Intranephron distribution and regulation of endothelin-converting enzyme-1 in cyclosporin A-induced acute renal failure in rats

Endothelin-1 (ET-1) is thought to play a significant role in acute renal failure induced by cyclosporin A (CsA). The cDNA sequence encoding endothelin-converting enzyme-1 (ECE-1), which produces the active form of ET-1 from big ET-1, was recently reported. To elicit the role of ECE-1 in the glomerular and tubular dysfunction induced by CsA, the effects of CsA on mRNA and protein expression of ECE-1 in rat kidney and on mRNA expression of prepro-ET-1 and ET A- and B-type receptors in glomeruli were studied. ECE-1 mRNA was detected in glomeruli and in whole nephron segments. ECE-1 mRNA expression was downregulated in all nephron segments at 24 h after CsA injection. Protein levels were also downregulated in glomeruli and in the outer and inner medulla. CsA rapidly increased prepro-ET-1 mRNA expression in glomeruli at 30 to 60 min after injection; this rapid increase was followed by an increase in plasma ET-1 levels. These increases were followed by decreased expression of ECE-1, ET A-type receptor, and ET B-type receptor mRNA at 6 h after injection, and serum creatinine levels were increased at 24 h after CsA injection. It is suggested that downregulation of glomerular and tubular ECE-1 expression may be caused by increased ET-1 synthesis in CsA-induced acute renal failure.

Effect of extradural analgesia on the paradoxical arousal response of the electroencephalogram

Despite widespread recognition of the potential role of the processed electroencephalogram (pEEG) as a monitor of depth of anaesthesia, few studies have examined the effects of surgical stimuli on the intraoperative pEEG. Two groups of gynaecological patients (n = 10 in each group), with or without pre-incisional extradural analgesia, undergoing gynaecological laparotomy under nitrous oxide and isoflurane anaesthesia were monitored with routine haemodynamic observations and pEEG. Patients who received pre-incisional extradural analgesia showed no significant changes in pEEG variables during surgery (mean spectral edge frequency 95 percentile (SEF95) 13.3 (SD 1.4) Hz), whereas in all patients without pre-incisional extradural analgesia, a significant decrease in SEF95 was noted (6.5 (1.1) Hz after incision compared with a pre-incisional value of 12.5 (1.4) Hz) together with an increase in arterial pressure (paradoxical response). In the latter group, SEF95 and arterial pressure returned to pre-incisional values after extradural analgesia was established during operation. During emergence from anaesthesia, both groups showed a significant increase in SEF95 (25.7 (1.4) Hz). This study suggests that intraoperative pEEG arousal response was different from changes detected when anaesthesia was terminated at the end of surgery. Surgical stimuli in the absence of adequate analgesia induced a paradoxical arousal response.

Risk factors for left ventricular hypertrophy in chronic hemodialysis patients

Left ventricular hypertrophy is reported to be common in chronic hemodialysis patients, and also to increase the risk for mortality in chronic hemodialysis patients. An echocardiographical and clinical study was carried out to investigate the risk factors for left ventricular hypertrophy in 151 non-diabetic chronic hemodialysis patients without valvular diseases or myocardial infarction in two hemodialysis units in Fukuoka, Japan. The left ventricular mass index (LVMI) correlated positively to age, systolic blood pressure and interdialysis weight gain while it correlated negatively to the duration of hemodialysis therapy and hematocrit. Resorting to a multivariate analysis, the LVMI was found to positively correlate to age and the systolic blood pressure while it correlated negatively with the duration of hemodialysis therapy and the hematocrit level. These findings suggest that hypertension and anemia may thus be independent risk factors for left ventricular hypertrophy.

Processed electroencephalogram during combined extradural and general anaesthesia

The processed electroencephalogram (pEEG) was monitored in eight patients undergoing gynaecological laparotomy under combined extradural and nitrous oxide-isoflurane anaesthesia. Pre-incisional mean spectral edge frequency 95 percentile (SEF95) and median frequency (MF) were 11.67 (SD 1.63) Hz and 3.74 (0.24) Hz, respectively. After skin incision, both SEF95 and MF decreased to 6.61 (2.04) Hz and 2.72 (0.32) Hz, respectively (P < 0.001). An increase in mean arterial pressure after incision suggested inadequate depth of anaesthesia. After introduction of extradural analgesia, these variables returned to pre-incisional values (SEF95 11.65 (1.73); MF 4.02 (0.41)). Reduction of end-tidal isoflurane from 1.0% to 0.5% after extradural analgesia did not cause significant pEEG changes. pEEG may assist anaesthetists to recognize adequacy of combined general-extradural anaesthesia.

Strategic locus for the activation of the superoxide dismutase gene in the nephron

Upon exposure to a transient ischemia, the distal tubule of the kidney often escapes the severe damage which afflicts the proximal tubule. To ascertain whether this feature of the distal tubule is attributable to its intrinsic cellular properties, we focused on two pairs of unique tubule segments; distal versus proximal convoluted tubules in the superficial cortex and distal versus proximal straight tubules in the outer stripe of the outer medulla. These tubules were chosen because, firstly, they can be identified by morphology and immunostaining, and secondly, each pair has the same anatomical relationship to the circulation. Detailed morphometric analyses were performed six hours following unilateral transient ischemia in adult rats to semiquantitate the local tissue damage in these specific nephron segments. The architecture of the distal convoluted and straight tubules was remarkably well preserved, contrasting to the moderate to extensive necrotic changes seen in the proximal tubules. In search of the potential intrinsic cellular mechanism that underlies the observed difference, we examined the segmental distribution along the nephron of manganese superoxide dismutase gene transcripts by in situ hybridization. This antioxidant enzyme gene was expressed primarily in the distal tubules with contrastingly low levels of expression in the proximal tubules. Moreover, following ischemia-reperfusion, this distal tubule-dominant pattern was further accentuated immediately following reperfusion. The study indicates that the marked difference between the proximal and distal tubules in their susceptibility to injury in vivo is attributable to their intrinsic cellular properties, which include the local level of antioxidants.

Developmental expression of renal angiotensin II receptor genes in the mouse

The cellular distribution of angiotensin II type 1 (AT1) and type 2 (AT2) receptor mRNA was examined in mouse kidneys at several embryonic stages (12 to 18 days; 19 days = full term) and up to three weeks after birth by in situ hybridization. The expression of both AT1 and AT2 mRNAs appeared simultaneously at 14 days of gestation. However, their distributions were contrasting: AT1 mRNA was expressed in mature glomeruli and maturing S-shaped bodies throughout the stages examined. AT1 expression was also detected at 16 days of gestation in the proximal and distal tubules and peaked at the end of gestation. Both the temporal and spatial expression of AT1 coincide with the differentiation and proliferation of glomerular mesangial and tubular cells during nephrogenesis. In contrast, AT2 mRNA was present only in the mesenchymal cells adjacent to the stalk of the ureter bud at early developmental stages, and, later, extended to the mesenchymal cells located near, but outside, the nephrogenic area of superficial cortex and also the cells between collecting ducts. AT2 expression in these regions decreased markedly within three weeks after birth. Temporally and spatially, AT2 mRNA expression coincides with the epithelial-mesenchymal interactions that take place during early phases of nephrogenesis. The site of AT2 expression also overlaps closely with that of a specific group of cells which undergo apoptosis following nephrogenesis. Thus, contrary to current belief, the activation of AT1 and AT2 genes takes place in different cell types of the kidney during embryonic development, and thereby conceivably contributes to the ontogeny of those specific renal cells.

[One-year experience as a clinical anaesthetist in England]

Current practice of British clinical anaesthesia is introduced, including anaesthesia in the operating theatre as well as obstetric analgesia in the labour ward. Although many people feel that British National Health Service has been affected by their chronic economic recession, the author's general impression is that the standard of anaesthetic care is kept at a quite high level despite financial difficulties. It is still valuable to experience clinical anaesthesia in the United Kingdom and the author encourages young Japanese anaesthetists to get an opportunity to work in British hospitals.

Inhibitory effects of antihypertensive drugs on mesangial cell proliferation after anti-thymocyte serum (ATS)-induced mesangiolysis in spontaneously hypertensive rats

The effects of antihypertensive drugs on mesangial cell proliferation were studied in spontaneously hypertensive rats (SHR) with anti-thymocyte serum (ATS)-induced glomerulo-nephritis. Rats were treated with either enalapril (Group 1), nifedipine (Group 2), or reserpine + hydrochlorothiazide + hydralazine (Group 3), or were untreated (Group 4). The animals were sacrificed 2, 4 and 7 days after ATS injection and the glomerular cell number and degree of mesangial area expansion were examined. A marked, similar decrease in glomerular nuclear cell number (NC) due to severe mesangiolysis was observed in all of the groups on day 2. Thereafter, an increase in NC reflecting mesangial cell proliferation after mesangiolysis occurred in Group 4 on days 4 and 7. In Group 1 and 2, the NC was significantly smaller than that in Group 4 on days 4 and 7, indicating suppression of mesangial cell proliferation. In Group 3, however, the number of NCs did not differ from that in Group 4 on days 4 and 7, indicating a lack of such suppression by conventional antihypertensive drugs. The degree of mesangial area expansion (MS) showed the same pattern as mesangial cell proliferation. That is, the rapid increases in MS seen in Group 4 on days 4 and 7 were apparently suppressed in Groups 1 and 2, but not in Group 3. Our in vivo observations that both an angiotensin converting enzyme (ACE) inhibitor and a calcium channel blocker suppress mesangial cell proliferation and mesangial area expansion suggest that these agents have practical implications in the treatment of mesangial proliferative glomerular diseases through the suppression of excess mesangial cell proliferation.

Effects of endothelin and angiotensin II on renal hemodynamics in experimental mesangial proliferative nephritis

The renal hemodynamic response to pressor substances in the diseased kidney has been suggested to be different from that in the normal kidney. The aim of this study was to investigate the effects of endothelin and angiotensin II on renal hemodynamics in experimental nephritis induced by the administration of antithymocyte serum in Wistar rats. This model showed mesangiolytic lesions in the glomeruli on day 2 and hypercellular lesions on day 8. Prior to the injection of either endothelin or angiotensin II, the glomerular filtration rate and renal plasma flow were significantly lower in model rats on day 2 or day 8 than in the control rats. The basal glomerular filtration rate and renal plasma flow on day 8 were negatively correlated with the mesangium cell number. The injection of endothelin (0.5 ng/kg BW) led to a decrease in both renal plasma flow and glomerular filtration rate in rats on day 8 which was significantly greater than that in the control rats. Similarly, angiotensin II infusion (0.2 micrograms/kg BW) reduced both renal plasma flow and glomerular filtration rate in the rats on day 8 and the reductions were significantly greater than those in the control rats. In conclusion, renal hemodynamics in rats with mesangial proliferation of the kidney were more sensitive to both endothelin and angiotensin II than those in the normal kidney.