Biomedical subjects

S B Jones

Publications and source records attributed to S B Jones.

At least 73 records · Page 4Linked to original sources

PubMed1993

Involvement of central vs. peripheral mechanisms in mediating sympathoadrenal activation in endotoxic rats.

The contribution of central vs. peripheral mechanisms in mediating increases in plasma norepinephrine (NE) and epinephrine (Epi) during endotoxicosis were studied. Plasma catecholamine responses after endotoxin were assessed in conscious animals and in animals without central regulatory mechanisms (pithed rats). In conscious rats, endotoxin (1.5 mg/kg i.v.) induced a marked elevation in plasma NE after 90 min (3-fold), but elevations were not seen in pithed rats. Endotoxin also induced a profound increase (12- to 13-fold) in plasma Epi in conscious rats, but increases were less (2- to 3-fold) and delayed in pithed rats. These results suggest that central mechanisms are essential in plasma NE response to endotoxic challenge, whereas plasma Epi response involves both central and peripheral mechanisms, with the former being dominant. In conscious adrenal-denervated animals, plasma Epi was not elevated until 90 min postendotoxin. This delayed Epi elevation was approximately one-third of the maximal response observed in conscious adrenal-intact rats. In pithed adrenal-denervated rats, plasma Epi at 90 min postendotoxin was also increased to a level comparable to that in pithed adrenal-intact rats. These results imply that a significant fraction of peripheral release of Epi with endotoxicosis is nonneurogenic.

Adrenal Glands↗

PubMed1993

Regulation of procollagen metabolism in the pressure-overloaded rat heart.

To determine the molecular events responsible for the disproportionate accumulation of myocardial fibrillar collagens during sustained hypertension, we examined the in vivo rate of procollagen synthesis, collagen accumulation, and intracellular procollagen degradation 1-16 wk after abdominal aortic banding in young rats. These measurements were correlated with tissue mRNA levels for type I and type III procollagen polypeptides. Banded animals developed moderate, sustained hypertension and mild left ventricular hypertrophy. Increased type III procollagen mRNA levels were detected early after banding and persisted for the entire observation period. Disproportionate collagen accumulation without histological evidence of fibrosis was noted within 1 wk after hypertension induction. Fibrillar collagen accumulation at this time point resulted not from a major increase in procollagen synthesis, but rather a marked decrease in the rate of intracellular procollagen degradation. Interstitial fibrosis, however, was observed 16 wk after banding. Type I procollagen mRNA levels were increased six-fold, but only after 16 wk of hypertension. These results correlated well with the results of in vivo procollagen synthesis experiments at 16 wk, which demonstrated a threefold increase in left ventricular procollagen biosynthesis. We conclude that pretranslational as well as posttranslational mechanisms regulate fibrillar collagen deposition in the myocardial extracellular matrix during sustained hypertension.

Animals↗

PubMed1992

Arterial baroreflexes are not essential in mediating sympathoadrenal activation in conscious endotoxic rats.

We examined the contributions of arterial baroreceptor reflexes in mediating sympathoadrenal activation during endotoxicosis. Conscious rats with chronic sinoaortic denervation (SAD) or sham-operation (SHAM) were subject to endotoxin treatment (5 mg/kg, i.v.). Hemodynamic responses, renal sympathetic nerve activity (RSNA) and plasma catecholamines were assessed at different times post endotoxin infusion. In both SAD and sham groups, intravenous endotoxin injection induced a rapid and significant sympathoadrenal activation, as indicated by a parallel elevation of RSNA and plasma catecholamines. Such activation peaked 15-30 min following endotoxin and was sustained throughout the 2-3 h protocol. The early response of the sympathoadrenal system to endotoxin is more profound in SAD rats compared to sham rats. We propose that the afferent neural input from arterial baroreceptors is not essential in mediating sympathoadrenal activation during sepsis. The elimination of feedback buffering mechanisms with SAD may account for the augmented sympathetic response seen in SAD animals.

Afferent Pathways↗

PubMed1992

Posttranslational modifications in the amino- terminal region of the large subunit of ribulose- 1,5-bisphosphate carboxylase/oxygenase from several plant species.

A combination of limited tryptic proteolysis, reverse phasehigh performance liquid chromatography, Edman degradative sequencing, amino acid analysis, and fast-atom bombardment mass-spectrometry was used to remove and identify the first 14 to 18 N-terminal amino acid residues of the large subunit of higher plant-type ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) from Chlamydomonas reinhardtii, Marchantia polymorpha, pea (Pisum sativum), tomato (Lycopersicon esculentum), potato (Solanum tuberosum), pepper (Capsicum annuum), soybean (Glycine max), petunia (Petunia x hybrida), cowpea (Vigna sinensis), and cucumber (Cucumis sativus) plants. The N-terminal tryptic peptide from acetylated Pro-3 to Lys-8 of the large subunit of Rubisco was identical in all species, but the amino acid sequence of the penultimate N-terminal tryptic peptide varied. Eight of the 10 species examined contained a trimethyllysyl residue at position 14 in the large subunit of Rubisco, whereas Chlamydomonas and Marchantia contained an unmodified lysyl residue at this position.

Journal Article↗

PubMed1992

Calcitonin gene-related peptide (CGRP) and neuropeptide Y (NPY) levels are elevated in plasma and decreased in vena cava during endotoxin shock in the rat.

Calcitonin gene-related peptide (CGRP), a potent vasodilator, and neuropeptide Y (NPY), a potent vasoconstrictor and potentiator of norepinephrine-induced vasoconstriction, were examined in an animal model of endotoxin shock. Gram-negative bacterial endotoxin (lipopolysaccharide B from Salmonella enteritidis) was administered as a bolus (16.7 mg/kg, i.v.) to conscious, unrestrained rats, previously cannulated for blood pressure measurements and blood withdrawal. At 30 min, endotoxin caused 35-40 mm Hg drop in mean arterial pressure and significant increases in heart rate and plasma levels of glucose and lactate. By 3 hr, blood pressure had returned to near normal levels and remained normal until cardiovascular collapse at 4-6 hr (approximately 70% of the rats). Endotoxin elevated plasma CGRP levels by fourfold at 30 min and 22-fold at 3 hr. Of the organs tested, only vena cava showed significant decreases in CGRP levels. Endotoxin also elevated plasma NPY levels by 67% and decreased NPY levels in adrenal gland and vena cava at 30 min and 3 hr. The data suggest that both CGRP and NPY are released into the circulation during development of endotoxin shock in the rat. NPY may contribute to the compensatory mechanism, tending to bring arterial pressure back to normal levels during intermediate stages of endotoxemia. CGRP, because of its extremely high potency as a hypotensive agent, may contribute to the hypotension at both early and late stages during pathogenesis of endotoxin shock.

Animals↗

PubMed1992

Employer-based private health insurance needs structural reform.

This paper argues that certain structural barriers in our employer-based health insurance system inevitably mean failure by employers, private insurers, and physicians to produce a system that provides affordable health care and insurance to the entire population with a minimum of government regulation and intervention. Key barriers that lead to failure in managing the physician-patient transaction and the competition among health care/health insuring plans are described. Finally, the minimal scale of needed reform is discussed.

Cost Allocation↗

PubMed1991

Altered phospholipase activities related to alpha 1-adrenergic receptor supersensitivity of aortas from aldosterone-salt hypertensive rats.

Many of the concepts presented in this paper are summarized in Fig. 7. Some aspects are well supported while others are speculative. The operation of PLC in VSM is well established, and in some hypertensive models (AHR, SHRSP) PLC assays exhibited altered activation. Currently this pathway leading to the production of IP3 and DAG is considered to be the major regulator of Ca release from sarcoplasmic reticulum (SR) and Ca entry by channels (CaC). Regulation of PKC by [Ca]i and DAG is thought to play a major role in controlling Ca entry. PKC has also been proposed to regulate PLA2 as well as PLD in conjunction with elevated [Ca]i. An important issue to be resolved is whether receptor regulation of other lipases occurs independently of the PLC-[Ca]i-PKC axis. Currently information supporting receptor regulation is lacking for VSM, but few studies have been conducted. Our observation that NE stimulation of PLD activity occurs in VSM indicates that the control of VSM by biochemical messengers is much more complicated than previously proposed. This seemingly redundant pathway may allow VSM to use alternate substrates for producing PA and DAG than are readily available to PLC. It also allows PA to be produced directly without phosphorylation of DAG. Although the role of PA in the regulation of Ca entry was proposed earlier, definitive studies establishing this linkage are still required. Any PLD activity on PIP2 would produce biochemical messengers (PA, DAG) which could stimulate Ca entry without producing the messenger, IP3, associated with Ca release (inactive IP2 would be produced). If PLC and PLD were independently regulated by receptor-guanine nucleotide-regulatory protein (G-protein) complexes, this would offer the potential for some agonists to excite VSM by Ca release and Ca entry mechanisms while others may excite by Ca entry alone. This system would also circumvent the problem of limited substrate for cellular regulation of [Ca]i if PIP2 were the primary substrate. This limitation does not exist with other phospholipids such as phosphatidylcholine which is a preferred substrate for PLD. The presence of multiple phospholipases under separate receptor regulation allows for a wider range of tissue responses to various agonists, than a system which is linked only through the PLC-[Ca]i-PKC axis. The presence of a PLD pathway also reopens the interpretation of previous studies which demonstrated a resetting between receptor occupancy and production of second messengers by PLC.(ABSTRACT TRUNCATED AT 400 WORDS)

Aldosterone↗

PubMed1991

A caring-based AIDS educational model for pre-adolescents: global health human caring perspective.

With the prolific messages shown to children today through the media and other sources about acquired immunodeficiency syndrome (AIDS), what sexual questions are on the minds of the fifth and sixth grade students as a result of this exposure? What is the role and responsibility of nurses with regard to this problem? This descriptive study focused on fifth and sixth graders' questions about AIDS and provides some directions for theory-based nursing interventions related to AIDS and children. This paper proposed a theory-based model of caring as a teaching intervention programme about AIDS for pre-adolescents. The model resulted from a sex education programme for fifth and sixth graders in an international school setting in Japan. The nature of the students' questions about AIDS revealed transcultural concerns which suggested that a model of human caring was needed to develop a systematic approach to AIDS education for pre-adolescents. The model proposed has global implications for nurses and other health professionals in schools and primary health-care settings in various parts of the world.

Acquired Immunodeficiency Syndrome↗

PubMed1991

Sympathoadrenal activation in sinoaortic-denervated rats following endotoxin.

We evaluated the role of the baroreceptor reflex in mediating the sympathoadrenal activation during endotoxicosis, using acutely as well as chronically denervated rats. Three groups of experiments were conducted. In the first experiment, hemodynamic and plasma catecholamine responses following endotoxin (5 mg/kg iv) were measured in alpha-chloralose-anesthetized rats with acute sinoaortic baroreceptor denervation (SAD) or sham operation. In the second experiment, chronically sinoaortic-denervated rats and sham controls were used and experiments were conducted as in acute preparations. In the third experiment hydralazine (1 mg/kg iv) was given to chronically denervated rats and sham controls to evaluate the singular contribution of hypotension-evoked baroreflex disinhibition in the absence of endotoxin. In both acute and chronic preparations, endotoxin induced marked elevation of plasma norepinephrine and epinephrine in the presence as well as the absence of arterial baroreceptors (P greater than 0.05). Plasma catecholamines were significantly increased by hydralazine-induced hypotension in the sham group, but this elevation was far less than that induced by endotoxin. Hypotension alone did not significantly increase plasma catecholamines in SAD rats. These results suggest that the baroreflex is not the major factor in mediating sympathoadrenal activation during endotoxicosis and that non-baroreflex mechanisms may be involved in stimulating such activation.

Adrenal Glands↗

PubMed1991

Mechanisms involved in the rapid dissipation of plasma epinephrine response to bacterial endotoxin in conscious rats.

Conscious rats treated with bolus endotoxin (ET; 4.0 mg/kg) increased plasma epinephrine (Epi) 48-fold (from 134 +/- 5 to 6,545 +/- 1,607 pg/ml) at 30 min, but by 6 h this elevation was less than 9-fold above control (1,174 +/- 166 pg/ml). In contrast, plasma norepinephrine (NE) elevation (6.5-fold above control) was maintained during the protocol. The present study was designed to test the hypothesis that the decreased Epi response following ET was due to 1) depletion of adrenal Epi content such that adrenomedullary stimulation would not release Epi, 2) decreased Epi release with direct stimulation, i.e., desensitization of release, or 3) decreased afferent signals generated by ET itself. In these experiments an initial low ET dose (0.5 mg/kg) was followed 3 h later by a second dose of either the same (0.5 mg/kg) or greater (4.0 mg/kg) magnitude. Plasma Epi was elevated following the initial (low) dose but not following the same second (0.5 mg/kg) dose, whereas the second higher dose (4.0 mg/kg) resulted in elevated plasma Epi. This response to high dose was 60% less than that observed with 4.0 mg/kg as an initial dose. Just before the second ET bolus, there was no depletion of adrenal Epi content (P greater than 0.05 saline vs. ET treated), and direct nerve stimulation demonstrated enhanced rather than attenuated Epi release from the adrenal medulla (P less than 0.05 saline vs. ET treated). These results suggest that the decline in Epi following the ET-induced elevation may be mediated by a decrease in the afferent signal that initiates Epi release.

Adrenal Glands↗

PubMed1991

Insulin-inhibiting effects of epinephrine are blunted during endotoxicosis in the rat.

This study was conducted to examine the conditions under which epinephrine (EPI) blocks glucose-induced hyperinsulinemia in normal and endotoxic rats. Nutritional state (fasting vs. feeding) and anesthetic state (conscious vs. sodium pentobarbital anesthesia) were explored as factors that could influence the effects of epinephrine on immunoreactive insulin (IRI) levels. Exogenous epinephrine infusion into control rats significantly blunted hyperinsulinemia in response to an exogenous glucose challenge in fed rats, but not fasted rats. Endotoxin-treated rats (3.3 mg/kg) showed endogenously elevated levels of both EPI and IRI during the hyperglycemic period that is characteristic of early endotoxicosis. All endotoxic rats showed hyperinsulinemia in response to an exogenous glucose challenge, despite the simultaneous presence of elevated catecholamine levels. However, hyperinsulinemia (induced by glucose challenge) was two-fold higher in pentobarbital-anesthetized, endotoxic rats (both fed and fasted) than in respective control rats under the same conditions. These results show that fasted rats are resistant to the insulin-inhibiting effects of epinephrine. In addition, since hyperinsulinemia occurs during endotoxicosis (in both fed and fasted states) despite the presence of elevated catecholamine levels, the results indicate that endotoxin treatment decreases the inhibitory effects of epinephrine on insulin levels. This effect is potentiated by pentobarbital anesthesia and is more pronounced in the fed rat than in the fasted rat.

Animals↗

PubMed1991

Alpha 2-adrenergic receptor stimulation of phospholipase A2 and of adenylate cyclase in transfected Chinese hamster ovary cells is mediated by different mechanisms.

The effect of alpha 2-adrenergic receptor activation on adenylate cyclase activity in Chinese hamster ovary cells stably transfected with the alpha 2A-adrenergic receptor gene is biphasic. At lower concentrations of epinephrine forskolin-stimulated cyclic AMP production is inhibited, but at higher concentrations the inhibition is reversed. Both of these effects are blocked by the alpha 2 antagonist yohimbine but not by the alpha 1 antagonist prazosin. Pretreatment with pertussis toxin attenuates inhibition at lower concentrations of epinephrine and greatly potentiates forskolin-stimulated cyclic AMP production at higher concentrations of epinephrine. alpha 2-Adrenergic receptor stimulation also causes arachidonic acid mobilization, presumably via phospholipase A2. This effect is blocked by yohimbine, quinacrine, removal of extracellular Ca2+, and pretreatment with pertussis toxin. Quinacrine and removal of extracellular Ca2+, in contrast, have no effect on the enhanced forskolin-stimulated cyclic AMP production. Thus, it appears that the alpha 2-adrenergic receptor in these cells can simultaneously activate distinct signal transduction systems; inhibition of adenylate cyclase and stimulation of phospholipase A2, both via G1, and potentiation of cyclic AMP production by a different (pertussis toxin-insensitive) mechanism.

Adenylate Cyclase Toxin↗

PubMed1991

Hypotension- and endotoxin-induced alterations in calcitonin gene-related peptide: modulation by dexamethasone.

Plasma levels of calcitonin gene-related peptide (CGRP) were studied in anesthetized rats during and after recovery from hemorrhagic hypotension as well as following administration of bacterial endotoxin. Hypotension of 35-40 mmHg maintained for 2 hr resulted in significant (P less than .05) elevation of plasma CGRP levels. Plasma levels at 120 min of hypotension were 49.5 +/- 5.9 pg/ml, over 4-fold above average control levels (11.1 +/- 1.1 pg/ml). Plasma CGRP levels at 90 min of hypotension (20.2 +/- 2.4 pg/ml) or before were not more than 2.5-fold above control levels. Ninety minutes after the return of shed blood in the 30 min group, blood pressure (83 +/- 3 mmHg) and CGRP (17.2 +/- 2.2 pg/ml) were not different from saline controls (88 +/- 3 mmHg and 15.1 +/- 1.7 pg/ml CGRP). However, if hypotension was maintained for 120 min before the return of shed blood, blood pressure following 90 min recovery was significantly lower (59 +/- 5 mmHg) and CGRP levels significantly higher (39.2 +/- 5.6 pg/ml) than saline control values (82 +/- 5 mmHg and 19.5 +/- 2.7 pg/ml). Dexamethasone treatment of the 120 min hypotension group when shed blood was returned resulted in CGRP values not different from saline treated, but hypotension persisted. Administration of bacterial endotoxin (16.7 mg/kg) to anesthetized rats caused significant elevations (P less than .05 vs. saline treatment at 3 hr) in plasma CGRP levels from aorta (82.2 +/- 5.0 pg/ml), vena cava (79.4 +/- 12.9), and portal vein (117.7 +/- 29 pg/ml) compared to levels in saline-treated control rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Comparative and interactive in vivo effects of tumor necrosis factor alpha and endotoxin.

A comparative and interactive analysis of the effects of tumor necrosis factor alpha (TNF) and endotoxin (ETX) on selected hemodynamic and glucoregulatory alterations was performed in conscious, unrestrained, adult male Holtzman rats. Rats with indwelling carotid artery and jugular vein cannulae were administered intravenous (i.v.) bolus injections of either (1) ETX at 1.55 or 30 mg/kg; (2) TNF at 0.1, 0.5, or 1.0 mg/kg; or (3) TNF plus ETX as a low dose co-treatment at 0.1 mg/kg plus 1.55 mg/kg, respectively. Control groups received either saline or heat-inactivated TNF. TNF induced a lethal response such that 1.0 mg/kg resulted in five out of six deaths within 6 hr. Elevated pulse rates, early hyperglycemia, late hypoglycemia, hyperlactacidemia, hypoinsulinemia, and elevated catecholamine concentrations were evident after injection of 1.0 mg/kg TNF. The pathophysiological alterations observed after 1.0 mg/kg TNF were comparable to the changes observed after the administration of a highly lethal, 30 mg/kg dose of ETX (six out of six deaths within 24 hr). Co-treatment with low doses of TNF plus ETX resulted in the rapid demise of the rats, resulting in six out of six deaths within 4 hr. The resultant shocklike state was accompanied by significant hypotension, hyperglycemia and hyperlactacidemia, similar to the changes induced by highly lethal doses of TNF or ETX alone. This study supports the involvement of TNF in the pathogenesis of gram-negative septic shock and documents the hemodynamic and glucoregulatory alterations which accompany the exacerbated shocklike state induced after co-treatment with separately, minimally lethal doses of TNF plus ETX.

Animals↗

PubMed1990

Effects of alpha 2-adrenergic agonist preincubation on subsequent forskolin-stimulated adenylate cyclase activity and [3H]forskolin binding in membranes from HT29 cells.

alpha 2-Adrenergic agonist preincubation resulted in a leftward shift in the subsequent concentration-response curve to forskolin-stimulated adenylate cyclase activity in membranes from HT29 cells, a human colon adenocarcinoma cell line. This effect was much less pronounced than the effect seen in the intact cell cyclic AMP production assays. Removal of GTP from the assay caused a further slight leftward shift in the concentration-response curve. In [3H]forskolin binding experiments, alpha 2-adrenergic agonist preincubation caused a doubling of the maximal number of binding sites (80 vs 31 fmol/mg protein) compared to control. The addition of MgCl2 and NaF to the assay buffer increased control binding 5-fold. With agonist preincubation, there was a further increase in binding in the presence of MgCl2 and NaF which was not significantly different from the appropriate control. Pertussis toxin pretreatment blocked both the leftward shift in the forskolin concentration-response curve and the increase in maximal number of binding sites, indicating that a pertussis toxin sensitive protein is involved in these changes. Activation of cyclic AMP production in the intact cell by cholera toxin followed by norepinephrine preincubation and then stimulation by forskolin resulted in a degree of sensitization similar to that seen in the membrane adenylate cyclase and binding assays. Pertussis toxin also blocked this sensitization. It appears that if the cyclase system is highly activated, then the degree of sensitization is similar in the membrane and intact cell assay.

Adenylate Cyclase Toxin↗

PubMed1990

An assessment of plasma histamine concentrations during documented endotoxic shock.

Recent reviews of the literature involving histamine release during sepsis and endotoxemia have reported that the majority of the studies are inconclusive due to inadequate assays or experimental protocols. In a controlled experimental setting we have employed a specific and sensitive radioenzymatic assay to determine plasma histamine concentrations temporally during documented endotoxin-induced shock in the conscious rat. Cardiovascular and metabolic measurements for the control group (n = 7) were normal during the study period. Endotoxin (n = 8, LD/90-24 hrs.) induced an early transient hypotensive episode and increase in systemic vascular resistance and a sustained decrease in cardiac index and central venous pressure and increase in heart and respiratory rates. Hypoglycemia and hyperlacticemia were present at the end of the four-hour study period. The small intestine was severely hemorrhaged in all animals given endotoxin. Histamine concentrations for the control group were unchanged throughout the study period. Contrary to previous reports, this model of endotoxemia revealed unchanging histamine concentrations during the first 30 minutes which were temporally coincident with the characteristic early hypotensive episode evoked by endotoxin. The histamine concentrations at 60 and 240 minutes following endotoxin were increased two and three-fold, respectively, compared to the control group. Three of the 8 rats given endotoxin died before four hours; histamine concentrations in plasma taken when death appeared certain were 42, 91, and 174, compared to the control value of approximately 8 ng/ml. There was no clear association of the increases in plasma histamine with any of the parameters measured in this study: however, established histamine effects may have been masked by the pre-existing effects of other mediators known to be active during endotoxemia. In separate groups of animals endotoxin (n = 5) elicited early increases in plasma concentrations of norepinephrine (5-fold) and epinephrine (8-fold) that remained elevated for the 4-hour study period while the control group (n = 4) remained stable. This study establishes that a) plasma histamine concentrations are increased during endotoxemia, b) plasma histamine is not elevated during the initial hypotension episode following endotoxin, c) plasma histamine increases during the progression of endotoxic shock, and d) plasma histamine concentrations are extremely high prior to death.

Animals↗

PubMed1990

Outcomes measurement: a report from the front.

In August of last year, a group of individuals representing providers, employers, insurers, government agencies, researchers, and policymakers gathered for two days at a study center in Woods Hole, Massachusetts to share information on current programs, explore the obstacles, and consider the possibilities for the application and use of outcomes measurement. Several reports on actual use of outcomes measures by purchasers of health care, hospitals, clinics, and third-party payers formed the basis for discussion on the systems in use and their purposes, and also on the strengths and weaknesses of outcomes measures and how they might be improved. The group also addressed how purchasers, providers, and patients might work together to develop the most effective and useful measures.

Employment↗

PubMed1990

Multiple choice health insurance: the lessons and challenge to private insurers.

A health policy consultant with 20 years of experience in public and private health insurance, and particularly multiple choice systems, suggests the evidence is in on our national effort to contain costs through competition, HMOs, and multiple choice health plans. Specifically, we have learned that 1) multiple choice plans are not containing costs for employers, 2) while group and staff model HMOs contain costs, few have cut employers' costs in multiple choice health plans, and 3) group and staff model HMOs' capacity to contain costs has not been matched by insurers' managed care plans. Three options for insurers and HMOs to offer employers are outlined. The options are aimed at changing the behavior of providers so they offer lower cost health care.

Community Participation↗