Arrhythmogenic Manifestations of Chagas Disease: Perspectives From the Bench to Bedside

Chagas cardiomyopathy caused by infection with the intracellular parasite Trypanosoma cruzi is the most common and severe expression of human Chagas disease. Heart failure, systemic and pulmonary thromboembolism, arrhythmia, and sudden cardiac death are the principal clinical manifestations of Chagas cardiomyopathy. Ventricular arrhythmias contribute significantly to morbidity and mortality and are the major cause of sudden cardiac death. Significant gaps still exist in the understanding of the pathogenesis mechanisms underlying the arrhythmogenic manifestations of Chagas cardiomyopathy. This article will review the data from experimental studies and translate those findings to draw hypotheses about clinical observations. Human- and animal-based studies at molecular, cellular, tissue, and organ levels suggest 5 main pillars of remodeling caused by the interaction of host and parasite: immunologic, electrical, autonomic, microvascular, and contractile. Integrating these 5 remodeling processes will bring insights into the current knowledge in the field, highlighting some key features for future management of this arrhythmogenic disease.

Atherosclerotic cardiovascular disease events among adults with high predicted risk without established risk factors

Objective

Age is the strongest contributor to 10-year predicted atherosclerotic cardiovascular disease (ASCVD) risk. Some older adults have a predicted ASCVD risk ≥7.5 %, without established risk factors. We sought to compare ASCVD incidence among adults with predicted ASCVD risk ≥7.5 %, with and without established ASCVD risk factors, to adults with predicted risk <7.5 %.

Methods

We analyzed data from REasons for Geographic and Racial Differences in Stroke study participants, 45-79 years old, without ASCVD or diabetes, not taking statins and with low-density lipoprotein cholesterol 70-189 mg/dL. Participants were categorized into 3 groups based on their 10-year predicted ASCVD risk and presence of established risk factors: <7.5 %, ≥7.5 % with established risk factors and ≥7.5 % without established risk factors. Established risk factors included smoking, systolic blood pressure ≥130 mmHg or antihypertensive medication use, total cholesterol ≥200 mg/dL, or high-density lipoprotein cholesterol <50 mg/dL for women (<40 mg/dL for men). Participants were followed for ASCVD events.

Results

Among 11,115 participants, 911 incident ASCVD events occurred over a median of 11.1 years. ASCVD incidence rates were 3.6, 12.8, and 9.8 per 1,000 person-years for participants with predicted risk <7.5 %, predicted risk ≥7.5 % with established risk factors and predicted risk ≥7.5 % without established risk factors, respectively. Compared to adults with predicted risk <7.5 %, hazard ratios for incident ASCVD in participants with risk ≥7.5 % with and without established risk factors were 3.58 (95 %CI 3.03 - 4.21) and 2.72 (95 %CI 1.91-3.88), respectively.

Conclusions

Adults with a 10-year predicted ASCVD risk ≥7.5 % but without established risk factors had a high ASCVD incidence.

The Transulnar Approach to Coronary Angiography and Intervention: Assessing the Anatomy of the Ulnar Artery Using Angiography

BACKGROUND

The transulnar approach (TUA) has been proposed as a safe alternative to the more established transradial approach (TRA) for cardiac catheterization. However, no study has assessed the anatomy and variability of the ulnar artery using angiography.

METHODS

A retrospective analysis of patients who underwent transradial cardiac catheterization during routine clinical care was conducted. Both quantitative and qualitative measurements of artery diameter were collected.

RESULTS

Among 700 consecutive patients, mean distal ulnar artery diameter (UAD) was larger in men (3.2 ± 0.9 mm) compared with women (2.7 ± 0.7 mm; P<.001). UAD was larger than radial artery diameter (RAD) at all measured sites (distal ulnar, 3.0 ± 0.8 mm; distal radial, 2.9 ± 0.7 mm; P=.046). Compared with the radial artery, the ulnar artery had more atresia (4.3% ulnar vs 0% radial; P<.001), fewer loops (0.6% ulnar vs 2.4% radial; P<.01), and less spasm (2.7% ulnar vs 23.4% radial; P<.001). UAD had more variability (distal variance, 0.68) as compared with the RAD (distal variance, 0.53; P<.001).

CONCLUSION

We found that the ulnar artery has a larger diameter, fewer loops, and less spasm, but more variance than the radial artery. Additionally, males have larger ulnar arteries than women. These findings have implications on the application of TUA either as an alternative to TRA or as the primary point of access.

A retrospective analysis of high sensitivity cardiac troponin-T ranges in non-myocardial infarction emergency department visits

Introduction

Current evidence suggests that high sensitivity cardiac troponin-T (hs-cTnT) values differ based on sex, race, age, and kidney function. However, most studies examining the relationship of hs-cTnT and these individual factors are in healthy participants, leading to difficulty in interpreting hs-cTnT values in the Emergency Department (ED) setting. We seek to examine the relationship between hs-cTnT values and sex, race, age, and kidney function in a contemporary, urban academic setting.

Methods

ED visits from June 2018 through April 2019 with at least 1 hs-cTnT and no diagnosis of acute myocardial infarction (AMI) at an academic medical center in the south side of Chicago were retrospectively analyzed. Median hs-cTnT values were stratified by sex (male or female), race (African American or Caucasian), age, estimated glomerular filtration rate (eGFR), and stage of chronic kidney disease.

Results

9679 encounters, representing 7989 distinct patients, were included for analysis (age 58 ± 18 years, 59% female, 85% black). Males had significantly higher median hs-cTnT values than females (16 [8–34] vs. 9 [6–22] ng/L, p < 0.001), African Americans had a significantly lower median value than Caucasians (10 [6–24] vs. 15 [6–29] ng/L, p < 0.001), and those with atrial fibrillation (27 [16–48] vs. 9 [6–19] ng/L, p < 0.001) and heart failure (28 [14–48] vs. 8 [6–15] ng/L, p < 0.001) had higher median values than those without. Median hs-cTnT values increased significantly with increased age and decreased eGFR. All relationships continued to be significant even after multivariable regression of sex, age, race, eGFR, presence of atrial fibrillation, and presence of heart failure (p < 0.01).

Conclusions

Analysis of hs-cTnT in non-AMI patients during ED encounters showed that males have higher values than females, African Americans have lower values than Caucasians, those with atrial fibrillation and heart failure have higher values than those without, and that older age and lower eGFR were associated with higher median values.

Takotsubo Syndrome Presenting as Cardiogenic Shock in Patients With COVID-19: A Case Series and Review of Current Literature

Takotsubo's syndrome (TTS) is a form of stress cardiomyopathy with a relatively benign long-term course, but may lead to arrhythmias and cardiogenic shock in the acute setting. Despite a recent rise in suspected stress-induced cardiomyopathy, the relationship between the novel coronavirus disease 19 (COVID-19) and TTS is not fully understood. Early recognition of TTS in these patients is important to guide management and treatment. We present 2 cases of TTS arising in the setting of COVID-19 with rapid progression to biventricular heart failure and cardiogenic shock.

Methylphenidate causes cytotoxicity on photoreceptor cells via autophagy

Methylphenidate (MPH) is used as the first-line treatment for attention-deficit hyperactivity disorder. However, there are concerns that this treatment may be associated with increased risk of retinal damage. This study was to investigate cytotoxicity of MPH on photoreceptor cells and explore its underlying mechanisms. MPH-caused cell toxicity was established in 661 W cells. Cytotoxicity was evaluated by 3-(4,5-dimethylthiazol)-2,5-diphenyltetrazolium-bromid and lactate dehydrogenase assays. Oxidative stress was measured by the markers: glutathione (GSH) reductase, catalase, and superoxide dismutase activities as well as GSH, reactive oxygen species, and malondialdehyde levels. Gene and protein expression was detected by real-time polymerase chain reaction (PCR) and western blot, respectively. Results showed that MPH decreased 661 W cell viability, increased caspase-3/9 activities, and induced oxidative stress. Furthermore, MPH treatment increased messenger RNA (mRNA) expression of Beclin-1 and microtubule-associated protein 1A/1B-light chain 3B (LC3B) protein expression in 661 W cells, suggesting autophagy was induced. MPH treatment also upregulated p-JAK1/p-STAT1 protein expression. These data demonstrated that MPH could increase oxidative stress in photoreceptor cells to cause cell toxicity via autophagy, providing the scientific rationale for the photoreceptor cell damage caused by the MPH administration.

C57BL/6J mouse apolipoprotein A2 gene is deterministic for apnea

RATIONALE

Brainstem apolipoprotein AII (apoa2) mRNA expression correlates with apnea in breathing present in the adult C57Bl/6J (B6) sleep apnea model.

OBJECTIVES

To test the hypothesis that the B6 apoa2 gene contributes to the trait, we performed plethysmographic testing in apoa2 knock out (KO: -/-) mice, an in situ brainstem-spinal cord preparation comparing KO to WT (+/+) mice, and B6xDBA recombinant inbred strains (RISs).

MEASUREMENTS AND MAIN RESULTS

Apoa2 WT do, but KO and heterozygote (+/-) mice do not exhibit apnea during post-hypoxic breathing, measured in vivo. In the in situ model, pauses and instability in fictive phrenic bursting are substantially reduced in KO vs. WT preparations. In 24 RISs, apnea number in vivo was higher in strains with B6 apoa2 than with DBA apoa2 alleles.

CONCLUSIONS

The B6 apoa2 polymorphism is directly involved in breath production, and its identification suggests a novel pathway influencing risk for adult sleep apnea.

Predicting 30-day Hospital Readmission with Publicly Available Administrative Database. A Conditional Logistic Regression Modeling Approach

INTRODUCTION

This article is part of the Focus Theme of Methods of Information in Medicine on "Big Data and Analytics in Healthcare".

BACKGROUND

Hospital readmissions raise healthcare costs and cause significant distress to providers and patients. It is, therefore, of great interest to healthcare organizations to predict what patients are at risk to be readmitted to their hospitals. However, current logistic regression based risk prediction models have limited prediction power when applied to hospital administrative data. Meanwhile, although decision trees and random forests have been applied, they tend to be too complex to understand among the hospital practitioners.

OBJECTIVES

Explore the use of conditional logistic regression to increase the prediction accuracy.

METHODS

We analyzed an HCUP statewide inpatient discharge record dataset, which includes patient demographics, clinical and care utilization data from California. We extracted records of heart failure Medicare beneficiaries who had inpatient experience during an 11-month period. We corrected the data imbalance issue with under-sampling. In our study, we first applied standard logistic regression and decision tree to obtain influential variables and derive practically meaning decision rules. We then stratified the original data set accordingly and applied logistic regression on each data stratum. We further explored the effect of interacting variables in the logistic regression modeling. We conducted cross validation to assess the overall prediction performance of conditional logistic regression (CLR) and compared it with standard classification models.

RESULTS

The developed CLR models outperformed several standard classification models (e.g., straightforward logistic regression, stepwise logistic regression, random forest, support vector machine). For example, the best CLR model improved the classification accuracy by nearly 20% over the straightforward logistic regression model. Furthermore, the developed CLR models tend to achieve better sensitivity of more than 10% over the standard classification models, which can be translated to correct labeling of additional 400 - 500 readmissions for heart failure patients in the state of California over a year. Lastly, several key predictor identified from the HCUP data include the disposition location from discharge, the number of chronic conditions, and the number of acute procedures.

CONCLUSIONS

It would be beneficial to apply simple decision rules obtained from the decision tree in an ad-hoc manner to guide the cohort stratification. It could be potentially beneficial to explore the effect of pairwise interactions between influential predictors when building the logistic regression models for different data strata. Judicious use of the ad-hoc CLR models developed offers insights into future development of prediction models for hospital readmissions, which can lead to better intuition in identifying high-risk patients and developing effective post-discharge care strategies. Lastly, this paper is expected to raise the awareness of collecting data on additional markers and developing necessary database infrastructure for larger-scale exploratory studies on readmission risk prediction.

Autophagy and chemotherapy resistance: a promising therapeutic target for cancer treatment

Induction of cell death and inhibition of cell survival are the main principles of cancer therapy. Resistance to chemotherapeutic agents is a major problem in oncology, which limits the effectiveness of anticancer drugs. A variety of factors contribute to drug resistance, including host factors, specific genetic or epigenetic alterations in the cancer cells and so on. Although various mechanisms by which cancer cells become resistant to anticancer drugs in the microenvironment have been well elucidated, how to circumvent this resistance to improve anticancer efficacy remains to be defined. Autophagy, an important homeostatic cellular recycling mechanism, is now emerging as a crucial player in response to metabolic and therapeutic stresses, which attempts to maintain/restore metabolic homeostasis through the catabolic lysis of excessive or unnecessary proteins and injured or aged organelles. Recently, several studies have shown that autophagy constitutes a potential target for cancer therapy and the induction of autophagy in response to therapeutics can be viewed as having a prodeath or a prosurvival role, which contributes to the anticancer efficacy of these drugs as well as drug resistance. Thus, understanding the novel function of autophagy may allow us to develop a promising therapeutic strategy to enhance the effects of chemotherapy and improve clinical outcomes in the treatment of cancer patients.

The cytoplasmic domain of neuropilin-1 regulates focal adhesion turnover

Though the vascular endothelial growth factor coreceptor neuropilin-1 (Nrp1) plays a critical role in vascular development, its precise function is not fully understood. We identified a group of novel binding partners of the cytoplasmic domain of Nrp1 that includes the focal adhesion regulator, Filamin A (FlnA). Endothelial cells (ECs) expressing a Nrp1 mutant devoid of the cytoplasmic domain (nrp1(cyto)(Δ/Δ)) migrated significantly slower in response to VEGF relative to the cells expressing wild-type Nrp1 (nrp1(+/+) cells). The rate of FA turnover in VEGF-treated nrp1(cyto)(Δ/Δ) ECs was an order of magnitude lower in comparison to nrp1(+/+) ECs, thus accounting for the slower migration rate of the nrp1(cyto)(Δ/Δ) ECs.

Graphical Overlays: Using Layered Elements to Aid Chart Reading

Reading a visualization can involve a number of tasks such as extracting, comparing or aggregating numerical values. Yet, most of the charts that are published in newspapers, reports, books, and on the Web only support a subset of these tasks. In this paper we introduce graphical overlays-visual elements that are layered onto charts to facilitate a larger set of chart reading tasks. These overlays directly support the lower-level perceptual and cognitive processes that viewers must perform to read a chart. We identify five main types of overlays that support these processes; the overlays can provide (1) reference structures such as gridlines, (2) highlights such as outlines around important marks, (3) redundant encodings such as numerical data labels, (4) summary statistics such as the mean or max and (5) annotations such as descriptive text for context. We then present an automated system that applies user-chosen graphical overlays to existing chart bitmaps. Our approach is based on the insight that generating most of these graphical overlays only requires knowing the properties of the visual marks and axes that encode the data, but does not require access to the underlying data values. Thus, our system analyzes the chart bitmap to extract only the properties necessary to generate the desired overlay. We also discuss techniques for generating interactive overlays that provide additional controls to viewers. We demonstrate several examples of each overlay type for bar, pie and line charts.

High-resolution melting analysis for the rapid detection of an intronic single nucleotide polymorphism in SLC22A12 in male patients with primary gout in China

OBJECTIVES

The human urate transporter 1 (URAT1, encoded by SLC22A12) was recently identified as the major absorptive urate transporter protein in the kidney responsible for regulating blood urate levels. The present study was designed to investigate the rs893006 polymorphism (GG, GT, and TT) in SLC22A12 in a total of 292 Chinese male subjects. Differences of clinical characteristics among the genotype groups were analysed.

METHODS

A total of 124 consecutive patients with diagnosis of primary gout and 168 healthy male volunteers were enrolled in this study. Demographic and clinical data were obtained from the patients and controls. DNA was purified from peripheral blood and the rs893006 polymorphism was determined with sequencing analysis. In addition, DNA samples were detected by high-resolution melting (HRM) analysis. Melting curves were analysed as fluorescence difference plots. The shift and curve shapes of melting profiles were used to distinguish the different genotypes.

RESULTS

GG, GT, and TT genotypes were unambiguously distinguished with HRM technology. Genotyping based on HRM analysis was fully concordant with the sequencing. Serum uric acid levels in the TT genotype subjects were significantly lower than those in the GG and GT genotypes. However, no differences among the groups were found in body mass index (BMI), blood pressure, creatinine, total cholesterol, and triglycerides. The TT genotype was observed more frequently among the low uric acid group than the high uric acid group.

CONCLUSIONS

HRM analysis is a simple, rapid and accurate one-tube assay for genotyping the SLCSSA12 gene. The rs893006 polymorphism in SLC22CA12 was confirmed to be a genetic risk for hyperuricaemia among the Chinese male population.

Synthesis and monoamine transporter affinity of 3beta-(4-(2-pyrrolyl)phenyl)-8-azabicycl

3Beta-(5-indolyl)-8-azabicyclo[3.2.1]octanes display potent binding affinity for both the dopamine and serotonin transporters, while certain 3beta-(4-(2-pyrrolyl)phenyl)-8-azabicyclo[3.2.1]octanes selectively bind to the serotonin transporter.

What is the role of between meal snacks with intensive basal bolus regimens using preprandial lispro?

AIMS

Hypoglycaemia avoidance for patients on intensive insulin regimens requires the eating of snacks between meals. Insulin lispro with its shorter action profile may permit omitting such snacks.

METHODS

Ten Type 1 diabetes mellitus (DM) patients were rendered euglycaemic with a morning intravenous insulin infusion. Each was studied on six afternoons in random order, with previously determined equal doses of Humulin S (HS) injected at -30min, or lispro injected at 0 min before a standard lunch. The snack was either eaten mid-afternoon, combined with the lunch or omitted altogether.

RESULTS

Lispro and lunch with a snack combined at 0 min gave equal control to HS at -30 min and lunch at 0 min with a mid-afternoon snack. Lispro and lunch at 0 min with a mid-afternoon snack gave a lower early postprandial glucose. At 120 min glucose (mean mmol/l +/- SEM) were 7.4+/-0.8 vs. 7.0+/-1.0 (P = 1.0) and 3.9+/-0.5 (P = 0.045), respectively. The area under the insulin curve over the whole afternoon was similar for HS and lispro (13193.3+/-974.6 vs. 13193.6+/-809.9 mIU/min, P = 1.0) but with a greater peak for lispro than HS with lispro falling more rapidly. Despite significantly lower lispro levels after 180 min, intermediary metabolites concentrations were similar in all HS and lispro study days.

CONCLUSIONS

Lispro injected immediately before combined snack and lunch and with no subsequent snack achieves equivalent control to conventional regimens using HS -30 min before lunch and mid-afternoon snack. Lispro taken with traditional meal patterns without dose reduction risks early postprandial hypoglycaemia and late hyperglycaemia.

Vancomycin administration in continuous ambulatory peritoneal dialysis: the risk of ototoxicity

A prospective study was undertaken in 16 patients with chronic renal failure on continuous ambulatory peritoneal dialysis, with 22 episodes of peritonitis treated with vancomycin, a known ototoxic agent. Twelve patients had one episode each, and four had recurrent peritonitis. Each treatment course consisted of two infusions of vancomycin (30 mg/kg body weight) in 2 L of peritoneal dialysate administered at 6-day intervals. Serum vancomycin analyzed by enzyme immunoassay showed a mean trough level of 11.00 microg/ml on day 6 and mean serum levels of 33.8 and 38.6 microg/ml about 12 hours after administration on days 1 and 7, respectively. Similar levels, well within the therapeutic range, were encountered with repeated vancomycin therapy for recurrent episodes of peritonitis, suggesting that no changes occurred in the pharmacokinetic profile of the drug. Pure-tone audiometry, electronystagmography, and clinical assessment performed during each course of treatment showed no evidence of ototoxicity even on repeated courses of vancomycin therapy. The results suggest that vancomycin therapy when given in appropriate concentrations as a single therapeutic agent is both effective and safe. We believe, however, that vancomycin administered in combination with an aminoglycoside may produce ototoxic effects that may be greatly aggravated, possibly because of synergism.

Instant electronic imaging systems are superior to Polaroid at detecting sight-threatening diabetic retinopathy

Polaroid photography in diabetic retinopathy screening allows instant image availability to enhance the results of ophthalmoscopy. Retinal cameras are now being developed which use video/digital imaging techniques to produce an instant enlarged retinal image on a computer monitor screen. We aimed to compare one such electronic imaging system, attached to a Canon CR5 45NM, with standard Polaroid retinal photography. Two hundred and thirteen eyes from 107 diabetic patients were photographed through dilated pupils by both systems in random order and the images were analysed blind. Diabetic retinopathy was present in 58 eyes of which 55/58 (95%) were detected on the electronic image and only 49/58 (84%) on the Polaroid. Of 34 eyes requiring ophthalmologist referral according to standard European criteria, 34/34 (100%) were detected on the electronic image and only 24/34 (71%) on the Polaroid. Side by side comparisons showed electronic imaging to be superior to Polaroid at lesion detection. Using linear analogue scales, the patients assessed the electronic imaging photographic flash as less uncomfortable than the Polaroid equivalent (p < 0.0001). Other advantages of electronic imaging include: ready storage of the images with other patient clinical data on the diabetes computerized register/database; potential for image enhancement and analysis using image analysis software and electronic transfer of images to ophthalmologist or general practitioner. Electronic imaging systems represent a potential major advance for the improvement of diabetic retinopathy screening.

Potential antidepressant effects of novel tropane compounds, selective for serotonin or dopamine transporters

The forced swimming test (FST) predicts the efficacy of clinically effective antidepressants. In the present study, using the FST we examined the antidepressant potential of three novel tropane analogs: 8-methyl-2beta-propanoyl-3beta-(4-(1-methylethyl)phenyl)-8-azabicy clo[3.2.1] (WF-31) and 2beta-propanoyl-3beta-(4-(1-methylethyl)phenyl)-8-azabicyclo[3.2.1 ]octane (WF-50), selective inhibitors of serotonin uptake, and 8-methyl-2beta-propanoyl-3beta-(4-(1-methylphenyl)-8-azabicyclo[3. 2.1] octane (PTT, WF-11), a selective inhibitor of dopamine uptake. Fluoxetine and GBR 12909 were used as controls for selective inhibitors of serotonin and dopamine, respectively. Drugs were administered three times in a 24-hr period between pretest and test sessions. Intraperitoneal administration of WF-31 (0.1-10.0 mg/kg), WF-50 (0.3-10.0 mg/kg) and fluoxetine (0.3-10.0 mg/kg) dose-dependently decreased immobility while increasing swimming. In contrast, WF-11 (0.3-3.0 mg/kg) dose-dependently decreased immobility and increased both swimming and climbing, whereas GBR 12909 (3.0-30.0 mg/kg) decreased immobility, increased climbing but did not affect swimming. In a separate experiment, WF-11 (1.0 mg/kg) increased locomotor activity, whereas a higher dose of WF-11 (3.0 mg/kg) and GBR-12909 (30.0 mg/kg) produced stereotypic behaviors, suggesting that the effects in the FST may have been attributable to increases in general activity. However, the effects of WF-11 on swimming in the FST indicate that WF-11 produces antidepressant-like effects in addition to motor stimulation. These results confirm previous results that behavioral patterns manifested in the FST are characteristic of specific monoamine uptake inhibitors. In addition, these results demonstrate that WF-31 and WF-50 produce behavioral patterns similar to fluoxetine in the FST without accompanying decreases in motor activity, suggesting a potential antidepressant action. Based on comparisons with fluoxetine, the data suggest WF-31 and WF-50 may be therapeutically useful as potential antidepressant medications.

Psychiatric disorder in Malaysians with systemic lupus erythematosus

All 79 patients who attended a University Systemic Lupus Erythematosus (SLE) Clinic over a 6 month period were assessed using the Clinical Interview Schedule for psychiatric disorder. Using the ICD-9 Classification, 40 were found to have psychiatric disorder, 26 having depressive neurosis, six anxiety neurosis, five endogenous depression and three dementia. The group with psychiatric disorder had significantly poor family support as well as lack of a confidant compared to the group without psychiatric disorder (P < 0.01). There was no difference between the group with psychiatric disorder and those without psychiatric disorder in terms of age, duration of illness, ethnicity and severity of SLE. Psychiatric disorder is common affecting more than half the subjects and depression was the most frequent diagnosis.

The secretory pathway is normal in dithiothreitol-treated cells, but disulfide-bonded proteins are reduced and reversibly retained in the endoplasmic reticulum

Addition of 2 mM dithiothreitol (DTT) to HepG2 human hepatoma cells blocks secretion of newly made albumin and causes it to accumulate in the endoplasmic reticulum in the reduced state. Subsequent incubation of the cells in the absence of DTT allows the reduced albumin to form apparently normal disulfide bonds and to be secreted normally. Similarly, DTT treatment causes all newly made subunits of the H1 subunit of the asialoglycoprotein receptor to be retained in the endoplasmic reticulum in the reduced state; following removal of DTT H1 subunits form disulfide bonds via a normal endoplasmic reticulum folding intermediate and mature to the Golgi. Thus, apparently normal formation of disulfide bonds on these two proteins can occur post-translationally, as has been shown previously for the influenza HA hemagglutinin (Braakman, I., Helenius, J., and Helenius, A. (1992) EMBO J. 11, 1717-1722; Braakman, I., Helenius, J., and Helenius, A. (1992) Nature 356, 260-262). alpha 1-Antitrypsin contains no disulfide bonds; in the continuous presence of DTT it acquires a normal complement of complex oligosaccharides and is secreted at an only slightly reduced rate. Thus, the secretory pathway functions efficiently even when it is reduced by DTT. Endoplasmic reticulum retention of albumin and H1 during treatment with DTT presumably occurs because, without disulfide bonds, these proteins cannot fold properly, not because of any defect in the overall processes of vesicular transport and protein secretion.

Gentamicin ototoxicity in continuous ambulatory peritoneal dialysis

A prospective study was undertaken of 10 chronic renal failure patients on Continuous Ambulatory Peritoneal Dialysis (CAPD) complicated by repeated bouts of peritonitis treated with gentamicin. Each 10-day treatment course consisted of a 120 mg loading dose, followed by 16 mg in 21 of peritoneal dialysate, given four times a day. Serum gentamicin analysed by enzyme immunoassay showed a mean level of 5.2 micrograms/ml, (range 3.7 to 6.6 mg/ml) four hours after the loading dose. Similar levels, well within the therapeutic range, were maintained on the 3rd, 5th, 7th and 9th days of intraperitoneal gentamicin therapy, suggesting no accumulation of gentamicin in the serum. Pure tone audiometry, electronystagmography and clinical assessment were performed during each course of treatment. Although no evidence of ototoxicity was found during the first two courses of gentamicin, but disequilibrium and bobbing oscillopsia were present during the third and fourth courses of gentamicin. These findings could be explained by cumulative injury to the vestibular apparatus caused by repeated therapeutic insults.

Calcium is required for folding of newly made subunits of the asialoglycoprotein receptor within the endoplasmic reticulum

By resolving immunoprecipitates on nonreducing sodium dodecyl sulfate gels, we have detected several disulfide-bonded intermediates in folding within the endoplasmic reticulum of newly made H1 subunits of the asialoglycoprotein receptor. H1 in the endoplasmic reticulum (ER) can be partially unfolded by treatment of cells with dithiothreitol, but H1 in Golgi or post-Golgi organelles is resistant to such unfolding. This defines a late step in H1 folding that occurs just prior to exit from the ER. Depletion of calcium from the endoplasmic reticulum, either by treatment with A23187 or thapsigargin, has no effect on folding or secretion of newly made albumin, but totally blocks H1 maturation from the ER. No ER intermediates in H1 folding are formed in cells treated with A23187 or thapsigargin, indicating that at least an early step in H1 folding requires a high Ca2+ concentration in the ER lumen. As judged by cross-linking experiments, formation of H1 dimers and trimers occurs immediately after biosynthesis of the peptide chain, before monomer folding, and occurs normally in cells in which ER Ca2+ is reduced and where the monomer never folds properly. Calcium is essential for the asialoglycoprotein receptor to bind galactose, and our results suggest that Ca2+ is also essential for the receptor polypeptides to fold in the ER.

Cyclosporin A inhibits an initial step in folding of transferrin within the endoplasmic reticulum

As resolved by electrophoresis in non-reducing SDS gels, transferrin newly made in Hep G2 cells migrates as a very diffuse set of species. During a subsequent 1-h chase all transferrin polypeptides are converted to a single, rapidly migrating species. These changes in gel mobility are due to alterations in the pattern of disulfide bonding, are not caused by carbohydrate processing, and occur while the protein is in the rough endoplasmic reticulum. Cyclosporin A causes an approximately 10-min lag in transferrin folding, after which folding resumes at the normal rate. Cyclosporin A also retards transferrin maturation from the endoplasmic reticulum and its secretion, at concentrations that do not affect secretion of other hepatoma proteins. Neither FK506 nor rapamycin affect transferrin folding. We conclude that an initial stage in transferrin folding is accelerated by an endoplasmic reticulum peptidyl-proline isomerase that is inhibited by cyclosporin A.

Asymptomatic proteinuria and/or haematuria in 265 Malaysian adults

Two-hundred and sixty-five patients with asymptomatic proteinuria and/or haematuria were studied at the Department of Medicine, Universiti Kebangsaan Malaysia and Department of Nephrology, General Hospital Kuala Lumpur. They represented 25.4% of all the renal biopsies performed during the period 1980-88. All the three races were affected with 71.3% occurring between the ages of 20-39 years and 41.1% were detected during routine medical examination. Excluding those patients with lupus nephritis, IgA nephropathy was the commonest histological diagnosis (51.7%). The presence of severe and advanced histological changes in a significant number of biopsies emphasises the need for more effective screening and early referral of this group of patients.

IgA nephropathy in Malaysia

A total of 164 patients with IgA nephropathy were diagnosed at the Department of Medicine, Universiti Kebangsaan Malaysia and the Department of Nephrology, General Hospital, Kuala Lumpur between 1981-1988. This represented an incidence of 20.1% of all primary glomerulopathies seen in both units. The 3 major ethnic groups were equally affected with 59.7% occurring between the ages of 20-36 years. It was not uncommon in females. The high prevalence of hypertension, renal failure, heavy proteinuria at presentation and the increased chronicity index in the biopsy, suggest that IgA nephropathy is progressive disease leading to chronic renal failure.

Perturbation of cellular calcium blocks exit of secretory proteins from the rough endoplasmic reticulum

In the cultured human hepatoma HepG2, Ca2+ ionophores block secretion of different secretary proteins to different extents, alpha 1-antitrypsin secretion being more sensitive to A23187 and ionomycin than is alpha 1-antichymotrypsin, and albumin secretion the least of the three proteins studied. As judged by subcellular fractionation experiments and by treatment of pulse chase labeled protein with endoglycosidase H, A23187 and ionomycin cause newly made secretory proteins to remain within the rough endoplasmic reticulum (ER). Experiments in which A23187 is added at different times during a pulse or chase show that secretion of newly made alpha 1-antitrypsin becomes resistant to the ionophore, on average, 15 min after synthesis; this is about 20 min before it reaches the trans-Golgi, and while it is still within the rough ER. We speculate that a high concentration of Ca2+ within the ER may be essential for certain secretory proteins to fold properly, that folding is inhibited when ER Ca2+ levels are lowered by ionophore treatment, and that unfolded proteins, particularly alpha 1-antitrypsin, cannot exit the rough ER. Treatment of murine 3T3 fibroblasts or human hepatoma HepG2 cells with the Ca2+ ionophores A23187 or ionomycin also induces a severalfold accumulation of the ER lumenal protein Bip (Grp78). These findings disagree with a recent report that Ca2+ ionophores cause secretion of Bip and other resident ER proteins, but is consistent with other reports that A23187 causes accumulation of mRNAs for Bip and other ER lumenal proteins.

A vesicular intermediate in the transport of hepatoma secretory proteins from the rough endoplasmic reticulum to the Golgi complex

We have identified a vesicle fraction that contains alpha 1-antitrypsin and other human HepG2 hepatoma secretory proteins en route from the rough endoplasmic reticulum (RER) to the cis face of the Golgi complex. [35S]Methionine pulse-labeled cells were chased for various periods of time, and then a postnuclear supernatant fraction was resolved on a shallow sucrose-D2O gradient. This intermediate fraction has a density lighter than RER or Golgi vesicles. Most alpha 1-antitrypsin in this fraction (P1) bears N-linked oligosaccharides of composition similar to that of alpha 1-antitrypsin within the RER; mainly Man8GlcNac2 with lesser amounts of Man7GlcNac2 and Man9GlcNac2; this suggests that the protein has not yet reacted with alpha-mannosidase-I on the cis face of the Golgi complex. This light vesicle species is the first post-ER fraction to be filled by labeled alpha 1-antitrypsin after a short chase, and newly made secretory proteins enter this compartment in proportion to their rate of exit from the RER and their rate of secretion from the cells: alpha 1-antitrypsin and albumin faster than preC3 and alpha 1-antichymotrypsin, faster, in turn, then transferrin. Deoxynojirimycin, a drug that blocks removal of glucose residues from alpha 1-antitrypsin in the RER and blocks its intracellular maturation, also blocks its appearance in this intermediate compartment. Upon further chase of the cells, we detect sequential maturation of alpha 1-antitrypsin to two other intracellular forms: first, P2, a form that has the same gel mobility as P1 but that bears an endoglycosidase H-resistant oligosaccharide and is found in a compartment--probably the medial Golgi complex--of density higher than that of the intermediate that contains P1; and second, the mature sialylated form of alpha 1-antitrypsin.

Glucose removal from N-linked oligosaccharides is required for efficient maturation of certain secretory glycoproteins from the rough endoplasmic reticulum to the Golgi complex

1- Deoxynojirimycin is a specific inhibitor of glucosidases I and II, the first enzymes that process N-linked oligosaccharides after their transfer to polypeptides in the rough endoplasmic reticulum. In a pulse-chase experiment, 1- deoxynojirimycin greatly reduced the rate of secretion of alpha 1-antitrypsin and alpha 1-antichymotrypsin by human hepatoma HepG2 cells, but had marginal effects on secretion of the glycoproteins C3 and transferrin, or of albumin. As judged by equilibrium gradient centrifugation, 1- deoxynojirimycin caused alpha 1-antitrypsin and alpha 1-antichymotrypsin to accumulate in the rough endoplasmic reticulum. The oligosaccharides on cell-associated alpha 1-antitrypsin and alpha 1-antichymotrypsin synthesized in the presence of 1- deoxynojirimycin , remained sensitive to Endoglycosidase H and most likely had the structure Glu1- 3Man9GlcNAc2 . Tunicamycin, an antibiotic that inhibits addition of N-linked oligosaccharide units to glycoproteins, had a similar differential effect on secretion of these proteins. Swainsonine , an inhibitor of the Golgi enzyme alpha-mannosidase II, had no effect on the rates of protein secretion, although the proteins were in this case secreted with an abnormal N-linked, partially complex, oligosaccharide. We conclude that the movement of alpha 1-antitrypsin and alpha 1-antichymotrypsin from the rough endoplasmic reticulum to the Golgi requires that the N-linked oligosaccharides be processed to at least the Man9GlcNAc2 form; possibly this oligosaccharide forms part of the recognition site of a transport receptor for certain secretory proteins.

Blastogenic response of human lymphocytes to early antigen(s) of human cytomegalovirus

The lymphocytes of asymptomatic, seropositive donors demonstrated blastogenic responses to early antigens of human cytomegalovirus whether or not antibodies to early antigens were detectable. The lymphocytes of six of nine patients with active cytomegalovirus infections gave stimulation indexes of greater than or equal to 2.00 with antigens of productively infected cells, whereas only two patients demonstrated comparable stimulation indexes with early antigens. Four patients with stimulation indexes of greater than or equal to 2.00 to productively infected antigens had stimulation indexes of less than or equal to 2.00 to early antigens. Viral polypeptides with molecular weights of 83,000, 72,000, 62,000, 56,000, and 40,000 were identified in early antigen preparations.

Hepatoma secretory proteins migrate from rough endoplasmic reticulum to Golgi at characteristic rates

In eukaryotic cells, secretory proteins and glycoproteins migrate from the rough endoplasmic reticulum, their site of synthesis, through Golgi vesicles before being released from the cell. Cellular and viral integral plasma membrane glycoproteins are co-translationally inserted into the rough endoplasmic reticulum membrane and follow a similar pathway to the cell surface. Previous studies using endoglycosidase H (Endo H) suggested that in rat hepatoma cells the vesicular stomatitis virus (VSV) G protein, albumin and transferrin migrate from the rough endoplasmic reticulum to the Golgi apparatus at different rates. Here we show directly that in human hepatoma HepG2 cells, five secreted proteins mature from the rough endoplasmic reticulum to Golgi vesicles at characteristic rates which differ at least threefold. The results are incompatible with bulk-phase movement of the luminal contents of the endoplasmic reticulum, and suggest that there is a membrane-bound receptor that selectively mediates the transport of secretory proteins from the rough endoplasmic reticulum to the Golgi.

Reversible block in intracellular transport and budding of mutant vesicular stomatitis virus glycoproteins

The blocks in intracellular maturation of glycoprotein (G protein) synthesized by two temperature-sensitive vesicular stomatite's virus (VSV) mutants are reversible. Our earlier work demonstrated that at 40 degrees, the nonpermissive temperature, mutant ts L513(V) G protein accumulates in the rough endoplasmic reticulum. Here we show that when the temperature is lowered the high-mannose oligosaccharides on a significant fraction of ts L513(V) G protein, synthesized at 40 degrees, will be modified to the complex type. Moreover, when the temperature is lowered ts L513(V) G protein accumulated at 40 degrees will mature to the cell surface, as evidenced by its accessibility to extracellular trinitrobenzene sulfonate, and into virions. G protein synthesized at 40 degrees in ts L511(V)-infected cells undergoes most of the processing events characteristic of the Golgi complex. Although we reported previously that no ts L511(V) G protein reaches the plasma membrane at 40 degrees, we now find, using more sensitive techniques, that an appreciable fraction does reach the cell surface. ts L511(V) G protein is lost from the cells but is not incorporated into virions. However, an appreciable fraction of the ts L511(V) G protein which accumulates in cells at 40 degrees will mature into virions when the temperature is lowered. These results exclude irreversible denaturation of mutant G proteins as a cause of the block in intracellular maturation and virus budding.

Computer-produced holograms for scanners utilizing an auxiliary reflector

Computer-produced holograms for scanners utilizing an auxiliary reflector have been constructed and demonstrated. Mathematic formalism for the calculation and detailed fabrication procedures are described. This method can be used for producing holograms for operation at any wavelengths whenever direct recording is not practical or inconvenient. This method is particularly suitable for producing holograms for 2-D scanners in the longer wavelengths, such as ir, far ir, mm, microwave, and ultrasonic waves. Simplicity in operation of the 2-D scanner will make real-tme imaging systems practical in the long-wavelength region.