Biomedical subjects

H Sundberg

Publications and source records attributed to H Sundberg.

At least 19 recordsLinked to original sources

PubMed2001

Honig's model of working memory and brain activation: an fMRI study.

The present study investigated changes in neuronal activation with fMRI related to Honig's model of working memory, which is much less studied compared with other working memory models. In contrast to other studies which have applied recognition procedures, the primary aim with the present study was to examine brain activation when subjects had to continuously recall and forget items held in working memory. The results showed that the mid-ventrolateral frontal cortex was particularly activated in the left hemisphere, whereas the mid-dorsolateral frontal cortex was particularly activated in the right hemisphere during execution of the working memory task. The findings are discussed in relation to process- and domain-specific accounts of working memory.

Adult↗

PubMed2001

A mouse knock-in model exposes sequential proteolytic pathways that regulate p27Kip1 in G1 and S phase.

The protein p27Kip1 is an inhibitor of cell division. An increase in p27 causes proliferating cells to exit from the cell cycle, and a decrease in p27 is necessary for quiescent cells to resume division. Abnormally low amounts of p27 are associated with pathological states of excessive cell proliferation, especially cancers. In normal and tumour cells, p27 is regulated primarily at the level of translation and protein turnover. Phosphorylation of p27 on threonine 187 (T187) by cyclin-dependent kinase 2 (Cdk2) is thought to initiate the major pathway for p27 proteolysis. To critically test the importance of this pathway in vivo, we replaced the murine p27 gene with one that encoded alanine instead of threonine at position 187 (p27T187A). Here we show that cells expressing p27T187A were unable to downregulate p27 during the S and G2 phases of the cell cycle, but that this had a surprisingly modest effect on cell proliferation both in vitro and in vivo. Our efforts to explain this unexpected result led to the discovery of a second proteolytic pathway for controlling p27, one that is activated by mitogens and degrades p27 exclusively during G1.

Animals↗

PubMed2001

Social inequality in oral health and use of dental care in Sweden.

OBJECTIVE: To describe oral health and use of dental care in relation to socio-economic determinants over time in Sweden. METHODS: Cross-sectional study based on interview data on two randomly sampled sequential populations consisting of 7,610 Swedish adult (25-64 years) residents and 4,315 children (3-15 years) in their households from the Survey of Living Conditions 1996-97, and 7,649 adult Swedish residents (25-64 years) from the survey of 1988-89. RESULTS: Low educational level, having no cash margin and being born outside of Sweden was associated with higher odds of problems with chewing, wearing a prosthesis and not having been treated by a dentist during the 24 months preceding the interview, in a logistic regression analysis of data from the 1996-97 survey in the adult study population (adjusted odds ratios 1.6-2.9). The same socio-economic determinants were associated with caries in children (adjusted odds ratios 1.2-1.5). The socio-economic differences in dental treatment and problems with chewing were greater in the age group 45-64 years compared to 25-44-year-olds. The prevalence of problems with chewing increased from 7.1% (95% CI 6.5-8.1) in the 1988-89 survey to 9.1% (8.4-9.8) in the 1996-97 survey. A similar increase, from 2.4% (2.2-2.6) to 4.4% (3.9-4.9) was observed for individuals not having been in dental treatment during the last 24 months. The socio-economic distribution of oral health and use of dental care in the adult population was similar in the two surveys. CONCLUSION: This study demonstrates that socio-economic differences in oral health and use of dental care are most marked in older (45-64 years) adults in Sweden, but are significant in young adults and, in terms of oral health, in children as well. A steep increase in user charges during the 1990s has been paralleled by a moderate increase in problems with chewing and the proportion of the population that has no regular dental care, which suggests a link that needs to be evaluated in further studies.

Adolescent↗

PubMed2001

Restorative treatment decisions on occlusal caries in Scandinavia.

In order to map variations in the operative treatment threshold for occlusal caries, a pre-coded questionnaire was sent to a random sample of 759 dentists in Norway, 923 in Sweden, and 173 in the Danish Public Dental Health Service inquiring about caries and treatment strategies. A further intention was to explore the type of operative treatment and filling material dentists in Scandinavia would use given an occlusal lesion in the lower 2nd molar in a 20-year-old. It is found that close to 70% of dentists in the 3 countries would put off carrying out operative treatment of occlusal caries until they registered a moderately sized cavity and/or any radiolucency in dentin. In Sweden, 26.7% of dentists and in Denmark 24.3% would postpone operative treatment until the lesion had a large cavity and/or until radiolucency could be observed in the middle third of the dentin; in Norway, only 11.5% of dentists indicated this. The majority of dentists in all 3 countries preferred to drill only the carious part of the fissure, though in Norway more dentists (30.9%) would tend to drill the whole fissure compared to their Swedish (23.4%) and Danish (9.5%) colleagues. The majority of Danish dentists (52.4%) suggested amalgam for restoring the occlusal surface, while 19.9% of Norwegian and 2.9% of Swedish dentists would use amalgam. Composite was the first material of choice for 71.5% of the Swedish dentists, the remaining 25.6% suggesting conventional glass ionomer cement, light-cured 'glass ionomer cement', or a combination of glass ionomer cement and composite. The corresponding values for the Norwegian dentists were 39.1% and 41.0%, respectively, and for the Danish dentists 29.2% and 18.4%. In Scandinavia, the leading strategy for occlusal caries seems to be to postpone operative treatment until a definite cavity or radiolucency in the outer third of dentin can be observed, and to carry out operative treatment only of the part of the fissure that is carious. Composite resin is the predominant material of choice in Sweden, while in Denmark the majority of dentists preferred amalgam. Composite, or composite in combination with glass ionomer cement material, was the choice of almost 80% of Norwegian dentists.

Adult↗

PubMed2001

Different brain areas activated during imagery of painful and non-painful 'finger movements' in a subject with an amputated arm.

The purpose of the present study was to investigate differences in brain activation with functional magnetic resonance imaging (fMRI) during imagery of painful and non-painful 'finger movements' and 'hand positioning' in a subject with an amputated arm. The subject was a right-handed man in his mid-thirties who lost his right arm just above the elbow in a car-train accident. MRI was performed with a 1.5 T Siemens Vision Plus scanner. The basic design involved four conditions: imagining 'painful finger movements', 'non-painful finger movements', 'painful hand positioning', 'non-painful hand positioning'. Imagery of finger movements uniquely activated the contralateral primary motor cortex which contains the classic 'hand area'. The lateral part of the anterior cerebellar lobe was also activated during imagery of finger movements. Imagery of pain uniquely activated the somatosensory area, and areas in the left insula and bilaterally in the ventral posterior lateral nucleus of the thalamus. It is suggested that the insula and thalamus may involve neuronal pathways that are critical for mental processing of pain-related experiences, which may relate to a better understanding of the neurobiology of phantom limb pain.

Adult↗

PubMed2000

Contribution of planar (0-1 ortho) and nonplanar (2-4 ortho) fractions of Aroclor 1260 to the induction of altered hepatic foci in female Sprague-Dawley rats.

The hepatic tumor promoting activity of the planar 0-1 ortho ( approximately 9.7% w/w) and the nonplanar 2-4 ortho ( approximately 90.3% w/w) fraction of the commercial PCB mixture Aroclor 1260 was studied using a medium-term two-stage initiation/promotion bioassay in female Sprague-Dawley rats. Fractionation was carried out on an activated charcoal column. The composition of the effluent from the column was tested by GC-ECD. The absence of planar compounds in the 2-4 ortho fraction was confirmed by GC-MS analysis. The dioxin-like toxic potency of the fractions was determined with the DR-CALUX assay. The animal experiment was started with the initiation procedure (diethylnitrosamine injection, 30 mg/kg body wt ip, 24 h after (2)/(3) hepatectomy), followed 6 weeks later by the promotion treatment, which consisted of a weekly subcutaneous injection during 20 weeks. Exposure groups (n = 10) received the following treatments (dose/kg body wt/week): Aroclor 1260 (10 mg), 0-1 ortho fraction (0.97 mg), 2-4 ortho fraction (1, 3, or 9 mg), a reconstituted 0-4 ortho fraction (9.97 mg), 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153; 1 or 9 mg), 2,3,7,8-TCDD (1 microg; positive control) or corn oil (1 ml; vehicle control). One group did not receive a promotion treatment. All exposure groups exhibited a significantly increased volume fraction of the liver occupied by hepatic foci positive for the placental form of glutathione-S-transferase-p compared to the corn oil control, except for the groups treated with 0-1 ortho fraction and 1 mg PCB 153/kg body wt/week. Approximately 80% of the total tumor promoting capacity of the reconstituted 0-4 ortho fraction could be explained by the 2-4 ortho PCB fraction while the 0-1 ortho fraction had only a negligible contribution. These results suggest that the majority of the tumor promotion potential of PCB mixtures resides in the non-dioxin-like fraction, which is not taken into account in the toxic equivalency factor (TEF) approach for risk assessment of PCBs. This may result in an underestimation of the tumor promotion potential of environmental PCB mixtures.

Animals↗

PubMed2000

Swedish dentists' decisions on preparation techniques and restorative materials.

This study aimed at mapping the preparation techniques and restorative materials that Swedish dentists are using for primary approximal and occlusal carious lesions. It involved sending a pre-coded questionnaire to a random sample of 923 dentists, with eight items concerning approximal and occlusal restorative preparation techniques and dental materials. Responses were received from 651 (70.5%) dentists. To restore a primary approximal carious lesion in an adolescent with low caries activity and good oral hygiene, the tunnel preparation was chosen by 48% of the dentists, the saucer-shaped preparation by 32%, and the traditional Class II preparation by 20%. The most common preparation technique for restoring an occlusal carious lesion was removal of the carious part only, which was chosen by 74% of the dentists. For a lower second molar with a minor occlusal caries lesion combined with a suspected dentin lesion as judged radiographically, about half of the dentists chose to restore the carious part only and 27% would seal the rest of the fissure system in addition. For a similar lesion with no obvious radiolucency in the dentin, about 1/3 chose the 'no treatment' alternative, 1/3 fluoride treatment, and the rest fissure sealing or other techniques. Composite was used most often and amalgam least often for both approximal and occlusal carious lesions.

Analysis of Variance↗

PubMed1999

Caries assessment and restorative treatment thresholds reported by Swedish dentists.

The aim was to study any variability in approximal and occlusal caries diagnoses and restorative treatment decisions among Swedish dentists. The material consisted of a pre-coded questionnaire sent to a random sample of 923 dentists with 4 items concerning approximal and occlusal caries diagnosis and restorative treatment decisions. Responses were received from 651 (70.5%) dentists. In an adolescent with low caries activity and good oral hygiene, more than 90% of the dentists stated that they would not automatically restore a primary approximal caries lesion if its radiographic appearance did not show obvious progression in the outer 1/3 to 1/2 of the dentin. Moreover, 67% of the dentists would only consider immediate restorative treatment of an occlusal surface if obvious cavitation and/or radiographic signs of dentin caries could be observed. When diagnosing questionable occlusal caries, the dentists largely relied on the radiographic appearance. Concerning both approximal and occlusal caries, the threshold for restorative treatment differed between the metropolitan regions in Sweden, and younger more often than older dentists would postpone restorative treatment of approximal caries until the lesion had reached a relatively advanced stage of progression. The responses also showed that dentists in private practice would restore approximal caries at an earlier stage of progression than the dentists in the Public Dental Health Service.

Adolescent↗

PubMed1999

Left frontal activation during a semantic categorization task: an fMRI-study.

In the present study we measured brain activation, with functional magnetic resonance imaging (fMRI) during the execution of a covert semantic categorization task. This involves activation of working memory and internal concept generation. Previous brain imaging studies of covert verbal fluency have shown widespread activation in the frontal and temporal lobes, and anterior cingulate. However, most of these studies have employed simple stimulus tasks with repetition of words e.g., beginning with a certain letter of the alphabet. Moreover, the subject is typically cued (either visually or auditory) every 2-5 second. In the present study we used a "single-cue" instruction at the beginning of each activation period where the subject was instructed to internally generate category specific names related to: "States in the USA," "UK Soccer clubs," and "Male names" during 54s periods. The three activation periods were compared to three baseline periods in which the subject was instructed to imagine mentally "lying on a beach and looking at the sky." Functional MRI was performed with a 1.5T Siemens Vision scanner. Initial TIW 3D FLASH scanning of anatomy was done, and thereafter, serial imaging with 60 BOLD sensitive echo planar whole brain measurements were done during the active and passive tasks. Main activation areas were found in the left middle frontal gyrus, partially overlapping with Brodmann area 9. This is in agreement with previous studies of increased activation in the left frontal lobe, and may indicate a left frontal neural network for accessing the mental lexicon.

Acoustic Stimulation↗

PubMed1996

Phantom limb imaginary fingertapping causes primary motor cortex activation: an fMRI study.

A conventional 1.0 T MR-scanner was used to detect signal intensity changes in blood oxygenation level dependent-sensitive acquisitions of motor cortex during real (left hand) and imaginary (right hand) fingertapping in a man who had his right arm amputated. The subject was instructed alternately to move the intact left hand fingers and to imagine tapping his 'fingers' on the amputated right hand. Activated areas were detected using a cross-correlation technique with superimposition of highly correlated voxels on to a corresponding high resolution, anatomical 3D image. Activation was observed in the right motor cortex during fingertapping with the intact left hand, and a corresponding activation in the left motor cortex for imaginary movements of the amputated right hand fingers.

Adult↗

PubMed1996

Reasons for the caries decline: what do the experts believe?

The aim of this paper was to describe what experts of today believe are the main reasons explaining the caries decline seen in many westernized countries over the past 3 decades. We have collected the views of a number of international experts, trying to answer the specific question "What are the main reasons why 20-25-year-old persons have less caries nowadays, compared to 30 years ago?". A questionnaire was mailed to 55 experts with a number of thinkable explanations to be scored according to a predetermined scale. The 25 items were divided into main groups under the heading of diet, fluorides, plaque, saliva, dentist/dental materials and other factors. The experts were asked to think of a specific country or area, and also to specify whether the chosen area had water fluoridation or not. The main finding of our study, based on a 95% response rate, was that there is a very large variation in how the experts graded the impact of various possible factors. For the use of fluoride toothpaste, there was a clear agreement of a definite positive effect.

Adult↗

PubMed1996

Changes in the prevalence of caries in children and adolescents in Sweden 1985-1994.

The prevalence of caries among 3-, 6-, 12- and 19-year-olds in Sweden was followed during the period 1985-1994 through county council reports to the National Board of Health and Welfare. Nearly all the county councils take part in this reporting, and the details for 1994 were based upon 74% of all the country's 12-year-olds and 81% of all the 19-year-olds. Particulars of caries are noted during the annual examination at national dental service clinics. Only manifest caries is recorded. For the age groups studied, the prevalence of caries diminished markedly during the period. The proportion of caries-free 3- and 6-year-olds increased. In 1994, 91% of the 3-year-olds and 64% of the 6-year-olds were free of caries in the deciduous dentition. DFT for 12-year-olds sank from 3.1 to 1.5 during 1985-1994. For 19-year-olds, DFT changed from 8.5 to 5.2, while the proportion of individuals who were caries-free on approximal surfaces increased from 36% to 58%. The change for DFS-a (carious or filled approximal surface) was from 3.4 in 1985 to 1.6 in 1994. These changes in the mean values were accompanied by changes in the frequency distribution of the values for DFT and DFS-a. The proportion of severely carious individuals decreased greatly during the 10-year period studied. At the same time, the differences in caries prevalence among the 26 county councils evened out.

Adolescent↗

PubMed1996

Estimation of prophylactic measures in Swedish public dental health care. Results from a questionnaire.

The aim of the present investigation was to map the presence of prophylactic measures in organized Swedish dental health care systems, focusing on personnel working with children and adolescents. The study was conducted by sending a questionnaire to all public dental clinics in Sweden (830 clinics in all). The results showed that collectively-performed prophylactic measures were given at 66% of the child health centers/ child day care centers and at 63% of the pre-schools. 57% of all clinics replied that they performed some kind of fluoride administration collectively (mainly fluoride varnish application or fluoride mouthrinses). 34% of all clinics used fluoride varnishes at the ages from 6 to 12 years, and collectively-performed fluoride mouthrinsing in schools at these ages was carried out by 16% of the clinics. 26% of all the clinics answered that they aimed at increasing the time spent on prophylactic measures compared to only 2% that were planning to decrease this time. The remaining 72% aimed at maintaining the time spent at the present. Prophylactic measures were performed individually by 49% of the clinics, whereas 50% of the clinics preferred a combination of individually and collectively performed measures. It can be concluded that the preventive measures against dental caries in Swedish public dental care is mainly focused on individually performed prophylaxis.

Adolescent↗

PubMed1995

Functional magnetic resonance imaging of primary visual processing using a 1.0 Tesla scanner.

Recent advances in functional magnetic resonance imaging (fMRI) at > or = 1.5 T magnetic field strength and with high speed single-shot echo planar imaging techniques have made it possible to monitor local changes in cerebral blood volume, cerebral blood flow, and blood oxygenation level in response to sensory stimulation, simple motor activity, and possibly also to more complex cognitive processing. However, fMRI has also been accomplished on conventional MR scanners of medium field strength (approximately 1.0 T) using special pulse sequences and appropriate methods for image analysis. We present results from six subjects on photic stimulation using a standard 1.0 T MR scanner together with special software for off-line image analysis. Continuous serial T2-weighted imaging were performed for 6 minutes in the plane of the calcarine fissure. There were 3 repetitions of 1 minute resting state of darkness (OFF) and 1 minute activated state (ON) with 8 Hz flicker stimulation. To directly map these functional images to the underlying anatomy we also acquired a high resolution T1-weighted image from the same axial slice. The results demonstrated that stimulus-related signals can be obtained from primary visual cortex with a conventional 1.0 T MR scanner. Further methodological improvements are discussed and related to present and future possibilities for the use of fMRI within psychophysiology.

Adult↗

PubMed1993

Poly(A) tail length of a heat shock protein RNA is increased by severe heat stress, but intron splicing is unaffected.

The small heat shock proteins (sHSPs) are induced in all eukaryotes in response to high temperature stress, but are most abundant among members of the plant kingdom where they accumulate in multiple subcellular compartments. We have analyzed the expression of the chloroplast-localized sHSP from Arabidopsis thaliana, HSP21, and characterized the structure of the gene encoding this protein to facilitate future genetic studies on the function of HSP21 in the heat shock response. HSP21 is encoded in Arabidopsis by a single gene whose coding region is interrupted by a single intron. Previous studies have shown that intron processing is disrupted by severe, abrupt heat stress but is protected by pretreatments that induce thermotolerance. The processing of the HSP21 transcript was investigated in response to an abrupt heat stress regime and a gradual heat stress regime, the latter of which is known to confer thermotolerance in plants. Under abrupt stress conditions the HSP21 transcript is somewhat longer than under gradual heat stress conditions. However, the molecular basis for the size difference is not impaired intron splicing, but rather a difference in the length of the poly(A) tail depending on the heat stress regime. The results suggest that an increase in poly(A) tail length may be a generalized response to severe, abrupt heat stress and that poly(A) tail metabolism may be one of numerous cellular processes normally protected in thermotolerant cells from the otherwise damaging effects of high temperature stress.

Amino Acid Sequence↗

PubMed1993

Nordic dentists' opinions on the safety of amalgam and other dental restorative materials.

The safety of amalgam and other restorative materials has caused concern among dental patients in recent years. The aim of this study was to obtain information on dentists' perceived competence in handling different filling materials and their opinions on the safety of these. A random sample of practising dentists in Denmark, Finland, Norway, and Sweden received a mail questionnaire in spring 1990. Answers were received from 1732 dentists (65%). The study showed that the respondents believed that their theoretic knowledge and clinical skills were generally at a high level regarding restorative materials. The risks of the side-effects of gold, ceramic materials, and glass ionomer were considered to be low by about 90% of the respondents. Amalgam was considered to be significantly more hazardous by the Swedish respondents than the others. Interestingly, composite was considered to be associated with a high risk of side-effects by about half of the dentists in all Nordic countries. The dentists' opinions were not found to be greatly influenced by their sex, age, or place of residence but rather by their country and service sector. Against the background of the present lack of scientific evidence on the hazardousness of amalgam or other restorative materials for patients' general health, these findings indicate that dentists are influenced by discussions in the mass media about dental treatment and materials and, of course, by the guidelines given by the health authorities in their own countries. Few dentists were shown to be concerned about occupational risks associated with the use of amalgam, and they had not had their own amalgam fillings replaced.(ABSTRACT TRUNCATED AT 250 WORDS)

Attitude of Health Personnel↗

PubMed1993

Quality of fixed prosthodontics after 15 years.

Interviews and/or clinical examinations by means of the California Dental Association quality evaluation system were carried out in a group of persons who had received extensive restorative treatments with fixed partial dentures 15 years before this study. The studied group consisted of 77 persons who agreed to participate from an original group of 150 persons selected at random from the Swedish Dental Insurance System records. Of the original group 20 had died, 17 were not traceable or not able to participate for medical reasons, and 36 declined to participate. Thirty-two per cent of the recorded reconstructions had been lost, and 8% partially lost during the 15-year period. Thirty-five per cent of the reconstructions were rated as Satisfactory, whereas the remaining ones had mixed clinical quality ratings. Failures and Not Acceptable quality ratings were found to be caused mainly by fractures, loss of retention, and/or dental caries.

Adult↗

PubMed1992

Fear of amalgam: dentists' experiences in the Nordic countries.

The purpose of the present investigation was to study Nordic dentists' experiences with patients concerned about the possible adverse effects of dental restorations, their perceived ability to deal with this problem and their views as to the suitability of amalgam as a filling material. A random sample of practising dentists in Denmark, Finland, Norway and Sweden were sent a questionnaire in spring 1990. Responses were received from 1732 dentists (65 per cent). In 1989, virtually every dentist had seen patients concerned about possible adverse effects of their dental restorations. The reported mean number of such patients per dentist per year was 80.5 (SD = 128.1) in Denmark, 39.3 (SD = 68.4) in Finland, 83.3 (SD = 194.1) in Norway, and 124.4 (SD = 210.3) in Sweden. Ninety-two per cent of the patients' questions concerned amalgam fillings. About 70 per cent of the dentists believed that inexplicable symptoms associated with amalgam fillings had a psychosomatic background. Only about a fifth of the respondents felt able to examine such patients without seeking medical expertise. In the absence of oral or medical indications, 65 per cent of the respondents in Sweden and 77 per cent in the other countries considered that dentists should advise patients against having their amalgam fillings replaced. About 5 per cent of the respondents were ready to stop using amalgam in the near future.

Attitude of Health Personnel↗