The distribution of lead in human hemopoietic tissue and spongy bone after lead poisoning and Ca-EDTA chelation therapy. Observations made by atomic absorption spectroscopy, laser microbeam mass analysis and electron microbeam X-ray analysis

Two iliac crest needle biopsies were taken from a 43-year-old lead-poisoned woman during and after completion of a Ca-EDTA treatment. By atomic absorption spectroscopy the first and second biopsy were found to contain 56, respectively 41.6 micrograms lead/g wet tissue. In both biopsies 36% of the lead was extractable in 0.1 N HCl. Electron microbeam X-ray analysis proved to have too low sensitivity for quantitation of the lead in these biopsies. Laser microbeam mass analysis (LAMMA), performed only on the second biopsy, revealed a high and fairly constant residual lead concentration in all bone marrow cell nuclei (approximately 55 micrograms/g) and a low lead concentration in the cytoplasm of the same cells (4-12 micrograms/g). The extracellular bone matrix lead was greatly concentrated in the superficial 3-6 microns osteoid zone of the bony trabeculae and totally absent from deeper parts of the mineralized matrix. The LAMMA results are in good agreement with those of subcellular fractionation experiments and atomic absorption spectroscopy, provided that the relative volume fraction of nucleus and cytoplasm is accounted for. The high residual osteoid lead after completed chelation therapy indicates that lead has a stronger affinity for the organic than the mineral components of bone matrix.

An organ culture system designed to study interaction of fetal rat calvaria with human head and neck squamous cell carcinoma

The development of permanent cell lines of human head and neck squamous cell carcinoma in culture has enabled these cell lines to be used to investigate the interaction of the tumor cells with bone. After the squamous carcinoma lines on fetal rat skulls were implanted the explants with their added tumor were maintained in long-term tissue culture by use of the procedures developed for growing these tumor cells. Results confirm direct interaction with the bone by the malignant cells. Specific surface and cytoplasmic markers have been demonstrated by use of monoclonal antibodies against the tumor cells. Furthermore, tumor angiogenesis without the addition of any endogenous endothelial components has been verified. Investigations into the degree of bone infiltration and susceptibility of these interacting tumor cells to various factors, radiation therapy, and chemotherapeutic agents have been carried out. The establishment of a model system for bony invasion by squamous cell carcinoma of the head and neck permits the investigation of the mechanism of tumor invasion and the study of various potential treatment modalities.

Tetracycline labeling of bone in vivo

We have analyzed various aspects of tetracycline labeling technique for the measurement of bone apposition rate in vivo. Our efforts were restricted to those aspects that are frequently questioned when data obtained using this technique are interpreted as representing the rate of bone apposition. Rat bone was labeled in vivo by sequential injections of oxytetracycline at a dose range of 3 to 24 mg/kg body weight and at intervals ranging from 24 to 72 h. The bone apposition rate was calculated by measuring the distance from the first dose of label to the subsequent ones. As these distances are by far too small to be determined accurately by any available micrometer eyepiece, we have used a scanning microscope photometer which allows measurements on slow-forming sites that otherwise would have been considered nongrowing sites. Using these techniques, we have demonstrated that oxytetracycline has no effect on the bone apposition rate when used in the concentrations indicated. In addition, we found that at labeling intervals of 96 h or more, periods of osteoblastic inactivity are likely to be included in measurements at individual sites. The instantaneous apposition rate is thus underestimated at these long time intervals.