Search PubMed⌕ Search

Biomedical subjects

M Johansson

Publications and source records attributed to M Johansson.

At least 163 records · Page 9Linked to original sources
PubMed1997

B-cell-deficient mice develop complete immune protection against genital tract infection with Chlamydia trachomatis.

We evaluated the ability of mice made genetically deficient for B cells to resolve a primary infection and to develop protective immunity against vaginal challenge with a human isolate of Chlamydia trachomatis bacteria. The B-cell-deficient microMT mice cleared a primary ascending infection with similar or faster kinetics compared with wild-type mice. The presence of chlamydial inclusion bodies and the degree of inflammation in the upper genital tract was comparable and showed similar kinetics in microMT as in wild-type mice. Following resolution of the primary infection the mice were challenged by 100 ID50 of live bacteria and the level of protection and the extent of local inflammation was assessed. Strikingly, all microMT mice, as well as most of the wild-type mice, demonstrated complete immune protection with no bacterial shedding. While high titres of chlamydia-specific antibodies were stimulated locally and systemically in wild-type mice, no antibodies were detected in microMT mice. However, in both strains, immunohistochemical analysis of the upper genital tract demonstrated the presence of large numbers of CD4+ T cells and increased levels of interferon-gamma (IFN-gamma)-producing cells. The results unequivocally demonstrate that antibodies are not required for full protection to develop against ascending infection with a high dose of C. trachomatis in the female genital tract. Our study confirms the notion that cell-mediated immunity, in particular that owing to CD4+ T helper I (Th1)-type cells, is critical for host resistance against C. trachomatis in mice.

Animals↗
PubMed1997

Studies in knockout mice reveal that anti-chlamydial protection requires TH1 cells producing IFN-gamma: is this true for humans?

Chlamydia trachomatis is one of the major causes of infertility and preventable blindness in the world. The organism is of particular interest from an immunological point of view because it is one of the few obligate intracellular bacterial pathogens. There is some evidence that repeated infections in humans stimulate protective immunity. However, until recently, it was unclear which components of the adaptive immune system give rise to protection. Studies in gene knockout mice reported here and elsewhere now give a coherent and cogent picture of the importance of the Th1 response, in particular IFN-gamma, for the localization and eradication of C. trachomatis genital tract infection. The key questions still to be addressed are the identity of the IFN-gamma responsive cells and whether the mouse is truly representative of host protection against chlamydiae in humans.

Animals↗
PubMed1997

Tumor blood flow and the cytotoxic effects of estramustine and its constituents in a rat glioma model.

OBJECTIVE: Estramustine (EaM) is a conjugate of nor-nitrogen mustard (NNM) and 17 beta-estradiol (E2) that has cytotoxic and radiosensitizing effects on experimental malignant glioma. Its mechanism of action is only partly understood. To further investigate the mechanism in vivo, the effects on tumor blood flow (TBF) and tumor growth were analyzed. METHODS: TBF was measured by radioactive microspheres, and tumor growth was measured by weight. Apoptosis was evaluated by in situ end labeling and gel electrophoresis. The effects of the constituents NNM and E2 were also evaluated. RESULTS: EaM increased TBF to 153.8 ml/100 g/min after 3 days and to 153.9 ml/100 g/min after 10 days of treatment, compared with 94.0 ml/100 g/min in untreated controls. Cerebral blood flow did not change after EaM treatment. NNM increased TBF but also showed a tendency to increase cerebral blood flow. E2 increased TBF, whereas cerebral blood flow was unchanged. EaM resulted in a rapid reduction in tumor weight from 230 mg in untreated animals to 146 mg after 3 days of treatment. EaM induced an early transient fragmentation of deoxyribonucleic acid in glioma but not in the normal brain. Neither NNM nor E2 affected tumor weight. CONCLUSION: EaM increases TBF in the BT4C rat glioma model with a concomitant rapid antitumoral effect. The increase in TBF could partially be induced by an estrogen-like action of EaM, but the rapid cytotoxic effect of the drug is obviously attributed to the intact EaM compound. This cytotoxic effect might be attributable to the induction of programmed cell death.

Animals↗
PubMed1997

Alexithymia in anorexia nervosa: a controlled study using the 20-item Toronto Alexithymia Scale.

The 20-item Toronto Alexithymia Scale (TAS) was completed at the age of 22 years by individuals who had previously suffered from anorexia nervosa (AN), and also by members of a comparison group. The AN and comparison groups had been recruited from community samples. Overall, the TAS scores did not clearly discriminate between the two groups. However, the AN group was significantly more often represented among subjects with the highest TAS scores. A subgroup with empathy disorder tended to have particularly high scores. It is concluded that alexithymia, as defined using the TAS-20, is found only in a subgroup of individuals with AN, and possibly more often in those who are also clinically diagnosed as suffering from empathy disorder. The TAS-20 is not suitable for screening of AN in the general population.

Adolescent↗
PubMed1997

Host MHC class I gene control of NK-cell specificity in the mouse.

The missing self model predicts that NK cells adapt somatically to the type as well as levels of MHC class I products expressed by their host. Transgenic and gene knock-out mice have provided conclusive evidence that MHC class I genes control specificity and tolerance of NK cells. The article describes this control and discusses the possible mechanisms behind it, starting from a genetic model to study how natural resistance to tumors is influenced by MHC class I expression in the host as well as in the target cells. Data on host gene regulation of NK-cell functional specificity as well as Ly49 receptor expression are reviewed, leading up to the central question: how does the system develop and maintain "useful" NK cells, while avoiding "harmful" and "useless" ones? The available data can be fitted within each of two mutually none-exclusive models: cellular adaptation and clonal selection. Recent studies supporting cellular adaptation bring the focus on different possibilities within this general mechanism, such as anergy, receptor calibration and, most importantly, whether the specificity of each NK cell is permanently fixed or subject to continuous regulation.

Animals↗
PubMed1997

Genital tract infection with Chlamydia trachomatis fails to induce protective immunity in gamma interferon receptor-deficient mice despite a strong local immunoglobulin A response.

CD4+ T cells have been found to play a critical role in immune protection against Chlamydia trachomatis infection. Since both humoral and cell-mediated antichlamydial immunity have been implicated in host protection, the crucial effector functions provided by the CD4+ T cells may rely on Th1 or Th2 functions or both. In the present study, we evaluated the development of natural immunity following vaginal infection with C. trachomatis serovar D in female gamma interferon receptor-deficient (IFN-gammaR-/-) mice with a disrupted Th1 effector system. We found that in comparison with wild-type mice, the IFN-gammaR-/- mice exhibited a severe ascending primary infection of prolonged duration which stimulated almost 10-fold-stronger specific local immunoglobulin A (IgA) and IgG responses in the genital tract. Following resolution of the primary infection and despite the augmented antibody responses to chlamydiae, the IFN-gammaR-/- mice were completely unprotected against reinfection, suggesting that local antibodies play a subordinate role in host protection against chlamydial infection. Immunohistochemical analysis of frozen sections of the genital tract revealed many CD4+ T cells in the IFN-gammaR-/- mice, with a dominance of interleukin 4-containing cells in mice following resolution of the secondary infection. However, in contrast to the findings with wild-type mice, the typical clusters of CD4+ T cells were not found in the IFN-gammaR-/- mice. Few and similarly distributed CD8+ T cells were observed in IFN-gammaR-/- and wild-type mice. Whereas chlamydia-infected macrophages from wild-type mice had no inclusion bodies (IB) and produced significant amounts of nitric oxide (NO) in the presence of IFN-gamma, macrophages from IFN-gammaR-/- mice contained many IB but no NO. These results indicate that CD4+ Th1 cells and IFN-gamma, rather than local antibodies, are critical elements in host immune protection stimulated by a natural ascending C. trachomatis infection in the female genital tract.

Animals↗
PubMed1997

Uridylylation of the P(II) protein in the photosynthetic bacterium Rhodospirillum rubrum.

The regulatory protein P(II) has been studied in great detail in enteric bacteria; however, its function in photosynthetic bacteria has not been clearly established. As a number of these bacteria have been shown to regulate nitrogenase activity by a metabolic control system, it is of special interest to establish the role of P(II) in these diazotrophs. In this study, we show that P(II) in Rhodospirillum rubrum is modified in response to the N status in the cell and that addition of ammonium or glutamine leads to demodification. We also provide evidence that P(II) is uridylylated. In addition, we show that not only these compounds but also NAD+ promotes demodification of P(II), which is of particular interest as this pyridine nucleotide has been shown to act as a switch-off effector of nitrogenase. Demodification of P(II) by ammonium or NAD+ did not occur in cultures treated with an inhibitor of glutamine synthetase (methionine sulfoximine), whereas treatment with the glutamate synthase inhibitor 6-diazo-5-oxo-norleucine led to total demodification of P(II) without any other addition. The results indicate that P(II) probably is not directly involved in darkness switch-off of nitrogenase but that a role in ammonium switch-off cannot be excluded.

Bacterial Proteins↗
PubMed1997

Cardiorenal epinephrine kinetics: evidence for neuronal release in the human heart.

There are experimental data suggesting that epinephrine (Epi) may act as a cotransmitter in sympathetic nerves, stimulating presynaptic beta 2-receptors and enhancing norepinephrine (NE) release. To examine neuronal Epi release, patients with congestive heart failure and hypertension and healthy subjects were examined with the isotope-dilution method. At baseline, small cardiac and renal Epi spillovers were found in patients. During intense supine exercise, cardiac NE and Epi spillovers increased concomitantly with similar magnitude, whereas no renal Epi spillover could be detected. Blockade of neuronal uptake 1 caused a consistent decrease in both cardiac and renal fractional extractions of NE and Epi. The present study demonstrates baseline cardiorenal Epi release in patients with congestive heart failure and renal Epi release in hypertensive patients. Furthermore, Epi is removed by neuronal uptake in both the heart and kidney, and cardiac Epi spillover increases during exercise. This study, in contrast to other results, provides evidence for cardiac neuronal Epi release.

Adult↗
PubMed1997

Examination of intrarenal blood flow by Doppler ultrasound before and after extracorporeal shock wave lithotripsy for urolithiasis.

This study was aimed to test whether therapeutical extracorporeal shock wave lithotripsy (ESWL) may induce changes in renal parenchymatous blood flow, thereby indirectly indicating shock wave side effects on the renal parenchyma. In 18 patients, a Duplex ultrasound investigation of both kidneys was performed before and after ESWL. Pulsatility Index (PI), which is an estimation of renovascular resistance, increased in both treated and untreated kidney. However, the increase was confined to a subgroup of seven patients, who had received meperidine (a morphine analgetic) for analgesia. This increase is more likely to be due to a pharmacological effect of meperidine rather than a direct effect of ESWL on renal hemodynamics. In conclusion, we did not find any evidence of ESWL related affection of renal blood flow measured with duplex ultrasound, a technique sensitive enough to detect changes in renal hemodynamics due to morphine analgetics.

Adult↗
PubMed1997

VEGF and tPA co-expressed in malignant glioma.

Neovascularisation and migration of tumour cells are two features of highly malignant glioma. Vascular endothelial growth factor (VEGF) and tissue plasminogen activator (tPA) seem to be of importance in the process of malignancy. In the present study a topographical co-expression of tPA mRNA and VEGF mRNA (VEGF121 and VEGF165 isoforms) was demonstrated in the tumour edge of a rat malignant glioma, using in situ hybridisation. No signs of co-expression was seen in the normal brain tissue. In the normal brain the forms of VEGF mainly expressed were VEGF121, VEGF165, and VEGF189. Further studies are required to show whether VEGF and tPA are produced by the same tumour cells and to elucidate the role of this co-expression.

Animals↗
PubMed1996

'Theory of mind' in the brain. Evidence from a PET scan study of Asperger syndrome.

The ability to attribute mental states to others ('theory of mind') pervades normal social interaction and is impaired in autistic individuals. In a previous positron emission tomography scan study of normal volunteers, performing a 'theory of mind' task was associated with activity in left medial prefrontal cortex. We used the same paradigm in five patients with Asperger syndrome, a mild variant of autism with normal intellectual functioning. No task-related activity was found in this region, but normal activity was observed in immediately adjacent areas. This result suggests that a highly circumscribed region of left medial prefrontal cortex is a crucial component of the brain system that underlies the normal understanding of other minds.

Adult↗
PubMed1996

Membrane topology of Kch, a putative K+ channel from Escherichia coli.

We have mapped the topology of the C-terminal half of the putative potassium channel protein Kch in the inner membrane of Escherichia coli using PhoA fusions. Our results are consistent with the widely assumed six-transmembrane helix model for eukaryotic voltage-gated ion channels and place both ends of the proposed channel-lining P-segment on the periplasmic side of the inner membrane. The rather hydrophobic P-segment is found to translocate only slowly across the inner membrane and seems to be near a threshold for stop-transfer function.

Amino Acid Sequence↗
PubMed1996

Cloning and expression of human deoxyguanosine kinase cDNA.

A human cDNA sequence homologous to human deoxycytidine kinase (dCK; EC 2.7.1.74) was identified in the GenBank sequence data base. The longest open reading frame encoded a protein that was 48% identical to dCK at the amino acid level. The cDNA was expressed in Escherichia coli and shown to encode a protein with the same substrate specificity as described for the mitochondrial deoxyguanosine kinase (dGK; EC 2.7.1.113). The N terminus of the deduced amino acid sequence had properties characteristic for a mitochondrial translocation signal, and cleavage at a putative mitochondrial peptidase cleavage site would give a mature protein size of 28 kDa. Northern blot analysis determined the length of dGK mRNA to 1.3 kbp with no cross-hybridization to the 2.8-kbp dCK mRNA. dGK mRNA was detected in all tissues investigated with the highest expression levels in muscle, brain, liver, and lymphoid tissues. Alignment of the dGK and herpes simplex virus type 1 thymidine kinase amino acid sequences showed that five regions, including the substrate-binding pocket and the ATP-binding glycine loop, were also conserved in dGK. To our knowledge, this is the first report of a cloned mitochondrial nucleoside kinase and the first demonstration of a general sequence homology between two mammalian deoxyribonucleoside kinases. Our findings suggest that dCK and dGK are evolutionarily related, as well as related to the family of herpes virus thymidine kinases.

Base Sequence↗
PubMed1996

Determination of morphine, morphine-3-glucuronide and morphine-6-glucuronide in human serum by solid-phase extraction and liquid chromatography-mass spectrometry with electrospray ionisation.

A high-performance liquid chromatographic (HPLC) method for the simultaneous determination of morphine and two of its metabolites, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G), in serum is described. The compounds are extracted from serum using Sep-Pak light C18 solid-phase extraction cartridges, separated on an ODS C18 analytical column (100 x 4.6 mm I.D.) and detected by electrospray ionisation mass spectrometry. The separation was achieved by running a linear gradient from 4 to 70% acetonitrile with formic acid added as modifier. The flow-rate in the column was 1.0 ml/min. After the column, the eluate was subjected to a 1:50 split, with 20 microliters/min delivered to the mass spectrometer and 980 microliters/min delivered to waste. The compounds were detected in the mass spectrometer by selected-ion monitoring for m/z 286.2 for morphine and 462.2 for M3G and M6G. The spray voltage was 2.4 kV and the sampling cone was set at 40 V. The compounds have been quantified in serum over a concentration range of 2.9-60 nmol/l (0.84-17 ng/ml) for morphine, 11-1080 nmol/l (5.0-500 ng/ml) for M3G and 4.3-220 nmol/l (2.0-100 ng/ml) for M6G using external standardisation. Intra-assay and inter-assay precision were in the range of 2.4-9.0% for all compounds. The major advantage with the present LC-MS method was the shorter analysis time, 10 min per sample compared to 45 min per sample with our previous LC method with dual detectors. The LC-MS method has proved to have both the selectivity and sensitivity needed for pharmacokinetic studies.

Calibration↗
PubMed1996

Differential uptake of chloroquine by human keratinocytes and melanocytes in culture.

The antimalarial drug chloroquine has a high affinity for melanin and accumulates in melanin-rich compartments such as those of the eye. Chloroquine is also deposited in cutaneous tissue, but whether the drug distribution is restricted to melanin-producing cells of the skin is not known. In the present study, the uptake of chloroquine by normal human epidermal keratinocytes was compared with that by melanocytes. Selectively cultivated cells were incubated at drug concentrations ranging between 0 and 10000 ng/ml for periods of up to 48 h. Chloroquine was quantified in cells and medium using high performance liquid chromatography and fluorometric detection. In both types of cells there was a rapid uptake of chloroquine within the first 2 h, followed by a slower uptake for 2-6 h until a steady-state condition was reached. Dose dependency was linear, with no sign of saturation, and approximately ten times higher drug concentrations were attained in melanocytes as compared with keratinocytes. No formation of desethylchloroquine, the major systemic metabolite, was detected in either cell type. The observed affinity of chloroquine for normal epidermal melanocytes in vitro suggests that the density and melanogenic activity of skin pigment cells may influence the cutaneous drug disposition of chloroquine.

Adult↗
PubMed1996

Acute and chronic noradrenergic regulation of neurotrophin messenger RNA expression in rat hippocampus: evidence from lesions and organotypic cultures.

Noradrenergic neurons from the locus coeruleus innervate several brain regions, such as hippocampus and cortex. The hippocampus exhibits the highest concentration of the neurotrophins nerve growth factor, brain-derived neurotrophic factor and neurotrophin-3 in the brain. To study the role of the noradrenergic system in the chronic regulation of neurotrophin messenger RNA expression, chemical [N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine, 6-hydroxydopamine] and mechanical (knife-cut axotomy) lesions were performed, in the rat, and neurotrophin messenger RNAs analysed after 14 and 35 days. The intensity of the lesion was verified by characterization of the noradrenergic system using immunohistochemistry and in situ hybridization for dopamine-beta-hydroxylase and the measurement of noradrenaline tissue levels. To study the acute regulation, hippocampal organotypic slice cultures were prepared and neurotrophin messenger RNAs analysed after incubation in different concentrations of noradrenaline. We report that the noradrenergic N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine depletion significantly increased nerve growth factor and brain-derived neurotrophic factor messenger RNAs but not neurotrophin-3 messenger RNA in hippocampal areas 35 days after the lesion, while the knife-cut axotomy had a less pronounced effect and the 6-hydroxydopamine lesion did not change the neurotrophins. When incubating the organotypic hippocampal cultures with different concentrations of noradrenaline, nerve growth factor and brain-derived neurotrophic factor messenger RNAs but not neurotrophin-3 messenger RNA were significantly reduced in the dentate gyrus. We conclude that nerve growth factor and brain-derived neurotrophic factor but not neurotrophin-3 expression are inhibited by noradrenaline, arising from the locus coeruleus.

Animals↗
PubMed1996

Adverse effects of hyperoxemia during cardiopulmonary bypass.

OBJECTIVE: Aiming at elucidating the effects on capillary blood flow and tissue oxygenation of hyperoxemia during cardiopulmonary bypass, we studied skeletal muscle surface oxygen tensions in 10 patients undergoing elective cardiac operations. METHODS: In a prospective investigation each patient was exposed to normoxemia (arterial oxygen tension 75 to 115 mm Hg) and hyperoxemia (arterial oxygen tension > 185 mm Hg, inspired oxygen fraction = 1.00) during normal anesthetized conditions before and after cardiopulmonary bypass, as well as during normothermic and hypothermic continuous-flow bypass. In each state hemodynamic variables and arterial and mixed venous blood gas and acid base values were measured. From these data oxygen transport variables were calculated. Tissue oxygenation was studied with the use of a multiple-point polarographic oxygen microelectrode, known to provide measures of oxygen tensions at the capillary level. The oxygen distribution profile of such a sample is also indicative of capillary blood flow distribution changes. RESULTS: In all patients and at each occasion of the investigation markedly low mean surface oxygen tensions in skeletal muscle were registered. When hyperoxemia was instituted, a significant decrease in these surface oxygen tensions together with an increase in distribution heterogeneity was seen during all stages. Contrary to prebypass, postbypass, and hypothermic bypass, where vascular resistance, oxygen delivery, and oxygen consumption remained similar during hyperoxemia and normoxemia, a significant (p < 0.05) increase in vascular resistance together with a decline in oxygen consumption was seen during hyperoxemic normothermic (35 degrees to 36 degrees C) cardiopulmonary bypass. CONCLUSION: These findings show that the microcirculatory response to hyperoxemia, seen under other circumstances, persists during continuous-flow cardiopulmonary bypass, normothermic as well as hypothermic. If these adverse effects on tissue oxygenation by hyperoxemia can be further verified and shown to be valid for other organs than skeletal muscle, we would suggest that hyperoxemia should be avoided, especially during normothermic cardiopulmonary bypass.

Acid-Base Equilibrium↗