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Biomedical subjects

R W Smith

Publications and source records attributed to R W Smith.

At least 19 recordsLinked to original sources
PubMed1992

Adenosine and its nucleotides stimulate proliferation of chick astrocytes and human astrocytoma cells.

Aqueous extracts of the brains of 18-day-old white Leghorn chicken embryos contain several substances that stimulate proliferation of primary cultures of chick brain astrocytes. Most of the mitogens are peptides. Purification of one mitogenic fraction was obtained by centrifugation, passage through Amicon Diaflo membranes of nominal molecular weight cutoffs 30, 1 and 0.5 kDa, ion exchange chromatography and reverse phase high performance liquid chromatography (HPLC) using a Deltapak C18 column. The mitogenic fraction contained no amino acids. On the basis of its behaviour on thin layer chromatography, its ultraviolet absorption spectrum, its 1H and 31P nuclear magnetic resonance spectra and its behaviour on positive and negative ion fast atom bombardment mass spectrometry, the mitogenic material was identified as adenosine-5'-monophosphate (AMP). Other adenosine compounds including adenosine, ADP and ATP also stimulated proliferation of and [3H]leucine incorporation into primary cultures of astrocytes. Nitrobenzylthyioinosine (NBTI), an inhibitor of nucleoside transport, did not prevent the stimulation of [3H]leucine incorporation into cultured astrocytes. Polyadenylic acid (Poly A), that mimics the effect of adenosine at adenosine receptors, also stimulated proliferation of the astrocytes. The effects of adenosine and Poly A were not inhibited by 1,3-dipropyl-8-(2-amino-4-chlorophenyl)xanthine (PACPX) but were inhibited by 1,3-dipropyl-7-methyl-xanthine (DPMX), indicating that adenosine and Poly A acted at the cell surface, likely through adenosine A2 receptors. The stimulatory effect of ATP was biphasic. The proliferative effect of low, but not of high, concentrations of ATP were abolished by DPMX. The purinergic P2 receptor agonist 2-methylthioATP and, at higher concentrations, the P2y agonist, alpha,beta-methyleneATP also stimulated incorporation of [3H]thymidine. These data indicate that high concentrations of ATP stimulate cell proliferation through at a P2, possibly a P2y receptor. These results have considerable biological significance. After brain injury, or when cells in brain die or become hypoxic, nucleotides and nucleosides are released from the cells. Their extracellular concentrations can exceed those required to stimulate astrocyte proliferation in vitro. Therefore they may be partly responsible for gliotic changes following cell death in brain.

Adenine Nucleotides↗
PubMed1992

Regulation of cortical blood flow by the dorsal raphe nucleus: topographic organization of cerebrovascular regulatory regions.

We examined in rat: (1) the time-course and magnitude of change in cortical blood flow (CoBF) following electrical stimulation of the dorsal raphe nucleus (DRN) and (2) whether DRN lesions affect resting CoBF or the cerebrovascular response to CO2. Animals were anesthetized (chloralose), paralyzed, and artificially ventilated. The effect of stimulus frequency (1-200 Hz) and intensity (10-100 microA) on arterial pressure, heart rate, and CoBF was examined; lesions were made electrolytically. CoBF was measured using a laser-Doppler flowmeter with the probe placed extradurally over the parietal sensorimotor cortex. The DRN was computer reconstructed in three dimensions from Nissl stained coronal sections for localization of electrode placements. Brief stimuli (8 s; n = 6) elicited frequency and intensity-dependent increases in arterial pressure, heart rate, and CoBF. Sustained intermittent trains of stimuli of rostral DRN (200 Hz; 1 s on/1 s off; 70 microA) elicited a decrease (85 +/- 12% of baseline; n = 9) in CoBF (p less than 0.05) while stimulation in caudal DRN resulted in increased CBF (126 +/- 13% of baseline; n = 9). Phenylephrine infusion (0.1-1 microgram; i.v.; n = 8) increased arterial pressure and CoBF less than that elicited by brief DRN stimulation (p less than 0.05). DRN lesions did not affect resting CoBF (140 +/- 25 perfusion units (PU) before; 127 +/- 16 PU after DRN lesion; p greater than 0.05, n = 5) or mean arterial pressure (127 +/- 13 before; 120 +/- 11 after); nor did it affect the cerebrovascular response to change in arterial PCO2. Sustained intermittent stimulation of the DRN can evoke either increases or decreases in CoBF depending on the anatomical sublocalization. The DRN does not tonically maintain resting CoBF, nor participate in the cerebrovascular response to change in PCO2.

Animals↗
PubMed1992

Blood flow imaging using electrical impedance tomography.

It is shown that a real-time electrical impedance tomography (EIT) system can be used to image the flow of saline through the human vascular system. A 10 ml bolus of 0.9% saline injected intravenously distal to an EIT imaging plane allows venous flow to be observed. Measurements on a cylindrical tank with flow along axial conductive tubes have been used to establish that the area under a concentration against time curve can be obtained from the EIT images and used to determine the flow rate down the tube. In vivo results show that flow images of the venous system in a limb can be obtained and that there is adequate sensitivity to follow the passage of a saline bolus though the cardiac chambers.

Blood Flow Velocity↗
PubMed1992

Great toe metatarsophalangeal joint arthrodesis: a user-friendly technique.

Thirty-four feet (23 patients) were treated with a metatarsophalangeal (MP) joint fusion of the hallux using five threaded 0.062-in K wires for fixation. Operations were done for the following diagnoses: rheumatoid arthritis (26 procedures), hallux rigidus (1), salvage of previous bunionectomies (3), hallux valgus with absent toe, bilateral fusion (2), severe hallux valgus with chronic MP joint synovitis (1), and congenital hallux varus (1). The ages ranged from 17 to 73 years, with an average of 55 years. Follow-up was available on 31 of the fusions by questionnaire and telephone contact, with an average follow-up of 24 months and a minimum of 1 year. The successful arthrodesis rate was 97%. In 9% of the procedures (three cases), the patients were dissatisfied: This was due to pain under the first metatarsal head in two cases and to impingement between the first and second toes in a third case. In 91% of the fusions (29 of 32 patient responses), the patients stated that they would have the surgery if they had to choose again. Patients indicated "complete satisfaction" in 15 fusions and "satisfaction with reservations" in 14. Patients felt that their ability to wear desired shoes was improved in 48% of the procedures, was unchanged by the fusions in 26%, and was worse than before the operation in 26%. Based on this study and review of the literature, a recommendation is made for fusing the rheumatoid hallux with 25 degrees to 30 degrees of valgus and 10 degrees of extension. In general, selection of toe position for fusion is based on reducing stress on the hallux interphalangeal joint and accommodating the position of the second toe. The multiple pin fixation technique gives a high incidence of fusion, it is easy to perform, and it is adaptable to the varying requirements for toe position.

Adolescent↗
PubMed1991

Monocortical miniplate fixation of mandibular angle fractures.

Noncompression monocortical miniplate fixation of mandibular fractures has become a reliable method of providing rigid fixation and eliminating the need for intermaxillary fixation. Recent studies, using a variety of internal fixation techniques, have described high complication rates at the mandibular angle. This article compares the use of one miniplate vs two miniplates in treatment of angle fractures. Since September 1985, 61 patients with 63 mandibular angle fractures have been treated with miniplates. Forty-four fractures were fixed with two miniplates. Six complications (3.1%) occurred, five of which were in the one-miniplate group. The complication rate in the double-miniplate group is the lowest reported of any plating technique. The use of two miniplates has proved to be an effective method of treating mandibular angle fractures.

Adolescent↗
PubMed1991

Purinergic stimulation of astroblast proliferation: guanosine and its nucleotides stimulate cell division in chick astroblasts.

A highly active fraction that was mitogenic for astroblasts but which contained no amino acids was identified during the purification of peptides from chick embryo brains. This material was purified by ultracentrifugation, ultrafiltration through Diaflo PM-30 and YM-2 membranes and retention on Diaflo YC-05, followed by ion exchange chromatography and reversed phase high performance liquid chromatography (HPLC) on a C18 Deltapak column. On thin layer chromatography and HPLC the material co-chromatographed with authentic commercially-obtained GMP. Its ultraviolet absorption spectrum was also identical with that of GMP. 1H and 31P nuclear magnetic resonance spectra of the isolated material were identical with those of GMP. The close match between the fast atom bombardment (FAB) mass spectra of the unknown material and authentic GMP indicated that the unknown material was GMP of molecular weight 363 Da. Authentic, commercial GMP stimulated the growth of cultured chick astroblasts in the same dose-dependent manner as the material from chick embryo brains; maximal stimulation was at 50 microM. Guanosine, GDP, and GTP also stimulated cell proliferation. The nucleotides were equally as effective as guanosine. 5'-Guanylyl imidodiphosphate, guanosine 5'-O-(2-thiodiphosphate), and guanosine 5'-N-(3-thiotriphosphate), guanine nucleotides which are relatively resistant to enzymatic hydrolysis, were also mitogenic, indicating that the nucleotides do not need to be degraded to nucleosides to be active and that they probably act extracellularly. Guanine nucleosides and nucleotides promoted astroblast growth when other growth factors were removed from the culture medium. The mitogenic effects of guanosine and its nucleotides were inhibited in a dose-dependent fashion by micromolar concentrations of theophylline, a characteristic of phenomena mediated by purinergic receptors. Guanosine and its nucleotides are released in micromolar concentrations by hypoxic or dying cells. Under these circumstances these compounds may stimulate division of adjacent cells in vivo.

Animals↗
PubMed1991

Open versus laparoscopic cholecystectomy. A comparison of postoperative pulmonary function.

Upper abdominal surgery is associated with characteristic changes in pulmonary function which increase the risk of lower lobe atelectasis. Sixteen patients undergoing open cholecystectomy and 20 patients undergoing laparoscopic cholecystectomy were prospectively evaluated by pulmonary function tests (forced vital capacity [FVC], forced expiratory volume [FEV-1], and forced expiratory flow [FEF] 25% to 75%) before operation and on the morning after surgery to determine if the laparoscopic technique lessens the pulmonary risk. Fraction of the baseline pulmonary function was calculated by dividing the postoperative pulmonary function by the preoperative pulmonary function and multiplying by 100%. Postoperative FVC measured 52% of preoperative function for open cholecystectomy and 73% for laparoscopic cholecystectomy (p = 0.002). Postoperative FEV-1 measured 53% of baseline function for open cholecystectomy and 72% for laparoscopic cholecystectomy (p = 0.006). Postoperative FEF 25% to 75% measured 53% for open cholecystectomy and 81% for laparoscopic cholecystectomy (p = 0.07). It is concluded that laparoscopic cholecystectomy offers improved pulmonary function compared to the open technique.

Adult↗
PubMed1991

Rupture of the flexor hallucis longus after hallux valgus surgery: case report and comments on technique for adductor release.

A case of flexor hallucis longus (FHL) rupture following hallux valgus surgery is reported here. The authors conjecture that the FHL rupture was caused by a partial laceration of the FHL at the time of the surgical hallux valgus correction. The authors treated the painful problem by surgically debriding the distal stump of the FHL from under the first metatarsophalangeal joint (MP) and tenodesing that the proximal stump to the flexor digitorum longus (FDL). The authors describe a technique that minimizes the complications of an adductor tenotomy associated with a distal chevron type of hallux valgus correction.

Adult↗
PubMed1990

A comparison of past and future leisure activity participation between spinal cord injured and non-disabled persons.

Leisure activity profiles of 81 male and 21 female SCI subjects were compared with profiles of 135 male and 151 female non-disabled individuals. These profiles, derived from the Leisure Activities Blank (McKechnie, 1985), revealed that SCI subjects had been more physically active (prior to injury) than those in a non-disabled comparison group; however, their post-injury expectations for future leisure activity involvement were considerably lower than a similar study of non-disabled individuals. These reduced expectations were found for both active and sedentary activity categories. It is suggested that awareness of pre-morbid leisure activity profiles, plus recognition that post-injury expectations for leisure activity participation are often reduced, could assist medical personnel to prescribe treatment or offer programmes that enable SCI patients to maintain their pre-morbid lifestyles and enhance future leisure activity expectations.

Adolescent↗
PubMed1989

Morphological and morphometric changes in revascularised bowel grafts reconstructing the cervical oesophagus.

Revascularised grafts of jejunum and colon have been used to reconstruct the cervical oesophagus in dogs. The grafts were examined at 2 months to assess their morphological and morphometric behaviour in their new position in the oesophagus. The colonic grafts appeared to adapt completely, while the jejunal ones manifest persisting mucosal changes attributable to their new environment.

Animals↗
PubMed1989

Problem-based ACLS instruction: a model approach for undergraduate emergency medical education.

The optimal format for teaching advanced cardiac life support (ACLS) to medical students and other groups with little emergency medicine experience has not been studied extensively. We report an ACLS provider course that was taught to sophomore medical students using a self-directed, problem-based learning model. The traditional two-day provider course format was replaced by a series of clinical problems that emphasized various aspects of the ACLS curriculum. Students then met weekly with an ACLS instructor who served as a tutor to discuss the problem. A specific set of learning objectives for the entire ACLS curriculum was developed into a study unit index and given to students at the beginning of the course. Enhanced practice time was offered to students in the form of traditional teaching stations and skills laboratories. Students were tested using standard ACLS criteria. The students in the problem-based course achieved a higher pass rate on the written test and skills stations than senior medical students did in a standard two-day course during the same time period. The problem-based format with enhanced practice time would appear to be an effective alternative for groups that need to acquire the basic skills needed in a resuscitation attempt but have little previous experience in this area.

Curriculum↗