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T R Scott

Publications and source records attributed to T R Scott.

At least 19 recordsLinked to original sources
PubMed1992

Administration of satiety factors and gustatory responsiveness in the nucleus tractus solitarius of the rat.

The administration of certain factors associated with postprandial satiety decreases gustatory responsiveness. We compared the effects of intravenous injections of glucose, insulin, pancreatic glucagon (PG), and cholecystokinin (CCK) on multiunit activity evoked from taste responsive neurons in the nucleus tractus solitarius of rats. Glucose, insulin, and PG reliably suppressed evoked responses to lingual application of 1.0M glucose, whereas responses that followed CCK remained unchanged. A common physiological consequence of glucose, insulin, and glucagon is increased glucose availability which may impact directly on gustatory neurons or indirectly through modifications in ventral forebrain or vagal afferent activity.

Animals↗
PubMed1992

Taste neurons in the cortex of the alert cynomolgus monkey.

The activity of single neurons in the gustatory cortex of alert cynomolgus monkeys was analyzed. Taste-evoked activity in response to the four prototypical taste stimuli was recorded from a cortical gustatory area comprising the frontal operculum and adjoining anterior insula. Spontaneous activity for 364 gustatory neurons was 3.9 +/- 4.9 (mean +/- SD) spikes/s. Mean net (gross minus spontaneous) discharge rates for all gustatory neurons were: 1.0 M glucose = 4.9 +/- 11.6, 0.3 M NaCl = 3.2 +/- 7.1, M quinine HCl = 2.6 +/- 5.8, and 0.01 M HCl = 1.7 +/- 4.6. The results from intensity-response functions imply that the perception of each basic taste quality in the nonhuman primate is based on the activity of the appropriate neural subgroup rather than on the mean activity of all taste cells. Therefore a more meaningful index of the effectiveness of a stimulus may be the discharge rate it evokes from the subset of gustatory neurons for which it is the best stimulus. Glucose was the best stimulus for 142 cells (including ties), from which it elicited a mean net response of 10.3 spikes/s; NaCl was best for 107 neurons which gave a mean 8.7 spikes/s; quinine HCl evoked 6.2 spikes/s from the 74 cells that responded best to it; HCl elicited 5.9 spikes/s from the 49 neurons for which it served as best stimulus. The response characteristics of cortical taste cells indicate heterogeneous features, and significantly different patterns from those reported in other nonchemical sensory systems.

Animals↗
PubMed1992

Plasma cell proliferation in the chicken harderian gland.

Studies to examine the percentages of proliferating plasma cells (PPC) in the Harderian gland (HG) were carried out in chicks between 5 and 12 weeks of age. Two methods, 5-bromo-2'-deoxyuridine (BrdUrd) incorporation into DNA and flow cytometric analysis of propidium iodide (PI) stained cells, were employed in control and emetine dihydrochloride treated birds. Flow cytometric analysis of PI stained cells showed the percentages of plasma cells in S phase were highest between 6 and 8 weeks of age. After this period of time, the number of S phase plasma cells decreased and remained low through 12 weeks of age. The lowest percentages of plasma cells in G0 + G1 were found at 6 and 8 weeks of age, and all ages had equal percentages of plasma cells in G2 + M phase. After administration of the protein synthesis inhibitor emetine dihydrochloride a common pattern of plasma cell depletion and repopulation in the HG was observed. At 3 and 5 days post-treatment the plasma cell population in the gland decreased and by 7 days post-treatment repopulation of the gland with plasma cells had taken place. Anti-BrdUrd staining of frozen sections revealed that the number of PPC were decreased at 3 days after emetine treatment but were as high as, or higher than, controls at 5 and 7 days post-treatment. Flow cytometric analysis indicated that some birds were more severely affected by emetine. Namely, the percentages of plasma cells in S phase were lower at 3 and 5 days post-treatment. Even though most birds were severely affected by emetine treatment during the experiments, they possessed a cell population with the proliferative capacity to quickly repopulate the HG by 7 days post-emetine treatment.

Animals↗
PubMed1992

Responses of lateral hypothalamic glucose-sensitive and glucose-insensitive neurons to chemical stimuli in behaving rhesus monkeys.

1. Extracellular single neuron activity was recorded in the lateral hypothalamic area (LHA) of awake, behaving monkeys, with particular regard to the feeding-related functional characteristics of glucose-sensitive (GS) versus glucose-insensitive (GIS) neurons. Firing rate changes were recorded by means of carbon fiber, multibarreled glass microelectrodes during 1) microelectrophoretic application of various chemicals, 2) gustatory and olfactory stimulation, and 3) a high fixed-ratio schedule (FR) bar press feeding task. 2. In 336 neurons examined, 91 (27%) were suppressed by electrophoretically administered glucose, and so they were designated as GS cells. The 245 neurons (73%) in which the firing rates did not change during glucose applications were pronounced GIS. The 179 GS and GIS cells tested exhibited different responses to the catecholamines (CAs), noradrenaline (NA) and dopamine (DA), both of which are intimately involved in the control of feeding. More GS neurons responded to NA than did GIS cells; the predominant effect of both CAs on GS neurons was inhibition. 3. The taste responsiveness of 111 LHA neurons was examined. Fifty-seven cells (52%) showed responses to gustatory stimulation. Of 50 GS neurons tested, 33 (66%) exhibited firing rate changes to tastes. On the contrary, only 24 (39%) of the 61 GIS neurons examined responded to gustatory stimuli. Activity changes of GS neurons commonly occurred to two or more tastants, in distinction to the relative gustatory specificity shown by GIS cells. 4. Two hundred fifty-six (84%) of the 303 neurons tested responded during one or more phases of the bar press feeding task. Most activity changes occurred during the bar press (BP) and reward (RW) periods, however numerous phasic responses to cue light (CL) and cue tone (CT) were also observed. A higher proportion of the GS neurons showed task-related activity changes than did the GIS cells (77, 95% and 179, 81%, respectively). GS neurons responded more during the BP phase and to the food reward; GIS cells were more responsive during the CL that enabled acquisition and the CT that signaled reward. Thus GS neurons were responsive during the acquisition and consumption of reward, whereas GIS cells responded to external cues signaling both of these events. The gustatory neurons displayed specific task-related activity changes only in the CL (GIS cells) and BP phases (GS neurons), that is, in phases most intimately involved in sensory-motor integration. 5. Two-thirds of the 30 GS neurons tested were responsive to both gustatory and olfactory stimulation as opposed to only one-third of GIS cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1992

Gustatory neural coding in the monkey cortex: L-amino acids.

1. Single-neuron activity in the primary gustatory cortex of the alert cynomolgus monkey (Macaca fascicularis) was analyzed in response to a range of taste stimuli. Tastants included the four prototypical stimuli (glucose, NaCl, HCl, and quinine), fruit juice, and 12 amino acids selected for their chemical characteristics, nutritional significance, and biological importance, as well as for the availability of human psychophysical data on their perceived qualities. 2. Taste-evoked responses could be recorded from a cortical area that measured 3.5 mm in its anteroposterior extent, 2.0 mm mediolaterally, and 6.0 mm dorsoventrally. Gustatory cells constituted 4.8% of the 1,129 neurons tested. Nongustatory cells gave responses associated with mouth movements (11.1%), somatosensory stimulation (3.8%), approach or anticipation of the taste stimulus (2.2%), and tongue extension (0.4%). 3. The most effective taste stimuli were those with qualities that humans describe as salty or sweet: NaCl, monosodium glutamate, glucose, proline, glycine, and fruit juice. The least effective tastants were those rated bitter or insipid: tyrosine, tryptophan, phenylalanine, and leucine. Accordingly, 79% of the gustatory neurons responded best to glucose (46%) or NaCl (33%) among the basic stimuli; only 19% responded best to quinine (13%) or HCl (6%). One cell (2%) responded exclusively to fruit juice. 4. Cortical gustatory neurons showed a moderate breadth of sensitivity, with a mean breadth of tuning coefficient of 0.71 across 54 cells. There was no evidence of chemotopic organization in the taste cortex. 5. The taste quality of each stimulus was inferred from the relative similarity of the profiles they evoked. The clearest distinction among stimuli was between those that humans characterize as sweet versus those with other qualities. Several amino acids that have dominant sweet (glycine and proline), salty (arginine and monosodium glutamate), sour (tryptophan), or bitter (phenylalanine) components to humans evoked activity profiles that were associated with those of the appropriate prototypical stimuli. Others (cysteine and lysine) were not closely related to any single prototype. 6. Conclusions based on the responses of cortical cells in the monkey are in close agreement with those that derive from human psychophysical studies of L-amino acids, reinforcing the value of this neural model for human taste perception.

Amino Acids↗
PubMed1992

Plasma cells expressing immunoglobulins M and A but not immunoglobulin G develop an intimate relationship with central canal epithelium in the harderian gland of the chicken.

In the Harderian gland of the chicken, the epithelial and plasma cell relationships were studied by light and electron microscopy and immunohistochemical methods. In the wall of the central canal a dark epithelial cell was identified that had long branching cell processes. An anticytokeratin monoclonal antibody demonstrated that the dark cells provided an extremely large contact area for the plasma cells. Although IgM-, IgG-, and IgA-producing plasma cells were present in the Harderian gland, only IgM- and IgA-positive cells were capable of a distinct relationship with dark epithelial cells. The surface of the primary branches contained scattered IgA deposits whereas the epithelial cells of the secondary branches possessed IgA along the lateral cell membrane but not on the surface. Anti-IgA and anti-cytokeratin antibodies produced a similar staining pattern in the acini and secondary branches. Taken together, these observations suggest that IgA secretion is a function of secondary branches and that intracellular transport is influenced by the cytoskeletal system.

Animals↗
PubMed1992

Laparoscopic cholecystectomy: a review of 12,397 patients.

We reviewed the cumulative experience with laparoscopic cholecystectomy reported in the surgical literature, including 12,397 patients selected to undergo laparoscopic cholecystectomy, 95% of which were performed on an elective basis. Although the indications for operation varied, 90% of patients had evidence of cholelithiasis and biliary colic. Conversion to open cholecystectomy was required in 534 patients (4%); of these, 52% were converted because of acute or chronic inflammation or adhesions. Laparoscopic cholangiography was attempted in 3,696 of 9,231 patients (40%) and was successful in 84%. The incidence of major bile duct injury, minor bile duct injury, bile leak, and overall morbidity was 0.3%, 0.1%, 0.4%, and 4%, respectively. The mortality rate was 0.08%. Results from individual reports indicate that 54% to 98% of patients were discharged on the 1st or 2nd postoperative day, and 77% to 98% returned to full activity within 7 to 14 days. The incidence of bile duct injury, overall morbidity, and mortality compare favorably with published reports for open cholecystectomy. The collective data would also indicate that laparoscopic cholecystectomy is a safe and efficacious procedure that offers a viable alternative to conventional cholecystectomy.

Cholangiography↗
PubMed1991

Polysaccharides as taste stimuli: their effect in the nucleus tractus solitarius of the rat.

Rats show a pronounced preference for the tastes of starch-derived polysaccharides. Three of these compounds--Polycose, maltotriose and amylopectin--were used along with a standard array of chemicals in a study of their effectiveness as taste stimuli, as monitored by evoked single unit activity in the nucleus tractus solitarii (NTS). Maltotriose and amylopectin elicited very few spikes and no clear quality-related pattern of neural activity. Polycose, however, was an effective taste stimulus. It evoked an activity profile across neurons and over time that was poorly correlated with that of the prototypical sugar (sucrose) and only moderately related to those of the non-sugar prototypes (NaCl, HCl and quinine-HCl). The 14 cells (23%) that responded particularly well to Polycose were all members of neuronal subgroups that emphasized salt, acid and quinine sensitivity. Thus, despite the strong behavioral preference shown to Polycose, its neural profile is unlike those of other preferred stimuli. Polycose may represent a unique taste stimulus whose quality cannot be readily associated with those of the traditional 4 basic tastes.

Amylopectin↗
PubMed1991

The effect of amiloride on taste-evoked activity in the nucleus tractus solitarius of the rat.

Amiloride is an inhibitor of passive sodium transport. Its application to taste receptors blocks inward sodium current, suppresses sodium-induced neural activity and reduces the perceived intensity of NaCl. We recorded taste-evoked responses of single neurons in the nucleus tractus solitarius (NTS) of the rat before and after the lingual application of amiloride to determine which neurons would be affected, the degree of the effect and the subsequent form of the neural code for sodium. Responses to all 7 stimuli that contained Na+ or Li+ were suppressed by amiloride. Activity evoked by the 8 other stimuli was unaltered. NTS neurons could be divided into 4 subsets according to their response profiles: Group 1 (salt-sugar), Group 2 (salt), Group 3 (salt-acid) and Group 4 (acid-salt-bitter). The entire effect of amiloride was discharged on cells in Groups 1 and 2; those in Groups 3 and 4 were unaffected. Following amiloride application, the neural code for sodium and lithium salts was highly similar to those for acids, bitter salts and quinine. Thus the activity of neurons in Groups 1 and 2 may be responsible for the distinction between 'saltiness' and sour-bitter tastes. The results imply that specific receptors are responsible for the recognition and transduction of sodium salts and that this specificity is maintained in the peripheral taste nerves to be manifested in the NTS.

Amiloride↗
PubMed1991

Glutathione S-transferases YcYfetus and YcYc--kinetic and inhibitor studies relating to their glutathione peroxidase activities.

The kinetic properties of the glutathione (GSH) peroxidase activities of GSH S-transferases YcYfetus and YcYc were compared. The catalytic efficiency of the fetal iso-enzyme with cumene hydroperoxide as substrate was approximately four times higher than the other. The effects of the non-substrate ligand rose-Bengal as well as the substrate ligands sulphobromophthalein and acrolein on the GSH peroxidase activity of these two iso-enzymes were also investigated. Depending on the ligand, the inhibition profiles of these two iso-enzymes when measured with either the peroxidase substrate, cumene hydroperoxide or the standard GSH S-transferase substrate 1-chloro-2,4-dinitrobenzene were found to be either very similar (sulphobromophthalein) or markedly different (rose Bengal and acrolein). Significantly, the GSH peroxidase activity of the fetal iso-enzyme was far less susceptible to inhibition by the teratogen, acrolein, than that of the YcYc isoenzyme. It is therefore attractive to suggest that should a similar situation arise in vivo, this resistance to peroxidase inhibition may play a role in preventing the fetotoxic effects of acrolein.

Acrolein↗
PubMed1991

Taste and olfactory modulation of feeding related neurons in behaving monkey.

Single neuron activity in the monkey lateral hypothalamus (LHA) was recorded by multibarreled electrode during a bar press feeding task. Activity of glucose-sensitive (GS) neurons decreased during bar press (BP) and reward (RW) periods. The inhibition was caused by activation of beta-adrenoceptors and opioid receptors respectively. Glucose-insensitive (GIS) neurons were excited during BP and RW, and at cue light (CL). Excitation at CL and BP was caused by activation of dopaminergic receptors. Among GS neurons, 66% responded to taste and 88% to odor. These responses were 39% and 52% in GIS neurons. GS neurons responded predominantly to two or more taste and odor stimuli while GIS neurons responded to only one stimulant. GS neurons have dense mutual connections with the prefrontal area, and GIS neurons are connected with the motor area. Gustatory and olfactory stimulation elicited responses in 67% of GS neurons and in only 21% of GIS neurons. Data suggest that GS and GIS neurons may have different functions in feeding: GS neurons process endogenous chemical information and integrated chemical sensations, and GIS neurons process external information processing, motor control and discriminative chemical sensations.

Animals↗
PubMed1991

Genetic selection for aflatoxin B1 resistance influences chicken T-cell and thymocyte proliferation.

Studies were conducted with two lines of chickens that were selected for high and low plasma protein concentrations in response to aflatoxin B1 (AFB1) exposure. The experiments were designed to determine genetic differences in the responses of T cells and thymocytes to the toxin. Chicks were orally administered AFB1 at a rate of 0, 100, or 500 micrograms/kg body weight up to 21 days of age. At 4 weeks of age, concanavalin A (Con A, 2.5 micrograms/mL) stimulated T-cell proliferation was similar for untreated chicks from the low line (LL) and the high line (HL). However, AFB1 reduced the responses of T cells with HL cells being more sensitive. In a second experiment, immature chickens were bled and peripheral blood lymphocytes were cultured with Con A and either 0, 3.125, 6.25, 12.5, or 25 micrograms/mL AFB1. T cells from LL had greater responses to Con A than those from HL, and LL T-cells were also more resistant to in vitro AFB1 exposure. Furthermore, thymocyte proliferation was greater for LL chicks; but when thymocytes were cultured with 25 micrograms/mL AFB1, 3H-thymidine incorporation was similarly reduced in both lines. Cell cycle analysis indicated that there were more LL thymocytes in S phase, and the percentages for both lines decreased with AFB1 treatment. Although there were no differences between the lines for percent G2/M cells, AFB1 treatment increased the percentages of thymocytes in G2/M. These studies showed that selection for plasma protein response also changed T-cell and thymocyte proliferative activity.

Aflatoxin B1↗
PubMed1991

Gustatory neural coding in the monkey cortex: stimulus intensity.

1. We analyzed the activity of single neurons in gustatory cortex of alert cynomolgus monkeys in response to a range of stimulus intensities. Chemicals were deionized water, fruit juice, and several concentrations of the four prototypical taste stimuli: 10(-3)-1.0 M glucose, 10(-3)-1.0 M NaCl, 10(-4)-3 x 10(-2) M HCl, and 10(-5)-3 x 10(-3) M quinine HCl. 2. Taste-evoked responses could be recorded from a cortical gustatory area that measured 2.5 mm in its anteroposterior extent, 6.0 mm dorsoventrally, and 3.0 mm mediolaterally. Taste-responsive cells constituted 62 (3.7%) of the 1,661 neurons tested. Nongustatory cells gave responses associated with mouth movement (10.1%), somatosensory stimulation (2.2%), and approach or anticipation (0.9%). 3. Intensity-response functions were determined across 62 gustatory neurons. Neural thresholds for each stimulus quality conformed well to human psychophysical thresholds. Mean discharge rate was a direct function of stimulus concentration for glucose, NaCl, and quinine HCl. The most effective of the basic stimuli was glucose. 4. Power function exponents were calculated from the responses of neural subgroups most responsive to each basic stimulus. Those for glucose, NaCl, and quinine were within the range of psychophysically derived values. Thus the perceived intensity of each basic quality is presumably based on the activity of the appropriate neural subgroup rather than on the mean activity of all taste cells. 5. The mean breadth-of-tuning (entropy) coefficient for 62 gustatory neurons was 0.65 (range, 0.00-0.98). 6. There was no clear evidence of chemotopic organization in the gustatory cortex. 7. An analysis of taste quality indicated that sweet stimuli evoked patterns of activity that were clearly distinct from those of the nonsweet chemicals. Among the latter group, NaCl was differentiable from HCl and quinine HCl, whose patterns were closely related. 8. The response characteristics of cortical taste cells imply gustatory thresholds and intensity-response functions for the nonhuman primate that conform well to those reported in psychophysical studies of humans, reinforcing the value of this neural model for human taste intensity perception.

Action Potentials↗
PubMed1991

Gustatory neural coding in the monkey cortex: stimulus quality.

1. Extracellular action potentials were recorded from 50 single neurons in the insular-opercular cortex of two alert cynomolgus monkeys during gustatory stimulation of the tongue and palate. 2. Sixteen stimuli, including salts, sugars, acids, alkaloids, monosodium glutamate, and aspartame, were chosen to represent a wide range of taste qualities. Concentrations were selected to elicit a moderate gustatory response, as determined by reference to previous electrophysiological data or to the human psychophysical literature. 3. The cortical region over which taste-evoked activity could be recorded included the frontal operculum and anterior insula, an area of approximately 75 mm3. Taste-responsive cells constituted 50 (2.7%) of the 1,863 neurons tested. Nongustatory cells responded to mouth movement (20.7%), somatosensory stimulation of the tongue (9.6%), stimulus approach or anticipation (1.7%), and tongue extension (0.6%). The sensitivities of 64.6% of these cortical neurons could not be identified by our stimulation techniques. 4. Taste cells had low spontaneous activity levels (3.7 +/- 3.0 spikes/s, mean +/- SD) and showed little inhibition. They were moderately broadly tuned, with a mean entropy coefficient of 0.76 +/- 0.17. Excitatory responses were typically not robust. 5. Hierarchical cluster analysis was used to determine whether neurons could be divided into discrete types, as defined by their response profiles to the entire stimulus array. There was an apparent division of response profiles into four general categories, with primary sensitivities to sodium (n = 18), glucose (n = 15), quinine (n = 12), and acid (n = 5). However, these categories were not statistically independent. Therefore the notion of functionally distinct neuron types was not supported by an analysis of the distribution of response profiles. It was the case, however, that neurons in the sodium category could be distinguished from other neurons by their relative specificity. 6. The similarity among the taste qualities represented by this stimulus array was assessed by calculating correlations between the activity profiles they elicited from these 50 neurons. The results generally confirmed expectations derived from human psychophysical studies. In a multidimensional representation of stimulus similarity, there were groups that contained acids, sodium salts, and chemicals that humans label bitter and sweet. 7. The small proportion of insular-opercular neurons that are taste sensitive and the low discharge rates that taste stimuli are able to evoke from them suggest a wider role for this cortical area than just gustatory coding.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1991

Research note: T-cell activity of White Leghorn chickens selected for high and low antibody responses to sheep erythrocytes.

Mitogen responses of peripheral blood lymphocytes (PBL) and the cell cycle analysis of T-cells were examined for lines of chickens selected for high (HA) and low (LA) antibody response to SRBC. At 6 wk of age, within each line, blood samples and thymic tissue were collected from chicks representing the B13B13, B13B21, B21B13, and B21B21 genotypes. Although no influence of Ea-B haplotype on T-cell activity was detected in either line, there were line differences in phytohemagglutin-M (PHA-M) and concanavalin A (Con A) mitogen responses and the percentage G0/G1 and S phase T-cells. The HA PBL had greater in vitro PHA-M and Con A responses, and the cell cycle analysis of T-cells revealed a greater percentage of cells in S phase for Line HA chicks than for LA chicks. There were significantly more resting cells in the G0/G1 phase of LA than HA chicks. Although there was no Ea-B haplotype effect observed on T-cells from either line, generalized selection for high or low antibody response did result in divergent T-cell activity.

Animals↗
PubMed1990

Coding channels in the taste system of the rat.

Basic taste qualities are thought to be perceived independently, yet discrete neural coding channels have not been demonstrated in the central nervous system. The response profiles of taste cells in the nucleus tractus solitarius (NTS) of the rat were categorized into four groups, and the effects of amiloride, a passive sodium channel blocker, on each were determined. NTS neurons that responded specifically to sodium chloride (NaCl) or to NaCl and sugars were suppressed by amiloride; those broadly sensitive to salts, acids, and bitter stimuli were unaffected. Moreover, the response profile evoked by NaCl lost its distinctiveness after treatment with amiloride, becoming similar to those evoked by acids and quinine. Receptors that respond to sodium must relay their information through independent coding channels to identifiable subgroups of NTS neurons, the activity of which is responsible for the perception of saltiness.

Amiloride↗
PubMed1990

A method for gustatory stimulus delivery in awake rhesus monkeys.

A novel taste stimulus delivery technique along with a simple electronic onset marking system, designed for complex, neurophysiological-behavioral experiments in awake monkeys, are described. Intraoral implantation of a polyethylene tubing fistula enabled us to perform repeated, well-standardized application of various taste solutions to broad areas of gustatory receptors on the tongue, palate, pharynx and epiglottis while activity of single neurons was extracellularly recorded in behaving rhesus monkeys. By introducing an electronic marking onset and duration of the stimulation could be determined.

Administration, Oral↗