Strategies to reduce the onset of sleeve gastrectomy associated bone loss (STRONG BONES): Trial design and methods

Background

Despite recognized improvements in obesity-related comorbidities, mounting evidence implicates surgical weight loss in the onset of skeletal fragility. Sleeve gastrectomy (SG) is the most commonly performed bariatric procedure and is associated with 3-7% axial bone loss in the year following surgery. Bisphosphonates are FDA-approved medications for the prevention and treatment of age-related bone loss and may represent a strategy to reduce bone loss following SG surgery.

Methods

The Strategies to Reduce the Onset of Sleeve Gastrectomy Associated Bone Loss (STRONG BONES) trial (NCT04922333) is designed to definitively test whether monthly administration of the bisphosphonate, risedronate, for six months can effectively counter SG-associated bone loss. Approximately 120 middle-aged and older (≥40 years) SG patients will be randomized to six months of risedronate or placebo treatment, with skeletal outcomes assessed at baseline, six, and 12-months post-surgery. The primary outcome of the trial is 12-month change in total hip areal bone mineral density (aBMD), measured by dual energy x-ray absorptiometry (DXA). This will be complemented by DXA-acquired aBMD assessment at other skeletal sites and quantitative computed tomography (QCT) derived changes in bone quality. Change in muscle mass and function will also be assessed, as well as biomarkers of bone health, turnover, and crosstalk, providing mechanistic insight into intervention-related changes to the bone-muscle unit.

Discussion

Results from the STRONG BONES trial have the potential to influence current clinical practice by determining the ability of bisphosphonate use to mitigate bone loss and concomitant fracture risk in middle-aged and older SG patients.

Weight changes during the COVID-19 shutdown in older individuals with type 2 diabetes: the Look AHEAD Study

OBJECTIVE

The aims of this study were as follows: 1) examine weight changes in older adults (mean age = 76 years) with type 2 diabetes and overweight or obesity during the COVID-19 shutdown; and 2) compare the behavioral and psychosocial effects of the shutdown in those who had large weight losses (>5%), those who had small weight losses (2%-5%), those who remained weight stable (±2%), or those who gained weight (>2%).

METHODS

Look AHEAD (Action for Health in Diabetes) participants (N = 2544) were surveyed during the COVID-19 shutdown (2020), and they self-reported their current weight, reasons for weight change, weight-related behaviors, psychosocial measures, and negative and positive effects of the pandemic on their lives.

RESULTS

Comparing self-reported weight during the COVID-19 shutdown with earlier measured weight, Look AHEAD participants lost, on average, 2.2 kg during the COVID-19 shutdown: 47% lost >2%, and only 18% gained >2% (p < 0.0001). Decreases in physical activity and increases in screen time were reported frequently in all weight-change categories. Similarly, there were few differences among the categories on standardized psychosocial measures or self-reported effects of the shutdown on participants' lives. However, when differences were seen, the most negative impact was in those who gained weight.

CONCLUSIONS

Although weight loss appeared more common than weight gain during the shutdown, the weight-change groups did not differ on most psychosocial and behavioral variables.

Impact of COVID-19 on life experiences reported by a diverse cohort of older adults with diabetes and obesity

OBJECTIVE

This study aimed to measure the impact of the COVID-19 pandemic on self-reported life experiences in older adults with diabetes and obesity.

METHODS

Participants were surveyed in 2020 regarding negative and positive impacts of the pandemic across domains of personal, social, and physical experiences. A cumulative negative risk index (a count of all reported negative impacts of 46 items) and a positive risk index (5 items) were characterized in relation to age, sex, race/ethnicity, BMI, and multimorbidity.

RESULTS

Response rate was high (2950/3193, 92%), average age was 76 years, 63% were women, and 39% were from underrepresented populations. Women reported more negative impacts than men (6.8 vs. 5.6; p < 0.001 [of 46 items]) as did persons with a greater multimorbidity index (p < 0.001). Participants reporting African American/Black race reported fewer negative impacts than White participants. Women also reported more positive impacts than men (1.9 vs. 1.6; p < 0.001 [of 5 items]).

CONCLUSIONS

Older adults with diabetes and obesity reported more positive impacts of the pandemic than negative impacts, relative to the number of positive (or negative) items presented. Some subgroups experienced greater negative impacts (e.g., for women, a greater multimorbidity index). Efforts to reestablish personal, social, and physical health after the pandemic could target certain groups.

Changes in the Prevalence of Symptoms of Depression, Loneliness, and Insomnia in U.S. Older Adults With Type 2 Diabetes During the COVID-19 Pandemic: The Look AHEAD Study

OBJECTIVE

To evaluate changes in the prevalence of depressive symptoms, loneliness, and insomnia among older adults with type 2 diabetes from 2016 to 2020 and to assess risk factors for these conditions including demographics, multimorbidity, BMI, treatment group, and pre-coronavirus 2019 (COVID-19) measure scores.

RESEARCH DESIGN AND METHODS

This was a prospective, observational study of participants from the Look AHEAD (Action for Health in Diabetes) cohort study. Data were from two assessments before COVID-19 (visit 1: April 2016-June 2018 and visit 2: February 2018-February 2020) and one assessment during COVID-19 (visit 3: July-December 2020). Surveys were administered to assess depressive symptoms, loneliness, and insomnia.

RESULTS

The study included 2829 adults (63.2% female, 60.6% White, mean [SD] age 75.6 [6.0] years). The prevalence of mild or greater depressive symptoms did not change significantly between the two pre-pandemic visits (P = 0.88) but increased significantly from pre- to during COVID-19 (19.3% at V2 to 30.4% at V3; P < 0.001). Higher odds of mild or greater depressive symptoms at V3 were associated with being female (adjusted odds ratio [OR] 1.4 [95% CI 1.1-1.7]), identifying as non-Hispanic White (OR 1.4 [95% CI 1.1-1.7]), having obesity (OR 1.3 [95% CI 1.0-1.5]), and reporting mild or greater depressive symptoms at V1 (OR 4.0 [95% CI 2.9-5.4]), V2 (OR 4.4 [95% CI 3.2-5.9]), or both visits (OR 13.4 [95% CI 9.7-18.4]). The prevalence of loneliness increased from 12.3% at V1 to 22.1% at V3 (P < 0.001), while the prevalence of insomnia remained stable across visits at 31.5-33.3%.

CONCLUSIONS

The prevalence of mild or greater depressive symptoms in older adults with diabetes was more than 1.6 times higher during COVID-19 than before the pandemic.

Wearable embroidered muscle activity sensing device for the human upper leg

Within the last decade, running has become one of the most popular physical activities in the world. Although the benefits of running are numerous, there is a risk of Running Related Injuries (RRIs) of the lower extremities. Electromyography (EMG) techniques have previously been used to study causes of RRIs, but the complexity of this technology limits its use to a laboratory setting. As running is primarily an outdoors activity, this lack of technology acts as a barrier to the study of RRIs in natural environments. This study presents a minimally invasive wearable muscle sensing device consisting of jogging leggings with embroidered surface EMG (sEMG) electrodes capable of recording muscle activity data of the quadriceps group. To test the use of the device, a proof of concept study consisting of N = 2 runners performing a set of 5 km running trials is presented in which the effect of running surfaces on muscle fatigue, a potential cause of RRIs, is evaluated. Results show that muscle fatigue can be analysed from the sEMG data obtained through the wearable device, and that running on soft surfaces (such as sand) may increase the likelihood of suffering from RRIs.

Distribution of Endo180 receptor and ligand in developing articular cartilage

OBJECTIVE

To investigate the expression of a novel member of the mannose receptor family, Endo180 (also known as uPARAP), and the distribution of Endo180 ligand(s) in the articular cartilage and growth plate of normal CBA mice and STR/ort mice, a well characterized model of spontaneous osteoarthritis.

DESIGN

A polyclonal anti-Endo180 antibody was used to determine receptor expression. The Endo180 extracellular domain fused to a human immunoglobulin Fc tail was used to detect ligand.

RESULTS

Endo180 receptor was strongly expressed in chondrocytes both in vitro and throughout the articular cartilage of young CBA and STR/ort mice. Expression decreased in older animals. In STR/ort mice with osteoarthritic lesions, no upregulation of Endo180 was detected. In the developing growth plate, Endo180 was expressed strongly by the proliferating chondrocytes. In contrast, Endo180 ligand was detected most strongly in hypertrophic zone of the growth plate and only at low levels in articular cartilage. In cultured chondrocytes, Endo180 was localized on the cell surface and in intracellular vesicles.

CONCLUSION

Constitutively recycling endocytic receptors function to internalize ligand from the extracellular milieu and the ability of Endo180 to bind both glycosylated ligands and collagens suggests a role in extracellular matrix remodeling. Expression of Endo180 in articular cartilage chondrocytes of young, but not old, mice and the reciprocal expression of Endo180 and its ligands in the growth plate suggest that this receptor is involved in cartilage development but not in cartilage homeostasis. In addition, our data indicates that Endo180 does not appear to play a role in the development or progression of murine osteoarthritis.

Two signal transduction pathways involved in the catecholaminergic differentiation of avian neural crest-derived cells in vitro

Molecules derived from the neural tube and found in chick embryo extract (CEE) and bone morphogenetic proteins (BMP) support the differentiation of neural crest-derived catecholaminergic (CA) neurons. We now report that intracellular signaling resulting in the activation of Map kinase (MapK) or translocation of Smad1 mediate the differentiation of CA neurons in response to CEE or BMP 4, respectively. The differentiation of CA neurons was significantly reduced by inhibiting MapK using PD98059 or by pan-specific blockade of tyrosine kinases using Herbimycin A. In the presence of BMP 4 and inhibitors of MapK signaling, differentiation of CA neurons was only moderately reduced. Independent of MapK, BMP 4 induced translocation of Smad1 from the cytosol to the nucleus and induced transcription of dHAND, a DNA binding protein required for the differentiation of CA neurons. The data suggest that CEE-derived factors and BMP4 support the differentiation of CA neurons via independent signaling pathways.

The ligand-binding loops in the tunicate C-type lectin TC14 are rigid

C-type lectin-like domains are very common components of extracellular proteins in animals. They bind to a variety of ligands, including carbohydrates, proteins, ice, and CaCO3 crystals. Their structure is characterized by long surface loops in the area of the protein usually involved in ligand binding. The C-type lectin TC14 from Polyandrocarpa misakiensis specifically binds to D-galactose by coordination of the sugar to a bound calcium atom. We have studied the dynamic properties of TC14 by measuring 15N longitudinal and transverse relaxation rates as well as [1H-15N] heteronuclear NOEs. Relaxation rates and heteronuclear NOE data for holo-TC14 show minimal variations, indicating that there is no substantial difference in rigidity between the elements of regular secondary structure and the extended surface loops. Anisotropic tumbling of the elongated TC14 dimer can account for the main fluctuations in relaxation rates. Loss of the bound calcium does not significantly alter the internal dynamics, suggesting that the stability of the loop region is intrinsic and not dependent on the coordination of the calcium ion. Chemical shift differences between the holo and apo form show that main structural changes occur in the calcium-binding site, but smaller structural changes are propagated throughout the molecule without affecting the overall fold. The disappearance of two resonances for residues following the conserved cis-proline 87 (which is located in the calcium-binding site) in the apo form indicates conformational change on an NMR time scale between the cis and trans configurations of this peptide bond in the absence of calcium. Possible implications of these findings for the ligand binding in C-type lectin-like domains are discussed.

The UBX domain: a widespread ubiquitin-like module

The UBX domain is an 80 amino acid residue module that is present typically at the carboxyl terminus of a variety of eukaryotic proteins. In an effort to elucidate the function of UBX domains, we solved the three-dimensional structure of the UBX domain of human Fas-associated factor-1 (FAF1) by NMR spectroscopy. The structure has a beta-Grasp fold characterised by a beta-beta-alpha-beta-beta-alpha-beta secondary-structure organisation. The five beta strands are arranged into a mixed sheet in the order 21534. The longer first helix packs across the first three strands of the sheet, and a second shorter 3(10) helix is located in an extended loop connecting strands 4 and 5. In the absence of significant sequence similarity, the UBX domain can be superimposed with ubiquitin with an r.m.s.d. of 1.9 A, suggesting that the two structures share the same superfold, and an evolutionary relationship. However, the absence of a carboxyl-terminal extension containing a double glycine motif and of suitably positioned lysine side-chains makes it highly unlikely that UBX domains are either conjugated to other proteins or part of mixed UBX-ubiquitin chains. Database searches revealed that most UBX domain-containing proteins belong to one of four evolutionarily conserved families represented by the human FAF1, p47, Y33K, and Rep8 proteins. A role of the UBX domain in ubiquitin-related processes is suggested.

Elucidating the mechanism of familial amyloidosis- Finnish type: NMR studies of human gelsolin domain 2

Familial amyloidosis-Finnish type (FAF) results from a single mutation at residue 187 (D187N or D187Y) within domain 2 of the actin-regulating protein gelsolin. The mutation somehow allows a masked cleavage site to be exposed, leading to the first step in the formation of an amyloidogenic fragment. We have performed NMR experiments investigating structural and dynamic changes between wild-type (WT) and D187N gelsolin domain 2 (D2). On mutation, no significant structural or dynamic changes occur at or near the cleavage site. Areas in conformational exchange are observed between beta-strand 4 and alpha-helix 1 and within the loop region following beta-strand 5. Chemical shift differences are noted along the face of alpha-helix 1 that packs onto the beta-sheet, suggesting an altered conformation. Conformational changes within these areas can have an effect on actin binding and may explain why D187N gelsolin is inactive. [(1)H-(15)N] nuclear Overhauser effect and chemical shift data suggest that the C-terminal tail of D187N gelsolin D2 is less structured than WT by up to six residues. In the crystal structure of equine gelsolin, the C-terminal tail of D2 lies across a large cleft between domains 1 and 2 where the masked cleavage site sits. We propose that the D187N mutation destabilizes the C-terminal tail of D2 resulting in a more exposed cleavage site leading to the first proteolysis step in the formation of the amyloidogenic fragment.

The transcription factor dHAND is a downstream effector of BMPs in sympathetic neuron specification

The dHAND basic helix-loop-helix transcription factor is expressed in neurons of sympathetic ganglia and has previously been shown to induce the differentiation of catecholaminergic neurons in avian neural crest cultures. We now demonstrate that dHAND expression is sufficient to elicit the generation of ectopic sympathetic neurons in vivo. The expression of the dHAND gene is controlled by bone morphogenetic proteins (BMPs), as suggested by BMP4 overexpression in vivo and in vitro, and by noggin-mediated inhibition of BMP function in vivo. The timing of dHAND expression in sympathetic ganglion primordia, together with the induction of dHAND expression in response to Phox2b implicate a role for dHAND as transcriptional regulator downstream of Phox2b in BMP-induced sympathetic neuron differentiation.

Biophysical characterization of elongin C from Saccharomyces cerevisiae

Elongin C (ELC) is an essential component of the mammalian CBC(VHL) E3 ubiquitin ligase complex. As a step toward understanding the role of ELC in assembly and function of CBC-type ubiquitin ligases, we analyzed the quaternary structure and backbone dynamics of the highly homologous Elc1 protein from Saccharomyces cerevisiae. Analytical ultracentrifugation experiments in conjunction with size exclusion chromatography showed that Elc1 is a nonglobular monomer over a wide range of concentrations. Pronounced line broadening in (1)H,(15)N-HSQC NMR spectra and failure to assign peaks corresponding to the carboxy-terminal helix 4 of Elc1 indicated that helix 4 is conformationally labile. Measurement of (15)N NMR relaxation parameters including T(1), T(2), and the (1)H-(15)N nuclear Overhauser effect revealed (i) surprisingly high flexibility of residues 69-77 in loop 5, and (ii) chemical exchange contributions for a large number of residues throughout the protein. Addition of 2,2,2-trifluoroethanol (TFE) stabilized helix 4 and reduced chemical exchange contributions, suggesting that stabilization of helix 4 suppresses the tendency of Elc1 to undergo conformational exchange on a micro- to millisecond time scale. Binding of a peptide representing the major ELC binding site of the von Hippel-Lindau (VHL) tumor suppressor protein almost completely eliminated chemical exchange processes, but induced substantial conformational changes in Elc1 leading to pronounced rotational anisotropy. These results suggest that elongin C interacts with various target proteins including the VHL protein by an induced fit mechanism involving the conformationally flexible carboxy-terminal helix 4.

Trithiacyclononane as a ligand for potential technetium and rhenium radiopharmaceuticals: synthesis of [M(9S3)(SC2H4SC2H4S)][BF4] (M = 99Tc, Re, 188Re) via C-S bond cleavage

Chemical or electrochemical reduction of the 1,4,7-trithiacyclononane (9S3) complexes [MII(9S3)2][BF4]2 (M = Re (3a) or Tc (3b)) results in instantaneous C-S bond cleavage to yield ethene and the stable MIII thiolate complexes [MIII(9S3)L][BF4] (M = Re (4a) or Tc (4b), L = SCH2CH2SCH2CH2S). Compounds 4 have been characterized by 1H NMR spectroscopy, and the pseudo-octahedral geometry of 4b has been confirmed by X-ray crystallography. Upon electrochemical reduction 4a loses ethene, while 4b can be reversibly reduced to [TcII(9S3)L], which is then further reduced to Tc(I) with loss of ethene. Successive ethene loss is observed in the mass spectra of compounds 3 and 4. The radiosynthesis of 4a with 188Re can be comfortably completed within 10 min starting with 188ReO4- from a 188W/188Re generator, with a radiochemical yield in excess of 90%, and thus represents a practical approach to the preparation of stable 188Re (and 99mTc) thioether complex derivatives/conjugates for clinical use. Crystal data: 4b, C10H20S6Tc, orthorhombic Pbca, a = 12.233(2) A, b = 14.341(2) A, c = 20.726(3) A, Z = 8.

Heteronuclear NMR studies of the specificity of the post-translational modification of biotinyl domains by biotinyl protein ligase

The lipoyl domains of 2-oxo acid dehydrogenase multienzyme complexes and the biotinyl domains of biotin-dependent enzymes have homologous structures, but the target lysine residue in each domain is correctly selected for posttranslational modification by lipoyl protein ligase and biotinyl protein ligase, respectively. We have applied two-dimensional heteronuclear NMR spectroscopy to investigate the interaction between the apo form of the biotinyl domain of the biotin carboxyl carrier protein of acetyl-CoA carboxylase and the biotinyl protein ligase (BPL) from Escherichia coli. Heteronuclear multiple quantum coherence NMR spectra of the 15N-labelled biotinyl domain were recorded in the presence and absence of the ligase and backbone amide 1H and 15N chemical shifts were evaluated. Small, but significant, changes in chemical shift were found in two regions, including the tight beta-turn that houses the lysine residue targetted for biotinylation, and the beta-strand 2 and the loop that precedes it in the domain. When compared with the three-dimensional structure, sequence alignments of other biotinyl and lipoyl domains, and mutagenesis data, these results give a clear indication of how the biotinyl domain is both recognised by BPL and distinguished from the structurally related lipoyl domain to ensure correct posttranslational modification.

Restricted motion of the lipoyl-lysine swinging arm in the pyruvate dehydrogenase complex of Escherichia coli

The three lipoyl (E2plip) domains of the dihydrolipoyl acetyltransferase component of the pyruvate dehydrogenase (PDH) complex of Escherichia coli house the lipoyl-lysine side chain essential for active-site coupling and substrate channelling within the complex. The structure of the unlipoylated form of the innermost domain (E2plip(apo)) was determined by multidimensional NMR spectroscopy and found to resemble closely that of a nonfunctional hybrid domain determined previously [Green et al. (1995) J. Mol. Biol. 248, 328-343]. The domain comprises two four-stranded beta-sheets, with the target lysine residue residing at the tip of a type-I beta-turn in one of the sheets; the N- and C-termini lie close together at the opposite end of the molecule in the other beta-sheet. Measurement of (15)N NMR relaxation parameters and backbone hydrogen/deuterium (H/D) exchange rates reveals that the residues in and surrounding the lipoyl-lysine beta-turn in the E2plip(apo) form of the domain become less flexible after lipoylation of the lysine residue. This implies that the lipoyl-lysine side chain may not sample the full range of conformational space once thought. Moreover, reductive acetylation of the lipoylated domain (E2plip(holo) --> E2plip(redac)) was accompanied by large changes in chemical shift between the two forms, and multiple resonances were observed for several residues. This implies a change in conformation and the existence of multiple conformations of the domain on reductive acetylation, which may be important in stabilizing this catalytic intermediate.

Embryonic stem cells differentiate into oligodendrocytes and myelinate in culture and after spinal cord transplantation

Demyelination contributes to the loss of function consequent to central nervous system (CNS) injury. Enhanced remyelination through transplantation of myelin-producing cells may offer a pragmatic approach to restoring meaningful neurological function. An unlimited source of cells suitable for such transplantation therapy can be derived from embryonic stem (ES) cells, which are both pluripotent and genetically flexible. In this paper we show that oligodendrocyte cultures can be reliably produced from retinoic acid-induced ES cells and that these oligodendrocytes can myelinate axons in vitro. Methods were further developed for generating highly enriched cultures of oligodendrocytes through an additional culturing step, producing an intermediate "oligosphere" stage. To test whether ES cells can survive, migrate, and differentiate into mature myelin-producing cells in areas of demyelination in the adult CNS, ES cells were transplanted into the dorsal columns of adult rat spinal cord 3 days after chemical demyelination. In the demyelination site, large numbers of ES cells survived and differentiated primarily into mature oligodendrocytes that were capable of myelinating axons. Furthermore, when oligosphere cells were transplanted into the spinal cords of myelin-deficient shiverer (shi/shi) mutant mice, the ES cell-derived oligodendrocytes migrated into the host tissue, produced myelin and myelinated host axons. These studies demonstrate the ability of ES cell-derived oligodendrocytes to myelinate axons in culture and to replace lost myelin in the injured adult CNS. Transplantation of ES cells may be a practical approach to treatment of primary and secondary demyelinating diseases in the adult CNS.

A light microscopy study of the migration of Naegleria fowleri from the nasal submucosa to the central nervous system during the early stage of primary amebic meningoencephalitis in mice

The migratory pathway of Naegleria fowleri from the nasal submucosa to the central nervous system (CNS) during the early stage of primary amebic meningoencephalitis (PAM) was investigated in mice. Twenty-one-day-old CD-1 mice were inoculated by intranasal instillation of 1 x 10(6) amebas. Animals were divided into 3 groups of 5 and, after being anesthetized, were killed at intervals of 24, 32, and 48 hr postinoculation by transcardial perfusion with formaldehyde, acetic acid, and methanol. The heads were decalcified, divided in the midsagittal plane, and the area of the cribriform plate removed and embedded in paraffin. Serial sections were cut at 8 microm and stained with a combination of celestin blue, Harris' hematoxylin, and acid fuchsin for light microscopy. Focal inflammation and amebas were observed in the submucosal nerve plexus, olfactory nerves penetrating the cribriform plate, and the olfactory bulb of the brain as early as 24 hr postinoculation. The time periods selected assured that the disease process would not obliterate soft tissue structures. Earlier studies used moribund mice in which the inflammation and the number of amebas were overwhelming. The present study provides convincing evidence that amebas gain initial access to the CNS through olfactory nerves within the cribriform plate during the early stages of PAM.

Protein-protein interaction revealed by NMR T(2) relaxation experiments: the lipoyl domain and E1 component of the pyruvate dehydrogenase multienzyme complex of Bacillus stearothermophilus

T(2) relaxation experiments in combination with chemical shift and site-directed mutagenesis data were used to identify sites involved in weak but specific protein-protein interactions in the pyruvate dehydrogenase multienzyme complex of Bacillus stearothermophilus. The pyruvate decarboxylase component, a heterotetramer E1(alpha(2)beta(2)), is responsible for the first committed and irreversible catalytic step. The accompanying reductive acetylation of the lipoyl group attached to the dihydrolipoyl acetyltransferase (E2) component involves weak, transient but specific interactions between E1 and the lipoyl domain of the E2 polypeptide chain. The interactions between the free lipoyl domain (9 kDa) and free E1alpha (41 kDa), E1beta (35 kDa) and intact E1alpha(2)beta(2) (152 kDa) components, all the products of genes or sub-genes over-expressed in Escherichia coli, were investigated using heteronuclear 2D NMR spectroscopy. The experiments were conducted with uniformly (15)N-labeled lipoyl domain and unlabeled E1 components. Major contact points on the lipoyl domain were identified from changes in the backbone (15)N spin-spin relaxation time in the presence and absence of E1(alpha(2)beta(2)) or its individual E1alpha or E1beta components. Although the E1alpha subunit houses the sequence motif associated with the essential cofactor, thiamin diphosphate, recognition of the lipoyl domain was distributed over sites in both E1alpha and E1beta. A single point mutation (N40A) on the lipoyl domain significantly reduces its ability to be reductively acetylated by the cognate E1. None the less, the N40A mutant domain appears to interact with E1 similarly to the wild-type domain. This suggests that the lipoyl group of the N40A lipoyl domain is not being presented to E1 in the correct orientation, owing perhaps to slight perturbations in the lipoyl domain structure, especially in the lipoyl-lysine beta-turn region, as indicated by chemical shift data. Interaction with E1 and subsequent reductive acetylation are not necessarily coupled.

The effect of matrix metalloproteinase complex formation on the conformational mobility of tissue inhibitor of metalloproteinases-2 (TIMP-2)

The backbone mobility of the N-terminal domain of tissue inhibitor of metalloproteinases-2 (N-TIMP-2) was determined both for the free protein and when bound to the catalytic domain of matrix metalloproteinase-3 (N-MMP-3). Regions of the protein with internal motion were identified by comparison of the T(1) and T(2) relaxation times and (1)H-(15)N nuclear Overhauser effect values for the backbone amide (15)N signals for each residue in the sequence. This analysis revealed rapid internal motion on the picosecond to nanosecond time scale for several regions of free N-TIMP-2, including the extended beta-hairpin between beta-strands A and B, which forms part of the MMP binding site. Evidence of relatively slow motion indicative of exchange between two or more local conformations on a microsecond to millisecond time scale was also found in the free protein, including two other regions of the MMP binding site (the CD and EF loops). On formation of a tight N-TIMP-2. N-MMP-3 complex, the rapid internal motion of the AB beta-hairpin was largely abolished, a change consistent with tight binding of this region to the MMP-3 catalytic domain. The extended AB beta-hairpin is not a feature of all members of the TIMP family; therefore, the binding of this highly mobile region to a site distant from the catalytic cleft of the MMPs suggests a key role in TIMP-2 binding specificity.

Hantavirus pulmonary syndrome in pregnancy

This comprehensive case review of hantavirus pulmonary syndrome (HPS) during pregnancy in 5 women characterizes the effect of Sin Nombre virus infection on maternal and fetal outcomes. Histopathologic, serological, and clinical information were evaluated for evidence of vertical transmission. Maternal ages ranged from 20 to 34 years and gestational ages from 13 to 29 weeks. Symptoms, physical findings, and laboratory values other than those related to pregnancy were not noticeably different from those of nonpregnant patients with HPS, although fevers were somewhat lower. One maternal death and 2 fetal losses occurred. Gross, microscopic, and immunohistochemical examination for hantavirus antigen were done on 2 fetal autopsies and 3 placentas showing no evidence of transplacental hantavirus transmission. There was no serological evidence of conversion in the 3 surviving children. Maternal and fetal outcomes of HPS appear similar to those of nonpregnant HPS patients and of pregnant patients with other causes of acute respiratory distress syndrome. No evidence of vertical transmission of Sin Nombre virus was found.

Resealing of transected myelinated mammalian axons in vivo: evidence for involvement of calpain

The mechanisms underlying resealing of transected myelinated rat dorsal root axons were investigated in vivo using an assay based on exclusion of a hydrophilic dye (Lucifer Yellow-biocytin conjugate). Smaller caliber axons (<5 microm outer diameter) resealed faster than larger axons. Resealing was Ca2+ dependent, requiring micromolar levels of extracellular [Ca2+] to proceed, and further accelerated in 1 mM Ca2+. Two hours after transection, 84% of axons had resealed in saline containing 2 mM Ca2+, 28% had resealed in saline containing no added Ca2+ and only 3% had resealed in the Ca2+ buffer BAPTA (3 mM). The enhancing effect of Ca2+ could be overcome by both non-specific cysteine protease inhibitors (e.g., leupeptin) and inhibitors specific for the calpain family of Ca2+ -activated proteases. Resealing in 2 mM Ca2+ was not inhibited by an inhibitor of phospholipase A2. Resealing in low [Ca2+] was not enhanced by agents which disrupt microtubules, but was enhanced by dimethylsulfoxide (0.5-5%). These results suggest that activation of endogenous calpain-like proteases by elevated intra-axonal [Ca2+] contributes importantly to membrane resealing in transected myelinated mammalian axons in vivo.

Solution structures of apo and holo biotinyl domains from acetyl coenzyme A carboxylase of Escherichia coli determined by triple-resonance nuclear magnetic resonance spectroscopy

A subgene encoding the 87 C-terminal amino acids of the biotinyl carboxy carrier protein (BCCP) from the acetyl CoA carboxylase of Escherichia coli was overexpressed and the apoprotein biotinylated in vitro. The structures of both the apo and holo forms of the biotinyl domain were determined by means of multidimensional NMR spectroscopy. That of the holo domain was well-defined, except for the 10 N-terminal residues, which form part of the flexible linker between the biotinyl and subunit-binding domains of BCCP. In agreement with X-ray crystallographic studies [Athappilly, F. K., and Hendrickson, W. A. (1995) Structure 3, 1407-1419], the structure comprises a flattened beta-barrel composed of two four-stranded beta-sheets with a 2-fold axis of quasi-symmetry and the biotinyl-lysine residue displayed in an exposed beta-turn on the side of the protein opposite from the N- and C-terminal residues. The biotin group is immobilized on the protein surface, with the ureido ring held down by interactions with a protruding polypeptide "thumb" formed by residues 94-101. However, at the site of carboxylation, no evidence could be found in solution for the predicted hydrogen bond between the main chain O of Thr94 and the ureido HN1'. The structure of the apo domain is essentially identical, although the packing of side chains is more favorable in the holo domain, and this may be reflected in differences in the dynamics of the two forms. The thumb region appears to be lacking in almost all other biotinyl domain sequences, and it may be that the immobilization of the biotinyl-lysine residue in the biotinyl domain of BCCP is an unusual requirement, needed for the catalytic reaction of acetyl CoA carboxylase.

SINNMR studies of acoustically induced rotation of suspended particles

Experiments and data analyses are reported on the 20 kHz acoustic manipulation of samples of trisodium phosphate dodecahydrate, of varying particle size, suspended in suitable support media. Data are obtained to expand the understanding and optimisation of the SINNMR (sonically induced narrowing of the nuclear magnetic resonance spectra of solids) technique, and use this to determine acoustically induced particle rotational correlation times. It is concluded that the average particle rotational correlation time decreases with increasing particle size and decreasing viscosity/density of the support media. Acoustic cavitation and accompanying interparticle collisions are shown to be important in the observation of SINNMR spectra.

Insulin stimulates pp120 endocytosis in cells co-expressing insulin receptors

pp120, a substrate of the insulin receptor tyrosine kinase, is a plasma membrane glycoprotein that is expressed in the hepatocyte as two spliced isoforms differing by the presence (full-length) or absence (truncated) of most of the intracellular domain including all phosphorylation sites. Co-expression of full-length pp120, but not its phosphorylation-defective isoforms, increased receptor-mediated insulin endocytosis and degradation in NIH 3T3 fibroblasts. We, herein, examined whether internalization of pp120 is required to mediate its effect on insulin endocytosis. The amount of full-length pp120 expressed at the cell surface membrane, as measured by biotin labeling, markedly decreased in response to insulin only when insulin receptors were co-expressed. In contrast, when phosphorylation-defective pp120 mutants were co-expressed, the amount of pp120 expressed at the cell surface did not decrease in response to insulin. Indirect immunofluorescence analysis revealed that upon insulin treatment of cells co-expressing insulin receptors, full-length, but not truncated, pp120 co-localized with alpha-adaptin in the adaptor protein complex that anchors endocytosed proteins to clathrin-coated pits. This suggests that full-length pp120 is part of a complex of proteins required for receptor-mediated insulin endocytosis and that formation of this complex is regulated by insulin-induced pp120 phosphorylation by the receptor tyrosine kinase. In vitro GST binding assays and co-immunoprecipitation experiments in intact cells further revealed that pp120 did not bind directly to the insulin receptor and that its association with the receptor may be mediated by other cellular proteins.

Three-dimensional structure of the major autoantigen in primary biliary cirrhosis

BACKGROUND & AIMS

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease characterized by the presence of antimitochondrial autoantibodies in patients' serum. The major autoantigen, recognized by antibodies from > 95% of patients with PBC, has been identified as the E2 component (E2p) of the pyruvate dehydrogenase multienzyme complex. Immunodominant sites on E2p have been localized to the inner of the two lipoyl domains, where the essential cofactor lipoic acid is attached covalently. The aim of this study was to determine the three-dimensional structure of the inner lipoyl domain of human E2p.

METHODS

The domain was expressed in Escherichia coli; after purification, its structure was analyzed using nuclear magnetic resonance spectroscopy.

RESULTS

The structure of the lipoyl domain from human E2p was determined, and the implications of the structure for autoimmune recognition were assessed.

CONCLUSIONS

Knowledge of the structure further defines the major epitope and may help in the design of antigen-specific immunotherapy for treatment of PBC.

Development of LBP110 expression by neural crest-derived enteric precursors: migration and differentiation potential in ls/ls mutant mice

Neural crest-derived cells acquire a 110-kD laminin-binding protein (LBP110) when they colonize the murine bowel. Laminin stimulates LBP110-expressing cells to develop as neurons. We have followed the development of LBP110 by neural crest-derived cells as they enter the gut of control and ls/ls mutant mice. The expression of neurofilament and choline acetyltransferase was used as markers of a neuronal phenotype. Tyrosine hydroxylase was used as a marker for the mash-1-dependent lineage of enteric precursors, while calcitonin gene-related peptide was used as a marker for the mash-1-independent lineage of crest-derived cells. A subset of cells expressing LBP110 was located along the vagi at E10 at cervical and thoracic levels. At E12, cells expressing LBP110 extended from the foregut to the midgut. The expression of neurofilament protein lagged behind that of LBP110 by about 0.5 day and then became coincident with LBP110 immunoreactivity. By E15, cells doubly labeled with antibodies to LBP110 and neurofilament protein were located along the entire extent of the bowel up to but not including the terminal colon. By E16, both the proximal and terminal colon contained cells expressing LBP110 and neurofilaments. The pattern of immunoreactivity could not be distinguished between ls/ls and control animals prior to E16. By E16, when the terminal colon of control animals contained many cells expressing LBP110 and neurofilaments, the terminal colon of ls/ls animals lacked cells expressing these proteins; nevertheless, structures outside of the terminal colon were heavily endowed with cells expressing LBP110 and neurofilaments. These ectopically located cells derived from both mash-1-dependent and -independent lineages of crest-derived precursors.

Chick ciliary ganglion neurons contain transcripts coding for acetylcholine receptor-associated protein at synapses (rapsyn)

A peripheral membrane protein of approximately 43 kDa (rapsyn) clusters muscle nicotinic acetylcholine receptors (AChRs), but molecules relevant to clustering neuronal AChRs have not been identified. Here, we have detected rapsyn transcripts in the chick nervous system, localized rapsyn mRNA in ciliary ganglion (CG) neurons, which are known to cluster AChRs, and identified three rapsyn cDNAs derived from the ganglion. Our initial Northern blots, performed using a mouse probe, revealed rapsyn-like transcripts in chick muscle and brain. To develop species-specific probes, we prepared a chick rapsyn cDNA construct, Ch43K.1, that encodes a protein having extensive homology to mouse rapsyn. Using primers designed to anneal near the 5' and 3' boundaries of Ch43K.1, three prominent cDNAs were amplified from chick muscle templates by reverse transcriptase based-PCR. Products of similar size were also amplified using cDNA prepared from neuronal tissues expected to contain clustered AChRs (CG and brain), whereas none were detected using templates from tissues not displaying clustered AChRs (sensory ganglia and liver). In situ hybridization confirmed that rapsyn mRNA is expressed both in chick muscle fibers and in CG neurons. Sequencing the three cDNAs amplified from CG templates revealed the largest to be Ch43K.1, whereas the smaller two may represent splice variants. These findings suggest that multiple rapsyn-like molecules are involved in clustering the distinct AChRs expressed by muscle fibers and neurons.

Three-dimensional structure of the lipoyl domain from the dihydrolipoyl succinyltransferase component of the 2-oxoglutarate dehydrogenase multienzyme complex of Escherichia coli

A sub-gene encoding the lipoyl domain of the dihydrolipoyl succinyltransferase polypeptide chain of the 2-oxoglutarate dehydrogenase multienzyme complex of Escherichia coli was over-expressed and the protein was purified uniformly labelled with 15N. The three-dimensional structure of the domain was determined by means of nuclear magnetic resonance spectroscopy, based on 905 nuclear Overhauser effect inter-proton distance restraints, 42 phi torsion angle restraints and hydrogen bond restraints from 24 slowly exchanging amide protons. The structure of the 80-residue domain is that of a flattened beta-barrel surrounding a hydrophobic core in which Trp22 plays a central role in anchoring two four-stranded sheets together. The polypeptide backbone exhibits a 2-fold axis of quasi-symmetry, with the lipoylation site, Lys43, located at the tip of an exposed beta-turn in one beta-sheet and the N and C-terminal residues close together in space in the other beta-sheet. The atomic r.m.s. distribution about the mean coordinate is 0.46 A for the backbone atoms in the highly structured region and 0.88 A along the entire backbone (residues Ser1 to Asn80), including a less well-defined surface loop and the lipoyl-lysine beta-turn. The structure closely resembles that of the lipoyl domains from pyruvate dehydrogenase complexes, in accord with the existence of strongly conserved residues at critical positions in the domains. The structures of the lipoyl domains throw light on the requirements for the specificity of reductive acylation of their pendant lipoyl groups in the parent 2-oxo acid dehydrogenase complexes; an important aspect of the mechanisms underlying active site coupling and substrate channelling.

Immunopathogenesis and immunoregulation in schistosomiasis. Distinct chronic pathologic syndromes in CBA/J mice

Inbred CBA/J mice with chronic (20-week) Schistosoma mansoni infections demonstrate two distinct syndromes. Hypersplenomegaly syndrome (HSS), characterized by a massive spleen, liver fibrosis, ascites, and anemia, resembles hepatosplenic human schistosomiasis, complete with portal hypertension and shunting. Moderate splenomegaly (MSS) syndrome, with less severe pathology, parallels most chronic human infections. Phenotypic analyses of spleen cells for CD44, CD62L, CD45RB, Ia, and CD25 indicate that HSS mice have more activated and memory CD4+ T cells than do MSS mice. HSS animals also have more B cells that highly express B7-2. Anti-CD3 stimulated spleen cells from 8-week or chronically infected mice produce IL-4 and IL-10 in a manner that appears not to involve the CD28/B7-2 costimulation pathway. By contrast IFN-gamma production is augmented in the presence of anti-CD28 and decreased in the presence of anti-B7-2. Infected mice make very little IL-2 to anti-CD3, even with added anti-CD28. As cytokines affect resultant B-cell responses and HSS and MSS mice display distinctive isotypes, differential regulatory or anergy hypotheses may best explain MSS/HSS differences.

Increased expression of laminin-1 and collagen (IV) subunits in the aganglionic bowel of ls/ls, but not c-ret -/- mice

Extracellular matrix molecules, including laminin, affect the development of enteric neurons and accumulate in the aganglionic colon of ls/ls mice. Quantitative Northern analysis revealed that mRNAs encoding the beta 1 and gamma 1 subunits of laminin and collagens alpha 1(IV) and alpha 2(IV) are increased in the colons of ls/ls mice. Transcripts of laminin alpha 1 were evaluated quantitatively with reverse transcription and the competitive polymerase chain reaction (RT-cPCR). The abundance of laminin alpha 1 transcripts was developmentally regulated, but greater in the ls/ls than the wild-type colon at each age examined. In situ hybridization revealed that transcripts in the colon encoding laminin alpha 1 and beta 1 and collagen alpha 2(IV) were initially expressed in the endoderm, but by E15, expression shifted to cells of the colonic mesenchyme (ls/ls > wild type) where crest-derived cells migrate. The expression of laminin alpha 1 was examined in the totally aganglionic intestine of E15 and newborn c-ret -/- mice, to determine whether an increase occurs when neurogenesis fails independently of the ls/ls defect. RT-cPCR revealed no difference from control in mRNA encoding laminin alpha 1 in the c-ret -/- colon in either E15 or newborn animals. The accumulation of immunohistochemically demonstrable laminin that is prominent in the newborn ls/ls colon could not be detected in that of c-ret -/- animals. These observations suggest that transcripts encoding laminin-1 and collagen (IV) are increased in the colon and surrounding pelvic mesenchyme of ls/ls mice because of an intrinsic lesion, rather than a secondary consequence of aganglionosis. The data are compatible with the hypothesis that the increased expression of laminin-1 contributes to the failure of crest-derived cells to complete their colonization of the ls/ls colon.

Protective immune responses to the E and NS1 proteins of Murray Valley encephalitis virus in hybrids of flavivirus-resistant mice

The lack of an effective animal model has been a major obstacle in attempts to define the role of humoral and cellular immune responses in protection against flavivirus infection. We have used F1 hybrid mice (BALB/c x C3H/RV) that are heterozygous for the flavivirus resistance allele F1vr and show reduced virus replication in the brain after intracerebral inoculation. F1 hybrid mice challenged by intracerebral inoculation with Murray Valley encephalitis (MVE) virus developed encephalitis 2-3 days later than a genetically susceptible strain (BALB/c) but showed a similar mortality rate. This delay in the onset of disease provided more opportunity for virus clearance by primed immune responses. Using F1 hybrid mice we were able to demonstrate protective immunity induced by structural and non-structural proteins of MVE virus by immunization with pure NS1 protein or recombinant vaccinia viruses that expressed various regions of the MVE genome. These constructs included VV-STR (C-prM-E-NS1-NS2A), VV-delta C (prM-E-Ns1-NS2A) and VV-NS1 (NS1-NS2A). VV-delta C vaccinated mice were completely protected (100% survival)from challenge with 1000 infectious units of MVE virus, while mice inoculated with VV-STR, VV-NS1 or pure NS1 were partially protected (40%, 47% and 85% respectively). Analysis of prechallenge sera and in vivo depletion studies revealed that the solid protection induced by VV-delta C was mediated by neutralizing antibody to the E protein and did not require a CD8+ T cell response. The partial protection provided by VV-STR, VV-NS1 and pure NS1 occurred after induction of antibody to NS1. However, depletion of CD8+ cells prior to virus challenge ablated the protection provided by VV-NS1 indicating some requirement for class I restricted cytotoxic T cells.

Infectious disease emergencies in disasters

This article discusses the relationship between disasters and infections. Infections that are reviewed include those resulting from (1) a breakdown of the usual mechanisms of infection control, (2) the introduction or emergence of pathogens, and (3) the movement of populations into new areas. Components of infectious-disease surveillance and disaster teams are detailed.

Techniques for isolating thermotolerant and pathogenic freeliving amebae

Several conditions of isolation were evaluated to determine which yielded the greatest number of thermotolerant and pathogenic freeliving amebae. Swab samples, easier to obtain and process, produced more pathogenic amebae than water samples. If water samples are required, 50-ml volumes gave the greatest percentage of pathogenic isolates. An incubating temperature of 42 degrees C yielded the most thermotolerant amebae. A total of 11 pathogenic isolates were obtained from 762 environmental samples and were Acanthamoeba (55%), Naegleria fowleri Carter, 1970 (27%), and N. australiensis De Jonckheere, 1981 (18%).

Expression of nicotinic acetylcholine receptors and subunit mRNA transcripts in cultures of neural crest cells

The expression of neuronal phenotypic characteristics by neural crest-derived neurons is dependent upon both environmental cues and intrinsic properties. Neuronal nicotinic acetylcholine receptors (nAChRs) are expressed by most neural crest-derived peripheral neurons; nevertheless, the factors that influence and modulate the early expression of nAChRs on neuronal precursor cells are unknown. We used RT-PCR to analyze the temporal sequence of the appearance of transcripts encoding alpha 3, alpha 5, alpha 7, beta 2, and beta 4 nAChR subunits in cultures of quail neural crest cells. At 2 days in culture, mRNA encoding each of these nAChR subunits was detectable and, except for alpha 7, remained so through 12 days. The appearance of NAPA 73 immunoreactivity during neural crest cell migration suggested that some cells express neuronal characteristics early in development and that the expression of nAChR subunits may be cell autonomous for some neural crest-derived cells. Between 8 and 10 days in culture, a 2.0-kb transcript encoding alpha 3 subunit appears in addition to the expected 3.5-kb transcript that is present at 8 days. nAChR protein was detected immunocytochemically at 7 days and was observed in immunoblots by 9 days. Whole-cell patch clamp recordings demonstrated that functional nAChRs develop concurrently in a subset of neural crest-derived neurons. In addition, both neuronal and nonneuronal cells showed inward and delayed outward currents in response to step depolarization. The appearance of functional nAChRs on neural crest-derived cells, in vitro, occurs independently of innervation and of the components in growth medium. The data suggest that neural crest-derived cells express transcripts encoding nAChR subunits, possibly as an intrinsic property of some peripheral neurons, early in development.

Immunodominant epitopes on the NS1 protein of MVE and KUN viruses serve as targets for a blocking ELISA to detect virus-specific antibodies in sentinel animal serum

Two mosquito-borne flaviviruses, Murray Valley encephalitis (MVE) and Kunjin (KUN), are the aetiological agents of Australian encephalitis. MVE causes a severe and potentially fatal form of the disease while KUN is responsible for only a few relatively mild cases. Therefore it is important that serological tests used in flavivirus surveillance differentiate between infections with these two viruses. However, this has been hampered in the past by the close antigenic relationships between flaviviruses in traditional serological assays. An epitope blocking ELISA using MVE-specific and KUN-specific monoclonal antibodies (mAb) reacting to the non-structural protein NS1 of these viruses and a flavivirus group-specific mAb reacting to the envelope (E) protein was assessed for testing sentinel animals for seroconversion to specific flavivirus infections. Using these assays we were able to detect serum antibodies to a variety of flavivirus in laboratory infected rabbits, and naturally infected chickens and in the case of primary infections, differentiate those caused by KUN or MVE. These assays are now used routinely in our laboratory for testing chicken sera from sentinel flocks in the Kimberley and Pilbara regions of north Western Australia.

Glycosylation and antigenic variation among Kunjin virus isolates

Previous studies have found Kunjin (KUN) virus isolates from within Australia to be genetically homogenous and that the envelope protein of the type strain (MRM61C) was unglycosylated and lacked a potential glycosylation site. We investigated the extent of antigenic variation between KUN virus isolates from Australia and Sarawak using an immunoperoxidase assay and a panel of six monoclonal antibodies. The glycosylation status of the E protein of each virus was also determined by N glycosidase F (PNGase F) digestion and limited sequence analysis. The results showed that KUN viruses isolated within Australia oscillated between three antigenic types defined by two epitopes whose expression was influenced by passage history and host cell type. In contrast an isolate from Sarawak formed a stable antigenic type that was not influenced by passage history and was distinct from all Australian isolates. PNGase F digestions of KUN isolates indicated that 19 of the 33 viruses possessed a glycosylated E protein. Nucleotide sequence of the 5' third of the E gene of selected KUN isolates revealed that a single base change in PNGase F sensitive strains changed the tripeptide N-Y-F (amino acids 154-156 of the published sequence) to the potential glycosylation site N-Y-S. Further analysis revealed that passage history also had a significant influence on glycosylation.

A novel complex formed between the flavivirus E and NS1 proteins: analysis of its structure and function

We examined the structural features and functional significance of a novel complex which forms between the envelope (E) protein and nonstructural protein NS1 of Murray Valley encephalitis (MVE) virus. Western blot analysis of virus-infected C6/36 cell lysates revealed that the undenatured form of this E-NS1 complex was a heat-sensitive E-(NS1 dimer) complex. Furthermore, the E-NS1 complex was observed in cells infected with Kunjin, Japanese encephalitis, West-Nile and Kokobera viruses which indicates the complex is a common feature of flavivirus infection. E-NS1 complex which had been immunoaffinity purified from MVE-infected cell lysates or eluted from gel slices exhibited partial breakdown into the individual monomers, demonstrating that the complex arose from the association of E and NS1 proteins and was not a single polypeptide created from incomplete gene cleavage. Radioimmunoprecipitation and western blot analysis of MVE-infected cell lysates and culture fluid preparations collected at various times after infection revealed that the E-NS1 complex has a long half life, accumulates in the virus-infected cell with time and is not secreted into the extracellular fluid. We have postulated that the E-NS1 complex, or at least a major portion of the complex, is a non-specific aggregation with no functional significance in the viral life cycle.

Eye-extract factors promote the expression of acetylcholine sensitivity in chick dorsal root ganglion neurons

We have examined the development of acetylcholine (ACh) responses in chick sensory neurons and their regulation by growth factors. Between Embryonic Days E13 and E18 in vivo, the proportion of freshly dissociated dorsal root ganglion (DRG) neurons that were appreciably sensitive to 500 microM ACh increased from approximately 40 to > 90% and the size of the ACh response per unit membrane area increased nearly 10-fold. Nerve growth factor (NGF) supports the survival, growth, and differentiation of central, sympathetic, and sensory neurons. NGF also promotes ACh sensitivity in PC12 cells and nodose ganglion neurons grown in cell culture. When E13 chick DRG neurons were maintained in culture with NGF for 4-6 days, however, only approximately 50% had appreciable ACh sensitivity, and large responses comparable to those observed at E18 in vivo were rare. Chick-eye extract contains a 21.5-kDa trophic factor termed growth-promoting activity (GPA) that supports survival of sympathetic and DRG neurons for 24 hr in culture and an activity of approximately 50 kDa that promotes increases in choline acetyltransferase activity, ACh sensitivity, and ACh receptors (AChRs) in ciliary ganglion neurons (Nishi and Berg, 1981; Halvorsen et al., 1991). In the present study, whole-eye extract supported full survival of E13 DRG neurons for up to 6 days in culture and promoted ACh sensitivity in > 90% of the neurons tested. GPA-containing eye-extract fractions and NGF individually supported full DRG neuron survival for up to 6 days in culture, but neither promoted ACh sensitivity. Adding eye-extract fractions containing material of approximately 50 kDa for 4-6 days to either GPA- or NGF-supplemented media led to appreciable ACh sensitivity in approximately 90% of the DRG neurons tested. The levels of ACh sensitivity observed in DRG neurons maintained either in whole-eye extract or in fractions containing 50-kDa material were close to those observed at an equivalent developmental age in vivo. The results indicate that components in the 50-kDa eye-extract fraction promote the ACh sensitivity of DRG neurons in culture and suggest that similar factors may influence the appearance of AChRs on the neurons in vivo.

Detection of the 5-HT1A receptor and 5-HT1A receptor mRNA in the rat bowel and pancreas: comparison with 5-HT1P receptors

We tested the hypothesis that the rat bowel and pancreas contain 5-HT1A receptors. 3H-8-hydroxy-2-(di-n-propylamino)tetralin (3H-8-OH-DPAT) was used as a radioligand. Binding of 3H-8-OH-DPAT to membranes derived from the myenteric plexus and the pancreas was investigated by rapid filtration. Alternatively, radioautography was employed to locate 3H-8-OH-DPAT binding sites in frozen sections of unfixed bowel or pancreas. An excess of 5-HT (10 microM) was used to define nonspecific binding. Saturable, high affinity binding of 3H-8-OH-DPAT to enteric (Kd = 2.8 +/- 1.1 nM; Bmax = 83.8 +/- 4.3 fmol/mg protein) and pancreatic (Kd = 6.6 +/- 1.3 nM; Bmax = 44 +/- 2.2 fmol/mg protein) membranes was found. The binding of 3H-8-OH-DPAT to enteric and pancreatic membranes was inhibited by 8-OH-DPAT, NAN-190, and spiperone. In contrast, the binding of 3H-8-OH-DPAT to enteric and pancreatic membranes was not inhibited by 5-carboxyamidotryptamine, or by a variety of compounds known to bind to other subtypes of 5-HT receptor. Digoxigenin-labeled oligonucleotides were found to detect mRNA encoding the 5-HT1A receptor in a subset of neurons in myenteric and submucosal ganglia. In contrast, 5-HT1A mRNA was not found in the pancreas. Radioautography revealed that the highest density of 3H-8-OH-DPAT binding sites was found in the stomach. These sites were especially numerous in the lamina propria adjacent to gastric glands, and in myenteric ganglia. Pancreatic 5-HT1A receptors were located on nerves, lymphoid tissue (especially the capsule of nodes), and on cells scattered in the pancreatic parenchyma. The concentration of 3H-8-OH-DPAT binding sites in the rat bowel and pancreas was less than that of 3H-5-HT binding sites; however, the distribution of 3H-8-OH-DPAT binding sites was similar to that of sites that bind 3H-5-HT. It is concluded that the rat gut and its extension in the pancreas contains 5-HT1A receptors. Many, if not all, of the nerve cells and processes that express 5-HT1A receptors express 5-HT1P receptors as well. The function of these receptors in the physiology of the entero-pancreatic innervation remains to be determined.

Role of growth factors in catecholaminergic expression by neural crest cells: in vitro effects of transforming growth factor beta 1

The differentiation of neural crest cells into catecholaminergic neurons is dependent upon both intrinsic properties and signals from the embryonic microenvironment. In tissue culture, the development of catecholaminergic traits is dependent upon factors present in chick embryo extract (CEE). This dependency suggests that soluble growth factors affect catecholaminergic differentiation in vivo. We have studied the role of CEE-derived factors and the potentially related influence of characterized growth factors on catecholaminergic phenotypic expression in avian neural crest cells. In this report, we show that CEE-derived factors and transforming growth factor beta1 (TGF-beta 1) differentially influence catecholaminergic phenotypic expression as well as melanogenesis. TGF-beta 1 substituted for CEE-derived factors and supported the in vitro differentiation of tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) immunoreactivities, as well as catecholamine biosynthesis and storage. Differentiation of catecholaminergic cells was dependent on factors present in 10% CEE during the first 1-4 days in culture suggesting an initial critical period for exposure. One day of initial exposure to either CEE-derived factors or TGF-beta 1 was sufficient to support the subsequent expression of catecholaminergic phenotypic characteristics. The time course of responsiveness to TGF-beta 1 was different than for CEE-derived factors. Neural crest cells remain responsive to TGF-beta 1 for at least 5 days, which is past the critical period for CEE-derived factors. Bioassay of CEE shows that endogenous levels of TGF-beta are less than or equal to 0.5 ng/ml. Immunoprecipitation of TGF-beta from CEE or blockade by neutralizing antibodies did not result in a loss of catecholaminergic differentiation by neural crest cells. Although CEE supports melanogenesis under all of the growth conditions tested, TGF-beta 1 was found to be inhibitory.

Decreased beta 2-adrenergic receptor mRNA expression in receptor-deficient S49 lymphoma cells

Many variants of the S49 mouse lymphoma cell have been isolated along the pathway of cyclic AMP generation and response. Two such variants, beta p and beta d, were isolated by Johnson and colleagues and described in 1979 [Mol. Pharmacol. 15:16-27 (1979)]. The beta p and beta d variants express one half and one quarter, respectively, of the wild-type number of beta 2-adrenergic receptors. This observation has now been extended through the use of DNA-excess solution hybridization. Using this exquisitely sensitive technique for quantitation of gene and mRNA, we have been able to demonstrate that the beta 2-adrenergic receptor-deficient variant cells contain the same quantity of the beta 2-adrenergic receptor gene as the wild-type cells. In contrast, the beta 2-adrenergic receptor-deficient variant cells express reduced quantities of beta 2-adrenergic receptor-specific mRNA. The amount of beta 2-adrenergic receptor-specific mRNA correlates very well with the reduction in receptor expression in these cells. Both gene and mRNA in the wild-type and variant cells appear to be the same size, as judged by Southern and Northern analysis. Thus, the diminution of beta 2-adrenergic receptors in the beta p and beta d variants appears to reflect primarily the relative paucity of gene transcripts in the variant cells. These data imply that variations in cellular content of beta 2-adrenergic receptor mRNA, which may occur among closely related cells, is one explanation for differences in receptor number.

Detection of immobilised Murray Valley encephalitis virus RNA using oligonucleotide probes with varying degrees of mismatch

The design of oligonucleotides used for hybridisation studies often utilises available sequence information of the type strain of a particular virus. If hybridisation studies, using such oligonucleotides, are carried out with field isolates of the same virus, the problem of base pair mismatches and consequent difficulties in detection may arise. This study examined the effect of base pair mismatches on the hybridisation between membrane-bound Murray Valley encephalitis virus (MVE) RNA derived from various strains and deliberately mismatched oligonucleotide probes. Under conditions of very low stringency, probes containing up to 5 mismatches were able to detect MVE RNA, but not yeast RNA. Under washing conditions of increased stringency, hybridisation could be detected between MVE virus RNA and probes with only 3 to 4 mismatches. However, the extent of this interaction was dependent on the number and type of mismatches and their relative sequence position.

Direction of gaze during vibrotactile choice reaction time tasks

A vibrotactile choice reaction time (RT) task was used, with the hands in their own hemispace (arms uncrossed), and in their opposite hemispace (arms crossed). Gaze was directed at the stimulated and responding hand, away from it at the other (inactive) hand, or at a central fixation point (a neutral control). Responses were slower in the crossed than the uncrossed condition. Further, in the crossed condition, responses were faster when subjects looked at the stimulated and responding hand, rather than at the inactive hand or at the central fixation point. As RT in the latter two conditions did not differ, there is a benefit when subjects look at the stimulated and responding hand, rather than a cost when they look at the inactive hand. In the look at condition, visual or attentional factors may reduce the response coding conflict which occurs when arms are crossed.

Networks strengthen ties, status of rural hospitals

Rural hospitals are a integral part of the health care system in this country. But a lack of funds and a shrinking patient-base are leaving many of them without the resources to provide state-of-the-art care in their communities. In the following article, the authors discuss a network model that brings urban hospitals to the financial and service aid of rural facilities.