Pharmacogenetics: role in modifying drug dosage regimens

With the advent of new molecular biology and scientific techniques, there is better understanding of genetic polymorphisms in oxidative drug metabolism systems today. These systems are important in pharmacogenetic studies which genotype polymorphic alleles encoding drug metabolising enzymes to enable the individual's drug metabolising phenotype to be found. Once found, the knowledge can be used to tailor drug dosage regimens to an individual to maximise therapeutic efficacy and minimise adverse drug reactions (ADRs). The knowledge could also be used to optimise drug development programmes so that all the subgroups within a target population are adequately represented in clinical trails.

Antioxidant lignans from Machilus thunbergii protect CCl4-injured primary cultures of rat hepatocytes

Eleven lignans (1-11) were isolated from the CH2Cl2 fraction of the bark of Machilus thunbergii Sieb. et Zucc. (Lauraceae). These were identified as (-)-acuminatin (1), (-)-isoguaiacin (2), meso-dihydroguaiaretic acid (3), (+)-galbacin (4), (-)-sesamin (5), (+)-galbelgin (6), machilin A (7), machilin G (8), licarin A (9), and nectandrin A (10) and B (11). Primary cultures of rat hepatocytes were co-incubated for 90 min with the hepatotoxin CCl4 and each of the 11 lignans (50 microM). Hepatoprotective activity was determined by measuring the level of glutamic pyruvic transaminase released into the medium from the primary cultures of rat hepatocytes. (-)-Acuminatin, (-)-isoguaiacin and meso-dihydroguaiaretic acid all significantly reduced the level of glutamic pyruvic transaminase released. Further investigation revealed that these three compounds significantly preserved the levels and the activities of glutathione, superoxide dismutase, glutathione peroxidase and catalase. (-)-Acuminatin, (-)-isoguaiacin and meso-dihydroguaiaretic acid also ameliorated lipid peroxidation as demonstrated by a reduction of malondialdehyde production. These results suggest that (-)-acuminatin, (-)-isoguaiacin and meso-dihydroguaiaretic acid exert diverse hepatoprotective activities, perhaps by serving as potent antioxidants.

Delayed treatment with nicotinamide (Vitamin B(3)) improves neurological outcome and reduces infarct volume after transient focal cerebral ischemia in Wistar rats

BACKGROUND AND PURPOSE

We have previously shown that nicotinamide (NAm) acutely reduces brain infarction induced by permanent middle cerebral artery occlusion (MCAo) in rats. In this study, we investigate whether NAm may protect against ischemia/reperfusion injury by improving sensory and motor behavior as well as brain infarction volumes in a model of transient focal cerebral ischemia.

METHODS

Forty-eight male Wistar rats were used, and transient focal cerebral ischemia was induced by MCAo for 2 hours, followed by reperfusion for either 3 or 7 days. Animals were treated with either intraperitoneal saline or NAm (500 mg/kg) 2 hours after the onset of MCAo (ie, on reperfusion). Sensory and motor behavior scores and body weight were obtained daily, and brain infarction volumes were measured on euthanasia.

RESULTS

Relative to treatment with saline, treatment with NAm (500 mg/kg IP) 2 hours after the onset of transient focal cerebral ischemia in Wistar rats significantly improved sensory (38%, P<0.005) and motor (42%, P<0.05) neurological behavior and weight gain (7%, P<0.05) up to 7 days after MCAo. The cerebral infarct volumes were also reduced 46% (P<0.05) at 3 days and 35% (P=0.09) at 7 days after MCAo.

CONCLUSIONS

NAm is a robust neuroprotective agent against ischemia/reperfusion-induced brain injury in rats, even when administered up to 2 hours after the onset of stroke. Delayed NAm treatment improved both anatomic and functional indices of brain damage. Further studies are needed to clarify whether multiple doses of NAm will improve the extent and duration of this neuroprotective effect and to determine the mechanism(s) of action underlying the neuroprotection observed. Because NAm is already used clinically in large doses and has few side effects, these results are encouraging for the further examination of the possible use of NAm as a therapeutic neuroprotective agent in the clinical treatment of acute ischemic stroke.

Involvement of brassinosteroids in the gravitropic response of primary root of maize

Exogenously applied brassinolide (BL, 10(-9)-10(-5) M) increased gravitropic curvature in maize (Zea mays) primary roots. The BL-enhanced gravitropic curvature was clearly promoted in the presence of indole-3-acetic acid (IAA, 10(-10)-10(-8) M), indicating that BL is interactive with IAA during the gravitropic response. The interactive effect between BL and IAA was completely diminished by treatment of p-chlorophenoxy isobutric acid, an auxin action antagonist. The activation of the gravitropic response by BL in the absence and in the presence of IAA was nullified by application of 2, 3,5-triiodobenzoic acid, a polar auxin transport inhibitor. The data indicate that brassinosteroids (BRs) might be involved in auxin-mediated processes for the gravitropic response. Gas chromotography-selected ion-monitoring analysis revealed that maize primary roots contained approximately 0.3 ng g(-1) fresh weight castasterone as an endogenous BR. Exogenously applied castasterone also increased the gravitropic response of maize roots in an IAA-dependent manner. This study provides the first evidence, to our knowledge, for occurrence and gravitropic activity of BRs in plant roots.

Immunomodulating activity of a polysaccharide isolated from Mori Cortex Radicis

The immunomodulating activity of a polysaccharide isolated from Morus alba (PMA) root bark was examined in murine splenic lymphocytes. PMA enhanced proliferation of splenic lymphocytes in a synergistic manner in the presence of mitogens. However, PMA suppressed primary IgM antibody production from B cells, which was activated with lipopolysaccharide, a polyclonal activator, or immunized with a T-cell dependent antigen sheep red blood cells. Our observations showed that the immunomodulating activity of PMA increased lymphocyte proliferation and that PMA decreased antibody production from B cells, which was distinct from those of other plant-originated polysaccharides.

Stereotactic injection of adenoviral vectors that target gene expression to specific pituitary cell types: implications for gene therapy

OBJECTIVE

Gene therapy is a potentially useful strategy for the treatment of pituitary adenomas or hormone deficiency disorders. We investigated the feasibility of targeting gene expression to specific pituitary cell types in vivo, using a combination of stereotactic injection and adenoviral vectors that carry pituitary-specific promoters.

METHODS

Recombinant adenoviruses containing the human growth hormone promoter (AdGHGal) or the human glycoprotein hormone alpha-subunit promoter (AdalphaGal) were used to drive expression of the beta-galactosidase gene. The expression of beta-galactosidase activity in the pituitary was analyzed after the administration of recombinant adenoviruses via the peripheral vein or the carotid artery, or by stereotactic injection into the rat pituitary. Double-label histology was used to evaluate cell-type expression in the pituitary.

RESULTS

Intravascular injection of AdGHGal or AdalphaGal failed to deliver the marker gene to the pituitary. However, direct stereotactic injection of recombinant adenoviral vectors into the pituitary achieved a high level of transgene expression. In addition, immunohistochemical staining revealed selective expression of the AdGHGal or AdalphaGal transgenes in pituitary cells that normally produce the respective hormones.

CONCLUSION

These findings indicate that adenoviral vectors carrying pituitary gland-specific promoters may be useful for targeted gene therapy of pituitary diseases. However, because of low transduction after peripheral administration, stereotactic injection or local administration of viruses at the time of pituitary surgery is probably required for efficient gene expression.

Adenosine triphosphate-induced heterologous desensitization of endothelin-1- and glutamate-evoked calcium increases in cultured rat cortical astrocytes

In rat cortical astrocytes, we investigated the occurrence of cross-talks between purinoceptor and endothelin (ET) receptor, or glutamate receptor. The treatments of adenosine triphosphate (ATP), ET-1, and glutamate induced the increase of intracellular calcium level in the astrocytes. In repetitive additions of ATP to astrocytes, the second application of ATP exhibited comparable amplitude of calcium response, but the stimulation with ATP completely blocked subsequent ET-1- or glutamate-evoked calcium responses showing complete heterologous desensitization. In contrast, ET-1 and glutamate failed to desensitize the response elicited by ATP. Preincubation with sphingosine, a protein kinase C (PKC) inhibitor, reversed the ATP-induced desensitization of ET-1- and glutamate-evoked calcium responses. Taken together, these results demonstrate the resistance of purinoceptor to homologous desensitization, and unidirectional desensitization between ATP and other receptors such as ET and glutamate receptors, suggesting a dominant role of purinoceptor in modulating calcium signal of astrocytes.

The stem of sinomenium acutum inhibits mast cell-mediated anaphylactic reactions and tumor necrosis factor-alpha production from rat peritoneal mast cells

The aqueous extract of Sinomenium acutum stem (SSAE) (0.1-1000 mg/kg) dose-dependently inhibited systemic anaphylactic reaction induced by compound 48/80 in mice. In particular, SSAE reduced compound 48/80-induced anaphylactic reaction with 50% at the dose of 1000 mg/kg. SSAE (100-1000 mg/kg) also significantly inhibited local anaphylactic reaction activated by anti-dinitrophenyl (DNP) IgE. When mice were pretreated with SSAE at a concentration ranging from 0.1 to 1000 mg/kg, the plasma histamine levels were reduced in a dose-dependent manner. SSAE (1-1000 microg/ml) dose-dependently inhibited histamine release from the rat peritoneal mast cells (RPMCs) activated by compound 48/80 or anti-DNP IgE. In addition, SSAE (0.1 microg/ml) had a significant inhibitory effect on anti-DNP IgE-induced tumor necrosis factor-alpha (TNF-alpha) production. These results indicate that SSAE inhibits mast cell-mediated anaphylactic reactions and TNF-alpha production from mast cells.

Divergent effects of putative anxiolytics on stress-induced fos expression in the mesoprefrontal system of the rat

Previously, we reported that R(+)HA-966, a weak partial agonist for the glycine/NMDA receptor, and guanfacine, a noradrenergic alpha2 agonist, have anxiolytic-like actions on the biochemical activation of the mesoprefrontal dopamine neurons and fear-induced behaviors. Here, we examined these two putative anxiolytic agents, both with primary actions independent of GABAergic systems, for their ability to alter stress-induced Fos-like immunoreactivity in the mesoprefrontal cortex and in tyrosine hydroxylase-stained, presumed dopaminergic, neurons in the ventral tegmental area. The benzodiazepine agonist, lorazepam, and partial agonist, bretazenil, were also tested in this footshock paradigm [10 x 0.5 sec, 0.8 mA paired with a 5-sec tone]. In saline-treated rats, footshock resulted in an increase in Fos-li in the prelimbic and infralimbic cortices and tyrosine hydroxylase-labeled cells in the ventral tegmental area. Treatment with lorazepam or bretazenil prevented the stress-induced activation in Fos-li nuclei in all regions of the medial prefrontal cortex and in dopaminergic neurons in the ventral tegmental area. In contrast, the actions of the novel anxiolytic-like agents on stress-induced Fos-li were different than those observed with benzodiazepine agonists. Both putative anxiolytics, R(+)HA-966 and guanfacine, did not reduce, but significantly enhanced the stress-induced Fos-li in the prelimbic region of the medial prefrontal cortex. Additionally, treatment with R(+)HA-966 completely blocked, while guanfacine attenuated, the stress-induced increase in the number of Fos-li, TH-li cells in the ventral tegmental area. These results indicate that the putative anxiolytics, R(+)HA-966 and guanfacine, have actions on the stress-sensitive mesoprefrontal system which appear distinct from those of traditional anxiolytics.

Pharmacogenetics: the molecular genetics of CYP2D6 dependent drug metabolism

INTRODUCTION

Genetic variation of drug metabolising enzymes has been recognised as one of the major causes of the inter-individual variability to drug response. The vast majority of drugs are degraded via a small number of metabolic pathways, mainly by microsomal P-450 enzymes localised in the liver and, to a minor extent, in the small intestine. Of these, CYP3A4 is the isozyme involved in the metabolism of most of the clinically useful drugs (50%). This is followed by CYP2D6 (20%), CYP2C9 and CYP2C19 (15%). In addition, minor pathways are catalysed by CYP2E1, CYP1A2, CYP2A6 and unidentified P-450s. Almost 40% of human P-450 dependent drug metabolism is carried out by genetically polymorphic enzymes. Polymorphisms generated by mutations in the genes for these enzymes cause quantitatively or qualitatively altered enzyme expression or activity through multiple molecular mechanisms. While CYP3A4 genetic polymorphisms are just beginning to be unraveled, extensive studies on the CYP2D6 gene over the last decade have identified at least 53 alleles. Of these, more than 20 of them are known to significantly alter the metabolism of CYP2D6 substrates.

METHODS

This article reviews the information derived from various studies over the past decade and explains the molecular basis of functional differences in CYP2D6 variants, especially with respect to inter-ethnic differences and their clinical implications.

RESULTS

CYP2D6 activity ranges from complete absence to ultra-rapid metabolism. Large inter-individual and inter-ethnic variability exists in the activity of the enzyme, and consequently in the disposition of drugs undergoing oxidative metabolism.

CONCLUSIONS

Pharmacokinetic differences resulting from these polymorphisms show potentially important clinical consequences.

Sauchinone, a lignan from Saururus chinensis, attenuates CCl4-induced toxicity in primary cultures of rat hepatocytes

We used primary cultures of rat hepatocytes injured by the hepatotoxin, carbon tetrachloride (CCl4), as a test system to screen for hepatoprotective compounds from natural products. Sauchinone was isolated from the aerial parts of Saururus chinensis (Saururaceae) by this method. At a concentration of 50 microM, sauchinone significantly reduced the release into the culture medium of glutamic pyruvic transaminase from CCl4-damaged cultures of rat hepatocytes. It has been determined that glutathione, superoxide dismutase and glutathione peroxidase all play important roles in the cellular defense against oxidative stress. Sauchinone appeared to protect primary cultured rat hepatocytes exposed to CCl4 from significant drops in the levels of each of these three specific markers, respectively. Sauchinone also seemed to ameliorate lipid peroxidation as demonstrated by a reduction in the production of the oxidized lipid byproduct, malondialdehyde. These results suggest that sauchinone may exert hepatoprotective activity through antioxidant activity.

Dosimetry of a W-188/Re-188 beta line source for endovascular brachytherapy

PURPOSE

The objective was to determine the dosimetry of a potential endovascular brachytherapy source consisting of a coiled tungsten wire mounted on the distal end of a drive wire and neutron-activated to contain the parent-daughter nuclides tungsten-188 (188W) and rhenium-188 (188Re).

METHODS

A coiled tungsten wire 40 mm in length was neutron-activated by double-neutron capture for 78 hours at 1.9 x 10(15) h/cm2/s to contain 925 MBq (25 mCi) of 188W/188Re in equilibrium. The dose-fall off from this source was determined using three independent methods: (a) Thermoluminescence dosimetry with small LiF-100 rods, (b) Gafchromic film dosimetry, and (c) Bang gel dosimetry. In addition, a Monte Carlo simulation was performed to compute the beta-dose.

RESULTS

Each of the three measurement methods recorded similar values for the dose fall-off within the distances useful for endovascular brachytherapy. The Monte Carlo calculations closely approximated the measured results in the treatment range between 1 and 3 mm and may thus be useful for evaluating changing geometries in the development of catheters and source setups. A 2 min restenosis treatment delivering 20 Gy at a radius of 2 mm would require a source of 1384.8 MBq/cm (37.4 mCi/cm).

CONCLUSIONS

The dose distribution from a 188W/188Re source is similar to that of a 90Y-source. An added advantage of the 188W/188Re source is that it can be used for at least two months and still provides fast treatment times because of the parent isotope's half-life of 69 days. The additional gamma emission from the source is too small to impose a serious radiological hazard. The high atomic number and density of the source material allows direct fluoroscopic imaging without additional markers.

The role of family: perceptions of children with sickle cell

The purpose of this study was to determine the perceptions of the quality of family relationships between children with sickle cell disease and their non-diseased siblings. In this study, 28 subjects were interviewed in their homes. The quality of family relations was assessed utilizing the Family Environment Scale (Moos & Moos, 1981). There was no significant difference in cohesion, expressiveness, conflict, or organization. Control was higher for boys than girls. Implications for family nursing practice are presented.

Immunohistochemical examination of the INK4 and Cip inhibitors in the rat neonatal cerebellum: cellular localization and the impact of protein calorie malnutrition

Expression of the cyclin-dependent kinase inhibitors (CKIs) has been linked to the inhibition of cellular proliferation and the induction of differentiation. Based on structure function analysis, two distinct families of CDKIs, the INK4 and the Cip/Kip family have been identified. The INK4 family member p16(Ink4), and the Cip/Kip protein p27(Kip1) have been implicated in normal development of the CNS and cerebellum. Recent studies have suggested a functional inter-dependence between the CKI and the abundance of cyclin D1 in orchestrating growth factor-induced cellular proliferation. The neonatal rat cerebellum undergoes proliferative growth and differentiation, localized to distinct topographical regions and cell types. The cell type and the temporal profile of CKI expression during postnatal cerebellar development had not been described. The current studies determined the specific cerebellar cell types in which the CKIs were expressed during post natal development by co-staining for cell-type specific markers. p16(Ink4a) and p27(Kip1) immunostaining was identified in both neurons and glial cells, increasing progressively between postnatal days 6 to 13 into adulthood. By contrast, neuronal and glial cell p21(Cip1) staining was prominent at days 6-11 and decreased thereafter. Cyclin D1 was expressed in the proliferating external granular cells, with occassional staining in the molecular, and internal granular layers. Dual immunostaining demonstrated cyclin D1 within cells expressing CKI (p16(Ink4a), p21(Cip1),p27(Kip1)). Cerebellar cellular growth arrest, induced by protein-calorie malnutrition, inhibited cyclin D1 protein levels without affecting CKI immunostaining suggesting CKI do not mediate the developmental arrest. These results demonstrate that the CKIs are induced by differentiation cues in specific cell types with distinct kinetics in the developing cerebellum in vivo.

12-O-tetradecanoyl phorbol 13-acetate, protein kinase C (PKC) activator, protects human leukemia HL-60 cells from taxol-induced apoptosis: possible role for extracellular signal-regulated kinase

The purpose of this study was to evaluate whether the mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK) signaling pathway contributes to 12-O-tertadecanoyl phorbol 13-acetate (TPA)-mediated protection from taxol-induced apoptosis of human leukemia HL-60 cells. Treatment of cells with taxol for 12 h resulted in apoptosis of HL-60 cells. TPA was protective against taxol-induced apoptosis and this anti-apoptotic effect was reversible when TPA was used in conjunction with staurosporine and H-7, PKC inhibitors, suggesting that TPA may protect HL-60 cells against taxol-induced apoptosis via the PKC-dependent pathway. Since TPA stimulates MEK signal transduction pathway in HL-60 cells, we postulated that MEK pathway may be playing a role in the ability of TPA to inhibit taxol-induced apoptosis. PD098059, a specific MEK kinase inhibitor, abolished the ability of TPA to inhibit taxol-induced apoptosis. These results suggest that activation of PKC in HL-60 cells confers protection against taxol-induced apoptosis and that MEK mediates anti-apoptotic signaling of PKC.

Functional MR imaging of working memory in the human brain

OBJECTIVE

In order to investigate the functional brain anatomy associated with verbal and visual working memory, functional magnetic resonance imaging was performed.

MATERIALS AND METHODS

In ten normal right handed subjects, functional MR images were obtained using a 1.5-T MR scanner and the EPI BOLD technique. An item recognition task was used for stimulation, and during the activation period of the verbal working memory task, consonant letters were used. During the activation period of the visual working memory task, symbols or diagrams were employed instead of letters. For the post-processing of images, the SPM program was used, with the threshold of significance set at p <.001. We assessed activated brain areas during the two stimulation tasks and compared the activated regions between the two tasks.

RESULTS

The prefrontal cortex and secondary visual cortex were activated bilaterally by both verbal and visual working memory tasks, and the patterns of activated signals were similar in both tasks. The superior parietal cortex was also activated by both tasks, with lateralization to the left in the verbal task, and bilaterally without lateralization in the visual task. The inferior frontal cortex, inferior parietal cortex and temporal gyrus were activated exclusively by the verbal working memory task, predominantly in the left hemisphere.

CONCLUSION

The prefrontal cortex is activated by two stimulation tasks, and this is related to the function of the central executive. The language areas activated by the verbal working memory task may be a function of the phonological loop. Bilateral prefrontal and superior parietal cortices activated by the visual working memory task may be related to the visual maintenance of objects, representing visual working memory.

A developmentally regulated catalase required for proper differentiation and osmoprotection of Streptomyces coelicolor

Streptomyces coelicolor produces at least three catalases, the expression of which varies under different conditions. We characterized a gene (catB) for developmentally controlled catalase of 779 amino acids (83408 Da), homologous to KatE of Escherichia coli and Bacillus subtilis. Expression of the catB gene increased at the stationary phase in liquid culture and after the onset of differentiation on solid culture. It was also increased by osmotic treatments. Transcription was initiated from a promoter (catBp), whose sequence (ATGCCTCG-N13-GGGTAC) resembled promoters recognized by sigmaB of B. subtilis. CatB protein underwent proteolytic cleavage of its N-terminal 95 amino acids and was secreted to the medium when cells sporulated. Disruption of the catB gene caused impairment in the formation of aerial mycelium and reduction in the synthesis of undecylprodigiosin. On the contrary, hyperproduction of actinorhodin was observed in accordance with the increase in actII-ORF4 transcription. In addition, catB mutant became hypersensitive to osmotic stresses. These results suggest that regulated synthesis of CatB protein is necessary to ensure proper differentiation as well as to protect S. coelicolor cells against osmotic stresses.

Use of the Cre/lox recombination system to develop a non-lethal knock-in murine model for osteogenesis imperfecta with an alpha1(I) G349C substitution. Variability in phenotype in BrtlIV mice

We utilized the Cre/lox recombination system to develop the first knock-in murine model for osteogenesis imperfecta (OI). The moderately severe OI phenotype was obtained from an alpha1(I) Gly(349) --> Cys substitution in type I collagen, reproducing the mutation in a type IV OI child. We introduced four single nucleotide (nt) changes into murine col1a1 exon 23: the disease causing G-->T transversion (nt 1546), an adjacent G-->T change (nt 1551) to generate a GUC ribozyme cleavage site, and two transversions (nt 1567 C-->A and nt 1569 C-->G) to cause a Leu --> Met substitution. We also introduced a 3.2-kilobase pair transcription/translation stop cassette in intron 22, flanked by directly repeating lox recombination sites. After homologous recombination in ES cells, two male chimeras were obtained. Chimeras were mated with transgenic females expressing Cre recombinase to remove the stop cassette from a portion of the progeny's cells. To generate mice with full expression of the Gly(349) --> Cys mutation, these offspring were then mated with wild-type females. Skeletal staining and bone histology of the F2 revealed a classical OI phenotype with deformity, fragility, osteoporosis and disorganized trabecular structure. We designate these mice BrtlIV (Brittle IV). BrtlIV mice have phenotypic variability ranging from perinatal lethality to long term survival with reproductive success. The phenotypic variability is not associated with differences in expression levels of the mutant allele in total RNA derived from tissue extracts. Expression of the mutant protein is also equivalent in different phenotypes. Thus, these mice are an excellent model for delineation of the modifying factors postulated to affect human OI phenotypes. In addition, we generated knock-in mice carrying an "intronic" inclusion by mating chimeras with wild-type females. Alternative splicing involving the stop cassette results in retention of non-collagenous sequences. These mice reproduce the lethal phenotype of similar human mutations and are designated BrtlII.

Isolated cleft palate in mice with a targeted mutation of the LIM homeobox gene lhx8

Formation of the mammalian secondary palate is a highly regulated and complex process whose impairment often results in cleft palate, a common birth defect in both humans and animals. Loss-of-function analysis has linked a growing number of genes to this process. Here we report that Lhx8, a recently identified LIM homeobox gene, is expressed in the mesenchyme of the mouse palatal structures throughout their development. To test the function of Lhx8 in vivo, we generated a mutant mouse with a targeted deletion of the Lhx8 gene. Our analysis of the mutant animals revealed a crucial role for Lhx8 in palatogenesis. In Lhx8 homozygous mutant embryos, the bilateral primordial palatal shelves formed and elevated normally, but they often failed to make contact and to fuse properly, resulting in a cleft secondary palate. Because development of other craniofacial structures appeared normal, the impaired palatal formation in Lhx8-mutant mice was most likely caused by an intrinsic primary defect in the mesenchyme of the palatal shelves. The cleft palate phenotype observed in Lhx8-mutant mice suggests that Lhx8 is a candidate gene for the isolated nonsyndromic form of cleft palate in humans.

Mechanism of silica- and titanium dioxide-induced cytotoxicity in alveolar macrophages

Particles can cause cytotoxicity in pulmonary alveolar macrophages (AM). Several mechanisms to explain this cytotoxicity have been suggested. However, the exact mechanism of particle-induced cytotoxicity in AM remains to be established. Silica and TiO2 produced a concentration-dependent cytotoxicity as evidenced by loss of cell viability and fall in ATP levels. While silica induced a greater cytotoxicity, TiO2 produced a higher reduction in ATP levels. Silica increased the release of LDH, but TiO2 did not affect enzymatic release. TiO2 suppressed succinate-triggered oxygen consumption, whereas silica did not markedly change the effect of succinate on oxygen consumption. Polyinosinic acid (PI), a ligand of the scavenger receptor, inhibited the TiO2-induced fall in ATP content, but could not prevent the effect of silica on cellular ATP content. Data suggest that silica and TiO2 can induce cytotoxicity in AM, probably through different mechanisms.

Early alterations in cerebral hemodynamics, brain metabolism, and blood-brain barrier permeability in experimental intracerebral hemorrhage

OBJECT

The authors sought to ascertain the nature of the hemodynamic and metabolic derangement underlying acute pathophysiological events that occur after intracerebral hemorrhage (ICH).

METHODS

Cerebral perfusion pressure (CPP), flow velocity (FV) of the middle cerebral artery, and the arteriovenous contents of oxygen and lactate were investigated in 24 dogs subjected to sham operations (Group A, four animals) or intracerebral injections of 3 ml (Group B, 11 animals) or 5 ml (Group C, nine animals) autologous arterial blood. Twelve additional dogs received intravenous injections of 2% Evans blue or trypan blue dye to evaluate blood-brain barrier (BBB) changes. Within 1 hour, animals with ICH exhibited a rise in FV associated with significant reductions (p<0.05) in CPP and the arteriovenous content difference (AVDO2). In Group C animals significant increases in lactate concentration were found in arterial and superior sagittal sinus (SSS) samples compared with those in the other two groups (p<0.05). Additionally, perihematomal dye extravasation was observed in animals subjected to ICH and trypan blue dye injections, with profound and mild leakages in Group C and Group B animals, respectively, but not in Group A and Evans blue dye-injected animals. During the subsequent 4 hours, the FV and AVDO2 returned to normal in Group B animals, indicating a balanced cerebral metabolic rate for oxygen (CMRO2) compared with a deranged CMRO2 in Group C animals due to their lowered FV and AVDO2. However, no coupling increase in brain lactate clearance in Group C animals accounted for either the early lactate elevation in SSS or the decrease in CMRO2.

CONCLUSIONS

Profound reductions in CPP and brain oxygenation after ICH may rapidly exhaust hemodynamic compensation and, thus, impede cerebral homeostasis; however, these reductions only modestly enhance anaerobic glycolysis. Furthermore, the data suggest that a selective increase in permeability, rather than anatomical disruption, of the BBB is involved in the acute pathophysiological events that occur after ICH, which may provide a possible gateway for systemic arterial lactate entering the SSS.

Immunocytological localization of dopamine in the guinea pig retina

We examined dopaminergic neurons in the guinea pig retina; antisera against tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DBH), phenylethanolamine N-methyltransferase (PNMT) and an antiserum against gamma-aminobutyric acid (GABA) were used. In the present study, two types of amacrine cells were labeled with an anti-TH antiserum. However, no DBH and PNMT immunoreactivities were seen. The type 1 cell had a larger-sized soma located in the inner nuclear layer with processes ramifying mainly in stratum 1 of the inner plexiform layer (IPL). The type 2 cell had a smaller-sized soma and processes branching in stratum 3 of the IPL. The mean densities were 56.4 +/- 11.5/mm2 for the type 1 cell and 166.6 +/- 30.3/mm2 for the type 2 cell. Double immunocytochemistry using an antiserum against GABA revealed that while none of the type 1 cells showed GABA immunoreactivity, all of the type 2 cells displayed GABA immunoreactivity. Our results suggest that, in the guinea pig retina, the type 1 amacrine cells are pure dopaminergic and the type 2 cells are dopaminergic elements that use GABA as their second transmitter.

Ileo-rectal fistula complicating advanced ovarian carcinoma

Fistula between the bowels and an ovarian carcinoma is recognized but rare complication. Internal malignant fistula of the gastrointestinal tract involving two or more loops of different segments of the bowel and genitourinary structure are rare. The colon is frequently one of the participating loops. In reviewing the literature, however, we were unable to find a previous report of ileo-rectal fistula as a complication of an ovarian carcinoma. A case report and review of the English medical literature are presented with emphasis on the cause, clinical presentation, and management of advanced ovarian cancer with ileo-rectal involvement.

Mexiletine and magnesium independently, but not combined, protect against permanent focal cerebral ischemia in Wistar rats

The neuroprotective effect of mexiletine (Mex), a potent Na(+) channel blocker which decreases neuronal energy demands and prevents energy depletion during ischemia, was evaluated in Wistar rats subjected to permanent middle cerebral artery (MCA) occlusion. Postmortem infarct volumes were determined by quantitative image analysis of triphenyltetrazolium (TTC)-stained brain sections. Pretreatment with Mex resulted in a significant infarct volume reduction when administered intraperitoneally, either at the dosage of 50 or 60 mg/kg, 1 hr before MCA occlusion (P < 0.05). Delayed treatment with Mex (50 mg/kg) also had neuroprotective effects when given at 0.5 hr (< 0.05), but not 2-4 hr, after MCA occlusion. Intraarterial administration of MgSO(4) (90 mg/kg), in combination with Mex at 60 mg/kg, showed no additive neuroprotective effect, although each agent independently reduced the MCA occlusion-induced infarction volume (P < 0.05). Our results indicate that a single, acute administration of Mex is neuroprotective against permanent focal cerebral ischemia, but perhaps chronic administration is needed to establish a more effective therapeutic window beyond 0.5 hr. Moreover, the present in vivo data do not favor a combined use of Mg(2+) with Mex for limiting ischemic injury in the brain, since these agents caused cardiopulmonary suppression, which may have led to the loss of the neuroprotective effect of each agent independently.

The application of transcranial Doppler sonography in patients with chronic subdural haematoma

The aim of this study was to evaluate the haemodynamic changes of the middle cerebral artery (MCA) and their clinical significance before and after surgical aspiration in patients with chronic subdural haematoma (CSDH). Nineteen patients with CSDH (17 unilateral and 2 bilateral) received transcranial Doppler sonography (TCD) examinations for cerebral blood flow velocity (CBFv) of the MCA prior to and 5 days after neurosurgical treatment. A total of 21 lesion and 10 non-lesion hemispheres were included. Cranial computerized tomography (CT) and clinical assessments were performed before and 3 months following surgery. The preoperative TCD study revealed that the lesion hemisphere had a modest decrease in CBFv in the MCA as compared to the non-lesion hemisphere. Postoperatively, the CBFv significantly improved in the lesion hemisphere, but not in the non-lesion hemisphere, compared to the preoperative data (P < 0.005). The improvement in CBFv showed no significant correlation with brain shift and haematoma volume of the initial cranial CT. Additionally, two patients, who were proved to have a postoperative complication of subdural pneumocephalus, failed to attend follow-up examinations of TCD. Our results support TCD as an alternative follow-up examination for patients with CSDH, although it may not be sensitive enough as a preoperative screening tool. Postoperatively, improvements in the CBFv of the lesion hemisphere are characteristic. An unexplained difficulty of accessing cerebral basal arteries in follow-up TCD examinations should suggest pneumocephalus in the primary differential diagnosis.