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Biomedical subjects

M W Smith

Publications and source records attributed to M W Smith.

At least 91 records · Page 5Linked to original sources
PubMed1996

The evolving science of pharmacogenetics: clinical and ethnic perspectives.

The field of pharmacogenetics has witnessed remarkable progress during the past several decades. Clinical observations of severe toxic reactions and findings of dramatic interindividual as well as cross-ethnic differences in response to therapeutic agents have been instrumental in fostering advances of the field. Research on cytochrome P450 isozymes may be of particular importance to the field of psychiatry, because most psychotropics depend on these enzymes for their biotransformation. This article traces the progress of research in this area and highlights the importance of clinical and cross-ethnic observations in providing the impetus and direction for the field. Knowledge derived from this line of research is likely to make important contributions toward establishment of rational guidelines for psychopharmacotherapy. In addition, research on these enzymes may also have profound implications in regard to the pathogenesis of a number of major disorders, including several types of commonly encountered cancers, as well as neuropsychiatric problems, including Parkinson's disease, tardive dyskinesia, addiction, and drug-induced neurotoxicity.

Cytochrome P-450 Enzyme System↗
PubMed1996

Brain imaging, antidepressants, and ethnicity: preliminary observations.

Magnetic resonance imaging (MRI) and single photon emission computed tomography (SPECT) using 99mTc-hexamethylpropylene amine oxime (HMPAO) evaluations were completed on African-American and Caucasian depressed patients prior to their participation in an antidepressant medication trial. The degree of white matter hyperintensities (WMH), ventricle-to-brain ratio (VBR), and uptake of HMPAO did not vary significantly between the groups. After 1 week of placebo run-in, patients received paroxetine in an 8-week, open-label, flexible-dose trial. Final dosages and side effects were similar between groups. There was a trend for the Caucasian patients to have a better treatment response, but the relatively small sample size makes this finding tentative. In general, there were no major differences in either baseline neuroimaging findings or response to paroxetine between these two ethnic groups.

Black or African American↗
PubMed1996

Clozapine dosage, serum levels, efficacy, and side-effect profiles: a comparison of Korean-American and Caucasian patients.

As the prototypic "atypical neuroleptic," clozapine plays an increasingly important role in the treatment of refractory psychotic patients. However, little is known about the efficacy and safety of the compound for Asian patients. This study compares dosage, efficacy, and side-effect profiles in 17 Korean-American and 17 Caucasian age- and sex-matched schizophrenia or schizoaffective patients treated with clozapine. Asians showed a greater change than Caucasians in total scores of the 8-item Brief Psychiatric Rating Scale while receiving a significantly lower mean dose of clozapine (t = 2.48; p < .025). Furthermore, Asians had significantly lower mean clozapine concentrations than Caucasians and were significantly more likely to experience anticholinergic and other side effects. No serious untoward effects, such as agranulocytosis were reported in either group. These data suggest that Asians may be treated effectively and safely with lower doses of clozapine than those used for Caucasians.

Adult↗
PubMed1996

Pharmacological characterization of U-101387, a dopamine D4 receptor selective antagonist.

Dopamine D2-like receptors play an important role in the pharmacotherapy of psychotic disorders. Molecular and cellular techniques have identified distinct gene products (D2-long, D2-short, D3 and D4) displaying the D2 receptor pharmacology. However, the contribution of each subtype in antipsychotic effects of or their physiological role remain unclear. Here we describe the pharmacological effects of a selective D4 antagonist, U-101387. U-101387 displayed moderately high affinity (Ki = 10 nM) and selectivity for the dopamine D4.2 receptor expressed in clonal cell lines. It lacked measurable affinity for not only other dopamine receptors but also noradrenalin, serotonin and histamine receptor families (Ki > 2000 nM). It fully and dose-dependently antagonized quinpirole-induced cAMP inhibition (without producing any effect by itself) in stably transfected cells. U-101387 also displayed excellent oral bioavailability, brain penetration and other pharmacokinetic characteristics. Unlike classical neuroleptics (e.g., haloperidol), U-101387 neither blocked acute behavioral effects of amphetamine or apomorphine nor did it alter spontaneous locomotion by itself. Additionally, U-101387 was without effect in behavioral and biochemical tests predictive of extrapyramidal and neuroendocrine side effects. Consistent with the lack of autoreceptor function of D4, acute administration of U-101387 failed to alter dopamine neuronal firing by itself or reverse the inhibition produced by dopamine agonists and to affect monoamine turnover in areas innervated by the mesencephalic or hypothalamic dopamine neurons. However, U-101387 potently induced c-fos mRNA expression in the infralimbic/ventral prelimbic cortex to a level similar to that produced by the atypical antipsychotic, clozapine. This is consistent with the predominantly cortical distribution of the D4 receptor. Taken together, these results demonstrate that the D4-selective antagonist, U-101387, produces effects that are distinct from those of the nonselective D2 antagonists as well as D3-preferring agents. U-101387 offers a unique tool to understand the role of dopamine D4 receptors in diseases involving central dopamine systems.

Amphetamines↗
PubMed1996

Particle uptake and translocation across epithelial membranes.

Oral delivery of drugs and vaccines has many advantages over other routes of administration. For example, for vaccination, enteric delivery may result in the induction of a mucosal immune response against pathogens which colonise and invade the mucosa. However, the oral delivery of peptide or protein drugs or antigens is beset with problems, such as gastrointestinal breakdown of labile molecules, low level of macromolecular absorption and, for vaccines, the poor immune response usually elicited by orally administered soluble antigens. Investigations are therefore in progress to develop means of increasing intestinal absorption and decreasing digestion of orally administered molecules. Molecules can be incorporated into biodegradable microparticles to reduce the effect of gut secretions and to enable the absorption of bioactive agents in an unaltered form. The uptake of microparticulates through the gut wall is accepted as a true biological phenomenon but the mechanism and route of uptake have not been established. Furthermore, in general, only small numbers of microparticles are translocated across epithelial membranes, possibly making these systems inappropriate for drug or vaccine delivery. This paper reviews particle uptake across the gastrointestinal tract and describes studies carried out to determine whether a humoral response can be elicited following oral administration of an antigen associated with biodegradable poly(DL lactide-coglycolide) microparticles. The use of lipid delivery vehicles to enhance microparticle uptake and the selective transport of microspheres across M cells is also described.

Administration, Oral↗
PubMed1996

Transforming growth factor beta modulation of the epidermal growth factor Ca2+ signal and c-Fos oncoprotein levels in A431 human epidermoid carcinoma cells.

Transforming growth factor beta (TGF beta) was examined regarding its regulation of the mitogen EGF. A431 human epidermoid carcinoma cells were treated with TGF beta and epidermal growth factor (EGF) (10 ng/ml each) to determine if TGF beta modulates EGF-induced Ca2+ signaling and c-Fos oncoprotein levels. Changes in [Ca2+]i were determined by digital imaging analysis or photon counting. In HBSS + Ca2+ (1.37 mM), EGF treatment resulted in a transient increase in [Ca2+]i from 75 to 150 nM, which lasted approximately 3.5 min and re-equilibrated to 90 nM. In nominally Ca(2+)-free (2-5 muM) HBSS, EGF caused a [Ca2+]i elevation that peaked at 140 nM and returned to baseline. TGF beta in HBSS + Ca2+ did not elicit a [Ca2+]i increase, although affinity labeling revealed types I, II, and III TGF beta receptors. TGF beta added simultaneously with EGF in HBSS + Ca2+ caused a gradual rise in [Ca2+]i from 50 to 100 nM over 16 min. Pretreatment with TGF beta (3 h; 10 ng/ml) abolished the EGF-induced [Ca2+]i elevation. EGF or TGF beta treatments increased c-Fos immunoreactivity by around 1 h. In summary, EGF elevated [Ca2+]i in the presence or absence of [Ca2+]e, resulting in high [Ca2+]n, associated with tyrosine and threonine phosphorylation, and increased c-Fos oncoprotein immunoreactivity. TGF beta did not increase [Ca2+]i but did increase c-Fos; TGF beta + EGF added simultaneously altered the EGF-induced [Ca2+]i elevation, and TGF beta pretreatment eliminated EGF-induced [Ca2+]i elevation. This suggests that TGF beta can regulate EGF in A431 cells and that increased c-Fos may not be mediated by Ca2+.

Calcium↗
PubMed1995

Structure-activity relationships in the 8-amino-6,7,8,9-tetrahydro-3H-benz[e]indole ring system. 1. Effects of substituents in the aromatic system on serotonin and dopamine receptor subtypes.

A series of 1-, 3-, and 4-substituted analogs to the potent 5-HT1A against 8-(dipropylamino)-6,7,8,9-tetrahydro-3H-benz[e]indole-1-carbaldehyde (5) were prepared and tested in vitro at 5-HT1A, 5-HT1D alpha, 5-HT1D beta, D2, and D3 receptors and in vivo for agonist activity in the 5-HTP and DOPA accumulation assays in reserpine-pretreated rats. Some of the compounds were resolved. The substituents used in the 1-position were chosen from a principal component analysis (PCA) plot constructed from both tabulated variables and variables calculated by semiempirical methods (PM3) and molecular mechanics software (MMX). Among the analogs prepared, some, e.g., compound 21, were equipotent to compound 5 with respect to 5-HT1A effects. All compounds were more or less selective for the 5-HT1A receptor, but many of the compounds displayed higher affinities for 5-HT1D alpha than for 5-HT1D beta receptors.

Animals↗
PubMed1995

Structure-activity relationships in the 8-amino-6,7,8,9-tetrahydro-3H-benz[e]indole ring system. 2. Effects of 8-amino nitrogen substitution on serotonin receptor binding and pharmacology.

A series of analogs of the potent and selective 5-HT1A agonist 8-(di-n-propylamino)-6,7,8,9-tetrahydro-3H-benz[e]indole-1-carbaldehyde (2b) (OSU191) was prepared in which the dipropylamino group was modified to bear a variety of substituents. These compounds were evaluated for both in vitro and in vivo effects, including the establishment of a receptor binding profile for these analogs at the 5-HT1A, dopamine D-2, dopamine D-3, 5-HT1D alpha, and 5-HT1D beta sites. Several of the analogs were evaluated for their biochemical effects in reserpinized rats, specifically with regard to in vivo changes in brain levels of 5-HTP and DOPA. Nearly all of the compounds prepared for this study were exceedingly potent at the 5-HT1A receptor, although most also displayed significant affinity for the dopamine D-2 receptor. A strong preference for the 5-HT1D alpha over the 5-HT1D beta receptor was also apparent. An analog bearing a butylglutarimide side chain, S-7k, was extremely selective for the 5-HT1A receptor. Although this compound possessed a Ki of 0.6 nM, it elicited only modest changes in 5-HTP brain levels. However, this compound did not appear as an antagonist when tested in a cyclic-AMP-based intrinsic activity assay.

Animals↗
PubMed1995

Physical mapping of complex genomes by sampled sequencing: a theoretical analysis.

A method for high-throughput, high-resolution physical mapping of complex genomes and human chromosomes called Genomic Sequence Sampling (GSS) has recently been proposed (Smith et al., 1994, Nature Genet. 7: 40-47). This mapping strategy employs high-density cosmid contig assembly over 200-kb to 1-Mb regions of the target genome coupled with DNA sequencing of the cosmid ends. The relative order and spacing of the sequence fragments is determined from the template contig, resulting in a physical map of 1- to 5-kb resolution that contains a substantial portion of the entire sequence at one-pass accuracy. The purpose of this paper is to determine the theoretical parameters for GSS mapping, to evaluate the effectiveness of the contig-building strategy, and to calculate the expected fraction of the target genome that can be recovered as mapped sequence. A novel aspect of the cosmid fingerprinting and contig-building strategy involves determining the orientation of the genomic inserts relative to the cloning vectors, so that the sampled sequence fragments can be mapped with high resolution. The algorithm is based upon complete restriction enzyme digestion, contig assembly by matching fragments, and end-orientation of individual cosmids by determining the best consistent fit of the labeled cosmid end fragments in the consensus restriction map.

Animals↗
PubMed1995

Synthesis and evaluation of pharmacological and pharmacokinetic properties of monopropyl analogs of 5-, 7-, and 8-[[(trifluoromethyl)sulfonyl]oxy]-2-aminotetralins: central dopamine and serotonin receptor activity.

In order to explore further the structure-activity relationships of serotonergic and dopaminergic ligands, a series of enantiopure 5-, 7-, or 8-triflate (-OTf)-substituted 2-(monopropylamino)-tetralins have been synthesized and evaluated in in vitro binding and in vivo biochemical and behavioral assays in rats. Consequently, the 8-OTf-substituted compound R-(+)-6 was found to be a potent and selective 5-HT1A (5-hydroxytryptamine) receptor agonist inducing a full-blown 5-HT syndrome in normal rats, while the corresponding 5-OTf-substituted compound S-(-)-12 was found to be a preferential dopamine (DA) autoreceptor agonist. A partial 5-HT syndrome was also observed for S-(-)-12, while the corresponding R-(+)-12 was found to be inactive at the DA and 5-HT receptors both in vitro and in vivo. Compounds 6 and 12 were found to be major urinary metabolites following oral administration of their dipropyl analogs (2 and 13, respectively). Thus 6 was proposed to be the metabolite responsible for the full-blown 5-HT syndrome seen after oral (but not subcutaneous) administration of 2. Similarly, 12 was proposed to be the metabolite responsible for the partial 5-HT syndrome seen after oral (but not subcutaneous) administration of 13. The bioavailability of R-(+)-6 (7.6 +/- 1.1%) appeared to be slightly lower than that of 2 (11.2 +/- 5.2%), although the in vitro metabolism of R-(+)-6 appeared to be slower than that of 2. Therefore first-pass metabolism was not thought to be the reason for the lower bioavailability of R-(+)-6, as compared to 2.

Animals↗
PubMed1995

Changes in [Ca2+]i in cultured rat proximal tubular epithelium: an in vitro model for renal ischemia.

Two components of ischemia, oxygen deprivation and glycolytic inhibition, were studied in primary cultures of rat proximal tubular epithelial cells (PTE). Changes in cytosolic Ca2+ ([Ca2+]i) and its relationship to loss of mitochondrial membrane potential (delta psi m) and cell killing were characterized in single cells whereas ATP and LDH release were determined in populations of monolayer PTE. (1) Inhibition of mitochondrial respiration with KCN or anoxia resulted in little decrease in ATP or cell killing and slight change in [Ca2+]i over many hours. (2) Inhibition of respiration and glycolysis with anoxic HBSS minus glucose resulted in decreased ATP (54.4%) and cell killing (20%) during 5 h anoxic exposure. In all cases, but at highly variable times (113 +/- 62 min), [Ca2+]i initially rose to > 1 microM. In some cases it immediately dropped, stabilizing at about 500 nM for up to 1 h and rising again just prior to cell death. (3) Inhibition with anoxia + 1 mM IAA resulted in rapid depletion of ATP and cell killing, with increases in [Ca2+]i to > 1 microM by 20 +/- 2 min. (4) Depletion of glycolytic metabolites by depriving cells of substrate for 12 h (in HBSS minus glucose) before subjecting to anoxia minus glucose resulted in increases in [Ca2+]i at 40 +/- 17 min followed by cell killing. (5) Injury with anoxic HBSS minus glucose was reversed by reaeration before or during the initial rise in [Ca2+]i. Later reaeration resulted in rapid cell killing. In all cases, delta psi m was dissipated only after [Ca2+]i was significantly elevated.

Adenosine Triphosphate↗
PubMed1995

High-resolution physical mapping of a 250-kb region of human chromosome 11q24 by genomic sequence sampling (GSS).

A physical map of the region of human chromosome 11q24 containing the FLI1 gene, disrupted by the t(11;22) translocation in Ewing sarcoma and primitive neuroectodermal tumors, was analyzed by genomic sequence sampling. Using a 4- to 5-fold coverage chromosome 11-specific library, 22 region-specific cosmid clones were identified by phenol emulsion reassociation hybridization, with a 245-kb yeast artificial chromosome clone containing the FLI1 gene, and by directed "walking" techniques. Cosmid contigs were constructed by individual clone fingerprinting using restriction enzyme digestion and assembly with the Genome Reconstruction and AsseMbly (GRAM) computer algorithm. The relative orientation and spacing of cosmid contigs with respect to the chromosome was determined by the structural analysis of cosmid clones and by direct visual in situ hybridization mapping. Each cosmid clone in the contig was subjected to "one-pass" end sequencing, and the resulting ordered sequence fragments represent approximately 5% of the complete DNA sequence, making the entire region accessible by PCR amplification. The sequence samples were analyzed for putative exons, repetitive DNAs, and simple sequence repeats using a variety of computer algorithms. Based upon the computer predictions, Southern and Northern blot experiments led to the independent identification and localization of the FLI1 gene as well as a previously unknown gene located in this region of chromosome 11q24. This approach to high-resolution physical analysis of human chromosomes allows the assembly of detailed sequence-based maps and provides a tool for further structural and functional analysis of the genome.

Base Sequence↗
PubMed1995

C-9 and N-substituted analogs of cis-(3aR)-(-)-2,3,3a,4,5,9b-hexahydro-3- propyl-1H-benz[e]indole-9-carboxamide: 5-HT1A receptor agonists with various degrees of metabolic stability.

Closely related analogs of the 5-HT1A receptor agonist cis-(3aR)-(-)-2,3,3a,4,5,9b-hexahydro-3-propyl-1H-benz[e]indole-9- carboxamide (1, U93385) were synthesized and pharmacologically evaluated. 9-Carboxamide analogs with varied nitrogen substitution (R2) were synthesized, and their serotonergic activity was evaluated in vitro and in vivo. Many of these compounds were incubated in the presence of rat hepatocytes, and the metabolic stability in vitro was compared to that of compound 1. Only the N-methyl and N-ethyl analogs ((-)-5a and (-)-5b) were more stable than compound 1, indicating that N-dealkylation is a major route of metabolism in this series. In addition, these analogs were found to be partial 5-HT1A receptor agonists in vivo. Modifications were also made to the carboxamide functionality of compound 1 (R1 in 2) to yield substituted amides or ketones. Among these analogs, the methyl ketone (-)-15a was found to be a 5-HT1A agonist with full intrinsic activity in vivo and was approximately 20 times more potent than compound 1 and 5 times more potent than 8-OH-DPAT.

Animals↗
PubMed1995

Primary sequence of a putative pyrophosphate-linked phosphofructokinase gene of Giardia lamblia.

Based on sequence information from a cosmid library, we obtained a genomic clone that encodes a putative inorganic pyrophosphate (PPi)-linked phosphofructokinase of Giardia lamblia. The open reading frame specified a protein of 59.8 kDa homologous to PPi- and ATP-linked phosphofructokinases. The greatest similarity (over 50% positional identity) was noted to the beta-subunits of both the Solanum tuberosum (potato) and Ricinus communis (castor bean) PPi-phosphofructokinases.

Amino Acid Sequence↗
PubMed1995

The effects of streptozotocin diabetes on sodium-glucose transporter (SGLT1) expression and function in rat jejunal and ileal villus-attached enterocytes.

Rats treated with streptozotocin for 17 days were used to determine the cellular origin of enhanced brush border glucose transport in the diabetic small intestine. In the jejunum of both normal and diabetic rats, phlorizin-sensitive (SGLT1-mediated) glucose transport was shown, by section autoradiography, to take place in upper villus enterocytes. The distribution of brush border SGLT1 transporters along villi, determined using immunogold cytochemistry, was similar to that found for glucose uptake. Longer villi, supporting a larger number of absorbing enterocytes in the diabetic jejunum, appeared to be responsible for increased glucose uptake in this condition. SGLT1 protein and SGLT1-mediated glucose transport were undetectable in normal distal ileal villi. However, following treatment with streptozotocin, both SGLT1 protein and SGLT1-mediated glucose transport were found to be present in basal ileal villus enterocytes. SGLT1 protein and SGLT1-mediated glucose transport both increased during enterocyte migration to the villus tip. Cellular induction of the SGLT1 transporter, as well as longer villi contribute to enhanced glucose transport in diabetic rat distal ileum. Close correlation between the positional expression of SGLT1 protein and absorptive function suggests that transporter density is an important determinant for up-regulation of sodium-dependent glucose transport in diabetes.

Animals↗