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The death and clearance of nurse cells is a consequential milestone in Drosophila melanogaster oogenesis. In preparation for oviposition, the germline-derived nurse cells bequeath to the developing oocyte all their cytoplasmic contents and undergo programmed cell death. The death of the nurse cells is controlled non-autonomously and is precipitated by epithelial follicle cells of somatic origin acquiring a squamous morphology and acidifying the nurse cells externally. Alternatively, stressors such as starvation can induce the death of nurse cells earlier in mid-oogenesis, manifesting apoptosis signatures, followed by their engulfment by epithelial follicle cells. To identify and contrast the molecular pathways underlying these morphologically and genetically distinct cell death paradigms, both mediated by follicle cells, we compared their genome-wide transcriptional, translational, and secretion profiles before and after differentiating to acquire a phagocytic capability, as well as during well-fed and nutrient-deprived conditions. By coupling the GAL4-UAS system to Translating Ribosome Affinity Purification (TRAP-seq) and proximity labeling (HRP-KDEL) followed by Liquid Chromatography tandem mass-spectrometry, we performed high-throughput screens to identify pathways selectively activated or repressed by follicle cells to employ nurse cell-clearance routines. We also integrated two publicly available single-cell RNAseq atlases of the Drosophila ovary to define the transcriptomic profiles of follicle cells. In this report, we describe the genes and major pathways identified in the screens and the striking consequences to Drosophila melanogaster oogenesis caused by RNAi perturbation of prioritized candidates. To our knowledge, our study is the first of its kind to comprehensively characterize two distinct apoptotic and non-apoptotic cell death paradigms in the same multi-cellular system. Beyond molecular differences in cell death, our investigation may also provide insights into how key systemic trade-offs are made between survival and reproduction when faced with physiological stress., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2025 Bandyadka et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

FlyBase (flybase.org) is a model organism database and knowledge base about Drosophila melanogaster, commonly known as the fruit fly. Researchers from around the world rely on the genetic, genomic, and functional information available in FlyBase, as well as its tools to view and interrogate these data. In this article, we describe the latest developments and updates to FlyBase. These include the introduction of single-cell RNA sequencing data, improved content and display of functional information, updated orthology pipelines, new chemical reports, and enhancements to our outreach resources., Competing Interests: Conflicts of interest: The author(s) declare no conflicts of interest., (© The Author(s) 2024. Published by Oxford University Press on behalf of The Genetics Society of America.)

FlyBase provides a centralized resource for the genetic and genomic data of Drosophila melanogaster. As FlyBase enters our fourth decade of service to the research community, we reflect on our unique aspects and look forward to our continued collaboration with the larger research and model organism communities. In this study, we emphasize the dedicated reports and tools we have constructed to meet the specialized needs of fly researchers but also to facilitate use by other research communities. We also highlight ways that we support the fly community, including an external resources page, help resources, and multiple avenues by which researchers can interact with FlyBase., (© The Author(s) 2022. Published by Oxford University Press on behalf of Genetics Society of America.)

Since 1992, FlyBase has provided a freely available online database of information about the model organism Drosophila melanogaster. Data in FlyBase is curated manually from research papers as well as computationally from a variety of relevant sources, to serve as an information hub that enables and accelerates research discovery. This chapter aims to give users new to the database an overview of the layout and types of data available, as well as introducing some tools with which to access the data. More experienced users will find useful information about recent improvements and descriptions to enable more efficient navigation of the database., (© 2022. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Programmed cell death and cell corpse clearance are an essential part of organismal health and development. Cell corpses are often cleared away by professional phagocytes such as macrophages. However, in certain tissues, neighboring cells known as nonprofessional phagocytes can also carry out clearance functions. Here, we use the Drosophila melanogaster ovary to identify novel genes required for clearance by nonprofessional phagocytes. In the Drosophila ovary, germline cells can die at multiple time points. As death proceeds, the epithelial follicle cells act as phagocytes to facilitate the clearance of these cells. We performed an unbiased kinase screen to identify novel proteins and pathways involved in cell clearance during two death events. Of 224 genes examined, 18 demonstrated severe phenotypes during developmental death and clearance while 12 demonstrated severe phenotypes during starvation-induced cell death and clearance, representing a number of pathways not previously implicated in phagocytosis. Interestingly, it was found that several genes not only affected the clearance process in the phagocytes, but also non-autonomously affected the process by which germline cells died. This kinase screen has revealed new avenues for further exploration and investigation., (© The Author(s) 2021. Published by Oxford University Press on behalf of Genetics Society of America.)

Multiple types of cell death exist including necrosis, apoptosis, and autophagic cell death. The Drosophila ovary provides a valuable model to study the diversity of cell death modalities, and we review recent progress to elucidate these pathways. At least five distinct types of cell death occur in the ovary, and we focus on two that have been studied extensively. Cell death of mid-stage egg chambers occurs through a novel caspase-dependent pathway that involves autophagy and triggers phagocytosis by surrounding somatic epithelial cells. For every egg, 15 germline nurse cells undergo developmental programmed cell death, which occurs independently of most known cell death genes. These forms of cell death are strikingly similar to cell death observed in the germlines of other organisms., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Hypertension leads to structural and functional changes at baroreceptor synapses in the medial nucleus tractus solitarius (NTS), but the underlying molecular mechanisms remain unknown. Our previous studies show that brain-derived neurotrophic factor (BDNF) is abundantly expressed by rat nodose ganglion (NG) neurons, including baroreceptor afferents and their central terminals in the medial NTS. We hypothesized that hypertension leads to upregulation of BDNF expression in NG neurons. To test this hypothesis, we used two mechanistically distinct models of hypertension, the spontaneously hypertensive rat (SHR) and the deoxycorticosterone acetate (DOCA)-salt rat. Young adult SHRs, whose blood pressure was significantly elevated compared with age-matched Wistar-Kyoto (WKY) control rats, exhibited dramatic upregulation of BDNF mRNA and protein in the NG. BDNF transcripts from exon 4, known to be regulated by activity, and exon 9 (protein-coding region) showed the largest increases. Electrical stimulation of dispersed NG neurons with patterns that mimic baroreceptor activity during blood pressure elevations led to increases in BDNF mRNA that were also mediated through promoter 4. The increase in BDNF content of the NG in vivo was associated with a significant increase in the percentage of BDNF-immunoreactive NG neurons. Moreover, upregulation of BDNF in cell bodies of NG neurons was accompanied by a significant increase in BDNF in the NTS region, the primary central target of NG afferents. A dramatic increase in BDNF in the NG was also detected in DOCA-salt hypertensive rats. Together, our study identifies BDNF as a candidate molecular mediator of activity-dependent changes at baroafferent synapses during hypertension., (Copyright © 2012 Wiley Periodicals, Inc.)

Rett syndrome is a neurodevelopmental disorder caused by loss-of-function mutations in the gene encoding the transcription factor methyl-CpG-binding protein 2 (MeCP2). One of its targets is the gene encoding brain-derived neurotrophic factor (bdnf). In vitro studies using cultured neurons have produced conflicting results with respect to the role of MeCP2 in BDNF expression. Acute intermittent hypoxia (AIH) induces plasticity in the respiratory system characterized by long-term facilitation of phrenic nerve amplitude. This paradigm induces an increase in BDNF protein. We hypothesized that AIH leads to augmentation of BDNF transcription in respiratory-related areas of the brainstem and that MeCP2 is necessary for this process. Wild-type and mecp2 null (mecp2(-/y)) mice were subjected to three 5-min episodes of exposure to 8% O(2)/4% CO(2)/88% N(2), delivered at 5-min intervals. Normoxia control wild-type and mecp2 null mice were exposed to room air for the total length of time, that is, 30 min. Following a recovery in room air, the pons and medulla were rapidly removed. Expression of BDNF protein and transcripts were determined by ELISA and quantitative PCR, respectively. AIH induced a significant increase in BDNF protein in the pons and medulla, and in mRNA transcript levels in the pons of wild-type animals. In contrast, there were no significant changes in either BDNF protein or transcripts in the pons or medulla of mice lacking MeCP2. The results indicate that MeCP2 is required for regulation of BDNF expression by acute intermittent hypoxia in vivo., (Copyright © 2012 IBRO. Published by Elsevier Ltd. All rights reserved.)

Nociceptive pathways with first-order neurons located in the trigeminal ganglion (TG) provide sensory innervation to the head, and are responsible for a number of common chronic pain conditions, including migraines, temporomandibular disorders and trigeminal neuralgias. Many of those conditions are associated with inflammation. Yet, the mechanisms of chronic inflammatory pain remain poorly understood. Our previous studies show that the neurotrophin brain-derived neurotrophic factor (BDNF) is expressed by adult rat TG neurons, and released from cultured newborn rat TG neurons by electrical stimulation and calcitonin gene-related peptide (CGRP), a well-established mediator of trigeminal inflammatory pain. These data suggest that BDNF plays a role in activity-dependent plasticity at first-order trigeminal synapses, including functional changes that take place in trigeminal nociceptive pathways during chronic inflammation. The present study was designed to determine the effects of peripheral inflammation, using tooth pulp inflammation as a model, on regulation of BDNF expression in TG neurons of juvenile rats and mice. Cavities were prepared in right-side maxillary first and second molars of 4-week-old animals, and left open to oral microflora. BDNF expression in right TG was compared with contralateral TG of the same animal, and with right TG of sham-operated controls, 7 and 28 days after cavity preparation. Our ELISA data indicate that exposing the tooth pulp for 28 days, with confirmed inflammation, leads to a significant upregulation of BDNF in the TG ipsilateral to the affected teeth. Double-immunohistochemistry with antibodies against BDNF combined with one of nociceptor markers, CGRP or transient receptor potential vanilloid type 1 (TRPV1), revealed that BDNF is significantly upregulated in TRPV1-immunoreactive (IR) neurons in both rats and mice, and CGRP-IR neurons in mice, but not rats. Overall, the inflammation-induced upregulation of BDNF is stronger in mice compared to rats. Thus, mouse TG provides a suitable model to study molecular mechanisms of inflammation-dependent regulation of BDNF expression in vivo., (Copyright 2010 IBRO. Published by Elsevier Ltd. All rights reserved.)

Functional characteristics of the arterial baroreceptor reflex change throughout ontogenesis, including perinatal adjustments of the reflex gain and adult resetting during hypertension. However, the cellular mechanisms that underlie these functional changes are not completely understood. Here, we provide evidence that brain-derived neurotrophic factor (BDNF), a neurotrophin with a well-established role in activity-dependent neuronal plasticity, is abundantly expressed in vivo by a large subset of developing and adult rat baroreceptor afferents. Immunoreactivity to BDNF is present in the cell bodies of baroafferent neurons in the nodose ganglion, their central projections in the solitary tract, and terminal-like structures in the lower brainstem nucleus tractus solitarius. Using ELISA in situ combined with electrical field stimulation, we show that native BDNF is released from cultured newborn nodose ganglion neurons in response to patterns that mimic the in vivo activity of baroreceptor afferents. In particular, high-frequency bursting patterns of baroreceptor firing, which are known to evoke plastic changes at baroreceptor synapses, are significantly more effective at releasing BDNF than tonic patterns of the same average frequency. Together, our study indicates that BDNF expressed by first-order baroreceptor neurons is a likely mediator of both developmental and post-developmental modifications at first-order synapses in arterial baroreceptor pathways.

Recent evidence indicates that endomorphins, endogenous mu-opioid receptor (MOR) agonists, modulate synaptic transmission in both somatic and visceral sensory pathways. Here we show that endomorphin-2 (END-2) is expressed in newborn rat dorsal root ganglion (DRG) and nodose-petrosal ganglion complex (NPG) neurons, and rarely co-localizes with brain-derived neurotrophic factor (BDNF). In order to examine activity-dependent release of END-2 from neurons, we established a model using dispersed cultures of DRG and NPG cells activated by patterned electrical field stimulation. To detect release of END-2, we developed a novel rapid capture enzyme-linked immunosorbent assay (ELISA), in which END-2 capture antibody was added to neuronal cultures shortly before their electrical stimulation. The conventional assay was effective at reliably detecting END-2 only when the cells were stimulated in the presence of CTAP, a MOR-selective antagonist. This suggests that the strength of the novel assay is related primarily to rapid capture of released END-2 before it binds to endogenous MORs. Using the rapid capture ELISA, we found that stimulation protocols known to induce plastic changes at sensory synapses were highly effective at releasing END-2. Removal of extracellular calcium or blocking voltage-activated calcium channels significantly reduced the release. Together, our data provide the first evidence that END-2 is expressed by newborn DRG neurons of all sizes found in this age group, and can be released from these, as well as from NPG neurons, in an activity-dependent manner. These results point to END-2 as a likely mediator of activity-dependent plasticity in sensory pathways.

Diflubenzuron (DFB) and Clanfenur (CFN) belong to a group of compounds called Benzoylphenyl Ureas (BPUs). Several BPUs regulate cell growth in insects and/or inhibit growth of B-16 murine melanomas. In view of potential clinical use for these compounds, DFB and CFN were selected as examples of BPUs and tested for effects on hematopoiesis in C57Bl/6 mice housed in a conventional environment. DFB and CFN exhibit anti-tumor activity in mice, cause little or no morbidity and mortality and rather than causing bone marrow suppression, which is usual for anti-cancer drugs, these agents stimulate hematopoiesis in vivo and in vitro. Stimulation in vivo was evidenced by increased (up to 112%) peripheral blood granulocytes 6 days after a single injection and enhanced granulopoiesis (approximately 25%) in bone marrow up to 18 days after treatment. That effects of DFB and CFN were on hematopoietic stem cells were indicated by 47% and 48%, respectively, increases in numbers of CFUs and 97% and 95%, respectively, increases in CFUgm. Further, bone marrow cells treated in vitro contained about twice the number of CFUs and CFUgm as control bone marrow cells. Almost all of the increase in number of spleen colonies, whether derived from donors treated in vivo or bone marrow cells treated in vitro, was accounted for by a corresponding increase in number of undifferentiated colonies. These data indicate that DFB and CFN treatment enhance numbers of pluripotential stem cells both in vivo and in vitro. The mechanism of enhancement, direct or indirect, remains to be determined.

Permanent cell lines and clones established from an untreated patient (AGS cells) with gastric carcinoma, and from a similar patient who had been treated with Adriamycin, 5FU and cytoxan (SII cells) were used in a study that compared their drug and radiation survival sensitivities to their glutathidine (GSH) values. The SII parental cell line was more resistant than the AGS cells in vitro to chlorambucil, ACT D, Adria, Bleo, and X-rays. This greater resistance was positively correlated with GSH values that were 1.77 times higher than in the AGS parental cell line. By contrast the SII parental cells were more sensitive than the AGS cells to MeCCNU and Melphalan. The drug and radiation sensitivities expressed among the clones of the two cell lines were heterogeneous and did not correlate with their GSH values.

The mean number of lymphocytes, response to phytohemagglutinin (PHA), and response to concanavalin A (Con A) in whole-blood cultures for 106 patients with head and neck cancer were 83%, 73%, and 64%, respectively, of values for healthy control individuals. During radiotherapy, lymphocyte counts declined to 44% and PHA and Con A responses declined to about one third of control values. Lymphocyte counts slowly increased after treatment to 77% of control values after two years, but responses to mitogens remained at about 40%. Responses to PHA and Con A for 38 patients who lived beyond 18 months were significantly greater before and after treatment than responses for 39 patients who died within 18 months. In general, a poor pretreatment response to PHA and Con A correlated with a poor clinical course, whereas responses near the control level indicated a good clinical course.

Several schedules of benzene exposure were evaluated for their effects on peripheral white blood cell counts, bone marrow cellularity and transplantable colony forming units (CFU-S) in male C57 Bl/6 mice. Intermittent exposure to 4000 ppm benzene in air produced leukopenia without altering the bone marrow cellularity. This same treatment, however, decreased the number of CFU-S to 30% of control values. Uninterrupted exposure to lower levels of benzene decreased peripheral cell counts within 24 h, and later decreased marrow cellularity. Exposure of a non-dividing population of stem cells (CFU-S) to benzene for up to 24 h produced no detectable effect on the subsequent development of spleen colonies, suggesting that the effect of benzene on CFU-S occurs only after peripheral cells are depleted. These findings indicate that benzene has affects on both differentiated cells and undifferentiated stem cells. An effect on the pluripotential stem cell is an important aspect of benzene toxicity, but not its exclusive or initial site of action.

Bone marrow cell responses to therapeutic doses of cis-diamminedichloroplatinum (II) (Cis-Pt) were evaluated in female C57B1/6 mice by determining bone marrow cellularity and content of transplantable colony forming units (CFUS) after treatment. Although limitation on the dosage of Cis-Pt is generally considered to be determined by renal toxicity, methods to increase the effective use of the drug such as hydration and diuresis, alteration of time-dose schedules and combination of Cis-Pt with other drugs and radiation, warrant studies on effects of the drug on other normal tissues such as bone marrow. Cis-Pt given on a time-dose schedule that is therapeutic for mice and, in general, is equivalent to regimens recommended for clinical use, was found to be myelosuppressive. The myelosuppression was dose related in that a total dose of 16 mg/kg (2 doses at weekly interval) reduced the number of CFUS/femur to 16% of the control value, 24 mg/kg (4 doses at weekly intervals) reduced the CFUS fraction to 10-14% of the value for controls and 32 mg/kg (4 doses at weekly intervals) reduced the fraction of CFUs to 6-7% of the control value. A quantitative extrapolation of these effects to man cannot be made, however, the data indicate that myelosuppression could become a significant factor as increased doses of Cis-Pt are used clinically.

Ffty-three patients with head and neck cancer tested before radiation treatment to determine numbers of blood lymphocytes and immunologic responses to mitogens of lymphocytes in whole-blood cultures had mean values that were 19% to 26% less than values for healthy individuals. Thirty patients whose disease was in stages III or IV had values similar to those in 23 patients whose disease was in stages I or II. Values for 45 patients tested at end of radiotherapy decreased to about 50% of pretreatment values; however, patients with advanced lesions experienced greater decreases (to 24% to 50%) than patients with localized lesions (to 71% to 84%). Patients with advanced lesions usually received radiation to larger areas than patients with localized lesions; therefore, the extent of decline in laboratory values was most likely dependent on volume of tissue treated.

We have shown in earlier studies that repeated weekly exposures of a human astrocytoma clone (AST 3-4) to MeCCNU (10 micrograms/ml for 1 h per week) produced a linear decrease in survival over the first 3 weekly treatments. But, after that time these cells became progressively more resistant to the 10 micrograms/ml concentration of the agent. In the studies reported here we show that these previously treated cells were also less responsive to other doses ranging from 1 to 30 micrograms MeCCNU/ml. This change in sensitivity to MeCCNU was accompanied by collateral changes in response to other agents: resistance to BCNU and Galactitol, increased sensitivity to Adriamycin, and no change to ionizing radiation. These experiments suggest that once repeated treatments with a single agent cause a tumor cell population to become more resistant, sensitivity to other agents may also change unpredictably.

The insect growth regulator diflubenzuron (DFB), which may also inhibit growth of imaginal epidermal cells in insects, was studied for antitumor activity in two mouse tumor models of epidermal origin. DFB inhibits chitin deposition, but the mechanisms by which DFB controls chitin deposition or regulates growth of insect epidermal cells are unknown. A single injection of 20 mg (800 mg/kg) of DFB into C57BL/6 mice with B16 malignant melanomas or AKR mice with skin tumors (CA 1025) induced a rapid (24 h) decrease in tumor volume in 78% and 66% of the tumors, respectively. In contrast, 85% of the melanomas and 91% of skin tumors in control mice increased in volume during the same 24-h period. Tumor volume decreased by as much as 55% for about 1% of the tumors, but the median decrease was 20% for both types of tumors. Since control tumors concommitantly increased, DFB-treated tumors decreased, relatively, to 60% of the volume of matched control tumors. After the initial volume decrease, both types of tumors resumed exponential growth resulting in an average growth curve delay, calculated for 12-14 days, of about 2.0 days. Subsequent treatment of melanomas with DFB 24 h after the initial treatment resulted in a further decrease in relative tumor volume to 40-50% of control tumor volume and a growth curve delay of 2.6 days. The most effective regimen used was 5 daily, 20-mg doses of DFB. Melanomas decreased to 40% of control tumor volume after the third injection and the mean growth curve delay was extended to 4.3 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Investigations of lymphatic dysfunction in animals infected with filarial parasites has been hampered by a paucity of techniques to measure efficiency of lymphatic drainage. In this study a 99mTc-sulfur colloid technique was used to assess the efficiency of lymphatic drainage in Patas monkeys infected with filarial nematodes. In all 15 uninfected hind limbs there was rapid and consistent appearance of labeled colloid in the primary lymph node (popliteal) and subsequently in the secondary nodes (abdomino-pelvic) in 11 of 15 limbs. In contrast, in all eight limbs tested 1-9 months after infection there was reduced rate of migration of the colloid and initial appearance in the abdomino-pelvic region: subsequent accumulation was seen in the popliteal region in only four of the limbs. This data indicated that lymphatic vessels were blocked and that collateral vessels channeled the colloid to the secondary lymph nodes. The lymph flow patterns demonstrated by the isotope technique were supported at autopsy.

Bone marrow cell responses to injections of nitrogen mustard, oncovin, procarbazine, hydrocortisone, and a regimen of all four drugs (MOPH) were evaluated in CRF1 and C57B1/6 mice by determining bone marrow cellularity and content of transplantable colony forming units (CFU) after treatment. The study was done to determine whether the combined regimen, which is widely used clinically in treatment of disseminated Hodgkin's disease, is more or less detrimental to the hemopoietic system than the same drugs used as single agents. Nitrogen mustard and procarbazine used clinically as single drugs are given in three and two times, respectively, greater doses than in the combined regimen. Hydrocortisone, given singly, was least toxic of the drugs, reducing the CFU/femur to 63% and 71% of control values. MOPH appeared slightly more toxic than hydrocortisone, resulting in 41% and 52% of the CFU/femur surviving, and was about equally as toxic as oncovin alone. Nitrogen mustard and procarbazine, administered as single drugs in high doses, were highly suppressive, resulting in only 10-19% survival of CFU/femur, whereas, reduced doses of the two drugs as used in the MOPH regimen spared 30-45% of the CFU/femur. Survival of CFU after MOPH treatment was three to four times greater than after high doses of nitrogen mustard or procarbazine alone. The component drugs of the combined regimen did not act on separate populations of stem cells to produce an additive effect but appeared to inactivate the same population of cells.

In vitro effects of radiation were studied in two permanent cell lines (AGS and SII) from two patients with adenocarcinoma of the stomach and three permanent sublines from each cell line. Radiation survival parameters for AGS and SII parent cell lines and sublines were determined after in vitro irradiation of their cells with 0.5 to 10 Gy of 60Co gamma rays. The AGS and SII cell lines had different growth properties, DNA contents and radiation survival curves. Surviving fractions of SII parent cells (76 chromosomes) after 2.0 and 10 Gy were 1.22 and 17.8 times greater, respectively, than values for AGS parent cells (47 chromosomes). Sensitivities (D0) were 1.08 and 1.45 Gy for AGS and SII parent lines, respectively. The D0 values for AGS parent cells and sublines were similar (1.01 to 1.08 Gy), but SII parent cells and sublines had D0 values of 1.45, 1.36, 1.37 and 1.12 Gy (for SII-A). Also, the SII parent cells had survival fractions after 2.0 and 10 Gy that were 1.3 and 11.3 times greater, respectively, than values for the SII-A cells. These data show differences in radiation responses among stomach cancer cell lines and sublines that may relate to DNA content, but there was no consistent correlation between radiation response and a particular cell characteristic.

It is axiomatic that a given dose of an antitumor agent will not produce the same effect in 100% of the treated subjects. Numerous explanations regarding the sources of this heterogeneous response to drugs have been offered; however, there is a scarcity of experimental data allowing critical evaluation of the sources of variance. It is possible to study heterogeneous antitumor drug response in experimental, inbred animals. One animal model system, the advanced Ridgway osteogenic sarcoma, exhibits marked variation in its response to maximally tolerated doses of a number of clinically active antitumor agents. To evaluate the role of the host in the variable drug response, the tumor was bilaterally implanted into the flank regions of recipient AKR male mice. Treatment of the advanced tumor (200 mg-1,500 mg) with maximally tolerated doses of vincristine or L-phenylalanine mustard produced marked, but variable antitumor responses. Evaluation of a number of quantal and graded parameters of the chemotherapeutic response suggested that host heterogeneity contributes to variability. The host contribution was more apparent in this experiment model when the agent was noncurative. The underlying biological basis for the host heterogeneity is not known; however, it appears likely that pharmacological, immunological or other differences between the inbred animals account for the heterogeneity. Identification of these factors may be experimentally feasible in this animal model and help in the design of future studies in humans.

The insect growth regulator diflubenzuron (DFB), which also inhibits growth of experimental tumors in mice, was studied to determine the influence of in vivo microsomal metabolism on its antitumor activity. DFB inhibits chitin synthesis and growth of imaginal epidermis in insects and suppresses melanogenesis and uptake of nucleosides in mouse melanoma cells, but the means of cell growth regulation and the role of metabolism of DFB in such regulation have not been established. Five daily injections of DFB (total of 4000 mg/kg) into C57BL/6 mice with B16 melanomas induced an acute 11-20% decrease in tumor volume and a 2-3 day increase in the initial tumor volume doubling time (Td), but at mid-treatment tumors regained maximum (control-like) rate of volume increase. Tumors in mice conditioned with a mixed function oxidase inhibitor (CoCl2) and treated with DFB did not decrease in mean volume, but their rate of volume increase was reduced by about 75% and the Td was increased by 4.2 days. In contrast, induction of mixed function oxidase with 3-methylcholanthrene (3-MC) or beta-napthaflavone (B-NF) enhanced the effects of DFB by a factor of 1.5 to 2.0. Therefore, aromatic hydroxylation of DFB may be required for tumor growth regulation. Three metabolites of DFB--two hydroxylated forms and a scission product, 4-chlorophenylurea (CPU), were also tested for tumor growth regulation. CPU was ineffective; a form oxidized at the 3 carbon of the phenyl ring (3-OH-DFB) was only marginally effective; but the 2-carbon form (2-OH-DFB) induced a 24% decrease in mean tumor volume and a 2.4 day increase in Td. Pretreatment with 3-MC and treatment with 2-OH-DFB also resulted in a 24% decrease in tumor volume and a 2.2 day increase in Td, but also reduced tumor volume increase to 20% between the 5th and 10th days after the initial 2-OH-DFB injection, compared to a 125% increase without 3-MC. Further, 3-MC pretreatment caused the otherwise marginally effective 3-OH-DFB to become almost as effective as 2-OH-DFB. These data support our previous report that DFB alters tumor growth and show that mixed function oxidase enhances effects of DFB, 2-OH-DFB and 3-OH-DFB.

An in vitro model has been devised so that mixtures of human tumor cells can be grown together for studies related to drug-induced or -selected changes in sensitivity. In the studies reported here, two human astrocytoma clones, one sensitive and one resistant to 1-(2-chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea (MeCCNU), were carefully matched for doubling times, cell cycle phase distributions, and colony-forming efficiencies. The clones were mixed and grown together, and after only three weekly treatments with MeCCNU (10 micrograms/ml for 1 h each week) the sensitive cells in the mixture were killed, leaving behind a population that was almost 100% resistant to further exposures to MeCCNU. The loss of the sensitive cells from the mixture each week was easily detected by visual observation of flow microfluorometry histograms since the clones had different DNA indices. Repeated weekly exposures of the unmixed resistant clone (AST 1-1) to MeCCNU caused very little accumulated cell kill. Similar exposures of the unmixed sensitive clone (AST 3-4) produced a linear decrease in survival over the first three weekly treatments with 10 micrograms MeCCNU/ml, but after that time these cells became progressively more resistant to MeCCNU. It is unlikely that the change to resistance in the AST 3-4 clone occurred because of contamination with the resistant AST 1-1 cells, because their DNA index remained stable. These data show that repeated treatments with a single agent can cause a tumor cell population to become more resistant. It remains to be tested whether this resistance was the result of cellular interactions, drug-induced changes in sensitivity, or selection for resistant cells already present in the populations. This mixture model may be useful in studies on how cellular interactions influence growth and drug sensitivity in tumor and normal cell populations.

Effects of radiation therapy for carcinoma of the breast on responsiveness to mitogens of blood lymphocytes of patients at different clinical stages were analysed. Patients at different clinical stages had comparable numbers and responses of lymphocytes. During therapy the mean lymphocyte numbers decreased to 31 per cent of the pre-treatment value and mean responses to mitogens in whole-blood cultures decreased to 15 to 39 per cent of pre-treatment values. Similar decreases occurred whether or not mastectomy was performed.

Quantitative determinations were made of the capacity of isogenic bone marrow, spleen, and thymic cells from primed and/or nonprimed mice to repopulate the hemopoietic tissues and to mount an inflammatory and antibody response to specific antigen (tetanus toxoid) in heavily irradiated and reconstituted recipients. Spleen cells from primed mice but not from normal mice had the capacity to adoptively transfer an anamnestic antitoxin titer in irradiated animals in the absence of transplanted bone marrow cells, and during retarded myeloid regeneration. Spleen cells alone or bone marrow cells alone produced an insignificant and a moderate peritoneal eosinophil response, respectively, to antigen. In the presence of bone marrow cells, normal spleen cells augment the capacity of recipient animals to mount an eosinophil response to antigen. A much greater augmentation occurs in animals reconstituted with splenic or thymic cells from primed animals. The increase in antitoxin titers appears to be independent of the response of eosinophils since: (a) marked accumulation of eosinophils can occur in animals with no measurable humoral antitoxin, and (b) high antitoxin titers can occur in animals which do not have marked eosinophil responses. It is suggested that a thymic-derived or thymic-dependent mononuclear cell population is necessary for optimal eosinophil response to antigen. The neutrophil and mononuclear cell responses to antigen are determined by different mechanisms from those which determine the eosinophil response. These studies together with earlier findings strongly indicate that the eosinophil granulocytes play a role in the immune response to antigen.

Granulocytic leukemia, induced in the primary mouse by x-irradiation, was serially transmitted to RF/Up mice. An extra chromosome, as well as a morphologicaly unusual chromosome, was found in the bone marrow cells of all the leukemic mice that had been injected previously either with leukemic spleen cells or with cell-free ultracentrifugates. This suggests that the changes in the chromosomes are caused by a virus.