A Possible Role of the Pineal Gland in Acute Immobilization-Related Suppression of Naloxone-Induced LH Release in Ovariectomized Estrogen-Primed Rats

It has been recently reported that acute immobilization stress almost completely suppresses the luteinizing hormone (LH) release induced by naloxone, a μ-opioid antagonist, in ovariectomized estrogen-primed rats. The present study examined the possible involvement of the pineal gland in the acute immobilization-related suppression of the naloxone-induced LH release. An intraventricular (ICV) injection of 15 μg naloxone produced an abrupt increase in circulating LH concentrations in non-stressed rats. The naloxone-induced LH release was completely eliminated when tested 60 min after the end of a 30 min session of acute immobilization. The same stress conditions did not affect LH-releasing hormone (LHRH)-induced LH release, suggesting that the stress-related suppression of the naloxone-induced LH release was a suprapituitary event. In chronically-pinealectomized rats, but not in sham-pinealectomized rats, naloxone injected 60 min after the end of the stress session evoked a significant increase in serum LH concentrations. However, naloxone injected ICV during the acute immobilization did not elicit LH release in either pinealectomized or sham-operated rats. Under non-stressed conditions, the LH secretory response to naloxone was similar in pinealectomized and sham-operated animals. The same stress (30 min immobilization) significantly increased pineal melatonin content as well as plasma melatonin concentrations in rats bearing intact pineal glands, indicating that stress actually affected the pineal function. These results provide evidence for a role of the pineal in the suppression of the LH response to naloxone after stress, but not during stress.     

Nascent peptide-mediated translation elongation arrest coupled with mRNA degradation in the CGS1 gene of Arabidopsis

Expression of the Arabidopsis CGS1 gene that codes for cystathionine gamma-synthase is feedback regulated at the step of mRNA stability in response to S-adenosyl-L-methionine (AdoMet). A short stretch of amino acid sequence, called the MTO1 region, encoded by the first exon of CGS1 itself is involved in this regulation. Here, we demonstrate, using a cell-free system, that AdoMet induces temporal translation elongation arrest at the Ser-94 codon located immediately downstream of the MTO1 region, by analyzing a translation intermediate and performing primer extension inhibition (toeprint) analysis. This translation arrest precedes the formation of a degradation intermediate of CGS1 mRNA, which has its 5' end points near the 5' edge of the stalled ribosome. The position of ribosome stalling also suggests that the MTO1 region in nascent peptide resides in the ribosomal exit tunnel when translation elongation is temporarily arrested. In addition to the MTO1 region amino acid sequence, downstream Trp-93 is also important for the AdoMet-induced translation arrest. This is the first example of nascent peptide-mediated translation elongation arrest coupled with mRNA degradation in eukaryotes. Furthermore, our data suggest that the ribosome stalls at the step of translocation rather than at the step of peptidyl transfer.     

Changes of hepatic vitronectin levels in patients with chronic hepatitis C treated with interferon alpha

Hepatic vitronectin expression was assessed in 27 patients with chronic hepatitis C before and after interferon alpha treatment and in 7 control patients. Before interferon therapy, vitronectin was localized in the hepatocytes and in the portal and central venous regions. A high correlation was found for the vitronectin expression level with the histological grading and staging scores in the hepatocytes as well as in the portal region. After interferon therapy, the hepatic vitronectin was significantly decreased in the sustained and transient responders, but it was not as markedly decreased in the nonresponders and the non-treated group. A good correlation was found for the vitronectin expression with the staging scores but not with the grading scores in the portal region. These findings suggest that hepatic vitronectin is influenced by interferon therapy and that it may play an important role as a hepatic adhesion molecule through the improvement of inflammation, necrosis and fibrogenesis.     

Responsiveness of measures in the effort-reward imbalance questionnaire to organizational changes: a validation study

OBJECTIVE: To examine the responsiveness of measures adopted in the effort-reward imbalance (ERI) questionnaire to organizational changes. METHOD: For the employees who had been affected by restructuring of their company due to the economic hardship, two consecutive questionnaire surveys were conducted over a specific period. A total of 544 full-time employees responded to both surveys. Changes in four summary measures from the situation-specific model component and the person-specific component, and items/subscales that constitute the questionnaire were evaluated. RESULTS: The summary measures on psychological deterioration in the total study population. The deterioration was prevalent in those employees who had presumably experienced the effects of stressful organizational changes related to the restructuring, while improvement in the summary measures was observed for those employees who were promoted during the period. On the whole, the measures for the items of the situation-specific component and subscales for the personal component changed in the expected direction. With regard to ERI, potentially stronger effects of multiple organizational changes on employees were indicated. CONCLUSION: Measurements of ERI at work are valid in terms of responsiveness to organizational changes.     

Sulfur-containing amino acids decrease cisplatin cytotoxicity and uptake in renal tubule epithelial cell lines

Purpose: Nephrotoxicity is one of the major dose-limiting side-effects of cisplatin (DDP). The disproportionate accumulation of cisplatin in kidney tissue may play an important role; however, therapeutic measures to prevent this prime cause of nephrotoxicity are not available. Because certain amino acids (AAs) have been reported to modulate DDP nephrotoxicity in vivo, we explored the potential of all 20 protein AAs, N-acetylcysteine and DL-homocysteine to reduce DDP cytotoxicity and uptake in S₁, S₃ (proximal tubule), and DCT (distal convoluted tubule) cell lines. Methods: Immortalized but non-transformed renal tubule epithelial cell lines, derived from specific portions of the nephron of an SV40 transgenic mouse, were grown to confluency and exposed to various concentrations of DDP for 1 h with or without concurrent exposure to AAs in an otherwise AA-free Krebs-Ringer buffer (KRB). After 1 h, cell layers were washed and replenished with medium for cytotoxicity assays, or processed immediately for the determination of DDP accumulation. Cytotoxicity was assessed 48 h later by an MTT assay, and DDP uptake after 1 h was determined by atomic absorption spectroscopy. Results: In an initial screening where the cells were concurrently incubated with 0.25 mM DDP and 1 mM AA for 1 h in KRB, only cysteine (Cys), methionine (Met), N-acetylcysteine and DL-homocysteine reduced DDP toxicity. This effect was enhanced at 5 mM AA and most potent for Cys, which reduced DDP cytotoxicity by 79 ± 3% in S₃ cells, by 78 ± 12.2% in DCT cells, and by 19 ± 3.6% in S₁ cells (P < 0.05). Reduction of cytotoxicity was less for Met, DL-homocysteine, and N-acetylcysteine, in decreasing order. All four AAs also inhibited DDP uptake in renal cells, with Cys as the strongest inhibitor. Inhibition of DDP accumulation by 1 mM Cys after 1 h was 39% in S₃ cells, 38% in DCT cells, and 28% in S₁ cells. Again, reduction of uptake was less for the three other AAs. Pre-complexing of DDP with Cys for 16 h increased its uptake by 8- to 30-fold compared with native DDP, but markedly inhibited its toxicity. Thus, pre-complexing of DDP with Cys could not explain the reduced uptake of DDP, but could partly account for the reduction in cytotoxicity. Double-reciprocal Lineweaver-Burk plots of DDP concentration-versus-uptake rates at a constant concentration of Cys suggested that Cys competitively inhibited DDP uptake in S₁ and DCT cells, and in a more complex fashion in S₃ cells. Conclusions: We conclude that Cys, Met, N-acetylcysteine, and DL-homocysteine differentially inhibit DDP toxicity and uptake in cultured S₁, S₃, and DCT cells, and that the inhibition of uptake, as well as the complexation of DDP with Cys within the cell, may prevent toxicity. The structural element R-CH(NH₂)-[CH₂]_1–2-S-R, which is common to all four molecules, may play a crucial role in blocking the transport of DDP, and could have future clinical applications. Received: 11 February 1999 / Accepted: 21 June 1999     

Sodium disorders in the elderly

Disorders of sodium imbalance are commonly encountered in clinical practice and can have a substantial impact on the prognosis of the patient. These disorders are more common in the elderly. Sodium disorders can cause serious neurologic symptoms and even death, particularly among hospitalized patients. The identification of sodium abnormalities and appropriate clinical intervention are critical for improving patient outcomes. Early recognition of hyponatremia and hypernatremia can provide a clue to an underlying disorder. In this update, we have summarized age-related homeostatic changes that impair sodium balance, medications that alter salt and water handling, and the recognition and management of sodium disorders in elderly patients.     

Differential effects of cisplatin in proximal and distal renal tubule epithelial cell lines

Pathological studies suggest that cisplatin injures different portions of the nephron to different extents. To investigate this issue further, we examined the cytotoxicity and uptake of cisplatin in cell lines derived from S₁ and S₃ proximal tubule and distal convoluted tubule segments isolated from a mouse carrying the SV40 large T-antigen transgene. S₁ cells displayed the highest sensitivity to cisplatin cytotoxicity, followed by S₃ and distal convuluted tubule (DCT) cells. These differences in cytotoxicity did not correlate with differences in cisplatin uptake. Cytotoxic concentrations of cisplatin triggered apoptosis in all three cell lines. Although BAX and BCL-2 expression was similar among the three cell lines, the expression of the anti-apoptotic protein, BCL-X_L, was significantly lower in S₁ cells than in S₃ and DCT cells, and this may have contributed to the heightened sensitivity of S₁ cells. Cisplatin transport characteristics demonstrated a saturable component of cisplatin uptake and differences in apparent K_M and V_max values among the three cell lines. The three cell lines were 43- to 176-fold more sensitive to cisplatin than to carboplatin. This distinction between the two drugs could not be fully explained by differences in the uptake rates of carboplatin and cisplatin. We conclude that cells from different portions of the nephron display different sensitivities to cisplatin, different transport characteristics for cisplatin and different levels of expression of BCL-X_L. In addition, the relative resistance of renal cells to carboplatin vs cisplatin is mostly due to the differential effects that follow internalization. © 1999 Cancer Research Campaign