Invasion of hereditary ovalocytes by Plasmodium falciparum in vitro and its relation to intracellular ATP concentration

Hereditary ovalocytes (stomatocytic ovalocytes), when examined within 1-2 days from the time that the blood sample is drawn, are invaded by Plasmodium falciparum in culture to the extent of at least 55% of normal control cells. The ovalocytes have extremely rigid membranes, characterised by a shear elastic modulus some 3-4 times greater than that of normal cells. The extent of invasion falls off very much more rapidly than that into normal cells on storage, and we surmise that this is the reason for earlier reports of resistance of ovalocytes to malarial invasion in vitro. The initial loss of susceptibility to invasion with time is not accompanied by any change in membrane rigidity, but is primarily a consequence of a rapid decline in intracellular ATP concentration: this falls to below the threshold level required for invasion (approx. 0.1 mM) over a period in which the ATP in normal cells remains almost constant. Incubation in a metabolic regenerating medium leads to a rise in the intracellular ATP concentration and invasion by P. falciparum is recovered, though to a much lower extent than in normal cells. The resistance of ovalocytes to invasion becomes irreversible, due possibly to degradative processes in the membrane, on further storage. The developing parasites in ovalocytes have a reduced number of merozoites and show distinct morphological abnormalities.     

A classification for incidents and accidents in the health-care system

Problems that arise from health-care management, rather than from a disease process, are now recognized as making a substantial contribution to patient morbidity and mortality and to the cost of health care. However, most classifications of these problems do not provide sufficient detail to allow comparisons or to develop better strategies for the prevention, detection and management of these problems. A 'Generic Occurrence Classification' was developed to record their salient features, place them in context and elicit any system or human error-based contributing factors. This was done by an iterative process in which 'natural categories', identified from over 2000 incidents and 800 adverse events, were placed in a hierarchical structure created using software written in Microsoft Visual Basic; data were stored in a Microsoft Access database. This was shown to be a valid and reliable way to compare incidents and accidents from different sources and to allow sufficient detail to be retrieved to develop preventive strategies.     

Relationships among lactate concentration, blood flow and histopathologic profiles in rat C6 glioma

Increased capacity for glycolytic metabolism is a well-known characteristic of neoplastic cells. Because lactic acid is the end product of glycolysis, in vivo MRS measurements of tumor lactate concentration ([lac]t) may provide valuable information about tumor metabolism, which will aid the development of therapies and the clinical diagnosis and treatment of tumors. In the present study, several hemodynamic and histologic parameters were evaluated with respect to their influence on [lac]t. Pronounced differences in [lac]t in two distinct populations of tumors suggested a putative perfusion threshold. Above this threshold, [lac]t was independent of hemodynamic and histologic factors including tumor blood flow (measured using MRS and the method of D2O washout), extent of necrosis and inflammatory cell infiltrate. Thus, for most tumors, [lac]t was not determined by any one single factor such as hypoxia, venous clearance, glucose supply, extent of necrosis or degree of inflammatory cell infiltrate. Rather, [lac]t may be equilibrated, at least in part, by an interplay of forces involving hemodynamics and substrate supply. In general, the data are consistent with the hypothesis that elevated lactate in most tumors is related to the high glycolytic activity of adequately perfused, viable neoplastic cells.     

Central adiposity and hemodynamic functioning at rest and during stress in adolescents

OBJECTIVE: To examine the impact of central adiposity upon hemodynamic functioning at rest and during stress in adolescents. DESIGN: Cross-sectional, correlational study. SUBJECTS: 46 White and 49 Black normotensive adolescents with family histories of essential hypertension. MEASUREMENTS: Systolic and diastolic blood pressure (SBP, DBP), cardiac output and total peripheral resistance responses were assessed at rest, during postural change, video game challenge and forehead cold stimulation. Specific lower and higher waist-to-hip ratio (WHR) tertiles were created for each gender and then integrated for analyses. This resulted in a lower WHR tertile of 11 Whites and 21 Blacks and an upper WHR tertile of 15 Whites and 17 Blacks. RESULTS: No differences in age, gender or ethnicity proportions were found between tertile groups (all P > 0.21). The upper WHR group showed greater body weight, waist and hip circumferences, body mass index (BMI), triceps skinfold and body surface area (all P < 0.001). Controlling for peripheral (that is, triceps skinfold) and overall (that is, BMI) adiposity, the upper WHR group exhibited greater SBP (that is, peak response minus mean pre-stressor level) to all three stressors and greater DBP reactivity to postural change and cold pressor (all P < 0.05). CONCLUSION: Central adiposity appears to adversely influence hemodynamic functioning during adolescence. Underlying mechanisms responsible for these associations require exploration.     

New-onset psychogenic seizures after surgery for epilepsy

BACKGROUND: The emergence of psychogenic seizures after surgery for epilepsy is not well recognized. OBJECTIVES: To identify the frequency of psychogenic seizures in an 11-year surgical experience and to characterize the patients with this complication. METHODS: Ninety-six patients underwent surgery for epilepsy between 1985 and 1996. The surgical database was reviewed and all patients who experienced postoperative psychogenic seizures were identified. Patients were characterized by sex, age, psychopathologic conditions, full-scale IQ, duration of epilepsy, surgical procedure, and operative complications. Patients were compared with the surgical group as a whole for these variables. SETTING: A comprehensive epilepsy center. RESULTS: Five patients were identified: 3 men and 2 women. Mean full-scale IQ was 73 (range, 66-82). Mean age was 29.8 years (range, 22-36 years). Three patients were diagnosed as having psychosis, 1 with borderline personality disorder and 1 with generalized anxiety. Operations included 4 anterior temporal lobectomies and 1 occipital lobectomy. Two patients experienced operative complications. Compared with the surgical cohort, patients had a higher frequency of preoperative psychopathologic conditions, lower mean full-scale IQ, and a greater occurrence of operative complications. CONCLUSIONS: (1) Patients can develop new-onset psychogenic seizures after surgery for epilepsy. (2) Low full-scale IQ, serious preoperative psychopathologic conditions, and major surgical complications may be risk factors. (3) Atypical postoperative seizures should be evaluated with video electroencephalographic monitoring before concluding that they are epileptic.