Showing papers by "University of Gothenburg published in 1989"

A twin study of autism in Denmark, Finland, Iceland, Norway and Sweden.

Abstract: The Nordic countries were screened for the occurrence of cases of autism with a same-sexed twin under age 25 years. Twenty-one pairs (11 monozygotic and 10 dizygotic) of twins and one set of identical triplets were found and extensively examined. The concordance for autism by pair was 91% in the monoygotic and 0% in the dizygotic pairs. The corresponding concordances for cognitive disorder were 91% and 30%, respectively. In most of the pairs discordant for autism, the autistic twin had more perinatal stress. The results lend support for the notion that autism sometimes has a hereditary component and that perinatal stress is involved in some cases.

Detection of activated T lymphocytes in the human atherosclerotic plaque.

Abstract: It was recently shown that the human atherosclerotic plaque contains significant amounts of T lymphocytes, and also that smooth muscle cells in these plaques express class II MHC (Ia) antigens. These antigens are not normally present on smooth muscle cells but are inducible by interferon-gamma, a secretory product of activated T cells. Therefore, T cell activation in the plaque was analyzed by immunofluorescent detection of activation markers on T cells isolated from the plaques and in cryostat sections of carotid endarterectomy specimens. Of cells isolated from the plaque, 5% exhibited the E rosettes characteristic of T cells. One third of these cells expressed HLA-DR and VLA-1 (very late activation antigen-1), which in T cells are synthesized only in the activated state. T cells were also identified in sections using immunofluorescent detection of the T cell-specific surface protein, CD3 (Leu-4), with rhodamine labeled second-step antibodies. The frequency of activated T cells was then determined by staining the same, or serial, sections with antibodies to HLA-DR or to the interleukin-2 receptor, followed by biotin-avidin-FITC detection. Of the T cells in the plaque, 34% and 6%, respectively, expressed these cell surface proteins. Taken together, these results indicated that a substantial proportion of the T cells in atherosclerotic plaque are in an activated state. The activation pattern, with a high frequency of HLA-DR and VLA-1 expression and a much lower frequency of interleukin-2 receptor expression, was similar to that reported to occur in chronic inflammatory conditions. Interferon-gamma could be detected in and around some of the lymphocytes, suggesting that paracrine secretion of this lymphokine may occur in the plaque. T cells may be activated locally, presumably by antigen(s) presented in the context of class II MHC expressing smooth muscle cells and/or macrophages, in the atherosclerotic lesion. Such activated T cells may in turn modulate the functions of other cells in the plaque.

Asperger syndrome--some epidemiological considerations: a research note.

Abstract: Asperger syndrome has so far been the subject at very little systematic empirical inquiry. This paper reviews those few studies in the literature and some data from a new Swedish study which has reported findings pertinent to estimations of Asperger syndrome prevalence. It is concluded that among children with normal intelligence, rates of 10–26 per 10,000 children are minimum figures. Another 0.4 per 10,000 Swedish teenagers showed the combination of Asperger syndrome and mild mental retardation.

Electrofishing — Theory and practice with special emphasis on salmonids

Abstract: This report attempts to establish guide-lines for electrofishing in population studies and is the result of literature studies and experience from electrofishing in Denmark, Finland, Norway and Sweden. Equipment, safety and training, sampling design and precision requirements for various types of investigations, population estimation and fishing practice are discussed. The results are put forward in the form of recommendations. Special attention is paid to the sampling design of surveys in streams of different types and for different purposes. Examples of the computation procedures are also included.

Glucose-inhibition of glucagon secretion involves activation of GABAA-receptor chloride channels.

Abstract: The endocrine part of the pancreas plays a central role in blood-glucose regulation. It is well established that an elevation of glucose concentration reduces secretion of the hyperglycaemia-associated hormone glucagon from pancreatic alpha 2 cells. The mechanisms involved, however, remain unknown. Electrophysiological studies have demonstrated that alpha 2 cells generate Ca2+-dependent action potentials. The frequency of these action potentials, which increases under conditions that stimulate glucagon release, is not affected by glucose or insulin. The inhibitory neurotransmitter gamma-aminobutyric acid (GABA) is present in the endocrine part of the pancreas at concentrations comparable to those encountered in the central nervous system, and co-localizes with insulin in pancreatic beta cells. We now describe a mechanism whereby GABA, co-secreted with insulin from beta cells, may mediate part of the inhibitory action of glucose on glucagon secretion by activating GABAA-receptor Cl- channels in alpha 2 cells. These observations provide a model for feedback regulation of glucagon release, which may be of significance for the understanding of the hypersecretion of glucagon frequently associated with diabetes.

Long-term beta-blockade in dilated cardiomyopathy. Effects of short- and long-term metoprolol treatment followed by withdrawal and readministration of metoprolol.

Abstract: To evaluate the short- and long-term effects of beta-adrenergic blockade (metoprolol) as well as the reaction to withdrawal and readministration of metoprolol in severe heart failure, 33 patients (25 men and eight women; mean age, 47.6 +/- 14.0 years) with dilated cardiomyopathy were studied by right and left heart catheterization, right ventricular biopsy, two-dimensional and Doppler echocardiography, and external pulse recordings. Twenty-six of 33 patients survived more than 6 months, and 24 of the 26 patients improved their functional class (from mean 3.3 to 1.8, p less than 0.0001). These 24 patients were subjected to withdrawal of metoprolol until the number of symptoms increased and deterioration occurred as observed noninvasively (group 1, n = 16), whereas the eight patients did not deteriorate during a 12-month period (group 2). During long-term treatment with metoprolol, there was an increase in ejection fraction from 0.24 to 0.42 (p less than 0.0001), whereas there was a decrease in the left ventricular (LV) end-diastolic dimension (from 7.3 to 6.4 cm, p less than 0.0001), in the grade of mitral regurgitation (from 1.7 to 0.4, p less than 0.0001), and in the grade of tricuspid regurgitation (from 0.6 to 0.05, p less than 0.007). There was a decrease in pulmonary wedge pressure (from 23.8 to 10.7 mm Hg, p less than 0.0001), LV end-diastolic pressure (from 24.1 to 13.4 mm Hg, p less than 0.002), and systolic vascular resistance (from 1,782 to 1,499 dynes/sec/cm, p less than 0.04). There was an increase in systolic blood pressure (from 116 to 132 mm Hg, p less than 0.003), cardiac index (from 2.17 to 2.58 l/min/m2, p less than 0.005), and LV stroke work index (from 31 to 65 g.m/m2, p less than 0.0001). During withdrawal of metoprolol, the heart rate and left atrial dimension increased (p less than 0.0001), whereas ejection fraction decreased (p less than 0.0001). The 12 (of 16) patients in group 1 who survived the withdrawal period had metoprolol readministered, and subsequently, ejection fraction increased (from 0.23 to 0.33, p less than 0.002). Patients had a low number of ventricular beta-adrenergic receptors compared with healthy control subjects (30.3 +/- 2.9 vs. 97.4 +/- 8.7 fmol/mg protein, p less than 0.001), but long-term treatment with metoprolol caused a moderate up-regulation (from 30.3 +/- 2.9 to 49.0 +/- 7.1 fmol/mg protein, p less than 0.05), which may facilitate a more normal response to sympathetic stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)

Asthma and allergic rhinitis in Swedish conscripts

Abstract: The computer records of Swedish conscript examinations in 1971 and 1981 were analysed regarding the prevalence of asthma and allergic rhinitis. The material comprised approximately 55,000 18-year-old males in each cohort. During the 10-year period the prevalence of asthma increased from 1.9 to 2.8% and of allergic rhinitis from 4.4 to 8.4%. The prevalence of allergic rhinitis was already higher in the northern than in the southern part of the country in 1971. The increase in both diseases was higher in the northern parts of Sweden, giving double prevalence figures in the northern part of the country compared to the southern part in 1981. The distribution of the prevalence was similar to the temperature pattern in the country, the higher prevalence being associated with a colder outdoor climate. Both diseases were more prevalent in urban than in rural areas.

Stress on and off the job as related to sex and occupational status in white‐collar workers

Abstract: Sixty healthy non-smoking white collar employees, aged 30–50, from a large corporation in Sweden participated in the study. There were four groups: 15 male and 15 female middle managers, 15 male and 15 female clerical workers. Each participant was examined individually with regard to cardiovascular and neuroendocrine functions and self-reports for 12 consecutive hours under each of two conditions: (1) a normal day at work (9 a.m.–5 p.m.) and after work (6–9 p.m.), and (2) for the same time period during work-free conditions at home. In addition, everyone was given a videotaped type A-interview and a general health check-up including blood-lipid determination. Attitudes towards work, total workload (including responsibilities outside the paid work) and sex role identity were examined by questionnaires. As expected, all groups showed a moderate increase in cardiovascular and neuroendocrine activity during the day at work. After work, however, interesting group differences emerged, suggesting slower unwinding in female managers. Differences related to occupational level and/ or sex were found for autonomy and social support at work, competitiveness, sex role and reported conflict between demands from paid work and other responsibilities. The stress profile of the female managers was considered in terms of possible long-term health risks.

Symptoms in the first two years of life. A preliminary population study of infantile autism.

Abstract: A population sample of autistic children (n = 26) were compared retrospectively with age-and sex-matched mentally retarded children (n = 20) and age- and sex-matched population-representative children (n = 25) on a 130-item questionnaire to the mother concerning characteristic features of the child's behaviour in the first 2 years of life. Thirteen items discriminated clearly between the groups. The results are discussed in the context of early screening for autism.

Assessment of patients' experience of discomforts during respirator therapy.

Abstract: Patients (n = 158) who had been respirator-treated and who could remember the treatment were retrospectively (after greater than 2 months) interviewed about their experiences. Of all patients, 47% had felt anxiety and/or fear during the treatment. These feelings were intimately related to the experience of agony/panic (p less than .001) and insecurity (p less than .001). Inability to talk and communicate was found to be the dominating reason (p less than .001) for evoking such feelings and also made it difficult for the patients to sleep and rest (p less than .05); no correlation to pain was found. Difficulties to synchronize with the respirator in connection with suctioning also caused feelings of anxiety/fear (p less than .01), agony/panic (p less than .01), and insecurity (p less than .001). Even as long as 4 yr after respirator treatment, most patients (90%) who remember the treatment still recall the situation as unpleasant and stress-evoking. The isolation due to communication difficulties was a greater problem than direct airway-related nursing care activities. This relationship between communication difficulties and severe emotional reactions should be considered in the nursing care of respirator-treated patients.

Adiposity and adipose tissue distribution in relation to incidence of diabetes in women: results from a prospective population study in Gothenburg, Sweden.

Abstract: The results refer to a 12-year longitudinal population study of women in Gothenburg, Sweden. Correlations were studied between initial adipose tissue amount and adipose tissue distribution on the one hand and incidence of diabetes and change in serum blood glucose concentration on the other. Body mass index, sum of two skinfolds and waist-to-hip circumference ratio were significantly associated with incidence of diabetes. The waist-to-hip ratio was also positively associated with an increase of serum glucose concentration in the fasting state during the followup period. The significant correlations remained in multivariate analysis and were independent of age, initial smoking habits, systolic blood pressure, intake of antihypertensive drugs and serum cholesterol, triglyceride and glucose concentrations. The correlations between the separate anthropometric variables and incidence of diabetes remained when the other anthropometric variables were considered as background factors. The distribution of fat to the abdominal region as well as the total amount of fat per se seem to be important risk factors for diabetes and the effect of one of these factors seems to add to the other.

Pulmonary Function and Symptoms after Inhalation of Endotoxin

Abstract: In previous experiments, a good relationship was demonstrated between the amount of airborne bacterial endotoxin and acute reactions after exposure to organic dusts. In the present study, 77 naive subjects were exposed to isolated endotoxin (IE) or endotoxin attached to bacterial cells (CE). Both preparations were obtained from Enterobacter agglomerans, which is a major bacterial species in many organic dusts. The major physiologic effect caused was a dose-related decrease in transfer factor, as measured by carbon monoxide diffusion. Half of the subjects reported fever and about one-third a subjective feeling of chest tightness. The exposure also caused a dose-related but small decrease in FEV1. A slightly increased bronchial reactivity was demonstrated at 4 h after endotoxin exposure. The minute volume after CO2 exposure was marginally affected. The results further support the conclusions from epidemiologic and experimental studies that the bacterial endotoxin is responsible for the acute reactions seen after exposure to many organic dusts, including that derived from cotton.

Ischemic Damage in Hippocampal CA1 is Dependent on Glutamate Release and Intact Innervation from CA3

Abstract: Summary: The removal of glutamatergic afferents to CAl by destruction of the CA3 region is known to protect CA I pyramidal cells against 10 min of transient global isch­ emia. To investigate further the pathogenetic significance of glutamate, we measured the release of glutamate in intact and CA3-lesioned CAl hippocampal tissue. In in­ tact CAl hippocampal tissue, glutamate increased sixfold during ischemia; in the CA3-lesioned CAl region, how­ ever, glutamate only increased 1.4-fold during ischemia. To assess the neurotoxic potential of the ischemia­ induced release of glutamate, we injected the same con­ centration of glutamate into the CAl region as is released during ischemia in normal, CA3-lesioned, and ischemic

Risk factors for heart failure in the general population: The study of men born in 1913

Abstract: In 1963 a sample of 973 men, all 50 years old, was drawn from the population register of Gothenburg, Sweden. These men have been followed up for 17 years with repeated examinations regarding a number of variables possibly related to cardiovascular disease. The latest examination, at the age of 67 years, focused on congestive heart failure (CHF). The incidence rate of manifest CHF varied from 1.5 to 10.2 cases (1000 population)-1 yr-1, depending on which age group was being studied. For the age group 50-67 years the incidence of manifest CHF was 5.5 (1000)-1 yr-1. A large number of factors associated with the risk of acquiring CHF were identified. In multivariate regression analyses, hypertension and smoking were the major independent risk factors. Body weight, heart volume, T-wave abnormalities, heart rate variability, peak expiratory flow rate, psychological stress and Fy-antigen (a genetic marker?) were also independent risk factors. Possible strategies for prevention are discussed.

Self-assessment of language proficiency: rationale and applications

Abstract: During the last 10 years there has been a surge of interest in methods for self- assessment of foreign language proficiency. Work has been undertaken in many parts of the world and several reports on both theoretical and practical issues have been published recently. This paper outlines the justification for adopting self-assessment principles in language teaching and learning, makes references to research and sources supporting the statements made, and also presents some ideas and materials that illustrate developments taking place.

Dentin matrix proteins: Composition and possible functions in calcification

Abstract: Dentin may be regarded as a mineralized connective tissue. In its composition as well as its mode of formation, dentin exhibits several similarities with bone, but also definite differences. The dentin organic phase, the matrix, determines its morphology and is believed to be instrumental in the formation of the mineral phase. A fibrous web of collagen type I dominates the organic matrix. Also, minor amounts of other collagen types may be present. The noncollagenous proteins (NCPs), which constitute about 10% of the matrix, fall into several categories: phosphoproteins, Gla-proteins of the osteocalcin type as well as matrix Gla-protein, proteoglycans, different acidic glycoproteins, and serum proteins. Some of these NCPs have unique chemical compositions that give them specific properties. Dentinogenesis occurs by two simultaneous processes: the formation of a collagenous web in predentin, which is followed by the formation of the inorganic phase at the mineralization front. The composition of the predentin organic matrix differs from that of dentin, as some NCP components are secreted extracellularly just in advance of the mineralization front. In addition, some constituents of predentin seem to be metabolized. The NCPs may be important to several processes during dentinogenesis. Much evidence indicates that noncollagenous components in the matrix are instrumental in mineral formation. New data show that polyanionic NCPs, such as phosphoprotein and proteoglycans, when immobilized on a solid support, induce apatite formation under physiological conditions. These data indicate that polyanionic NCPs may function as mineral nucleators in vivo. They may also act as size and rate regulators for crystallization and promote calcium ion diffusion in the tissue. In addition, NCPs may regulate collagen fibrillogenesis.

Interferon gamma inhibits both proliferation and expression of differentiation-specific alpha-smooth muscle actin in arterial smooth muscle cells.

Abstract: Differentiation of muscle cells is characterized morphologically by the acquisition of contractile filaments and characteristic shape changes, and on the molecular level by induction of the expression of several genes, including those for the muscle-specific alpha-actin isoforms. IFN-gamma is an inhibitor of proliferation for several cells, including vascular smooth muscle, and is also an inducer of differentiated properties for several hematopoietic cells. We have therefore investigated whether IFN-gamma affects the expression of alpha-smooth muscle actin in cultured arterial smooth muscle cells. Cells exposed to IFN-gamma show a reduction of alpha-smooth muscle actin-containing stress fibers, as detected by immunofluorescence. The effect was observed in all phases of the cell cycle, and was caused by a reduction of the synthesis of alpha-smooth muscle actin protein as revealed by two-dimensional electrophoretic analysis of actin isoforms. RNA hybridization using a cRNA probe that hybridizes to all actin mRNAs showed that IFN-gamma-treated cells have a reduced content of the 1.7-kb mRNA that codes for alpha-smooth muscle actin, and to a lesser extent, also of the 2.1-kb mRNA encoding the beta and gamma-cytoplasmic actins. The reduction of alpha-smooth muscle actin mRNA was confirmed using an alpha-smooth muscle actin-specific cRNA probe. The reduction of alpha-smooth muscle actin mRNA occurs within 12 h, and is dependent on protein synthesis, since cycloheximide treatment reversed the effect. The inhibition of this mRNA species was dose dependent, and detectable by RNA hybridization at a dose of 50 U/ml IFN-gamma. These results suggest that the differentiation of arterial smooth muscle cells is not necessarily coupled to an inhibition of cellular proliferation. Instead, IFN-gamma may regulate the expression of several genes that control both proliferation and expression of differentiation markers.

A 10–year retrospective study of periodontal disease progression

Abstract: The purpose of this study was to record the rate of periodontal disease progression over a 10-year period with respect to individual subject, age and tooth type. 283 subjects, who had undergone a full-mouth radiographic examination in 1974–76 and at that time were 25–70 years old, were randomly selected from a larger patient sample for a new radiographic examination in 1985–86. 201 subjects (71%) agreed to participate. For each respondent, tooth loss over the 10-year period was calculated-The radiographic bone height at the mesial and distal aspect of all teeth was assessed by measuring the distance between the cemento-enamel junction and the bone crest. Difference in periodontal bone height between the 2 examinations was calculated for each tooth site. The results revealed that the mean number of teeth lost over the 10-year period was 3.8 (SD 4.6). Tooth mortality, expressed as a % of the no. of teeth present at the initial examination, increased with age and varied between 2.9%-28.5%. In all age groups, molars had the highest and canines the lowest rate of tooth mortality. The frequency of subjects with loss of > 10 teeth was highest for the initially 45-year old individuals (20%). 7 individuals (3%) had become edentulous. The mean annual reduction of alveolar bone height varied between 0.07–0.14 mm in the age groups 25–65 years. The initially 70-year old subjects showed a statistically significant higher annual rate of bone loss (0.28 mm). A mean bone loss over the 10–year period of ≥0.5 mm was observed in ∼75% of all the subjects, while 7% showed a mean bone loss of ≥3 mm. About 55% of the tooth sites had lost between 0.5–2.0 mm in periodontal bone height and 16% showed a longitudinal bone loss of >2 mm. 10 sites or more with longitudinal bone loss of 6 mm were found in 4% of the subjects and ∼ 15% of the subjects accounted for half of the totally recorded tooth sites with a 6 mm longitudinal bone loss.

Mental disorder in youth suicide. DSM-III-R Axes I and II.

Abstract: A 3-year urban material of suicides in adolescents and young adults (age 15-29 years) was studied retrospectively by means of interviews with survivors (n = 58). Classification of mental disorders according to DSM-III-R showed that major depression was important as background to suicides in 41%, primary (22%) or secondary (19%) to other disorders. Adding major depression, depressive disorder, not otherwise specified, dysthymia and adjustment disorder with depressed mood gave a total of 64% depressive syndromes. Schizophrenia (14%) and borderline personality disorder (28%) constituted other relevant groups. Coexisting substance use disorder occurred in 47%. A majority of the subjects (72%) were known by psychiatric caregivers and 16% committed suicide during inpatient care. Language: en

Periodontal conditions in insulin-dependent diabetics.

Abstract: The aim of this study was to compare the prevalence and severity of periodontal disease in age- and sex-matched adult long- and short-duration insulin-dependent diabetics and non-diabetics. The study involved 82 subjects with long- and 72 with short-duration diabetes and 77 non-diabetics, all aged 20-70 years. The clinical and radiographic examination comprised recordings of the number of existing teeth, absence or presence of plaque and supra- and subgingival calculus, gingival conditions, probing pocket depth and alveolar bone level. There were no significant differences in the number of existing teeth or presence of plaque and supra- and subgingival calculus between long- and short-duration diabetics and non-diabetics. Diabetics, irrespective of the duration of the disease, had a higher prevalence of sites with gingivitis than non-diabetics. Overall, there were no significant differences between the groups regarding the prevalence of tooth surfaces with probing pocket depths of 4 and 5 mm. However, on comparison between age subgroups, long-duration diabetics younger than 45 years had significantly more 4 and 5 mm pockets than non-diabetics. Long-duration diabetics altogether had significantly more tooth surfaces with probing depth greater than or equal to 6 mm than non-diabetics. The radiographs of alveolar bone height exhibited significantly more extensive alveolar bone loss in long-duration diabetics aged 40-49 years than in short-duration diabetics and non-diabetics. This, together with the increased number of subjects belonging to classification groups with severe periodontal disease experience among long-duration diabetics, indicates more periodontal disease in these diabetics.

Anorexia nervosa in a Swedish urban region. A population-based study.

Abstract: The total population of 15-year-olds in Goteborg, Sweden, were screened in 1985 for anorexia nervosa using brief questionnaires, growth charts and individual school nurse reports. An accumulated frequency of anorexia of 0.84% for girls up to and including 15 years of age was obtained, with 85% of the cases fulfilling DSM-III-R criteria. Boys were affected just over one-tenth as often as girls. The frequency of anorexia nervosa appeared to be much higher in private than in comprehensive schools. The peak age of onset seemed to be 14 years.

Thoracic epidural anesthesia and central hemodynamics in patients with unstable angina pectoris.

Abstract: The effects of high thoracic epidural anesthesia (TEA) on central hemodynamics as measured by pulmonary arterial catheterization were studied in nine patients with severe coronary artery disease and unstable angina pectoris. The patients were also treated with a combination of beta-blockers, calcium antagonists, and nitrates, as well as salicylates, low-dose heparin, and nitroglycerin infusion for greater than 24 hr. Management of pain with high TEA was started with the bolus epidural injection of 4.3 +/- 0.2 mL bupivacaine (5 mg/mL), which induced a sympathetic blockade from Th. During ischemic chest pain, pulmonary artery and pulmonary capillary wedge pressures were significantly increased. TEA, while relieving the chest pain, significantly decreased systolic arterial blood pressure, heart rate, and pulmonary artery and pulmonary capillary wedge pressures, without any significant changes in coronary perfusion pressure, cardiac output, stroke volume, and systemic or pulmonary vascular resistances. In some patients, ST-segment depression was less pronounced during TEA. Thus, during ischemic chest pain, TEA has beneficial effects on the major determinants of myocardial oxygen consumption, without jeopardizing coronary perfusion pressure. TEA may therefore favorably alter the oxygen supply/demand ratio within ischemic myocardial areas.

Secretion of antibodies to types I and II collagen by synovial tissue cells in patients with rheumatoid arthritis.

Abstract: Production of antibodies to IgG and to type I and type II collagen (CI and CII) was analyzed by enzyme-linked immunospot assay in patients with rheumatoid arthritis (RA) and patients with other inflammatory or degenerative joint diseases. Anti-CII–secreting cells, generally in high numbers, were found among mono-nuclear cells eluted from inflamed synovial tissue in 12 of 13 patients with seropositive RA and 9 of 14 patients with seronegative RA or with undetermined serum rheumatoid factor levels. In contrast, no anti-CII–producing B cells were present among synoviocytes from 4 patients with other joint diseases. In none of 7 RA sera did we find significant levels of anti-CII. Synovial B cells secreting antibodies specific for CI were observed less frequently in patients with RA. These results indicate that measurement of serum antibody levels is not adequate to assess actual autoantibody production in rheumatoid joints and that local autoimmune reactions to CII are common in RA, which implies that collagen-reactive T cells are present within the inflamed joints of RA patients. The possible role of a local collagen auto-immunity in RA is discussed, particularly in relation to its putative role in rheumatoid factor production.

Vertical mixing in basin waters of fjords

Abstract: The rate of work against the buoyancy forces due to vertical mixing (W) has been determined from repeated measurements of vertical density profiles in a large number of fjordic sill basins (basins dammed by sills). It is found that there is a weak “background” rate of work W0, probably driven by the local wind. Superposed upon this is work driven by the tide. Thus W = W0 + RfE, where E is the mean energy flux from the surface tide to turbulence in the sill basin and Rf is an efficiency factor. We distinguish between “wave basins” and “jet basins.” In the former category progressive internal tides are generated in the mouths, while in the latter there are tidal jets at the mouths. For wave basins, about 5.6% of the energy flux E from the surface tide is used for work against the buoyancy forces in the basin water (i.e., Rf ≈ 0.056). The corresponding figure for jet basins appears to be less than 1%. We have also studied the dependence of the vertical diffusivity κ upon the vertical stratification ...

Guided tissue regeneration in the treatment of furcation defects in mandibular molars. A clinical study of degree III involvements.

Abstract: The present investigation was designed to evaluate the regenerative potential of the periodontal tissues in degree TIT furcation defects at mandibular molars using a treatment procedure based on the principle of guided tissue regeneration. The patient sample included 21 patients, 26–65 years of age, who presented periodontal lesions in the right and left molar regions including “through and through” furcation defects. After an initial examination, each patient was subjected to a series of full-mouth scaling and root planing. 2–3 months later, they were recalled for a baseline examination. The furcation-involved molars were randomly assigned in each patient to either a test or a control treatment procedure. The test procedure included the elevation of muco-periosteal flaps at the buccal and lingual aspects of the molars. Granulation tissue was removed and the exposed root surfaces were debrided and planed. The width and the height of the entrance openings to the furcation defects were assessed. A teflon membrane was adjusted to cover the entrances to the defects (buccal and lingual) and was retained in the manner described by Pontoriero et al. (1988). The flaps were repositioned on the outer surface of the membrane and secured by sutures which were removed after 10 days. Following surgery, the patients were instructed to rinse the mouth twice daily for 4 weeks with chlorhexidine gluconate. The membranes were removed after a healing period of 1–2 months. A surgical procedure identical to the test procedure was performed in the control tooth regions with the exception of the placement of membranes. During a 6-month period after surgery, the patients were maintained in a plaque control program including professional tooth cleaning every second week. At the end of this period, all patients were re-examined. The results of this re-examination demonstrated that out of 21 “through and through” furcation defects treated with the GTR therapy, 8 healed with complete closure of the defect. An additional 10 defects had become partially healed and only 3 defects were after a healing period of 6 months still open. In the control group, none of the previous “through and through” defects had healed with complete closure. 10 control defects were partially filled and 11 remained open. The potential for regeneration of periodontal tissues in furcation defects of varying dimensions is discussed.