Isolation of cDNA clones for the catalytic gamma subunit of mouse muscle phosphorylase kinase: expression of mRNA in normal and mutant Phk mice.

We have isolated and characterized cDNA clones for the gamma subunit of mouse muscle phosphorylase kinase (gamma-Phk). These clones were isolated from a lambda gt11 mouse muscle cDNA library via screening with a synthetic oligonucleotide probe corresponding to a portion of the rabbit gamma-Phk amino acid sequence. The gamma-Phk cDNA clones code for a 387-amino acid protein that shares 93% amino acid sequence identity with the corresponding rabbit amino acid sequence. RNA gel blot analysis reveals that the muscle gamma-Phk probe hybridizes to two mRNA species (2.4 and 1.6 kilobases) in skeletal muscle, cardiac muscle, and brain, but does not hybridize to liver RNA. Phk-deficient I-strain (Phk) mouse muscle contains reduced levels of gamma-Phk mRNA as compared with control mice. Although the Phk defect is an X-linked recessive trait, hybridization to a human-rodent somatic cell hybrid mapping panel shows that the gamma-Phk gene is not located on the X chromosome. Rather, the gamma-Phk cross-hybridizing human restriction fragments map to human chromosomes 7 (multiple) and 11 (single). Reduced gamma-Phk mRNA in I-strain mice, therefore, appears to be a consequence of the Phk-mutant trait and does not stem from a mutant gamma-subunit gene.     

A repertoire of monoclonal antibodies with human heavy chains from transgenic mice.

The introduction of human immunoglobulin gene segments in their unrearranged configuration into the germ line of mice might allow the production of a repertoire of human antibodies. Such transgenic mice could be used for the production of human monoclonal antibodies against human antigens. To test the feasibility of this approach, mice were created that carry a human heavy-chain minilocus comprising unrearranged immunoglobulin variable, diversity, and joining elements linked to a human mu-chain gene. The gene segments of this minilocus are rearranged in a large proportion of cells in thymus and spleen but not in nonlymphoid tissue. Some 4% of the B lymphocytes synthesize human mu chains resulting in a serum titer of about 50 micrograms of transgenic IgM antibody per ml. Hybridomas were established from the transgenic mice that stably secreted several micrograms of antibodies containing human mu heavy chains per milliliter.     

Identification of mutations leading to the Lesch-Nyhan syndrome by automated direct DNA sequencing of in vitro amplified cDNA.

The Lesch-Nyhan (LN) syndrome is a severe X chromosome-linked disease that results from a deficiency of the purine salvage enzyme hypoxanthine phosphoribosyltransferase (HPRT). The mutations leading to the disease are heterogeneous and frequently arise as de novo events. We have identified nucleotide alterations in 15 independently arising HPRT-deficiency cases by direct DNA sequencing of in vitro amplified HPRT cDNA. We also demonstrate that the direct DNA sequence analysis can be automated, further simplifying the detection of new mutations at this locus. The mutations include DNA base substitutions, small DNA deletions, a single DNA base insertion, and errors in RNA splicing. The application of these procedures allows DNA diagnosis and carrier identification by the direct detection of the mutant alleles within individual families affected by LN.     

Recovery of induced mutations for X chromosome-linked muscular dystrophy in mice.

We have used elevated levels of plasma creatine phosphokinase activity to identify muscular dystrophy phenotypes in mice and to screen the progeny of chemical mutagen-treated male mice for X chromosome-linked muscular dystrophy mutations. We were not successful in identifying heterozygous carriers of these induced muscular dystrophy mutations in greater than 8000 progeny. However, we were highly successful in identifying three additional alleles of the characterized mdx locus. These alleles of mdx were recovered from various mutagen-treated males and they occur on an X chromosome that carries flanking markers that allow us to follow the mutations in genetic crosses and in the development of corresponding mutant stocks. These alleles have been designated as mdx2Cv, mdx3Cv, and mdx4Cv. Preliminary data show that mice with mdx2Cv and mdx3Cv mutations have muscular dystrophic phenotypes that do not grossly differ from the characterized mdx mutation. These additional mdx mutations expand the value of mouse models of X chromosome-linked muscular dystrophy and potentially define additional sites of mutation that impair dystrophin expression.     

Cytochrome P450 epoxygenase-derived epoxyeicosatrienoic acids contribute to insulin sensitivity in mice and in humans

Aims/hypothesis

Insulin resistance is frequently associated with hypertension and type 2 diabetes. The cytochrome P450 (CYP) arachidonic acid epoxygenases (CYP2C, CYP2J) and their epoxyeicosatrienoic acid (EET) products lower blood pressure and may also improve glucose homeostasis. However, the direct contribution of endogenous EET production on insulin sensitivity has not been previously investigated. In this study, we tested the hypothesis that endogenous CYP2C-derived EETs alter insulin sensitivity by analysing mice lacking CYP2C44, a major EET producing enzyme, and by testing the association of plasma EETs with insulin sensitivity in humans.

Methods

We assessed insulin sensitivity in wild-type (WT) and Cyp2c44 ^?/? mice using hyperinsulinaemic–euglycaemic clamps and isolated skeletal muscle. Insulin secretory function was assessed using hyperglycaemic clamps and isolated islets. Vascular function was tested in isolated perfused mesenteric vessels. Insulin sensitivity and secretion were assessed in humans using frequently sampled intravenous glucose tolerance tests and plasma EETs were measured by mass spectrometry.

Results

Cyp2c44 ^?/? mice showed decreased glucose tolerance (639 ± 39.5 vs 808 ± 37.7 mmol/l × min for glucose tolerance tests, p = 0.004) and insulin sensitivity compared with WT controls (hyperinsulinaemic clamp glucose infusion rate average during terminal 30 min 0.22 ± 0.02 vs 0.33 ± 0.01 mmol kg^?1 min^?1 in WT and Cyp2c44 ^?/? mice respectively, p = 0.003). Although glucose uptake was diminished in Cyp2c44 ^?/? mice in vivo (gastrocnemius R_g 16.4 ± 2.0 vs 6.2 ± 1.7 μmol 100 g^?1 min^?1, p < 0.01) insulin-stimulated glucose uptake was unchanged ex vivo in isolated skeletal muscle. Capillary density was similar but vascular K_ATP-induced relaxation was impaired in isolated Cyp2c44 ^?/? vessels (maximal response 39.3 ± 6.5% of control, p < 0.001), suggesting that impaired vascular reactivity produces impaired insulin sensitivity in vivo. Similarly, plasma EETs positively correlated with insulin sensitivity in human participants.

Conclusions/interpretation

CYP2C-derived EETs contribute to insulin sensitivity in mice and in humans. Interventions to increase circulating EETs in humans could provide a novel approach to improve insulin sensitivity and treat hypertension.

     

Chromosomal rearrangement segregating with adrenoleukodystrophy: a molecular analysis.

The relationship between X chromosome-linked adrenoleukodystrophy and the red/green color pigment gene cluster on Xq28 was investigated in a large kindred. The DNA in a hemizygous male showed altered restriction fragment sizes compatible with at least a deletion extending from the 5' end of the color pigment genes. Segregation analysis using a DNA probe within the color pigment gene cluster showed significant linkage with adrenoleukodystrophy (logarithm of odds score of 3.19 at theta = 0.0). These data demonstrate linkage, rather than association, between a unique molecular rearrangement in the color pigment gene cluster and adrenoleukodystrophy. The DNA changes in this region are thus likely to be helpful for determining the location and identity of the responsible gene.     

Peptide Chain Termination with Mammalian Release Factor

We report a method for the in vitro study of peptide chain termination in mammals. A proteinaceous release factor has been isolated from rabbit reticulocyte extracts. This factor and a polyribonucleotide template containing the bases U and A stimulate the release of N-formylmethionine from mammalian [N-formylmethionyl-tRNA(f).ribosome] intermediates. Our studies suggest that UAA is a terminator codon for mammalian cells.     

alpha1-antitrypsin (A1AT) deficiency presenting with IgA nephropathy and nephrotic syndrome: is renal involvement caused by A1AT deposition?

The role of severe a1-antitrypsin (A1AT) deficiency in the predisposition of early-onset pulmonary emphysema and juvenile hepatic cirrhosis is well-established. Associated glomerulonephritis is unusual although it is well-recognized in children and young adults with the severe phenotype. We report the first adult case of A1AT deficiency presenting with nephrotic syndrome secondary to IgA nephropathy and explore the direct role of A1AT deposits in the pathogenesis of the renal involvement.     

Whole-grain Continuing Education for School Foodservice Personnel: Keeping Kids from Falling Short

ObjectiveThe purpose of this project was to develop and test whole-grain continuing education for school foodservice personnel.MethodsA continuing education program was developed to address planning, purchasing, preparing, and serving whole-grain food in schools. Participants completed a pre-post questionnaire to assess changes in knowledge, attitudes and intention.ResultsParticipants (n = 211) were mostly non-Hispanic white women. Pre-post test scores indicated improvements in whole-grain knowledge and intention to find whole-grain recipes for school menus (P < 0.05); however, attitudes about storage and cost issues became less positive. After 3–6 months, participants indicated more whole-grain food items were offered in schools.Conclusions and ImplicationsWhole-grain education for school foodservice personnel may increase awareness and menu placement and increase opportunities for whole-grain consumption by children.