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Biomedical subjects

J A Carr

Publications and source records attributed to J A Carr.

52 records · Page 3Linked to original sources
PubMed1993

Plasma catecholamine and corticosterone and their in vitro effects on lizard skeletal muscle lactate metabolism.

Lizard skeletal muscles utilize primarily lactate as a gluconeogenic substrate for glycogen replenishment following exercise. To understand the influence of selected hormones on this process, we measured changes in plasma catecholamines and corticosterone resulting from exercise in the lizard Dipsosaurus dorsalis and then investigated the physiological effects of those hormones on skeletal muscle lactate and glucose metabolism in vitro. Plasma epinephrine (Epi), norepinephrine, and corticosterone (Cort) increased 5.8, 10.2, and 2.2 times, respectively, after 5 min of exhaustive exercise. Epi and Cort levels remained elevated after 2 h of recovery. Skeletal muscle fiber bundles isolated from the red and white regions of the iliofibularis muscle were incubated 2 h at 40 degrees C in the presence of postexercise concentrations of [14C]lactate (15 mM) and glucose (8.5 mM) in the presence and absence of Epi or Cort. Red muscle oxidized both substrates at 2-3 times the rate of white muscle, and both red and white fibers oxidized lactate at 5-10 times the rate of glucose oxidation. Epi had a stimulatory effect on lactate oxidation by white muscle. Lactate incorporation into glycogen proceeded at 2-3 times the rate of glucose incorporation in both muscle types, with rates in red muscle again 2-3 times that for white muscle. Epi stimulated lactate carbon incorporation into glycogen by 50-140% in both red and white muscle but had no effect on glucose incorporation into glycogen in either tissue. We interpret these data as evidence that epinephrine stimulates lactate removal by skeletal muscle. Cort had no effect on lactate metabolism in either muscle type.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Monoamines and their metabolites in the amphibian (Ambystoma tigrinum) brain: quantitative changes during metamorphosis and captivity.

1. Monoamine neurotransmitters (epinephrine, norepinephrine, dopamine, serotonin and some of their metabolites (DOPEG, MHPG, DOPAC, 5-HIAA) were measured by HPLC in extracts from telencephalon (TEL) and diencephalon-midbrain (DM) before, during at the end of metamorphosis. 2. During metamorphosis MHPG increased and 5-HIAA decreased in TEL and DM while DOPEG decreased only in DM. 3. Monoamine levels were greater in the TEL and a larger increase in MHPG occurred there. 4. Captivity without metamorphosis also caused a significant depression of 5-HIAA in TEL and depression of DOPEG, MHPG and DOPAC in DM.

Ambystoma↗
PubMed1991

Organization of tyrosine hydroxylase-immunoreactive neurons in the di- and mesencephalon of the American bullfrog (Rana catesbeiana) during metamorphosis.

We examined the immunocytochemical distribution of tyrosine hydroxylase, the rate-limiting enzyme in catecholamine synthesis, in the di- and mesencephalon of developing bullfrog tadpoles. Special attention was given to catecholaminergic innervation of the median eminence and pituitary. In premetamorphic tadpoles, tyrosine hydroxylase-immunoreactive neurons were visualized in the suprachiasmatic and infundibular hypothalamus, the ventral thalamus, and midbrain tegmentum by Taylor-Kollros stage V. The number of labeled neurons in all these areas increased as metamorphosis progressed. By mid-prometamorphosis, labeled neurons appeared in the preoptic recess organ as well as in the posterior thalamic nucleus. The majority of cells in the preoptic recess organ, as well as occasional neurons in the suprachiasmatic nucleus, exhibited labeled processes which projected through the ependymal lining of the preoptic recess to contact cerebrospinal fluid. The modified CSF-contacting neurons of the nucleus of the periventricular organ were devoid of specific staining. By late prometamorphosis, labeled fibers from the suprachiasmatic nucleus were observed projecting caudally to enter the hypothalamo-hypophysial-tract en route to innervating the median eminence and pituitary. Labeled fibers arising from the dorsal infundibular nucleus projected ventrolaterally to contribute to catecholaminergic innervation of the median eminence and pituitary. Immunoperoxidase staining of tyrosine hydroxylase-immunoreactive fibers and terminal arborizations in the median eminence were restricted to non-ependymal layers, while labeled fibers in the pituitary were observed in the pars intermedia and pars nervosa. Staining of tyrosine hydroxylase-immunoreactive fibers in the median eminence and pituitary was sparse or absent in premetamorphic tadpoles, but became increasingly more intense as metamorphosis progressed.

Animals↗
PubMed1991

Interaction of corticotropin-releasing factor (CRF) and alpha-helical CRF on rat neurointermediate lobes: in vitro studies.

Neurointermediate lobes (NILS) of the pituitary glands of adult male Sprague-Dawley rats were incubated in media in the presence of corticotropin-releasing factor (CRF), a stimulator of proopiomelanocortin (POMC) peptide release. Alpha-helical CRF, a peptide known to inhibit CRF induced POMC peptide release from the anterior pituitary, was incubated with NILS for a period of 90 min, to study its potential ability to modulate peptide release from the intermediate lobe. The alpha-helical peptide reduced beta-endorphin release from NILS, as measured by radioimmunoassay (RIA), when added for the entire incubation, or when added 30 min after start of the incubation period, with CRF present. Alpha-helical CRF alone reduced beta-endorphin release, as compared to control or CRF-treated lobes. Ultrastructural examination of intermediate lobes fixed at the end of incubations revealed a reduction in the numbers of Golgi-associated dense granules, an indicator of new peptide synthesis, in intermediate lobe tissue treated with alpha-helical CRF alone, both peptides together, or with CRF followed by alpha-helical peptide. The in vitro studies demonstrate the effectiveness of the antagonist peptide on intermediate lobe peptide secretion, thereby extending its effects to both POMC-secreting areas of the pituitary gland.

Animals↗
PubMed1991

In vivo effects of serotonergic agents on alpha-melanocyte-stimulating hormone secretion.

We used an in vivo pharmacological approach to investigate the potential influence of serotonin (5-HT) on peptide release from the intermediate lobe (IL) of the rat pituitary. Plasma levels of alpha-melanocyte-stimulating hormone (alpha-MSH) as well as the ultrastructural appearance of IL cells were used as indicators of IL secretory activity. Plasma beta-endorphin levels were also measured to assess the effectiveness of 5-HT-acting drugs. Intraperitoneal administration of 5-hydroxy-L-tryptophan, the synthetic precursor of 5-HT, dramatically elevated the content of 5-HT in the neurointermediate lobe but did not alter plasma titers of alpha-MSH. Treatment with the 5-HT reuptake blocker fluoxetine elevated plasma levels of beta-endorphin but not alpha-MSH. Administration of the 5-HT1/5-HT2 agonist MK-212 produced an elevation in both plasma alpha-MSH and beta-endorphin levels. Quantitative morphometry of IL cells at the ultrastructural level revealed that MK-212 treatment selectively causes depletion of electron-lucent but not electron-dense secretory granules from the cytoplasm of IL cells. Pretreatment with the selective D2 dopamine agonist apomorphine blocked MK-212-induced release of alpha-MSH but not beta-endorphin. Our results show that manipulation of 5-HT synthesis/reuptake does not affect release of alpha-MSH, but that direct activation of 5-HT receptors with the nonselective agonist MK-212 stimulates alpha-MSH release. The ability of apomorphine to block MK-212-induced release of alpha-MSH suggests a direct antagonism between dopaminergic and serotonergic regulation of alpha-MSH release.

Animals↗
PubMed1990

Expression of cloned receptor subunits produces multiple receptors.

Expression in Xenopus oocytes of cloned nicotinic acetylcholine receptors (alpha, beta, gamma and delta subunits of BC3H1 receptor), produced more than one sort of functional receptor. This heterogeneity was detectable neither as heterogeneity in single channel conductance, nor as heterogeneity in the burst length. It was seen most obviously as differences from patch to patch in the maximum fraction of time for which the channels are held open at high acetylcholine concentrations, and it was also detectable as differences in the shut time distributions at low acetylcholine concentrations.

Acetylcholine↗
PubMed1990

Stress-induced peptide release from rat intermediate pituitary. An ultrastructural analysis.

We tested the hypothesis that acute restraint stress results in ultrastructural evidence for enhanced release of alpha-melanocyte-stimulating hormone (alpha-MSH) and beta-endorphin from the intermediate lobe (IL) of the rat pituitary. Measurements of plasma alpha-MSH- and beta-endorphin-immunoreactivity (ir) were used to confirm ultrastructural findings. Plasma alpha-MSH-ir was elevated after 20 and 30 min of restraint while plasma beta-endorphin-ir peaked 10 min after the onset of restraint. Ultrastructural analysis revealed a decrease in the content of secretory granules within IL cells of stressed rats. Analysis of Golgi-related immature secretory granules in IL cells indicated that new peptide synthesis was not enhanced after 30 min of restraint. These results confirm previous studies showing an elevation of plasma beta-endorphin and alpha-MSH-ir during acute restraint. Furthermore, these results indicate that quantitative analysis at the ultrastructural level can be used to assess peptide release from IL secretory cells during stress.

Animals↗
PubMed1990

Immunohistochemical localization of corticotropin-releasing factor- and arginine vasotocin-like immunoreactivities in the brain and pituitary of the American bullfrog (Rana catesbeiana) during development and metamorphosis.

Immunoperoxidase staining for corticotropin-releasing factor (CRF) in the median eminence was sparce or absent from premetamorphic tadpoles, but increased dramatically by late prometamorphosis. Quantitative photometry revealed that CRF-like immunostaining material in the median eminence was most dense in metamorphic climax tadpoles. Arginine vasotocin (AVT)-like immunostaining material was visualized in perikarya of the magnocellular nucleus, with extensive fiber staining seen in the medial basal and infundibular hypothalamus as well as in the median eminence and pars nervosa of the pituitary. AVT-like immunoreactive perikarya were virtually absent in premetamorphic tadpoles, but their number increased greatly by Taylor-Kollros stage XII and continued to increase after this stage. Quantitative photometry revealed that AVT-like immunoreactivity in the pars nervosa increased greatly at Taylor-Kollros stage XII and remained intense after this stage. AVT-like immunoreactivity did not appear in the median eminence until Taylor-Kollros stage XVI. Localization of AVT-like immunoperoxidase staining around portal vessels in the median eminence suggests an anatomical mechanism for delivery of AVT to anterior pituitary corticotropes. These results indicate that both CRF and vasotocinergic neuronal systems develop just before the activation of interrenal steroidogenesis which occurs during the later stages of metamorphosis in this species.

Adrenocorticotropic Hormone↗
PubMed1989

Detection of adrenocorticotropin-related and alpha-melanocyte-stimulating hormone-related substances in the anterior pituitary of larval and adult Ambystoma tigrinum (class: Amphibia).

Immunohistochemical analysis revealed the colocalization of ACTH-related immunoreactive forms and alpha-MSH-related immunoreactive forms in corticotropic cells of the anterior pituitary of larval Ambystoma tigrinum. Subsequent analysis of acid extracts of anterior pituitaries obtained from larval, neotene, and postmetamorphic adults indicated that the molar ratio of ACTH(1-39) to alpha-MSH was, respectively, 2.5:1, 1:1.5, and 1:1.3. However, in sexually mature adults the molar ratio of ACTH(1-39) to alpha-MSH was 8:1. These results indicate that before and immediately after metamorphosis, both ACTH(1-39) and alpha-MSH are major end products of corticotropic cells in this species. As postmetamorphic animals reach sexual maturity, ACTH(1-39) is a major end product of corticotropic cells and only trace amounts of alpha-MSH are produced. Thus in A. tigrinum the proteolytic processing of ACTH in corticotropic cells is developmentally regulated. The alpha-MSH-related peptide produced by the corticotropic cells appears to be an ACTH(1-13)amide-like form.

Adrenocorticotropic Hormone↗
PubMed1988

Interrenal activity during metamorphosis of the tiger salamander, Ambystoma tigrinum.

Plasma corticosterone concentrations were low in premetamorphic tiger salamander larvae (Norman Stage I; M. F. Norman (1985) Anat. Rec. 211, 102-109). Corticosterone levels were significantly elevated at midmetamorphosis (Norman Stage IV) but decreased at the end of metamorphosis (Norman Stage VII). Corticosterone levels remained low 2 weeks after metamorphosis. Interrenal 3 beta-hydroxysteroid dehydrogenase activity was low in premetamorphic larvae (Norman Stage I) but was significantly elevated by midmetamorphosis (Norman Stage IV) and remained elevated at the end of metamorphosis (Norman Stage VII). There were no significant changes in interrenal cell nuclear size during metamorphosis. There was a significant decrease in body weight as well as a significant increase in hematocrit accompanying metamorphosis. The increase in plasma corticosterone concentration seen during metamorphosis of the tiger salamander is accompanied by an increase in interrenal steroidogenesis.

Adrenal Glands↗
PubMed1987

Adenohypophysial-thyroid activity of the tiger salamander, Ambystoma tigrinum, as a function of metamorphosis and captivity.

The aim of this study was to determine the timing of adenohypophysial activation during metamorphosis of the tiger salamander, Ambystoma tigrinum. It consisted of two parts: 1) determination of plasma thyroid hormone concentrations and analysis of thyroid gland histology as a function of metamorphic stage and 2) analysis of the time-course of uptake of 125I by the thyroids during metamorphosis as an indicator of endogenous thyrotropin (TSH) levels. Significant increases in both triiodothyronine (T3) and thyroxine (T4) first were evident at the onset of metamorphic climax (stage II). Maximum levels of both hormones were not observed, however, until the completion of gill resorption (stage VII). No changes in thyroid histology were observed that could be unambiguously related to metamorphic transformation. The thyroids accumulated 125I in a slow but linear fashion in premetamorphic larvae (stage I). However, uptake exhibited a rapid peak during early climax (stage II), before maximum concentrations of thyroid hormones were observed. In addition, uptake was maintained above premetamorphic levels at stage VII, in conjunction with maximum levels of T4 and T3. Captivity alone produced a small but significant increase in plasma concentrations of T3. It produced no significant effect on either thyroid histology or uptake of 125I. These results indicate that adenohypophysial activation occurs rapidly and is maximal at the onset of metamorphic climax.

Ambystoma↗
PubMed1980

Flexible elastomer molds in burn scar control.

Burn scar hypertrophies and contractures have responded well to pressure techniques with pressure gradient burn garments except over soft tissue areas and concave body areas such as the axilla, hand, clavicle, neck, and face. Although these areas represent only 20 percent of the body area, when scarred from burns they pose perplexing functional and esthetic problems. Rigid splints and face masks have been used but their rigidity makes them uncomfortable for long-term wear. Silastic Medical Elastomer molds have proved highly successful in these areas when worn under pressure garments. They are flexible and of definite shape. The elastomer molds fill the concave gapping so that consistent definitive pressure can be maintained and scar hypertrophies prevented.

Burns↗
PubMedDate not supplied

Benzodiazepine suppression of corticotropin-releasing factor (CRF)-induced beta-endorphin release from rat neurointermediate pituitary.

Dopamine and gamma-aminobutyric acid (GABA) inhibit POMC peptide release from the pituitary intermediate lobe, via interaction with D2 or GABA-A/benzodiazepine receptors. Here, we examined the effects of an antianxiety triazolobenzodiazepine, adinazolam, on corticotropin-releasing factor (CRF)-stimulated POMC peptide secretion from the rat neurointermediate pituitary. Neurointermediate lobes (NILS) were incubated with CRF (10(-7) M), then adinazolam (10(-8) or (10(-9) M) was added, with CRF remaining in the medium. Aliquots were removed at 15-min intervals and frozen for radioimmunoassay of beta-endorphin. Adinazolam alone did not significantly affect secretion as compared to controls or CRF alone. Adinazolam incubated with CRF led to significant inhibition of beta-endorphin secretion, as compared to CRF alone. In addition, adinazolam was as effective as dopamine or the CRF antagonist, alpha-helical CRF, in preventing CRF-induced beta-endorphin release. Adinazolam appears to act directly on the pituitary to suppress hormone release induced by a stress-related hypothalamic peptide.

Animals↗
PubMedDate not supplied

Decrease in expenditures and selected nosocomial infections following implementation of an antimicrobial-prescribing improvement program.

OBJECTIVE: To evaluate changes in antimicrobial use and expenditures and the rates of selected nosocomial infections due to resistant organisms associated with implementation of an antimicrobial-prescribing improvement program. DESIGN: Before-after trial comparing 1992 (pre-program), 1993 (a transition year), and 1994 (after full implementation of the program). SETTING AND PARTICIPANTS: Academic medical center, all patients and physicians. INTERVENTION: An antimicrobial-prescribing improvement program with prior approval requirement for use of restricted agents. MAIN OUTCOME MEASURES: Antimicrobial use and expenditures, rates of selected nosocomial infection marker events. RESULTS: Between 1992 and 1994, there were substantial decreases in antimicrobial use, from 158,107 to 137,364 defined daily doses, and in expenditures from $2,486,902 ($24.01 per patient day) to $1,701,522 ($18.49 per patient day). After adjusting for changes in purchase prices and census days, we estimated savings attributable to the program of $279,573 in 1993 and $389,814 in 1994. In addition, we found significant decreases between 1992 and 1994 in the rates of enterococcal bacteremia (.34 vs .16 events per 1,000 patient days; P = .016), selected gram-negative bacteremia (.26 vs .11; P = .015), methicillin-resistant Staphylococcus aureus colonization or infection (.66 vs .20; P < .0001), and Stenotrophomonas colonization or infection (.35 vs .17; P = .019). No significant change occurred in rates of nosocomial candidemia or Clostridium difficile toxin-positive diarrhea. Values for 1993 were intermediate between those of 1992 and 1994. CONCLUSION: Implementation of an antimicrobial-prescribing improvement program was associated with substantial savings in antimicrobial use and expenditures and significant decreases in rates of selected nosocomial infections due to resistant organisms.

Anti-Infective Agents↗
PubMedDate not supplied

Stressors associated with coronary bypass surgery.

The purpose of this study was to: design and test an instrument to evaluate the incidence and severity of stressors associated with coronary bypass surgery and assess the concordance between patient and nurse perceptions of such stressors. The patient sample consisted of 30 patients recovering without complications from coronary bypass surgery. Patients were white, primarily male and employed, one-third with graduate education, with a mean age of 54. The nurse sample consisted of 18 registered nurses with cardiosurgical nursing care experience. A 30-item stressor scale was developed: 27 items were derived from literature review and 3 from comments of cardiovascular clinical specialists. Stressfulness of each item was rated on a 5-point scale. A pilot study with seven patients provided information for initial scale refinement. Content validity of the scale has both theoretical and empirical support because of the varied sources used to obtain and validate relevant items for the tool. Homogeneity reliability of the scale was supported by high coefficient alphas. Based on severity of stress ratings, two-way analysis of variance indicated that the cardiothoracic nurses generally rated all items as significantly more stressful for coronary bypass patients than did the patients themselves. Comparisons used by the nurses and the patients in assigning stressfulness ratings are discussed.

Adult↗