Rolf Ekman - Academia.edu (original) (raw)

Papers by Rolf Ekman

Peptides, 1985

immunoreactive material was detected in endocrine cells in the gut of a lizard, Lacerta vivipara,... more immunoreactive material was detected in endocrine cells in the gut of a lizard, Lacerta vivipara, and a frog, Rana temporaria. The findings are consistent with other reports on reptiles, amphibians and higher species. In addition, however. PYY-like material was found in neuronal elements both in the gut and in the brain. High performance liquid chromatography of frog brain extracts showed the PYY-like material to elute in one minor fraction (eluting position similar but not identical to that of porcine synthetic PYY) and two major fractions (distinct from PYY and probably representing smaller and more hydrophobic PYY-like peptides). 1982.

Clinica Chimica Acta, Dec 1, 1975

The plasma lipoproteins in normal and cholestatic pigs were isolated by zonal ultracentrifugation... more The plasma lipoproteins in normal and cholestatic pigs were isolated by zonal ultracentrifugation and studied with respect to apoprotein and lipid composition. In contrast with the distribution in human plasma, only one HDLpopulation but two LDL-populations were demonstrated. No cholestatic lipoprotein similar to the human lipoprotein X was observed. HDL and the lighter LDL component were largely unchanged in cholestasis. The immunochemical properties were changed to some extent. Thus HDL-reacting material was found in the heavier LDLcomponent and VLDL after cholestasis but not before.

Virchows Archiv. A. Pathological anatomy and histology, Dec 1, 1981

ABSTRACT

Scandinavian Journal of Clinical & Laboratory Investigation, 1977

In this work, egg yolk high density lipoprotein (HDL) was firstly extracted and solubilized with ... more In this work, egg yolk high density lipoprotein (HDL) was firstly extracted and solubilized with a salt-free method. The freshly purified egg yolk HDL was characterized for its physicochemical properties and the delivery potentials for hydrophobic bioactives were also investigated. Native chitosan (NACS) and its amphiphilic derivative (stearic acid conjugated chitosan, SACS) were adopted to fabricate polyelectrolyte nanocomplexes with egg yolk HDL and the fabrication as well as formulation of nanocomplexes were optimized. HDL/SACS and HDL/NACS nanocomplexes had a diameter of 75 nm and 97 nm, respectively. Gastrointestinal stability tests suggested that the nanocomplexes were more stable in gastric phase than in the intestinal condition with the presence of digestive enzymes (pepsin and pancreatin). Curcumin was selected as a model hydrophobic compound to assess the encapsulation and delivery potentials of HDL-based nanocomplexes. HDL/SACS nanocomplexes showed better encapsulation property than HDL/NACS nanocomplexes due to enhanced hydrophobic interactions, which was confirmed by fluorescence and surface hydrophobicity tests. The HDL/SACS nanocomplexes also exhibited sustained release, indicating the promising features as nanoscale oral delivery vehicles for hydrophobic phytochemicals.

Journal of Histochemistry and Cytochemistry, Nov 1, 1981

FEBS Letters, Feb 1, 1975

Alterations of plasma lipoprotein distribution and composition are common features in human chole... more Alterations of plasma lipoprotein distribution and composition are common features in human cholestasis. The most well-known change occurs in the low density lipoprotein class, with the appearance of an abnormal component called lipoprotein X (LP-X). This lipoprotein has been extensively studied in recent years [l-4]. High density lipoproteins, however, also undergo changes during biliary obstruction [2,5,6]. It is known that plasma levels of HDL decrease during the course of cholestasis, but the different HDLspecies have not been investigated as thoroughly as LP-X. This may be due to difficulties in obtaining pure preparations using the common differential flotation technique [7] applied to lipoproteins with density ranges which might differ from those of the normal plasma. Density gradient centrifugation in swing-out rotors can solve this problem, but these rotors can only hold small samples. By zonal ultracentrifugation in density gradients, however, samples large enough for studies of lipid and protein composition can be prepared [ 81. The present communication describes the isolation by zonal centrifugation of an abnormal HDL occurring in small amounts during prolonged cholestasis. The Volume 50, number 2 FEBS LETTERS

Regulatory Peptides, Nov 1, 1984

Summaff Gastrin releasing peptide (GRP) immunoreactive nerve fibres are numerous in the gut wall.... more Summaff Gastrin releasing peptide (GRP) immunoreactive nerve fibres are numerous in the gut wall. Nerve cell bodies containing GRP are regularly found in the myenteric ganglia. The projections of GRP neurones in the rat small intestine were studied after myectomy or transection of the gut wall. Operated rats were left for 8-10 days or 5 weeks. Specimens were studied by immunocytochemistry, immunochemistry and in vitro for motor activity. GRP fibres were absent and GRP was markedly reduced in the gut wall underlying the area of myectomy and 10 mm anally to the myectomy or site of transection. Further anally, GRP and the GRP fibres gradually returned and were back to normal 25-30 mm from the lesion. Myenteric GRP neurones in the rat small intestine thus project anally over a distance of approximately 20-25 mm. A series of experiments was performed in order to test the idea that GRP is directly involved in intestinal motor functions. The results did not support this view. Strips of longitudinal smooth muscle with adherent myenteric ganglia were taken orally and anally to the myectomy and the motor activity of the specimens was compared. Electrical stimulation evoked a contractile response in the oral segment that was 6 times greater than that of the anal segment. However, GRP (10 9-10-~ M) did not evoke contraction and the electrically induced contractile response was unaffected by GRP but could be blocked by atropine. The reduced contractile response in the 'denervated' anal segment is thus probably not due to a shortage of GRP fibres. neuropeptides; gastrin releasing peptide, GRP; myenteric neurones; neuronal projections; gut innervation

Regulatory Peptides, Dec 1, 1984

Immunoreactive vasoactive intestinal peptide (VIP) and substance P (SP) were studied in parotid, ... more Immunoreactive vasoactive intestinal peptide (VIP) and substance P (SP) were studied in parotid, submaxillary and sublingual glands of the rat. The concentration of VIP was highest in the submaxillary gland and lowest in the parotid gland. The concentration of SP was highest in the parotid gland; it was at, or below the limit of detection in the sublingual gland. In the parotid gland the total amounts of VIP and SP were reduced by 95% after parasympathetic denervation (section of the auriculo-temporal nerve). In the submaxillary gland the total amounts of the peptides were unchanged after parasympathetic decentralization (section of the chorda-lingual nerve). In this gland the total amount of SP was reduced by 92% and that of VIP by 50%, when the chorda tympani nerve fibres were cut deep into the hilum. Cutting the nerve fibres at the hilum left the total amounts of the peptides unchanged in the submaxillary gland, whereas in the sublingual gland the total amount of VIP was reduced by 70%. Sympathetic denervation did not reduce the total amounts of the peptides. Duct ligation caused gland atrophy. In the parotid gland the total amounts of VIP and SP were reduced by 40%. In the submaxillary gland the same percentage reduction occurred with regard to SP; however, the total amount of VIP was reduced by 99%. The VIP- and SP-containing nerve fibres reach the salivary glands by the parasympathetic nerves. In both submaxillary and sublingual glands a certain fraction of VIP originates within the glands.

Regulatory Peptides, Feb 1, 1993

Peptide YY (PYY) was demonstrated by immunochemical and/or immunocytochemical methods in endocrin... more Peptide YY (PYY) was demonstrated by immunochemical and/or immunocytochemical methods in endocrine cells in the pancreas of adult mice, rats, guinea-pigs, cats, dogs, pigs and cows. In the pancreas of mouse and rat, immunoreactive PYY was observed in a major subpopulation of the glucagon cells (splenic lobe of the pancreas); immunoreactive PYY also occurred in a subpopulation of the pancreatic polypeptide (PP) cells (duodenal lobe), and in a few extra-insular endocrine cells dispersed throughout the pancreatic parenchyma. In the pancreas of cat, dog and pig immunoreactive PYY was found to coexist with PP, but not with glucagon. Radioimmunoassay (RIA) revealed PYY-like material in extracts of pancreas (and colon) of all the species examined. The highest concentrations were found in the pancreas of cat and mouse; moderate amounts were found in the rat and only small amounts were detected in guinea-pig and pig. The concentrations in the pancreas were uniformly much lower than those in the colon. Analysis by high performance liquid chromatography (HPLC) showed that the PYY-immunoreactive material from pancreas (and rat colon) had an elution profile very similar to that of synthetic PYY, and distinct from that of PP and neuropeptide Y.

Endocrinology, Jul 1, 1983

Previously, vasoactive intestinal polypeptide was localized to intrathyroidal nerve fibers. It st... more Previously, vasoactive intestinal polypeptide was localized to intrathyroidal nerve fibers. It stimulates iodothyronine secretion in mice. In the present study two populations of nerve fibers containing substance P and gastrin/cholecystokinin (CCK)-like immunoreactivity, respectively, were demonstrated in the thyroid gland of several mammals. The substance P fibers occurred around blood vessels and follicles, whereas the gastrin/CCK fibers occurred mainly around follicles. In the chicken thyroid and ultimobranchial glands only substance P-containing fibers could be demonstrated. Such fibers were particularly numerous in the ultimobranchial gland. CCK-4, CCK-8, and substance P did not increase thyronine secretion measured as release of radioiodine into the circulation of mice pretreated with Na125I and T4. The TSH-induced release of radioiodine was also unaffected. Calcitonin secretion in rats was stimulated by CCK-4, CCK-8, substance P, and vasoactive intestinal polypeptide.

Regulatory Peptides, Dec 1, 1987

Two novel N-terminal fragment pairs of porcine pro-v-melanocyte-stimulating hormone (MSH)-(1-103)... more Two novel N-terminal fragment pairs of porcine pro-v-melanocyte-stimulating hormone (MSH)-(1-103), viz. pro-v-MSH-(1-30)/(2-30) and pro-~,-MSH-(1-67)/(2-67) were characterized. A third pair of peptides of still larger size was also detected. The two characterized peptide pairs terminate at sites different from the dibasic sequences typical of prohormone cleavage. This suggests either a different processing event or proteolysis during purification; in both cases cleavages are selective since the two peptides end at distinct positions. Unlike most previously described pro-7-MSH forms, which begin with Trp at position 1 in pro-opiomelanocortin (position-105 in relation to the start of ACTH), the novel peptide pairs show N-terminal heterogeneity with one of the components beginning with Trp as in other forms, and the second component (present in relative amounts of 10-70%) beginning with Cys at position 2 (corresponding to position-104).

Regulatory Peptides, 1980

Preparative biochemistry, 1978

Procedures for the separation of plasma lipoprotein classes and subclasses by zonal ultracentrifu... more Procedures for the separation of plasma lipoprotein classes and subclasses by zonal ultracentrifugation are described. The main density classes, very low density lipoproteins (VLDL), low density lipoproteins (LDL) and high density lipoproteins (HDL), in plasma can be separated in a single run for 20 hours. For the isolation of VLDL-LDL a centrifugation time of only 90 minutes is needed. Separations can be performed on plasma volumes varying from 10 to 400 ml in the Ti-14 rotor used; VLDL can in this way be isolated from 400 ml plasma in 30 minutes. The advantages and disadvantages of zonal ultracentrifugation in comparison with the commonly employed differential ultracentrifugation for separation of lipoproteins are discussed.

Regulatory Peptides, Jul 1, 1984

Extracts of porcine anterior pituitary contain several corticotrophic variants of ACTH 1-39. They... more Extracts of porcine anterior pituitary contain several corticotrophic variants of ACTH 1-39. They were isolated by adsorption chromatography, ion-exchange chromatography and reverse-phase high-performance liquid chromatography. Four variants were then identified as starting and ending at positions corresponding to ACTH 1-38, 1-37, 7-39 and 7-38. Several of these fragments were recovered in chromatographically multiple forms. Although all fragments isolated had corticotrophic activity (measured on isolated rat adrenal cells) those with a shortened N-terminal region had a lower potency than those with an intact N-terminal region. Corticotrophic activity of porcine ACTH 7-38 was detected in a preparation with a beta-aspartyl shift at position 25. However, in agreement with previous studies, synthetic human ACTH 7-38, in which an intact Asn-Gly bond was structurally proven, possessed no such activity. The results indicate that position 25 as well as positions 1-6 are important for corticotrophic activity, and that a deamidative beta-aspartyl shift at position 25 can influence the activity.

Neuroscience, 1988

AMtraet-Gastrin-releasing peptide is a neuropeptide with a wide distribution in the rat small int... more AMtraet-Gastrin-releasing peptide is a neuropeptide with a wide distribution in the rat small intestine. Most of the GRP-containing fibers are intramural in origin. Local severing of myenteric GRP neurons by circumferential removal of the outer longitudinal muscle layer together with the adherent myenteric ganglia (myectomy) in a segment of the rat jejunum resulted in the disappearance of GRP fibers from the myectomized circular muscle and from myenteric ganglia and both muscle layers for approximately 10 mm anally to the lesion. As examined at different time intervals up to 60 weeks postoperatively fine-varicose GRP fibers of a normal appearance were found to return gradually to the portion anal to the lesion beginning at 20 weeks, first in the more distal portions and then (after 40-60 weeks) also in the more proximally located portions. Also the circular muscle in the myectomized segment became reinnervated during this time period. These fibers were notably coarse, more numerous than in control circular muscle, and arranged in thick bundles (hyperinnervation). Such nerve bundles were particularly frequent 40 weeks after the operation. The results indicate a remarkable plasticity of enteric neurons.

Endocrinology, Aug 1, 1982

A RIA has been developed for natural porcine pro-γMSH, the 103-amino acid peptide that represents... more A RIA has been developed for natural porcine pro-γMSH, the 103-amino acid peptide that represents the amino-terminal part of proopiolipomelanocortin. Rabbits were immunized with the purified peptide polymerized with glutaraldehyde. The antiserum is directed against the amino-terminal end of the antigen and does not cross-react with corticotropin, βlipotropin, β-endorphin, γ3MSH, or Y2MSH. The minimum detectable concentration is 0.15 ng/ml standard pro-γMSH (15 pg/tube). Pro-yMSH-like immunoreactivity was detected in plasma and extracts of the hypothalamus and pituitary of pigs. Gel chromatography of these extracts revealed at least three immunoreactive peaks in the anterior and neurointermediate lobes of the pituitary, whereas two immunoreactive peaks were found in extracts of the hypothalamus.

Regulatory Peptides, Nov 1, 1988

Neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP) occur in nerve fibers around blood v... more Neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP) occur in nerve fibers around blood vessels and between follicles in the thyroid gland of the mouse and rat. VIP-immunoreactive fibers are numerous, while NPY-immunoreactive fibers are fewer. Most of the latter fibers contain noradrenaline (NA) as well as NPY, while a subpopulation was found to contain VIP instead of NA. We have determined the origins of rat thyroid nerve fibers containing NPY, VIP or NPY/VIP by investigating 3 conceivable sources, i.e. the superior cervical ganglion, the nodose ganglion and the thyroid ganglion. Chemical sympathectomy or removal of the superior cervical ganglion did not affect the frequency of VIP-immunoreactive fibers but eliminated most of the NPY-immunoreactive fibers as well as all NA-containing nerve fibers (recognized by antibodies to dopamine-/~-hydroxylase). The NPY-immunoreactive fibers that remained after sympathectomy occurred around blood vessels and between follicles and contained VIP. Cervical vagotomy (removal of the nodose ganglion including the adjacent vagus) did not overtly affect the frequency of N PY/VI P-, VIP-, or NPY/NAcontaining fibers in the thyroid. In contrast, extirpation of the thyroid ganglion, which is situated immediately outside the thyroid capsule, greatly reduced the number of V1P-and NPY/VIP-containing fibers in the rat thyroid. On the whole, the results of radioimmunoassay of NPY and VIP agreed well with the immunocytochemical findings. High performance liquid chromatography confirmed the identity of NPY

Journal of Histochemistry and Cytochemistry, 1975

Neuroscience, Sep 1, 1988

Neuroscience, Oct 1, 1983

Immunoreactive gastrin releasing peptide (GRP) was demonstrated in neuronal elements in the porci... more Immunoreactive gastrin releasing peptide (GRP) was demonstrated in neuronal elements in the porcine pancreas and in the gut of several mammals. Immunoreactive endocrine cells could not be detected. The results of radioimmunochemical analysis agreed well with those of immunocytochemistry. The occurrence of gastrin-releasing peptide-containing nerve cell bodies in the myenteric ganglia all along the gut indicates that gastrin-releasing peptide fibers are intramural in origin. The distribution of gastrin-releasing peptide fibers in all layers of the gut wall suggests multiple functions of gastrin-releasing peptide, including a role in the regulation of intramural neuronal activities, smooth muscle tone and in secretory and absorptive processes.