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Biomedical subjects

M Arditi

Publications and source records attributed to M Arditi.

At least 37 records · Page 2Linked to original sources
PubMed1995

BR1: a new ultrasonographic contrast agent based on sulfur hexafluoride-filled microbubbles.

RATIONALE AND OBJECTIVES: The basic characteristics of BR1, a novel echo contrast agent based on stabilized sulfur hexafluoride (SF6) microbubbles have been evaluated. METHODS: The authors determined the physicochemical properties (bubble concentration, bubble size distribution, resistance to pressure, and stability) and the acoustic properties (backscatter and attenuation coefficients) of BR1. The diagnostic value of BR1 was evaluated further in minipigs. Left heart images were recorded before and after injection of different doses of BR1. RESULTS: BR1 is formulated as a lyophilized product, which after addition of saline, provides a suspension containing 2 x 10(8) SF6 microbubbles/mL with a number mean diameter of 2.5 microns. More than 90% of the bubbles are below 8 microns. The use of SF6 rather than air provides an improved resistance to pressure increases such as the ones occuring in the left heart during systole. After reconstitution, the echogenicity and the bubble characteristics are unchanged for more than 8 hours. The high echogenicity remains almost constant over the entire medical frequency range (1-10 MHz). BR1 injections in animals resulted in a homogenous, dose-dependent opacification of the left heart. CONCLUSIONS: Considering its high echogenicity, outstanding stability, and resistance to pressure changes, BR1 is a very promising ultrasound contrast agent.

Animals↗
PubMed1995

Dexamethasone therapy for children with bacterial meningitis. Meningitis Study Group.

OBJECTIVE: To determine whether treatment with dexamethasone and ceftriaxone for children with bacterial meningitis reduces the frequency of either sensorineural hearing loss or other neurologic sequelae. DESIGN: This was a prospective, multicentered, placebo-controlled clinical trial. Subjects were followed for 1 year. SETTING: The study was conducted in six children's hospitals located in Pittsburgh, Houston, Los Angeles, Chicago, Washington, D.C., and Columbus, Ohio. PATIENTS: Enrolled were 173 children, 8 weeks to 12 years of age, with suspected bacterial meningitis; 143 children were evaluable. Eighty-seven percent of patients were followed for at least 6 weeks to 3 months, and 67% were followed for 1 year. INTERVENTIONS: Subjects were randomized to receive ceftriaxone with or without dexamethasone (0.15 mg/kg every 6 hours for 4 days). Auditory brainstem responses (ABR) were measured within 24 hours of admission. MAIN OUTCOME MEASURES: Hearing, development, and neurologic sequelae were assessed at the time of discharge and 6 weeks and 1 year later. MAIN RESULTS: One hundred forty-three patients (69 received dexamethasone and 74 received placebo) with bacterial meningitis were evaluable: Haemophilus influenzae type b (83), Streptococcus pneumoniae (33), Neisseria meningitidis (24), and three others. Overall, there was no significant difference in auditory outcome between dexamethasone and placebo recipients. Twenty-two children had bilateral moderate or more severe hearing loss at the time of the first ABR. At follow-up, the resolution of hearing impairment was nearly identical for each group. Nine of ten children who remained persistently deaf were deaf at the time of the first ABR. There were no differences in neurologic or developmental outcome between groups. CONCLUSION: All but one child with persistent bilateral moderate or more severe hearing loss had demonstrable deafness at the time of the first ABR. Dexamethasone did not significantly improve audiologic, neurologic, or developmental outcome in children with bacterial meningitis.

Ceftriaxone↗
PubMed1994

Bactericidal/permeability-increasing protein protects vascular endothelial cells from lipopolysaccharide-induced activation and injury.

Bactericidal/permeability-increasing protein (BPI), a human neutrophil granule protein, has been shown to bind lipopolysaccharide (LPS) and neutralize LPS-mediated cytokine production in adherent monocytes and the whole-blood system. In this study we investigated the ability of recombinant human BPI (rBPI) to inhibit LPS-induced vascular endothelial cell (EC) injury and activation. rBPI inhibited significantly both rough and smooth LPS-mediated injury for cultured bovine brain microvessel ECs, as measured by lactic dehydrogenase release, and blocked the LPS-induced interleukin-6 (IL-6) release from human umbilical vein ECs in a dose-dependent manner. BPI was able to inhibit LPS-mediated EC injury or activation whether it was added before or at the same time with LPS, but delaying the time of addition of rBPI resulted only in a partial inhibition. BPI also inhibited LPS-induced tumor necrosis factor alpha, IL-1 beta, and IL-6 release from human whole blood. This inhibition of tumor necrosis factor alpha, IL-1 beta, and IL-6 release from whole blood was maximal when BPI was premixed with LPS before addition to blood and was partial when BPI was added simultaneously with LPS, but no inhibition was observed when the addition of rBPI was delayed for 5 min. These findings suggest that rBPI is a potent inhibitor of LPS-mediated responses in ECs and whole blood and underscore the potential use of BPI in treatment or prevention of endotoxic shock. In contrast, the anti-lipid A monoclonal antibodies HA-1A and E5 were ineffective in inhibiting LPS-mediated EC injury and activation as well as LPS-induced cytokine release in whole blood.

Animals↗
PubMed1993

Antibiotic-induced bacterial killing stimulates tumor necrosis factor-alpha release in whole blood.

Rapid lysis of gram-negative bacteria is associated with considerable release of free endotoxin. Production of tumor necrosis factor (TNF) from adult whole blood ex vivo in response to bacterial products generated during antibiotic killing of Haemophilus influenzae type b (Hib) was investigated. Heparinized whole blood released TNF in a dose-dependent fashion in response to purified lipooligosaccharide of Hib. Bacteria (10(4)-10(7) cfu/mL) were placed into a Transwell filter insert (0.1 microns) and incubated with whole blood in the presence of various antibiotics. Exposure to ceftriaxone resulted in significantly greater release of TNF during killing of Hib than did exposure to imipenem, despite similar degrees of bacterial killing at 6 h. Polymyxin B inhibited the ceftriaxone-induced TNF release by 97%-99%, indicating that free endotoxin was the predominant stimulus for the increase in TNF release in this system. These observations suggest that ceftriaxone-induced killing of Hib results in bacterial cell wall products that are more proinflammatory than those produced by imipenem.

Adult↗
PubMed1993

Endotoxin-mediated endothelial cell injury and activation: role of soluble CD14.

Vascular endothelial cell (EC) injury by lipopolysaccharides (LPS) plays a major role in the pathogenesis of gram-negative bacterial sepsis and endotoxic shock. The studies described here were performed to define further the molecular mechanisms involved in the EC responses to LPS. We showed that serum was required for LPS-mediated cytotoxicity for bovine brain microvessel, pulmonary, and aortic ECs and that anti-human CD14 antibodies completely blocked LPS-mediated cytotoxicity for ECs in the presence of human serum. The addition of a recombinant soluble form of human CD14 to serum-free medium restored the LPS-mediated cytotoxicity, whereas the addition of LPS binding protein (LBP), a serum protein that potentiates LPS-induced responses to monocytes, had no effect. A similar dependency on serum or recombinant soluble CD14 (under serum-free conditions) was observed for LPS-induced secretion of interleukin-6 by human umbilical vein ECs. These findings indicate that soluble CD14 is required for LPS-mediated EC responses independently of LPB, suggesting that serum soluble CD14 represents a naturally occurring agonist for EC responses to LPS.

Acute-Phase Proteins↗
PubMed1992

Polymeric microballoons as ultrasound contrast agents. Physical and ultrasonic properties compared with sonicated albumin.

Air-filled polymeric microballoons were prepared with number-mean diameters of approximately 3 microns, volume-mean diameters of approximately 5 microns, and narrow particle-size distributions (standard deviation [SD] = 1.2 microns in number and SD = 2.0 microns in volume). More than 99% of the particles were below 8 microns. These particles were found to be highly echogenic for ultrasound, showing backscatter coefficients at 7.5 MHz, similar to the ones obtained with sonicated albumin microspheres. However, at 2.25 MHz, microballoons were less echogenic than albumin microspheres. These results are consistent with ultrasound attenuation measurements, which showed a maximum at 8 to 9 MHz for the microballoons compared with a reported value of 3.5 to 4.5 MHz for albumin microbubbles. Polymeric microballoons were found to be stable in plasma or under applied pressure as evidenced by unchanged particle concentration and echogenicity. Albumin microspheres were particularly unstable to applied pressure (150 mm Hg) and showed a rapid decrease in both particle counts and echogenicity.

Air↗
PubMed1991

Non-invasive estimate of the mechanical properties of peripheral arteries from ultrasonic and photoplethysmographic measurements.

The non-linear elastic response of arteries implies that their mechanical properties depend strongly on blood pressure. Thus, dynamic measurements of both the diameter and pressure curves over the whole cardiac cycle are necessary to characterise properly the elastic behaviour of an artery. We propose a novel method of estimating these mechanical properties based on the analysis of the arterial diameter against pressure curves derived from ultrasonic and photoplethysmographic measurements. An ultrasonic echo tracking device has been developed that allows continuous recording of the internal diameter of peripheral arteries. It measures the diameter 300 times per second with a resolution of 2.5 microns. This system is linked to a commercially available light-plethysmograph which continuously records the finger arterial pressure (0.25 kPa accuracy). Because of the finite pulse wave velocity, the separation between the diameter and the pressure measurement sites causes a hysteresis to appear in the recorded diameter-pressure curve. Using a model based on haemodynamic considerations, the delay between the diameter variations and the finger arterial pressure is first eliminated. As the pulse wave velocity depends on the pressure, the delay is determined for each pressure value. The relationship between pressure and diameter is then described by a non-linear mathematical expression with three parameters, which best fits the recorded data. The dynamic local behaviour of the vessel is fully characterised by these parameters. Compliance, distensibility and pulse wave velocity can then be calculated at each pressure level. Thus, the mechanical behaviour of peripheral human arteries can now be characterised non-invasively over the pressure range of the whole cardiac cycle. The results obtained in vivo on human radial and brachial arteries show that a thorough analysis of the compliance-pressure curves and their modifications (curving, shift) is needed in order to compare two different vessels in a meaningful way.

Adult↗
PubMed1991

Serum tumor necrosis factor alpha, interleukin 1-beta, p24 antigen concentrations and CD4+ cells at various stages of human immunodeficiency virus 1 infection in children.

We measured the serum concentrations of tumor necrosis factor (TNF-alpha), interleukin 1-beta (IL-1-beta), p24 antigen, CD4+/CD8+ cells and immunoglobulins in 35 children at various stages of human immunodeficiency virus infection. Serum TNF-alpha concentrations were significantly higher in children with lymphocytic interstitial pneumonitis and in children with mildly symptomatic illness than in asymptomatic children or children with acquired immunodeficiency syndrome. In addition serum IL-1 concentrations were significantly higher in patients with lymphocytic interstitial pneumonitis than in asymptomatic, mildly symptomatic, or acquired immunodeficiency syndrome patients. Children with lymphocytic interstitial pneumonitis had the highest serum TNF-alpha and IL-1 concentrations. Among symptomatic children serum TNF-alpha concentrations correlated positively with those of IL-1, and both were inversely related to the amount of p24 antigen. TNF-alpha values in excess of 50 pg/ml were observed more frequently among patients with CD4+ cell count greater than 400/mm3 than in those with CD4+ cell count less than 400/mm3. We did not find any association between elevated TNF-alpha concentrations and cachexia, opportunistic infections or progressive encephalopathy.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Apparatus for ultrasound tissue characterization of excised specimens.

Apparatus is described for measurement of sound speed and ultrasound attenuation coefficients by the substitution technique in the frequency range 3 to 8 MHz. Phase-cancellation artifacts leading to overestimation of attenuation coefficients are avoided by use of an acoustoelectric transducer. Specimens confined by polystyrene windows can be interrogated by focused ultrasound beams at selected locations spaced on a grid of 3 x 3 mm voxels. Pulse time of flight is measured with an accuracy of 30 ns, yielding sound speeds accurate to +/- 6.7 m/s, for samples 10 mm thick. Uncertainties in measured insertion losses range from 0.1 dB in low-loss (10 dB) specimens to 0.5 dB in high-loss (25 dB) specimens.

Algorithms↗
PubMed1990

Cerebrospinal fluid cachectin/tumor necrosis factor-alpha and platelet-activating factor concentrations and severity of bacterial meningitis in children.

In prospective studies, tumor necrosis factor (TNF alpha) was detected in cerebrospinal fluid (CSF) of 33 of 38 children with bacterial meningitis (BM) but in none of 15 with viral meningitis/encephalitis (P less than .001). BM CSF TNF alpha (less than 35 to greater than 25,500 pg/ml) correlated with CSF bacterial density (P less than .01), CSF protein (P less than .001), endotoxin (LPS) in gram-negative disease (P less than .01), and consecutive febrile hospital days (P less than .001); initial CSF TNF alpha greater than 1000 pg/ml was associated with seizures (P less than .05). Only 5 children with BM (13%) had detectable plasma TNF alpha activity on admission. A higher proportion who died had detectable plasma TNF alpha activity compared with survivors (3/4 vs. 2/34, P less than .005). Platelet-activating factor (PAF) in CSF was higher in 19 children with Haemophilus influenzae meningitis than in 17 controls (P less than .01) and correlated with bacterial density (P less than .01), CSF LPS (P less than .01), CSF TNF alpha levels (P less than .01), and the Herson-Todd severity score (P less than .01). Elevated CSF TNF alpha and PAF are often present in children with BM and are associated with seizures and severity of disease. Detectable CSF TNF alpha appears to distinguish BM from viral meningitis.

Adolescent↗
PubMed1990

Haemophilus influenzae type b conjugate vaccine (meningococcal protein conjugate): immunogenicity and safety at various doses.

The Haemophilus influenzae vaccine consisting of purified type b capsular polysaccharide (polyribosylribitol-phosphate [PRP]) was shown in Finland to be protective, with 90% efficacy in children older than 18 to 23 months of age. However, a wide range of estimates of vaccine efficacy has been reported in the United States after its licensure in 1985. These estimates range from -55% to +89%. In addition, the PRP vaccine was not effective in children younger than 18 months of age, in whom 70% to 80% of meningitis cases occur. A further development was the introduction of H influenzae type b polysaccharide-protein conjugate vaccines such as the PRP-D. These conjugate vaccines were found to be more immunogenic than PRP vaccine in children of all ages. Two doses of PRP-D in infants 7 months of age and older induced antibody levels equal to or greater than levels in infants 24 months of age who received the PRP vaccine alone. Recently, Eskola et al reported that repeat vaccinations with PRP-D at 3, 4, 6, and 14 months of age was 83% protective (95% confidence interval, 26% to 96%). Yet PRP-D vaccine elicits only low serum antibody levels in infants younger than 7 months of age. Because of the discrepancy in efficacy results for the PRP vaccine in the United States and Finland and the lack of data about the protective efficacy of PRP-D vaccine in infants in the United States, the PRP-D vaccine is currently recommended only for children 18 months of age or older.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Bacterial↗
PubMed1989

Cerebrospinal fluid endotoxin levels in children with H. influenzae meningitis before and after administration of intravenous ceftriaxone.

Total, cell-free, and cell-bound endotoxin and bacterial density were measured in cerebrospinal fluid (CSF) of 22 children with Hemophilus influenzae meningitis. Also the effect of ceftriaxone on CSF endotoxin levels was investigated in eight patients by reexamining their CSF 2-6 h after the initial dose. Initial CSF bacterial density correlated with initial CSF endotoxin levels (P less than .001). Ceftriaxone induced a marked increase of free endotoxin in CSF, from an initial (mean +/- SE) 0.75 +/- 0.21 to 1.29 +/- 0.23 log10 ng/ml (P less than .01). This increase correlated positively with the number of bacteria killed in the CSF (P less than .01). The increase in free endotoxin was associated with an increase in mean CSF lactate levels from 8.5 to 9.7 units/l (P less than .05) and mean lactate dehydrogenase levels from 102 to 180 mmol/l (P less than .02) and a decrease in mean CSF glucose from 1.17 to 0.46 mmol/l (P less than .05). Initial CSF total endotoxin concentrations correlated both with the Herson-Todd clinical severity score (P less than .001) and with the number of febrile hospital days (P less than .001). These findings suggest that highly bactericidal agents initially lead to release of free endotoxin from gram-negative organisms into CSF, with associated enhanced inflammatory response by the host.

Ceftriaxone↗
PubMed1989

In vitro interaction between rifampin and clindamycin against pathogenic coagulase-negative staphylococci.

The MICs and MBCs for 90% of strains tested (MIC90 and MBC90, respectively) of rifampin for 75 clinical isolates of pathogenic coagulase-negative staphylococci (PCNS) were 0.03 and 0.25 microgram/ml, respectively, while the MIC90 and MBC90 of clindamycin were both greater than 25 micrograms/ml. Although no synergy between rifampicin and clindamycin was found among the 15 strains studied by the checkerboard method, 6 of 12 selected strains showed synergy by the kill-curve method. No antagonism was observed by either method. All 30 strains rapidly developed resistance to rifampin in vitro, and this could be prevented by the simultaneous presence of 1.0 microgram of clindamycin per ml in the 24 methicillin-susceptible PCNS strains. The synergy between rifampin and clindamycin observed in vitro for some strains of PCNS, together with the prevention of emergence of resistance to rifampin by clindamycin, suggests that this antibiotic combination may be useful for the treatment of infections caused by methicillin-susceptible PCNS.

Clindamycin↗
PubMed1988

Aplastic anemia complicating orthotopic liver transplantation for non-A, non-B hepatitis.

Aplastic anemia developed in 9 of 32 patients (28 percent) undergoing orthotopic liver transplantation for acute non-A, non-B hepatitis, at one to seven weeks after the procedure. No patient previously had evidence of hematologic dysfunction or conditions known to be associated with aplastic anemia. No other cases of aplastic anemia were identified among 1463 patients undergoing liver transplantation for all other indications at the four centers participating in the study (chi-square = 415, P less than 0.001; 95 percent confidence interval for the incidence of aplastic anemia after transplantation for non-A, non-B hepatitis, 13 to 44 percent, vs. 0.00 to 0.13 percent for all other indications). The operative and postoperative treatment of these patients was not otherwise different, indicating that the aplastic anemia was a complication of the hepatitis, not of the transplantation procedure. Four of the nine patients died of complications due to infections. Three of the surviving patients have been followed for less than six months, one for one year, and one for two years. The two patients followed the longest have recovered marrow function to an appreciable degree, and two of the others have evidence of early recovery. We conclude that patients undergoing orthotopic liver transplantation for non-A, non-B hepatitis are at a high risk for the development of aplastic anemia.

Adolescent↗