Contribution to the structural characterization of eucaryotic PSI reaction centre—I. Critical analysis of the polypeptidic composition of different P700 enriched fractions

In thylakoid membranes, several peptides of high MW are present which may interfere with the study of CP1's components. Modifying Cleveland's technique [7] for limited proteolysis, we have characterized the polypeptides found in the 60 kD region. Some may result from incomplete washing of the CF1 while others come from the CP1; indeed, this chlorophyll protein complex, which has a higher MW (above 100 kD), very often undergoes a dissociation into smaller components of about 60 KD MW.Analysis of the protein content of different preparations commonly used to obtain PSI reaction centre enriched fractions has been performed. The and subunits of CF1 are among the main contaminants of most of these preparations. A further purification step is described which can be applied to all these preparations, but numerous peptides are still present in the active fractions. It is most unlikely that all these polypeptides are required for the primary photochemical event, and this emphasizes the necessity to find a new simple method to purify PSI reaction centres.     

Sialyl-transferase mitochondriale

A sialyl transferase activity is found in purified mitochondria. It is not due to residual contamination and this enzymatic system is located in the outer mitochondrial membrane. This proves mitochondrial autonomy in regard to glycoconjugate sialylation.     

Electron microscopic study of the mandibular glands of Kalotermes flavicollis Fabr. (Isoptera; Calotermitidae)

Summary The mandibular glands of Kalotermes were examined in different castes. They showed sexual dimorphism in the soldiers and primary reproductives. Moreover, in female soldiers and queens, mandibular gland cells contained numerous crystalline structures of mitochondrial origin. The role of these glands (secretion of saliva or pheromone) is discussed.

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Résumé Les glandes mandibulaires de Calotermes sont étudiées dans les différentes castes. Elles présentent un dimorphisme sexuel chez les soldats et les sexués. Après la mue imaginale, les cellules glandulaires ont toujours une activité sécrétrice. De plus, chez les soldats femelles et les reines, elles contiennent de nombreuses formations cristallines d'origine mitochondriale. Le rôle de ces glandes (sécrétion de salive ou de phéromone) est discuté.

     

Auer-rod positive myelocytic leukemia cells in diffusion chambers: differentiation along the eosinophilic pathway

Auer-rod positive acute myelocytic leukemia (AML) blasts from a 33-year-old patient were cultured in diffusion chambers (DC) in order to test their differentiation potential. The cells were labeled with anti-human granulocyte anti-serum known to be negative for eosinophils, and evaluated using the unlabeled peroxidase-antiperoxidase (PAP) method. Parallel to a decline in the number of leukemic blasts there was an increase of up to 86% in the number of granulocytic cells belonging to the eosinophilic series. Auer-rod bodies were found in the eosinophilic cells even after 20 days in culture. Staining with anti-granulocyte antiserum failed to demonstrate positive cells at any time during DC culture. Based on the negative reaction with the anti-granulocytic antibodies already at an early stage of development evidence is provided for the existence of a progenitor cell exclusively committed to the eosinophilic pathway.     

Iodine intakes assessed by urinary iodine concentrations in healthy children aged ten months,two years,and four years

Urinary iodine excretion was assessed in 642 healthy children aged 10 mo (n=243), 2 yr (n=183), and 4 yr (n=216) living in the Paris area and originating from continental France (60.3%), North Africa (13.8%), the West Indies (9.1%), West Africa (8.3%), Southeast Asia (4.8%), and southern Europe (3.8%). Mild impairment of neurological (reflexes, tone, audiometry) and intellectual development (Brunet-Lézine scale) was assessed in relation to iodine status. Iodine excretions (median values) were 18.4, 11.9, and 10.9 μg/100 mL at 10 mo, 2 yr, and 4 yr, respectively, and risk of mild iodine deficiency (5–10 μg/100 mL) was 18.1%, 34.8%, and 38.3% for the same age groups. No relationship was found between anthropometry, global development quotient, and iodine status. High hearing thresholds were more commonly associated with lower iodine excretion, suggesting mild hearing defects. In spite of iodine prophylaxis, the risk of mild to moderate iodine deficiency still exists in France and in a number of European countries. Evaluation of neurological sequels of borderline iodine status is a major public health problem in European communities.     

A 17-bp insertion and a Phe215----Cys missense mutation in the dihydrolipoyl transacylase (E2) mRNA from a thiamine-responsive maple syrup urine disease patient WG-34.

We have amplified the cDNA for the transacylase (E2) subunit of the branched-chain alpha-ketoacid dehydrogenase (BCKAD) complex from a thiamine-responsive MSUD cell line (WG-34) by the polymerase chain reaction. Sequencing of the amplified WG-34 cDNA showed a 17-bp insertion (AAATACCTTGTTACCAG) apparently resulting from an aberrant splicing of the E2 gene, and a missense (T----G) mutation that changes Phe215 to Cys in the E2 subunit. The existence of these two mutations was confirmed by probing the amplified E2 cDNA or genomic DNA with allele-specific oligonucleotides. The above results support the thesis that the thiamine-responsive MSUD patient (WG-34) is a compound heterozygote at the E2 locus. The implication of the E2 mutations for the thiamine-responsiveness observed in this patient is discussed.     

Effect of the natural ATPase inhibitor on the binding of adenine nucleotides and inorganic phosphate to mitochondrial F1-ATPase

(1) Incubation of the beef heart mitochondrial ATPase, F₁ with Mg-ATP was required for the binding of the natural inhibitor, IF₁, to F₁ to form the inactive F₁-IF₁ complex. When F₁ was incubated in the presence of [¹⁴C]ATP and MgCl₂, about 2 mol ¹⁴C-labeled adenine nucleotides were found to bind per mol of F₁; the bound ¹⁴C-labeled nucleotides consisted of [¹⁴C]ADP arising from [¹⁴C]ATP hydrolysis and [¹⁴C]ATP. The ¹⁴C-labeled nucleotide binding was not prevented by IF₁. These data are in agreement with the idea that the formation of the F₁-IF₁ complex requires an appropriate conformation of F₁. (2) The ¹⁴C-labeled adenine nucleotides bound to F₁ following preincubation of F₁ with Mg-[¹⁴C]ATP could be exchanged with added [³H]ADP or [³H]ATP. No exchange occurred between added [³H]ADP or [³H]ATP and the ¹⁴C-labeled adenine nucleotides bound to the F₁-IF₁ complex. These data suggest that the conformation of F₁ in the isolated F₁-IF₁ complex is further modified in such a way that the bound ¹⁴C-labeled nucleotides are no longer available for exchange. (3) ³²P_i was able to bind to isolated F₁ with a stoichiometry of about 1 mol of P_i per mol of F₁ (Penefsky, H.S. (1977) J. Biol. Chem. 252, 2891–2899). There was no binding of ³²P_i to the F₁-IF₁ complex. Thus, not only the nucleotides sites, but also the P_i site, are masked from interaction with external ligands in the isolated F₁-IF₁ complex.