Dihydropyrimidine dehydrogenase deficiency presenting at birth.

Dihydropyrimidine dehydrogenase (DPD) deficiency (McKusick 274270) is a clinically heterogeneous autosomal recessive disorder of pyrimidine metabolism. DPD is the enzyme that catalyses the first and the rate-limiting step in the catabolism of uracil, thymine and the analogue 5-fluorouracil. To date, more than 30 patients have been diagnosed with a complete enzyme deficiency. Here, we describe the fifth case with a complete DPD deficiency presenting at birth with severe neurological abnormalities. The patient was homozygous for the common splice-site mutation IVS14+1G > A.

Sociodemographic factors and primary headache syndromes in a Saudi community.

BACKGROUND AND PURPOSE: There is increasing evidence that the pathophysiologic mechanisms are different between migraine and tension-type headache. The aim of the study was to determine possible sociodemographic differences in Saudi Arabia subjects with headache. METHODOLOGY: A community-based door-to-door survey with identification of headache cases based on IHS criteria. A comparison of sociodemographic variables was made between subjects with migraine and tension-type headache. RESULTS: Headache prevalence was 8% (95% CI = 7.3-8.7%) with a preponderance of tension-type headache (39%). Females were more often affected than males (ratio 2:1). Migraine subjects were more often in the professional occupational group compared with tension-type headache (p < 0.05). CONCLUSION: Headache prevalence in the community was low. Subjects with migraine and tension-type headache were similar with respect to many demographic variables. Occupational association needs verification in further studies.

The human immunodeficiency virus type 1 Vpu protein: a potential regulator of proteolysis and protein transport in the mammalian secretory pathway.

HIV-1 Vpu is a small transmembrane phosphoprotein of 16 kDa which performs critical roles in CD4 proteolysis and virus release. Previous studies have demonstrated that Vpu-induced degradation of CD4 occurs in the endoplasmic reticulum (ER), and that the proteolytic process is sequence specific requiring both the transmembrane and cytoplasmic domains of CD4. In the present study, we investigated the effects of Vpu expression on the intracellular membrane trafficking pathway of mammalian cells. In singly transfected cells, the HIV envelope glycoproteins and vesicular stomatitis virus glycoprotein (VSV G) were properly transported to the cell surface undergoing oligosaccharide modifications characteristic of their movement through the Golgi complex. In contrast, the cell surface delivery of glycoproteins was severely impeded in cells expressing Vpu. Biochemical analyses revealed that Vpu expression blocked the transfer of proteins from the ER-Golgi complex to the plasma membrane in a dose- and protein-dependent manner. Soluble gp120 exhibited extreme transport defects in the presence of Vpu, whereas transmembrane proteins (e.g., gp160, VSV) responded only moderately to wild-type Vpu. To gain insight into Vpu-mediated transport inhibition, we performed mutational analysis of the CK-2 phosphorylation sites (serines at 52 and 56) in the Vpu protein. CK-2 phosphorylation of Vpu has been shown to regulate the activity of the protein in reactions that involve the proteolysis of CD4 in the ER. We demonstrate here that the phosphorylation mutant is defective in both sequence-specific degradation of VRE-containing substrates and the transport inhibition of gp120 and VSV-G in the secretory pathway. Thus, these experiments have revealed that Vpu-mediated proteolysis and transport inhibition are mechanistically coupled requiring the same structural elements of the Vpu protein in both processes. We propose that the primary effect of Vpu expression is to impede the secretion process and then access glycoproteins bearing the VRE for Vpu-mediated proteolysis in the ER of mammalian cells.

Vpu-mediated proteolysis of gp160/CD4 chimeric envelope glycoproteins in the endoplasmic reticulum: requirement of both the anchor and cytoplasmic domains of CD4.

The Vpu protein of HIV-1 induces degradation of CD4 in the endoplasmic reticulum. Previous studies have elucidated the role of the CD4 cytoplasmic domain in the Vpu-induced degradation process, and the minimal Vpu responsive element mapped to a small region in the CD4 tail. In the present study, we have carried out both biochemical and biological experiments to analyze the role of the CD4 anchor domain in the Vpu-induced degradation process. We generated chimeric proteins that possessed the ecto-anchor domains of gp160 and the cytoplasmic domain of CD4. The chimeric envelope glycoproteins were functionally active in the fusion of HeLa CD4+ cells, with the exception of those having the arginine to isoleucine (R to I) substitution in the gp160 anchor domain. Coexpression studies revealed that these chimeric glycoproteins were stable and functionally active in the presence of Vpu, as opposed to those having the anchor-cytoplasmic domains of CD4. The half-life of Vpu-sensitive chimeric glycoproteins was calculated to be approximately 60-90 min, whereas Vpu-resistant envelope glycoproteins exhibited relatively longer half-lives in the presence of Vpu. Taken together, these studies strongly suggest that the CD4 anchor domain appears to provide critical sequence or structural elements through which the Vpu protein could access CD4 or glycoproteins bearing the Vpu responsive element for degradation in the endoplasmic reticulum.

Subtentorial diverticulum of the third ventricle associated with a mural cavernous angioma in a child.

The authors describe a case of a large subtentorial supracollicular diverticulum of the third ventricle associated with a cavernous angioma in its wall in a 6-year-old girl who presented with developmental delay and obstructive hydrocephalus. This is the first case in which such association has been diagnosed and successfully treated. The literature is reviewed, and the possible relationship between these two rare lesions is discussed.

Mutations in two specific residues of testicular angiotensin-converting enzyme change its catalytic properties.

Chemical modifications of 2 specific residues present in angiotensin-converting enzyme (ACE) result in its inactivation, thereby suggesting that these 2 residues may be important for its enzyme activity. We directly tested this hypothesis by substituting Tyr-236 with Phe and Lys-154 with Glu in rabbit testicular ACE (ACET) using site-directed mutagenesis of the corresponding cDNA. Wild type ACET, the two single mutants, and the double mutant were expressed in HeLa cells using the vaccinia virus-T7 polymerase expression system. The rate of synthesis, post-translational modifications, and cleavage secretion pattern of all four proteins were indistinguishable. The enzymatic properties of the two single mutants and the wild type enzyme were also very similar. In contrast, the double mutant had about a 20-fold lower specific activity although its Km was only 6-fold higher than that of the wild type protein. The double mutant also had a 100-fold higher Ki for lisinopril, a competitive inhibitor of ACET, and was 17-fold less sensitive to stimulation by NaCl, an activator of ACET. These results directly demonstrate that Tyr-236 and Lys-154 are indeed critical for the catalytic activity, lisinopril inhibition, and NaCl activation of ACET.

Spinal tumors: Experience at King Khalid University Hospital.

This paper summarizes data on 30 consecutive spinal tumors treated at King Khalid University Hospital (KKUH) between 1984-1991. The male:female ratio was 2.75:1. Thirty percent of cases were less than 20 years of age while 71% were more than 60 years of age. The brain to spinal cord tumor ratio in our unit was 12.3:1. The ratio of Schwannoma to meningioma was 1.6:1. Metastatic carcinoma accounted for a mere 13% of cases and only 35% of tumors were located in the thoracic spine. Intramedullary tumors accounted for 17% of cases. An overall 63% of cases improved postoperatively while 37% remained unchanged.

Compliance in Saudi epileptic patients: Determinants of compliance in Saudi epileptic patients.

A one year prospective study was conducted (July 1990 to June 1991) on 104 Saudi epileptic patients (aged 15 to 45 years) to assess the degree of anti-epileptic drug (AED) compliance and factors that influence their compliance. One-third of the patients (30.8%) were non-compliant (NC), A logistic regression equation compared the data indicated. A low level of education and adverse effect of the disease on patients were the most important significant factors for poor compliance. Age, sex, marital status, family history, duration and type of seizure were not found to have a significant role in the patients' compliance to AED.

Signal processing, glycosylation, and secretion of mutant hemagglutinins of a human influenza virus by Saccharomyces cerevisiae.

We investigated the nature of signal recognition, transport, and secretion of mutant hemagglutinins (HAs) of a human influenza virus by the yeast Saccharomyces cerevisiae. The cDNA sequences encoding variant forms of influenza HA were expressed in S. cerevisiae. The HA polypeptides (HA500 and HA325) that were synthesized with their N-terminal signal peptides were correctly targeted to the membrane compartment where they were glycosylated. In contrast, the HA polypeptides (HA484 and HA308) lacking the signal peptide were expressed in the cytoplasm and did not undergo any glycosidic modification, demonstrating the importance of the heterologous signal sequence in the early steps of translocation in S. cerevisiae. The analysis of the N-terminal amino acid sequence of HA500 and HA325 polypeptides demonstrated the correct cleavage of the signal peptide, indicating the structural compatibility of a heterologous signal peptide for efficient recognition and processing by the yeast translocation machinery. The membrane-sequestered and glycosylated HA polypeptides were relatively stable in S. cerevisiae compared with the signal-minus, nonglycosylated HA molecules. Although both the anchor-minus HA (HA500) and HA1 (HA325) polypeptides were targeted efficiently to the membrane, their glycosylation and transport patterns were shown to be different. During pulse-chase, the HA500 remained cell-associated with no detectable secretion into the extracellular medium, whereas the HA325 secreted into the medium. Furthermore, only the cell-associated and secreted forms of HA325 and not HA500 appeared to have undergone hyperglycosylation with the extensive addition of high-molecular-weight outer-chain mannans. Possible reasons for the observed phenotypic behavior of these two mutant HAs are discussed.