scholarly journals Moderate Physical Activity as a Prevention Method for Knee Osteoarthritis and the Role of Synoviocytes as Biological Key

2019 ◽  
Vol 20 (3) ◽  
pp. 511 ◽  
Author(s):  
Paola Castrogiovanni ◽  
Michelino Di Rosa ◽  
Silvia Ravalli ◽  
Alessandro Castorina ◽  
Claudia Guglielmino ◽  
...  
Keyword(s):  
Physical Activity ◽  
Cruciate Ligament ◽  
Moderate Physical Activity ◽  
Group 4 ◽  
Tnf Α ◽  
Group 3 ◽  
Group 2 ◽  
Prevention Method ◽  
Anterior Cruciate

The purpose of this study was to investigate the influence of moderate physical activity (MPA) on the expression of osteoarthritis (OA)-related (IL-1β, IL-6, TNF-α, MMP-13) and anti-inflammatory and chondroprotective (IL-4, IL-10, lubricin) biomarkers in the synovium of an OA-induced rat model. A total of 32 rats were divided into four groups: Control rats (Group 1); rats performing MPA (Group 2); anterior cruciate ligament transection (ACLT)-rats with OA (Group 3); and, ACLT-rats performing MPA (Group 4). Analyses were performed using Hematoxylin & Eosin (H&E) staining, histomorphometry and immunohistochemistry. In Group 3, OA biomarkers were significantly increased, whereas, IL-4, IL-10, and lubricin were significantly lower than in the other experimental groups. We hypothesize that MPA might partake in rescuing type B synoviocyte dysfunction at the early stages of OA, delaying the progression of the disease.

Biomechanical Comparison of Four Methods of Fixation of a Polymeric Cranial Cruciate Ligament in the Canine Femur and Tibia

2019 ◽  
Vol 32 (02) ◽  
pp. 112-116
Author(s):  
Brian Bufkin ◽  
Alan Litsky ◽  
Matthew Barnhart
Keyword(s):  
Cruciate Ligament ◽  
Biomechanical Properties ◽  
Interference Screw ◽  
Fixation Strength ◽  
Artificial Ligament ◽  
Cranial Cruciate Ligament ◽  
Group 4 ◽  
Group 3 ◽  
Group 2 ◽  
Biomechanical Comparison

Objective The aim of this study was to compare the biomechanical properties of four different methods of artificial cranial cruciate ligament fixation in canine cadaveric tibias and femurs. Methods Femurs and tibias from skeletally mature large breed canine cadavers were assigned into four fixation groups: group 1, 4.5-mm interference screw (IS); group 2, 4.5-mm IS and 4.0-mm screw and spiked washer (SW); group 3, 5.0-mm IS; group 4, 5.0-mm IS + SW. Results The mean ultimate load was significantly greater for femur fixations than for tibias, when a SW was added, and for 5.0-mm IS compared with 4.5-mm sizes. There was also a significant interaction between SW and IS size. A SW significantly increased stiffness, a 5.0-mm IS in femurs provided more stiffness than 4.5-mm IS and was greater than 5.0-mm IS in tibias. In tibias, a 4.5-mm IS was stiffer than a 5.0-mm IS and a 4.5 IS + SW had greater stiffness than a 5.0-mm IS + SW. Groups 1 to 3 and tibias in group 4 failed by artificial ligament pullout. Nine femurs in group 4 failed by fracture, 5 by artificial ligament pullout, and 1 by artificial ligament tearing. Clinical Significance A 5.0-mm IS + SW provided superior artificial ligament fixation strength in femurs and tibias compared with a 4.5-mm IS without SW. Overall, artificial ligament fixation with 5.0-mm IS in femurs had the mechanical characteristics that most closely matched those reported in normal canine cranial cruciate ligaments.

Return to Sport and Reoperation Rates in Patients Under the Age of 20 After Primary Anterior Cruciate Ligament Reconstruction: Risk Profile Comparing 3 Patient Groups Predicated Upon Skeletal Age

2019 ◽  
Vol 47 (3) ◽  
pp. 628-639 ◽  
Author(s):  
Frank A. Cordasco ◽  
Sheena R. Black ◽  
Meghan Price ◽  
Colleen Wixted ◽  
Michael Heller ◽  
...  
Keyword(s):  
Ligament Reconstruction ◽  
Cruciate Ligament ◽  
Return To Sport ◽  
Risk Profile ◽  
Skeletal Age ◽  
Hamstring Autograft ◽  
Group 3 ◽  
Group 2 ◽  
Anterior Cruciate ◽  
Group 1

Background: With sports specialization and level of competition on the rise, anterior cruciate ligament reconstruction (ACLR) in athletes under the age of 20 has increased significantly in recent years. Reports have demonstrated that the revision ACLR rate is higher and return to sport (RTS) rate is lower in this population. Purpose: To evaluate the 2-year clinical outcomes of 3 cohorts of primary ACLR in pediatric and adolescent athletes under the age of 20 based on skeletal age with a focus on RTS and the incidence of second surgery. Study Design: Case series; Level of evidence, 4. Methods: This is a prospective evaluation of 324 athletes younger than 20 years of age who underwent ACLR with minimum 2-year follow-up. The surgical technique was selected predicated on skeletal age, which includes the all-epiphyseal technique with hamstring autograft in the youngest cohort in elementary and middle school (group 1), the partial transphyseal and complete transphyseal with hamstring autograft performed for athletes in the middle cohort (group 2), and bone-tendon-bone autograft in the skeletally mature high school athletes (group 3). Results: The mean chronological age of the entire cohort was 15 years (range, 8-19 years) with 55% males. The 3 cohorts included 49 patients (15%) in group 1 (mean age, 12 years), 66 (20%) in group 2 (mean age, 14.3 years), and 209 (65%) in group 3 (mean age, 16.2 years). Group 2 athletes had a significantly higher revision ACLR rate (20%) compared with group 1 (6%; P = .039) and group 3 (6%; P = .001). Similarly, group 2 athletes had significantly lower RTS rates (85%) compared with group 1 (100%) and group 3 (94%). Conclusion: The rate of revision ACLR was significantly higher and the RTS rates significantly lower in group 2 compared with groups 1 and 3. This age-related risk profile may be used to counsel athletes and parents preoperatively regarding the expectations of surgery with respect to revision ACLR and RTS rates.

P5392Epicardium derived cells promote sympathetic ganglionic outgrowth towards myocardium in vitro

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
Y Ge ◽  
A M Smits ◽  
J C Van Munsteren ◽  
T Van Herwaarden ◽  
A M D Vegh ◽  
...  
Keyword(s):  
Neurite Outgrowth ◽  
Autonomic Innervation ◽  
Cardiac Damage ◽  
Group 4 ◽  
Group 3 ◽  
Cervical Ganglia ◽  
Group 2 ◽  
Group 1

Abstract Background The autonomic nerve system is essential to maintain homeostasis in the body. In the heart, autonomic innervation is important for adjusting the physiology to the continuously changing demands such as stress responses. After cardiac damage, excessive neurite outgrowth, referred to as autonomic hyperinnervation, can occur which is related to ventricular arrhythmias and sudden cardiac death. The cellular basis for this hyperinnervation is as yet unresolved. Here we hypothesize a role for epicardium derived cells (EPDCs) in stimulating sympathetic neurite outgrowth. Purpose To investigate the potential role of adult EPDCs in promoting sympathetic ganglionic outgrowth towards adult myocardium. Method Fetal murine superior cervical ganglia were dissected and co-cultured with activated adult mesenchymal epicardium-derived cells (EPDCs) or/and adult myocardium in a 3D collagen gel culture system. Four experiment groups were included: Group 1: Vehicle cultures (ganglia cultured without EPDC/myocardium) (n=48); Group 2: ganglia co-cultured with EPDCs (n=38); Group 3: ganglia co-cultured with myocardium (n=95); and group 4: ganglia co-cultured with both EPDCs and myocardium (n=96). The occurrence of neurite outgrowth was assessed in each group. The density of neurites that showed directional sprouting (i.e. sprouting towards myocardium) was assessed as well with a semi-automatic quantification method. Finally, sub-analyses were made by taking gender into account. Results Cervical ganglia cultured with EPDCs alone (group 2) showed increased neurite outgrowth compared to vehicle cultures (group 1), however the neurites did not show directional sprouting towards EPDCs. When co-cultured with myocardium (group 3), directional neurite outgrowth towards myocardium was observed. Compared to the ganglia-myocardium co-cultures, directional outgrowth was significantly increased in co-cultures combining myocardium and EPDCs (group 4), and the neurite density was also significantly augmented. Comparison between males and female ganglia demonstrated that more neurite outgrowth occurred in female-derived ganglia than in male-derived ganglia under the same co-culture conditions. Conclusion Activated adult EPDCs promote sympathetic ganglionic outgrowth in vitro. Sex differences exist in the response of ganglia to EPDCs, and female-derived ganglia appear more sensitive to EPDC-signalling. Results support a role of EPDCs in cardiac autonomic innervation and open avenues for exploring of their role in ventricular hyperinnervation after cardiac damage.

Experimental model of posttraumatic syringomyelia: the role of adhesive arachnoiditis in syrinx formation

1994 ◽  
Vol 80 (1) ◽  
pp. 133-139 ◽  
Author(s):  
Ki Hong Cho ◽  
Yoshinobu Iwasaki ◽  
Hiroyuki Imamura ◽  
Kazutoshi Hida ◽  
Hiroshi Abe
Keyword(s):  
Normal Saline ◽  
Subarachnoid Space ◽  
Saline Solution ◽  
Traumatic Injury ◽  
Content Type ◽  
Group 4 ◽  
Kaolin Injection ◽  
Group 3 ◽  
Group 2

✓ An experimental model was devised to elucidate the role of spinal blockade in posttraumatic syringomyelia. Thirty-eight Japanese White rabbits, each weighing about 3 kg, were used in this study. The animals were divided into four groups: in Group 1, eight animals received traumatic injury only; in Group 2, 12 animals received traumatic injury following injection of 100 mg kaolin suspended in 1 cc normal saline solution into the subarachnoid space at the site of trauma; in Group 3, nine animals received traumatic injury following injection of 200 mg kaolin in 1 cc normal saline solution into the subarachnoid space at the site of trauma; and in Group 4, nine animals without traumatic injury received an injection of 200 mg kaolin in 1 cc normal saline solution into the subarachnoid space. The subjective criteria for syrinx formation were the presence of a definite round cyst having a smooth margin and an upper or lower extension of more than 2 cm from the injured site. Syrinx formation was seen in 12.5% (one of eight rabbits) in Group 1, 41.7% (five of 12 animals) in Group 2, 55.5% (five of nine rabbits) in Group 3 and 0% (none of nine animals) in Group 4 (p < 0.05). There was a tendency for the combined trauma/kaolin injection groups to be more prone to develop a syrinx. In the kaolin injection only group (Group 4), no animal showed a definite cyst or an extending cavity during the experimental period. The results suggest that kaolin enhances the extension of multiple small cavities that have already formed at the time of initial injury. The difference between the frequency of syrinx formation and the time of survival was statistically significant well beyond the 0.05% level. The overall difference, relating to the frequency of syrinx development, group, and duration of survival, was also statistically significant. In summary, subarachnoid block secondary to adhesive arachnoiditis is important in initiating the extension of the syringomyelia cavity.

scholarly journals Acute Phase Effect of Memantine Hydrochloride in Experimental Peripheral Nerve Injury

2019 ◽  
Vol 08 (02) ◽  
pp. 113-118
Author(s):  
Hakan AK ◽  
Iskender Samet Daltaban ◽  
Sevilay Vural
Keyword(s):  
Peripheral Nerve ◽  
Nerve Injury ◽  
Peripheral Nerve Injury ◽  
Group 4 ◽  
Tnf Α ◽  
Group 3 ◽  
The Mean ◽  
Cox 2 ◽  
Group 2 ◽  
Group 1

Abstract Aim In this experimental study, we aimed to investigate possible healing effects of memantine hydrochloride, an N-methyl-d-aspartate (NMDA) antagonist, with clinical, biochemical, and histopathologic methods on acute peripheral nerve injury (PNI). Material and Method Forty-eight adult Wistar albino rats were divided into four groups (n = 12). The groups were arranged as sham-operated group (group 1), acute compression model group (group 2), trauma + low-dose memantine group (group 3), and trauma + high-dose memantine group (group 4). Memantine was administered intraperitoneally for 7 days. Subjects were sacrificed after the measurement of the sciatic nerve function index (SNFI) on the eighth day. Cyclooxygenase 2 (COX-2) and tumor necrosis factor-α (TNF-α) levels were measured in nerve tissues. Histopathologic evaluation was performed by electron microscopy. Results The mean sciatic function index (SFI) scores of groups 1 to 4 were +3.27 (standard deviation [SD] ±4.66),–18.2 (SD = ±11.7),–8.5 (SD = ±7.5), and–2.5 (SD = ±9), respectively. The mean COX-2 values were 0.98 ng/mL (SD = ±0.51), 1.89 ng/mL (SD = ±0.22), 1.39 ng/mL (SD = ±0.36), and 1.35 ng/mL (SD = ±0.59), respectively. TNF-α values were 0.09 pg/mL (SD = ±0.23), 1 pg/mL (SD = ±0.96), 0.46 pg/mL (SD = ±0.55), and 0.48 pg/mL (SD = ±0.78), respectively. Group 1 showed normal histologic findings. Group 2 showed marked edema particularly in large-diameter myelins. Myelin configurations were detected in large myelinated axons in group 3. The number of mast cells in endoneurium was high in group 4. Conclusion The efficacy of memantine in the acute phase of PNI appears to be significant according to the SNFI and biochemical tests. However, histologic findings suggest that high doses of memantine have a negative effect on PNI.

scholarly journals Extracorporeal Shock Wave Therapy Protected the Functional and Architectural Integrity of Rodent Urinary Bladder against Ketamine-Induced Damage

Biomedicines ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 1391
Author(s):  
Yen-Ta Chen ◽  
Kuan-Hui Huang ◽  
John Y. Chiang ◽  
Pei-Hsun Sung ◽  
Chi-Ruei Huang ◽  
...  
Keyword(s):  
Urinary Bladder ◽  
Cyclophilin D ◽  
Group 4 ◽  
Extracorporeal Shock Wave ◽  
Tnf Α ◽  
Bladder Contraction ◽  
Group 3 ◽  
Group 2 ◽  
Cell Stress Response ◽  
Group 1

This study tested the hypothesis that extracorporeal-shock-wave (ECSW) protected the functional and anatomical integrity of rat urinary-bladder against ketamine-induced damage. In in vitro study, the rat bladder smooth muscle cells (RBdSMCs) were categorized into G1 (sham-control), G2 (RBdSMCs + menadione), G3 (RBdSMCs + ECSW) and G4 (RBdSMCs + menadione + ECSW). The results showed protein expressions of oxidative-stress/mitochondrial-damaged biomarkers (NOX-1/NOX-2/oxidized protein/cytosolic-cytochrome-C/cyclophilin-D), inflammatory markers (MyD88/TRAF6/p-IKB-α/NF-κB/TNF-α/IL-6/IL-1ß/MMP-9/iNOS), and cell-stress response signalings (ASK1/p-MKK4/p-MKK7/ERK1/2//p-JNK/p-p38/p-53) were significantly increased in G2 than in G1 and G3, and those were significantly reversed in G4 (all p < 0.0001). Adult-male SD rats (n = 24) were equally categorized into group 1 (sham-control), group 2 (ketamine/30 mg/kg/daily i.p. injection for four weeks), group 3 [ketamine/30 mg/kg + ECSW/optimal energy (0.12 mJ/mm2/120 impulses/at 3 h and days 3/7/14/21/28 after ketamine administration)] and group 4 [(ketamine/30 mg/kg + ECSW/higher energy (0.16 mJ/mm2/120 impulses)] and animals were euthanized by day 42. The results showed the urine levels of pro-inflammatory cytokines (TNF-α/IL-6) were lowest in group 1, highest in group 2 and significantly higher in group 3 than in group 4 at days 1/7/14/28 (all p < 0.0001). The duration of urinary bladder contraction was lowest in group 2, highest in group 1 and significantly higher in group 4 than in group 3, whereas the maximal pressure of urinary bladder exhibited an opposite pattern of bladder contraction among the groups (all p < 0.0001). The histopathological findings of fibrosis/inflammation/keratinization and protein expressions of oxidative-stress/mitochondrial-damaged biomarkers (NOX-1/NOX-2/oxidized protein/cytosolic-cytochrome-C/cyclophilin-D), and inflammatory (TLR-2/TLR-4/MyD88/TRAF6/p-IKB-α/NF-κB/TNF-α/IL-1ß/MMP-9/iNOS) and cell-stress response (ASK1/p-MKK4/p-MKK7/ERK1/2//p-JNK/p-p38) signalings and apoptotic/fibrotic biomarkers (cleaved-caspas3/cleaved-PARB/Smad3/TFG-ß) exhibited an identical pattern of urine proinflammatory cytokine among the groups (all p < 0.0001). ECSW effectively attenuated ketamine-induced bladder damage and dysfunction.

scholarly journals Evaluation of protective effect of myricetin, a bioflavonoid in dimethyl benzanthracene-induced breast cancer in female Wistar rats

2014 ◽  
Vol 03 (02) ◽  
pp. 107-111 ◽  
Author(s):  
J. K. Jayakumar ◽  
P. Nirmala ◽  
B.A. Praveen Kumar ◽  
Ashok P. Kumar
Keyword(s):  
Breast Cancer ◽  
Wistar Rats ◽  
Statistical Significance ◽  
Treated Animal ◽  
Group 4 ◽  
Female Wistar Rats ◽  
Group 3 ◽  
Group 2 ◽  
And Control

Abstract Background: Breast cancer is one of the most common cancers worldwide. Alarmingly, the incidence of breast cancer is rising rapidly in India. Aim: The present research was focused to assess the role of myricetin; a bioflavonoid in 7,12-dimethylbenzanthracene (DMBA)-induced breast cancer in female Wistar rats. Materials and Methods: A total of 36 female Wistar rats (total 6 groups, n = 6 per group) 6 - 8 weeks old, weighing 150 gm were used in the study. DMBA was given at the dose of 7.5 mg/kg subcutaneously in the mammary region once a week for 4 consecutive weeks in group 2. Vincristine was given in the dose of 500 μg/kg intraperitonially every week for 4 consecutive weeks in group 3. Myricetin was given orally in a dose of 50, 100, and 200 mg/kg in group 4, 5, and 6 respectively. The statistical significance of the data was determined using one way analysis of variance and Duncan’s multiple range test. Results: The result showed that myricetin increased the antioxidant levels in plasma, erythrocyte lysate, and breast tissue and was effective in preventing the oxidative damage induced by the carcinogen DMBA. Myricetin 50, 100, and 200 mg/kg/oral for 120 days treated animal resulted comparable results to that of standard vincristine and control groups. Conclusions: Myricetin was found to be either equieffective or more effective than vincristine in all the parameters studied. Myricetin proved the capacity of flavonols to act as antioxidant in cells represents a potential treatment in the field of oncology.

P5746Human induced pluripotent stem cell-derived mesenchymal stem cell therapy effectively reduced brain infarct volume and preserved neurological function in rat after acute intracranial hemorrhage

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
Y C Li ◽  
F Y Lee ◽  
S Chua ◽  
H K Yip
Keyword(s):  
Stem Cell ◽  
Mesenchymal Stem Cell ◽  
Induced Pluripotent Stem Cell ◽  
Neurological Function ◽  
Opposite Pattern ◽  
Group 4 ◽  
Tnf Α ◽  
Group 3 ◽  
Group 2 ◽  
Induced Pluripotent

Abstract Intracerebral hemorrhage (ICH) causes 10%-20% of all strokes and results in higher morbidity compared to other subtypes of cerebral stroke. Although early surgical intervention can clear the expanding hematoma, clinical outcomes following ICH have not significantly improved over the decades. Since ICH elicits neuroinflammation to exacerbate brain edema, damage the blood-brain barrier (BBB), lead to secondary neuronal injury, anti-inflammation may be a critical therapeutic strategy. Mesenchymal stem cell (MSC) therapy processes anti-inflammatory, immunomodulatory and tissue regenerative properties, suggesting that MSC therapy could be an effective therapy for ICH. Therefore, this study tested the hypothesis that human induced pluripotent stem cell-derived mesenchymal stem cell (iPSC-MSC) therapy could effectively reduce brain-infract volume (BIV) and improve neurological function in rat after acute ICH induced by a weight-drop device. Adult-male SD rats (n=40) were equally divided into group 1 (sham-operated control), group 2 (ICH), group 3 (ICH + hyaluronic acid (HA)/intracranial injection/3h after ICH), group 4 [ICH + HA + iPSC-MSC (1.2x106 cells/intracranial injection/3h after ICH)] and euthanized by day 28 after ICH procedure. In vitro study showed that hemorrhagic-brain tissue augmented protein expressions of inflammation (HMGB1/MyD88/TLR-4/TLR-2/NF-κB/TNF-α/iNOS/IL-1β) in cultured neurons that were significantly inhibited by iPSC-MSC treatment (all p<0.001). By days 7/14 after ICH procedure, circulating inflammatory levels of TNF-α/IL-6/MPO expressed were lowest in group 1, highest in group 2 and significantly lower in group 4 than in group 3 (all p<0.0001). By day 14 after ICH procedure, neurological function and BIV expressed an opposite pattern, whereas protein expressions of inflammation (HMGB1/MyD88/TLR-4/TLR-2/NF-κB/I-kB/TNF-α/iNOS/IL-1β/MMP-9), oxidative stress (NOX-1/NOX-2/oxidized protein) and apoptosis (mitochondrial-Bax/cleaved-caspase-2/PARP) in brain exhibited an identical pattern to circulating inflammation among the four groups (all p<0.001). Microscopy demonstrated that the number of vascular remodeling/GFAP+/53BP1+/γ-H2AX+ cells displayed an identical pattern of inflammation, whereas the NeuN+ cells displayed an opposite pattern of inflammation among the four groups (all p<0.001). In conclusion, iPSC-MSC therapy markedly reduced BIV and preserved neurological function mainly by inhibiting inflammatory/oxidative-stress generation. Acknowledgement/Funding Kaohsiung Chang Gung Memorial Hospital, Taiwan Society of Stem Cell Research

scholarly journals A Pilot Randomized Controlled Trial Evaluating Motivationally Matched Pedometer Feedback to Increase Physical Activity Behavior in Older Adults

2011 ◽  
Vol 8 (s2) ◽  
pp. S267-S274 ◽  
Author(s):  
Scott J. Strath ◽  
Ann M. Swartz ◽  
Sarah J. Parker ◽  
Nora E. Miller ◽  
Elizabeth K. Grimm ◽  
...  
Keyword(s):  
Physical Activity ◽  
Older Adults ◽  
Controlled Trial ◽  
Intervention Strategy ◽  
Physical Activity Behavior ◽  
Control Group ◽  
Group 4 ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

Background:Increasing physical activity (PA) levels in older adults represents an important public health challenge. The purpose of this study was to evaluate the feasibility of combining individualized motivational messaging with pedometer walking step targets to increase PA in previously inactive and insufficiently active older adults.Methods:In this 12-week intervention study older adults were randomized to 1 of 4 study arms: Group 1—control; Group 2—pedometer 10,000 step goal; Group 3—pedometer step goal plus individualized motivational feedback; or Group 4—everything in Group 3 augmented with biweekly telephone feedback.Results:81 participants were randomized into the study, 61 participants completed the study with an average age of 63.8 ± 6.0 years. Group 1 did not differ in accumulated steps/day following the 12-week intervention compared with participants in Group 2. Participants in Groups 3 and 4 took on average 2159 (P < .001) and 2488 (P < .001) more steps/day, respectively, than those in Group 1 after the 12-week intervention.Conclusion:In this 12-week pilot randomized control trial, a pedometer feedback intervention partnered with individually matched motivational messaging was an effective intervention strategy to significantly increase PA behavior in previously inactive and insufficiently active older adults.

Bacteriophages of Clostridium botulinum

1972 ◽  
Vol 18 (1) ◽  
pp. 67-76 ◽  
Author(s):  
C. E. Dolman ◽  
Eva Chang
Keyword(s):  
Clostridium Botulinum ◽  
Phage Type ◽  
Phage Group ◽  
Flexible Tail ◽  
Group 4 ◽  
Group 3 ◽  
Type C ◽  
Group 2 ◽  
Group 1

Temperate bacteriophages of diverse morphology were demonstrated by electron microscopy in toxigenic cultures of Clostridium botulinum. The 41 strains examined included 23 type E and multiple representatives of all other types. Cultures induced with mitomycin-C generally gave better yields, but phages were also demonstrable in untreated cultures.A provisional grouping of toxigenic types into four categories is suggested, based mainly upon associated phage patterns. Group 1 comprises types A, B, and F (all proteolytic), many of whose cultures showed an icosahedral contractile phage; others contained a "bullrushy" phage with elongated head and long flexible tail; some strains yielded both. Group 2, types B and F (non-proteolytic), were associated with icosahedral contractile phages; the latter also had an octahedral flexible phage. Group 3, types C and D, yielded conspicuously large phages with octahedral heads and very long sheathed tails. One type C strain produced a long-tailed icosahedral phage. Type E phages constituted group 4. These were icosahedral with tails generally contracted but sometimes flexible, often accompanied by superfluous sheathed tail-like structures resembling certain bacteriocins. Although non-toxigenic "OS" mutants of types A, B, E, and F were phageless, two non-toxic type E strains yielded phages. The possible role of lysogeny in the toxigenicity of certain types of this species is likely to prove difficult to elucidate.

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