Search PubMed⌕ Search

Biomedical subjects

R S Smith

Publications and source records attributed to R S Smith.

At least 91 records · Page 5Linked to original sources
PubMed1995

Ultrasonographic examination of wound tracts.

OBJECTIVE: To determine if ultrasonography is useful in evaluating penetrating injuries of the trunk to assess whether violation of the peritoneum or pleura has occurred. METHODS: The study group was 29 patients who suffered gunshot (n = 17), stab (n = 10), or shotgun (n = 2) wounds. The abdomen was at risk in 21 injuries, the thorax in eight. The results of physical examination and plain x-rays suggested the pleura and or peritoneum might be intact in all patients. Using a 7-MHz transducer, wound tract(s) were images, looking for the presence of soft-tissue air and/or echolucent areas consistent with soft-tissue blood. Injuries were deemed extraperitoneal or extrapleural if (1) the entire tract was visualized; (2) it appeared superficial to the deepest fascial structure in that area; and (3) in shotgun injuries, all visible pellets on x-ray films were identified by ultrasound in the abdominal wall. RESULTS: Evidence of penetration occurred in four abdominal wounds and one thoracic wound. These were confirmed by operation in the abdominal cases and by subsequent chest x-ray examination in the one thoracic wound. The diagnosis of nonpenetration was confirmed in all the remainder by serial benign abdominal examination (n = 15), chest x-ray examination (n = 8), and laparoscopy (n = 1). Positive and negative predictive accuracy were thus 100% in this pilot series. CONCLUSIONS: Ultrasonographic exploration of penetrating truncal injuries is feasible and accurate. Ultrasonographic wound exploration may serve as a noninvasive and safe replacement for diagnostic laparoscopy, conventional local wound exploration, peritoneal lavage, and 6-hour chest x-rays (repeated chest x-rays taken 6 hours after initial chest x-ray examination). If used as part of the initial physical examination, cost-effectiveness can also be realized.

Humans↗
PubMed1995

Ultrasonographic left cardiac axis deviation: a marker for fetal anomalies.

OBJECTIVE: To determine if a relation exists between left cardiac axis deviation and fetal anomalies. METHODS: Estimation of cardiac axis was attempted prospectively as part of the cardiac examination in approximately 41,500 second- and third-trimester fetuses scanned between 1987-1993. Those with heart axes greater than 75 degrees to the left were considered to have left axis deviation. Only cases with postnatal follow-up were included. RESULTS: Thirty-four fetuses with left cardiac axis deviation had postnatal follow-up; eight were normal and 26 abnormal (positive predictive value 76%). Twenty-one fetuses had cardiac abnormalities (ten of these had additional extracardiac findings), and five had extracardiac findings only. CONCLUSION: Although left cardiac axis deviation can occur as an isolated sonographic finding in an otherwise normal fetus, most cases will demonstrate abnormalities of cardiac and/or extracardiac anatomy. Left cardiac axis deviation is largely associated with cardiac abnormalities, especially conotruncal anomalies, which may not be detectable by a four-chamber view alone. Therefore, the cardiac axis should be examined routinely as part of the four-chamber view of the fetal heart.

Congenital Abnormalities↗
PubMed1995

Tetralogy of Fallot: prenatal diagnosis and postnatal survival.

OBJECTIVES: To correlate prenatal echocardiographic findings with infant outcome in a large screening population affected by tetralogy of Fallot. METHODS: Inclusion criteria required confirmed postnatal cardiac diagnosis, at least one fetal ultrasound examination with satisfactory heart visualization, and infant delivery at our institution. Aortic and pulmonary artery diameters were measured from real-time ultrasound or videotaped scans and compared against published nomograms. The pulmonary artery to aorta ratio was also evaluated in a similar manner. Infant survival was assessed 1 year after delivery. RESULTS: Seventeen fetuses were confirmed to have a ventricular septal defect and an overriding aorta with varying degrees of right ventricular outflow obstruction after delivery. All karyotypes were normal. Ultrasound screening identified 12 of 17 abnormal hearts at a mean gestational age of 22.9 +/- 5.1 weeks; two of these fetuses were thought to have only ventricular septal defect before delivery. Five fetuses had enlarged aortic roots during the initial scan. Only two of the ten fetuses with a measurable pulmonary artery had initial sonographic evidence for valve stenosis. Six other pulmonary arteries became abnormally small with advancing pregnancy. The pulmonary artery to aorta ratio was decreased in six of the ten fetuses with a measurable pulmonary artery. Sixteen infants survived at least 1 year after birth and successfully completed either corrective or palliative cardiac surgery. CONCLUSION: Fetuses with tetralogy of Fallot may present with only a ventricular septal defect and aortic septal override by prenatal ultrasound examination. Pulmonary artery stenosis is not always present at initial ultrasound examination, but this finding can develop or worsen during pregnancy. Furthermore, a normal aortic diameter does not exclude tetralogy of Fallot. Infant survival appears to be favorable in the absence of other major structural or chromosomal anomalies.

Female↗
PubMed1995

The macrophage-T-lymphocyte theory of schizophrenia: additional evidence.

Chronically activated macrophages and T-lymphocytes, along with excessive interleukin-2 and other cytokine secretions, were previously proposed as the fundamental mediators of schizophrenia. This paper provides further support for the immune model of schizophrenia, including evidence on neurotransmitter abnormalities, the low amplitude of the auditory P300 event-related potential, the neurodevelopmental model of schizophrenia and the possible involvement of the locus ceruleus in schizophrenia.

Acetylcholine↗
PubMed1995

Changes in fast axonal transport in sensory neurons during tadpole metamorphosis.

Fast axonal transport of radiolabeled protein was examined in lumbar and tail dorsal root ganglion (DRG) neurons at progressive stages of bullfrog tadpole metamorphosis. Accumulation of [35S]methionine-labeled protein proximal to a lumbar peripheral nerve ligature (at a fixed distance from the DRG) increased as tadpoles advanced from premetamorphosis through prometamorphosis to metamorphic climax. The rate of increase was steeper when expressed as a percentage of protein synthesized in the neurons of origin than when expressed as a percentage of total DRG protein synthesis. Further, the increase was not secondary to a rise in protein synthesis. In contrast, fast axonal transport decreased in DRG neurons of the tail at the onset of metamorphic climax, when tail resorption is initiated. The stage-related increase in protein transport in lumbar nerves is due, at least in part, to an increased rate of transport. As determined from optically detected anterograde organelles in individual lumbar nerve axons, an approximate doubling of the fast transport rate occurred between the premetamorphic stage and metamorphic climax. In addition, the rates of organelle transport in lumbar axons of adult bullfrogs were significantly greater than in corresponding axons of tadpoles at metamorphic climax, further suggesting that organelle velocity is a developmentally regulated parameter of fast axonal transport.

Animals↗
PubMed1995

Therapeutic laparoscopy in trauma.

PURPOSE: To assess the therapeutic potential of emergent laparoscopy in the trauma setting, a retrospective review was performed in a busy urban trauma center. PATIENTS AND METHODS: Between December 1991 and October 1993, 133 hemodynamically stable patients with suspected abdominal injury were evaluated laparoscopically. All laparoscopic procedures were performed in the operating room under general anesthesia. Mechanism of injury was stab wound (58), gunshot wound (57), and blunt trauma (18). No significant injuries were found in 72 patients (54%), and these patients received no further treatment. On the basis of laparoscopic findings, 52 patients underwent formal exploratory laparotomy. Surgical exploration confirmed the presence of significant injuries in 44 of the 52 patients (85%). Therapeutic laparoscopy was performed in 6 patients (5%) for diaphragm repair (4), gastrotomy repair (1), and splenorrhaphy (1). Additionally, 10 patients underwent laparoscopy-guided blood salvage for autotransfusion during laparoscopic evaluation of blunt trauma. Three small-bowel enterotomies were repaired during minilaparotomy. RESULTS: No significant injuries were missed as a result of our use of laparoscopy in trauma assessment. Complications--trocar enterotomy, trocar laceration of the inferior epigastric artery, and transient hypotension--occurred in 3 patients secondary to the use of laparoscopy. CONCLUSIONS: Trauma laparoscopy is a safe method for the evaluation of selected patients with abdominal trauma and can reduce the number of negative and nontherapeutic trauma laparotomies performed. Limited therapeutic intervention is possible in a small number of patients.

Abdominal Injuries↗
PubMed1995

Epstein-Barr virus-induced autoimmune responses. I. Immunoglobulin M autoantibodies to proteins mimicking and not mimicking Epstein-Barr virus nuclear antigen-1.

In previous studies of infectious mononucleosis, we found IgM autoantibodies which react with hematopoietic cell antigens. Many of these were inhibited by synthetic glycine/alanine peptides representing the glycine/alanine repeat of Epstein-Barr virus nuclear antigen-1. We have cloned and expressed fragments of genes encoding two of these autoantigens. One gene (p542) encodes a protein containing a glycine-rich 28-mer, which is its chief autoantigenic epitope and which represents a newly identified class of evolutionarily conserved autoepitopes. The other gene (p554) encodes a protein that is not demonstrably cross-reactive with Epstein-Barr virus nuclear antigen-1 or with any other EBV protein, but forms complexes with other proteins. Immunoaffinity-purified anti-p542 and anti-p554 have relatively high binding affinities, as evidenced by inhibition at 10(6)-10(8) M-1, and neither autoantibody showed polyreactivity with other common antigens. The data thus suggest that neither autoantibody is simply an expression of polyclonal B cell activation. We conclude that the two autoantigens stimulate autoantibody synthesis by different mechanisms. One autoantigen shares homology to a viral protein which generates cross-reacting antibodies to the autoantigenic epitope. The other has no recognizable cross-reaction with the infecting pathogen and may become immunogenic through complexing with other proteins.

Amino Acid Sequence↗
PubMed1995

Polysaccharide-mediated protection against abscess formation in experimental intra-abdominal sepsis.

Abscess formation is a major complication of intra-abdominal sepsis that causes significant morbidity and mortality. In such cases, Bacteroides fragilis is the predominant anaerobic isolate. In a rat model of intra-abdominal sepsis, the capsular polysaccharide complex (CPC) from B. fragilis promotes abscess formation and when administered sub-cutaneously, protects against this host response by a T cell-dependent immune mechanism. In the present study, the polysaccharide A (PS A) component of CPC protected animals against challenge with live heterologous bacterial species (mixtures of anaerobes and facultative organisms) that are most commonly isolated from intra-abdominal abscesses in humans. Protection against heterologous bacterial challenge was transferred by T cells. Administration of PS A shortly before or even after challenge with B. fragilis protected against this host response. In experiments designed to simulate fecal contamination of the human peritoneal cavity, PS A protected animals against abscess formation induced by a rat cecal contents inoculum. The surprisingly broad protective activity of PS A indicates that this molecule is likely suppressing a nonspecific host tissue reaction that forms in response to a variety of abscess-inducing organisms and that it might be useful in preventing abscess formation associated with intra-abdominal sepsis in the clinical setting.

Abdominal Abscess↗
PubMed1995

Isopneumic laparoscopy in general surgery and trauma: an update.

The purpose of this study was to assess the capability of a retractor system that permits laparoscopic surgery without carbon dioxide pneumoperitoneum and to determine if the system facilitates the use of traditional surgical instruments during minimally invasive surgery. This study was performed at a university-affiliated county hospital (Alameda County Medical Center, Highland General Hospital campus) in Oakland, California. The study design was prospective evaluation with data collection. Eighty-eight isopneumic laparoscopic procedures were performed between July 1992 and October 1993. A planar abdominal wall distention system consisting of an intra-abdominal fan retractor and an electrically powered mechanical arm was used to provide exposure. Conventional surgical instruments as well as laparoscopic instruments were used in each case. Laparoscopy without pneumoperitoneum was used in the evaluation of 43 patients with abdominal trauma (gunshot wound, 18; stab wound, 19; blunt trauma, 6). The need for formal abdominal exploration was obviated in 35 of 43 (81%) cases. Repair of three enterotomies, four diaphragmatic lacerations, and one gastric perforation was performed with conventional instruments. Isopneumic laparoscopic techniques were also used for cholecystectomy (n = 36), diagnosis laparoscopy (n = 4), appendectomy (n = 3), sigmoidopexy (n = 1), and closure of a perforated duodenal ulcer (n = 1). Abdominal exposure approximating that obtained by pneumoperitoneum was obtained in 37 of 45 cases. One major (trocar tip enterotomy) and two minor complications (superficial wound infection) occurred in this group of patients. The ability to use traditional surgical instruments was advantageous in several cases. Laparoscopic surgical procedures can be performed without pneumoperitoneum in the majority of cases. The ability to use conventional surgical instruments is an advantage of this technique. Further improvements in abdominal wall distention systems and modifications of existing surgical instruments are required to further expand the role of isopneumic laparoscopy.

Abdominal Injuries↗
PubMed1994

Reversal of rapidly transported protein and organelles at an axonal lesion.

The time required for both rapid axonally transported organelles (vesicles and tubulo-vesicular structures) and proteins to undergo anterograde to retrograde reversal at a crush site was examined using sciatic nerve preparations obtained from Xenopus laevis. The transport and reversal of a pulse of newly synthesized 35S-labeled proteins was studied with a position-sensitive detector of ionizing radiation. Organelle transport and reversal were studied using video microscopy. Both protein and organelle reversal were assessed in two bathing media: a physiological saline and a medium that was compatible with the intracellular environment (internal medium). The time required for protein transport to reverse at a ligature was determined as a function of the time interval between the application of the ligature and the arrival of the pulse at the ligature (lesion time). In physiological saline, reversal times were greatest, about 3.5 h, when the lesion time was 1 h or less and decreased to approximately 1.5 h for lesion times of 4-12 h. When corrected for the approximately 2 mm length of degeneration caused by the saline, the results were similar to those obtained in internal medium and indicated a minimal reversal time for proteins of about 2 h. Organelle transport was examined close to narrow lesions in single myelinated axons. That the organelles moving away from the lesion represented organelles that had undergone reversed transport was suggested by observation of the reversal of individual organelles, and by a correlation between the flux of organelles towards and away from the lesion. Analysis of organelle flux within and adjacent to a segment of axon isolated by two lesions indicated that 70-80% of organelles moving away from a lesion represented reversed transport. Observations in internal medium were consistent with a reversal time of < 15 min, and in physiological saline < 30 min. The substantially smaller reversal time for organelle transport as compared to protein transport is consistent either with the existence of two types of organelles with different reversal times and hence different reversal mechanisms, or with the possibility that during reversal proteins are off-loaded from carrier organelles and subsequently up-loaded to different organelles.

Animals↗
PubMed1994

Laparoscopic surgery without pneumoperitoneum. A preliminary report.

Laparoscopic surgery using pneumoperitoneum to create an operating field is known to have cardiopulmonary side effects. Conventional laparoscopic techniques require operating in a sealed environment. In July 1992, we initiated an investigation of the use of an electric-powered abdominal-wall lifter to expose an operating field. In our preliminary study, we have successfully completed 16 of 20 cases (80%) using this method of exposure. One trocar-related small-bowel injury was recognized immediately and repaired uneventfully. Two patients with dense adhesions made laparoscopic cholecystectomy impossible. One case of laparoscopic cholecystectomy was completed by conversion to pneumoperitoneum. Conventional instruments can be used through small incisions. Digital examination of abdominal contents can be achieved through the periumbilical incision or through other small incisions with the guidance of this retractor; this is superior to pneumoperitoneum since the surgeon can use more than just visual examination of intraabdominal pathology in laparoscopic surgery.

Adult↗
PubMed1994

Auditory ERPs to non-target stimuli in schizophrenia: relationship to probability, task-demands, and target ERPs.

The effects of task demands and stimulus probability on the N1 and P2 components of the auditory event-related potential (ERP) to non-target stimuli were investigated in normal and medicated schizophrenic subjects. Subjects either read a book while tones were presented, or counted the rare (low probability) tones in an auditory oddball paradigm. The mismatch negativity to rare tones in the reading condition was present, and did not differ between groups. N1 amplitude was smaller in schizophrenic patients in all conditions. When subjects counted the rare tones, the amplitude and latency of P2 increased. This task-related effect on P2 was much greater in control than in schizophrenic subjects. Difference ERPs were used to better characterize the effect of task demands by subtracting the ERP in the reading condition from the ERP in the counting condition. The difference ERP consisted of a negative deflection at 182 ms, and a positive deflection at 276 ms, which were both reduced in schizophrenic subjects. N2 and P3 amplitude to target stimuli were reduced in patients as well, but these abnormalities were uncorrelated with N1 and P2 abnormalities to non-target stimuli. Despite automatic registration of stimulus mismatch, and normal processing speed, patients showed deficient task-related modulation of processing to both non-target and target stimuli. Reduction of N1 amplitude in schizophrenia occurs regardless of task demands, and may reflect a chronic, early-stage disturbance in information processing.

Acoustic Stimulation↗
PubMed1994

Duplex scanning replaces arteriography and operative exploration in the diagnosis of potential cervical vascular injury.

BACKGROUND: The pursuit of a diagnosis is more aggressive in suspected cervical vascular injury than in extremity vascular proximity injury, since the complications of missing the neck injury may result in irreversible neurologic damage. Most institutions use arteriography and operative exploration, but these modalities identify only 10% of cervical vascular traumas. While duplex scanning is the screening test of choice for carotid occlusive disease, few published reports have described experience with this modality in cervical vascular trauma. PATIENTS AND METHODS: To determine if duplex scanning can replace arteriography or operative exploration as the initial screening modality in the assessment of potential cervical vascular trauma, we performed a prospective evaluation in two parts. First, we used duplex scanning and cervical arteriography, concomitantly, to rule out injury in 15 patients. We then used duplex scanning alone in 85 patients, reserving arteriography for cases in which the scan revealed an arterial injury. RESULTS: Duplex scans and arteriography and operation diagnosed cervical vascular trauma equally well. Eight injuries were identified in all areas of the cervical arterial tree. No duplex scans have been falsely negative or falsely positive. Use of duplex scans instead of arteriography saved $1,252 per case. CONCLUSIONS: Duplex scanning detects cervical vascular injuries as effectively as arteriography or operation, and is faster and less expensive. This approach expands the utility of diagnostic ultrasound in the evaluation of trauma patients. It has become the procedure of choice for diagnosing cervical vascular trauma at our institution.

Angiography↗
PubMed1994

Action of brefeldin A on amphibian neurons: passage of newly synthesized proteins through the Golgi complex is not required for continued fast organelle transport in axons.

The relation between the availability of newly synthesized protein and lipid and the axonal transport of optically detectable organelles was examined in peripheral nerve preparations of amphibia (Rana catesbeiana and Xenopus laevis) in which intracellular traffic from the endoplasmic reticulum to the Golgi complex was inhibited with brefeldin A (BFA). Accumulation of fast-transported radio-labeled protein or phospholipid proximal to a sciatic nerve ligature was monitored in vitro in preparations of dorsal root ganglia and sciatic nerve. Organelle transport was examined by computer-enhanced video microscopy of single myelinated axons. BFA reduced the amount of radiolabeled protein and lipid entering the fast-transport system of the axon without affecting either the synthesis or the transport rate of these molecules. The time course of the effect of BFA on axonal transport is consistent with an action at an early step in the intrasomal pathway, and with its action being related to the observed rapid (< 1 h) disassembly of the Golgi complex. At a concentration of BFA that reduced fast-transported protein by > 95%, no effect was observed on the flux or velocity of anterograde or retrograde organelle transport in axons for at least 20 h. Bidirectional axonal transport of organelles was similarly unaffected following suppression of protein synthesis by > 99%. The findings suggest that the anterograde flux of transport organelles is not critically dependent on a supply of newly synthesized membrane precursors. The possibilities are considered that anterograde organelles normally arise from membrane components supplied from a post-Golgi storage pool, as well as from recycled retrograde organelles.

Animals↗
PubMed1994

Thoracoscopic repair of missed diaphragmatic injury in penetrating trauma: case report.

We report two cases of missed diaphragmatic injury which were diagnosed and repaired using a thoracoscopic approach. A right diaphragmatic injury sustained via a stab wound to the chest was diagnosed and repaired thoracoscopically using a stapling technique. A second patient sustained an injury to the right diaphragm from a gunshot wound, which was sutured thoracoscopically. Both patients recovered uneventfully and had shortened hospital stays in spite of the nature of their injury and initial delay in diagnosis. With the increase in unsuspected diaphragmatic injuries being reported, we feel that combined thoracoscopy and laparoscopy may offer a therapeutic as well as diagnostic benefit in selected stable patients with penetrating injuries to the upper abdomen and lower chest. Although this initial report is encouraging, further investigation is needed to determine optimal patient selection criteria as well as the cost-effectiveness of this approach.

Adult↗
PubMed1994

Parametric manipulations of auditory stimuli differentially affect P3 amplitude in schizophrenics and controls.

Schizophrenics show P3 amplitude reduction and topographic asymmetries. It is unclear whether the underlying cause of these deficits is primarily functional or structural. This study examined the effect of stimulus discriminability and task instruction on behavioral performance and P3 in schizophrenics and normal control subjects. Stimulus discriminability was manipulated by varying the overall loudness and pitch disparity of the two tones in an auditory oddball paradigm. Instructions emphasized either speed or accuracy of response. Instructions had no significant effects on reaction time, perceptual sensitivity, response bias, or P3. With increased discriminability, however, both groups improved in mean reaction time to targets and perceptual sensitivity. In controls, P3 became earlier and larger with increased stimulus discriminability and was consistently larger over left temporal areas than over right temporal areas. In schizophrenics, P3 latency was related to stimulus discriminability, but amplitude was not; P3 amplitude did not increase with improvement of perceptual sensitivity and reaction time. Unlike normal controls, schizophrenics had a P3 asymmetry at temporal sites, with reduced left-sided voltages. The results are not consistent with a primarily functional cause of P3 aberrations in schizophrenia and are compatible with the hypothesis that P3 amplitude deficits in schizophrenia are related to underlying pathophysiology of temporal lobe generator sites.

Acoustic Stimulation↗
PubMed1994

Structural characteristics of polysaccharides that induce protection against intra-abdominal abscess formation.

Bacteroides fragilis is the anaerobe most commonly isolated from clinical cases of intra-abdominal sepsis. In a rodent model of this disease process, intraperitoneal injection of the capsular polysaccharide complex (CPC) from B. fragilis provokes abscess formation, while subcutaneous administration of this complex confers protection against B. fragilis-induced intra-abdominal abscesses. The CPC consists of two discrete polysaccharides, polysaccharides A and B (PS A and PS B), each possessing oppositely charged structural groups critical to the ability of these carbohydrates to induce the formation of abscesses. Other bacterial polysaccharides that possess oppositely charged groups (such as the group antigen or capsular polysaccharide from Streptococcus pneumoniae type 1 strains) also exhibited potent abscess-inducing capabilities. We report here that positively and negatively charged groups on polysaccharides are also essential for inducing protection against abscess formation. Vaccination of rats with B. fragilis PS A, PS B, or the S. pneumoniae type 1 capsule protected against intra-abdominal abscesses subsequent to intraperitoneal challenge with each of these polysaccharides. Chemical conversion of the free amino or carboxyl groups on PS A to uncharged N-acetyl or hydroxymethyl groups, respectively, abrogated the ability of this polymer to confer protection against polysaccharide-mediated abscess formation. Adoptive transfer of splenic T cells from polysaccharide-vaccinated rats to naive animals demonstrated that T cells mediated this protective activity. T cells transferred from animals vaccinated with a polysaccharide repeating unit (Salmonella typhi Vi antigen) that normally contains one carboxyl group but was chemically converted to a polymer that possesses both free amino and carboxyl groups (accomplished by de-N-acetylating the Vi antigen) protected naive T-cell recipients against polysaccharide-induced abscesses. These results demonstrate that a distinct structural motif associated with the B. fragilis polysaccharides is necessary for induction of protective immunity against abscess formation associated with intra-abdominal sepsis. However, protection is not antigen specific in a traditional sense. Rather, the protective ability of these structurally dissimilar polysaccharides is conferred by, and perhaps specific for, a motif of oppositely charged groups.

Abdominal Abscess↗