The palindromic LTR-LTR junction of Moloney murine leukemia virus is not an efficient substrate for proviral integration

We generated viral constructs to test the hypothesis that the major substrate on retroviral DNA that is utilized for proviral DNA integration is the palindromic sequence, termed the LTR-LTR junction, normally present in circular molecules formed by joining the two termini of linear proviral DNA. Recombinant viral genomes were built which carried a selectable marker and an extra copy of the LTR-LTR junction from a cloned circular provirus. The junction sequence in each case was positioned such that its use during integration would lead to an easily detected, aberrantly integrated proviral DNA. Analysis of DNA from cells infected with the virus constructs showed that the introduced junction sequence is used at least 1,000-fold less efficiently than the natural sequences at the ends of the genome. This suggests that a linear or more exotic DNA intermediate is most likely the true precursor for the integration reaction.

Construction and analysis of deletion mutations in the U5 region of Moloney murine leukemia virus: effects on RNA packaging and reverse transcription

A collection of deletion mutations was generated in the U5 region of cloned DNA copies of Moloney murine leukemia virus or a related retrovirus. Cell lines expressing the mutant DNAs were generated by cotransformation, and the virions released were characterized biochemically. Deletions in the 5' part of U5 profoundly reduced packaging of the viral RNA into virions; one deletion in the 3' part of U5 did not block packaging but affected reverse transcription. One mutant with a deletion in the central part of U5 was fully viable and served to separate the two functional parts of U5.

Piroxicam inhibits the growth of an adenocarcinoma isograft in Fischer rats

The effect of piroxicam, a nonsteroidal anti-inflammatory drug, on a transplantable adenocarcinoma in Fischer rats was studied. Forty male Fischer rats were injected with 1 X 10(6) DMH-F317 adenocarcinoma cells, and after 2 weeks were assigned to be treated with piroxicam or carrier solution. The groups were as follows: Group 1, control; Group 2, 4.0 mg/kg piroxicam; Group 3, 6.0 mg/kg piroxicam; and Group 4, 8.0 mg/kg piroxicam. Thirty-nine of forty rats developed measurable tumors during this study. At the conclusion, 60% (6/10) of the rats in Group 2 were tumor free compared to 0/10 controls, 0/10 Group 3 rats, and 1/8 Group 4 rats. (P less than 0.005, chi 2). Mean tumor volumes (mm3) were calculated for each group and converted to log10. At Week 6, the mean log10 tumor volume (+/- SEM) for Group 2 was 1.5 +/- 0.6 vs 4.1 +/- 0.1 for Group 1 (P less than 0.05). The mean log10 volume for Group 3 was 3.8 +/- 0.1 (P less than 0.05 vs Group 2). The mean log10 volume for Group 4 was 3.4 +/- 0.05 and was not significantly different from that for Group 2 (P greater than 0.05). Plasma PGE2 levels for each treatment group were determined at the conclusion of the study and no statistical difference between treatment groups was found. It is concluded that piroxicam inhibits tumor growth in this model, and may have a role as a biological response modifier in cancer therapy.

Hypothyroxinemia in cardiac arrest

Thyroid function was evaluated in cardiac arrest (CA), a condition associated with marked activation of the pituitary-adrenal axis. Blood samples were obtained in 24 patients immediately after diagnosis of CA and again ten minutes later. Samples were also obtained from 22 patients admitted consecutively to the intensive care unit (ICU). Abnormalities of thyroid indexes among patients on the ICU who had not experienced CA were low triiodothyronine (T3) in 45%, low thyroxine (T4) in 32%, low free T4 (equilibrium dialysis) in 21%, and elevated reverse T3 levels in 36%. The alterations of thyroid values were both more common and marked in patients with CA, with abnormally low T3 in 84% of the patients, low T4 in 65%, low free T4 in 65%, and high reverse T3 in 80%. Thyroxine-binding globulin and prealbumin concentrations were below the normal range in 40% and 21% of patients with CA. A thyroid hormone-binding inhibitor was detected in 38% of patients with CA. Thyroglobulin level was slightly high in patients with CA but not significantly different from controls on the ICU. The abnormalities present at zero minutes were further exaggerated ten minutes after CA. We conclude that abnormalities on tests measuring thyroid function are extremely common during the cardiovascular emergency of CA.

Aminoglycoside monitoring: use of a pharmacokinetic service versus physician recommendations

Two patient populations were evaluated regarding the monitoring of aminoglycoside serum concentrations by either a pharmacokinetic service (PKS) or staff physicians. Both groups were evenly matched by demographic characteristics, underlying disease state(s), and indication for aminoglycoside therapy. Patients in the PKS group showed increased incidence of clinical improvement after therapy when compared with the physicians' group; a decreased length of stay and duration of treatment were also observed in this group. Aminoglycoside dosing and monitoring by the PKS provided an estimated average cost savings of $491,00 per patient. The results indicate that the PKS may provide cost savings and benefit in aminoglycoside monitoring for the patient and/or the hospital.

A new acute transforming feline retrovirus and relationship of its oncogene v-kit with the protein kinase gene family

A new acute transforming feline retrovirus, the Hardy-Zuckerman 4 feline sarcoma virus (HZ4-FeSV), has been isolated from a feline fibrosarcoma. The viral genome of HZ4-FeSV contains a new oncogene designated v-kit, has the structure 5' delta gag-kit-delta pol-delta env 3' and specifies a gag-kit polyprotein of relative molecular mass 80,000. The predicted kit amino-acid sequence displays partial homology with tyrosine-specific protein kinase oncogenes. HZ4-FeSV appears to have been generated by transduction of feline c-kit sequences with feline leukaemia virus.

Correlation of pharmacokinetic indices with therapeutic outcome in patients receiving aminoglycosides

The influence of five pharmacokinetic indices on therapeutic response was retrospectively studied in 45 adult patients treated with aminoglycosides for bacterial infections. Subjects were treated for a minimum of five days, had culture and sensitivity reports, and had at least one set of steady-state peak and trough serum aminoglycoside concentrations. Serum drug concentrations were determined by enzyme-multiplied immunoassay or by fluorescence polarization assay. Minimum inhibitory concentrations (MICs) for the drugs were determined by microdilution assays. Cure was determined by negative cultures or absence of clinical evidence of infection. Values for five pharmacokinetic indices were determined for each patient: ratio of steady-state peak serum concentration to MIC (Cssmax/MIC); time that the serum concentration remained above the MIC during a 72-hour period (tsupra-MIC(72)); the intensity index for a 72-hour period (II(72)), which is related but not identical to the area under the curve (AUC), reflecting the contributions of Cssmax/MIC and tsupra-MIC(72); time that the serum concentration was greater than four times the MIC during a 72-hour period (tsupra-(4 X MIC)(72)), and the intensity index related but not identical to AUC greater than four times the MIC (II4 X MIC(72)), which reflects the contribution of Cssmax/(4 X MIC) and tsupra-(4 X MIC)(72). Statistical analysis revealed significant correlations between each of the five indices and the patients' therapeutic responses. The following index values were associated with cures: Cssmax/MIC greater than 4 (and ideally greater than 8); tsupra-MIC(72) of at least 40 hours; tsupra-(4 X MIC)(72) of at least 10 hours; (4) II(72) greater than 400; and II4 X MIC(72) greater than 50. All five pharmacokinetic indices were good predictors of patient outcome. The ratio of maximum steady-state serum aminoglycoside concentration to minimum inhibitory concentration is the index most easily monitored and interpreted.

gamma 3-Melanocyte-stimulating hormone immunoreactivity is a component of the neuroendocrine response to maximal stress (cardiac arrest)

The levels of gamma 3-MSH immunoreactivity (gamma 3MSH-IR), beta-endorphin immunoreactivity (beta-endorphin-IR), ACTH, PRL, and cortisol were determined in 23 patients with cardiac arrest (CA) and in a group of 22 patients consecutively admitted to the Intensive Care Unit (ICU controls). Blood was obtained immediately after CA and at frequent intervals for the next 2 h. In ICU patients, blood was obtained the morning after admission. gamma 3MSH-IR was consistently elevated after CA; it was present in all 23 patients and was detectable in 113 of 114 samples. The mean peak gamma 3MSH-IR level was 162 +/- 20 (+/- SE) pg/ml in CA patients and the mean gamma 3MSH-IR level was 35 +/- 6 pg/ml in ICU controls (P less than 0.01). gamma 3MSH-IR was undetectable (less than 20 pg/ml) in normal subjects. CA also was associated with increases in ACTH, beta-endorphin-IR, cortisol, and PRL. The group of ICU controls had stress hormone levels that were generally within the normal range. Distribution of plasma beta-endorphin-IR by gel chromatography showed two peaks of immunoreactivity corresponding to the beta-endorphin and beta-lipotropin standards in both the CA and ICU control groups. Distribution of gamma 3MSH-IR in CA plasma showed a major peak of immunoreactivity with a mol wt of approximately 6,000 daltons and two minor components of approximately 4,000 and 11,000 dalton. No immunoreactivity coeluted with a gamma 3MSH standard. We conclude that gamma 3MSH-immunoreactive peptides are a consistent component of the massive release of pituitary and adrenal glandular products after CA.

Prediction of theophylline clearance using condition correction factors

The predictive ability of different mathematical manipulations of condition correction factors in estimating total body clearance of theophylline in acutely ill hospitalized patients was evaluated. Fifty acutely ill patients who were treated with constant aminophylline infusions were evaluated. Twenty-one patients were evaluated prospectively. Initial serum theophylline concentrations were ordered, and second concentrations were obtained at steady state. Twenty-nine patients were evaluated retrospectively and were included if two steady-state serum theophylline concentrations had been obtained. Each condition correction factor was determined by calculating the predicted normal clearance using a literature-derived clearance value and dividing it into the actual clearance obtained. The FDA condition correction factors were obtained by dividing the theophylline dose recommended for patients with a particular disease by the dose recommended for a normal patient. Pearson correlation coefficients for 15 mathematical manipulations were used to examine the relationship between the predicted clearance and actual clearance. The predictability of theophylline clearance using the mathematical manipulations decreased as the number of condition correction factors increased. The mean actual clearance for four patients with no condition correction factors was only 2% greater than the mean standard clearance found in a previous study. The use of 0.041 L/hr/kg as a standard clearance appears justified for calculating initial theophylline dosages in all patients. Patients with only one condition correction factor may use this factor to adjust dosage, but when more than one factor is present, the use of the other manipulations studied may result in either subtherapeutic or toxic serum concentrations.

The Parodi-Irgens feline sarcoma virus and simian sarcoma virus have homologous oncogenes, but in different contexts of the viral genomes

We have identified the oncogene and the putative transforming protein of the Parodi-Irgens feline sarcoma virus (PI-FeSV). The PI-FeSV is defective and needs a helper virus for its replication. The v-onc sequences in the PI-FeSV were found to be related to the v-sis sequences of the simian sarcoma virus (SSV). PI-FeSV nonproducer cells express two viral RNAs, a 6.8-and a 3.3-kilobase RNA. The 6.8-kilobase RNA contains gag, sis, and env sequences but lacks the pol gene. The 3.3-kilobase RNA, on the other hand, contains only env sequences. We have detected one feline leukemia virus-related protein product in these cells, namely, a 76-kilodalton protein which contains determinants of the feline leukemia virus gag proteins p15 and p30. The v-sis sequences in the PI-FeSV have been located near the 5' end of the viral genome. Taken together, these results imply that the p76 protein contains both feline leukemia virus gag and sis sequences and probably is the transforming protein of this virus. In contrast, in SSV the sis sequences are located towards the 3' end of the viral genome, and the sis protein is thought to be expressed via a subgenomic RNA. PI-FeSV and SSV therefore use different schemes to express their onc-related sequences. The v-sis sequences in the PI-FeSV contain restriction sites which reflect the different origin of the v-sis sequences in the PI-FeSV and SSV. The homologous oncogenes of the PI-FeSV and SSV thus were transduced by two different retroviruses, feline leukemia virus and the simian sarcoma-associated virus, apparently from the genomes of different species.

In-vivo comparison of the adsorption capacity of "superactive charcoal" and fructose with activated charcoal and fructose

This study was undertaken to assess the in-vivo capacity of two activated charcoal products to adsorb aspirin after its ingestion by seven healthy volunteers. The two products, Norit-A and Super-Sorb, were combined with fructose solution and administered after the subjects ingested 975 mg of aspirin. Urinary excretion of salicylates was measured during both charcoal administration phases and after ingestion of aspirin alone in all subjects. Results showed statistically significant differences in salicylate excretion between all phases. Super-Sorb ("superactive charcoal") adsorbed almost twice (1.7) as much as aspirin as the regular activated charcoal, Norit-A. Super-Sorb therefore has a greater in-vivo adsorption capacity for aspirin and should be a more effective antidote in poisonings with this drug.

An evaluation of pyrisuccideanol maleate (Nadex) in the treatment of mild to moderate depression in patients aged 55 years and over, presenting in general practice

A randomized double-blind study was undertaken comparing the therapeutic efficacy of pyrisuccideanol maleate (Nadex) and placebo in sixteen general practices, involving a total of 100 patients presenting with mild to moderate depression. The trial duration period was 6 weeks with assessments being made initially, and at 4 and 6 weeks. A consistently higher proportion of those treated with Nadex demonstrated an improvement in their symptoms as compared to those treated with placebo and some of the differences proved to be statistically significant. Nadex was also observed to be well tolerated.

Clinical utility of six methods of predicting phenytoin doses and plasma concentrations

The usefulness of six reported methods of predicting phenytoin doses or plasma concentrations in epileptic patients is compared. Forty adult epileptic outpatients who were taking phenytoin sodium orally were followed prospectively for nine months; 16 met requirements for inclusion in the study. Six methods of predicting phenytoin dosage or plasma concentrations--one equation, two nomograms, and three graphs--were compared to actual phenytoin doses and corresponding steady-state serum levels. Criteria establishing good, high, and low predictions were specified for each method. No method produced consistently accurate results. Good dosage predictions occurred in 42-60% of the predictions with the six methods. Low predictions occurred in 0-50% of the estimates; 8-53% of the predictions were high. It is concluded that certain methods are clinically useful under some conditions if recommended cautions are observed.