[Absorbed dose during helical acquisition CT. Effect of acquisition parameters]

PURPOSE

European directive 97/43 specifies that the dose delivered to the patient during a radiological procedure should be estimated. In order to prepare for implementation of this new regulation, we have studied the dose delivered during spiral CT acquisition.

MATERIALS AND METHODS

We have studied the influence of slice thickness, pitch, tube voltage and intensity, and acquisition volume length. We present measurements for single and dual detector CT scanners. We used a pencil ionization chamber to measure air kerma. We measured absorbed dose in water with a waterproof ionization chamber set in a semi-customized phantom filled with water. Chambers were set on the rotation axis of the CT scanners. We studied the dose outside the acquisition volume.

RESULTS

We quantified the influence of each parameter on the absorbed dose. We used our measurements to calculate the dose for different acquisition protocols. Also we evaluated the dose to organs distant from the acquisition area.

CONCLUSION

This study is one step toward a systematic estimation of the dose delivered to patient during helical CT exams. To use these results in daily practice, we have to develop software using our measurements.

Targeted disruption of the three Rb-related genes leads to loss of G(1) control and immortalization

The retinoblastoma protein, pRB, and the closely related proteins p107 and p130 are important regulators of the mammalian cell cycle. Biochemical and genetic studies have demonstrated overlapping as well as distinct functions for the three proteins in cell cycle control and mouse development. However, the role of the pRB family as a whole in the regulation of cell proliferation, cell death, or cell differentiation is not known. We generated embryonic stem (ES) cells and other cell types mutant for all three genes. Triple knock-out mouse embryonic fibroblasts (TKO MEFs) had a shorter cell cycle than wild-type, single, or double knock-out control cells. TKO cells were resistant to G(1) arrest following DNA damage, despite retaining functional p53 activity. They were also insensitive to G(1) arrest signals following contact inhibition or serum starvation. Finally, TKO MEFs did not undergo senescence in culture and do possess some characteristics of transformed cells. Our results confirm the essential role of the Rb family in the control of the G(1)/S transition, place the three Rb family members downstream of multiple cell cycle control pathways, and further the link between loss of cell cycle control and tumorigenesis.

NF-kappa B is developmentally regulated during spermatogenesis in mice

To analyze NF-kappa B activity in the testis, we used murine transgenic lines carrying a LacZ reporter gene under the control of a NF-kappa B-responsive promoter (Schmidt-Ullrich et al. [1996] Dev 122:2117-2128). We constructed three independent lines containing the promoter of the gene encoding p105, the precursor of the p50 subunit. This promoter contains three NF-kappa B-binding sites in its proximal part. Our results show that in adult mice, the beta-galactosidase activity which reflects nuclear NF-kappa B activity, is first detected in spermatocytes at the pachytene stage and remains activated in the following steps of germ cell differentiation and maturation. Using transgenic mice carrying a p105nlslacZ construct with the 3 NF-kappa B sites mutated in the p105 promoter, we found a significant reduction in the transgene activity, confirming the important role of NF-kappa B in the activation of the transgene. To confirm the stage of induction during spermatogenesis, we analysed the beta-galactosidase activity in the testes from prepuberal mice in which cells synchrouneously enter meiosis. We detected the transgene activity at 18 days after birth, corresponding to the pachytene stage in spermatocytes. In nuclear extracts prepared from prepuberal mice, we found a peak of NF-kappa B DNA-binding activity made of p50 and p65 subunits at day 18 after birth, which remains high in the later stages. Further analysis showed that I kappa B alpha and beta, but not epsilon are expressed in the testes. Altogether, these data suggest that NF-kappa B factors are stage specifically controlled and may play a role during the development of sperm cells.

Sex hormone-induced carcinogenesis in Rb-deficient prostate tissue

The retinoblastoma (Rb) gene product is a prototypic tumor suppressor. Mice lacking the Rb gene are not viable and die in utero at approximately 13 days of gestation. In this study, we have rescued Rb-/- prostates by grafting pelvic organ rudiments from Rb-/- mouse embryos under the renal capsule of adult male nude mouse hosts. Grafts of embryonic pelvic organs developed into functional prostatic tissue. Some of the prostatic tissue generated was further used to construct chimeric prostatic tissue recombinants by combining wild-type rat urogenital mesenchyme (rUGM) with Rb-/- and Rb+/+ prostatic epithelium (PRE). The tissue recombinants were grown as subcapsular renal grafts and treated from the time of grafting with Silastic capsules containing 25 mg of testosterone plus 2.5 mg of estradiol. During 5-8 weeks of hormone treatment, rUGM+Rb+/+PRE tissue recombinants developed prostatic hyperplasia, whereas PRE in rUGM+Rb-/-PRE tissue recombinants developed hyperplasia, atypical hyperplasia, and carcinoma. During carcinogenesis in rUGM+Rb-/-PRE tissue recombinants, prostatic epithelial cells of the basal lineage disappeared, whereas the luminal cells underwent carcinogenesis. Epithelial E-cadherin almost totally disappeared. In all cases, epithelial PCNA labeling was elevated in tissue recombinants containing Rb-/- versus Rb+/+ epithelium. These epithelial changes were associated with almost total loss of smooth muscle cells in the stroma. In contrast, in untreated hosts rUGM+Rb+/+PRE tissue recombinants developed normally, and rUGM+Rb-/-PRE tissue recombinants developed mild epithelial hyperplasia. The results of this study demonstrate that Rb-/- prostatic tissue can be rescued from embryonic lethal mice and used to test its susceptibility to hormonal carcinogenesis. Deletion of the Rb gene predisposes prostatic epithelium to hyperplasia and increases proliferative activity Susceptibility to hormonal carcinogenesis in response to exogenous testosterone + estradiol is manifested in the progression from atypica hyperplasia to carcinoma. Thus, these findings demonstrate that the absence of the Rb tumor suppressor gene may predispose prostatic epithelial cells to carcinogenesis. Rescue of organs from Rb-/- embryos not only provides an opportunity to analyze the Rb gene pathway in the development and progression of prostate cancer but also provides an opportunity for specifically evaluating the role of the Rb pathway in development and carcinogenesis in other organs, such as the mammary gland and colon. Because rUGM greatly stimulates prostatic epithelial proliferation, the tissue recombinant model is a particularly useful tool for assessing the functional role of other genes in prostatic carcinogenesis through use of the appropriate transgenic or gene knockout mice.

Cell cycle inhibition by the anti-angiogenic agent TNP-470 is mediated by p53 and p21WAF1/CIP1

Angiogenesis has been demonstrated to be essential for tumor growth and metastasis, and inhibition of angiogenesis is emerging as a promising strategy for treating cancer. Among the most potent inhibitors of angiogenesis is the fumagillin family of natural products. An analog of fumagillin, known as TNP-470 or AGM-1470, has been undergoing clinical trials for treating a variety of cancers. TNP-470 has been shown to block endothelial cell cycle progression in the late G(1) phase. Although the direct molecular target for TNP-470 has been identified as the type 2 methionine aminopeptidase (MetAP2), how inhibition of this enzyme leads to cell cycle arrest has remained unclear. We report that treatment of endothelial and other drug-sensitive cell types leads to the activation of the p53 pathway, causing an accumulation of the G(1) cyclin-dependent kinase inhibitor p21(WAF1/CIP1). The requirement of p53 and p21(WAF1/CIP1) for the cell cycle inhibition by TNP-470 is underscored by the observation that cells deficient in p53 and p21(WAF1/CIP1) are resistant to TNP-470. These results shed significant light on the mechanism of cell cycle inhibition by TNP-470 and suggest an alternative method of activating p53 in endothelial cells to halt angiogenesis and tumor progression.

A novel quantitative method for 3D measurement of Parkinsonian tremor

OBJECTIVE

To demonstrate the usefulness of a three dimensional (3D) motion analysis system for the quantitative measurement of tremor in patients with Parkinson's disease (PD).

METHODS

Six PD patients with hand tremors were studied using a system that employed 3D electromagnetic position sensors to measure the actual, cumulative displacement of the tremoring finger. Patients were studied in different hand positions and activating conditions before and 30, 60, 90 and 120 min after intake of Pramipexole, a dopamine agonist known to reduce tremor. Tremor amplitude and frequency, before and after drug intake, were compared using Mann-Whitney U test and Wilcoxon rank test, respectively.

RESULTS

The motion analysis system allowed discrimination of tremor related events from movement artifact and allowed the calculation of real world movement of the finger tremor despite altered hand positions and orientation. Average 3D tremor frequency ranged from 3.71 to 4.34 Hz. Median tremor amplitude (total distance traveled per 5 s interval) decreased with drug from 4.9 to 1.6 cm for resting tremor, 4.5 to 3.7 cm for postural tremor, 3.4 to 3.3 cm for precision tremor, 10.2 to 3.3 cm for tapping activation and 108.6 to 5.7 cm for counting activation.

CONCLUSIONS

Our method of 3D analysis provides a robust, single quantitative measure of tremor amplitude that is intuitive and likely to reflect the functional impact of tremor. This methodology should be useful in comparing tremor across patients and in measuring the efficacy of therapeutic interventions.

Widespread alterations of alpha-synuclein in multiple system atrophy

Glial cytoplasmic inclusions (GCI) are the hallmark of multiple system atrophy (MSA), a rare movement disorder frequently associated with autonomic dysfunction. In this study of 21 cases of MSA, GCI were consistently immunoreactive for alpha-synuclein and double-immunostained for ubiquitin and oligodendroglial markers, but not glial fibrillary acidic protein. No statistically significant difference was found in the density of GCI in various brain regions in the two forms of MSA, striatonigral degeneration (SND) and olivopontocerebellar atrophy (OPCA). Postmortem brain samples from 9 cases of MSA were fractionated according to solubility in buffer, Triton-X 100, sodium dodecyl sulfate (SDS), and formic acid, and alpha-synuclein immunoreactivity was measured in Western blots. Total alpha-synuclein immunoreactivity was increased in MSA compared to controls, with no statistically significant difference between SND and OPCA. Most of the increase was due to alpha-synuclein in SDS fractions. In controls this fraction had little or no immunoreactivity. In 7 cases and 4 controls correlations were investigated between quantitative neuropathology and biochemical properties of alpha-synuclein. Surprisingly, the amount of SDS-soluble alpha-synuclein correlated poorly with the number of GCI in adjacent sections. Furthermore, areas with few or no GCI unexpectedly had abundant SDS-soluble alpha-synuclein. These findings provide evidence that modifications of alpha-synuclein in MSA may be more widespread than obvious histopathology. Moreover, these alterations may constitute a biochemical signature for the synucleinopathies.

Genomic structure and chromosomal localization of the mouse Hsf2 gene and promoter sequences

The mouse heat shock factor 2 (HSF2) cDNA was previously cloned by homology to HSF1, the heat shock factor involved in the cellular response to stress [Sarge, K.D., Zimarino, V., Holm, K., Wu, C., Morimoto, R.I., Cloning and characterization of two mouse heat shock factors with distinct inducible and constitutive DNA-binding ability. Genes Dev. 5 (1991) 1902-1911]. HSF2 is active in restricted cell types during pre- and post-implantation stages of development, and only in male germ cells of adult mice. However, the function of this factor remains elusive. We report here the cloning of the mouse Hsf2 gene and its genomic structure. We show that the gene is composed of 13 exons of variable sizes spanning at least 43kb in the genome. The transcription start site has been determined, and upstream sequences with promoter activity have been identified by their ability to direct the expression of a luciferase reporter gene in transfected cells. A preliminary analysis of the proximal promoter sequence determined that the TATA box is absent, but that a GC-rich region with several potential binding sites for transcription factors is present. The gene has been mapped to mouse chromosome 10 by in-situ hybridization on metaphase chromosomes.

Temporal and spatial control of the Sycp1 gene transcription in the mouse meiosis: regulatory elements active in the male are not sufficient for expression in the female gonad

Transcription controls active at the initial stages of meiosis are clearly key elements in the regulation of germinal differentiation. Transcription of the Sycp1 gene (synaptonemal complex protein 1) starts as early as the leptotene and zygotene stages. Constructs with Sycp1 5' upstream sequences directed the expression of reporter genes to pachytene spermatocytes in transgenic mice. A short fragment encompassing the transcription start (n.t. -54 to +102) was sufficient for stage-specific expression in the adult male and for temporal regulation during development. Upstream enhancer element(s) quantitatively regulating expression were localized in the region between -54 and -260. The gene is normally expressed both in the male and female gonads, but none of the promoter sequences active in the testis allowed the expression of reporter genes during meiosis in the ovary.

Stage-specific expression of the Kit receptor and its ligand (KL) during male gametogenesis in the mouse: a Kit-KL interaction critical for meiosis

The Kit receptor and its ligand KL, which together constitute an essential effector at various stages of embryonic development, are both present during adult gametogenesis. In the testis, KL is expressed in Sertoli cells, and Kit in germ cells, starting at the premeiotic stages. A series of observations indicated previously a role in spermatogonia survival, without excluding a possible function at later stages. We identified a complex pattern of expression of the two components in the adult murine testis, suggestive of a role in the meiotic progression of spermatocytes. At stages VII-VIII of the cycle of the seminiferous epithelium, the time when spermatocytes enter meiosis, the membrane-associated form of KL extends on the Sertoli cell from the peripheral to the adluminal compartment of the tubule. We also found that the receptor is present on the surface of germ cells up to the pachytene stage. The availability of differentiated Sertoli cell lines, which express the KL protein and support part of the maturation of germ cells in coculture, allowed us to ask whether, in the in vitro reconstructed system, transit of spermatocytes through meiosis requires the Kit-KL interaction. Addition of a blocking monoclonal antibody against the Kit receptor (ACK2) inhibited extensively the appearance of haploid cells and the expression of a haploid-phase-specific gene (Prm1). Recognition of the supporting Sertoli cell by germ cells was not affected, indicating a requirement for the activity of the receptor for either entering or completing meiosis. Involvement of the membrane-associated form of the ligand was suggested by the observation that addition of the soluble form of KL was equally inhibitory.

Cre expression in primary spermatocytes: a tool for genetic engineering of the germ line

Transgenic mice were generated expressing a testicular Cre recombinase driven by promoter sequences derived from the gene encoding Synaptonemal Complex Protein 1 (Sycp1), expressed at an early stage of the male meiosis (leptotene to zygotene). Recombination at target LoxP sites was examined during germinal differentiation in mice harboring Sycp1-Cre and a second transgene where LoxP sites flank either the beta geo coding region, the Pgk1 promoter, or a tk-neo cassette inserted into the Rxr alpha locus. The LoxP-flanked transgenes were stably maintained in the somatic tissues of the double transgenic animals, as well as in the progeny of the females. Mice born after mating the double-transgenic males with normal females showed extensive deletions of the LoxP-flanked sequences. When the males were hemizygous for the Sycp1-Cre transgene, the deletions were observed even in the fraction of the offspring which had not inherited the Cre gene, thus demonstrating that expression occurred in the male parent during spermatogenesis. The high efficiency of excision at the LoxP sites makes the Sycp1-Cre transgenic males suitable for evaluating the role of defined gene functions in the germinal differentiation process.

Germ cell-specific enhancer activity of a repeated element in a variable region of the mouse genome

We recently described a complex genetic structure on mouse chromosome 8, a region of the murine genome in which genetic rearrangements frequently occur. A large repeated element specific to this chromosome was found to overlap with one of the cadherin genes (Cad11). An additional degree of complexity became apparent with the identification, in a subset of laboratory strains of mice, of a retrogene integrated into one of the repeated units. Designated Sycp1-ps2, it originated from the early meiotic gene encoding Synaptonemal Complex Protein 1. We now report that, among wild Mus species in which the retrogene is not present, this region of Chr 8 shows a high degree of variability. Sequence analysis showed that integration of Sycp1-ps2 created a 5' transcription initiator element. Transcription of the pseudogene in the testis was directly demonstrated. A germ cell-specific enhancer activity was localized within a 1117 bp region of the repeat, which was sufficient to direct the expression of reporter genes in transgenic mice to late meiotic and post-meiotic spermatogenic cells.

A simple inexpensive device for monitoring patient respiration

A simple device is described that monitors respiration by sounding an alarm if respiration ceases. It is light and portable and performs well, even in a 60 dB noise environment.

The Sycp1 loci of the mouse genome: successive retropositions of a meiotic gene during the recent evolution of the genus

The murine Sycp1 gene is expressed at the early stages of meiosis. We show that it is composed of a number of small exons and localized on mouse chromosome 3. In the laboratory strains, two retrogenes were also identified. The first one (Sycp1-ps1), on chromosome 7, has accumulated point mutations and deletions and is not transcribed. A second retrogene (Sycp1-ps2), on chromosome 8, is inserted within the continuity of a moderately repeated element, in an intron of another gene (Cad11). The two retroposition events can be dated to distinct periods in the evolution of the Muridae. Sycp1-ps2 has kept features indicative of a relatively recent origin, namely a nearly intact coding region, a poly(A) tail, and 14-bp terminal repeats. Its recent origin was confirmed by the fact that it is found in all the laboratory strains of mice, but neither in a recent isolate from Mus musculus domesticus wild stocks nor in the closely related subspecies M. musculus musculus, M. m. molossinus, M. m. castaneus, and M. m. bactrianus. Appearance of the more ancient Sycp1-ps1 retrogene is concomitant with the radiation of the genus. It is present in various Mus species (M. spretus, M. spicilegus, M. macedonicus, and M. cookii), but neither in the rat nor in the more closely related Pyromis genus. Transposition of retrotranscripts during meiosis and their hereditary establishment thus appear to occur relatively frequently. They may, therefore, play a significant role in the evolutionary process.

Stage-specific signals in germ line differentiation: control of Sertoli cell phagocytic activity by spermatogenic cells

Differentiation of male germ cells requires a continuous cross-talk with their somatic support, the Sertoli cell. An in vitro model of Sertoli cells was recently provided by established cell lines which maintain Sertoli-specific characteristics, among which is a regulated phagocytic capacity. In vivo, Sertoli cells take up the residual cytoplasm expelled from the maturing sperm, a process restricted to a limited period of germinal maturation, and they also eliminate abnormally differentiated germ cells in case of hormonal deficiency. Cells of the Sertoli line efficiently take up latex beads, as well as dead cells in the cultures. A semiquantitative assay of phagocytosis was developed, based on the uptake of fluorescent latex beads. 15P-1 cultures were found to contain a minor fraction of active phagocytes. After addition of a defined fraction of germ cells, however, all the cells internalized beads as efficiently as macrophages. The inducing cell was identified as the pachytene spermatocyte, a cell type which, in vivo, is associated with Sertoli cells when they express their phagocytic potential. These inducing meiotic cells were not internalized themselves. Rather, they interacted with Sertoli cells via a surface signal that was resistant to formaldehyde fixation. The whole induction process does not involve changes in Sertoli gene expression, since it occurs even in the presence of high doses of cycloheximide. After the required initial contact, further maintenance of the activity was dependent on factor(s) secreted in the medium of the activated culture. Phagocytosis was, on the other hand, abrogated in the presence of factor(s) secreted by a distinct fraction of germ cells, enriched in the late stages (second division) of meiosis.

Self-image and people with learning disabilities

Self-image arises from a complex interaction of intrinsic and extrinsic factors. This article explores the importance of people with a learning disability attaining a positive self-image. It discusses the effect of society's perception of people with learning disabilities, and questions the willingness of the community to accept such people in a non-judgmental way. It argues that staff caring for this client group have a vital role to play in how people with learning disabilities are perceived by others and discusses the effects that a market philosophy (Fromm, 1978) and the popular media have on society regarding people with learning disabilities. Self-worth is important to everyone; however, the article concludes that a person with a learning disability is seriously disadvantaged in this respect. This aspect of care therefore requires insight, support and skills on the part of those healthcare professionals caring for this client group.

Complete sequencing of the murine USF gene and comparison of its genomic organization to that of mFIP/USF2

USF is a transcription factor able to stimulate promoter activity upon binding to an upstream sequence identical to that recognized by the protooncogene Myc. However, despite extensive biochemical characterization, nothing is known concerning its physiological function. A USF-related protein able to interact with Fos and known as FIP/USF2 has been reported. Its genomic structure in mouse has been recently characterized. We present here the cloning and characterization of the murine USF gene. It consists of 10 exons, the first of which is noncoding, and the gene spans 8 kb of DNA. We show that the murine USF protein is almost identical to its human counterpart, but that an intron not conserved between human and murine USF genes curiously has been conserved between human USF and murine FIP/USF2. Otherwise, the splicing pattern of murine USF and FIP/USF2 is exactly conserved. We also demonstrate that the murine USF promoter is located more than 2.5 kb upstream of the first coding ATG, in a region displaying divergent promoter activity. Finally, we show that an Mx1-related sequence is present less than 3 kb downstream of the murine USF gene, in a tail-to-tail position. Taken together, these data indicate that the murine USF gene is very similar to the murine FIP/USF2 gene and is potentially bracketed by two other transcription units on the other DNA strand.

An electrical impedance tomography microscope

A circular array of 16 electrodes has been constructed for use as an electrical impedance tomography (EIT) microscope. The electrodes were made from 60 microns diameter gold wires anchored to a printed circuit board. The internal diameter of the array was 0.9 mm giving a theoretical spatial resolution of about 100 microns. For EIT imaging, the array was connected to an imaging system operating at 82 kHz. Static images of conducting and insulating filaments (cooper wire and human hair) in saline solution were obtained as well as dynamic imaging sequences of glass microspheres migrating through the array. The interelectrode impedance was typically 5 k omega and the transimpedances ranged from 14 to 210 omega.

cDNA sequence of the murine synaptonemal complex protein 1 (SCP1)

We isolated and sequenced cDNAs for the murine synaptonemal complex protein 1 (SCP1). The whole cDNA sequence displays respectively 93% and 90% identity with the previously reported rat and hamster cDNAs. We show, however, that the encoded amino acid sequence extends for an additional stretch of 51 residues at its amino-terminal end.

Peri- and postoperative magnetic resonance imaging localization of pallidotomy

Postoperative magnetic resonance imaging (MRI) of basal ganglia functional lesions illustrates the accuracy of preoperative target localization. The technique of perioperative MRI and CT localization for pallidotomy will be discussed and correlated with the center of the lesion on postoperative standard MRI as well as three-dimensional (3-D) volume acquisition of image. Using a 1.5-tesla Signa system, a conventional acquisition of 128-slice, 256 x 256 matrix spoiled grass (SPGR) images were used for 3-D reformation. This allowed approximately 1 x 1 x 2 mm resolution over a 24-cm field of view in a T-1-weighted image. The display affords a volumetric analysis of the anatomic location and relation of the post-ventral pallidotomy to adjacent structures. Accuracy lesion placement based on perioperative MR coordinates and revealed on postoperative images is confirmed. The volume of the lesion as well as its location are factors that affect clinical outcome.

Transmeiotic differentiation of male germ cells in culture

A cell culture system that supports the differentiation of male germ cells through meiosis is described. It takes advantage of the properties of a cell line, 15P-1, established from testicular cells of transgenic mice that express the large T protein of polyoma virus in the seminiferous epithelium. This line exhibits features characteristics of Sertoli cells, including transcription of the Wilms' tumor (WT1) and Steel genes. Cells of the 15P-1 type support the meiotic and postmeiotic differentiation in cocultures of diploid premeiotic germ cells into haploid spermatids expressing the protamine (Prm-1) gene. When cocultured with 15P-1 cells, testicular cells explanted from immature 9-day-old animals, before the onset of the first meiosis, generated tetrads of haploid cells with the morphology of round spermatids and initiated protamine transcription.

Mood changes and "on-off" phenomena in Parkinson's disease

Ten patients with idiopathic Parkinson's disease and motor fluctuations were rated for mood changes during discrete "off," "on," and "on with dyskinesia" periods. The Profile of Mood States and visual analogue scales were used. Significant changes in mood and anxiety were found to parallel changes in motor fluctuations. One patient rated his moods as consistently improving from the "off" state to the "on" state and finally to the "on with dyskinesia" state, a finding that is consistent with concomitant central dopaminergic changes. All other patients showed moods that improved significantly from the "off" state to the "on" state but then worsened significantly in the "on with dyskinesia" state, a finding that is consistent with the fact that patients feel worse when impaired by dyskinesias. It is suggested that these results argue for multiple etiologies of depression in Parkinson's disease. The literature on dopamine and depression in Parkinson's disease is briefly reviewed and the opportunity provided by "on-off" phenomena to study the effect of dopamine on mood changes is discussed.

Low leukocyte glutamate dehydrogenase activity does not correlate with a particular type of multiple system atrophy

Leucocyte glutamate dehydrogenase (GDH) activity was measured in 26 normal control subjects, 20 patients with multiple system atrophy presenting features of either olivopontocerebellar atrophy or striatonigral degeneration and in a heterogenous group of 15 patients with spinocerebellar degenerations. A broad range of GDH activity was found in all three groups. Low activity failed to correlate with a specific clinical entity. Patients followed to post-mortem examination to date have demonstrated histological features of at least three distinct morbid entities. It is concluded, contrary to earlier reports including the authors', that low leukocyte GDH activity does not identify a particular type of multiple system atrophy.