Morphogenesis of the cranium of Cavia porcellus L. I: Introduction, classification and descriptive part

The craniogenesis of Cavia porcellus has been investigated in 7 embryos of different ages. From the developmental stage of 36 mm CRL, a reconstruction of the chondrocranium is described. As there is still a gap in the tectum posterius, the foramen magnum is not closed posteriorly. The course of the notochord is retrobasilar at the beginning, more rostrally it runs intrabasilar. After ossification, the place where the notochord enters the basioccipital is marked by a cavity. This cavity is not identical with the posterior basicranial fenestra. The laminae alares build up strong paracondylar processes. The auditory capsule is connected with the occipital region only by the exoccipitocapsular commissure, but there is no supraoccipitocapsular commissure. The fossa subarcuata is pierced by a subarcuate foramen. The very short lamina parietalis is not in contact with the orbital wing as there is no orbitoparietal commissure. The processus recessus divides the perilymphatic foramen into fenestra rotunda and aquaeductus cochleae. The suprafacial commissure arises from the upper margin of the canalicular part of the auditory capsule, but it does not reach the superior surface of the cochlear part at this stage. The tegmen tympani is well developed. The foramen singulare is not yet separated from the inferior acoustic foramen. At the stage of 36 mm CRL there is no septum spirale cartilagineum. Mm. tensor tympani et stapedius are developed in the typical way. The auditory capsule is connected with the basal plate by the anterior basicochlear and the alicochlear commissures. The floor of the orbitotemporal region is incomplete, the temporal wings are small. The alicochlear commissure, the alar process, the anterior basicochlear commissure, and the basal plate surround the carotid foramen, but there is no blood vessel passing through it. The temporal wing is at the beginning of ossification and shows a fissura ovalis for the mandibular nerve. Although the hypophysial canal is still present, there are no structures passing through it. There is no foramen rotundum. The orbital wing is still cartilagineous. The basal plate and the pre- and postoptic roots border the optical foramen. The straight muscles of the eyeball are attached to the ala hypochiasmatica which projects from the postoptic root. The interorbital septum is absent. The ophthalmic artery, which instead of the obliterated internal carotid artery, contributes to the circulus arteriosus cerebri is well developed. There is no orbitonasal commissure . The epiphanial foramina are present.(ABSTRACT TRUNCATED AT 400 WORDS)     

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.     

A First Generation Comparative Chromosome Map between Guinea Pig (Cavia porcellus) and Humans

The domesticated guinea pig, Cavia porcellus (Hystricomorpha, Rodentia), is an important laboratory species and a model for a number of human diseases. Nevertheless, genomic tools for this species are lacking; even its karyotype is poorly characterized. The guinea pig belongs to Hystricomorpha, a widespread and important group of rodents; so far the chromosomes of guinea pigs have not been compared with that of other hystricomorph species or with any other mammals. We generated full sets of chromosome-specific painting probes for the guinea pig by flow sorting and microdissection, and for the first time, mapped the chromosomal homologies between guinea pig and human by reciprocal chromosome painting. Our data demonstrate that the guinea pig karyotype has undergone extensive rearrangements: 78 synteny-conserved human autosomal segments were delimited in the guinea pig genome. The high rate of genome evolution in the guinea pig may explain why the HSA7/16 and HSA16/19 associations presumed ancestral for eutherians and the three syntenic associations (HSA1/10, 3/19, and 9/11) considered ancestral for rodents were not found in C. porcellus. The comparative chromosome map presented here is a starting point for further development of physical and genetic maps of the guinea pig as well as an aid for genome assembly assignment to specific chromosomes. Furthermore, the comparative mapping will allow a transfer of gene map data from other species. The probes developed here provide a genomic toolkit, which will make the guinea pig a key species to unravel the evolutionary biology of the Hystricomorph rodents.     

Collection and cryopreservation of preimplantation embryos of Cavia porcellus

Individual differences and a rather long-lasting reproductive cycle, as well as the relatively small number of oocytes that mature during one reproductive cycle makes it difficult to establish a cryopreserved stock of preimplantation embryos of the guineapig (Cavia porcellus) when compared with other laboratory rodents. Only a few data for superovulation protocols that can be used for routine laboratory use in guineapigs are available. However, a huge number of different strains exist for many purposes and the establishment of a frozen repository makes sense. Here, we describe the successful freezing of preimplatation embryos of the strain 2BS with a two-step freezing protocol in a freezing medium containing 1,2-propanediol as cryoprotectant. Human menopausal gonodotrophin induced superovulation in the embryo donors.     

Age at maturity in cavies and guinea-pigs (Cavia aperea and Cavia aperea f. porcellus): influence of social factors

Age at maturity, a particularly important parameter in the life history of small mammals, contributes greatly to fitness. Social influences on age at maturity have been demonstrated for altricial rodents, in particular, mice. Nothing is known about such effects in precocial small mammals. Wild cavies Cavia aperea are born in a highly precocial state and mature early in life, briefly after weaning. We investigated whether the wild cavy C. aperea and the domestic guinea-pig Cavia aperea f. porcellus reach maturity earlier in the presence of adults of the opposite sex. Juvenile females kept in pairs without males showed first vaginal opening (=oestrus) when 59 days old in cavies and at about 40 days in the guinea-pig. However, in the company of adult males, cavy females kept in pairs reached maturity when about 30 days old, and guinea-pig females when 26 days old. Most cavy females experienced successful pregnancy following first vaginal opening. In cavies, female mass at birth and at first oestrus was not correlated with age at first oestrus. In guinea-pigs, birth mass predicted age at maturity only when a male was present. The growth rate from birth to first oestrus related to age at first oestrus. In the wild cavy, the presence of a male appeared to influence maturation more between days 25 and 30 than earlier in life. Male C. aperea matured and had fully descended testes when about 65–70 days old. All male cavies produced abundant motile sperm from day 75. First successful copulations occurred at about the same age. Surprisingly, the priming effect of the presence of an adult male on female maturation proved stronger in these highly precocial caviomorphs than in altricial rodents investigated so far.     

Control of the estrous cycle in guinea-pig (Cavia porcellus)

The aim of this work was to look for a simple method to obtain synchronized ovulation in guinea pigs under farming conditions while respecting animal welfare. The luteolytic activity of three different prostaglandins F2alpha (PGF2α) analogs (D-cloprostenol, D,L-cloprostenol and luprostiol) and a daily treatment with oral progestagen (altrenogest) was tested successively at different stages of the estrous cycle on the same group of females during a period of 8 mo. The estrous cycle length was not modified by the administration of PGF2α analogs, whatever the stage of the estrous cycle when the treatment was initiated. Our results led us to reject the use of PGF2α analog to induce practical synchronization of the estrus in this species. In females (n = 29), given 15 days with altrenogest (0.1 mL po once a day), ovulation occurred 4.43 ± 0.13 days after the end of the treatment. Altrenogest treatment was followed by mating. No negative impacts of the treatment on the pregnancy rates, delivery rates and litter sizes were observed. This standard method of guinea-pig estrus synchronization is less stressful for the animals compared to techniques using progesterone tubing.     

Comparative analysis of the malate dehydrogenases isolated from the cytosolic fraction of several tissues of guinea-pig Cavia porcellus

The specific activities of the malate dehydrogenase and lactate dehydrogenase present in the soluble fraction of several guinea-pig tissues are reported. The electrophoretic patterns showed always two forms (A and B) with malate dehydrogenase activity and the five isoenzymes of lactate dehydrogenase. Chromatography of the different soluble fractions through 5' AMP-Sepharose allowed both molecular forms of malate dehydrogenase to be separated and obtained free from lactate dehydrogenase. Comparative studies of the two forms of malate dehydrogenase evidenced that the A and B forms exhibited cytosolic and mitochondrial characteristics, respectively.     

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.     

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.     

Origin of the v. portae and variability of its tributaries in laboratory animals. II. The guinea pig (Cavia aperea f. porcellus)

The authors investigated the origin of the v. portae and variability of its main tributaries in 30 adult guinea pigs (Cavia aperea f. porcellus). The venous bed was visualized by means of blue-dyed latex. The v. portae was formed the most frequently - in 17 cases (56.7%) - by the confluence of three veins - the v. mesenterica cranialis, the v. lienalis and the v. gastroepiploica dextra; less often it was formed from four or five tributaries and in one case only it was formed by union of the v. mesenterica cranialis and the v. lienalis. The v. gastrica sinistra was a tributary of the v. lienalis in 24 cases (80.0%). It arose on the ventral and the dorsal surface of the stomach, in the region adjacent to the curvatura minor ventriculi. In 21 cases (70.0%) it was joined by an independent v. cardiaca. The v. lienalis originated in the hilus lienis, usually as a result of the union of two venous trunks. Inter-organ anastomoses were found in 26 cases (86.7%); in 10 cases (33.3%) they occurred simultaneously between the spleen and the stomach and between the spleen and the pancreas, while in 16 cases (53.3%) they connected the superior pole of the spleen with the stomach. An independent v. gastroepiploica dextra was present in 19 cases (63.3%) as a tributary of the v. portae. In 22 cases it was joined by the v. pylorica. A v. pancreaticoduodenalis cranialis was present in 27 cases (90.0%). In 18 cases (60.0%) it united with the v. gastroepiploica dextra to form a common trunk, the v. gastroduodenalis, which joined the v. portae; in two cases (6.7%) it was an independent tributary of the v. portae. In six cases it was connected with the v. lienalis and in three cases (10.0%) it was replaced by a few vv. pancreaticae emptying into the v. lienalis. A typical v. pancreaticoduodenalis caudalis, as a tributary of the a. mesenterica cranialis, was found in 19 cases (63.3%). In two cases, together with the v. pancreaticoduodenalis cranialis, it formed a single trunk (the v. pancreaticoduodenalis communis). A comparison of the v. portae and its tributaries in the guinea pig and the cat has so far not brought to light any significant morphological differences relative to their different zoological classification and their different modes of life.