Reactivity of essential cysteine and lysine residues present at the catalytic domain of pig heart mitochondrial malate dehydrogenase

Pig heart mitochondrial malate dehydrogenase was inactivated very rapidly by omicron-phthalaldehyde as compared to 5,5'-dithio bis(2-nitrobenzoic acid) and pyridoxal 5'-phosphate. The omicron-phthalaldehyde reaction followed pseudo first order kinetics, and a second order rate constant of 38 M-1 S-1 was obtained. Cysteine and lysine residues participating in the omicron-phthalaldehyde reaction are located in the NADH binding region of malate dehydrogenase as shown by protection experiments. The decrease in the rate of inactivation in the presence of NADH was used to determine the dissociation constant of the enzyme-NADH complex. pH dependent studies and molar transition energy calculations of the omicron-phthalaldehyde-inactivated enzyme have indicated that cysteine and lysine residues involved in the isoindole derivative formation are located in a hydrophobic environment at the coenzyme binding site.

Button battery in the nose--an unusual foreign body

We present two rare, but similar, cases of button batteries in the nose in male children of Caucasian origin. The importance of early diagnosis, treatment and the long-term morbidity of such a foreign body in the nose are discussed.

Unilateral anterior jugular phlebectasia

We present a rare case of unilateral anterior jugular venous phlebectasia in an 82-year-old female patient presenting as a soft cystic lump in the anterior aspect of the neck increasing in size during straining and valsalva manoeuvre. Although cases of internal and external jugular phlebectasia have been reported, as far as we are aware no case of anterior jugular phlebectasia has been reported in the literature previously.

Investigation of the nature of o-phthalaldehyde reaction with octopine dehydrogenase

The effect of o-phthalaldehyde on octopine dehydrogenase inactivation has been studied. o-Phthalaldehyde binds to the proximal cysteine and lysine residues of the enzyme leading to the formation of isoindole derivative. Double inhibition studies with o-phthalaldehyde and p-chloromercuricphenyl sulfonic acid have indicated that o-phthalaldehyde does not bind to the functional cysteine present at the active site. Protection experiments have shown that L-arginine prevented o-phthalaldehyde inactivation. This could be only due to the reaction of the amino group of L-arginine with o-phthalaldehyde as per the mechanism proposed elsewhere since L-arginine cannot bind to the enzyme prior to NADH. Other substrates such as pyruvate oR NADH could not prevent the o-phthalaldehyde reaction with the enzyme. Fluorescence spectral studies demonstrated that in the presence of externally added amino acid no isoindole derivative formation occurs. However, a characteristic isoindole derivative is formed in the presence of beta-mercaptoethanol although the enzyme does not lose its activity. This indicated that o-phthalaldehyde can bind with lysine of the enzyme and thiol of externally added beta-mercaptoethanol. Pyridoxal 5'-phosphate, a lysine specific reagent also binds to the enzyme giving the characteristic absorption and fluroescence peak at 325 nm and 395 nm respectively. However, no loss of enzyme activity was observed. On the basis of these experiments we would suggest that o-phthalaldehyde binds to non-essential cysteine and lysine residues present in close proximity which results in conformational changes leading to enzyme inactivation.

Evidence for proximal cysteine and lysine residues present at the nucleotide domain of rabbit muscle creatine kinase

Inactivation of rabbit muscle creatine kinase by o-phthalaldehyde was investigated. The loss of enzyme activity was concomitant with the increase in fluorescence intensity at 410 nm. The modified enzyme showed a characteristic absorption peak at 336 nm. These evidences suggested that the mechanisms of inhibition of creatine kinase by o-phthalaldehyde involves binding of the thiol and the epsilon-amino group of enzyme leading to the formation of isoindole derivative. None of the substrates, except Mg-ATP, provided protection against o-phthalaldehyde inhibition. This was corroborated by fluorescence studies. Double inhibition experiments showed that p-chloromercuricphenyl sulphonic acid, a thiol-specific reagent, binds to the same cysteine which is also involved in the o-phthalaldehyde reaction. Stoichiometric results indicated that 2 mol of o-phthalaldehyde were incorporated per mole of enzyme molecule upon complete inactivation. Denaturation of creatine kinase by urea or heat treatment prior to o-phthalaldehyde addition resulted in the decrease of fluorescence intensity indicating that native conformation of the enzyme is essential for isoindole derivative formation.

Mechanisms of thrombin generation during surgery and cardiopulmonary bypass

Although in vitro studies have been invaluable in revealing the complex biochemistry of the blood coagulation system, the mechanisms involved during the in vivo response to hypercoagulable stimuli are still unclear. We have used plasma-based enzyme-linked immunosorbent assays (ELISAs) to study the mechanisms by which the coagulation system is activated in vivo during human cardiopulmonary bypass (CPB) surgery (n = 8). A novel immunoassay for factor XIIa was used to detect activation of the contact system, factor IX activation peptide (FIXAP) was used as a marker for activation of factor IX, and prothrombin fragment F1 + 2 (F1 + 2) was used as a marker for thrombin generation. The ELISA for FIXAP is described for the first time herein. F1 + 2 levels increased early in response to surgical intervention: from a baseline of 38.7 +/- 9.7 ng/mL (mean +/-SE), levels increased rapidly during surgery and bypass to a maximum of 448.5 +/- 92.0 ng/mL. A modest yet significant increase in factor XIIa levels from 3.47 +/- 0.54 ng/mL to 4.33 +/- 0.85 ng/mL was evident during surgery before bypass, but no further significant increase was detected on establishing extracorporeal circulation. FIXAP levels demonstrated a small and late increase during surgery from 4.98 +/- 0.55 ng/mL to a maximum of 10.20 +/- 1.23 ng/mL, the increase beginning at the time of near maximal F1 + 2 levels. There was no association between activation of the contact system (factor XIIa levels) and the generation of thrombin (F1 + 2 levels). However, a strong association (r = .705) was apparent between the generation of thrombin (F1 + 2 levels) and activation of factor IX (FIXAP levels), despite the delay between the activation of prothrombin and factor IX. The data do not support the established view that contact activation resulting from exposure of blood to foreign surfaces is the major procoagulant stimulus in CPB. Instead, the results suggest that the main trigger to coagulation during CPB surgery was provided via the tissue factor-factor VIIa mechanism in response to the cutting of blood vessels, which directly activated factor X and then prothrombin. The late activation of factor IX, which presumably also contributed to maximal prothrombin activation, could have arisen due to direct tissue factor-factor VIIa action, or by secondary feedback action of thrombin on the intrinsic system.

Chemical modification of octopine dehydrogenase by thiol-specific reagents: evidence for the presence of an essential cysteine at the catalytic site

Thiol-specific reagents, p-chloromercuricphenyl sulfonic acid (PCMS), 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) and N-ethyl-maleimide (NEM), incubated with octopine dehydrogenase resulted in the loss of catalytic activity. The kinetic profile of PCMS inactivated enzyme showed that the reaction followed pseudo-first-order kinetics during the initial phase of inactivation. The reversal of enzyme activity was obtained by thiol-containing reagents. The loss of enzyme activity was prevented only by NADH and not by other substrates. The dissociation constant for NADH calculated from the decrease in the enzyme inactivation rate was 45 microM. Cyanolysis of the DTNB-modified enzyme with KCN led to the release of 5-thio-2-nitrobenzoate (TNB) accompanied by the formation of thio-cyano enzyme. By correlating the enzyme activity with the formation of thio-cyano derivative it was found that no activity was recovered after KCN treatment. These evidences clearly established the critical involvement of the thiol group in catalysis. Double inhibition studies with PCMS and NEM on octopine dehydrogenase showed that the inactivating reagents bind to the same functional thiol present at the catalytic center. pH-dependent inactivation by PCMS indicated that a group with a pKa value of 7.4 is involved in the loss of enzyme activity. These approaches suggested that at least one thiol group present at the coenzyme-binding domain is essential for the catalytic reaction of octopine dehydrogenase.

Coxsackievirus B4 alters pancreatic glutamate decarboxylase expression in mice soon after infection

The 64,000-M(r) (64K) islet autoantigen, which is considered to be a target protein of beta cell destruction in insulin-dependent diabetes mellitus (IDDM), has recently been identified as the enzyme glutamic acid decarboxylase (GAD). We reported a two- to three-fold increased expression of the antigen in islets of diabetes-susceptible mice following infection with a diabetogenic strain of Coxsackievirus B4 (CB4) at 72-h postinfection (p.i.), a time point of active virus replication in the islets. Most of the infected animals subsequently developed 64K autoantibodies and hyperglycemia. Since the infection increases 64K expression, we have analysed immunoreactive GAD expression with a panel of peptide antisera and two widely-used polyclonal antisera against GAD, and measured GAD activity in the brain, pancreas and islets of these mice. Two isoforms, GAD65 and GAD67, are detected in these tissues from non-infected mice. Both GADs are also present in the infected mice brain at 72 h p.i.; however, their islets contain about three-fold more GAD65, and essentially no detectable GAD67. GAD activity is significantly higher in the brain compared with whole pancreas or islets, and islet GAD activity is higher than pancreas GAD activity. The infection significantly reduces islet GAD activity, but not brain GAD activity. CB4-induced abnormalities in islet GAD expression may play a role in virus-induced diabetes.

Thrombin production, inactivation and expression during open heart surgery measured by assays for activation fragments including a new ELISA for prothrombin fragment F1 + 2

Activation of coagulation was studied during the peri-operative period in patients undergoing cardiopulmonary bypass (CPB) surgery using activation markers which have recently become available: prothrombin fragment F1 + 2 (F1 + 2), which is a measure of total thrombin generation, and thrombin-antithrombin complex, which is a measure of inactivation of free thrombin by antithrombin. Levels of the specific marker of fibrin breakdown, D-dimer, were also determined. F1 + 2 levels were assessed using a newly developed ELISA described herein which employs a neoantigen-specific capture antibody raised using a synthetic peptide; the latter antibody has been pre-adsorbed against prothrombin to ensure high specificity for F1 + 2. Increased generation of thrombin during surgery was clearly demonstrated despite maintenance of a high concentration of heparin during the period of extracorporeal blood circulation. There was a close association (r = 0.882) between the generation of thrombin (F1 + 2 levels) and its inhibition (TAT levels). Differences were noted, however, between the information provided by F1 + 2 and TAT, which are interpreted with regard to the different in vivo fates of F1 + 2 and thrombin. The enhanced activation and inhibition of coagulation observed during CPB was suppressed once physiological blood circulation was restored, with F1 + 2 returning to pre-surgical levels within 24 h after surgery. During the post-operative period D-dimer levels, which rose in concert with F1 + 2 and TAT levels, remained highly elevated, suggesting that not all of the generated thrombin was inactivated by antithrombin.(ABSTRACT TRUNCATED AT 250 WORDS)

Involvement of different cysteines in the inactivation of octopine dehydrogenase by p-chloromercuricphenyl sulfonic acid and o-phthalaldehyde

Inactivation of octopine dehydrogenase by p-chloromercuricphenyl sulfonic acid (PCMS) and o-phthalaldehyde have been investigated. The activity loss due to the PCMS was faster than o-phthalaldehyde. PCMS associated inhibition was reversed by dithiothreitol completely which was not observed with o-phthalaldehyde inactivated enzyme. Fluorescence spectra of o-phthalaldehyde modified enzyme showed the formation of isoindole derivative with characteristic emission maximum at 410 nm. This derivative formation essentially involves cross-linking of proximal cysteine and lysine residues. Protection and selective reversible reaction studies have established that NADH prevents the enzyme against PCMS inactivation and the essential cysteine present at the NADH binding site is not involved in the o-phthalaldehyde reaction.

Active site mapping studies of malate dehydrogenase : identification of essential amino acid residues by o-phthalaldehyde

Mitochondrial malate dehydrogenase (MDH) was found to be rapidly inactivated by o-phthalaldehyde. MDH-o-phthalaldehyde adduct gives a characteristic absorption maximum at 337 nm. Moreover, this derivative shows fluorescence emission maxima at 405 nm when excited at 337 nm and 280 nm. These results were consistent with isoindole ring formation in which the -SH group of cysteine and epsilon-NH2 group of lysine participate in the reaction. The enzyme was found to be protected against o-phthalaldehyde inactivation by NADH, indicating that the essential residues are present at or near the coenzyme binding site. Stoichiometric results indicate that 4 isoindole derivatives are formed per enzyme molecule upon complete inactivation. However, 90% of the activity loss was accompanied by the formation of 2 moles of isoindole per mole of the enzyme. These approaches give consistent evidence that two cysteines along with two lysines in close proximity are essential for the enzymatic activity.

Level and diurnal variations of hormones of interest to the cardiovascular system in patients with heart transplants

The lack of a nocturnal decrease in blood pressure in cyclosporine-treated cardiac transplant recipients may indicate abnormalities in the mechanism(s) responsible for circadian variability in other physiologic parameters such as in circulating hormones. This possibility was addressed through repeated determinations of circulating catecholamines, neuropeptide Y, pancreatic polypeptide, calcitonin gene-related peptide, plasma renin activity, aldosterone, atrial natriuretic factor and cortisol. The results from 10 patients with heart transplants were compared with those of 12 age-matched, healthy control subjects. Both groups were studied during 24-hour supine rest. There was no difference between patients and control subjects in mean levels of catecholamines, neuropeptide Y, pancreatic polypeptide and aldosterone. Patients had higher levels (+/- SD) of plasma renin activity (6.4 +/- 1.3 vs 2.6 +/- 0.4 ng/ml/hour, p less than 0.001), calcitonin gene-related peptide (47.7 +/- 9.9 vs 33.3 +/- 5.7 pmol/liter, p less than 0.01) and atrial natriuretic factor (93.0 +/- 56.7 vs 20.7 +/- 8.9 pg/ml, p less than 0.001) than control subjects, respectively. Cortisol was not detected in patients. Abnormal diurnal profiles in patients were found for calcitonin gene-related peptide, aldosterone and atrial natriuretic factor, and for pancreatic polypeptide, together with decreased levels, in patients with greater than 6 months follow-up. Except for hormones reflecting sympathetic nervous activity, all hormonal systems studied showed abnormalities in level or circadian rhythmicity, or both. The pancreatic polypeptide results suggest that parasympathetic neuropathy could develop in cyclosporine-treated heart transplant recipients.

Neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP), but not galanin, are autonomic cotransmitters in the porcine pancreas

The neuropeptide galanin has been identified as a potential sympathetic cotransmitter in the canine pancreas. Immunoreactive galanin, also present in nerve fibers of the pig pancreas, was therefore measured in the effluent from isolated perfused pig pancreas with preserved sympathetic (splanchnic) or parasympathetic (vagal) innervation with radioimmunoassays directed against both the N-terminus and the C-terminus of galanin. Electrical vagus stimulation increased the pancreatic exocrine secretion, the secretion of insulin and glucagon, and the release of VIP, but did not influence galanin release. Splanchnic nerve stimulation increased perfusion pressure and glucagon secretion, inhibited insulin secretion, and increased the release of NPY, but galanin release was not affected. We conclude that the pancreatic galanin nerve fibers belong neither to the sympathetic nor to the parasympathetic divisions of the efferent nerve supply to the pig pancreas.

Cardiovascular and endocrine responses to haemorrhage in the pig

Heart rate (HR), mean arterial pressure (MAP), indices of sympathetic and parasympathetic activity (plasma concentrations of adrenaline, noradrenaline and pancreatic polypeptide, PP), vasopressin (VP) and aldosterone (ALDO) were measured in six pigs during continuous bleeding resulting in hypovolaemic shock, from which five survived. Three stages of haemorrhage could be defined. Stage I. Resting MAP was 85 +/- 6 mmHg and increased to 96 +/- 5 mmHg with a blood loss of 275 (range 250-300) (10 (9-12)% of the estimated blood volume) concomitant with an increase in HR from 105 +/- 5 to 113 +/- 6 beats min-1 (P less than 0.05). Stage II. After a blood loss of 375 (300-500) ml (15 (13-16)%) MAP fell to 62 +/- 9 mmHg and HR to 95 +/- 5 beats min-1 (P less than 0.05). Stage III. A blood loss of 1113 (825-1450) ml (44 (30-52)%) resulted in a MAP of 50 +/- 4 mmHg and an increase in HR to 206 +/- 3 beats min-1 (P less than 0.05). Adrenaline increased from 0.3 +/- 0.1 to 0.8 +/- 0.3 (stage II) and 3.6 +/- 1.1 nmol l-1 (stage III) (P less than 0.05); noradrenaline from 0.4 +/- 0.1 to 1.5 +/- 0.4 (stage II) and 5.9 +/- 1.7 nmol l-1 (stage III) (P less than 0.05); PP from 6.2 +/- 1.6 to 13.3 +/- 2.3 (stage II) and 20.9 +/- 7.8 pmol l-1 (stage III) (P less than 0.05). VP changed only marginally, but ALDO increased from 496 +/- 54 to 623 +/- 76 pmol l-1 (stage III) (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

On the regulatory functions of neuropeptide Y (NPY) with respect to vascular resistance and exocrine and endocrine secretion in the pig pancreas

We compared the effects of electrical stimulation of the splanchnic nerves and infusions of neuropeptide Y, noradrenaline or a combination of the two on pancreatic vascular resistance and exocrine and endocrine secretion. For these studies we used isolated perfused pig pancreas with preserved splanchnic nerve supply. The exocrine secretion was stimulated with physiological concentrations of secretin and cholecystokinin octapeptide. Noradrenaline and NPY at 10(-8) M both increased pancreatic perfusion pressure. Their effects were additive and similar in magnitude to that of electrical stimulation of the splanchnic nerves at 4-8 Hz. Nerve stimulation as well as NPY and noradrenaline infusions inhibited exocrine secretion, but an additive effect could not be demonstrated. Neither NPY nor noradrenaline could reproduce the stimulatory effect of nerve stimulation on glucagon secretion, nor the weak inhibitory effect on somatostatin secretion. NPY alone had no effect on insulin secretion and did not influence the inhibitory effect of noradrenaline. It is concluded that NPY is likely to cooperate with noradrenaline in the control of pancreatic blood flow, whereas its role in the control of pancreatic secretion is likely to be of minor importance, if any.

Hormonal and metabolic responses to exercise in humans: effect of sensory nervous blockade

Previous studies have indicated that motor center ("feedforward") activity is important for hormonal and metabolic responses to exercise. Now, epidural blockade at vertebrae L3-L4 was used to evaluate the importance of afferent neural feedback from working muscles. Six healthy, young males cycled for 20 min at 55 +/- 4% (mean +/- SE) of maximal oxygen uptake with, as well as without, epidural anesthesia. During anesthesia cutaneous sensory blockade was present below segment T11-12, the postexercise ischemic pressor response was attenuated from 34 +/- 9 to 14 +/- 4 mmHg, muscle strength reduced to 80 +/- 5% of control, and perceived exertion (Borg scale) was increased. At rest hormonal and metabolic parameters did not change in response to epidural anesthesia. During exercise, responses of catecholamines, insulin, glucagon, and growth hormone (GH) in plasma as well as glucose production and utilization, plasma free fatty acids, and plasma glycerol were similar in epidural and control experiments (P greater than 0.05). In contrast during submaximal exercise, plasma concentrations of adrenocorticotropin (ACTH) and beta-endorphin increased only in experiments without epidural anesthesia. The data indicate that impulses in afferent nerves from the working muscles are essential for the ACTH and beta-endorphin responses to submaximal dynamic exercise in humans. Afferent nervous activity is probably less important than efferent activity from motor centers for responses of GH, catecholamines and insulin, and, in turn, extramuscular fuel mobilization in exercise.

Interaction of NPY and VIP in regulation of myometrial blood flow and mechanical activity

The occurrence, molecular characteristics and biological function of neuropeptide Y (NPY) has been studied in the female genital tract of non-pregnant rabbits. NPY immunoreactivity was demonstrated throughout the genital tract. Maximum concentrations were found in the salpinx (fallopian tube), 570 pmol/g (median) lower within the uterine body (1.5 pmol/g), cervix (2.8 pmol/g) and vagina (3.6 pmol/g). In vitro, NPY had a dose-dependent stimulatory effect on non-vascular smooth muscle (ED50 10(-9) mol/l) as studied by myometrial tension recordings. In vivo, NPY (50 pmol/min.kg) induced a dose-related, non-adrenergic and non-cholinergic decrease in myometrial blood flow. Small C-terminal (NPY31-36) or N-terminal (NPY1-16) fragments of NPY had no effect on myometrial blood flow. NPY was found to interact with the smooth muscle effect of VIP; the presence of VIP (10(-8) mol/l) counteracted the contraction elicited by NPY (10(-8) mol/l) returning the response to control value. VIP and NPY displayed a similar physiological antagonism on myometrial blood flow. There was a clear difference in the response to VIP and NPY as the effect of NPY on myometrial blood flow first appeared after a lag period of 2 minutes whereas the effect of VIP was almost instantaneous. It is concluded that NPY and VIP may interact in the local nervous control of genital functions.

Hereditary perforating ulcers of the foot: "hereditary sensory radicular neuropathy"

In 4 cases of hereditary sensory radicular neuropathy the loss of pain and thermal sensibility resulting in perforating ulcers starts distally in lower extremities and progresses proximally. It has a sporadic and familial form as well as the hereditary type. In siblings inheritance appeared to be autosomal dominant. By early recognition of the disease and removing pressure from the involved areas, or spreading pressure equally over the foot with proper footwear ulcers are preventable.