Search PubMed⌕ Search

Biomedical subjects

G Jacobsson

Publications and source records attributed to G Jacobsson.

At least 37 records · Page 2Linked to original sources
PubMed1996

Molecular components of the exocytotic machinery in the rat pituitary gland.

Several protein components that are essential for exocytotic membrane fusion in neurons have recently been identified. The expression and cellular localization of such protein components were examined in the rat pituitary gland. In situ hybridization using isoform-specific oligonucleotide probes to different exocytotic protein messenger RNAs (mRNAs) showed strong hybridization signal for synaptotagmin I, cysteine string protein (CSP), VAMP-2 (vesicle-associated membrane protein), cellubrevin, munc-18 (mammalian homologue of unc-18), SNAP-25a (synaptosomal-associated protein of 25 kDa), syntaxin 1A, syntaxin 4, syntaxin 5, and alpha-SNAP (soluble NSF attachment protein) in the anterior and intermediate, but not in the posterior lobe of the pituitary. Moderate to weak hybridization signal was detected for synaptotagmin III, SNAP-25b, and syntaxin 2 mRNA in the anterior and intermediate, but not in the posterior lobe of the pituitary. Synaptotagmin II, VAMP-1, syntaxin 1B, or syntaxin 3 mRNA expression could not be detected in any part of the pituitary gland. Immunofluorescence histochemistry in combination with confocal laser microscopy revealed that synaptotagmin-, VAMP-, CSP-, NSF-, and alpha-SNAP-like immunoreactivities (-LI) were present in granules of cells in the anterior and intermediate lobe, whereas SNAP-25- and syntaxin-LI were primarily located to the plasma membrane. Synaptotagmin-, VAMP-, CSP-, NSF-, alpha-SNAP-, SNAP-25- and syntaxin-LI were all present in nerve fibers of the posterior lobe. Within cells of the anterior lobe, colocalization could be demonstrated for synaptotagmin I/II- and synaptotagmin III-LI with ACTH-, GH-, PRL- and TSH-, but not FSH- or LH-LI, whereas VAMP, CSP-, NSF-, alpha-SNAP-, SNAP-25- and syntaxin-LI were demonstrated in all hormone-containing cell types of the anterior pituitary. The results show the presence of several protein components and their isoform-specific mRNAs in the rat pituitary gland, suggesting that these proteins, similar to their roles in regulation of synaptic neurotransmitter release, may participate in exocytotic events in endocrine pituitary cells and in neurosecretory nerve endings of the neurohypophysis.

Animals↗
PubMed1996

Levodopa-induced changes in synaptic dopamine in patients with Parkinson's disease as measured by [11C]raclopride displacement and PET.

Changes in striatal binding of [11C]raclopride, a dopamine D2 receptor antagonist, induced by acute levodopa administration, were evaluated with PET in 10 patients with idiopathic Parkinson's disease (PD). The patients were scanned on two occasions: drug-free and 15 minutes after a 5-minute intravenous infusion of 3 mg/kg levodopa. Levodopa administration produced reductions in striatal [11C]raclopride uptake index with a rostrocaudal gradient. The most pronounced reduction was found in the posterior putamen (to 82% of baseline), followed by the anterior putamen (to 88% of baseline) and the caudate nucleus (to 94% of baseline). The magnitude of [11C]raclopride uptake index reduction correlated with drug-free disability. Moreover, in four hemiparkinsonian patients, a reduction in [11C]raclopride uptake index was measured in the putamen contralateral to the parkinsonian symptoms. The present results demonstrate a positive correlation between striatal dopaminergic nerve-terminal deficiency and the capacity for levodopa to increase synaptic dopamine and displace [11C]raclopride binding, which corresponds to an accelerated amine turnover in dopamine-depleted striatal tissue. We therefore suggest that dopaminergic degeneration in PD is paralleled by a progressive acceleration of amine turnover. This mechanistic consequence of nigrostriatal degeneration, the selective restoration of synaptic dopaminergic neurotransmission in denervated striatal subregions, may explain the effectiveness of levodopa in producing symptomatic benefits in early PD. However, we also suggest that in the vastly denervated striatum, as in advanced PD, an excessive acceleration of amine turnover results in swings in levodopa-induced synaptic dopamine levels that are far beyond normal. This phenomenon most likely plays a key role in the pathogenesis underlying the development of motor-response complications in PD.

Aged↗
PubMed1996

Catechol-O-methyltransferase inhibition increases the uptake of 11C-3-(3,4-dihydroxyphenyl)-L-alanine in the rat pancreas.

BACKGROUND: The objective of the present investigation was to evaluate the uptake and metabolism of 3-(3,4-dihydroxyphenyl-L-alanine) (L-DOPA) in the rat pancreas. METHODS: The procedure included intravenous injection of the positron-emitting radiotracer L-[beta-11C] DOPA (DOP) into unanaesthetized male Sprague-Dawley rats and evaluation of uptake of radioactivity in organs in animals only given the tracer and in animals given therapeutic doses of three different catechol-O-methyltransferase (COMT) inhibitors, OR-486, OR-611, or Ro 41-0960. Selected pancreati were homogenized, and the chemical form bearing the radioactivity was analysed with high-performance liquid chromatography (HPLC). RESULTS: The main finding was that the tracer uptake in the pancreas increased fourfold when the rats were pretreated with COMT inhibitors. Half maximum effect of OR-486 was found at a dose of 0.2 mg/kg. HPLC analysis showed that with COMT inhibitor, the radioactivity in the pancreas consisted of 90% DOPAC. When administering MAO-A and COMT inhibitor together, the pancreas radioactivity corresponded to dopamine. Also in the pig pancreas a significant increase of DOP was observed after COMT inhibition. CONCLUSIONS: This study has shown a high turnover of L-DOPA in the rat pancreas, which can be modulated to give enhanced levels of DOPAC or dopamine by COMT and MAO inhibition.

Analysis of Variance↗
PubMed1995

Expression of protein kinase C isoforms in renal tissue.

PKC plays a central role for the regulation of renal function. PKC consists of a family of isoenzymes. By employing Northern blot techniques we have demonstrated that mRNA transcripts for the classical Ca(2+)-dependent, diacylglycerol-activated isoform alpha, the novel, Ca(2+)-independent isoform delta and the atypical isoform zeta are abundantly expressed in the rat kidney. The novel PKC-epsilon was weakly expressed. The classical PKCs beta I, beta II and gamma could not be detected. The mRNA expression of PKC-delta and -zeta increased with age. The intrarenal localization of PKC-alpha, -delta and -zeta isoforms were studied in the adult kidney using in situ hybridization. In the cortex, the PKC-alpha isoform showed the strongest hybridization signal. PKC alpha, delta and zeta were all distributed in the outer medulla. The PKC-alpha probe detected particularly strong signal in the outer stripe of the outer medulla. Western blot confirmed the presence of the PKC-alpha, -delta and -zeta enzymes in renal tissue. The results show cell-specific and developmentally-dependent expression of three types of PKC isoforms with different responses to diacylglycerol and calcium. The developmental increase of both PKC-delta and PKC-zeta suggests a specific role for these isoforms for the functional regulation of the mature kidney.

Animals↗
PubMed1994

Identification of synaptic proteins and their isoform mRNAs in compartments of pancreatic endocrine cells.

Several proteins that are of importance for membrane trafficking in the nerve terminal have recently been characterized. We have used Western blot and immunohistochemistry to show that synaptotagmin, synaptobrevin/VAMP (vesicle-associated membrane protein), SNAP-25 (synaptosomal-associated protein of 25 kDa), and syntaxin proteins are present in cells of the islets of Langerhans in the endocrine pancreas. Synaptotagmin-like immunoreactivity (-LI) was localized to granules within the cytoplasm of a few endocrine cells located in the periphery of the islets, identified as somatostatin-containing cells, and in many nerve fibers within the islets. VAMP-LI was seen in granules of virtually all pancreatic islet cells and also in nerve fibers. SNAP-25-LI and syntaxin-LI were predominantly present in the plasma membrane of the endocrine cells, including insulin-producing beta cells. In situ hybridization, using isoform-specific oligonucleotide probes, detected VAMP-2, cellubrevin, SNAP-25, syntaxin 1A, 4, and 5, and munc-18 mRNAs in isolated pancreatic islets and in insulin-producing cells. The results show the presence of several synaptic proteins at protein and mRNA levels in pancreatic islet cells, suggesting that they may have specific roles in the molecular regulation of exocytosis also in insulin-secreting cells.

Animals↗
PubMed1994

Segment-specific expression of messenger RNA encoding for a glutamate transporter by renal tubule cells.

Transport of the amino acid glutamate across plasma membranes of neurons, glial cells and epithelial cells of the small intestine and kidney is carried out via specific transport proteins. Recently, a high-affinity Na(+)-dependent glutamate transporter was cloned from rabbit small intestine. We have designed oligonucleotide probes to sequences of rabbit glutamate transporter mRNA and used these for in situ hybridization histochemistry in order to define the cellular localization of glutamate transporter mRNA in the rabbit kidney. Strong hybridization with the probes to glutamate transporter mRNA was demonstrated in the outer stripe of the outer medulla, with tubular rays radiating into the cortex. In emulsion-dipped and hematoxylin-eosin counterstained sections, it could be seen that cells expressing glutamate transporter mRNA were localized in the outer stripe of the outer medulla, coinciding with the S3 segment of proximal tubules. The results show that glutamate transporter mRNA is expressed in proximal tubule cells of the rabbit kidney, suggesting that Na(+)-dependent uptake of glutamate occurs primarily within this nephron segment.

Amino Acid Transport System X-AG↗
PubMed1994

Hexokinase I messenger RNA in the rat central nervous system.

Hexokinase I (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1) is the first enzyme required in the metabolism of glucose in the central nervous system and plays a major role in regulation of the cerebral glycolytic rate. The distribution of hexokinase I mRNA was examined throughout the central nervous system of the rat by use of oligonucleotide probes and in situ hybridization histochemistry. In the rhinencephalon, strong hexokinase I mRNA labeling was demonstrated in the glomerular, mitral, internal granular, and internal plexiform layers, whereas the olfactory nerve, external plexiform, and subependymal layers and ependyma were devoid of labeling. Within the telencephalon, strong labeling was present in all layers (with the exception of the molecular layer) of the cerebral cortex, in the septum, in CA1-4 and dentate gyrus of the hippocampus, and in several amygdaloid nuclei. There was only weak labeling in the nucleus accumbens and caudate putamen. In the diencephalon, there was in general a strong labeling in the epithalamus, in several thalamic nuclei, including the anteriodorsal, anterioventral, anteriomedial, reticular, paravetricular, intermediodorsal, anteriomedial, interanteriomedial, rhomboid, reuniens, and parafascicular thalamic nuclei. Several hypothalamic regions, including the subfornical organ, the medial preoptic area, the suprachiasmatic, supraoptic, paraventricular, dorsomedial, ventromedial nuclei, and the zona incerta, were strongly labeled. In the mesencephalon, there was particularly strong labeling in the pars compacta and reticulata of the substantia nigra, central gray, and red nucleus, in the Darkschewitsch nucleus, and in the medial accessory oculomotor nucleus. In the rhombencephalon, there was strong hybridization in all raphe nuclei, pontine, tegmental, lateral parabrachial, olivary nuclei, and several cranial motor nuclei. All neurons of the locus ceruleus were heavily labeled. Very strong labeling was present in Purkinje and granular cells of the cerebellar cortex. Neurons of the medulla oblongata area postrema, nucleus tractus solitarius, reticular nucleus, nucleus cuneatus and several motor nuclei were strongly labeled. In the spinal cord, labeled cells were present in all laminae, and also neurons of the dorsal root ganglion were heavily labeled. Hexokinase I mRNA was also demonstrated in the epithelium lining the the choroid plexus. In the E15 fetus, very strong labeling was seen in the liver, heart, and trigeminal ganglion, with less intense labeling in in the brain and other tissues having more moderate labeling. Administration of 2% saline as drinking water resulted in a marked increase in hexokinase I mRNA in the magnocellular neurons of the supraoptics and paraventricular nuclei. In summary, the results show extensive neuronal distribution of hexokinase I mRNA with regional differences in the expression pattern.

Animals↗
PubMed1993

Glutamate transporter mRNA and glutamate-like immunoreactivity in spinal motoneurones.

Glutamate is the major excitatory neurotransmitter in the central nervous system. The release of glutamate is terminated by rapid uptake of glutamate into the presynaptic nerve terminals and into surrounding glial cells. Recently, a neuronal glutamate transporter was cloned from rabbit small intestine, thereby providing the possibility to study the distribution of cells that express glutamate transporter mRNA. Using oligonucleotide probes and in situ hybridization, glutamate transporter mRNA was demonstrated in large cell bodies, presumably motoneurones, in the thoracic spinal cord of the rabbit. Immunohistochemical analysis with rabbit polyclonal antibodies to glutamate showed immunoreactivity in the cytoplasm of large cell bodies in the ventral horn, presumably motoneurones, of the rat spinal cord. Glutamate-LI was in addition demonstrated in the motor end plate in hindlimb muscle of the rat, as visualized by double-labelling with mouse monoclonal antibodies to synaptophysin. Taken together, these data raise the possibility that glutamate has a function at the vertebrate neuromuscular junction.

Amino Acid Transport System X-AG↗
PubMed1993

Time course of ethanol-induced changes in serotonin metabolism.

The effect of acute ethanol consumption on serotonin metabolism was examined in healthy volunteers in the fasted and fed state by determination of plasma and urinary levels of the serotonin metabolites 5-hydroxyindole-3-acetic acid (5-HIAA) and 5-hydroxytryptophol (5-HTOL). The plasma and urinary levels of 5-HIAA were reduced by about 40% and 25%, while the 5-HTOL levels were increased on an average 7-fold and 50-fold, respectively, after oral intake of ethanol (0.8 g/kg) over 30 min in a fasted state. The maximal effect on both 5-HIAA and 5-HTOL levels was found 4-6 h after starting drinking. Urinary 5-HTOL and the 5-HTOL/5-HIAA ratio did not return to baseline until 19 h after the start of the administration (i.e., about 10 h after ethanol reached zero level). The mean 24-h excretion of 5-HTOL was increased 15-fold by the ethanol intake, while the 5-HIAA excretion was not significantly different. A clear dose dependent effect was observed in one individual who also ingested a lower amount of ethanol (0.5 g/kg). When ethanol (0.8 g/kg) was ingested over 3 h together with food, the urinary level of 5-HTOL and the 5-HTOL/5-HIAA ratio did not return to baseline until after 20-22 h. In other subjects who had unlimited access to ethanol and ingested between 1.3-2.3 g/kg together with food, the time to reach baseline 5-HTOL/5-HIAA ratio in urine ranged from 20 h to over 26 h.

Adult↗
PubMed1992

Urinary excretion of 5-hydroxyindole-3-acetic acid and 5-hydroxytryptophol after oral loading with serotonin.

The urinary excretion patterns of the serotonin (5-hydroxytryptamine; 5-HT) metabolites 5-hydroxyindole-3-acetic acid (5-HIAA) and 5-hydroxytryptophol (5-HTOL) were examined after ingestion of bananas, a food rich in 5-HT. The bananas contained on an average 25 micrograms 5-HT/g pulp. Both urinary 5-HIAA and 5-HTOL increased markedly (15- to 30-fold) shortly after eating 3-4 bananas, with the highest concentrations found in urine specimens collected after 2-4 h, and did not return to normal until after 8-10 h. The excretion of 5-HIAA increased from a control mean value of 3.9 mg/24 h to 12.7 mg/24 h, when conventional diets were supplemented with 3-4 bananas. The corresponding results for 5-HTOL were 16.8 micrograms/24 h and 60.7 micrograms/24 h, respectively. Of the banana-derived 5-HT ingested, 60-80% was recovered in the urine as 5-HIAA and only 0.3-0.5% as 5-HTOL. However, since both the time-course and relative increase in 5-HTOL was similar to that of 5-HIAA, there was no effect on the urinary 5-HTOL to 5-HIAA ratio. By contrast, acute alcohol consumption produced a considerable elevation of this ratio.

Administration, Oral↗
PubMed1991

Chiral analysis of methadone in plasma by high-performance liquid chromatography.

A method for the chiral high-performance liquid chromatographic analysis of methadone in plasma has been developed. The method employed organic solvent extraction, enantiomeric separation on a Chiral AGP column, and ultraviolet absorption detection at 212 nm. The intra-day variation in the quantification of methadone enantiomers was less than 9% at the 100 ng/ml level, and the values obtained correlated well with those from a gas chromatographic-mass spectrometric method. Results from patients indicate inter- and intra-individual differences in the ratio between l- and d-methadone in plasma during therapy with racemic methadone. In one patient, a higher level of d-methadone in plasma was caused by both faster elimination and lower bioavailability of l-methadone.

Chromatography, High Pressure Liquid↗
PubMed1991

Determination of urinary 5-hydroxyindole-3-acetic acid by high-performance liquid chromatography with electrochemical detection and direct sample injection.

A method for the routine quantitative determination of the major serotonin metabolite 5-hydroxyindole-3-acetic acid (5-HIAA) in urine is described. 5-HIAA was analyzed without prior sample cleanup, using an automated high-performance liquid chromatography system with isocratic elution and electrochemical detection (+0.60 V versus a Ag/AgCl reference electrode). The urine samples were mixed with a solution of the internal standard (5-hydroxyindole-3-propionic acid) and centrifuged. The supernatant was transferred to sealed glass vials, and a 2-microliters aliquot was injected directly onto a C18 reversed-phase analytical column, using an automatic sample injector. Samples of urine could be stored for several months at -80 or at +7 degrees C for 2 days without loss of 5-HIAA. However, a gradual decline with time occurred in crude samples stored at room temperature or above, as well as in urine samples diluted with the mobile phase. The detector response was linear in the range of 0-65 mumol/l 5-HIAA, and the intra- and interassay coefficients of variation were about 5 and 7%, respectively (n = 10).

Chromatography, High Pressure Liquid↗
PubMed1990

Monitoring of plasma methadone: intercorrelation between immunoassay and gas chromatography-mass spectrometry.

Determination of plasma methadone is essential in connection with dose adjustments for patients participating in methadone maintenance programs. We successfully adapted the existing fluorescence polarization immunoassay (FPIA) kit intended for urinary methadone to plasma assays. A concentration interval of 50-900 ng/ml could be covered. The coefficient of variation was less than 7%, and the limit of detection below 50 ng/ml. The intercorrelation between the immunoassay and a specific gas chromatographic-mass spectrometric (GC-MS) method was studied in samples from 19 heroin addicts in methadone maintenance treatment. A total number of 97 plasma samples with a concentration range of 31-842 ng/ml were used. The slope and intercept of the regression line (CFPIA = 0.93 X CGC-MS + 15) was in good agreement with the theoretical relation (CFPIA = CGC-MS), with a coefficient of correlation of 0.978. The mean ratio, in quantitative result, between the techniques (CFPIA/CGC-MS) was 1.03 +/- 0.01 (SEM). We conclude that the immunoassay proposed in this study can be safely used in patients participating in methadone maintenance programs.

Adult↗
PubMed1987

Isolation and characterization of neurokinin A, neurokinin A(3-10) and neurokinin A(4-10) from a neutral water extract of a metastatic ileal carcinoid tumour.

A metastasis to the right liver lobe of an argyrophil/argentaffin midgut carcinoid tumour in a patient with the classical carcinoid syndrome was examined for the presence of tachykinins other than substance P, using a specific antiserum. The extract was initially purified using SepPak cartridges, and subsequently subjected to cation-exchange chromatography on SP Sephadex C-25 which separated the immunoreactive material into two main components (components I and II). Both were further purified by anion-exchange chromatography on DEAE-Sephadex A-25, and by reverse-phase fast protein liquid chromatography. Component II was identified as neurokinin A by its immunochemical and chromatographic properties and amino acid sequence analysis. Component I consisted of two molecular forms which were identified as neurokinin A(3-10) and neurokinin A(4-10) by amino acid sequence analysis. The tumour tissue contained only small amounts of the eledoisin-like peptide that has earlier been demonstrated in mammalian tissues. Although this component behaved like the nonmammalian peptide eledoisin on reverse-phase HPLC and on reverse-phase ion-pair chromatography, eledoisin-specific antiserum E2 indicated that eledoisin-like peptide is not identical to eledoisin. Neurokinin A in carcinoid tumours has an N-terminal heterogeneity; this multiplicity constitutes a further support for the hypothesis that carcinoid tumours produce a number of tachykinins which may be present in different relative amounts in individual patients and may contribute to the individual differences in symptomatology.

Carcinoid Tumor↗