“Introduction: Intraperitoneal (IP) injection represents a

“Introduction: Intraperitoneal (IP) injection represents an attractive alternative route of radiotracer

administration for small animal imaging, e.g., for longitudinal studies in transgenic mouse models. We explored the cerebral kinetics of the reversible dopamine D2 receptor ligand [I-123]IBZM after IP injection in mice.

Methods: Cerebral [I-123]IBZM kinetics were assessed by ex vivo autoradiography in mice sacrificed between 30 and 200 min after IP or intravenous (IV) injection. The striatum-to-cerebellum (S/C) uptake ratio at 140 min was evaluated in wild-type mice and R6/2 transgenic mice (a Huntington’s disease model) in comparison with in vitro autoradiography using [H-3]raclopride.

Results: [I-123]IBZM uptake was slower and lower after IP injection [maximum uptake in striatum 5.6% injected dose per grain (ID/g) at 60 min] than IV injection (10.5%ID/g Selleckchem INCB024360 at 30 min). Between 60 and 120 min, striatal (cerebellar) uptake after IP injection reached 63% (91%) of the uptake after IV injection. The S/C uptake ratio increased to 15.5 at 200 min after IP injection, which corresponds IWR-1 cell line to 87% of the IV injection

value (17.8). Consistent with in vitro [H-3]raclopride autoradiography, the S/C ratio given by ex vivo [I-123]IBZM autoradiography (140 min after IP injection) was significantly reduced in R6/2 mice.

Conclusions: Although IP injection resulted in slower kinetics, relevant measures of dopamine D2 receptor availability were comparable. Thus, IP injection represents a promising route of tracer administration for small animal [I-123]IBZM SPECT. This should considerably simplify the implementation of longitudinal small animal neuroimaging studies, e.g., in transgenic mouse models. (C) 2008

Elsevier Inc. All rights reserved.”
“Development of a successful hepatitis C virus (HCV) vaccine requires the definition of neutralization epitopes that are conserved among different HCV genotypes. Five human monoclonal antibodies (HMAbs) are described that cross-compete with other antibodies to a cluster of overlapping SPTLC1 epitopes, previously designated domain B. Each HMAb broadly neutralizes retroviral pseudotype particles expressing HCV E1 and E2 glycoproteins, as well as the infectious chimeric genotype la and genotype 2a viruses. Alanine substitutions of residues within a region of E2 involved in binding to CD81 showed that critical E2 contact residues involved in the binding of representative antibodies are identical to those involved in the binding of E2 to CD81.”
“As potential new ligands targeting the binding site of gamma-aminobutyric acid (GABA) receptor ionophore, trans-5-tert-butyl-2-(4′-fluoropropynylplienyl)-2-methyl-1,1-dioxo-1,3-dithiane (1) and cis/trans-7tert-butyl-2-(4′-fluoropropynyphenyl)-2-methyl-1,1,3,3-tetroxo-1,3-dithiane (2) were selected for radiolabeling and initial evaluation as in vivo imaging agents for positron emission tomography (PET).

Destroying c-Jun:ATF2 heterodimers with dominant negative mutants

Destroying c-Jun:ATF2 heterodimers with dominant negative mutants of c-Jun and ATF2 or knockdown by small RNA interference reduced caspase-3 promoter activity and mRNA level. Furthermore, chromatin immunoprecipitation showed increased binding of c-Jun:ATF2 heterodimers to the caspase-3 promoter in response to activity deprivation in vivo. Site-directed mutagenesis of the caspase-3 promoter revealed that caspase-3 transcriptional activation depends primarily on an ATF site -233 to -225 nucleotides upstream of the start site. Taken together, these

data demonstrate that caspase-3 is a target gene of c-Jun:ATF2 heterodimers during apoptosis induced by activity deprivation in CGNs. (C) 2011 Elsevier Ireland Ltd. All rights reserved.”
“Brain-derived neurotrophic factor (BDNF) plays critical role in neuronal development, 17-AAG function, survival and plasticity of mature neurons. The present experiments investigated whether ACP-196 order BDNF ameliorates the damaging effect of prenatal ethanol and stress exposure on behavior in offspring. Prenatal exposure of ethanol and stress combined during gestation inverted sexual partner preference of male offspring, increased social contacts with juvenile male mouse and stereotypic burying activity in the marble-burying test suggesting predisposition to homosexuality and to obsessive-compulsive disorder. Centrally administered BDNF (300 ng i.c.v.)

restored sexual female preference of male adult offspring and decreased marble-burying activity. Ameliorative effect was shown in 7-10 days after BDNF administration. The results provide the first evidence that BDNF improves epigenetic impairment of behavior and may have profound implications in the treatment of neurologic disorders induced by early environmental challenges. (C) 2011 Elsevier Ireland

Ltd. All rights reserved.”
“In http://www.selleck.co.jp/products/Adrucil(Fluorouracil).html adults, oxytocin (OXT) has various central functions including social behavior and reproduction. Many of these functions are steroid dependent and are also influenced by naturally occurring phytoestrogens, isoflavones (IFs). The aim of this study was, therefore, to clarify the effects of IFs on OXT neurons in the brain. In particular, the influence of IFs on the central OXT system of infant animal needs to be examined, because IFs are increasingly consumed for weaning as well as dietary supplements. We have morphologically analyzed the central OXT neurons in neonatal mice using slice cultures treated with IFs, daidzein (Ddz) and genistein (Gen). In the supraoptic nucleus (SON) of male mice, Gen decreased the size of OXT neurons, but not of female nor in the paraventricular hypothalamic nucleus (PVN) of neither gender. In female PVN. Ddz and 17 beta-estradiol (E-2) increased the frequencies of varicosity on neurites in small OXT neurons (<21 mu m diameter of cell body).


Mutations in RAS, particularly HRAS, are f


Mutations in RAS, particularly HRAS, are frequent in cutaneous squamous-cell carcinomas and keratoacanthomas that develop in patients treated with vemurafenib. The molecular mechanism is consistent with the paradoxical activation of MAPK signaling and leads to accelerated growth of these lesions. (Funded by Hoffmann-La Roche and others; ClinicalTrials.gov numbers, NCT00405587, NCT00949702, NCT01001299, and NCT01006980.)”
“Aims: The main aims of this study were to clone and express a new outer membrane protein U (OmpU) from www.selleckchem.com/products/PLX-4720.html a pathogenic Vibrio harveyi

SF-1 and investigate its immune efficiency as a vaccine candidate against V. harveyi infection in turbot (Scophthalmus maximus).

Methods and Results: In this study, a new gene, ompU was cloned from the genomic DNA of pathogenic V. harveyi SF-1. The ompU gene encoded a 35 kDa protein, which was purified by Ni-NTA His-Bind Resin column. A DNA vaccine was constructed by inserting ompU gene into pEGFP-N1 plasmid. Turbot were injected intramuscularly with the purified OmpU protein and the recombinant pEGFP-N1/ompU plasmid, respectively. The fish vaccinated with the purified

OmpU protein were completely protected with a relative per cent of survival (RPS) of 100% against pathogenic V. harveyi infection. Efficient protection was also found in the pEGFP-N1/ompU vaccinated group, with a RPS of 51.4%. Significant specific antibody responses were detected in the vaccinated GDC-0973 datasheet turbot by indirect enzyme-linked immunosorbent assay.

Conclusions: A new OmpU was cloned and expressed. Both OmpU protein vaccine and DNA vaccine showed good immune protections in turbot.

Significance and Impact of the Study: The OmpU was identified to be a new effective vaccine candidate and could be used as subunit vaccine

and DNA vaccine for disease control caused Methocarbamol by pathogenic V. harveyi.”
“The bowels of humans contain resident bacterial communities, the members of which are numerous and biodiverse. Changes in the composition of bowel communities is accepted to occur in relation to antibiotic-associated colitis of the elderly, but compositional alterations could also be relevant to allergic diseases in children and inflammatory bowel diseases (i.e. Crohn’s disease and ulcerative colitis). It is timely, therefore, to reflect on current knowledge of the bacterial community of the human bowel in relation to disease. Modern analytical methods provide tools by which compositional shifts in bacterial communities can be detected, but inadequate bowel-sampling procedures and poorly designed studies hamper progress. Moreover, demonstration that population shifts cause the disease and are not just reflections of a diseased state is necessary.

Homomeric alpha 1 glycine receptors were expressed in Xenopus lae

Homomeric alpha 1 glycine receptors were expressed in Xenopus laevis oocytes, and the two-electrode voltage-clamp technique was used to measure glycine-mediated currents in the presence of combinations of zinc with ethanol, pentanol or isoflurane. The combined effects of zinc plus ethanol were greater than

the sum of the effects produced by either compound alone. However, this was not seen when zinc was combined with either pentanol or isoflurane. Chelation of zinc by tricine decreased the effects of sub-maximal, but not maximal, selleck chemical concentrations of glycine, and diminished the magnitude of ethanol enhancement observed. These findings suggest a zinc/ethanol interaction at the alpha 1 GlyR that results in the enhancement of the effects of ethanol action on GlyR function. (C) 2009 Elsevier Ltd. All rights reserved.”
“Background Oral cholera vaccines consisting of killed whole cells have been available for many years, but they have not been used extensively in

populations with endemic disease. An inexpensive, locally produced oral killed-whole-cell vaccine has been used in high-risk areas in Vietnam. To expand the use of this vaccine, it was modified to comply with WHO standards. We assessed the efficacy and safety of this modified vaccine AZD6094 in a population with endemic cholera.

Methods In this double-blind trial, 107 774 non-pregnant residents of Kolkata, India, aged 1 year

or older, were cluster-randomised by dwelling Methocarbamol to receive two doses of either modified killed-whole-cell cholera vaccine (n=52212; 1966 clusters) or heat-killed Escherichia coli K12 placebo (n=55 562; 1967 clusters), both delivered orally. Randomisation was done by computer-generated sequence in blocks of four. The primary endpoint was prevention of episodes of culture-confirmed Vibrio cholerae 01 diarrhoea severe enough for the patient to seek treatment in a health-care facility. We undertook an interim, per-protocol analysis at 2 years of follow-up that included individuals who received two completely ingested doses of vaccine or placebo. We assessed first episodes of cholera that occurred between 14 days and 730 days after receipt of the second dose. This study is registered with ClinicalTrials.gov, number NCT00289224.

Findings 31932 participants assigned to vaccine (1721 clusters) and 34 968 assigned to placebo (1757 clusters) received two doses of study treatment. There were 20 episodes of cholera in the vaccine group and 68 episodes in the placebo group (protective efficacy 67%; one-tailed 99% CI, lower bound 35%, p<0.0001). The vaccine protected individuals in age-groups 1.0-4.9 years, 5.0-14.9 years, and 15 years and older, and protective efficacy did not differ significantly between age-groups (p=0.28). We recorded no vaccine-related serious adverse events.

Heterologous production of brazzein is complicated by the fact th

Heterologous production of brazzein is complicated by the fact that the protein contains four disulfide bridges and requires a specific N-terminal sequence. Our previous protocol for producing the protein from Escherichia coli involved several steps with low overall yield: expression as a fusion protein, denaturation and renaturation, oxidation of the cysteines, and cleavage by cyanogen bromide at an engineered methionine adjacent to the desired N-terminus. The new protocol described here, which is much faster and leads to a higher yield

of native protein, involves the production of brazzein in E coli as a fusion with SUMO. The isolated protein product contains the brazzein domain folded with CHIR98014 chemical structure correct disulfide bonds formed and is then cleaved

with a specific SUMO protease to liberate native brazzein. This protocol represents an important advancement that will enable more efficient research into the interaction between brazzein and the receptor as well as investigations to test the potential of brazzein as a commercially viable natural low calorie sweetener. (C) 2007 Elsevier Inc. All rights reserved.”
“The process of gene expression has material costs caused by the quantities of carbon, nitrogen, sulfur and phosphorus that are needed to make mRNAs and proteins. When any such chemical element is ecologically limiting, mutations increasing these costs can reduce growth. Here, we ask if such mutations are ‘visible’ to natural selection in the yeast Saccharomyces cerevisiae. We find that mutations Acyl CoA dehydrogenase causing JAK inhibitor small increases in expression and even single amino acid replacements can be subject

to natural selection on the basis of their material costs.”
“This study relates two behaviours, each well documented within its own literature but not previously considered together: closing-in behaviour (CIB) and the effect of visual distractors on reaching. CIB is common in typically developing children, and in adults with dementia, and classically manifests as the tendency to perform graphic copying tasks very close to, or on the top of the model. The effect of visual distractors on reaching has been studied extensively in normal adults. Distractors induce characteristic deviations of the reach, usually away from the distractor, which imply that a competing response towards the distractor is automatically primed, and actively suppressed. It is possible that CIB reflects a failure to inhibit motor distraction, such that the acting hand is attracted automatically to a salient stimulus (the model, during copying tasks). This hypothesis predicts that CIB should be associated with distractor effects during reaching, characterised by veering towards, rather than away from the distractor.

The recent addition to the long list of technologies is metabolom

The recent addition to the long list of technologies is metabolomics using metabolite profiling and informatics-based filtering of information for biomarker discovery of ovarian cancer. Emerging technologies need to address ways to eliminate the limitations posed buy Temozolomide by the complex dynamic nature of body fluids as well as ways to enrich low-abundance tumor markers if they were to become a successful biomarker discovery tool. These new technologies hold significant promise in identifying more robust markers for ovarian cancer. Since the prevalence of this disease in the population is low, the test must have

a high specificity.”
“Bovine fertility is the eFT508 manufacturer subject of extensive research in animal sciences, especially because fertility of dairy cows has declined during the last decades. The regulation of estrus is controlled by the complex interplay of various organs

and hormones. Mathematical modeling of the bovine estrous cycle could help in understanding the dynamics of this complex biological system. In this paper we present a mechanistic mathematical model of the bovine estrous cycle that includes the processes of follicle and corpus luteum development and the key hormones that interact to control these processes. The model generates successive estrous cycles of 21 days, with three waves of follicle growth per cycle. The model contains 12 differential equations and 54 parameters. Focus in this paper is on development of the model, but also some simulation results are presented, showing that a set of equations and parameters is obtained that describes the system consistent with empirical knowledge. Even though the majority of the mechanisms that are included in the model are based on relations that in Cediranib (AZD2171) the literature have only been described qualitatively (i.e. stimulation and inhibition), the output of the

model is surprisingly well in line with empirical data. This model of the bovine estrous cycle could be used as a basis for more elaborate models with the ability to study effects of external manipulations and genetic differences. (C) 2011 Elsevier Ltd. All rights reserved.”
“This study investigated the effect of pre and perinatal exposure to di-(2-ethylhexyl) phthalate (DEHP) on the neuroendocrine parameters that regulate reproduction in prepubertal male and female rats. DEHP at doses of 3 and 30 mg/kg bw/day was administered orally in the drinking water to dam rats since pregnancy onset until the moment of pups sacrifice at 15 days of age. In these animals gonadotropin serum level and the hypothalamic contents of the amino acids aspartate, glutamate and gamma-aminobutyric acid were determined.

(C) 2009 Elsevier Ltd All rights reserved “
“Whole genome a

(C) 2009 Elsevier Ltd. All rights reserved.”
“Whole genome analysis provides new perspectives to determine phylogenetic relationships among microorganisms. The availability of whole nucleotide Sequences allows different levels of comparison among genomes by several approaches. In this work, self-attraction rates were considered for each cluster of orthologous groups of proteins (COGs) class in order to analyse gene aggregation levels in physical maps. Phylogenetic relationships among microorganisms www.selleckchem.com/products/pf-04929113.html were obtained by comparing self-attraction

coefficients. Eighteen-dimensional vectors were Computed for a set of 168 completely sequenced microbial genomes (19 archea, 149 bacteria). The components

of the vector represent the aggregation rate of the genes belonging to each of 18 COGs classes. Genes involved in nonessential functions or related to environmental conditions showed the highest aggregation rates. On the contrary genes involved in basic cellular tasks showed mTOR inhibitor a more uniform distribution along the genome, except for translation genes. Self-attraction clustering approach allowed classification of Proteobacteria, Bacilli and other species belonging to Firmicutes. Rearrangement and Lateral Gene Transfer events may influence divergences from classical taxonomy. Each set of COG classes’ aggregation values represents an intrinsic property of the microbial genome. This novel approach provides a new point of view for whole genome analysis and bacterial characterization. (c) 2009 Elsevier Ltd. All rights reserved.”
“Prenatal hypoxia ischemia is a major cause of neurodevelopmental impairment in the newborn, associated with risk for motor, behavioral and cognitive impaired outcomes.

We used an established

mouse model of maternal hypoxia to examine the immediate molecular responses of signaling pathways associated with both cell death and neurogenesis. We also characterized responses to maternal pre-treatment with MgSO(4.)

Maternal hypoxia at embryonic AZD9291 day 17 (E17) failed to trigger inflammation or cell death in fetal brain at 24 h after hypoxia. However, maternal hypoxia decreased levels of neuronal migration signaling: Reelin (53% of control), Disabled I (Dab1, 77% of control), and amyloid precursor protein (APP, 64% of control) 2 h after the insult. These changes persisted for 24 h. At later times, Reelin levels in hippocampi of newborns in the maternal hypoxia-treated group increased compared to controls. Full protection from maternal hypoxia effects on hippocampal Reelin levels resulted from maternal pretreatment with MgSO(4). Hypoxia and MgSO(4) increased radial and lateral migration distance in the CA1 four days after the insult, while in the DG the hypoxia treatment alone increased migration.

Kidneys were sectioned and examined grossly for evidence of tissu

Kidneys were sectioned and examined grossly for evidence of tissue fractionation, ie the presence of histotripsy paste, or fixed in formalin and prepared for histological analysis.

Results: Histotripsy of renal cortical tissue created

tissue defects in the cortical area treated. Histotripsy targeting the renal collecting system, medulla and renal cortex resulted in tissue fractionation in the area of Selleck VS-4718 the cortex, intermediate damage in the medulla and minimal damage to the collecting system.

Conclusions: There is a differential histotripsy treatment effect when comparing renal cortical tissue to renal collecting system. There is no significant architectural disruption of the renal collecting system after histotripsy. This differential effect is a notable finding that may prove useful in future planning of ablative treatments for renal tissue.”
“Purpose. – This fMRI study investigated phonological and lexicosemantic processing in dyslexic and in chronological age- and reading level-matched children in a pseudoword reading task.

Materials and methods. – The effective connectivity network was compared between the three groups using a structural model including the supramarginal cortex (BA 40; BA: Brodmann area), fusiform cortex (BA 37) and inferior frontal cortex (BA 44/45) areas RepSox of the left hemisphere.

Results. -

The results revealed differences in connectivity patterns. In dyslexic patients, in contrast 17-DMAG (Alvespimycin) HCl with chronological age- and reading level-matched groups, no causal relationship

was demonstrated between BA 40 and BA 44/45. However, a significant causal relationship was demonstrated between BA 37 and BA 44/45 both in dyslexic children and in the reading level-matched group.

Conclusions. – These findings were interpreted as evidence for a phonological deficit in developmental dyslexia. (C) 2008 Elsevier Masson SAS. All rights reserved.”
“Purpose: Frequent loss of heterozygosity of microsatellites on a specific chromosomal region has been reported in various types of human cancer. The same loss of heterozygosity has also been identified in matched serum or urine DNA. We determined a urine microsatellite marker profile specific to urothelial carcinoma of the upper urinary tract.

Materials and Methods: We analyzed the loss of heterozygosity of primary tumors and their matched urine DNA samples from 30 patients with urothelial carcinoma of the upper urinary tract. We investigated a total of 77 markers from 25 chromosomal regions and a total of 53 from 23 chromosomal regions for their preferential loss in urothelial carcinoma and renal cell carcinoma of the kidney, respectively. Specificity was then confirmed in a cohort of 22 renal cell carcinoma cases.

Results: Of 30 patients with urothelial carcinoma 25 (83.3%) were detected using the molecular urine test. Of 48 markers detected as loss of heterozygosity in urine 20 (41.

A correlation analysis showed that the A beta(40) levels were pos

A correlation analysis showed that the A beta(40) levels were positively correlated with the cortex

C-24:0 and C-26:0 levels. Additionally, the primary cerebral cortex neurons treated with this compound showed increases in A beta(751+770) mRNA, APP protein, BACE1 mRNA and protein, and secreted A beta 40 levels. This work supports an emerging viewpoint that impaired peroxisomal function may play an important role in the progression of AD pathology. (C) 2012 Elsevier Ireland Ltd. All rights reserved.”
“Pancreatic cancer is a highly lethal disease that is difficult to diagnose at early stage and even more difficult to cure. SW1990 and PANC-1 represent the two cancer cell lines, which are both derived from pancreatic duct, but at different cell differentiation stages. In this study, we applied the iTRAQ-labeling technology and 2-D strong cation exchange/reversed phase liquid chromatography – LC-MS/MS) to profile the secreted proteins

of SW1990 and PANC-1 cells in selleckchem a conditioned SCH727965 cell culture medium. A total of 401 proteins were identified by MS/MS and protein database searching, the percentages of these proteins predicted in the categories of plasma membrane, intracellular and secreted proteins were 29.2, 32.7 and 38.2%, respectively. Fifty six proteins were identified with unknown functions and 19 proteins were quantified with significant level changes between the two cancer cell lines under the specific cell condition with 12 proteins being up-regulated (> 1.3-fold change) in PANC-1 (e.g. FLJ31222 protein, 97 kDa protein, type IV collagenase precursor, 38 kDa protein and centaurin) and seven proteins being up-regulated in 4��8C SW1990 (e.g. fibroblast growth factor receptor substrate 2, putative p150, hypothetical protein LOC 654463 and LOC 55701). The proteins with significant level changes may provide a baseline to investigate mechanisms underlying the differentiation of two cell lines and can be further screened for better protein biomarkers

in pancreatic cancer.”
“Impaired learning performance in scholastic settings is a characteristic of attention deficit hyperactivity disorder (ADHD). Our present study compares the effect of a nicotinic acetylcholine receptor (nAChR) agonist, ABT-418, and methylphenidate (MPH) on spatial memory in spontaneously hypertensive rats (SHRs), an animal model of ADHD. Neither chronic administration of ABT-418 nor MPH affected the learning performance during training in the Morris water maze. However, both compounds significantly improved memory. SHRs treated with a combination of the compounds did not perform better than either drug alone. Furthermore, the cortical alpha 4 and beta 2 nAChR subunits and the hippocampal a4 subunit expression were significantly enhanced by ABT-418 treatments. Collectively, these results suggest that ABT-418 effectively improved spatial memory in an animal model of ADHD, providing a theoretical foundation for the use of a nAChR agonist in ADHD treatment.

However the roles of the individual receptor subtypes, mGlu2 and

However the roles of the individual receptor subtypes, mGlu2 and mGlu3, in LTD are not well understood. In particular, RG-7388 it is unclear whether activation of mGlu3 receptors is sufficient to induce LTD at synapses in the CNS. In the present study, advantage was taken of a Wistar rat strain not expressing mGlu2 receptors (Ceolin et al., 2011) to investigate the function of mGlu3 receptors in the amygdala. In this preparation, the group II agonist, DCG-IV induced an LTD of the cortical, but not the intra-nuclear, synaptic input to the lateral amygdala. This LTD was concentration dependent and was blocked by the group II mGlu receptor antagonist, LY341495. To investigate further the

role of mGlu3 receptors, we used BYL719 supplier LY395756 (an mGlu2 agonist and mGlu3 antagonist), which acts as a pure mGlu3 receptor antagonist in this

rat strain. This compound alone had no effect on basal synaptic transmission, but blocked the LTD induced by DCG-IV. Furthermore, we found that DCG-IV also induces LTD in mGlu2 receptor knock-out (KO) mice to a similar extent as in wild-type mice. This confirms that the activation of mGlu2 receptors alone is sufficient to induce LTD at this amygdala synapse. To address whether mGlu2 activation alone is also sufficient to induce LTD at this synapse we used LY541850 (the active enantiomer of LY395756) in wild-type mice. LY541850 induced a substantial LTD showing that either receptor alone is capable of inducing LTD in this DNA ligase pathway.


article is part of a Special Issue entitled ‘Metabotropic Glutamate Receptors’. (c) 2012 Elsevier Ltd. All rights reserved.”
“Research has demonstrated that the jackknifing procedure for estimating ERP latencies (J. Miller, T. Patterson, & R. Ulrich, 1998) yields more accurate estimates of differences between experimental conditions in ERP latency than other methods. However, the scores resulting from this procedure require special adjustments for further analyses and do not directly reflect each participant’s latency. Here, a simple transform is proposed that retrieves estimates of each participant’s latency from the subaverage scores, rendering further adjustments superfluous. Other advantages of working with participants’ latencies are discussed. Results of simulations support the validity of jackknifing and the retrieval transform.”
“Vasomotion, the name given to the physiological phenomenon whereby blood vessel walls exhibit rhythmic oscillations in diameter, is a complex process and very poorly understood. It has been proposed as a mechanism for protecting tissue when perfusion levels are reduced, since it has experimentally been shown to occur more frequently under such conditions. However, no quantitative evidence yet exists for whether the oscillation of the wall actually has any effect on mass transport to tissue.