Goldilocks effect in magnetic bistability: remote substituent modulation and lattice control of photoinduced valence tautomerism and light-induced thermal hysteresis.

The thermal-induced and photoinduced valence tautomerism of a series of Co(dioxolene)(2)(4-X-py)(2) complexes (dioxolene = 3,5-di-tert-butylcatecholate or 3,5-di-tert-butylsemiquinonate; 4-X-py = 4-(X)pyridine, X = H (1), OMe (2), Me (3), CN (4), Br (5), NO(2) (6)) is described. The thermal valence tautomerism (ls-Co(III)(SQ)(Cat)(4-X-py)(2) <--> hs-Co(II)(SQ)(SQ)(4-X-py)(2)) is only observed for complexes 4, 5, and 6 where each is accompanied by a hysteresis loop of ca. 5 K. When a crystalline sample of 4-6 is held at 10 K in a SQUID magnetometer and irradiated with white light (lambda = 400-850 nm), the hs-Co(II) tautomer is formed. When the light source is removed, and the sample is slowly heated, the hs-Co(II) tautomer persists until ca. 90 K, approximately 40 K higher than the thermal stability of previously reported complexes. Heating and cooling the sample while maintaining irradiation results in the appearance of a new light-induced thermal hysteresis loop below 90 K (DeltaT = ca. 25 K). Below 50 K, the hs-Co(II) tautomer displays temperature-independent relaxation to the ls-Co(III) form, and above 50 K, the relaxation is thermally activated with an activation energy E(a) > ca. 1500 cm(-1). The coordination geometry (trans-pyridines), pyridine substitution, and crystal packing forces conspire to create the comparatively thermally stable photogenerated hs-Co(II) tautomer, thus providing an excellent handle for molecular and crystal engineering studies.

Primate and feline lentivirus vector RNA packaging and propagation by heterologous lentivirus virions.

Development of safe and effective gene transfer systems is critical to the success of gene therapy protocols for human diseases. Currently, several primate lentivirus-based gene transfer systems, such as those based on human and simian immunodeficiency viruses (HIV/SIV), are being tested; however, their use in humans raises safety concerns, such as the generation of replication-competent viruses through recombination with related endogenous retroviruses or retrovirus-like elements. Due to the greater phylogenetic distance from primate lentiviruses, feline immunodeficiency virus (FIV) is becoming the lentivirus of choice for human gene transfer systems. However, the safety of FIV-based vector systems has not been tested experimentally. Since lentiviruses such as HIV-1 and SIV have been shown to cross-package their RNA genomes, we tested the ability of FIV RNA to get cross-packaged into primate lentivirus particles such as HIV-1 and SIV, as well as a nonlentiviral retrovirus such as Mason-Pfizer monkey virus (MPMV), and vice versa. Our results reveal that FIV RNA can be cross-packaged by primate lentivirus particles such as HIV-1 and SIV and vice versa; however, a nonlentivirus particle such as MPMV is unable to package FIV RNA. Interestingly, FIV particles can package MPMV RNA but cannot propagate the vector RNA further for other steps of the retrovirus life cycle. These findings reveal that diverse retroviruses are functionally more similar than originally thought and suggest that upon coinfection of the same host, cross- or copackaging may allow distinct retroviruses to generate chimeric variants with unknown pathogenic potential.

Mason-Pfizer monkey virus (MPMV) constitutive transport element (CTE) functions in a position-dependent manner.

The Mason-Pfizer monkey virus (MPMV) constitutive transport element (CTE) is a cis-acting RNA element located in the 3' untranslated region (UTR) of the viral genome. The HIV-1 and SIV Rev/RRE regulatory system can be replaced with MPMV CTE (Bray et al., 1994; Zolotukhin et al., 1994; Rizvi et al., 1996a); similarly, CTE function can also be replaced by the HIV or SIV Rev/RRE regulatory system (Rizvi et al., 1996b; Ernst et al., 1997). In addition, we have shown that in the context of the SIV genome, position is important for CTE function (Rizvi et al., 1996a). To determine the importance of position for CTE function in the context of the MPMV genome, MPMV molecular clones were generated by deleting CTE or removing it from the 3' UTR and placing it in the approximately 40 bp of intervening sequences between the pol termination codon and env initiation codon. A test of these molecular clones in a single round of replication assay revealed that deletion or displacement of CTE in the intervening sequences between pol and env completely abrogated virus replication. Western blot analysis of cell lysates and pelleted culture supernatants revealed negligible amounts of Pr78 Gag/Pol precursor and the processed p27(gag) when CTE was deleted or displaced. Slot blot analysis of fractionated RNAs revealed entrapment of the viral Gag/Pol mRNA in the nucleus with CTE deletion or displacement. Upon reinsertion of CTE in the original genomic position of clones with the deleted or displaced CTE, virus replication, Gag/Pol protein production, and nucleocytoplasmic transport of viral mRNA were restored to normal levels. Displacement of CTE to the 5' UTR immediately upstream of the Gag initiation codon also resulted in aberrant Gag/Pol protein production and nucleocytoplasmic transport of viral RNA. Reinsertion of CTE at the original genomic position of the clone with CTE displacement at the 5' UTR restored normal Gag/Pol protein production and RNA transport, demonstrating that the 3' terminal position of CTE is important for its function. To explore why the 3' terminal location of CTE is important, heterologous DNA sequences of increasing lengths were inserted between CTE and the polyadenylation (poly(A)) signal of the virus to augment the distance between the two cis-acting elements. Test of these constructs revealed that CTE function was progressively lost with incremental increase in distance between CTE and poly(A). To explore this relationship further, CTE was displaced to the env region approximately 2000 bp upstream of the poly(A) signal which abrogated CTE function. However, cloning of poly(A) signal to approximately 200 bp downstream of CTE in the env region (the natural distance between CTE and poly(A)) restored CTE function. Together, these results demonstrate that the close proximity of CTE to the poly(A) signal is important for CTE function, suggesting a functional interaction between CTE and the polyadenylation machinery.

Role of Mason-Pfizer monkey virus (MPMV) constitutive transport element (CTE) in the propagation of MPMV vectors by genetic complementation using homologous/heterologous env genes.

To study Mason-Pfizer monkey virus (MPMV) replication over a single round, virus particles were generated that contain a replication-defective vector encoding a dominant selectable marker, the hygromycin B phosphotransferase (hyg) gene. Genetic complementation with a homologous MPMV envelope glycoprotein (Env-gp) or pseudotyping by several heterologous Env-gps from a variety of viruses resulted in infectious MPMV particles containing the replication-defective RNA. Recently, it has been shown that human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV) Rev and Rev-responsive element (RRE) functions can be substituted in vitro by a cis-acting sequence, the constitutive transport element (CTE), from simian type D retroviruses like MPMV and simian retrovirus type 1 (SRV-1). To determine whether CTE of MPMV is necessary for MPMV nucleic acid propagation, an MPMV vector that lacked the terminally located CTE was generated. Propagation of this vector was completely abrogated in the absence of CTE, showing the importance of CTE in MPMV replication. Insertion of CTE back into the MPMV genome in the sense orientation rescued replication to wild-type levels. Slot-blot analysis of nuclear versus cytoplasmic RNA fractions revealed that most of the messages were sequestered in the nucleus of cells transfected with the CTE(-) vectors and very little was transported to the cytoplasm. To test whether HIV-1 or SIV RREs could complement CTE function, the HIV-1 or SIV RREs were inserted in the CTE(-) vectors, trans complementation of CTE(-)RRE(+) vectors with Env-and Rev-expression plasmids rescued propagation of the CTE(-) vectors. Computer analysis predicted an RNA secondary structure in MPMV CTE analogous to the HIV-1 and SIV RREs that could form three stable stem loops, the first of which contains a site similar to the Rev-binding domain in the HIV-1 RRE. The presence of a higher-order CTE structure was analyzed by mutational analysis. We conclude that CTE is important in the replication of MPMV and affects the nucleocytoplasmic transport and/or stability of viral messages similar to the Rev/RRE regulatory system of HIV-1 and SIV.

Rev/RRE-independent Mason-Pfizer monkey virus constitutive transport element-dependent propagation of SIVmac239 vectors using a single round of replication assay.

In a step toward creating live-attenuated or DNA subunit vaccines for AIDS, the replication of simian immunodeficiency virus (SIV) was studied independently of the Rev and RRE (Rev-responsive element) regulatory system, over a single round. To accomplish this, the env gene of an SIV vector was made defective by the insertion of a SV40 promoter/enhancer hygromycin B phosphotransferase gene cassette. Using this vector as the backbone, molecular clones of SIV were generated that contained a mutated Rev, Rev(-), a deleted RRE, RRE(-), or both, Rev(-)RRE(-). It has been shown recently that human immunodeficiency virus type 1 (HIV-1) Rev and RRE functions can be replaced in vitro by a cis-acting sequence, constitutive transport element (CTE), from simian type D retroviruses. To determine whether such a cis-acting element from Mason-Pfizer monkey virus (MPMV) would substitute for SIV Rev and RRE functions, the MPMV CTE was inserted either into the Nef ORF or at the junction of vpx and vpr of our Rev(-), RRE(-), and Rev(-)RRE(-) SIV molecular clones. Cell-free viral stocks harvested from Cos cells following transfections of these molecular clones revealed that these stocks were infectious over a single round of replication; however, their replication was attenuated 16-fold compared to that of wild-type virus. In addition, our experiments revealed that CTE functions in a position-dependent manner such that its insertion at the junction of vpx and vpr attenuated SIV replication 8- to 12-fold compared to the attenuation observed when it was inserted in the nef region. Our results demonstrate that MPMV CTE is capable of substituting for SIV Rev and RRE functions, resulting in an attenuated ability to produce infectious virus.

Effect of a transjugular intrahepatic portosystemic shunt on liver biochemical profiles.

PURPOSE: Transjugular intrahepatic portosystemic shunts (TIPS) have markedly simplified the care of patients with refractory variceal bleeding. Follow-up of liver biochemical profiles, however, has not been done in a prospective fashion. PATIENTS AND METHODS: Twenty-nine patients undergoing TIPS placement for refractory variceal bleeding underwent serial laboratory tests and assessment of encephalopathy to determine the effect of TIPS. Prothrombin time and aspartate aminotransferase, alanine aminotransferase, total bilirubin, alkaline phosphatase, serum albumin, serum creatinine, and venous ammonia levels were checked prior to the procedure, at the time of discharge, and at 3 weeks, 3 months, and 6 months following the procedure. RESULTS: There was no statistically significant change in any of the obtained laboratory values at up to 6 months of follow-up. The change in aspartate aminotransferase level approached but did not reach statistical significance at the time of discharge and was thought to be secondary to hepatocellular trauma associated with the procedure. New onset of encephalopathy occurred in 18.2% of patients and was easily controlled with medical therapy. CONCLUSIONS: TIPS does not appear to have a significant effect on the liver biochemical profile with short-term follow-up. Hepatic encephalopathy does occur, however, in a significant number of patients but is easily controlled with medical therapy.

Clinical efficacy and toxicity of doxorubicin encapsulated in glutaraldehyde-treated erythrocytes administered to dogs with lymphosarcoma.

Doxorubicin was encapsulated in canine erythrocytes, treated with 0.32% glutaraldehyde, and administered at a dosage equivalent to 30 mg of free doxorubicin/m2 of body surface area to dogs with diagnosis of lymphosarcoma. Compared with administration of free doxorubicin, this method of drug delivery substantially reduced peak plasma concentration and prolonged higher plasma concentration of doxorubicin. As such, this method was comparable to continuous IV infusion. Previous studies have indicated this method's potential for reduction in toxic side effects, particularly cardiotoxicosis, while allowing higher total doses of doxorubicin to be administered. In this study, doxorubicin encapsulated in glutaraldehyde-treated erythrocytes induced a triphasic exponential decay of doxorubicin from plasma, the highest relative contribution to the total area of the curve being the terminal phase. The treatment was effective in inducing complete and partial remissions of lymphosarcoma, with minimal acute toxicosis and no evidence of cardiotoxicosis. However, substantial, unanticipated, chronic, nonregenerative myelosuppression developed, and was mot strikingly expressed as profound thrombocytopenia. Efforts to ameliorate or circumvent this toxic effect will be required prior to further consideration of this doxorubicin delivery system for treatment of systemic neoplasia.

Infant botulism: a case series and review of the literature.

Little has been written about infant botulism in the emergency medicine literature, despite increasing references in the pediatric journals. We describe three cases diagnosed at The Children's Hospital in Denver, Colorado, over an 8-month period. A review of the literature follows, to discuss the clinical manifestations, differential diagnosis, diagnostic workup and treatment of the disease.

Nontraumatic spinal cord compression.

Nontraumatic spinal cord compression can have very dramatic clinical presentations with rapid onset of symptoms and quickly ensuing paralysis. The manifestations may be much more subtle. This text will discuss the four most common causes of myelopathy, including spinal canal hemorrhage, spinal abscess, compression by tumor, and skeletal disease. Compressive lesions to the spinal cord from other than these etiologies are rare.

Noncolloid neuroepithelial cysts in the lateral ventricle: magnetic resonance features.

Two patients with presumed intraventricular neuroepithelial cysts are reported. Their characteristic features on magnetic resonance imaging are described, and the importance of demonstrating the cysts' walls is underscored.

Effects of a raw food diet on hypertension and obesity.

We examined responses to cooked and uncooked food in 32 outpatients with essential hypertension; 28 were also overweight. By varying cooked and uncooked food percentages and salt intake, patients acted as their own control subjects in this unblinded study. After a mean duration of 6.7 months, average intake of uncooked food comprised 62% of calories ingested. Mean weight loss was 3.8 kg and mean diastolic pressure reduction 17.8 mm Hg, both statistically significant (P less than .00001). Eighty percent of those who smoked or drank alcohol abstained spontaneously.

Natriuresis in rats acutely depleted of chloride.

1. Acute chloride depletion, without sodium depletion, was produced in rats by a single exchange peritoneal dialysis against sodium bicarbonate solution. Blood volume was restored after dialysis by infusion of salt-free albumin, and exogenous deoxycorticosterone and antidiuretic hormone were given. 2. Clearance studies in the period (3 h) after dialysis revealed no difference in the glomerular filtration rate or in the filtered sodium load between experimental and control rats but urinary sodium concentrations and absolute and fractional sodium excretion were significantly higher in the chloride-depleted group. 3. There was also a significant kaliuresis, increased urinary flow rate and diminished free water reabsorption. Urinary bicarbonate excretion increased to a variable degree but the major rise in anion excretion was 'unmeasured' (Na+ + K+ - [Cl- + HCO3- + PO4(3-)]). 4. It is postulated that chloride depletion imposes limitations on sodium reabsorption in the ascending limb of the loop of Henle.