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Biomedical subjects

H Liu

Publications and source records attributed to H Liu.

At least 1,189 records · Page 66Linked to original sources
PubMed1991

Impact of Phase I Pew National Dental education Program on U.S. schools of dental medicine.

This paper presents the results of four telephone surveys conducted by the Leonard Davis Institute of Health Economics (LDI), University of Pennsylvania, as part of its evaluation of the Pew National Dental Education Program (PNDEP), a five year, +4F8.7 million program established by The Pew Charitable Trusts to help dental schools respond to the changing health care environment. The four annual surveys were conducted between 1985 and 1988. The interviews were conducted with the deans from nearly all dental schools operating in the United States at the time of study or the principal investigators of the schools funded under Phase I and Phase II PNDEP grants. Their purpose was to determine the level of each school's involvement in PNDEP and in specific strategic planning activities, as well as to evaluate the impact of the Pew Program on both the individual schools and dental education nationwide. All systematic differences between schools funded (FD) PNDEP and those not funded (NFD) were examined. Overall, schools gained a better understanding of their environment. Schools also reported increased participation in and commitment to planning among their different constituencies (e.g., faculty, administration, students, alumni). By the end of Phase I, more PNDEP Phase I funded schools reported being involved in implementing strategic plans. Funded schools also were more likely to report PNDEP increased their understanding of strategic planning, improved communication, and helped encourage the emergence of new leaders.

Administrative Personnel↗
PubMed1990

Detection of borderline oxacillin-resistant Staphylococcus aureus and differentiation from methicillin-resistant strains.

Eighty-eight Staphylococcus aureus clinical isolates meeting criteria for borderline oxacillin resistance (intermediate susceptibility or resistance to oxacillin but susceptibility to amoxicillin/clavulanic acid upon disk diffusion testing) were studied to determine optimal test techniques and conditions for differentiating borderline oxacillin-resistant Staphylococcus aureus (BORSA) from methicillin-resistant Staphylococcus aureus (MRSA). Further testing revealed three distinct resistance patterns: 61 strains (69%) consistently met BORSA criteria and had average beta-lactamase levels five- to six-fold higher than oxacillin-susceptible controls; 11 strains (13%) were markedly heteroresistant MRSA with delayed appearance of resistant colonies leading to spurious susceptibility to amoxicillin/clavulanic acid; 16 strains (18%) appeared to be oxacillin-susceptible on repetitive testing. Under conditions used to elicit intrinsic methicillin resistance in Staphylococcus aureus, a large percentage of BORSA appeared resistant to amoxicillin/clavulanic acid. This clearly shows that BORSA may be misidentified as MRSA while heteroresistant MRSA may appear to be BORSA. It is concluded that amoxicillin/clavulanic acid zone sizes should be measured after a full 24 hours of incubation, that susceptibility testing of Staphylococcus aureus under certain environmental conditions should be interpreted with caution, and that MIC testing is the most reliable technique for differentiating these two resistance patterns in Staphylococcus aureus.

Amoxicillin↗
PubMed1990

Regulation of platelet-activating factor receptor and PAF receptor-mediated arachidonic acid release by protein kinase C activation in rat Kupffer cells.

Phorbol 12-myristate 13-acetate (PMA), a potent protein kinase C activator, caused down-regulation of receptors for platelet-activating factor (AGEPC) on the plasma membrane of rat Kupffer cells (40-50% reduction) but had a relatively minor effect on the binding affinity of the receptors for AGEPC (Kd = 0.30 nM vs 0.56 nM) when incubated with the cells for a short period of time (30-60 min). As a consequence, the AGEPC receptor-mediated arachidonic acid release was attenuated. The PMA-induced down-regulation of AGEPC receptors was concentration-dependent, specific, and transient (the maximal effect was observed at about 1 h and the level of specific [3H]AGEPC binding gradually returned to the control level within 8.5 h and even higher than the control level at 24 h after addition of PMA). Upon removing PMA from the culture medium, more than half of the lost receptors were replaced within 1 h at 37 degrees C and the recovery process appeared to be independent of protein synthesis. The ability of PMA to down-regulate the AGEPC receptors was lost in cells "down-regulated" for protein kinase C, suggesting that the receptor-regulatory effect of PMA is protein kinase C-dependent. Protein kinase C appeared to be involved in the AGEPC-induced arachidonic acid release since 1-(5-isoquinolinesulfonyl)-2-methyl-piperazine dihydrochloride, a protein kinase C inhibitor, attenuated the stimulatory effect of AGEPC in this system. In addition, AGEPC-induced [3H]arachidonic acid release was inhibited significantly in cells down-regulated for protein kinase C. The present study thus demonstrates that protein kinase C has dual actions in the regulation of AGEPC-mediated events, i.e., a positive forward action, regulating AGEPC-stimulated arachidonic acid release, and a negative action, which inactivates or down-regulates AGEPC receptors.

Animals↗
PubMed1990

Immune T cells sorted by flow cytometry confer protection against infection with Treponema pallidum subsp. pertenue in hamsters.

The role of cell-mediated immunity against infection with Treponema pallidum subsp. pertenue in humans or experimental animals is unclear. Hamsters injected subcutaneously in the hind paws with 4 x 10(6) unfractionated lymph node cells or enriched lymph node T cells (immunoglobulin negative, Ia negative) from T. pallidum subsp. pertenue-immune hamsters were resistant to challenge with T. pallidum subsp. pertenue. The popliteal lymph nodes of hamsters that received immune cells weighed less and had significantly fewer treponemes than did lymph nodes from hamsters infused with cells from nonimmune donors. Furthermore, recipients of immune T cells failed to develop antitreponemal antibodies 21 days after challenge. Enriched T cells were obtained by flow cytometric separation by using monoclonal anti-Ia antibody 14-4-4s, which identified hamster B cells. Flow cytometric analysis by two-color immunofluorescent staining with anti-hamster-immunoglobulin and monoclonal anti-Ia antibody 14-4-4s confirmed that monoclonal anti-Ia antibody 14-4-4s recognized B cells. In addition, lymph node cells obtained after treatment with anti-Ia monoclonal antibody 14-4-4s and complement were 97% T cells, as determined by monoclonal antibody 20, a hamster T-cell marker. These results demonstrated that highly enriched T cells (immunoglobulin negative, Ia negative) from T. pallidum subsp. pertenue-immune hamsters conferred partial protection on hamsters against infection with T. pallidum subsp. pertenue.

Animals↗
PubMed1990

Primary lymphoma of the lung.

Two cases of primary lymphoma of the lung are reported, both of which were misdiagnosed preoperatively as bronchogenic carcinoma before undergoing successful resection. Accurate diagnosis was obtained after operation. These two patients were in good condition after a short period of follow-up. A discussion is presented concerning diagnosis, treatment and prognosis. Also, we point out the reason why so few primary lymphomas of the lung are reported: the mass of the lymphoma is typically so large that surgeons may consider it to be lung cancer in a late stage and thus abandon surgical intervention, or it may be erroneously diagnosed pathologically as undifferentiated small cell carcinoma of the lung.

Adult↗
PubMed1990

Preventive effect of aluminium citrate on silicosis.

Aluminium citrate (Al-cit) was shown to be biologically effective in preventing silicosis. A total of 917 cases selected from both engineering corps of railway and coalmines with stage 0 or 0+ by radiographs were studied. Cases were randomly divided into Al-cit treatment group and control group with continuing dust exposures. Workers in the treatment group were injected with Al-cit at a dose of 120 mg Al/year and these in the control group received a consolatant or nothing during the period of five years. The radiographic changes demonstrated that Al-cit showed clear-cut effects in both retardation of the dust-induced fibrosis and decrease of the morbidity of silicosis.

Adult↗
PubMed1990

[Amino acid analysis of the main organs during different growing periods of panax ginseng C.A. Mey].

Studies on different growing periods of Panax ginseng, its ages and the variation regularities of amino acids in its main organs are reported. The test has shown that it contains seventeen amino acids. The total amount of amino acids reaches its peak point during the sprouting period (in April), next to it is the withering period (in September), flowering and fruiting periods being the lowest (in June). The amount of these acids in the main root is higher than that in the fibrous root, the lowest being in the lateral root. Five-year-old Panax ginseng features the highest amount.

Amino Acids↗
PubMed1989

Regulation of platelet-activating factor receptors in rat Kupffer cells.

Ligand binding studies indicate that 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (AGEPC) down-regulates its own receptors on the plasma membrane of isolated rat Kupffer cells but has no significant effect on the binding affinity of the receptor for AGEPC. Exposure of isolated rat Kupffer cells to 10(-8) and 10(-6) M AGEPC resulted in a rapid, time-dependent reduction in the number of cell surface AGEPC receptors to a new steady state concentration (54.1 +/- 5.0% and 38.6 +/- 5.4% of control, respectively). During the observation period (6 h), the half-time of surface AGEPC receptors was about 60 and 45 min in the presence of 10(-8) and 10(-6) M AGEPC, respectively. Both the rate of loss and the maximal loss of the receptors were dependent upon the AGEPC concentration. With receptor synthesis inhibited by cycloheximide in the absence of AGEPC, the half-time of the surface AGEPC receptor was about 4 h, suggesting that AGEPC receptors are not recycled and that the loss of AGEPC receptors from the plasma membrane is accelerated by AGEPC binding. When incubated with Kupffer cells at 37 degrees C for 3 h, 1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine (1.0 microM), an inactive metabolite of AGEPC, did not cause the loss of AGEPC receptors. Under the same conditions, AGEPC antagonists such as BN52021 (2 x 10(-5) M) or U66985 (2 x 10(-5) M) alone had no effect (97.0 +/- 3.9% of control for BN52021) or only a relatively slight effect (78.4 +/- 1.8% for U66985) on the number of surface AGEPC receptors. However, AGEPC antagonists inhibited the AGEPC-induced down-regulation of AGEPC receptors in a concentration-dependent manner, suggesting that the AGEPC-induced down-regulation of AGEPC receptors is a receptor-mediated process. The AGEPC-mediated decrease in receptor number on rat Kupffer cells is reversible. Upon removing AGEPC from the culture medium, about 67% of the lost receptors were replaced within 2 h. Cycloheximide, an inhibitor of protein synthesis, prevented the restoration of the AGEPC receptors. Similar results were obtained when Kupffer cells were incubated with Pronase followed by removing Pronase and reincubating the cells with or without cycloheximide. These observations suggest that the restored AGEPC receptor is newly synthesized rather than recycled. The present study demonstrates that under non-stimulatory (i.e. in the absence of AGEPC) conditions AGEPC receptors are lost from the plasma membrane and are reformed in the cells continuously.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗