This study was designed to determine whether smooth muscle α-actin mRNA and smooth muscle α-actin contractile protein elements were present within the renal medullary pericytes. Extraction of total RNA from microdissected outer medullary descending vasa recta allowed for the detection of smooth muscle α-actin mRNA expression using reverse transcription-polymerase chain reaction (RT-PCR). Expression of smooth muscle α-actin was specific to the descending vasa recta and not a result of tubular contamination because RT-PCR amplification of the vasopressin V2 receptor, which is a specific tubular marker, did not occur. To determine the exact cell type(s) that translate the mRNA into protein, we performed immunohistochemistry on the renal outer and inner medulla using a monoclonal smooth muscle α-actin antibody, whose specificity was determined by immunoblot analysis. Smooth muscle α-actin protein was found selectively within the pericytes surrounding the descending vasa recta from the outer and inner medullary tissue sections. This study demonstrates that the pericytes alone that surround the descending vasa recta within the outer and inner medulla contain smooth muscle α-actin mRNA and protein and are therefore the site of the contractile elements that could play a vasomodulatory role in the control of renal medullary blood flow and its distribution within the renal medulla.
The pattern of nerves, ganglia, and fine nerve processes in the adult rabbit sinoatrial node, identified by microelectrode recording, was defined by staining histochemically for cholinesterase followed by silver impregnation. A generalized repeatable pattern of innervation was recognized, including 1) a large ganglionic complex inferior to the sinoatrial node; 2) two or three moderately large nerves traversing the sinoatrial node parallel to the crista terminalis; 3) nerves entering the region from the atrial septum, the superior vena cava, and the inferior vena cava; and 4) a fine network of nerve processes, particularly extensive in the morphologically dense small-cell part of the sinoatrial node. When the site of initial depolarization in the node was located and marked by a broken-off electrode tip, it was found, after cholinesterase staining, to be characterized by a cluster of cells enclosed in a nest or basket of fine nerves. Similar nested cell clusters were observed elsewhere in the sinoatrial node in this same preparation and in other hearts. A complex interweaving of atrial muscle fibers was observed medial and inferomedial to the sinoatrial node, which may form the anatomical basis for the lack of conduction through this region. The morphological pattern of nerves, ganglia, and myocardial cells described in this study emphasizes the complexity of innervation of the sinoatrial node, including its intrinsic neural elements. Cholinesterase/silver staining can be useful in the definition and comparison of electrophysiologically identified sites within the sinoatrial node.
Oxygen consumption of animals held in dark chambers was found to be minimal and stable over the night measuring the period (10 PM to 5 AM). Oxygen consumption stabilized by day 2 in the laboratory. There was no difference in mean weight specific metabolism at night of fasting animals in March measured on days 2 through 14. For three—day fasted animals (1 to 5 gms) measured at 30°C in March and April the exponent of weight (the value of b in the equation Qo2 = aWb) was 1.03. A lower value for b was obtained at other times of the year. Fasting lizards decreased their overall oxygen consumption in proportion to the weight lost. Two parallel lines formed boundaries enclosing all values obtained for minimum oxygen consumption. Values obtained during activity fell above the upper boundary. The increase in minimum oxygen consumption due to feeding averaged 160 mm3/hr or 32% of the previous minimum value. Multiple regression analysis of oxygen consumption measurements made at 3 temperatures (25, 30, 35°C) and 4 seasons (May, July, September, January) indicates that there is a clear seasonal difference, winter animals exhibiting higher rates of oxygen consumption. Juveniles showed high and variable rates of oxygen consumption when measured in July and August. By January juveniles are probably indistinguishable from adults. Lizards measured in the field in January had a lower mean body temperature and increased range of body temperatures as compared to September animals. There was little overlap in 2 ranges. Seasonal change in oxygen consumption may represent thermal acclimation accompanying the seasonal change in body temperatures. It is probably in part, however, due to the changing age composition of the population.
These results suggest that opioid withdrawal activates signaling pathways associated with neuronal survival and transcriptional control, two processes implicated in neuronal development and synaptic plasticity.
The morphological innervation pattern of developing fetal and neonatal rabbit hearts was delineated histochemically by a cholinesterase/silver procedure and immunohistochemically with the monoclonal antibody HNK1, an antibody which recognizes some cells derived from neuroectoderm. Cholinesterase-containing nerves appeared distally on the outflow tract by gestational day 15 (G15). Isolated cells with cholinesterase-stained fine processes were present near the base of the pulmonary trunk. HNK1 antibody stained the same nerves and ganglia revealed by the cholinesterase reaction and other nerves in the rabbit heart. It was used to confirm that cells with fine neuron-like processes were present before nerve ingrowth. The G14 heart contained many HNK1 staining cells in the right atrium, outflow, and inflow tracts; cells with fine processes were few but increased at G16. By G17, a plexus of interweaving nerves and associated cells began to form at the base of the pulmonary trunk. Fine nerves encircled the base of the aorta, and others crossed the intercaval region dorsally. At G19, nerves 1) extended downward from a rich "bulbar" plexus along the front ventricular surface, 2) grew near the epicardial surface at the base of the heart along the atrial floor and ventricular roof, 3) traversed the vena cavae and intercaval region to enter the atrial roof, and 4) crossed the coronary sinus to reach the back ventricular walls. By G23, cholinesterase-staining nerves and ganglia in the atria and, epicardially, in the ventricles formed the general innervation pattern of the newborn and adult rabbit heart.
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