Biomedical subjects

F Mao

Publications and source records attributed to F Mao.

26 records · Page 2Linked to original sources

PubMed1995

Purification and photoaffinity labeling of herpes simplex virus type-1 thymidine kinase.

The molecular basis for the treatment of human herpesviruses with nucleoside drugs is the phosphorylation of these drugs by the viral-encoded thymidine kinases. In order to better understand the structural and enzymatic mechanisms by which herpesviral thymidine kinases recognize their substrates, photoaffinity labeling with [alpha-32P]5-azido-2'-deoxyuridine-5'-monophosphate and [ gamma-32P]8-azidoadenosine-5'-triphosphate was used to characterize the thymidine, thymidylate, and ATP active sites of the herpes simplex virus-1 (HSV-1) thymidine kinase. For this study, HSV-1 thymidine kinase and a site-specific mutant enzyme (C336Y, known to confer acyclovir resistance) were expressed in bacteria and purified by a rapid, two-step protocol. The specificity of photoaffinity labeling of these HSV-1 thymidine kinases was demonstrated by the ability of site-directed substrates such as thymidine, thymidylate, acyclovir, 5-bromovinyl-2'-deoxyuridine, and ATP to inhibit photoinsertion. Differences in inhibition patterns of photoaffinity labeling correlated with kinetic differences between the wild-type and C336Y HSV-1 thymidine kinases. Cumulative results suggest that the acyclovir-resistant cysteine 336 mutation primarily affects the ATP binding site; yet it also leads to alteration in the binding affinity of nucleoside drugs in the thymidine site. In this study, azidonucleotide photoaffinity analogs are shown to be effective tools for studying the active-site environment of HSV-1 thymidine kinase and related site-specific mutants.

Adenosine Triphosphate↗

PubMed1994

Optical measurements of activity-dependent membrane recycling in motor nerve terminals of mammalian skeletal muscle.

Motor nerve terminals in a variety of rat and mouse skeletal muscles were stained in an activity-dependent fashion using the styryl dyes FM1-43 or FM2-10. Low-light video microscopy and digital image processing techniques were used to evaluate destaining of the preparations during application of depolarizing stimuli. Best results were obtained with the mouse triangularis sterni muscle. Quantitative analysis of the destaining of dye-loaded terminals supports the suggestion that FM1-43 stains a recycling membrane compartment, most probably synaptic vesicles. However, the pattern of staining and destaining were not the same as those reported previously for frog neuromuscular junctions. The pattern of nerve terminal staining was less punctate and the rate and amount of activity-dependent destaining were less than in frog muscle. Part of the explanation may be a more acute susceptibility of mammalian terminals to phototoxicity.

Animals↗

PubMed1994

Activity-dependent expression and distribution of M1 muscarinic ACh receptors in visual cortex neuronal cultures.

The fluorescently labeled muscarinic M1 receptor-selective antagonist BODIPY FL pirenzepine has been employed to study the activity-dependent distribution and expression of muscarinic M1 ACh receptors (M1AChRs) in cultured neurons derived from rat visual cortex. Displacement experiments showed that like pirenzepine, binding of BODIPY FL pirenzepine was specific to M1 receptors and its K(i) was similar to that of unlabeled pirenzepine. Using confocal laser scanning microscopy, M1 receptors were predominantly localized to cell bodies early in development in the culture environment. After 2 weeks in culture, the receptors showed labeling not only in cell bodies but also in neuritic processes, especially on the initial segments of the processes. Chronic membrane depolarization with 40 mM potassium chloride caused a dramatic increase in M1 receptor expression on these neurons. Conversely, blockade of neuronal activity with 0.1 microM TTX decreased expression of the receptors. Receptor expression increased after cells were treated chronically with 50 nM pirenzepine, whereas it decreased after exposure to 10 microM carbachol. The results demonstrate for the first time the exact location of muscarinic receptors in living cultured neurons and also the activity-dependent expression of M1 receptors on these neurons. Both chronic membrane depolarization and antagonist application upregulate receptor expression, whereas blocking bioelectrical activity or chronic agonist application downregulates expression.

Animals↗

PubMed1993

An interactive program for pharmacokinetic modeling.

A computer program, PharmK, was developed for pharmacokinetic modeling of experimental data. The program was written in C computer language based on the high-level user-interface Macintosh operating system. The intention was to provide a user-friendly tool for users of Macintosh computers. An interactive algorithm based on the exponential stripping method is used for the initial parameter estimation. Nonlinear pharmacokinetic model fitting is based on the maximum likelihood estimation method and is performed by the Levenberg-Marquardt method based on chi 2 criterion. Several methods are available to aid the evaluation of the fitting results. Pharmacokinetic data sets have been examined with the PharmK program, and the results are comparable with those obtained with other programs that are currently available for IBM PC-compatible and other types of computers.

Administration, Oral↗

PubMed1992

[Studies on polypeptides. IX. Synthesis and antigen specificity of pre-S region fragments of hepatitis B surface antigen].

Seven peptide fragments of HBsAg Pre-S region have been synthesized by liquid phase and solid phase methods. All peptide fragments were linked to protein carrier by carbodiimide and glutaraldehyde methods. The antigen specificity of the peptide--protein conjugates was assayed by anti-HBsAg polyclonal antibodies and anti--"a" monoclonal antibody. P1 and P5 were found to have higher antigen specificity.

Amino Acid Sequence↗

PubMed1992

Activity-dependent fluorescent staining and destaining of living vertebrate motor nerve terminals.

Living motor nerve terminals from several species can be stained in an activity-dependent fashion by certain styryl dyes, such as RH414, RH795, and a new dye, FM1-43, which can be imaged independently of the others. The dyes evidently become trapped within recycled synaptic vesicles. In frog cutaneus pectoris muscle, bright fluorescent spots spaced regularly along the length of the nerve terminals appear after stimulation in the presence of the dye. The spots align well with postsynaptic ACh receptors and are persistent for many hours, unless further stimulation is given, in which case the spots disappear. Destaining, like staining, requires transmitter release and proceeds gradually over several minutes at high stimulus frequencies (e.g., 30 Hz), and fluorescent spots in the same terminal disappear at about the same rate. We suggest that each spot is a cluster of hundred of synaptic vesicles and that the mechanism of staining involves the ability of the dyes to partition reversibly into the outer leaflet of surface membranes, without being able to penetrate the entire membrane thickness. Then, during endocytosis following transmitter release, dye molecules become trapped in recycled synaptic vesicle membranes. The dyes therefore make it possible optically to study vesicle exocytosis and recycling in living nerve terminals in real time, and should be useful for marking terminals in a variety of preparations according to their level of activity.

Animals↗

PubMed1991

[Synthesis of new test reagents for the estrogen receptor in human breast cancer tissues].

According to the character of structure and activity of the test reagents I-IV, two new reagents V and VI for detecting estrogen receptor of human mammary cancer cells were synthesized. This simplifies the route of synthesis and increases activity. Key intermediates VIII and IX were confirmed by IR, MS, UV and elemental analysis. The quantification of the final products V and VI were determined by UV. The result of preliminary clinico-pathological test shows compound V to be effective on estrogen receptor.

Breast Neoplasms↗

PubMed1991

[Synthesis of receptor reagent--estradiol-polyethyleneglycol-fluorescein isothiocyanate].

Estradiol conjugate has been used as a tracer to detect estrogen receptor of human mammary cancer cells. In order to look for more stable carrier of fluorescent estradiol conjugate, we substituted polyethyleneglycol (PEG) for bovine serum albumin (BSA) and synthsized 17 beta-estradiol-6-carboxymethyl-oxime-PEG-fluorescein isothiocyanate. The structure of the title compound was confirmed by IR and UV. In this paper, we also describe another procedure to convert the terminal hydroxyl groups of PEG to the more reactive primary amino PEG by tosylation, azide group substitution and catalytic hydrogenation. The ratio of conversion is about 87%.

Estradiol↗