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Biomedical subjects

R S Smith

Publications and source records attributed to R S Smith.

At least 73 records · Page 4Linked to original sources
PubMed1997

Transvaginal ultrasonography for all placentas that appear to be low-lying or over the internal cervical os.

The purpose of this study was to determine in what percentage of cases the assessment of placental localization using transabdominal sonography (TAS) was changed after transvaginal sonography (TVS) was applied. TVS was prospectively performed on all pregnant women of at least 15 weeks' gestation, when the placental edge using TAS appeared to be over or within 2 cm (low-lying) of the internal cervical os. The time required for the TVS scan and the distance of the placental edge from the internal cervical os were recorded. Of the 168 patients entered into the study, 131 were analyzed. Landmarks were poorly seen in 50% of the cases when using TAS. In 66 cases, the placenta appeared low or possibly over the internal cervical os using TAS, but a definitive diagnosis could not be made due to suboptimal visualization. In the remaining 65 cases, visualization of the internal os and placental edge was possible using both TAS and TVS. In this group, there was a change in the diagnosis in 26% of the cases after TVS was performed. Our results suggest that optimal visualization of the placental edge and internal cervical os is usually difficult with TAS when the placenta appears low-lying or over the internal cervical os. The assessment of placental localization was changed in over one-quarter of cases (26%) after transvaginal sonography was performed. The use of transvaginal ultrasound should be seriously considered when the placenta appears to be low or over the internal cervical os by transabdominal ultrasound.

Cervix Uteri↗
PubMed1997

Diagnostic and therapeutic laparoscopy for penetrating abdominal trauma: a multicenter experience.

BACKGROUND: Considerable skepticism still exists about the role of diagnostic laparoscopy in the evaluation of penetrating abdominal trauma. The reported experience with therapeutic laparoscopy has been limited. METHODS: Retrospective analysis of a collective experience from three large urban trauma centers with 510 patients (316 stab wounds, 194 gunshot wounds) who were hemodynamically stable and had no urgent indications for celiotomy. RESULTS: Laparotomy was avoided in 277 of the 510 patients (54.3%) either because of nonpenetration or insignificant findings on laparoscopy. All were discharged uneventfully after a mean hospital stay of 1.7 days. Twenty-six had successful therapeutic procedures on laparoscopy (diaphragmatic repair in 16 patients, cholecystectomy in 1 patient, hepatic repair in 6 patients, and closure of gastrotomy in 3 patients) with uneventful recovery. In the remaining 203 patients, laparotomy was therapeutic in 155. Fifty-two patients had nontherapeutic celiotomy for exclusion of bowel injuries or as mandatory laparotomy for penetrating gunshot wounds (19.7%). The overall incidence of nontherapeutic laparotomy was 10.2%. Complications from laparoscopy were minimal (10 of 510) and minor. CONCLUSIONS: Laparoscopy has an important diagnostic role in stable patients with penetrating abdominal trauma. In carefully selected patients, therapeutic laparoscopy is practical, feasible, and offers all the advantages of minimally invasive surgery.

Abdominal Injuries↗
PubMed1997

Mouse mutations as models for studying cataracts.

Human cataracts may be congenital or appear later in life; nuclear, cortical and lens epithelial proliferation forms have all been described. Due to the high degree of genetic homology, it is not surprising that multiple spontaneous or induced single gene mutations result in morphologically similar forms in the mouse. There are many different mutations in inbred strains of mice in which cataracts are a part of the phenotype. These mutations are of potential value in deciphering the molecular mechanisms involved in cataract formation. This report reviews the currently published cataract mutations in mice.

Animals↗
PubMed1997

Birthweight prediction by three-dimensional ultrasonographic volumes of the fetal thigh and abdomen.

Our validation study examined a three-dimensional ultrasonographic phantom that contained irregularly shaped volume targets ranging from 0.5 to 76.1 milliliters. Four different examiners made blinded measurements from volume datasets that were acquired by 4 and 7 MHz transducers. Birthweight predictions using abdominal and thigh volumes from 18 term fetuses also were compared with two-dimensional ultrasonographic methods. In vitro volume measurements were accurate, precise, and repeatable despite a small systematic overestimation with increasing object size. Mean systematic error and precision for birthweight predictions by three-dimensional ultrasonography (-0.03% +/- 6.1%) were not significantly different from those by two-dimensional ultrasonography (-0.60% +/- 8.8%). Conventional prediction methods yielded three birthweights with greater than 15% error. By comparison, except for one infant whose birthweight indicated an 11% error, all predictions based on fetal volume parameters were within 10% of true values. Accurate birthweight predictions by fetal volume parameters appear to be technically feasible at term gestation although their practical clinical application requires further investigation. Birthweight predictions in this manner may allow remote consultants to evaluate the fetus over wide-area computer networks despite the physical absence of the patient.

Abdomen↗
PubMed1997

Sonographic examination of abdominal trauma by senior surgical residents.

The focused ultrasound examination is assuming an important role in the evaluation of abdominal trauma. We evaluated the ability of senior surgical residents to independently use this technique. We also evaluated the efficacy of a single sonographic examination instead of serial examinations. Senior surgical residents underwent sonography instruction by two attending surgeons certified in the technique. Once proficiency was attained, a single sonographic examination was performed on patients with abdominal trauma triaged to a Level I trauma center. Residents obtained additional diagnostic studies deemed appropriate. Ultrasound results were compared with other diagnostic studies and clinical course. Sonography was performed on 518 patients between January 10, 1995 and June 30, 1996. Mechanism of injury was blunt in 92 per cent of patients and penetrating in 8 per cent. There were 22 true positives, 12 false positives, 8 false negatives, and 476 true negatives. Five of the eight false negatives were secondary to limited hollow viscus injuries with minimal associated intraperitoneal fluid. Sensitivity, specificity, accuracy, positive predictive value, and negative predictive value were 73.3, 97.5, 96.1, 64.7, and 98.3 per cent, respectively. The use of computed tomography and diagnostic peritoneal lavage decreased from 25 to 18 per cent and 3.2 to 0.2 per cent, respectively, as diagnostic tools. We conclude that surgical residents can competently perform trauma ultrasound. A single sonographic examination is effective and reliable. Sonography has essentially replaced diagnostic peritoneal lavage in our institution.

Abdominal Injuries↗
PubMed1997

Fibroblasts as sentinel cells. Synthesis of chemokines and regulation of inflammation.

In this commentary, we have suggested that the fibroblast should be considered a sentinel cell. This concept is based on the fibroblast's ability to function both as a structural element and as a vital immunoregulatory cell. In some tissues, these capabilities may be ascribable to subsets of fibroblasts, rather than to some of the general fibroblast populations. The pioneering research of Xia et al, as well as that of others, highlights the need to explore the importance of fibroblasts as playing critical roles in disease. Emerging concepts regarding tissue-specific fibroblasts and fibroblast heterogeneity need to be considered in studies of their biosynthetic capabilities. Of special importance is the recent insight that the NF kappa B/RelB family of transcription proteins have apparently different regulatory roles in fibroblasts and hematopoietic cells. Therefore, with regard to therapeutic strategies targeting molecules such as RelB, caution should be exercised as their interruption may have very different consequences in macrophages compared with fibroblasts. For example, inhibition of RelB in macrophages may well prevent enhanced chemokine expression, whereas in fibroblasts, a critical governor for preventing chemokine expression would be lost. Overall, this could lead to exacerbation of inflammation rather than to an attenuation of the process.

Animals↗
PubMed1997

Circadian rhythms and enhanced athletic performance in the National Football League.

Circadian rhythms produce daily changes in critical elements of athletic performance. We explored the significance of performing at different circadian times in the National Football League (NFL) over the last 25 seasons. West Coast (WC) NFL teams should have a circadian advantage over East Coast (EC) teams during Monday Night Football (MNF) games because WC teams are essentially playing closer to the proposed peak athletic performance time of day. Retrospective data analysis was applied to all games involving WC versus EC teams playing on MNF with start times of 9:00 p.m. Eastern Standard Time (EST) from the 1970-1994 seasons. Logistic regression analysis of win-loss records relative to point spreads and home-field advantage was examined. West Coast teams win more often (p < 0.01) and by more points per game than EC teams. West Coast teams are performing significantly (p < 0.01) better than is predicted by the Las Vegas odds (the point spread). This apparent advantage enhances home-field advantage for WC teams and essentially eliminates the beneficial effects of home-field advantage for EC teams during MNF games. These results support the presence of an enhancement of athletic performance at certain circadian times of the day.

Circadian Rhythm↗
PubMed1996

Direct current shocks to the heart generate free radicals: an electron paramagnetic resonance study.

OBJECTIVES: We sought to demonstrate that direct current (DC) shocks to the heart generate free radicals. BACKGROUND: Although it is a lifesaving maneuver, defibrillation is known to have myocardial toxicity. The mechanism of this toxicity is unknown. If DC shocks generate free radicals, free radicals could be a mechanism of myocardial injury. METHODS: In a canine model, DC shocks of 10 to 100 J were delivered to the epicardium of both beating and fibrillating hearts, and 200-J transthoracic shocks were administered in dogs with beating hearts. Ascorbate free radical (AFR) concentration was measured in arterial blood and blood continuously withdrawn from the coronary sinus. In some dogs, the antioxidant enzymes superoxide dismutase (15,000 U/kg) and catalase (55,000 U/kg) (SOD/Cat) were administered before shocks. RESULTS: Ascorbate free radicals were generated by DC shocks. A peak AFR increase of 14 +/- 2% (mean +/- SEM) was seen 5 to 6 min after 100-J epicardial shocks. A peak AFR increase of 7 +/- 5% occurred after transthoracic shocks. There was a significant linear relation between the shock energy and peak percent AFR increase: %AFR increase = 0.18 (Shock energy) + 2.9 (r = 0.73, p < 0.0001). Shocks delivered to hearts in ventricular fibrillation (30 s) resulted in generation of AFR equal to but not greater than that observed during similar shocks delivered to beating hearts in sinus rhythm. Multiple successive shocks (100 J delivered twice or five times) did not result in a greater AFR increase than single 100-J shocks, indicating that peak, not cumulative, energy is the principal determinant of AFR increase. Animals receiving SOD/Cat before shock administration showed significant attenuation of the AFR increase. CONCLUSIONS: Direct current epicardial and transthoracic shocks generate free radicals; antioxidant enzymes reduce the free radical generation by shocks.

Animals↗
PubMed1996

Chromosomal localization of a new mouse lens opacity gene (lop18)

Examination of mouse strains with a slit lamp and indirect ophthalmoscopy revealed that strain CBA/CaGnLe has a white cataract obvious at weaning age. It soon progresses to a large white nuclear cataract with mild cortical changes. Crosses with C57BL/6J showed that this is inherited as a single recessive fully penetrant gene, which we have designated lop18 (lens opacity 18). Linkage analysis using visible marker T (brachyury), histocompatibility marker H2, and microsatellite markers D17Mit21, D17Mit28, D17Mit38, and D17Mit46 shows that the lop18 gene is located, approximately 16 cM from the centromere on mouse Chromosome 17. It is a likely candidate mutation for the alpha-crystallin (Crya1) gene.

Animals↗
PubMed1996

Analysis of hypermutation in immunoglobulin heavy chain passenger transgenes.

Somatic hypermutation of immunoglobulin (Ig) genes plays a critical role in the maturation of the human antibody response. The molecular basis of this important process is, however, unknown. To identify cis-acting sequences that initiate and target hypermutation, we have made three minitransgenes containing different portions of an Ig heavy chain (IgH) locus. Each transgene is a passenger, bearing a nonsense mutation preventing its translation; thus, transgene mutations reflect the endogenous mutational process and are not subject to affinity selection. To study transgenes after their circulation through the compartment associated with hypermutation in vivo, we rescued B cells as hybridomas after hyperimmunizing mice with the hapten 4-hydroxy-3-nitrophenyl acetyl (NP). Hybridoma transgene and endogenous variable regions were amplified by polymerase chain reaction, subcloned, and sequenced. Endogenous anti-NP VDJ regions show the expected, at times extensive degree of base substitution. In mice bearing the smallest construct, which includes 2.4 kb of 5' IgH sequences, a rearranged VDJ region, the 5' matrix attachment region, and the intron enhancer, one of four evaluable hybridomas demonstrates two base substitutions in the V segment of one transgene copy. The two larger constructs include additional 3' IgH sequences (an alpha constant region and the 3' enhancer) and either the original VDJ segment or a substituted T cell receptor beta segment. Ten hybridomas derived from mice bearing these larger constructs demonstrate no evidence of targeted mutation, despite demonstrable transgene transcription in all hybridomas. In our system, mutation of a rearranged VDJ segment and surrounding promoter/enhancer regions is not increased by the juxtaposition of a constant region segment and the IgH 3' enhancer.

Animals↗
PubMed1996

Videothoracoscopy an effective method for evaluating and managing thoracic trauma patients.

BACKGROUND: The objective of this study was to assess the diagnostic and therapeutic effectiveness of videothoracoscopy in thoracic trauma patients. METHODS: The design was a retrospective review. The setting was a major trauma center at an urban county hospital. Forty-one hemodynamically stable patients sustaining thoracic trauma were reviewed (34 penetrating and 7 blunt injuries). In the acute setting (< 24 h), videothoracoscopy was used for continued bleeding(6) and suspected diaphragmatic injury(17). Thoracoscopy was used in delayed settings (> 24 h) for treatment of thoracic trauma complications(18) including clotted hemothorax(14), persistent air leak(1), widened mediastinum(1), and suspected diaphragmatic injury(2). RESULTS: The average Injury Severity Score (ISS) of these patients was 18.9 +/- 10.0. Three of 6 patients (50%) with continued bleeding were successfully treated thoracoscopically. Nine of 10 (90%) diaphragmatic injuries were confirmed by thoracoscopy, and 7 of these 9 patients (77%) were repaired thoracoscopically. Thirteen of 14 patients (93%) with clotted hemothoraces and one with a persistent air leak were treated successfully using thoracoscopy. An aortic injury was ruled out in one patient. CONCLUSIONS: Videothoracoscopy is a safe, accurate, minimally invasive, and potentially cost-effective method for the diagnosis and therapeutic management of thoracic trauma patients.

Adolescent↗
PubMed1996

The significance of ultrasonographically diagnosed fetal wrist position anomalies.

OBJECTIVE: Our purpose was to determine the clinical significance of ultrasonographically diagnosed fetal wrist position anomalies. STUDY DESIGN: The relationship of the fetal hand to the forearm was prospectively evaluated in all second- and third-trimester scans over a 5-year period. If an abnormal wrist position was detected, a targeted scan, including echocardiography, was performed. The outcomes of abnormal pregnancies were obtained. RESULTS: An abnormal relationship of the hand to the forearm was found in 22 fetuses in 27,467 scans. Nine had a normal karyotype, and 13 had an abnormal karyotype. Among the nine with normal chromosomes, three had evidence of a movement disorder. Three with normal karyotypes are alive; two of these are the only normally functioning survivors. They had no other major anomalies and were shown prenatally to have normal movement of the limbs. CONCLUSIONS: An abnormal fetal wrist position is associated with a high incidence of karyotype and movement abnormalities.

Chromosome Aberrations↗
PubMed1996

The use of second-trimester transvaginal sonography to predict placenta previa.

Our objective was to determine the incidence and rate of persistence of placenta previa diagnosed at 15-20 weeks' gestation by using transvaginal sonography (TVS), and to describe the characteristics of TVS that predict placenta previa at delivery. Patients having placental tissue within 20 mm of the cervical os were prospectively identified by transabdominal ultrasound and underwent TVS. The distance of the placental edge from the cervical os was measured in millimeters. Characteristics of TVS predicting placenta previa at delivery were analyzed by logistic regression. The incidence of placenta previa diagnosed by TVS at 15-20 weeks was 1.1%; 14% persisted until delivery. Gestational age at the time of TVS and the distance of the placental edge to the cervical os helped predict placenta previa at delivery. Between 15 and 24 weeks' gestation, placenta overlapping the internal os by > or = 10 mm identified patients at risk of placenta previa at delivery with 100% sensitivity and 85% specificity. The use of TVS in the second trimester to diagnose placenta previa resulted in a lower incidence than was historically reported with the use of transabdominal ultrasound. The distance of the placental edge from the cervical os helps identify patients at risk of previa at delivery.

Female↗
PubMed1996

Corn1: a mouse model for corneal surface disease and neovascularization.

PURPOSE: To describe a new mouse model of corneal surface disease and neovascularization. METHODS: Anatomic changes were demonstrated in corn1 and control A.By/SnJ mice from day 10 of gestation of 8 months of age by routine techniques of light microscopic and scanning electron microscopy. Corneal epithelial cell kinetics were evaluated by labeling cells in the "S" phase of the cell cycle by intraperitoneal injection of tritiated thymidine. Labeled cells were counted under 250X magnification, and the length of the corneal epithelial chord was measured by morphometric techniques. Results were expressed as labeled cells per linear millimeter of corneal epithelium. The corn1 locus was mapped using selected back-crosses. RESULTS: Corn1 is characterized by early, irregular thickening of the corneal epithelium, development of stromal neovascularization by 20 days of age, and cataract by 48 days of age. Corneal epithelial cell kinetics demonstrated prominent labelling of corn1 mice at 30 days of age compared to the control mice. Corn1 behaves as an autosomal recessive gene and is located on mouse chromosome 2, approximately 5.2 cM from the agouti locus. Heterozygotes have no corneal disease. CONCLUSIONS: Corn1 mice, with genetically determined corneal epithelial hyperplasia and stromal neovascularization, may be particularly useful in studies of neovascularization and corneal surface proliferative disease.

Animals↗
PubMed1996

Trauma experience of Navy surgeons: assessment and commentary.

Numerous reports have suggested that surgical readiness during Operation Desert Storm was poor. We surveyed active duty Navy surgeons to assess current trauma experience and capability. A survey concerning trauma and critical care experience, as well as self-rating of skills, was mailed to all active duty surgeons (n = 185) in 1993. The response rate was 79% (146/185). A high turnover rate of surgeons was indicated by: (1) 51% (75/146) of surgeons had less than 3 years of experience following residency; and (2) only 42% (61/146) had served in the Gulf War. Only 12% of active duty surgeons (18/146) were involved in trauma care. Only 10% (14/146) had performed more than 20 operations for trauma in the preceding 1 years, and 85% (124/146) had performed fewer than 10 operations. In the preceding 5 years, 84% (122/146) had performed fewer than 100 operations for trauma, and 42% (61/146) had performed none. Critical care experience ranged from 0 to 20 patients per month (mean = 3). Despite limited recent experience, 84% (123/146) of respondents rated their trauma skills as adequate (n = 43), good (n = 49), or excellent (n = 31). We conclude that most Navy surgeons have minimal recent experience in trauma care. A high rate of turnover mandates training strategies that provide an ongoing exposure to injured patients. This could be accomplished by designating military hospitals as trauma centers or by placing military surgeons in civilian trauma centers.

Clinical Competence↗
PubMed1995

Predictive value of fetal serum beta 2-microglobulin for neonatal renal function.

When fetal urinary-tract malformations (UTM) are discovered, management is based on the prediction of postnatal renal function, currently made by fetal urinary biochemistry and sonography. Serum beta 2-microglobulin has been used postnatally to estimate renal function and does not cross the placenta. We investigated the relation between fetal serum beta 2-microglobulin and renal function by comparing 64 unaffected fetuses and 15 fetuses with UTM. A beta 2-microglobulin above a 5.6 mg/L cut-off gave cross-validated sensitivity of 80.0%, specificity of 98.6%, a positive predictive value of 88.9%, and a negative predictive value of 97.1% for our cohort study.

Cohort Studies↗
PubMed1995

Anterograde to retrograde reversal of fast axonal transport within cold blocked and rewarmed intact axons.

The possibility that anterograde to retrograde reversal of axonal transport might take place in mid axon at a site distant from any nerve termination was investigated in sciatic nerve preparations from Xenopus laevis. The nerve, containing a pulse of anterogradely transported protein labeled with [35S]methionine, was kept in a two-compartment temperature controlled chamber. One compartment containing the proximal nerve was maintained at room temperature throughout the duration of an experiment while the second compartment containing the distal nerve, and separated from the first by a thermal barrier, was initially cooled to 3-4 degrees C and later warmed to room temperature. Transport of labeled proteins in the nerve was detected with a position-sensitive detector of ionizing radiation. With the distal portion of the nerve cold, the pulse of labeled protein transported up to the thermal barrier and stopped. When the distal part of the nerve was warmed to room temperature, retrograde and anterograde pulses of label propagated away from the thermal barrier with no time delay. The retrograde pulse could be collected on the distal side of a proximally placed tie and could be eliminated by treatment of the proximal nerve with vinblastine or dinitrophenol. Functional and structural evidence indicated that the cold block and thermal barrier were not destructive to the axons. Electron microscopy showed that the numerical density of axonal microtubules distal to the cold block was decreased about seven fold during the cold treatment and that this decrease could be prevented by 10 mumol/l taxol.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗