Pathophysiology of blood pressure variability in patients with chronic renal failure under maintenance hemodialysis

The rise of blood pressure is negatively related with the glomerullar filtration rate(GFR) in patients with terminal renal failure. Hypertension may be a mechanism to maintain renal blood flow and GFR constant by the increased driving force of blood to the kidney. Elevated levels of a so-called third factor, now designated as endogenous digitalis, are found in those patients. The most likely candidate of the endogenous digitalis is ouabain, which causes hypertension with chronic administration. On the other hand, extreme hypotension often occurs during maintenance hemodialysis, and since hemodynamic alterations closely resemble endotoxin shock, the involvement of nitric oxide(NO) over-production has been suggested. When we measured nitrate anion as the final metabolite of NO, the concentration was significantly higher in patients with marked hypotension during hemodialysis than those without hypotension. Since reflex tachycardia was not observed during hypotension, we speculated that those patients had autonomic disturbances, and assessed autonomic function by heart rate spectral analysis. Although the high frequency spectral power, regarded as the vagal tone, was not significantly different between the groups, low/high frequency spectral power ratio, which was thought to be a sympathetic component, was significantly lower in patients with hypotension during hemodialysis than that in patients without hypotension. We speculated that NO synthase may be induced by the stimuli to monocytes by tubes and dialyser membrane made of synthetic materials leading to the over production of NO during and after regular hemodialysis. Thus, cytokines may be the mediator of the induction of NO synthase. Dilated capacitance vessels decrease the venous return to the heart, which may be the direct cause of dialysis-induced hypotension.     

Both the HLA-CPB1 and -DRB1 alleles correlate with risk for multiple sclerosis in Japanese: clinical phenotypes and gender as important factors

The purpose of this study was to clarify the association of HLA-DRB1 and -DPB1 alleles with multiple sclerosis (MS) in Japanese, to determine whether optico-spinal MS (OS-MS) and conventional MS are immunogenetically distinct, and to verify the role of gender difference in HLA associations of MS. We studied HLA-DRB1 and -DPB1 polymorphisms in 166 Japanese patients with MS. Forty-seven patients were classified as having the optico-spinal MS (OS-MS) and 119 as having conventional MS. A lack of DPB1*0301 and a higher frequency of DPB1*0501 compared with controls (corrected P<0.0074; odds ratio=9.48) were found in OS-MS. By contrast, we found for the first time an association of DPB1*0301 with conventional MS in Japanese (corrected P=0.0444; odds ratio=3.28). Logistic analysis, adjusted for sex and age, revealed independent associations of DPB1*0301 (P=0.0004, adjusted odds ratio (aOR)=4.70), DPB1*0501 (P=0.0081, aOR= 2.50) and DRB1*1501 (P=0.0252, aOR=2.21) with conventional MS. However, the frequencies of DRB1*1501 and DPB1*0501 in male patients with conventional MS were equal to those in male controls while the DPB1*0301 frequency was increased in both male and female patients. We did not find any association of these HLA alleles with disease course and severity. In conclusion, OS-MS is a DPB1*0501-associated distinct subtype of MS, and DPB1*0301 is the most strongly associated allele with conventional MS in Japanese. In addition, gender plays an important role in HLA association with MS.     

Colchicine-induced Inhibition of Fat Globule Development in Hepatocytes of Rats Injected with Ethionine

To examine the effect of colchicine on ethionine induced fatty liver, adult female rats were starved overnight and then injected i.p. with 1 g kg ethionine at 11th hour of fasting; then a half of the rats were also injected i.p. with 2.5 mg kg colchicine twice at 3 and 6 h after the single administration of ethionine. Similarly, fasted control rats were injected i.p. with vehicle alone at the above times. All of the rats were sacrificed after a 20 h fast, and the hepatocytes in periportal areas were observed ultra-structurally. In addition, total lipids in the liver tissue were extracted and determined biochemically. Although similar significant increases of triglyceride were observed in the liver tissue of all ethionine-injected rats, the hapatocytes in the group treated with both chemicals had fewer cytoplasmic fat globules (CFG) than those in the group treated with ethionine only. On the other hand, the diameters of markedly increased membrane-bound lipid particles (MLP) in the double treated group were distributed mainly in the range 0.2–0.4 μm, compared with those (0.1-0.2 μm) in the other groups. These findings indicate that colchicine inhibits the development of CFG in ethionine injured hapatocytes. Acta Pathol Jpn 39: 281∼288, 1989.     

Sexual and aggressive interactions in a visible burrow system with provisioned burrows

The visible burrow system (VBS) is a habitat providing burrows and an open area for mixed-set rat colonies. Provisioning of food and water in the burrows makes it unnecessary for potentially defensive animals to leave the burrows to eat/drink on the surface, and enables evaluation of new types of agonistic interactions that may emerge when this necessity is removed. In such colonies, subordinate males showed high magnitude tunnel guarding behavior, occupying a tunnel opening onto the surface and confronting the dominant. Dominants, in response, made lunges into the tunnels, but quickly retreated without gaining entry, apparently stopped by contact with the defender's vibrissae. Dominants also made and continued to make lateral attacks to the wall adjacent to the tunnels guarded by subordinates, although these were useless in terms of affording contact with the subordinate. Dominant-female agonistic interactions were more frequent than those of dominants and subordinates. These were largely initiated by the male, and involved female defensive behavior. Nonetheless, females, unlike subordinates, failed to show tunnel guarding and continued to utilize the surface freely. They also spent more time in the vicinity of the dominant over days of colony formation. This apparent paradox may reflect that females were seldom wounded, and that the initial site of male contact with females was the female's anogenital area, findings suggesting that interactions of males and females often reflect male sexual advances, countered by female defenses that effectively protect nonestrus females from mounting and copulation.     

Inhibition of skin xenograft rejection by depleting T-cell receptor alpha beta-bearing cells without T-cell receptor gamma delta-bearing cells or natural killer cells by monoclonal antibody.

We compared the effects of in vivo administration of the anti-T-cell receptor (TCR) alpha beta monoclonal antibody (mAb) (H57-597) to those of the anti-CD3 mAb (145-2C11), with or without anti-NK1.1 mAb (PK136), on xenogeneic skin graft survival in mice. In anti-TCR alpha beta mAb-treated B6 mice, F344 rat skin grafts survived for about 54 days, whereas in anti-CD3 mAb-treated B6 mice with or without anti-NK1.1 mAb treatment grafts survived about 25 days. In anti-TCR alpha beta mAb-treated B6 mice, TCR alpha beta-bearing T-lymphocyte function was completely abrogated, although TCR gamma delta-bearing T-lymphocyte function was still intact on day 9. In the anti-CD3 mAb-treated mice, the functions of both types of T lymphocytes were completely abrogated. On day 32, when most of the skin xenografts had been rejected in the anti-CD3 mAb-treated mice, the functions of both T lymphocytes had recovered considerably, and could actually respond to F344 antigens. In contrast, the function of TCR alpha beta-bearing cells had only partially recovered in the anti-TCR alpha beta mAb-treated mice. Finally, natural killer (NK) activity in the anti-TCR alpha beta mAb-treated mice was intact on day 32, when rat skin grafts still survived. In contrast, NK activity in the anti-CD3 mAb plus anti-NK1.1 mAb-treated mice did not recover on day 32, when skin xenografts had already been rejected. These results suggest that TCR gamma delta-bearing T cells and NK cells by themselves, at least in the absence of TCR alpha beta-bearing T cells, do not mediate xenogeneic skin graft rejection in mouse/rat combinations.     

Spontaneous and secretagogue-induced changes in cytosolic free Ca concentration measured by microfluorimetry with fura-2 on single bovine adrenal chromaffin cells

The concentration of cytosolic Ca2+ ([Ca]in) was examined in single bovine adrenal chromaffin cells by monitoring fura-2 fluorescence with microspectrofluorimetry. To see the correlation between [Ca]in and secretion, we also measured the rates of catecholamine (CA) secretion and 45Ca efflux from populations of cells. [Ca]in was constant in the majority of single cells, but the small oscillatory changes in [Ca]in were observed in a population of cells. These spontaneous Ca oscillations, when observed, disappeared either after removal of extracellular Ca2+ or by addition of D-600 or Mn2+, but still persisted in the presence of tetrodotoxin (TTX) or after removal of extracellular Na+. In the silent cells the Ca fluctuations were often induced by Bay-K-8644. The characteristics of Bay-K-8644-induced Ca fluctuations were very similar to those of spontaneous ones. Low concentrations of nicotine (1 microM), acetylcholine (ACh; 1-2 microM), or KCl (12.5 mM) often induced oscillations riding on a steady rise in [Ca]in. These changes were rapidly suppressed by removal of either extracellular Ca2+ or Na+, or by addition of either D-600 (methoxyverapamil) or TTX. A low concentration of ACh (1 microM) or KCl (12.5 mM) also increased the rate of 45Ca efflux, but substantial secretion was not detected. On the other hand, the sustained rise in [Ca]in was evoked by 0.1 mM ACh, 20 microM nicotine, or 30 mM KCl, which was suppressed by removal of extracellular Ca2+, but was little affected by TTX. A sustained increase in 45Ca efflux upon exposure to ACh was observed, possibly reflecting the sustained rise in [Ca]in. ACh also stimulated CA secretion, which was faded out during the prolonged application. Veratridine, a Na channel activator, caused repetitive sequence of Ca transients followed by a sustained rise in [Ca]in. These results, together with the previous electrophysiological findings, suggest that: (1) the spontaneous Ca fluctuations are closely associated with occurrence of spontaneous Ca2+ and Na+ action potentials; (2) the rise in [Ca]in induced by a low concentration of nicotinic agonists of KCl is mediated by Na+ action potentials as well as gradual membrane depolarizations; (3) the oscillatory changes subsequent to a rise in [Ca]in reflect fluctuations in Ca2+ influx through the Ca2+ channels; (4) the critical [Ca]in needs to be attained before the CA secretion takes place.     

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.     

Novel and recurrent EBP mutations in X-linked dominant chondrodysplasia punctata

Chondrodysplasia punctata (CDP) is a heterogeneous group of skeletal dysplasias characterized by stippled epiphyses. A subtype of CDP, X-linked dominant chondrodysplasia punctata (CDPX2), known also as Conradi-Hünermann-Happle syndrome, is a rare skeletal dysplasia characterized by short stature, craniofacial defects, cataracts, ichthyosis, coarse hair, and alopecia. The cause of CDPX2 was unknown until recent identification of mutations in the gene encoding Delta(8),Delta(7) sterol isomerase emopamil-binding protein (EBP). Twelve different EBP mutations have been reported in 14 patients with CDPX2 or unclassified CDP, but with no evidence of correlation between phenotype and nature of the mutation. To characterize additional mutations and investigate possible phenotype-genotype correlation, we sequenced the entire EBP gene in 8 Japanese individuals with CDP; 5 of them presented with a CDPX2 phenotypes. We found EBP mutations in all 5 CDPX2 individuals, but none in non-CDPX2 individuals. Three of these CDPX2 individuals carried novel nonsense mutations in EBPand the other two, separate missense mutations that had been reported also in different ethnic groups. Our results, combined with previous information, suggest all EBP mutations that produce truncated proteins result in typical CDPX2, whereas the phenotypes resulted from missense mutations are not always typical for CDPX2. Patients with nonsense mutations showed abnormal sterol profiles consistent with a defect in Delta(8), Delta(7) sterol isomerase. X-inactivation patterns of the patients showed no skewing, an observation that supports the assumption that inactivation of the EBP gene occurs at random in affected individuals.     

Cats are protected against feline immunodeficiency virus infection following vaccination with a homologous AP-1 binding site-deleted mutant

Summary.  Following establishment, via the vaginal route, of infection with an AP-1 binding-site deleted mutant (ΔAP-1) of feline immunodeficiency virus (FIV), cats were challenged with a homologous intact strain (TM2) of FIV. The cats were observed for 23 weeks to evaluate the efficacy of the ΔAP-1 against the homologous TM2 strain challenge. These two viruses were differentiated by Southern blotting after amplification of proviral DNA by semi-nested polymerase chain reaction in DNAs of peripheral blood mononuclear cells and tissues. A TM2-specific band was detected in one cat exposed to but not infected with ΔAP-1, but not in two ΔAP-1-infected. These results indicate that ΔAP-1 could protect against subsequent challenge with homologous FIV TM2 strain. Received December 23, 1998 Accepted March 31, 1998     

Heterotopic transplantation of the failing rat heart as a model of left ventricular mechanical unloading toward recovery

The left ventricular assist device (LVAD) is usually used in patients with end-stage heart failure as a bridge to transplantation. Recently, some studies have reported functional recovery with the use of an LVAD, although the mechanisms responsible for recovery are not fully understood. We investigated the functional recovery of the infarcted, failing rat heart in response to mechanical unloading after heterotopic transplantation. Heart failure was induced in Lewis rats by ligating the left anterior descending artery. After 4 weeks, the infarcted hearts were harvested and heterotopically transplanted. The transplanted infarcted heart was removed after 2 weeks of unloading and examined for hypertrophy and fibrosis, as well as for mRNA levels encoding for brain natriuretic peptide, sarco(endo)plasmic reticulum Ca(2+)-ATPase2a (SERCA2a), and beta1- and beta2-adrenergic receptors. Normal and infarcted rats without transplantation served as control animals. The infarcted heart was hypertrophied as evidenced by an increase in heart weight and myocyte diameter. After unloading the infarcted heart for 2 weeks, there was a decrease in heart weight and myocyte diameter. However, the percentage of myocardial fibrosis increased after unloading. The mRNA expression of brain natriuretic peptide and the beta2-adrenergic receptor significantly improved after mechanical unloading. The levels of SERCA2a mRNA tended to increase after unloading. In conclusion, unloading the failing, infarcted heart can help normalize left ventricular hypertrophy and cardiac gene expression. This unloading model appears to partially mimic the conditions of hemodynamic support with an LVAD in heart failure patients and potentially offers insights into the mechanisms of functional recovery.