Negative chronotropic actions of endothelin-1 on rabbit sinoatrial node pacemaker cells

1. The effects of endothelin-1 (ET-1) on sinoatrial (SA) node preparations of the rabbit heart were studied by means of whole-cell clamp techniques.
2. ET-1 at 1 nM slowed the spontaneous beating activity and rendered half of the cells quiescent. At a higher concentration of 10 nM, the slowing and cessation of spontaneous activity were accompanied by hyperpolarization.
3. In voltage-clamp experiments, ET-1 decreased the basal L-type Ca²⁺ current (I_Ca(L)) dose-dependently with a half-maximal inhibitory concentration (EC₅₀) of 0.42 nM and maximal inhibitory response (E_max) of 49.5%. The delayed rectifying K⁺ current (I_K) was also reduced by 33.2±11.1% at 1 nM. In addition, an inwardly rectifying K⁺ current was activated by ET-1 at higher concentrations (EC₅₀=4.8 nM). These ET-1-induced changes in membrane currents were abolished by BQ485 (0.3 μM), a highly selective ET_A receptor antagonist.
4. When I_Ca(L) was inhibited by ET-1 (1 nM), subsequent application of 10 μM ACh showed no additional decrease in I_Ca(L), suggesting the involvement of cyclic AMP in the effects of ET-1 on I_Ca(L). In contrast, 1 nM ET-1 further decreased I_Ca(L) in the presence of 10 μM ACh, suggesting that ET-1 activates some additional mechanism(s) which inhibit I_Ca(L). The ET-1-induced I_Ca(L) inhibition was abolished by protein kinase A inhibitory peptide (PKI, 20 μM) or H-89 (5 μM). However, the I_Ca(L) inhibition was not affected by methylene blue (10 μM), suggesting a minor role for cyclic GMP in the effect of ET-1 under basal conditions.
5. ET-1 failed to inhibit I_Ca(L) when the pipette contained GDPβS (200 μM). However, incubation of the cells with pertussis toxin (PTX, 5 μg ml⁻¹, >6 h) only reduced the ET-1-induced inhibition to 21.5±9.5%, whereas it abolished the inhibitory effect of ACh on I_Ca(L).
6. Intracellular perfusion of 8-bromo cyclicAMP (8-Br cyclicAMP, 500 μM) attenuated, but did not abolish the inhibitory effect of ET-1 on I_Ca(L). This 8-Br cyclicAMP-resistant component (17.5±14.4%, n=20) was not affected by combined application of 8-Br cyclicAMP with 8-bromo cyclicGMP (500 μM), ryanodine (1 μM) or phorbol-12-myristate-13-acetate (TPA; 50 nM).
7. In summary, ET-1 exerts negative chronotropic effects on the SA node via ET_A-receptors. ET-1 inhibits both I_Ca(L) and I_K, and increases background K⁺ current. The inhibition of I_Ca(L) by ET-1 is mainly due to reduction of the cyclicAMP levels via PTX-sensitive G protein, but some other mechanism(s) also seems to be operative.

     

Gene expression of histamine H1 receptor in guinea pig primary sensory neurons: a relationship between H1 receptor mRNA-expressing neurons and peptidergic neurons

Pharmacological studies have suggested that a subgroup of primary sensory neurons is responsive to histamine via the histamine H1 receptor. We addressed this issue using in situ hybridization histochemistry with a cRNA probe for the guinea pig H1 receptor gene. About 15% of the trigeminal and lumber dorsal root ganglion (DRG) neurons, but none of nodose ganglion neurons, were intensely labeled with this probe. The H1 receptor mRNA-positive neurons were exclusively small in size, and were demonstrated to give rise to unmyelinated fibers by ultrastructural analysis of isolectin B4-labeling. However, the H1 receptor mRNA-expressing DRG neurons were not immunoreactive to substance P (SP) and calcitonin gene-related peptide (CGRP). A marked increase in the number of mRNA-positive DRG neurons were observed 1-5 days after a crush injury of the sciatic nerve (3-4-fold of the control value). These neurons turned mRNA-positive after the nerve crush were also mainly small-sized. The mRNA signals were detected in many peptidergic (SP/CGRP) neurons, in contrast to the normal state. On the other hand, in the neurons which showed intense labeling in the normal condition, the mRNA signals were down-regulated. These results suggest that primary sensory neurons include two kinds of H1 receptor-expressing sensory neurons, one expressing H1 receptor mRNAs in the normal state and the other up-regulating the mRNAs following the peripheral nerve damage.     

Glomerular hypertrophy in preeclamptic patients with focal segmental glomerulosclerosis. A morphometric analysis

BACKGROUND: Focal segmental glomerulosclerotic lesion (FSGS lesion) is frequently observed in preeclamptic patients with nephrotic syndrome. PATIENTS AND METHODS: We performed a morphometric analysis of renal biopsies from 20 patients with severe preeclampsia to evaluate the pathogenetic role of glomerular hypertrophy in preeclamptic nephropathy associated with FSGS lesion. We also analyzed biopsies obtained from 6 preeclamptic patients without FSGS lesion and 10 patients with isolated hematuria. Nonsclerotic glomeruli were examined. RESULTS: The mean glomerular tuft area (GTA), the whole glomerular area (WGA), and the extracellular matrix area (EMA) were significantly and negatively correlated with the postpartum day at biopsy in preeclamptic patients with FSGS lesion who underwent renal biopsy within 40 days after delivery. The mean GTA, WGA, EMA and number of mesangial cells (MN) were significantly increased in preeclamptic patients with FSGS lesion compared with patients with isolated hematuria and compared with those without FSGS lesion when the biopsy time was matched between patients with and without FSGS lesion. The GTA and WGA were not different between preeclamptic patients without FSGS lesion and patients with isolated hematuria. CONCLUSION: These results support the assumption that glomerular hypertrophy that develops during severe toxemic pregnancy plays an important role in the pathogenesis of FSGS lesion and is reversible about 40 days after delivery.     

The relationship between waist-to-hip ratio and occupational status and life-style factors among middle-aged male and female Japanese workers.

As a marker of body fat distribution and therefore level of obesity, the waist-to-hip ratio (W:H) is a good indicator of coronary heart disease risk status. The present study investigated the association between occupational status and life-style factors, and W:H of middle-aged Japanese male (n = 2,550) and female (n = 1,283) workers in a metal-products factory. A higher W:H was observed in the management level males as compared with the other male workers and we suggest this was promoted by the sedentary aspect of their work, as well as their higher levels of alcohol consumption and lower levels of leisure-time physical activity. In contrast, a higher W:H was recorded in female labourers, whose work was typically less sedentary as compared with female managers. Life-style factors included in the study were not related to this observation. We conclude that other unmeasured psychosocial factors may be important in promoting higher W:H in female labourers.     

The effect of tulobuterol tape on histamine-induced bronchoconstriction in conscious guinea pigs: long duration of action

The objective of the present study was to determine the action duration of tulobuterol tape within a 24-hr period in conscious guinea pigs. The bronchoconstriction induced by histamine-inhalation was significantly inhibited by tulobuterol tape in comparison with its placebo tape 8 and 12 hr after binding, and the inhibitory rate was 50+/-11% and 35+/-13%, respectively. Twenty-four hours after binding, the inhibitory effect of tulobuterol tape gradually diminished, but the inhibitory rate was maintained at 30+/-14%. These results suggest that tulobuterol tape has a long lasting bronchodilatory action.     

Long-term survival after radical resection of advanced pancreatic cancer

A 65-yr-old man who underwent pancreaticoduodenectomy with portal vein resection for pancreatic cancer is alive 8 yr after surgery. Originally, computed tomography (CT) revealed an 8-cm tumor in the pancreatic head. The tumor had infiltrated the portal vein, but grew expansively, so there was neither biliary obstruction nor jaundice. Pancreaticoduodenectomy with resection of the portal vein was performed for pancreatic cancer. Many tumor-infiltrating lymphocytes were seen within cancer cell nests on routine histopathology. We performed immunostaining for CD8, and found that a large number of the lymphocytes were CD8⁺ T cells. The patient’s prognosis was considered poor because the tumor was large and had infiltrated the portal vein. We suspect that long-term survival may be related to the response of CD8⁺ T cells to the cancer.     

CSF phosphorylated tau protein and mild cognitive impairment: a prospective study

Cerebrospinal fluid (CSF) tau protein phosphorylated at both Thr231 and Ser235 sites (CSF/phospho-tau(231-235)) and total tau (CSF/total-tau) were quantified by sandwich ELISA in 20 patients with mild cognitive impairment (MCI) who eventually developed AD on follow-up as well as seven memory complainers with no objective memory loss. 13/20 (65%) of the MCI patients had high CSF/total-tau and detectable levels of CSF/phospho-tau(231-235), whereas these markers were low and under a detectable level in all of the memory complainers. Although either a total-tau, phospho-tau measurement or a combination of these can help in predicting if MCI will develop AD, our results suggest that the pathogenic steps of AD may be at the stage that finally leads to an accumulation of abnormally phosphorylated tau and neuron death, at least in some brain areas, when MCI patients present with the earliest detectable clinical symptoms of dementia.     

Comparison of short inversion time inversion recovery (STIR) and fat-saturated (chemsat) techniques for background fat intensity suppression in cervical and thoracic MR imaging

The purpose of this study was to compare short inversion time inversion recovery (STIR) fast spin-echo (FSE), and fat-saturated T2-weighted FSE sequences in terms of uniformity of fat suppression and lesion conspicuity for magnetic resonance (MR) imaging of the neck and thorax. STIR FSE and fat-saturated T2-weighted FSE images were scored for uniformity of fat suppression (n = 40) and lesion conspicuity (n = 35). Five-point rank score analyses were utilized by three experienced radiologists. The mean scores of STIR and fat-saturated FSE techniques for uniformity of fat suppression were 4.3 and 2.3, respectively (P < 0.0001). The mean scores of STIR and fat-saturated FSE techniques for lesion conspicuity were 4.2 and 3.5, respectively (P < 0.0001). Insufficient fat suppression was prominent in the mandible, supraclavicular region, anterior mediastinum, epipericardial fat, and subdiaphragmatic fat. In addition, fat-saturated T2-weighted FSE showed inadvertent water suppression in 25%. The STIR FSE technique was superior to the fat-saturated FSE technique for cervical and thoracic MR imaging.