Adenine nucleotide metabolism in hearts of diabetic rats. Comparison to diaphragm, liver, and kidney.

High-performance liquid chromatography analysis of acid-extracted tissues revealed decreases of high-energy nucleotides and increases in low-energy nucleotides and metabolites in heart, diaphragm, and liver but not in kidneys of diabetic rats. In comparison with nondiabetic rats, the total adenine nucleotide content of diabetic rat heart and diaphragm but not liver decreased, indicating an increase in catabolism of AMP. Maximal initial rates of the AMP catabolic enzymes 5'-nucleotidase, adenosine deaminase, and AMP deaminase were elevated in the hearts of BB/Wistar and streptozocin-induced diabetic rats. Nucleotide salvage enzymes adenylosuccinate synthetase and adenylosuccinate lyase were elevated above normal in the diabetic heart, whereas hypoxanthine-guanine phosphoribosyl transferase was not altered. Cytosolic-to-mitochondrial ratios from maximal initial rates after correction for mitochondrial breakage were increased above controls in diabetic hearts for nucleoside diphosphokinase and aspartate aminotransferase. Nucleotide levels, degradation rates, and substrate compartmentation between cytosol and mitochondria are discussed in relation to concurrent diabetes.

Macaque dendritic cells infected with SIV-recombinant canarypox ex vivo induce SIV-specific immune responses in vivo.

Dendritic cells (DCs) infected with recombinant avipox vectors express the introduced genes and activate antigen-specific T cells. DCs exhibit distinct differentiation-dependent immune functions. Moreover, immature DCs are readily infected by canarypox vectors, but undergo tumor necrosis factor (TNF)-alpha-dependent death, while fewer mature DCs get infected and resist dying. A pilot study was performed using the rhesus macaque system to explore whether immature and mature DCs infected with SIV-recombinant canarypox (vCP180) ex vivo could induce primary virus-specific immune responses in vivo. After subcutaneous (sc) reinjection, functional monocyte-derived DCs migrated to lymph nodes (LNs) within 1-2 days and primed T cells in vivo. This was observed by monitoring dye-labeled DCs in the draining LNs and tetanus toxoid (TT)-specific T cell responses after injection of TT-loaded DCs. DCs from simian immunodeficiency virus (SIV)-naïve rhesus macaques were infected with vCP180 (SIVmac142 gag, pol, and env genes), and sc reinjected into donor animals. Low-level SIV-specific T cell proliferation, but little if any interferon (IFN)-gamma production was detected. DCs pulsed with vCP180 in combination with TT and keyhole limpet hemocyanin (KLH) (to activate additional T cells and provide "helper" cytokines) induced SIV-, TT-, and KLH-specific T cell responses, including IFN-gamma responses not seen when vCP180-carrying DCs were used alone. Interleukin (IL)-10 and low-level antibody responses were also observed. This pilot study provides the proof of principle that sc injected ex vivo SIV-recombinant canarypox-infected DCs safely induce low-level SIV-specific immune responses in vivo.

Medical practice and informatics tools: a vignette.

In this article the authors recreate an improvisational vignette originally presented at the Third Annual Information Connection in Burlington, Vermont, in January 1998. The vignette illustrates various state-of-the-art decision-support systems for clinical care and their promises and problems in real-world medical practice. The characters are Dr. Alex Grant, a rural physician in solo practice; Anna Everett, a patient suffering from chronic headaches; Bob, a hospital librarian; and Sarah, Dr. Grant's nurse. The short play centers on Dr. Grant's attempt to diagnose the cause of Anna's headaches (which he and she believe to be sinus-related) and the roles information technologies--Medline searching, Anna's own Internet searches, the use of MDConsult, which provides Internet access to standard medical texts, journals, etc., and a desktop decision-support tool called Problem Knowledge Couplers--play in this process. The vignette concludes with the realization that while computer technologies can be of great help in medicine "there is still a need for a good doctor to pull it all together."

Microepithelial cysts observed in extended contact-lens wearing subjects.

After 18 weeks of a controlled comparative study of extended contact lens wear a male subject presented with ocular symptoms. Microepithelial cysts were observed in both eyes and, after examination, in the eyes of 44 other participating patients. The cysts have been photographed and the rate of recovery monitored.

Adolescent substance abuse: the challenge for clinicians.

Substance abusing adolescents represent a unique population of patients within substance abusing communities. The interrelationship between the characteristics of problem substance use and the developmental tasks of adolescence is considerable and often presents the clinician with a diagnostic and treatment challenge. The identification, evaluation, treatment, and prevention of substance abuse among teens requires extensive knowledge of substance abuse as well as knowledge of the typical developmental tasks of adolescence.

Randomized, placebo controlled, double blind trial evaluating early pregnancy phytonutrient supplementation in the prevention of preeclampsia.

OBJECTIVE: Daily provision of pregnant patients with dietary supplements containing antioxidants and phytonutrients, if initiated in the first trimester of pregnancy and continued throughout the gestation, may significantly decrease the incidence of preeclampsia. STUDY DESIGN: We conducted a single center, randomized, placebo-controlled investigation in which women were randomized by their risk status and assigned to daily ingestion of a supplement consisting primarily of a blended fruit and vegetable juice powder concentrate or placebo. RESULT: Of the 684 patients randomized to the trial, 267 (39.0%) completed it. The final analysis is based on those participants who completed the study. For the primary outcome of preeclampsia, there was no difference observed between the phytonutrient supplement group and the placebo group: 15.9% vs 16.3%, respectively, (R.R. 0.97 (0.56-1.69)). Non-significant trends toward lower placenta-related obstetrical complications were observed in the supplement group compared with the placebo cohort (8.3% vs 15.5%, respectively, (R.R. 0.57 (0.29-1.14). Those infants born to mothers taking the supplement in the high-risk stratified group demonstrated non-significant trends toward lower rates of respiratory distress syndrome (RDS); 5.3% in the supplement group vs 15.4% in the placebo group: R.R. 0.34 (0.12-1.01). CONCLUSION: Initiation of antioxidant/phytonutrient supplementation in the first trimester did not decrease rates of preeclampsia. Non-significant trends toward lower incidences of placental derived morbidity in those mothers taking the supplement in addition to decreased rates of RDS in infants born to supplemented mothers considered to be high-risk for preeclampsia, warrant further investigation.

Distinct roles for RDE-1 and RDE-4 during RNA interference in Caenorhabditis elegans.

RNA interference (RNAi) is a cellular defense mechanism that uses double-stranded RNA (dsRNA) as a sequence-specific trigger to guide the degradation of homologous single-stranded RNAs. RNAi is a multistep process involving several proteins and at least one type of RNA intermediate, a population of small 21-25 nt RNAs (called siRNAs) that are initially derived from cleavage of the dsRNA trigger. Genetic screens in Caenorhabditis elegans have identified numerous mutations that cause partial or complete loss of RNAi. In this work, we analyzed cleavage of injected dsRNA to produce the initial siRNA population in animals mutant for rde-1 and rde-4, two genes that are essential for RNAi but that are not required for organismal viability or fertility. Our results suggest distinct roles for RDE-1 and RDE-4 in the interference process. Although null mutants lacking rde-1 show no phenotypic response to dsRNA, the amount of siRNAs generated from an injected dsRNA trigger was comparable to that of wild-type. By contrast, mutations in rde-4 substantially reduced the population of siRNAs derived from an injected dsRNA trigger. Injection of chemically synthesized 24- or 25-nt siRNAs could circumvent RNAi resistance in rde-4 mutants, whereas no bypass was observed in rde-1 mutants. These results support a model in which RDE-4 is involved before or during production of siRNAs, whereas RDE-1 acts after the siRNAs have been formed.

Special report on labor and employment. The Department of Labor issues final regulations for the federal Family and Medical Leave Act.

The FMLA is a complicated and comprehensive regulatory scheme, and it is impossible to review any but the most basic provisions in this article. The final regulations provide very detailed guidance on such issues as benefits continuation, reinstatement rights, notice requirements, and enforcement measures. Personnel policies and practices must be revised to be consistent with these final regulations, and care must be taken that leave policies do not restrict rights under the FMLA or unintentionally create expanded leave rights. In complying with the FMLA, employers must also keep in mind that there are complex interplays between the federal FMLA, state laws that provide family and medical leave, the Americans with Disabilities Act, and state workers' compensation laws, that can require expert advice depending on the particular circumstances.

Corneal epithelial oxygen uptake rate in diabetes mellitus.

Corneal epithelial oxygen uptake rate (CEOUR) has been measured using a non-invasive polarographic electrode technique in patients with diabetes mellitus (DM), all with varying degrees of retinopathy. CEOUR was found to be significantly reduced in diabetic patients when compared to age-matched non-diabetic controls--Type I diabetics p less than 0.001; Type 2 diabetics p less than 0.01. Known duration of DM and assay of instantaneous, medium and long term glycaemic control showed no significant correlation with CEOUR in the patients studied. These results give further evidence of abnormal corneal metabolism in DM. Reduced CEOUR may be a contributory factor in the pathogenesis of diabetic corneal epitheliopathy.

Ribosomal protein gene expression is cell type specific during development in Dictyostelium discoideum.

Starvation for amino acids initiates the developmental cycle in the cellular slime mold, Dictyostelium discoideum. Upon starvation one of the earliest developmental events is the selective loss of the ribosomal protein mRNAs from polysomes. This loss depends upon sequences in the 5' non-translated leader of the ribosomal protein (r-protein) mRNAs. Here evidence is presented which indicates that those cells which will become prestalk cells express the ribosomal protein genes during development under starvation conditions. Cells which enter the prespore pathway shut off r-protein synthesis. The promoter and 5' non-translated leader sequences from two ribosomal protein genes, the rp-L11 and the rp-S9 genes, are fused to the Escherichia coli beta-galactosidase reporter gene. While beta-galactosidase enzyme activity is detected in situ in most growing cells, by 15 h of development beta-galactosidase enzyme activity is largely lost from the prespore cells although strong beta-galactosidase enzyme activity is present in the prestalk cells. These observations suggest the possibility that the ribosomal protein mRNAs are excluded from polysomes in a cell-type-specific manner.

Demonstration of the adenosine reservoirs with nitrobenzylthioinosine in liver and diaphragm by high-performance liquid chromatography.

Purine nucleotides, nucleosides, nucleobases, dinucleotides and nucleosides derivatives from acid-extracted rat liver and diaphragm were separated and quantitated by reversed-phase ion-pair high-performance liquid chromatography with a mobile phase composed of 90 mM potassium phosphate, 15 mM tetrabutylammonium hydroxide and a 1-30% methanol gradient. During 5 min of ischemia, adenine and guanine nucleotides decreased along with significant declines in NAD and increases in adenosine, inosine, hypoxanthine, xanthine, NADP and adenylosuccinate. Nitrobenzylthioinosine by gavage (5 mg/kg per day for five days) increased adenosine levels but without any alteration in nucleobase levels. Adenosine was shuttled to every available intracellular reservoir which included in declining order of magnitude GDP greater than adenosylhomocysteine greater than adenosine greater than ADP greater than AMP greater than IMP = XMP = GMP.

Association-dissociation studies of bovine and rat liver glutamic dehydrogenase by high-performance liquid chromatography gel filtration.

The concentration-dependent association-dissociation tendency of purified bovine liver and rat liver glutamic dehydrogenase (GDH) has been demonstrated by high-performance liquid chromatographic gel filtration. In the concentration range of 100 to 1.0 micrograms bovine GDH/ml molecular species ranged from dimer and unimer to subunimeric forms. The dissociation process of the unimeric hexapeptide, consisting of six polypeptide chains, to the subunimeric tripeptide, consisting of three polypeptide chains, was irreversible without added ionic support, but reversible with added ionic support. In dilute Tris-HCl bovine liver GDH was dispersed to subunimeric sizes. Increasing the ionic strength in 20 mM phosphate as the mobile phase increased dissociation to a subunimeric tripeptide while sustaining as much as 80% of its activity. Activity of a eluting subunimer was verified by the inclusion of reaction substrates (NAD and glutamute) in the mobile phase and quantification of reaction products (NADH) in chromatograms. Gel filtration of GDH in the presence of GTP with NADH rendered a subunimeric tripeptide, largely independent of ionic strength or GDH concentration. Rat liver GDH, differing from bovine liver GDH, was dissociated by gel filtration to an active tripeptide independent of ionic or buffer conditions.

Specific inhibition of gene expression by small double-stranded RNAs in invertebrate and vertebrate systems.

Short interfering RNAs (siRNAs) are double-stranded RNAs of approximately 21-25 nucleotides that have been shown to function as key intermediaries in triggering sequence-specific RNA degradation during posttranscriptional gene silencing in plants and RNA interference in invertebrates. siRNAs have a characteristic structure, with 5'-phosphate/3'-hydroxyl ends and a 2-base 3' overhang on each strand of the duplex. In this study, we present data that synthetic siRNAs can induce gene-specific inhibition of expression in Caenorhabditis elegans and in cell lines from humans and mice. In each case, the interference by siRNAs was superior to the inhibition of gene expression mediated by single-stranded antisense oligonucleotides. The siRNAs seem to avoid the well documented nonspecific effects triggered by longer double-stranded RNAs in mammalian cells. These observations may open a path toward the use of siRNAs as a reverse genetic and therapeutic tool in mammalian cells.

Functional anatomy of a dsRNA trigger: differential requirement for the two trigger strands in RNA interference.

In RNA-mediated interference (RNAi), externally provided mixtures of sense and antisense RNA trigger concerted degradation of homologous cellular RNAs. We show that RNAi requires duplex formation between the two trigger strands, that the duplex must include a region of identity between trigger and target RNAs, and that duplexes as short as 26 bp can trigger RNAi. Consistent with in vitro observations, a fraction of input dsRNA is converted in vivo to short segments of approximately 25 nt. Interference assays with modified dsRNAs indicate precise chemical requirements for both bases and backbone of the RNA trigger. Strikingly, certain modifications are well tolerated on the sense, but not the antisense, strand, indicating that the two trigger strands have distinct roles in the interference process.