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Biomedical subjects

H Smith

Publications and source records attributed to H Smith.

At least 217 records · Page 12Linked to original sources
PubMed1994

Increased cyclosporine sensitivity of T cells from cord blood compared with those from the adult.

Despite the increasing numbers of paediatric transplants performed, little is known about the immune responses of T lymphocytes in human neonates. Here we have compared the effects of cyclosporine on the phytohaemagglutinin (PHA) response of immature (cord) and mature (adult) lymphocytes using the following parameters of activation: (i) proliferation, measured by 3H-thymidine uptake; (ii) expression of cell surface IL-2 receptor; (iii) release of IL-2 into the supernatant. Cyclosporine was added to cultures of PHA-stimulated lymphocytes at doses ranging from 5 to 5000 ng/ml. The proliferative response of cord lymphocytes was considerably more sensitive to cyclosporine at each dose, so that 50% inhibition was achieved by 6 ng/ml and 21.5 ng/ml doses of cyclosporine on cord and adult lymphocytes, respectively. Expression of the IL-2 receptor by PHA-activated T cells and their subsets was assessed by flow cytometry. Cyclosporine inhibited IL-2 receptor expression to a significantly greater degree in cord CD4 and CD8 cells (49.7% and 70.1%) than in adults (17.9% and 30.0%). Biologically active IL-2 release was measured using the IL-2-dependent cell line CTLL-2. Cyclosporine at doses 50-5000 ng/ml produced 80-99% inhibition of both cord and adult responses. However, at very low doses (5 ng/ml) cyclosporine produced 69.3% inhibition of cord lymphocytes, compared with 42.0% of adult lymphocytes. These results suggest that the T cells of neonates are considerably more sensitive to cyclosporine than are adult T cells.

Adult↗
PubMed1994

Chronic inflammatory demyelinating polyneuropathy.

Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) is a rare neurological disease. Definitive therapy is not yet established. We report our use of intravenous Immunoglobulin (iv IgG) in two cases of CIDP and review the therapeutic options available. Intravenous IgG is a ubiquitous practical treatment particularly in patients who do not respond to steroids and where a rapid response is required.

Adult↗
PubMed1994

Significant Changes in the Lipid-Lipoprotein Status of Premenopausal Morbidly Obese Females following Gastric Bypass Surgery.

The morbidly obese premenopausal female may be more dyslipoproteinemic and at greater risk for developing coronary heart disease than her lean or less seriously obese counterparts. The purpose of the present study was to examine the effects of weight loss with Roux-en-Y gastric bypass surgery on the lipid-lipoprotein status of morbidly obese, premenopausal females. Anthropometrics and blood samples for lipid-lipoprotein analyses were obtained before surgery and 6 - 12 months postoperatively. Following surgery, patients lost 30% of their initial body weight, along with a 40% decline (p < 0.01) in total triglyceride and a 20% decrease (p < 0.01) in total cholesterol. Levels of cholesterol in the high density lipoprotein (HDL) fraction were unaffected by weight loss, but there was a significant (p < 0.05) increase in the proportion of HDL in its more buoyant and anti-atherogenic form, i.e. HDL-L. The apolipoprotein B-containing lipoproteins, very low density lipoprotein (VLDL), intermediate density lipoprotein (IDL), and low density lipoprotein (LDL), were reduced up to 70% following surgery. There were no significant changes in VLDL or IDL particle composition, i.e. cholesterol/triglyceride, cholesterol/ protein, but there was a significant (p < 0.01) increase in the ratio of cholesterol/apolipoprotein B in LDL, suggesting a shift from the small, dense atherogenic LDL to a larger, less atherogenic particle. We conclude that weight loss following gastric bypass surgery markedly improves the lipid-lipoprotein status of morbidly obese premenopausal females and, thereby, significantly reduces the risk of coronary disease.

Journal Article↗
PubMed1994

Radiation hormesis in relation to radiation protection.

A radiation-induced adaptive response has been convincingly demonstrated in a variety of cultured cells. It is associated with the activation of genes and the up-regulation of protein enzymes, resulting in a delay in cell-cycling and the opportunity to repair radiation-damaged DNA as a transient phenomenon. Just how the adaptive response operates in a multi-cellular organism is still obscure, but there is little or no evidence in rodents and the beagle dog of a shortening of lifespan after exposure to acute doses up to a few hundreds of mGy or after chronic daily exposure resulting in accumulated doses of up to a few Gy. Nevertheless there is an increase in both non-neoplastic and neoplastic diseases which need not be life-threatening. A prudent approach has been used by the ICRP in deriving a value for radiation-induced detriment at low doses from which to recommend individual dose and risk limits in their system of radiological protection. This is not to deny the possible existence of an adaptive response. However, in the opinion of the author, there is no overwhelming evidence to date which justifies the belief that exposure to low doses in the range of natural background up to a few tens of mSv reduces the incidence of radiation-induced cancer in a population composed of persons of all ages with a wide spectrum of diseases and with widely different sensitivities to radiation.

Adaptation, Physiological↗
PubMed1993

Characterization of Ca2+/calmodulin-dependent protein kinase in rat pancreatic islets.

We have attempted to identify islet Ca2+/calmodulin-dependent protein kinase (CaM kinase) by comparing its activity with purified brain CaM kinase II. Islet CaM kinase, in the presence of calmodulin and Ca2+, phosphorylated major endogenous substrates of 102, 57 and 53 kDa and also exogenous glycogen synthase; brain CaM kinase II phosphorylated glycogen synthase and peptides of 57 and 53 kDa. Alloxan (1 mM) inhibited the phosphorylation of glycogen synthase and the 102, 57 and 53 kDa islet peptides by islet CaM kinase; the phosphorylation of glycogen synthase and the 57 and 53 kDa substrates by brain CaM kinase II was also inhibited by alloxan. The Ca2+ and calmodulin-dependencies of phosphorylation of the endogenous islet substrates differed. In the presence of 400 nM calmodulin, half-maximal phosphorylation was attained at Ca2+ concentrations of 80 +/- 9, 401 +/- 61 and 459 +/- 59 nM for the 102, 57 and 53 kDa substrates respectively. In the presence of 10 microM Ca2+, half-maximal phosphorylation was attained at calmodulin concentrations of 9 +/- 2, 38 +/- 2.5 and 37 +/- 2 nM for the 102, 57 and 53 kDa substrates respectively. Differential centrifugation located the 102 kDa substrate in the post-100,000 g supernatant and the 57 and 53 kDa substrates in the particulate fraction. These data suggest that islet CaM kinase is similar to, if not identical with, brain CaM kinase II, but that phosphorylation of the endogenous 102 kDa substrate occurs by a distinct kinase which shows different sensitivities to Ca2+ and calmodulin. This kinase probably corresponds to CaM kinase III and the 102 kDa peptide to elongation factor 2 (EF-2), since the 102 kDa peptide was shown to undergo ADP-ribosylation in the presence of diphtheria toxin and NAD+.

Adenosine Diphosphate↗
PubMed1993

Three-dimensional structure of the FK506 binding protein/ascomycin complex in solution by heteronuclear three- and four-dimensional NMR.

A high-resolution three-dimensional solution structure of the FKBP/ascomycin complex has been determined using heteronuclear multidimensional nuclear magnetic resonance spectroscopy (NMR) and a distance geometry/simulated annealing protocol. A total of 43 structures of the complex, including 3 tightly bound water molecules, were obtained using 1958 experimental restraints consisting of 1724 nuclear Overhauser effect (NOE) derived distances, 66 chi 1 and 46 phi angular restraints, and 122 hydrogen bond restraints. The root mean square (rms) deviations between the 43 FKBP/ascomycin solution structures and the mean atomic coordinates were 0.43 +/- 0.08 A for the backbone heavy atoms and 0.80 +/- 0.08 A for all non-hydrogen atoms. Angular order parameters for the family of 43 conformations were calculated to determine dihedral convergence. Order parameters for phi, psi, and chi 1 angles exhibited mean values of 0.98, 0.97, and 0.95, respectively, while the mean of the chi 2 order parameter was 0.63. Comparisons were made between the FKBP/ascomycin complex and two NMR-derived solution structures of unbound FKBP and the X-ray crystal structure of an FKBP/FK506 complex. Differences were observed between the FKBP/ascomycin complex and uncomplexed FKBP for residues 33-45 and 78-92. In contrast, the NMR-derived solution structure of the FKBP/ascomycin complex and the X-ray crystal structure of the FKBP/FK506 complex were very similar. Differences between the two complexes were mainly observed in the conformations of some highly solvent exposed side chains.

Carrier Proteins↗
PubMed1993

Nonrandom X chromosome inactivation in natural killer cells from obligate carriers of X-linked severe combined immunodeficiency.

X-linked severe combined immunodeficiency (XSCID) is characterized by hypogammaglobulinemia, markedly reduced numbers of T cells, absent mitogen responses, decreased numbers of NK cells, and normal or elevated numbers of B cells. The abnormalities in the NK cell and B cell lineages could be attributed to dependence of these cell lineages on T cells or T cell-derived factors, or to expression of the XSCID gene defect in these cell lineages. In past experiments, we have examined X chromosome inactivation patterns in T cells and cultured B cells from female obligate carriers of XSCID and have found that both cell lineages demonstrate nonrandom X chromosome inactivation. This indicates that the gene defect is intrinsic to both of these cell lineages. In the present experiments, a polymerase chain reaction technique was used to evaluate X chromosome inactivation patterns in highly purified populations of freshly isolated NK cells, B cells, CD4+ cells, and CD8+ cells from three obligate carriers of XSCID. All four lymphoid cell populations from these three women exhibited exclusive use of a single X as the active X. In contrast, both X chromosomes were used as the active X in neutrophils and monocytes. These findings indicate that the XSCID gene is expressed in the NK cell lineage as well as in T cells and B cells. This observation makes it highly unlikely that the XSCID gene is involved in Ag receptor gene rearrangements.

B-Lymphocytes↗
PubMed1993

Detection and some properties of the sialyltransferase implicated in the sialylation of lipopolysaccharide of Neisseria gonorrhoeae.

A sensitive assay for sialyltransferase (STase activity extracted from gonococci with 0.5% Triton X100 was developed. Enzyme activity was optimal in the pH range 5.8-8.0 and was strongly inhibited by CMP, CDP and CTP, but not by other nucleotides, 10 mM Mg2+, Zn2+, Ca2+ or Mn2+, or by 18 mM EDTA. More than 90% of the activity was lost after 30 s at 67 degrees C. The apparent Vmax and apparent Km of the STase for cytidine 5'-monophospho-N-acetylneuraminic acid were 1.7 nmol of NANA incorporated/min/mg protein and 5.3 microM, respectively.

Culture Media↗
PubMed1993

Distribution of a lipooligosaccharide-specific sialyltransferase in pathogenic and non-pathogenic Neisseria.

Sialyltransferase activity has been detected in Triton X100 extracts of all examined strains of pathogenic Neisseria as well as in 17 out of 18 Neisseria lactamica isolates. The enzyme was detected both in strains able to synthesize the 4.5 kDa lipooligosaccharide (LOS) component known to be sialylated in vivo and in vitro by cytidine 5'-monophospho-N-acetylneuraminic acid, and in some strains which lack this component. Exogenous 4.5 kDa+ LOS was required to detect the sialyltransferase activity in strains which lacked the LOS component. Sialyltransferase activity in a serogroup A, L11 (4.5 kDa-) meningococcal strain sialylated exogenous purified LOS from gonococci. The meningococcal serogroup B and C strain sialyltransferases active with LOS acceptors appeared to be distinct from the sialyltransferase required for the synthesis of the meningococcal polysialic acid capsule.

Lipopolysaccharides↗
PubMed1993

Identification by mass spectrometry of CMP-NANA in diffusible material released from high M(r) blood cell fractions that confers serum resistance on gonococci.

In previous work, a low M(r) component from human blood which converts serum-sensitive gonococci to resistance was shown to be indistinguishable from cytidine 5'-monophospho-N-acetyl neuraminic acid (CMP-NANA) by seven criteria. However, the presence of CMP-NANA was not proved by physicochemical methods. Purified, high M(r) fractions from human blood cells, which confer serum resistance on gonococci and enhance the transfer of sialyl groups from CMP-NANA to lipopolysaccharide (LPS) by a sialyltransferase in gonococcal extracts, were rechromatographed on DEAE Sepharose CL-6B. Both activities co-eluted from the column but on dialysis were found in the diffusate. After desalting the diffusate with Sephadex G10, the presence of CMP-NANA was proved by mass spectrometry. This confirmed previous work and is the first unequivocal demonstration of CMP-NANA in constituents of human blood cells.

Blood Cells↗
PubMed1993

B-mode ultrasound images of the carotid artery wall: correlation of ultrasound with histological measurements.

B-mode ultrasound is being used to assess carotid atherosclerosis in epidemiological studies and clinical trials. Recently the interpretation of measurements made from ultrasound images has been questioned. This study examines the anatomical correlates of B-mode ultrasound of carotid arteries in vitro and in situ in cadavers. Twenty-seven segments of human carotid artery were collected at autopsy, pressure perfusion fixed in buffered 2.5% glutaraldehyde and 4% paraformaldehyde and imaged using an ATL UM-8 (10 MHz single crystal mechanical probe). Each artery was then frozen, sectioned and stained with van Gieson or elastin van Gieson. The thickness of the intima, media and adventitia were measured to an accuracy of 0.01 mm from histological sections using a calibrated eye graticule on a light microscope. Shrinkage artifact induced by histological preparation was determined to be 7.8%. Digitised ultrasound images of the artery wall were analysed off-line. The distance from the leading edge of the first interface (LE1) to the leading edge of the second interface (LE2) was measured using a dedicated programme. LE1-LE2 measurements were correlated against histological measurements corrected for shrinkage. Mean values for the far wall were: ultrasound LE1-LE2 (0.97 mm, S.D. 0.26), total wall thickness (1.05 mm, S.D. 0.37), adventitia (0.35 mm, S.D. 0.16), media (0.61 mm, S.D. 0.18), intima (0.09 mm, S.D. 0.13). Ultrasound measurements corresponded best with total wall thickness, rather than elastin or the intima-media complex. Excision of part of the intima plus media or removal of the adventitia resulted in a corresponding decrease in the LE1-LE2 distance of the B-mode image. Furthermore, increased wall thickness due to intimal atherosclerotic thickening correlated well with LE1-LE2 distance of the B-mode images. B-mode images obtained from the carotid arteries in situ in four cadavers also corresponded best with total wall thickness measured from histological sections and not with the thickness of the intima plus media. In conclusion, the LE1-LE2 distance measured on B-mode images of the carotid artery best represents total wall thickness of intima plus media plus adventitia and not intima plus media alone.

Adult↗
PubMed1993

Risks and cost-effectiveness of sublaminar wiring in posterior fusion of cervical spine trauma.

A report on the use of sublaminar wiring in the fusions of 34 patients with cervical spine injuries is given. No neurologic deficits were incurred in the use of this technique. There were no wire failures nor clinically significant complications. When compared with other forms of instrumentation to achieve similar results, the use of sublaminar wire is the most cost-effective.

Adolescent↗
PubMed1993

Detection of bovine immunodeficiency-like virus by the polymerase chain reaction.

This report describes a test for the bovine lentivirus, bovine immunodeficiency-like virus, in which polymerase chain reaction (PCR) technology is employed. Two pairs of oligonucleotide primers directed to sequences within the coding regions of the gag and pol genes generated the expected PCR products from molecular BIV clones and from DNA of BIV-infected cell cultures but not from DNA of uninfected cultures. Data indicating the specificity and sensitivity of these PCRs for BIV detection and the potential utility of this technology for diagnostic applications are presented.

Animals↗