Extensibility and scanning electron microscopy evaluation of 5 pediatric anterior capsulotomy techniques in a porcine model

PURPOSE: To compare the extensibility and scanning electron microscopy (SEM) of 5 currently used pediatric anterior capsulotomy techniques: vitrectorhexis, manual continuous curvilinear capsulorhexis (CCC), can-opener, radio frequency diathermy, and plasma blade in a porcine model. SETTING: Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. METHODS: Extensibility was determined by stretching each capsulotomy until it ruptured and measuring it by calculating the mean stretch-to-rupture circumference of each capsulotomy (20 eyes per technique) as a percentage of its baseline circumference. Edge characteristics were evaluated using SEM. RESULTS: The mean extensibility of each technique tested (vitrectorhexis 161%, CCC 185%, can opener 149%, radio frequency 145%, plasma blade 170%) was significantly different (P<.001, 1-way analysis of variance). The SEM examination found that the vitrectorhexis had a scalloped edge with the whole edge rolled over, presenting a smooth surface toward the inside of the capsulotomy; the manual CCC produced the smoothest edge, with no irregularities noted; the can-opener edge was irregular, showing each puncture of the needle had created a small arc, with occasional regions of the edge rolled over in a "hit-and-miss" fashion; the radio-frequency diathermy capsulotomy edge was ragged, rough, and irregular; and the plasma blade capsulotomy edge was rougher than the manual CCC, but there were fewer irregularities than the radio-frequency diathermy edge had. CONCLUSIONS: The manual CCC technique produced the most extensible porcine capsulotomy, followed by the plasma blade, vitrectorhexis, can-opener, and radio-frequency techniques, in a porcine model. The manual CCC technique also produced the smoothest anterior capsulotomy edge according SEM evaluation.     

Heparin-induced thrombocytopenia: principles for early recognition and management

Heparin-induced thrombocytopenia (HIT) is a potentially devastating complication of therapy with either unfractionated or low-molecular-weight heparin. Thrombocytopenia is no longer essential for the diagnosis of HIT, since a 50% drop in the platelet count may be a more specific indicator. Once HIT is clinically suspected, heparin should be stopped immediately and direct thrombin inhibitor therapy started; waiting for laboratory confirmation may be catastrophic.     

The Evi1 proto-oncoprotein blocks endomitosis in megakaryocytes by inhibiting sustained cyclin-dependent kinase 2 catalytic activity

The 3q21q26 syndrome leukaemias are characterised by dystrophic megakaryocytes, elevated platelet counts, ectopic EVI1 protein production and poor prognosis. To investigate the molecular basis of this disease, we developed a model system to examine the biological activity of EVI1 in a megakaryocyte progenitor cell line. For this purpose, Evi1 was conditionally expressed in human erythroleukaemia cells (HEL) that progress along the megakaryocyte lineage in the presence of 12-O-tetradecanoylphorbol 13-acetate (TPA). TPA-stimulated HEL cells normally undergo: (1) growth arrest; (2) altered morphology; (3) endomitosis and (4) characteristic changes in gene expression, including reduction of the erythroid-specific glycophoryn A and elevation of the specific glycoproteins GPIIIa and GPVI. Enforced Evi1 expression alone had no effect upon HEL cell proliferation or differentiation but a phenotype was manifest upon stimulation to differentiate. Evi1-expressing, TPA-treated HEL cells still showed growth arrest, had reduced and enhanced glycophoryn A and GPIIIa mRNA's, respectively, but failed to significantly elevate GPVI mRNA. This was accompanied by inhibition of endomitosis and altered cell morphology. Sustained CDK2 catalytic activity, typically associated with megakaryocyte endomitosis, was dramatically decreased in TPA-stimulated Evi1-expressing HEL cells because of significantly reduced levels of cyclin A. Therefore, enforced Evi1 expression could inhibit megakaryocyte differentiation although retention of some characteristic molecular changes, in combination with a block in endomitosis and altered morphology, suggest a defect in lineage progression. These results suggest that ectopic Evi1 expression contributes to a defective megakaryocyte differentiation programme and is likely to contribute to the phenotype observed in 3q21q26 syndrome leukaemias.     

Effects of HFE gene mutations and alcohol on iron status, liver biochemistry and morbidity

BACKGROUND AND AIMS: The aims of the present study were to determine: (i) whether alcohol consumption is greater in individuals with HFE mutations; and (ii) whether common HFE mutations modify the effects of alcohol on serum iron and liver biochemistry or morbidity. METHODS: The residents of the town of Busselton in Western Australia were subject to cross-sectional health surveys between 1966 and 1983. In 1994/1995 all surviving participants of the earlier surveys were invited to take part in a follow-up survey. Logistic, linear and Poisson log-linear regression analyses were performed in 1490 men and 1452 women from the 1994/1995 survey to assess the relationships between HFE mutations, alcohol, iron levels, liver biochemistry and morbidity. RESULTS: Heavy or moderate alcohol consumption was present in 7% or 36% of men and 0.5% or 12% of women, respectively. Alcohol consumption strongly influenced levels of serum ferritin and gamma glutamyl transpeptidase (GGT) and mean cell volume (MCV) in men and women but only alanine aminotransferase (ALT) levels in women. These effects were independent of HFE gene mutations. Hospital admission rates for respiratory disorders were higher in men with the C282Y mutation. CONCLUSIONS: Alcohol consumption strongly influences serum ferritin and GGT levels and MCV in men and women but only ALT levels in women, and these effects are independent of HFE mutations. HFE gene mutations do not predispose to moderate or heavy alcohol consumption. The C282Y mutation is associated with increased respiratory admission rates in men.     

Pretreatment blood concentrations of chloroquine in patients with malaria infection: relation to response to treatment

Resistance of Plasmodium falciparum to chloroquine has been reported in many areas in Ghana. Most of these reports, which are from hospital-based studies, indicate RI and RII rather than RIII type of resistance. Since high pretreatment levels of chloroquine have also been measured in patients with malaria infection in Ghana, we hypothesized that the 'added effect' of the pretreatment ingested drug to the full dose given at the hospital may be responsible for the low proportion of RIII type of resistance observed. To ascertain this, pretreatment blood levels of chloroquine were correlated with treatment outcomes in 231 paediatric malaria patients, referred to a major hospital in Ghana. The rate of parasite clearance and prevalence of recrudescence, 14 days post-treatment, were determined for each patient. Results from this study showed no correlation between pretreatment chloroquine levels and day 0 parasitaemia. Two hundred and seven patients (89.6 per cent) had parasites that were sensitive to chloroquine whilst 24 (10.4 per cent) had resistant parasites. Of the latter group 17, six, and one patients had P. falciparum parasites, which were resistant at RI, RII and RIII levels, respectively. Seventy-five per cent of the patients without any detectable pretreatment blood chloroquine had parasites that were sensitive to chloroquine whilst 89.8 per cent, 98 per cent, and 100 per cent with pretreatment blood chloroquine concentration ranges of 0.5--100.5 ng/ml, 100.5--200 ng/ml, and >200 ng/ml, respectively, had chloroquine-sensitive parasites. An inverse relationship was thus observed between pretreatment blood chloroquine concentration and the degree of resistance in this study. We conclude that pre-hospital treatment ingested chloroquine contributes significantly to the resolution of malaria in children in Ghana, in the presence of chloroquine resistance.     

ErbB and Nrg: potential molecular targets for vestibular schwannoma pharmacotherapy.

OBJECTIVE: Identify molecular targets for development of tumor-specific pharmacotherapeutics aimed at treating vestibular schwannomas (VSs). Activated epidermal growth factor receptor B (ErbB) 2 and ErbB3 are abundantly expressed in VS. ErbB2 signaling is essential for Schwann cell differentiation, survival, and proliferation. VS arise after loss of functional merlin, a putative tumor suppressor. Merlin internalizes ErbB2 receptors in rodent Schwann cells.Unregulated ErbB signaling may contribute to VS tumorigenesis. STUDY DESIGN: Molecular analyses, retrospective clinical correlation. SETTING: Tertiary referral center. PATIENTS: Thirty-eight specimens from patients operated for sporadic (n=21) and neurofibromatosis (NF) 2-related (n=17) VS. INTERVENTION(S): VS analyses via real-time polymerase chain reaction, immunohistochemistry, and correlation with patient clinical data. MAIN OUTCOME MEASURE(S): ErbB signaling molecule expression, tumor size, age, and NF2 status. RESULTS: VS upregulated epidermal growth factor (EGF) receptor in 68% (62% sporadic and 75% NF2-associated VS) and ErbB2 in 84% (76% sporadic and 94% NF2-related VS). ErbB3 was upregulated in 34%, and ErbB4 is downregulated in NF2-related VS. Of EGF receptor (EGFR) ligands, EGF was upregulated in all NF2-related VS, but none of the sporadic VS (p<0.01), and transforming growth factor alpha and beta-cellulin showed upregulation in 67% of NF2-related VS but not sporadic VS (p=0.02 and p=0.01, respectively). Neuregulin (Nrg) was upregulated in 86% of sporadic VS versus 19% of NF2-related VS (p<0.01). EGFR expression levels correlated directly with VS tumor size and inversely with patient age, whereas Nrg expression correlated directly with age (p=0.0005). EGF expression predicts NF2 status, whereas Nrg predicts non-NF2 status (p<0.01). CONCLUSION: These findings implicate the ErbB pathway in VS growth and as potential molecular targets for VS pharmacotherapy.