High pulsatile load ex vivo decreases arterial stiffness by altering the viscous, but not elastic, mechanical properties of the arterial wall

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): Research Foundation - Flanders (Brussels, BE):

==> [DUTCH]: "Fonds voor Wetenschappelijk Onderzoek (FWO) - Vlaanderen"

Introduction

The pulsatile character of blood flow in the central arteries results in a local transmission of energy to the arterial wall, acting on both the viscous and elastic components of the arterial wall. The amplitude of the "pulsatile load" is known to modulate the mechanosensitive properties of blood vessels.

Purpose

To evaluate the behavior of both the viscous and elastic components of the mouse aorta under altered pulsatile loading. Moreover, we aimed to assess regional differences in (arterial) tissue stiffness, as well as the contribution of vascular smooth muscle cell (VSMC) contractility under altered pulsatile conditions.

Methods

Aortic segments from C57Bl6 (n=9) mice were mounted in a Rodent Oscillatory Set-up for Arterial Compliance (ROTSAC), and subjected to high frequency (10 Hz) cyclic stretch at alternating loads (i.e. 20 to 100 mmHg with mean pressures ranging from 80 to 200 mmHg). Diastolic and systolic diameter, compliance, and the Peterson elastic modulus (Ep), as a measure of aortic stiffness, were determined. Viscous modulus (EV) was extracted from pressure-diameter tracings by eliminating loop hysteresis. Afterwards, the elastic modulus (EE) was calculated as the slope of the resulting pressure-diameter tracing:

(P_elastic)= (P_total) - (EV * (dD/dt))

To assess regional differences in response to changes in pulsatile load, the most proximal aortic region (i.e., thoracic ascending aorta) was compared to a more distal aortic region (i.e., abdominal infrarenal aorta).

Results

Increasing pulse pressure from 40 to 100 mmHg decreased arterial stiffness (298 ± 9 vs. 270 ± 9 mmHg; p < 0.0001). Analyzing viscoelasticity revealed that increasing pulsatile load from 40 to 100 mmHg decreased EV (0.24 ± 0.02 vs. 0.21 ± 0.02 mmHg.s/mm; p < 0.01) but not EE. 50 mM KCl-induced VSMC contraction increased vessel stiffness (298 ± 9 mmHg vs. 395 ± 12 mmHg; p < 0.0001). This effect was pronounced at low pulse pressures (20 and 40 mmHg) while at higher pulse pressures (60, 80 and 100 mmHg) contraction-induced stiffness did not occur. Interestingly, the distal region of the aorta was stiffer than the proximal region (367 ± 60 vs. 289 ± 36 mmHg; p < 0.01) and had a higher EV (0.77 ± 0.2 vs. 0.21 ± 0.05 mmHg.s/mm; p < 0.0001). Increasing pulsatile load from 40 to 100 mmHg decreased the EV from distal aortic tissue more than the EV of tissue from the proximal region (-0.26 ± 0.02 vs. -0.06 ± 0.007 mmHg.s/mm).

Conclusion

High pulsatile load decreased arterial stiffness by decreasing the viscous mechanical properties. This effect was more pronounced in the distal region of the aorta.

Downregulation of CCR5 on activated CD4 T cells in HIV-infected Indians

BACKGROUND

HIV infection in India is unique as it occurs predominantly by CCR5-utilizing isolates that exhibit no co-receptor switch.

OBJECTIVES

To study HIV-1 co-receptor dynamics on T cells and monocytes following viral infection.

STUDY DESIGN

HIV co-receptor expression was evaluated by flow cytometry on various cell subsets in HIV-infected Indians and in vitro in human peripheral blood mononuclear cells infected with CCR5- or CXCR4-utilizing HIV-1. Transfection of the T cell line CEM-CCR5 (which expresses CD4, CCR5 and CXCR4) with HIV-1 Nef or Vpu expression vectors, or treatment with recombinant soluble gp120 from CCR5- and CXCR4-tropic HIV-1, was carried out to determine their effects on co-receptor expression.

RESULTS

Indian HIV patients had fewer CD4+CCR5+ T cells and CCR5-expressing activated CD4+ T cells, but higher CXCR4-expressing activated CD4+ T cells compared with controls. Expression of CCR5 was not different on monocytes in HIV patients as compared to controls. The CCR5 downregulation on T cells was HIV infection specific and was governed by the co-receptor-utilization phenotype of the virus. The Nef and soluble gp120 proteins induced CCR5 downregulation, the latter in a co-receptor-utilization phenotype specific manner.

CONCLUSIONS

The HIV-1 co-receptor dynamics in Indian patients is distinct from western patients and depends upon the virus surface protein. We propose this to be a viral survival strategy.

Comparative evaluation of Löwenstein-Jensen proportion method, BacT/ALERT 3D system, and enzymatic pyrazinamidase assay for pyrazinamide susceptibility testing of Mycobacterium tuberculosis

Pyrazinamide (PZA) is an important first-line antituberculosis drug because of its sterilizing activity against semidormant tubercle bacilli. In spite of its very high in vivo activity, its in vitro activity is not apparent unless an acidic environment is available, which makes PZA susceptibility testing difficult by conventional methods. The present study was, therefore, planned to assess the performance of the colorimetric BacT/ALERT 3D system and compare the results with those from conventional tests, i.e., the Löwenstein-Jensen (LJ) proportion method (pH 4.85) and Wayne's pyrazinamidase (PZase) assay, using 107 clinical isolates. The concordance among all of these tests was 89.71% after the first round of testing and reached 92.52% after resolution of the discordant results by retesting. Prolonged incubation of the PZase tube for up to 10 days was found to increase the specificity of the PZase test. The concordances between LJ proportion and BacT/ALERT 3D, LJ proportion and the PZase assay, and BacT/ALERT 3D and the PZase assay were found to be 99.06%, 93.46%, and 92.52%, respectively. Using the LJ results as the gold standard, the sensitivities of BacT/ALERT 3D and the PZase assay were 100 and 82.85%, respectively, while the specificity was 98.61% for both of the tests. The difference between the sensitivities of BacT/ALERT 3D and the PZase assay was significant (P = 0.025). The mean turnaround times for the detection of resistant and susceptible results by BacT/ALERT 3D were 8.04 and 11.32 days, respectively. While the major limitations associated with the PZase assay and the LJ proportion method are lower sensitivity in previously treated patients and a longer time requirement, respectively, the BacT/ALERT 3D system was found to be rapid, highly sensitive, and specific.

Scabrous complexes with Notch to mediate boundary formation

The mechanisms that establish and sharpen pattern across epithelia are poorly understood. In the developing nervous system, the first pattern elements appear as 'proneural clusters' In the morphogenetic furrow of the immature Drosophila retina proneural clusters emerge in a wave as a patterned array of 6-10-cell groups, which are recognizable by expression of Atonal, a basic helix-loop-helix transcription factor that is required to establish and pattern the first cell fate. The establishment and subsequent patterning of Atonal expression requires activity of the signalling transmembrane receptor Notch. Here we present in vivo and biochemical evidence that the secreted protein Scabrous associates with Notch, and can stabilize Notch protein at the surface. The result is a regulation of Notch activity that sharpens proneural cluster boundaries and ensures establishment of single pioneer neurons.

Accumulation of P elements in minority inversions in natural populations of Drosophila melanogaster

The accumulation of a transposable element inside chromosomal inversions is examined theoretically by a mathematical model, and empirically by counts of P elements associated with inversion polymorphisms in natural populations of Drosophila melanogaster. The model demonstrates that, if heterozygosity for an inversion effectively reduces element associated production of detrimental chromosome rearrangements, a differential accumulation of elements is expected, with increased copy number inside the minority inversion. Several-fold differential accumulations are possible with certain parameter values. We present data on P element counts for inversion polymorphisms on all five chromosome arms of 157 haploid genomes from two African populations. Our observations show significantly increased numbers of elements within the regions associated with the least common, or minority arrangements, in natural inversion polymorphisms.

Restriction-map variation associated with the G6PD polymorphism in natural populations of Drosophila melanogaster

Restriction-map variation was studied in 126 copies of the G6pd region in X chromosome lines of Drosophila melanogaster from North America, Europe, and Africa. Special attention was focused on the distribution of variation relative to the geographically variable polymorphism for two electrophoretic variants. Nucleotide heterozygosity as determined by eight six-cutter restriction enzymes for the 13-kb region is estimated, on the basis of the worldwide sample, to be 0.065%, which is the lowest value reported for any comparable region in the D. melanogaster genome. Significant linkage disequilibrium between electrophoretic alleles and restriction-site variation is observed for several sites. In contrast to published studies of other genetic regions, there are large insertions that reach significant frequencies and are found across considerable geographic distances. There is a clustering of this variation inside the first large intervening sequence of the G6PD gene.

[Incomplete regressive obstruction of the internal carotid artery in a female patient with fibromuscular dysplasia]

The authors report on the case of a 48-year-old woman, with no history of cardiovascular disease, presenting with a progressive right cerebral deficiency syndrome predominating in the parietal region. X-ray, arteriography and CT scan findings led to the diagnosis of right middle cerebral artery ischemic stroke, in the proximal territory, due to a practically complete occlusion of the right internal carotid artery. The patient recovered and a right carotid arteriography performed 8 months after the initial one showed repermeation of the carotid artery, as well as evidence of fibromuscular dysplasia (FMD). The authors then reviewed the literature dealing with cervico-cephalic FMD and concluded that FMD only exceptionally leads to arterial occlusion, whether by arterial dissection, intimal hyperplasia or thrombosis. This case is remarkable by its favorable outcome: the thrombus, which was unquestionably responsible for the clinical picture, dissolved spontaneously.

[Occlusive arteriopathy of the circle of Willis with outlined "Moya-Moya" network in a woman with migraine under oral contraception. Regressive course]

A 19-year-old woman with migraine under contraceptive therapy had transient right hemiparesis due to a minor lesion in the left hemisphere, which was probably hemorrhagic rather than ischemic. On the left side, angiography showed nearly complete obstruction of the terminal portion of the internal carotid artery, extending to the initial portion of its terminal branches, with an outlined "Moya-Moya" network. On the right side, moderate annular stenosis of the cervical portion of the internal carotid was visible. On subsequent angiographies, done 7 and 19 months later, blood flow was reestablished in the left internal carotid artery as well as in its terminal branches, but with persistent segmental stenosis. Since the stroke, the symptomatology of migrainous attacks has been altered, pointing to a left hemispheric spreading.

Aortography with the long catheter needle

The addition of side holes to the Teflon catheter used for translumbar aortography results in improved flow of contrast material and good visualization of the aorta and brachiocephalic vessels. Details of the technique and precautions for safe use are discussed.

[Granular cell pituicytoma (choristoma) of the pituitary stalk]

A case of granular cell tumour in the pituitary stalk is described marked by the sudden loss of visual acuity in the left eye, followed by the right years later. A comparison with 17 cases previously published and with cases of asymptomatic granular cell nodules leads the authors to suggest the term granular cell pituicytoma. They discuss the place of this neoformation among other systemic granular cell tumours (granular cell myoblastoma). Fifteen patients were operated on, complete excision being carried out in only three (including the case published). Whether complementary cobalt therapy is useful remains problematical since very few cases have been published because of the slow development of the neoplasm.