What's new in lysozyme research?

The present review is focused on the main achievements realized in the lysozyme research field since the meeting held in 1972 to commemorate the fiftieth anniversary of the discovery of this enzyme. Despite of extensive structural, physico-chemical, crystallographic, genetic, immunological and evolutionary studies devoted to lysozymes, their biological role is still not exactly known.     

Characterization of the amino acids of bovine fibrinogen involved in the fibrinogen-thrombin interaction of the blood clotting process. Comparison with the milk clotting process

Summary Bovine fibrinogen and the A and B chains of bovine fibrinogen have been subjected to chemical modification by a number of reagents and the effects of these procedures on the susceptibility of the proteins to thrombin hydrolysis is described. The reagents used were rose bengal (for photo-oxidation), 2-hydroxy-5-nitrobenzyl bromide, N-acetylimidazole, iodoacetic acid and diethyl pyrocarbonate. Evidence is presented which indicates that the tryptophan and tyrosine residues of fibrinogen are not involved to any great extent in the interaction of this protein with thrombin. Modification with iodoacetic acid suggests that methionine residues play a major role in such interactions, but the fibrinogen chains on which the important residues reside remain uncertain. The use of diethyl pyrocarbonate indicates the participation also of histidine in fibrinogen-thrombin interactions and that, whereas the histidine residues of the B chain are involved to a great extent, it appears that those of the Aa chain are not. The similarities which exist between the fibrinogen-thrombin and the -casein-chymosin systems are discussed.Abbreviations used DEP diethyl pyrocarbonate (ethoxyformic anhydride) - HNBB 2-hydroxy-5-nitrobenzyl bromide - N-Acl N-acetylimidazole - PTC phenylthiocarbamyl - PTH 3-phenyl-2-thiohydantoin.     

Congenital defects of the upper lateral incisors (ULI): Condition and measurements of the other teeth,measurements of the superior arch,head and face

We surveyed a French male population for the incidence of missing or reduced upper lateral incisors (ULI). In 5,738 subjects, we observed an incidence of 1.59% with one or two reduced ULI (the other normal) and 1.90% with one or two missing ULI (the other normal or reduced), altogether, 3.49% affected subjects. Furthermore, 250 random controls were observed. Agenesis of other teeth is more frequent in propositi. Missing third molars were 12.4% in controls, 24.0% in propositi with reduced ULI and 39.6% in propositi with two missing ULI. Furthermore, agenesis of incisors, canines and premolars ranges from 0.4% in controls to 1.3% in propositi having reduced ULI and 5.0% in propositi with two missing ULI. So, propositi with reduced ULI are intermediate between the controls and the propositi with missing ULI with respect to the frequency of agenesis of other teeth. On the other hand, a different ranking is observed with respect to the teeth measurements: reduction of tooth size is more marked in propositi with reduced ULI than in propositi with missing ULI. The reduction mainly affects canines, incisors and to a lesser degree, premolars. Arch length and interpremolar diameters are smaller in propositi with missing ULI, compared with controls.     

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.

     

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.     

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.