Glucocorticoid regulation of rat whey acidic protein gene expression involves hormone-induced alterations of chromatin structure in the distal promoter region

Milk protein gene expression is regulated by the synergistic interactions of several lactogenic hormones, including insulin, PRL, and glucocorticoids. Whey acidic protein (WAP) gene expression is highly dependent on glucocorticoids, and to a lesser extent than casein gene expression, on the presence of PRL. Previous studies have demonstrated that a distal DNase I hypersensitive site in the rat WAP gene 5'-flanking region containing several binding sites for nuclear factor I is required for high level WAP gene expression in transgenic mice. In this study several specific glucocorticoid receptor (GR) binding sites were identified flanking these nuclear factor I sites using an in vitro DNase I footprinting assay with baculovirus-expressed GR. These sites were able to confer dexamethasone inducibility to a heterologous thymidine kinase-chloramphenicol acetyltransferase reporter gene construct in transient cotransfection experiments with GR in CV1 cells. Administration of dexamethasone to adrenal-ectomized mice carrying the +2020 rat WAP transgene during lactation demonstrated that glucocorticoids are required to maintain transgene expression in the mammary gland. Furthermore, glucocorticoid-induced changes in transgene expression were correlated with the appearance of DNase I hypersensitive sites. These results indicate that at least part of glucocorticoid regulation of WAP gene expression is mediated through the direct interaction of GR with glucocorticoid response elements in the distal promoter region resulting in steroid hormone-dependent alterations in chromatin structure.

Single breath counting in the assessment of pulmonary function

STUDY OBJECTIVES

To assess the correlation of single breath counting (SBC) and peak expiratory flow rate (PEFR) to forced expiratory volume in the first second (FEV1).

DESIGN

Prospective comparison of pulmonary function measurements.

SETTING

University hospital pulmonary function test (PFT) laboratory.

TYPE OF PARTICIPANTS

Consenting patients scheduled to have PFTs May 1, 1992, through November 1, 1992.

INTERVENTIONS

SBC was measured by asking patients to take a deep breath and count as far as possible in their normal speaking voice without taking another breath. Counting was timed to a metronome set at 2 counts per second. A hand-held peak flowmeter was then used to measure PEFR. Standard PFTs then were performed.

MEASUREMENTS AND MAIN RESULTS

Twenty-two patients were enrolled. The correlation of SBC to FEV1 (r = .68) was slightly better than of PEFR to FEV1 (r = .63). SBC was also found to correlate well with PEFR (r = .68).

CONCLUSION

SBC is a reasonable alternative to PEFR. Further investigation in an emergency department setting is warranted.

Postoperative changes on brain SPECT imaging after aneurysmal subarachnoid hemorrhage. A potential pitfall in the evaluation of vasospasm

Serial brain SPECT imaging was performed on patients after subarachnoid hemorrhage and surgical clipping of intracranial aneurysms. A total of 20 HMPAO scans were performed on 9 patients in whom clinical vasospasm did not develop. Areas of diminished regional cerebral blood flow (rCBF) were found near the operative site in 17 of 20 studies, which did not correlate with the patients' neurologic condition and were suggestive of postoperative edema. Brain SPECT imaging has a potentially valuable role to play in the evaluation of postoperative patients susceptible to vasospasm; however, it is important to be aware of postoperative changes in rCBF that are not related to vasospasm.

Preferential overexpression of a 172Arg-->Leu mutant p53 in the mammary gland of transgenic mice results in altered lobuloalveolar development

Regulatory sequences derived from the rat whey acidic protein gene have been used to preferentially overexpress a murine 172Arg-->Leu mutant p53 in the mammary gland of transgenic mice. Several different lines of mice expressing the 172Arg-->Leu mutant p53 displayed an impaired ability to lactate, and the mice expressing the highest levels of mutant p53 were unable to nurse their young. This failure was related to the inhibition of normal lobuloalveolar development that occurred during late pregnancy and a marked decrease in milk protein gene expression at early lactation. Interestingly, immunohistochemical analysis revealed that the mutant p53 was localized predominantly in the cytoplasm of alveolar cells. Ductal development was not overtly impaired in these mice. Expression of the 172Arg-->Leu mutant p53 resulted in radiation-induced apoptosis, and transactivation or repression of the expression of a number of genes, including mdm-2 and proliferating cell nuclear antigen, known properties of wild-type p53. The availability of lines of mice preferentially expressing specific p53 mutants in the mammary gland should facilitate evaluation of the roles of other factors, such as hormones, oncogenes and chemical carcinogens, in the etiology of breast cancer.

Distal regulatory elements required for rat whey acidic protein gene expression in transgenic mice

Previous studies have demonstrated that a 3.0-kilobase, rat whey acidic protein (WAP) transgene containing 949 base pairs (bp) 5'- and 70 bp 3'-flanking DNA is expressed specifically in the mammary gland of transgenic mice in a copy number-dependent, position-independent manner (1). In order to localize the critical regulatory elements important for tissue-specific, high level WAP gene expression, DNase I hypersensitivity mapping studies of WAP transgenes were performed in nuclei isolated from mammary gland and liver. Two regions of DNase I hypersensitivity located at approximately -150 and -800 by from the site of transcription initiation, respectively, were detected only in nuclei isolated from the lactating mammary gland. Within the distal hypersensitive region several binding sites for members of the CTF/NFI family of transcription factors were identified using in vitro DNase I and dimethyl sulfate interference footprinting and electrophoretic mobility shift assays. Genomic footprinting established that such protein-DNA interactions occur preferentially in the lactating mammary gland. The analysis of several 5' deletion constructs identified the region between -853 and -729 bp as essential for WAP transgene expression. These results suggest that the distal DNase I hypersensitive region contains binding sites for CTF/NFI and plays a critical role in the regulation of WAP gene expression in transgenic mice.

The rat probasin gene promoter directs hormonally and developmentally regulated expression of a heterologous gene specifically to the prostate in transgenic mice

An expression cassette carrying 426 basepairs of the rat probasin (PB) gene promoter and 28 basepairs of 5'-untranslated region is sufficient to target the expression of the bacterial chloramphenicol acetyltransferase (CAT) gene specifically to the prostate in transgenic mice. The PB-CAT transgene was expressed in three of five (60%) independent lines of mice, and this expression, as reported previously for the endogenous rat gene, was male specific, restricted primarily to the lateral, dorsal, and ventral lobes of the prostate, with only very low levels of CAT activity detected in the anterior prostate and seminal vesicles. The developmental and hormonal regulation of the transgene also paralleled that reported for the rat gene, with a 70-fold increase in CAT activity in the mouse prostate observed between 2-7 weeks of age, a time corresponding to sexual maturation. PB-CAT activity in the prostate declined after castration to 3.5% of the precastration level, and the CAT activity in castrated males approached precastration levels when mice were supplemented with testosterone. Transgene expression in castrated males was not induced by dexamethasone. Coinjection of PB-CAT with a chicken lysozyme gene matrix attachment region resulted in their cointegration and further restricted the pattern of PB-CAT to the dorsolateral prostate, with suppressed expression observed in the ventral prostate. These studies demonstrate that a minimal rat probasin promoter can target heterologous gene expression specifically to the prostate in a developmentally and hormonally regulated fashion.

Differential temporal and spatial gene expression of fibroblast growth factor family members during mouse mammary gland development

Mammary gland development is dependent upon local regulatory factors as well as systemic hormones to mediate gland morphogenesis and associated mesenchymal-epithelial interactions. FGF-3 (int-2) has been implicated as an oncogenic growth factor produced locally in mouse mammary tumor virus-induced mammary tumorigenesis. The observation that FGF-3 is not expressed during normal mammary development as well as the high degree of cellular proliferation and angiogenesis that accompany mammary gland growth suggest roles for other FGF family members in this process. In this study, we have examined expression of FGF family members at various stages of mouse mammary growth and tumorigenesis. FGF-1, FGF-2, FGF-4, and FGF-7 were expressed during the ductal stage of mammary development. The majority of FGF-1 gene expression was in the luminal epithelial cells, whereas FGF-2 expression was in the mammary stroma and possibly the myoepithelial cells. The presence of mammary epithelium induced the expression of both FGF-2 and FGF-7 in the stroma. FGF-1 and FGF-2 expression declined during pregnancy and dropped again during lactation, but quantitative analysis showed a much more dramatic decrease in FGF-2 expression. FGF-7 transcripts were also detected during pregnancy and lactation, but an alternate transcript size was observed at these stages. FGF-1, FGF-2, and FGF-7 transcripts were detected in mammary preneoplasias, tumors, and immortal cell lines, but at levels less than those seen during normal mammary growth. These results support the hypothesis that FGF family members play a role in local regulation of mammary development. The differential spatial and temporal pattern of FGF-1, FGF-2 and FGF-7 gene expression indicate that they each have unique functions in the gland.

The nerve gap dilemma: a comparison of nerves repaired end to end under tension with nerve grafts in a primate model

The objective of this study was to compare, in a clinically relevant primate model, axon regeneration after epineurial repair under tension (15 mm gap) with interfascicular nerve grafts with the use of either standard microsuture techniques or a new interfascicular nerve graft technique termed fascicular tubulization that uses a hypoantigenic collagen membrane formed into a tube to approximate nerve ends. Electrophysiologic analysis demonstrated that the percentage of proximal axons that conducted across the repair site was greater in those nerves repaired under tension with epineurially placed sutures than in either of the tensionless repairs involving interfascicular graft techniques. The mean diameters of the regenerated axons repaired under tension with epineurial sutures were greater than those of the nerves repaired with interfascicular grafts, although the difference was not statistically significant. Interfascicular nerve grafting with tubulization using the current collagen tube resulted in regeneration equal to the sutured interfascicular nerve grafts. For modest defects (perhaps up to 3 to 4 cm in the adult), it seems advantageous to accept the modest tension associated with an epineurial repair rather than to use an autograft (or artificial graft) to achieve a tension-free repair.

Application of high-tech three-dimensional imaging and computer-generated models in complex facial reconstructions with vascularized bone grafts

We present a series of six patients with eight flaps in whom computer-generated models were used for fabrication of vascularized bone grafts in complex facial restorations. Preoperative CT data, digitalized on tape, were converted by the CEMAX (Santa Clara, Calif.) 1500 Integrated Hardware and Software System to a three-dimensional visualization of the bone and soft-tissue deficiencies. These data were transmitted by direct computer link to a CNC milling machine that produced full-size slices "stacked" into a three-dimensional template. The acrylic replica aided selection of appropriate donor sites and intraoperative "carving" of bone transfers. Reconstructions included three zygomas, two maxillae, two mandibles, and one frontal bone. Donor sites were iliac crest, scapula, and outer calvarium. Four were free flaps and four island pedicle flaps. All healed without infection. Bone resorption was less than 10 percent. One flap was lost to thrombosis. Other complications included a transient facial palsy in one patient and temporary radial palsy from shoulder traction in another. Computer-generated templates for vascularized grafts are expensive and thus are not indicated or necessary in every patient. The advantages, however, are several. Custom models facilitate preoperative planning, with less guesswork of size, contour, and orientation of the graft, which is especially desirable with vascularized grafts, since the position of the pedicle is critical. Anesthesia time is decreased. Grafts can be fitted exactly, without reshaping and "nibbling." Nuances of depth and tapering are directly carved into the bone. By merging high-tech imaging and microsurgery, the best chance of optimal results can be achieved.

Localization and quantification of Wnt-2 gene expression in mouse mammary development

The Wnt gene family encodes a group of proteins probably involved in cell-cell communication during several stages of vertebrate development. More than 10 members of this family have been identified and shown to be expressed mainly in developing neural tissue. Using a reverse transcription-polymerase chain reaction (RT-PCR)-based approach with degenerate oligonucleotides directed against conserved sequences in the Wnt genes, Wnt-2 transcripts were detected in RNA isolated from mammary glands of 4- to 6-week-old virgin C3H mice, a period characterized by extensive end bud and ductal proliferation. The spatial and temporal expression of Wnt-2 in the developing mouse mammary gland was studied by in situ hybridization, quantitative RT-PCR, and Northern analysis. Wnt-2 is expressed during the ductal phase of mammary gland development, primarily in the basal layer of mammary ducts and in the body cells of end buds. Wnt-2 RNA transcripts were readily detected in poly(A) RNA isolated from 5-week-old C3H and Balb/c mice. RNA transcript levels measured as molecules per nanogram of total RNA by RT-PCR decreased 10- to 40-fold within 2 days after the onset of pregnancy and remained low during pregnancy and lactation. This is in contrast to the patterns of expression of other Wnt family members, Wnt-5a and -5b, whose expression was either barely or not detectable in the 4- to 6-week-old mammary gland, but increased markedly during pregnancy. These results confirm the differential expression of Wnt gene family members during mammary gland development. Furthermore, they suggest that Wnt-2, as well as several other family members, may play a role in pattern formation during early mammary gland development.

Diffuse pulmonary tumor microemboli from adenocarcinoma of the colon

We have presented a rare case of pulmonary tumor microemboli from adenocarcinoma of the colon. The majority of primary tumors are adenocarcinomas, with gastric, breast, and liver carcinomas most frequently identified. Dyspnea and respiratory distress without an obvious cause is common. The history, physical examination, chest roentgenogram, ventilation-perfusion lung scan, and pulmonary angiogram are often not helpful in establishing the diagnosis. Pulmonary hypertension, present in our patient, and cor pulmonale are well described in association with diffuse pulmonary tumor microemboli. The pathologic findings are limited to the intravascular compartment exclusively, frequently in association with thrombus. The true incidence of pulmonary tumor microemboli is not known and may be underestimated. Appropriate management requires a high index of suspicion to establish the diagnosis.

Regeneration microelectrode array for peripheral nerve recording and stimulation

A microelectrode array capable of recording from and stimulating peripheral nerves at prolonged intervals after surgical implantation has been demonstrated. The microelectrode array, fabricated on a silicon substrate perforated by multiple holes (referred to as via holes), is implanted between the ends of a surgically severed nerve. Regenerating tissue fixes the device in place to provide a stable mapping between the microelectrodes and the axons in the nerve. Processes were developed for the fabrication of thin-film iridium microelectrodes, micromachined via holes, and silicon nitride passivation layers. All fabrication methods were designed to be compatible with standard CMOS/BiCMOS processes to allow for on-chip signal processing circuits in future designs. Such arrays, implanted in the peroneal nerves of rats, were used to record from and stimulate the nerves at up to 13 months postoperatively.

Differential effects of the simian virus 40 early genes on mammary epithelial cell growth, morphology, and gene expression

To study the effect of SV40 T-antigen in mammary epithelial cells, a rat beta-casein promoter-driven SV40 early-region construct was stably introduced into the clonal mouse mammary epithelial cell line HC11. With the expression of the viral T-antigens under the control of a hormone-inducible promoter, it was possible to dissociate the effects of different levels of T-antigen expression on cell growth, morphology, and gene expression. Following hormonal induction, a rapid but transient induction of T-antigen was observed, followed by a delayed induction of H4 histone mRNA. In T-antigen-positive HC11 cells cultured in the absence of EGF, the expression of basal levels of T-antigen (in the absence of hormonal induction) led to a decreased doubling time and an increased cell density. In the presence of EGF, T-antigen expression resulted additionally in an altered cell morphology. Despite the effects of T-antigen on cell growth and gene expression, the cells were unable to form colonies in soft agar and were nontumorigenic when transplanted into cleared mammary fat pads. They were, however, weakly tumorigenic in nude mice. Relatively high levels of p53 protein synthesis were observed in both the transfected HC11 cells and the parental COMMA-D cells, as compared to 3T3E fibroblasts and another mammary epithelial cell line. The HC11 and COMMA-D cells synthesized approximately equal levels of wild-type and mutated p53 proteins as defined by their reactivities with monoclonal antibodies PAb246 and PAb240, respectively. Interactions between excess p53 and T-antigen may, in part, explain the failure of these cells to display a completely transformed phenotype.

Correlation of in vitro release rate and in vivo absorption characteristics of four chlorpheniramine maleate extended-release formulations

An in vitro/in vivo correlation was established for four formulations of chlorpheniramine maleate (histamine, H1-blocker) extended-release tablets exhibiting different in vitro release rate characteristics. In vitro release rate data were obtained for 12 individual tablets of each formulation using the USP Apparatus 2, paddle stirrer at 50 rpm in 1000 ml of distilled water at 37.0 +/- 0.5 degrees C. Inspection of the individual and mean release rate data indicated that the in vitro release rate of chlorpheniramine maleate was consistent with the intended design of the four extended-release formulations. The in vivo bioavailability and pharmacokinetics of these formulations were evaluated in 24 healthy subjects under fasting conditions. Wagner Nelson analyses of the in vivo data revealed extended release absorption profiles for all four formulations. Linear regression analyses of the mean percentage of dose absorbed versus the mean in vitro release resulted in a statistically significant correlation (r2 greater than 0.98, P less than 0.001) for each formulation. Qualitative rank-order correlations were observed among all combinations of in vitro and in vivo parameters. These data support a Level A correlation between the in vitro release rate profiles and the in vivo absorption for chlorpheniramine maleate determined under fasting conditions.

High-level expression of the rat whey acidic protein gene is mediated by elements in the promoter and 3' untranslated region

The high-level expression of the rat whey acidic protein (WAP) gene in transgenic mice depends on the interaction of 5'-flanking promoter sequences and intragenic sequences. Constructs containing 949 bp of promoter sequences and only 70 bp of 3'-flanking DNA were expressed at uniformly high levels, comparable to or higher than that of the endogenous gene. Although this WAP transgene was developmentally regulated, it was expressed earlier during pregnancy than was the endogenous WAP gene. Replacement of 3' sequences, including the WAP poly(A) addition site, with simian virus 40 late poly(A) sequences resulted in an approximately 20-fold reduction in the expression of WAP mRNA in the mammary gland during lactation. Nevertheless, position-independent expression of the transgene was still observed. Further deletion of 91 bp of conserved WAP 3' untranslated region (UTR) led to integration site-dependent expression. Position independence was restored following reinsertion of the WAP 3' UTR into the deleted construct at the same location, but only when the insertion was in the sense orientation. The marked differences observed between the expression levels of the 3'-end deletion constructs in transgenic mice were not seen in transfected CID 9 mammary epithelial cells. In these cells, expression of the endogenous WAP gene was dependent on the interaction of these cells with a complex extracellular matrix. In contrast, the transfected WAP constructs were not dependent on extracellular matrix for expression. Thus, both the abnormal expression of WAP in cells cultured on plastic and the precocious developmental expression of WAP in transgenic mice may reflect the absence of a negative control element(s) within these recombinant constructs.

Artificial nerve graft using glycolide trimethylene carbonate as a nerve conduit filled with collagen compared to sutured autograft in a rat model

A study was conducted to compare the regeneration of rat peroneal nerves across 0.5 cm gaps repaired with artificial nerve grafts (ANG) versus sutured autografts (SAG). The ANG model is composed of a synthetic biodegradable passive conduit made of glycolide trimethylene carbonate (GTMC) filled with a collagen matrix (predominantly Type I collagen, derived from calf skin, and with the telopeptide ends left intact). Axonal regeneration was studied in 11 long-term animals (two at 6 months and nine at 9 months). The nerves were studied by qualitative and quantitative histological, electrophysiological, and functional assays. Axonal regeneration with the ANG was equal to SAGs as measured by axonal diameters, physiological, and functional methods, although the SAG demonstrated statistically higher axonal counts.

Expression of biologically active heterodimeric bovine follicle-stimulating hormone in milk of transgenic mice

Follicle-stimulating hormone (FSH; follitropin) is a pituitary glycoprotein composed of two post-translationally modified subunits, which must properly assemble to be biologically active. FSH has been difficult to purify and to obtain in quantities sufficient for detailed biochemical studies. We have targeted FSH expression to the mammary gland of transgenic mice by using cDNAs encoding the bovine alpha and FSH beta subunits and a modified rat beta-casein gene-based expression system. Lines of bigenic mice expressing both subunits have been generated either by coinjection of the subunit transgenes or by mating mice that acquired and expressed transgenes encoding an individual subunit. Up to 60 international units (15 micrograms) of biologically active FSH per ml was detected in the milk of the bigenic mice. These lines provide a model system for studying the post-transcriptional mechanisms that effect the expression and secretion of this heterodimeric hormone.

A heterologous hormone response element enhances expression of rat beta-casein promoter-driven chloramphenicol acetyltransferase fusion genes in the mammary gland of transgenic mice

Previous studies have demonstrated that the entire rat beta-casein (R beta C) gene and a -524/+490 R beta C fragment-chloramphenicol acetyltransferase (CAT) fusion gene are expressed preferentially in the mammary gland of transgenic mice in a developmentally regulated fashion. However, transgene expression was infrequent, less than 1% of that observed for the endogenous gene, and varied as much as 500-fold, presumably due to the site of chromosomal integration. To determine whether a heterologous hormone-responsive enhancer could be used to increase both the level and frequency of expression in the mammary gland, a fragment derived from the mouse mammary tumor virus long terminal repeat containing four hormone response elements (HREs) was inserted into the R beta C promoter at a site not known to contain transcriptional regulatory elements. Transgenic mice generated which carried HRE-enhanced R beta C-CAT fusion genes expressed CAT activity in the mammary glands of all founder lines examined at levels that were on average 13-fold greater than for lines generated with similar constructs not carrying HREs. In the highest expressing line, the level of HRE-enhanced transgene expression was found to be developmentally regulated, increasing 14-fold in the mammary gland from virgin to day 10 of lactation. In this line, expression was also observed in the thymus and spleen; however, the level of CAT activity was 4-fold lower than in the mammary gland and was not developmentally regulated. In adrenalectomized mice, the administration of dexamethasone stimulated CAT expression in the mammary gland but not in the thymus and spleen. These studies demonstrate that in the context of the R beta C promoter, the HRE functions in the mammary gland to increase both the frequency and level of transgene expression.