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L A Miller

Publications and source records attributed to L A Miller.

At least 145 records · Page 8Linked to original sources
PubMed1985

Segmental differences in pathways between crayfish giant axons and fast flexor motoneurons.

We have used electrophysiological techniques to document segmental differences in the pathways between the giant, escape command axons, lateral giants (LG) and medial giants (MG), and the nongiant, fast flexor (FF) motoneurons. We found no difference in the input from LG and MG axons to FF motoneurons in the posterior (4th and 5th) ganglia. Since flexor motor output in these segments would be inconsistent with the LG-evoked behavior pattern, this finding was puzzling. Electromyographic (EMG) recordings during escape responses by intact unrestrained animals confirm that the FF muscles innervated by the posterior ganglia are not excited during LG-mediated tailflips, but are excited during MG-mediated tailflips. In the 2nd and 3rd ganglia, the command axons fire the FF motoneurons with high probability, in part via electrical excitatory postsynaptic potentials (EPSPs) from premotor neurons, the segmental giants (SG). In the 4th and 5th ganglia, the equivalent pathway is much less effective. Single, directly elicited impulses in SGs in ganglia 2 and 3 fire their respective FF motoneurons with high probability, while those in ganglia 4 and 5 rarely fire FF motoneurons. The command axons fire the SGs reliably in all segments. The amplitude of the SG-evoked EPSP in FF motoneurons is significantly smaller in posterior vs. anterior ganglia. For technical reasons, we are unable to present conclusive evidence on ganglionic variations in FF-motoneuron thresholds. The FF motoneurons receive additional excitatory input from intersegmental interneurons recruited by the command neurons. Motoneurons in ganglia 4 and 5 are excited by large interneurons that do not synapse on motoneurons in ganglia 2 and 3, but this additional input is not sufficient to compensate for the weaker effect of SG input. Unlike the all-or-none segmental differences demonstrated previously for the LG-to-motor giant pathway (24), the SG-to-FF pathway changes gradually, retains significant though subthreshold strength in posterior ganglia, and is common to both LGs and MGs. These features provide opportunities for variation in the spatial patterning of flexion and in the resulting escape trajectories.

Animals↗
PubMed1984

Nadolol compared to propranolol for treating chronic stable angina pectoris.

In order to determine the relative efficacy and dose equivalency of propranolol four times a day and nadolol once daily for the treatment of stable angina pectoris, ten patients were studied in a double blind randomized placebo controlled crossover study. Total daily doses of propranolol and nadolol were determined by titrating until an equivalent degree of reduction in the heart rate response to exercise was achieved. At these doses, the treadmill exercise time to 0.1 mV of electrocardiographic ST-segment depression was increased from 248 +/- 75 seconds on placebo to 405 +/- 56 seconds on propranolol (p less than 0.05) and 471 +/- 46 seconds on nadolol (p less than 0.01). Also, the mean frequency of angina decreased from eight attacks per week on placebo to three on propranolol and nadolol (both p less than 0.05). In six of the ten patients, the effective total daily dose of propranolol and nadolol was identical, and the dose ratio for all ten patients was 1.17:1, propranolol to nadolol. However, individual dose titration is recommended when switching from propranolol four times a day to nadolol once daily because of the dosage variability noted in 40 percent of the patients.

Adrenergic beta-Antagonists↗
PubMed1983

Histaminergic mechanism for drinking elicited by insulin in the rat.

Sprague-Dawley male albino rats showed in a dose-response study a maximal drinking response to a 5 U/kg dose of SC insulin in a 2-hr test. Drinking elicited by 5 U/kg insulin was reduced to baseline (i.e., no insulin) level by combined antagonism of H1 and H2 receptors for histamine using IP 1 mg/kg dexbrompheniramine plus 16 mg/kg cimetidine. Antagonism of histamine receptors in this fashion was specific for drinking elicited by histamine because such antagonism reduced to baseline level drinking elicited by 2.5 mg/kg SC histamine, but failed to inhibit drinking after 8- or 24-hr water deprivation or drinking after 0.63 mg/kg SC serotonin (5-HT). These results demonstrate a histaminergic mechanism for drinking elicited by exogenous insulin which is consistent with the published report that exogenous insulin can release gastric mucosal histamine in the rat. Moreover, because eating is known to elicit the release of endogenous insulin, the results reported here suggest a working hypothesis that endogenous insulin is a component for drinking around mealtime in the rat.

Animals↗
PubMed1983

Diurnal variation for inhibition of eating by bombesin in the rat.

Sprague-Dawley male albino rats ate sweet milk at the midpoint of the day or night phase of a 12:12 light/dark cycle 1 min after IP 0.9% NaCl or synthetic bombesin (BBS; 2-32 micrograms/kg) following 24-hr food deprivation. Exogenous BBS inhibited food intake in a dose-related manner during the day; a linear regression line accounted for 85% of the total variance for percentage suppression of food intake by BBS in 30 min. In contrast, inhibition of eating by BBS at night was not dose-related; a linear regression line accounted for only 16% of the variance. Rats were tested under identical conditions following 3-hr food deprivation. Exogenous BBS (4-64 micrograms/kg) inhibited food intake in a dose-related manner at night; a linear regression line accounted for 92% of the total variance. In contrast, inhibition of eating by BBS during the day was not as orderly; a linear regression line accounted for only 44% of the variance. The 8 micrograms/kg dose was twice as potent for inhibition of eating of 25% GIBCO 116EC liquid diet than it was for inhibition of eating sweet milk at the midpoint of the day phase. These results describe diurnal variation in potency of exogenous BBS for inhibition of food intake in the rat. Whether BBS is more or less potent at night than during the day depends upon the particular dose, degree of hunger of the rat, and probably the type of food being eaten.

Animals↗
PubMed1982

Histamine-elicited drinking is dependent upon gastric vagal afferents and peripheral angiotensin II in the rat.

While transection of either the anterior (including hepatic) or posterior (including coeliac) vagal trunk failed to alter drinking in response to subcutaneous histamine (0.312--20 mg/kg), selective gastric vagotomy severely attenuated drinking after systemic histamine (1.25--40 mg/kg) in male Sprague-Dawley rats. The dose-response curve for rats with gastric vagotomy was shifted to the right. Vagotomy increased the threshold dose nearly tenfold and more than doubled the ED50. Because the effect of vagotomy on histamine-elicited drinking was not mimicked by cholinergic blockade of vagal efferents using atropine methyl nitrate (10 mg/kg), these results demonstrate that gastric vagal afferents are necessary for a normal drinking response to systemic histamine. When gastric vagotomy was combined with intragastric SQ14,225 (to inhibit the conversion of peripheral angiotensin I to angiotensin II) drinking after systemic histamine was abolished. These results suggest that gastric vagal afferents and angiotensin II are necessary for systemic histamine to elicit drinking in the rat.

Angiotensin II↗
PubMed1982

Nocturnal food-related hyperdipsia in the adult spontaneously hypertensive rat.

Male adult spontaneously hypertensive rats (SHR) ate the same but drank more and had a higher water to food ratio (W:F) than did Wistar-Kyoto (WKY) rats in 24-hr when they had continuous access to standard laboratory pellets and tap water. When rats ate in the day phase of a 12:12 light/dark cycle after 24-hr food deprivation, SHR rats ate and drank the same ad did WKY rats in a 60-min test. When the same rats ate at night after 24-hr food deprivation, however, SHR rats were hyperdipsic: They ate the same as did WKY rats, but SHR rats drank more and had a higher W:F. This relative hyperdipsia reflected the increased ability of ingestion of food to stimulate drinking in SHR, because when food was absent for a 60-min test at night SHR drank the same as did WKY rats. Three dipsogens which are candidate components for eating-elicited drinking in the rat, cellular dehydration, histamine and angiotensin II, elicited drinking differentially in SHR and WKY rats: SHR drank more than did WKY rats in response to (1) cellular dehydration produced by IP hypertonic saline, (2) large doses of SC histamine, and (3) SC angiotensin II. These results demonstrate that SHR exhibit a nocturnal food-related hyperdipsia which may reflect differential sensitivity to stimuli important for eating-elicited drinking such as increased osmolality and endogenous histamine or angiotensin.

Angiotensin II↗
PubMed1978

Ion transport in tonic and phasic vascular smooth muscle and changes during deoxycorticosterone hypertension.

The washout of radioisotopes was studied in aorta, femoral artery and portal mesenteric vein from controls and rats made hypertensive with injection of deoxycorticosterone (DOC) acetate. Experiments were also conducted on tonic (pulmonary artery) and phasic (portal mesenteric vein) smooth muscle from rabbits. The rate constants for the washout of 42K, 36Cl and 24Na from aorta were significantly elevated in the DOC hypertensives. Acute removal of extracellular K slowed the washout of 24Na by 50%, however, the rate constant for the DOC group remained higher than the controls. Increased turnover of 42K was also observed in the femoral artery and in a vessel (portal mesenteric vein) not exposed to the effects of high blood pressure in the rat. The rate constants for the washout of 42K, 36Cl and 24Na from phasic smooth muscle in rabbit were greater than the tonic type. Ouabain significantly slowed 24Na washout, however, the rate constant for the portal mesenteric vein remained higher than the pulmonary artery. DOC hypertension was associated with increased ion transport at several vascular sites. A similar change was observed for the phasic vascular smooth muscle from normal rabbits. A question is raised whether increased spontaneous activity of arteries reported to accompany DOC hypertension is the consequence of a membrane in transition from tonic to phasic behavior.

Animals↗
PubMed1973

Comparison of three culture media for isolation of Mycobacterium tuberculosis: a 6-year study.

Among 2,648 specimens positive on culture for Mycobacterium tuberculosis over a 6-year period, 82% grew on Lowenstein-Jensen medium (LJ), 79% on American Trudeau Society (ATS), and 56% on Middlebrook 7H10 (7H10). When these commercial culture media were compared in regard to the number of acid-fast bacilli seen on the original smears, LJ cultures were found to have the highest isolation rates for each smear category, and 7H10 had the lowest rates. Comparing the media from the aspect of number of mycobacterial colonies produced, LJ and ATS had the highest average colony counts, followed by 7H10. These findings were relatively constant over the 6-year period. One possible reason for the low positive rate of 7H10 was the lack of CO(2) enrichment.

Bacteriological Techniques↗