Form Of CK Research Articles

Small-world features of real-world networks

It is well known that there are a large number of complex networks that have vertex-degree distributions in a power-law form of ck−γ, where k is the degree variable and c and γ are scaling and exponent constants. Recently, we found that it is effective to reveal the underlying mechanism of power-law formation in real-world networks by analyzing their vertex-degree sequences. We showed before that, for a scale-free network of size N, if its vertex-degree sequence is k 2 2 l , where {k 1 , k 2 , …, k l } is the set of all non-equal vertex degrees in the network, and if its power exponent satisfies γ > 1, then the length l of the above vertex-degree sequence is of order log N. We underline that this conclusion is important, which proves that the length of the vertex-degree sequence is a fundamental characteristic of a scale-free network. In this paper, we further investigate complex networks with more general distributions and we prove that the same conclusion about the vertex-degree sequences holds even for non-network type of complex systems. We thereby conclude that real-world networks typically possess small-world features. We support this conclusion by verifying a large number of real-world networks and systems. To that end, we discuss some potential applications of the new finding in various fields of science, engineering and society, demonstrating that the conclusion is important with many real applications.

Characterizing general scale-free networks by vertex-degree sequences.

Many complex networks possess a scale-free vertex-degree distribution in a power-law form of ck(-γ), where k is the vertex-degree variable and c and γ are constants. To better understand the mechanism of the power-law formation in scale-free networks, it is important to understand and analyze their vertex-degree sequences. We had shown before that, for a scale-free network of size N, if its vertex-degree sequence is k1 <k2<⋯<kl, where {k1,k2,...,kl} is the set of all non-equal vertex degrees in the network, and if its power exponent satisfies γ>1, then the length l of the vertex-degree sequence is of order log N. In the present paper, we further study complex networks with a more general vertex-degree distribution, not restricted to the power-law, and prove that the same conclusion holds as well. In addition, we verify the new result by real data from a large number of real-world examples. We finally discuss some potential applications of the new finding in various fields of science, technology, and society.

Regularity for the CR vector bundle problem II

We derive a Ck+ 2 Holder estimate for Pφ, where P is either of the two solution operators in Henkin’s local homotopy formula for ∂b on a strongly pseudoconvex real hypersurface M in Cn , φ is a (0, q)-form of class Ck on M , and k ≥ 0 is an integer. We also derive a Ca estimate for Pφ, when φ is of class Ca and a ≥ 0 is a real number. These estimates require that M be of class Ck+ 2 , or Ca+2, respectively. The explicit bounds for the constants occurring in these estimates also considerably improve previously known such results. These estimates are then applied to the integrability problem for CR vector bundles to gain improved regularity. They also constitute a major ingredient in a forthcoming work of the authors on the local CR embedding problem. Mathematics Subject Classification (2010): 32V05 (primary); 32A26, 32T15 (secondary).

Phosphoglycerate mutase, 2,3-bisphosphoglycerate phosphatase and creatine kinase activity and isoenzymes in human brain tumours

The distribution of phosphoglycerate mutase (EC 5.4.2.1, PGM), 2,3-bisphosphoglycerate phosphatase (EC 3.1.3.13, BPGP) and creatine kinase (EC 2.7.3.2, CK) activity and isoenzymes in various regions of adult human brain and in brain tumours (astrocytomas, anaplastic astrocytomas, glioblastomas and meningiomas) has been determined using electrophoresis. PGM and cytosolic CK exist in mammalian tissues as three isoenzymes that result from the homodimeric and heterodimeric combinations of two subunits [types M (muscle) and B (brain)] coded by separated genes. In addition, a dimeric form and an octameric form of mitochondrial CK exist in mammals. Type BB-PGM was the major PGM isoenzyme found in normal brain, although type MB-PGM and type MM-PGM were also detected. All brain tumours possessed lower PGM activity than normal brain, and meningiomas showed higher BPGP activity. In astrocytic tumours, the proportion of type MB- and type MM-PGM decreased, and in meningiomas these isoenzymes were not detected. Type BB-CK and mitochondrial CK were the only CK isoenzymes detected in normal brain. Astrocytomas possessed lower CK activity than anaplastic astrocytomas and glioblastomas and, in addition, tended to possess lower CK content than normal brain. No qualitative changes of the normal CK isoenzyme pattern were observed in the tumours.

Cytokeratin 8 released by breast carcinoma cells in vitro binds plasminogen and tissue-type plasminogen activator and promotes plasminogen activation.

Cell-surface activation of plasminogen may be important in diseases that involve cellular migration, including atherosclerosis and tumour invasion/metastasis. Cytokeratin 8 (CK 8) has been identified as a plasminogen-binding protein expressed on the external surfaces of hepatocytes and breast carcinoma cells [Hembrough, Vasudevan, Allietta, Glass and Gonias (1995) J. Cell Sci. 108, 1071-1082]. In this investigation, we demonstrate that a soluble form of CK 8 is released into the culture medium of breast cancer cell lines. The released CK 8 is in the form of variably sized polymers that bind plasminogen and promote the activation of [Glu1]plasminogen and [Lys78]plasminogen by single-chain tissue-type plasminogen activator (sct-PA). To assess the mechanism by which CK 8 promotes plasminogen activation, CK 8 was purified from rat hepatocytes and immobilized in microtitre plates. Immobilized CK 8 bound 125I-plasminogen and 125I-sct-PA in a specific and saturable manner. The KDs were 160 +/- 40 nM and 250 +/- 48 nM, respectively. Activation of plasminogen bound to immobilized CK 8 was accelerated compared with plasminogen in solution, as determined using a coupled-substrate fluorescence assay and SDS/PAGE. The ability of CK 8 to promote plasminogen activation may be important in the pericellular spaces surrounding breast cancer cells and at the cell surface.

APPARENT ELEVATION OF SERUM CK‐MB NOT DUE TO ACUTE MYOCARDIAL INFARCTION

SUMMARYAn increased serum level of the MB isoenzyme of creatine kinase (CK‐MB) is a useful marker for acute myocardial infarction. Although described extensively in clinical chemistry literature, there is little information in standard medical references about false positives for this test. We report two cases where high levels of measured CK‐MB activity were in fact due to another form of CK, associated with internal malignancy.

Intracellular alterations of the creatine kinase isoforms in brains of schizophrenic patients

Postmortem brain tissues of schizophrenic patients were found to contain 5-10 times less water-soluble creatine kinase (BB CK) and 1.5-3 times less mitochondrial creatine kinase as compared to control. The major part of BB CK in schizophrenic brain tissues, contrary to control, was found to be insoluble in water (particulate form of BB CK) and could be extracted from brain tissue with strong denaturating agents. The particulate form of BB CK did not have any enzymatic activity but activity was found after the solubilization of this isoenzyme. The observed BB CK translocation into the particulate inactive form and the decrease of mitochondrial CK content to schizophrenic brains may reflect changes in the synthesis and the utilization of creatine phosphate.

Developmental changes in fiber type-related proteins in soleus, rectus femoris, and heart muscles of normal and dystrophic mice

By using sensitive enzyme immunoassay methods, several isoenzymes or isoproteins related to muscle fiber types were determined in the soleus (SOL), rectus femoris (RFM), and heart muscles of normal and dystrophic ( dy/dy) mice of various ages. In normal adult mice, the S-100 protein α subunit (S-100α) and creatine kinase B subunit (CK-B), which are known to be distributed predominantly in type I muscle fibers as S-100a 0 (αα form of the S-100 protein) and the MB form of CK, respectively, were enhanced several-fold in the “aerobic” SOL muscle as compared with the “anaerobic” RFM muscle. The enolase β subunit (β-enolase) and the M subunit of CK (CK-M) were present in the RFM at levels increased several-fold compared to levels in the SOL of the same mice. In age-matched dystrophic adult mice, however, the compositions of these muscle-related proteins in the RFM muscle shifted to those of the SOL muscle: S-100α and CK-B increased several-fold, β-enolase and CK-M decreased markedly as compared with the normal RFM. On the other hand, the SOL and heart muscles of dystrophic mice showed only a slight increase of CK-B or decrease of CK-M. In the RFM of 3-week-old dystrophic mice, S-100α and β-enolase levels were similar to those in the RFM of control littermates, but a significant increase of CK-B and a decrease of CK-M were already observed in this early stage of dystrophy. These results indicate that changes in muscle-related proteins in the dystrophic muscles are apparently displayed mainly in the anaerobic muscles and feature a decrease in type II fiber-related proteins and a relative increase in type I fiber-related proteins. The mechanism of these changes in dystrophic mice is discussed.

Tetrathionate-blocked creatine kinase as a substrate for human plasma ‘creatine kinase conversion factor’

‘Creatine kinase conversion factor’ has been partially purified from whole plasma. The preparation has the ability to convert slowly migrating, native CK-MM into a faster electrophoretic form through a form of intermediate mobility. These changes are accompanied by a loss in CK activity. The rates of both electrophoretic conversion and loss of enzyme activity are reduced or prevented by the presence of 2-mercaptoethanol, EDTA, or by formation of the creatine-MgADP-nitrate dead-end complex. When the thiol group essential for enzyme activity found at the CK active site is first blocked by treatment with potassium tetrathionate, full activity may be retained under conditions that fully convert CK to the faster electrophoretic forms. The conversion factor activity was not inhibited by a pre-incubation with the protease inhibitor, PMSF and the converted form of CK showed no evidence of proteolytic cleavage. The molecular basis of the chemical alteration caused by the conversion is discussed.

Macro creatine kinase types 1 and 2: clinical significance in neonates and children as compared with adults.

We examined the case histories of seven pediatric patients (ages four days to 12 years) whose sera showed significant activities of "macro" creatine kinase (CK; EC 2.7.3.2): two cases of macro CK type 1 (CK-BB isoenzyme bound to IgG) and five cases of macro CK type 2 (polymeric complexes of mitochondrial CK). The diagnoses of the two children with macro CK type 1 were similar to those in 55 adult patients with this form of CK found earlier during screening of a population of 5000. Macro CK type 1 has generally been noted only in older women; this is the first report of it in children. In four of the five cases of macro CK type 2 we found in children, myocardial muscle damage was clinically evident. In contrast, the 26 cases of adults with macro CK type 2 found during the same screening generally had neoplasms, most with metastases to the liver. We suggest that the finding of macro CK type 2 is an indicator of cellular necrosis; in pediatric cases with myocardial damage the associated conditions may be reversible but in adults with malignancies the finding is associated with an extremely poor prognosis.

Mitochondrial CK (EC 2.7.3.2) in the human heart

CK m, a mitochondrial form of CK, can be isolated from human cardiac muscle. It occurs in two forms, separable on the basis of the difference in net charge. Both molecules have a dimeric structure and consist of two identical subunits. Upon incubation in a human serum, the CK isozyme with the faster cathodal mobility is rapidly converted into the slower form, which has an isoelectric point of 6.94. This makes it impossible to separate this slow CK M form from CK MM (isoelectric point: 6.86) by means of any method that separates on a basis of differences in net charge. Furthermore the two molecules have an almost identical molecular weight. The only difference between the two molecules we have been able to detect is the different behaviour against anti-M antibodies.

Subcellular compartmentation of creatine kinase isoenzymes in guinea pig heart.

In an attempt to determine whether a subcellular compartmentation of creatine kinase exists and if so, whether there is a different distribution of the 3 isoenzymes of CK in the cell, studies were carried out with the guinea pig heart which had been subfractionated by either isopycnic density gradient centrifugation or differential pelleting. Isoenzyme analysis of CK in the isolated subcellular fractions by electrophoresis on agarose gels, revealed that the MM isoenzyme occurred in the cytosol, myofibrils, and the microsomes while the MB isoenzyme (which is cardio-specific) was only found in the cytosol. Trace amounts of the BB isoenzyme were detected in the cytosol. Considerable CK activity was associated with the mitochondria, this did not represent the MM, the MB, or the BB isoenzymes but was a distinct and additional mitochondrial-specific form of CK. PH optima and kinetic studies were carried out to characterise and distinguish the mitochondrial isoenzyme from other CK isoenzyme activity. The evidence for a differential compartmentation of MM, MB, BB, and mitochondrial CK is discussed in relation to their possible cellular roles.