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Biomedical subjects

A B Kier

Publications and source records attributed to A B Kier.

At least 37 records · Page 2Linked to original sources
PubMed1996

Liver and intestinal fatty acid binding proteins in control and TGF beta 1 gene targeted deficient mice.

The effect of transforming growth factor beta-1 (TGF beta 1) expression on fatty acid binding proteins was examined in control and two strains of gene targeted TGF beta 1-deficient mice. Homozygous TGF beta 1-deficient 129 x CF-1, expressing multifocal inflammatory syndrome, had 25% less liver fatty acid binding protein (L-FABP) when compared to control mice. The decrease in L-FABP expression was not due to multifocal inflammatory syndrome since homozygous TGF beta 1-deficient/immunodeficient C3H mice on a SCID background had 36% lower liver L-FABP than controls. This effect was developmentally related and specific to liver, but not the proximal intestine, where L-FABP is also expressed. Finally, the proximal intestine also expresses intestinal-FABP (I-FABP) which decreased 3-fold in the TGF beta 1-deficient/immunodeficient C3H mice only. Thus, TGF beta 1 appears to regulate the expression of L-FABP and I-FABP in the liver and the proximal intestine, respectively.

Animals↗
PubMed1996

Acyl-CoA binding proteins: multiplicity and function.

The physiological role of long-chain fatty acyl-CoA is thought to be primarily in intermediary metabolism of fatty acids. However, recent data show that nM to microM levels of these lipophilic molecules are potent regulators of cell functions in vitro. Although long-chain fatty acyl-CoA are present at several hundred microM concentration in the cell, very little long-chain fatty acyl-CoA actually exists as free or unbound molecules, but rather is bound with high affinity to membrane lipids and/or proteins. Recently, there is growing awareness that cytosol contains nonenzymatic proteins also capable of binding long-chain fatty acyl-CoA with high affinity. Although the identity of the cytosolic long-chain fatty acyl-CoA binding protein(s) has been the subject of some controversy, there is growing evidence that several diverse nonenzymatic cytosolic proteins will bind long-chain fatty acyl-CoA. Not only does acyl-CoA binding protein specifically bind medium and long-chain fatty acyl-CoA (LCFA-CoA), but ubiquitous proteins with multiple ligand specificities such as the fatty acid binding proteins and sterol carrier protein-2 also bind LCFA-CoA with high affinity. The potential of these acyl-CoA binding proteins to influence the level of free LCFA-CoA and thereby the amount of LCFA-CoA bound to regulatory sites in proteins and enzymes is only now being examined in detail. The purpose of this article is to explore the identity, nature, function, and pathobiology of these fascinating newly discovered long-chain fatty acyl-CoA binding proteins. The relative contributions of these three different protein families to LCFA-CoA utilization and/or regulation of cellular activities are the focus of new directions in this field.

Animals↗
PubMed1996

Cycloheximide-induced apoptosis in melanoma cells derived from regressing cutaneous tumours of Sinclair swine.

The role of apoptosis in the spontaneous regression of Sinclair swine melanoma was investigated in vitro with swine melanoma cell lines. Growth characteristics and sensitivity to cycloheximide-induced apoptosis were determined in melanoma cell lines derived from tumours that were progressing or undergoing regression in vivo. In contrast to cell lines derived from progressing tumours, those derived from regressing tumours showed induction of apoptosis; this phenomenon was dependent on dose but independent of cell growth stage in culture. Chromatin condensation, cell shrinkage, and fragmentation into apoptotic bodies, as well as DNA fragmentation into large kilobase fragments, occurred in cell lines from regressing tumours but not from progressing tumours. These findings suggest that swine melanoma cells are inherently more sensitive to cell death during tumour regression. The apoptosis-sensitive and resistant cell lines will be important for further studies of the roles of cell signalling pathways and gene expression in tumour regression.

Animals↗
PubMed1996

Effects of chronic ethanol consumption on sterol transfer proteins in mouse brain.

Although lipids are essential to brain function, almost nothing is known of lipid transfer proteins in the brain. Early reports indicates cross-reactivity of brain proteins with antisera against two native liver sterol transfer proteins, sterol carrier protein-2 (SCP-2) and the liver form of fatty acid-binding protein (L-FABP). Herein, polyclonal antibodies raised against the recombinant liver sterol transfer proteins SCP-2 and L-FABP were used to identify the lipid transfer proteins in the brains of alcohol-treated and control mice. L-FABP was not detectable in brain of either control or chronic ethanol-treated mice. In contrast, SCP-2 not only was present, but its level was significantly (p < 0.05) increased 23 and 50%, respectively, in brain homogenates and synaptosomes of mice exposed to alcohol. To determine whether antibodies against the recombinant liver SCP-2 reflected true levels of SCP-2 in brain, the cDNA sequence for brain SCP-2 was isolated from a brain cDNA library. The mouse brain SCP-2 sequence was 99.99% identical to the mouse liver SCP-2 sequence. The translated sequence differed by only one amino acid, and the replacement was conservative. Thus, unlike the fatty acid binding proteins, the SCP-2 moieties of brain and liver are essentially identical. Polyclonal antibodies against acyl-CoA binding protein, a lipid-binding protein that does not bind or transfer sterol, showed that increased levels of brain SCP-2 with chronic ethanol consumption did not represent a general increase in content of all lipid transfer proteins. Changes in the amount of SCP-2 may contribute to membrane tolerance to ethanol.

Alcoholism↗
PubMed1996

Effects of altered prenatal hormonal environment on expression of autoimmune disease in NZB/NZW mice.

F1 hybrid New Zealand Black (NZB) x New Zealand White (NZM) (NZB/NZW) mice spontaneously develop an autoimmune disease analogous to systemic lupus erythematosus (SLE). Testosterone experts a powerful suppressive effect on this disorder in adult NZB/NZW mice. A series of experiments was designed to determine if disease would also be suppressed by exposing fetal NZB/NZW mice to increased testosterone. A model was developed in which NZB dams carrying NZB/NZW fetuses were treated with testosterone in a dose adequate to masculinize the external genitalia in female fetuses. NZB/NZW mice that were derived from testosterone-treated dams and control NZB/NZW offspring were followed in a longevity study and had serial assays to assess development of SLE. Additional experiments were carried out to measure lymphocyte subsets and responses to mitogens. Results were compared with F1 hybrid offspring of C57BL/6 dams crossed with DBA/2 males, which are not autoimmune and do not develop SLE. Spleen cells from these groups were tested for Thy 1.2, CD4, CD8, and IgM receptors, and for responses to the mitogens Concanavalin A (ConA) and lipopolysaccharide. Control male NZB/NZW fetuses had unexpectedly high serum estradiol, which decreased significantly with maternal testosterone treatment. The testosterone-exposed male NZB/NZW fetuses developed into adults that lived longer than male NZB/NZW controls. Testosterone treatment of the dam was associated with elevated terminal anti-DNA levels but did not alter markers of renal diseases in adult NZB/NZW mice of either sex. Testosterone-exposed NZB/NZW females had altered T-lymphocyte subsets and testosterone-exposed males had increased response to ConA compared to controls. In male NZB/NZW fetuses whose mothers were administered testosterone, the naturally high level of circulating estradiol observed in untreated male fetuses was decreased significantly. This decrease was associated with an increase in longevity. This unique observation has important implications for fetal exposure to endocrine disruptors in the environment.

Animals↗
PubMed1996

Recent advances in membrane cholesterol domain dynamics and intracellular cholesterol trafficking.

Cholesterol is distributed nonrandomly in and between biological membranes. Despite over two decades' investigation of these phenomena, the origin, regulation, and function of membrane cholesterol asymmetry are not known. Likewise, although pathways of cellular cholesterol absorption/utilization as well as de novo synthesis have been investigated in depth, parallel progress in elucidating pathways of intracellular cholesterol trafficking and final deposition of cholesterol within membranes remains undefined. Understanding the nature and regulation of these processes is essential to resolving molecular mechanisms of cholesterol uptake, reverse cholesterol transport, steroidogenesis, and modulation of membrane function. Based on the fundamental observation that cholesterol is not distributed uniformly in the cell, three key concepts have contributed to recent advances in this field: First, cholesterol is asymmetrically distributed across the cell surface plasma membrane, wherein it translocates rapidly. Second, cholesterol is distributed within the plane of biomembrane bilayers into dynamic and static domains, with the latter predominating. The exact nature and physiological functions of such cholesterol domains or pools remain an enigma. Third, regulation of the size and kinetics of biomembrane cholesterol domains may be determining factors in intracellular cholesterol trafficking, targeting, and efflux. Contributions of both cytosolic carrier proteins and vesicular processes are recognized.

Animals↗
PubMed1995

Molecular and physiological effects of overexpressing striated muscle beta-tropomyosin in the adult murine heart.

Tropomyosins comprise a family of actin-binding proteins that are central to the control of calcium-regulated striated muscle contraction. To understand the functional role of tropomyosin isoform differences in cardiac muscle, we generated transgenic mice that overexpress striated muscle-specific beta-tropomyosin in the adult heart. Nine transgenic lines show a 150-fold increase in beta-tropomyosin mRNA expression in the heart, along with a 34-fold increase in the associated protein. This increase in beta-tropomyosin message and protein causes a concomitant decrease in the level of alpha-tropomyosin transcripts and their associated protein. There is a preferential formation of the alpha beta-heterodimer in the transgenic mouse myofibrils, and there are no detectable alterations in the expression of other contractile protein genes, including the endogenous beta-tropomyosin isoform. When expression from the beta-tropomyosin transgene is terminated, alpha-tropomyosin expression returns to normal levels. No structural changes were observed in these transgenic hearts nor in the associated sarcomeres. Interestingly, physiological analyses of these hearts using a work-performing model reveal a significant effect on diastolic function. As such, this study demonstrates that a coordinate regulatory mechanism exists between alpha- and beta-tropomyosin gene expression in the murine heart, which results in a functional correlation between alpha- and beta-tropomyosin isoform content and cardiac performance.

Animals↗
PubMed1995

Onset and progression of pathological lesions in transforming growth factor-beta 1-deficient mice.

Null-mutant (knockout) mice were obtained through disruption of the sixth exon of the endogenous transforming growth factor-beta 1 allele in murine embryonic stem cells via homologous recombination. Mice lacking transforming growth factor-beta 1 (mutants) were born grossly indistinguishable from wild-type littermates. With time, mutant mice exhibited a wasting phenotype that manifested itself in severe weight loss and dishevelled appearance (between 15 and 36 days of age). Examination of these moribund mice histologically revealed that transforming growth factor-beta 1-deficient mice exhibit a moderate to severe, multifocal, organ-dependent, mixed inflammatory cell response adversely affecting the heart, stomach, diaphragm, liver, lung, salivary gland, and pancreas. Because of the known multifunctional nature of transforming growth factor-beta 1 on the control of growth and differentiation of many different cell types, it is important to determine the degree to which the inflammatory response interacts with or masks other deficiencies that are present. To this end, we examined the extent and nature of the inflammatory lesions in different ages of neonatal knockout mice (5, 7, 10, and 14 days of age) and older moribund mice (> 15 days of age) and compared them with the histology seen in wild-type normal animals. Mild inflammatory infiltrates were first observed in 5-day mutant mice in the heart, by day 7 in the lung, salivary gland, and pancreas, and by day 14 inflammatory lesions were found in almost all organs examined. Moderate to severe inflammation was not present until the mice were 10 to 14 days old. In the older animals, there was a slight increase in the severity of the inflammatory lesions as the mice aged.

Animals↗
PubMed1993

Evaluation of HPMPC therapy for primary and recurrent genital herpes in mice and guinea pigs.

The nucleoside analogue (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMPC) inhibited the replication of herpes simplex virus (HSV) types 1 and 2 in tissue culture cells at about 1.0 micrograms/ml, whereas Acyclovir (ACV) had an EC50 of about 0.10-0.50 micrograms/ml. The purpose of these studies was to evaluate the efficacy of topically applied HPMPC in animal models of primary and recurrent genital HSV-2 infections. Mice treated with 5%, 1% or 0.5% HPMPC three times daily, beginning 6 or 24 h after virus inoculation had reduced vaginal viral replication regardless of time of initiation of therapy. ACV at 5% also reduced vaginal viral replication, but not as effectively as HPMPC. In primary infection of guinea pigs, therapy with 5% or 1% HPMPC beginning at 24 h but not 72 h significantly altered lesion development. However, 5% HPMPC was highly toxic to guinea pigs. Vaginal viral replication was reduced significantly with either 1% or 0.3% HPMPC initiated at 24 h. In these studies, HPMPC was also more efficacious than 5% ACV. Topical treatment with 1% HPMPC did not reduce the incidence or severity of spontaneous or UV-induced recurrent genital lesions. These results indicate that topical therapy with 1%, 0.5% or 0.3% HPMPC was more effective than 5% ACV in the treatment of primary genital HSV-2 infections of guinea pigs and mice and suggest that HPMPC should be considered for topical use in humans.

Acyclovir↗
PubMed1992

Dominant mutation of the murine Hox-2.2 gene results in developmental abnormalities.

Genes carrying the homeobox were originally identified in Drosophila, in which they are now known to play key roles in establishing segmentation patterns and in determining segment identities. A number of genes with striking homology to the Drosophila homeobox genes have now been found in the mouse genome, and mutational analysis is beginning to shed light on their function in mammalian development. To understand better the developmental significance of the murine Hox-2.2 gene, we have generated gain of function mutants by using the chicken beta-actin promoter to drive ubiquitous expression in transgenic mice. The resulting Hox-2.2 misexpression produces early postnatal lethality as well as craniofacial and axial skeletal perturbations that include open eyes at birth, cleft palate, micrognathia, microtia, skull bone deficiencies, and structural and positional alterations in the vertebral column. We repeatedly observe complete or partial absence of the supraoccipital bone and malformations of the exoccipital and the basioccipital bones. These results suggests a role for the Hox-2.2 gene in specifying positional identity along the anterior-posterior axis.

Abnormalities, Multiple↗
PubMed1992

Targeted disruption of the mouse transforming growth factor-beta 1 gene results in multifocal inflammatory disease.

Transforming growth factor-beta 1 (TGF-beta 1) is a multifunctional growth factor that has profound regulatory effects on many developmental and physiological processes. Disruption of the TGF-beta 1 gene by homologous recombination in murine embryonic stem cells enables mice to be generated that carry the disrupted allele. Animals homozygous for the mutated TGF-beta 1 allele show no gross developmental abnormalities, but about 20 days after birth they succumb to a wasting syndrome accompanied by a multifocal, mixed inflammatory cell response and tissue necrosis, leading to organ failure and death. TGF-beta 1-deficient mice may be valuable models for human immune and inflammatory disorders, including autoimmune diseases, transplant rejection and graft versus host reactions.

Animals↗
PubMed1991

A functional c-myb gene is required for normal murine fetal hepatic hematopoiesis.

The c-myb proto-oncogene encodes a sequence-specific DNA-binding protein. To better understand its normal biological function, we have altered the c-myb gene by homologous recombination in mouse embryonic stem cells. Resulting homozygous c-myb mutant mice displayed an interesting phenotype. At day 13 of gestation these mice appeared normal, suggesting that c-myb is not essential for early development. By day 15, however, the mutant mice were severely anemic. Analysis indicated that embryonic erythropoiesis, which occurs in the yolk sac, was not impaired by the c-myb alteration. Adult-type erythropoiesis, which first takes place in the fetal liver, was greatly diminished in c-myb mutants, however. Additional hematopoietic lineages were similarly affected. These results are compatible with a role for c-myb in maintaining the proliferative state of hematopoietic progenitor cells.

Animals↗
PubMed1991

Therapeutic responses of spontaneous canine malignancies to combinations of radiotherapy and hyperthermia.

The goals of this ongoing Phase III study of adjuvant local hyperthermia with radiotherapy were to evaluate how tumor control and normal tissue complications were related to patient and treatment variables. Canine veterinary patients with localized malignancies were stratified by histology and anatomic site and randomized into three groups. All patients received radiotherapy (60CO) in 3.5 Gy fractions given Mon-Wed-Fri to 14 treatments (49 Gy). One group received radiotherapy alone while the others also received microwave-induced hyperthermia (44 degrees C) for 30 minutes once each week. Hyperthermia followed radiotherapy and was given to one group immediately and delayed 4-5 hours in the other. Adjuvant hyperthermia resulted in a significant (p less than .05) increase in complete response rate, reduction in the frequency of non-responders, and increased persistent local control relative to radiotherapy alone. Hyperthermia increased the complete response rate regardless of histology, site, or volume and with the current sample size control was significantly (p less than .05) greater for sarcomas, tumors of the trunk and extremities, and those with volumes less than 10 cc. Quantitative clinical assessment of the acute response of skin and oral mucosa indicated that hyperthermia significantly enhanced these acute reactions, which required roughly twice the healing time observed with radiotherapy alone. Quantitative histologic scoring of changes seen between pre- and post-therapy skin biopsies indicated that a treatment induced decline in the frequency of dermal blood vessels, sebaceous glands, and hair follicles was enhanced by adjuvant hyperthermia, particularly in the late response evaluation interval. The probability of tumor control and adverse normal tissue responses correlated with several measures of thermal dose. Thermal doses in excess of 120 equivalent minutes at 43 degrees C correlated positively with increased skin reactions and negatively with the complete response rate, and these trends were usually evident during the animals' first treatment.

Animals↗
PubMed1991

Effects of prolonged administration of the 19-nor-testosterone derivatives norethindrone and norgestrel to female NZB/W mice: comparison with medroxyprogesterone and ethinyl estradiol.

To evaluate effects of commonly used progestational estrogenic contraceptive steroids in a hormone-responsive model of lupus, we treated female NZB/W mice before clinical disease (6 wks of age) and after onset of lupus (24 wks of age) with doses of hormones titered to suppress reproduction. We report efficacy of norethindrone (NE) and norgestrel (NG), progestins derived from 19-nor-testosterone, in delaying expression of anti-DNA antibodies. Mice implanted with NG at 24 wks of age had prolonged lifespans. In contrast, the hydroxyprogesterone derivative, medroxyprogesterone acetate (MP), did not affect autoimmune disease. These observations suggest that prolonged administration of 19-nor-testosterone derivatives, in small doses adequate to suppress reproduction, may have ameliorative effects in systemic lupus erythematosus. Mice receiving ethinyl estradiol (EE) plus courses of tetracycline to suppress cystitis had active anti-DNA responses. In 60% of EE-treated mice, however, early deaths resulted from malignant lymphomas and complications of obstructive uropathy. Estrogen toxicity, rather than accelerated lupus, was the major cause of death in NZB/W mice treated with EE.

Animals↗
PubMed1991

Membrane cholesterol dynamics: cholesterol domains and kinetic pools.

Nonreceptor mediated cholesterol uptake and reverse cholesterol transport in cells occur through cellular membranes. Thus, elucidation of cholesterol dynamics in membranes is essential to understanding cellular cholesterol accumulation and loss. To this end, it has become increasingly evident that cholesterol is not randomly distributed in either model or biologic membranes. Instead, membrane cholesterol appears to be organized into structural and kinetic domains or pools. Cholesterol-rich and poor domains can even be observed histochemically and physically isolated from epithelial cell surface membranes. The physiologic importance of these domains is 2-fold: (i) Select membrane proteins (receptors, transporters, etc.) are localized in either cholesterol-rich or cholesterol-poor domains. Consequently, the structure and properties of the domains rather than of the bulk lipid may selectively affect the function of proteins residing therein. (ii) Kinetic evidence suggests that cholesterol transport through and between membranes may occur through specific domains or pools. Regulation of the size and properties of such domains may be controlling factors of cholesterol transport or accumulation in cells. Recent technologic advances in the use of fluorescent sterols have allowed examination of cholesterol domain structure in model and biologic membranes. These techniques have been applied to examine the role of high-density lipoprotein, cholesterol lowering drugs, and intracellular lipid transfer proteins in membrane sterol domain structure and sterol movement between membranes.

Animals↗
PubMed1991

Membranes of high- and low-metastatic L tumor cell variants.

A model system of metastasis, L-929 fibroblasts and a derivative cell line, A-9 cells, was developed in order to compare the membrane properties of high- and low-metastatic cells cultured in chemically defined medium. The metastatic ability of L-929 and A-9 cells in athymic (nude) mice was examined. Both cell lines produced local tumors, but only L-929 fibroblasts metastasized to the lung. The plasma membranes of L-929 cells had lower sterol/phospholipid ratios and their phospholipids were more unsaturated than those of A-9 cells. The fluorescence probe 1,6-diphenyl-1,3,5-hexatriene and multifrequency phase and modulation fluorometry indicated that the plasma membranes of L-929 cells were less rigid (lower polarization and limiting anisotropy; shorter rotational relaxation time and lifetime) than those of A-9 cells. Thus, the membranes of highly metastatic cells had more unsaturated fatty acids, a lower sterol/phospholipid ratio and were consequently less ordered than those of their less malignant counterparts that formed only local tumors.

Animals↗