S-trityl-L-cysteine is a reversible, tight binding inhibitor of the human kinesin Eg5 that specifically blocks mitotic progression

Human Eg5, responsible for the formation of the bipolar mitotic spindle, has been identified recently as one of the targets of S-trityl-L-cysteine, a potent tumor growth inhibitor in the NCI 60 tumor cell line screen. Here we show that in cell-based assays S-trityl-L-cysteine does not prevent cell cycle progression at the S or G(2) phases but inhibits both separation of the duplicated centrosomes and bipolar spindle formation, thereby blocking cells specifically in the M phase of the cell cycle with monoastral spindles. Following removal of S-trityl-L-cysteine, mitotically arrested cells exit mitosis normally. In vitro, S-trityl-L-cysteine targets the catalytic domain of Eg5 and inhibits Eg5 basal and microtubule-activated ATPase activity as well as mant-ADP release. S-trityl-L-cysteine is a tight binding inhibitor (estimation of K(i,app) <150 nm at 300 mm NaCl and 600 nm at 25 mm KCl). S-trityl-L-cysteine binds more tightly than monastrol because it has both an approximately 8-fold faster association rate and approximately 4-fold slower release rate (6.1 microM(-1) s(-1) and 3.6 s(-1) for S-trityl-L-cysteine versus 0.78 microM(-1) s(-1) and 15 s(-1) for monastrol). S-trityl-L-cysteine inhibits Eg5-driven microtubule sliding velocity in a reversible fashion with an IC(50) of 500 nm. The S and D-enantiomers of S-tritylcysteine are nearly equally potent, indicating that there is no significant stereospecificity. Among nine different human kinesins tested, S-trityl-L-cysteine is specific for Eg5. The results presented here together with the proven effect on human tumor cell line growth make S-trityl-L-cysteine a very attractive starting point for the development of more potent mitotic inhibitors.

Kinesin heads fused to hinge-free myosin tails drive efficient motility

The rat kinesin motor domain was fused at residues 433, 411, 376 or 367, respectively, to the C-terminal 1185, 1187, 1197 or 1185 residues of the brush border myosin tail. In motility assays, K433myt and K411myt, which preserve the head-proximal kinesin hinge, and K367myt, which deletes it, drove rapid microtubule sliding ( approximately 0.6 microms(-1)) that was optimal when the head-pairs were spaced apart by adding 1:1 headless myosin tails. K376myt, which partially deletes the head-proximal hinge, showed poor motility in sliding assays but wild type processivity, velocity and stall force in single molecule optical trapping. Accordingly, the head-proximal kinesin hinge is functionally dispensable.

Recovery of metabolic activity in retinofugal targets after traumatic optic nerve injury is independent of retinofugal input

Traumatic injury of the adult optic nerve causes a progressive degeneration of retinal ganglion cells. Despite this ongoing degeneration, a partial recovery of visual behavioral function and of local cerebral glucose use (LCGU) has been observed. To evaluate whether this partial recovery of LCGU is due to a recovery of visual conductance (extrinsic) or intrinsic neuronal activity, visual stimulation alone and combined with physostigmine,an acetylcholinesterase inhibitor, were used to activate the retinofugal pathway. LCGU was determined in 30 male adult rats with or without physostigmine treatment 2 or 9 days after crush or 8 days after cut of the right optic nerve. Analysis of LCGU in contralateral first-order projection areas revealed no differences 8 days after cut and 9 days after optic nerve crush. Furthermore, LCGU in the contralateral areas could not be stimulated by the treatment with physostigmine. We therefore conclude that the increase in LCGU from 2 to 9 days after crush is not due to a recovery in the conductance of visual input. We hypothesize a relief of an injury-dependent active suppression (diaschisis) of LCGU. This reversal of diaschisis may, in part, account for the return of visual functions after mild optic nerve injury.

Player sensitivity to changes in string tension in a tennis racket

Forty-one advanced recreational tennis players were tested to determine their ability to detect differences in string tension in a tennis racket. Subjects were given pairs of rackets that varied in tension by up to 98 N (10 kg) and were asked whether they noticed a difference in tension and if so, which racket was strung at a higher tension. Only 11 (27%) of those tested could correctly identify a tension difference of 5 kg (11 lb) or less. Fifteen (37%) could not pick a difference of 10 kg (22 lb). To examine the importance of sound as a means of discrimination, an additional test was undertaken where participants wore earplugs. Of the 26 subjects undertaking this additional test, only 6 (23%) were successful. It was concluded that advanced recreational tennis players demonstrated limited ability to correctly identify differences in string tension and that impact sound was an important factor for those participants who were successful at various levels of discrimination.

Interaction of the mitotic inhibitor monastrol with human kinesin Eg5

The microtubule-dependent kinesin-like protein Eg5 from Homo sapiens is involved in the assembly of the mitotic spindle. It shows a three-domain structure with an N-terminal motor domain, a central coiled coil, and a C-terminal tail domain. In vivo HsEg5 is reversibly inhibited by monastrol, a small cell-permeable molecule that causes cells to be arrested in mitosis. Both monomeric and dimeric Eg5 constructs have been examined in order to define the minimal monastrol binding domain on HsEg5. NMR relaxation experiments show that monastrol interacts with all of the Eg5 constructs used in this study. Enzymatic techniques indicate that monastrol partially inhibits Eg5 ATPase activity by binding directly to the motor domain. The binding is noncompetitive with respect to microtubules, indicating that monastrol does not interfere with the formation of the motor-MT complex. The binding is not competitive with respect to ATP. Both enzymology and in vivo assays show that the S enantiomer of monastrol is more active than the R enantiomer and racemic monastrol. Stopped-flow fluorometry indicates that monastrol inhibits ADP release by forming an Eg5-ADP-monastrol ternary complex. Monastrol reversibly inhibits the motility of human Eg5. Monastrol has no inhibitory effect on the following members of the kinesin superfamily: MC5 (Drosophila melanogaster Ncd), HK379 (H. sapiens conventional kinesin), DKH392 (D. melanogaster conventional kinesin), BimC1-428 (Aspergillus nidulans BimC), Klp15 (Caenorhabditis elegans C-terminal motor), or Nkin460GST (Neurospora crassa conventional kinesin).

Alterations in brain glutathione homeostasis induced by the nerve gas soman

Public awareness of the dangers of chemical and biological warfare has been heightened in recent times. In particular, chemical nerve agents such as soman and its analogs have been developed and used in war as well as recent incidents, such as in Iraq and Japan. Soman, a rapid acting acetylcholinesterase inhibitor, produces a status epilepticus that leads to extensive neuropathology in vulnerable brain regions (eg, piriform cortex and hippocampus). This study was undertaken to determine whether oxidative mechanisms are involved in brain pathology during soman toxicity. Intracellular thiols such as glutathione (GSH) and protein sulfhydryls (PrSH) are among the most critical antioxidants used to combat oxidative stress. Here we report that during the seizure phase (1 h post soman exposure), PrSH levels in piriform cortex and hippocampus were decreased without changes in glutathione (GSH) levels. However, by 24 h post soman exposure (pathology phase), GSH levels were decreased by nearly 50% in the piriform cortex with a corresponding decrease in PrSH groups. The shift to a more oxidized thiol status indicates that oxygen free radicals likely participate in the neuropathology associated with soman-induced seizures.

Soman-induced seizures: limbic activity, oxidative stress and neuroprotective proteins

Soman, a potent acetylcholinesterase inhibitor, induces status epilepticus in rats followed by conspicuous neuropathology, most prominent in piriform cortex and the CA3 region of the hippocampus. Cholinergic seizures originate in striatal-nigral pathways and with fast-acting agents (soman) rapidly spread to limbic related areas and finally culminate in a full-blown status epilepticus. This leads to neurochemical changes, some of which may be neuroprotective whereas others may cause brain damage. Pretreatment with lithium sensitizes the brain to cholinergic seizures. Likewise, other agents that increase limbic hyperactivity may sensitize the brain to cholinergic agents. The hyperactivity associated with the seizure state leads to an increase in intracellular calcium, cellular edema and metal delocalization producing an oxidative stress. These changes induce the synthesis of stress-related proteins such as heat shock proteins, metallothioneins and heme oxygenases. We show that soman-induced seizures cause a depletion in tissue glutathione and an increase in tissue 'catalytic' iron, metallothioneins and heme oxygenase-1. The oxidative stress induces the synthesis of stress-related proteins, which are indicators of 'stress' and possibly provide neuroprotection. These findings suggest that delocalization of iron may catalyze Fenton-like reactions, causing progressive cellular damage via free radical products.

Unusual properties of the fungal conventional kinesin neck domain from Neurospora crassa

Fungal conventional kinesins are unusually fast microtubule motor proteins. To compare the functional organization of fungal and animal conventional kinesins, a set of C-terminal deletion mutants of the Neurospora crassa conventional kinesin, NcKin, was investigated for its biochemical and biophysical properties. While the shortest, monomeric construct comprising the catalytic core and the neck-linker (NcKin343) displays very high steady-state ATPase (k(cat) = 260/s), constructs including both the full neck and adjacent hinge domains (NcKin400, NcKin433 and NcKin480) show wild-type behaviour: they are dimeric, show fast gliding and slower ATP turnover rates (k(cat) = 60-84/s), and are chemically processive. Unexpectedly, a construct (NcKin378, corresponding to Drosophila KHC381) that includes just the entire coiled-coil neck is a monomer. Its ATPase activity is slow (k(cat) = 27/s), and chemical processivity is abolished. Together with a structural analysis of synthetic neck peptides, our data demonstrate that the NcKin neck domain behaves differently from that of animal conventional kinesins and may be tuned to drive fast, processive motility.

KIF1D is a fast non-processive kinesin that demonstrates novel K-loop-dependent mechanochemistry

The KIF1 subfamily members are monomeric and contain a number of amino acid inserts in surface loops. A particularly striking insertion of several lysine/arginine residues occurs in L12 and is called the K-loop. Two recent studies have employed both kinetic and single-molecule methods to investigate KIF1 motor properties and have produced very different conclusions about how these motors generate motility. Here we show that a hitherto unstudied member of this group, KIF1D, is not chemically processive and drives fast motility despite demonstrating a slow ATPase. The K-loop of KIF1D was analysed by deletion and insertion mutagenesis coupled with characterization by steady state and transient kinetics. Together, the results indicate that the K-loop not only increases the affinity of the motor for the MT, but crucially also inhibits its subsequent isomerization from weak to strong binding, with coupled ADP release. By stabilizing the weak binding, the K-loop establishes a pool of motors primed to undergo their power stroke.

Concurrent naive and memory CD8(+) T cell responses to an influenza A virus

Memory Thy-1(+)CD8(+) T cells specific for the influenza A virus nucleoprotein (NP(366-374)) peptide were sorted after staining with the D(b)NP(366) tetramer, labeled with CFSE, and transferred into normal Thy-1.2(+) recipients. The donor D(b)NP(366)(+) T cells recovered 2 days later from the spleens of the Thy-1.2(+) hosts showed the CD62L(low)CD44(high)CD69(low) phenotype, characteristic of the population analyzed before transfer, and were present at frequencies equivalent to those detected previously in mice primed once by a single exposure to an influenza A virus. Analysis of CFSE-staining profiles established that resting tetramer(+) T cells divided slowly over the next 30 days, while the numbers in the spleen decreased about 3-fold. Intranasal infection shortly after cell transfer with a noncross-reactive influenza B virus induced some of the donor D(b)NP(366)(+) T cells to cycle, but there was no increase in the total number of transferred cells. By contrast, comparable challenge with an influenza A virus caused substantial clonal expansion, and loss of the CFSE label. Unexpectedly, the recruitment of naive Thy-1.2(+)CD8(+)D(b)NP(366)(+) host D(b)NP(366)(+) T cells following influenza A challenge was not obviously diminished by the presence of the memory Thy-1.1(+)CD8(+)D(b)NP(366)(+) donor D(b)NP(366)(+) set. Furthermore, the splenic response to an epitope (D(b)PA(224)) derived from the influenza acid polymerase (PA(224-233)) was significantly enhanced in the mice given the donor D(b)NP(366)(+) memory population. These experiments indicate that an apparent recall response may be comprised of both naive and memory CD8(+) T cells.

Enzymatic removal of nitric oxide catalyzed by cytochrome c' in Rhodobacter capsulatus

Cytochrome c' from Rhodobacter capsulatus has been shown to confer resistance to nitric oxide (NO). In this study, we demonstrated that the amount of cytochrome c' synthesized for buffering of NO is insufficient to account for the resistance to NO but that the cytochrome-dependent resistance mechanism involves the catalytic breakdown of NO, under aerobic and anaerobic conditions. Even under aerobic conditions, the NO removal is independent of molecular oxygen, suggesting cytochrome c' is a NO reductase. Indeed, we have measured the product of NO breakdown to be nitrous oxide (N(2)O), thus showing that cytochrome c' is behaving as a NO reductase. The increased resistance to NO conferred by cytochrome c' is distinct from the NO reductase pathway that is involved in denitrification. Cytochrome c' is not required for denitrification, but it has a role in the removal of externally supplied NO. Cytochrome c' synthesis occurs aerobically and anaerobically but is partly repressed under denitrifying growth conditions when other NO removal systems are operative. The inhibition of respiratory oxidase activity of R. capsulatus by NO suggests that one role for cytochrome c' is to maintain oxidase activity when both NO and O(2) are present.

Lymphocyte subsets in cord blood of preterm infants: effect of antenatal steroids

The objective of this study was to evaluate prospectively the influence of gestational age (GA) and short-term antenatal steroids on total lymphocyte count and lymphocyte subsets in cord blood from preterm infants. Two-color flow cytometric analyses of lymphocyte subsets were performed on cord blood collected from 67 infants. These infants were grouped according to GA: group I (term, n = 19); group II (GA 33-37 weeks, n = 25); group III (GA <33 weeks, n = 23). The mean absolute lymphocyte counts (ALC) in groups I, II and III were 5.6 +/- 2.5 x 10(3)/ microl, 4.3 +/- 1.5 x 10(3)/ microl and 3. 5 +/- 1.8 x 10(3)/ microl respectively. The mean values for CD4+ lymphocytes in groups I, II and III were 2.7 +/- 0.8 x 10(3)/ microl, 2.0 +/- 0.8 x 10(3)/ microl and 1.6 +/- 0.9 x 10(3)/ microl respectively. Mean values for CD8+ lymphocytes were 0.9 +/- 0.3 x 10(3)/ microl, 0.6 +/- 0.3 x 10(3)/ microl and 0.5 +/- 0.3 x 10(3)/ microl respectively. With decreasing GA, there was a statistically significant decrease in ALC (p = 0.0035), CD4+ lymphocytes (p = 0. 0013) and CD8+ lymphocytes (p = 0.0064). We then evaluated the effect of antenatal steroids, now routinely administered to women with preterm onset of labor to facilitate fetal lung maturation, and found that after adjusting for GA, infants of women on antenatal steroids had significantly fewer ALC (p = 0.0001), CD4+ lymphocytes (p = 0.02) and CD25+ lymphocytes (p = 0.03). In this population of infants, the decreased number of lymphocytes seen at younger GAs is associated with antenatal steroid use.

Advanced life support: retention of registered nurses' knowledge 18 months after initial training

In 1996, The Wesley Hospital introduced a 2 day Advanced Life Support (ALS) course, targeted at all critical care registered nurses and medical officers. The purpose of this study was to explore the retention of theoretical knowledge and clinical skills of registered nurses who had successfully completed the 2 day ALS course 18 months previously and to establish effective retesting timeframes. The study utilised a repeated post-test measure design. Forty registered nurses participated in the study. Data were collected during ALS retesting using scores from a theoretical examination and from the results of four practical skill assessments (basic life support, airway management, defibrillation and code management). Using Wilcoxon test, data were analysed with and compared to the participant's original scores from the training program 18 months previously. The findings demonstrate that the participant's theoretical knowledge remained at an equivalent level over the 18 month timeframe. However, 18 months after successfully completing an ALS course, only 75 per cent (n = 30) of participants passed the practical skill assessment components, with the 25 per cent (n = 10) requiring a second attempt to pass. The implications from this study focus on the model of assessment utilised and the dichotomy between theoretical and practical skill assessment results. Additional study is required to determine the optimal timeframe for ALS retesting and educational strategies to help retain skills over time.

Suppression of Phytophthora cinnamomi in Potting Mixes Amended with Uncomposted and Composted Animal Manures

ABSTRACT We examined the effects of fresh and composted animal manures on the development of root rot, dieback, and plant death caused by Phytophthora cinnamomi. Fresh chicken manure, or chicken manure composted for 5 weeks before incorporation into the potting mix (25%, vol/vol), significantly reduced pathogen survival and the development of symptoms on Lupinus albus seedlings. Chicken manure composted for 2 weeks was less suppressive. Cow, sheep, and horse manure, whether fresh or composted, did not consistently suppress populations of P. cinnamomi or disease symptoms at the rates used (25%, vol/vol). All composts increased organic matter content, total biological activity, and populations of actinomycetes, fluorescent pseudomonads, and fungi. Only chicken manure stimulated endospore-forming bacteria, a factor that was strongly associated with seedling survival. Fallowing the potting mix for an additional 8 weeks after the first harvest increased the survival of lupin seedlings in a second bioassay, with survival rates in chicken manure compost-amended potting mix exceeding 90%. These data suggest that the ability of composted manure to stimulate sustained biological activity, in particular the activity of endospore-forming bacteria, is the key factor in reducing disease symptoms caused by P. cinnamomi. Supporting these results, the survival of rooted cuttings of Thryptomene calycina was significantly higher in sand-peat potting mix following amendment with commercially available chicken manure (15% vol/vol). However, this protection was reduced if the potting mix was steam pasteurized before amendment, indicating that suppression was due to endogenous as well as introduced microbes. Chicken manure compost incorporated at 5% (vol/vol) or more was strongly phytotoxic to young Banksia spinulosa plants and is not suitable as an amendment for phosphorus-sensitive plants.

Contact dynamics during keratocyte motility

BACKGROUND

Keratocytes are specialised, rapidly moving cells that generate substantial contractile force perpendicular to their direction of locomotion. Potential roles for contractile force in cell motility include cell-body transport, regulation of adhesion, and retraction of the cell's trailing edge.

RESULTS

To investigate contact dynamics, we used simultaneous confocal fluorescence and interference reflection microscopy to image keratocytes injected with fluorescent vinculin. We found that contacts formed behind the leading edge and grew beneath both the lamellipodium and the cell body. Contacts in the middle of the cell remained stationary relative to the substrate and began to disassemble as the cell body passed over them. In contrast, contacts in the lobes of the cell grew continuously and more rapidly, incorporated more vinculin, and slid inwards towards the sides of the cell body. Contact sliding often led to merging of contacts before their removal from the substrate.

CONCLUSIONS

We suggest a synthesis of two existing, apparently conflicting models for keratocyte motility, in which network contraction progressively reorients actin filaments using the contacts as pivots, forming bundles that then generate lateral tension by a sliding-filament mechanism. Contact dynamics vary between the middle of the cell and the lobes. We propose that laterally opposed contractile forces first enhance contact growth and stability, but escalating force eventually pulls contacts from the substrate at the back of the cell, without interfering with the cell's forward progress.

Protein profiled features patterned via confocal microscopy

Protein patterns were printed using conventional microlithographic materials in a bilayer arrangement and unconventional exposure tools. The bilayer resist stack consisted of a lower poly(tert-butyl methacrylate) layer and an upper diazonaphtoquinone/novolak layer. The protein features were printed in either 'contact printing', or 'step and repeat' mode. The latter printing mode can be managed in a flow-cell consisting of a standard microscope slide and cover slip, spaced apart by about 20 microm, as follows: (i) the exposure step is carried out in the cell using focused 488 nm beam of a confocal laser scanning microscope; (ii) the development step is performed by flowing the photoresist developer through the cell; (iii) the selective deposition of the protein (FITC-labelled avidin) is achieved via the flow of the protein solution through the cell until a desired contrast has been reached; (iv) the control of the process is assured using on-line monitoring of the photo-activated red fluorescence of the developing resist layer, and of the green fluorescence of the FITC-protein patterns, respectively. The protein printing technique uses equipment routinely available in biological laboratory. The 'step and repeat' patterning yields high and controllable resolution. The process can be applied in the fabrication of medical microanalysis devices.

Cytochrome c' from Rhodobacter capsulatus confers increased resistance to nitric oxide

We report the cloning and sequencing of the gene containing cytochrome c' (cycP) from the photosynthetic purple bacterium Rhodobacter capsulatus and the regions flanking that gene. Mutant strains unable to synthesize cytochrome c' had increased sensitivity to nitrosothiols and to nitric oxide (which binds to the heme moiety of cytochrome c').

Coupled chemical and mechanical reaction steps in a processive Neurospora kinesin

We show using single molecule optical trapping and transient kinetics that the unusually fast Neurospora kinesin is mechanically processive, and we investigate the coupling between ATP turnover and the mechanical actions of the motor. Beads carrying single two-headed Neurospora kinesin molecules move in discrete 8 nm steps, and stall at approximately 5 pN of retroactive force. Using microtubule-activated release of the fluorescent analogue 2'-(3')-O-(N-methylanthraniloyl) adenosine 5'-diphosphate (mantADP) to report microtubule binding, we found that initially only one of the two motor heads binds, and that the binding of the other requires a nucleotide 'chase'. mantADP was released from the second head at 4 s(-1) by an ADP chase, 5 s(-1) by 5'-adenylylimidodiphosphate (AMPPNP), 27 s(-1) by ATPgammaS and 60 s(-1) by ATP. We infer a coordination mechanism for molecular walking, in which ATP hydrolysis on the trailing head accelerates leading head binding at least 15-fold, and leading head binding then accelerates trailing head unbinding at least 6-fold.

Comparison of two 3-day Helicobacter pylori eradication regimens with a standard 1-week regimen

BACKGROUND

The duration of Helicobacter pylori eradication regimens has decreased to 1 week with cure rates of over 90%. This can be attributed to the use of triple drug regimens including potent inhibitors of gastric acid secretion and clarithromycin. There is no theoretical reason why shorter regimens should not be possible.

AIM

To compare two 3-day, low-dose, twice daily regimens with 1 week of omeprazole 20 mg b.d., clarithromycin 250 mg b.d., and metronidazole 400 mg b.d. (OCM) METHODS: Outpatients referred for gastroscopy were screened by biopsy urease test. H. pylori-positive patients were randomized to receive either lansoprazole 30 mg b.d., tri-potassium dicitrato bismuthate one tablet b.d., clarithromycin 250 mg b.d., and amoxycillin 1 g b.d. for 3 days (LTdbCA), or ranitidine bismuth citrate 400 mg b.d., clarithromycin 250 mg b.d. and amoxycillin 1 g b.d. for 3 days (RbcCA) or omeprazole 20 mg b.d., clarithromycin 250 mg b.d. and metronidazole 400 mg b.d. for 1 week (OCM). They were not pre-treated with a gastric acid inhibitor. After 8 weeks, H. pylori status was assessed by 13C urea breath test.

RESULTS

974 out of 1114 patients referred for gastroscopy were screened by biopsy urease test. 140 patients were not screened either because they were anticoagulated or for technical reasons. 334 patients were H. pylori-positive: 154 were excluded mostly because of allergy to penicillin and personal reasons but 180 were randomized to treatment All regimens were well tolerated. For LTdbCA (n=60), RbcCA (n=59), and OCM (n=61) the H. pylori cure rates (95% CI) were 23% (12-34), 14% (5-23) and 87% (79-95), respectively, using intention-to-treat analysis and 25% (14-36), 15% (6-24) and 88% (80-96), respectively, if analysed per protocol. OCM was significantly superior to LTdbCA and RbcCA (P < 0.001) but there was no significant difference between regimens LTdbCA and RbcCA.

CONCLUSIONS

OCM is an extremely effective H. pylori eradication regimen. The 3-day regimens tested both have poor cure rates. Pre-treatment with a proton pump inhibitor, higher doses or more frequent dosing may be necessary to increase the cure rate of short duration regimens. However, this could make them less acceptable than the H. pylori eradication regimens currently available.

TRAP transporters: a new family of periplasmic solute transport systems encoded by the dctPQM genes of Rhodobacter capsulatus and by homologs in diverse gram-negative bacteria

The dct locus of Rhodobacter capsulatus encodes a high-affinity transport system for the C4-dicarboxylates malate, succinate, and fumarate. The nucleotide sequence of the region downstream of the previously sequenced dctP gene (encoding a periplasmic C4-dicarboxylate-binding protein) was determined. Two open reading frames (ORFs) of 681 bp (dctQ) and 1,320 bp (dctM) were identified as additional dct genes by insertional mutagenesis and complementation studies. DctQ (24,763 Da) and DctM (46,827 Da) had hydropathic profiles consistent with the presence of 4 and 12 potential transmembrane segments, respectively, and were localized in the cytoplasmic membrane fraction after heterologous expression of the dctQM ORFs in Escherichia coli. DctP, DctQ, and DctM were found to be unrelated to known transport proteins in the ABC (ATP-binding cassette) superfamily but were shown to be homologous with the products of previously unidentified ORFs in a number of gram-negative bacteria, including Bordetella pertussis, E. coli, Salmonella typhimurium, Haemophilus influenzae, and Synechocystis sp. strain PCC6803. An additional ORF (rypA) downstream of dctM encodes a protein with sequence similarity to eukaryotic protein-tyrosine phosphatases, but interposon mutagenesis of this ORF did not result in a Dct- phenotype. Complementation of a Rhizobium meliloti dctABD deletion mutant by heterologous expression of the dctPQM genes from R. capsulatus demonstrated that no additional structural genes were required to form a functional transport system. Transport via the Dct system was vanadate insensitive, and in uncoupler titrations with intact cells, the decrease in the rate of succinate transport correlated closely with the fall in membrane potential but not with the cellular ATP concentration, implying that the proton motive force, rather than ATP hydrolysis, drives uptake. It is concluded that the R. capsulatus Dct system is a new type of periplasmic secondary transporter and that similar, hitherto-unrecognized systems are widespread in gram-negative bacteria. The name TRAP (for tripartite ATP-independent periplasmic) transporters is proposed for this new group.

Role of T-lymphocytes in the resolution of endotoxin-induced lung injury

An acute neutrophilic lung injury was compared in Balb/c normal and nu/nu (nude) mice to assess the role of T lymphocytes in the resolution of acute pulmonary neutrophilic inflammation following the administration of endotoxin. Maximal neutrophilic infiltration occurred on day 1 post-endotoxin treatment and declined to near normal levels by day 5. In contrast, the percentage of lymphocytes in the bronchoalveolar lavage (BAL) fluid increased from 1.8% on day 1 post-endotoxin to greater than 11% on days three and five, during which time neutrophil resolution was occurring. On days 1-5 after endotoxin administration, approximately 40% of the CD4 lymphocytes expressed the cell surface activation marker, CD69. Despite being CD69+, CD4 cells did not express the high affinity IL-2 receptor chain, CD25, to any significant extent on any of the days studied. To assess the contribution of T cells to the rate of clearance of neutrophils from the BAL, normal and nude Balb/c mice were compared for the percentage of neutrophils following nasal administration of endotoxin. Endotoxin-treated nude mice did not demonstrate significant differences in either the total white blood cell counts or in the clearance of neutrophils from the BAL, as compared to normal Balb/c mice. These data indicate that the influx of activated T cells during the resolution of neutrophilic pneumonitis does not contribute to the rate of neutrophil clearance during acute lung injury.

Apoptosis occurs in endothelial cells during hypertension-induced microvascular rarefaction

Disappearance of microvessels (microvascular rarefaction) during hypertension is a process that exacerbates the hypertensive condition. The cellular process by which the vessels disappear is not known. In the present study, we investigate the pathogenic role of cell death, specifically apoptosis, in hypertension-induced microvascular rarefaction. An established rodent one kidney/one clip (1K1C) Goldblatt model of hypertension was used. Histological and ultrastructural characteristics of apoptosis and necrosis were used to define incidence of the two types of cell death. The new method of in situ end-labeling DNA fragmentation known to occur in apoptosis was analyzed, and expression of an apoptosis-related gene, clusterin, identified using Northern blots and in situ hybridization. Microvessels in skeletal muscle were compared in 1K1C animals (n = 3 per time point) and control animals (n = 6) at experimental times after surgery up to established hypertension (1, 2, and 4 days and 1, 2, and 6 weeks). Loss of microvessels in hypertensive animals was verified. Endothelial cell apoptosis, not necrosis, was identified and was more frequent in hypertensive animals than in controls. Apoptosis of endothelial cells was found most often within 1 week after 1K1C surgery. Clusterin mRNA transcripts were increased above control levels in all 1K1C treatments, but expression was not localized specifically above endothelial cells. In this instance, increased expression of clusterin in hypertensive animals may be an epiphenomenon, not directly related to the presence of apoptosis. The results demonstrate a role for apoptosis in the development of microvascular rarefaction in hypertension. The significance of this novel finding is that these results may now be used to direct site-specific anti-apoptosis therapy for treatment of structural rarefaction, at present unaffected by conventional anti-hypertensive therapies.

Combined Hoechst 33342 and merocyanine 540 staining to examine murine B cell cycle stage, viability and apoptosis

A procedure is described for the dual staining of lymphocytes with Hoechst 33342 (Ho342) to examine cell cycle position, and merocyanine 540 (MC540) that allows for the analysis of cells entering the early stages of apoptosis. Ho342 is a DNA specific dye and MC540 detects membrane phospholipid domain changes, some of which are associated with apoptotic cells. Flow analysis of B cells dually stained with Ho342 and MC540 allows for the discrimination of five distinct subpopulations. Two of these subpopulations represent viable, MC540 negative/dull cells with either 2n or 4n DNA. As 2n and 4n DNA B cells become MC540 bright they move into two distinct subpopulations representing cells entering and progressing through the early stages of apoptosis. As the apoptotic, MC540 bright cells move into the latter stages of apoptosis, they localize into a fifth subpopulation displaying reduced staining with Ho342 indicative of late stage apoptotic cells in the process of fragmenting their DNA. This experimental approach enables the characterization of lymphocyte populations for percentages of viable, early apoptotic, and late apoptotic cells. The cells are not fixed during this procedure, and since both dyes are viable dyes there is an additional opportunity to obtain sorted cells from any of the defined subpopulations for reculturing and functional analysis.

Loss and subsequent recovery of local cerebral glucose use in visual targets after controlled optic nerve crush in adult rats

A mild crush of the adult rat optic nerve serves as a model to study the restoration of function after traumatic brain injury. It causes a progressive degeneration of retinal ganglion cells, but visually guided behavior is partially restored within 2-3 weeks. The purpose of this study was to determine to what extent local cerebral glucose use (LCGU) decreases and if it recovers in retinofugal targets following unilateral optic nerve crush. At intervals of 2, 9, and 22 days after crush, LCGU was monitored in rats in which the visual system was stimulated by a strobe-light and pattern. In the ipsilateral retinofugal targets there was only a minimal loss of LCGU use, but in the contralateral retinofugal targets, LCGU was reduced at Postlesion Day 2: to 50% in the superior colliculus (SC), to 60% in the lateral geniculate nucleus of the thalamus (LGN), and to 87% in the visual cortex. On Postoperative Days 9 and 22 we observed a partial restoration of LCGU in the contralateral SC and LGN to 68 and 79%, respectively. As recovery of visual performance is known to follow a similar time course, we conclude that restoration of metabolic activity in target structures may contribute to the restoration of vision after optic nerve crush.

Major histocompatibility complex class I-restricted cytotoxic T-lymphocyte responses in horses infected with equine herpesvirus 1

An experimental system that permits sensitive and reproducible detection of equine herpesvirus 1 (EHV-1)-specific cytotoxic T-lymphocyte (CTL) activity in the horse was developed. Peripheral blood mononuclear cells (PBMC) collected from immune horses were restimulated in vitro by culture with live EHV-1. Cytotoxic activity against virus-infected, pokeweed mitogen-stimulated lymphoblast targets was assessed in a 4-h 51Cr release assay. The optimal conditions for in vitro stimulation of equine memory CTLs and for preparation of EHV-1-infected target cells expressing viral antigens were systematically identified by individually testing the effects of variations in responder cell concentration, culture medium composition, serum type, incubation time, antigen form, and exogenous mediator content. By using this optimized system for generation and assay of equine CTLs, the development of EHV-1-specific cytotoxic responses in 12 horses was evaluated after experimental viral infection. CTLs with the capacity for killing EHV-1-infected target cells were detected in equine PBMC as early as 1 week postinfection, reached maximal levels by 2 to 3 weeks, and remained detectable for a year after infection. Equine effector cells mediating lysis of EHV-1-infected targets were predominantly CD8+ T lymphocytes, and the cytotoxicity was specific for virus and restricted by major histocompatibility complex class I molecules. The results define a reliable and convenient experimental system for generation and assay of EHV-1 CTLs which can now be used for more-detailed characterization of the equine CTL response to infection by this herpesvirus pathogen.

Is there an energy conservation "system" in brain that protects against the consequences of energy depletion?

A poorly understood marked decrease (circa 50% of control) in local cerebral glucose utilization is caused by sublethal doses of NaCN. The decrease is global, occurring in essentially all brain regions and is entirely reversible within hours, leaving no obvious pathology. This event is not unique to NaCN in so far as a strikingly similar pattern of decreased glucose utilization occurs with some other toxins. Nor can it be attributed to a direct action of NaCN since local application by microdialysis to the striatum produces a global depression. These results imply that some widely distributed "system" or substance is involved. We speculate the existence of a "system" possibly related to the reticular activating system that senses a fall in energy production and acts globally to make cells quiescent and thus would give some protection from excitotoxic driven damage.

Role of the COOH-terminal nonhelical tailpiece in the assembly of a vertebrate nonmuscle myosin rod

A short nonhelical sequence at the COOH-terminus of vertebrate nonmuscle myosin has been shown to enhance myosin filament assembly. We have analyzed the role of this sequence in chicken intestinal epithelial brush border myosin, using protein engineering/site-directed mutagenesis. Clones encoding the rod region of this myosin were isolated and sequenced. They were truncated at various restriction sites and expressed in Escherichia coli, yielding a series of mutant myosin rods with or without the COOH-terminal tailpiece and with serial deletions from their NH2-termini. Deletion of the 35 residue COOH-terminal nonhelical tailpiece was sufficient to increase the critical concentration for myosin rod assembly by 50-fold (at 150 mM NaCl, pH 7.5), whereas NH2-terminal deletions had only minor effects. The only exception was the longest NH2-terminal deletion, which reduced the rod to 119 amino acids and rendered it assembly incompetent. The COOH-terminal tailpiece could be reduced by 15 amino acids and it still efficiently promoted assembly. We also found that the tailpiece promoted assembly of both filaments and segments; assemblies which have different molecular overlaps. Rod fragments carrying the COOH-terminal tailpiece did not promote the assembly of COOH-terminally deleted material when the two were mixed together. The tailpiece sequence thus has profound effects on assembly, yet it is apparently unstructured and can be bisected without affecting its function. Taken together these observations suggest that the nonhelical tailpiece may act sterically to block an otherwise dominant but unproductive molecular interaction in the self assembly process and does not, as has been previously thought, bind to a specific target site(s) on a neighboring molecule.

Prophylactic and early therapeutic use of the Greenfield filter in hip and knee joint arthroplasty

The orthopaedic literature does not provide clear guidelines for the protection of the extremely high-risk thromboembolic patient undergoing hip and knee total joint or related reconstructive surgery. Nor is there agreement of how to protect the immediate postoperative patient with thromboembolic complications. The authors, believing that routine anticoagulation measures are ill-advised in these two circumstances, elected instead to place a Greenfield vena cava filter for prevention of life-threatening thromboembolism. Using prospective selection criteria, 47 patients could be followed over a 24-76-month period. There were no clinical embolic episodes in either group and no late complications of the filter placement. The few complications in this series were related to insertion, only one of which lead to minor long-term disability. The caval patency rate was 96%. The authors have concluded that such prophylactic use of the Greenfield vena cava filter is justified since it contributes to safer and more reliable total hip and total knee surgery with only minor morbidity.

Hemorrhagic colitis and pseudomelanosis coli in ipecac ingestion by proxy

This report describes a toddler with chronic diarrhea, vomiting, and hypotonia due to surreptitious administration of syrup of ipecac by his mother (Munchausen's syndrome by proxy). Several features of this case distinguish it from previous reports of chronic ipecac ingestion in childhood: the development of grossly bloody stools; radiologic, endoscopic, and biopsy evidence of a chronic moderate colitis resembling ulcerative colitis; and the histologic finding of pseudomelanosis coli, providing an important clue to toxic ingestion. The significance and possible mechanism for genesis of pseudomelanosis coli is discussed. This case emphasizes the variability in presentation and difficulty in diagnosing long-term ipecac ingestion by proxy. Ipecac toxicity should be considered in children with unexplained colitis and vomiting.

Effect of duration of lidocaine infusion and route of cimetidine administration on lidocaine pharmacokinetics

The effects of the duration of lidocaine infusion and the route of cimetidine administration on lidocaine pharmacokinetics were evaluated in a randomized, three-phase crossover study of six healthy men. Lidocaine hydrochloride 100 mg was administered intravenously over two minutes, and plasma lidocaine concentrations were determined before treatment and at various intervals for three hours. Immediately after the three-hour sample was obtained, a second 100-mg dose of lidocaine hydrochloride was given, followed by a 21-hour constant infusion at a rate of 2 mg/min. Plasma lidocaine concentrations were determined at various intervals during the infusion and for eight hours afterward. Urine was collected during the last five hours of the infusion and assayed for lidocaine, monoethylglycinexylidide (MEGX), and glycinexylidide (GX). The following treatments were administered to each subject in a crossover manner: a placebo tablet every six hours, beginning two days before lidocaine administration; cimetidine 300 mg orally every six hours, beginning two days before lidocaine administration; and cimetidine hydrochloride 300 mg i.v. every six hours, beginning one hour before lidocaine administration. Each medication was given until the lidocaine infusion was discontinued. Subjects fasted and remained supine throughout each treatment period. Oral cimetidine increased the area under the concentration-time curve for lidocaine by 14.7% and increased the elimination half-life of lidocaine; i.v. cimetidine did not have a significant effect on lidocaine disposition. Lidocaine clearance was 34% lower under steady-state than single-dose conditions, but the effects of cimetidine on lidocaine disposition were similar under both conditions.(ABSTRACT TRUNCATED AT 250 WORDS)