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Biomedical subjects

M S Smith

Publications and source records attributed to M S Smith.

At least 73 records · Page 4Linked to original sources
PubMed1998

Oral immunization of macaques with attenuated vaccine virus induces protection against vaginally transmitted AIDS.

The chimeric simian-human immunodeficiency virus SHIVKU-1, bearing the envelope of human immunodeficiency virus type 1 (HIV-1), causes fulminant infection with subtotal loss of CD4(+) T cells followed by development of AIDS in intravaginally inoculated macaques and thus provides a highly relevant model of sexually transmitted disease caused by HIV-1 in human beings. Previous studies using this SHIV model had shown that the vpu and nef genes were important in pathogenesis of the infection, and so we deleted portions of these genes to create two vaccines, DeltavpuDeltanefSHIV-4 (vaccine 1) and DeltavpuSHIVPPc (vaccine 2). Six adult macaques were immunized subcutaneously with vaccine 1, and six were immunized orally with vaccine 2. Both viruses caused infection in all inoculated animals, but whereas vaccine 1 virus caused only a nonproductive type of infection, vaccine 2 virus replicated productively but transiently for a 6- to 10-week period. Both groups were challenged 6 to 7 months later with pathogenic SHIVKU-1 by the intravaginal route. All four unvaccinated controls developed low CD4(+) T-cell counts (<200/microliter) and AIDS. The 12 vaccinated animals all became infected with SHIVKU-1, and two in group 1 developed a persistent productive infection followed by development of AIDS in one. The other 10 have maintained almost complete control over virus replication even though spliced viral RNA was detected in lymph nodes. This suppression of virus replication correlated with robust antiviral cell-mediated immune responses. This is the first demonstration of protection against virulent SHIV administered by the intravaginal route. This study supports the concept that sexually transmitted HIV disease can be prevented by parenteral or oral immunization.

AIDS Vaccines↗
PubMed1998

The acute suckling stimulus induces expression of neuropeptide Y (NPY) in cells in the dorsomedial hypothalamus and increases NPY expression in the arcuate nucleus.

Elevated neuropeptide Y (NPY) levels in the hypothalamus have been reported during lactation in the rat. The increase in NPY neuronal activity may be important in modulating a number of changes in hypothalamic neuronal function that are associated with lactation. The aims of the present study were to determine 1) if NPY neurons in the hypothalamus can be activated by the suckling stimulus; and 2) the time course of the activation in response to the suckling stimulus. In the first experiment, lactating rats were deprived of their 8-pup litters on day 9 post partum for 48 h. On day 11, the animals were divided into three groups and exposed to the suckling stimulus for varying periods of time up to 24 h. NPY neuronal activity was assessed by measuring changes in NPY messenger RNA (mRNA) levels, using in situ hybridization. NPY mRNA levels in the caudal portion of the hypothalamic arcuate nucleus (ARH) were approximately doubled by 24 h of suckling. NPY mRNA levels in the rostral portion of the ARH were not affected by suckling throughout the time examined. In addition to increased NPY mRNA in the ARH, resuckling for as little as 3 h induced NPY mRNA expression in cells located dorsal and lateral to the compact zone of the dorsomedial nucleus of the hypothalamus (DMH). NPY expression in these cells was not observed in the nonresuckled controls. These data demonstrate that the acute suckling stimulus activates two specific populations of NPY neurons in the hypothalamus: in the caudal portion of the ARH and in the DMH. The increased NPY neuronal activity may play an important role in modulating changes in hypothalamic regulation of hormone secretion and food intake.

Animals↗
PubMed1997

Alpha1-adrenergic receptor blockade blocks LH secretion but not LHRH cFos activation.

Long-standing pharmacological evidence supports a role of alpha-noradrenergic receptors in regulating LH release, yet little is known of the action of these receptors on LHRH neurons at the cellular level. We conducted a series of studies aimed at examining the effects of alpha-adrenergic receptor blockade on LH secretion and the cellular activation of LHRH neurons on proestrus. Our initial study used an irreversible alpha-receptor blocker, phenoxybenzamine (alpha1 > alpha2). A group of proestrous rats were treated with phenoxybenzamine at doses of 20 mg/kg, intraperitoneally, or 2, 10 and 20 mg/kg, intravenously, and compared with vehicle injected controls. Phenoxybenzamine administered intraperitoneally did not completely block the LH surge in all animals, whereas all intravenous doses consistently blocked the LH surge. cFos activation of LHRH neurons, on the other hand, was either unaffected or only slightly reduced by phenoxybenzamine treatment intraperitoneally. The effects of intravenous phenoxybenzamine were different, in that at all dose levels phenoxybenzamine completely blocked the LH surge and reduced by approximately half, the cFos activation in LHRH neurons (independent of dose). The effects of intravenous phenoxybenzamine could be mimicked by substitution of prazosin (an alpha1 antagonist, 4 mg/kg), but not idazoxan (an alpha2 antagonist, 1 mg/kg), administered intravenously at 11.00 h and 13.00 h on proestrus. These data provide evidence that noradrenergic systems operating through alpha1-receptors in the neuronal chain leading to the LH surge, while critical for the release of LHRH at the time of an LH surge, are not responsible for the cFos transcriptional changes in LHRH neurons that accompany the natural LH surge.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1997

Antibody responses to gut bacteria in ankylosing spondylitis, rheumatoid arthritis, Crohn's disease and ulcerative colitis.

Specific immunoreactive anti-Klebsiella antibodies are found in patients with ankylosing spondylitis (AS), a significant proportion of whom have occult inflammatory bowel disease. Molecular mimicry between Klebsiella or other bacterial antigens and HLA-B27 has been suggested in the pathogenesis of AS. The specificity of increased immunoreactivity against Klebsiella remains to be assessed against the abundant anaerobic bacterial flora, present either in healthy controls or in patients with ulcerative colitis (UC) and Crohn's disease (CD). Total immunoglobulin (Ig; IgG, IgA, IgM) immunoreactivity was measured by ELISA against Klebsiella pneumoniae, Proteus mirabilis, Escherichia coli and ten anaerobic isolates of the predominant normal bowel flora in 35 patients with active AS, 60 patients with inflammatory bowel disease (30 CD, 30 UC), 60 patients with active rheumatoid arthritis (RA) and 60 healthy controls. Ig immunoreactivity to K. pneumoniae was significantly elevated in AS (P < 0.001), CD (P < 0.001) and UC (P < 0.001) patients compared with RA patients and healthy controls. Furthermore, Ig immunoreactivity to P. mirabilis was significantly elevated only in RA patients, compared with the other inflammatory groups (P < 0.001) and controls (P < 0.001). There was no significant antibody response against E. coli or the ten obligate anaerobes in any of the test groups. The data suggested an increased immune response to Klebsiella in patients with AS, UC, CD and to Proteus in patients with RA. The specificity of these responses in some patients supported a possible role for enteric Klebsiella in the pathogenesis of AS and Proteus in RA. The role of Klebsiella in inflammatory bowel disease requires further study.

Adult↗
PubMed1997

Amyloidosis.

Explore the source record for details and available documents.

Aged↗
PubMed1997

Characterisation of impurities in bulk drug batches of fluticasone propionate using directly coupled HPLC-NMR spectroscopy and HPLC-MS.

Directly coupled HPLC NMR spectroscopic and HPLC-MS approaches have been used to confirm the identity of four known dimeric impurities in a partially purified batch of fluticasone propionate each at levels of 0.06-0.9% of parent compound based on UV absorption. It is also shown that HPLC NMR spectroscopy of the main drug peak in the 'time-slice' mode of operation, in which the elution of the HPLC peak is sampled a short time intervals, can be used to investigate the purity profile of the single HPLC peak detected by UV absorption. These studies show that HPLC-NMR is of considerable value in rapidly assessing HPLC peak purity and hence will be of benefit in providing additional information to support submission for drug registration to regulatory agencies.

Androstadienes↗
PubMed1997

In situ hybridization: identification of rare mRNAs in human tissues.

In situ hybridization is used for detection of RNA expression when conservation of tissue architecture is important. Most in situ hybridization protocols are written for tissues from animals (i.e., rat) which can be harvested and preserved rapidly. In contrast, human tissue is more difficult to obtain, hence in situ hybridization experiments must frequently be performed with less than optimal tissue preservation. This procedure details hybridization of a radiolabeled single-stranded RNA probe (riboprobe) to complementary sequences of cellular RNA in human tissue sections. This method enables detection of rare mRNA species in specific cell types of human tissue, offering distinct advantages over other in situ methods due to increased sensitivity. In particular, we have found that UV cross-linking and ribonuclease treatment protocols need to be altered for human tissues to ensure successful results, making this protocol unique to those previously described. In situ hybridization experiments can be performed using either DNA or RNA probes. RNA probes are advantageous since they form stable hybrids, are single-stranded, have little or no reannealing during hybridization, and can be synthesized to high specific activity. RNA probes can be readily created utilizing SP6, T3, or T7 promoters in both sense and antisense orientations to provide non-specific (control) and specific probes. Disadvantages of RNA riboprobes include a tendency for RNA to stick non-selectively more than DNA, and degradation by RNase (hence strict adherence to RNase-free precautions is mandatory during most of the protocol). The following protocol includes: (1) preparation of human tissues (tissue fixation and sectioning are highlighted as critical for probe penetration, preservation of tissue architecture, retention of tissue RNA, and overall success); (2) generation of radiolabeled riboprobes (total incorporation of radionucleotide is important to increase sensitivity; 35S was chosen as a compromise between excellent sensitivity, cellular resolution, and required exposure times (compared with 32P or 3H); non-isotopic methods have not been tested in a side-by-side comparison with 35S in human tissues by us, but theoretically might offer faster exposure times while maintaining high resolution); (3) hybridization conditions (stringency, temperature, washes, tissue dehydration); and (4) sample visualization (application of photographic emulsion, developing, fixing, staining, and counterstaining of individual slides).

Humans↗
PubMed1997

Facilitation or inhibition of the estradiol-induced gonadotropin surge in the immature rat by progesterone: regulation of GnRH and LH messenger RNAs and activation of GnRH neurons.

UNLABELLED: We have developed and extensively characterized immature female rat models to demonstrate inhibition or facilitation of the estradiol (E2)-induced gonadotropin surge by progesterone (P). We show here that the surge of free alpha-subunit is regulated similarly by P in these models. To investigate the possibility that P alters the biosynthesis of GnRH and/or LH, we measured levels of LH subunit mRNAs by Northern blot hybridization and GnRH mRNA by a solution hybridization-RNase protection assay. In the P inhibition model, alpha-subunit mRNA was significantly decreased when P was administered together with E2 for 32 or 48 h, and LHbeta, at 29 h. In the facilitation model, neither alpha-subunit nor LHbeta mRNA increased with premature and enhanced release of LH and free alpha-subunit. Levels of GnRH mRNA in E2-treated rats were significantly higher on the afternoon of the LH surge than on that or the following morning. There was no effect of P on GnRH mRNA levels, however, before, during, or after the LH surge in either paradigm. The time course of activation of GnRH neurons in P-facilitated rats was determined by double-label immunocytochemistry for GnRH and cFos. When serum LH concentrations were basal there was no expression of cFos in GnRH neurons. LH secretion in P-facilitated rats was initiated at 14.00 h and remained elevated until at least 19.00 h. During this time 63-78% of GnRH neurons were cFos positive. Both serum LH concentrations and the percentage of cFos-activated GnRH neurons were significantly lower in control rats treated with E2 alone than in those treated also with P. IN CONCLUSION: 1) suppression of LH and free alpha-subunit secretion by P can be accounted for at least partly by suppression of alpha-subunit mRNA levels; 2) P facilitation is not associated with changes in LH subunit or GnRH mRNA levels; 3) the large proportion of cFos-positive GnRH neurons in P-facilitated rats closely parallels increases in serum LH concentrations but is not accompanied by changes in GnRH mRNA levels. It is likely, therefore, that P acts in the facilitation model to trigger release of pre-existing GnRH stores by altering synthesis or activity of neuro-transmitters/neuropeptides involved in GnRH regulation and/or release of LH stores by altering, for example, pituitary responsiveness to GnRH (including self-priming) and components of the LH secretory apparatus. Similar possibilities may also obtain for the blockade of the gonadotropin surge in the inhibition model.

Animals↗
PubMed1997

Detection of human herpesvirus 8 DNA in Kaposi's sarcoma lesions and peripheral blood of human immunodeficiency virus-positive patients and correlation with serologic measurements.

Polymerase chain reaction (PCR) was used to examine human herpesvirus 8 (HHV-8) DNA from Kaposi's sarcoma (KS) lesions, normal skin, and peripheral blood mononuclear cells (PBMC) from human immunodeficiency virus (HIV)-infected patients who did or did not have KS. Of 9 KS biopsies, 8 were positive for five HHV-8 open-reading frames and ranged from 1 viral genome per 2.5-12.7 cells. Two putative replicative gene RNAs were detected by reverse transcription-PCR at low levels in 1 KS lesion. HHV-8 DNA was detected in 4 of 8 PBMC samples from patients with KS and in 2 of 18 PBMC samples from patients without KS. Sera were tested for reactivity with BCBL-1 cells (HHV-8 positive): High immunofluorescence antibody titers against HHV-8 lytic and latent antigens were detected in samples from KS-positive patients, and >20 polypeptides from induced BCBL-1 cells were recognized. Sera from 6 of 18 patients without KS showed low levels of antibodies against HHV-8 lytic and latent antigens.

Adolescent↗
PubMed1997

Light versus heavy sedation after cardiac surgery: myocardial ischemia and the stress response. Maritime Heart Centre and Dalhousie University.

UNLABELLED: The influence of light versus heavy sedation after coronary artery bypass graft (CABG) surgery on the development of postoperative myocardial ischemia has not been described. After uncomplicated CABG surgery, 50 patients were randomly assigned to receive LOW (n = 24; target Ramsay Sedation Score [RSS] = 2) or HIGH (n = 26; target RSS = 4) sedation with propofol. Analgesia was provided to maintain a visual analog scale (VAS) pain score <7. Myocardial ischemia was identified perioperatively using continuous 3-lead Holter monitoring. By measuring creatine kinase (CK) MB levels preoperatively, at entry to the intensive care unit (ICU), and every 12 h for 48 h; and by obtaining serial 12-lead electrocardiograms (ECG) (preoperatively; 2, 4, 12, 24, and 48 h after ICU admission, 8:00 AM the morning after surgery; and 5 min pre- and postextubation), myocardial infarction was identified. Endocrine stress response was assessed by measuring serum cortisol levels preoperatively, on admission to the ICU, and 24 h postoperatively. In a subset of patients (LOW n = 10, HIGH n = 11), plasma and urinary catecholamine levels were also measured. There were no between-group differences in demographics, operative course, hemodynamic variables, or cortisol levels while in the ICU. The VAS pain score and target RSS were achieved and sustained, and they differed between groups. There were three myocardial infarctions in each group by CKMB criteria alone. No ECG-identifiable myocardial infarction occurred. The ST segment versus time curve (LOW 187 +/- 295 versus HIGH 1071 +/- 2137 mm/min) differed between groups. Urinary and plasma catecholamine levels were similar between groups over the observation period. We conclude that the use of a reduced sedation regimen in combination with adequate analgesia did not result in an increased endocrine stress response or risk of myocardial ischemia. IMPLICATIONS: This randomized study of patients after coronary artery bypass surgery examined whether light (versus heavy) sedation with propofol in the intensive care unit was associated with an increased degree of myocardial ischemia. Using techniques to detect myocardial ischemia, including Holter monitoring, electrocardiogram, and myocardial enzyme measurements, no differences were found. We conclude that light sedation does not increase the endocrine stress response or the risk of myocardial infarction.

Aged↗
PubMed1997

Psychoactive cannabinoids increase mortality and alter acute phase cytokine responses in mice sublethally infected with Legionella pneumophila.

Marijuana contains both psychoactive and nonpsychoactive cannabinoids which have varying effects on the immune response system. Previous studies with delta-9-tetrahydrocannabinol (THC), the major psychoactive component of marijuana, showed that this substance augmented the susceptibility of mice to infection with the opportunistic pathogen Legionella pneumophila. The present study compared the enhancement of Legionella-induced mortality in mice due to two other major of marijuana components, cannabinol and cannabidiol, as well as the synthetic psychoactive cannabinoid CP 55,940. Inbred BALB/c mice, relatively resistant to infection with Legionella, were given the marijuana component 1 day before and 1 day after a sublethal intravenous infection with Legionella. Unlike the effect of THC, an 8 mg/kg dose of either cannabinol or cannabidiol did not affect mortality of the mice sublethally infected with Legionella. Mice given a 16 mg/kg dose of these components of marijuana, however, showed a slight to moderately increased mortality following the sublethal infection with Legionella. In contrast, a dose of 6 mg/kg of the synthetic psychoactive cannabinoid CP 55,940 given 1 day before and 1 day after infection with Legionella resulted in about 50% of the animals dying, the same level of augmentation of lethality induced by THC. Liver, spleen, and lung tissues were removed from the surviving mice 24 hr after the second THC injection and tested for the presence of viable Legionella using a standard CFU assay. The mice injected with THC before and after infection showed significantly higher levels of bacteria in their lung than mice that were not given any cannabinoid but were infected sublethally with the Legionella. Mice injected with the other cannabinoids, including the synthetic cannabinoid, showed a much smaller increase in the number of Legionella in their lung when infected with Legionella and treated with the drug. The number of bacteria recovered from the kidney and liver of the mice regardless of treatment with a cannabinoid, including with THC, did not show significant changes. RNA isolated from the spleen of the THC- and Legionella-treated animals was examined to determine at the molecular level whether acute phase pro-inflammatory cytokines (i.e., IL-1, IL-6 and TNF-alpha) were altered following drug treatment and infection, since previous studies had shown there were increased serum levels of these cytokines in the mice. It was found that the mRNA levels for IL-1 remained generally constant regardless of whether the infected animals were treated with a cannabinoid. However, the mRNA level for IL-6 was markedly increased following treatment of the infected animals with THC, suggesting the possible involvement of this pro-inflammatory cytokine in increased mortality. The mRNA level for TNF-alpha was generally low and not significantly altered in the drug treated animals. Mice given other cannabinoids, including cannabinol and cannabidiol, as well as the synthetic CP 55,940, showed no significant change in the level of mRNA for any of the cytokines tested.

Acute-Phase Proteins↗
PubMed1997

Rift Valley fever virus: a seroepidemiologic study of small terrestrial vertebrates in South Africa.

Epizootics of Rift Valley fever (RVF) are often associated with periods of heavy rainfall, which are favorable for mosquito vectors. However, in seasons with normal or low rainfall, enzootic circulation occurs, suggesting the existence of a natural host that can act as a cryptic carrier during interepizootic periods. To confirm the role of heavy rainfall in epizootic circulation, and to identify a possible natural host of RVF virus, serum samples from small terrestrial mammals in the Free State and Northern Cape regions of South Africa were collected before and after the 1988 floods. These areas are known to support epizootic circulation of RVF virus. The samples were tested for the presence of RVF virus-specific IgG using an ELISA and positive sera were confirmed by a neutralization test. Forty-seven (15%) of 312 Aethomys namaquensis (Namaqua rock rat) had antibodies to RVF virus. Of these positive sera, nine (6%) of 141 were collected before the floods of 1988 and 38 (22%) of 171 were collected afterwards (P = 0.001). Naive A. namaquensis were inoculated with RVF virus and developed a viremia, but no clinical symptoms, suggesting that they can act as temporary asymptomatic carriers of the virus. These results suggest a role for A. namaquensis as a cryptic carrier for RVF virus during interepizootic periods and support the results of other studies suggesting an amplifying role for heavy rainfall in the circulation of RVF virus.

Animals↗
PubMed1997

The binding potential of commercial antibody conjugates with sera of various small terrestrial mammals.

Infectious diseases of wild animals are of increasing importance, both from an economic viewpoint and because several of these diseases are pathogenic to man. However, serosurveys to determine the circulation of infectious organisms in wildlife are complicated by the fact that antibodies to species-specific immunoglobulins are not available for use in serological assays such as enzyme-linked immunosorbent assays (ELISAs) or immunofluorescence assays. To determine the binding potential of four commercially available antibody conjugates with the sera of wild animals, sera from 27 species of small terrestrial mammals were allowed to react with alkaline phosphatase-labelled protein A, anti-rabbit IgG, anti-mouse IgG and anti-human IgG by by the use of an ELISA. It was found that sera from some species of the order Lagomorpha bound optimally to anti-rabbit IgG, while anti-mouse IgG could be used for most species of Rodentia. For all Carnivora, Insectivora, Macroscelidea, Hyracoidea and other Rodentia, staphylococcal protein A demonstrated optimal binding. None of the sera that was tested bound to anti-human IgG. These results demonstrate that commercial conjugates can be used in serological assays in which wild animal sera are used, and should be useful for future serosurveys to determine the circulation of infectious agents in small terrestrial mammals.

Animals↗
PubMed1996

Central hypotensive effects of the alpha2a-adrenergic receptor subtype.

alpha2-Adrenergic receptors (alpha2ARs) present in the brainstem decrease blood pressure and are targets for clinically effective antihypertensive drugs. The existence of three alpha2AR subtypes, the lack of subtype-specific ligands, and the cross-reactivity of alpha2AR agonists with imidazoline receptors has precluded an understanding of the role of individual alpha2AR subtypes in the hypotensive response. Gene targeting was used to introduce a point mutation into the alpha2aAR subtype in the mouse genome. The hypotensive response to alpha2AR agonists was lost in the mutant mice, demonstrating that the alpha2aAR subtype plays a principal role in this response.

Adrenergic alpha-2 Receptor Agonists↗
PubMed1996

An introduction to transoesophageal echocardiography: II. Clinical applications.

PURPOSE: As progress has been made in the acquisition of cardiac images with transoesophageal echocardiography, the technique has moved from the confines of the cardiology laboratory into the operating room, the intensive care unit, and the emergency department. This has afforded anaesthetists the opportunity to become familiar with, and develop expertise in its practice. The purpose of this article is to present a review of transoesophageal echocardiography with reference to anaesthetic practice. SOURCE: The principle source of material was a computerized MedlineTM search of the English language literature from 1986 to 1995. PRINCIPLE FINDINGS: After discussing the technique of probe insertion, and describing some of the standard images, transoesophageal echocardiography's clinical utility is critically assessed. Comparisons with available monitoring techniques are made with reference to ventricular function, valvular heart disease, pericardial, aortic and congenital heart disease, and the management of the multiple traumatized patient. Issues of certification and maintenance of competence are also discussed. CONCLUSION: Although the benefit of transoesophageal echocardiography is intuitive in many clinical situations, in others, it has not been shown to improve upon presently existing monitoring techniques. The need for adequate training and collaboration with cardiology colleagues is emphasized.

Anesthesiology↗