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Biomedical subjects

H Pollard

Publications and source records attributed to H Pollard.

At least 109 records · Page 6Linked to original sources
PubMed1969

On the geometrical arrangement of the protein subunits of human serum low-density lipoprotein: evidence for a dodecahedral model.

Ultracentrifugal and electron microscopic studies of human serum low-density lipoprotein (LDL) and several of its derivatives led to the formulation of a model in which the 20 protein subunits, probably globular, are arranged in a dodecahedral pattern with icosahedral symmetry. In such a model the LDL surface is occupied by both protein and lipids, predominantly phospholipids, as supported by the results of the hydrolysis of LDL by phospholipase A and C. Neutral lipids (cholesterol esters and glycerides) would be in the interior of the molecule.

Adult↗
PubMed1968

Properties of human serum low density lipoproteins after modification by succinic anhydride.

Human serum low density lipoprotein of d 1.019-1.063 (LDL(2)) treated with succinic anhydride at pH 7.5-8.0 showed the same chemical composition, hydrodynamic properties (flotation and sedimentation coefficients, intrinsic viscosity) and optical properties (circular dichroism) as untreated LDL(2). However, in contrast to LDL(2), the succinylated product (s-LDL(2)) failed to react with rabbit anti-LDL(2) antisera. Extraction with ethanol-ether 3:1 yielded the succinylated apoprotein (s-apo-LDL(2)), which was, unlike untreated apoprotein, soluble in aqueous buffers. Succinylated apoprotein, which was also immunologically unreactive, appeared to differ in structure from s-LDL(2), as assessed by the parameters of intrinsic viscosity and circular dichroism. The molecular weights of both LDL(2) and s-LDL(2) obtained by the technique of sedimentation equilibrium were 2.1-2.3 x 10(6). By the same method, s-apo-LDL(2) gave an uncorrected figure of 3.95-4.15 x 10(4) and, after correction for succinyl functions, of 3.60-3.80 x 10(4). Because of the assumptions made in the computations, the latter figure was considered approximate. The marked differences in molecular weight between s-apo-LDL(2) and whole apo-LDL(2) ( approximately 5 x 10(5)) were taken to support the subunit structure of apo-LDL(2), which is envisaged as an aggregate of about 12 subunits which dissociate upon succinylation. Further, the large percentage (about 90%) of the free amino groups of LDL(2) found to react with succinic anhydride suggests that these groups are at the surface of the molecule.

Amino Acids↗
PubMedDate not supplied

Ca2+-sensitive cytosolic nucleases prevent efficient delivery to the nucleus of injected plasmids.

BACKGROUND: Efficient gene delivery by synthetic vectors is a major challenge in gene therapy. However, inefficient nuclear delivery of cDNA is thought to be a major limiting step in gene transfer using non-viral vectors. It is commonly thought that, in the cytosol, cDNA has to be released from its vector before importation to the nucleus. The stability of naked cDNA in the cytoplasm is not well established. METHODS: cDNA plasmids, either free or complexed with poly(ethyleneimine) (PEI), were microinjected into the cytoplasm of mammalian cells and their turnover was assessed by fluorescence in situ hybridization (FISH). Incubations of cDNA plasmids in cytosolic extracts were also performed. RESULTS: FISH experiments showed that naked cDNA rapidly fade with time when injected into the cytosol. Fading was not observed when naked cDNA plasmids were injected into the nucleus. Incubation of naked cDNA in a cytosolic fraction isolated from mammalian cells reproduced cDNA degradation as observed in microinjection experiments. Nuclease inhibitors, including aurin tricarboxylic acid or Zn2+, prevented in vitro cDNA degradation. The cytosolic nuclease activity was optimal at physiological pH and physiological Ca2+ concentration. By contrast, it was insensitive to Mg2+ or Na+ concentrations. Finally, cDNA complexation with PEI or addition of oligonucleotides prevented in vitro cDNA degradation. CONCLUSION: Altogether, these experiments suggest that cDNA digestion by cytosolic nucleases occur when the decomplexed transgene is present in the cytosol. We propose that the inefficient transfer of cDNA into the nucleus during transfection with synthetic vectors may result from rapid digestion of naked cDNA by a Ca2+-sensitive cytosolic nuclease.

Animals↗
PubMedDate not supplied

Localization of enkephalinase mRNA in rat brain by in situ hybridization: comparison with immunohistochemical localization of the protein.

The messenger RNA (mRNA) encoding enkephalinase (EC. 3.4.24.11; neutral endopeptidase) has been localized in rat brain by in situ hybridization using 35S- or 32P-labelled cRNA probes. Hybridization was observed only in few brain areas, and was particularly strong in the striatum, olfactory bulb and pontine nuclei. The enkephalinase protein was also localized in brain sections using a radiolabelled monoclonal antibody. While some brain regions contained both the mRNA and its translation product, others, including in particular the substantia nigra, were rich in enkephalinase but did not contain any detectable amount of enkephalinase mRNA. Enkephalinase mRNA-containing cells could be identified in regions containing neurons known to project to the substantia nigra. The discrepancy between the mRNA and the protein labelling is likely to reflect the fact that the mRNA is exclusively located within the soma of the cells while the translated protein may be found anywhere along the axonal processes.

Animals↗
PubMedDate not supplied

Bilateral simultaneous optic nerve dysfunction after periorbital trauma: recovery of vision in association with with chiropractic spinal manipulation therapy.

OBJECTIVE: To discuss the recovery of optic nerve function after chiropractic spinal manipulation in a patient with loss of vision as a result of facial fracture from a fall. CLINICAL FEATURES: In a fall down a stairwell, a 53-year-old woman with migraines fractured her right zygomatic arch, which was later treated surgically. Approximately 3 weeks after the accident, vision in her contralateral eye became reduced to light perception. Electrophysiologic studies revealed that the function of both optic nerves was diminished, the right significantly more than the left. Single photon emission tomography showed pancerebral ischemic foci. INTERVENTION AND OUTCOME: Chiropractic spinal manipulation was used to aid recovery of vision to normal over a course of 20 treatment sessions. At times, significant improvement in vision occurred immediately after spinal manipulation. Progressive recovery of vision was monitored by serial visual field tests and by electrophysiologic studies. Unfortunately, the patient refused a further single photon emission tomographic study when visual recovery was complete. CONCLUSION: This case report adds to previous accounts of progressive and expeditious recovery of optic nerve function in association with spinal manipulation therapy.

Chiropractic↗
PubMedDate not supplied

On-line echocardiographic assessment of hemodynamic indexes by an adaptive Doppler analysis algorithm and signal/noise ratio calculation.

Assessment of cardiac diseases commonly involves the use of spectral Doppler echocardiography. Its use, however, often requires manual digitization of various transvalvular flow profiles. A new approach has been developed for on-line analysis of Doppler data, which involves thresholding based on the signal/noise ratio, calculating instantaneous values, and plotting on the spectral display in real time. We examined the reliability of this new method in 32 patients with 59 various flow jets by comparing it with the data derived by manual analysis. Correlations between the algorithm analysis and manual analysis for peak velocity, peak gradient, velocity-time integral, and acceleration time were excellent. These indexes were obtained with the algorithm in a shorter time and with better reproducibility than with manual analysis. Thus this new adaptive Doppler analysis algorithm yields reliable on-line quantification of valuable hemodynamic variables and represents an advance in quantitative echocardiography.

Algorithms↗
PubMedDate not supplied

Highly potent and selective ligands for histamine H3-receptors.

New drugs selective for histamine H3-receptors can be used to establish that these receptors are involved in the feedback control of histamine synthesis and release, and to demonstrate their distribution in the brain and peripheral tissues. These drugs provide new tools for affecting physiological and possibly pathological conditions in which histamine is involved.

Animals↗
PubMedDate not supplied

[Activity of enkephalinase (EC.3.4.24.11). Neutral endopeptidase (NEP)in human digestive tract epithelial cells].

The activity was studied of enkephalinase (endopeptidase 24.11, neutral endopeptidase)--a membrane enzyme of epithelial cells within human digestive tract (in the stomach, duodenum, small intestine, ascending, descending and sigmoid colon, and rectum). The enzyme activity was determined by column method using the labelled substrate (H-D-AlaLeu)--enkephalin and the selective enkephalin inhibitor--thiorfan in the presence of bestatin and captopril--inhibitors of aminopeptidases and angiotensin converting enzyme respectively. The highest enkephalinase activity was found in the duodenal epithelium (77.3 8.0 fmol of the substrate/min/mg of protein) and in the small intestine (23.4 0.9 fmol/min/mg of protein) with its gradual decrease when progressing down the gastrointestinal tract. This result confirms the hypothesis of enkephalinase participation in protein hydrolysis processes.

Digestive System↗