Isolation of monospecific antisera to guinea pig immunoglobulins

The results of the production and analysis of monospecific rabbit antisera to guinea pig IgG1, IgG2, IgA and IgM are presented. Isolated immunoglobulins of different isotypes, as well as immune precipitates obtained by immunoelectrophoresis, were used for immunization. After adsorption antisera of each type there formed one precipitation line with guinea pig serum in immunoelectrophoresis, thus indicating that they contained antibodies to immunoglobulins of the definite isotype.     

Preparation and properties of antisera to glycolipid of guinea pig erythrocyte membrane

Antibodies against a glycolipid of guinea pig erythrocyte membranes were prepared in rabbits by immunization with guinea pig erythrocyte stroma or the purified glycolipid, gangliotriaosylceramide. The antibodies agglutinated guinea pig erythrocytes. The specificity of antibodies could be revealed by several immunochemical methods, including inhibition of hemagglutination, immunodiffusion, agglutination of liposomes, and complement fixation. The antibodies were specific for gangliotriaosylceramide.     

Antibodies to guinea pig lymphokines. II. Suppression of delayed hypersensitivity reactions by a "second generation" goat antibody against guinea pig lymphokines.

A "second generation" antibody to a highly purified lymphocyte product was raised in a goat against material eluted from a rabbit anti-guinea pig lymphokine immunoadsorbent column. This anti-lymphokine serum, in constrast to anti-lymphocyte serum (ALS) did not appear to contain cytotoxic antibodies directed against membrane antigens on guinea pig lymph node lymphocytes. Furthermore, the anti-lymphokine serum did not inhibit the formation of spontaneous T rosettes nor significantly depress lymphocyte response to mitogens. The anti-lymphokine serum totally suppressed the delayed skin reactivity to PPD and contact sensitivity to DNCB when injected intradermally around the site of antigen challenge. By contrast, intradermally injected ALS did not appear to suppress the PPD response in sensitized guinea pigs. Intravenously and i.p. administered anti-lymphokine serum was somewhat less effective in suppressing the delayed skin response to PPD. The intradermal injection of the antiserum had no effect on nonspecific inflammation evoked by turpentine-olive oil or on the extravasation of circulating Evans blue evoked by intradermally injected histamine. Histologic examination of 24-hr DNCB-induced skin lesions from sensitized guinea pigs treated with intradermally injected anti-lymphokine serum showed marked reduction of mononuclear infiltration of the dermis and of epidermal lesions, as compared with skin sites taken from sensitized animals pretreated with normal goat serum. The anti-lymphokine serum injected i.v. also markedly reduced the perivascular infiltration of the dermis and subcutis in skin reaction sites from sensitized animals challenged with PPD. Intravenous treatment with ALS for 3 consecutive days caused extensive depletion of the paracortical areas of peripheral lymph nodes whereas treatment with normal serum and anti-lymphokine serum caused no such depletion. It is proposed that the anti-lymphokine serum is directed against activated lymphocyte products, one of them being MIF. These products are involved in the mediation of delayed hypersensitivity reactions. This is in marked contrast to ALS, the suppressive action of which appears to be central rather than peripheral.     

Primary structure of mouse, rat, and guinea pig cytochrome c.

For immunochemical and evolutionary reasons we determined the primary structure of cytochrome c from two strains of laboratory mice. Thioacetylthioethane and thioacetylthioglycolic acid were used in addition to conventional reagents for sequence determinations. The sequence was found to be identical with that of the rabbit except for residues 44 and 89 and consistent with the peptide compositional data reported by Hennig (Hennig, B. (1975), Eur. J. Biochem. 55, 167-183). The rat cytochrome c cymotryptic peptides were identical with those of the mouse in amino acid composition and amino-terminal residues. Further, peptide maps of cytochromes c of the guinea pig and two strains of rat indicate that all these animals have the same cytochrome c as the laboratory mouse. It is concluded that rodent cytochromes c are evolutionarily conservative and that there is no evidence for a generation-time effect in cytochrome c evolution.     

Fatty acid effects on gluconeogenesis in goat, calf and guinea pig hepatocytes

1. Regulation of hepatic gluconeogenesis by fatty acid was studied in goat, calf and guinea pig hepatocytes. 2. Fatty acid effects on gluconeogenesis were dependent upon species; fatty acid and gluconeogenic substrate. 3. Oleate and octanoate inhibited gluconeogenesis from propionate in guinea pig hepatocytes and stimulated it in goat hepatocytes. 4. Oleate and octanoate markedly inhibited gluconeogenesis from lactate in guinea pig hepatocytes whereas octanoate, but not oleate, decreased glucose production from lactate in goat hepatocytes. 5. Effects of fatty acids on gluconeogenesis in calf hepatocytes were similar to goat hepatocytes suggesting control of gluconeogenesis is similar among ruminant species but differs from guinea pigs.     

Production and secretion of C-19 steroids by rat and guinea pig adrenals

The concentrations of C-19 steroids were measured in guinea pig and rat adrenals before and after castration as well as after stimulation with adrenocorticotropin hormone (ACTH). Characterization of adrenal C-19 steroids was also carried out by isolation with high-performance liquid chromatography and gas chromatography/mass spectrometry (GC/MS). From radioimmunoassay (RIA) data, androstenedione (4-DIONE) and 11 beta hydroxyandrostenedione (11 beta-DIONE) were the major C-19 steroids found in guinea pig adrenals, and castration induced a decrease of 4-DIONE levels only while all other C-19 steroids remained unchanged. In rat adrenals, the major C-19 steroids were 4-DIONE and testosterone, and they were also markedly inhibited after castration. With the exception of 11 beta-DIONE, all other C-19 steroids in circulation were eliminated after castration in both animals species. After ACTH administration in the guinea pig, adrenal 4-DIONE and 11 beta-DIONE levels were markedly stimulated, while an increase of only 11 beta-DIONE was observed in plasma. In the rat, ACTH had a small stimulatory effect on adrenal 52-androstane-3 alpha, 17 beta-diol (3 alpha-DIOL) and plasma 11 beta-DIONE levels. Analysis of guinea pig adrenal steroids by GC/MS confirmed the presence of C-19 steroids in adrenals (namely, 4-DIONE and 11 beta-DIONE) while, in the rat, this could not be confirmed. Our data indicate that production of C-19 steroids occurs in guinea pig adrenals, and 11 beta-DIONE is the major C-19 steroid as well as the only C-19 steroid secreted into the circulation. In the rat, the production of C-19 steroids detected by RIA is not supported by GC/MS data.     

Soman levels in kidney and urine following administration to rat, guinea pig, and marmoset.

Concentrations of C(+/-)P(+/-)-soman (1,2,2-trimethylpropyl methylphosphonofluoridate) in urine of anaesthetized, atropinized and artificially ventilated rats, guinea pigs and marmosets were determined 1-4 h after iv administration of 1-6 LD50 of the agent and in the kidneys 1 h after iv administration of 2-6 LD50 14C-C(+/-)P(+/-)-soman. The concentrations of the toxic C(+/-)P(-)-isomers in both urine and kidneys of the rat were at least two orders of magnitude higher than the corresponding levels in the two other species. Relatively high urine concentrations were also found for C(+/-)P(+/-)-soman-intoxicated (6 LD50) rats pretreated with the nontoxic soman analogue PDP (1,2,2-trimethyl dimethylphosphinate), which considerably decreases the persistence of C(+/-)P(-)-soman in rats, or the carboxylesterase inhibitor CBDP [2-(o-cresyl)-4H-1:3:2-benzodioxaphosphorin-2-oxide]. The lethal effect brought about by intravesical administration of C(+/-)P(+/-)-soman in rats showed that the agent can easily be reabsorbed from the bladder. It is concluded, that this reabsorption does probably not explain the previously observed persistence and "late toxicity" of C(+/-)P(+/-)-soman in rats, although the amount of renally excreted C(+/-)P(-)-soman (ca. 1% of the administered dose) should be sufficient for a toxicologically significant effect.     

Hydrogen exchange of the tryptophan residues in bovine, goat, guinea pig, and human alpha-lactalbumin

Hydrogen exchange of the individual tryptophan residues of bovine, goat, guinea pig, and human alpha-lactalbumin has been studied by both ultraviolet and NMR spectra. The assignment of the slowly exchanging imino proton resonances to the tryptophan residues (Trp26 and Trp60) was obtained by comparison of the nuclear Overhauser effect difference spectra of bovine, guinea pig, and human alpha-lactalbumin. Taking account of the thermal unfolding of each alpha-lactalbumin, the hydrogen exchange rates of the individual tryptophan residues are analyzed. The temperature dependence of the exchange rates classified their exchange mechanisms into two exchange processes: the "low activation energy process" and the "high activation energy process" which is associated directly with the global thermal unfolding of the protein. Trp26 of alpha-lactalbumin exchanges through the high activation energy process. The exchange behavior of Trp26 of guinea pig alpha-lactalbumin suggests a difference of the globally unfolded state of the protein from the other species. The exchange mechanism of Trp60 of human alpha-lactalbumin is the low activation energy process in contrast with those of the bovine and goat proteins, although their global thermodynamic properties are similar to each other. Trp104 and Trp118 of alpha-lactalbumin exchange through the low activation energy process, and the reaction rates are affected by the local structural differences around the tryptophan residues among these proteins. The results presented in this paper indicate that the hydrogen exchange rate through the low activation energy process provides the information only about the local nature of a protein while that through the high activation energy process provides the information about the global nature of a protein.     

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.     

Receptor binding of guinea pig and pig vasoactive intestinal peptides by rat lung.

Guinea pig vasoactive intestinal peptide (gpVIP) differs from other mammalian VIPs in four of its 28 amino acid residues. In the present study, the gpVIP displaced 125I-labelled pig VIP (pVIP) binding by rat lung membranes with 7.7-fold lower potency than pVIP. Degradation of gpVIP by rat lung membranes, assessed by radioimmunoassay and h.p.l.c., was 1.9-fold greater than that of pVIP. This difference in degradation of the two peptides was not large enough to account for the lower receptor-binding potency of gpVIP. The amino acid residues that distinguish pVIP from gpVIP are likely to contribute to the interaction of VIP with receptors and peptide hydrolases in lung membranes.     

Differences in microtubule stability to colchicine in extracts of guinea pig, rat and rabbit brain.

1. Microtubules (MT) from a guinea pig brain 25,000 g supernatant are not depolymerized by colchicine in contrast to MT from similar preparations of rat and rabbit. 2. The colchicine-stability was lost if the guinea pig brain homogenate was centrifuged at a higher g-level, further purified or if only the grey matter was used. 3. The association constant of colchicine to tubulin did not differ between a stable and a labile guinea pig brain preparation. 4. The GTP-hydrolysis was higher in the guinea pig preparation containing stable MT, than in the preparation containing labile MT. Additional GTP added to the polymerized MT before colchicine exposure, labilized the MT. Preincubation with NaF decreased the GTP-hydrolysis and caused a colchicine depolymerization. 5. The results indicate species differences in colchicine sensitivity of in vitro polymerized MT, probably depending on differences in GTP-hydrolysis.     

Comparative study of ethynyloestradiol metabolism in the rabbit, guinea pig and rat.

Ethynyloestradiol was administered to rabbits, guinea pigs and rats, and the concentration of the steroid in blood was measured by radioimmunoassay. In both rabbits and guinea pigs, levels of conjugated steroid were much higher than those of the freely extractable form. Whereas considerable amounts of steroid were present in a congugated form in plasma 24 h after injection, none was present at this time in a freely extractable form. There were significant differences between young and adult rabbits and guinea pigs in the rate at which ethynyloestradiol was metabolized. The amounts present in the freely extractable form in rats were higher than in the other two species but no steroid was detected in the conjugated fraction. The results are compared with previous findings in humans.