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Biomedical subjects

A Wennberg

Publications and source records attributed to A Wennberg.

At least 19 recordsLinked to original sources
PubMed2005

Interface double-exchange ferromagnetism in the Mn-Zn-O system: new class of biphase magnetism.

In this Letter, we experimentally show that the room temperature ferromagnetism in the Mn-Zn-O system recently observed is associated with the coexistence of Mn(3+) and Mn(4+) via a double-exchange mechanism. The presence of the ZnO around MnO(2) modifies the kinetics of MnO(2)-->Mn(2)O(3) reduction and favors the coexistence of both Mn oxidation states. The ferromagnetic phase is associated with the interface formed at the Zn diffusion front into Mn oxide, corroborated by preparing thin film multilayers that exhibit saturation magnetization 2 orders of magnitude higher than bulk samples.

Journal Article↗
PubMed2001

Effects on the nervous system in different groups of workers exposed to aluminium.

OBJECTIVE: To investigate possible neurotoxic effects in groups of aluminium pot room and foundry workers, aluminium welders, and a small group of workers exposed to aluminium in the production of flake powder. METHODS: Exposure to aluminium was evaluated with aluminium concentrations in blood and urine as well as a questionnaire. The groups exposed to aluminium were compared with a group of mild steel welders. Neurotoxic effects were studied with mood and symptom questionnaires and several psychological and neurophysiological tests. RESULTS: The pot room and foundry workers showed very low aluminium uptake as their aluminium concentrations in blood and urine were close to normal, and no effects on the nervous system were detected. The group of workers exposed to flake powder had high concentrations of aluminium in blood and urine, even higher than those of the aluminium welders. However, aluminium could not be shown to affect the functioning of the nervous system in flake powder producers. Although significant effects could not be shown in the present analysis of the data on welders, the performance of the welders exposed to high concentrations of aluminium was affected according to the analyses in the original paper from this group. CONCLUSIONS: For the pot room and foundry workers no effects related to the exposure to aluminium could be found. For the group of flake powder producers exposed for a short term no effects on the nervous systems were evident despite high levels of exposure. Due to the high concentrations of aluminium in the biological samples of this group, measures to reduce the exposure to aluminium are recommended, as effects on the central nervous system might develop after protracted exposures. However, this assumption needs to be verified in further studies.

Adult↗
PubMed1998

Safety and tolerance of medical nutritional products as sole sources of nutrition in people on hemodialysis.

OBJECTIVE: Establish and compare the safety and tolerance of three medical nutritional products when used as sole sources of nutrition in stable hemodialysis patients. DESIGN: Prospectively randomized, controlled, single blind, parallel design. SETTING: Three outpatient hemodialysis clinics. PARTICIPANTS: Seventy-nine normally nourished, stable, anuric, adequately dialyzed, adult outpatients with end-stage renal disease (ESRD) and requiring thrice weekly hemodialysis. INTERVENTION: A 3-week trial was conducted. During the first week, baseline medical history and physical examination, gastrointestinal symptom, urea kinetic, bowel habit, and biochemical data were collected while participants ingested their usual diet. During the last 2 weeks, the same data were collected while participants orally ingested 35 kcal/kg actual weight/d of one of three medical nutritional products as a sole source of nutrition. Products were a standard medical nutritional (EN-9527) and two renal nutritionals (EN-9528 and EN-9529). The latter product was a reformulation of EN-9528 and contained added beta-carotene and fructooligosaccharides. MAIN OUTCOME MEASURES: Gastrointestinal symptoms, bowel habits (stool frequency and consistency), routine blood chemistries, urea kinetics, and normalized protein catabolic rate (nPCR) RESULTS: All three groups achieved a mean energy and protein intake of approximately 35 kcal/kg/d and 1.25 g protein/kg/d during the last 10 days of the sole source feeding period. Adherence with the formula ingestion targets was assessed using both a patient-completed product consumption log and nPCR. By intent to treat analysis, there were no changes in number or severity of gastrointestinal symptoms, stool frequency or stool consistency, or urea kinetics between the baseline week and during product consumption. In comparison to the standard formulation, the disease-specific formulations resulted in improved serum phosphorus and calcium-phosphorus product. Patients receiving the fructooligosaccharide-containing product (EN-9529), by Chi-squared analysis, had less constipation than for the comparable product without oligosaccharides (EN-9528) or the standard medical nutritional (EN-9527). CONCLUSION: Use of enteral nutritionals as a sole source of nutrition is both possible and well tolerated in hemodialyzed patients. Selection of a disease-specific formulation offered advantages over a standard formulation in the management of biochemical complications of renal disease when the products were used as a sole source of nutrition.

Blood Urea Nitrogen↗
PubMed1996

Effects on the nervous system among welders exposed to aluminium and manganese.

OBJECTIVES: The purpose was to study the effects on the nervous system in welders exposed to aluminium and manganese. METHODS: The investigation included questionnaires on symptoms, psychological methods (simple reaction time, finger tapping speed and endurance, digit span, vocabulary, tracking, symbol digit, cylinders, olfactory threshold, Luria-Nebraska motor scale), neurophysiological methods (electroencephalography, event related auditory evoked potential (P-300), brainstem auditory evoked potential, and diadochokinesometry) and assessments of blood and urine concentrations of metals (aluminium, lead, and manganese). RESULTS: The welders exposed to aluminium (n = 38) reported more symptoms from the central nervous system than the control group (n = 39). They also had a decreased motor function in five tests. The effect was dose related in two of these five tests. The median exposure of aluminium welders was 7065 hours and they had about seven times higher concentrations of aluminium in urine than the controls. The welders exposed to manganese (n = 12) had a decreased motor function in five tests. An increased latency of event related auditory evoked potential was also found in this group. The median manganese exposure was 270 hours. These welders did not have higher concentrations of manganese in blood than the controls. CONCLUSIONS: The neurotoxic effects found in the groups of welders exposed to aluminium and manganese are probably caused by the aluminium and manganese exposure, respectively. These effects indicate a need for improvements in the work environments of these welders.

Adult↗
PubMed1994

Glutamine supplementation does not prevent small bowel mucosal atrophy after total parenteral nutrition in the rat.

Glutamine supplementation to non-lipid parenteral nutrition has been demonstrated to attenuate villus atrophy and increase mucosal DNA content in the rat. This study was performed in order to determine the effects of glutamine supplementation to a balanced TPN mixture (including lipids) on epithelial cell kinetics using autoradiography. Male Sprague-Dawley rats were used. Group 1 (control) received food and an intravenous saline infusion. Group 2 received an intravenous TPN mixture including lipids but without glutamine. The same TPN mixture, glutamine replacing an isonitrogenous amount of non-essential amino acids, was given to Group 3. Animals were fed for 7 days, whereafter blood and intestinal samples were taken 1 h after injection of tritiated thymidine. Microscopy of specimens from proximal jejunum revealed a significant reduction in the number of cells in crypts and villi in both TPN groups (2 and 3) compared to orally fed animals (p < 0.001). Epithelial cell numbers were not significantly different in Group 2 and 3. Similarly, the labelling index (number of labelled cells/number of crypt cells) was not affected by glutamine administration. In plasma, glucagon concentrations in Group 2 (TPN without glutamine) seemed to decrease compared to Group 1 and 3 (p = 0.06). In this study, glutamine supplementation did not affect apithelial atrophy or cell proliferation. It is concluded, that the effects of glutamine on mucosal atrophy and renewal in jejunum may depend on the composition of the TPN mixture supplied during parenteral feeding.

Journal Article↗
PubMed1994

Biocompatibility of new, clinically used, and recycled orthodontic samarium-cobalt magnets.

The aim of this study was to compare the cytotoxic effect of new, clinically used, and recycled samarium-cobalt magnets (SmCO5). Cytotoxicity was assessed by two in vitro methods, the millipore filter method and an extraction method. In the filter method, the test material and the target cells are separated by a thin, permeable membrane. The test assesses the cytotoxicity of both water soluble and nonwater soluble components of the test material. The extraction test, which has a higher sensitivity, assesses the cytotoxicity of water soluble components only. According to the filter method, one magnet (new) showed a mild cytotoxic effect; all other tested magnets showed no cytotoxicity. Judged by the extraction test, new as well as clinically used magnets demonstrated a weak cytotoxic effect, suggesting the presence of a small amount of leachable cytotoxic components. The level of exerted cytotoxicity of such components was significantly lower for clinically used than for new magnets. When recycled magnets were tested, the cytotoxicity had significantly decreased, (p < 0.001), and the cytotoxicity could be considered negligible. The results thus revealed that SmCO5 magnets can be recycled with maintained good biocompatibility. Because a small amount of water soluble cytotoxic agents seem to leach out from new partially stainless steel-coated samarium-cobalt magnets, it is recommended that they be stored in water for 24 hours before clinical use, thereby conceivably decreasing the oral exposure of water soluble cytotoxic agents.

Animals↗
PubMed1994

Testing of sealing ability of endodontic filling materials.

Incomplete obturation of the root canal system is the major cause of endodontic failure. Endodontic filling materials with ability to seal the root canal are, therefore, essential for successful endodontic therapy. However, assessment of sealing ability is not included in the requirements specified in the current international standard covering root canal sealers. A number of different in vitro methods have been used to evaluate the sealing quality of endodontic filling materials. The tests have usually been leakage tests, i.e. based on assessment of penetration of a tracer along the obturated root canal. Leakage tests have poor reproducibility and are, therefore, not suited for standardized test programs. By selecting the properties necessary for sealing ability and testing them separately, it might be possible to find a number of tests, which individually are suitable for a standardized test program, and which combined will give information on the sealing ability of the test material.

Animals↗
PubMed1994

Orthodontic rare earth magnets--in vitro assessment of cytotoxicity.

The aim of this study was to assess and compare in vitro the cytotoxic effects of uncoated and parylene-coated rare earth magnets, used in orthodontics. Cytotoxicity of samarium-cobalt magnets (SmCo5 and Sm2Co17) and neodymium-iron-boron magnets (Nd2Fe14B) was assessed by two in vitro methods, the millipore filter method and an extraction method. Orthodontic stainless steel brackets served as controls. Uncoated SmCo5-magnets showed high cytotoxicity while uncoated Sm2Co17-magnets demonstrated moderate cytotoxicity. Uncoated neodymium-iron-boron magnets, as well as parylene coated Sm2Co17-magnets and parylene-coated neodymium-iron-boron magnets, showed negligible cytotoxicity. Short-term exposure to a static magnetic field did not cause any cytotoxic effect on the cells.

Animals↗
PubMed1994

Anxiety and cancer-related worry of cancer patients at routine follow-up visits.

Anxiety and cancer-related worry were assessed in 197 consecutive cancer patients attending follow-up visits. Participants completed questionnaires on three occasions: at the visit, some days later, and three weeks later. Results show that while a majority of patients feel no or only mild anxiety in conjunction to the follow-up visit, about one-fifth report moderate or strong anxiety. Many patients (46%) worry about suffering a recurrence and about overlooking symptoms of new cancer (33%). Patients who were not in complete remission reported higher levels of cancer-related worry concerning the follow-up visit than did patients in remission. Among patients in remission, those who recently terminated treatment reported more overall distress than patients two or more years since treatment termination.

Adult↗
PubMed1994

Coping, psychosocial well-being and anxiety in cancer patients at follow-up visits.

Coping, psychosocial well-being, situation-specific anxiety and cancer-related worry were assessed in 197 consecutive cancer patients attending follow-up visits. Participants completed questionnaire on three occasions: at the follow-up visit, some days later (n = 175) and three weeks later (n = 125). High levels of coping styles 'Anxious Preoccupation' and 'Helplessness/Hopelessness' were associated with low levels of psychosocial well-being, more situation-specific anxiety and more cancer-related worry. High levels of 'Fighting Spirit' and 'Fatalistic' were found to be associated with high psychosocial well-being and, for 'Fighting Spirit', also with less cancer-related worry. Patients with a 'dismal' prognosis were found to have higher levels of 'Helplessness/Hopelessness' than patients with a more 'favorable' prognosis. Clinical implications of these findings are discussed.

Adaptation, Psychological↗
PubMed1994

Methodological approach to the evaluation of neurotoxicity data and the classification of neurotoxic chemicals.

This text is the result of the authors' involvement in a working group on criteria for the identification and classification of neurotoxic chemicals. (The work of the group does not necessarily represent the official stand of the affiliated institutes.) A definition of neurotoxicity and criteria for evaluating studies dealing with neurotoxicology are presented. The evaluation is a stepwise process that ends with assigning the chemicals to groups depending on the available evidence for neurotoxicity (ie, neurotoxic, probably neurotoxic, possibly neurotoxic, probably not neurotoxic, or not classifiable). Finally, the description of the potency of neurotoxic chemicals is briefly discussed. The model has been tested by evaluating selected research papers on the following 10 chemicals: manganese, aluminum, tetrahydrofuran, cyclohexanone, dichlorvos, trichloroethylene, formaldehyde, tri-ortho-cresyl phosphate, n-hexane, and vinyl chloride. There was sufficient evidence for classifying five of the ten chemicals (aluminum, manganese, n-hexane, trichloroethylene, tri-ortho-cresyl phosphate) as definitely neurotoxic to humans, and three were considered to be possibly neurotoxic to humans (dichlorvos, tetrahydrofuran, vinyl chloride). Cyclohexanone and formaldehyde were not classifiable according to the model.

Animals↗
PubMed1994

Neurotoxic effects of selected metals.

A chemical is considered to be neurotoxic if it is capable of inducing a consistent pattern of neural dysfunction or lesion in the nervous system. Several metals are known as neurotoxic. Among them, four have been selected as being especially important from the occupational point of view, lead, manganese, aluminium, and mercury. All four have proved to be neurotoxic even though the toxic mechanisms may be unclear or unknown. This paper reviews the recently published documentation on the neurotoxic properties of these metals, from the general as well the occupational point of view.

Adult↗
PubMed1993

Occupational exposure to electromagnetic fields in relation to leukemia and brain tumors: a case-control study in Sweden.

Occupational exposure to low-frequency electromagnetic fields (EMF) was studied in 250 leukemia patients and 261 brain-tumor cases, diagnosed in 1983-87 and compared with a control group of 1,121 randomly selected men, from the mid-region of Sweden, 1983-87. We based the exposure assessment on measurements from 1,015 different workplaces. On the basis of the job held longest during the 10-year period before diagnosis, we found an association between the average, daily, mean level of EMF and chronic lymphocytic leukemia (CLL). The risk increased with increasing level of exposure. The odds ratios (OR) and the 95 percent confidence interval (CI) for three consecutive levels of exposure were: 1.1 (CI = 0.5-2.3); 2.2 (CI = 1.1-4.3); 3.0 (CI = 1.6-5.8), respectively. No association was observed for acute myeloid leukemia (OR = 1.0, CI = 0.5-1.8; OR = 0.8, CI = 0.4-1.6; OR = 1.0, CI = 0.6-1.9). For brain tumors, the corresponding risk estimates were 1.0 (CI = 0.7-1.6); 1.5 (CI = 1.0-2.2); 1.4 (CI = 0.9-2.1). Different EMF indices were tested. Tasks with frequent or large variations between high and low field-densities (high standard deviation) were more common among CLL subjects. For brain tumors, a prolonged high level (high median values) showed the strongest association. Confounding by place of residence, smoking, benzene, ionizing radiation, pesticides, and solvents was evaluated, and these factors did not seem to have a decisive influence on the associations. We also analyzed other potential sources of bias. For CLL, there were indications of an excess number of low-exposure subjects among non-responders, which, to some extent, may have enhanced but not caused the risk estimates obtained. Our conclusion is that the study supports the hypothesis that occupational EMF exposure is a hazard in the development of certain cancers.

Acute Disease↗
PubMed1993

Biocompatibility of dentin bonding agents.

Dentin bonding agents were introduced to enhance the bonding of composite resins to dentin. Many commercial brands of bonding agents are now available for clinical use, and they are getting more and more popular. The third generation of dentin bonding agents seems to be more effective than earlier generations, although more complex to use. Dentin bonding agents have different chemical compositions, different mechanism of action, and different clinical application procedures and, conceivably, different biological effects on the pulpal tissues are expected. The reported biological effects of dentin bonding agents ranged from none to severe, depending on several factors. Opinions varied whether the inflammatory reactions associated with some bonding agents were due to the material per se, to bacterial ingrowth at the tooth restoration interface, or due to a combination of both factors.

Animals↗
PubMed1992

The effect of short-term lipid infusion on liver function and biliary secretion in rats.

This study was undertaken to determine the effect of various lipid emulsions on the hepato-biliary system in rats. Rats were randomly divided into six groups and infused continuously for 48 hr with either long-chain triglycerides (LCT), medium-chain triglycerides (MCT) or a mixture of MCT and LCT. One group infused with physiological saline solution served as controls. Throughout this period the rats received a fat free diet ad libitum. During the last hour of lipid infusion bile was collected for determination of bile flow and composition. Subsequently, the rats were sacrificed and the morphology and lipid content of the liver determined. Only LCT lipid emulsions induced morphological changes and increased liver cholesterol content. In two rats infused with radiolabeled LCT, no labeled cholesterol was found in the liver, indicating that the excess hepatic cholesterol level may originate from enhanced cholesterol mobilization to the liver. Biliary cholesterol and phospholipid concentrations in LCT-treated rats were also elevated, as was the lithogenic index, whereas the other emulsions had no such effects. None of the emulsions affected the plasma liver function tests or bile flow. We therefore conclude that the lithogenicity of the bile in rats is directly related to the lipid components of the total parenteral nutrition and the type of triglyceride infused.

Animals↗
PubMed1992

Prevalence of carnitine depletion in critically ill patients with undernutrition.

The aim of this study was to evaluate to what extent secondary carnitine deficiency may exist based on the prevalence of subnormal carnitine status in patients with critical illness and abnormal nutritional state. Healthy control patients (n = 12) were investigated and compared with patients with possible secondary carnitine deficiency, ie, patients with overt severe protein-energy malnutrition (PEM, n = 28), postoperative long-term (greater than 14 days) parenteral glucose feeding (250 g glucose/d, n = 7), severe liver disease (n = 10), renal insufficiency (n = 7), and sustained septicemia with increased metabolic rate (n = 8). Nutritional status, energy expenditure, creatinine excretion, and blood biochemical tests were measured in relationship to free and total carnitine concentrations in plasma and skeletal muscle tissue, as well as urinary excretion of free and total carnitine. The overall mortality rate was 48% within 30 days of the investigation in study patients with the highest mortality in liver disease (90%). The hospitalization range was 14 to 129 days in study patients. Most study patients had lost weight (4% to 19%) and had abnormal body composition. Patients with liver disease, septicemia, renal insufficiency, and those on long-term glucose feeding had significantly higher than predicted metabolic rate (+25% +/- 3%), while patients with severe malnutrition had decreased metabolic rate compared with controls. Patients with liver disease had increased plasma concentrations of free (96 +/- 16 mumol/L) and total (144 +/- 27 mumol/L) carnitine compared with controls (45 +/- 3, 58 +/- 7 mumol/L, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Prevalence and distribution of cervical dentine hypersensitivity in a population in Rio de Janeiro, Brazil.

The prevalence, distribution and possible causal factors of cervical dentine hypersensitivity were studied in a population from a Marine Dental Clinic in the city of Rio de Janeiro, Brazil. A total of 635 patients were examined for the presence of cervical dentine hypersensitivity by means of a questionnaire and intraoral tests (air and probe stimuli). There were 157 patients (25%) reporting to have hypersensitive teeth, but only 108 patients (17%) were diagnosed as having cervical dentine hypersensitivity. The prevalence of hypersensitivity was higher among females than males, but this difference was not statistically significant. Most females with hypersensitivity were aged 20-49 and most males were aged 40-59. Incisors and premolars had the highest prevalence of dentine hypersensitivity to air and probe stimuli, while molars had the lowest. The presence and history of dentine hypersensitivity were positively correlated with previous exposure to periodontal treatment. Only a few of the patients who claimed to have dentine hypersensitivity had tried treatment with desensitizing toothpastes or sought professional help.

Adolescent↗