Hospital Topics: The Hospital Consultant's Secretary

Analysis of work done by the secretaries attached to one medical unit in a general hospital showed that much was discretionary in character and entailed making decisions. Work in the unit was made easier and more efficient by this intelligent use of initiative by the secretaries. At present the pay given to medical secretaries in hospital is below a level that would be commensurate with their responsibility.     

Precision of theGonyaulax circadian clock

Under constant conditions, the circadian bioluminescent glow rhythm in populations (10⁵ cells) ofGonyaulax polyedra is accurate to within 2 min/day. On successive days following the transfer to constant conditions, however, the glow exhibits a progressively broader waveform, implying that individual clocks in the population are drifting out of synchrony. Analysis of the glow waveform suggests that the standard deviation in circadian period among individual clocks is about 18 min and that the period of a given clock varies by less than this from one day to the next.     

Enhanced bactericidal activity of platelet β-lysin forE. coli in the presence of membrane perturbation

Inhibition by sodium chloride of the growth of 19 strains ofLegionella pneumophila and of 10 strains of otherLegionella spp. was studied. Results from growth in buffered -ketoglutarate cysteine yeast extract (BAYE) broth containing 0 to 2.0% sodium chloride indicated that 15/19 laboratory strains ofL. pneumophila were capable of growing in 1.0% to 1.5% sodium chloride, whereas 4 strains ofL. pneumophila and 10 strains of 6 other species were not.L. micdadei andL. longebeachae were the most inhibited in BAYE broth, growing only in concentrations of 0.5% sodium chloride. These in vitro studies indicate thatL. micdadei andL. longbeachae might be differentiated from other species by their low tolerance to salt in BAYE broth, and thatL. pneumophila may be more tolerant to salt concentrations found in brackish water environments.     

Preparation, characterization, and functions of rabbit lymph node populations. III. Antigen-induced uptake of thymidine and dibutyryl cyclic AMP: inhibition of thymidine uptake by cholera toxin and dibutyryl cyclic AMP.

Keyhole limpet hemocyanin (KLH)-primed lymph node cell (LNC) populations were incubated with various amounts of KLH and the cellular incorporation of tritiated thymidine ([³H]TdR) or tritiated N⁶, O^2′ dibutyryl cyclic AMP ([³H]DbcAMP) was determined. T LNC responded more vigorously than did complement receptor lymphocytes (CRL), i.e., B cells, at all KLH concentrations, during all time intervals examined, and in the presence or absence of normal rabbit serum (NRS). The depletion of adherent cells from KLH-primed LNC resulted in no significant decrease in KLH-induced incorporation of either [³H]TdR or [³H]DbcAMP in any of the LNC populations. Thus it appeared that variation among LNC populations in the incidence of macrophages did not account for the marked variation in their responses. Cultures containing equal numbers of T and CRL were induced to incorporate more [³H]TdR or [³H]DbcAMP than either population cultured separately or the sum of their individual responses. It was concluded that KLH-induced incorporation of these substances into primed, isolated LNC, was primarily manifested in the T-cell population. The synergism seen in cultures containing mixtures of T and CRL suggested that B cells are induced to incorporate [³H]TdR or [³H]DbcAMP in the presence of antigen and T-cell product(s). KLH-induced incorporation of [³H]TdR into KLH-primed LNC was inhibited by cholera enterotoxin (CT) and DbcAMP as previously reported. However, CT or DbcAMP inhibited this incorporation into T LNC to a greater extent than into CRL or unfractionated LNC.     

Mechanical stimulation of tissue engineered tendon constructs: effect of scaffold materials

Our group has shown that numerous factors can influence how tissue engineered tendon constructs respond to in vitro mechanical stimulation. Although one study showed that stimulating mesenchymal stem cell (MSC)-collagen sponge constructs significantly increased construct linear stiffness and repair biomechanics, a second study showed no such effect when a collagen gel replaced the sponge. While these results suggest that scaffold material impacts the response of MSCs to mechanical stimulation, a well-designed intra-animal study was needed to directly compare the effects of type-I collagen gel versus type-I collagen sponge in regulating MSC response to a mechanical stimulus. Eight constructs from each cell line (n=8 cell lines) were created in specially designed silicone dishes. Four constructs were created by seeding MSCs on a type-I bovine collagen sponge, and the other four were formed by seeding MSCs in a purified bovine collagen gel. In each dish, two cell-sponge and two cell-gel constructs from each line were then mechanically stimulated once every 5 min to a peak strain of 2.4%, for 8 h/day for 2 weeks. The other dish remained in an incubator without stimulation for 2 weeks. After 14 days, all constructs were failed to determine mechanical properties. Mechanical stimulation significantly improved the linear stiffness (0.048+/-0.009 versus 0.015+/-0.004; mean+/-SEM (standard error of the mean ) N/mm) and linear modulus (0.016+/-0.004 versus 0.005+/-0.001; mean+/-SEM MPa) of cell-sponge constructs. However, the same stimulus produced no such improvement in cell-gel construct properties. These results confirm that collagen sponge rather than collagen gel facilitates how cells respond to a mechanical stimulus and may be the scaffold of choice in mechanical stimulation studies to produce functional tissue engineered structures.     

A fluorimetric method for determination of calcineurin activity

Calcineurin is a calcium-dependent, serine/threonine phosphatase that is involved in a variety of signaling pathways. Calcineurin is distinct among phosphatases because its activity requires calcium and is not sensitive to inhibition by compounds that block the related phosphatases PP1A and PP2A. Therefore, the most common methods to measure calcineurin activity rely on calcium-dependent dephosphorylation of a substrate derived from the RII subunit of protein kinase A in the presence of PP1A/PP2A inhibitors. However, current techniques quantify activity by measurement of released radioactive phosphate or detection of free phosphate with malachite green. Both methods involve technical challenges and have undesirable features. We report a new calcineurin fluorimetric assay that utilizes a fluorescently labeled phosphopeptide substrate and separation of dephosphorylated peptide product by titanium-oxide. The method is rapid, quantitative, involves no radioactivity and is suitable for high throughput assays. Furthermore, with the use of a standard curve, precise measurements of calcineurin activity can be obtained.     

The path toward identifying prostatic stem cells

Abstract The concept that stem cells reside in prostate epithelia is well accepted and has led to significant efforts aimed at isolating and characterizing adult prostate stem/progenitor cells from both human and rodent prostate tissues. Understanding how prostatic stem and/or progenitor cells give rise to prostate epithelia during development and maintain homeostasis of the prostate gland in adulthood is a major research focus. Furthermore, the ability to identify and manipulate prostatic stem cells (PSCs) holds enormous promise for the development of new approaches to manage and treat prostate cancer. This review maps the pathways to identifying, isolating, characterizing, and understanding the differentiation capacity of PSCs.