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Biomedical subjects

T Christiansen

Publications and source records attributed to T Christiansen.

At least 19 recordsLinked to original sources
PubMed1999

On-line study of growth kinetics of single hyphae of Aspergillus oryzae in a flow-through cell.

Using image analysis the growth kinetics of the single hyphae of the filamentous fungus Aspergillus oryzae has been determined on-line in a flow-through cell at different glucose concentrations in the range from 26 mg L-1 to 20 g L-1. The tip extension rate of the individual hyphae can be described with saturation type kinetics with respect to the length of the hyphae. The maximum tip extension rate is constant for all hyphae measured at the same glucose concentration, whereas the saturation constant for the hyphae varies significantly between the hyphae even within the same hyphal element. When apical branching occurs, it is observed that the tip extension rate decreases temporarily. The number of branches formed on a hypha is proportional to the length of the hypha that exceeds a certain minimum length required to support the growth of a new branch. The observed kinetics has been used to simulate the outgrowth of a hyphal element from a single spore using a Monte Carlo simulation technique. The simulations shows that the observed kinetics for the individual hyphae result in an experimentally verified growth pattern with exponential growth in both total hyphal length and number of tips.

Aspergillus oryzae↗
PubMed1998

Effects of nonylphenol and 17 beta-oestradiol on vitellogenin synthesis, testicular structure and cytology in male eelpout Zoarces viviparus.

Nonylphenol has been found to be oestrogenic in fish and may influence the reproductive system of male fish. In the present study, the effects of low (10 microg g-1 week-1) and high (100 microg g-1 week-1) doses of nonylphenol and of 17 beta-oestradiol on the synthesis of vitellogenin and on testicular structure and cytology were investigated in male eelpout Zoarces viviparus during active spermatogenesis (May) and late spermatogenesis (June). Twenty-five days after injection, a significant dose-dependent increase in the plasma vitellogenin concentration, measured by enzyme-linked immunosorbent assay, was observed in the treated groups. A highly significant reduction in the gonadosomatic index was observed concomitant with the increase in the plasma vitellogenin concentration. Macroscopically, milt was observed to be present in the control fish, but was sparse or absent in the treated fish. Histological examination using light microscopy revealed severe effects of nonylphenol as well as of oestradiol treatment on testicular structure. Control fish had seminiferous lobules containing spermatogenic cysts and only a few spermatozoa (May) or had the walls of their seminiferous lobules lined with cuboidal Sertoli cells (June). In the treated fish, the seminiferous lobules were degenerated (May) or were filled with numerous spermatozoa and the Sertoli cells appeared very squamous (June). Electron microscopy revealed greater numbers of phagocytosed spermatozoa in these Sertoli cells. In rats, -glutamyl transpeptidase (-GTP) has been used as a specific marker of Sertoli cell function. In the present study, both nonylphenol and 17 beta-oestradiol treatment resulted in a reduction in the activity of this enzyme. The study provides evidence that nonylphenol is oestrogenic, as indicated by the large increase in vitellogenin synthesis, and that both nonylphenol and oestradiol have marked effects on the testicular structure and cytology of germ cells and Sertoli cells of male Z. viviparus.

Animals↗
PubMed1997

Measurement of renal vein blood flow in rats by high-field magnetic resonance.

The aim of the present study was to examine whether magnetic resonance imaging (MRI) based method for non-invasive in vivo measurement of vein blood flow in rats could be used to estimate renal blood flow (RBF). Measurements were performed using a high-field (7 Tesla) MRI scanner with a short echo time phase contrast velocity measurement pulse sequence. The method was evaluated in vitro by flow measurements in an acrylic pipe and in vivo by recording left renal vein blood flow in normal and unilaterally nephrectomized rats. In a subset of animals RBF was measured by a direct method using 14C-tetraethylammoniumbromide. In vitro a high accuracy was found between applied and MRI measured flow rates in the range from 0.5 to 33 ml/min (r = 0.997; P < 0.001). In vivo the MRI measured left renal vein blood flow was 70% higher in unilaterally nephrectomized animals compared to control animals (3.4 +/- 0.4 ml/min/ 100 g body wt vs. 2.0 +/- 0.1 ml/min/100 g body wt, P < 0.001). Direct measurements of RBF revealed comparable values (3.4 +/- 0.3 ml/min/100 g body wt vs. 2.3 +/- 0.4 ml/min/100 g body wt, P = 0.05). In addition, the left kidney volume was recorded by MRI with an increase amounting to 40% (1.18 +/- 0.05 ml vs. 0.84 +/- 0.02 ml; P < 0.001) in the nephrectomized group compared to controls. Finally, a positive correlation was seen between left renal vein blood flow and MRI measured renal volume (r = 0.91; P < 0.001). In summary, MRI is a non-invasive tool by which measurement of renal vein blood flow can be performed, and it is concluded that MRI-based renal vein flow measurements can be used to estimate RBF in small rodents.

Animals↗
PubMed1997

Relationship between MRI and morphometric kidney measurements in diabetic and non-diabetic rats.

The aim of the present study was to determine the applicability of magnetic resonance imaging (MRI) as a non-invasive measure of kidney volume in vivo in diabetic and non-diabetic rats. Magnetic resonance, T1 weighted Spin Echo, images were obtained after injection of contrast in anesthetized control (N = 14) and hyperglycemic streptozotocin (STZ)-diabetic rats (N = 14). On MRI imaging the total kidney, cortex, medullary and pelvic volumes were calculated. Immediately after MRI measurements the left kidneys were removed before weighing either as a clamped kidney weight (that is, the kidney containing blood and urine) or as a wet kidney weight (the kidney drained of blood and urine), while the right kidneys were perfusion-fixed for morphometric measurements. On thin kidney slices obtained from perfusion-fixed kidneys the cortex, medullary and pelvic fractions were measured and subsequently the cortex, medulla and pelvic volumes were calculated. The cortical volume was measured according to three different approaches. The corticomedullary boundary was defined either to the arcuate arteries, to a curved line following the glomeruli, or to a line at the top of the medullary rays. Both in control and diabetic rats, MRI measured kidney volumes were similar to the volume of perfusion-fixed kidneys, while the clamped kidney weight, and in particular the wet kidney weights, were smaller than the MRI obtained volumes. Good agreement was found between the MRI measured cortex and medulla volumes when the cortex was defined to the top of the medullary rays in the morphometric analysis. In conclusion, the present study demonstrates that MRI allows a reliable non-invasive estimate of renal morphology at a macroscopic level in both diabetic and non-diabetic rats.

Animals↗
PubMed1997

Magnetic resonance imaging as a monitor of kidney enlargement and regression in experimental diabetes in rats.

The aim of the present study was to use magnetic resonance imaging as a non-invasive measure of renal enlargement and regression in experimental diabetes in rats. Rats were randomized into three groups: (1) non-diabetic control animals, (2) diabetic animals, untreated for 30 days after streptozotocin treatment and (3) diabetic animals treated with insulin from day 21 to day 30 after streptozotocin administration. Magnetic resonance images were obtained from anaesthetized rats and kidney, cortex, medulla and pelvis volumes were calculated throughout the experiment until day 30. In untreated diabetic animals, a marked increase in kidney volume was seen 4 days after the induction of diabetes (P < 0.05) and after 30 days this increase amounted to 73%, with similar increases in the cortex (63%) and medulla (69%). No change was seen in the pelvis volume. Insulin administration on day 21 to untreated diabetic rats abruptly reduced kidney volume by 21%, cortex volume by 27% and medulla volume by 18%, and after 4 days all three parameters were similar to those seen in non-diabetic controls. In conclusion, the present study has demonstrated the applicability of magnetic resonance imaging as a non-invasive measure of renal enlargement and regression in experimental diabetes in rats. In untreated hyperglycaemic diabetic rats, with manifest diabetic renal enlargement, acute regression in renal volume was observed concomitant with insulin-induced normoglycaemia.

Animals↗
PubMed1995

Current health as a general health indicator. II: Evaluation of reliability and validity.

OBJECTIVE: To examine whether a Current Health scale produces reliable and valid measures of self perceived health status. DESIGN: Examination of reliability, based on internal consistency (Cronbach's alpha coefficient). Examination of validity focusing on convergent and discriminant validity. SUBJECTS: 2263 male and female heads of households who participated in The Danish Health Study 1982-83. The survey used items pertaining to health status from Rand's Health Insurance Study. RESULTS: The scale has acceptable properties and is preferable to a single item measure of general health status. It can be used in general practice.

Activities of Daily Living↗
PubMed1994

Prospective study of prevalence and endoscopic and histopathologic characteristics of duodenal polyps in patients submitted to upper endoscopy.

BACKGROUND: Retrospective studies of duodenal polyps have shown a prevalence of 0.3%-1.5% in patients referred to upper endoscopy, and histopathologic classifications have been inconsistent. METHODS: A prospective consecutive study was carried out in 584 patients referred to diagnostic upper endoscopy. Symptoms were registered on a questionnaire, endoscopic and histopathologic findings on standard forms. The same pathologist evaluated all biopsy specimens. RESULTS: Twenty-seven patients had polyps in the first and/or second part of the duodenum, for a prevalence 4.6%. Sixteen polyps were either inflammatory (nine polyps) or ectopic gastric mucosa (seven polyps). Both of these polyp types were practically always non-solitary, sessile, small, and located in the duodenal bulb. Seven polyps were covered by normal mucosa, three being endoscopically typical lipomas. Two polyps were adenomas (0.4% of all the patients and 7% of the polyps), and both were found in the descending part. One hyperplastic polyp of the gastric type and one case of fibrosis were found. CONCLUSIONS: 1) Duodenal polyps are found in 4.6% of patients referred to upper endoscopy and should therefore be looked for. 2) Multiple, small polyps in the duodenal bulb are always benign and need neither biopsy nor treatment (in patients with familial polyposis biopsy is recommended). 3) In the descending duodenum polyps are rare, but a substantial number of them are adenomas. Biopsy is therefore mandatory in this localization.

Adenoma↗
PubMed1993

Current health as a general health indicator. I: Evaluation of scaling properties.

OBJECTIVE: To examine to which extent 9 items pertaining to health perception fulfil the Likert criteria for adding the scores for each item to make up a Current Health scale. The term "scaling" denotes the process of constructing a scale from questionnaire items. DESIGN: Examination of convergent and discriminant validity of items, groupings of items, item variance, and information content of each item. SUBJECTS: 2,263 male and female heads of households who participated in The Danish Health Study 1982-83. The survey used items pertaining to health status from Rand's Health Insurance Study. RESULTS: The Likert criteria for constructing a scale of the nine items are fulfilled except for one item. The lack of fulfillment for this item can eventually be attributed to the translation.

Adult↗
PubMed1992

Equity in the finance of health care: some international comparisons.

This paper presents the results of a ten-country comparative study of health care financing systems and their progressivity characteristics. It distinguishes between the tax-financed systems of Denmark, Portugal and the U.K., the social insurance systems of France, the Netherlands and Spain, and the predominantly private systems of Switzerland and the U.S. It concludes that tax-financed systems tend to be proportional or mildly progressive, that social insurance systems are regressive and that private systems are even more regressive. Out-of-pocket payments are in most countries an especially regressive means of raising health care revenues.

Cross-Cultural Comparison↗
PubMed1992

Equity in the delivery of health care: some international comparisons.

This paper presents the results of an eight-country comparative study of equity in the delivery of health care. Equity is taken to mean that persons in equal need of health care should be treated the same, irrespective of their income. Two methods are used to investigate inequity: an index of inequity based on standardized expenditure shares, and a regression-based test. The results suggest that inequity exists in most of the eight countries, but there is no simple one-to-one correspondence between a country's delivery system and the degree to which persons in equal need are treated the same.

Cross-Cultural Comparison↗
PubMed1989

An investigation of the effect of regional variation in the treatment of hypertension.

Over a period both a monetary and physical measure of antihypertensive drug consumption has increased in Denmark, but the consumption has varied considerably between counties in any given year. Concurrently, SMR for myocardial infarctions and cerebrovascular diseases due to hypertension has declined. The relation between intensity of treatment and outcome in terms of reduced loss of life time or healthy time is analyzed at an aggregate level within a health economic framework. The relation is analyzed by using a pooled time series cross section regression analysis. Two models, a covariance and an error component model are used. Within the range of observed drug consumption, loss of life years and loss of good health show a tendency towards negative regression on consumption of drugs when controlled for relevant variables such as occupational structure, degree of urbanization, and hardness of the drinking water.

Antihypertensive Agents↗
PubMed1989

Self-care within a model for demand for medical care.

Self-care is interpreted from a health economic point of view. Various approaches are presented. It is stressed that the decision-oriented approach used by other health service researchers is an integral part of the economic approach to the topic as is the idea of a continuum of care, from self-care to professional care. A new approach is taken to the modeling of self-care, in that self-care becomes part of a four-part demand for care model. This makes it possible to model the demand for care for three different groups separately: 1--persons with zero episodes; 2--persons with pure illness episodes and illness episodes with self-care; 3--persons with episodes involving professional care or professional care combined with self-care. Another contribution is due to the so-called episodic approach to the demand for care. The natural counting units are illness and treatment episodes, i.e. instead of counting for instance number of times a general practitioner is consulted we ought to count the number of episodes involving professional care, self-care or both types of care. The episodic approach seems to be well suited for work with self-care. The empirical part is based on a unique Danish panel study using health diaries returned weekly. Data from 27 of the 52 reporting weeks are used, involving more than 14,000 episodes distributed across about 2800 persons belonging to about 1000 households. The use of health diaries seems to be very well suited to the study of self-care in that less salient events and activities than professional care are picked up far better in prospective health diary studies than in retrospective questionnaire based surveys. Descriptive and regression (logistic and ordinary) results are presented.

Choice Behavior↗