper visual field, whereas orienting responses were obtained from a region apparently representing the lower visual field. Stimulation of the area containing the cells of origin of the predorsal bundle produced orientation and approach movements, whereas the avoidance and escape movements were probably mediated by parts of the ipsilateral descending pathway. The stimulation-induced avoidance and escape may reflect the importance of such responses to visual "events," particularly in the upper part of the visual field, in animals, like rats, with many predators.

Animals↗
PubMed1985

The LLNL high-speed sorter: design features, operational characteristics, and biological utility.

This report describes a dual-beam, high-speed sorter (HiSS) with a droplet production rate of 220,000 s-1 now in routine use at the Lawrence Livermore National Laboratory. The system can process and sort objects at rates in excess of 20,000 s-1. We report here on the development of HiSS, describe its operational characteristics, and evaluate its utility for analysis and purification of human chromosomes, human erythrocytes, and living Chinese hamster ovary cells.

Cell Separation↗
PubMed1985

Detection of visual stimuli in far periphery by rats: possible role of superior colliculus.

Previous work has been shown that rats with lesions of the superior colliculus fail to respond to distracting visual stimuli presented in the peripheral field while the animals are running towards a central stimulus. To assess how far this peripheral neglect is due to an attentional deficit, rats were trained before operation to obtain reward by running towards either peripheral or central lights that were presented when the animals' heads were stationary in a known position. Response to stimuli presented 120 deg from the midline was severely impaired after removal of the superior colliculus: the animals behaved as if they had difficulty in detecting the onset of the light. In contrast, response to stimuli 40 deg from midline was unaffected. Control lesions of striate cortex did not significantly impair performance at any position. The finding that collicular animals were impaired at responding to stimuli in the far periphery, that were not irrelevant distractors but instead predicted reward, suggests that one component of the visual neglect produced by damage to the superior colliculus in rats may be a sensory deficit in the far peripheral field. In addition, comparison with previous results indicates that training to attend to visual stimuli in more central regions does improve performance, as would be expected if the deficit were an attentional one. It is therefore argued that collicular neglect in rats should be regarded as a multicomponent impairment.

Animals↗
PubMed1985

Tonic desynchronisation of cortical electroencephalogram by electrical and chemical stimulation of superior colliculus and surrounding structures in urethane-anaesthetised rats.

Damage to the superior colliculus in rats impairs desynchronisation of the cortical electroencephalogram in response to light flashes. However, it is unclear which elements within the superior colliculus, and which efferent collicular pathways, might be involved in alerting cerebral cortex to visual stimuli. To investigate this problem, the superior colliculus and surrounding structures were stimulated either electrically (3 s trains of 0.2 ms 100 Hz cathodal pulses), or chemically (200 nl of 5 mM sodium L-glutamate), in rats anaesthetised with urethane. The cortical electroencephalogram was recorded bilaterally from frontal cortex. At each site tested with electrical stimulation the threshold current (up to 60 microA) required to produce tonic desynchronisation (outlasting stimulation-offset by at least 10 s) was determined. Comparison of the effects of electrical and chemical stimulation suggested the following: (1) stimulation of cells in the deep layers of the superior colliculus can desynchronise the cortical electroencephalogram. There may also be an additional effective area in the rostral part of the superficial layers, but this needs to be confirmed in unanaesthetised animals. (2) Stimulation of fibres in the deep white layers of caudal superior colliculus, and of cells in a wide area of caudal midbrain reticular formation, are also effective at desynchronising the cortical electroencephalogram. It is therefore possible that the ipsilateral descending pathway, that runs from the superior colliculus to terminate in the parabigeminal and cuneiform nuclei and surrounding reticular formation, is involved in mediating cortical desynchronisation initiated by the superior colliculus. Evidence from other studies indicates that some sites in this pathway may be part of a "defence arousal system". (3) Sites on the ascending pathways from the superior colliculus, to structures including dorsal thalamus, pretectum, zona incerta and rostral midbrain reticular formation, were relatively ineffective at tonically desynchronising the cortex. However, some of these pathways might mediate phasic, movement-related arousal of collicular origin.

Animals↗
PubMed1985

[Primary retroperitoneal tumors (clinical findings in yolk sac tumor, vascular leiomyosarcoma and extraosseous chondrosarcoma)].

Primary retroperitoneal tumors (PRT) constitute about 0.02 per cent of all tumors examined in the Department of Pathology of our hospital. We report 3 cases of malignant PRT - yolk-sac tumour, vascular leiomyosarcoma and extraskeletal chondrosarcoma - selected for their histological rarity and clinical features. Recent techniques available for the diagnosis of these neoplasms and surgical treatment are discussed. The role of radio-chemotherapy is also dealt with.

Adult↗
PubMed1985

[Adenoma nephrogenic. Morphologic aspects].

Nephrogenic adenoma is a rare lesion of urothelial mucous membrane. At present, the cases described in literature are 85. In this work the Authors study the morphologic aspects and etiopathogenetic theories.

Adenoma↗