Control Mechanisms of Renal Functions : Effects of Cardiovascular Drugs on Vasoconstrictive and Antinatriuretic Stimuli in the In Vivo Kidney

Filopodia are dynamic, actin-rich structures that transiently form on a variety of cell types. To understand the underlying control mechanisms requires precise monitoring of localization and concentration of individual regulatory and structural proteins as filopodia elongate and subsequently retract. Although several methods exist that analyze changes in filopodial shape, a software solution to reliably correlate growth dynamics with spatially resolved protein concentration along the filopodium independent of bending, lateral shift, or tilting is missing. Here we introduce a novel approach based on the convex-hull algorithm for parallel analysis of growth dynamics and relative spatiotemporal protein concentration along flexible filopodial protrusions. Detailed in silico tests using various geometries confirm that our technique accurately tracks growth dynamics and relative protein concentration along the filopodial length for a broad range of signal distributions. To validate our technique in living cells, we measure filopodial dynamics and quantify spatiotemporal localization of filopodia-associated proteins during the filopodial extension–retraction cycle in a variety of cell types in vitro and in vivo. Together these results show that the technique is suitable for simultaneous analysis of growth dynamics and spatiotemporal protein enrichment along filopodia. To allow readily application by other laboratories, we share source code and instructions for software handling.

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Spatial quality control bypasses cell-based limitations on proteostasis to promote prion curing

eLife ◽

10.7554/elife.04288 ◽

2014 ◽

Vol 3 ◽

Cited By ~ 32

Author(s):

Courtney L Klaips ◽

Megan L Hochstrasser ◽

Christine R Langlois ◽

Tricia R Serio

Keyword(s):

Quality Control ◽

Molecular Chaperone ◽

Protein Misfolding ◽

Elevated Temperatures ◽

Control Factor ◽

Control Mechanisms ◽

Cellular Environment ◽

Effective Activity ◽

Spatial Quality

The proteostasis network has evolved to support protein folding under normal conditions and to expand this capacity in response to proteotoxic stresses. Nevertheless, many pathogenic states are associated with protein misfolding, revealing in vivo limitations on quality control mechanisms. One contributor to these limitations is the physical characteristics of misfolded proteins, as exemplified by amyloids, which are largely resistant to clearance. However, other limitations imposed by the cellular environment are poorly understood. To identify cell-based restrictions on proteostasis capacity, we determined the mechanism by which thermal stress cures the [PSI+]/Sup35 prion. Remarkably, Sup35 amyloid is disassembled at elevated temperatures by the molecular chaperone Hsp104. This process requires Hsp104 engagement with heat-induced non-prion aggregates in late cell-cycle stage cells, which promotes its asymmetric retention and thereby effective activity. Thus, cell division imposes a potent limitation on proteostasis capacity that can be bypassed by the spatial engagement of a quality control factor.

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Relationship of Motor Mechanisms to Gastroparesis Symptoms: Towards Individualized Treatment

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00006.2021 ◽

2021 ◽

Author(s):

Michael Camilleri

Keyword(s):

Animal Studies ◽

Gastrointestinal Symptoms ◽

Feedback Regulation ◽

Individualized Treatment ◽

Control Mechanisms ◽

Gastric Accommodation ◽

Billroth I ◽

Gastric Sensitivity

Following a classical paper by Dr. Keith A. Kelly published in this journal, and over the past 40 years, there has been increased understanding of the functions of different regions of the stomach, specifically the fundus, antrum, and pylorus. Several of the important physiological principles were based on in vivo animal studies that led to the appreciation of regional function and control mechanisms. These include the roles of the extrinsic parasympathetic vagal innervation, the gastric enteric nervous system and electrical syncytium consisting of pacemaker cells and smooth muscle cells, and duodenogastric reflexes providing feedback regulation following the arrival of food and hydrogen ions stimulating the release of hormones and vagal afferent mechanisms that inhibit gastric motility and stimulate pyloric contractility. Further insights on the role of regional motor functions in gastric emptying were obtained from observations in patients following diverse gastric surgeries or bariatric procedures, including fundoplication, Billroth I and sleeve gastrectomy, and sleeve gastroplasty. Antropyloroduodenal manometry as well as measurements of pyloric diameter and distensibility index provided important assessments of the role of antral hypomotility and pylorospasm, and these constitute specific targets for individualized treatment of patients with gastroparesis. Moreover, in patients with upper gastrointestinal symptoms suggestive of gastroparesis, the availability of measurements of gastric accommodation as well as pharmacological agents to reduced gastric sensitivity or enhance gastric accommodation provide additional specific targets for individualized treatment. It is anticipated that, in the future, such physiological measurements will be applied in patients to optimize choice of therapy, possibly including identifying the best candidate for pyloric interventions.

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Growth and differentiation of Tubularia cells in a chemically defined physiological medium

Development ◽

10.1242/dev.20.1.73 ◽

1968 ◽

Vol 20 (1) ◽

pp. 73-80

Author(s):

Allison L. Burnett ◽

Faith E. Ruffing ◽

June Zongker ◽

Anna Necco

Keyword(s):

Defined Medium ◽

Control Mechanisms ◽

Mucous Cells ◽

Chemically Defined Medium ◽

Experimental Animals ◽

Molecular Weights ◽

Large Numbers ◽

High Degree ◽

I Cells

Although hydroids have proven valuable experimental animals for studies involving polarity and regeneration, they have not been extensively used by chemical embryologists studying control mechanisms in differentiation. Ideally, hydroids should be valuable tools for such a study. Their morpohology is relatively simple since they are diploblastic; their cells achieve a high degree of specialization (cnidoblasts, nerve cells, gland and mucous cells); cell differentiation (and morphogenesis) from a reserve stock of interstitial or i-cells is rapid; and many species can be cultured in large numbers under controlled environmental conditions. Probably one of the reasons for this lack of attention is that no one has succeeded in cloning cells of a particular type in a chemically defined medium. In vivo systems, mainly because of their impermeability to most exogenous materials with molecular weights over 200, have not proven to be especially reliable.

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Myogenic mechanism for peristalsis in the cat esophagus

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1999.277.2.g306 ◽

1999 ◽

Vol 277 (2) ◽

pp. G306-G313 ◽

Cited By ~ 6

Author(s):

Harold G. Preiksaitis ◽

Nicholas E. Diamant

Keyword(s):

Muscle Contraction ◽

Slow Wave ◽

Circular Muscle ◽

Smooth Muscle Contraction ◽

Slow Waves ◽

Mechanical Activity ◽

Control Mechanisms ◽

Slow Wave Oscillations

A myogenic control system (MCS) is a fundamental determinant of peristalsis in the stomach, small bowel, and colon. In the esophagus, attention has focused on neuronal control, the potential for a MCS receiving less attention. The myogenic properties of the cat esophagus were studied in vitro with and without nerves blocked by 1 μM TTX. Muscle contraction was recorded, while electrical activity was monitored by suction electrodes. Spontaneous, nonperistaltic, electrical, and mechanical activity was seen in the longitudinal muscle and persisted after TTX. Spontaneous circular muscle activity was minimal, and peristalsis was not observed without pharmacological activation. Direct electrical stimulation (ES) in the presence of bethanechol or tetraethylammonium chloride (TEA) produced slow-wave oscillations and spike potentials accompanying smooth muscle contraction that progressed along the esophagus. Increased concentrations of either drug in the presence of TTX produced slow waves and spike discharges, accompanied by peristalsis in 5 of 8 TEA- and 2 of 11 bethanechol-stimulated preparations without ES. Depolarization of the muscle by increasing K+ concentration also produced slow waves but no peristalsis. We conclude that the MCS in the esophagus requires specific activation and is manifest by slow-wave oscillations of the membrane potential, which appear to be necessary, but are not sufficient for myogenic peristalsis. In vivo, additional control mechanisms are likely supplied by nerves.

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Counter-regulation in the IKK family

Biochemical Journal ◽

10.1042/bj20102168 ◽

2011 ◽

Vol 434 (1) ◽

pp. e1-e2 ◽

Cited By ~ 2

Author(s):

Luke A. J. O'Neill

Keyword(s):

Inflammatory Diseases ◽

Interleukin 1 ◽

Nuclear Factor Κb ◽

Type I Interferons ◽

Poly I:C ◽

Type I ◽

Control Mechanisms ◽

Biochemical Journal ◽

Regulatory Feedback Loop

The human IKK [IκB (inhibitor of NF-κB) kinase] family has four members; they are the central kinases of innate immunity. Two members, IKKα and IKKβ, the so-called canonical members, phosphoryate IκBα, leading to activation of the transcription factor NF-κB (nuclear factor κB), which controls the expression of many immune and inflammatory genes. The IKK-related proteins TBK-1 (TANK-binding kinase 1) and IKKϵ have a different substrate – IRF3 (interferon regulatory factor 3) – which regulates a different set of genes, the products of which include Type I interferons. Toll-like receptors (TLRs) such as the lipopolysaccharide receptor TLR4 or the poly(I:C) receptor TLR3 activate each of the IKKs, but the pro-inflammatory cytokine IL-1 (interleukin 1), which signals in a broadly similar way to the TLRs, has so far been shown to activate only the canonical IKKs. In this issue of the Biochemical Journal, Clark et al. bring new insights into the regulation of IKKs. They demonstrate that IL-1 is in fact able to activate IKKϵ/TBK-1, which occurs via IKKα/IKKβ. The consequence of this is not IRF3 activation, but a negative feedback effect on IKKα/IKKβ. This provides us with yet another regulatory feedback loop in a system already replete with control mechanisms. It attests yet again to the importance of keeping these innate immune pathways in check, since if they proceed uncontrolled, inflammatory diseases can occur. Importantly, this study utilized new and specific inhibitors of these kinases, suggesting that the interpretation of any effects the compound might have in vivo may be complex, since for example the inhibition of IKKϵ/TBK-1 might actually have a pro-inflammatory effect.

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Synthesis of new exenatide analogs and investigation of their influence on glycemia and renal function in rats

Problems of Endocrinology ◽

10.14341/probl201157342-47 ◽

2011 ◽

Vol 57 (3) ◽

pp. 42-47

Author(s):

A E Bogolepova ◽

A V Kutina ◽

A S Marina ◽

S K Nikol'skaia ◽

E I Shakhmatova ◽

...

Keyword(s):

Renal Excretion ◽

Free Water ◽

Potassium Ions ◽

Magnesium Ions ◽

Glucose Loading ◽

Rat Models ◽

Renal Functions ◽

In Vivo Testing ◽

Physiologically Active Compounds

New analogs of exenatide with amino acid substitutions at 14, 35, and 39 have been synthesized. They were shown to be more stable than original exenatide in aqueous solutions. In vivo testing on rat models of glucose loading showed that exenatide and its novel analogs possess hypoglycemic activity and stimulate renal excretion of sodium and magnesium ions and osmotically free water but have virtually no effect on the elimination of potassium ions. Experiments with isolated skin and urinary bladder preparations from male frogs showed that exenatide and its analogs promote biosynthesis of physiologically active compounds modulating renal functions.

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Oogenesis in Atlantic salmon (Salmo salar L.) occurs by zonagenesis preceding vitellogenesis in vivo and in vitro

Journal of Endocrinology ◽

10.1677/joe.0.1580259 ◽

1998 ◽

Vol 158 (2) ◽

pp. 259-266 ◽

Cited By ~ 45

Author(s):

T Celius ◽

BT Walther

Keyword(s):

Atlantic Salmon ◽

Salmo Salar ◽

Polyclonal Antiserum ◽

Control Mechanisms ◽

Zona Radiata ◽

Atlantic Salmon Salmo Salar ◽

Molecular Components ◽

Hepatic Synthesis

Fish oogenesis represents pleiotropic cytodifferentiative programs including hepatic synthesis of the molecular components for both the eggshell and the oocytic energy deposits. Both hepatic processes are directly controlled by plasma levels of estradiol (E2), and injected E2 induces both biogenetic processes in prepubertal fish of both sexes. This work compares the temporal pattern of E2-induced biosynthesis of zona radiata proteins (zr-proteins) and vitellogenin in Atlantic salmon (Salmo salar L.) in vivo and in vitro. We monitored the presence of plasma zr-proteins and vitellogenin, using homologous polyclonal antiserum to zr-proteins and a monoclonal antibody to vitellogenin. Zr-proteins were induced by all E2 concentrations (0.001-1.1 mg/kg body weight (bw)) within one week of exposure while vitellogenin was not induced until two weeks post-injection and then only in plasma from fish injected with high E2 concentrations (0.4 mg or 1.1 mg/kg bw). After E2 treatment, hepatocytes isolated from male fish synthesized zr-proteins and vitellogenin in vitro. However, zr-proteins were secreted into the medium two days before vitellogenin, as measured by ELISA. The data indicate a preferential induction of zr-proteins compared with vitellogenin, both with regard to E2 sensitivity and response time to E2 treatment. These findings suggest an obligate sequence in salmon oogenesis. During sexual maturation low E2 levels at first induce only zonagenesis, while increasing levels of E2 subsequently induce both zonagenesis and vitellogenesis. In nature, the interval between zonagenesis and vitellogenesis may, therefore, be considerable. The data suggest new control mechanisms in fish oogenesis.

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