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Biomedical subjects

R O Jones

Publications and source records attributed to R O Jones.

At least 37 records · Page 2Linked to original sources
PubMed1995

Role of intestinal fluid in restitution of blood volume and plasma protein after hemorrhage in awake rats.

To determine whether food and/or water in the gastrointestinal tract affects restitution of blood volume and plasma protein after hemorrhage, fed and 24-h-fasted awake rats received a 20 ml.kg-1 x 3 min-1 hemorrhage, and restitution of blood volume was measured by Evans blue dye and dilution of hematocrit. Restitution of blood volume and plasma protein in fed rats was complete by 2-4 h. In contrast, restitution was severely attenuated in fasted rats and was not complete by 24 h. Because initial blood volume was significantly lower in the fasted rats (55.4 +/- 1.7 vs. 64.9 +/- 2.5 ml/kg in fed), the percent blood lost during hemorrhage was significantly greater (36 vs. 31%). However, the attenuated restitution was not the result of the larger hemorrhage, as fed rats receiving a 36% hemorrhage also restored blood volume completely by 4 h. In fasted rats, complete restitution of blood volume did occur when either water or food and water were given 4 h after hemorrhage. Gastrointestinal water content fell (from 65.5 +/- 4.8 to 47.9 +/- 1.6 ml/kg) 2h after hemorrhage in fed but not in fasted rats (33.5 +/- 2.4 to 30.6 +/- 2.5 ml/kg). These data suggest that gastrointestinal fluid is essential for complete restoration of blood volume in the awake rat.

Animals↗
PubMed1995

Changes in regional vascular resistance and blood volume after hemorrhage in fed and fasted awake rats.

To determine whether fasting alters the response of blood flow to hemorrhage, blood flow was measured by radiolabeled microspheres before and after a 20 ml.kg-1.3 min-1 hemorrhage in fed and fasted chronically cannulated male Sprague-Dawley rats. Restitution of blood volume, as determined by dilution of hematocrit, was attenuated in fasted rats, although the responses of arterial blood pressure, heart rate, cardiac output, and total peripheral resistance were not significantly different. Fasting only affected resting blood flow in the bronchial artery and fat and had no effect on resting vascular resistance in any organ studied. In both fed and fasted rats, hemorrhage led to a significant fall in blood flow to the stomach, small intestine, cecum, colon, spleen, pancreas, kidney, bronchial artery, thymus, and muscle and a rise in blood flow to the adrenals. However, fasting did not significantly alter the response of flow or vascular resistance to these organs. Fasting did alter the blood flow response to hemorrhage in bone, fat, and the hepatic artery. These results demonstrate that 24 h of fasting does not affect the responses of blood flow and vascular resistance to hemorrhage in most organs, even though restitution of blood volume is attenuated.

Animals↗
PubMed1994

A circulating shock protein that depolarizes cells in vitro depresses myocardial contractility and rate in isolated rat hearts.

Previously, we identified the presence of a circulating shock protein (CSP) in the plasma of hemorrhaged rats that depolarizes a variety of cells in vitro. In isolated perfused rat hearts, partially purified CSP produced dose-dependent decreases in contractility and heart rate associated with an increase in coronary perfusion pressure (CPP). Electrical pacing failed to prevent the negative inotropic effects. Preventing the coronary vasoconstriction with nitroglycerin or attenuating it with a cyclooxygenase inhibitor also failed to prevent the inotropic or chronotropic effects of CSP. Carbocyclic thromboxane A2 (50ng/min) caused a similar increase in CPP to CSP but had no effect on contractility or rate during the first minute of infusion. These data indicate that the protein that appears in rat plasma after hemorrhage produces negative inotropic and chronotropic effects on the isolated heart that are independent of changes in CPP. Vasoactive arachidonic acid metabolites elicited by CSP are partially responsible for the increase in coronary vascular resistance.

Animals↗
PubMed1994

Anomalies of the branchial apparatus: a case report and review of embryology, anatomy and development.

The majority of congenital anomalies occurring in the neck are related to the development of the branchial apparatus. This area is responsible for the development of multiple structures in the head and neck and thus its anatomy and embryology are complex. Although cysts, sinuses, and fistulas of the branchial region are not common occurrences, they do present in a variety of settings and are generally easily managed if diagnosed early. A fundamental understanding of their anatomy, embryology, and presentation is needed to appropriately diagnose and manage them. These fundamentals are reviewed and a case report is used to illustrate one of the more common presentations.

Branchial Region↗
PubMed1994

The neuroanatomy of pain.

Pain is the most frequent complaint of patients visiting all types of physicians. With pain perception, sensation is described and perceived as causing actual tissue damage. In contrast, nocioception is defined as a response specific to a potentially tissue-damaging stimuli. This articles defines the various nocioceptive pathways and connections.

Axons↗
PubMed1993

The ongoing development of a problem-based surgery clerkship: year three.

The third-year clerkship at one college of medicine was modified to reflect an emphasis on adult learning principles and life-long learning habits. Problem-based learning was selected as the educational method, and the development of a cognitive knowledge base, clinical problem-solving skills, and appropriate clinical skills was stressed. At a yearly faculty education retreat, strengths and weaknesses of the clerkship were discussed. As a result of this meeting, several changes were made in the clerkship, including additional stress on students' usage of the medical library and computerized databases, a tutor development program, the addition of expert resource sessions, and more emphasis on students' development of clinical skills through a preceptor program. A comprehensive evaluation program designed to support the educational goals of the clerkship is in place. The major challenge of the program remains the proper synchronization of curricular, clinical, and student self-study activities essential for an ideal learning experience.

Clinical Clerkship↗
PubMed1992

Podiatric utilization referral patterns at an Army medical center.

Presented is the first descriptive data on a large military Podiatry Clinic supporting largely combat troops. Data consist of initial podiatric problems of soldiers and other beneficiaries of podiatric care. Demographic, physician referral patterns, and other pertinent summarized survey information of outpatient utilization at the Podiatry Clinic, Madigan Army Medical Center, Fort Lewis, Washington, are examined. Findings are based on new and initial consult referrals from the month of November 1988. The results indicated that some clinics needed inservices and further education concerning podiatric care. This study has led to the implementation of changes which have resulted in better and more timely patient care.

Adolescent↗
PubMed1991

Use of dilute epinephrine as an aid in facial nerve monitoring.

Facial nerve monitoring during otologic and neurotologic procedures has been previously described, and its use is becoming routine. Although these procedures are done under general anesthesia, lidocaine is often used as a vehicle for epinephrine to aid hemostasis during the procedure. The routine use of lidocaine in these preparations presents the theoretical and sometimes real problem of anesthetizing the facial nerve at the start of the procedure, thereby invalidating subsequent attempts at monitoring and stimulation. We present the data from our experience with 74 patients using an epinephrine solution 1:100,000 for infiltration without any local anesthetic. We have found this procedure to be effective in maintaining hemostasis, quite safe and well tolerated, and without adverse effects on the desired monitoring of the facial nerve.

Blood Pressure↗
PubMed1991

Rupture of low transverse cesarean scars during trial of labor.

We report eight cases of rupture of low transverse cesarean scars occurring during trials of labor. The cases occurred in five hospitals in the Denver metropolitan area during a 13-month period. The estimated incidence was 0.7% of planned trials of labor. Complications of rupture included one neonatal death, two cases of severe neonatal asphyxia, three maternal bladder lacerations, and one hysterectomy.

Adult↗
PubMed1990

Contribution of baroreceptor reflexes to blood pressure and sympathetic responses to cholecystokinin and vasoactive intestinal peptide in anesthetized dogs.

The effects of synthetic vasoactive intestinal peptide (VIP) and cholecystokinin (CCK) on systemic blood pressure and renal nerve activity were studied before and after cervical vagotomy, and sino-aortic denervation with vagotomy in anesthetized dogs. Intravenous injection of VIP (5 micrograms/kg) in animals with an intact neuraxis produced a significant decrease in systemic blood pressure and a significant increase in renal nerve activity. These responses to VIP did not change after vagotomy and after complete denervation, VIP did not cause any change in renal nerve activity, even during hypotension. The level of hypotension after complete denervation was greater than that under other conditions. These results indicate that the cardiovascular effects of VIP are reduced by activation of the systemic baroreceptors. Intravenous injection of CCK (10 micrograms/kg) in animals with an intact neuraxis produced significant decreases in blood pressure and renal nerve activity. These responses to CCK were abolished in animals with cervical vagotomy only. However, following complete denervation of the carotid sinus and total section of the vagal nerves, CCK caused a significant increase in blood pressure and renal sympathetic nerve activity. These results indicate that the sympathetic depressor effect of CCK may be mediated by activation of the vagal afferents, and that the sympathetic pressor effect may be due to a direct action of CCK on the central nervous system. Thus, each gastrointestinal peptide may regulate the cardiovascular system through a different mechanism.

Anesthesia↗
PubMed1990

Reflex effects on renal nerve activity and renal vascular tone during occlusion of superior mesenteric artery in anesthetized dogs.

This study was designed to evaluate the contribution of the systemic baroreceptor reflex on renal nerve activity (RNA) and renal vascular resistance (RVR) during occlusion of the superior mesenteric artery (SMAO) in anesthetized dogs. Animals were divided into two groups; RVR evaluated group and RNA measured group. For evaluation of changes in RVR, the left kidney was perfused at a constant flow with heparinized blood by using a pulsatile roller pump. Renal perfusion pressure, arterial blood pressure and heart rate were measured simultaneously. During SMAO, MAP and RVR increased significantly in animals with intact systemic baroreceptors. After combined denervation of the carotid sinus and vagal nerves, a significant enhancement of this RVR response during SMAO occurred and the level of changes in RVR were significantly greater than those in animals with an intact neuraxis. In the RNA measured group, renal sympathetic nerve activity, arterial blood pressure and heart rate were measured simultaneously before and during SMAO. During SMAO, MAP and RNA increased significantly in animals with intact systemic baroreceptors. These MAP and RNA responses to SMAO were significantly enhanced in animals with combined denervation of the carotid sinus and vagal nerves. These results indicate that SMAO evokes an increase in arterial blood pressure, renal sympathetic nerve activity and renal vascular resistance. The reflex increase in renal nerve activity and renal vascular tone during SMAO is modified and minimized by an activation of systemic baroreceptors.

Adrenergic Fibers↗
PubMed1990

The involvement of the midbrain periaqueductal grey in the cardiovascular response to injury in the conscious and anaesthetized rat.

Cell bodies within the periaqueductal grey (PAG) of the midbrain of the propofol-anaesthetized rat were stimulated using the excitotoxin kainic acid. This resulted in a rise in arterial blood pressure and a tachycardia, together with a reduction in the sensitivity and a rightward resetting of the baroreflex. These changes mimicked the cardiovascular effect of bilateral hindlimb ischaemia in the rat. Further experiments in conscious rats indicated that electrolytic lesions in the PAG prevented the reduction in baroreflex sensitivity induced by limb ischaemia, but did not abolish the rightward resetting of the reflex or the pressor response and tachycardia when compared with sham-lesioned controls. It is postulated that the PAG, a site of importance both in the integration of the defence reaction and the processing of afferent nociceptive information, may form part of a pathway involved in the reduction of the sensitivity of the baroreflex following injury. This pathway is suggested to be separate from a second, as yet undefined, pathway mediating the baroreflex resetting and pressor responses associated with injury.

Anesthesia, Local↗
PubMed1990

The uptake of amino acids and oxygen across the rabbit uterus in normal and postterm pregnancies.

Nineteen pregnant rabbits were studied at three different gestational ages in terms of uterine uptake of amino acids and oxygen under unstressed, steady-state conditions. The three gestational age groups were: (1) 23-25 days, (2) 26-31 days, and (3) 32-34 days (post term). The arteriovenous differences for all amino acids except glutamate and aspartate were significant in groups 1 and 2. Uterine amino acid coefficients of extraction were markedly reduced in the postterm animals (3), despite an increased uterine coefficient of extraction for oxygen. The uterine coefficients of extraction of amino acids were 2-2.5 times greater than those across the pregnant Uterus of the sheep. There was also an increased uptake of amino acid per millimoles/liter of oxygen in the rabbit compared to the sheep. Maternal arterial amino acid concentrations were not significantly different in groups 1 and 2, but the gluconeogenic amino acids serine and alanine were significantly increased in maternal arterial blood of postterm animals.

Absorption↗
PubMed1990

Reflex responses on blood pressure and renal nerve activity to local intra-arterial injection of capsaicin in anesthetized dogs.

The present study was performed to examine effects of intra-arterial and intravenous injection of capsaicin on efferent renal sympathetic nerve activity (RNA) in pentobarbital anesthetized dogs. In animals with intact baroreceptors, intra-arterial injection of capsaicin (4 +/- 1 microgram) produced significant increases in mean blood pressure (MBP) and heart rate (HR) by +43 +/- 8 mmHg and +33 +/- 15 beats/min at 20 s after the injection, respectively. There followed a recovery toward the control so that 60 s after the intra-arterial injection changes in MBP and HR were +8 +/- 5 mmHg and +18 +/- 8 beats/min, respectively. RNA showed a biphasic response, comprising of an initial increase (+52 +/- 28% of the control at 20 s) followed by a decrease by -30 +/- 8% of the control 60 s after the injection. Following bilateral cervical vagotomy the initial increase in RNA did not differ significantly from the value of RNA in animals with intact baroreceptors. However, the later decrease in RNA reversed above the control so that 60 s after the injection change in RNA was +5 +/- 10% of the control. Complete baroreceptor denervation showed a similar response on RNA in the vagotomized animals (+49 +/- 9 and +14 +/- 10% of the control at 20 and 60 s after the injection, respectively). In contrast, intravenous injection of capsaicin (6 +/- 1 microgram/kg) resulted in significant decreases in MBP (-19 +/- 11 mmHg) and HR (-9 +/- 4 beats/min). RNA at 20 s after the injection showed a unidirectional decrease by -16 +/- 7% of the control in animals with intact baroreceptors. These responses reversed above the control after cervical vagotomy. Thus, these data indicate that activation of C-fiber afferents in skeletal muscles by intra-arterial injection of capsaicin results in renal sympathoexcitation, and that the later sympathoinhibition is mediated by combined activation of systemic baroreceptors.

Animals↗