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Biomedical subjects

L Fernandez

Publications and source records attributed to L Fernandez.

At least 19 recordsLinked to original sources
PubMed1999

In vitro comparison of the retention capacity of new aesthetic brackets.

Tensile bond strength and bond failure location were evaluated in vitro for two types of aesthetic brackets (non-silanated ceramic, polycarbonate) and one stainless steel bracket, using bovine teeth as the substrate and diacrylate resin as the adhesive. The results show that metallic bracket had the highest bond strength (13.21 N) followed by the new plastic bracket (12.01 N), which does not require the use of a primer. The non-silanated ceramic bracket produced the lowest bond strength (8.88 N). Bond failures occurred mainly between bracket and cement, although a small percentage occurred between the enamel-cement interface with the metal and plastic brackets and within the cement for the plastic bracket. With the ceramic bracket all the failures occurred at the bracket-cement interface. This suggests that the problems of enamel lesions produced by this type of bracket may have been eliminated. The results also show that the enamel/adhesive bond is stronger than the adhesive/bracket bond in this in vitro study.

Acid Etching, Dental↗
PubMed1998

Genetic uncoupling of the dsRNA-binding and RNA cleavage activities of the Escherichia coli endoribonuclease RNase III--the effect of dsRNA binding on gene expression.

RNase III, a double-stranded RNA-specific endonuclease, is proposed to be one of Escherichia coli's global regulators because of its ability to affect the expression of a large number of unrelated genes by influencing post-transcriptional control of mRNA stability or mRNA translational efficiency. Here, we describe the phenotypes of bacteria carrying point mutations in rnc, the gene encoding RNase III. The substrate recognition and RNA-processing properties of mutant proteins were analysed in vivo by measuring expression from known RNase III-modulated genes and in vitro from the proteins' binding and cleavage activities on known double-stranded RNA substrates. Our results show that although the point mutation rnc70 exhibited all the usual rnc null-like phenotypes, unlike other mutations, it was dominant over the wild-type allele. Multicopy expression of rnc70 could suppress a lethal phenotype of the wild-type rnc allele in a certain genetic background; it could also inhibit the RNase III-mediated activation of lambdaN gene translation by competing for the RNA-binding site of the wild-type endonuclease. The mutant protein failed to cleave the standard RNase III substrates in vitro but exhibited an affinity for double-stranded RNA when passed through poly(rI):poly(rC) columns. Filter binding and gel-shift assays with purified Rnc70 showed that the mutant protein binds to known RNase III mRNA substrates in a site-specific manner. In vitro processing reactions with purified enzyme and labelled RNA showed that the in vivo dominant effect of the mutant enzyme over the wild-type was not necessarily caused by formation of mixed dimers. Thus, the rnc70 mutation generates a mutant RNase III with impaired endonucleolytic activity but without blocking its ability to recognize and bind double-stranded RNA substrates.

Alleles↗
PubMed1998

Can surgeons evaluate emergency ultrasound scans for blunt abdominal trauma?

OBJECTIVE: To determine whether surgeons and residents with minimal training can evaluate accurately emergency ultrasound (US) examinations compared with radiologists for blunt abdominal trauma. METHODS: Over 7 months, we conducted a prospective study comparing the evaluation of emergency US for blunt abdominal trauma by surgeons and attending radiologists. US readings from the surgical team and the radiologists were correlated with outcome. RESULTS: One hundred-twelve patients were included in the study. Ninety-two patients had an US read as negative by the surgical and radiology services with no subsequent injuries identified. Eighteen patients had an US deemed positive by the surgical service and radiologists. Injuries were confirmed in this group by operation or computed tomography. One patient had an US deemed positive by the surgical team and subsequently negative by the radiologist. A diagnostic peritoneal lavage was performed which was negative. Another patient had an US interpreted as negative by the surgical evaluator and positive by the radiologist. Exploratory laparotomy was negative for intraabdominal hemorrhage or organ injury. Overall results reveal an accuracy on US reading of 99% for the surgical team and 99% for the attending radiologists. CONCLUSION: Surgeons and surgical residents at different levels of training can accurately interpret emergency ultrasound examinations for blunt trauma from the real-time images, at a level comparable to attending radiologists.

Abdominal Injuries↗
PubMed1998

University of Miami Division of Clinical Pharmacology Therapeutic Rounds: managing hypertension in patients with kidney disease-implications for preservation of renal function.

Renal parenchymal hypertension is defined as hypertension caused by disease of the kidneys. Impaired renal sodium excretion leading to extracellular fluid volume (ECFV) expansion is the most clinically important mechanism leading to hypertension in patients with kidney disease. Most patients with renal parenchymal hypertension have sodium-sensitive hypertension, and, consequently, sodium restriction and loop diuretics constitute the initial steps in effective antihypertensive therapy in patients with renal disease. The loop diuretics (furosemide, ethacrynic acid, bumetanide, torasemide) are used for the management of ECFV and hypertension in patients with renal disease because thiazide diuretics are generally not effective in patients with serum creatinine values above 2.0 mg/dL or creatinine clearances below 30 mL/min. The Joint National Committee VI recommends the use of angiotensin-converting enzyme (ACE) inhibitors in patients with hypertension and chronic renal disease to control hypertension and to slow progressive renal failure. Antihypertensive treatment with ACE inhibitors may favorably alter renal hemodynamics, thereby slowing the progression of renal dysfunction. ACE inhibitors have been found to be useful agents in preventing the progression of renal disease in the settings of established insulin-dependent diabetes mellitus (IDDM) nephropathy, non-insulin-dependent diabetes mellitus (NIDDM) nephropathy, IDDM patients with normal blood pressures and microalbuminuria, NIDDM patients with microalbuminuria and normal renal function, and a variety of non-diabetic renal diseases, especially in the setting of significant proteinuria. Calcium antagonists are effective for treating hypertensive patients with chronic renal impairment, and the initial results for calcium antagonists and for combination calcium antagonist-ACE inhibitor therapy have been encouraging. Although promising, the calcium antagonists and the new angiotensin II antagonists have not been studied as intensively as ACE inhibitors in regard to their ability to slow the progression of renal insufficiency.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1997

Expression of hepatocyte nuclear factor 6 in rat liver is sex-dependent and regulated by growth hormone.

Growth hormone (GH) binding to its receptor modulates gene transcription by influencing the amount or activity of transcription factors. In the rat, GH exerts sexually dimorphic effects on liver gene transcription through its pattern of secretion which is intermittent in males and continuous in females. The expression of the CYP2C12 gene coding for the female-specific cytochrome P450 2C12 protein is dependent on the continuous exposure to GH. To identify the transcription factor(s) that mediate(s) this sex-dependent GH effect, we studied the interactions of the CYP2C12 promoter with liver nuclear proteins obtained from male and female rats and from hypophysectomized animals treated or not by continuous GH infusion. GH treatment induced the binding of a protein that we identified as hepatocyte nuclear factor (HNF) 6, the prototype of a novel class of homeodomain transcription factors. HNF-6 competed with HNF-3 for binding to the same site in the CYP2C12 promoter. This HNF-6/HNF-3 binding site conveyed both HNF-6- and HNF-3-stimulated transcription of a reporter gene construct in transient cotransfection experiments. Electrophoretic mobility shift assays showed more HNF-6 DNA-binding activity in female than in male liver nuclear extracts. Liver HNF-6 mRNA was barely detectable in the hypophysectomized rats and was restored to normal levels by GH treatment. This work provides an example of a homeodomain-containing transcription factor that is GH-regulated and also reports on the hormonal regulation of HNF-6.

Animals↗
PubMed1997

High-dose donor bone marrow infusions to enhance allograft survival: the effect of timing.

BACKGROUND: The development of strategies to enhance survival of transplanted organs and to potentially lower or even discontinue immunosuppressive therapy would represent a significant advance in posttransplant patient care. The aim of this clinical trial was to determine the effect of timing and dose of peripheral donor bone marrow cell (DBMC) infusion on graft and patient survival after liver transplantation. METHODS: DBMC, obtained from vertebral bodies, were administered in 101 recipients of liver allografts (OLTX). There were 107 patients for whom DBMC could not be obtained; they received OLTX alone (controls). A total of 5 x 10(8)/kg DBMC were infused at day 0 (group 1; n=9); at days 0 and 11 (group 2; n=26); or at days 5 and 11 (group 3; n=26). In group 4 (n=40), patients received up to five infusions of 2 x 10(8)/kg DBMC at days 5, 14, 21, 28, and 90 after OLTX. RESULTS: When the results from patients receiving two or more DBMC infusions (groups 2, 3, and 4) are considered, both patient and graft survival were significantly improved compared with the control group (P=0.02 and P=0.01, respectively). In groups 3 and 4, 88.5% and 95% of patients were alive with mean follow-up of 536 and 265 days, respectively, compared with 77.6% of patients in the control group (average follow-up of 452 days) (P=0.02). Graft survival was also significantly improved in groups 3 (88.5%) and 4 (92.5%), compared with the controls (72%) (P=0.007). CONCLUSIONS: The results suggest that dose and timing of DBMC infusions may be important variables affecting allograft survival. A randomized prospective trial is now in progress to compare group 3 DBMC infusion protocol with controls receiving OLTX alone.

Adult↗
PubMed1997

Massive subcutaneous and intraosseous fat necrosis associated with pancreatitis. Natural evolution of the radiographic picture.

A 44-year-old man developed high fever, polyarthralgias, erythematous tender nodules and plaques on feet, ankles, knees and dorsum of the hands, as well as swelling of ankles and several joints of hands and feet. Laboratory evaluation showed high serum pancreatic amylase and lipase. Histological study of a subcutaneous nodule demonstrated fat necrosis. X-ray examination revealed numerous lytic lesions involving cancellous and cortical bone in phalanges, metacarpals, radius, tibia, tarsus and metatarsals, with areas of widened bone. The patient never referred any abdominal symptom. He evolved favourably within the following months. A year later, resolution of most of the bone lesions was observed.

Bone Diseases↗