Digestion and absorption of trioleoyl-thioglycerol in the rat

A triacylglycerol analogue, rac-1,2-di-O-oleoyl-3-S-oleoyl-3-thioglycerol, was fed to rats and chyle acylglycerols were analyzed. Triacylglycerol was the dominating chyle lipid but X-triacyl-1-thioglycerol constituted approx. 6% of total chyle lipids. Its identity was verified by ultraviolet and mass spectra and its stereochemical structure by ORD and CD. The proportions of triacyl-1-thio-sn-glycerol/triacyl-3-thio-sn-glycerol were $\text{63}\text{37}$ and $\text{78}\text{22}$ in two experiments. Possible reasons for this stereospecificity are discussed. The study shows that the stereochemical configuration of lipids isolated from biological material can be assessed by ORD and CD.     

Prostaglandins contribute to the vasodilation induced by nicotinic acid

The significance of endogenously formed prostaglandins in the vasodilation induced by nicotinic acid (NIC) was investigated. The forearm venous plasma level of radioimmunoassayed PGE (R-PGE) and the forearm blood flow (FBF) were measured in 13 healthy male volunteers at rest and during infusion of NIC. Each subject was subsequently re-studied after pretreatment with the PG synthesis inhibitor, naproxen. In the absence of naproxen, NIC infusion resulted in an almost four-fold rise in the release of R-PGE and a 60% increase in FBF. Pretreatment with naproxen did not affect the basal release of R-PGE or the basal FBF but inhibited both the release of R-PGE and the increase in FBF following NIC. The data support the hypothesis that the vasolidating effect of NIC is largely dependent upon an increased vascular formation of PG.     

Hydrophobic affinity partition of spinach chloroplasts in aqueous two-phase systems

The surface properties of spinach chloroplasts, both of intact chloroplasts with surrounding envelope and broken chloroplasts consisting of the inner lamellar system, have been studied by partitioning them between two aqueous phases, especially using counter-current distribution technique. The two-phase system consists of poly(ethyleneglycol), dextran and water. The two polymers are enriched in opposite phases and by binding deoxycholate or palmitate to one of the polymers the affinity of chloroplasts for the corresponding phase is strongly enhanced. The partition of the two classes of chloroplasts, however, is not affected to the same degree and the affinity of the chloroplast envelope for deoxycholate and palmitate is stronger than that of the lamellar system. This has been correlated to the chemical composition of the two types of membranes. By studying the effect of salts on the partition it has been found that the lamellar system bears a larger number of negative charges as compared to the envelope of the intact chloroplast.     

Fluorescence-microscopical demonstration of a population of gastro-intestinal nerve fibres with a selective affinity for Quinacrine

Summary A population of nerve fibres in the gastro-intestinal tract of mice showing a high affinity for quinacrine was revealed by fluorescence microscopy. Similar results were obtained in rats and guinea pigs. Whole-mounts of sheets of the smooth muscle layer following incubation in 10^-6-10^-7 M quinacrine for 15–60 min revealed fine fluorescent varicose nerve fibers in the myenteric plexus of Auerbach both around nerve cell bodies and in the interconnecting strands. Many fibers were also present between the strands of the plexus, especially running parallel to the circular muscle layer. Such fibers were not seen in similarly quinacrine-incubated irides. A proportion of the cell bodies in Auerbach's plexus also showed quinacrine accumulation. These cells were apparently smaller neurons, sometimes with fluorescent processes. Intraperitoneal injections of quinacrine failed to demonstrate nerve fibers, but some cell bodies in Auerbach's plexus were positive. Subsequent paraformaldehyde treatment for monoamine visualization showed persistent adrenergic nerve terminals in the intestine and iris. These nerves seemed to be fewer and had a more yellow fluorescence than normally. The identity of the quinacrine-positive fibers is discussed with respect to recent suggestions that purinergic, substance P, enkephalin, and somatosin-containing nerves, in addition to adrenergic and cholinergic nerves, are present in the gut wall.Supported by the Swedish Medical Research Council (04X-03185). Magnus Bergvalls Stiftelse and Karolinska Institutets Fonder. For generous gifts of Mepacrine we thank Winthrop, Skärholmen, Stockholm, Sweden. The skilful technical assistance of Miss Gerd Boetius and Miss Maud Eriksson is gratefully acknowledged     

The use of dispersed pancreatic islet cells in measurements of transmembrane transport

Suspensions of dispersed islet cells were prepared by shaking collagenaseisolated pancreatic islets of $\text{ob}\text{ob}\text{-}\text{mice}$ in Ca²⁺-free buffer. The dispersed cells exhibited a glucose uptake with stereospecificity for the d isomer and concentrated Rb⁺ about 30-fold from a medium containing 70 μm RbCl. These results compare well with previous observations on unbroken islets and indicate that the dispersion procedure does not cause serious damage to the plasma membranes of the β-cells. By double isotope labeling and centrifuging the incubated cells through oil, incubation times as short as only a few seconds can be used. The elimination of the extracellular tissue space and the short incubation times should facilitate the study of transport kinetics in the pancreatic islet cells.     

Formation of a functional adrenergic input to intraocular cerebellar grafts: Ingrowth of inhibitory sympathetic fibers

The intraocular transplantation technique was used to study the ingrowth of peripheral sympathetic adrenergic nerves from the iris into transplants of fetal rat cerebellum, and the possible function of these nerves. The transplants, grown in oculo for one-half to eight months, were analyzed by fluorescence histochemistry and electrophysiological techniques. Peripheral sympathetic adrenergic fibers from the iris were able to grow into the cerebellar transplants and arborize in a pattern similar to that in situ, appearing in all three cortical layers and the noncortical areas of the transplants. The density of visible nerves without pretreatment and after preincubation in 10⁻⁶ or 10⁻⁵ M α-methylnorepinephrine was comparable to mature rat cerebellum. The spontaneous discharge of the Purkinje cells in oculo was inhibited by microiontophoresis of norepinephrine (NE) and amphetamine in sympathetically innervated, as well as sympathectomized transplants denervated by ganglionectomy. The NE response was blocked by the adrenergic β-receptor blocker MJ-1999. GABA also inhibited the Purkinje cell activity while glutamate accelerated the discharge. Parenteral amphetamine inhibited Purkinje cell activity in sympathetically innervated transplants, but was ineffective in denervated transplants. The Purkinje cell spontaneous activity was inhibited by electrical stimulation of the NE fiber input through the cervical sympathetic trunk. This inhibition could be antagonized by parenteral reserpine or the β-adrenergic antagonist propranolol. The responses of the Purkinje cells within the transplants to drugs and transmitters mimic those of the adult rat in situ. In view of the fluorescence histochemical evidence for an ingrowth of peripheral sympathetic adrenergic fibers into the cerebellar transplants, and the results of stimulating the sympathetic trunk, it is suggested that peripheral adrenergic fibers may be able to establish functional connections with the Purkinje cells similar to the cerebellar adrenergic synapses normally formed in situ by fibers from the locus coeruleus.     

Cannot see the diversity for all the species: Evaluating inclusion criteria for local species lists when using abundant citizen science data

Abundant citizen science data on species occurrences are becoming increasingly available and enable identifying composition of communities occurring at multiple sites with high temporal resolution. However, for species displaying temporary patterns of local occurrences that are transient to some sites, biodiversity measures are clearly dependent on the criteria used to include species into local species lists. Using abundant opportunistic citizen science data from frequently visited wetlands, we investigated the sensitivity of α‐ and β‐diversity estimates to the use raw versus detection‐corrected data and to the use of inclusion criteria for species presence reflecting alternative site use. We tested seven inclusion criteria (with varying number of days required to be present) on time series of daily occurrence status during a breeding season of 90 days for 77 wetland bird species. We show that even when opportunistic presence‐only observation data are abundant, raw data may not produce reliable local species richness estimates and rank sites very differently in terms of species richness. Furthermore, occupancy model based α‐ and β‐diversity estimates were sensitive to the inclusion criteria used. Total species lists (all species observed at least once during a season) may therefore mask diversity differences among sites in local communities of species, by including vagrant species on potentially breeding communities and change the relative rank order of sites in terms of species richness. Very high sampling effort does not necessarily free opportunistic data from its inherent bias and can produce a pattern in which many species are observed at least once almost everywhere, thus leading to a possible paradox: The large amount of biological information may hinder its usefulness. Therefore, when prioritizing among sites to manage or preserve species diversity estimates need to be carefully related to relevant inclusion criteria depending on the diversity estimate in focus.