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Biomedical subjects

M Fernandez

Publications and source records attributed to M Fernandez.

At least 109 records · Page 6Linked to original sources
PubMed1996

P300 and allocation of attention in dual-tasks.

P300 in dual-tasks has been reported to be distributed reciprocally across the tasks, i.e. larger P300 associated with one task implies smaller P300 associated with the other (Wickens et al., 1983; Sirevääg et al., 1989). In these studies, however, the dual-tasks stimuli were either presented simultaneously, precluding a direct, within-trial assessment of relative magnitudes of P300, or they were separated by intervals of 1 s or more, thereby minimizing overlap of the ERP epochs, but at the cost of reduced competition for shared processing resources. The present experiment used an inter-stimulus interval of 400 ms between the auditory (tones) and visual (colored LEDs) stimuli that defined the dual-task and found that, when deviant tones elicited a prominent auditory P300, they were followed by a greatly reduced P300 for the deviant LED. The findings were interpreted from viewpoints that considered the effects of neural inhibition versus neural recovery cycles on the amplitude of P300.

Acoustic Stimulation↗
PubMed1996

Radionuclide imaging in interstitial lung disease.

The use of radionuclides to evaluate interstitial lung disease (ILD) has a long history. In the mid- and late 1970 s, it was appreciated that gallium uptake was seen in the lungs of patients with sarcoidosis or idiopathic pulmonary fibrosis. In both of these conditions, the amount of uptake seemed to correlate with other measures of inflammation in the lung. Gallium uptake was shown to predict response to therapy and persistent disease. However, several limitations to gallium scanning soon became apparent. The procedure is costly, it requires 48 to 72 hours for proper interpretation, and the uptake reverses quickly during corticosteroid therapy. The use of aerosol scanning with 99mTc-pentetic acid (DTPA) has also been shown to be useful in ILD. The clearance of 99mTc-DTPA aerosol is markedly increased in both sarcoidosis and other inflammatory lung diseases. However, the limitations of 99mTc-DTPA include the fact that cigarette smoking will also cause increased clearance. Therefore, the value of 99mTc-DTPA scanning value seems to be limited to nonsmokers. Several recent papers published on these and other techniques are reviewed here.

Administration, Inhalation↗
PubMed1996

Evidence of impaired glomerular charge selectivity in nondiabetic subjects with microalbuminuria: relevance to cardiovascular disease.

Microalbuminuria is associated with excess cardiovascular morbidity and mortality in diabetic and nondiabetic subjects. Loss of glomerular charge selectivity may explain the development of microalbuminuria in diabetic subjects. The primary population in this cross-sectional study was 124 subjects aged 40 to 75 years without glucose intolerance and with a previous (3 years before the present study) urinary albumin excretion rate (UAE) in the normal (<20 microgram/min) or microalbuminuric (>20 microgram/min) range. The secondary population consisted of 39 offspring aged 15 to 40 years. The main outcome measures included UAE, urinary IgG/IgG4 selectivity index (SI), and the presence of ischemic heart disease as determined by questionnaire or ECG. Among the primary population, a significant inverse correlation was found between SI and UAE (r=-.40, P<.001). Reduction in SI could be demonstrated in subjects with UAE >10 microgram/min. In multiple regression analysis reduction in SI was found with increasing age, independent of UAE. In 20 subjects with clinical cardiovascular disease a reduction in SI was found (1.9+/-0.6 versus 2.6+/-1.3, P=.001) without concomitant elevation in UAE (P=.99). Offspring from parents with microalbuminuria had an SI comparable to offspring from parents with normal UAE (2.7+/-0.7 versus 3.3+/-1.6, P=.17). In nondiabetic subjects the development of microalbuminuria is associated with reduced SI, suggesting impairment of glomerular charge selectivity. SI may offer a more sensitive monitoring of abnormalities in glomerular permselectivity than does measurements of UAE, but the ability of SI to predict development of cardiovascular disease needs to be evaluated prospectively.

Adolescent↗
PubMed1996

Clinical cross-reactivity between amoxicillin and cephadroxil in patients allergic to amoxicillin and with good tolerance of penicillin.

In recent years, patients allergic to amoxicillin (AX) but with good tolerance of penicillin G (PG) have been described. It has been suggested that the epitope implicated in this type of sensitization might be located on the side-chain of the AX molecule. Thus, cross-reactivity between AX and cephadroxil (CEPH), a cephalosporin which shares an identical side-chain with AX, is suspected. This study aimed to demonstrate clinical cross-reactivity between AX and CEPH in patients allergic to AX and showing good tolerance of PG. In 76 of 576 subjects with suspected allergic reaction to PG and/or AX, the diagnosis of allergy was confirmed. All of these had specific IgE to PG, penicillin V, or AX, and/or positive skin tests to PPL (penicilloyl-polylysine), or MDM (minor determinant mixture), or PG, or AX, and/or positive challenge tests with PG and/or AX. Sixteen subjects (21%) allergic to AX (11 with positive skin test and five with positive challenge test to AX) and good tolerance of PG (all with negative parenteral challenge test) were selected. These 16 patients were subsequently challenged with CEPH (up to 500 mg). Fourteen patients tolerated CEPH, and two (12%) had an immediate allergic reaction. Our study indicates that allergy to the side-chain of aminopenicillins seems to have little clinical relevance in patients with allergic reactions to aminopenicillins but with good tolerance of PG, as 88% of patients with this clinical characteristic tolerate a cephalosporin which shares an identical side-chain. It seems that IgE from most of these patients recognizes an epitope different from the side-chain and the beta-lactam ring.

Adolescent↗
PubMed1995

Effect of 5-azacytidine and sinefungin on Streptomyces development.

The effect of two DNA-methyltransferase inhibitors, 5-azacytidine (5azaC) and sinefungin (Sf), on the development of Streptomyces antibioticus ETH7451 (Sa) was studied. Pulse labeling experiments and SDS-PAGE analysis of proteins from cells grown in sporulation synthetic medium showed that both inhibitors affect a limited number of systems. Synthesis of the antibiotic rhodomycin was increased in the presence of 5azaC. 5azaC also stimulated the production of actinorhodin in cultures of S. coelicolor A3(2) grown in minimal medium. The analog did not affect the expression of whiB and whiG, two sporulation genes from S. coelicolor A3(2) whose homologues are present in Sa. Overall results indicated that 5azaC and Sf affect specific events associated with differentiation and secondary metabolism in Streptomyces.

Adenosine↗
PubMed1995

Coronary stenting decreases restenosis in lesions with early loss in luminal diameter 24 hours after successful PTCA.

BACKGROUND: Early loss of minimal luminal diameter (MLD) after successful percutaneous transluminal coronary angioplasty (PTCA) is associated with a higher incidence of late restenosis. METHODS AND RESULTS: Sixty-six patients (66 lesions) with > 0.3 mm MLD loss at 24-hour on-line quantitative coronary angiography were randomized into two groups: 1, Gianturco-Roubin stent (n = 33) and 2, Control, who received medical therapy only (n = 33). All lesions were suitable for stenting. Baseline demographic, clinical, and angiographic characteristics were similar in the two groups. Restenosis (> or = 50% stenosis) for the overall group occurred in 32 of 66 patients (48.4%) at 3.6 +/- 1-month follow-up angiography. Restenosis was significantly greater in group 2 than in group 1 (75.7% versus 21.2%, P < .001). Vascular complications (21.2% versus 0%) and length of hospital stay (7.3 +/- 1 versus 2.4 +/- 0.5 days, P < .01) were higher for the stent group. Although at follow-up there were no differences in mortality or incidence of acute myocardial infarction between the two groups, patients in the control group had a higher incidence of repeat revascularization procedures (73% versus 21%, P < .001). CONCLUSIONS: In patients with successful PTCA but reduced luminal diameter demonstrated by repeat angiography at 24 hours, the Gianturco-Roubin stent appears to reduce angiographic restenosis at follow-up.

Angioplasty, Balloon, Coronary↗
PubMed1995

Activation and hapten inhibition of mast cells sensitized with monoclonal IgE anti-penicillin antibodies: evidence for two-site recognition of the penicillin derived determinant.

We utilized an in vitro mast cell activation assay and hapten inhibition of mediator release to characterize the fine specificity of two IgE anti-penicillin monoclonal antibodies (mAb). Cultured mouse mast cells were passively sensitized with IgE mAb anti-benzylpenicillin (BP) or anti-amoxicillin (AX) and challenged with a range of penicillin-human serum albumin (HSA) conjugates. Mast cells sensitized with IgE anti-BP degranulated in response to BP-HSA, but not to AX-HSA or ampicillin(AMP)-HSA, whereas mast cells sensitized with IgE anti-AX responded to AX-HSA but not to BP-HSA or AMP-HSA. Because BP, AX and AMP differ chemically only in the structure of their side chain, these results show that this part of the drug molecule is essential for recognition by IgE antibody. Unexpectedly, although IgE-sensitized mast cells responded to only one penicillin in protein-conjugated form, antigen-induced degranulation was inhibited by the monomeric derivative of more than one penicillin. Furthermore, antigen activation of IgE-sensitized cells was inhibited, although less potently, by haptens representative of the specific penicillin side chain or the binuclear portion of the drug molecule. These patterns of recognition and hapten inhibition were also seen in solid-phase enzyme-linked immunosorbent assay (ELISA), although all haptenic inhibitors were approximately 100 times less potent in the ELISA compared to the mast cell assay. To explain these findings we propose a model in which IgE binding to penicillin-protein antigen is dependent on recognition of two distinct epitopes on the drug molecule: the first comprising the side chain, and the second comprising the binuclear portion plus the proximal region of the side chain. This two-site hypothesis provides a generally applicable model of antibody recognition of penicillins and provides a rational basis for understanding the specificity and cross-reactivity of IgE-mediated allergic reactions to penicillins.

Animals↗
PubMed1995

Intestinal parasites of sympatric gorillas and chimpanzees in the Lopé Reserve, Gabon.

A coprological survey of intestinal parasites of wild chimpanzees (Pan t. troglodytes) and western lowland gorillas (Gorilla g. gorilla) was carried out in the Lopé Reserve in central Gabon. Most samples (69%) were positive but the prevalence of intestinal parasites in the 61 gorilla samples (84%) was higher than in the 66 chimpanzee samples (56%). At least 11 species of parasite were observed: six protozoan, one trematode and at least four nematodes. Six of the species were found in gorillas and chimpanzees but the remainder only occurred in chimpanzees. All but one parasite occurred at low prevalences. Entodiniomorph ciliates, which occurred frequently in both ape species (particularly in gorillas) in the Lopé survey and in all previous coprological surveys of wild apes, may be symbionts involved in cellulose digestion. The dietary and behavioural strategies of wild primates that serve to reduce infection by pathogenic parasites are reviewed.

Animals↗
PubMed1995

Detection of hepatitis B and hepatitis C viral sequences in fulminant hepatic failure of unknown etiology.

In a significant number of patients, the etiology of fulminant hepatic failure (FHF) is unknown. To determine whether hepatitis B virus (HBV) and hepatitis C virus (HCV) play a role in patients without serologic markers of HBV and HCV infection, the authors examined tissue samples from 15 liver explants with massive hepatic necrosis for the presence of viral sequences by the polymerase chain reaction (PCR). The specimens were derived from nine patients with FHF of unknown etiology; two with serum hepatitis B surface antigen (HBsAg); two with antibodies to HCV; one with antibodies to hepatitis A virus (HAV) and anti-HBc of the IgM class; and one with isoniazid toxicity. Nucleic acids were extracted from frozen liver samples. RNA was used as a template for reverse transcription, followed by double PCR with nested primers for the 5'-untranslated region of HCV. DNA was tested by single PCR for S gene sequences of HBV. Hepatitis B virus sequences were detected in the specimens of the two HBsAg positive patients, the anti-HAV/anti-HBc positive patient, and three of nine patients with FHF of unknown etiology. Hepatitis C virus sequences were present in the explant of one patient with FHF of unknown etiology, but not in the two patients with antibodies to HCV. In two specimens with molecular findings of HBV infection (1 from a patient with serum HBsAg and 1 without), there was immunohistochemical evidence of coinfection or superinfection with hepatitis delta virus (HDV). In conclusion, in this patient population, HBV, alone or with HDV or HAV, causes fulminant hepatic failure more often than HCV infection. However, in the majority of patients, the etiology of fulminant hepatic failure remains unknown.

Adult↗
PubMed1995

Computed tomographic findings in pseudomembranous colitis: an important clue to the diagnosis.

Computed tomography (CT) is increasingly used to evaluate abdominal diseases, including those of the colon. Recent CT studies have documented colonic abnormalities in patients with pseudomembranous colitis; however, these findings are not widely appreciated by primary care physicians. Over a 25-month period, we prospectively identified 13 patients who had proven pseudomembranous colitis evaluated by abdominal CT. The primary indications for CT were abdominal pain with or without fever in 9 patients, fever of unknown origin in 1, evaluation of other abdominal processes in 1, and as part of this study after documentation of pseudomembranous colitis in 2. Importantly, the diagnosis of pseudomembranous colitis was first considered on the basis of the CT findings in 9 patients with abdominal pain or fever. Diffuse thickening of the colonic wall, ranging from 4 to 40 mm, was the most common radiologic finding, seen in 8 patients (62%). In 3 cases, wall thickening was seen in the descending colon and rectosigmoid, with one of these also having a thickened transverse colon. Colonic wall thickening, which may be dramatic, appears to be an almost uniform accompaniment of pseudomembranous colitis and may be present without clinically severe disease. These CT findings in the appropriate clinical setting should suggest colitis due to Clostridium difficile and prompt the appropriate evaluation for this disease.

Abdominal Pain↗
PubMed1995

Alterations in soluble and leukocyte surface L-selectin (CD 62L) in hemodialysis patients.

Hemodialysis (HD) patients can develop acute reactions during treatment as well as increased long-term susceptibility to infections and malignancy. Leukocyte-membrane interactions may contribute to these processes. The effects of a single HD session on L-selectin, a leukocyte adhesion molecule for endothelium, were examined. Serum levels of soluble L-selectin were measured in 23 patients by enzyme-linked immunosorbent assay before and after a 3-h dialysis session. There was a statistically significant increase in soluble L-selectin from 1.36 +/- 0.12 (SE) to 1.57 +/- 0.18 micrograms/mL (P < 0.001). An increase in shed L-selectin was observed for the "venous" compared with the "arterial" part of the dialyser (P < 0.01) 15 min into HD. Soluble L-selectin levels were found to remain increased at 3 h after treatment. Leukocyte-bound L-selectin and CD11b was examined by the use of flow cytometry. Neutrophil L-selectin decreased to 69 +/- 7% at 15 min (P < 0.01) and then rebounded to 98 +/- 7% at 180 min. Monocyte and lymphocyte L-selectin did not decrease. Because L-selectin is important for leukocyte attachment to endothelium at sites of inflammation, alterations of shed L-selectin and cell-surface L-selectin levels may play a role in the immunologic consequences of HD treatment.

Adult↗
PubMed1995

Maxillary sinus marrow hyperplasia in sickle cell anemia.

Marrow hyperplasia is a sequela of sickle cell anemia (SCA) and may be seen in the skull in children after 5 years of age [1]. The facial bones, except for the mandible and orbits, are usually not involved [1-3]. We report an unusual case of a 28-month-old black boy with SCA who presented with extensive marrow hyperplasia of the maxillary sinuses in addition to severe calvarial and mandibular changes. The imaging characteristics on CT (similar to other sites of marrow hyperplasia) and MR (low signal on both T1 and T2 sequences) should aid in making the correct diagnosis.

Anemia, Sickle Cell↗
PubMed1995

Danazol for systemic lupus erythematosus with refractory autoimmune thrombocytopenia or Evans' syndrome.

OBJECTIVE: To determine the efficacy of danazol for refractory autoimmune thrombocytopenia or Evans' syndrome complicating systemic lupus erythematosus (SLE). METHODS: We studied 16 consecutive patients with SLE and corticosteroid refractory autoimmune thrombocytopenia; 3 patients had coexisting autoimmune hemolysis (Evans' syndrome). Five patients had undergone splenectomy. Danazol was commenced at 200 mg/day, and increased stepwise (maximum 1200 mg/day) until benefit or toxicity was observed. After remission the danazol dose was gradually reduced to 200-400 mg/day. RESULTS: All 16 patients achieved a complete remission (platelet count >100 x 10(9)/l, hematocrit >39%) 2 months after starting danazol (range 6 weeks-8 months). Remission persisted during continued danazol therapy (mean followup 18.2 months, range 2-49 months). One patient with Evans' syndrome required discontinuation of danazol because of jaundice and biopsy proven minimal hepatic necrosis: hemolysis recurred after discontinuation of danazol. CONCLUSION: Danazol is effective for the treatment of autoimmune thrombocytopenia or Evans' syndrome complicating SLE irrespective of splenectomy status. Longer followup will be needed to determine whether the remission persists after withdrawal of danazol.

Adult↗