TRANSIENT UNCROSSED CORTICOSPINAL FIBRES IN THE NEWBORN RAT

A small number of uncrossed corticospinal fibres were demonstrated in a 1-day-old rat by injection of horseradish peroxidase into one hemisphere of the cerebral cortex. These fibres were not demonstrable after the age of 7 days.     

Influence of a Bacterial Lipopolysaccharide on the Pharmacokinetics of Tobramycin in Rats

Abstract— The effects of Klebsiella pneumoniae O3 lipopolysaccharide on the renal handling and distribution characteristics of the aminoglycoside tobramycin were investigated in rats. Tobramycin (2 mg kg^?1) and inulin (100 mg kg^?1) were administered intravenously 2 h after administration of 50,250 or 500 μg kg^?1 lipopolysaccharide. Lipopolysaccharide delayed the disappearance of tobramycin from plasma in a dose-dependent manner. A dose-dependent decrease in systemic clearance of tobramycin was observed, although the elimination rate constant and fraction of urinary recovery of unchanged drug were not significantly different in any group. Lipopolysaccharide significantly decreased the central compartment volume of distribution of tobramycin, but did not influence the steady-state volume of distribution. A dose-related increase in the ratio of the rate constant of transfer to the peripheral compartment to the rate constant of transfer from peripheral compartment to central compartment was observed. The glomerular filtration rate was significantly decreased by pretreatment with 250 μg kg^?1 lipopolysaccharide and the clearance ratio was decreased by 20%, indicating that lipopolysaccharide increases the tubular reabsorption of tobramycin. Our findings suggest that K. pneumoniae O3 lipopolysaccharide modifies the glomerular filtration rate and tubular reabsorption without change in the terminal half-life and that drug distribution characteristics from the rapidly-distributing compartment to the peripheral compartment were altered without expansion of the extracellular fluid volume.     

Umbilical cord blood as a rich source of immature hematopoietic stem cells

To investigate immaturity of hematopoietic progenitor cells in umbilical cord blood mononuclear cells (CB-MNC), the formation of macroscopic colonies and mixed-cell colonies was assayed by methylcellulose culture with various combinations of cytokines (stem cell factor [SCF], interleukin [IL]-3, IL-6, granulocyte-colony stimulating factor [G-CSF], erythropoietin [EPO]) and compared with bone marrow (BM)-MNC. Moreover, distribution of the subpopulations divided by CD34, CD38, HLA-DR and CD33 was compared by flow-cytometry. Colonies derived from CB-MNC were so large that they could be observed with the naked eye and consisted of a variety of types of hematopoietic cells. Mixed-cell colonies were formed to a much greater extent in CB-MNC than in BM-MNC. Addition of EPO, IL-3, and SCF had rapid effects on the growth of mixed-cell colonies. The subpopulations of immature hematopoietic progenitor cells (CD34⁺, CD38⁻, HLA-DR⁻), which are supposed to be able to differentiate into hematopoietic precursors and stromal cells, were significantly higher in CB-MNC (8.7±6.6%) than in BM-MNC (0.0±0.1%; P < 0.001). These results suggest that CB is a rich source of immature hematopoietic progenitor cells compared to BM.     

Demonstration of the intralobular lymphatics in the guinea pig pancreas by an enzyme-histochemical method

Intralobular lymphatics in the guinea pig pancreas were demonstrated enzyme-histochemically showing the extent, distribution and fine structure by combined light and transmission electron microscopy. 5'-nucleotidase(5'-Nase)-positive lymphatic vessels were present throughout the pancreas. Intralobular lymphatics among the acini were comparatively rare and generally independent of the blood capillaries, pancreatic ducts and acini. These lymphatics revealed the usual structural features, such as typical intercellular junctions and very tenuous vascular walls without continuous basal laminae. Fine precipitates of the cerium-based reaction product for 5'-Nase activity were found to be associated with cell membranes of the lymphatic endothelium and pinocytotic vesicles. Lymphatics were not closely related to the endocrine islets, although alkaline phosphatase(ALPase)-positive blood capillaries were well developed. Collecting lymphatic vessels with valves with weaker 5'-Nase activity were also detected in the interlobular connective tissue. ALPase activity, absent in the lymphatics, was positive in the blood capillaries, suggesting that it is also a useful way of demonstrating, histochemically, the blood capillaries in the guinea pig pancreas.     

Dynamic ultrastructure of mouse pulmonary alveoli revealed by an in vivo cryotechnique in combination with freeze-substitution

A morphological approach to cell dynamics is usually difficult, since routine preparative techniques for electron microscopy always induce artifacts due to cessation of the blood supply into organs. An in vivo cryotechnique followed by the freeze-substitution method probably reduces such problems. It was applied for examining the pulmonary alveoli of BALB/c mice in vivo. The following ultrastructural features were revealed. (1) A surfactant layer provided a continuous covering to the alveolar epithelium. (2) Pleural epithelial cells, alveolar cells and endothelial cells contained many small vesicles and pits. In the alveolar epithelium, they were often localised near microtubules. (3) Typical lamellar structures in large alveolar epithelial cells were rarely detected. (4) Circulating erythrocytes with various shapes were observed in branching blood capillaries. (5) A close association between erythrocytes and the endothelium was seen at the peripheral alveolar septum. Such ultrastructural arrangements may be appropriate for the physiological functions of the pulmonary alveoli, such as exchanges of gases or materials in vivo.