The number and location of genes for 5S ribonucleic acid within the genome of Drosophila melanogaster

DNA was prepared from wild-type and two mutant stocks of Drosophila melanogaster that differed in their dosage of the nucleolar organizer region. The relative amounts of DNA from the nucleolar organizer region in these preparations of DNA were determined by hybridization with (3)H-labelled 28S rRNA. As expected, the amount of (3)H-labelled 28S rRNA that hybridized was directly related to the dosage of nucleolar organizer region. No positive correlation was observed between the amount of (3)H-labelled 5S RNA that hybridized and the dosage of nucleolar organizer region. Thus genes for 5S RNA are located primarily, if not exclusively, outside the nucleolar organizer region. The haploid genome of the wild-type D. melanogaster used in this work has 106 genes for 28S rRNA and 96–105 genes for 5S RNA

The effect of Lidocaine on the viability of cultivated mature human cartilage cells: an in vitro study

More and more orthopedic procedures are performed in an outpatient setting. A commonly used strategy in pain management is the intra-articular injection of local anesthetics. Recent attention has been drawn to their possible toxic effect on chondrocytes. Local anesthetics, and in particular Lidocaine, are also used for diagnostic joint infiltrations. A controlled laboratory study was performed to investigate the possible toxic effect of Lidocaine on human articular chondrocytes. Mature human articular chondrocytes were harvested from the knees of human tissue donors or patients undergoing total knee replacement. The cells were exposed to Lidocaine 1 and 2% with and without epinephrine and to a saline 0.9% control group, with variable exposure times in different experiments. The activity and viability of the cells were assessed by lactate dehydrogenase activity, interleukin-6 production and a live/dead cell count. After a 1-h exposure, devastating results were seen for Lidocaine 1, 2 and 2% with epinephrine showing cell death rates of 91, 99 and 97%, respectively, compared with 26% in the saline control group (P-values of 0.004, 0.010, 0.006, respectively). Exposing the chondrocytes to a 50/50 mixture of culture medium and local anesthetics substantially decreased cytotoxicity but still showed high toxicity when compared with the saline group (90% dead cells for Lidocaine 2%, P = 0.047). Lidocaine also showed a time-dependent cytotoxicity with gradually more dead cells after exposure for 15, 30 or 60 min. In vitro, local anesthetics containing Lidocaine are significantly more toxic to mature human articular chondrocytes than a saline 0.9% control group. The effect of Lidocaine on the viability of human chondrocytes in vivo needs further investigation. However, based on our in vitro results, cautious use of intra-articular Lidocaine in clinical practice is recommended