Strain Guinea Pigs Research Articles

Cutting edge: guinea pigs with a natural C3a-receptor defect exhibit decreased bronchoconstriction in allergic airway disease: evidence for an involvement of the C3a anaphylatoxin in the pathogenesis of asthma.

Asthma is a major cause of morbidity worldwide with prevalence and severity still increasing at an alarming pace. Hallmarks of this disease include early-phase bronchoconstriction with subsequent eosinophil infiltration, symptoms that may be mimicked in vivo by the complement-derived C3a anaphylatoxin, following its interaction with the single-copy C3aR. We analyzed the pathophysiological role of the C3a anaphylatoxin in a model of experimental OVA-induced allergic asthma, using an inbred guinea pig strain phenotypically unresponsive to C3a. Molecular analysis of this defect revealed a point mutation within the coding region of the C3aR that creates a stop codon, thereby effectively inactivating gene function. When challenged by OVA inhalation, sensitized animals of this strain exhibited a bronchoconstriction decreased by approximately 30% in comparison to the corresponding wild-type strain. These data suggest an important role of C3a in the pathogenesis of asthma and define a novel target for drug intervention strategies.

Does inhibition of tumor necrosis factor alpha affect chlamydial genital tract infection in mice and guinea pigs?

The role of tumor necrosis factor alpha (TNF-alpha) in host defense against chlamydial infection remains unclear. In order to further evaluate the relevance of TNF-alpha to host resistance in chlamydial genital tract infection, we examined the effect of local inhibition of the TNF-alpha response in normal C57 mice and in interferon gamma gene-deficient C57 mice infected intravaginally with the mouse pneumonitis agent of Chlamydia trachomatis. Since the guinea pig model of female genital tract infection more closely approximates the human in terms of ascending infection and development of pathology, we also examined the effect of local inhibition of the TNF-alpha response in guinea pigs infected intravaginally with the guinea pig strain of Chlamydia psittaci. We successfully blocked the early TNF-alpha response in the respective animal models. This blockade had no effect on the numbers of organisms isolated from the genital tract during the time of TNF-alpha inhibition in mice or guinea pigs. Analysis of interleukin-1beta, macrophage inflammatory protein-2, and granulocyte macrophage-colony stimulating factor in the mouse model revealed that blockade of the TNF-alpha response did not alter the release of these proinflammatory proteins. Yet, in TNF-alpha-depleted mice, increased numbers of neutrophils were detected in the genital tract, and, in TNF-alpha-depleted guinea pigs, increased numbers of neutrophils as well as infiltrating lymphocytes were seen in the endocervix. Blockade of TNF-alpha does not affect the level of infection in mice or guinea pigs, but it may decrease TNF-alpha-induced apoptosis of infiltrating inflammatory cells.

A C3a-receptor defective guinea pig strain exhibits decreased bronchial reactivity in an ovalbumin-induced asthma model

A C3a-receptor defective guinea pig strain exhibits decreased bronchial reactivity in an ovalbumin-induced asthma model

Recombinant RNA replicons derived from attenuated Venezuelan equine encephalitis virus protect guinea pigs and mice from Ebola hemorrhagic fever virus

RNA replicons derived from an attenuated strain of Venezuelan equine encephalitis virus (VEE), an alphavirus, were configured as candidate vaccines for Ebola hemorrhagic fever. The Ebola nucleoprotein (NP) or glycoprotein (GP) genes were introduced into the VEE RNA downstream from the VEE 26S promoter in place of the VEE structural protein genes. The resulting recombinant replicons, expressing the NP or GP genes, were packaged into VEE replicon particles (NP–VRP and GP–VRP, respectively) using a bipartite helper system that provided the VEE structural proteins in trans and prevented the regeneration of replication-competent VEE during packaging. The immunogenicity of NP–VRP and GP–VRP and their ability to protect against lethal Ebola infection were evaluated in BALB/c mice and in two strains of guinea pigs. The GP–VRP alone, or in combination with NP–VRP, protected both strains of guinea pigs and BALB/c mice, while immunization with NP–VRP alone protected BALB/c mice, but neither strain of guinea pig. Passive transfer of sera from VRP-immunized animals did not confer protection against lethal challenge. However, the complete protection achieved with active immunization with VRP, as well as the unique characteristics of the VEE replicon vector, warrant further testing of the safety and efficacy of NP–VRP and GP–VRP in primates as candidate vaccines against Ebola hemorrhagic fever.

Phage infection of the obligate intracellular bacterium, Chlamydia psittaci strain Guinea Pig Inclusion Conjunctivitis

The infectious cycle of φCPG1, a bacteriophage that infects the obligate intracellular pathogen, Chlamydia psittaci strain Guinea Pig Inclusion Conjunctivitis, was observed using transmission electron microscopy of phage-hyperinfected, Chlamydia-infected HeLa cells. Phage attachment to extracellular, metabolically dormant, infectious elementary bodies and cointernalisation are demonstrated. Following entry, phage infection takes place as soon as elementary bodies differentiate into metabolically active reticulate bodies. Phage-infected bacteria follow an altered developmental path whereby cell division is inhibited, producing abnormally large reticulate bodies, termed maxi-reticulate bodies, which do not mature to elementary bodies. These forms eventually lyse late in the chlamydial developmental cycle, releasing abundant phage progeny in the inclusion and, upon lysis of the inclusion membrane, into the cytosol of the host cell. Structural integrity of the hyperinfected HeLa cell is markedly compromised at late stages. Released phage particles attach avidly to the outer leaflet of the outer membranes of lysed and unlysed Chlamydiae at different stages of development, suggesting the presence of specific phage receptors in the outer membrane uniformly during the chlamydial developmental cycle. A mechanism for phage infection is proposed, whereby phage gains access to replicating chlamydiae by attaching to the infectious elementary body, subsequently subverting the chlamydial developmental cycle to its own replicative needs. The implications of phage infection in the context of chlamydial infection and disease are discussed.

Effects of growth factors and cytokines on proteoglycan and collagen synthesis by chondrocytes in guinea pigs with spontaneous osteoarthritis

We examined the effects of various growth factors and cytokines on proteoglycan (PG) and collagen synthesis by chondrocytes isolated from osteoarthritic and normal articular cartilage of Hartley strain guinea pigs. The guinea pig represents a useful animal model of spontaneous osteoarthritis (OA). Cartilage tissue samples were obtained from the knee joints of under-3-month-old guinea pigs (control group) as well as 5- to 8-month-old guinea pigs with OA changes (OA group). Chondrocytes were isolated enzymatically and maintained in suspension culture. Growth factor addition groups were then prepared from both the OA group and the control group, using the factors TGF-β, bFGF, and IGF-1 (1.25 ng/ml each). Cytokine addition groups were also prepared using IL-1α and IL-1β (10 ng/ml each). An addition group was also prepared for sodium hyaluronate (HA) (500 μg/ml). In each group, 35S was added as a PG metabolic marker, 3H-proline was added as a collagen metabolic marker, and the groups were cultured. Next, 35S and 3H-proline uptake was measured by a liquid scintillation counter. The results revealed that (1) both PG synthesis and collagen synthesis were promoted significantly more in OA chondrocytes than in normal chondrocytes; (2) with the addition of growth factors, PG and collagen synthesis was enhanced in OA chondrocytes; and (3) PG synthesis and collagen synthesis were inhibited in both normal and OA chondrocytes with the addition of IL-1α and -β. This result suggests that the repair function is activated more in OA chondrocytes than in normal chondrocytes, thereby promoting the synthesis of the cartilage matrix by chondrocytes. This synthesizing capability is enhanced and acts to effectively repair degenerative articular cartilage further through the addition of growth factors.

Central GABAergic innervation of the mammalian pineal gland: a light and electron microscopic immunocytochemical investigation in rodent and nonrodent species.

Light and electron microscopic immunocytochemical observations were made to demonstrate central pinealopetal fibers immunoreactive for gamma-aminobutyric acid (GABA) and synapses between their terminals and pinealocytes in the pineal gland of four rodent (Wistar-King rat; mouse; Syrian hamster, Mesocricetus auratus; Hartley strain guinea pig) and one nonrodent (tree shrew, Tupaia glis) species. GABA-immunoreactive myelinated and unmyelinated fibers and endings were found in the parenchyma of the pineal gland of all the animals examined. In the rodent species, GABAergic fibers were mainly found in the intermediate and proximal portions of the pineal gland and were nearly or entirely absent in the distal portion of the gland. Abundant GABAergic fibers were evenly distributed throughout the gland of the tree shrew. In all the animals, the habenular and posterior commissures contained abundant GABA-positive fibers, and some of them were followed to the pineal gland. GABA-positive endings made synaptic contact with pinealocytes, occasionally in mice and guinea pigs, and frequently in tree shrews; no synapses were observed in Syrian hamsters and rats. In the pineal gland of all the animals, GABA-immunoreactive cell bodies were not detected, and sympathetic fibers were not immunoreactive for GABA. These data indicate that GABAergic fibers are main pinealopetal projections from the brain. In view of the difference in the distribution of these fibers, central GABAergic innervation may play a more significant role in nonrodents than in rodents. The frequent occurrence of GABAergic synapses on pinealocytes in the tree shrew suggests that GABA released at these synapses directly controls activity of pinealocytes of this animal.

PKC translocation without changes in Galphaq and PLC-beta protein abundance in cardiac hypertrophy and failure.

Activation of protein kinase C (PKC) has been implicated as playing a key role in the pathogenesis of cardiac hypertrophy. This study investigates the response of several signal transduction proteins responsible for PKC activation during the transition from compensated pressure-overload hypertrophy (POH) to congestive heart failure (CHF). Pressure overload was produced on male, adult, Hartley strain guinea pigs using a ligature around the descending thoracic aorta. Sham-operated controls, POH, and CHF groups were identified based on left ventricular hypertrophy, pulmonary congestion, and isolated heart Langendorff mechanics. Quantitative immunoblotting revealed phospholipase C (PLC)-betaI and Galphaq were unchanged during POH and CHF, as were RGS2, RGS3, and RGS4 (regulators of G protein signaling, which are activators of intrinsic GTPase activity). Translocation of PKC-alpha, -epsilon, and -gamma from cytosolic to membranous fractions were significantly increased during POH and CHF. Cytosolic PKC activity was also elevated during POH. We conclude that differential PKC activation may be mediated by increases in Galphaq and PLC-betaI activity rather than upregulation of expression.

Reporter expression persists 1 year after adeno-associated virus-mediated gene transfer to the optic nerve.

To determine the foci and duration of protein expression following virus-mediated gene transfer to the optic nerve. A cytomegalovirus (CMV) promoter was linked to a lacZ-SV40 polyA reporter gene or a humanized green fluorescent protein (hgfp) reporter gene, then inserted into a bacterial plasmid containing adeno-associated virus (AAV) terminal repeat sequences. The CMV-lacZ or the CMV-hgfp construct were injected into the vitreous cavity of strain-13 guinea pigs. Controls consisted of eyes injected with AAV without the promoter and reporter elements or eyes that received no injections. The eyes and optic nerves were processed for beta-galactosidase immunohistochemistry and hgfp fluorescence analyses. Cellular transduction at the messenger RNA (mRNA) level was evaluated by in situ reverse transcription-polymerase chain reaction. Weekly fundus photography, done for 1 month, documented the absence of any ocular abnormality due to the viral injections. No in vivo hgfp fluorescence of the retina was visualized. Beta-galactosidase histochemical analysis of eye cups that received the lacZ gene construct showed blue lacZ staining of the optic nerve head at 2 weeks. Light microscopy revealed the blue beta-galactosidase reaction product in fibers, glial cells, and blood vessels of the optic nerve head and retrobulbar nerve. Histochemistry showed absence of beta-galactosidase in the optic nerve at 3 to 12 months, but immunochemistry showed the persistence of beta-galactosidase in fibers, glial cells, and blood vessels as late as 1 year after a single ocular injection. In the retina, histochemical staining showed evidence of lacZ at 3 months, but not later. In situ reverse transcription-polymerase chain reaction revealed brown lacZ mRNA reaction product in ganglion cells of the retina. Control eyes that received AAV without the promoter and reporter elements and the eyes that received no viral injections and were processed for beta-galactosidase showed no reporter gene expression in any ocular tissue or cell type. Viral-mediated gene transfer can be successfully accomplished in the optic nerve. Further evaluation is needed to determine whether the level of protein expression at 1 year after injection, which is clearly reduced relative to shorter postinjection time, is sufficient for therapeutic purposes. We have previously shown that gene therapy with catalase suppressed experimental optic neuritis at 1 month after injection. Viral-mediated gene transfer may be a powerful technique for the treatment of optic neuropathies, particularly for recurrences of optic neuritis, if long-term expression of transduced protein can be demonstrated in the optic nerve.

Bone remodeling in osteoarthritis: subchondral and osteophytic responses

OSTEOARTHRITIS can be considered a collective endstage for heterogeneous etiopathologic conditions a#ecting joint tissues. Such etiopathologic factors are multifactorial and include biochemical, enzymatic, genetic and biomechanical factors amongst others. Characteristic pathologic findings include joint space narrowing, peripheral osteophytes, subchondral bony sclerosis and cyst formation. Although commonly considered a disease primarily involving cartilage, studies support variable roles for synovium, muscle, ligaments and bone. Radin and co-workers [1, 2] suggested an important role for subchondral bone changes as an etiologic factor in the early development of degenerative joint disease. Repetitive impulsive loading resulted in early responses characterized by increased bone formation, associated with relative sti#ening of bone; articular cartilage degeneration followed [3]. Subchondral bone changes preceding cartilage damage in osteoarthritis have been demonstrated in other animal models. Examination of trabecular bone within the femoral head of Hartley strain guinea pigs, a strain predisposed to osteoarthritis, demonstrated subchondral trabecular remodeling as an early event in this model of OA [4]. Serial observations in this model utilizing magnetic resonance imaging revealed significant progression of subchondral sclerosis as well as osteophytes during disease development [5]. A longitudinal study of subchondral bone responses in dogs undergoing anterior cruciate ligament transection revealed subchondral sclerosis at 18 months and 54 months, but not at 3 months; findings were associated with loss of subchondral trabecular bone at all three time points. Findings suggested that bony changes were associated with progression of cartilage degeneration, rather than initial development [6]. Experimentally induced osteoarthritis following partial meniscectomy (PM) in the rabbit was associated with prominent osteophyte formation [7]. Increased cellular replication was noted early (at

The time-dependent clearance of virulent Treponema pallidum in susceptible and resistant strains of guinea pigs is significantly different.

The kinetics of clearance of Treponema pallidum spp. pallidum Nichols from skin and testes of susceptible C4-deficient (C4D) and -resistant Albany (Alb) strains of guinea pigs (gps) was evaluated using the polymerase chain reaction (PCR) and the rabbit infectivity test (RIT). For each strain there were two groups of animals, one infected with virulent T. pallidum (TP) and one control injected with heat-killed treponemes (HKTP). The kinetic studies and their statistical analysis showed that in the C4D strain the microbial clearance in both tissues was significantly slower (p < 0.005) and still incomplete at 3 months after infection. In the Alb strain the clearance was faster and apparently completed within a month. A greater permissiveness in bacterial growth in C4D compared to Alb appears to be one critical factor determining the different rate of local elimination after primary infection. In both strains there was some correlation between the severity and duration of cutaneous lesions and the local persistence of viable organisms. This correlation was not observed in testes. These studies suggest a genetic basis for the strain-specific susceptibility and resistance phenotypes in the pathogenesis of syphilis.

Superoxide mediates cigarette smoke-induced infiltration of neutrophils into the airways through nuclear factor-kappaB activation and IL-8 mRNA expression in guinea pigs in vivo.

We examined the hypothesis that superoxide mediates infiltration of neutrophils to the airways through nuclear factor (NF)-kappaB and interleukin-8 (IL-8) after acute exposure to cigarette smoke (CS) in vivo. Male Hartley strain guinea pigs were exposed to air or 20 puffs of CS and killed 5 h after the exposure. The differential cell count of bronchoalveolar lavage fluid and specific myeloperoxidase enzyme assay demonstrated that acute exposure to CS caused neutrophil accumulation to the airways and parenchyma, respectively. Acute exposure to CS increased DNA-binding activity of NF-kappaB in the lung. Acute exposure to CS also increased IL-8 messenger RNA (mRNA) expression in the lung. Pretreatment of guinea pigs with recombinant human superoxide dismutase (rhSOD) aerosols reduced the CS-induced neutrophil accumulation to the airways. Both activation of NF-kappaB and increased IL-8 mRNA expression were also inhibited by the pretreatment of rhSOD aerosols. Strong immunoreactivities for p65 and p50 were detected in the nuclei of alveolar macrophages after acute exposure to CS. The signal for IL-8 mRNA expression was demonstrated in the alveolar space after acute exposure to CS. Neither significant immunoreactivities for p65 and p50 nor IL-8 mRNA signals were observed in airway epithelium. These observations suggest that acute exposure to CS initiates superoxide-dependent mechanism that, through NF-kappaB activation and IL-8 mRNA expression, produces infiltration of neutrophils to the airways in vivo. It was also suggested that the alveolar macrophage is one potential source of NF-kappaB activation and IL-8 mRNA expression after acute exposure to CS.

Roles of oxygen radicals and elastase in citric acid-induced airway constriction of guinea-pigs.

Antioxidants attenuate noncholinergic airway constriction. To further investigate the relationship between tachykinin-mediated airway constriction and oxygen radicals, we explored citric acid-induced bronchial constriction in 48 young Hartley strain guinea-pigs, divided into six groups: control; citric acid; hexa(sulphobutyl)fullerenes + citric acid; hexa(sulphobutyl)fullerenes + phosphoramidon + citric acid; dimethylthiourea (DMTU) + citric acid; and DMTU + phosphoramidon + citric acid. Hexa(sulphobutyl)fullerenes and DMTU are scavengers of oxygen radicals while phosphoramidon is an inhibitor of the major degradation enzyme for tachykinins. Animals were anaesthetized, paralyzed, and artificially ventilated. Each animal was given 50 breaths of 4 ml saline or citric acid aerosol. We measured dynamic respiratory compliance (Crs), forced expiratory volume in 0.1 (FEV0.1), and maximal expiratory flow at 30% total lung capacity (Vmax30) to evaluate the degree of airway constriction. Citric acid, but not saline, aerosol inhalation caused marked decreases in Crs, FEV0.1 and Vmax30, indicating marked airway constriction. This constriction was significantly attenuated by either hexa(sulphobutyl)fullerenes or by DMTU. In addition, phosphoramidon significantly reversed the attenuating action of hexa(sulphobutyl)fullerenes, but not that of DMTU. Citric acid aerosol inhalation caused increases in both lucigenin- and t-butyl hydroperoxide-initiated chemiluminescence counts, indicating citric acid-induced increase in oxygen radicals and decrease in antioxidants in bronchoalveolar lavage fluid. These alterations were significantly suppressed by either hexa(sulphobutyl)fullerenes or DMTU. An elastase inhibitor eglin-c also significantly attenuated citric acid-induced airway constriction, indicating the contributing role of elastase in this type of constriction. We conclude that both oxygen radicals and elastase play an important role in tachykinin-mediated, citric acid-induced airway constriction.

Spontaneous cytokine gene expression in normal guinea pig blood and tissues

The authors report, for the first time, the cloning, characterization and sequencing of guinea pig cDNAs for interleukin (IL)-2, IL-10, IL-12p40, and transforming growth factor β (TGF-β). Partial cDNAs for two additional cytokines, IL-1α and TNF-α, whose sequences are present in the GenEMBL database, were also cloned. The IL-10 clone is a full-length cDNA, while the remaining clones are partial cDNAs. The guinea pig cDNA sequences have high identity with their mouse and human counterparts. Northern blot analysis revealed that the guinea pig transcripts range in size from 1.0 kb to 2.2 kb. The constitutive expression of cytokines in two strains of guinea pig (C4D, Albany) that differ in susceptibility to infection with Treponema pallidum was examined. Since susceptibility to T. pallidum is also age dependent, both neonates and adults were examined. Spontaneous cytokine expression was examined in peripheral blood, skin, spleen, lymph node, brain, and peritoneal cells. In skin, lymph node, and peripheral blood, very low levels of IL-1α, IL-12p40, tumour necrosis factor α (TNF-α), and TGF-β and moderate levels of IL-2 and IL-10 were observed. Cytokine gene expression was not observed in spleen and brain. Peritoneal cells expressed only TGF-β. Age- and strain-associated differences were not observed, except for IL-12p40, which was elevated in guinea pigs resistant to T. pallidum infection (C4D neonates, Albany adults).

An animal model of autism: behavioural studies in the GS guinea-pig

Autism is a human behavioural pathology marked by major difficulties in abnormal socialization, language comprehension and stereotypic motor patterns. These behavioural abnormalities have been associated with corticocerebral and cerebellar abnormalities in autistic patients, particularly in vermal folia VI and VII. Progress in understanding this disease has been hindered by the absence of a non-primate animal model. GS guinea-pigs are a partially inbred, non-ataxic guinea-pig strain with cerebellar and corticocerebral abnormalities similar to those reported to exist in human patients with autism. In order to determine if GS guinea-pigs represent an animal model of autism, their behaviour was compared with that of Hartley strain guinea-pigs. GS animals learned a motor task significantly more rapidly than Hartley guinea-pigs, but performed it in a more stereotypic manner and were less influenced by environmental stimuli than Hartleys. GS animals exhibited significantly less exploratory behaviour in a novel environment and were significantly less responsive to 50–95 dBA pure tones than Hartley guinea-pigs. In a social interaction assay, GS guinea-pigs interacted significantly less frequently with each other or with Hartley guinea-pigs than Hartleys did under the same conditions. GS behaviour thus exhibits autistic-like behaviour patterns: motor stereotypy, lack of exploration and response to environment and poor social interaction. Coupled with the neuropathological findings, this abnormal behaviour suggests that GS guinea-pigs could be a useful animal model of autism.

An animal model of autism: behavioural studies in the GS guinea-pig.

Autism is a human behavioural pathology marked by major difficulties in abnormal socialization, language comprehension and stereotypic motor patterns. These behavioural abnormalities have been associated with corticocerebral and cerebellar abnormalities in autistic patients, particularly in vermal folia VI and VII. Progress in understanding this disease has been hindered by the absence of a non-primate animal model. GS guinea-pigs are a partially inbred, non-ataxic guinea-pig strain with cerebellar and corticocerebral abnormalities similar to those reported to exist in human patients with autism. In order to determine if GS guinea-pigs represent an animal model of autism, their behaviour was compared with that of Hartley strain guinea-pigs. GS animals learned a motor task significantly more rapidly than Hartley guinea-pigs, but performed it in a more stereotypic manner and were less influenced by environmental stimuli than Hartleys. GS animals exhibited significantly less exploratory behaviour in a novel environment and were significantly less responsive to 50-95 dBA pure tones than Hartley guinea-pigs. In a social interaction assay, GS guinea-pigs interacted significantly less frequently with each other or with Hartley guinea-pigs than Hartleys did under the same conditions. GS behaviour thus exhibits autistic-like behaviour patterns: motor stereotypy, lack of exploration and response to environment and poor social interaction. Coupled with the neuropathological findings, this abnormal behaviour suggests that GS guinea-pigs could be a useful animal model of autism.

Modification of Maternal CMV by Pre-infection α-gB Antibody Transfer in Guinea Pigs † 821

Inbred JY-9 strain guinea pigs (gp) were infected with gpCMV in early pregnancy. 7 pregnant dams were treated with pooled hyperimmune serum from non-infected animals previously immunized with glycoprotein B (gB), on days 0, 2 and 5, day 1 being the day of infection. 6 control pregnant dams received pooled non-immune(NI) serum as above. NI dams appeared sicker and had 83% pregnancy loss by in utero resorption and abortion compared to 14% in passively immunized (PI) dams(p<0.01). Mean placental weight was 4.3g in NI dams and 5.6g in PI dams(p=0.02). Mean pup weight was 9.8g in NI dams and 31.5g in PI dams(p<0.02). Mean pup length was 3.7cm in NI dams vs. 6.6cm in PI dams(p<0.02). All maternal blood cultures were positive on day 7 post-infection. On day 12-14, 83% of NI dams vs. 28% PI dams had positive blood cultures(p<0.05). Placental tissue cultures were positive in 80% of NI dams compared to 33% of PI dams(p<0.05). Pup tissue cultures were positive in 50% of NI dams compared to 25% of PI dams(NS). All placentae showed features of immaturity consistent with mid-term gestation, on H&E stains. NI placentae had marked lobular congestion with focal mononuclear cell infiltrates in the lobules and foci of necrosis with neutrophilic infiltrates in the trophoblastic septae. Less severe mononuclear cell infiltrates and no necrosis or neutrophilic infiltrates were seen in PI placentae. Frozen sections of PI placentae showed less disorganization of structure with decreased number of infected cells by immunoperoxidase stains. Passive transfer of anti-gB serum initiated 24 hours pre-infection does not prevent, but significantly modifies the effects of primary maternal CMV.

Strain differences in adrenal microsomal steroid metabolism in guinea pigs

We recently reported that CYP2D16, a xenobiotic-metabolizing P450 isozyme, was expressed at higher levels in adrenal microsomes from inbred Strain 13 guinea pigs than in those from outbred English Short Hair (ESH) animals. Studies were done to determine if there also were strain differences in adrenal microsomal steroid metabolism. In both inner (zona reticularis) and outer (zona fasciculata plus zona glomerulosa) zone preparations of the adrenal cortex, 21-hydroxylase activities were greater in microsomes from ESH than from Strain 13 guinea pigs. By contrast, 17 α-hydroxylase activities were similar in the two strains. In both strains, 21-hydroxylase activities were greater in inner than outer zone microsomes, but the opposite was found for 17 α-hydroxylase activities (outer>inner). Northern and Western analyses revealed higher levels of CYP21 mRNA and protein in adrenals from ESH than Strain 13 guinea pigs, but there were no strain differences in CYP17 mRNA or protein concentrations. Despite the zonal differences in adrenal 17 α-hydroxylase and 21-hydroxylase activities, CYP17 and CYP21 mRNA and protein levels were similar in the inner and outer zones within each strain of guinea pig. The results demonstrate strain differences in microsomal steroid metabolism that are explained by differences in CYP21 expression. By contrast, the zonal differences in steroid hydroxylase activities may be attributable to post-translational mechanisms.

Histological study of spontaneous osteoarthritis in the knee joint of guinea pigs

The process of spontaneous OA in female Hartley strain guinea pigs was examined, in terms of age-related changes, using pathohistological, immunohistological, and histomorphometric techniques. Histological changes in the knee joints began to appear at age 3 months; these consisted of a decrease in chondrocytes in sites in the tangential zone not covered with the meniscus. At these sites, fibrillation occurred at age 5 months, and extended to the radial zone at ages 8-12 months. The incidence of fibrillation was 0% at age 3 months, 50% at age 5 months, and 100% at age 8 months. At ages 1 and 3 months, almost all chondrocytes in the tangential zone were matrix metalloproteinase-1 (MMP-1)-positive, and the positive chondrocytes extended to the deeper zones with age, concomitantly with fibrillation of the cartilage matrix. Clusters of chordrocytes at ages 12 and 18 months old were MMP-1-positive. Cartilage thickness began to decline significantly only at age 18 months. Animals that showed fibrillation had a slightly higher bone volume, significantly greater trabecular thickness, and significantly smaller bone surface than the non-fibrillation group. Guinea pigs may be a useful OA animal model for studying the pathogenesis, pathology, and pharmacotherapy of this disease.

Type III secretion genes identify a putative virulence locus of Chlamydia.

Four genes of Chlamydia psittaci strain guinea pig inclusion conjunctivitis (GPIC), whose predicted products are highly homologous to structural and regulatory components of a contact-dependent or type III secretion apparatus, were isolated. Related to genes present in several animal and plant bacterial pathogens, these genes may represent a section of a previously undetected chromosomal virulence locus analogous to several recently described virulence-associated type III secretion loci. The existence of contact-dependent secretion in Chlamydia strongly suggests that these bacteria use pathogenic mechanisms that are similar to those of other intracellular bacterial pathogens. Unlike other intracellular bacteria, however, chlamydiae are metabolically inactive extracellularly and only become capable of global protein synthesis several hours after infection. This implies that chlamydial contact-dependent secretion is only active from within, uniquely after the bacteria have been internalized by eukaryotic cells. The possible role(s) of this pathway in chlamydial pathogenesis are discussed.