Biomedical subjects

S C MacDonald

Publications and source records attributed to S C MacDonald.

3 recordsLinked to original sources

PubMed1997

A variation of the tissue print technique for studying isolated spinal cord cells in situ.

We present a novel variation of the tissue print technique which yields isolated spinal cells that retain their original topographical organization in situ. A light papain digestion combined with a low-melting-point agarose as the adhesive substrate is used to "print' a monolayer of cells from spinal cord slices. Printed cells are viable for studies using electrophysiological approaches. This technique provides a means to bridge the gap between properties of isolated cells and their topographical identity in spinal cord.

Animals↗

PubMed1990

Sampling clinicians' activities using electronic pagers.

Pager-based activity sampling (PAS) is described as a cost-effective and unobtrusive method for sampling residents' activities in clinical settings. A sample program evaluation is presented using residents in an urban children's hospital resident-training program. The purposes of the program evaluation were: (a) to establish a behavioral baseline that would help clinical faculty understand how residents were using their time, and (b) to determine whether alterations in the way residents were assigned within the hospital resulted in desired changes to time spent. The primary rationale for changing resident-assignment policies were: (a) to decrease the time residents were spending in transit between various locations within the hospital, and (b) to increase the time spent by residents in educational activities and in direct contact with patients and their families. This PAS application demonstrates that the technique can produce statistically supportable conclusions, at minimal cost, without unduly disrupting either the residents or their patients. PAS is compared with other time-sampling methods, its limitations are discussed, and suggestions for future applications are provided.

Confidence Intervals↗

PubMed1982

Regulation of extraadrenal steroid 21-hydroxylase activity. Increased conversion of plasma progesterone to deoxycorticosterone during estrogen treatment of women pregnant with a dead fetus.

We measured deoxycorticosterone (DOC) and progesterone (P) in plasma of 47 women pregnant with a dead fetus and sequentially throughout gestation in 35 women pregnant with a live fetus. When P levels in plasma were low, the plasma levels of DOC in women pregnant with a dead fetus varied but usually were similar to those in women pregnant with a live fetus. However, when P levels were high, the levels of DOC in some women pregnant with a dead fetus were considerably lower than those in women pregnant with a live fetus. To test whether this finding was due to loss of transfer of DOC from fetus to mother or else loss of extraadrenal steroid 21-hydroxylase activity in the mother after death of the fetus, we conducted several studies. The levels of P and DOC in plasma of one woman remained constant from 30 min after fetal death until delivery occurred 13 h later. Estrogen treatment of four women pregnant with a dead fetus brought about an increase in plasma levels of DOC in three of the women. In one woman the ratio of plasma DOC to P was 0.015, a value similar to that found before fetal death, but was 0.003 after fetal death but before estrogen treatment. In two women pregnant with a dead fetus the transfer constants of conversion of plasma P to DOC were 0.011 and 0.005 before, and 0.024 and 0.013, respectively, during estrogen treatment. In one woman pregnant with a deformed fetus with adrenal agenesis, the metabolic clearance rates of DOC before and during estrogen treatment were similar, whereas the plasma production rates of DOC were 2.75 before and 4.31 mg/24 h during estrogen treatment. We suggest that (a) the DOC in plasma of near-term pregnant women arises in part by extraadrenal 21-hydroxylation of plasma P and (b) estrogen stimulates steroid 21-hydroxylase activity in extraadrenal tissues.

Adrenal Glands↗