ABSTRACT
There is an increasing need for novel biomarkers that enable better diagnostic and prognostic stratification of patients with suspected infection. A proprotein convertase enzyme FURIN is upregulated upon immune cell activation, and it promotes infectivity by cleaving and activating pathogens. In this study, we determined FURIN levels in plasma using ELISA from 537 patients that were admitted to emergency room with suspected infection. Patients were sorted to high- and low-level FURIN groups with a cut-off level of 370 pg/ml. The study cohort included five diagnostic groups: Group 1, no systemic inflammatory response syndrome (SIRS, n = 59 patients); Group 2, bacterial infection without SIRS (n = 67); Group 3, SIRS, but no bacterial infection (n = 308); Group 4, sepsis without organ failure (n = 308); and Group 5, severe sepsis (n = 49). Statistically significant associations were not found between the plasma level of FURIN and the prevalence of sepsis (P = 0.957), diagnostic group of a patient (P = 0.737) or the bacteria in blood culture (P = 0.499). Additionally, the concentration of FURIN did not predict the severity or case fatality of the infectious disease. However, statistically significant associations were found between high plasma level of FURIN and diagnosed rheumatic disease (P < 0.001) as well as with the prevalence of non-smokers (P = 0.034). Thus, albeit the plasma level of FURIN does not predict the severity of infectious disease, it may be of use in the diagnostics of autoimmune diseases.
Subject(s)
Autoimmune Diseases/diagnosis , Bacterial Infections/diagnosis , Furin/blood , Sepsis/diagnosis , Adolescent , Adult , Aged , Aged, 80 and over , Autoimmune Diseases/blood , Bacterial Infections/blood , Bacterial Infections/complications , Biomarkers/blood , Emergency Service, Hospital , Female , Humans , Male , Middle Aged , Prospective Studies , Rheumatic Diseases/blood , Sepsis/blood , Sepsis/complications , Young AdultABSTRACT
OBJECTIVES: The soluble form of urokinase-type plasminogen activator (suPAR) was evaluated as an early prognostic marker of sepsis in patients with suspected infection. DESIGN: A single-centre prospective cohort study. METHODS: The cohort comprised 539 patients in the emergency department with suspected infection: 59 without systemic inflammatory response syndrome (SIRS) and without bacterial infection (group 1), 68 with bacterial infection and without SIRS (group 2), 54 with SIRS and without bacterial infection (group 3), 309 with sepsis (SIRS and bacterial infection) and without organ failure (group 4) and 49 with severe sepsis (SIRS, bacterial infection and organ failure) (group 5). suPAR was measured on admission using a commercial solid-phase enzyme-linked immunosorbent assay. RESULTS: The median soluble form of the receptor (suPAR) concentrations in groups 1-5 were 4.7, 5.0, 4.4, 4.8 and 7.9 ng mL(-1) , respectively (P < 0.001). The levels were significantly higher in nonsurvivors compared with survivors (8.3 vs. 4.9 ng mL(-1) , P < 0.001) and in patients with severe sepsis (group 5) compared with those in the other groups (7.9 vs. 4.8 ng mL(-1) , P < 0.001). Area under the receiver operating characteristics curve (AUC(ROC) ) for the prediction of case fatality was 0.79 (95% confidence interval [CI]: 0.72-0.86, P < 0.0001) and 0.75 for severe sepsis (95% CI: 0.68-0.81, P < 0.0001). At a cut-off level of 6.4 ng mL(-1) , suPAR had 76% sensitivity and 69% specificity for fatal disease; at a cut-off level of 6.6 ng mL(-1) , the sensitivity and specificity for severe sepsis were 67% and 72%, respectively. In multivariate models, high suPAR remained an independent predictor of case fatality and severe sepsis after adjusting for potential confounders. CONCLUSIONS: A high suPAR level predicts case fatality and severe sepsis in patients with suspected infection.
Subject(s)
Bacterial Infections/diagnosis , Sepsis/diagnosis , Severity of Illness Index , Systemic Inflammatory Response Syndrome/diagnosis , Urokinase-Type Plasminogen Activator/blood , Adolescent , Adult , Aged , Aged, 80 and over , Bacterial Infections/blood , Bacterial Infections/mortality , Biomarkers/blood , Calcitonin/blood , Emergency Service, Hospital , Enzyme-Linked Immunosorbent Assay , Female , Humans , Interleukin-6/blood , Male , Middle Aged , Multivariate Analysis , Prognosis , Prospective Studies , Protein Precursors/blood , ROC Curve , Sensitivity and Specificity , Sepsis/blood , Sepsis/mortality , Systemic Inflammatory Response Syndrome/blood , Systemic Inflammatory Response Syndrome/mortality , Young AdultABSTRACT
AIM: Anography is a radiological investigation for fistula-in-ano that identifies the primary fistula track through the internal opening. The efficacy of anography as a radiological method of identifying the location of the internal opening was investigated. METHOD: A retrospective study of 50 patients with a clinical diagnosis of fistula-in-ano of criptoglandular aetiology was performed. During anography, the location of the internal opening was recorded with respect to the quadrant of anal canal and distance from the anal verge. These data were compared with the findings during examination under anaesthesia (EUA), which was used as the gold standard for the identification of the internal opening. RESULTS: The sensitivity of anography for identifying a patent internal opening was 91% and specificity 100%. There was complete agreement between anography reports and findings at EUA regarding the quadrant of anal canal in which the internal opening was located. In more than 90% of patients, the internal opening was found at EUA within 1 cm from the site described on anography. CONCLUSION: Anography is an accurate test for predicting the exact quadrant of the anal canal in which the internal opening is located, as well as the distance of the internal opening from the anal verge. This inexpensive and simple radiological investigation should be the test of first choice in the evaluation of patients with fistula-in-ano when difficulty is anticipated in identifying the internal opening.
Subject(s)
Rectal Fistula/diagnostic imaging , Adult , Aged , Barium , Contrast Media , Female , Humans , Male , Middle Aged , Radiography , Retrospective Studies , Sensitivity and Specificity , Young AdultABSTRACT
The Roux-en-Y gastric bypass is one of the most common operations for morbid obesity. Although rare, gastropulmonary fistulas are an important complication of this procedure. There is only one recently reported case of this complication. The present report describes the serious nature of this complication in a patient after an uneventful laparoscopic gastric bypass surgery.
Subject(s)
Gastric Bypass/adverse effects , Gastric Fistula/etiology , Respiratory Tract Fistula/etiology , Female , Humans , Laparoscopy , Middle Aged , Obesity, Morbid/surgery , Postoperative Complications , Time FactorsABSTRACT
OBJECTIVES: Prostate cancer detection in biopsies increases with the number of sites and total tissue sampled. Its dependence on needle core fragment length is uncertain. METHODS: We surveyed two consecutive series of sextant needle biopsies from two practices in 1998 to 2000: 251 patients from Pennsylvania (group P) and 1596 from Virginia (group V). We tabulated the gross needle core lengths per sextant site and classified the diagnoses as benign or into four nonbenign categories: high-grade prostatic intraepithelial neoplasia; atypical small acinar proliferation, suspicious; atypical small acinar proliferation, suspicious plus high-grade prostatic intraepithelial neoplasia; and cancer. Logistic regression analysis was used to correlate cancer or a nonbenign diagnosis with the total length (sum of six sites) and, after excluding the sites with more than one core, with the length per single core, and the anatomic site of origin (apex, mid-gland, base). RESULTS: The mean total tissue length sampled was 108 +/- 27 mm (range 30 to 275) in group P and 81 +/- 22 mm (range 30 to 228) in group V. Sextant sites with a single core contained a mean of 12.8 +/- 3.5 mm tissue, with a 3.6-fold variation among the middle 95%. Group V core lengths at the apex averaged 11.8 mm, shorter (P = 0.0001) than mid (13.3 mm) or base (12.7 mm). A predictive value of longer length for a nonbenign diagnosis was noted in four of six sextants (P <0.04), with trend strongest at the apex, for which detection was influenced by abnormal digital rectal examination (P = 0.02) or ultrasound (P = 0.04) findings. CONCLUSIONS: The length of single cores sampled by sextant biopsy can vary more than 3.6-fold and represents a quality assurance consideration. The effect of length on cancer or nonbenign detection was maximal at the prostatic apex where the cores were shortest.
Subject(s)
Biopsy, Needle , Prostate/pathology , Prostatic Neoplasms/pathology , Humans , Logistic Models , Male , Retrospective StudiesABSTRACT
Sialuria is a rare inborn error of metabolism in which excessive free sialic acid (N-acetylneuraminic acid, NeuAc) is synthesized. A defect in the feedback inhibition of UDP-N-acetylglucosamine (UDP-GlcNAc) 2-epimerase by the end-product of the sialic acid synthetic pathway, CMP-NeuAc, is the mechanism underlying this overproduction. Recent evidence suggests that sialuria is an autosomal dominant disorder. Only five patients have been documented to have such an enzymatic defect. We report a longitudinal study of one of the original sialuria patients, to age 11 years. Although he has coarse features and massive hepatomegaly, he has shown normal growth and relatively normal development. Pulmonary function testing showed minimal small airway obstruction. At 11 years, he developed intermittent abdominal pain and transient transaminase elevation above his baseline. Sialuria should be considered in the differential diagnosis of a patient with a phenotype suggestive of a mucopolysaccharidosis or oligosaccharidosis in the absence of developmental regression or prominent dysostosis multiplex. We recommend close monitoring of liver and pulmonary function in sialuria patients.
Subject(s)
Escherichia coli Proteins , Sialic Acid Storage Disease/diagnosis , Abdominal Pain , Allosteric Site/genetics , Carbohydrate Epimerases/genetics , Diagnosis, Differential , Feedback , Hepatomegaly , Humans , Infant , Liver/physiopathology , Longitudinal Studies , Lung/physiopathology , Lung/ultrastructure , Male , Microscopy, Electron , Mutation, Missense , Sialic Acid Storage Disease/genetics , Sialic Acid Storage Disease/physiopathologyABSTRACT
"French type" sialuria, a presumably dominant disorder that, until now, had been documented in only five patients, manifests with mildly coarse facies, slight motor delay, and urinary excretion of large quantities (>1 g/d) of free N-acetylneuraminic acid (NeuAc). The basic defect consists of the very rare occurrence of failed feedback inhibition of a rate-limiting enzyme, in this case uridinediphosphate-N-acetylglucosamine (UDP-GlcNAc) 2-epimerase, by a downstream product, in this case cytidine monophosphate (CMP)-NeuAc. We report a new patient with sialuria who has a heterozygous G-->A substitution in nucleotide 848 of the epimerase gene, which results in an R266Q change. The proband's other allele, as expected, had no mutation. However, the heterozygous R266Q mutation was detected in the patient's mother, who has similarly increased urinary levels of free NeuAc, thereby confirming, for the first time, the dominant mode of inheritance of this inborn error. The biochemical diagnosis of the proband was verified by the greatly increased level of free NeuAc in his cultured fibroblasts, the NeuAc distribution, mainly (59%) in the cytoplasm, and by the complete failure of 100 microM CMP-NeuAc to inhibit UDP-GlcNAc 2-epimerase activity in the mutant cells. These findings call for expansion of the phenotype to include adults and for more-extensive assaying of free NeuAc in the urine of children with mild developmental delay. The prevalence of sialuria is probably grossly underestimated.
Subject(s)
Carbohydrate Epimerases/genetics , Escherichia coli Proteins , Genes, Dominant/genetics , Metabolism, Inborn Errors/enzymology , Metabolism, Inborn Errors/genetics , Sialic Acids/urine , Adult , Base Sequence , Carbohydrate Epimerases/antagonists & inhibitors , Carbohydrate Epimerases/metabolism , Child , Child, Preschool , Cytidine Monophosphate N-Acetylneuraminic Acid/metabolism , Cytoplasm/metabolism , Developmental Disabilities/enzymology , Developmental Disabilities/genetics , Developmental Disabilities/physiopathology , Developmental Disabilities/urine , Feedback , Female , Fibroblasts , France , Heterozygote , Humans , Infant , Infant, Newborn , Male , Metabolism, Inborn Errors/physiopathology , Metabolism, Inborn Errors/urine , Middle Aged , Molecular Sequence Data , Mutation, Missense/genetics , Pedigree , Sialic Acids/analysis , Uridine Diphosphate N-Acetylglucosamine/metabolismABSTRACT
Sialuria, a disorder of sialic acid (NeuAc) metabolism characterized by increased free NeuAc in the cytoplasm of cells, is due to failure of CMP-Neu5Ac to feedback inhibit UDP-N-acetylglucosamine (UDP-GlcNAc) 2-epimerase. We now describe the fifth patient in the world with sialuria, a 7-year-old Portuguese girl with developmental delay, hepatomegaly, coarse facies, and urinary excretion of 19 micromol of free NeuAc/mg creatinine. The patient's fibroblasts stored excess free NeuAc in the cytosolic fraction, and fibroblast UDP-GlcNAc 2-epimerase activity was only 26% inhibited by 100 microM CMP-Neu5Ac (normal, 79%). The patient's UDP-GlcNAc 2-epimerase gene displayed an R266Q mutation in only one allele, consistent with known sialuria mutations and with the proposed dominant nature of this disorder. Extensive description of sialuria patients will help to define the clinical and biochemical spectrum of this disease.
Subject(s)
Escherichia coli Proteins , Metabolism, Inborn Errors/enzymology , Metabolism, Inborn Errors/genetics , Sialic Acids/urine , Abnormalities, Multiple/enzymology , Abnormalities, Multiple/genetics , Carbohydrate Epimerases/antagonists & inhibitors , Carbohydrate Epimerases/genetics , Carbohydrate Epimerases/metabolism , Cells, Cultured , Child , Cytidine Monophosphate N-Acetylneuraminic Acid/pharmacology , Female , Fibroblasts/enzymology , Fibroblasts/metabolism , Humans , Intellectual Disability/enzymology , Intellectual Disability/genetics , Metabolism, Inborn Errors/pathology , Metabolism, Inborn Errors/urine , N-Acetylneuraminic Acid/metabolism , Point Mutation , Sialic Acids/metabolism , Subcellular Fractions/enzymology , Subcellular Fractions/metabolismABSTRACT
Sialuria is a rare inborn error of metabolism characterized by cytoplasmic accumulation and increased urinary excretion of free N-acetylneuraminic acid (NeuAc, sialic acid). Overproduction of NeuAc is believed to result from loss of feedback inhibition of uridinediphosphate-N-acetylglucosamine 2-epimerase (UDP-GlcNAc 2-epimerase) by cytidine monophosphate-N-acetylneuraminic acid (CMP-Neu5Ac). We report the cloning and characterization of human UDP-GlcNAc 2-epimerase cDNA, with mutation analysis of three patients with sialuria. Their heterozygote mutations, R266W, R266Q, and R263L, indicate that the allosteric site of the epimerase resides in the region of codons 263-266. The heterozygous nature of the mutant allele in all three patients reveals a dominant mechanism of inheritance for sialuria.
Subject(s)
Carbohydrate Epimerases/genetics , Carrier Proteins , Metabolism, Inborn Errors/genetics , Mutation , N-Acetylneuraminic Acid/urine , Allosteric Site , Amino Acid Sequence , Base Sequence , Carbohydrate Epimerases/metabolism , Child, Preschool , DNA, Complementary , Female , Humans , Male , Metabolism, Inborn Errors/enzymology , Metabolism, Inborn Errors/urine , Molecular Sequence DataSubject(s)
Ileal Neoplasms/diagnostic imaging , Neurofibromatoses/diagnostic imaging , Adult , Barium Sulfate , Carcinoma, Squamous Cell/pathology , Contrast Media , Enema , Female , Humans , Neoplasm Staging , Neoplasms, Multiple Primary , Tomography, X-Ray Computed , Uterine Cervical Neoplasms/pathologyABSTRACT
The effects of air pollutants on forests around the eastern part of the Gulf of Finland were studied by measurement of the sulphur and calcium content of pine needles and evaluation of the ecological conditions of pine forests. Several parameters for pine trees and their needles were chosen as well as the species composition and condition of epiphytic lichens. Very high pine needle S- and Ca-contents were measured in the vicinity of the Narva and Slantsy plants. In this region both the acid and basic pollutant load is massive, partly neutralizing each other. It is suggested that the total load will, sooner or later, cause unexpected environmental damage. Wide 'lichen desert' areas were detected around Narva and Slantsy. Near the margins of these areas extraordinary epiphytes on pines were observed namely Xanthoria parietina (L.) Th.Fr. and red-coloured green alga Trentepohlia umbrina. They are regarded as indicators of alkaline pollution. The lowest pine needle S- and Ca-contents of the study area were measured in south-eastern Finland. The condition of pine forests and their needles was, however, better on the neighbouring Karelian Isthmus although the species number of epiphytic lichens was very low and the condition of the lichens was poor. It is suggested that these most sensitive indicators of air pollutants are damaged by pollutants from St Petersburg and Narva. Vast virgin forests of the Karelian Isthmus act as pollutant sinks reducing the effect of pollutants on trees. On the Finnish side intensive forest management has been carried on for many decades making forests and trees more sensitive to pollutants.
ABSTRACT
Aspartylglucosaminidase (AGA, EC 3.5.1.26) is an essential enzyme in the degradation of asparagine-linked glycoproteins. In man, deficient activity of this enzyme leads to aspartylglucosaminuria (AGU), a recessively inherited lysosomal storage disease. Here we used affinity-purified polyclonal antibodies against the native AGA and its denatured subunits to establish the molecular structure and intracellular location of the enzyme in normal and AGU fibroblasts. Inactivation of the enzyme was found to coincide with the dissociation of the heterodimeric enzyme complex into subunits. Although the subunits were not linked by covalent forces, the intrapolypeptide disulphide bridges were found to be essential for the normal function of AGA. AGA was localized into lysosomes in control fibroblasts by both immunofluorescence microscopy and immuno-electron microscopy, whereas in AGU cells the location of antigen was different, suggesting that, owing to the mutation, a missing disulphide bridge, most of the enzyme molecules get retarded in the cis-Golgi region and most probably face intracellular degradation.
Subject(s)
Aspartylglucosaminuria , Aspartylglucosylaminase/metabolism , Fibroblasts/enzymology , Aspartylglucosylaminase/immunology , Blotting, Western , Cells, Cultured , Electrophoresis, Polyacrylamide Gel , Humans , Immunohistochemistry , Leukocytes/enzymology , Microscopy, Fluorescence , Microscopy, Immunoelectron , Peptide Fragments/immunology , Peptide Fragments/metabolism , Precipitin Tests , TemperatureABSTRACT
Sialuria is a rare inborn error of metabolism caused by excessive synthesis of sialic acid (N-acetylneuraminic acid, NeuAc). Fibroblasts cultured from the three known cases of sialuria contained 70-200-fold increases in soluble sialic acid, but normal concentrations of bound sialic acid. The sialic acid appeared in the cytosolic fraction of the cells on differential centrifugation, and was susceptible to borohydride reduction, suggesting that accumulated sialic acid was in the form of NeuAc and not CMP-NeuAc. In biochemical studies, CMP-NeuAc (50 microM) inhibited the UDP-N-acetylglucosamine (UDP-GlcNAc) 2-epimerase of normal fibroblasts by 84-100%, but inhibited the epimerase from sialuria cells by only 19-31%. Feeding sialuria cells up to 5 mM D-glucosamine for 72 h increased free sialic acid content 20-60%, but normal cells were unaffected by this treatment. Cytidine feeding (5 mM, 72 h) reduced the NeuAc content of sialuria cells, initially 112, 104, and 266 nmol/mg protein, by 63-71 nmol/mg protein; CMP-NeuAc concentrations, initially 4, 2, and 5 nmol/mg protein, increased by 14-33 nmol/mg protein. Consequently, the total cellular content of soluble sialic acid (NeuAc + CMP-NeuAc) was lowered 14-46% by cytidine feeding. The inheritance pattern of sialuria has not been determined. However, cells from both parents of one sialuria patient contained normal concentrations of free sialic acid, and the parental epimerase activity also responded normally to CMP-NeuAc. We conclude that the basic biochemical defect in all known cases of sialuria is a failure of CMP-NeuAc to feedback-inhibit UDP-GlcNAc 2-epimerase and cytidine feeding can lower the intracellular soluble sialic acid concentration of sialuria cells.
Subject(s)
Metabolism, Inborn Errors/metabolism , Sialic Acids/metabolism , Child, Preschool , Chromatography, High Pressure Liquid , Cytidine/pharmacology , Female , Fibroblasts/metabolism , Humans , Male , Metabolism, Inborn Errors/urine , N-Acetylneuraminic Acid , Sialic Acids/urineABSTRACT
The renal handling of free sialic acid, a negatively charged sugar, was investigated in normal humans and in patients with impaired sialic acid metabolism or impaired renal function. A sensitive assay for sialic acid, based upon the specific degradation of free sialic acid by N-acetylneuraminic acid aldolase, was developed to measure small amounts of sialic acid in human plasma. Using this assay on plasma from patients with disorders of sialic acid metabolism, we determined that the fractional excretion of sialic acid was maintained at approximately 98% over a wide range of filtered loads, i.e., from 40 to 2617 nmoles/minute. In other patients with different degrees of renal insufficiency, free sialic acid clearance varied directly with creatinine clearance, indicating filtration of this sugar by renal glomeruli. In patients with renal Fanconi syndrome, the urinary excretion of free sialic acid was independent of the severity of the generalized tubular defect, indicating that sialic acid was not reabsorbed by renal tubular cells. These findings indicate that sialic acid is filtered but not reabsorbed by the human kidney, in contrast with the handling of other sugars known to be reabsorbed by renal tubular cells. In addition, three of eight patients with Salla disease, a storage disorder due to impaired lysosomal transport of free sialic acid, were found to have reduced creatinine clearances, but all Salla disease patients had entirely normal renal tubular function.
Subject(s)
Carbohydrate Metabolism, Inborn Errors/metabolism , Kidney Diseases/metabolism , Kidney/metabolism , Sialic Acids/metabolism , Circadian Rhythm , Fanconi Syndrome/metabolism , Humans , N-Acetylneuraminic Acid , Sialic Acids/blood , Sialic Acids/urineABSTRACT
Separation by h.p.l.c. and pulsed amperometric detection were employed to measure glucuronic acid (GlcUA) and other acidic monosaccharides in fibroblasts from patients with infantile free sialic acid storage disease (ISSD) and Salla disease. These lysosomal storage disorders result from defective carrier-mediated transport of free N-acetylneuraminic acid (NeuAc) out of cellular lysosomes. Three Salla disease fibroblast strains stored approx. 0.4 nmol of free GlcUA/mg of cell protein, whereas four ISSD strains stored approx. 5 nmol GlcUA/mg (normal is undetectable). The GlcUA content of the mutant cell strains, which by differential centrifugation and Percoll gradient fractionation was localized to the lysosomes, averaged 5% of the free NeuAc content of the cells. N-Glycolylneuraminic acid (NeuGc) also accumulated in ISSD cells, but only when they were grown in the presence of fetal calf serum, which contains abundant NeuGc. No other acidic monosaccharides were detected in any of the mutant cell strains. GlcUA egress studies revealed that 56% of the initial GlcUA content was lost from normal granular fractions after 2 min at 37 degrees C. For similarly loaded ISSD granular fractions, virtually no GlcUA was lost even after 6 min. The results indicate that GlcUA is recognized and transported by the lysosomal NeuAc carrier, and that GlcUA transport is impaired in the lysosomal disorders of free NeuAc storage.
Subject(s)
Glucuronates/pharmacokinetics , Lysosomes/metabolism , Metabolism, Inborn Errors/metabolism , Sialic Acids/metabolism , Biological Transport , Cells, Cultured , Fibroblasts/metabolism , Glucuronates/analysis , Glucuronic Acid , Humans , Metabolism, Inborn Errors/genetics , Mutation , Neuraminic Acids/analysis , Neuraminic Acids/pharmacokinetics , Sugar Acids/analysisABSTRACT
Sialuria is a rare inborn error of metabolism, the hallmarks of which are moderate developmental retardation, coarse facial features, and an enormous amount of free N-acetylneuraminic acid (sialic acid) in the urine. Until now, the basic biochemical defect in this disorder has remained uncertain. In this report, the activity of the rate-limiting enzyme in the biosynthesis of sialic acid has been measured directly in whole cell lysates by a highly sensitive assay. With this technique, the basic defect in sialuria has been identified unequivocally as the loss of feedback control of uridine diphosphate N-acetylglucosamine 2-epimerase by cytidine monophosphate N-acetylneuraminic acid with resultant overproduction of sialic acid.
Subject(s)
Carbohydrate Metabolism, Inborn Errors/metabolism , Carrier Proteins , Sialic Acids/urine , Carbohydrate Epimerases/metabolism , Cells, Cultured , Feedback , Fibroblasts/metabolism , Hexosamines , Humans , Kinetics , N-Acetylneuraminic Acid , Reference Values , Skin/metabolismABSTRACT
Egress of free NeuAc from normal lysosome-rich granular fractions was assessed at NeuAc concentrations of up to 221 pmol/hexosaminidase unit, achieved by exposure of growing fibroblasts to 40-125 nM N-acetylmannosamine for up to 7 days. The normal velocity of NeuAc egress increased with NeuAc loading and with temperature, exhibiting a Q10 of 2.4, characteristic of carrier-mediated transport. Fibroblasts cultured from five patients with infantile free sialic acid storage disease (ISSD) contained approximately 139 nmol of free NeuAc/mg of whole cell protein, or 100 times the normal level. Differential centrifugation, as well as density gradient analysis using 25% Percoll, showed that the stored NeuAc cosedimented with the lysosomal enzyme beta-hexosaminidase. The velocity of appearance of free NeuAc outside ISSD granular fractions was negligible, even at initial loading levels of up to 3500 pmol/hexosaminidase unit. The lack of egress from ISSD granular fractions was found for both endogenous and N-acetylmannosamine-derived NeuAc. Fibroblasts from ISSD parents did not accumulate excess free NeuAc and did not display a velocity of NeuAc egress significantly different from normal. The defect in ISSD, like that in Salla disease, appears to be an impairment of carrier-mediated transport of free NeuAc across the lysosomal membrane. Clinical and biochemical differences between Salla disease and ISSD may reflect differences in the amount of residual NeuAc transport capacity.