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Biomedical subjects

R B Harris

Publications and source records attributed to R B Harris.

175 records · Page 10Linked to original sources
PubMedDate not supplied

ABO blood group and cardiovacular disease: the Framingham study.

Following determination of ABO blood type at the sixth biennial examination, the Framingham Heart Study cohort was followed for the occurrence of cardiovascular events for a period of 10 years. A significant association was found between blood type and intermittent claudication, with blood group O showing the lowest rates. Slight but non-significant excesses for certain other CHD events were also found in non-O individuals. Serum cholesterol showed marginally significant but consistent elevations in non-O subjects but the increased risk in non-O individuals was found to occur independently of the known intermittent claudication risk factors. Since the observed relationship between blood type and intermittent claudication occurs independently of the usual atherosclerotic risk factors, blood type, possibily through an effect on clotting, should be considered in the pathogenesis of intermittent claudication.

ABO Blood-Group System↗
PubMedDate not supplied

Conversion of atriopeptin II to atriopeptin I by atrial dipeptidyl carboxy hydrolase.

We are examining the substrate specificity of atrial dipeptidyl carboxyhydrolase, a membrane-bound metallo enzyme that we isolated from bovine atrial tissue homogenates. This enzyme readily removes the dipeptide, Phe-Arg, from Bz-Gly-Ser-Phe-Arg, a stand-in substrate for atriopeptin II, one of several atrial natriuretic factors. We now report that the atrial enzyme cleaves the C-terminal dipeptide, Phe-Arg, from atriopeptin II to form atriopeptin I. The km (pH 7.5) is 25 microM and the ratio of relative Vmax/km as a measure of substrate specificity indicates that atriopeptin II is a 240-fold better substrate than Bz-Gly-His-Leu. Only Phe-Arg was detected as a hydrolysis product, indicating that sequential cleavage of Asn-Ser from atriopeptin II does not occur, and that atriopeptin I is not a substrate. Bz-Gly-Asn-Ser was as good a substrate for the atrial enzyme as Bz-Gly-His-Leu, but Bz-Cys(bzl)-Asn-Ser was not hydrolyzed. This result suggests that the presence of an intact disulfide bond or an S-alkylated residue in the P1 position of a substrate (as in atriopeptin I) prevents hydrolysis by the atrial enzyme. Comparative studies were made with the angiotensin I converting enzyme. Atriopeptin II was not a substrate. The stand-in substrates for atriopeptin I, Bz-Cys(bzl)-Asn-Ser and Bz-Gly-Asn-Ser were barely hydrolyzed, which by itself suggests that atriopeptin I is not a substrate of the angiotensin converting enzyme. Our results strongly suggest that atriopeptin II is converted to atriopeptin I and that hydrolysis is mediated by the atrial enzyme. The angiotensin I converting enzyme plays no role in processing these peptides. We suggest that the atrial enzyme be named atrial peptide convertase.

Animals↗
PubMedDate not supplied

Identification of an endogenous protease that processes atrial natriuretic peptide at its amino terminus.

We have partially purified a thiol-dependent protease from bovine atrial tissue that cleaves the Arg98-Ser99 bond of rat natriuretic peptide (Gly96-Tyr126) to produce the natriuretic Ser99-Tyr126 peptide (cardionatrin I). This was the only hydrolytic product we detected. The existence of the atrial natriuretic peptide system implicates the mammalian heart as an endocrine organ which participates in the hormonal regulation of extracellular fluid volume, electrolyte balance and vascular tone. This enzyme appears to be part of that system. The atrial protease also hydrolyzes the Arg-2-Napthylamide bond of natriuretic peptide stand-in substrates; on the basis of relative Vmax/Km as a measure of substrate specificity, Bz-Leu-Arg-Arg-2-Napthylamide (NA) greater than Bz-Leu-Arg-2-NA greater than Arg-2-NA. There is little or no cleavage between the Arg-Arg pair of the first substrate. Since in the Gly96-Tyr126 peptide the Arg-Arg pair is not the principle cleavage site for this enzyme, it is very unlikely that it is a principle cleavage site for this enzyme in pro-atrial natriuretic factor. It is possible that it is a cleavage site for a different enzyme or the pair may serve as a signal for cleavage at Arg98.

Amino Acid Sequence↗
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Substrate specificity of a hypothalamic neurosecretory granule enzyme capable of processing pro-gonadotropin releasing hormone precursor protein.

We examined the specificity of a bovine hypothalamic neurosecretory granule enzyme which we discovered and which is capable of processing pro-gonadotropin releasing hormone precursor protein to yield gonadotropin associated peptide and a C-terminal extended form of gonadotropin releasing hormone (Palen et al.). The sequence in the precursor protein that separates the two active peptides is -Gly-Gly-Lys-Arg- where the pair of basic residues, -Lys-Arg-, is the anticipated cleavage site. On the basis of Vmax/Km as the measure of substrate specificity, Benzoyl(Bz)-Gly-Gly-Lys-Arg-2-Napthylamide (NA) greater than Bz-Gly-Gly-Arg-Lys-2-NA much greater than Bz-Gly-Gly-Arg-Arg-2-NA approximately equal to Bz-Gly-Gly-Lys-Lys-2-NA. Bz-Gly-Gly-Lys(N(epsilon)-acetyl)-Arg-2-NA is a very poor substrate. Our results indicate that the composition and sequence of the pair of basic residues at the primary cleavage site is important for enzyme specificity and that changes in the P1 or P2 residues of a potential substrate may affect both Km and Vmax. Hydrolysis of all substrates occurs at the P1-2-NA bond. We had previously shown that there is no cleavage between the pair of basic residues. With longer peptide substrates, Bz-Gly-Leu-Arg-Pro-Gly-Gly-Lys-Arg-2-NA greater than Bz-Gly-Leu-Arg(NO2)-Pro-Gly-Gly-Lys-Arg-2-NA greater than Bz-Gly-Gly-Lys-Arg-2-NA. Extending the substrate sequence to more closely resemble the amino acid sequence in the precursor protein improves Km 10-fold and Vmax about 5-fold.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Atrial dipeptidyl carboxyhydrolase is a zinc-metallo proteinase which possesses tripeptidyl carboxyhydrolase activity.

Atrial dipeptidyl carboxyhydrolase readily converts one atrial natriuretic peptide, atriopeptin II (Ser103-Arg125 peptide), to another, atriopeptin I (Ser103-Ser123 peptide), by selective removal of the C-terminal dipeptide, Phe-Arg. The atrial peptides possess natriuretic, diuretic, smooth muscle relaxant, and cardiodynamic properties and their existence has shown the mammalian heart to be an endocrine organ. After inactivating the bovine atrial enzyme with EDTA, activity is restored by the addition of Co+2, Zn+2 and Mn+2 but not by Cu+2, Mg+2, Ca+2, or Cd+2. The enzyme is thus likely to be a zinc-metallo proteinase. In addition to its dipeptidyl activity, the enzyme also displays tripeptidyl carboxyhydrolase activity with atriopeptin III (Ser103-Try126 peptide) as substrate. The hydrolytic products resulting from tripeptidyl cleavage are atriopeptin I and Phe-Arg-Tyr. However, with [mercaptopropionyl105,(D)Ala107]-atriopeptin III-NH2 peptide (a potent agonist of atriopeptin III) as substrate, the enzyme acts exclusively as a tripeptidyl carboxyhydrolase. To examine the basis for this shift in cleavage point, pentapeptides based on the C-terminal sequence of atriopeptin III were prepared; a C-terminal Tyr or Tyr-NH2 residue is not sufficient to cause the change in cleavage point. The amidated pentapeptide is not a substrate but is a competitive inhibitor of hydrolysis of the corresponding free-acid peptide.

Animals↗
PubMedDate not supplied

Conformational analysis of synthetic peptides encompassing the factor XI and prekallikrein overlapping binding domains of high molecular weight kininogen.

High molecular weight kininogen, a plasma glycoprotein, circulates as a noncovalent complex with either prekallikrein or factor XI, two other plasma glycoproteins. The binding domain for factor XI within kininogen, Pro556-Met613 (58 residues), wholly contains the binding domain for prekallikrein, Ser565-Lys595 (31 residues), but Trp569-Lys595 (27 residues) retains some ability to bind prekallikrein. Complex formation between these proteins is mediated by recognition between complementary domains. The 58-residue factor XI peptide domain has now been prepared following a strategy of condensation of long-chain peptide fragments prepared using orthogonal chemistry protocols. The 58-, 31-, and 27-residue peptides assume very different structures in aqueous solution as revealed by differential scanning calorimetry, intrinsic fluorescence emission, and circular dichroism spectroscopies. Thus, the 31-residue peptide shows a broad endothermic transition in differential scanning calorimetry (DSC), but the 58-mer undergoes a well-defined, two-state transition (Tm 43 degrees C; transition enthalpy approximately 30 kcal/mol). The 58- and 27-residue peptides continuously lose structure with increasing temperature, but the 31-mer retains significant structure even at temperatures approaching 90 degrees C. Lys595 plays a critical role in maintaining structure through electrostatic contacts, probably with Asp572 in the N-terminal segment of the 31-residue sequence. Isothermal ligand titration calorimetry was used to directly assess the ability of the 31-, 27-, and 58-residue peptides to bind prekallikrein. The 31-residue peptide binds prekallikrein with 25-fold higher affinity (Kd = 1.0 x 10(-6) M) than the 58-residue peptide and with 5.4-fold higher affinity than the 27-residue peptide. Hence, the essential features of the 31-residue peptide domain required for binding prekallikrein are absent in the 58-residue peptide, which is optimized for binding factor XI. The results suggest that a conformational change may occur within kininogen that causes expression of one domain structure in preference to the other.

Amino Acid Sequence↗
PubMedDate not supplied

The effects of restraint stress on intake of preferred and nonpreferred solutions in rodents.

In these experiments we determined whether stress influenced intake of different flavored test solutions or only those that were preferred. In a series of studies, rats or hamsters were exposed to acute (1 h) or repeated (3 h/day for 3 days) restraint stress immediately followed by access to one of four tastants (saccharin, salt, citric acid, or quinine solutions) paired with water in a 24-h preference test. As rats prefer salt and hamsters do not, both species were used to test the effects of stress on preferred vs. nonpreferred solutions using the same stimulus. Acute restraint inhibited intake of saccharin in rats but had no effect on preference, indicating that suppression of intake was not due to changes in hedonic response. Restraint had no effect on saccharin intake of hamsters but significantly increased salt intake. However, as the preference ratio remained low for the solution (0.26), the stress-induced increase in salt intake was probably associated with a disturbance of sodium and fluid balance rather than a change in sensory perception. This was supported by stress having no effect on intake of nonpreferred solutions in rats or hamsters. Repeated restraint had no effect on salt or saccharin intake of rats when test solutions were presented after stress, but rats showed no preference for saccharin in a subsequent study in which the solution was associated with onset of stress. These results indicate that stress has specific effects on saccharin and salt intake that are not limited to preferred solutions.

Animals↗
PubMedDate not supplied

Immune privilege of the testis for islet xenotransplantation (rat to mouse).

The testis has been suggested as an immune privileged site for islet transplantation. The present study evaluated this hypothesis by transplanting islets from Wistar Furth rats into (a) the testes; (b) the subcapsular space of the kidneys; or (c) the cryptorchid abdominal testes of streptozotocin-induced diabetic Swiss ND4 mice. Transplantation of 800 rat islets into the cryptorchid testes normalized blood glucose for 9.3 +/- 1.4 (Mean +/- SD) days, not significantly different from that of the scrotal testis site (12.4 +/- 1.3), or when the subcapsular space of the kidneys was used (11.5 +/- 1.2). When mouse islets were isotransplanted into the cryptorchid testes of diabetic mice, normoglycemia was maintained for the entire 3 month study period. Histologic examination of the islet xenograft-bearing cryptorchid testes at day 7 post transplantation and 2 days after returning to hyperglycemia revealed lymphocyte infiltration surrounding and inside the graft. No lymphocyte infiltration was seen in the isograft bearing-testes at 3 mo after transplantation. Cyclosporine A (CsA, 15 mg/kg/day) administration to the islet xenograft recipient slightly prolonged the normoglycemic period to 13.7 +/- 1.8 days (p < 0.01). Increasing CsA dose to 25 mg/kg induced a 66% (4/6) mortality, and did not further prolong the normoglycemic period. Using a lower number of rat islets (200 or 400 islets), prolonged graft survival was achieved in some (4 out of 20) animals when the cryptorchid testis was used. In contrast, transplantation of 400 rat islets into the subcapsular space of the kidneys was not associated with prolonged graft survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Immunosuppressive effect of 2'-deoxycoformycin (Pentostatin) for rat islet allotransplantation.

Adenosine deaminase (ADA) is an important enzyme for proper function of lymphocytes and congenital absence of ADA results in a form of severe combined immunodeficiency syndrome. 2'-Deoxycoformycin (Pentostatin, DCF) irreversibly inhibits ADA and therefore has been suggested as an immunosuppressive drug. The present study evaluated the immunosuppressive effect of DCF for islet allotransplantation in rats. Isolated islets (1,500 islets) from Lewis rats were transplanted into the kidney subcapsular space of streptozotocin-induced diabetic Wistar-Furth rats. DCF was administered IP either as a single injection at 1 mg/kg/wk, 1 mg/kg twice weekly, 5 mg/kg/twice weekly or 1 mg/kg/day, or as a continuous infusion at 0.8 or 1 mg/kg/day. Daily administration of DCF at 0.8 mg/kg in both methods, single daily injection or continuous infusion, resulted in a lymphopenia and a decrease in concanavalin A stimulation of splenic lymphocytes. However, DCF (in all doses) was not effective in preventing islet allograft rejection as evaluated by measuring the duration of normoglycemia following islet transplantation and by microscopic examination of the islet grafts. In fact, the duration of normoglycemia following islet transplantation was 7.5 +/- 0.9 and 9.0 +/- 1.0 days in rats receiving DCF in single daily injection or continuous infusion, respectively. This was not significantly different from control nontreated transplanted rats (8.5 +/- 0.7 days). Increasing the dose of DCF to 1 mg/kg, administered by continuous infusion, resulted in 100% mortality. For comparison, cyclosporine A (20 mg/kg, IP daily injection for 14 days) prolonged islet allograft survival to 27.3 +/- 1.5 days (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

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Strategies for positioning fluorescent probes and crosslinkers on formyl peptide ligands.

Chemoattractant receptors represent a major subset of the G-protein coupled receptor (GPCR) family. One of the best characterized, the N-formyl peptide receptor (FPR), participates in host defense responses of neutrophils. The features of the ligand which regulate its interaction with the FPR are well-known. By manipulating these features we have developed new ligands to probe structural and mechanistic aspects of the peptide-receptor interaction. Three ligand groups have been developed: 1) ligands containing a Lys residue located in positions 2 through 7 that can be conjugated to FITC (N-formyl-Met1-Lys2-Phe3-Phe4, N-formyl-Met1-Leu2-Lys3-Phe4, N-formyl-Met1-Leu2-Phe3-Lys4, N-formyl-Met1-Leu2-Phe3-Phe4-Lys5, N-formyl-nLeu1-Leu2-Phe3-nLeu4-Tyr5-Lys6 and N-formyl-Met1-Leu2-Phe3-Phe4-Gly5-Gly6-Lys7; 2) fluorescent pentapeptide ligands (N-formyl-Met-X-Phe-Phe-Lys(FITC) where X = Leu, Ala, Val or Gly); and 3) small crosslinking ligands where the photoaffinity crosslinker 4-azidosalicylic acid (ASA) was conjugated to Lys in positions 3 and 4 and p-benzoyl-phenylalanine (Bpa) was located in position 2 in N-formyl-Met1-Bpa2-Phe3-Tyr4. The peptides were characterized according to activity and affinity in human neutrophils and cell lines transfected with FPR. All of the peptides were agonists, with parallel affinity and activity. In the first group, the peptide activity decreases as Lys is placed closer to the N-formyl group and the activity is improved by 1-3 orders of magnitude by conjugation with FITC. In the second group, the dissociation rate of the peptide from the receptor increases as position 2 is replaced by aliphatic amino acids with smaller alkyl groups. In the third group, crosslinking ligands remain biologically active, display nM affinity and covalently label the FPR.

Animals↗
PubMedDate not supplied

The effects of relaxation training on clinical symptoms: a meta-analysis.

Forty-eight experimental studies of nonmechanically assisted relaxation techniques used to control a variety of clinical symptoms were synthesized using meta-analysis. Effect sizes for three types of comparisons, experimental-control, experimental-placebo, and pre-post, ranged from .43 to .66, demonstrating that treatment of any type included in the analysis moved the client from the 50th to the 67th percentile of an untreated group at minimum and from the 50th to the 75th percentile at maximum. All treatments included in the analysis except Benson's relaxation technique demonstrated evidence of effectiveness, particularly for nonsurgical samples with chronic problems such as hypertension, headache, and insomnia.

Adult↗
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Clean vs. sterile tracheotomy care and level of pulmonary infection.

As reported in the literature and observed in clinical practice, a variety of tracheotomy care procedures (tracheotomy suctioning and cleaning techniques) are currently used. The purpose of this research was to determine if clean tracheotomy care was more effective than sterile as measured by levels of postoperative pulmonary infection. Ten hospitals with large Head and Neck/ENT services were selected as data collection sites. At these centers a minimum of 15 tracheostomy patient charts were reviewed pre- and postoperatively for clinical and laboratory data related to infection. Patient level of infection was defined using the Weighted Level of Pulmonary Infection Tool, which was constructed for this study. Three categories of aseptic type emerged (clean, sterile, and mixed) because existing tracheotomy care procedures did not fall into one of the two hypothesized types. Data were analyzed using a maximum likelihood approach to mixed model analysis of variance or covariance. The findings indicated significant differences among the three procedures with laboratory, but not clinical, data. Laboratory data supported practicing clean procedures as those associated with the least postoperative infection.

Analysis of Variance↗