Defective lysosomal enzyme secretion in kidneys of Chediak-Higashi (beige) mice.

The beige mouse is an animal model for the human Chediak-Higashi syndrome, a disease characterized by giant lysosomes in most cell types. In mice, treatment with androgenic hormones causes a 20-50-fold elevation in at least one kidney lysosomal enzyme, beta-glucuronidase. Beige mice treated with androgen had significantly higher kidney beta-glucuronidase, beta-galactosidase, and N-acetyl-beta-D-glucosaminidase (hexosaminidase) levels than normal mice. Other androgen-inducible enzymes and enzyme markers for the cytosol, mitochondria, and peroxisomes were not increased in kidney of beige mice. No significant lysosomal enzyme elevation was observed in five other organs of beige mice with or without androgen treatment, nor in kidneys of beige females not treated with androgen. Histochemical staining for glucuronidase together with subcellular fractionation showed that the higher glucuronidase content of beige mouse kidney is caused by a striking accumulation of giant glucuronidase-containing lysosomes in tubule cells near the corticomedullary boundary. In normal mice lysosomal enzymes are coordinately released into the lumen of the kidney tubules and appreciable amounts of lysosomal enzymes are present in the urine. Levels of urinary lysosomal enzymes are much lower in beige mice than in normal mice. It appears that lysosomes may accumulate in beige mice because of defective exocytosis resulting either from decreased intracellular motility of lysosomes or from their improper fusion with the plasma membrane. A similar defect could account for characteristics of the Chediak-Higashi syndrome.

A search for transmission ratio distortions in offspring from crosses between inbred mice.

Equal transmission of the two alleles at a locus from a heterozygote parent to the offspring is rarely violated. Beside the differential embryonic mortality, nondisjunction and gene conversion that are rather irregular forms of transmission-ratio distortion (TRD), there are two major forms of departure from Mendelian segregation. The first, found in females, based on the asymmetric nature of female meiosis, is usually referred to as meiotic drive, and has been well documented in a few cases. The second is segregation distortion found in males. There are several known male-related segregation distortion systems that are caused by different fertilizing capacity of sperm cells carrying alternative alleles at a particular locus. Observation of TRD effects requires a sufficient number of offspring produced by a parental pair. As individuals in a population most likely have different genotypes in TRD affecting loci, the total transmission ratio is close to the expected Mendelian ratio and masks potential TRD effects. Highly inbred strains of laboratory mice provide a very good model for studying this phenomenon, because comparing two mice strains is effectively similar as comparison of two individuals in a population. This study tests both forms of TRD in progeny of F1 hybrids from reciprocal crosses of inbred mice. Three previously unknown instances of TRD in females were observed. Therefore, this study concludes that some genes in females may carry alleles that can cause segregation distortion.

Expression and functional analysis of fibulin-1 (Fbln1) during normal and abnormal placental development of the mouse.

The extracellular matrix protein fibulin-1 (FBLN1) is an important component of blood vessel walls, as shown by the lethality of mice with homozygous targeted deletion of the Fbln1 gene. Here, we show that a murine placental overgrowth phenotype is associated with elevated Fbln1 transcript levels, suggesting that the gene and its product have a functional role in placentation. Fbln1 exhibits a specific expression pattern in the mouse placenta. Transcripts could not be detected prior to day 12. In subsequent stages, Fbln1 was expressed strongly in the spongiotrophoblast. Other sites of expression were endothelia of large fetal blood vessels, a tissue type reported to not express this gene. In addition, a subset of giant cells expressed the gene. This giant cell specific expression was strongly increased in hyperplastic placentas. Analysis of the placentation in fibulin null mice did not show any abnormality. Attempts to rescue the placental phenotypes of a congenic model of interspecies hybrid placental dysplasia (IHPD) by normalizing expression of Fbln1 proved that Fbln1 alone is not the key cause of phenotypes in these models of placental hyperplasia.

Construction of a D2.B6-Fv-2r congenic mouse strain: nonlethality of the homozygous Fv-2' genotype.

Starting from the (C57BL/6 x DBA/2)F1 generation (Fv-2s/Fv-2r), 16 serial backcrosses to mice of the parental DBA/2 strain (Fv-2s/Fv-2s) were bred. In each generation, heterozygous Fv-2s/Fv-2r segregants were selected and backcrossed with a DBA/2 parent. In the 16th generation, Fv-2s/Fv-2r heterozygotes were intercrossed, and Fv-2r/Fv-2r homozygotes were selected for interbreeding to establish a congenic strain, D2.B6-Fv-2r. The successful establishment of this congenic strain is in contrast with previous findings suggesting that homozygosity for the Fv-2r allele might be a lethal genotype on the DBA/2 genetic background. At least 10 centimorgans of Fv-2r-linked chromosomal material originating from the C57BL/6 ancestor remains in the D2.B6-Fv-2r genome, as shown by the continued presence of C57BL/6 alleles at the flanking Kfo-1 and Bgl-s loci. The observed recombination frequency for the intervals between Fv-2 and Bgl-s was 6.8%.

Use of two-dimensional electrophoresis to identify and map new mouse genes.

Cytosol polypeptides from mouse liver have been examined using two-dimensional electrophoresis. About 250 spots were readily discernible. When cytosols from strains BALB/cBy and C57BL/6By were compared eight genetically determined differences were observed. Other strain pairs show comparable numbers of differences. These eight phenotypes were scored in seven recombinant inbred lines derived from the two parental strains, and their strain distribution patterns were compared with previously determined patterns for other genetic markers that differ between the two progenitor strains. Using this information, tentative chromosomes assignments for the genes controlling five of the variant phenotypes have been made, and two of the assignments have been confirmed using congenic resistant strains. These eight genes will be useful reference markers in future crosses designed to map new genes.

Genetic analysis of a mouse t complex locus that is homologous to a kidney cDNA clone.

A mouse kidney cDNA clone, pMK174, identifies restriction fragment length polymorphisms (RFLPs) that map to two unlinked loci. One, designated D17Rp17, has been mapped near quaking, (qk), on chromosome 17 using three sets of recombinant inbred (RI) strains. A study of several t haplotypes resulted in the identification of t-specific alleles of D17Rp17 that map to the proximal half of the t complex. Neither t-specific nor wild-type D17Rp17 alleles are present in chromosomes carrying either the T Orleans (TtOrl) or the T hairpin tail (Thp) deletions. Comparison with other molecular markers indicates that pMK174 identifies a new proximal t complex locus, Rp17. The second locus identified by pMK174, termed D4Rp18, is tentatively assigned to chromosome 4 by mouse-Chinese hamster somatic cell hybrid analysis.

Nonhomologous pairing in mice heterozygous for a t haplotype can produce recombinant chromosomes with duplications and deletions.

We have investigated the structure and properties of a chromosomal product recovered from a rare recombination event between a t haplotype and a wild-type form of mouse chromosome 17. Our embryological and molecular studies indicate that this chromosome (twLub2) is characterized by both a deletion and duplication of adjacent genetic material. The deletion appears to be responsible for a dominant lethal maternal effect and a recessive embryonic lethality. The duplication provides an explanation for the twLub2 suppression of the dominant T locus phenotype. A reanalysis of previously described results with another chromosome 17 variant called TtOrl indicates a structure for this chromosome that is reciprocal to that observed for twLub2. We have postulated the existence of an inversion over the proximal portion of all complete t haplotypes in order to explain the generation of the partial t haplotypes twLub2 and TtOrl. This proximal inversion and the previously described distal inversion are sufficient to account for all of the recombination properties that are characteristic of complete t haplotypes. The structures determined for twLub2 and TtOrl indicate that rare recombination can occur between nonequivalent genomic sequences within the inverted proximal t region when wild-type and t chromosomes are paired in a linear, nonhomologous configuration.

A new finding relating to transfusion and renal transplants.

Results in 29 recipients of second renal transplants from cadaver donors show a significantly better graft survival at 1 year of 90% in 10 recipients who had not received blood transfusion before their first transplant compared to 41% in 19 recipients who had been transfused prior to their first transplant (P = 0.025).

Immunosuppression with polyunsaturated fatty acids in renal transplantation.

A double-blind controlled trial has been undertaken to assess the value of a preparation containing polyunsaturated fatty acids (PUFA) in human cadaveric renal transplantation. Eighty-nine patients were studied and followed for 6 months after transplantation. Forty-four took the PUFA preparation and 45 the placebo (oleic acid). Other immunosuppression was standardised. Functional graft survival was significantly better in the PUFA group than in those taking the placebo during the first 3 to 4 months post-transplant. At 6 months, however, although the difference between the groups persisted, it was no longer statistically significant. Complications were equally distributed between the groups.

Characterization of murine middle repetitive DNA.

We have characterized four sequences from a small library containing a subset of the repetitive families of the mouse. Each clone has a repetition frequency of less than 1,100 copies per genome and each clone represents a unique family of middle repetitive DNA. One clone (pMR111) shares homology with mouse intracisternal A-particle (IAP) elements, a second clone (pMR89) has partial homology with a sequence in the 3' untranslated region of the human fibulin gene, while two clones (pMR6, pMR66) are new that have no homology to any reported DNA sequence. Each clone hybridizes to one or two discrete RNA transcripts from one or more tissues of the mouse. Clone pMR66 detected restriction fragment length polymorphisms (RFLPs) at three loci in genomic mouse DNA, defining loci at the distal end of chromosome 5 and the proximal end of chromosome 7. The third locus is unmapped. This study demonstrates that cloned repeats from a repetitive DNA library are a potential source of genetic markers.

Characterization of the cDNA coding for mouse prothrombin and localization of the gene on mouse chromosome 2.

A series of overlapping cDNAs coding for mouse prothrombin (coagulation factor II) have been isolated and the composite DNA sequence has been determined. The complete prothrombin cDNA is 1,987 bp in length [excluding the poly(A) tail] and codes for 18 bp of 5' untranslated sequence, an open reading frame coding for 618 amino acids, a stop codon, and a 3' untranslated region of 112 bp followed by a poly(A) tail. The translated amino acid sequence predicts a molecular weight of 66,087, which includes 10 residues of gamma-carboxyglutamic acid. There are five potential N-linked glycosylation sites. Mouse prothrombin is 81.4% and 77.3% identical to the human and bovine proteins, respectively. Comparison of the cDNA coding for mouse prothrombin to the human and bovine cDNAs indicates 79.9% and 76.5% identity, respectively. Amino acid residues important for the structure and function of human prothrombin are conserved in the mouse and bovine proteins. In the adult mouse and rat, prothrombin is primarily synthesized in the liver, where is constitutes 0.07% of total mRNA as determined by solution hybridization analysis. The genetic locus for mouse prothrombin, Cf-2, has been mapped using an interspecies backcross and DNA fragment differences between the two species. The prothrombin locus lies on mouse chromosome 2, 1.8 +/- 1.3 map units proximal to the catalase locus. The gene order in this region is Cen-Acra-Cf-2-Cas-1-A-Tel. This localization extends the proximal boundary of the known region of homology between mouse chromosome 2 and human chromosome 11p from Cas-1 about 2 map units toward the centromere.

The effect of recurrent early homograft rejection on subsequent patient and renal graft survival.

The effect of recurrent early homograft rejection on subsequent patient and renal graft survival. Two hundred renal transplants performed in Newcastle between 1968 and 1974 and followed up for at least 6 months are reviewed. There was a significant fall ingraft survival at 1 year in those patients who suffered a rejection episode during the first two months post-transplant and this fall became greater with each successive rejection episode. The rise in patient mortality with increasing numbers of rejections showed a similar trend but was less (40-50% at 1 year in those suffering 3 or 4 rejection episodes) and did not reach statistical significance beyond the first episode. We, therefore, conclude that in patients not suitable for home dialysis and in whom, because of uncommon tissue type, a second transplant is not likely to be offered under prevailing conditions of kidney donor shortage, it is justifiable to treat third and fourth rejections occurring during the first two months.

Expression and chromosomal mapping of mouse Gpx2 gene encoding the gastrointestinal form of glutathione peroxidase, GPX-GI.

GPX-GI is a cytosolic tetrameric Se-dependent glutathione peroxidase, similar in properties to GPX-1. Unlike the almost ubiquitous GPX-1, GPX-GI is mainly expressed in the epithelium of gastrointestinal tract. GPX-GI contributes to at least fifty percent of GPX activity in rodent small intestinal epithelium. The total GPX activity consists of at least 70% of selenium-dependent GPX activity in this compartment. By analyzing a panel of mouse interspecies DNA from the Jackson Laboratory's backcross resource, we mapped Gpx2 gene to mouse chromosome 12 between D12Mit4 and D12Mit5, near the Ccs1 locus which contains a colon cancer susceptibility gene. A pseudogene, Gpx2-ps is mapped to mouse chromosome 7. Comparison of Gpx2 gene expression in three pairs of C57BL/6Ha and ICR/Ha mice which are respectively resistant and sensitive to dimethylhydrazine-induced colon cancer, we found a higher Gpx2 mRNA level in C57BL/6Ha colon than ICR/Ha colon. Interestingly, a lower level of GPX activity is found in the resistant strain of mice. Because GPX-1 has three times higher specific activity than GPX-GI, our data suggest that the decreased GPX activity may result from a higher level of Gpx2 gene expression in those cells co-express Gpx1 gene.

Organization of the Navy Dental Corps.

The US Navy Dental Corps was established by an act of Congress in 1912. Its membership consists of dental officers of the Regular Navy and Naval Reserve. The primary mission of the Corps is to prevent or remedy dental conditions that may interfere with the performance of duty by members of the active naval forces. The organizational structure within which the Dental Corps functions is discussed at some length. The Chief of the Dental Corps, under the Surgeon General, is responsible for the planning and direction of programs providing dental care to Navy and Marine Corps personnel and others authorized by law. Until recently, the majority of dental personnel received only technical assistance control from the Bureau of Medicine and Surgery; but in consonance with the goals of improving management effectiveness and achieving efficient use of personnel and material resources, the Navy Dental Corps has undertaken a program of regionalization of its facilities. The establishment of regional dental centers under one command permits immediate response to the needs of populations and the activities they serve, while at the same time reducing layering of administrative and fiscal burdens of existing dental departments at various commands, which allows more dental officers to devote their time to dental health care delivery.

Reproducibility of the centric relation bite registration technique.

Many orthodontists today are using diagnostic casts mounted in centric relation (CR) because they can reveal a completely different malocclusion than what is seen in maximum intercuspation (MI). The CR to MI slide can be measured at the condyles using a semi-adjustable articulator and a condylar position indicator device (CPI). However, before planning treatment from casts mounted in CR, the reliability of the method must be established. Therefore, the purposes of this investigation were: i) to determine the reproducibility, measured with the CPI, of the two-piece wax CR bite registration technique as described by Roth; ii) to determine the direction of the centric slide; iii) to determine differences in overjet measured from CR and MI and; iv) to evaluate the location of the initial tooth contacts in CR. The condylar displacements for 39 subjects were measured in vertical and horizontal components from mounted models. A CR bite registration was taken five times (approximately every five days) and used to remount the lower cast and record the data five times. Since there was not a significant difference between the five CPI readings (p > .05), the Roth CR bite registration is highly reproducible. The condyle moved inferiorly with a small distal component from CR to MI. A statistically significant difference (p < .001) was found in the overjet measurements between CR and MI. Thirty six out of 39 subjects had an initial tooth contact in CR on the most posterior tooth.