Polymorphism of rRNA gene loci in the dog.

We examined the number of ribosomal gene (rDNA) loci in the metaphase spreads of 54 dogs by FISH method. We found that in 16 dogs (30%) one or two loci were missing. The total number of rDNA loci was varied from 5 to 7 in males and from 4 to 6 in females.

Patterns of efferent lymphatics of the rabbit testis.

The present study examined the courses of testicular efferent lymphatics in the rabbit, by injections of India ink directly into testicular parenchyma. In 58% of the testes examined, testicular efferent lymphatics were observed to course along the testicular artery to the lumbar trunk. In other testes, efferent lymphatics were found along the testicular artery as well as along either the ductus deferens (26%) or cremasteric muscle (8%).

Visualization of the thoracic duct with injections of dyes or contrast media into the testicular parenchyma in the rabbit.

The thoracic duct drains lymph from the caudal part of the body to the venous system. The visualization of the thoracic duct is important for diagnosis of chylothorax, which may be caused by the damage of the duct. However, it is not easy to visualize the thoracic duct by injecting dyes and/or contrast media into peripheral lymph nodes and mesenteric lymphatics.

Donor age reflects the replicative lifespan of human fibroblasts in culture.

Human fibroblasts, which have a finite lifespan in cultures, have been widely used as a model system for cellular aging, and frequently used as one model of human aging. But whether cellular aging contributes to organismal aging has been controversial. To reinvestigate this question, we cultured human fibroblasts from the skin of one individual volunteer collected at different ages.

Mapping of rRNA gene loci in the mice, Mus musculus molossinus (Japan) and Mus musculus musculus (Russia) by double color FISH.

Ribosomal RNA gene (rDNA) loci of Russian Mus musculus musculus and of Japanese Mus musuculus molossinus were mapped by double color FISH. The total number of rDNA loci was varied from 5 to 12, although the loci on chromosomes 12, 15, 16, 18, and 19 were common to all mice examined. Instead, polymorphisms of the rDNA loci were found on chromosomes 1, 5, 8, 9, 10, 11, 13 and 17.

Identification of rRNA gene loci in the wild mouse (Mus musculus molossinus) captured at Hachioji, Tokyo.

Mus musculus (M. m.) molossinus has been considered an independent subspecies of Mus musculus.

Klotho insufficiency causes decrease of ribosomal RNA gene transcription activity, cytoplasmic RNA and rough ER in the spinal anterior horn cells.

The klotho gene was identified in 1997 as the gene whose severe insufficiency (kl/kl) causes a syndrome resembling human aging, such as osteoporosis, arteriosclerosis, gonadal atrophy, emphysema, and short life span in a mouse strain. Regarding the gait disturbance reported in kl/kl mice, the present study examined the spinal cord of kl/kl mice, and revealed decreases in the number of large anterior horn cells (AHCs), the amount of cytoplasmic RNA, the number of ribosomes and rough endoplasmic reticulum (rER), and the activity of ribosomal (r) RNA gene transcription without significant loss of the total number of neurons in the ventral gray matter. Increased immunostaining of phosphorylated neurofilament in the AHCs and of glial fibrillary acidic protein in reactive astrocytes in the anterior horn of kl/kl mice were also observed.

Overexpression of telomerase confers a survival advantage through suppression of TRF1 gene expression while maintaining differentiation characteristics in K562 cells.

Leukemic stem cells that expressed endogenous telomerase activity were induced to show overexpression of exogenous hTERT and were analyzed for biological changes in order to assess the possible influence of telomerase gene therapy on the transplantation of normal hematopoietic stem cells. Introduction of hTERT into K562, a telomerase-positive immortal cell line, resulted in a 2.5-fold elevation of telomerase activity and the lengthening of telomeres by 6 kb to 23 kb.

Telomerase overexpression in K562 leukemia cells protects against apoptosis by serum deprivation and double-stranded DNA break inducing agents, but not against DNA synthesis inhibitors.

Telomeres are specialized DNA/protein structures that act as protective caps to prevent end fusions. The maintenance of telomeres is essential for chromosomal stability. Telomerase is regulated by human telomerase reverse transcriptase (hTERT).