Collaborative study of an assay for progestational steroids in individual contraceptive tablets

A single tablet assay method has been developed for determining norethindrone, norethynodrel, and norgestrel in commercial contraceptive tablets. The steroid is separated from the tablet constituents on a diatomaceous earth column, the chloroform eluate is reacted with isonicotinic acid hydrazide, and the steroid is determined by colorimetry. Norethynodrel is isomerized to a conjugated ketosteroid before the colorimetric determination. Fourteen laboratories collaboratively tested the method. The average recoveries in 3 brands of tablets were as follows: 102.6% for the sample labeled as containing 0.35 mg norethindrone/tablet, 99.4% for the 2.5 mg norethynodrel/tablet, and 98.2% for the 0.5 mg norgestrel/tablet. The assay method has been adopted as official first action.

Immunocytochemical localization of glutamate decarboxylase in rat spinal cord

The GABA synthesizing enzyme, glutamate decarboxylase (GAD), has been localized by light and electron microscopy in the rat lumbosacral spinal cord using a peroxidase-labeling antibody technique. The light microscopic localization shows heavy, punctate reaction product for GAD in the dorsal horn laminae I-III. Moderately heavy reaction product is also seen in the deeper dorsal horn laminae IV-VI, the medial aspect of the intermediate gray (lamina VII) and the region around the central canal (lamina X). A moderately light concentration of GAD reaction product is observed in the ventral horn, and punctate deposits of reaction product also are seen on motoneuron cell bodies. The punctate distribution of reaction product for GAD in both ventral and dorsal horns, as visualized by light microscopy, corresponds to GAD-containing synaptic terminals seen by electron microscopy in comparable regions of the spinal gray. Many more GAD-positive terminals are observed in dorsal horn laminae I-III than in deeper laminae IV-VI. GAD-containing terminals in the dorsal horn are presynpatic to dendrites and cell bodies. Gad-containing terminals presynaptic to other axon terminals are observed also, and they are more numerous in laminae II and III. In the ventral horn motor nuclei, GAD-positive knobs are presynaptic to large and small dendrites and motoneuror cell bodies. In addition, small GAD-containing terminals also are presynaptic to larger axonal terminals which are in turn presynaptic to motoneuron somata. The observation of GAD-containing terminals presynaptic to dendrites and cell bodies in both dorsal and ventral horns is compatible with the evidence suggesting that GABA terminals may mediate postsynaptic inhibition of spinal interneurons and motoneurons. The additional finding of GAD-positive terminals presynaptic to other axonal terminals in the dorsal horn and motor nuclei is consistent with the growing evidence that GABA also may be the transmises mediating presynaptic inhibition via axo-axond synapses in the spinal cord.

The fine structural localization of glutamate decarboxylase in developing axonal processes and presynaptic terminals of rodent cerebellum

The immunocytochemical localization of L-glutamate decarboxylase (GAD), the enzyme which which forms gamma-aminobutyric acid (GABA), has been studied in developing rodent cerebellum. During the first 3-4 postnatal days, GAD is distributed along non-terminal portions of axonal processes in close association with small vesicles. Some of the axonal processes emanate from profiles which resemble growth cone varicosities, and are presumed to be foliopodia which extend distally from axonal growth regions. At the end of the first postnatal week the GAD-containing axonal processes are seen to form protosynaptic contacts, and GAD is localized around synaptic vesicles and at presynaptic junctional membranes. During the second and third postnatal weeks GAD gradually becomes localized to mature synaptic terminals in association with synaptic vesicle, mitochondrial, and presynaptic junctional membranes. The results suggest that GAD is present in growing neurites in close association with small vesicles prior to the time the neurites make protosynaptic contacts, and that differentiation of these contacts results in a sequestering of GAD into synaptic terminals.

Colorimetric determination of mestranol in combination with ethynodiol diacetate

Mestranol in combination with ethynodiol diacetate, an oral contraceptive formulation, is isolated from the sample on a partition chromatographic column prior to colorimetric determination. The color reaction which is specific for estrogens is formed by shaking an aliquot of the heptane eluate of mestranol with a 30% methanol-sulfuric acid solution. A collaborative study of the method gave results of 99.8% of added mestranol for the simulated mix and 100.7% of labelled mestranol for the commercial tablet. The method has been adopted as official first aciton.

Immunochemical studies of brain glutamate decarboxylase and GABA-transaminase of six inbred strains of mice

Six different inbred strains of mice (C57BL/6J, CBA/CaJ, CE/J, DBA/2J, LP/J and RF/J) were compared in terms of specific activities and immunochemical properties of brain L-glutamate decarboxylase (GAD) and gamma-aminobutyrate transaminase (GABA-T), the enzymes responsible for the synthesis and degradation of GABA, respectively. GAD from the brains of the different strains was indistinguishable on the basis of specific activities, double diffusion tests, immunoelectrophoresis and inhibition by antibody. However, microcomplement fixation tests showed GAD from DBA and C57BL mice to be most distinctly different from GAD extracted from the Swiss mouse, from which the original antigen was prepared and that the enzyme from the CE, LP and RF also differed. Similar fixation curves were obtained for the GAD from CBA and Swiss mice. GABA-T from the different strains was indistinguishable on the basis of all the tests employed.