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Biomedical subjects

M Hermansson

Publications and source records attributed to M Hermansson.

At least 19 recordsLinked to original sources
PubMed2000

Formation of cytoplasmic turns between two closely spaced transmembrane helices during membrane protein integration into the ER membrane.

The helical hairpin, two closely spaced transmembrane helices separated by a short turn, is a recurring structural element in integral membrane proteins, and may serve as a compact unit that inserts into the membrane en bloc. Previously, we have determined the propensities of the 20 natural amino acids, when present in the middle of a long hydrophobic stretch, to induce the formation of a helical hairpin with a lumenally exposed turn during membrane protein assembly into the endoplasmic reticulum membrane. Here, we present results from a similar set of measurements, but with the turn placed on the cytoplasmic side of the membrane. We find that a significantly higher number of turn-promoting residues need to be present to induce a cytoplasmic turn compared to a lumenal turn, and that, in contrast to the lumenal turn, the positively charged residues Arg and Lys are the strongest turn-promoters in cytoplasmic turns. These results suggest that the process of turn formation between transmembrane helices is different for lumenal and cytoplasmic turns.

Amino Acid Sequence↗
PubMed1999

A turn propensity scale for transmembrane helices.

Using a model protein with a 40 residue hydrophobic transmembrane segment, we have measured the ability of all the 20 naturally occurring amino acids to form a tight turn when placed in the middle of the hydrophobic segment. Turn propensities in a transmembrane helix are found to be markedly different from those of globular proteins, and in most cases correlate closely with the hydrophobicity of the residue. The turn propensity scale may be used to improve current methods for membrane protein topology prediction.

Amino Acid Substitution↗
PubMed1999

Surgical approach and prognostic factors after peptic ulcer perforation.

OBJECTIVE: To find out which prognostic factors were important in predicting postoperative mortality and length of hospital stay in patients with perforated peptic ulcers. DESIGN: Retrospective study. SETTING: Teaching hospital, Lund, Sweden. SUBJECTS: 246 patients with perforated peptic ulcer who presented between January 1974 and December 1992. INTERVENTION: Cox proportional hazards analysis. MAIN OUTCOME MEASURES: Influence of age, sex, coexisting disease, duration of symptoms, site of perforation and operative technique on mortality and length of hospital stay. RESULTS: Age over 75 years (p = 0.002), coexisting cardiac or pulmonary disease (p = 0.02), perforation of the cardia or body of the stomach (p = 0.02), lapse of more than 12 hours between start of symptoms and operation (p = 0.006) and type of operation (p < 0.0001) had a significant influence on hospital mortality. Age over 75 years (p < 0.0001) and lapse of more than 12 hours between start of symptoms and operation (p = 0.03) significant influenced the likelihood of a prolonged stay in hospital. CONCLUSION: Patients with perforated peptic ulcers should be operated on as soon as possible. Simple closure is simple and safe with relatively low mortality and short stay in hospital.

Duodenal Ulcer↗
PubMed1999

Effect of ionic strength on initial interactions of Escherichia coli with surfaces, studied on-line by a novel quartz crystal microbalance technique.

A novel quartz crystal microbalance (QCM) technique was used to study the adhesion of nonfimbriated and fimbriated Escherichia coli mutant strains to hydrophilic and hydrophobic surfaces at different ionic strengths. This technique enabled us to measure both frequency shifts (Deltaf), i.e., the increase in mass on the surface, and dissipation shifts (DeltaD), i.e., the viscoelastic energy losses on the surface. Changes in the parameters measured by the extended QCM technique reflect the dynamic character of the adhesion process. We were able to show clear differences in the viscoelastic behavior of fimbriated and nonfimbriated cells attached to surfaces. The interactions between bacterial cells and quartz crystal surfaces at various ionic strengths followed different trends, depending on the cell surface structures in direct contact with the surface. While Deltaf and DeltaD per attached cell increased for nonfimbriated cells with increasing ionic strengths (particularly on hydrophobic surfaces), the adhesion of the fimbriated strain caused only low-level frequency and dissipation shifts on both kinds of surfaces at all ionic strengths tested. We propose that nonfimbriated cells may get better contact with increasing ionic strengths due to an increased area of contact between the cell and the surface, whereas fimbriated cells seem to have a flexible contact with the surface at all ionic strengths tested. The area of contact between fimbriated cells and the surface does not increase with increasing ionic strengths, but on hydrophobic surfaces each contact point seems to contribute relatively more to the total energy loss. Independent of ionic strength, attached cells undergo time-dependent interactions with the surface leading to increased contact area and viscoelastic losses per cell, which may be due to the establishment of a more intimate contact between the cell and the surface. Hence, the extended QCM technique provides new qualitative information about the direct contact of bacterial cells to surfaces and the adhesion mechanisms involved.

Bacterial Adhesion↗
PubMed1998

In Situ Detection of High Levels of Horizontal Plasmid Transfer in Marine Bacterial Communities.

Gene transfer of the conjugative plasmid pBF1 from Pseudomonas putida to indigenous bacteria in seawater was investigated with a detection system for gene transfer based on the green fluorescent protein (GFP) (C. Dahlberg et al., Mol. Biol. Evol. 15:385-390, 1998). pBF1 was tagged with the gfp gene controlled by a lac promoter which is down regulated in the donor cell by a chromosomal repressor (lacIq). The plasmid donor cells (Pseudomonas putida KT2442) subsequently do not express gfp. Transfer to recipient strains lacking the repressor results in expression of gfp. The transconjugant can subsequently be detected by epifluorescence microscopy on a single-cell level. By using this method, transfer of pBF1::gfp and expression of the gfp gene were first shown to occur during nutrient-limiting conditions to several defined recipient bacteria in artificial seawater. Second, we measured transfer of pBF1 from P. putida to the marine bacterial community directly in seawater samples, on a single-cell level, without limiting the detection of gene transfer to the culturable fraction of bacteria. Plasmid transfer was detected on surfaces and in bulk seawater. Seawater bacteria with different morphologies were shown to receive the plasmid. Gene transfer frequencies of 2.3 x 10(-6) to 2.2 x 10(-4) transconjugants per recipient were recorded after 3 days of incubation.

Journal Article↗
PubMed1998

A FISH cosmid 'cocktail' for detection of 13q deletions in chronic lymphocytic leukaemia--comparison with cytogenetics and Southern hybridization.

The most frequent structural chromosome abnormality in chronic lymphocytic leukaemia (CLL) is deletion at chromosome 13q14. Studies with Southern blot hybridisation have revealed deletions in the region located telomeric of the retinoblastoma gene in more than 40% of cases. The highest frequency of homozygous deletions has been found at the D13S319 locus and it is likely that a new tumour suppressor gene is located close to this region. We have analysed deletions in the D13S319 region in 20 selected CLL patients using conventional cytogenetic analysis, fluorescence in situ hybridisation (FISH) and Southern blot hybridisation. FISH and Southern hybridisation are equally efficient in detecting deleted clones in our study. However, FISH analysis indicate that subclones with different numbers of alleles in the D13S319 region can exist simultaneously. The cytogenetic analyses confirm that clones with different chromosomal abnormalities can occur in patients with CLL and that 13q14 deletions can be limited to one of these subclones. Furthermore, the FISH analyses show that trisomy 12 and deletion of 13q14 can occur in the same cell clone. Finally, our study confirms that mitogen stimulation of peripheral blood cells from CLL patients before FISH analysis may result in a sharp increase in normal appearing cells, which can hide leukaemic clones with deletions in the D13S319 region.

Blotting, Southern↗
PubMed1998

Growth hormone treatment prevents the decrease in insulin-like growth factor I gene expression in patients undergoing abdominal surgery.

Acquired GH resistance together with reduced skeletal muscle mass are found in patients with increased protein catabolism due, for example, to sepsis, trauma, or major surgery. Both administration of glutamine-containing parenteral nutrition and GH treatment have been found to diminish this catabolism. The effects of GH are mediated in part by insulin-like growth factor I (IGF-I) that is produced in the liver and locally in GH target tissues. The aim of this study was to investigate the effect of GH treatment on expression of the IGF-I gene and GH receptor (GHR) gene in skeletal muscle after major surgery. A new quantitative RT-PCR-based assay was established to measure IGF-I gene expression. Metabolically healthy patients, without significant preoperative weight loss, who were undergoing elective abdominal surgery were included in the study. Five patients (one woman and four men) were treated with daily injections of GH (0.3 IU/kg.day) in addition to being given total parenteral nutrition including glutamine (0.28 g/kg.day). The control group consisted of eight patients (three women and five men), who were given glutamine-enriched total parenteral nutrition but no GH. A muscle biopsy was taken from the lateral portion of the quadriceps femoris muscle preoperatively (day 0) after induction of anesthesia. A second biopsy was taken under local anesthesia on postoperative day 3. Total ribonucleic acid (RNA) was extracted from the muscle biopsies, and IGF-I messenger RNA (mRNA) and GHR mRNA were measured by competitive quantitative RT-PCR assays. IGF-I mRNA and GHR mRNA levels were related to the expression of a housekeeping gene (cyclophilin). In the control group, IGF-I mRNA levels decreased from 1505 +/- 265 (mean +/- SEM) transcripts/cpm cyclophilin on day 0 to 828 +/- 172 on day 3 (P < 0.05). In contrast, IGF-I mRNA levels did not change in the GH-treated group (1188 +/- 400 transcripts/cpm cyclophilin on day 0 vs. 1089 +/- 342 transcripts/cpm cyclophilin on day 3). No statistically significant changes were seen in GHR expression. We conclude that administration of GH prevents the reduction in IGF-I gene expression in skeletal muscle after abdominal surgery.

Abdomen↗
PubMed1997

Determination of bacterial cell surface hydrophobicity of single cells in cultures and in wastewater in situ.

Bacterial cell surface hydrophobicity is one of the most important factors that influence bacterial adhesion. A new method microsphere adhesion to cells, for measuring bacterial cell surface hydrophobicity was developed. Microsphere adhesion to cells is based on microscopic enumeration of hydrophobic, fluorescent microspheres attaching to the bacterial surface. Cell surface hydrophobicity estimated by microsphere adhesion to cells correlates well with adhesion of bacteria to hydrocarbons or hydrophobic interaction chromatography for a set of hydrophilic and hydrophobic bacteria (linear correlation coefficients, R2, were 0.845 and 0.981 respectively). We also used microsphere adhesion to cells to investigate the in situ properties of individual free-living bacteria directly in activated sludge. Results showed that the majority of the bacteria were hydrophilic, indicating the importance of cell surface hydrophobicity for bacterial adhesion in sludge, and for the overall success of the wastewater treatment process.

Bacterial Adhesion↗
PubMed1997

Conjugative plasmids isolated from bacteria in marine environments show various degrees of homology to each other and are not closely related to well-characterized plasmids.

Mercury resistance plasmids were exogenously isolated, i.e., recovered after transfer to a model recipient bacterium, from marine air-water interface, bulk water, and biofilm communities during incubation in artificial seawater without added nutrients. Ninety-five plasmids from different environments were classified by restriction endonuclease digestion, and 12 different structural plasmid groups were revealed. The plasmid types isolated from different habitats and from different sampling occasions showed little similarity to each other based on their restriction endonuclease patterns, indicating high variation and possibly a low transfer between microhabitats and/or a different composition of the microbial communities at different sites and times. With another approach in which probes derived from one of the isolated plasmids and a mercury resistance (mer) probe from Tn501 were used, similarities between plasmids from several different groups were found. The plasmids were further tested for their incompatibility by use of the collection of inc/rep probes (B/O, com9, FI, FII, HI1, HI2, I1, L/M, N, P, Q, U, W, Y) described by Couturier et al. (M. F. Couturier, P. Bex, L. Bergquist, and W. K. Maas, Microbiol. Rev. 52:375-395, 1988). Hybridizations did not reveal any identity between the 12 plasmid groups and any of the inc/rep probes tested. The results indicate that plasmids isolated from different marine habitats have replication and/or incompatibility systems that are different from the well-characterized plasmids that are commonly used in plasmid biology. This shows the need for the use of more relevant plasmids in studies of plasmid activity in the environment and development of new inc/rep probes for their characterization.

Bacteria↗
PubMed1997

Measurement of human growth hormone receptor messenger ribonucleic acid by a quantitative polymerase chain reaction-based assay: demonstration of reduced expression after elective surgery.

Studies of GH receptor (GHR) gene expression in human tissues have been hampered by the limited amount of tissue available for analysis and the low sensitivity of conventional methods. We have developed a quantitative reverse transcriptase-PCR assay for measurement of GHR messenger ribonucleic acid levels in small human tissue biopsies. To compensate for sample to sample variation, an internal RNA standard, which differs from the wild-type GHR transcript by only a few nucleotides, was reverse transcribed and amplified together with the GHR transcripts. PCR was carried out using one biotinylated primer to permit the purification of single stranded PCR products on streptavidin-coated microtiter plates. The ratio between the wild-type and mutated transcripts was determined by two separate minisequence reactions in which a primer, annealed immediately 3' of a variable nucleotide, was extended by a single 3H-labeled nucleotide, complementary to either the wild-type or mutated sequence. The assay range was 0.125-8 x 10(5) transcripts/sample, the mean intraassay coefficient of variation was 8.7%, and the lower limit of detection was 0.125 x 10(5) transcripts/sample. GHR messenger ribonucleic acid levels were detectable in small amounts (10-100 ng) of total RNA extracted from adipose tissue, skeletal muscle, and liver. The GHR gene expression in liver was approximately 10-fold higher than that in skeletal muscle, whereas intermediate levels were found in adipose tissue. In nine patients undergoing elective abdominal surgery, GHR gene expression in skeletal muscle was reduced on day 3 after surgery compared to the baseline level. The decrease in GHR gene expression was accompanied by a decrease in skeletal muscle glutamine. This suggests that the postoperative protein catabolism may be caused at least partly by acquired GH insensitivity due to reduced expression of the GHR gene.

Abdomen↗
PubMed1997

Peptic ulcer perforation before and after the introduction of H2-receptor blockers and proton pump inhibitors.

BACKGROUND: The aim of this retrospective study was to compare patients treated for perforated peptic ulcer before and after the introduction of the H2-receptor antagonists and proton pump inhibitors (PPI) with regard to their medical history, clinical features, methods of diagnosis and treatment, complications, and mortality. METHODS AND RESULTS: During the study period 1974 to 1992 we found a significant reduction in the incidence of peptic ulcer perforation (P < 0.001). Patients admitted during the later period of the study were older and more seriously ill. The incidence of perforation among men decreased, but that among women was stable, thus changing the sex ratio towards a female preponderance at the end of the study period. After the introduction of PPI the relative number of gastric perforations decreased compared with the number of perforations in the duodenum. A relatively higher proportion of patients with gastric perforations was taking acetylsalicylic acid or non-steroid, anti-inflammatory drugs at the time of admission compared with patients with duodenal perforation. Simple suture of the perforation was the operative procedure used in 80% of the patients. CONCLUSIONS: Even though patients were increasingly older and more ill, neither the mortality nor the rate of postoperative complications changed during the study period.

Age Factors↗
PubMed1995

Abundance of Tn3, Tn21, and Tn501 transposase (tnpA) sequences in bacterial community DNA from marine environments.

The occurrence of the tnpA genes of the transposons Tn3, Tn21, and Tn501 was assessed in total bacterial community DNA isolated from different marine environments. The PCR technique was employed, together with most probable number statistics, to determine the abundance of the target tnpA genes. All three genes could be detected, and the Tn21 tnpA sequences predominated in all samples. The smallest amount of total community DNA in which the Tn21 tnpA sequence could be detected was 0.037 ng, and on the basis of our results, we estimated that this sequence was present in 1 of 1,000 to 10,000 bacteria. Hybridization of the PCR products with the respective tnpA probes verified the Tn21 and Tn501 tnpA sequences but only some of the Tn3 tnpA amplification products. The distribution and dissemination of transposons in natural bacterial communities are discussed.

Bacteria↗
PubMed1990

Expression of PDGF beta-receptors in human meningioma cells.

Meningioma is a generally benign tumor derived from arachnoid tissue. We have investigated the presence of functionally active PDGF-receptors on human meningioma cells in culture. Tumor samples were obtained from 3 surgically removed benign meningiomas and normal arachnoid tissue from an autopsy case. Binding studies were performed by using 125I-labelled recombinant PDGF-AA and PDGF-BB. Only 125I-PDGF-BB showed specific binding to all tumor-cell cultures after incubation of cells for 2 hr at 4 degrees C. Effects of PDGF-AA and PDGF-BB on DNA synthesis were measured as 3H-thymidine incorporation during 48 hr of labelling cells maintained in Eagle's minimum essential medium 0.5% fetal calf serum. PDGF-BB but not PDGF-AA stimulated DNA synthesis in all 3 tumor-cell cultures. Total cellular RNA was analyzed by Northern blotting and hybridization with a 32P-labelled human PDGF beta-receptor probe, and PDGF beta-receptor mRNA was found in both tumor and arachnoid cell cultures. Furthermore, PDGF beta-receptor mRNA was shown to be present in 2 meningioma biopsies and immunohistochemical staining revealed that PDGF beta-receptors are present in meningioma and arachnoid tissues in vivo. It appears that a possible way of maintaining human meningioma cell growth in vivo is through activation of PDGF beta-receptors.

Adult↗
PubMed1989

Rat brain capillary endothelial cells express functional PDGF B-type receptors.

Immunohistochemical staining revealed the presence of platelet-derived growth factor (PDGF) B-type receptors on capillaries of normal rat brain. Furthermore, capillary endothelial cells isolated from rat brain and grown in tissue culture bound [125I]PDGF-BB but not [125I]PDGF-AA, suggesting that they expressed B-type, but not A-type, PDGF receptors. PDGF-BB and PDGF-AB, but not PDGF-AA, also stimulated incorporation of [3H]thymidine into these cells. Thus, rat brain capillary endothelial cells have functional B-type receptors, and thereby differ from endothelial cells derived from large blood vessels, that do not express PDGF receptors. Our data suggest a possible role for PDGF-BB as an angiogenic factor.

Angiogenesis Inducing Agents↗
PubMed1988

Endothelial cell hyperplasia in human glioblastoma: coexpression of mRNA for platelet-derived growth factor (PDGF) B chain and PDGF receptor suggests autocrine growth stimulation.

The genes for platelet-derived growth factor (PDGF) A chain, B chain/c-sis, and the PDGF receptor are expressed in human malignant glioma cell lines. In the present investigation we have studied the expression of these genes in biopsy specimens from human glioblastomas. Hyperplasia of the vascular endothelium is a prominent characteristic of human glioblastoma multiforme and simian sarcoma virus-induced gliomas in primates. RNA transfer blot analysis of biopsies from glioblastoma multiforme showed transcripts for PDGF A and B chains and the PDGF receptor. Tissue sections from this tumor examined by in situ hybridization techniques revealed that the proliferating vascular endothelial cells contained large quantities of mRNA for PDGF B chain/c-sis and its receptor and, to a lesser extent, for PDGF A chain. In contrast, the tumor cells expressed more mRNA for PDGF A chain than for PDGF B chain and PDGF receptor. The latter two were also expressed at higher levels in glioma cells than in glial cells of nontumorous human brain tissue. Thus, an autocrine stimulation by the PDGF B chain/c-sis product via its receptor, evoked by interaction with surrounding glioma cells, could be the mechanism behind the pathological proliferation of endothelial cells characteristically found in this type of malignancy.

Animals↗
PubMed1987

Frequency of antibiotic and heavy metal resistance, pigmentation, and plasmids in bacteria of the marine air-water interface.

A field investigation of marine coastal waters revealed that the frequency of pigmented bacteria and the occurrence of bacterial antibiotic resistance were higher at the air-water interface than in the bulk water. The differences in the frequency of pigmented colonies at the surface and in the bulk-water samples could not be explained by the degree of cell surface hydrophobicity or by bacterial adhesion to air-water interfaces. Pigmented strains exhibited a higher degree of multiple drug resistance than did nonpigmented strains. However, the frequency of multiple drug resistance in nonpigmented strains was also substantial. An average of 91% of all strains were resistant to more than one antibiotic, and 21% of the bacteria isolated were resistant to five of the eight antibiotics tested. High numbers of plasmid-carrying strains were found among selected surface isolates, but the presence of detectable plasmids could not be correlated with either pigmentation or multiple drug resistance. Furthermore, selected surface isolates were significantly more resistant to mercury than were bulk-water bacteria. The higher frequency of pigmented, antibiotic-resistant, and mercury resistant strains at the air-water interface than in the bulk water are discussed in terms of various forms of selective pressure and genetic exchange at the surface.

Anti-Bacterial Agents↗