Biomedical subjects

J E Smith

Publications and source records attributed to J E Smith.

At least 73 records · Page 4Linked to original sources

PubMed2001

Multiple phosphorylated isoforms of NRL are expressed in rod photoreceptors.

NRL, a bZIP transcription factor of the Maf subfamily, interacts with the homeodomain protein CRX and synergistically regulates rhodopsin expression. Here we report that six isoforms of NRL (29-35 kDa) are generated by phosphorylation and expressed specifically in the mammalian retina. The anti-NRL antibody also cross-reacts with a cytosolic 45-kDa protein, which is detected in neuronal tissues but is not encoded by the NRL gene. In both human retinal cell cultures and sections of fetal and adult human retina, NRL is present in the nuclei of developing and mature rods but not cones. We propose that NRL regulates rod photoreceptor-specific gene expression and is involved in rod differentiation.

Alkaline Phosphatase↗

PubMed2001

Localization of pigment epithelium derived factor (PEDF) in developing and adult human ocular tissues.

PURPOSE: To localize pigment epithelium-derived factor (PEDF) in developing and adult human ocular tissues. METHODS: PEDF was localized in fetal and adult eyes by immunofluorescence with a polyclonal antibody (pAb) against amino acids 327-343 of PEDF, or a monoclonal antibody (mAb) against the C-terminal 155 amino acids of PEDF. Specificity of the antibodies was documented by Western blotting. PEDF mRNA was localized in adult retina by in situ hybridization. RESULTS: In developing retinas (7.4 to 21.5 fetal weeks, Fwks), pAb anti-PEDF labeled retinal pigment epithelium (RPE) granules, developing cones, some neuroblasts and many cells in the ganglion cell layer (GCL). In adult retinas, pAb anti-PEDF labeled rod and cone cytoplasm and nuclei of rods but not cones. Cells in the INL and GCL, choroid, corneal epithelium and endothelium, and ciliary body were also pAb PEDF-positive. Preadsorption of pAb anti-PEDF with the immunizing peptide blocked specific labeling in retina and other tissues, except for photoreceptor outer segments. In agreement with the immunolocalization with pAb anti-PEDF, in situ hybridization revealed PEDF mRNA in the RPE, photoreceptors, inner nuclear layer cells and ganglion cells in adult retina. In developing retinas 18 Fwks and older, and in adult retinas, mAb anti-PEDF labeled the interphotoreceptor matrix (IPM). Western blots of retina, cornea, and ciliary body/iris with pAb anti-PEDF produced several bands at about 46 kDa. With mAb anti-PEDF, retina produced one band at about 46 kDa; cornea and ciliary body/iris had several bands at about 46 kDa. CONCLUSIONS: PEDF, originally reported as a product of RPE cells, is present in photoreceptors and inner retinal cell types in developing and adult human eyes. Photoreceptors and RPE may secrete PEDF into the IPM.

Aged↗

PubMed2001

Cardiorespiratory reflexes in a working heart-brainstem preparation of the house musk shrew, Suncus murinus.

In this study, we adapted the working heart-brainstem preparation (WHBP) from rodents to the Insectivore, Suncus murinus. Suncus WHBPs had a baseline heart rate of 333 +/- 8 beats min(-1), a perfusion pressure of 69 +/- 2 mm Hg and a respiratory cycle length of 6.5 +/- 0.7 s. Administration of atropine produced an increase in heart rate of 26 +/- 9 beats min(-1) indicative of the presence of cardiac vagal tone. Activation of baroreceptors produced pressure-dependent reflex falls in heart rate and reduced respiratory cycle length. The baroreceptor reflex sensitivity in Suncus WHBP was a decrease in heart rate of 8.1 +/- 1.4 beats min(-1) mm Hg(-1). Activation of peripheral chemoreceptors with aortic injections of sodium cyanide (0.1-12.5 microg) produced a dose-dependent reflex fall in heart rate and reduced respiratory cycle length. The reflex falls in heart rate evoked by baroreceptor and peripheral chemoreceptor stimulation were both atropine-sensitive. We conclude that viable WHBP can be prepared from Suncus and that Suncus WHBP is a novel non-rodent model in which to study brainstem-mediated reflexes.

Animals↗

PubMed2001

T (tail)-rhythm oscillators: principles of nervous control of the vasculature revealed?

This review focuses on the nervous control of the caudal ventral artery of the rat tail, and aims to convince the reader that sympathetic control of the vasculature can be mediated via neural oscillators intrinsic to the sympathetic nervous system. The definitive functional significance of these oscillators is unknown at present. However, it is expected that through dynamic relationships with modulating and driving inputs, such oscillators would permit graded vascular responses.

Animals↗

PubMed2001

The positive influence of maternal identification on body image, eating attitudes, and self-esteem of Hispanic and Anglo girls.

OBJECTIVE: The role of maternal identification in the development of girls' body image, eating attitudes, and self-esteem was examined. METHOD: Hispanic and Anglo girls (n = 410) ages 8-13 were surveyed using the Body Esteem Scale (BES), the Children's Eating Attitudes Test, the Piers-Harris Children's Self-Concept Scale, and the Child Figure Drawing task. From this sample, normal-weight girls with high or low scores on the BES were selected for the main study. Ninety-two mother-daughter pairs participated in this second phase in which mothers completed similar questionnaires and girls performed a Q-sort task measuring maternal identification. RESULTS: Maternal identification was positively correlated with girls' self-esteem and negatively correlated with eating problems and body dissatisfaction. Also, mothers with high self-esteem tended to have daughters with high self-esteem. The mothers of girls with low BES scores found a significantly greater discrepancy than the mothers of girls with high BES scores when contrasting their daughters' current shape with either the ideal figure for their daughter or the figure they believed boys would find attractive. DISCUSSION: Girls who aspired to be like their mothers in terms of personality traits felt better about themselves and their bodies compared with girls with low maternal identification.

Adolescent↗

PubMed2001

Body image treatment for a community sample of obligatory and nonobligatory exercisers.

OBJECTIVE: Cognitive-behavioral therapy (CBT) was used to treat body dissatisfaction in obligatory and nonobligatory exercisers within a community sample of normal weight women. METHOD: Ninety-four women (36% obligatory exercisers, 64% nonobligatory exercisers) were assigned randomly to CBT or the waiting-list (WL) control group. RESULTS: The hypotheses that obligatory exercisers would show poorer pretreatment body image and greater compulsiveness than nonobligatory exercisers were supported partially. The prediction that obligatory exercisers would respond less favorably to treatment was not supported. Overall, CBT participants evidenced significantly better body image outcomes than the WL at posttreatment, but many effects were lost by the follow-up. DISCUSSION: Treatment response is considered in light of the unique characteristics of this ethnically diverse, older community sample when compared with the young students in earlier body image intervention studies. The high rate of physical activity among even the nonobligatory exercisers is highlighted for its mood-regulation properties and its treatment implications.

Adult↗

PubMed2001

Concentric retinitis pigmentosa: clinicopathologic correlations.

Progressive concentric (centripetal) loss of vision is one pattern of visual field loss in retinitis pigmentosa. This study provides the first clinicopathologic correlations for this form of retinitis pigmentosa. A family with autosomal dominant concentric retinitis pigmentosa was examined clinically and with visual function tests. A post-mortem eye of an affected 94 year old family member was processed for histopathology and immunocytochemistry with retinal cell specific antibodies. Unrelated simplex/multiplex patients with concentric retinitis pigmentosa were also examined. Affected family members of the eye donor and patients from the other families had prominent peripheral pigmentary retinopathy with more normal appearing central retina, good visual acuity, concentric field loss, normal or near normal rod and cone sensitivity within the preserved visual field, and reduced rod and cone electroretinograms. The eye donor, at age 90, had good acuity and function in a central island. Grossly, the central region of the donor retina appeared thinned but otherwise normal, while the far periphery contained heavy bone spicule pigment. Microscopically the central retina showed photoreceptor outer segment shortening and some photoreceptor cell loss. The mid periphery had a sharp line of demarcation where more central photoreceptors were near normal except for very short outer segments and peripheral photoreceptors were absent. Rods and cones showed abrupt loss of outer segments and cell death at this interface. It is concluded that concentric retinitis pigmentosa is a rare but recognizable phenotype with slowly progressive photoreceptor death from the far periphery toward the central retina. The disease is retina-wide but shows regional variation in severity of degeneration; photoreceptor death is severe in the peripheral retina with an abrupt edge between viable and degenerate photoreceptors. Peripheral to central gradients of unknown retinal molecule(s) may be defective or modify photoreceptor degeneration in concentric retinitis pigmentosa.

Adolescent↗

PubMed2001

Identifying influences on model uncertainty: an application using a forest carbon budget model.

Uncertainty is an important consideration for both developers and users of environmental simulation models. Establishing quantitative estimates of uncertainty for deterministic models can be difficult when the underlying bases for such information are scarce. We demonstrate an application of probabilistic uncertainty analysis that provides for refinements in quantifying input uncertainty even with little information. Uncertainties in forest carbon budget projections were examined with Monte Carlo analyses of the model FORCARB. We identified model sensitivity to range, shape, and covariability among model probability density functions, even under conditions of limited initial information. Distributional forms of probabilities were not as important as covariability or ranges of values. Covariability among FORCARB model parameters emerged as a very influential component of uncertainty, especially for estimates of average annual carbon flux.

Carbon↗

PubMed2001

MGE-PCR: a novel approach to the analysis of Toxoplasma gondii strain differentiation using mobile genetic elements.

The position of mobile genetic elements (MGE) within eukaryotic genomes is often highly variable and we have exploited this phenomenon to develop a novel approach to strain differentiation in Toxoplasma gondii. Two PCR based strategies were designed in which specific primers were used to amplify T. gondii MGE's revealing information on element size and positional variation. The first PCR strategy involved the use of a standard two primer PCR while the second strategy used a single specific primer in a step-up PCR protocol. This approach was applied to T. gondii reference strains which were either acute virulent or avirulent to mice. The use of a standard two primer PCR reaction revealed the presence of a virulence related marker in which all avirulent strains possessed an additional 688 bp band. The single primer PCR strategy demonstrated that all virulent strains had identical banding patterns suggesting invariance within this group of strains. However, all avirulent strains had different banding patterns indicating the presence of a number of individual lineages within this group. The applicability and sensitivity of MGE-PCR in epidemiological studies was demonstrated by direct amplification of T. gondii from sheep tissue samples. All sheep isolates, tested in this way, gave identical banding patterns suggesting the presence of an endemic Toxoplasma strain on this farm.

Animals↗

PubMed2001

High levels of congenital transmission of Toxoplasma gondii in a commercial sheep flock.

Our current understanding of congenital transmission of Toxoplasma gondii from ewe to lamb dictates that infection frequently results in abortion and the death of the developing foetus, that the birth of live infected lambs occurs rarely and that the cat is the predominant source of infection in ewes. Using direct polymerase chain reaction detection of T. gondii, we report high levels of congenital transmission occurring in a commercially managed sheep flock. We sampled foetal-derived placental tissue and tissues from aborted lambs and showed that congenital transmission was detected in these tissues from 61% of all pregnancies. Where pregnancies resulted in the death of one or more lambs, T. gondii was detected in the lamb tissue for all but one of 18 (94%) pregnancies. Of the successful pregnancies resulting in the birth of live lambs we were able to detect T. gondii in foetal-derived placental tissue from 37 of 70 (42%) pregnancies. These results show that congenital transmission is occurring in a high percentage of lambings including normal healthy lambings, at this farm, suggesting that this route of transmission from generation to generation may be much more significant than that reported previously. These results may have implications for sheep husbandry and future epidemiological studies of T. gondii.

Animals↗

PubMed2001

Conditioned food aversion in Suncus murinus (house musk shrew) - a new model for the study of nausea in a species with an emetic reflex.

The lack of a small animal model with an emetic reflex in which the relationship between conditioned food aversion and emesis could be investigated prompted a study of the insectivore, Suncus murinus (the house musk shrew). A novel food (either tuna or chicken cat food) was paired (C+) with a single exposure to either nicotine (4 mg/kg sc), motion (1 Hz, 4 cm, 10 min) or lithium chloride (100 mg/kg ip) or was paired (C-) with either saline or sham exposure to motion. Nicotine and motion both induced emesis (retching/vomiting) but lithium chloride did not. All three treatments produced a conditioned food aversion after a single pairing with consumption of C+ food. When given a choice between the two foods, S. murinus given lithium chloride, motion exposure and nicotine consumed, respectively, only 25%, 23% and 1% of their total intake from the C+ food. This study shows that a conditioned food aversion can be readily induced in S. murinus and that the induction of emesis can be uncoupled from food aversion. S. murinus provides a promising new model in which the relationship between emesis, nausea and conditioned food aversion can be investigated.

Animals↗

PubMed2001

Transovarial transmission in the microsporidia.

The microsporidia are an ancient and diverse group of protists which have many unusual characteristics. These include prokaryotic-like 70s ribosomes, enclosed nuclear division, a lack of mitochondria and complex life cycles which frequently involve vertical transmission. This use of vertical transmission is unparalleled by other protists and is seen only among bacterial endosymbionts and sex ratio distorters and in host cell organelles. Transovarially transmitted microsporidia can have unusual and profound effects on host population sex ratios. We here consider the mechanisms of transovarial transmission and its implications for parasite evolution. We review parasite/host relationships and the evolution of virulence under transovarial transmission and consider the implications of these parasites for host ecology and evolution.

Animals↗

PubMed2001

Evaluation of retinal photoreceptors and pigment epithelium in a female carrier of choroideremia.

PURPOSE: To clarify the pathogenesis of choroideremia. STUDY DESIGN: Human tissue study. TISSUES: Eyes of an 88-year-old symptomatic female carrier of choroideremia (CHM) and six normal, age-matched donors. METHODS: The eyes were processed for histopathologic examination, including immunocytochemistry with an antibody against the CHM gene product, REP-1, and retinal cell-specific markers. RESULTS: The CHM carrier retina showed patchy degeneration, but the photoreceptor and retinal pigment epithelium (RPE) loss appeared to be independent. The choriocapillaris was normal except where retinal areas were severely degenerate. The CHM gene product, REP-1, was localized to the cytoplasm of rods but not cones. CONCLUSIONS: It has generally been considered that photoreceptor degeneration in CHM is secondary to loss of the choriocapillaris or RPE. This study suggests that the rod photoreceptors are a primary site of disease in CHM.

Adaptor Proteins, Signal Transducing↗

PubMed2001

Determining effective interfacial tension and predicting finger spacing for DNAPL penetration into water-saturated porous media.

The difficulty in determining the effective interfacial tension limits the prediction of the wavelength of fingering of immiscible fluids in porous media. A method to estimate the effective interfacial tension using fractal concepts was presented by Chang et al. [Water Resour. Res. 30 (1994) 125]. We modified the method in that the macroscopic interface length was used instead of the system width. Methods to determine the macroscopic and the microscopic interface length are given. Lab experiments of dense nonaqueous phase liquid (DNAPL) penetrating into water-saturated glass beads were carried out in a two-dimensional (2-D) transparent chamber. The displacement processes were recorded using a 35-mm camera or a video camera, which was directly connected to and controlled by a computer. Unlike the method of Chang et al. (1994), the modified method used here gives a constant value of the effective interfacial tension over time. The predicted wavelengths of fingering are relatively close to those observed except for the fine beads.

Fractals↗

PubMed2001

The velocity of DNAPL fingering in water-saturated porous media: laboratory experiments and a mobile-immobile-zone model.

Dense nonaqueous phase liquids (DNAPLs) are immiscible with water and can give rise to highly fingered fluid distributions when infiltrating through water-saturated porous media. In this paper, a conceptual mobile-immobile-zone (MIZ) model is presented to describe the structure of a DNAPL finger in water-saturated porous media and the velocity of finger propagation. A finger is composed of a finger body and a tip. The finger body has a mobile core and an immobile sheath. All the DNAPL within the tip of a finger is mobile. Lab experiments utilizing image analyses of a DNAPL (PCE) penetrating into water-saturated homogeneous glass beads were carried out in a two-dimensional transparent chamber. The results show that the fingers elongated almost linearly with time. The fingers did not grow laterally after the tip of the finger had passed. The average finger diameters were between 3.9 and 5.4 mm for PCE propagation in water-saturated glass bead porous media with mean particle diameters from 0.32 to 1.36 mm. The estimated mobile core diameters were 51-60% of the average finger diameters.

Glass↗

PubMed2001

Microsporidian life cycles and diversity: the relationship between virulence and transmission.

The microsporidia are obligate intracellular parasites which have diverse life cycles involving both horizontal and vertical transmission and parasitise a wide range of vertebrate and invertebrate hosts. In this paper we consider the life cycles and diversity of the microsporidia. We focus in particular on the relationship between parasite transmission and virulence and its implications for host-parasite coevolution. The use of horizontal and vertical routes of transmission varies between species and there is a strong link between transmission and virulence. Horizontal transmission is characterised by a high parasite burden and associated pathogenicity. In contrast, vertical transmission is characterised by low virulence, which has led to under-reporting of this important transmission route. Vertically transmitted microsporidia may also cause male killing or feminisation of their host, with implications for host population sex ratio and stability. Phylogenetic analysis shows that vertical transmission occurs in diverse branches of the Microspora. We find that there is evidence for vertical transmission in both vertebrate and invertebrate hosts and conclude that it is a common or possibly even ubiquitous transmission route within this phylum.

Animals↗

PubMed2001

Identifying the more patent nostril before nasotracheal intubation.

We have studied the reliability of two simple pre-induction tests used to select the more patent nostril for nasotracheal intubation by comparing their results with those obtained from fibreoptic examination of the nostrils, in 75 maxillo-facial patients requiring nasotracheal intubation under general anaesthesia, who had no history of nasal obstruction. The tests comprised (1) estimation of the rate of airflow through each nostril during expiration by palpating the passage of air when the contralateral nostril was occluded, and (2) asking for the patient's assessment of airflow through the nostrils, following the administration of a vasoconstrictor. After each test, noses were classified as left or right nostril clearer or nostrils equally clear. After the induction of general anaesthesia, bilateral nasendoscopies were performed and videotape recordings of these were later analysed by an otolaryngologist who had no knowledge of the test results. Intranasal abnormalities were identified and noses were again classified as left or right nostril clearer or nostrils equally clear. There was no significant difference between the overall diagnostic success rates of the two tests (44% and 47%, respectively). In patients with intranasal abnormalities, the numbers of correct diagnoses made by the two tests were not significantly different and were also not significantly different from the number of correct selections made if only the right nostril or only the left nostril had been used for the intubation. In view of the relatively high diagnostic failure rates, anaesthetists should not rely on the two tests investigated when selecting the best nostril for nasotracheal intubation.

Adolescent↗

PubMed2001

A survey of ethnic foods for microbial quality and aflatoxin content.

A range of ethnic foods was examined for their microbiological content in relation to total viable counts (TVC) of aerobic bacteria, counts of presumptive coliforms, yeast and mould counts; presence of Salmonella spp., Listeria monocytogenes, Escherichia coli O157:H7 and Campylobacter spp.; total enumeration of Clostridium perfringens, Staphylococcus aureus and Bacillus spp.; identification of moulds and the presence of total aflatoxins. Samples, which included cereals, nuts, dried fruits, herbs and spices, were obtained from local retail outlets and distributors. It was established that three samples of pistachio nuts contained significant levels of aflatoxins. The concentration of total aflatoxins in these three nut samples ranged from 15 to 259 microg/kg of sample. Only two other samples contained trace amounts of aflatoxins, all other samples analysed were found to be free of any detectable level of aflatoxins. TVCs, coliform counts and yeast and mould counts varied widely depending on the matrix tested. Generally, rice, wheat and peanuts produced low counts whereas other nuts, gram flour and spices produced much higher counts. Cl. perfringens, Staph. aureus, and Bacillus spp. were common in spices, nuts and gram flour, however, Listeria monocytogenes was only detected in four samples and in no sample could Salmonella spp, E. coli O157:H7 or Campylobacter spp. be detected.

Aflatoxins↗