Oleosomes (Spherosomes) from Daucus carota suspension culture cells

Isolated oleosomes from Daucus carota L. cells are lipid droplets consisting mainly of triacylglycerols (>97%) and very little protein (1–2%). The boundary between the lipid phase and the cytosol, which is visible on electron micrographs, is not built up by a true phospholipid-containing unit or half unit membrane. Enzymatic activities of lipid metabolism were not found to be associated with oleosomes with the exception of very low (contaminating) acyl-CoA:1,2-diacylglycerol acyltransferase (EC 2.3.1.20) and relatively high acyl-CoA hydrolase (EC 3.1.2.2) activities. The triacylglycerols exhibited a half life time of about 70 h, which is below the generation time of the cells (80–90 h). The fatty acid pattern of triacylglycerols was very similar to that of polar cellular membrane lipids.     

Histoautoradiographic analysis of the thermoinductive processes in the shoot apex of Arabidopsis thaliana L. Heynh, vernalized at different stages of development

The cytochemical reactions of various zones of the shoot apexof an annual winter plant (Arabidopsis thaliana), vernalizedat two different ages (26 and 85 days), were analyzed usinghistoautoradiography after incorporation of tritiated thymidine.The following sequence of events was observed during a coldtreatment of 40 days: subapical activation (in DNA synthesis)of the rib meristem (this took place regardless of the age ofthe plants; dedifferentiation of axial cells (the beginningof which was earlier in the older plants). After cold treatment, the plants were resubmitted to warm temperaturesunder long day conditions. A re-establishment of the zonationin the meristem was seen during the first week for plants inthe "intermediate stage". The activation of axial cells increasedduring the next two weeks and a few days later both groups ofplants entered the prefloral stage followed by the formationof their first floral buds. These apical reactions were comparedto those of a French variety of A. thaliana, a quantitativelong-day plant, submitted to different photoperiods and to gibberellicacid (GA₃). (Received January 17, 1977; )     

Composition and photoinduced biosynthesis of the carotenoids of a protoplast-like Neurospora crass “slime” mutant

A spheroplast-like slime mutant of Neurospora crassa (lacking a rigid cell wall) was found to synthesize an identical spectrum of carotenoids as wild type strains except for -carotene. Furthermore strict photoregulation of the biosynthesis of these pigments as well as the characteristics of photoinduced carotenogenesis were also nearly identical in the mutant and in the wild type.     

Neurotoxicity of macrophages infected by HIV1

Conclusion Neuronal astrocytes and perhaps oligodendrocytic lesions occur during the course of HIVinfection of CNS cells. Most of the results suggest that these lesions are indirectlyinduced by infected macrophages, probably monocytes, present in the brain. Twomechanisms of neurotoxicity have been studied to date, one testing soluble factors presentin supernatant of infected monocytes and the other the direct effect of adhering HIV-infected monocytes to neurons and astrocytes. These two mechanisms are not mutually exclusive. They both indicate a major role for monocytes in the induction of brain lesionsand the crucial importance of the neurotoxic approach in the study of HIV inducedencephalopathy.     

Functional analysis of internal transcribed spacer 2 of Saccharomyces cerevisiae ribosomal DNA.

Using the previously described "tagged ribosome" (pORCS) system for in vivo mutational analysis of yeast rDNA, we show that small deletions in the 5'-terminal portion of ITS2 completely block maturation of 26 S rRNA at the level of the 29 SB precursor (5.8 S rRNA-ITS2-26 S rRNA). Various deletions in the 3'-terminal part, although severely reducing the efficiency of processing, still allow some mature 26 S rRNA to be formed. On the other hand, none of the ITS2 deletions affect the production of mature 17 S rRNA. Since all of the deletions severely disturb the recently proposed secondary structure of ITS2, these findings suggest an important role for higher order structure of ITS2 in processing. Analysis of the effect of complete or partial replacement of S. cerevisiae ITS2 with its counterpart sequences from Saccharomyces rosei or Hansenula wingei, points to helix V of the secondary structure model as an important element for correct and efficient processing. Direct mutational analysis shows that disruption of base-pairing in the middle of helix V does not detectably affect 26 S rRNA formation. In contrast, introduction of clustered point mutations at the apical end of helix V that both disrupt base-pairing and change the sequence of the loop, severely reduces processing. Since a mutant containing only point mutations in the sequence of the loop produces normal amounts of mature 26 S rRNA, we conclude that the precise (secondary and/or primary) structure at the lower end of helix V, but excluding the loop, is of crucial importance for efficient removal of ITS2.     

Somatic and flagellar antigens ofSerratia ficaria from the United States and the Mediterranean region

Somatic (O) and flagellar (H) antigens of 37Serratia ficaria strains were studied. All strains shared a common H antigen (H1). Four O antigens were identified that defined four serovars (O1:H1, O2:H1, O3:H1, and O4:H1). All American strains studied (isolated from the fig-fig wasp biological cycle or from a human patient) belonged to serotype O1:H1. Strains from the Mediterranean region (Sicily, Tunisia, France) were not so antigenically uniform and all four serotypes were found in figs from Sicily.     

The early development of cranial sensory ganglia and the potentialities of their component cells studied in quail-chick chimeras

The quail-chick marker system has been used to study the early developmental stages of the ganglia located along cranial nerves VII, IX, and X. The streams of neural crest cells arising from the rhombencephalic-vagal neural crest were followed from the onset of their migration up to the localization of crest cells in the trunk and root ganglia of these nerves. It was shown that two different populations of crest cells are segregated early as a result of morphogenetic movements in the hypobranchial region. The dorsal population gives rise to the root ganglia of nerves IX and X located close to the encephalic vesicles, where the crest cells differentiate both into neurons and into glia. In contrast, the ventral stream of neural crest cells contributes together with cells from epibranchial placodes to the trunk ganglia (geniculate, petrous, and nodose ganglia) of cranial nerves VII, IX, and X. The successive steps of the invasion of the placodal anlage by crest cells can be followed owing to the selective labeling of the neural crest cells. It appears that the latter give rise to the satellite cells of the geniculate, petrous, and nodose ganglia while the large sensory neurons originate from the placodes. The nodose ganglion has been the subject of further studies aimed to investigate whether neuronal potentialities can be elicited in the neural crest-derived cells that it contains. The ability to label selectively either the neurons or the glia by the quail nuclear marker made this investigation possible in the particular case of the nodose ganglion whose neurons and satellite cells have a different embryonic origin. By the technique already described (N. M. Le Douarin, M. A. Teillet, C. Ziller, and J. Smith, 1978, Proc. Nat. Acad. Sci. USA75, 2030–2034) of back-transplantation into the neural crest migration pathway of a younger host, it was shown that the presumptive glial cells of the nodose ganglion are able to remigrate when transplanted into a 2-day chick host and to differentiate into autonomic structures (sympathetic ganglion cells, adrenomedullary cells, and enteric ganglia). It is proposed as a working hypothesis that neuronal potentialities contained in the neural crest cells which invade the placodal primordium of the nodose ganglion are repressed through cell-cell interactions occurring between placodal and crest cells.     

Regionalized expression of CD52 in rat epididymis is related to mRNA poly(A) tail length

The regional pattern of CD52 expression in the rat epididymis was followed by Northern analyses and carbohydrate-labelling of glycoconjugates on Western blots. CD52 mRNA showed a novel aspect of regionalization, namely region-dependent length differences in its poly(A) tail. ‘Short’ CD52 mRNA molecules were present in all parts of this organ and also in the seminal vesicles. Additionally, the cauda epididymidis contained mRNA molecules with an extended poly(A) tail. Their appearance coincided with the occurance of the principal M_r ≈ 26 kDa glycopeptide in the cauda region, representing the CD52 product. CD52 expression seemed to be regulated or modulated synergistically by androgens, temperature, and (an) unknown testicular factor(s), depending on the poly(A) tail length of its mRNA. Androgens alone exerted an effect only on molecules with ‘short’ poly(A) tails. They were down-regulated in castrated animals, and restored to normal levels upon testosterone supplementation. However, ‘long’ CD52 mRNA molecules were not affected. Only if combined with the exposure of the epididymis to the elevated temperature of the abdomen, castration of animals resulted in a complete loss of the CD52 mRNA, including the ‘long’ cauda species. Loss of ‘long’ CD52 mRNA molecules was also observed when the abdominal location was combined with efferent duct ligation. This combination of treatments, however, did not affect ‘short’ CD52 mRNA levels. Loss of the ‘long’ CD52 mRNA molecules by any treatment coincided with a loss of the principal M_r ≈ 26 kDa glycopeptide from caudal protein extracts. Mol. Reprod. Dev. 48:433–441, 1997. © 1997 Wiley-Liss, Inc.     

Insertional inactivation by Tn3701 of pIP964 hemolysin expression in Enterococcus faecalis

Abstract Transposition of the conjugative mobile element (Tn 3701 ) of Etreptococcus pyogenes strain A454 onto the Enterococcus feacalis hemolysin plasmid pIP964 modified the expression of the genes involved in hemolysin production. By hemolysis complementation tests the genes coding for two components required for the hemolytic activity expression were found to be located on the Eco RI E and G fragments of pIP964.