Correction to: CD4 T cell count is positively associated with lumbar spine bone mass in HIV-infected men under the age of 50 years

Two sentences in the Discussion section were incorrect.

CD4 T cell count is inversely associated with lumbar spine bone mass in HIV-infected men under the age of 50 years

HIV-infected men under the age of 50 years had a lower bone mass compared to that of HIV-uninfected men. Lower CD4 T cell counts, independent of whether antiretroviral therapy (ART) was used, were associated with lower BMD. HIV-infected patients with low CD4 T cell counts may need follow-up and intervention regarding bone health, including younger patients.

INTRODUCTION

HIV-infected patients have a low bone mineral density (BMD) owing to multifactorial interaction between common osteoporosis risk factors and HIV-related factors, including chronic inflammation and ART. Although HIV infection and ART might affect bone metabolism, little data is available for patients aged under 50 years. We aimed to investigate the association of HIV infection-induced low CD4 T cell counts and ART with BMD in men aged under 50 years.

METHODS

We performed an age- and body mass index-matched case-control study. BMD values of HIV-infected and HIV-uninfected men (< 50 years) were compared, and HIV-infected men were stratified by CD4 T cell counts and ART use.

RESULTS

After adjusting confounders, HIV-infected men with CD4 T cell counts ≥ 500 cells/μL (n = 28) and < 500 cells/μL (n = 139) had lower BMD at the femoral neck (FN, p < 0.001) and total hip (TH, p < 0.001) than HIV-uninfected men (n = 167). HIV-infected men with CD4 T cell counts < 500/μL had lower BMD at the lumbar spine (LS, p = 0.034) than those with counts of ≥ 500 cells/μL, but not at FN and TH. The CD4 T cell count (γ = 0.169, p = 0.031) was positively correlated with BMD at LS. There was no significant difference in the BMD (p = 0.499-> 0.999) between the ART-naïve (n = 75) and ART-user group (n = 92).

CONCLUSIONS

Despite their relatively younger age, HIV-infected men had a lower BMD than HIV-uninfected men. Lower CD4 T cell counts, irrespective of ART, might result in lower bone mass.

Studies on human pregnancy-induced insulin-like growth factor (IGF)-binding protein-4 proteases in serum: determination of IGF-II dependency and localization of cleavage site

Insulin-like growth factor (IGF)-binding protein-4 (IGFBP-4), a consistent inhibitor of IGF action, is subject to proteolytic cleavage by the IGF-II-dependent IGFBP-4 protease. However, regulation of the IGF-II-dependent IGFBP-4 protease in vivo is not known. As IGFBP proteases are known to be triggered during pregnancy, we systematically evaluated the changes in IGFBP-4 proteolysis by serum collected throughout human pregnancy. Results from in vitro protease assays using recombinant IGFBP-4 revealed that IGFBP-4 proteolysis determined in both the presence and absence of exogenous IGF-II significantly increased during the first and second trimesters and reached a plateau by the third trimester. However, in the absence of IGF-II, IGFBP-4 proteolysis by pregnancy serum was only observed after prolonged incubation. IGF-II dose dependently increased IGFBP-4 proteolysis by pregnancy serum, with maximal stimulation observed at a concentration of 0.7 mol/L relative to IGFBP-4. In contrast, IGF-II at an equimolar dose had little effect on proteolysis of recombinant human IGFBP-3, whereas excess IGF-II reproducibly inhibited recombinant human IGFBP-3 proteolysis by pregnancy serum. Although IGF-II enhanced IGFBP-4 proteolysis, results from N-terminal sequence and mass spectrometric analyses of IGFBP-4 proteolytic fragments demonstrate that the cleavage site (Met135-Lys136) in human IGFBP-4 was not altered by IGF-II. Deletion of the residues 121-141 containing this cleavage site blocked IGFBP-4 proteolysis. These findings demonstrate that the increase in IGFBP-4 proteolysis during pregnancy was accounted for mainly by the IGF-II-dependent IGFBP-4 proteolysis. Because IGFBP-4 is a potent inhibitor of IGF actions, it can be speculated that the pregnancy-induced IGFBP-4 proteases may play an important role in regulating fetal growth.

Epidemiology of methicillin-resistant Staphylococcus aureus in three Canadian tertiary-care centers

OBJECTIVE

To describe the epidemiology and spread of methicillin-resistant Staphylococcus aureus (MRSA) in three tertiary-care centers in Ottawa, Ontario, Canada, where MRSA is encountered infrequently.

DESIGN

Retrospective review over a 6-year period, from January 1, 1990, through December 31, 1995.

SETTING

Three tertiary-care teaching hospitals in Ottawa.

PARTICIPANTS

Patients and healthcare workers (HCWs) with MRSA isolated from any body site.

METHODS

Patients and HCWs were identified retrospectively through hospital microbiology and infection control records. Patient charts were reviewed for clinical and epidemiological data, including age, gender, previous hospital admissions (where noted), and current and recent antibiotic use. MRSA isolates that were available were typed using pulsed-field gel electrophoresis (PFGE). Methicillin resistance was confirmed by standard methods and by polymerase chain reaction using mecA-specific primers.

RESULTS

MRSA was identified in 53 patients and 2 HCWs. Three patients were excluded from further analysis because medical records were incomplete. Epidemiological data were collected on the remaining 52 individuals. Thirty-nine isolates from 31 patients and 2 HCWs were available for PFGE typing. Five epidemiologically linked nosocomial clusters involving 10 patients and 2 HCWs were identified and were confirmed by PFGE. MRSA isolates from a sixth cluster were not available for PFGE. In each cluster, nosocomial spread was minimized by standard infection control practices, including strict isolation of patients and screening of contacts. There was no evidence of secondary spread of MRSA involving the remaining 36 patients. Recent antibiotic use, surgery, admission to an intensive-care unit, and previous hospitalization were common among patients. There was no evidence of spread of MRSA among the three hospitals, and no endemic strains were apparent in any of these centers.

CONCLUSIONS

MRSA remains an infrequent isolate in our centers, with no apparent interhospital spread. In institutions with little or no endemic MRSA, rigorous application of standard infection control practices is effective in limiting nosocomial transmission of this organism.

Design and characterization of coherent integrated fiber-optic imaging probes

An integrated fiber-optic probe comprising a short length of multimode fiber that is fusion spliced to a monomode optical fiber has been fabricated for imaging and nonimaging applications. The fiber probe, typically 250 µm in diameter, can deliver a focused Gaussian spot approximately 25 µm in diameter at a distance of approximately 500 µm from the tip. Two off-the-shelf graded-index multimode fibers have been used in the fabrication of imaging and nonimaging probes. These integrated probes have considerably improved the spatial resolution of backscatter lensless fiber probes being utilized in the dynamic light-scattering characterization of colloidal suspension.

The role of parasympathetic modulation of the reentrant arrhythmic substrate in the genesis of sustained ventricular tachycardia

The influence of parasympathetic activity on the reentrant arrhythmic substrate in the genesis of sustained ventricular tachycardia remains unclear. To assess this influence, we studied the heart rate variability in 59 patients referred for invasive electrophysiological testing. In addition, the presence of late potentials and high grade ventricular ectopy, and the left ventricular ejection fraction was determined. The 28 patients with inducible sustained ventricular tachycardia were found to have lower heart rate variability by time- and frequency-domain measurements over 24 hours when compared to the 31 subjects who were noninducible. PNN50 was 4% in the inducible patients, whereas it was 9% in the subjects who were noninducible (P = 0.03). Similarly, HFP24H was 9 and 14 msec, respectively (P = 0.02). MAXHFP1H also differed (20 vs 27 msec [P = 0.04]) but not MINHFP1H (5 vs 6 msec). There was no association between heart rate variability and late potentials, degree of ventricular ectopy, or left ventricular ejection fraction. Thus, vagal tone does not appear to correlate with the presence of late potentials, ventricular ectopy, or left ventricular dysfunction. Low mean as well as maximal vagal tone, in contrast to minimal vagal tone, predicts inducibility of sustained ventricular tachycardia. Our data suggest that the inability to modulate parasympathetic tone appears to be an important determinant in the genesis of reentrant sustained ventricular tachycardia.

The relations of emotionality and regulation to dispositional and situational empathy-related responding

The purpose of the present study was to examine the prediction of adults' situational and dispositional empathy-related responses from measures of emotionality (emotional intensity and positive and negative affect) and regulation. A multimethod approach including self-reported, facial, and heart rate (HR) responses was used to assess situational vicarious emotional responding; Ss' (and sometimes friends') reports were used to assess the dispositional characteristics. In general, dispositional sympathy, personal distress, and perspective taking exhibited different, conceptually logical patterns of association with indexes of emotionality and regulation. The relations of situational measures of vicarious emotional responding to dispositional emotionality and regulation varied somewhat by type of measure and gender. Findings for facial and HR (for men) measures were primarily for the more evocative empathy-inducing stimulus. In general, the findings provided support for the role of individual differences in emotionality and regulation in empathy-related responding.

The relations of emotionality and regulation to dispositional and situational empathy-related responding

The purpose of the present study was to examine the prediction of adults' situational and dispositional empathy-related responses from measures of emotionality (emotional intensity and positive and negative affect) and regulation. A multimethod approach including self-reported, facial, and heart rate (HR) responses was used to assess situational vicarious emotional responding; Ss' (and sometimes friends') reports were used to assess the dispositional characteristics. In general, dispositional sympathy, personal distress, and perspective taking exhibited different, conceptually logical patterns of association with indexes of emotionality and regulation. The relations of situational measures of vicarious emotional responding to dispositional emotionality and regulation varied somewhat by type of measure and gender. Findings for facial and HR (for men) measures were primarily for the more evocative empathy-inducing stimulus. In general, the findings provided support for the role of individual differences in emotionality and regulation in empathy-related responding.

Integrated fiber optic probe for dynamic light scattering

An integrated fiber optic probe, comprising a monomode optical fiber fusion spliced to a short length of a graded-index multimode fiber, is fabricated for use as a coherent receiver in dynamic light scattering. The multimode fiber is cleaved to provide a gradient-index fiber lens with a focal length of 125 µm and an ƒ-number close to unity. An integrated fiber receiver is used to measure the intensity-intensity autocorrelation data from a 0.05% by weight concentration of an aqueous suspension of polystyrene latex spheres. Analysis of 100 independent data sets indicates that the particle size can be recovered with an accuracy of ±1%.

Identification of a novel mechanism for the removal of glucose residues from high mannose-type oligosaccharides

The role of glucosylated oligosaccharides in the biogenesis of the glycoprotein (G protein) of vesicular stomatitis virus was studied in PhaR2.7, a mouse lymphoma cell line deficient in glucosidase II activity. As expected, the great majority of cell-associated G protein remained glucosylated in PhaR2.7, and the G protein was rapidly deglucosylated in BW5147, the parental cell line. Despite these differences in glucosylation, the rates of G protein trimerization and transport to the cell surface were as rapid and efficient in the PhaR2.7 mutant as in BW5147. Surprisingly, greater than 73% of the oligosaccharides on G proteins recovered from released virions were complex-type units. The efficient processing of the G protein oligosaccharides coincided with the efficient removal of glucose residues from its oligosaccharides. After treatment with deoxynojirimycin, an inhibitor of endoplasmic reticulum (ER) glucosidases I and II, the total percentage of G protein-associated high mannose-type oligosaccharides increased more in the parental cells than in the mutant cells. Furthermore, when the G protein was retained in the ER of PhaR2.7 cells by depletion of the cellular ATP pools with carbonyl cyanide m-chlorophenylhydrazone, its oligosaccharides remained glucosylated. Under identical conditions, BW5147 cells removed the glucose residues from > 90% of the retained G protein's oligosaccharides. Thus, PhaR2.7 cells efficiently remove glucose residues from high mannose-type oligosaccharides of selected proteins using a deoxynojirimycin-insensitive enzyme located in a post-ER compartment. The existence of a second mechanism for the deglucosylation of N-linked oligosaccharides provides evidence for the important role of glucose removal in glycoprotein maturation.

A 58-kDa resident protein of the cis Golgi cisterna is not terminally glycosylated

A 58-kDa Golgi protein (gp58) was previously identified and found to be concentrated in cis Golgi cisternae in several cell types (Saraste, J., Palade, G.E., and Farquhar, M.G. (1987) J. Cell Biol. 105, 2021-2029). In this study the protein was partially purified from rat pancreas and mouse myeloma cells in order to characterize its oligosaccharides. It migrated on sodium dodecyl sulfate-polyacrylamide gels as a 57-58-kDa doublet under reducing conditions or as a single approximately 116-kDa band under nonreducing conditions. Pancreatic gp58 was susceptible to alpha-N-acetylgalactosaminidase digestion and it bound concanavalin A, Helix pomatia, Dolichos biflorus, soybean agglutinin, and Bauhinia purpurea lectins, but not Ricinus communis agglutinin or lectins from Griffonia simplicifolia-1, Arachis hypogaea, and Limulus polyphemus. It bound Ricinus communis agglutinin after galactosylation with GlcNAc galactosyltransferase. These data demonstrate that pancreatic p58 contains immature N-linked moieties with nonreducing terminal GlcNAc residues as well as the initiating GalNAc of O-linked glycoproteins. Myeloma gp58 was sensitive to endo-beta-N-acetylglucosaminidase H, and oligosaccharide analysis of its [3H]glucosamine-labeled glycopeptides indicated that it also contained immature N-linked glycans. Some of the latter consist of high mannose chains (high affinity for concanavalin A, endo-beta-N-acetylglucosaminidase H-sensitive), but the predominant (95%) species are neutral tri- or tetraantennary N-linked chains containing GlcNAc (no binding to concanavalin A). Glycopeptides from biosynthetically labeled myeloma cells did not contain detectable base labile oligosaccharides, indicating that unlike pancreatic p58, myeloma gp58 may not be an O-linked glycoprotein. Neither pancreatic nor myeloma gp58 contained terminally processed oligosaccharides, indicating that gp58 has not been modified by trans-Golgi glycosyltransferases. Thus, the oligosaccharide content of gp58 is consistent with the assumption that this protein is retained in the cis Golgi cisternae during biosynthesis instead of being transported across the Golgi stacks and targeted back to the cis Golgi from the trans side.

The role of silent ischemia, the arrhythmic substrate and the short-long sequence in the genesis of sudden cardiac death

To study the role of silent ischemia and the arrhythmic substrate in the genesis of sudden cardiac death, 67 patients were studied (mean age 62 +/- 12 years). Of these, 14 patients (Group 1) had an in-hospital episode of ventricular tachycardia or fibrillation while wearing a 24 h Holter ambulatory electrocardiographic (ECG) monitor, 33 (Group II) had a documented episode of sustained ventricular tachycardia or fibrillation, or both, and 20 (Group III) had angina pectoris but no ventricular tachycardia or fibrillation. Eight Group I survivors underwent programmed electrical stimulation or ECG signal averaging, or both. All Group II patients underwent 24 h Holter monitoring and ECG signal averaging to detect late potentials before programmed electrical stimulation. Group III patients underwent both 24 h Holter recording and coronary angiography. The 24 h ECG tapes were analyzed for ST segment changes, prematurity index and characteristics of ventricular premature depolarizations. Any ST depression greater than or equal to 1 mm for greater than 30 s was considered to be a reflection of silent ischemia, and the induction of ventricular tachycardia or fibrillation by programmed electrical stimulation or the presence of late potentials, or both, was considered to be a reflection of the arrhythmia substrate. Silent ischemia preceded ventricular tachycardia in only 2 (14%) of the 14 Group I patients. The prematurity index was less than 1 in only 18% of ventricular tachycardia episodes.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective retention of monoglucosylated high mannose oligosaccharides by a class of mutant vesicular stomatitis virus G proteins

Cells infected with a temperature-sensitive mutant of vesicular stomatitis virus, ts045, or transfected with the plasmid vector pdTM12 produce mutant forms of the G protein that remain within the ER. The mutant G proteins were isolated by immunoprecipitation from cells metabolically labeled with [2-3H]mannose to facilitate analysis of the protein-linked oligosaccharides. The 3H-labeled glycopeptides recovered from the immunoprecipitated G proteins contained high mannose-type oligosaccharides. Structural analysis, however, indicated that 60-78% of the 3H-mannose-labeled oligosaccharides contained a single glucose residue and no fewer than eight mannose residues. The 3H-labeled ts045 oligosaccharides were deglucosylated and processed to complex-type units after the infected cells were returned to the permissive temperature. When shifted to the permissive temperature in the presence of a proton ionophore, the G protein oligosaccharides were deglucosylated but remained as high mannose-type units. The glucosylated state was observed, therefore, when the G protein existed in an altered conformation. The ts045 G protein oligosaccharides were deglucosylated in vitro by glucosidase II at both the permissive and nonpermissive temperatures. G protein isolated from ts045-infected cells labeled with [6-3H]galactose in the presence of cycloheximide contained 3H-glucose-labeled monoglucosylated oligosaccharides, indicating that the high mannose oligosaccharides were glucosylated in a posttranslational process. These results suggest that aberrant G proteins are selectively modified by resident ER enzymes to retain monoglucosylated oligosaccharides.

Immunolocalization of a neuronal growth-dependent membrane glycoprotein

Monoclonal antibody (mAb) 5B4 recognizes in the rat a large, developmentally regulated membrane glycoprotein. The larger form of this antigen (185-255 kD) occurs in the developing nervous system and is present in membranes of nerve growth cones, as determined by analysis of a growth cone particle fraction. An immunochemical characterization of this antigen and of a smaller form (140 kD), sparsely present in the mature nervous system, has been described (Ellis, L., I. Wallis, E. Abreu, and K. H. Pfenninger, 1985, J. Cell. Biol., 101:1977-1989). The present paper reports on the localization by immunofluorescence of 5B4 antigen in cultured cortical neurons, developing spinal cord, and the mature olfactory system. In culture, mAb 5B4 stains only neurons; it is sparsely present in neurons at the onset of sprouting while, during sprouting, it appears to be concentrated at the growth cone and in regions of the perikaryon. In the developing spinal cord, 5B4 labeling is faintly detectable on embryonic day 11 but is intense on fetal day 13. At this stage, the fluorescence is observed in regions of the cord where axonal growth is occurring, while areas composed of dividing or migrating neural cells are nonfluorescent. With maturation of the spinal cord, this basic pattern of fluorescence persists initially, but the staining intensity decreases dramatically. In the adult, faint fluorescence is detectable only in gray matter, presumably indicating the presence of the 140 kD rather than the fetal antigen. The only known structure of the adult mammalian nervous system where axonal growth normally occurs is the olfactory nerve. mAb 5B4 intensely stains a variable proportion of olfactory axons in the mucosa as well as in the olfactory bulb. Based on both immunochemical and immunofluorescence data, the 5B4 antigen of 185-255 kD is associated specifically with growing neurons, i.e., neurons that are generating neurites.