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Biomedical subjects

R Strong

Publications and source records attributed to R Strong.

At least 109 records · Page 6Linked to original sources
PubMed1986

Metabolic characteristics of aorta from spontaneously hypertensive and renal and deoxycorticosterone acetate-salt hypertensive rats.

The purpose of this study was to determine if any changes occurred in the basal and stimulated rates of oxygen consumption and lactate production of thoracic aortas from spontaneously hypertensive rats (SHR) and renal and deoxycorticosterone acetate (DOCA)-salt hypertensive rats, and, if so, whether these changes were similar in these three models of hypertension. Rings of thoracic aorta were placed in an isothermic (37 degrees C) muscle bath, and isometric tension development, oxygen consumption, and lactate production were measured. The results indicated that under basal conditions oxygen consumption, but not lactate production, was higher in aortas from all three hypertensive models; the elevation above control was greatest in the renal model (95%) and smallest in SHR (34%). On stimulation with 60 mM KCl, a significant increase in oxygen consumption above basal value occurred in all aorta samples (p less than 0.05); however, lactate production was increased above basal only in aortas from hypertensive animals. Only in aortas from renal and DOCA-salt models was the rate of oxygen consumption during stimulation significantly greater than that of their normotensive controls (p less than 0.05). Developed active stress in response to KCl was the same in all groups, and when the change in lactate production or oxygen consumption was expressed relative to the amount of active stress developed, no differences were observed. These results suggest that, 1) compared to values in aortas from normotensive animals, only the basal rate of oxygen consumption is higher; 2) this higher level of basal metabolic activity is not associated with an alteration in the metabolic cost of force development.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Comparison of the hepatic mixed function oxidase system of young, adult, and old non-human primates (Macaca nemestrina).

The influence of age on the mixed function oxidase system from a non-human primate was studied. Microsomes were isolated from the livers of female Macaca nemestrina ranging from 2 to 21 years of age. No significant age-related change was observed in either the cytochrome P-450 content or the NADPH cytochrome c reductase activity. In addition, the ability of the microsomes to metabolize benzo [a]pyrene did not change significantly with age. These observations contradict studies with liver tissue from laboratory rodents in which an age-related decline in the mixed function oxidase system is generally observed. The lipid composition of the liver microsomes was studied also. Both the cholesterol and total phospholipid content of the liver microsomes increased significantly with age; however, the ratio of cholesterol to phospholipid remained constant. The percentage of individual phospholipids in the microsomes changed only slightly with age. These results provide new information on the effect of age on the mixed function oxidase system and indicate that one must be cautious in extrapolating from studies with liver tissue from laboratory rodents to primates.

Age Factors↗
PubMed1985

Morbidity and mortality of operative intubation for malignant oesophageal obstruction.

In 33 patients who underwent operative intubation of carcinoma of the oesophagus or gastric cardia, there were nine postoperative deaths (mortality 27%). Only 15 patients (46%) had no further operative procedure or anaesthetics, but their mean survival was only 3.7 months. Nine patients (27%) required a total of 17 procedures after the placement of their original tube. Operative intubation has a similar mortality to resection but the survival times are short. Whenever possible palliative resection or endoscopic intubation is to be recommended.

Aged↗
PubMed1984

Changes in lipid composition of cortical synaptosomes from different age groups of mice.

Lipid composition of cortical synaptosomes differed with age in C57BL/6NNIA mice. Significant age differences were observed for cholesterol and the ratio of cholesterol to total phospholipid phosphorus content. The phospholipid to protein ratio of individual phospholipids also increased with age with diacyl-sn-glycero-3-phosphocholine (PC) increasing the most. Acyl group composition of individual phospholipids, however, showed little age difference. The double bond index for PC decreased significantly with age. Changes in membrane composition may help explain differences in the effects of ethanol on the physical and biochemical properties of membranes from different age groups that have been reported previously.

Aging↗
PubMed1984

Regional analysis of neostriatal cholinergic and dopaminergic receptor binding and tyrosine hydroxylase activity as a function of aging.

Tyrosine hydroxylase (TH) activity, as well as dopaminergic and cholinergic muscarinic receptor binding were measured in discrete regions of the neostriatum of rats 7, 17, and 27 months old. Activity of TH was highest in the rostral neostriatum as compared to the caudal region. Age-related differences in TH were detected in only one region. The density of dopamine receptors was also highest in the rostral neostriatum of all age groups, but there were no significant age-related differences. The distribution of cholinergic muscarinic receptor binding was similar to that of TH and dopaminergic receptors, and showed age-related changes in discrete regions. These results, when considered with previous data, suggest that in selected striatal regions in the Sprague Dawley rat the cholinergic system is more vulnerable than the dopaminergic system to aging effects.

Aging↗
PubMed1984

High-affinity uptake of neurotransmitters in rat neostriatum: effects of aging.

High-affinity uptake of dopamine (DA), glutamate, and gamma-aminobutyric acid (GABA) was determined in crude synaptosomal preparations from neostriatal regions of rats 7, 17, and 27 months of age. Dopamine uptake was highest in rostral neostriatum, but no age-related differences were detected. On the other hand, the high-affinity uptake of both GABA and glutamate was increased with age. This may reflect astrocytic hypertrophy or hyperplasia, which have been reported to occur in the neostriatum during the aging process.

Aging↗
PubMed1984

Membrane properties and aging: in vivo and in vitro effects of ethanol on synaptosomal gamma-aminobutyric acid (GABA) release.

It has been reported previously that biological membranes from aged mice are disordered less by ethanol as compared with membranes from younger animals. The purpose of this study was to determine whether those age differences would be associated with changes in membrane transport as measured by release of gamma-aminobutyric acid (GABA). GABA release in the presence and absence of ethanol was measured in synaptosomes from young (4 months), middle (14 months) and aged (28 months) C57BL/ 6NNIA male mice. In addition, the effects of chronic ethanol administration on GABA release was examined in young and aged mice. GABA release was inhibited more by ethanol in synaptosomes from young mice as compared with older mice. The IC50 for ethanol was significantly lower for the younger mice than for the older mice. GABA release in the presence of ethanol was affected by chronic ethanol administration. Inhibition of release was significantly less for young ethanol-tolerant as compared with young control animals. Release did not differ significantly between the old ethanol and old control groups. Inhibition of GABA release was found to be highly related to the membrane/buffer partition coefficient of n-alcohols. The results of the present study are consistent with our earlier finding that membranes from aged mice are disordered less by ethanol as compared with younger mice.

Aging↗
PubMed1983

The cholinergic system in rat striatum during morphine tolerance and dependence.

Male Sprague-Dawley rats were used in the present study to assess the effects of chronic treatment of morphine on the striatal cholinergic system. The results demonstrate that neither short nor long-term morphine treatment had an effect on choline acetyltransferase (ChAT) activity or 3H-quinuclidinylbenzilate (3HQNB) binding in discrete striatal regions of the rat brain.

Acetylcholine↗
PubMed1983

Ethanol-induced disordering of membranes from different age groups of C57BL/6NNIA mice.

In previous studies, we have shown that many of the pharmacological effects of ethanol administered in vivo are greater in older mice compared to younger mice. This study determined if there are age-related differences in membrane order when ethanol is administered in vitro. Synaptic plasma membranes, brain microsomal membranes and erythrocyte membranes were isolated from young (3-5 month), middle (11-13 months), and old (22-24 months) C57BL/6NNIA mice. The order parameter of each age group was measured using a 5-nitroxide stearic acid spin label in the presence of 0, 250 and 500 mM ethanol added in vitro. No age-related differences in order parameter were seen in the absence of ethanol. However, membranes from young animals were disordered to the greatest degree by ethanol. The synaptic plasma and erythrocyte membranes from young mice were disordered by both 250 and 500 mM ethanol. Membranes from old mice were disordered significantly by 500 mM ethanol only and the disordering was not as great as was seen in the membranes from the young mice. In the microsomal membrane preparation, 500 mM ethanol significantly disordered the membranes from the young animals, but it had no effect on membranes from old animals. Age differences were also observed generally for cholesterol and total phospholipid which both increased with increasing age for synaptic plasma and brain microsomes. Membrane disorder induced by ethanol differs with age and is associated with cholesterol and phospholipid content of membranes.

Age Factors↗
PubMed1982

Regional mapping of neostriatal neurotransmitter systems as a function of aging.

The purpose of the present investigation was to map chemically the distribution of certain neurotransmitter systems in the neostriatum of rats aged 6, 16, and 26 months. This mapping was carried out by microdissection of discrete striatal regions coupled with radiometric assays for choline acetyltransferase (ChAT), glutamate decarboxylase (GAD), dopamine (DA), and norepinephrine (NA). In all age groups, ChAT, DA, and NA were highest in the rostral relative to the caudal neostriatum. Additionally, ChAT was higher in the lateral than in the medial region, whereas GAD was more homogeneously distributed within the striatum. ChAT activity was decreased significantly primarily in the caudal regions in rats aged 16 and 26 months. DA levels were decreased in the caudal striatum in rats aged 26 months. NA levels were found to be significantly decreased primarily in the rostral neostriatal regions of the oldest rats. GAD activity remained unchanged in all age groups. These regional changes in selected neurotransmitter systems may underlie specific motor and cognitive deficits that often occur during aging.

Aging↗
PubMed1981

Impact of a cardiology data bank on physicians' prognostic estimates. Evidence that cardiology fellows change their estimates to become as accurate as the faculty.

To determine whether physicians would be influenced by the prognostic information in a large coronary artery disease data bank, cardiology faculty and fellows made initial estimates of the prognoses of their patients and then made revised final estimates after seeing the outcome of matched patients (OMP) from the data bank. The faculty cardiologists' original estimates proved to be as accurate as those of the data bank's OMP, and the faculty revised their estimates minimally in response to the data bank's OMP. Conversely, the cardiology fellows' original estimates were less accurate than the data bank's OMP, and under all observed circumstances the fellows responded more to the data bank's OMP than did the faculty. As a result, the accuracy of the fellows' final estimates was similar to the accuracies of both the faculty cardiologists and the data bank's OMP. Computerized data banks seem more likely to have impact when their information is provided to physicians who are relatively inexperienced with the disease in question.

Cardiology↗
PubMed1980

Age-related alterations in the rodent brain cholinergic system and behavior.

Pre- and postsynaptic cholinergic markers were studied in various brain regions of mice and rats aged 6 to 30 months in an attempt to determine whether alterations in this transmitter system occur during the normal aging process. Reliable decreases in cholinergic receptor binding and choline acetyltransferase (CAT) activity were found in the cerebral cortex and corpus striatum. These alterations in the cholinergic system were typically more consistent and robust than changes involving glutamic acid decarboxylase, and enzyme marker for GABA neurons. No statistically significant changes in any markers were found in the hippocampus of either species. Significant age-related changes in retention of passive avoidance learning and locomotor activity were also observed in these same animals. These findings demonstrate that changes in the cholinergic system occur naturally in aged mice and rats and that both the loss of cholinergic receptors and decrease in cat activity may contribute to the motor and mental impairments that often accompany old age.

Aging↗
PubMed1980

Phasic vagal influence on inspiratory motor output in anesthetized human subjects.

Vagal influence on inspiratory motor output was assessed in 20 normal subjects and in 12 patients with respiratory disorders under enflurane anethesia using the method of airway occlusion. The change in inspiratory duration during occlusion (delta TI) was measured from mechanical parameters (respiratory flow and tracheal pressure). In eight of the subjects, however, the effect of occlusion and augmentation of tidal volume was further evaluated from diaphragmatic electromyogram. In normal subjects delta TI (mechanical) averaged 0.15 s (range -0.1 to +0.77 s) and correlated with the duration of inspiration during occlusion. Electromyographic observations indicated that the change in neural TI exceeds the change in mechanical TI by approximately 0.2 s and that augmentation of tidal volume shortens TI with no apparent volume threshold. There was a tendency for vagal influence to be higher with restrictive lung disease and lower with obstructive airway disease. These observations indicate that a majority of humans display a significant vagal influence on TI in the spontaneous tidal volume range under anesthesia.

Aged↗
PubMed1979

A simple electrophoretic technique for the estimation of complement C3 conversion: specific application to the investigation of anaphylactoid response to I.V. agents.

A simple electrophoretic technique employing commercially available agarose films is described for the routine estimation of plasma complement C3 conversion. This technique has particular value in the investigation of anaphylactoid responses in patients following the administration of intravenous hypnotic drugs, plasma substitutes or radio-contrast media.

Alfaxalone Alfadolone Mixture↗