Chondronectin: physical and chemical properties

Chondronectin, the chondrocyte attachment factor, was purified from chicken serum and characterized as to its physical and chemical properties. From sedimentation equilibrium data it was found to have a native molecular weight of 175,800 +/- 800 and a subunit molecular weight of 55,540 +/- 800 in the presence of guanidinium chloride and cysteine, suggesting a trimeric structure linked by disulfide bonds. As visualized by electron microscopy after rotary shadowing, the protein appears compact and globular. The amino acid and carbohydrate compositions of chondronectin are distinct from fibronectin, the fibroblast attachment factor, and laminin, the epithelial cell attachment factor. The activity of chondronectin in promoting attachment of chondrocytes is stable to digestion by collagenase, elastase, and neuraminidase, but is destroyed by trypsin treatment. The data suggest that chondronectin is structurally and chemically distinct from fibronectin and laminin.     

A test of a model for estimating production in the sea

Primary productivity was measured in the sea off the coasts of Florida and Georgia with the radiocarbon method at four stations during March, 1971. Integral photosynthesis per square meter surface was determined with a mathematical model from empirical data gathered from in situ and shipboard incubation experiments. The mathematical model provided shipboard incubators to be used to estimate primary production rates while overcoming the problem of relating light quality and quantity simulated by the incubators to that found in the euphotic zone. The use of shipboard incubation can allow for measurements to be made on a moving vessel, more stations visited per day and water samples incubated at a constant light intensity. Primary productivity at the four sampling stations ranged from 0.026 to 0.042 mg C/M² hr.     

Subcellular distribution of enkephalins and endogenous opioid activity in rat brain.

The subcellular distribution of leucine- and methionine-enkephalin in rat brain was studied using a highly selective and sensitive radioimmunoassay. About 85% of the total recoverable activity of each peptide was present in crude synaptosomal and microsomal fractions which contained about 60% and 25% respectively. Total opioid activity in brain subcellular extracts was measured by competition for opiat receptor binding. It is concluded that enkephalin accounts for the majority of the opioid activity in the brain extracts. It seems unlikely that the enkephalin in microsomal fractions are exclusively associated with opiate receptors present in these fractions.     

The Relationship of Slide Maturity and Trypsin Exposure Time in the Differential Giemsa Banding of Chromosomes

Difficulty has been reported in attaining consistent chromosome banding using trypsin-Giemsa techniques. When trypsin concentration, incubation temperature, and the duration of staining are held constant, a logarithmic relationship has been found to exist between the length of time since a slide was made and the length of trypsin treatment necessary to produce optimal banding when it is stained. Under the conditions specified in this report, ten seconds digestion was optimal for ten-day-old slides. This time approximately doubled for each additional eight days that slides were allowed to age. From a plot of the experimental results, treatment times appropriate for slides of any age from 10 to 60 days were obtained. Use of these times produced satisfactory banding in 85% of mitoses.