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Biomedical subjects

R C Rogers

Publications and source records attributed to R C Rogers.

At least 55 records · Page 3Linked to original sources
PubMed1995

Effects of pregnancy and progesterone metabolites on regulation of sympathetic outflow.

1. Pregnancy is characterized by a 40% increase in blood volume and cardiac output, a decrease in arterial blood pressure and thus a substantial decrease in total peripheral resistance. The aims of the experiments described in this manuscript were: (i) to determine if pregnancy resulted in alterations in baroreflex control of sympathetic outflow; and (ii) to evaluate possible mechanisms for pregnancy-induced changes in control of sympathetic outflow. 2. Arterial baroreflex control of efferent renal sympathetic nerve activity was examined in female pregnant and non-pregnant normotensive Sprague-Dawley and Wistar-Kyoto rats. In both rat strains, pregnancy was associated with a decrease in baseline arterial pressure, a shift in the baroreflex function curve to a lower operating pressure range and an attenuated ability to reflexly increase sympathetic outflow above baseline levels during a hypotensive challenge. Pregnant Sprague-Dawley rats retained their ability to respond to a hypertensive challenge, whereas pregnant Wistar-Kyoto rats exhibited a decreased sensitivity to hypertensive as well as hypotensive challenges. 3. The inhibitory amino acid transmitter, GABA, mediates baroreflex sympatho-inhibition within the rostral ventral lateral medulla (RVLM) of the brainstem. Since 3 alpha-OH dihydroprogesterone (3 alpha-OH-DHP), a major metabolite of progesterone, is elevated in pregnancy and has been reported to potentiate central nervous system GABAA inhibitory responses, experiments were performed to determine if effects of this metabolite of progesterone could contribute to the pregnancy associated changes in control of sympathetic outflow.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Vagovagal reflex control of digestion: afferent modulation by neural and "endoneurocrine" factors.

Vagovagal reflex control circuits in the dorsal vagal complex of the brain stem provide overall coordination of gastric, small intestinal, and pancreatic digestive functions. The neural components forming these reflex circuits are under substantial descending neural control. By adjusting the excitability of the differing components of the reflex, significant alterations in digestion control can be produced by the central nervous system. Additionally, the dorsal vagal complex is situated within a circumventricular region without a "blood-brain barrier." As a result, vagovagal reflex circuitry is also exposed to humoral influences, which can profoundly alter digestive functions by acting directly on brain stem neurons.

Afferent Pathways↗
PubMed1995

Intracisternal rat pancreatic polypeptide stimulates gastric emptying in the rat.

Pancreatic polypeptide (PP) has been shown to alter gastrointestinal functions, including increased gastric acid secretion and motility following brain stem injections of PP. The present study investigated the effect of an intracisternal injection of PP on the rate of gastric emptying. Additionally, the efficacy of the rat and bovine forms of the peptide was compared. Rats anesthetized with ether received an intracisternal injection of rat PP, bovine PP, or vehicle and, upon regaining consciousness, were fed a liquid test "meal." Intracisternal rat PP produced a marked enhancement in gastric emptying compared with control animals. Bovine PP, at doses equimolar to or three times greater than the effective rat PP dose, produced no change in gastric emptying. Pretreatment with systemic atropine prior to central injection of rat PP eliminated the stimulation of emptying, suggesting that PP acts through a cholinergic mechanism. When equimolar doses of rat or bovine PP were microinjected directly into the dorsal vagal complex, the region containing PP receptors, both were capable of stimulating antral motility. The response to bovine PP, however, was delayed and reduced compared with that seen following rat PP. The results suggest that rat PP strongly stimulates gastric emptying in rats and that bovine PP, depending on the route of administration, is either ineffectual or a weaker agonist for central PP receptors.

Animals↗
PubMed1995

Central inhibitory action of peptide YY on gastric motility in rats.

Specific peptide YY (PYY) binding sites have recently been identified autoradiographically in the area postrema, nucleus of the solitary tract, and dorsal motor nucleus regions [collectively referred to as the dorsal vagal complex (DVC)] in rats. These medullary brain stem regions are responsible for vagovagal reflex control of gastric function, including gastric motility. We propose that PYY can modulate gastrointestinal functions, such as gastric motility, by interacting with PYY binding sites found in DVC. Furthermore, we predict that central PYY effects on gastric function are mediated by the vagus nerve. In the present study, urethan-anesthetized rats were used. PYY (20.0 and 2.0 fmol) injected directly into DVCs of the animals produced significant inhibition of gastric motility that was stimulated by centrally applied thyrotropin-releasing hormone (TRH). TRH is a well-accepted central stimulator of vagal efferent pathway to the stomach. Otherwise, an excitatory effect of PYY (2 pmol) on basal gastric motility was observed and considered as being pharmacological. The inhibitory effect of PYY was abolished completely by unilateral (the injection side) cervical vagotomy, suggesting that the inhibition was vagally dependent. These results support the view that physiological concentrations of PYY may inhibit proximal gut function as part of the "ileal brake" mechanism by acting directly on vagovagal control circuits in the dorsal medulla. However, extremely high doses of PYY may activate gastric function through pharmacological action at pancreatic polypeptide receptors in the DVC.

Animals↗
PubMed1995

Pancreatic polypeptide stimulates gastric acid secretion through a vagal mechanism in rats.

The present study examined the effect of pancreatic polypeptide (PP) on gastric acid secretion. A 45-min infusion of PP was delivered into the jugular vein of urethan-anesthetized rats. Rat PP (100 pmol) significantly increased acid secretion over baseline; bilateral cervical vagotomy or peripheral atropine both eliminated this acid response. Neither intraperitoneal infusion nor close intra-arterial infusion of 100 pmol PP into the gastric circulation altered acid secretion. These results suggest that although PP requires intact vagal reflexes to stimulate acid output, it does not act on afferent or presynaptic efferent terminals of the vagus or directly within the stomach. Given that vagal reflexes consist of an afferent limb, an efferent limb, and a central relay, it may be that the target of circulating PP lies within the central nervous system. Indeed, previous studies from our laboratory have shown that microinjection of PP into the dorsal vagal complex results in long-lasting vagal-dependent elevation of gastric acid secretion.

Animals↗
PubMed1995

Unilateral renal agenesis.

Unilateral renal agenesis is a relatively common congenital urinary malformation that is usually diagnosed during fetal ultrasonography. Some cases of URA may represent involution of a previous MCDK. Unilateral renal agenesis may be an isolated congenital malformation or may be associated with chromosomal abnormalities or a variety of nonchromosomal syndromes including the VACTERL and MURCS associations. Congenital cardiac malformations are the most common malformations associated with URA. Girls with URA should have a pelvic ultrasound to look for abnormalities in the müllerian structures. Vesicoureteral reflux is the most common abnormality noted in the contralateral kidney. The prognosis of individuals with isolated URA is good. There are reports of hypertension and renal insufficiency in long-term studies of patients with a single kidney, and lifetime follow-up is recommended.

Aftercare↗
PubMed1994

Variations in the ospB gene of Borrelia burgdorferi result in differences in monoclonal antibody reactivity and in production of escape variants.

An escape variant of Borrelia burgdorferi, selected with a monoclonal antibody to OspB, expressed a truncated form of OspB, the result of point mutations in the ospB gene leading to a premature termination codon. A single amino acid position in the C terminus of OspB was critical for monoclonal antibody recognition. The variations in the ospB gene suggest a mechanism for the evasion of the immune response by these organisms and may also have implications for current diagnostic and vaccine efforts.

Amino Acid Sequence↗
PubMed1993

Brachmann-de Lange syndrome: diagnostic difficulties posed by the mild phenotype.

We describe 4 patients with facial changes of Brachmann-de Lange syndrome but without limb defects. Mental retardation ranged from moderate to severe and the degree of prenatal and postnatal growth deficiency was variable. These patients exemplify the diagnostic difficulties and counseling dilemmas posed by the mild Branchmann-de Lange phenotype. The relationship of the mild phenotype to the full syndrome will not be understood until the pathogenetic or causal factor(s) are delineated.

Adult↗
PubMed1993

Intramedullary connections of the gastric region in the solitary nucleus: a biocytin histochemical tracing study in the rat.

The local circuit neurons in the solitary nucleus that form part of a gastro-gastric vago-vagal reflex were examined using a biocytin/avidin-peroxidase histochemical tracing method in the male Long-Evans rat. Iontophoretic deposits of very small amounts of biocytin were made into the ventral commissural nucleus of the solitary tract (vcNTS) where the excitatory neuronal response to antral distension was recorded. The tracing study revealed substantial axonal projections from the vcNTS to the immediately subjacent dorsal motor nucleus of the vagus (DMN) as well as the parvocellular reticular formation (pcRF). Some axons also appeared to terminate on neurons of the nucleus retroambiguus (nRAm) in the same coronal plane as the injection site. Labeled NTS neurons in the immediate area of the injection site revealed a clear horizontally-oriented pattern of dendrites, some of which extended from the midline to the solitary tract. Some of these dendrites could be found within the walls of arterioles, the central canal or in the area postrema. This finding suggests that vcNTS neurons activated by antral inflation are probably influenced by a number of other neural and chemical afferent signals.

Animals↗
PubMed1993

Pancreatic polypeptide in dorsal vagal complex stimulates gastric acid secretion and motility in rats.

High concentrations of receptors for pancreatic polypeptide (PP), a pancreatic hormone, were recently discovered in the dorsomedial region of the dorsal vagal complex (DVC). We hypothesized that gastric acid secretion and motility, digestive functions strongly influenced by vagovagal reflexes organized within the DVC, would be affected by PP applied directly to this vagal sensorimotor integration area. After urethan-anesthetized rats were prepared for antral motility recording or titrometric analysis of gastric acid output, phosphate-buffered saline or various doses of PP in phosphate-buffered saline were micropressure injected into the medial DVC. Injections of PP into the DVC produced significant, long-lasting, and dose-dependent increases in gastric acid secretion and antral motility. These gastric responses were blocked by bilateral cervical vagotomy and by atropine, suggesting that intramedullary PP stimulates vagal cholinergic pathways, resulting in enhanced gastric functions. Because PP is not synthesized within the central nervous system, these results point to a new mechanism whereby the digestive tract may modulate its own autonomic control: direct humoral action on vagovagal reflex circuits within the brain stem.

Animals↗
PubMed1992

Thyrotropin-releasing hormone analogue and serotonin interact within the dorsal vagal complex to augment gastric acid secretion.

The effects of serotonin (5HT) and a thyrotropin-releasing hormone (TRH) analogue, RX77368, on vagal control of gastric acid secretion were studied. Microinjection of RX77368 (0.66 pmol in 10 nl), but not 5HT (8 pmol in 10 nl), into the dorsal vagal complex (DVC) evoked a significant increase in acid output. When the same doses of RX77368 and 5HT were co-injected, the amount of acid secreted was significantly greater than that due to RX77368 alone. Thus, 5HT and the TRH analogue interact within the DVC to enhance vagal stimulation of acid secretion. The study suggests a possible functional significance of raphe TRH/serotonergic tracts projecting to the DVC.

Animals↗
PubMed1992

Impact of antral mechanoreceptor activation on the vago-vagal reflex in the rat: functional zonation of responses.

1. Activation of gastric sensory afferents alters gastric motor and secretory function via the gastric vago-vagal reflex. In this report, we investigated in the rat the impact of gastric mechanoreceptor activation on the brain stem components of the reflex, which are located in the dorsal vagal complex (DVC), i.e. the nucleus of the solitary tract (NTS) and the subjacent dorsal motor nucleus (DMN). 2. In our extracellular recordings of single-cell activity in the DVC, we observed a relation between the response to antral distention and the location of the cell in the DVC. Specifically, cells that were excited by antral distention (ON cells) were located dorsal to those that were inhibited (OFF cells) by the same stimulus (mean depth = 536 +/- 15 and 627 +/- 14 microns for ON and OFF cells, respectively). 3. For a subset of DVC cells, the location was marked by ionophoretic ejection of Pontamine Blue from the recording barrel. Histological analysis indicated that ON cells were located in the NTS, and OFF cells were located in the ventral NTS or within the boundaries of the DMN. Together, these data led to the hypothesis that ON and OFF cells are functionally different groups of neurones, i.e. ON cells may be NTS neurones, and OFF cells may be DMN neurones. We tested this directly by employing both an intragastric balloon and a non-traumatic vagal stimulating electrode to determine whether inflation-related cells were NTS or DMN cells via orthodromic and antidromic activation, respectively. 4. Almost all ON cells (12/13) were orthodromically activated by vagal stimulation, i.e. they were NTS neurones. One ON cell was antidromically activated, and therefore was a DMN neurone. Of the twenty-eight OFF cells that were encountered, ten were classified as NTS neurones because they were orthodromically inhibited by vagal stimulation. The remaining eighteen OFF cells were orthodromically inhibited and antidromically activated (i.e. DMN neurones). Thus, our results support the hypothesis that ON and OFF cells can be functionally distinct populations of neurones, in that almost all ON cells are NTS cells and approximately 2/3 of the OFF cells are DMN neurones. 5. The response to mechanoreceptor activation was different for NTS and DMN neurones. NTS cells were activated (55%) or inhibited (45%) by balloon distention of the stomach, whereas DMN cells were almost exclusively inhibited (95%) by this stimulus. This information provides insight into the organization of excitatory and inhibitory connections of the brain stem components that mediate gastric vago-vagal reflexes.

Animals↗
PubMed1992

Selection of an escape variant of Borrelia burgdorferi by use of bactericidal monoclonal antibodies to OspB.

Two immunoglobulin G (IgG) monoclonal antibodies (MAbs) to outer surface protein B (CB2 and CB6), affinity purified from mouse ascitic fluid, exhibited concentration-dependent inhibitory and bactericidal properties against Borrelia burgdorferi after a 24-h incubation period in spirochete medium. Fab fragments derived from these MAbs showed the same effects, indicating that they were not caused by agglutination of the organisms by the intact MAbs. The inhibition of spirochete growth in cultures containing MAbs was also detected by spectrophotometric analysis of the media. CB2 did not inhibit the growth of Borrelia hermsii or the BEP4 strain of B. burgdorferi, neither of which is recognized by the MAb. Affinity-purified IgG from hybridoma supernatants had similar effects on B. burgdorferi as the ascitic-fluid-derived IgG did, indicating that the inhibitory and bactericidal properties were not due to nonspecific toxic contaminants. The bactericidal properties of the MAbs were not complement dependent as there was none in the serum-free system. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of B. burgdorferi organisms surviving after exposure to CB2 revealed an escape variant which failed to express OspB. The continued presence of OspA in these escape variants indicates that the lack of OspB was not due to the loss of the plasmid which contains the genes for both of these proteins.

Animals↗
PubMed1992

Borrelia burgdorferi and other related spirochetes bind to galactocerebroside.

Spirochetes are agents of neurologic disease that may utilize specific neural cell surface molecules for adhesion. Borrelia burgdorferi, the etiologic agent of Lyme disease, bound to galactocerebroside (GalCer) in numbers that were two- to threefold greater than to ceramide and glucocerebroside, and four- to fivefold greater than to sphingosine, psychosine, sulfatide, cholesterol, and three membrane phospholipids. The adherence was greater to GalCer and ceramide with a higher content of alpha-hydroxyl fatty acids. Treponema phagedenis Reiter and Borrelia hermsii also bound to GalCer. The binding of B burgdorferi to GalCer was inhibited in a concentration-dependent manner by rabbit polyclonal and murine monoclonal antibodies to this glycosphingolipid component of myelin. The monoclonal antibody to GalCer also inhibited adhesion of the organisms to Schwann cells. Neither free D or L monosaccharides nor the lectin peanut agglutinin inhibited binding. Since B burgdorferi and other spirochetes cause neurologic disease, these results suggest a role for GalCer as a binding site in both the central and peripheral nervous systems.

Animals↗
PubMed1991

Dorsal medullary injection of atrial natriuretic factor (ANF) excites vagal efferents and inhibits gastric motility.

Atrial natriuretic factor (ANF)-immunoreactive fibers are found in the dorsal motor nucleus of the vagus (DMN) along with receptors for that peptide. Previous investigations showed that ANF injections into the DMN did not influence cardiovascular functions. Since the DMN is largely (but not exclusively) involved with the control of gastrointestinal functions, we hypothesized that ANF may act on gastric, rather than cardiovascular vagal efferents. Injections of ANF (20 pmol rat atriopeptin III in 20 nl) into the DMN evoked a vagally dependent reduction in gastric motility. In a separate electrophysiological study, 10 of 15 (66%) antidromically identified DMN neurons were excited by micropressure-applied ANF (25-500 fmol in 50-1000 pl). We propose that ANF-containing neurons in the DMN reduce gastric motility by activating vagal efferents that synapse with inhibitory neurons in the gastric enteric nervous system.

Animals↗