Body composition of inactivated growth hormone (oMt1a-oGH) transgenic mice: generation of an obese phenotype

The consequences of a 42 d exposure to elevated growth hormone (GH) on adipose tissue were assessed using the regulatable ovine metallothionein- ovine GH (oMt1a-oGH) transgene in male and female GH transgenic (TG) mice. Activation of transgene expression at 21 d of age followed by inactivation of transgene expression at 63 d of age (TG-on/off) increased individual white adipose tissue (WAT) depots and total body lipid stores in both males and females. WAT, expressed as a percentage of fasted body weight, did not differ in wildtype (WT) and continuously activated TG males and females up to 105 d of age, but was increased approximately 270% following inactivation of the transgene. Inguinal depot adipocytes were more numerous in both male and female TG +/- relative to WT or TG animals. The ensuring obesity was not accompanied by a decrease in thermogenic capacity of brown adipose tissue, as indexed by uncoupling protein quantity. GH transgene expression was accompanied by elevated insulin levels that were restored to WT levels upon cessation of transgene expression (p > 0.1). Early, transient exposure to elevated GH increased total body lipid by nearly threefold independent of gender; the increased lipid content was sustained and reflected WAT hypertrophy and hyperplasia. The oMt1a-oGH mouse provides a novel model of induced obesity in response to inactivation of a GH-transgene by the withdrawal of the transgene stimulus.

Mental health service delivery in rural areas: organizational and clinical issues

The mental health funding cuts and the block grant shift of the last decade have placed an increased emphasis on fee-generating services. In already underserved rural areas, this has generated immense challenges for mental health professionals on how to provide services to persons other than those with chronic mental illness. This chapter has discussed alternatives and innovations that have proven successful. Linkages with primary care physicians and indigenous residents who have been trained to provide basic mental health services under the supervision of mental health professionals are just two of the ways in which mental health professionals have risen to meet the challenges placed before them. A review of the literature produced few articles about rural programs addressing the issues of substance abuse, services to women, children, the elderly, those with severe mental illness or developmental disability, and the homeless, or crisis intervention programs. Much work needs to be done to provide adequate services to these special rural populations. It is hoped that the renewed interest in rural areas generated by the farm crisis will produce additional programs addressing the needs of these often underserved populations.

Outpatient management of superficial venous insufficiency at a naval medical facility

Superficial venous insufficiency is common in a young, working population. It can result in disability and lost time from work because of chronic pain, inflammation, and/or ulceration. We reviewed our experience in the management of 104 patients with superficial venous insufficiency secondary to saphenofemoral and/or perforator venous incompetence. The main treatment objective was to control venous insufficiency in a manner that would allow a rapid return to duty. The technique involved ligation of the incompetent saphenofemoral junction and/or perforating veins (i.e., point ligation) under local anesthesia. Patients returned to normal duty status the day after treatment. Six weeks later any persistent disease was controlled with compression sclerotherapy. Significant morbidity included postoperative wound complications in 4% and thrombophlebitis in 14%. Objectives of treatment, with excellent functional and cosmetic results, were achieved. True recurrence was noted in 8% of patients, whereas new disease developed in only 4%; the total recurrence rate was 12%. This mode of therapy is ideally suited to outpatient management. This study demonstrates the excellent control of venous dysfunction that is achievable with the use of selective therapy based on proximal venous ligation and staged sclerotherapy.

A mechanical model for the formation of vascular networks in vitro

Endothelial cells, when cultured on gelled basement membrane matrix exert forces of tension through which they deform the matrix and at the same time they aggregate into clusters. The cells eventually form a network of cord-like structures connecting cell aggregates. In this network, almost all of the matrix has been pulled underneath the cell cords and cell clusters. This phenomenon has been proposed as a possible model for the growth and development of planar vascular systems in vitro. Our hypothesis is that the matrix is reorganized and the cellular networks form as a result of traction forces exerted by the cells on the matrix and the latter's elasticity. We construct and analyze a mathematical model based on this hypothesis and examine conditions necessary for the formation of the pattern. We show cell migration is not necessary for pattern formation and that isotropic, strain-stimulated traction is sufficient to form the observed patterns.

Antisense and ribozyme constructs in transgenic animals

Geneticists have long sought the ability to add or subtract individual genes from an organism's genome, or to be able to alter the level of expression of a gene in a targeted, developmentally and tissue-specific manner. The development of transgenic technology realized the possibilities of increasing the expression of a specific gene or the transfer of a new gene into an animal. Homologous recombination techniques allow the deletion or alteration of a gene in vivo. The production of transgenic animals incorporating a gene construct that expresses a complimentary antisense RNA to a targeted gene, or an antisense RNA incorporating a catalytic, ribozyme sequence, have been suggested as a potential mechanism for obtaining the developmentally and tissue-specific down-regulation of expression of a targeted gene in vivo. In this paper we review the current literature with respect to the application of antisense and ribozyme constructs in transgenic animals and conclude that such constructs can effectively downregulate the level of mRNA from a target gene, the amount of protein produced in the cell, and result in phenotypic consequences.

Quantitative genetics of transgenic mice: components of phenotypic variation in body weights and weight gains

Transgenic mice possessing an ovine growth hormone gene were used to study the effects of elevated growth hormone on quantitative genetic variation. Males hemizygous for the transgene were mated to wild-type females to produce half- and full-sib families in which approximately half the progeny were transgenic and half were wild type. Analyses of body weights at 3-10 weeks, and weight gains from 3 to 6, and 6 to 10 weeks produced estimates of the proportion of total variance due to additive genetic effects (h2) and common litter effects (c2), and the genetic correlation between transgenic and wild-type expression of each trait. At 10 weeks, body weight of transgenics exceeded that of wild types by 26 and 49% in males and females, respectively. Estimated genetic variances in the transgenic group were significantly greater than zero for body weights at most ages and for both measurements of gain. Common litter effects accounted for a similar proportion of variation in the wild-type and transgenic groups. Additive genetic correlations between wild-type and transgenic expression of body weights tended to decline with age, indicating that a partially different array of genes may have begun to affect body weight in the transgenic group.

Relationship between stage of development and sex of bovine IVM-IVF embryos cultured in vitro versus in the sheep oviduct

We have confirmed more rapid development of male compared with female in vitro-cultured bovine embryos during the first 7 d after in vitro fertilization. The male-to-female sex ratio of expanded blastocysts after 10 d of in vitro culture was 1.37:1.00, which was significantly different from the expected 1:1 ratio, but no deviation from a 1:1 ratio was observed for male and female expanded blastocysts derived from culture of bovine embryos in the sheep oviduct (1.11:1.00). When embryos that developed only to the morula stage were analyzed for sex, a greater number of female than male bovine embryos was observed from in vitro culture but not after culture in the sheep oviduct. Possible causes of these sex-related differences in development of cultured bovine embryos are discussed.

Expression of a bovine kappa-CN cDNA in the mammary gland of transgenic mice utilizing a genomic milk protein gene as an expression cassette

Transgenic mice were produced by microinjection of a DNA construct composed of the bovine kappa-casein (kappa-CN) cDNA under the control of the goat beta-CN 5' promoter elements and 3' flanking regions into pronuclear-stage embryos. The gene construct targeted the expression of bovine kappa-CN RNA to the mammary gland and secretion of bovine kappa-CN in the milk. In the three lines studied (BC-7, BC-31 and BC-67) the transgene was stably integrated and propagated as a Mendelian locus. Expression of the bovine protein in lactating mice from the three transgenic lines was demonstrated by northern and western blots. In ten different tissues analysed by northern blotting, expression was confined to the mammary gland of lactating transgenic mice from line BC-7, with low-level expression also observed in the salivary gland of lines BC-31 and BC-67. Transgene expression in the mammary gland paralleled normal casein gene expression during lactation and was not observed in virgin females. The level of bovine kappa-CN mRNA expression on day 10 of lactation in hemizygous transgenic females in relation to endogenous mRNA of whey acid protein (WAP) gene expression was 14%, 69%, and 127% in lines BC-7, BC-31 and BC-67, respectively. No association between transgene copy number and expression was observed. The bovine kappa-CN concentration in milk on day 10 of lactation ranged from 0.94 to 3.85 mg of protein per ml of milk. The bovine kappa-CN expressed in mouse milk had the same molecular mass and immunoactivity with polyclonal antibodies as did kappa-CN from bovine milk. A high degree of variation in the production of bovine kappa-CN within each of the transgenic lines was observed.

A mathematical model of glioma growth: the effect of extent of surgical resection

We have developed a mathematical model based on proliferation and infiltration of neoplastic cells that allows predictions to be made concerning the life expectancies following various extents of surgical resection of gliomas of all grades of malignancy. The key model parameters are the growth rate and the diffusion rate. These rates were initially derived from analysis of a case of recurrent anaplastic astrocytoma treated by chemotherapies. Numerical simulations allow us to estimate what would have happened to that patient if various extents of surgical resection, rather than chemotherapies, had been used. In each case, the shell of the infiltrating tumour that remains after 'gross total removal' or even a maximal excision continues to grow and regenerates the tumour mass remarkably rapidly. By developing a model that allows the growth and diffusion rates to define the distribution of cells at the time of diagnosis, and then varying these rates by about 50%, we created a hypothetical tumour patient population whose survival times show good agreement with the results recently reported by Kreth for treatments of glioblastomas. Tenfold decreases in the rates of growth and diffusion mimic the results reported by many other investigators with more slowly growing gliomas. Thus, the model quantitatively supports the ideas that (i) gliomas infiltrate so diffusely that they cannot be cured by resection alone, surgical or radiological, no matter how extensive that may be; (ii) the more extensive the resection, regardless of the degree of malignancy of the glioma, the greater the life expectancy; and (iii) measurements of the two rates, growth and diffusion, may be able to predict survival rates better than the current histological estimates of the type and grade of gliomas.

Alterations of the physical characteristics of milk from transgenic mice producing bovine kappa-casein

kappa-Casein is the protein fraction of milk that allows formation of micelles and determines micelle size and function, thus affecting many of the physical characteristics of milk. Several lines of transgenic mice were generated bearing the B allele of the bovine kappa-CN gene under the control of the regulatory sequences of the caprine beta-CN gene that specifically directed expression of bovine kappa-CN to the lactating mammary tissue of these mice. High expression of bovine kappa-CN protein was observed in the lines studied; the total level of protein in milk was not significantly affected. A high degree of conservation in the amino acids involved in the predicted three-dimensional structure exists between murine and bovine kappa-CN. Milk from transgenic lines expressing high bovine kappa-CN had a significantly smaller micelle size than did control milk. Therefore, bovine kappa-CN appears to have effectively participated in assembly of murine casein micelles. There was no effect on the time of rennet coagulation, but the association was significant between the milk of transgenic lines and the production of a stronger curd in rennet-induced gels. We conclude that bovine kappa-CN is an appropriate candidate for transgenic technology that would increase the ratio of kappa-CN to the calcium-sensitive caseins, therefore affecting the physical properties of the colloidal casein suspension.

Increased hepatic delta 6-desaturase activity with growth hormone expression in the MG101 transgenic mouse

Growth hormone (GH) has many metabolic effects, but its mechanism(s) of action are not fully understood. We studied the short-term effects of endogenously produced GH on liver delta 6-desaturase activity and adipose and liver lipid fraction fatty acid composition in transgenic mice. MG101 transgenic mice ages 73-114 d received zinc to activate the ovine GH transgene for 7 d. Nontransgenic littermates, used as controls, also received zinc. Liver lipids were fractionated into phospholipids (PL), cholesteryl esters, and triglycerides (TG), and retroperitoneal adipose fractionated into PL and TG for fatty acid analysis. Liver microsomes were assayed for delta 6-desaturase activity. Animals expressing the ovine growth hormone transgene had a 2.5-fold higher liver delta 6-desaturase activity than controls. Arachidonate and docosahexaenoate were significantly higher in liver PL of GH transgenic animals compared to controls, but both were decreased in adipose PL in the GH animals. We conclude that increased production of GH affects both production and organ distribution of highly unsaturated fatty acids. The changes in arachidonate in various lipid pools following transgene expression may mediate the systemic actions of GH.

Competition in a spatially heterogeneous environment: modelling the risk of spread of a genetically engineered population

In recent years regulations have been developed to address the risks of releasing genetically engineered organisms into the natural environment. These risks are generally considered to be proportional to the exposure multiplied by the hazard. Exposure is, in part, determined by the spatial spread of the organisms, a component of risk suited to mathematical analysis. In this paper we exampine a mathematical model describing the spread of organisms introduced into a hetereogeneous environment, focusing on the risk of spread and plausibility of containment strategies. Two competing populations are assumed, one the natural species and the other an engineered species or strain, both of which move randomly in a spatially heterogenous environment consisting of alternating favourable and unfavourable patches. The classical Lotka-Volterra competition model with diffusion is used. Analyses of the possible spread and invasion of engineered organisms are thus reduced to finding periodic travelling wave solutions to the model equations. We focus on whether a very small number of engineered organisms can spatially invade a natural population. Initially we investigate the problem for spatially periodic diffusion coefficients and demonstrate that, under the right circumstances and a large enough unfavourable patch, invasion does not succeed. However, if spatially periodic carrying capacities are assumed along with spatially varying diffusion rates, the situation is far more complex. In this case containment of the engineered species is no longer only a simple function of the unfavourable patch length. By using perturbation solutions to the nonuniform steady states, approximate invasion conditions are obtained.

Skeletal muscle growth of oMTla-oGH transgenic mice

Forty-eight transgenic mice carrying an ovine metallothionein 1a-ovine growth hormone (oMTla-oGH) transgene and 48 littermate control mice were used to investigate the effect of GH transgene on the growth and biochemical characteristics of skeletal muscle. Transgene expression was initiated in the transgenic mice by the addition of zinc sulfate to the water at 21 d of age; control mice were also supplemented with zinc sulfate. These mice were maintained on zinc sulfate until 84 d of age. Groups of mice (16 controls, 16 transgenics) were killed at 21, 42 and 84 d of age and muscles from the hind leg were dissected, weighed and analyzed. At 84 d, male transgenics were 32% heavier than controls, while female transgenics were 47% heavier. Transgenic mice of both sexes had smaller (p < 0.01) muscles than controls at weaning (21 d). In spite of significantly heavier body weights of transgenic mice at 84 d of age, there were no significant differences in muscle weights. This was due to a significantly lower (p < 0.01) proportion of muscle, expressed as percentages of body weights, in transgenic mice compared with controls. Higher DNA and RNA concentrations at 42 d of age and elevated cathepsins C and H activities at 42 and 84 d of age indicate that muscle protein metabolism is more active in transgenic mice, which are growing at a greater rate than controls from weaning to 84 d of age. The fact that oMTla-oGH transgenic mice inherently have a lower proportion of muscle, compared to controls and that this proportion does not change in spite of transgene activation and 30 fold increase in plasma GH levels, suggests the hypothesis that muscle growth may be controlled by locally produced IGFs, which are essentially independent of circulating GH concentrations.

Internal iliac artery aneurysm following aortic reconstruction

Fewer than 100 internal iliac artery aneurysms have been reported in the English literature. Of these the incidence of true aneurysms occurring after aortic reconstruction is exceedingly low. A 73-year old man presented with 7 cm asymptomatic left internal iliac artery aneurysm 12 years after repair of an abdominal aortic aneurysm with a bifurcation graft. We report our experience with this patient along with a review of the literature and recommendations for aneurysm surveillance.

Simple versus sophisticated models of breath alcohol exhalation profiles

For medicolegal purposes, breath alcohol content is typically determined from an end-expiratory sample. Measurements obtained by this method necessarily underestimate the alveolar breath alcohol content, and therefore underestimate the blood alcohol content. We suggest and analyse an improved paradigm which uses the entire time-series of breath alcohol measurements during exhalation, not simply the last recorded value. We present two mathematical models for the exhaling lung, and discuss the implications of each for more accurate and therefore more reliable breath alcohol measurement.

Development of obesity following inactivation of a growth hormone transgene in mice

Mice with a temporally regulatable ovine metallothionein 1a--ovine growth hormone transgene (oMT1a-oGH) were utilized to study the effects of withdrawal of elevated circulating levels of growth hormone (GH) on growth and body composition. The transgene was activated from 21-42 days of age by provision of zinc sulfate in the drinking water. At 42 days, mice were allocated to either activated transgenic (remain on zinc sulfate) or inactivated transgenic (removal of zinc sulfate) groups, and to receive either ad libitum or restricted (80-90% of ad libitum) access to feed. Non-transgenic control mice were treated similarly. Body weights and intakes were recorded weekly. Mice were killed at 70 d and epididymal and subcutaneous fat pads, trimmed hind carcass and various organs were weighed. The main findings of this study are: (1) food-restricted mice possessing an activated oMT1a-oGH transgene fail to demonstrate increased growth, but exhibit significantly reduced levels of fat (P < 0.05) relative to all other genotype x feed level combinations; and (2) inactivation of the oMT1a-oGH transgene, following a period of elevated GH levels, leads to development of obesity as evidenced by two to three fold increases in epididymal and subcutaneous fat pad weights (P < 0.01) relative to both activated transgenic and non-transgenic control mice. These large increases in fat deposition also occurred when intake was restricted to 80-90% of ad libitum levels, indicating that metabolic changes independent of intake occur in these inactivated transgenic mice. It is possible that highly elevated production of GH in activated oMT1a-oGH transgenic mice leads to (1) enhanced promotion of preadipocyte differentiation, leading to increased numbers of adipocytes that, upon cessation of oGH production, are available for lipid deposition resulting in obesity, or (2) alterations in production of or responsiveness to insulin, leading to increased fat deposition upon removal of the chronic anti-lipogenic actions of GH. The oMT1a-oGH transgenic mouse line should provide a new genetic model with which to investigate the mechanisms by which growth hormone affects obesity.

Mammary gland expression of transgenes and the potential for altering the properties of milk

Transgenic animals are a useful in vivo experimental model for assessing the ability and impact of foreign gene expression in a biological system. Transgenic mice are most commonly used, while transgenic sheep, goats, pigs and cows have also been developed for specific, "applied" purposes. Most of the work directed at targeting expression of transgenes to the mammary gland of an animal, by using a milk gene promoter, has been with the intent of either studying promoter function or recovering the desired protein from the milk. Transgenic technology can also be used to alter the functional and physical properties of milk resulting in novel manufacturing properties. The properties of milk have been altered by adding a new protein with the aim of improving the milk, not of recovering the protein for other uses.

The effect of mammary gland expression of human lysozyme on the properties of milk from transgenic mice

Transgenic mice were used as model systems to evaluate the impact of human lysozyme expression in the mammary gland. We previously generated two lines of transgenic mice that express human lysozyme mRNA in the mammary gland under the tissue-specific and developmentally correct control of the bovine gene promoter for alpha s1-casein. Concentrations of human lysozyme protein in milk of transgenic mice varied from .25 to .71 micrograms/microliters of milk. Human lysozyme secreted into mouse milk retained its antimicrobial activity, as determined by a denaturing polyacrylamide gel activity assay. The physical and functional properties of the milk were also altered, because mouse milk containing human lysozyme had a 35% decrease in rennet clotting time, a smaller median micelle size (157 nm vs. 172 nm), and a 2.5- to 3-fold greater gel strength than control milk. From these results, we conclude that the use of transgenic animals producing lysozyme in the milk is feasible and potentially useful to the dairy industry.

Spatio-temporal patterns generated by Salmonella typhimurium

We present experimental results on the bacterium Salmonella typhimurium which show that cells of chemotactic strains aggregate in response to gradients of amino acids, attractants that they themselves excrete. Depending on the conditions under which cells are cultured, they form periodic arrays of continuous or perforated rings, which arise sequentially within a spreading bacterial lawn. Based on these experiments, we develop a biologically realistic cell-chemotaxis model to describe the self-organization of bacteria. Numerical and analytical investigations of the model mechanism show how the two types of observed geometric patterns can be generated by the interaction of the cells with chemoattractant they produce.

A mathematical model of glioma growth: the effect of chemotherapy on spatio-temporal growth

During the past two decades computerized tomography (CT) and magnetic resonance imaging (MRI) have permitted the detection of tumours at much earlier stages in their development than was previously possible. In spite of this earlier diagnosis the effects of earlier and more extensive treatments have been difficult to document. This failure has led to an increasing awareness of the importance of infiltration of glioma cells into surrounding grossly normal brain tissue such that recurrence still occurs. In this paper a simple mathematical model for the proliferation and infiltration of such tumours is introduced, based in part on quantitative image analysis of histological sections of a human brain glioma and especially on cross-sectional area/volume measurements of serial CT images while the patient was undergoing chemotherapy. The model parameters were estimated using optimization techniques to give the best fit of the simulated tumour area to the CT scan data. Numerical solution of the model on a two-dimensional domain, which took into account the geometry of the brain and its natural barriers to diffusion, was used to determine the effect of chemotherapy on the spatio-temporal growth of the tumour.

A mechanism for early branching in lung morphogenesis

The lung is a highly branched fluid-filled structure, that develops by repeated dichotomous branching of a single bud off the foregut, of epithelium invaginating into mesenchyme. Incorporating the known stress response of developing lung tissues, we model the developing embryonic lung in fluid mechanical terms. We suggest that the repeated branching of the early embryonic lung can be understood as the natural physical consequence of the interactions of two or more plastic substances with surface tension between them. The model makes qualitative and quantitative predictions, as well as suggesting an explanation for such observed phenomena as the asymmetric second branching of the embryonic bronchi.