Action of phospholipase A2 of rabbit neuronal and glial cells on 1,2-diacyl-, 2-acyl-1-alk-1′-enyl-, and 2-acyl-1-alkyl-glycerophosphatides

Pronounced differences in the phospholipase A₂ activities were found in neurons and glia, the enzyme activity being two- to threefold higher in neurons than in glial cells. Both phospholipases A₂ hydrolyzed the 1,2-diacylglycerophosphatides more rapidly than the acylalkyl and acylalkenyl compounds. Choline plasmalogen and the corresponding alkyl derivative were cleaved at similar rates by the phospholipase A₂ from both glia and neurons. There was a tendency by the neuronal phospholipase A₂ to release arachidonic acid faster than linolenic acid from both phosphatidylcholine and ethanolamine, while arachidonic acid was removed less actively from phosphatidylethanolamine by the glial enzyme. The glial phospholipase A₂ showed a lag period of 10 or 20 min. Norepinephrine, injected into the lateral ventricle of the rabbit brain, stimulated the hydrolysis of the various 1,2-diacyl-, acylalkyl-, and acylalkenyl-glycerophosphatides by the phospholipase A₂ from both glia and neurons.     

The CD45 locus in cattle: allelic polymorphism and evidence for exceptional positive natural selection

Cattle in Africa are a genetically diverse population that has resulted from successive introduction of Asian Bos indicus and European B. taurus cattle. However, analysis of mitochondrial genetic diversity in African cattle identified three lineages, one associated with Asian B. indicus, one with European B. taurus, and a third ascribed to an indigenous African sub-species of cattle. Due to their extended coevolution, indigenous African herbivores are generally tolerant to endemic African pathogens. We are interested in identifying alleles derived from the indigenous African cattle that may be associated with tolerance to African pathogens. An analysis of the locus which encodes the abundant plasma membrane-associated tyrosine phosphatase, CD45, identified three highly divergent allelic families in Kenya Boran cattle. Analysis of allelic distribution in a diverse range of cattle populations suggests a European B. taurus, an Asian B. indicus, and an African origin. This demonstrates not only significant allelic polymorphism at the CD45 locus in cattle but also convincing autosomal evidence for a distinct African sub-species of cattle. Furthermore, maximum-likelihood analysis of selection pressures revealed that the CD45 locus is subject to exceptionally strong natural selection which we suggest may be pathogen driven.     

Seroprevalence of <Emphasis Type="Italic">Borrelia burgdorferi</Emphasis> sensu lato and <Emphasis Type="Italic">Anaplasma phagocytophilum</Emphasis> in Danish horses

Background

Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum are able to infect horses. However, the extend to which Danish horses are infected and seroconvert due to these two bacteria is unknown. The aim of the present study was to evaluate the seroprevalence of B. burgdorferi sensu lato and A. phagocytophilum in Danish horses.

Methods

A total of 390 blood samples collected from all major regions of Denmark and with a geographical distribution corresponding to the density of the Danish horse population were analyzed. All samples were examined for the presence of antibodies against B. burgdorferi sensu lato and A. phagocytophilum by the use of the SNAP^®4DX ^® ELISA test.

Results

Overall, 29.0% of the horses were seropositive for B. burgdorferi sensu lato whereas 22.3% were seropositive for A. phagocytophilum.

Conclusions

Antibodies against B burgdorferi sensu lato and A. phagocytophilum are commonly found among Danish horses thus showing that Danish horses are frequently infected by these organisms.

     

INCORPORATION OF 32P INTO THE PHOSPHOLIPIDS OF NEURONAL AND GLIAL CELL ENRICHED FRACTIONS ISOLATED FROM RABBIT CEREBRAL CORTEX: EFFECT OF NOREPINEPHRINE

Abstract— Glial cells isolated from rabbit cerebral cortex contained approximately one-third more phospholipids per unit protein than the neuronal cell bodies. The pattern of individual phospholipids was rather similar in both cell types. The incorporation of intracisternally administered ³²P into neuronal and glial phospholipid classes of rabbit brain was studied at intervals ranging from 5 to 60min. In general, for all investigated phospholipids the incorporation of the label was somewhat faster in neurons than in glial cells. Phosphatidylinositol showed the fastest and ethanolamine plasmalogen the slowest incorporation of ³²P in both neurons and glial cells. A lag phase of about 10 min could be observed before labelling of the glial phosphatidylcholine, phosphatidylethanolamine, ethanolamine plasmalogen, phosphatidylserine and sphingomyelin had occurred. Among the neuronal phospholipids a lag phase was found only for the labelling of the ethanolamine plasmalogen. Norepinephrine increased the incoropration of ³²P into phosphatidylinositol of both glia and neurons but had no effect on the specific radioactivity of ethanolamine plasmalogen and sphingomyelin. Labelling of phosphatidylcholine was slightly inhibited in both cell types by the administration of norepinephrine.     

The Ca2+-dependent incorporation of nitrogenous bases into brain microsomal phospholipid subspecies in vitro.

The specificity of the Ca2+-stimulated choline and ethanolamine incorporation into the molecular subspecies of the correspondent choline and ethanolamine phosphoglycerides has been investigated in vitro in rat brain microsomes. In the presence of 5.0 mM Ca2+-ions and at pH 8.1, choline was incorporated 6 times faster into the tetraenoic diacyl-glycero-3-phosphorylcholines (diacyl-GPCs or lecithins) than into the saturated subspecies. The specific activities of the other species were intermediary, and decreased with increasing saturation. Hexaenoic species of lecithins were however weakly labelled. The rate of labelling of diacyl-GPC molecular subspecies was affected noticeably by changing the pH and the Ca2+-ion concentration of the incubation medium. Ethanolamine was incorporated in the presence of 2.5 mM Ca2+-ions and at pH 8.1 preferentially into the monoenoic species of total ethanolamine phosphoglycerides of rat brain microsomes. The rate of incorporation into the monoenoic species was twice that into the trienoic, tetraenoic and hexaenoic and 4 times faster that into the dienoic species. When the pattern of labelling was determined specifically for the molecular subspecies of diacyl-glycero-3-phosphorylethanolamines (diacyl-GPEs or phosphatidylethanolamines), the rate of incorporation of ethanolamine into the hexaenoic species resulted three times faster that into the saturated and monoenoic species and about twice that into the trienoic and tetraenoic species, in accordance with data for liver microsomes. The pattern of labelling of the molecular subspecies of ethanolamine phosphoglycerides and of diacyl-GPEs was not influenced by changing the pH and the Ca2+-ion concentration of the incubation medium.     

Estimates of DNA and protein sequence divergence: an examination of some assumptions

Some of the assumptions underlying estimates of DNA and protein sequence divergence are examined. A solution for the variance of these estimates that allows for different mutation rates and different population sizes in each species and for an arbitrary structure in the initial population is obtained. It is shown that these conditions do not strongly affect estimates of divergence. In general, they cause the variance of divergence to be smaller than a binomial variance. Thus, the binomial variance that is usually assumed for these estimates is safely conservative. It is shown that variability in the mutation rate among sites can have an effect as large as or larger than variability in the mutation rate among bases. Variability in the mutation rate among bases and among sites causes the number of substitutions between two sequences to be underestimated. Protein and DNA sequences from several species are collected to estimate the variability in mutation rates among sites. When many homologous sequences are known, standard methods to estimate this variability can be used. The estimates of this variability show that this factor is important when considering the spectrum of spontaneous mutations and is strongly reflected in the divergence of sequences. Smaller variability is found for the third position of codons than for the first and second codon positions. This may be because of less selective constraints on this position or because the third position has been saturated with mutations for the sequences examined.      

PHOSPHOLIPID METABOLISM IN EXPERIMENTAL ALLERGIC ENCEPHALOMYELITIS: ACTIVITY OF MITOCHONDRIAL PHOSPHOLIPASE A2 OF RAT BRAIN TOWARDS SPECIFICALLY LABELLED 1,2-DIACYL-, 1-ALK-1''-ENYL-2-ACYL- AND 1-ALKYL-2-ACYL-SN-GLYCERO- 3-PHOSPHORYLCHOLINE

—1,2-Diacyl-, 1-alk-1′-enyl-2-acyl-and 1-alkyl-2-acyl-sn-glycero-3-phosphorylcholine, specifically labelled with different fatty acids at the 2 position, were prepared enzymically using the acyltransferase system of rabbit sarcoplasmic reticulum. The substrates were submitted to hydrolysis by mitochondrial phospholipase A₂ (phosphatide acyl-hydrolase, EC 3.1.1.4) obtained from normal and from rat brain afflicted with EAE. In the acute stage of the disease an increase of approximately 25 per cent in phospholipase A ₂ activity could be observed in comparison to that from the control animals for all investigated substrates. Phospholipase A₂ obtained from normal rat brains and from those afflicted with EAE had a higher affinity for 1,2-diacyl-sn-glycero-3-phosphorylcholine when compared to the corresponding alkyl acyl- and alkenyl acyl-analogues. Choline plasmalogen was cleaved more slowly than the corresponding alkyl acyl derivative. The enzyme activity returned to the control level in the recovery stage of the demyelinating disease.