Genetically engineered mice. Husbandry and resources.
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Animal Husbandry↗
Biomedical subjects
C C Linder
Publications and source records attributed to C C Linder.
The influence of genetic background on spontaneous and genetically engineered mouse models of complex diseases.
In recent years, the use of genetically altered mice as models of complex human disease has revolutionized biomedical research into the genetics of disease pathogenesis and potential therapeutic interventions. Whether a mouse expresses a spontaneous or induced mutation, it is critical to remember that the observed phenotype is not always the direct result of the genetic alteration. The author points out the importance of considering the genetic background of the strain used to create these important models.
Animals↗
Genetic variation among 129 substrains and its importance for targeted mutagenesis in mice.
Targeted mutagenesis in mice, a powerful tool for the analysis of gene function and human disease, makes extensive use of 129 mouse substrains. Although all are named 129, we document that outcrossing of these substrains, both deliberate and accidental, has lead to extensive genetic variability among substrains and embryonic stem cells derived from them. This clearer understanding of 129 substrain variability allows consideration of its negative impact on targeting technology, including: homologous recombination frequencies, preparation of inbred animals, and availability of appropriate controls. Based on these considerations we suggest a number of recommendations for future experimental design.
Animals↗
Mouse mutations as models for studying cataracts.
Human cataracts may be congenital or appear later in life; nuclear, cortical and lens epithelial proliferation forms have all been described. Due to the high degree of genetic homology, it is not surprising that multiple spontaneous or induced single gene mutations result in morphologically similar forms in the mouse. There are many different mutations in inbred strains of mice in which cataracts are a part of the phenotype. These mutations are of potential value in deciphering the molecular mechanisms involved in cataract formation. This report reviews the currently published cataract mutations in mice.
Animals↗
Relationship of a mouse Sertoli cell line (MSC-1) to normal Sertoli cells.
Recently, a mouse Sertoli cell line (MSC-1) was established from transgenic mice carrying a fusion gene composed of human Müllerian inhibitory substance transcriptional regulatory sequences linked to the SV40 T-antigen gene. This cell line contained a morphologically heterogeneous population of cells that expressed characteristic Sertoli cell mRNAs such as transferrin, the beta-subunit for inhibin, and sulfated glycoprotein-2 (SGP-2). In this study, we compared various characteristics of MSC-1 cells to primary cultures of Sertoli cells from immature rats or adult mice. Our observations indicated that: 1) These cells were ultrastructurally similar to mouse Sertoli cells in culture; 2) MSC-1 cells expressed mRNA for androgen-binding protein (ABP) and SGP-1, but not the receptor for FSH; 3) The expression of SGP-2 mRNA and secretion of SGP-2 increased approximately 2-fold when cells were cultured at 41 degrees C, the nonpermissive temperature for the SV40 virus, while SGP-1 and transferrin mRNA levels and secretion were unaffected; 4) Proliferation of these cells was serum-dose dependent and temperature dependent and could be inhibited by incubating MSC-1 cells at 41 degrees C; 5) Proliferation was also significantly reduced after cells were incubated in the presence of dibutyryl cAMP (dbcAMP) for 6 days; 6) Fifteen subcultures produced from single MSC-1 cells displayed similar levels of mRNA expression for transferrin or SGP-1. Together these data indicate that the MSC-1 cell line is composed of a single cell type displaying numerous characteristics of Sertoli cells. This cell line may provide a unique source of tissue for studying various aspects of Sertoli cell behavior.
Androgen-Binding Protein↗
CFTR expression is regulated during both the cycle of the seminiferous epithelium and the oestrous cycle of rodents.
Severely reduced fertility is a common finding in cystic fibrosis (CF). We used in situ hybridization to examine the cell-specific expression of CFTR in the reproductive organs of rodents. In males CFTR mRNA is found in the round spermatids (spermatogenic stages V-X) and in the principal cells that line the initial segment of the epididymis. In both the testis and the epididymis, CFTR expression is developmentally regulated suggesting that the defect in the genital tract of male CF patients is of developmental origin. CFTR expression in the luminal and glandular epithelium of the uterus is regulated during the oestrous cycle and is maximal at pro-oestrus. Our results provide a biological rationale for the reduced fertility of CF patients, and suggest a possible cause for the comparatively poorer prognosis for women with CF.
Animals↗
Testicular synchrony: evaluation and analysis of different protocols.
Using the vitamin A depletion-replacement rat model to obtain testicular synchrony, we examined the reproducibility and degree of synchronization obtained by two different protocols. In the original protocol (A), synchrony was achieved by use of retinol alone. In protocol B, retinoic acid was used during the final days of vitamin A depletion as a supplement to retinol. With protocol A, a total of 56 rats were analyzed by an adaptation of a previously published method for quantifying synchrony. Animals treated by protocol A demonstrated a reproducible degree of synchrony although variability was high among individual animals. A smaller group of animals treated with protocol B demonstrated a lower degree of synchrony. In contrast, the midpoint of synchrony (point in the cycle at which 50% of the stages are more advanced and 50% are less advanced) was a more constant value and was not different between the two treatments. The midpoints of synchrony obtained from both protocols were used to calculate a cycle duration of 300 h for our strain of Sprague-Dawley rats. Our results indicate that while the use of either protocol can reproducibly provide testicular synchrony, protocol A results in a higher degree of synchrony. The ability to synchronize testes to selected stages provides sufficient experimental material for the study of the molecular and cellular events of spermatogenesis.
Animals↗
Expression of receptors during the cycle of the seminiferous epithelium.
The data presented in this manuscript are all based on some inferences drawn from past experimental observations. The first is that the synchronized testis model is representative of the normal testis. Support for this premise comes from the studies on SGP-2, SGP-1 and transferrin where results using in situ hybridization and Northern blots are similar for normal and for synchronized testes. The second inference is that normalizing all of the data to the relative levels of SGP-1 mRNA adjusts for the possible differential loading of mRNA samples. The logic of this practice is based on the observation obtained using in situ hybridization that SGP-1 mRNA levels did not change across the cycle. The third assumption was that total mRNA levels do not change greatly across the cycle. Wholesale changes in testicular mRNA such as the doubling of all of the mRNA transcripts per testis would not be accounted for by these studies. We feel that this is an unlikely complication because of the strong correlation between much of the data and the known biology. In addition, there is a strong correlation between our data on the FSHR mRNA and the binding data for FSH obtained by another laboratory and different techniques. The available data in the literature reveals that most of the Sertoli cell products which change in relative concentrations during the cycle of the seminiferous epithelium appear to have a maximum in either stages VII or IX or in stages XIII to III. Thus, the Sertoli cells in the cycle could be described has having two different functional modes. In mode A maximal levels of mRNA for a specific Sertoli cell product are roughly found in stages VII-IX and in mode B the maximal levels are found in stages XIII to III (Fig. 5). The distribution of the receptor mRNA and ABP mRNA can also be described in terms of these two modes of Sertoli cell function. Transferrin receptors, retinoic acid receptors, and androgen-binding protein appear to fall into mode A while FSH and androgen receptors fall into mode B (Table 1). Products which have antithetical functions such as FSH and inhibin or cystatin and cathepsin L are found in different modes. We propose that most of the actions of the Sertoli cell during the cycle can be specified by the dual modes described above rather than by an infinite number of operational modes.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Fetal heart rate monitoring casebook. Checkmark fetal heart rate pattern and normal neonatal outcome.
BACKGROUND: A checkmark pattern of the fetal heart rate (FHR) had been seen in association with hypoxia in human and animal fetuses. CASE: We report a checkmark pattern in a fetus of a 26-year-old primigravida who underwent induction of labor at term. Scalp pH was 7.32. Comprehensive ultrasound examination revealed normal results. The neonate was born in satisfactory condition. Apgar scores were 7 and 10 at 1 at 5 minutes of life, respectively. CONCLUSION: Checkmark FHR pattern may be a benign finding; however, if it is detected, it should be closely monitored.
Adult↗
Expression of apolipoprotein E mRNA in the epithelium and interstitium of the testis and the epididymis.
Apolipoprotein E (apo E) is an important constituent of plasma lipoproteins and is believed to be involved in the regulation of lipid transport and distribution between tissues. The production of this apolipoprotein in extra-hepatic tissues such as the testis and epididymis could facilitate specific local functions. Apo E mRNA was detected in testis, epididymis, seminal vesicles, and prostate. In the epididymis, apo E was detected using in situ hybridization in epithelial cells and in some cells in the interstitium throughout the organ (i.e., caput, corpus, and cauda). Northern blot analysis showed that apo E mRNA is present in Sertoli cells and germ cells, but not peritubular myoid cells. Interstitial cells of the testis displayed the most intense signal for apo E message using in situ hybridization. Messenger RNA for apo E was also detected in the interstitium of rat testes at 3 and 6 days after animals were treated with ethylene dimethanesulfonate (EDS) to eliminate Leydig cells. Thus, in addition to Leydig cells, other cell types within the interstitium are capable of producing apo E message. Levels of testicular apo E mRNA increased between 30 and 60 days pc during which the germ cell population is increasing. As determined by northern blot analysis of RNA from stage synchronized testes, the levels of apo E mRNA fluctuate in relation to the cycle of the seminiferous epithelium. The cells responsible for this stage-specific variation in message could not be identified by in situ hybridization. Apolipoprotein Al (apo Al) mRNA was also found to be expressed in the epididymis but not in the testis of adult rats. The role of apolipoproteins in spermatogenesis and sperm maturation has not been elucidated. The results of this study demonstrate the specific tissues and cells types which play a role in the production and possible regulation of apo E mRNA in the male reproductive tract. These data will help in the elucidation of the function of apo E in spermatogenesis and sperm maturation.
Age Factors↗