Diagnostic findings in sinonasal aspergillosis in dogs in the United Kingdom: 475 cases (2011-2021)

OBJECTIVES

To describe the diagnostic tests used and their comparative performance in dogs diagnosed with sinonasal aspergillosis in the United Kingdom. A secondary objective was to describe the signalment, clinical findings and common clinicopathologic abnormalities in sinonasal aspergillosis.

MATERIALS AND METHODS

A multi-centre retrospective survey was performed involving 23 referral centres in the United Kingdom to identify dogs diagnosed with sinonasal aspergillosis from January 2011 to December 2021. Dogs were included if fungal plaques were seen during rhinoscopy or if ancillary testing (via histopathology, culture, cytology, serology or PCR) was positive and other differential diagnoses were excluded.

RESULTS

A total of 662 cases were entered into the database across the 23 referral centres. Four hundred and seventy-five cases met the study inclusion criteria. Of these, 419 dogs had fungal plaques and compatible clinical signs. Fungal plaques were not seen in 56 dogs with turbinate destruction that had compatible clinical signs and a positive ancillary test result. Ancillary diagnostics were performed in 312 of 419 (74%) dogs with observed fungal plaques permitting calculation of sensitivity of cytology as 67%, fungal culture 59%, histopathology 47% and PCR 71%.

CLINICAL SIGNIFICANCE

The sensitivities of ancillary diagnostics in this study were lower than previously reported challenging the clinical utility of such tests in sinonasal aspergillosis. Treatment and management decisions should be based on a combination of diagnostics including imaging findings, visual inspection, and ancillary testing, rather than ancillary tests alone.

Letter: Transperineal ultrasonography for ulcerative proctitis- Applicability in the pregnant population?

This article is linked to Sagami et al papers. To view these articles, visit https://doi.org/10.1111/apt.16817 and https://doi.org/10.1111/apt.17705

Impact of a pharmacist led thiopurine monitoring service in outpatients with inflammatory bowel disease

BACKGROUND

Thiopurines are effective therapies for inflammatory bowel disease (IBD), however treatment comes with safety concerns and adverse effects. Knowledge of the impact of pharmacists performing thiopurine monitoring is limited.

AIMS

To determine the impact of a pharmacist led monitoring service in patients with IBD commencing thiopurine therapy managed in the ambulatory care setting.

METHODS

Patients commencing thiopurine therapy for IBD pre and post introduction of a pharmacist led monitoring intervention were assessed. Pre-intervention patients received standard of care, while the post-intervention cohort were managed by the pharmacist. Data was acquired via retrospective audit of hospital medical records. The primary endpoint was the proportion of patients with documented review for thiopurine adverse effects within the initial three weeks. Secondary endpoints included achievement of therapeutic drug levels, persistence with thiopurine therapy, IBD related episodes of care and number of outpatient medical reviews.

RESULTS

Pre and post intervention cohorts comprised of 37 and 33 patients respectively. Pharmacist intervention increased the proportion of patients with documented monitoring within three weeks from 8.1% to 84.8% (p <0.01). No difference in thiopurine dose optimisation was seen (27% vs 27.3%). Persistence with thiopurine therapy increased from 65.7 to 87.9% (p <0.03) at six months. IBD related emergency department presentations were not significantly decreased (8.1% vs 3%, p=0.62). No significant change was observed in hospital admissions (16.2% vs 12.1%, p=0.74) or outpatient medical reviews.

CONCLUSIONS

Pharmacist monitoring of thiopurine therapy initiation in IBD outpatients improves adverse effect monitoring and increases medication persistence. This article is protected by copyright. All rights reserved.

Intensive drug therapy versus standard drug therapy for symptomatic intestinal Crohn's disease strictures (STRIDENT): an open-label, single-centre, randomised controlled trial

BACKGROUND

Strictures are the most common structural complication of Crohn's disease. Surgery and endoscopic balloon dilation are the main treatments; drug therapy has been considered contraindicated. Given that most strictures have an inflammatory component, we aimed to find out whether strictures are responsive to drug treatment and whether intensive drug therapy is more effective than standard drug therapy.

METHODS

This open-label, single-centre, randomised controlled trial was performed in one specialist inflammatory bowel disease centre in Australia. Patients aged 18 years or older with Crohn's disease were included. Eligible patients had a de novo or postoperative anastomotic intestinal stricture on MRI or ileocolonoscopy, symptoms consistent with chronic or subacute intestinal obstruction (postprandial abdominal pain in the presence of a confirmed stricture), and evidence of active intestinal inflammation. Patients were randomly assigned (2:1) to receive intensive high-dose adalimumab (160 mg adalimumab once per week for 4 weeks followed by 40 mg every 2 weeks, with escalation of dose at 4 months and 8 months if assessment of disease activity indicated active inflammation) plus thiopurine (initial dose of azathioprine 2·5 mg/kg or mercaptopurine 1·5 mg/kg, with dose adjustment based on thiopurine metabolite testing) or standard adalimumab monotherapy (160 mg at week 0, 80 mg at week 2, then 40 mg every 2 weeks) using stratified fixed block randomisation. Stratification factors were stricture dilation at study baseline colonoscopy and current biologic drug use. The primary endpoint was improvement (decrease) in the 14-day obstructive symptom score at 12 months by one or more points compared with baseline. This trial is registered with ClinicalTrials.gov, NCT03220841, and is completed.

FINDINGS

Between Sept 10, 2017, and Sept 6, 2019, 123 patients were screened and 77 randomly assigned to intensive adalimumab plus thiopurine treatment (n=52) or standard adalimumab treatment (n=25). At 12 months, improvement in obstructive symptom score was noted in 41 (79%) of 52 patients in the intensive treatment group and 16 (64%) of 25 in the standard treatment group (odds ratio [OR] 2·10 [95% CI 0·73-6·01]; p=0·17). Treatment failure occurred in five (10%) patients in the intensive treatment group versus seven (28%) in the standard treatment group (OR 0·27 [95% CI 0·08-0·97]; p=0·045); four patients in each group required stricture surgery (0·44 [0·10-1·92]; p=0·27). Crohn's Disease Activity Index was less than 150 in 36 (69%) patients in the intensive treatment group versus 15 (60%) in the standard treatment group (1·50 [0·56-4·05]; p=0·42). MRI at 12 months showed improvement using the stricture MaRIA score (≥25%) in 31 (61%) of 51 versus seven (28%) of 25 patients (3·99 [1·41-11·26]; p=0·0091). MRI complete stricture resolution was seen in ten (20%) versus four (16%) patients (1·28 [0·36 to 4·57]; p=0·70). Intestinal ultrasound at 12 months showed improvement (>25%) in bowel wall thickness in 22 (51%) of 43 versus seven (33%) of 21 patients (2·10 [0·71 to 6·21]; p=0·18). Faecal calprotectin normalised in 32 (62%) versus 11 (44%) patients (2·04 [0·77-5·36]; p=0·15). Normalisation of CRP was seen in 32 (62%) versus 11 (44%) patients (2·04 [0·77-5·36]; p=0·15). Eight (15%) patients in the intensive treatment group and four (16%) in the standard treatment group reported serious adverse events. No deaths occurred during the study.

INTERPRETATION

Crohn's disease strictures are responsive to drug treatment. Most patients had improved symptoms and stricture morphology. Treat-to-target therapy intensification resulted in less treatment failure, a reduction in stricture-associated inflammation, and greater improvement in stricture morphology, although these differences were not significantly different from standard therapy.

FUNDING

Australian National Health and Medical Research Council, Gastroenterological Society of Australia Ferring IBD Clinician Establishment Award, Australasian Gastro Intestinal Research Foundation, AbbVie, and the Spotlight Foundation.

A Single Educational Intervention Improves Pregnancy-Related Knowledge and Emotional Health Among Women With IBD Who Are Pregnant or Wish to Conceive

BACKGROUND

There is considerable interest in improving the education and care of women with inflammatory bowel disease (IBD) to improve pregnancy outcomes. Despite increased awareness, not all women with IBD have access to pregnancy-related education and the quality of counseling is variable. We aimed to assess the effectiveness of a simple educational intervention for improving pregnancy-related knowledge and to evaluate the effect of education on patient outcomes including anxiety, depression, and quality of life in women with IBD.

METHODS

This prospective study of women with IBD who were pregnant or planning a pregnancy evaluated the effectiveness of a single gastroenterologist-led educational intervention in improving pregnancy-related knowledge, measured using the Crohn's and Colitis Pregnancy Knowledge score 1 month postintervention. Secondary outcomes included the effect on anxiety and depression, quality of life, medication adherence, and patient satisfaction.

RESULTS

One hundred women with IBD were recruited. Fifty percent were pregnant at the time of the intervention. Baseline knowledge scores were similar independent of the patients' pregnancy status or whether they had previously received counseling from their gastroenterologist. Median Crohn's and Colitis Pregnancy Knowledge scores postintervention (n = 82) were higher than preintervention scores (14/17 vs 10/17; P < 0.001). In addition, 32% of patients had poor knowledge at baseline (score ≤7/17), compared to only 5% after the intervention (P < 0.001). There was a significant improvement in total anxiety and depression and quality of life scores postintervention. Medication adherence and patient satisfaction were excellent.

CONCLUSIONS

Uptake of this gastroenterologist-led educational intervention has the potential to improve pregnancy knowledge, promote medication adherence, and enhance quality of life for women with IBD globally.

Risk of COVID 19 in patients with inflammatory bowel diseases compared to a control population

BACKGROUND

It is unclear whether patients with inflammatory bowel disease (IBD) are at increased risk of COVID-19.

OBJECTIVES

This observational study compared the prevalence of COVID-19 symptoms, diagnosis and hospitalization in IBD patients with a control population with non-inflammatory bowel disorders.

METHODS

This multicentre study, included 2733 outpatients (1397 IBD patients and 1336 controls), from eight major gastrointestinal centres in Lombardy, Italy. Patients were invited to complete a web-based questionnaire regarding demographic, historical and clinical features over the previous 6 weeks. The prevalence of COVID-19 symptoms, diagnosis and hospitalization for COVID-19 was assessed.

RESULTS

1810 patients (64%) responded to the questionnaire (941 IBD patients and 869 controls). IBD patients were significantly younger and of male sex than controls. NSAID use and smoking were more frequent in controls. IBD patients were more likely treated with vitamin-D and vaccinated for influenza. Highly probable COVID-19 on the basis of symptoms and signs was less frequent in the IBD group (3.8% vs 6.3%; OR:0.45, 95%CI:0.28-0.75). IBD patients had a lower rate of nasopharyngeal swab-PCR confirmed diagnosis (0.2% vs 1.2%; OR:0.14, 95%CI:0.03-0.67). There was no difference in hospitalization between the groups (0.1% vs 0.6%; OR:0.14, 95%CI:0.02-1.17).

CONCLUSION

IBD patients do not have an increased risk of COVID-19 specific symptoms or more severe disease compared with a control group of gastroenterology patients.

Infliximab, adalimumab and vedolizumab concentrations across pregnancy and vedolizumab concentrations in infants following intrauterine exposure

BACKGROUND

The impact of pregnancy on levels of biologic agents in patients with IBD is undefined and time to elimination in vedolizumab-exposed infants is unknown.

AIMS

To determine the effect of pregnancy on infliximab, adalimumab and vedolizumab levels and to study infant vedolizumab clearance METHODS: In a prospective observational study, maternal drug levels were measured pre-conception, in each trimester, at delivery and postpartum. The association between drug levels and gestation in weeks was assessed using generalised estimating equation modelling. Infant vedolizumab levels were performed at birth (cord blood), 6 weeks and 3 months or until undetectable.

RESULTS

We included 50 IBD patients (23 on infliximab, 15 on adalimumab and 12 on vedolizumab) with at least two intrapartum observations, plus 5 patients on vedolizumab with only mother and baby samples at delivery. Modelling showed no change in adalimumab levels, an increase in infliximab levels of 0.16 (95% CI 0.08-0.24) µg/L/week (P < 0.001) and a decrease of 0.18 (95% CI: -0.33 to -0.02) µg/L/week (P = 0.03) for vedolizumab. In 17 mother-baby pairs, median infant vedolizumab levels at birth were lower than maternal levels (P < 0.05) with an infant:maternal ratio of 0.7 (IQR 0.5-0.9). Vedolizumab was undetectable between 15 and 16 weeks of age in all 12 infants completing follow-up testing.

CONCLUSIONS

During pregnancy, adalimumab levels remain stable, while infliximab levels increase and vedolizumab levels decrease. However, the increments were small suggesting that intrapartum therapeutic drug monitoring and dose adjustment are not indicated. Unlike infliximab and adalimumab, infant vedolizumab levels are lower in cord blood than in mothers and appear to clear rapidly.

Comparison of Adalimumab Serum Drug Levels When Delivered by Pen Versus Syringe in Patients With Inflammatory Bowel Disease. An International, Multicentre Cohort Analysis

BACKGROUND

Adalimumab is administered via a pre-filled syringe or spring-loaded pen. In a previous study in Crohn's disease, higher drug levels were observed in syringe users. The aim of this study was to evaluate the impact of delivery device on adalimumab drug levels in patients with Crohn's disease.

METHODS

Consecutive Crohn's disease patients treated with maintenance adalimumab [40 mg fortnightly] were recruited from five centres. The first recorded drug level with matched clinical and biochemical markers of disease activity was compared between pen and syringe users.

RESULTS

Of 218 patients, 64% used pen, with a median faecal calprotectin 110 μg/g and serum C-reactive protein 4 mg/L. In comparison to pen, syringe users had higher albumin [39 vs 42 g/L; p = 0.016], lower Harvey-Bradshaw Index [2 vs 1; p = 0.017], and higher rates of concomitant immunomodulation [54% vs 71%; p = 0.014]. Drug levels were equivalent between pen and syringe users [median 5.3 vs 5.2 μg/ml; p = 0.584], even after controlling for disease activity and immunomodulation. Syringe users at Alfred Health had higher drug levels than pen [6.1 vs 4.5 μg/ml; p = 0.039]; a greater proportion achieved therapeutic levels [75% vs 44%; p = 0.045]. A higher proportion of pen users from Saint-Étienne had therapeutic levels [79% vs 42%; p = 0.027], yet no significant difference in drug levels [7.9 vs 4.5 μg/ml; p = 0.119].

CONCLUSIONS

Delivery device does not appear to significantly affect adalimumab drug levels. Given differences between study sites, studies evaluating administration education and technique are warranted.

Cancer Recurrence Following Immune-Suppressive Therapies in Patients With Immune-Mediated Diseases: A Systematic Review and Meta-analysis

BACKGROUND & AIMS

Physicians frequently encounter patients with immune-mediated diseases and a history of malignancy. There are limited data on the safety of immunosuppressive therapy for these patients. Published studies have been small with few events, precluding robust estimates of risk.

METHODS

We searched Medline, EMBASE, and conference proceedings for terms related to immune-mediated disease, immune-suppressive therapy, and cancer recurrence from inception to April 2015. We included 16 studies (9 of patients with rheumatoid arthritis, 8 of patients with inflammatory bowel disease, and 1 of patients with psoriasis) and stratified studies by type of immune-suppressive therapy (monoclonal antibodies to tumor necrosis factor [anti-TNF], conventional immune-modulatory agents, or no immune suppression). A random-effects meta-analysis was performed to calculate the pooled incidence rates as well as risk differences between the various treatments.

RESULTS

Our analysis included 11,702 persons contributing 31,258 person-years (p-y) of follow-up evaluation after a prior diagnosis of cancer. Rates of cancer recurrence were similar among individuals receiving anti-TNF therapy (33.8 per 1000 p-y), immune-modulator therapy (36.2 per 1000 p-y), or no immunosuppression (37.5 per 1000 p-y), but were numerically higher among patients receiving combination immune suppression (54.5 per 1000 p-y) (P > .1 for all). Subgroup analysis of new and recurrent cancers separately, type of immune-modulator therapy, or immune-mediated disease showed similar results, with no increase in risk. We found similar pooled incidence values for new or primary cancers when immunosuppression was initiated within 6 years (33.6 per 1000 p-y for immune-modulatory agents and 43.7 per 1000 p-y for anti-TNF agents) vs more than 6 years after the index cancer (32.9 per 1000 p-y for immune-modulatory agents, P = .86; and 21.0 per 1000 p-y for anti-TNF agents, P = .43).

CONCLUSIONS

In a meta-analysis of 16 studies, we observed similar rates of cancer recurrence among individuals with prior cancer who received no immunosuppression, anti-TNF therapy, immune-modulator therapy, or combination treatments. Prospective studies are needed to ascertain optimal intervals for re-initiation of immune-suppressive therapies for individuals with specific cancers.

New onset idiosyncratic liver enzyme elevations with biological therapy in inflammatory bowel disease

BACKGROUND

Anti-tumour necrosis factor α (anti-TNF) agents have been implicated in drug-induced liver injury. There is minimal data on this occurrence in inflammatory bowel disease (IBD) patients.

AIM

To identify the characteristics of liver enzyme elevations following anti-TNF therapy initiation in IBD.

METHODS

A retrospective cohort of patients initiating anti-TNF therapy were analysed for new onset alanine transaminase (ALT) elevation (≥60 U/L). We collected data on natural history, outcomes and patient characteristics compared with controls with persistent normal liver enzymes. Likelihood of causal association was assessed using the RUCAM score.

RESULTS

From 1753 patients initiating an anti-TNF (1170 infliximab, 575 adalimumab, 8 certolizumab), 102 (6%) developed new onset ALT elevation. In 54 (53%), this could be linked to an alternate aetiology. Among those with idiopathic ALT elevations, the median time to ALT elevation from anti-TNF initiation was 18 weeks and median peak ALT was 96 U/L. Six underwent liver biopsy, all demonstrating hepatitis with autoimmune features. Compared to controls, cases were on a lower dose of infliximab (5.7 vs. 6.7 mg/kg, P = 0.02) but were otherwise similar in body mass index, sex and age. On follow-up, 34 continued the anti-TNF, 14 stopped therapy and 4 initiated steroids. Most (85%) normalised their LFTs after a median of 17 weeks including 28 (82%) of those who continued anti-TNF therapy. Ten patients were transitioned to a second anti-TNF without recurrence.

CONCLUSIONS

ALT elevations occurred in 6% of IBD patients initiating anti-TNF therapy. Most idiopathic elevations were mild, transient and resolved despite therapy continuation.

A randomized controlled study of trimethoprim-sulfamethoxazole versus norfloxacin for the prevention of infection in cirrhotic patients

OBJECTIVE

To prospectively compare norfloxacin (N) with trimethoprim-sulfamethoxazole (T-S) in preventing infection in cirrhotic patients.

METHODS

Cirrhotic patients at high risk of spontaneous bacterial peritonitis (SBP) were recruited and assigned N (400 mg daily) or T-S (160/800 mg daily). Patients were followed up for 12 months. The primary end-point was the incidence of infection. Secondary end-points included the incidence of SBP, bacteremia, extraperitoneal infection requiring antibiotic treatment, liver transplantation, death, side effects and rate of resistance to N or T-S.

RESULTS

A total of 80 patients with a mean age of 53.0 ± 9.3 years were prescribed N (n = 40) or T-S (n = 40). Child-Pugh status, model for end-stage liver disease and risk factors for SBP were similar between the groups. There were 10 episodes of infections in the N group and 9 in the T-S group (P = 0.79). Two patients each in the N and T-S group developed SBP (P = 0.60). There was a difference in the rate of transplantation favoring N (P = 0.03) but not death. The number of adverse events for N (n = 7) and T-S (n = 10) were similar (P = 0.59), with T-S being associated with an increased risk of developing a definite or probable adverse event compared to N (22.5% vs 0%, P = 0.01).

CONCLUSIONS

This study failed to demonstrate a difference between N and T-S groups in their effects on preventing infection in patients with liver cirrhosis. T-S can be considered an alternative first-line therapy for infection prophylaxis.

Risk stratification of upper GI bleeding with an esophageal capsule

BACKGROUND

Analysis of upper GI bleeding (UGIB) presentations to our institutions suggests that many patients admitted for endoscopic investigation could be managed safely as outpatients.

OBJECTIVE

To learn whether an esophageal capsule could identify a low-risk group of patients with UGIB who could safely wait for elective EGD.

DESIGN

Diagnostic, nonrandomized, single-blind (investigator) study.

SETTING

Three tertiary-care referral centers.

PATIENTS

Eighty-three consecutive adult patients referred for management of UGIB.

INTERVENTION

A capsule endoscopy (CE) was performed before EGD for the investigation and management of UGIB.

MAIN OUTCOME MEASUREMENTS

Detection rates of UGIB source and identification of a low-risk group of patients who would have been suitable for outpatient EGD based on CE findings.

RESULTS

In total, 62 of 83 patients (75%) had a cause for bleeding identified. Findings were concordant across both modalities in 34 patients (55%). Twenty-one patients (38%) with positive EGD results had negative CE results, 7 of whom were due to lack of duodenal visualization alone. However, 7 of 28 patients (25%) with normal EGD results had positive CE results. The subgroup of patients with duodenal visualization on CE, 23 of 25 (92%), were concordant with EGD for low-risk lesions that would have been suitable for outpatient management.

LIMITATIONS

Low duodenal visualization rates with CE and low concordance between EGD and CE.

CONCLUSION

Although CE is not currently ready to be used as a triage tool, when duodenal visualization was achieved CE correlated well with EGD findings and identified 92% of patients who may have been managed as outpatients.

Delta-aminolevulinic acid dehydratase genotype and lead toxicity: a HuGE review

The ALAD gene (chromosome 9q34) codes for delta-aminolevulinic acid dehydratase (ALAD) (E.C. 4.2.1.24). ALAD catalyzes the second step of heme synthesis and is polymorphic. The ALAD G177C polymorphism yields two codominant alleles, ALAD-1 and ALAD-2, and it has been implicated in susceptibility to lead toxicity. Genotype frequencies vary by geography and race. The rarer ALAD-2 allele has been associated with high blood lead levels and has been thought to increase the risk of lead toxicity by generating a protein that binds lead more tightly than the ALAD-1 protein. Other evidence suggests that ALAD-2 may confer resistance to the harmful effects of lead by sequestering lead, making it unavailable for pathophysiologic participation. Recent studies have shown that individuals who are homozygous for the ALAD-1 allele have higher cortical bone lead levels; this implies that they may have a greater body lead burden and may be at higher risk of the long-term effects of lead. Individuals exposed to lead in occupational settings have been the most frequent subjects of study. Genotype selection bias may limit inferences from these studies. No firm evidence exists for an association between ALAD genotype and susceptibility to lead toxicity at background exposure levels; therefore, population testing for the ALAD polymorphism is not justified.

Increased gene expression of Alzheimer disease beta-amyloid precursor protein in senescent cultured fibroblasts

The pathological hallmark of Alzheimer disease is the accumulation of neurofibrillary tangles and neuritic plaques in the brains of patients. Plaque cores contain a 4- to 5-kDa amyloid beta-protein fragment which is also found in the cerebral blood vessels of affected individuals. Since amyloid deposition in the brain increases with age even in normal people, we sought to establish whether the disease state bears a direct relationship with normal aging processes. As a model for biological aging, the process of cellular senescence in vitro was used. mRNA levels of beta-amyloid precursor protein associated with Alzheimer disease were compared in human fibroblasts in culture at early passage and when the same fibroblasts were grown to senescence after more than 52 population doublings. A dramatic increase in mRNA was observed in senescent IMR-90 fibroblasts compared with early-passage cells. Hybridization of mRNA from senescent and early proliferating fibroblasts with oligonucleotide probes specific for the three alternatively spliced transcripts of the gene gave similar results, indicating an increase during senescence of all three forms. A similar, though more modest, increase in message levels was also observed in early-passage fibroblasts made quiescent by serum deprivation; with repletion of serum, however, the expression returned to previous low levels. ELISAs were performed on cell extracts from senescent, early proliferating, and quiescent fibroblasts, and quiescent fibroblasts repleted with serum for over 48 hr, using polyclonal antibodies to a synthetic peptide of the beta-amyloid precursor. The results confirmed that the differences in mRNA expression were partially reflected at the protein level. Regulated expression of beta-amyloid precursor protein may be an important determinant of growth and metabolic responses to serum and growth factors under physiological as well as pathological conditions.

Conformational studies of Escherichia coli pyruvate oxidase

Pyruvate oxidase (pyruvate:oxygen oxidoreductase (phosphorylating), EC 1.2.3.3) is a peripheral membrane enzyme from Escherichia coli which utilizes the cofactors thiamin pyrophosphate (TPP) and flavin-adenine dinucleotide (FAD) to catalyze the decarboxylation of pyruvate to acetic acid and carbon dioxide. The specific activity of the oxidase is enhanced 25-fold when assayed in the presence of certain lipids and detergents. Previous studies have demonstrated that the affinity of pyruvate oxidase for phospholipids and detergents is substantially increased when the flavin is reduced. In this paper, several techniques are utilized to probe both the nature of the active site and the conformational changes in the protein which are concomitant with flavin reduction and with the binding of lipids to the enzyme. Analysis of the circular dichroism spectrum in the far ultraviolet region indicates that neither the binding of lipid activators to the oxidase nor reduction of the enzyme-bound flavin by pyruvate has a significant effect on the average secondary structure of the enzyme. High-resolution electron microscopy demonstrates that at low enzyme concentrations, i.e., assay conditions, incubation of the reduced flavoprotein in the presence of an amphiphilic activator does not alter the quaternary structure of pyruvate oxidase. The results indicate that the conformational changes in the protein due either to reduction of the flavin or to the binding of lipid activators are localized.

Effect of uncouplers of oxidative phosphorylation on microtubule location and surface structure in murine mast cells

"Uncouplers" of oxidative phosphorylation (sodium azide, DNP, and oligomycin) alter the location of microtubules within murine mast cells. Both cytoplasmic microtubules, perpendicular to the plasma membrane within cell surface folds, and intranuclear microtubules were observed. In addition, one or more dense plaque-like structures adjacent the plasma membrane in mast cells appeared following incubation in the antimetabolities. Intranuclear microtubules and cytoplasmic microtubules within the cell surface ridges disappeared in azide-treated mast cells that were reincubated or "recovered" in PBS. However, both these structures remained in oligomycin- and DNP-treated murine mast cells following reincubation.

Regulation of surface topography of mouse peritoneal cells. Formation of microvilli and vesiculated pits on omental mesothelial cells by serum and other proteins

The mesothelial cells of the mouse omentum provide an in vivo model for the study of the mobilization of labile microvilli on the cell surface. These mesothelial cells are sparsely covered with microvilli and large pits 150--400 nm in diameter, termed vesiculated pits. On the unstimulated cell, the microvilli average 44/100 microns2 and pits, 30/100 microns 2 of surface and they are rapidly induced to increase in number by the intraperitoneal injection of isologous mouse serum. After 2 min, microvilli increase threefold, continue to sevenfold at 30 min, and decrease to fourfold at 90 min. Vesiculated pits increased with similar kinetics. Bovine serum albumin and gamma globulin also stimulate the microvilli and pits to form, but the response is a slow, gradual rise to five- or sixfold the normal value at 90 min. Evidence indicates that multiple factors, possibly including insulin and immunoglobulins, are involved in the effect of serum. The close physical and temporal relationship between microvilli and pits suggests that a correlation exists in their mobilization by the cell and it is hypothesized that microvilli function in the regulation of the cortical microfilament network in effecting this mobilization.

Membrane phenomena accompanying erythrophagocytosis. A scanning electron microscope study

Mouse peritoneal macrophages phagocytose opsonized sheep red blood cells in two distinct ways. The unflattened macrophage with its highly folded plasma membrane envelops erythrocytes by multiple pseudopodia that are frequently of unequal size and have overlapping margins. The flat macrophage with a smooth surface, acquired as a result of spreading on an artificial substrate or from engulfing several erythrocytes, internalizes erythrocytes by a single cuplike or funnel-like pseudopod. Both patterns are observed in in situ and in vitro preparations of macrophages from A and C3H/HeN strain mice, that are normal, sensitized to sheep red blood cells, or treated with pyran. These membrane patterns are observed on macrophages engulfing erythrocytes that had been coated with antibody from A strain mice, or with rabbit antisheep erythrocyte antibody. The factor that appears to determine the membrane pattern is the number of discrete points of contact made by the erythrocyte as it attaches to the folded or smooth surface of a macrophage.

Characterization of C-reactive protein and the complement subcomponent C1t as homologous proteins displaying cyclic pentameric symmetry (pentraxins)

Partial amino acid sequences of rabbit C-reactive protein, a peptide derived from human C-reactive protein by cyanogen bromide cleavage, and the C1t subcomponent of the human complement component C1 have been determined. Extensive sequence homology between these proteins establish their evolutionary relationships. In addition, examination of C-reactive proteins by negative-stain electron microscopy revealed that the protein is composed of five subunits arranged in cyclic symmetry. This structure is similar to that reported for both C1t and the amyloid P-component. The extensive structural relationship suggests similar or overlapping functions and the term pentraxin is proposed to describe these homologous proteins.

Studies of the quaternary structure and the chemical properties of phosphoribosylpyrophosphate synthetase from Salmonella typhimurium

Phosphoribosylpyrophosphate (PRPP) synthetase (EC 2.7.6.1) was purified to virtual homogeneity from Salmonella typhimurium cells by a modification of previously published procedures. The molecular weight of the subunit was determined to be 31,000 +/- 3,000 by polyacrylamide gel electrophoresis in sodium dodecyl sulfate and sedimentation equilibrium analysis of the enzyme dissolved in 6 M guanidine hydrochloride. The amino acid composition of the enzyme was determined. Proline was identified as the only NH2-terminal residue. PRPP synthetase is apparently composed of identical or nearly identical subunits. NATIVE PRPP synthetase exists in multiple states of aggregation under all conditions. However, two predominant states were demonstrated under certain conditions. A form with molecular weight of 320,000 +/- 20,000 was found at pH 7.5 in the presence of MgATP. At pH 8.2 to 8.6, with or without MgATP, the predominant form corresponded to a molecular weight of 150,000 to 200,000; sedimentation equilibrium and velocity analysis indicated 160,000 +/- 15,000 as the most reliable molecular weight. More highly aggregated forms were observed at 4 degrees and higher protein concentrations. Removal of inorganic phosphate from PRPP synthetase by dilution or dialysis resulted in disaggregation. The fundamental unit of PRPP synthetase appears to consist of five (or possibly six) subunits, which can associate to form a dimer (10 or 12 subunits) and more highly aggregated forms. A pentameric subunit structure is consistent with the multiple species resolved by electrophoresis of the native enzyme in discontinuous polyacrylamide gel systems. Visualization of PRPP synthetase by negative staining with uranyl acetate and electron microscopy revealed fields of very asymmetric molecules, the dimensions of which corresponded to the M = 160,000 form. Dimers and higher aggregates of this unit were also seen. An unusual model, in which the five subunits are asymmetrically arranged, accounts very well for the electron microscopic appearance of the enzyme. The tendency of the enzyme to aggregate is viewed as a consequence of the unsatisfied bonding regions of the fundamental asymmetric unit.

Association of DNA with melanin granules

Melanin granules were isolated from the Cloudman S91 mouse melanoma and from Amphiuma liver in highly purified form, as judged by electron microscopy and the lack of a mitochondrial enzyme marker. The granules from both tissues contained small amounts of DNA (less than or equal to 1% of the cell content) that was distinguished from nuclear DNA by the broadness of its buoyant density band in cesium chloride, by its sedimentation rate, and by a two-phased melting curve. The melanosome DNA could not be distinguished from nuclear and mitochondrial DNA by the amount of tritiated thymidine incorporated. The results are discussed and the suggestion made that the melanin DNA may provide the information that led to the production of the granules.

Association of ribosomes with intracellular vesicular stomatitis virus particles

Ribosomes are observed intimately associated with nucleocapsids of vesicular, stomatitis virus, especially those that line structures that are either cytoplasmic vesicles or invaginations of the plasma membrane.

Regulation of homoserine transacetylase in whole cells of Bacillus polymyxa

The levels of homoserine transacetylase (EC 2.3.1.31) in Bacillus polymyxa grown in minimal medium can vary over a 40-fold range, depending on whether methionine limits growth or is present in excess. This suggests that the synthesis of the enzyme is under control by methionine or one of its metabolites. The stability of homoserine transacetylase in growing cells was measured after repression of further synthesis by the addition of methionine. At 30 degrees, the enzyme was stable for 2 hours, whereas at 37 degrees it decayed with a half-life of 40 min. This contrasts with the striking instability in cell-free extracts described in the preceding paper (Wyman, A., and Paulus, H. (1975) J. Biol. Chem. 250, 3897-3903). The properties of homoserine transacetylase were also studied in cells of B. polymyxa that had been made permeable to small molecules by treatment with toluene. They differed in two important respects from those of the enzyme in cell-free extracts described in the preceding paper: the enzyme was relatively stable, with a half-life of 15 min at 37 degrees, and responded in a sigmoid manner to increasing concentrations of the inhibitors L-methionine and S-adenosylmethionine. These observations suggest that homoserine transacetylase is an oligomeric protein within the bacterial cell but dissociates into monomers in cell-free extracts. When B. polymyxa was transferred at 39 degrees from a rich medium to one without amino acids, growth resumed only very slowly. The growth lag after shift-down was not observed at 37 degrees or in the presence of methionine or cystathionine. This phenomenon appears to be due to a need for derepression of homoserine transacetylase upon shift-down which is thwarted at 39 degrees by the rapid thermal inactivation of the enzyme. A possible physiological function of the striking thermolability of the first enzyme in methionine biosynthesis is discussed.

Ultrastructure of the human complement component, Clq (negative staining-glutamine synthetase-biologically active Clq)

The human complement component, Clq, is a fragile molecule of delicate structure consisting of three distinct parts, a central subunit, connecting strands, and terminal subunits. Each terminal subunit is further subdivided into a large and a small subunit, and the central subunit appears to be divided into two equal parts. In the intact molecule, six connecting strands link six terminal subunits by their larger subdivision to the central subunit. The overall diameter of the molecule when viewed from the "top" is about 35 nm (350 A).

Ultrastructural Study of Clq

Purified C1q was diluted in buffer to between 10 and 50 µg/ml and droplets were placed on carbon-coated 400-mesh copper grids. Some grids were rinsed with dilute buffered formaldehyde or glutaraldehyde in order to fix the molecules. All grids were rinsed and stained in either 2% potassium phosphotungstate or 1% uranyl acetate. Approximately 200 photomicrographs from six different preparations were analyzed.

The whole C1q molecule is made up of an undetermined number of dense subunits which measure, on the average, 65 to 70 Å in diameter. These sub-units are joined at a central attachment area by strands estimated to be 60 to 100 Å in length and 15 to 20 Å in width. The structure of the central attachment area is hard to define, but is definitely less complicated than the central region of the IgM molecule.

Tetrameric immune macroglobulins in three orders of bony fishes

The immune IgM-like macroglobulins were isolated from three species of bony fishes (Ictalurus punctatus, Lepisosteus osseus, and Polyodon spathula) representing the three orders of the subclass Actinopterygii. These macroglobulins were found to have sedimentation coefficients of 14 S and molecular weights of 600,000-630,000. The carbohydrate compositions were determined and found to be different from that of human macroglobulins. After reduction and alkylation, the heavy and light chains could be separated by gel filtration and were found to have molecular weights of approximately 70,000 and 23,000 respectively. The amino acid compositions of these chains were similar to those of mammalian IgM heavy and light chains. The macroglobulins were found by electron microscopy to have a tetrameric structure, in contrast to the pentameric structure found in mammalian, chicken, and shark IgM, i.e. in species later on the evolutionary scale.