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Biomedical subjects

T Lee

Publications and source records attributed to T Lee.

At least 289 records · Page 16Linked to original sources
PubMed1990

Transforming growth factor-beta modulates proliferation and differentiation of mouse clonal osteoblastic MC3T3-E1 cells depending on their maturation stages.

The effect of transforming growth factor-beta (TGF-beta) on proliferation and differentiation of mouse clonal osteoblastic cells (MC3T3-E1) was examined in vitro in three different stages of their differentiation. Stage I (1-3 days after plating) was characterized by rapid cell growth, negligible alkaline phosphatase (ALP) activity and high proteoglycan synthesis, but low collagen production. In stage II (3-5 days after plating), proteoglycan synthesis sharply decreased and ALP activity and collagen synthesis began to increase. Stage III (7-9 days after plating) was characterized by maximal osteoblastic phenotypes. Treating MC3T3-E1 cells with 1 ng/ml of TGF-beta greatly inhibited DNA synthesis in stage I but not in stage II. In contrast, TGF-beta dose-dependently stimulated the synthesis of collagenase digestible proteins (CDP), noncollagenous proteins (NCP) and proteoglycan, especially in stage II. The minimum effective dose of TGF-beta in this stage was as low as 0.04-0.2 ng/ml. In stages I and III, the MC3T3-E1 cells were rather insensitive to TGF-beta in increasing three osteoblastic phenotypes. The increase in ALP activity in stages II and III was inhibited by 1 ng/ml of TGF-beta. These results indicate that the response to TGF-beta of mouse clonal osteoblastic MC3T3-E1 cells changes depending on their maturation stages.

Alkaline Phosphatase↗
PubMed1990

Poliovirus-mediated entry of pokeweed antiviral protein.

Infection of HeLa cells with poliovirus results in cell permeabilization to pokeweed antiviral protein. Cell permeabilization was dependent on the integrity of virus capsid proteins and directly proportional to the multiplicity of infection. This study demonstrates that virus adsorption is sufficient for the entry of pokeweed antiviral protein into poliovirus-infected cells.

Antiviral Agents↗
PubMed1990

Estrogen regulates the gene expression of vasoactive intestinal peptide in the anterior pituitary.

Vasoactive intestinal peptide (VIP), a prolactin (PRL)-releasing factor, has been shown to be synthesized within the anterior pituitary. To test the hypothesis that estrogens increase PRL secretion, at least in part, by stimulating VIP secretion, the concentrations of VIP, peptide histidine isoleucine (PHI) and prepro VIP mRNA were measured in the anterior pituitaries of oophorectomized rats treated with 17 beta-estradiol benzoate 25 micrograms/kg/day s.c. for 5 days. For comparison, changes in the hypothalamus were also measured. Estrogen treatment resulted in a marked increase in pituitary VIP content without detectable changes in PHI content, suggesting that estrogen may regulate differentially the enzymes involved in the posttranslational processing of the VIP prohormone. A VIP mRNA-transcript of about 1.7 kilobases was detected in all tissues studied, being most abundant in the cortex, less abundant in the hypothalamus and barely detectable in the untreated pituitary. Estrogen treatment resulted in an increase in VIP gene expression in the pituitary but not in the hypothalamus or cerebral cortex. This marked increase in prepro VIP mRNA rendered possible the demonstration in the estrogen-treated pituitary of a second VIP transcript of about 1.0 kilobase which was present in only very low quantities in the cortex and hypothalamus. We conclude that estrogen regulates the gene expression of VIP in the anterior pituitary. Changes in VIP secretion may contribute to the stimulatory effect of estrogen on PRL secretion.

Animals↗
PubMed1990

Measuring the workload of the anesthesiologist.

Workload is an important determinant of human performance during complex dynamic tasks. We indirectly measured the mental workload of nine anesthesia residents during 19 cases using a secondary (subsidiary) task paradigm in which performance on an extra task (problems in mathematical addition occurring approximately every 45 s) was used as a probe of a subject's "spare capacity." Excess response time (above baseline) correlated with activities like "manual task" and "speaking with the attending anesthesiologist." The addition problem was either skipped or had a high excess response time (greater than 30 s) in 40% of presentations. The complexity of a case and the experience level of the resident interacted in determining the workload. Subjective workload ratings confirmed that induction of and emergence from anesthesia were periods of highest workload, with "attention" as the dominant cognitive requirement. The anesthesiologist's spare capacity may often be limited during anesthesia. These types of workload measurement techniques should be applied in controlled studies to better define the factors that increase workload.

Anesthesiology↗
PubMed1990

Pasteurella multocida: a rare case of shunt infection.

Pasteurella multocida, the major pathogen following an animal bite, is a rare cause of intracranial infection. This report documents the first case of ventriculo-peritoneal shunt infection with Pasteurella multocida.

Adult↗
PubMed1990

A double blind placebo controlled trial of the calcium entry blocking drug, nicardipine, in the treatment of vasospasm following severe head injury.

A double blind, placebo controlled trial of nicardipine in the treatment of high Doppler Flow Velocity (DFV) following severe head injury (Glasgow Coma Score (GSC) less than or equal to 8) was performed. Thirty patients with high DFV (greater than or equal to 100 cm/s for 6 h duration) on transcranial Doppler ultrasound, were treated with nicardipine or placebo for 24 h (2.5 mg/h, increasing in steps of 2.5 mg/h at 2 h intervals (maximum rate 7.5 mg/h) depending on response of DFV). DFV was measured hourly for 24 h and then every 12 h for 2 days. Nicardipine significantly reduced DFV below the threshold of 100 cm/s (16/19 cf placebo 3/11, chi-square p less than 0.001). In the nicardipine treated group maximum DFV was significantly reduced (p less than 0.001) and time with DFV below 100 was significantly longer. Rises in DFV were significantly reduced by the drug if the DFV was normal at the time of entry. High DFV returned on cessation of the infusion. No unexpected or adverse side effects were seen. No clinical benefit was demonstrable.

Adolescent↗
PubMed1989

Stable expression of hepatitis B virus genome in a primate kidney cell.

Transfection of Vero cells with cloned hepatitis B virus (HBV) DNA resulted in the secretion of hepatitis B surface protein (HBsAg) and core proteins (HBc/eAg). Syntheses of both viral antigens in the transformed Vero cells continued for at least 50 days after cultivation. HBsAg particles were composed of many spherical and some filamentous particles containing both pre-S1 and pre-S2 domains. Restriction analysis of the transfected cellular DNA showed that one copy of HBV DNA was integrated in the cells. Some species of HBV-specific RNA were detected by Northern blot, and among these a major transcript was found to migrate at 2.1 kb by S1-mapping analysis. Viral core proteins present in the culture medium were fractionated and characterized by cesium chloride gradient and found to form particles.

Animals↗