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Following infection by HIV or SIV, reverse transcriptase (RT) directs the conversion of the single-stranded RNA genome into a double-stranded DNA molecule that integrates into the host cell genome. RT encodes for several immunogenic epitopes that are desirable for inclusion in a human vaccine for HIV infection, however, issues of safety have dampened enthusiasm for inclusion of an enzymatically-active RT molecule into an AIDS vaccine. In this study, virally-regulated, replication-incompetent lentiviral particles were expressed from DNA plasmids. The sequences for integrase, Vpr, Vif, Nef, and the long terminal repeats (LTRs) were deleted and mutations were engineered into capsid to decreases RNA packaging. Virus-like particles incorporated no RT (HIV-VLP DeltaRT or SHIV-VLP DeltaRT) or contained a full-length enzymatically-inactivated RT molecule (HIV-VLP or SHIV-VLP). Each secreted VLP was enveloped with a lipid bilayer derived from primate cells with embedded, native viral envelopes in similar concentrations as infectious virions. BALB/c mice were vaccinated (weeks 0, 3, and 6) with purified VLPs via intranasal inoculation in the presence of cytosine-phosphate-guanosine oligodeoxynucleotides (CpG ODNs). All VLPs, with or without RT, elicited both robust humoral and cellular immune responses to Gag, Pol, and Env antigens. Therefore, the lack of RT enhances the safety of these VLPs for use in future human clinical trials without a significant reduction in the overall immunogenicity of these VLP immunogens.

The study was done to assess the performance of a system that measures the partial pressures of oxygen (pO2) from the lifetimes of oxygen-quenched luminescence of ruthenium compounds immobilized at the tip of fiber-optic optodes (Oxylite system). The system was used to measure the pO2 in brain tissue (thalamus and hypothalamus) and in the sagittal sinus of isoflurane-anesthetized rats at different FiO2's. The pO2 recorded in the hypothalamus (HPtO2) was consistently higher than the pO2 in the thalamus (TPtO2) at all FiO2. HPtO2 was closely related to PvO2 during normoxia but not during hypoxia. The equilibrium time of Oxylite system was found to be rapid compared to in vivo tissue response to changes in FiO2.

Ketamine-xylazine is a commonly used anesthetic for laboratory rats. Previous results showed that rats anesthetized with ketamine-xylazine can have a much lower cerebral partial pressure of oxygen (P(t)O(2)), compared to unanesthetized and isoflurane anesthetized rats. The underlying mechanisms for the P(t)O(2) reduction need to be elucidated. In this study, we measured regional cerebral blood flow (CBF) using nuclear magnetic resonance (NMR) perfusion imaging and cortical P(t)O(2) using electron paramagnetic resonance (EPR) oximetry in the forebrain of rats under isoflurane, ketamine, ketamine-xylazine and isoflurane-xylazine anesthesia. The results show that in ventilated rats ketamine at a dose of 50 mg/kg does not induce significant changes in CBF, compared to isoflurane. Ketamine-xylazine in combination causes 25-65% reductions in forebrain CBF in a region-dependent manner. Adding xylazine to isoflurane anesthesia results in similar regional reductions in CBF. EPR oximetry measurements show ketamine increases cortical P(t)O(2) while xylazine decreases cortical P(t)O(2). The xylazine induced reduction in CBF could explain the reduced brain oxygenation observed in ketamine-xylazine anesthetized rats.

Factors regulating cerebral tissue PO2 (PtO2) are complex. With the increased use of clinical PtO2 monitors, it has become important to elucidate these mechanisms. The authors are investigating a new methodology (electron paramagnetic resonance oximetry) for use in monitoring cerebral PtO2 in awake animals over time courses of weeks. The authors used this to study cerebral PtO2 in rats during chronic acclimation to hypoxia predicting that such acclimation would cause an increase in PtO2 because of increases that occur in capillary density and oxygen carrying capacity. The average PtO2 between 7 and 21 days was increased by 228% over controls.

Previous studies have shown that cortical tissue oxygenation is impaired during hyperventilation. However, it is important to quantify the effect of hyperventilation on brain tissue PO(2) and cerebrovenous PO(2) simultaneously especially since cerebral venous oxygenation is often used to assess brain tissue oxygenation. The present study was designed to measure the sagittal sinus PO(2) (PvO(2)), brain tissue PO(2) in the thalamus (PtO(2)), and brain temperature (Bt) simultaneously during acute hyperventilation. Isoflurane-anesthetized rats were hyperventilated for 10 min during which time the arterial carbon dioxide tension (PaCO(2)) dropped from 40.3+4.9 mmHg to 23.5+2.8 mmHg. PtO(2) declined from 26.0+/-4.2 mmHg to 14.8+/-5.2 mmHg (P=0.004) while brain temperature decreased from 36.5+0.3 degrees C to 36.2+0.3 degrees C (P=0.02). However, PvO(2) and arterial blood pressure (BP) did not change during hyperventilation. The maintenance of PvO(2) when perfusion is thought to decline and PtO(2) decreases suggests that there may be a diffusion limitation, possibly due to selective perfusion. Therefore, cerebrovenous PO(2) may not give a good assessment of brain tissue oxygenation especially in conditions of acute hyperventilation, and deeper brain regions other than the cortex also show impaired tissue oxygenation following hyperventilation.

This is the first publication using a fiber optic "optode" and a luminescence based pO2 detection method for assessing neural tissue oxygenation. The system was used to simultaneously monitor pO2 in tissue (PtO2) and venous blood (PvO2) during normoxia, hyperoxia and hypoxia. PaO2 was varied by changing inspired oxygen (FiO2) from 0.3 to 0.13. Tissue and arterial pO2 were measured in 5 rats while the simultaneous venous measurements were undertaken in 3 animals. The PtO2 was 29 +/- 10 at an arterial pO2 of 116 +/- 10 (mean +/- SE, n = 5). The PvO2 was consistently higher than PtO2 although PvO2 approached PtO2 as PaO2 declined to 50 mmHg and was lower than tissue pO2 during the complete hypoxic period in one animal. These data indicate that brain venous pO2 is not representative of brain tissue pO2 and support published models predicting that in brain PvO2 is higher than PtO2.

This study was performed to investigate the effect of chloroquine (CQ) on the contractility of isolated smooth muscles of the rat uterus, urinary bladder; and trachea. Chloroquine, 4 x 10(-4) mol.l-1 completely abolished uterine contractions produced by 10(-2) IU/ml oxytocin, and 10(-6) mol.l-1 5-hydroxytryptamine (5-HT) and acetylcholine (Ach). Chloroquine also caused a concentration-dependent relaxation of 10(-6) mol.l-1 Ach-contracted rat trachea. Cumulative addition of CQ (10(-8)-10(-3) mol.l-1) to spontaneously contracting rat urinary bladder did not produce any significant effect. It also did not affect the contractile response of the bladder to Ach and 5-HT. The results suggest that CQ inhibits the contractile process in the rat uterus and trachea but not the urinary bladder.