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Biomedical subjects

M Fabian

Publications and source records attributed to M Fabian.

At least 19 recordsLinked to original sources
PubMed2005

[Molecular aspects of alterations in normal normal conjunctival epithelium. Role of apoptosis-associated genes].

BACKGROUND: The aim of the present study was to evaluate the age-dependent physiological expression pattern of apoptosis-related genes in the normal conjunctiva. PATIENTS AND METHODS: Healthy probands (group A: 24 probands and group B: 24 probands) were subjected to modified impression cytology using a PTFE membrane for evaluation of age-dependent expression of apoptosis-related genes in the normal conjunctiva. RNA was isolated from the cytologic impression specimens and used for cDNA synthesis employing SuperScriptTM II reverse transcriptase. RESULTS: RT-PCR revealed the detection of apoptosis-related mRNAs as follows (group A compared to group B): Apaf-1: 4.2/4.2%, Bcl-2: 41.7/41.7%, Bim: 0/0%, Bag-1: 70.8/100%, p53: 0/8.3%, Casp-3: 4.2/66.7%, Casp-5: 70.8/37.5%, Casp-8: 62.5/20.8%, Casp-9: 25/12.5%, c-myc: 83.3/95.8%, BAX: 91.7/70.8%, and BAD: 95.8/87.5%. CONCLUSION: The results revealed an age-dependent expression of apoptosis-associated genes (proapoptotic: Casp-3, Casp-5, Casp-8, antiapoptotic Bag-1) in normal human conjunctiva. Taken together these investigations provide basic information to understand the expression of apoptosis-associated genes in various diseases of the conjunctiva.

Adult↗
PubMed2001

Cyanide stimulated dissociation of chloride from the catalytic center of oxidized cytochrome c oxidase.

A comparison of bovine cytochrome c oxidase isolated in the presence and the absence of chloride salts reveals that only enzyme isolated in the presence of chloride salts is a mixture of a complex of oxidized enzyme with chloride (CcO.Cl) and chloride-free enzyme (CcO). Using a spectrophotometric method for chloride determination, it was shown that CcO.Cl contains one chloride ion that is released into the medium by a single turnover or by cyanide binding. Chloride is bound slowly within the heme a(3)-Cu(B) binuclear center of oxidized enzyme in a manner similar to the binding of azide. The pH dependence of the dissociation constant for the formation of the CcO.Cl complex reveals that chloride binding proceeds with the uptake of one proton. With both forms of the enzyme the dependence of the rate of reaction for cyanide binding upon cyanide concentration asymptotes a limiting value indicating the existence of an intermediate. With CcO.Cl this limiting rate is 10(3) higher than the rate of the spontaneous dissociation of chloride from the binuclear center and we propose that the initial step is the coordination of cyanide to Cu(B) and in this intermediate state the rate of dissociation of chloride is substantially enhanced.

Animals↗
PubMed2001

Proton involvement in the transition from the "peroxy" to the ferryl intermediate of cytochrome c oxidase.

In the absence of any external electron donor, the "peroxy" intermediate of cytochrome c oxidase (CcO-607) is converted to the ferryl form (CcO-580) and subsequently to oxidized enzyme. The rate of conversion of CcO-607 to the CcO-580 form is pH dependent between pH 3.0 and pH 7.6. A plot of the logarithm of the rate constant for this conversion is a linear function of pH with a slope of -0.92, implying the involvement of a single proton in the transition. Upon rapidly lowering the pH from 8.1 to 5.8, the uptake of one proton was observed by direct pH measurement, and the kinetics of proton uptake coincide with the spectral conversion of CcO-607 to CcO-580. We interpret the slow endogenous decay of CcO-607 to CcO-580 to be the result of proton transfer to a deprotonated group generated in the binuclear cavity during CcO-607 formation. This group is not freely accessible to protons from the medium, and its pK(a) is probably higher than 9.0.

Buffers↗
PubMed1999

Mass spectrometric determination of dioxygen bond splitting in the "peroxy" intermediate of cytochrome c oxidase.

The "peroxy" intermediate (P form) of bovine cytochrome c oxidase was prepared by reaction of the two-electron reduced mixed-valence CO complex with (18)O(2) after photolytic removal of CO. The water present in the reaction mixture was recovered and analyzed for (18)O enrichment by mass spectrometry. It was found that approximately one oxygen atom ((18)O) per one equivalent of the P form was present in the bulk water. The data show that the oxygen-oxygen dioxygen bond is already broken in the P intermediate and that one oxygen atom can be readily released or exchanged with the oxygen of the solvent water.

Animals↗
PubMed1999

Redox state of peroxy and ferryl intermediates in cytochrome c oxidase catalysis.

The redox states of the "peroxy" (P) and "ferryl" (F) intermediates formed during reoxidation of reduced bovine cytochrome c oxidase have been probed by reduction with both ferrocytochrome c and acetylpyridine NADH under anaerobic conditions using optical spectroscopy. The reduction of the P and F forms revealed that both are in very similar redox states. One-electron reduction of either the P or F form yields an optical spectrum primarily due to oxidized enzyme implying that the heme iron of cytochrome a3 is in the ferryl state in both forms. The F and P forms were found to be 1 and less than 1.3 oxidizing equiv, respectively, above the oxidized enzyme. The slightly higher oxidation state in the P form is interpreted as being due to an optically undetectable redox center presumably located in the binuclear cavity.

Catalysis↗
PubMed1999

Absolute Intensity of the NH(3) nu(2) Band.

Absolute line intensities of NH(3) in the nu(2) band were measured for a number of rovibrational lines using a high-resolution Fourier transform infrared spectrometer. The transition dipole moments calculated from the absolute intensities showed significant and systematic deviations from the usual rotational dependencies predicted from the J, K dependence of the direction-cosine matrix elements. The anomalous rotational dependencies may be explained by vibration-rotation interactions, and the Herman-Wallis-type rotational correction factors for a symmetric top molecule were determined experimentally for the first time in the present study. The self-broadening coefficients were determined as well. Copyright 1999 Academic Press.

Journal Article↗
PubMed1998

Hydrogen peroxide is not released following reaction of cyanide with several catalytically important derivatives of cytochrome c oxidase.

We have looked for the production of hydrogen peroxide following reaction of oxidized cytochrome c oxidase and two oxy derivatives (compounds P and F) with cyanide. In each case the final product was the cyanide adduct of cytochrome c oxidase. In no case release of hydrogen peroxide was detected, as gauged by the scopoletin plus horse radish peroxidase assay. The simplest conclusion is that none of these forms of the enzyme contains intact hydrogen peroxide.

Cyanides↗
PubMed1998

Control of vascular smooth muscle cell growth in fowl.

In adult domestic fowl, angiotensin (ANG) receptors are present in the vascular smooth muscles (VSM) and in the endothelium, mediating vasorelaxation via endothelium-derived relaxing factor/cGMP. ANG II-induced relaxation is minor in chicks and becomes more marked as they mature but diminishes in adult birds, whereas ANG II neither relaxes nor contracts endothelium-denuded aortae from mature chickens. The present study examines in cultured fowl aortic SM cells whether (1) ANG II stimulates or inhibits VSM cell growth and, if so, whether this growth-stimulatory or -inhibitory effect changes with maturation/aging, and (2) S-nitroso-N-acetylpenicillamine (SNAP), a nitric oxide donor, and cGMP attenuate the basal or stimulated VSM cell growth. [Asp1, Val5]ANG II (native fowl ANG II, 10(-6) M) markedly increased (increase from vehicle control, 226.5%; P < 0.01) [3H]thymidine (Thd) incorporation into DNA of quiescent VSM cells (first subculture) from 6-week-old chicks. This growth-stimulating effect was reduced with age (41.4, 29.6, and 3.2% at 9, 19, and 43 weeks of age, respectively). In contrast, platelet-derived growth factor (PDGF, 20 ng/ml) increased [3H]Thd incorporation similarly in chicks, pullets, and hens. Furthermore, ANG II significantly (45.9%, P < 0.01) attenuated the growth-promoting effect of fetal calf serum in cultured VSM cells from 6-week-old chicks. This inhibitory effect also decreased in older birds. ANG II showed neither a growth-stimulatory nor -inhibitory effect in cultured neointimal cells. SNAP attenuated dose dependently (20-60 microM) the basal and PDGF-induced VSM cell growth, whereas cGMP inhibited basal growth only at a high dose (100 microM). These results indicate that in fowl VSM cells, ANG II is mitogenic and antimitogenic in chicks but not in mature birds, suggesting that phenotypic modulation occurs in the ANG receptors/signaling mechanism with maturation/age or in neointimal cells, whereas the mitogenic mechanism via PDGF remains in both young and mature birds.

Anesthesia↗
PubMed1998

Analysis of the Line Profiles of CH3CN for the J = 5 <-- 4 and J = 6 <-- 5 Rotational Transitions.

The pressure broadening, pressure shift coefficients, and absolute intensities have been obtained for the J = 6 <-- 5 and the J = 5 <-- 4 absorption lines of acetonitrile CH3CN at 110 and 92 GHz, respectively. The absorption line shapes have been directly recorded modulating the radiation beam by an optical chopper. In addition to the self-effects, the foreign-broadening coefficients have also been measured for N2, O2, and Ar. Copyright 1998 Academic Press.

Journal Article↗
PubMed1997

High-J Rotational Transitions of NNO Measured with the NAIR Terahertz Spectrometer

A BWO-based terahertz spectrometer has been constructed and tested by measuring some high-J rotational transitions of NNO in the frequency region from 620 to 730 GHz. The observed line center frequencies confirm the previously reported ones obtained by FTIR spectroscopy. The high sensitivity of the present spectrometer allowed us to record spectra of singly substituted isotopomers, 15NNO, N15NO, NN18O, and NN17O, in natural abundance. The rotational and centrifugal distortion constants have been revised. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1997

Use of recombinant hemoglobin solution in reversing lethal hemorrhagic hypovolemic oxygen debt shock.

OBJECTIVE: To compare recombinant hemoglobin solution (rHb1.1) with colloid/blood (CB) resuscitation in a hemorrhagic shock (HS) model based on oxygen debt (O2D). METHODS: Twenty-two anesthetized canines (weight 23.3 +/- 0.2 kg) were bled to an O2D of 99.9 +/- 2.1 mL/kg over 60 minutes (estimated lethal dose 31%), blood loss 65.9 +/- 2.3% of estimated blood volume, - 199 g hemoglobin (Hgb). Prospectively randomized resuscitation done in 20 minutes with 120% of shed blood volume, either colloid 60%/blood 60% shed blood volume (CB), 118 g Hgb, or 120% shed blood volume as 5% rHb1.1, 85 g Hgb, and fall in O2D was quantified over 80 minutes. Six animals died during HS, one after CB resuscitation (32% actual mortality). Blood lactate (L) and base deficit (BEA) were related to O2D. RESULTS: Both lactate (L) and BEA quantified O2D during hemorrhage: L = 0.0671 (O2D) + 1.209; r2 = 0.90, p < 0.0001; BEA = 0.1313 (O2D) + 1.764; r2 = 0.90, p < 0.0001, but L was a better indicator than BEA of fall in O2D during resuscitation (L = 0.069 (O2D) + 1.083; r2 = 0.80). Both groups were followed for 7 days after HS and had normal renal and hepatic function by day 7. However, at equal resuscitation volume, rHb1.1 resuscitation with 41% of Hgb loss produced a more rapid initial fall in O2D than CB at 60% of Hgb loss (p < 0.002). rHb1.1 resuscitation also caused a more complete washout of metabolic acids than CB. CONCLUSIONS: Lactate and BEA accurately quantify O2D in HS and resuscitation. rHb1.1 replacement is as good as CB with regard to survival, but leads to a more uniform reperfusion and produces a more complete resolution of ischemic acidosis.

Animals↗
PubMed1995

The interaction of cytochrome oxidase with hydrogen peroxide: the relationship of compounds P and F.

Upon reaction of cytochrome oxidase with hydrogen peroxide, the spectral changes are complete, with slightly less than 1 equiv of hydrogen peroxide per cytochrome oxidase. At pH 8 the product is a mixture of the P and F forms, while at pH 6 the product is exclusively the F form. These data are inconsistent with current interpretations of the structure of compounds P and F. Two stable radical species are detected by EPR; the relative amounts of these species are pH dependent. The MCD spectra of pure P and F are reported. It is suggested that compound F is a hydrogen peroxide adduct of cytochrome oxidase with cytochrome a3 in the low-spin state and that compound P is an oxyferryl state of cytochrome alpha 3 in support of the recent Raman data of Proshlyakov et al. [(1994) J. Biol. Chem. 269, 29385-29388]. We also suggest that copper B is in the trivalent state in compound P.

Carbon Monoxide↗
PubMed1995

The reaction of cyanide with peroxidatic forms of cytochrome oxidase.

The interaction of peroxidatic derivatives of cytochrome c oxidase with cyanide has been investigated by optical spectroscopy and the stopped-flow method. Two reactions were found in the conversion of peroxy cytochrome oxidase to its cyanide complex. The first reaction is characterized by the loss of the 607 nm band, an increase in absorbance at 655 nm, and a decrease in absorbance at 432 nm resulting from a blue-shift of the Soret band; this reaction occurred with a bimolecular rate constant of about 90 M-1 s-1. The second reaction is observed as an absorbance increase at 585 and 432 nm; the latter was due to a red-shift of the Soret band. This second process proceeded with a rate constant of about 22 M-1 s-1. Both reaction rates are linearly dependent on the concentration of cyanide between 5 and 100 mM. The reappearance of the 655 nm band at the completion of the first reaction suggests that cytochrome a3 becomes transiently high-spin, a finding which implies that cyanide is not initially bound to this heme center. It appears that preparations of oxidized CcO contain small but variable amounts of the peroxy form. The variable content of this form is probably responsible for the different response of oxidized oxidase to low concentrations of cyanide [Berka, V., Vygodina, T., Musatov, A., Nicholls, P., & Konstantinov, A. A. (1993) FEBS Lett. 315, 237-241] and may explain the biphasic reduction of the binuclear center with dithionite [Cooper, C. E., Junemann, S., Ioannidis, N., & Wrigglesworth, J. M. (1993) Biochim. Biophys. Acta 1144, 149-160].

Cyanides↗
PubMed1991

Oxygen debt and metabolic acidemia as quantitative predictors of mortality and the severity of the ischemic insult in hemorrhagic shock.

BACKGROUND AND METHODS: An experimental canine model of hemorrhagic, hypovolemic shock is described that uses oxygen debt and its metabolic consequences of lactic acidemia and metabolic base deficit as independent variables for the prediction of probability of death. RESULTS: Lactic acidemia and metabolic base deficit are compared with the conventional hemodynamic variables of BP and cardiac output (Qt) as predictors of outcome and are shown to be superior using a modified Kaplan-Meier probability statistic. The LD50 for oxygen debt is shown to be 113.5 mL/kg, 12.9 mmol/L for lactate, and -18.8 mmol/L for base excess (BE). Comparison is made between the ability of Qt, BP, shed blood, BE, and lactate to predict oxygen debt. CONCLUSIONS: Of the single-variable predictors, BE shows the highest explained variability. However, a combined prediction from both lactate and BE appears superior to the use of either alone. Using this regression to compute the oxygen debt, it is possible to estimate accurately the actual level of oxygen debt from the BE and lactate values obtained during hemorrhagic hypovolemia. From serial determinations over time of the increase in these biochemical variables above the oxygen debt baseline, it is possible to estimate the rate of oxygen debt accumulation and the time remaining until the LD50 will be reached as indicators of the severity of the total body ischemia resulting from hemorrhagic shock.

Acid-Base Equilibrium↗
PubMed1991

Hepatic insufficiency and increased proteolysis, cardiac output, and oxygen consumption following hemorrhage.

Thirty dogs underwent hemorrhage over a 60-min period to a predetermined O2 debt of 60-120 mL O2/kg, monitored with a Beckman metabolic cart, and then were resuscitated with 120% of the shed volume. Twenty survived and were followed over the next 7 days. On day 4, hepatic insufficiency was suggested by an elevation in [total amino acids] and [lactate] and a decrease in [urea] and [branched-chain amino acids]/[aromatic amino acids]. Net whole body catabolism on day 4 is suggested by a decrease in [glutamine] and an increase in plasma [3-methylhistidine], [phenylalanine], and [tyrosine]. These changes were significantly related to cardiac index, mean blood pressure, [lactate], O2 debt, and shed volume during the hemorrhage 4 days earlier. On day 7 there was a significant increase in the cardiac index and the VO2. These data suggest that hemorrhage induces sequelae similar to major injury or sepsis: hepatic insufficiency, net catabolism, hypermetabolism, and a hyperdynamic circulation. The hyperdynamic circulation may be necessary to meet increased tissue delivery requirements for O2 and amino acids.

Amino Acids↗
PubMed1991

Relationship of plasma amino acids to oxygen debt during hemorrhagic shock.

Thirty dogs underwent hemorrhage over a 60 minute period to a predetermined O2 debt of 60-120 mL O2/kg, quantified real-time by a Beckman metabolic cart; they were then resuscitated with 120% of the shed volume. The [total amino acids], [lactate], and [alanine]/[glutamine] rose during hemorrhage and resuscitation. Blood pressure, VO2, cardiac index, circulating amino acid pool, and systemic amino acid transport decreased during hemorrhage, but rose during resuscitation. The [total amino acids], [alanine]/[glutamine], cardiac index, blood pressure, and [lactate] were significantly related to O2 debt. The O2 debt during hemorrhage was substantially better related to [lactate] compared to shed volume or blood pressure. The changes in [total amino acids] and [alanine]/[glutamine] and their relationship to O2 debt suggest a hemorrhagic-induced alteration in tissue amino acid kinetics. These data further suggest that using a metabolic substrate parameter such as O2 utilization is useful to stratify other cellular alterations such as amino acid uptake and release and lactic acidosis.

Alanine↗
PubMed1991

Portacaval shunt as an experimental model of impaired hepatic release of vitamin A in liver disease.

Vitamin A concentrations in serum and liver were studied in rats with a portacaval shunt for 48 days after shunt surgery. In addition, serum and tissue concentrations of zinc were analyzed. Following portacaval shunting serum vitamin A concentration decreased to 25% of the level in sham-operated controls, whereas serum zinc concentration decreased to 80%. The mean urinary excretion rate of zinc increased in shunted rats [18.7 +/- 2.1 micrograms/day (0.28 +/- 0.03 mumol/day)] compared with controls [13.8 +/- 1.7 micrograms/day (0.21 +/- 0.03 mumol/day)] (P less than 0.01). The concentration of retinol and total retinoids in liver tissue increased 2-3-fold in rats with a portacaval shunt, and the ratio of retinol to retinoids was slightly increased. The differences were reduced when the total organ content was calculated, because of the reduced liver weight in the shunted rats. The concentration of zinc in liver tissue decreased in rats with portacaval shunts [30.8 +/- 4.9 micrograms/g wet wt (0.47 +/- 0.07 mumol/g) vs. 35.6 +/- 3.7 micrograms/g wet wt (0.54 +/- 0.06 mumol/g) in controls; P less than 0.01]. The concentration of zinc was inversely correlated with retinol (r = -0.52, P less than 0.05) and total retinoid levels (r = -0.70, P less than 0.05) in rats with portacaval shunts but not in controls. The data are consistent with the hypothesis of an impaired release of vitamin A from the liver in rats with portacaval shunts, an impairment that could be due to liver zinc deficiency.

Animals↗