Biomedical subjects

N Hu

Publications and source records attributed to N Hu.

At least 55 records · Page 3Linked to original sources

PubMed1998

Quantitative fluorescence image analysis of DNA content and nuclear morphology on esophageal balloon cytology smears and subsequent development of esophageal and gastric cardia cancer in Linxian, China.

The highest incidences of esophageal and gastric cardia cancer in the world occur in northern China. Chinese scientists have developed esophageal balloon cytology screening to detect these cancers, but traditional cytology is sometimes inadequate to find some early, curable lesions. Several studies suggest that quantitative fluorescence image analysis (QFIA) of DNA ploidy and nuclear morphology may be able to improve upon traditional cytology results. In October 1987, esophageal balloon cytology was performed on 1331 adults in Linxian, China, and all samples were evaluated both by traditional cytology and QFIA. From 1987 to May 1991, 62 new squamous esophageal cancers and 44 new adenocarcinomas of the cardia were identified in this cohort. Proportional hazards models were used to evaluate the relationship of cytological diagnoses and six QFIA variables to subsequent cancer risk. These models showed significant trends for increasing esophageal cancer risk, with increasing values in five of the QFIA variables and with increasing severity of the traditional cytological diagnoses. A comparison of models with only cytology variables versus models with both cytology and QFIA variables indicated that the QFIA provided an important additional predictive value. Persons with both cytological dysplasia and high cellular DNA were 8 times more likely to develop esophageal cancer than were individuals with neither of these conditions. For cardia cancer, associations between QFIA variables or cytological diagnoses and later cancer were more limited. This study suggests that the QFIA variables evaluated here are independent predictors of squamous esophageal cancer and that combining QFIA with traditional cytology can improve prediction of esophageal cancer risk.

Adenocarcinoma↗

PubMed1997

Retinoblastoma gene deficiency has mitogenic but not tumorigenic effects on erythropoiesis.

The retinoblastoma protein (Rb), an important ubiquitous cell cycle regulator, was initially identified as the retinoblastoma tumor suppressor. To further address the activities of Rb in proliferation and tumorigenesis in the hematopoietic lineage, we transplanted Rb-/- fetal liver cells into sibling mice and assessed the outcome of Rb-/- hematopoietic cells in both short-term and long-term studies. Rb-/- hematopoietic cells rescued lethally irradiated mice with an efficiency comparable to that of wild-type cells. In spleen colony-forming unit assays, proliferation rates of the Rb-/- cells were greater than those of the wild-type cells. Similarly, in vitro burst-forming unit-erythroid and colony-forming unit-erythroid assays showed increased erythroid colony numbers from Rb-/- embryonic livers. Recipients of Rb-/- cells lived for more than 15-18 months, and most blood cell lineages matured normally with the expected switch from fetal to adult hemoglobin. However, the continued presence of nucleated erythrocytes in the peripheral blood and extensive extramedullary erythropoiesis indicated that the Rb-/- erythrocytes were not completely normal. No erythroleukemia developed during the 15-18 month period following transplantation. These results demonstrate the mitogenic effect but not tumorigenic transformation in erythrocyte lineage in the absence of Rb, which is distinct from the effect of Rb deficiency in neuroectodermal cells. The study supports the prevalent model that loss of the ubiquitously expressed tumor suppressor gene predisposes to only a limited spectrum of tumors.

Animals↗

PubMed1997

Developmental changes in the myocardial architecture of the chick.

BACKGROUND: Numerous studies describing myocardial architecture have been performed on the adult heart but considerably fewer have been made during embryonic or fetal development. To serve as a basis for interspecies comparison of ventricular morphology, and as a reference for studying the effects of experimental perturbations, we examined the development of chick throughout the entire incubation period. METHODS: Chick hearts from stage 14 (day 2) to stage 46 (day 21) were perfusion-fixed, and sectioned in transverse, frontal and sagittal planes. The ventricular myocardial architecture was examined and photographed in the scanning electron microscope. RESULTS: At embryonic stage 16 and earlier, the smooth-walled heart loop had an outer myocardial mantle, cardiac jelly, and endocardium. From stage 18, there was an outer compact and inner trabeculated myocardium. Trabeculated myocardium could be subdivided into the outer (basal) portion adjacent to the compact layer and the central (luminal) part. The outer basal layer could be distinguished from the inner luminal by shorter and finer trabeculae with small, round intertrabecular spaces. From stage 24, the patterns of trabeculae and intertrabecular spaces were ventricle-specific. Between stages 24 to 31, abundant trabeculations were present throughout both ventricular cavities. The trabeculae were initially radially arranged, but later adopted a spiral course, which persisted in a simplified form into adulthood. CONCLUSIONS: The ventricular myocardium undergoes distinctive morphogenesis, characterized by changes in trabecular patterning and orientation. We speculate that the embryonic trabecular architecture reflects the directions of the main stresses. Unlike fetal and adult hearts, which rely mostly on the compact myocardial layer, the trabeculae play a crucial role in the contractile function of the embryonic heart.

Animals↗

PubMed1997

Cell death in the gastrulating chick embryo: potential roles for tumor necrosis factor-alpha (TNF-alpha).

We have examined the expression of TNF-alpha and its receptors, TNFR1 and TNFR2, during gastrulation in the chick embryo, and have investigated the possible role of this factor in the control of cell death at this early stage of development. TNF-alpha, immunoreactive at approximately 17 kD, was found both in vivo and in vitro, most intensely associated with the cell surface and cytoskeleton of endoderm cells. TNFR2 was especially immunoreactive in endoderm cells of the marginal zone. TNFR1 was found in nuclei throughout the embryo. Embryos also showed widespread expression of both the bcl-2 and Bax gene products, which are both associated with cell death pathways. Intact embryos in culture were sensitive to the addition of TNF-alpha (approx. 110 ng/ml), responding by significantly increasing the incidence of DNA fragmentation in cells from all tissues of the embryo. This effect was abrogated by immunological pre-absorption of the cytokine. Cultured cells from these embryos also responded to the addition of agonistic antibodies to TNF-alpha receptors by increasing DNA fragmentation. A similar response to TNF-alpha antiserum by cultured cells appeared to be related to a concomitant decrease in cell-substratum adhesion caused by the antibody. Decreased cell adhesion, induced non-specifically with anti-integrin antiserum, also resulted in increased DNA fragmentation. TNF-alpha, synthesized and secreted by the embryo itself, may be able to exert a paracrine effect on the incidence of cell death in tissues of the embryo, and the cell death process may be related to the expression of bcl-2 and Bax gene products. The influence of TNF-alpha may be exerted by the activation of cell death signalling pathways directly, or indirectly through perturbation of the cytoskeleton or of integrin-mediated cell adhesion.

Journal Article↗

PubMed1997

The plasma concentrations of lidocaine after slow versus rapid administration of an initial dose of epidural anesthesia.

We measured venous blood concentrations of lidocaine in 15 patients undergoing lower abdominal or extremity surgery after epidural injection of lidocaine. Patients were divided into either an infusion group (Group I, n = 6) or a bolus injection group (Group II, n = 9). We administered 15 ml of 2% lidocaine into the epidural space at 1 mL/min in Group I and at 1 mL/3 in Group II. Venous blood was drawn at 3, 6, 9, 12, 15, 18, 21, 30, 60, and 90 min after injection for measurement of plasma lidocaine concentrations. The peak plasma concentration (Cmax) of lidocaine in Group I was significantly less than that in Group II (P < 0.0005). We conclude that slow epidural infusion can produce a lower Cmax of lidocaine compared with that of a bolus administration and thereby decrease the potential for systemic toxicity of the local anesthetic.

Anesthesia, Epidural↗

PubMed1996

Molecular cloning and developmental expression of mouse p130, a member of the retinoblastoma gene family.

With sequence homology to the SV40 T antigen-binding domain of the retinoblastoma protein (Rb), p107 and p130 constitute two additional members of the Rb family. To explore the potential function of p130 in mouse development, we cloned the full-length mouse cDNA for p130 and characterized p130 mRNA expression in mice. The deduced mouse p130 protein sequence shares a higher degree of similarity with mouse p107 than with mouse Rb. In adult mice, p130 mRNA is found in all tissues examined. Levels of p130 mRNA vary among different adult tissues, with the highest level in testis. Within testis, p130 mRNA is found predominantly in Leydig cells. Additionally, p130 expression in testis correlates with sexual maturation, suggesting p130 is important for the development of testis and, in particular, Leydig cells. In situ hybridization shows that in post coitus day 12.5 and 14.5 mouse embryos, distribution of p130 mRNA is quite uniform with the exception of a few tissues. Little differences in mRNA levels of either p130 or p107 were found between normal and Rb-deficient embryos, suggesting that p130 and p107 are expressed independently of Rb. Our data are consistent with the hypothesis that p130 and p107 do not compensate for the loss of Rb and support the view that p130 is related to, yet distinct from, the RB gene.

Aging↗

PubMed1996

Dorsal aortic impedance in stage 24 chick embryo following acute changes in circulating blood volume.

The effects of acute changes in circulating blood volume on embryonic vascular hemodynamics were evaluated with the use of input impedance. We simultaneously measured dorsal aortic pressure with a servo-null system and flow velocity with a 20-MHz pulsed Doppler system in n = 90 stage 24 chick embryos. We withdrew or infused 1,3, or 5 microliters of blood via a second-order vitelline vein (n = 10 per group). In addition, we withdrew and then infused or infused and then withdrew 3 microliters (n = 5 per group). Characteristic impedance, peripheral resistance, arterial compliance and elastance, and hydraulic power as well as basic hemodynamic parameters were evaluated on the basis of the three-element windkessel model. In response to withdrawal, mean and pulse pressure, mean flow, arterial compliance, and hydraulic power decreased, whereas peripheral resistance and arterial elastance increased in a dose-dependent manner. Results in response to infusion were converse in effect. Characteristic impedance was unchanged by volume alternations. Oscillatory fraction of hydraulic power was higher than mature circulation and remained relatively constant during interventions, which indicates well-regulated energy efficiency for vascular growth in the embryonic circulation. A hysteresis relevant to altered peripheral resistance was present after multiple interventions. Embryonic vasculature is sensitive to circulating blood volume and preserve blood pressure at the expense of blood flow. In the absence of autonomic innervation, embryonic vascular tone may be regulated by mechanical properties of the vessel (the law of Laplace) and/or vasoactive substances.

Animals↗

PubMed1996

Distribution of blood flow between embryo and vitelline bed in the stage 18, 21 and 24 chick embryo.

OBJECTIVE: We defined the distribution of blood flow between the embryo and the extraembryonic vascular bed as an initial step in understanding the control of flow distribution in the early developing heart. METHODS: Dorsal aortic blood flow of stage 18, 21, and 24 chick embryo (n > or = 7 at each stage) was measured with a 20 MHz pulsed-Doppler velocity meter. Analog waveforms were digitally sampled at 500 Hz. 1-5 x 10(3) yellow microspheres in saline suspension were injected into the vitelline vein. The embryo and the extraembryonic vascular bed were harvested and separated from each other. The dye on the microspheres from each portion was extracted and extrapolated from the standard curve of the absorbance of dye concentrations per number of microspheres quantified by spectrophotometry. Blood flow was calculated from the integral of blood velocity and aortic cross-sectional area multiplied by the fraction distribution of microspheres in the embryo and extraembryonic vascular bed. Data were presented as mean +/- standard error of the mean. RESULTS: The proportion distribution of microspheres between embryo and extraembryonic vascular bed shifted from 18.7 +/- 2.5 vs. 81.3 +/- 2.5% at stage 18, 25.1 +/- 3.0 vs. 74.9 +/- 3.0% at stage 21, and 34.2 +/- 2.4 vs. 65.8 +/- 2.4% at stage 24. Indices of blood flow normalized to wet weight (mean +/- 95% confidence interval) were similar between the embryo and the extraembryonic vascular bed, but increased throughout the stages. CONCLUSION: During embryogenesis, blood flow per unit mass is evenly distributed between the metabolically active embryo and the extraembryonic vascular bed.

Animals↗

PubMed1996

Embryonic hypertension following exposure to teratogenic doses of 5-fluoro-2'-deoxyuridine.

The teratogenicity of 5-fluoro-2'-deoxyuridine (FdU) is well established. Previously, we have demonstrated that teratogenic doses of FdU produce hematomas and suggested that those hematomas produced skeletal malformations in chicken embryos. In this study, the cardiovascular effects of teratogenic doses of FdU in chicken embryos were studied. A dose of either 0.026 micrograms FdU or 0.030 micrograms FdU was injected into the yolk sacs of fertile chicken eggs containing embryos at Hamburger and Hamilton stages 17-19 of development. The embryos were then returned to the incubator. Aortic systolic and diastolic blood pressure, blood velocity and heart rate were measured at stages 21, 24 or 27 using a servonull system and Doppler ultrasound. In addition, mean arterial blood pressure, blood flow, and stroke volume were calculated from these data. Similar data were also recorded from uninjected and saline injected control embryos. Systolic and mean arterial blood pressures were significantly increased in FdU-treated embryos at stage 27. The other parameters measured or calculated were not significantly different from control embryos. Our study suggests that elevated systolic blood pressure in chicken embryos treated with FdU may lead to hematoma formation and subsequent birth defects.

Animals↗

PubMed1996

[The mechanisms of ET-1-induced lung edema].

OBJECTIVE: To investigate the machanisms of ET-1-induced lung edema. METHODS: Different doses of ET-1 were added to isolate rat lungs perfused by Ringer's solution containing albumin to explore the mechanisms of ET-1 induced pulmonary edema. The lung weight gain, pulmonary vascular permeability to water (Wf) and albumin (Ps) were observed. RESULTS: It was found that low dose ET-1 increased lung weight gain, pulmonary artery pressure, pulmonary capillary pressure, pulmonary vascular post-resistance and total resistance, but no significant changes of vascular permeability were observed. CONCLUSION: The mechanisms of lung edema induced by ET-1 are different. Low dose ET-1 may induce lung edema by increasing pulmonary vascular permeability while large dose ET-1 by increasing pulmonary vascular pressure.

Animals↗

PubMed1996

[The ultrastructure of the Eustachian tube].

To observe the ultrastructure of mucous membrane of Eustachian tube in human being, ninteen human's Eustachian tube from various ages, were divided into tympanic segment, isthmus and pharyngeal segment and observed under SEM. The results showed that the epithelium of Eustachian tube consisted of ciliated cells, nonciliated cells and goblet cells. At the isthmus, the bone and cartilage junction, the cells got crowded, and there were more and more goblet cells from tympanic side to pharyngeal side, as well as the cilia of ciliated cell leaned towards the pharyngeal side. The upper one third part of Eustachian tube was covered mostly by nonciliated cells, the floor and lower parts were ciliated cells. It was concluded that the upper parts of Eustachian tube's wall played an important role in maintaining equation of pressure in middle ear, and the floor and lower parts in providing an active mucociliary mechnism. The defence system of the Eustachian tube mucous membrane had developed during the fetal stage and was well established at birth.

Adult↗

PubMed1995

Relationship of simultaneous atrial and ventricular pressures in stage 16-27 chick embryos.

Ventricular filling is determined by a dynamic balance between atrial and ventricular load and function. The embryonic cardiovascular system undergoes simultaneous growth and morphogenesis at the cellular, tissue, and organ levels to match the embryo's geometrically increasing metabolic demands. As part of our long-term investigation of atrial/ventricular coupling during primary cardiac morphogenesis, we defined the relationship between simultaneous atrial and ventricular pressures in the stage 16-27 white Leghorn chick embryo. We measured atrial and ventricular blood pressures with servo-null micropressure systems and sampled analog waveforms digitally at 500 Hz. Peak atrial pressure increased geometrically from 0.38 +/- 0.03 to 1.21 +/- 0.17 mmHg, while ventricular end-diastolic pressure increased linearly from 0.18 +/- 0.03 to 0.55 +/- 0.04 mmHg. The passive and active mean pressure gradients increased from 0.23 +/- 0.04 and 0.20 +/- 0.03 mmHg at stage 16 to 0.52 +/- 0.10 and 0.62 +/- 0.11 mmHg at stage 27, respectively. The atrioventricular pressure gradients were similar for stages 16, 18, and 21, then increased to stage 27. This diastolic pressure gradient identifies the atrioventricular orifice and developing endocardial cushions as a site of flow resistance that may influence both ventricular filling and chamber morphogenesis.

Animals↗

PubMed1995

Effect of atrial natriuretic peptide on diastolic filling in the stage 21 chick embryo.

Atrial natriuretic peptide (ANP) exerts hemodynamic effects by direct venodilation in the chick embryo. We hypothesized that ANP-induced venodilation affects ventricular diastolic filling resulting in reduced ventricular preload. Chick ANP (0.1 microgram in 10 microL of normal saline) was suffused onto the vitelline vascular bed in stage 21 (3 1/2 d) chick embryos. Equivalent aliquots of normal saline were suffused as sham controls, and normal embryos received no suffusion. We measured simultaneously dorsal aortic blood velocity and atrioventricular blood velocity with a 20-MHz pulsed-Doppler velocity meter. Analog wave forms were digitally sampled at 500 Hz, and the dorsal aortic cross-sectional area was used to calculate dorsal aortic blood flow. Passive ventricular filling volume equaled dorsal aortic stroke volume multiplied by the fraction of passive area; active filling volume equaled dorsal aortic stroke volume multiplied by the fraction of active area. Data were summarized as mean +/- SEM (n > or = 7 per group) and analyzed by analysis of variance. Cycle lengths were similar in ANP-suffused, sham control, and normal embryos. Dorsal aortic blood flow decreased from 0.49 +/- 0.04 mm3/S at baseline to 0.27 +/- 0.05 mm3/S at 4 min post-ANP suffusion (p < 0.05) and was unchanged in sham control and normal embryos (p > 0.05). Passive ventricular filling was reduced by ANP suffusion, whereas active filling was unaffected, resulting in a decreased passive/active filling ratio from 0.64 +/- 0.07 at baseline to 0.32 +/- 0.08 at 4 min in ANP-suffused embryos (p < 0.05). Passive/active ratio was unchanged in sham control and normal embryos. Thus, ANP-mediated vasodilation reduces cardiac output via decreased passive ventricular filling in the embryonic heart.

Analysis of Variance↗

PubMed1995

Nutritional intervention to prevent hereditary cancer.

To determine if the effect of nutritional interventions differs by genetic susceptibility to cancer, we must have both an effective intervention as well as a documented marker of genetic susceptibility. The first large clinical trials to test nutritional intervention strategies have recently been reported, and apparent efficacy has been observed for selected antioxidants in the primary prevention of several cancers, including esophageal, stomach, prostate, and colorectal cancers. At the same time, increasing numbers of markers of genetic susceptibility are being identified. Although susceptibility markers have not yet been evaluated in the context of nutritional interventions in humans, preliminary data in animals indicate that calorie restriction reduces spontaneous tumor mortality in p53-knockout mice. Linking the results from nutritional interventions in humans with markers of genetic susceptibility will allow us to better understand gene-environment interactions.

Animals↗

PubMed1994

Dual roles of the retinoblastoma protein in cell cycle regulation and neuron differentiation.

To assess the functions of the retinoblastoma protein (RB) during normal development, we have analyzed mouse embryos that lack a functional copy of the retinoblastoma gene (genotype: Rb-1 delta 20/Rb-1 delta 20). Our findings demonstrate that RB plays an important role in the regulation of the neuronal cell cycle. In mutant embryos, dividing cells are found well outside of the normal neurogenic regions in both the central and peripheral nervous systems. In addition to abnormal cell cycle regulation, however, the mutant embryos show two less expected phenotypes. First, many of the ectopically dividing cells die by apoptosis shortly after their entrance into S phase. In sensory ganglia, most nerve cells die by this process, beginning at about the same time as normal target-related neuronal death. Second, although the expression of certain differentiation markers such as N-CAM and Brn-3.0 appears to be near normal, nerve cells, especially in sensory ganglia, do not mature properly. Their morphology is stunted and expression of neuronal beta II tubulin is greatly reduced. Preferential reduction in the expression of TrkA, TrkB, and the low-affinity neurotrophin receptor p75LNGFR may be relevant to neuronal cell death and lack of neuronal differentiation seen in the mutant embryos. Primary cultures of dorsal root and trigeminal ganglion cells from later stage mutant embryos reveal a decrease in neuronal cell survival and in neurite outgrowth even in the presence of the appropriate neurotrophins. Taken together, these results suggest that the p110RB protein not only regulates progression through the cell cycle but is also important for cell survival and differentiation.

Animals↗

PubMed1994

Expression of TGF beta 1/beta 3 during early chick embryo development.

We have used an antibody against a TGF beta peptide fragment to localize this growth factor in the early chick embryo from laying to the ten-somite stage of development. Western blotting showed that the antibody reacted with both mammalian TGF beta 1 and chicken TGF beta 3. By immunocytochemistry we find that at the earliest developmental stage (stage X of Eyal-Giladi and Kochav) immunoreactivity to this antibody is primarily located in the cells of the area opaca and marginal zone, as well as in the most peripheral edge cells of the blastoderm. The yolk is non-reactive, except in a highly localized region subjacent to the edge cells. This pattern persists at stage XII, and at both stages individual isolated cells in the epiblast and hypoblast are also reactive. By the time of gastrulation, reactivity in the epiblast is polarized to the ventral extremity of the cells, and again some isolated cells in this layer are intensely immunoreactive. At this stage also, the endoderm cells, particularly those underlying the primitive streak, are positive, as are the mesoderm cells lateral to the streak. At somite stages, the neuroepithelium is not reactive but the ectoderm lateral to it is strongly positive. At the caudal primitive streak levels of early somite embryos, the ectoderm and endoderm are immunoreactive while the mesoderm loses the reactivity it showed at the early gastrulation stages. The neuroepithelial cells later show reactivity at their apical poles, and, as at the earlier stages, individual cells show intense labelling. These results indicate that TGF beta 1 and/or TGF beta 3 immunoreactivity is developmentally regulated from very early stages of morphogenesis in the chick, and together with data from earlier functional studies, suggest that this factor has roles in embryonic axis formation and in blastoderm expansion.

Animals↗

PubMed1994

Guidance of filopodial extension by fibronectin-rich extracellular matrix fibrils during avian gastrulation. A study using confocal microscopy.

We have used double-label confocal microscopy to examine the relationships between the orientation of filopodial extension in mesoderm cells and the orientation of fibronectin-rich extracellular matrix fibrils during chick embryo gastrulation. We fluorescently labeled mesoderm tissue dissected from donor embryos by immersion in carboxyfluorescein and then grafted it into unlabeled host embryos at the same stage of gastrulation. After further incubation, the host embryos were fixed, the endoderm removed, and the extracellular matrix was immunostained with antibodies to fibronectin conjugated to Texas Red. We found that both the general shape of the mesoderm cells and the orientation of filopodial extension were influenced by the surrounding matrix fibrils. Elongated shape was associated with individual fibrils which impinge on only one side of the cell. Similarly, filopodial extension followed a single fibronectin-rich fibril, although filopodia were also observed to be channeled between pairs of parallel fibrils. Cells attached to non-aligned regions of substratum showed no polarity. The mesoderm cells themselves apparently synthesize their own fibronectin, and deposit this on the cell surface not attached to the substratum. We conclude that individual fibronectin-rich substratum fibrils, in the size range 0.7-2.8 microns, are able to exert contact guidance on the mesoderm cells, despite the production of endogenous fibronectin by the cells themselves. These results support the contention that contact guidance is a physiological mechanism influencing the orientation and directionality of cells during the morphogenetic movements of embryogenesis.

Animals↗

PubMed1994

Heterozygous Rb-1 delta 20/+mice are predisposed to tumors of the pituitary gland with a nearly complete penetrance.

Humans with a germline mutation of the RB gene are predisposed to retinoblastoma with a 90% penetrance and are at higher risk for other rare tumors. We have established a mouse strain carrying a germ-line mutation of the Rb-1 gene. Here we describe a nearly 100% incidence of spontaneous pituitary tumors which arise in Rb-1 heterozygous mice from ages 2 to 11 months. Histological and immunological analysis indicate that these tumors originate from the intermediate lobe of the pituitary gland, which is a vestigial structure in adult humans. Progression of the tumors can be followed by the elevated level of a specific proteolytic product of pro-opiomelanocortin prohormone, alpha-melanocyte stimulating hormone, in the circulating blood of the tumor-bearing animals. Multiple foci are frequently seen in the tiny intermediate lobe of the pituitary gland which contains approximately 1.5 x 10(5) cells. The tumor tissues invariably lose expression of full-length Rb protein due to loss of the single wild-type Rb-1 allele. The Rb knock out mouse strain provides a unique model for addressing tissue-specific tumor predisposition by inactivation of a ubiquitously expressed tumor suppressor gene.

Age Factors↗