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Biomedical subjects

J Ballard

Publications and source records attributed to J Ballard.

At least 19 recordsLinked to original sources
PubMed2002

Anterior physeal separation. A sign indicating a high risk for avascular necrosis after slipped capital femoral epiphysis.

A study of 78 children (110 hips) was undertaken in an attempt to assess the risk of avascular necrosis (AVN) after slipped capital femoral epiphysis based on the radiological appearances of the hip at the time of presentation. Physeal separation, which was defined as the amount of separation of the anterior lip of the epiphysis from the metaphysis on the frog lateral view, was assessed. Of the eight hips which developed AVN, seven had anterior physeal separation. We conclude that anterior physeal separation is associated with a high incidence of subsequent AVN after slipped capital femoral epiphysis and that screw fixation may not be appropriate in these patients.

Adolescent↗
PubMed2001

Albuterol delivery in a neonatal ventilated lung model: Nebulization versus chlorofluorocarbon- and hydrofluoroalkane-pressurized metered dose inhalers.

The aim of this study was to compare albuterol delivery in a neonatal ventilated lung model, using three delivery methods: 1) jet nebulizer; 2) chlorofluorocarbon-pressurized metered dose inhaler (CFC-MDI) actuated into an ACE(R) spacer; and 3) hydrofluoroalkane-pressurized MDI (HFA-MDI) actuated into an ACE(R) spacer. The bench model consisted of a mechanically ventilated infant test lung with ventilator settings to simulate a very low birth weight neonate with moderate lung disease. Albuterol solution (0.5%) was nebulized at the humidifier and temperature port, 125 cm and 30 cm from the Y-piece, respectively. Albuterol metered dose inhalers (MDIs) were actuated into an ACE(R) spacer that was tested in two positions: 1) inline between the endotracheal (ET) tube and the Y-piece; and 2) attached to the ET tube and administered by manual ventilation. Albuterol was collected on a filter at the distal end of the ET tube and was quantitatively analyzed by high performance liquid chromatography. Albuterol delivery by CFC-MDI (position 1, 4.8 +/- 1.0%, vs. position 2, 3.8 +/- 1.6%, P > 0.05) and HFA-MDI (position 1, 5.7 +/- 1.6%, vs. position 2, 5.5 +/- 2.4%, P > 0.05) were significantly greater than delivery by nebulization at 30 cm (0.16 +/- 0.07%) and 125 cm (0.15 +/- 0.03%) from the Y-piece (P < 0.001). A single actuation of albuterol MDI delivered the equivalent of nebulizing 2.5-3.7 mg of albuterol solution. We conclude that albuterol administered by MDI and ACE(R) spacer resulted in more efficient delivery than by nebulization in this mechanically ventilated neonatal lung model. There was no significant difference in drug delivery between CFC-MDI and HFA-MDI; nor did the placement of the spacer significantly affect drug delivery.

Administration, Inhalation↗
PubMed2001

Community health promotion and the randomized controlled trial: approaches to finding common ground.

The randomized controlled trial is the model against which research designs are judged. Concurrent with rising standards of evidence, however, is a trend toward greater inclusiveness in community-based research, exemplified by the Centers for Disease Control and Prevention-funded Prevention Research Centers, a nationwide network of academic-community partnerships engaged in community-based health promotion and disease prevention research. The Yale-Griffin Prevention Research Center developed a replicable process for devising randomized trials in the context of community collaboration. Several examples of trials developed this way and their interim results are provided.

Cardiovascular Diseases↗
PubMed1999

A High-Resolution Analysis of the nu3 and nu9 Absorption Bands of Difluoromethane.

High-resolution (up to 0.0016 cm-1 unapodized) room temperature and collision-cooled (at approximately 100 K) mid-infrared (1000-1300 cm-1, 7.7-10 µm) absorption measurements of the nu3 and nu9 vibrational bands of difluoromethane (CH2F2, HFC-32) vapor were made with a Fourier transform spectrometer. A ro-vibrational analysis of over 900 infrared transitions has yielded quartic rotational constants, and the C-type Coriolis coupling xic39 = 0.28802(11) cm-1. The results are compared with a previous analysis [J. Matuszeski and M. Marshall, Spectrochim. Acta. A 52, 1069-1077 (1996)] of a jet-cooled spectrum. Copyright 1999 Academic Press.

Journal Article↗
PubMed1998

Sweet's syndrome without granulocytosis.

BACKGROUND: Sweet's syndrome (SS), acute febrile neutrophilic dermatosis, has been linked to hematologic malignancies and presents with characteristic edematous dermal plaques. Peripheral blood neutrophilia is frequently seen in association with SS and is one of the diagnostic criteria. OBJECTIVE: To report the clinical, laboratory, and hematologic data of four patients with myeloid leukemia who developed SS after chemotherapy. Three of these patients were neutropenic. METHODS: A retrospective study of four patients with SS and hematologic malignancies was undertaken. Three patients had de novo acute myelogenous leukemia and one was in the acute blast crisis of chronic myelogenous leukemia. RESULTS: Sweet's syndrome was not originally suspected in these patients because of the low peripheral white blood cell counts caused by chemotherapy. All of the patients presented with fevers, arthralgias, and an eruption. They had been treated with antibiotics because of a presumed infection. Once the correct diagnosis was made and oral prednisolone was started, a rapid response followed. CONCLUSIONS: Sweet's syndrome should be considered in the differential diagnosis when acute myeloid leukemic patients develop skin lesions and unexplained fevers regardless of the peripheral blood counts.

Acute Disease↗
PubMed1996

Comparison of nonrandomized trials with slow-release sodium fluoride with a randomized placebo-controlled trial in postmenopausal osteoporosis.

The results of slow-release sodium fluoride (SR-NaF) treatment in two nonrandomized trials involving 65 patients with postmenopausal osteoporosis from the primary site and 121 patients from collaborative sites were compared with those obtained from 54 treated patients and 56 patients taking placebo from a randomized controlled trial. Spinal fracture data were analyzed separately in mild to moderate bone loss of lumbar spine (baseline L2-L4 bone density [BD] > or = 65% young normal) and in severe bone loss (BD < 65%). Since demographic and fracture data were similar among fluoride-treated patients from the three trials at each stratum of bone loss, their data were combined. In mild to moderate bone loss, SR-NaF treatment in the combined group virtually eliminated new spinal fractures with 96.6% of patients remaining fracture-free. The Fluoride group had a markedly lower individual vertebral fracture rate (0.025 vs. 0.188/patient year, p = 0.0001) and group vertebral fracture rate (0.029 vs. 0.175/patient year, relative risk [RR] 0.12, p = 0.0001) than the Placebo group. In severe bone loss, the combined treated group had a significantly lower new spinal fracture rate than the Placebo group, although the differences were not as marked (group vertebral fracture rate of 0.150 vs. 0.276/patient year, RR 0.54, p = 0.03). In the combined fluoride-treated group, the L2-L4 bone mass rose by 4-6%/year for 4 years, and the femoral neck BD increased by 1-2%/year during first 2 years. The radial shaft BD did not change. The Placebo group did not show a change in bone mass at any site. The prevalence (percentage) of patients with related gastrointestinal side effects and nonvertebral fracture rates did not differ significantly between the combined SR-NaF group and the Placebo group (hip fracture rate of 0.0045/patient year in SR-NaF and 0.0053/patient year in Placebo; appendicular fracture other than hip (see text) rate of 0.0193/patient year in SR-NaF and 0.0159/patient year in Placebo). A subgroup analysis showed a low baseline L2-L4 BD, high prevalent spinal fractures, and reduced body weight to be important determinants of the development of spinal fracture during SR-NaF treatment. Concomitant medications (estrogen, vitamin D, thiazide and thyroid hormone) were not independent predictors of the spinal fracture risk. Only 17% of fluoride-treated patients were nonresponders (new spinal fractures or a fall/no change in L2-L4 bone mass). Thus, the effects of SR-NaF treatment on the spinal fracture rate from nonrandomized trials were similar to those of the treated group of the randomized trial but different from those of the Placebo group. The similarity of response of nonrandomized trials with that of the randomized controlled trial and the resultant combined analysis further validate the efficacy and safety of SR-NaF in the treatment of postmenopausal osteoporosis.

Bone Density↗
PubMed1995

The primary structure of Clostridium septicum alpha-toxin exhibits similarity with that of Aeromonas hydrophila aerolysin.

The gene for Clostridium septicum alpha-toxin was cloned and expressed in Escherichia coli from C. septicum BX96. The toxin was determined to be 443 amino acids in length, with a 31-residue signal peptide that was removed from the toxin during secretion. No extended hydrophobic regions were observed in the mature toxin sequence. Expression of alpha-toxin in E. coli BL21 resulted in the production of ATpro, which was identical to native toxin from C. septicum with respect to activity and activation. The proteolytic activation site for alpha-toxin was determined to be on the carboxy-terminal side of arginine 398, which lies within the sequence KKRRGKR-398SVD. Previous work showing similarities in activation and mechanism between alpha-toxin and Aeromonas hydrophila aerolysin was extended to the primary structures of both toxins. The DNA-derived primary sequence of alpha-toxin exhibited 27% identity and 72% similarity over a 387-residue region with the primary structure of the A. hydrophila aerolysin toxin, a level of similarity heretofore unobserved between toxins produced by a gram-positive organism and a gram-negative organism.

Aeromonas hydrophila↗
PubMed1994

Clinical courses of seven survivors of Clostridium septicum infection and their immunologic responses to alpha toxin.

Clostridium septicum bacteremia typically portends a fulminant disease associated with high mortality. We describe the clinical courses of seven survivors of C. septicum infection and their antibody responses to the alpha toxin produced by C. septicum. Three patients had clinical syndromes ranging from uncomplicated bacteremia to early typhlitis, and three patients had syndromes ranging from abscess to myonecrosis and septic shock. In addition, an AIDS patient who developed septic shock and who had extensive gas in the retroperitoneal musculature did not undergo surgery but survived after receiving antimicrobial therapy and intensive supportive care. Both immunocompetent patients with myonecrosis had detectable IgG to alpha toxin by immunoblot analysis. IgG to alpha toxin was not detected in the four immunocompetent patients who had C. septicum bacteremia but who did not have myonecrosis or in the AIDS patient with myonecrosis. Therefore, humoral responses to alpha toxin during C. septicum infection may be related to the host's clinical syndrome and immune status.

Adult↗
PubMed1994

Genetic analysis of the brahma gene of Drosophila melanogaster and polytene chromosome subdivisions 72AB.

The brahma gene is required for activation of the homeotic genes of the Antennapedia and bithorax complexes in Drosophila. We have isolated and characterized 21 mutations in brahma. We show that both maternal and zygotic functions of brahma are required during embryogenesis. In addition, the severe abnormalities caused by loss of maternal brahma expression show that the homeotic genes are not the only targets for brahma activation. The complex pattern of interallelic complementation for the 21 brahma alleles suggests that brahama may act as a multimer. In addition to mutations in brahma, we have isolated mutations in four other essential genes within polytene chromosome subdivisions 72AB. Based on a compilation of similar studies that include about 24% of the genome, we estimate that about 3600 genes in Drosophila can mutate to cause recessive lethality, with fewer than 900 additional genes essential only for gametogenesis. We have identified three times more transcripts than lethal complementation groups in 72AB. One transcript in 72AB is the product of the essential arf-like gene and encodes a member of the ARF subfamily of small GTP-binding proteins. Two other transcripts are probably the products of a single gene whose protein products are similar to the catalytic subunits of cAMP-dependent protein kinases.

ADP-Ribosylation Factors↗
PubMed1993

Activation and mechanism of Clostridium septicum alpha toxin.

Clostridium septicum produces a single lethal factor, alpha toxin (AT), which is a cytolytic protein with a molecular mass of approximately 48 kDa. The 48 kDa toxin was found to be an inactive protoxin (ATpro) which could be activated via a carboxy-terminal cleavage with trypsin. The cleavage site was located approximately 4 kDa from the carboxy-terminus. Proteolytically activated ATpro had a specific activity of approximately 1.5 x 10(6) haemolytic units mg-1. The trypsin-activated toxin (ATact) was haemolytic, stimulated a prelytic release of potassium ions from erythrocytes which was followed by haemoglobin release, induced channel formation in planar membranes and aggregated into a complex of M(r) > 210,000 on erythrocyte membranes. ATpro did not exhibit these properties. ATact formed pores with a diameter of at least 1.3-1.6 nm. We suggest that pore formation on target cell membranes is responsible for the cytolytic activity of alpha toxin.

Amino Acid Sequence↗
PubMed1992

Purification and characterization of the lethal toxin (alpha-toxin) of Clostridium septicum.

Clostridium septicum lethal (alpha-toxin) was purified and found to be a basic protein (pI 8.4) of approximately 48 kDa that is both lethal and hemolytic. The alpha-toxin had a hemolytic activity of approximately 2 x 10(7) hemolytic units per mg and a 50% lethal dose of approximately 10 micrograms/kg of body weight for mice. The alpha-toxin formed concentration-dependent, sodium dodecyl sulfate-resistant aggregates of approximately 230 kDa. Mice immunized with alpha-toxin showed a significant increase in survival time over mock-immunized mice when challenged with C. septicum. Rabbit polyclonal antibody was generated against the purified toxin and was used to confirm that toxin with the same molecular weight was present in seven different C. septicum isolates. No proteins in the supernatants from cultures of Clostridium perfringens, Clostridium histolyticum, Clostridium chauvoei, or Clostridium difficile were found to react with the C. septicum alpha-toxin-specific antibody.

Animals↗
PubMed1992

Effect of hypercalcemia on renal sympathetic nervous system activity.

Since calcium plays a modulatory role in the activity of the sympathetic nervous system (SNS), in these studies, we have tested the hypothesis that hypercalcemia may alter renal SNS activity, and, consequently, renal function. Acute hypercalcemia was induced in Sprague-Dawley rats by infusion of calcium 30 mg/kg/2 h in 0.45% saline. A control group of rats received only 0.45% saline. Two more groups of rats received either calcium or 0.45% saline 7-10 days after total renal denervation. Calcium infusion increased serum calcium by 1.8 +/- 0.23 mg/dl in rats with intact renal nerves and by 2.7 +/- 0.48 mg/dl in renal denervated rats. Mean arterial pressure and inulin clearance did not change during calcium or 0.45% saline in rats with intact renal nerves. Renal sympathetic nerve activity (RSNA) decreased by 44% in rats infused with calcium, but it did not change in control animals. Calcium caused a significantly greater rise in urine volume, sodium excretion and fractional excretion of sodium than the infusion of 0.45% saline. Rats with renal denervation manifested greater baseline urine volume, sodium excretion and fractional excretion of sodium than rats with intact renal nerves. Infusion of calcium, however, caused no further rise in urine sodium excretion in these animals. alpha-Methyltyrosine, an inhibitor of norepinephrine (NE) synthesis, also increased natriuresis in rats. Calcium reduced by 27% the NE content in the kidney but not in the heart. Methyltyrosine, on the other hand, reduced NE content in both the heart and the kidney.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗