Marked reduction in bile acid synthesis in cholesterol 7alpha-hydroxylase-deficient mice does not lead to diminished tissue cholesterol turnover or to hypercholesterolemia

These studies used mice that were deficient in cholesterol 7alpha-hydroxylase to determine the effects of reduced bile acid synthesis on cholesterol homeostasis. In mice lacking this enzyme, bile acid synthesis was reduced from 8.3 to 3.4 micromol/day per 100 g body weight, the intestinal bile acid pool was decreased from 62.5 to 13.2 micromol/100 g bw, and the proportion of hyodeoxycholate, relative to cholate, in this pool was significantly increased. Associated with these changes, intestinal cholesterol absorption decreased from 37% to <1% while triacylglycerol absorption and animal weight gain remained essentially unaffected. The very low rate of cholesterol absorption could be corrected by feeding the mutant mice cholate, but not hyodeoxycholate. The reduction in sterol uptake across the intestine was associated with a 2-fold increase in cholesterol synthesis in the small bowel and liver and an increase in fecal neutral sterol excretion from 15.2 to 35.7 micromol/day per 100 g bw. The size of the cholesterol pools in the plasma, various organs and whole animal remained constant. Thus, under circumstances where the excretion of sterol as bile acids was markedly reduced, total cholesterol turnover actually increased from 164 to 239 mg/day per kg bw. This study demonstrates the complex interactions between bile acid and cholesterol metabolism and the dramatic effects of eliminating a single gene product; however, even though a major catabolic pathway was deleted, cholesterol balance across the animal was maintained.

Reasoned action and social reaction: willingness and intention as independent predictors of health risk

Three studies are described that assess elements of a new model of adolescent health-risk behavior, the prototype/willingness (P/W) model (F. X. Gibbons & M. Gerrard, 1995, 1997). The 1st analysis examined whether a central element of the prototype model, behavioral willingness, adds significantly to behavioral expectation in predicting adolescents' smoking behavior. The 2nd set of analyses used structural-equation-modeling procedures to provide the 1st test of the complete model in predicting college students' pregnancy-risk behavior. Finally, the 3rd study used confirmatory factor analysis to assess the independence of elements of the model from similar elements in other health behavior models. Results of the 3 studies provided support for the prototype model and, in particular, for 2 of its primary contentions: (a) that much adolescent health-risk behavior is not planned and (b) that willingness and intention are related but independent constructs, each of which can be an antecedent to risk behavior.

Reasoned action and social reaction: willingness and intention as independent predictors of health risk

Three studies are described that assess elements of a new model of adolescent health-risk behavior, the prototype/willingness (P/W) model (F. X. Gibbons & M. Gerrard, 1995, 1997). The 1st analysis examined whether a central element of the prototype model, behavioral willingness, adds significantly to behavioral expectation in predicting adolescents' smoking behavior. The 2nd set of analyses used structural-equation-modeling procedures to provide the 1st test of the complete model in predicting college students' pregnancy-risk behavior. Finally, the 3rd study used confirmatory factor analysis to assess the independence of elements of the model from similar elements in other health behavior models. Results of the 3 studies provided support for the prototype model and, in particular, for 2 of its primary contentions: (a) that much adolescent health-risk behavior is not planned and (b) that willingness and intention are related but independent constructs, each of which can be an antecedent to risk behavior.

Two 7 alpha-hydroxylase enzymes in bile acid biosynthesis

The addition of a 7-hydroxyl group is an early and often rate-limiting step in the synthesis of bile acids. This reaction is catalysed by two cytochrome P450 enzymes known as cholesterol 7 alpha-hydroxylase and oxysterol 7 alpha-hydroxylase. cDNAs encoding these proteins have been isolated and used to define two evolutionarily conserved pathways that produce 7 alpha-hydroxylated bile acids.

Human gene targeting by viral vectors

Stable transduction of mammalian cells typically involves random integration of viral vectors by non-homologous recombination. Here we report that vectors based on adeno-associated virus (AAV) can efficiently modify homologous human chromosomal target sequences. Both integrated neomycin phosphotransferase genes and the hypoxanthine phosphoribosyltransferase gene were targeted by AAV vectors. Site-specific genetic modifications could be introduced into approximately 1% of cells, with the highest targeting rates occurring in normal human fibroblasts. These results suggest that AAV vectors could be used to introduce specific genetic changes into the genomic DNA of a wide variety of mammalian cells, including therapeutic gene targeting applications.

Loneliness and nursing home admission among rural older adults

In this study, the authors tested the relation between loneliness and subsequent admission to a nursing home over a 4-year time period in a sample of approximately 3,000 rural older Iowans. Higher levels of loneliness were found to increase the likelihood of nursing home admission and to decrease the time until nursing home admission. The influence of extremely high loneliness on nursing home admission remained statistically significant after controlling for other variables, such as age, education, income, mental status, physical health, morale, and social contact, that were also predictive of nursing home admission. Several mechanisms are proposed to explain the link between extreme loneliness and nursing home admission. These include loneliness as a precipitant of declines in mental and physical health and nursing home placement as a strategy to gain social contact with others. Implications for preventative interventions are discussed.

Infectious clones and vectors derived from adeno-associated virus (AAV) serotypes other than AAV type 2

Adeno-associated viruses (AAVs) are single-stranded dependent parvoviruses being developed as transducing vectors. Although at least five serotypes exist (AAV types 1 to 5 [AAV1 to -5]), only AAV2, AAV3, and AAV4 have been sequenced, and the vectors in use were almost all derived from AAV2. Here we report the cloning and sequencing of a second AAV3 genome and a new AAV serotype designated AAV6 that is related to AAV1. AAV2, AAV3, and AAV6 were 82% identical at the nucleotide sequence level, and AAV4 was 75 to 78% identical to these AAVs. Significant sequence variation was noted in portions of the capsid proteins that presumably are responsible for serotype-specific functions. Vectors produced from AAV3 and AAV6 differed from AAV2 vectors in host range and serologic reactivity. The AAV3 and AAV6 vector serotypes were able to transduce cells in the presence of serum from animals previously exposed to AAV2 vectors. Our results suggest that vectors based on alternative AAV serotypes will have advantages over existing AAV2 vectors, including the transduction of different cell types, and resistance to neutralizing antibodies against AAV2. This could be especially important for gene therapy, as significant immunity against AAV2 exists in human populations and many protocols will likely require multiple vector doses.

Loneliness and nursing home admission among rural older adults

In this study, the authors tested the relation between loneliness and subsequent admission to a nursing home over a 4-year time period in a sample of approximately 3,000 rural older Iowans. Higher levels of loneliness were found to increase the likelihood of nursing home admission and to decrease the time until nursing home admission. The influence of extremely high loneliness on nursing home admission remained statistically significant after controlling for other variables, such as age, education, income, mental status, physical health, morale, and social contact, that were also predictive of nursing home admission. Several mechanisms are proposed to explain the link between extreme loneliness and nursing home admission. These include loneliness as a precipitant of declines in mental and physical health and nursing home placement as a strategy to gain social contact with others. Implications for preventative interventions are discussed.

Transfer of contaminants in adeno-associated virus vector stocks can mimic transduction and lead to artifactual results

The potential of adeno-associated virus (AAV) vectors for gene transfer and gene therapy applications is currently being intensively investigated. Although much progress has been made in defining AAV vector biology, inconsistencies remain in the literature regarding the efficiency of AAV transduction in various cell types. In the course of exploring these differences, we have identified a problem associated with the use of AAV vector stocks that results in overestimation of gene transfer efficiencies. We show here that biologically active vector-encoded proteins can contaminate AAV vector stocks, especially cell lysate preparations that have not been further purified, and can be transferred in a virion-independent manner to target cells, a phenomenon called pseudotransduction. This observation is significant because impure cell lysate stocks have been widely employed in the AAV literature, and we demonstrate here that this phenomenon can occur with commonly used reporter proteins such as beta-galactosidase and alkaline phosphatase. We conclude that although there are many potential explanations for apparently conflicting results in the literature, the possibility of pseudotransduction must be considered, especially when cell lysate stocks of AAV vectors have been employed. This artifact can be avoided by further vector purification.

Adeno-associated virus vector integration junctions

Vectors derived from adeno-associated virus (AAV) have the potential to stably transduce mammalian cells by integrating into host chromosomes. Despite active research on the use of AAV vectors for gene therapy, the structure of integrated vector proviruses has not previously been analyzed at the DNA sequence level. Studies on the integration of wild-type AAV have identified a common site-specific integration locus on human chromosome 19; however, most AAV vectors do not appear to integrate at this locus. To improve our understanding of AAV vector integration, we analyzed the DNA sequences of several integrated vector proviruses. HeLa cells were transduced with an AAV shuttle vector, and integrated proviruses containing flanking human DNA were recovered as bacterial plasmids for further analysis. We found that AAV vectors integrated as single-copy proviruses at random chromosomal locations and that the flanking HeLa DNA at integration sites was not homologous to AAV or the site-specific integration locus of wild-type AAV. Recombination junctions were scattered throughout the vector terminal repeats with no apparent site specificity. None of the integrated vectors were fully intact. Vector proviruses with nearly intact terminal repeats were excised and amplified after infection with wild-type AAV and adenovirus. Our results suggest that AAV vectors integrate by nonhomologous recombination after partial degradation of entering vector genomes. These findings have important implications for the mechanism of AAV vector integration and the use of these vectors in human gene therapy.

Identification and characterization of a mouse oxysterol 7alpha-hydroxylase cDNA

The synthesis of essential 7alpha-hydroxylated bile acids in the liver is mediated by two pathways that involve distinct 7alpha-hydroxylases. One pathway is initiated in the endoplasmic reticulum by cholesterol 7alpha-hydroxylase, a well studied cytochrome P450 enzyme. A second pathway is initiated by a less well defined oxysterol 7alpha-hydroxylase. Here, we show that a mouse hepatic oxysterol 7alpha-hydroxylase is encoded by Cyp7b1, a cytochrome P450 cDNA originally isolated from the hippocampus. Expression of a Cyp7b1 cDNA in cultured cells produces an enzyme with the same biochemical and pharmacological properties as those of the hepatic oxysterol 7alpha-hydroxylase. Cyp7b1 mRNA and protein are induced in the third week of life commensurate with an increase in hepatic oxysterol 7alpha-hydroxylase activity. In the adult mouse, dietary cholesterol or colestipol induce cholesterol 7alpha-hydroxylase mRNA levels but do not affect oxysterol 7alpha-hydroxylase enzyme activity, mRNA, or protein levels. Cholesterol 7alpha-hydroxylase mRNA is reduced to undetectable levels in response to bile acids, whereas expression of oxysterol 7alpha-hydroxylase is modestly decreased. The liver thus maintains the capacity to synthesize 7alpha-hydroxylated bile acids regardless of dietary composition, underscoring the central role of 7alpha-hydroxylated bile acids in lipid metabolism.

Personality, social networks, and perceived social support among alcoholics: a structural equation analysis

In this study we tested relations among personality characteristics, social network properties, and perceived social support both concurrently and prospectively. A sample of 294 men in treatment at a Department of Veterans Affairs Alcohol Treatment Unit was assessed during treatment and 3 months after discharge. Results of the cross-sectional structural equation analyses indicated that the personality characteristics of extraversion and neuroticism were related to both social network properties and perceived social support. Characteristics of the alcoholic's social network were also related to perceived availability of support. Longitudinal analyses of perceived social support after treatment indicated that two social network properties (size of the network and the proportion of confidants) were predictive net of initial levels of social support. Extraversion and neuroticism were found to be indirectly related to perceived social support at Time 2 through their effects on social network properties and perceived social support during treatment. Implications of these findings for models of the nature and determinants of perceived social support are discussed.

Transduction by adeno-associated virus vectors in the rabbit airway: efficiency, persistence, and readministration

The ability of recombinant adeno-associated virus (AAV) vectors to integrate into the host genome and to transduce nondividing cells makes them attractive as vehicles for gene delivery. In this study, we assessed the ability of several AAV vectors to transduce airway cells in rabbits by measuring marker gene expression. AAV vectors that transferred either a beta-galactosidase (beta-gal) or a human placental alkaline phosphatase (AP) gene were delivered to one lobe of the rabbit lung by use of a balloon catheter placed under fluoroscopic guidance. We observed vector-encoded beta-gal or AP staining almost exclusively in the epithelial and smooth muscle cells in the bronchus at the region of balloon placement. The overall efficiency of transduction in the balloon-treated bronchial epithelium was low but reached 20% in some areas. The majority of the staining was in ciliated cells but was also observed in basal cells and airway smooth muscle cells. We observed an 80-fold decrease in marker-positive epithelial cells during the 60-day period after vector infusion, whereas the number of marker-positive smooth muscle cells stayed constant. Although treatment with the topoisomerase inhibitor etoposide dramatically enhanced AAV transduction in primary airway epithelial cells in culture, treatment of rabbits did not improve transduction rates in the airway. Vector readministration failed to produce additional transduction events, which correlated with the appearance of neutralizing antibodies. These results indicate that both readministration and immune modulation will be required in the use of AAV vectors for gene therapy to the airway epithelium.

Expression cloning and characterization of oxidative 17beta- and 3alpha-hydroxysteroid dehydrogenases from rat and human prostate

Intracellular levels of active steroid hormones are determined by their relative rates of synthesis and breakdown. In the case of the potent androgen dihydrotestosterone, synthesis from the precursor testosterone is mediated by steroid 5alpha-reductase, whereas breakdown to the inactive androgens 5alpha-androstane-3alpha, 17beta-diol (3alpha-adiol), and androsterone is mediated by reductive 3alpha-hydroxysteroid dehydrogenases (3alpha-HSD) and oxidative 17beta-hydroxysteroid dehydrogenases (17beta-HSD), respectively. We report the isolation by expression cloning of a cDNA encoding a 17beta-HSD6 isozyme that oxidizes 3alpha-adiol to androsterone. 17beta-HSD6 is a member of the short chain dehydrogenase/reductase family and shares 65% sequence identity with retinol dehydrogenase 1 (RoDH1), which catalyzes the oxidation of retinol to retinal. Expression of rat and human RoDH cDNAs in mammalian cells is associated with the oxidative conversion of 3alpha-adiol to dihydrotestosterone. Thus, 17beta-HSD6 and RoDH play opposing roles in androgen action; 17beta-HSD6 inactivates 3alpha-adiol by conversion to androsterone and RoDH activates 3alpha-adiol by conversion to dihydrotestosterone. The synthesis of an active steroid hormone by back conversion of an inactive metabolite represents a potentially important mechanism by which the steady state level of a transcriptional effector can be regulated.

Fetal death in mice lacking 5alpha-reductase type 1 caused by estrogen excess

Female mice deficient in steroid 5alpha-reductase type 1 have a decreased litter size. The average litter in homozygous deficient females is 2.7 pups vs. 8.0 pups in wild type controls. Oogenesis, fertilization, implantation, and placental morphology appear normal in the mutant animals. Fetal loss occurs between gestation days 10.75 and 11.0 commensurate with a midpregnancy surge in placental androgen production and an induction of 5alpha-reductase type 1 expression in the decidua of wild type mice. Plasma levels of androstenedione and testosterone are 2- to 3-fold higher on gestation day 9, and estradiol levels are chronically elevated by 2- to 3-fold throughout early and midgestation in the knockout mice. Administration of an estrogen receptor antagonist or inhibitors of aromatase reverse the high rate of fetal death in the mutant mice, and estradiol treatment of wild type pregnant mice causes fetal wastage. The results suggest that in the deficient mice, a failure to 5alpha-reduce androgens leads to their conversion to estrogens, which in turn causes fetal death in midgestation. These findings indicate that the 5alpha-reduction of androgens in female animals plays a crucial role in guarding against estrogen toxicity during pregnancy.

Cyp7b, a novel brain cytochrome P450, catalyzes the synthesis of neurosteroids 7alpha-hydroxy dehydroepiandrosterone and 7alpha-hydroxy pregnenolone

Steroids produced locally in brain (neurosteroids), including dehydroepiandrosterone (DHEA), influence cognition and behavior. We previously described a novel cytochrome P450, Cyp7b, strongly expressed in rat and mouse brain, particularly in hippocampus. Cyp7b is most similar to steroidogenic P450s and potentially could play a role in neurosteroid metabolism. To examine the catalytic activity of the enzyme mouse Cyp7b cDNA was introduced into a vaccinia virus vector. Extracts from cells infected with the recombinant showed NADPH-dependent conversion of DHEA (Km, 13.6 microM) and pregnenolone (Km, 4.0 microM) to slower migrating forms on thin layer chromatography. The expressed enzyme was less active against 25-hydroxycholesterol, 17beta-estradiol and 5alpha-androstane-3beta,17beta-diol, with low to undetectable activity against progesterone, corticosterone, and testosterone. On gas chromatography and mass spectrometry of the Cyp7b metabolite of DHEA the retention time and fragmentation patterns were identical to those obtained with authentic 7alpha-hydroxy DHEA. The reaction product also comigrated on thin layer chromatography with 7alpha-hydroxy DHEA but not with 7beta-hydroxy DHEA; when [7alpha-3H]pregnenolone was incubated with Cyp7b extracts the extent of release of radioactivity into the medium suggested that hydroxylation was preferentially at the 7alpha position. Brain extracts also efficiently liberated tritium from [7alpha-3H]pregnenolone and converted DHEA to a product with a chromatographic mobility indistinguishable from 7alpha-hydroxy DHEA. We conclude that Cyp7b is a 7alpha-hydroxylase participating in the synthesis, in brain, of neurosteroids 7alpha-hydroxy DHEA, and 7alpha-hydroxy pregnenolone.

Expression and regulation of steroid 5 alpha-reductase in the genital tubercle of the fetal rat

The genital tubercle is a bipotential anlage that can develop into a penis or a clitoris. Formation of the penis requires synthesis within the tubercle of the androgen dihydrotestosterone by steroid 5 alpha-reductase isozymes. Isozyme 1 mRNA and protein were present in epithelial cells, whereas isozyme 2 transcripts were present in mesenchymal cells of developing genital tubercles from day 17, 19, and 21 rat embryos. These expression patterns were observed in both uncommitted anlagen and in committed male or female structures. Androgens did not significantly influence levels of 5 alpha-reductase mRNAs or affect their cellular distributions. Together with genetic data, the results implicate the mesenchyme as the crucial cell type in formation of the male external genitalia.

Conservation of function between mammalian and plant steroid 5alpha-reductases

Arabidopsis det2 mutants are small dark-green dwarfs displaying pleiotropic defects in light-regulated development during multiple stages of the plant life cycle. The DET2 gene encodes a protein that shares approximately 40% sequence identity with mammalian steroid 5alpha-reductases and is implicated in the synthesis of a class of plant steroids, the brassinosteroids. Here we show that the DET2 protein, when expressed in human embryonic kidney 293 cells, catalyzes the 5alpha-reduction of several animal steroid substrates and has similar kinetic properties to the mammalian steroid 5alpha-reductase enzymes. Moreover, human steroid 5alpha-reductases expressed in det2 mutant plants can substitute for DET2 in brassinosteroid biosynthesis. These data indicate that DET2 is an ortholog of the mammalian steroid 5alpha-reductases and provide further evidence that brassinosteroids play an essential role in light-regulated plant development. The structural and functional conservation between DET2 and human steroid 5alpha-reductases raise interesting issues concerning the evolutionary origin of the steroid hormone signaling system.

Persistent expression of human clotting factor IX from mouse liver after intravenous injection of adeno-associated virus vectors

We previously found that gene transduction by adeno-associated virus (AAV) vectors in cell culture can be stimulated over 100-fold by treatment of the target cells with agents that affect DNA metabolism, such as irradiation or topoisomerase inhibitors. Here we show that previous gamma-irradiation increased the transduction rate in mouse liver by up to 900-fold, and the topoisomerase inhibitor etoposide increased transduction by about 20-fold. Similar rates of hepatic transduction were obtained by direct injection of the liver or by systemic delivery via tail vein injection. Hepatocytes were much more efficiently transduced than other cells after systemic delivery, and up to 3% of all hepatocytes could be transduced after one vector injection. The presence of wild-type AAV, which contaminates many AAV vector preparations, was required to observe a full response to gamma-irradiation. Injection of mice with AAV vectors encoding human clotting factor IX after gamma-irradiation resulted in synthesis of low levels of human clotting factor IX for the 5-month period of observation. These studies show the potential of targeted gene transduction of the liver by AAV vectors for treatment of various hematological or metabolic diseases.

Molecular characterization of two mammalian bHLH-PAS domain proteins selectively expressed in the central nervous system

Here we describe two mammalian transcription factors selectively expressed in the central nervous system. Both proteins, neuronal PAS domain protein (NPAS) 1 and NPAS2, are members of the basic helix-loop-helix-PAS family of transcription factors. cDNAs encoding mouse and human forms of NPAS1 and NPAS2 have been isolated and sequenced. RNA blotting assays demonstrated the selective presence of NPAS1 and NPAS2 mRNAs in brain and spinal cord tissues of adult mice. NPAS1 mRNA was first detected at embryonic day 15 of mouse development, shortly after early organogenesis of the brain. NPAS2 mRNA was first detected during early postnatal development of the mouse brain. In situ hybridization assays using brain tissue of postnatal mice revealed an exclusively neuronal pattern of expression for NPAS1 and NPAS2 mRNAs. The human NPAS1 gene was mapped to chromosome 19q13.2-q13.3, and the mouse Npas1 gene to chromosome 7 at 2 centimorgans. Similarly, the human NPAS2 gene was assigned to chromosome 2p11.2-2q13, and the mouse Npas2 gene to chromosome 1 at 21-22 centimorgans. The chromosomal regions to which human NPAS1 and NPAS2 map are syntenic with those containing the mouse Npas1 and Npas2 genes, indicating that the mouse and human genes are true homologs.

Endothelial PAS domain protein 1 (EPAS1), a transcription factor selectively expressed in endothelial cells

Here we describe the cloning and characterization of a PAS domain transcription factor termed endothelial PAS-1 (EPAS1). This protein shares 48% sequence identity with hypoxia inducible factor (HIF-1alpha) and lesser similarity with other members of the basic helix-loop-helix/PAS domain family of transcription factors. Like HIF-1alpha, EPAS1 binds to and activates transcription from a DNA element originally isolated from the erythropoietin gene and containing the sequence 5'-GCCCTACGTGCTGTCTCA-3'. Activation by both HIF-1alpha and EPAS1 is stimulated by hypoxic conditions. EPAS1 forms a heterodimeric complex with the aryl hydrocarbon nuclear transporter prior to transcriptional activation of target genes. EPAS1 expression is limited to the endothelium of mouse embryos and, in agreement with its cell type-specific expression pattern, is capable of specifically activating the transcription of the endothelial tyrosine kinase gene Tie-2. These observations raise the possibility that EPAS1 may represent an important regulator of vascularization, perhaps involving the regulation of endothelial cell gene expression in response to hypoxia.

Transduction of hematopoietic cells by foamy virus vectors

Foamy viruses are retroviruses of the spumavirus family that are often isolated from primary cultures of primate cells. We previously constructed vectors based on human foamy virus (HFV) and found that they were able to transduce a wide variety of vertebrate cells by integration of the vector genome. Here we show that several types of hematopoietic cells are efficiently transduced by an HFV vector that encodes alkaline phosphatase (AP). These cell types include transformed cell lines and primary hematopoietic progenitors from mice, baboons, and humans. The transduction rates of HFV vectors compare favorably with those obtained by murine leukemia virus vectors, which suggests that HFV vectors may be effective in the treatment of hematologic diseases by gene therapy.

Disruption of cholesterol 7alpha-hydroxylase gene in mice. I. Postnatal lethality reversed by bile acid and vitamin supplementation

Mice deficient in cholesterol 7alpha-hydroxylase, the rate-limiting enzyme of bile acid biosynthesis, were constructed by targeted disruption of the Cyp7 gene. The introduced mutation removed exons 3-5 of the gene and gave rise to a null allele that encoded no immunoreactive or enzymatically active protein. Heterozygous carriers of the disrupted gene (Cyp7+/-) were phenotypically normal. Homozygous animals (Cyp7-/-) appeared normal at birth, but died within the first 18 days of life. Approximately 40% of the animals died between postnatal days 1 and 4 and 45% between days 11 and 18. The addition of vitamins to the water of nursing mothers prevented deaths in the early period, whereas the addition of cholic acid to chow prevented deaths in the later period. Newborn Cyp7-/- mice whose mothers were maintained on unsupplemented chow failed to gain weight at a normal rate and developed oily coats, hyperkeratosis, and apparent vision defects. These symptoms waned at 3 weeks of life, and their disappearance was accompanied by a marked increase in survival. In the accompanying study, the induction of an alternate pathway of bile acid biosynthesis is shown to underlie this unusual time course (Schwarz, M., Lund, E. G., Setchell, K. D. R., Kayden, H. J., Zerwekh, J. E., Björkhem, I., Herz, J., and Russell, D. W. (1996) J. Biol. Chem. 271, 18024-18031). We conclude that cholesterol 7alpha-hydroxylase is an essential enzyme for normal postnatal development.

17beta-Hydroxysteroid dehydrogenase 3 deficiency

Five known isoenzymes catalyze the 17beta-hydroxysteroid dehydrogenase reaction that controls the interconversion of estrone and estradiol and of testosterone and androstenedione. Mutations in the 17beta-hydroxysteroid dehydrogenase 3 gene impair the formation of testosterone in the fetal testis and give rise to genetic males with normal male Wolffian duct structures but female external genitalia. Such individuals are usually raised as females but virilize at the time of puberty as the result of a rise in serum testosterone. The 14 mutations characterized to date in 17 affected families include 10 missense mutations, 3 splice junction abnormalities, and 1 frame shift mutation. Three of the mutations have occurred in more than 1 family. The usual mechanism for testosterone formation in affected individuals at puberty appears to be conversion of androstenedione to testosterone in extraglandular tissues by one or more of the unaffected 17beta-hydroxysteroid dehydrogenase isoenzymes.

Effects of gamma irradiation on the transduction of dividing and nondividing cells in brain and muscle of rats by adeno-associated virus vectors

Vectors based on adeno-associated virus (AAV) are under investigation for use in gene therapy applications. Critical aspects of AAV vector biology remain undefined, in particular the intracellular events and activities mediating transduction and determining host cell permissiveness for transduction. Using cultured primary human fibroblasts, we previously showed that AAV vectors preferentially, but not exclusively, transduce cells in the S phase of the cell cycle, and that transduction can be markedly enhanced by pretreatment of target cells with physical and chemical agents that perturb DNA metabolism. In this study, we tested whether similar improvements in AAV vector performance might be achievable in vivo. The adult rat brain and overlying scalp muscle were selected for vector inoculation because of the presence of well-defined populations of dividing, quiescent, and post-mitotic cells, and gamma irradiation was chosen as a reproducible means of inducing DNA repair in these cells. We find that gamma irradiation markedly enhances the transduction of dividing cell populations in the pia-arachnoid and choroid epithelium within the central nervous system, and of mature nondividing muscle cells in the scalp, whereas gamma irradiation did not increase the basal transduction level of post-mitotic neurons in the hippocampus. These data confirm that replicative cellular DNA synthesis is not required for transduction by AAV vectors and show that the mitotic state of target cells is not necessarily predictive of responsiveness to transduction-enhancing treatments. Most importantly, these data demonstrate that target cells can be manipulated in vivo to render them more permissive for AAV vector transduction.

Steroid 5 alpha-reductase 2 deficiency: virilization in early infancy may be due to partial function of mutant enzyme

Male pseudohermaphroditism due to steroid 5 alpha-reductase deficiency is the consequence of mutations in the gene encoding the type 2 isoenzyme. Most (60%) affected subjects have homozygous mutations, and the remainder are compound heterozygotes or presumed compound heterozygotes. We report an Italian subject with phenotypic and endocrine features of 5 alpha-reductase 2 deficiency who is homozygous for a substitution mutation (H231R). Although close consanguinity is not present, genealogical data demonstrated that the parents are distantly related, and both parents and the maternal grandmother are heterozygous carriers of the mutation. The fact that this particular mutation results in the formation of an enzyme with considerable residual activity may explain in part the significant degree of virilization that took place in this subject in early infancy. This same mutation (H231R) is present in heterozygous form in two other families, an African-American family and an American family of northern European descent.

5 alpha-reduced androgens play a key role in murine parturition

Two steroid 5 alpha-reductase isozymes designated type 1 and 2 synthesize 5 alpha-reduced androgens and other 5 alpha-reduced steroid hormones. Naturally occurring mutations in the gene encoding 5 alpha-reductase type 2 cause male pseudohermaphroditism, indicating that this isozyme is responsible for the synthesis of dihydrotestosterone required for virilization of the embryonic male urogenital tract. To determine the physiological role of 5 alpha-reductase type 1, homologous recombination in mouse embryonic stem cells was used to produce male and female mice with a disruption (null allele) in the type 1 gene (Srd5a1). Male mice lacking 5 alpha-reductase type 1 appear normal. Females exhibit a parturition defect that is maternal in origin. The parturition defect is reversed by administration of 5 alpha-androstan-3 alpha, 17 beta-diol (3 alpha-Adiol), a 5 alpha-reduced androgen previously thought to be a breakdown product. Enzymes that synthesize 3 alpha-Adiol, including 5 alpha-reductase type 1 and 3 alpha-hydroxysteroid dehydrogenase, are induced in wild type uterus during late gestation. Induction leads to peak circulating levels of 3 alpha-Adiol on days 17/18 of gestation in wild type but not mutant mice. The results document a role for 5 alpha-reduced androgens synthesized by the type 1 isozyme in normal female physiology, and they suggest that 3 alpha-Adiol is a new hormone required for parturition in mice.

Increased expression of early growth response-1 messenger ribonucleic acid in prostatic adenocarcinoma

PURPOSE

We isolated genes whose expression differs between normal and malignant prostate.

MATERIALS AND METHODS

Differential display polymerase chain reactions revealed a messenger ribonucleic acid (mRNA) with higher expression in prostatic adenocarcinoma versus age matched normal tissue. Deoxyribonucleic acid sequencing identified this mRNA as the product of the early growth response-1 gene.

RESULTS

Early growth response-1 mRNA levels were elevated in 12 of 12 intraprostatic adenocarcinomas but not in breast or ovarian cancers, or in rapidly dividing rat ventral prostate cells. Early growth response-1 mRNA was detected in epithelial and stromal cells at tumor margins but not in lymph node metastases.

CONCLUSIONS

Early growth response-1, a nuclear transcription factor, is implicated in the growth and invasion of intraprostatic cancers.

UCLA Loneliness Scale (Version 3): reliability, validity, and factor structure

In this article I evaluated the psychometric properties of the UCLA Loneliness Scale (Version 3). Using data from prior studies of college students, nurses, teachers, and the elderly, analyses of the reliability, validity, and factor structure of this new version of the UCLA Loneliness Scale were conducted. Results indicated that the measure was highly reliable, both in terms of internal consistency (coefficient alpha ranging from .89 to .94) and test-retest reliability over a 1-year period (r = .73). Convergent validity for the scale was indicated by significant correlations with other measures of loneliness. Construct validity was supported by significant relations with measures of the adequacy of the individual's interpersonal relationships, and by correlations between loneliness and measures of health and well-being. Confirmatory factor analyses indicated that a model incorporating a global bipolar loneliness factor along with two method factor reflecting direction of item wording provided a very good fit to the data across samples. Implications of these results for future measurement research on loneliness are discussed.

Foamy virus vectors

Human foamy virus (HFV) is a retrovirus of the spumavirus family. We have constructed vectors based on HFV that encode neomycin phosphotransferase and alkaline phosphatase. These vectors are able to transduce a wide variety of vertebrate cells by integration of the vector genome. Unlike vectors based on murine leukemia virus, HFV vectors are not inactivated by human serum, and they transduce stationary-phase cultures more efficiently than murine leukemia virus vectors. These properties, as well as their large packaging capacity, make HFV vectors promising gene transfer vehicles.

Immunohistochemical localization of steroid 5 alpha-reductase 2 in the human male fetal reproductive tract and adult prostate

The activity of the type 2 isozyme of steroid 5 alpha-reductase is crucial for normal development of the external genitalia and prostate in human males. We used immunohistochemistry to localize type 2 isozyme expression in the human male fetal reproductive tract and adult prostate. In fetal tissue, the stroma of the seminal vesicles, corpus cavernosum, corpus spongiosum, dorsal vein complex, scrotal skin, and prostate expressed the enzyme. In addition, the epithelial cells of the fetal urethra and proximal prostatic ducts stained positively. The type 2 isozyme could not be detected in epithelial cells of the fetal prostatic acini, seminal vesicles, prostatic utricle, ejaculatory ducts, epididymides, and Cowper's glands. Adult prostate specimens were derived from transurethral prostatectomies performed for benign prostatic hyperplasia. Enzyme expression in these benign prostatic hyperplasia samples localized to the stroma and epithelial cells of the urethra and proximal ducts. No staining was detected in the acinar (luminal and basal) epithelial cells. Double staining with an antismooth muscle actin antibody localized type 2 isozyme expression to the stromal fibroblast cells of the prostate. Double staining with an androgen receptor antibody localized AR expression to the acinar epithelial cells and stromal fibroblasts. These data indicate that 5 alpha-reductase type 2 is expressed throughout the developing male genitourinary tract and functions as both an autocrine and a paracrine mediator of growth and differentiation.

Expression and regulation of steroid 5 alpha-reductase in the urogenital tract of the fetal rat

Two androgens, testosterone and dihydrotestosterone, are required for the development of the male urogenital tract in the rat. Testosterone is secreted by the fetal testes and is thought to elicit differentiation of the Wolffian ducts into seminal vesicles, vas deferens, and epididymides. Testosterone is converted into dihydrotestosterone by steroid 5 alpha-reductase in the urogenital tract, and this conversion is necessary for the differentiation of the prostate and external genitalia. Genes encoding two 5 alpha-reductase isozymes, designated type 1 and type 2, have been identified. We examined the expression and regulation of these genes on days 17-21 in the urogenital tracts of male and female fetuses. Expression of the type 1 gene predominated in epithelial cells, whereas type 2 gene expression was limited to mesenchymal cells. Surprisingly, this expression pattern was detected in both testosterone-dependent and dihydrotestosterone-dependent anlagen of the urogenital tract and was the same in both male and female fetuses. Furthermore, transcripts encoding the two isozymes were present in their respective cell types before the overt differentiation of internal genitalia. Androgens stimulated expression of the type 2 gene in the urogenital tracts of both sexes, but did not effect expression of the type 1 gene or the cell type-specific expression patterns of the 5 alpha-reductase genes. In the adult prostate, 5 alpha-reductase gene expression is under feedforward control, in which the product of the enzyme, dihydrotestosterone, stimulates the expression of the gene. However, no evidence for feedforward regulation of either 5 alpha-reductase gene was detected in the fetus.

Women with steroid 5 alpha-reductase 2 deficiency have normal concentrations of plasma 5 alpha-dihydroprogesterone during the luteal phase

Steroid 5 alpha-reductase 2 deficiency has been identified in two adult women from unrelated families, one a homozygote and the other a compound heterozygote. The homozygote carries the G183S mutation and is the sister of an affected male; the compound heterozygote (R246W/splice junction abnormality) is married to a heterozygote (splice junction abnormality) and is the mother of two compound heterozygotes and two homozygotes. The fact that these two women are the mothers of seven children and appear to be endocrinologically normal confirms the previous deduction that this disorder is not manifest in women. Concentrations of plasma 5 alpha-dihydroprogesterone were normal in these two women during the luteal phase; this finding implies that circulating 5 alpha-dihydroprogesterone in women is derived principally from the steroid 5 alpha-reductase 1 isoenzyme and leaves unresolved the question of whether 5 alpha-dihydroprogesterone plays a physiological role in women.

Outcome of domiciliary care after inpatient alcoholism treatment in male veterans

Current literature is ambiguous as to the impact of extended treatment services following hospitalization on outcomes such as abstinence. This study compares the outcomes of care for 276 veterans who completed inpatient treatment for alcoholism, 77 of whom (28%) were transferred to a domiciliary and the remainder of whom were discharged directly into the community. The domiciliary group of alcoholics differed at baseline from alcoholics discharged to the community with significantly higher psychiatric comorbidity and lower social support, both negative predictors of treatment outcome. A multiple logistic regression model was used to assess the impact of domiciliary placement on: (a) 3-month abstinence comparing the time after discharge from either the domiciliary or the inpatient treatment unit and (b) 12-month abstinence after discharge from the inpatient treatment unit, including patients placed in the domiciliary. Controlling for baseline differences, domiciliary placement was found to be a significant predictor of abstinence (odds ratios of 2.3 for 3-month and 2.5 for 12-month abstinence, p < or = 0.01). In a survival analysis, domiciliary placement was also a significant predictor of time to readmission after treatment discharge with a risk ratio of 0.2 (p < 0.01). Our results demonstrate a protective effect of domiciliary after-care for high risk alcoholics after inpatient treatment.

DNA synthesis and topoisomerase inhibitors increase transduction by adeno-associated virus vectors

Viral vectors based on adeno-associated virus (AAV) preferentially transduce cells in S phase of the cell cycle. We recently found that DNA-damaging agents increased the transduction of nondividing cells. However, the optimal concentrations were toxic to cells. Here we show that the transduction of normal human fibroblasts by AAV vectors is increased by prior exposure to DNA synthesis inhibitors, such as aphidicolin or hydroxyurea, and topoisomerase inhibitors, such as etoposide or camptothecin. Transduction efficiencies could be increased > 300-fold in stationary cultures at concentrations that did not affect cell viability or proliferative potential. Both S-phase and non-S-phase cells were affected, suggesting that cellular functions other than replicative DNA synthesis may be involved. Applying these methods to gene transfer protocols should improve prospects for gene therapy by AAV vectors.

The effects of human serum and cerebrospinal fluid on retroviral vectors and packaging cell lines

Human serum is known to inactivate many retroviruses, including murine leukemia viruses (MLV). Exposure of vectors based on MLV to human serum components would presumably decrease the efficiency of gene transfer in vivo. Human serum also lyses xenogeneic cells, which would affect the survival of retroviral vector packaging cells in vivo. The effects of other body fluids, such as cerebrospinal fluid (CSF), on MLV vectors and packaging lines have not been studied. We have found that retroviral vectors packaged in ecotropic, amphotropic, and gibbon ape leukemia virus (GALV) envelope proteins were all inactivated by human sera, and human sera also lysed mouse NIH-3T3 cells and the retroviral vector packaging cells derived from them. Human fibroblasts producing amphotropic vector particles were resistant to lysis, but the particles produced by them were inactivated. In contrast, CSF did not inactivate MLV vectors, nor did it lyse murine retrovirus packaging cells. Our results suggest that exposure to human serum may prevent in vivo gene transfer by MLV vectors and xenogeneic packaging lines, but gene transfer within the central nervous system should be more successful.

DNA-damaging agents greatly increase the transduction of nondividing cells by adeno-associated virus vectors

None of the vector systems currently available for gene therapy applications have been shown to be capable of both efficient gene transfer into nondividing cells and long-term expression through stable integration into host cell DNA. While integrating vectors based on adeno-associated virus are capable of mediating gene transfer into nondividing cells, this process is 200-fold less efficient than transduction of dividing cells. We demonstrate that the transduction efficiency of adeno-associated virus vectors can be increased by treatment with DNA-damaging agents. Nondividing cells are especially responsive, with increases in transduction efficiency of up to 750-fold. This finding has the potential to facilitate gene therapy applications requiring gene transfer to nondividing cells.

Adeno-associated virus vectors preferentially transduce cells in S phase

Vectors based on adeno-associated virus can stably transfer genes by chromosomal integration in recipient cells. In this study we have infected stationary and dividing primary human fibroblast cultures with adeno-associated virus vectors encoding alkaline phosphatase and neomycin phosphotransferase. We find that the transduction frequency of S phase cells is about 200 times that of non-S phase cells. However, neither S phase nor mitosis is essential for transduction. Single-stranded vector genomes survive in stationary cultures and can be recruited for transduction by stimulating these cultures to divide. Stable transductants contain randomly integrated vector sequences. These findings have important implications for the use of adeno-associated virus vectors in gene therapy.

Cell type specific expression of steroid 5 alpha-reductase 2

Isozymes of steroid 5 alpha-reductase (5 alpha-reductase) have crucial roles in androgen physiology by synthesizing the potent hormone dihydrotestosterone. The expression pattern of the 5 alpha-reductase type 2 isozyme was determined in genital and extragenital tissues by developing an immunohistochemical assay using formalin-fixed tissue and affinity purified polyclonal antibodies that specifically recognize this isozyme. Expression was detected in basal epithelial and stromal cells of the normal prostate but not in luminal epithelial cells. Stromal cells of the seminal vesicle also expressed the type 2 isozyme. In contrast, staining was detected in epithelial cells of the epididymis but not in the surrounding stroma. Myofibroblasts in foreskin samples of normal and hypospadiac individuals expressed antigen and were distributed in bands throughout the prepuce, suggesting a clonal origin. In most cells the type 2 isozyme exhibited a perinuclear subcellular distribution. However, in liver hepatocytes the protein was distributed throughout the intracellular membrane compartment.

Expression and regulation of steroid 5 alpha-reductase 2 in prostate disease

The androgen dihydrotestosterone is synthesized by the enzyme steroid 5 alpha-reductase, and it is required for growth and development of the prostate. We used immunohistochemistry to examine the expression of the type 2 isozyme of 5 alpha-reductase in benign prostatic hyperplasia and prostate cancer. The type 2 isozyme is highly expressed within stromal cells in both disease states. No type 2 isozyme is detectable in a lymph node metastasis. Immunoblotting studies show that androgen ablation therapies substantially decrease isozyme expression in the epididymis but have a lesser effect on expression in the prostate. Finasteride therapy (2 weeks to 3 years) did not abolish expression of the prostatic type 2 isozyme nor did this drug treatment induce expression of the type 1 isozyme.

Perceived parental social support and academic achievement: an attachment theory perspective

The study tested the extent to which parental social support predicted college grade point average among undergraduate students. A sample of 418 undergraduates completed the Social Provisions Scale--Parent Form (C.E. Cutrona, 1989) and measures of family conflict and achievement orientation. American College Testing Assessment Program college entrance exam scores (ACT; American College Testing Program, 1986) and grade point average were obtained from the university registrar. Parental social support, especially reassurance of worth, predicted college grade point average when controlling for academic aptitude (ACT scores), family achievement orientation, and family conflict. Support from parents, but not from friends or romantic partners, significantly predicted grade point average. Results are interpreted in the context of adult attachment theory.

Male pseudohermaphroditism caused by mutations of testicular 17 beta-hydroxysteroid dehydrogenase 3

Defects in the conversion of androstenedione to testosterone in the fetal testes by the enzyme 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) give rise to genetic males with female external genitalia. We have used expression cloning to isolate cDNAs encoding a microsomal 17 beta-HSD type 3 isozyme that shares 23% sequence identity with other 17 beta-HSD enzymes, uses NADPh as a cofactor, and is expressed predominantly in the testes. The 17 beta HSD3 gene on chromosome 9q22 contains 11 exons. Four substitution and two splice junction mutations were identified in the 17 beta HSD3 genes of five unrelated male pseudohermaphrodites. The substitution mutations severely compromised the activity of the 17 beta-HSD type 3 isozyme.

Natural mutagenesis study of the human steroid 5 alpha-reductase 2 isozyme

The enzyme steroid 5 alpha-reductase utilizes NADPH to reduce the double bonds of a variety of steroid substrates with generalized 3-oxo, delta 4,5 structures. One substrate for this membrane-bound enzyme is testosterone, whose reduction to dihydrotestosterone is required for the embryonic differentiation of the external male genitalia and prostate. There are two 5 alpha-reductase isozymes, designated types 1 and 2, which have different biochemical and pharmacological properties. Inherited deficiencies of 5 alpha-reductase type 2 result in a form of male pseudohermaphroditism in which the external genitalia fail to develop normally. Here, nine additional mutations in the 5 alpha-reductase 2 gene in subjects with 5 alpha-reductase deficiency are described. The biochemical consequences of these mutations, as well as 13 previously identified missense mutations, were characterized by recreating the mutations in an expressible cDNA and transfecting into mammalian cells. Twelve of the 22 mutations inactivated the enzyme. The remaining 10 mutations impaired enzyme function by affecting either substrate or cofactor binding. Almost all mutations decreased the half-life of the protein, and all but one of the impaired enzymes had an altered pH optimum. The mutations provide insight into functional domains in the protein as well as an unusual acidic pH optimum characteristic of the 5 alpha-reductase type 2 isozyme.

Perceived parental social support and academic achievement: an attachment theory perspective

The study tested the extent to which parental social support predicted college grade point average among undergraduate students. A sample of 418 undergraduates completed the Social Provisions Scale--Parent Form (C.E. Cutrona, 1989) and measures of family conflict and achievement orientation. American College Testing Assessment Program college entrance exam scores (ACT; American College Testing Program, 1986) and grade point average were obtained from the university registrar. Parental social support, especially reassurance of worth, predicted college grade point average when controlling for academic aptitude (ACT scores), family achievement orientation, and family conflict. Support from parents, but not from friends or romantic partners, significantly predicted grade point average. Results are interpreted in the context of adult attachment theory.

Cell-type-specific expression of rat steroid 5 alpha-reductase isozymes

The enzyme steroid 5 alpha-reductase (EC 1.3.99.5) is a component of an intercellular signaling pathway that determines cell fate in the primordium of the mammalian reproductive tract. During male phenotypic sexual differentiation, the dihydrotestosterone product of this enzyme binds to the androgen receptor and initiates development of the external genitalia and prostate. Genes encoding two isozymes of steroid 5 alpha-reductase with different biochemical properties and tissue distributions have recently been isolated. In the current study, we utilize in situ hybridization analysis to determine cell-type-specific expression patterns of the 5 alpha-reductase isozyme mRNAs in two androgen target tissues (regenerating ventral prostate and epididymis) and a peripheral tissue (liver). In regenerating ventral prostate, the type 1 mRNA is expressed in basal epithelial cells whereas expression of the type 2 mRNA is largely confined to stromal cells. These results were confirmed by immunohistochemical analysis and are consistent with distinct roles played by the isozymes in the prostate. In the epididymis, both 5 alpha-reductase isozyme mRNAs are expressed in epithelial cells. Only the type 1 mRNA is present in the liver. This mRNA is distributed in a striking spatial gradient extending from hepatocytes surrounding the portal triad (high expression) to those surrounding the central vein (low to absent expression). These findings demonstrate cell-type-specific expression of the steroid 5 alpha-reductase isozymes and underscore their distinct and overlapping functions in androgen physiology.