Acute and chronic morphine administration in swine.

Functional responses to acute and chronic morphine administration in domestic swine were examined and correlated with pharmacokinetic profiles. Acute effects of morphine sulfate were monitored in pigs for 24 h and the chronic actions of morphine alkaloid were monitored for 21 days. Serum morphine levels, nociception, locomotor activity, respiratory rate, body temperature, and body weight were monitored during all studies. To assess nociception in a large laboratory animal, a portable thermal stimulating device was constructed. Morphine sulfate administered IV and SC had a half-life of approximately 1 h whereas delayed-release morphine alkaloid delivered SC had a half-life of 28 h. The degree of antinociception paralleled decline in blood morphine levels for both SC- and IV-administered animals. Tolerance occurred to both antinociception as well as weight gain despite morphine levels remaining constant over the 21-day period. Morphine dependence was demonstrated by precipitation of an abstinence syndrome using naloxone. Animals in withdrawal displayed consistent signs, including wet-dog shakes, posture changes, vocalization, and salivation. Collectively, these results indicate that swine may be reliably employed as a model to study the actions of morphine and opiate-like compounds.     

Subthreshold oscillations generated by TTX-sensitive sodium currents in dorsal cochlear nucleus pyramidal cells

During intracellular recordings in rodent brainstem slice preparations, dorsal cochlear nucleus (DCN) pyramidal cells (PCs) exhibit characteristic discharge patterns to depolarizing current injection that depend on the membrane potential from which the responses are evoked. When depolarized from hyperpolarized potentials, PCs can respond with a short-latency action potential followed by a long silent interval (pauser) or a train of action potentials with a long latency (buildup). During the silent intervals in a pauser or a buildup response, the membrane potential slowly depolarizes towards spike threshold, often exhibiting distinct voltage oscillations of 1–2 mV before the first spike. The subthreshold voltage oscillations were investigated using whole cell recordings from DCN PCs in rat pup (P10–14) brainstem slices. The oscillations were unaffected by excitatory and inhibitory neurotransmitter antagonists, and were not temporally locked to the onset of the depolarization. The oscillations typically became larger as spike threshold was approached, and had a characteristic frequency between 40 and 100 Hz. In the presence of tetrodotoxin (TTX, 500 nM), the oscillations were significantly suppressed, and could not be evoked at any voltage below or above spike threshold. The oscillations were not blocked by phenytoin or Cd²⁺, but they were affected by prior activity in the neuron for approximately 1 s. We conclude that voltage-gated Na⁺ channels are required to generate membrane oscillations during the buildup phase. We suggest that the subthreshold oscillations play a role in controlling spike timing in PCs when the membrane potential slowly approaches, or hovers near, spike threshold.     

Polymerase chain reaction (PCR) amplification for the detection of porcine parvovirus

A polymerase chain reaction (PCR) amplification method was developed and evaluated to detect porcine parvovirus (PPV). A pair of 20-base primers and an oligonucleotide probe were derived from the DNA sequences common to two isolates of PPV, NADL-8 and NADL-2. The primers flanked 118-bp nucleotides within the region coding for the major structural protein VP2. After DNA amplification of PPV replicative form (RF), a 158-bp fragment was detected in agarose gels. This amplified fragment was shown to be specific for PPV DNA after Southern transfer and hybridization to a 20-base internal probe. The amplified fragment also contained a single EcoRI cleavage site. Various conditions, such as number of cycles and annealing temperature, were examined to optimize the conditions for detecting viral DNAs from infected cell cultures and swine fetal tissues. Four different isolates of PPV, NADL-8, NADL-2, KBSH and Kresse, and two other viruses, canine parvovirus (CPV) and pseudorabies virus (PRV), were included to determine specificity of amplification. Slot blot hybridization with a radiolabeled probe was used to evaluate the sensitivity of PCR amplification. The optimized protocol was specific for PPV detecting equally all four strains of PPV, but failing to amplify CPV or PRV sequences. The PCR method could detect at least 100 fg of viral replicative form (RF) DNA or the equivalent of 1 PFU of infectious virus. The applications of this method include routine detection of PPV in clinical samples and as a contaminant in mammalian cell lines.     

Inhibition of porcine parvovirus replication by empty virus particles

The influence of empty porcine parvovirus (PPV) particles on viral replication was examined in cell cultures and in swine. Following extensive purification, homogeneous preparations of full and empty PPV preparations were obtained and used for in vitro and in vivo analyses. In the first in vitro experiment, swine testes cells were infected with mixtures of various ratios of empty and full (E/F) particles. The production of both intracellular and extracellular virus was markedly inhibited in the presence of empty particles. This inhibition was dependent upon the concentration of empty particles present in the mixture. In the second in vitro study, various concentrations of empty particles were added prior to full virus infection. Again, marked inhibition of progeny virus production was evident and related to the concentrations of empty particles added. Based on the results of in vitro studies, the influence of empty particles on PPV infection in swine was tested by infecting mid-term and late-term gestation swine fetuses with various E/F particle ratios. Both mid-term and late-term fetuses exposed to 0:1, 1:1 and 5:1 E/F ratios displayed gross pathological evidence of PPV infection whereas fetuses exposed to E/F ratios of 30:1 or greater were grossly normal in appearance. However, fetuses infected with 30:1, 50:1 and 300:1 E/F ratios showed evidence of virus in their tissues by DNA hybridization. Regardless of the E/F ratios, late-term infected fetuses responded with high antibody titers ranging from 1024 to 4096. The results from these studies suggested that empty particles interfered with viral replication in both cell culture and in animals.     

Emotion regulation behavior during a separation procedure in 18-month-old children of mothers using cocaine and other drugs

This study examined the association between maternal cocaine use and children's emotional regulation. Using a brief separation procedure, we observed 78 18-month-old at-risk children and their mothers from three defined maternal groups: no drug use; no cocaine use but a positive history for alcohol, tobacco, and/or marijuana; and cocaine use with or without alcohol, tobacco, and/or marijuana. Coded videotaped behavior identified three maternal constructs (separation style, physical engagement, and emotional engagement) and three child constructs (negative reactivity to separation, initial regulatory activity, and follow-up positive emotional engagement). Cocaine-using mothers displayed less emotional engagement than other mothers. Children with cocaine-using mothers displayed less negative reactivity and follow-up positive emotional engagement than their counterparts. Child reactivity was connected to maternal drug use, whereas emotional engagement during reunion was linked to birthweight and maternal behavior. Results suggest a possible impairment or restriction of emotional expression and regulation in the face of stress and/or maternal disengagement that is more common among cocaine-exposed children with their mothers.     

The detection and differentiation of foot-and-mouth disease viruses using solid-phase nucleic acid hybridization

Thirteen complementary DNA (cDNA) probes were used to detect the presence of foot-and-mouth disease virus (FMDV) RNA extracted from cell cultures. When labelled with 32P, these probes enabled the detection of 1 pg of FMDV-RNA, or 1 virus copy per cell. Two FMDV A12 probes that coded for the leader, structural protein VP1 region and part of the polymerase gene respectively, showed no hybridization with other closely related picornaviruses. Differentiation between FMDV serotypes A, O and C was possible, using cDNA probes from individual serotypes that corresponded to structural protein VP1.     

Vulnerability to HIV Among Women Formerly Incarcerated and Women with Incarcerated Sexual Partners

HIV risk was assessed in association with a history of incarceration and having a sexual partner with a history of incarceration in a population sample of low-income young women residing in San Francisco. Of the 235 women surveyed, 23% reported prior incarceration and 42% reported having a sexual partner with a history of incarceration. Prevalence of sexually transmitted infections (STIs) (including HIV) was no higher among previously incarcerated women or those with a sexual partner with a history of incarceration. Women with a prior incarceration were significantly more likely to report injecting drugs, exchanging sex for money or drugs, and history of forced sex. Women reporting sexual partners with a history of incarceration were significantly more likely to report incarceration history, history of STIs, and history of forced sex. Interventions aimed at reducing substance abuse, STIs, commercial/survival sex, and the effects of sexual coercion need to be strengthened for women within and transitioning out of correctional facilities.