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Biomedical subjects

P A Jansen

Publications and source records attributed to P A Jansen.

At least 19 recordsLinked to original sources
PubMed1991

Temperature-dependent reproduction and survival of Gyrodactylus salaris Malmberg, 1957 (Platyhelminthes: Monogenea) on Atlantic salmon (Salmo salar L.).

The relationship of survival and reproduction of Gyrodactylus salaris Malmberg on the Atlantic salmon (Salmo salar) to water temperature (2.5-19.0 degrees C), was studied on the basis of temporal sequence of births and age at death of individual parasites on isolated salmon, and of infrapopulation growth on isolated and grouped salmon. Mean life-span of the parasite was negatively correlated with water temperature: 33.7 days at 2.5 degrees C and 4.5 days at 19.0 degrees C. The average number of offspring per parasite peaked between 6.5 and 13.0 degrees C, and was approximately 2.4 at these two temperatures. Both the period between the successive births of the offspring (max 4) and the estimated generation time were negatively correlated with temperature. The innate capacity for increase (rm) was positively correlated with temperature: from 0.02 (/parasite/day) at 2.5 degrees C to 0.22 (/parasite/day) at 19.0 degrees C. Growth of the infrapopulations was positively correlated with water temperature and was higher on isolated fish than on grouped fish, though less than the potential parasite population growth estimated from rm. In the infrapopulations the mean intensity of parasites continued to increase throughout all the experiments on both isolated fish and on grouped fish.

Analysis of Variance↗
PubMed1990

[Lithium in the treatment of depressed elderly patients].

In the geriatric department of a Dutch psychiatric hospital the charts of 65 patients treated with lithium for depression were reviewed. We assessed efficacy and adverse effects. The sample included 65 patients, 12 men and 53 women, mean age 77 (64-91) years. A complete or partial response was seen in 30 out of 43 patients (70%) treated with lithium in addition to a cyclic antidepressant. Six out of 22 patients treated with lithium as a sole antidepressant responded completely or partially. During lithium therapy 16 patients suffered from severe adverse effects. In our view and in spite of severe adverse effects, with expert monitoring lithium can be of value in the treatment of (very) old and depressed patients.

Aged↗
PubMed1990

Lithium augmentation in geriatric depression.

In the geriatric department of a Dutch psychiatric hospital the charts of 51 patients treated with lithium in addition to cyclic antidepressants were reviewed. A response was seen in 33 patients (65%). For patients with recurrent depressive episodes, a statistical trend was found towards more responders with more complete responses, compared to patients with first depressive episodes. During lithium augmentation, 10 patients suffered from severe adverse effects 12 times. In spite of adverse effects, with expert monitoring lithium augmentation can, in our opinion, be of value in the treatment of older depressed patients.

Aged↗
PubMed1988

Blood pressure and both venous and urinary catecholamines after cerebral infarction.

Blood pressure, both venous and urinary catecholamines and plasma renin activity (PRA) were studied in 10 patients (6 men and 4 women, mean age 70 +/- 10 years) on the first three days after cerebral infarction. Blood pressure fell significantly (p less than 0.02) on the second and third day after stroke. There was a small but significant (p less than 0.01) decrease in plasma epinephrine concentration on the third day. The norepinephrine values remained constant on the three days. The PRA showed a significant (p less than 0.01) rise on the third day. No significant correlation was detected between the course of the blood pressure and the plasma catecholamines or PRA. When blood pressure was correlated with the urinary catecholamines, however, a significant correlation with epinephrine (r = 0.45; p less than 0.05) and with norepinephrine (r = 0.44; p less than 0.05) was found. We conclude that the changes in blood pressure after stroke are at least partly mediated by the changes in catecholamine production.

Aged↗
PubMed1988

Pharmacokinetics of high-dosage naproxen in elderly patients.

After multiple oral doses of 500 mg naproxen twice daily, eight young healthy male volunteers and six male and female elderly patients participated in a pharmacokinetic study. Serum naproxen levels were measured by high-pressure liquid chromatography; protein-unbound drug was determined after equilibrium dialysis. A significantly lower maximal serum concentration (Cpeak), smaller area under the curve during one dose interval [AUC(0-12)], larger total body clearance (CL/F) and apparent volume of distribution (V/F body wt-1) were found for the total drug in elderly patients. The pharmacokinetics of the protein-unbound drug showed higher trough and peak concentrations, larger AUC(0-12)u, and smaller (CL/F)u and (V/F)u in the elderly patients. The unbound fraction (less than 1% of total naproxen) showed concentration dependency; in the elderly, a larger unbound fraction was found. Pharmacokinetic differences between the elderly and the young may be explained by a lower serum albumin concentration in the aged, together with a decrement in binding affinity of naproxen to albumin; moreover, the clearance of unbound drug was significantly reduced in the elderly (281 +/- 96 l/h) as compared with the young (713 +/- 164 l/h). We conclude that age-related factors increase serum unbound naproxen concentrations. It is, therefore, advisable to start treatment with naproxen in the elderly at a low dosage.

Adult↗
PubMed1987

Course of blood pressure after cerebral infarction and transient ischemic attack.

In 63 patients, admitted for cerebral infarction or transient ischemic attack (TIA), the blood pressure course was studied. The blood pressure before the event was studied retrospectively; 32 patients were normotensive, in 31 patients existed hypertension, with antihypertensive treatment in 15 of these cases. The blood pressure after the event was studied prospectively, and turned out to be risen in 67% of the patients on the day of admission. It fell in the first day after infarction or TIA, mainly on the second day, to a plateau level reached on the fifth day. Only 3 patients (5%) remained hypertensive until discharge from the hospital. In 48 patients blood pressure values were available as measured two to six months after discharge, without a change in antihypertensive medication. Blood pressure was increased compared to the value measured before discharge. In 14 patients (29%) hypertensive blood pressure figures were measured at that time. It is concluded that blood pressure is elevated in the acute phase of cerebral infarction and TIA, but falls spontaneously in the first days to normotensive levels in most patients; because blood pressure may increase again, measurements of blood pressure within the first months after discharge are needed.

Aged↗
PubMed1986

Contribution of inappropriate treatment for hypertension to pathogenesis of stroke in the elderly.

One hundred and seventy eight patients admitted to hospital with acute cerebral infarction or transient ischaemic attack were studied to determine if their treatment had been changed during the previous three weeks and to compare their blood pressure after the stroke with premorbid values. Blood pressure measurements taken within one year before the stroke were available for 100 patients; seven of these had had a recent change in antihypertensive or diuretic treatment. Of these, three patients who had started taking frusemide because of hypertension and one whose dosage of a reserpine combination drug had been increased experienced an appreciable decrease in blood pressure immediately after the stroke; they also showed signs of haemoconcentration. The change in treatment probably contributed to the stroke in these four patients. The other three showed a smaller decrease or even an increase in blood pressure and no signs of haemoconcentration; the relation between the change in treatment and stroke is less likely in these patients. The use of high ceiling diuretics such as frusemide in the treatment of hypertension may induce hypovolaemia and hypotension, resulting in cerebral ischaemia, and are therefore best avoided in such treatment.

Aged↗
PubMed1986

Antihypertensive treatment as a possible cause of stroke in the elderly.

There have been a few reports on stroke as a side-effect of antihypertensive treatment. To study the occurrence of this side-effect, a questionnaire was sent to all Dutch nursing homes (n = 322). Thirty patients were reported with signs of cerebral ischaemia shortly after starting antihypertensive and diuretic drugs. Nine of these cases were well documented with full data on blood pressure, measured immediately after the event and compared with pretreatment levels. A review of cases reported in the literature is presented. It is concluded that, especially in elderly patients, an abrupt fall in blood pressure may induce cerebral ischaemia, sometimes resulting in stroke. Antihypertensive treatment in the elderly should therefore start with a small dose, the aim being to reduce blood pressure gradually.

Aged↗
PubMed1976

Biochemical aspects of the visual process. XXXIV. Relation between sulfhydryl groups and properties of rhodopsin studied by means of methylmercuric iodide.

1. Treatment of isolated bovine rod outer segment membranes with the very reactive, small and uncharged sulfhydryl reagent methylmercuric iodide shows all six SH groups of rhodopsin can be modified without loss of its typical absorbance spectrum. 2. The partial loss of regeneration capacity, which occurs under these circumstances, can be attributed to secondary conformational changes following the actual modification reaction. 3. These observations plead against a direct involvement of SH groups in these two important parameters of rhodopsin. 4. Upon modification of SH groups, the normal photolytic sequence of rhodopsin is increasingly disturbed. When four or more SH groups are modified, the appearance of a photointermediate resembling metarhodopsin I dominates under conditions where native rhodopsin yields the transition of metarhodopsin II to metarhodopsin III.

Animals↗