Comparison of mutant and parent strains of Clostridium acetobutylicum: butyrate uptake at different temperatures

A high butanol producing mutant strain of Clostridium acetobutylicum ATCC 4259 was obtained by chemical mutagenesis. Both mutant and parent strains were evaluated for butyrate uptake using the culture effluents of solventogenic fermentor-2 of the two-fermentor continuous system. Batch incubation of fermentor-2 culture effluents at 37?°C indicated lower butyrate uptake rates for mutant and parent strain, at 0.05 and 0.03?g?l^?1?h^?1, respectively. Increased butyrate uptake rates of 0.33 and 0.26 g l^?1 h^?1 for mutant and parent strain, respectively, were observed when effluents were batch incubated at lower temperature of 30?°C. Butyrate conversion efficiency, at 5?±?0.1 g l^?1 of externally added butyrate, were 98.8% and 96.9% for mutant and parent strain, respectively. Butyrate up to the externally added concentration of 11.4 g l^?1 did not inhibit butyrate uptake. The maximum butyrate consumption at a slightly reduced uptake rate was seen at 10.2 g l^?1 butyrate concentration at 27?°C. Based on the results under different temperatures, the electron flow pattern has been computed and the mechanism for butyrate uptake has been hypothesized.     

Rapid detection of rectal cancer by gloved digital-scrape cytology

To evaluate the use of cytology for the rapid detection of rectal cancer, 39 suspected cases of carcinoma of the rectum and anal canal and 7 age- and sex-matched control cases were studied by the gloved digital-scrape method. The cytologic findings were then correlated with the histopathologic diagnoses. Of 30 evaluable cases with follow-up, a correct cytologic diagnosis was made in 28 cases (93.4%), with 1 false-negative diagnosis (3.3%) and 1 false-positive diagnosis (3.3%). Gloved digital-scrape cytology is very simple, quick and inexpensive and can be carried out an out-patient basis without any complications.     

Continuous acetone-butanol fermentation: influence of vitamins on the metabolic activity of Clostridium acetobutylicum

Summary A detailed investigation was undertaken to examine the influence of biotin and paminobenzoic acid (PABA) in chemostat cultures of Clostridium acetobutylicum ATCC 824. Initiation of chemostat cultures with a basic synthetic medium (biotin 0.01 mg l^–1; PABA 1.0 mg l^–1) have resulted in a low biomass together with a low specific rate of solvent production. A different picture emerged on elevating the concentration of both vitamins 8-fold: biomass and specific rates (solvent production, glucose consumption) were increased and a solvent productivity of 2.54 g l^–1 h^–1 at the solvent concentration of 13.1 g l^–1 was achieved. It has also been shown that PABA was the only limiting factor for the metabolism of Clostridium acetobutylicum in the basic synthetic medium and that the optimised concentration was 8 mg l^–1 in the chemostat cultures with the growth conditions employed.     

Carbamoylethylation of guar gum

Carbamoylethylation of guar gum was carried out with acrylamide in presence of sodium hydroxide under different reaction conditions. Variables studied were concentration of sodium hydroxide, acrylamide, guar gum as well as reaction temperature and time. The nitrogen content, carboxyl content and total ether content were determined. Rheological properties of carbamoylethyl guar gum solutions showed non-Newtonian pseudoplastic behavior regardless of the %N. At a constant rate of shear, the apparent viscosity of carbamoylethyl guar gum solutions decreases with the increase in %N of the product.     

Sudden infant death syndrome and postneonatal mortality in immigrants in England and Wales.

To examine ethnic differences in postneonatal mortality and the incidence of sudden infant death in England and Wales during 1982-5 records were analysed, the mother''s country of birth being used to determine ethnic group. Postneonatal mortality was highest in infants of mothers born in Pakistan (6.4/1000 live births) followed by infants of mothers born in the Caribbean (4.5) and the United Kingdom and Republic of Ireland (4.1). Crude rates were lower in infants of mothers born in India (3.9/1000), east and west Africa (3.0), and Bangladesh (2.8) than in infants of mothers born in the United Kingdom despite less favourable birth weights. Mortality ratios standardised separately for maternal age, parity, and social class were significantly higher in infants of mothers born in Pakistan and lower in those of mothers born in Bangladesh. The ratio for infants of Caribbean mothers was significantly higher when adjusted for maternal age. Ratios for infants of Indian and east African mothers did not show significant differences after standardisation. An important finding was a low incidence of sudden infant death in infants of Asian origin. This was paralleled by lower mortality from respiratory causes. During 1975-85 postneonatal mortality in all immigrant groups except Pakistanis fell to a similar or lower rate than that in the United Kingdom group; Pakistanis showed a persistent excess. During 1984-5 several immigrant groups (from the Republic of Ireland, India, west Africa, and the Caribbean) recorded an increase in postneonatal mortality. Surveillance of postneonatal mortality among ethnic communities should be continued, and research is needed to identify the causes underlying the differences.     

Iloprost-induced desensitization of the prostacyclin receptor in isolated rabbit lungs

Background

The rapid desensitization of the human prostacyclin (IP) in response to agonist binding has been shown in cell culture. Phosphorylation of the IP receptor by protein kinase C (PKC) has been suggested to be involved in this process.

Methods and results

In this study we investigated the vasodilatory effects of iloprost, a stable prostacyclin analogue, in perfused rabbit lungs. Continuous infusion of the thromboxane mimetic U46619 was employed to establish stable pulmonary hypertension. A complete loss of the vasodilatory response to iloprost was observed in experiments with continuous iloprost perfusion, maintaining the intravascular concentration of this prostanoid over a 180 min period. When lungs under chronic iloprost infusion were acutely challenged with inhaled iloprost, a corresponding complete loss of vasoreactivity was observed. This desensitization was not dependent on upregulation of cAMP-specific phosphodiesterases or changes in adenylate cyclase activity, as suggested by unaltered dose-response curves to agents directly affecting these enzymes. Application of a prostaglandin E1 receptor antagonist 6-isopropoxy-9-oxoxanthene-2-carboxylic acid (AH 6809) or the PKC inhibitor bisindolylmaleimide I (BIM) enhanced the vasodilatory response to infused iloprost and partially prevented tachyphylaxis.

Conclusion

A three-hour infusion of iloprost in pulmonary hypertensive rabbit lungs results in complete loss of the lung vasodilatory response to this prostanoid. This rapid desensitization is apparently not linked to changes in adenylate cyclase and phosphodiesterase activation, but may involve PKC function and co-stimulation of the EP1 receptor in addition to the IP receptor by this prostacyclin analogue.     

Nd3+‐Yb3+/Nd3+‐Yb3+‐Li+ co‐doped Gd2O3 phosphors for up and down conversion luminescence

Frequency up‐conversion (UC) emission from the Nd³⁺‐Yb³⁺/Nd³⁺‐Yb³⁺‐Li⁺ co‐doped gadolinium oxide (Gd₂O₃) phosphors prepared by the solution combustion technique in the visible range have been studied by using 980 nm near infrared (NIR) laser diode excitation. The crystalline structure and formation of the cubic phase has been confirmed with the help of X‐ray diffraction (XRD) studies. XRD peak shifts have been found towards the lower diffraction angle side in the case of the Nd³⁺‐Yb³⁺‐Li⁺ co‐doped phosphors. Surface morphology and particle size information have been observed by using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analysis. Down‐conversion emission study under 351 nm excitation in the visible region for the Nd³⁺‐Yb³⁺/Nd³⁺‐Yb³⁺‐Li⁺ co‐doped phosphors has been performed. The UC emission bands lying in the green and red region arising from the Nd³⁺ ions have been enhanced by ~260 times, ~113 times due to incorporation of Li⁺ ions in the Nd³⁺‐Yb³⁺ co‐doped phosphors. Photometric characterization has been done for the Nd³⁺‐Yb³⁺/Nd³⁺‐Yb³⁺‐Li⁺ co‐doped phosphors. The present study suggests the capability of the synthesized phosphors in near‐infrared (NIR) to visible upconverter and luminescent device applications.     

m-Calpain-mediated cleavage of Na+/Ca2+ exchanger-1 in caveolae vesicles isolated from pulmonary artery smooth muscle

Using m-calpain antibody, we have identified two major bands corresponding to the 80 kDa large and the 28 kDa small subunit of m-calpain in caveolae vesicles isolated from bovine pulmonary artery smooth muscle plasma membrane. In addition, 78, 35, and 18 kDa immunoreactive bands of m-calpain have also been detected. Casein zymogram studies also revealed the presence of m-calpain in the caveolae vesicles. We have also identified Na⁺/Ca²⁺ exchanger-1 (NCX1) in the caveolae vesicles. Purification and N-terminal sequence analyses of these two proteins confirmed their identities as m-calpain and NCX1, respectively. We further sought to determine the role of m-calpain on calcium-dependent proteolytic cleavage of NCX1 in the caveolae vesicles. Treatment of the caveolae vesicles with the calcium ionophore, A23187 (1 μM) in presence of CaCl₂ (1 mM) appears to cleave NCX1 (120 kDa) to an 82 kDa fragment as revealed by immunoblot study using NCX1 monoclonal antibody; while pretreatment with the calpain inhibitors, calpeptin or MDL28170; or the Ca²⁺ chelator, BAPTA-AM did not cause a discernible change in the NCX protein profile. In vitro cleavage of the purified NCX1 by the purified m-calpain supports this finding. The cleavage of NCX1 by m-calpain in the caveolae vesicles may be interpreted as an important mechanism of Ca²⁺ overload, which could arise due to inhibition of Ca²⁺ efflux by the forward-mode NCX and that could lead to sustained Ca²⁺ overload in the smooth muscle leading to pulmonary hypertension.