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Biomedical subjects

Q Shi

Publications and source records attributed to Q Shi.

234 records · Page 13Linked to original sources
PubMed1990

Re-endothelialization of isolated segments of the canine carotid artery with reference to the possible role of the adventitial vasa vasorum.

This study was designed to determine if the adventitial vasa vasorum contribute to re-endothelialization of the canine carotid artery after removal of the endothelial flow surface. Casting studies demonstrated that vasa vasorum are present only in the adventitia of the canine carotid artery. Ninety autograft segments of the carotid artery from which the endothelium had been removed were implanted in both carotid arteries of 45 dogs. Glutaraldehyde-processed canine carotid allografts were positioned at each end to prevent pannus ingrowth and a Gore-Tex wrap to prevent periarterial tissue growth was placed into the outer wall. Three methods were used, with observations at 4 and 8 weeks. In method 1 the test segment was treated with superficial endarterectomy. In method 2 a balloon catheter was used to remove the endothelium. In method 3 balloon catheter denudation of the flow surface was also employed and, in addition, the adventitia was removed surgically as completely as possible, although a few vasa vasorum were shown to remain in some grafts. In method 1 all the patent endarterectomized arteries were partially re-endothelialized at both the 4- and 8-week intervals. In method 2, 72% of the balloon-denuded patent arteries with intact adventitial vasa vasorum were partially re-endothelialized at 4 weeks and 84% at 8 weeks. However, in method 3 the flow surfaces had no endothelium at 4 weeks and 83% still had none at 8 weeks. These findings suggest that, in the absence of pannus ingrowth, re-endothelialization of the canine carotid artery depends on not only the presence but also the number of adventitial vasa vasorum.

Animals↗
PubMed1990

[Cytogenetic effects of attenuated live measles vaccine on male mice].

The cytogenetic effects of attenuated live measles vaccine on somatic and germinal cells of C57BL/6J mice were studied. The frequencies of micronuclei of polychromatic erythrocytes, nucleated cells, chromatid breaks, fragments in bone marrow cells, and micronuclei of spermatids in testes were increased, which have dose- and time-dependent relationship. However, there were no statistical difference between the treated and control mice in chromosomal breaks and fragments of spermatogonia primary and secondary spermatocytes. The results and their possible biological significance were also discussed.

Animals↗
PubMed1989

[Effect of myocardial alpha 1-adrenoceptor stimulation on the guinea-pig ventricular papillary muscle].

The alpha-adrenoceptor agonist phenylephrine (5.0 x 10(-6) mol/L) was used to stimulate myocardial alpha-adrenoceptors of the guinea-pig ventricular papillary muscle, and changes of transmembrane action potential and contractile force of the muscle were observed. The alpha 1-adrenoceptor blocker prazosin (5.0 x 10(-7) mol/L) and the alpha 2-adrenoceptor blocker yohimbine (5.0 x 10(-7) mol/L) were used to determine which subtype of alpha-adrenoceptor is responsible for the effects. The beta-adrenoceptor blocker propranolol (1.0 x 10(-6) mol/L) was used throughout the experiment. The results show that the myocardial alpha 1-adrenoceptor stimulation (1) increases the contractile force of the guinea-pig ventricular papillary muscle, (2) prolongs the time to peak contractile force while the duration of relaxation is not altered, (3) prolongs the fast response action potential duration, and (4) increases the maximal rate of depolarization during the phase 0 of the slow response action potential. It is suggested that the electrophysiological and positive inotropic effects of myocardial alpha 1-adrenoceptor stimulation might be due to the activation of the slow inward current and an increase in Ca2+ influx.

Action Potentials↗
PubMedDate not supplied

Reasons for intracranial hypertension and hemodynamic instability during acute elevations of intra-abdominal pressure: observations in a large animal model.

In previous studies we reported that an acute elevation in intra-abdominal pressure (IAP) is responsible for the elevation in intracranial pressure (ICP) and mean blood pressure (MBP). Thus far, the reasons for the increased ICP during an acute elevation in IAP and the combined effects of increased IAP and ICP on hemodynamics have not been reported. Five large animals (swine) were studied. Each animal served as its own control. A subarachnoid screw was placed for ICP monitoring. The jugular vein, femoral vein, and femoral artery were cannulated. ICP, MBP, central venous pressure above (CVPA) and below (CVPB) the diaphragm, and PaC02 were monitored after a pneumoperitoneum with C02 was established at 5, 15, and 30 mm Hg of IAP. Cavography was performed to evaluate the morphology of the inferior vena cava at different increments of IAP. Measurements were obtained in reverse Trendelenburg (group 1), supine (group 2), and Trendelenburg (group 3) positions. Multiple regression analysis was used to examine the effects of IAP and positioning in separate models with different blood pressures as dependent variables. Increased IAP significantly increased CVPA, CVPB, ICP, and MBP. There were no changes in cerebral perfusion pressure. The change in position (from group 1 to group 3) significantly increased CVPA and decreased the CVPB. Cavograms performed on animals in the supine position with increased IAP showed a narrowing of the IVC at the level of the diaphragm. Increases in IAP will increase ICP and MBP without altering the cerebral perfusion pressure. A mechanical effect mediated by compression of the inferior vena cava at the level of the diaphragm with increased central venous pressure and decreased drainage from the lumbar plexus and central nervous system is responsible for this effect.

Abdomen↗
PubMedDate not supplied

Development of a symmetric canine abdominal aortic aneurysm model with clinical relevance for endovascular graft studies.

This study was designed to develop a large-animal model to study and validate transluminally placed endovascular grafts and related techniques for treating abdominal aortic aneurysms with minimal trauma. In four dogs, a segment of infrarenal abdominal aorta was dissected and an endarterectomy was performed through an aortotomy to remove the entire intima of this controlled aortic segment. The opening was patched with chemically processed bovine pericardium, and an identical patch was applied after aortotomy of the opposite side of the aorta. Aortic diameter and flow were measured before and after the procedure. Angiograms were obtained just before retrieval. All dogs recovered quickly with no complications. Aortic diameter increased approximately 2.7-fold. Aneurysm size and shape remained stable until the end of the experiments at 4 or 8 weeks. Gross and histologic studies for 4- and 8-week specimens were similar. Factor VIII/von Willebrand factor staining showed complete reendothelialization of the endarterectomized wall, with a moderate degree of intimal hyperplasia. The patch material retained its acellular nature and its surface was covered with thrombus or fibrinous material mixed with blood cells and inflammatory cells. Thus, this model is feasible and suitable for endovascular graft healing studies.

Angiography↗
PubMedDate not supplied

Dynamic and comparative vascular graft healing studies using multiple sequential biopsies.

In order to follow the dynamic healing processes of vascular grafts and to minimize the possible animal-to-animal variables involved in study results, we developed a carotid-femoral bypass model with multiple sequential biopsies. After bilateral implantation of 70 cm x 6 mm gelatin-impregnated carotid-femoral bypass grafts in 5 dogs, we biopsied and replaced three 10-cm-long segments of each bypass at 2, 4, and 6 weeks, with final retrieval at 8 weeks after the initial implant. The first surgery and later biopsy procedures were well tolerated with no mortality or morbidity, except for some seroma formation. We observed a dynamic progression of healing processes related to the time course, including perigraft tissue reaction to the graft material and surgical trauma, gradual absorption of the impregnated gelatin, tissue ingrowth into the graft wall, and changes in and healing of the graft surface. Because of the sizeable tissue sample generated from each biopsy, this model also allowed various study approaches to be performed on the same specimen. This experimental model enables study of the continuous dynamic healing processes of the same graft in the same animal, providing the practical advantage of reduction of the number of animals required.

Anastomosis, Surgical↗
PubMedDate not supplied

Monoclonal antibodies, antigens and molecular diagnostics: a practical overview.

The development of monoclonal antibody-based immunochemical assays to measure antibodies, antigens and small molecules, such as drugs, ushered in a revolution in modern diagnostic medicine. The impact of monoclonal antibodies on diagnostic imaging technologies and therapeutic regimes was equally dramatic. Additionally, the application of immunological techniques to the biochemical research lab was partially responsible for the exponential growth in our understanding of human physiology, biochemistry and genetics. Monoclonal antibody technology is limited, however, by the manner in which antigen-antibody interactions can be controlled and by the ability to consistently produce antibodies with appropriate affinity and specificity. Recent advances in recombinant antigen preparation and antibody engineering have been used to enhance the applications of this technology. In this review, current strategies to generate and engineer monoclonal antibodies as well as their clinical applications are summarized. A brief review of molecular diagnostics and its future trend is also included.

Animals↗
PubMedDate not supplied

Genetic relationships of infectious bronchitis virus isolates from Mississippi broilers.

A 582-base pair segment located in the nucleocapsid protein terminal part of the S1 gene of 26 Arkansas (Ark)-type infectious bronchitis virus (IBV) isolates from Mississippi broilers was amplified and sequenced. Reverse transcription-polymerase chain reaction and cycle sequencing techniques were used to elucidate the genetic and deduced amino acid relationships among the isolates. Analysis suggested that the nucleotide and amino acid sequences of the isolates were highly conserved, with greater than 99.4% nucleotide and 98.4% amino acid homology among the Mississippi isolates. The Mississippi isolates had less than 2.3% nucleotide and 5.2% amino acid variation when compared with the vaccine strain Ark DPI and less than 3.0% nucleotide and 5.2% amino acid variation when compared with the Ark-type Georgia variant. This study suggests that the 26 IBV isolates that are genetically closely related to the vaccine strain may be derived from the vaccine strain by point mutation. The results also indicate that within a 1-yr period Ark-type IBV in Mississippi was spread with little or no change in its genetic sequence. The 21 identical isolates appeared in different farms and companies, suggesting that poor biosecurity was practiced and contributed to the spreading of the disease.

Amino Acid Sequence↗
PubMedDate not supplied

Sex, drugs, and syringe exchange in New York City: women's experiences.

The sex and drug human immunodeficiency virus (HIV) risk factors of drug-injecting women participating in New York City syringe exchange programs were studied and racial/ethnic differences examined. African-American women reported injecting least frequently and had lower rates of injecting with borrowed or used syringes. Women attending syringe exchange reported high levels of sexual risk behavior, and syringe exchange provides an opportunity for a sexual risk reduction intervention. Women were more likely to "always" use condoms with causal partners than with primary partners. About 60% of the women engaging in commercial sex work reported "always" using condoms. Three independent predictors for consistent condom use with primary partners were: knowing one's HIV status, any risky injection during the past 30 days, and being African-American, compared with white or Latina. The profile of African-American women attending syringe exchange in New York City suggests a higher level of stabilization than is found in the other groups of women. White women appear to be more socially isolated and to engage in higher risk behaviors. Although women attending New York City syringe exchange programs have significantly reduced risky drug injection, consistent with other studies, sexual risk behavior has remained at a high level. Syringe exchange and drug treatment programs have a great opportunity to target drug-injecting women for sexual risk reduction interventions.

Adult↗