Structural properties of phospholipids in the rat liver inner mitochondrial membrane. A P-NMR study

1. 1. The ³¹P-NMR characteristics of intact rat liver mitochondria, mitoplasts and isolated inner mitochondrial membranes, as well as mitochondrial phosphatidylethanolamine and phosphatidylcholine, have been examined.

2. 2. Rat liver mitochondrial phosphatidylethanolamine hydrated in excess aqueous buffer undergoes a bilayer-to-hexagonal (H_II) polymorphic phase transition as the temperature is increased through 10°C, and thus prefers the H_II) arrangement at 37°C. Rat liver mitochondrial phosphatidylcholine, on the other hand, adopts the bilayer phase at 37°C.

3. 3. Total inner mitochondrial membrane lipids, dispersed in an excess of aqueous buffer, exhibit ³¹P-NMR spectra consistent with a bilayer arrangement for the majority of the endogeneous phospholipids; the remainder exhibit spectra consistent with structure allowing isotropic motional averaging. Addition of Ca²⁺ results in hexagonal (H_II) phase formation for a portion of the phospholipids, as well as formation of ‘lipidic particles’ as detected by freeze-fracture techniques.

4. 4. Preparations of inner mitochondrial membrane at 4 and 37°C exhibit ³¹P-NMR spectra consistent with a bilayer arrangement of the large majority of the endogenous phospholipids which are detected. Approx. 10% of the signal intensity has characteristics indicating isotropic motional averaging processes. Addition of Ca²⁺ results in an increase in the size of this component, which can become the dominant spectral feature.

5. 5. Intact mitochondria, at 4°C, exhibit ³¹P-NMR spectra arising from both phospholipid and small water-soluble molecules (ADP, P_i, etc.). The phospholipid spectrum is characteristic of a bilayer arrangement. At 37°C the phospholipids again give spectra consistent with a bilayer; however, the labile nature of these systems is reflected by increased isotropic motion at longer (at least 30 min) incubation times.

6. 6. It is suggested that the uncoupling action of high Ca²⁺ concentrations on intact mitochondria may be related to a Ca²⁺-induced disruption of the integrity of the inner mitochondrial phospholipid bilayer. Further, the possibility that non-bilayer lipid structures such as inverted micelles occur in the inner mitochondrial membrane cannot be excluded.

Effect of NMDA-receptor ligands on neocortical and hippocampal EEG activity of rat brain.

Neocortex and hippocampus play important role in motor activity, neuronal plasticity and learning and memory mechanisms. Electroencephalographic (EEG) activity of neocortex and hippocampus of rat following NMDA-receptor agonist, N-methyl-D-aspartate (NMDA), 0.25-2 nmol in 10 microliters, ICV and noncompetitive NMDA-receptor antagonists, MK 801 (0.025-0.1 mg/kg, ip) and ketamine (10-50 mg/kg, ip) at OH, 1/2H, 4H, 8H and 24H was recorded. The electrodes were implanted stereotaxically in hippocampus and neocortex respectively. NMDA (0.25 and 1 nmol) showed longer lasting decrease in amplitude in hippocampus and in frequency in cortical neurons while 2 nmol produced epileptogenic neurotoxicity. Opposite effect i.e. increase in amplitude in both, hippocampus and neocortex was observed with MK 801 and ketamine and these agents also showed longer lasting influence. Administration of MK 801 (0.05 mg/kg) and ketamine (50 mg/kg) prior to NMDA 2 nmol protected 40% animals from NMDA-induced neurotoxicity and blockade of NMDA-induced long term influence. The EEG effect of NMDA agonist and NMDA-induced neurotoxicity at higher dose and its modification by NMDA-antagonist, MK 801 and ketamine suggest that beside NMDA agonists (NMDA), its antagonists may, also affect long lasting changes in hippocampus and cortex. These antagonists reverse NMDA-mediated long term influence in these brain areas.     

Brugia malayi and Brugia pahangi: transmission blocking activity of ivermectin and brugian filarial infections in Aedes aegypti

Brugia malayi- or Brugia pahangi-infected, microfilaremic jirds (Meriones unguiculatus) were treated with ivermectin at a single dose of 200 micrograms/kg body weight, administered subcutaneously. After different time intervals, Aedes aegypti mosquitoes were fed on treated or untreated jirds. Sausage stage, L2, and L3 larvae failed to develop in mosquitoes that fed on jirds from 15 to 30 days post-treatment. After 1 month, the numbers of L3 larvae recovered from mosquitoes fed on treated B. pahangi jirds were comparable to controls. However, the number of L3's recovered from mosquitoes fed on B. malayi jirds remained significantly lower than controls, 2 and 3 months after treatment. This reduction suggests that ivermectin may be more effective in blocking transmission of B. malayi than B. pahangi. Ivermectin treatment had no effect on the mean number of circulating microfilariae in treated jirds. Therefore, mosquitoes ingested comparable numbers of microfilariae when compared to those mosquitoes fed on untreated controls. Only in the case of jirds infected with B. malayi did the circulating microfilarial counts fall 30 days after treatment. The failure of microfilariae to develop to the L3 stage in mosquitoes fed on jirds within 30 days of treatment was not due to failure of mosquitoes to ingest microfilariae. Brugia malayi microfilariae also failed to develop to L3 in mosquitoes that were allowed to feed on microfilaremic jird blood treated with ivermectin (50 ng/ml) in vitro, indicating its efficacy at low concentrations. In addition to N-acetyl glucosamine, microfilariae obtained for a period of 15 days from ivermectin-treated but not control jirds showed D-mannose, N-acetyl galactosamine, and L-fucose moieties on the surface of the sheath.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nucleoside phosphorylase 2 (Np-2) of mice

Isozyme patterns of nucleoside phosphorylase (NP) in 16 inbred strains, two recombinant inbred, one congenic, and three species of wild mice were studied. Evidence is provided for a genetic locus, Np-2, encoding an electrophoretic variant which is expressed exclusively in erythrocytes of certain inbred strains. This finding establishes the occurrence of genetic polymorphism of NP among inbred strains of mice. In addition, the Npla allele previously reported only in inbred strains has been observed in one of the species of wild mice (Mus musculus castaneus) studied.     

Physiological basis of host susceptibility of Florida mosquitoes to Dirofilaria immitis.

Young females of seven species of Florida mosquitoes were fed a meal of dog blood infected with Dirofilaria immitis to repletion to study the physiological mechanisms which control susceptibility and resistance in these mosquitoes. Various species of mosquitoes showed different grades of susceptibility. In all mosquitoes, microfilariae reached the midgut immediately after ingestion. Their movement from midgut to the specific host tissue—the Malpighian tubules—was either facilitated or inhibited depending on the presence or absence of anticoagulins in the salivary glands of these mosquitoes. In Anopheles quadrimaculatus, Aedes taeniorhynchus, and Aedes sollicitans, microfilariae move freely from the midgut to the Malpighian tubules, because of the presence of substantial amounts of anticoagulins in their salivary glands, and 30 to 60 mf/female developed normally to an infective stage. Very few microfilariae reached the tubules of Mansonia titillans as most of them were defaecated within a very short time after ingestion. In Aedes aegypti, Culex nigripalpus, and Culex pipiens quinquefasciatus movement of microfilariae from the midgut to the Malpighian tubules was obstructed by the coagulation of blood soon after ingestion. Coagulation of blood was followed by formation of oxyhaemoglobin crystals in C. nigripalpus and C. p. quinquefasciatus. It is suggested that secretions from symbiotic bacteria in the midgut of these mosquitoes lyse ingested red blood cells, and the released haemoglobin is oxidized to oxyhaemoglobin crystals which hinder the further movement of microfilariae and kill them.Microfilariae developed normally in A. quadrimaculatus, thus making them potentially the most susceptible mosquitoes, even though these mosquitoes did not survive to be effective potential vectors. A few microfilariae or their later developmental stages were melanized in the tubules of most A. sollicitans and A. taeniorhynchus, but the numbers of melanized stages were too few to affect the vectoring potentials of these species. In 20 per cent of A. sollicitans, 60 per cent of M. titillans, and ca. 80 per cent A. aegypti substantial numbers of the microfilariae after reaching the Malpighian tubules did not advance beyond the prelarval stage, and very few microfilariae developed successfully in the remaining mosquitoes. Very few microfilariae reached the Malpighian tubules of a small percentage of C. nigripalpus and C. p. quinquefasciatus and developed normally. The vectoring potentials of A. sollicitans, M. titillans, A. aegypti, and both Culex species were greatly hampered. These studies suggested that host-specificity of mosquitoes to D. immitis infection is controlled by the presence or absence of secondary physiological factors in their digestive tracts or in the Malpighian tubules.     

Myelin lipids in vitamin B12 deficiency in chicks

Lipid profile of the spinal cord myelin was studied in normal and vitamin B₁₂ deficient chicks. The significant findings were a reduction in the total galactolipids and an increase in the total phospholipids of myelin in vitamin B₁₂ deficiency. The altered molar ratios of these lipids suggest a relative immaturity of the myelin in this condition. These changes may initiate the degenerative changes in the central nervous system in vitamin B₁₂ deficiency.Vitamin B₁₂ is essential for normal functioning of both the hemopoietic and the nervous system. Sub-acute combined degeneration of the spinal cord is seen both in association with pernicious anemia and in megaloblastic anemia of dietary origin (1,2). Though many biochemical postulates (3, 4) have been advanced to explain the neurological changes, the role of vitamin B₁₂ in maintaining the integrity of myelin is still obscure. So far only in two animal species the monkey (5) and the chick (6) has myelin degeneration been reported in vitamin B₁₂ deficiency. However, in neither of these reports, have changes in the composition of myelin been described. The results of a study in chicks wherein the effects of vitamin B₁₂ on the lipid profile of myelin were investigated are reported here.     

Synthesis and Docking Studies of Novel Carbazole-Thiazolidinedione Hybrid Derivatives as Antibacterial Agents

Russian Journal of Bioorganic Chemistry - A series of novel carbazol-thiazolidinedione hybrid derivatives were designed, synthesised and screened for antimicrobial activity against gram-positive...     

Lipase production by Serratia marcescens strain SN5gR isolated from the scat of lion-tailed macaque (Macaca silenus) in Silent Valley National Park, a biodiversity hotspot in India

An extracellular lipase-producing bacterium was isolated from a fecal sample of lion-tailed macaque (Macaca silenus), an endangered Old World monkey that is endemic to the Western Ghats of South India. Morphological, biochemical and molecular analyses identified the bacterium as Serratia marcescens. Production of lipase was investigated in shake-flask culture. Optimum tributyrin concentration of 1.5 % was found to be the most suitable triglyceride to increase lipase production (13.3 U ml^?1). The next best lipid source observed was olive oil (11.94 U ml^?1), followed by castor oil, coconut oil and palm oil. Analyzing the effect of different carbon sources on lipase production revealed that 2 % glucose yielded higher lipase production than the other tested carbon sources. Investigations on suitable nitrogen source for lipase production revealed that 2 % meat extract yielded higher lipase production. The most suitable trace element for maximum lipase production was zinc sulfate, followed by magnesium sulfate and copper sulfate. Partial characterization of the crude lipase revealed that pH 7.0 and a temperature of 40 °C gave optimal lipase activity. Enzymatic activity of the crude sample was retained over a wide temperature range (20–75 °C), and 70 % of enzyme activity was retained at 60 °C. Testing the effect of various organic solvents on lipase activity revealed that hexadecane increased lipase activity by 85 % over the control.