Monitoring Gait and Physical Activity of Elderly Frail Individuals in Free-Living Environment: A Feasibility Study

INTRODUCTION

Frailty is conventionally diagnosed using clinical tests and self-reported assessments. However, digital health technologies (DHTs), such as wearable accelerometers, can capture physical activity and gait during daily life, enabling more objective assessments. In this study, we assess the feasibility of deploying DHTs in community-dwelling older individuals, and investigate the relationship between digital measurements of physical activity and gait in naturalistic environments and participants' frailty status, as measured by conventional assessments.

METHODS

Fried Frailty Score (FFS) was used to classify fifty healthy individuals as non-frail (FFS = 0, n/female = 21/11, mean ± SD age: 71.10 ± 3.59 years), pre-frail (FFS = 1-2, n/female = 23/9, age: 73.74 ± 5.52 years), or frail (FFS = 3+, n/female = 6/6, age: 70.70 ± 6.53 years). Participants wore wrist-worn and lumbar-worn GENEActiv accelerometers (Activinsights Ltd., Kimbolton, UK) during three in-laboratory visits, and at-home for 2 weeks, to measure physical activity and gait. After this period, they completed a comfort and usability questionnaire. Compliant days at-home were defined as follows: those with ≥18 h of wear time, for the wrist-worn accelerometer, and those with ≥1 detected walking bout, for the lumbar-worn accelerometer. For each at-home measurement, a group analysis was performed using a linear regression model followed by ANOVA, to investigate the effect of frailty on physical activity and gait. Correlation between at-home digital measurements and conventional in-laboratory assessments was also investigated.

RESULTS

Participants were highly compliant in wearing the accelerometers, as 94% indicated willingness to wear the wrist device, and 66% the lumbar device, for at least 1 week. Time spent in sedentary activity and time spent in moderate activity as measured from the wrist device, as well as average gait speed and its 95th percentile from the lumbar device were significantly different between frailty groups. Moderate correlations between digital measurements and self-reported physical activity were found.

CONCLUSIONS

This work highlights the feasibility of deploying DHTs in studies involving older individuals. The potential of digital measurements in distinguishing frailty phenotypes, while unobtrusively collecting unbiased data, thus minimizing participants' travels to sites, will be further assessed in a follow-up study.

Improving Surveillance of Human Tick-Borne Disease Risks: Spatial Analysis Using Multimodal Databases

BACKGROUND

The extent of tick-borne disease (TBD) risk in the United States is generally unknown. Active surveillance using entomological measures, such as presence and density of infected nymphal Ixodes scapularis ticks, have served as indicators for assessing human risk, but results have been inconsistent and passive surveillance via public health systems suggests TBDs are underreported.

OBJECTIVE

Research using various data sources and collection methods (eg, Google Trends, apps, and tick bite encounters [TBEs] reports) has shown promise for assessing human TBD risk. In that vein, and engaging a One Health perspective, this study used multimodal databases, geographically overlaying patient survey data on TBEs and concomitant reports of TBDs with data drawn from other sources, such as canine serological reports, to glean insights and to determine and assess the use of various indicators as proxies for human TBD risk.

METHODS

This study used a mixed methods research strategy, relying on triangulation techniques and drawing on multiple data sources to provide insights into various aspects of human disease risk from TBEs and TBDs in the United States. A web-based survey was conducted over a 15-month period beginning in December 2020 to collect data on TBEs. To maximize the value of the covariate data, related analyses included TBE reports that occurred in the United States between January 1, 2000, and March 31, 2021. TBEs among patients diagnosed with Lyme disease were analyzed at the county level and compared to I scapularis and I pacificus tick presence, human cases identified by the Centers for Disease Control and Prevention (CDC), and canine serological data. Spatial analyses employed multilayer thematic mapping and other techniques.

RESULTS

After cleaning, survey results showed a total of 249 (75.7%) TBEs spread across 148 respondents (61.9% of all respondents, 81.7% of TBE-positive respondents); 144 (4.7%) counties in 30 states (60%) remained eligible for analysis, with an average of 1.68 (SD 1.00) and median of 1 (IQR 1) TBEs per respondent. Analysis revealed significant spatial matching at the county level among patient survey reports of TBEs and disease risk indicators from the CDC and other official sources. Thematic mapping results included one-for-one county-level matching of reported TBEs with at least 1 designated source of human disease risk (ie, positive canine serological tests, CDC-reported Lyme disease, or known tick presence).

CONCLUSIONS

Use of triangulation methods to integrate patient data on TBE recall with established canine serological reports, tick presence, and official human TBD information offers more granular, county-level information regarding TBD risk to inform clinicians and public health officials. Such data may supplement public health sources to offer improved surveillance and provide bases for developing robust proxies for TBD risk among humans.

Neurological Pain, Psychological Symptoms, and Diagnostic Struggles among Patients with Tick-Borne Diseases

Public health reports contain limited information regarding the psychological and neurological symptoms of tick-borne diseases (TBDs). Employing a mixed-method approach, this analysis triangulates three sources of symptomology and provides a comparison of official public health information, case reports, medical literature, and the self-reported symptoms of patients with Lyme disease and other TBDs. Out of the fifteen neuropsychiatric symptoms reported in the medical literature for common TBDs, headaches and fatigue and/or malaise are the only two symptoms fully recognized by public health officials. Of TBDs, Lyme disease is the least recognized by public health officials for presenting with neuropsychiatric symptoms; only headaches and fatigue are recognized as overlapping symptoms of Lyme disease. Comparisons from a patient symptoms survey indicate that self-reports of TBDs and the associated symptoms align with medical and case reports. Anxiety, depression, panic attacks, hallucinations, delusions, and pain—ranging from headaches to neck stiffness and arthritis—are common among patients who report a TBD diagnosis. Given the multitude of non-specific patient symptoms, and the number and range of neuropsychiatric presentations that do not align with public health guidance, this study indicates the need for a revised approach to TBD diagnosis and for improved communication from official public health sources regarding the wide range of associated symptoms.

Using an unbiased symbolic movement representation to characterize Parkinson's disease states

Unconstrained human movement can be broken down into a series of stereotyped motifs or 'syllables' in an unsupervised fashion. Sequences of these syllables can be represented by symbols and characterized by a statistical grammar which varies with external situational context and internal neurological state. By first constructing a Markov chain from the transitions between these syllables then calculating the stationary distribution of this chain, we estimate the overall severity of Parkinson's symptoms by capturing the increasingly disorganized transitions between syllables as motor impairment increases. Comparing stationary distributions of movement syllables has several advantages over traditional neurologist administered in-clinic assessments. This technique can be used on unconstrained at-home behavior as well as scripted in-clinic exercises, it avoids differences across human evaluators, and can be used continuously without requiring scripted tasks be performed. We demonstrate the effectiveness of this technique using movement data captured with commercially available wrist worn sensors in 35 participants with Parkinson's disease in-clinic and 25 participants monitored at home.

mHealth and wearable technology should replace motor diaries to track motor fluctuations in Parkinson's disease

Accurately monitoring motor and non-motor symptoms as well as complications in people with Parkinson's disease (PD) is a major challenge, both during clinical management and when conducting clinical trials investigating new treatments. A variety of strategies have been relied upon including questionnaires, motor diaries, and the serial administration of structured clinical exams like part III of the MDS-UPDRS. To evaluate the potential use of mobile and wearable technologies in clinical trials of new pharmacotherapies targeting PD symptoms, we carried out a project (project BlueSky) encompassing four clinical studies, in which 60 healthy volunteers (aged 23-69; 33 females) and 95 people with PD (aged 42-80; 37 females; years since diagnosis 1-24 years; Hoehn and Yahr 1-3) participated and were monitored in either a laboratory environment, a simulated apartment, or at home and in the community. In this paper, we investigated (i) the utility and reliability of self-reports for describing motor fluctuations; (ii) the agreement between participants and clinical raters on the presence of motor complications; (iii) the ability of video raters to accurately assess motor symptoms, and (iv) the dynamics of tremor, dyskinesia, and bradykinesia as they evolve over the medication cycle. Future papers will explore methods for estimating symptom severity based on sensor data. We found that 38% of participants who were asked to complete an electronic motor diary at home missed ~25% of total possible entries and otherwise made entries with an average delay of >4 h. During clinical evaluations by PD specialists, self-reports of dyskinesia were marked by ~35% false negatives and 15% false positives. Compared with live evaluation, the video evaluation of part III of the MDS-UPDRS significantly underestimated the subtle features of tremor and extremity bradykinesia, suggesting that these aspects of the disease may be underappreciated during remote assessments. On the other hand, live and video raters agreed on aspects of postural instability and gait. Our results highlight the significant opportunity for objective, high-resolution, continuous monitoring afforded by wearable technology to improve upon the monitoring of PD symptoms.

Family Experiences with the Diagnosis of Autism Spectrum Disorder: System Barriers and Facilitators of Efficient Diagnosis

This paper examines family experiences with the efficiency of ASD diagnosis. Children were age 8 or younger with ASD (n = 450). Outcomes were delay from first parent concern to diagnosis, shifting diagnoses, and being told child did not have ASD. Predictors were screening, travel distance, and problems finding providers. Logit models were used to examine associations. Screening was associated with reduced delay in diagnosis; problems finding providers were associated with greater delay. Screening, travel distance, and delay in diagnosis were associated with shifting diagnoses and being told child did not have ASD. Physician and parent training in communication and addressing mental health professional shortages and maldistribution may improve the diagnosis experiences of families of children with ASD.

Evaluation of the use of the Scale for the Assessment and Rating of Ataxia (SARA) in healthy volunteers and patients with schizophrenia

OBJECTIVE

The Scale for the Assessment and Rating of Ataxia (SARA) is a semi-quantitative assessment used to evaluate ataxia. The goal of these studies was to assess and evaluate the utility of this instrument in a Healthy Volunteer (HV) group and subjects with Schizophrenia (SCZ).

METHODS

Two studies were completed to collect SARA data, in a HV group and in a stable SCZ group. 177 HVs (18-65 years) and 16 SCZs (18-58 years) provided written consent and were assessed using the SARA. Of 177 HV subjects, 88 had 2 SARA assessments (within 2 days of initial visit) while all 16 SCZ had 3 SARA assessments (within 14 days of initial visit).

RESULTS

For the HV group, the mean score ± Std for the SARA on visit-1 was 0.39 ± 0.72, and 0.34 ± 0.64 for visit-2. The Pearson correlation coefficient between visit-1 and visit-2 was 0.7486 and an ICC of 0.743. For the SCZ group, the mean score for the SARA was 0.63 ± 0.65 on visit-1, 0.84 ± 1.19 on visit-2, and 0.84 ± 0.94 on visit-3. The Pearson correlation coefficient between visit-1 and visit-2 was 0.6545, between visit-1 and visit-3 was 0.6635 and between visit-2 and visit-3 was 0.7613 and an ICC of 0.650. There was no significant difference in baseline SARA scores between the HV and SCZ group p = .063. A statistically significant positive association between age and total SARA scores was observed in HV (r = 0.345) and SCZ (r = 0.676).

CONCLUSIONS

A strong association was observed in both the HV and SCZ groups in the reassessment of signs of ataxia using the SARA scale. Both groups demonstrated minimal signs of ataxia, with no statistically significant difference between the two groups in their visit-1 scores.

The importance of interpersonal communication in poison centers

BACKGROUND

Poison control center (PCC) personnel face many challenges in communicating with callers and with each other. The purpose of this study was to identify interpersonal communication issues that affect the work environment within PCCs.

METHODS

As part of a larger questionnaire study distributed electronically to members of the American Association of Poison Control Centers (AAPCC) to assess communication training needs for PCCs, three questions were included to assess interpersonal communication within the work environment: (1) How important is interpersonal communication within your center to a positive work environment? (not at all to extremely important, 1-7); (2) How disruptive is interpersonal communication to your work? (not at all to extremely disruptive, 1-7); and (3) What communication issues do you find most disruptive to your work? (free-text response). Descriptive and qualitative content analyses were used to identify themes in responses.

RESULTS

A total of 537 responses were received from SPIs, directors, medical directors, and other PCC staff. Interpersonal communication within the PCC was rated as extremely important to a positive work environment (median = 7 and IQR = 6-7; 62.3% rated as extremely important). Interpersonal communication was rated as less than moderately disruptive on average (median = 3 and IQR = 2-4). Free-text responses were received from 335 (62%) respondents. Free-text comments were broadly categorized as relating to PCC personnel and work environment and issues related to PCC callers. Categories that emerged from the PCC personnel and work environment category included the following: poor interpersonal communication (n = 104; 31%); background noise (n = 96; 29%); poor work procedures (n = 51; 15%); and poor management communication (n = 38; 11%).

CONCLUSION

Interpersonal communication within PCCs was considered to be important for a positive work environment. Although not found to be strongly disruptive by most respondents, several specific interpersonal communication issues were identified by PCC personnel as disruptive to their work.

Control of Lactobacillus contaminants in continuous fuel ethanol fermentations by constant or pulsed addition of penicillin G

The addition of penicillin G to combat microbial contamination in continuous fuel alcohol fermentations was performed using both continuous and pulsed addition regimes. In continuous fermentations where both Saccharomyces cerevisiae and Lactobacillus paracasei were present, the mode of addition of penicillin G determined final numbers of viable L. paracasei. When the same overall average concentration of penicillin G was added in both pulsed and continuous modes, the initial viable number of L. paracasei (8.0 x 10(9) cfu ml(-1)) decreased to a greater degree (1.02 x 10(5) cfu ml(-1) L. paracasei) when penicillin G was pulsed at 6 h frequencies at an overall average concentration of 2,475 U/l than when penicillin G was added continuously at 2,475 U/l (2.77 x 10(5) cfu ml(-1) L. paracasei). Pulsed additions over longer frequencies at 2,475 U/l were not as effective in reducing viable bacteria. Viable yeasts increased during both treatment conditions by more than 2-fold. The two addition regimes also eliminated the 40% decrease in ethanol concentration caused by the intentional bacterial infection. Although there was 3 times more bacterial death with 6 h pulsed additions compared to continuous additions of penicillin G at 2,475 U/l, there was, by that point, no practical difference in either final ethanol concentration or relative ethanol recovery.

Influence of medium buffering capacity on inhibition of Saccharomyces cerevisiae growth by acetic and lactic acids

Acetic acid (167 mM) and lactic acid (548 mM) completely inhibited growth of Saccharomyces cerevisiae both in minimal medium and in media which contained supplements, such as yeast extract, corn steep powder, or a mixture of amino acids. However, the yeast grew when the pH of the medium containing acetic acid or lactic acid was adjusted to 4.5, even though the medium still contained the undissociated form of either acid at a concentration of 102 mM. The results indicated that the buffer pair formed when the pH was adjusted to 4.5 stabilized the pH of the medium by sequestering protons and by lessening the negative impact of the pH drop on yeast growth, and it also decreased the difference between the extracellular and intracellular pH values (Delta(pH)), the driving force for the intracellular accumulation of acid. Increasing the undissociated acetic acid concentration at pH 4.5 to 163 mM by raising the concentration of the total acid to 267 mM did not increase inhibition. It is suggested that this may be the direct result of decreased acidification of the cytosol because of the intracellular buffering by the buffer pair formed from the acid already accumulated. At a concentration of 102 mM undissociated acetic acid, the yeast grew to higher cell density at pH 3.0 than at pH 4.5, suggesting that it is the total concentration of acetic acid (104 mM at pH 3.0 and 167 mM at pH 4.5) that determines the extent of growth inhibition, not the concentration of undissociated acid alone.

Effect of lactobacilli on yeast growth, viability and batch and semi-continuous alcoholic fermentation of corn mash

AIMS

The aim of this study was to evaluate interactions between Saccharomyces cerevisiae and selected strains of lactobacilli regarding cell viabilities, and production of organic acids and ethanol during fermentation.

METHODS AND RESULTS

Corn mashes were inoculated with yeasts and selected strains of lactobacilli, and fermented in batch or semi-continuous (cascade) mode. Ethanolic fermentation rates and viabilities of yeast were not affected by lactobacilli unless the mash was pre-cultured with lactobacilli. Then, yeast growth was inhibited and the production of ethanol was reduced by as much as 22%.

CONCLUSION

Yeasts inhibited the multiplication of lactobacilli and this resulted in reduced production of acetic and lactic acids. The self-regulating nature of the cascade system allowed the yeast to recover, even when the lactobacilli had a head start, and reduced the size of the population of the contaminating Lactobacillus to a level which had an insignificant effect on fermentation rate or ethanol yield.

SIGNIFICANCE AND IMPACT OF THE STUDY

Contamination during fermentation is normally taken care of by the large yeast inoculum, although yeast growth and fermentation rates could be adversely affected by the presence of high numbers of lactobacilli in incoming mash or in transfer lines.

Effects of acetic acid and lactic acid on the growth of Saccharomyces cerevisiae in a minimal medium

Specific growth rates (mu) of two strains of Saccharomyces cerevisiae decreased exponentially (R2 > 0.9) as the concentrations of acetic acid or lactic acid were increased in minimal media at 30 degrees C. Moreover, the length of the lag phase of each growth curve (h) increased exponentially as increasing concentrations of acetic or lactic acid were added to the media. The minimum inhibitory concentration (MIC) of acetic acid for yeast growth was 0.6% w/v (100 mM) and that of lactic acid was 2.5% w/v (278 mM) for both strains of yeast. However, acetic acid at concentrations as low as 0.05-0.1% w/v and lactic acid at concentrations of 0.2-0.8% w/v begin to stress the yeasts as seen by reduced growth rates and decreased rates of glucose consumption and ethanol production as the concentration of acetic or lactic acid in the media was raised. In the presence of increasing acetic acid, all the glucose in the medium was eventually consumed even though the rates of consumption differed. However, this was not observed in the presence of increasing lactic acid where glucose consumption was extremely protracted even at a concentration of 0.6% w/v (66 mM). A response surface central composite design was used to evaluate the interaction between acetic and lactic acids on the specific growth rate of both yeast strains at 30 degrees C. The data were analysed using the General Linear Models (GLM) procedure. From the analysis, the interaction between acetic acid and lactic acid was statistically significant (P < or = 0.001), i.e., the inhibitory effect of the two acids present together in a medium is highly synergistic.

Urea hydrogen peroxide reduces the numbers of lactobacilli, nourishes yeast, and leaves no residues in the ethanol fermentation

Urea hydrogen peroxide (UHP) at a concentration of 30 to 32 mmol/liter reduced the numbers of five Lactobacillus spp. (Lactobacillus plantarum, L. paracasei, Lactobacillus sp. strain 3, L. rhamnosus, and L. fermentum) from approximately 10(7) to approximately 10(2) CFU/ml in a 2-h preincubation at 30 degrees C of normal-gravity wheat mash at approximately 21 g of dissolved solids per ml containing normal levels of suspended grain particles. Fermentation was completed 36 h after inoculation of Saccharomyces cerevisiae in the presence of UHP, even when wheat mash was deliberately contaminated (infected) with L. paracasei at approximately 10(7) CFU/ml. There were no significant differences in the maximum ethanol produced between treatments when urea hydrogen peroxide was used to kill the bacteria and controls (in which no bacteria were added). However, the presence of L. paracasei at approximately 10(7) CFU/ml without added agent resulted in a 5.84% reduction in the maximum ethanol produced compared to the control. The bactericidal activity of UHP is greatly affected by the presence of particulate matter. In fact, only 2 mmol of urea hydrogen peroxide per liter was required for disinfection when mashes had little or no particulate matter present. No significant differences were observed in the decomposition of hydrogen peroxide in normal-gravity wheat mash at 30 degrees C whether the bactericidal agent was added as H(2)O(2) or as urea hydrogen peroxide. NADH peroxidase activity (involved in degrading H(2)O(2)) increased significantly (P = 0.05) in the presence of 0.75 mM hydrogen peroxide (sublethal level) in all five strains of lactobacilli tested but did not persist in cells regrown in the absence of H(2)O(2). H(2)O(2)-resistant mutants were not expected or found when lethal levels of H(2)O(2) or UHP were used. Contaminating lactobacilli can be effectively managed by UHP, a compound which when used at ca. 30 mmol/liter happens to provide near-optimum levels of assimilable nitrogen and oxygen that aid in vigorous fermentation performance by yeast.

Effects of lactobacilli on yeast-catalyzed ethanol fermentations

Normal-gravity (22 to 24 degrees Plato) wheat mashes were inoculated with five industrially important strains of lactobacilli at approximately 10(5), approximately 10(6), approximately 10(7), approximately 10(8), and approximately 10(9) CFU/ml in order to study the effects of the lactobacilli on yeast growth and ethanol productivity. Lactobacillus plantarum, Lactobacillus paracasei, Lactobacillus #3, Lactobacillus rhamnosus, and Lactobacillus fermentum were used. Controls with yeast cells but no bacterial inoculation and additional treatments with bacteria alone inoculated at approximately 10(7) CFU/ml of mash were included. Decreased ethanol yields were due to the diversion of carbohydrates for bacterial growth and the production of lactic acid. As higher numbers of the bacteria were produced (depending on the strain), 1 to 1.5% (wt/vol) lactic acid resulted in the case of homofermentative organisms. L. fermentum, a heterofermentative organism, produced only 0.5% (wt/vol) lactic acid. When L. plantarum, L. rhamnosus, and L. fermentum were inoculated at approximately 10(6) CFU/ml, an approximately 2% decrease in the final ethanol concentration was observed. Smaller initial numbers (only 10(5) CFU/ml) of L. paracasei or Lactobacillus #3 were sufficient to cause more than 2% decreases in the final ethanol concentrations measured compared to the control. Such effects after an inoculation of only 10(5) CFU/ml may have been due to the higher tolerance to ethanol of the latter two bacteria, to the more rapid adaptation (shorter lag phase) of these two industrial organisms to fermentation conditions, and/or to their more rapid growth and metabolism. When up to 10(9) CFU of bacteria/ml was present in mash, approximately 3.8 to 7.6% reductions in ethanol concentration occurred depending on the strain. Production of lactic acid and a suspected competition with yeast cells for essential growth factors in the fermenting medium were the major reasons for reductions in yeast growth and final ethanol yield when lactic acid bacteria were present.

Use of virginiamycin to control the growth of lactic acid bacteria during alcohol fermentation

The antibiotic virginiamycin was investigated for its effects on growth and lactic acid production by seven strains of lactobacilli during the alcoholic fermentation of wheat mash by yeast. The lowest concentration of virginiamycin tested (0.5 mg Lactrol kg-1 mash), was effective against most of the lactic acid bacteria under study, but Lactobacillus plantarum was not significantly inhibited at this concentration. The use of virginiamycin prevented or reduced potential yield losses of up to 11% of the produced ethanol due to the growth and metabolism of lactobacilli. However, when the same concentration of virginiamycin was added to mash not inoculated with yeast, Lactobacillus rhamnosus and L. paracasei grew after an extensive lag of 48 h and L. plantarum grew after a similar lag even in the presence of 2 mg virginiamycin kg-1 mash. Results showed a variation in sensitivity to virginiamycin between the different strains tested and also a possible reduction in effectiveness of virginiamycin over prolonged incubation in wheat mash, especially in the absence of yeast.

Effects of particulate materials and osmoprotectants on very-high-gravity ethanolic fermentation by Saccharomyces cerevisiae

The effects of osmoprotectants (such as glycine betaine and proline) and particulate materials on the fermentation of very high concentrations of glucose by the brewing strain Saccharomyces cerevisiae (uvarum) NCYC 1324 were studied. The yeast growing at 20 degrees C consumed only 15 g of the sugar per 100 ml from a minimal medium which initially contained 35% (wt/vol) glucose. Supplementing the medium with a mixture of glycine betaine, glycine, and proline increased the amount of sugar fermented to 30.5 g/100 ml. With such supplementation, the viability of the yeast cells was maintained above 80% throughout the fermentation, while it dropped to less than 12% in the unsupplemented controls. Among single additives, glycine was more effective than proline or glycine betaine. On incubating the cultures for 10 days, the viability decreased to only 55% with glycine, while it dropped to 36 and 27%, respectively, with glycine betaine and proline. It is suggested that glycine and proline, known to be poor nitrogen sources for growth, may serve directly or indirectly as osmoprotectants. Nutrients such as tryptone, yeast extract, and a mixture of purine and pyrimidine bases increased the sugar uptake and ethanol production but did not allow the population to maintain the high level of cell viability. While only 43% of the sugar was fermented in unsupplemented medium, the presence of particulate materials such as wheat bran, wheat mash insolubles, alumina, and soy flour increased sugar utilization to 68, 75, 81, and 82%, respectively.

Relationship of low lysine and high arginine concentrations to efficient ethanolic fermentation of wheat mash

Very high gravity wheat mashes containing 20 or more grams of carbohydrates per 100 mL were fermented completely by Saccharomyces cerevisiae, even though these mashes contained low amounts of assimilable nitrogen. Supplementation of wheat mashes with various amino acids or with yeast extract, urea, or ammonium sulfate reduced the fermentation time. However, lysine or glycine added as single supplements, inhibited yeast growth and fermentation. With lysine, yeast growth was severely inhibited, and a loss of cell viability as high as 80% was seen. Partial or complete reversal of lysine-induced inhibition was achieved by the addition of a number of nitrogen sources. All nitrogen sources that relieved lysine-induced inhibition of yeast growth also promoted uptake of lysine and restored cell viability to the level observed in the control. They also increased the rate of fermentation. Experiments with minimal media showed that for lysine to be inhibitory to yeast growth, assimilable nitrogen in the medium must be in growth-limiting concentrations or totally absent. In the presence of excess nitrogen, lysine stimulated yeast growth and fermentation. Results indicate that supplementing wheat mash with other nitrogen sources increases the rate of fermentation not only by providing extra nitrogen but also by reducing or eliminating the inhibitory effect of lysine on yeast growth.

Comparison of enzyme immunoassay and fluorescence polarization immunoassay as techniques for measuring anticonvulsant drugs on the same analytical instrument

We have applied kits for enzyme immunoassay and fluorescence polarization immunoassay of anticonvulsant drugs to the same centrifugal analyser. There was a good correlation between the two techniques for the assay of phenytoin, carbamazepine, and phenobarbitone. Within- and between-batch reproducibility was also comparable but only the fluorescence polarization system allowed the use of stored calibration curves. The ability to use stored curves may be particularly advantageous to laboratories required to run a large number of stat assays or who are handling low workloads of particular analytes.

Fuel alcohol production: effects of free amino nitrogen on fermentation of very-high-gravity wheat mashes

Although wheat mashes contain only growth-limiting amounts of free amino nitrogen, fermentations by active dry yeast (Saccharomyces cerevisiae) were completed (all fermentable sugars consumed) in 8 days at 20 degrees C even when the mash contained 35 g of dissolved solids per 100 ml. Supplementing wheat mashes with yeast extract, Casamino Acids, or a single amino acid such as glutamic acid stimulated growth of the yeast and reduced the fermentation time. With 0.9% yeast extract as the supplement, the fermentation time was reduced from 8 to 3 days, and a final ethanol yield of 17.1% (vol/vol) was achieved. Free amino nitrogen derived in situ through the hydrolysis of wheat proteins by a protease could substitute for the exogenous nitrogen source. Studies indicated, however, that exogenously added glycine (although readily taken up by the yeast) reduced the cell yield and prolonged the fermentation time. The results suggested that there are qualitative differences among amino acids with regard to their suitability to serve as nitrogen sources for the growth of yeast. The complete utilization of carbohydrates in wheat mashes containing very little free amino nitrogen presumably resulted because they had the "right" kind of amino acids.

Effect of pH on the rate of Candida utilis cell cycle initiation

The rate of cell cycle initiation (as determined by the rate of bud emergence) in yeast Candida utilis under ammonium-limited phased cultivation was dependent on the pH at which the yeast was grown.

Neuromuscular drug interactions of clinical importance

The addition of marginally effective concentrations of d-tubocurarine (d-Tc), neomycin, or polymyxin B to the organ bath of rat phrenic nerve-hemidiaphragm preparations significantly (p < 0.05 to 0.001) increased the neuromuscular (NM) blocking effect of lidocaine. When both d-Tc and neomycin or polymyxin B were added the increase of the NM effect of lidocaine was even greater (p < 0.001). Washout re-established NM transmission. The NM block produced by combinations of d-Tc, neomycin, or polymyxin and lidocaine could be reversed partially by Ca2+ or neostigmine, and completely by 4-aminopyridine. The block caused by d-Tc and lidocaine was partially antagonized by neostigmine or 4-aminopyridine., The neomycin-lidocaine or the polymyxin B-lidocaine block, however, was not antagonized by thse compounds. The concentrations of d-Tc, antibiotics, and lidocaine that caused significant block in this in vitro preparation may be present at the NM junction of patients, who in the perioperative period had received combinations of therapeutic doses of d-Tc, neomycin, other aminoglycosides, or polymyxin B and lidocaine. This may cause impairment of spontaneous respiration requiring assisted ventilation.

Relationship between cell size and efficiency of synchronization during nitrogen-limited phased cultivation of Candida utilis

Under the phased method of cultivation the yeast Candida utilis grew and divided synchronously. The newly formed cells were relatively small, and a new cell cycle was not initiated until the cells could attain a certain minimum size (critical size). Although the cells expanded to some extent after division, the critical size was not reached until a fresh supply of medium was provided. With the arrival of the fresh supply of growth medium at the beginning of the phasing period, the cells expanded rapidly, and new cell cycles were initiated. The cells continued to expand until the growth-limiting nutrient (nitrogen source) was exhausted or until 90 min, which ever occurred first. Usually, buds emerged at a constant time after the start of the phasing period. The time of bud emergence was independent of the size attained by the cells during the expansion phase of growth. The results indicated that it was initiation of the cell cycle that was under size control, and not bud emergence. Bud emergence seemed to be under the control of a timer. The start of this timer seemed to be at or immediately after the beginning of the phasing period. Protein synthesis was essential for the initiation and expansion of buds. However, inhibition of protein synthesis by cycloheximide did not prevent unbudded cells or the parent portion of budded cells from expanding. Cycloheximide seemed to abolish the control mechanism(s) which prevented the cells from expanding after they had reached the maximum size.

Differential growth rates of Candida utilis mother and daughter cells under phased cultivation

The yeast Candida utilis was continuously synchronized by the phased method of cultivation with the nitrogen source as the growth-limiting nutrient. The doubling time (phasing period) of cells was 6 h. Both cell number and deoxyribonucleic acid synthesis showed a characteristic stepwise increase during the phased growth. The time of bud emergence coincided with the time of initiation of deoxyribonucleic acid synthesis. Size distribution studies combined with microscopic analysis showed that the cells expanded only during the unbudded phase of growth. Usually the cells stopped increasing in size about 30 min before bud emergence, and the arrest of the increase in cell volume coincided with the exhaustion of nitron from the medium. There was no net change in the volume of cells during the bud expansion phase of growth, suggesting that as the bud expanded, the volume of the mother portion of the cell decreased. After division the cells expanded slightly. The postdivision expansion of cells, unlike the growth before bud initiation, occurred in the absence of the growth-limiting nutrient. The newly formed daughter cells were smaller than the mother cells and expanded at a faster rate, so that both types of cells reached maximum size at the same time. Possible reasons for the different rates of expansion of mother and daughter cells are discussed.

Mutual potentiation of the neuromuscular effects of antibiotics and relaxants

The interaction of d-tubocurarine, pancuronium, or succinylcholine with neomycin, streptomycin, or polymyxin B was investigated using a rat phrenic nerve-hemidiaphragm preparation. All neuromuscular blocking agents (relaxants) mutually potentiated the neuromuscular blocking action of one another; combinations of ineffective concentrations of relaxants and antibiotics caused an 82 to 98% neuromuscular block. This extensive potentiation of the neuromuscular effects of relaxants by antibiotics can be attributed to the fact that antibiotics not only have a curare-like stabilizing effect on the postjunctional membrane, but also decrease presynaptic acetylcholine release. Neostigmine (0.25 microgram/ml) only partially antagonized the neuromuscular block caused by the various drug combinations. In contrast, 4 microgram/ml of 4-aminopyridine returned the twitch tension, depressed by combined administration of relaxants and antibiotics, to or above control values except in the case of neuromuscular block caused by the combinations of succinylcholine and polymyxin B.

Evolution of ethylene by Saccharomyces cerevisiae as influenced by the carbon source for growth and the presence of air

Effects of the carbon source and oxygen on ethylene production by the yeast Saccharomyces cerevisiae have been studied. The amounts of ethylene evolved by the yeast culture were less than those detected in the blank (an equal volume of uninoculated medium), suggesting a net absorption of ethylene by the yeast cells. Addition of glucose to the lactate-grown yeast culture induced ethylene production. This glucose-induced stimulation of ethylene production was inhibited to a great extent by cycloheximide. Results suggested that the yeast cells in the presence of glucose synthesized an ethylene precursor and passed it into the medium. The conversion of this precursor to ethylene might be stimulated by oxygen. The fact that ethylene was produced by the yeast growing anaerobically and also by respiration-deficient mutants isolated from the wild-type yeast suggested that mitochondrial ATP synthesis was not an absolute requirement for ethylene biogenesis.

Relationship between iron-limited growth and energy limitation during phased cultivation of Candida utilis

The yeast Candida utilis was continuously synchronized by the phasing technique (6 h doubling time) with either iron or nitrogen as the limiting nutrient. Iron limitations resulted in decreased molar growth yields with respect to the carbon substrates and ammonia and in increased specific rates of oxygen uptake. Relatively low energy-charge values were maintained by the iron-limited culture. All these taken together seemed to indicate that the growth of the yeast under iron limitation was also limited by metabolically available energy. Consideralbe amounts of ethyl acetate were produced by the yeast under phased cultivation when the growth was limited by iron but not by nitrogen. In vitro studies using cell-free extracts showed that the substrates for ethyl acetate synthesis were acetyl coenzyme A (acetyl CoA) and ethanol. Under iron-limited growth acetyl CoA seemed to be diverted to ethyl acetate formation rather than being oxidized through the tricarboxylic acid (TCA) cycle. The possibility of energy limitation under iron-limited growth being brought about by the reduced capacity of the yeast to oxidize acetyl CoA through the TCA cycle is considered.

Effects of ethylene on the metabolism of Saccharomyces cerevisiae

Supply of exogenous ethylene to lactate-grown yeast initially accelerated the rate of ethanol production from glucose, but later reduced the rate, with the overall effect being to reduce the total ethanol production. The rate of ethanol production by ethylene-treated yeast was not changed by removal of metabolic carbon dioxide. However, if CO2 was allowed to build up in the absence of applied ethylene, the ethanol production decreased. Ethylene increased the activities of a number of pentose phosphate and glycolytic pathway enzymes. The largest increase in activity was observed for phosphofructokinase (EC 2.7.1.11), regulatory enzyme of the glycolytic pathway. After an initial stimulation, glucose (and also 3-O-methyl glucose) uptake was reduced by ethylene. Ethylene appears to inhibit non-competitively the glucose transport system.

L-methionine as an ethylene precursor in Saccharomyces cerevisiae

L-Methionine induced production of ethylene by Saccharomyces cerevisiae growing in lactate medium. The production induced by L-methionine was inhibited by pyruvate, and elevated by glucose. Labeled ethylene was produced when L-[U-14C]methionine, but not [U-14C]glucose, was fed to the yeast. The mutant S. cerevisiae G1332 (ade-, met-) did not produce significant amounts of ethylene unless L-methionine was added. Thus L-methionine acts as a precursor of ethylene in S. cerevisiae. The role of glucose appears to be other than as a precursor.

Variations in the adenylate energy charge during phased growth (cell cycle) of Candida utilis under energy excess and energy-limiting growth conditions

The variations in the levels of adenine nucleotides during the phased growth (cell cycle) of the yeast Candida utilis growing under nitrogen, sulfate, or iron limitation with glycerol as carbon source have been determined. Synchronous cultures were obtained by the continuous phasing technique, and the results were compared with those of chemostat cultures growing at similar growth rates and under the same types of nutrient limitation. Whereas the chemostat experiments indicated only the average energy status of cultures growing at random, results from phased cultures showed that the adenylate energy charge, defined as (ATP + (1/2)ADP)/(ATP + ADP + AMP) (where ATP, ADP, and AMP signify adenosine 5'-triphosphate, -diphosphate, and -monophosphate, respectively), varied during the phased growth of the yeast. These variations were related to the stage of development of the cells and to the type of nutrient limitation. In every case the energy charge dropped to a low value during the first half of the phasing cycle (cell cycle). Whereas the energy charge was maintained at relatively high levels (ranging from 0.78 to 0.94), for sulfate- or nitrogen-limited cultures, it was very low when iron was the growth-limiting nutrient (0.44 to 0.78). In spite of the low energy charge, the yeast continued to grow under iron limitation. The main component of the adenylate pool of the iron-limited culture was ADP and not ATP as observed with other types of nutrient limitation. It is concluded that under iron limitation the growth of the organism is limited by energy and that under energy-limited growth the energy charge of a growing organism is maintained at low levels. The reason for maintaining a low energy charge in an energy-limited culture is discussed.