Biomedical subjects

Q M Zhu

Publications and source records attributed to Q M Zhu.

3 recordsLinked to original sources

PubMed1991

Edge extraction by active defocusing.

A novel edge extraction method that employs an active defocusing technique is presented. The method is based on the principle that a Laplacian-of-Gaussian (LOG) operation can be approximated by a Difference-of-Gaussian (DOG) operation. While such an operation is usually done in digital image processing, it can also be very effective conducted in a combination of optical techniques and digital processing. In this edge extraction method, a focused image of an object in a scene is first acquired. The image of the scene is then slightly defocused by changing the focal length of the camera. A real time subtraction operation is applied to subtract the defocused image from the previously acquired image. It produces a residual image that emphasizes abrupt intensity variations. An objective evaluation, called an edge index, is performed on the resulting image. The amount of defocusing is carefully adjusted according to this measurement so that a desired edge image is generated. Boundaries of objects can then be obtained by further enhancement of the edge image. Since this edge detection method is an optical-based process aided by digital processing, it is fast and relatively inexpensive.

Artificial Intelligence↗

PubMed1989

Tissue selectivity of propranolol derivatives in vivo. A confirmation of in vitro findings.

The beta-adrenergic antagonist activities of a p-toluidide and a p-trifluoromethylanilide derivative of propranolol were tested in intact rats to determine whether the unusual in vitro profiles on myocardium and adipose tissue were found in vivo. The relative potencies of p-toluidide derivatives studied in pithed rats were 1.3 for the rate of change in left ventricular pressure with respect to time (dP/dt) and 4.6 for heart rate (HR) compared to propranolol. The values for p-trifluoromethylanilide were 2.5 (dP/dt) and 4.6 (HR). The SR-isomer of the p-toluidide derivative was 81 times more potent than propranolol in inhibiting effects on dP/dt and 27 times more effective than propranolol on HR, whereas the SS-isomer was 0.17 times (dP/dt) and 0.16 times (HR) as potent as the parent compound. In fasted rats, infusion of isoproterenol resulted in an increase of 10.6 +/- 3.1 mg/dl in plasma non-esterified fatty acid (NEFA) and an increase of 46 +/- 9 mg/dl in glucose. Unlike propranolol, neither the p-toluidide nor the p-trifluoromethylanilide derivative blocked the increase in plasma NEFA, although they both blocked the increase in plasma glucose. It appeared that the p-toluidide and p-trifluoromethylanilide derivatives of propranolol were more selective for the beta 1-adrenergic receptors on the heart as opposed to the beta 1-like adrenoceptors on adipose tissue. These findings were qualitatively and generally quantitatively in agreement with our previous findings in vitro. Therefore, the in vitro data may be useful in predicting atypical and tissue selective in vivo effects of these types of compounds.

Adipose Tissue↗

PubMedDate not supplied

Fluconazole is a potent inhibitor of antipyrine metabolism in vivo in mice.

Fluconazole, a bis-triazole antifungal, is distinguished from imidazole antifungals (e.g. ketoconazole) by its potency and pharmacokinetic characteristics. Imidazole-containing compounds are well documented to inhibit the hepatic cytochrome P-450-dependent enzyme system; whether this effect occurs with a bis-triazole agent is unknown. The [14C]antipyrine breath test was employed to investigate the effects of fluconazole on this enzyme system in CD-1 male mice. Control, ketoconazole (100 mg/kg), and fluconazole (1 and 10 mg/kg) were studied in single- and multiple-dose experiments. Fluconazole had potent inhibitory effects on the total (mean = -73% +/- 2%), demethylase (mean = -90% +/- 2%), and nondemethylase (mean = -60% +/- 4%) elimination rate constants (all p less than 0.001). The fraction of the administered radioactivity excreted as 14CO2 was decreased by 50-80% in the fluconazole groups (p less than 0.001). These effects were seen after single- and multiple-dose studies; however, return to baseline occurred more quickly in the multiple-dose group. These effects were significantly more pronounced than those observed with equipotent doses of ketoconazole. These results provide evidence that fluconazole is a potent, partially selective, and reversible inhibitor of the cytochrome P-450-dependent enzyme system in mice. Future studies will be required to assess this property and possible interactions with drugs metabolized by this enzyme system in humans.

Animals↗