"Putting things in context": literal and discourse approaches to comprehension assessment

Research on receptive language development in typical children, especially as explicated in a classic paper by Robin Chapman, is reviewed. These findings raise three challenges for clinicians assessing comprehension in children with language disorders: (1) contrary to popular wisdom, comprehension does not always precede production in a simple step-by-step way; (2) comprehension is a private event; indicators of comprehension must be used to assess it, and these indicators can be misleading; and (3) children with subtle comprehension deficits may do well on standardized tests that are not sensitive to their difficulties with real-time discourse. Some strategies for addressing these challenges, as well as a framework for assessing comprehension, are offered.

Neurocognitive performance enhanced by highly active antiretroviral therapy in HIV-infected women

OBJECTIVE

To determine whether highly active retroviral therapy (HAART) is associated with better neurocognitive outcome over time among HIV-infected women with severely impaired immune function.

METHODS

A semiannual neurocognitive examination on four tasks was administered: Color Trail Making, Controlled Oral Word Association, Grooved Pegboard and Four-Word Learning. This protocol was initiated in the HIV Epidemiological Research study (HERS) study when a woman's CD4 cell count fell to < 100 x 10(6) cells/l. Immune function (CD4), viral load status and depression severity (CESD) were also assessed semi-annually, along with an interview to determine medication intake and illicit drug use.

RESULTS

HAART was not available to any participant at the time of enrollment (baseline), while 44% reported taking HAART at their most recent visit (mean duration of HAART 36.3 +/- 12.6 months). HAART-treated women had improved neurocognitive performance compared with those not treated with HAART. Women taking HAART for 18 months or more showed the strongest neurocognitive performance with improved verbal fluency, psychomotor and executive functions. These functions worsened among women not taking HAART. Substance abuse status, severity of depressive symptoms, age and educational level did not influence the HAART treatment effects on neurocognitive performance. Neurocognitive improvements were strongly associated with the magnitude of CD4 cell count increases.

CONCLUSIONS

HAART appeared to produce beneficial effect on neurocognitive functioning in HIV-infected women with severely impaired immune systems. Benefits were greatest for women who reported receiving HAART for more than 18 months.

Characterization of RNase P from Thermotoga maritima

The protein subunit of RNase P from a thermophilic bacterium, Thermotoga maritima, was overexpressed in and purified from Escherichia coli. The cloned protein was reconstituted with the RNA subunit transcribed in vitro. The temperature optimum of the holoenzyme is near 50 degrees C, with no enzymatic activity at 65 degrees C or above. This finding is in sharp contrast to the optimal growth temperature of T.maritima, which is near 80 degrees C. However, in heterologous reconstitution experiments in vitro with RNase P subunits from other species, we found that the protein subunit from T.maritima was responsible for the comparative thermal stability of such complexes.

Giant malignant mesenchymoma of the spermatic cord with bidirectional differentiation

BACKGROUND

Spermatic cord neoplasms are a rare tumor entity and, moreover, of benign behavior. Malignant tumors of the spermatic cord are mostly of mesenchymal origin. We present the unusual case of a giant malignant mesenchymoma of the spermatic cord with bidirectional differentiation into a liposarcoma and a leiomyosarcoma.

CASE REPORT

A 84-year-old male patient presented with a scrotal mass on the left side which was observed growing since 1 year and misdiagnosed as scrotal hernia or testicular hydrocele. Ultrasound and computed tomography demonstrated a solid tumor suggesting a spermatic cord tumor. The patient underwent hemiscrotectomy, and the histological examination of the 2,500-gram specimen revealed a malignant mesenchymoma originating from the spermatic cord with two distinct histopathological compartments of liposarcoma and leiomyosarcoma. Because an adjuvant therapy protocol is of questionable effect and because of the patient's age no further therapy was applied. The patient was closely followed and is now, 5 years after surgery, still free of disease.

CONCLUSION

Even in older patients, scrotal masses should be considered malignant tumors as long as no benign diagnosis has been proven. Although malignant mesenchymomas are rare tumors with poor prognosis, in selected cases even large tumor masses, as presented, can be cured by surgery.

Src deficiency or blockade of Src activity in mice provides cerebral protection following stroke

Vascular endothelial growth factor (VEGF), an angiogenic factor produced in response to ischemic injury, promotes vascular permeability (VP). Evidence is provided that Src kinase regulates VEGF-mediated VP in the brain following stroke and that suppression of Src activity decreases VP thereby minimizing brain injury. Mice lacking pp60c-src are resistant to VEGF-induced VP and show decreased infarct volumes after stroke whereas mice deficient in pp59c-fyn, another Src family member, have normal VEGF-mediated VP and infarct size. Systemic application of a Src-inhibitor given up to six hours following stroke suppressed VP protecting wild-type mice from ischemia-induced brain damage without influencing VEGF expression. This was associated with reduced edema, improved cerebral perfusion and decreased infarct volume 24 hours after injury as measured by magnetic resonance imaging and histological analysis. Thus, Src represents a key intermediate and novel therapeutic target in the pathophysiology of cerebral ischemia where it appears to regulate neuronal damage by influencing VEGF-mediated VP.

Pharmacologic interference with NF-kappaB activation attenuates central nervous system complications in experimental Pneumococcal meningitis

This study assessed the effects of 2 different inhibitors of NF-kappaB activation on central nervous system complications and clinical symptoms in an advanced stage of experimental pneumococcal meningitis: the calpain inhibitor I N-acetyl-leucinyl-leucinyl-norleucinal (ALLN), which interferes with IkappaB proteolysis, and BAY 11-7085, which inhibits IkappaB phosphorylation. Pneumococcal meningitis was associated with an increase in NF-kappaB activity, as determined by immunohistochemistry and Western blot analysis of rat brains 24 h after infection. Treatment with ALLN or BAY 11-7085 improved the clinical scores of infected rats, compared with those of untreated infected rats. This beneficial effect was parallelled by a significant reduction of the increase in intracranial pressure, blood-brain barrier permeability (as measured by the Evans blue-extravasation technique), cerebrospinal fluid (CSF) pleocytosis, CSF interleukin-6 levels, and impairment of cerebrovascular CO(2) reactivity and autoregulation. Thus, pharmacologic interference with NF-kappaB activation might be a possible target for adjunctive therapy in bacterial meningitis.

Antiandrogen withdrawal syndrome associated with prostate cancer therapies: incidence and clinical significance

The antiandrogen withdrawal syndrome is a well established phenomenon in prostate cancer. It is widely accepted that a subset of patients will benefit from the withdrawal of antiandrogen or steroidal hormone from hormonal therapy, exhibiting decreasing prostate-specific antigen (PSA) values and clinical improvement. The pathophysiology of antiandrogen withdrawal syndrome is not completely understood, although androgen receptor gene mutations seem to be the likely explanation. Currently, it is not possible to identify the subset of patients whose tumours will respond to antiandrogen or steroid withdrawal. Tumours that will respond may be classified as androgen-independent and hormone-sensitive tumours as opposed to androgen-independent and hormone-insensitive tumours that do not respond. Patients who respond to antiandrogen withdrawal experience approximately 6 months with improved quality of life; however, it is unknown if this translates into prolonged survival. At the very least, antiandrogen withdrawal offers a therapeutic modality that is not associated with adverse effects and improves quality of life even if only for a very limited time. Recent reports suggest that adding a secondary hormonal therapy such as amino- glutethimide, ketoconazole or steroidal hormones may enhance the response rate and prolong response time to the antiandrogen withdrawal syndrome. However, unless there is proof that this secondary hormonal manipulation prolongs survival, maintenance of quality of life is mandatory because of the possible adverse effects from these potent drugs. The fact that about 30% of patients will respond to antiandrogen or steroid withdrawal in hormone refractory prostate cancer must be taken into account in clinical trials of new cytotoxic agents which have been and will be conducted. Cessation of flutamide for at least 4 weeks and, in the case of bicalutamide, even 8 weeks, is mandatory before antiandrogen withdrawal syndrome can be excluded as the cause of decreasing PSA values. The antiandrogen withdrawal syndrome offers another piece of the puzzle of prostatic carcinoma, but at the same time it demonstrates how different advanced prostate cancer cells may react to therapeutic strategies and, therefore, hormone refractory prostate cancer remains a difficult challenge which must be solved in the future.

Theory of Frequency-Dependent Polarization of General Planar Electrodes with Zeta Potentials of Arbitrary Magnitude in Ionic Media

Electrode polarization effects have long aggravated the efforts of low frequency analysis, particularly those investigations carried out on biological material or in highly conductive media. Beginning from elementary equations of electrostatics and hydrodynamics, a comprehensive model is devised to account for the screening of a general planar electrode by an ionic double layer. The surface geometry of the planar electrode is left unspecified to include any type of micromachined array. Building on the previous work by DeLacey and White (1982, J. Chem. Soc. Faraday Trans. 2 78, 457) using a variational theorem, we extend their numerical results with compact analytic solutions, analogous to the Debye-Hückel potential for dc systems, but applicable now to dynamic ac experiments. The variational approach generates functions that are not restricted by perturbation expansions or numerical convergence, representing optimal approximations to the exact solutions. Copyright 2000 Academic Press.

Theory of Frequency-Dependent Polarization of General Planar Electrodes with Zeta Potentials of Arbitrary Magnitude in Ionic Media

The expressions obtained in the previous paper for electrode polarization are applied to a homogeneous planar electrode and a planar array of electrodes used in the generation of nonuniform fields. The effective far field experienced outside the double layer is computed for both electrodes, and sample spectra are provided. The effective far field expression contains the electrode impedance and the effects of concentration polarization due to the static double layer on the electrode generated by the zeta potential. The effective far field results are compact and contain simple integrals that can be evaluated numerically. Copyright 2000 Academic Press.

Reduction of intracranial pressure by nimodipine in experimental pneumococcal meningitis

OBJECTIVE

In this study, we investigated the effect of the calcium channel blocker nimodipine on the pathophysiologic alterations during experimental pneumococcal meningitis in rats.

DESIGN

Prospective, controlled trial.

SETTING

University center, animal laboratory.

SUBJECTS

A total of 37 adult male Wistar rats (290-360 g).

INTERVENTIONS

Meningitis was induced by the intracisternal injection of pneumococci. Anaesthetized animals were treated with nimodipine (30 microg/kg/hr iv) either 15 mins before (pretreatment) or 5 hrs after (posttreatment) pneumococcal challenge.

MEASUREMENTS AND MAIN RESULTS

Treatment with nimodipine (30 microg/kg/hr iv) significantly decreased the pneumococci-induced rise in intracranial pressure irrespective of the time of administration. Moreover, pretreament with nimodipine also significantly reduced the pneumococci-induced increase in cerebrospinal fluid white blood cell counts. To ascertain possible mechanisms of the beneficial effect, we investigated the influence of nimodipine on reactive oxygen species (ROS) and cytokine production. By using lucigenin-enhanced chemiluminescence, we found that nimodipine inhibited the pneumococci-induced production of ROS in human whole blood samples. Moreover, nimodipine significantly reduced the pneumococci-induced increase in the interleukin-6 concentrations in the cerebrospinal fluid.

CONCLUSION

Our results demonstrate that nimodipine decreases the intracranial pressure during experimental pneumococcal meningitis, possibly by mechanisms including the reduction of ROS and interleukin-6 production.

Importance of searching for associated mitochondrial DNA alterations in patients with multiple deletions

Multiple mitochondrial DNA (mtDNA) deletions have been reported in patients with autosomal dominant and recessive disorders. We studied several affected and one non-affected individuals belonging to a pedigree in which the inheritance of the pathological trait was compatible with an autosomique dominant transmission. Affected members had late-onset multisystem disorders with multiple mtDNA deletions in skeletal muscle. But this family presented a striking difference from previously described cases, because none of the patients had progressive external ophthalmoplegia (PEO). We also studied one young boy with a no contributary family history. He had a cerebellar ataxia with PEO and multiple mtDNA deletions in muscle. Molecular analysis revealed that in the first family, repeated sequences were present at the breakpoint junctions, whereas such motifs were not found in the young patient's case. In the first family, we evidenced mtDNA point mutations in clones containing breakpoint junctions and a 9-bp motif triplication in the intergenic COII/tRNA(Lys) region, whereas this sequence is repeated twice in the wild type mtDNA. Our results suggest that multiple deletions observed in the two pedigrees result from different molecular mechanisms and point out the role of repeated sequences in the first pedigree. No mtDNA repair system has been described in mammals so far, but the molecular abnormalities found in the first family suggest that a defect in an mtDNA repair system, homologous to the E. coli MutHLS pathway, could be responsible for such a phenotype.

Hypertensive disorders in twin versus singleton gestations. National Institute of Child Health and Human Development Network of Maternal-Fetal Medicine Units

OBJECTIVE

This study was undertaken to compare rates and severity of gestational hypertension and preeclampsia, as well as perinatal outcomes when these complications develop, between women with twin gestations and those with singleton gestations.

STUDY DESIGN

This was a secondary analysis of prospective data from women with twin (n = 684) and singleton (n = 2946) gestations enrolled in two separate multicenter trials of low-dose aspirin for prevention of preeclampsia. End points were rates of gestational hypertension, rates of preeclampsia, and perinatal outcomes among women with hypertensive disorders.

RESULTS

Women with twin gestations had higher rates of gestational hypertension (relative risk, 2.04; 95% confidence interval, 1.60-2.59) and preeclampsia (relative risk, 2. 62; 95% confidence interval, 2.03-3.38). In addition, women with gestational hypertension during twin gestations had higher rates of preterm delivery at both <37 weeks' gestation (51.1% vs 5.9%; P <. 0001) and <35 weeks' gestation (18.2% vs 1.6%; P <.0001) and also had higher rates of small-for-gestational-age infants (14.8% vs 7. 0%; P =.04). Moreover, when outcomes associated with preeclampsia were compared, women with twin gestations had significantly higher rates of preterm delivery at <37 weeks' gestation (66.7% vs 19.6%; P <.0001), preterm delivery at <35 weeks' gestation (34.5% vs 6.3%; P <.0001), and abruptio placentae (4.7% vs 0.7%; P =.07). In contrast, among women with twin pregnancies, those who remained normotensive had more adverse neonatal outcomes than did those in whom hypertensive complications developed.

CONCLUSIONS

Rates for both gestational hypertension and preeclampsia are significantly higher among women with twin gestations than among those with singleton gestations. Moreover, women with twin pregnancies and hypertensive complications have higher rates of adverse neonatal outcomes than do those with singleton pregnancies.

Upregulation of matrix metalloproteinase-9 in the cerebrospinal fluid of patients with acute Lyme neuroborreliosis

It was investigated (1) whether metalloproteinase-9 (MMP-9), MMP-3, and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1, the natural tissue inhibitor of MMP-9) are increased in the CSF of patients with Lyme neuroborreliosis and (2) whether macrophages can express MMP-9 when stimulated with Borrelia burgdorferi. Zymography showed MMP-9 activity in 26 of 31 (84%) CSF samples from patients with acute stage 2 Lyme neuroborreliosis, but not in 20 controls with non-inflammatory neurological disorders. Activity of MMP-2 was detected in all CSF samples in both patients with neuroborreliosis and controls, suggesting a constitutive release of MMP-2. Using enzyme linked immunosorbent assay (ELISA) MMP-3 (which can activate MMP-9) was detected in low concentrations in the CSF of 13 of 29 patients with neuroborreliosis, but not in controls. TIMP-1 was increased twofold in CSF samples from patients with neuroborreliosis in comparison with the controls. MMP-9 activity was induced in vitro in a mouse macrophage cell line (RAW 264.7) when stimulated with two different genospecies of B burgdorferi (B garinii, B afzelii ). This MMP-9 activity was reduced in a dose dependent manner when macrophages stimulated with B burgdorferi were coincubated with NF-kappaB SN50, a cell permeable peptide which inhibits the translocation of NF-kappaB into the nucleus of stimulated cells. The data show that (1) MMP-9 activity is present in the CSF of patients with neuroborreliosis, (2) macrophages stimulated with B burgdorferi are a possible source of MMP-9 increase, and (3) activation of NF-kappaB may play a part in the upregulation of MMP-9 by B burgdorferi.

Risks of preeclampsia and adverse neonatal outcomes among women with pregestational diabetes mellitus. National Institute of Child Health and Human Development Network of Maternal-Fetal Medicine Units

OBJECTIVES

This study was undertaken to determine the frequencies of preeclampsia and adverse neonatal outcomes among women with pregestational diabetes.

STUDY DESIGN

This was a prospective observation of pregnancy outcomes among 462 women with pregestational diabetes mellitus (White classes B-F) and singleton pregnancies who were enrolled in a multicenter trial to compare low-dose aspirin with placebo for preeclampsia prevention. The main outcome measures were preeclampsia and neonatal outcomes.

RESULTS

Among 462 women with pregestational diabetes, 92 (20%) had preeclampsia. Preeclampsia frequency rose significantly with increasing severity of diabetes according to White classification (class B, 11%; class C, 22%; class D, 21%; class R plus class F, 36%; P <.0001). Preeclampsia was also more common among women who had proteinuria at baseline (28% vs 18%; odds ratio, 1.75; 95% confidence interval, 1.02-3.01). Frequency of preterm delivery at <35 weeks' gestation rose greatly with increasing severity of diabetes (P =.0002). Women with proteinuria at baseline were significantly more likely to be delivered at <35 weeks' gestation (29% vs 13%; odds ratio, 2.6; 95% confidence interval, 1.5-4.6) and to have small-for-gestational-age infants (14% vs 3%; odds ratio, 5. 4; 95% confidence interval, 2.7-17.7), and they were less likely to have large-for-gestational-age infants (14% vs 40%; odds ratio, 0.2; 95% confidence interval, 0.1-0.5).

CONCLUSION

Among women with pregestational diabetes mellitus, the frequency of preeclampsia rose with increasing severity of diabetes. Proteinuria early in pregnancy was associated with marked increases in adverse neonatal outcomes independent of preeclampsia development.

Human immunodeficiency virus type-1 Nef protein induces blood-brain barrier disruption in the rat: role of matrix metalloproteinase-9

We recently showed that MMP-9 activity was detectable in the cerebrospinal fluid (CSF) of about half of neurologically symptomatic HIV-infected patients. Using an experimental animal model, we detected MMP-9 activity in CSF samples from rats that had been injected intracisternally with recombinant HIV-1 Nef protein, but not after injection of heat-treated Nef, gp120, gp160 or PBS. Nef also induced a breaching of the blood-brain barrier (BBB), which could be inhibited by pretreatment with the matrix metalloproteinase (MMP) inhibitor batimastat. In vitro Nef only slightly induced MMP-9 activity in freshly isolated human peripheral blood mononuclear cells and in the murine macrophage cell line RAW 264.7, but not in endothelial, neuronal or astroglial cell lines. Taken together, our findings indicate that HIV-1 Nef protein can induce BBB disruption in the rat - presumably via MMP induction.

Velocities, shear stresses and blood damage potential of the leakage jets of the Medtronic Parallel bileaflet valve

Even nowadays, the essential problem of mechanical heart valve prostheses is the risk of thromboembolic events mainly caused by unnatural hemodynamics, e.g. just a few years ago the Medtronic Parallel (MP) showed unsatisfactory clinical results caused by thrombi. Therefore, in vitro investigations of the whole leakage jets were performed at the MP in mitral position by means of a pulse duplicator using a two channel laser Doppler anemometer. From the measured data, mean velocity profiles and the distribution of Reynolds shear stresses, as a function of the location within the jet, were calculated. From this data the potential of blood damage is evaluated computing a Blood Damage Index (BDI) of hemolysis and platelet damage. Four regurgitant free jets right above the hinges were observed during systole at the inflow side of the MP. The peak velocities at the origin of the jets were in the order of 1.6-2.1 m/s. Two jets experienced maximum turbulent shear stresses around 100 N/m2 within this area. The BDI for platelets of the MP is around ten times higher than the BDI of the St.-Jude-Medical. The study shows that besides the flow structure within the hinges of a mechanical heart valve, the whole regurgitant jet has a large blood damage potential. This potential is measurable, respectively calculable and seems to be (on account of it's support of the clinical outcome) one piece of the puzzle that explains the negative trials of the MP.

Selective requirement for Src kinases during VEGF-induced angiogenesis and vascular permeability

Src kinase activity was found to protect endothelial cells from apoptosis during vascular endothelial growth factor (VEGF)-, but not basic fibroblast growth factor (bFGF)-, mediated angiogenesis in chick embryos and mice. In fact, retroviral targeting of kinase-deleted Src to tumor-associated blood vessels suppressed angiogenesis and the growth of a VEGF-producing tumor. Although mice lacking individual Src family kinases (SFKs) showed normal angiogenesis, mice deficient in pp60c-src or pp62c-yes showed no VEGF-induced vascular permeability (VP), yet fyn-/- mice displayed normal VP. In contrast, inflammation-mediated VP appeared normal in Src-deficient mice. Therefore, VEGF-, but not bFGF-, mediated angiogenesis requires SFK activity in general, whereas the VP activity of VEGF specifically depends on the SFKs, Src, or Yes.

Safety of labor epidural anesthesia for women with severe hypertensive disease. National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network

OBJECTIVE

The aim of this study was to determine whether epidural anesthesia during labor increased the frequencies of cesarean delivery, pulmonary edema, and renal failure among women with severe hypertensive disease.

STUDY DESIGN

We performed a secondary retrospective analysis of a subgroup population within a multicenter double-blind trial of low-dose aspirin therapy for women at high risk for development of preeclampsia. Subjects in whom severe hypertensive disease developed were selected. The primary outcomes were the overall frequencies of cesarean delivery among women with severe hypertensive disease who had labor with and without epidural anesthesia. Other maternal and neonatal outcomes were also compared between women who did and did not receive epidural anesthesia.

RESULTS

Among the women with severe hypertensive disease (n = 444) 327 had labor. Among the women with severe disease who had labor there was no difference in either the overall cesarean delivery rate (32.1% vs 28.0%; P =.44) or the rate of cesarean delivery for fetal distress or failure to progress (27.8% vs 22.0%; P =.26) between women who did and did not receive epidural analgesia. Women with chronic hypertension were more likely to have a cesarean delivery overall if they received epidural anesthesia, but there was otherwise no difference in the frequencies of cesarean delivery for these indications between women with and without epidural anesthesia within each of the high-risk groups. Pulmonary edema was rare and acute renal failure did not develop in any women.

CONCLUSION

Epidural anesthesia use did not increase the frequencies of cesarean delivery, pulmonary edema, and renal failure among women with severe hypertensive disease.

Differential expression of matrix metalloproteinases in bacterial meningitis

Matrix metalloproteinases (MMPs) are implicated in the pathogenesis of various inflammatory diseases of the central nervous system. Evidence is accumulating that gelatinase B (MMP-9) might be involved in the pathogenesis of meningitis, but the spectrum of different MMPs involved in the inflammatory reaction of this disease has not been determined. We investigated the temporal and spatial mRNA expression pattern of gelatinase B in experimental meningococcal meningitis in rats. In contrast to controls, increased mRNA levels with peak values 6 h after injection with menigococci were found in brain specimens of the animals. Elevated MMP-9 mRNA expression was accompanied by enhanced proteolytic activity, as demonstrated by gelatin zymography, and positive immunoreactivity. The mRNA expression pattern of six other MMPs was investigated. Collagenase-3 and stromelysin-1 mRNAs were also found to be upregulated. In contrast, mRNA levels for gelatinase A, matrilysin, stromelysin-2 and stromelysin-3 remained unchanged. As evidenced by significantly increased intracranial pressure and by leakage of intravenously injected Evans blue through the blood vessel walls into the brain parenchyma, the animals injected with meningococci revealed signs of blood-brain barrier disruption. Augmented proteolytic activity of MMP-9 could also be demonstrated in CSF samples obtained from patients with bacterial meningitis, underlining the clinical relevance of our experimental findings. Our data indicate that gelatinase B, collagenase-3 and stromelysin-1 are selectively upregulated in bacterial meningitis and thus may contribute to the pathogenesis of this infectious disease of the central nervous system.

Novel multidrug resistance reversal agents

A series of 59 alpha-aryl-alpha-thioether-alkyl, -alkanenitrile, and -alkanecarboxylic acid methyl ester tetrahydroisoquinoline and isoindoline derivatives (15a-48) were synthesized and evaluated as multidrug resistance (MDR) reversal agents. The compounds were tested on S1-B1-20 human colon carcinoma cells selected for resistance to bisantrene. Both the cytotoxicity of the reversal agents and their ability to resensitize the cells to bisantrene were determined. All but two of these compounds (15q, 40) were more effective MDR reversal agents in vitro than verapamil (VRP), a calcium channel antagonist which also has been shown to possess MDR modulating activity. Several showed good activity in this assay (IC50's < 0.5 microM), the most potent being isoindolines 44 (IC50 0.26 microM) and 46 (IC50 0.26 microM) and tetrahydroisoquinolines 47 (IC50 0.29 microM) and 15m (IC50 0.30 microM). A number of compounds were evaluated in vivo against vincristine (VCR)-resistant murine P388 leukemia, as well as against human epidermoid carcinoma KB/8.5 implanted sc in athymic mice. The reversal agents which consistently showed the highest activity, together with low toxicity, were alpha-aryl-alpha-thiotolylalkanenitrile tetrahydroisoquinoline derivatives with electron-rich alkoxy substituents on the aromatic rings. Of the tested compounds, the most effective reversal agents for both tumor lines were 15h (33% increased life span at 12.5 mg/kg, 0.2 mg/kg VCR versus VCR alone in the VCR-resistant P388 leukemia model and 59% relative tumor growth at 50 mg/kg, 8 mg/kg doxorubicin versus doxorubicin alone in the KB/8.5 model) and 39a (48% increased life span at 50 mg/kg, 0.2 mg/kg VCR versus VCR alone in the VCR-resistant P388 leukemia model and 46% relative tumor growth at 25 mg/kg, 8 mg/kg doxorubicin versus doxorubicin alone in the KB/8.5 model). The mechanism of action of these compounds is believed to involve blocking the drug efflux pump, P-glycoprotein.

Acute Meningitis

Recent major epidemiologic trends in bacterial meningitis include a dramatic decline in the incidence of Haemophilus influenzae meningitis since the introduction of the protein-conjugated H. influenzae vaccines, and a worldwide increase in infections with antibiotic-resistant strains of bacterial pathogens. Cases of meningitis caused by resistant strains require an alternative therapeutic strategy. Animal studies have identified inflammatory mediators, eg, chemokines, excitatory amino acids, and endothelins, which are involved in the pathophysiology of bacterial meningitis. There is increasing evidence that reactive oxygen species (ROS), reactive nitrogen species, peroxynitrite, and matrix metalloproteinases contribute to brain damage during bacterial meningitis. The cytotoxic effects of ROS and peroxynitrite include the initiation of lipid peroxidation and the induction of DNA single-strand breakage. Damaged DNA activates poly(ADP-ribose) polymerase (PARP). Recent experimental data suggest that lipid peroxidation and PARP activation play a role in the development of meningitis-associated intracranial complications and brain injury. Agents that interfere with the production of ROS and peroxynitrite, and interfere with lipid peroxidation and PARP activation, may represent novel, therapeutic strategies by which meningitis-associated brain damage can be limited, therefore improving the outcome of this serious disease.

Leakage flow at mechanical heart valve prostheses: improved washout or increased blood damage?

BACKGROUND AND AIMS OF THE STUDY

An essential problem of mechanical heart valve (MHV) prostheses is the risk of thromboembolic events and consequent need of lifetime anticoagulation due to unnatural hemodynamics that results in traumatization of red blood cells and platelets. The precise spatial and tidal localization of blood-damaging events within the flow is poorly understood. The present study addresses the question whether leakage flow at MHV, which is claimed to improve washout in the hinge areas of microthrombi and platelet-activating agents, is responsible for significant blood damage.

METHODS

This study investigated leakage flow in vitro, primarily within turbulent leakage jets of currently used mechanical valves. St. Jude Medical, Sorin Bicarbon, Duromedics-Edwards and CarboMedics valves were analyzed in the mitral position of a circulatory mock loop. Jet configuration was determined by echocardiography; velocity and shear stress distributions within jets were measured using laser-Doppler anemometry (LDA). A blood damage index (BDI) was developed in terms of lactate dehydrogenase release by platelets and hemoglobin release by red blood cells (RBC), as a function of exposure time and shear stresses within the flow field. BDIs were validated by direct measurement of hemolysis caused by leakage flow, using porcine blood.

RESULTS

All valves showed characteristic and reproducible jet patterns, mainly emerging from the hinge areas. Maximum velocities up to 1.7 m/s were measured. Maximum turbulent shear stresses > 80 Pa were found. The investigated MHV revealed significant differences in calculated BDIs. The Sorin Bicarbon had a significantly lower BDI for RBC damage, as well as for platelet damage; this was validated by direct hemolysis measurements.

CONCLUSIONS

The relevance of the leakage-induced blood damage was demonstrated from a literature investigation of hemolysis as a function of valve type and implant position.