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Biomedical subjects

C Merriman

Publications and source records attributed to C Merriman.

6 recordsLinked to original sources
PubMed2001

A simple method for orienting silk and other flexible fibres in transmission electron microscopy specimens.

When microstructures are characterized by transmission electron microscopy (TEM), the interpretation of results is facilitated if the material can be sectioned in defined orientations. In the case of fibres, it is especially useful if transverse and longitudinal sections can be obtained reliably. Here we describe a procedure for orienting spider silk and other flexible fibres for TEM investigation. Prior to embedding in epoxy resin, the silk is wound around a notched support made from polyester film. No glue is required. After the silk and its supporting film have been embedded and the resin has been cured the film can be peeled away to reveal nearly perfectly orientated silk threads. Both transverse and longitudinal sections can then be cut with a microtome. The method can be extended to obtain sections at any intermediate orientation.

Animals↗
PubMed1998

Transdifferentiation of mature cortical cells to functional abscission cells in bean

Abscission explants of bean (Phaseolus vulgaris L.) were treated with ethylene to induce cell separation at the primary abscission zone. After several days of further incubation of the remaining petiole in endogenously produced ethylene, the distal two-thirds of the petiole became senescent, and the remaining (proximal) portion stayed green. Cell-to-cell separation (secondary abscission) takes place precisely at the interface between the senescing yellow and the enlarging green cells. The expression of the abscission-associated isoform of beta-1,4-glucanhydrolase, the activation of the Golgi apparatus, and enhanced vesicle formation occurred only in the enlarging cortical cells on the green side. These changes were indistinguishable from those that occur in normal abscission cells and confirm the conversion of the cortical cells to abscission-type cells. Secondary abscission cells were also induced by applying auxin to the exposed primary abscission surface after the pulvinus was shed, provided ethylene was added. Then, the orientation of development of green and yellow tissue was reversed; the distal tissue remained green and the proximal tissue yellowed. Nevertheless, separation still occurred at the junction between green and yellow cells and, again, it was one to two cell layers of the green side that enlarged and separated from their senescing neighbors. Evaluation of Feulgen-stained tissue establishes that, although nuclear changes occur, the conversion of the cortical cell to an abscission zone cell is a true transdifferentiation event, occurring in the absence of cell division.

Journal Article↗
PubMed1993

A comparison of 1- and 2-cell ova production by F2 50% Meishan versus F1 White line gilts.

The objective of this study was to compare recovery of pronuclear and 2-cell ova from F2 50% Meishan (MX) gilts versus F1 White line (L42) gilts. Sexually mature MX and L42 gilts were allocated across 2 treatments: Super (MX:n=9; L42:n=10) and Control (MX:n=6; L42:n=5) in a 2 x 2 factorial experiment. Allyl trenbolone (AT) was used to synchronize estrus in all gilts. Super gilts were given pregnant mare serum gonadotropin (PMSG: 1250 IU) at 24 h after AT withdrawal. Eighty-five hours after PMSG administration, all Super gilts received 750 IU of human chorionic gonadotropin (hCG). Super gilts which exhibited estrus within 24 h of hCG administration (MX-Super: n=6; L42-Super: n=5) and all Control gilts were bred naturally to Line 3 boars at 12 and 24 hours after the onset of estrus. Ova were recovered from Super gilts between 60 and 64 h after hCG and Control gilts at 48 h after the onset of estrus. All 1- and 2-cell ova were centrifuged at 15000 x g and observed using differential interference contrast microscopy. The mean ovulation rate was greater (P<0.05) for both MX-Super and L42-Super gilts in comparison to their respective Control groups. No differences were detected in the mean ovulation rate (P>0.38) or the mean number of 1- and 2-cell ova recovered (P>0.50) between MX-Super and L42-Super gilts. The proportion of 1- and 2-cell ova which exhibited visible pronuclei or nuclei was also similar among MX-SUPER and L42-SUPER gilts. This study demonstrates that MX gilts respond/perform comparably to L42 gilts with respect to estrus synchronization, superovulation, ova yield, and the ease of visibility of pronuclei or nuclei in the ova.

Journal Article↗
PubMedDate not supplied

The NURSE Center: A peer mentor-tutor project for disadvantaged nursing students in Appalachia.

To assist disadvantaged Appalachian nursing students, a grant-supported peer mentor-tutor project was initiated in a regional university. Located in the NURSE Center (Nursing Undergraduate Resource for Successful Education), the goals of the project were to improve participants'academic achievement, increase retention, encourage timely academic progression, and improve NCLEX-RN passing rates. The authors describe the project, the first year of operation, and future directions.

Adult↗