ACTH-like immunoreactivity in the gastrin cell. Independent changes in gastrin and ACTH-like immunoreactivity during ontogeny.

Rat antral gastrin cells have been shown to contain ACTH-like immunoreactivity. Studies on the ontogeny of the antral gastrin cells reveal that these cells start to store gastrin before they contain detectable quantities of ACTH-like immunoreactivity. At no stage studied were duodenal gastrin cells found to contain ACTH-like peptides. The data indicate that the G cells synthetizes and/or releases the two hormonal peptides independently.     

Studies on the in vitro incubation procedure for [35]sulphate labelling of articular cartilage glycosaminoglycans

Articular cartilage from cow and calf femoral condyles was incubated in Tyrodes solution containing [³⁵S]sulphate for different periods up to 80 min. Glycosaminoglycans from the cartilage tissue and incubation medium were fractionated on Cetylpyridinium chloride and ECTEOLA cellulose microcolumns.The incorporation of [³⁵S]sulphate into all individual fractions of chondroitin sulphate and keratan sulphate was found to be linear from 20 to 80 min incubation time. As a rule the total specific activities of keratan sulphate and chondroitin sulphate were similar for both calves and cows.The proteoglycan material recovered from the medium amounted to about 1% of the tissue dry weight and was found to have a higher chondroitin sulphate: keratan sulphate ratio than the corresponding cartilage tissue for both calf and cow.The solubility profiles for the newly synthesised glycosaminoglycans, obtained from determination of the radioactivity in the individual fractions, were compared with those of glycosaminoglycans already present. These curves indicated that newly synthesised chondroitin sulphate had a higher average molecular size than that present in the tissue whereas the newly synthesised keratan sulphate had a smaller average molecular size. These newly synthesised components were also detected in the proteoglycans recovered from the incubation medium.     

Temporary peripartal impairment in memory and attention and its possible relation to oxytocin concentration

The aim of the present study was to investigate peripartal performance on cognitive tests and its possible relationship with plasma oxytocin concentrations. Twenty women (cases) were tested on five experimental occasions, the first toward the end of pregnancy and the last 12 months postpartum. On each experimental occasion performance on cognitive tests of memory and attention was recorded and oxytocin concentrations were simultaneously assayed in plasma-samples. Twenty non-pregnant women (controls) were investigated at similar intervals. Cases were found to have improved their performance on some cognitive tests significantly more than controls when results at 6 and 12 months after delivery were compared with those from the end of pregnancy and up to three months after partus. This observation strongly suggests impairment in cognitive performance during the peripartal period. Cases had significantly higher oxytocin concentrations than controls in plasma samples up to three months post partum. No correlation was, however, found between cognitive test results and levels of oxytocin concentration.     

Reaction of proteinases with alpha 2-macroglobulin: evidence for alternate reaction pathways in the inhibition of trypsin

Titration experiments were employed to measure the binding stoichiometry of alpha 2M for trypsin at high and low concentrations of reactants. These titration experiments were performed by measuring the SBTI-resistant trypsin activity and by direct binding measurements using 125I-labeled trypsin. The binding stoichiometry displayed a marked dependence upon protein concentration. At high alpha 2M concentrations (micromolar), 2 mol of trypsin are bound/mol of inhibitor. However, at low alpha 2M concentrations (e.g., 0.5 nM), only 1.3 mol of trypsin were bound/mol of inhibitor. Sequential additions of subsaturating amounts of trypsin to a single aliquot of alpha 2M also resulted in a reduction in the final binding ratio. A model has been formulated to account for these observations. A key element of this model is the observation that purified 1:1 alpha 2M-proteinase complexes are not capable of binding a full mole of additional proteinase [Strickland et al. (1988) Biochemistry 27, 1458-1466]. The model predicts that once the 1:1 alpha 2M-proteinase complex forms, this species undergoes a time-dependent conformational rearrangement to yield a complex with greatly reduced proteinase binding ability. According to this model, the ability of alpha 2M to bind 2 mol of proteinase depends upon the association rate of the second enzyme molecule with the binary (1:1) complex, the enzyme concentration, and the rate of the conformational alteration that occurs once the initial complex forms. Modeling experiments suggest that the magnitude of the rate constant for this conformational change is in the order of 1-2 s-1.     

Consumption by needle-eating insects on Scots pine in relation to season and stand age

Trapping of frass-drop from needle-eating insects in three Scots pine stands, 18-, 55-and 120-yr-old, respectively, in three years, revealed that the consumption rate in the two older stands on average displayed three peaks: in July (consumption by Panolis flammea and a first wave of diprionids), late August/early September (lasiocampid/sphingids, a second wave of diprionids), and September/October ( Bupalus piniarius ). Annual consumption was the same in these two stands, on average 7 kg dw ha⁻¹. In the young stand, there was no late season peak (due to the absence of B. piniarius ,) consumption ceasing one month earlier, at 0.2 kg dw ha⁻¹. Consumption intensity (consumption per needle biomass) corresponded to 0.05%, 0.5% and 1.2% of new needle production, respectively, in the three stands, and increased approximately linearly with the needle biomass of the tree. This increase with size (age) of the tree seems to be due to the multiplicative effect of a larger complexity of the grazer guild and a higher population density of single insect species.     

Oms38 is the first identified pore-forming protein in the outer membrane of relapsing fever spirochetes

Relapsing fever is a worldwide, endemic disease caused by several spirochetal species belonging to the genus Borrelia. During the recurring fever peaks, borreliae proliferate remarkably quickly compared to the slow dissemination of Lyme disease Borrelia and therefore require efficient nutrient uptake from the blood of their hosts. This study describes the identification and characterization of the first relapsing fever porin, which is present in the outer membranes of B. duttonii, B. hermsii, B. recurrentis, and B. turicatae. The pore-forming protein was purified by hydroxyapatite chromatography and designated Oms38, for outer membrane-spanning protein of 38 kDa. Biophysical characterization of Oms38 was done by using the black lipid bilayer method, demonstrating that Oms38 forms small, water-filled channels of 80 pS in 1 M KCl that did not exhibit voltage-dependent closure. The Oms38 channel is slightly selective for anions and shows a ratio of permeability for cations over anions of 0.41 in KCl. Analysis of the deduced amino acid sequences demonstrated that Oms38 contains an N-terminal signal sequence which is processed under in vivo conditions. Oms38 is highly conserved within the four studied relapsing fever species, sharing an overall amino acid identity of 58% and with a strong indication for the presence of amphipathic β-sheets.