Genetic Deletion of AT1a Receptor or Na+/H+ Exchanger 3 Selectively in the Proximal Tubules of the Kidney Attenuates Two-Kidney, One-Clip Goldblatt Hypertension in Mice

The roles of angiotensin II (Ang II) AT1 (AT1a) receptors and its downstream target Na+/H+ exchanger 3 (NHE3) in the proximal tubules in the development of two-kidney, 1-clip (2K1C) Goldblatt hypertension have not been investigated previously. The present study tested the hypothesis that deletion of the AT1a receptor or NHE3 selectively in the proximal tubules of the kidney attenuates the development of 2K1C hypertension using novel mouse models with proximal tubule-specific deletion of AT1a receptors or NHE3. 2K1C Goldblatt hypertension was induced by placing a silver clip (0.12 mm) on the left renal artery for 4 weeks in adult male wild-type (WT), global Agtr1a−/−, proximal tubule (PT)-specific PT-Agtr1a−/− or PT-Nhe3−/− mice, respectively. As expected, telemetry blood pressure increased in a time-dependent manner in WT mice, reaching a maximal response by Week 3 (p < 0.01). 2K1C hypertension in WT mice was associated with increases in renin expression in the clipped kidney and decreases in the nonclipped kidney (p < 0.05). Plasma and kidney Ang II were significantly increased in WT mice with 2K1C hypertension (p < 0.05). Tubulointerstitial fibrotic responses were significantly increased in the clipped kidney (p < 0.01). Whole-body deletion of AT1a receptors completely blocked the development of 2K1C hypertension in Agtr1a−/− mice (p < 0.01 vs. WT). Likewise, proximal tubule-specific deletion of Agtr1a in PT-Agtr1a−/− mice or NHE3 in PT-Nhe3−/− mice also blocked the development of 2K1C hypertension (p < 0.01 vs. WT). Taken together, the present study provides new evidence for a critical role of proximal tubule Ang II/AT1 (AT1a)/NHE3 axis in the development of 2K1C Goldblatt hypertension.

Maternal and Neonatal Antibody And T Cell Responses To SARS-CoV-2 Following Maternal Infection And/Or Vaccination

Pregnant women and neonates are at risk for adverse SARS CoV-2 infection outcomes, but few studies have evaluated this population for adaptive immunity. Here, we utilized samples collected from pregnant women 18 years or older reporting two or more respiratory symptoms. Information about trimester of COVID positive test or history of vaccination was also collected. Maternal blood (MB) samples were collected at prenatal clinic visits, or at delivery together with the fetal cord blood (CB)(n=70 dyads). Groups were selected based on trimester of infection, vaccination only, or no history of vaccination or infection (n=9–24) and compared with banked samples from a non-pregnant, age-matched woman from the same time period (n=7–12). Data shows IgG transfer to baby irrespective of trimester of infection (n=9–24 per group). Highest levels of antibodies were observed with vaccinated, uninfected women. Functional antibodies are transferred from mother to fetus following infection and vaccination. CD4 and CD8 T-cell activation and cytokine secretion were detected in maternal PBMCs, with highly variable expression between subjects. In at least one dyad with a PCR-confirmed infection during second trimester, both maternal and cord blood samples had low level expression of anti-S, N, RBD antibodies at delivery and the cord blood mononuclear cells showed CD4 T cell activation (CD134+) and cytokine secretion (IL-2, IL-6, TNFalpha) to spike antigens. These results indicate the unusual immunity to SARS CoV-2 infection during pregnancy and suggest at least one case of a neonate with anti-viral cellular immunity. Ongoing analyses and surveillance for perinatal outcomes may reveal how these immune responses impact infant respiratory outcomes.

Abstract 17: Genetic Deletion Of Angiotensin Ii AT 1a Receptors Selectively In The Proximal Tubules Of The Kidney Attenuates Two-kidney, One-clip Goldblatt Hypertension In Pt- Agtr1a -/- Mice

The activation of the renin-angiotensin system (RAS) in the clipped kidney plays a critical role in the development of two-kidney, one-clip Goldblatt hypertension (2K1C), but the roles of angiotensin II (Ang II) and AT 1a receptors in the proximal tubules has not been determined previously. The present study tested the hypothesis that genetic deletion of AT 1a receptors selectively in the proximal tubules attenuates the development of 2K1C Goldblatt hypertension via AT 1a receptor-mediated, Na + /H + exchanger 3 (NHE3)-dependent mechanisms. To test the hypothesis, 2K1C Goldblatt hypertension was induced by placing a silver clip, 0.2 mm internal diameter, on the left renal artery for 4 weeks in adult male wild-type (WT), global AT 1a receptor knockout ( Agtr1a -/- ), proximal tubule (PT)-specific Agtr1a -/- (PT- Agtr1a -/- ), or PT- Nhe3 -/- mice, respectively. In WT mice, systolic blood pressure increased in a time-dependent manner reaching a maximal response by Week 3 (Basal: 112 ± 2 vs. 2K1C: 149 ± 4 mmHg, n=12, P <0.01). 2K1C Goldblatt hypertension in WT mice was associated with significant increases in renin mRNA expression in the clipped kidney (Control: 2366 ± 255 vs. Clipped: 3144 ± 569 copies/ng RNA, P <0.01) and decreases in renin mRNA expression in the nonclipped kidney (1738 ± 341 copies/ng RNA, P <0.05). Plasma Ang II levels were significantly increased in WT mice with 2K1C Goldblatt hypertension (Control: 50.2 ± 7.2 vs. 2K1C: 109.7 ± 17.2 pg/ml, P <0.05). Glomerular and tubulointerstitial fibrotic responses were also significantly increased in the clipped kidney ( P <0.01). In contrast to WT mice, the development of 2K1C hypertension was completely attenuated in Agtr1a -/- (Basal: 88 ± 4 vs. 2K1C: 92 ± 2 mmHg, n=9, n.s .), PT- Agtr1a -/- mice (Basal: 101 ± 2 vs. 2K1C: 104 ± 3 mmHg, n=12, n.s .) and PT- Nhe3 -/- mice (Basal: 103 ± 3 vs. 109 ± 5 mmHg, n=12, n.s .). Renin mRNA expression was not different in clipped and nonclipped kidney of Agtr1a -/- mice, but it was decreased in the nonclipped kidney of PT- Agtr1a -/- mice ( P <0.05). Taken together, these data suggest that genetic deletion of AT 1a receptors selectively in the proximal tubules attenuates the development of 2K1C Goldblatt hypertension via AT 1a receptor-mediated, Na + /H + exchanger 3 (NHE3)-dependent mechanisms.

Three-Dimensional Movement Trajectories in Fitts' Task: Implications for Control

According to Fitts (1954), movement time (MT) is a function of the combined effects of movement amplitude and target width (index of difficulty). Aiming movements with the same index of difficulty and MT may have different planning and control processes depending on the specific combination of movement amplitude and target size. Trajectories were evaluated for a broad range of amplitudes and target sizes. A three-dimensional motion recording system (WATSMART) monitored the position of a stylus during aiming movements. MT results replicated Fitts’ Law. Analysis of the resultant velocity profiles indicated the following significant effects: As amplitude of movement increased, so did the time to peak resultant velocity; peak resultant velocity increased slightly with target size, and to a greater extent with increases in the amplitude of movement; the time after peak resultant velocity was a function of both amplitude and target size. Resultant velocity profiles were normalized in the time domain to look for scalar relation in the trajectory shape. This revealed that: the resultant velocity profiles were not symmetrical; the proportion of time spent prior to and after peak speed was sensitive to target size only, i.e. as target size decreased, the profiles became more skewed to the right, indicating a longer decelerative phase; for a given target size, a family of curves might be defined and scaled on movement amplitude. These results suggest that a generalized program (base trajectory representation) exists for a given target width and is parameterized or scaled according to the amplitude of movement.

Collecting Duct Nitric Oxide Synthase 1ß Activation Maintains Sodium Homeostasis During High Sodium Intake Through Suppression of Aldosterone and Renal Angiotensin II Pathways

BACKGROUND

During high sodium intake, the renin-angiotensin-aldosterone system is downregulated and nitric oxide signaling is upregulated in order to remain in sodium balance. Recently, we showed that collecting duct nitric oxide synthase 1β is critical for fluid-electrolyte balance and subsequently blood pressure regulation during high sodium feeding. The current study tested the hypothesis that high sodium activation of the collecting duct nitric oxide synthase 1β pathway is critical for maintaining sodium homeostasis and for the downregulation of the renin-angiotensin-aldosterone system-epithelial sodium channel axis.

METHODS AND RESULTS

Male control and collecting duct nitric oxide synthase 1β knockout (CDNOS1KO) mice were placed on low, normal, and high sodium diets for 1 week. In response to the high sodium diet, plasma sodium was significantly increased in control mice and to a significantly greater level in CDNOS1KO mice. CDNOS1KO mice did not suppress plasma aldosterone in response to the high sodium diet, which may be partially explained by increased adrenal AT1R expression. Plasma renin concentration was appropriately suppressed in both genotypes. Furthermore, CDNOS1KO mice had significantly higher intrarenal angiotensin II with high sodium diet, although intrarenal angiotensinogen levels and angiotensin-converting enzyme activity were similar between knockout mice and controls. In agreement with inappropriate renin-angiotensin-aldosterone system activation in the CDNOS1KO mice on a high sodium diet, epithelial sodium channel activity and sodium transporter abundance were significantly higher compared with controls.

CONCLUSIONS

These data demonstrate that high sodium activation of collecting duct nitric oxide synthase 1β signaling induces suppression of systemic and intrarenal renin-angiotensin-aldosterone system, thereby modulating epithelial sodium channel and other sodium transporter abundance and activity to maintain sodium homeostasis.

Regulation of Nephron Progenitor Cell Self-Renewal by Intermediary Metabolism

Nephron progenitor cells (NPCs) show an age-dependent capacity to balance self-renewal with differentiation. Older NPCs (postnatal day 0) exit the progenitor niche at a higher rate than younger (embryonic day 13.5) NPCs do. This behavior is reflected in the transcript profiles of young and old NPCs. Bioenergetic pathways have emerged as important regulators of stem cell fate. Here, we investigated the mechanisms underlying this regulation in murine NPCs. Upon isolation and culture in NPC renewal medium, younger NPCs displayed a higher glycolysis rate than older NPCs. Inhibition of glycolysis enhanced nephrogenesis in cultured embryonic kidneys, without increasing ureteric tree branching, and promoted mesenchymal-to-epithelial transition in cultured isolated metanephric mesenchyme. Cotreatment with a canonical Wnt signaling inhibitor attenuated but did not entirely block the increase in nephrogenesis observed after glycolysis inhibition. Furthermore, inhibition of the phosphatidylinositol 3-kinase/Akt self-renewal signaling pathway or stimulation of differentiation pathways in the NPC decreased glycolytic flux. Our findings suggest that glycolysis is a pivotal, cell-intrinsic determinant of NPC fate, with a high glycolytic flux supporting self-renewal and inhibition of glycolysis stimulating differentiation.

High salt induces autocrine actions of ET-1 on inner medullary collecting duct NO production via upregulated ETB receptor expression

The collecting duct endothelin-1 (ET-1), endothelin B (ETB) receptor, and nitric oxide synthase-1 (NOS1) pathways are critical for regulation of fluid-electrolyte balance and blood pressure control during high-salt feeding. ET-1, ETB receptor, and NOS1 are highly expressed in the inner medullary collecting duct (IMCD) and vasa recta, suggesting that there may be cross talk or paracrine signaling between the vasa recta and IMCD. The purpose of this study was to test the hypothesis that endothelial cell-derived ET-1 (paracrine) and collecting duct-derived ET-1 (autocrine) promote IMCD nitric oxide (NO) production through activation of the ETB receptor during high-salt feeding. We determined that after 7 days of a high-salt diet (HS7), there was a shift to 100% ETB expression in IMCDs, as well as a twofold increase in nitrite production (a metabolite of NO), and this increase could be prevented by acute inhibition of the ETB receptor. ETB receptor blockade or NOS1 inhibition also prevented the ET-1-dependent decrease in ion transport from primary IMCDs, as determined by transepithelial resistance. IMCD were also isolated from vascular endothelial ET-1 knockout mice (VEETKO), collecting duct ET-1 KO (CDET-1KO), and flox controls. Nitrite production by IMCD from VEETKO and flox mice was similarly increased twofold with HS7. However, IMCD NO production from CDET-1KO mice was significantly blunted with HS7 compared with flox control. Taken together, these data indicate that during high-salt feeding, the autocrine actions of ET-1 via upregulation of the ETB receptor are critical for IMCD NO production, facilitating inhibition of ion reabsorption.

Developmental changes in prehension during childhood

Recent evidence has shown that the anticipatory control of grip and load force is not innate and develops over several years in childhood. The present study examined the development of grasping behavior by quantifying the relationship between grip force and the vertical acceleration of an object. Children and adults were requested to use a precision grip to lift an instrumented object which varied in size and weight. Grip force, grip force rate and the vertical position and acceleration profiles of the test object were measured or calculated. The results demonstrated the presence of distinct developmental milestones in the maturation of precision grip from 2 to 9 years of age. With 2-year-old children, the peak acceleration was negatively correlated (r=-0.51, n=34, P<0.01) with peak grip force during lifting. By 3 years of age, peak acceleration and peak grip force during lifting became positively correlated (r=0.28, n=104, P<0.01) and the correlation continued to strengthen up to 9 years of age. Variations in the temporal coupling of both peak grip force and peak acceleration also decreased with maturation. Furthermore, starting at 4-years-old, children clearly controlled the acceleration and deceleration of the object in a symmetrical pattern and used a single burst of grip force rate to grasp the object with some regularity, suggesting that the emergence of an anticipatory control strategy had already begun.

Comparing cerebellar and motor cortical activity in reaching and grasping

The activity of single cells in the cerebellar and motor cortex of awake monkeys was recorded during separate studies of whole-arm reaching movements and during the application of force-pulse perturbations to hand-held objects. Two general observations about the contribution of the cerebellum to the control of movement emerge from the data. The first, derived from the study of whole arm reaching, suggests that although both the motor cortex and cerebellum generate a signal related to movement direction, the cerebellar signal is less precise and varies from trial to trial even when the movement kinematics remain unchanged. The second observation, derived from the study of predictable perturbations of a hand-held object, indicates that cerebellar cortical neurons better reflect preparatory motor strategies formed from the anticipation of cutaneous and proprioceptive stimuli acquired by previous experience. In spite of strong relations to grip force and receptive fields stimulated by preparatory grip forces increase, the neurons of the percentral motor cortex showed very little anticipatory activity compared with either the premotor areas or the cerebellum.

Responses of cerebellar Purkinje cells to slip of a hand-held object

1. Two monkeys were trained to grasp, lift, and hold a device between the thumb and forefinger for 1 s. The device was equipped with a position transducer and strain gauges that measured the horizontal grip force and the vertical lifting or load force. On selected blocks of 20-30 trials, a force-pulse perturbation was applied to the object during static holding to simulate object slip. The animals were required to resist this displacement by stiffening the joints of their wrists and fingers to obtain a fruit juice reward. Single cells in the hand representation area of the paravermal anterior lobe of the cerebellar cortex were recorded during perturbed and unperturbed holding. If conditions permitted, the cell discharge was also recorded during lifting of objects of various weights (15, 65, or 115 g) or different surface textures (sandpaper or polished metal), and when possible the cutaneous or proprioceptive fields of the neurons were characterized with the use of natural stimulation. 2. On perturbed trials, the force pulse was always applied to the manipulandum after it had been held stationary within the position window for 750 ms. The perturbation invariably elicited a reflexlike increase of electromyographic (EMG) activity in wrist and finger muscles, resulting in a time-locked increase in grip force that peaked at a latency between 50 and 100 ms. 3. The object-slip perturbation had a powerful effect on cerebellar cortical neurons at a mean latency of 45 +/- 14 (SD) ms. Reflexlike increases or decreases in simple spike discharge occurred in 55% (53/97) of unidentified cells and 49% (21/43) of Purkinje cells recorded in the anterior paravermal and lateral cerebellar cortex. 4. The perturbation failed to evoke complex spike responses from any of the Purkinje cells examined. All the perturbation-evoked activity changes involved modulation of the simple spike discharge. The perturbations stimulated the simple-spike receptive field of most Purkinje cells recorded here, which suggests that the short-latency unit responses were triggered by afferent stimulation. Only one Purkinje cell was found with a distinct complex-spike receptive field on the thumb, but this neuron did not respond to the perturbation. It appears that simple- and complex-spike to receptive fields are not always identical or even closely related. 5. The majority of Purkinje and unidentified neurons that responded to the perturbation had cutaneous receptive fields, although some had proprioceptive fields. Seventy-seven neurons were examined for peripheral receptive fields and were also tested with the perturbation.(ABSTRACT TRUNCATED AT 400 WORDS)

Cutaneous afferent activity in the median nerve during grasping in the primate

Neural activity was recorded from the median nerve of a monkey during grasping and lifting, using a chronically implanted cuff electrode. At the onset of lifting, there was an initial dynamic response during which the intensity of the neural signal increased rapidly. This neural response attained its peak value well before the displacement, the load force or the grip force. The time course and peak of the rectified, integrated neurogram were best correlated with the rate of change of grip force. The neural activity declined exponentially to a steady value following the initial peak. During steady holding the mean amplitude of the neurogram was best correlated with the mean grip force. At the end of the holding phase there was a short burst of neural activity as the monkey relaxed the grip force and released the object. During some blocks of trials pulse perturbations were applied to the object. When the monkey did not increase the grip force in advance of the perturbation, the perturbation produced a relatively large displacement of the object and a burst of neural activity whose onset coincided with the onset of displacement. When the monkey anticipated the perturbation by increasing the grip force during the holding period preceding the perturbation, the perturbation produced a relatively small displacement and relatively little increase in neural activity.

[The evolution of ethnic structure in Quebec's peripheral regions]

"The main purpose of this paper is to analyse, on the basis of census data, the evolution of the ethnic structure of the population in five peripheral regions of Quebec. After some methodological considerations and a brief discussion of the settlement structure, the author describes the evolution of ethnic structure over two sub-periods: 1871-1971 and 1971-1986." (SUMMARY IN ENG AND SPA)

Strategy and learning effects on perturbed movements: an electromyographic and kinematic study

The effects of practice and movement strategy were studied in a goal-directed movement with different levels of perturbation applied in four independent groups (0%, 20%, 50% or 100%). The phase-plane trajectory data revealed that for all subjects there was a decrease in the mean trajectory variability with learning and that variability was affected by the level of uncertainty confronting the subjects. Both the average electromyographic (EMG) profiles and the mean subject variability for agonist and antagonist muscles decreased with learning. In each experimental group a specific interaction developed between reflex responses and voluntary activity to create a balanced level of EMG activity to improve the performance with learning.

[Decision making by intercollegiate basketball players]

The results of several studies suggest that in an event incertitude situation, elite athletes can select the appropriate response faster than the novice. There are at least two possibilities to explain such a difference. First, it could be that the elite athlete has more facility to reduce the amount of information he/she is confronted with, that is he/she is able to identify more easily certain sequences and patterns in the play of his/her opponents. Secondly, it is possible that the athlete uses the available information in a different manner. The purpose of this study was to verify the second hypothesis. 10 subjects (5 novices and 4 intercollegiate basketball players) were submitted to a choice time task where the required response was a total body displacement over 2 meters. The results suggest that elite athletes use their knowledge of probability of events in the same way as the novice subjects.