[Effects of lead exposure to rat placenta and pups during different gestation periods].

OBJECTIVE: To investigate the effects of lead exposure to rat placenta and pups during different gestation periods. METHODS: All 108 Wistar rats (72 females, 36 males) were randomly divided into four groups. All rats were orally fed with 0.025% lead acetate during different gestation periods. Blood was obtained from the abdominal vena cava and the lead level in maternal blood was measured by means of atomic absorption spectrometry at the end of the pregnancy. The number of pups, their body weight, body length and tail length were measured. The effects of lead to rat placenta were observed by level of microscopy, optical microscopy and electronic microscopy. RESULTS: Experimental groups the blood lead level at the end of gestation were above 0.483 micromol/L. There were significant differences among, of pups, during different groups (P < 0.01). Among them the drinking lead group of whole distant was the lowest in placenta weight [(0.31 +/- 0.13) g] body weight of pups [(2.08 +/- 0.88) g] length and tail length of pups [(2.37 +/- 0.32) cm, (0.98 +/- 0.09) cm]. There were significantly differences between the experimental groups and controls. Maternal blood lead level was negatively related to placenta weight (r = 0.652, P < 0.01), and had no relation with the body weight of pups (r = -0.107, P = 0.46). In the experimental groups of lead poisoned rats, the placenta showed focus necrosis in the deciduas, and increased the trophoblastic giant cells and light staining cells in the trophospongium. Trophoblast in the labyrinth and trophospongium showed degeneration; fibrin deposition around the villi was increased. Microvilli around the trophoblast were shorter and less, mitochondrion was swollen and decreased in number, rough endoplasmic reticulum was distended and ribosomal number on membrane decreased. CONCLUSION: Lead exposure during different gestation periods should have a traumatic effect on the trophoblast, leading to interference of nutrition and oxygen exchange. Furthermore, the blood supply to the placenta and nutrition and oxygen exchange between mother and pups were also interfered, leading to reduction of placenta weight and retardation of development of pups.

[Observation on the ultrastructure of Pneumocystis carinii].

OBJECTIVE: To study the life cycle and morphology of Pneumocystis carinii by ultrastructural observation. METHODS: Wistar rat model of P. carinii infection was established by subcutaneous injection with dexamethasone. Lung tissue of the infected rats was used for the transmission electron microscopical study. RESULTS: The organisms were mainly present in the lung alveolar cavity, and also in the alveolar septum, pulmonary macrophages and neutrophils. More trophozoites of P. carinii attached to the type I alveolar epithelial cells, and rarely to the type II alveolar epithelial cells. Most of these trophozoites showed pseudopodial evaginations on their pellicles. The nucleus-associated organelle and spindle microtubules were observed in some trophozoites. The precyst phase was in three forms: early, intermediate and late form. Synaptonemal complexes indicating meiotic nuclear divisions and a clump of mitochondria were also observed in the precyst. The pellicle of the cyst has a thickened portion with a pore. There were nucleus with nucleolus, mitochondrion, vesicles, endoplasmic reticulum and numerous ribosomes in the organisms, and tubular expansions on its surface. CONCLUSION: The life cycle of P. carinii consists of trophozoite, precyst and cyst stages. The presence of a single pore in the cyst wall reveals that pore formation may be a mode of excystation for intracystic bodies of P. carinii.

[The characterization of scaffold made of N,O-carboxymethyl chitosan and tricalcium phosphate].

PURPOSE: To study the mechanical and chemical characterization of scaffold made of N,O-carboxymethyl chitosan (N,O-CMCS) and tricalcium phosphate(TCP) with various weight ratios. METHODS: Three composites of N,O-CMCS/TCP with weight ratios of 2:1,1:1 and 1:2 were mixed using the same volume of distilled water. The characteristic bands, morphologic structure, compressive strength and Young modulus of the composites were analyzed by infrared spectroscopy (IR),scanning electron microscopy(SEM) and universal testing machine respectively. RESULTS: The shift of IR characteristic bands of -COO(-)and -NH(2) to lower wave number was observed in three composites gradually, which resulted from the complexation of -COO(-) and -NH(2) with calcium ions. The pores of the three-dimensional porous structure and compressive strength of the composite increased when there were more N,O-CMCS in the composite. When there were more TCP in the composite, its porosity became less and Young modulus increased, so that the composite demonstrated more rigidity. CONCLUSIONS: N,O-CMCS had the capability of complexing with calcium ions. The scaffold made of N,O-CMCS and TCP had the properties of three-dimensional porous structure, flexible remolding and mechanical strength, so it will be a promising biomaterial for bone substitute.