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Biomedical subjects

Q Zhao

Publications and source records attributed to Q Zhao.

At least 235 records · Page 13Linked to original sources
PubMed1995

An experimental study of spinal cord evoked potential.

The characteristics of spinal cord-evoked potentials were investigated by using an in vitro spinal cord preparation. The spinal cord isolated from adult rats was immersed in a bathing chamber filled with oxygenated artificial cerebrospinal fluid (aCSF). The spinal cord-evoked potentials elicited by the stimulation of the spinal cord were recorded by using bipolar platinum electrodes. The potentials recorded consisted of early and late negative components (N1, N2). The inhibitory effect of lowered temperature on the N1 potential was clearly demonstrated. The oxygen deprivation of aCSF showed the higher sensitivity of N2 potential to hypoxia than that of N1. It was also possible to analyze the effects of potassium and magnesium ion concentration and pH on the evoked potentials. These results showed that the pure effects of various physiological and chemical factors on the spinal cord-evoked potentials can be analyzed by this experimental model.

Animals↗
PubMed1995

Multiple subpial transection for treatment of intractable epilepsy.

On the basis of experimental study, we applied multiple subpial transection (MST) to treat 50 patients with intractable epilepsy in which epileptigenic lesion involved functional areas such as pericentral gyrus, postcentral gyrus, Broca's area, Wernicke's area, visual cortex, etc. They were followed up for 6 to 40 months. Complete control of seizures was obtained in 32 patients, significant reduction of seizure (more than 50%) in 13, reduction (less than 50%) in 3, and no effect in 2. The total effective rate was 96%. No functional defect was found in all patients. The mechanism of the disease and surgical technique were discussed in detail. We consider that MST could replace some standard excisional therapy for local epilepsy.

Adolescent↗
PubMed1995

Molecular role of sulfated glycoprotein-1 (SGP-1/prosaposin) in Sertoli cells.

Sulfated Glycoprotein-1 (SGP-1) is a major polypeptide secreted by rat Sertoli cells. Sequence analysis revealed a 70% sequence similarity with human prosaposin and a 80% similarity with mouse prosaposin. Both human and mouse prosaposin are 65-70 kDa proteins cleaved in the lysosomes into four 10-15 kDa proteins designated saposins A, B, C and D. Lysosomal saposins function as enzymatic activators that promote the hydrolysis of certain glycolipids. SGP-1 (70 kDa) was first considered as being exclusively secreted to the extracellular space. However, recent immunocytochemical studies using an anti SGP-1 antibody demonstrated the presence of this protein in Sertoli cell lysosomes. In addition Sertoli cell lysosomes isolated by cellular fractionation were found to contain a 65 kDa form of SGP-1 or lysosomal prosaposin, as well as, the 15 kDa saposins. Morphological and immunocytochemical evidences also indicated that both prosaposin and saposins may reach Sertoli cell phagosomes by lysosomal fusion. These phagosomes contain cytoplasmic residual bodies detached from spermatids during spermiation. Thus, prosaposin and their derived saposins must play a role in the hydrolysis of membrane glycolipids present in phagocytosed residual bodies. On the other hand, the function of the secreted form of SGP-1 is still unclear. However, SGP-1 was seen to interact with the plasma membrane of developing spermatids. Due to its capacity to bind certain types of gangliosides, SGP-1 appears to act as glycolipid transfer between Sertoli cells and the developing spermatids.

Amino Acid Sequence↗
PubMed1994

Pre-degenerated nerve grafts enhance regeneration by shortening the initial delay period.

In the present study we tested how nerve grafts with different pre-degeneration periods (1-28 days) influenced the early regenerative response in the rat sciatic nerve. The sciatic nerve on the right side was crushed and after 1-28 days of pre-degeneration, a 10 mm segment was used as an autologous nerve graft and transposed to a freshly made 10 mm long nerve defect on the left side. The regeneration distance was measured by the sensory pinch test 2-10 days after nerve repair. A newly developed mathematical model was used to calculate regeneration rates and initial delay periods from the measured regeneration distances. Pre-degenerated nerve grafts improved nerve regeneration by decreasing the initial delay period as compared to fresh nerve grafts without affecting the regeneration rate. Only one day of pre-degeneration was sufficient to reduce the initial delay period from 3.6 days to 1.7 days. The maximal effect on the initial delay period was achieved after 3 days of pre-degeneration. The initial delay period at later pre-degeneration intervals (7-14 days) was about 1 day. The effect persisted for at least 28 days of pre-degeneration. The regeneration rate was 1.5 mm/day for fresh nerve grafts and between 1.8-2.1 mm/day for pre-degenerated grafts. The results suggest that the effects of pre-degeneration are not only due to the increased cell proliferation in the graft, but that also trophic and/or inflammatory mechanisms may be of importance. Grafts pre-degenerated by crush may have clinical implications since they are easy to perform if an elective nerve grafting procedure is planned.

Animals↗
PubMed1994

Stage-specific oligonucleotide uptake in murine bone marrow B-cell precursors.

Fluorescein isothiocyanate (FITC)-conjugated phosphodiester and phosphorothioate oligonucleotides were used in four-color flow cytometry with murine bone marrow cells stained with monoclonal antibody specific for the differentiation markers B220, S7 (CD43), and BP-1 to show possible stage-specific oligonucleotide uptake. Relatively low uptake was observed among pre-Pro- and early Pro-B cells. Late Pro-B- and pre-B cells had increased oligonucleotide uptake, whereas B cells had a lower level. Cell membrane binding of oligonucleotides varied during B-cell differentiation in parallel with internalization, which was documented by confocal microscopy. An FITC-conjugated polyanionic dextran sulfate also showed differentiation-related B-cell association, suggesting the presence of cell membrane binding sites specific for polyanions as opposed to a unique feature of the DNA backbone. Interpretation of antisense experiments in murine bone marrow cells will need to account for the heterogeneous oligonucleotide uptake among differentiating B cells.

Animals↗
PubMed1994

High-performance anion exchange of small anions with polyethyleneimine-coated porous zirconia.

The preparation and chromatographic characterization of an ion-exchange high-performance liquid chromatographic support by deposition and crosslinking of polyethyleneimine (PEI) on the surface of porous zirconia is described. Adsorption and evaporation methods were used for coating PEI onto the zirconia particles. These two stationary phases were compared by elemental analysis, ion-exchange capacity and by chromatography. High efficiency and good selectivity were observed for inorganic and organic anions. The addition of a strong, hard Lewis base to the mobile phase dramatically improved the peak shape and efficiency of para benzoic acid derivatives. PEI-coated zirconia showed a distinct elution sequence for organic anions when compared to bare zirconia or silica-based phases. The polyamine coated zirconia was stable over a pH range from 2.75 to 9. Flow studies, using nitrite as a probe solute, showed that both coating procedures produced packed columns with good mass-transfer properties.

Anions↗
PubMed1994

Enantioselective and reversible inhibition of trypsin and alpha-chymotrypsin by phosphonate esters.

Trypsin is inactivated by the levorotatory enantiomers (most likely PS) of 4-nitrophenyl 4-H-, 4-CH3-,4-OCH3-, and 4-Cl-phenacyl methylphosphonates (PMNs) with second-order rate constants between 231 and 884 M-1 s-1. 4-NO2-PMN hydrolyzes before inhibiting the enzyme. The second-order rate constants for the inactivation of alpha-chymotrypsin by the levorotatory enantiomers of the five PMNs are between 37,000 and 770,000 M-1 s-1, and those for the dextrorotatory enantiomers are between 400 and 640 M-1 s-1; the enantioselectivity is 90-1880. Specific rotation [alpha]22D of the faster-reacting enantiomer of 4-CH3-PMN with trypsin and alpha-chymotrypsin is -30 +/- 6 degrees. 31P NMR of the adducts shows a signal at 41.0 ppm, 10 ppm downfield from the parent compound. Results of molecular mechanics and dynamics calculations show that the principal interactions are between the phosphonyl group and constituents of the oxyanion hole and between the aromatic fragment and residues in the binding regions of the enzymes. Trypsin activity returns from its phenacyl methylphosphonyl adducts on the hour time scale and in reversed order to the rates of inactivation within the series. Recovery of alpha-chymotrypsin activity from the adducts formed with the (-) enantiomers is on a slower time scale still, whereas its recovery from the adducts formed with the (+) enantiomers is on the second to minute time scale. The data support a mechanism of reactivation involving rate-determining intramolecular displacement of Ser by the carbonyl hydrate of the phenacyl moiety. The pH-rate profiles for trypsin reactivation from its adducts indicate involvement of an ionizable group with pKa approximately 8.0. The pH dependence and solvent isotope effects are small in most cases. The compounds demonstrate favorable properties for controllable and temporary modulation of enzyme activity.

Chymotrypsin↗
PubMed1994

Hyperthermia complicates middle cerebral artery occlusion induced by an intraluminal filament.

The present experiments were designed to study under what circumstances middle cerebral artery (MCA) occlusion by an intraluminal filament technique leads to hyperthermia and what the mechanisms are. We found that permanent MCA occlusion by this technique lead to a rise in body (core) temperature to 39.0-39.5 degrees C during the first 2-4 h, and to sustained hyperthermia thereafter (38.5-39.0 degrees C). After 2 h of transient MCA occlusion hyperthermia could only be avoided if anesthesia (with control of temperature) was maintained for 2 h of ischemia and 1 h of recirculation or, in unanesthetized animals, if external cooling was maintained for 2 h of ischemia and 2 h of recirculation. Control of temperature only during ischemia did not prevent a postischemic rise in temperature. One hour of MCA occlusion had less effect on body temperature. Results are presented which suggest that the hyperthermia observed is due to an interference, by the intraluminal filament, of circulation to hypothalamic centers regulating body temperature. It is speculated that the hyperthermia induced may blunt or obliterate the effect of drugs, normally considered to ameliorate brain damage due to focal ischemia.

Animals↗
PubMed1994

Effects of predegeneration on nerve regeneration through silicone Y-chambers.

The effects of nerve predegeneration on the preferential growth of regenerating axons were studied using a silicone Y-chamber model. This system provided a choice for axons to grow towards two distal nerve options, either a 7-day predegenerated nerve segment (PNS) or a fresh nerve segment (FNS). The rat peroneal or tibial nerve was inserted into the proximal intlet and the PNS and FNS of the corresponding nerve were inserted into the distal outlets. At 28 days postoperative, the size of the distal regenerate was significantly greater (26%) towards the PNS for the tibial nerve group. The density and number of regenerated myelinated axons in the distal nerve segment was greater on the PNS for both the tibial (97 and 88%, respectively) and peroneal (221 and 221%, respectively) nerve groups. In contrast, the elevated density and number of nonvascular nuclei was relatively constant for both PNS and FNS. Immunocytochemical and ultrastructural evidence support the hypothesis that the early activation of Schwann cells is primarily responsible for the enhanced regeneration and maturation observed in PNS. It is suggested that PNS might improve the outcome after clinical repair of injured peripheral nerves.

Animals↗
PubMed1994

Growth-inhibitory effects of coumarin (1,2-benzopyrone) and 7-hydroxycoumarin on human malignant cell lines in vitro.

Coumarin (1,2-benzopyrone) is a natural substance that has shown antitumor activity in vivo. The major human metabolite of coumarin, 7-hydroxycoumarin (7-HC), is the active form of the drug. While the exact mechanism(s) of action of coumarin is unknown, it has been shown previously that this drug possesses immunomodulatory activity in vitro and in vivo. The present investigations examined the direct (non-immunological) antitumor effects of coumarin and 7-HC in vitro. Both coumarin and 7-HC were found to be growth-inhibitory (cytostatic) for the following human malignant cell lines: A549, ACHN, Caki-2, Dakiki, HS-Sultan, H727, HCT-15, HL-60, K562, LNCaP, PC-3, Du 145 COLO-232, MCF-7 and RP-1788. The growth inhibition was dependent on dose and time and was reversible upon removal of cells from medium containing the drug. Coumarin and 7-HC inhibited [3H]thymidine, [3H]uridine and [3H]leucine incorporation. In a similar fashion, coumarin and 7-HC inhibited the intracellular production of prostate-specific antigen by LNCaP cells. Coumarin and 7-HC stimulated apoptosis in HL-60 cells but not in other cell lines tested. It is concluded that coumarin and 7-HC have direct antitumor (cytostatic) activity as well as immunomodulatory activity. Further information is needed in order to determine which activities are responsible for antitumor activity in vivo.

Apoptosis↗
PubMed1994

Synthesis of 11-substituted androstenediones and testosterones as human decidual cell growth inhibitors.

11 alpha-Hydroxytestosterone (1a), 11 beta-hydroxytestosterone (1b), 11 alpha-methoxytestosterone (1c), 11 beta-methoxytestosterone (1d), 11-ketotestosterone (1e), and delta 9(11)-testosterone (1f) were synthesized from hydrocortisone (4b) or 11-epi-hydrocortisone (4a). The six target compounds, together with 11 alpha-methoxyandrostenedione (2c), 11 beta-methoxyandrostenedione, (2d) and their lead compound, testosterone (1), were found to effectively inhibit the growth and differentiation of human decidual cells in culture. There is no observable binding of these compounds to estrogen receptor of rabbit uterus. The introduction of a polar group (e.g., hydroxyl and carbonyl) to C-11 of androstenes decreases both the relative binding affinities to progesterone receptor and the inhibitory effects on human decidual cell growth, while the methylation of 11-hydroxyl group minimizes these effects. The similar effects of a polar group at C-11 of testosterone (1) on the inhibitory effects on human decidual cell growth and the relative binding affinities to progesterone receptor of rabbit uterus may suggest that one of the mechanisms of human decidual cell growth inhibition by these compounds is the anti-progestational activity of these androgens.

Androstenedione↗
PubMed1994

Can sensory and motor collateral sprouting be induced from intact peripheral nerve by end-to-side anastomosis?

The possibility that collateral sprouting could occur from intact axons in an undamaged sciatic nerve was studied in the rat by suturing either a 7-day predegenerated or a fresh nerve segment in an end-to-side fashion to the sciatic nerve proper. Following a 14- or 35-day recovery period, the pinch reflex test was performed on the transplanted segment to demonstrate the presence of sensory axons. The majority of cases, using a predegenerated nerve segment but not a fresh segment, responded positively. Neurofilament staining and histological examination confirmed the presence of axons in the attached nerve segment. In another series of experiments, the proximal peroneal fascicle was ligated and cut. Following a 7-day predegeneration period the distal stump was sutured end-to-side to the ipsilateral tibial fascicle. After 90 days, stimulation of the tibial nerve proximal to the attached site induced substantial contraction in both the native gastrocnemius muscle and the foreign tibialis anterior muscle. These findings suggest that collateral sprouting may occur from intact axons, perhaps induced by factors emanating from the attached nerve segment, and subsequently make functional peripheral connections.

Anastomosis, Surgical↗
PubMed1994

Trophism, tropism, and specificity in nerve regeneration.

Target-derived neurotrophic factors are of basic importance for survival of neurons. In the normal state, such neurotrophic factors, synthesized by the target tissues, are taken up by nerve terminals and transported by retrograde axonal transport in axons to the nerve-cell bodies to maintain their viability. After nerve injury, neurotrophic factors are synthesized by non-neuronal cells (Schwann cells and fibroblasts) in the nerve trunk, thereby supporting the outgrowth of axons. Neurite-outgrowth-promoting factors on cell surfaces (cell adhesion molecules, "recognition molecules") or in the extracellular matrix promote extension of the axons by providing an appropriate "adhesiveness" in the substrate. Both neurotrophic and neurite-outgrowth-promoting factors are essential for axonal growth after injury. Specificity in end-organ reinnervation is a complex phenomenon which may be based on physical factors at the zone of injury, as well as on molecular interaction between axons and substrate cells along the pathways and at the target level. Such processes may include molecular recognition of appropriate axons and maintenance of such axons by trophic mechanisms, as well as the pruning of inappropriate axons. The ultimate errors in target reinnervation are reflected in a cortical re-organization in the somatosensory cortex. The capacity of the brain to "reprogram" itself and adapt to this functional re-organization is critical for the ultimate recovery of functional sensory/motor function after nerve injuries.

Animals↗