Blood flow velocity comparison in the eye capillaries and postcapillary venules between normal pregnant and non-pregnant women

Background: There is no consensus on how much and at what diameters the blood flow velocity changes in the female microcirculation during normal pregnancy. Methods: A non-contact, digital slit-lamp biomicroscopy system was used to measure axial blood velocity (Vax) and diameter (D) in the conjunctival microcirculation of 28 normal non-pregnant women (Control Group), 17 women in the first semester of their normal pregnancy (Group 1) and 16 women in the third trimester of their normal pregnancy (Group 2). Blood volume flow (Q) was estimated from Vax and D. Microvessels were classified as “capillaries” (CAP) with D < 9 μm, “postcapillary venules of size 1” (PC1) with 9 ≤ D < 14 μm and “postcapillary venules of size 2” (PC2) with 14 ≤ D ≤ 24 μm. Results: The women groups did not differ significantly in age, diastolic and systolic pressure and diameter of each size. Taking as baseline the capillary Vax of 0.51 mm/s of the Control Group, there was a statistically significant (p < 0.001) increase to 0.74 mm/s (45%) in Group 1 and to 0.95 mm/s (86%) in Group 2. This significant Vax increase in capillaries (CAP) was a consistent finding irrespective of the exact vessel size cut-off value for discriminating CAP from PC1. There was no statistical difference in Vax among groups at postcapillary venules of size 2 (PC2). Statistical conclusions for blood volume flows were similar to velocities. Conclusions: Normal pregnancy increases significantly axial blood velocity (Vax) in capillaries (CAP) with diameter <9 μm. © 2019 Elsevier Inc

The importance of ophthalmic artery hemodynamics in patients with atheromatous carotid artery disease

Aim. The aim of this paper was to provide an insight on the role of the ophthalmic artery blood flow changes due to significant carotid stenosis and the effects of carotid revascularization on the eye and cerebral circulation. Methods. An electronic search (Medline) of the English literature was attempted. Measurements of Peak Systolic Velocity (PSV), end-diastolic velocity (EDV), mean velocity (Vmean), Resistance Index (RI) and flow direction, obtained in OA and its branches using transcranial Doppler, in to patients with significant stenosis >70% subjected to surgical or endovascular treatment, or in those with occlusion (unilateral or bilateral), symptomatic or not, in both eyes, prior to or/and after endarterectomy or stenting. Results. As the degree of internal carotid artery (ICA) stenosis increases, the PSV in ophthalmic artery (OA) decreases. In severe stenoses the flow is not detectable or a reversed flow may be present. Following carotid endarterctomy or stenting, in almost all patients antegrade flow was detected, while in the patients with preoperative antegrade flow, an increase of the velocities was detected postoperatively. Conclusion. The reduced blood flow in the OA has consequences in the eye circulation. OA contributes to the collateral pathways in the perfusion of the brain but the importance of this collateral pathway has not been completely clarified. [Int Angiol 2011;30:547-54

Blood velocity pulse quantification in the human conjunctival pre-capillary arterioles

Axial red blood cell velocity pulse was quantified throughout its period by high speed video microcinematography in the human eye. In 30 conjunctival precapillary arterioles (6 to 12 mu m in diameter) from 15 healthy humans, axial velocities ranged from 0.4 (the minimum of all the end diastolic values) to 5.84 mm/s (the maximum of all the peak systolic values). With the velocity pulse properly quantified, two parameters can be estimated: (1) the average velocity of the pulse during a cardiac cycle AVV (average velocity value) and (2) the magnitude of the pulsation using Pourcelot's resistive index RI. These parameters are important for the estimation of other hemodynamic parameters such as the average volume flow and the average shear stress. The results of this study revealed that the AVV in the human precapillary arterioles ranged between 0.52 and 3.26 mm/s with a mean value for all microvessels of 1.66 mm/s +/- 0.11 (SE). The RI ranged between 35.5% and 81.8% with a mean value of 53.1%+/- 2.2. Quantitative information was obtained for the first time on the velocity pulse characteristics just before the human capillary bed. (C) 2010 Elsevier Inc. All rights reserved

Volume flow and wall shear stress quantification in the human conjunctival capillaries and post-capillary venules in vivo

Understanding the mathematical relationships of volume blood flow and wall shear stress with respect to microvessel diameter is necessary for the study of vascular design. Here, for the first time, volume flow and wall shear stress were quantified from axial red blood cell velocity measurements in 104 conjunctival microvessels of 17 normal human volunteers. Measurements were taken with a slit lamp based imaging system from the post capillary side of the bulbar conjunctiva in microvessel diameters ranging from 4 to 24 micrometers. The variation of the velocity profile with diameter was taken into account by using a profile factor function. Volume flow ranged from 5 to 462 pl/s with a mean value of 102 pl/s and gave a second power law best fitting line (r = 0.97) deviating significantly from the third power law relation with diameter. The estimated wall shear stress declined hyperbolically (r = 0.93) from a maximum of 9.55 N/m(2) at the smallest capillaries, down to a minimum of 0.28 N/m(2) at the higher diameter post capillary venules. The mean wall shear stress value for all microvessels was 1.54 N/m(2)

Serpin family E member 1 tag single-nucleotide polymorphisms in patients with diabetic nephropathy: An association study and meta-analysis using a genetic model-free approach

Background: Many lines of evidence highlight the genetic contribution on the development of diabetic nephropathy (DN). One of the studied genes is SERPINE1 whose the role in the risk of developing DN remains questionable. In order to elucidate the contribution of SERPINE1 in DN progression in the context of type 2 diabetes mellitus (T2DM), we conducted an association study and meta-analysis of SERPINE1 genetic variants. Materials and Methods: A total of 190 patients with DN, 150 T2DM (type 2 diabetes mellitus) patients without DN and 238 healthy controls were recruited. We selected five tag single-nucleotide polymorphisms (SNPs) from the HapMap. The generalized odds ratio (ORG) was calculated to estimate the risk on DN development. Subgroup analyses based on ethnicity and type of diabetes were also performed. Results: Both the present association study regarding SERPINE1 SNPs (rs2227667, rs2070682, rs1050813, rs2227690, rs2227692) did not found any significant association between SERPINE1 variants and DN and the meta-analysis of variant 4G&gt;5G (rs1799889) did not also reveal a significant association between 4G&gt;5G variant and DN in main and subgroup analyses. Discussion: In conclusion, the present association study and meta-analysis provides strong evidence that SERPINE1 genetic variant 4G&gt;5G is not implicated in the risk or development of DN in Caucasians. Further studies in other populations remain to further investigate the role of this variant in the course of DN. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

The contribution of genetic variants of SLC2A1 gene in T2DM and T2DM-nephropathy: association study and meta-analysis

An association study was conducted to investigate the relation between 14 variants of glucose transporter 1 gene (SLC2A1) and the risk of type 2 diabetes (T2DM) leading to nephropathy. We also performed a meta-analysis of 11 studies investigating association between diabetic nephropathy (DN) and SLC2A1 variants. The cohort included 197 cases (T2DM with nephropathy), 155 diseased controls (T2DM without nephropathy) and 246 healthy controls. The association of variants with disease progression was tested using generalized odds ratio (ORG). The risk of type 2 diabetes leading to nephropathy was estimated by the OR of additive and co-dominant models. The mode of inheritance was assessed using the degree of dominance index (h-index). We synthesized results of 11 studies examining association between 5 SLC2A1 variants and DN. ORG was used to assess the association between variants and DN using random effects models. Significant results were derived for co-dominant model of rs12407920 [OR = 2.01 (1.17–3.45)], rs841847 [OR = 1.73 (1.17–2.56)] and rs841853 [OR = 1.74 (1.18–2.55)] and for additive model of rs3729548 [OR = 0.52 (0.29–0.90)]. The mode of inheritance for rs12407920, rs841847 and rs841853 was ‘dominance of each minor allele’ and for rs3729548 ‘non-dominance’. Frequency of one haplotype (C-G-G-A-T-C-C-T-G-T-C-C-A-G) differed significantly between cases and healthy controls [p = .014]. Regarding meta-analysis, rs841853 contributed to an increased risk of DN [(ORG = 1.43 (1.09–1.88); ORG = 1.58 (1.01–2.48)] between diseased controls versus cases and healthy controls versus cases, respectively. Further studies confirm the association of rs12407920, rs841847, rs841853, as well as rs3729548 and the risk of T2DM leading to nephropathy