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Biomedical subjects

T Guo

Publications and source records attributed to T Guo.

At least 55 records · Page 3Linked to original sources
PubMed1998

[The effects of the multiple structural layer of Ti-cast on bond of porcelain fused to titanium].

OBJECTIVE: To study the effects of the multiple structural layer of Ti-cast on the bond of porcelain fused to titanium. METHODS: The interfacial state and bond strength of porcelain-titanium were observed by EPM analysis and a shear test. RESULTS: The results showed cracks were observed in the interface of porcelain-titanium in R1 (the group of multiple structural layer of Ti-cast), but there were no cracks in the interface of porcelain-titanium in R2 (the group of removed multiple structural layer from Ti-cast) and R3 (the group of wrought titanium). The width of elemental diffusion layer of R1, R2 and R3 were 29.03 microns, 6.90 microns and 7.01 microns respectively. The shear bond srength of R1, R2 and R3 were 29.45 MPa, 52.75 MPa and 48.32 MPa respectively. There were significant difference in the width of elemental diffusion layer and shear bond strength between R1 and R2, R3 (P < 0.01). CONCLUSION: This investigation indicates that the multiple structural layer of Ti-cast should be removed before firing of porcelain.

Dental Casting Technique↗
PubMed1998

[The three-dimensional analysis of mandibular overdenture supported by implants].

In recent decade, the treatment in which two or four implants are placed in an edentulous patient to support an overdenture has been more effective and safe, and the retention and stability of overdenture have been improved by the use of attachments fabricated on implant abutments. This study aimed to investigate the supporting tissue stress distributions of implant-overdenture with a 3-D finite element model built by CT scan and CAD technology when various attachments and loads were used respectively. The results demonstrated that the establishment of the three-dimensional finite element model with CT scan and CAD technique had saved time and effort, and it did not damage the experiment model. The tissue structure was quite distinct in imaging. In terms of the stress distribution of bone tissue in the overdenture supported by implant, there was a difference between bar attachment and stud attachment. However, such a difference was minor as compared with the difference caused by the bite force direction. The stress value of cortical bone around abutment with 20 degree oblique force was 2.2-3 times that with vertical force. Therefore, to reduce high stress peaks, attention must be paid to the direction of the bite force, as this variable is much more important than the design of superstructure.

Aged↗
PubMed1998

[Surface treatments for dental titanium castings].

Because pure titanium is highly reactive at high temperature, its casting surface is easily coated with a thick contaminated layer that affects its physical and chemical properties, and consequently a stable superficial oxide membrane develops in the presence of air or water even at room temperature, which makes the surface discolored. Therefore, surface treatments for pure titanium castings are more important than those for other dental alloy castings. This article reviews the methods of surface treatments for dental titanium castings in four aspects: physical finishing, chemical finishing, electro-chemical finishing and surface modification technology.

Dental Casting Investment↗
PubMed1997

A versatile synthetic dimerizer for the regulation of protein-protein interactions.

The use of low molecular weight organic compounds to induce dimerization or oligomerization of engineered proteins has wide-ranging utility in biological research as well as in gene and cell therapies. Chemically induced dimerization can be used to activate intracellular signal transduction pathways or to control the activity of a bipartite transcription factor. Dimerizer systems based on the natural products cyclosporin, FK506, rapamycin, and coumermycin have been described. However, owing to the complexity of these compounds, adjusting their binding or pharmacological properties by chemical modification is difficult. We have investigated several families of readily prepared, totally synthetic, cell-permeable dimerizers composed of ligands for human FKBP12. These molecules have significantly reduced complexity and greater adaptability than natural product dimers. We report here the efficacies of several of these new synthetic compounds in regulating two types of protein dimerization events inside engineered cells--induction of apoptosis through dimerization of engineered Fas proteins and regulation of transcription through dimerization of transcription factor fusion proteins. One dimerizer in particular, AP1510, proved to be exceptionally potent and versatile in all experimental contexts tested.

Apoptosis↗
PubMed1997

[The effect of the mold temperature on the mechanical properties and reaction layer structure of the titanium castings].

Titanium is very reactive at the high temperature, easily oxidized, and reacts with investment components. The mold temperature is an important factor on the quality of the titanium castings. The paper investigated the effect of the mold temperature on the mechanical properties and reaction layer structure of the titanium castings with the tensile test and modern surface analysis technique. The results indicated that the tensile strength and yield strength of titanium castings increased but elongation rate decreased, and the hardness layer become thicker when the mold temperature raised. The hardness layer of titanium castings was 50 microns for the room temperature mold, 125 microns for the 850 degrees C mold. SX-macro electric probe analysis indicated the spreading depth of Zr, Al elements on the surface of titanium castings was not increased when the mold temperature raised, but, the spreading depth of Si element became deeper on the surface of titanium casting, Si layer was about 30 microns for the room temperature mold, 40 microns for the 250 degrees C mold, 50 microns for the 450 degrees C mold, 70 microns for the 650 degrees C mold, 90 microns for the 850 degrees C mold. So, it is necessary to consider the effect of the mold temperature on the qualities of titanium castings when titanium castings for prosthodontics were made in clinic.

Dental Casting Technique↗
PubMed1996

[Preparation of huichun zhibao oral liquid (HZOL)].

The formulation, preparing method, quality standards, pharmacodynamic experinents and toxicological experiments of HZOL are described. The content of icariin, which is and effective component of epimedium herb as well as one of the main ingredients in HZOL, was successfully determined through HPLC, with an average recovery of 98.98% and RSD = 1.53%.

Animals↗
PubMed1993

The UNOS OPTN waiting list from 1988 to 1993.

Based on data from the OPTN Waiting List and the Scientific Registry between 1988 and 1992: 1. On October 31, 1993 the combined waiting list for a solid organ transplant contained 32,603 registrations. This represents more than a 100% increase since 1988. Specifically, registrations for a lung transplant grew by more than 1600% and registrations for a liver transplant increased by 356% during the period. The intestine waiting list contained 900 registrations on October 31, 1993. 2. The distribution of patient characteristics on the waiting list snapshot as of October 31, 1993 was not markedly different from that on previous snapshots. Slight increases in the percentage of older (65 years) kidney, liver, and heart registrants were apparent. A slight decrease in the percentage of highly sensitized (PRA > or = 80%) kidney registrants was observed. 3. In general, median waiting times to transplant have increased each year between 1988 and 1992. During this period, the most significant increases were observed for kidney-pancreas registrants (277% increase) and lung registrants (205% increase). 4. For all waiting lists except heart-lung, registrants with blood type O waited substantially longer for a transplant than registrants with blood type A. This was especially true for kidney registrants. Other notable differences in waiting times on the kidney waiting list occurred between Blacks and Whites and between adults and pediatric registrants. Males waited on the heart waiting list for a transplant over twice as long as females. 5. The overall percentage of registrants who died while waiting for a transplant in 1992 was 5.8%, compared with 5.5% in 1988. The highest death rates occurred for thoracic registrants (13.1%, 16.2%, and 12.7% for heart, heart-lung, and lung, respectively). The lowest death rates occurred for kidney (3.5%) and kidney-pancreas registrants (1.2%). The death rate for pancreas registrants (9.4%) was greater than the death rate for liver registrants (8.5%). The number who died while waiting increased each year between 1988 and 1992, but the rate of increase may be declining.

Adolescent↗
PubMed1992

The UNOS OPTN (Organ Procurement and Transplantation Network) waiting list: 1988 through November 30, 1992.

Based on data from the OPTN Waiting List and the Scientific Registry between 1988 and 1992: 1. The number of registrations on the overall waiting list increased by 81% between December 31, 1988 and November 30, 1992. On November 30, 1992, there were 29,047 registrations for a transplant in the United States. Organ-specific waiting lists showing strong increases during the period were lung (1,277%), liver (262%), and heart (162%). The number of heart-lung registrants decreased during the period. 2. Overall, Whites comprised the largest percentage of waiting-list registrants, followed by Blacks and Hispanics. This frequency distribution remained relatively constant between 1988 and 1991. On the organ-specific waiting lists, the percentage of Whites ranged from 80% on the liver waiting list to 90% on the pancreas waiting list. Blacks make up about 12% of the United States population, but about 32% of the kidney waiting list, due to the high incidence of end-stage renal disease among Blacks in the United States. 3. The frequency distribution of age on the waiting lists is shifting toward a greater proportion of potential recipients age 45 or older. This trend was especially true for the liver, lung, and pancreas waiting lists. 4. The percentage of highly sensitized registrants (PRA > or = 80%) on the kidney waiting list decreased by 8% between 1988 and 1991. The percentage of registrants with PRA less than 20% increased by 11.3%, probably as a result of longer waiting times for low-PRA registrants. 5. A result of the growth of the waiting lists was an increase in the median waiting time to transplant during the period. This effect was observed on every waiting list except the heart-lung. The wait for a liver transplant was the shortest (67 days in 1991), whereas the wait for a heart-lung transplant was the longest (543 days in 1990). 6. The overall death rate remained relatively stable, but was up slightly in 1991, when 6.1% of registrants died while waiting for a transplant (compared with 5.6% in 1990). The death rate on the heart-lung waiting list fell from 23.5% in 1988 to 14.8% in 1991, probably because of fewer heart-lung registrations. In 1991, the death rates were highest on the thoracic waiting lists (11.7-14.8%), followed by liver (9.3%), kidney (3.7%), and pancreas (3.0%). 7. The percentage of patients in the most urgent medical status categories remained stable on the heart waiting list and has decreased on the liver waiting list.

ABO Blood-Group System↗
PubMed1992

[Study of primary CMV infection in pregnant women].

Clinical data and samples of blood for detecting CMV antibodies were obtained from 716 pregnant women of whom, 6.84% and 95.61% had CMV IgM and CMV IgG antibody, respectively. Statistic analysis showed that high positivity rates of CMV IgM antibody were correlated with lower socioeconomic status, first pregnancy at less than or equal to 22 or greater than or equal to 29 years of age, and history of abortion, especially natural abortion. In the pregnant women primary CMV infection rates were not uniform in those of different occupations. Positivity rates of CMV IgM antibody were higher in medical workers and peasants (P less than 0.05).

Adult↗
PubMed1991

The therapeutic and biological effects of total lymph node irradiation and autologous bone marrow infusion on malignant lymphoma patients.

Forty patients with malignant lymphoma were treated by 60Co total lymphoid irradiation (TLI): 21 cases received 6 Gy and 19 received 8 Gy. Ten also received autologous bone marrow infusion (ABMI). Acute radiation damage with digestive tract reaction and hemopoietic and immunological depression was observed. Bone marrow was depressed. WBC and platelets decreased rapidly. Lymphocytes showed quantitative and qualitative changes even at the early stage. All these symptoms subsided within 40 days. TLI accompanied by irradiation of the tumor site could result in effective control. The 1-, 3-, and 5-year survival rates of malignant lymphoma patients were 30/40 (75%), 14/24 (58%) and 4/12 (33%), respectively, while in those with Hodgkin's disease alone, the 1- and 3-year survival rates were 10/13 (76%) and 5/7 (71.4%), respectively. ABMI hastened hemopoietic reconstitution, which recovered relatively quickly after TLI.

Adolescent↗
PubMed1990

Surface tension measurements show that chaotropic salting-in denaturants are not just water-structure breakers.

Since the salting-in agents guanidinium chloride, urea, and lithium perchlorate increase the surface tension of water, the salting-in phenomenon does not reflect easier cavity formation in water. Therefore, these salting-in agents must be directly contributing to the solvation of a solute such as benzene in water, probably by a direct solvation interaction. The increased surface-tension effects do not overbalance these solvation effects since they are smaller than the large surface-tension increases with lithium chloride, a typical salting-out agent. The salting-in agent tetra-n-butylammonium chloride differs in that it lowers the surface tension of water. Thus, it probably contributes both to easier cavity formation and to direct solvation of the substrate. The previous findings that most salting-in agents switch to become salting-out agents in other polar solvents such as ethylene glycol and formamide but that tetra-n-butylammonium chloride does not switch in these solvents can be understood in terms of relative polarities.

Benzene↗