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Biomedical subjects

H Zhan

Publications and source records attributed to H Zhan.

51 records · Page 3Linked to original sources
PubMed1993

Erythrocyte haemolysate interacts with ATP-Fe to form a complex containing iron, ATP and 13 800 MW polypeptide.

Iron first entering the reticulocyte is bound to ATP in the low MW cytosolic pool; some is also 'loosely bound' to haemoglobin, coeluting with haemoglobin from a molecular sieve column though not incorporated into haem. When haemolysate is mixed with ATP-Fe in vitro a similar high MW iron-containing complex is formed: the ATP-Fe interacts with a non-haemoglobin constituent of the haemolysate to form a high MW ATP-Fe complex in which the ratio of ATP:Fe (originally 6:1) is reversed, so that the complex contains more iron than ATP. The high MW ATP-Fe complex is formed even when ATP is in 150-fold molar excess and is formed without detectable hydrolysis of the ATP. The activity of haemolysate in forming the high MW ATP-Fe complex is not diminished by dialysis; all of the activity is recovered in the haemoglobin-containing fraction obtained from an Ultrogel AcA 44 column. The activity does not derive from haemoglobin since 85% of the activity is removed when haemoglobin is purified from haemolysate with DEAE-Sephadex. The chelatable iron pool of the cell probably includes both the high MW ATP-Fe complex and low MW ATP-Fe. Shunting of ATP-Fe to a high MW aggregate reduces the amount of iron present in the highly reactive low MW form and thus probably serves to limit the formation of cell damaging radicals.

Adenosine Triphosphate↗
PubMed1992

Age-related change of free radical generation in liver and sex glands of rats.

Many investigations have been made on age-related changes of lipid peroxidation in tissue homogenates and subcellular fractions. However, to date there are few reports on the age-related change of free radicals in living organs during aging. In our study, we investigated free radical concentration in liver and sex glands of different aged rats by using electron spin resonance (ESR) technique. A significant reduction of free radicals in liver and sex glands of old aged rats was observed when compared with those of young or middle-aged ones. The decrease of free radical generation during aging is discussed.

Aging↗
PubMed1992

Long-term effects of percutaneous laser balloon ablation from the canine coronary sinus.

BACKGROUND: Radiofrequency catheter ablation of left-sided accessory pathways is becoming the first line of therapy for patients with symptomatic Wolff-Parkinson-White syndrome. Nevertheless, alternative ablation techniques merit development, at least as supplementary modalities for cases in which conventional ablation approaches may prove unsuccessful. We recently reported the short-term results with transcatheter laser balloon ablation from the coronary sinus in a canine model, proving that the procedure is feasible for the potential ablation of left-sided accessory pathways. We now report the effects of percutaneous transcatheter laser balloon ablation in a chronic canine model. METHODS AND RESULTS: Twenty adult mongrel dogs were studied. After baseline coronary arteriography, left ventriculography, and coronary sinus angiography were obtained, 15 dogs received two or three consecutive laser doses from the coronary sinus of 30-40 W for 15-30 seconds, for a total cumulative energy of 1,200-2,400 J. The five remaining animals underwent a procedure consisting of balloon sham inflation without laser exposure and served as controls. After a mean follow-up of 6 weeks, the angiographic procedures were repeated, and the animals were killed. The mean extent of the fibrotic lesion was 15 mm long, 6 mm wide, and 4.5 mm deep and involved the coronary sinus wall, atrium, and, frequently, the summit of the posterior left ventricular wall. Six animals (four in the study group and two in the control group) showed asymptomatic narrowing of the coronary sinus lumen but always with total angiographic reconstitution due to extensive collateral circulation. The circumflex artery and mitral valve were intact angiographically and histologically in all animals. CONCLUSIONS: Percutaneous transcatheter laser balloon ablation via the coronary sinus produces a lesion that may be anatomically well suited for left-sided accessory pathway ablation. Although coronary sinus narrowing may occur, adverse physiological effects are unlikely due to the development of extensive collateral circulation. Systematic clinical studies of this new approach to catheter ablation appear warranted.

Animals↗
PubMed1990

Mitochondria have Fe(III) receptors.

Recent work has provided new evidence that ATP is the major constituent of the low-Mr iron pool in the reticulocyte. The interaction of the iron complex of ATP with mitochondria was investigated in the present experiments. When ATP-Fe3+ was incubated with mitochondria, Fe3+, free of ATP, bound with high affinity to Fe3+ receptors on the mitochondria. The binding was saturable and reversible. Iron which was complexed to PPi, nitrilotriacetate, citrate, ADP and GTP also showed saturable binding to mitochondria; Fe3+ complexed to AMP bound non-specifically, as did Fe2+/ascorbate complexed to AMP bound non-specifically, as did Fe2+/ascorbate and Fe2+/dithionite.

Adenosine Triphosphate↗
PubMed1990

Iron bound to low MW ligands: interactions with mitochondria and cytosolic proteins.

The iron in the low MW pool of the cell is the precursor of iron in haem and is bound primarily to ATP. This precursor-product relationship suggested that reticulocytes might accumulate ATP-iron if their haem synthesis were blocked. However reticulocytes, treated with succinylacetone or rotenone and taking up iron from transferrin, accumulated iron in nonhaem cytosolic proteins and in mitochondria and not in the low MW pool. This was demonstrated by NMR and also by disrupting the cell with shear stress, separating the cytosol and pellet and fractionating the cytosol with ammonium sulfate. This constancy of the low MW iron pool in the face of blocked haem synthesis could not be explained by saturation of cytosolic ATP or by sluggish exchange of the low MW pool with other compartments. Rather, nonhaem cytosolic proteins and mitochondria appeared to have a higher affinity for iron and to exchange it rapidly with that in the low MW pool.

Animals↗
PubMed1990

Two pathways for iron uptake by guinea pig reticulocytes.

We have demonstrated that the intracellular processing of transferrin to effect iron removal involves two pathways, one sensitive to rotenone and the other not. We have also found that the effect of the rotenone is dependent on the transferrin concentration: iron uptake was suppressed with concentrations of transferrin in the micromolar range, and was not suppressed at physiologic concentrations of transferrin. Rotenone does not disturb transferrin's interaction with its extracellular receptor, indicating that its action must be intracellular. The following model is suggested: that separate pathways are entered by transferrin in the cell. The first pathway is preferentially utilized when transferrin is in short supply. It begins with an intracellular site which has a high affinity (and low capacity) for either iron or transferrin. The second pathway begins with an intracellular site which has a high capacity (but low affinity) for either iron or transferrin and is utilized when transferrin is in physiologic concentration (and the low-capacity, high-affinity site is saturated); the pathway it initiates is dominant when transferrin is abundant. We speculate that the high-affinity low-capacity pathway may serve to direct intracellular iron to sites which would be critically injured by iron excess.

Animals↗
PubMed1990

[Age-dependent changes of some body functions in male Wistar rats].

It was shown in this experiment that many systematic functions in male Wistar rats gradually declined during aging. Compared with young rats, thymus weight or the weight index decreased significantly in the 13- and 24-month rats (P less than 0.001). Age-dependent decreases of proliferation rate of splenic T lymphocyte, plasma testosterone (T) and estradiol (E2) level, concentration of cytochrome P-450 and activity of mixed functional oxidase (MFO) in liver microsomes were also observed.

Aging↗
PubMed1989

Hemolysates reduce iron released from transferrin.

Transferrin donates iron to reticulocytes as follows: it binds to a receptor on the reticulocyte surface; the complex is endocytosed; both irons are released and the transferrin is recycled to the cell exterior. It has been proposed that the trigger for iron release after transferrin endocytosis is acidification of the endocytic vesicle. But this could account for removal of only one of transferrin's two irons, since only one of the irons is labile at acid pH. Moreover, iron continues to be removed from transferrin when acidification of the vesicle is blocked by a chloride-transport inhibitor. Thus a detailed explanation of iron removal from transferrin remains elusive. In earlier work we showed that iron can be removed from transferrin by whole hemolysates and also by the combined action of hemoglobin and ATP at pH 7. We now show that the iron released from transferrin by hemolysates, and by hemoglobin and ATP, is in the Fe(II) oxidation state. We also show that ADP and DPG can substitute for ATP and that NADH and NADPH can substitute for the hemoglobin, although with these substitutions Fe(II) is generated less efficiently. The reductive release of iron from transferrin is rapid enough to account for all the iron processed by a young reticulocyte. We speculate that transferrin iron may be reduced to Fe(II) before reaching the mitochondria.

Animals↗
PubMed1989

Low molecular weight iron from guinea pig reticulocytes isolated by Sephadex G-25 chromatography.

As part of a continuing study of the low MW iron pool, guinea pig reticulocytes were incubated with 59Fe-labeled transferrin, and the reticulocyte hemolysate was chromatographed on Sephadex G-25. 59Fe, in amounts corresponding to that which was in a low MW peak eluting from an Ultrogel column and to that not precipitated by ammonium sulfate, adsorbed to the Sephadex column. The adsorbing 59Fe, on elution from the Sephadex with dilute formic acid, coeluted with phosphate and pentose. When EDTA was added to disrupt the putative iron complex, neither iron nor P adsorbed to the column, supporting the argument that they exist as a compound in the cytosol and adsorb and elute together for that reason. These observations provide additional evidence that P-containing compounds, probably originating as nucleotides, are important components of the low MW iron pool of cells.

Adsorption↗
PubMedDate not supplied

Peptidases play an important role in cataractogenesis: an immunohistochemical study on lenses derived from Shumiya cataract rats.

The role of proteolytic enzymes in Shumiya cataract rats in alterations to lens proteins during cataract formation was studied immunohistochemically using antibodies against exopeptidases, such as lysosomal dipeptidyl peptidase II (DPP II), cytosolic dipeptidyl peptidase III, and soluble and membrane-bound alanyl aminopeptidases, and against cytosolic endopeptidases such as mu- and m-calpains, and 20S proteasome. AlphaB-crystallin was detected as a proteolytic marker in the lenses. A constant immunoreactivity against all the antibodies employed was observed in the lens epithelium independent of the strain and age of the rats. A weak immunoreactivity against exo- and endopeptidases and an intense reactivity against alphaB-crystallin were observed in the lens fibres of control rats at all ages. The immunoreactivity of these peptidases in lens fibres increased with age in cataract rats, but that of alphaB-crystallin decreased. No reactivity against exo- and endopeptidases was seen in the perinuclear region of lenses of control rats at all ages or in Shumiya cataract rats at 8 and 10 weeks of age, but an intense reactivity against these peptidases was observed in the lens perinuclear region of lenses in cataract rats at 12 and 14 weeks of age. AlphaB-crystallin immunoreactivity was observed with ordered striations in the lens perinuclear region of all control rats whereas the striations in this area of cataract rat lens were disorganized. Membrane-bound alanyl aminopeptidase was detected feebly in the lens epithelium and fibres of both types of rat at all weeks of age. These findings indicate that exo- and endopeptidases, except for membrane-bound alanyl aminopeptidase, are expressed intensively and are age-dependent. Conversely, the amount of alphaB-crystallin decreased with age in lens fibres of cataract rats. Calpains (mu- and m-), 20S proteasome, dipeptidyl peptidases II and III and soluble alanyl aminopeptidase are thought to induce lens opacification kinetically during cataract formation in Shumiya cataract rats through the intracellular turnover of lens proteins.

Age Factors↗
PubMedDate not supplied

Removal and recovery of chromium(III) from aqueous solutions by a spheroidal cellulose adsorbent.

The removal and recovery of chromium(III) (Cr3+) from aqueous solutions with a spheroidal cellulose adsorbent containing the carboxyl anionic group was investigated. The adsorption of Cr3+ ion on the adsorbent has been found to be time, concentration, pH, and temperature dependent. The adsorption process follows both the Freundlich and Langmuir adsorption isotherms, and has been found to be endothermic (enthalpy change, deltaH = 31.35 kJ/mol). The Cr3+ ion adsorbed on the adsorbent can be recovered by treating with a sodium hydroxide (NaOH) or hydrochloric acid (HCl) solution in one of two methods, static desorption or mobile desorption (column operation). A 1.2 mol/L HCl aqueous solution was finally chosen to recover the Cr3+ ion using column operation. The recovery percentage is approximately 85.2%. The exhausted column can be chemically regenerated by treatment with 1 mol/L NaOH aqueous solution and no dismantling is required. The adsorption mechanism is explained on the basis of complexation and ion exchange, between which the complexation adsorption is predominant.

Adsorption↗