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Biomedical subjects

M Bergman

Publications and source records attributed to M Bergman.

At least 55 records · Page 3Linked to original sources
PubMed1998

Effect of sodium thiopentone anesthesia on the phagocytic activity of rat peritoneal macrophages.

To elucidate the effect of sodium thiopentone anesthesia on the function of phagocytic cells, albino rats were anesthetized with 60 mg/kg. of sodium thiopentone. After 90 min., peritoneal macrophages were harvested and their capacity for superoxide anion generation was detected. Following anesthesia for 90 min. latex particles were injected intraperitoneally, and after additional 30 min. the macrophages were derived, embedded in agar and the number of cells engaged in phagocytosis, as well as the number of latex particles engulfed by each individual cell were counted in semi-thick sections. Macrophages of anesthetized animals showed a statistically significant decrease of both superoxide anion generation and mean number of phagocytic cells, and engulfed fewer particles than those of the controls. Similar results were obtained following incubation of the cells with sodium thiopentone in vitro. The serum corticosterone level in anesthetized rats was significantly higher than that of the control animals. The results indicate that impaired phagocytosis following anesthesia induced by sodium thiopentone, in addition to alterations of the immune system caused by surgical trauma, may be one of the reasons for increased susceptibility to infections of surgical patients during the postoperative period.

Anesthesia↗
PubMed1998

Effect of three days starvation on the phagocytic activity of rat peritoneal macrophages.

To examine the effect of starvation on the phagocytic activity of rat peritoneal macrophages, 8 animals were kept for 3 days on water supply only. The cells showed an increased capacity for superoxide anion production and a marked decrease in their ability to engulf latex particles. The corticosterone level of the fasting animals was markedly increased, an observation suggesting that the alteration of macrophage function could be hormonally mediated. The findings in the present study indicate that the decreased phagocytic capacity of peritoneal macrophages following starvation may be one of the factors responsible for the increased susceptibility to infections in malnourished individuals.

Animals↗
PubMed1997

Identification of csk tyrosine phosphorylation sites and a tyrosine residue important for kinase domain structure.

The lack of a conserved tyrosine autophosphorylation site is a unique feature of the C-terminal Src-kinase, Csk, although this protein tyrosine kinase can be autophosphorylated on tyrosine residues in vitro and in bacteria. Here we show that human Csk is tyrosine phosphorylated in HeLa cells treated with sodium pervanadate. Phosphorylation in vivo occurs mainly at Tyr-184 and in vitro mainly at Tyr-304. A Y304F mutation strongly decreased Csk phosphorylation in vitro, and a Y184F mutation abolished tyrosine phosphorylation in vivo. A catalytically inactive form of Csk was also phosphorylated on Tyr-184 in vivo, suggesting that this is not a site of autophosphorylation. The kinase activity of the Y184F protein was not changed, while the Y304F protein showed one-third of wild-type activity. Three-dimensional modelling of the Csk kinase domain indicated that the Y304F mutation abolishes one of two conserved hydrogen bonds between the upper and the lower lobes in the open conformation of the kinase domain. Phosphopeptide binding studies suggested that phosphorylation of Tyr-184 creates a binding site for low-molecular-mass proteins. Cellular Csk was associated with several phosphoproteins, some of which were interacting with the Csk SH2 domain. Taken together these results indicate that Csk can be phosphorylated in vivo at Tyr-184 by an as yet unknown tyrosine kinase, and that autophosphorylation of Tyr-304 occurs only at abnormally high Csk concentrations in vitro. Furthermore, Tyr-304 is required for the maintenance of the structure of the Csk kinase domain.

CSK Tyrosine-Protein Kinase↗
PubMed1997

Multisensory speech perception of young children with profound hearing loss.

The contribution of a two-channel vibrotactile aid (Trill VTA 2/3, AVR Communications LTD) to the audiovisual perception of speech was evaluated in four young children with profound hearing loss using words and speech pattern contrasts. An intensive, hierarchical, and systematic training program was provided. The results show that the addition of the tactile (T) modality to the auditory and visual (A+V) modalities enhanced speech perception performance significantly on all tests. Specifically, at the end of the training sessions, the tactile supplementation increased word recognition scores in a 44-word, closed-set task by 12 percentage points; detection of consonant in final position by 50 percentage points; detection of sibilant in final position by 30 percentage points; and detection of voicing in final position by 25 percentage points. Significant learning over time was evident for all test materials, in all modalities. As expected, fastest learning (i.e., smallest time constants) was found for the AVT condition. The results of this study provide further evidence that sensory information provided by the tactile modality can enhance speech perception in young children.

Child, Preschool↗
PubMed1997

Do drug costs affect physicians' prescription decisions?

OBJECTIVE: To study the impact of the cost of pharmaceuticals on physicians' decisions about drug prescription. DESIGN: A simulation protocol for the treatment of two patients, one with mild and the other with a severe form of urinary tract infection (UTI), was designed. Thirty family physicians in outpatient clinics and 30 physicians in the internal medicine wards of a Community Hospital participated in the project. They had to prescribe treatment for the patients twice: at phase I, when the drug cost was unknown, and at phase II, after 2 months, when the price of the drugs was brought to their attention. The physicians selected the medication from a list of drugs commonly used for the treatment of UTIs. RESULTS: Analysis of the findings indicates that an awareness of drug costs affects prescription decisions among physicians in hospital wards, whereas family physicians showed a preference for less expensive drugs even before they were informed about drug costs. An extrapolation of the results shows that knowledge about the cost of the drugs usually administered for treatment of UTI, could save at least IS 112,883 ($34,207) a month to Kupat Holim Klalit (KHK) the health insurance institution to which the outpatient clinics and the hospital belong. CONCLUSIONS: When economic aspects of healthcare are considered, information on drug costs may be an important factor in physicians' decision-making processes and for saving pharmaceutical expenses.

Anti-Bacterial Agents↗
PubMed1997

Comparison of induced and independent major depressive disorders in 2,945 alcoholics.

OBJECTIVE: Depressive episodes among alcohol-dependent men and women are heterogeneous in causation and clinical course. This study tested three hypotheses regarding the rates and clinical characteristics of two potential subtypes of these affective states: those that appear to be substance-induced mood disorders and those that are independent major depressive episodes. METHOD: Semistructured, detailed interviews were administered to 2,945 alcohol-dependent subjects as part of the Collaborative Study on the Genetics of Alcoholism. With the use of a time line method for determining the type of mood disorder among probands, relatives, and comparison subjects, individuals with histories of the two types of mood disorders were compared. RESULTS: Major depressive episodes with an onset before the development of alcohol dependence or during a subsequent long abstinence period (i.e., independent depressions) were observed in 15.2% of the alcoholics, while 26.4% reported at least one substance-induced depressive episode. According to a logistic regression analysis, the subjects with independent (as compared to substance-induced) major depressive episodes were more likely to be married, Caucasian, and female, to have had experience with fewer drugs and less treatment for alcoholism, to have attempted suicide, and, on the basis of personal interviews with family members, to have a close relative with a major mood disorder. CONCLUSIONS: These results support the contention that it is possible to differentiate between what appear to be substance-induced and independent depressive episodes in alcoholics. Such differentiation might be important for establishing prognosis and optimal treatment.

Adult↗
PubMed1997

Connections between polarization curves and log(a[i]/a[ref])-pe diagram.

When reading papers concerning studies of corrosion of dental amalgam and its phases by means of polarization curves, one often finds it difficult to understand the reasons for the chemical reactions proposed from the form of the polarization curve. Thermodynamic data represented in the form of log(a[i]/a[ref])-pe diagrams, i.e., the logarithm of the activity of a metal or an alloy with reference to the activity of the corresponding metal ion, as a function of pe (a recalculated form of the potential), make it possible for one to determine which chemical reactions can occur on the specimen surface or in the solution within the potential difference used in the polarization experiment and to decide which of these reactions is the most probable. The hypothesis examined in this study is that a log(a[i]/a[ref])-pe diagram can be used in the interpretation of polarization curves. Potentiodynamic polarization curves and log(a[i]/a[ref])-pe diagrams were compared for the corrosion of Ag, Hg, and gamma 1 with and without Sn. It was found that there was a connection between the polarization curves and the log(a[i]/a[ref])-pe diagrams. From the composition of the specimens and the solution and by means of thermodynamic data, pe values for solid corrosion products and relative concentrations of soluble complexes at these pe values were obtained independently of the polarization curves. A much more reliable value for the nobility of metals and alloys was attained by use of the log(a[i]/a[ref])-pe diagrams than by use of the potential of the starting point of the polarization curves. It was found that pe corresponding to the potential of the starting point of the polarization curves in de-aerated synthetic saliva was obtained about two pe units before pe of the most insoluble solid compound formed on the specimen surface or in the solution.

Corrosion↗
PubMed1997

The tradeoffs of successful simulation.

This presentation will discuss the decision process we followed to develop an ultrasound simulator. The development of an advanced technology medical device always requires tradeoffs and compromises between what is desired, and what can be realistically achieved. The medical applications of computer based education are increasingly important to the process of medical education. Product developers will be required to address these concerns. Some tradeoffs result from technical, scientific, and engineering factors; while others are the result of marketing, financial, or competitive constraints. All of these factors will influence the design and production of simulation tools. A manager, scientist, or engineer who is involved in development of this kind of innovative product may be helped by considering the impact of some of these decisions earlier in the process. Forewarned is fore-armed. The most basic design issue we faced was the conflict between the requirements we envisioned for the ultrasound simulator, and the limitations of realistic simulation. Our goal was to achieve a product which would be affordable to the academic institutions who would be using it. Simulation will be defined and presented with examples from our experience.

Biomedical Engineering↗
PubMed1997

In vitro and in vivo effects of beta-carotene on rat epidermal lipoxygenases.

The in vitro and in vivo interaction between beta-carotene (BC) and lipoxygenase (LOX) was studied in rat skin. Significant in vitro inhibitory effects of BC on epidermal LOX activity were observed with both linoleic acid or arachidonic acid as substrate. Lineweaver-Burk plots for the inhibition of epidermal purified LOX indicated mixed competitive/non-competitive inhibition. In vivo effects of BC were examined in an ultraviolet A (UVA) irradiation model. Following UVA irradiation (200 Kjoule/m2) significant increases in LOX activity and malondialdehyde (MDA) values were found, whereas catalase activity was significantly decreased. Topical pretreatment of skin with BC prevented increases in LOX activity and MDA values 4 hr post-irradiation. Catalase activity was not affected by BC treatment. BC was more effective at preventing UVA induced lipid peroxidation at low then at high concentrations. Our present results indicate the protective potential of BC on in vivo UVA induced skin damage by reduction of non-enzymatic and enzymatic lipid peroxidation.

Animals↗
PubMed1996

Metal-ceramic bond strength.

No currently available bond test for dental metal ceramic systems has yet gained general acceptance. Such a bond test cannot be established without careful analysis of the stress distribution within the adherence region. The objective of the present study was to establish a mechanical shear stress test and combine the results with a finite element stress analysis of an idealized crown to enable comparisons of different metal-ceramic systems. The titanium-ceramic systems tested, both machined and cast titanium, showed higher shear strength values than the high gold-ceramic system used as a reference. Since the latter system has been used successfully in the clinic for many years, it seems reasonable to assume that the bond strength of titanium-ceramic systems is quite satisfactory for dental crown-and-bridge work. In conclusion, the interfacial bond strength test proposed in the present study should be applicable to all of the currently known material combinations in which a brittle fracture might be expected to occur.

Ceramics↗
PubMed1996

Cardiomyocytes in culture--a model to study the cellular actions of amiodarone.

The extensive use of amiodarone as an anti-arrhythmic drug is hampered by numerous side effects and by insufficient knowledge of its cellular action. The use of cell cultures for studying the mechanism of amiodarone action has been questioned, since available information has indicated that the doses employed for the experiments induce cell damage. We have defined conditions to obtain the amiodarone effect on cardiac cells in culture with no detectable damage. Amiodarone, 1 microg/ml, a concentration comparable to serum levels of the drug in acute and chronically treated humans and rats, reduces cell contractions, modifies membrane electrical properties accordingly, increases ATP content, but does not alter cell substructure or change enzyme activities. We strongly support the use of cell cultures for studying the cellular action(s) of amiodarone and offer conditions suitable for such experiments.

Adenosine Triphosphate↗
PubMed1995

Interactions between the tyrosine kinases p56lck, p59fyn and p50csk in CD4 signaling in T cells.

Interaction of the CD4 co-receptor with major histocompatibility complex (MHC) class II molecules during antigen presentation results in enhancement of antigen receptor signaling. The synergism between the two receptors is believed to result from the juxtaposition of the CD4-associated tyrosine kinase p56lck with the cytoplasmic domains of CD3 complex components. Here, we report that cross-linking of CD4 on the surface of Jurkat cells using monoclonal antibodies results in activation of the CD3-associated kinase p59fyn. Co-cross-linking of CD4 and CD3 results in synergistic activation of p59fyn. The p59fyn kinase is also hyperactive in a Jurkat cell line stably transfected with a constitutively active p56lck mutant, indicating that p56lck mediates CD4 activation of p59fyn. In support of this hypothesis, expression of a dominant inhibitory mutant of p59fyn blocks CD4 signals involved in gene activation. In addition, the p59fyn dominant inhibitor mutant blocks gene-activating signals induced by expression of a constitutively active mutant of p56lck. Overexpression of the regulatory kinase p50csk, which attenuates TcR signaling by inactivation of p59fyn, inhibits signaling from the constitutively active form of p56lck. Taken together, these data suggest that CD4/p56lck enhancement of TcR signaling is, at least in part, mediated by activation of p59fyn, and may be regulated by p50csk.

CD4 Antigens↗
PubMed1995

Effects of amiodarone on beating rate and Na-K-ATPase activity in cultured neonatal rat heart myocytes.

1. The purpose of this study was to examine the possibility that the cellular action of amiodarone is mediated by inhibition of thyroid hormone regulatory functions within the myocardial cell. We measured the rate of cell beating and the activity of Na-K-ATPase in cultured neonatal rat heart myocytes. 2. Amiodarone (0.25 and 1 microgram/ml) reduced beating rate up to 75% within 20 min, and Na-K-ATPase activity up to 40% within 2 hr. No toxic effects were detected in the treated cells. 3. The inhibitory actions of amiodarone on beating rate and Na-K-ATPase activity were the same in myocytes grown in the presence or absence of 3-iodothyronine (T3, 5 nM). 4. These data indicate that amiodarone affects beating rate and Na-K-ATPase activity independently of thyroid hormone. It is suggested that interference of amiodarone with thyroid hormone action is not the only mechanism by which this drug modulates some functions of the myocardial cell.

Amiodarone↗
PubMed1995

The use of combination internal fixation and hybrid external fixation in severe proximal tibia fractures.

Forty-eight patients with 50 severe fractures of the proximal tibia were followed prospectively for 2-4 years (mean 2.7 years) to evaluate the use of limited internal fixation combined with external fixation in the treatment of these injuries. There were 27 men and 21 women ranging in age from 20 to 74 years. Fractures were classified according to the A0 system (Mast J, Ganz R, Jacob R: Planning and reduction technique in fracture surgery. Berlin, Springer-Verlag, 1989), which included 5 A3, 6 C1, 16 C2, and 23 C3 fractures. All patients in this series healed; 48 fractures healed in an average of 12 weeks without subsequent surgery. There were two (4%) nonunions requiring bone graft. The average hospital special surgery knee score was 90 (68-100). Grading criteria for anatomical outcome revealed there were 17 (34%) excellent results, 24 (48%) good results, 6 (12%) fair results, and 3 (6%) poor results. In conclusion, this treatment method is associated with a high percentage of good and excellent results. Combined internal and external fixation combines the advantages of anatomic, stable fixation with less soft-tissue dissection and eliminates the need for large implants.

Adult↗
PubMed1995

Overexpressed Csk tyrosine kinase is localized in focal adhesions, causes reorganization of alpha v beta 5 integrin, and interferes with HeLa cell spreading.

The C-terminal Src kinase p50csk phosphorylates Src family tyrosine kinases and down-regulates their activity in vitro. To gain insight into the cellular functions of this potentially antioncogenic enzyme, we have overexpressed the csk cDNA by using an inducible promoter in HeLa cells. Despite some differences in basal Src activity in the clones analyzed, Src activity was not significantly suppressed, while the amount of p50csk and Csk activity increased at least 10-fold during 3 days of induction. Immunofluorescence for the induced p50csk was localized in the cytoplasm and distinctly in focal adhesions, in which the amount of phosphotyrosine containing proteins was also increased. Point and deletion mutagenesis experiments showed that localization in focal adhesions was dependent on the SH2 and SH3 domains of Csk but not on its catalytic activity. Csk formed a complex with the focal adhesion protein paxillin in cells, and its SH2 domain was shown to interact with pp125FAK and paxillin in vitro. After Csk induction, the cells became spherical and more loosely attached to the culture substratum, and the alpha v beta 5 integrin complex (vitronectin receptor) of focal adhesions was redistributed to a novel type of structure consisting of punctate plaques on the ventral cell surface. These phenotypic changes occurred in several clones analyzed and were totally reversible when Csk was switched off, but they did not occur in cells overexpressing the catalytically inactive Csk R-222 mutant or luciferase. Our results thus show that a fraction of cellular Csk is targeted to focal adhesions via its SH2 and SH3 domains, probably interacting with tyrosyl-phosphorylated focal adhesion proteins. They also suggest that Csk is involved in the regulation of integrins controlling cell attachment and shape.

CSK Tyrosine-Protein Kinase↗
PubMed1995

The dentist's exposure to elemental mercury vapor during clinical work with amalgam.

Continuous measurements of mercury vapor in the breathing zone of the dentist were made under ordinary clinical conditions. Fifty old amalgam fillings were removed and replaced by new ones. The mercury vapor measurements were performed by means of atomic absorption spectrophotometry. On the basis of the type of suction device used, the measurements were divided into seven groups, each of which consisted of a series of measurements. During the cutting, filling, and polishing operations the mean mercury vapor levels in the breathing zone of the dentist were in the range of 1-2 micrograms Hg m-3 air when proper mercury hygiene measures were taken. This is far below the currently valid threshold limit value (30 micrograms Hg m-3 air) in Sweden. The saliva extractor and the dental mirror-evacuator did not influence the mercury vapor levels when used together with the high-volume evacuator. However, when only a saliva extractor was used, the cutting of amalgam fillings caused highly fluctuating mercury vapor levels, which were 2-15 times higher than the threshold limit value.

Air Pollution, Indoor↗