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Biomedical subjects

W C Smith

Publications and source records attributed to W C Smith.

At least 73 records · Page 4Linked to original sources
PubMed1997

Direct neural induction and selective inhibition of mesoderm and epidermis inducers by Xnr3.

During gastrulation in amphibians, secreted factors from Spemann's organizer act on dorsal ectoderm to induce the central nervous system. A number of secreted factors produced by Spemann's organizer have recently been identified. The TGFbeta family member Xnr3 is similar in amino acid sequence to the mouse factor nodal and is expressed in a restricted group of cells in the superficial layer of Spemann's organizer. Xnr3, unlike the related factors nodal, Xnr1 and Xnr2, lacks mesoderm-inducing activity. We report here that Xnr3 can directly induce neural tissue in Xenopus ectoderm explants (animal caps). Injection of animal caps with either Xnr3 RNA or plasmids induces the expression of the pan-neural genes NCAM and nrp1, as well as the anterior neural marker Cpl1. A growing body of evidence suggests that neural induction in Xenopus proceeds as the default in the absence of epidermis inducers. The best candidates for the endogenous epidermis inducers are BMP-4 and BMP-7. The neural inducing activity of Xnr3 can be inhibited by overexpression of BMP-4, as has been observed with the neural inducers noggin, chordin and follistatin. Furthermore, Xnr3 can block mesoderm induction by BMP-4 and activin, but not by Xnr2. The structural basis underlying the divergent activities of Xnr2 and Xnr3 was analyzed using site-directed mutagenesis. Mutations introduced to the conserved cysteine residues characteristic of the TGFbeta family were found to inactivate Xnr2, but not Xnr3. The most unique feature of Xnr3 is the absence of a conserved cysteine at the C terminus of the protein. This feature distinguishes Xnr3 from other TGFbeta family members, including Xnr2. However, we observed that changing the C terminus of Xnr3 to more closely resemble other TGFbeta family members did not significantly alter its activity, suggesting that other structural features of Xnr3 distinguish its biological activity from Xnr2.

Amino Acid Sequence↗
PubMed1997

Transmission and protection in leprosy: indications of the role of mucosal immunity.

Recent advances in treatment have achieved a large drop in the prevalence of active leprosy cases, but the incidence is at best decreasing slowly. Most people within leprosy-endemic populations have been exposed to Mycobacterium leprae, but few develop disease and it seems likely that the majority of the population develops protective immunity. If the site of initial infection is in the nose, dissemination of bacilli around the body to skin and nerve implies that the initial infection is bacilliferous and it has been shown that nasal M. leprae are detectable by polymerase chain reaction (PCR) of nasal swabs. Since salivary anti-M. leprae IgA (sMLIgA) levels are correlated with protection, we have surveyed groups of leprosy patients, contacts and the general population for both their sMLIgA and nasal PCR positivity. A total of 304 subjects were enrolled in the study: PCR and mucosal challenge tests were performed in 204 of these individuals. sMLIgA was present in 66% of treated patients, 76% of leprosy workers and 72% of healthy contacts. However, only 33% of indigenous subjects were sMLIgA+, in contrast to the earlier studies showing 74% positivity. PCR for M. leprae was present in both household contacts (2%) and indigenous controls (5%). In a subsequent follow-up study, nasal swabs were taken from 97 of those studied in the first series: three PCR+ individuals followed up after one year became negative, while of the remaining 94 PCR- individuals retested, 2 became positive. Of 112 subjects retested with the mucosal challenge test for sMLIgA: 22 converted from positive to negative and 12 from negative to positive. These results suggest that there is widespread subclinical transmission of M. leprae with transient infection of the nose resulting in the development of a mucosal immune response, despite the fact that few individuals will develop clinical disease. This may explain the current lack of effect of multidrug therapy (MDT) control programmes on incidence, although the reduction in general population immunity is consistent with some effect of MDT on transmission.

Adolescent↗
PubMed1997

Field treatment of acute nerve function impairment in leprosy using a standardized corticosteroid regimen--first year's experience with 100 patients.

In this study, a fixed regimen of prednisolone for the treatment of acute nerve function impairment (NFI) in leprosy patients was developed and introduced at field level in one area (Thakurgaon) of the Danish-Bangladesh Leprosy Mission's field in NW Bangladesh. The assessment, management and follow-up of patients was undertaken by leprosy control supervisors and physiotechnicians. One hundred patients were treated and followed up 6-8 months after completion of a 4-month course of prednisolone. At a level of change of 2 points (where a change of at least 2 points in the motor/sensory score was taken to indicate a change of status, i.e. full or partial recovery, or deterioration), 42/65 (64.6%) patients with sensory loss experienced some sensory recovery at completion of prednisolone treatment, and 40/65 (61.5%) at 6-8 months' follow-up. 41/85 (48.3%) of patients with motor loss experienced improvement, and 42/85 (49.4%) at follow-up. Analysis of the mean scores at start of prednisolone treatment, completion and at follow-up using Student's t-test showed highly significant (p < 0.001) differences between scores before and after treatment. The benefit is maintained as seen after a period of 6-8 months follow-up. It was concluded that treatment of acute nerve function impairment at field level by paramedical workers, using a standardized regimen of prednisolone is feasible, practical and effective.

Adolescent↗
PubMed1996

Differential effects of the incorporation of 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-5-iodouracil (FIAU) on the binding of the transcription factors, AP-1 and TFIID, to their cognate target DNA sequences.

The thymidine analog, 1-(2-deoxy-2-fluoro-beta-D-arabino-furanosyl)-5-iodouracil (FIAU), is incorporated into DNA in cell culture and in vivo. To investigate the effect of incorporation of FIAU into DNA on the binding of transcription factors, oligonucleotide duplexes which bind specifically to activator protein 1 (AP-1) or to TFIID were synthesized and binding of these oligonucleotides to their respective proteins was studied using gel-shift analysis. When thymidine at position -3, -1, 1 or 7 (relative to the first thymidine of the core binding sequence) was replaced with FIAU, binding to AP-1 was approximately 82, 28, 86 and 51%, respectively, of the binding to the non-substituted oligonucleotide to AP-1. When thymidine at position 3 or 5 (each adjacent to the center of dyad symmetry) was replaced with FIAU, binding to AP-1 was abrogated. Oligonucleotides containing FIAU at positions -1, 3 or 5, were much less able to compete with radiolabeled wild-type oligonucleotides for binding to AP-1. In contrast, the presence of FIAU, depending on its location, resulted in the increased binding of TFIID to its consensus target DNA sequence. These results indicate that incorporation of FIAU into DNA may induce local conformational changes resulting in the altered ability of transcriptional factors to bind to their cognate DNA sequences. Additional studies demonstrated that the presence of FIAU at a position 5' to the cleavage site in the consensus sequence T*TAA (where * is the cleavage site) inhibited restriction of the oligomeric duplex by MseI.

Antiviral Agents↗
PubMed1996

Cloning of the gene encoding honeybee long-wavelength rhodopsin: a new class of insect visual pigments.

Rhodopsins (Rh), G-protein-coupled receptors with seven transmembrane (TM) helices, form the first step in visual transduction in most organisms. Although many long-wavelength (LW) vertebrate opsin sequences are known, less information is available for invertebrate LW sequences. By a combination of RT-PCR and cDNA library screening, we have cloned and sequenced the honeybee LW Rh gene. The deduced protein is composed of 378 amino acids (aa), appears to have seven TM regions, and contains many of the structures and key aa thought to be important for Rh function. Phylogenetic analysis of this sequence in relation to other invertebrate Rh reveals it to be a member of a new group of insect LW Rh.

Amino Acid Sequence↗
PubMed1996

cDNA and protein sequence of a major form of P450, CYP2L, in the hepatopancreas of the spiny lobster, Panulirus argus.

A P450 fraction was previously isolated from spiny lobster hepatopancreas microsomes and shown in reconstitution experiments to be efficient in catalyzing the monooxygenation of benzphetamine, aminopyrine, benzo(a)pyrene, progesterone, and testosterone. In this study, N-terminal sequence information up to residue 39 was obtained from this P450 and used to design degenerate primers for screening a cDNA library constructed from hepatopancreas mRNA. Clones were obtained that contained part of the coding region of a P450 protein. Further exact primers were designed that permitted the isolation of clones containing coding information for other parts of the P450 sequence, as well as a clone that coded for the complete P450 protein sequence. The open reading frame of the complete coding region corresponded to a protein of 492 amino acids. The deduced amino acid sequence of this P450 was about 36% similar to individual mammalian P450s in the 2 family and did not show strong matches with other proteins in the data base. Based on sequence and the previously determined function, this spiny lobster P450 was assigned by the P450 nomenclature committee to a new P450 subfamily, CYP2L. This is the first description of a P450 primary sequence from a marine crustacean species and the first assignment of an invertebrate P450 into the 2 family.

Amino Acid Sequence↗
PubMed1996

Application of experimental design techniques to optimize a competitive ELISA.

This paper describes the application of experimental design techniques to optimize a sensitive ELISA for a hapten molecule with a calibration range of 0-1000 pg/ml. Ten factors that were expected to affect the assay performance were initially screened, followed by factorial experiments to delineate the effects of the critical factors identified at the screening stage. Assay performance was evaluated using a unique rating system based on standard curve reproducibility, assay detection limits and the use of desirability functions. This rating system allowed multiple responses to be evaluated simultaneously. It was found that the substrate incubation time and enzyme label lot played an important role, while dilutions of the enzyme label and the anti-hapten antibody showed significant interaction. These observations were in good agreement with optimal assay conditions based on historical data collected over a period of two to three years. Application of experimental design techniques enabled us to confirm the significance of the factors affecting the assay within a three month period, with a minimum number of experiments. In addition, information on interaction between factors were determined.

Animals↗
PubMed1996

A splice variant of arrestin from human retina.

Retinal arrestin is known to participate in the quenching of phototransduction through binding to light-activated and phosphorylated rhodopsin. Recently, a splice variant of retinal arrestin was identified in bovine photoreceptors which could bind unphosphorylated photoactive rhodopsin. In this report, a splice variant of retinal arrestin is identified in the human retina. The variant of human arrestin is produced by splicing out exon 12, unlike the bovine variant which is produced by splicing out exon 16. This 78 bp deletion in the human splice variant produces a polypeptide with a calculated molecular weight of 42.2 kDa that lacks 26 amino acids when compared to the full-length retinal arrestin. The use of quantitative competitive PCR indicates that the mRNA for the human splice variant of arrestin is present at approximately one-twentieth of the level of human arrestin mRNA.

Alternative Splicing↗
PubMed1996

Dose-dependent induction of GST-P+ staining foci by the rat hepatocarcinogen methapyrilene in the medium-term bioassay.

Previous studies have demonstrated that methapyrilene hydrochloride (MP) is a rat-specific nongenotoxic carcinogen which induces liver tumors in a dose-dependent manner following chronic exposure in the diet. This study was conducted to determine the dose response of MP in the medium-term bioassay and to compare the response to tumor incidence. Two weeks following a single initiating dose of diethylnitrosamine (DEN), male F344 rats were administered MP at doses of 0, 62.5, 125, 250, or 1000 ppm in the diet for 6 weeks. A 2/3 partial hepatectomy was performed 3 weeks post-DEN. At termination, sections from the remaining three lobes were stained with GST-P antibody. Number and size of foci were measured using an image analysis system with a digitizing board. MP induced a dose-dependent increase in the number of GST-P+ foci/cm2 (0 ppm = 0.85 foci/cm2; 62.5 ppm = 1.29 foci/cm2; 125 ppm = 1.59 foci/cm2; 250 ppm = 6.55 foci/cm2; 1000 ppm = 28.23 foci/cm2). A significantly greater number of foci were observed in the caudate lobe than in the anterior and posterior lobes. The size of individual foci was largely unaffected. This study demonstrates a strong correlation between foci induction and tumor incidence and suggests that this assay may have utility in predicting dose responses for the chronic bioassay.

Administration, Oral↗
PubMed1996

Ant opsins: sequences from the Saharan silver ant and the carpenter ant.

cDNA clones encoding opsins from compound eyes of carpenter ant, Camponotus abdominalis, and Saharan silver ant, Cataglyphis bombycina, were isolated from cDNA libraries. The opsin cDNAs from each species code for deduced proteins with 378 amino acids which are 92% identical. Of the 30 amino acid differences between the two proteins, 13 are non-conservative. Eight of these non-conservative substitutions are within the membrane spanning domain. The presence of a potential Schiff-base counterion in helix III in both species suggests that these opsins are the protein moiety of the visible range pigments. When compared to all known opsins, these opsins are most similar to the opsin from preying mantis (76% identity at the amino acid level). Phyletic comparisons group the two ant opsins with the other arthropod long wavelength opsins.

Amino Acid Sequence↗
PubMed1996

Cardiovascular effects of the macrolide antibiotic tilmicosin, administered alone and in combination with propranolol or dobutamine, in conscious unrestrained dogs.

Tilmicosin(TM), a macrolide antibiotic and active ingredient in formulated Micotil 300 (Eli Lilly and Co., Indianapolis, IN, USA), is the active ingredient in a formulated animal product used for the treatment of respiratory tract infections in cattle. Owing to the concern of governmental regulatory agencies over the possibility of an accidental injection of the antibiotic to a livestock handler, the cardiovascular effects of sub lethal doses of TM were evaluated in conscious mixed-breed dogs. Left ventricular function, systemic arterial blood pressure, and heart rate (HR) responses to TM alone and in combination with propranolol(P) or dobutamine HCl(DOB) were evaluated. Dogs were instrumented with indwelling micromanometers implanted in the left ventricular chamber and in the thoracic aorta. Cardiovascular variables were recorded, and the peak value of the first derivative of left ventricular pressure (dp/dt(max)) was used as an index of left ventricular inotropic state. Six treatments were randomly assigned to each of the six dogs using a Latin square design. The six treatments were vehicle, TM alone (2.5 mg/kg of body weight), TM immediately followed by P, and TM immediately followed by 1 of 3 dosages of DOB infused for approximately 45 min. Additionally, doses of TM alone (0.25, 1.0, 2.5, and 5.0 mg/kg) were administered to complete a dose-response curve. TM caused dose dependent decreases in (dp/dt(max)) and aortic pulse pressure. HR increased dose-dependently. Left ventricular end-diastolic pressure increased at the 2.5 and 5.0 mg/kg dosages. Left ventricular systolic pressure was reduced dose-dependently at the 2.5 and 5.0 mg/kg dosages. Treatment with P exacerbated the negative inotropic effect and the decrease in left ventricular systolic pressure, but did not attenuate the tachycardia associated with TM treatment. DOB attenuated the changes in ventricular inotropic state in a dose-dependent manner. DOB infusion also restored left ventricular systolic pressure at dosages of 3 or 10 micrograms/min/kg. Our data indicate that toxic doses of TM may have a negative inotropic effect in conscious dogs. HR increased in a dose-dependent manner and was not the result of beta 1-receptor stimulation. DOB reversed some, but not all, of the effects caused by TM administration.

Adrenergic beta-Agonists↗
PubMed1996

Prevention of disability in leprosy -- ILEP medical bulletin.

A survey of the prevention of disability policy and activities in a random sample of 200 ILEP assisted projects was conducted in 1995. This was followed by a workshop of field experts in different aspects of prevention of disability who work in different geographical regions. The survey findings and state of current knowledge on prevention of disability were reviewed during the workshop and recommendations on the planning, implementation and evaluation of simple and effective prevention of disability developed. Prevention of disability includes complex activities, such as nerve decompression and reconstructive surgery, however these recommendations focus on the simple techniques and approaches which can be implemented through leprosy control programmes, primary health care and community-based rehabilitation. These recommendations have been approved by the ILEP Medical Commission.

Data Collection↗
PubMed1996

Nerve function impairment in leprosy at diagnosis and at completion of MDT: a retrospective cohort study of 786 patients in Bangladesh.

This retrospective cohort study includes all new leprosy patients registered for multidrug therapy (MDT) in 1990 at the Danish-Bangladesh Leprosy Mission project in Bangladesh. The main objective was to determine the extent of nerve-function impairment (NFI) at diagnosis and at completion of MDT, and to identify opportunities for intervention and their relative impact on the prevention of disabilities (POD). A total of 786 patients were included; 486 males and 300 females. There were 315 PB, and 471 MB patients. In terms of the WHO leprosy disability grading system, at the time of diagnosis 31/315 (9.8%) had grade 1 or grade 2 disability in the PB group, and 177/471 (37.6%) in the MB group. The incidence rate of NFI during MDT was 3.5 per 100 person years at risk (PYR) in the PB group, and 7.5 per 100 PYR in the MB group. In the MB group 37 (7.9%) previously normal patients sustained NFI during MDT, whilst 19 (4.0%) with NFI at diagnosis showed complete recovery at completion of MDT. The most commonly involved nerves were the ulnar (motor function) and the posterior tibial nerves (sensibility). Reversal reactions were observed in 0.6% of the PB patients during MDT, giving an incidence rate of 1 per 100 PYR. The percentage of MB patients diagnosed with reversal during MDT was 14.2%, giving an incidence rate of 6 per 100 PYR. The percentage of MB patients diagnosed with ENL during MDT was 2.1%, with an incidence rate of 1 per 100 PYR. It was concluded that early detection of new cases of leprosy would prevent disabilities in more than 30% of all patients, thus having the highest impact in the quest for the prevention of disabilities. POD activities during and after MDT will prevent disabilities in approximately 10% of all cases. This study also indicates that treatment with prednisolone is effective and should be available at field level for all patients with recent NFI.

Adolescent↗
PubMed1996

The quantitation of turbinate atrophy in pigs to measure the severity of induced atrophic rhinitis.

The two-fold purpose of this study was to establish a useful image analysis technique for quantitation of turbinate atrophy and to determine an optimum bacterial dose for inducing atrophic rhinitis (AR). Two morphometric analysis methods were compared to determine a turbinate area ratio (TAR) and a turbinate perimeter ratio (TPR); the ratios of turbinate area to total nostril area and of turbinate perimeter to total nostril perimeter, respectively. Our first image analysis method differed from Collins et al (1) in that we used direct image capture (digitalization) via a video camera and a Macintosh microcomputer, rather than photographs and a digitizer tablet. The tracing techniques were the same as those used by Collins et al. The second morphometric method was modified from the first by exclusion of dorsal turbinate when tracing the nostril area and directly tracing only the ventral turbinate to get a turbinate measurement without subtracting. Area and perimeter ratios, for both methods, were compared to conventional visual snout scores, ventral measurements, and to each other. The results of the two image analysis methods correlated well, both with each other and with the visual scores. Doses of Pasteurella multocida (Pm) at a constant level, and Bordetella bronchiseptica (Bb) at various concentrations, were administered to 36 Hampshire-Duroc F1 SPF pigs to determine the best dose and frequency for inducing AR. Although the dose selection may have been somewhat affected by the pre-existing presence of Bb, the optimal dose per naris in this study was 2 mL Bb at 10(7) cfu/mL combined with 2 mL Pm at 10(9) cfu/mL inoculum. The frequency of administration (1 x or 2 x) did not greatly affect results. Turbinate area ratio was the best tool for quantitating gross morphological turbinate changes associated with atrophic rhinitis in this study. Our simplified modification of Collins et al image analysis method (exclusion of dorsal turbinates and direct measurement of ventral turbinates) correlated well with visual scores, and, when compared to Collins et al method, required less data manipulation and labour.

Animals↗