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Biomedical subjects

H Hendrickson

Publications and source records attributed to H Hendrickson.

16 recordsLinked to original sources
PubMed2003

Influence of caveolin on constitutively activated recombinant eNOS: insights into eNOS dysfunction in BDL rat liver.

Diminished endothelial nitric oxide (NO) synthase (eNOS)-derived NO production from the hepatic vascular endothelium contributes to hepatic vasoconstriction in portal hypertension. The aim of this study was to examine the mechanism of this process by testing the influence of a constitutively active form of eNOS (S1179DeNOS) in both primary and propagated liver cells in vitro and in the sham and bile duct ligated (BDL) rat liver in vivo, using an adenoviral vector encoding green fluorescent protein (AdGFP) and S1179DeNOS (AdS1179DeNOS). AdS1179DeNOS transduction augmented basal and agonist-stimulated NO generation in nonparenchymal liver cells. Sham rats transduced in vivo with AdS1179DeNOS evidenced a decreased pressor response to incremental doses of the vasoconstrictor methoxamine compared with sham rats transduced with AdGFP. However, BDL rats transduced with AdS1179DeNOS did not display improved vasodilatory responses as evidenced by similar flow-dependent pressure increases to that observed in BDL rats transduced with AdGFP, despite similar levels of viral transgene expression. We next examined the influence of the eNOS inhibitory protein caveolin on S1179DeNOS dysfunction in cirrhotic liver. Immunogold electron microscopic analysis of caveolin in BDL liver demonstrated prominent expression not only in liver endothelial cells, but also in hepatic stellate cells. In vitro studies in the LX2 hepatic stellate cell line demonstrate that caveolin precipitates recombinant S1179DeNOS in LX2 cells, that recombinant S1179DeNOS coprecipitates caveolin, and that binding is enhanced in the presence of overexpression of caveolin. Furthermore, caveolin overexpression inhibits recombinant S1179DeNOS activity. These studies indicate that recombinant S1179DeNOS protein functions appropriately in normal liver cells and tissue but evidences dysfunction in the cirrhotic rat liver and that caveolin expression and inhibition in BDL nonparenchymal cells, including hepatic stellate cells, may account for this dysfunction.

Animals↗
PubMed2001

Regulation of hepatic eNOS by caveolin and calmodulin after bile duct ligation in rats.

In carbon tetrachloride-induced liver cirrhosis, diminution of hepatic endothelial nitric oxide synthase (eNOS) activity may contribute to impaired hepatic vasodilation and portal hypertension. The mechanisms responsible for these events remain unknown; however, a role for the NOS-associated proteins caveolin and calmodulin has been postulated. The purpose of this study is to characterize the expression and cellular localization of the NOS inhibitory protein caveolin-1 in normal rat liver and to then examine the role of caveolin in conjunction with calmodulin in regulation of NOS activity in cholestatic portal hypertension. In normal liver, caveolin protein is expressed preferentially in nonparenchymal cells compared with hepatocytes as assessed by Western blot analysis of isolated cell preparations. Additionally, within the nonparenchymal cell populations, caveolin expression is detected within both liver endothelial cells and hepatic stellate cells. Next, studies were performed 4 wk after bile duct ligation (BDL), a model of portal hypertension characterized by prominent cholestasis, as evidenced by a significant increase in serum cholesterol in BDL animals. After BDL, caveolin protein levels from detergent-soluble liver lysates are significantly increased as assessed by Western blot analysis. Immunoperoxidase staining demonstrates that this increase is most prominent within sinusoids and venules. Additionally, caveolin-1 upregulation is associated with a significant reduction in NOS catalytic activity in BDL liver lysates, an event that is corrected with provision of excess calmodulin, a protein that competitively binds eNOS from caveolin. We conclude that, in cholestatic portal hypertension, caveolin may negatively regulate NOS activity in a manner that is reversible by excess calmodulin.

Animals↗
PubMed2000

Gene transfer of recombinant endothelial nitric oxide synthase to liver in vivo and in vitro.

Endothelial nitric oxide synthase (eNOS)-derived nitric oxide (NO) contributes to hepatic vascular homeostasis. The aim of this study was to examine whether delivery of an adenoviral vector encoding eNOS gene to liver affects vasomotor function in vivo and the mechanism of NO production in vitro. Rats were administered adenoviruses encoding beta-galactosidase (AdCMVLacZ) or eNOS (AdCMVeNOS) via tail vein injection and studied 1 wk later. In animals transduced with AdCMVLacZ, beta-galactosidase activity was increased in the liver, most prominently in hepatocytes. In AdCMVeNOS-transduced animals, eNOS protein levels and catalytic activity were significantly increased. Overexpression of eNOS diminished baseline perfusion pressure and constriction in response to the alpha(1)-agonist methoxamine in the perfused liver. Transduction of cultured hepatocytes with AdCMVeNOS resulted in the targeting of recombinant eNOS to a perinuclear distribution and binding with the NOS-activating protein heat shock protein 90. These events were associated with increased ionomycin-stimulated NO release. In summary, this is the first study to demonstrate successful delivery of the recombinant eNOS gene to liver in vivo and in vitro with ensuing NO production.

Adenoviridae↗
PubMed1996

Cognitive therapy versus fluoxetine in the treatment of dysthymic disorder.

We studied the effects of a fixed dose of fluoxetine (20 mg) or cognitive psychotherapy in a 16 week trial of patients with dysthymic disorder. More patients assigned to fluoxetine dropped out of the 16 week treatment (33%) than those assigned to cognitive therapy (9%), but this difference did not attain statistical significance. Both treatments showed improvement over baseline conditions at 8 weeks and further improvement at 16 weeks. There were no statistically significant group differences in treatment response. No follow-up data were collected so the enduring effects of the treatments are unknown. An optimal treatment for dysthymic disorder may be combined psychotherapy and pharmacotherapy for a longer period of time.

Adolescent↗
PubMed1990

Chronic exposure of cultured endothelial cells to eicosapentaenoic acid potentiates the release of endothelium-derived relaxing factor(s).

1. The effect of chronic exposure of cultured porcine aortic endothelial cells to eicosapentaenoic acid on the release of indomethacin-insensitive relaxing factor(s) was investigated (a) under bioassay conditions using preconstricted canine coronary artery rings without endothelium and (b) by the measurement of guanosine 3':5'-cyclic monophosphate (cyclic GMP) content of endothelial cells. 2. Exposure of endothelial cells for 8-10 days to eicosapentaenoic acid (2.5 x 10(-5) M) did not affect the relaxing activity of the perfusate from unstimulated endothelial cells. 3. The treatment with eicosapentaenoic acid significantly increased the relaxation of the bioassay ring observed upon stimulation of the endothelial cells with adenosine diphosphate (3 x 10(-8) M to 3 x 10(-4) M) and, to a lesser extent with bradykinin (10(-8) to 3 x 10(-8) M), while the relaxing activity evoked by the calcium ionophore A23187 (3 x 10(-7) M) was not affected. Neither acetylcholine (10(-6) M) nor 5-hydroxytryptamine (10(-6) M) stimulated the release of relaxing factor(s) from control or eicosapentaenoic acid-treated endothelial cells. 4. Bradykinin (10(-7) M), adenosine diphosphate (3 x 10(-5) M), the calcium ionophore A23187 (10(-6) M) and nitric oxide (2 x 10(-6) M) stimulated haemoglobin-sensitive increases in cyclic GMP content of porcine endothelial cells which were unaffected by prior chronic exposure to eicosapentaenoic acid. 5. These results suggest that chronic exposure of porcine aortic endothelial cells to eicosapentaenoic acid increases the release of relaxing factor(s) in response to activation of membrane-associated receptors for purines and kinins. The lack of effect of eicosapentaenoic acid treatment on agonist-stimulated production of cyclic GMP suggests that the enhanced relaxation observed under bioassay conditions is not due to an increased production of nitric oxide.

Animals↗
PubMed1989

Release of different relaxing factors by cultured porcine endothelial cells.

Experiments were performed to determine the effect of ouabain on the release of relaxing factor(s) from cultured endothelial cells, and its action on the effect of the relaxing factor(s) on arterial smooth muscle. A column of porcine aortic endothelial cells grown on microcarrier beads in suspension culture was perfused with modified Krebs-Ringer bicarbonate solution. The release of relaxing factor(s) by the endothelial cells was detected under bioassay conditions by measuring the relaxing activity of the perfusate overflowing a ring of canine coronary artery (without endothelium) contracted with prostaglandin F2 alpha. Incubation of the endothelial cells with ouabain did not affect the relaxation of the bioassay ring under basal conditions or upon stimulation of the endothelial cells with ADP but impaired the relaxation induced by bradykinin or the calcium ionophore A23187. Incubation of the bioassay ring with ouabain reduced the relaxation under basal conditions as well as the relaxation induced by ADP but did not affect the relaxation observed upon stimulation with bradykinin and A23187 and the endothelium-independent relaxations induced by nitric oxide. These experiments suggest that cultured porcine aortic endothelial cells release two endothelium-derived relaxing factors; one is released under basal conditions and upon stimulation with adenosine diphosphate and the other (which presumably is nitric oxide) upon stimulation with bradykinin and the calcium ionophore A23187.

Adenosine Diphosphate↗
PubMed1977

Prevention and enhancement: future needs.

The objective of prevention of eye and visual problems, and the objective of enhancement of vision performance are primary and most urgent for undergraduate, postgraduate and/or continuing optometric education. Prevention is something done before the need occurs. The concept of enhancement assumes performance far beyond so-called normals. The future needs of the public and the profession should determine the content and scope of optometric education pre and post graduation. Occupying the unique areas of prevention and enhancement can expand optometry's role, insure its continued growth and vital service to the public.

Optometry↗
PubMed1976

Qualitative and quantitative studies on human myelin basic protein in situ with respect to time interval between death and autopsy.

Normal human frontal lobe white matter obtained at autopsy was used to determine the extent of in situ post-mortem degradation of myelin basic protein (BP). Effects of the following two factors were studied: 1) time interval between death and autopsy, and 2) freezing and thawing the tissue. Quantitative extraction of BP from the autopsy material showed only minimal loss of BP that could be attributed to the time interval between death and autopsy (up to 48 h). The purified BP from these samples was electrophoresed on acrylamide gels at pH 4.3 and it was found that the electrophoretic patterns were comparable to zero hour bovine BP samples. The BP obtained from the autopsy samples was found to be encephalitogenic in guinea pigs. When tested against rabbit anti-human-BP serum, the purified BP preparations gave a single arc in immunoprecipitin test. BP extracted and purified from tissue that was frozen once and processed before it could thaw showed yields, encephalitogenic activity and acrylamide disc gel electrophoretic patterns that were similar to those of BP from tissue that was never frozen. However, frozen tissue that was thawed and then incubated for 8 h at room temperature before processing yielded only 13-25% of the total extractable protein. This BP also was encephalitogenic and showed acrylamide banding pattern that was similar to BP from tissue that was never frozen. Samples of white matter were examined by electron microscope. Unfrozen autopsy material showed some separation of myelin lamellae. Myelin in sections of frozen and thawed white matter showed separation as well as disruption of the lamellae. Samples that were frozen, thawed and then incubated at room temperature for 8 h showed sporadic loss of dense line material in addition to lamellar separation and disruption. The results a) show that BP is quite resistant to autolytic changes and b) are consistent with the location of BP along the cytoplasmic surface of the myelin membrane.

Aged↗
PubMed1972

Surface properties of membrane systems: apoprotein of the Folch-Lees proteolipid from beef-brain myelin.

Structural proteins in biological membranes are bimodal and ideally possess a unique surface activity that should be amenable to study by monolayer techniques. Proteins so studied, however, display, of necessity, a surface activity that reflects the laboratory history of the protein. The Folch-Lees proteolipid apoprotein was isolated from calf-brain myelin in both an organic solvent (CHCl(3)-CH(3)OH-CH(3)COOH; 50:50:1) and water. The apoprotein did not spread as a film from water, but did spread readily from the organic solvent into films that had high saturation pressures. The partitioning of the apoprotein from organic solvent to water was found to be reversible, as was the gain and loss of surface activity. Infrared spectroscopy demonstrated that the preponderant structure in films of the apoprotein was not that of extended polypeptide chains. The results suggested that the preferred structures at the interface are bimodal coils of alpha helix. This structure can sustain the high film pressures observed, whereas beta keratin structures would build films with high surface viscosity and very low surface pressure.

Animals↗
PubMed1970

Isolation of rat liver plasma membranes. Use of nucleotide pyrophosphatase and phosphodiesterase I as marker enzymes.

Nucleotide pyrophosphatase and phosphodiesterase I of rat liver have been found to be localized primarily in cell particulates highly enriched with respect to the most commonly accepted plasma membrane marker, 5'-nucleotidase, and therefore should themselves be assigned a plasma membrane localization. The observation that plasma membranes sediment in isotonic sucrose with both nuclear and microsomal fractions was exploited to obtain plasma membrane preparations from each fraction. Both preparations are similar in chemical and enzymic composition. Moreover, the preparative method developed in this study appears to give the best combination of yield, purity, and reproducibility available. The question of the possible identity of nucleotide pyrophosphatase and phosphodiesterase I is considered, and evidence is presented suggesting that these activities may be manifestations of the same enzyme.

Animals↗
PubMedDate not supplied

Electrophoretic and morphologic studies on normal human white matter obtained at surgery with special reference to its basic protein component.

Histologically confirmed normal pieces of human white matter removed during surgical approach to underlying pathology were studied by acrylamide disc gel electrophoresis and electron microscopy. A basic electrophoretic pattern of the white matter homogenates from three separate patients is described. Aliquots of white matter from two of these patients were incubated at 4 degrees C and 23 degrees C for intervals up to 18 hours, then homogenized and electrophoresed to detect any degradative changes in the basic protein band. Results of these studies indicated that the basic protein band of freshly obtained normal human white matter was unaffected by incubation at 23 degrees C for as long as 18 hours. Electron microscopic examination of white matter that was incubated for 2 hours at room temperature prior to fixation, showed sporadic areas of lamellar separation, a finding similar to but not as extensive as that described earlier in white matter obtained at autopsy that was performed 8 hours post-mortem. These findings 1) confirm earlier observations made on autopsy material, 2) are compatible with location of basic protein along the cytoplasmic surface of myelin lamellae, and 3) further emphasize the remarkable resistance of basic protein in situ to autolytic degradation.

Adult↗