[Effects of Epimedium sagittatum Maxim. Polysaccharides on DNA synthesis of bone marrow cells of "yang deficiency" animal model caused by hydroxyurea]

A study was made on the effects of Epimedium sagittatum polysaccharides on DNA synthesis of bone marrow cells of "yang deficiency" animal model caused by hydroxyurea with methods of cell culture in vitro and determination of 3H-TdR incorporating DNA of bone marrow cells. The results showed that after the treatment with 100 micrograms of Epimedium sagittatum polysaccharides, the cell multiplication rate was increased by 72% and DNA synthesis rate increased by 68%, in 1 x 10(6) cells.

[Experimental study of thyroid hormone and bone metabolism in the rat]

Thyroid hormones (T3, T4) stimulate bone turnover. Calcitonin is a potent inhibitor of osteoporostic bone resorption. In patients with thyrotoxicosis, bone mineral content is reduced. We investigated the influence of calcitonin deficiency in thyroidectomized parathyroid-autotransplanted rats with L-thyroxine (T4) supplementation. Thyroidectomy resulted in a reduction of bone volume, bone calcium content and in a decrease in trabecular bone volume. T4-supplementation corrected this loss of bone calcium content but not trabecular bone volume. In thyroidectomized parathyroid-autotransplanted rats matched for T3-levels to intact controls, there was still a reduction in both bone calcium content and trabecular bone volume. We assume this decrease in bone mass in thyroidectomized parathyroid-autotransplanted animals to be caused by the lack of calcitonin.

Role of vesicular transport in ADH-stimulated aggregate delivery

It has been assumed from studies in toad bladder that antidiuretic hormone (ADH)-stimulated particle delivery to the luminal membrane is mediated by particle-carrying tubular structures (aggrephores). We report studies in frog and toad urinary bladder showing that vesicles, rather than aggrephores, appear to play the major role in particle delivery in the frog and that vesicle and aggrephore delivery proceed in parallel in the toad. Our principal evidence for this view is that in the frog, transmission electron microscopy shows virtually no fused aggrephores. Supporting evidence includes the following. 1) Freeze-fracture studies show that the diameters of fusion events delivering particles can be quite small, indicating that they are formed by fused vesicles rather than fused aggrephores. 2) A significant population of small fusion events is also seen in the toad, along with larger fusion events related to both aggrephores and large vesicles. 3) Surface aggregate areas in both species are small, consistent with vesicular delivery. 4) Freeze-fracture replicas indicate delivery from shallow pits. We propose a system of transport of particles in which aggrephores act largely as intermediate storage organelles in the frog and as storage and fusion organelles in the toad.

Evidence for cycling of aggregate-containing tubules in toad urinary bladder

Antidiuretic hormone (ADH) promotes the fusion of cytoplasmic tubular structures with the luminal membrane of receptor tissues such as toad urinary bladder. To determine whether fusion is a continuous cyclic process, bladders were stimulated with ADH with colloidal gold in the luminal bathing medium. After as little as 15 min of stimulation, gold-filled tubules were seen in the cytoplasm, evidence that cycling was indeed taking place. Serial sections confirmed that these tubules had no connection with the luminal membrane, and had returned to the cytoplasm. Cessation of ADH stimulation, followed by a second stimulation, greatly reduced the number of gold-filled cytoplasmic tubules, suggesting that many tubules were capable of refusion. Mean fusion event diameter underwent significant changes, enlarging at 15 min, and contracting at 60 min. Thus, ADH initiates a process of continuous cycling of cytoplasmic tubules between cytoplasm and luminal membrane.