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Biomedical subjects

D D Smith

Publications and source records attributed to D D Smith.

At least 19 recordsLinked to original sources
PubMed1992

Evidence for two histidine ligands at the diiron site of methane monooxygenase.

Circular dichroism spectroscopy has shown the hydroxylase component of methane monooxygenase to have a high helical content. The apoprotein has the same secondary structure as the holoenzyme. Chemical modification shows 12 histidines to be reactive with diethylpyrocarbonate in the holoenzyme, whereas 14 are reactive in the apoenzyme. Two histidine residues are implicated as iron ligands. Further chemical modification results suggest a cysteine residue is in close proximity to the diiron centre.

Apoenzymes↗
PubMed1992

Isolation and primary structure of urotensin II from the brain of a tetrapod, the frog Rana ridibunda.

A peptide related to urotensin II has been isolated in pure form from an extract of the brain of the European green frog, Rana ridibunda. The primary structure of the peptide was established as Ala-Gly-Asn-Leu-Ser-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val and this sequence was confirmed by chemical synthesis. Frog urotensin II contains an additional amino acid residue compared with fish urotensin II peptides but the structure of the cyclic region of the molecule has been fully conserved. The data show that urotensin II is not confined to the caudal neurosecretory system of fish but is present in the central nervous system of a tetrapod.

Amino Acid Sequence↗
PubMed1992

Measurement of T-kinin in rat plasma using a specific radioimmunoassay.

T-kinin (Ile-Ser-Bradykinin) has been isolated only from the plasma of the rat and it is unclear whether the peptide, or its biosynthetic precursor, T-kininogen, circulates in the human. An NH2-terminally directed antiserum to T-kinin was raised in rabbits using an immunogen prepared by coupling the free -SH group of T-kinin extended from its COOH-terminus by a cysteinyl residue to an -NH2 group on human serum albumin. A radioimmunoassay was developed using this antiserum and 125I-labelled [Tyr10]T-kinin as tracer that was sensitive (least-detectable concentration 3 fmol/tube) and relatively specific for T-kinin (cross-reactivity with bradykinin and kallidin less than 1%). Treatment of rat plasma with an excess of trypsin in the presence of a kininase inhibitor generated T-kinin immunoreactivity equivalent to 455 +/- 71 pmol/ml (mean +/- S.E.M.; n = 9) and this immunoreactivity was eluted from a reversed-phase HPLC column as a single peak with the same retention time as synthetic T-kinin. In contrast, treatment of plasma from healthy human subjects (n = 8) and from patients (n = 8) with inflammation due to acute or chronic gastrointestinal disease under the same conditions did not generate any detectable T-kinin immunoreactivity. It is concluded, therefore, that T-kininogen, the biosynthetic precursor of T-kinin in the rat, is either absent from the plasma of human subjects or is present in a concentration less than 30 fmol/ml. Similarly, T-kininogen is probably not an acute phase reactant in humans.

Adult↗
PubMed1992

Structure-activity studies of a novel bicyclic oxytocin antagonist.

In this report, we describe structure-activity studies of the bicyclic oxytocin antagonist [Mpa1,cyclo(Glu4,Lys8)]oxytocin. The monocylic analogue [dPen1, (Glu4,Lys8)]oxytocin was a weak oxytocin antagonist with a pA2 value of 5.8 in the uterotonic assay. Bicyclization of this analogue yielded [dPen1,cyclo(Glu4,Lys8)]oxytocin, a potent antagonist of oxytocin in the uterotonic assay (pA2 8.74) with a potency 3 times greater than that of [Mpa1,cyclo(Glu4,Lys8)]oxytocin. [dPen1,cyclo(Glu4,Lys8)]oxytocin also was a weak antagonist in the pressor assay with a pA2 of 6.3. To establish if the potent antagonistic effects of these bicyclic compounds was because of the lactam ring or merely the result of obtaining an optimal degree of lipophilicity of the side chains in positions 4 and 8, we synthesized a series of analogues containing neutral and/or charged groups on these side chains. Monocyclic derivatives of [Mpa1,Gln4,Lys(CHO)8]oxytocin were moderate to weak agonists of oxytocin all following classical structure-activity profiles of oxytocin. The monocyclic derivatives of [dPen1,Gln4,Lys(CHO)8]oxytocin were antagonists of oxytocin which was attributed to the dPen1 substitution. However, the potency of all of these latter derivatives was at least 1 order of magnitude less than [dPen1,cyclo(Glu4,Lys8)]oxytocin. These results suggest that the potent antagonistic properties of the bicyclic analogues [Mpa1,cyclo(Glu4,Lys8)]oxytocin and [dPen1,cyclo(Glu4,Lys8)]oxytocin can be attributed to the effect of the lactam bridge on the conformational flexibility and topographical properties of the analogues, rendering them more favorable for binding to the receptor in such a manner as to prevent transduction of a biological response.

Amino Acid Sequence↗
PubMed1992

Regulation of the expression of adhesion molecules by human synoviocytes.

The capacity of synoviocytes to participate in inflammatory responses may be altered by the cytokine-enhanced expression of adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1). To examine this possibility, the ability of selected cytokines to enhance ICAM-1 expression was examined. The data indicated that each of these cytokines (interleukin-1 beta greater than tumor necrosis factor-alpha, interferon-gamma much greater than interleukin-6) can up-regulate synoviocyte ICAM-1 expression. This can potentially increase the ability of these cells to interact with infiltrating inflammatory cells, thereby propagating immunologically mediated inflammation such as occurs in rheumatoid synovitis.

Cell Adhesion Molecules↗
PubMed1992

Metabolic compartmentation of vertebrate glutamine synthetase: putative mitochondrial targeting signal in avian liver glutamine synthetase.

The evolution of uricoteley as a mechanism for hepatic ammonia detoxication in vertebrates required targeting of glutamine synthetase (GS) to liver mitochondria in the sauropsid line of descent leading to the squamate reptiles and archosaurs. Previous studies have shown that in birds and crocodilians, sole survivors of the archosaurian line, hepatic GS is translated without a transient, N-terminal targeting signal common to other mitochondrial matrix proteins. To identify a putative internal targeting sequence in the avian enzyme, the amino acid sequence of chicken liver GS was derived by a combination of sequencing of cloned cDNA, direct sequencing of mRNA, and sequencing of polymerase chain reaction (PCR) products amplified from reverse-transcribed mRNA. Analysis of the first 20 or so N-terminal amino acids of the derived sequence for the chicken enzyme shows that they are devoid of acidic amino acids, contain several hydroxy amino acids, and can be predicted to form a positively charged, amphipathic helix, all of which are characteristic properties of mitochondrial targeting signals. A comparison of the N-terminus of chicken GS with the N-termini of cytosolic mammalian GSs indicates that at least three amino acid replacements may have been responsible for converting the N-terminus of the cytosolic mammalian enzyme into a mitochondrial targeting signal. Two of these, His15 and Lys19, result in additional positive charges, as well as in changes in hydrophilicity. Both could have resulted from third-base-codon substitutions. A third replacement, Ala12, may contribute to the helicity of the N-terminus of the chicken enzyme. The N-terminus of the cytosolic chicken brain GS (positions 1-36) was found to be identical to that of the liver enzyme. The complete sequence of chicken retinal GS is also identical to that of the liver enzyme. GS is coded by a single gene in birds, so these sequence data suggest that, unlike the situation in other tissue-specific compartmental isozymes, differential targeting of avian GS to the mitochondrial or cytosolic compartments is not dependent on the sequence of the primary translation product of its mRNA but may involve some other tissue-specific factor(s).

Amino Acid Sequence↗
PubMed1992

Purification and characterization of urotensin II and parvalbumin from an elasmobranch fish, Scyliorhinus canicula (common dogfish).

The caudal portion of the spinal cord of elasmobranch fish incorporates a diffuse neuroendocrine system. Using an antiserum raised against urotensin II from a teleost fish (goby) to facilitate purification, a peptide structurally related to urotensin II was isolated in pure form from an extract of neuroendocrine tissue from the spinal cord of the European common dogfish, Scyliorhinus canicula. The primary structure of the peptide was established as: Asn-Asn-Phe-Ser-Asp-Cys-Phe-Trp-Lys-Tyr-Cys-Val. The amino acid sequence was confirmed by chemical synthesis. A comparison of this sequence with those of the known teleost urotensin II peptides shows that the cyclic region of the molecule has been fully conserved between species and suggests that the presence of an acidic residue at position 5 and a hydrophobic residue at position 12 are important features for the biological activity of the peptide. The dogfish spinal cord extract also contained a high concentration of the calcium-binding protein, parvalbumin and the amino acid sequence at its NH2 terminus [residues (1-50)] was determined.

Amino Acid Sequence↗
PubMed1991

Ranakinin: a novel NK1 tachykinin receptor agonist isolated with neurokinin B from the brain of the frog Rana ridibunda.

An extract of the whole brain of the frog Rana ridibunda contained high concentrations of substance P-like immunoreactivity, measured with an antiserum directed against the COOH-terminal region of mammalian substance P and neurokinin B-like immunoreactivity, measured with an antiserum directed against the NH2-terminus of neurokinin B. The primary structure of the substance P-related peptide (ranakinin) was established as: Lys-Pro-Asn-Pro-Glu-Arg-Phe-Tyr-Gly-Leu-Met-NH2. Mammalian substance P was not present in the extract. The primary structure of the neurokinin B-related peptide was established as: Asp-Met-His-Asp-Phe-Phe-Val-Gly-Leu-Met-NH2. This amino acid sequence is the same as that of mammalian neurokinin B. Ranakinin was equipotent with substance P and [Sar9,Met(O2)11]substance P in inhibiting the binding of 125I-Bolton-Hunter-[Sar9,Met(O2)11]substance P, a selective radioligand for the NK1 receptor, to binding sites in rat submandibular gland membranes (IC50 1.6 +/- 0.3 nM; n = 5). It is concluded that ranakinin is a preferred agonist for the mammalian NK1 tachykinin receptor subtype.

Amino Acid Sequence↗
PubMed1991

Indeterminacy in psychology.

There is an irreducible uncertainty in the prediction of human behavior because the dynamics of the brain, as a self-organizing system consisting of many millions of elements, are inherently indeterminate. Thus the Laplacian ideal of universal laws relating knowable causes to predictable effects cannot be realized in psychology.

Brain↗
PubMed1991

Prospective vaccine prepared from a new mutant of Toxoplasma gondii for use in cats.

Kittens are the principal disseminators of Toxoplasma gondii. They can shed greater than 10(8) oocysts in the feces after initial infection with bradyzoites in tissue cysts. Thereafter, most kittens develop protective immunity and do not shed oocysts again if they are reinfected. Bradyzoites of a T gondii mutant, designated T-263, were used to vaccinate kittens. Their use did not result in oocyst shedding, but successfully prevented 84% (31/37) of the kittens from shedding oocysts when challenge exposed with a normal isolate of T gondii. Vaccination of outdoor-roaming cats and kittens would be a useful public health measure to prevent transmission of toxoplasmosis near homes, on farms, and in zoos. It is anticipated that several years will be required for a lyophilized bradyzoite vaccine to be ready for licensing and possible commercial availability.

Animals↗
PubMed1990

A uterotonic antagonist blocks the oxytocin-induced facilitation of female sexual receptivity.

The nonapeptide oxytocin (OXT) has been shown to facilitate female sexual receptivity when infused into the cerebral ventricles or the basal forebrain. Various selective antagonists have been used to block other behavioral effects of centrally administered OXT. In this study we compared the effects of equal doses of uterotonic, antidiuretic (V2) or vasopressor (V1) antagonists in blocking the facilitative effects of a simultaneous infusion of OXT into the basal forebrain. Ovariectomized (OVXed) animals were implanted with chronic cannulas in the basal forebrain. All animals were then given 0.5 micrograms estradiol benzoate daily for 3 days before testing. On the fourth day animals were tested to 8-10 mounts with a sexually vigorous male before and 20, 40 and 90 min after infusions of 500 ng OXT alone or in combination with a uterotonic, V2 or a V1 antagonist analogue. OXT significantly increased lordosis responding 20 and 40 min after its infusion into the medial preoptic area and anterior hypothalamus when compared to the receptivity of normal saline vehicle infused animals. The uterotonic antagonist significantly blocked the facilitation seen after OXT. The V1 and V2 antagonists at equal doses had no effect on the OXT-induced facilitation of lordosis postures. The V1 antagonist itself facilitated sexual receptivity 90 min after infusion. The facilitative effect of OXT on receptivity appears to be mediated by central uterotonic receptors, while central vasopressor receptors may serve an inhibitory role.

Animals↗
PubMed1990

Enhanced prostaglandin E2 secretion by cytokine-stimulated human synoviocytes in the presence of subtherapeutic concentrations of nonsteroidal antiinflammatory drugs.

Human synoviocytes were stimulated for 48 hours or 72 hours with cytokines (recombinant interleukin-1 beta and/or recombinant tumor necrosis factor alpha) in the presence or absence of selected nonsteroidal antiinflammatory drugs. The drugs were tested at subtherapeutic and clinically therapeutic levels, as follows: piroxicam 0.3 pM to 3 X 10(6) pM, sodium salicylate 30 nM to 3 X 10(6) nM, and indomethacin 3 pM to 3 X 10(6) pM. At low concentrations, all 3 drugs showed significant enhancement of prostaglandin E2 (PGE2) secretion (piroxicam, salicylate greater than indomethacin). At high, clinically therapeutic concentrations, all drugs showed suppression of PGE2 secretion (indomethacin greater than piroxicam greater than salicylate). The enhancement of PGE2 secretion may be partially responsible for the flare of arthralgia or arthritis frequently seen after termination of drug therapy.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1990

Coexpression of glutamine synthetase and carbamoylphosphate synthase I genes in pancreatic hepatocytes of rat.

In the mammalian liver the distribution of ammonia-detoxifying enzymes, glutamine synthetase (GS) and carbamoylphosphate synthase I (ammonia) (CPS-I), is mutually exclusive in that these enzymes are expressed in two distinct populations of hepatocytes that are zonally demarcated in the liver acinus. In the present study we examined the distribution of GS and CPS-I in pancreatic hepatocytes to ascertain if the expression of these two genes in these hepatocytes is also mutually exclusive. Multiple foci of hepatocytes showing no clear acinar organization develop in the adult rat pancreas as a result of a change in the differentiation commitment after dietary copper deficiency. Unlike liver, GS and CPS-I are detected by immunofluorescence in all pancreatic hepatocytes. In situ hybridization revealed that all pancreatic hepatocytes contain GS and CPS-I mRNAs. The sizes of these two mRNAs in pancreas with hepatocytes are similar to those of the liver. The concomitant expression of GS and CPS-I genes in pancreatic hepatocytes may be attributed, in part, to the absence of portal blood supply to the pancreas vis-à-vis the lack of hormonal/metabolic gradients as well as to possible matrix homogeneity in the pancreas.

Animals↗
PubMed1990

A follow-up study of recent special education graduates of learning disabilities programs.

This study investigated the postschool vocational and community adjustment of recent special education graduates from a southwestern metropolitan school district. Sixty-four students with learning disabilities (LD) who had attended self-contained classes at 12 high schools were randomly selected. A questionnaire, administered either via the telephone or in person, was the source of data. Thirty-eight of the LD sample were in competitive employment. In general, the LD students received very few community services. For the most part, they received no agency support after graduation. Most of the LD subjects lived with parents or other relatives and most had a driver's license and car. Implications for postsecondary services and future research are discussed.

Adolescent↗
PubMed1990

Isolation and biological activity of a novel kinin ([Thr6] bradykinin) from the turtle, Pseudemys scripta.

Incubation of plasma from the red-eared turtle with glass beads in the presence of the kininase inhibitor 1,10-phenanthroline resulted in activation of the kallikrein-kinin system and generation of bradykinin-like immunoreactivity. The immunoreactive material comprised a single molecular form that was purified to homogeneity by reverse phase HPLC. The primary structure of the peptide was determined by automated Edman degradation and fast atom bombardment mass spectrometry. The amino acid sequence of the turtle kinin Arg-Pro-Pro-Gly-Phe-Thr-Pro-Phe-Arg contains the substitution Thr for Ser at position 6 compared with mammalian bradykinin. [Thr6] bradykinin was synthesized using solid phase methodology, and bolus injections of the peptide into the left atrium of the anaesthetized turtle produced rapid vasodilation. A dose-dependent increase in blood flow in the left aortic arch was accompanied by a decrease in peripheral vascular resistance, so that systemic blood pressure did not change. The data suggest that the kallikrein-kinin system may play an important physiological role in the regulation of cardiovascular function in reptiles.

Amino Acid Sequence↗
PubMed1990

The pulmonary sequelae associated with accidental inhalation of chlorine gas.

Twenty previously healthy individuals were accidentally exposed to high concentrations of chlorine gas in 1975. Pulmonary function tests were performed on these individuals on several occasions over the next 12 years. On average, each subject was followed up for 8.5 years and 13 of the 20 exposed persons were tested 12 years following the exposure. Pulmonary function tests obtained one day following the accident were most notable for the high prevalence of airflow obstruction and air trapping. Over the ensuing years, the airflow obstruction persisted; however, the high prevalence of air trapping resolved. Of note, the prevalence of a low residual volume consistently increased during the follow-up period (p less than 0.001) and at year 12, 67 percent of those tested had residual volumes below 80 percent of their predicted value. We also found that five of 13 subjects tested at year 12 had an increase in airway reactivity (greater than 15 percent decline in FEV1) to inhaled methacholine. Those individuals with reactive airways were older (p = 0.004) and had more marked airflow obstruction (p = 0.03) and air trapping (p = 0.03) immediately following the exposure. These data suggest that exposure to high concentrations of chlorine gas may result in long-term pulmonary complications that are characterized by a reduced residual volume. Unfortunately, these data preclude us from determining whether the chlorine exposure led to the development of airway reactivity or the presence of reactive airways accounted for the air trapping that was observed following the exposure to chlorine gas.

Accidents, Occupational↗