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Biomedical subjects

A S Harris

Publications and source records attributed to A S Harris.

At least 19 recordsLinked to original sources
PubMed1995

Nucleotide sequence and genomic organization of cichlid fish minisatellites.

We have cloned, sequenced, and determined the genomic organization of minisatellites from the African cichlid fish, Oroechromis niloticus. We estimate that minisatellites related in sequence to the Jeffreys' core probes 33.6 and 33.15 occur approximately every 1000 kilobase pairs in the cichlid fish genome. Sequencing of three minisatellites revealed that the size of the monomer units of the tandem arrays ranged from 7 to 24 base pairs (bp). One minisatellite appeared to contain a higher ordered periodicity of 90-120 bp superimposed on the apparent 15 bp monomer repeat, indicating a particularly large unit of homogenization for a minisatellite array. Sequence heterogeneity of repeat units within tandem arrays varied considerably from one minisatellite to another. Hybridization of cloned minisatellites to genomic DNA of cichlid fishes generated, in most instances, multilocus fingerprint patterns, indicating that families of minisatellites related by sequence exist in the cichlid genome. Two minisatellite clones, however, generated polymorphic single locus fingerprints, suggesting that these loci are conserved in closely related African cichlids. The cross hybridization of these cichlid minisatellites within and between related taxa, as well as to unrelated fish species such as Atlantic salmon (Salmo salar), complement the human minisatellite sequences for the study of genetic relationships among individuals from a wide range of fish species.

Animals↗
PubMed1995

The effect of desmopressin on reducing blood loss in cardiac surgery--a meta-analysis of double-blind, placebo-controlled trials.

The effect of desmopressin (DDAVP) on reducing postoperative blood loss after cardiac surgery has been studied in several randomized clinical trials with conflicting outcomes. Since most trials had insufficient statistical power to detect true differences in blood loss, we performed a meta-analysis of data from relevant studies. Seventeen randomized, double-blind, placebo-controlled trials were analyzed, which included 1171 patients undergoing cardiac surgery for various indications; 579 of them were treated with desmopressin and 592 with placebo. Efficacy parameters were blood loss volumes and transfusion requirements. Desmopressin significantly reduced postoperative blood loss by 9%, but had no statistically significant effect on transfusion requirements. A subanalysis revealed that desmopressin had no protective effects in trials in which the mean blood loss in placebo-treated patients fell in the lower and middle thirds of distribution of blood losses (687-1108 ml/24 h). In contrast, in trials in which the mean blood loss in placebo-treated patients fell in the upper third of distribution (> 1109 ml/24 h), desmopressin significantly decreased postoperative blood loss by 34%. Insufficient data were available to perform a sub-analysis on transfusion requirements. Therefore, desmopressin significantly reduces blood loss only in cardiac operations which induce excessive blood loss. Further studies are called to validate the results of this meta-analysis and to identify predictors of excessive blood loss after cardiac surgery.

Adult↗
PubMed1993

Cloning of a portion of the chromosomal gene and cDNA for human beta-fodrin, the nonerythroid form of beta-spectrin.

A 96-bp synthetic oligonucleotide corresponding to an amino acid sequence near the N-terminus of erythroid beta-spectrin was used to screen a human genomic library, and two overlapping recombinants were isolated. DNA sequence analysis established that the genomic fragment encoded beta-fodrin, the nonerythroid form of beta-spectrin, by correlation to a known amino acid sequence of human brain beta-fodrin. The genomic DNA contained regions that cross-hybridized with an erythroid beta-spectrin cDNA probe, and the DNA sequence of these regions revealed a high degree of identity with that of erythroid beta-spectrin and a similar exon/intron organization. A single-copy DNA fragment of the beta-fodrin genomic clone was used to screen a lymphoid cell cDNA library and two recombinants were isolated. The composite DNA sequence of these various genomic and cDNA clones encoded almost all of the first twelve 106 amino acid repeat segments of beta-fodrin that shared 58% identity and 75.5% similarity with the amino acid sequence of beta-spectrin and 66% identity with the nucleotide sequence of beta-spectrin cDNA. The chromosomal localization of the gene was determined to be chromosome 2 by hybridization of a single-copy probe derived from the cloned genomic DNA to DNA of a panel of somatic hybrid cell lines, and in situ hybridization localized the gene to band 2p21. beta-Fodrin was assigned the gene symbol SPTBN1.

Amino Acid Sequence↗
PubMed1993

Review: clinical opportunities provided by the nasal administration of peptides.

Peptides are rapidly being developed as potential new therapeutic agents and the nasal route is being evaluated as a means of achieving systemic absorption. Current research in man is being directed at a number of polypeptides, including calcitonin, growth hormone releasing hormones (GHRH), insulin, gonadotropin hormone releasing hormones (GnRH) and vasopressin analogues. The underlying protective functions of the nose provide anatomical, temporal and enzymatic barriers to absorption of peptides. The nasal route is relatively unsuccessful when used for high molecular weight polypeptides. Penetration enhancers improve bioavailability but are poorly tolerated. Reproducibility of effect is highly variable, major contributing factors including the site of deposition and type of delivery system as well as changes in the mucous secretion and mucociliary clearance, compounded by the presence of allergy, hay fever and the common cold in treated subjects. The future potential for this route lies in development of effective and well tolerated formulations in highly accurate delivery systems for the chronic administration of peptides, enabling the replacement of impractical and invasive intravenous injections in patients on lifelong substitution treatment for various deficiency states.

Administration, Intranasal↗
PubMed1992

Amino acids and serotonin in Limax maximum after a tryptophan devoid diet.

1. Animals avoid diets lacking an essential amino acid, such as tryptophan (TRP), the precursor for serotonin (5-HT). 5-HT is important in the control of feeding. 2. To study the effects of TRP deprivation, slugs were fed TRP-devoid (DEV) or control (COR) diets. 3. Food intake was depressed in DEV, as expected, but after 2 weeks, the serontonergic metacerebral giant cell in DEV was still functional. 4. Neither brain 5-HT nor plasma TRP concentration was affected. 5. Compared with food-restricted animals that had reductions in most amino acids, the DEV group sustained a marked plasma amino acid imbalance.

Amino Acids↗
PubMed1990

Intranasal desmopressin (DDAVP) by spray in mild hemophilia A and von Willebrand's disease type I.

Desmopressin acetate (1-desamino-8-D-arginine vasopressin, DDAVP) has mostly been given by the parenteral route for the treatment of mild hemophilia A and von Willebrand's disease type I. In the present study the hemostatic effects of desmopressin acetate administered intranasally by spray in a dose of 300 micrograms and intravenously 0.3-0.4 micrograms/kg were assessed and compared in 8 patients with hemophilia A and 22 patients with von Willebrand's disease type I. A bioequivalent response to intravenous and intranasal desmopressin acetate was found in Factor VIII coagulant activity (VIII:C) in the hemophilia patients. In the von Willebrand patients, an equivalent shortening of the bleeding time was seen after the two modes of administration, even though intravenous injection gave a higher increase in plasma levels of VIII:C and vWF:Ag. In five patients with von Willebrand's disease the duration of the spray effect on VIII:C and vWF:Ag was followed for 24 h. After 12 h the mean level of VIII:C was 1.4, and of vWF:Ag 1.5, times the basal level. The findings suggest that the spray can be recommended for home or prophylactic treatment of patients with mild hemophilia A and von Willebrand's disease.

Administration, Intranasal↗
PubMed1990

Calmodulin and calcium-dependent protease I coordinately regulate the interaction of fodrin with actin.

The calcium-dependent proteolysis of fodrin has been implicated in the regulation of secretion, neutrophil and platelet activation, and long-term potentiation in neurons. In vitro studies indicate that calcium-dependent protease I (calpain I) cleaves fodrin in the middle of the alpha subunit and in the COOH-terminal third of the beta subunit. Cleavage at the beta site requires calmodulin, which binds with high affinity to a single site in the alpha subunit. In vitro binding assays, nondenaturing gel electrophoresis, and velocity sedimentation identify a linkage between calcium-dependent protease I proteolysis of fodrin and the ability of calmodulin to regulate the self-association of fodrin and its interaction with actin. Three functional states appear to exist: (i) intact fodrin, which constitutively forms tetramers and binds F-actin; (ii) alpha-cleaved fodrin, which loses its ability to self-associate and bind F-actin in the presence of calmodulin; and (iii) alpha,beta-cleaved fodrin, a form that is incompetent to establish tetramers or bind actin. Because actin binding and fodrin self-association occur at opposite ends of the molecule, whereas calmodulin binds at its center, these results indicate that long-range interactions exist within fodrin. They also offer an example of how two calcium-dependent regulatory processes may act synergistically to reversibly regulate a linkage between the membrane and the cytoskeleton.

Actins↗
PubMed1989

Calmodulin regulates fodrin susceptibility to cleavage by calcium-dependent protease I.

The intracellular calcium-dependent proteolysis of fodrin has been postulated to be central to the regulation of plasticity of the cortical cytoskeleton of many eukaryotic cells. The close proximity of the sites of calmodulin (CaM) binding and calcium-dependent protease I (CDP-I) cleavage in mammalian alpha-fodrin suggested that their action may be linked. In hypotonic and isotonic buffers, CDP-I proteolysis of the beta subunit of fodrin was absolutely dependent upon the presence of active CaM. The stimulation by CaM was inhibited by CaM antagonists. The rate of CDP-I proteolysis of both subunits was enhanced by CaM, while the rate of fodrin proteolysis with other proteases was not influenced by CaM. The increase in the susceptibility of fodrin to CDP-I proteolysis was half-maximal at 80 nM CaM, and maximal at 200 nM CaM. The unusual and differential susceptibility of alpha- and beta-fodrin to proteolysis by CDP-I in the absence of CaM was exploited to investigate the quaternary structure of fodrin in which only the alpha subunit was cleaved. Cleavage of the alpha subunit alone did not destroy the tetrameric form of the molecule, whereas CDP-I cleavage of both subunits rendered the molecule incapable of reforming tetramers. These results provide structural and functional evidence that CaM and CDP-I act synergistically in the regulated proteolysis of fodrin.

Animals↗
PubMed1989

Effect of viscosity on the pharmacokinetics and biological response to intranasal desmopressin.

The effect of viscosity on the nasal absorption and biological response to desmopressin was studied in humans. Nasal solutions of desmopressin with and without the addition of 0.25% (w/v) methylcellulose were administered by a precompression nasal spray pump to 10 volunteers. Plasma levels of desmopressin were assayed by radioimmunoassay and the biological response was measured by determination of the antihemophilia factors (Factor VIII and von Willebrand factor). The results showed that the addition of methylcellulose produced a more sustained and slower absorption, with a longer time to maximum plasma concentration (tmax). However, the areas under the plasma concentration-time curve were not different, indicating a similar total bioavailability. The biological response showed a similar effect. Peak Factor VIII activity was not different, but the presence of methylcellulose produced a slower onset of activity. These findings indicate that although the addition of a viscous agent to nasal formulations may produce a more sustained effect, it delays the onset of activity and no enhancement is achieved in the total bioavailability.

Administration, Intranasal↗
PubMed1989

Combined therapy of enuresis alarm and desmopressin in the treatment of nocturnal enuresis.

Twenty-eight children with primary nocturnal enuresis were blindly allocated at random to a combination of enuresis alarm and 20 micrograms intranasal desmopressin or alarm and placebo for 2 weeks. Patients received the other therapy after a 2-week treatment-free period. The combined treatment of desmopressin and alarm showed 5.1 +/- 0.4 (mean +/- SEM) dry nights per week and resulted in significantly more dry nights per week during the 2 weeks of observation than placebo and alarm (4.1 +/- 0.4, P less than 0.05).

Adolescent↗
PubMed1989

Clinical experience with desmopressin: efficacy and safety in central diabetes insipidus and other conditions.

Because of its selective antidiuretic activity, desmopressin is recognized as the drug of choice for central diabetes insipidus. Compared with previously available treatments, it has a greatly enhanced therapeutic profile, allowing more specific antidiuresis without adverse reactions. Its selective antidiuretic activity is used with advantage in the treatment of nocturnal enuresis and as a diagnostic test of tubular function. Desmopressin is available for intranasal and parenteral administration; antidiuretic doses range from 10 to 40 micrograms intranasally and from 2 to 4 micrograms intravenously or subcutaneously. For its hemostatic effect, a single infusion of desmopressin at a dose of 0.3 microgram/kg has been used in most studies. Well-documented evidence shows that desmopressin is safe and efficacious as a selective antidiuretic agent for the treatment of central diabetes insipidus and nocturnal enuresis and as a diagnostic test of tubular function. Even at the 15-fold higher doses used in bleeding disorders, desmopressin appears to be well tolerated.

Adult↗
PubMed1989

Fodrin as a differentiation marker. Redistributions in colonic neoplasia.

Fodrin (nonerythroid spectrin) is a 475,000 molecular weight (MW) (apparent) heterodimeric actin-binding protein usually found in mature cells at the cytoplasmic face of the plasma membrane. While its precise role is uncertain, it may participate in the establishment and/or maintenance of cell polarity, shape, and specialized receptor domains. In polarized epithelial cells, an asymmetric distribution of fodrin appears to signal phenotypic maturity. Using immunohistochemical techniques, the distribution of fodrin in enterocytes during normal crypt-to-villus maturation, and in adenomas, adenocarcinomas, and cultured Madin-Darby Canine Kidney (MDCK) cells has been studied and its abundance quantitated by immunoblotting and digital immunofluorescent confocal microscopy. During normal maturation, fodrin was found to assemble at the apex of the enterocyte, presumably in the terminal web, only in those cells near the villus tip. Villin was found in an apical location in both crypt and surface enterocytes. In adenocarcinomas of the colon (n = 11), there were enhanced levels of fodrin at the apex, and an approximately threefold increase in the total amount of fodrin per cell relative to normal crypt enterocytes. An increased percentage of this protein was also found in the cytoplasm. Adenomas (n = 7), nonconfluent MDCK cells in culture, and two (of two) cases of ductal carcinoma of the breast also demonstrated enhanced cytoplasmic and total fodrin. Supranormal levels of fodrin at the apex of enterocytes were also observed in Crohn's disease samples and in the normal-appearing enterocytes adjacent to a tumor. It is hypothesized that increased apical fodrin may signal a reaction of the microvillar brush border to pathologic stress, while increased cytoplasmic and total pools of fodrin may mark neoplastic activity. These findings may be of diagnostic value, particularly in the evaluation of small biopsies or cytologic material.

Adenocarcinoma↗
PubMed1988

The calmodulin-binding site in alpha-fodrin is near the calcium-dependent protease-I cleavage site.

Fodrin (brain spectrin) binds calmodulin and is susceptible to proteolysis by calcium-dependent protease I (CDP-I, calcium-activated neutral protease I, or calpain I). Both events involve the central region of the alpha-fodrin subunit, and calmodulin binding enhances the sensitivity of fodrin to CDP-I mediated proteolysis. Fragments of fodrin, generated chemically or proteolytically, which retain calmodulin binding activity have been identified and analyzed by two-dimensional peptide mapping and by direct protein sequencing. Both CDP-I and calmodulin interact with the terminal portion of the eleventh repetitive unit in fodrin, which is at the center of the molecule. CDP-I cleavage occurs between Tyr104 and Gly105 and preserves the calmodulin binding activity of the carboxyl-terminal fragment. In contrast, chymotryptic cleavage at Trp120 reduces the ability of this fragment to bind calmodulin, and tryptic cleavage beyond Trp120 completely eliminates calmodulin binding activity. It is concluded that Ser-Lys-Thr-Ala-Ser-Pro-Trp-Lys-Ser-Ala-Arg-Leu-Met-Val-His-Thr-Val-Ala- Thr- Phe-Asn-Ser-Ile-Lys, a 24-residue peptide which bridges repeats 11 and 12 of brain alpha spectrin contains the high affinity calmodulin binding domain.

Binding Sites↗
PubMed1988

Effects of concentration and volume on nasal bioavailability and biological response to desmopressin.

The effects of concentration and dose volume on the nasal bioavailability and biological response to desmopressin [DDAVP; 1-(3-mercaptoproprionic acid)-8-D-arginine vasopressin] were investigated in humans. A nasal formulation of 300 micrograms of desmopressin was administered using a premetered spray device in doses of either 1 x 50-, 2 x 50-, or 1 x 100- microL actuations to both nostrils. Intravenous administration of 0.2 micrograms/kg was also given as a reference for bioavailability calculations. Plasma levels of desmopressin were measured by radioimmunoassay. The biological response was determined by measuring circulating levels of Factor VIII (F VIII), the antihemophilia factor. Peak plasma levels of desmopressin were greatest after the 2 x 50-microL dose, followed by the 1 x 50- and 1 x 100-microL doses. The bioavailability of desmopressin from the 2 x 50-microL dose was 20%, which was significantly greater than the 11% after the 1 x 50-microL (p less than 0.01) and 9% after the 1 x 100-microL (p less than 0.001) doses. The biological response was clearly enhanced after the 2 x 50-microL dose compared with the 1 x 50- and 1 x 100-microL doses. The interindividual response in F VIII levels to nasal desmopressin ranged from 20 (CV) to 30%, which compared favorably with the 36% variation after intravenous administration. This study confirms the premetered spray device as the preferred intranasal drug delivery system, and shows that by optimizing concentration, volume, and technique of administration, a significant enhancement can be obtained in bioavailability and clinical efficacy.

Administration, Intranasal↗
PubMed1988

Effect of viscosity on particle size, deposition, and clearance of nasal delivery systems containing desmopressin.

The effect of methylcellulose on the particle size distribution and dosing accuracy of pre-metered spray pump devices containing the peptide desmopressin (DDAVP) was investigated. Using gamma scintigraphy, the influence of methylcellulose on the in vivo deposition and clearance of nasal solutions administered as drops or spray was studied. Nasal formulations containing 0, 0.25, and 0.50% methylcellulose produced a dose-related increase in average particle size from 51 micron for 0% to 81 and 200 micron for 0.25 and 0.50% methylcellulose, respectively. However, no effect was observed on the dosing accuracy of the spray pumps. The addition of methylcellulose gave a more localized in vivo deposition in the anterior region of the nasal vestibule. However, the net effect on clearance followed a biphasic pattern which showed an increase in retention time for the 0.25% solution, followed by a decrease in retention time and faster clearance time for the 0.50% solution. The spray delivers well-controlled doses to the nasal cavity. These findings show that viscosity, particle size, and nasal clearance are important parameters in the design of nasal delivery systems.

Administration, Intranasal↗
PubMed1988

Comparison of nonerythroid alpha-spectrin genes reveals strict homology among diverse species.

The spectrins are a family of widely distributed filamentous proteins. In association with actin, spectrins form a supporting and organizing scaffold for cell membranes. Using antibodies specific for human brain alpha-spectrin (alpha-fodrin), we have cloned a rat brain alpha-spectrin cDNA from an expression library. Several closely related human clones were also isolated by hybridization. Comparison of sequences of these and other overlapping nonerythroid and erythroid alpha-spectrin genes demonstrated that the nonerythroid genes are strictly conserved across species, while the mammalian erythroid genes have diverged rapidly. Peptide sequences deduced from these cDNAs revealed that the nonerythroid alpha-spectrin chain, like the erythroid spectrin, is composed of multiple 106-amino-acid repeating units, with the characteristic invariant tryptophan as well as other charged and hydrophobic residues in conserved locations. However, the carboxy-terminal sequence varies markedly from this internal repeat pattern and may represent a specialized functional site. The nonerythroid alpha-spectrin gene was mapped to human chromosome 9, in contrast to the erythroid alpha-spectrin gene, which has previously been assigned to a locus on chromosome 1.

Amino Acid Sequence↗