ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

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Effects of cytochalasin B and dihydrocytochalasin B on calcium transport by intestinal absorptive cells (1981)

Jande, Sohan S. ; Liskova-Kiar, M.

Springer

Calcified tissue international 33 (1981), S. 143-151

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ISSN: 1432-0827

Keywords: Calcium transport ; Cytochalasin B ; Dihydrocytochalasin B ; Colchicine ; Electron microscopy

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine , Physics

Notes: Summary In vivo calcium absorption was studied in normal and rachitic chicks. Cytochalasin B (CB) at a concentration of 25 µg/ml added to the medium inside the duodenal lumen inhibited calcium absorption (20 min) from 82.5±1.9% of calcium absorbed in the controls to 59.2±3% in normal and from 70.0±2.3% to 47.0±2.1% in rachitic chicks. In vitro studies by everted ileal sacs of young rabbits also showed an inhibition of active transport of calcium due to CB. Whereas in the controls the ratio of45Ca concentrations in serosal and mucosal media (60 min) was 7.2±0.32, the ratios were 5.24±0.52; 4.40±0.36; 3.40±0.42; 5.77±0.52; 1.38±0.08; and 1.06±0.02 in the presence of CB at concentrations of 5, 10 and 25 µg/ml; colchicine 10−4M, Na citrate 0.02M, and heat-devitalized conditions, respectively.45Ca concentration in the mucosal scrapings was also affected. It showed an increase from controls (15,101±404 cpm/mg) and correlated with CB concentration: 17,378±489, 19,015±1000, and 20,201±362 at 5, 10, and 25 µg/ml, respectively. Dihydrocytochalasin B also inhibited active calcium transport and caused an increase in45Ca concentration in the mucosal scrapings. Correlated electron microscopic studies showed certain changes in the brush border, especially in some actin microfilaments in the terminal web region. It seems that these morphological alterations may be related to transcytoplasmic movement of calcium.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02409427

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2

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Ultrastructure of the rat epiphyseal growth plate following chronic ethanol ingestion (1981)

Fallon, Michael D. ; Baran, Daniel T. ; Craig, R. Bruce ; [et al.]

Springer

Calcified tissue international 33 (1981), S. 381-384

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ISSN: 1432-0827

Keywords: Alcohol ; Electron microscopy ; Growth plate

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine , Physics

Notes: Summary We have previously demonstrated that ethanol has a direct toxic effect on the rat skeleton characterized by decreased trabecular bone volume. In the present study, we examined the ultrastructure of the distal radial epiphyseal growth plates in these same animals. Eight weeks of ethanol administration to 12 male rats results in serum alcohol levels of 140 mg/dl but did not alter the width or light microscopic appearance of the radial growth plate. Quantitative electron microscopy failed to demonstrate morphologic evidence of toxicity in the skeletal cells. We conclude that although ethanol appears to have a direct effect on rat bone characterized by enhanced resorption, toxicity is not attended by ultrastructural changes in the skeletal cells.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02409460

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3

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Biochemical and histological studies on various bone cell preparations (1981)

Nijweide, P. J. ; Plas, A. ; Scherft, J. P.

Springer

Calcified tissue international 33 (1981), S. 529-540

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ISSN: 1432-0827

Keywords: Bone cells ; Electron microscopy ; PTH ; PGE1

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine , Physics

Notes: Summary Four different cell populations—designated PF, OB, OC, and PC—were isolated from calvaria of 18-day-old chick embryos for analysis of the effects of hormones on bone tissue. The cell populations were studied with histological and biochemical methods. Apart from the well-known cell types present in calvaria, a new cell type was found in the noncalcified organic matrix between the osteoblastic layer and the calcified matrix. These cells were provisionally called osteocytic osteoblasts. They represent the “transition state” between osteoblasts and osteocytes. On the basis of histological studies with light microscopy (LM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM), the PF population was considered to originate primarily from the periosteal fibroblasts, the OB population from the osteoblasts and osteocytic osteoblasts. The population of cells still present in calvaria after removal of periosteal fibroblasts and osteoblasts was called the OC population. This cell population was very much enriched with osteocytes. The fourth isolated population (PC) was a mixed population of fibroblasts, osteoblasts, and preosteoblasts. On exposure to parathyroid hormone (PTH), all four cell populations showed increased lactate production, but only the OB and OC populations displayed increased cAMP production. Prostaglandin E1 (PGE1) stimulated cAMP production in both OB and PF cells. From the results of this study it was concluded that PTH receptors are present on all of the cell types studied, but that occupancy of the receptor induces adenylate cyclase stimulation only in osteocytes and fully differentiated osteoblasts.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02409485

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4

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Crystal orientation in the shell of the domestic fowl: An electron diffraction study (1981)

Perrott, H. R. ; Scott, V. D. ; Board, R. G.

Springer

Calcified tissue international 33 (1981), S. 119-124

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ISSN: 1432-0827

Keywords: Avian eggshell ; Microstructure ; Electron microscopy ; Electron diffraction ; Calcite growth

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine , Physics

Notes: Summary The eggshell of the domestic fowl has been studied by transmission electron microscopy and diffraction. Thin sections of shell were prepared by chemical and ion-beam thinning techniques. Each calcite column of the palisade layer consisted of crystallites of diameter 20 to 30 µm with some tendency for crystallite alignment within a single column. Evidence indicates that there was no significant preferred orientation in the palisade layer as a whole. Only in the surface layer was any preferred orientation detected, and here {1014} planes tended to lie parallel to the surface. The results are compared with previously published data, and calcite nucleation and growth are discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02409423

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5

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Variable planar particle arrangements in the photosynthetic membrane of Rhodopseudomonas viridis (1981)

Welte, W. ; Hodapp, N. ; Aehnelt, C. ; [et al.]

Springer

European biophysics journal 7 (1981), S. 209-212

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ISSN: 1432-1017

Keywords: Photosynthetic bacteria ; Electron microscopy ; Planar lattices

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Physics

Notes: Abstract The thylakoids of Rhodopseudomonas viridis have been studied by freeze-fracturing whole cells. Depending on growth conditions and treatment before freezing, three different types of particle arrangements in the photosynthetic membrane are reported: a random arrangement, an isometric (quadratic) lattice arrangement with a lattice constant of 12.5 ± 0.8 nm, and a hexagonal lattice arrangement with a lattice constant of 12.5 ± 0.8 nm.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00539181

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6

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Withdrawal of guanfacine after long-term treatment in essential hypertension (1981)

Zamboulis, C. ; Reid, J. L.

Springer

European journal of clinical pharmacology 19 (1981), S. 19-24

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ISSN: 1432-1041

Keywords: hypertension ; guanfacine ; central antihypertensives ; withdrawal ; catecholamines

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Medicine

Notes: Summary 1. Guanfacine (2–6 mg/day) a centrally acting antihypertensive drug, was effective in controlling blood pressure in 5 essential hypertensives and lowered plasma noradrenaline and urinary catecholamine excretion. 2. Withdrawal of guanfacine by blind substitution of identical placebo tablets under observation in hospital led to a gradual recovery of blood pressure over 2–4 days. 3. Salivary flow, which was reduced on guanfacine, returned to pretreatment levels by 2 days after withdrawal and significantly exceeded control for the next two days. 4. Urinary catecholamine excretion returned to pretreatment levels by 3 days but did not exceed control levels during the period of study. 5. Plasma noradrenaline returned gradually to pretreatment levels, and by day 4 significantly exceeded them. 6. No patient experienced symptoms suggesting catecholamine excess although four out of five reported a headache from the second day onwards. 7. Guanfacine, a centrally acting drug which pharmacologically resembles clonidine, has a slow offset of hypotensive effect over 2–3 days. Symptoms or biochemical evidence of catecholamine excess were not encountered within 48 h of withdrawal, possibly reflecting the longer duration of action and plasma half-life of guanfacine.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00558376

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7

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Double-blind trial comparing guanfacine and methyldopa in patients with essential hypertension (1981)

Bune, A. J. ; Chalmers, J. P. ; Graham, J. R. ; [et al.]

Springer

European journal of clinical pharmacology 19 (1981), S. 309-315

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ISSN: 1432-1041

Keywords: guanfacine ; methyldopa ; hypertension ; rebound hypertension ; withdrawal symptoms ; plasma noradrenaline

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Medicine

Notes: Summary Nine patients with essential hypertension completed a clinical trial designed to study the effects and side effects of administration and withdrawal of guanfacine (2 mg tds) and methyldopa (250 mg tds) on blood pressure, heart rate, and plasma noradrenaline. The study was of randomised doubleblind crossover design with two active therapy phases of eight weeks each, preceded by an initial 4 week placebo phase, separated by an intermediate 2 week placebo phase, and followed by a final 2 week placebo phase. Patients took bendrofluazide 5 mgs daily throughout the entire trial, during both active and placebo periods. Each patient was admitted to hospital at the end of the 8 week active treatment phases, so that the effects of drug withdrawal on blood pressure, heart rate, plasma noradrenaline and side reactions, could be closely observed and monitored. The main conclusions from analysis of the results were that: 1. The hypotensive efficacy of guanfacine and methyldopa was very similar in the doses used, each of the two drugs lowering the supine mean arterial pressure by about 15 mm Hg and the supine diastolic pressure by about 10 mm Hg. 2. The frequency of side effects was greater with guanfacine than with methyldopa. 3. There was no signficant early rebound phenomenon after withdrawal of either methyldopa or guanfacine. 4. There was tendency for the blood pressure to rise slowly and marginally above initial placebo values, 2 weeks after cessation of guanfacine treatment though this was not significant. It was however, accompanied by a significant increase in plasma noradrenaline at 2 weeks. This was not seen 2 weeks after cessation of methyldopa. There was no single incidence of worrying rebound hypertension or withdrawal symptoms either early or late in any patient following cessation of methyldopa or guanfacine.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00544579

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8

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Haemodynamic profile of captopril treatment in various forms of hypertension (1981)

Bruyn, J. H. B. ; Man in 't Veld, A. J. ; Wenting, G. J. ; [et al.]

Springer

European journal of clinical pharmacology 20 (1981), S. 163-168

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ISSN: 1432-1041

Keywords: hypertension ; captopril ; cardiac output ; extracellular fluid volume ; renin

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Medicine

Notes: Summary The effects of captopril 450 mg/day for 4 weeks on blood pressure, heart rate, cardiac output and extracellular fluid volume were compared in severe, often drug-resistant hypertension (n=23), mild to moderate hypertension associated with renal artery stenosis (n=10) and mild to moderate essential hypertension (n=20). Plasma renin in the three groups was 52±19, 58±17 and 20±4 µU/ml (mean ± SEM), respectively. Blood pressure fell by 18±4%, 21±2% and 18±1%. The pressure drop was mainly due to a fall in peripheral vascular resistance. Addition of the diuretic hydrochlorothiazide (25–100 mg/day) caused a further fall in resistance. Despite the vasodilator effect of captopril, reflex cardiostimulation and reactive fluid retention were not observed. In severe hypertension, captopril alone was more effective in lowering blood pressure than combined diuretic-betablocker-vasodilator therapy. Moreover, cardiac output in these patients was higher and resistance was lower after captopril than during combined treatment. Thus, captopril was capable of normalising the abnormal haemodynamic state in patients with essential hypertension, and in hypertension associated with renal artery stenosis. Despite marked differences in pre-treatment plasma renin, the effects of captopril on systemic haemodynamics were similar in all the patients.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00544593

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9

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Acute effects of a new vasodilator, Ro 12-4713, on blood pressure, plasma renin activity, aldosterone and catecholamine levels, and renal function in hypertensive and normal subjects (1981)

Grimm, M. ; Weidmann, P. ; Meier, A. ; [et al.]

Springer

European journal of clinical pharmacology 20 (1981), S. 169-177

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ISSN: 1432-1041

Keywords: vasodilator ; hypertension ; haemodynamic effects ; renal plasma flow ; renal tubular function ; plasma renin activity ; aldosterone ; Ro 12-4713

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Medicine

Notes: Summary Selected cardiovascular and endocrine effects of the new oral vasodilator Ro 12-4713 have been evaluated in an acute single dose study. In five patients with essential hypertension, Ro 12-4713 caused a dose-dependent decrease in supine and upright blood pressure and an increase in heart rate. Initial effects occurred one to 2 h after drug ingestion and maximal effects were noted after five hours and persisted for at least 8 h. Blood pressure was normalized, and the antihypertensive and chronotropic effects persisted for 24 h after a dose of about 300 mg/1.73 m2. Plasma and urinary norepinephrine and plasma renin levels tended to be raised, whereas plasma and urinary epinephrine and plasma aldosterone did not change. Changes in supine heart rate were inversely correlated with changes in mean blood pressure (r=−0.60; P〈0.02), and positively with those in plasma norepinephrine (r=0.55; P〈0.05) and renin (r=0.62, P〈0.01); changes in supine plasma renin level were also inversely correlated with those in mean blood pressure (r=−0.65; P〈0.01), and positively with those in plasma norepinephrine (r=0.58; P〈0.05). 24 h-urinary sodium excretion was significantly (P〈0.001) decreased; it was positively correlated with mean blood pressure (r=0.51; P〈0.05) and inversely with supine plasma renin activity (r=−0.63; P〈0.01). In six normal subjects and six patients with essential hypertension, effective renal plasma flow and the renal clearance of sodium, potassium, calcium and uric acid were not significantly altered five hours after a dose of Ro 12-4713 of about 250 mg/1.73 m2; glomerular filtration rate tended to be slightly decreased, and filtration fraction was significantly (P〈0.05) reduced in the hypertensive patients. At the same time blood pressure was decreased and plasma norepinephrine (P〈0.01) and renin (ns) were slightly increased in both groups. Ro 12-4713 in a single oral dose of about 300 mg appeared to be a potent, long acting, hypotensive vasodilator.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00544594

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10

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Long-term clonidine effects on autonomic function in essential hypertensive man (1981)

Cohen, I. M. ; O'Connor, D. T. ; Preston, R. A. ; [et al.]

Springer

European journal of clinical pharmacology 19 (1981), S. 25-32

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ISSN: 1432-1041

Keywords: clonidine ; hypertension ; baroreceptor reflex ; mode of action ; sympathetic activity ; urinary catecholamines

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Medicine

Notes: Summary Acute studies of clonidine suggest that it lowers blood pressure by central enhancement of baroreflex sensitivity coupled with diminished evidence of sympathetic outflow, but longterm clonidine data have not been conclusive. We examined effects of one month of low dose clonidine (0.4 ± 0.15 mg/day) alone in 13 essential hypertensive men, assessing several biochemical indices of sympathetic function, as well as physiologic parameters, including baroreflex sensitivity, the cold pressor test, and the hypotensive response to alpha adrenergic blockade. Clonidine diminished mean arterial pressure (from 104±5 to 84±3 mmHg;p〈0.01), without associated changes in several biochemical parameters of sympathetic outflow (urinary excretion of catecholamines, metanephrines, and vanillylmandelic acid; allp〉0.1). Circulatory baroreflex function was not enhanced by clonidine, during either the amylnitrite test or the phenylephrine test, before or after parasympathetic blockade with atropine. The cold pressor test, an index of efferent sympathetic pressor function, was also unaltered. The enhanced mean arterial pressure response to phentolamine during clonidine therapy (from a fall of 14.8±4.3 to 39.4±5.2 mmHg,p〈0.01), suggested an increase in alpha adrenergic vascular tone, perhaps mediated by clonidine's alpha agonist properties in vascular smooth muscle. The antihypertensive mechanism of longterm low dose clonidine cannot reliably be ascribed either to baroreflex enhancement or to suppression of sympathetic outflow.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00558378

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