Skull growth in the albino rat (Rattus norvegicus)

A longitudinal study of growth in the rat skull, based on serial radiographs, has shown that by the age of one month after birth, the braincase attains some 93% of its adult (fifth-month) size whilst the facial skeleton and mandible attain but 75% of their adult size. By the third month, growth in the braincase has virtually ceased, whereas significant facial growth continues until the age of five months.     

Muscular function and skull growth in the laboratory rat (Rattus norvegicus)

Bilateral masseterectomy in newly-born rats results in a diminution in cranial weight and size. Such reduction affects the facial skeleton to a greater overall extent than the braincase, although in each region it is the dimensions of length that are affected to a greater extent that are those of height or width. Such contrasts are not dependent upon changes in body weight.
Removal of both temporal muscles—a smaller component of the masticatory musculature—results in little change in cranial proportions other than an increase in width of the braincase.
Such findings can be related, first, to contrasts in the timing of growth in the braincase and facial skeleton and, second, to the extent to which muscular function is reduced.     

Polymorphic microsatellite loci of the rat (Rattus norvegicus)

The EMBL and GenBank DNA databases were searched for microsatellite sequences of the rat containing dinucleotide repeats of (CA)_n and (GA)_n. Among those obtained, 23 sequences were analyzed by polymerase chain reaction to examine the size variation of the amplified fragment in inbred rat strains. All of the 23 microsatellite sequences varied in size among the strains tested. The 23 microsatellite loci in a pair of substrains separated from the same progenitor strain were then analyzed. Fragments identical in size were observed in all loci of the two substrains, indicating the stability of the microsatellite over a large number of generations. The microsatellite loci, therefore, should be useful markers for linkage analyses in the rat.     

Idiopathic megaesophagus in a rat (Rattus norvegicus)

Necropsy and histopathologic examination of a rat (Rattus norvegicus) revealed megaesophagus and gangrenous bronchopneumonia. The esophageal dilitation, mural atrophy with persistence of neural structures, regurgitation and bronchopneumonia seen in this case were similar to findings in other animals with megaesophagus.     

The major histocompatibility complex of the rat (Rattus norvegicus)

This review of the RT1 complex, the major histocompatibility complex (MHC) of the rat, focuses on genetic, genomic, evolutionary, and functional aspects at the molecular level. The class I, class II, and framework genes are listed. The physical map of the RT1 complex as revealed by analysis of clonal contigs is compared with the human and mouse MHC, and the degree of orthologous relationship is outlined. Elucidation of the RT1 complex provides important information for using the rat as a model of experimental transplantation and complex diseases.     

Changes in testicular lactate dehydrogenases of the rat (Rattus norvegicus) during growth and development

1. We have quantified lactate dehydrogenase (LDH) A, B and C enzyme levels during the first twelve weeks of life in rat testes. 2. Proteins were electrophoresed under non-denaturing conditions, isoenzymes identified by activity staining and quantified by densitometry scanning. 3. LDH A declined 2-3-fold during testes growth, changing from the most to the least abundant isoenzyme form. LDH B remained fairly constant, and LDH C increased from undetectable levels at birth to become the most abundant of the three polypeptides from week 3 onwards.     

Biochemical genetics of methylglyoxal dehydrogenases in the laboratory rat (Rattus norvegicus)

A genetic locus controlling the electrophoretic mobility of a methylglyoxal dehydrogenase (EC 1.2.1.23) in the rat is described. The locus, designatedMgd1, is expressed in liver and kidney. Inbred rat strains have fixed either alleleMgd1 ^a or alleleMgd1 ^b . Codominant expression is observed in heterozygotes, providing evidence for a tetrameric enzyme structure. Backcross progenies showed the expected 1:1 segregation ratio, and there is evidence thatMgd1 is linked toPep3 andFh1 on chromosome 13. There is also evidence for two additional methylglyoxal dehydrogenases:Mgd2, present in liver and kidney, andMgd3, present only in heart.Supported by the Deutsche Forschungsgemeinschaft (Grant Be 352/18-1).     

Electron microscopy and microcalorimetry of the postnatal rat heart (Rattus norvegicus)

The interplay of ultrastructure and tissue metabolism was examined in neonatal, infant and adult rat hearts by electron microscopy and microcalorimetry. Morphometry was used to determine parameters of oxygen diffusion capacity (distance between capillaries and mitochondria, capillary surface density) and oxidative metabolic capacity (mitochondrial volume fraction). Thin slices and large samples of living tissue were examined calorimetrically to quantify aerobic metabolism and ischemia tolerance, respectively. After birth, rat hearts grow in parallel to body mass and show characteristics of cellular hypertrophy. Capillary surface density increases from neonatal to infant rats, and decreases to an intermediate value in adult rats. The distance between capillaries and mitochondria shows no significant changes throughout postnatal development. Mitochondrial volume fraction increases continuously until adulthood. The specific aerobic tissue metabolic rate is higher in the neonatal than in the infant and adult rat. However, the ischemic decline in metabolic rate is much slower in the neonatal rat, reflecting an elevated hypoxia tolerance. In conclusion, the neonatal rat heart exhibits a high metabolic rate despite a low mitochondrial volume fraction. The subsequent structural rearrangements can be interpreted as long-term adaptations to the increased postnatal workload and may contribute to the progressive loss of hypoxia tolerance.     

Genetic control of two esterases of rat plasma (Rattus norvegicus)

Three electrophoretic variants of plasma esterase in the albumin zone, presumably carboxylesterase, have been demonstrated in 250 rats representing a laboratory population of Wistar rats. Electrophoretic variants of the enzyme are believed to be controlled by two codominant alleles at the autosomal locus referred to as Es-2. The variant of carboxylesterase represented by a fast-migrating single band on starch gel electrophoresis is determined by the gene named Es-2 ^a, whereas the slow-migrating variant, represented by two bands, is under control of the allelic gene Es-2 ^b. Animals with Es-2 ^a/Es-2 ^b genotype have three bands of carboxylesterase in the albumin zone. Genetically determined polymorphism of plasma esterase, presumably carboxylesterase, in the prealbumin zone was shown in both laboratory and wild populations of rats. Breeding tests suggest that the gene referred to as Es-1 ^a, responsible for the presence of carboxylesterase in the prealbumin zone, is inherited dominantly, whereas animals homozygous for the allele Es-1 ^b locked this esterase fraction.     

Metabolism of fluoroacetate in the skink (Tiliqua rugosa) and the rat (Rattus norvegicus)

Administration of 100 mg sodium fluoroacetate (compound 1080) per kilogram body weight to T. rugosa resulted in a 3.4-fold increase in plasma citrate levels 48 h after dosing while administration of 3 mg sodium fluoroacetate per kilogram body weight to R. norvegicus produced a fivefold increase in plasma citrate levels within 4 h. Administration of 300 mg sodium fluoroacetate per kilogram body weight reduced the oxygen consumption of the skink by between 2.5 and 11% while in the rat, 2 mg sodium fluoroacetate per kilogram body weight reduced oxygen consumption by between 28 and 57%. Aconitate hydratase activity in extracts of liver acetone powders from T. rugosa was less inhibited by (-)erythrofluorocitrate (Ki: 0.065 mM) than that in extracts derived from R. norvegicus (Ki: 0.026 mM). The rate of defluorination of fluoroacetate in erythrocytes and in extracts of liver acetone powders of T. rugosa was 8- and 4.5-fold greater, respectively, than that found in similar preparations from R. norvegicus. A rapid rate of defluorination together with a low reliance on aerobic respiration favoured detoxification of fluoroacetate in T. rugosa rather than its conversion into fluorocitrate. Though defluorination in this species helped to minimize the immediate effects of fluoroacetate on aerobic respiration, it resulted in rapid depletion of liver glutathione levels.     

Palmar and plantar pads and flexion creases of the rat (Rattus norvegicus)

The recent detection of dermal ridge configurations on the volar pads of the rat (Rattus norvegicus) has created opportunities for experimental studies of dermatoglyphics. In the present work, the palmar and plantar surfaces of the rat were studied to establish the feasibility of comparative rat and human dermatoglyphic investigations. The studied features included the volar pads and flexion creases. The number and location of the palmar and plantar pads in the rat were found to be similar to those of humans. The exception was a previously unrecognized small pad on the palms and soles of the rat, located on the radial and tibial side, respectively, of the proximal component of the first interdigital pad. This pad has no parallel in human embryos. Rats were found to have flexion creases in the non-pad areas between the neighboring pads, similar in location and appearance to those of humans. Unlike humans, however, rats also have boundary creases, separating the pad and non-pad areas. The marked similarities in the morphology of the volar areas between rats and humans make the rat ideally suitable for experimental studies of dermatoglyphics and flexion creases. Results of such studies should be applicable to human developmental dermatoglyphics, including those pertaining to medical disorders. © 1994 Wiley-Liss, Inc.     

A new polymorphic pepsinogen locus (Pg-2) in the rat (Rattus norvegicus)

Only two types of pepsinogens, which are products of the Pg-1 locus, are present in rat urine. In gastric mucosa, however, additional pepsinogen isozymes are expressed. We have found a polymorphism for rat gastric mucosa pepsinogen using agarose gel electrophoresis. Some inbred rat strains expressed a pepsinogen band, while others did not. The trait was found to be controlled by a single autosomal locus. We tentatively designated the locus as Pg-2 with two alleles, Pg-2a for the one controlling presence of the band and Pg-2o for the one controlling absence. Linkage analysis using BN and TM strains revealed that Pg-2 was closely linked to Pg-1 (3.7 +/- 1.8 cM), and that it did not belong to LG I (Hbb and p), LG II (Acon-1 and Mup-1), LG IV (Hao-1 and Svp-1), LG V (Es-1 and Es-3), LG VI (Gc and h), LG IX (RT1), LG X (Fh and Pep-3), nor a LG containing Ahd-2 (as yet undetermined).     

Linkage analyses among five esterase loci in the laboratory rat (Rattus norvegicus)

A cluster of esterase loci has been identified on a segment of a rat linkage group V; however, the linear order of all the loci has not been established. We estimated the recombination frequencies of two locus combinations among five esterase loci (Es-1, Es-2, Es-3, Es-4, and Es-Si) and the linear order of the loci by using three sets of backcross matings: (1) (K:W × IS) × IS, (2) (K:W × IS) × IS, and (3) (SHR × W) × W). The linear order was determined to be Es-1-Es-4-Es-2-Es-3-Es-Si, although the order of Es-2 and Es-4 remains tentative. The sexinfluenced esterase (Es-Si) was demonstrated to be distinct from Es-1 and was proposed to be Es-Si locus with two alleles of Es-Si ^a (positive) and Es-Si ^b (null).This work was partly supported by Grants-in-Aid for Scientific Research, No. 339020 (1978), from the Ministry of Education, Science and Culture, Japan.     

Evidence for linkage between four esterase loci in the rat (Rattus norvegicus)

Two new esterase polymorphisms have been described in tissue homogenates of the four rat strains August/Orl, LEW/Orl, Long Evans/Orl, and WAG/Orl. Independent expression of these polymorphisms in the different strains and in various tissues of a particular animal agrees with the separate genetic control hypothesis; the gene symbols Es-4 and Es-5 have been assigned to the loci. Transmission of both genes follows a normal autosomal recessive Mendelian pattern; preliminary data indicate tight linkage between these loci and the previously described Es-2 and Es-3 loci.