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Biomedical subjects

S D Smith

Publications and source records attributed to S D Smith.

At least 37 records · Page 2Linked to original sources
PubMed2001

The slipping rib syndrome in children.

The slipping rib syndrome is an infrequent cause of thoracic and upper abdominal pain and is thought to arise from the inadequacy or rupture of the interchondral fibrous attachments of the anterior ribs. This disruption allows the costal cartilage tips to sublux, impinging on the intercostal nerves. Children with this entity are seldom described in the literature. We present a retrospective review of 12 children and young adults with slipping rib syndrome and a systematic approach for evaluation and treatment.

Adolescent↗
PubMed2001

Acidification of formula reduces bacterial translocation and gut colonization in a neonatal rabbit model.

BACKGROUND/PURPOSE: The authors hypothesized that gastric acidity is protective because it is bactericidal. They tested acidified formula for protection against gut colonization and bacterial translocation. METHODS: In vitro: Formula was acidified to pH of 2, 3, 4, 5 and innoculated with Enterobacter. Growth over time was quantitatively assessed. In vivo: 442 premature rabbit pups were sorted randomly and fed formula of pH 2, 3, 4, or 7, with ranitidine. Two models were utilized: (1) with bacterial challenge using a known acid sensitive organism, (2) without bacterial challenge to simulate natural gut colonization and to test against organisms of unknown acid sensitivity. Normal acid animals received pH 7 formula, no ranitidine. On day 3, the mesenteric lymph nodes (MLN), spleen, liver, and cecum were harvested and cultured. RESULTS: Bacterial growth was inhibited at pH 2 and 3, growth was logarithmic above pH 4 (P<.001). Total and organ-specific translocation was reduced at pH 3 and below in both models (P<.05). Translocation with formula pH 3 equaled normal acid animals. Quantitative cecal colonization was reduced in pups receiving pH 3 and below in both models (P<.05). CONCLUSION: Acidification of formula below pH 4 is bactericidal to enteric organisms. Acidified formula decreases bacterial translocation and gut colonization.

Animals↗
PubMed2001

Congenital abdominal aortic aneurysm in the infant: case report and review of the literature.

Congenital abdominal aortic aneurysms are a distinct entity from acquired aortic aneurysms. The authors present the case of a 6-week-old boy with a 6-cm aneurysm involving the abdominal aorta and common iliac arteries. Three other cases of congenital aortic aneurysms are reviewed, and an approach to these rare patients is discussed. J Pediatr Surg 36:657-658.

Abnormalities, Multiple↗
PubMed2001

Recurrent congenital diaphragmatic hernia: A novel repair.

BACKGROUND/PURPOSE: Repair of recurrent diaphragmatic hernia continues to be a difficult problem. An innovative method using a nonabsorbable polypropylene prosthetic mesh plug placed via the thoracic approach using minimal dissection is presented. METHODS: A retrospective analysis showed 39 children with congenital diaphragmatic hernia (CDH) who underwent repair between January 1997 and March 2000. Five children suffered a recurrence and underwent repair via the thoracic approach using the Bard Marlex Mesh Perfix Plug (C.R. Bard Inc, Billerica, MA). Follow-up was available in all children and ranged from 1 to 33 months (average, 13.8 months). RESULTS: Age at recurrence ranged from 2 to 48 months (average, 14.8 months), and the average time between initial repair and recurrence was 8.2 months (range, 2 to 16 months). There were no recurrences after the transthoracic mesh plug diaphragmatic hernioplasty. One child died of multiple congenital anomalies 6 months after repair. CONCLUSION: The transthoracic repair of recurrent diaphragmatic hernias using a nonabsorbable polypropylene prosthetic mesh plug represents an innovative approach to a difficult problem in which 5 repairs have been accomplished without recurrence in nearly 14 months of follow-up. J Pediatr Surg 36:1768-1769.

Child, Preschool↗
PubMed2001

Relationships between neurologic disorders and hereditary hearing loss.

Hearing loss is a common disorder that often has a neurologic etiology. Recently, there has been significant progress in the discovery of the genes that cause sensorineural hearing loss, and this has led to increased understanding of the pathophysiology of both syndromic and nonsyndromic hearing problems. These genes cover the range of processes involved in neurologic development and function, including structural genes, transcription factors, and tumor suppressors; genes involved in signal transduction processes, such as ion homeostasis and intracellular transport; and mitochondrial genes responsible for oxidative phosphorylation and energy production. Interactions between genes as well as between genes and environmental factors have also been documented. Understanding of these processes should lead to earlier and more accurate diagnosis and more effective treatment for neurologic disorders and hearing loss.

Adolescent↗
PubMed2001

Catheter materials affect the incidence of late blood-borne catheter infection.

BACKGROUND: Adherence of bacteria and subsequent catheter-related infections (CRI) are greatly enhanced by the fibrin sheath that develops on indwelling catheters. Since the infection rate of catheters without fibrin sheaths is low and the fibrin sheath mediates bacterial adherence, catheter material is not thought to affect the incidence of late catheter-related infection. METHODS: A total of 276 rats had catheters placed in the right jugular vein with the proximal end buried subcutaneously to eliminate exit site infection. Rats were divided into two groups: silastic catheters (SC; n = 133) and polyurethane catheters (PC; n = 143). Injections of 1 x 10(8) CFU/mL of Staphylococcus epidermidis were given via the tail vein on either the day of surgery, day 0 (n = 53 SC, n = 51 PC), or on postoperative day 10 (n = 50 SC, n = 62 PC). Thirty animals from each group (SC, PC) received sterile saline injections on day 10 and served as controls. Animals were sacrificed on postinjection day 3. Catheters were removed via the chest and placed into trypticase soy broth. Broth was incubated at 37 degrees C for 48 h. Microscopy for the fibrin sheath was done on 20 randomly selected catheters (10/group). Data were compared using Fisher's exact test, with p < 0.05 considered significant. RESULTS: Incidence of CRI was equal prior to the formation of the fibrin sheath, while CRI was significantly higher in silastic catheters in the presence of a fibrin sheath. Without a fibrin sheath (day 0), 8/53 silastic catheters and 3/51 polyurethane catheters were infected (p = NS). With a fibrin sheath (day 10), 31/50 silastic catheters were infected versus 20/62 polyurethane catheters (p < 0.05). Control catheters were all culture negative (30/group). With light microscopy, 20/20 catheters had fibrin sheaths at day 10 with no visible difference between silastic and polyurethane catheters. CONCLUSION: Catheter material does affect the incidence of catheter-related infection even when catheters are coated with a fibrin sheath. This difference may relate to a difference in the fibrin sheath itself as it forms on different catheter materials.

Animals↗
PubMed2001

Coffee, microscopy, and the Lancet's Analytical Sanitary Commission.

Coffee was the most frequently analysed commodity in the Lancet's Analytical Sanitary Commission's reports on adulteration published between 1851 and 1854. Techniques of sample collection and microscopical investigation developed to analyse coffee were applied to other foods and drinks by Arthur Hill Hassall, and his findings were instrumental in establishing the first parliamentary select committee to investigate food purity in 1855. The committee's recommendations formed the basis of the 1860 Act to Prevent the Adulteration of Food and Drink. Hassall's research in applied microscopy has been interpreted by historians as marking a critical point in the campaign to secure tighter food controls and as an example of a public health debate being transformed by the precise measurements of a dispassionate scientist. This article questions the objectivity with which the ASC selected foodstuffs for analysis, the superiority of microscopy over techniques of chemical analysis, and the extent to which coffee was an adulterated commodity in the middle of the nineteenth century.

Coffee↗
PubMed2001

Thromboxane A(2) limits differentiation and enhances apoptosis of cultured human trophoblasts.

Prostanoids influence differentiation in diverse cell types. Altered expression of cyclooxygenase and prostaglandins has been implicated in the pathophysiology of placental dysfunction, which results in preeclampsia and fetal growth restriction. We hypothesized that prostanoids modulate differentiation and apoptosis in cultured human trophoblasts. Villous cytotrophoblasts were isolated from term human placentas and cultured in serum-free medium. The level of human chorionic gonadotropin was used as a marker of biochemical differentiation of primary trophoblasts, and syncytia formation was used as a marker of morphologic differentiation. Of the prostanoids tested, we found exposure to thromboxane A(2) hindered both biochemical and morphologic differentiation of cultured trophoblasts. As expected, human chorionic gonadotropin levels in the media were elevated in a concentration-dependent manner in the presence of the thromboxane synthase inhibitor, sodium furegrelate, or the thromboxane A(2) receptor blocker SQ 29,548. Furthermore, thromboxane A(2) enhanced trophoblast apoptosis, determined using terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining, cell morphology, and a concentration-dependent increase in p53 expression. We conclude that thromboxane A(2) hinders differentiation and enhances apoptosis in cultured trophoblasts from term human placenta. We speculate that thromboxane may contribute to placental dysfunction by restricting differentiation and enhancing apoptosis in human trophoblasts.

Apoptosis↗
PubMed2000

Elevated CO2 increases productivity and invasive species success in an arid ecosystem.

Arid ecosystems, which occupy about 20% of the earth's terrestrial surface area, have been predicted to be one of the most responsive ecosystem types to elevated atmospheric CO2 and associated global climate change. Here we show, using free-air CO2 enrichment (FACE) technology in an intact Mojave Desert ecosystem, that new shoot production of a dominant perennial shrub is doubled by a 50% increase in atmospheric CO2 concentration in a high rainfall year. However, elevated CO2 does not enhance production in a drought year. We also found that above-ground production and seed rain of an invasive annual grass increases more at elevated CO2 than in several species of native annuals. Consequently, elevated CO2 might enhance the long-term success and dominance of exotic annual grasses in the region. This shift in species composition in favour of exotic annual grasses, driven by global change, has the potential to accelerate the fire cycle, reduce biodiversity and alter ecosystem function in the deserts of western North America.

Carbon Dioxide↗
PubMed2000

Isolation and tissue profiles of a large panel of phage antibodies binding to the human adipocyte cell surface.

Phage display is a powerful technique for the rapid selection and isolation of antibodies to any given target antigen. We have applied this technology to isolate over 100 different human antibodies that bind to antigens expressed in situ on the human adipocyte cell surface. This is a diverse panel of antibodies, as indicated by the V-region sequences. The binding profile of each anti-adipocyte antibody has been characterised using phage antibody immunocytochemistry against a panel of normal human tissues. Although there was some variation in the intensity of the adipocyte staining, each antibody consistently recognised adipocytes, where present, irrespective of the tissue source. In addition, all of the antibodies recognised at least one other cell type other than the adipocyte cell surface. In total, over 50 different tissue-binding profiles were recorded, with the most frequently recognised tissues identified as capillaries or smooth muscle. Extensive tissue binding profiles were generated for some antibodies using a panel of 37 different human tissues. This identified anti-adipocyte antibodies with unexpected profiles, such as FAT.13, which binds only to adipocytes and capillaries in the entire tissue panel. We believe this is the most extensive survey ever undertaken of the human adipocyte cell surface. Moreover, similar methodology could be used to derive complete tissue-binding profiles of antibodies against cell-surface antigens of any cell type. Indeed, by screening antibodies on both normal and diseased tissues, it may be possible to identify antigenic associations between different cell types and the pathologies of many diseases.

Adipocytes↗
PubMed2000

Rb and p130 regulate RNA polymerase I transcription: Rb disrupts the interaction between UBF and SL-1.

We have previously demonstrated that the protein encoded by the retinoblastoma susceptibility gene (Rb) functions as a regulator of transcription by RNA polymerase I (rDNA transcription) by inhibiting UBF-mediated transcription. In the present study, we have examined the mechanism by which Rb represses UBF-dependent rDNA transcription and determined if other Rb-like proteins have similar effects. We demonstrate that authentic or recombinant UBF and Rb interact directly and this requires a functional A/B pocket. DNase footprinting and band-shift assays demonstrated that the interaction between Rb and UBF does not inhibit the binding of UBF to DNA. However, the formation of an UBF/Rb complex does block the interaction of UBF with SL-1, as indicated by using the 48 kDa subunit as a marker for SL-1. Additional evidence is presented that another pocket protein, p130 but not p107, can be found in a complex with UBF. Interestingly, the cellular content of p130 inversely correlated with the rate of rDNA transcription in two physiological systems, and overexpression of p130 inhibited rDNA transcription. These results suggest that p130 may regulate rDNA transcription in a similar manner to Rb.

Animals↗
PubMed2000

Gene expression, localization, and pharmacological characterization of endothelin receptors in diabetic rat bladder dome.

As there are significant amounts of functional endothelin receptors in the mammalian urinary tract, we examined the effect of experimental diabetes on the expression of endothelin receptors and their mRNAs in the rat bladder dome. The density of endothelin receptors in the rat bladder dome was higher (8 and 16 weeks following the onset of diabetes) than in age-matched controls. Insulin treatment, started 8 weeks after the induction of diabetes, partially reversed the endothelin receptor alterations. The pharmacological profile of the endothelin receptors in the bladder dome was similar in all groups and was consistent with the predominance of the endothelin ET(A) receptor subtype (ET(A):ET(B)=approximately 4:1). Autoradiographic studies demonstrated that the endothelin receptors were located in all tissue components of the bladder, including epithelial and muscular layers. Semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) data indicated that diabetes increased the expression level of gene transcripts for both endothelin receptor subtypes and that insulin treatment reversed the mRNA upregulation.

Animals↗
PubMed2000

Direct measurement of interfacial curvature distributions in a bicontinuous block copolymer morphology.

Self-consistent field theory predicts that the complex phase behavior of block copolymers does not originate solely from the interface seeking constant mean curvature as once thought, but instead reflects competing minimization of interfacial tension and packing frustration. To test this prediction, we directly measure interfacial curvature distributions from a 3D image reconstruction of the bicontinuous gyroid morphology. Results obtained here reveal that the gyroid interface is not constant mean curvature and confirm the importance of packing frustration in the stabilization of such complex nanostructures.

Butadienes↗
PubMed2000

Intussusception following the Ladd procedure.

HYPOTHESIS: The Ladd procedure for malrotation predisposes children to postoperative intussusception (POI). DESIGN: Retrospective case-control review. SETTING: University-affiliated tertiary care pediatric hospital. PATIENTS: Five of 159 patients undergoing the Ladd procedure between 1995 and 1998 developed POI. Predisposing factors were sought by comparison with age-matched controls who underwent the Ladd procedure during the same period. The entire Ladd group was compared with all 1717 patients undergoing any other laparotomy during the same period for incidence of POI. MAIN OUTCOME MEASURES: Differences in weight, percentile weight, age, length of nasogastric suction, time to oral intake, and length of stay between Ladd patients developing POI and age-matched controls from the Ladd group were compared using the Mann-Whitney U test. Incidence of POI after the Ladd procedure and "other laparotomy" was compared using chi2 analysis. RESULTS: In the Ladd group, there were 5 cases of POI (3.1%). There was 1 case of POI (0.05%) after all other laparotomies (P<.001). Symptoms developed at a mean +/- SD of 7.2 +/- 2.1 days. Upper gastrointestinal tract with small bowel follow-through showed partial bowel obstruction in 4 cases and was normal in 1 case. Reexploration took place at a mean +/- SD of 9.2 +/- 2.8 days. Children developing POI after undergoing the Ladd procedure were less likely to be small for their age (P= .03) than age-matched controls undergoing the Ladd procedure. CONCLUSIONS: The Ladd procedure predisposes children to POI. Aggressive investigation, including reexploration, should not be delayed if a child has symptoms of prolonged ileus within 2 weeks after undergoing a Ladd procedure.

Case-Control Studies↗
PubMed2000

Ahmed glaucoma valve implant vs trabeculectomy in the surgical treatment of glaucoma: a randomized clinical trial.

PURPOSE: To compare the short- and intermediate-term results of two commonly used glaucoma surgical procedures, trabeculectomy and Ahmed glaucoma valve implant. METHODS: A randomized clinical trial was performed at two international centers. One eye each of consecutive patients requiring glaucoma surgery for intraocular pressure control was randomized to receive either trabeculectomy or the Ahmed implant. RESULTS: Of the 117 patients, 62 were randomized to trabeculectomy and 55 to the Ahmed implant. With a mean follow-up of 9.7 months, the trabeculectomy group had statistically lower intraocular pressures at weeks 6 to 15 (12.6 mm Hg vs 16.4 mm Hg) and months 11 to 13 (11.4 mm Hg vs 17.2 mm Hg) than the Ahmed implant group. Compared with preoperative status, no statistically significant differences between groups were noted for visual acuity, visual field, lens status, and final anterior chamber depth. The cumulative probabilities of success (intraocular pressure <21 mm Hg and at least 15% reduction in intraocular pressure from preoperative level) were 83.6% for trabeculectomy and 88.1% for Ahmed implant (P =.43). However, the Ahmed implant group had a greater adjunctive medication requirement. On the last visit, 10 of the trabeculectomy eyes and 19 of the Ahmed implant eyes required at least one topical medication (P =.01). There was no statistically significant difference in the rate of complications between the two groups. CONCLUSIONS: Lower mean intraocular pressures were noted for the trabeculectomy group. All other results, including success (as defined in this study) and frequency of complications, were comparable between the two groups.

Female↗
PubMed2000

Development of human oocytes matured in vitro for 28 or 36 hours.

OBJECTIVE: To compare the effects on human oocytes of in vitro maturation periods of 28 hours and 36 hours. DESIGN: Retrospective analysis. SETTING: University teaching hospital. PATIENT(S): A total of 48 infertile patients undergoing 55 cycles who volunteered for the experimental treatments. INTERVENTION(S): Immature oocytes were aspirated with use of transvaginal ultrasonography. Oocytes were matured, fertilized by intracytoplasmic sperm injection, and cultured for 2.5 or 3 days before being replaced into the uterus. MAIN OUTCOME MEASURE(S): Oocyte maturation, fertilization and cleavage rates, and clinical pregnancy rate. RESULT(S): Maturation of oocytes for either 28 hours or 36 hours before insemination resulted in similar rates of maturation, fertilization, and cleavage. The clinical pregnancy rate was similar in both groups (14%-15%). CONCLUSION(S): Shortening the in vitro maturation period does not compromise subsequent embryonic development.

Cell Size↗
PubMed2000

Modeling differences in the vibration response characteristics of the human body.

Mathematical models may provide a useful tool for the development and evaluation of seating systems for vibration mitigation. A five-degree-of-freedom (DOF) model was formulated based on the measured driving-point impedance and transmissibilities of major anatomical structures contributing to the observed resonance behaviors. The model was limited in its ability to simulate differences observed in the resonance behaviors of a broader population and was unable to simulate the multiple resonances observed in the thigh. This paper describes the effectiveness of a modified five DOF model in simulating the major resonance behaviors observed in the population using representative data from a 56 kg female and 75 kg male. In addition, the model was also evaluated for its ability to predict the effects of selected seat cushions. The modified lumped-parameter model improved the peak chest and spine transmissibility simulations. The model was effective in simulating both the lower impedance peak observed in the primary resonance region (4-8 Hz) and the prevalent impedance peak observed in the second resonance region (7-10 Hz) in the smaller subjects. However, the model was not effective in predicting the dampening observed in the second resonance peak with the use of cushions. Redistribution of the model coefficients for the legs and the consideration of coupling between the legs and other anatomical structures may further improve the ability of the lumped-parameter model to predict the effects of seating systems on vibration transmission in the human body.

Biomechanical Phenomena↗