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PubMed2003

The Himalayan rabbit (Oryctolagus cuniculus L.): spontaneous incidences of endpoints from prenatal developmental toxicity studies.

The historical database represents the spontaneous, i.e. normal changes of characters, in laboratory animals, and is a must for the assessment of toxic effects of compounds. For the Himalayan rabbit (CHBB:HM, SPF) background data were collected from the control groups of regulatory studies between 1968-1999 in the Biberach laboratory of Boehringer Ingelheim (Germany). In the present study these data were compared with the background data from the years 1974-1984, with those from the Ingelheim laboratory, Germany (1977-1984) and those from the breeding colony at Kawanishi, Japan (1971-1991, 1972-1984). Fertility in the Biberach laboratory was relatively constant through the years, due to the strict breeding system. Litter parameters (corpora lutea, implantations and viable fetuses), including fetal sex distribution and fetal weight, were constant in the Biberach laboratory through the years and compared well with the data from Ingelheim and Kawanishi. From these three laboratories the results of spontaneous changes in fetal morphology above 0.1% incidence suggest a pattern of deviations from the Bauplan (fundamental body plan). These comprise synosteosis of sternebrae, lumbar (additional) ribs, hypoplasia of 12th rib, status of ossification, aplasia of gall bladder, hypoplasia of gall bladder, incompletely subdivided lung, dilated ventricle of heart, deviations at the A. carotis and at the aortic arch and flexure of paw. The absence of a time-dependent statistical trend indicates that the spontaneous change of endpoints remained constant through the time axis. Comparison with the spontaneously changed fetal morphology of the other strains (NZW, JW, SF rabbits) does not provide support for their being a totally strain-specific pattern, and this pattern may be closer to the species than specific to a single strain. The firm patterns of deviations in fetal morphology provide suitable and valuable markers for assessing toxic effects on ontogenesis. According to our experience these morphological endpoints react very sensitively to teratogenic compounds, which is demonstrated by increased incidences. Our knowledge of evolution of organisms and of mechanisms leading to morphological deviations points to a strict selection of phenotypes. For laboratory animals the decisive selection factors are defined by man. These are nutritive factors, environmental conditions, the mating system, handling and treatment, and experimental design. All these factors have to be held constant through the years, which is an absolute pre-condition for the application of valid historical data. The Himalayan rabbit is highly suitable for use in developmental toxicity studies due to the stability of reproductive data within the same laboratory over a period of more than 30 years, due to the similarity of reproductive data among three different laboratories, and due to an absence of relevant differences to the reproductive data of other rabbit strains.

Abnormalities, Drug-Induced↗
PubMed1996

Salamander pigment patterns: how can they be used to study developmental mechanisms and their evolutionary transformation?

Neural crest cells of ectothermic vertebrates give rise to three types of pigment cells: melanophores, xanthophores, and iridophores. In early larval salamanders, these cells can combine to generate a variety of pigment patterns across taxa, including vertical bars and horizontal stripes. Such patterns offer an opportunity to study neural crest morphogenesis and differentiation, as well as the evolution of these processes and the morphologies that arise from them. This review examines the phylogenetic distribution of specific pigment patterns, our current understanding of the mechanisms underlying these patterns, and how evolutionary transformations of these mechanisms may have resulted in alternative pigment patterns across taxa.

Animals↗
PubMed2005

Role of development in the evolution of the scapula of the giant sthenurine kangaroos (Macropodidae: Sthenurinae).

Extinct giant sthenurine kangaroos possessed scapulae morphologically distinct from those of all other extant and extinct adult macropodids, but qualitatively resembling those of newborn macropodids. The similarity between adult sthenurine and neonatal macropodid scapulae suggests that a developmental process, such as heterochrony, might have been behind the evolution of the unique sthenurine scapular morphology. By incorporating adult and ontogenetic data, this study examines the evolution and development of the sthenurine scapula. This study quantitatively upholds the previous qualitative morphological observations of macropodid scapulae and finds that ontogenetic and evolutionary morphological changes are correlated in macropodids. The similarity of scapula morphology in sthenurines and newborn macropodids, the correlation between ontogenetic and evolutionary morphological change, and information from other sources (i.e., sthenurine evolutionary history) suggests that pedomorphic shifts in morphology, most likely due to neotenic processes, occurred within the development of the scapula of giant sthenurines.

Animals↗
PubMed2001

Tripedal knuckle-walking: a proposal for the evolution of human locomotion and handedness.

A comparative morphological analysis of human and non-human hominoids was conducted in an attempt to determine the mode of locomotion of the protohominid. Although the generalized hominoid anatomy permits variation of locomotion: brachiation, knuckle-walking, etc., minor variations in structure determine which behavior is favored. Arboreal arm swinging requires a flexible forelimb while terrestrial fist or knuckle-walking demands more rigidity of the hand and wrist. It is demonstrated that the large human thumb accompanied by the strong adduction of the thenar, hypothenar, and palmar interosseous muscles offer powerful rigidity to the hand, while fusion of the os centrale with the scaphoid during gestation permits the formation of an arch of carpals which imbue the wrist with the stability necessary for weight bearing. Fascialization of the contrahentes and dorsiepitrochlearis muscles in the human as well as depilation of the middle phalanges; the webbing (syndactyly) of the palm; the direction of the fibers of the interosseous membrane of the forearm; the shape of the puerile annular ligament, and the direction of the human glenoid fossa strongly suggest that the ancestor of man used a knuckle-walking form of locomotion prior to becoming bipedal. A model is presented that suggests that bipedalism was attained through an intermediate stage of tripedalism. The model is based on the fact that man's anatomy is much more asymmetric than that of the great apes. A presumption is made that due to the absence of trees for climbing in the transition from forest to open plain, the protohominid needed to carry tools (stones) at all times for protection. Stones could be carried for long distances on the posterior iliac crest since the weight would be shifted posteriorly over the legs. Pick up, medial rotation and adduction of the stone would employ a two-muscle chain of biceps brachii and latissimus dorsi. On the iliac crest, the stone is posterior to the coronal plane of the glenohumeral joint, and with the contraction of this two-muscle chain, the shoulder on one side is moved posteriorly effecting a semi-erect posture. It is proposed that tripedalism of the protohominid may be an explanation for the handedness unique to hominids.

Animals↗
PubMed1978

Some aspects of monogenean existence.

This paper deals with some ecology and evolution problems of monogeneans--gill parasites of fishes, such as congeneric simultaneous doublets, spatial distribution of species on the gills, interspecific restrictions of biotopes etc. The author proves competitive character of site selection in monogeneans. The role of hermaphroditism in the evolution and biology of monogeneans, and morphological adaptations (mainly androgynous) directed to increasing of mating chance are discussed. The author concentrates on analyzing the cases of monoxenous distribution and speciation and also on examining the concept of symxenity and alloxenity. He attaches great importance to ecological and evolutionary investigations of Monogenoidea.

Animals↗
PubMed1990

[Structure and evolution of Trichomonadida].

In the article the survey of data on morphology and ultrastructure of flagellates of the order Trichomonadida is given with special attention paid to Monocercomonadidae and Trichomonadidae. The evolution within these flagellates is considered as a series of changes leading to formation of undulating membrane and reinforcement of the cytoskeleton. In both families other two evolutionary tendencies may be also observed: reduction of the flagellar apparatus (in Monocercomonadidae) and enlargement of the number of free flagella (in both families).

Animals↗
PubMed2006

Dental microwear in relation to changes in the direction of mastication during the evolution of Myodonta (Rodentia, Mammalia).

Observations of dental microwear are used to analyse the correlation between changes in molar tooth crown morphology and the direction of masticatory movement during the evolution of Myodonta (Rodentia, Mammalia). The studied sample includes 36 specimens representing both superfamilies of Myodonta (Muroidea and Dipodoidea) spanning 16 dipodoid and 9 muroid species. Microscopic scratches on occlusal surfaces resulting from contact between opposite teeth during mastication are analysed. Using these features, we determine the direction of masticatory movements. Microwear patterns display diverse orientations among Dipodoidea: oblique in Sicistinae, Euchoreutinae and Zapodinae, propalinal in Dipodinae and intermediary in Allactaginae. Similarly, Muroidea exhibit the following orientations: oblique in Cricetinae and propalinal in Arvicolinae, Cricetomyinae, Gerbillinae and Murinae. These various chewing types illustrate different evolutionary grades within the superfamilies. Acquisition of the antero-posterior masticatory movement in Dipodoidea is related to flattening of the molar occlusal surface. However, in some muroid subfamilies, this direction of mastication is associated with low-crowned and cuspidate molars (Cricetomyinae, Murinae).

Animals↗
PubMed2004

Detecting genetic drift versus selection in human evolution.

Recent paleoanthropological discoveries reveal a diverse, potentially speciose human fossil record. Such extensive morphological diversity results from the action of divergent evolutionary forces on an evolving lineage. Here, we apply quantitative evolutionary theory to test whether random evolutionary processes alone can explain the morphological diversity seen among fossil australopith and early Homo crania from the Plio-Pleistocene. We show that although selection may have played an important role in diversifying hominin facial morphology in the late Pliocene, this is not the case during the early evolution of the genus Homo, where genetic drift was probably the primary force responsible for facial diversification.

Animals↗
PubMed1980

Evolution of DNA sequences has been retarded in Malagasy primates.

It is generally accepted that there are six major groups of living primates: (1) lemurs (including all the primates of Madagascar), (2) lorises (including galago and potto), (3) tarsiers, (4) New World monkeys, (5) Old World monkeys and (6) apes (including man). Tree shrews, once considered to be primates, are now generally recognized as not significantly more closely related to the six groups than other mammals. The first surviving primate lines to diverge from the common primate ancestor are believed to have given rise to one or more of the first three groups. However, the fossil record is insufficient to determine their relative branching order. Furthermore, neither morphological considerations nor studies of protein evolution produce unanimity as to whether tarsiers are more closely related to the prosimians (the lemurs plus lorises) or the simians (the monkeys and apes). In an attempt to resolve these discrepancies, we have measured the DNA sequence difference between several primates. We report here that the evolution of DNA of primates from Madagascar is significantly less than that of all other groups of living primates. This is not expected in the simplest form of the theory of neutral selection and may be important for our understanding of evolution at the molecular level.

Animals↗
PubMed2005

Reconstructing the evolutionary history of the Lorisidae using morphological, molecular, and geological data.

Major aspects of lorisid phylogeny and systematics remain unresolved, despite several studies (involving morphology, histology, karyology, immunology, and DNA sequencing) aimed at elucidating them. Our study is the first to investigate the evolution of this enigmatic group using molecular and morphological data for all four well-established genera: Arctocebus, Loris, Nycticebus, and Perodicticus. Data sets consisting of 386 bp of 12S rRNA, 535 bp of 16S rRNA, and 36 craniodental characters were analyzed separately and in combination, using maximum parsimony and maximum likelihood. Outgroups, consisting of two galagid taxa (Otolemur and Galagoides) and a lemuroid (Microcebus), were also varied. The morphological data set yielded a paraphyletic lorisid clade with the robust Nycticebus and Perodicticus grouped as sister taxa, and the galagids allied with Arctocebus. All molecular analyses maximum parsimony (MP) or maximum likelihood (ML) which included Microcebus as an outgroup rendered a paraphyletic lorisid clade, with one exception: the 12S + 16S data set analyzed with ML. The position of the galagids in these paraphyletic topologies was inconsistent, however, and bootstrap values were low. Exclusion of Microcebus generated a monophyletic Lorisidae with Asian and African subclades; bootstrap values for all three clades in the total evidence tree were over 90%. We estimated mean genetic distances for lemuroids vs. lorisoids, lorisids vs. galagids, and Asian vs. African lorisids as a guide to relative divergence times. We present information regarding a temporary land bridge that linked the two now widely separated regions inhabited by lorisids that may explain their distribution. Finally, we make taxonomic recommendations based on our results.

Animals↗
PubMed1998

Squamous change in bladder cancer and its relevance to understanding clonal evolution in development of bladder cancer.

Using conventional morphological assessment, squamous change in bladder epithelium has been observed in 73% of bilharzial associated squamous cancers but only 28% of pure transitional cancers. However, more detailed studies of patients with TCC suggest that the latter figure may be an underestimate, since in one series it was reported to be more than 50%. The most significant risk factor for development of squamous carcinoma in the bladder is chronic persistent bacterial cystitis, although in the areas of the world where bilharzia is endemic this infestation also increases the risk of both squamous bladder cancer and chronic bacterial cystitis. Although it is clear that carcinogens are involved as co-factors in transformation from squamous metaplasia to cancer, the fact that in Zimbabwe one author has observed that TCC is more frequent in whites than squamous cancer is in bilharzia infected blacks is evidence that other unidentified risk factors are involved. This is increasing evidence for involvement of HPV subtypes in cervix, oropharynx and lung cancer. As all three of these tumours are associated with squamous metaplasia, there could be a case for investigation of bladder squamous tumours for HPV involvement. This is particularly so given the observation of the "hit and run" type of transient infection in cattle that develop BPV associated tumours and the tenfold difference (30% vs 3%) in frequency of HPV detection in squamous skin tumours developing in immunosuppressed individuals compared with those arising spontaneously. With new technology for cytological screening techniques using dot ELISA and evidence of differences in TP53 mutations that support the involvement of nitrous oxide, it is clear that there is more to learn from study of this tumour type that may be of general interest in understanding the clonal development of cancer.

Animals↗
PubMedDate not supplied

[The natural history of carcinoma of the cervix uteri: from morphology to multidisciplinary interpretation of the pathogenesis].

The evolution of research on cervical cancerogenesis in the forty years from 1951 to 1990 is reviewed by the Author, who took part in it under the guidance of prof. G.B. Candiani. The modifications of the views on the subject by both the gynecologist and the pathologist, that have led through new guidelines of Health politics and of clinical behaviour, to a substantial decrease of the mortality from this disease, are highlighted.

Carcinoma↗
PubMed1981

Lung catecholamines and cyclic nucleotides during perinatal development in the rat. Possible relationships with biochemical and morphological differentiation.

In this study, we investigated in parallel the evolution of endogenous catecholamine and cyclic nucleotide levels in lung tissue in the course of normal fetal development of the rat from day 17 of gestation to day 10 postpartum; the findings were correlated with the successive stages of lung differentiation. These were assessed morphologically by electron microscopy, and biochemically by measuring the levels of the main lung tissue phospholipids and studying their fatty acid composition. Dopamine levels were low and always remained under 5 ng/g of wet tissue. Nevertheless, slight rises were observed between days 17 and 19 of gestation (1.8 and 2.78 ng/g, respectively) and between days 21 of gestation and birth (2.56 and 4.25 ng/g, respectively). These changes were significant (P less than 0.05). Norepinephrine (NE) levels first decreased by about 50% between days 17 and 19 of gestation (7.34 and 3.88 ng/g, respectively), (P less than 0.01) and then rose sharply about 4 times until birth (17.24 +/- 3.90 ng/g), and more slowly from then on. On day 10 postpartum, the mean NE level was 34.31 +/- 3.28 ng/g. The levels of the two cyclic nucleotides [cyclic adenosine 3':5'-monophosphate and cyclic guanosine 5'-monophosphate (cGMP)] were quite high on day 17 and remained so until day 19 (cAMP = 220 pmoles /g; cGMP = 20 pmoles/g). From day 19 until day 21, the levels of the two nucleotides decreased (cAMP = 140 pmoles/g; cGMP = 8 pmoles/g; P less than 0.05). During this period, the decrease in cGMP level was about twice that of cAMP. During the last day of gestation, the cAMP level was still decreasing, whereas cGMP was increasing. After birth, the levels of the two cyclic nucleotides rapidly increased to day 5. Between days 5 and 10 postpartum, no significant changes were observed in either cAMP or cGMP levels. The time course of the variations reported suggests that they are related to the maturation processes of lung assessed on the basis of morphological and biochemical criteria. On day 19 of gestation, when the first lamellar bodies appear, large changes occur in the evolution of NE and cyclic nucleotide levels, suggesting that these changes may be related to the onset of surfactant synthesis. On day 21 of gestation, the cAMP and cGMP ratio rises sharply; at the same time, the total phospholipid level is increased by 50%. At this stage, lamellar bodies are actively differentiating within type II pneumocytes and massively released into the fetal airways. The relationships between the variations of the studied biochemical parameters and the maturation processes of lung suggest that dopamine and NE could be involved in surfactant synthesis and release via their second messenger, the cyclic nucleotides. Further investigations are needed to elucidate the mechanisms regulating these changes.

Animals↗
PubMed1976

[Evolution of the pulp chamber and pseudodentin in the selachians the Brazilian coast (suborder Galeoidea). Morphological study].

The author made a morphological study of Selachii (Suborder Galeoidae) of the Brazil coast using ground sections. Dental structures undergo modifications as one studies species of different evolutionary stages. The lower Selachii have an osteodentine nucleus which suffer alterations until it disappears leaving a pulp chamber in its place. The layer of pseudodentine shows modification too. It consists of pseudodentine in lower Selachii but its modifications are such that in higher Selachii (Sphyrnidae, for instance) one may suppose it is made of orthodentine. Based on these and other published data the author concludes that the degree of evolution of the pulp chamber and pseudodentine allows the establishment, with great probability, of the phylogenitic position of the Selachii within the Galeoidea Suborder.

Animals↗
PubMed1985

Aplastic anaemia and the hypocellular myelodysplastic syndrome: histomorphological, diagnostic, and prognostic features.

In a retrospective study of 111 patients with aplastic anaemia iliac crest biopsies were evaluated for the presence of morphological features statistically related to the evolution of the disease. Prognostic variables for a transition to acute non-lymphatic leukaemia were: cellular atypias of the three haemopoietic lineages, as observed in the myelodysplastic syndrome, and especially "micromegakaryocytes"; high numbers or irregular distribution of megakaryocytes, or both; and (slight) marrow fibrosis. Clinical variables did not influence these prognostic correlations. Prognosis in relation to death from bone marrow failure without leukaemia might well have been influenced by a strong plasma cell reaction, but this correlation was weakened by clinical factors. On the basis of this study aplastic anaemia can thus be subdivided morphologically into two disease entities--namely, hypocellular myelodysplastic syndrome with a 23-82% risk of acute non-lymphatic leukaemia developing within three years, depending on how many variables associated with acute non-lymphatic leukaemia are present, and non-dysplastic myelohypoplasia.

Adolescent↗
PubMed2001

Frogs without polliwogs: evolution of anuran direct development.

Direct development is the assumption of the adult morphology without progression through an intervening, morphologically distinct, free-living larval phase. We discuss the ecological factors contributing to the evolution of this derived life-history strategy in frogs, and the developmental modifications that facilitate such an unusual mode of embryogenesis. Studies on the Puerto Rican tree frog, Eleutherodactylus coqui, have identified several such modifications, including developmental adaptations for dealing with increased egg size, and loss of tadpole structures. Surprisingly, this direct developer still undergoes a thyroid hormone-dependent metamorphosis, which occurs before hatching. We suggest how the ancestral biphasic developmental pattern may have been rearranged during the evolution of direct development.

Animals↗