Reinterpretation of the ultrastructure of cartilage matrix

Summary The epiphyseal cartilage from new-born mouse was treated with collagenase in two ways: either before fixation or after glutaraldehyde fixation. The electron dense granules of the matrix were not seen in the micrographs of cartilage treated with collagenase before fixation. It is concluded that collagen plays a definite role in the formation of the granules at the time of tissue fixation and that the granules are fixation artifacts.Commonwealth Academic Staff Fellow. Permanent address: Department of Zoology, University of Poona, Poona 411007, India.     

Hydrolyse enzymatique de la propionylcholine,de l'acétylthiocholine et de la butyrylthiocholine par le rectus de grenouille

Summary The enzymatic hydrolysis of propionylcholine (PrCh), acetylthiocholine (AcThCh), and butyrylthiocholine (BuThCh), by extracts of the muscle rectus abdominis, was determined. Inhibition of this hydrolysis by D.F.P. and 3318 CT [bis(pipéridinométhylcoumaranyl- 5)cétone diméthiodide] — utilized over a range of concentrations covering both specific and non-specific concentrations—showed that PrCh is hydrolyzed by an acetylcholinesterase (70%) and an Xcholinesterase (30%), AcThCh by the AcChE (70%), the XChE (15%) and a thioesterase (15%) and BuThCh by the XChE (70%) and a thioesterase (30%).     

High affinity binding of 5-hydroxytryptamine to some membrane preparations from cattle brain. Relationship to lysergic acid diethylamide (LSD)]

5 hydroxytryptamine binds to crude brain membrane preparations with two different affinities (KD = 1 to 2 X 10(-9) M for the highest, 1 to 2 X 10(-8) M for the lowest). LSD also binds with two affinities (KD = 3 to 4 X 10(-9) M and KD = 2 to 3 X 10(-8) M). Subcellular distribution of these sites shows that binding involves the two binding affinities in microsomal membranes but solely the high affinity binding sites are present in purified synaptosomal membranes. High affinity sites for 5 HT and for LSD are different as no direct competitive inhibition is observed in that case. On microsomal membranes, direct relationship occurs between low affinity binding for 5 HT and high affinity binding for LSD.     

Replication of intranucleolar DNA in smittia (diptera,chironomidae)

Riassunto Ghiandole salivari di larve diSmittia (Chironomidae) sono state incubate in vitro in presenza di timidina tritiata. Le modalità di marcatura dei cromosomi e dei nucleoli dimostrano che in questo materiale non esiste correlazione tra frequenza di marcatura del DNA intranucleolare e modalità o intensità di marcatura del DNA cromosomico. In particolare sono stati riscontrati casi in cui il DNA intranucleolare appare marcato mentre il DNA cromosomico non è in fase di replicazione. I risultati ottenuti sembrano indicare che il DNA intra-nucleolare inSmittia sia costituito da una o più unità di replicazione autonome.     

Actions de la néostigmine,du D.F.P. et du 3318 CT sur la sensibilité du rectus de grenouille aux esters acétique,propionique et butyrique de la choline

Summary The potentiating effects of Neostigmine, D.F.P. and 3318 CT (a selective true cholinesterase inhibitor) on acetylcholine (ACh), propionylcholine (PrCh), butyrylcholine (BuCh) and amyltrimethylammonium (AmT), have been studied using the frog's rectus abdominis. Neostigmine increases the actions of the three esters much more than that of AmT. Low concentrations of D.F.P. potentiate maximally BuCh but have practically no effect on ACh, PrCh, and AmT. 3318 CT potentiates AcCh and PrCh but inhibits BuCh and AmT.These results indicate the specificity of the hydrolysis of pharmacologically active doses of BuCh, on the one hand, of AcCh and PrCh, on the other hand, by different enzymes or the frog's rectus.Results obtained with high concentrations of D.F.P. and with association of the different anticholinesterases indicate that a maximal or nearly maximal potentiation of one of these esters is already obtained with the specific inhibitor concerned; the supplementary inhibition of the non-specific enzymes thus appears to have no or only a poor effect.     

ERAAP customizes peptides for MHC class I molecules in the endoplasmic reticulum

The ability of killer T cells carrying the CD8 antigen to detect tumours or intracellular pathogens requires an extensive display of antigenic peptides by major histocompatibility complex (MHC) class I molecules on the surface of potential target cells. These peptides are derived from almost all intracellular proteins and reveal the presence of foreign pathogens and mutations. How cells produce thousands of distinct peptides cleaved to the precise lengths required for binding different MHC class I molecules remains unknown. The peptides are cleaved from endogenously synthesized proteins by the proteasome in the cytoplasm and then trimmed by an unknown aminopeptidase in the endoplasmic reticulum (ER). Here we identify ERAAP, the aminopeptidase associated with antigen processing in the ER. ERAAP has a broad substrate specificity, and its expression is strongly upregulated by interferon-gamma. Reducing the expression of ERAAP through RNA interference prevents the trimming of peptides for MHC class I molecules in the ER and greatly reduces the expression of MHC class I molecules on the cell surface. Thus, ERAAP is the missing link between the products of cytosolic processing and the final peptides presented by MHC class I molecules on the cell surface.     

Isoelectrically focused carboxyesterases as a biological marker in chimeras

Summary Species-specific multiple forms of carboxyesterases (CE) were determined in zymograms obtained by isoelectric focusing (IEF) using homogenized wing zeugopodal tissues of chick, quail and quail-chick chimeras. The validity of the CE pattern of chimeric tissues was verified by the nuclear marker technique. Analytical IEF of CE was found to be useful for investigation of the origin of tissues in chimeras.Acknowledgment. This work was supported by grant AM21026.