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Biomedical subjects

Q Luo

Publications and source records attributed to Q Luo.

88 records · Page 5Linked to original sources
PubMed1995

Cyclin B and Cdc2 expression and Cd2 kinase activity during Dictyostelium differentiation.

Although Dictyostelium differentiation occurs in the absence of external nutrients, two periods of mitosis occur, one during early development and one during the formation of the migrating pseudoplasmodium. We showed previously that cyclin B mRNA levels vary in a cell cycle dependent manner during vegetative cell growth. In the present study, we report that cyclin B mRNA levels change dramatically during development, reaching a maximum at the tipped aggregate stage. However, amounts of cyclin B protein vary only slightly, peaking during early development and decreasing during late aggregation and pseudoplasmodial formation. Cdc2 protein levels also remain relatively constant during development. Cdc2-histone H1 kinase activity was considerably higher in vegetative cell extracts of transformants that expressed large amounts of truncated cyclin B protein in comparison to extracts of the parental Ax-2 cells. These results suggest that Cdc2 kinase activity is dependent upon the level of cyclin B in vegetative cells. This result is consistent with the idea that variations in the level of cyclin B during growth regulate the cell cycle. When Cdc2 histone H1 kinase activity was determined during development, it was also found that activity correlated reasonably well with the amount of cyclin B protein. Thus, there was an increase in Cdc2 histone H1 kinase activity early in development, and then levels decreased as development progressed. The increase in Cdc2 histone H1 kinase activity that occurs early in development following starvation may be important in accelerating G2-phase cells through into mitosis. There was no increase in Cdc2 histone H1 kinase that accompanied the previously reported late developmental mitosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1995

Study of lymphocyte dynamics in the ocular circulation: technique of labeling cells.

The purpose of this experiment was to study in vivo the dynamic behavior of the lymphocyte in the retinal circulation. We developed a new technique capable of visualization of lymphocyte motion in the retinal and choroidal vessels using a rat model. Live cells freshly removed on a donor animal were labeled by a simple method using fluorescein isothiocyanate. Labeled cells were injected systemically into another animal. Retinal images were reconstituted on a video screen with a scanning laser ophthalmoscope (SLO) utilizing the argon green laser excitation wavelength (514.5 nm) to detect cell fluorescence. Lymphocytes were clearly seen and followed in the retinal vessels. Some slowed down in the capillary system, or even stopped for a few seconds, or were definitively caught in it. Labeled cells remained visible after circulating several times. A method was developed for in vivo visualization of lymphocytes in the retinal circulation. This method has the potential for application in the study of lymphocyte cell behavior under physiological as well as pathological conditions.

Animals↗
PubMed1994

Effects of an intravitreal daunomycin implant on experimental proliferative vitreoretinopathy: simultaneous pharmacokinetic and pharmacodynamic evaluations.

Intravitreal daunomycin (D) effectively suppresses cellular proliferation in experimental proliferative vitreoretinopathy (PVR) but has a narrow therapeutic safety range. Studies were undertaken to reduce toxicity of D by preparing a slow-release implant using polysulfone capillary fiber (PCF). Fabrication of the implant involved loading PCF with 1% D in tristearin (w/w), an excipient with diffusion-retardant properties. Two dose levels of the PCF-D device (15 micrograms and 30 micrograms/device) were prepared and sterilized prior to use. To examine the kinetics and efficacy of the device, rabbits were randomized and eyes were implanted as follows: 1) control group (PCF vehicle); 2) PCF-D (15 micrograms/device); 3) PCF-D (30 micrograms/device). Immediately after implantation, all eyes received an intravitreal injection of 2.5 x 10(5) retinal pigmented epithelial (RPE) cells. Thereafter, tractional retinal detachments (TRD) were graded by ophthalmoscopic examination. Also, fluorophotometry scanning from the retina to the anterior chamber was performed to determine the intraocular bioavailability of D. Results showed a therapeutically sustained level of D up to 21 days after device implantation. Midvitreous concentration of D was greater in group 3 than group 2 at all time points examined, indicating a dose-proportional increase in D release. Results of the PVR study showed that by 7 days after treatment, all eyes implanted with the PCF vehicle developed stage 2 TRD or greater; only 1 eye in each of groups 2 and 3 developed stage 2. By 2 weeks, most eyes in groups 2 and 3 remained in stages 1 and 2 with only 2 eyes progressing to stages 3 and 4 TRD. By 5 weeks, all eyes in group 1 showed stages 4 and 5 TRD, while most eyes in groups 2 and 3 remained in stages 1 and 2. The device with 30 micrograms D was more effective in preventing TRD. In conclusion, these data indicate that PCF can reduce the toxicity of D and may be a useful implant for treatment of PVR.

Animals↗
PubMed1994

Overexpression of a truncated cyclin B gene arrests Dictyostelium cell division during mitosis.

A cyclin gene has been isolated from Dictyostelium discoideum and the available evidence indicates that the gene encodes a B type cyclin. The cyclin box region of the protein encoded by the gene, clb1, has the highest degree of sequence identity with the B-type cyclins of other species. Levels of cyclin B mRNA and protein oscillate during the cell cycle with maximum accumulation of mRNA occurring prior to cell division and maximum levels of protein occurring during cell division. Overexpression of a N-terminally truncated cyclin B protein lacking the destruction box inhibits cell growth by arresting cell division during mitosis. The gene is present as a single copy in the Dictyostelium genome and there is no evidence for any other highly related cyclin B genes.

Amino Acid Sequence↗
PubMed1994

Interaction of Listeria species with human cell monolayers.

In foodborne listeriosis, the first step of infection must be attachment to, and invasion of, the gastrointestinal epithelium by virulent Listeria monocytogenes. Virulence factors affecting this invasion are only now being determined. We examined the interaction of L. monocytogenes, serotypes 4b and 1/2a strains with "smooth" and "rough" characteristics. In addition, flagellated and non-flagellated isogenic strains altered by transposon mutagenesis were examined to study the effect of flagellae on virulence. Strains of Listeria ivanovii and Listeria innocua were also studied. L. ivanovii demonstrated the greatest degree of internalization and L. innocua, the least. L. monocytogenes strains were intermediate and there were no significant differences between "rough" and "smooth" isolates. The presence or absence of flagellae did not effect cell association in this model. Minor differences between cell lines for the same strains were demonstrated. Variations in cell association for differing inocula temperatures (4 degrees, 22 degrees, 37 degrees) were also noted for all strains. The interaction of Listeria species with human cell monolayers appears to be complex. Hemolysin clearly play a significant role but other virulence factors may also be important.

Bacterial Adhesion↗
PubMed1993

Effects of copper coordinate complexes on the scavenging of reactive oxygen species.

Effects of a 20-membered macrocyclic bicopper complex and dioxotetramine copper complexes with linear or cyclic structure on the scavenging of ROS have been studied by ESR. The results indicated that all three copper coordinate complexes have SOD mimetic activity. The dioxotetramine copper complex with linear or cyclic structure did not have the scavenging effect on .OH produced by H2O2-Fe++ and 1O2 produced by the H2O2-NaOCl system, but the 20-membered macrocyclic bicopper complex was found to be capable of depressing the intensity of the ESR spectrum of the adduct formed from TMP and 1O2 as well as making the spectrum of DMPO-OH adduct splittings. This fact may suggest that there are interactions between the ROS and 20-membered macrocyclic ring in the SOD mimic.

Cells, Cultured↗
PubMed1993

[A study on transmission of dengue virus by Culex fatigans].

Patients with acute dengue fever within 2 days of onset were simultaneously bitten by Culex fatigans, Aedes aegypti and Aedes albopictus, which were fed and incubated in the laboratory. Isolation and quantitative assay of dengue virus and transmission experiment were conducted on specimens collected from 3 kinds of mosquitoes at different time. The result showed a positive rate of 5.13% (2/39) and an average viral titer of 2.41 logTCID50, for Culex fatigans, which indicates that Culex fatigans might be naturally infected with dengue virus and might transmit dengue virus after infection. But the positive rate and infection rate of Culex fatigans were significantly lower than those of Aedes aegypti and Aedes albopitus, which indicates that Culex fatigans might play a less important role in the transmission of dengue virus.

Aedes↗
PubMed1992

The calcium binding proteins parvalbumin and calbindin-D 28K form complementary patterns in the cat superior colliculus.

Parvalbumin (PV) and calbindin-D 28K (CaBP) are calcium binding proteins involved in calcium regulation in the brain. In some regions they coexist in the same neuron, while in other regions they are found in different cell types. We have studied the distribution and morphology of PV labeled neurons in the cat superior colliculus (SC) with antibody immunocytochemistry and compared this labeling to that of CaBP. PV neurons were concentrated in a dense tier within the deep superficial gray and upper optic layers. Scattered PV neurons also were found within the deep layers of SC. By contrast, CaBP neurons were concentrated in three tiers: one within the zonal and upper superficial gray layers, a second within the deep optic and upper intermediate gray layers (IGL), and a third within the deep gray layer. The distribution of PV neurons is thus complementary to that of CaBP neurons, with the CaBP cell tiers bordering the dense tier of PV neurons. PV neurons varied in size and morphology. The average diameter of labeled cells was 20 microns, almost twice the size of CaBP neurons. The cells were predominantly round, vertical fusiform, or stellate, and included the very large neurons found scattered in the IGL. Horseradish peroxidase injections into the lateral geniculate nucleus, the lateral posterior nucleus, the opposite superior colliculus, the dorsal lateral pontine gray nucleus, and two descending pathways--the crossed predorsal bundle and the tecto-ponto-bulbar tracts--each labeled SC neurons that were also labeled by PV. A large percentage (84%) of projection neurons contained PV. This result also differs from CaBP neurons in SC, most of which are interneurons. Two antigen double-label experiments did not produce any cells that contained both PV and CaBP. The two calcium binding proteins thus reveal a unique sublaminar organization in SC that consists of alternating small cell interneuron groups and large cell projection neuron groups.

Animals↗
PubMed1992

The inhibitory effects of 21 mimics of superoxide dismutase on luminol-mediated chemiluminescence emitted from PMA-stimulated polymorphonuclear leukocyte.

Four groups comprising 21 superoxide dismutase (SOD) mimics synthesized by us were comparatively studied for their inhibitory effects on luminol-mediated chemiluminescence emitted from phorbol myristate acetate (PMA)-stimulated polymorphonuclear leukocyte (PMNL). Among these groups, 20-membered macrocyclic bicopper(II) complexes and 13-membered macrocyclic dioxotetramine copper(II) complexes exhibited relatively higher activities of scavenging reactive oxygen species (ROS) produced by PMA-stimulated PMNL as compared with polyamine Cu(II)-Zn(II) complexes and copper(II) complexes of bis-shiff-base. Moreover, distinctly different effects of SOD mimics in the biological system have been found even in the same group. It is suggested that the biological effects of some SOD mimics are related to their structures.

Chelating Agents↗
PubMed1992

Visual deprivation fails to reduce calbindin 28kD or GABA immunoreactivity in the rhesus monkey superior colliculus.

Antibody labeling of the calcium-binding protein calbindin 28kD (CaBP) and gamma-aminobutyric acid (GABA) is altered by short-term monocular deprivation in the lateral geniculate nucleus and visual cortex of adult primates. It is not known whether these alterations occur in other subcortical visual structures. We therefore have examined antibody labeling to CaBP and GABA in the superior colliculus (SC) of visually deprived Rhesus monkeys. One group was monocularly enucleated as adults. The other monkeys experienced different types of monocular and binocular deprivation from birth, including occlusion of one eye, and/or surgically induced aphakia, optically corrected with extended-wear contact lenses, or an intraocular lens implant. Some of these monkeys also had one eye enucleated prior to perfusion. In the SC of normal monkeys, CaBP-immunoreactive neurons formed three laminar tiers within SC, one within the zonal layer (ZL) and upper superficial gray layer (SGL), another bridging the optic and intermediate gray layers, and a third within the deep gray layer. CaBP neurons within the upper tier had small pyriform or stellate morphologies while those in the deeper tiers were slightly larger neurons, most with a stellate morphology. GABA-immunoreactive neurons were densely distributed within the SGL and more sparsely distributed within the deeper layers. These cells were mostly small neurons with horizontal, pyriform, or stellate morphologies. Neither monocular enucleation nor occlusion nor aphakia combined with continuous occlusion of the fellow eye produced any visible reduction in antibody labeling in cells or neuropil within the SC. Full-field measures of labeling intensity (optical density) within the ZL and upper SGL revealed no consistent differences between the SC contralateral or ipsilateral to the affected eye in either CaBP- or GABA-labeled sections. Measures of the optical density, number, and size of labeled neurons also showed no consistent effects of enucleation and/or occlusion. We therefore conclude that the retino-geniculostriate and retino-collicular systems differ in their response to deprivation which is likely due to the significant overlap of retinal axons from the two eyes that occurs in the SC of the Rhesus monkey.

Animals↗
PubMed1992

Monocular enucleation reduces immunoreactivity to the calcium-binding protein calbindin 28 kD in the rhesus monkey lateral geniculate nucleus.

The calcium-binding proteins calbindin (CaBP) and parvalbumin (PV) are important in regulating intracellular calcium in brain cells. PV immunoreactivity is reduced by enucleation in the lateral geniculate nucleus (LGN) and by enucleation and visual deprivation in the striate cortex of adult monkeys. The effects of enucleation and visual deprivation on CaBP immunoreactivity in the LGN are not known. We therefore have studied cells and neuropil in the LGN that are labeled by antibodies to CaBP in normal and visually deprived Rhesus monkeys to determine if there is an effect on this calcium-binding protein. One group of monkeys had one eye removed 2 weeks to 4.3 years before sacrifice. A second group had one eye occluded with opaque lenses from infancy without enucleation. A final group had one eye occluded long-term followed by short-term enucleation 2 weeks before sacrifice. In normal monkeys, CaBP-immunoreactive neurons were found throughout the LGN. They were sparsely distributed within the six main laminae, and more densely distributed within layer S and the interlaminar zones (ILZ). The labeled ILZ neurons had a distinct morphology, with fusiform somata and elaborate dendritic trees that were confined primarily to the ILZ. Most CaBP-labeled neurons in the main layers had dendrites that radiated in all directions from the soma. ILZ and main layer cells labeled by CaBP thus probably represent two different cell types. Monocular enucleation with or without occlusion produced a significant reduction in antibody labeling in the deafferented laminae. Field measures revealed an average 11.5% reduction in optical density in each deafferented lamina compared to its adjacent, nondeprived layer. The differences in field optical density between deprived and nondeprived layers were statistically significant. CaBP neurons were still visible, but the optical density of antibody labeling in these cells also was reduced. Occlusion without enucleation had no effect. Thus, deafferentation, but not light deprivation, reduces concentrations of CaBP in monkey LGN. This effect is different than that seen in striate cortex of adult monkeys, where visual deprivation as well as enucleation alters CaBP immunoreactivity.

Animals↗
PubMed1991

The calcium binding protein calbindin-D 28K reveals subpopulations of projection and interneurons in the cat superior colliculus.

The calcium binding protein calbindin-D 28K (CaBP) has been localized in the cat superior colliculus (SC). Four important features of SC organization have been revealed by using CaBP immunocytochemistry. 1) CaBP neurons formed three laminar tiers in SC, one within the upper one half of the superficial gray layer (SGL), the second bridging the deep optic (OL) and intermediate gray layers (IGL), and the third within the deep gray layer (DGL). 2) CaBP labeled several classes of interneuron in SC. In the upper CaBP tier, the labeled neurons were all small, but they varied in morphology and included horizontal, pyriform, and stellate neurons. A unique class of interneuron was labeled by anti-CaBP in the OL-IGL tier. This cell was stellate-like with highly varicose dendrites and broad dendritic trees. Other labeled neurons in the intermediate and deep tiers included nonvaricose stellate neurons and rare large neurons in the DGL. 3) A few anti-CaBP neurons were projection neurons. Virtually no CaBP neurons were retrogradely labeled after injections of HRP into the predorsal bundle and dorsolateral midbrain tegmentum or into the lateral posterior nucleus. However, 2.4% of anti-CaBP neurons were retrogradely labeled after HRP injections into the dorsal and ventral lateral geniculate nuclei. These represented 14.7% of all neurons projecting to the LGN complex. 4) A small percentage of CaBP neurons co-localized GABA. A two-chromagen double-labeling technique showed that about 4.0% of labeled neurons were labeled by both antibodies. In summary, antibodies to CaBP densely labeled subpopulations of neurons in the cat SC, most of which were interneurons, some of which projected to the LGN, and a few of which co-localized GABA.

Animals↗
PubMedDate not supplied

A Dictyostelium discoideum gene, which is highly related to mo15 from Xenopus, is expressed during growth but not during development.

We have isolated a cDNA from the cellular slime mold Dictyostelium discoideum encoding a protein that is 52% identical to the Xenopus Mo15 kinase and highly related to the equivalent proteins from human (52% identity), rice (52.7% identity), and yeast (47.6% identity). Mo15 is responsible for the activation of Cdc2 kinase and is itself a member of the large Cdc2-related family of protein kinases. The Dictyostelium protein is more related to the Xenopus Mo15 protein than it is to either the Dictyostelium Cdc2 or Crp proteins. Southern blot analysis of genomic V12-M2 DNA indicated that mo15 is present as a single copy gene that cross hybridizes with cdc2 at low stringency. Northern blot analysis of RNA from different stages of Dictyostelium development showed that mo15 is only expressed during vegetative cell growth.

Amino Acid Sequence↗