First morphogenetic analysis of parasite eggs from Schistosomiasis haematobium infected sub-Saharan migrants in Spain and proposal for a new standardised study methodology.

Schistosomiasis is a Neglected Tropical Disease caused by trematode species of the genus Schistosoma. Both, autochthonous and imported cases of urogenital schistosomiasis have been described in Europe. The present study focuses on eggs, considered pure S. haematobium by genetic characterisation (intergenic ITS region of the rDNA and cox1 mtDNA). A phenotypic characterisation of S. haematobium eggs was made by morphometric comparison with experimental populations of S. bovis and S. mansoni, to help in the diagnosis of S. haematobium populations infecting sub-Saharan migrants in Spain. Analyses were made by Computer Image Analysis System (CIAS) applied on the basis of new standardised measurements and geometric morphometric tools. The principal component analysis (PCA), including seventeen non-redundant measurements, showed three phenotypic patterns in eggs of S. haematobium, S. bovis and S. mansoni. PCA showed that the S. bovis population presented a large egg size range with a pronouncedly larger maximum size. Similarly, S. bovis shows bigger spine values than S. haematobium. Mahalanobis distances between each pair of groups were calculated for each discriminant analysis performed. In general, S. mansoni and S. bovis present larger distances between them than with S. haematobium, i.e. they present the greatest differences. Regarding the spine, S. haematobium and S. mansoni are the most distant species. Results show the usefulness of this methodology for the phenotypic differentiation between eggs from these Schistosoma species, capable of discerning morphologically close eggs, as is the case of the haematobium group. Schistosoma egg phenotyping approaches may be applied to assess not only hybrid forms but also potential influences of a variety of other factors.

Estudio estadístico de la acción terapéutica del ácido retinoico tópico en los trastornos de queratinización / A statistical study of the topical retinoid´s therapeutic action in keratin disorders

Los retinoides han adquirido con el paso del tiempo la condición de fármaco indispensable en la práctica clínica diaria tras la observación de un gran número de resultados efectivos en un amplio abanico de procesos cutáneos. De hecho, los retinoides son los fármacos de elección en el tratamiento de los trastornos importantes de la queratinización. Ello se debe al amplio espectro de acción que poseen, el cual a su vez se explica por la gran diversidad de actividades farmacológicas que tienen los retinoides debido a los efectos que se derivan de la acción que ejercen sobre receptores celulares. Estas acciones incluyen, entre otras, la normalización de los desórdenes de queratinización al inducir el crecimiento de una nueva población de queratinocitos de apariencia normal. El presente estudio tiene como objetivo principal demostrar la efectividad que tiene la aplicación de ácido retinoico al 0,1% para el tratamiento del heloma neurovascular, una lesión dérmica que si bien su primera opción terapéutica es actualmente la extirpación quirúrgica, en ciertas ocasiones nos veremos obligados a recurrir a otra estrategia terapéutica. Será en estos casos en los que los retinoides tópicos constituirán un fármaco de elección para el tratamiento del trastorno de queratinización que se desarrolla durante la formación del heloma neuro vascular. Asimismo, otro objetivo de este estudio es valorar la efectividad de la aplicación de retinoides por via tópica como elemento coadyuvante al tratamiento ortopodológico (AU)

The success of retinoids in dermatology and skin care has made these chemical compounds to be a potential treatment for skin and dermatological diseases, being a key compound in the treatment of keratin disorders. Retinoids work by triggering molecular switches in skin cells called retinoid receptors. These switches affect many intracellular processes including the control of cell proliferation and cell differentiation. All these functions determine their usefulness in clinical dermatology being effective in the treatment of a number of dermatological conditions. The principal objective of the following article is to show retinoid acid cream 0,1% effect in the treatment of a specific keratin disorder, the neurovascular corn. The neurovascular corn is a dermatological disease whose principal treatment is the surgical excision. However, we should resort to others therapeutic strategies in different cases. Is in these situations when the retinoid acid will be a key compound for the treatment of the keratin disorder that takes place during the neurovascular corn evolution. Another objective of this study is to value the effectiveness of the retinoid acid cream as an adjuvant treatment of foot orthoses. An exploration protocol has been developed to covers from statistical dates to a clinical and dermoscopic exam of each neurovascular corn. Finally, a pain scale has been designed to value the degree of pain before starting the treatment and once topic treatment is completed. Based on the results we can conclude that topical retinoids are a very effective therapeutic tool in the treatment of dermatological conditions that are accompanied by a keratin disorder (AU)

Complex chromatin condensation patterns and nuclear protein transitions during spermiogenesis: examples from mollusks.

In this paper we review and analyze the chromatin condensation pattern during spermiogenesis in several species of mollusks. Previously, we had described the nuclear protein transitions during spermiogenesis in these species. The results of our study show two types of condensation pattern: simple patterns and complex patterns, with the following general characteristics: (a) When histones (always present in the early spermatid nucleus) are directly replaced by SNBP (sperm nuclear basic proteins) of the protamine type, the spermiogenic chromatin condensation pattern is simple. However, if the replacement is not direct but through intermediate proteins, the condensation pattern is complex. (b) The intermediate proteins found in mollusks are precursor molecules that are processed during spermiogenesis to the final protamine molecules. Some of these final protamines represent proteins with the highest basic amino acid content known to date, which results in the establishment of a very strong electrostatic interaction with DNA. (c) In some instances, the presence of complex patterns of chromatin condensation clearly correlates with the acquisition of specialized forms of the mature sperm nuclei. In contrast, simple condensation patterns always lead to rounded, oval or slightly cylindrical nuclei. (d) All known cases of complex spermiogenic chromatin condensation patterns are restricted to species with specialized sperm cells (introsperm). At the time of writing, we do not know of any report on complex condensation pattern in species with external fertilization and, therefore, with sperm cells of the primitive type (ect-aquasperm). (e) Some of the mollusk an spermiogenic chromatin condensation patterns of the complex type are very similar (almost identical) to those present in other groups of animals. Interestingly, the intermediate proteins involved in these cases can be very different.In this study, we discuss the biological significance of all these features and conclude that the appearance of precursor (intermediate) molecules facilitated the development of complex patterns of condensation and, as a consequence, a great diversity of forms in the sperm cell nuclei

Preliminary study of sperm chromatin characteristics of the brachyuran crab Maja brachydactyla. Histones and nucleosome-like structures in decapod crustacean sperm nuclei previously described without SNBPs.

An interesting characteristic of decapod crustacean sperm nuclei is that they do not contain highly packaged chromatin. In the present study we re-examine the presence of DNA-interacting proteins in sperm nuclei of the brachyuran Maja brachydactyla. Although previous reports have indicated that, unlike the majority of sperm cells, DNA of decapod sperm is not organized by basic proteins, in this work we show that: (1) histones are present in sperm of M. brachydactyla; (2) histones are associated with sperm DNA; (3) histone H3 appears in lower proportions than the other core histones, while histone H2B appears in higher proportions; and (4) histone H3 in sperm nuclei is acetylated. This work complements a previous study of sperm histones of Cancer pagurus and supports the suggestion that decapod crustacean sperm chromatin deserves further attention.

[Self-care behavior and patients' knowledge about self-care predict rehospitalization among older adults with heart failure]. / El autocuidado y el conocimiento del manejo de la enfermedad predicen la rehospitalización en ancianos con insuficiencia cardíaca.

INTRODUCTION: This study examined the association of self-care behavior and patients' knowledge about self-care with rehospitalization among older adults with heart failure (HF). METHODS: Case-control comparison (116 cases and 209 controls) nested in a prospective cohort of patients aged 65 years and older admitted for HF at 4 Spanish hospitals. Cases were patients experiencing a first emergency rehospitalization in the 6 months following the index hospital admission. Controls were patients who did not undergo a rehospitalization during such time-period. RESULTS: The number of self-care behaviors was inversely associated with the frequency of readmission (p for linear trend: 0.006). Compared with patients showing the appropriate self-care behavior, hospital readmission was more frequent among those who did no go for a walk daily or did not engage in any daily physical activity (hazard ratio [HR] 1.55; 95% confidence limits [CL] 1.04-2.29), and among those who did not keep their medical appointments (HR 1.82; 95% CL 1.10-3.02). Hospital readmission was also more frequent among patients who: failed to take their medication at the scheduled time (HR 2.07; 95% CL 1.15-3.72); stopped taking their medication when it disagreed with them (HR 1.76; 95% CL 1.08-2.85); and failed to adhere to their drug treatment (HR 1.96; 95% CL 1.29-2.98). Furthermore, the fewer the number of behaviors which patients knew to be required for self-care, the greater the frequency of rehospitalization (p for linear trend:0.029). CONCLUSIONS: A lower degree of self-care and of patients' knowledge about self-care predicted a higher risk of hospital readmission.

El autocuidado y el conocimiento del manejo de la enfermedad predicen la rehospitalización en ancianos con insuficiencia cardíaca / Self-care behavior and patients’ knowledge about self-care predict rehospitalization among older adults with heart failure

Introducción. Este trabajo examinó la asociacióndel autocuidado y del conocimiento de los pacientesacerca del autocuidado con la rehospitalizaciónen adultos mayores con insuficiencia cardíaca (IC).Métodos. Análisis de casos y controles (116 casos y209 controles) alojado en una cohorte prospectivade pacientes de 65 y más años de edad ingresadospor IC en 4 hospitales españoles. Los casoseran pacientes rehospitalizados de urgencia en los6 meses siguientes a la hospitalización índice.Los controles fueron pacientes que no serehospitalizaron durante esos 6 meses. Resultados. El número de actividades de autocuidado se asoció de forma inversa con la frecuencia de reingreso (p tendencia lineal: 0,006). En comparación con los pacientes que realizaron el autocuidado apropiado, el reingreso hospitalario fue más frecuente entre los que no paseaban ni realizaban actividad física a diario (hazard ratio [HR] 1,55; límites de confianza [LC] 95% 1,04-2,29), y entre los que se saltaban la visita al médico en la fecha programada (HR 1,82; LC 95% 1,10-3,02). El reingreso hospitalario también fue más frecuente entre los pacientes que no tomaban la medicación a su hora (HR 2,07; LC 95% 1,15-3,72), los quedejaban de tomarla cuando les sentaba mal (HR1,76; LC 95% 1,08-2,85), y los que no mostraronadherencia al tratamiento farmacológico (HR 1,96;LC 95% 1,29-2,98). Además, a menor número de actividades de manejo de la IC que se conocía que debían realizarse, mayor fue la frecuencia de rehospitalización (p tendencia lineal: 0,029).Conclusión. A menor autocuidado y menor conocimiento del manejo de la IC, mayor riesgo de reingreso hospitalario

Introduction. This study examined the associationof self-care behavior and patients’ knowledge aboutself-care with rehospitalization among older adultswith heart failure (HF).Methods. Case-control comparison (116 cases and209 controls) nested in a prospective cohort ofpatients aged 65 years and older admitted for HF at4 Spanish hospitals. Cases were patientsexperiencing a first emergency rehospitalization inthe 6 months following the index hospital admission.Controls were patients who did not undergo arehospitalization during such time-period.Results. The number of self-care behaviors wasinversely associated with the frequency of readmission (p for linear trend: 0.006). Compared with patients showing the appropriate self-care behavior, hospital readmission was more frequent among those who did no go for a walk daily or did not engage in any daily physical activity (hazard ratio [HR] 1.55; 95% confidence limits [CL] 1.04-2.29), and among those who did not keep their medical appointments (HR 1.82; 95% CL 1.10-3.02).Hospital readmission was also more frequent amongpatients who: failed to take their medication at thescheduled time (HR 2.07; 95% CL 1.15-3.72);stopped taking their medication when it disagreedwith them (HR 1.76; 95% CL 1.08-2.85); andfailed to adhere to their drug treatment (HR 1.96;95% CL 1.29-2.98). Furthermore, the fewer thenumber of behaviors which patients knew to berequired for self-care, the greater the frequencyof rehospitalization (p for linear trend:0.029).Conclusions. A lower degree of self-care and ofpatients’ knowledge about self-care predicted ahigher risk of hospital readmission

[Mobile liver and colonic volvulus. A case report]. / Hígado móvil y vólvulo de colon. Presentación de un caso.

A <> liver is an exceptional situation in which the laxness or absence of the ligaments supporting liver allow it to move in the transversal plane so that it is always located on the dependent side. This condition is usually associated to a long and lax mesocolon, which is usually responsible for the symptoms. Very few cases have been described in the literature. To our knowledge, this is the first report of the computed tomography (CT) findings of a mobile liver with acute abdomen caused by associated colonic volvulus.

Hígado móvil y vólvulo de colon. Presentación de un caso / Mobile liver and colonic volvulus. A case report

El hígado «móvil» es una situación excepcional en la que el hígado, debido a la laxitud o ausencia de ligamentos de soporte, puede moverse en el plano transversal, situándose cada vez en el lado dependiente. Habitualmente se asocia también a un mesocolon largo y laxo que es generalmente responsable de los síntomas. Se han descrito muy pocos casos en la literatura. Nosotros presentamos, por primera vez, los hallazgos en tomografía computarizada (TC) de un caso de hígado móvil con abdomen agudo causado por vólvulo de colon asociado (AU)

A «mobile» liver is an exceptional situation in which the laxness or absence of the ligaments supporting liver allow it to move in the transversal plane so that it is always located on the dependent side. This condition is usually associated to a long and lax mesocolon, which is usually responsible for the symptoms. Very few cases have been described in the literature. To our knowledge, this is the first report of the computed tomography (CT) findings of a mobile liver with acute abdomen caused by associated colonic volvulus (AU)

Sperm nucleomorphogenesis in the cephalopod Sepia officinalis.

Sperm nucleomorphogenesis in the cephalopod Sepia officinalis is the product of the interaction between perinuclear microtubules and condensing chromatin. This interaction occurs during spermiogenesis and is established through the nuclear membrane. As in other cephalopod species, the perinuclear microtubules are transient structures. In the case of S. officinalis, they begin to appear in the basal area of the early spermatid and progress from there, establishing contact with the external nuclear membrane and follow a defined, but not symmetric, geometry. Thus, the microtubules accumulate preferentially in one area of the nuclear membrane which we refer to here as the "dorsal zone". Later, the microtubules will be eliminated before the mature spermatid migrates to the epidydimis. The chromatin is condensed within the nucleus following a complex pattern, beginning as fibro-granular structures until forming fibres of approximately 45 nm diameter (patterning phases). From this stage on, an increase in the chemical basicity of DNA-interacting proteins is produced, and chromatin fibres coalesce together, being recruited to the dorsal zone of the membrane, where there is a higher density of microtubules. This last step (condensation phases) allows the chromatin fibres to be arranged parallel to the axis of the elongating nucleus, and more importantly, is deduced to cause a lateral compression of the nucleus. This lateral compression is in fact a recruitment of the ventral zone toward the dorsal zone, which brings about an important reduction in nuclear volume. The detailed observations which comprise this work complement previous studies of spermiogenesis of Sepia and other cephalopods, and will help to better understand the process of cellular morphology implicated in the evolution of sperm nuclear shape in this taxonomic group.

Transition of nuclear proteins and chromatin structure in spermiogenesis of Sepia officinalis.

During spermiogenesis of Sepia officinalis histones are directly substituted by a molecule of precursor protamine, which is later transformed into the protamine through a deletion of the amino terminal end. In the present work, it is shown that the pattern of spermiogenic chromatin condensation consists of a phase of "patterning" and a phase of "condensation." In the phase of patterning, three structural remodelings are produced in the chromatin structure: [somatic-like chromatin --> 18 nm granules --> 25 nm fibers --> 44 nm fibers]. The first remodeling of the chromatin into granules of 18 nm takes place without the entrance of specific proteins in the spermiogenic nuclei. The second remodeling [granules of 18 nm --> fibers of 25 nm] is due to the entrance of the precursor protamine and its interaction with the DNA-histone complex. The third remodeling [fibers of 25 nm --> fibers of 44 nm] occurs simultaneously with the disappearance of histones from the chromatin. In the phase of condensation, the fibers of 44 nm coalesce among themselves to form progressively larger aggregates of chromatin. In this phase there are no substantial variations in the nuclear proteins, so that the condensation of the chromatin must respond to posttranscriptional changes of the precursor protamine (dephosphorylation, deletion of the amino-terminal end).

Chromatin reorganization during spermiogenesis of the mollusc Thais hemostoma (Muricidae): implications for sperm nuclear morphogenesis in cenogastropods.

Thais is a cenogastropod mollusc belonging to the Muricidae family. The sperm nuclear morphogenesis of Thais develops in two well-defined and peculiar steps. In the first one, the round early spermatidyl nucleus is penetrated by an endonuclear channel, which arranges as a helix at the inner nuclear surface and organizes the condensing chromatin all around. In the second step, the spiral channel stretches, dragging along the associated chromatin and leading to a definitive cylinder-shaped sperm nucleus. Simultaneously with these changes in nuclear shape, the chromatin is sequentially organized in granules, fibres, lamellae, and, finally, in a very condensed structure, whereas the spermiogenic DNA-associated proteins become more basic and simple. The sperm nucleus contains a small group of protamines consisting of only four types of amino acid (lysine, arginine, glycine, and serine). The most remarkable fact on nuclear spermiogenesis in Thais is that, whereas the chromatin condensation process, the nuclear proteins, and the final shape of sperm nucleus are very similar to those in other muricidae studied, the pathway of nuclear morphogenesis is completely different. We propose an independent genetic control for those two spermiogenic events (chromatin condensation and nucleomorphogenesis). Finally we discuss briefly the main traits of nucleomorphogenesis of muricid molluscs.

Characterization and evolutionary relevance of the sperm nuclear basic proteins from stickleback fish.

We have characterized the sperm nuclear basic proteins (SNBPs) of the sticklebacks in the suborder Gasterosteoidei. The complete amino acid sequence of the protamines from Aulorhynchus flavidus, Pungitius pungitius, Gasterosteus aculeatus, (anadromous) and G. wheatlandi, as well as the sequences of the protamines of several species pairs of freshwater G. aculeatus, have been determined. Analysis of the primary structure of these proteins has shown that: a) despite the relatively low amino acid complexity and small molecular mass of these basic proteins, they are very good molecular markers at the generic level. The bootstrap parsimony analysis using their sequences provides a phylogenetic relationship for the old anadromous species of Gasterosteoidei which is identical to that obtained from morphological and behavioral analysis; b) the comparison of the sequences also suggests that protamines from the suborder Gasterosteoidei have most likely evolved from a common gene in the early Acanthopterygii by an extension of the carboxy terminal portion of the molecule; c) protamines are not good markers for recent postglacial freshwater isolates of G. aculeatus. However, in the unique case of Enos Lake (British Columbia), we have been able to detect an additional minor protamine component in the benthic forms of G. aculeatus that is not present in the limnetic forms. Thus, this new protamine must have appeared during the past 12,000 years concomitantly with the speciation of benthics and limnetics in this lake.

DNA-interacting proteins in the spermiogenesis of the mollusc Murex brandaris.

Sperm chromatin of Murex brandaris (a neogastropod mollusc) undergoes a series of structural transitions during spermiogenesis. The DNA-interacting proteins responsible for these changes as well as the mature protamines present in the ripe sperm nucleus have been characterized. The results reveal that spermiogenic nuclear proteins are protamine precursors that are subjected to a substantial number of small N-terminal deletions that gradually modify their overall charge. The composition of mature protamines is remarkably simple in turn, promoting an efficient and extremely tight packaging of DNA. The pattern of spermiogenic chromatin condensation in M. brandaris clearly departs from that corresponding to vertebrate chromatin.

Physicochemical and functional comparison of Xenopus laevis nucleoplasmin obtained from oocytes and from overexpression in bacteria.

We compare the physicochemical and functional characteristics of nucleoplasmin obtained from Xenopus laevis oocytes and by bacterial overexpression of a plasmid containing the nucleoplasmin gene. The comparison shows that, while the secondary structure of the protein is not affected by the method used to obtain this protein, the bacterial expressed form exhibits a marked tendency to form large aggregates and an impaired ability to displace protamines from sperm nuclei. These results add a word of caution to the indiscriminate use, in functional or structural (crystallographic) studies, of bacterially overproduced proteins that have been end-terminally tagged with polyhistidine.

Primary structure of scombrine alpha: two different species with an identical protamine.

We have studied the protamine scombrine alpha from the mackerel Scomber scombrus. Scombrine alpha is found phosphorylated in spermatid nuclei, but not in nuclei of ripe sperm. It is a typical fish protamine, made up of two distinct molecular species, each of 34 amino acid residues. The primary structure of the main component of scombrine alpha is 100% identical to scombrine gamma, the nonmicroheterogeneous protamine from Scomber australasicus (11). The second component of scombrine alpha is a very minor molecular species that has an isoleucine instead of a valine in position 11. Nuclear sperm-specific basic proteins display an enormous interspecific variability and it is very surprising that two different species show identical protamines. In this work we suggest that evolutionary changes in primary structure of protamines are restricted by several constitutive factors, especially when protamines either lack or have a low degree of microheterogeneity.

Sperm nuclear basic proteins (SNBPs) of agnathans and chondrichthyans: variability and evolution of sperm proteins in fish.

We have characterized for the first time SNBPs from the hagfish Eptatratus stouti (Myxini) and the lamprey Lampetra tridentatus (Cephalaspidomorphi) and have found that histones are the major protein components of the sperm of these agnathans. We have also conducted a systematic analysis of SNBPs from different groups of chondrichthyan fishes, including the skate Raja rhina and seven species of sharks. Together with our previous data showing the sporadic nature of SNBP evolution in bony fish (Saperas, N., Ausio, J., Lloris, D. and Chiva, M. [1994] J. Mol. Evol. 39: 282-295), the present study provides a unique insight into the overall evolutionary complexity and variability of the nuclear sperm proteins of fishes. It would appear that despite the discontinuous evolution of these proteins, the macroevolutionary pattern of histone (H type) --> protamine-like (PL type) --> protamine (P type) has been conserved in fish evolution, as it has in the evolution of other Deuterostomes.

Cultural aspects of meals and meal frequency.

The present paper presents a certain number of cultural elements which interact in the determination of the frequency of food intake. Approaches from various perspectives (historical, ethnological, anthropological, sociological) draw attention to two major aspects relating to the periodicity of food intake: the extreme cultural diversity and the continual modifications which have occurred over time and space. The various cultural models change and are subject to multiple influences, for example, cross-cultural, economic and historical. In addition, there are interactions between the models. The definitions of food intake and frequency play a major role in building up consumers' perceptions. These various perceptions are multiple (perception of self, of food and its virtues, the rules and moral values of consumption) and finally influence behaviours. Finally, and taking into account the systems of beliefs, the very nature of feeding behaviours may carry feelings of guilt for the subject. The study of real behaviours and their relationship with health is still incomplete for reasons of methodology and also of conceptual definition. In future, data collection has to take into account real behaviour as well as subjective perceptions and value judgements. A specific effort has to be made in the future to develop methodology. This should allow the collection of reliable data and particularly comparisons between studies, without oversimplifying and distorting cultural specificities.

The primary structure of a chondrichthyan protamine: a new apparent contradiction in protamine evolution.

We have determined the primary structure of protamine R3 from ratfish (Hydrolagus colliei), a species belonging to the order Chimaeriformes (an old phylogenetic line among the chondrichthyes). Protamine R3 contains 48 residues organized as follows: ARRRH SMKKK RKSVR RRKTR KNQRK RKNSL GRSFK (Q/A)HGFL KQPPR FRP. Comparison of this sequence with both protamine Z3 from Scyliorhinus canicula (a chondrichthyan) and typical protamines from bony fish generates an apparent contradiction: Two relatively close species (H. colliei and S. canicula, both chondichthyes) display different protamines, whereas species more distant in evolution (S. canicula and bony fish) contain very similar protamine molecules. We note that this is not an isolated case in the evolution of sperm nuclear basic proteins (SNBPs) and discuss the possible significance of this fact.

Sequence analysis and structural features of the largest known protamine isolated from the sperm of the archaeogastropod Monodonta turbinata.

Protamine of the archaeogastropod mollusc Monodonta turbinata has been isolated and characterized. With a mass of 13,476 Da, it is the largest known protamine. Amino acid sequence of this protamine (106 residues) was established from data provided by automated sequence analysis and mass spectrometry of the protein and of its fragments. The primary structure of the NH2-terminal region exhibits repetitive sequence motifs "Basic-Ser" (mainly R-S) and both central and COOH-terminal regions are composed by arginine clusters. The amino acid sequence of Monodonta turbinata protamine shows structural similarities with other protamines from invertebrates and from birds and mammals.

On the evolution of protamines in bony fish: alternatives to the "retroviral horizontal transmission" hypothesis.

Fish protamines are highly specialized molecules which are responsible for chromatin condensation during the last stages of spermatogenesis (spermiogenesis). However, not all fish contain protamines in their sperm nuclei; rather, there seems to be a random distribution of protamines within this group. The origin of this sporadic presence of protamines in the sperm and its significance have not yet been precisely determined. In this paper we have conducted an exhaustive survey of the literature available on the different types of nuclear protein composition of the sperm of teleost fish in order to try to correlate these data with what is presently known about the taxonomy of this group. The results of this analysis have allowed us to make the following observations. The divergence between protamines and histones has occurred several times during the evolution of the bony fish. However, the relative frequency of this divergence is almost negligible during the differentiation of genera and species (intrafamily variation) and is very small during the differentiation of families (interfamily variation). Nevertheless, the divergence is very noticeable among the different orders. It is therefore possible to conclude from all this that the sporadic distribution of protamines in bony fish is not a random event as initially believed. Furthermore, such a heterogeneous distribution of protamines cannot be easily accounted for by a mechanism of horizontal retroviral transmission through repeated and independent acquisition of a protamine gene as has been recently proposed (Jankowski, Stater, Dixon (1986) J Mol Evol 23:1-10). Rather, it could possibly be explained by a repeated and independent loss of the expression of the protamine gene (or loss of the gene itself) which mainly occurred during the diversification of the orders of this group.