3H-thymidine long survival autoradiography as a method for dating the time of neuronal origin in the chick embryo: The locus coeruleus and cerebellar Purkinje cells

Contrary to previous assumptions, we have found that a single dose of ³H-thymidine (25 μCi), injected into the yolk sac of White Leghorn chick eggs on 2 days of incubation (d.i.) only remains available for DNA-synthesizing (proliferating) cells for 48 hours following the time of injection. This finding now makes it possible to date the time of neuronal origin in the avian embryo using a single injection of isotope and a long survival time (30 days posthatch) as in mammalian studies where ³H-thymidine is only available as a short “pulse.” Using this method, we have determined that neurons in the chick locus coeruleus (LC) cease proliferation on 2–6 d.i. with a peak of neuronal genesis on 3–5 d.i. In addition, neuronal genesis is not homogeneous throughout the LC cell population, but occurs in a predominantly caudorostral gradient. Conversely, the cerebellar Purkinje cells cease division on 3–8 d.i. with a peak of heavy labeling on 4–6 d.i., 1 day later than that observed in the LC.     

Macrophage infiltration of breast tumours: a prospective study.

In 50 cases of infiltrating breast cancer investigated in a prospective study the number of macrophages within each tumour was assessed. The macrophages were identified by their cytoplasmic acid phosphatase activity. The number of lymphocytes and plasma cells within the tumours were graded by a scoring technique. Significantly fewer cases with metastases were found among those with high macrophage and plasma cell scores. There was no correlation between lymphoreticular infiltration and the degree of tumour differentiation, but in cases without metastases the lymphoreticular infiltration between tumour cells was nearly always only slight when the macrophage score was low.     

Teaching theoretical nursing.

Nursing science has been described as being either alive or inert. Acceptance of one or the other paradigm has important implications for the way in which theories of nursing are taught in the curriculum. In this paper these conflicting paradigms are discussed and the implications for nurse teachers are outlined. It is suggested that this may involve a reconceptualisation of where nursing theories are derived and a consequent shift of power from nurse teachers to the practising nurse.     

Development of an ex vivo simulated training model for laparoscopic liver resection

Background  

The number of patients who have undergone laparoscopic liver surgery has increased in the last 15 years. It is technically challenging surgery, requiring both advanced laparoscopic and liver resection skills. Surgeons often require familiarisation with much of the equipment and techniques used in this type of surgery. No ex vivo model currently exists for laparoscopic liver resection (LLR). The aim of this study was to develop a model for acquiring the technical skills involved in LLR that was also able to assess and measure surgical performance.     

Signal peptide mutations in RANK prevent downstream activation of NF‐κB

Familial expansile osteolysis and related disorders are caused by heterozygous tandem duplication mutations in the signal peptide region of the gene encoding receptor activator of NF‐κB (RANK), a receptor critical for osteoclast formation and function. Previous studies have shown that overexpression of these mutant proteins causes constitutive activation of NF‐κB signaling in vitro, and it has been assumed that this accounts for the focal osteolytic lesions that are seen in vivo. We show here that constitutive activation of NF‐κB occurred in HEK293 cells overexpressing wild‐type or mutant RANK but not in stably transfected cell lines expressing low levels of each RANK gene. Importantly, only cells expressing wild‐type RANK demonstrated ligand‐dependent activation of NF‐κB. When overexpressed, mutant RANK did not localize to the plasma membrane but localized to extensive areas of organized smooth endoplasmic reticulum, whereas, as expected, wild‐type RANK was detected at the plasma membrane and in the Golgi apparatus. This intracellular accumulation of the mutant proteins is probably the result of lack of signal peptide cleavage because, using two in vitro translation systems, we demonstrate that the mutations in RANK prevent cleavage of the signal peptide. In conclusion, signal peptide mutations lead to accumulation of RANK in the endoplasmic reticulum and prevent direct activation by RANK ligand. These results strongly suggest that the increased osteoclast formation/activity caused by these mutations cannot be explained by studying the homozygous phenotype alone but requires further detailed investigation of the heterozygous expression of the mutant RANK proteins. © 2011 American Society for Bone and Mineral Research