A simple model of recurrent epidemics

A cellular automaton conceived as a simple model of disease spreading is investigated. We show that the steady-state of the model is described by a spatial organization of the infectious individuals on fronts and undamped temporal oscillations in the number of infectious individuals. This behaviour is observed both for a deterministic and a stochastic input of susceptible individuals, hence showing that recurrent epidemic behaviour can be persistent without any external forcing. The simplicity of the model suggests that such spatio--temporal behaviour can be obtained from nothing, but a direct transmission mechanism between nearest neighbors provided some mechanism for the introduction of new susceptible individuals, e.g., loss of immunity is present.

[Changing market for Oslo physicians. Justification for and consequences of changes in agreements]

During the 1970s the number of salaried general practitioners in Oslo rose to approximately half of all general practitioners in the city. However, during the last ten years, increasing differences in wages between general practitioners on salary and fee-for-service general practitioners has led to difficulties in recruiting doctors to salaried positions. As a result many doctors have negotiated new contracts with the sub-municipalities of Oslo, a typical arrangement being a combination of fee-for-service payment for work with patients and a fixed salary for one or two days per week for work in nursing homes and mother-and-child clinics. General practitioners in four sub-municipalities of Oslo reported better opportunities for recruiting staff, greater autonomy and higher income as the main driving forces behind the changes. The increase in income has indeed been formidable, approximately NOK 100,000-200,000 per year, depending on the specific contract. The number of consultations has increased substantially in centres where general practitioners have switched to fee-for-service payment and waiting lists have been eliminated, partly as a consequence of higher turnover of consultations, and partly because of fewer vacant posts. The economic consequences to the municipalities are more uncertain, and the experiences of auxilliary staff in regard to the charges that have occurred are mixed.

Observer variability in the assessment of type and dysplasia of colorectal adenomas, analyzed using kappa statistics

PURPOSE

The aim of this study was to establish the intraobserver and interobserver variability in the assessment of histologic type (tubular, villous, and tubulovillous) and grade of cytologic dysplasia (mild, moderate, and severe) in colorectal adenomas.

METHODS

One hundred eighty-seven slides of adenomas were assessed twice by three experienced pathologists, with an interval of two months. Results were analyzed using kappa statistics.

RESULTS

For agreement between first and second assessment (both type and grade of dysplasia), kappa values for the three specialists were 0.5345, 0.9022, and 0.4100, respectively. Agreement was better for type than for dysplasia. The strength of agreement was moderate for Observers A and C and almost perfect for Observer B. Agreement between all three observers was seen in 35.2 percent for both type and dysplasia in 61 percent for type and in 47.8 percent for dysplasia. The kappa values for Observer A vs. B and Observer C vs. B were 0.3480 and 0.3770, respectively (both type and dysplasia). Values for type were better than for dysplasia, but agreement was only fair to moderate.

CONCLUSION

The interobserver agreement was moderate to almost perfect, but the intraobserver agreement was only fair to moderate. A simpler classification system or a centralization of assessments would probably increase kappa values.

Salaried and fee-for-service general practitioners: is there a difference in patient turnover?

OBJECTIVE

To compare use of working hours, patient turnover, and patient characteristics in two general practitioner groups which differed in contractual arrangements and income levels (partly fee-for-service vs. salary).

DESIGN

Cross-sectional study of all patient contacts during one week.

PARTICIPANTS

All general practitioners (GPs) in Oslo (N = 263) with contracts with the municipality. 83% participated.

MAIN OUTCOME MEASURE

Time spent in various types of work and patient turnover; the number of patients seen per hour of consultation time.

RESULTS

Fee-for-service GPs worked almost exclusively with patients in their own practice, while salaried GPs spent more time out of office (consultation-based patient work constituting 55% of the working hours). The fee-for-service group registered on average 2.68 consultations per hour of patient contact (95% confidence interval: 2.51-2.84). The corresponding numbers for the salaried group were 2.37 (2.24-2.50). Salaried GPs had somewhat more telephone consultations per hour (2.01 vs 1.66 for fee-for-service GPs), leaving a picture of two GP groups with small differences in patient turnover. The two patient populations were remarkably similar and so was the general practitioners' own evaluation of the consultations.

CONCLUSIONS

Over a number of years the GPs in Oslo have practised under different contractual arrangements. As a consequence of different expectations and incentives it was expected that consultation activity and patient populations had evolved differently. This proved not to be the case.

Iodine status in neonates in Denmark: regional variations and dependency on maternal iodine supplementation

Iodine status of 147 neonates born in five different regions of Denmark was evaluated in relation to the iodine content of breast milk and iodine supplementation taken by the mother. Approximately two-thirds of the women had not received iodine supplementation. They had low iodine concentrations in breast milk and urinary iodine concentrations of the neonates at day 5 were low. The median values (milk/urine) were 33.6/31.7 micrograms/l (Randers 22/26, Ringkøbing 29/16, Aalborg 36/31. Arhus 54/41 and Copenhagen 55/59 micrograms/l). Higher values were found in the group where tablets containing iodine had been taken (milk/urine: 57.0/61.0 micrograms/l). In general, the values are low compared with internationally recommended levels. We suggest that mothers without autoimmune thyroid disease should receive iodine supplementation in the form of vitamin/mineral tablets containing iodine (150 micrograms per tablet).

[Carbohydrate-deficient transferrin--a reliable marker of high alcohol consumption?]

Carbohydrate deficient transferrin has been proposed as an important marker for alcohol abuse. Using isoelectric focusing and two different radioimmunoassays we measured carbohydrate deficient transferrin throughout an alcohol withdrawal period in ten abusing men. Values within the normal range were found in two to four individuals, depending on the method. Nevertheless, carbohydrate deficient transferrin was more frequent pathologically (in two out of three methods) than any other of the common markers (glutamyl transferase, alanine transferase, aspartate transferase, mean corpuscular volume). During the withdrawal period, the carbohydrate deficient transferrin value increased in two patients after a new alcohol intake. However, it also increased on other occasions when a new alcohol intake was highly unlikely. Therefore, a single test or even repeated tests of carbohydrate deficient transferrin may give a wrong conclusion. Since the cost of the analysis is high, the clinical benefit should be evaluated more closely before the test is used in pure clinical settings.

Recovery of lysozyme from scallop waste

A crude lysozyme preparation was recovered in waste from the scallop processing industry. Lysozyme was then purified 229-fold in preparative scale by chromatography on S Sepharose and Blue Sepharose. Further purification on Sephacryl S-200 resulted in a lysozyme preparation with a specific activity of 64,000 units/mg protein. The apparent molecular mass of the partially purified lysozyme was 10 kDa as judged by gel filtration. Optimum pH for lysis of Micrococus luteus under the present conditions was 5.2. The enzyme was very active at low temperatures. At 4 degrees C the scallop viscera lysozyme exhibits about 55% of the activity measured at 37 degrees C.

The rôle of ultrasound scan in childhood ovarian tumors

Seven cases with childhood ovarian tumors are presented. All underwent an ultrasound scan which gave the the preliminary diagnosis of ovarian tumor. Treatment differs according to the status of the child and whether malignity is involved. The numerous differential diagnoses must be kept in mind. The management of children with an unexplained abdominal mass should include an ultrasound scan.

Cancer in association with polymyalgia rheumatica and temporal arteritis

In our prospective controlled study, a total of 185 patients with polymyalgia rheumatica (PMR) and temporal arteritis (TA) diagnosed during 1978-83 and their 925 matched controls were cross checked with the data files at the Cancer Registry of Norway at the end of 1987. Malignancy was registered in 27 patients (14.6%) and 131 controls (14.2%) between 1953 and the end of 1987. Malignancy was registered in 16 (24.6%) of the patients with biopsy demonstrating arteritis temporalis. The hazard rate for developing malignancy after diagnosis for the whole patient population was not significantly different from the controls. The hazard rate for developing malignancy in patients with positive biopsy, however, was 2.35 times higher than in the controls (p = 0.036) and 4.40 times higher than the rest of the patient population (p = 0.007) (Cox proportional hazards model). The general long interval between diagnosis of PMR and/or TA and registration of malignancy (mean 6.5 years) is not consistent with a paraneoplastic mechanism.

Iodine deficiency in pregnancy in Denmark. Regional variations and frequency of individual iodine supplementation

Iodine requirements are increased during pregnancy and lactation and adequate iodine intake is important for normal brain development of the fetus/newborn child. The aim of the present study was to evaluate the extent to which this increase in iodine requirement is met in pregnant women living in various regions of Denmark. One hundred and fifty-two healthy pregnant women admitted to five different Danish departments of obstetrics participated in the study. Iodine status was evaluated by measurement of iodine in spot urine at day five after delivery and by careful history of the intake of iodine containing vitamin/mineral tablets. Approximately one third of the women had received tablets containing iodine. In women who had not received iodine supplementation urinary iodine was low with a median value of 39.7 micrograms/g creatinine (Aalborg 28, Randers 33, Ringkøbing 34, Arhus 43 and Copenhagen 62 micrograms/g creatinine). These values are far below internationally recommended levels. The consequences remain to be evaluated and no firm recommendations can be given. It seems reasonable, however, to recommend a high intake of food containing iodine (e.g. milk products) during pregnancy and lactation. Since nearly all the women took some kind of vitamin/mineral supplementation it could be considered to advocate intake of vitamin/mineral tablets containing iodine.

Hyphal transport of 15 N-labelled nitrogen by a vesicular-arbuscular mycorrhizal fungus and its effect on depletion of inorganic soil N

Hyphal transport of nitrogen from a ¹⁵ N-labelled ammonium source by a VA-mycorrhizal fungus was studied under controlled experimental conditions. Cucumis sativus L. cv. Aminex (F1 hybrid) was grown alone or together with Glomus intraradices Schenck and Smith in containers with a hyphal compartment separated from the rooting medium by a fine nylon mesh. Lateral movement of the applied ¹⁵ N towards the roots was minimized by using a nitrification inhibitor (N-serve) and a hyphal buffer compartment. Recovery of ¹⁵ N by mycorrhizal and non-mycorrhizal plants was 6 and 0%, respectively, after a labelling period of 23 days. The corresponding figures, without N-serve added, were 4 and 7%. A prolongation of the labelling period by 8 days (N-serve applied) resulted in an increase in the ¹⁵ N recovery by mycorrhizal plants to 30% of the applied ¹⁵ N. Non-mycorrhizal plants contained only traces of ¹⁵ N. The external hyphae depleted the soil in the hyphal compartment efficiently for inorganic N. In contrast, hyphal compartments of control containers still contained considerable amounts of inorganic N. The ¹⁵ N assimilated by the external hyphae in one hyphal compartment was not translocated in significant amounts to the external hyphae in another hyphal compartment. The possible implication of this for inter-plant N transfer by VA hyphal connections is discussed.

A double blind study of single dose azithromycin and doxycycline in the treatment of chlamydial urethritis in males

OBJECTIVE

To compare the efficacy and safety of azithromycin and doxycycline in the treatment of males with uncomplicated urethritis caused by chlamydia trachomatis.

DESIGN

A multicentre, double-blind, randomised treatment study.

SUBJECTS

130 male outpatients with clinical signs and symptoms of urethritis.

SETTING

STD clinics at four Norwegian University Hospitals.

METHODS

Patients were randomly allocated to 1000 mg azithromycin as single dose or doxycycline 100 mg twice daily for 7 days. Clinical, bacteriological and safety assessments were made at entry and after 1 and 2 weeks. Safety data were also repeated after 4 weeks.

RESULTS

Demographic data were similar in both groups. At the week 1 assessment bacteriological eradication was achieved in 44 of 44 evaluable azithromycintreated patients and in 42 of 42 in the doxycycline group. At the week 2 assessment the corresponding figures were 35 of 35 and 34 of 34 respectively.

CONCLUSION

Azithromycin 1000 mg single dose was as effective as doxycycline 100 mg twice daily for 7 days in male patients with chlamydial urethritis.

Danish primary schoolteachers' knowledge about asthma: results of a questionnaire

We present an anonymous questionnaire inquiry involving 334 primary schoolteachers in the Randers area with the purpose of elucidating teachers' knowledge about asthma. To a series of statements about asthma, the teachers answered yes, no or don't know. A limited knowledge of different aspects of asthma in children was found, although 57% had asthma children in their classes. Specially limited was knowledge about medical treatment. Five percent had received proper instruction about asthma and had a significantly better knowledge of medical treatment (p less than 0.001-0.05). Only 57% knew that wheezing after physical exertion is a strong indicator of asthma and only 33% knew that exertion in cold weather increases the risk of an attack. It is recommended that instruction in children's diseases, especially asthma, is introduced in teacher training colleges.

Electrical potential difference across the stomach wall and gastric morphology in anaesthetized pigs after intravenous administration of cytotoxic drugs

Nausea and vomiting are frequent side-effects of cancer chemotherapy. To investigate whether such therapy has an acute toxic effect on the gastric mucosa, cyclophosphamide, epirubicin and fluorouracil were administered intravenously to anaesthetized pigs. Gastric mucosal function was evaluated by continuous measurements of the gastric transmucosal electrical potential difference (PD) and the intragastric pH by using a newly developed microelectrode principle. After sacrifice, gastric histology was examined. During chemotherapy a significant decline in gastric PD was observed two hours after drug infusion, indicating a hampered gastric mucosal function. Apart from a slight hyperemia, gastric histology was normal. In this animal model a change in gastric mucosal function developed at the same time after chemotherapy as the gastric side-effects in humans.

Enzyme-linked immunosorbent assays for detection of Pseudomonas fluorescens in sediment samples

A strain-specific antibody to Pseudomonas fluorescens was used to develop two enzyme-linked immunosorbent assays: a sandwich and a competitive assay. Both assay types could be used to perform rapid and sensitive detection of the target organism in extracts of sediment samples.

Neoplasms of the central nervous system in Norway. IV. A population-based epidemiological study of meningiomas

All 1632 cases of meningioma reported to the Norwegian Cancer Registry from 1955 to 1986 have been studied: a) 96% appeared in patients over 30 years of age, b) 95% were histologically benign, c) 88% were located intracranially, and d) 66% occurred in females. The female predominance manifested itself in the middle age period. Eighty-seven percent of the intraspinal meningiomas presented in females, but the ratio between intracranial and intraspinal meningiomas was significantly lower in females (5.4) than in males (20.4). Increased incidence rates of meningioma in females are revealed for the birth-cohorts after 1930. The reason for this change is unclear so both environmental and hormonal factors should be explored. Based upon the epidemiological data, it appears that female sex hormone(s) could act as a growth stimulus in the development of meningiomas, but are neither sufficient nor necessary for tumourigenesis.

Optimal matching between canine left ventricle and afterload

A parabolic relationship exists between ventricular external work and arterial load at given preload and contractility. Previous data indicate that the working point falls close to the parabola optimum. By combining the left ventricular (LV) end-systolic pressure-volume relationship (ESPVR) and an equation describing external stroke work, optimum values of stroke volume (SV), the slope (Emax) of the ESPVR, and arterial resistance (Rp) corresponding with the optimum (i.e., mSV, mEmax, mRp) were obtained. Experiments in anesthetized dogs were performed to test whether mSV, mEmax, and mRp also correspond to observed SV, Emax, and Rp at three different levels of volume load (right atrial pressure, RAP) before and after acute depression of LV contractility. Comparisons of observed and optimal values of SV, Emax, and Rp were made before and after LV depression. Before embolization, the ratios were SV/mSV 1.10-1.20 (RAP 5-15 mmHg); Emax/mEmax 1.21-1.41; and Rp/mRp 0.84-0.69. After LV depression, SV/mSV was 0.80-0.83, Emax/mEmax was 0.78-0.71, and Rp/mRp was 1.56-1.46. The ratios were all significantly changed (P less than 0.01) by the induced LV depression. The present analysis may offer a new tool to detect nonoptimal relations between cardiac and arterial functions.

The effect of acetyl salicylic acid and indomethacin on cell proliferation kinetics in the human gastric mucosa

To determine the effect of acetyl salicylic acid and Indomethacin on the rate of cell proliferation in the human gastric stomach, 6 healthy volunteers received daily 3 g of acetyl salicylic acid or 150 mg of indomethacin for one week in a double-blind crossover trial. Cell proliferation was assessed by means of tritiated thymidine and autoradiography. The labelling index did not change, indicating that cell proliferation to compensate for the exfoliation caused by ASA and indomethacin does not increase.

Dysplasia in gastric mucosa: prognostic significance

Forty-seven patients having dysplasia in biopsies from the gastric mucosa were subjected to re-investigation. Twenty-three patients were alive at follow-up and 14 underwent gastroscopy with removal of random biopsies. The median duration of observation was 39 months, range 10-63 months. Regression of the dysplasia was found in all patients; in nine there was normal mucosa without dysplastic alterations in the control biopsies, mild dysplasia was still present in five of the patients. Our results suggest that the incidental finding of mild or moderate dysplasia does not, per se, indicate the necessity of further control, whereas severe dysplasia indicates repeat gastroscopies with biopsies, as such epithelial changes can occur together with gastric carcinoma.

Influence of the prostaglandin E1 analogue Rioprostil on the human gastric mucosa

Ten healthy volunteers received the prostaglandin E1 analogue Rioprostil 300 micrograms b.i.d. for 1 week. Endoscopically obtained biopsies were investigated with tritiated thymidine and autoradiography to determine the rate of cell proliferation and with a texture-analyzing system to measure the intracellular amount of mucus in the epithelial cells. Rioprostil did not alter the tritiated thymidine labeling index in the antral area but did significantly depress it in the fundic area. The mucus content was unchanged in the antrum but was significantly increased in the fundus. These observations indicate that Rioprostil given orally causes an enhanced cell maturation in the fundic area as well as an increased intracellular mucus content. Rioprostil seems to have no influence on the human antral area.

Effect of cimetidine on gastric mucosal cell proliferation in man

Seven duodenal ulcer patients were treated for 3 months with cimetidine. Before and after treatment endoscopic biopsy specimens were taken for autoradiographic estimation of cell proliferation in the gastric mucosa in the antral and fundic part of the stomach and from the duodenum. In all three areas the estimated labeling index was increased during medication with cimetidine. The increase in epithelial cell renewal may participate in the ulcer healing effect of cimetidine.

The effect of contractility and preload on matching between the canine left ventricle and afterload

We define matching between ventricle and afterload to imply that the ventricle is adapted to its afterload to yield maximum external work output. For the ventricle, this optimal adaption will depend on end-diastolic dimension, heart rate, and contractility. Because contractility is impaired during ventricular failure, we propose that the adaption between ventricle and load is not as good during failure as during normal conditions. According to our definition, this implies that during failure external work output is less than maximum. Ventricle-load matching is then not present, i.e., a mismatch exists between ventricle and load. This hypothesis was tested in a canine preparation in which arterial load of the left ventricle was varied from one beat to the next. Left ventricular depression was induced by injections of 50 micron microspheres into the left coronary bed. We observed left ventricular stroke volume and external work during afterload variations at three different preload levels before and after microembolization. Before embolization the control observations of work and stroke volume were positioned at the apex of parabolas relating work to stroke volume. After embolization, however, control observations fell down along the left limb of the parabolas. These observations were independent of preload. Thus this study, carried out in a preparation with the heart in situ, supports the idea that the normal left ventricle is matched to its load and demonstrates ventricle-load mismatch when the left ventricle is failing.

Postoperative survival of patients with potentially curable cancer of the colon

The association between histopathologic findings and postoperative survival in 442 patients with potentially curable carcinomas of the colon has been analyzed using Cox's regression model. The prognostic variables included in the study were age, sex, stage of disease according to Dukes' classification and Broders' grading, as well as presence/absence at the time of operation of venous and nerve invasion. The overall five-year postoperative survival rate was 46.6 percent. Using a model including all prognostic factors, sex and Dukes' classification were not found to be associated with survival. Broders' grading and/or nerve invasion yielded only a borderline statistical significance in the model that included all factors. The invasion of veins was almost always associated with invasion of nerves.

Complexed autoantibodies in patients with juvenile connective tissue diseases, isolated by rate-zonal ultracentrifugation

Selected sera from one patient with systemic lupus erythematosus, two with mixed connective tissue disease, one with dermatomyositis, one with progressive systemic sclerosis and one with juvenile rheumatoid arthritis were investigated for autoantibodies after fractionation by computerized rate-zonal ultracentrifugation. Anti-Smith antibodies sedimented in an area from 6-11 S and anti-ribonucleoprotein from 6-13 S. IgG anti-IgG and IgG antinuclear antibodies (ANA) were present in free or complexed form in the 6-13 S area. IgM ANA occurred as 7 S IgM in patients with systemic lupus erythematosus and mixed connective tissue disease, whereas IgM ANA sedimented in the 19 S area in patients with dermatomyositis and progressive systemic sclerosis. Complexes containing IgG anti-IgG and ANA, positioned in the 6-13 S area are likely to play a significant role in the pathogenesis of systemic lupus erythematosus and mixed connective tissue disease.

Gastroduodenal polyps in familial polyposis coli

A total of 26 patients with familial polyposis coli without extracolonic manifestations were examined by gastroduodenoscopy. Histologically verified polyps were found in 18 patients (69 percent, 95 percent confidence limits 48-86). Gastric adenoma was diagnosed in one patient, fundic gland polyposis in six patients, and duodenal adenomas in 12 patients. It is concluded that the incidence of gastroduodenal polyps is independent of the clinical presence of other extracolonic manifestations. It is advisable that polyposis patients should be followed with gastroduodenoscopy and biopsy of polyps.

Brown bowel syndrome

The brown bowel syndrome (BBS) is a rare disease characterized by malabsorption and accumulation of lipofuscin in the smooth muscle cells of the muscularis externa of the small intestine. Recently, we incidentally observed a case of BBS in a colon operated on because of a neoplasm. Our ultrastructural investigation, which demonstrated changes in the mitochondria, further supports the significance of mitochondrial damage in BBS.

Venous and nerve invasion as prognostic factors in postoperative survival of patients with resectable cancer of the rectum

The histopathologic and clinical findings in 682 patients with carcinoma of the rectum have been analyzed. Invasion of veins and nerves by primary growth was found in 38.9 and 34.9 per cent, respectively. The five-year survival rate for patients with resectable tumors was 49 per cent. The age, Dukes' staging, and presence and/or absence of liver metastases, of venous invasion, and of nerve invasion were found to be of statistically significant importance for the prognosis. Sex was found to be on the borderline of significance and Broders' grading was even less significant. Invasion of veins was found statistically significant more frequently than nerve invasion, but the present investigation revealed the importance of the invasion of veins as well as of nerves. When venous invasion was observed, liver metastases developed over three times as frequently in these patients as when metastases were not demonstrated. In contrast to Dukes' staging. Broders' grading can be applied to tumor biopsies preoperatively. The importance of venous and nerve invasion for the selection of patients for adjuvant therapy after termination of surgical treatment is discussed.