Allelopathic effects of nicotine on maize

Nicotine treatment of maize seeds at 5.0 and 7.5 mM concentrations caused an increase of 6.2 and 18.7% in amylase activity, respectively. It is being suggested that the positive effect of nicotine on maize is, at least, partially due to increased solubilization of the stored starch through induction of the synthesis or the activity of amylase.     

Simian immunodeficiency virus RNA is efficiently encapsidated by human immunodeficiency virus type 1 particles.

Packaging of retroviral RNA is attained through the specific recognition of a cis-acting encapsidation site (located near the 5' end of the viral RNA) by components of the Gag precursor protein. Human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV) are two lentiviruses that lack apparent sequence similarity in their putative encapsidation regions. We used SIV vectors to determine whether HIV-1 particles can recognize the SIV encapsidation site and functionally propagate SIV nucleic acid. SIV nucleic acid was replicated by HIV-1 proteins. Thus, efficient lentivirus pseudotyping can take place at the RNA level. Direct examination of the RNA contents of virus particles indicated that encapsidation of this heterologous RNA is efficient. Characterization of deletion mutants in the untranslated leader region of SIV RNA indicates that only a very short region at the 5' end of the SIV RNA is needed for packaging. Comparison of this region with the corresponding region of HIV-1 reveals that both are marked by secondary structures that are likely to be similar. Thus, it is likely that a similar higher-order RNA structure is required for encapsidation.     

Investigation on the role of nodule cytokinins in regulation of nitrate reductase activity ofPhaseolus mungo (L.)

The effects of some nodular cytokinis, zeatin (Z), zeatin riboside (ZR), N⁶ (²-isopentenyl) adenine (IPA), and N⁶ (²-isopentenyI) adenosine (IPAS) on nitrate reductase (E.C 1.9.6.1) activity of root nodules ofPhaseolus mungo were investigated. The cytokinis were also tested for their effect on nitrate uptake by nodules. The results show that IPAS is the most effective of all the four cytokinins tested. Z and IPA, which caused higherin vivo activity than ZR and IPAS, stimulated uptake of nitrate by nodules. The other two (ZR and IPAS) while inhibiting uptake showed greaterin vitro activity than Z and IPA. It may be concluded that some cytokinins, in addition to their direct effects on the enzyme, may increase the substrate availability to it, whereas others may have only an direct effect on the enzyme activation or degradation.Deceased.     

Diaminopimelic Acid Synthesis in Cultures of an Escherichia coli Double Auxotroph: Effects of Cultural Conditions

The metabolic response to L-lysine of Escherichia coli ATCC 13002, a lysine-histidine double auxotroph, has been examined in a synthetic medium containing sucrose. In shaken cultures largest amounts of extracellular DAP were produced with an initial lysine concentration of 7·5 mg/1 and in static cultures of 2·5 mg/1. Considerably smaller amounts of DAP accumulated under stationary conditions. In cultures shaken for 20 and 43 h there was an overall decrease in the yields of DAP, expressed in terms of cell biomass and of sucrose consumed, as the initial concentration of lysine was increased from 0·75 mg/1 in steps up to 25 mg/1. The regulatory effect of lysine on DAP production was also observed when lysine was supplied to cultures at a constant rate employing diffusion capsules.     

Effect of alkylation on the secondary structure of DNA

S1 nuclease hydrolysis and bezoylated naphthoylated DEAE-cellulose (BND-cellulose) chromatography have been used to demonstrate that alkylation of DNA by dimethyl sulfate at neutral pH leads to the production of partially denatured molecules under conditions where no significant depurination occurs. DNA was alkylated with increasing concentrations of the alkylating agent, and subjected to enzymatic degradation and binding to BND cellulose. An increasing degree of DNA hydrolysis and adherence to BND cellulose was seen. On hydroxyapatite chromatography the alkylated DNA still eluted at the position of double-stranded molecules suggesting the presence of partially denatured regions. The presence of salt had a preventive effect on such denaturation.     

Fungi intercepted from Afghanistan

Fungi obtained and isolated from plant material coming in from Afghanistan and intercepted at Quarantine Station, Jamrud have been described. Out of eight species of fungi isolated from different seeds, at least one is not known to occur in Pakistan. Importance of studying seed borne fungi from Quarantine point of view is discussed.

---

Zusammenfassung Pilze, die von Pflanzenmaterial von Afghanistan erhalten, isoliert und bei der Auarantänestelle Jamrud erwischt worden sind, sind hier beschrieben. Von acht Pilzarten, die von verschiedenen Samen isoliert worden sind, ist eine in Pakistan noch nicht vorgefunden worden. Die Wichtigkeit der Untersuchung von den mit den Pilzen behafteten Samen vom Standpunkt der Quarantäne ist diskutiert.

---

---

Department of Plant Protection     

Azotobacter: A potential bio-fertilizer for soil and plant health management

Stressor (biotic as well as abiotic) generally hijack the plant growth and yield characters in hostile environment leading to poor germination of the plants and yield. Among the plant growth promoting rhizobacteria, Azotobacter spp. (Gram-negative prokaryote) are considered to improve the plant health. Various mechanisms are implicated behind improved plant health in Azotobacter spp. inoculated plants. For example, acceleration of phytohormone like Indole-3-Acetic Acid production, obviation of various stressors, nitrogen fixation, pesticides and oil globules degradation, heavy metals metabolization, etc. are the key characteristics of Azotobacter spp. action. In addition, application of this bacteria has also become helpful in the reclamation of soil suggesting to be a putative agent which can be used in the transformation of virgin land to fertile one. Application of pesticides of chemical origin are being put on suspension mode as the related awareness program is still on. As far as the limitations of this microbe is concerned, commercial level formulations availability is still a great menace. Present review has been aimed to appraise the researchers pertaining to utility of Azotobacter spp. in the amelioration of plant health in sustainable agroecosystem. The article has been written with the target to gather maximum information into single pot so that it could reach to the dedicated researchers.     

Phagocytosis of degenerating myelin in transected feline optic nerve: an immunohistochemical study

The phagocytic activity of neuroglial cells in adult feline degenerating optic nerve was investigated by immunocytochemistry at both light and electron microscopy levels. Degeneration was initiated by unilateral eye enucleation and the segment distal to the transection showing true Wallerian degeneration was examined. Following enucleation, twelve adult domestic cats were examined over a period of seven to 215 days. All cases showed slow clearance of myelin debris and absence of proliferating monocytes throughout the post-enucleation period. All phagocytic cells present were neuroglial cells, and many of these cells expressed oligodendroglial antigens. These findings demonstrate the persistence of an active population of oligodendrocytes that might play an additional functional role during Wallerian degeneration of feline optic nerve.     

Protective effect of capsaicin on the osmotic fragility of human erythrocytes

Capsaicin exerts a stabilizing effect on erythrocytes making them more resistant to lysis under hypotonic stress. The protective action of capsaicin on osmotic fragility (OF) was not receptor mediated since no dose responsive effect was observed. The results suggest that this protective effect of capsaicin on OF is due to a direct interaction of capsaicin with the erythrocyte membrane rather than due to any alteration in the intracellular metabolism of erythrocytes.