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Die chronisch mesenteriale Ischämie (CMI) ist meist Folge atherosklerotischer Verschlussprozesse an den unpaaren Eingeweidearterien. Bei langstreckigen Gefäßverschlüssen und/oder ostiumnahen Stenosen mit hoher Kalklast sind operative Verfahren zu bevorzugen. Häufig werden Bypässe von der Aorta zu den Viszeralarterien angelegt, wobei körpereigenes Venenmaterial zu bevorzugen ist. Aufgrund atherosklerotischer Veränderungen sind die aortalen Bypassanastomosen schwierig und komplikationsträchtig. Anhand einer Fallbeschreibung wird eine Operationstechnik vorgestellt, die das aortoviszeralarterielle Bypassverfahren vereinfacht. Bei allen 6 Patienten sind die Bypässe nach 27 Monaten offen, die mittlere Gewichtszunahme betrug 13 kg innerhalb der ersten 6 Monate postoperativ. [ABSTRACT FROM AUTHOR]

EuroBionet, the ‘European Network for the Assessment of Air Quality by the Use of Bioindicator Plants’, is an EU-funded cooperative project currently consisting of public authorities and scientific institutes from 12 cities in 8 countries. In 2000, the bioindicator plants tobacco ( Nicotiana tabacum Bel W3), poplar ( Populus nigra ‘Brandaris’), spiderwort ( Tradescantia sp. clone 4430), Italian rye grass ( Lolium multiflorum italicum) and curly kale ( Brassica oleracea acephala) were exposed to ambient air at 90 monitoring sites according to standardised methods. Visible injuries and growth parameters were assessed and the accumulation of toxic substances in leaves determined. The exposure of tobacco resulted in a gradient with low levels of ozone-induced foliar injury in N and NW Europe, and medium to high values in the southern and central regions. The results of heavy metal and sulphur analyses in rye grass samples generally showed low to very low sulphur and low to medium heavy metal concentrations in leaves. In some cities, however, local hot spots of heavy metal contamination were detected. Analyses of the PAH contents in curly kale leaves gave low to medium values, with locally elevated levels at traffic-exposed sites. [ABSTRACT FROM AUTHOR]

The technique of orthograde tubular microperfusion has been used to test the functional integrity of tubuloglomerular feedback control in adrenalectomized rats. Kidneys of these animals display high renin contents, as well as an impairment of electrolyte transport in the loop of Henle, which was demonstrated by monitoring the electrical conductivity of fluid entering the distal tubule over a perfusion range of 10-50 nl/min. The calculated electrolyte concentration of the perfusion fluid leaving the loop of Henle was significantly higher in adrenalectomized rats than in controls. Intratubular stop flow pressure (SFP) during perfusion with a modified 'endproximal' Ringer's solution was recorded continuously in early proximal segments at rates of 0-40 nl/min. Direct pressure transmission from perfused endproximal tubular segments to the pressure recording capillary was prevented by paraffin blockade of the intermediate proximal segment. An intact feedback response in each of the 32 tubules of the adrenalectomized rats studied was observed, which was reversible and could be demonstrated repetitively in individual tubules. Thus ΔSFP at 40 nl/min was −11.2±1.3 mm Hg in adx rats as compared to −8.1±1.3 in control rats. An increased freedback sensitivity was observed in dexamethasone treated adrenalectomized rats despite normal renal renin content. Here ΔSFP at 40 nl/min was −15±1.1. Thus, the feedback signal can be mediated in the apparent absence of adrenal steroid hormones and a high sensitivity of tubuloglomerular feedback control is not necessarily paralleled by high renin content of renal tissue. [ABSTRACT FROM AUTHOR]

Oil blocked superficial segments of late proximal tubules were perfused with salt free isosmolal mannitol solution. Time course of total net ion influx into the lumen after sudden stop of perfusion was monitored by continuous measurement of the conductivity of tubular fluid inside the lumen. Double barreled microelectrodes with high coupling resistance ( R=350-450 kOhm) were used as microconductivity probes. The observed time course was interpreted in terms of a two compartment system. Time constants for equilibration were 5.9±2.8 (SD) s in control rats, 14.4±8.0 s in adrenalectomized rats and 5.5±2.3 s in adrenalectomized rats substituted with 100 μg·kg · d aldosterone for 3 days. The observed effect of aldosterone on the equilibration time constant indicates that this hormone increases the leakiness of proximal tubular epithelium for passive ion influx into the lumen. [ABSTRACT FROM AUTHOR]

Micropuncture experiments were performed to evaluate the electrolyte concentration of the tubular fluid (TF) in different segments of the rat nephron using the continuous, in situ measurement of electrical conductivity (ϰ) with a recently developed conductivity microprobe. In mid to late portions of proximal convoluted tubules (PCT) and in superficial distal tubules (DT) under free flow conditions the conductivities were 18.3±0.3 and 7.7±0.4 mS · cm at 37°C, respectively. These values correspond to the conductivities of 137 and 58 mmol · l sodium chloride solutions. The conductivity of the fluid in the inaccessible loop of Henle was examined by rapidly propelling its contents towards the conductivity pipette situated in the first accessible distal loop by a perfusion burst from the late proximal tubule. Thus, the free flow concentration profile existing along the ascending and descending limbs could be monitored with little distorsion. The transport functions of the different segments of Henle's loop, particularly of the diluting segment, were recorded using a 'stop/pulse flow' method. Following blockade of a PCT the corresponding loop of Henle was perfused with a proximal equilibrium solution. Subsequently perfusion was interrupted for intervals of increasing duration to allow equilibration. The fluid collumn was then rapidly propelled into the distal tubule by suddenly re-establishing perfusion. Dilution of TF was found to proceed exponentially as a function of equilibration time. Minimal conductivity of TF in the thick ascending limb was reached after 25-30 s, the steady-state conductivity minimum being 3.9±0.24 mS · cm. This corresponds to the conductivity of a 27 mmol · l NaCl solution. Addition of furosemide to the perfusion fluid (10 mol · l) resulted in a significant decrease of the dilution capacity, an effect which was enhanced by saline expansion of the animals. TF in contact with more proximal segments of Henle's loop i.e. the descending limb revealed a steady state conductivity of 17.7±0.3 mS · cm, which after correction for dilution in the ascending limb is equivalent to a 133 mmol · l NaCl solution. The present technique provides a means to examine some of the transport properties of Henle's loop in vivo, particularly the dilution capacity of the ascending limb, which normally is not accessible to micropuncture. [ABSTRACT FROM AUTHOR]

Variations in flow rate through the loop of Henle in the range of 0-50 nl/min were induced using pressure controlled microperfusion. Simultaneously, with the aid of a second pressure-microperfusionsystem, the glomerular function of the same nephron was studied by continuous measurement of two parameters, early proximal flow rate (EPFR) and/or stop flow pressure (SFP). Elevation of loop perfusion above physiological values (40 nl/min) resulted in a drop of EPFR and SFP, whereas lowering perfusion rates had no effect. This feedback behaviour was studied in kidneys with different renin contents to test the role of the renin-angiotensin system in the mediation of the macula densa signal to the adjacent glomerular vessels. Renal renin content, measured after micropuncture experiments by incubation with substrate followed by radioimmunoassay of angiotensin I, was unaltered in control (Ia) and heminephrectomized rats (Ib), lowered in contralateral kidneys of 2 kidneys Goldblatt hypertensive rats (IIa), in DOCA- and salt-loaded rats (IIb), and in DOCA-, salt-loaded and heminephrectomized rats (IIc), and it was elevated in clipped kidneys of Goldblatt hypertension rats (IIIa). Micropuncture evaluation of the tubuloglomerular feedback behaviour in these experimental groups revealed the following results: 1. a feedback response under all conditions independent of the widely varying renin contents (1000-fold), 2. an asymmetrical behaviour of the feedback response in all kidneys as demonstrated by suppression of EPFR and SFP at elevated loop flow rates, but no change of these parameters when loop flow was interrupted, 3. compared to controls the decrease of each GFR parameter between 0 and 40 nl/min loop perfusion was lower in DOCA- and salt-loaded rats (IIb, IIc). Additional heminephrectomy (IIc) had no further influence on the reduced feedback response in DOCA- and salt-loaded rats, whereas this manoeuvre reduced the renal renin content drastically. A somewhat higher response than in controls was found in heminephrectomized rats (IIb) and in clipped kidneys of Goldblatt hypertensive rats (IIIa). These different magnitudes of feedback responses do not correlate with the renal renin content. It has been concluded, therefore, that renal renin activity is not the sole determinant of the effectiveness of the tubuloglomerular feedback response. [ABSTRACT FROM AUTHOR]

Criteria for a reliable blockade of tubular flow are generally discussed and experimental evidence is presented that solid paraffin meets all the necessary criteria in rat kidney tubules when an immobile and tight sealing intratubular blockade is requested. A special microinjection apparatus for the application of paraffin is described. Furthermore, several alternative methods and materials have been tested and have been found to be inferior to solid paraffin. [ABSTRACT FROM AUTHOR]

A new pressure transducer microperfusion system has been used to measure quantitatively SN GFR, early proximal free flow pressure and stop flow pressure of varying flow rates through the loop of Henle in the range of 0 to 50 nl/min. Perfusing the loop with an isoosmolal artificial tubular fluid at physiological flow rates SN GFR was 19.9±1.1 and 27.7±1.0 nl/min in two different strains of antidiuretic rats. SN GFR increased when loop perfusion was interrupted. The question whether a feedback control mechanism of SN GFR is operative in the rat kidney was evaluated in further experiments in which early proximal tubular pressure was measured in functionally isolated proximal convolutions in vivo under conditions of constant flow as well as stopped flow. Experiments in which perfusion rate through the loop of Henle was varied demonstrated the existence of a feedback signal which originates downstream of the late proximal convolution and which affects filtration into individual early proximal segments. This feedback mechanism exhibited an asymmetrical behaviour: Elevation of loop perfusion above the control value resulted in an early proximal pressure drop, under simulated free flow conditions as well as under stop flow conditions. In contrast lowering of perfusion rate below the predetermined physiological value had no significant effect on early proximal pressures. [ABSTRACT FROM AUTHOR]

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