Effects of simulated browsing on growth and leaf chemical properties in Colophospermum mopane saplings

Browsing intensity influences a plant's response to herbivory. Plants face a trade-off between investment in the production of secondary compounds and investment in growth. To elucidate this trade-off, we simulated four browsing intensities (0%, 50%, 75% and 100%) on mopane saplings, Colophospermum mopane (J.Kirk ex Benth.) J.Léonard, in a greenhouse experiment. This showed that, with increasing defoliation intensity, plants change their investment strategy. At intermediate levels of defoliation (50%), mopane saplings increased the synthesis of condensed tannins, so that tannin concentrations followed a hump-shaped relation with defoliation intensity, with significantly higher tannin concentration at intermediate defoliation levels. When defoliated heavily (75% and 100%), tannin concentrations dropped, and plants were carbon stressed as indicated by a reduced growth rate of the stem diameter, and leaf production and mean individual leaf mass were reduced. This suggests that, at intermediate defoliation intensity, the strategy of the plants is towards induced chemical defences. With increasing defoliation, the relative costs of the secondary metabolite synthesis become too high, and therefore, the plants change their growing strategy. Hence, browsers should be able to benefit from earlier browsing by either adopting a low or a relatively high browsing pressure.     

Allosteric serine hydroxymethyltransferase from monkey liver: Temperature induced conformational transitions

The homogeneous serine hydroxymethyltransferase from monkey liver was optimally activate at 60°C and the Arrhenius plot for the enzyme was nonlinear with a break at 15°C. The monkey liver enzyme showed high thermal stability of 62°C, as monitored by circular dichroism at 222 nm, absorbance at 280 nm and enzyme activity. The enzyme exhibited a sharp co-operative thermal transition in the range of 50°–70°(T _m= 65°C), as monitored by circular dichroism. L-Serine protected the enzyme against both thermal inactivation and thermal disruption of the secondary structure. The homotropic interactions of tetrahydrofolate with the enzyme was abolished at high temperatures (at 70°C, the Hill coefficient value was 1.0). A plot ofh values vs. assay temperature of tetrahydrofolate saturation experiments, showed the presence of an intermediate conformer with anh value of 1.7 in the temperature range of 45°–60°C. Inclusion of a heat denaturation step in the scheme employed for the purification of serine hydroxymethyltransferase resulted in the loss of cooperative interactions with tetrahydrofolate. The temperature effects on the serine hydroxylmethyltransferase, reported for the first time, lead to a better understanding of the heat induced alterations in conformation and activity for this oligomeric protein.     

Improved radioimmunotherapy of colorectal cancer xenografts using antibody mixtures against carcinoembryonic antigen and colon-specific antigen-p

Summary Radioimmunotherapy of GW-39 human colonic tumor xenografts grown in the hamster cheek pouch with¹³¹I-labeled NP-4 anti-(carcinoembryonic antigen) (CEA) and¹³¹I-labeled Mu-9 anti-(color-specific antigen-p) (CSAp) murine monoclonal antibodies, administered in combination, was more effective than using either antibody alone for tumor masses less than 0.5 cm³ in size. The antibody mixture had no therapeutic advantage for larger tumors. Therapeutic efficacy was determined by measuring the change in tumor size over time, quantifying the absolute number of tumors responding to radioantibody therapy, and determining the percentage growth inhibition of each treatment at various times after radioantibody administration. Several mechanisms are discussed to explain the improved tumoricidal effect of the antibody mixture noted in this model system, such as (a) the possibility that an antibody mixture could target a greater number of tumor cells, (b) the potential for antibody mixtures to provide better tumor distribution and (c) the possibility that antibodies administered in combination can increase the magnitude of tumor uptake of individual radioantibodies, thereby resulting in a greater radiation dose delivered to the tumor.     

Computational Design of Plant-Based Antistress Agents Targeting Nociceptin Receptor

Stress is the body's reaction to the challenges it faces, and it produces a multitude of chemical molecules known as stressors as a result of these reactions. It's also a misalignment of the sympathetic and parasympathetic nervous systems causing changes in a variety of physiological reactions and perhaps leading to stress disorders. The reduction in neurotransmitter & neurohormonal hormones is mainly governed by the nociceptin receptor as G-protein coupled receptor and increased the level of reactive oxygen species. Various synthetic medicines that target nociceptin receptors were utilized to reduce the effects of stress but they come up with a variety of side effects. Because of the widespread utilization and renewed interest in medicinal herbal plants considered to be alternative antistress therapy. Our present work is an approach to decipher the molecular nature of novel herbal leads by targeting nociceptin receptor, under which herbal compounds were screened and validated through in-silico methods. Among screened leads, withanolide-B showed stable association in the active site of the nociceptin receptor as an antistress agent with no side effects. Furthermore, the selected lead was also evaluated for stability by molecular dynamic stimulation as well as for pharmacokinetics and toxicity profile. It has been concluded stable conformation of withanolide-B without presence of any major toxic effects. As a result, the in silico molecular docking technique is a highly successful method for selecting a prospective herbal lead molecule with respect to a specific target, and future research can pave the way for further exploration in the drug development field.     

Adsorption of β-amylase from Bacillus carotarum B6 onto different native starches

β-Amylase from Bacillus carotarum B₆, a soil isolate, was readily adsorbed onto native raw starch from various sources. The absorbability was highest toward arrowroot starch and was complete within 30 min of exposure. Adsorption was remarkably affected in the presence of surfactants like Tween 80.     

Changes in the Growth Hormone-IGF-I Axis in Non-obese Diabetic Mice

We investigated the changes in GH-IGF-I axis in non-obese diabetic (NOD)-mice, a model of insulin dependent diabetes mellitus. Diabetic female NOD mice and their age- and sex-matched controls were sacrificed at 4, 14, 21 and 30 days (30d DM) after the onset of glycosuria. Serum GH levels increased and serum IGF-I levels decreased in the 30d DM group (182 ± 32% and 45 ± 24% of age-matched controls respectively, p < 0.05). Another group (30d DM + I) was given SC insulin, and its serum IGF-I levels remained decreased. Liver GH receptor (GHR) and GH binding protein (GHBP) mRNA levels, as well as liver membrane GH binding assays were deeply decreased in the 30d DM group in comparison to controls. GHR message and binding capacity remained decreased in the 30d DM + I group. Renal GHR mRNA was decreased at 21d DM but not at 14d DM, whereas GHBP mRNA remained unchanged throughout the experiment. In conclusion, increased serum GH levels are documented in NOD diabetic mice, similarly to the changes described in humans. The decrease in GHR levels and decreased serum IGF-I in spite of increased circulating GH suggest a state of GH resistance.