Biosynthesis of lipids in chloroplasts isolated from jack pine needles

Suspensions of isolated pine needle chloroplasts were shown to incorporate galactose from UDP galactose-[¹⁴C] into galactolipids. The incorporation of the label among galactolipids was always considerably higher in the monogalactosyl diglycerides than in the digalactosyl diglycerides. The galactosyl incorporation into both galactolipid fractions was optimal at pH 8.0 and was inhibited by sulphydryl reagents (p-chloromercuribenzoate, N-ethyl maleimide and CdCl₂). The chloroplast preparations were also able to biosynthesize various phospholipids and galactolipids from palmitoyl-[1-¹⁴C]-CoA; the major portion of the label appeared in phosphatidyl choline. The incorporation of palmitic-[1-¹⁴C] acid into various lipids was very poor compared to that of palmitoyl-[1-¹⁴C]-CoA. However, addition of ATP and CoA markedly stimulated lipid biosynthesis from palmitic-[1-¹⁴C] acid, suggesting the presence of activating enzymes. These chloroplast suspensions did not show any de novo fatty acid synthesis.     

Involvement of pp60c-src in platelet-activating factor-stimulated platelets. Evidence for translocation from cytosol to membrane.

We have investigated the characteristics of platelet-activating factor (PAF)-stimulated protein tyrosine phosphorylation in rabbit platelets and its relationship to pp60c-src. 32P-Labeled platelets were challenged with PAF (10(-7) M) for 15 s, the reaction was killed by lysis at 4 degrees C, and samples were loaded onto a phosphotyrosine monoclonal antibody (Tyr(P)-mAb)-agarose column. The column was eluted with 10 mM phenyl phosphate, and the fractions were collected. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis, followed by autoradiography of the column fractions, showed that PAF increased the radioactivity of about a dozen protein bands with predominant ones of approximate molecular masses of 50, 60, 71, 82, and 300 kDa. When Tyr(P)-mAb-agarose column fractions were subjected to immunoblotting with pp60v-src mAb, it was observed that PAF treatment increased the reactivity of 50- and 60-kDa protein species. Immunoprecipitation with pp60v-src mAb further confirmed that PAF treatment increased phosphorylation of the 60- and 50-kDa proteins. Polyclonal antibody to G-protein (alpha-subunit) did not exhibit any reactivity to the column fractions and thus ruled out this protein as substrate for the tyrosine kinase. We next attempted to localize the pp60c-src. Platelet membrane particulate and cytosol fractions were separated from control and PAF-treated platelets, and it was observed that the immunoreactivity to pp60v-src mAb dramatically increased in the particulate membrane fraction from PAF-treated platelets. A concomitant decrease in the immunoreactivity in the cytosol fraction of PAF-treated platelets was also noted. It is concluded that PAF stimulates phosphorylation of pp60c-src tyrosine kinase and causes its rapid translocation from cytosol to membranes in rabbit platelets.     

The premenstrual syndrome and its treatment

The premenstrual syndrome has been described briefly and the literature relating to its pathophysiology and treatment have been reviewed. The great number of theories as to etiology and many different kinds of treatments attest to our ignorance of the exact nature of this problem. Although it is obvious that the hypothalamo-pituitary-ovarian axis must be involved, the exact mechanism whereby the symptoms come about remains elusive. Progestin in the presence of estrogen appears to be essential. Excess estrogen may aggravate the condition. The popular theory of progesterone deficiency has not been supported by double blind trials of progesterone in various forms versus placebo. Because of the important placebo effect in this condition, double blind trials are essential in the assessment of any form of treatment.     

Acidic and basic protein contents in Gastrocnemii and pectoralis muscles of chick under denervation and work-induced stress conditions.

Biochemical estimation of acidic and basic proteins of chick gastrocnemii (G. externus, G. medius and G. internus) and pectoralis muscles has been done under normal, denervated and work stress conditions from 1-56 days of postnatal growth. The reciprocal relationship of the two protein groups is clearly established. It is evident that muscle denervation acts as a stimulant for proteosynthetic activities and probably may also be an inhibitory factor for protein degradative reactions. During work overload stress, the rapid growth of muscles has been related to high rate of contractile activity.     

Variability in T cell receptor V beta gene usage in human peripheral blood lymphocytes. Studies of identical twins, siblings, and insulin-dependent diabetes mellitus patients.

Recent studies focused on the diversity and molecular organization of the human TCR-beta complex have begun to establish the genetic basis for the potential repertoire of V beta specificities in T cells. The scope and variability of the actual repertoire derived from this potential repertoire, however, remains to be clarified. In this study, V beta usage by human peripheral T cells derived from serial samples of the same individual, identical twins, and the members of three nuclear families that include four members with insulin-dependent diabetes mellitus (IDDM) was assessed by both quantitative polymerase chain reaction and Northern blotting with V beta subfamily-specific probes. Samples taken from the same individual over a period of 21 months and analyzed in separate experiments indicated stability in the peripheral repertoire, whereas the similarity in peripheral V beta usage in a pair of identical twins suggested a strong role for genetics in shaping the peripheral T cell repertoire. In contrast, V beta usage in siblings and in unrelated individuals was observed to differ substantially. In particular, peripheral expression of V beta 3 and V beta 20 differed by more than sixfold among members of two different families. Segregation analysis of TCR and HLA haplotypes in these families suggested that variation in V beta 20 expression was TCR haplotype specific. Subsequent nucleotide sequence analysis of the V beta 20 gene segment in multiple members of these families revealed the presence of a null allele for V beta 20 expression. No consistent significant differences in V beta usage were observed in IDDM patients relative to their siblings or between identical twins discordant for IDDM. These results suggest that the repertoire of peripheral T cell specificities present in different individuals in human populations varies dramatically because of the effects of multiple factors, including TCR germ-line polymorphism.     

Substrate-Induced Stability of Glyceraldehyde 3-Phosphate Dehydrogenase from Mung Beans (Vigna radiata L.)

Time-dependent thermal inactivation of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) present in the extract of mung beans at different periods of germination showed biphasic kinetics in the 12-h germinated seeds but single exponential decay at 24 h of germination. The glyceraldehyde 3-phosphate (G-3-P) concentration in the deproteinated extracts was found to increase with period of germination up to 36 h, parallel to that of GAPDH activity. G-3-P was found to offer protection of the enzyme against thermal inactivation and trypsin digestion. It is suggested that accumulation of G-3-P in germinating mung beans may be of physiological significance and it might offer protection to the enzyme in vivo against thermal inactivation and proteolysis.     

An enzyme immunoassay of phaseolinone and its application in estimation of the amount of toxin in Macrophomina phaseolina-infected seeds.

A microtiter plate-based enzyme immunoassay has been developed for phaseolinone, a phytotoxin isolated from the culture filtrate of the plant-pathogenic fungus Macrophomina phaseolina (Tassi) Goid. The smallest amount of phaseolinone detectable by the method is 5 pg per well. The method is validated by comparison with high-performance liquid chromatography and used to confirm and estimate phaseolinone production in seeds infected with the fungus. The degree of seed inhibition correlated well with the amount of toxin produced in infected seeds, 50% inhibition being observed at a toxin concentration of 0.60 micrograms/g of wet tissue.