Biomedical subjects
Publications and source records attributed to W Liao.
[reaction: see text] The opening of methylketene dimer, followed by aldol reactions of the resulting enolate, provides a convenient access to syn,syn-dipropionate aldol adducts of a variety of aldehydes. These aldol adducts are useful precursors in the synthesis of complex polypropionates.
Structural studies by three-dimensional electron microscopy of the Saccharomyces cerevisiae truncated dihydrolipoamide acetyltransferase (tE(2)) component of the pyruvate dehydrogenase complex reveal an extraordinary example of protein dynamics. The tE(2) forms a 60-subunit core with the morphology of a pentagonal dodecahedron and consists of 20 cone-shaped trimers interconnected by 30 bridges. Frozen-hydrated and stained molecules of tE(2) in the same field vary in size approximately 20%. Analyses of the data show that the size distribution is bell-shaped, and there is an approximately 40-A difference in the diameter of the smallest and largest structures that corresponds to approximately 14 A of variation in the length of the bridge between interconnected trimers. Companion studies of mature E(2) show that the complex of the intact subunit exhibits a similar size variation. The x-ray structure of Bacillus stearothermophilus tE(2) shows that there is an approximately 10-A gap between adjacent trimers and that the trimers are interconnected by the potentially flexible C-terminal ends of two adjacent subunits. We propose that this springlike feature is involved in a thermally driven expansion and contraction of the core and, since it appears to be a common feature in the phylogeny of pyruvate dehydrogenase complexes, protein dynamics is an integral component of the function of these multienzyme complexes.
Apolipoprotein (apo) B-100 is an essential component of atherogenic plasma lipoproteins. Previous studies have demonstrated that the production of apoB-100 is regulated largely by intracellular degradation at both the co-translational and post-translational levels and that proteasome-mediated and non-proteasome-mediated pathways are involved in this process. ApoB-100 is a glycoprotein. The present study was undertaken to address the question of whether the inhibition of N-linked glycosylation with tunicamycin would interfere with apoB-100 production. We demonstrated that the treatment of HepG2 cells with tunicamycin decreased the net production of apoB-100 by enhancing co-translational degradation of the protein. This effect of tunicamycin was partly prevented by lactacystin, a specific proteasome inhibitor. Because lactacystin only partly reversed the effects of tunicamycin on apoB biogenesis, tunicamycin seemed also to induce apoB co-translational degradation in HepG2 cells by one or more non-proteasomal pathways. Furthermore, tunicamycin increased apoB ubiquitination approx. 4-fold. The proportion of the newly synthesized apoB-100 that was secreted and incorporated into the nascent lipoprotein particles was unaffected by tunicamycin. Thus the tunicamycin-mediated inhibition of N-linked glycosylation interferes with the production of apoB-100 that is mediated by both proteasomal and non-proteasomal pathways.
Activation of IkappaB kinase (IKK) is the key step in stimulation of the transcription factor NF-kappaB, which regulates many genes in the inflammatory response pathway. The molecular mechanism that underlies IKK activation in response to tumor necrosis factor (TNF) is still unknown. Using mitogen-activated protein kinase kinase kinase 3 (MEKK3)-deficient fibroblast cells, we found that MEKK3 plays a critical role in TNF-induced NF-kappaB activation. We have shown that MEKK3 is required for IKK activation and functions downstream of receptor-interacting protein (RIP) and TNF receptor- associated factor 2. We have also shown that MEKK3 interacts with RIP and directly phosphorylates IKK. The kinase activity of MEKK3 is pivotal to its function and, therefore, MEKK3 links RIP and IKK in TNF-induced NF-kappaB activation.
SV129 or C57BL/6 mice were exposed to hyperbaric oxygenation (HBO, 5 days, 1 h every day, 100% O(2) at 3 atm absolute). One day after the 5th HBO session focal cerebral ischemia was induced. In SV129 mice, HBO induced tolerance against permanent focal cerebral ischemia (n=42, mean infarct volume reduction 27%, P=0.001), but not against transient (30 or 60 min) focal cerebral ischemia. In the C57BL/6 strain of mice, HBO did not induce tolerance against focal cerebral ischemia, even when the duration of ischemia or the HBO protocol were modified. For the first time we demonstrate that HBO can induce tolerance to focal cerebral ischemia, but this effect is strain dependent.
An efficient synthesis of the mucin core-2 analogue 1a was accomplished using N-p-nitrobenzyloxycarbonyl(PNZ)-protected trichloroacetimidate 4 as a novel glycosyl donor.
Studies in different liver-derived cells in culture indicate that apolipoprotein (apo) B-100 production is regulated largely by intracellular degradation and the ubiquitin-proteasome pathway is a major mechanism for the degradation. The proteasomal degradation of apoB-100 was postulated to be an intrinsic property of the protein that occurs even in the presence of optimal amounts of lipids supplied to the cell. We examined apoB-100 and apoB-48 biogenesis in CaCo2, a human colon carcinoma cell line. To our surprise, apoB-100 and apoB-48 were quantitatively secreted by CaCo2 cells; essentially none of the newly synthesized apoB was degraded before secretion in a 2-h period whether the cells were cultured on filter or on plastic. Furthermore, although ubiquitin immunoreactivity was readily detected in the intracellular apoB isolated from HepG2 cells, little or no ubiquitin was detectable in the intracellular apoB from CaCo2 cells. The amounts of free ubiquitin and total and non-apoB ubiquitinated proteins were comparable in HepG2 and CaCo2 cells, indicating that CaCo2 cells have the necessary machinery for tagging ubiquitin chains onto cellular proteins for proteasomal degradation. Incubation in lipoprotein-deficient serum did not induce apoB degradation, but the addition of a microsomal triglyceride transfer protein inhibitor led to apoB degradation in CaCo2 cells. Finally, similar proportions of apoB polypeptide in isolated microsomes from CaCo2 and HepG2 cells were accessible to exogenously added trypsin, indicating that the mere exposure of apoB nascent chains to the cytosolic compartment is insufficient to cause the proteasomal degradation. Therefore, the intracellular degradation of apoB is not an intrinsic property of the protein, and the phenomenon is neither universal nor inevitable. The unconditional use of apoB as a paradigm for intracellular protein degradation is not warranted.
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We report the generation and characterization of transgenic mouse and zebrafish expressing green fluorescent protein (GFP) specifically in vascular endothelial cells in a relatively uniform fashion. These reporter lines exhibit fluorescent vessels in developing embryos and throughout adulthood, allowing visualization of the general vascular patterns with single cell resolution. Furthermore, we show the ability to purify endothelial cells from whole embryos and adult organs by a single step fluorescence activated cell sorting. We expect that these transgenic reporters will be useful tools for imaging vascular morphogenesis, global gene expression profile analysis of endothelial cells, and high throughput screening for vascular mutations.
The influence of glucose, fructose, lactose, and glycerol on the color and appearance of surfactant-stabilized oil-in-water emulsions containing a red dye was investigated. A stabilized (Tween-20) oil-in-water emulsion was diluted into sugar solutions to give a range of oil droplet and sugar concentrations. Tristimulus coordinates (L, a, b) and reflectance spectra were measured using a spectrophotometer. With increasing sugar concentration, reflectance spectra shifted to lower reflectance values. Tristimulus coordinates were reduced by approximately 50% for emulsions containing high concentrations of sugar. Adding fructose to emulsions reduced L, a, b values more significantly than adding glucose, lactose, or glycerol. Tristimulus coordinates remained constant when the temperature was raised from 20 to 80 degrees C. The experimental results were explained in terms of the change of relative refractive index at the water-oil interface. The results have important implications for the food industry as they offer a new means to control and optimize the color of food emulsions.
Information from clinical and pharmacokinetic studies of angiotensin-converting enzyme inhibitors (ACEIs) has come from subjects who are mostly male and Caucasian, but the use of ACEIs extends to populations worldwide. Significant differences between Chinese in general and male Caucasians have been demonstrated in the pharmacokinetics/dynamics of other drug classes that could have implications for the use of ACEIs in the Chinese population. These include: significant Chinese/Caucasian genetic variation in the renin-angiotensin system based on an insertion/deletion (O/D) polymorphism of the ACE gene; the genetic determination of plasma ACE activity in the Chinese population; and genetic factors involving the disease substrate which may also influence the response to treatment. Oral and IV pharmacokinetic data from various studies of Chinese and Caucasian subjects are available for cilazapril, fosinopril, and perindopril, and pharmacodynamic data are available for eight different ACEIs. Based on these data, there are few differences among the pharmacokinetics of ACEIs between Chinese and Caucasians. Most ACEIs showed good blood pressure lowering efficacy in Chinese (benazepril, enalapril, fosinopril and spirapril), with perhaps less blood pressure lowering with cilazapril or a relatively shorter-term effect with cilazapril or perindopril compared to Caucasions. Chinese experience more cough from ACEIs (captopril and enalapril) than Caucasians. Data suggest that fosinopril may not induce cough in as many subjects as other ACEIs, and this seems to be true of Chinese as well. The mechanism, currently unknown, could involve fosinopril's dual elimination pathway (hepatic and renal). Pharmacokinetic data also support the use of fosinopril in congestive heart failure where elimination pathways may be impaired. In conclusion, ethnic differences between Chinese and Caucasians with respect to ACE and AGT gene polymorphism, which might be expected to differentially affect the action of ACEIs in these two ethnic groups, do not, in fact, have such an effect. Rather, differences among the ACEIs appear to be more important. Journal of Human Hypertension (2000) 14, 163-170.
A case of cerebral cryptococcal granuloma is reported. The diagnosis was based on histological examination and rDNA-PCR identification. Complete cure was achieved with fluconazole.
OBJECTIVE: Seventy-seven cases of native valve infective endocarditis as determined by the Duke criteria, were reviewed to determine the incidence and clinical features of multi-valvular endocarditis. METHODS: Fourteen of 77 patients (18%) had multi-valvular endocarditis most commonly involving the mitral and aortic valves. Staphylococcus aureus (43%) and viridans streptococci (36%) were the most common organisms causing multi-valvular endocarditis. RESULTS: Definite or probable vegetations were found in 50% of the patients by two-dimensional transthoracic echocardiograph and/or transesophageal echocardiograph, and possible vegetations were detected in 21%. The overall mortality in our series was 21%; 29% underwent valve replacement and 50% were treated medically. The major complications of multi-valvular endocarditis were congestive heart failure (64%), acute renal failure (50%), embolic events (21%), and splenic abscess/infarcts (21%). CONCLUSIONS: Our data suggests complications of multi-valvular endocarditis, compared with uni-valvular endocarditis are similar except for heart failure. Heart failure is statistically more common in multi-valvular endocarditis (P < or = 0.002).
BACKGROUND: Omapatrilat, a vasopeptidase inhibitor, preserves natriuretic peptides and inhibits the renin angiotensin aldosterone system by simultaneously inhibiting neutral endopeptidase and angiotensin-converting enzyme. METHODS: Oral omapatrilat, 10 mg/d, was administered for 8 to 9 days to three groups of eight subjects with varying degrees of renal function (CLCR values, normal > or = 80; mild to moderate impairment < 80 to > or = 30; severe impairment < 30 mL/min/1.73 mL2) and to six subjects undergoing maintenance hemodialysis. Omapatrilat and its metabolites (phenylmercaptopropionic acid, S-methylomapatrilat, S-methylphenylmercaptopropionic acid, and cyclic S-oxide-omapatrilat) were quantified in plasma by a validated liquid chromatography/mass spectrometry method. The model, Cmax or AUC(0-T) = intercept + slope x CLCR, was tested for a possible linear correlation between Cmax (peak plasma concentrations) or AUC(0-T) (area under plasma concentration versus time curve) and CLCR. RESULTS: For omapatrilat and its inactive metabolites, phenylmercaptopropionic acid, S-methylomapatrilat, and S-methylphenylmercaptopropionic acid, the median times to peak plasma concentrations (tmax) were 1.5 to 2, 2 to 3, 2.5 to 3.5, and 7 to 10 hours, respectively, and were independent of renal function. After Cmax attainment, plasma concentrations declined rapidly to about 10% of Cmax values. Cyclic S-oxide-omapatrilat, a potentially active metabolite, was undetectable at all sampling time points. Hemodialysis did not decrease circulating levels of omapatrilat. There was minimal accumulation of omapatrilat and phenylmercaptopropionic acid and moderate accumulation of the S-methylated metabolites. For omapatrilat and S-methylphenylmercaptopropionic acid, neither Cmax nor AUC(0-T) was CLCR dependent. However, AUC(0-T) for phenylmercaptopropionic acid and both the Cmax and AUC(0-T) for S-methylomapatrilat were CLCR dependent. CONCLUSIONS: The pharmacokinetics of omapatrilat, the only clinically relevant active compound studied, was independent of CLCR. For patients with reduced renal function, adjusting initial omapatrilat dose is not suggested. Hemodialysis did not significantly contribute to the clearance of omapatrilat. The long-term pharmacodynamic response to omapatrilat will dictate dose-adjustment needs.
During embryogenesis, endothelial and blood precursors are hypothesized to arise from a common progenitor, the hemangioblast. Several genes that affect the differentiation of, or are expressed early in, both the endothelial and blood lineages may in fact function at the level of the hemangioblast. For example, the zebrafish cloche mutation disrupts the differentiation of both endothelial and blood cells. The transcription factor gene scl is expressed in both endothelial and blood lineages from an early stage and can regulate their differentiation. Here we report that in zebrafish the homeobox gene hhex (previously called hex) is also expressed in endothelial and blood lineages from an early stage. We find that hhex expression in these lineages is significantly reduced in cloche mutant embryos, indicating that hhex functions downstream of cloche to regulate endothelial and blood differentiation. Ectopic expression of hhex through injection of a DNA construct leads to the premature and ectopic expression of early endothelial and blood differentiation genes such as fli1, flk1 and gata1, indicating that Hhex can positively regulate endothelial and blood differentiation. However, analysis of a hhex deficiency allele shows that hhex is not essential for early endothelial and blood differentiation, suggesting that another gene, perhaps scl, compensates for the absence of Hhex function. Furthermore, we find that hhex and scl can induce each other's expression, suggesting that these two genes cross-regulate each other during early endothelial and blood differentiation. Together, these data provide the initial framework of a pathway that can be used to further integrate the molecular events regulating hemangioblast differentiation.
Because physicians from different nations frequently acquire the use of a new medication at different times, the international exchange of experiences with the new medication is valuable in maximizing its efficacy worldwide. In recent years, many new therapeutic agents have been approved for treating psoriasis in the United States. These include the topical agent calcipotriol and the systemic agents acitretin and cyclosporine. In addition to new agents, a new therapeutic paradigm, sequential therapy, has been introduced recently. It is the hope of the authors that by sharing this paradigm and experiences with these agents in the United States, dermatologists in Japan may gain further insight into optimizing the use of these agents in the treatment of psoriasis.
Apolipoprotein (apo) B, the protein component of low-density lipoproteins (LDLs), has been under intense investigation for the last three decades. During the first decade after its initial description, most reports dealt with the physical-chemical characterization of apoB in its natural environment (i.e., intact LDL particles). A few studies dealing with attempts to elucidate the primary structure of apoB were published at this time (Deutsch et al., 1978; Bradley et al., 1980). However, most of these, in retrospect, represented heroic efforts that were doomed to failure because of the huge size and insoluble nature of apoB, once it is separated from its lipid environment. Indeed, during the 1970s, there was no universal agreement on the true molecular weight of the protein, which was not established until sometime into the second decade of apoB research (Yang et al., 1986b). The next 10 years were punctuated by breakthroughs on three different fronts in our understanding of apoB. The first exciting discovery was that apoB exists in two forms, apoB-100 and apoB-48 (Kane et al., 1980; Elovson et al., 1981). The next breakthrough was the elucidation of the primary structure of apoB-100 by a combination of cDNA cloning (Chen et al., 1986; Knott et al., 1986; Yang et al., 1986a) and direct peptide sequencing (Yang et al., 1986a, 1989). This decade of renaissance in apoB research was concluded by the elucidation of the structure of apoB-48. More important in terms of basic cellular molecular biology was the discovery of RNA editing, when apoB-48 was found to be the translation product of an edited apoB mRNA (Chen et al., 1987; Powell et al., 1987). RNA editing had just been described for a kinetoplastid protozoa the year before (Benne et al., 1986). ApoB mRNA editing was the first instance of RNA editing described in a higher eukaryote (Chan and Seeburg, 1995; Grosjean and Benne. 1998). The last decade, which brings us to the present, has been marked by studies that benefited from the breakthroughs of the 1980s. which enabled many different laboratories to examine various aspects of apoB structure, function, and expression. The function of apoB in vivo was analyzed in different animal models (e.g., transgenic animals that overexpress apoB) (Linton et al., 1993; Callow and Rubin, 1995; Veniant et al., 1997) and in knockout animals that have no functional apoB (Farese et al., 1995,1996; Huang et al., 1995,1996). Furthermore, the structure-function relationship of apoB has been investigated in mice that express site-specific apoB mutants (Callow and Rubin, 1995; Veniant et al., 1997: Borén et al., 1998). A breakthrough in a related area led to the identification and cloning of microsomal triglyceride transfer protein (MTP) (Wetterau and Zilversmitt, 1984: Wetterau et al., 1992; Sharp et al., 1993) and the demonstration that MTP is essential for apoB production (Gordon et al., 1994; Leiper et al., 1994). The absence of MTP was found to lead to the complete degradation of apoB, which harks back to an observation in 1987 that, even in the presence of MTP, a substantial proportion of newly synthesized apoB-100 undergoes intracellular degradation before secretion (Borchardt and Davis, 1987). Indeed, the intracellular degradation of apoB-100 is the major determinant of its production rate from the liver, since the transcription of apoB appears to be constitutive and not subject to much regulation (Pullinger et al., 1989). It was in 1996, almost a decade after the first description of apoB's destruction inside the cell, that the proteasome-ubiquitin pathway was found to be the major mechanism for the intracellular degradation of apoB-100 (Yeung et al., 1996). Another important development within the last decade was the cloning of APOBEC-1, the catalytic subunit of the apoB mRNA editing complex (editosome) (Teng et al., 1993). This chapter will review some of the major landmarks in apoB research in the last 10 to 15 years, concentrating mainl
We developed an algorithm based on Fourier Descriptors(FD) to match brain sections and specially aimed to pool electro-physiological data from individual animals and composite the results on a single brain. To test this algorithm, curvilinear features were first extracted from each section image of the midbrain of the rat resulting in three closed boundaries. A set of boundaries of 38 consecutive sections was then taken as standard templates for matching with any other brain sections processed in a similar way. Each section was represented by Fourier descriptors of these boundaries. Matching was done by minimizing the similarity function between an experimental brain section and the set of standard templates. This algorithm has been successfully used for the study of functional organization of AM-sound sensitive auditory neurons in the midbrain.