A flexible class of generalized joint frailty models for the analysis of survival endpoints

This article focuses on shared frailty models for correlated failure times, as well as joint frailty models for the simultaneous analysis of recurrent events (eg, appearance of new cancerous lesions or hospital readmissions) and a major terminal event (typically, death). As extensions of the Cox model, these joint models usually assume a frailty proportional hazards model for each of the recurrent and terminal event processes. In order to extend these models beyond the proportional hazards assumption, our proposal is to replace these proportional hazards models with generalized survival models, for which the survival function is modeled as a linear predictor through a link function. Depending on the link function considered, these can be reduced to proportional hazards, proportional odds, additive hazards, or probit models. We first consider a fully parametric framework for the time and covariate effects. For proportional and additive hazards models, our approach also allows the use of smooth functions for baseline hazard functions and time-varying coefficients. The dependence between recurrent and terminal event processes is modeled by conditioning on a shared frailty acting differently on the two processes. Parameter estimates are provided using the maximum (penalized) likelihood method, implemented in the R package frailtypack (function GenfrailtyPenal). We perform simulation studies to assess the method, which is also illustrated on real datasets.

Isolation of a trypsin-like enzyme from Streptomyces paromomycinus (paromotrypsin) by affinity adsorption through Kunitz inhibitor-sepharose

A trypsin-like enzyme has been isolated from the filtrate of a Streptomyces rimosus forma paromomycinus culture. Purification involves acetone fractionated precipitation, ultrafiltration on a Diaflo UM 10 membrane and affinity adsorption on to Kunitz pancreatic trypsin inhibitor linked to Sepharose. The trypsin-like enzyme (paromotrypsin) appears homogeneous by zone electrophoresis on gelatinized cellulose acetate. Specific activity toward Tos-Arg-OMe, calculated from amino acid analysis, is about 220 mu mg-1. The overall yield in activity is about 30%. The molecular weight of the trypsin-like enzyme, determined by gel filtration, is around 22,000-25,000 daltons. Electrophoretic migration on cellulose acetate strips indicates an isoelectric point around 8. Amino acid composition has been determined; the protein comprises about 210 residues on the basis of a single histidine residue per molecule. Paromotrypsin is unstable in acidic medium and is not stabilized by calcium ions. Enzymic activity towards Bz-Argo-OEt is not increased by the addition of calcium ion in contrast to the activating effect observed on bovine trypsin. Paromotrypsin is inhbited by TLCK and NPGB; it interacts with naturally occurring bovine trypsin inhibitors such as soya bean and Kunitz pancreatic inhibitors, but not with chicken ovomucoid. Proteolytic specificity, examined by hydrolysis of oxidized Kunitz pancreatic inhibitor and characterization of resulting peptides, seems similar to that of bovine trypsin.

Unique evolution of neurohypophysial hormones in cartilaginous fishes: possible implications for urea-based osmoregulation

Most bony vertebrate species display a great evolutionary stability of their two neurohypophysial hormones, so that two molecular lineages, isotocin-mesotocin-oxytocin and vasotocin-vasopressin, have been traced from bony fishes to mammals. Chondrichthyes, in contrast, show a striking diversity of their oxytocin-like hormones, yet show a substantial decrease in vasotocin stored in neurohypophysis when compared to nonmammalian bony vertebrates. In the rays, glumitocin ([Ser(4),Gln(8)]-oxytocin) has been identified. In the spiny dogfish, aspargtocin ([Asn4]-oxytocin) and valitocin ([Val(8)]-oxytocin) have been characterized whereas in the spotted dogfish, asvatocin ([Asn(4),Val(8)]-oxytocin) and phasvatocin ([Phe(3),Asn(4),Val(8)]-oxytocin) have been found. Finally, in the holocephalian Pacific ratfish, oxytocin, the typical peptide of placental mammals, has been discovered. The duplication of the oxytocin-like hormone gene found in dogfishes has been observed only in some Australian and American marsupials. Cartilaginous fishes have developed an original urea-based osmoregulation involving a glutamine-dependent urea synthesis and blood urea retention through renal urea transporters. Furthermore, marine species use a rectal salt gland for sodium chloride excretion. Although vasopressin, in mammals, and vasotocin, in nonmammalian tetrapods, are clearly implied in water and salt homeostasis, the hormones involved in the blood osmotic pressure regulation of elasmobranchs are still largely unknown. It is suggested that the great diversity of oxytocin-like hormones in elasmobranchs expresses a release from an evolutionary receptor-binding constraint, so that amino-acid substitutions reflect neutral evolution. In contrast, the preservation of vasotocin suggests a selective pressure, which may be related to the regulation of renal urea transporter-recruitment mechanisms, as it has been shown for vasopressin in mammals. J. Exp. Zool. 284:475-484, 1999.

Adaptive evolution of water homeostasis regulation in amphibians: vasotocin and hydrins

Volemia and osmolality homeostasis is ensured in vertebrates through neuroendocrine reflexes, involving an afferent neural branch from baro- and osmo-receptors to hypothalamus and an efferent endocrine branch from secretory neurons to target hydroosmotic cells equipped with receptors and effectors. Whereas the osmoregulatory system in the tadpole comprises three organs, namely gut, kidney and gills, as in freshwater fishes, the adult displays a quaternary strategy with gut, kidney, urinary bladder and skin. In particular, the cutaneous permeability entails a great evaporative water loss when the animal is in the open air, loss that must be compensated by water reabsorption through the nephron and the urinary bladder and mainly by water uptake through the skin. Adaptation occurred at the level of these organs by regulation of their permeability through neurohypophysial hormones. Aside from vasotocin, active on the three organs, all anuran Amphibia possess hydrin 2 (vasotocinyl-Gly), a peptide resulting from a down-regulation of provasotocin processing. Exceptionally Xenopus laevis, a permanent aquatic toad, has hydrin 1 (vasotocinyl-Gly-Lys-Arg) instead of hydrin 2. Hydrins are somewhat more active than vasotocin on water permeation of skin and bladder but are devoid of antidiuretic activity. Adaptive evolution has created, along with the vasotocin-nephron system, preserved in all terrestrial non-mammalian tetrapods, additional functions such as the hydrin-skin and hydrin-bladder rehydration mechanisms. Specific hydrin receptors might exist in the skin and the bladder, different from those of vasotocin in the kidney. It is assumed that the water channel recruitment mechanism, found for vasopressin acting on the collecting duct principal cells in mammals, is also involved when vasotocin and hydrins stimulate their hydroosmotic target cells and that hormone-regulated aquaporin 2-like proteins could be identified in the three osmoregulatory organs of amphibians.

Distinct hydro-osmotic receptors for the neurohypophysial peptides vasotocin and hydrins in the frog Rana esculenta

The biological properties of vasotocin, hydrin 1 (vasotocinyl-Gly-Lys-Arg) and hydrin 2 (vasotocinyl-Gly), in particular the hydro-osmotic activities on the frog skin, the frog urinary bladder and the frog kidney, have been compared. Hydrins are as active or more active than vasotocin on the first two organs but they are virtually devoid of antidiuretic activity in the rat and the frog, in contrast to vasotocin. It appears that where the oxytocin ring (residues 1-6), present in the three peptides, is necessary for the action on the three organs, the C-terminal amidated group of vasotocin is necessary for the renal receptor but not for the skin and bladder receptors. It is known that amphibians have two types of vasotocin receptors, V1 and V2, homologous to the vascular/hepatic V1 and the renal V2 vasopressin receptors of mammals, respectively. We suggest that adaptation has led to specialization of (at least) two subtypes of hydro-osmotic V2 receptors, the renal subtype on which vasotocin is mainly active for the reabsorption of tubular water, and the skin/bladder subtype on which hydrin 2 is specifically involved in ensuring the rehydration of the animal. Cooperative evolution might have created in anuran Amphibia, on the one hand, two hydro-osmotic peptides, vasotocin and hydrin 2, derived from a single precursor through differential processing; and on the other hand, two corresponding receptors in kidney and skin for internal and external water recovery.

The neurohypophysial endocrine regulatory cascade: precursors, mediators, receptors, and effectors

The neurohypophysial endocrine regulatory cascade has been described as a molecular model of neuroendocrine control of organismal functions. Any physiological function can be analyzed in molecular terms as a succession of interactions occurring either in a solution or in a membrane system. The key mechanism in the ordering of the cascade is the conformational recognition of the two partners at each step. Each interaction results in a change of conformation of a recognized protein that in turn becomes a recognizer for the following molecule. The cascade starts within the secretory cell by the processing of the expressed precursor along the secretory pathway until the storage of the mature mediator in vesicles and its subsequent exocytic secretion in blood. The circulating mediator recognizes the target cell through specific membrane receptors that transduce the message within this target cell. A second intracellular cascade leads to activation of the effector, the protein fulfilling the physiological function. The complexity of the messages is, in part, due to the duplication propensity of the genomic DNA, the frequent occurrence of multiple copies for precursors, mediators, receptors, and effectors, and therefore, a combinatorial diversity that increases during the course of evolution. Vertebrate neurohypophysial hormones can be ordered in two main evolutionary lineages, culminating in oxytocin and vasopressin in placental mammals. In this field, diversification of the messages was made by differential processing of the precursors, secondary gene duplications, the emergence of several types of receptors for each hormone, and a variety of effectors triggered by the second messengers within differentiated target cells. This review is an attempt to integrate neurohypophysial functions at the molecular, cellular, and organismal levels.

A new neurohypophysial peptide, seritocin ([Ser5,Ile8]-oxytocin), identified in a dryness-resistant African toad, Bufo regularis

From the pituitary neurointermediate lobe of the African toad Bufo regularis, vasotocin, hydrin 2 (vasotocinyl-Gly) and a mesotocin-like peptide have been isolated by HPLC and characterized by mass spectrometry, amino acid sequence and chromatographic coelution with synthetic peptides. The mesotocin-like peptide has been identified as [Ser5,Ile8]-oxytocin in place of mesotocin ([Ile8]-oxytocin) found in all other amphibians investigated to date. The name seritocin is suggested. The molecule is virtually devoid of oxytocic activity on rat uterus in contrast to mesotocin. On the other hand, the molar ratio of hydrin 2 to vasotocin in the pituitary reaches 2, whereas it is about 1 in toads and frogs from temperate regions. B. regularis is an anuran species able to withstand a hot and dry season by burrowing. The possible relationship between occurrence of seritocin and adaptation to arid environment remains to be demonstrated.

Special evolution of neurohypophysial hormones in cartilaginous fishes: asvatocin and phasvatocin, two oxytocin-like peptides isolated from the spotted dogfish (Scyliorhinus caniculus)

In contrast to most vertebrate species that possess one oxytocin-like hormone and one vasopressin-like hormone, a few groups, such as marsupials or cartilaginous fishes, are endowed with two peptides of either or both types, suggesting possible gene duplications. We have now isolated two oxytocin-like hormones from the pituitary of the spotted dogfish Scyliorhinus caniculus (suborder Galeoidei). Microsequencing as well as chromatographic and pharmacological comparisons with synthetic peptides show that these peptides are [Asn4,Val8]oxytocin (asvatocin) and [Phe3,Asn4,Val8]-oxytocin (phasvatocin). Asvatocin and phasvatocin display oxytocic activity on rat uterus, about 80 and 5 milliunits per nmol, respectively, and virtually no pressor activity on anesthetized rats. They occur in roughly equal molar amounts in the gland; vasotocin is also present in a proportional amount that is lower by about a factor of 20. In addition to the duality, conservative amino acid substitutions are observed in the two oxytocic peptides in positions 4 (Gln-4-->Asn) and 8 (Leu-8-->Val), when compared with oxytocin. Furthermore, replacement of the isoleucine residue found in position 3 of all other oxytocin-like hormones by phenylalanine in phasvatocin is exceptional; it determines a dramatic decrease of the oxytocic activity. Preservation of the C-terminal-amidated nonapeptide pattern in the 12 vertebrate neurohypophysial hormones known to date suggests that both precursors and processing enzymes have coevolved tightly. On the other hand, whereas the great evolutionary stability of the mature hormones (generally observed in vertebrates) suggests a strict messenger-receptor coevolution, the exceptional diversity found in cartilaginous fishes (six oxytocin-like peptides identified out of eight known) might be due to a looseness of selective constraints, perhaps in relationship with their specific urea osmoregulation.

Action of neurohypophysial granule Lys-Arg endopeptidase on synthetic polypeptides comprising the processing sequence of provasopressin-neurophysin

Neurohypophysial granule Ca(2+)-dependent endopeptidases have been allowed to act on synthetic polypeptides derived from the N-terminal sequence of bovine provasopressin-neurophysin, namely vasopressinyl-glycyl-lysyl-arginyl-alanylamide and vasopressinyl-glycyl-lysyl-arginyl-alanyl-methionyl-serinamide+ ++. Membrane-bound enzymes have been used at pH 5.5 for 16 hr at 37 degrees C. Products have been identified by high-pressure liquid chromatography (HPLC) and by mass spectrometry performed on substances isolated by HPLC. With both substrates, vasopressinyl-Gly-Lys-Arg(OH) has been identified as a product confirming the Lys-Arg specificity previously observed on small peptide fluorogenic substrates. Cleavage yields, however, appear low suggesting that some factors are missing, for example a targeting action of the precursor neurophysin domain to the granule membrane.

Bony fish neurophysins. Identification of MSEL- and VLDV-neurophysins of the pollack (Pollachius virens)

The two types of neurophysins known in vertebrate species, namely MSEL-neurophysin (vasopressin-like hormone-associated neurophysin) and VLDV-neurophysin (oxytocin-like hormone-associated neurophysin) have been purified from the pollack (Pollachius virens) pituitary through a combination of molecular sieving and high-pressure liquid chromatography (HPLC). Homogeneity has been checked by gel electrophoresis and return in HPLC. The apparent molecular masses measured by SDS-electrophoresis are near 12 kDa, significantly higher than those found for their mammalian homologues (10 kDa). The two types of neurophysins have been recognized through their N-terminal amino acid sequences. The primary structure of MSEL-neurophysin has been partially determined using automated Edman degradation applied on native and reduced-alkylated protein, as well as peptides derived by trypsin or staphylococcal proteinase hydrolyses. Comparison of pollack MSEL-neurophysin with ox, goose and frog counterparts reveals that particular positions in the polypeptide chain are subjected to substitutions and that the numbers of substitutions do not seem closely related to the paleontological times of divergence between the different vertebrate classes.

Chemical identification of the mammalian oxytocin in a holocephalian fish, the ratfish (Hydrolagus colliei)

The neurohypophysial hormones of the ratfish (Hydrolagus colliei), a species belonging to the subclass Holocephali of cartilaginous fishes, have been investigated. An oxytocin-like hormone has been isolated from acetone-desiccated pituitary glands by using successively molecular sieving and high-pressure liquid chromatography. The peptide has been identified as oxytocin by coelution with synthetic oxytocin in HPLC, amino acid sequencing, mass spectrometry, and C-terminal sequencing through carboxypeptidase Y. Vasotocin may be present in a very small amount. Cartilaginous fishes appear to display a great diversity in their oxytocin-like hormones since five different peptides have been identified in rays and sharks that belong to the second subclass Selachii.

Lungfish neurohypophysial hormones: chemical identification of mesotocin in the neurointermediate pituitary of the Australian lungfish Neoceratodus forsteri

The neurohypophysial hormones contained in the neurointermediate lobe of the pituitary of the Australian lungfish Neoceratodus forsteri have been investigated. Mesotocin was identified by coelution with the synthetic peptide in high-pressure liquid chromatography, by Edman amino acid sequencing, by mass spectrometry, by C-terminal sequencing through carboxypeptidase Y, and cleavage with prolyl endopeptidase. Vasotocin, if present, would be in very small amounts and hydrins were not detected. Oxytocin appears absent. Although Neoceratodus and Protopterus have different habitats, the former being permanently aquatic, the latter burrowing during estivation, the proportions of neurohypophysial hormones stored in neurohypophysis were roughly similar in the two species and not apparently affected by environmental conditions.

Differential processing of provasotocin: relative increase of hydrin 2 (vasotocinyl-Gly) in amphibians able to adapt to an arid environment

Hydrin 2 (vasotocinyl-Gly) is an intermediate in pro-vasotocin processing found, along with vasotocin, only in the neurohypophysis of anuran amphibians. It increases cutaneous water permeability in the frog and is likely involved in neuroendocrine control of osmoregulation. The relative amounts of vasotocin and hydrin 2 stored in neurohypophysis have been measured on the one hand in amphibian species known not to adapt in dry areas, on the other hand in two species, Bufo regularis (Africa) and Bufo viridis (Near-East) able to survive in an arid environment. In the first group, the proportions of the two peptides are approximately equal whereas in the two toads the molar ratio hydrin 2 to vasotocin reaches 2. The ratio does not appear to vary significantly when these toads are either submitted to dehydration or placed in saline solutions. Predominance of hydrin 2 suggests an adaptive decrease of the activity of the alpha-amidating enzymatic system involved in the conversion of vasotocinyl-Gly into mature amidated vasotocin.

[Coronary disease with normal coronarography in the black Africans: epidemiological and clinical data in 31 cases. Role of abnormal hemoglobins]

The authors studied 31 cases of coronary artery disease with normal or minimally diseases coronary arteries in black Africans, 29.8% of 104 coronary patients undergoing coronary angiography in this series. These 31 cases comprised 16 cases of infarction, 10 cases of angina, 3 ventricular aneurysms and 2 cases of silent ischemia in diabetic patients. Twenty-five patients were men (80.6%). There were 6 women (19.3%) two of whom presented in the post-partum period. The average age of these patients was 45 years (males: 47.7 years; females: 41.8 years). The following risk factors were noted: smoking (60%), hypertension (25.8%), obesity (29%), diabetes (12.9%), serum cholesterol (average 2.15 g/l), serum triglycerides (average 1.25 g/l). The risk index per patient was 1.29. In comparison with coronary patients with angiographic coronary lesions (n = 73), the patients with normal angiography were significantly younger, comprised more females and had fewer risk factors (especially hypertension and diabetes), though this was not statistically significant. The prevalence of inaugural infarction was 81.2% in the cases of infarction with normal coronary arteries. These infarcts may be complicated by ventricular aneurysm formation. Spontaneous spasm was observed in 3 out of 31 patients (9.6%) at coronary angiography. A provocative test was performed in only 2 cases and 1 was positive. This deserves further study and may have therapeutic implications. The authors emphasise the high incidence of hemoglobin S or C traits (57.1%). These heterozygotic hemoglobinopathies could be a risk factor in these coronary patients with normal coronary angiography.

Vasotocin and hydrin 2 (vasotocinyl-Gly) in the African toad Bufo regularis: study under various environmental conditions

1. The neurohypophysial osmoregulatory hormones of the African toad Bufo regularis, a species adapted to estivate under dry and hot conditions, have been investigated. Vasotocin and hydrin 2 (vasotocinyl-Gly) have been identified by their retention times in high-pressure reverse-phase liquid chromatography and coelution with synthetic peptides, their pharmacological properties (vasotocin) and microsequencing. 2. Vasotocin-associated neurophysin (MSEL-neurophysin type) has been characterized by its N-terminal amino acid sequence. 3. In toads subjected to dehydration by evaporation (20% weight loss) or to osmotic stress by immersion in 2% NaCl for 3 hr (6% weight loss), the molar ratio hydrin 2/vasotocin (about 2:1) remained similar to the one observed in control animals. 4. In toads exposed to saline solution, there was a large decrease (roughly 30%) in the amounts of both hormones in the neuro-hypophysis. Environmental conditions for distinct secretions of vasotocin and hydrin 2 remain to be found.

[Spontaneous coronary artery dissection: apropos of a case with associated spasm and regression of the dissection]

The authors report the case of a 34 year old woman with postpartum myocardial infarction due to spontaneous coronary dissection of the distal circumflex artery. A spontaneously regressive spasm of the right coronary artery was also observed. The outcome with heparin, glyceryl trinitrate and calcium antagonist therapy was favourable. Over one year later, coronary angiography showed total resolution of the dissection and a large aneurysm of the inferior and septal walls of the left ventricle. This case is an example of post-partum spontaneous coronary dissection, in a particular vascular context. There are, however, other causes of spontaneous coronary artery dissection (atherosclerosis, eosinophilic syndrome...). Spasm may aggravate the consequences of coronary artery dissection and cause worse myocardial damage. The medical treatment, especially with regards to thrombolytic therapy, requires further codification.

Processing endopeptidase deficiency in neurohypophysial secretory granules of the diabetes insipidus (Brattleboro) rat

The homozygote Brattleboro rat exhibits a hereditary diabetes insipidus due to a deficiency of vasopressin, the antidiuretic hormone. It has previously been shown that in this animal a single nucleotide deletion in the provasopressin gene leads to a mutant precursor with a C-terminal amino acid sequence different from that of the wild-type. However the N-terminal region including the hormone moiety, the processing signal as well as the first two-thirds of the neurophysin is entirely preserved and absence of maturation has to be explained by an additional cause. We show here that the neurohypophysis of the homozygote Brattleboro rat, in contrast to the adenohypophysis, displays a significant decrease in the Lys-Arg processing endopeptidase activity when compared to the heterozygote or the wild-type Wistar. It is suggested that hypothalamic vasopressinergic neurons of the homozygote Brattleboro rat display a deficiency in the processing enzyme in contrast to the oxytocinergic neurons in which processing of prooxytocin is normal.

A neurosecretory granule Lys-Arg Ca(2+)-dependent endopeptidase putatively involved in prooxytocin and provasopressin processing

A Ca(2+)-dependent endopeptidase cleaving at the carboxyl side of the paired Lys-Arg residues has been found in the neurosecretory granules of the rat neurointermediate pituitary. The specificity pattern on synthetic fluorogenic substrates, the inhibitor profile, the pH optimum of 5.0 and the Ca(2+)-dependence are compatible with an involvement of this enzyme in the prooxytocin and the provasopressin processing within the granules. The enzymatic features of the neurohypophysial granule endopeptidase resemble those of the insulinoma granule type II endopeptidase and suggest that the same Ca(2+)-dependent protease or closely related enzymes could be involved in processing Lys-Arg-containing prohormones in neuroendocrine cells.

Partial conversion of vasopressinyl-Gly-Lys-Arg into pharmacologically active vasopressin through secretory granule carboxypeptidase E and alpha-amidating processing enzymes

Vasopressinyl-Gly-Lys-Arg, the first intermediate derived from vasopressin protein precursor, has been converted into mature vasopressin by an "in vitro" two-step reaction through neurohypophysial secretory granule enzymes. Whereas the conversion into vasopressinyl-Gly is virtually complete at pH 5.5 as judged by HPLC, the conversion of vasopressinyl-Gly into vasopressin is weak at pHs 6.0 or 8.0 as judged by HPLC and measure of generated pressor activity. It is suggested that the high conversion yield usually seen in mammalian neurohypophysis, where no intermediate is detected, might be due to additional "in vivo" factors such as particular membrane-association or binding of the intermediate onto a neurophysin carrier.

Evidence for distinct dibasic processing endopeptidases with Lys-Arg and Arg-Arg specificities in neurohypophysial secretory granules

Two Ca(2+)-dependent endopeptidases endowed with specificities for paired basic residues have been disclosed in rat and ox neurohypophysial secretory granules. Specificities investigated by using synthetic fluorogenic substrates showed the presence of a Lys-Arg endopeptidase with optimum pH close to the granule pH (5.5) and of an Arg-Arg endopeptidase more active at pH 7.0. Granule extracts have virtually no activity towards Lys-Lys-containing substrate or monobasic substrates. Pro-Gly-Lys-Arg-chloromethylketone appears a very efficient inhibitor for the Lys-Arg enzyme. Soluble and membrane-bound forms of both endopeptidases have been detected. pH-dependence of membrane binding and partitioning into Triton X-114 suggest that the membrane-bound form of Lys-Arg endopeptidase is associated through an amphiphilic alpha-helix. It is proposed that the enzyme Lys-Arg cleaves prooxytocin and provasopressin at their signal sequence Gly-Lys-Arg when these precursors arrive in the neurosecretory granules. The processing proceeds in the granules through carboxypeptidase E and alpha-amidating enzyme complex for giving mature pharmacologically active nonapeptide hormones.

The hormone-binding site of neurophysins: binding of vasopressin to the N-terminal sub-domain dissected from human MSEL-neurophysin through endopeptidase Lys-C

Human MSEL-neurophysin has been dissected into two halves by endopeptidase Lys-C, taking advantage of a peculiar Lys59-Ala60 bond. Two sub-domains, N-terminal (1-59) and C-terminal (60-93), have been separated. These sub-domains have been purified by reverse-phase high pressure liquid chromatography and identified by their N-terminal sequences. The N-terminal fragment comprises two chains 1-18 and 19-59, because of the presence of a second lysine residue in position 18, whereas the C-terminal fragment (60-93) is a single chain. Hormone-binding experiments have been carried out using vasopressin or vasopressinyl-Gly-Lys-Arg and testing the ability of the hormone-neurophysin complex to precipitate at pH 3.9 with 10% NaCl. The N-terminal sub-domain precipitates in presence of vasopressin in the same way as native neurophysin whereas the C-terminal sub-domain does not. It can be concluded that the hormone-binding site is located in the 1-59 region of neurophysin.

Study of frog (Rana esculenta) proopiomelanocortin processing in the intermediate pituitary. Identification of alpha-melanotropin, beta-melanotropin, Lys-gamma-melanotropin, and corticotropin-like intermediate lobe peptide

The proteolytic processing of frog (Rana esculenta) proopiomelanocortin in melanotropic cells of the intermediate pituitary gland has been examined through purification of the mature fragments by reverse-phase high-pressure liquid chromatography and microsequencing of isolated peptides. alpha-Melanotropin, beta-melanotropin, Lys-gamma-melanotropin, corticotropin-like intermediate lobe peptide, and hinge peptide have been isolated and chemically characterized. The results show a high preservation in the processing sites of frog proopiomelanotropin when compared to bovine counterparts. They reveal also a great conservation of the processing enzyme equipment of melanotropic cells in tetrapods species. Identification of Lys-gamma-melanotropin suggests the occurrence of an endopeptidase able to cleave between two basic residues. On the other hand alpha-melanotropin does not appear to be N-acetylated, as previously found in the clawed-toad Xenopus laevis, and this feature might distinguish amphibian from mammalian proopiomelanocortin processing.

Heterologue conversion of amphibian hydrin 2 into vasotocin through bovine granule alpha-amidating enzyme

Abstract Hydrin 2 (vasotocinyl-Gly), found along with vasotocin in the neurohypophysis of frogs and toads but not of other vasotocin-bearers such as birds and reptiles, is believed to act on water permeability of frog skin, whereas vasotocin mainly fulfils the antidiuretic function on the kidney. In order to understand the peculiar regulation of provasotocin differential processing in amphibians, conversion of hydrin 2 into vasotocin has been attempted using bovine pituitary granule alpha-amidating enzyme. Generated vasotocin has pharmacological properties and Chromatographic behaviour in high-performance liquid chromatography identical to those of synthetic vasotocin. However, the low yield of conversion (5% to 10%) suggests that additional factor(s) might be involved in the physiological processing.

Complete amino acid sequence of goose VLDV-neurophysin. Traces of a putative gene conversion between promesotocin and provasotocin genes

Goose VLDV-neurophysin (mesotocin-associated neurophysin) has been purified from posterior pituitary glands through molecular sieving on Sephadex G-75 and high-pressure reverse-phase liquid chromatography on Nucleosil C-18 columns. Despite apparent molecular mass of unreduced VLDV-neurophysin measured by polyacrylamide gel electrophoresis with sodium dodecylsulfate appeared near 17 kDa, this value fell to 11 kDa after reduction with mercaptoethanol, suggesting the existence of a homodimer. Complete amino acid sequence (93 residues) of goose VLDV-neurophysin has been determined. N- and C-terminal sequences of the protein have been established by Edman degradation (microsequencing) and use of carboxypeptidase Y, respectively. Peptides derived from oxidized or carboxamidomethylated neurophysin by trypsin or staphylococcal proteinase hydrolyses have been isolated by high-pressure liquid chromatography and microsequenced, allowing determination of the complete sequence. Comparison within the vertebrate VLDV-neurophysin lineage, namely goose VLDV-neurophysin to mammalian VLDV-neurophysins and to deduced toad VLDV-neurophysin, reveals a residue insertion between positions 66 and 67 in the nonmammalian VLDV-neurophysins. When goose MSEL-neurophysin (vasotocin-associated neurophysin) and goose VLDV-neurophysin are compared to their bovine counterparts, identical substitutions are found in positions 17 (Asn in both goose neurophysins instead of Gly in both ox neurophysins), 18 (Arg instead of Lys), 35 (Tyr instead of Phe), and 41 (Thr instead of Ala). Identity of the sequences 10-74 in both ox neurophysins has been explained by partial gene conversion between oxytocin and vasopressin genes, and identical substitutions in both goose neurophysins might reveal a similar gene conversion between mesotocin and vasopressin genes in birds.

Non-mammalian "big" neurophysins--complete amino acid sequence of a two-domain MSEL-neurophysin from goose

Vasotocin-associated neurophysin (MSEL-neurophysin) has been purified from goose neurohypophysis through molecular sieving and high-pressure reverse-phase liquid chromatography (HPLC). The protein has a molecular mass (measured by SDS-polyacrylamide gel electrophoresis) of 17 kDa in contrast to 10 kDa found for the mammalian MSEL-neurophysins. Complete amino acid sequence (131 residues) has been determined mainly through tryptic or staphylococcal proteinase peptides derived from carboxyamidomethylated neurophysin, isolated by HPLC and microsequenced. N- and C-terminal sequences have been established by Edman degradation or action of carboxypeptidase Y, respectively, applied on the native protein. Goose MSEL-neurophysin is homologous to the two-domain "big" MSEL-neurophysin previously identified in the frog. It appears that in non-mammalian tetrapods, namely birds and amphibians, the proteolytic processing of the pro-vasotocin involves only one cleavage, releasing the hormone moiety and a "big" neurophysin with two domains homologous to mammalian MSEL-neurophysin and copeptin, respectively. Comparison of the avian protein with its mammalian and amphibian counterparts reveals that the first half of the polypeptide chain is evolutionarily much less variable than the second and that the goose protein resembles the frog protein much more than the mammalian one.

Evolutionary specificity of hydrins, new hydroosmotic neuropeptides: occurrence of hydrin 2 (vasotocinyl-Gly) in the toad Bufo marinus but not in the viper Vipera aspis

Hydrin 2 (vasotocinyl-Gly), a hydroosmotic peptide resulting from differential processing of provasotocin and recently identified in frog neurohypophysis, has been looked for in the pituitary gland of an exotic toad (Bufo marinus) and of a reptile (Vipera aspis). Hydrin 2 has been found in the amphibian but not in the reptile. This result confirms the evolutionary specificity of hydrin 2 that has been identified only in frogs and toads but not in birds and reptiles. Occurrence of hydrin 2 is explained by its regulatory function on the water permeability of the skin of anurans.

[Transposition of the great vessels in western Africa. Apropos of 17 cases observed at the Institute of Cardiology in Abidjan]

During the last 10 years, 17 children with transposition of the great arteries (TGA) were admitted to the Cardiology Institute of Abidjan: 1 case between March 1978 and December 1985, 16 cases between January 1986 and December 1989. The average age was 58 days (range 5 to 270 days) at the first consultation, and 90 days (5 to 270 days) at the time of admission. The diagnosis was confirmed by echocardiography and hemodynamic investigation in 12 cases. There were 9 simple forms of TGA, 7 with ventricular septal defects (VSD) and 1 with VSD and pulmonary stenosis. Two children were taken back by their parents before any treatment was given. A Rashkind atrial septostomy was carried out in 11 children which increased aortic oxygen saturation from 35 +/- 18 percent to 57 +/- 19 percent; there were 3 unsuccessful procedures in children aged 2, 3 and 5 months with 2 deaths. Five patients later underwent surgical correction by a Senning procedure in 4 cases and anatomical correction in 1 case with VSD. All are well after an average 15 months follow-up (1 to 48 months). One of the 8 children awaiting surgery died. Therefore, TGA is not a rare abnormality in Black Africa; it represents 2 percent of the 887 cases of congenital heart disease observed during the same period. The inadequacy of means of diagnosis is certainly the cause of the relatively low incidence of this malformation, of the considerable delay in under specialist care and, as a consequence, of the greater difficulties in treatment, especially with regards to atrial septostomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of two types of neurophysins in Xenopus laevis neurointermediate pituitary homologous to mammalian MSEL- and VLDV-neurophysins

Xenopus laevis neurophysins have been purified from neurointermediate pituitaries through high-pressure reverse-phase liquid chromatography and their N-terminal amino acid sequences have been determined by microsequencing. Two types of neurophysins, corresponding to mammalian MSEL- and VLDV-neurophysins, have been distinguished. A strong homology exists between neurophysins of Xenopus (Pipidae), frog (Ranidae) and toad (Bufonidae). Xenopus MSEL-neurophysin, as frog MSEL-neurophysin, has a high molecular mass suggesting that the C-terminal domain of the vasotocin precursor is not processed in contrast to the two-step processing observed for mammalian vasopressin precursor.

ABBREVIATIONS

Mammalian neurophysins are termed MSEL- and VLDV-neurophysins according to the nature of residues in positions 2, 3, 6 and 7 (one-letter symbols for amino acids).

Occurrence of hydrin 2 (vasotocinyl-Gly), a new hydroosmotic neurohypophyseal peptide, in secretory granules isolated from the frog (Rana esculenta) neurointermediate pituitary

Neurohypophyseal secretory granules have been purified from the frog (Rana esculenta) neurointermediate pituitary gland by sucrose gradient centrifugation, and their polypeptide content has been analyzed by reverse-phase high-pressure liquid chromatography. Aside from vasotocin, mesotocin, and their associated neurophysins, hydrin 2 (vasotocinyl-Gly), previously identified in hydrochloric acid extracts, has been recognized. This finding supports the previous suggestion that hydrin 2, a peptide active on the water permeability of frog bladder and frog skin, is a secreted hormone involved in osmoregulation specific to amphibians. Hydrin 2 has not been found in neurosecretory granules of birds such as the goose.

Hydrins, hydroosmotic neurohypophysial peptides: osmoregulatory adaptation in amphibians through vasotocin precursor processing

From neurointermediate pituitary glands of Xenopus laevis and Rana esculenta, previously unreported peptides termed hydrins, active on water permeability of frog urinary bladder and frog skin (Brunn or "water-balance" effect), have been isolated and sequenced. These peptides seem to be derived from the pro-vasotocin-neurophysin precursor. Hydrin 1, found in Xenopus, has been identified as vasotocin C-terminally extended with the Gly-Lys-Arg sequence; hydrin 2, found in Rana, has been identified as vasotocin C-terminally extended with glycine. Hydrin 2 has been detected in several Ranidae (R. esculenta, Rana temporaria, Rana pipiens) and Bufonidae (Bufo bufo, Bufo ictericus) and appears to have a large distribution in terrestrial or semiaquatic anurans. Hydrins, in contrast to vasotocin, are not active on rat uterus or rat blood pressure. They are absent from other vasotocin-bearers such as birds and could be involved specifically in water-electrolyte regulation of amphibians.

Isolation of neurosecretory granules containing vasotocin, mesotocin, MSEL- and VLDV-neurophysins from goose neurohypophysis

Neurosecretory granules have been isolated from goose posterior pituitaries and their contents have been analyzed by reverse-phase high-pressure liquid chromatography and polyacrylamide gel electrophoresis. Vasotocin and mesotocin have been identified by their biological activities and their retention times compared with those of synthetic peptides. MSEL- and VLDV-neurophysins have been characterized by their N-terminal sequences, their electrophoretic migrations and their retention times, compared with those of purified goose neurophysins. In contrast to the two-step processing of mammalian provasopressin, processing of the vasotocin - MSEL-neurophysin precursor appears to involve only one cleavage giving the hormone and a "big" MSEL-neurophysin homologous to mammalian MSEL-neurophysin extended by copeptin.

Particular processing of pro-opiomelanocortin in Xenopus laevis intermediate pituitary. Sequencing of alpha- and beta-melanocyte-stimulating hormones

alpha- and beta-melanocyte-stimulating hormones (alpha-MSH and beta-MSH) have been isolated from Xenopus laevis neurointermediate pituitary and microsequenced. Intracellular alpha-MSH is not N-acetylated after proteolytic processing of pro-opiomelanocortin in contrast to mammalian alpha-MSHs. There is a high preservation of the melanotropic amino acid sequence common to all MSHs although in Xenopus beta-MSH a histidine residue replaces the glutamic acid residue found in position 8 of mammalian beta-MSHs.

Vasopressin neuron is the target of monoclonal antibodies raised against vasopressin-neurophysin injected in vivo

Monoclonal antibodies (MAbs) raised against the neurophysin (NP) specifically synthesized with vasopressin (VP, VP-NP) were injected into the paraventricular nucleus (PVN) of the rat hypothalamus. Their fate was studied by immunocytochemistry from 1 min to 3 h after the end of injection. It could be demonstrated that the VP-NP MAbs penetrated in vivo into some magnocellular neurons of the injected PVN and were transported ipsi- and contralaterally in individual neurons and in accessory magnocellular groups. When the time after injection was longer than 15 min, the VP-NP MAbs were also carried in the fibers of the median eminence. The prior treatment of rats with colchicine did not prevent the uptake of VP-NP MAb in the neurons but inhibited the transport towards the eminential fibers, the individual neurons and accessory groups. The detection of the PVN endogenous peptides (VP and oxytocin) on the same brain sections indicates that the neuronal uptake was specific. It only occurred in the neurons which synthesized VP and never appeared in the brain of rats suffering from a genetic defect of the central VP synthesis (Brattleboro rat). These data support the hypothesis of the location on the cell surface of the VP-NP precursor in magnocellular neurons which synthesize VP. This membrane signal identifies the neuron and allows the immunological recognition of the neurosecretory neurons in vivo.

The distribution of lysine vasopressin (lysipressin) in placental mammals: a reinvestigation of the Hippopotamidae (Hippopotamus amphibius) and Tayassuidae (Tayassu angulatus) families

The neurohypophyseal hormones of the hippopotamus (Hippopotamus amphibius) and collared peccary (Tayassu angulatus) were isolated by molecular sieving and preparative high-pressure liquid chromatography (HPLC). Oxytocin and arginine vasopressin have been identified by their amino acid compositions and their retention times in HPLC. Lysipressin (lysine vasopressin) was not detected in posterior pituitaries of two hippopotami and nine peccaries (less than 2% of arginine vasopressin in molar ratios). Among the suborder Suiformes of Artiodactyla, the families Hippopotamidae and Tayassuidae do not seem to possess lysipressin, in contrast to the family Suidae in which the pig has lysipressin in place of arginine vasopressin.

Structure, processing and evolution of the neurohypophysial hormone-neurophysin precursors

Neurohypophysial hormones and neurophysins are derived from common precursors processed during the axonal transport from the hypothalamus to the neurohypophysis. Two neurohormones, an oxytocin-like and a vasopressin-like, on one hand, two neurophysins, termed VLDV-and MSEL-neurophysins according to residues in positions 2, 3, 6 and 7, on the other, are usually found in vertebrate species. In contrast to placental mammals that have oxytocin and arginine vasopressin, marsupials have undergone a peculiar evolution. Two pressor peptides, lysipressin and vasopressin for American species, lysipressin and phenylpressin for Australian macropods, have been identified in individual glands and it is assumed that the primordial vasopressin gene has been duplicated in these lineages. On the other hand, the reptilian mesotocin is still present in Australian species instead of the mammalian oxytocin, while the North American opossum has both hormones and South American opossums have only oxytocin. The neurophysin domain of each precursor is encoded by 3 exons and different evolutionary rates have been found for the 3 corresponding parts of the protein. The central parts, encoded by the central exons, are evolutionarily very stable and nearly identical in the 2 neurophysins of a given species. Recurrent gene conversions have apparently linked the evolutions of the 2 precursor lineages. In mammals, the 3-domain precursor of vasopressin is processed in 2 stages: a first cleavage splitting off vasopressin and a second cleavage separating MSEL-neurophysin from copeptin. Two distinct enzymatic systems seem to be involved in these cleavages. Processing is usually complete at the level of the neurohypophysis, but an intermediate precursor encompassing MSEL -neurophysin and copeptin linked by an arginine residue has been characterized in guinea pig. In vitro processing of this intermediate through trypsin--Sepharose reveals cleavages only in the interdomain region. In non-mammalian tetrapods, such as birds and amphibians, mesotocin and vasotocin are associated with neurophysins in precursors similar to those found in mammals. However, processing of the vasotocin precursor seems to be different from the processing of the vasopressin precursor, with a single cleavage leading to the hormone release.

Neurohypophysial hormones of the 1-month-old bovine fetus: absence of vasotocin during mammal development

The neurohypophysial hormones of the 1-month-old bovine fetus have been identified by their positions in ion-exchange chromatography and their retention times in high-pressure reverse-phase partition chromatography. Arginine vasopressin and oxytocin have been recognized. The molar ratio vasopressin/oxytocin in neurohypophysis is about 6 in the 1-month-old fetus compared with 4 in the 3-month-old fetus, 2.7 in the 7-month-old fetus and 1 in the adult. Vasotocin is virtually absent even in the early fetus (less than 0.1% of arginine vasopressin). The occurrence of a vasotocin gene expressed in the fetus but silent in the adult appears unlikely.

Dual duplication of neurohypophysial hormones in an Australian marsupial: mesotocin, oxytocin, lysine vasopressin and arginine vasopressin in a single gland of the northern bandicoot (Isoodon macrourus)

Neurohypophysial hormones of an Australian marsupial, the Northern bandicoot (Isoodon macrourus), have been identified by their retention times in high-pressure reverse-phase liquid chromatography using two solvent systems and by their molar pressor or uterotonic activities. Two pressor peptides, arginine vasopressin and lysipressin, and two uterotonic peptides, mesotocin and oxytocin, have been characterized. Because mesotocin and arginine vasopressin have been identified in three other Australian marsupial families, it is assumed that a duplication of each ancestral gene occurred in Peramelidae and subsequent mutations in one copy led to the additional oxytocin and lysipressin. A similar dual duplication of neurohypophysial hormones has previously been discovered in the North-American opossum (Didelphis virginiana) so that the duplication propensity seems peculiar to marsupials in contrast to placental mammals.

[Chronic left parietal endocarditis. Clinical, paraclinical and peroperative study of 22 cases]

From 22 patients with left chronic parietal endocarditis (CPE), conducted an epidemiological, clinical, paraclinical and per-operative study. The CPE is frequently encountered in the Ivory Coast in Akan children living in forest areas in 81 p. cent of the cases. It causes a mitral insufficiency, of the which the essential mechanism is fibrosis of the sub-valvular apparatus. The clinical examination is that of a severe advanced mitral insufficiency. Cardiomegaly is the rule. In 31 p. cent of cases, the ECG shows a Qr in V1. The dip plateau on the apexocardiogram is never found and the protodiastolic endocardial resonance is inconstant on phonomechanical processor. The aspect in M of the interventricular septum, found in 72 p. cent of the cases on echo TM is of major importance when direct signs are missing on bidimensional sonograms. Angiocardiography remains the reference diagnostic examination. But only the surgical survey enables to demonstrate limited forms.

An amphibian two-domain 'big' neurophysin: conformational homology with the mammalian MSEL-neurophysin/copeptin intermediate precursor shown by trypsin-sepharose proteolysis

A 'big' frog (Rana esculenta) neurophysin, encompassing sequences homologous to mammalian MSEL-neurophysin and copeptin, has been passed through a trypsin-Sepharose column in order to compare its conformation with that of the two-domain intermediate precursor isolated from guinea pig. Whereas the polypeptide possesses 8 arginine residues, only two cleavages were observed located in a putative inter-domain sequence (at Arg-94 and Arg-114). Because free vasotocin has been isolated from the frog, it is assumed that pro-vasotocin has a three-domain conformation similar to that of pro-vasopressin but processing in amphibians involves only one step rather than two steps as in mammals.

Isolation of neurosecretory granules containing vasopressin and MSEL-neurophysin from guinea pig neurointermediate pituitary

Neurosecretory granules have been isolated from rat and guinea pig neurointermediate pituitaries and their contents have been analyzed by reverse-phase high-pressure liquid chromatography and polyacrylamide gel electrophoresis. Granule components have been compared with synthetic neurohypophysial hormones and chemically characterized neurophysins. In rat granules, oxytocin, arginine vasopressin and MSEL- and VLDV-neurophysins have been identified. In isolated guinea pig granules, only arginine vasopressin and mature MSEL-neurophysin have been found. From these results it can be concluded that both the "dibasic" cleavage between vasopressin and MSEL-neurophysin and the "monobasic" cleavage between MSEL-neurophysin and copeptin occur within the granule compartment. Previous isolation from frozen guinea pig glands of a partially processed precursor encompassing MSEL-neurophysin and copeptin suggests a two-step processing of the three-domain vasopressin precursor, each involving a distinct enzymic system.

One-step processing of the amphibian vasotocin precursor: structure of a frog (Rana esculenta) "big" neurophysin

Vasotocin-associated neurophysin (MSEL-neurophysin) from the frog Rana esculenta has been isolated and sequenced through tryptic and staphylococcal proteinase peptides and cyanogen bromide fragments. This protein appears homologous to the mammalian vasopressin-associated neurophysin with a C-terminal glycopeptide extension homologous to the mammalian copeptin. In contrast to the two-step processing of mammalian vasopressin/MSEL-neurophysin/copeptin precursor, a single cleavage is therefore involved in the processing of the amphibian vasotocin/neurophysin precursor. It appears that the physiological release of the vasopressin-like hormone from the N-terminal end of the protein precursor is not dependent upon a previous trimming of the C-terminal copeptin-like moiety.

Guinea pig MSEL-neurophysin. Sequence comparison of eight mammalian MSEL-neurophysins

The amino acid sequence of guinea pig MSEL-neurophysin has been determined using tryptic peptides derived from the performic acid-oxidized protein and staphylococcal proteinase peptides obtained from the reduced-carboxamidomethylated neurophysin. Guinea pig MSEL-neurophysin consists of a 93-residue polypeptide chain that shows 12 substitutions and 2 deletions when compared to bovine MSEL-neurophysin. It displays the highest number of variations among known mammalian MSEL-neurophysins. These variations are mainly found in the C-terminal region (residues 88-93). Moreover guinea pig MSEL-neurophysin, like rat homologous protein, exhibits substitutions in positions 2, 5, 29 and 81 and lacks an arginine in the penultimate position. Comparison between eight mammalian MSEL-neurophysins reveals a highly conserved region (residues 1 to 88) and a hypervariable region (residues 89 to 93/95). On the other hand the eight species examined are endowed with arginine vasopressin except pig, which has a lysine vasopressin. In the vasopressin-MSEL-neurophysin precursor, the hormonal moiety and the MSEL region of neurophysin (residues 1-9) are encoded by a common exon in ox, rat and man; it can be concluded that this exon is evolutionarily conservative in contrast to the one encoding the C-terminal region of MSEL-neurophysin.

Evolution of marsupials traced by their neurohypophyseal hormones: microidentification of mesotocin and arginine vasopressin in two Australian families, Dasyuridae and Phascolarctidae

Neurohypophyseal hormones of two species belonging to the family Dasyuridae, namely Dasyurus viverrinus (Eastern native cat) and Dasyuroides byrnei (Kowari), and of the single living member of the family Phascolarctidae, Phascolarctos cinereus (Koala) have been isolated and characterized by their retention times in high-pressure reverse-phase partition chromatography and either amino acid composition or amino acid sequence through a gas-phase microsequencer. Mesotocin and arginine vasopressin have been identified in the three species. The same hormones have previously been found in a species belonging to the family Phalangeridae, Trichosurus vulpecula (brush-tailed possum), whereas in five species of Macropodidae, mesotocin, lysipressin, and phenypressin have been characterized. Because the four Australian marsupial families examined up to now possess mesotocin and at least a vasopressin-like peptide, it is assumed that the primitive marsupial settler in Australia was endowed with mesotocin and arginine vasopressin.

Coronary heart disease in the diabetic African: frequency clinical and angiographic features

The frequency and clinical and coronarographic features of coronary heart disease (CHD) in black African diabetic patients were assessed in a two-part study. The aim of part I was to determine the frequency of CHD in 50 diabetic patients selected by the following criteria: male, age between 40 and 60 years, diabetes history less than 20 years, no history of CHD and normal E.K.G. All 50 of these patients underwent a stress test and those who failed or for whom results were inconclusive were submitted to coronary arteriography. Part II was a retrospective study of 104 patients with CHD. Its aim was to compare the clinical and coronarographic features of CHD patients with (27 cases) and without (77 cases) diabetes mellitus. The frequency of CHD in the 50 diabetics selected for this study was 10% (31 negative exercise tests, 19 inconclusive exercise tests, 5 coronary arteriographies with significant narrowing). Of these 5 diabetics with CHD, 3 had single vessel involvement (left descending artery: 2 cases, circumflex artery: 1 case), 1 patient had double vessel involvement (right coronary circumflex artery) and 1 had triple vessel involvement (left descending, circumflex, and right coronary artery). In the retrospective study the clinical profile of the diabetic and non-diabetic CHD patients was the same with respect to sex, age, angina, myocardial infarction, and death rate. As regard the risk factors, blood cholesterol level was higher in diabetics while cigarette smoking was higher in non-diabetics. The frequency of hypertension was the same in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Gene conversion in avian mesotocin and vasotocin genes: a recurrent mechanism linking two neurohypophysial precursor lineages?

Amino acid sequences of the first half of MSEL- and VLDV-neurophysins from goose and chicken have been determined. Identical substitutions in positions 17, 18, 35, 36 and 41 of both neurophysins of a given species when compared with their mammalian counterparts suggest a gene conversion between vasotocin--MSEL-neurophysin and mesotocin--VLDV-neurophysin genes. This event, which has already been observed for three mammalian species, seems recurrent and would link the evolution of the two neurohypophysial hormone precursors.