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Background: As the lowest natural site on earth (-415 meters), the Dead Sea is unique for its high pressure and oxygen tension in addition to the unparalleled combination of natural resources. Furthermore, its balneotherapeutic resorts have been reported to be beneficial for patients with various chronic diseases., Objectives: To evaluate the safety, quality of life (QoL), exercise capacity, heart failure, and arrhythmia parameters in patients with systolic congestive heart failure (SCHF) and implantable cardioverter defibrillator (ICD) following descent and stay at the Dead Sea., Methods: The study group comprised patients with SCHF, New York Heart Association functional class II-III after ICD implantation. The following parameters were tested at sea level one week prior to the descent, during a 4 day stay at the Dead Sea, and one week after return: blood pressure, 02 saturation, ejection fraction (echocardiography), weight, B-type natriuretic peptide (BNP), arrhythmias, heart rate, heart rate variability (HRV), and QoL assessed by the Minnesota Living with Heart Failure questionnaire., Results: We evaluated 19 patients, age 65.3 +/- 9.6 years, of whom 16 (84%) were males and 18 (95%) had ICD-cardiac resynchronization therapy. The trip to and from and the stay at the Dead Sea were uneventful and well tolerated. The QoL score improved by 11 points, and the 6 minute walk increased by 63 meters (P < 0.001). BNP levels increased slightly with no statistical significance. The HRV decreased (P = 0.018). There were no significant changes in blood pressure, weight, 02 saturation or ejection fraction., Conclusions: Descent to, ascent from, and stay at a Dead Sea resort are safe and might be beneficial in some aspects for patients with SCHF and an ICD.

Muscle-specific deficiency of phosphorylase kinase (Phk) causes glycogen storage disease, clinically manifesting in exercise intolerance with early fatiguability, pain, cramps and occasionally myoglobinuria. In two patients and in a mouse mutant with muscle Phk deficiency, mutations were previously found in the muscle isoform of the Phk alpha subunit, encoded by the X-chromosomal PHKA1 gene (MIM # 311870). No mutations have been identified in the muscle isoform of the Phk gamma subunit (PHKG1). In the present study, we determined Q1the structure of the PHKG1 gene and characterized its relationship to several pseudogenes. In six patients with adult- or juvenile-onset muscle glycogenosis and low Phk activity, we then searched for mutations in eight candidate genes. The coding sequences of all six genes that contribute to Phk in muscle were analysed: PHKA1, PHKB, PHKG1, CALM1, CALM2 and CALM3. We also analysed the genes of the muscle isoform of glycogen phosphorylase (PYGM), of a muscle-specific regulatory subunit of the AMP-dependent protein kinase (PRKAG3), and the promoter regions of PHKA1, PHKB and PHKG1. Only in one male patient did we find a PHKA1 missense mutation (D299V) that explains the enzyme deficiency. Two patients were heterozygous for single amino-acid replacements in PHKB that are of unclear significance (Q657K and Y770C). No sequence abnormalities were found in the other three patients. If these results can be generalized, only a fraction of cases with muscle glycogenosis and a biochemical diagnosis of low Phk activity are caused by coding, splice-site or promoter mutations in PHKA1, PHKG1 or other Phk subunit genes. Most patients with this diagnosis probably are affected either by elusive mutations of Phk subunit genes or by defects in other, unidentified genes.

Glycogen storage disease type 1b (GSD-1b) is proposed to be caused by a deficiency in microsomal glucose 6-phosphate (G6P) transport, causing a loss of glucose-6-phosphatase activity and glucose homeostasis. However, for decades, this disorder has defied molecular characterization. In this study, we characterize the structural organization of the G6P transporter gene and identify mutations in the gene that segregate with the GSD-1b disorder. We report the functional characterization of the recombinant G6P transporter and demonstrate that mutations uncovered in GSD-1b patients disrupt G6P transport. Our results, for the first time, define a molecular basis for functional deficiency in GSD-1b and raise the possibility that the defective G6P transporter contributes to neutropenia and neutrophil/monocyte dysfunctions characteristic of GSD-1b patients.

Deficiency of glycogen phosphorylase in the liver gives rise to glycogen-storage disease type VI (Hers disease; MIM 232700). We report the identification of the first mutations in PYGL, the gene encoding the liver isoform of glycogen phosphorylase, in three patients with Hers disease. These are two splice-site mutations and two missense mutations. A mutation of the 5' splice-site consensus of intron 14 causes the retention of intron 14 and the utilization of two illegitimate 5' splice sites, whereas a mutation of the 3' splice-site consensus of intron 4 causes the skipping of exon 5. Two missense mutations, N338S and N376K, both cause nonconservative replacements of amino acids that are absolutely conserved even in yeast and bacterial phosphorylases. We also report corrections of the PYGL coding sequence, sequence polymorphisms, and a partial PYGL gene structure with introns in the same positions as in PYGM, the gene of the muscle isoform of phosphorylase. Our findings demonstrate that PYGL mutations cause Hers disease, and they may improve laboratory diagnosis of deficiencies of the liver phosphorylase system.

Glycogen-storage disease type 1 (GSD-1), also known as "von Gierke disease," is caused by a deficiency in microsomal glucose-6-phosphatase (G6Pase) activity. There are four distinct subgroups of this autosomal recessive disorder: 1a, 1b, 1c, and 1d. All share the same clinical manifestations, which are caused by abnormalities in the metabolism of glucose-6-phosphate (G6P). However, only GSD-1b patients suffer infectious complications, which are due to both the heritable neutropenia and the functional deficiencies of neutrophils and monocytes. Whereas G6Pase deficiency in GSD-1a patients arises from mutations in the G6Pase gene, this gene is normal in GSD-1b patients, indicating a separate locus for the disorder in the 1b subgroup. We now report the linkage of the GSD-1b locus to genetic markers spanning a 3-cM region on chromosome 11q23. Eventual molecular characterization of this disease will provide new insights into the genetic bases of G6P metabolism and neutrophil-monocyte dysfunction.

We have identified mutations in the phosphorylase kinase (Phk) beta subunit gene in a male patient with liver glycogenosis caused by Phk deficiency. The patient's DNA has been analyzed for mutations in the genes encoding the alpha L, beta, and gamma TL subunits of Phk, all of which can be responsible for liver glycogenosis, by a strategy primarily based on reverse transcription/polymerase chain reaction of blood RNA and complemented by analysis of genomic DNA. His alpha L and gamma TL coding sequences are normal, whereas he is compound-heterozygous for two mutations in the beta subunit gene, PHKB. The first is a splice-site mutation (IVS4 [-2A-->G]) causing the reading-frame-disrupting deletion of exon 5 in the mRNA from this allele. The second is an Ala117Pro missense mutation, also in exon 5. This is the first missense mutation identified in PHKB, as opposed to nine translation-terminating mutations described to date. It offers an explanation for the unique biochemical phenotype of this patient. In his leukocytes, low Phk activity is measured when tested with the endogenous liver isoform of phosphorylase as the protein substrate, but normal activity is observed when tested with muscle phosphorylase added in vitro. In contrast, Phk activity in his erythrocytes is low with both substrates. The missense mutation may selectively impair the interaction of Phk with one isoform of its substrate protein and may destabilize the enzyme in a cell-type-specific way. This phenotype shares some aspects with X-linked liver glycogenosis subtype 2 (XLG2), a variant of liver Phk deficiency arising from missense mutations in the alpha L subunit gene (PHKA2), but differs from XLG2 in other respects. The present case demonstrates that mutations in Phk genes other than PHKA2 can also be associated with untypically high activity in certain blood cell types. Moreover, it emphasizes that missense mutations in Phk may cause unusual patterns of tissue involvement that would not be predicted a priori from the tissue specificity of expression of the mutated gene sequences.

Neutrophil functions and glucose metabolism are known to be impaired in glycogen storage disease (GSD) Ib patients. The uptake of nonmetabolizing glucose analogues into polymorphonuclear leukocytes (PMN) of GSD Ib patients was studied. 2-Deoxyglucose (2-DOG) and 3-O-methylglucose are transported across the cell membrane by facilitated diffusion mediated by the glucose transporter. Because 2-DOG is phosphorylated within the cell, its uptake rate reflects hexose transport as long as phosphorylation is not rate-limiting. These conditions prevail only at low 2-DOG concentrations. Transport of 5 microM DOG into GSD Ib patient PMN was found to be similar to controls (4.3 +/- 0.5 and 4.65 +/- 1.77 pmol/min X 10(6), respectively). In contrast, 2-DOG uptake at high concentrations (2 mM) decreased by 70% in patient PMN compared with control cells (0.17 +/- 0.06 and 0.51 +/- 0.11 nmol/min X 10(6), for patients and controls, respectively). Transport of 3-O-methylglucose (a glucose analogue that does not undergo intracellular phosphorylation) was not different in patient PMN compared with controls (1.86 +/- 0.53 and 2.19 +/- 0.30 nmol/min X 10(6), respectively). Hexose monophosphate shunt activity in PMN of GSD Ib patients at a glucose concentration of 2 mM was 43% of control values, whereas at 10 microM it was similar to controls. Taken together, these results suggest that the defect in glucose uptake and metabolism found in GSD Ib patient PMN is due to an impairment in hexose phosphorylation rather than in a reduction in the transmembrane glucose transport activity.

The effect of ingestion of uncooked cornstarch (2 g/kg body weight) in water, uncooked starch (1 g/kg) added to a meal, and glucose (2 g/kg) in water, was studied in eight patients with type IA glycogen storage disease (GSD) and one patient with type IB GSD. Blood glucose concentrations were determined at 30-min intervals during each tolerance test; blood lactate, blood insulin, and expiratory hydrogen were determined at 60-min intervals. The glucose levels remained in the normal range (greater than or equal to 1.8 mM) during approximately 6.5-9.0 h, 3.5-6.5 h, and 2.25-4.0 h during the three tolerance tests, respectively. The lactate levels differed markedly for the different tests per patient, and for the same type of test between the patients. Blood insulin concentrations after starch administration did not exceed values of 50 mU/liter above fasting levels and were markedly lower than those after glucose administration (maximum levels of 280 mU/liter). The expiratory hydrogen excretion did not increase or only slightly increased after cornstarch administration (less than 20 ppm).

A four-year-old Israeli Arab boy was found to have glycogen accumulation in both liver and muscle without clinical symptoms. Liver phosphorylase kinase (PK) activity was 20% of normal, resulting in undetectable activity of phosphorylase a. Muscle PK activity was about 25% of normal, resulting in a marked decrease of phosphorylase a activity. Two sisters showed a similar pattern, whereas one brother had normal PK activity. The patient's liver protein kinase activity was normal Addition of exogenous protein kinase did not affect PK activity, whereas exogenous PK restored phosphorylase activity to normal. These findings indicate that these patients are affected by a rare variant of PK deficiency, which involves both muscle and liver and which apparently is not sex linked. It is possible that this defect represents an unusual mutation of a subunit of the phosphorylase kinase enzyme.

This study measures hexose monophosphate (HMP) shunt activity, glycolytic rate, and glucose transport in PMN and lymphocytes of patients with glycogen storage disease (GSD) type Ib as compared with controls and with GSD Ia patients. HMP shunt activity and glycolysis were significantly lower in intact PMN cells of GSD Ib patients as compared with GSD Ia patients and with controls. These activities were above normal levels in disrupted GSD Ib PMN. HMP shunt activity and glycolytic rates in lymphocytes were similar in all three groups studied. The rate of 2-deoxyglucose transport into GSD Ib PMN was 30% of that into cells of normal controls. In GSD Ib lymphocytes or in GSD Ia PMN and lymphocytes transport was normal. The striking limitation of glucose transport across the cell membrane of the PMN of GSD Ib patients may account for the impairment of leukocyte function that is characteristic of GSD Ib, but not found in GSD Ia patients.

Active glycogen metabolism has been demonstrated in both normal and glycogen-rich erythrocytes taken from patients with type III glycogen storage disease. Activity of all enzymes catalyzing the reactions required for the synthesis and degradation of glycogen have been demonstrated in the mature erythrocytes. Uniformly labeled glucose-(14)C is incorporated into glycogen in intact cells of both types during incubation. Replacement of the glucose-(14)C by unlabeled glucose in the medium resulted in a significant loss of radioactivity from cellular glycogen. In the absence of the substrate a progressive shortening of outer branches occurred during incubation of intact glucogen-rich cells. Using cells from patients with type III glycogen storage disease, which have sufficient glycogen content to be analyzed by beta-amylolysis, we demonstrated that the glucosyl units are first incorporated in the outer tiers, then transferred to the core where they tend to accumulate due to the absence of amylo-1,6-glucosidase. The glycogen-rich cells have a more rapid rate of glucose utilization upon incubation which is not reflected by a higher lactate production. The increased rate of glucose utilization did not result from an increased rate of glucose incorporation into glycogen in affected cells. The rate of (14)CO(2) production from glucose-1-(14)C during incubation was not significantly different in the two types of cells unless methylene blue was added as an electron acceptor, in which case the glycogen-rich cells oxidized glucose to CO(2) more rapidly.