Cellulolytic cocci isolated from the cecum of guinea pigs (Cavia porcellus).

Five strains of anaerobic, gram-variable cellulolytic cocci, belonging to the genus Ruminococcus, were isolated from the cecum of a guinea pig. They differed from most previously described strains of cellulolytic ruminococci as follows. (i) Lactate was the major fermentation product; lesser amounts of formate and ethanol and a trace of succinate were also produced, along with an uptake of acetate. (ii) No growth occurred at 30 degrees C; however, good growth was observed at 38 and 45 degrees C, (iii) Glucose, cellobiose, cellulose, xylose, arabinose, xylan, sucrose, and lactose were fermented by all strains. Rumen fluid was required for growth in a complete medium containing all nutrients previously found to be required by species in this genus. Limited growth occurred when rumen fluid was replaced by yeast extract, and maximum, but delayed, growth occurred when a water extract of alfalfa was added to the complete medium. No qualitative differences were found in the cell wall amino acids and sugar composition of these strains as compared to Ruminococcus flavefaciens and Ruminococcus albus; however, cell walls of the guinea pig strains appeared to contain a higher proportion of glucose.     

Immunoglobulin genomics in the guinea pig (Cavia porcellus)

In science, the guinea pig is known as one of the gold standards for modeling human disease. It is especially important as a molecular and cellular biology model for studying the human immune system, as its immunological genes are more similar to human genes than are those of mice. The utility of the guinea pig as a model organism can be further enhanced by further characterization of the genes encoding components of the immune system. Here, we report the genomic organization of the guinea pig immunoglobulin (Ig) heavy and light chain genes. The guinea pig IgH locus is located in genomic scaffolds 54 and 75, and spans approximately 6,480 kb. 507 V(H) segments (94 potentially functional genes and 413 pseudogenes), 41 D(H) segments, six J(H) segments, four constant region genes (μ, γ, ε, and α), and one reverse δ remnant fragment were identified within the two scaffolds. Many V(H) pseudogenes were found within the guinea pig, and likely constituted a potential donor pool for gene conversion during evolution. The Igκ locus mapped to a 4,029 kb region of scaffold 37 and 24 is composed of 349 V(κ) (111 potentially functional genes and 238 pseudogenes), three J(κ) and one C(κ) genes. The Igλ locus spans 1,642 kb in scaffold 4 and consists of 142 V(λ) (58 potentially functional genes and 84 pseudogenes) and 11 J(λ) -C(λ) clusters. Phylogenetic analysis suggested the guinea pig's large germline V(H) gene segments appear to form limited gene families. Therefore, this species may generate antibody diversity via a gene conversion-like mechanism associated with its pseudogene reserves.     

Urethral catheterization of the male guinea pig (Cavia porcellus)

Urethral catheterization of the male guinea pig has potential diagnostic, therapeutic, and research applications. Urethral catheter placement requires an understanding of the unique anatomy of the lower urinary tract in order to avoid iatrogenic injury to the urethra and to ensure successful catheterization.     

Microbes associated with the epithelium of the oesophagus and stomach of guinea pigs (Cavia porcellus)

Histological examination of oesophagus and stomach specimens from 28 guinea pigs (Cavia porcellus) revealed microbes associated with the epithelial surface of these organs. Layers of Gram-positive cocci were associated with oesophageal tissue in all the animals. Yeasts (Torulop-sid pintolopesii) were associated with stomach tissue in most animals 1 week of age or older.     

Effect of dietary salt (NaCl) supplementation on urinary profile of guinea pigs (Cavia porcellus).

Sodium chloride supplementation (120 mg/kg of body weight/day) for 12 days increased the urinary excretion of calcium from 91.6 +/- 9.0 to 159.4 +/- 16.0 mumol/day and of sulphate from 266.8 +/- 24.5 to 1176.9 +/- 87.2 mumol/day in guinea pigs. The stone risk due to increased urinary calcium excretion could possibly be counterbalanced by increasing urinary sulphate excretion. High salt intake, thus, could not increase the risk of stone formation.     

Urethral catheterization in the female guinea pig (Cavia porcellus)

Urethral catheterization of the female guinea pig has potential diagnostic, therapeutic and research applications. Urethral catheter placement in the female guinea pig is relatively easy to carry out and has fewer potential complications than does catheter placement in male guinea pigs.     

Ancient and modern steps during the domestication of guinea pigs (Cavia porcellus L.)

To test whether there are differences between living lineages of domestic guinea pigs Cavia porcellus , we studied 118 specimens from six breeds collected along six Andean countries as well as 15 from the wild cavy species ( Cavia tschudii ). The mean weight and body length of 15 adult wild cavies (295±31 g, 242±8.3 mm) were significantly smaller than 25 creole guinea pigs from Bolivia and Chile (639±157 g, 287±23.7 mm, respectively). Eighteen laboratory/pet guinea pigs (including the English Pirbright breed) were also smaller (900±173 g, 308±21 mm) than 25 improved ones from Peru (Tamborada breed, 1241±75.4 g, 317±12 mm) and Ecuador (Auqui breed, 1138±65.5 g, 307±8 mm). Similar size increases appeared in the first axis of a principal component analysis of six skeletal measurements, recovering 84% of total variation. Phylogenetic and haplotype analyses of complete cytochrome b gene sequences consistently joined all 22 domestic individuals (13 shared unambiguous substitutions, 100% bootstrap in 1000 replicates), probably from a single first ancient domestication in the western Andes. Six laboratory/pet sequences were also joined within a common branch (six shared substitutions, 96% bootstrap), probably from a documented European second phase. By contrast, those from improved Auqui joined a northern creole subgroup (one shared substitution, 84% bootstrap), and those from Nativa and improved Tamborada clustered together and with a southern creole subgroup (four shared substitutions, 86% bootstrap); this suggests at least two independent modern events during a more complex third phase, producing two improved guinea pigs selected for size and meat. Cavia tschudii sequences showed some unexpected geographic variation.     

Ontogenesis of the electroretinogram in a precocial mammal, the guinea pig (Cavia porcellus)

1. Ontogenesis of the electroretinogram, the mass electrical response of the retina to flash light stimuli, was studied in the guinea pig (Cavia porcellus), a precocial species with visual function at birth. 2. a-Wave components, b-wave, oscillatory potentials, slow PIII, and c-wave responses to flash stimuli developed between 55 and 64 days of gestation (full term is 68-69 days). 3. a-Waves attributable to photoreceptor functions were fully mature at 60 days. 4. ERG development lagged behind the reported critical milestones in retinal development; its prenatal onset indicates that no history of light entrainment is required for initiation of a mature ERG response.     

An outbreak of Streptococcus pyogenes infection associated with calcium oxalate urolithiasis in guinea pigs (Cavia porcellus)

An outbreak of Streptococcus pyogenes infection occurred in a colony of 800 Dunkin-Hartley guinea pigs resulting in 364 (46%) deaths involving breeders, sucklings, weaners, but mainly adults used as a source of blood meals for haematophagus flies (Glossina palpalis). Clinical signs included bleeding from the nose, mouth and vagina before death. Necropsy revealed pneumonia with consolidation of one or both lungs, haemopericardium and haemothorax. There were yellowish-grey deposits in the urinary bladder of more than 50% of both affected breeders and adults used for feeding haematophagus flies. Beta-haemolytic Streptococcus pyogenes was isolated in pure culture from many tissues including the urinary bladder. The survivors were treated with oxytetracycline (Terramycin-LA; Pfizer) using the intra-muscular route and the response was good.     

True pregnancy toxemia (preeclampsia) in the guinea pig (Cavia porcellus)

In this study, normal nonpregnant, normal full-term pregnant, fasting ketotic and spontaneous pregnancy toxemic guinea pigs were compared to define the mechanism of this disease. In addition to conventional clinical, laboratory and pathologic studies, arterial blood pressure (thoracic and abdominal aortic) measurements and angiography were used. The results showed that in spontaneous cases of pregnancy toxemia, there is an aortic compression just caudal to the renal arteries. This compression reduced the aortic diameter by 22% of prerenal level as compared to 10% for fasting ketotic and normal pregnant guinea pigs. The aortic compression also resulted in a 30% postcompression reduction in blood pressure. No pressure differences were seen in the other groups. The postulated etiology for true toxemia of pregnancy in guinea pigs is, therefore, similar to that of man where aortic compression produces uterine ischemia and the resultant syndrome.     

Tooth regeneration in the guinea pig (Cavia porcellus)]

The first inferior molar has been extracted, a part of its being reimplanted or not. A new molar of normal form regenerated, apparently from the apex of the tooth germ, in all cases in which the alveolus was left free or implanted with a tooth freagment deprived of pulpa.     

Sexual dimorphism in the craniofacial growth of the guinea pig (Cavia porcellus)

Variation between the sexes during ontogeny is frequently overlooked in discussions of the phylogenetic patterns of adult sexual dimorphism. Different growth trajectories can produce identical degrees and direction of adult dimorphism and the possibility exists that similarities in adults may be the result of differing growth patterns, suggesting independent evolutionary pathways among species to the seemingly identical adult morphology. We quantified the sexual dimorphism in craniofacial skeletal growth of Cavia porcellus, the guinea pig, using longitudinally collected radiographs. Guinea pigs have male-biased sexual dimorphism in size and in growth parameters, despite literature reports to the contrary. These results, analyzed with equivalent data for five species of rodents, and two outgroups representing similarly sized mammals, a rabbit and a marsupial, indicate that some aspects of sexual differences in growth follow phylogenetic lines, while others are a function of whether the species has male- or female-biased dimorphism.     

Collateral vessels of the aortic arch of the guinea pig Cavia porcellus (Rodentia)

The distribution of the principle arteries of the aortic arch in male and female guinea pigs is highly variable.     

Mandibular movement and muscle activity during mastication in the guinea pig (Cavia porcellus)

Optoelectronic analysis of mandibular movement and electromyography (EMG) of masticatory muscles in Cavia porcellus indicate bilateral, unilateral, and gnawing cycles. During bilateral and unilateral cycles, the mandibular tip moves forward, lateral, and down during the lingual phase of the power stroke to bring the teeth into occlusion. EMG activity is generally asymmetric, with the exception of activity of the temporalis muscle during bilateral cycles. During gnawing cycles, the mandible moves in an anteroposterior direction that is opposite that during bilateral and unilateral chew cycles. Bilateral and unilateral cycles of pellets were significantly longer than carrot. With the exception of the width of bilateral cycles, the magnitude of cycle width, length, and height during the mastication of carrots was greater than that during the mastication of pellets. Significant differences exist between EMG durations during mastication of pellets and carrots. The lateral pterygoid displays continuous activity during gnawing cycles. Significant differences also exist in the durations of EMG activity between the working and balancing side during all three cycle types. High level activity of balancing side temporalis and anterior belly of digastric (ABD) during bilateral cycles occurs during rotation and depression of the mandible during the power stroke. The temporalis apparently provides a ?braking”? or compensatory role during closing and power strokes. Differences between Cavia masticatory patterns and those shown by Rattus and Mesocricetus are apparently due to differences in dental morphology, occlusal relationships, and, possibly, the poorly developed temporalis in Cavia. The large number and wide diversity of rodent groups afford students of mammalian mastication an opportunity to investigate and compare different masticatory specializations.     

Sand accumulation in the digestive tract of rabbits (Oryctolagus cuniculus) and guinea pigs (Cavia porcellus): The role of the appendix

We determined location and amount of accumulated sand in the gastrointestinal tract (GIT) of rabbits (Oryctolagus cuniculus) and guinea pigs (Cavia porcellus) fed diets containing external (silicate) abrasives. Computed tomographic abdominal images of rabbits (n = 44) and guinea pigs (n = 16) that each received varying numbers (4–7) of different diets for 14 days each (total n = 311 computed tomographs), and radiographs of dissected GIT and presence of silica in GIT content (n = 46 animals) were evaluated. In rabbits, the majority of accumulated sand was located in the caecal appendix, an elongated, intestinal structure in the left side of the abdomen. The ‘wash-back’ colonic separation mechanism in rabbits may be partly responsible for a retrograde transport of sand back to the caecum, where dense, small particles accumulate in the appendix. The appendix likely acted as a reservoir of these particles, leading to significant effects not only of the momentary but also of the previous diet on recorded sand volumes in the rabbits. Guinea pigs have no caecal appendix and a colonic separation mechanism not based on a ‘wash-back’. Less sand accumulation was found in their GIT without a specific location pattern, and there were less previous diet effects in this species. None of the rabbits or guinea pigs developed clinical signs of obstruction during the study, and the recorded sand volumes represented 1.0 ± 1.2% of the 14-d sand intake in rabbits and 0.2 ± 0.2% in guinea pigs. Accumulation of sand in volumes up to 10 cm³ in the GIT of rabbits does not seem to cause clinical health impairment. Large inter-individual differences in rabbits indicate inter-individual variation in proneness to sand accumulation. The reason for the presence of a sand-trapping caecal appendix in animals that are, due to their burrowing lifestyle and feeding close to the ground, predestined for accidental sand ingestion, remains to be unveiled.