Allelopathic effects of nicotine on maize I. Its possible importance in crop rotation

Nicotine adversely affected the germination, germination relative index (GRI), radicle and plumule length, and seedling vigour of rice but affected favourably the growth of maize. Also, inin vivo conditions nicotine increased height, specific leaf weight and chlorophyll content of the maize plant.     

1,3,7-Trimethylxanthine,an allelochemical from seeds ofCoffea arabica: Some aspects of its mode of action as a natural herbicide

Summary Certain aspects of selective toxicity of 1,3,7-trimethylxanthine (1,3,7-T), a natural herbicide, were studied inPhaseolus mungo andAmaranthus spinosus. Treatment of seeds ofA. spinosus with 1,3,7-T (sub-lethal concentration) caused a marked decrease (29.5%) in amylase activity. Kinetic studies with respect to substrate saturation and Km values as well asin vitro treatments of the cell-free enzyme indicated no effect on its catalytic property. The inhibitory effect of 1,3,7-T on amylase activity could not be counteracted with treatments of GA₃. A general biochemical analysis revealed that the starch/sugar ratio increased in the seedlings grown from treated seeds. Analysis also showed a higher ratio for insoluble/soluble nitrogen. It is suggested that inhibition of germination is caused by reduced synthesis of amylase which is not mediated through gibberelic acid. Treatment of seeds ofPhaseolus mungo with, 1,3,7-T. caused no change in amylase activity,in vivo nitrate reductase activity, ethanol soluble and insoluble nitrogen and protein content.     

Possible modulation of N-methyl-D,L-aspartic acid induced prolactin release by testicular steroids in the adult male rhesus monkey

N-methyl-D,L-aspartic acid (NMA), an agonist of the neurotransmitter glutamate has been shown to acutely stimulate the release of prolactin (PRL) in intact rats and monkeys. To further investigate the role of neuroexcitatory amino acids in PRL secretion, the effects of NMA administration were examined on PRL release in long term orchidectomized adult rhesus monkeys, in both the absence and presence of testosterone. Intact and long term castrated adult male monkeys weighing between 8-13 kg, were implanted with a catheter via the saphenous vein for blood withdrawal and drug infusion. Blood samples were collected at 10 min intervals for 50 min before and 70 min after administration of the drug or vehicle. Plasma PRL concentrations were estimated using radioimmunoassay. Whereas a single iv injection of NMA (15 mg/kg BW) induced a prompt discharge of PRL in intact monkeys, an identical dose had surprisingly no effect on PRL secretion in orchidectomized animals. On the other hand, plasma PRL increases in response to a challenge dose of thyrotropin releasing hormone (TRH; 6 micrograms/kg BW, iv) were similar in magnitude in the two groups of monkeys. Testosterone replacement in orchidectomized animals by parenteral administration of testosterone enanthate (200 mg/wk) reinitiated the PRL responsiveness to acute NMA stimulation. These results indicate that N-methyl-D-aspartic acid (NMDA) dependent drive to PRL release in the adult male rhesus monkey may be overtly influenced by the sex steroid milieu.     

Erythrocyte membrane acetylcholinesterase in type 1 (insulin-dependent) diabetes mellitus.

1. The erythrocyte membrane acetylcholinesterase activity is significantly (P less than 0.001) decreased in insulin-dependent diabetes mellitus. 2. The activity is negatively correlated (r = -0.97) with the fasting blood glucose level. 3. Insulin treatment restores the activity to normal. 4. The Km of the enzyme for acetylthiocholine iodide was unchanged; however, the Vmax. was decreased, suggesting a decrease in the number of active enzyme molecules in diabetes.     

Degradation of DNA by silicic acid

S1 nuclease hydrolysis and hydroxyapatite chromatography were used to study the effect of silicic acid on DNA. Native calf thymus DNA was incubated with increasing concentrations of silicic acid (DNA nucleotide/silicic acid molar ratios of 1:0.25, 1:0.5 and 1:1) and subjected to S1 nuclease hydrolysis. An increasing degree of DNA degradation was seen suggesting a destabilization of the secondary structure. A decrease in melting temperature was also observed. Hydroxyapatite chromatography indicated that incubation at the molar ratio of 1:1 resulted in denaturation and degradation of DNA.     

Fungi intercepted from abroad

In a previous paper fungi intercepted on plant consignments imported from Afghanistan were described. The present paper gives an account of some more fungi that have been intercepted from time to time on plants and plant material imported from different countries.     

Antibiotic resistance and extended spectrum beta-lactamases: Types,epidemiology and treatment

Antibiotic resistance is a problem of deep scientific concern both in hospital and community settings. Rapid detection in clinical laboratories is essential for the judicious recognition of antimicrobial resistant organisms. Production of extended-spectrum β-lactamases (ESBLs) is a significant resistance-mechanism that impedes the antimicrobial treatment of infections caused by Enterobacteriaceae and is a serious threat to the currently available antibiotic armory. ESBLs are classified into several groups according to their amino acid sequence homology. Proper infection control practices and barriers are essential to prevent spread and outbreaks of ESBL producing bacteria. As bacteria have developed different strategies to counter the effects of antibiotics, the identification of the resistance mechanism may help in the discovery and design of new antimicrobial agents. The carbapenems are widely regarded as the drugs of choice for the treatment of severe infections caused by ESBL-producing Enterobacteriaceae, although comparative clinical trials are scarce. Hence, more expeditious diagnostic testing of ESBL-producing bacteria and the feasible modification of guidelines for community-onset bacteremia associated with different infections are prescribed.     

Synthesis and SAR of pyridothiazole substituted pyrimidine derived HCV replication inhibitors

Introduction of a nitrogen atom into the benzene ring of a previously identified HCV replication (replicase) benzothiazole inhibitor 1, resulted in the discovery of the more potent pyridothiazole analogues 3. The potency and PK properties of the compounds were attenuated by the introductions of various functionalities at the R(1), R(2) or R(3) positions of the molecule (compound 3). Inhibitors 38 and 44 displayed excellent potency, selectivity (GAPDH/MTS CC(50)), PK parameters in all species studied, and cross genotype activity.     

Mechanisms of Function of Tapasin,a Critical Major Histocompatibility Complex Class I Assembly Factor

For their efficient assembly in the endoplasmic reticulum (ER), major histocompatibility complex (MHC) class I molecules require the specific assembly factors transporter associated with antigen processing (TAP) and tapasin, as well as generic ER folding factors, including the oxidoreductases ERp57 and protein disulfide isomerase (PDI), and the chaperone calreticulin. TAP transports peptides from the cytosol into the ER. Tapasin promotes the assembly of MHC class I molecules with peptides. The formation of disulfide‐linked conjugates of tapasin with ERp57 is suggested to be crucial for tapasin function. Important functional roles are also suggested for the tapasin transmembrane and cytoplasmic domains, sites of tapasin interaction with TAP. We show that interactions of tapasin with both TAP and ERp57 are correlated with strong MHC class I recruitment and assembly enhancement. The presence of the transmembrane/cytosolic regions of tapasin is critical for efficient tapasin–MHC class I binding in interferon‐γ‐treated cells, and contributes to an ERp57‐independent mode of MHC class I assembly enhancement. A second ERp57‐dependent mode of tapasin function correlates with enhanced MHC class I binding to tapasin and calreticulin. We also show that PDI binds to TAP in a tapasin‐independent manner, but forms disulfide‐linked conjugates with soluble tapasin. Thus, full‐length tapasin is important for enhancing recruitment of MHC class I molecules and increasing specificity of tapasin–ERp57 conjugation. Furthermore, tapasin or the TAP/tapasin complex has an intrinsic ability to recruit MHC class I molecules and promote assembly, but also uses generic folding factors to enhance MHC class I recruitment and assembly.