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Biomedical subjects

H Birn

Publications and source records attributed to H Birn.

At least 37 records · Page 2Linked to original sources
PubMed1995

Effects of microtubule disruption on endocytosis, membrane recycling and polarized distribution of Aquaporin-1 and gp330 in proximal tubule cells.

Microtubules are critically involved in membrane traffic and maintenance of epithelial cell polarity. In this study we examined the effect of microtubule disruption by colchicine on 1) the subcellular organization of the apical endocytic apparatus, 2) apical endocytosis, and 3) subcellular distribution of gp330 and Aquaporin-1 water channels in renal proximal tubule cells. Rats were treated in vivo with colchicine for 5 h before fixation of the kidneys, and sections of proximal tubules were studied using electron microscopy, morphometry and immunocytochemistry. In proximal tubule cells from colchicine-treated animals, virtually no endocytic invaginations are present, indicating that colchicine blocks the formation of endocytic invaginations. Furthermore, no large endocytic vacuoles are present, also consistent with a block of endocytosis. This was confirmed by functional studies revealing a colchicine-induced arrest in apical endocytosis of peroxidase. There is a marked reduction in dense apical tubules (the exocytic vehicle for membrane recycling) but an extensive accumulation of small vesicles, suggesting a disruption in membrane recycling. This disruption may be primary or secondary to the block of endocytosis. Immunofluorescence and immunoelectron microscopy reveal extensive colchicine-induced changes in the subcellular distribution of gp330 and Aquaporin-1. The localization of gp330 is normally restricted to the apical endocytic apparatus. However, after colchicine treatment gp330 is localized to numerous vesicles distributed throughout the entire cytoplasm, as previously shown (Gutmann et al., Am. J. Physiol. 257, C397-C407 (1989). Also Aquaporin-1 water channels, which are normally almost exclusively present in the plasma membranes, are redistributed to small vesicles in addition to the plasma membrane localization after colchicine treatment. In summary, the present study suggests that cytoplasmic microtubules are critically involved in 1) formation and stabilization of endocytic invaginations, 2) formation of large endocytic vacuoles, 3) apical endocytosis, 4) maintaining the polarized distribution of vesicles in the apical part of the cell, and 5) maintaining the polarized organization of gp330 in the apical endocytic apparatus, and maintaining Aquaporin-1 water channels in the plasma membranes.

Animals↗
PubMed1993

Prevalence and characteristics of dental anxiety in Danish adults.

Prevalence, characteristics and consequences of dental anxiety in a randomly selected sample of 645 Danish adults were explored in telephone interviews. Participation rate was 88%. Demographics, fear of specific procedures, negative dentist contacts, general fear tendency, treatment utilization and perceived oral conditions were explored by level of dental anxiety using a modified Dental Anxiety Scale (DAS). A Seattle fear survey item and a summary item from the Dental Fear Survey (DFS) were also included for fear description comparisons. Correlation between these indices (DAS-DFS: rs = 0.72; DAS-Seattle item: rs = 0.68) aided semantic validation of DAS anxiety intensity levels. Extreme dental anxiety (DAS > or = 15) was found in 4.2% of the sample and 6% reported moderate anxiety (DAS scores 14-12). Bivariate (B) and logistic regression (L) odds ratios (OR) showed that high dental anxiety was associated with gender, education and income, but not with age. Extreme dental anxiety for dentate subjects was characterized by fear of drilling (ORL = 38.7), negative dentist contacts (ORL = 9.3), general fear tendency (ORL = 3.4), avoidance of treatment (ORL = 16.8) and increased oral symptoms (ORB = 4.4). Moderate dental anxiety was also related to drilling (ORL = 22.3), but with less avoidance due to anxiety (ORL = 6.8) compared with low fear subjects.

Adolescent↗
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

Internalization and intracellular transport of folate-binding protein in rat kidney proximal tubule.

Folate-binding protein (FBP) is involved in folate reabsorption in the renal proximal tubule. Immunocytochemical studies have located FBP to the brush-border membrane, endocytic vacuoles, and dense apical tubules. We applied the same polyclonal antibody (anti-FBP) against FBP to investigate the dynamic relationship between FBP in the different compartments by microinjecting the antibody into rat kidney proximal tubules in situ. Specific binding of anti-FBP in vivo to the brush-border membrane was followed by fixation at various times. Protein A-gold labeling shows that anti-FBP is transported from endocytic invaginations into vacuoles followed by transport into dense apical tubules within 15 s. Thus FBP is rapidly internalized, and together with previous studies this study strongly suggests recycling of FBP back to the luminal plasma membrane through dense apical tubules. The results are consistent with reabsorption of folate through endocytosis of the FBP-folate complex followed by dissociation and recycling of FBP. When time is allowed there is a steady accumulation of FBP in dense apical tubules combined with an increase in surface density of the same compartment. A possible explanation involves partial inhibition of the fusion between dense apical tubules and plasma membrane because of the anti-FBP labeling of the receptor.

Animals↗
PubMed1993

Kinetics of endocytosis in renal proximal tubule studied with ruthenium red as membrane marker.

This study was performed to determine the membrane area of the different compartments involved in endocytosis in rat kidney proximal tubule. This enables a direct estimation of the kinetics of the membrane turnover in the subprocesses of endocytosis and recycling of membrane constituents. To accomplish this, cross-sectioned invaginations have to be distinguished from endocytic vesicles. To obtain a continuous heavy staining of the apical plasma membrane, we have developed a sandwich-staining technique involving initial staining with ruthenium red, osmium, and thiocarbohydrazide functioning as a molecular bridge between osmium molecules. The distribution of invaginations, noncoated and coated endocytic vesicles, as well as the surface density of invaginations, small endocytic vesicles, large endocytic vacuoles, lysosomes, and dense apical tubules are determined in segment 1 (S1) and 2 (S2) of the proximal tubule. This has shown that invaginations constitute most [54% (S1 and 62% (S2)] of the membrane in small membrane-bounded structures in the apical cytoplasm. No morphological characteristics enabled direct differentiation between cross-sectioned invaginations and small endocytic vesicles, but a method for correct identification of 72% of all invaginations and 82% of all small endocytic vesicles is presented. Using the surface densities of various compartments together with previous data on the internalization of membrane markers, we developed a kinetic model enabling calculation of the velocity of membrane internalization and subsequent recycling. The velocity of internalization is 6.4 X 10(-3) microns2.micron-3.s-1, corresponding to internalization of a membrane area equivalent to the entire surface of invaginations within 78 s. The velocity of membrane transfer from the vacuolar compartment to dense apical tubules and of recycling from dense apical tubules to the luminal membrane is 6.2 x 10(-3) microns 2.microns-3.s-1. The entire membrane area equivalent to the surface of the vacuolar compartment and dense apical tubules is transferred in 43 and 92 s, respectively. The amount of membrane that surrounds lysosomes is transported from the vacuolar compartment within 23 min.

Animals↗
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↗
PubMed1991

Manifestations, acquisition and diagnostic categories of dental fear in a self-referred population.

This study aimed to clarify how manifestations and acquisition relate to diagnostic categories of dental fear in a population of self-referred dental fear patients, since diagnostic criteria specifically related to dental fear have not been validated. DSM III-R diagnostic criteria for phobias were used to compare with four existing dental fear diagnostic categories, referred to as the Seattle system. Subjects were 208 persons with dental fear who were telephone interviewed, of whom a subsample of 155 responded to a mailed Dental Anxiety Scale (DAS), State-Trait Anxiety Inventory and a modified FSS-II Geer Fear Scale (GFS). Personal interviews and a Dental Beliefs Scale of perceived trust and social interaction with dentists were also used to evaluate a subsample of 80 patients selected by sex and high dental fear. Results showed that the majority of the 80 patients (66%), suffered from social embarrassment about their dental fear problem and their inability to do something about it. The largest cause of their fear (84%) was reported to be traumatic dental experiences, especially in childhood (70%). A minority of patients (16%) could not isolate traumatic experiences and had a history of general fearfulness or anxiety. Analysis of GFS data for the 155 subjects showed that fear of snakes and injuries were highest among women; heights and injections among men. Fear of blood was rarely reported. Spearman correlations between GFS individual items and DAS scores indicated functional independence between dental fear and common fears such as blood, injections and enclosures in most cases. Only in specific types of dental fear did these results support Rachman and Lopatka's contention that fears are thought to summate.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Dental students' views on their education and study circumstances in Nordic countries.

The curricula at the Nordic dental schools are similar in their content but may vary in the placement of different subjects and the way of teaching them. The aim of this study was to analyse Nordic dental students social background, and their reasons for choosing dentistry, their opinions on the course, and their future professional plans. A combination of an open-ended and structured questionnaire was given to final year dental students at the dental schools in Aarhus, Bergen, Kuopio and Stockholm. The response rate as 83%. The main reasons for choosing dentistry were its combination of theory and practice (29%), and a wish to work with people (20%), whereas only 4% mentioned the "high status" of the profession. Regular day-time work was emphasized by female students. Most students considered the teaching load heavy. The time devoted to the different subjects was considered sufficient, except for behavioural science and medicine, where the time was too short. There was general dissatisfaction with the teachers pedagogical skills, and there was a feeling that teaching was regarded as secondary to research. Most students planned to become private practitioners. Between 25-55% of the students wanted to specialize, and oral surgery was the most popular specialization.

Adult↗
PubMed1990

[Phenomenon of dental fear].

Odontophobia is a rather unique phobia with special psychosomatic components that impact on the dental health of odontophobic persons. It also has psychosocial components largely as a result of destruction of the teeth and subsequent embarrassment that can affect a person and cause a vicious cycle of dental fear. The phenomenon is facilitated by misunderstandings and myths generated by both patients and dentists. The most common reasons given in the literature for such strong fears of dental treatment are: 1) bad experiences in childhood for 85% of cases, 2) feeling of powerlessness and lack of control over personal emotional reactions and over the social situation in the dental chair, 3) social learning processes in which the image of the dentist is cast in a negative light by the mass media or by the person's relatives or friends and 4) that the person has other psychologic problems (in 20% of cases), such as serious phobias and/or neuroses. A strategy of researching and thus tackling the problem is presented which focuses on three essential targets that require studying and change: 1) the community at large and their image of the dentist, 2) the patient role and 3) the dentist role. Various model projects are presented along with their diagnostic systems. These are seen to focus in varying degrees on different elements of the target groups that effect the dentist-patient relationship but the need to come out into the community and make the social environment right for these patients is an important factor in all strategies.(ABSTRACT TRUNCATED AT 250 WORDS)

Communication↗
PubMed1990

[How to evaluate dental fear].

The measurement of complex behavioral phenomena like dental fear requires allegiance to two great domains that often seem to conflict with one another: natural scientific method and the seemingly unpredictable human psyche. The need to preserve strict objectivity in scientific observations and yet flexibility enough to appreciate the contextual facets of psychological and social variables are a difficult combination. There are differing scientific philosophies that are presented here not as incompatible opposites, but as a complementary team of approaches to aid human behavioral problem solving in dental clinical science. The "positivistic falsification" tradition requires "objective" double-blind type experimental hypothesis testing, while the "phenomenologic-hermaneutic" tradition requires the researcher to grasp the context of the phenomena to be studied in order to understand and thereafter test the most relevant variables. Thus, there is a need for both traditions, since the relevant variables should be systematically evaluated (qualitative phase) before they can be adequately tested (quantitative phase). Clinical evaluation of dental fear draws on information gathered about a patient's verbal (cognitive) descriptions, behavioral symptoms and physiologic reactions. Commonly used psychometric testing scales developed to differentiate fears specific to dentistry, as opposed to general anxiety syndromes, are the result of observations made in several qualitative studies that not all dental phobics have general anxiety symptoms. Examples of these and other tests are listed and described, noting that verbal and behavioral testing appear more reliable than physiologic indicators. The patient's subjective sense of improvement is deemed to be an important factor in their confidence and efficacy to deal with the threats that the dental environment can bring them.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Care↗
PubMed1989

Simple and time-saving computer programs for chairside assistants.

The purpose of this study was to test the hypothesis that CAI used at low cognitive levels is as effective and motivating as conventional teaching, while requiring fewer teacher resources. Seventy-six chairside-assistant students were randomly allocated to either a CAI-group or a control group receiving conventional teaching. The subject taught was the clinical armamentarium and its use. A performance and attitude test was given to both groups. Time used for constructing the CAI program and for conventional teaching was registered. The results confirmed the hypothesis.

Attitude to Computers↗
PubMed1987

The self-fulfilling prophecy in dental prophylaxis.

This report deals with the influence of the self-fulfilling prophecy on dental prophylaxis. The aim was to test if this phenomenon had any influence on the treatment of patients, they and their therapeutist's perception of each other and the result of the prophylactic work. Sixty patients and 34 students were involved. The patients were randomly classified as "good" or "bad". Twenty-seven students had a patient from each group. Dental plaque and gingival inflammation were recorded before and after the treatment. No difference in improvement between the two groups could be shown. Both patients and students were interviewed about their experiences and feelings during the treatment. All patients were satisfied with their therapeutist. The students generally accepted the classification although they were made aware of the self-fulfilling prophecy. This was confirmed by a significantly higher frequency of patient drop-outs, broken appointments and critical notes about the patients in the "bad" group compared to the "good". The conclusions are that the self-fulfilling prophecy can be initiated by even minor notes in patient files, and that this affects the treatment of patients.

Appointments and Schedules↗