Biomedical subjects

K Wei

Publications and source records attributed to K Wei.

At least 55 records · Page 3Linked to original sources

PubMed1999

Identification of possible quantitative trait loci responsible for hyperglycaemia after 70% pancreatectomy using a spontaneously diabetogenic rat.

The Otsuka Long-Evans Tokushima Fatty (OLETF) rat is an animal model for obese-type non-insulin-dependent diabetes mellitus (NIDDM) in humans. The OLETF rat exhibits sustained hyperglycaemia after partial pancreatectomy, while the normal control rat does not. This difference is thought to be genetically determined and to be caused by impairment of beta-cell regrowth, a possible event involved in the pathogenesis of NIDDM. Our investigation was designed to identify quantitative trait loci (QTL) responsible for post-pancreatectomy hyperglycaemia by performing a genome-wide scan in an F2 intercross obtained by mating the OLETF and Fischer-344 (F344) rats. We have identified three possible QTL on rat chromosomes (Chrs) 3, 14 and 19 that account for a total of approximately 75% of the genetic variance in the F2. For the QTL on Chr 14, the OLETF allele corresponds with increased glucose levels, as expected. Surprisingly, for the QTL on Chr 19, the F344 allele corresponds with increased glucose levels. The Chr 3 QTL exhibits heterosis, heterozygotes showing significantly higher glucose levels than OLETF or F344 homozygotes. We also found evidence for interaction (epistasis) between the QTL on Chrs 14 and 19.

Animals↗

PubMed1999

A canine model of chronic ischemic cardiomyopathy: characterization of regional flow-function relations.

The controversy regarding the mechanism(s) of left ventricular (LV) dysfunction in chronic coronary artery disease is, in part, related to the lack of an appropriate animal model for this condition. We have developed such a model by placing Ameroid constrictors on proximal portions of coronary arteries in dogs who were euthanized (mean of 6 wk) after the development of severe global LV dysfunction noted on two-dimensional echocardiography. The LV end-systolic size nearly doubled (P < 0.001) over the observation period, and the percent change in LV size from end diastole to end systole decreased by >50% (P < 0.001). Regional dysfunction was noted in 23 of 24 myocardial beds analyzed within regions showing no gross evidence of infarction. In 10 of these beds, severe dysfunction was noted without a decrease in radiolabeled microsphere-derived myocardial blood flow (MBF). In 13 myocardial beds, decrease in function was associated with a decrease in MBF (P < 0.001), with close coupling noted between percent wall thickening and MBF. In the beds that exhibited an ultimate decrease in MBF, the decrease in function preceded the decrease in MBF. In conclusion, we describe chronic LV dysfunction in a canine model of multivessel stenosis that closely mimics chronic ischemic LV dysfunction in humans. Whereas regional function is severely reduced in this model, MBF is varied in different segments and at different times during the observation period. These results provide new insights regarding flow-function relations in chronic ischemic LV dysfunction.

Animals↗

PubMed1999

Role of capillaries in determining CBF reserve: new insights using myocardial contrast echocardiography.

To define the role of capillaries in the control of coronary blood flow (CBF) reserve, we developed a model of the coronary circulation and evaluated experimental data in its context. Our model comprised three compartments connected in series (arterial, capillary, and venous), each with its own resistance. The resistance in each vascular compartment was derived from the model based on hemodynamic data obtained in nine dogs during baseline and stenosis, both at rest and during hyperemia. The capillary hydrostatic pressure was assumed to be constant in all stages. Although in the absence of stenosis, the contribution of capillaries to total myocardial vascular resistance was only 25 +/- 5% at rest, it increased to 75 +/- 14% during hyperemia, despite the total myocardial vascular resistance decreasing by 51 +/- 13%. In the presence of a noncritical stenosis, total myocardial vascular resistance decreased by 22 +/- 10% at rest, with no change in capillary resistance. During hyperemia, total myocardial vascular resistance increased by 58 +/- 50% in the presence of the noncritical stenosis. In this situation, because arteriolar and venular resistances were already minimal, the increase in myocardial vascular resistance was due to increased capillary resistance, making it the predominant source (84 +/- 8%) of total myocardial vascular resistance. Myocardial video intensity (VI) on myocardial contrast echocardiography (MCE), which reflects capillary blood volume, decreased distal to the stenosis during hyperemia. In the presence of a flow-limiting stenosis at rest, myocardial VI also decreased, indicating that decrease in CBF was associated with an increase in capillary resistance. Our findings also provide an alternative explanation for the critical coronary closing pressure. Thus, contrary to previously held notions, capillaries play a vital role in the regulation of CBF.

Animals↗

PubMed1999

Identification of the chondrogenic-inducing activity from bovine dentin (bCIA) as a low-molecular-mass amelogenin polypeptide.

Dentin extracellular matrix has been shown to contain components capable of inducing chondrogenesis and osteogenesis at ectopic sites when implanted in vivo, and chondrogenesis in cultures of embryonic muscle-derived fibroblasts (EMF) in vitro. The polypeptide responsible, called the chondrogenic-inducing agent (CIA), has been isolated from a 4.0-M guanidinium hydrochloride extract of demineralized bovine dentin matrix. Following Sephacryl S-100 chromatography, CIA activity was identified in fractions by assay for uptake of [35S]-SO4 into proteoglycan by the EMF after 24 hrs in culture. The active fraction induced the EMF to produce type II collagen mRNA and decrease production of type I collagen mRNA after 5 days in culture. The EMF + CIA, cultured for 4 to 7 wks, formed toluidine-blue- and alizarin-red-stainable nodules, indicative of chondrogenic induction. In vivo implants in rat muscle with collagen carrier produced ectopic bone after 7 wks. The CIA was brought to near-homogeneity by reverse-phase high-performance liquid chromatography, tested at each step by EMF [35S]-SO4-incorporation assays. The CIA components had masses in the ranges of 6000 to 10,000 Da by both mass spectroscopy and gel electrophoresis. The CIA amino acid composition, NH2-terminal, and internal amino acid sequences were determined. These data showed unequivocally that the CIA peptides were derived from bovine amelogenin. The peptides contain the amino-terminal portion of the bovine amelogenin. The presence of these chondrogenic/osteogenic amelogenin-polypeptides in dentin matrix leads us to hypothesize that they may be involved in epithelial-mesenchymal signaling during tooth development interactions-the first time a function has been indicated for these molecules.

Amelogenin↗

PubMed1999

Identification of a locus for susceptibility to renal cell carcinoma in the Long-Evans Cinnamon rat.

The Long-Evans Cinnamon (LEC) mutant rat shows higher incidence of renal cell carcinomas induced by a treatment with the chemical carcinogen N-diethylnitrosamine, as compared to the normal control rat. We performed the first genome-wide scan for genes responsible for susceptibility to chemically induced renal cell carcinoma in an F2 intercross obtained by mating the LEC and Fischer-344 (F344) rats. The genotype of 71 (F344 x LEC) F2 progenies was determined with the use of 338 simple sequence length polymorphisms (SSLPs) spread over the genome. The F2 rats which carried renal cell carcinoma were shown to possess the incidence of homozygosity of the LEC allele which is higher than that of the other genotypes at SSLP markers on chromosome 5 (chi2 = 17.5 for D5Rat21). Our linkage analysis has led to the revelation of a novel gene that influences susceptibility to renal cell carcinoma on rat chromosome 5.

Alkylating Agents↗

PubMed1999

An efficient multiplex PCR suitable for large scale typing in linkage mapping.

The dissection of polygenic traits is made possible with the development of microsatellite markers. Linkage study of this kind involves many markers with tens of hundreds of samples. Although typing essentially contains only two steps: PCR amplification and gel electrophoresis. Such work is still heavy when a large number of samples had to be genotyped. Multiplex PCR may reduce the work, but one has to optimize the conditions from marker to marker. Here we describe a dye-compatible multiplex PCR that works under standardized condition without the need to pre-determine the combinational primer concentration and the time-consuming step to mix many samples with gel loading dye before electrophoresis. This successful protocol should greatly reduce the cost and labor for genetic study of polygenic traits.

Animals↗

PubMed1999

Effect of a single bolus of intracoronary basic fibroblast growth factor on perfusion in an ischemic porcine model.

Basic fibroblast growth factor (bFGF) has been shown to induce angiogenesis in various animal models, but the methods of administration used experimentally are not clinically feasible. The objective of this study was to determine whether a single intracoronary bolus injection of bFGF would improve coronary perfusion in a porcine ischemic model that mimics clinical chronic ischemia. A copper coil studded with gold was delivered into the proximal right coronary artery of juvenile Yorkshire pigs and deployed by interventional techniques. After a four-week interval for stenosis maturation, bFGF (100 micrograms) was administered by bolus injection into the left coronary artery in five animals, and vehicle alone was administered in four animals. Angiogenesis and change in right coronary perfusion area were assessed two weeks later by angiography, myocardial contrast echocardiography and immunohistochemistry. The right coronary perfusion area increased significantly after treatment in all but one of the animals that received bFGF but not in any of the controls. Intimal hyperplasia was not induced by bFGF. Capillary density determined histochemically was not different in the two groups. In conclusion, in a porcine ischemic model, bFGF administered by a single bolus intracoronary injection into the contralateral artery improved antegrade perfusion into the ischemic territory although without histological evidence of angiogenesis. This preliminary work merits further investigation.

Animals↗

PubMed1999

[Influence of the synthetic peptide recognized by neutralizing antibody on IFN-induced biological responses].

OBJECTIVE: The influence of synthetic peptide WLDPRH on IFN-induced biologic activity was studied. METHODS: Based on our earlier studies in which two peptides were recognized by neutralizing antibody from the hexapeptide library displayed on the phage, one of the peptides synthesized, with amino acid sequence WLDPRH. RESULTS: Computer-building approach showed that the synthetic peptide WLDPRH exhibited structural homology with LoopAB (29-35), the binding domain of type I IFN receptor. In the competitive ELISA studies, the synthetic peptide WLDPRH in 25 micrograms/ml could inhibit IFN binding neutralizing antibody 4C1. IFN-induced antiviral assay showed that the protective effects of suboptimal dose (20-70 pg/ml) of IFN were increased from 40% to 86% in the presence of the synthetic peptide WLDPRH and 1.4 micrograms/ml of the synthetic peptide WLDPRH was the lowest dose with the best protection. But potentiating effect on IFN-induced growth inhibition was fewer noticeable in 1.4 micrograms/ml of synthetic peptide. CONCLUSION: The results indicated that synthetic peptide WLDPRH can mimic the structure and activity of Loop AB in the IFN molecule and can be applied to immunotherapy as well as the mimic minimolecular design of IFN.

Antibodies, Monoclonal↗

PubMed1998

Spontaneous redistribution after reperfusion: a unique property of AIP 201, an ultrasound contrast agent.

OBJECTIVES: We sought to determine the mechanism of spontaneous redistribution of AIP 201 microbubbles after reperfusion from a single left heart injection performed during coronary occlusion. BACKGROUND: AIP 201, an ultrasound contrast agent consisting of 10-microm sized microbubbles, has demonstrated spontaneous myocardial redistribution in preliminary studies. METHODS: Myocardial video intensity (VI) and radiolabeled microsphere-derived myocardial blood flow (MBF) were measured serially after reperfusion in seven dogs undergoing an AIP 201 injection during coronary occlusion. The behavior of these bubbles was also assessed in the rat spinotrapezius muscle using intravital microscopy (IM), both with and without ultrasound. The effect of ultrasound on these bubbles was also determined in vitro. RESULTS: A spontaneous and gradual increase in myocardial VI was noted after reperfusion, which was related to the magnitude of increase in MBF to that region (r=0.82, p < 0.001). On IM, most of the microbubbles were seen entrapped in small arterioles. Some larger arterioles had aggregates of microbubbles that periodically became dislodged and moved downstream. This behavior was not affected in vivo by ultrasound. In vitro, however, microbubble aggregation was noted only during ultrasound exposure. CONCLUSIONS: The magnitude of redistribution of AIP 201 microbubbles to the reperfused myocardium is related to changes in MBF and occurs from their dislodgement from microbubble aggregates entrapped in large arterioles. In vitro microbubble aggregation seen during ultrasound exposure was not reproduced in vivo. These results may have important implications for studying the effects of interventions in acute coronary syndromes and after coronary artery bypass graft surgery.

Animals↗

PubMed1998

Assessment of transmural distribution of myocardial perfusion with contrast echocardiography.

BACKGROUND: We hypothesized that by using our newly defined method of destroying microbubbles and measuring their rate of tissue replenishment, we could assess the transmural distribution of myocardial perfusion. METHODS AND RESULTS: We studied 12 dogs before and after creation of left anterior descending coronary artery stenoses both at rest and during hyperemia (n=62 stages). Microbubbles were administered as a constant infusion, and myocardial contrast echocardiography (MCE) was performed with the use of different pulsing intervals. The video intensity versus pulsing interval plots derived from each myocardial pixel were fitted to an exponential function: y=A(1-ebetat), where A reflects microvascular cross-sectional area (or myocardial blood volume), and beta reflects mean myocardial microbubble velocity. The product A . beta represents myocardial blood flow (MBF). Average values for these parameters were derived from the endocardial and epicardial regions of interest placed over the left anterior descending coronary artery bed. Radiolabeled microsphere-derived MBF was also measured from the same regions. There was poor correlation between radiolabeled microsphere-derived MBF and A-endocardial/epicardial ratios (EER) (r=0.46). The correlation with beta-EER was better (r=0. 69, P<0.01). The best correlation with radiolabeled microsphere-derived MBF-EER was noted with A . beta-EER (r=0.88, P<0. 01). CONCLUSIONS: The transmural distribution of myocardial perfusion can be accurately assessed with MCE with the use of our newly described method of tissue replenishment of microbubbles after their ultrasound-induced destruction. In the model studied, an uncoupling of the transmural distribution of MBF and myocardial blood volume was observed during reversal of the MBF-EER.

Air↗

PubMed1998

Quantification of myocardial blood flow with ultrasound-induced destruction of microbubbles administered as a constant venous infusion.

BACKGROUND: Ultrasound can cause microbubble destruction. If microbubbles are administered as a continuous infusion, then their destruction within the myocardium and measurement of their myocardial reappearance rate at steady state will provide a measure of mean myocardial microbubble velocity. Conversely, measurement of their myocardial concentration at steady state will provide an assessment of microvascular cross-sectional area. Myocardial blood flow (MBF) can then be calculated from the product of the two. METHODS AND RESULTS: Ex vivo and in vitro experiments were performed in which either flow was held constant and pulsing interval (interval between microbubble destruction and replenishment) was altered, or vice versa. In vivo experiments were performed in 21 dogs. In group 1 dogs (n=7), MBF was mechanically altered in a model in which coronary blood volume was constant. In group 2 dogs (n=5), MBF was altered by direct coronary infusions of vasodilators. In group 3 dogs (n=9), non-flow-limiting coronary stenoses were created, and MBF was measured before and after the venous administration of a coronary vasodilator. In all experiments, microbubbles were delivered as a constant infusion, and myocardial contrast echocardiography was performed using different pulsing intervals. The myocardial video intensity versus pulsing interval plots were fitted to an exponential function: y=A(1-e[-betat]), where A is the plateau video intensity reflecting the microvascular cross-sectional area, and beta reflects the rate of rise of video intensity and, hence, microbubble velocity. Excellent correlations were found between flow and beta, as well as flow and the product of A and beta. CONCLUSIONS: MBF can be quantified with myocardial contrast echocardiography during a venous infusion of microbubbles. This novel approach has potential for measuring tissue perfusion in any organ accessible to ultrasound.

Animals↗

PubMed1998

A major quantitative trait locus co-localizing with cholecystokinin type A receptor gene influences poor pancreatic proliferation in a spontaneously diabetogenic rat.

The Otsuka Long-Evans Tokushima Fatty (OLETF) rat is an animal model for obese-type, non-insulin-dependent diabetes mellitus (NIDDM) in humans. The OLETF rat has poor capacity for pancreatic proliferation, which may be the critical pathogenetic event in NIDDM development. Our investigation was designed to identify quantitative trait loci (QTLs) responsible for poor pancreatic proliferation by examining compensatory proliferation of the pancreatic remnant after partial pancreatectomy and performing a genome-wide scan in an F2 intercross obtained by mating the OLETF and the Fischer-344 (F344) rats. We identified a highly significant QTL on rat Chromosome 14 with a maximum lod score of 16.7, which accounts for 55% of the total variance. The QTL co-localizes with the gene encoding cholecystokinin type A receptor (CCKAR) which is likely to mediate the trophic effect of cholecystokinin on pancreas and is defective in the OLETF rat.

Animals↗

PubMed1998

An integrated genetic map of the rat with 562 markers from different sources.

Genetic maps are the primary resources for genetic study. Genetic map construction was quite difficult in the past decade for lack of polymorphic markers. This situation has been changed since the development of microsatellite markers or simple sequence length polymorphisms (SSLPs) because they are abundant and more polymorphic. Here we report the construction of an integrated genetic map of the rat derived from two F2 intercrosses. A map of 376 markers from 160 (OLETF x F344)F2 progenies and a map of 333 markers from 71 (F344 x LEC)F2 animals are integrated by use of common set of 120 anchor markers chosen to be spaced at an average of 15 cM in the genome. The resulting integrated map with 194 newly developed rat markers from WIBR/MIT CGR, 269 Mit/Mgh markers, 94 Wox markers, and 5 markers of various origins covers the majority of 21 chromosomes of the rat with a total genetic distance of 1797 cM and an average marker spacing of 3.2 cM. The current map provides detailed information for markers from different sources and, therefore, should be helpful to the research community.

Animals↗

PubMed1998

Radioresistant cell strain of human fibrosarcoma cells obtained after long-term exposure to x-rays.

A radioresistant cell strain from human fibrosarcoma HT 1080 has been obtained after prolonged exposure to x-rays for 7 months (2 Gy per day, 5 days per week). This new strain, HT1080R, differs from HT1080 in a significantly increased ability of clonogenical survival, with coefficient alpha decreasing from 0.161 to 0.123 Gy(-1) and coefficient beta decreasing from 0.0950 to 0.0565 Gy(-2). Furthermore, the radioresistance of HT1080R proved to be stable in long-term passaged cultures as well as in frozen samples. Differences between the two cell lines are also observed in the G-banded karyotype; the new cell line shows monosomy of chromosome 17 and loss of 5p+ and 11q+ present in the parental cells. These data suggest that the radioresistance may have been caused by radiation-induced cell mutation and that the resistant cells may have been selected by repeated irradiations. In order to characterize this new strain, the ability of the cells to rejoin DNA double-strand breaks, the cell cycle distribution and the amount of apoptosis after irradiation have been estimated; however, no differences are observed between these two cell strains. Although the mechanism of the elevated radioresistance remains unknown, this pair of cell strains can provide a new model system for further investigations with regard to the mechanisms of cellular radioresistance. The results also show that any type of irradiation similar to the schedules used in radiotherapy can lead to the formation and selection of more radioresistant cell clones in vitro, a phenomenon with possible implications for radiotherapy.

Apoptosis↗

PubMed1998

Basis for detection of stenosis using venous administration of microbubbles during myocardial contrast echocardiography: bolus or continuous infusion?

OBJECTIVES: This study sought to determine the basis of detection of stenosis by myocardial contrast echocardiography using venous administration of microbubbles and to define the relative merits of bolus injection versus continuous infusion. BACKGROUND: The degree of video intensity (VI) disparity in myocardial beds supplied by stenosed and normal coronary arteries can be used to quantify stenosis severity after venous administration of microbubbles. However, the comparative merits of administering microbubbles as a bolus injection or continuous infusion has not been studied. METHODS: Coronary stenoses of varying severity were created in either the left anterior descending or the left circumflex coronary artery in 18 dogs. Imagent US (AF0150) was given as a bolus injection in 10 dogs (Group I) and as both a bolus injection and a continuous infusion in 8 dogs (Group II). For bolus injections, peak VI was derived from time-intensity plots. During continuous infusion, microbubble velocity and microvascular cross-sectional area were derived from pulsing interval versus VI plots. Myocardial blood flow (MBF) was determined using radiolabeled microspheres. RESULTS: During hyperemia, VI ratios from the stenosed versus normal beds correlated with radiolabeled microsphere-derived MBF ratios from those beds for both bolus injections (r = 0.81) and continuous infusion (r = 0.79). The basis for detection of stenosis common to both techniques was the decrease in myocardial blood volume distal to the stenosis during hyperemia. The advantage of continuous infusion over bolus injection was the abolition of posterior wall attenuation and the ability to quantify MBF. CONCLUSIONS: Both bolus injection and continuous infusion provide quantitative assessment of relative stenosis severity. Compared with bolus injection, continuous infusion also allows quantification of MBF and data acquisition without attenuation of any myocardial bed.

Animals↗

PubMed1998

Myocardial perfusion characteristics and hemodynamic profile of MRX-115, a venous echocardiographic contrast agent, during acute myocardial infarction.

We sought to determine whether MRX-115, a new venous echocardiographic contrast agent, could accurately assess risk area during coronary occlusion and infarct size after reperfusion by using novel imaging modalities meant to selectively enhance contrast signals. In 12 open-chest dogs, venous injections of 0.5 ml of MRX-115 were performed during baseline and coronary occlusion and after reperfusion in the presence of exogenous hyperemia. Ultrasound was transmitted at 2 MHz and received at both 2 MHz (fundamental) and 4 MHz (harmonic) frequencies during continuous and intermittent (end-systolic only) imaging. The risk area during coronary occlusion was compared with technetium autoradiography, and the infarct size after reperfusion was compared with postmortem tissue staining. MRX-115 produced no alterations in hemodynamic or pulmonary gas exchange at any stage. During continuous (both fundamental and harmonic) and intermittent fundamental imaging, measurements of perfusion defects were precluded in many dogs by either poor signal enhancement or posterior wall attenuation. By comparison, these measurements were possible during intermittent harmonic imaging in all dogs except one, which had a very small infarction during reflow. Correlation analysis between perfusion defect size on intermittent harmonic imaging and either autoradiographic risk area or postmortem infarct size gave r values of 0.83 and 0.92, respectively. We conclude that MRX-115 is hemodynamically well tolerated and, when imaging is performed after venous injection, can accurately assess regions of hypoperfusion when combined with intermittent harmonic imaging. These results are promising for the use of this approach in patients with acute myocardial infarction.

Animals↗

PubMed1998

Unresponsiveness of CD4-8+/- thymocytes to lectin stimulation in LEC mutant rats.

A mutant strain of rat, LEC, shows a novel arrest of T-cell maturation from CD4+8+ to CD4+8-, but not to CD4-8+ cells in the thymus. The responsible mutant locus is designated the thid, which was acted upon in a recessive manner of inheritance. We found that LEC rat thymocytes failed to respond to interleukin (IL)-1, IL-6 and IL-7 in the presence of the mitogenic lectins, Allo A or concanavalin A (Con A). The unresponsiveness appeared to be due to unresponsiveness to the lectin stimulation rather than because of cytokine stimulation. Normal rat CD4-8+/- (consisting of CD4-8+ and CD4-8- thymocytes), CD4+/-8- (consisting of CD4+8- and CD4-8- thymocytes), and CD4-8- thymocyte subsets normally responded to mitogenic stimulation, while CD4+8+ thymocytes did not. In contrast, all LEC rat CD4-8+/-, CD4+/-8-, CD4-8- and CD4-8+ thymocytes did not respond to the mitogenic stimulation, suggesting that the unresponsiveness of the CD4-8+/- thymocytes seems to be responsible for the unresponsiveness of whole thymocytes in LEC rats. LEC rat CD4-8+/- thymocytes normally expressed Con A receptor (R), lymphocyte function-associated antigen-1 (LFA-1), and CD45, which are thought to be important molecules for lectin stimulation. When backcross rats from (F344xLEC)F1xLEC were examined, the phenotype for the thid mutation correlated with the [3H]thymidine deoxyribose (TdR) incorporation level in response to Con A stimulation; thymocytes from backcross rats showing +/thid phenotype responded to Con A stimulation normally, whereas thymocytes from backcross rats showing thid/thid phenotype showed significantly lower responsiveness compared with +/thid rats. However, in WKAH.C-thid congenic rat thymocytes that carry the thid mutation, the responsiveness to mitogenic stimulation was comparable to that of normal rat thymocytes. These results suggest that a defect in responsiveness to mitogenic stimulation in LEC rat thymocytes is controlled by multiple genetic loci and the thid locus is one of the important loci for the development of this abnormal phenotype.

Animals↗

PubMed1998

Properties of the (DSS)n triplet repeat domain of rat dentin phosphophoryn.

Phosphophoryns (PPs) are unique aspartic acid and phosphoserine-rich proteins present in all species of dentin. Rat incisor odontoblast cDNA libraries contain messages encoding several acidic phosphorylated, serine-rich proteins. At least two of these share a common C-terminal domain coding region sequence. The polypeptide sequences in the N-terminal direction immediately adjacent to the conserved C-terminal domains of these two proteins (DMP2, DMP3) are distinctly different. In this domain, the DMP2 has extensive sequences of (DSS)n repeats with n as large as 24. DMP3 has fewer and shorter triplet sequences, n = 3, 4. The major rat incisor PPs (90-95 kDa) probably have the (DSS)n>>3. We propose that the name phosphophoryn be reserved for the extracellular matrix proteins with these extended repeats. DMPI, although strongly acidic, does not fit this category. If the S residues are phosphorylated and n > 3, conformational energy minimization computations show the (DSS)n sequence to assume a unique extended structure with parallel arrays of carboxylate and phosphate groups which may function as Ca2+ ion interaction edges. The phosphorylation of recombinant DMP2 C-terminal domain by various kinases has been examined. The repeat domains are not direct substrates for the CK2-like kinases but the kinases act in concert, so that the phosphorylation is hierarchical, apparently controlled by the presence of specific interruptions between the triplet domains.

Amino Acid Sequence↗