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Biomedical subjects

G Smith

Publications and source records attributed to G Smith.

At least 325 records · Page 18Linked to original sources
PubMed1996

Expression of Fos in rat brain in relation to sodium appetite: furosemide and cerebroventricular renin.

Two experiments were performed to investigate the relationship between the expression of sodium appetite and the appearance of Fos-like immunoreactivity (Fos-IR) in the brain of rats. In the first experiment, rats were depleted of sodium by treatment with furosemide 24 h prior to sacrifice and without access to either food or sodium solution. Some rats had access to distilled water, and others had no fluids available during the 24 h. All of the furosemide-treated rats showed Fos-IR in both the subfornical organ (SFO) and around the organum vasculosum laminae terminalis (OVLT). Rats with access to distilled water during the depletion period showed no Fos-IR in the supraoptic (SON) or paraventricular hypothalamic nuclei (PVN) and, in parallel behavioral studies, comparably-treated rats consumed only 0.3 M NaCl solution at the end of the 24 h. In rats that had no fluids during the deprivation period, only about one half showed Fos-IR in SON and PVN and, in parallel behavioral studies, comparably treated rats consumed both water and 0.3 M NaCl solution at the end of 24 h. In a second experiment, cerebroventricular administration of renin stimulated short latency intake of 0.3 M NaCl and water. The relative intakes of water and NaCl were comparable at a low dose of renin, but intake of water exceeded that of NaCl after higher doses. Renin induced Fos-IR in SFO, MnPO, peri-OVLT region, SON and PVN. Both Fos-IR and fluid intake were antagonized by administration of losartan, an angiotensin II type 1 receptor antagonist. Thus, only the circumventricular organs of the lamina terminalis showed Fos-IR during each natriorexigenic regimen in these studies. These data support the view that Ang II of both central and peripheral origin activates the SFO and/or peri-OVLT region and contributes to sodium appetite.

Animals↗
PubMed1996

Active-site topologies of human CYP2D6 and its aspartate-301 --> glutamate, asparagine, and glycine mutants.

Cytochrome P450 2D6 (CYP2D6) catalyzes the oxidation of substrates with a positively charged nitrogen atom 5-7 angstroms from the site of the oxidation. The active-site topology of CYP2D6 is examined here with phenyl-, 2-naphthyl-, and p-biphenyldiazene, which react with P450 enzymes to form sigma-bonded aryl-iron (Fe-Ar) complexes. Ferricyanide-mediated migration of the aryl group from the iron to the porphyrin nitrogens produces the N-arylprotoporphyrin IX regioisomers (NB:NA:NC:ND, in which the aryl group is bound to the nitrogen of pyrrole rings B, A, C, and D, respectively) in the following ratios (zero means <5%): phenyl, 10:90:00:00; 2-naphthyl, 09:91:00:00; and p-biphenyl, 16:84:00:00. These results suggest that the CYP2D6 active site is open above pyrrole ring A and to a small extent above pyrrole ring B but is closed above pyrrole rings C and D. This geometry differs from those determined by the same method for P450s for which crystal structures are available. Replacement of Asp-301 by a Glu, which preserves the carboxylate side chain, causes no detectable change in the N-aryl porphyrin regioisomer patterns and only minor changes in the catalytic activity. Replacement of Asp-301 by an Asn or Gly, which eliminates the negatively charged side chain, suppresses migration of the aryl groups to pyrrole ring B without impairing migration to pyrrole ring A and virtually abolishes catalytic activity. These results provide a refined model of the active site of CYP2D6. They confirm, furthermore, that the loss of activity observed when Asp-301 is replaced by a neutral residue is due to loss of the charge-pairing interaction with the substrate positive charge and/or subtle structural effects in the vicinity of pyrrole ring B, but not to major structural reorganization of the active site.

Asparagine↗
PubMed1996

Effects of propofol and thiopentone on potassium- and carbachol-evoked [3H]noradrenaline release and increased [Ca2+]i from SH-SY5Y human neuroblastoma cells.

We have examined the effects of two intravenous anaesthetic induction agents, propofol and thiopentone, on K+ and carbachol evoked [3H]noradrenaline release from a human neuroblastoma cell line, SH-SY5Y. In this model, we have previously demonstrated that K+ evoked [3H]noradrenaline release was dependent on Ca2+ entry and carbachol evoked release was extracellular Ca(2+)- independent. Propofol inhibited K+ (100 mM)-evoked (IC50 of 42 +/- 11 microM), but not carbachol (1 mM)-evoked, [3H]noradrenaline release. Thiopentone inhibited both K+- and carbachol-evoked release with IC50 values of 116 +/- 15 microM and 169 +/- 39 microM, respectively. These inhibitory effects were not due to changes in the release dynamics, as assessed using perfused cells. Furthermore, thiopentone inhibition of carbachol-evoked release was not due to muscarinic receptor antagonism. Both propofol and thiopentone caused noncompetitive inhibition of K+-stimulated Ca2+ influx, with IC50 values of 127 +/- 7 microM and 121 +/- 10 microM, respectively. These effects were not due to interaction with GABAA receptors, but suggest that both compounds block voltage-sensitive Ca2+ channels. Thiopentone, but not propofol, inhibited carbachol-stimulated increased intracellular Ca2+ concentrations in the presence and absence of extracellular Ca2+. However, thiopentone had no effect on carbachol-stimulated inositol (1,4,5)-triphosphate formation, suggesting that thiopentone may directly inhibit Ca2+ release from intracellular stores.

Calcium↗
PubMed1996

Lineage commitment of transformed haematopoietic progenitors is determined by the level of PKC activity.

Our previous work showed that haematopoietic precursors transformed by the E26 avian leukemia virus undergo multilineage differentiation in response to the phorbol ester phorbol 12-myristate 13-acetate (PMA). Treatment of the cells with high concentrations of PMA (100 nM) favours myelomonocytic differentiation, while lower concentrations (20 nM) induce predominantly eosinophil differentiation. Here we have investigated the role of protein kinase C (PKC) in this process and found that 100 nM, but not 20 nM, PMA dramatically down-regulates total cellular PKC activity, indicating that high PMA concentrations result in less efficient signalling than lower PMA concentrations. Consistent with these findings is the observation that very low PMA concentrations (1 nM), which presumably only moderately activate PKC, induce myeloid differentiation. This suggests the existence of two PKC thresholds which play a role in lineage commitment. To test the model, alpha- and epsilon-PKC isoforms were expressed in E26-transformed progenitors. These cells exhibited myelomonocytic differentiation even in the absence of PMA, while treatment with concentrations of PMA as high as 100 nM led to the differentiation of predominantly eosinophils and failed to downregulate the exogenous PKC. Our results suggest that different levels of PKC activity result in three different phenotypes: (i) no PKC activity maintains the progenitor phenotype; (ii) low PKC activity favours myelomonocytic differentiation; (iii) high PKC favours eosinophil differentiation.

Animals↗
PubMed1996

Time-dependent effects of a haloperidol challenge on energy metabolism in the normal human brain.

Positron emission tomography and the fluorodeoxyglucose method were used to measure regional brain metabolism before and 2 h after haloperidol (5 mg, i.m.) in 11 young normal men. These data were compared with measures obtained from nine previously studied normal men who had received no drug intervention. Although a previously published study had demonstrated significantly decreased metabolism in whole brain, neocortex, limbic cortex, thalamus, and caudate nucleus 12 h after a 5-mg dose of haloperidol, the present 2-h study did not show significant metabolic changes despite the fact that significant extrapyramidal effects occurred. Taken together, these studies demonstrate differences in the temporal organization of behavioral and metabolic responses to haloperidol challenge.

Adult↗
PubMed1996

cDNA cloning and characterization of murine transcriptional enhancer factor-1-related protein 1, a transcription factor that binds to the M-CAT motif.

The M-CAT motif is a cis-regulatory DNA sequence that is essential for muscle-specific transcription of several genes. Previously, we had shown that both muscle-specific (A1) and ubiquitous (A2) factors bind to an essential M-CAT motif in the myosin heavy chain beta gene and that the ubiquitous factor is transcriptional enhancer factor (TEF)-1. Here we report the isolation of mouse cDNAs encoding two forms (a and b) of a TEF-1-related protein, TEFR1. The TEFR1a cDNA encodes a 427-amino acid protein. The coding region of TEFR1b is identical to 1a in both nucleotide and predicted amino acid sequence except for the absence of 43 amino acids downstream of the TEA DNA-binding domain. Three TEFR1 transcripts (approximately 7, approximately 3.5, and approximately 2 kilobase pairs) are enriched in differentiated skeletal muscle (myotubes) relative to undifferentiated skeletal muscle (myoblasts) and non-muscle cells in culture. In situ hybridization analysis indicated that TEFR1 transcripts are enriched in the skeletal muscle lineage during mouse embryogenesis. Transient expression of fusion proteins of TEFR1 and the yeast GAL4 DNA-binding domain in cell lines activated the expression of chloramphenicol acetyltransferase (CAT) reporter constructs containing GAL4 binding sites, indicating that TEFR1 contains an activation domain. An anti-TEFR1 polyclonal antibody supershifted the muscle-specific M-CAT.A1 factor complex in gel mobility shift assays, suggesting that TEFR1 is a major component of this complex. Our results suggest that TEFR1 might play a role in the embryonic development of skeletal muscle in the mouse.

Amino Acid Sequence↗
PubMed1996

The eosinophil-specific cell surface antigen, EOS47, is a chicken homologue of the oncofetal antigen melanotransferrin.

The EOS47 antigen is a 100-kD cell surface glycoprotein selectively expressed by avian retrovirus-transformed eosinophils and their precursors. We have purified the EOS47 protein to homogeneity and used peptide sequence information to clone EOS47-encoding cDNAs. The open reading frames from these cDNAs predict a 738 amino acid protein with homology to human melanotransferrin, a membrane-found, transferrin-like protein that is expressed at high levels by a subset of melanomas, tumor cell lines, fetal intestine, and liver, but not by most normal adult tissues. The predicted protein sequence of EOS47 displays a 61% sequence identity with melanotransferrin and conservation of all 28 cysteine residues, indicating a similar tertiary structure. The finding that EOS47 lacks several of the iron-coordinating amino acids present in all transferrins suggests that it may be impaired in its ability to bind iron. In nonhematopoietic tissues, EOS47 is expressed at high levels by epithelial brush borders of small intestine and kidney and at lower levels by cells lining the sinusoids of the liver. Within hematopoietic tissues, EOS47 is restricted to a subpopulation of cells (1% to 5%) in bone marrow and early spleen and fluorescence-activated cell sorting of EOS47+ cells leads to a dramatic ( > 30-fold) enrichment of peroxidase+ eosinophils. In contrast, peripheral blood eosinophils are EOS47-, suggesting that the antigen is expressed by newly formed eosinophils and that expression ceases shortly before these cells emigrate from the bone marrow into the peripheral blood. Our results show that melanotransferrin is a stage-specific marker of eosinophils and should be useful for their isolation and further characterization.

Amino Acid Sequence↗
PubMed1996

A longitudinal evaluation of prevalent negative beliefs about residential placement for troubled adolescents.

To investigate the validity of five prevalent negative beliefs about residential placement, we followed adolescents from a residential program and a comparison group at 3-month intervals for 4 to 8 years. This residential program in the Midwest uses the Teaching-Family Model in which six to eight adolescents live in a family-style environment. The interviews included five scales reflecting youths' views about important aspects of their lives in placement: (1) Delivery of Helpful Treatment, (2) Satisfaction with Supervising Adults, (3) Isolation from Family, (4) Isolation from Friends, and (5) Sense of Personal Control. Hierarchical linear modeling allowed us to estimate group differences while controlling for developmental trends, demographic factors, and prior differences between groups. The two groups were equivalent on all scales before the study. During the following placement, however, the treatment group's ratings were significantly more positive than the comparison group on four of the five scales and approached significance on the fifth. These findings suggest that negative beliefs about life in residential placement for adolescents may not apply to all programs.

Adolescent↗
PubMed1996

The use of ultrasound to study the prevalence of hydatid cysts in the right lung and liver of sheep and goats in Turkana, Kenya.

Ultrasound examination of the liver and right lung was performed in 260 sheep and 320 goats from the Turkana district of Kenya. Hydatid cysts were visualized in 9.2% of the sheep and 2.5% of the goats. Of the animals positive on ultrasound, 87.5% received post-mortem examinations. Eighteen (6.9%) sheep and 5 (1.5%) goats were positive for hydatid cysts on ultrasound and post-mortem examination. False-positives were a result of Taenia hydatigena cysticerci present in the liver in all but 1 case. Positive predictive value of ultrasound for diagnosis of hydatidosis in sheep and goats was 82.1%.

Animals↗
PubMed1996

Serum albumin distribution in early treated anorexia nervosa.

We investigated the effects of malnutrition and refeeding on albumin distribution and metabolism in patients undergoing treatment for anorexia nervosa. Using autologous 125I-labelled albumin, we measured the fractional catabolic rate and calculated the relative sizes of the plasma and extravascular albumin pools in 6 female anorexia nervosa subjects and 6 matched controls. We were unable to demonstrate any differences in either the catabolic rate of albumin (fractional or absolute) or in serum albumin concentration between anorexia nervosa and control subjects. There was a large expansion of the extravascular albumin pool in the anorexia nervosa subjects--36% when expressed in relation to body weight. We conclude that, at the time of study, there were no effects of anorexia nervosa on albumin catabolism in these subjects. However, the condition and its treatment are associated with a significant relative expansion of the extravascular albumin pool. This contrasts to some extent with previous work, which suggested that in protein depletion the plasma albumin pool is maintained at the expense of the extravascular albumin pool. The expansion of the extravascular albumin pool is possibly related to the relative excess of interstitial fluid seen in starvation and in the initial phases of refeeding.

Adult↗
PubMed1996

Oxygen free radical and cytokine generation during endovascular and conventional aneurysm repair.

OBJECTIVES: Endovascular aneurysm repair has been proposed as a "minimally invasive" alternative to conventional aneurysm resection. One of the most important potential benefits of endoluminal surgery is the avoidance of aortic cross clamping, which may attenuate the ischaemia-reperfusion injury that complicates open aneurysm repair. This study aimed to quantify the metabolic response to both conventional and endovascular aortic surgery. DESIGN: Prospective clinical study. SETTING: University hospital. METHODS: Femoral vein blood samples (pre-clamp, during aneurysm repair and 5 and 30 min post reperfusion) were obtained from 12 patients undergoing aortoaortic aneurysm repair, six by conventional transperitoneal inlay replacement (median age 71 years, median aneurysm diameter 5.8 cm), and six by endoluminal deployment of a straight endograft (median age 73 years, median aneurysm diameter 5.5 cm). All endovascular procedures were completed satisfactorily with no conversions to conventional surgery. OUTCOME MEASURES: Venous blood samples were analysed for oxygen free radical (OFR) production using the quantifiable oxidation of IgG in plasma, and cytokine (IL-1 beta and TNF-alpha) generation by radioimmunoassay. [table: see text] RESULTS: The results are given as median values with interquartile ranges: CONCLUSIONS: These results suggest that the ischaemia-reperfusion response associated with conventional aneurysm surgery may be largely negated by endovascular techniques. This may have significant consequences as the generation of oxygen free radicals and cytokines have been implicated in the development of systemic organ failure following aortic surgery.

Aged↗
PubMed1996

Dielectric analysis of phosphorylcholine head group mobility in egg lecithin liposomes.

PURPOSE: A knowledge of the interfacial properties of lecithin underpins our understanding of many of the physicochemical characteristics of drug delivery systems such as liposomes and lecithin stabilized microemulsions. In order to further this understanding, a high frequency dielectric study of the interfacial properties of egg lecithin liposomes was undertaken. METHODS: The effect of temperature, lecithin concentration and probe sonication on the interfacial dielectric properties of liposomal suspensions was investigated by high frequency dielectric relaxation spectroscopy between 0.2-6 GHz. RESULTS: The frequency dependent permittivity of each suspension exhibited a dielectric dispersion centred around 100 MHz, corresponding to the relaxation of zwitterionic head groups. The activation energy for head group reorientation was estimated as delta H = 6.3 kJ mol-1. There was an increase in extent of inter-head group interactions on increasing the liposome volume fraction, whereas the effect of probe sonication showed that: (i) head groups in both the outer and inner lamellae contribute to the dielectric response; (ii) the head groups may be less restricted in liposomes of high surface curvature with few lamellae; (iii) the high frequency permittivity of the suspension increased on sonication, as a result of a reduction in the amount of (depolarized) interlamellar water following a reduction in the number of lamellae per liposome. CONCLUSIONS: Dielectric analysis of the zwitterionic head groups of lecithin therefore provides a means for investigating the surface of lecithin liposomes, and may be used to investigate the effect of drugs and other solutes on membranes.

Eggs↗
PubMed1996

Overexpression of p53 protein and its significance for recurrent progressive bladder tumours.

OBJECTIVE: To determine the prognostic value of the overexpression of p53 protein as determined by immunohistochemistry in recurrent progressive transitional cell carcinomas of the bladder. PATIENTS AND METHODS: A total of 222 tumours from 86 patients with recurrent disease, 20 from patients with no evidence of recurrence after resection of initial tumour and 11 normal bladder (controls) were investigated. Using a microwave technique to expose antigens, formalin-fixed sections were immunohistochemically stained for p53 using a polyclonal antiserum. Two independent observers scored the sections for evidence of overexpression of p53. RESULTS: Of 86 patients with recurrent disease, 51 demonstrated overexpression of p53 protein, as did six of 20 patients with non-recurrent disease. Overexpression was not linked to recurrence (P = 0.5) but was related to worsening histological stage (P < 0.01) and increasing grade (P < 0.01). Regression analysis showed that overexpression of p53 for the primary tumour was not of predictive prognostic value for death from bladder cancer, time to progression or time to recurrence. Tumour grade was the only variable of prognostic value in all the statistical models. Patients with overexpression of p53 showed no reduction in overall survival. CONCLUSION: These findings suggest that overexpression of p53, as determined immunohistochemically, appears to have no predictive prognostic value over stage and grade in bladder tumours.

Aged↗
PubMed1996

A randomized, placebo-controlled study of the immunogenicity of human immunodeficiency virus (HIV) rgp160 vaccine in HIV-infected subjects with > or = 400/mm3 CD4 T lymphocytes (AIDS Clinical Trials Group Protocol 137).

Immune responses provoked by human immunodeficiency virus (HIV) infection ultimately are insufficient to control the disease and do not include strong lymphocyte-proliferative responses to HIV antigens or antibodies to many viral epitopes. A randomized double-blind, placebo-controlled trial evaluated the immunogenicity of recombinant HIV envelope vaccine (rgp160) in HIV-infected subjects with > or = 400/mm3 CD4 T cells. Controls received hepatitis B vaccine. Of subjects receiving rgp160, 98% developed lymphocyte-proliferative responses to the immunogen, 33% to a different envelope protein, and 56% and 60% to p24 and p66, respectively. All doses of vaccine (20, 80, 320, 1280 microgram) induced new responses. New antibodies to epitopes on rgp160 developed only in recipients of higher doses of rgp160. CD4 T cell percentages declined less rapidly in recipients of rgp160 than in controls. Vaccination of HIV-infected subjects with rgp160 results in cellular and humoral immune responses to HIV that infection itself had not stimulated.

AIDS Vaccines↗
PubMed1996

Reversible ovulatory failure associated with the development of luteinized unruptured follicles in women with inflammatory arthritis taking non-steroidal anti-inflammatory drugs.

The case histories of three young women with ankylosing spondylitis, rheumatoid arthritis and a seronegative inflammatory polyarthritis undergoing investigations for infertility are presented. In each, non-steroidal anti-inflammatory drug (NSAID) therapy was associated with the recurrent development of luteinized unruptured ovarian follicles and normal ovulation following drug withdrawal. It is suggested that NSAID therapy may be an important and frequently overlooked cause of anovulation and infertility.

Adult↗