Band 3 protein: structure, flexibility and function

The oxidation of antibody carbohydrate residues is a common approach used for site-specific antibody immobilization or modification. In this study a flow injection analysis system (FIA) was developed for monitoring antibody oxidation. Antibodies were oxidized with periodate and the resulting aldehyde groups were labeled with Lucifer yellow CH (LyCH). The labeled antibodies were then injected onto an FIA system where the amount of LyCH label was determined by absorbance measurements at 428 nm and the amount of antibody was determined using an on-line bicinchoninic acid protein assay. The analysis time was 2 min per 20 microliters sample injection. The limits of detection for rabbit immunoglobulin G (IgG) and LyCH were 1 x 10(-8) and 4 x 10(-7) M, respectively. The dynamic ranges for IgG and LyCH extended to 2 x 10(-5) and 7 x 10(-3) M. The within-run precision was +/- 5% or less for both analytes. Studies with known LyCH/antibody mixtures indicated that the FIA system had greater accuracy than manual methods at high LyCH levels. One specific application studied for this system was its use in monitoring the time course of periodate-antibody oxidation.     

Effect of niflumic acid on noradrenaline-induced contractions of the rat aorta

1. The effects of niflumic acid, an inhibitor of calcium-activated chloride channels, were compared with the actions of the calcium channel antagonist nifedipine on noradrenaline-evoked contractions in isolated preparations of the rat aorta. 2. The cumulative concentration-effect curve to noradrenaline (NA) was depressed by both nifedipine and niflumic acid in a reversible and concentration-dependent manner. The degree of inhibition of the maximal contractile response to NA (1 microM) produced by 10 microM niflumic acid (38%) was similar to the effect of 1 microM nifedipine (39%). 3. Contractions to brief applications (30 s) of 1 microM NA were inhibited by 55% and 62% respectively by 10 microM niflumic acid and 1 microM nifedipine. 4. In the presence of 0.1 microM nifedipine, niflumic acid (10 microM) produced no further inhibition of the NA-evoked contractions. Thus, the actions of niflumic acid and nifedipine were not additive. 5. In Ca-free conditions the transient contraction induced by 1 microM NA was not inhibited by niflumic acid (10 microM) and therefore this agent does not reduce the amount of calcium released from the intracellular store or reduce the sensitivity of the contractile apparatus to calcium. 6. Niflumic acid 10 microM did not inhibit the contractions produced by KCl (up to 120 mM) which were totally blocked by nifedipine. Contractions induced by 25 mM KCl were completely inhibited by 1 microM levcromakalim but were unaffected by niflumic acid. 7. It was concluded that niflumic acid produces selective inhibition of a component of NA-evoked contraction which is probably mediated by voltage-gated calcium channels. These data are consistent with a model in which NA stimulates a calcium-activated chloride conductance which leads to the opening of voltage-gated calcium channels to produce contraction.     

Significance of radioisotope bone marrow uptake on 99m technetium sulphocolloid scan in portal hypertension

A prospective study of 101 consecutive patients of portal hypertension was carried out to study the possible relationships between bone marrow activity on 99m technetium labelled sulphocolloid scan and severity of liver disease, etiology of portal hypertension and cirrhosis, as well as presence and extent of collateral circulation, including esophageal varices. The patients were divided into 4 etiological groups: alcoholic cirrhosis (ALD), (38) non-alcoholic cirrhosis (NALD) (35) non-cirrhotic portal fibrosis (NCPF) (14) and extrahepatic portal vein obstruction (EHPVO) (14). Patients of cirrhosis were categorised according to modified Child-Pugh's classification. Esophageal varices were graded endoscopically as (1) no varix (2) small varices (< 5mm) (3) large varices (> 5mm). All patients underwent radionuclide imaging using 99m Technetium labelled sulphocolloid and bone marrow activity was studied. Evaluation of portasystemic collaterals was done ultrasonically. We found that 16.6%, 44.6% and 72.72% patients with Child A, B and C cirrhosis respectively, had increased marrow activity (p < 0.05). There was no significant difference between marrow activity of patients with ALD (52.6%) and NALD (40%). None of the non-cirrhotic patients demonstrated bone marrow uptake of radioisotope. There was no significant difference between bone marrow uptake presence of lienorenal collaterals and presence or size of esophageal varices. We thus conclude the bone marrow activity on radioisotope scanning depends only on the severity of liver disease and does not vary a according to the etiology of cirrhosis, or presence and extent of portasystemic collaterals, including esophageal varices.     

Microemboli during carotid angiography. Association with stroke risk factors or subsequent magnetic resonance imaging changes?

BACKGROUND AND PURPOSE: Carotid angiography is associated with a 1% risk of major stroke. Recently, transcranial Doppler ultrasonography (TCD) has shown cerebral microemboli during carotid angiography. To determine their significance, we correlated the number of microemboli during angiography with clinical characteristics, angiography findings, and preangiography and postangiography cerebral magnetic resonance imaging (MRI). METHODS: One middle cerebral artery was monitored with TCD in 24 patients during angiography for carotid territory ischemia. The number of microemboli was correlated with angiographic and clinical characteristics. T2-weighted cerebral MRI was performed before and < or = 48 hours after angiography, and the number of new ischemic lesions was determined in a blinded review. RESULTS: Microemboli were seen in all patients, with an average of 51 per procedure (range, 12 to 154). The majority of microemboli had signal characteristics typical of air. Sixteen of the 24 patients had both preangiography and postangiography MRI. One of 24 patients had an angiographic stroke, with a single new thalamic lesion on MRI. No other patient had a new lesion. The microembolus count correlated with the angiographic contrast volume (P < .001) but not with any other radiological or clinical characteristic. CONCLUSIONS: This study confirmed the presence of numerous cerebral microemboli during carotid angiography. The microembolic signal characteristics and the correlation with contrast volume indicate that introduced air is the cause. These microemboli are usually clinically silent and do not lead to new changes on cerebral MRI.     

ORK1, a potassium-selective leak channel with two pore domains cloned from Drosophila melanogaster by expression in Saccharomyces cerevisiae

A K+ channel gene has been cloned from Drosophila melanogaster by complementation in Saccharomyces cerevisiae cells defective for K+ uptake. Naturally expressed in the neuromuscular tissues of adult flies, this gene confers K+ transport capacity on yeast cells when heterologously expressed. In Xenopus laevis oocytes, expression yields an ungated K(+)-selective current whose attributes resemble the "leak" conductance thought to mediate the resting potential of vertebrate myelinated neurons but whose molecular nature has long remained elusive. The predicted protein has two pore (P) domains and four membrane-spanning helices and is a member of a newly recognized K+ channel family. Expression of the channel in flies and yeast cells makes feasible studies of structure and in vivo function using genetic approaches that are not possible in higher animals.     

Compound heterozygous protein C deficiency resulting in the presence of only the beta-form of protein C in plasma

About 30% of human plasma protein C (PC) is of lower molecular weight than the predominant alpha-form. The minor beta-form arises as a consequence of the lack of glycosylation at Asn329. Although the functional role of Asn329 has been investigated by in vitro mutagenesis, until now no naturally occurring mutations have been reported at this site. We describe here the case of two identical twin sisters compound heterozygous for two novel PC mutations: Cys78-->Stop inherited from the maternal side and Asn329-->Thr inherited from the paternal side, associated with the presence of only the beta-form of PC in plasma. The Cys78-->Stop substitution is predicted to abolish PC synthesis from one allele, whereas the Asn329-->Thr substitution results in the reduced synthesis of a beta PC variant with decreased functional activity. PCN329T from the two monovular twin sisters was purified and its active form APCN329T was assessed for its ability to inactivate factor Va. Whereas no differences were observed between the activation rates of normal PC and PCN329T, APCN329T inactivated human factor Va with a rate slower than the normal APC. This is the first report of a PC defect involving glycosylation of the molecule. This defect results in the presence of only the beta-form of PC in human plasma and is responsible for the reduced anticoagulant activity observed.     

Seizure disorders in burned children: a retrospective review

This review shows that hyponatremia is the most common cause of burn seizures in children, followed by a history of epilepsy, hypoxia, sepsis with high fever, unknown aetiology and drug toxicity or sudden drug withdrawal. This study also shows that burn seizure is most common in younger children and is related to size and degree of burn. We recommend close monitoring of metabolism, haemodynamics, arterial blood gases, wound and blood cultures, and levels of abnormalities in serum, electrolytes, glucose, Ca, P and Mg. Prompt corrections of any problems in these areas can be vital. Invasive procedures for the diagnosis of seizures, including lumbar puncture and EEG, should be reserved for infrequent non-responding cases.