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Biomedical subjects

J Moran

Publications and source records attributed to J Moran.

At least 145 records · Page 8Linked to original sources
PubMed1986

Glutamate receptor agonists release [3H]GABA preferentially from horizontal cells.

A total of 5-6 different cell types in vertebrate retinas accumulate [3H]gamma-aminobutyric acid (GABA). In frog retina, specific populations of cells in the horizontal, amacrine and ganglion cell layers are labeled autoradiographically after a 15-min in vitro incubation with [3H]GABA. Cells which may be bipolar or interplexiform cells are also labeled. Similar autoradiographic patterns are observed in chick retina except for the absence of labeled bipolar or interplexiform cells. In rat retinas, [3H]GABA uptake is limited primarily to Muller and amacrine cells. Depolarizing glutamate receptor agonists (glutamate, aspartate and kainic acid) applied in an in vitro perfusion system, stimulated massive release of [3H]GABA from frog and chick retina but not from rat retina. Under these conditions, autoradiographic labeling of horizontal cells was virtually depleted, while labeling of other cell types remained robust. In contrast, potassium caused release of the label from all 3 types of retina, and loss of autoradiographic labeling occurred uniformly in all cell types. We conclude that [3H]GABA-accumulating horizontal cells possess depolarizing glutamate receptors and that activation of these receptors leads to a release of GABA stores. On the other hand, Muller cells and the various subclasses of [3H]GABA-accumulating amacrine, bipolar and/or interplexiform cells, do not release GABA in response to glutamate receptor stimulation and thus appear to be relatively insensitive to excitatory amino acids.

Animals↗
PubMed1986

Visual behavior of monocularly deprived kittens treated with 6-hydroxydopamine.

Several investigators have reported that treating the visual cortex with 6-hydroxydopamine (6-OHDA) preserves the ability of a monocularly deprived eye to drive cells in the visual cortex. If 6-OHDA provides useful protection from the effects of monocular deprivation, it should also prevent the behavioral blindness that normally accompanies monocular deprivation. To test this prediction we compared the visual behavior of monocularly deprived kittens pretreated with 6-OHDA with that of kittens similarly deprived, but not drug-treated. Kittens were trained on a visual discrimination task before drug treatment or suture. Starting at about 5 weeks of age the kittens were given 6-OHDA via ventricular cannula, given vehicle solution, or given no treatment at all. At about 6 weeks of age all kittens were monocularly deprived for one week. When the deprived eye was opened at 7 weeks of age, most kittens not receiving 6-OHDA were blind when tested with the deprived eye. In contrast, none of the kittens receiving 6-OHDA intraventricularly were blind when tested with the deprived eye. 6-OHDA had no effect on performance with the non-deprived eye. We conclude that 6-OHDA protects vision through the monocularly deprived eye without impairing vision through the non-deprived eye.

Animals↗
PubMed1986

Utility of echocardiography in the management of patients with penetrating missile wounds of the heart.

Nine consecutive patients with penetrating missile wounds of the heart were evaluated by M-mode and two-dimensional echocardiography for localization of retained missile fragments noted to be moving in synchrony with the heart by fluoroscopy. Echocardiography precisely located all 12 moving fragments: 2 in the pericardium, 5 in the anterior right ventricular wall, 3 in the free left ventricular wall, 1 in the interventricular septum and 1 in the right posterior atrioventricular groove. Five patients had echocardiographic evidence of pericardial effusion and only one manifested a wall motion abnormality, indicating that direct myocardial perforation does not always result in detectable intrapericardial bleeding or asynergy. Localization of the missile fragments to be in danger of endocardial perforation, in danger of eroding the right coronary artery and creating a clinically unsuspected membranous ventricular septal defect led directly to surgical intervention in three different patients. In all three, intraoperative echocardiography quickly localized the missile fragments and significantly reduced patient cardiopulmonary bypass time. In the remaining six patients, localization of missile fragments well within the myocardium with no danger of erosion led to decisions against surgical removal.

Adolescent↗
PubMed1986

Magnetic resonance imaging of spiral vein graft bypass of superior vena cava in fibrosing mediastinitis.

Magnetic resonance imaging (MRI) was used for postoperative evaluation of spiral vein grafts in three patients with fibrosing mediastinitis who had undergone bypass of the superior vena cava (SVC) for SVC syndrome. The MRI images, obtained without ECG triggering, were compared retrospectively with postoperative bilateral arm venograms. Patent grafts were identified by MRI in all patients. Significant stenoses at innominate vein-spiral vein graft anastomoses in two patients were better demonstrated by venography than by MRI. MRI shows promise as a non-invasive technique for postoperative evaluation of spiral vein bypass grafts.

Adult↗
PubMed1985

Selective attention gates visual processing in the extrastriate cortex.

Single cells were recorded in the visual cortex of monkeys trained to attend to stimuli at one location in the visual field and ignore stimuli at another. When both locations were within the receptive field of a cell in prestriate area V4 or the inferior temporal cortex, the response to the unattended stimulus was dramatically reduced. Cells in the striate cortex were unaffected by attention. The filtering of irrelevant information from the receptive fields of extrastriate neurons may underlie the ability to identify and remember the properties of a particular object out of the many that may be represented on the retina.

Animals↗
PubMed1985

Contour, color and shape analysis beyond the striate cortex.

The corticocortical pathway from striate cortex into the temporal lobe plays a crucial role in the visual recognition of objects. Anatomical studies indicate that this pathway is mainly organized as a serial hierarchy of multiple visual areas, including V1, V2, V3, V4, and inferior temporal cortex (IT). As expected from the anatomy, we have found that neurons in V4 and IT, like those in V1 and V2, are sensitive to many kinds of information relevant to object recognition. In the spatial domain, many V4 cells exhibit length, width, orientation, direction of motion and spatial frequency selectivity. In the spectral domain, many V4 cells are also tuned to wavelength. Thus, V4 is not specialized to analyze one particular attribute of a visual stimulus; rather, V4 appears to process both spatial and spectral information in parallel. A special contribution of V4 neurons to visual processing may lie in specific spatial and spectral interactions between their small excitatory receptive fields and large silent suppressive surrounds. Thus, although the excitatory receptive fields of V4 neurons are small, the responses of V4 neurons are influenced by stimuli throughout a much larger portion of the visual field. In IT, neurons also appear to process both spatial and spectral information throughout a large portion of the visual field. However, unlike V4 neurons, the excitatory receptive fields of IT neurons are very large. Many IT neurons, for example, are selective for the overall shape, color, or texture of a stimulus, anywhere within the central visual field. Together, these results suggest that within the areas of the occipito-temporal pathway, many different stimulus qualities are processed in parallel, but the type of analysis may become more global at each stage of processing.

Animals↗
PubMed1985

The pattern of adsorption of cationic antiseptics to polymethylmethacrylate.

Few studies have reported the maximum potential of surfaces to adsorb the cationic antiseptics and few comparisons between antiseptics have been carried out. The purpose of this investigation was to measure the maximum uptake of alexidine, cetyl pyridinium chloride, chlorhexidine gluconate and chlorhexidine acetate to polymethylmethacrylate and by the construction of adsorption isotherms determine the pattern of molecular attachment to the recipient surface. The mean maximum adsorption findings for these antiseptics demonstrated significantly greater uptake of cetyl pyridinium chloride than the other antiseptics and significantly less uptake of alexidine compared with the other antiseptics. All four antiseptics showed a Langmuir type adsorption isotherm consistent with the formation of a monolayer of molecules on the recipient surface. For chlorhexidine preliminary studies demonstrated that the pattern of adsorption was not altered by saliva pre-treatment of surfaces. No evidence of molecular multilayering was observed even at higher concentrations of the antiseptics. However, the maximum uptake on to the surface was significantly increased when no post-treatment washings were carried out. It was concluded that this increased uptake would be unlikely to play an important role in antiplaque activity because of its relative instability. The pH dependency for the adsorption of these antiseptics was demonstrated such that as previously observed for chlorhexidine gluconate at low pH adsorption is almost completely, or completely, prevented.

Adsorption↗
PubMed1985

Acute effect of ketotifen on the dose-response curve of histamine and methacholine in asthma.

This study was designed to assess the acute effect of 1 mg of orally administered ketotifen on the dose-response curve to both histamine and methacholine, in 15 patients with bronchial asthma. From this curve we measured the concentration that produced a 20% fall in FEV1 (PC20) and reactivity, defined as the slope of the curve beyond the threshold dose. Results were analysed comparing the change in log PC20 and in reactivity before and after a double-blind administration of ketotifen and placebo. Ketotifen, compared to placebo, significantly increased the histamine PC20 (P less than 0.001) and reduced reactivity (P less than 0.001). After adjusting for starting FEV1 the difference of effect between ketotifen and placebo was still significant, although to a lesser degree (P less than 0.01). In contrast, ketotifen did not modify the methacholine dose-response curve. No significant changes were observed in FEV1 after ketotifen. The results suggest that acute administration of ketotifen has a selective action on histamine-activated pathways of bronchoconstriction.

Adolescent↗
PubMed1984

The effect of surface adsorption and staining reactions on the antimicrobial properties of some cationic antiseptic mouthwashes.

The phenomenon of surface adsorption appears fundamental to the antiplaque activity of the cationic antiseptics. Moreover, reaction with chromogenic material is relevant to the local side effect of staining. The purpose of this investigation was to determine how such local reactions affect the antibacterial activity of some of these antiseptics. The minimum inhibitory concentration (MIC) of commercial mouthrinses containing alexidine, cetyl pyridinium chloride, chlorhexidine gluconate and hexetidine against Oxford staphylococcus (NCTC 6571) and Escherichia coli (NCTC 10418) was established by tube dilution. The effect on the MIC values against O. staphylococcus of adding polymethylmethacrylate polymer or against E coli of adding a standard tea solution was then measured. The zones of inhibition around acrylic blocks soaked in the respective antiseptics, with and without postexposure washings, were measured. The effects on zone width of placing the antiseptic-soaked blocks in tea were recorded. The MIC values of alexidine, cetyl pyridinium chloride and chlorhexidine gluconate, but not hexetidine, were all increased by adding polymethylmethacrylate to cultures. Tea added to the culture increased the MIC values against E. coli for alexidine, chlorhexidine and hexetidine, but not for cetyl pyridinium chloride. Zones of inhibition around antiseptic-treated blocks were reduced by washing and, in the case of hexetidine, completely abolished. Tea-soaking further reduced the zones of inhibition for alexidine and chlorhexidine, but not cetyl pyridinium chloride.(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption↗
PubMed1983

Comparison of plaque accumulation after topical application and mouth rinsing with chlorhexidine gluconate.

This study measured plaque accumulation on anterior teeth after topical or mouth rinse application of 0.2% chlorhexidine gluconate. Compared with water plaque scores were highly significantly reduced. There was no significant difference in plaque scores between topical application or mouth rinsing. The importance of locally adsorbed chlorhexidine is emphasised and the relevance of an oral reservoir effect questioned.

Administration, Topical↗
PubMed1983

Effect of eye rotation on visual-field map onto superior colliculus and visual cortex.

We used multiunit recording to assess the effect of rotating one eye approximately 90 degrees at about the time of normal eye opening. Rotation of the eye did not alter the topography of the retinal maps onto visual cortex or superior colliculus. The intorted eye drove cells at most recording points in the contralateral visual cortex and superior colliculus. In its ipsilateral colliculus the intorted eye drove cells at about 10% of the recording points; that is, the temporal retina of this eye was quite ineffective in driving collicular cells. In its ipsilateral cortex the intorted eye drove cells at about 30% of the recording sites. The unoperated eye drove cells at all locations in both colliculus and cortex on both sides of the brain. The effects of extorsion were studied only in the superior colliculus. Extorsion and intorsion produced similar results except that extorsion produced a less severe deficit in the ability of the temporal retina to drive cells in its ipsilateral colliculus. Cutting all the extraocular muscles without eye rotation was studied only in the colliculus and produced results similar to those produced by intorsion and extorsion. However, the temporal retina of the operated eye was more effective after muscle cut alone than after intorsion or extorsion. Forcing the animal to use the rotated right eye alone on alternate days during the first 3 mo of life did not decrease the deficits. Almost all recording sites in the right colliculus were driven only by the unoperated left eye. If the left eye was sutured when the right eye was rotated, only the right eye drove cells in the left colliculus, but the two eyes were about equally effective in the right colliculus; however, rather few sites in the right colliculus were binocularly driven. We conclude that both extraocular muscle section and eye rotation reduce the effectiveness of the uncrossed input from the operated eye to the superior colliculus and visual cortex. The effects on the superior colliculus are, however, greater.

Animals↗
PubMed1983

Effects of eye rotation on visually guided behavior.

Visually guided behavior was examined in cats reared with one eye intorted, one eye extorted, or monocular section of the extraocular muscles. Kittens from 2 to 4 mo old jumped from a tower onto a platform in a pan of water. They refused to jump or missed the platform more often when forced to use the rotated eye than when forced to use the unoperated eye. This deficit was eliminated if the non-rotated eye was sutured at the time of eye rotation. Further, when the extraocular muscles were cut but the eye was not rotated, jumping was normal. Acuity was measured using an alley box in which the cats were required to distinguish between horizontal and vertical stripes. No cats were blind when tested with the operated eye. Although not conclusive, the data suggest that the acuity of the rotated eye was slightly lower than that of the unoperated eye. The visual field of the rotated eye was also abnormal. Regardless of the direction of eye rotation, the cats appeared blind in the contralateral and lower visual quadrants. This field deficit was much less severe in animals with extraocular muscle section alone and did not occur in rotation-plus-suture animals. The visual-field deficits in the contralateral field can be explained by assuming that each collicular or cortical region always controls orienting to the same region of the visual field. We are, however, unable to explain the deficits in the lower field in terms of the mapping data from the previous paper (4).

Animals↗