Rabies

Rabies is an important disease in wildlife in the United States and Canada, and dog rabies is still a major public health problem in many developing countries of the world. Rabies virus is transmitted in saliva by animal bites. Bats transmitted most recent cases of human rabies in the United States, often without known exposures. There have been recent developments in our understanding of rabies pathogenesis. Characteristic clinical features should raise the possibility of a diagnosis of rabies and initiation of appropriate diagnostic tests. Therapy of human rabies has been futile except in four patients who were immunized with rabies vaccine prior to the onset of their disease. Rabies can be prevented after an exposure in unimmunized patients with local wound cleansing and administration of rabies vaccine and human rabies immune globulin.

Receptor-mediated internalization of somatostatin in rat cortical and hippocampal neurons

Binding of neuropeptides to their receptors usually results in internalization of receptor-ligand complexes. This process serves a crucial role in receptor downregulation, resensitization, and transmembrane signaling. It has mainly been investigated in cells ectopically expressing recombinant receptors. In the present study, we investigated whether rat central neurons and astrocytes naturally expressing somatostatin (SRIF) receptors internalized this neuropeptide. We demonstrated that 29% of cortical and 45% of hippocampal neurons in culture expressed the SRIF receptor sst(2A) and that 40-50% of the neurons internalized fluorescent SRIF. Similarly, an important proportion of astrocytes expressed sst(2A) (up to 60% in cortical cultures) and internalized fluo-SRIF. Competition experiments using the sst(2)/sst(5)-preferring agonist SMS 201-995 (octreotide) showed that a subpopulation of neurons internalized fluo-SRIF via sst(2) and/or sst(5) receptors, but that others also did so via other subtypes. Fluo-SRIF labeling was barely competed for by the sst(1)-selective agonist CH-275, indicating that sst(1) was unlikely to be mediating SRIF internalization in hippocampal and cortical neurons. Given the paucity of sst(5) receptors in cerebral cortex and hippocampus and the poor yield of sst(4) internalization in transfected cells, we conclude that sst(2) and sst(3) subtypes are the most likely to be responsible for SRIF internalization in our culture systems.

Infection of Bergmann glia in the cerebellum of a skunk experimentally infected with street rabies virus

Rabies virus is a highly neuronotropic virus and glial cell infection is not prominent in the central nervous system (CNS). Paraffin-embedded tissues from the cerebella of skunks experimentally infected with either a skunk salivary gland isolate of street rabies virus or the challenge virus standard (CVS) strain of fixed rabies virus were examined with immunoperoxidase staining for rabies virus antigen by using an anti-rabies virus nucleocapsid protein monoclonal antibody. A skunk infected with street rabies virus showed prominent infection of Bergmann glia. Although infected Purkinje cells were observed, they usually demonstrated a relatively small amount of antigen in their perikarya. A CVS-infected skunk showed many intensely labeled Purkinje cells and a relatively small number of infected Bergmann glia. These findings indicate that although rabies virus is a highly neuronotropic virus, street rabies virus strains do not always demonstrate strict neuronotropism in the central nervous system.

Ectopic expression of a tomato 9-cis-epoxycarotenoid dioxygenase gene causes over-production of abscisic acid

The tomato mutant notabilis has a wilty phenotype as a result of abscisic acid (ABA) deficiency. The wild-type allele of notabilis, LeNCED1, encodes a putative 9-cis-epoxycarotenoid dioxygenase (NCED) with a potential regulatory role in ABA biosynthesis. We have created transgenic tobacco plants in which expression of the LeNCED1 coding region is under tetracycline-inducible control. When leaf explants from these plants were treated with tetracycline, NCED mRNA was induced and bulk leaf ABA content increased by up to 10-fold. Transgenic tomato plants were also produced containing the LeNCED1 coding region under the control of one of two strong constitutive promoters, either the doubly enhanced CaMV 35S promoter or the chimaeric 'Super-Promoter'. Many of these plants were wilty, suggesting co-suppression of endogenous gene activity; however three transformants displayed a common, heritable phenotype that could be due to enhanced ABA biosynthesis, showing increased guttation and seed dormancy. Progeny from two of these transformants were further characterized, and it was shown that they also exhibited reduced stomatal conductance, increased NCED mRNA and elevated seed ABA content. Progeny of one transformant had significantly higher bulk leaf ABA content compared to the wild type. The increased seed dormancy was reversed by addition of the carotenoid biosynthesis inhibitor norflurazon. These data provide strong evidence that NCED is indeed a key regulatory enzyme in ABA biosynthesis in leaves, and demonstrate for the first time that plant ABA content can be increased through manipulating NCED.

Rabies

Human rabies is fatal except in the small number of patients who received rabies immunization before the onset of clinical rabies. Therapy has been futile in all other cases once rabies has developed. Rabies is always preventable after an exposure if current recommendations are followed. After a potential rabies exposure, details about the contact, the animal, and the local epidemiologic situation are important in making a decision whether to initiate postexposure prophylaxis (PEP). Rabies PEP includes thorough local wound cleansing and both active and passive immunization. Five doses of rabies vaccine should be administered intramuscularly in the deltoid muscle on days 0, 3, 7, 14, and 28 in individuals previously unimmunized against rabies virus. Human rabies immune globulin (20 IU/kg) should be given on day 0 with administration into and around the wounds; the remaining volume is given intramuscularly at a site distant from the vaccine site. Certain individuals at high risk for rabies exposure are candidates for preexposure prophylaxis with three doses of rabies vaccine. Booster doses should be given as required.

Abscisic acid biosynthesis in tomato: regulation of zeaxanthin epoxidase and 9-cis-epoxycarotenoid dioxygenase mRNAs by light/dark cycles, water stress and abscisic acid

Two genes encoding enzymes in the abscisic acid (ABA) biosynthesis pathway, zeaxanthin epoxidase (ZEP) and 9-cis-epoxycarotenoid dioxygenase (NCED), have previously been cloned by transposon tagging in Nicotiana plumbaginifolia and maize respectively. We demonstrate that antisense down-regulation of the tomato gene LeZEP1 causes accumulation of zeaxanthin in leaves, suggesting that this gene also encodes ZEP. LeNCED1 is known to encode NCED from characterization of a null mutation (notabilis) in tomato. We have used LeZEP1 and LeNCED1 as probes to study gene expression in leaves and roots of whole plants given drought treatments, during light/dark cycles, and during dehydration of detached leaves. During drought stress, NCED mRNA increased in both leaves and roots, whereas ZEP mRNA increased in roots but not leaves. When detached leaves were dehydrated, NCED mRNA responded rapidly to small reductions in water content. Using a detached leaf system with ABA-deficient mutants and ABA feeding, we investigated the possibility that NCED mRNA is regulated by the end product of the pathway, ABA, but found no evidence that this is the case. We also describe strong diurnal expression patterns for both ZEP and NCED, with the two genes displaying distinctly different patterns. ZEP mRNA oscillated with a phase very similar to light-harvesting complex II (LHCII) mRNA, and oscillations continued in a 48 h dark period. NCED mRNA oscillated with a different phase and remained low during a 48 h dark period. Implications for regulation of water stress-induced ABA biosynthesis are discussed.

Intracellular dynamics of sst5 receptors in transfected COS-7 cells: maintenance of cell surface receptors during ligand-induced endocytosis

Internalization of G protein-coupled receptors is crucial for resensitization of phosphorylation-desensitized receptors, but also for their long term desensitization through sequestration. To elucidate the mechanisms regulating cell surface availability of the somatostatin (SRIF) receptor subtype sst5, we characterized its internalization properties in transfected COS-7 cells using biochemical, confocal microscopic, and electron microscopic techniques. Our results demonstrated rapid and efficient sequestration of specifically bound [125I]Tyr0-D-Trp8-SRIF (up to 45% of bound radioactivity). Combined immunocytochemical detection of sst5 and visualization of a fluorescent SRIF analog by confocal microscopy revealed that whereas the internalized ligand progressively clustered toward the cell center with time, immunoreactive receptors remained predominantly associated with the plasma membrane. The preservation of cell surface receptors was confirmed by binding experiments on whole cells revealing a lack of saturability of [125I]Tyr0-D-Trp8-SRIF binding at 37 C. Binding was rendered saturable by the drug monensin, showing that receptor recycling played a key role in the preservation of cell surface receptors. Electron microscopy demonstrated that in addition to receptor recycling, internalization of receptor-ligand complexes triggered a massive recruitment of sst5 receptor molecules from intracellular stores to the membrane. This combination of recycling and recruitment of spare receptors may protect sst5 from long term down-regulation through sequestration and, therefore, facilitate extended SRIF signaling.

Experimental rabies virus infection of p75 neurotrophin receptor-deficient mice

The low-affinity neurotrophin (NT) receptor, p75(NTR), has complex biologic functions. A recent report provided evidence that the p75(NTR) is a rabies virus receptor in cultured BSR cells. We studied the experimental infection of 6-day-old p75(NTR)-deficient mice with the challenge virus standard strain of fixed rabies virus inoculated intracerebrally. The mice developed a fatal encephalitis. There were morphologic changes of apoptotic cell death involving neurons in widespread areas of the brain, which were associated with in situ evidence of oligonucleosomal DNA fragmentation. The findings were very similar to those that we previously reported in wild-type ICR mice of the same age. If the p75(NTR) is an important receptor of rabies virus in animal hosts, then a greater effect on the clinical and pathologic features of rabies virus-infected p75(NTR)-deficient mice would have been expected.

Basis of rabies virus neurovirulence in mice: expression of major histocompatibility complex class I and class II mRNAs

Expression of major histocompatibility complex (MHC) molecules on cells of the central nervous system (CNS) plays an important role in the pathogenesis of acute viral encephalitis. We have compared the induction of MHC class I and II mRNA transcripts in mice upon infection with the virulent challenge virus standard (CVS) strain of rabies virus and avirulent rabies virus variant RV194-2. Rabies virus antigen was detected with immunoperoxidase staining and 35S-labeled RNA probes were used to detect MHC class I and class II mRNA transcripts by in situ hybridization in infected brains. In CVS and RV194-2 infected animals, MHC class I mRNA expression occurred in the brain in neurons, glia, choroid plexus epithelial cells, ependymal cells, and inflammatory cells; expression was moderately higher in CVS-infected mice. In contrast, MHC class II mRNA expression was minimal in CVS-infected mice and it was markedly upregulated in CNS inflammatory cells upon RV194-2 infection. Both viruses induced an acute inflammatory reaction in the cerebrospinal fluid (CSF), which was more pronounced in CVS-infected mice. Both viruses also induced an antigen specific T and B cell response detectable in lymph nodes and spleen. These studies, which show a correlation between greater expression of MHC class II mRNA in the brain following intracerebral RV194-2 infection and protection against RV194-2 infection in the brain, suggest that recovery from avirulent rabies virus infection of neural cells involves T helper cells produced and/or retained in the brain for reasons that are not entirely clear.

Apoptosis in experimental rabies in bax-deficient mice

The challenge virus standard (CVS) of fixed rabies virus produces a fatal encephalitis in adult and suckling mice after intracerebral inoculation. The infection is associated with apoptotic cell death in brain neurons and increased immunoreactivity to the Bax protein in the hippocampus and cerebral cortex. Five- to 7-day-old bax-deficient mice and their wild-type littermates were inoculated intracerebrally with either CVS or the RV194-2 variant of rabies virus, which is avirulent in adult mice after intracerebral inoculation. The clinical disease was similar with both viruses in bax-deficient and wild-type mice with 100% mortality. CVS produced similar apoptotic changes in bax-deficient and wild-type mice, except that apoptosis was more marked in neurons of the dentate gyrus and cortical neurons in the wild-type mice. After inoculation with RV194-2, the morphologic changes of apoptosis were markedly less severe in the cerebral cortex, hippocampus, and cerebellum of the bax-deficient mice than wild-type mice. However, apoptotic changes were moderate to severe in the brain stem in both wild-type and bax-deficient mice with both viruses. Although apoptotic cell death was much less prominent in bax-deficient mice after inoculation with RV194-2, apoptosis of infected brain stem neurons occurred in this fatal infection. Although the Bax protein plays an important role in modulating rabies virus-induced apoptosis under specific experimental conditions, other modulators are also likely important.

Airway and tissue resistance in wheezy infants: effects of albuterol

We partitioned total respiratory system resistance into airway (Raw) and tissue (Rti) resistance in 16 sedated infants (age 15 to 88 wk) with a history of wheezing disorders before and after inhalation of albuterol. Using systems identification methods, airway (Raw-z) and tissue resistance (Rti-z) were extracted from measurements of respiratory system transfer impedance (Ztr[omega]) over a wide frequency range (typically, 4 < f < 140 Hz). Baseline Raw-z (80.6 +/- 31.5 cm H(2)O/L/s) was significantly (p < 0.01) reduced after albuterol inhalation (60.6 +/- 22.2 cm H(2)O/L/s) but pre- and postalbuterol Rti-z were not significantly different (2.3 +/- 1.7 and 2.7 +/- 2.4 cm H(2)O/L/s, respectively). Raw-z was compared with airway resistance measured with whole-body plethysmography (Raw-p) in 10 of the 16 infants. Raw-z and Raw-p were significantly different in baseline as well as postalbuterol conditions (86.4 +/- 36.9 versus 19.0 +/- 7.0, and 60.6 +/- 22.0 versus 22.5 +/- 14.7, respectively) and they were not correlated. There was no significant difference between Raw-p under baseline and postalbuterol conditions. We conclude that airway resistance estimated from Ztr measurements comprises the major portion of total resistance (approximately 97%) in infants with wheezing disorders in baseline as well as post-beta agonist inhalation, and it is significantly reduced by albuterol inhalation.

Subpopulations of GABAergic and non-GABAergic rat dorsal horn neurons express Ca2+-permeable AMPA receptors

Subpopulations of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors that are either permeable or impermeable to Ca2+ are expressed on dorsal horn neurons in culture. While both mediate synaptic transmission, the Ca2+ -permeable AMPA receptors provide a Ca2+ signal that may result in a transient change in synaptic strength [Gu, J.G., Albuquerque, C., Lee, C.J. & MacDermott, A.B. (1996) Nature, 381, 793]. To appreciate the relevance of these receptors to dorsal horn physiology, we have investigated whether they show selective expression in identified subpopulations of dorsal horn neurons. Expression of Ca2+-permeable AMPA receptors was assayed using the kainate-induced cobalt loading technique first developed by Pruss et al. [Pruss, R.M., Akeson, R.L., Racke, M.M. & Wilburn, J.L. (1991) Neuron, 7, 509]. Subpopulations of dorsal horn neurons were identified using immunocytochemistry for gamma-aminobutyric acid (GABA), glycine, substance P receptor (NK1 receptor) and the Ca2+-binding proteins, calretinin and calbindin D28K. We demonstrate that, in dorsal horn neurons in culture, kainate-induced cobalt uptake is selectively mediated by Ca2+-permeable AMPA receptors, and that a majority of GABA and NK1 receptor-expressing neurons express Ca2+-permeable AMPA receptors. GABAergic dorsal horn neurons are important in local inhibition as well as in the regulation of transmitter release from primary afferent terminals. NK1 receptor-expressing dorsal horn neurons include many of the projection neurons in the nociceptive spino-thalamic pathway. Thus, we have identified two populations of dorsal horn neurons representing important components of dorsal horn function that express Ca2+-permeable AMPA receptors. Furthermore, we show that several subpopulations of putative excitatory interneurons defined by calretinin and calbindin expression do not express Ca2+-permeable AMPA receptors.

Extraneural organ involvement in human rabies

Human rabies is a fatal encephalomyelitis. After the development of the central nervous system infection, there is centrifugal spread of the rabies virus to extraneural (systemic) organs. With histochemical staining and localization of rabies virus antigen (RVA) with immunoperoxidase staining, we have examined tissue sections of organs from 14 postmortem pediatric and adult cases of human rabies acquired in Mexico and the People's Republic of China. RVA was found in nerve plexuses in multiple organs, including the gastrointestinal tract. RVA was observed in muscle fibers of the heart, tongue, and larynx. RVA frequently was observed in the adrenal medulla with an associated inflammatory reaction. Minor salivary glands of the tongue contained RVA and major salivary glands showed RVA in plexuses, but not in either acini or ducts. Epithelial cells of the tongue and taste buds were occasionally infected. RVA was observed in hair follicles of the skin and rarely in pancreatic islets. The infection of extraneural organs was sometimes, but not always, associated with an inflammatory reaction. These findings indicate that centrifugal spread of rabies virus to extraneural organs occurs frequently in human rabies.

Clinical genetics of familial progressive supranuclear palsy

Recent studies have shown that progressive supranuclear palsy (PSP) could be inherited, but the pattern of inheritance and the spectrum of the clinical findings in relatives are unknown. We here report 12 pedigrees, confirmed by pathology in four probands, with familial PSP. Pathological diagnosis was confirmed according to recently reported internationally agreed criteria. The spectrum of the clinical phenotypes in these families was variable including 34 typical cases of PSP (12 probands plus 22 secondary cases), three patients with postural tremor, three with dementia, one with parkinsonism, two with tremor, dystonia, gaze palsy and tics, and one with gait disturbance. The presence of affected members in at least two generations in eight of the families and the absence of consanguinity suggests autosomal dominant transmission with incomplete penetrance. We conclude that hereditary PSP is more frequent than previously thought and that the scarcity of familial cases may be related to a lack of recognition of the variable phenotypic expression of the disease.

High-frequency respiratory impedance measured by forced-oscillation technique in infants

Measurements of respiratory input impedance (Zin) in infants using forced oscillations at the airway opening up to 256 Hz have been shown to include a first antiresonance (ar,1). We wondered whether features derived from high-frequency Zin change during methacholine-induced airway obstruction in infants, whether those changes could be explained by a lumped parameter model as in dogs (providing a value for respiratory resistance [Rrs]), or whether they are similar to Zin data in human adults with airway obstruction. In 13 wheezy infants (age 58 +/- 19 wk) Zin(omega) was assessed at baseline, and in nine infants after methacholine challenge, using a provocation dose defined by fall of more than 30% in VmaxFRC (rapid chest-compression technique). Following methacholine challenge, VmaxFRC decreased significantly (p < 0.0005), the frequency at which ar,1 occurred ( far,1) increased significantly (p = 0.0007), and the relative maximum in the real part at far,1 [Zinre( far,1)] increased significantly (p = 0.02), whereas Rrs did not change. We conclude that in wheezy infants ar,1 is highly sensitive to changes in lung mechanics. Although ar,1 cannot be explained by a simple lumped-parameter model, it is likely due to wave propagation phenomena, as in human adults. In either case, far,1 potentially contains information about airway wall compliance, which is important for the understanding of flow limitation in infant wheezing disorders.

High-frequency respiratory input impedance measurements in infants assessed by the high speed interrupter technique

High-frequency input impedance (Z(f)) measurements, including antiresonances, provide useful noninvasive information on airway geometry and especially airway wall mechanics in the canine and human adult respiratory system. A knowledge of airway wall mechanics would be particularly important in understanding flow limitation phenomena in infants. High-frequency Z(f) has not been measured in infants above 256 Hz, because the high impedance of the infantile respiratory system would be expected to result in low amplitudes of oscillatory flow at higher frequencies. The aim of this study was to develop a technique to measure high-frequency Z(f) in infants and to elucidate the nature of the antiresonance phenomena in the Z(f) spectrum in infants. Z(f) was measured from 32-900 Hz during rapid airflow interruption by the high-speed interrupter technique (HIT) in 18 infants (aged 24-149 weeks) with wheezing disorders. The HIT enables the excitement of higher flow amplitudes at high frequencies using a pseudostep forcing function. In all infants Z(f) showed a mean (SD) first antiresonance (far,1) of 172 (35) Hz (real part of Z(f) at far,1 (Z(f)re(far,1)): 4.9 (1.1) kPa x L(-1) x s) and in five infants a second antiresonance (far,2) of 564 (51) Hz (Z(f)re(far,2): 2.0 (0.7) kPa x L(-1) x s). The antiresonances were found to be related to wave propagation in the airways (acoustic antiresonances), because they increased by a factor of approximately 2 when He-O2 was inhaled. This implies that far,1 and its harmonics are a function of airway wall compliance. In conclusion, the first and second antiresonances may be helpful in understanding flow limitation in wheezing disorders in infants, because flow limitation is related not only to airway diameter but also to airway wall compliance.

Differences in airway wall compliance as a possible mechanism for wheezing disorders in infants

High-frequency input impedance measurements (Z(f)) provide useful noninvasive information on airway geometry and especially airway wall mechanics in the canine and human adult respiratory system. Using the high-speed interrupter technique (HIT), we have shown that it is possible to measure high-frequency Z(f) in infants up to 900 Hz, including antiresonant phenomena which are known to be related to wave propagation velocity. This implies that the first antiresonant frequency (far,1) is a function of airway wall compliance. Since, airway wall mechanics are particularly important for the flow limitation phenomena, we wondered whether we could find evidence that airway wall properties were important for the occurrence of flow limitation during incremental methacholine challenge in infants. We measured Z(f) from 32-900 Hz and maximal flow at functional residual capacity (V'maxFRC) by the rapid chest compression technique in 10 infants (aged 36-81 weeks) with wheezing disorders. far,1 increased significantly at very low doses of mch before any decline could be detected in V'maxFRC. We hypothesize that these changes in far,1 are determined by mch-induced decrease in airway wall compliance. High-speed interrupter technique in combination with rapid chest compression technique can be used to study developmental differences in airway function (particularly of airway wall properties) and their contribution to airway disease and response to bronchodilator therapy in infants.

Vocal cord paralysis and respiratory muscle weakness: an unusual presentation of chronic polyneuropathy

A case of chronic polyneuropathy that manifested with an unusual combination of vocal cord paralysis and respiratory muscle weakness is reported. In addition, results of an exercise test carried out to assess the severity and mechanisms of exertional breathlessness in this unique condition with combined obstructive and restrictive disorders are described.

Use of transfer impedance measurements for clinical assessment of lung mechanics

Respiratory transfer impedance (Ztr) measured using the forced oscillation technique requires virtually no patient cooperation and provides a noninvasive approach for acquiring data reflective of lung mechanics. Also, model analysis of Ztr provides reliable estimates of separate airway and tissue properties (1), but only if data out to 64 Hz are acquired. The current study evaluated the clinical utility of Ztr from 1-80 Hz for assessing the degree and type of impaired lung function. Spirometry and Ztr measurements were made on 37 individuals: 11 healthy subjects and 26 patients with lung disease including chronic obstructive pulmonary disease (COPD), asthma, lung cancer, and sarcoidosis. Over the entire patient group, 12 were also smokers. We first established normal ranges for several Ztr features and model estimated mechanical properties. The COPD and smokers groups showed significant differences in portions of their Ztr spectra from that of the healthy group. Key Ztr spectral features included R0, the frequency at which the real part of impedance is zero; and Re4, the real part of impedance at 4 Hz. The key model parameter was airway resistance, Raw. We found Raw, Re4, and R0 to be significantly elevated during disease (p < 0.0005) and to significantly decrease with bronchodilator therapy (p < 0.025). Moreover, we found moderate to strong correlations between R0, Raw, and Re4 versus FVC and R0 versus FEV1. After bronchodilator, changes in R0, Re4, and Raw were correlated with changes in several spirometric indices. The R0 feature has not been previously evaluated since it is typically above 32 Hz (well above 32 Hz in diseased individuals) and not encompassed in previous clinical studies.

Apoptotic cell death in experimental rabies in suckling mice

A fatal encephalomyelitis developed after intracerebral inoculation of 6-day-old ICR mice with the challenge virus standard (CVS) strain of fixed rabies virus. The brains of CVS-infected mice showed widespread morphologic changes of apoptosis, which were particularly prominent in pyramidal neurons of the hippocampus and in the cerebral cortex. Evidence of oligonucleosomal DNA fragmentation was sought in situ using the TUNEL method. TUNEL staining was observed in many neurons, and rabies virus antigen was usually demonstrated with immunoperoxidase staining in similar regions. Neurons in the dentate gyrus of the hippocampus demonstrated expression of viral antigen, apoptotic changes, and positive TUNEL staining. This region normally demonstrates little infection in CVS-infected adult mice. Double labeling of neurons with TUNEL and viral antigen indicated that infected neurons actually underwent apoptosis. Increased immunoreactivity against the Bax protein was demonstrated compared to uninfected mice. Purkinje cells expressed viral antigen, but did not show significant morphologic changes of apoptosis or TUNEL staining. In contrast, neurons in the external granular layer of the cerebellum did not express viral antigen, but demonstrated greater morphologic changes of apoptosis and positive TUNEL staining than uninfected controls. Apoptotic cell death likely plays an important role in the pathogenesis of rabies virus infection in suckling mice. There was evidence of more apoptosis in the brains of suckling mice than in those of adult mice and this finding explains the greater neurovirulence of rabies virus in younger mice. Rabies virus likely induces apoptosis in vivo by both direct and indirect mechanisms.

Determination of airway and tissue resistances after antigen and methacholine in nonhuman primates

Antigen challenge of Ascaris suum-sensitive animals has been used as a model of asthma in humans. However, no reports have separated total respiratory resistance into airway (Raw) and tissue (Rti) components. We compared input impedance (Zin) and transfer impedance (Ztr) to determine Raw and Rti in anesthetized cynomolgus monkeys under control and bronchoconstricted conditions. Zin data between 1 and 64 Hz are frequency dependent during baseline conditions, and this frequency dependence shifts in response to A. suum or methacholine. Thus it cannot be modeled with the DuBois model, and estimates of Raw and Rti cannot be determined. With Ztr, baseline data were much less variable than Zin in all monkeys. After bronchial challenge with A. suum or methacholine, the absolute amplitude of the resistive component of Ztr increased and its zero crossing shifted to higher frequencies. These data can estimate Raw and Rti with the six-element DuBois model. Therefore, in monkeys, Ztr has advantages over other measures of lung function, since it provides a methodology to separate estimates of Raw and Rti. In conclusion, Ztr shows spectral features similar to those reported in healthy and asthmatic humans.

Apoptosis plays an important role in experimental rabies virus infection

Cultured rat prostatic adenocarcinoma (AT3) cells infected with the challenge virus standard (CVS) strain of fixed rabies virus showed characteristic morphologic features of apoptosis, evidence of oligonucleosomal DNA fragmentation, and expression of the Bax protein. CVS-infected Bcl-2-transfected AT3 cells did not demonstrate these features. Adult ICR mice inoculated intracerebrally with CVS showed morphologic changes of apoptosis, DNA fragmentation, and increased Bax expression in neurons, with changes most marked in the hippocampus and cerebral cortex. Ultrastructurally, some neurons demonstrated morphologic features more typical of necrosis. These studies provide evidence that apoptosis plays an important role in the pathogenesis of rabies virus infection.