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Biomedical subjects

Y Hu

Publications and source records attributed to Y Hu.

At least 433 records · Page 24Linked to original sources
PubMed1997

A temporary local energy pool coupled to neuronal activity: fluctuations of extracellular lactate levels in rat brain monitored with rapid-response enzyme-based sensor.

A successfully developed enzyme-based lactate microsensor with rapid response time allows the direct and continuous in vivo measurement of lactic acid concentration with high temporal resolution in brain extracellular fluid. The fluctuations coupled to neuronal activity in extracellular lactate concentration were explored in the dentate gyrus of the hippocampus of the rat brain after electrical stimulation of the perforant pathway. Extracellular glucose and oxygen levels were also detected simultaneously by coimplantation of a fast-response glucose sensor and an oxygen electrode, to provide novel information of trafficking of energy substances in real time related to local neuronal activity. The results first give a comprehensive picture of complementary energy supply and use of lactate and glucose in the intact brain tissue. In response to acute neuronal activation, the brain tissue shifts immediately to significant energy supply by lactate. A local temporary fuel "reservoir" is established behind the blood-brain barrier, evidenced by increased extracellular lactate concentration. The pool can be depleted rapidly, up to 28% in 10-12 s, by massive, acute neuronal use after stimulation and can be replenished in approximately 20 s. Glutamate-stimulated astrocytic glycolysis and the increase of regional blood flow may regulate the lactate concentration of the pool in different time scales to maintain local energy homeostasis.

Animals↗
PubMed1997

Cloning and functional analysis of rat cyclin D2 promoter: multiple prolactin-responsive elements.

Structure and function of the promoter region of rat cyclin D2 gene were investigated by cloning, sequence analysis and DNA mobility shift assay using nuclear extracts of prolactin-stimulated Nb2 cells. The results show that the expression of rat cyclin D2 gene is not dependent on the TATA-box but is stimulated by multiple transcription factors induced by prolactin at an immediate-early stage of the cell cycle.

Amino Acid Sequence↗
PubMed1997

Destabilization of potato spindle tuber viroid by mutations in the left terminal loop.

Infectivity studies with highly infectious RNA inocula generated by ribozyme cleavage were used to compare the biological properties of three apparently nonviable mutants of potato spindle tuber viroid (PSTVd). One of these mutants (PSTVd-P) contains three nucleotide substitutions in the left terminal loop, and mechanical inoculation of tomato seedlings with RNA transcripts at levels equivalent to 10(3)-10(5) times the ID50 for PSTVd-Intermediate failed to result in systemic infection. Viable progeny containing a spontaneous C-->G change at position 4 could, however, be recovered from transgenic Nicotiana benthamiana plants that constitutively expressed PSTVd-P RNA. The initial mutations in PSTVd-P led to an overall weakening of its native structure in vitro, and the precisely-full-length molecule released by ribozyme cleavage in vivo was also unstable. Even RT-PCR analysis failed to reveal detectable amounts of circularized PSTVd-P among the RNAs isolated from uninfected plants. Predicted stabilizing effects of a spontaneous mutation at position 4 suggest that the appearance of viable progeny was dependent on a combination of events: errors by host RNA polymerase II during transcription of the mutant transgene coupled with a strong selective pressure against alterations in the native structure of PSTVd.

Mutation↗
PubMed1997

Role of mesangial cells in macula densa to afferent arteriole information transfer.

1. Extraglomerular mesangial cells are strategically positioned between the macula densa and the afferent arteriole. These cells form a syncytium and are connected with glomerular mesangial cells via gap junctions. The model of immunoablation of mesangial cells in anti-Thy-1 glomerulonephritis carries the promise for understanding the function of mesangial cells as potential transmitters of information between the macula densa and the afferent arteriole. 2. The above anatomical relations between structures in the juxtaglomerular apparatus predict several possible routes of information flow. This review charts some hypothetical routes. 3. Research into the messenger systems involved in the transfer of signals from the macula densa to mesangial cells and from mesangial cells to the afferent arteriole suggests several candidate molecules to function in this capacity. Mechanisms of action for each candidate are discussed. 4. The oscillating nature of the afferent signal and efferent function in the tubuloglomerular feedback system, as well as other discoveries, offer a fertile field for future studies.

Animals↗
PubMed1997

V(D)J recombination: in vitro coding joint formation.

Antigen receptor genes are assembled through a mechanism known as V(D)J recombination, which involves two different joining reactions: signal and coding joining. Formation of these joints is essential for antigen receptor assembly as well as maintaining chromosomal integrity. Here we report on a cell-free system for coding joint formation using deletion and inversion recombination substrates. In vitro coding joint formation requires RAG1, RAG2, and heat-labile factors present in the nuclear extract of nonlymphoid cells. Both inversion- and deletion-mediated coding joint reactions produce diverse coding joints, with deletions and P nucleotide addition. We also show that deletion-mediated coding joint formation follows the 12/23 rule and requires the catalytic subunit of DNA-dependent protein kinase.

Cell Nucleus↗
PubMed1997

Activation of mitogen-activated protein kinases (ERK/JNK) and AP-1 transcription factor in rat carotid arteries after balloon injury.

Smooth muscle cell proliferation is a key event in neointimal formation after balloon angioplasty. The molecular signals that mediate this process have yet to be identified. Mitogen-activated protein (MAP) kinases are thought to play a pivotal role in transmitting transmembrane signals required for cell proliferation in vitro. The present studies were designed to investigate whether the signal transduction pathways of MAP kinases were involved in the development of restenosis in the injured arteries. Rat carotid arteries were isolated at various time points after balloon injury, and activities of MAP kinases, including extracellular signal-regulated kinases (ERK), and stress activated protein kinases (SAPK)/c-Jun N-terminal protein kinases (JNK), were determined in protein extracts of the vasculature using protein kinase assay and Western blot analysis. After balloon angioplasty, ERK2 and JNK1 activities in the vessel wall increased rapidly, reached a high level in 5 minutes and maintained for 1 hour. A sustained increase in ERK2 kinase activity was observed over the next 7 days in the arterial wall and 14 days in neointima after injury. In contrast, opposite and uninjured arteries did not show significant changes in these kinase activities. Concomitantly, Western blot analysis confirmed that the ERK2 kinase in the injured vessels was indeed activated or phosphorylated, showing a slowly migrating species of a 42-kDa protein containing phosphorylated tyrosine. Kinase activation is followed by an increase in c-fos and c-jun gene expression and enhanced activator protein 1 (AP-1) DNA-binding activity. Thus, balloon injury rapidly activates the MAP kinases in rat carotid arteries. These kinase activations may be crucial in mediating smooth muscle cell proliferation in response to vascular angioplasty.

Angioplasty, Balloon↗
PubMed1997

Intracerebroventricular leptin increases lumbar and renal sympathetic nerve activity and blood pressure in normal rats.

Obesity and hyperinsulinism are known to be major stimuli of leptin production by adipose tissue, leading to increased leptin levels in the circulation. It has also been demonstrated that increased leptin production leads to satiety, possibly by decreasing the levels of neuropeptide Y (NPY) in the central nervous system (CNS). Because obesity and hyperinsulinism are also frequently associated with hypertension, we studied the effect of the intracerebroventricular (ICV) administration of leptin on mean arterial pressure (MAP), heart rate, vascular flows, and lumbar and renal sympathetic nerve activity (SNA). Normal Wistar rats were implanted with an ICV cannula and allowed to recover. On the day of the study, the animals were fasted and anesthetized with chloralose/urethane. Catheters were placed in a femoral artery and vein, and Doppler flow probes were placed around the iliac, renal, and superior mesenteric arteries for measurement of MAP, heart rate, and blood flows. In other experiments, lumbar SNA and renal SNA were recorded. ICV leptin administration resulted in an MAP that was slowly but progressively increasing. Blood flows decreased in the iliac and superior mesenteric arteries, but not in the renal artery. Leptin injection increased the lumbar SNA and renal SNA. The plasma glucose and insulin levels were not changed. We concluded that ICV leptin increases MAP by decreasing arterial blood flow to the skeletal muscle and the splanchnic vascular bed. This increased peripheral resistance is the result of an increased activity of the sympathetic nerves. We suggest that increased leptin may serve as a link in the triad of obesity and hyperinsulinism and hypertension.

Animals↗
PubMed1997

[Effect of interleukins on proliferation of cultured rat anterior pituitary cells].

The present study investigated whether IL-1 and IL-6 involved in the control of proliferation in cultured anterior pituitary (AP) cells. Primary culture of AP cell were obtained from either male and female Sprague-Dawley rats. The effects of IL-1 and IL-6 assessed by [3H]-thymidine incorporation rate. It was found that: (1) IL-1(1-100 ng/ml) stimulated 3H-TdR incorporation into AP cells of male and female rats. (2) The lower concentration of IL-6 (0.1 ng/ml) inhibited 3H-TdR incorporation rate, but higher concentration of IL-6 (1-10 ng/ml) stimulated 3H-TdR incorporation into AP cells of male rats. (3) IL-6 (0.1-10 ng/ml) stimulated 3H-TdR incorporation into AP cells of female rats. These results indicated that IL-1 and IL-6 can modulate the endocrine activity as well as the proliferation of AP cells.

Animals↗
PubMed1997

[The study of women's bone density in Beijing].

Bone mass of 434 healthy women aged from 20-65 years was measured at both distal and mid-radius of the non-dominant arm by using a single-photon absorptiometer (SPA) with an 241Am source (model SD-1000), and bone density and related factors were studied. The bone density in women reached the peak value around 40 years old and the bone loss began around 45 years old. Bone loss was accelerated after menopause, with faster speed in trabecular bone than in cortical bone. The effect of menopause on bone loss was more significant than the effect of advancing age. Among 174 menopausal women, 9.8% had fractures. The bone density of postmenopausal women with history of bone fracture was lower than that of those without fracture. The results of this study suggest that the measurement of bone density can be used to predict the risk of osteoporotic fractures.

Absorptiometry, Photon↗
PubMed1997

[The effect of calcium content in bovine cancellous bone as carrier on expression of tumor necrosis factor-alpha gene in mice].

We investigated the expression of tumor necrosis factor-alpha (TNF alpha) gene in the area of implanted calf cancellous bone with different calcium content and the influence of calcium salts on local cellular immunity. The particles of mineralized and partially demineralized bone were implanted in the mouse's muscle pouch, and removed 3, 5, 10 and 20 days after implantation of the bone particles. The specimens were processed for determining the expression of mRNA encoding TNF alpha, which was performed by a nonradioactive in situ hybridization technique. The expression of TNF alpha mRNA was markedly higher in the mineralized bone group than in the partially demineralized bone group (P < 0.01). The positive rate of TNF alpha gene expression was highest by 10 days after implantation. There was a strong hybridization signal localization to the cytoplasm of morphologically identifiable monocytes and multinucleated giant cells. Similar activity was detected in the cytoplasm or nuclei of mesenchymal cells, fibroblasts as well as striated muscle fibers. This finding suggests that the calcium content in calf cancellous bone possesses a significantly stimulative effect on TNF alpha mRNA expression, and calcium salts may be of importance for the modulation of local cellular immunity.

Animals↗
PubMed1997

[Effect of extended lymph nodes dissection on curative resection of lung cancer].

We evaluated the effect of extended lymph nodes dissection on curative resection in 386 patients with lung cancer surgically treated for 9 years. The extended lymph node dissection of the hilar and mediastinum was performed on the basis of mapping system for mediastinal lymph nodes developed by Naruke. Altogether 2603 groups of lymph nodes were dissected (mean 6.74 groups). The overall metastatic rate was 49.2% (190/386), including simple N1 diseases (43 cases, 11.1%) and N2 diseases (147, 38.1%). The metastatic rate for squamous cell carcinoma, adenocarcinoma, small cell carcinoma and large cell carcinoma was 30.1%, 44.1%, 48.0% and 50.0%, respectively. The lymphatic metastases in lung cancer showed the features of saltatory infiltration and multiple levels of involvement. Cure could be achieved only after extended dissection of intrapulmonary and mediastinal lymph nodes.

Adenocarcinoma↗
PubMed1997

[Microwave heating and neoadjuvant chemotherapy for malignant bone tumor].

Limb salvage is widely used but has different disadvantages. Attempting to establish a new limb conservative procedure, we treate patients with malignant bone tumor by intraoperative microwave heating on tumor bearing bone in place and neoadjvant chemotherapy. The tumors were localized at distal femur in 16, proximal tibia in 5, femur shaft in 2, and illia in 2. Pathological diagnosis showed osteosarcoma in 16 patents, parosteoal osteosarcoma in 4, chondrosarcoma in 3, and leiomyosarcoma in 2. The stage of tumor was II b in 18 patients, II a in 6, and III b in 3. Operative technique was wide resection for tumor in soft tissue, protecting the surrounding tissue from heat injury by copper net, and cheating tumor bone at 50 C for 15 minutes. Follow-up varied from 4 to 180 months (mean 57 months). The 5-, 10-years surviral rates were 70.19% and 54.83% respectively. Functional results of 21 patients were > 15 points by Enneking system. The advantages of the method and keeping the shape and continuity of the tumor bearing bone without osteotomy and internal fixation, controlling the time and temperature of heating treatment easily, benefiting for bone remodeling of heated bone. The indications, complications, and surgical procedure of this method were discussed in detail.

Adolescent↗
PubMed1997

[A study of parotid salivary proteins from caries-free and caries-active people by high performance liquid chromatography].

In this study, we isolated and analysed parotid salivary proteins of different individuals with different caries-susceptibility. Protein fractions isolated were identified by biochemical methods. The results showed that six proteins were isolated from parotid saliva by HIC (hydrophobic interaction chromatography). Four proteins were found in all hydrophobic interaction chromatography. Three of them were identified as different polymorphic forms of proline-rich proteins (PRPS) and the other as alpha-amylase. Comparing chromatography of fifteen healthy caries-free adults with ten caries-active adults, we found that there was no difference in salivary protein composition. Three different phenotypes of PRPS had different relations with caries-susceptibility and relative ratios of the three PRPS were different between two groups. It suggested that abnormal proportions of salivary proteins may be another important determinant in caries-susceptibility.

Adult↗
PubMed1997

[The experimental studies of immune response of antigen-extracted bovine cancellous bone grafting].

Xenogeneic bone grafting is an alternative to autogeneic bone grafting, but the intense immune rejection makes its clinical practice limited. We performed lymphocytes proliferation assay, enzyme-linked immunosorbent assay, and histological observation to evaluate the levels of cellular and humoral immunity, and the tissue reaction to the grafting of BALB/c mice receiving fresh bovine cancellous bone (FCB), antigen-extracted bovine massive cancellous bone (MCB), antigen-extracted bovine granular cancellous bone (GCB). Lymphocyte proliferation was increased in an early phase of the grafting and persisted for a long period in FCB group. Meanwhile higher levels of specific antibody were detected. In MCB and GCB groups, lymphocyte proliferation and specific antibody production were not ascended and no significant difference was observed between MCB and GCB groups in these immunological responses. There were no appreciable histologic signs of immune or foreign body reaction both in MCB and GCB groups. The results suggested that MCB, GCB were characterized less antigenicity and can be used as osteoconductive material or a carrier of bone growth factors.

Animals↗
PubMed1997

[Hepatic resection and hepatic arterial chemoembolization for primary liver carcinoma].

Three hundreds of primary liver carcinoma (PLC) were subjected to hepatic resection and hepatic chemoembolization (HACE). Among them, hepatic resetion was performed in 106 cases, and HACE in 194. The two-stage operation after HACE was performed in 23 cases. Hepatitis B antigen was positive in 69.8%. PLC with cirrhosis accounted for 81.6%. The effect of hepatic resection was superior to HACE. The cause of early local recurrence after HACE can be a valuable therapy in the hepervascular PLC. However, HACE should be unsuitable for ischemic PLC. Quantitative estimation of hepatic resection of PLC with cirrhosis was dependent on 5 parameters (ALT, serum bilirubin, PT and R15TCG), and morphological changes of cirrhotic liver.

Adult↗
PubMed1997

[The effects of microwave heating on osteoinduction of demineralized bone matrix in rabbits].

In order to study the change of the autograft demineralized bone matrix, twenty-four new-Zealand rabbits were randomly divided into four groups of 2, 4, 8, 12 week by sacrified time, each group had 7, 7, 5, 5 rabbits. Autoradiography was done for 2 rabbits in 2, 4 weeks respectively. The tibiae were removed by amputation at knee joint level, then they were cleansed of marrow and periosteun, cut into six pieces in length of 0.8 cm heated with microwave. Demineralized bone matrix were made by defated and decalcified, and implanted into abdomenal walls autograft. The results showed that the implants heated at 45 degrees C 30 min had same osteoinduction as control group. The 65 degrees C 30 minutes heating may reduce implant's osteoinduction slightly. The osteoinduction of the groups heated 75 degrees C for 30-60 minutes were impaired severely. The implants boiled at 100 degrees C 30 minuts had no osteoinduction at all, 65 degrees C 30 minutes may be a "safty" limit when heat treatment on bone clinically. Otherwise, bone formation ability would be reduced and remodelling was delayed.

Abdominal Muscles↗