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K Dale

Publications and source records attributed to K Dale.

At least 19 recordsLinked to original sources
PubMed2001

Using artificial evolution and selection to model insect navigation.

BACKGROUND: An animal's behavioral strategies are often constrained by its evolutionary history and the resources available to it. Artificial evolution allows one to manipulate such constraints and explore how they influence evolved strategies. Here we compare the navigational strategies of flying insects with those of artificially evolved "animats" endowed with various motor architectures. Using evolutionary algorithms, we generated artificial neural networks that controlled a virtual animat's navigation within a 2D, simulated world. Like a flying insect, the animat possessed motors that generated thrust and torque, a compass, and visual sensors. Some animats were limited to forward motion, while others could also move sideways. Animats were selected for the precision with which they reached a target specified by a visual landmark. RESULTS: Animats given sideways motors could alter flight direction without changing body orientation and evolved strategies similar to those of flying bees or wasps performing the same task. Both animats and insects first aimed at the landmark. In the last phase, both adopted a fixed body orientation and adjusted their position to keep the landmark at a fixed retinal location. Animats unable to uncouple flight direction and body orientation evolved subtly different strategies and performed less robustly. CONCLUSIONS: This convergence between the navigational strategies of animals and animats suggests that the insect's strategies are primarily an adaptation to the demands of using visual information and compass direction to reach a position in space and that they are not significantly compromised by the insect's evolutionary history.

Animals↗
PubMed2000

Oscillating expression of c-Hey2 in the presomitic mesoderm suggests that the segmentation clock may use combinatorial signaling through multiple interacting bHLH factors.

Vertebrate somitogenesis comprises the generation of a temporal periodicity, the establishment of anteroposterior compartment identity, and the translation of the temporal periodicity into the metameric pattern of somites. Molecular players at each of these steps are beginning to be identified. Especially, members of the Notch signaling cascade appear to be involved in setting up the somitogenesis clock and subsequent events. We had previously demonstrated specific expression of the mHey1 and mHey2 basic helix-loop-helix (bHLH) factors during somitogenesis. Here we show that perturbed Notch signaling in Dll1 and Notch1 knockout mutants affects this expression in the presomitic mesoderm (PSM) and the somites. In the caudal PSM, however, mHey2 expression is maintained and thus is likely to be independent of Notch signaling. Furthermore, we analysed the dynamic expression of the respective chicken c-Hey1 and c-Hey2 genes during somitogenesis. Not only is c-Hey2 rhythmically expressed across the chicken presomitic mesoderm like c-hairy1, but its transcription is similarly independent of de novo protein synthesis. In contrast, the dynamic expression of c-Hey1 is restricted to the anterior segmental plate. Both c-Hey genes are coexpressed with c-hairy1 in the posterior somite half. Further in vitro and in vivo interaction assays demonstrated direct homo- and heterodimerisation between these hairy-related bHLH proteins, suggesting a combinatorial action in both the generation of a temporal periodicity and the anterior-posterior somite compartmentalisation.

Amino Acid Sequence↗
PubMed2000

Dynamic MR-imaging in the diagnosis of pigmented villonodular synovitis of the knee.

The aim of this report was to study the rate of contrast enhancement at MRI in pigmented villonodular synovitis (PVNS). Dynamic MRI was performed in a patient with PVNS just before and 1 week and 3 years following synovectomy of the knee. As opposed to patients with rheumatic disease the patient with PVNS showed a slower enhancement rate before synovectomy than 1 week after. At 3 years follow-up the patient with PVNS showed an enhancement rate just above that of the normal controls. The results indicate that PVNS has features more common to hyperplastic or neoplastic lesions than to inflammatory ones. The results at 3 years follow-up also suggest that dynamic MRI may indicate the efficacy of arthroscopic synovectomy.

Adolescent↗
PubMed1999

Differential patterning of ventral midline cells by axial mesoderm is regulated by BMP7 and chordin.

Ventral midline cells in the neural tube have distinct properties at different rostrocaudal levels, apparently in response to differential signalling by axial mesoderm. Floor plate cells are induced by sonic hedgehog (SHH) secreted from the notochord whereas ventral midline cells of the rostral diencephalon (RDVM cells) appear to be induced by the dual actions of SHH and bone morphogenetic protein 7 (BMP7) from prechordal mesoderm. We have examined the cellular and molecular events that govern the program of differentiation of RDVM cells under the influence of the axial mesoderm. By fate mapping, we show that prospective RDVM cells migrate rostrally within the neural plate, passing over rostral notochord before establishing register with prechordal mesoderm at stage 7. Despite the co-expression of SHH and BMP7 by rostral notochord, prospective RDVM cells appear to be specified initially as caudal ventral midline neurectodermal cells and to acquire RDVM properties only at stage 7. We provide evidence that the signalling properties of axial mesoderm over this period are regulated by the BMP antagonist, chordin. Chordin is expressed throughout the axial mesoderm as it extends, but is downregulated in prechordal mesoderm coincident with the onset of RDVM cell differentiation. Addition of chordin to conjugate explant cultures of prechordal mesoderm and neural tissue prevents the rostralization of ventral midline cells by prechordal mesoderm. Chordin may thus act to refine the patterning of the ventral midline along the rostrocaudal axis.

Animals↗
PubMed1994

[The chemical working environment among car painters in Bergen].

Official guidelines have been prepared for the working environment in Norwegian spraylacquering garages, in order to reduce the incidence of symptoms and diseases related to exposure to organic solvents. 11 garages were visited to see if the guidelines were being followed. All the sprayers (n = 28) were examined by questionnaire about the occurrence of acute symptoms connected to the central nervous system, the skin, the eyes and the airways during work, and about their use of personal protective equipment. All the garages had specially ventilated rooms for the lacquering procedure, and all the workers used personal respiratory protective equipment. The sprayers did not report more acute symptoms than a control group of office workers employed in the same companies.

Air Pollutants, Occupational↗
PubMed1993

Arthroscopic and radiographic examination of patients with juvenile rheumatoid arthritis before and after open synovectomy of the knee joint. A prospective study with a 5-year follow-up.

In a 5-year follow-up after open knee joint synovectomy in 18 patients with juvenile rheumatoid arthritis (JRA) there was no radiographic progression of the juvenile rheumatoid arthritic changes. Radiographic evidence indicative of osteoarthrosis and of the soft tissue swelling were scored separately. Radiographic changes consistent with osteoarthrosis increased significantly during the observation period (P < 0.001). Arthroscopic evaluation of cartilage changes and radiographic evaluation of osteoarthrosis correlated significantly (P = 0.004). These were the only parameters found predicting the development of further cartilage destruction (P = 0.001). Clinically, the patients had significant improvement five years following synovectomy (P = 0.018), even though three patients required resynovectomy (one successfully after four years, and two patients are waiting for resynovectomy). At the 5-year follow-up both radiographic and clinical data indicate that juvenile rheumatoid arthritic activity of the knee joint was reduced following open synovectomy while osteoarthrosis developed. A new system of scoring radiographic JRA changes of the knee joint was found useful.

Arthritis, Juvenile↗
PubMed1992

Diagnosis of pneumonia in adults in general practice. Relative importance of typical symptoms and abnormal chest signs evaluated against a radiographic reference standard.

The diagnostic value of typical symptoms and abnormal chest signs for pneumonia have been evaluated against a radiographic reference standard in 402 adult patients with respiratory tract infection in general practice. Pneumonia was diagnosed in 20 patients by a positive chest radiograph. The doctors diagnosed pneumonia in seven of these on the basis of history and physical examination alone, and in addition in 22 patients with normal radiographs. The diagnostic value of the typical symptoms cough, chest pain, and dyspnoea, reported by the patients on a questionnaire, increased with increasing intensity of the symptoms, and both "very annoying lateral chest pain" and "very annoying dyspnoea" had likelihood ratios (LR) between 4 and 5. The LR of crackles was 3.7. When evaluated against the doctor's clinical diagnosis of pneumonia as reference standard, crackles achieved an LR of 14.8, while the typical symptoms achieved lower LRs than when evaluated against the radiographic reference standard. These discrepancies, which were confirmed by logistic regression, indicate that crackles and other abnormal chest findings are interpreted too frequently as features of pneumonia and that the importance of typical symptoms is underestimated in the diagnosis of pneumonia.

Adult↗
PubMed1992

The prevalence of ankylosing spondylitis among Norwegian Samis (Lapps).

A population survey of the Sami (Lapp) population of the municipalities Karasjok and Kautokeino in north Norway revealed a prevalence of ankylosing spondylitis (AS) according to the New York criteria of 1.8%. Eleven cases of AS were found, 7 men and 4 women. Only 4 of the 11 observed cases of AS were aware of the diagnosis of AS prior to the survey. Ten of 11 patients with AS possessed HLA-B27 (91%) which is found in 24% of the general Sami population in this area. It was calculated that 6.8% of B27 positive persons had AS.

Adult↗
PubMed1992

Quantitative radio-isotope scanning of the sacroiliac joints in ankylosing spondylitis.

A method for applying 99mTc-MDP for dynamic and static quantitative radioisotope scanning (QRS) of the sacroiliac joints (SI) in early progressive sacroiliitis in ankylosing spondylitis (AS) is described. In a prospective study, 2 groups of male AS patients were investigated, one with increased elevated erythrocytic sedimentation rate (ESR) (group A, n = 7) and one with normal ESR (group B, n = 8). In both groups an increased uptake of the radiotracer was found in the static part of the study versus a control group C (n = 9). An increased uptake versus group C was also found for group A in the dynamic part of the study (p = 0.01) while there was no significant difference dynamically between groups B and C. The results of the dynamic study in group A indicate ESR to be a parameter of inflammatory activity in the SI joints. The study also seems to indicate QRS to be a valuable diagnostic method in early AS without definite radiographic changes in the SI joints.

Adult↗
PubMed1992

Interobserver variability in the radiographic diagnosis of adult outpatient pneumonia.

Acute chest radiographs were obtained from 319 adult patients with acute respiratory infections. Where a lower respiratory infection was diagnosed, follow-up chest radiographs were obtained in most patients. A radiologic panel diagnosed pneumonia in 21 patients. The agreements between the panel and 3 independent interpreters, 2 residents in radiology, and one senior chest physician, were assessed. Also the reports given by the specialist in radiology at the Department of Radiology were compared with the panel's evaluation. While the kappa-agreements between the panel's interpretations and those by the Department of Radiology and the consultant in chest medicine was 0.71 and 0.72, respectively, the corresponding kappa-values between the residents and the panel was only 0.50. The proportion of agreement when pneumonia was diagnosed was 0.56 between the panel and the Department of Radiology, and 0.59 between the panel and the chest consultant, compared to 0.36 between the panel and the residents. The study demonstrates the difficulty of diagnosing outpatient pneumonia and the importance of experience.

Adolescent↗
PubMed1990

[Osteitis fibrosa cystica von Recklinghausen].

We present the case of a woman with classical osteitis fibrosa cystica generalisata von Recklinghausen, caused by a single adenoma of the left inferior parathyroid gland. After six months with increasing bone pain, pathological fractures and cystic lesions radiologically, hyperparathyroidism was diagnosed by persistent elevated levels of serum calcium, and elevated levels of PTH. Surgical extirpation of the parathyroid adenoma caused a period with severe hypocalcemia followed by complete clinical restitution. The diagnosis should be considered in any case of persistent bone pain and uncharacteristic fatigue.

Adenoma↗
PubMed1990

Low osmolality contrast media and metabolic changes in the myocardium during free and reduced coronary flow in the dog.

The authors assessed whether intracoronary injection of low osmolality contrast media induces metabolic and electrocardiographic changes consistent with myocardial ischemia in anesthetized dogs. Ioxaglate and iohexol were injected into the left main coronary artery (eight dogs) and into a carotid-coronary artery shunt (eight dogs), during free coronary flow and during 50% flow reduction. Blood samples were obtained simultaneously from a femoral artery and from a small cardiac vein draining the contrast perfused area. Contrast media had no immediate or late effects on lactate balance during free or reduced flow. Early depression of the ST segment in epicardial ECG did not reflect ischemia. The authors conclude that the two low-osmolality contrast media, iohexol and ioxaglate, did not induce ischemic changes in the myocardium.

Analysis of Variance↗
PubMed1990

Effects of contrast media on myocardial function during acute left ventricular failure in the dog.

We studied the hemodynamic side effects of intracoronary injection of contrast media during acute ischemic heart failure by using anesthetized dogs. Induction of failure was performed by microembolization of the area supplied by the left main coronary artery. Six ml of iohexol (Omnipaque) increased contractility during the normal state, while this contrast medium induced no alterations in any of the recorded hemodynamic variables during left ventricular failure. Ioxaglate (Hexabrix) was also well tolerated during the normal state, while sodium-meglumine diatrizoate (Renografin) markedly decreased systolic variables. However, in the failing heart both ioxaglate and diatrizoate resulted in greater reduction in all systolic variables than in the normal heart. We conclude that both ionic contrast media may be harmful in acute ischemic heart failure. Non-ionic iohexol appears safer in this condition.

Animals↗
PubMed1986

Pulmonary fibrosis in cable plant workers exposed to mist and vapor of petroleum distillates.

Twenty-five cable plant workers exposed to mists and vapors of mineral oils and kerosene for 5-35 years have been investigated in a cross-sectional, matched pairs study. The exposed cohort and the referents were examined by radiology, pulmonary function measurements, and a questionnaire for symptoms of respiratory disease. Lung tissue from a deceased worker with 35 years of exposure was investigated by histopathologic methods and by scanning electron microscopy. Exposure measurements were performed by personal sampling. Previous employment and smoking habits were recorded for all subjects. An increased prevalence of slight basal lung fibrosis was found in chest films of the exposed workers. Pulmonary fibrosis was confirmed histopathologically. A moderately decreased vital capacity (VC) and forced expiratory volume (FEV1) was found. Oil mist was measured to time-weighted average levels of 0.15-0.30 mg/m3 with short-term vapor exposure of up to 4000 mg/m3. It is concluded that mists and vapors from petroleum distillates are the most probable causes of the findings.

Adult↗
PubMed1985

Radiographic evaluation of patients with Bechterew's syndrome (ankylosing spondylitis). Findings in peripheral joints, tendon insertions and the pubic symphysis and relations to non-radiographic findings.

One hundred and twenty-two consecutive hospitalized patients aged 35 years or more, and with definite radiographic bilateral sacro-iliitis were re-examined. All but 3 met established criteria for definite ankylosing spondylitis (AS). All peripheral joints from 114 of these patients were radiographed, and definite arthritis in one or several joints was demonstrated in 47 (41%) of them. The distribution pattern of arthritis was generally symmetric or slightly asymmetric. Articular new bone formation was a common finding in arthritic joints. The frequency of patients with hip arthritis was low (24% including patients with hip joint replacements); possible explanations include the selection of patients examined and difficulties in distinguishing between a primary osteoarthritis and osteoarthritis secondary to arthritis in a single radiographic examination in such patients. Although the hip joints were often severely affected, with extensive new bone formation, the erosions were generally small and protrusion of the acetabulum was not seen. Arthritis of the shoulder or of the hip was associated with an early onset of AS. Arthritis in the finger joints was associated with clinical psoriasis but was also a frequent finding in HLA B27-positive patients free from this condition (23%). Arthritic changes of small joints with extensive new bone formation ('egg in shell', 'pencil in cup' or 'gull wing' appearance) were seen in patients without clinical psoriasis. New bone formation of the ischium was frequent in HLA B27-positive patients (36%), but was not seen in HLA B27-negative patients. No differences concerning the frequency or severity of different radiographic pathologic changes recorded were observed between the sexes.

Adult↗
PubMed1985

Juvenile ankylosing spondylitis and HLA B27 homozygosity.

Ten consecutive patients with juvenile ankylosing spondylitis were investigated in a prospective study. At least one of the parents of each patient had a positive history of probable or definite ankylosing spondylitis, Reiter's syndrome, or acute anterior uveitis. The patients and their parents were examined clinically and were HLA-typed. Nine of the 10 patients exhibited the genetic marker HLA B27, but only one patient was homozygous for HLA B27. This prevalence of homozygosity among HLA B27 positive persons could be expected to occur by chance alone. Based on the limited material studied, we cautiously conclude that HLA B27 homozygosity is probably not responsible for disease onset in childhood.

Adolescent↗