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Biomedical subjects

N G Moss

Publications and source records attributed to N G Moss.

At least 19 recordsLinked to original sources
PubMed1997

Static and dynamic responses of renal chemoreceptor neurons to intrapelvic pressure increases in the rat.

Multiunit afferent renal nerve activity (ARNA) and single unit activity from R2 chemoreceptors were recorded in anesthetized male Sprague Dawley rats during rapid and graded increases in intrapelvic pressure. Multiunit ARNA in 9 rats was excited by rapid intrapelvic pressure increases to 20 mmHg with non-diuretic urine (285.5 +/- 76.2% above control) but not when isotonic saline was used to fill the pelvis (13.0 +/- 9.0%). Similar responses were recorded from 27 single R2 chemoreceptors. Multiunit ARNA showed a direct, linear relationship with ramp increases in intrapelvic pressure between 0 and 20 mmHg at rates of 0.05, 0.15 and 0.3 mmHg/s. The responses were dynamically linked to intrapelvic pressure and maximum activations showed a positive linear relationship with the rate of pressure increase. Individual R2 chemoreceptor activity showed a similar dynamic relationship with intrapelvic pressure. ARNA was also excited by intrapelvic backflow of diuretic urine (10% expansion of extracellular volume) but the response in impulses/s was depressed by 58.6 +/- 9% in multiunit preparations and 30.1 +/- 10.8% for R2 chemoreceptors. Basal activities were also reduced during diuresis by 49.0 +/- 16% and 36.7 +/- 12.3% for multiunit and single unit preparations, respectively, and the percent increases over background during urine backflow were not different in non-diuresis and diuresis. Both multiunit ARNA and R2 chemoreceptors were also activated by ramp increases in intrapelvic pressure during diuresis, but the dynamic component was lost and responses to each pressure ramp were not different. The similarity in responses between multiunit ARNA and individual R2 chemoreceptors indicates that the multiunit ARNA activation during intrapelvic pressure increases is largely composed of activity from R2 chemoreceptors.

Animals↗
PubMed1997

Pressure, volume, and chemosensitivity in afferent innervation of urinary bladder in rats.

Bladder afferent nerve activity was recorded from the pelvic and hypogastric nerves of rats anesthetized with pentobarbital sodium. Bladder filling with isotonic NaCl at a rate of 250 microl/min excited multiunit afferent activity in the hypogastric nerve by 190 +/- 38% over background at a pressure of 30 mmHg, whereas 150 meq/l KCl at the same filling rate excited hypogastric nerve activity by 498 +/- 103% (P < 0.0001). This difference was localized to a group of chemosensitive fibers that are excited by bladder filling with KCl in a concentration-dependent fashion but are insensitive to bladder filling with NaCl. Bladder filling with 200 meq/l KCl at different filling rates caused a bursting pattern of discharge in these fibers at consistent bladder volumes but with a pressure threshold that increased proportionately with filling rate. Other hypogastric bladder afferent fibers were activated to a similar extent by NaCl and KCl solutions. Chemoreceptive bladder afferent fibers were rare in the pelvic nerve (1 of 15 units), and multiunit preparations showed comparable excitations during bladder filling with NaCl and KCl solutions. The bursting activation of bladder chemoreceptive afferent nerves in hypogastric nerves could signal noxious overdistension and/or inflammation of the bladder.

Afferent Pathways↗
PubMed1996

Age-related changes in calcitonin gene-related peptide and substance P in renal afferent nerve soma in the rat. Association with afferent renal nerve activity.

Renal afferent neurons were retrogradely labeled with FluoroGold in Sprague-Dawley rats at 50, 60, 70, 80, 90, 110, 130 and 200 days of age. Recordings of afferent renal nerve activity (ARNA) and immunofluorescent assessment of calcitonin gene-related peptide (CGRP)-like immunoreactivity (LI) and substance P (SP)-LI in spinal ganglia T10-L1 were obtained in the same rats. The frequency of renal afferent neurons positive for CGRP-LI declined abruptly from 88% in animals younger than 100 days of age (342 of 388 total cells) to 63% in rats older than 100 days of age (223 of the 353 total cells). The intensity of CGRP-LI (scaled 1-3) in renal afferent CGRP-positive neurons also declined significantly from a mean of 2.23 +/- 0.04 before 100 days to 1.48 +/- 0.05 in older rats (P < 0.001 in each age group). SP-LI positive neurons declined from 44% to 28% (P < 0.001). These changes in neuropeptide immunofluorescence coincided with an altered pattern of ARNA in which the excitatory response to complete renal ischemia increased from 274 +/- 69% above background to 1167 +/- 124% after the age of 100 days. Previous studies have shown that this alteration in the ARNA response to renal ischemia is due to the appearance of activity from R1 chemoreceptor nerves in ARNA. These data demonstrated that this transition in the electrophysiologic characteristics of ARNA is accompanied by profound alterations in CGRP-LI and SP-LI levels in renal afferent nerve cell bodies.

Afferent Pathways↗
PubMed1992

Age-dependent changes in afferent renal nerve activity in genetically hypertensive rats.

Multiunit and single-unit recordings of afferent renal nerve activity (ARNA) were obtained in anesthetized spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats between 35 and 150 days of age. Intrapelvic backflow of urine at 20 mmHg excited ARNA at all ages in SHR (152 +/- 18% above control) and WKY rats (262 +/- 24%). In SHR, complete renal ischemia was more excitatory in rats older than 120 days (1,233 +/- 103%, n = 8) than in younger SHR (317 +/- 28%, n = 42). Single-unit recordings showed that this was related to the appearance of R1 chemoreceptors in older SHR and coincided with a decline in the proportion of R2 chemoreceptors in the renal nerves. Other chemoreceptive responses were identified in single units that did not show complete R1 or R2 characteristics, some of which showed responses consistent with a transformation process from R2 to R1 receptor type. R1 chemoreceptors were not present in WKY rats studied up to 150 days of age and, unlike SHR, the proportion of R2 chemoreceptors did not decline with age. Accordingly, complete renal ischemia in WKY rats caused a comparable excitation in multiunit ARNA at all ages (285 +/- 33%, n = 43). Oral enalapril from weaning to 100 days of age prevented hypertension in SHR but did not impair the responsiveness of ARNA to any stimulus. In WKY rats, enalapril treatment for the same period resulted in exaggerated ARNA response to renal ischemia (1,250 +/- 377% above control).(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗
PubMed1990

Reduced renal perfusion pressure causes prostaglandin-dependent excitation of R2 chemoreceptors in rats.

The activity of multiunit preparations of afferent renal nerve activity (ARNA) and single R2 chemoreceptors was recorded during graded reductions in renal perfusion pressure (RPP) produced by tightening an aortic snare in anesthetized rats. In 13 multiunit preparations an initial RPP reduction from 117 +/- 2 to 101 +/- 2 mmHg caused ARNA to increase 29 +/- 5% above control. Further reductions in RPP produced a 65 +/- 11% increase in ARNA at 80 +/- 1 mmHg, 87 +/- 24% at 59 +/- 1 mmHg, and 127 +/- 38% at 37 +/- 1 mmHg (P less than 0.01 ARNA vs. RPP). Renal blood flow was measured by pulsed Doppler flowmeter in these rats and showed good autoregulation and minimal reduction (-4 +/- 2%) during the initial pressure drop. Ten single R2 chemoreceptors increased their firing rate by 129 +/- 4% when RPP was reduced from 109 +/- 2 to 85 +/- 2 mmHg and showed a peak response of 494 +/- 105% at 27 +/- 2 mmHg. The activity of 11 R2 receptors increased from 3.7 +/- 1.0 to 6.8 +/- 0.8 impulses/10 s when RPP was reduced from 112 +/- 4 to 79 +/- 2 mmHg. Prostaglandin blockade with indomethacin (6 rats) or meclofenamate (7 rats) caused a decrease in basal activity in the same units to 1.8 +/- 0.5 impulses/10 s and eliminated their excitatory response to a similar reduction in RPP (108 +/- 4 to 75 +/- 3 mmHg). These data support a role for R2 chemoreceptors in neurocirculatory reflexes elicited by reductions in RPP.

Afferent Pathways↗
PubMed1989

The neuropsychology of de novo patients with idiopathic Parkinson's disease: the effects of age of onset.

One hundred de novo patients with Parkinson's disease (PD) were classified into two groups according to age of onset of symptoms. Seventy two patients were under 70 years and 28 were 70 years and over. All patients were given neurological and neuropsychological assessments, and the severity of the signs was rated on a modified Columbia scale. The neuropsychological assessment was also administered to 50 age-and-education-matched controls. The neuropsychological test battery included tests of verbal learning, visual memory, verbal fluency, visuospatial skill, simple and choice reaction time, language and maze learning. The late-onset patients had significant impairment in nonverbal reasoning, auditory verbal learning, visual memory and choice reaction time in contrast to early-onset patients and controls. A relationship was found between bradykinesia and widespread cognitive impairment. Severity of tremor was found to be significantly correlated with impairment in auditory verbal learning, visual memory and increased choice reaction time, while rigidity was found to be associated with cognitive impairment in verbal fluency and visuospatial skill. Using DSM II criteria, 39% of the late-onset and 8% of the early-onset group were classified as demented. Dementia was more common in patients with bilateral symmetrical disease and in those patients with marked tremor and bradykinesia. The pattern of cognitive impairment in PD was consistent with that associated with a subcortical dementia. This study confirms that the expression of PD is markedly influenced by the age of onset.

Age Factors↗
PubMed1989

Electrophysiological characteristics of renal sensory receptors and afferent renal nerves.

The characteristics of afferent renal nerves are described. Renal baroreceptors are excited by increases in renal arterial pressure, venous pressure or interstitial pressure. Increases in intrapelvic pressure also excite renal afferent nerves though these have not been dissociated from renal tissue pressure receptors or renal chemoreceptors which are also excited by increased intrapelvic pressure with urine. The renal chemoreceptors are excited by renal ischemia, backflow of urine into the renal pelvis and pelvic perfusion with solutions of KCl. Injections of bradykinin and capsaicin also activate these receptors. These sensitivities are discussed with respect to other visceral afferent nerves and their role in renal nociception.

Afferent Pathways↗
PubMed1987

Electrophysiological characteristics of sensory mechanisms in the kidney.

R2 chemoreceptors are excited by backflow of urine or isotonic KCl into the renal pelvis, they do not respond to backflow of isotonic saline at the same intrapelvic pressure but are excited during periods of renal ischemia. R1 chemoreceptors are excited during complete renal ischemia but otherwise exhibit no activity. The responses of multiunit afferent renal nerve activity (ARNA) to these stimuli in Sprague Dawley rats follow the same patterns exhibited by R2 chemoreceptors, and the data do not support the presence of mechanoreceptive nerves which are excited by increases in intrapelvic pressure in these animals. The responses of multiunit ARNA in SHR and WKY rats were not different from Sprague Dawley rats. In contrast, while the response of WKY rats during renal ischemia was not different from Sprague Dawley rats the excitation of SHR during ischemia was more than 10 fold greater than that of the normotensive animals.

Afferent Pathways↗
PubMed1986

Prostaglandin blockade impairs denervation diuresis and natriuresis in the rat.

Acute unilateral renal denervation of control rats produced an ipsilateral diuresis (5.5 +/- 0.8 to 10.0 +/- 1.0 microliter/min, P less than 0.01) and natriuresis (579 +/- 202 to 2,668 +/- 225 neq/min, P less than 0.01) without a significant change in glomerular filtration rate or effective renal plasma flow. Inhibition of prostaglandin synthesis with indomethacin or meclofenamate (4 mg/kg iv) after acute unilateral denervation eliminated the diuresis (13.3 +/- 1.6 to 5.0 +/- 0.9 microliter/min, P less than 0.01) and attenuated the natriuresis (3,098 +/- 462 to 1,097 +/- 163 neq/min, P less than 0.01). Denervation diuresis and natriuresis were significantly impaired to the same extent when denervation was performed after inhibition of prostaglandin synthesis (3.2 +/- 0.3 to 4.9 +/- 0.4 microliter/min, NS; and 490 +/- 154 to 1,036 +/- 274 neq/min, P less than 0.05 vs. control, respectively). These results indicate that the natriuresis and diuresis seen after acute unilateral denervation in anesthetized rats are highly dependent upon prostaglandins and cannot be initiated or maintained when prostaglandin synthesis is impaired by indomethacin or meclofenamate.

Animals↗
PubMed1985

Intravenous cyclosporine activates afferent and efferent renal nerves and causes sodium retention in innervated kidneys in rats.

The effect of acute intravenous infusion of cyclosporine (10 mg/kg) on efferent renal and genitofemoral nerve activity and afferent renal nerve activity was studied in anesthetized rats. All animals were studied after unilateral renal denervation and extracellular fluid volume expansion. Activity of both efferent sympathetic nerves was increased significantly by cyclosporine infusion (renal, 69%; genitofemoral, 60%). Afferent renal nerve activity was increased 82% after cyclosporine (P less than 0.05). Urine flow rate and both absolute and fractional sodium excretion from the innervated kidney were reduced 50% after cyclosporine infusion (P less than 0.01). Absolute and fractional sodium excretion from the denervated kidney were significantly increased after cyclosporine. Infusion of vehicle had no significant effect on any measured variable in innervated or denervated kidneys. These studies demonstrate the capacity of cyclosporine to increase efferent sympathetic nerve activity and afferent nerve activity. It is also shown that sodium retention resulting from acute infusion of cyclosporine can be attributed to the increase in efferent renal nerve activity.

Afferent Pathways↗
PubMed1985

Electrophysiology of afferent renal nerves.

The electrophysiological characteristics of afferent renal nerves (renal mechanoreceptors [MR] and renal chemoreceptors [CR]) are discussed with reference to the literature on this subject published in the last 25 years. Recent information gained from histochemical and electrophysiological studies is provided in a description of the central projections of these nerves. The electrophysiology of renal MR is discussed in the context of their location within the kidney and the mechanical stimuli that lead to their excitation. Arterial, venous, tissue, and ureteral locations are considered. The special characteristics of renal CR are described and the stimuli responsible for their activation are discussed.

Acetylcholine↗
PubMed1984

Child therapy groups: in the real world.

In an inner city university outpatient clinic, group leaders used the literature for guidance and for goal setting, but they often worked with children and their families under less than ideal circumstances to provide needed support and facilitate change. Even without the desired continuity of leadership and consistent structure, they found that an ongoing middle childhood group could continue its task of laying the groundwork for basic changes in children. Children with a variety of problems continued to build relationships, deal with feelings and modify behavior in a supportive atmosphere throughout a chaotic summer.

Adolescent↗
PubMed1982

Renal function and renal afferent and efferent nerve activity.

Recent microperfusion studies have fully substantiated the direct action of catecholamines on renal tubular reabsorptive rates. Surprisingly, these techniques have not provided consistent information on the nature of the adrenoceptor responsible for the stimulation of proximal tubular reabsorption. Both alpha- and beta-receptors have been favored for this role. These techniques have confirmed earlier reports that dopamine may have a direct natriuretic action on the renal tubules. The demonstration that renal efferent nerves contain both noradrenergic and dopaminergic fibers lends further support for the participation of dopamine in the regulation of salt and water excretion. Efferent renal nerve activity is modulated by a number of different afferent inputs to the central nervous system. One of these is the renal afferent innervation, which is composed of both chemoreceptor and mechanoreceptor fibers. A number of different reflexes that affect efferent renal nerve activity have been identified by electrical stimulation of renal afferent nerves or by selective stimulation of renal mechanoreceptors and chemoreceptors. These renorenal reflexes may have importance in the coordination of excretory activity between the two kidneys. Studies of these aspects of renal nerve function are reviewed. The importance of the renal nerves in conscious animals is also discussed in the light of evidence that their influence on renal function may be more apparent in abnormal or pathological circumstances.

Afferent Pathways↗
PubMed1981

Renal chemoreceptors.

A study of the renal receptors and types of stimuli which give origin to supraspinal and spinal-mediated autonomic reflexes is presented. Multiunit and single unit recordings from the afferent renal nerves of male Sprague-Dawley rats have revealed two groups of renal chemosensitive receptors (chemoreceptors). These we have called renal R1 and R2 "chemoceptive" receptors. R1 receptors do not have a resting discharge but are activated after 38.7 +/- 3.3 (S.E) sec (n = 40) of complete renal ischemia (occlusion of the renal artery). Other activating stimuli are associated with a marked impairment in renal blood flow (prolonged occlusion of the renal vein and the hypotension of systemic asphyxia or hemorrhage). Their discharge is characterized by trains of impulses which cease abruptly upon re-entry of blood into the kidney. They are not responsive to increases or decreases in renal perfusion pressure or to increases in renal venous or ureteral pressure. In contrast, R2 receptors have a resting discharge and respond vigorously to backflow of normal urine (nondiuretic) into the renal pelvis. The results of the backflow into the pelvis of different test solutions (diuretic and nondiuretic urine, 1 M urea, 1 M mannitol and solutions of NaCl and KCl) indicate that this response is dependent upon the composition of the fluid bathing the renal pelvis rather than the increase in pelvic pressure or pelvic distension. The resting discharge rate is highest in nondiuretic conditions and declines substantially after diuresis is induced by extracellular volume expansion. R2 receptors are also activated by renal ischemia produced by clamping the renal artery. It is concluded that these two groups of afferent sensory units are renal chemosensitive receptors, (chemoreceptors) which respond to the chemical environment of renal interstitium.

Afferent Pathways↗
PubMed1980

Functional evidence for renorenal reflexes in the rat.

Acute left renal denervation in anesthetized volume-expanded rats produced an ipsilateral diuresis and natriuresis in 19 animals. A simultaneous decrease of glomerular filtration rate, p-aminohippurate clearance, urinary volume (P < 0.002), and percentage of filtered sodium excreted (4.0 +/- 0.6 (SE) vs. 1.9 +/- 0.4%, P < 0.003) occurred in the right innervated kidney in 10 rats. Prior denervation of the right kidney in the other nine rats prevented the renal hemodynamic changes and the fall of urinary volume and of sodium excretion (3.9 +/- 0.6 vs. 4.3 +/- 0.5%) by the right kidney after left renal denervation. Nerve traffic to the right kidney was measured in six other animals after left renal denervation and was found to increase to a mean value 33.8 +/- 6.3% above control levels (P < 0.007) 0-30 min after denervation, with a further significant increase to 66.2 +/- 16.1% above control levels (P < 0.025) 30-60 min after denervation. These results indicate that the functional changes in the right kidney after contralateral renal denervation in volume-expanded rats are caused by a reflex increase in nerve traffic to the right kidney, possibly as a consequence of an interruption of afferent nerve activity originating in the left kidney.

Animals↗
PubMed1978

Renal chemoreceptors in the rat.

There are afferent nerve fibers responsive to alterations of the kidney's chemical environment in the renal nerves of the rat. In anesthetized, artificially ventilated, male Sprague-Dawley rats, single unit recordings were prepared by dissection of the centrally cut nerves of the right kidney. The stimuli used included occlusion of the renal artery, systemic asphyxia, changes in renal arterial and venous pressures, changes in ureteral pressure, and cyanide infusion. We found a population of sensory nerve fibers whose endings are activated only during markedly impaired renal blood flow (produced by clamping the renal artery, severe hypotension below 40 mm Hg, and prolonged occlusion of the renal vein), and during systemic asphyxia. The same units are not responsive to increases and decreases in systemic arterial pressure (range: 40--190 mm Hg), to ureteral pressure (range: 0--50 mm Hg), or to changes in renal venous pressure. None of the 40 single units studied was spontaneously active; their pattern of activation during renal ischemia always was characterized by trains of impulses. These sensory units have functional properties distinctly different from those of known renal mechanoreceptors. They appear to be a homogeneous group of sensory elements, and we have termed them renal ("R") chemoreceptors. Evidence also is presented which is consistent with the concept that a chemical substance released by or accumulated within the kidney might be the agent activating these chemoreceptors during renal ischemia.

Animals↗