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Biomedical subjects

J K Butler

Publications and source records attributed to J K Butler.

15 recordsLinked to original sources
PubMed1997

Mouse-Torpedo chimeric alpha-subunit used to probe channel-gating determinants on the nicotinic acetylcholine receptor primary sequence.

1. To determine if structural domains are important for nicotinic acetylcholine receptor (nAChr) channel function, six mouse-Torpedo chimeric alpha-subunits were constructed (Fig. 2) and coexpressed with Torpedo californica beta-, gamma-, and delta-subunits in Xenopus laevis oocytes. 2. nAChRs containing a chimeric alpha-subunit were examined by voltage- and patch-clamp methods to determine their functional characteristics. Dose-response curves from voltage-clamped oocytes were used to estimate EC50's and Hill coefficients. Whole-cell currents were normalized against the alpha-bungarotoxin (alpha-BTX) binding sites to obtain normalized responses to acetylcholine (ACh). Open time constants at 4 microM ACh were used to examine single-channel behavior. 3. The EC50 for ACh was modulated by the N-terminal half of the alpha-subunit. When the Torpedo subunit sequence between position 1 and position 268 was replaced by mouse sequence, the EC50 shifted toward the value for the wild-type mouse subunit. Replacement of either the 1-159 or the 160-268 positions of the Torpedo sequence with the mouse sequence lowered the EC50. This suggests that at least two regions play a role in determining the EC50. 4. When the primary sequence (160-268) of the Torpedo alpha-subunit was introduced in the mouse alpha-subunit (T160-268), the expressed chimeric receptor was nonfunctional. The inverse chimera (M160-268) was functional and the open time constant and EC50 were similar to those of mouse but the normalized response was characteristic of Torpedo. 5. The normalized macroscopic response to ACh (300 microM) of the chimera containing the mouse alpha-subunit showed a ninefold increase relative to the Torpedo wild type. Receptors which contain the C terminal of the mouse alpha-subunit also show an increase in the maximum normalized current. Receptors with the alpha-subunit which contain the Torpedo C-terminal sequence have a lower normalized response. 6. The combined results suggest that AChR channel function is modulated by structural determinants within the primary sequence. These structural domains might modulate channel function through specific allosteric interactions. The lack of response of the T160-268 chimera suggests that a critical interaction essential for the coupling of agonist binding and channel gating was disrupted. This result suggests that the interaction of structural domains within the nAChR primary structure are essential for channel function and that these intractions could be very specific within different nAChR species.

Amino Acid Sequence↗
PubMed1984

Improved methods for molding, facing and sectioning glycol methacrylate embedded tissue blocks.

Improvements in glycol methacrylate embedding, block facing, trimming, and sectioning are described. The improvements are derived from a novel molding system, a multipurpose instrument for rapid block facing, trimming and examination, and a device for removing unwanted sections from the microtome knife while sectioning is in progress. Together, these methods facilitate specimen preparation and result in a significant reduction of the time required to prepare high resolution, very thin sections for light microscopy.

Animals↗
PubMed1979

Bioavailability and pharmacokinetics of norethisterone in women after oral doses of ethynodiol diacetate.

Measurement by radioimmunoassay of plasma norethisterone (NE) has been used to compare the bioavailability of tablets containing ethynodiol diacetate (EDA) with that of a standard oral solution of this progestogen in 12 normal women. The tablets investigated were from three batches which showed different in vitro dissolution rates. There were no significant differences in the bioavailability of the tablet formulations, which were essentially bioequivalent to the solution. Peak blood levels of NE were reached within 4h of EDA administration in solution or tablets. After the peak, NE plasma levels declined in two phases, with a mean terminal elimination half lives of 4 to 6.9h. The pharmacokinetics of NE after EDA administration showed some similarity to those observed by other workers after oral doses of NE itself.

Adult↗
PubMed1979

Methods for improved light microscope microtomy.

Experiments undertaken to improve the ease and quality of preparing tissue for light microscopy have resulted in methods for routine production of high quality serial paraffin and glycol methacrylate sections in the 1 to 4 micrometer range using a standard rotary microtome. These methods involve sectioning with mechanically-broken Ralph-type knives, inspected for quality before mounting with double-stick tape on a holder-fluid trough in which the ribbon floats over an immersed slide and sections are mounted by lowering the fluid level in the trough. Specimen return stroke retraction, necessary for quality sectioning of plastic or with a fluid trough, is inexpensively provided by an attachable specimen holder that fits into the rotary microtome's chuck and, actuated by the microtome mechanisms, retracts the specimen during each return stroke. Descriptions of four instruments: a mechanical breaker for Ralph knives, a knife edge inspection device, an attachable specimen retractor for rotary microtomes, and a section collecting-mounting device as well as details of their use are included. Differences in cutting speed and cutting cycle cadence critical to quality sectioning with different embedments are detailed. Factors important in choosing the best embedment and most appropriate section thickness as well as choosing between dry or wet sectioning methods are also considered.

Fixatives↗
PubMed1978

Is it ethical to conduct volunteer studies within the pharmaceutical industry?

There is a case for appropriately selected drug studies within the pharmaceutical industry in which employee volunteers are used. Provided the organisation and conduct of such studies are approached in an ethical manner, with attention to safe-guarding the volunteer and recognising the limitations, this work can be done expeditiously, cheaply, and safely. Some details are given of the arrangements made for volunteer studies within a company.

Adolescent↗
PubMed1977

Ethical review in the pharmaceutical industry.

1. There seems no reason why clinical pharmacology studies conducted within the pharmaceutical industry should be exempt from the requirement of ethical review, and independent review in this situation reduces the vulnerability of the company and its employees, in addition to serving its primary function of protecting the volunteer subjects. 2. Experience within one company has shown that independent ethical review need not seriously influence the pace of research. 3. It is important that such committees should be seen to be independent and competent.

Drug Evaluation↗
PubMed1976

An illuminator for ultramicrotome knife orientation and block approach.

The construction and operation of a simple, inexpensive illuminator that produces high quality illumination of the ultramicrotome knife edge and the edge to block face gap resembling dark field is described. Use of the illuminator greatly speeds knife adjustment and reduces the likelihood of specimen or knife edge damage. The illuminator uses a grain-of-wheat light bulb and an adjustable bulb holder fashioned from bent paper clips. The holder permits both lateral and axial adjustment of the bulb position, which is necessary to achieve satisfactory illumination with different specimens and knives. The illuminator, with slight modification, can be adapted for use on any ultramicrotome.

Lighting↗