The importance of iron chelation and iron availability during PpIX-induced photodynamic therapy

Background:

Protoporphyrin IX (PpIX)-induced photodynamic therapy (PDT) is being utilised as a topical method of localised ablation of certain non-melanoma skin cancers and precancers. Standardised protocols have been implemented to good effect when the disease remains superficial but improvement is required to treat thicker or acrally located conditions. Concurrent administration of an iron chelator during PpIX-PDT has been demonstrated to increase cellular accumulation of PpIX by reducing its bioconversion to haem (an iron dependent process) thus increasing cell kill on subsequent irradiation. Iron however, can also play a role in reactive oxygen species (ROS) generation and limiting its availability via chemical chelation could theoretically reduce the efficacy of PpIX-PDT, so that a response less than that maximally feasible is produced.

Materials and methods:

The effects of iron availability and chelation on PpIX-PDT have therefore been investigated via fluorescence quantification of PpIX accumulation, single-cell gel electrophoresis (comet assay) measurement of ROS-induced DNA damage and trypan blue exclusion assessment of cell viability. Cultured human cells were utilised and incubated in standardised iron conditions with the PpIX precursor’s aminolaevulinic acid (ALA) or its methyl ester (MAL) in the presence or absence of either of the iron chelating agents desferrioxamine (DFO) or hydroxypyridinone (CP94), or alternatively iron sulphate as a source of iron.

Results:

ALA or MAL incubation was found to significantly increase cellular PpIX accumulation pre-irradiation as anticipated and this observation correlated with both significantly increased DNA damage and reduced cellular viability following irradiation. Co-incubation with either of the iron chelators investigated (DFO or CP94) significantly increased pre-irradiation PpIX accumulation as well as DNA damage and cell death on irradiation indicating the positive effect of iron chelation on the effectiveness of PpIX-induced PDT. The opposite effects were observed however, when the cells were co-incubated with iron sulphate, with significant reductions in pre-irradiation PpIX accumulation (ALA only) and DNA damage (ALA and MAL) being recorded indicating the negative effects excessive iron can have on PpIX-PDT effectiveness. Some dark toxicity produced by iron sulphate administration in non-irradiated control groups was also observed.

Conclusion:

Iron chelation and availability have therefore been observed to positively and adversely affect the PpIX-PDT process respectively and it is concluded that the effects of increased PpIX accumulation pre-irradiation produced via iron chelation outweigh any limitations reduced iron availability may have on the ability of iron to catalyse ROS generation/cascades following PpIX-induced PDT. Further investigation of iron chelation within dermatological applications where enhanced PpIX-PDT treatment effects would be beneficial is therefore warranted.

Disease associations in alpha-1-antitrypsin deficiency

INTRODUCTION

In addition to emphysema alpha-1-antitrypsin deficiency (AATD) has been shown to be associated with several inflammatory conditions, including bronchiectasis, vasculitis, (in particular Wegener's granulomatosis), and panniculitis, suggesting neutrophil proteinases also play a role in their pathophysiology. However, it remains unknown whether other inflammatory diseases are also more prevalent in AATD than the general population. The current study describes the prevalence of other co-morbidities in AATD with particular emphasis on inflammatory bowel disease.

METHODS AND RESULTS

The case notes of 651 PiZZ or PiZnull patients attending the UK national centre for AATD between 1996 and 2011 were reviewed. The prevalence of inflammatory bowel disease (1.5%) was higher than that predicted in the UK (0.4%). Ten patients had a confirmed diagnosis of ulcerative colitis, and 1 had Crohn's disease. In 2 cases there was a family history of inflammatory bowel disease and all but 1 patient were ex or never smokers. There was also a higher prevalence of hypothyroidism in this patient group than expected for the UK population - 26 cases (7.2% of females and 1.3% of males).

CONCLUSIONS

The current study of the UK cohort of patients with AATD confirmed a higher prevalence of ulcerative colitis than would be expected in the general population, providing further evidence of a potential link between these 2 conditions. In addition, the data suggested a potential link between hypothyroidism and AATD.

How long do fibre-reinforced resin-bonded fixed partial dentures last?

DATA SOURCES

Searches were made for data using Medline and the reference lists of identified papers by two independent readers. Only papers published in English were considered and reviews, case reports, descriptive reports and in-vitro studies were excluded.

STUDY SELECTION

Prospective or retrospective cohort studies were selected.

DATA EXTRACTION AND SYNTHESIS

Information on the design, location and the choice of material was extracted. Retainer type (inlay, surface, crown retainer), number of abutment teeth, and different span distances were recorded and, as far as possible, the survival period for each fixed partial denture (FPD) was extracted on an individual basis. Technical complications and number of failures were extracted, if reported. FPD survival was defined as the FPD remaining in situ, with or without modification, during the observation period. An overall survival curve was constructed using the Kaplan-Meier method and the possibility of performing a regression analysis on different types and locations of FPD was investigated.

RESULTS

In all, 15 articles dealing with 13 sets of patients and 435 FPD were included, with observation periods that varied between 10 months and 5.7 years. Of 435 FPD, 88 failed within 5 years, with a calculated survival rate of 4.5 per year (73.4%; 95% confidence interval, 69.4-77.4%). Converted survival rates at 2 years' follow up showed substantial heterogeneity between studies. It was not possible to build a reliable regression model that indicated risk factors. The technical problems most commonly described were fracture of the FPD and delamination of the veneering composite.

CONCLUSIONS

The majority of the studies showed a survival rate of approx. 72% after 2-5 years. This study highlights the need for good-quality randomised clinical trials (RCT).

Clinical investigation of the novel iron-chelating agent, CP94, to enhance topical photodynamic therapy of nodular basal cell carcinoma

BACKGROUND

Photodynamic therapy (PDT) involves the activation of a photosensitizer by visible light to produce activated oxygen species within target cells, resulting in their destruction. Evidence-based guidelines support the efficacy of PDT using topical 5-aminolaevulinic acid (ALA-PDT) in actinic keratoses, Bowen disease and basal cell carcinoma (BCC). Efficacy for nodular BCC appears inferior to that for superficial BCC unless prior debulking or repeat treatments are performed. Objectives The aim of this study was to assess the safety and efficacy of adding a novel iron-chelating agent, CP94 (1,2-diethyl-3-hydroxypyridin-4-one hydrochloride), to topical ALA, to temporarily increase the accumulation of the photosensitizer in the tumour.

METHODS

A mixed topical formulation of ALA + increasing concentrations of CP94 was used to carry out PDT on previously biopsied nodular BCC with no prior lesion preparation using standard light delivery. The area was assessed clinically and surgically excised 6 weeks later for histological examination.

RESULTS

Enhanced PDT using 40% CP94 resulted in significantly greater clearance rates in nodular BCC than with ALA-PDT alone, in our protocol of single-treatment PDT with no lesion preparation.

CONCLUSIONS

The results of this study demonstrate the safe and effective use of an enhanced ALA-PDT protocol for nodular BCC using CP94, with no adverse reactions to this modification. This is the first time this formulation has been used in patients. This formulation is now the focus of further study.

Biochemical manipulation via iron chelation to enhance porphyrin production from porphyrin precursors

Topical protoporphyrin IX (PPIX) induced photodynamic therapy (PDT) of basal cell carcinoma (BCC) produces good clinical outcomes with excellent cosmesis as long as the disease remains superficial. Efficacy for nodular BCC, however, appears inferior to standard treatment unless repeat treatments are performed. Enhancement is therefore required and may be possible by employing iron chelating agents to temporarily increase PPIX accumulation above the levels normally obtained using aminolaevulinic acid (ALA) or the methyl ester of ALA (MAL) alone. In vitro studies investigated the efficacies of the novel iron chelator, CP94 (1,2-diethyl-3-hydroxypyridin-4-one hydrochloride), and the established iron chelator, desferrioxamine (DFO), at increasing PPIX fluorescence in cultured human lung fibroblasts and squamous carcinoma cells incubated with ALA/MAL. CP94 was found to produce greater PPIX fluorescence when administered with ALA/MAL than either congener could produce alone. CP94 was also found to be superior to DFO in the enhancement of PPIX fluorescence and could be employed to accumulate the same levels of PPIX within a shorter time period. Clinical utilization of CP94 to enhance ALA/MAL-PDT could potentially result in greater PPIX accumulation or alternatively could be employed to reduce the length of the required drug-light interval. Clinical investigation of this is currently underway.

Effect of storage and postage on recovery and quantitation of bacteria in sputum samples

AIMS

The aims of the study were to compare bacterial recovery following storage of sputum samples at 20 degrees C room temperature and 4 degrees C (refrigerated) for 24 h, and to determine the effect of postage on viable bacterial numbers.

METHODS

A total of 38 individual sputum samples from clinically stable patients with bronchiectasis were split into three equal aliquots and quantitative bacterial culture was performed (i) immediately, (ii) following storage at 4 degrees C for 24 h or (iii) following storage at 20 degrees C for 24 h. A further 42 sputum samples were split into two equal aliquots and quantitative bacterial culture was performed either immediately or following postage back to the laboratory by first-class mail from an outside location.

RESULTS

The predominant organism could still be recovered following storage at 4 degrees C and 20 degrees C, but viable numbers were significantly reduced following storage at 4 degrees C (p<0.004) by at least an order of magnitude (10-fold) in 24% of samples stored at 4 degrees C compared with only 8% stored at 20 degrees C. Posting samples back to the laboratory did not affect the recovery of bacterial species and there was no difference in viable numbers isolated.

CONCLUSIONS

The results suggest that storage at room temperature is preferable to refrigeration as it retains the species isolated and the viable number. The data also confirm that sputum samples can be posted to the laboratory from patients in the community without affecting qualitative or quantitative results.

Direct Comparison of δ-Aminolevulinic Acid and Methyl-Aminolevulinate-Derived Protoporphyrin IX Accumulations Potentiated by Desferrioxamine or the Novel Hydroxypyridinone Iron Chelator CP94 in Cultured Human Cells

Aminolevulinic acid photodynamic therapy (ALA-PDT) is a cancer therapy that combines the selective accumulation of a photosensitizer in tumor tissue with visible light (and tissue oxygen) to produce reactive oxygen species. This results in cellular damage and ablation of tumor tissue. The use of iron chelators in combination with ALA has the potential to increase the accumulation of the photosensitizer protoporphyrin IX (PpIX) by reducing its bioconversion to heme. This study compares directly for the first time the effects of the novel hydroxypyridinone iron chelating agent CP94 and the more clinically established iron chelator desferrioxamine (DFO) on the enhancement of ALA and methyl-aminolevulinate (MAL)-induced PpIX accumulations in cultured human cells. Cultured human cells were incubated with a combination of ALA, MAL, CP94 and DFO concentrations; the resulting PpIX accumulations being quantified fluorometrically. The use of iron chelators in combination with ALA or MAL was shown to significantly increase the amount of PpIX accumulating in the fetal lung fibroblasts and epidermal carcinoma cells; while minimal enhancement was observed in the normal skin cells investigated (fibroblasts and keratinocytes). Where enhancement was observed CP94 was shown to be significantly superior to DFO in the enhancement of PpIX accumulation.

Hg(II) exposure exacerbates UV-induced DNA damage in MRC5 fibroblasts: a comet assay study

When exposed to UVR, MRC5 fibroblasts incubated with mercuric chloride (0-15 microM) for 1 hour show increased DNA damage (as measured by the comet assay) compared to control cells (UVR irradiated but no mercuric chloride). This demonstrates that mercuric chloride and UVR in combination increase DNA damage in a synergistic manner. This may have implications to those exposed to mercury as it suggests that exposure to mercury in the environment may increase sensitivity to sunlight-induced carcinogenesis.

Relationship of sputum color to nature and outpatient management of acute exacerbations of COPD

STUDY OBJECTIVES

To stratify COPD patients presenting with an acute exacerbation on the basis of sputum color and to relate this to the isolation and viable numbers of bacteria recovered on culture.

DESIGN

Open, longitudinal study of sputum characteristics and acute-phase proteins.

SETTING

Patients presenting to primary-care physicians in the United Kingdom. Patients were followed up as outpatients in specialist clinic.

PATIENTS

One hundred twenty-one patients with acute exacerbations of COPD were assessed together with a single sputum sample on the day of presentation (89 of whom produced a satisfactory sputum sample for analysis). One hundred nine patients were assessed 2 months later when they had returned to their stable clinical state.

INTERVENTIONS

The expectoration of green, purulent sputum was taken as the primary indication for antibiotic therapy, whereas white or clear sputum was not considered representative of a bacterial episode and the need for antibiotic therapy.

RESULTS

A positive bacterial culture was obtained from 84% of patients sputum if it was purulent on presentation compared with only 38% if it was mucoid (p < 0.0001). When restudied in the stable clinical state, the incidence of a positive bacterial culture was similar for both groups (38% and 41%, respectively). C-reactive protein concentrations were significantly raised (p < 0.0001) if the sputum was purulent (median, 4.5 mg/L; interquartile range [IQR], 6. 2 to 35.8). In the stable clinical state, sputum color improved significantly in the group who presented with purulent sputum from a median color number of 4.0 (IQR, 4.0 to 5.0) to 3.0 (IQR, 2.0 to 4. 0; p < 0.0001), and this was associated with a fall in median C-reactive protein level to 2.7 mg/L (IQR, 1.0 to 6.6; p < 0.0001).

CONCLUSIONS

The presence of green (purulent) sputum was 94.4% sensitive and 77.0% specific for the yield of a high bacterial load and indicates a clear subset of patient episodes identified at presentation that is likely to benefit most from antibiotic therapy. All patients who produced white (mucoid) sputum during the acute exacerbation improved without antibiotic therapy, and sputum characteristics remained the same even when the patients had returned to their stable clinical state.

Dynamics of respiratory tract colonization by Branhamella catarrhalis in bronchiectasis

Branhamella catarrhalis is increasingly recognized as a lower respiratory tract pathogen, particularly in chronic lung diseases. This project defines a population of patients in whom the dynamics of colonization and infection caused by this organism could be studied. A method employing pulsed field gel electrophoresis (PFGE) of genomic DNA was developed. Twenty-eight patients with bronchiectasis followed prospectively for 26.8 mo (mean) were seen monthly or bimonthly and at the time of a purulent exacerbation. Quantitative bacterial cultures were performed on sputum obtained at each visit. Six of 28 had B. catarrhalis isolated repeatedly. Viable numbers of B. catarrhalis were similar to other bacterial pathogens. Restriction fragment length polymorphism (RFLP) analysis of chromosomal DNA using PFGE was performed on 37 of the 47 isolates recovered. Each patient was colonized by two to four strains with different RFLP patterns. Duration of colonization by the same strain was 2.3 mo (mean). Strain acquisition did not correlate with exacerbation, antibiotic therapy, or season. We conclude that (1) a subset of bronchiectatic patients is colonized with B. catarrhalis, (2) RFLP is a sensitive tool to study strain acquisition, and (3) acquisition and clearance of B. catarrhalis from the respiratory tract is a dynamic process.

In vivo study of indomethacin in bronchiectasis: effect on neutrophil function and lung secretion

Bronchiectasis is associated with sputum containing high levels of the proteolytic enzyme elastase, which is thought to be involved in the pathogenesis of the disease. Agents which inhibit neutrophil function and interfere with neutrophil elastase release may have a beneficial effect on the development and progression of such diseases. We have studied the effects of the nonsteroidal anti-inflammatory agent indomethacin on neutrophil function in nine patients with clinically stable bronchiectasis. All patients remained clinically stable during the study. We observed a significant reduction in peripheral neutrophil chemotaxis to 10 nmol.L-1 N-formyl-methionyl-leucyl-phenylalanine (FMLP) from a mean of 19.86 (SEM 1.35) to 8.46 (0.68) cells.field-1 after 4 weeks of therapy. There was also a significant reduction in fibronectin degradation both by resting and FMLP-stimulated neutrophils, from a mean of 1.90 (0.19) micrograms x 3 x 10(5) cells at the start of therapy to 0.87 (0.08) micrograms after 4 weeks, and from 3.17 (0.35) micrograms to 1.48 (0.05) micrograms, respectively. There was no effect on spontaneous or stimulated superoxide anion generation by neutrophils. Despite the marked changes in peripheral neutrophil function, no adverse effect was observed on viable bacterial load in the bronchial secretions. In addition, there was no difference in sputum albumin, elastase or myeloperoxidase levels, and only minor changes in the chemotactic activity of the sputum. These results suggest that nonsteroidal anti-inflammatory agents have a major effect on peripheral neutrophil function but do not appear to have an adverse effect on bacterial colonization of the airways.

In vivo study of indomethacin in bronchiectasis: effect on neutrophil function and lung secretion

Bronchiectasis is associated with sputum containing high levels of the proteolytic enzyme elastase, which is thought to be involved in the pathogenesis of the disease. Agents which inhibit neutrophil function and interfere with neutrophil elastase release may have a beneficial effect on the development and progression of such diseases. We have studied the effects of the nonsteroidal anti-inflammatory agent indomethacin on neutrophil function in nine patients with clinically stable bronchiectasis. All patients remained clinically stable during the study. We observed a significant reduction in peripheral neutrophil chemotaxis to 10 nmol.L-1 N-formyl-methionyl-leucyl-phenylalanine (FMLP) from a mean of 19.86 (SEM 1.35) to 8.46 (0.68) cells.field-1 after 4 weeks of therapy. There was also a significant reduction in fibronectin degradation both by resting and FMLP-stimulated neutrophils, from a mean of 1.90 (0.19) micrograms x 3 x 10(5) cells at the start of therapy to 0.87 (0.08) micrograms after 4 weeks, and from 3.17 (0.35) micrograms to 1.48 (0.05) micrograms, respectively. There was no effect on spontaneous or stimulated superoxide anion generation by neutrophils. Despite the marked changes in peripheral neutrophil function, no adverse effect was observed on viable bacterial load in the bronchial secretions. In addition, there was no difference in sputum albumin, elastase or myeloperoxidase levels, and only minor changes in the chemotactic activity of the sputum. These results suggest that nonsteroidal anti-inflammatory agents have a major effect on peripheral neutrophil function but do not appear to have an adverse effect on bacterial colonization of the airways.

Simple method for quantifying viable bacterial numbers in sputum

AIMS

To establish a simple method of quantitative culture for determining the viable bacterial numbers present in expectorated sputum samples.

METHODS

Sputum samples were homogenised with dithiothreitol, sterile saline or glass beads to determine which method recovered the greatest number of viable bacteria. Culture broths were also incubated with dithiothreitol and sampled over time to determine its effect on bacterial viability. Sputum samples homogenised with dithiothreitol were diluted in sterile saline and sampled using either standard bacteriological loops or a precision pipette to determine which method resulted in the least variation.

RESULTS

Homogenisation of sputum using dithiothreitol increased the recovery of viable bacteria compared with sterile glass beads and/or saline, with no apparent effect on bacterial viability when incubated with culture broths. By inoculating agar plates with 10(-3), 10(-4) and 10(-5) dilutions of the homogenised sputum sample, all potential pathogens could easily be identified. A 10 microliter sample volume dispensed by precision pipette and spread with a "hockey stick" resulted in the least variation between plates (less than 16%) and an even distribution of bacterial colonies. Numbers of viable bacteria recovered from different aliquots of individual sputum samples were generally of the same order of magnitude.

CONCLUSIONS

This method represents a relatively quick and simple technique for accurately quantifying viable bacteria present in sputum samples. The use of a small portion appears to be representative of the sample as a whole.

The isolation and characterization of non-typeable Haemophilus influenzae from the sputum of adult cystic fibrosis patients

The role of non-typeable Haemophilus influenzae in cystic fibrosis (CF) remains unclear. We wanted, therefore, to determine the presence and characteristics of non-typeable H. influenzae in sputum samples from patients with CF. In order to do this, we have assessed sputum samples from 55 consecutive clinically stable patients seen routinely at an adult CF out-patient clinic. Quantitative bacterial culture was performed using a selective media containing cefsoludin, and isolates were characterized by biotyping and outer membrane protein profile analysis. In 17 (30%) of these samples, non-typeable H. influenzae was isolated and was present in similar viable numbers (mean 7.7 x 10(8) colony-forming units (cfu).mL-1; SEM 3.1) to Pseudomonas aeruginosa (mean 8 x 10(8) cfu.mL-1: SEM 2.4). All non-typeable H. influenzae isolates recovered were beta-lactamase negative and sensitive to a range of antibiotics. Several biotypes and outer membrane protein profiles were observed, with no apparent association between these two phenotypic characteristics. The study showed that large numbers of non-typeable H. influenzae are often present in sputum from adult patients with CF. Further longitudinal studies of outer-membrane protein profile analysis are required to determine the dynamics of non-typeable H. influenzae colonization in individual patients and the clinical significance.

The isolation and characterization of non-typeable Haemophilus influenzae from the sputum of adult cystic fibrosis patients

The role of non-typeable Haemophilus influenzae in cystic fibrosis (CF) remains unclear. We wanted, therefore, to determine the presence and characteristics of non-typeable H. influenzae in sputum samples from patients with CF. In order to do this, we have assessed sputum samples from 55 consecutive clinically stable patients seen routinely at an adult CF out-patient clinic. Quantitative bacterial culture was performed using a selective media containing cefsoludin, and isolates were characterized by biotyping and outer membrane protein profile analysis. In 17 (30%) of these samples, non-typeable H. influenzae was isolated and was present in similar viable numbers (mean 7.7 x 10(8) colony-forming units (cfu).mL-1; SEM 3.1) to Pseudomonas aeruginosa (mean 8 x 10(8) cfu.mL-1: SEM 2.4). All non-typeable H. influenzae isolates recovered were beta-lactamase negative and sensitive to a range of antibiotics. Several biotypes and outer membrane protein profiles were observed, with no apparent association between these two phenotypic characteristics. The study showed that large numbers of non-typeable H. influenzae are often present in sputum from adult patients with CF. Further longitudinal studies of outer-membrane protein profile analysis are required to determine the dynamics of non-typeable H. influenzae colonization in individual patients and the clinical significance.

Sputum and serum pharmacokinetics of loracarbef (LY163892) in patients with chronic bronchial sepsis

Sputum and serum pharmacokinetics of loracarbef (LY163892) were performed in 19 patients with purulent bronchiectasis. Nine of the patients received 200 mg twice daily and ten patients, 400 mg twice daily, for a total of 14 days. beta-Lactamase activity was measurable in the lung secretions of all 19 patients at the start of therapy. Mean peak serum concentrations of 11.7 mg/L (S.E.M. 1.7) were recorded at 1 h after administration of 200 mg doses on day 2 of therapy and were 18.5 mg/L (S.E.M. 1.9) at 1.5 h in the 400 mg group. Loracarbef was shown to penetrate lung secretions even in the presence of beta-lactamase activity. Mean peak sputum concentrations were achieved between 2 and 4 h following dosing and were 0.2 mg/L (S.E.M. 0.05) in the 200 mg group and 0.4 mg/L (S.E.M. 0.08) in the 400 mg group. On days 7 and 14 of therapy, sputum loracarbef concentrations were similar 4 h after the morning dose (0.23 mg/L following 200 mg; 0.35 mg/L after 400 mg). These concentrations were approximately 2% of the peak serum concentration and penetration into lung secretions is similar to other beta-lactams.

Cochlear damage in guinea pigs following contralateral sound stimulation with and without gentamicin

The effect of a minimally damaging sound exposure and a sub-ototoxic dose of gentamicin on cochlear hair cells contralateral to the sound exposure was evaluated. The cochleae of pigmented guinea pigs exposed to an 8 kHz pure tone at 116 dB SPL for 1 h and/or 50 mg/kg/day of gentamicin for 10 consecutive days and repeated after an interval of 3 weeks, were used for this purpose. Hair cell loss was found to have occurred in the contralateral cochleae following the sound exposure alone. The occurrence of potentiation, synergism and differential synergism between the agents in the contralateral ears was also seen. Possible explanations for these phenomena are proposed.

Interaction between sound and gentamicin: immediate threshold and stereociliary changes

Our aim was to determine whether the immediate effects of a just-damaging sound exposure (8 kHz at 116 dB SPL for 1 h) might be potentiated by a single sub-ototoxic dose of gentamicin (50 mg kg-1). Auditory brainstem responses in pigmented guinea pigs were measured before and after treatment and used to calculate threshold shift (TS). Histological disturbances to sensory hair cells were assessed by scanning electron microscopy. All experimental ears excepting the gentamicin only group showed TS and histological changes. The largest TSs occurred at half an octave above the exposure frequency, and were greatest in the gentamicin + sound (G + S) group. First row outer hair cells showed most histological disturbances, followed by inner hair cells. The severest histological damage occurred at the exposure frequency and basally from it, the G + S group being most affected. Generally, there was good correlation between the severity of TS and histological damage. Results from both analyses indicated greater changes with gentamicin present.

A comparison of initial and permanent surface changes to guinea pig hair cells after acoustic overstimulation

Groups of pigmented guinea pigs were exposed unilaterally to a 15 kHz pure tone at 133 dB SPL for 7.5 min. The inner ears of one group were examined by light microscopy to count damaged hair cells 3 weeks after exposure. Four other groups were investigated using scanning electron microscopy to assess the progression of initial surface changes after sound exposure. Hair cells were examined at 0, 10 and 30 min and compared with those seen at 3 weeks. Drastic stereociliary disturbances were present immediately after this short sound stimulation. Changes initially affected the first row of outer hair cells, followed by the inner hair cell row, and then spread to all rows at the centre of a damaged area. These changes appeared more advanced in specimens from the later groups. At 3 weeks, primarily phalangeal scars were seen at the main damaged area, with partially degenerating cells at the periphery. The latter still showed stereociliary disturbances, but the types predominating were different from those seen initially. However, no differences were found in the extens of damage when the various exposure groups were compared. No changes due to overstimulation were present in the contralateral ears.

Comparison of various short noise exposures in albino and pigmented guinea pigs

Albino and pigmented guinea pigs were exposed to 20 kHz at 120 dB SPL for exposure durations of 30, 7.5, 6.5, 5 and 3.25 min. In a second series of experiments, the two shortest exposures were repeated after an interval of 6 or 24 h. Sensory hair cell loss was assessed 3 weeks post-exposure by surface preparations and quantified as percentage cell loss per segment per row, total numbers of outer and inner hair cells lost and the area of total outer hair cell damage. A variable but discrete area of damage resulted from these exposures. The main differences between the two strains were that in albino guinea pigs fewer ears were damaged after the shortest single exposures and generally more damage occurred after repeated exposures. However, no differences were detected in either strain when the interval between repeated exposures was changed.

Sensory hair cell damage from high frequency noise exposure

Fifteen guinea pigs were exposed to the noise of an 'ultrasonic' cleaning bath which gave maximum airborne radiation at 12.5 kHz amounting to 104 dB SPL in the one-third octave band. The animals were exposed for 2.5, 8 or 16 h and killed either 4 or 8 weeks after exposure, following which any damaged sensory hair cells were quantified. One third of the cochleae showed no sign of damage, but one animal had quite severe, scattered hair cell loss throughout both cochleae. The remainder showed some scattered hair cell loss, but only in the basal turn. Great variation was found in the damage to the cochleae of the exposed animals.

Acoustic trauma effects with varying exposure times

Guinea pigs have been exposed to 20 kHz for 2 h, 1 h, 30 min, 15 min, or 7.5 min, and the resultant damage was observed 3, 6, and 12 weeks post exposure. The areas of outer hair cell damage were statistically compared. Significant differences were obtained after a 3-week survival time with the shorter exposure times, but this difference was no longer apparent after 12 weeks. Myelinated nerve fibre and inner hair cell damage occurred only with total outer hair cell loss.

Acoustic trauma effects from doubling the exposure time

Guinea pigs were exposed to 20 kHz for a period of 1 or 2 h, with and without an intermediate recovery period. Statistically smaller areas of damage were obtained after doubling the exposure time, especially without a recovery period. For a double exposure with a recovery period the areas of damage were the same as for the single exposures.

Acoustic trauma effects from doubling the exposure time

Guinea pigs were used to test acoustic trauma effects from doubling the exposure time. Previously, two frequencies (20 kHz and 4 kHz) were used in conjunction with each other (ie double exposure) to see whether a prior exposure of the cochlea to one frequency would alter the extent of damage caused by a secondary frequency, when compared with damage caused by either frequency alone. A reduced area of damage was attained after double exposures. To complete the series, the same two frequencies were used separately, but the exposure time was doubled. The results from the 20 kHz series surprisingly indicated that a reduced area of damage was obtained after doubling the exposure time. No significant differences were found in the 4 kHz series.

Insect immunity. 11. Simultaneous induction of antibacterial activity and selection synthesis of some hemolymph proteins in diapausing pupae of Hyalophora cecropia and Samia cynthia

We have previously shown that pupae of the giant silkmoth Samia cynthia have a humoral antibacterial activity, which was induced by viable, nonpathogenic gram-negative bacteria (H.G. Boman et al., 1974). We show here that this activity was formed simultaneously with a selective incorporation of amino acids into eight polypeptide chains characterized by their electrophoretic behavior. If actinomycin D or cycloheximide were given at an early time, no antibacterial activity was found. If the inhibitors were given at the time of maximum activity, there was no effect with actinomycin D but a rapid decrease of the activity in the case of cycloheximide. The results imply that the messenger ribonucleic acid was stable, but that at least one protein component was turning over. Hemolymph from immunized pupae of another giant silkmoth, Hyalophora cecropia, was fractionated by ammonium sulfate precipitation. This procedure, together with the isotope distribution after co-electrophoresis in polyarylamide gels, was used for comparing the response to injury and to different infections. Almost identical polypeptide patterns were obtained as a response to an infection with either viable Enterobacter cloacae or Bacillus subtilis. These patterns differed both qualitatively and quantitatively from the injury effect created by an injection as such. There was only a low antibacterial activity in each of the four fractions obtained by ammonium sulfate precipitation. However, a combination of three fractions restored a high killing activity. Fractionation of hemolymph from untreated pupae provided evidence for at least one preexisting factor which stimulated the killing of Escherichia coli. The osmotic pressure of the bacteria contributed to the antibacterial activity towards E. coli, but not towards B. subtitlis. The killing of E. coli was inhibited by liped A and, to a lesser extent, by an inhibitor of proteolytic enzymes. The similarities and differences with the mammalian complement system are discussed.

The effects of short noise exposures in the guinea pig

Guinea pigs have been exposed to 20 kHz at 120 dB SPL for exposure durations of 7.5, 6.5, 5.0, and 3.25-min and killed either 3 or 12 weeks post-exposure. One series of guinea pigs exposed for 30-min had cochlear potentials recorded 3 weeks post-exposure. The damage was assessed by surface preparations and quantified as percentage hair cell loss per segment in every row, total number of outer, and inner hair cells missing and the area of total outer hair cell damage. A significantly smaller number of ears were found to be damaged after the shortest exposures, but no significant differences could be detected in the amounts of damage when all the series were compared. Myelinated nerve fibre degeneration had increased after the longer post-exposure interval, but no such differences were observed in the sensory hair cell degeneration.