New endogenous herpesvirus of guinea pigs: biological and molecular characterization.

Two known guinea pig herpesviruses, guinea pig cytomegalovirus (GPCMV) and guinea pig herpes-like virus (GPHLV), and well characterized. A third herpesvirus (GPXV) was originally isolated from leukocytes of healthy strain 2 guinea pigs. Growth of GPXV in guinea pig embryo fibroblastic cells produced a characteristic cytopathic effect. Electron microscopy of guinea pig cells infected with GPXV revealed the morphological development of a herpesvirus. Cross-neutralization tests and immunoferritin electron microscopy demonstrated that GPXV, GPCMV, and GPHLV were serologically distinct herpeviruses of guinea pigs. To confirm the distinction between these three herpesviruses, DNA genomes were compared by CsCl equilibrium buoyant density measurements and restriction endonuclease cleavage analysis. 32P-labeled viral DNA ws obtained from nucleocapsids isolated from virus-infected cells, and the buoyant density of GPXV DNA differed from that of GPCMV and GPHLV. Cleavage of viral DNAs with restriction endonucleases followed by gel electrophoresis revealed distinct patterns for each virus.     

Guinea pig homologues of TL and QA-2 antigens.

The H-2, thymus-leukemia (TL), and Qa-2 antigens of mice are encoded by closely linked genes on murine chromosome 17, and have structural similiarity in that each antigen is borne on a approximately 44,000 dalton molecule associated with beta2 microglobulin (beta2mu). The extensive homology of major histocompatibility complex (MHC) products that exists for the mouse and guinea pig suggested that a similar homology might exist for products of genetic regions closely linked to the MHC. By taking advantage of the selective association of beta2mu with H-2, Qa-2, and TL antigens, and by using the technique of sequential immunoprecipitation, we demonstrated two previously undescribed guinea pig molecules reactive with anti-guinea pig beta2mu. The first molecule was composed of a 36,000 dalton glycoprotein associated with beta2mu and was found on guinea pig thymocytes, but not lymphocytes. The second molecule was composed of a 40,000 dalton glycoprotein associated with beta2mu, and was found on both guinea pig thymocytes and lymphocytes. By structure, chemical composition, association with beta2mu, and tissue distribution, the first molecule is an attractive candidate for the guinea pig homologue of TL antigen, whereas the second fits the criteria for the guinea pig homologue of Qa-2 antigen.     

Tissue distribution of cholesterol feedback control in the guinea pig.

The level of cholesterol synthesis and the activity of the cholesterol feedback system were studied in tissue slices from a number of organs of the guinea pig. In contrast to the tissue distribution of sterol synthesis in the rat, liver slices of the guinea pig have a low rate of sterologenesis, with ileum and lung being the most active sterologenic tissues. More surprising, all tissues studied in the guinea pig, including lung, ileum, and brain, were shown to possess an active cholesterol feedback system. The basis for the widespread organ distribution of cholesterol feedback control in the guinea pig is probably the ability of the various tissues of the guinea pig to take up and concentrate exogenous cholesterol and is not the result of any inherent differences in the lipoprotein composition in this species.     

Calcium uptake and calcium release by subcellular fractions of smooth muscle. II. Kinetics of calcium uptake by microsomes and mitochondria from pig coronary artery and guinea pig ileum.

Calcium uptake by the microsomal and mitochondrial fractions of pig coronary artery and guinea pig ileum was studied in the presence of ATP, ATP plus oxalate and without ATP and oxalate. Microsomes and mitochondria of both smooth muscles were found to be unable to accumulate appreciable amounts of calcium in the absence of ATP. Oxalate noticeably stimulated the calcium uptake of the mitochondrial fraction from pig coronary artery but had little effect on calcium uptake by the microsomal fraction of this smooth muscle. The calcium uptake of microsomes and mitochondria from guinea pig ileum was not or only slightly enhanced by oxalate. There are typical kinetics regarding the time course and the extent of calcium uptake by microsomes and mitochondria from pig coronary artery and guinea pig ileum. In comparison, considerable qualitative and quantitative differences between both smooth muscles are observed. The high ATP-dependent calcium uptake capacity of the mitochondria from pig coronary artery and guinea pig ileum are a further argument for the hypothesis that these organelles may play an important role in the contraction-relaxation mechanism of smooth muscle.     

Cloning of the guinea pig 5-lipoxygenase gene and nucleotide sequence of its promoter.

The guinea pig 5-lipoxygenase (5-LO) gene and its promoter were cloned from a guinea pig genomic DNA library. Sequencing analysis of the guinea pig promoter revealed that expression of the 5-LO gene in this rodent is probably governed by cis acting nucleotide sequences quite similar to the human gene. Nucleotide sequences that bind factors like Sp-1, AP-2, NF-kB and c-Ha-ras were identified in the guinea pig 5-LO promoter region.     

A Quantitative study of histamine H2-receptor bockade by burimamide in isolated artica.

The onset of burimamide inhibition of histamine stimulation of rabbit atria is rapid, and a near steady-state blockade occurs at approximately 15 min ( larger than or equal to 90% complete). The blockade is reversible but requires several washings suggesting the disassociation is slow. The administration of histamine may accelerate the decay of the burimamide effect. Reciprocal plots (rate response versus histamine concentration) of dose-response curves are linear for both rabbit and guinea pig atria. In the presence of low concentrations of burimamide; (2.4 times 10-5 M), the displacement of curves suggests a competitive type of inhibition both for rabbit and guinea guinea pig atria. The apparent association constants calculated from these curves are: K1 (rabbit) 3.7 times 10-6M and K-1 (guinea pig) 6.7 times 10-6M. These results for guinea pig atria are in satisfactory agreement with the value obtained in another laboratory (2). At higher concentrations of burimamide, inhibition curves showed distinct evidence of departure from competitive character for both guinea pig and rabbit atria.     

A novel guinea pig macrophage-specific polymorphic molecule. I. Biochemistry, genetics, and tissue distribution

In the course of studying Ia molecules from strain 2 and strain 13 guinea pig macrophages, with the intent of comparing them to B cell Ia molecules, it was observed that guinea pig alloserum prepared by cross-immunization of guinea pig lymphocyte Ag non-identical inbred guinea pigs immunoprecipitated not only conventional class I and class II molecules, but also a 98,000-Da molecule, termed gp98. Two different forms of the molecule were detected, indicating it is polymorphic. The genes encoding gp98 were shown not to be linked to the guinea pig lymphocyte Ag complex. The molecule gp98 was found on macrophages within populations of peritoneal exudate cells, resident peritoneal cells, bone marrow cells, and spleen. All gp98-bearing macrophages were also Ia-positive. However, only a subpopulation of macrophages bore gp98. The gp98 was not found on Ly-1 or Ig-bearing cells, indicating that B and T cells do not bear Ia. Thus, gp98 appears to be a highly immunogenic polymorphic macrophage-specific molecule that allows the characterization of guinea pig macrophage subsets.     

Guinea pig plasma trypsin inhibitors. Purification and characterization of two functionally distinct proteinase inhibitors.

Two trypsin inhibitors (TI-1, TI-2) were isolated from guinea pig plasma and purified to homogeneity. In amino-acid composition as well as molecular masses, TI-1 (Mr 58,000) and TI-2 (Mr 57,000) are similar to each other and to human and mouse alpha 1-proteinase inhibitors, and mouse con-trapsin. The two inhibitors form equimolar complexes with proteinases. The effectiveness of the inhibitors was characterized by association rate constants under second-order rate conditions. The inhibitory action of TI-1 was rapid for bovine trypsin, porcine pancreatic elastase and guinea pig plasma kallikrein, but slow for bovine thrombin and guinea pig plasmin and not detectable for bovine chymotrypsin and porcine pancreatic kallikrein. The inhibitory action of TI-2 was rapid for trypsin and chymotrypsin, but slow for guinea pig plasma kallikrein and not detectable for other proteinases. These results show that TI-1 and TI-2 are physicochemically similar but functionally distinct from each other and from human alpha 1-proteinase inhibitor that inhibits trypsin, chymotrypsin and elastase.     

Different tolerance to hypothermia and rewarming of isolated rat and guinea pig hearts.

We examined the effect of hypothermia and rewarming on myocardial function and calcium control in Langendorff-perfused hearts from rat and guinea pig. Both rat and guinea pig hearts demonstrated a rise in myocardial calcium ([Ca]total) in response to hypothermic perfusion (40 min, 10 degrees C), which was accompanied by an increase in left ventricular end diastolic pressure (LVEDP). The elevation in [Ca]total was severalfold higher in guinea pig than in rat hearts, reaching 12.9 +/- 0.8 and 3.1 +/- 0.6 micromol.g dry wt-1, respectively. The rise in LVEDP, however, was comparable in the two species: 62.5 +/- 2.5 (guinea pig) and 52.5 +/- 5.1 mm Hg (rat). Following rewarming, [Ca]total remained elevated in guinea pig, whereas a moderate decline in [Ca]total was observed in the rat (13.6 +/- 1.9 and 2.2 +/- 0.3 micromol.g dry wt-1, respectively). Posthypothermic values of LVEDP were also significantly higher in guinea pig compared to rat hearts (42.5 +/- 6.8 vs 20.5 +/- 5.1 mm Hg, P < 0.027). Furthermore, whereas rat hearts demonstrated a 78 +/- 7% recovery of left ventricular developed pressure, there was only a 15 +/- 7% recovery in guinea pig hearts. Measurements of tissue levels of high energy phosphates and glycogen utilization indicated a higher metabolic requirement in guinea pig than in rat hearts in order to oppose the hypothermia-induced calcium load. Thus, we conclude that isolated guinea pig hearts are more sensitive to a hypothermic insult than rat hearts.     

Differences in activation of human and guinea pig complement by retroviruses.

C type murine leukemia viruses (retroviruses) have been shown previously to possess a receptor for human C1 that activated human but not guinea pig complement. In the present study we provide evidence that the viral receptor also binds guinea pig C1 but that such binding does not lead to activation. However, incorporation of human C1s into guinea pig C1 to form a C1 hybrid results in activation of that hybrid and in viral lysis. In contrast, incorporation of guinea pig C1s into human C1 abolishes activation by the virus. These results demonstrate that C1s governs the activation of C1 of the viral receptor.     

Guinea pig very low density lipoproteins are a good substrate for lipoprotein lipase.

In contrast to plasma from most other animals, guinea pig plasma causes little or no stimulation of lipoprotein lipase activity. Very low density lipoproteins (VLDL) isolated by ultracentrifugation of guinea pig serum caused a definite stimulation of lipase activity, whereas the infranatant inhibited the activity. Gel filtration in 5 M guanidinium hydrochloride of delipidated VLDL demonstrated that the activation was caused by a low molecular weight protein. The VLDL themselves were hydrolized at similar rates as human VLDL both by guinea pig and by bovine lipoprotein lipases. Thus, guinea pig VLDL contain an activator for lipoprotein lipase analogous to that in other animals and there is enough of the activator to support rapid hydrolysis of the VLDL lipids by the lipase.     

Biological activity of leukotriene B4 analogs: inhibition of guinea pig eosinophil migration in vitro by the 2,6-disubstituted pyridine analogs U-75,302 and U-75,485.

A "late phase" antigen-induced bronchoalveolar eosinophilia has been demonstrated in ovalbumin sensitized guinea pigs (1,2). This in vivo response to antigen inhalation can be inhibited by a 2,6-disubstituted pyridine analog of LTB4, U-75,302(2) (3). In the present study, the mechanism of the drug action was studied by assessing the activity of U-75,302 and a second analog, U-75,485 to displace [3H]-leukotriene B4 binding at the guinea pig eosinophil membrane, as well as their action as chemoattractants or inhibitors of the directional migration of guinea pig eosinophils in vitro. Radioligand competition experiments demonstrated that both analogs interacted strongly with the high affinity LTB4 binding sites on guinea pig eosinophil membrane. Both analogs are powerful chemoattractants for guinea pig eosinophils since they induced directional migration of guinea pig eosinophils when administered alone. In addition, when the cells were treated with either analog and their chemotaxis response was measured in response to a natural chemoattractant, both U-75,302 and U-75,485 at concentrations of 0.1 to 100 microM dose dependently inhibited the LTB4 induced chemotaxis response. The EC50s obtained for U-75,302 and U-75,485 as inhibitors of LTB4 induced guinea pig eosinophil chemotaxis were estimated to be 11.5 +/- 5.5 microM and 5.4 +/- 2.5 microM respectively. Under the same conditions, they had no significant effect upon eosinophil migration induced by zymosan activated plasma at concentrations below 100 microM. We suggest that the inhibition of antigen-induced eosinophil infiltration in guinea pig airway in vivo by U-75,302 or U-75,485 may be a result of partial antagonism or desensitization at the LTB4 receptor level of guinea pig eosinophils.     

Leukocyte migration in guinea pigs. II. Partial characterization of a leukocyte migration inhibitory factor distinct from macrophage migration inhibitory factor.

In this study we present data on the partial biological and biochemical characterization of guinea pig leukocyte migration inhibition factor (LIF) and migration inhibition factor (MIF). The results indicate that guinea pig LIF and MIF are distinct mediators of cellular immunity, in terms of indicator cells affected and molecular weight. This is in agreement with previous reports showing distinctions between human LIF and MIF. Partial characterization of guinea pig LIF suggested that it is a heat-stable protein of molecular weight 68,000–158,000 and does not contain terminal sialic acid groups.     

Uptake of uric acid and p-aminohippurate (PAH) by renal cortical slices of various mammals.

1. Accumulation of uric acid and PAH was measured in renal cortical slices of various mammalian species. 2. The slice to medium ratio of uric acid was above unity in the rabbit, guinea pig, pig and cow, suggesting an active accumulation of uric acid, while it was near or below unity in the rat and mongrel dog. 3. Uric acid uptake in the rabbit, guinea pig and cow was significantly inhibited by PAH. 4. Uric acid was a potent inhibitor of PAH uptake in the rabbit, guinea pig, dog and pig, but much less potent in the rat and cow. 5. Kinetic analysis showed that uric acid inhibited PAH uptake in a competitive manner in all species studied except for the cow showing a noncompetitive type. 6. These results indicate that uric acid and PAH share a common transport mechanism at the basolateral membrane of the rabbit, guinea pig and pig.     

Studies on the mechanism of PMN activation III. by lymphokines

The influence of a guinea pig lymphokine preparation on the oxidative metabolism of human and guinea pig granulocytes of various sources was investigated. A dose-dependent increase of the oxidative burst following lymphokine challenge was observed. It occurred in unstimulated guinea pig peripheral polymorphonuclear leukocytes (PMN) and in prestimulated PMN obtained from the peritoneal cavity after glycogen injection as well. The lymphokine effect on the oxidative metabolism is not species-restricted because the guinea pig lymphokine preparation elicits an oxidative burst in human PMN, too. The increase caused by lymphokines is nearly of the same order of magnitude as that obtained with zymosan.     

Cyclic nucleotide levels during carbachol-induced smooth muscle contractions.

Cyclic nucleotide levels and tension were measured at various times during carbachol-induced smooth muscle contractions. Cyclic GMP levels were markedly increased during contractions of rat vas deferens, guinea pig myometrium and guinea pig taenia coli, but were unchanged during contractions of rat uterus or guinea pig ileum. No significant changes in cyclic GMP levels could be detected in estrogen-primed rat uteri at any of the times or drug concentrations studied. Even in tissues in which large increases in cyclic GMP levels could be detected during carbachol-induced contractions (i.e. guinea pig myometrium and taenia coli) the contractions appeared to precede the cyclic GMP increases by several seconds. No significant changes in cyclic AMP levels were observed during carbachol-induced contractions in any of the smooth muscles studied. Thus, changes in tissue levels of the cyclic nucleotides do not appear to be responsible for the initiation of carbachol-induced smooth muscle contractions.     

Guinea pig proinsulin. Primary structure of the C-peptide isolated from pancreas.

The amino acid sequence of the proinsulin C-peptide isolated from guinea pig pancreas was determined and experimental data are presented. Digestion of the C-peptide with chymotrypsin provided two dodecapeptides, a tetrapeptide, and glutamine, which account for the intact chain. Reaction of the C-peptide with cyanogen bromide resulted in cleavage at the single methionine and provided two additional fragments. Digestion of the large peptides with papain provided a variety of small peptides and the complete sequence was assigned by identification of the fragments. Although guinea pig insulin differs markedly from mammalian insulins, guinea pig C-peptide has many features of primary structure in common with the C-peptides of other mammals. The conservation of specific residues in C-peptides indicates that these residues form essential elements in the three-dimensional structure of proinsulin.     

Lysis of tumor cells by antibody and complement. III. Lack of correlation between antigen movement and cell lysis.

The increase in susceptibility to killing by rabbit antibody and guinea pig complement of guinea pig hepatoma cells (line-10), after treatment with certain metabolic inhibitors, did not correlate with the mobility of antigen on the cell surface as measured by indirect immunofluorescence.     

A reevaluation of rabbit anti-allotype antibody for the presence of cross-reactive idiotypes. I. A species-specific idiotype on rabbit anti-a1 antibody is recognized by guinea pig anti-IdX antibody

Rabbit reagents previously thought to display specificity for a cross-reactive idiotype on anti-VHa allotype antibody from all tested rabbits have recently been shown to be contaminated with an induced (latent) molecule similar or identical to the original antigen (rabbit a1 or a2 allotype). In an attempt to circumvent this problem, we have immunized guinea pigs with rabbit anti-a1 allotype antibody to produce heterologous anti-idiotype antibody. The resulting guinea pig antibody (GP anti-R IdX) recognizes anti-a1 antibody from each of 17 immunized rabbits, and in four tested samples reacts with 22 to 100% of the molecules. Neither goat nor guinea pig anti-a1 reacts with the guinea pig anti-R IdX antibody, even though the goat, guinea pig, and rabbit anti-a1 Ab all recognize a similar set of a1 determinants. The reaction between IdX-bearing rabbit anti-a1 and guinea pig anti-R IdX is inhibited by the original antigen (a1 IgG), demonstrating that the IdX is at or near the antigen combining site of anti-a1 antibody. Immunoelectron microscopy of immune complexes supports this conclusion and demonstrates that the reactive site on the GP anti-R IdX is at or near its antigen combining site.