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Biomedical subjects

D Pei

Publications and source records attributed to D Pei.

At least 73 records · Page 4Linked to original sources
PubMed1996

The stress response to ionizing radiation involoves c-Abl-dependent phosphorylation of SHPTP1.

c-Abl is a nonreceptor tyrosine kinase that is activated by certain DNA-damaging agents. The present studies demonstrate that nuclear c-Abl binds constitutively to the protein tyrosine phosphatase SHPTP1. Treatment with ionizing radiation is associated with c-Abl-dependent tyrosine phosphorylation of SHPTP1. The results demonstrate that the SH3 domain of c-Abl interacts with a WPDHGVPSEP motif (residues 417-426) in the catalytic domain of SHPTP1 and that c-Abl phosphorylates C terminal Y536 and Y564 sites. The functional significance of the c-Abl-SHPTP1 interaction is supported by the demonstration that, like c-Abl, SHPTP1 regulates the induction of Jun kinase activity following DNA damage. These findings indicate that SHPTP1 is involved in the response to genotoxic stress through a c-Abl-dependent mechanism.

3T3 Cells↗
PubMed1996

Transmembrane-deletion mutants of the membrane-type matrix metalloproteinase-1 process progelatinase A and express intrinsic matrix-degrading activity.

Membrane-type matrix metalloproteinase-1 (MT-MMP-1) has been proposed to play a critical role in regulating the expression of tissue-invasive phenotypes in normal and neoplastic cells by directly or indirectly mediating the activation of progelatinase A. To begin characterizing MT-MMP-1 structure-function relationships, transmembrane-deletion mutants were constructed, and the processing of the zymogens as well as the enzymic activity of the mature proteinases was analyzed. We now demonstrate that pro-MT-MMP-1 mutants are efficiently processed to active proteinases following post-translational endoproteolysis immediately downstream of an Arg108-Arg-Lys-Arg basic motif by a proprotein convertase-dependent pathway. The secreted form of active MT-MMP-1 not only displays an N terminus identical with that described for the processed wild-type enzyme at Tyr112 (Strongin, A. Y., Collier, I., Bannikov, G., Marmer, B. L., Grants, G. A., and Goldberg, G. I. (1995) J. Biol. Chem. 270, 5331-5338), but also directly mediated progelatinase A activation via a two-step proteolytic cascade indistinguishable from that observed with intact cells. Furthermore, although the only function previously ascribed to MT-MMP-1 is its ability to act as a progelatinase A activator, purified transmembrane deletion mutants also expressed proteolytic activities against a wide range of extracellular matrix molecules. Given recent reports that MT-MMP-1 ectodomains may undergo intercellular transfer in vivo (Okada, A., Bellocq, J.-P., Rouyer, N., Chenard, M.-P., Rio, M.-C., Chambon, P., and Basset, P. (1995) Proc. Natl. Acad. Sci. U. S. A. 92, 2730-2734), our data suggest that soluble forms of the proteinase confer recipient cells with the ability to not only process progelatinase A, but also directly degrade extracellular matrix components.

Amino Acid Sequence↗
PubMed1996

Differential functions of the two Src homology 2 domains in protein tyrosine phosphatase SH-PTP1.

SH-PTP1 (also known as PTP1C, HCP, and SHP) is a non-transmembrane protein tyrosine phosphatase (PTPase) containing two tandem Src homology 2 (SH2) domains. We show here that the two SH2 (N-SH2 and C-SH2) domains in SH-PTP1 have different functions in regulation of the PTPase domain and thereby signal transduction. While the N-terminal SH2 domain is both necessary and sufficient for autoinhibition through an intramolecular association with the PTPase domain, truncation of the C-SH2 domain [SH-PTP1 (delta CSH2) construct] has little effect on SH-PTP1 activity. A synthetic phosphotyrosine residue (pY) peptide derived from the erythropoietin receptor (EpoR pY429) binds to the N-SH2 domain and activates both wild-type SH-PTP1 and SH-PTP1 (delta CSH2) 60- to 80-fold. Another pY peptide corresponding to a phosphorylation site on the IgG Fc receptor (Fc gamma RIIB1 pY309) associates with both the C-SH2 domain (Kd = 2.8 microM and the N-SH2 domain (Kd = 15.0 microM) and also activates SH-PTP1 12-fold. By analysis of the effect of the Fc gamma RIIB1 pY309 peptide on SH-PTP1 (delta CSH2), SH-PTP1 (R30K/R33E), SH-PTP1 (R30K/R136K), and SH-PTP1 (R136K) mutants in which the function of either the N- or C-SH2 domain has been impaired, we have determined that both synthetic pY peptides stimulate SH-PTP1 by binding to its N-SH2 domain; binding of pY ligand to the C-SH2 domain has no effect on SH-PTP1 activity. We propose that the N-terminal SH2 domain serves both as a regulatory domain and as a recruiting unit, whereas the C-terminal SH2 domain acts merely as a recruiting unit.

Amino Acid Sequence↗
PubMed1995

Furin-dependent intracellular activation of the human stromelysin-3 zymogen.

Human stromelysin-3, a new member of the matrix metalloproteinase family, is expressed in tissues undergoing the active remodelling associated with embryonic development, wound healing and tumour invasion. But like all other members of the matrix metalloproteinase gene family, stromelysin-3 is synthesized as an inactive precursor that must be processed to its mature form in order to express enzymic activity. Here we identify stromelysin-3 as the first matrix metalloproteinase to be discovered that can be processed directly to its enzymically active form by an obligate intracellular proteolytic event that occurs within the constitutive secretory pathway. Intracellular activation is regulated by an unusual 10-amino-acid insert sandwiched between the pro- and catalytic-domains of stromelysin-3, which is encrypted with an Arg-X-Arg-X-Lys-Arg recognition motif for the Golgi-associated proteinase, furin, a mammalian homologue of the yeast Kex2 pheromone convertase. A furin-stromelysin-3 processing axis not only differentiates the regulation of this enzyme from all previously characterized matrix metalloproteinases, but also identifies pro-protein convertases as potential targets for therapeutic intervention in matrix-destructive disease states.

Amino Acid Sequence↗
PubMed1995

Comparison of the hemodynamic and metabolic effects of low-dose hydrochlorothiazide and lisinopril treatment in obese patients with high blood pressure.

Patients with high blood pressure tend to be insulin resistant, glucose intolerant, hyperinsulinemic, and dyslipidemic. Since these metabolic defects are accentuated by obesity, we thought it important to compare the effects of 3 months' treatment with either lisinopril (20 mg/day) or low dose hydrochlorothiazide (12.5 mg/day) on blood pressure and glucose, insulin, and lipoprotein metabolism in obese patients with hypertension. There were 14 patients in each group, and they were similar (mean +/- SE) in age (54 +/- 3 v 50 +/- 4 years), gender (nine men/five women), and body mass index (33.4 +/- 0.8 v 33.9 +/- 0.9 kg/m2). Patients treated with lisinopril had a somewhat greater fall in both systolic (18 +/- 3 v 10 +/- 3 mm Hg) and diastolic (12 +/- 2 v 8 +/- 1 mm Hg) blood pressure, but only the change in systolic pressure was statistically significant (P < .05). Plasma glucose, insulin, and triglyceride concentrations were measured at hourly intervals from 8 AM to 4 PM (breakfast at 8 AM and lunch at 12 PM), and there was a modest increase in all three variables following hydrochlorothiazide treatment (P < .05 to P < .09). However, daylong plasma glucose, insulin, and triglyceride concentration did not change with lisinopril treatment. Finally, neither the ability of insulin to mediate glucose disposal nor fasting lipid and lipoprotein concentrations, changed with either treatment. In conclusion blood pressure decreased significantly following treatment with either lisinopril (20 mg/day) or hydrochlorothiazide (12.5 mg/day).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1995

Resistance to insulin-mediated glucose uptake and hyperinsulinemia in women who had preeclampsia during pregnancy.

Plasma glucose and insulin responses to a 75-g oral glucose load, and the steady-state plasma insulin (SSPI) and glucose (SSPG) concentrations after an infusion of somatostatin, insulin, and glucose, were determined 2 months after delivery in 26 women; 13 who had a normal pregnancy and 13 who developed preeclampsia. The plasma glucose response to oral glucose was not different in the two groups, but the plasma insulin response was significantly greater (P < .02) in those who had been preeclamptic. Although the mean (+/- SE) SSPI concentrations during the infusion study were similar in the two groups (51 +/- 2 v 56 +/- 2 microU/mL), the SSPG concentrations were significantly higher (P < .02) in those who developed preeclampsia (160 +/- 17 v 119 +/- 17 mg/dL). Thus, when studied 2 months after delivery, women who developed preeclampsia were relatively insulin resistant and hyperinsulinemic when compared to those who had an uncomplicated pregnancy.

Adult↗
PubMed1995

Relationship between insulin-mediated glucose disposal by muscle and adipose tissue lipolysis in healthy volunteers.

The present study was performed in 17 nondiabetic subjects and was initiated to determine whether enhanced adipose tissue lipolysis, either basal or catecholamine induced (isoproterenol), and/or resistance to insulin inhibition of isoproterenol-stimulated lipolysis were correlated with resistance to insulin-mediated glucose disposal by muscle. Insulin-mediated glucose disposal was assessed by determining the steady state plasma glucose (SSPG) concentration during the insulin suppression test [180 min infusion of somatostatin (350 micrograms/h), insulin (25 mU/m2min), and glucose (240 mg/m2.min)]. On another occasion, plasma FFA and glycerol concentrations were determined at the end of 3 sequential infusion periods (IP): IP1, somatostatin (350 micrograms/h) plus basal insulin replacement (5 mU/m2.min); IP2, somatostatin (350 micrograms/h), insulin (5 mU/m2.min), and isoproterenol (270 ng/m2.min); and IP3, somatostatin (350 micrograms/h), isoproterenol (270 ng/m2.min), and insulin (10 mU/m2.min). SSPG concentrations correlated with FFA concentrations during all 3 infusion periods after adjustment for age, gender, body mass index, insulin concentration, and ratio of waist to hip girth (IP1:r = 0.61; P < 0.03; IP2: r = 0.70; P < 0.01; IP3: r = 0.65; P < 0.02). Correlations between SSPG and glycerol concentrations were also highly statistically significant (IP1: r = 0.62; P < 0.03; IP2: r = 0.65; P < 0.02; IP3: r = 0.70; P < 0.01). These results demonstrate for the first time that plasma FFA and glycerol concentrations are increased commensurate with the degree of resistance to insulin-mediated glucose disposal at a basal insulin level, in response to isoproterenol stimulation, and after insulin inhibition of isoproterenol-stimulated lipolysis.

Adipose Tissue↗
PubMed1994

Intramolecular regulation of protein tyrosine phosphatase SH-PTP1: a new function for Src homology 2 domains.

The steady-state kinetic properties of SH-PTP1 (PTP1C, SHP, HCP), a Src homology 2 (SH2) domain-containing protein tyrosine phosphatase (PTPase), were assessed and compared with those of three truncation mutants, using p-nitrophenyl phosphate, phosphotyrosyl (pY) peptides, and reduced, carboxyamido-methylated, maleylated, and tyrosyl-phosphorylated lysozyme as substrates. At physiological pH (7.4), truncation of the two N-terminal SH2 domains [SH-PTP1(delta SH2)] or the last 35 amino acids of the C-terminus [SH-PTP1(delta C35)] activated the phosphatase activity by 30-fold and 20-34-fold relative to the wild-type enzyme, respectively. Truncation of the last 60 amino acids resulted in a mutant [SH-PTP1(delta C60)] with wild-type activity. SH-PTP1 and SH-PTP1(delta C60) displayed apparent saturation kinetics toward pNPP only at acidic pH (pH < or = 5.4); as pH increased above 5.5, their apparent KM values increased dramatically. In contrast, SH-PTP1(delta SH2) obeyed normal Michaelis-Menten kinetics at all pH values tested (pH 5.1-7.4) with a constant KM (10-14 mM). Furthermore, two synthetic pY peptides corresponding to known and potential phosphorylation sites on the erythropoietin (EPOR pY429) and interleukin-3 (IL-3R pY628) receptors bound specifically to the N-terminal SH2 domain of SH-PTP1 (KD = 1.8-10 microM) and activated the catalytic activity of SH-PTP1 and SH-PTP1(delta C60) but not SH-PTP1(delta SH2), in a concentration-dependent manner. Maximal activation (25-30-fold) of SH-PTP1 was achieved at 70 microM EPOR pY429, and the maximally activated enzyme approached the activity of SH-PTP1(delta SH2). Addition of EPOR pY429 peptide, which corresponds to the recently identified in vivo binding site for SH-PTP1, at 40 microM also completely restored the saturation kinetic behavior of SH-PTP1 (at pH 7.4) toward pNPP, with catalytic parameters (KM = 12.8 mM, kcat = 3.2 s-1) similar to those of SH-PTP1(delta SH2). These data suggest that the SH2 domains of SH-PTP1 serve to autoinhibit the phosphatase activity of the PTPase domain. A model is proposed in which the SH2 domains interact with the PTPase domain in a pY-independent fashion and drive the PTPase domain into an inactive conformation.

Amino Acid Sequence↗
PubMed1994

Hydrolytic inactivation of a breast carcinoma cell-derived serpin by human stromelysin-3.

To elucidate structure-function relationships of stromelysin-3, a putative matrix metalloproteinase originally identified at the tumor-stromal cell interface in breast carcinomas, the human cDNA was expressed in mammalian cells, and its products were isolated and characterized. In stably transfected cells, stromelysin-3 was recovered as a complex mixture of species ranging in size from approximately 20 to 65 kDa. Among these products, a major 45-kDa species with an N terminus of Phe98 and an intact C-terminal domain was identified as a true endopeptidase on the basis of its ability to cleave the bait region of alpha 2-macroglobulin between Phe684 and Tyr685, a site identical to that recognized by stromelysin-1. However, unlike stromelysin-1 or other members of the matrix metalloproteinase family, the mature form of stromelysin-3 was unable to hydrolyze a range of extracellular matrix molecules associated with either the basement membrane or interstitium. To probe for alternate substrates among tumor cell-derived products, purified stromelysin-3 was incubated with [35S]methionine-labeled medium conditioned by the breast cancer cell line, MCF-7. Under these conditions, a single, tumor cell-derived protein was hydrolyzed as assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. Following anion-exchange chromatography and preparative gel electrophoresis, the stromelysin-3 substrate was identified by N-terminal sequencing as the serine proteinase inhibitor, alpha 1-proteinase inhibitor. Further studies demonstrated that stromelysin-3 rapidly destroyed the antiproteolytic function of alpha 1-proteinase inhibitor by cleaving the antiproteinase at a distinct site between Ala350 and Met351 within the reactive-site loop. Together, these data not only demonstrate that human stromelysin-3 acts as a powerful endopeptidase with a restricted substrate specificity distinct from all other matrix metalloproteinases, but also serve to identify serine proteinase inhibitors as potential physiologic targets at sites of extracellular matrix remodeling.

Amino Acid Sequence↗
PubMed1994

The phosphopeptide-binding specificity of Src family SH2 domains.

BACKGROUND: Src homology 2 (SH2) domains mediate protein/protein interactions by binding phosphotyrosyl proteins with high specificity. The protein Lck, a Src-like lymphocyte-specific tyrosine kinase which is important in signals involved in T-cell development, contains one such domain. The crystal structure of a complex of the Lck SH2 domain with a high-affinity ligand, pY324, is known. This ligand has the sequence EPQpYEEIPIYL. RESULTS: We designed and synthesized a series of phosphopeptides with single amino-acid changes in the four residues C-terminal to the phosphotyrosine (pTyr) in pY324. Surprisingly, the Glu one residue C-terminal to the phosphotyrosine (at position pY + 1) is sensitive to substitution, whereas the Ile at position pY + 3 is much less sensitive, accommodating a Glu with only modest loss of binding affinity. Replacement of the Glu and Pro on either side of the Ile had little effect, as predicted. Truncated phosphopeptides that end at position pY + 5 and have only an acetyl group N-terminal to the pTyr bound with only slightly lower affinity than pY324. In addition, naturally occurring phosphopeptide sequences that span a 1,000-fold range in binding affinity for the Lck SH2 domain have been identified. CONCLUSIONS: The Lck SH2 domain is highly selective for phosphotyrosyl-peptide binding; its specificity is dictated by the first and third residues C-terminal to the pTyr. The unexpected effects of some amino-acid substitutions indicate that the interactions seen between SH2 domains and ligand in the crystal structure may not be identical to those that occur in solution.

Crystallography, X-Ray↗
PubMed1994

Lck-dependent tyrosyl phosphorylation of the phosphotyrosine phosphatase SH-PTP1 in murine T cells.

The phosphorylation and dephosphorylation of proteins on tyrosyl residues are key regulatory mechanisms in T-cell signal transduction and are controlled by the opposing activities of protein tyrosine kinases and phosphotyrosyl phosphatases (PTPs). In T cells, several nontransmembrane protein tyrosine kinases are associated with receptors; for example, Lck is bound to the coreceptors CD4 and CD8 and becomes activated upon their stimulation. In comparison, little is known about the role of nontransmembrane PTPs in early T-cell signaling. SH-PTP1 (PTP1C, HCP, SHP) is a nontransmembrane PTP expressed primarily in hematopoietic cells, including T cells. We have found that SH-PTP1 is basally phosphorylated on serine in resting T cells. Upon stimulation of CD4 or CD8 either in a T-cell hybridoma cell line or in primary thymocytes, SH-PTP1 becomes tyrosyl phosphorylated. Moreover, SH-PTP1 is constitutively phosphorylated on tyrosine in the Lck-overexpressing lymphoma cell line LSTRA. SH-PTP1 is also a good substrate for recombinant Lck in vitro. Comparisons of the tryptic phosphopeptide maps of wild-type SH-PTP1 and deletion and point mutations establish that the two sites (Y-536 and Y-564) which are directly phosphorylated by Lck in vitro are also phosphorylated in vivo in LSTRA cells. One of these sites (Y-564) is phosphorylated in T cells in response to Lck activation. We conclude that SH-PTP1 undergoes Lck-dependent tyrosyl phosphorylation in T cells and likely plays a role in early T-cell signaling.

Amino Acid Sequence↗
PubMed1994

A comparison between the minimal model and the glucose clamp in the assessment of insulin sensitivity across the spectrum of glucose tolerance. Insulin Resistance Atherosclerosis Study.

An insulin-modified frequently sampled intravenous glucose tolerance test (FSIGTT) with minimal model analysis was compared with the glucose clamp in 11 subjects with normal glucose tolerance (NGT), 20 with impaired glucose tolerance (IGT), and 24 with non-insulin-dependent diabetes mellitus (NIDDM). The insulin sensitivity index (SI) was calculated from FSIGTT using 22- and 12-sample protocols (SI(22) and SI(12), respectively). Insulin sensitivity from the clamp was expressed as SI(clamp) and SIP(clamp). Minimal model parameters were similar when calculated with SI(22) and SI(12). SI could not be distinguished from 0 in approximately 50% of diabetic patients with either protocol. SI(22) correlated significantly with SI(clamp) in the whole group (r = 0.62), and in the NGT (r = 0.53), IGT (r = 0.48), and NIDDM (r = 0.41) groups (P < 0.05 for each). SI(12) correlated significantly with SI(clamp) in the whole group (r = 0.55, P < 0.001) and in the NGT (r = 0.53, P = 0.046) and IGT (r = 0.58, P = 0.008) but not NIDDM (r = 0.30, P = 0.085) groups. When SI(22), SI(clamp), and SIP(clamp) were expressed in the same units, SI(22) was 66 +/- 5% (mean +/- SE) and 50 +/- 8% lower than SI(clamp) and SIP(clamp), respectively. Thus, minimal model analysis of the insulin-modified FSIGTT provides estimates of insulin sensitivity that correlate significantly with those from the glucose clamp. The correlation was weaker, however, in NIDDM. The insulin-modified FSIGTT can be used as a simple test for assessment of insulin sensitivity in population studies involving nondiabetic subjects. Additional studies are needed before using this test routinely in patients with NIDDM.

Analysis of Variance↗
PubMed1993

Overexpression, purification, and characterization of SHPTP1, a Src homology 2-containing protein-tyrosine-phosphatase.

A protein-tyrosine-phosphatase (PTPase; EC 3.1.3.48) containing two Src homology 2 (SH2) domains, SHPTP1, was previously identified in hematopoietic and epithelial cells. By placing the coding sequence of the PTPase behind a bacteriophage T7 promoter, we have overexpressed both the full-length enzyme and a truncated PTPase domain in Escherichia coli. In each case, the soluble enzyme was expressed at levels of 3-4% of total soluble E. coli protein. The recombinant proteins had molecular weights of 63,000 and 45,000 for the full-length protein and the truncated PTPase domain, respectively, as determined by SDS/PAGE. The recombinant enzymes dephosphorylated p-nitrophenyl phosphate, phosphotyrosine, and phosphotyrosyl peptides but not phosphoserine, phosphothreonine, or phosphoseryl peptides. The enzymes showed a strong dependence on pH and ionic strength for their activity, with pH optima of 5.5 and 6.3 for the full-length enzyme and the catalytic domain, respectively, and an optimal NaCl concentration of 250-300 mM. The recombinant PTPases had high Km values for p-nitrophenyl phosphate and exhibited non-Michaelis-Menten kinetics for phosphotyrosyl peptides.

Amino Acid Sequence↗
PubMed1993

Efficacy of thyroxine-suppressive therapy and its relation to serum thyroglobulin levels in solitary nontoxic thyroid nodules.

Patients with nontoxic thyroid nodules are often treated with thyroxine (T4) in order to reduce the size of the nodule, but the efficacy of thyrotropin-suppressive therapy with thyroxine remains uncertain. In this study, 35 patients with a solitary thyroid nodule were given thyroxine (0.1 mg/day) for three months. High resolution (7.5 MHz) sonography was used to measure the size of the nodules before and after thyroxine therapy. The volume of the nodules in 12 patients (34.3%, responders) decreased by more than 50% after thyroxine therapy. In this group, the mean serum thyroglobulin (Tg) level decreased significantly (from 424 to 107 ng/mL, p < 0.001). In the nonresponders, the mean serum Tg level did not change significantly after thyroxine therapy (291 vs 261 ng/mL, p > 0.05). The mean serum total T4 and free T4 concentrations increased significantly in both groups after thyroxine therapy (p < 0.01), the serum total triiodothyronine (T3) level did not change (p > 0.05), and the serum thyrotropin level (TSH) and T3/T4 ratio decreased markedly (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Exposure of fertile chicken eggs to microwave radiation (2.45 GHz, CW) during incubation: technique and evaluation.

A multi-mode cavity constructed of 22-gauge perforated galvanized steel with a horn irradiator was used to expose chicken embryos to microwave (MW) radiation during incubation. The MW exposure system was placed within an environmental chamber. Mean +/- standard error of mean (SEM) power level was 3.6 +/- 0.02 mW/cm2 and mean egg specific absorption rate was 0.8 mW/g per mW/cm2. Mean temperature of the MW-exposed eggs was 37.5 +/- 0.9 degrees C as monitored by a Luxtron fluoroptic thermometer. Non-irradiated eggs were incubated at 37.5 +/- 0.1 degrees C and 55% relative humidity. There was no significant different in percent fertile eggs hatched between eggs exposed to MW radiation during incubation or eggs incubated conventionally (82.9% and 87.7%, respectively).

Animals↗
PubMed1990

Site-specific cleavage of duplex DNA by a semisynthetic nuclease via triple-helix formation.

A Lys-84----Cys mutant staphylococcal nuclease was selectively linked to the 5' and/or 3' terminus of a thiol-containing polypyrimidine oligonucleotide via a disulfide bond. The oligonucleotide-staphylococcal nuclease adduct is capable of binding to a homopurine-homopyrimidine region of Watson-Crick duplex DNA by the formation of a triple-helical structure. Upon the addition of Ca2+, the nuclease cleaves DNA at sites adjacent to the homopurine tract. Specific double-strand cleavage occurred predominantly at A + T-rich sites to the 5' side of the homopurine tract for both the 5'-derivatized and the 5',3'-diderivatized nucleases; the 3'-derivatized nuclease gave no cleavage. The cleavage pattern is asymmetric and consists of multiple cleavage sites shifted to the 5' side on each strand, centered at the terminal base pair of the binding site. Microgram amounts of plasmid pDP20 DNA (4433 base pairs) containing a homopurine-homopyrimidine tract were selectively cleaved by a semisynthetic nuclease with greater than 75% efficiency at room temperature within 1 hr. Cleavage reaction conditions were optimized with respect to pH, temperature, reaction times, and reaction components. Semisynthetic nucleases of this type should provide a powerful tool in chromosomal DNA manipulations.

Base Sequence↗
PubMed1990

[Microalbuminuria in insulin-dependent diabetes mellitus: a comparison of specimen collection, analytic methods and relationship with glycemic control and blood pressure].

The excretion of small quantities of urinary albumin (microalbuminuria = urinary albumin excretion rate, UAER = 20-200 micrograms/min) may predict renal function in both insulin-dependent and noninsulin-dependent diabetes. We compared radioimmunoassay with the immunoturbidimetric method to detect early increases in urine albumin concentration. More problems have been encountered in deciding which method of collecting urine best differentiate between early onset diabetic nephropathy and normality. Random urine samples collected at clinics are convenient but show wide variations in concentration and the effects of exercise. Such variations may be overcome by using a rest period and correcting for urine creatinine concentration. We studied 21 IDDM patients (12 female, 9 male), aged 13-33 years old (mean 21) and 11 nondiabetics (6 female, 5 male), aged 15-30 years old (mean 23). All gave negative results on testing with Albustix at clinic visits. All subjects passed urine immediately after they got up in the morning. The results disclosed: (1) The correlation coefficient of albumin excretion (micrograms/ml) in the urine collected overnight with that collected over 24 hours was good (r = 0.89, p less than 0.001). (2) When the albumin excretion rate of the urine collected overnight was expressed as microgram albumin/mg creatinine, the correlation was also as good as the 24-hr urine albumin excretion (microgram albumin/mg creatinine) (r = 0.87, p less than 0.001). (3) The results of our study support the use of urine samples collected overnight, corrected for creatinine, to estimate microalbuminuria.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗