The polyhedral inclusions of Thiobacillus neapolitanus have been isolated; they contain ribulose diphosphate carboxylase.

The auxiliary subunit ␣ 2 ␦3 modulates the expression and function of voltage-gated calcium channels. Here we show that ␣ 2 ␦3 mRNA is expressed in spiral ganglion neurons and auditory brainstem nuclei and that the protein is required for normal acoustic responses. Genetic deletion of ␣ 2 ␦3 led to impaired auditory processing, with reduced acoustic startle and distorted auditory brainstem responses. ␣ 2 ␦3 Ϫ/Ϫ mice learned to discriminate pure tones, but they failed to discriminate temporally structured amplitude-modulated tones. Light and electron microscopy analyses revealed reduced levels of presynaptic Ca 2ϩ channels and smaller auditory nerve fiber terminals contacting cochlear nucleus bushy cells. Juxtacellular in vivo recordings of sound-evoked activity in ␣ 2 ␦3 Ϫ/Ϫ mice demonstrated impaired transmission at these synapses. Together, our results identify a novel role for the ␣ 2 ␦3 auxiliary subunit in the structure and function of specific synapses in the mammalian auditory pathway and in auditory processing disorders.

An a-glucosidase has been purified 1300-fold from the lysosomal fraction of rat liver. The preparation appears to be homogeneous when subjected to equilibrium ultracentrifugation. The degree of purification of the enzyme at each step in its preparation was essentially the same whether the assay substrate was maltose, glycogen, or isomaltose. Thus, the enzyme appears to have a-1,6-glucosidase as well as a-l,4-glucosidase activity. Both of these activities sedimented at the same rate when the purified enzyme was centrifuged in a linear sucrose gradient. The apparent molecular weight of the protein is about 114,000. The enzyme has maximal activity toward maltose at pH 3.7, toward isomaltose at pH 4.2, and toward glycogen at pH 4.4. Similar pH optima were found in acetate and citrate buffers. Glucose formation from glycogen can be stimulated fivefold at pH 4.0 by 0.2 M KCl. This T he lysosomes which are present in liver are known to contain a large number of hydrolases with specificities directed toward a variety of intracellular and extracellular macromolecular substances as well as toward compounds of simpler structure which occur within the cell. Presumably, the

Although "amylopectinosis" was originally described in 1952 as a type of glycogen storage disease,' very few additional cases have been observed in the intervening years either because the disease is very rare or because it is not easily recognized clinically. The original designation of the disease was based on the accumulation in the liver of a polysaccharide whose structure resembled that of amylopectin rather than that of glycogen. Thus, the polysaccharide had long outer chains with relatively few branch points and was highly chromogenic with I2-KI; the I2 complex had an absorption peak at 530 mji as compared to 460 msA for glycogen. The cause of the accumulation of such an unusual polysaccharide was postulated to be a relative deficiency of the branching enzyme. 12 No enzymic assays could be performed. A detailed clinical description of this case was published by Andersen,3' 4 and the observations on polysaccharide structure were reported by Illingworth and Cori.' A second case of Type IV glycogenosis was described by Sidbury et al. in 1962,5 and a third case by Holleman et al. in 1966.6 We recently received tissues taken by biopsy from a 19-month-old child (M. G.) suspected of having Type IV glycogenosis. The purpose of this paper is to describe some new chemical and enzymatic findings which have been made on this material. A full clinical report of the case will be presented by Donnell.7 Methods and Results.-The liver had a polysaccharide content of 3.5 per cent, and the isolated material was shown to be highly chromogenic with 12-KI (maximum absorption at 525 mIu), and to have long outer chains (degraded by phosphorylase to the extent of 47%) and a relatively low branch point percentage (6.0%). Muscle samples taken upon two different occasions had polysaccharide contents of 0.5 and 1.0 per cent. Unlike the polysaccharide from liver, that from muscle contained 7.4 per cent branch points and could be degraded by phosphorylase to the extent of 36 per cent, a value characteristic of glycogen. The absorption spectrum of the

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