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Biomedical subjects

R Smith

Publications and source records attributed to R Smith.

At least 289 records · Page 16Linked to original sources
PubMed2000

Hyalinizing spindle cell tumor with giant rosettes--a soft tissue tumor with mesenchymal and neuroendocrine features. An immunohistochemical, ultrastructural, and cytogenetic analysis.

CONTEXT: Hyalinizing spindle cell tumor with giant rosettes is a recently described biphasic neoplasm of soft tissues that shares mesenchymal and neuroendocrine features. Its morphologic structure is distinctive, with the presence of hyalinized paucicellular foci that are termed rosettes. The cells around the latter display positive immunoreactivity for neuroendocrine markers. The small number of cases described to date indicates that they tend to be localized in the extremities. OBJECTIVE: To describe the clinicopathologic features of 2 unusual cases of hyalinizing spindle cell tumor with giant rosettes. METHODS AND RESULTS: One tumor was located in the prestyloid parapharyngeal space and the second in the left thigh. Both tumors were well circumscribed and surrounded by a thin capsule-like fibrous band without infiltrating projections. The rosettes were embedded in a spindle cell proliferation. Immunohistochemical stains showed positive results for S100 protein, synaptophysin, CD57, protein gene product 9.5, and neuron-specific enolase exclusively in the cells palisading the rosettes. These markers were negative in the spindle cell portions of the tumor. The latter were immunoreactive for factor XIIIa, vimentin, HAM56, collagen IV, and CD68. Vimentin was the only marker shared by the rosette-forming cells and the spindle cells. Ultrastructurally, the rosette-forming cells contained neurosecretory granules. This study describes the first cytogenetic analysis in this type of tumor revealing 2 cell lines, both containing a balanced translocation between chromosomes 7 and 16. Follow-up of the patients at 16 and 8 months did not disclose evidence of recurrence. CONCLUSIONS: These 2 new cases increase the awareness of hyalinizing spindle cell tumor with giant rosettes and demonstrate that it is a spindle cell neoplasm of unique cytogenetic rearrangements composed of dendritic, histiocytic, and fibroblastic cells admixed with cells that have neuroendocrine differentiation.

Adult↗
PubMed2000

Percutaneous ablation of caliceal diverticulum: long-term followup.

PURPOSE: A caliceal diverticulum is a nonsecretory cavity that serves as a conduit for urinary stasis and its ensuing complications. Indications for intervention and modes of therapy are controversial. We report a series of patients treated with a percutaneous endourological approach to ablation of the diverticular cavity. MATERIALS AND METHODS: A total of 14 patients underwent percutaneous ablation of a caliceal diverticulum for flank pain a mean of 15.5 months in duration. These caliceal diverticula were associated with urinary tract infection in 43% of cases and/or renal calculi in 78%. Mean calculus diameter was 10.2 mm. and mean diverticular diameter was 10.9 mm. An open ended ureteral catheter was placed into the renal pelvis via cystoscopy. Retrograde instillation of radiopaque contrast medium facilitated the localization of a percutaneous renal puncture made directly into the caliceal diverticulum. A flexible tip guide wire was coiled in the diverticulum, and no effort was made to traverse the infundibulum and establish continuity with the remainder of the collecting system. Tract dilation into the caliceal diverticulum was performed, and percutaneous stone fragmentation and extraction were accomplished. The lining of the caliceal diverticulum was electrocauterized using a roller ball electrode. A balloon nephrostomy tube consisting of a Foley catheter with the tip cut off was positioned into the diverticulum. An indwelling ureteral stent was placed and a Foley catheter provided bladder drainage for 48 hours to maintain a low pressure system. The nephrostomy tube was removed after 24 to 48 hours and the ureteral stent was removed after 2 to 4 weeks. RESULTS: Mean operative time was 162 minutes and mean hospital stay was 2.3 days. Obliteration of the diverticular infundibulum and cavity was documented by contrast radiography (excretory urography or retrograde pyelography), and noncontrast and contrast enhanced computerized tomography, respectively, in all 14 patients. No patients have had recurrent symptoms, calculi or urinary tract infection at a mean 38-month followup. CONCLUSIONS: Percutaneous electrocautery ablation of caliceal diverticula without cannulation or dilation of the diverticular infundibulum represents a safe and effective mode of therapy. Careful patient selection and preparation optimize the efficacy of this technique.

Adolescent↗
PubMed2000

[Autonomic nervous system and sleep apnea syndromes].

Understanding of the pathophysiology of obstructive sleep apnoea, a common yet relatively newly recognised condition, has advanced rapidly in recent years. This condition produces major acute haemodynamic changes and causal relationships with arterial hypertension and cardiovascular morbidity have been proposed. The role that the autonomic nervous system plays in mediating these cardiovascular changes has been the focus of intensive research activity and the development of new techniques in physiological monitoring, such as spectral analysis of heart rate variability, Finapres blood pressure monitoring, measurement of muscle sympathetic nerve activity, radionuclide tests and animal models of obstructive sleep apnoea have substantially increased the knowledge base. The acute haemodynamic changes are associated with high levels of sympathetic discharge and with fluctuating parasympathetic activity. There are also chronic changes in baroreceptor and chemoreceptor reflexes associated with an increase in baseline daytime sympathetic activity and abnormal vagal reflex responses to voluntary respiratory maneuvers. These acute autonomic changes appear to be provoked by a combination of stimuli triggered by hypoxaemia, upper airway responses, ventilatory changes and arousal. The mechanisms of the chronic autonomic changes are less clear; it is likely that recurrent hypoxaemia is important, but the roles of recurrent ventilatory stress and arousal are not clear. Normalising respiration with CPAP therapy prevents the acute cardiovascular changes and reduces the acute sympathetic over-activity, and in compliant patients, restores abnormal vagal responses to normal and reduces excess chronic sympathetic activity. Whether or not this produces a reduction in long term cardiovascular morbidity is not established.

Acute Disease↗
PubMed2000

Growth factors and embryo development.

In this review are cited and discussed the possible roles of growth factors on preimplantation embryo development of different species. In first term, is considered the mRNA detection in early stages of development. The distribution pattern was not uniform for the different peptides evaluated. For some of them, the mRNAs are detected at the oocyte stage and the level declines to the blastocyst stage, which suggests a maternal origin for them. For others, the level increased from 2-4 cells to blastocyst stage. On the other hand, transcripts of growth factor receptors have been detected in preimplantation embryos. This suggests that growth factors of maternal or embryo origin interact with specific receptors on preimplantation embryo surface and regulate the early development. On the other hand, culture media supplemented with different growth factors have been used to study the possible effects on in vitro development. Some investigators have found no effect. Others, however, have demonstrated changes in protein synthesis, cell number, differentiation and hatching processes. Embryo development modulation by growth factors probably involves a balance between stimulatory and inhibitory effects, although works are needed to determine the precise roles played by these polypeptides during early stages of mammalian development.

Animals↗
PubMed2000

Screening for transmission behaviors among HIV-infected adults.

Existing data suggest that a substantial proportion of HIV seropositive adults reduce their substance use and sexual risk behaviors after learning their serostatus. Given the importance of implementing preventive interventions, a screening tool is desirable to allow for a brief method of identifying those who continue to engage in transmission acts. This report explores the sensitivity and specificity of a brief screener used to identify persons living with HIV who engage in unprotected sexual intercourse and/or injection drug use. HIV positive clients of a large AIDS service organization in Los Angeles (N = 178) were screened with a brief, 7-item questionnaire, and responses on the screening interview were compared with self-reports obtained in an in-depth computerized assessment administered on the same day. Participants were randomized to receive the in-depth computerized assessment administered by an interviewer, or a self-administered audio-computer assisted interview. Screener sensitivity and specificity rates were relatively low (68% and 78%, respectively), and sensitivity was lower among African Americans than non-African Americans. Multivariate logistic regression analyses indicated that false negative screener responses were associated with recent sexually transmitted disease experience, controlling for gender, ethnicity, and interview administration mode. Effective strategies need to be developed that screen persons living with HIV who may be transmitting HIV to their sexual or drug-injecting partners.

Adult↗
PubMed2000

Preoperative cardiopulmonary risk assessment by cardiopulmonary exercise testing.

OBJECTIVE: To review the strategies for identification and subsequent management of high-risk patients that have been proposed to reduce perioperative morbidity and mortality. DATA SOURCES: Articles and published reviews of studies on evaluation and management of patients to reduce perioperative morbidity and mortality. SUMMARY OF REVIEW: Many strategies have been devised to evaluate the perioperative risk in elderly patients, particularly those who are about to undergo major intra-abdominal surgery. An assessment of cardiac and pulmonary responses to exercise-induced stress (i.e. cardiopulmonary exercise testing) using a bicycle ergometer, metabolic cart (to measure oxygen uptake and carbon dioxide excretion) and a 12 lead electrocardiograph has been found to be a non.invasive test that is quick, cheap, easy to perform and requires no special preparation. It has advantages over any other preoperative test by defining operative risk and allowing logical triage according to objective risk assessment. It is able to objectively evaluate the extent of any cardiac failure (by assessing the anaerobic threshold), myocardial ischaemia, provides insight into stroke index, the presence of pulmonary artery hypertension and defines obstructive and restrictive lung disease and ventilation perfusion inequality better than conventional preoperative respiratory function tests. CONCLUSIONS: In patients who are about to undergo major intra-abdominal surgery, preoperative cardiopulmonary exercise testing is an excellent predictor of risk in the postoperative period. No other test is able to offer such a comprehensive preoperative risk evaluation for an operative patient.

Journal Article↗
PubMed1999

Mutational analysis of a heterogeneous nuclear ribonucleoprotein A2 response element for RNA trafficking.

Cytoplasmic transport and localization of mRNA has been reported for a range of oocytes and somatic cells. The heterogeneous nuclear ribonucleoprotein (hnRNP) A2 response element (A2RE) is a 21-nucleotide segment of the myelin basic protein mRNA that is necessary and sufficient for cytoplasmic transport of this message in oligodendrocytes. The predominant A2RE-binding protein in rat brain has previously been identified as hnRNP A2. Here we report that an 11-nucleotide subsegment of the A2RE (A2RE11) was as effective as the full-length A2RE in binding hnRNP A2 and mediating transport of heterologous RNA in oligodendrocytes. Point mutations of the A2RE11 that eliminated binding to hnRNP A2 also markedly reduced the ability of these oligoribonucleotides to support RNA transport. Oligodendrocytes treated with antisense oligonucleotides directed against the translation start site of hnRNP A2 had reduced levels of this protein and disrupted transport of microinjected myelin basic protein RNA. Several A2RE-like sequences from localized neuronal RNAs also bound hnRNP A2 and promoted RNA transport in oligodendrocytes. These data demonstrate the specificity of A2RE recognition by hnRNP A2, provide direct evidence for the involvement of hnRNP A2 in cytoplasmic RNA transport, and suggest that this protein may interact with a wide variety of localized messages that possess A2RE-like sequences.

Animals↗
PubMed1999

Polytopic anomalies with agenesis of the lower vertebral column.

We describe clinical, pathological and radiological findings in 15 cases of sporadic and familial lower spine agenesis with additional anomalies of the axial skeleton and internal organs and speculate about the cause and pathogenesis of this malformation complex. We show that all of these findings are defects of blastogenesis, originate in the primary developmental field and/or the progenitor fields, thus representing polytopic field defects. This concept appears applicable in our cases and makes such terms such as "caudal regression syndrome" or "axial mesodermal dysplasia spectrum" redundant.

Abnormalities, Multiple↗