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Biomedical subjects

J E Smith

Publications and source records attributed to J E Smith.

At least 37 records · Page 2Linked to original sources
PubMed2004

Cardiovascular changes following insertion of oropharyngeal and nasopharyngeal airways.

BACKGROUND: The cardiovascular responses following the insertion of oropharyngeal airways in anaesthetized patients have been found to be of little consequence. However, those following the insertion of nasopharyngeal airways have not been studied. The aim of this investigation was to compare the cardiovascular responses to the insertion of oropharyngeal and nasopharyngeal airways in anaesthetized patients. METHODS: Twenty-four ASA I or II patients aged 16-65 yr, requiring nasotracheal intubation as part of their anaesthetic management, received a standardized general anaesthetic and were randomly allocated to receive either a nasopharyngeal or an oropharyngeal airway. RESULTS: The two groups were similar with respect to age, weight and gender. There was a significant decrease in systolic pressure following the induction of anaesthesia in both groups. Following nasopharyngeal airway insertion, there was a significant rise in systolic pressure above pre-insertion levels (P< or =0.001), though not above pre-induction levels (P=0.808). There was no significant change in the oropharyngeal airway insertion group (P=0.619). At 1 min post-insertion, the mean (sd) systolic pressure in the nasopharyngeal insertion group, 122 (21.6) mm Hg, was significantly greater than that in the oropharyngeal insertion group, 103 (15.3) mm Hg (P=0.017). Diastolic pressure followed a similar pattern. In both groups, heart rate fell after induction and fell further after insertion, and at 4 min post-insertion was significantly lower than pre-induction and pre-insertion levels. There was no significant difference in heart rates between the two groups (P=0.372). CONCLUSIONS: The pressor response following the insertion of nasopharyngeal airways in anaesthetized patients is significantly greater than that following the insertion of oropharyngeal airways. However, the mean rise in arterial pressure does not exceed pre-induction level, and thus the response is less severe than that likely to be associated with orotracheal or nasotracheal intubation.

Adolescent↗
PubMed2004

Laboratory evidence of natural remobilization of multicomponent DNAPL pools due to dissolution.

Mixtures of dense non-aqueous phase liquids (DNAPLs) trapped in the subsurface can act as long-term sources of contamination by dissolving into flowing groundwater. In general, the components of higher solubility are removed more quickly, thus altering the composition of the remaining DNAPL, and possibly leading to changes in its physical properties. Through the development of a simple compositional model, Roy et al. [J. Contam. Hydrol. 2002 (59) 163] showed that preferential dissolution of a mixed DNAPL could potentially result in changes in density and interfacial tension that could subsequently lead to remobilization of an initially static DNAPL pool. The laboratory experiments presented in this next paper provide a proof-of-concept for the previously presented theory, demonstrating and quantifying this process of remobilization. In addition, the experiments provide a data set for evaluation of the model presented by Roy et al. [J. Contam. Hydrol. 2002 (59) 163]. In the four experiments, a DNAPL pool comprised of tetrachloroethene and benzene was created as an open pool overlying glass beads within a water-saturated 2-D flow box. Experiments included rectangular and triangular pools. In each of the experiments, remobilization (as breakthrough) was observed more than 2 weeks after formation of the initial pool. During each experiment, the pool height declined as mass was lost by dissolution, while sampling indicated a decrease in the mole fraction of benzene, the more soluble component. Small protuberances formed along the bottom of the pool as its composition changed with time and the displacement pressure was achieved for various pore throats. Eventually one of the protuberances extended further, forming a finger (breakthrough). In general, the pool emptied as the finger proceeded further into the beads. It was also shown theoretically and experimentally that remobilization will occur sooner for pools with a triangular (pointing down), rather than rectangular, shape. The experimental results were simulated using the model developed by Roy et al. [J. Contam. Hydrol. 2002 (59) 163]. The model matched the observations well, suggesting that it accurately represents the primary mechanisms involved with natural remobilization under the conditions of the study.

Benzene↗
PubMed2004

Immune, neuroendocrine, and somatic alterations in animal models of human heroin abuse.

We investigated immune, endocrine, and somatic alterations using two animal models of human heroin administration. In a heroin self-administration paradigm, we observed changes in immune function which suggest that the cycle of intermittent drug use is actually a stressor, which in turn not only exacerbates craving and drug-seeking behavior but also collaterally causes suppression of immune function and therefore susceptibility to disease. In another model of rats made physically dependent to heroin, we show that immune function is more broadly compromised, leading to evidence of infection, followed by chronic activation of innate immune function, cachexia, and weight loss.

Animals↗
PubMed2004

Detection of high levels of congenital transmission of Toxoplasma gondii in natural urban populations of Mus domesticus.

The relative importance of different transmission routes of Toxoplasma gondii has been a matter for debate. This ubiquitous parasite is generally thought to be transmitted by infective oocysts excreted by the definitive host, the cat. Ingestion of undercooked meat has also been considered an important route of transmission in many mammals while congenital transmission has generally been considered relatively rare. Experimental studies demonstrate the ability of T. gondii to be transmitted congenitally, but few studies have investigated the frequency of this transmission route in natural populations. We use PCR amplification of the SAG1 gene to investigate the frequency of congenital transmission in a wild population of mice (Mus domesticus) and show that congenital transmission is occurring in 75% of pregnancies in this population. Furthermore, for infected pregnant mice, transmission occurs to at least one foetus in 100% of cases while variable penetrance of congenital infection is observed. These high levels of congenital transmission in this wild population of mice, taken together with other recent data on congenital transmission in sheep, suggests that this phenomenon might be more widespread than previously thought.

Animals↗
PubMed2004

Toxoplasma gondii major surface antigen (SAG1): in vitro analysis of host cell binding.

Previous studies have indicated that SAG1, the major surface molecule of the protozoan parasite Toxoplasma gondii, is an important attachment ligand for the host cell. However, the research data that supports this claim comes largely from studies investigating tachyzoite binding, and not SAG1 binding per se. In this study we successfully developed an in vitro attachment assay to directly evaluate the mechanism of SAG1-host cell binding. Competition experiments were then performed using SAG1 that had been pre-treated with the neoglycoprotein BSA-glucosamide or with antibody. Soluble BSA-glucosamide blocked SAG1 attachment to MDBK cells in a dose-dependent manner, implying that SAGI binding is mediated, in part, via attachment to host cell surface glucosamine. Interestingly, pre-incubation of SAG1 in polyclonal sera from chronically infected mice failed to block binding. This challenges the assumption that anti-SAG1 antibodies block parasite attachment through the masking of SAG1 host cell binding domains. Taken together, this evidence presents new strategies for understanding SAG1-mediated attachment.

Animals↗
PubMed2004

Effects of prolonged strenuous exercise (marathon running) on biochemical and haematological markers used in the investigation of patients in the emergency department.

OBJECTIVES: To investigate the effects of strenuous exercise on commonly used biochemical and haematological variables in subjects running the 2002 London marathon. METHODS: 34 healthy volunteers (7 female, 27 male) were recruited for the study. Blood was taken before the start (at registration) and immediately after completion of the marathon. Samples were analysed for urea and electrolytes, liver function tests, creatine kinase (CK), CK-MB isoenzyme, myoglobin, troponin I, full blood count, a clotting screen, and D-dimers. The results before and after exercise were compared. Pearson's correlation coefficients were calculated for all variables. RESULTS: Significant increases were found in CK, CK-MB, aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and myoglobin following the marathon. However, there was no significant change in the level of troponin I. There was also evidence of activation of the coagulation and fibrinolytic cascades following the marathon, with a reduction in activated partial thromboplastin time, a reduction in fibrinogen, and an increase in D-dimers. CONCLUSIONS: The results confirm previous individual studies on marathon running and the biochemical and haematological tests routinely carried out in hospital. These are affected by prolonged exercise, and "abnormal" results in these tests may be normal after prolonged exercise and therefore not diagnostic of a disease process. The results of investigations in patients who have been exercising should be interpreted with caution.

Adult↗
PubMed2004

Hypertonic saline.

The optimal fluid for the resuscitation of critically ill and injured patients remains the subject of considerable controversy. Hypertonic crystalloid solutions such as hypertonic saline provide rapid volume expansion, have an acceptable safety profile, and are easy to store and transport. Recent meta-analyses suggest a trend toward increased survival in patients given hypertonic saline, and it has been suggested that they may have particular benefit in certain groups of patients such as hypovolaemic head injury patients. This short review examines the physiological and experimental evidence supporting the use of hypertonic saline in fluid resuscitation.

Brain Injuries↗
PubMed2004

The pathophysiology of exertional heatstroke.

Exertional heat illness remains a major cause of morbidity and occasional mortality within the Armed Forces. This review explores the normal responses to heat, known causes of exertional heatstroke, and suggests possible answers to the question of why one member of a military unit collapses with heat stroke, while matched controls at his side remain unaffected.

Body Temperature Regulation↗
PubMed2003

Establishment of the new genus Paranosema based on the ultrastructure and molecular phylogeny of the type species Paranosema grylli Gen. Nov., Comb. Nov. (Sokolova, Selezniov, Dolgikh, Issi 1994), from the cricket Gryllus bimaculatus Deg.

The ultrastructure of the microsporidian parasite Nosema grylli, which parasitizes primarily fat body cells and haemocytes of the cricket Gryllus bimaculatus (Orthoptera, Gryllidae) is described. All observed stages (meront, meront/sporont transitional stage ("second meront"), sporont, sporoblast, and spore) are found in direct contact with the host cell cytoplasm. Nuclei are diplokaryotic during almost all stages of the life cycle, but a brief stage with one nucleus containing an abundance of electron-dense material is observed during a "second merogony." Sporogony is disporous. Mature spores are ovocylindrical in shape and measure 4.5+/-0.16micromx2.2+/-0.07 microm (n=10) on fresh smears and 3.3+/-0.06 micromx1.4+/-0.07 microm (n=10) on ultrathin sections. Spores contain 15-18 coils of an isofilar polar filament arranged in one or two layers. Comparative phylogenetic analysis using rDNA shows N. grylli to be closely related to another orthopteran microsporidian, Nosema locustae, and to Nosema whitei from the confused flour beetle, Tribolium confusum. Antonospora scoticae, a parasite of the communal bee Andrena scotica, is a sister taxon to these three Nosema species. The sequence divergence and morphological traits clearly separate this group of "Nosema" parasites from the "true" Nosema clade containing Nosema bombycis. We therefore propose to change the generic name of N. grylli and its close relative N. locustae to Paranosema n. comb. We leave N. whitei in former status until more data on fine morphology of the species are obtained.

Animals↗
PubMed2003

Brain neurotransmitter turnover rates during rat intravenous cocaine self-administration.

The turnover rates of dopamine, norepinephrine, serotonin, aspartate, glutamate and GABA were measured in 27 brain regions of rats self-administering cocaine and in yoked cocaine- and yoked vehicle-infused controls using radioactive pulse-labeling procedures to identify brain neuronal systems underlying self-administration. Changes in the activity of heretofore unrecognized dopamine, norepinephrine, serotonin, glutamate and GABA innervations of the forebrain specific to cocaine self-administration were found. This included innervations of the nucleus accumbens, ventral pallidum, lateral hypothalamus and the anterior and posterior cingulate, entorhinal-subicular and visual cortices. Turnover rates also were calculated using metabolite/neurotransmitter ratios which were inconsistent with the pulse-label technologies indicating that ratio procedures are not accurate measures of neurotransmitter utilization. Results with the pulse-label technique provide evidence of the involvement of neuronal systems in cocaine self-administration not previously known, some of which may have a broader role in brain reinforcement processes for natural reinforcers (i.e. food, water, etc.) since drugs of abuse are thought to produce reinforcing effects by modulating activity in these endogenous systems.

Animals↗
PubMed2003

Two species of feminizing microsporidian parasite coexist in populations of Gammarus duebeni.

The amphipod crustacean Gammarus duebeni hosts two species of vertically transmitted microsporidian parasites, Nosema granulosis and Microsporidium sp. A. Here it is demonstrated that these co-occurring parasite species both cause infected females to produce female-biased broods. A survey of European G. duebeni populations demonstrates that these two parasites co-occur in six of 10 populations. These findings contrast with the theoretical prediction that two vertically transmitted feminizing parasites should not coexist in a panmictic population of susceptible hosts at equilibrium. Possible explanations for the co-occurrence of the two feminizing microsporidia in G. duebeni include the recent invasion of a new parasite, horizontal transmission of one or both parasites and the spread of alleles for resistance to the dominant parasite in host populations.

Amphipoda↗
PubMed2003

Association with host mitochondrial haplotypes suggests that feminizing microsporidia lack horizontal transmission.

The amphipod crustacean Gammarus duebeni hosts two feminizing microsporidian parasites, Nosema granulosis and Microsporidium sp. Samples of G. duebeni were collected from three sites on the Scottish island of Great Cumbrae and screened for microsporidia using polymerase chain reaction. Associations between the prevalence of the two feminizing parasites and haplotypes of the host mitochondrial gene cytochrome oxidase I (COI) were investigated. The prevalence of both parasites varied significantly among the host's COI haplotypes, suggesting that horizontal transmission is rare or absent in the life cycles of the feminizing microsporidia and that all transmission must therefore be vertical. Life cycles in which all transmission is vertical are common among bacterial parasites but have never before been demonstrated in Eukaryotic parasites.

Amphipoda↗
PubMed2003

Cardiovascular changes after the three stages of nasotracheal intubation.

BACKGROUND: Nasotracheal intubation typically comprises three distinct stages: (i) nasopharyngeal intubation; (ii) direct laryngoscopy to identify the vocal cords; and (iii) the passage of the tracheal tube into the trachea. The aim of this study was to identify and compare the cardiovascular responses associated with each of these stages. METHODS: Seventy-five ASA I or II patients, aged 16-65 yr, requiring nasotracheal intubation as part of their anaesthetic management, received a standardized general anaesthetic and were allocated randomly to receive either nasopharyngeal intubation or nasopharyngeal intubation plus direct laryngoscopy or full nasotracheal intubation. RESULTS: There was a significant hypertensive response, compared with pre-induction levels, in all three groups. The maximum mean (SD) mean arterial pressure in the nasotracheal intubation group was 113 (17.1) mm Hg, which was significantly greater than that in the nasopharyngeal intubation (97 (13) mm Hg) (P<0.001) and in the nasopharyngeal intubation plus laryngoscopy (103 (10.3) mm Hg) (P=0.007) groups. There was no significant difference between the nasopharyngeal intubation and nasopharyngeal intubation plus laryngoscopy groups (P=0.206). A similar pattern was seen for both systolic and diastolic arterial pressure. Nasotracheal intubation caused a significant increase in maximum mean (SD) heart rate, compared with pre-induction values, whereas the other two groups caused significant falls. The heart rate in the nasotracheal intubation group (92 (16.5) beats min(-1)) was significantly greater than in the other two groups (74 (8.6) (P<0.001) and 76 (12) (P<0.001) beats min(-1) respectively). There was no significant difference in heart rates between the nasopharyngeal intubation and nasopharyngeal intubation plus laryngoscopy groups (P=0.420). CONCLUSIONS: Nasopharyngeal intubation causes a significant pressor response. Stimulation of the larynx and trachea by the passage of the tracheal tube, but not direct laryngoscopy, causes a significant increase in this response.

Adolescent↗