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PubMed1996

Why do women menstruate? Historical and evolutionary review.

Theories regarding the significance of menstruation from the time of Aristotle to the present are reviewed, followed by a brief description of the evolutionary changes in the uterus. A specific duct for the transport of ova first appears in jawed fishes. Its important role in the evolution of internal fertilisation and the protection and nourishment of the embryo is followed through the vertebrate orders, amphibia, reptiles and mammals. The problems associated with the presence of a gamete or zygote of different genetic make up inside the maternal tract is stressed, and the mechanisms to overcome or modify the maternal inflammation reaction discussed. In egg laying reptiles and birds, the secretion of coverings around the embryo presumably shields the foreignness of the tissue, while in viviparous animals, the secretion of progesterone plays a major role in controlling the inflammatory reaction. In some mammals, for example the mouse, the invasiveness of the trophoblast is such that the blastocyst penetrates inside the wall of the endometrium. The stroma responds under the influence of progesterone, to undergo an implantation/decidual reaction which bears considerable resemblance to an inflammatory/granulation tissue reaction. A similar reaction occurs in women during the luteal phase in anticipation of a very invasive blastocyst. When there is no fertilisation the progesterone drops and the differentiated stromal tissue is shed with bleeding; menstruation.

Animals↗
PubMed2001

Biochemical characterization and expression analysis of the Xenopus laevis corticotropin-releasing hormone binding protein.

Corticotropin-releasing hormone (CRH) plays a key role in the regulation of responses to stress. The presence of a high affinity binding protein for CRH (CRH-BP) has been reported in mammals. We have characterized the biochemical properties and expression of CRH-BP in the South African clawed frog, Xenopus laevis. Apparent inhibition constants (K(i[app])) for different ligands were determined by competitive binding assay. Xenopus CRH-BP (xCRH-BP) exhibited a high affinity for xCRH (K(i[app])=1.08 nM) and sauvagine (1.36 nM). Similar to rodent and human CRH-BPs, the frog protein binds urotensin I and urocortin with high affinity, and ovine CRH with low affinity. RT-PCR analysis showed that xCRH-BP is expressed in brain, pituitary, liver, tail, and intestine. Brain xCRH-BP mRNA is expressed at a relatively constant level throughout metamorphosis and increases slightly in the metamorphic frog. By contrast, the gene is strongly upregulated in the tail at metamorphic climax. Thus, regulation of xCRH-BP gene expression is tissue specific. Because xCRH-BP binds CRH-like peptides with high affinity the protein may regulated, the bioavailability of CRH in amphibia as it does in mammals.

Amino Acid Sequence↗
PubMed2001

Hydroxysteroid dehydrogenases: ancient and modern regulators of adrenal and sex steroid action.

The adrenal and sex steroids receptor clade arose from an ancestral nuclear receptor in a primitive vertebrate at least 540 million years ago during the early Cambrian. At that time, these receptors had less specificity for their canonical ligands than their descendents in mammals have, which raises the question of how specificity for responses to different steroids was regulated. We propose that hydroxysteroid dehydrogenases that metabolized functional groups at different sites on steroids (e.g. C3, C11, C17 and C20) had a key role in providing specificity for steroid regulation of gene transcription in primitive vertebrates. Later, with increased physiological complexity in land animals due to innovations such as the placenta, hydroxysteroid dehydrogenases were recruited for new roles in regulating steroid-mediated physiological responses. Hydroxysteroid dehydrogenases in fish, amphibia and mammals are likely have different affinities for some xenobiotics, which needs to be considered in evaluating their hazards as endocrine disruptors.

Adrenal Cortex Hormones↗
PubMed1999

Regulatory properties of Rana esculenta liver D-fructose-1,6-bisphosphate 1-phosphohydrolase and their comparison with properties of other vertebrate liver isoenzymes.

D-Fructose-1,6-bisphosphate 1-phosphohydrolase [EC 3.1.3.11] (Fru-1,6P2ase), a regulatory enzyme of gluconeogenesis, was isolated from Rana esculenta liver in homogeneous from with approximately 30% yield. Basic kinetic properties of the enzyme and its subunit molecular weight were determined. Km is 1.72 microM. Like other vertebrate Fru-1,6P2ase, the frog liver enzyme is inhibited by fructose-2,6-bisphosphate (Fru-2,6P2) competitively, Ki is 78 nM and by AMP allosterically, I0.5 is 10.9 microM. Both inhibitors (Fru-2,6P2 and AMP) act synergistically on liver Fru-1,6-P2ase. Ki for Fru-2,6P2 determined in the presence of 1-10 microM of AMP were 35-2 nM, respectively. Maximum activity was found at pH 7.5. Like other Fru-1,6P2ases, the frog enzyme requires magnesium ions for its activity and is activated by potassium ions; the Ka for Mg2+ is 267 microM, Ka for K+ is 77 mM. The subunit molecular weight of the frog liver Fru-1,6P2ase was 37,300 Da. A great similarity between regulatory properties of frog liver Fru-1,6P2ase and liver enzymes of other vertebrates, suggests a similar regulation of gluconeogenesis in amphibia and other vertebrates.

Adenosine Monophosphate↗
PubMed1999

The amino acid sequence of a lamprey (Entosphenus japonicus) liver fatty acid-binding protein identified its close relationship to cardiac fatty acid-binding proteins of Mammalia.

Fatty acid-binding proteins (FABPs) constitute a large, tissue-specific multigene family in animals. While liver FABPs of Aves, Reptilia, and Amphibia are close homologs of mammalian liver FABPs, the shark liver protein belongs to the mammalian heart FABP subfamily. We purified an FABP from the liver of lamprey, Entosphenus japonicus, by gel filtration and anion-exchange chromatography. Amino acid sequences determined for lysyl endopeptidase peptides covered nearly the entire molecule except for N- and C-terminal short segments. Examination of the phylogenetic relationship from the sequence identified the lamprey liver protein as a member of mammalian heart-type FABPs. Since livers of bony fish contain both hepatic and cardiac FABPs, expression of the FABP gene in the vertebrate liver appears to change from the heart-type to liver-type within Pisciformes, with bony fish being in a transition stage. This may be related to the evolutionary and physiological divergence of liver function and lipid metabolism of these lower vertebrates.

Amino Acid Sequence↗
PubMed2001

Subfamilies of CR1 non-LTR retrotransposons have different 5'UTR sequences but are otherwise conserved.

CR1 elements and CR1-related (CR1-like) elements are a novel family of non-LTR retrotransposons that are found in all vertebrates (reptilia, amphibia, fish, and mammals), whereas more distantly related elements are found in several invertebrate species. CR1 elements have several features that distinguish them from other non-LTR retrotransposons. Most notably, their 3' termini lack a polyadenylic acid (poly A) tail and instead contain 2-4 copies of a unique 8 bp repeat. CR1 elements are present at approximately 100,000 copies in the chicken genome. The vast majority of these elements are severely 5' truncated and mutated; however, six subfamilies (CR1-A through CR1-F) are resolved by sequence comparisons. One of these subfamilies (i.e. CR1-B) previously was analyzed in detail. In the present study, we identified several full-length elements from the CR1-F subfamily. Although regions within the open reading frames and 3' untranslated regions of CR1-F and CR1-B elements are well conserved, their respective 5' untranslated regions are unrelated. Thus, our results suggest that new CR1 subfamilies form when elements with intact open reading frames acquire new 5' UTRs, which could, in principle, function as promoters.

Amino Acid Sequence↗
PubMed2003

Complete nucleotide sequence of the mitochondrial genome of a salamander, Mertensiella luschani.

The complete nucleotide sequence (16,650 bp) of the mitochondrial genome of the salamander Mertensiella luschani (Caudata, Amphibia) was determined. This molecule conforms to the consensus vertebrate mitochondrial gene order. However, it is characterized by a long non-coding intervening sequence with two 124-bp repeats between the tRNA(Thr) and tRNA(Pro) genes. The new sequence data were used to reconstruct a phylogeny of jawed vertebrates. Phylogenetic analyses of all mitochondrial protein-coding genes at the amino acid level recovered a robust vertebrate tree in which lungfishes are the closest living relatives of tetrapods, salamanders and frogs are grouped together to the exclusion of caecilians (the Batrachia hypothesis) in a monophyletic amphibian clade, turtles show diapsid affinities and are placed as sister group of crocodiles+birds, and the marsupials are grouped together with monotremes and basal to placental mammals. The deduced phylogeny was used to characterize the molecular evolution of vertebrate mitochondrial proteins. Amino acid frequencies were analyzed across the main lineages of jawed vertebrates, and leucine and cysteine were found to be the most and least abundant amino acids in mitochondrial proteins, respectively. Patterns of amino acid replacements were conserved among vertebrates. Overall, cartilaginous fishes showed the least variation in amino acid frequencies and replacements. Constancy of rates of evolution among the main lineages of jawed vertebrates was rejected.

Amino Acid Sequence↗
PubMed1999

Retention of nociceptor responses during deep barbiturate anesthesia in frogs.

Bullfrogs (Rana catesbeiana) anesthetized with a large dose of thiopental (42.8 mg/kg) retained movement responses to nociceptor stimuli despite an average plasma drug level of 51 mg/l, of which 63% was bound to plasma proteins. This concentration, when corrected to include only unbound and uncharged drug, was 2-fold greater than those reported to abolish nociceptor response (NR) during surgical anesthesia in man. The median anesthetic dose (AD50) for loss of the righting reflex was 11.2 mg/kg by s.c. injection into the abdominal lymph sac; however, at 54.0 mg/kg, all frogs retained NRs, although otherwise deeply anesthetized. The ratio of NR-blocking dose to light AD was thus > 4.8, as compared to < 2 in mammalian studies. Whole body levels of thiopental determined at 3 h after intralymphatic injection showed that about half the injected drug had been eliminated by this time and that termination of anesthesia was chiefly due to drug elimination. Even though the pharmacokinetics of thiopental appears to differ markedly in frogs and men, the poor analgesia seen in the present study frequently has been reported during clinical barbiturate anesthesia. Since this deficiency is much more pronounced in the bullfrog than in man, its neurophysiological basis might profitably be studied using the bullfrog as a model; however, the high mortality associated with deep thiopental anesthesia in the frog should preclude its use as a practical anesthetic in amphibia.

Anesthetics↗
PubMedDate not supplied

Ultrastructural cytology of Basidiobolus haptosporus: morphology and electron cytochemistry of microbodies.

Vegetative and reproductive cells of Basidiobolus haptosporus possess naturally occurring organelles identified as microbodies. Cells of four other species of the genus contained morphologically indistinguishable organelles. Microbodies were invariably present in cells of the fungi grown on routine mycological media. The constitutive microbody was characterized by a single, intensely electron-opaque crystalloid body which rapidly enlarged to fill the organellar compartment. The microbody then underwent degeneration by an autolytic-like process. Growth of the fungi on xanthine and its catabolites as sole nitrogen sources (but not urea) greatly enhanced the production of new microbodies in which protein was initially accumulated as paracrystalline arrays. These inclusions then underwent reorganization and compaction to form crystalloid bodies. Key enzymes of the purine degradation pathway are believed to be core proteins of the crystalloid. D-amino acid oxidase, alpha-hydroxy acid oxidase, xanthine oxidase and urate oxidase (but not catalase) were detected cytochemically in mature microbodies. Significant levels of phosphorus and molybdenum were present in the microbody crystalloid by X-ray dispersive microanalysis; iron and copper were not detected. The ability of Basidiobolus species to assimilate xanthine and its catabolites might explain their ecological association with the gut and cloacal contents of various amphibia, reptiles and fish.

Alcohol Oxidoreductases↗
PubMed1996

Parallel evolution and coexpression of the proteolipid proteins and protein zero in vertebrate myelin.

Vertebrate myelin contains two proteins that mediate compaction: protein zero (P0), an immunoglobulin gene superfamily member, or proteolipid proteins, 4-hydrophobic domain-motif proteins biogenetically unrelated to P0. The prevailing view has been that expression of P0 and proteolipid proteins is mutually exclusive; P0, which mediates myelin compaction in fish, is thought to be completely replaced by the newer proteolipid proteins in the terrestrial vertebrate CNS. However, we now find that proteolipid proteins are actually major myelin constituents in bony fish and amphibia, and so are coexpressed with P0. Clearly, myelin proteolipids are not new additions to the myelin protein repertoire, but instead were ancestral sheath components, expressed approximately 440 million years ago in the first myelinated fish that existed at least approximately 100 million years before the origin of amphibians. In conclusion, P0 and the proteolipid proteins are evolving in parallel in myelinating cells of most vertebrate species.

Amino Acid Sequence↗
PubMed2001

Overlapping expression of zebrafish T-brain-1 and eomesodermin during forebrain development.

T-box transcription factors are important determinants of embryonic cell fate and behaviour. Two T-box genes are expressed in the developing telencephalon of several vertebrate species, including amphibia, birds and mammals. Here we report the cloning of zebrafish T-brain-1 (tbr1) and eomesodermin (eom). As a prelude to genetic studies of neuro-ectodermal fate determination we studied their expression pattern during embryogenesis and early larval development. Eom is expressed in the presumptive telencephalon from around the 4-5 somite stage in bilaterally symmetric groups of cells; the number of positive cells increases dramatically with time and encompasses the entire dorsal telencephalon by the 22 somite stage. Tbr1 is expressed from the 18 somite stage in a subset of eom-expressing cells. By 24 hpf eom and tbr1 are expressed in largely overlapping domains in the dorsal telencephalon, tbr1 is expressed in postmitotic cells whereas eomes is also expressed in proliferative ventricular zone cells. Both genes are also found in a small domain of the diencephalon bordering the telencephalon. A detailed analysis of the expression of tbr1 and eom in the brain of 4 day old larvae shows that the two T-box genes are differentially expressed in various cell populations of the developing brain.

Amino Acid Sequence↗
PubMed1998

The specification of the pronephric tubules and duct in Xenopus laevis.

We have examined the timing of specification of the pronephric tubules and duct in Xenopus laevis by explanting the presumptive pronephric rudiments into blastula ectodermal wraps. We have established the time point of specification using the monoclonal antibody markers 3G8 and 4A6 which recognize antigens in pronephric tubule and duct, respectively. We show that, by experimental analysis in explants, kidney tubules are specified by stage 12.5 in the pronephric anlagen whereas pronephric duct is specified later between stages 13 and 14. Furthermore we show that signals involved in tubulogenesis of the pronephric tubules are normally received between stage 12.5 and 13. These experiments unambiguously pinpoint the timing of pronephros specification analyzed by explant experimentation to a developmental stage prior to that demonstrated for urodele amphibia, and provide an essential biological backdrop to a search for the molecular nature of pronephric inducers.

Animals↗
PubMed1997

Blood supply to the retina in the laboratory shrew (Suncus murinus).

The blood supply to both retinae was studied light microscopically and by scanning electron microscopy in 48 adult laboratory shrews (Suncus murinus) of both sexes. Thirty-eight of the animals were injected into the left ventricle with Neoprene latex (Du Pont. 601A) or with Mercox (Dai Nippon Ink Ltd., CL-2R) to elucidate the blood supply to the retina from the ophthalmic artery. The remaining animals were kept for histological study of the retina. The central retinal artery, originating from the ophthalmic artery in the muscular part of the orbit, enters the optic nerve, passes through the optic disk together with the central retinal vein and penetrates the vitreous space (cavity of the eye) between the lens and the inner limiting membrane of the retina, where it divides into the dorsal, ventral, and caudal branches. Each branch, moreover, bifurcates into nasal and temporal arterioles and is distributed throughout the retina on the inner limiting membrane as far as the ciliary body and the lens. On the way they obliquely send small vessels through the inner limiting membrane into the outer plexiform layer of the retina. Their vascularization appears to correspond to the membrana vasculosa retinae found in teleosts, amphibia and reptiles.

Animals↗
PubMed1998

Dentition and dentigerous bones in juveniles and adults of Polypterus senegalus (Cladistia, Actinopterygii).

Tooth types, their arrangement and the mode of tooth replacement were studied in juvenile and adult specimens of Polypterus senegalus by means of scanning electron microscopy of cleared and stained specimens as well as sections. All the dermal bones of the oropharynx are almost completely covered with teeth except for the angulare. The same is true for the branchial apparatus where only the hyoid skeleton is toothless. The teeth are uniformly monocuspid and conical, but can be classified according to shape and size into three types. These types and the mode of tooth replacement are characteristic for each dermal bone. In some of the jaw bones each tooth possesses a lingually situated replacement tooth. This is true for the teeth of the premaxillary, the maxillary, and the dentary which are arranged in a single line, and those of the dermopalatine, the coronoids, and the vomer which are in several lines and graded in size. Replacement teeth of all the other dentigerous elements develop on top of existing pulpal openings, forming an anastomosing common pulpal complex only after resorption of the previous tooth. The tooth plates of the dermal bones of the branchial apparatus are connected by syndesmosis only to the perichondrally ossified and to the cartilaginous or connective tissue material of the elements of the gill-arches. The dentition and its association with the bones of the head in Polypterus senegalus bear resemblances to advanced actinopterygians on the one hand (e.g. differentiation of tooth-types, arrangement), but also some similarities to living Amphibia (anchoring material and mode of replacement) on the other. The accentuation of a single marginal line of large teeth in both, the outer and the inner dental arcade of the jaws is a peculiarity of Polypterus that in a way parallels the derived state of similar monolinear tooth arrangements in Actinopterygii and Tetrapoda.

Aging↗
PubMed2002

The NH(2)-terminal propeptides of fibrillar collagens: highly conserved domains with poorly understood functions.

The impetus for this review comes from the recent finding that the absence of the majority of the non-triple-helical sequence in the NH(2)-terminal propeptide (N-propeptide) of the pro alpha 1(I) collagen chain fails to generate a significant phenotype in the mouse (Bornstein et al., J. Biol. Chem., 277:2605-2613, 2002). This result is in apparent conflict with those of numerous studies in vitro that have implicated the N-propeptide in a number of processes that are involved in the biogenesis, maturation and function of type 1 collagen. To seek an explanation for this discrepancy, the sequences of the highly conserved, 55-57-amino acid, cysteine-rich repeats (CRR), which constitute the majority of the globular domains in the N-propeptides, were compared among 13 vertebrate species. Surprisingly, the CRR in mice and rats differs substantially from those in other mammalian species. Indeed, the CRR in birds, fish and amphibia are more similar to those of other mammals than are the CRR in rodents. This finding raises the possibility that the mutant mouse, which lacks exon 2 that encodes the CRR in the N-propeptide, might not be an appropriate model in which to study the function of the N-propeptide in other mammals. Alternatively, compensation, possibly by procollagens II or III, could account for the mild phenotype of the exon 2-deleted mouse. Yet another possibility is that the CRR plays a developmental role in the mouse, akin to that recently proposed for the N-propeptide in type IIA procollagen, rather than a function in collagen biogenesis. Some support for the latter possibility is provided by the observation that, on one background, the breeding of heterozygous exon 2-deleted mice generated homozygous mutants at less than the expected frequency. Experiments to examine these possibilities are proposed.

Amino Acid Sequence↗
PubMedDate not supplied

An enzyme-linked immunosorbent assay for measuring anti-sheep red blood cells antibodies in lead-exposed toads.

INTRODUCTION: Immune function assays to screen immunotoxic effects of xenobiotics has recently become of major interest. In the framework of our studies, we standardized methods to quantify the humoral response of an amphibian species (Bufo arenarum, Amphibia, Anura) exposed to sublethal lead (as acetate). METHODS: The levels of agglutinins to heterologous red blood cells (RBC) were measured in serum from adult B. arenarum. Since agglutinin titers were very low, a noncompetitive enzyme-linked immunosorbent assay (ELISA) method was carried out. As toad serum showed marked nonspecific binding, we developed a new ELISA on microtiter plates for the quantitative determination of the heterophile antibodies. The method was based on that described by Hirvonen et al. [Vox Sang. 69 (1995) 341], employing sheep red blood cells (SRBC) sensitized with amphibian antibodies that were transferred to microplates; later the measurement of bound immunoglobulins was performed. Different variables such as the amount of antigen, blocking agents, and other experimental conditions (fixing solution and commercial plates) were studied. Toads (n=22) received a weekly subcutaneous injection of 50 mg/kg lead (acetate) for 6 weeks, and the control ones (n=26) were injected with Na acetate at the same time. RESULTS: The anti-sheep RBC antibodies titers of adult toads were obtained with the improved ELISA method, being the absorbance range 0.12 to 1.58 AU (1/200 diluted serum). Titers from lead-exposed toads were also determined, being the final titers (expressed as (-)x +/-S.E.M.) higher (0.79+/-0.06 AU), than those of Day 0 (0.57+/-0.06) (P<.01). DISCUSSION: It was concluded that the ELISA technique we developed was useful for measuring the humoral immune response in this animal model and that in these preliminary studies, lead showed an immunostimulating action on the humoral immune system.

Animals↗
PubMed2002

Multilocus isozyme systems in African lungfish, Protopterus annectens: distribution, differential expression and variation in dipnoans.

Distribution of ADH, ALP, FBALD, GAPDH, G3PDH, G6PDH, GPI, LDH, MDH, PGM, and SOD was identified in retina, heart, muscle, liver, kidney, gills, brain, gut, lung and ovary of the African lungfish. Data are compared with patterns previously described in dipnoans and other vertebrates. The number of loci expressed for all enzymes was found to be similar to those of diploid Actinopterygii. Differences in the number of loci expressed in Amphibia were found for ALP, sG3PDH, GPI, LDH, MDH and SOD. Differences in tissue distribution were noted in ALP due to the absence of an intestinal-specific form typical of teleostean fish, amphibians, reptiles and birds, and in GPI and MDH, due to the tissue expression, as in primitive fish. There were also differences in LDH, where a third locus (LDH-C*) was expressed in the gills of Protopterus annectens and not in the retina or liver tissues, as in teleosts. LDH-A4 was most common in all the tissues. Major differences were noted in the tissue patterns of protein expression in the three dipnoans compared. As expected, the least divergence was found between the two species belonging to the same family (Lepidosirenidae). The highest index of divergence was observed between Neoceratodus forsteri and Lepidosiren paradoxa, belonging to the families Ceratontidae and Lepidosirenidae, respectively. The divergence is revealed by changes at the enzyme and morphological levels. These results suggest that P. annectens occupies an interesting systematic position, its biochemical characteristics distinguishing it from N. forsteri, L. paradoxa, the advanced fish and amphibians.

Animals↗
PubMed2002

Glyceraldehyde-3-phosphate dehydrogenase from the newt Pleurodeles waltl. Protein purification and characterization of a GapC gene.

The NAD(+)-dependent cytosolic glyceraldehyde-3-phosphate dehydrogenase (GAPDH, EC 1.2.1.12) has been purified to homogeneity from skeletal muscle of the newt Pleurodeles waltl (Amphibia, Urodela). The purification procedure including ammonium sulfate fractionation followed by Blue Sepharose CL-6B chromatography resulted in a 24-fold increase in specific activity and a final yield of approximately 46%. The native protein exhibited an apparent molecular weight of approximately 146 kDa with absolute specificity for NAD(+). Only one GAPDH isoform (pI 7.57) was obtained by chromatofocusing. The enzyme is an homotetrameric protein composed of identical subunits with an apparent molecular weight of approximately 37 kDa. Monospecific polyclonal antibodies raised in rabbits against the purified newt GAPDH immunostained a single 37-kDa GAPDH band in extracts from different tissues blotted onto nitrocellulose. A 510-bp cDNA fragment that corresponds to an internal region of a GapC gene was obtained by RT-PCR amplification using degenerate primers. The deduced amino acid sequence has been used to establish the phylogenetic relationships of the Pleurodeles enzyme--the first GAPDH from an amphibian of the Caudata group studied so far--with other GAPDHs of major vertebrate phyla.

Amino Acid Sequence↗