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Summary An epidemiological, cross-sectional study was conducted in order to assess non-neoplasic effects on the lung due to chronic exposure to arc welding fumes and gases. The study involved 346 arc welders and 214 control workers from a factory producing industrial vehicles. These workers (welders and controls) had never been exposed to asbestos. Respiratory impairments were evaluated by using a standardized questionnaire, a clinical examination, chest radiophotography and several lung function tests (spirometry, bronchial challenge test to acetylcholine, CO transfer tests according to the breath-holding and the steady-state methods, N2 washout test). The only significant differences between the welders overall compared to the controls were a slightly higher bronchial hyper-reactivity to acetylcholine and a lower lung diffusing capacity for CO in the welders. However, non-specific, radiologic abnormalities (reticulation, micronodulation) and obstructive signs were more frequent in the most exposed welders (welding inside tanks) than in welders working in well ventilated workplaces. The nature of the metal welded (mild-steel, stainless steel, aluminium) did not seem to have an influence on respiratory impairments. In the mild-steel welders, respiratory symptoms (dyspnoea, recurrent bronchitis) and obstructive signs were more frequent in the welders using a manual process than in the welders involved with the semi-automatic process (MIG). For all the workers (welders and controls), smoking had a markedly adverse effect on respiratory symptoms and lung function. Moreover, smoking seemed to interact with welding since CO lung transfer was more impaired in smoking welders than in smoking controls.

Bovine Hb (hemoglobin) has a low oxygen affinity in the absence of chloride ions and DPG. Because of the increasing interest of this Hb as a potential blood substitute we have engineered a human Hb mutant with the aim of mimicking the functional properties of bovine Hb. This was achieved by deleting residue βNA1 Val and substituting a methionine for histidine at the βNA2 position as previously suggested by Perutz and Imai in 1980. Our results show that the artificial mutant exhibits some of the characteristics of bovine Hb but does not show the low oxygen affinity which is measured in bovine blood.

The aim of this research is to built a language for quantitative/qualitative representation in expert supervisory process control. The specification of such a language led to the definition of ALCMEN (Automaticians Language for Causal Modelisation of Expert kNowledge). Its purpose is to represent in a qualitative way imprecision and uncertainty, as well as classical numerical equations, in order to solve the communication problem between process experts and control engineers; it appears as a network of interconnected blocks and a list of structured variables.

Our goal was to design a single hemoglobin subunit able to assemble into a stable tetrameric structure with cooperative O2 binding and low oxygen affinity. We have synthesized in E. coll a chimeric β/α globin subunit composed of the first 73 residues of the β chain and the last 73 residues of the α chain. Molecular building indicated that this construction could result in Hb homotetramers possessing the α1β2 interface, responsible for the heme-heme interaction in Hb heterotetramers. The results show that the chimeric subunits assemble into tetramers which bind oxygen reversibly without cooperativity but with an oxygen affinity slightly lower than observed for human Hb. The strong effector RSR 4 lowers the oxygen affinity. Kinetics of CO recombination in the presence of RSR 4 reveal a biphasic bimolecular rebinding. Functional studies suggest that the quaternary structure of the oligomer is intermediary between R-and T-state.

In hemoglobin (Hb) S the hydrophobic mutated residue Val-beta6(A3) (donor site) closely interacts with the hydrophobic side groups of Phe-beta85(F1) and Leu-beta88(F4) (EF pocket, acceptor site) of a neighboring tetramer, resulting in decreased solubility and polymerization of the deoxy-Hb. The beta6(A3) residue is followed by two charged residues Glu-beta7(A4) and Lys-beta8(A5). This cluster has no attraction for the hydrophobic EF pocket. We have modified the beta7(A4) residue next to the donor site Val-beta6(A3), replacing the charged Glu by a hydrophobic Ala-(rHb betaE6V/E7A). The single mutant Glu-beta7 --> Ala-(rHb betaE7A) was also engineered. Both rHbs exhibit a heat instability and an increased oxygen affinity compared to Hb A and Hb S. There was a concentration dependence of the ligand binding properties (1-300 microM in heme) indicating an increased amount of dimers relative to Hb A. The deoxy form of rHb betaE6V/E7A polymerizes in vitro, with a decreased rate of polymer formation relative to Hb S, while the single mutant betaE7A does not polymerize in the same experimental conditions. The Glu-beta7(A4) --> Ala substitution does not increase the hydrophobic interaction between donor and acceptor site. We speculate that the loss of the normal saline bridge between Glu-beta7(A4) and Lys-beta132(H10) leads to an increased flexibility of the A helix and may account for the difference of the polymerization for this Hb S mutant.

The replacement of β35(A2)Pro by Arg in Hb Warwickshire appears to be without an effect on the functional properties of human Hb A, despite adding two external positive charges close to the central cavity of the hemoglobin tetramer, along the dyad axis. To clarify the role of this portion of the molecule involved in oxygen-linked anion binding, we have engineered the recombinant hemoglobin α2β5(A2)Pro→Ala [rHD β5(A2)Pro→Ala]. The rHb β5(A2)Pro→Ala exhibits an increased oxygen affinity compared to Hb A, with normal heterotropic effects in standard conditions. The increased oxygen affinity may be attributed to the absence of proline, which would render the A helix more flexible, thus destabilizing the T structure. The normal functional properties of Hb Warwickshire may be due to the regulation of oxygen affinity by electrostatic effects involving diffusible anions not bound to any specific site.

Hb S variants containing Lys-beta132 --> Ala or Asn substitutions were engineered to evaluate the consequences of the A helix destabilization in the polymerization process. Previous studies suggested that the loss of the Glu-beta7-Lys-beta132 salt bridge in the recombinant Hb betaE6V/E7A could be responsible for the destabilization of the A helix. The recombinant Hb (rHb) S/beta132 variants polymerized with an increased delay time as well as decreased maximum absorbance and Hb solubility values similar to that of Hb S. These data indicate that the strength of the donor-acceptor site interaction may be reduced due to an altered conformation of the A helix. The question arises whether this alteration leads to a true inhibition of the polymerization process or to qualitatively different polymers. The oxygen affinity of the beta132 mutated rHbs was similar to that of Hb A and S, whereas the cooperativity and effects of organic phosphates were reduced. This could be attributed to modifications in the central cavity due to loss of the positively charged lysine. Since Lys-beta132 is involved in the stabilization of the alpha1-beta1 interface, the loss of the beta132(H10)-beta128(H6) salt bridge may be responsible for the marked thermal instability of the beta132 mutated rHbs.

In the stereochemical model proposed by Perutz [1], the Fe‐His(F8) bond plays a significant role in the allosteric transition in hemoglobin and the resulting cooperativity in ligand binding. When this bond is ruptured, there is a loss in the transmission of the information concerning ligand binding; examples are Hb(NO)4in the presence of inositol hexakisphosphate (IHP), or nickel substituted Hb hybrids which, despite being liganded, exhibit deoxy‐like properties. To study the effects of the loss of the iron proximal histidine bond, we have engineered the α2β2(F8)H92A recombinant Hb. The replacement of the highly conserved proximal histidine F8 residue by an alanine results in a low affinity for the heme group and a loss of the allosteric properties; kinetics of CO recombination after photodissociation show only the rapid bimolecular phase, characteristic of the high affinity R‐state. However, a significant amount of deoxy (T‐state) kinetics are observed after addition of external effectors such as IHP. The iron‐histidine bond is apparently crucial for the heme‐heme interaction, but the allosteric equilibrium may still be influenced by external constraints.

It is generally accepted that human beta-melanocyte-stimulating hormone (h beta MSH) does not normally exist in humans but was merely an artifactually generated 22-amino acid peptide corresponding to a lipotropin (LPH) fragment (residues 35-56). We examined whether the shorter 18-amino acid peptide h beta MSH-(5-22) could be detected in some human tissues. Normal human pituitaries and hypothalami as well as corticotropin-secreting pituitary and nonpituitary tumors were extracted and chromatographed on Sephadex G-50, and the fractions were measured with two radioimmunoassays using either a COOH-terminal human gamma LPH (h gamma LPH) antiserum that recognized equally h gamma LPH, h beta MSH, and h beta MSH-(5-22) or a mid-portion h gamma LPH antiserum that recognized h gamma LPH and h beta MSH but not h beta MSH-(5-22). Normal pituitaries and pituitary tumors contained a single immunoreactive material coeluting with h gamma LPH. The hypothalami and the nonpituitary tumors all contained h gamma LPH and a smaller molecular weight material that was only detected in the COOH-terminal h gamma LPH radioimmunoassay; its elution volume (Ve/V, 0.75) was identical to that of h beta MSH-(5-22) but different from that of h beta MSH (Ve/V, 0.60); on reversed-phase HPLC, it coeluted with synthetic h beta MSH-(5-22) with a retention time different from that of h beta MSH. It is concluded that h beta MSH-(5-22) that corresponds to the 18-amino acid peptide h beta LPH-(39-56), flanked by two pairs of basic amino acids within the h beta LPH molecule, is a normal maturation product of proopiomelanocortin in human nonpituitary tissues.

The respiratory health of 138 arc welders and 106 control subjects in the same company was studied in 1981 and in 1986. Most of the subjects welded mild steel using the Metal Inert Gas (MIG) process. The controls were workers in the same company, not exposed to any known pulmonary risk. The welders and controls in the analysis had not changed their professional activity nor their smoking habits during these five years. The examinations consisted of a questionnaire on respiratory symptoms, a thoracic auscultation, a chest X-ray and lung function tests: flow-volume curve and steady state CO transfer test. The examinations in 1986 confirmed the risk of non specific radiological impairment (pulmonary reticulo-micronodulation) and of obstruction in the small bronchi, which had already been observed in 1981 in the arc welders in this company. These impairments did not seem to have evolved more than in the controls, but do however justify regular surveillance of the respiratory health of arc welders.