Over three decades ago, it was established that deficiency of either vitamin D or parathyroid hormone may lead to tetany and hypocalcemia (1, 2). Since then, there has been continued interest in the relationship between the biologic effects of these two agents. At one time it was believed that the D vitamins exerted their effects by stimulating the parathyroid glands, but this concept became untenable after it was established that vitamin D could induce hypercalcemia in hypoparathyroid organisms. More after the initiation of specific therapy (6). Harrison and Harrison (6) have favored the view that this retention is due to a direct action of vitamin D upon the renal tubular reabsorption of phosphate, whereas others (5) have considered it a consequence of decreased parathyroid gland activity.A possible new insight into the nature of the vitamin D and parathyroid hormone relationship has come from mitochondrial studies (7-11). It has been found that vitamin D and parathyroid hormone promote the release of calcium (as a phosphate salt or ion pair) from isolated mitochondria (7), that they act synergistically, and that the presence of the vitamin is necessary for the hormone to exert this effect, although the converse is not true. The hormone has other effects upon the mitochondria that are neither produced by, nor dependent upon, the presence of vitamin D. These are the stimulation of phosphate (11), sulfate, and arsenate (9) accumulation, and a stimulation of respiration (8, 9) that appears to be coupled to the translocations of these ions. These effects are presented in schematic form in Figure 1.Certain predictions concerning the physiological actions of vitamin D and parathyroid hormone can be made on the basis of these in vitro observations. The most important prediction, in the present context, is that parathyroid hormone will exert its effects upon calcium translocations only in the presence of vitamin D, but will continue to exert effects upon phosphate metabolism in the D-deficient organism.The purpose of this paper is to report experiments designed to test this prediction. The results indicate that parathyroid hormone has a dramatic effect upon phosphate metabolism in the D-deficient rat, but has little apparent effect upon calcium mobilization, at least in moderate doses. 1940

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The effects of intravenous administration of potassium phosphate in the treatment of diabetic ketoacidosis were studied in nine children, ages 9 9/12 to 17 10/12 yr. During phosphate infusion (20--40 meq/L of fluid), all children maintained normal serum concentrations of phosphorus. Transient hypocalcemia occurred in six and transient hypomagnesemia in five patients. One child developed carpopedal spasms refractory to intravenous infusion of calcium gluconate but responsive to intramuscular injection of magnesium sulfate. In three patients, serum levels of intact parathyroid hormone were low at the time of hypocalcemia, an observation that suggests transient hypoparathyroidism. This study indicates that the use of potassium phosphate as the sole source of potassium replacement might potentiate ketoacidosis-induced hypocalcemia through multiple mechanisms.

Clinical laboratory automation has blossomed since the 1989 AACC meeting, at which Dr. Masahide Sasaki first showed a western audience what his laboratory had implemented. Many diagnostics and other vendors are now offering a variety of automated options for laboratories of all sizes. Replacing manual processing and handling procedures with automation was embraced by the laboratory community because of the obvious benefits of labor savings and improvement in turnaround time and quality. Automation was also embraced by the diagnostics vendors who saw automation as a means of incorporating the analyzers purchased by their customers into larger systems in which the benefits of automation were integrated to the analyzers.This report reviews the options that are available to laboratory customers. These options include so called task-targeted automation-modules that range from single function devices that automate single tasks (e.g., decapping or aliquoting) to multifunction workstations that incorporate several of the functions of a laboratory sample processing department. The options also include total laboratory automation systems that use conveyors to link sample processing functions to analyzers and often include postanalytical features such as refrigerated storage and sample retrieval.Most importantly, this report reviews a recommended process for evaluating the need for new automation and for identifying the specific requirements of a laboratory and developing solutions that can meet those requirements. The report also discusses some of the practical considerations facing a laboratory in a new implementation and reviews the concept of machine vision to replace human inspections.

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