Biomedical subjects

W A Fletcher

Publications and source records attributed to W A Fletcher.

46 records · Page 3Linked to original sources

PubMed1986

Origins of afferents to visual suprageniculate nucleus of the cat.

Small iontophoretic ejections of horseradish peroxidase (HRP) were made from recording-multibarrel micropipette assemblies in areas of the cat's suprageniculate nucleus (SGn) that contained visually responsive neurones. The sources of afferents of the SGn were determined by locating the labeled cell bodies of neurones that were presumed to send their axons to the area of the SGn containing the light-sensitive cells. The greatest concentration of labeled cell bodies was found in the granular insular cortex and the adjacent area of agranular insula. Most cells projecting to SGn from these areas were distributed in the middle and lower laminae. A second intensely labeled region was found in stratum opticum and stratum griseum intermediate of the superior colliculus. Other areas containing labeled cells that were distributed with intermediate density included the ventral thalamic nuclear complex (basal, medial, and lateral divisions), periaqueductal gray (PAG), zona incerta, and pretectal nuclei (posterior, medial, and anterior divisions). Sparsely labeled sites included the fields of Forel, substantia nigra (pars reticulata), peri-insular cortex, superior colliculus (profundum), lateral suprasylvian cortex (posterolateral lateral suprasylvian, PLLS and posteromedial lateral suprasylvian, PMLS), anterior ectosylvian cortex, thalamic reticular complex, nucleus of the optic tract, basal part of the ventromedial hypothalamic nucleus, and the pontine reticular nucleus (oralis) and adjacent reticular formation. Together with previous electrophysiological and neuroanatomical studies, the findings suggest that the SGn provides an integrating link between limbic structures and certain modalities of sensory information.

Action Potentials↗

PubMed1986

Saccadic eye movement dysfunction in Alzheimer's disease.

Saccades were measured by magnetic search coil technique in 13 patients with Alzheimer's disease and compared with those of 11 age-matched control subjects. We analyzed responses to target motion of predictable and unpredictable timing or amplitude, and responses to briefly flashed targets. Latencies were significantly prolonged and peak velocities reduced only when the timing of target motion was unpredictable. Saccades to predictable amplitude targets were abnormally hypometric. In 8 patients, impersistence of gaze was manifested by large-amplitude saccadic intrusions away from the intended position of gaze. When instructed to make saccades away from a flashed target, patients made reflexive saccades toward the target. We attribute this visual grasp reflex to frontal lobe degeneration. These eye movement deficits can be used to quantify motor dysfunction in Alzheimer's disease.

Aged↗

PubMed1986

Tonic pupils in neurosyphilis.

Of 60 patients with tonic pupils, 29 had serologic tests for syphilis. Five patients had positive blood serology and confirmatory tests; four had other manifestations of neurosyphilis and positive CSF serology. All seropositive patients had bilateral tonic pupils with light-near dissociation and denervation hypersensitivity. Of the 10 tonic pupils, only 1 was miotic and 1 dilated. Although tonic pupils tend to become small and bilateral, they should be distinguished readily from Argyll Robertson pupils, which react briskly, not tonically, to near stimuli. Patients with bilateral tonic pupils should have serologic tests for syphilis.

Diagnosis, Differential↗

PubMed1986

Chiasmal gliomas: appearance and long-term changes demonstrated by computerized tomography.

A survey of 22 cases showed the broad spectrum of lesions collectively termed "chiasmal gliomas." Three computerized tomography (CT) patterns were diagnostic: a tubular thickening of the optic nerve and chiasm, a suprasellar tumor with contiguous optic nerve expansion, and a suprasellar tumor with optic tract involvement. Globular suprasellar tumors lacking these features required a histological examination for diagnosis. Tumor growth was documented by CT in only three chiasmal gliomas; all were the globular type. Failing visual function did not reflect chiasmal tumor growth, and stable vision did not exclude it. Both patients with tubular optic nerve thickening and two of three patients with unilateral optic nerve expansion had neurofibromatosis. Five tumors became smaller after irradiation. Complications of radiation therapy included calcification of lenticular nuclei and remote infarcts. In patients who underwent biopsy, the CT appearance did not differentiate juvenile pilocytic astrocytoma from anaplastic astrocytoma. Thus, CT guides the diagnosis and neurosurgical treatment of chiasmal gliomas, establishing the need for biopsy or ventricular shunting.

Astrocytoma↗

PubMed1985

Monoclonal antibodies directed against Brucella abortus cell surface antigens.

A panel of monoclonal antibodies (MAb) has been raised against Brucella abortus cell surface antigens from mice immunized with either heat/phenol treated or UV killed bacterial suspensions of B. abortus. The hybridomas were screened by either a microagglutination procedure or by an indirect enzyme immunoassay (EIA) on sonicated bacterial preparations. From a large number of MAb generated by various procedures, two distinct types of MAb emerged. The most numerous type was capable of agglutinating B. abortus and reacting with a soluble preparation of lipopolysaccharide (LPS). A second type was not capable of agglutinating the bacterial suspensions or of binding to the soluble LPS preparation but reacted with an antigen present in bacterial sonicates. Two MAb of this type react differentially with sonicates prepared from virulent and avirulent strains of B. abortus. There appeared to be sufficient evidence from our analysis of the relative degree of cross reaction with antigens present on a range of B. abortus strains and Brucella and xenogenic bacterial species to conclude that each of the seven MAb was recognising a separate antigenic site on the B. abortus cell surface.

Animals↗

PubMed1985

Contralateral gaze deviation after frontal lobe haemorrhage.

Contralateral deviation of the eyes was sustained for a week in a patient with discrete subcortical frontal lobe haematoma. When deviation recovered, ipsilateral saccades were hypo-metric and saccadic latencies were prolonged in both horizontal directions. Smooth pursuit was paretic during tracking toward the side of the haematoma. Pursuit gain was higher during tracking to the contralateral side. Smooth eye movement imbalance may explain the unusual finding of contralateral gaze deviation with frontal lobe damage.

Adolescent↗

PubMed1984

Saccadic intrusions and oscillations.

There are a number of different types of involuntary saccadic eye movements which differ from normal saccades in that they take the fovea away from its target. This article presents a classification and description of these abnormal eye movements and indicates how they may be used to increase the precision of neurologic diagnosis.

Adult↗

PubMed1983

An immunoassay for human D dimer using monoclonal antibodies.

Monoclonal antibodies (MAb) were raised against human D dimer. The hybridomas were screened with a solid phase enzyme immunoassay against D dimer and fibrinogen degradation products. Among the panel of MAb identified, two distinct patterns emerged; the majority belonging to a panspecific class reacting against epitopes present on both D dimer and fibrinogen degradation product Dcate and a monospecific class reacting with determinants apparently present only on D dimer. A number of MAb were further characterised for their ability to specifically capture antigen in a solid phase enzyme immunoassay and assays were developed which have a sensitivity of 10 ng/ml for D dimer or crosslinked fibrin derivatives and may be suitable for detection of crosslinked derivatives in serum and plasma samples in a clinical situation.

Animals↗

PubMed1979

Pulmonary epithelial-mesenchymal interactions: beyond organogenesis.

Epithelial-mesenchymal interactions are important regulators of lung growth and organogenesis, but later functional maturation of the fetal lung is though to be primarily under hormonal control. Recent evidence, however, suggests that hormonal effects on pulmonary cellular and biochemical maturation continue to involve intercellular interactions. Communication between cells may have wider importance than has hitherto been appreciated. It should be noted that in addition to organogenesis and biochemical development, mature lung requires an extensive capillary network in close proximity to areas of gas exchange. Recent attempts to isolate and culture pumonary endothelium may be expected to provide new insights into this neglected aspect of lung maturation. The possibility of hormonal or intercellular mediation of the differentiation of airway epithelium might also merit investigation.

Animals↗

PubMedDate not supplied

Photodynamic endometrial ablation in the nonhuman primate.

OBJECTIVE: To test the effectiveness of 5-aminolevulinic acid (ALA)-induced photodynamic endometrial ablation in the rhesus monkey under varying conditions of light delivery (fractionated versus continuous) and steroid priming. METHODS: Photodynamic endometrial ablation was carried out in 17 rhesus monkeys that were either postmenopausal or in the early proliferative phase. Four hours after intralumenal injection of ALA (250 mg in 1 mL hyskon), a quartz fiber with a diffusing tip was inserted. A KTP tunable dye laser delivered 300 mW of light (635 nm) for 60 minutes in either continuous or fractionated fashion (20 minutes on, 5 minutes off, and 40 minutes on). In some experiments, thermistors were used to monitor temperature in the lumen and myometrium during light treatment. Hysterectomy was performed 3 or 4 days after treatment, and endometrial damage was assessed histologically. Two additional monkeys (one rhesus and one cynomolgus monkey) were exposed to the same protocol, except hyskon was substituted for ALA to control for potential ablative effects due to light treatment alone. RESULTS: Endometrial ablation was evident in all ALA-photosensitized specimens. The degree of ablation around the light fiber ranged from moderate to complete. The depth of ablation ranged from 1.14 +/- 0.54 to 2.15 +/- 1.62 mm (mean +/- standard deviation). Ablation was most complete in uteri of menopausal monkeys. Light treatment after ALA increased lumenal temperature from 36 C to 50 C, whereas temperature was not significantly increased by light treatment in the controls. CONCLUSION: This is the first report of endometrial destruction in the primate using a photodynamic approach. Whereas clinical application of photodynamic therapy (PDT) requires complete endometrial ablation to produce long-lasting amenorrhea, our results suggest that PDT may offer a simple office-based approach to endometrial ablation.

Aminolevulinic Acid↗