Biomedical subjects

A Gorea

Publications and source records attributed to A Gorea.

At least 19 recordsLinked to original sources

PubMed1992

Penetration of ceftriaxone and cefoperazone into bile and gallbladder tissue in patients with acute cholecystitis.

The penetration of ceftriaxone and cefoperazone into bile and gallbladder tissue was prospectively studied in 21 adult patients undergoing early surgery for acute cholecystitis. Comparable tissue, bile, and serum concentrations of the drugs were demonstrable; however, significantly fewer preoperative doses of ceftriaxone were required for adequate perioperative treatment. In view of its higher serum half-life and superior antibacterial activity toward common biliary pathogens, ceftriaxone appears to be a useful drug for the perioperative management of acute cholecystitis.

Acute Disease↗

PubMed1992

Sensitivity to colour- and to orientation-carried motion respectively improves and deteriorates under equiluminant background conditions.

This study presents two distinct effects produced by manipulation of the background illumination on the directional sensitivity to colour- and orientation-carried motion. The two motion percepts were produced with two of a class of stimuli extensively used by the first and last authors in apparent-motion studies. The stimuli were designed to produce motion perception by virtue of spatiotemporal matching of (a) colour with orientation systematically mismatched (Colour across Orientation, CxO) and of (b) orientation with colour systematically mismatched (OxC). An increase in background illumination from dark to the equiluminance point (relative to the luminance of the discrete stimulus microelements) entails a significant increase and decrease of directional performances with CxO and OxC stimuli, respectively. It is proposed that these anti-symmetrical background effects have distinct neurophysiological origins. For CxO stimuli, improvement of directional performances at the equiluminant point is presumably due to the inactivation of the inhibitory effect of the luminance-motion pathway on the chromatic-motion pathway. The opposite effect obtained with OxC stimuli, previously referred to as the veto effect (Gorea and Papathomas, 1988 Invest. Ophthal. Vis. Sci. Suppl., 29, 265), is supposed to be entailed by the inactivation of the luminance-oriented mechanism, the only motion sensitive mechanism activated by this stimulus configuration.

Color Perception↗

PubMed1991

Two carriers for motion perception: color and luminance.

Starting with the experiments of Ramachandran and Gregory (Nature, 275, 55-56, 1978), several psychophysical studies in apparent motion (AM) have established that the perception of motion is significantly impaired at equiluminance. Still debated, however, is whether color alone can resolve ambiguities in AM. We report here on several psychophysical experiments, the quantitative results of which indicate that color does play a substantial role in AM. These findings seem to support recently proposed neurophysiological frameworks according to which there exist significant interactions among the neuronal pathways mediating the perception of basic visual attributes such as color, motion, form and depth.

Color Perception↗

PubMed1991

Penetration of ofloxacin into human lung tissue following a single oral dose of 200 milligrams.

The penetration of ofloxacin into lung tissue was studied in 10 patients subjected to pulmonary surgery. Samples of blood and lung tissue were obtained 3 to 8 h (mean, 5 h) after oral administration of 200 mg. The mean level in tissue was 2.17 +/- 0.5 micrograms/g, while the mean level in serum was 0.85 +/- 0.23 micrograms/ml. The mean lung tissue/serum concentration ratio was 2.55 +/- 0.30. The achievable levels of ofloxacin in lung tissue are above the MICs for most pulmonary pathogens.

Administration, Oral↗

PubMed1991

Directional performances with moving plaids: component-related and plaid-related processing modes coexist.

A moving grating oriented +/- 45 degrees to the vertical can be perceived at choice as drifting along a left-right or up-down directional axis. When the drifting stimulus is presented alone, direction discrimination thresholds are independent of the specified response-axis. However, they strongly depend on it when the moving stimulus is superimposed on a vertical or horizontal stationary grating. Facilitation is always obtained when the drift direction of the intersections of the two gratings ('blobs') is collinear with the response-axis (i.e. when the orientations of the stationary grating and of the response-axis coincide), while inhibition is observed in the 'noncollinear' cases (i.e. when the orientations of the stationary grating and of the response-axis are orthogonal). These results are generalized in a series of reaction time (RT) experiments where the stimulus configuration described above was set at suprathreshold contrasts and where the orientation/direction of the drifting grating was variable. RT increased when the angle between the response-axis and the direction of the drifting grating increased (uncertainty effect), whether the test stimulus was presented alone, or superimposed on the stationary grating. The uncertainty effect was, however, significantly decreased under 'collinearity' conditions. The attenuation of the uncertainty effect was proportional with the velocity of the blobs and about equal in amount to the RT decrease obtained through the manipulation of the velocity of the drifting grating when presented alone (velocity effect). This observation strongly suggests that both component- and blob/plaid-related information contribute to the directional perception of a compound stimulus and that they sum algebraically.

Contrast Sensitivity↗

PubMed1991

Texture segregation by chromatic and achromatic visual pathways: an analogy with motion processing.

We present results to show that texture segregation can be obtained through the so-called coherent spatial grouping of local shape (orientation) and of local color under both nonequiluminant and equiluminant conditions. Color grouping entails texture segregation independent of orientation grouping, while the reverse is not true under equiluminant conditions. The experiments permit the isolation of chromatic- and luminance-oriented mechanisms, as well as of chromatic nonoriented mechanisms, all of which contribute to texture discrimination. As a general rule, the present results (including the asymmetry between color and orientation grouping) are similar to those obtained by us in a series of motion-perception experiments. This similarity suggests that the perceptual rules governing spatial grouping are analogous (if not identical) to those governing spatiotemporal grouping. As in the case of directional discrimination, texture-discrimination performances may be accounted for by the activation of higher-order units receiving inputs from subunits, all of which display similar tuning properties within a multidimensional space.

Color Perception↗

PubMed1990

All-D-magainin: chirality, antimicrobial activity and proteolytic resistance.

All-D-magainin-2 was synthesized to corroborate experimentally the notion that the biological function of a surface-active peptide stems primarily from its unique amphiphilic alpha-helical structure. Indeed, the peptide exhibited antibacterial potency nearly identical to that of the all-L-enantiomer. Being highly resistant to proteolysis and non-hemolytic all-D-magainin might have considerable therapeutic importance.

Amino Acid Sequence↗

PubMed1990

Concentration of ofloxacin and ciprofloxacin in human semen following a single oral dose.

A single oral dose of ofloxacin (400 mg.) or ciprofloxacin (500 mg.) was administered to each of 40 men. The mean concentrations of ofloxacin in semen exceeded those of ciprofloxacin at 1 hour (p = 0.035) and 24 hours (p = 0.028), while the levels of the 2 drugs at 2 and 4 hours were comparable. Semen concentrations of ofloxacin but not ciprofloxacin exceeded the reported minimal inhibitory concentration of Enterobacteriaceae, Chlamydia trachomatis and genital Mycoplasma species 24 hours after dosage.

Administration, Oral↗

PubMed1990

Context superiority in a detection task with line-element stimuli: a low-level effect.

Detection and identification performances for vertical and horizontal target elements embedded within an array of oriented noise elements were measured as a function of the orientation difference between the target and noise elements. Detection performances obtained with one vertical and three horizontal target elements clustered together and displayed such that they formed a schematic face-like pattern were significantly better than those obtained with the same clustered target elements displayed in an arbitrary, symmetrical or asymmetrical, configuration. This was so even though the identification of the face and nonface stimuli was well below the detection threshold of their parts. Detection thresholds for the clustered nonface patterns were slightly but significantly lower than those for the same target elements dispersed among the noise elements. Probability summation calculations based on the detection results obtained with one single target element predict detection thresholds which are intermediate between those of the clustered and dispersed targets, suggesting that inhibitory and facilitatory spatial interactions respectively are at work for the two types of stimuli. The existence of a context(face)-superiority effect at the detection level indicates top-down/bottom-up interactions between remote visual processing stages.

Attention↗

PubMed1990

Ambiguity in 3-D patterns induced by lighting assumptions.

A bistable pattern is shown with white and black bars with horizontal and vertical orientations which produce an impression of thin slabs stacked up in depth either toward or away from the observer. It is postulated that the ambiguity is induced by the observer's assumption of the direction of the light source.

Attention↗

PubMed1990

Penetration of clindamycin, cefoxitin, and metronidazole into pelvic peritoneal fluid of women undergoing diagnostic laparoscopy.

A single dose of clindamycin, cefoxitin, or metronidazole was administered to each of 30 women. The mean concentration of cefoxitin in pelvic fluid at 1 h exceeded those of the other two drugs (P less than 0.007). Cefoxitin concentrations were inferior to those of the other drugs when compared with the published MIC for 90% of Bacteroides fragilis strains.

Adult↗

PubMed1990

Cross resistance to ciprofloxacin and other antimicrobial agents among clinical isolates of Acinetobacter calcoaceticus biovar anitratus.

Using an agar dilution assay, for 66 of 104 (63.5%) clinical isolates of Acinetobacter calcoaceticus biovar anitratus, the MIC of ciprofloxacin was greater than or equal to 1.0 micrograms/ml. Cross resistance was demonstrable to ciprofloxacin and gentamicin (P less than 0.001), amikacin (P less than 0.01), cefotaxime (P less than 0.001), azlocillin (P less than 0.001), ceftazidime (P less than 0.001), trimethoprim-sulfamethoxazole (P less than 0.001), and minocycline (P less than 0.05). The mean MIC of ciprofloxacin for drug-susceptible isolates was consistently lower than that for resistant isolates; however, these differences were significant only for amikacin (P = 0.036).

Acinetobacter↗

PubMed1990

Penetration of aminoglycosides into human peritoneal tissue.

Each of 30 patients underwent elective laparotomy following administration of a single intravenous dose of amikacin, netilmicin or tobramycin. Therapeutic concentrations of amikacin were achieved in peritoneal tissue in 10/10 patients. Only 13/20 samples from patients receiving the other two antibiotics showed antibacterial activity. Our data suggest that the penetrability of tobramycin (53%) and amikacin (39%) into the uninflamed peritoneal tissue is superior to that of netilmicin (16%).

Amikacin↗

PubMed1989

Penetration of clindamycin and metronidazole into the appendix and peritoneal fluid in children.

Thirty-one children underwent appendectomy following administration of a single i.v. dose of clindamycin 10 mg/kg or metronidazole 7.5 mg/kg. The serum levels of the antibiotics at that time were comparable, but the tissue concentration of clindamycin in the appendix (mean 7.23 micrograms/g) exceeded that of metronidazole (mean 2.27 micrograms/g). The concurrent mean concentration of metronidazole in peritoneal fluid (14.26 micrograms/ml) was higher than that of clindamycin (7.72 micrograms/ml).

Appendix↗

PubMed1989

Inaccuracy in the doses of injectable medications dispensed from rubber-stoppered vials.

The literature of pharmacology often assumes that a full dosage is utilized when the contents of a vial have been administered by syringe. Five hundred discarded medication vials were assayed. The residues amounted to 1.98% to 8.81% of the listed dosages. An additional 0.7% to 8.66% remained in the syringes and needles used to aspirate the vials. Routine preparation techniques do not recover medication trapped on glass and rubber surfaces; losses are greatest when small diluent volumes are added to prepare intramuscular injections. The mean dose of gentamicin recovered from 80-mg ampules was 78.65 mg, and comparable vials of tobramycin yielded 76.01 mg. The discrepancy may contribute to the "increased toxicity" of gentamicin. Each year, more than $40,000,000 worth of antibiotics are lost to a biopharmaceutical dead space. Used antibiotic and controlled substance vials pose a potential threat to the environment. Although the amount of drug lost during preparation and administration may be of little therapeutic consequence, the discrepancy between intended and administered dosage is reflected in economic loss and pharmacological confusion. Pharmacological data should be adjusted for such losses. Medication wastage could be reduced by redesign of vials and alterations in practice of the administration.

Anti-Bacterial Agents↗

PubMed1989

Penetration of prophylactic antibiotics into peritoneal fluid.

This study evaluates the penetration of cephalosporins into the peritoneal fluid. Forty-six patients scheduled for abdominal surgery were randomized into three groups. On call to the operating room each patient was given a single 1 g dose of cefazolin, cefuroxime, or ceftazidime. Samples of the peritoneal fluid and blood were simultaneously obtained immediately after opening the peritoneal cavity. The mean serum cefazolin concentration was the highest. High peritoneal fluid levels of all three antibiotics were found; however, the antibacterial activity against common intestinal pathogens varied significantly. Cefazolin is the only study drug that possesses marginal in vitro activity against Streptococcus faecalis, a species generally considered resistent to cephalosporins. This study suggests that prophylactic second and third generation cephalosporins are not superior to cefazolin.

Abdomen↗

PubMed1989

Widespread quinolone resistance among methicillin-resistant Staphylococcus aureus isolates in a general hospital.

Ofloxacin and ciprofloxacin resistance (MIC, greater than 4 micrograms/ml) was encountered in 45 of 50 clinical isolates of methicillin-resistant Staphylococcus aureus. None of 20 methicillin-susceptible strains was resistant to the quinolones (P less than 10(-6). Quinolone-susceptible and -resistant isolates did not differ with respect to culture source or bacteriophage type. The future usefulness of quinolones for S. aureus infection may be limited.

4-Quinolones↗

PubMed1989

Penetration of third-generation cephalosporins into human peritoneal tissue.

Each of 40 patients underwent elective laparotomy following administration of a single 1.0-gram intravenous dose of ceftizoxime, ceftriaxone, cefoperazone or cefotaxime. Therapeutic concentrations of cefoperazone and ceftriaxone were achieved in peritoneal tissue in 20/20 patients. Only 9/20 samples from patients receiving the other two antibiotics had detectable antibiotic activity. The antibiotic concentration in peritoneal fluid (7 samples) was 2.36-11.15 times higher than that of concurrently obtained peritoneal tissue. When adjusted for the in vitro susceptibility (MIC) of potential peritoneal pathogens, our data suggest that ceftriaxone and cefoperazone may be preferable to other third-generation cephalosporins for the prophylaxis and therapy of intraabdominal infection.

Ascitic Fluid↗