Deprenyl Protects Dopamine Neurons from the Neurotoxic Effect of 1-Methyl-4-Phenylpyridinium Ion

1-Methyl-4-phenylpyridinium ion (MPP+) is the product of the metabolic oxidation of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) by monoamine oxidase (MAO). MPP+ is toxic to 3,4-dihydroxyphenylethylamine (dopamine, DA) neurons in explant cultures of rat embryonic midbrain. Addition of 2.5 microM MPP+ to the feeding medium for 6 days results in significant reduction of the DA levels in the cultures (to 19% of control) as well as in the uptake of [3H]DA (to 32% of control). When the cultures are treated with the MAO inhibitor deprenyl (10 microM) 24 h prior to and during exposure to MPP+, the DA neurons are protected from the toxicity of the drug. In the combined deprenyl plus MPP+ treatment, the levels of DA in the cultures remain at the control range and the [3H]DA uptake is reduced to only 73% of control. These results indicate that MAO is involved in the toxicity of MPP+ on DA neurons.     

Hybridization in the genus Lens by means of embryo culture

Summary The cultivated lentil L. culinaris and the wild lentil L. ervoides are reproductively isolated from one another due to their hybrid embryo breakdowns. Using embryo culture, vegetatively normal hybrids were obtained. One specific hybrid, heterozygous for a reciprocal translocation, had about 50% gamete viability and produced aborted and viable embryos in a 11 ratio. In the F₂, vegetatively normal and highly fertile plants were selected. With the aid of embryo culture techniques, L. ervoides can be included in the wild gene pool of the cultivated lentil.     

The integrated and free states of Streptomyces griseus plasmid pSG1

A 16.6-kb plasmid-pSG1-was isolated from Streptomyces griseus following transformation of protoplasts with unrelated plasmids. Southern hybridization experiments with radioactive probes prepared from pSG1 fragments and immobilized S. griseus DNA fragments indicated that the plasmid was present in the progenitor strain, in an integrated state. In the pSG1+ isolates plasmid sequences existed both as integrated sequences and as free plasmids. The integrated state of maintenance persisted in strains which have been cured of the free plasmid. The junction site on the plasmid was located on a 0.5-kb EcoRI-SalI fragment. The chromosomal integration site was demonstrated to be the same in all strains derived from S. griseus NRRL3851. The occurrence of both states of plasmid maintenance in the same clones indicates that an integrated pSG1 sequence does not interfere with free plasmid replication and partition. It suggests that the establishment of the free state may involve a replicative excision of pSG1 from the S. griseus chromosome.     

Cellular systems for the study of the biosynthesis of polyamines and ethylene,as well as of virus multiplication

Leaves of Chinese cabbage from healthy plants or from those infected with turnip yellow mosaic virus yield protoplasts which convert methionine to protein, S-adenosylmethionine, decarboxylated S-adenosylmethionine, spermidine, spermine and 1-aminocyclopropane-1-carboxylate. The enzyme spermidine synthase is entirely cytosolic and has been purified extensively. An inhibitor of this enzyme, dicyclohexylamine, blocks spermidine synthesis in intact protoplasts, and in so doing stimulates spermine synthesis. Aminoethoxyvinylglycine blocks the conversion of S-adenosylmethionine to 1-aminocyclopropane-1-carboxylate, the precursor to ethylene, in protoplasts. This inhibitor markedly stimulates the synthesis of both spermidine and spermine. Essentially all the protoplasts obtained from new leaves of plants infected 7 days earlier are infected. On incubation, such protoplasts convert exogenous methionine to viral protein and viral spermidine whose specific radioactivity is twice that of total cell spermidine. Exogeneous spermidine is also converted to cell putrescine and viral spermidine and spermine. Normal and virus-infected cells are being studied for their content of phenolic acid amides of the polyamines.     

The possible involvement of polyamines in the development of tomato fruits in vitro

The apparent involvement of ornithine decarboxylase (ODC) and putrescine in the early stages of fruit growth in tomato (Lycopersicon esculentum Mill.) has been previously described. Further evidence presented here supports the direct involvement of ODC and putrescine in the cell division process in tomato fruits. In tomato fruits grown in vitro, in which basic growth processes are inhibited, the activity of ODC and arginine decarboxylase (ADC) and the level of free polyamines were reduced. While ODC and ADC activity was correlated with the period of cell division in the tomato fruit, the free polyamine content was correlated with the DNA content, cell size, and fruit fresh weight. The addition of exogenous putrescine, however, did not restore the basic growth processes in the fruits grown in vitro.     

ACTH 1-24-induced potentiation of norepinephrine contractile responses in aortic strips from spontaneously hypertensive (SH) and normotensive (WKY) rats

Norepinephrine (NE)-induced contractile responses were less in aortic strips from SH compared to WKY rats. ACTH 1-24 potentiated NE responses in both SH and WKY aortic strips. This effect was more potent in SH aortic strips. NE-induced contractions in SH aortic strips were less sensitive to changes in external Ca2+ levels than were those of WKY aortic strips. ACTH 1-24 did not potentiate NE responses under low external Ca2+ conditions in SH aortic strips or under high external Ca2+ conditions in WKY aortic strips. The greater sensitivity of NE responses following ACTH 1-24 in SH aortic strips may imply that this peptide is modulating a mechanism related to an impaired contractility and that Ca2+ plays a key role in the observed effects.     

Analysis of the sheep MHC using HLA class I,II, and C4 cDNA probes

Four cDNA probes for the human major histocompatibility complex (MHC) were used to investigate the sheep MHC, in conjunction with serological typing for ovine lymphocyte antigen (OLA). Lymphocytes from a family (two parents and five offspring) of Romanov sheep were subjected to genomic DNA digestion by the restriction endonuclease Eco RI, followed by gel electrophoresis. A single Southern blot representing all seven individuals was then consecutively hybridized with the class I, alpha-DC, beta-DR, and C4 probes, which were originally designed to identify HLA class I, class II (DC and DR), and C4 products, respectively. Using each of the three class I/class II probes, several bands showing DNA polymorphism were detected. The segregation of these bands in the five offspring exactly paralleled the OLA haplotype segregation established by serological typing. A further eight individuals carrying haplotypes which were phenotypically identical to those in the above-mentioned family showed bands in the corresponding positions when tested with the same three probes. Using the C4 probe, no polymorphism was detected in these fifteen individuals.Abbreviations used in this paper MHC major histocompatibility complex - OLA ovine lymphocyte antigen - kbp kilobase pair(s) - MLR mixed lymphocyte reaction - RFLP restriction fragment length polymorphism     

Autocides produced by Myxococcus xanthus.

Ethanol extracts of Myxococcus xanthus contained several substances, referred to as autocides, which were bactericidal to the producing strain but showed no activity against other bacteria. The autocides were produced by growing cells and remained largely cell bound throughout the growth cycle; ca. 5% of the autocidal activity was found in the supernatant fluid at the time cell lysis began. The autocides were separated by sequential-column and thin-layer chromatography into five active fractions (AM I through AM V). Each of the fractions was at least 20 times more active against M. xanthus than against the other gram-negative or gram-positive bacteria tested. AM I, AM IV, and AM V were inactive against yeasts, whereas a mixture of fractions AM II and AM III was active against Rhodotorula sp. At low concentrations, AM I reversibly inhibited the growth of M. xanthus; at higher concentrations of AM I, the cells lysed within 1 h. The lowest concentration of AM IV that showed any activity caused rapid cell death and lysis. The mode of action of the major autocide, AM V, was different from that of AM I and AM IV. During the initial 2 h of treatment, the viable count of M. xanthus cells remained constant; during the next few hours killing occurred without lysis; within 24 h lysis was complete. The autocidal activity of each of the fractions was expressed when the cells were suspended in buffer, as well as in growth medium. The possible role of autocides in developmental lysis of M. xanthus is discussed.     

Female sex hormone and nephropathy in Cohen diabetic rat (genetically selected sucrose-fed)

In the Cohen diabetic rat (genetically-selected sucrose-fed) ovariectomy resulted in a significantly decreased incidence of nephropathy, while estradiol treatment to the ovariectomized animal increased the rate of nephropathy to the levels occurring in the uncastrated untreated diabetic female. In the male diabetic animal orchidectomy caused a slight decrease in the rate of nephropathy whereas estradiol treatment to the orchidectomized animal resulted in a slight increase in the rate. No difference was found between the ovariectomized and the uncastrated diabetic female as to the spontaneous blood glucose, plasma insulin, serum cholesterol or TG levels, but a significant difference was found in their plasma estradiol levels.     

Biochemical characterization of complex formation by human erythrocyte spectrin, protein 4.1, and actin

Ternary complex formation between the major human erythrocyte membrane skeletal proteins spectrin, protein 4.1, and actin was quantified by measuring cosedimentation of spectrin and band 4.1 with F-actin. Complex formation was dependent upon the concentration of spectrin and band 4.1, each of which promoted the binding of the other to F-actin. Simultaneous measurement of the concentrations of spectrin and band 4.1 in the sedimentable complex showed that a single molecule of band 4.1 was sufficient to promote the binding of a spectrin dimer to F-actin. However, the molar ratio of band 4.1/spectrin in the complex was not fixed, ranging from approximately 0.6 to 2.2 as the relative concentration of added spectrin to band 4.1 was decreased. A mole ratio of 0.6 band 4.1/spectrin suggests that a single molecule of band 4.1 can promote the binding of more than one spectrin dimer to an actin filament. Saturation binding studies showed that in the presence of band 4.1 every actin monomer in a filament could bind at least one molecule of spectrin, yielding ternary complexes with spectrin/actin mole ratios as high as 1.4. Electron microscopy of such complexes showed them to consist of actin filaments heavily decorated with spectrin dimers. Ternary complex formation was not affected by alteration in Mg2+ or Ca2+ concentration but was markedly inhibited by KCl above 100 mM and nearly abolished by 10 mM 2,3-diphosphoglycerate or 10 mM adenosine 5'-triphosphate. Our data are used to refine the molecular model of the red cell membrane skeleton.