Ataxia with isolated vitamin E deficiency is caused by mutations in the alpha-tocopherol transfer protein

Ataxia with isolated vitamin E deficiency (AVED) is an autosomal recessive neurodegenerative disease which maps to chromosome 8q13. AVED patients have an impaired ability to incorporate alpha-tocopherol into lipoproteins secreted by the liver, a function putatively attributable to the alpha-tocopherol transfer protein (alpha-TTP). Here we report the identification of three frame-shift mutations in the alpha TTP gene. A 744delA mutation accounts for 68% of the mutant alleles in the 17 families analysed and appears to have spread in North Africa and Italy. This mutation correlates with a severe phenotype but alters only the C-terminal tenth of the protein. Two other mutations were found in single families. The finding of alpha TTP gene mutations in AVED patients substantiates the therapeutic role of vitamin E as a protective agent against neurological damage in this disease.

Effects of catecholamines on the residual sodium channel dependent slow conduction in guinea pig ventricular muscles under normoxia and hypoxia

OBJECTIVE

The aim was to study the effects of catecholamines (isoprenaline and noradrenaline) on the action potential upstroke and conduction velocity in guinea pig ventricular papillary muscles.

METHODS

The upstroke velocity and the conduction velocity of the action potential were recorded by conventional two-microelectrode techniques in the guinea pig ventricular papillary muscle superfused with normoxic and hypoxic Tyrode solution of various potassium concentrations ([K+]o 2.7-16.7 mM), stimulated at 0.2 Hz.

RESULTS

Under normoxic conditions, the upstroke of action potentials is composed of two components, dV/dtmax,fast followed by dV/dtmax,slow, when the muscle were perfused with relatively high [K+]o (10.8-16.7 mM). The dV/dtmax,fast is a measure of the residual (mostly inactivated) sodium current, while the dV/dtmax,slow is a measure of calcium current. The conduction velocity at 13-17 mM [K+]o ranged from 30-40 cm.s-1 (slow conduction) with depolarised membrane potentials of about -60 mV. Isoprenaline in increasing concentrations (0.01-1 microM) did not significantly alter the conduction velocity but altered the ionic channels responsible for the slow conduction from residual sodium channel to calcium channel. In the presence of D600 (2 microM) or 1-verapamil (2.2 microM), isoprenaline (0.1 microM) rapidly decreased dV/dtmax,fast without increasing dV/dtmax,slow and a conduction block occurred. In the presence of pindolol (2 microM), all the effects of isoprenaline on dV/dtmax,fast, dV/dtmax,slow, and conduction velocity were abolished. Noradrenaline has the same effects as isoprenaline, although the potency was much less. Under hypoxic conditions, the effects of catecholamines on the dV/dtmax,fast was the same as under normoxic conditions.

CONCLUSIONS

Catecholamines alter the ionic channel responsible for the slow conduction of reentry circuit from residual sodium to calcium channel, or vice versa, depending on the local concentrations of catecholamines. In the presence of a calcium antagonist, catecholamines strongly depress the (dV/dtmax,fast dependent) slow conduction, leading to a complete block of conduction, under both normoxia and hypoxia.

Long-term follow-up of the reproducibility of carotid sinus hypersensitivity in patients with carotid sinus syndrome

The reproducibility of carotid sinus hypersensitivity to carotid sinus massage was studied in the long-term follow-up of 8 patients with carotid sinus syndrome. A cardioinhibitory response was induced in 7 patients, while a vasodepressor response was found in the remaining patient. The 7 patients were treated with dual-chamber pacemaker implantation and the remaining patient was treated with propranolol. All of the patients remained asymptomatic during a follow-up period of 48 +/- 11 months. Carotid sinus massage during the follow-up period in patients with a cardioinhibitory response revealed asystolic intervals of 3 s or longer in 4 patients and in 3 patients at the second and third follow-up examinations, respectively, although there were no significant differences in the ventricular asystolic intervals between before, and 34 +/- 11 months and 48 +/- 11 months after treatment. However, each patient showed a wide variation in asystolic intervals. The differences in asystolic intervals between prior to treatment (first) and the third test were significantly greater than those between the first and the second test (2.4 +/- 1.2 s vs 0.7 +/- 0.6 s; p < 0.05). The one patient with a vasodepressor response had a decreased systolic blood pressure greater than 50 mmHg by carotid sinus massage at all three occasions. In conclusion, most patients with carotid sinus syndrome showed abnormal and variable responses to carotid sinus massage during long-term follow-up period although there was no recurrence of symptoms after treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Rate-dependent prolongation of action potential duration in single ventricular myocytes obtained from hearts of rats with streptozotocin-induced chronic diabetes sustained for 30-32 weeks

We examined the characteristics of the action potentials of single ventricular myocytes obtained from the hearts of rats with chronically-induced diabetes. Male Wistar rats were made diabetic by injecting streptozotocin (65 mg/kg) and 30-32 weeks later the hearts were excised and used for an electrophysiological study. Action potentials were recorded from isolated right ventricular myocytes by an electrode fabricated for patch clamp in the whole-cell recording configuration. The action potential durations (APDs) of steady state chronic diabetic rat myocytes were longer than those of age-matched normal rat myocytes at all levels of repolarization (APD25, APD50, APD75, and APD90). As the stimulation frequency was increased (0.2-2 Hz), the APDs were lengthened in both diabetic and normal rats, and the difference of APDs between the groups was greater when the stimulation frequency was higher. When we examined alterations of APDs under conditions of train stimulation (2Hz, 20 stimuli), (1) the APDs in both groups were prolonged, and (2) the degree of prolongation of APD was significantly greater and the rate of APD prolongation was significantly faster in myocytes from the diabetic rats. The prolongation of APD in these heart cells is probably secondary to alteration of the transient outward current Ito, and sheds light on repolarization abnormality in cases of diabetic cardiomyopathy.

Effects of KT-362, a new antiarrhythmic agent, on membrane ionic currents of guinea pig ventricular myocytes

We studied the effects of KT-362, (5-[3[2-(3,4-dimethoxyphenyl)ethyl]amino]-1-oxopropyl]-2,3,4,5- tetrahydro-1,5-benzothiazepine fumarate), a newly synthesized vasodilating and antiarrhythmic agent, on membrane currents of single guinea pig ventricular cells, using whole-cell voltage-clamp techniques. In the steady state with a stimulation frequency of 0.5 Hz, KT-362 at concentrations of 10 and 30 microM decreased the peak sodium current (INa) in a concentration-dependent manner, i.e., by 27% and 49%, respectively. The inhibition of INa by this agent was use-dependent: KT-362 (30 microM) inhibited INa by 21% at 0.2 Hz and by 51% at 1 Hz. In addition, KT-362 (10-30 microM) decreased the L-type Ca current (ICa) in a concentration-dependent fashion. The delayed rectifier potassium current and the inward rectifier potassium current were also inhibited by KT-362. The effects of KT-362 on INa and ICa were confirmed in experiments using ventricular papillary muscle preparations and microelectrode techniques. KT-362 (10-300 microM) decreased the maximum rate of rise of action potentials provoked at normal (2.7 mM) K+ concentration and that provoked at high (20 mM) K+ concentration. KT-362 at concentrations over 100 microM significantly depolarized the resting membrane, and the action potential duration remained unaltered. From these findings, we conclude that apart from the alleged inhibitory effects of this agent on the release of calcium from sarcoplasmic reticulum (it is therefore termed "an intracellular Ca++ blocker"), KT-362 suppresses a variety of membrane ionic currents of cardiac cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of cibenzoline, a new class Ia antiarrhythmic drug, on various membrane ionic currents and action potentials of guinea-pig ventricular cells

We examined the effects of cibenzoline, a new class Ia antiarrhythmic drug, on various membrane ionic currents and action potentials of guinea-pig single ventricular cells, using patch clamp techniques in whole-cell configuration. Action potentials and the membrane currents were evoked at a clamping rate of 0.2 Hz, and all experiments were performed at 32-33 degrees C. 1) Cibenzoline (5, 10 and 30 microM) decreased the Na+ current (INa), in a concentration-dependent manner. The concentration of the half-maximal inhibition (Kd) for INa was estimated to be 7.8 microM. 2) In addition to the inhibition of INa, this drug (5, 10, and 30 microM) decreased, in a concentration-dependent manner, all other membrane currents examined, such as L-type Ca2+ current (ICa), delayed rectifier K+ current (IK), and inward rectifier K+ current (IK1). The Kd (apparent dissociation constant) values were 14.4 microM for ICa, 23.0 microM for IK, and 33.7 microM for IK1 respectively. 3) Cibenzoline (5, 10, and 30 microns) significantly shortened the action potential duration measured at both 30% and 90% repolarization without altering the resting membrane potential. From these findings, we conclude that apart from potent inhibitory effects on INa, cibenzoline possesses multiple blocking effects on other currents, e.g., ICa, IK and IK1, with a different potency (INa > ICa > IK > IK1) and with essentially the same efficacy. These effects may explain, at least in part, the alleged, potent antiarrhythmic effects of this drug.

Monoclonal antibody raised against apoprotein of C-1027: effect on biochemical and biological activities of the holoantibiotic

A monoclonal antibody raised against C-1027 apoprotein recognized not only the apoprotein, but also the holoantibiotic (Antibiotic C-1027) almost equally. Among the biochemical and biological activities of the holoantibiotic, the antibody inhibited the aminopeptidase activity and the cytotoxicity to Ehrlich carcinoma cells in cultures, but not the DNA-cleaving activity in vitro. The immunohistogram, using this antibody, of Ehrlich carcinoma cells that had been exposed to the holoantibiotic suggested penetration of the holoantibiotic into target cells.

Correlation between cell-associated mannose-sensitive hemagglutination by Vibrio parahaemolyticus and adherence to a human colonic cell line Caco-2

Cell-associated hemagglutination (cHA) activity with human erythrocytes was examined for 468 clinical and 71 environmental strains of Vibrio parahaemolyticus. Approximately 95% of the strains tested were cHA positive irrespective of source or Kanagawa phenomenon. 75% of clinical strains showed relatively strong mannose-sensitive hemagglutination (MSHA), whereas 88% of the environmental strains showed relatively weak mannose-resistant hemagglutination (MRHA). Adherence of V. parahaemolyticus to Caco-2 cells was also determined. A clear positive correlation between cell-associated MSHA and adherence to Caco-2 cells was observed.

Effect of temocapril on haemodynamic and humoral responses to exercise in patients with mild essential hypertension

1. This study was carried out to evaluate the effect of temocapril on haemodynamic and humoral responses to exercise in nine patients with mild essential hypertension (WHO stages I and II). 2. After a 4-week placebo period, temocapril was administered at a dose of 1.0 mg once daily for 2-4 weeks. Graded submaximal bicycle ergometer exercise was performed before and after temocapril treatment, and the changes in arterial blood pressure, heart rate, cardiac output (CO), and systemic vascular resistance (SVR) were evaluated. In addition, the plasma norepinephrine (NE) level was determined both at rest and peak exercise before and after temocapril treatment. 3. Both the systolic and diastolic blood pressure were reduced at rest and during exercise by temocapril treatment. No significant change in the resting heart rate and CO was observed, and the exercise-induced increase of these parameters was also not affected by temocapril. In contrast, the resting SVR was significantly decreased by temocapril, although the exercise SVR was similar during both temocapril and placebo treatment. 4. Although there was no significant change in the plasma NE level with temocapril treatment, the exercise-induced increase of plasma NE was significantly suppressed by temocapril. 5. These results indicate that temocapril reduces the blood pressure without causing any significant changes in the heart rate and CO at rest, and that it does not produce any changes in the haemodynamic response to exercise.

Comparison of the effects of single morning and single bedtime doses of famotidine on intragastric acidity in patients with gastric ulcer

The effects of single morning and single bedtime doses of famotidine on intragastric acidity were studied by 24-h intragastric pH monitoring in 16 patients with gastric ulcer. The patients were randomly allocated to the following regimen: one group (n = 8) received 40 mg famotidine at 8:30 AM and another group (n = 8) received the same dose at 10 PM. The morning group showed significant inhibition of gastric acidity during the 24-h and daytime measurements, compared to those of the bedtime group (p < 0.05 in 24 h, p < 0.01 in daytime). Conversely, the bedtime group showed a significant inhibition of gastric acidity during the nocturnal period compared to the morning group (p < 0.01). These results indicate that the relative importance of suppression of gastric acidity on the gastric ulcer healing process should be evaluated in a clinical trial.

Molecular cloning and expression of chick embryo Gal beta 1,4GlcNAc alpha 2,6-sialyltransferase. Comparison with the mammalian enzyme

DNA clones encoding beta-galactoside alpha 2,6-sialyltransferase have been isolated from chick embryonic cDNA libraries using sequence information obtained from the conserved amino acid sequence of the previously cloned enzymes. The cDNA sequence revealed an open-reading frame coding for 413 amino acids, and the deduced amino acid sequence showed 57.6% identity with the sequence of rat liver Gal beta 1,4GlcNAc alpha 2,6-sialyltransferase. The primary structure of this enzyme suggested a putative domain structure, similar to structures found in other glycosyltransferases, consisting of a short N-terminal cytoplasmic domain, a signal-membrane anchor domain, a proteolytically sensitive stem region and a large C-terminal active domain. The identity of this enzyme was confirmed by construction of a recombinant sialyltransferase in which the N-terminus part including the cytoplasmic tail, signal anchor domain and stem region was replaced with an immunoglobulin signal peptide sequence. The expression of this recombinant protein in COS-7 cells resulted in secretion of a catalytically active and soluble form of the enzyme into the medium. The expressed enzyme exhibited activity only towards the disaccharide moiety of Gal beta 1,4GlcNAc in glycoproteins.

Modification of cardiac sodium current by intracellular application of cAMP

We examined the effects of intracellular perfusion of cyclic adenosine monophosphate (cAMP) on the sodium current (INa) of guinea-pig ventricular myocytes, using the whole-cell clamp technique. INa was elicited by depolarizing voltage steps (-20 mV) from a variety of holding potentials (-120 to -50 mV), under conditions of 60 mM extracellular Na+ concentration ([Na+]o) and at the temperature of 24-26 degrees C. Intracellular perfusion of cAMP decreased the INa elicited from the holding potentials less negative than -90 mV. In the presence of 1 mM cAMP, for example, the peak INa elicited from -80 mV decreased from 6.0 +/- 2.0 nA to 4.0 +/- 2.2 nA (mean +/- SD, P < 0.02, n = 7) within 3-6 min. In the presence of extracellular 3-isobutyl-1-methylxanthine (IBMX, 20 microM), much lower concentrations of cAMP (0.2 mM) yielded a comparable effect. On the other hand, intracellular perfusion of cAMP increased the INa elicited from very negative holding potentials (< -100 mV). For instance, the application of cAMP (1 mM) increased the INa elicited by step depolarizations from -120 mV (to -20 mV), from 9.9 +/- 2.1 nA to 11.0 +/- 3.1 nA (P < 0.05, n = 5). The former effect was attributed to a marked shift of the steady-state inactivation curve of INa to the negative direction; the voltage of half-inactivation shifted from -77.9 +/- 1.0 to -83.5 +/- 1.4 mV, or by -5.6 mV. The latter effect may be explained by increases in maximum available conductance of INa.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical studies of extracellular matrix components and integrins in IgA nephropathy

Localization of adhesive glycoproteins as the extracellular matrix and their cell surface receptors (integrins) were studied in an attempt to clarify their roles in the progression and aggravation of IgA nephropathy. The relationship between their localization and factors associated with clinical progression was then investigated in 65 patients with IgA nephropathy. The indirect immunoperoxidase method was used to study the distribution of fibronectin (FN), vitronectin (VN), fibronectin receptor (FNR) and vitronectin receptor (VNR). In all cases, FN was present in the glomeruli, mainly confined to the mesangial region, and in some cases, it was observed along the glomerular capillary loops. An expanded mesangial region accompanied higher FN distribution. FNR was present in the mesangial region and glomerular capillary loops, and was higher in the expanded mesangial region. VN was positive in 51 of 65 cases. In all cases, VNR was present in the mesangium and glomerular capillary loops, and its distribution was more predominant in and along the capillary loops than in the mesangial region. The expanded mesangium accompanied higher VNR distribution. There was a significant correlation in distribution between all factors with the exception of VN and FNR. FN, FNR and VNR increased significantly as a degree of histological damage. However, VN was not significantly associated with the degree of histological damage in positive and negative groups. The distribution of FN, FNR and VNR was associated with clinical aggravation factors although the distribution of VN was not. In conclusion, the distribution and functional alteration of FN and integrins in the glomeruli appear to be involved in the progression and exacerbation of IgA nephropathy.(ABSTRACT TRUNCATED AT 250 WORDS)

Biochemical components and myocardial performance after reversal of left ventricular hypertrophy in spontaneously hypertensive rats

OBJECTIVE

This study was undertaken to determine the biochemical and left ventricular functional changes associated with reversal of left ventricular hypertrophy (LVH) in spontaneously hypertensive rats (SHR).

DESIGN

Male SHR and normotensive Wistar-Kyoto (WKY) rats, aged 19 weeks, were treated for 3 weeks with vehicle, amlodipine (10 mg/kg), benazepril (10 mg/kg) or the combination of both agents (4 mg/kg amlodipine and 4 mg/kg benazepril). Left ventricular function was assessed while blood was infused rapidly, at pharmacologically reduced and pretreatment mean arterial pressure (MAP).

RESULTS

All treatments reduced MAP and left ventricular mass significantly in SHR. Myocardial protein, RNA and myocardial collagen content were reduced proportionately in all treatment groups in SHR, but not in WKY rats. DNA remained unchanged in all groups. Increased right ventricular mass was produced by amlodipine in both SHR and WKY rats (SHR +11.3%; WKY +9.8%), but this was prevented by cotreatment with benazepril. Right ventricular protein and collagen increased significantly with amlodipine in SHR but not WKY rats, and there were no changes in right ventricular RNA and DNA contents in either strain. Amlodipine improved, benazepril impaired and the combination of both agents maintained left ventricular pumping ability when pressure was increased abruptly to pretreatment levels in WKY rats. In contrast, when afterload was increased abruptly in SHR to pretreatment levels, neither amlodipine nor benazepril affected pumping ability, although it was enhanced by the combination.

CONCLUSIONS

These data demonstrate that amlodipine, benazepril and their combination reduced left ventricular mass in SHR. This reversal of LVH was associated with proportional reductions in mycotic protein, RNA and collagen, but not DNA. Therefore, it seems unlikely that LVH reversal with these agents was associated with increased fibrous tissue or impaired left ventricular performance. Finally, addition of the angiotensin converting enzyme inhibitor prevents the increase in right ventricular mass produced by the calcium antagonist.

Bepridil prolongs the action potential duration of guinea pig ventricular muscle only at rapid rates of stimulation

1. We examined the electromechanical effects of the calcium antagonist, bepridil (1-20 microM), on isolated guinea pig ventricular muscles, driven at various stimulus frequencies (0.1, 0.5, 1, 2 and 5 Hz) in Tyrode's solution containing various K+ concentrations (1.4-43.2 mM). 2. Conventional microelectrode and tension-recording techniques were used. 3. We found that bepridil decreased the maximum upstroke velocity (Vmax) of the action potential with no change in the resting membrane potential (RMP). 4. The former effect depended on both stimulus frequency and the drug concentration used. 5. Bepridil lengthened the duration of the action potential at the level of 25% repolarization (APD25) at the highest frequency (5 Hz), but shortened it at lower frequencies (< or = 2 Hz). 6. The drug also lengthened the APD90 at the highest frequency (5 Hz) but without significant effect at lower frequencies (< or = 2 Hz). 7. Bepridil depolarized the RMP at relatively low extracellular K+ concentrations (< or = 2.7 mM), accompanied by a prolongation of APD90. 8. There were no such effects at much higher K+ concentrations (> or = 5.4 mM), and the drug markedly depressed the Vmax and the action potential amplitude. 9. The drug eliminated the positive staircase phenomenon of twitch contraction, in a concentration-dependent manner. 10. All these findings taken together suggest that bepridil prolongs the action potential duration by inhibiting outward potassium currents (IK and IK1), at rapid rates of stimulation (approximately 300/min), which is comparable to the physiological heart rate of a guinea pig. 11. The prolongation of APD seemed to be secondary to the bepridil-induced reduction of intracellular Ca2+ concentration, [Ca2+]i.

Heterogeneity of motilin-immunoreactive cells in the duodenum and pyloric region of several avian species

Immunohistochemical characterizations of motilin-immunoreactive cells were examined in gastric and duodenal mucosae of nine species of birds from seven orders using five different region-specific motilin antisera. Motilin-immunoreactive cells appeared as open-type cells in the mucosal epithelium and showed varying immunoreactivities to antisera used in all the birds examined except for the cormorant and penguin, which did not show any kinds of immunoreactivity to motilin. Motilin-immunoreactive cells of the emu duodenum were detected by all the motilin-antisera used. The present results suggest that there is a wide range of heterogeneity between motilin molecules among avian species, or perhaps alternatively the existence of a family of motilin-like peptide. Furthermore, the present results should prove useful for a molecular biological study on the evolution of avian motilin.

Time course of plasma histamine and tryptase following food challenges in children with suspected food allergy

This study was undertaken to investigate the kinetics of histamine and tryptase in the circulation of patients with food allergy and to determine whether the measurements of plasma histamine and tryptase concentrations after food challenges provided additional predictive markers for the diagnosis and evaluation of food allergy. Twenty-one open food challenges were performed on 13 patients with suspected food allergy. Plasma histamine and tryptase concentrations were measured during 4 hours after challenge. In the group of patients with immediate reactions after challenges, the mean plasma histamine concentration rose significantly at 120 and 240 minutes after the challenge, and the mean plasma tryptase concentration was increased significantly at 240 minutes after challenge. Plasma histamine and tryptase concentrations were measured during 24 hours after 8 open food challenges in 7 other patients with suspected food allergy. In each patient with a nonimmediate reaction, plasma histamine concentrations were increased at the onset of symptoms after challenge, but no plasma tryptase concentrations increased. The elevation of plasma histamine and tryptase in patients with immediate reactions following food challenge indicates mast cell activation. On the other hand, the elevation of plasma histamine without elevated plasma tryptase in the patients with nonimmediate reactions following food challenge may indicate basophil activation rather than mast cell activation. Plasma histamine and tryptase measurements after food challenge may be useful in the detection and evaluation of food allergy.

Ionic mechanisms of action potential prolongation at low temperature in guinea-pig ventricular myocytes

1. We studied the effects of low temperature on the action potentials and membrane currents of guinea-pig ventricular myocytes, using a tight-seal whole-cell clamp technique. 2. The action potential duration at 95% repolarization was prolonged from 146 +/- 33 ms (mean +/- S.D., n = 6) at 33-34 degrees C (control temperature) to 314 +/- 83 ms at 24-25 degrees C (low temperature). 3. In whole-cell clamp experiments, low temperature decreased the calcium current (ICa), the delayed rectifier potassium current (IK), and the inwardly rectifying potassium current (IK1) with 'apparent' Q10 (temperature coefficient) values of 2.3 +/- 0.6 for ICa, 4.4 +/- 1.2 for IK tail current and 1.5 +/- 0.3 for IK1 (n = 7). 4. The effect of low temperature on IK was further studied in the presence of 0.6 microM nicardipine to block ICa. The decay phase of the IK tail consisted of two exponential components. The fast but not the slow component was highly sensitive to the temperature change with an apparent Q10 of 4.5. 5. We found that a component of time-independent current is also sensitive to the temperature. The current had a linear I-V relationship and remained almost unchanged after inhibition of Na(+) -K+ pump in K(+)-free external solution. 6. Using our mathematical model of the ventricular action potential (a modification from the DiFrancesco-Noble model), we simulated the action potential at low temperature by modifying some of the membrane currents, namely IK, IK1, ICa and a component of background current. It was shown that simultaneous changes in these currents could reproduce approximately 75% of the action prolongation induced by low temperature.