Alteration of muscle and red cell sodium and potassium in 20,25-diazacholesterol-induced myotonia

Myotonia was induced in rats by a single oral dose of 20,25-diazacholesterol. Myotonia as determined by electromyography developed in 12 days, and was maintained for 20 days. Accompanying the myotonia there was a significant decrease in intracellular sodium that, when compared with controls, was most marked in white glycolytic muscles such as white vastus lateralis [24.6 (se ± 4.3) percentage of decrease (P < 0.005)], and the paraspinal muscles [18.0 (se ± 4.4) percentage of decrease (P < 0.01)], and least in red oxidative muscles such as soleus (3.8 (se ± 4.4) percentage of decrease, not significant). No change in intracellular potassium was observed. The changes in muscles are probably the result of a decreased membrane permeability for sodium. No alteration in serum, or red cell sodium, potassium, or chloride was observed, and (Na⁺ + K⁺)ATPase of the red cells remained constant.     

The effect of a high protein diet on leucine and alanine turnover in acid maltase deficiency.

Leucine and alanine production rate was measured in 5 patients with acid maltase deficiency in the postabsorptive state, following 6 months on a normal diet with placebo and 6 months on an isocaloric high protein diet (16-22% protein). Whole body leucine production rate, a measure of protein degradation, expressed in terms of lean body mass was significantly greater than in five control subjects. Following the high protein diet, leucine production rate was decreased in four of the five patients but this was not statistically significant. Alanine production rate expressed in terms of lean body mass was significantly greater than in control subjects. After the high protein diet, alanine production rate and concentration were significantly decreased (p less than 0.05). There were no significant improvements in any of the clinically relevant variables measured in these patients. It is possible that a larger increase in protein intake over a longer time period may have a clinical effect.     

Membrane desmosterol and the kinetics of the sarcolemmal Na,K-ATPase in myotonia induced by 20,25-diazacholesterol

The kinetics of the sarcolemmal Na⁺,K⁺-ATPase were studied in rats made myotonic by treatment with 20,25-diazacholesterol (20,25-D; 200 mg/kg every 14 days). Overall Na⁺,K⁺-ATPase activity in purified sarcolemma increased from 44.6 ± 8.7 nmol P_i/mg protein⁻¹ min⁻¹ in controls to 77.7 ± 7.9 nmol mg⁻¹ min⁻¹ in treated animals whose membrane desmosterol concentrations exceeded 70% of total membrane sterol. In general the activity of this enzyme paralleled the desmosterol content of the sarcolemma. The total number of enzyme units, however, was not changed as evidenced by [³H]ouabain binding and by measurements of steady-state phosphorylated intermediate in the absence of K⁺. Independent measurements of the Na⁺,K⁺-ATPase dephosphorylation partial reaction in 20,25-D sarcolemma revealed no change from control rats at any temperature between 5 and 40°C; the K⁺ dependence of this reaction was also unchanged. Rates of phosphoprotein formation inferred from measurements of steady-state phosphorylated intermediate under various ionic conditions were also not altered by increasing desmosterol. Kinetic analysis suggests that the increase in overall Na⁺,K⁺-ATPase activity in membranes with high concentrations of desmosterol may reflect an increase in the rate of conformational interchange between two states of the enzyme during its activity cycle.     

Vascular changes in rat hippocampus following a high saturated fat and cholesterol diet

The long-term effects of a diet rich in saturated fat and cholesterol on the hippocampus were evaluated in this study. It has previously been shown that this type of diet is detrimental to health, particularly affecting peripheral organs such as the heart and liver. However, effects on the brain have not been fully evaluated. This study focused on the hippocampus, a brain region instrumental for learning and memory and vulnerable to ischemic damage. Reduced blood-brain barrier (BBB) integrity and increased microgliosis were observed in the hippocampus of rats fed a high-saturated-fat and cholesterol (HFHC) diet for 6 months. Interestingly, an increase in hippocampal protein levels of occludin, a tight junction protein, was found in HFHC-treated rats as well. Further investigation revealed decreased expression of the occludin protein in blood vessels and increased expression in the dentate gyrus hilar neurons and mossy fibers of the hippocampal cornus ammonis 3 in HFHC-treated rats. Our results show alterations in BBB integrity and expression of tight junction proteins after long-term exposure to HFHC diet in rats. These findings may suggest a biologic mechanism for previously observed behavioral deficits occurring in rats fed this diet.     

The effect of denervation on subsequent in vitro induction of myotonia

In order to study the influence of innervation on myotonia, an attempt was made to induce myotonia in previously denervated rat hemidiaphragm preparations in vitro with use of 2,4-dichlorophenoxy acetic acid (2,4-D) and low chloride solutions. Prior denervation prevented the onset of myotonia in both media except during the first 24 hours after nerve section. On the basis of already available data, we propose that the reduced potassium conductance accompanying denervation may be the main factor preventing induciton of myotonia in denervated muscle.     

Effect of high cholesterol diet on spatial learning and memory in a rat model of Alzheimer’s disease☆

BACKGROUND： Recently study indicates a potentially important link between cholesterol, Aβ deposit, and clinicopathological manifestation of Alzheimer＇s disease （AD）. OBJECTIVE： To study the effect of high cholesterol diet on cognitive function and neuronal loss of hippocampal dentate gyrus in AD model rats. DESIGN, TIME AND SETTING： A randomized controlled animal study, which was performed in the Laboratory of Stem Cells, Department of Pathology, Third Military Medical University of Chinese PLA from February 2006 to March 2007. MATERIALS： Twenty healthy, male, Wistar rats, aged 3-4 months and weighing （300 ± 20） g, were selected for this study. A β 1- 40 was provided by Sigma Company, USA. Standard diet and high cholesterol diet mixed with cholesterol （5%）, sodium hypocholic acid （1%）, lard （10%）, and ordinary rat food （84%） were provided by Experimental Animal Center, Institute of Field Surgery, Daping Hospital, Third Military Medical University of Chinese PLA. METHODS： Rats were fed on high cholesterol diet or standard diet for eight successive weeks. Then, rats were randomly divided into cholesterol diet ＋A β, high cholesterol diet ＋ phosphate buffered saline（PBS）, standard diet ＋ A β, and standard diet ＋ PBS group, with five rats in each group. AD rat models were established by local injection of A β 1-40 solution （10 μ L） into the hippocampal dentate gyrus. Rats in the control group were injected with the same volume of PBS. After injection, rat were fed for two weeks MAIN OUTCOME MEASURES： Neuronal cells in the hippocampal dentate gyrus were detected by Nissl staining; spatial navigation and spatial probe were detected by Morris water maze to reflect learning and memory. RESULTS： Twenty rats were included in the final analysis, without any loss. （1） Neuronal numbers： neuronal loss in the high cholesterol diet ＋ A β and standard diet ＋ A β groups was significantly higher than in the PBS groups （P 〈 0.01）. In particular, loss of     

Effects of a saturated fat and high cholesterol diet on memory and hippocampal morphology in the middle-aged rat

Diets rich in cholesterol and/or saturated fats have been shown to be detrimental to cognitive performance. Therefore, we fed a cholesterol (2%) and saturated fat (hydrogenated coconut oil, Sat Fat 10%) diet to 16-month old rats for 8 weeks to explore the effects on the working memory performance of middle-aged rats. Lipid profiles revealed elevated plasma triglycerides, total cholesterol, HDL, and LDL for the Sat-Fat group as compared to an iso-caloric control diet (12% soybean oil). Weight gain and food consumption were similar in both groups. Sat-Fat treated rats committed more working memory errors in the water radial arm maze, especially at higher memory loads. Cholesterol, amyloid-beta peptide of 40 (Abeta40) or 42 (Abeta42) residues, and nerve growth factor in cortical regions was unaffected, but hippocampal Map-2 staining was reduced in rats fed a Sat-Fat diet, indicating a loss of dendritic integrity. Map-2 reduction correlated with memory errors. Microglial activation, indicating inflammation and/or gliosis, was also observed in the hippocampus of Sat-Fat fed rats. These data suggest that saturated fat, hydrogenated fat and cholesterol can profoundly impair memory and hippocampal morphology.     

A high cholesterol diet ameliorates hippocampus-related cognitive and pathological deficits in ovariectomized mice

Both sex hormone deficiency and hypercholesterolemia are related to cognitive decline or Alzheimer's disease. However, their interactive influence on the neurodegenerative progress is not clear. This study was designed to assess the effects of ovarian hormone depletion and high cholesterol diet alone or in combination on hippocampus-related cognitive and pathological deficits in adult female ICR mice. Depletion of ovarian hormones by ovariectomy for 9 weeks resulted in significant spatial learning and memory deficits as revealed by the water maze testing. Such cognitive alteration was accompanied with increases in neuron death and decreases in choline acetyltransferase activity and synaptopysin expression in the hippocampus. On the other hand, the high cholesterol diet (3% cholesterol plus normal chow) did not exacerbate, but slightly alleviated cognitive decline and significantly attenuated hippocampal pathological changes in ovariectomized mice. Moreover, ovariectomized mice fed high cholesterol had increased serum estrogen levels compared with those fed a normal chow. These results indicate that high cholesterol intake increases the sex hormone synthesis and in turn partially attenuates hippocampus-related cognitive and pathological deficits caused by ovariectomy.     

Founder mutations and the high prevalence of myotonia congenita in northern Finland.

OBJECTIVE AND BACKGROUND: To find an explanation at the molecular level for the high prevalence of myotonia congenita in northern Finland and the exceptional pattern of inheritance of the disease in many families, and to study genotype-phenotype correlation in the patients. METHODS: Forty-six patients with myotonia congenita and 16 unaffected relatives from 24 families were studied. All 23 exons and their flanking regions of the gene for the chloride channel protein (ClC-1) were sequenced from at least one patient from all families. RESULTS: There were three different mutations of ClC-1 in the patients: one in exon 11, a T-to-G transversion that resulted in the substitution of cysteine for phenylalanine at amino acid position 413 (F413C); one in exon 15, a C-to-T transition that resulted in the substitution of valine for alanine at amino acid position 531 (A531V); and one in exon 23, a C-to-T transition that resulted in the substitution of a stop codon for an arginine codon at amino acid position 894 (R894X). CONCLUSIONS: Molecular studies showed that even in families with apparent dominant inheritance, the actual mode of inheritance was autosomal recessive. This was explained not only by the observed consanguinity in some families but by an enrichment of three different mutations of the ClC-1 gene and a consequent high number of compound heterozygotes in the population. One of the mutations is unique to northern Finland. The conspicuous enrichment of the mutations is likely due to the founder effect and isolation by distance, as in other diseases in the Finnish heritage.     

Fenoterol precipitating myotonia in a minimally affected case of recessive myotonia congenita

Summary Fenoterol is used in patients with premature labor to delay delivery. A young woman treated with fenoterol developed severe generalized myotonia. Symptoms disappeared after medication had been stopped. In a later study myotonic discharges were found electromyographically in the muscles of the patient and her brother. Both suffered from subclinical recessive myotonia congenita (Becker). A heterozygous manifestation may be supposed.

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Zusammenfassung Fenoterol (Partusisten^®) wird als wehenhemmendes Mittel verwendet. Bei einer jungen Frau trat unter Fenoterol eine schwere generalisierte Myotonie auf, die nach Absetzen des Medikamentes wieder verschwand. Bei der Patientin und bei ihrem Bruder fand sich später elektromyographisch eine subklinische Myotonie. Wahrscheinlich sind beide Geschwister heterozygote Genträger der rezessiven generalisierten Myotonie (Becker).

     

The effects of taurine on pharmacologically induced myotonia

Taurine reduces the excitability of striated muscle fibers by increasing the membrane conductance to chloride ions (GCl). This action was tested on rats made myotonic by drugs that block GCl by different mechanisms. Experiments were made "in vivo" using electromyographic (EMG) recordings and "in vitro" with intracellular microelectrode recordings from extensor digitorum longus muscle fibers. Taurine did not antagonize the myotonic discharges produced in vivo by anthracene-9-carboxylic acid, nor did it restore GCl lowered in vitro by this agent. However, when myotonia was chronically induced by 20,25 diazacholesterol, taurine given chronically in vivo or acutely in vitro antagonized the EMG myotonia as well as the reduced GCl and increased excitability of single fibers. We conclude that taurine acts directly on chloride channels to modify their kinetics. Our findings suggest that further clinical studies on the use of taurine in muscle disease involving abnormal excitability or chloride channel function will be useful.     

Muscle pathology of myotonia congenita.

We have investigated the muscle biopsies of 8 patients with myotonia congenita. There were 2 families with autosomal recessive inheritance (5 cases), 1 with autosomal dominant inheritance, and 2 sporadic cases. Mild abnormalities were seen with routine pathological preparations which were nondiagnostic. Histochemical studies of fiber subtypes demonstrated a complete absence of Type 2B muscle fibers in all of our patients regardless of the type of inheritance. this is the first reporot of an entity in which there is a consistent absence of a muscle fiber type, and some speculation has been made as to the possible causes.     

Linkage of atypical myotonia congenita to a sodium channel locus.

We performed linkage analysis in a pedigree segregating an allele for autosomal dominant, painful myotonia that is potassium sensitive and responsive to acetazolamide. This allele was tightly linked to a skeletal-muscle, sodium channel locus which is now a candidate for the site of the mutational defect in acetazolamide-responsive myotonia congenita. Since this sodium channel locus is completely linked to the disease allele in all hyperkalemic periodic paralysis and paramyotonia congenita pedigrees studied, the molecular alteration causing acetazolamide-responsive myotonia congenita is likely an allelic defect in this human, skeletal-muscle, sodium channel gene.