Localization of PNA-binding and nonbinding thymus cells in peripheral lymphoid organs

Thymus cells were labeled in vitro with FITC and injected into syngeneic recipients. In cell suspensions of lymphoid organs green cells were inspected for PNA receptors with double immunofluorescence. A striking preference of PNA-negative cells to localize in lymph nodes and the lymphoid compartment of the spleen was demonstrated. Incubation with anti-Ly sera revealed that Ly 1⁺ PNA-negative cells homed in popliteal lymph nodes and Peyer's patch but not in mesenteric lymph nodes.     

Molecular alterations produced in bacterial cells by ionizing radiation

Biochemical effects of high doses of 0.8 Mev electrons onEscherichia coli B were studied using infrared spectroscopy (IR). Aqueous suspensions of the bacterial cells were irradiated in open petri dishes. After exposure, films of these cells were examined for absorption of light between 4000 cm^–1 to 600 cm^–1. The qualitative aspects of the changes in the absorption spectra indicative of molecular alteration were noted and attempts were made to interpret them. The damage is selective in that some molecular groups are affected more than others. In general the changes indicate breakup of biopolymers and overall oxidation. All exposure doses given were above 1.0×10⁶ Roentgen.     

Plant regeneration from indica rice (Oryza sativa L.) protoplasts

Rice (Oryza sativa L.) plants of the indica cultivar IR54 were regenerated from protoplasts. Conditions were developed for isolating and purifying protoplasts from suspension cultures with protoplast yields ranging from 1·10⁶ to 15·10⁶ viable protoplasts/1 g fresh weight. Protoplast viability after purification was generally over 90%. Protoplasts were cultured in a slightly modified Kao medium in a Petri plate by placing them onto a Millipore filter positioned on top of a feeder (nurse) culture containing cells from a suspension culture of the japonica rice, Calrose 76. Plating efficiencies of protoplasts ranged from 0.5 to 3.0%; it was zero in the absence of the nurse culture. Protoplast preparations usually contained no contaminating cells, and when present, the number of cells never exceeded 0.1% of the protoplasts. After three weeks the Millipore filter with callus colonies were transferred off feeder cells and onto a Linsmaier and Skoog-type medium for an additional three weeks. Selected callus colonies that had embryo-like structures were then transferred to regeneration medium containing cytokinins, and regeneration frequencies up to 80% were obtained. Small shoots emerged and were transferred to jars for root development prior to transferring to pots of soil and growing the plants to maturity in growth chambers. Of the cytokinins evaluated, N⁶-benzylaminopurine was the most effective in promoting shoot formation; however, kinetin was also somewhat effective. Regeneration medium could be either an N₆ or Murashige and Skoog basal medium. Of 76 plants grown to maturity, 62 were fertile, and the plant heights averaged about three-fourths the height of seed-grown plants.Two other suspension cultures of IR54, one developed from the protoplast callus of the initial IR54 line, and the other developed from callus produced by mature seeds, have yielded protoplasts capable of regenerating plants when using cells of the Calrose 76 suspension as a nurse culture. In addition, protoplasts obtained from three-week-old primary callus of immature embryos of IR54 were capable of regenerating plants when using the same culture conditions.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - pcy packed cell volume - BAP N⁶-benzylaminopurine - FDA fluorescein diacetate - FW fresh weight - IAA indole-3-acetic acid Media AA Muller and Grafe (1978) - CPW Frearson et al. (1973) - Kao^* Kao (1977) - LS Linsmaier and Skoog (1965) - MS Murashige and Skoog (1962) - N₆ Chu et al. (1975) - PCM Ludwig et al. (1985)     

Calcium Homeostasis Change in CD4<Superscript>+</Superscript> T Lymphocytes from Human Peripheral Blood during Differentiation <Emphasis Type="Italic">in vivo</Emphasis>

Resting naive CD4⁺CD45R0^?CD45RA⁺ T cells are sensitive to ionomycin. In contrast, resting CD4⁺CD45RA^?CD45R0⁺ memory T cells show resistance to this Ca²⁺ ionophore. In the present study, the ability of activated T lymphocytes to respond to ionomycin during the transition from naive precursors into memory T cells has been analyzed. Activated CD4⁺CD45RA⁺CD45R0⁺ T cells are always present both in human peripheral blood (HPB) and in the ionomycin-resistant (IR) fraction. Therefore, some activated T cells are resistant toward the Ca²⁺ ionophore. CD69 molecules are markers of the very early stage of T cell activation. However, CD4⁺CD69⁺ T cells have never been found in the IR fraction. Thus, the majority of CD4⁺ T lymphocytes at the early stage of activation are ionomycin-sensitive cells. The proportion of CD4⁺CD25⁺ T cells did not differ significantly in HPB and in the IR fraction. The presence of CD4⁺CD25⁺ T lymphocytes in the IR fraction reflects changes in the Ca²⁺-signaling pathway at this differentiation step of activated cells. Depending on the expression level of CD25 molecules, the population of CD4⁺CD25⁺ cells is divided in T-regulatory (CD25^high) and proliferating (CD25^low) subpopulations. The action of ionomycin results in a decrease in the portion of the CD4⁺CD25^low T-cells, but it leads to an increase in the proportion of the CD4⁺CD25^high T lymphocytes. Consequently, greater portion of CD4⁺CD25^high T lymphocytes and smaller portion of CD4⁺CD25^low T cells are IR cells. Expression of HLA-DR molecules can be used as the marker for the late activation step. The IR fraction is significantly rich in CD4⁺HLA-DR⁺ T lymphocytes in comparison to the blood of the same donor. The link between different differentiation steps of CD4⁺ T-lymphocytes and alterations in calcium ion homeostasis is discussed.     

Reduction in parvalbumin expression in the zona incerta after 6OHDA lesion in rats

In an effort to understand better the neurochemical changes that occur in Parkinson disease, we have examined the expression patterns of the calcium-binding protein parvalbumin in the zona incerta in parkinsonian rats. Sprague-Dawley rats had small volumes of either saline (control) or 6 hydroxydopamine (6OHDA) injected into the medial forebrain bundle, the major tract carrying dopaminergic nigrostriatal axons. After various post-lesion survival periods, ranging from 2 hrs to 84 days, rats were perfused with formaldehyde and their brains processed for routine tyrosine hydroxylase (TH) or parvalbumin immunocytochemistry. In the 3 to 84 days post-lesion cases, there was an overall 50% reduction in the number of parvalbumin⁺ cells in the zona incerta on the 6OHDA-lesioned side when compared to control. In the 2 hrs post-lesion cases, there was no substantial loss of parvalbumin⁺ cells in the zona incerta after 6OHDA lesion, although in these cases (unlike the longer survival periods), there was limited loss of TH⁺ cells in the midbrain on the lesion side. The loss of parvalbumin⁺ cells from the zona incerta was due to a loss of antigen expression rather than a loss of the cells themselves, since the number of Nissl-stained cells in the zona incerta was similar on the control and 6OHDA-lesioned sides. In summary, our results indicate that a loss of the midbrain dopaminergic cells induces a major change in parvalbumin expression within the zona incerta. This change may have key functional and clinical implications.     

Increase in visfatin after weight loss induced by gastroplastic surgery

Objective: The recently described adipokine visfatin is produced in visceral fat and has been suggested to influence insulin resistance. To investigate whether visfatin concentrations are related to changes in body weight, this adipokine was measured in insulin‐resistant severely obese patients before and after gastroplastic surgery. Research Methods and Procedures: Visfatin, interleukin‐6, high‐sensitivity C‐reactive protein, homeostasis model assessment of insulin resistance (HOMA‐IR), and other clinical parameters were assessed in 36 severely obese subjects (28 female; mean age, 43 years) with a median BMI of 44.3 kg/m² (95% confidence interval, 43.3 to 48.1 kg/m²). Results: After surgery, BMI decreased to a median of 31.9 kg/m² (30.1 to 35.1 kg/m²) (p < 0.0001). Median visfatin concentrations increased significantly after weight loss [70.9 ng/mL (61.4 to 75.6 ng/mL) vs. 86.4 ng/mL (79.4 to 89.8 ng/mL); p < 0.0005]. This increase correlated with the decrease of insulin and HOMA‐IR and was associated with a reduction in plasma interleukin‐6 and high‐sensitivity C‐reactive protein concentrations. Discussion: Massive weight loss after gastroplastic surgery is accompanied by an increase in circulating concentrations of the novel adipokine visfatin. This increase correlates with the decrease in plasma insulin concentrations and HOMA‐IR.     

Insulin receptor overexpression in 184B5 human mammary epithelial cells induces a ligand-dependent transformed phenotype

To determine the role of the insulin receptor overexpression in breast epithelial cell transformation, the 184B5 human breast epithelial cell line was transfected with human insulin receptor cDNA. In two cell lines transfected with and overexpressing human insulin receptors (IR) (223.8 and 184.5 ng IR/10⁶ cells), but not in untransfected cells, insulin binding and tyrosine kinase activity were elevated, and insulin induced a dose-dependent increase in colony formation in soft agar.     

Molecular lesions associated with white gene mutations induced by I-R hybrid dysgenesis in Drosophila melanogaster

We have identified molecular lesions associated with six mutations, w^IR2 and w^IR4-8, of the white gene of Drosophila melanogaster. These mutations arose in flies subject to I-R hybrid dysgenesis. Four of the mutations give rise to coloured eyes and are associated with insertions of 5.4-kb elements indistinguishable from the I factor controlling I-R dysgenesis. The insertion associated with w^IR4 is at a site which, within the resolution of these experiments, is identical to that of two previously studied I factors. This appears to be a hot-spot for I factor insertion. We have compared the sites of these insertions with sequences complementary to white gene mRNA identified by Pirrotta and Bröckl. The hot-spot is in the fourth intron. The insertion carried by w^IR5 is either within, or just beyond, the last exon. The insertion carried by w^IR6 is near the junction of the first exon and first intron. The w^IR2 mutation is a derivative of w¹. It contains an insertion of I factor DNA within, or immediately adjacent to, the F-like element associated with w¹, and results in restoration of some eye colour. This insertion is just upstream of the start of the white mRNA. Mutations w^IR7 and w^IR8 are deletions removing mRNA coding sequences. Both determine a bleached white phenotype.     

Synthesis and anti-glioma activity of 25(R)-spirostan-3β,5α,6β,19-tetrol

Malignant gliomas are common and aggressive brain tumours in adults. The rapid proliferation and diffuse brain migration are the main obstacles to successful treatment. Here, we show 25(R)-spirostan-3β,5α,6β,19-tetrol, a polyhydroxy steroid, is capable of suppressing proliferation and migration of C6 malignant glioma cells in a concentration-dependent manner. The compound 25(R)-spirostan-3β,5α,6β,19-tetrol was synthesised by seven steps starting from diosgenin in 8.55% overall yield. The structures of the synthetic compounds were characterised by infrared (IR), ¹H nuclear magnetic resonance (NMR), ¹³C NMR spectra and EA.     

Exogenous NADP increases the level of histone H2AX phosphorylation in mouse heart cells after ionizing radiation

Phosphorylation of replacement histone H2AX occurs in megabase chromatin domains around DNA double-strand breaks (DSBs), and this modification called γ-H2AX can be used as an effective marker for DSBs repair and DNA damage response. Using Western blotting and immunohistochemistry techniques we have studied here the influence of exogenous nicotinamide adenine dinucleotide phosphate (NADP), which can potentially increase the level of intracellular NAD⁺, on the level of γ-H2AX formation in mouse heart cells after ionizing radiation (IR). We have found that injection of NADP in different doses immediately after IR causes an increased level of γ-H2AX in mouse heart cells 20 min after IR at the dose of 3 Gy compared to control mice after IR exposure. It indicates that there could be a relationship between intracellular NAD⁺ content and DNA damage response in vivo.     

The Effects of p38 MAPK Inhibition Combined with G-CSF Administration on the Hematoimmune System in Mice with Irradiation Injury

The acute and residual (or long-term) bone marrow (BM) injury induced by ionizing radiation (IR) is a major clinic concern for patients receiving conventional radiotherapy and victims accidentally exposed to a moderate-to-high dose of IR. In this study, we investigated the effects of the treatment with the p38 inhibitor SB203580 (SB) and/or granulocyte colony-stimulating factor (G-CSF) on the hematoimmune damage induced by IR in a mouse model. Specifically, C57BL/6 mice were exposed to a sublethal dose (6 Gy) of total body irradiation (TBI) and then treated with vehicle, G-CSF, SB, and G-CSF plus SB. G-CSF (1 µg/mouse) was administrated to mice by intraperitoneal (ip) injection twice a day for six successive days; SB (15 mg/kg) by ip injection every other day for 10 days. It was found that the treatment with SB and/or G-CSF significantly enhanced the recovery of various peripheral blood cell counts and the number of BM mononuclear cells 10 and 30 days after the mice were exposed to TBI compared with vehicle treatment. Moreover, SB and/or G-CSF treatment also increased the clonogenic function of BM hematopoietic progenitor cells (HPCs) and the frequency of BM lineage⁻Sca1⁺c-kit⁺ cells (LSK cells) and short-term and long term hematopoietic stem cells (HSCs) 30 days after TBI, in comparison with vehicle treated controls. However, the recovery of peripheral blood B cells and CD4⁺ and CD8⁺ T cells was not significantly affected by SB and/or G-CSF treatment. These results suggest that the treatment with SB and/or G-CSF can reduce IR-induced BM injury probably in part via promoting HSC and HPC regeneration.     

All‐Polymer Solar Cells with over 12% Efficiency and a Small Voltage Loss Enabled by a Polymer Acceptor Based on an Extended Fused Ring Core

Although the field of all‐polymer solar cells (all‐PSCs) has seen rapid progress in device efficiencies during the past few years, there are limited choices of polymer acceptors that exhibit strong absorption in the near‐IR region and achieve high open‐circuit voltage (V_OC) at the same time. In this paper, an all‐PSC device is demonstrated with a 12.06% efficiency based on a new polymer acceptor (named PT‐IDTTIC) that exhibits strong absorption (maximum absorption coefficient: 2.41 × 10⁵ cm^?1) and a narrow optical bandgap (1.49 eV). Compared to previously reported polymer acceptors such as those based on the indacenodithiophene (IDT) core, the indacenodithienothiophene (IDTT) core has further extended fused ring, providing the polymer with extended absorption into the near‐IR region and also increases the electron mobility of the polymer. By blending PT‐IDTTIC with the donor polymer, PM6, a high‐efficiency all‐PSC is achieved with a small voltage loss of 0.52 V, without sacrificing J_SC and FF, which demonstrates the great potential of high‐performance all‐PSCs.     

Jejunal Proteins Secreted by db/db Mice or Insulin-Resistant Humans Impair the Insulin Signaling and Determine Insulin Resistance

Background

Two recent studies demonstrated that bariatric surgery induced remission of type 2 diabetes very soon after surgery and far too early to be attributed to weight loss. In this study, we sought to explore the mechanism/s of this phenomenon by testing the effects of proteins from the duodenum-jejunum conditioned-medium (CM) of db/db or Swiss mice on glucose uptake in vivo in Swiss mice and in vitro in both Swiss mice soleus and L6 cells. We studied the effect of sera and CM proteins from insulin resistant (IR) and insulin-sensitive subjects on insulin signaling in human myoblasts.

Methodology/Principal Findings

db/db proteins induced massive IR either in vivo or in vitro, while Swiss proteins did not. In L6 cells, only db/db proteins produced a noticeable increase in basal ⁴⁷³Ser-Akt phosphorylation, lack of GSK3β inhibition and a reduced basal ³⁸⁹Thr-p70-S6K1 phosphorylation. Human IR serum markedly increased basal ⁴⁷³Ser-Akt phosphorylation in a dose-dependent manner. Human CM IR proteins increased by about twofold both basal and insulin-stimulated ⁴⁷³Ser-Akt. Basal ⁹Ser-GSK3β phosphorylation was increased by IR subjects serum with a smaller potentiating effect of insulin.

Conclusions

These findings show that jejunal proteins either from db/db mice or from insulin resistant subjects impair muscle insulin signaling, thus inducing insulin resistance.     

ATM pathway is essential for ionizing radiation-induced autophagy

BackgroundATM plays an important role in response to DNA damage, while the roles of ATM in radiation-induced autophagy are still unclear in cervical cancer cells.MethodsHuman cervical cancer cells, Hela, were used, and cell models with ATM^?/? and MAPK14^?/? were established by gene engineering. Western blot was implemented to detect protein expression. MDC staining and GFP-LC3 relocalization were used to detect autophagy. CCK-8 was used to detect cell viability. Radiosensitivity was analyzed by colony formation assays. Co-immunoprecipitation was used to detect the interaction between different proteins, and apoptosis was detected by flow cytometry.ResultsAfter radiation autophagy was induced, illustrated by the increase of MAPLC3-II/MAPLC3-I ratio and decrease of p62, and phosphorylation of ATM simultaneously increased. ATM^?/? cells displayed hypersensitivity but had no influence on IR-induced apoptosis. Then inhibitor of ATM, KU55933, ATM and MAPK14 silencing were used, and autophagy was induced by IR more than 200% in control, and only by 35.72%, 53.18% and 24.76% in KU55933-treated cells, ATM^?/? and MAPK14^?/? cells, respectively. KU55933 inhibited IR-induced autophagy by activating mTOR pathways. ATM silencing decreased the expression of MAPK14 and mTOR signals significantly. Beclin's bond to PI3KIII and their interaction increased after IR, while in ATM^?/? and MAPK14^?/? cells this interaction decreased after IR. Both ATM and MAPK14 interacted with Beclin, while ATM^?/? and MAPK14^?/? cells showed no interaction.ConclusionsATM could promote IR-induced autophagy via the MAPK14 pathway, the mTOR pathway, and Beclin/PI3KIII complexes, which contributed to the effect of ATM on radiosensitivity.     

Restoring the Secretory Function of Irradiation-Damaged Salivary Gland by Administrating Deferoxamine in Mice

Objectives

One of the major side effects of radiotherapy for treatments of the head and neck cancer is the radiation-induced dysfunction of salivary glands. The aim of the present study is to investigate the efficacy of deferoxamine (DFO) to restore the secretory function of radiation-damaged salivary glands in mice.

Methods

DFO (50 mg/kg/d) was administered intraperitoneally in C₅₇BL/6 mice for 3 days before and/or after point-fixed irradiation (18 Gy) of submandibular glands. The total 55 mice were randomly divided into: (1) Normal group: mice received no treatment (n = 5); (2) Irradiation group (IR): mice only received irradiation (n = 5); (3) Pre-DFO group (D+IR) (n = 10); (4) Pre+Post DFO group (D+IR+D) (n = 10); (5) Post-DFO group (IR+D) (n = 10); (6) For each DFO-treated group, the mice were intraperitoneally injected with 0.1 ml sterilized water alone (by which DFO was dissolved) for 3 days before and/or after irradiation, and served as control. Sham1: Pre-sterilized water group (n = 5); sham2: Pre+Post sterilized water group (n = 5); sham3: Post-sterilized water group (n = 5). The salivary flow rate (SFR) was assessed at 30^th, 60^th and 90^th day after irradiation, respectively. After 90 days, all mice were sacrificed and their submandibular glands were removed for further examinations.

Results

The salivary glands showed remarkable dysfunction and tissue damage after irradiation. DFO restored SFR in the irradiated glands to a level comparable to that in normal glands and angiogenesis in damaged tissue was greatly increased. DFO also increased the expression levels of HIF-1α and VEGF while reduced apoptotic cells. Furthermore, Sca-1⁺cells were preserved in the salivary glands treated with DFO before IR.

Conclusions

Our results indicate DFO could prevent the radiation-induced dysfunction of salivary glands in mice. The mechanism of this protective effect may involve increased angiogenesis, reduced apoptosis of acinar cells and more preserved stem cells.     

TubeSpin bioreactor 50 for the high-density cultivation of Sf-9 insect cells in suspension

Here we present the TubeSpin bioreactor 50 (TubeSpins) as a simple and disposable culture system for Sf-9 insect cells in suspension. Sf-9 cells had substantially better growth in TubeSpins than in spinner flasks. After inoculation with 10⁶ cells/ml, maximal cell densities of 16 × 10⁶ and 6 × 10⁶ cells/ml were reached in TubeSpins and spinner flasks, respectively. In addition the cell viability in these batch cultures remained above 90% for 10 days in TubeSpins but only for 4 days in spinner flasks. Inoculation at even higher cell densities reduced the duration of the lag phase. After inoculation at 2.5 × 10⁶ cells/ml, the culture reached the maximum cell density within 3 days instead of 7 days as observed for inoculation with 10⁶ cells/ml. Infection of Sf-9 cells in TubeSpins or spinner flasks with a recombinant baculovirus coding for green fluorescent protein (GFP) resulted in similar GFP-specific fluorescence levels. TubeSpins are thus an attractive option for the small-scale cultivation of Sf-9 cells in suspension and for baculovirus-mediated recombinant protein production.     

T-cell differentiation in lethally irradiated and reconstituted mice

During the first 3 days after irradiation and reconstitution (IR) with hemopoietic stem cells a small number of cells with the capacity to form colonies (CFU-s) can be detected in the thymus. This number is increased when thymectomized mice are used as recipients for colony determination. In thymus-cell suspensions from animals 4 days after IR no CFU-s can be found either in normal or in thymectomized recipients. Tracer studies with ¹¹¹In-labeled oxine revealed that thymocytes obtained from animals 3 days after IR contain a large number of cells with a strong preference for the thymus. This number decreases in the following days after irradiation; these cells are thought to represent an intermediate cell between stem cell and T cell.     

Micro-heterogenous expression of peanut agglutinin-binding sites in the extracellular matrix of cultured cells

Using double-label techniques with fluorochrome-conjugated peanut agglutinin (PNA) and indirect immunofluorescence with rabbit species-specific anti-fibronectin antibodies and a mouse monoclonal anti-fibronectin, the extracellular matrix (ECM) of cultured human and mouse fibroblasts (Hell7 and 3T3K) and human bladder epithelial cells (T24) was studied. The antibodies and PNA co-localized extensively. However, a small but consistent degree of micro-heterogeneity was revealed insofar as both PNA-positive fibronectin-negative fibrils as well as PNA-negative fibronectin-positive fibrils were observed. Fibronectin production by T24 cells (but not fibroblasts) was influenced by the growth medium, but this did not affect the heterogeneity. Trypsin removed most cell-surface fibronectin and all PNA-binding sites, but did not account for the observed phenomenon. Intracellular fibronectin, whether present naturally or induced to accumulate by culture in presence of Monensin, was PNA-negative. These data suggest that PNA-binding sites appear on fibronectin as a consequence of incorporation into the extracellular matrix, and that the resultant heterogeneity of spatial expression of beta-galactose-like residues may offer a mechanism whereby mesenchymal cells could modulate the behaviour of overlying cell-types.     

Apoptosis-inducing factor deficiency decreases the proliferation rate and protects the subventricular zone against ionizing radiation

Cranial radiotherapy in children often leads to progressive cognitive decline. We have established a rodent model of irradiation-induced injury to the young brain. A single dose of 8 Gy was administered to the left hemisphere of postnatal day 10 (P10) mice. Harlequin (Hq) mice, carrying the hypomorphic apoptosis-inducing factor AIF^Hq mutation, express 60% less AIF at P10 and displayed significantly fewer dying cells in the subventricular zone (SVZ) 6 h after IR, compared with wild type (Wt) littermates. Irradiated cyclophilin A-deficient (CypA^−/−) mice confirmed that CypA has an essential role in AIF-induced apoptosis after IR. Hq mice displayed no reduction in SVZ size 7 days after IR, whereas 48% of the SVZ was lost in Wt mice. The proliferation rate was lower in the SVZ of Hq mice. Cultured neural precursor cells from the SVZ of Hq mice displayed a slower proliferation rate and were more resistant to IR. IR preferentially kills proliferating cells, and the slower proliferation rate in the SVZ of Hq mice may, at least partly, explain the protective effect of the Hq mutation. Together, these results indicate that targeting AIF may provide a fruitful strategy for protection of normal brain tissue against the detrimental side effects of IR.     

Autoradiographic localization of 3H-γ-aminobutyric acid uptake in the lamina ganglionaris of Musca and Drosophila

Summary The uptake of ³H-GABA in the visual system of half-head preparations of Musca and Drosophila was studied by means of light and electron microscope autoradiography. Of all three ganglia, only the first synaptic region, the lamina ganglionaris, showed accumulation of radioactive grains, and there a preferential glial uptake could be found. Under normal light conditions at incubation (constant light flux of 100 Lux) the maximum of radio-activity was found in the marginal glia cells. Increasing the time of incubation produced also an increase in the number of grains per surface unit in the marginal glia cells. After changing the light intensity during incubation, quantitative modifications of the distribution of radio-activity were observed: incubating with stroboscopic illumination, the number of grains diminished in the marginal glia cells and remained constant in the epithelial cells; incubated in darkness, the epithelial cells became more intensely labelled whilst the number of grains decreased in the marginal cells.The possibility is discussed that the receptor axons 1–6 are the neurological elements of the lamina which use GABA as a transmitter. This hypothesis is lent some support from results of similar experiments with neurological mutants of Drosophila. In opm 18 there was a delayed uptake of ³H-GABA whereas in opm 3 and ebony the results were comparable to those found in Musca incubated in darkness. Behavioral studies on these mutants have demonstrated a defect, most probably related to the receptor system 1–6.