Guinea Pig Species Research Articles

Instituting Dark-Colored Cover to Improve Central Space Use Within Guinea Pig Enclosure

Domestic guinea pigs (Cavia aperea f. porcellus) in laboratories have been shown to actively avoid the centers of their cages. This experiment tested a novel, dark-colored “shader” placed over the central portion of a cage. Based on the observed behavior of wild guinea pig species, it was hypothesized that utilization of the central portion of the cage would increase when the shader was present. Eleven male and 11 female albino, 3-week-old Hartley guinea pigs (Crl:HA) experienced the control and treatment conditions in a crossover study design. They spent more time in central cage sections when the shader was present and spent more time in and around the food hopper when the shader was absent (p < .001). Differences between sexes included increased inactivity in males versus females (p < .05) and a difference in time spent in a corner section of the cage (p < .001), likely associated with location in the room. We concluded that the presence of a shader increased utilization of cage space, which appeared to provide a similar increase in space utilization as structural enrichments.

Similarities and differences among the chromosomes of the wild guinea pig Cavia tschudii and the domestic guinea pig Cavia porcellus (Rodentia, Caviidae).

Cavia tschudii Fitzinger, 1867 is a wild guinea pig species living in South America that according to the analysis of mitochondrial genes is the closest wild form of the domestic guinea pig. To investigate the genetic divergence between the wild and domestic species of guinea pigs from a cytogenetic perspective, we characterized and compared the C, G and AgNOR banded karyotypes of molecularly identified Cavia tschudii and Cavia porcellus Linnaeus, 1758 specimens for the first time. Both species showed 64 chromosomes of similar morphology, although C. tschudii had four medium size submetacentric pairs that were not observed in the C. porcellus karyotype. Differences in the C bands size and the mean number of AgNOR bands between the karyotypes of the two species were detected. Most of the two species chromosomes showed total G band correspondence, suggesting that they probably represent large syntenic blocks conserved over time. Partial G band correspondence detected among the four submetacentric chromosomes present only in the C. tschudii karyotype and their subtelocentric homologues in C. porcellus may be explained by the occurrence of four pericentric inversions that probably emerged and were fixed in the C. tschudii populations under domestication. The role of the chromosomal and genomic differences in the divergence of these two Cavia species is discussed.

Recovery of human basophils after FMLP‐stimulated secretion

Basophils are circulating, secretory granulocytes that are generally considered to be end-stage cells. In one species of guinea-pigs, basophilic leucocytes have been shown to recover from stimulated secretion in short-term cultures. Similar studies have not been done using human basophils. The purpose of this study was to examine human basophils in short-term recovery intervals following stimulation of secretion to determine whether visual evidence of recovery occurred. We examined the ultrastructural morphology of early recovery (10 min-6 h) of human basophils following secretion stimulated by formyl-methionyl-leucyl-phenyl-alanine (FMLP). A combined technique for electron microscopy consisted of post-fixation exposure to cationized ferritin and reduced osmium, providing maximum quality images and allowing identification of intracellular spaces/organelles that opened to the cell surface, often out of the plane of section. The ultrastructural evaluation revealed that control basophils (0 time-6 h) did not undergo regulated secretion or develop the morphologies associated with recovery following secretion. FMLP-stimulated basophils underwent an overlapping continuum of piecemeal degranulation-->anaphylactic degranulation (0 time-1 min), producing vesicle- and granule-free, completely degranulated, viable, mature basophils with polylobed nuclei. The early recovery period (10 min-6 h) following FMLP stimulation was characterized by reconstitution of granules. Morphological mechanisms for granule reconstitution included a mixture of conservation, condensation, and synthetic events. Human basophils, like guinea pig basophils, have the potential to recover from regulated secretion.

Nuclear magnetic resonance characterization of aromatic residues of alpha-lactalbumins. Laser photo chemically induced dynamic nuclear polarization nuclear magnetic resonance studies of surface exposure.

The alpha-lactalbumins are involved as modifier proteins in lactose biosynthesis. Lactalbumins from different mammalian species are cross-reactive with the galactosyltransferases from others because of their homologous primary and tertiary structure. We have studied the surface exposure of several alpha-lactalbumins (bovine, goat, human, guinea pig, and rabbit) by the laser photo-CIDNP technique, an NMR method which measures the access of a photoexcited flavin dye to surface exposed Tyr, Trp, and His residues. An exposed histidine-68 residue exists in the bovine and goat species but is missing in other species and is replaced with a His-10 in the guinea pig species. The only exposed tryptophan residue was Trp-104, which cross-relaxed to nearby Trp-60. Cross-polarization to the latter residue was proven by taking free induction decays after extremely short light pulses (0.1 s). Furthermore, this cross-polarized Trp-60 resonance was absent in the guinea pig species, which has a substitution at position 60. The chemical shifts of these Trp residues were extremely similar in all species but rabbit, which has substituted His for a Tyr at position 103, situated close to both Trp-104 and -60. Three of the four tyrosines in bovine, goat, human, and guinea pig alpha-lactalbumin were exposed (the latter species has an extra Tyr in its sequence which was apparently not accessible). The rabbit species contains only two Tyr residues, the one which was not accessible (Tyr-50) being common to all species.