The distribution of neuropeptides in the ocular tissues of several mammals: a comparative study.

1. The distribution of several neuropeptides (vasoactive intestinal peptide, substance P, somatostatin and neurotensin) was assessed in ocular tissues from the cow, sheep, rabbit and rat. 2. Vasoactive intestinal peptide was most abundant in the choroid and sclera in all species except the rat. Substance P was most abundant in the retina of cow and rat and in the iris/ciliary body of sheep and rabbit. Somatostatin and neurotensin were most abundant in the retina of all species examined. 3. Regulatory peptides thus display distinct regional distributions within the ocular tissues of a single species of mammal and, in addition, exhibit interspecific variation.     

Egress of alphaherpesviruses: comparative ultrastructural study

Egress of four important alphaherpesviruses, equine herpesvirus 1 (EHV-1), herpes simplex virus type 1 (HSV-1), infectious laryngotracheitis virus (ILTV), and pseudorabies virus (PrV), was investigated by electron microscopy of infected cell lines of different origins. In all virus-cell systems analyzed, similar observations were made concerning the different stages of virion morphogenesis. After intranuclear assembly, nucleocapsids bud at the inner leaflet of the nuclear membrane, resulting in enveloped particles in the perinuclear space that contain a sharply bordered rim of tegument and a smooth envelope surface. Egress from the perinuclear cisterna primarily occurs by fusion of the primary envelope with the outer leaflet of the nuclear membrane, which has been visualized for HSV-1 and EHV-1 for the first time. The resulting intracytoplasmic naked nucleocapsids are enveloped at membranes of the trans-Golgi network (TGN), as shown by immunogold labeling with a TGN-specific antiserum. Virions containing their final envelope differ in morphology from particles within the perinuclear cisterna by visible surface projections and a diffuse tegument. Particularly striking was the addition of a large amount of tegument material to ILTV capsids in the cytoplasm. Extracellular virions were morphologically identical to virions within Golgi-derived vesicles, but distinct from virions in the perinuclear space. Studies with gB- and gH-deleted PrV mutants indicated that these two glycoproteins, which are essential for virus entry and direct cell-to-cell spread, are dispensable for egress. Taken together, our studies indicate that the deenvelopment-reenvelopment process of herpesvirus maturation also occurs in EHV-1, HSV-1, and ILTV and that membrane fusion processes occurring during egress are substantially different from those during entry and direct viral cell-to-cell spread.     

Topographic patterns of odorant receptor expression in mammals: a comparative study

In a comparative study, molecular probes for various odorant receptor subtypes were employed in in situ hybridization experiments on tissue sections through the nose from different mammalian species. OR37 reactive neurons were found exclusively in the rodent species, where they were clustered in very similar position within the nasal cavities; an OR37-related receptor subtype was not detectable in the rabbit. All other subtypes tested, hybridized across species borders to neurons that were distributed within distinct zones of the olfactory epithelium. Most receptor types were found in the same zone in all species; however, a few subtypes which are expressed in the medial zone in rat were found in the dorsal zone in guinea pig.     

Egg envelopes in diplopods, a comparative ultrastructural study

By means of electron microscopy two types of egg envelope have been described in representatives of two diplopod subclasses, the Chilognatha and the Pselaphognatha. The vitelline envelope appears on the oocyte surface in early previtellogenesis and persists till ovulation. In its thin and filamentous structure it resembles basement membranes. During vitellogenesis electron dense material is deposited on filamentous scaffolding which fills the space between the oolemma and the vitelline envelope. As a result, the thick and spongy or filamentous chorion is formed. In the present study it has been shown that regardless of the type of oogenesis (solitary-the Chilognatha, or follicular-the Pselaphognatha) both envelopes in diplopods are produced by the oocyte itself, and although completely different in structure and time of appearance, they must be both considered as primary.     

The integument in troglobitic and epigean woodlice (Isopoda: Oniscidea): a comparative ultrastructural study

We compared the ultrastructure and the relative thickness of the integumental cuticle in several species of troglobitic and non-troglobitic woodlice. Measurements of tergal cuticle thickness on histological sections demonstrated that the cuticles in non-troglobites are thicker than those in troglobites of similar body sizes. As revealed by scanning electron microscopy, the endocuticles in troglobites consist of more numerous and thinner lamellae compared to cuticles of similar thickness in non-troglobites. Similar differences in the number and thickness of cuticular lamellae were not found in the exocuticle. As demonstrated by transmission electron microscopy of the epicuticles in troglobitic and non-troglobitic woodlice, the simple inner epicuticle is thinner relative to the total epicuticle thickness in troglobites, but this is not the case for the outer epicuticle. Outer epicuticles consisting of different numbers of sublayers can be found in troglobites as well as in non-troglobites and more complex outer epicuticles are not characteristic of representatives of any of the two ecological groups. Our results indicate that the thickness and structure of the integumental cuticle are important for evolutionary success in the subterranean environment. Nevertheless, the cuticles of troglobites are diverse in their ultrastructural features, likely reflecting different lifestyles of various troglobites.     

Acetylcholinesterase enzyme localization in the amygdala: a comparative histochemical and ultrastructural study

The distribution of acetylcholinesterase enzyme was studied in the amygdala of some rodents, subprimates and several primates. The cytoarchitecture of the amygdala has presented various problems to anatomists, including the question as to how many nuclear groups and subgroups should be identified. Among the mammals examined, the arrangement of the amygdaloid nuclei is remarkably uniform and no clear phylogenetic trend can be recognised. Although there are minor differences, there seems to be a general similarity between most mammals examined in so far as the distribution of cholinesterase is concerned. The staining is less intense in the brains of the monkeys examined. The sole exception to the rule, that cholinesterase distribution is slightly different from nucleus to nucleus in different animals, is the magnocellular part of the basal nucleus. This amygdaloid nucleus stains quite strongly in all animals examined. From these findings, and those of others studying the distribution of choline acetyltransferase, it was concluded that the basal amygdaloid nucleus is cholinergic and possible cholinoceptive. The ultrastructural investigations appear to confirm this point. This is particularly applicable to the magnocellular part of the basal amygdaloid nucleus.     

The Johnston's organ of three homopteran species: A comparative ultrastructural study

A transmission electron-microscopy study has been carried out on the pedicel of three homopteran species, with particular focus on the leafhopper Scaphoideus titanus Ball. The two other species, the planthoppers Hyalesthes obsoletus Signoret and Metcalfa pruinosa Say, were investigated in order to compare the ultrastructure of the Johnston's organ (JO) among representatives of the Auchenorrhyncha group. The results showed the presence of a well developed JO located within the pedicel. Depending on the species the JO is made of 25 up to 72 scolopidia arranged in a coronal array. Each scolopidium is connective, heterodynal, amphinematic and hosts three structurally dissimilar sensory neurons. Two of them have a type 1 ciliary segment while the third bears a type 2 cilium. The type 2 dendrite tip is associated with a tubular cap and is longer than the others, ending into the cuticle at the base of the flagellum. Other scolopidia with one or two neurons were found in S. titanus, forming an accessory organ. The presence of such a well developed mechanosensory apparatus is discussed in relation with the lifestyle of the three species.     

The Clara cell and pulmonary surfactant: A study using selective chemical ablation

Administration of 3-hydroxymethylfuran-N-ethylcarbamate (HFC) to female hamsters via the jugular vein under pentobarbitone anaesthetic at 20 mg per kg body weight produced pronounced necrosis of the Clara cells without apparent morphological effect on other cell types as judged by transmission electron microscope examination. The surfactant material recoverable by minimal lavage followed by purification by sucrose gradient ultracentrifugation increased, reaching a maximum around 48 h after treatment. At this time static pressure/volume measurements on isolated lungs indicated an increase in airway surface compliance. Lavageable surfactant phospholipid composition was examined by ³¹P nuclear magnetic resonance (n.m.r.). The distribution of phospholipids between the various classes was unchanged by HFC treatment. No change in the total lung surfactant pool size was seen. These results are discussed in relation to the possible roles of the Clara cell in influencing airway surfactant levels.     

Sensory organs in a cavernicolous insect after cryofixation without cryoprotectants: a comparative ultrastructural study

Three different sensory organs (one mechanoreceptor, one chemoreceptor and one chemo-mechanoreceptor) of the antennae of the cavernicolous Coleoptera Speonomus hydrophilus and S. zophosinus have been compared by means of electron microscopy after chemical fixation or cryofixation without cryoprotectant; when cryofixation succeeds, cells and organelles have a different appearance from the chemically fixed ones: they have rounded and smooth outlines and are more electron-dense; some very fine details, such as tubulinc sub-units of microtubules, are perceptible after cryofixation only. However, chemical fixation gives much more reproducible results than cryofixation; moreover, when good cryofixation is achieved preservation of cells and organelles is satisfactory only for the peripheral region; large ice-crystals more or less destroying the central zone, except the nerves. In short, chemical fixation and cryofixation appear as complementary techniques: chemical fixation must be used as a routine fixation and cryofixation when specially good cell and molecular preservation must be achieved for peripheral tissues only.     

Neoductular progenitor cells regenerate hepatocytes in severely damaged liver: a comparative ultrastructural study

In severely injured liver, stem cells give rise to progeny that tend to replace lost hepatocytes. Neoductular reaction appears as an inherent stage of liver reconstruction following severe damage caused by different pathological mechanisms. Few ultrastructural types of progenitor cells have been described, and some molecular phenotypes of progenitor stages have been characterized, but the details of the differentiation process are largely unknown. We prepared for light and electron microscopy examination human liver from biopsies of patients with chronic active hepatitis, and rat liver with allyl alcohol-induced periportal necrosis. We found that progenitor neoductular cells acquire the hepatocytic polarity pattern during a multi-step process apparently involving cell migration and dissolution of neoductular basement membrane. An intermediate stage with "mixed" ductular and hepatocytic polarity was described.     

The distribution of neuropeptides in the ocular tissues of several mammals: A comparative study

1. The distribution of several neuropeptides (vasoactive intestinal peptide, substance P, somatostatin and neurotensin) was assessed in ocular tissues from the cow, sheep, rabbit and rat.2. Vasoactive intestinal peptide was most abundant in the choroid and sciera in all species except the rat. Substance P was most abundant in the retina of cow and rat and in the iris/ciliary body of sheep and rabbit. Somatostatin and neurotensin were most abundant in the retina of all species examined.3. Regulatory peptides thus display distinct regional distributions within the ocular tissues of a single species of mammal and, in addition, exhibit interspecific variation.     

The morphogenesis of the human Paneth cell. An immunocytochemical ultrastructural study

In human duodenal mucosa Paneth cells originate away from the base of crypts and migrate towards the base during maturation. The earliest cells in the Paneth cell lineage could be identified by labelling of lysozyme in the Golgi apparatus. Specific labelling for lysozyme was present in the rough endoplasmic reticulum, Golgi apparatus, condensing vacuoles, granules and many lysosomes of mature Paneth cells. The maturation of the Paneth cell is accompanied by an increase in the content of lysozyme in the secretory granules and with senescence lysozyme diffuses into the cytoplasm.     

Mandible shape in marsupial and placental carnivorous mammals: a morphological comparative study using geometric morphometrics

We analysed mandible shape of the orders Dasyuromorpha, Didelphimorphia, and Carnivora using two‐dimensional geometric morphometrics, in order to explore the relationship between shape, size, and phylogeny. We studied 541 specimens, covering most of the genera of the terrestrial Carnivora (115 species) and a wide sample of marsupials (36 species). The observed shape variation had an ecological component. As an example, omnivorous carnivores have thick mandibles and large talonids in the carnassials, while hypercarnivores possess short mandibles and reduced talonids. There is also a discrimination between different taxonomic groups (i.e. marsupials and Carnivora), indicating some kind of constraint. Size explains a large percentage of total variance (large species had shorter and stronger mandibles, with anteriorly displaced carnassials), was significant when phylogeny was taken into account with a comparative method, but not when size and shape were optimized on the phylogeny. Carnivora presents a larger disparity and variation in body size, which could be related to the difference in teeth replacement. The optimization of mandible shape on the phylogenetic tree indicates that functional aspects, such as diet, are a key factor in the evolution of the carnivore mandible, but also that there is a phylogenetic pattern that cannot be explained by differences in diet alone. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 164 , 836–855.     

Red cell uridine monophosphate kinase: a comparative study in various vertebrate species.

1. Starch gel electrophoretic patterns and activity of red cell UMP-kinase were compared in different species of vertebrates. 2. A characteristic electrophoretic pattern for each species of animal studied was found. 3. The mammals differed markedly from the rest of the vertebrate compared in having a faster electrophoretic migration. 4. Significant species differences in total UMPkinase activity could be observed.