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Biomedical subjects

Y H Zhu

Publications and source records attributed to Y H Zhu.

At least 19 recordsLinked to original sources
PubMed1992

Dilatation in anastomosed arteries can be an artifact of explantation.

Fusiform dilation of the anastomotic site was found at explantation in the majority of rabbit femoral arteries anastomosed with newly developed microclips. This observation was also noted at sutured anastomoses. The mechanism responsible for this morphologic finding was studied by the following experiments: 1) measuring and explanting anastomosed arteries relaxed with 20% lidocaine, 2) latex casts of microclipped arteries, 3) comparing angiographic and histologic morphometric data, and 4) examining synthetic vascular graft anastomoses with identical dilatation. The observations demonstrate that trauma associated with explantation (direct dissection and fixative perfusion) leads to arterial vasoconstriction, but focal medial damage at the anastomotic site prevents constriction at this site.

Anastomosis, Surgical↗
PubMed1992

Sutureless vasovasostomy: new technique using experimental microclip in rat model.

Standard microscopic suture vasovasostomy represents a challenge to many urologists. It is technically demanding, and requires two to five hours of operative time. In an attempt to decrease the technical demand and the time requirement, we report the use of a microvascular anastomotic clip and compare this microclip to a standard eight-suture nonstented technique and a six-suture stented technique using a hollow, absorbable 0.5-mm polyglycolic acid stent. The control group with suture required an average of 38.5 minutes per anastomosis for the nonstented group and twenty-two minutes for the stented group. The clip group required 7.6 minutes for the unstented vasovasostomy and 6.5 minutes for the stented vasovasostomy. We obtained a 91 percent patency rate for the stented clip group and 100 percent patency for the unstented clip group. In a rat vasovasostomy, the operative time as well as the inherent technical demand were significantly reduced.

Animals↗
PubMed1992

[Preparation and identification of anti-Trichomonas vaginalis monoclonal antibodies].

Hybridomas producing monoclonal antibodies (McAb) directed against Trichomonas vaginalis have been produced by fusing NSI myeloma cells with spleen cells of BALB/c mice immunized with Trichomonas vaginalis. IFA technique was used to test the binding activity of four McAbs produced. The McAb belonged to the IgG subtypes IgG1 (2A2, 2A4 McAb), IgG3 (2H9 McAb) and IgG 2b (2A12 McAb). Three McAbs, designated 2A2, 2A4, 2A12, reacted with a surface membrane component of live Trichomonas vaginalis. One (2A12) of them produced complement-dependent cytolysis of the parasites. Others (2A2,2A4) produced complement-independent cytotoxicity of the parasites. 2H9 McAb which reacted with the nucleus of the organisms did not agglutinate the parasites. The four McAbs which did not have cross reaction with some protozoa of Zoomastigophorea species were specific antibodies against Trichomonas vaginalis. (Figs. 1-3).

Animals↗
PubMed1992

A new method for microvascular anastomosis: report of experimental and clinical research.

Principles of microvascular anastomotic surgery are uncertain in contrast to the standardized suture methods for the repair of large arteries. Complications of early thromboses or late stricture at the microvascular anastomotic line can be related to the inherent biologic response of these delicate tissues to penetrating needle and suture. A new method for microvascular reconstruction based on the principle of flanged, nonpenetrated, intimal approximation by an arcuate-legged clip has proven biologically and technically superior to the penetrating microsuture. These conclusions are based on extensive testing in multiple surgical laboratories of the following parameters: long- and short-term patency, morphology of wound repair, and burst and tensile strength. Details of the new surgical system and experimental studies are described.

Anastomosis, Surgical↗
PubMed1992

Tissue reconstruction with nonpenetrating arcuate-legged clips. Potential endoscopic applications.

A new system for tissue approximation consisting of a nonpenetrating arcuate-legged clip applied to everted tissue edges to form an elastomeric flanged joint is described. The flanged joint has unusual physical and morphologic properties. Novel systems for tissue eversion, clip application and clip removal have been tested at the micro scale in blood vessels and the rat vas deferens (vasovasostomy). Human applications have been successful (cerebrovascular reconstruction, free-flap transfer, skin grafting, A-V access). The system is biologically and technically equivalent to or superior to the needle-and-suture technique. Avoidance of intimal or mucosal penetration or intraluminal foreign body is associated with prompt wound healing and the reconstitution of tubular integrity. The system is readily adaptable for endoscopic surgical reconstructions, providing the surgeon with enhanced reconstructive abilities.

Anastomosis, Surgical↗
PubMed1991

Neural network programming in bioprocess variable estimation and state prediction.

A neural network program with efficient learning ability for bioprocess variable estimation and state prediction was developed. A 3 layer, feed-forward neural network architecture was used, and the program was written in Quick C ver 2.5 for an IBM compatible computer with a 80486/33 MHz processor. A back propagation training algorithm was used based on learning by pattern and momentum in a combination as used to adjust the connection of weights of the neurons in adjacent layers. The delta rule was applied in a gradient descent search technique to minimize a cost function equal to the mean square difference between the target and the network output. A non-linear, sigmoidal logistic transfer function was used in squashing the weighted sum of the inputs of each neuron to a limited range output. A good neural network prediction model was obtained by training with a sequence of past time course data of a typical bioprocess. The well trained neural network estimated accurately and rapidly the state variables with or without noise even under varying process dynamics.

Algorithms↗
PubMed1991

[Pharmacokinetics of cyclosporin A in renal transplant patients after infusion].

Seventeen patients after renal transplantation were infused iv cyclosporin A (CsA) 0.65 +/- 0.13 mg.kg-1.h-1. Blood CsA was determined by fluorescence polarization immunoassay (FPIA). Pharmacokinetic parameters were calculated from micro-computer pharmacokinetic programme T1/2 beta = 8.6 +/- 3.4 h, Vd = 3.2 +/- 1.3 L.kg-1. No significant difference was found between sexes and between age groups.

Adult↗
PubMed1990

Comparative cross-over pharmacokinetic study on two types of postcoital contraceptive tablets containing levonorgestrel.

A pharmaceutical and pharmacokinetic study was carried out on levonorgestrel tablets from two different sources (Hungarian- and Chinese-made). Both preparations contained 0.75 mg levonorgestrel and had been shown to have similar contraceptive efficacy and side effects when used for postcoital contraception. Absorption and bioavailability of the Hungarian-made tablets were greater as evidenced by higher serum concentrations of levonorgestrel, a greater area under the concentration-time curve during the first 24 hours, and a more marked suppressive effect on SHBG levels. These differences most probably reflect differences in their pharmaceutical formulation, in particular the extent of tablet dissolution and the degree of micronisation of levonorgestrel.

Absorption↗
PubMed1989

[Zhongxu-qizhi type of chronic gastritis and Campylobacter pyloridis infection].

According to the syndrome differentiation of TCM, one hundred cases of chronic gastritis were recognized as Zhongxu-Qizhi type (Group I, 57 cases) and the other types (Group II, 43 cases), the latter further divided into 36 cases of disharmony of Liver and Stomach type and 7 cases of deficiency of Stomach Yin type. The pathohistological investigation and urease test showed that the campylobacter pyloridis (CP) infected rate in the Group I (92.9%) was very significantly higher than that in Group II (58.1%, P less than 0.01); severe degree and deep location of CP infection occurred more significantly in Zhongxu-Qizhi type (52.8% and 73.6% respectively). Between the two groups, active chronic gastritis and severe invasion of polymorphonuclear cells were significantly different (P less than 0.05). All these findings suggest that there were some relationships between CP infection and syndrome differentiation of TCM.

Campylobacter↗
PubMed1988

Pharmacokinetic study of levonorgestrel used as a postcoital agent.

The pharmacokinetics and pharmacodynamics of levonorgestrel (LNG) were studied in six women given 0.75 mg LNG orally for seven days during the periovulatory phase of the menstrual cycle. Steady-state concentrations of LNG were reached within three days and serum LNG concentrations at various times on day 7 were generally lower than on day 1, presumably due to a reduced serum level of SHBG. On day 7 the volume of distribution was significantly increased and Co significantly decreased and both the clearance and elimination half-life were higher on day 7 than on day 1. Half-lives varied from 5.6 to 25.1 hours. The day-to-day intra-subject variations in serum LNG concentrations ranged from 23% to 80%. Serum concentrations of pituitary and ovarian hormones suggested that ovulation was not inhibited in four of the six subjects and was delayed in the remaining two. No significant changes in serum prolactin levels were observed.

Absorption↗
PubMed1985

Studies on the chemical modification of hemorrhagic toxin I from five pace snake (Agkistrodon acutus) venom.

The chemical modification of hemorrhagic toxin I (AaHI) from Agkistrodon acutus has been studied. Inactivation was observed upon modification of 3 out of 7 histidine residues with diethyl pyrocarbonate. The His residues are deblocked, accompanied by a return of activity, upon treatment with neutral hydroxylamine. The circular dichroism and fluorescence spectra of diethyl pyrocarbonate inactivated toxin and the native toxin are the same, indicating that modification with diethyl pyrocarbonate does not cause any gross change in the structure of the protein. At least one His residue may thus play an essential role in the enzyme activity. Reaction of the toxin with N-bromosuccimide abolished the enzyme activity, with modification of Trp, Tyr and His residues. The loss of Trp did not parallel the inactivation. Hydrogen peroxide, dioxane and 2-hydroxy-5-nitrobenzyl-bromide treatment damaged the Trp residues, but did not affect the activity. Therefore, the modified tryptophan side chains are not essential for activity. Modification of 2.5-3.0 Tyr residues out of 9 with acetylimidazole did not affect the enzyme activity, nor did nitration of the toxin with tetranitromethane. The reactive tyrosines are apparently not essential.

Amino Acids↗