Biomedical subjects

C Lee

Publications and source records attributed to C Lee.

At least 19 recordsLinked to original sources

PubMed1992

Diagnosis of hepatitis C virus (HCV) infection using an immunodominant chimeric polyprotein to capture circulating antibodies: reevaluation of the role of HCV in liver disease.

Structural and nonstructural regions of the HCV-encoded polyprotein have been expressed in recombinant yeast, bacteria, or insect cells and used to capture and measure reactive antibodies circulating in different individuals. The putative nucleocapsid protein (C) and nonstructural proteins 3-5 (NS3-NS5) were found to contain the most immunodominant epitopes. The NS3, NS4, and C regions were expressed in yeast in the form of a fused, chimeric polyprotein (C25) and a capture assay for reactive antibody was developed. This anti-C25 assay detects all previously identified HCV-seropositive cases and provides a substantially more sensitive diagnostic for both acute and chronic HCV infections than the current anti-C100-3 (NS4) assay. Anti-C25 was detected more frequently than anti-C100-3 in chronic, transfusion-associated non-A, non-B hepatitis patients from the United States (95% vs. 71%) and Japan (98% vs. 82%), in cryptogenic cirrhosis patients from the United States (62% vs. 28%), and in hepatitis B surface antigen-negative cases of hepatocellular carcinoma from Japan (83% vs. 63%). These data indicate that HCV has a greater role in these liver diseases than was previously thought. In volunteer United States blood donors sampled following the introduction of anti-C100-3 screening, the prevalence of anti-C25 and anti-C100-3 was 0.5% and 0.08%, respectively.

Antigens, Viral↗

PubMed1992

Epidermal growth factor receptor monoclonal antibody inhibits constitutive receptor phosphorylation, reduces autonomous growth, and sensitizes androgen-independent prostatic carcinoma cells to tumor necrosis factor alpha.

Results of recent studies indicate that cultured, androgen-independent prostatic carcinoma cells synthesize and secrete transforming growth factor alpha, which interacts with epidermal growth factor receptors (EGFRs) to promote autonomous growth. In the present study, we evaluated the expression and constitutive activation of EGFRs in normal prostatic epithelial cells and the androgen-independent prostatic carcinoma cell lines PC3 and DU145. Our studies showed that cultured normal epithelial cells and androgen-independent prostatic carcinoma cells actively synthesize and exhibit constitutive phosphorylation of the M(r) 170,000 EGFR. The addition of monoclonal anti-EGFR reduced receptor phosphorylation and significantly inhibited the proliferation of prostatic tumor cells. The observed reduction in EGFR phosphorylation could be partially attributed to an antibody-induced decrease in the expression of metabolically labeled EGFR. Results of further studies showed that anti-EGFR enhanced the sensitivity of PC3 cells to the cytotoxic and cytostatic effects of tumor necrosis factor alpha. These studies demonstrate that constitutive activation of EGFR in androgen-independent prostatic carcinoma plays a functional role in the regulation of cellular proliferation in vitro. In addition, the enhanced sensitivity of prostatic carcinoma cells to tumor necrosis factor alpha in the presence of anti-EGFR provides a rationale for the further investigation of combination therapy in the treatment of disseminated, androgen-independent disease.

Antibodies, Monoclonal↗

PubMed1992

Thymus-independent development and negative selection of T cells expressing T cell receptor alpha/beta in the intestinal epithelium: evidence for distinct circulation patterns of gut- and thymus-derived T lymphocytes.

We demonstrate that mouse intestinal intraepithelial lymphocytes (IEL) can be divided into subsets based on the differential expression of functional T cell receptor alpha/beta (TCR-alpha/beta) signaling complexes. Two subsets, CD4+ 8 alpha + beta - and CD8 alpha + beta -, are refractory to stimulation with anti-TCR-alpha/beta and contain high frequencies of potentially self-reactive cells. In contrast, the CD4+ and CD8 alpha + beta + IEL subsets are responsive to anti-TCR-alpha/beta and depleted of potentially self-reactive cells. The analysis of fetal liver radiation chimeras using adult thymectomized recipients demonstrates that the four TCR-alpha/beta + IEL subsets are generated in normal numbers in the absence of the thymus. Moreover, expression of the major histocompatibility complex class II-encoded I-E molecule and Mls1a in the gut of the athymic host results in the negative selection of potentially self-reactive T cells expressing V beta 11 and V beta 6, respectively, from those IEL subsets that express functional TCR-alpha/beta signaling complexes. Neither the spleen nor the Peyer's patches of athymic recipients contain T cells of donor origin. In contrast, normal numbers of phenotypically and functionally mature CD4+ and CD8 alpha + beta + T cells of donor origin are found in the lamina propria of chimeric animals. The phenotypic analysis of lymphocytes obtained from Ly5 congenic parabionts reveals that peripheral T cells migrate rapidly to the Peyer's patches and lamina propria, but not to the intestinal epithelium. Taken together, these results demonstrate that the intestinal epithelium is a thymus-independent site of T lymphopoiesis, where selection of the T cell repertoire involves the deletion of potentially self-reactive cells in situ. Moreover, the appearance of donor-derived, phenotypically mature T cells, exclusively in the lamina propria of athymic radiation chimeras, suggests that mature IEL expressing functional TCR-alpha/beta migrate to this site.

Alleles↗

PubMed1992

A highly specific D-hydroxyisovalerate dehydrogenase from the enniatin producer Fusarium sambucinum.

A highly specific D-hydroxyisovalerate (D-HIV) dehydrogenase, which is a key enzyme in depsipeptide synthesis, was purified to near homogeneity from the enniatin-producing fungus Fusarium sambucinum. The enzyme catalyzes the reversible reaction of 2-ketoisovalerate (2-KIV) to D-HIV. It is strictly dependent on NADPH and exhibits a high substrate specificity with respect to 2-KIV. NADH was not accepted by the enzyme. Km values for 2-KIV and NADPH were found to be 200 and 333 microM, respectively. D-HIV dehydrogenase consists of a single polypeptide chain with a molecular mass of about 53 kDa. Optimum temperature for the reduction of 2-KIV was 35 degrees C and for the oxidation reaction was 45 degrees C. The optimum pH was found to be 7 for the reduction and 8-9 for the oxidation reaction.

Alcohol Oxidoreductases↗

PubMed1992

The dynamics of assembly of a cytoplasmic membrane protein in Escherichia coli.

The topology of integral cytoplasmic membrane proteins can be analyzed using alkaline phosphatase fusions by determining which constructs have low and which have high specific activity. We show that in all cases the enzymatic activity is due to the fraction of the alkaline phosphatase moiety of the fusion protein localized to the periplasm. We present evidence that these fusions can also be used to analyze the process of assembly of cytoplasmic proteins into the membrane. The rate of acquisition of protease resistance of the alkaline phosphatase moiety of such hybrid proteins is compared for fusions to periplasmic and cytoplasmic domains. We show that this process, which is assumed to be representative of export of alkaline phosphatase, is significantly slower for fusions to cytoplasmic and certain periplasmic domains than for most periplasmic domains. These results are discussed in the context of the normal assembly of integral membrane proteins.

ATP-Binding Cassette Transporters↗

PubMed1992

FK-506 binding protein from Tolypocladium inflatum: resistance of FKBP/FK-506 complex against proteolysis.

A 12-kDa peptidyl-prolyl-cis/trans-isomerase was purified 225-fold to homogeneity from the cyclosporin producing fungus Tolypocladium inflatum. The enzyme is highly sensitive to the immunosuppressant FK-506 but not to cyclosporin and thus belongs to the class of FK-506 binding proteins (FKBP). Interestingly the FKBP/FK-506 complex is resistant against proteolytic digestion by the endoproteases GluC and LysC, in contrast to the free FKBP, which is readily cleaved by these proteases. This protection may play a role in the effects of FK-506 in the living cell.

Amino Acid Isomerases↗

PubMed1992

Criteria for diagnosing Parkinson's disease.

Parkinson's disease evolves slowly, and there is current interest in exploring the earliest stages of the disorder, because of new approaches to studying pathogenesis and developing potential neuroprotective treatment. Recognizing early Parkinson's disease is not easy. The certainty of diagnosis increases as the disease advances. To address the problem of identifying Parkinson's disease in its initial phases of clinical expression, we propose the following designated levels of confidence for the diagnosis: (1) clinically possible, (2) clinically probable, and (3) clinically definite. Laboratory support for the diagnosis may be applied to each category. Criteria are provided as a framework underpinning this classification.

Humans↗

PubMed1992

Immunological evidence for a P2 protamine precursor in mature rat sperm.

High molecular weight proteins in Rattus norvegicus that are immunoreactive with an anti-protamine 2 specific antibody but not with an anti-protamine 1 specific antibody are described. These proteins were detected by coupling high-performance liquid chromatography (HPLC) with an enzyme-linked immunosorbent assay (ELISA). Briefly, following HPLC separation of rat sperm nuclear proteins, the HPLC fractions were probed with the antibodies. We estimate that the antibody probes are 100-1000 times more sensitive than UV absorbance measurements. Immunoblot analysis following acid-urea electrophoretic separation of rat sperm nuclear proteins, and of the HPLC fractions, also detected putative protamine 2 precursor proteins. The proteins reactive with the anti-protamine 2 antibody are most likely not mature protamine 2, since they were detected in a region of the chromatogram where we would not expect protamine 2 to migrate based on the chromatographic locations of human and mouse protamine 2. Likewise, the immunoblotting experiments demonstrated that the anti-protamine 2 antibody recognized proteins with slower electrophoretic mobilities than would be expected for a mature protamine 2. An anti-protamine 1 monoclonal antibody, Hup1N, that binds rat protamine 1 is also described. Hup1N allowed for identification of the HPLC fractions that contained rat protamine 1. Finally, we demonstrated that Hup1N binds protamine 1 from a large number of species, suggesting a conserved epitope for Hup1N.

Animals↗

PubMed1992

A local direct effect of pituitary graft on growth of the lateral prostate in rats.

Prolactin and testosterone are synergistic in stimulating growth of the rat prostate. The lateral lobe is more sensitive to this synergism than the ventral and dorsal lobes. To investigate whether prolactin acts directly in the rat prostate or indirectly through another systemic mediator, anterior pituitary grafts (1 mm3) were implanted in the lateral prostate of castrated Sprague-Dawley rats in whom a 0.5 cm or 1.0 cm testosterone-filled silastic tubing was implanted subcutaneously at the same time. Rats were randomly assigned to receive either the pituitary or a muscle chip of similar size grafted beneath the fascia lateral to the lateral prostate. Twenty-one days later, serum prolactin levels were not elevated in pituitary-grafted animals and were not significantly different from those in muscle-grafted rats. The mean lateral prostate weight on the grafted side in pituitary-implanted rats with 1.0 cm testosterone tubing was 43% heavier than either that of the contralateral side or the corresponding weights in muscle-implanted rats. In pituitary-implanted rats with 0.5 cm testosterone tubing, the mean lateral prostate weight on the grafted side was 60% heavier than either that of the contralateral side or that of the corresponding weights in muscle-implanted rats. The weight of the ventral and dorsal lobes of the prostate was not significantly affected by the presence of pituitary grafts in one of the lateral lobes. The local effect of prolactin on the lateral prostate was further demonstrated by an overall decline in tissue concentrations of dihydrotestosterone in the grafted side. These results provided evidence to indicate that there was a direct effect of prolactin on growth of the lateral prostate in rats.

Animals↗

PubMed1992

Regulation of prostatic carcinoma cell proliferation and secretory activity by extracellular matrix and stromal secretions.

Previous studies from our laboratory have shown that reconstituted basement membrane and stromal secretory products are important regulators of benign prostatic epithelial cell growth and differentiation. In the present study we evaluated the impact of extracellular matrix (ECM) and soluble stromal secretory products on the proliferation and secretory activity of the androgen-responsive prostatic carcinoma cell line LNCaP. In these studies, dihydrotestosterone (DHT) was a potent mitogen for LNCaP cells cultured on plastic or on type I collagen. The growth response to DHT was greatly attenuated when LNCaP cells were grown on prostatic stromal ECM. Cells grown on stromal ECM also exhibited clustered morphology compared to the monolayer growth observed on plastic and secreted elevated levels of prostate specific antigen (PSA) and prostatic acid phosphatase (PAP). These findings indicate that cultivation of LNCaP on stromal ECM will promote the expression of differentiated functions. In additional studies, stromal cell conditioned medium (SCM) significantly increased PSA/PAP secretion by LNCaP cells in the presence of 10 nM DHT. The enhancement of DHT-induced PSA/PAP secretion by SCM was most pronounced when LNCaP cells were grown on stromal ECM. SCM did not significantly alter LNCaP proliferation. These studies indicate that prostatic stromal ECM and soluble secretory products will promote differentiated function in cultured LNCaP cells. In addition, we show that DHT can act as either a growth or differentiation-promoting stimulus depending on the presence of stromal factors.

Acid Phosphatase↗

PubMed1992

Interaction of epidermal growth factor and transforming growth factor beta in human prostatic epithelial cells in culture.

The present study was conducted to study the interaction between epidermal growth factor (EGF) and transforming growth factor-beta (TGF-beta) in benign human prostatic epithelial cells in culture. Primary cultures of human prostatic epithelial cells were grown in complete WAJC, which consisted of WAJC-404 medium and, in addition to other defined additives, EGF and bovine pituitary extract (BPE). Incomplete WAJC contained the same composition except EGF and BPE were deleted. TGF-beta was added into media at concentrations of 0, 0.1, and 1.0 ng/ml. When cells were grown in complete WAJC, they proliferated rapidly. Cell proliferation was greatly suppressed when incomplete WAJC was used. Addition of TGF-beta to these cultures caused a significant reduction in the final cell number when either complete WAJC or incomplete WAJC was used. In additional experiments, cells were prelabeled with 3H-thymidine for 72 hr prior to treatment with TGF-beta. The percentage of radioactivity released into the medium at the end of a 6-day culture was used as an indication of the extent of cell death. Trypan blue exclusion test was also used to assess the extent of cell death. Addition of TGF-beta into complete WAJC did not significantly affect the extent of cell death beyond what was considered as the result of normal cellular turnover. Addition of TGF-beta into incomplete WAJC, however, caused a significant increase in the percent of cell death in the culture. These results demonstrated an interaction between EGF and TGF-beta in proliferation and cell death in human prostatic epithelia in culture. In the presence of EGF alone in the culture medium, prostatic epithelial cells were stimulated to proliferate. The rate of proliferation was greatly diminished when EGF was deleted from the medium or when TGF-beta was added in the presence of EGF. Finally, cell death was induced when TGF-beta was added into the medium in the absence of EGF.

Analysis of Variance↗

PubMed1992

Essential fatty acid deficiency in cultured SK-N-SH human neuroblastoma cells.

SK-N-SH neuroblastoma cells grown under standard culture conditions contain significant amounts of Mead acid (20:3 omega 9) in phospholipids, indicating essential fatty acid (EFA) deficiency. The amount of esterified 20:3 omega 9 was augmented by growth in a chemically defined EFA-free medium, whereas its presence could be virtually eliminated by supplementation of the culture medium with either arachidonic (20:4 omega 6; AA), eicosapentaenoic (20:5 omega 3; EPA), or linolenic (18:3 omega 3) acids. Substitution of Mead acid for omega 6 fatty acids, particularly evident in phosphatidylinositol (PI), indicates a compensatory replacement of omega 9 for omega 6 fatty acids during EFA deficiency. Studies evaluating [3H]scopolamine binding to the M3 muscarinic acetylcholine receptors (mAChRs) present in these neurotumor cells as well as effects of carbachol on phosphoinositide turnover and intracellular Ca2+ mobilization, indicate that the biosubstitution of 20:4 omega 6 with 20:3 omega 9 does not detectably impair these measures of signal transduction. Stimulation of mAChRs with carbachol increased the cellular mass of diacylglycerol (DAG) approximately 60%. On the basis of distinctive fatty acid "signatures" of each of the phospholipid classes, it is concluded that the DAG initially released following muscarinic stimulation is derived from phosphoinositide breakdown. After several minutes, however, a significant amount of DAG comes from phosphatidylcholine (PC) as well. In contrast to DAG, the composition of phosphatidate (PA) following receptor stimulation closely resembles that of the phosphoinositides, even at the later time points examined. These results support a selective phosphorylation of DAG arising from the stimulated breakdown of phosphoinositides, favoring the conservation of the 1-stearoyl, 2-arachidonoyl (or 20:3 omega 9) moiety.

8,11,14-Eicosatrienoic Acid↗

PubMed1992

Effects of diazepam on behavioural and antinociceptive responses to the elevated plus-maze in male mice depend upon treatment regimen and prior maze experience.

Recent studies have shown that brief exposure to an elevated plus-maze (EPM) produces non-opioid antinociception in male mice. The present experiments were designed to assess the effects of diazepam on this phenomenon. When acutely administered, low doses (0.5-1.0 mg/kg) of diazepam failed to produce an anxiolytic profile and exerted rather inconsistent effects on EPM-induced elevations in tail-flick latencies. In EPM-experienced mice, chronic treatment with higher doses of diazepam (2-4 mg/kg, 8 days) produced a weak anxiolytic action and inhibited the early phase of EPM antinociception only. However, in EPM-naive mice, 8-day diazepam pretreatment exerted a marked anxiolytic effect and completely eliminated the antinociceptive response to the maze. Together, these data support the view that anxiety is a key factor in certain forms of adaptive pain inhibition and suggest a possible mediational role for benzodiazepine receptors. Our findings also show that prior exposure to the EPM, rather than chronic handling/injection, greatly reduces the anti-anxiety effect of diazepam. Furthermore, since re-exposure to the maze, per se, decreased time spent on the open arms and central platform, a shift in behavioural baseline ("retest anxiogenesis") may have contributed to the weak behavioural effects of diazepam in test-experienced animals. Importantly, as chronic treatment with diazepam did not influence this anxiogenic-like retest profile, our data suggest that a single prior experience of the EPM may radically alter the nature of the anxiety reaction provoked by this test.

Analgesia↗

PubMed1992

On cognitive theories and causation in human behavior.

Modern theories of social behavior are based on the largely unquestioned assumption that human activity is determined by cognitive variables. Physiology, environment, and behavior are seen as peripheral to the understanding of cognition, seen as central to the understanding of human nature. This paper argues that these approaches to psychology are essentially metaphorical models of behavior, inadequate as explanatory theories, because they rely on untestable assumptions concerning the centrality to human behavior of hypothetical and unmeasurable cognitive variables. Their lack of precision does not allow for the testing of specific predictions. This paper argues that contemporary cognitive-behavioral and cognitive-social theories cannot be salvaged as explanatory models.

Cognitive Behavioral Therapy↗

PubMed1992

Leeches: controlled trial in venous compromised rat epigastric flaps.

Leeches were studied for their efficacy to improve survival of venous compromised rat skin flaps. In 22 rats, bilateral epigastric island flaps were created and subjected to 6 h of venous occlusion. One flap in each animal was randomised to leech treatment, while the contralateral flap served as its own control. Flap survival, leech feeding time, weight gained by the leech and bleeding time from leech bites were measured. The area of flap survival was significantly increased in leech treated flaps compared to contralateral controls (n = 22 pairs, p = 0.03; Wilcoxon signed rank test). Weight gained in the feeding leech averaged 1.3 +/- 0.2 g (n = 18). Leech feeding time was 107 +/- 13 min (n = 18). Bleeding time from each leech bite averaged 79 +/- 12 min (n = 18). Hence, the extent of flap necrosis resulting from venous impairment can be partly diminished by leech treatment until definitive surgical venous revascularisation.

Animals↗

PubMed1992

Characterization of the hepatitis C virus E2/NS1 gene product expressed in mammalian cells.

Truncated and full-length versions of the hepatitis C virus protein domain encoding a presumptive envelope glycoprotein designated E2/NS1 were stably expressed in CHO cell lines. Characterization of the processing events involved in the maturation of E2/NS1 revealed that a high-mannose form resident in the endoplasmic reticulum was the most abundant form detected intracellularly. The ionophore carboxyl cyanide m-chlorophenyl-hydrazone was used to show that the E2/NS1 glycoprotein resided in the endoplasmic reticulum. The full-length form of E2/NS1 appeared to be cell-associated and could not be detected as a secreted product. C-terminal truncated molecules could be detected in the extracellular media as fully processed glycoproteins containing terminal sialic acid additions. These truncated glycoproteins are predicted to be biologically relevant targets of the host immune response and are therefore potential subunit vaccine candidates.

Animals↗

PubMed1992

Evidence for a non-androgenic role of testis and epididymis in androgen-supported growth of the rat ventral prostate.

A widely held view is that the role of testis in prostatic growth is through its ability to secrete androgen. Our earlier observation suggested a non-androgenic role for the testis, and perhaps the epididymis, in promoting growth of the ventral prostate in rats. The present study was conducted to evaluate the separate role of the testis and the epididymis in this phenomenon. In the first study, increasing quantities of silastic tubing filled with crystalline testosterone were implanted into adult Sprague-Dawley rats at the time of bilateral epididymo-orchiectomy or sham-operation. Twenty-eight days later, growth of the ventral prostate, as determined by fresh weight, DNA, and protein content, was significantly greater in sham-operated rats than in those receiving combined epididymo-orchiectomy, confirming our previous observation using dihydrotestosterone. In the second and third studies, rats were subjected to selective surgical procedures to evaluate the independent role of the testis and the epididymis. At the same time, 12 cm silastic tubing filled with testosterone or dihydrotestosterone were implanted subcutaneously into each of these animals for 28 days. Results indicated that the ventral prostate was significantly smaller in rats receiving the combined epididymo-orchiectomy than that of sham-operated controls. Simple orchiectomy or simple epididymectomy resulted in an increased weight of the ventral prostate between the two values obtained from the above two groups. Ligation of either the efferent duct or the vas deferens yielded ventral prostatic weights comparable to the androgen-treated, sham-operated controls. These results indicated that in order to achieve a maximal effect on androgen-supported growth of the ventral prostate, the presence of both the testis and the epididymis is required.

Androgens↗

PubMed1992

Inhibitory effects of suramin on a human renal cell carcinoma line, causing nephrogenic hepatic dysfunction.

A sarcomatoid renal cell carcinoma has been isolated from a patient with Stauffer's syndrome. The tumor, designated BA1119, has been established in tissue culture over 80 passages. Subcutaneous deposition of BA1119 in athymic mice induced splenomegaly and hepatic dysfunction which became fatal within four weeks without metastasis. Suramin is a synthetic polyanionic compound which is capable of altering the function of a number of biologic systems and inhibiting the activity of a variety of protein and growth factors. In this study we attempted to study the effect of suramin on growth of BA1119 in culture and in nude mice. Suramin, at 300 micrograms/ml., had a profound inhibitory effect on cell growth during a six-day culture period. Suramin given i.p. weekly to nude mice at clinically relevant doses (200 mg./kg.) caused significant shrinkage of subcapsular tumor deposits. Splenic hypertrophy secondary to BA1119-induced Stauffer's syndrome was inhibited by suramin. Synergistic effect with enhanced cytotoxicity on BA1119 cells was observed when suramin (100 micrograms/ml.) was used in combination with lymphokines, such as gamma interferon (500 units/ml.) and alpha tumor necrosis factor (300 ng./ml.). These results may suggest a therapeutic efficacy of suramin in renal cell carcinoma patients with Stauffer's syndrome.

Animals↗