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L T Lee

Publications and source records attributed to L T Lee.

At least 37 records · Page 2Linked to original sources
PubMed1990

Responses of the optic tectum to telencephalic stimulation in catfish.

In order to test physiologically for cerebrotectal connections in a fish, averaged evoked potentials and unit responses were recorded from the optic tectum following electrical stimulation applied to the telencephalon in the siluroid teleost Ictalurus nebulosus. A single shock applied to the area dorsalis centralis (Dc) of the telencephalon, and only to this area, elicits a sequence of deflections in the ipsilateral optic tectum: an initial negative peak at about 8 ms, (= N8), a larger N25 and a slow P50-N95. The configurations, depth profiles, latencies and susceptibility to repetitive stimulation, together with the known tectal anatomy, suggest that the first wave is due to the afferent fibers from the telencephalon and that N25 is due to deep tectal neurons. Telencephalic input exerts a conditioning effect on the field potentials and unit responses evoked by direct optic nerve shock. Such a shock elicits, in the contralateral tectum, small negative, optic tract axon peaks followed by a large N6, believed to be postsynaptic, and a still later P12. As a first approximation it is argued that the telencephalic input and the retinal input are activating different sets of neuronal elements in the optic tectum, since the configuration and depth profile of the telencephalic and optic nerve shock-elicited potentials are different. A conditioning Dc stimulus has a long-lasting effect on the form of the optic nerve field potential, maximally when the pallial shock precedes the optic by about 90 ms. The effect, observed by subtracting the conditioned from the unconditioned tectal response to optic nerve shock, is a difference wave with N11 and P20. The unit activity from deep tectal laminae is either activated or accelerated following Dc stimulation, while superficially located neurons are not affected. In another group of tectal units, the optic nerve shock-induced response is depressed by a preceding pallial dorsalis centralis stimulus. The evidence is compatible with the assumption of direct projections from Dc to the deep layers of the tectum, but the timing could also permit indirect pathways. In any case, the influence is not simple or identical for different tectal cell classes.

Animals↗
PubMed1989

Efficient electroblotting of human very-low-density lipoproteins and low-density lipoproteins from composite gradient gels to nylon membranes.

Rinsing of gradient composite acrylamide/agarose gels with 1% Triton X-100 permits the efficient electrotransfer of very-low-density and low-density lipoproteins from the gels and does not appear to interfere with subsequent capture of the lipoproteins by charged nylon membranes. Overall efficiency of the transfer/capture process can approach 95% and does not appear to be significantly affected by total lipoprotein concentrations up to 5000 mg/dl. Direct immunoquantification of transferred apolipoproteins on the membrane is feasible as well. The nylon membranes used, however, must be pretested to ensure capture efficiency.

Detergents↗
PubMed1987

Gradient acrylamide/agarose gels for electrophoretic separation of intact human very low density lipoproteins, intermediate density lipoproteins, lipoprotein a, and low density lipoproteins.

An exponential gradient gel with 0-10% acrylamide and 0.5% agarose was developed for electrophoresis of intact high molecular weight lipoproteins. This system resolves very low density lipoproteins, intermediate density lipoproteins, lipoprotein a, and low density lipoproteins in a size-dependent fashion. The characteristic relative mobility of these species can be determined in relation to protein and colloidal gold reference materials. Electron microscopy of selected lipoprotein fractions confirmed that relative mobility was related to apparent lipoprotein diameter. The composite gel medium can be used with prestained lipoproteins and permits immunoelectroblotting for qualitative analysis of apolipoprotein constituents.

Electrochemistry↗
PubMed1985

Identification of a mouse monoclonal antibody, LHLP-1, specific for human Lp(a).

Heretofore, immunologic reagents used to define and quantify human Lp(a) have been polyclonal in origin and therefore heterogeneous in antigenic specificity. We report here the isolation of a mouse monoclonal antibody, LHLP-1, monospecific for Lp(a). The antigen reactive with LHLP-1 was expressed in both lipoprotein Lp(a) as well as apolipoprotein Lp(a) delipidated by SDS treatment; however, disulfide reduction of apolipoprotein Lp(a) inhibited LHLP-1 reactivity. The antigen reactive with LHLP-1 on Lp(a), therefore, appears not to require lipid for expression of its conformationally dependent (disulfide-inhibitable) epitope. Antigen reactivity was virtually absent in the apoB and other proteins contained in very low density, low density, and high density lipoprotein particles. Immunologic quantification of Lp(a) in individual serum samples with a rabbit reference antiserum or LHLP-1 showed good correlation. We conclude that the monoclonal antibody LHLP-1 identifies an antigen unique to Lp(a) and that this antibody may therefore be useful in the further characterization and measurement of human Lp(a).

Animals↗
PubMed1984

Sensory representation in the cerebellum of the catfish.

Sensory representation in the catfish cerebellum was studied with physiological stimuli, with electric shocks applied to peripheral nerves and with electric shocks to central structures of the brain. Evoked field potentials and unit responses were recorded in different places in the cerebellum. In the catfish, different sensory modalities are represented by discrete, only partly overlapping areas of the cerebellum. Most units are unimodal by present criteria; only in the valvula a fraction of the units are responsive to two or more modalities. Visual and somatosensory areas are the largest and they occupy the bulk of the corpus cerebelli and the valvula. In the corpus, most of the visual units are near the midline and in the dorsal tier while the somatosensory units are more lateral and ventral. Mechanical lateral line input is represented in the eminentia granularis and the valvula. Acoustic units are found in the valvula. Electroreceptive units are recorded from the lateral lobus caudalis, and to a lesser degree, from the eminentia granularis and valvula. Sinusoidal tilting and vibration units are in the lobus caudalis pars medialis. Receptive fields of units, regardless of modality, are generally large and diffuse. Some visual units respond best to moving objects. Topographical organization of receptive fields only exists among the somatosensory units. Besides these findings of modality segregation, the features of interest for comparative neurology are the following. Most units are identifiable as Purkinje cells with a characteristic mossy fiber-granular cell pattern, and but in contrast to most experience with mammals, in response to direct brain or nerve stimulations, the simple spikes have different dynamic responses for different modalities. Some are first excited, then inhibited, others vice versa. Some units are not responsive to any sensory input we delivered. Some units not meeting the criteria for Purkinje cells meet several criteria for eurydendroid cells; they give large spikes and are influenced by sensory stimuli after relative long latencies. Complex spikes, however, were only consistently observed in some of the visual units.

Animals↗
PubMed1984

Response of cerebellum to stimulation of telencephalon in the catfish (Ictalurus nebulosus).

In the siluroid teleost Ictalurus nebulosus, averaged evoked potentials and unit responses were recorded from various parts of the cerebellum following electrical stimulation applied to the telencephalon. Responses are most readily evoked in the cerebellum when area dorsalis pars centralis (Dc), a group of scattered large cells in the middle of the telencephalon, is stimulated. The configuration of the evoked field potentials differs according to the rate of stimulation. At a relatively low repetition rate, 0.5/s or lower, the response takes the shape of a positive wave, Pmol2, peaking at about 58 ms in the molecular layer. In the granular layer, the response is primarily a negative wave, Ngr1, followed by a slow positive deflection, Pgr3, with peak latencies of 52 and 130 ms, respectively. Ngr1 appears to be the result of summed mossy fiber-granule cell synaptic activations, with Pmol2 its concomitant passive source. No neuronal basis can be proposed for Pgr3. At higher rates of stimulation (greater than 2/S), the response to each shock is of longer latency and more complex. The stabilized waveform (i.e., after 5-9 cycles) is dominated by a surface-negative wave, Nmol, peaking at about 80 ms. The negative wave disappears at about 300 micron below the surface (slightly above the level where Purkinje cells are located) where it is replaced by a positive and negative sequence, P-Npur, peaking at about 80 and 160 ms, respectively. Both responses are bilaterally distributed but the ipsilateral responses are usually larger in amplitude and shorter in latency. Rostrocaudally, a latency gradient with longer rostral latencies is also found in both responses. To facilitate further comparative studies, the changes of peak latency and amplitude with stimulus strength of these two patterns of response were examined. Other dynamic characteristics of these two patterns of response were also examined and compared by stimulating with pairs and short trains of electric shocks. In discussing the functional implications of these findings, this telencephalocerebellar pathway appears to be a striocerebellar pathway.

Action Potentials↗
PubMed1981

Competitive inhibition by soluble erythrocyte glycoproteins of penetration by Plasmodium falciparum.

Glycophorin, the major sialoglycoprotein of the erythrocyte membrane, was extracted from human erythrocyte ghosts by the lithium diiodosalicylate phenol (LIS) or chloroform-methanol (CM) methods. The products (LISgp and CMgp) were examined for their capacity to inhibit invasion of erythrocytes by Plasmodium falciparum in vitro. In the presence of either glycoprotein, parasitemia was significantly less than in control cultures, indicating competitive inhibition of attachment. Desialylation resulted in only partial loss of this inhibitory potency. Neither crystalline NANA nor the dialyzates of either hydrolyzed glycoprotein had any inhibitory effect. We conclude that the receptor for merozoites of P. falciparum probably resides in the protein portion of glycophorin, in which NANA plays a secondary role, possibly related to hydration of the cell surface. The parasite itself contains no detectable neuraminidase activity.

Erythrocyte Membrane↗
PubMed1981

Immunochemical studies on Tn erythrocyte glycoprotein.

Glycoproteins were extracted from membranes of erythrocytes that displayed Tn polyagglutination and were compared chemically and immunologically with glycoproteins of group O, MN cells. Tn glycoprotein had lower than normal NANA : protein and sugar : protein ratios, as revealed by direct analysis and polyacrylamide gel electrophoresis, and displayed slower immunoelectrophoretic mobility than glycoproteins of group O, MN cells. Agglutination of Tn cells by Salvia sclarea lectin was inhibited by Tn glycoprotein but not by O, MN glycoprotein. Tn and MN glycoproteins were equally potent inhibitors of influenza virus HA. Our findings indicate than Tn-specific determinants are part of the glycophorin molecule.

ABO Blood-Group System↗
PubMed1979

Immune electron microscopy of cross-reactions between Mycoplasma pneumoniae and human erythrocytes.

Respiratory infection with Mycoplasma pneumoniae evokes immunoglobulin M autoantibody which agglutinates human erythrocytes at 4 degrees C (cold agglutinin) and is specific for I antigen. Cross-reactions between surface antigens of M. pneumoniae and human erythrocytes, previously examined by serological analysis, were examined by transmission and scanning electron microscopy. Ferritin-labeled human antimycoplasmal and rabbit antisera to erythrocyte membrane components reacted with antigens on the surface of both M. pneumoniae and erythrocytes. Adsorption of human erythrocytes to M. pneumoniae was blocked by the same antisera without ferritin label. It is proposed that the cross-reactive specificity lies in peripheral areas of the mycoplasmal cell, probably in a surface carbohydrate which has antigenic identity with erythrocyte glycoprotein.

Antigens, Surface↗
PubMed1978

Removal of unbound sodium dodecyl sulfate (SDS) from proteins in solution by electrophoresis through triton x-100-agarose.

Residual sodium dodecyl sulfate (SDS) introduces artifacts into immuno- and counterimmunoelectrophoretic analysis of proteins which have been eluted from preparative SDS-polyacrylamide gels. Unbound SDS can be removed by electrophoretic passage of eluted solutions through a barrier of Triton X-100 in agarose in which the anionic and non-ionic detergents interact to form micelles.

Counterimmunoelectrophoresis↗
PubMed1978

Cold hemagglutinin cross-reactivity with Mycoplasma pneumoniae.

Convalescent sera from proven cases of infection with Mycoplasma pneumoniae, and rabbit antisera to M. pneumoniae and to human erythrocyte glycoprotein contained cold hemagglutinins which were reactive only for human erythrocytes. Only the human serum cold agglutinins were inhibited by soluble integral glycoproteins derived from human erythrocyte ghosts by treatment with chloroform-methanol. Rabbit antiserum to chloroform-methanol glycoprotein, as well as to M. pneumoniae, fixed complement with either M. pneumoniae or chloroform-methanol glycoprotein antigens. The findings support the hypothesis that the cold agglutinins elicited by M. pneumoniae infection represent a cross-reaction between determinants common to erythrocyte glycoprotein containing I antigen and the membrane of M. pneumoniae.

Agglutinins↗