Enzymes of the jejunal enterochromaffine cells in man

Summary A study of enzymatic equipment of enterochromaffine cells (e.c.) in jenual biopsies obtained with a Crosby capsule in normal humans and patients with nontropical sprue was undertaken. The following enzymes were demonstrated: alkaline phosphatase and adenosine triphosphatase (cell membrane), acid phosphatase (corpuscular), non-specific esterase (diffuse and corpuscular, predominantly eserine resistant, in corpuscular localization E 600 resistant), DPN- and TPN-diaphorases and dehydrogenases of lactic acid, malic acid, isocitric acid, glucoso-6-phosphoric acid, succinic acid, -hydroxybutyric acid and -glycerophosphoric acid. Enzyme activities were not equal in all cells suggesting some type of secretory cycle. In most patients with untreated nontropical sprue or with the disease in relapse e.c. were more numerous and hypertrophic with elevated activities of non-specific esterase and acid phosphatase. Implications of these results are briefly discussed.With 8 Figures in the Text, of which 2 in Colour     

Evolution of pollen morphology in Loranthaceae

Earlier studies indicate a strong correlation of pollen morphology and ultrastructure with taxonomy in Loranthaceae. Using high-resolution light microscopy and scanning electron microscopy imaging of the same pollen grains, we document pollen types of 35 genera including 15 studied for the first time. Using a molecular phylogenetic framework based on currently available sequence data with good genus-coverage, we reconstruct trends in the evolution of Loranthaceae pollen and pinpoint traits of high diagnostic value, partly confirming earlier intuitive hypotheses based on morphological observations. We find that pollen morphology in Loranthaceae is strongly linked to phylogenetic relationships. Some pollen types are diagnostic for discrete genera or evolutionary lineages, opening the avenue to recruit dispersed fossil pollen as age constraints for dated phylogenies and as independent data for testing biogeographic scenarios; so far based exclusively on modern-day data. Correspondences and discrepancies between palynological and molecular data and current taxonomic/systematic concepts are identified and suggestions made for future palynological and molecular investigations of Loranthaceae.     

The first Loranthaceae fossils from Africa

An ongoing re-investigation of the early Miocene Saldanha Bay (South Africa) palynoflora, using combined light and scanning electron microscopy (single grain method), is revealing several pollen types new to the African fossil record. One of the elements identified is Loranthaceae pollen. These grains represent the first and only fossil record of Loranthaceae in Africa. The fossil pollen grains resemble those produced by the core Lorantheae and are comparable to recent Asian as well as some African taxa/lineages. Molecular and fossil signals indicate that Loranthaceae dispersed into Africa via Asia sometime during the Eocene. The present host range of African Loranthaceae and the composition of the palynoflora suggest that the fossil had a range of potential host taxa to parasitise during the early Miocene in the Saldanha Bay region.     

The middle Miocene palynoflora and palaeoenvironments of Eskihisar (Yatağan basin,south‐western Anatolia): a combined LM and SEM investigation

We investigated a palynological section from middle Miocene sediments at Eskihisar (south‐western Anatolia) to establish biogeographic links of the palynoflora and to infer the palaeoenvironment. Four algal palynomorphs, nine spore taxa, eight gymnosperms, three monocots and 67 dicot pollen types were encountered and investigated using the ‘single grain method’ that combines light microscopy and scanning electron microscopy. Two pollen zones reflect different phases of basin development. Zonal vegetation remained fairly stable across the section and reflects heterogeneous environments including broad‐leaved deciduous forest, subtropical forest and sclerophyllous and semi‐evergreen oak forest. Conifers were accessory elements in the broad‐leaved deciduous forest communities and replaced these at higher elevations. Some herbaceous taxa (Plumbaginaceae) indicate scattered occurrences of sandy and/or rocky soils. Biogeographic affinities are general Northern Hemisphere, North American and East Asian, as also suggested by the macrofossil record. Only two taxa provide potential biogeographic links with the African flora. This suggests that biome shifts of plant taxa between African subtropical/tropical biomes and Anatolian (western Eurasian) temperate forests and shrublands may have been rare in the middle Miocene.     

The last meal of an Eocene pollen-feeding fly

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Incorporation of 18 O into homovanillic acid of rat brain during exposure to oxygen 18 containing atmospheres

Rats were exposed to air containing ¹⁸O₂ at atmospheric pressure. $\text{In vivo}$ incorporation of ¹⁸O in brain homovanillic acid (HVA) was determined by gas chromatography-mass spectrometry. One ¹⁸O atom was incorporated into each molecule of HVA indicating that tyrosine is the predominant precursor of brain dopamine and that the oxygen in the 3-position is of atmospheric origin. Intraperitoneal administration of ¹⁸O-enriched water did not alter the ¹⁸O content of brain HVA Mass fragmentography (2) was used to measure the increase in ¹⁸O and the decrease in ¹⁶O in HVA from rat brain over several hours of exposure to an ¹⁸O enriched atmosphere. These experiments demonstrate the possibility to pulse label brain dopamine and its metabolites by $\text{in vivo}$ inhalation of stable oxygen isotopes. The procedure should be useful for quantitative determinations of the turnover of brain dopamine in animals and man.     

The effect of deleting a putative salt bridge on the properties of the thermostable subtilisin-like proteinase, aqualysin I

Aqualysin I, is a subtilisin-like serine proteinase, from the thermophilic bacterium Thermus aquaticus. It is predicted that the enzyme contains a salt bridge, D17-R259, connecting the N- and C-terminal regions of the enzyme. Previously we reported on the stabilizing effect of the incorporation of a salt bridge at a corresponding site in VPR, a related cold adapted enzyme from a marine Vibrio sp. Here we describe the effect of the reverse change, i.e. the elimination of the salt bridge on the thermal stability and kinetic properties of aqualysin I. Deletion of the putative salt bridge in the D17N mutant of the enzyme destabilized the enzyme by 8-9 °C in terms of T??%, determined by thermal inactivation and over 4 °C in T(m), as measured from melting curves of the inhibited enzyme. The mutation, however, had no significant effect on the kinetic parameters of the enzyme under standard assay conditions.