Combined immunodeficiency (CVID and CD4 lymphopenia) is associated with a high risk of malignancy among adults with primary immune deficiency

Primary immunodeficiency disorders (PID) are a group of heterogeneous disorders characterized by recurrent infections, autoimmunity, increased lymphoproliferative disorders and other malignancies. PID is classified into cellular or humoral disorders or a combination of both. We evaluated the clinical differences among adult patients with three variants of PID: common variable immunodeficiency (CVID), idiopathic CD4 lymphopenia (ICL) and combined immunodeficiency (CID). We retrospectively compared demographics, immunological characteristics, clinical presentations and outcomes of CVID, CID and ICL patients followed from 2012 to 2018. In our cohort, we identified 44 adult patients diagnosed with CVID (22), CID (11) and ICL (11). Malignancy was associated with CID, as seven of 11 patients in this group were diagnosed with malignancy compared to CVID (three of 22) or ICL (two of 11) (P = 0·002 and 0·03, respectively). Malignancies were also linked to male gender [odds ratio (OR) = 5, 95% confidence interval (CI) = 1·12-22·18) P = 0·0342] and a low ratio of CD4/CD8 < 0·8 (OR = 5·1, 95% CI = 1·22-21·28, P = 0·025). Among CID and ICL, two of 11 patients died in each group, while no death was documented among CVID group (P = 0·04). Autoimmune manifestations did not differ between groups. Similarly, the rate of infections was similar between groups, although infectious agents vary. CID is associated with a high risk of malignancy compare to CVID or ICL. Among adults with PID, male gender, low CD4 and a CD4/CD8 ratio of < 0·8 may serve as risk factors of concomitant malignancy. Surveillance of lymphocyte subpopulations should be considered for all adults.

Hydroxychloroquine desensitization, an effective method to overcome hypersensitivity-a multicenter experience.

Hydroxychloroquine (HCQ) is widely used to treat autoimmune/rheumatic diseases such as systemic lupus erythematosus (SLE). The immune modulation effects of HCQ have been highlighted as beneficial for maintaining remission of SLE as well as ameliorating skin, joint and other manifestations. Moreover, HCQ exposure for prolonged periods as well as during pregnancy is considered safe, therefore it is recommended for the vast majority of SLE patients. Although HCQ therapy requires follow-up by a specialist, its most common side effects are mild gastrointestinal disturbances, sensitivity to light and skin rashes. Of these side effects, hypersensitivity skin reactions have been suggested to play a role in reduced compliance to HCQ therapy. In the current study we present a two-stage HCQ desensitization protocol that was successfully implemented among 12 out of 13 patients. We exhibit that prolonged HCQ oral desensitization is an effective method for overcoming mild to moderate late hypersensitivity reactions and thoroughly address possible mechanisms of action.

A randomised controlled trial comparing high-flow nasal oxygen with standard management for conscious sedation during bronchoscopy.

Traditional conscious sedation for endobronchial ultrasound procedures places patients at risk of desaturation, and high-flow nasal oxygen may reduce the risk. We designed a parallel-group randomised controlled trial of high-flow nasal oxygen at a flow rate of 30-70 l.min-1 via nasal cannulae, compared with standard oxygen therapy at 10 l.min-1 via a bite block in adults planned for conscious sedation for endobronchial ultrasound. The primary outcome was the proportion of patients experiencing desaturation (defined as SpO2 < 90%). Secondary outcomes included oxygen saturation after pre-oxygenation, lowest oxygen saturation during procedure, number of hypoxic episodes, duration of hypoxia, end-procedure end-tidal CO2 , satisfaction scores and complications. Thirty participants were allocated to each group. Baseline patient characteristics, procedure time and anaesthetic agents used were similar between the groups. Desaturation occurred in 4 out of 30 patients allocated to the high-flow nasal oxygen group, compared with 10 out of 30 allocated to the standard oxygenation group, a non-significant difference (p = 0.07) with intention to treat analysis. The difference was significant (p = 0.047) when using a per-protocol analysis. Oxygen saturation after pre-oxygenation and the lowest oxygen saturation during procedure were significantly higher in the high-flow nasal oxygen group compared with the standard oxygenation group; median (IQR [range] 100 (99-100 [93-100]) vs. 98 (97-99 [94-100]), p = 0.0001 and 97.5 (94-99 [77-100]) vs. 92 (88-95 [79-98]), p < 0.001, respectively. There were no differences in other secondary outcomes. Although high-flow nasal oxygen may prevent desaturation due to some causes, it does not protect against hypoxaemia in all circumstances.

Exercise for people with cancer: a clinical practice guideline.

BACKGROUND: Development of this guideline was undertaken by the Exercise for People with Cancer Guideline Development Group, a group organized by Cancer Care Ontario's Program in Evidence-Based Care (pebc). The purpose of the guideline was to provide guidance for clinicians with respect to exercise for patients living with cancer, focusing on the benefits of specific types of exercise, recommendations about screening requirements for new referrals, and safety concerns. METHODS: Consistent with the pebc's standardized approach, a systematic search was conducted for existing guidelines, and systematic literature searches were performed in medline and embase for both systematic reviews and primary literature. Content and methodology experts performed an internal review, which was followed by an external review by targeted experts and intended users. RESULTS: The search identified three guidelines, eighteen systematic reviews, and twenty-nine randomized controlled trials with relevance to the topic. The present guideline provides recommendations for the duration, frequency, and intensity of exercise appropriate for people living with cancer. It also provides recommendations for pre-exercise assessment, safety concerns, and delivery models. CONCLUSIONS: There is sufficient evidence to show that exercise provides benefits in quality of life and muscular and aerobic fitness for people with cancer both during and after treatment, and that it does not cause harm. The present guideline is intended to support the Canadian Society for Exercise Physiology's Canadian physical activity guidelines. The recommendations are intended for clinicians and institutions treating cancer patients in Ontario, and for policymakers and program planners involved in the delivery of exercise programs for cancer patients.

Exercise for people with cancer: a systematic review.

BACKGROUND: This systematic review was completed by the Exercise for People with Cancer Guideline Development Group, a group organized by Cancer Care Ontario's Program in Evidence-Based Care (pebc). It provides background and guidance for clinicians with respect to exercise for people living with cancer in active and post treatment. It focuses on the benefits of specific types of exercise, pre-screening requirements for new referrals, safety concerns, and delivery models. METHODS: Using the pebc's standardized approach, medline and embase were systematically searched for existing guidelines, systematic reviews, and primary literature. RESULTS: The search identified two guidelines, eighteen systematic reviews, and twenty-nine randomized controlled trials with relevance to the topic. The present review provides conclusions about the duration, frequency, and intensity of exercise appropriate for people living with cancer. CONCLUSIONS: The evidence shows that exercise is safe and provides benefit in quality of life and in muscular and aerobic fitness for people with cancer both during and after treatment. The evidence is sufficient to support the promotion of exercise for adults with cancer, and some evidence supports the promotion of exercise in group or supervised settings and for a long period of time to improve quality of life and muscular and aerobic fitness. Exercise at moderate intensities could also be sustainable for longer periods and could encourage exercise to be continued over an individual's lifetime. It is important that a pre-screening assessment be conducted to evaluate the effects of disease, treatments, and comorbidities.

Can the referring surgeon enhance accrual of breast cancer patients to medical and radiation oncology trials? The ENHANCE study.

INTRODUCTION: The accrual rate to clinical trials in oncology remains low. In this exploratory pilot study, we prospectively assessed the role that engaging a referring surgeon plays in enhancing nonsurgical oncologic clinical trial accrual. METHODS: Newly diagnosed breast cancer patients were seen by a surgeon who actively introduced specific patient-and physician-centred strategies to increase clinical trial accrual. Patient-centred strategies included providing patients, before their oncology appointment, with information about specific clinical trials for which they might be eligible, as evaluated by the surgeon. The attitudes of the patients about clinical trials and the interventions used to improve accrual were assessed at the end of the study. The primary outcome was the clinical trial accrual rate during the study period. RESULTS: Overall clinical trial enrolment during the study period among the 34 participating patients was 15% (5 of 34), which is greater than the institution's historical average of 7%. All patients found the information delivered by the surgeon before the oncology appointment to be very helpful. Almost three quarters of the patients (73%) were informed about clinical trials by their oncologist. The top reasons for nonparticipation reported by the patients who did not participate in clinical trials included lack of interest (35%), failure of the oncologist to mention clinical trials (33%), and inconvenience (19%). CONCLUSIONS: Accrual of patients to clinical trials is a complex multistep process with multiple potential barriers. The findings of this exploratory pilot study demonstrate a potential role for the referring surgeon in enhancing nonsurgical clinical trial accrual.

Wellness Beyond Cancer Program: building an effective survivorship program.

BACKGROUND: The Wellness Beyond Cancer Program (wbcp) was launched in 2012, first accepting patients with colorectal cancer (crc) and, subsequently, those with breast cancer (bca), with the aim of standardizing and streamlining the discharge process from our cancer centre. Patients are discharged either to the wbcp nurse practitioner or to their primary care provider (pcp). The program incorporates survivorship care plans (scps) and education classes; it also has a rapid re-entry system in case of recurrence. The objective of this paper is to describe the process by which a cancer survivorship program was developed at our institution and to present preliminary evaluation results. METHODS: Qualitative surveys were mailed to patients and pcps 1 year after patients had been referred to the wbcp. The surveys addressed knowledge of the program content, satisfaction on the part of patients and providers, and whether scp recommendations were followed. Questions were scored on the level of agreement with each of a list of statements (1 = strongly disagree to 5 = strongly agree). RESULTS: From March 2012 to November 2014, 2630 patients were referred to the wbcp (809 with crc, 1821 with bca). Surveys were received from 289 patients and 412 pcps. Patients and pcps gave similar scores (average: 4) to statements about satisfaction; pcps gave scores below 4 to statements about communication with the wbcp. CONCLUSIONS: At 1 year after discharge, patients and pcps were satisfied with program content, but there is an opportunity to improve on communication and provision of cancer-specific information to the pcps. Using the wbcp to ensure a safe transition to the most appropriate health care provider, we have standardized the discharge process for crc and bca patients.

Subgroup effects in a randomised trial of different types and doses of exercise during breast cancer chemotherapy.

BACKGROUND: The Combined Aerobic and Resistance Exercise Trial tested different types and doses of exercise in breast cancer patients receiving chemotherapy. Here, we explore potential moderators of the exercise training responses. METHODS: Breast cancer patients initiating chemotherapy (N=301) were randomly assigned to three times a week, supervised exercise of a standard dose of 25-30 min of aerobic exercise, a higher dose of 50-60 min of aerobic exercise, or a higher dose of 50-60 min of combined aerobic and resistance exercise. Outcomes were patient-reported symptoms and health-related fitness. Moderators were baseline demographic, exercise/fitness, and cancer variables. RESULTS: Body mass index moderated the effects of the exercise interventions on bodily pain (P for interaction=0.038), endocrine symptoms (P for interaction=0.029), taxane/neuropathy symptoms (P for interaction=0.013), aerobic fitness (P for interaction=0.041), muscular strength (P for interaction=0.007), and fat mass (P for interaction=0.005). In general, healthy weight patients responded better to the higher-dose exercise interventions than overweight/obese patients. Menopausal status, age, and baseline fitness moderated the effects on patient-reported symptoms. Premenopausal, younger, and fitter patients achieved greater benefits from the higher-dose exercise interventions. CONCLUSIONS: Healthy weight, fitter, and premenopausal/younger breast cancer patients receiving chemotherapy are more likely to benefit from higher-dose exercise interventions.

A prospective randomised controlled trial comparing tracheal intubation plus manual in-line stabilisation of the cervical spine using the Macintosh laryngoscope vs the McGrath(®) Series 5 videolaryngoscope.

Cervical spine immobilisation can make direct laryngoscopy difficult, which might lead to airway complications. This randomised control trial compared the time to successful intubation using either the Macintosh laryngoscope or the McGrath(®) Series 5 videolaryngoscope in 128 patients who had cervical immobilisation applied. Intubation difficulty score, Cormack & Lehane laryngoscopic view, intubation failures, changes in cardiovascular variables and the incidence of any complications were recorded. The mean (SD) successful intubation time with the Macintosh laryngoscope was significantly shorter compared with the McGrath laryngoscope, 50.0 (32.6) s vs 82.7 (80.0) s, respectively (p = 0.0003), despite the McGrath laryngoscope's having a lower intubation difficulty score and a superior glottic view. There were five McGrath laryngoscope intubation failures, three owing to difficulty in passing the tracheal tube and two to equipment malfunction. Equipment malfunction is a major concern as a reliable intubating device is vital when faced with an airway crisis.

Preference weights for chemotherapy side effects from the perspective of women with breast cancer.

Perceptions among women with breast cancer about the relative importance of different potential chemotherapy side effects is not well understood. A survey was performed by women receiving chemotherapy for breast cancer. Grade I/II (mild to moderate) and III/IV (moderate to severe) descriptions of nine common chemotherapy side effects were assigned preference weights using the standard gamble technique. For each hypothetical side effect, patients could choose to stay in the respective side effect state or take a gamble between full health (probability p) or being dead (1 - p). For each side effect, p was varied until the patient was indifferent between these options. The survey also included questions about the importance of survival, slowing cancer growth, and quality of life. This analysis included 69 patients; mean age 54 years (range 35-84), representing all cancer stages. Standard gamble preferences were lowest (i.e., least preferred) for grade III/IV nausea/vomiting (0.621), indicating that patients would, on average, risk a 38 % chance of being dead to avoid having grade III/IV nausea/vomiting for the rest of their lives. The next least preferred side effects were grade III/IV diarrhea (0.677) and grade III/IV sensory neuropathy (0.694). Survival appeared more important than slowing cancer growth and maintaining quality of life across cancer stages. Nevertheless, patients with advanced disease placed less importance on survival (p = 0.09) and higher importance on quality of life (p = 0.05). These standard gamble utilities provide unique insights into chemotherapy toxicities from the patient perspective. Differences in the relative importance of overall survival and quality of life with treatment existed between patients with different stages of disease. These studies should be expanded as the data may also be used to calculate quality-adjusted life expectancy in cost-effectiveness evaluations of breast cancer chemotherapies.

Randomized controlled trial comparing the McGrath videolaryngoscope with the C-MAC videolaryngoscope in intubating adult patients with potential difficult airways.

BACKGROUND: Difficult and failed intubations, although rarely encountered, are major causes of morbidity and mortality in the current anaesthetic practice. To reduce the incidence of difficult and failed intubations, several devices including the recently developed videolaryngoscopes are available. This randomized controlled study aims to compare the use of the McGrath videolaryngoscope with the C-MAC videolaryngoscope in adult patients with potential difficult airways. METHODS: A total of 130 patients with the Mallampati grade of ≥3, requiring orotracheal intubation, were randomized to either having intubation with the McGrath videolaryngoscope or the C-MAC videolaryngoscope. The primary outcome was time to intubation. The laryngoscopic view, the number of intubation attempts, the proportion of intubation success, the ease of intubation, the haemodynamic responses to intubation, and the incidence of any complications were also recorded. RESULTS: Time to successful intubation with the C-MAC videolaryngoscope was shorter when compared with the McGrath videolaryngoscope {50 s [inter-quartile range (IQR) 38-70] vs 67 s (IQR 49-108), P<0.001}, despite the McGrath videolaryngoscope providing significantly more grade 1 laryngoscopic views. The C-MAC videolaryngoscope also resulted in significantly fewer intubation attempts and greater ease of intubation when compared with the McGrath videolaryngoscope. There were no statistically significant differences in the proportion of intubation success, the number of complications, and the changes in haemodynamic responses between the two videolaryngoscopes. CONCLUSIONS: The C-MAC videolaryngoscope allowed a quicker intubation time, fewer intubation attempts, and greater ease of intubation compared with the McGrath videolaryngoscope when used in patients with the Mallampati grade of ≥3.

Beneficial effects of synthetic KL4 surfactant in experimental lung transplantation.

The aim of this study was to investigate whether intratracheal administration of a new synthetic surfactant that includes the cationic, hydrophobic 21-residue peptide KLLLLKLLLLKLLLLKLLLLK (KL4), might be effective in reducing ischaemia-reperfusion injury after lung transplantation. Single left lung transplantation was performed in Landrace pigs 22 h post-harvest. KL4 surfactant at a dose of 25 mg total phospholipid·kg body weight⁻¹ (2.5 mL·kg body weight⁻¹) was instilled at 37°C to the donor left lung (n = 8) prior to explantation. Saline (2.5 mL·kg body weight⁻¹; 37°C) was instilled into the donor left lung of the untreated group (n = 6). Lung function in recipients was measured during 2 h of reperfusion. Recipient left lung bronchoalveolar lavage (BAL) provided native cytometric, inflammatory marker and surfactant data. KL(4) surfactant treatment recovered oxygen levels in the recipient blood (mean ± sd arterial oxygen tension/inspiratory oxygen fraction 424 ± 60 versus 263 ± 101 mmHg in untreated group; p=0.01) and normalised alveolar-arterial oxygen tension difference. Surfactant biophysical function was also recovered in KL4 surfactant-treated lungs. This was associated with decreased C-reactive protein levels in BAL, and recovery of surfactant protein A content, normalised protein/phospholipid ratios, and lower levels of both lipid peroxides and protein carbonyls in large surfactant aggregates. These findings suggest an important protective role for KL4 surfactant treatment in lung transplantation.

A randomised controlled trial comparing the McGrath(®) videolaryngoscope with the straight blade laryngoscope when used in adult patients with potential difficult airways.

Studies show that both straight blade laryngoscopy and videolaryngoscopy can improve the view of the larynx when compared with the Macintosh blade laryngoscopy. However, no study has compared these two devices. A total of 80 patients with Mallampati grade ≥ 3 were randomly assigned to either have orotracheal intubation with the McGrath(®) videolaryngoscope or the Henderson straight blade. The primary outcome was laryngoscopic view. Time to intubation, number of attempts, ease of intubation and complications were also recorded. Thirty-nine out of 40 patients had grade-1 views in the McGrath group, compared with 29 out of 40 cases in the Henderson group (p = 0.003). There were no statistically significant differences in the secondary outcomes. Two patients suffered from minor oropharyngeal injuries in the Henderson group. Apart from offering significantly more grade-1 laryngoscopic views, the McGrath videolaryngoscope did not improve other clinical outcomes compared with the straight blade, when used in patients with poor Mallampati scores.

Impacts on staff after implementation of a respiratory protection program in a Victorian public hospital.

BACKGROUND: In October 2020, the Royal Melbourne Hospital implemented a Respiratory Protection Program (RPP), which was initiated by the Victorian Government. This study was to evaluate the effectiveness of the program. METHODS: A cohort of 158 employees, who were identified as high risk to respiratory biohazard exposure, were invited to participate in the RPP. We provided a bundle of interventions, which included an online training package, and mandatory quantitative fit testing. The main outcomes included the participants' knowledge and attitude toward respiratory protection equipment (RPE), which were assessed via an online survey. Their donning and doffing skills, and user seal check techniques on four different types of N95 respirators were also assessed by an observer using a pre-determined marking sheet. We compared these outcomes before and after participation in the program. RESULTS: There was a total of 125 participants, all of whom completed the knowledge and attitude assessment, and 69 completed the skill assessment before and after the program. There was a statistically significant improvement in their knowledge scores, donning and doffing skills, and user seal check techniques after participation in the RPP. Participants also reported significant increased level of confidence in their RPE knowledge, training and skills; and workplace safety. CONCLUSION: This initial report of the implementation of a novel RPP in a Victorian major tertiary hospital provides guidance on the benefits to respiratory protection, staff knowledge, skills, confidence and morale that can be acquired from a scalable online training package combined with mandatory quantitative fit testing.

Is antiepileptic drug use related to depression and suicidal ideation among patients with epilepsy?

Depression and suicide are increased in patients with epilepsy. The U.S. Food and Drug Administration warns that antiepileptic drugs (AEDs) are associated with increased risk of suicidality. This study examines the relationship among depression, suicidal ideation, and AEDs in a prospective cohort of 163 patients with epilepsy from a registry at the University of Florida (January 2006 to August 2008). The Neurological Disorders Depression Inventory for Epilepsy (NDDI-E) was used to measure mood and suicidal ideation across two time points (median = 154 days). Groups included: (1) No AED Change, (2) New AED Added, (3) AED Dose Increased, (4) AED Reduced/Stopped, (5) Multiple AED Changes, and (6) Combined Any AED Change (groups 2-5 combined). No group had worsening mood or suicidal ideation. Significant improvements in proportions of depression and suicidal ideation were seen only for the No AED Change group, which differed only with the AED Dose Increased group with respect to suicidal ideation.

Proficient manipulation of fibreoptic bronchoscope to carina by novices on first clinical attempt after specialized bench practice.

BACKGROUND: Proficient manipulation of the fibreoptic bronchoscope is an important component of competent bronchoscopic airway management. We studied the duration of specialized bench training necessary to achieve this proficiency and the subsequent transfer of this psychomotor skill to human subjects. METHODS: Twenty-nine novice endoscopists undertook the training associated with a commercial non-anatomic endoscopic dexterity training system, Dexter. Bronchoscopic driving performance was assessed after each hour of self-directed training, using a global rating scale from 1 (unskilled) to 5 (expert) with a score of 3 linked to proficiency. The scale was applied to anonymized recordings of the endoscopic view as the bronchoscope was manipulated from the mouth to the carina of an anatomic manikin. Once bench proficiency was achieved, the ability of participants to perform the skill on volunteer co-participants was assessed. RESULTS: Ninety-six per cent of participants achieved proficiency on the manikin within 4 h of practice. Ninety-three per cent then drove the bronchoscope proficiently from the mouth to the carina of clinical volunteers on the first attempt. CONCLUSIONS: The endoscopic dexterity required to proficiently drive a bronchoscope in human subjects to an anatomic endpoint relevant to fibreoptic intubation is achievable after 2-4 h of specialized bench training. Training in the local environment may be more conducive to success than in time-limited workshops. Achieving a defined proficiency standard on bench models contributes to the development of basic bronchoscopic competence. This has the potential to protect patients from novice learning curves, optimize clinical education and efficiency, and assist compliance with difficult airway algorithms.

Phosphorylation in isolated Chlamydomonas axonemes: a phosphoprotein may mediate the Ca2+-dependent photophobic response.

An in vitro system was devised for studying phosphorylation of Chlamydomonas reinhardtii axonemal proteins. Many of the polypeptides phosphorylated in this system could be identified as previously described axonemal components that are phosphorylated in vivo. The in vitro system apparently preserved the activities of diverse axonemal kinases without greatly altering the substrate specificity of the enzymes. The in vitro system was used to study the effect of calcium concentration on axonemal protein phosphorylation. Calcium has previously been demonstrated to initiate the axonemal reversal reaction of the photophobic response; the in vitro system made it possible to investigate the possibility that this calcium effect is mediated by protein phosphorylation. Calcium specifically altered the phosphorylation of only two axonemal proteins; the phosphorylation of an otherwise unidentified 85,000 Mr protein was repressed by calcium concentrations greater than or equal to 10(-6) M, while the phosphorylation of the previously identified 95,000 Mr protein b4 was stimulated by calcium at concentrations greater than 10(-6) M. Protein b4 is one of six polypeptides that are deficient in the mbo mutants, strains that do not exhibit a photophobic reversal reaction. Therefore, this calcium-stimulated phosphorylation may be involved in initiating the photophobic response. Neither calmodulin nor the C-kinase could be implicated in b4 phosphorylation. The calcium-dependent activation of the b4 kinase was not affected by several drugs that bind to and inhibit calmodulin, or by the addition of exogenous calmodulin. Activators and inhibitors of the calcium-phospholipid-dependent C kinase also had no effect on b4 phosphorylation.

Studies of fibronectin matrices in living cells with fluoresceinated gelatin.

We have used fluorescein isosthiocyanate-conjugated gelatin (FITC-gelatin) (1 mg/ml) to localize cell surface fibronectin in unfixed live cells in cultures. FITC-gelatin stains the fibronectin matrix on primary cultures of rat and chick embryo fibroblasts as well as untransformed, established cell lines. In live cultured cells, fibronectin in many areas of the extracellular matrix is inaccessible to antibody and cannot be visualized by immunofluorescence staining. In contrast, fibronectin in these areas is fully stainable by FITC-gelatin. At a low concentration (20 micrograms/ml), FITC-gelatin stains the fibronectin matrix of primary cultured cells but not of "untransformed" established cell lines. SEM can detect only the matrix stainable with the low concentration of FITC-gelatin, such as that expressed by primary chick embryo fibroblasts. The binding of fibronectin to the extracellular matrix is very stable and FITC-gelatin remained bound to the matrix for at least 10 d in culture. Radioiodinated gelatin has been used to quantitate the level of cell surface fibronectin in living normal and transformed cells. FITC-gelatin appears to be a useful probe for studying the fibronectin of living cells in culture.

Mutant strains of Chlamydomonas reinhardtii that move backwards only.

Mutations at three independent loci in Chlamydomonas reinhardtii result in a striking alteration of cell motility. Mutant cells representing the three mbo loci move backwards only, propelled by a symmetrical "flagellar" type of bending pattern. The characteristic asymmetric "ciliary" type of flagellar bend pattern responsible for forward movement that predominates in wild-type cells is seldom seen in the mutants. This defect in motility was found to be a property of the mutant axonemes themselves: the isolated axonemes, reactivated by addition of ATP, showed exclusively the symmetrical wave form, and the protein composition of these axonemes differed from the wild-type composition. Axonemes obtained from mbo1 , mbo2 , and mbo3 cells were found to be deficient in six polypeptides regularly present in wild type. The mbo2 axonemes were deficient in two additional polypeptides. The polypeptides were identified in autoradiograms of two-dimensional SDS polyacrylamide gel electrophoretograms of 35S- or 32P-labeled axonemes. One of the six polypeptides has previously been identified; it is a component missing in a mutant deficient for inner dynein arms. Of the five axonemal polypeptides newly identified by the mbo mutants, four were shown to be present as phosphoproteins in wild-type axonemes. One of the additional polypeptides deficient in mbo2 axonemes was also shown to be phosphorylated in wild-type axonemes. Detailed ultrastructural analysis of the mbo1 flagella and the mbo1 , mbo2A , and mbo3 axonemes revealed that the mutants specifically lack the beak-like projections found within the B-tubules of outer doublets 5 and 6.