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J Marsden

Publications and source records attributed to J Marsden.

15 recordsLinked to original sources
PubMed1983

The G1 distribution of "G1-less" V79 Chinese hamster cells.

The V79-8 line of Chinese hamster cells has been reported to lack a measurable G1 phase. However, using a combination of time-lapse cinemicroscopy and [3H]thymidine autoradiography, we have found these cells to have a median G1 duration ranging from 1.4 to 2.6 h in different experiments, accounting for more than 15% of the median cycle time. The youngest cell labelled (in seven experiments) was 0.73 h old at the time of fixation suggesting a minimum G1 of between 0.40 and 0.73 h (the duration of the [3H]thymidine pulse being 0.33 h). In those experiments where steady-state proliferation could be established unequivocally, variability in G1 times accounted for all of the variability in cycle times. In addition, the distribution of G1 times (and cycle times) was well described by the two-transition version of the transition probability model. Nevertheless, changes in the average duration of G1 (and hence changes in the transition probabilities) played a comparatively minor role in determining proliferation rate. Instead, the length of S + G2 was markedly influenced by the composition of the culture medium. For purposes of comparison with the 'G1-less' V79-8 line, we have also examined a revertant derived from it (G1+5c) reported to have regained a substantial G1 phase. We are able to confirm that its G1 is indeed longer, the youngest labelled cell being 2.48 h old at the time of fixation. Unlike the parent line, there appeared to be more variability in G1 times than could be explained by two random transitions alone. The proliferation rate of the G1+5c revertant was unusually sensitive to the composition of the culture medium, suggesting the possibility of a metabolic defect.

Animals↗
PubMed1975

Subglottic enlargement using cartilage-mucosa autograft. A preliminary experimental study.

Subglottic stenosis in the infant currently has no well-accepted surgical correction. Our experimental study was designed to determine the effectiveness of a nasal septal cartilage-mucosa autograft in increasing the subglottic circumference and its effect on subsequent subglottic growth. Six pairs of matched mongrel puppy litter mates were used; one underwent surgery, the other served as a control. The cricoid and first tracheal rings were split anteriorly, and widened 5 mm to accept an autogenous nasal septal cartilage-mucosa graft. All animals were killed after six months of postoperative growth. The autografts appeared to be partially or completely replaced by fibrous tissue but a persistent enlargement in the subglottic airway was found in the animals that underwent surgery, with glottic measurements the same in both groups. Thus, a septal cartilage autograft to the subglottic larynx in puppies appears to result in persistent enlargement of the subglottic area, but produces no interference with subsequent normal laryngeal growth and development.

Animals↗
PubMedDate not supplied

Setting up nurse practitioner roles: issues in practice.

This article examines the process of developing a nurse practitioner role. Areas which must be considered before and during the implementation of such a role are general and may be applied to any area of practice, although examples here are from the author's own practice.

Humans↗