Single-cycle Treatments Research Articles

Leveraging intracellular ALDH1A1 activity for selective cancer stem-like cell labeling and targeted treatment via in vivo click reaction

Inhibition of overexpressed enzymes is among the most promising approaches for targeted cancer treatment. However, many cancer-expressed enzymes are "nonlethal," in that the inhibition of the enzymes' activity is insufficient to kill cancer cells. Conventional antibody-based therapeutics can mediate efficient treatment by targeting extracellular nonlethal targets but can hardly target intracellular enzymes. Herein, we report a cancer targeting and treatment strategy to utilize intracellular nonlethal enzymes through a combination of selective cancer stem-like cell (CSC) labeling and Click chemistry-mediated drug delivery. A de novo designed compound, AAMCHO [N-(3,4,6-triacetyl- N-azidoacetylmannosamine)-cis-2-ethyl-3-formylacrylamideglycoside], selectively labeled cancer CSCs in vitro and in vivo through enzymatic oxidation by intracellular aldehyde dehydrogenase 1A1. Notably, azide labeling is more efficient in identifying tumorigenic cell populations than endogenous markers such as CD44. A dibenzocyclooctyne (DBCO)-toxin conjugate, DBCO-MMAE (Monomethylauristatin E), could next target the labeled CSCs in vivo via bioorthogonal Click reaction to achieve excellent anticancer efficacy against a series of tumor models, including orthotopic xenograft, drug-resistant tumor, and lung metastasis with low toxicity. A 5/7 complete remission was observed after single-cycle treatment of an advanced triple-negative breast cancer xenograft (~500 mm3).

Improving pregnancy rate in infertile patients with polycystic ovarian syndrome receiving clomiphene citrate and cabergoline in euprolactinomic women in single cycle treatment.

To assess the therapeutic efficacy of cabergoline when given routinely with clomiphene citrate (CC) in infertile women with polycystic ovarian syndrome (PCOS) and normal serum prolactin in single cycle therapy. This prospective study included a total of 110 infertile women with polycystic ovaries and normal serum prolactin divided into two groups. The first group received only a single cycle clomiphene citrate 100 mg in two divided doses (50 mg × 2) from Day 2 to Day 6. The second group received the same regimen of clomiphene citrate along with cabergoline in two divided doses of 0.5 mg each week at Day 2 and Day 9, respectively. All patients were evaluated through full history and physical examination. Blood was extracted from all patients for hormonal assay and ultrasound for the assessment of ovulation. The success rate of ovulation induction was statistically significant. Biochemical pregnancy elevated to (36.0%, n = 18) with using combined drugs while it was 14.0%, n = 7, with the use of clomiphene citrate alone (p = 0.011). The clinical pregnancy rate in the study group was elevated to 32.0%, n = 16, which is statistically significant. No significant association was found between abortion and the type of treatment. There were no significant differences between the groups regarding drug side effect like ovarian hyper stimulation rate, multiple pregnancy rate as well as other adverse effects. Adding cabergoline in small doses together with clomiphene citrate in PCOS infertile women and normal serum prolactin increases the success rate of ovulation & significantly improves pregnancy rate with minimal drug side effects.

Intraperitoneal Pretargeted Radioimmunotherapy for Colorectal Peritoneal Carcinomatosis.

Peritoneal carcinomatosis (PC) is considered incurable, and more effective therapies are needed. Herein we test the hypothesis that GPA33-directed intracompartmental pretargeted radioimmunotherapy (PRIT) can cure colorectal peritoneal carcinomatosis. Nude mice were implanted intraperitoneally with luciferase-transduced GPA33-expressing SW1222 cells for aggressive peritoneal carcinomatosis (e.g., resected tumor mass 0.369 ± 0.246 g; n = 17 on day 29). For GPA33-PRIT, we administered intraperitoneally a high-affinity anti-GPA33/anti-DOTA bispecific antibody (BsAb), followed by clearing agent (intravenous), and lutetium-177 (Lu-177) or yttrium-86 (Y-86) radiolabeled DOTA-radiohapten (intraperitoneal) for beta/gamma-emitter therapy and PET imaging, respectively. The DOTA-radiohaptens were prepared from S-2-(4-aminobenzyl)-1,4,7, 10-tetraazacyclododecane tetraacetic acid chelate (DOTA-Bn). Efficacy and toxicity of single- versus three-cycle therapy were evaluated in mice 26-27 days post-tumor implantation. Single-cycle treatment ([177Lu]LuDOTA-Bn 111 MBq; tumor dose: 4,992 cGy) significantly prolonged median survival (MS) approximately 2-fold to 84.5 days in comparison with controls (P = 0.007). With three-cycle therapy (once weekly, total 333 MBq; tumor dose: 14,975 cGy), 6/8 (75%) survived long-term (MS > 183 days). Furthermore, for these treated long-term survivors, 1 mouse was completely disease free (microscopic "cure") at necropsy; the others showed stabilized disease, which was detectable during PET-CT using [86Y]DOTA-Bn. Treatment controls had MS ranging from 42-52.5 days (P < 0.001) and 19/20 mice succumbed to progressive intraperitoneal disease by 69 days. Multi-cycle GPA33 DOTA-PRIT significantly prolongs survival with reversible myelosuppression and no chronic marrow (929 cGy to blood) or kidney (982 cGy) radiotoxicity, with therapeutic indices of 12 for blood and 12 for kidneys. MTD was not reached.

Alpha radioimmunotherapy using 225Ac-proteus-DOTA for solid tumors - safety at curative doses.

This is the initial report of an α-based pre-targeted radioimmunotherapy (PRIT) using 225Ac and its theranostic pair, 111In. We call our novel tumor-targeting DOTA-hapten PRIT system “proteus-DOTA” or “Pr.” Herein we report the first results of radiochemistry development, radiopharmacology, and stoichiometry of tumor antigen binding, including the role of specific activity, anti-tumor efficacy, and normal tissue toxicity with the Pr-PRIT approach (as α-DOTA-PRIT). A series of α-DOTA-PRIT therapy studies were performed in three solid human cancer xenograft models of colorectal cancer (GPA33), breast cancer (HER2), and neuroblastoma (GD2), including evaluation of chronic toxicity at ~20 weeks of select survivors.Methods: Preliminary biodistribution experiments in SW1222 tumor-bearing mice revealed that 225Ac could not be efficiently pretargeted with current DOTA-Bn hapten utilized for 177Lu or 90Y, leading to poor tumor uptake in vivo. Therefore, we synthesized Pr consisting of an empty DOTA-chelate for 225Ac, tethered via a short polyethylene glycol linker to a lutetium-complexed DOTA for picomolar anti-DOTA chelate single-chain variable fragment (scFv) binding. Pr was radiolabeled with 225Ac and its imaging surrogate, 111In. In vitro studies verified anti-DOTA scFv recognition of [225Ac]Pr, and in vivo biodistribution and clearance studies were performed to evaluate hapten suitability and in vivo targeting efficiency.Results: Intravenously (i.v.) administered 225Ac- or 111In-radiolabeled Pr in mice showed rapid renal clearance and minimal normal tissue retention. In vivo pretargeting studies show high tumor accumulation of Pr (16.71 ± 5.11 %IA/g or 13.19 ± 3.88 %IA/g at 24 h p.i. for [225Ac]Pr and [111In]Pr, respectively) and relatively low uptake in normal tissues (all average ≤ 1.4 %IA/g at 24 h p.i.). Maximum tolerated dose (MTD) was not reached for either [225Ac]Pr alone or pretargeted [225Ac]Pr at administered activities up to 296 kBq/mouse. Single-cycle treatment consisting of α-DOTA-PRIT with either huA33-C825 bispecific anti-tumor/anti-DOTA-hapten antibody (BsAb), anti-HER2-C825 BsAb, or hu3F8-C825 BsAb for targeting GPA33, HER2, or GD2, respectively, was highly effective. In the GPA33 model, no complete responses (CRs) were observed but prolonged overall survival of treated animals was 42 d for α-DOTA-PRIT vs. 25 d for [225Ac]Pr only (P < 0.0001); for GD2, CRs (7/7, 100%) and histologic cures (4/7, 57%); and for HER2, CRs (7/19, 37%) and histologic cures (10/19, 56%) with no acute or chronic toxicity.Conclusions: [225Ac]Pr and its imaging biomarker [111In]Pr demonstrate optimal radiopharmacologic behavior for theranostic applications of α-DOTA-PRIT. For this initial evaluation of efficacy and toxicity, single-cycle treatment regimens were performed in all three systems. Histologic toxicity was not observed, so MTD was not observed. Prolonged overall survival, CRs, and histologic cures were observed in treated animals. In comparison to RIT with anti-tumor IgG antibodies, [225Ac]Pr has a much improved safety profile. Ultimately, these data will be used to guide clinical development of toxicity and efficacy studies of [225Ac]Pr, with the goal of delivering massive lethal doses of radiation to achieve a high probability of cure without toxicity.

Lu-177 PSMA I&amp;T Therapy for Prostate Cancer; Treatment Response, Treatment Toxicity, and Survival Results

Purpose: This study aims to evaluate the serum PSA response, Ga-68 PSMA PET/CT response, hematological/nephrological toxicity and survival results of patients with castration-resistant metastatic prostate cancer who are receiving Lu-177 PSMA therapy.Methods: The data of 57 patients with a mean age of 68 years who were treated with Lu-177 PSMA I&T were retrospectively reviewed. Secondary toxicity to treatment was determined using the criteria of the Common Toxicity Criteria for Adverse Events v5.0. The Kaplan Meier method was used for survival and progression-free survival analysis.Results: Forty percent of patients’ serum PSA values’ showed >25% regression after the first cycle of treatment. Serum PSA values were stable/regressed in 75% of the patients. While 2/57 patients showed grade 3 anemia, none showed grade 3 leukopenia or thrombocytopenia. One of 57 patient showed transient nephrotoxicity. Hematological and nephrological toxicity were not observed after treatment of eight cycles, and the serum PSA values of the patients were decreased by 97%. The mean survival time was 11.6 months in all patients, and 17.2 months in patients with serum PSA response. Progression-free survival was an average of 9.9 months.Conclusion: Providing a stable or regressed disease via single cycle treatment in 75% of patients with progression despite the treatments improving survival is an indicator of the success of the therapy. The low rate of hematological and nephrological toxicity in patients none of the patients that received eight cycles suggests that the treatment is reliable. Survival was longer in patients with serum PSA response after treatment

Comparison of microbiological loads and physicochemical properties of raw milk treated with single-/multiple-cycle high hydrostatic pressure and ultraviolet-C light

The effects of ultraviolet-C radiation (UV-C, 11.8 W/m2), single-cycle and multiple-cycle high hydrostatic pressure (HHP at 200, 400 or 600 MPa) on microbial load and physicochemical quality of raw milk were evaluated. Reductions of aerobic plate count (APC) and coliform count (CC) by HHP were more than 99.9% and 98.7%, respectively. Inactivation efficiency of microorganisms increased with pressure level. At the same pressure level, two-cycle treatments caused lower APC, but did not show CC differences compared with single-cycle treatments. Reductions of APC and CC by UV-C were somewhere between 200 MPa and 400/600 MPa. Both HHP and UV-C significantly decreased lightness and increased pH, but did not change soluble solids content and thiobarbituric acid-reactive substances’ values. Two 2.5 min cycles of HHP at 600 MPa caused minimum APC and CC, and maximum conductivity. Compared with HHP, UV-C markedly increased protein oxidation and reduced darkening.

Effect of single- and two-cycle high hydrostatic pressure treatments on water properties, physicochemical and microbial qualities of minimally processed squids (todarodes pacificus).

This study investigated the effect of single- and two-cycle high hydrostatic pressure (HHP) treatments on water properties, physicochemical, and microbial qualities of squids (Todarodes pacificus) during 4 °C storage for up to 10 d. Single-cycle treatments were applied at 200, 400, or 600 MPa for 20 min (S-200, S-400, and S-600), and two-cycle treatments consisted of two 10 min cycles at 200, 400, or 600 MPa, respectively (T-200, T-400, and T-600). HHP-treated samples had higher (P < 0.05) content of P2b (immobilized water) and P21 (myofibril water), but lower P22 (free water) than those of control. The single- and two-cycle HHP treatments at the same pressure level caused no significant difference in water state of squids. The two-cycle HHP treatment was more effective in controlling total volatile basic nitrogen, pH, and total plate counts (TPC) of squids during storage, in which TPC of S-600 and T-600 was 2.9 and 1.8 log CFU/g at 10 d, respectively, compared with 7.5 log CFU/g in control. HHP treatments delayed browning discoloration of the squids during storage, and the higher pressure level and two-cycle HHP were more effective. Water properties highly corresponded with color and texture indices of squids. This study demonstrated that the two-cycle HHP treatment was more effective in controlling microbial growth and quality deterioration while having similar impact on the physicochemical and water properties of squids in comparison with the single-cycle treatment, thus more desirable for extending shelf-life of fresh squids.

Cryolipolysis for safe and effective inner thigh fat reduction

Background and ObjectivesWhile cryolipolysis initially received FDA clearance for fat reduction in the abdomen and flanks, there was significant interest in non‐surgical fat reduction for other sites, such as the inner and outer thighs. This article reports the results of an inner thigh study which contributed to FDA clearance of cryolipolysis for treatment of thighs.Study Design/Material and MethodsA flat cup vacuum applicator (CoolFit applicator, CoolSculpting System) was used to treat 45 subjects bilaterally in the inner thighs. Single cycle treatments were delivered at Cooling Intensity Factor (CIF) 41.6 for 60 minutes followed by 2 minutes of manual massage. Follow‐up visits were conducted at 8 and 16 weeks. Efficacy was assessed by ultrasound imaging, circumference measurements, and photographs. Safety was assessed by monitoring adverse events. Patient satisfaction was evaluated by questionnaire.ResultsData is presented for n = 42 patients that completed the 16 week study follow‐up and maintained their weight within 5 lbs. of baseline. Independent photo review from three blinded physicians found 91% correct identification of baseline clinical photographs. Ultrasound data indicate fat layer reduction of 2.8 mm. Circumferential measurements indicate mean reduction of 0.9 cm. Patient questionnaires reveal 93% were satisfied with the CoolSculpting procedure; 84% noticed visible fat reduction; 89% would recommend to a friend; and 91% were likely to have a second treatment. There were no device‐ or procedure‐related serious adverse events.ConclusionThe CoolFit flat cup vacuum applicator was found to deliver safe and effective cryolipolysis treatment to reduce inner thigh fat. Completed 16‐week data from 42 subjects show 2.8 mm reduction in fat thickness and 0.9 cm reduction in circumference. Assessment of clinical photographs found 91% correct identification of baseline images. The results of this prospective, multi‐center, interventional clinical study contributed to FDA clearance of cryolipolysis for treatment of thighs in April 2014. Lasers Surg. Med. 47:120–127, 2015. © 2015 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.

Combined therapeutic effects of adenoviral vector-mediated GLIPR1 gene therapy and radiotherapy in prostate and bladder cancer models

ObjectivesThe objectives of this study are to explore the potential benefits of combining AdGlipr1 (or AdGLIPR1) gene therapy with radiotherapy using subcutaneous prostate and bladder cancer models. Materials and methodsCombination adenoviral vector-mediated gene therapy and radiotherapy were applied to 178-2 BMA and TSU-Pr1 cells in vitro and colony formation and apoptosis were analyzed. In addition, combination therapies were administered to mice bearing subcutaneous 178-2 BMA and TSU-Pr1 tumors, and tumor growth suppression and survival extension were compared with the monotherapies (AdGlipr1/AdGLIPR1 and radiotherapy) or control vector Adv/CMV/βgal, as well as single-cycle treatment with 2-cycle treatment. ResultsCombination treatment significantly suppressed colony formation and increased apoptosis in vitro. In vivo, combination therapy produced significant 178-2 BMA and TSU-Pr1 tumor growth suppression and survival extension compared with the monotherapies or the control. Further tumor growth suppression and survival extension were observed after 2 cycles of the combination treatment. ConclusionsCombining AdGlipr1 (AdGLIPR1) with radiotherapy may achieve additive or synergistic tumor control in selected prostate and bladder tumors, and additional therapeutic effects may result with repeated treatment cycles.

Effect of single-cycle and multiple-cycle high-pressure treatments on the colour and texture of chicken breast fillets

Abstract High-pressure processing, a useful tool to improve the microbiological quality and safety of foods, may also bring about changes in the colour and texture of foods, which might influence their acceptability by consumers. In the present work, the effect of single-cycle and multiple-cycle high-pressure treatments at 400 MPa on the colour and texture of chicken breast fillets was investigated. Colour parameters L *, a * and b * were significantly higher for all pressurized fillets than for the vacuum-packaged control fillets. When single-cycle treatments were applied, maximum values of texture parameters were generally found for fillets pressurized for 10 or 15 min, depending on whether Kramer or Warner-Bratzler cells were used, and decreased for fillets submitted to longer cycles. In the case of multiple-cycle treatments, texture parameters initially increased with the number of 1-min cycles, but fillets submitted to the most severe treatments showed lower values. Industrial relevance The objective of the present study was to evaluate the effect of single-cycle and multiple-cycle high-pressure processing at 400 MPa on the colour and texture of chicken breast fillets. Significant changes in colour occurred even for the shortest treatment applied, a 1-min cycle. Texture parameters increased with length of treatment, but beyond a certain severity of treatment these parameters declined. Acceptability by consumers, and marketing of high-pressure treated chicken breast fillets, might be negatively affected by changes in visual appearance.

Inactivation ofSalmonellaEnteritidis in Chicken Breast Fillets by Single-Cycle and Multiple-Cycle High Pressure Treatments

The effect of single-cycle and multiple-cycle high hydrostatic pressure (HHP) treatments on the survival of three Salmonella Enteritidis strains in chicken breast fillets was investigated. The surface of fillets was inoculated with a cocktail of three Salmonella strains at approximately 10(7) colony-forming units (CFU)/g, and held at 4 degrees C for 20 hours before HHP treatments. Reduction of Salmonella counts on tryptic soy agar (TSA) by single-cycle treatments at 300 MPa and 12 degrees C ranged from 0.58 log CFU/g for a 0-minute (no dwell time) cycle to 3.35 log CFU/g for a 20-minute cycle, whereas with 400 MPa treatments the decline ranged from 0.93 log CFU/g to more than 5 log CFU/g, respectively. The 4.8 log unit reduction in Salmonella counts on TSA achieved by a 15-minute treatment at 400 MPa should suffice to eliminate the pathogen naturally present in contaminated chicken meat. When plated on Salmonella Shigella agar (SSA), the reduction of Salmonella counts by single-cycle treatments at 300 MPa and 12 degrees C ranged from 0.69 log CFU/g for a 0-minute cycle to 4.21 log CFU/g for a 20-minute cycle, and with 400 MPa treatments from 1.25 log CFU/g to more than 5 log CFU/g, respectively. From the comparison of Salmonella counts on SSA and TSA it was concluded that not only the lethality but also the proportion of injured Salmonella cells increased with the length of HHP treatments. The use of multiple-cycle treatments instead of single-cycle treatments of the same HHP time for the inactivation of Salmonella Enteritidis inoculated on chicken breast fillets showed to be more advantageous at 400 MPa than at 300 MPa. No recovery of injured Salmonella cells was observed when fillets treated at 300 or 400 MPa for 5 minutes were held for 72 hours at 4 degrees C.

Inactivation of Escherichia coli O157:H7 in Ground Beef by Single-Cycle and Multiple-Cycle High-Pressure Treatments

The effect of single- and multiple-cycle high-pressure treatments on the survival of Escherichia coli CECT 4972, a strain belonging to the O157:H7 serotype, in ground beef was investigated. Beef patties were inoculated with 107 CFU/g E. coli O157:H7, and held at 4°C for 20 h before high-pressure treatments. Reduction of the E. coli O157:H7 population by single-cycle treatments at 400 MPa and 12°C ranged from 0.82 log CFU/g for a 1-min cycle to 4.39 log CFU/g for a 20-min cycle. Multiple-cycle treatments were very effective, with four 1-min cycles at 400 MPa and 12°C reducing the E. coli O157:H7 population by 4.38 log CFU/g, and three 5-min cycles by 4.96 log CFU/g. The color parameter L* increased significantly with high-pressure treatments in the interior and the exterior of beef patties, whereas a* decreased in the interior, and b* increased in the exterior—changes that might diminish consumer acceptance of the product. Kramer shear force and energy were generally higher in pressurized than in control ground beef. Maximum values for these texture parameters, which corresponded to tougher patties, were reached after one 10-min cycle in the case of single-cycle treatments or two 5-min cycles in the case of multiple-cycle treatments. High-pressure treatments had no significant effect on Warner-Bratzler shear force.

Selection of radioimmunoconjugates for the therapy of well-established or micrometastatic colon carcinoma

In order to optimize radioimmunotherapy (RAIT) as a cancer-treatment modality, it is necessary to select the appropriate radionuclide and antibody carrier. We evaluated the therapeutic potential of a single cycle of Mu-9 anti-CSAp monoclonal antibody (MAb) labeled with 3 different radionuclides, 131I, 90Y and 188Re. Intact antibodies and bivalent fragments with different blood clearance kinetics, normal organ distribution and varying tumor accretion and retention are also evaluated. Efficacy of treatment for large and small tumor burden was assessed in nude mice bearing s.c. GW-39 human colonic-carcinoma xenografts or intrapulmonary micrometastatic GW-39 colonies at the maximal tolerated dose of each agent. The magnitude and duration of myelosuppression associated with each radioantibody was considered by monitoring peripheral blood counts, marrow colony-forming unit activity and hematopoietic tissue weight. Radiation-dose estimates were calculated based on the kinetics of antibody accretion and elimination from tumor and normal tissues, and the results were correlated with tumoricidal activity and dose-limiting toxicity results. These studies, therefore, represent a detailed analysis, in a well-defined experimental tumor system, of several parameters (antibody form, radioisotope, tumor size) influencing the overall outcome of RAIT using equitoxic doses. It was found that myelosuppression is the primary dose-limiting toxicity for all radioantibodies except 90Y-F(ab')2, even though the different agents showed varied organ distribution. In a single-cycle treatment schedule of Mu-9 MAb, the 131I-labeled IgG is the radioimmunoconjugate of choice for the treatment of s.c. and intrapulmonary growth of the GW-39 human colonic-carcinoma xenograft in nude mice.

Selection of radioimmunoconjugates for the therapy of well‐established or micrometastatic colon carcinoma

In order to optimize radioimmunotherapy (RAIT) as a cancer-treatment modality, it is necessary to select the appropriate radionuclide and antibody carrier. We evaluated the therapeutic potential of a single cycle of Mu-9 anti-CSAp monoclonal antibody (MAb) labeled with 3 different radionuclides, 131I, 90Y and 188Re. Intact antibodies and bivalent fragments with different blood clearance kinetics, normal organ distribution and varying tumor accretion and retention are also evaluated. Efficacy of treatment for large and small tumor burden was assessed in nude mice bearing s.c. GW-39 human colonic-carcinoma xenografts or intrapulmonary micrometastatic GW-39 colonies at the maximal tolerated dose of each agent. The magnitude and duration of myelosuppression associated with each radioantibody was considered by monitoring peripheral blood counts, marrow colony-forming unit activity and hematopoietic tissue weight. Radiation-dose estimates were calculated based on the kinetics of antibody accretion and elimination from tumor and normal tissues, and the results were correlated with tumoricidal activity and dose-limiting toxicity results. These studies, therefore, represent a detailed analysis, in a well-defined experimental tumor system, of several parameters (antibody form, radioisotope, tumor size) influencing the overall outcome of RAIT using equitoxic doses. It was found that myelosuppression is the primary dose-limiting toxicity for all radioantibodies except 90Y-F(ab′)2, even though the different agents showed varied organ distribution. In a single-cycle treatment schedule of Mu-9 MAb, the 131I-labeled IgG is the radioimmunoconjugate of choice for the treatment of s.c. and intrapulmonary growth of the GW-39 human colonic-carcinoma xenograft in nude mice. Int. J. Cancer 72:477–485, 1997. © 1997 Wiley-Liss, Inc.

THE SPORULATION OF HELMINTHOSPORIUM ORYZAE AS AFFECTED BY EXPOSURE TO NEAR ULTRAVIOLET RADIATION AND DARK PERIODS

Investigated was the interrelation of near ultraviolet radiation (3100–4000 Å) and darkness to the sporulation of Helminthosporium oryzae. When H. oryzae was grown on potato dextrose agar at 70–75° F and irradiated at intensities of 76–470 μw per cm2: (1) Near ultraviolet stimulated sporulation while visible light did not. (2) Conidiophore development was initiated under irradiation but not in darkness. Both continuous irradiation and intermittent irradiation (2-hour ultraviolet, 2-hour dark cycle) caused formation of conidiophores. (3) Conidia developed only when a period of irradiation was followed by a period of darkness. No conidia developed under continuous irradiation or in continuous darkness. (4) Under a single cycle treatment, the minimum dark period necessary for conidial development following an extended period of continuous irradiation was [Formula: see text] hours. (5) Under a single cycle treatment, the minimum exposure to ultraviolet followed by an extended dark period necessary to cause moderate to profuse conidial development was 4 hours, although conidia did form sparsely after shorter exposures. (6) Under alternating cycles of dark and irradiation of 2, 4, 6, 8, and 12 hours (e.g. 2 hours dark, 2 hours ultraviolet, etc.), conidia developed under the 8- and 12-hour cycles, but not under the shorter cycles. Conidia developed under shorter cycles when the cyclical exposures were followed by a dark period of 12 hours. (7) Continuous irradiation of nutrient broth cultures caused a significant increase in dry weight growth over cultures kept in darkness.