Experimental studies of St. Louis encephalitis virus in vertebrates

Serologically negative birds and mammals of species, known from other studies to be exposed naturally to St. Louis encephalitis (SLE) virus in Memphis, Tennessee, and other selected species were inoculated experimentally with strains of SLE virus to determine their potential as natural hosts. Mosquitoes (Culex sp.) were allowed to feed on some of the inoculated vertebrate species, held for 14 days, and tested for SLE infection. The cardinals (Richmondena cardinalis), robins (Turdus migratorius), and baby chicks (Gallus gallus) all became viremic; 97% of the bobwhites (Colinus virginianus) and 20% of the Japanese quail (Coturnix coturnix) became viremic. No viremia was detected in raccoons (Procyon lotor), opossums (Didelphis virginiana), or adult cotton rats (Sigmodon hispidus). Only 20% of cottontail rabbits (Sylvilagus audubonii), 50% of wood rats (Neotoma mexicana), and 75% of hamsters (Mesocricetus auratus) but all the young cotton rats and least chipmunks (Eutamias minimus) were susceptible. Robins had the highest titered viremia but were viremic for the shortest period of time. Bobwhites had lower peak viremia titers but for a longer duration. Biologic differences in the response of some vertebrates to different SLE strains were noted. Culex pipiens quinquefasciatus mosquitoes readily became infected after feeding on viremic cardinals. Comparisons of the experimental data with information obtained from field investigations provided a better understanding of the contributions of the various vertebrate species to the transmission and maintenance of SLE virus in nature.     

Modeling of pathogen survival during simulated gastric digestion

The objective of the present study was to develop a mathematical model of pathogenic bacterial inactivation kinetics in a gastric environment in order to further understand a part of the infectious dose-response mechanism. The major bacterial pathogens Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella spp. were examined by using simulated gastric fluid adjusted to various pH values. To correspond to the various pHs in a stomach during digestion, a modified logistic differential equation model and the Weibull differential equation model were examined. The specific inactivation rate for each pathogen was successfully described by a square-root model as a function of pH. The square-root models were combined with the modified logistic differential equation to obtain a complete inactivation curve. Both the modified logistic and Weibull models provided a highly accurate fitting of the static pH conditions for every pathogen. However, while the residuals plots of the modified logistic model indicated no systematic bias and/or regional prediction problems, the residuals plots of the Weibull model showed a systematic bias. The modified logistic model appropriately predicted the pathogen behavior in the simulated gastric digestion process with actual food, including cut lettuce, minced tuna, hamburger, and scrambled egg. Although the developed model enabled us to predict pathogen inactivation during gastric digestion, its results also suggested that the ingested bacteria in the stomach would barely be inactivated in the real digestion process. The results of this study will provide important information on a part of the dose-response mechanism of bacterial pathogens.     

Use of complementary methods for experimental animal studies of digestion in the 18th and 19th centuries

The use of complementary methods to animal experiments is very old. Spallanzani (1785) apparently was the first who used such methods in his studies on digestion. In the 19th century Eberle, Pappenheim, Purkyné and others used on their studies on the process of digestion artificial chyme. On this view, Beaumont published in 1834 an interesting paper on the digestion of men after observations in vivo and parallel in vitro. All papers show, that the using of complementary methods to animal experiments was not unusual in the 19th century.     

Discrimination of normal gastric mucosa from Helicobacter pylori gastritis using standard endoscopes and a single observation site: studies in children and young adults

Background. In the Helicobacter pylori‐negative normal stomach, collecting venules are visible in the gastric corpus as numerous minute points. This finding has been termed ‘regular arrangement of collecting venules’ (RAC). The aim of the present study was to investigate the reliability of the presence of the RAC pattern for discrimination of normal gastric mucosa from H. pylori gastritis in pediatric patients. Methods. Fifty‐two consecutive children, adolescents and young adults (male:female 24 : 28; median age 15 years, range 8–29 years) referred for endoscopy and assessed for H. pylori infection were prospectively studied. The lower lesser curvature of the corpus near the incisura was evaluated for the RAC pattern using a standard endoscope with the tip close to, but not in contact with, the gastric surface. Gastric biopsies were taken after the endoscopic observation. Results. In all the 29 RAC‐positive patients, active H. pylori gastritis was absent, whereas H. pylori gastritis was found in 20 of 23 RAC‐negative patients (86.9%). Conclusions. Identification of the RAC pattern at the lower lesser curvature of the corpus using close observation with a standard endoscope proved to be an effective and practical marker to discriminate normal histology from H. pylori gastritis among both children and young adults. Absence of the RAC pattern should prompt gastric mucosal biopsies despite otherwise normal‐appearing gastric mucosa.     

Review of fate-mapping studies of osteogenic cranial neural crest in vertebrates

Recent years have witnessed renewed interest in defining the embryonic cell populations that directly contribute to the bony skull. This question lies at the intersection of several important developmental, clinical and evolutionary interests. Until recently, our collective understanding of the embryonic origin of the vertebrate osteocranium has been based on a small number of reports published solely using avian models. As data gradually accumulates from other, distantly related species (e.g., mouse and frog), we can begin to evaluate long-standing assumptions regarding the behavior of osteogenic (bone-forming) neural crest cells within a wider phylogenetic and comparative context. In this review, we summarize data collected to date in three major vertebrate taxa: amphibians, birds and mammals. We highlight three largely unexplored topics within the field of osteogenic neural crest development: 1) disagreements in bone tissue origin within and across current model systems; 2) whether the pattern of neural crest cell contribution to skull bone is evolutionarily conservative or labile; and 3) how our understanding of development and morphology will benefit from fate maps using currently unexamined animal models.     

Relationships between feeding, digestion and water balance in a carnivorous vertebrate, the toad Bufo bufo L.

1. Toads fed meal worms retained water, amounting to about the mass of the meal. 2. Secretion of gastric juice in the initial phase of digestion of a large meal would deplete the extracellular fluid of about half of the chloride ions. 3. Ingestion and rapid digestion of large meals in toads and other carnivorous vertebrates imply tolerance of large variations in anion composition and acidity of the extracellular fluid.     

Ajoene prevents fat digestion by human gastric lipase in vitro

Human gastric lipase (HGL) is a sulfhydryl enzyme which has been shown by Gargouri et al. (Gargouri, Y., Moreau, H., Piéroni, G. and Verger, R. (1988) J. Biol. Chem. 263, 2159-2162) to be inhibited by hydrophobic disulfides. Since HGL is involved in the digestion and absorption of dietary fats we have investigated in vitro the ability of ajoene, a natural disulfide to inactivate HGL. Ajoene is derived from ethanolic garlic extracts. The finding that ajoene inactivates HGL is consistent with the fact that it is reactive towards sulfhydryl compounds and also corroborates previous reports on the ability of garlic to lower triacylglycerol blood levels. These data may explain the age-old Mediterranean and Oriental belief in the 'blood-thinning' effects of garlic on a molecular and physiological basis.     

Tissue digestion for aluminum determination in experimental animal studies

Four different procedures for the determination of aluminum in tissues by atomic absorption spectrometry (AAS) were investigated. They consisted of conventional acid digestion carried out before and after sample drying, associated or not with fat extraction. Drying was carried out in a conventional oven at 65 °C for 24 h. For fat extraction, different solvents and solvent mixtures were investigated considering both extraction yield and sample adequacy for further AAS measurement. Acid digestion was carried out with pure HNO₃ or with its mixture with HClO₄. After digestion, aluminum was measured by graphite furnace atomic absorption spectrometry. Tissues were collected from Al-exposed and nonexposed mice. The results indicated that drying the sample prior to digestion is advantageous as the amount of acid necessary can be significantly reduced. This procedure does not contribute to increase the aluminum level in the samples providing that careful measures to avoid contamination are taken, as the same procedures carried out without taking any precautions to avoid contamination produced imprecise results. Finally, aluminum was not found in the fatty fraction of any sample, even in exposed mice, demonstrating that aluminum does not accumulate in this part of the tissues.     

Reproductive costs in terrestrial male vertebrates: insights from bird studies

Reproduction requires resources that cannot be allocated to other functions resulting in direct reproductive costs (i.e. trade-offs between current reproduction and subsequent survival/reproduction). In wild vertebrates, direct reproductive costs have been widely described in females, but their occurrence in males remains to be explored. To fill this gap, we gathered 53 studies on 48 species testing direct reproductive costs in male vertebrates. We found a trade-off between current reproduction and subsequent performances in 29% of the species and in every clade. As 73% of the studied species are birds, we focused on that clade to investigate whether such trade-offs are associated with (i) levels of paternal care, (ii) polygyny or (iii) pace of life. More precisely for this third question, it is expected that fast species (i.e. short lifespan, early maturity, high fecundity) pay a cost in terms of survival, whereas slow species (with opposite characteristics) do so in terms of fecundity. Our findings tend to support this hypothesis. Finally, we pointed out the potential confounding effects that should be accounted for when investigating reproductive costs in males and strongly encourage the investigation of such costs in more clades to understand to what extent our results are relevant for other vertebrates.     

Histomorphology and proteolytic activity in the gastric apparatus of frugivorous, carnivorous and omnivorous species of birds.

The histomorphology of the gastric apparatus, the pepsin level and the optimum pH for pepsin were investigated in Psittacula krameri (frugivore), Lanius schach (carnivore) and Acridotheres tristis (omnivore) species of birds. The proventricular glands were found to be made up of oxynticopeptic cells. The lobules of the oxynticopeptic cells are polyhedral; they are the largest in P. krameri, and the smallest in A. tristis. However, their greater number in A. tristis enables a higher secretion of hydrochloric acid and pepsin. The villi are more developed in A. tristis than in L. schach and P. krameri. The gizzard is larger in A. tristis than in P. krameri and A. tritis than in the carnivore L. schach. Koilin lining is beset with horny cones, which were well developed in A. tristis, moderately developed in P. krameri and absent in L. schach. The pepsin activity is higher in the proventriculus of the carnivorous L. schach and the omnivorous A. tristis than in the frugivorous P. krameri. Slight pepsin activity was also observed in gizzard tissue extracts in all the three species. The optimum pH for pepsin was found to be 1.5 for P. krameri and 1.8 for both L. schach and A. tristis.     

Ultrastructural studies on neurophysine-containing vesicles of the neurosecretory system of vertebrates

Summary A new method described in the present paper allows identification of neurophysine-containing (NP) vesicles of the magnocellular neurosecretory system of vertebrates. After oxidation of ultrathin sections, the content of NP vesicles can be dissolved specifically in an alkaline medium. This procedure marks NP vesicles selectively in all portions of the classical neurosecretory system.Dedicated to Professor Dr. Dres h.c. W. Bargmann on the occasion of his 70^th birthday.Granted by the Ministerium für Wissenschaft und Technik der DDR.     

Morphometric studies of prepyramidal and pyramidal neurons of various vertebrates]

Praepyramidal and pyramidal neurons were demonstrated in homologous telencephalic areas of Salmo irideus (Gibbons 1855), Rana temporaria L., Rattus norvegicus, forma alba, by means of the Golgi-technique. A comparative morphometrical analysis was made concerning the following parameters: main dendritic length, length of the pericaryon, number of dendritic spines in the first 50-micrometer-dendritic segment and length of the spines-free zone. From these data a quotient was calculated and expressing the theoretical dendritic length per ten spines. There is an increase of length of the pericaryon, length of the spines-free zone, main dendritic length and a pseudo-decrease of the number of dendritic spines in the first 50 micrometer-dendritic segment in rats, as compared with Rana and Salmo. The results are discussed with respect to following problems: homology, phylogenesis and corticalisation.