Refined solution structures of the Escherichia coli trp holo- and aporepressor

The solution structures of the trp-repressor from Escherichia coli in both the liganded (holo-) and unliganded (apo-) form, have been refined by restrained molecular dynamics with simulated annealing using the program XPLOR and additional experimental constraints. The ensemble of refined holorepressor structures have a root-mean-square deviation (r.m.s.d.) of 0.8 A relative to the average structure for the backbone of the dimer core (helices A, B, C, A', B', C') and 2.5 A for the helix-turn-helix DNA-binding domain (helices D and E). The corresponding values for the aporepressor are 0.9 A for the backbone of the ABC-dimer core and 3.2 A for the DE helix-turn-helix. The r.m.s.d. of the average structures from the corresponding crystal structures are 2.3 A for the holorepressor ABC core and 4.2 A for its DE region; 2.3 A for the aporepressor core and 5.5 A for its DE region. The relative disorder of the DNA-binding domain is reflected in a number of experimental parameters including substantially more rapid backbone proton exchange rates, exchange-limited relaxation times and crystallographic B-factors. The stabilizing effect of the L-Trp ligand is evident in these measurements, as it is in the higher precision of the holorepressor structure.

[The epidemiology of coronary heart disease (CHD) in 16 provinces of China. Multi-province Cooperative Group of Cardiovascular Disease Surveillance (MONICA Project)]

This paper presents the cross-section results of epidemiological survey for acute CHD event in sixteen provinces of China, using the data of Multi-province Cooperative Surveillance Study on Cardiovascular Disease (MONICA Project), 1987-1989. The results showed that there were significant differences in geographical distribution of the morbidity and of the mortality of CHD event. The northern provinces had higher rates than southern provinces. There was a positive correlation between the morbidity of CHD and the geographical altitudes. The coefficients of correlation were 0.5 and 0.57 for male and female, respectively (P < 0.05). Male had higher morbidity and mortality than female. The average sex ratio (male/female) for the morbidity was 2.20. There were higher rates in urban areas as compared with those in rural areas. There were higher case fatality rates in most provinces. The average percentage for the death out-of-hospital was 43.91% of the total number of CHD death. The percentage of death within 1 hour after onset accounted for 35.13% of the total number of CHD death. The duration from onset to death was less than 24 hours in 72.96% of the total number of CHD death. The results are of important values for the prevention, treatment and the etiologic study of CHD.

Morphometry of the liver after liver transplantation in the rat: significance of an intact arterial supply

Two models of orthotopic liver transplantation in the rat currently used are with and without reconstruction of the hepatic artery. The aim of this study was to assess the importance of the arterial blood supply to liver structure after orthotopic liver transplantation with advanced morphometric methods. Orthotopic liver transplantation was performed in male Lewis rats, of which 11 underwent reconstruction of the hepatic artery and 11 did not. A group of untreated controls (n = 5) and a group of animals with hepatic artery ligation (n = 4) were included. Eight weeks after surgery liver tissue was harvested and subjected to systematic random sampling. A point-counting method was used, volume fractions of tissue components were determined. Liver samples from rats that underwent hepatic artery reconstruction had preserved lobular architecture, and estimated bile duct (0.71% +/- 0.33% [S.D.]) and connective tissue (1.89% +/- 0.52%) volumes were not significantly different from those of controls (bile duct, 0.34% +/- 0.17%; connective tissue, 0.70% +/- 0.07%). In contrast, liver samples from rats that did not undergo hepatic artery reconstruction showed bile duct proliferation (7.19% +/- 4.83%; p < 0.05) and an increase in connective tissue volume (7.54% +/- 3.68%; p < 0.05) associated with a decrease in hepatocyte volume (controls, 87.3% +/- 0.3%; rats that underwent arterialization, 85.5% +/- 1.0%; rats that did not undergo arterialization, 73.2% +/- 8.2% [p < 0.05]). Interestingly, hepatic artery ligation had no significant effect on any parameter.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective sympathectomy of the liver: a comparison of orthotopic liver transplantation and intraportal 6-hydroxydopamine injection

1. Tissue noradrenaline (NA) levels correlate well with the extent of sympathetic innervation of that tissue. 2. In this study the distribution of NA throughout the different lobes of the rat liver was studied. The extent of sympathectomy by means of either orthotopic liver transplantation (OLT) (n = 7) or chemical denervation by intraportal administration of 6-hydroxydopamine (6-OH-DA) (n = 8) was examined. 3. In the normally innervated rat liver, NA was homogeneously distributed throughout the organ. Tissue NA was decreased both by OLT (> 99%) and 6-OH-DA (93%) (both P < 0.001 versus control). 4. Samples of the renal cortex and left ventricle were taken as reference tissues. OLT did not result in any change in reference tissue NA, however, 6-OH-DA decreased renal cortex NA by 93% and ventricular NA by 76%, respectively (both P < 0.01 versus OLT). 5. We conclude that OLT causes selective and complete hepatic sympathectomy but that 6-OH-DA causes incomplete denervation of the liver and significant denervation of other organs.

Orthotopic liver transplantation in the rat: comparison of models with and without rearterialization of the graft

A total of 112 orthotopic liver transplants with (AOLT) and without (NOLT) rearterialization were performed in 2 series using male Lewis rats as donors and recipients. In the first series, the 2-week survival rates were 5/11 (45.5%) in the NOLT group and 22/31 (71%) in the AOLT group. The difference in survival was due to operative experience, as the NOLT transplants were performed before the AOLT transplants. In the second series, the NOLT (n = 30) and AOLT transplants (n = 40) were performed in random order. No differences in 2-week survival rates were found [NOLT, 29/30 (96.7%); AOLT, 37/40 (92.5%)]. Recovery of pre-operative body weight was, however, faster in the AOLT (7 days) than in the NOLT group (14 days). In the NOLT group, elevation of serum levels of GOT (p < 0.05 vs. AOLT at 3 days) and alkaline phosphatase (p < 0.01 vs. AOLT at 3 days and 1 week; p < 0.05 at 4 weeks) were found. We conclude from our results that in OLT without prolonged graft storage, survival is a sensitive marker of operative success only in the training phase. Once operative technique has been mastered, a success rate of greater than 90% should be achieved before inclusion of the animals in further scientific studies. As the AOLT animals recover body weight faster and have less evidence of liver injury up to 4 weeks post-transplantation, one is led to the conclusion that AOLT in the rat may be a better model for use in all liver transplantation research.

Isolation and characterization of cDNAs encoding the rat pituitary gonadotropin-releasing hormone receptor

Rat pituitary cDNAs encoding the full peptide coding sequence of the rat gonadotropin-releasing hormone receptor were isolated and characterized. The deduced amino acid sequence encodes a protein of 327 residues with seven putative transmembrane domains characteristic of the family of G-protein coupled receptors. It is 95% identical at the amino acid level with the mouse gonadotropin-releasing hormone receptor. An mRNA of 4.5 Kb was identified in the rat pituitary, ovary, and testis, and in murine alpha T3 cells. In addition, a larger mRNA species of 5.0-5.5 Kb was present in these rat tissues, and a smaller mRNA species of 1.8 Kb was present in the rat pituitary and ovary, and in alpha T3 cells. The receptor mRNA levels were increased in the female rat pituitary after ovariectomy compared to levels in intact female rats.

Comparison of an endogenous protein kinase C substrate in rat aorta with rat brain MARCKS

We have compared the properties of a rat aorta-derived protein kinase C substrate (p75) with those of 80 kDa kinase C substrates from rat brain (MARCKS) and rabbit aorta (p80). Rat aortic p75 appeared to be closely related to rat brain MARCKS on the basis of: solubility in perchloric acid and trichloroacetic acid, heat stability, isoelectric point (pI approximately 4.2), overall V8 protease phosphopeptide map, and immunocrossreactivity with an antibody directed against the N-terminal domain of MARCKS. However, p75 could be distinguished from rat brain MARCKS and from the rabbit aorta-derived p80 on the basis of its consistently more rapid electrophoretic mobility in SDS-containing gels, and in terms of a unique proteolytic phosphopeptide found in MARCKS but not in aortic p75. We conclude that p75 probably belongs to the family of protein kinase C substrates represented by MARCKS, and that differences in post-translational processing (glycosylation) or mRNA processing may account for the unique properties of the p75 protein in rat aortic tissue.

[Further studies of collagen biosynthesis by hepatocytes]

Electron microscopic observation was carried out on 32 biopsies from liver and biliary system diseases. It was found that proliferative collagen in the liver was located not only in the portal space and Disse space, but also in the hepatocytes. Most of the collagen seen in hepatocytes were in the form of collagen fibrils, oriented irregularly, intermingled with the organelles and without a delimiting membrane. Therefore, the authors suggest that these collagen fibrils were produced by the hepatocytes themselves.

Interim report of Sino-Monica-Beijing for the years 1985-1989

Interim results of Sino-Monica-Beijing for the 5 year period 1985-1989 are reported. The cardiovascular disease (CVD) risk factors increased between the surveys carried out in 1984-1985 and 1988-1989, especially blood cholesterol and body mass index.

Hippocampal kindling induced paired-pulse depression in the dentate gyrus and paired-pulse facilitation in CA3

Rats received high frequency (100 Hz, 1 s) hippocampal stimulations that evoked afterdischarges (ADs) in a partial kindling model of epilepsy. Kindled rats were given 15 ADs over 3 days. Control rats received the same stimulation pulses at 0.17 Hz (low frequency stimulation, LFSs). Subsequent to in vivo stimulations, hippocampal slices were obtained from the rats and extracellular field responses were recorded in the CA3 cell layer following CA1 stratum radiatum stimulation, and in the granule cell layer of the dentate gyrus (DG) following perforant path stimulation. At the DG, the paired-pulse facilitation of the population spike was depressed in the kindled than the control group, on 1 day or 23 days post ADs/LFSs. The excitatory postsynaptic potential (EPSP) responses in DG following single or paired pulses were not different between kindled and control slices. At CA3, paired-pulse facilitation of both the population spike and the population EPSP was increased in the kindled compared to the control group.

Molecular cloning of a complementary deoxyribonucleic acid encoding the thyrotropin-releasing hormone receptor and regulation of its messenger ribonucleic acid in rat GH cells

Rat pituitary GH cells have been used extensively to study the biochemical actions of TRH on lactotropic cells. To investigate the structure and regulation of the rat TRH receptor (rTRHR), we have cloned its cDNA from GH4C1 cells. Using the polymerase chain reaction with degenerate primers and pools of cloned cDNAs from a GH4C1 cDNA library, a fragment sharing high similarity to the mouse thyrotrope TRHR (mTRHR) was identified. Conventional library screening with this fragment was used to isolate a single cDNA. mRNA synthesized in vitro from this cDNA was injected into Xenopus oocytes, and a characteristic conductance response to TRH was detected by voltage clamp recording. DNA sequence analysis revealed a molecule of 412 amino acid residues, with 96% similarity to the mTRHR. However, in contrast to the mTRHR, the rTRHR had an additional 19 amino acid residues at its carboxy-terminus. A mRNA of about 4 kilobases was identified in GH3 cells. Regulation of the rTRHR mRNA concentration was studied in GH3 cells. Steady state rTRHR mRNA levels were decreased to 30% of the control level by incubation with TRH for 48 h and increased 4-fold by incubation with dexamethasone for 12 h. Southern blot analysis of genomic DNA from GH3 cells gave a simple banding pattern consistent with a single copy gene. We conclude that the rTRHR shares high primary sequence similarity to the mTRHR, but the rTRHR has an extension of 19 amino acids at its carboxy-terminus, which is lacking in the mTRHR.

A statistical analysis of phase aberration correction using image quality factors in coherent imaging systems

A fundamental analysis of phase aberration correction techniques which use speckle brightness-based image equality factors (QFs) to iteratively reduce phase errors is presented. Phase aberration arises from the spatial inhomogeneity of acoustic velocity in human tissue and degrades the performance of diagnostic ultrasonic imaging systems. A theoretical analysis is presented indicating that the mean speckle brightness decreases with root-mean-square (RMS) phase error. A general definition of QFs is given using the probability of error as a criterion of performance. The QF is optimized through minimization of the probability of error under different conditions. The analysis provides a theoretical framework for the current correction technique using QFs under a variety of conditions, and is a useful tool to evaluate new QFs and correction techniques.

Effects of hippocampal kindling on paired-pulse response in CA1 in vitro

Kindled rats were given high-frequency stimulations delivered to hippocampal CA1 on one side to induce afterdischarges (ADs). Control rats received the same number of pulses of a similar intensity at 0.17 Hz (low-frequency stimulations (LFSs)). On 1-2 days or on 21-23 days after fifteen ADs/LFSs (delivered hourly, 5 times a day over 3 days), hippocampal slices were prepared and incubated in vitro, with the experimenter blind to the previous history of stimulation of the rat. Extracellular responses following single or paired-pulse stimulation of the Schaffer collaterals (stratum radiatum) were recorded at the CA1 cell layer in vitro, and analyzed as population excitatory postsynaptic potentials (EPSPs) and population spikes. At 1.5, 2 or 4 times the response threshold, and on either day 1 or day 23 after the last AD/LFS, the paired-pulse response at interpulse intervals of 30-200 ms was significantly larger for the kindled group of slices than for the control group (ANOVA, typically P less than 0.0001), for either the population spike or the population EPSP. Stimulus thresholds for the evoked response did not differ between kindled and control group of slices. The population EPSP and spike in response to a single pulse were enhanced (as compared to the control group) on day 1 but not on day 23 after kindling. The facilitation of paired-pulse response may be interpreted as caused by a decrease in postsynaptic (and possibly presynaptic) inhibition in the hippocampal CA1 region, which persisted to at least 3 weeks after hippocampal kindling.

Characterization of the purified rat heart plasma membrane Ca2+/Mg2+ ATPase

The purified Ca2+/Mg2+ ATPase from rat heart plasma membrane was activated by Ca2+ and Mg2+ with Ka values of 1.47 mM and 2.51 mM, respectively; other divalent cations also activated the enzyme but to a lesser extent. Divalent cations like Cu2+, Zn2+, Ni2+, Cd2+ were potent inhibitors of the enzyme activity in the presence of Ca2+ or Mg2+ whereas Na+, K+ or HCO3- did not affect the Ca2+/Mg2+ ATPase activity; the pH optima was 8.5. The enzyme hydrolyzed ATP with a Km of 0.34 mM for Ca2+ ATPase and 0.48 mM for Mg2+ ATPase; various nucleoside triphosphate such as ITP, CTP, GTP, and UTP were also hydrolyzed. Phospholipase A and C as well as neuraminidase decreased the Ca2+/Mg2+ ATPase activity whereas phospholipase D was ineffective. The purified Ca2+/Mg2+ ATPase was found to bind ATP-r-35S with two affinities; the KD values were 50.9 +/- 0.8 and 1160 +/- 198 nM and the Bmax values were 8.71 +/- 0.16 and 145 +/- 9.7 nmol/mg protein for high and low affinity sites, respectively. Treatment of the enzyme preparation with phospholipases and neuraminidase did not affect the ATP-r-35S binding. Ca2+ was also found to bind with Ca2+/Mg2+ ATPase with a KD of 0.384 mM and a Bmax of 1.85 mumol/mg protein; Ni2+, Mn2+, Zn2+ at 1 mM concentrations inhibited the Ca2+ binding but Mg2+ and verapamil were without effect. Phospholipase A and neuraminidase decreased the Ca2+ binding by 20-30%; this indicated that Ca2+ binding with the purified enzyme may be partly due to the phospholipids and sialic acid residues associated with the enzyme. These results show that the purified Ca2+/Mg2+ ATPase is a Ca2+ binding glycoprotein having two binding sites for ATP. Furthermore, this study suggests that phospholipids associated with purified Ca2+/Mg2+ ATPase are required for maximal activity.

Purification and composition of Ca2+/Mg2+ ATPase from rat heart plasma membrane

The Ca2+/Mg2+ ATPase, which is activated by millimolar concentrations of Ca2+ or Mg2+, was solubilized from rat heart plasma membrane by employing lysophosphatidylcholine, CHAPS, NaI, EDTA and Tris-HCl at pH 7.4. The enzyme was purified by sucrose density gradient, Affi-Gel Blue column and Sepharose 6B column chromatography. The purified enzyme was seen as a single peptide band in the sodium dodecyl sulfate polyacrylamide gel electrophoresis with a molecular weight of about 90,000. The apparent molecular weight of the holoenzyme as determined under non-dissociating conditions by gel filtration on Sepharose 6B column was about 180,000 indicating two subunits. The enzyme was insensitive to ouabain, verapamil, vanadate, oligomycin, N,N-dicyclohexylcarbodiimide and NaN3, but was markedly inhibited by 20 microM gramicidin S and 50 microM trifluoperazine. Analysis of the purified Ca2+/Mg2+ ATPase revealed the presence of 17 amino acids where leucine, glutamic acid and aspartic acid were the major components and histidine, cysteine and methionine were the minor components. The purified enzyme was associated with 19.7 mumol phospholipid/mg protein which was 60 times higher than the phospholipid content in plasma membrane. The cholesterol content in the purified enzyme preparation was 0.75 mumol/mg protein and this represented an 8-fold enrichment over plasma membrane. The glycoprotein nature of the enzyme was evident from the positive periodic acid-Schiff staining of the purified Ca2+/Mg2+ ATPase in the sodium dodecyl sulfate polyacrylamide gel. The polysaccharide content of the enzyme was enriched 8-fold over plasma membrane; neuraminidase treatment decreased the polysaccharide content. Concanavalin A prevented the ATP-dependent inactivation of the purified Ca2+/Mg2+ ATPase and was found to bind to the purified enzyme with a KD of 576 nM and Bmax of 4.52 nmol/mg protein. The results indicate that Ca2+/Mg2+ ATPase is a glycoprotein and contains a large amount of lipids.

Prostaglandin protects against bile salt induced increases in proton permeation of duodenal brush border membrane

A direct protective action of prostaglandin on luminal cell membranes was investigated by preincubating rabbit duodenal brush border membrane vesicles with prostaglandin E2 (PGE2) before incubation with bile salts. Membrane perturbation was assessed by measuring the net proton permeability (Pnet). Bile salts (deoxycholate, glycodeoxycholate, and taurodeoxycholate; 0.1-1.0 mmol/l) resulted in concentration dependent increases in Pnet: from (mean (SE] 5.42 (0.17) (n = 20) to 8.44 (0.24) x 10(-4) (n = 13) cm/s with 0.5 mmol/l deoxycholate. PGE2, 10(-8)-10(-6) mol/l, when added alone had no effect on Pnet: 5.41 (0.21) x 10(-4) (n = 14) cm/s with 10(-6) M PGE2. When duodenal brush border membranes were preincubated with PGE2, 10(-7)-10(-6) mol/l, however, the bile salt induced increase in Pnet was significantly reduced: 7.22 (0.18) x 10(-4) (n = 13) cm/s with 10(-7) mol/l PGE2 and 0.5 mmol/l deoxycholate. These findings indicate that PGE2 exerts a direct protective action on duodenal luminal membranes.

[Comparison of Spatholobus suberectus Dum, Euonymus alatus (Thunb.) Sieb. and Eupolyphaga sinensis Walker on regulation of plasma lipid]

The Spatholobus suberectus (SS) of hexue type, the Euonymus alatus (EA) of huoxue type and the Eupolyphaga sinensis (ES) of poxue type were selected and their influence on plasma lipid in the experimental hyperlipidemia quails was observed. The ES could raise plasma HDL-C/TC ratio and increase LCAT activity. The SS could raise plasma HDL2-C/HDL3-C ratio. The effect of EA on plasma HDL-C/TC, HDL2-C/HDL3-C and LCAT levels was between SS and ES. All the three huoxue huayu Chinese drugs could lower plasma HDL3-C level and slow down the progress of atherosclerosis to a certain degree. The above-mentioned results show that certain orders exist between the action range of huoxue huayu drugs and their effect on regulating plasma lipid.

Comparisons of image quality factors for phase aberration correction with diffuse and point targets: theory and experiments

The use of several alternative image-brightness-based quality factors for phase aberration correction with diffuse and point targets in coherent ultrasonic imaging systems is explored. The factors are similar to the sharpness functions proposed by R.A. Muller et al. (1974) for incoherent imaging systems. Different region of interest (ROI) sizes are used to compare the quality factors. Good agreement is found between theoretical analysis, computer simulations, and phantom experiments. For a point target, the mean of the magnitude of echo signals is inferior to the other studied quality factors in correcting phase aberration. All of the quality factors studied are similar in their ability to correct phase errors for diffuse target images.

[Ultrastructural study of moniliformin-induced lesions on the myocardium of rats and mice]

Effects of moniliformin on the ultrastructure of the myocardium of mice and rats were studied. Mice were given moniliformin orally at the dosage of 29.46 mg/kg. One hour later lesions of the mitochondria of the myocardial cells were found which became more severe 2-3 hours later. Ultrastructural lesions were also observed in the myofibrils and sarcolemma. Rats were given moniliformin orally at the dosage of 6 mg/kg once daily for 56 days. Lesions of the mitochondria and myofibrils were relatively mild. Myocardiac specimens taken 21 days after toxin administration, lesions of the sarcolemma became more obvious. Various amounts of collagen were produced by the myocardiac cells. These moniliformin-induced lesions were similar to the ultrastructural changes in the myocardium of patients with Keshan disease. Our findings indicate that there may be a close and important relationship between moniliformin intoxication and Keshan disease.