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Biomedical subjects

M Nyberg

Publications and source records attributed to M Nyberg.

At least 19 recordsLinked to original sources
PubMed2005

Electronic structure of a vapor-deposited metal-free phthalocyanine thin film.

The electronic structure of a vapor-sublimated thin film of metal-free phthalocyanine (H2Pc) is studied experimentally and theoretically. An atom-specific picture of the occupied and unoccupied electronic states is obtained using x-ray-absorption spectroscopy (XAS), core- and valence-level x-ray photoelectron spectroscopy (XPS), and density-functional theory (DFT) calculations. The DFT calculations allow for an identification of the contributions from individual nitrogen atoms to the experimental N1s XAS and valence XPS spectra. This comprehensive study of metal-free phthalocyanine is relevant for the application of such molecules in molecular electronics and provides a solid foundation for identifying modifications in the electronic structure induced by various substituent groups.

Journal Article↗
PubMed2005

The hydrogen bond in ice probed by soft x-ray spectroscopy and density functional theory.

We combine photoelectron and x-ray absorption spectroscopy with density functional theory to derive a molecular orbital picture of the hydrogen bond in ice. We find that the hydrogen bond involves donation and back-donation of charge between the oxygen lone pair and the O-H antibonding orbitals on neighboring molecules. Together with internal s-p rehybridization this minimizes the repulsive charge overlap of the connecting oxygen and hydrogen atoms, which is essential for a strong attractive electrostatic interaction. Our joint experimental and theoretical results demonstrate that an electrostatic model based on only charge induction from the surrounding medium fails to properly describe the internal charge redistributions upon hydrogen bonding.

Journal Article↗
PubMed2004

Efficiency of different extraction solvent mixtures used in analyses of aflatoxins from a certified peanut meal reference material.

Four analytical methods with different extraction solvent mixtures were used to compare the efficiency of the extraction step in the analysis of aflatoxins from a reference material with a certified value of 206 +/- 13 microg aflatoxin B(1) kg(-1). The extraction mixtures used were chloroform-water (100 + 10), acetonitrile-water (60 + 40), acetone-water (85 + 15) and methanol-water (80 + 20). The analytical values determined from the extraction mixtures after correction for recovery were 211, 204, 163 and 120 microg kg(-1), respectively. The small amounts of aflatoxin B(2) in the reference material followed the same pattern. The selection of extraction solvent mixture is very important for achieving the true value and that correction for recovery does not always fully compensate for getting the correct analytical value.

Acetone↗
PubMed2003

Bonding of saturated hydrocarbons to metal surfaces.

The adsorption of octane on Cu(110) was studied by x-ray absorption and x-ray emission spectroscopy, in combination with spectrum calculations in the framework of density functional theory, as a model system for alkane adsorption on transition metals. Significant electron sharing between the adsorbate and metal surface and involvement of both bonding and antibonding C-H molecular orbitals in the molecule-metal bond was found. The calculations were extended to the case of octane adsorbed on Ni(110), and the position of the metal d band was found to be important for the bonding. The results were generalized to show that this is important for the efficiency as an alkane dehydrogenation catalyst.

Journal Article↗
PubMed2003

Ochratoxin A in raisins and currants: basic extraction procedure used in two small marketing surveys of the occurrence and control of the heterogeneity of the toxins in samples.

A basic extraction procedure for analysis of ochratoxin A (OTA) in currants and raisins is described, as well as the occurrence of OTA and a control of heterogeneity of the toxin in samples bought for two small marketing surveys 1999/2000 and 2001/02. Most samples in the surveys were divided into two subsamples that were individually prepared as slurries and analysed separately. The limit of quantification for the method was estimated as 0.1 microg kg(-1) and recoveries of 85, 90 and 115% were achieved in recovery experiments at 10, 5 and 0.1 microg kg(-1), respectively. Of all 118 subsamples analysed in the surveys, 96 (84%) contained ochratoxin A at levels above the quantification level and five samples (4%) contained more than the European Community legislation of 10 microg kg(-1). The OTA concentrations found in the first survey were in the range < 0.1-19.0 microg kg(-1) with a median concentration of 0.9 microg kg(-1). In the 2001/02 study, the range was < 0.1-34.6 microg kg(-1) with a median of 0.2 microg kg(-1). Big differences were often achieved between individual subsamples of the original sample, which indicate a wide heterogeneous distribution of the toxin. Data from the repeatability test as well as recovery experiments from the same slurries showed that preparation of slurries as described here seemed to give a homogeneous and representative sample. The extraction with the basic sodium bicarbonate-methanol mixture used in the surveys gave similar or somewhat higher OTA values on some samples tested in a comparison with a weak phosphoric acid water-methanol extraction mixture.

Carcinogens↗
PubMed2003

Effect of work with visual display units on musculo-skeletal disorders in the office environment.

BACKGROUND: The increase in computer and mouse use has been associated with an increased prevalence of disorders in the neck and upper extremities. Furthermore, poor workstation design has been associated with an increased risk of developing these symptoms. Aim The aims of this study were (i) to estimate the prevalence of musculo-skeletal disorders among full-time visual display unit (VDU) users; (ii) to examine how the prevalence varies by work environment; and (iii) to explore the association with work factors. METHOD: A survey was carried out on the effect of work with VDUs on musculo-skeletal disorders in workers in the office environment of 56 workplaces. Office workers (n = 298), customer service workers (n = 238) and designers (n = 247) were studied. RESULTS: For all the occupations combined, the 12 month prevalences of musculo-skeletal symptoms in the neck, shoulders, elbows, lower arms and wrists, and fingers were 63, 24, 18, 35 and 16%, respectively. The study indicated that musculo-skeletal pain is common among computer workers in offices. There was no strong association between the duration of computer work and pain or between the duration of mouse use and pain, but workers' perception of their workstation as being poor ergonomically was strongly associated with an increased prevalence of pain. CONCLUSIONS: Musculo-skeletal symptoms are common, but the duration of daily keyboard and mouse use had no connection with musculo-skeletal symptoms. Instead, more consideration should be paid to the ergonomics of workstations, the placing of the mouse, the postures of the upper extremities and the handling of the mouse.

Adult↗
PubMed2002

Structure and bonding of water on Pt(111).

We address the adsorption of water on Pt(111) using x-ray absorption, x-ray emission, and x-ray photoelectron spectroscopy along with calculations in the framework of density functional theory. Using the direct relationship between the electronic structure and adsorbate geometry, we show that in the first layer all the molecules bind directly to the surface and to each other through the in-layer H bonds without dissociation, creating a nearly flat overlayer. The water molecules are adsorbed through alternating metal-oxygen (M-O) and metal-hydrogen (M-HO) bonds.

Journal Article↗
PubMed2001

Electronic structure effects from hydrogen bonding in the liquid phase and in chemisorption: an integrated theory and experimental effort.

A closely integrated theoretical and experimental effort to understand chemical bonding using X-ray spectroscopic probes is presented. Theoretical techniques to simulate XAS (X-ray absorption spectroscopy), XES (X-ray emission spectroscopy), RIXS (resonant inelastic X-ray scattering) and XPS (X-ray photoelectron spectroscopy) spectra have been developed and implemented within a density functional theory (DFT) framework. In combination with new experimental techniques, such as high-resolution XAS on liquid water under ambient conditions and XES on complicated surface adsorbates, new insight into e.g. hydrogen-bonded systems is obtained. For the (3x2) overlayer structure of glycine/Cu(110), earlier work has been extended to include adsorbate-adsorbate interactions. Structures are optimized for large cluster models and for periodic boundary conditions. It is found that specific features in the spectra arise from hydrogen-bonding interactions, which thus have important effects at the molecular-orbital level. XAS on liquid water shows a pronounced pre-edge feature with significant intensity, while the spectrum of ice shows only little intensity in this region. Theoretical spectrum calculations, based on instantaneous structures obtained from molecular-dynamics (MD) simulations, show that the pre-edge feature in the liquid is caused by water molecules with unsaturated hydrogen bonding. Some aspects of the theoretical simulations will be briefly discussed.

Journal Article↗
PubMed2001

Inguinal hernia after radical retropubic prostatectomy for prostate cancer: a study of incidence and risk factors in comparison to no operation and lymphadenectomy.

PURPOSE: The incidence, mechanisms and risk factors of inguinal hernia after radical retropubic prostatectomy are sparsely elucidated in the literature. We determined the rate of inguinal hernia after radical retropubic prostatectomy and compared it to the incidence in patients with prostate cancer who did not undergo operation or underwent only pelvic lymph node dissection. MATERIALS AND METHODS: We followed 375, 184 and 65 men who underwent radical retropubic prostatectomy plus pelvic lymph node dissection, pelvic lymph node dissection only and no surgery with respect to inguinal hernia for a mean of 39, 47 and 45 months, respectively. The prostatectomy group was also evaluated in regard to the potential risk factors of previous hernia surgery and post-prostatectomy anastomotic stricture. RESULTS: The incidence of hernia was 13.6%, 7.6% and 3.1% in the prostatectomy, lymph node dissection and unoperated group, respectively. The difference was statistically significant in the prostatectomy and unoperated groups according to the Mantel-Cox log rank test and Cox proportional hazards rate. Previous hernial surgery and post-prostatectomy anastomotic stricture were more common in patients with an inguinal hernia after prostatectomy. CONCLUSIONS: The incidence of inguinal hernia is clearly increased in men who have undergone radical retropubic prostatectomy plus pelvic lymph node dissection compared with those who undergo no surgery for prostate cancer. Inguinal hernia appears to develop more often in men with prostate cancer who undergo radical retropubic prostatectomy and pelvic lymph node dissection than in those who undergo pelvic lymph node dissection only. While surgical factors trigger hernial development, previous hernial surgery and post-prostatectomy anastomotic stricture may be important risk factors. In fact, the latter may largely explain the difference in the incidence of inguinal hernia in our lymph node dissection and prostatectomy groups. Prophylactic surgical procedures must be evaluated to address this problem.

Aged↗
PubMed2000

How carbon monoxide adsorbs in different sites.

The interplay between the electronic and the geometric structure of adsorbates is of fundamental importance for the understanding of many surface phenomena. Using x-ray emission spectroscopy and ab initio cluster calculations, this issue has been investigated in unprecedented detail for CO adsorption in different adsorption sites. The investigation establishes pi bonding and sigma repulsion, both increasing with the number of coordinated metal atoms. The two contributions partly compensate each other, leading to only small differences in adsorption energies for the different adsorption sites despite very large variations in the electronic structure.

Journal Article↗
PubMed1998

The effect of propranolol versus placebo on resident surgical performance.

PURPOSE: To determine whether propranolol can decrease surgical tremor and anxiety in residents performing ocular microsurgery without impairing patient or physician safety. METHODS: In this randomized, double-masked, crossover study, 5 third-year ophthalmology residents ingested a capsule containing either propranolol, 40 mg, or placebo 1 hour prior to performing ophthalmic microsurgery. All residents were healthy men under age 30 years. Prior to commencement of the study, all participants had successfully been administered a test dose of propranolol without side effects. The study took place over a 10-week period. At the conclusion of each case, both the resident and attending surgeon observer independently completed a form grading, on a sliding scale: (1) amount of overall tremor; (2) amount of tremor during placement of the first 3 sutures after lens or nucleus extraction; (3) anticipated difficulty of the case; (4) actual difficulty with the case; and (5) anxiety (surgeon only). In addition, the type of procedure performed, complications encountered, and surgeon side effects were recorded. The data were analyzed with a 2-way analysis of variance for unbalanced data. RESULTS: A total of 73 surgical cases were performed; the surgeons were administered propranolol for 40 cases and placebo for 33. As judged by the resident surgeon, there was a highly significant effect of propranolol in decreasing anxiety (P = .0058), reducing surgical tremor overall (P < .0001), and reducing tremor while placing the first 3 sutures following lens extraction (P < .0001). There was no treatment-by-surgeon interaction for any of the measures. Complications and difficulty of the case, as judged by both the resident and attending surgeons, were not significantly different in the propranolol versus placebo groups (P > .05). There were no side effects reported or observed in any of the surgeons. CONCLUSIONS: Propranolol, 40 mg, administered 1 hour prior to surgery, significantly decreases tremor and anxiety in the surgeon without untoward effects to the surgeon and the patient. However, it is unknown whether decreased tremor and anxiety improved surgical outcome.

Adrenergic beta-Antagonists↗
PubMed1995

Abundant expression of HIV Nef and Rev proteins in brain astrocytes in vivo is associated with dementia.

OBJECTIVE: To relate the expression of HIV regulatory proteins and HIV-specific mRNA in the brain cells of infected individuals with clinical neurological disease. DESIGN: Formalin-fixed postmortem brain tissue from 14 HIV-infected adult patients, with previous repeated neurological and neuroradiological examinations, was studied by immunohistochemical and molecular biological methods. Samples from non-infected brains served as controls. METHODS: Immunohistochemistry with monoclonal antibodies (MAb) was combined with in situ RNA hybridization. Target cells were identified with MAb to glial fibrillary acidic protein (GFAP; astrocytes), CD68 (activated macrophages) and Ricinus communis agglutinin (RCA-1; microglia, endothelial cells). For HIV, a panel of MAb against HIV Nef, Tat, Rev and Env proteins or probes specific for all classes of mRNA (nef), for singly or non-spliced mRNA (env) and for non-spliced mRNA (gag/pol) were used. RESULTS: Nef protein was detected in subcortical or subpial astrocytes in seven out of 14 samples, and in multinucleated giant cells in two cases. Gag/pol or env mRNA-expressing astrocytes were detected in four cases. In four out of five cases studied, HIV Rev, but not Tat, was also expressed in astrocytes. Six out of the seven patients with Nef-positive astrocytes had suffered from moderate to severe dementia. The patient with most rapidly progressing severe dementia showed extensive HIV mRNA expression together with Nef and Rev expression in astrocytes. CONCLUSION: In adult human brain, astrocytes are infected by HIV and preferentially express HIV Nef and Rev proteins but are also sometimes productively infected. Astrocyte infection is associated with moderate to severe dementia which agrees with recent knowledge on the housekeeping activities of astrocytes and their eventual role in learning and memory.

AIDS Dementia Complex↗
PubMed1994

Stability of human immunodeficiency virus (HIV) antibodies in postmortem samples.

The stability of human immunodeficiency virus (HIV) antibodies was studied for samples of sera, vitreous fluid and bile obtained from eight HIV-positive autopsy cases. The autopsy delay was on average 5 days. The samples were stored at room temperature (20 degrees C) for 51 to 314 days and tested repeatedly. In Western blotting on fresh postmortem samples, the antibodies detected most of the proteins of the virus. Antibodies against all major envelope, core and transmembrane proteins, although weakened, were also detected in stored sera. In stored vitreous fluid and bile the envelope protein gp 160, the transmembrane protein gp 41 and in half of the cases also the major core protein p 24 could still be detected. The disappearance of p 24 was associated with AIDS, but was detected in all samples from patients with early infection. Of screening tests, the enzyme-linked immunosorbent assay applying synthetic peptide as an antigen detected antibodies from all serum samples, but was less applicable to vitreous fluid or bile. Another immunoassay, applying recombinant antigen, succeeded in vitreous fluid and bile but not in sera. The rapid visually read assay detected antibodies in most samples of fresh whole blood, bile and in most of the vitreous samples, but was less useful on stored specimens.

Autopsy↗
PubMed1992

An epidemic of sylvatic rabies in Finland--descriptive epidemiology and results of oral vaccination.

When rabies reappeared in Finland in April 1988, the country had been rabies free since 1959. Soon a picture of sylvatic rabies become evident, its main vector and victim being the raccoon dog (Nyctereutes procyonoides). Between 8 April 1988 and 16 February 1989, 66 virologically verified cases were recorded (48 raccoon dogs, 12 red foxes, 2 badgers, 2 cats, 1 dog and 1 dairy bull) in an area estimated at 1700 km2 in south-eastern Finland. The greatest distance between recorded cases was 67 km. A positive reaction with monoclonal antibody p-41 indicated that the virus was an arctic-type strain. A field trial on oral immunization of small predators was initiated in September 1988 using Tübingen fox baits according to the Bavarian model of bait distribution. Each bait contained 5*10(7) TCID50/ml modified live rabies virus (SAD-B19). The 6 months' surveillance indicate a seroconversion rate of 72% (N = 126) in the raccoon dog population, 67% (N = 56) in the red foxes and 13% (N = 16) in the badgers, when titers greater than or equal to 1.0 IU/ml are considered seropositive. In the whole follow-up period, no statistically significant difference could be detected between the raccoon dogs and red foxes in the rate of seroconversion or in the uptake of tetracycline from the baits. Notably high antibody levels were recorded in both raccoon dogs and red foxes within 4-5 months after vaccination. Of the seropositive animals, the proportion of animals with titers 3.0 IU/ml or greater was higher in raccoon dogs (73%) than in red foxes (51%) (x2 = 5.29, p less than 0.05). The trial shows that raccoon dogs can be immunized against rabies in the field with vaccine baits originally developed for controlling sylvatic rabies in foxes.

Animals↗
PubMed1991

Turnaround time. A financially troubled Philadelphia hospital goes out of the red and into the black.

A large Medicare population, a higher than average length of stay, an aging medical staff, and difficulty in retaining professional staff were a few of the indications that Nazareth Hospital, Philadelphia, was headed for financial difficulties. Unfortunately, Nazareth leaders overlooked these warnings because the hospital was concentrating on a major construction project. In 1989 the hospital lost approximately $5 million from operations, resulting in debt covenant violations on a $33 million bond issue. Nazareth then adopted a revitalization program with the following basic components: Establishing extensive cost-cutting measures to help reverse the financial deficits Retaining outside consultants to serve as management advocates and to keep the repositioning effort moving forward Enhancing long-range strategic planning to lay firm groundwork for the hospital's future As a result of these efforts, Nazareth went from a fiscal year 1989 operating loss to a 1990 year-end break-even position. Nazareth leaders attribute this success to the total commitment by the involved constituencies: board, managers, medical staff, and employees.

Attitude of Health Personnel↗
PubMed1990

Isolation of human immunodeficiency virus (HIV) at autopsy one to six days postmortem.

Blood and tissue were studied for potential infectivity at autopsy of ten patients with human immunodeficiency virus (HIV) infection. Special attention was paid to the possibility of detecting HIV in bone at craniotomy. Postmortem intervals were one to six days. Specimens for HIV isolation included skull bone, brain, blood, bone marrow, spleen, and lymph node, and cerebrospinal fluid in one case. HIV grew in culture from at least one specimen from eight autopsies, one of which was performed six days postmortem. HIV was recovered from the blood of five patients and the tissue of five patients, including three with negative blood cultures. Skull bone contained HIV in two cases. HIV also grew from native spleen specimens stored for up to 14 days postmortem at 20 degrees C. Recommended precautions, including those for bone, are indicated at autopsy of HIV-infected patients even after long postmortem intervals.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Thyroid-infiltrating lymphocytes, thyroid function, and HLA-DR in juvenile autoimmune thyroiditis.

Eighteen patients with juvenile autoimmune thyroiditis were studied. At diagnosis 8 (44%) of the patients were euthyroid and 10 hypothyroid, whereas at the end of 6 to 12 months follow-up, 12 (66%) were euthyroid and 6 hypothyroid. All the patients were HLA-typed. The frequency of HLA-DR4 was increased in the patients when compared with the normal population, 63 vs 28% (p less than 0.01). An analysis of thyroid-infiltrating mononuclear cells revealed that the majority of the thyroid-infiltrating lymphocytes were T cells. More T lymphocytes and fewer B lymphocytes and HLA class II positive lymphocytes were found among the thyroid-infiltrating mononuclear cells in euthyroid than hypothyroid patients. The numbers of thyroid-infiltrating B lymphocytes correlated with the levels of thyroid microsomal antibodies. No correlation was found between thyroid function and thyroid antibodies.

Adolescent↗