Automated multi-attribute method sample preparation using high-throughput buffer exchange tips

RATIONALE

The multi-attribute method (MAM) has become a valuable mass spectrometry (MS)-based tool that can identify and quantify the site-specific product attributes and purity information for biotherapeutics such as monoclonal antibodies (mAbs) and fusion molecules in recent years. As we expand the use of the MAM at various stages of drug development, it is critical to enhance the sample preparation throughput without additional chemical modifications and variability.

METHODS

In this study, a fully automated MAM sample preparation protocol is presented, where rapid desalting in less than 15 minutes is achieved using miniaturized size-exclusion chromatography columns in pipette tips on an automated liquid handler. The peptide samples were analyzed using an electrospray ionization (ESI) orbitrap mass spectrometer coupled to an ultra-high-performance liquid chromatography (UHPLC) system with a dual column switching system.

RESULTS

No significant change was observed in product attributes and their quantities compared with manual, low-artifact sample preparation. The sample recovery using the buffer exchange tips was greatly enhanced over the manual spin cartridges while still demonstrating excellent reproducibility for a wide variety of starting sample concentrations. Unlike a plate desalting system, the individual columns provide flexibility in the number of samples prepared at a time and sample locations within plates.

CONCLUSIONS

This automated protocol enables the preparation of up to 96 samples with less "at-bench" time than the manual preparation of a smaller batch of samples, thereby greatly facilitating support of process development and the use of the MAM in quality control.

Inhibition of Listeria monocytogenes growth in cured ready-to-eat meat products by use of sodium benzoate and sodium diacetate

The effect of sodium benzoate (0.08 to 0.25%) in combination with different concentrations of sodium diacetate (0.05 to 0.15%) and NaClI (0.8 to 2%) and different finished product moisture (55 to 75%) on the growth of Listeria monocytogenes in ready-to-eat meat products was evaluated using a central composite design over 18 weeks of storage at 4 degrees C. The effects of these factors on time to growth were analyzed using a time-to-failure regression method. All main effects were significant except product moisture, which was significant when included in the two- and three-way interactions (P < 0.05). Sodium benzoate was more effective (lengthening time to growth) when used with increasing concentrations of sodium diacetate and salt and decreasing finished product moisture. The model indicated that low-moisture products, e.g., bologna or wieners, could have time-to-growth values longer than 18 weeks if they were formulated with 0.1% sodium benzoate and 0.1% sodium diacetate. Time to growth in high-moisture products, e.g., ham or cured turkey breast at 75% moisture, was predicted to be much shorter for the same basic formulation (0.1% sodium benzoate and 0.1% sodium diacetate). Consequently, high-moisture ready-to-eat products in which sodium benzoate is limited to 0.1% (current standard for generally recognized as safe) may need additional ingredients to effectively inhibit growth of L. monocytogenes.

Nerve conduction and sensorineural function in dental hygienists using high frequency ultrasound handpieces

BACKGROUND

Oscillatory vibration from industrial power tools poses a well-recognized risk of peripheral nerve injury. There have been reports of elevated vibrotactile perception thresholds (VPT) among dentists, dental technicians, and dental hygienists, using rotary devices and ultrasonics. Elevated VPTs are an indicator of small fiber nerve or mechanoreceptor injury, but the high frequencies associated with dental instruments are presumed by the ISO to exceed physiological response upper thresholds. This study examines nerve conduction and sensorineural deficits in dental hygienists.

METHODS

A cross-sectional study of 94 experienced dental hygienists was conducted to assess peripheral nerve function and clinical signs and symptoms. Specialized testing included measurement of VPTs for three different categories of mechanoreceptors, sensory nerve conduction tests with fractionated digit and palmar segments, and measurement of calibrated pinch force with force sensitive resistors (FSRs) during a simulated procedure.

RESULTS

Chronic hand paresthesias were described by 44.7% of experienced dental hygienists. Sensory nerve conduction velocity (SNCV) across the wrist-palm segment of the median nerve. VPTs were particularly elevated at the FAII mechanoreceptor among experienced dental hygienists. Compared to participants without carpal tunnel syndrome (CTS), as defined by study criteria, 14 experienced hygienists with diagnosed CTS had almost twice the average weekly use of vibratory instruments -8.3 hr versus 4.5 hr, and had SNCV deficits along the digit -47.11 m/sec (+8.70) versus 42.57 m/sec (+8.25), and across the wrist -44.04 m/sec (+7.15) versus 41.36 m/sec (+9.27). There was a distinct subset of dental hygienists (27%) with a combination of low calibrated pinch force in simulations, subjective loss of strength and elevated VPTs, especially in the FAII mechanoreceptor population -110.82 db (+8.57) versus 104.84 db (+6.80) in the rest of the cohort. This subset also had a higher prevalence of paresthesias (67% vs. 39%) and greater cumulative vibration exposure (OR = 1.206 [CI 1.005-1.448]), than other hygienists.

CONCLUSIONS

The high levels of paresthesias observed among dental hygienists appear to be attributable to several pathophysiological mechanisms, including, sensory nerve demyelination at the carpal tunnel and intrinsic to the digits, and dysfunction of fingertip mechanoreceptors. A distinct sub-population appears to exhibit a high level of accumulated abnormality.

Infrared spectroscopic studies of protein formulations containing glycine

Glycine is extensively used as an excipient in protein formulations. However, it absorbs significant infrared (IR) radiation in the conformationally sensitive amide I region (1700-1600 cm(-1)) of proteins. Furthermore, glycine can form a number of polymorphs, as well as an amorphous phase. Each of these forms possibly exhibits a different IR absorption spectrum. Accurate subtraction of glycine signals, in order to obtain reliable amide I spectra, was found to be possible only if the protein-to-glycine ratio was >/=1:1. In those cases, the solid-state conformation of the protein could be determined. In addition, a new method for estimating the degree of crystallinity of freeze-dried glycine is described, using IR bands in the 1350-1300 cm(-1) region.

Effects of Potassium Bromide Disk Formation on the Infrared Spectra of Dried Model Proteins

The most common method of sample preparation for Fourier transform infrared spectroscopic analysis of proteins in the solid state is compression after mixing with potassium bromide (KBr). Recently, questions have arisen as to whether proteins are conformationally altered by this process. In this study, the amide I Fourier transform infrared spectra of two model proteins, lysozyme and alpha-chymotrypsinogen, were measured before and after compression in KBr, and the effects of moisture exposure and the ratio of KBr to protein were examined. Contrary to earlier reports, compaction of the KBr/protein mixtures did not foster aggregation, and only minor apparent structural alterations were observed.

Occupational contact dermatitis to nickel: experience of the British dermatologists (EPIDERM) and occupational physicians (OPRA) surveillance schemes

AIMS

To examine, from occupational surveillance reporting data, whether scheme reporters considered nickel exposure to play a role in occupational contact dermatitis (OCD) in the UK.

METHODS

Data on occupational skin disease in the UK are collected by two occupational disease surveillance schemes, EPIDERM and OPRA. Cases of OCD believed to have relevant nickel exposure reported to EPIDERM or OPRA from February 1993 to January 1999 were studied.

RESULTS

An estimate of 1190 cases of occupational contact dermatitis thought to have relevant nickel exposure (12% of total estimated OCD) was derived from reports by dermatologists, an average of 198 per year. The highest incidence rates were seen in hairdressers (23.9/100 000 workers/year), bar staff (4.7), chefs and cooks (4.4), retail cash and checkout operators (2.8), and catering assistants (2.5). From May 1994 to January 1999, 158 cases of nickel associated dermatitis (1.9% of total OCD cases) were estimated; the most frequently reported occupations were electronic assemblers, nurses, sales assistants, and general assemblers. From July 1997 to January 1999, 547 positive patch tests to nickel were reported; in 195 cases (36%), nickel was felt to be a relevant occupational allergen (for example, coin handling). In hairdressers, nurses, cooks, and beauticians, nickel was usually considered, if relevant at all, to be only one of several causes of dermatitis.

CONCLUSIONS

Up to 12% of total estimated cases of OCD were thought to be due in part to nickel. Results suggest that nickel hypersensitivity is one of several contributors to OCD in subjects with multiple occupational exposures. Coin handling may be a source of OCD to nickel.

Inhibition of nonproteolytic, psychrotrophic clostridia and anaerobic sporeformers by sodium diacetate and sodium lactate in cook-in-bag turkey breast

A nonproteolytic, psychrotrophic Clostridium isolate, designated strain OMFRI1, was recovered from cook-in-bag turkey breasts (CIBTB) that displayed an intense pink discoloration and an off-odor following extended refrigerated storage. The viability of strain OMFRI1 in CIBTB containing sodium diacetate (at 0, 0.25, and 0.5%) and/or sodium lactate (at 0, 1.25, and 2.5%) was subsequently evaluated. Raw CIBTB batter was inoculated with 9 to 30 spores of strain OMFRI1 per g, vacuum packaged, cooked to an instantaneous internal temperature of 71.1 degrees C, chilled, and incubated at 4 degrees C for up to 22 weeks. In the absence of food-grade antimicrobial agents, spoilage (i.e., an off-odor) occurred within 6 weeks, and anaerobic plate counts reached 6.6 log10 CFU/g. The CIBTB containing sodium diacetate (0.25%) and that containing sodium lactate (1.25%) required 12 weeks for spoilage to occur and for anaerobic plate counts to reach 7.0 and 6.0 log10 CFU/g, respectively. When sodium diacetate (0.25%) and sodium lactate (1.25%) were used in combination, no off-odor was detected and anaerobic plate counts did not exceed 2.3 log10 CFU/g over 22 weeks of storage at 4 degrees C. In related experiments, sodium diacetate (at 0, 0.25, and 0.5%), sodium lactate (at 0, 1.25, and 2.5%), and combinations of both ingredients were evaluated in uninoculated CIBTB incubated at 25 degrees C for up to 22 days. In the absence of antimicrobial agents and in CIBTB containing sodium diacetate (0.5%), spoilage occurred within 8 days and anaerobic plate counts reached 6.8 and 6.6 log10 CFU/g, respectively. Samples of CIBTB containing sodium lactate (2.5%) showed signs of spoilage within 22 days, and anaerobic plate counts for these samples ranged from < or = 1.0 to 6.3 log10 CFU/g. In CIBTB containing both sodium lactate (2.5%) and sodium diacetate (0.25%), spoilage was not evident and anaerobic plate counts were < or = 1.0 log10 CFU/g within 22 days. These data validate the efficacy of sodium lactate and sodium diacetate in extending the shelf life of CIBTB.

Effects of conformation on the chemical stability of pharmaceutically relevant polypeptides

Control of chemical instability in protein pharmaceuticals continues to be a critical issue in developing stable formulations. While the effects of pH, buffer composition, ionic strength and temperature remain the most effective methods for controlling hydrolysis and oxidation reactions, it appears that conformational control may also be important. Addition of excipients to maintain native structure and reduce the propensity of the protein to denature and/or aggregate is already a central theme in stabilizing proteins (Arakawa et al., 1993). The same additives have now been found to slow both deamidation and oxidation, whether in solution or in the solid state. What is emerging is an additional approach for producing protein pharmaceuticals that maintain native structure and activity during long-term storage.

Lipid unsaturation determines the interaction of AFP type I with model membranes during thermotropic phase transitions

We have previously shown that antifreeze protein (AFP) type I from winter flounder interacts with the acyl chains of lipids in model membranes containing a mixture of dimyristoylphosphatidylcholine (DMPC) and the plant thylakoid lipid digalactosyldiacylglycerol (DGDG), most likely through hydrophobic interactions. By contrast, in studies with pure phospholipid membranes, no such interaction was seen. DGDG is a highly unsaturated lipid, which renders these studies quite different from the previous studies of AFP-membrane interaction where the lipids were saturated or trans-unsaturated. Therefore, it seemed possible that either the digalactose headgroups or the unsaturated DGDG acyl chains, or both, may be important for interactions of membranes with AFP type I. To distinguish between these possibilities, we catalytically hydrogenated the DGDG to obtain a galactolipid with completely saturated fatty acyl chains. The results with the hydrogenated DGDG were strikingly different from those obtained previously with the unsaturated DGDG; the clear binding of AFPs to the bilayer appeared to be lost. Nevertheless, the temperature-dependent folding of AFP type I was inhibited in the presence of liposomes containing either the unsaturated or the hydrogenated DGDG. The results indicate that the liposomes and protein still interact, even following hydrogenation of the acyl chains, perhaps at the membrane-solution interface.

Characterization of the solution conformations of leuprolide acetate

Leuprolide acetate (pGlu-His-Trp-Ser-Tyr-d-Leu-Leu-Arg-Pro-NHEt), a potent LHRH agonist in wide clinical use, was characterized conformationally by NMR and circular dichroism. It displayed quite different preferred conformations under different solution conditions: two low population beta-turns in water, a nascent helix in TFE/water at low pH, and a high population beta-turn in TFE/water at slightly acidic pH. The pH-related conformational change in TFE/water is attributed to the pK(a) of the acetate counterion, not to ionizable groups on the peptide. None of these conformations are in exact agreement with previous computational predictions.

Prognosis and work absence due to occupational contact dermatitis

The consequences of a diagnosis of occupational contact dermatitis (OCD) were investigated using cases available from the voluntary surveillance scheme, EPIDERM. Cases of OCD reported from November 1994 to September 1995 were identified and sampled to give at least 100 cases of allergic, irritant and mixed OCD reported by consultant dermatologists (344 cases) and occupational physicians (377 cases). A questionnaire was sent to the reporting physician to elicit further information. 512 completed questionnaires were returned, of which 510 were eligible for analysis. Among cases reported by dermatologists (n = 286) and occupational physicians (n = 224), 7% (6.3%) had been unemployed and 16.8% (20.1%) had taken sick leave. 3 factors independently predicted time off work in a logistic regression analysis: age OR = 1.25 (95% CI, 1.05-1.49), allergic dermatitis OR = 1.77 (95% CI, 1.13-2.79) and medicolegal assessment OR = 4.42 (95% CI, 2.20-8.89). Overall, 15.7% did not improve clinically between the first and last visit. Those who did not improve had been exposed to the agent for longer (mean 7.6 years) than those who did (5.3 years) (p = 0.09). In patients <or= 45 years, those reported to be atopic failed to improve (25.4%) more often than those not atopic (13.4%) (p = 0.04). The substantial numbers (21%) with time off work and with persistent dermatitis suggest that OCD continues to have a significant impact on workers and their employers.

Modeling the growth of Listeria monocytogenes in cured ready-to-eat processed meat products by manipulation of sodium chloride, sodium diacetate, potassium lactate, and product moisture content

A central composite second-order response surface design was employed to determine the influences of added sodium chloride (0.8 to 3.6%), sodium diacetate (0 to 0.2%), potassium lactate syrup (0.25 to 9.25%), and finished-product moisture (45.5 to 83.5%) on the predicted growth rate of Listeria monocytogenes in cured ready-to-eat (RTE) meat products. Increased amounts of both sodium diacetate (P < 0.11) and potassium lactate (P < 0.001) resulted in significant reductions in the growth rate constants of L monocytogenes. Increased finished-product moisture (P < 0.11) significantly increased growth rate constants. The nfluence of sodium chloride was not statistically significant. The second-order statistical factor for lactate was significant (P < 0.01), but all two-way interactions were not. In general, predicted growth rates exceeded actual growth rates obtained from inoculation studies of four cured RTE meat products (wieners, smoked-cooked ham, light bologna, and cotto salami). The final model will be useful to food technologists in determining formulations that will result in finished cured RTE meat products in which L. monocytogenes is not likely to grow.

Surveillance for work-related hearing loss in the UK: OSSA and OPRA 1997-2000

Surveillance data on occupational audiological disorders have been collected by the Occupational Surveillance Scheme for Audiological Physicians (OSSA) since October 1997 and by the Occupational Physicians Reporting Activity (OPRA) from January 1996. During the 3 years ending in September 2000, a total of 1620 new cases were received from consultant audiological physicians; 988 new cases were estimated from reports by occupational physicians in the period from October 1997 to September 2000. The annual incidence of occupational noise-induced hearing loss (NIHL) was 1.94 and 1.23 per 100 000 workers for the OSSA and OPRA schemes, respectively. The median age at diagnosis with NIHL was 59 years in OSSA reports and 50 years in OPRA; nearly all cases were seen in men (95.6 and 92.5% male cases for OSSA and OPRA, respectively). High incidence rates based on OSSA reports were seen in foundry labourers (64.0 per 100 000 employed), coal gas and coke oven furnace workers (54.6), workers in transport and communication (43.1), metal workers (31.3), and members of the armed forces (28.3). Data from occupational physicians point to high rates in sawyers and woodworking machinists, metal furnace workers, coach and carriage builders, maintenance fitters, and engineering labourers. Among workers aged < or =45 years, those in manufacturing and the armed forces were prominent. The long latency of occupational hearing loss makes surveillance difficult, but consistent patterns in occupational risk suggest targets for preventive efforts.

[Iliopsoas impingement after cementless total hip arthroplasty. Case reports]

Postoperative pain after total hip arthroplasty can be caused by several conditions. We describe two cases of postoperative persistent iliopsoas impingement after cementless implantation of the acetabular component. The groin pain was relieved after revision with a more anteverted acetabular component. We describe the diagnostic methods as well as the principles of the revision.

The reported incidence of work-related musculoskeletal disease in the UK: MOSS 1997-2000

Consultant rheumatologists participate in surveillance of work-related musculoskeletal conditions under the Musculoskeletal Occupational Surveillance Scheme (MOSS), which has been in operation since 1997. During the first 3 years of the scheme, an estimated total of 8070 cases and 8442 diagnoses were obtained, an average of slightly less than 2700 estimated cases each year. Disorders of the upper limb accounted for approximately 66% (5502) of the total, with hand/wrist/arm conditions (3693 cases) comprising the majority of these. Conditions of the lumbar spine and trunk (13% of cases), the cervical spine (12%) and the shoulder (12%) were also frequently reported. Pain with ill-defined pathology was reported in 35% of cases with hand and forearm disorders. Overall, 82% of cases were related to repetitive rather than single injury. The largest numbers of cases were seen in workers in craft occupations (1659) and in clerical and secretarial workers (1524). High rates of musculoskeletal conditions, particularly of upper limb disorders, are notable in mining. In most occupations, and overall, women were at greater risk than men.

Spark-source mass spectrometric assessment of silicon concentrations in silicon-doped gallium arsenide single crystals

The spark-source mass spectrometric assessment of silicon concentrations in silicon-doped vertical-gradient-freeze gallium arsenide is presented. The silicon concentrations determined are compared with the charge-carrier densities measured by means of the Hall effect with van der Pauw symmetry along the axis of a single crystal.

SWORD '99: surveillance of work-related and occupational respiratory disease in the UK

Systematic reports from chest and occupational physicians under the SWORD and OPRA (Occupational Physicians Reporting Activity) surveillance schemes continue to provide a picture of the incidence of occupational respiratory disease in the UK. An estimated total of 4393 incident cases (comprising 4530 diagnoses) were reported during the 1999 calendar year, an increase of 1427 cases over the previous year. Benign pleural disease was the single most frequently reported condition (28% of all diagnoses reported). Occupational asthma cases (1168; 26%) remained high, as did mesothelioma (1032; 23%). Analysis of trends over the past 8 years shows an increase in mesothelioma cases, but little change in asthma. The annual incidence per 100,000 employed people, 1996-1999, for mesothelioma, lung cancer and pneumoconiosis was high amongst construction workers (28.7), miners and quarrymen (26.5), woodworkers (18.9) and gas, coal and chemical workers (15.2). Trends in mesothelioma incidence by birth cohort continue to show an increase in construction workers and a continuing decline in shipyard and insulation workers. The relative proportion of pneumoconiosis cases attributed to coal mining has fallen steadily in workers born since approximately 1920 and most cases are now in men who have been employed in quarrying and rock drilling.

Effect of zinc binding and precipitation on structures of recombinant human growth hormone and nerve growth factor

Metal-induced precipitation of protein therapeutics is being used and further developed as a processing step in protein formulation and may have utility in protein purification and bulk storage. In such processes, it is imperative that native protein structure is maintained and the metal complexation is reversible. In the current study, we investigated the effects of zinc-induced precipitation on recombinant human growth hormone (rhGH) and recombinant human nerve growth factor (rhNGF). On the addition of ethylenediaminetetraacetic acid (EDTA), the precipitates were dissolved, yielding complete recovery of native protein in both cases. Both proteins have specific metal binding sites and require specific molar ratios of zinc to protein to initiate precipitation (zinc:rhGH > 2:1; zinc:rhNGF > 18:1). Furthermore, the secondary structures of both proteins were unperturbed in soluble zinc complexes and zinc-induced precipitates, as measured by infrared and circular dichroism spectroscopies. The soluble zinc complex of rhGH had minor tertiary structural alterations, whereas zinc binding did not alter the tertiary structure of rhNGF. These studies indicated that metal-induced precipitation provides a method to maintain proteins in their native state in precipitates, which may be useful for purification, storage, and formulation.

Comparative fourier transform infrared and circular dichroism spectroscopic analysis of alpha1-proteinase inhibitor and ovalbumin in aqueous solution

Alpha1-proteinase inhibitor (alpha1Pi) and ovalbumin are both members of the serpin superfamily. They share about a 30% sequence identity and exhibit great similarity in their three-dimensional structures. However, no apparent functional relationship has been found between the two proteins. Unlike alpha1Pi, ovalbumin shows no inhibitory effect to serine proteases. To see whether or not a conformational factor(s) may contribute to the functional difference, we carried out comparative analysis of the two proteins' secondary structure, thermal stability, and H-D exchange using FT-IR and CD spectroscopy. FT-IR analysis reveals significant differences in the amide I spectral patterns of the two proteins. Upon thermal denaturation, both proteins exhibit a strong low-wavenumber beta-sheet band at 1624 cm(-1) and a weak high-wavenumber beta-sheet band at 1694 cm(-1), indicative of intermolecular aggregate formation. However, the midpoint of the thermal-induced transition of alpha1Pi (approximately 55 degrees C) is 18 degrees C lower than that of ovalbumin (approximately 73 degrees C). The thermal stability analysis provides new insight into the structural changes associated with denaturation. The result of H-D exchange explains some puzzling spectral differences between the two proteins in D2O reported previously.

Surveillance of work-related diseases by occupational physicians in the UK: OPRA 1996-1999

The Occupational Physicians' Reporting Activity (OPRA) surveillance scheme for occupational physicians has now been in place for 4 years. During this period, an estimated 43,764 new cases of work-related disease have been reported. Musculoskeletal conditions make up nearly half (49%) of all cases; mental ill-health and skin disease account for 20% each, with respiratory conditions (8%) and hearing loss (5%) seen in lower proportions. Overall, eight of 42 diagnoses made up four-fifths of the new cases reported by occupational physicians. These were hand and arm disorders (8052 estimated cases), contact dermatitis (7104), disorders of the lumbar spine (6000), anxiety and depression (4788), work-related stress (3336), hearing loss (2100), elbow disorders (2040), and asthma (1680). Dermatitis and hearing loss were most frequent in manufacturing industries, lower back complaints in health care, and upper limb disorders in automotive manufacture. Psychiatric illnesses presented a different pattern, mainly affecting those in health, education and social service.

Long chain arginine esters: a new class of cationic detergents for preparation of hydrophobic ion-paired complexes

The ability of stoichiometric amounts (based on charged groups) of ionic detergents to bind to oppositely charged ionic compounds has been recently reviewed. These hydrophobic ion-paired (HIP) complexes display altered solubility properties. Most of the work to date on HIP compelxes has focused on basic drugs and anionic detergents. It would be extremely useful to extend this approach to acidic compounds, including DNA and RNA. However, most cationic detergents are relatively toxic. It is hypothesized that detergents constructed from naturally occurring or well tolerated components, coupled by labile linkages, will be less toxic and still able to form strong HIP complexes. This study describes the synthesis and characterization of long chain alkyl esters of arginine. This class of cationic detergents, which have not been reported previously, are less cytotoxic than alkyltrimethylammonium detergents, possibly making them more acceptable in drug delivery applications. These arginine esters exhibit detergent-like properties. For example, the dodecyl ester of arginine has a critical micelle concentration of 0.07 mM, while being approximately 5-10 fold less toxic than tetradecyltrimethylammonium bromide. The arginine dodecyl ester forms stable HIP complexes with plasmid DNA. The complex is sufficiently stable to allow some modest level of transfection with Cos-7 cells in a time- and concentration-dependent fashion. This work demonstrates that arginine-based cationic detergents are effective ion-pairing agents, appear to be less toxic than alkyltrimethylammonium compounds, and form stable complexes with DNA.

Surveillance of occupational skin disease: EPIDERM and OPRA

Consultant dermatologists in the U.K. have been reporting to EPIDERM, a voluntary surveillance scheme for occupational skin disease, since February 1993; reporting by occupational physicians to the scheme began in May 1994 and was superseded in January 1996 by OPRA (Occupational Physicians Reporting Activity). Currently 244 dermatologists and 790 occupational physicians report incident cases to these schemes. During the 6 years to January 1999 a total of 12, 574 new cases of occupational skin disease was estimated from reports by consultant dermatologists and 10,136 cases estimated from occupational physicians (since May 1994). The annual incidence of occupational contact dermatitis using data from both schemes was 12. 9 per 100,000 workers. The incidence of contact dermatitis per 100, 000 workers increased with age in men from 4.9 (age 16-29 years) to 6.6 (age 45-60 years); in women a higher rate (9.5) was apparent in the younger age group, with lower rates in older female workers. High rates in young workers were associated with wet work and in older workers with exposure to oils. For men, high rates of contact dermatitis were seen in reports from both schemes for chemical operatives, machine tool setters and operatives, coach and spray painters and metal workers. For women, high rates were found for hairdressers, biological scientists and laboratory workers, nurses and those working in catering. The most frequent agents for contact dermatitis were rubber chemicals and materials (14.1% of cases reported by dermatologists), soaps and cleaners (12.7%), nickel (11. 9%), wet work (11.1%), personal protective equipment (6.2%), petroleum products (6.3%), cutting oils and coolants (5.6%), and epoxy and other resins (6.1%). In the 1608 estimated cases of skin cancer all but 4% were attributed to ultraviolet radiation. Cases of contact urticaria attributed to latex peaked in 1996, with a decline in cases since that time.

Occupational contact dermatitis in the UK: a surveillance report from EPIDERM and OPRA

Since February 1993 the EPIDERM surveillance scheme has collected data on occupational skin disease from consultant dermatologists in the UK. Reporting by occupational physicians to the scheme began in May 1994 and was superseded in January 1996 by the Occupational Physicians Reporting Activity (OPRA). The schemes currently receive reports on incident cases from 244 dermatologists and 790 occupational physicians. An estimated total of 9937 cases of contact dermatitis reported by dermatologists was calculated from surveillance data; 8129 contact dermatitis cases were estimated from reports by occupational physicians. The annual incidence of occupational contact dermatitis from dermatologist reports was 6.4 cases per 100,000 workers and 6.5 per 100,000 from reports by occupational physicians, an overall rate of 12.9 cases per 100,000 workers. Manufacturing industries account for the greatest number of cases seen by both sets of reporting physicians, with health care employment second. Reports from dermatologists also indicate high rates of dermatitis in the personal service industries (mainly hairdressers and barbers) and in agriculture. With the exception of an increase in cases seen in nurses in both schemes, the numbers and proportions of cases of contact dermatitis within occupations have remained fairly constant over the 6-year reporting period. Agents accounting for the highest number of allergic contact dermatitis cases were rubber (23.4% of allergic cases reported by dermatologists), nickel (18.2), epoxies and other resins (15.6), aromatic amines (8.6), chromium and chromates (8.1), fragrances and cosmetics (8.0), and preservatives (7.3). Soaps (22.0% of cases), wet work (19.8), petroleum products (8.7), solvents (8.0), and cutting oils and coolants (7.8) were the most frequently cited agents in cases of irritant dermatitis. The national scope of the data, together with the parallel structure by which both dermatologists and occupational physicians report incident cases, is useful in determining the extent of skin hazards in UK industry and may help in better targeting efforts to reduce the burden of skin disease at work.

Stability of human serum albumin during bioprocessing: denaturation and aggregation during processing of albumin paste

PURPOSE

To assess the impact of various bioprocessing steps on the stability of freshly precipitated human serum albumin (HSA) obtained from pooled human plasma.

METHODS

After initial precipitation of HSA from plasma, the resultant paste is either (a) lyophilized or (b) washed with acetone and then air-dried in order to obtain a dry powder. The structure of HSA was examined using Fourier transform infrared (IR) spectroscopy. The extent of aggregation of redissolved HSA was measured using both dynamic light scattering and SDS-polyacrylamide gel electrophoresis (SDS-PAGE).

RESULTS

Both lyophilization and air-drying perturb the secondary structural composition of HSA, as detected by infrared (IR) spectroscopy. Upon dissolution of dried paste, most of the protein refolds to a native-like conformation. However, a small fraction of the protein molecules form soluble aggregates that can be detected by both dynamic light scattering and SDS-PAGE. The level of aggregation is so low that it could not be detected in the bulk by either circular dichroism or IR spectroscopy. The lyophilized protein, which appears to be more unfolded in the solid state than the acetone washed/air-dried material, exhibits a higher level of aggregation upon dissolution.

CONCLUSIONS

There is a direct correlation between the extent of unfolding in the solid state and the amount of soluble aggregate present after dissolution. Moreover, the presence of the aggregates persists throughout the remainder of the purification process, which includes dissolution, chromatography, sterile filtration and viral inactivation steps. Analytical methods used to monitor the stability of biopharmaceuticals in the final product can be used to assess damage inflicted during processing of protein pharmaceuticals.

Long chain arginine esters: A new class of cationic detergents for preparation of hydrophobic ion-paired complexes

The ability of stoichiometric amounts (based on charged groups) of ionic detergents to bind to oppositely charged ionic compounds has been recently reviewed. These hydrophobic ion-paired (HIP) complexes display altered solubility properties. Most of the work to date on HIP compelxes has focused on basic drugs and anionic detergents. It would be extremely useful to extend this approach to acidic compounds, including DNA and RNA. However, most cationic detergents are relatively toxic. It is hypothesized that detergents constructed from naturally occurring or well tolerated components, coupled by labile linkages, will be less toxic and still able to form strong HIP complexes. This study describes the synthesis and characterization of long chain alkyl esters of arginine. This class of cationic detergents, which have not been reported previously, are less cytotoxic than alkyltrimethylammonium detergents, possibly making them more acceptable in drug delivery applications. These arginine esters exhibit detergent-like properties. For example, the dodecyl ester of arginine has a critical micelle concentration of 0.07 mM, while being approximately 5-10 fold less toxic than tetradecyltrimethylammonium bromide. The arginine dodecyl ester forms stable HIP complexes with plasmid DNA. The complex is sufficiently stable to allow some modest level of transfection with Cos-7 cells in a time- and concentration-dependent fashion. This work demonstrates that arginine-based cationic detergents are effective ion-pairing agents, appear to be less toxic than alkyltrimethylammonium compounds, and form stable complexes with DNA.

Development of positive selectable markers for the fungal pathogen Cryptococcus neoformans

Cryptococcus neoformans is an opportunistic fungal pathogen that causes meningitis in approximately 10% of patients with AIDS. New selectable markers which confer resistance to G418 or phleomycin when transformed into C. neoformans were made. A hygromycin-selectable marker was modified to allow selection with a single copy of the marker.

SWORD '98: surveillance of work-related and occupational respiratory disease in the UK

The SWORD surveillance scheme, now 10 years old, uses systematic reporting from physicians to provide a picture of the incidence of occupational respiratory disease in the United Kingdom. An estimated total of 2966 incident cases was derived from reports by chest and occupational physicians during the 1998 calendar year. Occupational asthma continues to be the most-reported respiratory condition, with an estimated 822 cases (27% of total cases). The proportion of cases of mesothelioma (23%), benign pleural disease (21%) pneumoconiosis (7%) and inhalation injuries (6%) remain similar to those estimated in past years, although fewer cases overall were reported. The most commonly identified agents causing asthma in 1998 were enzymes, isocyanates, laboratory animals and insects, colophony and fluxes, flour, latex, and glutaraldehyde. An increased incidence of respiratory diseases of short latency was seen in mining, whilst cases in chemical, mineral products and motor vehicle manufacture remained high; lower rates were noted in wood products and textile manufacture when compared with 1997 figures. Inhalation accidents over the past 3 years were reviewed; gaseous agents and combustion products accounted for nearly half of cases. High rates for inhalation injuries were seen in coal miners, fuel production, motor vehicle manufacturing, water purification, and chemical manufacturing.

[Rectal carcinoma. Optimizing therapy by partial or total mesorectum removal]

The role of total mesorectal excision for rectal cancer treatment is one of the most exciting findings in surgical oncology of the recent years. The patient's prognosis largely depends on the surgical quality of rectal resection. The excision of the cancer bearing rectum has to follow very precisely along the mesorectal fascia by sharp dissection without damaging the mesorectum itself. This technique reduces the local recurrence rate to below 10% and allows long-term survival in two thirds of all patients. Rectal cancers of the middle and lower third of the rectum need to be treated by total mesorectal excision down to the muscular pelvic floor, the ones of the upper third and the sigmoideo-rectal junction are appropriately treated by partial mesorectal excision down to 5 cm below the tumor. No additional survival benefit may be expected when pelvic lymphadenectomy has been performed. The direct tumor spread along the bowel wall and the lymphatic tumor spread in a caudal direction are uncommon and late findings in rectal cancer disease. Low and ultralow rectal carcinomas may therefore be treated by a sphincter preserving procedure respecting a safety margin of at least 1 to 2 cm. Thus, continence preserving surgery may be performed in over 80% of patients suffering from rectal cancer without compromising long-term outcome.

The West Virginia Occupational Safety and Health Initiative: practicum training for a new marketplace

CONTEXT

Occupational medicine practice has experienced a shift from larger corporate medical departments to organizations providing services for a variety of industries. Specific training needs will accompany this shift in practice patterns; these may differ from those developed in the traditional industrial or corporate medical department setting.

METHODS

The West Virginia Occupational Health and Safety Initiative involves occupational medicine residents in consultation to a variety of small industries and businesses. It uses the expertise of occupational physicians, health and safety extension faculty, and faculty in engineering and industrial hygiene. Residents participate in multidisciplinary evaluations of worksites, and develop competencies in team-building, workplace health and safety evaluation, and occupational medical consulting.

OUTCOME MEASURES

Specific competencies that address requirements for practicum training are used to measure the trainee's acquisition of knowledge and skills. Particular attention is paid to the acquisition of group problem-solving expertise, skills relevant to the current market in practice opportunities, and the specific career interests of the resident physician. Preliminary evaluation indicates the usefulness of training in evaluation of diverse industries and worksites.

CONCLUSIONS

We offer this program as a training model that can prepare residents for the challenges of a changing marketplace for occupational health and safety services.

Binding of pyridoxal 5'-phosphate to the heme protein human cystathionine beta-synthase

Cystathionine beta-synthase (CBS), a pyridoxal 5'-phosphate (PLP) dependent enzyme, catalyzes the condensation of serine and homocysteine to form cystathionine. Mammalian CBS was recently shown to be a heme protein. While the role of heme in CBS is unknown, catalysis by CBS can be explained solely by participation of PLP in the reaction mechanism. In this study, treatment of CBS with sodium borohydride selectively reduced the Schiff base but did not affect the heme. Purification and sequencing of the PLP-cross-linked peptide from a trypsin digest of the reduced enzyme revealed the evolutionarily conserved Lys119 to be the residue forming the Schiff base. Serine and hydroxylamine form an alpha-aminoacrylate and an oxime with PLP in CBS, respectively. The sulfhydryl-containing substrate, homocysteine, disturbs the heme environment but does not interact with PLP. In contrast to other PLP-dependent enzymes, CBS emits no PLP-related fluorescence when excited at 296 or 330 nm. PLP but not heme dissociates from the enzyme in the presence of hydroxylamine. The dissociation of PLP is a multistage process involving a short approximately 500 s lag phase, followed by a rapid inactivation and a slower PLP-oxime formation. PLP-free CBS exhibits a decrease of secondary structure as well as loss of CBS activity that can be only partially restored by PLP. This study constitutes the first comprehensive investigation of PLP interaction with a heme protein.

Injuries in home health care workers: an analysis of occupational morbidity from a state compensation database

BACKGROUND

Home health services represent one of the fastest-growing segments of the US economy. Home health care workers (HHCWs) might be expected to have a high incidence and increased severity of injury because of inherent difficulty in control over their work environment, and the limited amount of research on injuries in home health care appears to support this hypothesis.

METHODS

Using data on workers' compensation claims for 1995-1996 from a large state database, we calculated the incidence, frequency, and types of injuries occurring in this working population. Comparison data were drawn from nursing home (NH) and hospital-based nursing personnel.

RESULTS

An incidence of 52 injuries per 1,000 workers per year was calculated; this rate lies between nursing home workers (132/1,000) and hospital-based workers (46/1,000). The percentage of indemnified (> 3 days lost-time) injuries was increased over those occurring in nursing home personnel. Mean number of days lost from work by home health workers was 44, significantly increased from the average 18 and 14 days lost by NH and hospital nursing workers, respectively. Mean indemnity payment was $1,523 and mean medical costs were $1,276 per injury. Permanent partial disability awards were made to 19 (4.9%) of the injured HHCWs during the 2-year study period; back injuries accounted for 63% (12) of these awards. Overexertion injuries and falls accounted for 63% of total injuries in this group of workers, while 13.5% occurred as a result of motor vehicle accidents. The incidence of injury attributed to motor vehicles in HHCWs was 7 per 1,000 workers per year, an order of magnitude greater than in NH and hospital workers.

CONCLUSIONS

These data indicate that injuries to HHCWs, though less frequent than in their nursing home counterparts, result in greater lost time from work and accompanying costs, which may indicate greater severity of injury. Characteristics of home health work, including increased intensity and speed of work, adverse working conditions, and the necessity of motor vehicle transportation as a condition of work may be contributors to injury in this setting. Further investigation of determinants of accidents and injuries in home health care, both in the actual setting where the work takes place and in the way it is structured, is warranted.

Cloning, expression, and characterization of a DNA binding domain of gpNu1, a phage lambda DNA packaging protein

Terminase is an enzyme from bacteriophage lambda that is required for insertion of the viral genome into an empty pro-capsid. This enzyme is composed of the viral proteins gpNu1 (20.4 kDa) and gpA (73.3 kDa) in a holoenzyme complex. Current models for terminase assembly onto DNA suggest that gpNu1 binds to three repeating elements within a region of the lambda genome known as cosB which, in turn, stimulates the assembly of a gpA dimer at the cosN subsite. This prenicking complex is the first of several stable nucleoprotein intermediates required for DNA packaging. We have noted a hydrophobic region within the primary amino acid sequence of the terminase gpNu1 subunit and hypothesized that this region constitutes a protein-protein interaction domain required for cooperative assembly at cosB and that is also responsible for the observed aggregation behavior of the isolated protein. We therefore constructed a mutant of gpNu1 in which this hydrophobic "domain" has been deleted in order to test these hypotheses. The deletion mutant protein, gpNu1DeltaK, is fully soluble and, unlike full-length protein, shows no tendency toward aggregation; However, the protein is a dimer under all experimental conditions examined as determined by gel permeation and sedimentation equilibrium analysis. The truncated protein is folded with evidence of secondary and tertiary structural elements by circular dichroism and NMR spectroscopy. While physical and biological assays demonstrate that gpNu1DeltaK does not interact with the terminase gpA subunit, the deletion mutant binds with specificity to cos-containing DNA. We have thus constructed a deletion mutant of the phage lambda terminase gpNu1 subunit which constitutes a highly soluble DNA binding domain of the protein. We further propose that the hydrophobic amino acids found between Lys100 and Pro141 define a self-association domain that is required for the assembly of stable nucleoprotein packaging complexes and that the C-terminal tail of the protein defines a distinct gpA-binding site that is responsible for terminase holoenzyme formation.

In vitro release kinetics of gentamycin from a sodium hyaluronate gel delivery system suitable for the treatment of peripheral vestibular disease

For certain patients who experience intense vertigo arising from unilateral vestibular lesions, the primary therapy is a vestibular nerve section, an intracranial surgical procedure. One alternative to this treatment is therapeutic ablation of vestibular function on the unaffected side using an ototoxic agent. We prepared a biodegradable sustained-release gel delivery system using sodium hyaluronate that can be administered into the middle ear using only a local anesthetic. The gel contains gentamycin sulfate, the ototoxic agent of choice for treatment of unilateral vestibulopathy, and it exhibits diffusion-controlled release of the drug over a period of hours. The released gentamycin could then diffuse into the inner ear through the round membrane. This represents an important advance over previous formulations, which used only gentamycin sulfate solutions, in that it should allow more careful control of the dose, it should reduce loss of the drug from the middle ear site, and it should maintain intimate contact with the round membrane. By carefully controlling the dose, it should be possible to inhibit vestibular function while minimizing hearing loss. Herein we describe the in vitro release kinetics of gentamycin sulfate from sodium hyaluronate gels and find that the system obeys Fickian behavior.

Preparation and in vitro characterization of gentamycin-impregnated biodegradable beads suitable for treatment of osteomyelitis

A new method for preparing poly(L-lactide) (PLA) biodegradable beads impregnated with an ionic aminoglycoside, gentamycin, is described. The process employs hydrophobic ion pairing to solubilize gentamycin in a solvent compatible with PLA, followed by precipitation with a compressed antisolvent (supercritical carbon dioxide). The resulting precipitate is a homogeneous dispersion of the ion-paired drug in PLA microspheres. The microspheres are approximately 1 microm in diameter and can be compressed into beads (3-6 mm in diameter) strung on surgical sutures for implantation. The bead strings exhibit no significant change in release kinetics upon sterilization with a hydrogen peroxide plasma (Ster-Rad). The kinetics of gentamycin release from the PLA beads are consistent with a matrix-controlled diffusion mechanism. While nonbiodegradable poly(methyl methacrylate) (PMMA) beads initially release gentamycin in a similar manner, the drug release from PMMA ceases after 8 or 9 weeks, while the PLA beads continue to release drug for over 4 months. Moreover, only 10% of the gentamycin is released from the PMMA beads, while PLA beads release more than 60% of their load, if serum is present in the release medium. The PLA system displays improved release kinetics relative to PMMA, is biodegradable, is unaltered by gas sterilization, can be used for a range of antibiotics, and can be manipulated without disintegration. These are all desirable properties for an implantable drug delivery system for the prevention or treatment of osteomyelitis.

The phage lambda terminase enzyme: 1. Reconstitution of the holoenzyme from the individual subunits enhances the thermal stability of the small subunit

The terminase enzyme from bacteriophage lambda is a hetero-trimeric complex composed of the viral gpA and gpNu1 proteins (gpA1.gpNu1(2)) and is responsible for packaging a single genome within the viral capsid. Current expression systems for these proteins require thermal induction which may be responsible for the formation of insoluble aggregates observed in E. coli. We report the re-cloning of the terminase subunits into vectors which allow low temperature induction. While this has resulted in increased solubility of the large gpA subunit of the enzyme, the small gpNu1 subunit remains insoluble under all conditions examined. This paper describes the solublization of gpNu1 with guanidinium hydrochloride and purification of the protein to homogeneity. Reconstitution of the enzyme from the individually purified subunits yields a catalytically-competent complex which exhibits activity identical to wild-type enzyme. Thermal denaturation of the proteins was monitored by circular dichroism (CD) spectroscopy and demonstrates that while unfolding of gpA is irreversible, the gpNu1 subunit refolds into a conformation which is essentially identical to the pre-heated protein. Moreover, while denaturation of gpA is highly cooperative, the small subunit unfolds over a wide temperature range and with thermodynamic parameters lower than expected for a small globular protein. Thermally-induced denaturation of the enzyme reconstituted from the individual subunits is highly cooperative with no evidence of multiple transitions. Our data demonstrate that the terminase subunits directly interact in solution, and that this interaction alters the thermal stability of the smaller gpNu1 subunit. The implication of these results with respect to assembly of a catalytically competent enzyme complex are discussed.

The phage lambda terminase enzyme: 2. Refolding of the gpNu1 subunit from the detergent-denatured and guanidinium hydrochloride-denatured state yields different oligomerization states and altered protein stabilities

The terminase enzyme from bacteriophage lambda is responsible for packaging a single genome within the viral capsid. Gold and co-workers have developed a scheme for the solubilization of the small terminase subunit (gpNu1) from inclusion bodies using the strong detergent sarkosyl and purification of the protein to homogeneity (gpNu1SRK) (Parris et al., J Biol Chem 1994;269:13564-13574). We have developed a similar purification scheme except that guanidinium hydrochloride was used to denature the insoluble protein (gpNu1GDN). The circular dichroism (CD) spectra of both protein preparations suggest that they are predominantly alpha-helical when purified and stored in Tris buffers. Moreover, thermal denaturation of the proteins thus purified yielded similar thermodynamic parameters for unfolding (T(m), delta Hm and delta Sm of unfolding of approximately 306 K, approximately 22 kcal/mol and approximately 70 cal/mol.K, respectively). Interestingly, however, when the proteins were purified and stored in imidazole buffers, the gpNu1SRK preparation lost a significant amount of secondary structure and was more stable to both thermally-induced and guanidinium HCl-induced denaturation than was gpNu1GDN. The purified gpNu1 monomers oligomerize into apparent tetramers and hexamers in solution and the distribution between these two oligomeric states and into higher order aggregates depends upon buffer composition, salt concentration and protein concentration. Moreover, differences in the oligomerization state of gpNu1SRK and gpNu1GDN under identical buffer conditions were observed. The significance of these results with respect to the biological role of the phage lambda gpNu1 protein are discussed.

Hydrophobic ion pairing: altering the solubility properties of biomolecules

The high aqueous solubility of ionic compounds can be attributed to the ease of solvation of the counter ions. Replacement of the counter ions with ionic detergents dramatically alters the solubility properties of the molecule. Not only does the aqueous solubility drop precipitously, but the solubility in organic phases increases as well. Consequently, the partition coefficient changes by orders of magnitude. This ion pairing phenomenon, which we term hydrophobic ion pairing (HIP), has been extended to polyelectrolytes, such as proteins and polynucleotides. These materials form HIP complexes that dissolve in a range of organic solvents, often with retention of native structure and enzymatic activity. The HIP process has been used to purify protein mixtures, conduct enzymatic reactions in nonaqueous environments, increase structural stability, enhance bioavailability, and prepare new dosage forms.

Hydrophobic ion pairing as a method for enhancing structure and activity of lyophilized subtilisin BPN' suspended in isooctane

The use of enzymes in low water environments permits reactions to occur that are difficult or impossible in aqueous solution. In this manner, proteases can be used to form, rather than hydrolyze, ester and amide linkages. Presumably, the native-like structure of the enzyme must remain intact for catalysis to transpire. However, little is known regarding the integrity of the overall structure of lyophilized proteins suspended in organic media. In this study, the structural changes that occur during the freeze-drying process and those effected by suspension in the organic solvent were examined. Using Fourier-transform infrared spectroscopy, the secondary structure of lyophilized subtilisin BPN' was monitored and correlated to the level of enzymatic activity when suspended in isooctane. In addition, the ability of ionic detergents to stabilize subtilisin BPN' via ion pairing was evaluated. It was found that subtilisin unfolds to some degree during lyophilization, whether it is ion paired or not. Furthermore, there are structural changes observed when the enzyme is placed in isooctane, although the effects are less with ion-paired subtilisin. This higher level of retention of secondary structure results in increased enzymatic activity.

Use of circular dichroism spectroscopy in determining the conformation of a monoclonal antibody prior to its incorporation in an immunoliposome

Attachment of antibodies to liposomes endows target specificity to liposomes for a certain cell or organ that express the targeted antigenic determinant. These so-called immunoliposomes hold high promise as targeted drug carriers. One approach of immunoliposome preparation involves conjugating antibodies to hydrophobic anchors (e.g. fatty acids or phospholipid molecules) for incorporation into the liposome membrane. Often, these conjugation reactions are harsh and may result in undesirable chemical and structural changes in the antibody molecule. This necessitates confirmation of the target specificity of the derivatized antibody prior to its incorporation into the liposome. Our approach to this problem is to utilize circular dichroism spectroscopy, which can detect subtle structural differences in proteins with high reproducibility and accuracy in relatively short period of time. In addition, circular dichroism is a non-destructive technique. In this study, we demonstrate the ability of circular dichroism to confirm the conformation of a model antibody, HYB-241, conjugated to N-glutarylphosphatidylethanolamine, prior to its mixing with dioleoylphosphatidylethanolamine/dioleoylphosphatidic acid to form a target-sensitive immunoliposome.

alphaT244M mutation affects the redox, kinetic, and in vitro folding properties of Paracoccus denitrificans electron transfer flavoprotein

Threonine 244 in the alpha subunit of Paracoccus denitrificans transfer flavoprotein (ETF) lies seven residues to the amino terminus of a proposed dinucleotide binding motif for the ADP moiety of the FAD prosthetic group. This residue is highly conserved in the alpha subunits of all known ETFs, and the most frequent pathogenic mutation in human ETF encodes a methionine substitution at the corresponding position, alphaT266. The X-ray crystal structures of human and P. denitrificans ETFs are very similar. The hydroxyl hydrogen and a backbone amide hydrogen of alphaT266 are hydrogen bonded to N(5) and C(4)O of the flavin, respectively, and the corresponding alphaT244 has the same structural role in P. denitrificans ETF. We substituted a methionine for T244 in the alpha subunit of P. denitrificans ETF and expressed the mutant ETF in Escherichia coli. The mutant protein was purified, characterized, and compared with wild type P. denitrificans ETF. The mutation has no significant effect on the global structure of the protein as inferred from visible and near-ultraviolet absorption and circular dichroism spectra, far-ultraviolet circular dichroism spectra, and infrared spectra in 1H2O and 2H2O. Intrinsic fluorescence due to tryptophan of the mutant protein is 60% greater than that of the wild type ETF. This increased tryptophan fluorescence is probably due to a change in the environment of the nearby W239. Tyrosine fluorescence is unchanged in the mutant protein, although two tyrosine residues are close to the site of the mutation. These results indicate that a change in structure is minor and localized. Kinetic constants of the reductive half-reaction of ETF with porcine medium chain acyl-CoA dehydrogenase are unaltered when alphaT244M ETF serves as the substrate; however, the mutant ETF fails to exhibit saturation kinetics when the semiquinone form of the protein is used as the substrate in the disproportionation reaction catalyzed by P. denitrificans electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO). The redox behavior of the mutant ETF was also altered as determined from the equilibrium constant of the disproportionation reaction. The separation of flavin redox potentials between the oxidized/semiquinone couple and semiquinone/hydroquinone couple are -6 mV in the wild type ETF and -27 mV in the mutant ETF. The mutation does not alter the AMP content of the protein, although the extent and fidelity of AMP-dependent, in vitro renaturation of the mutant AMP-free apoETF is reduced by 57% compared to renaturation of wild type apoETF, likely due to the absence of the potential hydrogen bond donor T244.

Prevalence of small lung opacities in populations unexposed to dusts. A literature analysis

OBJECTIVES

Despite the wide use of the International Labor Organization (ILO) system for reading chest radiographs, little information is available regarding the prevalence of abnormalities in populations unexposed to dusts. Prevalence studies of radiographic changes consistent with dust inhalation, as classified by the system, would be more meaningful if there were better understanding regarding the extent of abnormalities in unexposed populations.

DESIGN

To determine small opacity prevalence in unexposed populations, a review of articles published since 1970 that used the ILO system to classify radiographs of the unexposed, either as subjects or control subjects, was performed. Criteria for inclusion in this review included ascertainment of the lack of exposure of subjects to occupational dusts, and independent reading of radiographs by at least two readers certified in the ILO system (B readers) or experienced in its use. A total of eight published articles presenting data on nine study populations were included in this study.

RESULTS

The prevalence of small opacities graded 1/0 or greater varied widely, with a range from 0.21 to 11.7%. A meta-analysis of the published data yielded a population prevalence of 5.3% (95% confidence interval [CI] = 2.9 to 7.7%). The prevalence was significantly greater in Europe than in North America (Europe, 11.3%; 95% CI = 10.1 to 12.5%; North America, 1.6%; 95% CI = 0.6 to 2.6%). A subset of the studies contained information on gender that showed greater prevalence of lung opacities in male subjects than female subjects (male subjects, 5.5%; 95% CI = 3.4 to 7.6%; female subjects, 3.5%; 95% CI = 1.3 to 5.8%). Based on estimated age information, the studies were divided into two strata (mean age < 50 years vs > or = 50 years). The age-specific pooled prevalence was higher in the studies with mean age > or = 50 years than studies with mean age < 50 years in both Europe (11.7% vs 9.6%) and North America (2.3% vs 0.6%). Prevalence of lung opacities remained significantly higher in Europe and North America in each age stratum. The large difference in the prevalence between Europe and North America could not be explained on the basis of age, gender, or smoking history, although available age and smoking data are less robust.

CONCLUSIONS

These results indicate that a background level of opacities consistent with the radiographic appearance of pneumoconiosis exists in populations considered to be free of occupational dust exposure. Environmental and unaccounted occupational exposures, as well as reader variability, all may play a role in the determination of small opacity prevalence in these subjects and may explain the large differences between Europe and North America. Thorough ascertainments of occupational and environmental exposures are essential to determine the true significance of opacities in populations who are not exposed to dust.

Effect of secondary structure on the activity of enzymes suspended in organic solvents

Despite the extensive use and study of enzymes suspended in organic solvents, whether activity differences between different preparations can be accounted for by differences in protein secondary structure is still unknown. To address this issue, in the current study two model enzymes, alpha-chymotrypsin and subtilisin Carlsberg, were lyophilized and suspended in both polar and nonpolar organic solvents. The secondary structures of the proteins in the initial aqueous solution, in the lyophilized powder, and in the subsequent suspensions in organic solvents were determined using infrared spectroscopy. Lyophilization perturbed the secondary structure of both enzymes. With alpha-chymotrypsin, lyophilization from buffer followed by suspension in ethanol, hexane, or pyridine did not alter the unfolded structure observed in the dried powder. In contrast, with subtilisin Carlsberg, suspension of the dried enzyme in ethanol led to further perturbation of structure, whereas in hexane, and more so in pyridine, there was some return toward native structure. Lyophilization of the aqueous protein solutions in the presence of either trehalose or sorbitol led to retention of more native-like structure of both enzymes in the dried solid. However, large structural perturbations arose when these samples were suspended in organic solvents. The only exception was the subtilisin-trehalose mixture, which regained some native structure in ethanol and hexane. The greatest changes were noted in samples suspended in pyridine, in which the infrared spectra indicated extensive intermolecular beta-sheet formation from protein aggregates. There was not any consistent correlation between activity in organic solvents and either the initial structure obtained in the dried powders or the final structure when suspended in organic solvents. Nor could differences in residual water contents in dried samples or the total water content in the organic solvent reaction system account for the activity differences.

Generation of soluble and active subtilisin and alpha-chymotrypsin in organic solvents via hydrophobic ion pairing

With very low concentrations of anionic detergents, such as sodium dodecyl sulfate (SDS) and Aerosol OT (AOT), it is possible to solubilize proteases in organic solvents, while retaining enzymatic activity. For example, the SDS-subtilisin BPN' complex catalyzes transesterification of Ac-Phe-OMe in ethanol with a kcat/Km of 36 M-1 s-1 for mutant M1 and 39 M-1 s-1 for the wild type. By comparison, M1 suspended in ethanol is approximately 1000-fold less active, with a kcat/Km of 0.03 M-1 s-1. Similarly, AOT complexes of alpha-chymotrypsin were found to be approximately 1000 times more active (kcat/Km = 100-350 M-1 s-1) than the suspended enzyme.

Combined NRA, channeling-RBS and FTIR ellipsometry analyses for the determination of the interface and bonding state of thin SiO x and SiN x O y layers

The molecular ions O(+)(2) and NO(+) are im- planted at room temperature into single-crystal silicon with an energy of E=6 keV/atom at fluences ranging from 2.5x10(16) to 3.5x10(17) at/cm(2). The samples are processed by electron beam rapid thermal annealing at 1100 ( degrees )C for 15 s. The depth distributions of the implanted specimens ((18)O) are determined by nuclear reaction analyses using the reaction (18)O(p,alpha)(15)N. Channeling-RBS measurements are performed to obtain the interface structure between the implanted layer and the single-crystal Si substrate. The chemical bonding state of as-implanted and implanted-annealed specimens is observed by FTIR ellipsometry measurements.