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L Barajas

Publications and source records attributed to L Barajas.

At least 55 records · Page 3Linked to original sources
PubMed1985

Innervation of the late distal nephron: an autoradiographic and ultrastructural study.

A study of the monoaminergic innervation of the cortical distal nephron beyond the thick ascending limb of Henle (TALH) was carried out by surveying nine autoradiograms, from three rats injected with exogenous tritiated norepinephrine, for overlapping of the tubule by accumulations of autoradiographic grains (AAGs). The largest number of the AAGs appeared on the late distal convoluted tubule-connecting tubule (LDCT-CNT) portion and the vast majority of the AAGs were related to the afferent arteriole. The distal convoluted tubule (DCT) and cortical collecting duct (CCD) showed half of their AAGs related to the efferent arterioles and capillary-interstitium although a substantial amount was associated with the afferent arterioles or arteries. Electron microscopy of reembedded autoradiograms demonstrated the presence of neuroeffector junctions with the CNT and CCD at sites of AAG overlap. The presence of adrenoceptors in the late distal nephron suggests the possibility of a local response of the nephron to the action of the adrenergic nerves shown in this study.

Animals↗
PubMed1984

Innervation of the renal cortical tubules: a quantitative study.

A quantitative assessment of the innervation of the different portions of the cortical tubular nephron in the rat was made using tritiated norepinephrine uptake to label monoaminergic nerves, followed by autoradiography. The proximal tubules (PT) showed the greatest number of innervated profiles (IPs) [i.e., tubular profiles overlapped by accumulations of autoradiographic grains (AAG)] followed by the thick ascending limb of Henle (TALH), the distal convoluted tubule (DCT), and the collecting duct (CD). However, the highest relative frequency of innervation (RFI), i.e., the ratio of the number of IPs to the total number of profiles surveyed, occurred in the TALH followed by the DCT and PT. The number of IPs of the CDs was too low to permit adequate statistical evaluation. The PT showed the largest number of AAGs facing the interstitium or in contact with capillaries, while the TALH had the highest number in contact with the efferent arteriole. The DCT showed a disproportionately high number of AAGs in contact with the afferent arteriole. Our results suggest that all portions of the cortical tubular nephron are under some degree of neural influence.

Animals↗
PubMed1983

Vasoactive intestinal polypeptide-immunoreactive nerves in the kidney.

Nerve fibers immunoreactive for vasoactive intestinal polypeptide (VIP) were demonstrated by immunocytochemistry in the dog and rat kidney. They were seen in association with the renal artery and its branches. In the dog, VIP-immunoreactive fibers were rarely seen close to small blood vessels suggestive of arterioles. The possible existence of neuroeffector junctions between VIP-positive fibers and renin-secreting juxtaglomerular cells requires further investigation. VIP-positive renal nerves, however, might have a vasodilatatory role.

Animals↗
PubMed1983

Simultaneous ultrastructural visualization of acetylcholinesterase activity and tritiated norepinephrine uptake in renal nerves.

In this investigation we have combined the methods of ultrastructural demonstration of acetylcholinesterase activity with electron microscopic autoradiography for the demonstration of norepinephrine uptake. The results show electron-dense deposits indicative of acetylcholinesterase activity associated with perivascular axons overlaid by concentrations of silver grains representing exogenous tritiated norepinephrine. Forty-five percent of the intervaricose regions and 19% of the varicosities overlaid by autoradiographic grains showed "moderate" amounts of cholinesterase staining. A greater proportion of autoradiographic grains was observed on the varicosities than in the intervaricose regions; however, the amount of acetylcholinesterase activity was greater in the intervaricose regions than in the varicosities. This investigation provides evidence for the presence of periaxonal acetylcholinesterase staining in adrenergic axons in the rat kidney.

Acetylcholinesterase↗
PubMed1982

Premature lambs rescued from respiratory failure with natural surfactant: clinical and biophysical correlates.

Thirty-four Western mixed breed lambs were delivered prematurely at 120 days gestational age (term = 150 days). Four lambs were sacrificed at birth, and four lambs were sacrificed with the onset of respiratory failure (PCO2 greater than 80 torr) at about 30 min of age. The remaining lambs were treated by tracheal instillation with 50 mg of natural sheep surfactant lipid/kg body weight. These lambs were sacrificed 10 min, 40 min, 1.5 h and 3 h after surfactant treatment. Frequent blood gas and compliance measurements documented the clinical responses of the lambs. Lungs from treated lambs showed large increase relative to untreated lungs in air volumes as assessed by pressure-volume curves and by histology. However, the pressure-volume and histologic measurements did not distinguish between the posttreatment groups of lambs. Minimum surface tensions of alveolar washes fell from greater than 30 dynes/cm to 6.3 dynes/cm 10 min after treatment and again rose to 21.6 dynes/cm within 3 h. Minimum surface tensions correlated well with the PO2 values but not with the PCO2 values measured before sacrifice. The combination of dilated distal airways and atelectasis resulted from increasing surface tensions with time and mechanical ventilation and may explain the clinical deterioration without much change in the volume of gas within the airways.

Animals↗
PubMed1981

Innervation of rat antral gastrin-producing cells.

The innervation of rat antral gastrin-producing cells (G-cells) was studied by light and electron microscopy. Combination of histochemistry for acetylcholinesterase and immunofluorescence for gastrin in the same tissue section showed apparent contact between some of the G-cells and acetylcholinesterase-positive nerves. Electron microscopic observation, however, revealed gaps of 200-500 nm or more between the G-cells and the closest nerve axons which often contained large dense-cored vesicles. The latter may represent the storage sites for neuropeptides previously localized by immunohistochemistry in gastric nerves.

Acetylcholinesterase↗
PubMed1981

The juxtaglomerular apparatus: anatomical considerations in feedback control of glomerular filtration rate.

The juxtaglomerular apparatus is an anatomical unit located at the hilus of the glomerulus and is believed to be involved in feedback control of renal blood flow and glomerular filtration rate. In the mammal, it consists of the glomerular arterioles and extraglomerular mesangium (the vascular component) and the macula densa (the tubular component). Juxtaglomerular granular cells are modified smooth muscle cells and are believed to be the source of renin. They are present in the vascular component, being most numerous in the afferent arteriole. The macula densa segment of the distal tubule is characterized by closely packed nuclei, the basal or lateral position of the Golgi apparatus, and dispersed mitochondria that show little association with the reduced infoldings of the basal membrane. In addition to these morphological differences, there are marked histochemical differences between the macula densa and the adjacent segments of the distal tubule. Tubule-vessel contact appears to vary in extent and ultrastructure. The macula densa forms extensive and complex contact with the extraglomerular mesangial region. Contact with the arterioles may consist of simple apposition of basement membranes. Fluorescent histochemistry and electron microscopy demonstrate a consistent monoaminergic innervation of the juxtaglomerular apparatus. Autoradiography shows that axons associated with the juxtaglomerular apparatus are able to incorporate exogenous tritiated norepinephrine. Nerve endings are observed on cells of the vascular component and less frequently on the tubules of the juxtaglomerular region.

Animals↗
PubMed1980

Cupular secretion by Xenopus laevis line organs: autoradiographic evidence for incorporation of 3H-glucose and 35S-sulfate.

Autoradiographic evidence for incorporation of 3H-glucose and 35S-sulfate into the cupulae of Xenopus laevis (African clawed toad) lateral line organs was obtained after injection into the dorsal lymph sacs of adult animals. Time intervals of 15 minutes to 4 hours after administration of these labeled metabolic precursors were used to examine the time course of the apparent mechanism of growth of the cupulae. Our results suggest that the two layers of accessory cells (the sustentacular cells and inner layer of mantle cells), concentrically arranged around the organ's central sensory (hair) cells, elaborate distinct cupular components. Sustentacular cells, immediately adjacent to the sensory cells, appear to produce and extrude at their exposed apices a cupular "core" substance labeled by 3H-glucose, but not by 35S-sulfate. The layer of inner mantle cells, external to the sustentacular cells, was labeled by both precursors and is spatially situated to secrete a cupular sheath enclosing the cupular core. Ultrastructural differences between the secretory products within the two cell types were marked. Electron microscopic autoradiography of toads killed 4 hours after 3H-glucose injection showed that silver grains were associated with accumulations of the respective secretory products in sustentacular and inner mantle cells, and label was found over the cupular trough area, where the bases of the cupulae are attached. These results suggest that the cupular core and sheath may both contain mucopolysaccharide, and the sheath, a sulfated mucopolysaccharide.

Animals↗
PubMed1980

Surfactant metabolism of newborn lamb lungs studied in vivo.

Surfactant, microsomal, and lamellar body fractions were isolated from the lungs of 5-day-old lambs 0.21-55 h after the intravenous injection of radiolabeled palmitic acid. The specific activities as cpm/mumol phospholipid phosphate of phosphatidylcholine, saturated phosphatidylcholine, phosphatidylglycerol, and phosphatidylethanolamine were measured. The palmitate-labeled phospholipids disappeared from the lung parenchyma with a half-life of approximately 50 h. The radiolabel disappeared from phosphatidylcholine, saturated phosphatidylcholine, phosphatidylglycerol, and phosphatidylethanolamine of microsomal fractions with initial half-life values of 4.5, 4.6, 1.9, and 23.9 h, respectively. The labeled phospholipids rapidly appeared in the lamellar body fraction and accumulated in the surfactant of the lambs in a linear fashion for 35 h. The curves for the labeling of surfactant with radiolabeled saturated phosphatidylcholine, phosphatidylglycerol, and phosphatidylethanolamine were similar to the curve for phosphatidylcholine.

Animals↗
PubMed1979

Localization of tritiated norepinephrine in the renal arteriolar nerves.

The innervation of the glomerular arterioles was investigated by light and electron microscopy autoradiography for localization of exogenous tritiated norepinephrine. By light microscopy accumulations of grains were seen associated with afferent arterioles and in lesser numbers with efferent arterioles and neighboring tubules. Accumulations of grains were noted to be in contact with juxtaglomerular granular cells. Electron microscopy autoradiography revealed that nearly two-thirds of the silver grains were on axons. Most of the label was on varicosities packed with small, clear and dense-cored, vesicles. Most varicosities, including those in contact with smooth muscle, juxtaglomerular granular or tubular cells, were labeled. Some varicosities which appeared unlabeled in a given section were labeled in subsequent sections. These findings are consistent with the notion that the glomerular arterioles are innervated mainly by adrenergic nerves. This view is supported by the previously reported observations of the concomitant virtual disappearance of fluorescent and acetylcholinesterase-positive nerves from the region of the glomerular arterioles after two injections of six-hydroxydoapmine (a drug which selectively destroys adrenergic nerves) and the presence of small dense-cored vesicles in all axons of the juxtaglomerular region when examined by serial section electron microscopy.

Adrenergic Fibers↗
PubMed1979

Anatomy of the juxtaglomerular apparatus.

The juxtaglomerular apparatus, located in the glomerular hilum, consists of a vascular component (afferent and efferent arterioles and extraglomerular mesangium) and a tubular component (macula densa). Two types of contact between vascular and tubular components are observed: a) a complex type, involving distal tubule, extraglomerular mesangium, and proximal efferent arteriole, and b) a simple type, consisting of apposition of the basement membranes of the vascular and tubular components. Juxtaglomerular granular cells, the source of renin, are present throughout the vascular component but are more numerous in the afferent arteriole. They can be considered as "myoendocrine" cells, since they contain myofibrils and attachment bodies, together with secretory granules and crystalline protogranules. Macula densa cells differ from those elsewhere in the distal tubule in that their nuclei are closer to each other, the Golgi apparatus is basally located, and their basal membrane infoldings are less prominent. Adrenergic nerves are demonstrable by fluorescence histochemistry in the juxtaglomerular region. Electron microscopy reveals unmyelinated nerve fibers containing small dense-cored vesicles and capable, as shown by ultrastructural autoradiography, of incorporating exogenous tritiated norepinephrine. Neuroeffector junctions occur between nerves and cells of the vascular and, less frequently, the tubular component. In addition, adrenergic axons are observed in a juxtaglomerular cell tumor. Nerve terminals are seen in direct contact with the tumor cells.

Acetylcholinesterase↗
PubMed1978

Juxtaglomerular cell tumor.

A 15-year-old female with primary reninism presented with benign hypertension, normokalemia, normal aortagram and normal intravenous pyelogram. The diagnosis was suggested only by a remarkably elevated plasma renin activity (PRA). Selective catheterization of renal vein branches was necessary to make the diagnosis of a tumor. A local resection of the tumor resulted in normalization of blood pressure and PRA. Prior to the definitive surgery, oral propranolol was effective in lowering PRA and blood pressure.

Adolescent↗
PubMed1978

Studies on the characterization of isolated renin-containing granules: the storage form of renin.

Renin-containing granules isolated by isopycnic zonal centrifugation were partially characterized biochemically. Extracts of the granules were found to have a dual pH optimum at 5.5-6.0 and 7.0-7.5 and possess linear time-dependence of product formation when reacted with homologous renin substrate. Extracts also possessed a first order reaction constant of 0.713 X 10(-2). Treatment of the extracts with ammonium sulfate increased the velocity of the renin/renin substrate reaction though it continued to be linear with respect to time. This partially purified renin preparation was found to have a Km=3.9 X 10(3) ng/ml. Gel filtration of this preparation of renin demonstrated the presence of an active protein with renin activity and a molecular weight of 59,000 daltons in addition to an inactive protein of molecular weight 13, 750 daltons which may be a potential inhibitor of the renin/renin substrate reaction. The former protein or "big renin" may be the storage form or porhormone state of renin within the renin-containing granules of the juxtaglomerular cells.

Angiotensin I↗
PubMed1978

Innervation of the renal cortex.

Morphologic studies of renal innervation have utilized the methods of histochemistry and electron microscopy. Much information has been derived from examination of the renal cortex in monkey and rat. Fluorescence histochemistry shows a rich adrenergic innervation. Acetylcholinesterase can be demonstrated histochemically in the renal nerves by light and electron microscopy. Studies in the rat using 6-hydroxydopamine, a drug that selectively destroys adrenergic nerves, indicate that the glomerular arterioles and surrounding tubules are innervated by adrenergic nerves containing acetylcholinesterase. Distinct neurovascular and neurotubular junctions are observed the electron microscope. They are anatomically consistent with being the sites of synaptic transmission. Ultrastructural analysis of serial sections reveals that single individual axons contact multiple vascular cells and renal tubules. We now have a considerable body of information concerning the morphology of renal innervation are are beginning to appreciate the role of the renal nerves in kidney function.

Acetylcholinesterase↗