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S L Zhou

Publications and source records attributed to S L Zhou.

At least 19 recordsLinked to original sources
PubMed2001

Experimental investigation on moving chemical reaction boundary theory for weak-acid-strong-base system with background electrolyte KCl in large concentration.

In this report, the moving chemical reaction boundary (MCRB) was formed with the weak acid of acetic acid (HAc) and the strong alkali of NaOH, coupled with the excess of background electrolyte KCl. The experiments were compared with the predictions by the moving chemical reaction boundary equation (MCRBE). It is very interesting that (1) the experimental results are in good agreement with the predictions with the original MCRBE if the MCRB is an anodic moving boundary, (2) however, the experiments are extremely far away from the predictions with the original MCRBE if a cathodic moving boundary. Hence, the original MCRBE must be corrected under the later situation of cathodic moving MCRB. The corrected MCRBE was well quantitatively proved to be valid for the cathodic moving MNRB formed with the same electrolytes of HAc, NaOH and KCl.

Acids↗
PubMed2001

Corrections to moving chemical reaction boundary equation for weak reactive electrolytes under the existence of background electrolyte KCl in large concentrations.

In this report, the moving chemical reaction boundary (MCRB) was formed by the weak reaction electrolytes of NH3.H2O and CH3COOH under the existence of background electrolyte KCl in large concentrations, the experiments were compared with the predictions by the moving chemical reaction boundary equation (MCRBE) for weak reactive electrolytes. It was found that the experimental results are far from the predictions with the MCRBE. So the MCRBEs must be corrected under the given experimental conditions. The corrected MCRBEs are given for the MCRB formed with weak reactive electrolytes coupled with KCl at high concentrations.

Electrolytes↗
PubMed2000

Experimental study on moving neutralization reaction boundary created with the strong reactive electrolytes of HCl and NaOH in agarose gel.

In this paper, a moving neutralization reaction boundary (MNRB) is created with the strong reactive electrolytes of HCl and NaOH in agarose gel. The motions of the MNRB are investigated and compared with the predictions with the theory of the moving chemical reaction boundary (MCRB). The results show that, under appreciate experimental conditions, the experiments on the MNRB are exactly in coincidence with the predictions with the MCRB theory. Thus, the results excellently demonstrate that the MCRB theory is valid for the MNRB formed with the strong reactive electrolytes of HCl and NaOH. Additionally, it is, as discussed in this paper, imperative to develop a method to obtain ionic mobility at different temperatures and ionic strengths, in order to investigate the movements of the MCRB more efficiently.

Electrolytes↗
PubMed1998

Ethanol up-regulates fatty acid uptake and plasma membrane expression and export of mitochondrial aspartate aminotransferase in HepG2 cells.

To explain the increased plasma mitochondrial aspartate aminotransferase (mAspAT) observed in alcoholics, we cultured HepG2 hepatoma cells in ethanol. Acute (24 hour) exposure to 0, 20, 40, or 80 mmol/L ethanol produced a dose-dependent (r = .98) increase in mAspAT messenger RNA (mRNA) of < or = thirteen-fold, with no significant change in the cellular content of mAspAT or of several other enzymes. The recovery of mAspAT in the medium over 24 hours of ethanol exposure correlated with both ethanol concentration and with mAspAT mRNA (r = .90), reaching 808% of cellular enzyme content/24 hours at 80 mmol/L. Recovery of all other enzymes studied was < or = 20% of cellular content and unaffected by ethanol. Plasma membrane mAspAT content also correlated with mAspAT mRNA (r = .96) and mitochondrial levels were unchanged. No mitochondrial morphologic abnormalities were observed at any ethanol concentration studied. In cells cultured chronically at 0 to 80 mmol/L ethanol, fatty acid uptake Vmax increased in parallel with plasma membrane expression of mAspAT (r = .98). Cellular triglyceride content was highly correlated with Vmax. Thus, the data suggest that: 1) the increased plasma mAspAT observed in alcoholics may reflect pharmacologic upregulation of mAspAT mRNA and of mAspAT synthesis by ethanol; and 2) increased mAspAT-mediated fatty acid uptake may contribute to alcoholic fatty liver.

Aspartate Aminotransferases↗
PubMed1997

Uptake of long chain free fatty acids is selectively up-regulated in adipocytes of Zucker rats with genetic obesity and non-insulin-dependent diabetes mellitus.

To examine whether fatty acid transport is abnormal in obesity, the kinetics of [3H]oleate uptake by hepatocytes, cardiac myocytes, and adipocytes from adult male Wistar (+/+), Zucker lean (fa/+) and fatty (fa/fa), and Zucker diabetic fatty (ZDF) rats were studied. A tissue-specific increase in oleate uptake was found in fa/fa and ZDF adipocytes, in which the Vmax was increased 9-fold (p < 0.005) and 13-fold (p < 0.001), respectively. This increase greatly exceeded the 2-fold increase in the surface area of adipocytes from obese animals, and did not result from trans-stimulation secondary to increased lipolysis. Adipocyte tumor necrosis factor-alpha mRNA levels, assayed by Northern hybridization, increased in the order +/+ < fa/fa < ZDF. Oleate uptake was also studied in adipocytes from 20-24-day-old male +/+, fa/+, and fa/fa weanlings. These animals were not obese, and had equivalent plasma fatty acid and glucose levels. Tumor necrosis factor-alpha mRNA levels in +/+ and fa/fa cells also were similar. Nevertheless, Vmax was increased 2.9-fold (p < 0.005) in fa/fa compared +/+ cells. These studies indicate 1) that regulation of fatty acid uptake is tissue-specific and 2) that up-regulation of adipocyte fatty acid uptake is an early event in Zucker fa/fa rats. These findings are independent of the role of any particular fatty acid transporter. Adipocyte mRNA levels of three putative transporters, mitochondrial aspartate aminotransferase, fatty acid translocase, and fatty acid transporting protein (FATP) were also determined; mitochondrial aspartate aminotransferase and FATP mRNAs correlated strongly with fatty acid uptake.

Adipocytes↗
PubMed1996

Characterization of membrane transport processes: lessons from the study of BSP, bilirubin, and fatty acid uptake.

Recent efforts to identify plasma membrane transporters mediating the selective uptake of specific classes of organic anions have employed expression cloning techniques. The transporters identified by these procedures have, almost without exception, differed from putative transporters identified earlier by classical methods. In this review, the classical and molecular approaches to the identification of membrane transporters are examined and compared, with particular attention paid to the results obtained by each with respect to sulfobromophthalein, bilirubin, and fatty acid transport. The classical approach requires the initial identification and purification of a candidate transport protein, proof of its function as a transporter by antibody inhibition or liposome reconstitution studies, and following the cloning of its cDNA, genetic expression in transfected mammalian cells or in Xenopus laevis oocytes. Expression cloning affords more rapid identification of proteins which (by definition) influence uptake, avoids several potential artifacts (e.g., of conventional cDNA library screening techniques), and yields rapid access to sequence information and derived structural characteristics. However, it is ultimately necessary to express and purify the recombinant protein product, produce antibodies against synthetic peptides and/or the purified recombinant protein, use the antibodies to identify the subcellular location of the cloned protein, demonstrate that the protein binds the ligand of interest, and document that the protein mediates a facilitated process with the characteristics of the one under study. Hence, the two approaches ultimately require similar efforts. It is argued that the different putative BSP/bilirubin and fatty acid transporters identified by the two approaches may mediate different parallel transport pathways.

Animals↗
PubMed1996

Oleate uptake by isolated hepatocytes and the perfused rat liver is competitively inhibited by palmitate.

Competition for uptake between long-chain free fatty acids has been difficult to document, because there has been no algorithm for computing unbound concentrations of two fatty acids simultaneously in solution with albumin. We modified an iterative procedure to permit this computation and studied initial [3H]oleate uptake by isolated hepatocytes and steady-state uptake by the single-pass perfused rat liver from 600 microM bovine serum albumin solutions containing various concentrations of oleate in the presence and absence of palmitate. In both systems, the Michaelis-Menten constant was significantly higher in the presence of palmitate than in its absence, whereas the maximal reaction velocity was unaltered, indicating competitive inhibition. In additional experiments employing the multiple transhepatic indicator-dilution technique, the influx rate constant and permeability-surface area product for oleate influx were significantly reduced by palmitate, confirming that the competition observed in the conventional perfused liver studies was at the influx step. Long-chain fatty acid uptake has now been shown to exhibit all the kinetic properties of facilitated transport and cannot be attributed solely to passive diffusion.

Animals↗
PubMed1995

3T3 fibroblasts transfected with a cDNA for mitochondrial aspartate aminotransferase express plasma membrane fatty acid-binding protein and saturable fatty acid uptake.

To explore the relationship between mitochondrial aspartate aminotransferase (mAspAT; EC 2.6.1.1) and plasma membrane fatty acid-binding protein (FABPpm) and their role in cellular fatty acid uptake, 3T3 fibroblasts were cotransfected with plasmid pMAAT2, containing a full-length mAspAT cDNA downstream of a Zn(2+)-inducible metallothionein promoter, and pFR400, which conveys methotrexate resistance. Transfectants were selected in methotrexate, cloned, and exposed to increasing methotrexate concentrations to induce gene amplification. Stably transfected clones were characterized by Southern blotting; those with highest copy numbers of pFR400 alone (pFR400) or pFR400 and pMAAT2 (pFR400/pMAAT2) were expanded for further study. [3H]Oleate uptake was measured in medium containing 500 microM bovine serum albumin and 125-1000 microM total oleate (unbound oleate, 18-420 nM) and consisted of saturable and nonsaturable components. pFR400/pMAAT2 cells exhibited no increase in the rate constant for nonsaturable oleate uptake or in the uptake rate of [14C]octanoate under any conditions. By contrast, Vmax (fmol/sec per 50,000 cells) of the saturable oleate uptake component increased 3.5-fold in pFR400/pMAAT2 cells compared to pFR400, with a further 3.2-fold increase in the presence of Zn2+. Zn2+ had no effect in pFR400 controls (P > 0.5). The overall increase in Vmax between pFR400 and pFR400/pMAAT2 in the presence of Zn2+ was 10.4-fold (P < 0.01) and was highly correlated (r = 0.99) with expression of FABPpm in plasma membranes as determined by Western blotting. Neither untransfected 3T3 nor pFR400 cells expressed cell surface FABPpm detectable by immunofluorescence. By contrast, plasma membrane immunofluorescence was detected in pFR400/pMAAT2 cells, especially if cultured in 100 microM Zn2+. The data support the dual hypotheses that mAspAT and FABPpm are identical and mediate saturable long-chain free fatty acid uptake.

3T3 Cells↗
PubMed1995

Mitochondrial aspartate aminotransferase expressed on the surface of 3T3-L1 adipocytes mediates saturable fatty acid uptake.

Physicochemical studies have suggested that the 43-kDa plasma membrane fatty acid binding protein (FABPpm) is closely related to the mitochondrial isoform of aspartate aminotransferase (mAspAT). In the present studies, mAspAT was not detected immunohistochemically or by immunoblotting in plasma membranes of proliferating 3T3-L1 fibroblasts. During controlled differentiation to an adipocyte phenotype, mAspAT became detectable by the second day of confluent growth, prior to accumulation of visible lipid droplets, and was strongly expressed in 8-day differentiated 3T3-L1 adipocytes. The pattern of expression paralleled the previously reported expression both of FABPpm and of the Vmax for saturable uptake of long chain free fatty acids. As with anti-FABPpm, antibodies to mAspAT selectively inhibited the uptake of [3H]-oleate in 3T3-L1 adipocytes but not in fibroblasts, while having no effect on uptake of either 2-deoxyglucose or the medium chain fatty acid octanoate. Preabsorption of anti-FABPpm with mAspAT, or of anti-mAspAT with FABPpm, abolished immunopositivity in immunohistochemical and immunoblotting studies, as well as the ability of either antibody to inhibit [3H]-oleate uptake. These studies provide strong biologic evidence for the identity of FABPpm and mAspAT, and for the hypothesis that FABPpm/mAspAT mediates the uptake of long chain free fatty acids.

3T3 Cells↗
PubMed1994

Constitutive expression of a saturable transport system for non-esterified fatty acids in Xenopus laevis oocytes.

In the presence of 150 microM BSA, uptake of [3H]oleate by Xenopus laevis oocytes was a saturable function of the unbound oleate concentration (Vmax. 110 +/- 4 pmol/h per oocyte; Km 193 +/- 11 nM unbound oleate). Oleate uptake was three orders of magnitude faster than that of another test substance, [35S]bromosulphophthalein, and was competitively inhibited by 55 nM unbound palmitate (Vmax. 111 +/- 14 pmol/h per oocyte; Km 424 +/- 63 nM unbound oleate) (P < 0.01). Oleate uptake was also inhibited by antibodies to a 43 kDa rat liver plasma-membrane fatty acid-binding protein, a putative transporter of long-chain fatty acids in mammalian cells; uptake of the medium-chain fatty acid [14C]octanoate was unaffected. Immunofluorescence and immunoblotting demonstrated that the antiserum reacted with a single 43 kDa protein on the oocyte surface. Hence a protein related to the mammalian plasma-membrane fatty acid-binding protein may play a role in saturable uptake of long-chain fatty acids by Xenopus oocytes.

Animals↗
PubMed1994

The hepatocellular uptake of free fatty acids is selectively preserved during starvation.

BACKGROUND/AIMS: The liver loses protein during fasting. This study sought to determine if hepatic protein loss during fasting selectively preserves functions important to survival such as uptake of fatty acids, which are major energy substrates in that condition. METHODS: Initial [3H]oleate uptake and efflux rates in hepatocytes from starved (for 48 hours) and fed male rats were measured in media containing 250 mumol/L albumin at oleate/albumin ratios of 0.2:1-2:1. Uptake rates of sulfobromophthalein, taurocholate, and glucose were also determined. RESULTS: Initial oleate uptake rate was saturable with respect to unbound oleate concentration. Maximum initial velocity expressed per cell number did not differ between fasted and fed animals, but measured cell volume and estimated surface area were decreased in starved vs. fed hepatocytes (921 +/- 21 vs. 1623 +/- 58 microns2, respectively; P < 0.001). Consequently, when expressed per surface area, maximum initial velocity was greater in starved cells (17 +/- 3 vs. 10 +/- 2 [pmol.min-1.micron2] x 10(-7); P < 0.02). Expressed similarly, oleate efflux was also greater from starved hepatocytes and was inhibited by an antibody to plasma membrane fatty acid binding protein (FABPpm). FABPpm concentration per unit area of plasma membrane also increased in starved hepatocytes (P < 0.05). By contrast, uptake rates of sulfobromophthalein, taurocholate, and glucose by starved hepatocytes were decreased when expressed per cell number and unchanged per unit area. CONCLUSIONS: During fasting, the hepatocellular uptake mechanism for oleate is selectively preserved compared with those for sulfobromophthalein, taurocholate, or glucose.

Animals↗
PubMed1994

Early hair-cell degeneration in the extreme apex of the guinea pig cochlea.

Guinea pigs, aged from 3 weeks before term to 31 weeks after birth, were prepared for scanning electron microscopy. Examination of the extreme apex of the cochlea showed apparently pathological hair cells, even 3 weeks before term. The pathologies included loss and fusion of stereocilia, and the formation of giant stereocilia. The pathologies were most prevalent on row 3 of outer hair cells, declining to outer hair cell rows 2 and 1, with the inner hair cells being least affected. The abnormalities increased with time, increasing rapidly over the first few weeks of life, and more slowly thereafter. It is suggested that early degeneration in the extreme cochlear apex forms a novel model for spontaneous hair cell degeneration, with applicability to other types of spontaneous hair cell degeneration.

Animals↗
PubMed1994

[Chinese strain of hepatitis D virus: molecular cloning and sequencing, and the significance of its genome divergence].

The hepatitis D virus (HDV) obtained from a chronic asymptomatic HDV/HBsAg carrier (SZ 93) in Sichuan province was cloned with 1,684 nucleotides in full-length genome by reverse transcription-PCR. Comparison of SZ 93 with those obtained from different geographic area: i.e., Italia, United States, British, Nauru, Taiwan, Netherland, showed 81.8%-95.4% homology in nucleotide sequence of whole genome, 88.9%-96.1% homology in nucleotide sequence of HDAg-coding region, and 86.4%-93.0% homology in amino acid sequence of HDAg protein. Also, another isolate (SZ 92) obtained from a chronic severe hepatitis patient in Sichuan was cloned with HDAg-coding region. There were some mutations in SZ 92 compared with SZ 93 as well as the other clones mentioned above. The meaning for the genome divergence of HDV SZ 93 and SZ 92 was discussed.

Adult↗
PubMed1994

Recent studies of the cellular uptake of long chain free fatty acids.

Over the last 12 years, we and others have demonstrated that fatty acid uptake is not simply a passive, diffusive process, but an interesting, facilitated mechanism the regulation of which has specific implications for disease. This work also tells another tale. Our earliest experiments were called "squirt studies" by our technician because they involved "squirting" a bolus of labelled metabolite intravenously into one limb of the subject and drawing blood samples from another. These studies were conducted in patients, and later in intact animals. From these we moved progressively to investigations in isolated perfused organs, isolated cells, and sub-cellular organelles and membrane vesicles; to the chemistry of membrane proteins, and most recently, to studies combining recombinant DNA technology with cellular biologic studies of controlled differentiation in tissue culture (Figure 5). The work has been not only a continuing process of scientific investigation but, for the investigators, an on-going process of self-education.

Animals↗
PubMed1994

von Willebrand factor binding to collagen in patients with end-stage renal disease.

Bleeding abnormalities are common in patients with end-stage renal disease (ESRD). Although von Willebrand factor (vWF) abnormalities have been suspected in patients with ESRD, none have been clearly defined. Because vWF function is related to its collagen-binding capacity, we investigated whether this parameter might be altered in patients with ESRD. We measured vWF binding to type III collagen and levels of vWF antigen and ristocetin cofactor in 20 patients undergoing hemodialysis before and after routine hemodialysis sessions, in 10 patients with ESRD who had not previously undergone dialysis, and in 22 healthy, nonsmoking persons who served as controls. We found significant increases of vWF antigen levels in all patients with ESRD (undialyzed: mean, 6.4 +/- 3.0 U/ml, p < 0.001; before dialysis: mean, 5.1 +/- 4.0 U/ml, p < 0.001; after dialysis: mean, 4.8 +/- 3.4 U/ml, versus 0.81 +/- 0.26 U/ml in controls, p < 0.001). The ristocetin cofactor levels were increased in the patients who had not undergone dialysis (mean, 1.30 +/- 1.26 U/ml, p = 0.04), whereas both before and after hemodialysis groups (means, 0.71 U/ml and 0.75 U/ml, respectively) were not significantly different from controls (mean, 0.72 +/- 0.30 U/ml, p = 0.96 and p = 0.8, respectively). Patients with ESRD who had not undergone dialysis showed no difference in vWF binding to collagen (mean, 1.21 +/- 0.63 U/ml) compared with the control group (mean, 1.16 +/- 0.13).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Avian auditory pathways show met-enkephalin-like immunoreactivity.

Pathways associated with a recently defined region of the avian auditory thalamus, the shell of the nucleus ovoidalis (Ov), were examined for met-enkephalin immunoreactivity. The presence of enkephalin-like immunoreactive (ELI) perikarya within the medial margin of the inferior colliculus (ICM), afferent to the Ov shell, implicated ICM as a source of ELI fibers within the Ov shell and tract. The shell also contained ELI perikarya and its targets, including the ventromedial hypothalamus and caudoventral paleostriatal complex, were characterized by ELI fields. These data suggest that enkephalinergic auditory pathways, in parallel with traditionally recognized auditory projections, target regions of the avian basal forebrain.

Animals↗