Endothelin-converting enzyme: substrate specificity and inhibition by novel analogs of phosphoramidon

Endothelin converting enzyme was partially purified by detergent extraction and ion exchange chromatography from porcine aortic endothelial cells. This kinetically homogeneous preparation catalyzes the hydrolysis of porcine big endothelin-1 to endothelin-1 with a pH optimum of 7. Human big endothelins-1, -2, and -3 are also hydrolyzed, but at progressively lower rates. Fragments of big porcine endothelin-1 comprising residues 16-39 and 16-29 are good substrates, but additional C-terminal truncations are devoid of substrate activity. Endothelin converting enzyme is characteristically inhibited by phosphoramidon and other metalloproteinase inhibitors including EDTA, o-phenanthroline, and diethylpyrocarbonate, but not by inhibitors of other classes of proteases or thiorphan. The inhibition by phosphoramidon is competitive with big porcine endothelin-1 suggestive of a common binding site for substrate and inhibitor. A number of novel analogs of phosphoramidon were synthesized by modifying various regions of the molecule and tested for inhibitory activity. The most potent of these, a methylphosphonic acid, has an IC50 of 0.05 microM.

Fetal cerebral Doppler studies as a predictor of perinatal outcome and subsequent neurologic handicap

OBJECTIVE

To study the use of middle cerebral arterial Doppler findings in a group of high-risk fetuses as a predictor of adverse perinatal outcome, including subsequent neurologic handicap.

METHODS

A group of very high-risk fetuses was recruited over a 2-year period for study. Weekly fetal biometries and Doppler studies of the umbilical artery and middle cerebral arteries were carried out until delivery. Main outcome indices analyzed included birth weight ratio (ratio of observed birth weight to mean birth weight for gestation), days of ventilator requirement, neonatal intracranial hemorrhage or periventricular leukomalacia, necrotizing enterocolitis, and follow-up data on major neurologic handicap and death.

RESULTS

Seventy-four patients were recruited. One hundred thirty-four sets of examinations were made and prospective follow-up data were available for up to 2 years. The ratio of the umbilical and middle cerebral arterial resistance index was found to be inversely proportional to the birth weight ratio. Fetuses who had a high prenatal umbilical-cerebral Doppler ratio had significantly lower birth weight ratios than those with normal findings (0.72 versus 0.92; P < .001). The ratio was a more sensitive marker for growth restriction (sensitivity 78%) than conventional fetal biometry and umbilical arterial systolic-diastolic ratio. However, fetuses with high ratios did not have higher incidences of perinatal complications or subsequent neurologic handicap.

CONCLUSION

Prenatal cerebral vasodilation is a sensitive marker for growth restriction and it seems to be a physiologic response to hypoxia. Fetuses with intrauterine cerebral vasodilation do not have increased risk for subsequent gross neurologic damage.

P/O ratios reassessed: mitochondrial P/O ratios consistently exceed 1.5 with succinate and 2.5 with NAD-linked substrates

The efficiency of ATP synthesis coupled to cell respiration, commonly referred to as the P/O ratio, has been the subject of extensive studies for more that 50 years. The general conclusion from these studies is that respiring mitochondria can convert external ADP to ATP at a maximal P/O ratio of 3 for NAD-linked substrates and 2 for succinate. However, in recent years the validity of these "integral" values has been questioned on both mechanistic and thermodynamic grounds, and a mechanistic P/O ratio of 2.5 for NAD-linked substrates and 1.5 for succinate have been concluded on the basis of experiments with isolated mitochondria. These values have been widely adopted in the scientific literature, including several recent textbooks. In this paper we report that under optimal conditions with respect to preparation and assay procedures, the P/O ratios obtained with isolated rat liver mitochondria consistently exceed 2.5 with NAD-linked substrates and 1.5 with succinate. These results, although not excluding "nonintegral" P/O ratios due to various energy-dissipating side reactions, warrant caution in accepting the reported lower values and, in general, in referring to mechanistic considerations unless the underlying molecular mechanisms are understood.

Chemical approaches to improve the oral bioavailability of peptidergic molecules

This review discusses both tools and strategies that may be employed as approaches towards the pursuit of orally active compounds from peptidergic molecules. Besides providing a review of these subjects, this paper provides an example of how these were utilized in a research programme at SmithKline Beecham involving the development of orally active GPIIb/IIIa antagonists. The tools for studying oral drug absorption in-vitro include variants of the Ussing chamber which utilize either intestinal tissues or cultured epithelial cells that permit the measurement of intestinal permeability. Example absorption studies that are described are mannitol, cephalexin, the growth hormone-releasing peptide SK&F 110679 and two GPIIb/IIIa antagonist peptides SK&F 106760 and SK&F 107260. With the exception of cephalexin, these compounds cross the intestine by passive paracellular diffusion. Cephalexin, on the other hand, crosses the intestine via the oligopeptide transporter. Structure-transport studies are reviewed for this transporter. The tools for studying oral drug absorption in-vivo involve animals bearing in-dwelling intestinal or portal vein catheters. A study of the segmental absorption of SK&F 106760 is provided. The review concludes with two chemical strategies that may be taken towards the enhancement of oral bioavailability of peptidergic molecules. The first strategy involves the chemical modification of peptides which enhance intestinal permeability, specifically the modification of amide bonds. The second strategy involves the design of compounds bearing nonpeptide templates, which are more amenable to the discovery of compounds with oral activity, from peptide pharmacophore models. An example is given regarding the discovery of SB 208651, a potent orally active GPIIb/IIIa antagonist, designed from the peptides SK&F 106760 and SK&F 107260.

Postpartum anaemia is not related to maternal iron status in the third trimester

OBJECTIVE

To determine whether the maternal haemoglobin and iron stores of non-anaemic mothers (haemoglobin > or = 10 g/dl) who developed postpartum anaemia were lower compared to mothers who did not develop postpartum anaemia.

STUDY DESIGN

A prospective study was conducted in a teaching hospital on 467 low-risk mothers recruited from the antenatal clinic over a 3-month period, who were given only low dose iron supplement and delivered in the same hospital. Blood was drawn at 28-30 weeks for the measurement of haemoglobin, mean cell volume, serum ferritin, serum iron and total iron binding capacity. These results were compared between mothers with a postpartum day 3 haemoglobin of > or = 10 g/dl and those < 10 g/dl. Statistical analysis was performed with parametric and non-parametric methods as appropriate.

RESULTS

Mothers with postpartum anaemia had a higher incidence of postpartum haemorrhage (19.6% vs. 3.9%, P < 0.001) as well as heavier mean intrapartum blood loss (444 ml vs. 304 ml, P < 0.001), but there was no difference in the haemoglobin, mean cell volume, serum ferritin, serum iron and total iron binding capacity.

CONCLUSIONS

In mothers without antenatal anaemia, the development of postpartum anaemia is not related to the maternal iron status in the third trimester.

Corneal ulcers in two institutions in Singapore: analysis of causative factors, organisms and antibiotic resistance

The aim of this study was to determine the causative factors, organisms and antibiotic resistance in patients with bacterial keratitis in Singapore. We analysed retrospectively 103 cases of bacterial keratitis admitted to the Singapore General Hospital or the Singapore National Eye Centre during a 21-month period from March 1992 to December 1993. Contact lens wear represented the largest single predisposing factor (35 eyes, 34.0%), followed by ocular trauma (28 eyes, 27.2%) and pre-existing ocular disease (28 eyes, 27.2%). Thirteen of the twenty-eight cases of trauma-related keratitis were work-related injuries. Gram-negative organisms formed the largest group (41 cultures, 80.4%), with Pseudomonas aeruginosa being the most common organism identified (30 eyes). Pseudomonas was also responsible for 78.6% of all contact lens ulcers (11 out of 14 eyes). Resistance to gentamicin was only encountered in 1 case of Proteus mirabilis keratitis. All cases of Pseudomonas infection and 3 of the 10 Gram-positive cases were also resistant to chloramphenicol. All Gram-positive cases were sensitive to cephalosporins. Contact lens wear and ocular trauma are the major preventable risk factors for bacterial keratitis in young sighted eyes in Singapore. Gentamicin continues to be the antibiotic of choice for Gram-negative corneal infections in view of the low incidence of resistance. The routine use of chloramphenicol as the topical antibiotic of choice for corneal infection is not recommended due to the high resistance in Gram-positive and Gram-negative organisms locally.

Site-directed isotope labeling and FTIR spectroscopy: assignment of tyrosine bands in the bR-->M difference spectrum of bacteriorhodopsin

Fourier transform infrared difference spectroscopy has been used extensively to probe structural changes in bacteriorthodopsin and other retinal proteins. However, the absence of a general method to assign bands to individual chemical groups in a protein has limited the application of this technique. While site-directed mutagenesis has been successful in special cases for such assignments, in general, this approach induces perturbations in the structure and function of the protein, thereby preventing unambiguous band assignments. A new approach has recently been reported (Sonar et al., Nature Struct. Biol. 1 (1994) 512-517) which involves cell-free expression of bacteriorhodopsin and site-directed isotope labeling (SDIL). We have now used this method to re-examine bands assigned in the bR-->M difference spectrum to tyrosine residues. Our results show that out of 11 tyrosines in bR, only Tyr 185 is structurally active. This work further demonstrates the power of SDIL and FTIR to probe conformational changes at the level of individual amino acid residues in proteins.

[Angioplasty for subclavian artery stenosis: report of two cases]

We present our experience of percutaneous transluminal angioplasty (PTA) in the treatment of subclavian artery stenosis in two patients. One patient was a 66-year-old asymptomatic man. His left arm systolic blood pressure was 40 mmHg lower than that of his right arm. He had irregular segmental stenotic lesions (50% to 80%) at the proximal portion of the left subclavian artery. PTA was attempted via the left brachial artery. After the procedure, the stenotic lesion seemed totally dilated and his left arm systolic blood pressure was 8 mmHg lower than that of his right arm. Restenosis of the left subclavian artery was noted four months after the procedure. The second patient was a 51-year-old man with symptoms of intermittent dizziness, nausea and vertigo. His left arm systolic blood pressure was 30 mmHg lower than that of his right arm. He had 43% diameter stenotic lesion at the proximal portion of the left subclavian artery. PTA was attempted via right femoral artery. After the procedure, the stenotic lesion seemed markedly dilated and his left arm systolic blood pressure was 14 mmHg lower than that of his right arm. He is well three years post-procedure without evidence of restenosis.

Biochemical studies of isolated mitochondria from normal and diseased tissues

Isolated mitochondria have served as useful tools for identifying the site(s) of impairment associated with respiratory chain-linked oxidative phosphorylation at the molecular level. Over the last three decades, a number of diseases associated with mitochondrial dysfunction have been identified. The literature is large and diverse. This paper presents a brief survey of the current state of knowledge concerning biochemical studies of mitochondrial diseases associated with skeletal muscle, such as mitochondrial myopathies and, with brain injury such as that induced by ischemia/reperfusion. Various mitochondrial preparations and assay conditions are evaluated. The importance of fresh tissue for the isolation of tightly coupled mitochondria and the selection of suitable assay conditions for characterization have been demonstrated. Appropriate methodologies for isolation and characterization of tightly coupled mitochondria from both skeletal muscle and brain are presented.

Pregnancy screening by uterine artery Doppler velocimetry--which criterion performs best?

OBJECTIVE

To test whether repeating Doppler studies of the uteroplacental circulation late in gestation will improve the test's power for predicting pregnancy-induced hypertension and fetal growth restriction (FGR), and whether analysis based on a combination of quantitative and qualitative assessments of the uterine arterial waveforms will yield better results than analysis based on either alone.

METHODS

A total of 358 patients considered to be at medium risk for the development of pregnancy-induced hypertension and FGR were recruited. Continuous-wave Doppler studies of the uterine arteries were performed serially at 20, 28, and 36 weeks' gestation. The values of various Doppler indices in the prediction of subsequent pregnancy complications were tested at different gestations and different cutoff levels. The overall significance of performance of the Doppler indices was assessed by the Cohen kappa index, which tests the extent of agreement between the test and the "truth" over that by random chance agreement.

RESULTS

A total of 974 examination results on 334 patients were available for analysis. We found that Doppler studies of the uterine arteries at 28 and 36 weeks were less useful than studies performed at 20 weeks. Serial studies at 20 and 28 weeks showed only marginal improvement when compared with a single study at 20 weeks. The best criteria were a mean resistance index (RI) of uterine arteries above the 90th percentile and the presence of diastolic notches in both uterine arteries at 20 weeks. Although the overall kappa index only suggested fair to good agreement beyond chance, the positive predictive value for subsequent complications was good: 57% for severe complications and 93% for any complications.

CONCLUSION

Doppler studies of the uterine artery as a test for the subsequent development of pregnancy complications are best performed at 20 weeks with a combination of RI measurements and the assessment of the presence of diastolic notches.

Nonpeptide endothelin receptor antagonists: IV. Identification of receptors in rabbit colonic mucosa and smooth muscle and correlation with physiological effects

Endothelin (ET) has been previously demonstrated to be a potent intestinal secretory stimuli and to elicit intestinal smooth muscle contractions. In rat distal colon, the ETA receptor antagonist cyclo[D-Asp-L-Pro-D-Val-L-Leu-D-Trp] abolishes the changes in ion transport (as measured by short-circuit current) elicited by ET-1. In this study, effects of ET-1, sarafotoxin 6c and "big" ET in the absence and presence of the endothelin receptor antagonists cyclo [D-Asp-L-Pro-D-Val-L-Leu-D-Trp] and (+/-)-3-[2-(carboxymethoxy)-4-methoxyphenyl]-1-[3,4- (methylenedioxy)phenyl]-5-(prop-1-yloxy)indan-2-carboxylic acid on ion transport in rabbit distal colon were assessed through measurement of short-circuit current changes in segments of muscle-stripped mucosa in Ussing chambers. In addition, changes in smooth muscle contraction in response to acetylcholine, ET-1, ET-3 and sarafotoxin 6c in the absence and presence of (+/-)-3-[2-(carboxymethoxy)-4-methoxyphenyl]-1-[3,4- (methylenedioxy)phenyl]-5-(prop-1-yloxy)indan-2-carboxylic acid and of cyclo [D-Asp-L-Pro-D-Val-L-Leu-D-Trp] were measured in mucosa-free preparations oriented along their longitudinal axes. Receptor binding studies with mucosal or smooth muscle homogenates were conducted with [125I]ET-1, with [125I]ET-3 and with [125I]Tyr13Suc-[Glu9,Ala11,15]-endothelin-1(8-21 ) to identify the subtypes of ET receptors present in these preparations. From studies with rabbit colonic mucosa, both binding studies and measurement of short-circuit current confirm that the ETB receptor subtype is the predominant subtype and is responsible for the changes observed in ion transport.(ABSTRACT TRUNCATED AT 250 WORDS)

Successful percutaneous transluminal angioplasty in native coarctation of aorta in young adult: a case report

Coarctation of aorta is a rare cause of secondary hypertension, premature death will occur if no appropriate treatment is given. Before 1980, the only effective treatment was surgery, and recurrent stenosis was frequent. After then several works on percutaneous transluminal angioplasty of this disease were reported, with promising short-term and long-term results, especially in children and young adults. This report concerns a 19-year-old male who had hypertension for four years; the hypertension was caused by coarctation of the aorta, confirmed by cardiac catheterization and angiography. Average blood pressure (BP) of his upper extremities was 200/110 mmHg which dropped to 150/90 mmHg immediately, and still two years, after angioplasty, whereas BP of the lower extremities maintained at about 150/80 mmHg measured by Korotkoff technique. Follow-up transesophageal echocardiography found no coarctation or aneurysm at the dilatation site one year later. Magnetic resonance imaging, performed two years later, showed an almost normal aortic wall at the coaxctation. The postoperative course was uneventful, and patient follow-up at the cardiology clinic has regularly shown an average BP around 150/80 mmHg.

Site-directed isotope labeling and ATR-FTIR difference spectroscopy of bacteriorhodopsin: the peptide carbonyl group of Tyr 185 is structurally active during the bR-->N transition

The largest secondary structural change occurs in the bacteriorhodopsin (bR) photocycle during the M-->N transition. In this work site-directed isotope labeling (SDIL) and attenuated total reflection Fourier transform infrared (ATR-FTIR) difference spectroscopy were used to investigate this conformational change. L-Tyrosine containing a 13C isotope at the carbonyl carbon was selectively incorporated at Tyr 57, Tyr 147, and Tyr 185 by SDIL. This involves the cell-free expression of bR in the presence of Escherichia coli suppressor tRNA(CUATyr) aminoacylated with L-[1-13C]Tyr. ATR-FTIR difference spectroscopy reveals that of the 11 tyrosines, only the peptide carbonyl group of Tyr 185 undergoes a significant structural change during the bR-->N transition. Along with other spectroscopic evidence, this result suggests that the Tyr 185-Pro 186 region of the protein is structurally active and may function as a hinge which facilitates the tilt of the cytoplasmic portion of the F-helix in bacteriorhodopsin during the M-->N transition.

Cytogenetics and immunophenotypes of childhood acute lymphoblastic leukemia in Hong Kong

We present the cytogenetics and immunophenotypes of 55 cases of childhood acute lymphoblastic leukemia in Hong Kong. Although the pattern of immunophenotypes is similar to that of the west, hyperdiploidy is rarely observed locally. Our preliminary analysis also reveals some new translocations.

Taxonomic clustering and frequency associations as features of semantic memory development in children with learning disabilities

This study investigated taxonomic clustering and use of frequency associations as features in the semantic memory development of children with learning disabilities (LD). Free-recall organization of second- and sixth-grade children with and without LD was analyzed for two types of primary and secondary word lists: (a) items associated with frequency (FA), and (b) items related by category members (CM). In contrast to expected findings, younger, non-disabled children organized words categorically as proficiently as their older nondisabled peers, and the categorization abilities of children with LD were comparable to those of nondisabled subjects, with one exception: Subjects with LD showed less clustering for secondary FA. These results indicate that when individual child-generated word lists (i.e., meaningful and familiar words) are used, children with LD may not be impaired in their ability to recognize and utilize semantic structure to facilitate learning.

Site-directed isotope labelling and FTIR spectroscopy of bacteriorhodopsin

Insight into integral membrane proteins function is presently limited by the difficulty of producing three-dimensional crystals. In addition, X-ray structures of proteins normally do not provide information about the protonation state and structural changes of individual residues. We report here the first use of site-directed isotope labelling and Fourier transform infrared (FTIR) difference spectroscopy to detect structural changes at the level of single residues in an integral membrane protein. Two site-directed isotope labeled (SDIL) tyrosine analogues of bacteriorhodopsin were produced which exhibit normal activity. FTIR spectroscopy shows that out of 11 tyrosines, only Tyr 185 is structurally active during the early photocycle and may be part of a proton wire.

Flow cytometric measurement of glycosylphosphatidyl-inositol-linked surface proteins on blood cells of patients with paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired disorder of hematopoiesis in which affected cells are deficient in glycosylphosphatidyl-inositol (GPI) anchored surface proteins. The authors used flow cytometry to study 10 patients with PNH. They used a comprehensive panel of monoclonal antibodies against all nine currently known GPI-linked surface proteins (CD14, CD16, CD24, CD48, CD55, CD58, CD59, CD67, CD73) on cells of various lineages. Deficient cells were identified in the granulocytic-monocytic and erythroid lineages in all patients. However, the lymphoid lineage was affected in only eight patients. The patterns of deficiency were variable, with deficient cells constituting a part to all of the cells in the lineages tested. Certain proteins, including CD16, CD58, and CD59, appeared to be preferentially expressed, despite severe deficiencies of other GPI-linked proteins. Moreover, a trimodal pattern of expression of CD16, CD48, and CD59 was observed, in which a population of cells with intermediate levels of expression were identified in addition to positive and deficient cells. The authors' findings indicated a great degree of heterogeneity in the patterns and levels of expression of the GPI-linked proteins in the various cell types, as well as a possible heterogeneity in lineage involvement. The different patterns of expression of GPI-linked proteins should be considered when using flow cytometry to diagnose PNH. Finally, the clinical progression in some of the patients suggested a possible link between PNH, aplastic anemia, and myelodysplasia.

Umbilical artery Doppler velocimetry compared with fetal heart rate monitoring as a labor admission test

A total of 155 patients admitted in early labor to the delivery unit of the University of Hong Kong were recruited into a study comparing the value of umbilical artery Doppler velocimetry and fetal heart rate (FHR) monitoring in early labor as an admission test. FHR monitoring for 30 min was recorded on admission, and umbilical A/B ratio was simultaneously performed. The FHR tracing was scored according to the Lyons score by a third independent observer after delivery. Outcome variables studied included small for gestational age (SGA), intrapartum FHR abnormalities, operative deliveries for fetal distress, umbilical cord pH, Apgar scores, admission into the special care baby unit, and a combination of the variables. It was found that at cut-off values of Lyons score < 7 and umbilical A/B ratio > 2.6 at term, about 19% of cases were abnormal for either tests, with only a few cases of overlap. Umbilical A/B ratio was found to be significantly correlated with SGA. The sensitivity and positive predictive values were, however, low. Both tests were relatively poor predictors for most of the outcome variables studied. Interestingly, FHR monitoring did not seem to have any advantage over Doppler velocimetry as a labor admission test. Further larger scale studies to evaluate their usefulness in medium and low risk populations are indicated.

Complete membranous obstruction of the inferior vena cava: clinical characteristics of Chinese patients

OBJECTIVES

To analyse the clinical presentations of membranous-type Budd-Chiari syndrome and the long-term outcome of balloon angioplasty.

DESIGN

A case-control study. Patients who received abdominal sonography and were suspected of having hepatic venous outflow obstruction were advised to receive cardiac catheterization and angiography.

SETTING

Patients were collected from Chung Hisao Hospital and Chang Gung Medical Centre. Angioplasty was done at Chang Gung Medical Centre.

SUBJECTS

Seventeen patients who had the symptoms and signs of portal hypertension were suspected of having hepatic venous outflow obstruction after abdominal sonography and a radionuclide liver scan and eight of them were confirmed as having membranous-type obstruction.

INTERVENTIONS

Simultaneous catheterization and contrast angiography was performed via the right brachial and femoral veins. Angioplasty was performed afterwards.

MAIN OUTCOME MEASURES

The remission of clinical symptoms and signs and a decrease of the pressure gradient between the right atrium and inferior vena cava were used as indicators of successful intervention.

RESULTS

All patients had remarkable remission of symptoms and signs. The average pressure gradient between right atrium and inferior vena cava dropped from 16.5 +/- 1.6 to 6.5 +/- 1 mmHg (mean +/- SD).

CONCLUSION

The clinical presentations of membranous-type Budd-Chiari syndrome are somewhat different from hepatic vein occlusion. Balloon angioplasty may be a modality for curing this disease. A larger patient population is necessary to confirm this study.

Diagnostic use of metoclopramide in hypertension caused by pheochromocytoma

We studied 5-mg metoclopramide provocation in six pheochromocytomatous patients with different tumor locations, varying secretory patterns and large tumor sizes (> 12 g or equivalently) and in 14 patients with essential hypertension as part of diagnostic work-up, usually after screening with vanillylmandelic acid assay by the colorimetric method. Antihypertensive medication continued in three and five patients, respectively. Despite similar basal blood pressures patients with pheochromocytomas developed more prominent pressor responses in five of six patients than the nonpheochromocytomatous patients (P < 0.01), most (10) of the latter with negligible pressor responses. Basal plasma catecholamines were higher in each of the pheochromocytomatous patients of different secretory patterns. Further rises after provocation were seen in all pheochromocytomatous patients except one with early pressor response, and also in one nonpheochromocytomatous patient. All tests were well tolerated. Thus, we concluded that the metoclopramide test based upon joint pressor response and plasma catecholamine response can be safely used in the diagnosis of pheochromocytoma. A less stringent protocol including a short drug-off preparatory period may be a warranted compromise between feasibility and diagnostic accuracy.

Transient myeloproliferative disorder in a Down's neonate with rearranged T-cell receptor beta gene and evidence of in vivo maturation demonstrated by dual-colour flow cytometric DNA ploidy analysis

Neonates with Down's syndrome may develop a transient myeloproliferative disorder (TMPD) which on presentation is indistinguishable from acute leukemia, with the difference manifest only on follow-up. The clinical course is one of spontaneous remission in TMPD and relentless progression in leukemia. We describe a Down's neonate presenting with hyperleucocytosis and circulating blasts which were positive for CD34, myeloid (CD33), megakaryocytic (CD41, CD42b, CD61), and T-lineage (CD3, CD7), but not B-lineage, associated antigens. Clonal rearrangement of the T-cell receptor beta (TCR beta) gene was found, with the immunoglobulin heavy chain gene in germline configuration, showing the disease to be a clonal proliferation of a multipotential stem cell involving the myeloid and T lineages. Dual-colour flow cytometric DNA ploidy analysis of CD41 positive blasts showed initially a predominant 2N population, but polyploidization to 6N and 8N cells was found on follow-up, concomitant with a progressive decrease in circulating blasts, suggesting maturation of the abnormal clone and a provisional diagnosis of TMPD. This was shown by the eventual resumption of normal haemopoiesis with the disappearance of blasts and the clonally rearranged TCR beta gene.

Ischemia/reperfusion-induced injury of forebrain mitochondria and protection by ascorbate

Complete, reversible forebrain ischemia was induced with a seven-vessel occlusion rat model. Previous studies of ischemic (M. A. Sciamanna, J. Zinkel, A. Y. Fabi, and C. P. Lee, 1992, Biochim. Biophys. Acta 1134, 223-232) rat brain mitochondria (RBM) showed that ischemia of 30 min caused an approximately 60% decrease in State 3 respiratory rates with both succinate and NAD-linked substrates and also in energy-linked Ca2+ transport. No significant change was seen in the State 4 rates. The inhibition of respiration could be prevented by EGTA or ruthenium red. In this paper it is shown that reperfusion (5 h) following ischemia (30 min) further impaired RBM respiratory activities (succinate and NAD-linked substrates). The presence of EGTA or ruthenium red in the assay medium did not protect against ischemia/reperfusion-induced injury. The effects of ascorbate, an oxygen radical scavenger, were studied. RBM isolated from ascorbate-treated animals (0.8 mg ascorbate/kg body weight) after ischemia (30 min) alone showed only a slight increase in State 3 (approximately 25%) and a decrease in State 4 (approximately 20%) activities with succinate, when compared to untreated 30-min ischemic animals, whereas, with glutamate+malate little or no effect was seen. The respiratory activities of RBM from ascorbate-treated, ischemic/reperfused (30 min/5 h) rats were restored to approximately 65% of controls levels. Ascorbate protection was dose-dependent with maximum protection at 0.8 mg ascorbate/kg body weight of rat. The k of succinate oxidase-supported Ca2+ uptake also returned to 62% of control values. Protection by ascorbate was most effective when administered prior to the onset of ischemia and provided partial protection when administered after the onset of reperfusion. These results suggest that ischemia-induced injury is primarily mediated by disruption of cellular Ca2+ homeostasis, and reperfusion-induced injury by peroxidative events.