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Biomedical subjects

A Hartmann

Publications and source records attributed to A Hartmann.

At least 505 records · Page 28Linked to original sources
PubMed1983

Segmental distribution of vascular resistances during ureteral occlusion. The vasoconstrictive effects of angiotensin and CaCl2 differ from those of catecholamines and renal nerve stimulation.

UNLABELLED: Examinations of renal autoregulation and renin release suggest that alpha-adrenergic agonists, in contrast to other vasoconstrictors, preferentially constrict the preglomerular arteries. To examine this hypothesis, experiments were performed in anesthetized dogs during ureteral occlusion. At a ureteral pressure (UP) of 100 mmHg the afferent arterioles are dilated and mechanical constriction of the renal artery does not alter intrarenal vascular resistances. Whereas angiotensin and CaCl2 infused into the renal artery reduced renal blood flow (RBF) by 25-30% without reducing UP, renal nerve stimulation reduced RBF and UP in proportion. During angiotensin and catecholamine infusion, measurements of UP and intrarenal venous pressure permitted calculations of preglomerular, efferent vascular and intrarenal venous resistances. Until RBF was reduced by 25%, angiotensin raised both preglomerular and efferent vascular resistances, whereas norepinephrine and the alpha-adrenergic agonists, phenylephrine and methoxamine, raised preglomerular more than efferent vascular resistance. When RBF was reduced by more than 25%, all vasoconstrictors showed a similar pattern with large increments both in preglomerular and efferent vascular resistances. CONCLUSIONS: Humoral and nervous stimulation of alpha-adrenergic receptors reduce glomerular capillary pressure by preferentially constricting the preglomerular arteries and may affect renal autoregulation and renin release by reducing the transmural pressure of the afferent arterioles.

Adrenergic alpha-Agonists↗
PubMed1983

Evidence for bicarbonate-dependent magnesium reabsorption.

During ethacrynic acid administration about 50% of the filtered load of magnesium is reabsorbed. To examine whether the remaining component of magnesium reabsorption is bicarbonate-dependent, i.e. varies with factors known to alter passive reabsorption, experiments were performed in anesthetized dogs. During ethacrynic acid administration MgCl2 infusion raised the plasma concentration of magnesium (PMg) from 0.64 +/- 0.05 to 3.06 +/- 0.27 mM and doubled magnesium reabsorption. The infusion of acetazolamide at high PMg reduced bicarbonate reabsorption by 41 +/- 3% and magnesium reabsorption by 31 +/- 16%. When plasma pH was reduced to 7.04 +/- 0.02 and increased to 7.83 +/- 0.02 by altering PCO2 at a constant plasma bicarbonate concentration of 31.2 +/- 0.8 mM, magnesium and bicarbonate reabsorption were correlated (r = 0.82). The infusion of mannitol, which acts by reducing passive solute transport without affecting bicarbonate reabsorption, halved magnesium reabsorption. By combining mannitol and acetazolamide infusions, only 6 +/- 4% of the filtered magnesium was still reabsorbed. These results indicate that the reabsorption of magnesium remaining after the infusion of ethacrynic acid and after raising PMg varies with changes in PCO2 and is inhibited by the infusion of acetazolamide and mannitol as expected for bicarbonate-dependent passive reabsorption.

Acetazolamide↗
PubMed1983

Effect of pentoxifylline on regional cerebral blood flow in patients with cerebral vascular disorders.

In two studies using the 133Xe clearance method the effect of chronic intravenous and oral administration of pentoxifylline on regional cerebral blood flow (rCBF) in patients with chronic cerebrovascular diseases was evaluated. In both studies rCBF increased significantly. The effect was more prominent in hypoemic than in normoemic tissue which led to the suggestion that not only viscosity but other local factors were also positively influenced by the drug.

Cerebrovascular Circulation↗
PubMed1982

[Occupation-related lung diseases in hard metal production and manufacturing. An allergic process?].

The clinical heterogeneity of hard metal disease lung with its two basic forms, i.e. hart metal pneumonitis and hard metal asthma, supports the view of different pathogenetic mechanisms. Cobalt, which is generally considered the noxious agent in hard metal diseases, is cytotoxic on the one hand and allergenic on the other. Four typical, extensively investigated cases are presented, i.e. hard metal pneumoconiosis, hypersensitivity pneumonitis, toxic-irritative hard metal asthma and allergic cobalt asthma. The immunological results were negative in the patient with hard metal pneumoconiosis. A hard metal grinder with typical occupational hypersensitivity pneumonitis showed a high level of precipitating antibodies against Aureobasidium pullulans, a well-known antigen in humidifier fever and sequoiosis. The inhalative provocation test induced on both patients with hard metal asthma an immediate and prolonged, i.e. a dual asthmatic reaction. Only the patient with allergic contact eczema due to cobalt and a positive epicutaneous test of the delayed type and a positive scratch tests of the immediate type with cobalt chloride.

Adult↗
PubMed1982

[Occupational lung diseases in Swiss cotton industry].

Classical byssinosis is hardly ever observed in Switzerland. The clinical picture of the other diseases of the lung occurring in the cotton industry is heterogeneous. In the present study the pathogenesis is considered allergic in the majority of the cases. Five typical, extensively investigated cases are presented. In provocation tests immediate asthmatic reactions were induced in the three patients who had positive immediate wheal-and-flare response to skin tests with an extract of cotton industry dust. Skin tests to common inhalants were negative. In addition, one patient showing a higher titer of precipitating antibodies against the cotton dust extract developed a 'dual' asthmatic reaction, with recurrent airway obstruction 6-7 h later, which was only partly reversible by beta 2-stimulation.

Adult↗
PubMed1981

Iron uptake and iron limited growth of Escherichia coli K-12.

Cells of Escherichia coli K-12 could grow aerobically at an iron concentration as low as 0.05 micrometer without any of the known iron ionophores present. The growth rate increased between 0.05 and 2 micrometer iron. Supplementation with the iron ligands ferrichrome and citrate resulted in optimal growth already at 0.05 micrometer iron. Under certain conditions iron uptake preceded growth of cells by more than an hour. During logarithmic growth the rate of iron uptake matched the growth rate. The radioactive tracer method revealed a cellular iron content of 4 nmol/mg dry weight. After consumption of the iron in the medium cells continued to grow with high rate for 1-2 generations. The iron uptake activity was increased during iron starvation.

Biological Transport↗
PubMed1981

[Cooperation of engineers and physicians in accident prevention].

Technical protection represents one of several conditions which are necessary to protect the health of working people. As men are themselves part of technical systems, an integrated approach of safety and health protection is needed. The task is not only interdisciplinary but also transdisciplinary. Safety efforts have to take into account the three elements hardware, procedures and people as well as the three interfaces between these elements. The cooperation between engineers and medical doctors on workplace inspections, on accident investigations and on reintegration of injured workers are described.

Accidents, Occupational↗
PubMed1981

Transcellular and intercellular transport of anions in the kidney tubules of dogs.

Fractional reabsorption of 4 anions was measured in anesthetized dogs either during inhibition of bicarbonate-dependent intercellular NaCl transport by acetazolamide or mannitol, or during inhibition of transcellular NaCl reabsorption in the diluting segment by ethacrynic acid or ouabain. When administered subsequent to ethacrynic acid, acetazolamide reduced fractional reabsorption of SCN, Br, Cl and I by 0.28 +/- 0.03, 0.28 +/- 0.02, 0.27 +/- 0.03 and 0.31 +/- 0.03. Mannitol given after ethacrynic acid reduced fractional reabsorptions by 0.23 +/- 0.04, 0.20 +/- 0.04, 0.20 +/- 0.05 and 0.20 +/- 0.05, respectively. Thus, the bicarbonate-dependent reabsorption system does not discriminate between these anions. Ethacrynic acid reduced fractional reabsorption of SCN, Br and Cl by 0.28 +/- 0.05, 0.24 +/- 0.03, 0.22 +/- 0.03 in one group, by 0.32 /+- 0.04, 0.34 +/- 0.03, 0.31 +/- 0.04 in another group, with significantly smaller reductions for I, 0.07 +/- 0.03, in both groups. Ouabain reduced fractional reabsorption of Br, Cl and I by 0.48 +/- 0.04, 0.46 +/- 0.04 and 0.24 +/- 0.03, respectively. Thus, anion permeability or transport affinity for bromide, chloride and iodide are equal both for inter- and transcellular transport, while iodide transport is slow along the transcellular route. No specific transport mechanism for chloride was detected.

Absorption↗
PubMed1981

Ethacrynic acid inhibits transcellular NaCl reabsorption in dog kidneys in doses of 1 to 10 mg.kg-1 and proximal bicarbonate-dependent reabsorption at higher doses.

In anesthetized dogs, sodium reabsorption in the kidney tubule was continuously reduced with increasing dosage of ethacrynic acid until 59% of the filtered load was excreted with 25 mg.kg-1 at constant glomerular filtration rate. With 50 mg.kg-1, glomerular filtration rate fell, but fractional sodium reabsorption was further reduced by 7%. In the dosage range of 1 to 10 mg.kg-1, ethacrynic acid inhibited chloride but not bicarbonate reabsorption, and the ratio between reductions in sodium reabsorption and oxygen consumption (delta Na/delta O2) averaged 25.5 +/- 5.2. With doses of 25 and 50 mg.kg-1, ethacrynic acid further reduced chloride reabsorption, reduced fractional bicarbonate reabsorption by 17% and almost halved phosphate reabsorption, whereas delta Na/delta O2 rose significantly to 65.3 +/- 12.2. Renal cortical carbonic anhydrase activity was normal and the inhibitory effect of acetazolamide, a carbonic anhydrase inhibitor, on bicarbonate reabsorption was unimpaired. We conclude that ethacrynic acid in doses up to 10 mg.kg-1 exclusively inhibits transcellular NaCl reabsorption, but in higher doses interferes with bicarbonate reabsorption and bicarbonate-dependent passive reabsorption of NaCl in the proximal tubules without inhibiting carbonic anhydrase activity.

Absorption↗
PubMed1981

Cerebral blood flow in patients with cerebrovascular disorders: study with pentoxifylline.

Twenty outpatients (8 women and 12 men; age range 52-66 years) with mild to moderate degree of cerebrovascular disorders and arteriosclerotic dementia, were randomly assigned to either control or pentoxifylline group (400 mg X 3/day/4 weeks p.o.). Measurements of cerebral blood flow (133Xe) show in the right hemisphere of the treated group a significant increase of fast perfused brain substance flow (Fg) in 7 out of the 10 cases and in the left hemisphere in 4 patients. In none of all treated subjects a significant reduction of mean Fg was observed. In the control group significant increase in 1 and significant reduction in another out of 20 hemispheres was observed. As for regional data, while significant elevation of Fg was observed in 36.7% of all recorded areas (114 out of 311) after pentoxifylline, this occurred only in 6.4% in the control group. The effect of pentoxifylline on cerebral perfusion in the different areas was independent of their location but was more pronounced in hypoperfused tissue.

Aged↗