Unlocking the power of virtual networking for early-career researchers

Many successful researchers in the biomedical sciences have benefitted from mentors and networks earlier in their career. However, early-career researchers from minoritized and underrepresented groups do not have the same access to potential mentors and networks as many of their peers. In this article we describe how 'cold emails' and social media platforms - notably Twitter/X and LinkedIn - can be used to build virtual networks, and stress the need to invest in maintaining networks once they have been established.

Injectable pulverized electrospun poly(lactic-co-glycolic acid) fibers improve human adipose tissue engraftment and volume retention

Autologous adipose tissue is commonly used for tissue engraftment for the purposes of soft tissue reconstruction due to its relative abundance in the human body and ease of acquisition using liposuction methods. This has led to the adoption of autologous adipose engraftment procedures that allow for the injection of adipose tissues to be used as a "filler" for correcting cosmetic defects and deformities in soft tissues. However, the clinical use of such methods has several limitations, including high resorption rates and poor cell survivability, which lead to low graft volume retention and inconsistent outcomes. Here, we describe a novel application of milled electrospun poly(lactic-co-glycolic acid) (PLGA) fibers, which can be co-injected with adipose tissue to improve engraftment outcomes. These PLGA fibers had no significant negative impact on the viability of adipocytes in vitro and did not elicit long-term proinflammatory responses in vivo. Furthermore, co-delivery of human adipose tissue with pulverized electrospun PLGA fibers led to significant improvements in reperfusion, vascularity, and retention of graft volume compared to injections of adipose tissue alone. Taken together, the use of milled electrospun fibers to enhance autologous adipose engraftment techniques represents a novel approach for improving upon the shortcomings of such methods.

Characterizing CD38 Expression and Enzymatic Activity in the Brain of Spontaneously Hypertensive Stroke-Prone Rats

Background: CD38 is a transmembrane glycoprotein that catabolizes nicotinamide adenine dinucleotide (NAD+) and is the main source for the age-dependent decrease in NAD+ levels. Increased CD38 enzymatic activity has been implicated in several neurological diseases. However, its role in the pathogenesis of cerebral small vessel disease (CSVD) remains unknown. We aimed to characterize CD38 expression and enzymatic activity in the brain of spontaneously hypertensive stroke-prone rats (SHRSP), a genetic model for hypertension and human CSVD, in comparison to age-matched normotensive Wistar Kyoto rats (WKY). Materials and Methods: Age-matched male 7- and 24-week-old WKY and SHRSP were studied. CD38 enzymatic activity was determined in the brain homogenate. Immunohistochemistry and Western Blotting (WB) were used to characterize CD38 expression and localize it in the different cell types within the brain. In addition, expression of nitric oxide synthase (NOS) isoforms and the levels of nitric oxide (NO), superoxide, nicotinamide dinucleotide (phosphate) NAD(P)H were measured the brain of in WKY and SHRSP. Results: CD38 expression and enzymatic activity were increased in SHRSP brains compared to age matched WKY starting at 7 weeks of age. CD38 expression was localized to the endothelial cells, astrocytes, and microglia. We also identified increased CD38 expression using WB with age in SHRSP and WKY. CD38 enzymatic activity was also increased in 24-week SHRSP compared to 7-week SHRSP. In association, we identified evidence of oxidative stress, reduced NO level, reduced NAD(P)H level and endothelial NOS expression in SHRSP compared to age matched WKY. NAD(P)H also decreased with age in WKY and SHRSP. Additionally, activation of astrocytes and microglia were present in SHRSP compared to WKY. Conclusions: CD38 is overexpressed, and its enzymatic activity is increased in SHRSP, a genetic model for marked hypertension and human CSVD. Our results suggest a potential role for CD38 enzymatic activation in the pathogenesis of CSVD and points to the need for future mechanistic and pharmacological studies.

In Situ Deployment of Engineered Extracellular Vesicles into the Tumor Niche via Myeloid-Derived Suppressor Cells

Extracellular vesicles (EVs) have emerged as a promising carrier system for the delivery of therapeutic payloads in multiple disease models, including cancer. However, effective targeting of EVs to cancerous tissue remains a challenge. Here, it is shown that nonviral transfection of myeloid-derived suppressor cells (MDSCs) can be leveraged to drive targeted release of engineered EVs that can modulate transfer and overexpression of therapeutic anticancer genes in tumor cells and tissue. MDSCs are immature immune cells that exhibit enhanced tropism toward tumor tissue and play a role in modulating tumor progression. Current MDSC research has been mostly focused on mitigating immunosuppression in the tumor niche; however, the tumor homing abilities of these cells present untapped potential to deliver EV therapeutics directly to cancerous tissue. In vivo and ex vivo studies with murine models of breast cancer show that nonviral transfection of MDSCs does not hinder their ability to home to cancerous tissue. Moreover, transfected MDSCs can release engineered EVs and mediate antitumoral responses via paracrine signaling, including decreased invasion/metastatic activity and increased apoptosis/necrosis. Altogether, these findings indicate that MDSCs can be a powerful tool for the deployment of EV-based therapeutics to tumor tissue.

Nanotransfection-based vasculogenic cell reprogramming drives functional recovery in a mouse model of ischemic stroke

Ischemic stroke causes vascular and neuronal tissue deficiencies that could lead to substantial functional impairment and/or death. Although progenitor-based vasculogenic cell therapies have shown promise as a potential rescue strategy following ischemic stroke, current approaches face major hurdles. Here, we used fibroblasts nanotransfected with Etv2, Foxc2, and Fli1 (EFF) to drive reprogramming-based vasculogenesis, intracranially, as a potential therapy for ischemic stroke. Perfusion analyses suggest that intracranial delivery of EFF-nanotransfected fibroblasts led to a dose-dependent increase in perfusion 14 days after injection. MRI and behavioral tests revealed ~70% infarct resolution and up to ~90% motor recovery for mice treated with EFF-nanotransfected fibroblasts. Immunohistological analysis confirmed increases in vascularity and neuronal cellularity, as well as reduced glial scar formation in response to treatment with EFF-nanotransfected fibroblasts. Together, our results suggest that vasculogenic cell therapies based on nanotransfection-driven (i.e., nonviral) cellular reprogramming represent a promising strategy for the treatment of ischemic stroke.

Nanochannel-Based Poration Drives Benign and Effective Nonviral Gene Delivery to Peripheral Nerve Tissue

While gene and cell therapies have emerged as promising treatment strategies for various neurological conditions, heavy reliance on viral vectors can hamper widespread clinical implementation. Here, the use of tissue nanotransfection as a platform nanotechnology to drive nonviral gene delivery to nerve tissue via nanochannels, in an effective, controlled, and benign manner is explored. TNT facilitates plasmid DNA delivery to the sciatic nerve of mice in a voltage-dependent manner. Compared to standard bulk electroporation (BEP), impairment in toe-spread and pinprick response is not caused by TNT, and has limited to no impact on electrophysiological parameters. BEP, however, induces significant nerve damage and increases macrophage immunoreactivity. TNT is subsequently used to deliver vasculogenic cell therapies to crushed nerves via delivery of reprogramming factor genes Etv2, Foxc2, and Fli1 (EFF). The results indicate the TNT-based delivery of EFF in a sciatic nerve crush model leads to increased vascularity, reduced macrophage infiltration, and improved recovery in electrophysiological parameters compared to crushed nerves that are TNT-treated with sham/empty plasmids. Altogether, the results indicate that TNT can be a powerful platform nanotechnology for localized nonviral gene delivery to nerve tissue, in vivo, and the deployment of reprogramming-based cell therapies for nerve repair/regeneration.

Inguinal hernia repair: results using an open preperitoneal approach

BACKGROUND

Laparoscopic surgical approaches to the repair of inguinal hernias have shown the advantages of placing mesh in the preperitoneal space. Despite those advantages, laparoscopic hernia repairs have been associated with increased cost, longer operating times, and advanced laparoscopic skills. An open preperitoneal approach has the benefit of mesh in the preperitoneal position without the disadvantages of a laparoscopic procedure.

METHODS

We present our experience with the use of an open preperitoneal mesh repair (KugelMesh, Bard, Inc.). The study was conducted in a prospective fashion from January 1998 through October 2001. 1072 hernias were repaired in two community hospitals by three general surgeons. Patients with recurrent hernias were excluded if the initial repair was from a preperitoneal approach. Operative time, cost, post-operative pain, and complications were analyzed.

RESULTS

Recurrences occurred in five patients (0.47%) during a mean follow-up time of 23 months (range: 2-47). The average operating time was 32.4 min (range: 16-62). Post-operative narcotic pain medication usage averaged 5.8 pills (range: 0-26) per repair. Average surgical charges were less for the open preperitoneal approach ($2253) than for laparoscopic repairs ($4826).

CONCLUSIONS

The open preperitoneal hernia repair using the Kugel mesh offers many advantages. It is inexpensive, has a low recurrence rate, and allows the surgeon to cover all potential defects with one piece of mesh. Postoperative recovery is short and postoperative pain is minimal.

Nursing interventions in the Kingston Paediatric and Perinatal HIV/AIDS Programme in Jamaica

BACKGROUND

Nursing care has been the "grass roots" of healthcare management even before nursing became a profession. Literature on the nursing experience with HIV is minimal and so it is challenging to comment on, or to compare experiences.

PURPOSE

This paper highlights the nursing interventions as a key feature in the ongoing development and success of a prevention of mother-to-child HIV transmission (pMTCT) programme in a resource-limited setting.

METHOD

In the Kingston Paediatric and Perinatal HIV/AIDS Programme, the nurses and midwives were carefully selected and then trained in the management of preventing mother-to-child transmission (pMTCT) of HIV/AIDS, voluntary counselling and testing and the identification and nursing management of paediatric and perinatal HIV/AIDS. The sites of the programme included three large maternity centres and four paediatric centres, with several feeder clinics for pregnant women. A nurse coordinator supervised the interventions at each site. A multidisciplinary team followed protocol-driven management for the care of pregnant HIV-positive women and children. There was strong collaboration with the Jamaican government and other agencies.

RESULTS

The nursing interventions served to: sensitize and encourage other healthcare workers in the care of persons living with HIV/AIDS; sensitize persons in the community about the disease; improve the comfort level of women and families with accessing healthcare; enable prospective data collection for programme assessment and research purposes and to enhance multidisciplinary collaboration to widen the scope of patient care and prevent duplication of healthcare services.

CONCLUSION

Nursing intervention is a vital part of a pMTCT HIV programme; however, ongoing education and training of the entire healthcare team needs to be continued in order to strengthen the programme. It is hoped that much of what is done in the Kingston Paediatric and Perinatal HIV/AIDS Programme will become integrated in the nursing management of maternal and child health nationally.

Volvulus of the gallbladder: laparoscopic detorsion and removal

A 73-year-old woman who presented with symptoms of acute cholecystitis was found to have a gangrenous gallbladder wrapped in three complete rotations around its pedicle. Detorsion and removal of the gallbladder were accomplished laparoscopically. Our review of the literature found no other case in which this degree of torsion was successfully treated laparoscopically.

Novel use of an established agent: Topotecan is anti-angiogenic in experimental Wilms tumor

BACKGROUND/PURPOSE

Antiangiogenic agents offer a new approach to the treatment of aggressive neoplasms, yet very few agents are available for current use. The authors have shown previously the efficacy of antiangiogenic therapy in experimental Wilms tumor, using an investigative antibody. They hypothesized that topotecan, administered in a regimen targeting endothelial cells, would suppress tumor growth and angiogenesis in experimental Wilms tumor.

METHODS

Experimental tumors were induced in the left kidneys of athymic mice by injection of cultured Wilms tumor cells. Topotecan (0.36, 0.6, 1.0, 2.0, and 3.0 mg/kg) or vehicle was injected intraperitoneally in 2 cycles over a 6-week period. Fluorescein angiograms and platelet endothelial cell adhesion molecule-1 staining of primary tumors were performed to ascertain vascular architecture. Endothelial apoptosis was assessed by TdT-mediated dUTP nick end labeling assay.

RESULTS

Tumor weights were reduced significantly in treated versus control animals, even in the lowest-dose group. Endothelial cell staining and angiography results showed relatively sparse vascularity in treated xenografts. Endothelial apoptosis was observed in treated but not control tumors.

CONCLUSIONS

Topotecan, delivered in an "antiangiogenic" regimen, even at very low doses, significantly inhibited growth of experimental Wilms tumors. No adverse effects were noted at low doses. Thus, the established chemotherapy agent topotecan may be useful in a novel role: as antiangiogenic therapy. J Pediatr Surg 36:1781-1784.

Structural determinants of ligand binding selectivity between the peroxisome proliferator-activated receptors

The peroxisome proliferator-activated receptors (PPARs) are transcriptional regulators of glucose, lipid, and cholesterol metabolism. We report the x-ray crystal structure of the ligand binding domain of PPAR alpha (NR1C1) as a complex with the agonist ligand GW409544 and a coactivator motif from the steroid receptor coactivator 1. Through comparison of the crystal structures of the ligand binding domains of the three human PPARs, we have identified molecular determinants of subtype selectivity. A single amino acid, which is tyrosine in PPAR alpha and histidine in PPAR gamma, imparts subtype selectivity for both thiazolidinedione and nonthiazolidinedione ligands. The availability of high-resolution cocrystal structures of the three PPAR subtypes will aid the design of drugs for the treatments of metabolic and cardiovascular diseases.

Chemical genomics: functional analysis of orphan nuclear receptors in the regulation of bile acid metabolism

Chemical genomics is the name we have given to the analysis of gene function through use of small molecule chemical tools. Orphan nuclear receptors are ideally suited to this technique of functional analysis, since their activity as transcription factors is regulated by small hydrophobic ligands. GW4064 is a potent and selective nonsteroidal ligand for the nuclear bile acid receptor FXR (NR1H4). Using GW4064 as a chemical tool, we have identified genes regulated by FXR in the liver, including those involved in bile acid synthesis and transport. We have also discovered that PXR (NR1I2) is a lithocholic acid receptor that controls the biosynthesis and metabolism of bile acids. Together FXR and PXR cooperate to control biliary and urinary bile acid excretion. These functions suggest that potent PXR and FXR ligands may offer a new approach to the treatment of cholestatic liver disease.

Identifying substrates for endothelium-specific Tie-2 receptor tyrosine kinase from phage-displayed peptide libraries for high throughput screening

The peptide substrate specificity of Tie-2 was probed using the phage display method in order to identify efficient substrate for high throughput screening. Two random peptide libraries, pGWX3YX4 and pGWX4YX4, were constructed, in which all twenty amino acid residues were represented at the X positions flanking the fixed tyrosine residue Y. A fusion protein of GST and the catalytic domain of human Tie-2 was used to perform the phage phosphorylation. The phosphorylated phage particles were enriched by panning over immobilized anti-phosphotyrosine antibody pY20 for a total of 5 rounds. Four phage clones (3T61, 3T68, C1-90 and D1-15) that express a peptide sequence that can be phosphorylated by the recombinant catalytic domain of human Tie-2 were identified. Synthetic peptides made according to the sequences of the 4 selected clones from the two libraries, which had widely different sequences, were active substrates of Tie-2. Kinetic analysis revealed that D1-15 had the best catalytic efficiency with a k(cat)/K(m) of 5.9x10(4) M(-1) s(-1). Three high throughput screening assay formats, dissociation-enhanced lanthanide fluoroimmunoassay (DELFIA), radioactive plate binding (RPB) and time-resolved fluorescent resonance energy transfer (TR-FRET) were developed to assess the suitability of these phage display selected peptides in screening Tie-2 inhibitors. Three out of four peptides were functional in the DELFIA assay and D1-15 was functional in the TR-FRET assay.

Combination antiangiogenic therapy: increased efficacy in a murine model of Wilms tumor

BACKGROUND/PURPOSE

Antibody to vascular endothelial growth factor (anti-VEGF) suppresses tumor growth and metastasis in experimental Wilms tumor. However, tumor growth accelerates if antibody is withdrawn. As recently shown, low-dose, frequently administered topotecan, a topoisomerase-1 inhibitor, has anti-angiogenic activity. The authors hypothesized that combined topotecan/anti-VEGF therapy would suppress tumor growth and metastasis more durably than either agent alone.

METHODS

Xenografts were induced by intrarenal injection of human Wilms tumor cells in athymic mice (n = 59). Mice were divided into control (n = 10), anti-VEGF (n = 16), topotecan (n = 17), and topotecan plus anti-VEGF (n = 16) groups. All control and half the treated mice were killed at week 6. Remaining ("rebound") mice were maintained without treatment until week 8. Tumor vasculature was mapped by fluorescein angiography/PECAM immunostaining. Endothelial apoptosis was assessed by TUNEL assay.

RESULTS

6 weeks: Tumor weights were reduced significantly in treated mice (P <.003 v control). Seven of ten control and 1 of 25 treated mice displayed lung metastases (P <.003). Rebound tumors were largest in topotecan-only, intermediate in antibody-treated, and smallest in combination-treated mice. Immunostaining and angiography results showed sparse vascularity in treated xenografts. Endothelial apoptosis was observed only in treated tumors.

CONCLUSION

Combination low-dose topotecan and anti-VEGF antibody therapy is antiangiogenic and suppresses tumor growth and metastasis in experimental Wilms tumor more durably than either agent alone.

Pharmacophore analysis of the nuclear oxysterol receptor LXRalpha

A cell-free assay was developed for the orphan nuclear receptor LXRalpha that measures the ligand-dependent recruitment of a peptide from the steroid receptor coactivator 1 (SRC1) to the nuclear receptor. Using this ligand-sensing assay (LiSA), the structural requirements for activation of the receptor by oxysterols and related compounds were studied. The minimal pharmacophore for receptor activation was shown to be a sterol with a hydrogen bond acceptor at C24. 24(S),25-Epoxycholesterol (1), which meets this criterion, is among the most efficacious of the oxysterols and is an attractive candidate as the LXRalpha natural hormone. Cholenic acid dimethylamide (14) showed increased efficacy compared to 1, whereas the unnatural oxysterol 22(S)-hydroxycholesterol (4) was shown to be an antagonist of 1 in the LiSA. The structural requirements for SRC1 recruitment in the LiSA correlated with the transcriptional activity of compounds in a cell-based reporter assay employing LXRalpha-GAL4 chimeric receptors. Site-directed mutagenesis identified Trp(443) as an amino acid critical for activation of LXRalpha by oxysterol ligands. This information was combined with the structure-activity relationship developed from the LiSA to develop a 3D homology model of LXRalpha. This model may aid the design of synthetic drugs targeted at this transcriptional regulator of cholesterol homeostasis.

Production and characterization of an estrogen receptor beta subtype-specific mouse monoclonal antibody

An important step in differentiating the unique physiological roles of the alpha and beta forms of estrogen receptor is to determine the precise expression pattern of each of these receptors. We report the generation and characterization of a murine IgG1 monoclonal antibody (MAb), ER15.64A that is ERbeta subtype-specific and capable of recognizing full-length human ERbeta as well as all of its known protein isoforms. ER15.64A, raised against a ERbeta peptide (aa2-18)-keyhole limpet hemocyanine conjugate, reacted to the immunizing peptide and the full-length E. coli expressed ERbeta in ELISA and BIAcore assays. It also immunostained nuclei of Sf9 insect cells that were infected with an ERbeta-baculovirus. In Western analysis, ER15.64A recognized ERbeta1 and ERbeta2 proteins from a reticulocyte in vitro transcription/translation preparation. This antibody did not cross-react with recombinant ERalpha in ELISA, BIAcore, immunocytochemistry, or Western blot analysis. The specificity of ER15.64A should make this antibody a useful tool for monitoring expression of ERbeta and its isoforms at the protein level and should aid in distinguishing the pattern of ERbeta receptor expression from that of ERalpha.

Use of the nuclear receptor PXR to predict drug interactions

We recently cloned the human, rabbit, rat, and mouse orthologs of a novel member of the steroid/retinoid/thyroid hormone receptor family, which we have named the Pregnane X Receptor (PXRs). The discovery and characterization of PXR has led to an increased understanding of the molecular basis of many drug-drug interactions as well as a better understanding of xenobiotic metabolism in general. The key insights into PXR action was the finding that this nuclear receptor is linked to regulation of the cytochrome P450 3A monooxygenase (CYP3A) genes. Several lines of evidence indicate that PXR mediates the induction of CYP3A gene transcription. First, PXR is selectively expressed in the liver and intestine, the same tissues in which CYP3A gene expression is induced. Second, PXR binds as a heterodimer with the retinoid X receptor (RXR) to xenobiotic response elements that have been identified in CYP3A gene promoters. Third, PXR is activated by the remarkable array of compounds that are known to induce CYP3A gene transcription. And finally, PXRs from different species are differentially activated by certain compounds such as rifampicin and pregnenolone 16alpha-carbonitrile (PCN) in a manner that correlates with species-specific induction of CYP3A gene expression. We are now employing high throughput PXR activation and binding assays to identify drug candidates that induce CYP3A gene expression so that these compounds can be removed from the drug development process.

Structure of the Tie2 RTK domain: self-inhibition by the nucleotide binding loop, activation loop, and C-terminal tail

BACKGROUND

Angiogenesis, the formation of new vessels from the existing vasculature, is a critical process during early development as well as in a number of disease processes. Tie2 (also known as Tek) is an endothelium-specific receptor tyrosine kinase involved in both angiogenesis and vasculature maintenance.

RESULTS

We have determined the crystal structure of the Tie2 kinase domain to 2.2 A resolution. The structure contains the catalytic core, the kinase insert domain (KID), and the C-terminal tail. The overall fold is similar to that observed in other serine/threonine and tyrosine kinase structures; however, several unique features distinguish the Tie2 structure from those of other kinases. The Tie2 nucleotide binding loop is in an inhibitory conformation, which is not seen in other kinase structures, while its activation loop adopts an "activated-like" conformation in the absence of phosphorylation. Tyr-897, located in the N-terminal domain, may negatively regulate the activity of Tie2 by preventing dimerization of the kinase domains or by recruiting phosphatases when it is phosphorylated.

CONCLUSION

Regulation of the kinase activity of Tie2 is a complex process. Conformational changes in the nucleotide binding loop, activation loop, C helix, and the C-terminal tail are required for ATP and substrate binding.

Identification of the human Mnk2 gene (MKNK2) through protein interaction with estrogen receptor beta

We have identified and characterized the human Mnk2 gene (HGMW-approved gene symbol MKNK2) through a yeast two-hybrid screen in which the Mnk2 protein interacted with the ligand-binding domain of estrogen receptor beta (ERbeta). Human Mnk2 is homologous to murine Mnk2 ( approximately 94% identical) and human Mnk1 (71% identical), both of which encode MAP kinase interacting kinases that are phosphorylated and activated by ERK1 and 2. This report presents a thorough genomic sequence analysis revealing that the human Mnk2 gene has two C-terminal splice variants, designated here as Mnk2a and Mnk2b. These two isoforms are identical over the first 385 amino acids of the coding sequence and differ only in the final exon which encodes an additional 80 residues for Mnk2a and 29 residues for Mnk2b. A more detailed biological analysis in yeast showed that the Mnk2 interaction was selective for ERbeta as opposed to ERalpha and that the interaction was specific to Mnk2b as opposed to Mnk2a or Mnk1. This pattern was reproduced in a mammalian two-hybrid system using a completely different set of fusion partners; and in both yeast and mammalian systems, the addition of estradiol decreased the interaction. While it remains unknown whether ERbeta is a substrate of Mnk2, the interaction of these two proteins is reminiscent of ERalpha and ribosomal S6 kinase (p90-RSK), another MAP kinase-regulated kinase homologous to Mnk2 that is known to phosphorylate ERalpha.

The pregnane X receptor: a promiscuous xenobiotic receptor that has diverged during evolution

Transcription of genes encoding cytochrome P450 3A (CYP3A) monooxygenases is induced by a variety of xenobiotics and natural steroids. There are marked differences in the compounds that induce CYP3A gene expression between species. Recently, the mouse and human pregnane X receptor (PXR) were shown to be activated by compounds that induce CYP3A expression. However, most studies of CYP3A regulation have been performed using rabbit and rat hepatocytes. Here, we report the cloning and characterization of PXR from these two species. PXR is remarkably divergent between species, with the rabbit, rat, and human receptors sharing only approximately 80% amino acid identity in their ligand-binding domains. This sequence divergence is reflected by marked pharmacological differences in PXR activation profiles. For example, the macrolide antibiotic rifampicin, the antidiabetic drug troglitazone, and the hypocholesterolemic drug SR12813 are efficacious activators of the human and rabbit PXR but have little activity on the rat and mouse PXR. Conversely, pregnane 16alpha-carbonitrile is a more potent activator of the rat and mouse PXR than the human and rabbit receptor. The activities of xenobiotics in PXR activation assays correlate well with their ability to induce CYP3A expression in primary hepatocytes. Through the use of a novel scintillation proximity binding assay, we demonstrate that many of the compounds that induce CYP3A expression bind directly to human PXR. These data establish PXR as a promiscuous xenobiotic receptor that has diverged during evolution.

The pregnane X receptor: a promiscuous xenobiotic receptor that has diverged during evolution

Transcription of genes encoding cytochrome P450 3A (CYP3A) monooxygenases is induced by a variety of xenobiotics and natural steroids. There are marked differences in the compounds that induce CYP3A gene expression between species. Recently, the mouse and human pregnane X receptor (PXR) were shown to be activated by compounds that induce CYP3A expression. However, most studies of CYP3A regulation have been performed using rabbit and rat hepatocytes. Here, we report the cloning and characterization of PXR from these two species. PXR is remarkably divergent between species, with the rabbit, rat, and human receptors sharing only approximately 80% amino acid identity in their ligand-binding domains. This sequence divergence is reflected by marked pharmacological differences in PXR activation profiles. For example, the macrolide antibiotic rifampicin, the antidiabetic drug troglitazone, and the hypocholesterolemic drug SR12813 are efficacious activators of the human and rabbit PXR but have little activity on the rat and mouse PXR. Conversely, pregnane 16alpha-carbonitrile is a more potent activator of the rat and mouse PXR than the human and rabbit receptor. The activities of xenobiotics in PXR activation assays correlate well with their ability to induce CYP3A expression in primary hepatocytes. Through the use of a novel scintillation proximity binding assay, we demonstrate that many of the compounds that induce CYP3A expression bind directly to human PXR. These data establish PXR as a promiscuous xenobiotic receptor that has diverged during evolution.

Expression of wild-type estrogen receptor beta and variant isoforms in human breast cancer

It has been shown in previous studies that a variety of estrogen receptor (ER) beta mRNA transcripts are expressed in human breast cancer cell lines and tumors. To complement the RNA expression studies, we have developed ER-beta-specific antibodies to characterize ER-beta protein expression in breast cancer cell lines and tumors. Monoclonal antibodies were made against a peptide representing the first 18 amino acids of the longest ER-beta open reading frame reported to date, and polyclonal antibodies were made against a peptide within the ER-beta B domain. By Western blot analysis, we show that ER-beta protein is expressed in all cancer cell lines tested and in three of five breast tumor samples. The breast cancer cell lines showed variation in the size of the expressed ER-beta protein. The longest form detected was consistent with the 530-amino acid, full-length ER-beta sequence. Shorter ER-beta isoforms were detected in the ER-alpha-negative MDA-MB-231 and MDA-MB-435 breast cancer cell lines, likely corresponding to previously described COOH-terminal RNA variant isoforms.

Human influenza: viral mutations and altered tropisms

Influenza is a virus that is capable of causing a pandemic of the human race. Influenza has the ability to infect humans by mutating and altering its pathogenic characteristics. Efforts must be made worldwide to educate people about the possibilities of a potential outbreak. Awareness of optimal conditions which could lead to viral mutation and human to human transmission of a neogenetic strain of influenza appears to be a key deterrent against future cases.

The human orphan nuclear receptor PXR is activated by compounds that regulate CYP3A4 gene expression and cause drug interactions

The cytochrome P-450 monooxygenase 3A4 (CYP3A4) is responsible for the oxidative metabolism of a wide variety of xenobiotics including an estimated 60% of all clinically used drugs. Although expression of the CYP3A4 gene is known to be induced in response to a variety of compounds, the mechanism underlying this induction, which represents a basis for drug interactions in patients, has remained unclear. We report the identification of a human (h) orphan nuclear receptor, termed the pregnane X receptor (PXR), that binds to a response element in the CYP3A4 promoter and is activated by a range of drugs known to induce CYP3A4 expression. Comparison of hPXR with the recently cloned mouse PXR reveals marked differences in their activation by certain drugs, which may account in part for the species-specific effects of compounds on CYP3A gene expression. These findings provide a molecular explanation for the ability of disparate chemicals to induce CYP3A4 levels and, furthermore, provide a basis for developing in vitro assays to aid in predicting whether drugs will interact in humans.

Cloning and characterization of human estrogen receptor beta isoforms

Multiple transcripts which arise from the human estrogen receptor beta (ER beta) gene have been characterized. Three full length isoforms of the hER beta gene, designated hER beta 1-3, were identified in a testis cDNA library. An additional two isoforms, designated hER beta 4 and hER beta 5, were identified by PCR amplification from testis cDNA and from the MDA-MB 435 cell line. hER beta 1 corresponds to the previously described hER beta. All five isoforms diverge at a common position within the predicted helix 10 of the ligand binding domain of hER beta, with nucleotide sequences consistent with differential exon usage. The hER beta isoform mRNAs displayed a differential pattern of expression in human tissues and in tumor cell lines when analyzed by RT-PCR. Further characterization of the three full length isoforms, hER beta 1-3, by in vitro band shift studies indicated that the isoforms were able to form DNA-binding homodimers and heterodimers with each other and with the ER alpha subtype.

An orphan nuclear receptor activated by pregnanes defines a novel steroid signaling pathway

Steroid hormones exert profound effects on differentiation, development, and homeostasis in higher eukaryotes through interactions with nuclear receptors. We describe a novel orphan nuclear receptor, termed the pregnane X receptor (PXR), that is activated by naturally occurring steroids such as pregnenolone and progesterone, and synthetic glucocorticoids and antiglucocorticoids. PXR exists as two isoforms, PXR.1 and PXR.2, that are differentially activated by steroids. Notably, PXR.1 is efficaciously activated by pregnenolone 16alpha-carbonitrile, a glucocorticoid receptor antagonist that induces the expression of the CYP3A family of steroid hydroxylases and modulates sterol and bile acid biosynthesis in vivo. Our results provide evidence for the existence of a novel steroid hormone signaling pathway with potential implications in the regulation of steroid hormone and sterol homeostasis.

Thoracoscopic excision of mediastinal parathyroid adenomas: a report of two cases and review of the literature

BACKGROUND

Most abnormal parathyroid glands can be removed through a standard cervical incision; even those in the superior mediastinum. Those located in certain areas of the mediastinum, for example posteriorly or in the aortopulmonic window, historically have required excision through a median sternotomy or thoracotomy. Angioablation is a nonsurgical alternative to management of these lesions.

STUDY DESIGN

We present two case reports of mediastinal parathyroid adenomas that were excised thoracoscopically, and review the literature regarding the management of mediastinal parathyroid adenomas.

RESULTS

Both patients who underwent precise localization and thoracoscopic excision of their mediastinal parathyroid adenomas had resolution of their hypercalcemia with minimal associated morbidity and shortened recovery periods.

CONCLUSIONS

We suggest that thoracoscopic excision of mediastinal parathyroid adenomas is the better means of controlling hypercalcemia secondary to parathyroid adenoma in those patients considered for either median sternotomy, thoracotomy or angiographic ablation where the exact location of the lesion can be established preoperatively.

Applications of S-layers

The wealth of information existing on the general principle of S-layers has revealed a broad application potential. The most relevant features exploited in applied S-layer research are: (i) pores passing through S-layers show identical size and morphology and are in the range of ultrafiltration membranes; (ii) functional groups on the surface and in the pores are aligned in well-defined positions and orientations and accessible for binding functional molecules in very precise fashion; (iii) isolated S-layer subunits from many organisms are capable of recrystallizing as closed monolayers onto solid supports at the air-water interface, on lipid monolayers or onto the surface of liposomes. Particularly their repetitive physicochemical properties down to the subnanometer scale make S-layers unique structures for functionalization of surfaces and interfaces down to the ultimate resolution limit. The following review focuses on selected applications in biotechnology, diagnostics, vaccine development, biomimetic membranes, supramolecular engineering and nanotechnology. Despite progress in the characterization of S-layers and the exploitation of S-layers for the applications described in this chapter, it is clear that the field lags behind others (e.g. enzyme engineering) in applying recent advances in protein engineering. Genetic modification and targeted chemical modification would allow several possibilities including the manipulation of pore permeation properties, the introduction of switches to open and close the pores, and the covalent attachment to surfaces or other macromolecules through defined sites on the S-layer protein. The application of protein engineering to S-layers will require the development of straightforward expression systems, the development of simple assays for assembly and function that are suitable for the rapid screening of numerous mutants and the acquisition of structural information at atomic resolution. Attention should be given to these areas in the coming years.

Explantation of silicone breast implants

Silicone gel-filled breast implants have been employed clinically for decades for aesthetic augmentation or postmastectomy reconstruction. Most patients and surgeons attest to the efficacy and safety of these devices. However, more recently in the medical literature and popular media, silicone gel-filled breast implants have been claimed to incite an array of clinical sequelae such as capsular formation, granulomatous disease, arthritis, arthralgia, fibromyalgia, autoimmune collagen vascular disease, human adjuvant disease, siliconosis, silicone-related disease, and silicone implant-associated syndrome. During a recent 24-month period, 25 referred patients underwent explantation of bilateral silicone gel-filled prostheses at the University of South Alabama. Patient-reported symptoms and signs included mastodynia, arthralgia, fibromyalgia, xerophthalmia, xerostomia, hypesthesia, and amblyopia. Clinical examination and mammography were reliable in diagnosing implant rupture, but only re-exploration reliably detected implant leakage. Most patients underwent concurrent replacement with saline-filled devices. Histopathologic analyses of all tissue samples revealed chronic inflammation. Subjective improvement of patient-reported symptoms and signs occurred over the course of months postoperatively. There was no mortality associated with explantation, with or without replacement, but an overall morbidity incidence of 20 per cent (5 of 25) was observed. Predicated upon review of the available scientific literature and analysis of this modest number of patients, the following perspectives are germane. 1) A small cohort of patients of status postimplantation of silicone gel-filled devices will manifest chronic morbidity. Identifying such patients prospectively remains problematic. 2) Whether or not silicone gel incites adverse systemic phenomena is unproven, although it has been implicated. 3) Symptomatic patients with silicone gel-filled implants in place should be considered for removal, with full knowledge of the morbidity associated with revisional procedures. 4) Patients currently undergoing breast augmentation or reconstruction employing prosthetics are perhaps best served by insertion of saline-filled devices. 5) Patient-physician dialogue regarding the risk-benefit analysis of prosthetic implantation is imperative. Patients consenting to such procedures must be willing to assume risks.

The development of beta-lactamase as a highly versatile genetic reporter for eukaryotic cells

We describe in this report that TEM-1 beta-lactamase has several desirable characteristics as a genetic reporter. First, it has no endogenous counterpart in eukaryotic cells and therefore provides a background-free measure of gene expression. Second, because of the uniqueness of the substrate cleavage reaction, a wide variety of substrates which are efficiently cleaved can be synthesized for beta-lactamase. Third, since the assays involve no more than addition of substrate to media, it is possible to continuously monitor a culture without destruction of the cells. Fourth, the enzyme is extremely versatile in that it can be fused to other proteins and retain activity. To demonstrate the versatility of beta-lactamase, we created three forms of the enzyme including secreted, intracellular, and membrane-bound forms of the enzyme, each form having distinct advantages as a reporter system. We also showed that levels of secreted beta-lactamase were proportional to both the levels of transfected DNA, beta-lactamase mRNA, as well as activity of the chloramphenicol acetyl transferase gene controlled by the same promoter, validating the reliability of this reporter. beta-Lactamase thus represents a novel and highly versatile genetic reporter.

Protein-protein interactions involving T4 phage-coded deoxycytidylate deaminase and thymidylate synthase

The enzymes deoxycytidylate deaminase (EC) and thymidylate synthase (EC) are functionally associated with one another, since they catalyze sequential reactions. In T4 coliphage infection the two enzymes are found in dNTP synthetase, a multienzyme complex for deoxyribonucleotide biosynthesis. Protein-protein interactions involving the phage-coded forms of these two enzymes have been explored in three experiments that use the respective purified protein as an affinity ligand. First, an extract of radiolabeled T4 proteins was passed through a column of immobilized enzyme (either dTMP synthase or dCMP deaminase), and the specifically bound proteins were identified. Second, two mutant form of dCMP deaminase (H90N and H94N), altered in presumed zinc-binding sites, were analyzed similarly, with the results suggesting that some, but not all, interactions require normal structure near the catalytic site. Third, affinity chromatography using either enzyme as the immobilized ligand, revealed interactions between the two purified enzymes in the absence of other proteins. In these experiments we noted a significant effect of dCTP, an allosteric modifier of dCMP deaminase, upon the interactions.

Metastatic breast carcinoma presenting as cholecystitis

We report two cases of metastatic breast cancer presenting as cholecystitis. Each patient had undergone a mastectomy years earlier. Biopsy of the gallbladder removed during cholecystectomy revealed metastatic infiltrating ductal carcinoma in one patient and infiltrating lobular carcinoma in the other.

The anti-human immunodeficiency virus agent 3'-fluorothymidine induces DNA damage and apoptosis in human lymphoblastoid cells

Patients infected with the human immunodeficiency virus experienced severe hematopoietic toxicity after treatment with the deoxynucleoside analog 3'-fluorothymidine (FLT). Using several methods for the analysis of genome integrity, including histochemical staining of the 3' ends of DNA and both conventional and pulsed-field agarose gel electrophoresis, we demonstrated that FLT caused extensive DNA fragmentation in CEM cells that was not observed when these cells were treated with other, less toxic thymidine analogs. In addition, a distinctive pattern of small DNA fragments that is characteristic of cells in the process of programmed cell death was observed in the genomic DNA of CEM cells treated with FLT. We conclude that FLT induces DNA fragmentation and apoptosis in a human cell line of hematopoietic origin, and we offer this observation as a possible explanation for the severe toxicity of FLT observed in vivo.

Extramedullary hematopoiesis during therapy with granulocyte colony-stimulating factor

Granulocyte colony-stimulating factor is a glycoprotein that promotes the proliferation and differentiation of neutrophils. It also results in an increase in circulating hematopoietic progenitor cells. We describe two cases of extramedullary hematopoiesis in patients receiving granulocyte colony-stimulating factor with chemotherapy for metastatic breast cancer.

Relationship between sleep spindles and hypersomnia

Sleep spindles (SS) and K complexes constitute the physiological markers of stage 2 sleep. Because sleep allows a spontaneous thalamic manifestation in the form of SS, one could hypothesize that there is some kind of relationship between SS and the complaint of hypersomnia. To investigate this possible relationship we compared nonhypersomnolent subjects with hypersomnolent patients who carried a diagnosis of narcolepsy or idiopathic hypersomnia. SS were counted in well-defined nocturnal stage 2 sleep segments, and the average SS density (number of SS in stage 2/minute stage 2) was tabulated for the entire night. Agreement between two independent scores was higher than 95%. The results show that the average SS density is higher in both cerebral hemispheres in the hypersomnolent group, especially in the idiopathic hypersomnia patients. At the beginning and at the end of the nocturnal sleep time, SS density is increased in this group compared with the normal one. These findings support the complaint of hypersomnia, mainly in idiopathic hypersomnia patients. This is in agreement with the notion that SS are generated by thalamic structures that serve a gatekeeping function during nonrapid eye movement sleep, and further suggests that their relative abundance expresses the power of that control.

Identification of a site necessary for allosteric regulation in T4-phage deoxycytidylate deaminase

An allosteric inhibitor of dCMP deaminase, dTTP, forms a photolabile covalent bond with T4-phage dCMP deaminase in the presence of UV light at 254 nm. The importance of the methyl group in this process is supported by the findings that dUTP, also an allosteric inhibitor, does not photofix to the enzyme and that tritium is released from [methyl-3H dTTP during the course of the photofixation. That the bond formed is photolabile is demonstrated by the fact that tritium is released by about 10-fold over the amount of nucleotide that is photofixed. The amino acid that covalently binds dTTP in T4-dCMP deaminase was identified as Phe112. On conversion of Phe112 to an alanine by site-directed mutagenesis, there was a dramatic change in the enzyme's response to its allosteric effectors when measured early in the reaction, in that the mutant enzyme was as active as the wild-type even in the absence of dCTP and was only weakly inhibited by dTTP. However, after 10-15% of the substrate had been deaminated, the reaction rate fell off rather markedly, indicating either that an inhibitor was being accumulated on the enzyme or that the enzyme was being irreversibly inactivated with time. That the latter was not the case was shown by the addition of dCTP to the reaction, which restored the rate to that expected when it was present initially. Furthermore, we showed that, consistent with the observed loss of allosteric regulation by dCTP and dTTP, the affinity of the mutant enzyme for dTTP and dCTP as determined by binding studies was greatly reduced relative to the wild-type enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

Fabrication and evaluation of an etched infrared diffraction grating

We evaluated the optical performance of an IR echelle grating produced on a silicon wafer with anisotropic etching techniques. We measured the diffraction efficiency of a sample with a 55° blaze angle and 25-µm groove spacing. We also calculated the efficiency for typical triangular and trapezoidal groove profiles of etched gratings. The diffraction efficiency for unpolarized light can be approximately as high as the efficiency of right-angle groove gratings. The great potential of the etched silicon grating lies in its ease of fabrication, its excellent surface quality, and the high reproducibility of the production process. Compact high-resolution diffraction gratings can be produced by etching the grating pattern into the rear side of a transparent prism. When used in internal reflection, this increases the resolving power of the grating by a factor equal to the refractive index of the prism over a front surface grating of the same length.

Overcoming inclusion body formation in a high-level expression system

Attempts at overexpressing T4-phage deoxycytidylate deaminase using the pET3c/BL21(DE3)/pLysS system resulted in this enzyme being part of an inactive inclusion-body complex. However, by employing an enriched growth medium it was found that the deaminase could be induced in a soluble active form to at least 20% of this organism's cellular protein. Insoluble inclusion bodies were obtained with less rich media. This procedure was employed successfully with other highly expressed proteins that formed inclusion bodies. The use of a rich growth medium during the course of protein induction may be a valuable adjunct to limiting inclusion body formation with this as well as other expression systems.

T4-phage deoxycytidylate deaminase is a metalloprotein containing two zinc atoms per subunit

Deoxycytidylate (dCMP) deaminase, a hexameric allosteric enzyme induced on infection of Escherichia coli by bacteriophage T4, was shown to contain two atoms of zinc per subunit by atomic absorption spectroscopy. One zinc appears to be involved in catalysis, as described for adenosine deaminase (Sharaff, A. J., Wilson, D. K., Chang, Z., and Quiocho, F. A. (1992) J. Mol. Biol. 226, 917-921) and cytidine deaminase (Yang, C., Carlow, D., Wolfenden, R., and Short, S. A. (1992) Biochemistry 31, 4168-4174). This thesis is supported by the finding that the enzyme loses about 80% of its activity in the presence of o-phenanthroline. It has also been found that zinc is released when the enzyme is denatured in the presence of the metallochromic indicator, 4-(2-pyridylazo)resorcinol. Renaturation of the deaminase to an active form occurred in the presence but not in the absence of zinc. The second atom of zinc is proposed to be located in a region of T4-dCMP deaminase that resembles a zinc finger. This region, which has the sequence His-X3-Cys-X14-His-X3-His, would represent a zinc-binding motif that has not been described previously.

[Treatment with continuous positive nasal pressure in obstructive sleep apnea syndrome]

BACKGROUND

The collapse of the soft tissues of the upper airway during sleep is decisive in the pathogenesis of the obstructive sleep apnea syndrome. The administration of an air flow of adjustable pressure through the nose is efficient to overcome the obstruction and favor respiration without apnea.

METHODS

Twenty-two patients with obstructive sleep apnea syndrome were treated with continuous positive pressure of the upper airway with the aim of evaluating the effect of this treatment on sleep, respiration and cardiac rhythm following the first night of treatment.

RESULTS

Following the night of treatment an increase of the III, IV states and sleep REM with a shortening of REM latency was observed. The number of apneas diminished drastically thus improving cardiac arrhythmias detected in the basal study.

CONCLUSIONS

Treatment of the upper airway with continuous positive pressure is efficient not only for the correction of apneas and cardiac arrhythmia but also for the consolidation of a normal sleep cycle.

[The multiple sleep latency test in the diagnosis of narcolepsy and idiopathic hypersomnia]

The diagnostic differential between narcolepsy and idiopathic hypersomnia may be difficult in those cases which clinically manifest only hypersomnia and the nocturnal polygraphic study does not show any differences between both diseases, particularly when the beginning of REM sleep is not presented in narcoleptic patients. The multiple sleep latency test is an objective test of daytime hypersomnia in both diseases. Moreover, if 2 or more REM periods are registered altogether in the 4 or 5 siestas studied, the test is highly suggestive of narcolepsy and permits sure differentiation with idiopathic hypersomnia. In the present study, the multiple sleep latency test permitted the diagnosis of the cases of oligosymptomatic narcolepsy and absence of the beginning of REM sleep.

Surgical complications of continuous ambulatory peritoneal dialysis

Surgical experience with 260 consecutive patients with chronic renal failure receiving continuous ambulatory peritoneal dialysis (CAPD) at one medical center from 1980 to 1989 is reviewed. Patients received CAPD for a mean of 24.2 months (range: 3 days to 91 months). Catheter longevity consistently improved in all but 1 year from 1984 to 1989, as did exit-site and tunnel infections. Of 311 catheters inserted, 151 (49%) required removal, of which 111 (74%) were attributed to peritonitis. Cumulative patient survival was 80%, 60%, and 53% at 1, 2, and 3 years, respectively. Diabetic patients had statistically significant lower survival rates. Additional complications including catheter leakage, catheter malposition, catheter obstruction, and abdominal wall hernias were negligible. Although CAPD is not free from serious complications, our data show remarkable improvement since 1980 in catheter longevity, hospital stay, and infection rates.

Characterization of IMP-E3, a gene active during imaginal disc morphogenesis in Drosophila melanogaster

The steroid hormone 20-hydroxyecdysone (20-HE) induces imaginal discs to form adult appendages in Drosophila. We have isolated a set of six ecdysone-responsive genes that apparently encode disc cell-surface or secreted proteins. Transcripts from one of these genes, IMP-E3, accumulate rapidly within 1-2 h in response to hormone. Developmentally, IMP-E3 transcripts reach maximum levels during the first stages of metamorphosis (white prepupae, WPP) and are primarily limited to imaginal tissues. Transcripts are also present during embryogenesis (0-3 h and 12-18 h). Two different-sized transcripts (1.2 and 1.4 kb) result from differential polyadenylation, with the larger transcript predominating in WPP. The conceptual IMP-E3 protein contains a signal peptide, an RGD sequence, and a potential glycosylphosphatidylinositol anchor. We speculate that the protein provides a transient cue important for imaginal disc morphogenesis.

Magnetic resonance findings in REM sleep behavior disorder

Rapid eye movement (REM) sleep behavior disorder is characterized by bizarre acts during nocturnal sleep that may lead to physical injuries. Dream content suggests that motor overactivity is an attempted dream enactment and polygraphic studies reveal REM stage without atonia, an alteration of REM sleep generation that facilitates excessive motor activity. In 6 patients with REM sleep behavior disorder. MRI of the brain showed multifocal signal intensity lesions suggestive of lacunar infarcts in periventricular regions (5 patients) and in dorsal pontomesencephalic areas (3 patients). REM sleep behavior disorder may be the result of injury to the midrostral tegmentum nuclei, the tegmentoreticular tracts, or both. This condition is easily controlled with clonazepam.

Processing of two protein precursors yields four mature guinea pig seminal vesicle secretory proteins

The translation of the two most abundant guinea pig seminal vesicle epithelium mRNAs (1800 nucleotides and 950 nucleotides) and the subsequent processing of their protein products were studied in an effort to elucidate the mechanism by which the four mature guinea pig seminal vesicle epithelium (GPSVE) secretory proteins are produced. The primary translation products of the 1800 nt and 950 nt mRNAs are two secretory protein precursors of 45 kDa and 20 kDa, respectively. Removal of signal peptides from these two precursors produces proteins of 43 kDa and 18.5 kDa, which are recognized by polyclonal antisera directed against the four mature secretory proteins. The existence of further processing intermediates in the production of the secretory proteins is suggested by the appearance of other immunoreactive polypeptides following incubation of GPSVE in nutrient medium containing [3H] leucine. Immunological and pulse-chase analysis strongly suggests that the 43-kDa protein gives rise to SVP-1, -3, and -4 and that SVP-2 is derived from the 18.5-kDa protein.

Significance of premorbid adjustment and psychotherapy in selected case studies

Although psychiatric symptoms are common among elderly individuals, these symptoms are seldom treated by psychotherapy. This article proposes a model to help explain genesis of psychiatric symptoms in late life. The model, which is illustrated by case examples, suggests psychotherapeutic strategies and helps define methods of assessing therapeutic outcomes. The model emphasizes the importance of losses, premorbid adjustment, and mediating factors in determining whether stresses result in adaptation or symptom formation.