The genome of black cottonwood, Populus trichocarpa (Torr. & Gray)

We report the draft genome of the black cottonwood tree, Populus trichocarpa. Integration of shotgun sequence assembly with genetic mapping enabled chromosome-scale reconstruction of the genome. More than 45,000 putative protein-coding genes were identified. Analysis of the assembled genome revealed a whole-genome duplication event; about 8000 pairs of duplicated genes from that event survived in the Populus genome. A second, older duplication event is indistinguishably coincident with the divergence of the Populus and Arabidopsis lineages. Nucleotide substitution, tandem gene duplication, and gross chromosomal rearrangement appear to proceed substantially more slowly in Populus than in Arabidopsis. Populus has more protein-coding genes than Arabidopsis, ranging on average from 1.4 to 1.6 putative Populus homologs for each Arabidopsis gene. However, the relative frequency of protein domains in the two genomes is similar. Overrepresented exceptions in Populus include genes associated with lignocellulosic wall biosynthesis, meristem development, disease resistance, and metabolite transport.

Smoking in China: findings of the 1996 National Prevalence Survey

CONTEXT

As the world's largest producer and consumer of tobacco products, China bears a large proportion of the global burden of smoking-related disease and may be experiencing a tobacco epidemic.

OBJECTIVE

To develop an evidence-based approach supporting tobacco control initiatives in China.

DESIGN AND SETTING

A population-based survey consisting of a 52-item questionnaire that included information on demographics, smoking history, smoking-related knowledge and attitudes, cessation, passive smoke exposure, and health status was administered in 145 disease surveillance points in the 30 provinces of China from March through July 1996.

PARTICIPANTS

A nationally representative random sample of 128766 persons aged 15 to 69 years were asked to participate; 120298 (93.8%) provided data and were included in the final analysis. About two thirds of those sampled were from rural areas and one third were from urban areas.

MAIN OUTCOME MEASURES

Current smoking patterns and attitudes; changes in smoking patterns and attitudes compared with results of a previous national survey conducted in 1984.

RESULTS

A total of 41187 respondents smoked at least 1 cigarette per day, accounting for 34.1% of the total number of respondents, an increase of 3.4 percentage points since 1984. Current smoking continues to be prevalent among more men (63%) than women (3.8%). Age at smoking initiation declined by about 3 years for both men and women (from 28 to 25 years). Only a minority of smokers recognized that lung cancer (36%) and heart disease (4%) can be caused by smoking. Of the nonsmokers, 53.5% were exposed to environmental tobacco smoke at least 15 minutes per day on more than 1 day per week. Respondents were generally supportive of tobacco control measures.

CONCLUSION

The high rates of smoking in men found in this study signal an urgent need for smoking prevention and cessation efforts; tobacco control initiatives are needed to maintain or decrease the currently low smoking prevalence in women.

Human copper-zinc superoxide dismutase transgenic mice are highly resistant to reperfusion injury after focal cerebral ischemia

BACKGROUND AND PURPOSE

We have demonstrated in a previous study that superoxide radicals play a role in the pathogenesis of cerebral infarction, using a transgenic mouse model of distal middle cerebral artery occlusion, permanent ipsilateral cerebral carotid artery occlusion, and 1-hour contralateral cerebral carotid artery occlusion that produced infarction only in the cortex. However, the role of superoxide radicals in reperfusion injury in transgenic mice overexpressing superoxide dismutase (SOD) is unknown. Using a mouse model of intraluminal blockade of middle cerebral artery that produced both cortical and striatal infarction, we now further examined the role of superoxide radicals in ischemic cerebral infarction after reperfusion in transgenic mice overexpressing human CuZn-SOD activity.

METHODS

Transgenic mice of strain Tg HS/SF-218, carrying human SOD-1 genes, and nontransgenic littermates were anesthetized with chloral hydrate (350 mg/kg IP) and xylazine (4 mg/kg IP). Physiological parameters were maintained at a normal range using a 30% O2/70% N2O gas mixture inserted via an inhalation mask. Body temperature was maintained at 37 +/- 0.5 degrees C by using a heating pad throughout the studies. The middle cerebral artery occlusion was achieved with a 5-0 rounded nylon suture placed within the internal cerebral artery for 3 hours followed by the removal of the suture to allow reperfusion for another 3 hours. Cerebral infarct size in brain slices and infarct volume, neurological deficit, cortical blood flow, and glutathione levels were measured in both transgenic and nontransgenic mice.

RESULTS

Compared with the nontransgenic mice, the infarcted areas were significantly decreased in coronal slices from transgenic mice. The infarct volume (in cubic millimeters) was reduced by 26% in transgenic mice after ischemia and reperfusion. This decrease in the infarct volume in transgenic mice closely paralleled the reduced neurological deficits. Introduction of the suture to block blood supply to the middle cerebral artery territory produced a rapid decrease in the relative surface blood flow in the ipsilateral core and the peri-ischemic (penumbra) areas. There were no significant differences in the local cerebral blood flow in the ischemic core or the penumbra areas between the transgenic and nontransgenic groups. However, the level of reduced glutathione in the penumbra area was significantly higher in transgenic mice than in nontransgenic mice, whereas there was no difference in the reduced glutathione levels in the ischemic core between these two groups.

CONCLUSIONS

Our study demonstrated that superoxide radicals play a major role in the pathogenesis of cerebral infarction in reperfusion injury after a focal stroke. The reduction in infarct volume and neurological deficits is not dependent on the changes in cerebral blood flow but rather correlate with reduced oxidative stress in the ischemic brain tissue, which was indicated by the relatively high levels of endogenous reduced glutathione in transgenic mice.

Validity and reproducibility of the food frequency questionnaire used in the Shanghai Women's Health Study

To evaluate the validity and reliability of the food frequency questionnaire (FFQ) used in the Shanghai Women's Health Study (SWHS), 200 SWHS participants were recruited for a dietary calibration study. Study participants completed an FFQ at baseline and 24-h dietary recalls (24-HDR) twice per month consecutively for 12 months. At the end of the study, a second FFQ was administered. Of the 200 study participants, 196 completed 24 or more days of 24-h dietary recalls, 191 completed two FFQs from whom the results of this report were based. The FFQ included the foods that accounted for 86% of the foods recorded in the 24-HDR surveys. Validity of the FFQ was evaluated by comparing intake levels of major nutrients and foods obtained from the second FFQ with those derived from the multiple 24-HDR. The median intake for major nutrients, rice, poultry and meat derived from the second FFQ and the 24-HDR was similar, with the differences ranging from 1.3 to 12.1%. The FFQ tended to overestimate the intake level of total vegetables and total fruits, and the differences were explained mainly by over-reporting seasonal vegetables and fruits consumption in the FFQ. Nutrient and food intake assessed by the FFQ and the multiple 24-HDR correlated very well, with the correlation coefficients being 0.59-0.66 for macronutrients, 0.41-0.59 for micronutrients, and 0.41-0.66 for major food groups. The reliability of the FFQ was assessed by comparing the correlation and median intake of nutrients and food groups obtained from the two FFQs that were administered approximately 2 y apart. The median intake levels for selected nutrients and food groups derived from the two FFQs were similar with differences below 10%. At the individual level, the intake levels of these dietary variables obtained from two FFQs also correlated well. When nutrient and food group intakes were categorized into quartiles, FFQ and 24-HDR produced exact agreement rates between 33 and 50%. Misclassification to adjacent quartile was common, ranging from 34-48%, while misclassification to an extreme quartile was rare (1-6%). These data indicate that the SWHS FFQ can reliably and accurately measure usual intake of major nutrients and food groups among women in Shanghai.

Studies on the relations of selenium and Keshan disease

Keshan disease is an endemic cardiomyopathy of unknown cause in The People's Republic of China that occurs most frequently in children under 15 years of age and women of child-bearing age. Studies of children 1-9 years old in Mianing County of Sichuan Province have indicated that Keshan disease is a selenium responsive condition. Incidence rates of 9.5-13.5/1000 in 1974-1975 were reduced to 1-2/1000 in children treated with a tablet weekly of 0.5-1 mg sodium selenite. During 1974-1977, only 21 cases of the disease occurred in 36,603 treated children, compared with 106 cases in 9430 untreated children, of whom 53 died and 5 still have insufficient heart function. Occurrence of the disease was invariably associated with a lower selenium content of cereals, and of hair (less than 0.12 ppm Se) in residents from affected, compared with non-affected, areas. The dose relationship between selenium and regional characteristics of Keshan disease suggests that it is probably a biogeochemical disease; other etiological factors have also been considered.

Tea and tea polyphenols in cancer prevention

The inhibitory action of tea (Camellia sinensis) and tea components against cancer formation has been demonstrated in different animal models involving different organ sites in many laboratories. The possible preventive activity of tea against cancer in humans, however, is not clear. A critical question is whether the information obtained from animal studies is applicable to humans because of possible species differences or the difference in the quantity of tea used in animal studies and that consumed by humans. This article will discuss the results from animal studies and possible cancer inhibitory mechanisms that might be applicable to human cancer prevention. To provide a basis for more quantitative analyses of the effect of tea on carcinogenesis, the levels of tea polyphenols in blood, urine and tissue samples have been analyzed, and the pharmacokinetic properties of tea polyphenols studied. Studies with cell lines have demonstrated that tea polyphenols affect signal transduction pathways, inhibit cell proliferation and induce apoptosis, but the effective concentrations are usually much higher than those observed in blood and tissues. More mechanistic studies in these areas will help us to understand the inhibitory action of tea against carcinogenesis and provide background for evaluating the effects of tea consumption on human carcinogenesis.

Development of an antioxidant system after early weaning in piglets

The objective of this experiment was to investigate oxidative injury and the development of an antioxidant system after early weaning in piglets. A total of 40 piglets (Landrace× Large White, weaned at 14 d after birth) were randomly slaughtered 0 (w0d), 1 (w1d), 3 (w3d), 5 (w5d), or 7 d (w7d; n = 8) after weaning. Concentrations of malondialdehyde (MDA), 8-hydroxydeoxyguanosine (8-OHdG), and protein carbonyl and the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase were measured in plasma. Gene expressions of antioxidant enzymes were determined by quantitative reverse transcription PCR analysis. The mediation of transcription factor 65 (p65) and the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathways by oxidative stress was determined by Western blot analysis. Results showed that the plasma MDA level was significantly higher at 3 d (P < 0.05) and that the protein carbonyl level increased at 1, 3, and 5 d (P < 0.05) compared with w0d. In addition, early weaning suppressed the plasma activity of SOD at 1 d (P < 0.05) and reduced the GSH-Px activity at 3 d (P < 0.05). The expression results in the jejunum indicate that the genes related to antioxidant enzymes were downregulated (P < 0.05) at 3 and 5 d after weaning. Uncoupling protein 2 (Ucp2), which is considered to be a feedback regulation on reactive oxygen species generation, tended to decrease in the ileum (P < 0.05) after weaning. Tumor protein 53 (p53), which regulates reactive oxygen species generation, was enhanced (P < 0.05) in the jejunum after weaning. Meanwhile, early weaning suppressed p65 (at 3, 5, and 7 d; P < 0.05) and Nrf2 (at 5 and 7 d; P < 0.05) signals in the jejunum, which might feedback-regulate antioxidant gene expression and promote the development of the antioxidant system. Therefore, we speculate that weaning disrupted oxidative balance and caused oxidative injury in piglets, and this imbalance can recover with the development of an antioxidant system via feedback regulation.

Cerebral ischemia after bilateral carotid artery occlusion and intraluminal suture occlusion in mice: evaluation of the patency of the posterior communicating artery

Cerebral ischemia models using mice have drawn increasing attention, particularly because of the availability of transgenic animals. However, the variability of intracranial vasculature at the circle of Willis in mice can influence the degree of ischemia in both the bilateral common carotid artery (CCA) occlusion and intraluminal suture occlusion models. We have developed a method to predict the extent of the anastomosis between carotid and vertebrobasilar circulation in three mouse strains (C57BL/6, CBA, and DBA/2) by measuring cortical microperfusion with laser Doppler flowmetry during a 1-minute occlusion of both CCA. When animals showed residual cortical microperfusion of less than 12% during bilateral CCA occlusion, the mice showed absence of functional anastomosis, developed ATP depletion in the frontal cortex during occlusion, and had ischemic neuronal death in the hippocampus and caudoputamen after occlusion for 15 minutes and recirculation for 7 days. Furthermore, those mice exhibited decreased local cerebral blood flow and associated ischemic neuronal death in the hippocampus, within the territory supplied by the posterior cerebral artery, with the intraluminal suture occlusion model. The current study demonstrates the need for assessment of intracranial vasculature in each animal by measuring cortical microperfusion during temporary occlusion of both CCA, no matter whether cerebral ischemia is produced by bilateral CCA occlusion or intraluminal suture occlusion in transgenic mice.

Simultaneous blood oxygenation level-dependent and cerebral blood flow functional magnetic resonance imaging during forepaw stimulation in the rat

The blood oxygenation level-dependent (BOLD) contrast mechanism can be modeled as a complex interplay between CBF, cerebral blood volume (CBV), and CMRO2. Positive BOLD signal changes are presumably caused by CBF changes in excess of increases in CMRO2. Because this uncoupling between CBF and CMRO2 may not always be present, the magnitude of BOLD changes may not be a good index of CBF changes. In this study, the relation between BOLD and CBF was investigated further. Continuous arterial spin labeling was combined with a single-shot, multislice echo-planar imaging to enable simultaneous measurements of BOLD and CBF changes in a well-established model of functional brain activation, the electrical forepaw stimulation of alpha-chloralose-anesthetized rats. The paradigm consisted of two 18- to 30-second stimulation periods separated by a 1-minute resting interval. Stimulation parameters were optimized by laser Doppler flowmetry. For the same cross-correlation threshold, the BOLD and CBF active maps were centered within the size of one pixel (470 microm). However, the BOLD map was significantly larger than the CBF map. Measurements taken from 15 rats at 9.4 T using a 10-millisecond echo-time showed 3.7 +/- 1.7% BOLD and 125.67 +/- 81.7% CBF increases in the contralateral somatosensory cortex during the first stimulation, and 2.6 +/- 1.2% BOLD and 79.3 +/- 43.6% CBF increases during the second stimulation. The correlation coefficient between BOLD and CBF changes was 0.89. The overall temporal correlation coefficient between BOLD and CBF time-courses was 0.97. These results show that under the experimental conditions of the current study, the BOLD signal changes follow the changes in CBF.

Relative changes of cerebral arterial and venous blood volumes during increased cerebral blood flow: implications for BOLD fMRI

Measurement of cerebral arterial and venous blood volumes during increased cerebral blood flow can provide important information regarding hemodynamic regulation under normal, pathological, and neuronally active conditions. In particular, the change in venous blood volume induced by neural activity is one critical component of the blood oxygenation level-dependent (BOLD) signal because BOLD contrast is dependent only on venous blood, not arterial blood. Thus, relative venous and arterial blood volume (rCBV) and cerebral blood flow (rCBF) in alpha-chlorolase-anesthetized rats under hypercapnia were measured by novel diffusion-weighted (19)F NMR following an i.v. administration of intravascular tracer, perfluorocarbons, and continuous arterial spin labeling methods, respectively. The relationship between rCBF and total rCBV during hypercapnia was rCBV(total) = rCBF(0.40), which is consistent with previous PET measurement in monkeys. This relationship can be linearized in a CBF range of 50-130 ml/100 g/min as DeltarCBV(total)/ DeltarCBF = 0.31 where DeltarCBV and DeltarCBF represent rCBV and rCBF changes. The average arterial volume fraction was 0.25 at a basal condition with CBF of approximately 60 ml/100 g/min and increased up to 0.4 during hypercapnia. The change in venous rCBV was 2-fold smaller than that of total rCBV (DeltarCBV(vein)/DeltarCBF = 0.15), while the arterial rCBV change was 2.5 times larger than that of total rCBV (DeltarCBV(artery)/DeltarCBF = 0.79). These NMR results were confirmed by vessel diameter measurements with in vivo videomicroscopy. The absolute venous blood volume change contributes up to 36% of the total blood volume change during hypercapnia. Our findings provide a quantitative physiological model of BOLD contrast.

C57BL/6 strain is most susceptible to cerebral ischemia following bilateral common carotid occlusion among seven mouse strains: selective neuronal death in the murine transient forebrain ischemia

Rats and gerbils have been used widely to investigate the molecular mechanism of selective neuronal death following transient global ischemia. Recently, the availability of transgenic mice has enabled us to examine the involvement of specific gene products in various pathophysiological conditions. However, there has been only limited information about the experimental model of cerebral ischemia in mice, particularly in regard to selective neuronal death. We examined whether bilateral carotid occlusion produced global forebrain ischemia in seven common mouse strains including C57BL/6, ICR, BALB/c, C3H, CBA, ddY and DBA/2, based on neurological signs, histological findings and cortical microcirculatory as well as India ink perfusion patterns. The C57BL/6 strain was found to be the most susceptible among seven strains. All C57BL/6 mice died within 6 h after permanent bilateral carotid occlusion. After transient bilateral carotid occlusion for 20 min, more than 90% of C57BL/6 mice showed typical neurological signs such as torsion of the neck and rolling fits, and developed selective neuronal death in the hippocampus and caudoputamen. Hypothermia prevented the neuronal death. Visualization of brain vasculature by India ink perfusion indicated that the susceptibility of the mice after bilateral carotid occlusion depended mainly on the degree of anastomosis between carotid and basilar arteries. Our results showed the feasibility of investigating selective neuronal death in transgenic mice with simple temporary occlusion of both common carotid arteries, when those from the C57BL/6 strain or inbred transgenic mice from other strains with the C57BL/6 strain in a back-cross manner are used.

Interaction of myeloperoxidase with peroxynitrite. A comparison with lactoperoxidase, horseradish peroxidase and catalase

Polymorphonuclear neutrophils generate both nitric oxide and superoxide and these molecules can combine to form peroxynitrite. Neutrophils also contain myeloperoxidase which reacts with peroxynitrous acid (HOONO). On mixing myeloperoxidase with HOONO compound II was formed. Compound I could not be detected as an intermediate. The apparent second-order rate constant of formation of compound II was strongly pH-dependent (2.5 x 10(5) M-1 x s-1 at pH 8.9 and 6.2 x 10(6) M-1 x s-1 at pH 7.2). The pKa of this effect is 6.9 and it was concluded that the enzyme reacts with the protonated form of the peroxide, that is peroxynitrous acid, with a pH-independent second-order rate constant of 2.0 x 10(7) M-1 x s-1 at 12 degrees C. The interaction of HOONO with lactoperoxidase was studied for comparison. As was observed for myeloperoxidase, compound I could not be detected as an intermediate. The apparent second-order rate constant of compound II formation is pH-dependent and is 3.3 x 10(5) M-1 x s-1 at pH 7.4 and 8.4 x 10(4) M-1 x s-1 at pH 9.0. In contrast, horseradish peroxidase reacts with HOONO to form compound I, which is subsequently followed by the formation of compound II. The second-order rate constant for the formation of compound I is 3.2 x 10(6) M-1 x s-1 and is pH-dependent, the pKa for this effect is 6.8. Catalase (up to 3 microM) does not affect the rate of decomposition of peroxynitrite and no compound I formation is observed. Since nitrite may be present in the peroxynitrite preparation and to discriminate between the reaction of the enzyme with nitrite or peroxynitrite, the effect of nitrite on myeloperoxidase was studied. The dissociation constant for the myeloperoxidase-nitrite complex is pH-dependent and has values of 580 microM at pH 6.0 and 55 mM at pH 8.5.

Three-dimensional structure of extended chromatin fibers as revealed by tapping-mode scanning force microscopy

Unfixed chicken erythrocyte chromatin fibers in very low salt have been imaged with a scanning force microscope operating in the tapping mode in air at ambient humidity. These images reveal a three-dimensional organization of the fibers. The planar "zig-zag" conformation is rare, and extended "beads-on-a-string" fibers are seen only in chromatin depleted of histones H1 and H5. Glutaraldehyde fixation reveals very similar structures. Fibers fixed in 10 mM salt appear somewhat more compacted. These results, when compared with modeling studies, suggest that chromatin fibers may exist as irregular three-dimensional arrays of nucleosomes even at low ionic strength.

Local and propagated vascular responses evoked by focal synaptic activity in cerebellar cortex

We investigated the local and remote vascular changes evoked by activation of the cerebellar parallel fibers (PFs). The PFs were stimulated (25-150 microA, 30 Hz) in halothane-anesthetized rats equipped with a cranial window. The changes in arteriolar and venular diameter produced by PF stimulation were measured with the use of a videomicroscopy system. Cerebellar blood flow (BFcrb) was monitored by laser Doppler flowmetry and the field potentials evoked by PF stimulation were recorded with the use of microelectrodes. PF stimulation increased the diameter of local arterioles (+26 +/- 1%, mean +/- SE) in the activated folium (n = 10, P < 0.05). The vasodilation was greatest in smaller arterioles (16.5 +/- 0.8 microm), was graded with the intensity of stimulation, and was less marked than the vasodilation produced by hypercapnia in comparably sized vessels (+58 +/- 5%, CO2 pressure = 50-60 mmHg, n = 8). In addition, the vasodilation was greatest along the horizontal beam of activated PFs and was reduced in arterioles located away from the stimulated site in a rostrocaudal direction. The increases in vascular diameter were associated with increases in BFcrb in the activated area (+55 +/- 4%, n = 5). PF stimulation increased vascular diameter (+10 +/- 0.5%, n = 10) also in larger arterioles (30-40 microm) located in the folium adjacent to that in which the PFs were stimulated. Higher-order branches of these arterioles supplied the activated area. No field potentials were evoked by PF stimulation in the area where these upstream vessels were located. The data suggest that increased synaptic activity in the PF system produces a "local" hemodynamic response mediated by synaptic release of vasoactive agents and a "remote" response that is propagated to upstream arterioles from vessels residing in the activated folium. These propagated vascular responses are important in the coordination of segmental vascular resistance that is required to increase flow effectively during functional brain hyperemia.

Changes and relations of circulating visfatin, apelin, and resistin levels in normal, impaired glucose tolerance, and type 2 diabetic subjects

Visfatin and apelin are two novel adipocyte- secreted hormone proposed to link obesity with insulin resistance. In this study we investigated whether plasma visfatin and apelin levels were altered in normal, impaired glucose tolerance, and type 2 diabetic subjects. We also assessed the association between plasma visfatin, or apelin and body composition, metabolic parameters, and resistin concentrations in these subjects. The visfatin levels of fasting and 2-h post-glucose load were found to be significantly decreased in diabetics compared with the controls ( P<0.05). In contrast, basal apelin levels were significantly increased in the IGT and diabetic subjects compared with the controls ( P<0.05 and P<0.01). The apelin levels of 2-h post-glucose load were significantly higher than the basal levels in every group (all P<0.05). Fasting plasma visfatin was found to correlate positively and significantly with BMI, WHR, and fasting plasma resistin, but negatively with HbA1c and 2 h OGTT glucose. Multiple regression analysis showed that WHR, HbA1c, 2 h OGTT glucose were independent related factors influencing plasma visfatin levels. Fasting plasma apelin levels correlated positively with HOMA-IR, BMI, TC, LDL-C, FBG and Fasting plasma insulin. Multiple regression analysis also showed that HOMA-IR, BMI, and TC were independent related factors influencing plasma apelin levels. The present work indicates the potential link of visfatin and apelin with the pathogenesis of insulin resistance and T2DM.

SAR650984 directly induces multiple myeloma cell death via lysosomal-associated and apoptotic pathways, which is further enhanced by pomalidomide

The anti-CD38 monoclonal antibody SAR650984 (SAR) is showing promising clinical activity in treatment of relapsed and refractory multiple myeloma (MM). Besides effector-mediated antibody-dependent cellular cytotoxicity and complement-mediated cytotoxicity, we here define molecular mechanisms of SAR-directed MM cell death and enhanced anti-MM activity triggered by SAR with Pomalidomide (Pom). Without Fc-cross-linking agents or effector cells, SAR specifically induces homotypic aggregation (HA)-associated cell death in MM cells dependent on the level of cell surface CD38 expression, actin cytoskeleton and membrane lipid raft. SAR and its F(ab)'2 fragments trigger caspase 3/7-dependent apoptosis in MM cells highly expressing CD38, even with p53 mutation. Importantly, SAR specifically induces lysosome-dependent cell death (LCD) by enlarging lysosomes and increasing lysosomal membrane permeabilization associated with leakage of cathepsin B and LAMP-1, regardless of the presence of interleukin-6 or bone marrow stromal cells. Conversely, the lysosomal vacuolar H+-ATPase inhibitor blocks SAR-induced LCD. SAR further upregulates reactive oxygen species. Pom enhances SAR-induced direct and indirect killing even in MM cells resistant to Pom/Len. Taken together, SAR is the first therapeutic monoclonal antibody mediating direct cytotoxicity against MM cells via multiple mechanisms of action. Our data show that Pom augments both direct and effector cell-mediated MM cytotoxicity of SAR, providing the framework for combination clinical trials.

Direct observation of one-dimensional diffusion and transcription by Escherichia coli RNA polymerase

The dynamics of nonspecific and specific Escherichia coli RNA polymerase (RNAP)-DNA complexes have been directly observed using scanning force microscopy operating in buffer. To this end, imaging conditions had to be found in which DNA molecules were adsorbed onto mica strongly enough to be imaged, but loosely enough to be able to diffuse on the surface. In sequential images of nonspecific complexes, RNAP was seen to slide along DNA, performing a one-dimensional random walk. Heparin, a substance known to disrupt nonspecific RNAP-DNA interactions, prevented sliding. These observations suggest that diffusion of RNAP along DNA constitutes a mechanism for accelerated promoter location. Sequential images of single, transcribing RNAP molecules were also investigated. Upon addition of 5 microM nucleoside triphosphates to stalled elongation complexes in the liquid chamber, RNAP molecules were seen to processively thread their template at rates of 1.5 nucleotide/s in a direction consistent with the promoter orientation. Transcription assays, performed with radiolabeled, mica-bound transcription complexes, confirmed this rate, which was about three times smaller than the rate of complexes in solution. This assay also showed that the pattern of pause sites and the termination site were affected by the surface. By using the Einstein-Sutherland friction-diffusion relation the loading force experienced by RNAP due to DNA-surface friction is estimated and discussed.

Isolation and characterization of lymphokine cDNA clones encoding mouse and human IgA-enhancing factor and eosinophil colony-stimulating factor activities: relationship to interleukin 5

Conditioned medium from the Con A-treated mouse helper T-cell clone Ly1+2-/9 contains activities that enhance the production of IgA by mouse B cells and induce human cord blood cells to form eosinophil colonies. We have isolated a cDNA sequence that expresses IgA-enhancing factor and eosinophil colony-stimulating factor activities from a cDNA library prepared from activated Ly1+2-/9 cells. Based on homology with the mouse cDNA sequence, a human cDNA sequence coding for an interleukin with IgA-enhancing factor and eosinophil colony-stimulating factor activities was isolated from a cDNA library prepared from a human T-cell clone stimulated with anti-T3 antibody and phorbol 12-myristate 13-acetate. DNA sequence analyses revealed that mouse and human cDNA clones encode proteins of 133 and 134 amino acids, respectively, that are identical to cDNA clones encoding the T-cell replacing factor I and B-cell growth factor II activities. These results establish that a single cDNA clone encodes a protein that acts as a growth and differentiation factor for both B cells and eosinophils.

Solid-state synthesis and mechanical unfolding of polymers of T4 lysozyme

Recent advances in single molecule manipulation methods offer a novel approach to investigating the protein folding problem. These studies usually are done on molecules that are naturally organized as linear arrays of globular domains. To extend these techniques to study proteins that normally exist as monomers, we have developed a method of synthesizing polymers of protein molecules in the solid state. By introducing cysteines at locations where bacteriophage T4 lysozyme molecules contact each other in a crystal and taking advantage of the alignment provided by the lattice, we have obtained polymers of defined polarity up to 25 molecules long that retain enzymatic activity. These polymers then were manipulated mechanically by using a modified scanning force microscope to characterize the force-induced reversible unfolding of the individual lysozyme molecules. This approach should be general and adaptable to many other proteins with known crystal structures. For T4 lysozyme, the force required to unfold the monomers was 64 +/- 16 pN at the pulling speed used. Refolding occurred within 1 sec of relaxation with an efficiency close to 100%. Analysis of the force versus extension curves suggests that the mechanical unfolding transition follows a two-state model. The unfolding forces determined in 1 M guanidine hydrochloride indicate that in these conditions the activation barrier for unfolding is reduced by 2 kcal/mol.

Tagged mutations at the Tox1 locus of Cochliobolus heterostrophus by restriction enzyme-mediated integration

We have used the restriction enzyme-mediated integration insertional mutagenesis procedure to tag the Tox1 locus in the filamentous Ascomycete Cochliobolus heterostrophus. Mutations at other, unselected, loci were also identified and a high proportion (30-50%) of them were tagged. This procedure may be of general utility for simultaneously mutating and tagging genes in fungi and in other eukaryotes. The Tox1 locus of C. heterostrophus has been defined by Mendelian analysis as a single genetic element that controls production of T toxin, a linear polyketide involved in virulence of the fungus to its host plant, corn. To tag Tox1, protoplasts of a Tox1+ (T-toxin producing) strain were transformed with a linearized, nonhomologous plasmid along with an excess of the restriction enzyme used to linearize the plasmid. Of 1310 transformants recovered, two produced no detectable T toxin in culture or on corn plants. In each of these transformants, the Tox- mutation mapped at Tox1, was tagged with the selectable marker (hygB) on the transforming plasmid, and was tightly linked to the other tagged Tox- mutation. The two mutations, however, represent two different points of plasmid insertion at the Tox1 locus.

Evidence of DNA bending in transcription complexes imaged by scanning force microscopy

Complexes of Escherichia coli RNA polymerase with DNA containing the lambda PL promoter have been deposited on mica and imaged in air with a scanning force microscope. The topographic images reveal the gross spatial relations of the polymerase relative to the DNA template. The DNA appears bent in open promoter complexes containing RNA polymerase bound to the promoter and appears more severely bent in elongation complexes in which RNA polymerase has synthesized a 15-nucleotide transcript. This difference could be related to the conformational changes that accompany the maturation of open promoter complexes into elongation complexes and suggests that formation of the elongation complex involves a considerable modification of the spatial relations between the polymerase and the DNA template.

Oxygen toxicity and iron accumulation in the lungs of mice lacking heme oxygenase-2

Heme oxygenase (HO) activity leads to accumulation of the antioxidant bilirubin, and degradation of the prooxidant heme. Moderate overexpression of the inducible form, HO-1, is associated with protection against oxidative injury. However, the role of HO-2 in oxidative stress has not been explored. We evaluated survival, indices of oxidative injury, and lung and HO expression in HO-2 null mutant mice exposed to > 95% O2 compared with wild-type controls. Similar basal levels of major lung antioxidants were observed, except that the knockouts had a twofold increase in total glutathione content. Despite increased HO-1 expression from HO-1 induction, knockout animals were sensitized to hyperoxia-induced oxidative injury and mortality, and also had significantly increased markers of oxidative injury before hyperoxic exposure. Furthermore, during hyperoxia, lung hemoproteins and iron content were significantly increased without increased ferritin, suggesting accumulation of available redox-active iron. These results demonstrate that the absence of HO-2 is associated with induction of HO-1 and increased oxygen toxicity in vivo, apparently due to accumulation of lung iron. These results suggest that HO-2 functions to augment the turnover of lung iron during oxidative stress, and that this function does not appear to be compensated for by induction of HO-1 in the knockouts.

Thromboprophylaxis rates in US medical centers: success or failure?

BACKGROUND

As hospitalized medical patients may be at risk of venous thromboembolism (VTE), evidence-based guidelines are available to help physicians assess patients' risk for VTE, and to recommend prophylaxis options. The rate of appropriate thromboprophylaxis use in at-risk medical inpatients was assessed in accordance with the 6th American College of Chest Physicians (ACCP) guidelines.

METHODS

Hospital discharge information from the Premier Perspective(trade mark) inpatient data base from January 2002 to September 2005 was used. Included patients were 40 years old or more, with a length of hospital stay of 6 days or more, and had no contraindications for anticoagulation. The appropriateness of VTE thromboprophylaxis was determined in seven groups with acute medical conditions by comparing the daily thromboprophylaxis usage, including type of thromboprophylaxis, dosage of anticoagulant and duration of thromboprophylaxis, with the ACCP recommendations.

RESULTS

A total of 196 104 discharges from 227 hospitals met the inclusion criteria. The overall VTE thromboprophylaxis rate was 61.8%, although the appropriate thromboprophylaxis rate was only 33.9%. Of the 66.1% discharged patients who did not receive appropriate thromboprophylaxis, 38.4% received no prophylaxis, 4.7% received mechanical prophylaxis only, 6.3% received an inappropriate dosage, and 16.7% received an inappropriate prophylaxis duration based on ACCP recommendations.

CONCLUSIONS

This study highlights the low rates of appropriate thromboprophylaxis in US acute-care hospitals, with two-thirds of discharged patients not receiving prophylaxis in accordance with the 6th ACCP guidelines. More effort is required to improve the use of appropriate thromboprophylaxis in accordance with the ACCP recommendations.

Interleukin 4 (B-cell stimulatory factor 1) can enhance or antagonize the factor-dependent growth of hemopoietic progenitor cells

Our studies show that although interleukin 4 (IL-4) fails to stimulate significant colony formation by bone marrow progenitor cells, it enhances erythroid, granulocyte, macrophage, and mast-cell colony formation when used as a costimulant with erythropoietin, granulocyte colony-stimulating factor, macrophage colony-stimulating factor, and interleukin 3 (IL-3), respectively. In contrast, IL-4 suppresses IL-3-dependent colony formation by granulocyte and macrophage progenitor cells and by multipotential progenitor cells. Furthermore, it appears to inhibit the in vitro generation of colony-forming progenitor cells from immature IL-3-dependent stem cells. We also found that IL-4 inhibits stromal cell-dependent growth of bone marrow-derived pre-B cells. The ability of IL-4 to directly or indirectly regulate both positive and negative aspects of progenitor cell growth is discussed.