Folate binding and transport by rat kidney brush-border membrane vesicles

[3H]Pteroylglutamic acid (PteGlu) uptake was studied using brush-border membrane vesicles isolated from rat kidney. Results on the uptake of [3H]PteGlu by brush-border membrane vesicles incubated in media of increasing osmolarities demonstrated that uptake was contributed by two components, intravesicular transport and membrane binding. Both the components of the uptake exhibited similar pH dependence, with maxima at pH 5.6, and were found to be saturable mechanisms with Km values of 6.7.10(-7) and 11.2.10(-7) M, respectively. These studies show that PteGlu is transported by isolated rat kidney brush-border membrane vesicles in a manner consistent with a saturable system and that a binding component may be functionally associated with this.     

Role of endogenous opioids and histamine in morphine induced emesis

The role of opioid and histaminergic system in morphine induced emesis was investigated in dogs. Morphine (25 micrograms, icv) consistently evoked emesis with an average latency of 195 +/- 29 sec which was fully accounted for by an action on the chemoreceptor trigger zone (CTZ) as its ablation rendered animals refractory to vomiting. Intraventricular pretreatment with opioid antagonist naloxone, histamine H1 antagonist mepyramine and H2 antagonists metiamide and cimetidine afforded protection to icv morphine emesis. The CSF histamine concentration was significantly raised 5 min after icv morphine administration. The results suggest that both endogenous opioid and histamine are involved in morphine emesis. Naloxone in high doses (1600 micrograms, icv) elicited emesis which was not blocked by CTZ ablation confirming our earlier report.     

1H-NMR study of mobility and conformational constraints within the proline-rich N-terminal of the LC1 alkali light chain of skeletal myosin. Correlation with similar segments in other protein systems

Analysis by 1H-NMR spectroscopic techniques of the conformation of the N-terminal segment of the LC1 alkali light chain of rabbit skeletal muscle has shown that this portion of the molecule adopts a well-defined elongated configuration. This rod-like feature is a consequence of the Ala/Pro-rich composition and the functional aspects of such conformational preference in this and similar segments in other proteins are discussed.     

Prevention of aortic lesions and hyperlipidaemia by alfalfa seed extract in cholesterol fed rabbit

Extract of alfalfa seed (ethanolic 50 % v/v) prevents the development of plaque formation and hyperlipidaemia in cholesterol fed rabbits. It inhibits the elevation of serum total cholesterol, triglycerides, phospholipids, LDL-cholesterol and total cholesterol/phospholipid ratio, while HDL-cholesterol/total cholesterol ratio increases, which is associated with a reduced incidence of atherosclerosis. Further reduction in total cholesterol and phospholipid contents of liver and heart muscle are suggestive of a beneficial role of the seed extract. The possible mechanisms of action are discussed.     

Ameloblastic odontoma in a rat

A spontaneous ameloblastic odontoma was found in an 86-week-old male Fischer 344 rat. Radiographic and histopathologic characteristics confirmed the diagnosis as a true benign neoplasm.     

Functional relationship between ammonia and gangliosides in brain

The functional significance of ammonia production in brain under physiological or pathological conditions is not clearly known. NH₄ ⁺ stimulates Na⁺, K⁺ activated ATPase causing stabilization of neuronal membranes of which gangliosides are major structural components. Moreover ammonia is known to inhibit lysosomal enzymes which include enzymes degrading gangliosides. Gangliosides have been shown to stimulate neuritogenesis in neuronal cultures and prevent the damage of the neurons from glutamate toxicity particularly in areas of brain ischemia. Hyperammonemia without any behavioural changes was induced in experimental rats by intraperitoneal administration of either a single dose (0.8 mmol/100 g wt.) or by six hourly doses (0.6 mmol/100 g wt.) of ammonium acetate. An increase in the content of gangliosides along with a rise in the content of GD_1A and GD_1B without any change in -galactosidase and N-acetylhexosaminidase was observed in cerebral cortex, cerebellum, and brain stem, following the administration of single dose of ammonium acetate. Gangliosides, after extraction from the different brain regions, were estimated by the thiobarbituric acid method and expressed in terms of sialic acid. Individual gangliosides were separated and estimated by thin layer chromatography using resorcinol as the staining agent. These results suggest that ammonia production in the neuronal pathways in brain either as a result of repeated stimulation under physiological conditions or as a result of focal ischemia or injury, may likewise cause an increase in the content of gangliosides which may help in neuritic growth (physiological conditions facilitating synaptic plasticity) and may exert a protective effect on the neurons in the ischemic area against glutamate toxicity.Former Professor of Biochemistry, OMC, Hyderabad.     

Nano-biotechnology in tumour and cancerous disease: A perspective review

In recent years, drug manufacturers and researchers have begun to consider the nanobiotechnology approach to improve the drug delivery system for tumour and cancer diseases. In this article, we review current strategies to improve tumour and cancer drug delivery, which mainly focuses on sustaining biocompatibility, biodistribution, and active targeting. The conventional therapy using cornerstone drugs such as fludarabine, cisplatin etoposide, and paclitaxel has its own challenges especially not being able to discriminate between tumour versus normal cells which eventually led to toxicity and side effects in the patients. In contrast to the conventional approach, nanoparticle-based drug delivery provides target-specific delivery and controlled release of the drug, which provides a better therapeutic window for treatment options by focusing on the eradication of diseased cells via active targeting and sparing normal cells via passive targeting. Additionally, treatment of tumours associated with the brain is hampered by the impermeability of the blood–brain barriers to the drugs, which eventually led to poor survival in the patients. Nanoparticle-based therapy offers superior delivery of drugs to the target by breaching the blood–brain barriers. Herein, we provide an overview of the properties of nanoparticles that are crucial for nanotechnology applications. We address the potential future applications of nanobiotechnology targeting specific or desired areas. In particular, the use of nanomaterials, biostructures, and drug delivery methods for the targeted treatment of tumours and cancer are explored.     

Denitrification of nitrate to nitrogen gas by washed cells ofRhizobium japonicum and by bacteroids fromGlycine max

Nitrate, nitrite and nitrous oxide were denitrified to N₂ gas by washed cells ofRhizobium japonicum CC706 as well as by bacteroids prepared from root nodules ofGlycine max (L.) Merr. (CV. Clark 63). Radiolabelled N₂ was produced from either K¹⁵NO₃ or Na¹⁵NO₂ by washed cells ofRh. japonicum CC705 grown with either nitrate only (5 mM) or nitrate (5 mM) plus glutamate (10 mM). Nitrogen gas was also produced from N₂O. Similar results were obtained with bacteroids ofG. max. The stoichiometry for the utilization of¹⁵NO ₃ ^- or¹⁵NO ₂ ^- and the produciton of¹⁵N₂ was 2:1 and for N₂O utilization and N₂ production it was 1:1. Some of the¹⁵N₂ gas produced by denitrification of¹⁵NO ₃ ^- in bacteroids was recycled via nitrogenase into cell nitrogen.     

Dynamic quenching studies of fluorophore-labelled myosin subfragment 1 and its alkali light chain subunits

The technique of fluorescence quenching by the non-ionic quenchers acrylamide and nicotinamide has been used to probe the accessibility of the environmentally sensitive N-(bromoacetyl)-N'-(1-sulpho-5-naphthyl) ethylenediamine (1,5-Br-AEDANS) fluorophore attached to either Cys-177 of the A1-light chain or the SH1 thiol (Cys-707) of the myosin subfragment (S1) heavy chain. Neither quencher caused any detrimental effects to the ATPase activities of S1 under the conditions of the experiments. It was found that the fluorophore on the isolated light chain was highly exposed to solvent and although this exposure was reduced on hybridization into S1(A1-AEDANS), the probe was still accessible to solvent. This exposure was unaltered by formation of binary complexes with either Mg.ATP or actin or by the formation of a weakly associated acto-S1 complex (in which the Cys-697 and Cys-707 residues of S1 were crosslinked with p-phenylenedimaleimide). The lack of corresponding change in lambda max of emission and quantum yield supported the quenching date and indicated that actin neither binds directly to this region nor induces any significant conformational changes in this locality despite the observation that the A1-Cys-707 moves some 3 nm closer to a point on actin in the weak-binding state (Trayer, H.R. and Trayer, I.P. (1988) Biochemistry, 27, 5718-5727). Parallel experiments with the fluorophore attached to the Cys-707 of the S1 indicated that this region was less accessible to solvent than the light chain thiol despite its ease of labelling. This exposure was not significantly altered by binary complex formation with actin and Mg.ATP, although spectral changes in the absence of quencher support the notion that some conformational change is occurring in this region.     

Lipofuscin like compound in mango

Thin layer chromatographic separation of chloroform-methanol extracts of mango on silica gel revealed a fluorescent substance in mango peel and pulp. The compound had fluorescence spectrum similar to that of lipofuscin, the age pigment of animal tissues and was found to be water insoluble and stable to ultraviolet irradiation. The fluorescent material appeared to be a lipoprotein.