Development and Temporal Validation of a Machine Learning Model to Predict Clinical Deterioration

OBJECTIVES

Early warning scores detecting clinical deterioration in pediatric inpatients have wide-ranging performance and use a limited number of clinical features. This study developed a machine learning model leveraging multiple static and dynamic clinical features from the electronic health record to predict the composite outcome of unplanned transfer to the ICU within 24 hours and inpatient mortality within 48 hours in hospitalized children.

METHODS

Using a retrospective development cohort of 17 630 encounters across 10 388 patients, 2 machine learning models (light gradient boosting machine [LGBM] and random forest) were trained on 542 features and compared with our institutional Pediatric Early Warning Score (I-PEWS).

RESULTS

The LGBM model significantly outperformed I-PEWS based on receiver operating characteristic curve (AUROC) for the composite outcome of ICU transfer or mortality for both internal validation and temporal validation cohorts (AUROC 0.785 95% confidence interval [0.780-0.791] vs 0.708 [0.701-0.715] for temporal validation) as well as lead-time before deterioration events (median 11 hours vs 3 hours; P = .004). However, LGBM performance as evaluated by precision recall curve was lesser in the temporal validation cohort with associated decreased positive predictive value (6% vs 29%) and increased number needed to evaluate (17 vs 3) compared with I-PEWS.

CONCLUSIONS

Our electronic health record based machine learning model demonstrated improved AUROC and lead-time in predicting clinical deterioration in pediatric inpatients 24 to 48 hours in advance compared with I-PEWS. Further work is needed to optimize model positive predictive value to allow for integration into clinical practice.

Development of a Human Immunodeficiency Virus Risk Prediction Model Using Electronic Health Record Data From an Academic Health System in the Southern United States

BACKGROUND

Human immunodeficiency virus (HIV) pre-exposure prophylaxis (PrEP) is underutilized in the southern United States. Rapid identification of individuals vulnerable to diagnosis of HIV using electronic health record (EHR)-based tools may augment PrEP uptake in the region.

METHODS

Using machine learning, we developed EHR-based models to predict incident HIV diagnosis as a surrogate for PrEP candidacy. We included patients from a southern medical system with encounters between October 2014 and August 2016, training the model to predict incident HIV diagnosis between September 2016 and August 2018. We obtained 74 EHR variables as potential predictors. We compared Extreme Gradient Boosting (XGBoost) versus least absolute shrinkage selection operator (LASSO) logistic regression models, and assessed performance, overall and among women, using area under the receiver operating characteristic curve (AUROC) and area under precision recall curve (AUPRC).

RESULTS

Of 998 787 eligible patients, 162 had an incident HIV diagnosis, of whom 49 were women. The XGBoost model outperformed the LASSO model for the total cohort, achieving an AUROC of 0.89 and AUPRC of 0.01. The female-only cohort XGBoost model resulted in an AUROC of 0.78 and AUPRC of 0.00025. The most predictive variables for the overall cohort were race, sex, and male partner. The strongest positive predictors for the female-only cohort were history of pelvic inflammatory disease, drug use, and tobacco use.

CONCLUSIONS

Our machine-learning models were able to effectively predict incident HIV diagnoses including among women. This study establishes feasibility of using these models to identify persons most suitable for PrEP in the South.

Seven key parameters that facilitate clinical pharmacy practice: a comparison between Israel and the United States

Clinical pharmacists have advanced training that enables them to manage medication therapy, including prescribing, titrating, and discontinuing medications, in order to achieve therapeutic goals. In some countries, such as the United States, advances in training, responsibility, legal frameworks, and public acceptance of new roles have proceeded in parallel to expand the scope and contribution of clinical pharmacists over several decades. In this manuscript, we detail seven discrete key parameters of professional advancement for clinical pharmacists, corresponding to the seven areas in which they must advance in order to contribute fully to delivering high-quality medical care. For each key parameter, we briefly summarize the progress made in the United States to date, as well as goals for future progress. We then compare this to the development of the analogous key parameter in Israel. We found that on some key parameters, the development of clinical pharmacy in Israel lags behind the United States. This manuscript can provide a roadmap for the future advancement of clinical pharmacy in Israel, toward its full realization as a profession that can contribute to delivering high-quality medical care.

Association between Flash Glucose Monitors and A1C: A Retrospective Pre-Post Analysis

Background: Randomized controlled trials have investigated the effect of continuous glucose monitors on hemoglobin A1C; however, more evidence is needed to justify their use and expand insurance coverage. Additionally, there are few published studies investigating the A1C lowering effect of flash glucose monitors (FGMs) in broad diabetes populations with varying insulin requirements. This analysis aimed to help fill this gap in medical literature and help clinicians evaluate costs/benefits when considering FGMs for their patients with diabetes. Objectives: To determine the association between FGM use and A1C reduction in patients with type 1 or type 2 diabetes mellitus regardless of insulin dependence. Methods: Pharmacy dispensing records were used to identify patients for inclusion. Patients who received a FGM from a University of Utah pharmacy between July 7, 2018 and July 7, 2020 were included. Patients who did not receive at least an 84-day supply of FGM sensors or did not have a baseline or follow-up A1C were excluded. Baseline and follow-up A1Cs, defined as A1Cs that are within one year before and 3-12 months after the FGM dispense date, were collected for each patient. New diabetes medications within a six-month window of the initial FGM dispense date were also recorded. Outcome variables were collected before and after patients received their first FGM (pre-FGM vs. post-FGM, respectively). The primary outcome was the difference between baseline and follow-up A1C for each patient. Secondary outcomes were the difference in baseline and follow-up A1C for various clinical subgroups within the overall sample. Descriptive statistics were used to summarize baseline characteristics and outcome data. Paired Student's t-tests were used to evaluate outcome differences (α=0.05). Results: Fifty-seven patients (50.8% male; mean age: 49 years) were included. For the primary outcome, the average baseline and follow-up A1Cs were 9.33% and 8.32%, respectively for a difference of -1.01% ([95%CI -1.31:-0.72]; p<0.0001). Conclusions: The use of FGMs is associated with decreases in A1C within a cohort of patients at one health system. Further effort to determine impact of FGM on clinical and economic outcomes is warranted.

Wearable sensors enable personalized predictions of clinical laboratory measurements

Vital signs, including heart rate and body temperature, are useful in detecting or monitoring medical conditions, but are typically measured in the clinic and require follow-up laboratory testing for more definitive diagnoses. Here we examined whether vital signs as measured by consumer wearable devices (that is, continuously monitored heart rate, body temperature, electrodermal activity and movement) can predict clinical laboratory test results using machine learning models, including random forest and Lasso models. Our results demonstrate that vital sign data collected from wearables give a more consistent and precise depiction of resting heart rate than do measurements taken in the clinic. Vital sign data collected from wearables can also predict several clinical laboratory measurements with lower prediction error than predictions made using clinically obtained vital sign measurements. The length of time over which vital signs are monitored and the proximity of the monitoring period to the date of prediction play a critical role in the performance of the machine learning models. These results demonstrate the value of commercial wearable devices for continuous and longitudinal assessment of physiological measurements that today can be measured only with clinical laboratory tests.

Effect of different scoring approaches upon credit assignment when using Multiple True-False items in dental undergraduate examinations

INTRODUCTION

Various scoring approaches for Multiple True-False (MTF) items exist. This study aimed at comparing scoring results obtained with different scoring approaches and to assess the effect of item cues on each scoring approaches' result.

MATERIALS AND METHODS

Different scoring approaches (MTF, Count-2, Count-3, "Vorkauf-Method," PS₅₀ , Dichotomized MTF, "Blasberg-Method," Multiple response (MR), Correction for Guessing, "Ripkey-Method," Morgan-Method, Balanced Scoring Method) were retrospectively applied to all MTF items used within electronic examinations of undergraduate dental students at the University Medical Center Göttingen in the winter term 2016/2017 (1297 marking events). Item quality was evaluated regarding formal parameters such as presence of cues and correctness of content. Differences between scoring results of all scoring approaches and the differences between each methods' scoring results of items with and without cues were calculated by Wilcoxon rank sum tests (P < .05).

RESULTS

Average scoring results per item highly differed between the scoring approaches and ranged from 0.46 (MR) to 0.92 (Dichotomized MTF). Presence of cues leads to significantly higher scoring in case of all scoring approaches (P < .001; +0.14 on average). However, effect of cues differed amongst scoring approaches and ranged from +0.04 (Dichotomized MTF) to +0.20 (MR).

CONCLUSION

Scoring of MTF items is complex. The data presented in this manuscript may help educators make informed choices about scoring algorithms.

Convenient and efficient synthesis of functionalized unsymmetrical Z-alkenyl disulfanes

We developed a simple and efficient method for the synthesis of functionalized unsymmetrical Z-alkenyl disulfanes under mild conditions in moderate to good yields. The designed method is based on the reaction of Z-alkenyl thiotosylates with thiols in the presence of base. The developed method allows the preparation of unsymmetrical Z-alkenyl disulfanes bearing additional hydroxy, carboxy, or amino functionalities.

We developed a simple and efficient method for the synthesis of functionalized unsymmetrical Z-alkenyl disulfanes under mild conditions in moderate to good yields.

Convenient and efficient synthesis of functionalized unsymmetrical alkynyl sulfides

We developed a simple and efficient method for the synthesis of functionalized unsymmetrical alkynyl sulfides under mild conditions in good yields.

Comparison between tracheal foreign body and bronchial foreign body: a review of 1,007 cases

OBJECTIVE

To determine the differences between tracheal foreign body aspiration and bronchial foreign body aspiration.

METHODS

This retrospective study includes 1007 patients with the diagnosis of foreign body aspiration according to rigid bronchoscopy. Patients were divided into two groups: tracheal and bronchial foreign body groups. Age, sex, clinical presentation, pre-operative radiographic findings, rigid bronchoscopy findings, types of foreign body, and the complications of each group were observed and analyzed.

RESULTS

Out of 989 study patients, there were 146 patients (14.5%) in the tracheal foreign body group and 843 patients (83.7%) in the bronchial foreign body group. Eighteen patients with FBs located in the larynx and presenting with multiple FBs located in the tracheal and bronchial regions were excluded from this study. The majority of the patients were under the age of three for both groups. The male to female ratio was significantly higher in the bronchial foreign body group (P<0.001). More patients in the bronchial foreign body group were misdiagnosed upon first clinical visit (P=0.001), referred from another hospital (P<0.05), or had delayed diagnosis (P<0.05). The most prominent symptom in both groups was cough, followed by decreased breath sounds, wheezing, and dyspnea. More patients in the bronchial foreign body group experienced decreased breath sounds (P<0.001), while more patients in the tracheal foreign body group experienced dyspnea (P<0.05). Chest fluoroscopy abnormalities were observed at a higher frequency in the bronchial foreign body group (P<0.001). Lateral neck X-ray results showed higher frequencies of abnormalities in the tracheal foreign body patients. Out of 30 patients in the tracheal foreign body group received a CT scan, 27 had abnormal scan results, while all 253 patients in the bronchial foreign body subgroup had abnormal results. The majority of foreign bodies were organic materials and were removed by rigid bronchoscopy at the first clinical session in 96.6% of tracheal foreign body cases and 96.0% of bronchial foreign body cases (P=0.727). Major complications, including one death, were observed only in the bronchial foreign body group.

CONCLUSIONS

The nature of tracheal foreign body aspiration is different from bronchial aspiration. Clinical presentation and pre-operative radiographic findings are helpful for diagnosis. The clinician should understand the differences between tracheal and bronchial FB cases and provide the appropriate management when either is presented.

Self-association of facially amphiphilic methylene bridged glycoluril dimers

[structure: see text] Facially amphiphilic derivatives of methylene bridged glycoluril dimers are a versatile model system for systematic studies of self-assembly in water. Thorough physical organic characterization, including analytical ultracentrifugation, a technique rarely used in synthetic self-assembly studies, allows us to conclude that this class of molecules undergoes hydrophobically driven self-association to yield tightly associated discrete dimeric assemblies.

Tumor necrosis factor alpha regulates CXC chemokine receptor expression and function

The alpha chemokine family is central to the participation of neutrophils in the acute inflammatory response. These substances interact with neutrophils through two cell surface receptors, CXCR-1 and CXCR-2 (formally known as IL-8R-1 and IL-8R-2). We investigated the possible regulatory effects of tumor necrosis factor alpha (TNFalpha) pretreatment on CXCR-1 and CXCR-2. To this end, we examined these receptors with flow cytometry, radioligand binding, Northern blot analyzes, calcium mobilization, and chemotaxis experiments on human neutrophils. In flow cytometry experiments, TNFalpha pretreatment substantially decreased cell surface CXCR-2 receptor levels but showed partial recovery at 120 min. On the other hand, CXCR-1 receptor levels had a sharp decline at 15 min and maintained that level to 120 min. Northern blot analyzes showed that mRNA levels of both IL-8 receptors were essentially unchanged after 45 min of TNFalpha pretreatment, but declined markedly following 2 h of pretreatment. Chemotaxis experiments on cells treated with TNFalpha for 5-120 min showed a substantial down-regulation of chemotaxis to IL-8 and GROalpha. This was noted to be much greater than the decline in cell surface receptors. Calcium mobilization experiments revealed minimal inhibition of the IL-8-induced increase in calcium after pretreatment with TNFalpha, but the response to NAP-2 was substantially inhibited. The data demonstrate differential regulation of the IL-8 receptor.

Defining the interleukin-8-binding domain of heparan sulfate

Interleukin-8, a member of the CXC chemokine family, has been shown to bind to glycosaminoglycans. It has been suggested that heparan sulfate on cell surfaces could provide specific ligand sites on endothelial cells to retain the highly diffusible inflammatory chemokine for presentation to leukocytes. By using selectively modified heparin and heparan sulfate fragments in a nitrocellulose filter trapping system, we have analyzed sequence requirements for interleukin-8 binding to heparin/heparan sulfate. We demonstrate that the affinity of a monomeric interleukin-8 molecule for heparin/heparan sulfate is too weak to allow binding at physiological ionic strength, whereas the dimeric form of the protein mediates binding to two sulfated domains of heparan sulfate. These domains, each an N-sulfated block of approximately 6 monosaccharide units, are contained within an approximately 22-24-mer sequence and are separated by a region of </=14 monosaccharide residues that may be fully N-acetylated. Binding to interleukin-8 correlates with the occurrence of the di-O-sulfated disaccharide unit -IdceA(2-OSO3)-GlcNSO3(6-OSO3)-. We suggest that the heparan sulfate sequence binds in horseshoe fashion over two antiparallel-oriented helical regions on the dimeric protein.

The effects of dilution on the outcome of pooled plasma testing with HIV type 1 (HIV-1) RNA genome amplification as compared to the outcome of individual-unit testing with other HIV-1 markers

BACKGROUND

Proposed testing of large plasma pools with genome amplification technology (GAT) for detection of transfusion-transmissible viruses may have unanticipated complications not associated with individual unit testing. One such potential complication, the effect of dilution resulting from pool formation, was the subject of the present study.

STUDY DESIGN AND METHODS

Specimens from three plasma donor HIV type 1 (HIV-1) seroconversion panels were tested with a quantitative HIV-1 RNA GAT assay (lower detection limit, 400 copies). GAT results were compared to HIV-1 p24 antigen and anti-HIV-1/2 enzyme immunoassay results. Effects of dilution on the detection of GAT-positive panel specimens were assessed by terminal dilution with pooled volunteer-donor EDTA plasma samples.

RESULTS

Low HIV-1 RNA copy numbers (755 and 890 copies/0.1-mL input) that were detectable in two individual plasma specimens before HIV-1 p24 antigen were subsequently undetectable by GAT upon dilution with an equal volume of nonreactive plasma from a single donor. HIV-1 RNA at higher copy numbers (15,500 copies/0.1-mL input) in an HIV-1 p24 antigen-reactive and anti-HIV-1/2-nonreactive specimen was undetectable when diluted to 1-in-50 (1-in-50). Terminal dilution of seven HIV-1 RNA-containing plasma panel specimens indicated a proportional loss of HIV-1 RNA detectability with increasing dilution.

CONCLUSION

GAT for detection of HIV-1 RNA in individual specimens was more sensitive than other HIV markers. For pooled plasma testing, GAT-independent constraints, such as effects of dilution, may preclude the use of GAT detection as a replacement for individual unit testing with HIV serologic assays.

Effects of specimen collection, processing, and storage conditions on stability of human immunodeficiency virus type 1 RNA levels in plasma

To define the optimal blood collection parameters for plasma human immunodeficiency virus type 1 (HIV-1) viral load testing, plasma HIV-1 RNA levels were quantitated with the NASBA HIV-1 RNA QT System from blood specimens that were collected, processed, and stored under a variety of conditions that might have affected HIV-1 RNA stability. We determined that when whole blood was processed within 2 h of specimen collection the levels of HIV-1 RNA detected in EDTA-, heparin-, and acid citrate dextrose (ACD)-anticoagulated plasma samples were comparable. The levels of HIV-1 RNA in serum specimens (mean = 4.126 log units) were significantly lower (P < 0.01) than the levels in corresponding plasma samples (mean = 4.501 log units). One cycle of freeze-thaw (-70 degrees C) did not significantly reduce the level of HIV-1 RNA detected in EDTA-, heparin-, or ACD-anticoagulated plasmas. The EDTA-anticoagulated plasmas showed the smallest decrease in HIV-1 RNA copies (0.050 log units). HIV-1 RNA levels decreased over a 6-month time period in serum as well as in EDTA-, ACD-, and heparin-anticoagulated plasmas stored at -70 degrees C. However, the only significant decreases were for serum (mean decrease = 0.317 log units) and heparin-anticoagulated samples (mean decrease = 0.384 log units). A comparison of the levels of HIV-1 RNA in cell-free plasma collected in VACUTAINER EDTA Plasma Preparation Tubes and in standard VACUTAINER EDTA tubes determined that HIV-1 RNA levels were stable for up to 30 h after collection when stored at either room temperature (mean standard deviation [SD] = +/- 0.101 log units) or at 4 degrees C (mean SD = +/- 0.102 log units) as cell-free plasma or as EDTA-anticoagulated whole blood (mean SD = +/- 0.109 log units). These data indicate that EDTA-anticoagulated plasma is the most suitable and stable matrix for HIV-1 RNA quantitation.

High-affinity binding of corticosterone to mammalian neuronal membranes: possible role of corticosteroid binding globulin

The signal transduction mechanisms mediating rapid steroid actions are poorly understood. To characterize corticosteroid interaction with neuronal membranes in a species with rapid behavioral responses to corticosterone, we examined [3H]corticosterone binding to membranes prepared from prairie vole brains. At 22 degrees C, the rates of association and dissociation of [3H]corticosterone with well-washed synaptosomal membranes were very rapid. Specific binding was characterized by high affinity (Kd = 6.01 nM) and low density (Bmax = 63.1 fmol/mg protein). The binding sites were highly specific for naturally occurring glucocorticoids and the density of binding sites appeared to vary by neuroanatomical region. Unlike most G-protein-coupled receptors, the high-affinity binding of [3H]corticosterone to vole brain membranes was unaffected by the addition of Mg2+ or guanyl nucleotides. Surprisingly, saline perfusion of vole brains before tissue homogenization greatly reduced high-affinity binding. In addition, the affinity and specificity of corticosteroid binding sites were similar in vole neuronal membranes and vole plasma. These data suggest that corticosteroid binding globulins may facilitate [3H]corticosterone binding to neuronal membranes. However, the addition of blood to perfused brains before homogenization did not restore high-affinity binding, so the role of plasma binding globulins is unclear. Whether these binding phenomena represent a technical artifact or a regulatory mechanism for corticosteroid action has yet to be determined.

beta-phosphorylated nitroxides in the pyrrolidine series: reduction by ascorbate

Reduction-resistant nitroxides are particularly interesting for biomedical applications. beta-Phosphorylated pyrrolidinyl nitroxides, a new series of stable pyrrolidinoxyl radicals prepared in our laboratory, were tested toward ascorbate reduction in phosphate buffer at pH 7.4. The kinetics of decay were monitored by ESR and compared to those of two reference nitroxides, PCA and Proxyl. The introduction of a beta-phosphoryl group on a pyrrolidinoxyl structure resulted in a moderate increase of the reduction rate constant. However, inside the phosphorylated series, slight structural modifications can induce significant changes in the rate constants.

Clinical phenotypes of different MPZ (P0) mutations may include Charcot-Marie-Tooth type 1B, Dejerine-Sottas, and congenital hypomyelination

Hereditary demyelinating peripheral neuropathies consist of a heterogeneous group of genetic disorders that includes hereditary neuropathy with liability to pressure palsies (HNPP), Charcot-Marie-Tooth disease (CMT), Dejerine-Sottas syndrome (DSS), and congenital hypomyelination (CH). The clinical classification of these neuropathies into discrete categories can sometimes be difficult because there can be both clinical and pathologic variation and overlap between these disorders. We have identified five novel mutations in the myelin protein zero (MPZ) gene, encoding the major structural protein (P0) of peripheral nerve myelin, in patients with either CMT1B, DSS, or CH. This finding suggests that these disorders may not be distinct pathophysiologic entities, but rather represent a spectrum of related "myelinopathies" due to an underlying defect in myelination. Furthermore, we hypothesize the differences in clinical severity seen with mutations in MPZ are related to the type of mutation and its subsequent effect on protein function (i.e., loss of function versus dominant negative).

Multiplex PCR amplification from the CFTR gene using DNA prepared from buccal brushes/swabs

Traditionally, DNA used for PCR-based diagnostic analysis has originated from white cells fractionated from whole blood. Although this method yields substantial quantities of DNA, there are some drawbacks to the procedure, including the inconvenience of drawing blood, risk of exposure to blood-borne pathogens, liquid sample handling, and the somewhat involved extraction procedure. Alternatively, DNA for genetic diagnosis has been derived from finger stick blood samples, hair roots, cheek scrapings, and urine samples. Oral saline rinses have also been used extensively as a means of collecting buccal epithelial cells as a DNA source. However, this method still requires liquid sample handling. Herein, we present our results involving the rapid extraction of DNA from buccal cells collected on cytology brushes and swabs for use in PCR reactions, specifically the multiplex amplification of 5 exons within the CFTR gene. The quality of DNA isolated from buccal cells, collected in this manner, has been sufficient to reproducibly support multiplex amplification. Cheek cell samples and the DNA prepared from them as described here are highly stable. The success rate of PCR amplification on DNA prepared from buccal cells is 99%. In a blind study comparing the analysis of 12 mutations responsible for cystic fibrosis in multiplex products amplified with DNA from both blood and buccal cell samples from 464 individuals, there was 100% correlation of results for blood and cheek cell DNA, validating the use of DNA extracted from cheek cells collected on cytology brushes for use in genetic testing.

Amino terminus of the interleukin-8 receptor is a major determinant of receptor subtype specificity

Interleukin-8 (IL-8) is a key mediator in the migration of neutrophils from the circulation to the site of inflammation in the tissue. IL-8 is secreted by many cell types in response to proinflammatory stimuli such as interleukin 1, tumor necrosis factor, and lipopolysaccharide and is a potent chemoattractant and activator of neutrophils. Neutrophil activating peptide-2 (NAP-2) and melanoma growth-stimulatory activity (MGSA/GRO) are structurally and functionally related to IL-8 and, like IL-8, bind to specific G protein-coupled receptors on neutrophils. In the present study two closely related cloned IL-8 receptor subtypes are characterized by expression of the cDNA clones in monkey kidney cells (COS-7) or chinese hamster ovary cells and analysis of their ligand binding profiles. Both receptor subtypes bind 125I-labeled IL-8 with similar high affinity, however, the F3R receptor binds IL-8 exclusively, while the 4Ab receptor binds both IL-8 and MGSA/GRO with high affinity and NAP-2 with lesser affinity. Furthermore, we demonstrate with the use of intersubtype chimeric receptors that the specificity of ligand binding to both IL-8 receptor subtypes is dictated by the heterogeneous NH2-terminal domain. The F3R receptor is representative of a restricted IL-8 receptor subtype, and 4Ab represents a nonrestricted receptor subtype. It is proposed that these subtypes be named IL-8 receptors alpha and beta, respectively.

Ribosomal RNA and rDNA sequence analyses

The potential of ribosomal (r) RNA and the encoding genes (rDNA) to elucidate natural relationships has been dramatically extended by improved sequencing approaches and the application of polymerase chain reaction. Sequence information on 16S and 23S rRNA/DNA from 69 strains of 53 Streptomyces species allows determination of regions that can be used as target sites for diagnostic probes, and for amplification and sequencing primers. To generate phylogenetic trees, sequence similarities are converted into distance values. The topologies of the trees based on different parts of the molecule are compared among each other and to the numerical phenotypic clustering of the strains.

Designation of Streptomycete 16S and 23S rRNA-based target regions for oligonucleotide probes

The 16S and 23S rRNA of various Streptomyces species were partially sequenced and screened for the presence of stretches that could define all members of the genus, groups of species, or individual species. Nucleotide 929 (Streptomyces ambofaciens nomenclature [J.L. Pernodet, M.T. Alegre, F. Boccard, and M. Guerineau, Gene 79:33-46, 1989]) is a nucleotide highly unique to Streptomyces species which, in combination with flanking regions, allowed the designation of a genus-specific probe. Regions 158 through 203 of the 16S rRNA and 1518 through 1645 of the 23S rRNA (helix 54 [Pernodet et al., Gene 79:33-46, 1989]) have a high potential to define species, whereas the degree of variation in regions 982 through 998 and 1102 through 1122 of the 16S rRNA is less pronounced but characteristic for at least certain species. Alone or in combination with each other, these regions may serve as target sites for synthetic oligonucleotide probes and primers to be used in the determination of pure cultures and in the characterization of community structures. The specificity of several probes is demonstrated by dot blot hybridization.

Ammonia and lactate: differential information on monitoring training load in sprint events

Two hypotheses were tested concerning training relevance of ammonia in capillary blood compared with lactate after extensive and intensive high-paced runs. 1. There is a load threshold at which ammonia concentration deviates statistically significantly from the pre-load level, while lactate indicates already anaerobic metabolic processes at extensive training loads. Increased ammonia concentration is understood as the activation of type IIb fibers. 2. The increase in ammonia is primarily a consequence of increasing training load intensity. The hypotheses were tested in a field experiment with male sprinters n = 13. The experimental plan followed a design of repeated measures in a 4 x 4 Latin-square. The subjects completed four high-pace runs (300 m) at 82.5%, 85%, 87.5%, and 90% of the maximum running intensity (identified in a contest). The results confirmed our first hypothesis. Significant increase in ammonia concentration was not found until after four runs at an intensity of 87.5% or after one 300-m run at maximum running speed. In contrast to this, a glycolytic reaction became evident in one run at 82.5% of the maximum intensity. Lactate concentration exceeded the anaerobic threshold at this point. Definite instructions for training practice cannot be made at the present state of research.

Amycolatopsis methanolica sp. nov., a facultatively methylotrophic actinomycete

The generic position of a gram-positive, facultatively methylotrophic actinomycete known as Nocardia sp. strain 239 was determined by comparing reverse transcriptase sequences of 16S rRNA. The assignment of the organism to the genus Amycolatopsis was strongly supported by chemotaxonomic and morphological data. A comparison with the type strains of validly described Amycolatopsis species showed that the organism formed the nucleus of a new species. The name proposed for this new species is Amycolatopsis methanolica. The organism has been deposited in the National Collection of Industrial Bacteria as NCIB 11946.

Nucleotide sequence of 16S rRNA and phylogenetic position of the green sulfur bacterium Clathrochloris sulfurica

The almost complete primary structure of the 16S rRNA from the green sulfur bacterium "Clathrochloris sulfurica" was determined by reverse transcriptase sequencing. Comparison of defined invariable parts of the molecule from representatives of 9 major lines of descent from the eubacterial kingdom shows C. sulfurica to be highly related to Chlorobium vibrioforme. The relationship between "Clathrochloris" and Chlorobium is in accord with the present allocation of these two genera into the family Chlorobiaceae.

Clinical use of the total dose intravenous infusion of iron dextran

Eighty-seven patients with anemia and absent bone marrow hemosiderin were given treatment with total dose intravenous infusions of iron dextran. The effect of rate of infusion and premedication with diphenhydramine, aspirin, and methylprednisolone on acute and delayed reactions was assessed. All patients were monitored for 72 hours after infusion. Two patients reacted to the test dose. One responded with generalized body pain that lasted approximately 5 minutes. In one an anaphylactoid reaction developed, which was promptly terminated by intravenous methylprednisolone, subcutaneous epinephrine, and intravenous diphenhydramine. Transient delayed adverse reactions easily controlled by nonsteroidal anti-inflammatory drugs occurred in 37 patients. The most common delayed reaction was a syndrome characterized by arthralgia, myalgia, and fever. Seven subjects had a chronic disease in addition to anemia with absent bone marrow iron. In all seven normal hemoglobin and hematocrit values were attained after treatment. The results of our experience with total dose intravenous iron dextran therapy suggest that it be the preferred method of replenishment in clinical situations where parenteral administration of iron is indicated. An unexpected benefit was the efficaciousness of this method of administration in patients with iron deficiency and coexisting chronic disease. A protocol for its administration is proposed.

Acquired immune deficiency syndrome presenting as bone marrow and mediastinal cryptococcosis

Disseminated cryptococcosis developed as the first manifestation of the acquired immune deficiency syndrome in a previously healthy Haitian man. Following presentation with a febrile illness that included massive mediastinal and peripheral lymphadenopathy, the patient died of overwhelming pulmonary, visceral, and meningeal cryptococcosis.

Bacteremic W-135 meningococcal pneumonia

Two epidemiologically unrelated cases of bacteremic meningococcal pneumonia are reported. Both patients were civilians without antecedent viral illness. The organism involved was Neisseria meningitidis, Group W-135, a serogroup of rapidly increasing importance in the United States. The difficulties in diagnosis and scope of meningococcal pneumonia are discussed.

Etiology of hepatitis B surface antigen (HBsAg)-negative chronic hepatitis

A study was undertaken to elucidate the etiology of HBsAg-negative chronic hepatitis. Form 37 individuals with HBsAg-negative chronic hepatitis, 11 had liver membrane autoantibody (LMA) and were thus classified as autoimmune. 6 patients had anti-HBc, 1 of which was also positive for LMA. The majority of individuals with HBsAg-negative chronic hepatitis had antibodies to hepatitis A antigen (anti-HAV), in general at low titer. We conclude from our data that hepatitis A and hepatitis B virus infections are unlikely to play a significant role in inducing or maintaining HBs-Ag-negative chronic hepatitis. The etiological role of non-A non-B hepatitis agent(s) is difficult to estimate and must await the detection of appropriate markers for type non-A non-B hepatitis.