Aqueous construction of raspberry-like ZIF-8 hierarchical structures with enhanced superhydrophobic performance

Materials with super-wetting ability have attracted wide attention from both academia and industry due to their great potential applications. A straightforward and versatile route was proposed for the large-scale synthesis of a monodisperse raspberry-like metal-organic framework (ZIF-8) using zinc nitrate as a zinc source and dimethylimidazole as an organic ligand in aqueous solution. After hydrophobic treatment with hexadecyltrimethoxysilane, the ethanolic suspension of three-dimensional raspberry-like ZIF-8 showed excellent superhydrophobic properties. Furthermore, commercial adhesives were used to blend with the suspension to improve the bonding strength to different substrates. These surfaces retained their water resistance after 50 finger-wipe cycles, 40 sandpaper abrasions and knife scratches. Moreover, the prepared hydrophobic surface can withstand the impact of water flow for 10 minutes. The formulations developed can be used for superhydrophobic coating applications on different substrate surfaces such as aluminum foil, glass, paper and cotton.

[A multicenter randomized controlled study of bismuth-containing quadruple therapy followed by Jing-Hua-Wei-Kang in the treatment of patients newly diagnosed with Helicobacter pylori infection and dyspepsia]

Objective: To investigate the Helicobacter pylori (H. pylori) eradication rate and improvement of dyspepsia in patients who were newly diagnosed with H. pylori infection and dyspepsia and treated by bismuth-containing quadruple therapy followed by Jing-Hua-Wei-Kang(JHWK). Methods: Patients who were newly diagnosed with dyspepsia and H. pylori infection and treated in 16 medical centers in China between December 1, 2017 and September 30, 2019 were randomly divided into two groups. The experimental group received bismuth-containing quadruple therapy (esomeprazole+amoxicillin+furazolidone+colloidal bismuth pectin capsule, 14 days), followed by JHWK (30 days), and the course of treatment was 44 days in total. In the control group, the administration regimen was bismuth-containing quadruple therapy (esomeprazole+amoxicillin+furazolidone+colloidal bismuth pectin capsule, 14 days). The main outcome measure was H. pylori eradication rate, while the secondary outcome measures were dyspepsia symptom changes and adverse events during the treatment and the 1st month after treatment. Results: A total of 1 054 patients were included in the study. There were 522 cases enrolled in the experimental group, including 224(42.91%) men and 298(57.09%) women, and the age was 53(26, 73) years old; 532 cases enrolled in the control group, including 221(41.54%) men and 311(58.46%) women, and the age was 46(22, 71) years old. Based on PP analysis, it was found that the H. pylori eradication rate in the experimental group was significantly higher than those in the control group (93.85% vs 87.88%, P=0.001). In the group of all enrolled patients, the symptom dyspepsia after H. pylori eradication was significantly improved compared with that before treatment [4(4, 7) vs 15(10, 22), P<0.001], so was the superior and middle abdominal pain [1(1, 4) vs 4(1, 8), P<0.001], the postprandial fullness [1(1, 4) vs 4(4, 9), P<0.001], the early satiety [1(1, 1) vs 4(1, 4), P<0.001], and the heartburn [1(1, 1) vs 1(1, 4), P<0.001]. The symptom dyspepsia after treatment was significantly improved compared with that before treatment in the experimental, the control groups, the successful and the unsuccessful H. pylori eradication groups. The superior and middle abdominal pain after treatment was signifcantly improved than that before treatment [1(1, 2) vs 1(1, 4), P<0.001], so were the postprandial fullness [1(1, 3) vs 1(1, 4), P=0.002] and the dyspepsia[4(4, 7) VS 7(4, 10), P<0.001]. There was no statistically significant difference in the incidence of adverse events between the experimental group and the control group (1.34% vs 0.38%, P=0.09). Conclusions: Compared with bismuth-containing quadruple therapy, bismuth-containing quadruple therapy followed by JHWK significantly improves the H. pylori eradication rate without increasing the incidence of adverse events. H. pylori eradication therapy can improve symptoms of patients with H. pylori infection and dyspepsia.

[One patient with severe phenol burn complicated with acute poisoning]

On April 26, 2018, a 55-year-old male patient with severe phenol burn complicated with acute poisoning was admitted to the Second Affiliated Hospital of Zhejiang University School of Medicine. The patient quickly developed the symptoms of central nervous system including blurred consciousness and restlessness, anuria, and respiratory failure. After self-rescue before admission and a series of measures in hospital including wound decontamination to reduce phenol absorption, rapid massive infusion and hemodialysis+ hemoperfusion, continuous renal replacement therapy for speeding up phenol excretion and organ function maintenance, the poisoning symptoms were effectively alleviated, and the patient was finally rescued successfully and discharged on post injury day 29. This case suggests that early hemodialysis combined with hemoperfusion and continuous renal replacement therapy are effective methods for treating severe phenol burn complicated with acute poisoning.

Long non-coding RNA expression profile in permanent atrial fibrillation patients with rheumatic heart disease

OBJECTIVE

Atrial fibrillation (AF) is the most common type of arrhythmia, especially in rheumatic heart disease (RHD) patients. The differences in structural remodeling and electrical remodeling between the left and right atrium associated with AF in RHD patients are well known, and alterations in the expression profiles of long noncoding RNAs (lncRNAs) in the left atrium have also been investigated. However, the role of lncRNAs in the right atrium (RA) remains largely unknown.

PATIENTS AND METHODS

We identified differentially expressed lncRNAs in RA tissues of RHD patients with AF or a normal sinus rhythm (NSR) using microarray analysis. Then, we performed gene ontology (GO) and KEGG pathway analyses for functional annotation of the deregulated lncRNAs. Finally, we constructed a lncRNA-mRNA co-expression network.

RESULTS

Of the 22,829 human non-coding RNAs analyzed, a total of 1,909 long non-coding RNAs were detected. A total of 182 lncRNAs (117 downregulated and 65 upregulated) were shown to be differentially expressed (fold-change > 1.5) in AF patients compared with NSR patients. Many lncRNAs might be partially involved in an AF-related pathway.

CONCLUSIONS

AF dysregulates the expression of lncRNAs in the RA of RHD patients. These findings may be useful for exploring potential therapeutic treatments for AF in RHD patients.

Measurement of the Hall effect at nanoscale with three probes

The Hall effect and its varieties such as quantum, anomalous, and spin Hall effects provide indispensable tools for the characterization of electronic and magnetic properties of materials, metrology, and spintronics. The conventional four-probe Hall configuration is generally not amenable to measurements at nanoscale due to current shunting by the Hall electrodes. We demonstrate that Hall measurements on the nanoscale can be facilitated by the three-probe Hall configuration that avoids the shunting problem. We illustrate the efficiency of the proposed approach with anomalous Hall effect-based measurements of individual activation events during domain wall motion in magnetic films with perpendicular anisotropy.

The effect of curcumin on bladder tumor in rat model

OBJECTIVE

Bladder cancer is the most commonly malignant tumor in the urogenital tract, only next to prostate cancer with a higher incidence in China. Curcumin is the major component of curcuma longa and has multiple biological effects including anti-tumor. This study aimed to investigate the effect of curcumin on bladder cancer.

MATERIALS AND METHODS

SPF-grade Wistar rats were used for establishing bladder cancer model through injection of N-methyl-N-nitrosourea (MNU). Rats were then randomly divided into experimental, model and control group. 160 μmol/L curcumin were applied in the experimental group while model group received an equal volume of saline. General condition, morphology changes and cell cycle of bladder cancer cells were examined. Meanwhile, apoptotic proteins including Bcl-2, Bax and surviving were also measured by Western blot.

RESULTS

Model rats displayed fever, hematuria, decreased food and water intake, dispersed fur, lower body mass and decreased activity. Under microscopy, the bladder wall was thickened with the cauliflower-like lesion, in which significant necrotic and hemorrhagic lesions were found. Experimental group rats improved general condition without decrease of body mass. The only minor lesion was found without significant necrosis or hemorrhage without invasion into the muscular layer. The number of G1 phase cells was increased while S phase cell number was decreased after drug intervention, suggesting suppression of G1/S transition (p < 0.05). In curcumin-treated rats, the expression of Bcl-2 and Survivin were significantly decreased while Bax protein expression was significantly elevated (p < 0.05).

CONCLUSIONS

Curcumin can inhibit the growth and invasion of rat bladder cancer cells, possibly through the arresting of G1/S transition and subsequently increased apoptosis.

Effects of low temperature on photosynthetic characteristics in the super-high-yield hybrid rice 'Liangyoupeijiu' at the seedling stage

To elucidate the resistance of high-yield hybrid rice (Oryza sativa L.) at the seedling stage to low temperature, photosynthetic characteristics, such as membrane lipid peroxidation, fatty acid composition, and chloroplast ultrastructure, were investigated in a newly developed super-hybrid rice ('Liangyoupeijiu') and a traditional chill-sensitive hybrid rice ('Shanyou63'), with 20°C as the control condition and 10°C as the low temperature treatment. Chlorophyll content, oxygen consumption by photosystem I, and oxygen production by photosystem II in the thylakoid membrane mainly decreased under the low-temperature treatment. The malondialdehyde content of 'Liangyoupeijiu' decreased slightly, while increases in membrane lipid peroxidation were greater in 10°C-treated than in 25°C-treated 'Shanyou63' seedlings. The index of unsaturated fatty acids increased in the two cultivars, particularly in 'Liangyoupeijiu'. No severe chloroplast ultrastructure damage was observed under cold stress, but the number of osmiophilic granules in 'Shanyou63' increased rapidly. The results indicate that compared to 'Shanyou63', 'Liangyoupeijiu' is more chill-resistant at the seedling stage.

[Expression of Slit3/Robo signal pathway in mouse aortic smooth muscle cell and its impact on proliferation and migration]

OBJECTIVE

To observe the expression of neural axon guidance molecules Slit3 and Robo receptors in mouse aortic smooth muscle cell(MASMC) and investigate the effect of exogenous Slit3 protein on migration and proliferation of MASMC.

METHODS

The primary cultured MASMC were identified by immunofluorescent assay. The expression of Slit3/Robo signal pathway was detected by RT-PCR and immunocytochemical staining. MASMC were divided into 6 groups: the negative control group (DMEM medium containing bovine serum albumin 86 μg/L), Slit3 0 μg/L group (DMEM medium without Slit3), Slit3 24 μg/L group (DMEM medium containing Slit3 24 μg/L), Slit3 40 μg/L group (DMEM medium containing Slit3 40 μg/L), Slit3 80 μg/L group (DMEM medium containing Slit3 80 μg/L) and the positive control group (DMEM medium containing platelet derived growth factor 10 μg/L). The effects of exogenous Slit3 on MASMC proliferation and migration were detected by CCK-8 and scratched cells and transwell chambers respectively.

RESULTS

(1) The mRNA and protein expressions of Slit2, Slit3, Robo1 and Robo4 were detected in MASMC. mRNA level of Slit2 was lower than Slit3 (P<0.05) and there were no significant difference between mRNA level of Robo1 and Robo4. (2) The mitogenic responses of MASMC were significantly enhanced in Slit3 24 μg/L group, Slit3 40 μg/L group and Slit3 80 μg/L group compared with negative control group (1.13±0.04, 1.19±0.02, 1.18±0.08 and 0.64±0.10 respectively, all P<0.05). The mitogenic activity of MASMC was the strongest in Slit3 40 μg/L group (compared with positive control group 1.27±0.05, P>0.05). (3)The autonomous migration activity of MASMC were significantly increased in Slit3 24 μg/L group, Slit3 40 μg/L group, Slit3 80 μg/L group compared with negative control group (cell scratch width were (0.40±0.03)cm, (0.32±0.03)cm, (0.30±0.02)cm and (0.49±0.01)cm respectively, all P<0.05). The autonomous migration activity of MASMC was the strongest in Slit3 80 μg/L group (compared with positive control group (0.22±0.01)cm, P>0.05). The transmembrane migration activity of MASMC were significantly increased in Slit3 24 μg/L group, Slit3 40 μg/L group, Slit3 80 μg/L group compared with negative control group (the number of cell migration were 46.67±2.23, 65.33±3.43, 81.67±4.22 and 39.33±2.03 respectively, all P<0.05). The transmembrane migration activity of MASMC was the strongest in Slit3 80 μg/L group (compared with positive control group 84.00±2.02, P>0.05).

CONCLUSION

Slit2, Slit3, Robo1 and Robo4 were expressed in MASMC, and exogenous Slit3 could promote proliferation and migration of MASMC in vitro.

Prognostic value of ZFP36 and SOCS3 expressions in human prostate cancer

PURPOSE

ZFP36 ring finger protein (ZFP36) and the suppressor of cytokine signaling 3 (SOCS3) have been reported to, respectively, regulate NF-κB and STAT3 signaling pathways. To better understand the correlation of NF-κB and STAT3 negative regulates pathway, we have investigated the involvement of ZFP36 and SOCS3 expressions in human prostate cancer (PCa).

METHODS

In the present study, paired patient tissue microarrays were analyzed by immunohistochemistry, and the ZFP36 protein expression was quantitated as immunoreactive scores in patients with PCa. Associations between ZFP36/SOCS3 expression and various clinicopathological features and prognosis of PCa patients were statistically analyzed based on the Taylor database. Then, the functions of ZFP36 and SOCS3 in cancerous inflammation were determined using qPCR and immunohistochemistry in vitro and in vivo.

RESULTS

ZFP36 protein expression in PCa tissues was significantly lower than those in non-cancerous prostate tissues (P < 0.05). In mRNA level, ZFP36 and SOCS3 had a close correlation with each other (P < 0.01, Pearson r = 0.848), and its upregulation was both significantly associated with low Gleason score (P < 0.001 and P < 0.001, respectively), negative metastasis (P < 0.001 and P < 0.001, respectively), favorable overall survival (P < 0.001 and P < 0.05, respectively), and negative biochemical recurrence (P < 0.001 and P < 0.001, respectively). Functionally, LPS treatment could lead to the overexpression of ZFP36 and SOCS3 in vitro and vivo.

CONCLUSIONS

Our data offer the convincing evidence for the first time that the aberrant expressions of ZFP36 and SOCS3 may be involved into the progression and patients' prognosis of PCa, implying their potentials as candidate markers of this cancer.

Mid-infrared emission characteristic and energy transfer of Ho3+-doped tellurite glass sensitized by Tm 3+

We report on 2.0-microm emission characteristic and energy transfer of Ho3+-doped tellurite glass sensitized by Tm3+ upon excitation of a conventional 808 nm laser diode. The Judd-Ofelt strength parameters, spontaneous radiative transition probabilities and radiative lifetime of Ho3+ have been calculated from the absorption spectra by using the Judd-Ofelt theory. Significant enhancement of 2.0-microm emission of Ho3+ has been observed with increasing Tm3+ doping up to 0.7 mol%. The energy transfer coefficient of the forward Tm3+-->Ho3+ is approximately 17 times larger than that of the backward Tm3+<--Ho3+ energy transfer. Our result indicates that the maximum gain of 2.0-microm emission, assigned to the transition of (5)I7-->(5)I8 of Ho3+, might be achieved from the tellurite glass at the concentration of 0.5 mol% of Tm2O3 and 0.15 mol% of Ho2O3. The high gain coefficient and quantum efficiency (1.16) along with the large value of the product of the stimulated emission cross-section and the measured radiative lifetime (4.12 x 10(-27) m(2)s) of the Ho3+/Tm3+-codoped tellurite glasses might find potential applications in efficient 2.0-microm laser.

Photosynthetic and biochemical activities in flag leaves of a newly developed superhigh-yield hybrid rice (Oryza sativa) and its parents during the reproductive stage

Responses of net photosynthetic rates to intercellular CO(2) concentration (P (n)/C (i) curves) and photochemical characteristics were investigated in flag leaves of newly developed superhigh-yield hybrid rice (Oryza sativa L.) LiangYouPeiJiu (LYPJ) and its maternal PeiAi64S (PA64S) and paternal WuMang9311 (WM9311) lines grown in the field during the reproductive stage. The results showed that photosynthetic functions, such as the electron transport activities of photosystems and photophosphorylation, assessed in vivo from P (n)/C (i) curves under field conditions declined more or earlier than those obtained in vitro. The degradation of polypeptides of thylakoid membranes was slower than those for P (Ca=360) (light-saturated net photosynthetic rate measured at 360 mumol mol(-1)) and CE (carboxylation efficiency, obtained from the initial slope of the P (n)/C (i) curve). The initial inhibition of the PSII electron transport and oxygen-evolving activity induced by senescence occurred before the degradation of the oxygen-evolving complex. In comparison, LYPJ had intermediate photosynthetic functions in the early stage of leaf development, but greater photochemical activities in the mid and late stages. WM9311 showed a similar pattern of changes but lower values, and PA64S had higher values in the early stage but showed a faster rate of senescence than LYPJ. These findings implied that the hybrid LYPJ demonstrated intermediate photosynthetic activities between its parents in the early stage of leaf development, whereas it had higher photosynthetic activities than its parents in the mid and late stages, which may be responsible for its high yield.

The 3C/3D line ratio in Ni XIX: New Ab Initio theory and experimental results

We report a fully relativistic close-coupling calculation of the electron impact excitation of Ni xix to derive the 3C/3D line intensity ratio, with an uncertainty of 5%. Convergence of the calculation with respect to both channel coupling effects and the many interacting Rydberg series of resonances has been achieved. New measurements in an electron beam ion trap agree with our calculation. We show that the 3C/3D x-ray line ratio depends sensitively on both electron energy and beamwidth in an optically thin plasma. Accounting for this dependence improves the accuracy of the Ni abundance determination in astrophysical sources.

Effect of petroleum-containing wastewater irrigation on bacterial diversities and enzymatic activities in a paddy soil irrigation area

Effects of petroleum contamination on bacterial diversities and enzymatic activities in paddy soils were investigated in the Shenfu irrigation area, the largest area irrigated by oil-containing wastewater for more than 50 yr in northeastern China. Bacterial diversities were determined by conventional colony morphology typing techniques and 16S rDNA polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE). Dehydrogenase, hydrogen peroxidase, polyphenol oxidase, urease, and substrate-induced respiration (SIR) were measured to evaluate the effects of petroleum-containing wastewater irrigation on soil biochemical characteristics. Results showed that paddy soil total petroleum hydrocarbon (TPH) concentration in the irrigation area varied from 277.11 to 5213.37 mg kg(-1) dry soil. Soil TPH concentration declined along the gradient of the irrigation channel from up- to downstream. At the current pollution level, the paddy soil TPH concentration was positively correlated with the colony forming units (CFU) of aerobic heterotrophic bacteria (AHB) (r = 0.928, p < 0.001) and the genetic diversity based on DGGE profiles (r = 0.655, p < 0.05). The bacterial diversities in the soils based on colony morphotypes of AHB also increased with TPH concentration (r = 0.598), but not significant statistically (p = 0.052). Analysis of soil enzyme activities indicated a significant positive correlation between soil TPH concentration and activities of dehydrogenases (r = 0.974, p < 0.001), hydrogen peroxidases (r = 0.957, p < 0.001), polyphenol oxidases (r = 0.886, p < 0.001), and SIR (r = 0.916, p < 0.001). On the contrary, the urease activity showed a negative correlation with paddy soil TPH concentration (r = -0.814, p = 0.002), and could be used as a sensitive indicator of petroleum contamination.

Effects of cultivation on N2O emission and seasonal quantitative variations of related microbes in a temperate grassland soil

Laboratory and in situ experiments were done to investigate the influences of cultivation on temperate semi-arid grassland (for 17 years spring wheat planted once every two years without fertilisation) on soil N2O emission and quantitative variations of related soil microbes. In the laboratory (25 degrees C and soil moisture 18%), cultivation increased soil transformations of fertilizer nitrogen (100 micrograms N/g as NaNO3, urea, or as urea with dicyandiamide 1 microgram N/g). The N2O emissions from the cultivated and uncultivated soils with or without nitrogen additions were relatively low, and mainly originated from the nitrification. The soil N2O emission due to cultivation decreased somewhat upon no fertilization or NaNO3 addition, but significantly upon urea addition. The role of dicyandiamide as nitrification inhibitor was only considerable in the cultivated soil, and had small influence on decreasing N2O emission in the two soils. The influence of cultivation on soil N2O emission was also reflected by the number variations of microbes related with soil nitrogen transformation in the two soils. Compared to the uncultivated grassland, in situ ammonifiers and denitrifiers in the cultivated grassland quantitatively averagely increased, and aerobic no-symbiotic azotobacters were quantitatively similar, leading to the continued decrease of organic matter content and the decrease of N2O emission from the cultivated grassland soil.

Metabolites of Colletotrichum gloeosporioides, an endophytic fungus in Artemisia mongolica

A new antimicrobial metabolite, named colletotric acid (1), was isolated from a liquid culture of Colletotrichum gloeosporioides, an endophytic fungus colonized inside the stem of Artemisia mongolica. The structure was determined using spectroscopic methods (EIMS and FABMS,(1)H and (13)C NMR, (1)H-(1)H COSY, HMBC, and HMQC). Compound 1 inhibited the growth of Bacillus subtilis, Staphylococcusaureus, and Sarcina lutea with minimal inhibitory concentrations (MICs) of 25, 50, and 50 microg/mL, respectively, and the crop pathogenic fungus Helminthosporium sativum (MIC: 50 microg/mL).

Pattern selection induced by electroconvection in the electrodeposition of iron

The morphology of iron electrodeposit is shown to relate closely to the pH of the electrolyte solution. Macroscopically, depending on the strength of the interbranch convection, which is associated with the concentration of H3O+ in the electrolyte, the deposit morphology varies from treelike pattern to meshlike pattern and dense-branching morphology. Microscopically the deposit is ramified and dense-branching at lower concentration of H3O+, while it becomes relatively smooth and stringy at higher H3O+ concentration. The symmetry of the convective vortices on the two sides of the growing tip is observed to decide the growth behavior of the tip. We suggest that H3O+ influences the pattern formation and pattern selection in the electrodeposition of iron from FeSO4 solution by either initiating interbranch convection or changing the effective interfacial energy of the deposit and the electrolyte.

Expanded analysis of injury mortality among unionized construction workers

BACKGROUND

To evaluate the utility of expanding the number and precision of injury categories used in previous occupational mortality studies, this study reanalyzed data from four previous studies of unionized construction workers (construction laborers, ironworkers, sheet metal workers, and operating engineers), by expanding the number of injury categories from 6 to 33.

METHODS

Proportionate mortality ratios (PMRs) were computed using the distribution of deaths from the National Occupational Mortality Surveillance System, a mortality surveillance system from 28 states, as a comparison. A blue collar comparison group was also used in additional analyses to adjust for socioeconomic and other factors.

RESULTS

This reanalysis identified significantly elevated PMRs in at least one of the four worker groups for falls, motor vehicle crashes, machinery incidents, electrocutions, being struck by falling objects, being struck by flying objects, explosions, suffocation, and water transport incidents. Limiting the comparison population to deaths among blue collar workers did not change the results substantially.

CONCLUSIONS

This study demonstrates that increasing the precision of categories of death from injury routinely used in mortality studies will provide improved information to guide prevention. Am. J. Ind. Med. 37:364-373, 2000. Published 2000 Wiley-Liss, Inc.

[Changes of potassium and sodium content in erythrocyte of rabbit cardiac blood after death and timing of death]

We studied the changes of potassium and sodium contents in erythrocytes and the activity of erythrocyte membrane Na(+)-K(+)-ATPase in 40 cardiac blood samples of rabbit corpses at different postmortem intervals (PMI). The erythrocyte potassium content (RBCK) decreased linearly as the PMI increased (R = -0.829, P < 0.025). during postmortem 48 hours. The erythrocyte potassium content and the time after death had significant correlation. The activity of erythrocyte membrane Na(+)-K(+)-ATPase had no significant changes over postmortem 48 hours.

Replacing Solvent Drying Technique for Nanometer Particle Preparation

A prepration technique for nanometer particles, namely the replacing solvent drying technique, was developed. The main process of the technique including replacement of water in gel with special organic solvent and the removal of the solvent by distillation. No collapse of gel structure took place because of low interface tension between water and the solvent as well as low surface tension of the solvent. Where special apparatus and strictly limited preparation conditions were not necessary. The technique is noted for its low preparation cost and high universality. Titanium oxide and copper borate were prepared using the technique and were characterized using XRD, nitrogen physical adsorption, TEM, and small angle X-ray scattering. Results indicated that the titanium oxide and copper borate possessed particle sizes of 7-10 and 7-20 nm as well as a specific surface area of 235 m2/g and 360 m2/g, respectively. The specific surface area were even much higher than that of the samples prepared using supercritical drying technique. Copyright 1998 Academic Press.

Tuberculosis Mortality and Silica Exposure: A Case-Control Study Based on a National Mortality Database for the Years 1983-1992

A case-control study (8,740 cases; 83,338 controls) was done to evaluate the association between potential occupational exposure to silica and risk of tuberculosis (TB) mortality, using the National Occupational Mortality Surveillance database for 1983-1992. Potential silica exposure was based on the decedent's usual industry and occupation. Assignment of potential exposure to silica was based on the entire range of industries and occupations. Odds ratios (ORs) for mortality from respiratory TB associated with potential high and intermediate exposures to silica were 1.30 (95% CI 1.14-1.48) and 1.07 (95% CI 0.77-1.47), respectively, adjusting for silicosis, other pneumoconioses, age, gender, race, socioeconomic status, and potential exposure to active TB. The elevated OR was seen in all subgroups: male, female, white, and black. The average age at death among respiratory TB cases with potential silica exposure was significantly younger by four years than that among cases without potential silica exposure. The findings suggest that potential occupational exposure to silica alone, in the absence of silicosis, is associated with respiratory TB mortality, with a dose-response relationship.

[Effects of composite xueliting on four gastric ulcer models in rats and mice]

Composite Xueliting (CXLT) was found to be an effective anti-ulcer agent in four experimental models in rats and mice, namely, the stress restraint-induced, histamin-induced, salicylic acid-induced and reserpine-induced ulcers. In above-mentioned models, CXLT (0.214-0.856 g/kg, 1/d x 5, per os) could inhibit gastric ulcer by 40%-63%, 48%-85%, 68%-87% and 27%-65% respectively. Among these, the salicylic acid-induced ulcer was more markedly inhibited. The result suggested that CXLT had the protective function against the gastric ulcer.

Superoxide contributes to the rapid inactivation of specific secondary donors of the photosystem II reaction center during photodamage of manganese-depleted photosystem II membranes

The role of superoxide in the mechanism of photoinactivation of the secondary donors of the reaction center of photosystem II membranes depleted of Mn by extraction with NH2OH plus EDTA (NH2OH/EDTA-PSII) was assessed. EPR analyses (g = 2 region) in continuous light, optical kinetic spectrophotometric analyses of P680+ and Car+, and AT-band emission measurements were made after various durations of weak and strong light treatment of NH2OH/EDTA-PSII in the presence and absence of superoxide dismutase, or of PSII electron acceptors to suppress superoxide formation. Additionally, flash-induced variable fluorescence of chlorophyll a and the capabilities of the membranes of photooxidize Mn2+ (in the presence of H2O2) via a high-affinity site (Km approximately 180 nM) and to carry out the photoactivation of the Mn-cluster were determined. In the absence of any additions to the NH2OH/EDTA-PSII membranes which were highly depleted of Mn, weak light treatment caused rapid (t1/2 approximately 20 s) and parallel losses of (a) the approximately 10 microseconds phase of P680+ reduction, which reflects the TyrZ-->P680+ reaction, (b) the amplitude of chlorophyll a variable fluorescence, (c) the capability to accumulate the TyrZ(+)-radical in continuous light, and (d) the capability to photooxidize Mn2+/H2O2 in continuous light. As reported previously [Blubaugh et al. (1991) Biochemistry 30, 7586-7597], a dark-stable 12-G-wide featureless EPR signal centered at g = 2.004 was formed rapidly during illumination. This signal previously was tentatively identified as a Car+ radical and was suggested to contribute to the quenching of chlorophyll a variable fluorescence and to the slowing of the TyrZ-->P680+ reaction. However, we failed to detect Car+ formation by sensitive optical spectrophotometry and obtained no definable evidence for either a quencher of fluorescence other than P680+ itself or a slowing of the TyrZ-->P680+ reaction. Addition of a saturating concentration (96 units/mL) of superoxide dismutase diminished the rate of photodamage(s) by approximately 30-fold, but did not abolish it completely. Superoxide dismutase similarly suppressed strong light-induced photodamages, causing the loss of capability to photooxidize Mn2+/H2O2, to carry out photoactivation, and to generate the AT-band emission as well as TyrZ+ EPR signal. In contrast to others, we found no evidence that the initial target(s) of photodamage is (are) different in weak versus strong light treatment. The totality of the results suggests that the initial event in either weak light or strong light photodamage of NH2OH/EDTA-PSII is a decoupling of the redox activity of TyrZ from P680.(ABSTRACT TRUNCATED AT 400 WORDS)

Photoinactivation of photosystem II by in situ-photoproduced hydroxyurea radicals

Oxygenic photosystem (PS) II complex from spinach photooxidized hydroxyurea (HU) to produce its aminoxy radical, which was identified by its electron spin resonance spectrum. HU was apparently photooxidized by the water-oxidizing enzyme (WOE) since the photooxidation reaction was blocked by carbonyl cyanide m-chlorophenylhydrazone (CCCP). HU radicals photoproduced by the WOE inhibited the electron transfer between the redox-active tyrosine residue (YZ), which is involved in electron transfer from the WOE to the reaction center chlorophyll of PS II, and the secondary quinone electron acceptor. Treatment of PS II complex with Tris resulted in the appearance of a CCCP-insensitive photooxidation site for HU. Photoproduced HU radicals in oxygenic and Tris-treated PS II complex decayed with first-order kinetics, an indication that the radicals reacted primarily with surrounding molecules rather than decayed through spontaneous dismutation or recombination. HU inhibited the diphenylcarbazide-supported photoreduction of 2,6-dichlorophenolindophenol (DCIP) in Tris-treated PS II complex preincubated only under illumination, but this inhibition was suppressed when ascorbate was added to scavenge HU radicals. If examined in darkness, HU radicals could not, however, inhibit subsequent photoreduction of DCIP. Therefore, the photoproduced HU radicals interact with a photogenerated site(s) in the PS II complex. The photoproduction of YZ., a radical of YZ, was suppressed to about 40% in Tris-treated PS II complex by the in situ-photogenerated HU radicals, and the yield of a cation radical of chlorophyll, close to the PS II reaction center, was increased, while the production of a radical of another redox-active tyrosine residue in PS II (YD.) was hardly affected.(ABSTRACT TRUNCATED AT 250 WORDS)

[Pathomorphologic changes on 150 chronic atrophic gastritis patients by treatment based on syndrome differentiation]

Xiang-sha Warming (XSW) and Shashen Nourishing Decoction (SSN) were used in treating Yang Deficiency Syndrome (YaDS) and Yin Deficiency Syndrome (YiDS) of chronic atrophic gastritis (CAG) respectively. 121 cases with Spleen YaDS, and 29 cases with Spleen YiDS were selected. 26 and 30 specimens were taken from gastric mucosa for observation under the SEM and TEM, including 12 and 12 YaDS cases, 14 and 12 Spleen Qi Deficiency cases respectively, 2 cases of YiDS were also observed with TEM. The specimens were taken from the same site of the gastric mucosa directly under the gastroscope pre- and post-treatment. 43 patients (35.6%) with spleen YaDS and 5 cases (17.2%) in Spleen YiDS showed marked effect after 3-month treatment. It showed that the effect in Spleen YaDS was better than YiDS. The XSW was superior than that of SSN. The effects were related to the syndromes and the degrees of pathologic change. This showed that the recipe could somewhat reverse and restore the abnormal glands of gastric mucosa.

[Effect of intravenous atropine on the induction of paroxysmal supraventricular tachycardia]

Sixty nine patients with the history of paroxysmal supraventricular tachycardia (PSVT) or possible history of PSVT failed to have PSVT provoked by transesophageal atrial pacing (TEAP). After intravenous administration of 0.02 mg/kg atropine, 42 patients had PSVT provoked during the second TEAP. The electrophysiologic parameters showed that atropine could increase the inducibility of PSVT. The main effect was to decrease the anterograde AV node effective refractory period (ERP) or fast pathway ERP and provide an available condition for the reentry of impulses. The conclusion is that atropine could definitely increase the diagnostic value of TEAP.

Photoinhibition of hydroxylamine-extracted photosystem II membranes: studies of the mechanism

The effects of photosystem II (PSII) exogenous electron donors and acceptors on the kinetics of weak light photoinhibition of NH2OH/EDTA-extracted spinach PSII membranes were examined. Under aerobic conditions, Mn2+ (approximately 1 Mn/reaction center; Km approximately 400 nM) inhibited photoinactivation and approximately 1 Mn/reaction center plus 100 microM NH2NH2 gave almost complete protection. In the absence of electron donors, strict anaerobiosis greatly inhibited photoinactivation even in the presence of an electron acceptor. Under aerobic conditions, the addition of electron acceptors (FeCN, DCIP), oxyradical scavengers, or superoxide dismutase strongly suppressed rates of photodamages. Increase in the concentrations of superoxide above those produced by illuminated NH2OH/EDTA-photosystem II membranes increased the rates of damage in the light but gave no damage in the dark. Scavengers of hydroxyl radicals and singlet oxygen did not suppress the rates of aerobic photoinhibition. These findings, along with others, lead us to conclude that photodamage of the secondary donors of the PSII reaction center occurs by two mechanisms: (1) a rapid superoxide and tyrosine YZ+ dependent process and (2) a slower process in which P680+/Chl+ catalyze the damages.

Etiological investigation of farmer's lung disease: a serological study

To confirm the main etiological antigen of farmer's lung in Dafeng County, Jiangsu Province, People's Republic of China, precipitins in serum from 30 patients with farmer's lung were tested with several strains of antigens. Reactions against two strains of T.vulgaris were shown in 46.7% and 66.7% of the patients group, which were significantly higher than in the controls, while the percentage of reactions against Faenia rectivirgula and A. fumigates were low in the patients group and had no significant difference with the controls. The results indicate that the main etiological agents were some strains of T. vulgaris. This finding was consistent with the microbiological study of sputum of the patients and moldy hay samples from the working area.

Bioartificial thyroid. The in vitro culture of microencapsulated rabbit thyroid tissue

A new technique of encapsulating thyroid tissue with an artificial membrane for protection against immune attack is reported. The membrane was made of calcium alginate and a poly-L-lysin coating. The membrane prevents the diffusion of large molecules such as hemoglobin but freely permits the passage of smaller molecules such as T4 and culture medium 1640. Because larger molecules are barred, the contents of the microcapsules are safe from immune system rejection. In vitro cultured, microencapsulated rabbit thyroid tissue secreted T3 and T4, achieving a concentration of 8.68 +/- 2.93 nmol/L and 245.23 +/- 124.87 nmol/L, after 3 days; this level remained steady for 6 to 9 days of incubation. These microcapsules show promise as a treatment modality and as a possible solution to the problem of immuno-isolation.

A Plasmodium falciparum-specific reverse target capture assay

Plasmodium falciparum DNA is detected with an assay modeled according to the reverse target capture assay described by Morrissey et al. [19] for the detection of Listeria cells. A poly(A)-tailed oligonucleotide (pWZ34), derived from the partial sequence of a 4-kb repetitive unit of P. falciparum, functions as a capture probe and the labelled 21-bp repetitive units specific for P. falciparum serve as a reporter probe. Both probes are complementary to non-overlapping regions of the target DNA and in the presence of high concentration of chaotropic salts, hybridization efficiently takes place at relatively low temperatures (15 min. 37 degrees C). The addition of poly(dT)-derivatized ferromagnetic beads allows the formation of A:T base pairing between the tailed beads and the tailed capture probe. Upon applying magnetic force, the target-capture-reporter-probe complex attached to the beads is removed from the reaction mixture, leaving the bulk of unreacted reporter molecules behind. Subsequent washings of the immobilized complex reduces the amount of non-specifically bound reporter probe. After elution of the complex from the beads a new cycle of capture, washing and release of the target-capture-reporter-probe complex is initiated by the additions of unused (dT)-tailed beads. After 3 cycles, the signal-to-noise ratio with 0.1 pg of P. falciparum DNA as a target was as high as 21-27, with a background of 8-10 cpm. The assay is unique in its speed, well suited for large sample numbers, and allows the manipulation of the background at will by simply increasing the number of capture rounds.

The cytochemical changes and the adherence of neutrophil during cross-linked agarose encapsulated activated charcoal hemoperfusion

After one hour cross-linked agarose encapsulated activated charcoal hemoperfusion, there was slight increase of total white cells and neutrophil count, but the neutrophil adherence was 16.87 +/- 5.26% and marked lower than that before hemoperfusion (59.91 +/- 5.26%, p less than 0.05). Using glassball hemoperfusion as control, the neutrophil adherence also decreased but not so obvious as the former. Adherence is a cell property that may affect granulocyte margination, diapedesis, chemotaxis and phagocytic function, so the above investigations showed that both the hemoperfusion process and the charcoal itself may reduce the host defence mechanism. There were no change of the peroxidase and alkaline phosphatase activities of neutrophils during one hour cross-linked agarose encapsulated activated charcoal hemoperfusion.

[Radiotherapy for extrahepatic bile duct cancer--an analysis of 12 cases]

During the past 8 years, 12 patients with extrahepatic bile duct adenocarcinoma which was contra-indicated to operation or who underwent conservative resection wer treated by radiotherapy in our hospital. Five patients were given post-operative radiation of 60-70 Gy/7-9 weeks, 3 patients received 12 Mev beta beam of one single 30 Gy intra-operative radiotherapy and 4 were treated by intra-operative radiotherapy of 20 Gy plus external irradiation of 40 Gy/5 weeks after the operation. The results indicated that most of the patients died around 1 year and 2 are still alive for over 2 years. The present results are more favorable as compared with those treated before 1980 because biliary drainage had been done before timely high dose radiotherapy after the operation. The author considers that intra-operative radiotherapy or its combination with external irradiation might be helpful to improve the prognosis in extrahepatic bile duct cancer.

Non-CS pre-erythrocytic protective antigens

Three novel non-CS antigens have been identified on P. falciparum and P. berghei sporozoites and exoerythrocytic parasites. CSP-2 is a sporozoite surface protein common to P. falciparum and P. berghei that elicits antibody-mediated protection, and is also found within P. berghei EE parasites. LSA is a P. falciparum EE-specific antigen localized within the parasitophorous vacuole. LSA-2 is a P. berghei EE-specific antigen, localized on the parasitophorous vacuole membrane, that protected mice to P. berghei sporozoite challenge, and elicited cytotoxic T cells that killed P. berghei EE parasites in vitro.

Detection of pyrimethamine resistance in Plasmodium falciparum by mutation-specific polymerase chain reaction

The point mutation at nucleotide 323 within the dihydrofolate reductase-thymidylate synthase gene of Plasmodium falciparum, which distinguishes pyrimethamine-sensitive from drug-resistant isolates, can be discriminated by the polymerase chain reaction using mutation-specific primers. The technique makes use of the principle that short oligonucleotides with a perfect match at their 3' ends, complementary to the mutation to be detected, will initiate the polymerization by Taq polymerase far more efficiently than primers with a single mismatch in this position. The Asn-108 codon was detected using a primer of 17 nucleotides with an adenosine at its 3' end, the Thr-108 codon with a 14-mer primer ending with a cytosine and the Ser-108 codon with a 16-mer containing guanidine at the critical 3' end. By selecting appropriate counterprimers, the size of the amplification products is either indicative of pyrimethamine-resistant parasites of the 7G8 type, or of pyrimethamine-sensitive parasites of the FCR-3 type or 3D7 type. The fragments obtained can be easily separated in a single lane after agarose gel electrophoresis. Coded P. falciparum DNA samples were typed unambiguously using these primers as were reconstituted parasitized blood samples stored as high salt lysates. Sensitivity, speed and specificity make this assay a realistic alternative to in vitro drug testing to monitor the resistance of P. falciparum to inhibitors of the dihydrofolate reductase.

Hydroxyurea and p-aminophenol are the suicide inhibitors of ascorbate peroxidase

Guaiacol peroxidase from spinach catalyzes the oxidation of p-aminophenol to produce the aminophenoxy radical as the primary product which is converted further into a stable oxidation product with an absorption peak at 470 nm. The p-aminophenol radicals oxidize ascorbate (AsA) to produce monodehydroascorbate radicals. Kinetic analysis indicates that p-aminophenol radicals also oxidize monodehydroascorbate to dehydroascorbate. Incubation of AsA peroxidase from tea leaves and hydrogen peroxide with p-aminophenol, p-cresol, hydroxyurea, or hydroxylamine results in the inactivation of the enzyme. No inactivation of the enzyme was found upon incubation of the enzyme with these compounds either in the absence of hydrogen peroxide or with the stable oxidized products of these compounds. The enzyme was protected from inactivation by the inclusion of AsA in the incubation mixture. The radicals of p-aminophenol and hydroxyurea were produced by AsA peroxidase as detected by their ESR signals. These signals disappeared upon the addition of AsA, and the signal characteristic of monodehydroascorbate was found. Thus, AsA peroxidase is inactivated by the radicals of p-aminophenol, p-cresol, hydroxyurea, and hydroxylamine which are produced by the peroxidase reaction, and it is protected from inactivation by AsA via the scavenging of the radicals. Thus, these compounds are the suicide inhibitors for AsA peroxidase. Isozyme II of AsA peroxidase, which is localized in chloroplasts, is more sensitive to these compounds than isozyme I. In contrast to AsA peroxidase, guaiacol peroxidase was not affected by these various compounds, even though each was oxidized by it and the corresponding radicals were produced.

Pre-erythrocytic stage malaria parasites: non-circumsporozoite protein antigens

A series of non-circumsporozoite proteins found in pre-erythrocytic parasites are being developed as putative vaccine candidates. It is anticipated that these will be useful in addition to, rather than instead of, the CS (circumsporozoite) vaccines. It is likely that a greater understanding of the basic biology of malaria parasite-host relationships will lead to development of improved malarial vaccines.

Point mutations in the dihydrofolate reductase-thymidylate synthase gene as the molecular basis for pyrimethamine resistance in Plasmodium falciparum

The dihydrofolate reductase-thymidylate synthase (DHFR-TS) bifunctional complex from pyrimethamine-sensitive (3D7) and drug-resistant (HB3 and 7G8) clones from Plasmodium falciparum was purified to homogeneity. A modified sequence of purification steps with a 10-formylfolate affinity column at its center, allows the isolation of the enzyme complex with a 10-fold higher yield than previously reported, irrespective of the pyrimethamine resistance of the parasites. Titration of the homogenous DHFR-TS complex with the inhibitor revealed a 500-fold lower affinity of the enzyme from clone 7G8 for the drug than found with the enzyme from clone 3D7. Direct comparison of the homogenous enzyme preparations on SDS-PAGE revealed no difference in the molecular mass of the DHFR-TS from the 3 clones, nor could a reproducible difference be detected in the peptide patterns obtained after digesting the DHFR-TS complex with various proteases. The amplification of segments from the DHFR-TS coding region of the 3 clones and 7 isolates of P. falciparum by polymerase chain reaction resulted in fragments of the predicted length without any size heterogeneity. The DNA sequence of the DHFR coding region from FCR-3, 3D7, HB3 and 7G8 differs in a total of 4 nucleotides. One point mutation changes amino acid residue 108 from threonine (FCR-3) or serine (3D7) to asparagine (HB3 and 7G8). The presence of asparagine-108 appears to be the molecular basis of pyrimethamine resistance of HB3 and 7G8. The degree of resistance is associated with a point mutation affecting the codon for amino acid 51 in 7G8.

Paramyosin and the catch mechanism

We propose here the formation by molluscan and notochord muscles in the catch state of three-dimensional, entangled network structures composed of bent and sometimes entwined paramyosin thick filaments including myosin intermediate filaments and disordered actin thin filaments; in the relaxed state the three forms lie in parallel. The intact forms of bivalve (Andonta pacifica, Heude) muscle paramyosin are those of 120 and 95 kDa (beta-paramyosin). The 102 kDa form (alpha-paramyosin) is the proteinase cleavage product of 120 kDa paramyosin. Paramyosin could be phosphorylated in vitro by cyclic AMP-dependent protein kinase. The amino acid phosphorylated was at the serine residue. Paramyosin from muscles treated with acetylcholine (catch state) was phosphorylated to a greater extent than that of untreated muscles (normal state) and even more so in the case of serotonin-treated muscles (relaxed state). Actin markedly inhibited the phosphorylation of paramyosin in vitro.

Purification of the bifunctional thymidylate synthase-dihydrofolate reductase complex from the human malaria parasite Plasmodium falciparum

The bifunctional thymidylate synthase-dihydrofolate reductase complex from the human malaria parasite Plasmodium falciparum has been purified to homogeneity using a sequence of separation steps including phenyl-Superose, gel filtration, dye affinity matrix, hydroxyapatite, and anion exchange chromatography. The specific activity of dihydrofolate reductase increased approximately 24,000-fold from 3.3 units mg-1 protein to 79,000 units mg-1 protein after five successive chromatographic steps with a yield of 31%. Both enzyme activities coeluted as a symmetric peak in highly purified preparations, indicating the existence of a bifunctional enzyme complex in P. falciparum. The apparent molecular weight of the native complex was approximately 120,000 as determined by gel filtration. When individual fractions of the anion exchange column were subject to polyacrylamide electrophoresis under denaturing conditions, the increase in intensity of a single band correlated with the amount of both the thymidylate synthase and dihydrofolate reductase activity. Further purification led to an electrophoretically pure protein (yield 2.6%) with an apparent molecular weight of 67,000, suggesting that the bifunctional enzyme complex from P. falciparum is composed of two subunits of identical size and charge.

Kinetic and molecular properties of the dihydrofolate reductase from pyrimethamine-sensitive and pyrimethamine-resistant clones of the human malaria parasite Plasmodium falciparum

Dihydrofolate reductase (DHFR) (5,6,7,8-tetrahydrofolate: NADPH+-oxidoreductase; EC 1.5.1.3) was partially purified by affinity chromatography from three clones of the human malaria parasite Plasmodium falciparum. The three clones were representative of pyrimethamine-sensitive (clone 3D7) and pyrimethamine-resistant (clone HB3 and clone 7G8) parasites with ID50 values of 0.53 nM (3D7), 210 nM (HB3), and 540 nM (7G8), when tested in vitro against the drug. The specific activities of the partially purified DHFR differed by less than a factor of 2 between the sensitive clone 3D7 (442 +/- 39 nmol min-1 mg-1 protein) and the resistant clones HB3 (634 +/- 25 nmol min-1 mg-1 protein) and 7G8 (565 +/- 85 nmol min-1 mg-1 protein). The number of catalytic sites in partially purified DHFR from the three clones was similar and ranged from 151 to 194 pmol mg-1 protein. The Km value for NADPH was similar in all three clones (4.5-11.6 microM). The Km value for dihydrofolate was altered 13-fold comparing the sensitive clone 3D7 (3.2 +/- 0.6 microM) with the resistant clone HB3 (42.6 +/- 1.6 microM), with the Km for the resistant clone 7G8 falling in between (11.9 +/- 1.2 microM). The inhibition constants for pyrimethamine increased from 0.19 +/- 0.08 nM (3D7) to 2.0 +/- 0.3 nM (HB3) to 8.9 +/- 0.8 nM (7G8). The inhibition by pyrimethamine of the sensitive clone 3D7 was noncompetitive and competitive for the two other clones. The titration of partially purified DHFR with pyrimethamine revealed a 500-fold increase in the concentration of the drug needed to inhibit the DHFR activity by 50%, when the sensitive clone 3D7 (0.18 +/- 0.02 nM) was compared to the resistant clone 7G8 (95 +/- 16 nM). From the comparison of the specific activities and the catalytic center activities with the Km values for the substrate and the inhibition constants for pyrimethamine, both of which are altered in the resistant clones, we conclude that the molecular mechanism for pyrimethamine resistance in the three clones studied is not based on an overproduction of the DHFR but is due to a decreased affinity to antifolates by a structurally altered enzyme.

The oxidative folding of proteins by disulfide plus thiol does not correlate with redox potential

The rate and yield of oxidative renaturation of reduced RNase A has been studied as a function of [-S-S-]/[-SH]. The principal conclusion of these studies is that rates and yields of oxidative renaturation are strongly dependent on the low mol. wt disulfide/thiol ratio. The relationships are complex and do not parallel the redox potential of the system. The present results are consistent with earlier findings on other proteins, and lead us to believe that the above conclusion is general. Kinetic studies of oxidative renaturation should recognize and account for the dependence of reaction rate and extent on the disulfide/thiol ratio. This ratio can change substantially over the course of a reaction, either due to stoichiometric transfer of disulfide to protein, and/or adventitious air oxidation of thiols. Failure to account for changes in the disulfide/thiol ratio may compromise the interpretation of such experiments.

A new sensitive Edman-type reagent: 4-(N-1-dimethylaminonaphthalene-5-sulfonylamino)phenyl isothiocyanate. Its synthesis and application for micro-sequencing of polypeptides

A new fluorescent PITC homologue Edman-type reagent, 4-(N-1-dimethylaminonaphthalene-5-sulfonylamino)phenyl isothiocyanate (DNSAPITC), was synthesized following a simple three-step synthetic route. The reagent was crystallized and characterized by thin-layer chromatography, IR and electron impact mass spectrometry. Reference DNSAPTH-amino acid derivatives were prepared and a two-dimensional chromatography system on micro-polyamide sheets was developed for separating this mixture. On these sheets the sensitivity was 1-5 pmol, by exposure at 366 nm. Model peptides and proteins were subjected to Edman degradations with this new reagent. A similar coupling efficiency and repetitive degradation yield to those of PITC were found with this reagent. The advantages and limitations of this reagent for sensitive microsequencing are discussed.

The catch mechanism of molluscan smooth muscles

We have examined the arrangements of the thick and thin filaments of the smooth muscle of the adductor of the bivalve Cristaria plicata, Leach, in the catch state induced by acetylcholine, both in ultrathin sections and in separate filaments. The thick filaments are heavily bent and entangled and the thin filaments irregularly arranged. One thin filament may be attached to several thick filaments. When the muscle is in the relaxed state, the two kinds of filaments are seen to be in parallel. However, no difference could be observed in the periodic structure of the paramyosin core of the thick filaments in the relaxed state or in catch. Both cross-striated and checkerboard types coexist. It seems that phase transition is not directly related to catch. We propose that the disordered arrangements of the thick and thin filaments and the formation of three-dimensional anastomosed networks are the structural basis for catch, with a consequent loss of the capability of directional sliding of the filaments and requiring time to restore orderliness.