Hyperparameter Optimization of Bayesian Neural Network Using Bayesian Optimization and Intelligent Feature Engineering for Load Forecasting

This paper proposes a new hybrid framework for short-term load forecasting (STLF) by combining the Feature Engineering (FE) and Bayesian Optimization (BO) algorithms with a Bayesian Neural Network (BNN). The FE module comprises feature selection and extraction phases. Firstly, by merging the Random Forest (RaF) and Relief-F (ReF) algorithms, we developed a hybrid feature selector based on grey correlation analysis (GCA) to eliminate feature redundancy. Secondly, a radial basis Kernel function and principal component analysis (KPCA) are integrated into the feature-extraction module for dimensional reduction. Thirdly, the Bayesian Optimization (BO) algorithm is used to fine-tune the control parameters of a BNN and provides more accurate results by avoiding the optimal local trapping. The proposed FE-BNN-BO framework works in such a way to ensure stability, convergence, and accuracy. The proposed FE-BNN-BO model is tested on the hourly load data obtained from the PJM, USA, electricity market. In addition, the simulation results are also compared with other benchmark models such as Bi-Level, long short-term memory (LSTM), an accurate and fast convergence-based ANN (ANN-AFC), and a mutual-information-based ANN (ANN-MI). The results show that the proposed model has significantly improved the accuracy with a fast convergence rate and reduced the mean absolute percent error (MAPE).

Phageome-based vaccination and human innate immune modulation could be a useful strategy to control human Coronavirus infections

Human Coronavirus (CoV) infections, including SARS-COV, MERS-COV, and SARS-CoV-2, usually cause fatal lower and upper respiratory tract infections due to exacerbated expression of pro-inflammatory cytokines and chemokines. We aim to summarize different aspects, such as CoV immune evasion mechanisms and host innate immune response to these infections, and their role in pathogenesis. We have also elaborated the up-to-date findings on different vaccine development strategies and progress against CoVs in both humans and non-human models. Most importantly, we have described the Phageome-human immune interaction, its therapeutic usage as anti-viral, anti-inflammatory agent, and implications for multiple vaccine development systems. The data suggest that endogenous phages might play a vital role in eliminating the infection and regulating the body's immune system. Considering the innate-immune-induced pathogenesis against CoVs and the therapeutic aptitude of phageome, we propose that the prophylactic administration of phages and phage-based vaccines could be a useful strategy to control the emerging CoV infections.

Effects of Bacillus sp. MR-1/2 and magnetite nanoparticles on yield improvement of rice by urea fertilizer under different watering regimes

AIMS

The present research aimed to examine the use of magnetite nanoparticles (MNPs) in combination with phyto-beneficial rhizobacterium (PhBR) for improvement of applied N recovery (ANR) from urea fertilizer in rice grown under deficient and optimum watering conditions.

METHODS AND RESULTS

The Bacillus sp. MR-1/2 was positive for acetylene reduction, phosphate solubilization and ACC deaminase activity at temperature ranges 35-45°C. In a pot experiment, urea, MNPs and Bacillus sp. MR-1/2 were applied either alone or in combination to rice plants grown in pots under water deficit and optimal watering conditions. Combined application of urea, MNPs and Bacillus sp. MR-1/2 increased the plant N content and ANR by 27 and 65%, respectively, over their respective control values in rice grown under optimum watering conditions, whereas these increases were 27 and 41%, respectively, in rice grown under water deficit conditions. This treatment also increased the kernel weight and plant dry matter by 36 and 60%, respectively, over control (urea alone) values in rice grown under water deficit conditions, whereas these increases were 31 and 21·8%, respectively, in rice grown under optimum watering conditions. Values of malondialdehyde (MDA) contents, ascorbate peroxidase (APX), catalase and ethylene concentration were higher in control treatment under both the watering regimes. The application of Bacillus sp. MR-1/2 either alone or in combination with MNPs and urea reduced MDA contents, APX, catalase and ethylene production in the rice plants.

CONCLUSION

The combined application of MNPs+Bacillus sp. MR-1/2 reduced the N losses from applied urea, increased N uptake and ANR in rice, decreased MDA contents, APX and catalase activity and ethylene level in rice grown under deficit and optimum water conditions.

SIGNIFICANCE AND IMPACT OF THE STUDY

The application of MNPs together with Bacillus sp. MR-1/2 may help to increase ANR and rice productivity under water deficit conditions with low cost of production.

Interactions of dipalmitoylphosphatidylcholine with ceramide-based mixtures

The outermost layer of the skin, the stratum corneum (SC), acts as the natural physical barrier. The SC consists of corneocytes embedded in a crystalline lipid matrix consisting of ceramides, free fatty acids and cholesterol. Although phospholipids are frequently present in topical formulations, no detailed information is reported on the interactions between phospholipids and SC lipids. The aim of this study was to examine the interactions between a model phospholipid, dipalmitoylphosphatidylcholine (DPPC) and synthetic ceramide-based mixtures (referred to as SC lipids). (Perdeuterated) DPPC was mixed with SC lipids and the lipid organization and mixing properties were examined. The studies revealed that DPPC participates in the same lattice as SC lipids thereby enhancing a hexagonal packing. Even at a high DPPC level, no phase separated pure DPPC was observed. When a DPPC containing formulation is applied to the skin surface it must partition into the SC lipid matrix prior to any mixing with the SC lipids. To mimic this, DPPC was applied on top of a SC lipid membrane. DPPC applied in a liquid crystalline state was able to mix with the SC lipids and participated in the same lattice as the SC lipids. However, when DPPC was applied in a rippled gel-state very limited partitioning of DPPC into the SC lipid matrix occurred. Thus, when applied to the skin, liquid crystalline DPPC will have very different interactions with SC lipids than DPPC in a (rippled-)gel phase.

A calibration rig for multi-component internal strain gauge balance using the new design-of-experiment (DOE) approach

In a closed water-tunnel circuit, the multi-component strain gauge force and moment sensor (also known as balance) are generally used to measure hydrodynamic forces and moments acting on scaled models. These balances are periodically calibrated by static loading. Their performance and accuracy depend significantly on the rig and the method of calibration. In this research, a new calibration rig was designed and constructed to calibrate multi-component internal strain gauge balances. The calibration rig has six degrees of freedom and six different component-loading structures that can be applied separately and synchronously. The system was designed based on the applicability of formal experimental design techniques, using gravity for balance loading and balance positioning and alignment relative to gravity. To evaluate the calibration rig, a six-component internal balance developed by Iran University of Science and Technology was calibrated using response surface methodology. According to the results, calibration rig met all design criteria. This rig provides the means by which various methods of formal experimental design techniques can be implemented. The simplicity of the rig saves time and money in the design of experiments and in balance calibration while simultaneously increasing the accuracy of these activities.

Aurora kinase A regulates Survivin stability through targeting FBXL7 in gastric cancer drug resistance and prognosis

Aurora kinase A (AURKA) has been implicated in the regulation of cell cycle progression, mitosis and a key number of oncogenic signaling pathways in various malignancies. However, little is known about its role in gastric cancer prognosis and genotoxic resistance. Here we found that AURKA was highly overexpressed in gastric cancer and inversely correlated with disease prognosis. Overexpression of AURKA exacerbated gastric cancer drug resistance through upregulating the expression of the anti-apoptotic protein Survivin. Conversely, we demonstrated that AURKA depletion caused a decrease in Survivin protein levels by increasing its ubiquitylation and degradation. Mass spectrometric analysis revealed that upon AURKA depletion, Survivin bound to the FBXL7 E3 ubiquitin ligase, which induced ubiquitin-proteasome degradation of Survivin. In addition, we showed that AURKA regulated FBXL7 both at the levels of transcription and translation. Moreover, proteomic analysis of nuclear AURKA-interacting proteins identified Forkhead box protein P1 (FOXP1). We next showed that AURKA was required for FBXL7 transcription and that AURKA negatively regulated FOXP1-mediated FBXL7 expression. The physiological relevance of the regulation of Survivin by AURKA through the FOXP1–FBXL7 axis was further underscored by the significant positive correlations between AURKA and Survivin expression in gastric cancer patient samples. Moreover, the AURKA depletion or kinase inhibition-induced apoptotic cell death could be reversed by Survivin ectopic overexpression, further supporting that AURKA regulated Survivin to enhance drug resistance. In agreement, inhibition of AURKA synergistically enhanced the cytotoxic effect of DNA-damaging agents in cancer cells by suppressing Survivin expression. Taken together, our data suggest that AURKA restricts Survivin ubiquitylation and degradation in gastric cancer to promote drug resistance and hence the AURKA–Survivin axis can be targeted to promote the efficacy of DNA-damaging agents in gastric cancer.

p62/SQSTM1 enhances breast cancer stem-like properties by stabilizing MYC mRNA

Aberrant p62 overexpression has been implicated in breast cancer development. Here, we found that p62 expression was elevated in breast cancer stem cells (BCSCs), including CD44⁺CD24^- fractions, mammospheres, ALDH1⁺ populations and side population cells. Indeed, short-hairpin RNA (shRNA)-mediated knockdown of p62 impaired breast cancer cells from self-renewing under anchorage-independent conditions, whereas ectopic overexpression of p62 enhanced the self-renewal ability of breast cancer cells in vitro. Genetic depletion of p62 robustly inhibited tumor-initiating frequencies, as well as growth rates of BCSC-derived tumor xenografts in immunodeficient mice. Consistently, immunohistochemical analysis of clinical breast tumor tissues showed that high p62 expression levels were linked to poorer clinical outcome. Further gene expression profiling analysis revealed that p62 was positively correlated with MYC expression level, which mediated the function of p62 in promoting breast cancer stem-like properties. MYC mRNA level was reduced upon p62 deletion by siRNA and increased with p62 overexpression in breast cancer cells, suggesting that p62 positively regulated MYC mRNA. Interestingly, p62 did not transactivate MYC promoter. Instead, p62 delayed the degradation of MYC mRNA by repressing the expression of let-7a and let-7b, thus promoting MYC mRNA stabilization at the post-transcriptional level. Consistently, let-7a and let-7b mimics attenuated p62-mediated MYC mRNA stabilization. Together, these findings unveiled a previously unappreciated role of p62 in the regulation of BCSCs, assigning p62 as a promising therapeutic target for breast cancer treatments.

Mesenchymal stem cell (MSC) viability on PVA and PCL polymer coated hydroxyapatite scaffolds derived from cuttlefish

In the present study, cuttlefish bones are used to prepare highly porous hydroxyapatite (HA) scaffolds via hydrothermal treatment at 200 °C.

C-Arm Flat Detector CT Parenchymal Blood Volume Thresholds for Identification of Infarcted Parenchyma in the Neurointerventional Suite

BACKGROUND AND PURPOSE

C-arm flat detector CT parenchymal blood volume imaging allows functional assessment of the brain parenchyma in the neurointerventional suite. This study aimed to determine the optimal C-arm flat detector CT parenchymal blood volume thresholds for demarcating irreversibly infarcted brain parenchyma by using areas of restricted diffusion on MR imaging as a surrogate marker for infarction.

MATERIALS AND METHODS

Twenty-six patients with delayed cerebral ischemia following aneurysmal SAH underwent research C-arm CT parenchymal blood volume scans by using a biplane angiography system and contemporaneous MR imaging. Infarct and peri-infarct tissue VOIs and their homologous VOIs in the contralateral uninvolved hemisphere were delineated on the basis of the review of DWI, PWI, and ADC images. Voxel-based receiver operating characteristic curve analysis was performed to estimate the optimal absolute and normalized parenchymal blood volume values for demarcating the infarct voxels.

RESULTS

For 12 patients with areas of restricted diffusion (infarct volume, 6.38 ± 7.09 mL; peri-infarct tissue volume, 22.89 ± 21.76 mL) based on the voxel-based receiver operating characteristic curve analysis, optimal absolute and normalized parenchymal blood volume thresholds for infarction were 2.49 mL/100 g (area under curve, 0.76; sensitivity, 0.69; specificity, 0.71) and 0.67 (area under curve, 0.77; sensitivity, 0.69; specificity, 0.72), respectively (P value < .01). For the moderate-to-severely ischemic peri-infarct zone, mean parenchymal blood volume values of the involved hemisphere VOIs were lower compared with the uninvolved hemisphere VOIs (P value < .01). However, for the mild-to-moderately ischemic peri-infarct zone, there was no statistically significant difference between the mean parenchymal blood volume values of the involved and uninvolved hemisphere VOIs (P value > .05).

CONCLUSIONS

C-arm flat detector CT parenchymal blood volume maps in conjunction with optimal thresholds are sensitive and specific for the estimation of irreversibly infarcted parenchyma. Parenchymal blood volume maps allow reliable detection of moderate-to-severe ischemia; however, the potential for underestimation of mild-to-moderate ischemia exists.

Frequency of thyroid incidentalomas in Karachi population

Objectives: The aim of this study was to determine frequency of thyroid incidentalomas (TI) through ultrasound (US) and its association with age, gender and ethnicities.

Methods: It was a cross-sectional study. Total 269 adults who were asymptomatic for thyroid disease aged 21 years and above underwent ultrasound examination of their thyroid.

Results: Frequency of TI found was 21%. TI was detected in 25% of females and 16% males (P= 0.078). 61% had thyroid nodules (TNs) in one lobe (right, left or isthmus) and 39% had TNs in more than one location. About 55% had single TN and 45% had multiple TNs. 38% had TNs greater than 1cm while 57% had TNs smaller than 1 cm. 5% had TNs greater and smaller than 1 cm. TI was equally common in individuals of different ethinicities (P= 0.758).

Conclusion: Frequency of thyroid incidentalomas found in our study was higher than most of the other iodine sufficient states. Unlike other studies, incidentalomas were equally common in both the genders of our study. This may be due to the previous iodine deficient status of Pakistan which was prevalent. However further studies on the same topic will help us in identifying the correct status of thyroid incidentalomas if Pakistan retains it’s status as an iodine sufficient state.

Critical Study on Rotational Flow of a Fractional Oldroyd-B Fluid Induced by a Circular Cylinder

We considered the unsteady flow of a fractional Oldroyd-B fluid through an infinite circular cylinder with the help of infinite Hankel and Laplace transforms. The motion of the fluid is produced by the cylinder that, at time t=0+ is subject to a time-dependent angular velocity. The established solutions have been presented under series form in terms of the generalized G functions satisfy all imposed initial and boundary conditions. The corresponding solutions for ordinary Oldroyd-B, ordinary and fractional Maxwell, ordinary and fractional second-grade, and Newtonian fluids, performing the same motion, are acquired as limiting cases of general solutions. The keynote points regarding this work to mention are that (1) we extracted the expressions for velocity field and shear stress corresponding to the motion of fractional second-grade fluid as a limiting case of general solutions; (2) the expressions for velocity field and shear stress are in the most simplified form in contrast with the studies of Siddique and Sajid (2011), in which the expression for the velocity field involves the convolution product as well as the integral of the product of generalized G functions. Finally, numerical results are presented graphically and discussed in order to reveal some physical aspects of obtained results.

Exact Solutions for the Axial Couette Flow of a Fractional Maxwell Fluid in an Annulus

The velocity field and the adequate shear stress corresponding to the rotational flow of a fractional Maxwell fluid, between two infinite coaxial circular cylinders, are determined by applying the Laplace and finite Hankel transforms. The solutions that have been obtained are presented in terms of generalized Ga,b,c(·,t) and Ra,b(·,t) functions. Moreover, these solutions satisfy both the governing differential equations and all imposed initial and boundary conditions. The corresponding solutions for ordinary Maxwell and Newtonian fluids are obtained as limiting cases of our general solutions. Finally, the influence of the material parameters on the velocity and shear stress of the fluid is analyzed by graphical illustrations.

Taylor–Couette flow of a fractional second grade fluid in an annulus due to a time-dependent couple

Exact solutions for the velocity field and the associated shear stress, corresponding to the flow of a fractional second grade fluid between two infinite coaxial cylinders, are determined by means of Laplace and finite Hankel transforms. The motion is produced by the inner cylinder which is rotating about its axis due to a time-dependent torque per unit length 2πR1ft2. The solutions that have been obtained satisfy all imposed initial and boundary conditions. For β → 1, respectively β → 1 and α1 → 0, the corresponding solutions for ordinary second grade fluids and Newtonian fluids, performing the same motion, are obtained as limiting cases.

Exact solutions for the unsteady rotational flow of a generalized second grade fluid through a circular cylinder

Here the velocity field and the associated tangential stress corresponding to the rotational flow of a generalized second grade fluid within an infinite circular cylinder are determined by means of the Laplace and finite Hankel transforms. At time t = 0 the fluid is at rest and the motion is produced by the rotation of the cylinder around its axis with a time dependent angular velocity Ωt. The solutions that have been obtained are presented under series form in terms of the generalized G-functions. The similar solutions for the ordinary second grade and Newtonian fluids, performing the same motion, are obtained as special cases of our general solution.

Taylor–Couette flow of a generalized second grade fluid due to a constant couple

The velocity field and the adequate shear stress, corresponding to the flow of a generalized second grade fluid in an annular region between two infinite coaxial cylinders, are determined by means of Laplace and finite Hankel transforms. The motion is produced by the inner cylinder which is rotating about its axis due to a constant torque f per unit length. The solutions that have been obtained satisfy all imposed initial and boundary conditions. For β → 1 or β → 1 and α1 → 0, the corresponding solutions for an ordinary second grade fluid, respectively, for the Newtonian fluid, performing the same motion, are obtained as limiting cases.

Surface-plasmon-polariton assisted diffraction in periodic subwavelength holes of metal films with reduced interplane coupling

Metal films grown on an Si wafer perforated with a periodic array of subwavelength holes have been fabricated and anomalous enhanced transmission in the midinfrared regime has been observed. High order transmission peaks up to Si(2,2) are clearly revealed due to the large dielectric constant contrast of the dielectrics at the opposite interfaces. The Si(1,1) peak splits at oblique incidence both in TE and TM polarization, which confirms that anomalous enhanced transmission is a surface-plasmon-polariton (SPP) assisted diffraction phenomenon. Theoretical transmission spectra agree excellently with the experimental results and confirm the role of SPP diffraction by the lattice.

Planar imaging versus gated blood-pool SPECT for the assessment of ventricular performance: a multicenter study

Gated blood-pool SPECT (GBPS), inherently 3-dimensional (3D), has the potential to replace planar equilibrium radionuclide angiography (ERNA) for computation of left ventricular ejection fraction (LVEF), analysis of regional wall motion (RWM), and analysis of right heart function. The purpose of this study was to compare GBPS and ERNA for the assessment of ventricular function in a large, multicenter cohort of patients.

METHODS

One hundred seventy-eight patients referred in the usual manner for nuclear medicine studies underwent ERNA followed by GBPS. Each clinical site followed a GBPS acquisition protocol that included 180 degrees rotation, a 64 by 64 matrix, and 64 or 32 views using single- or double-head cameras. Transverse GBPS images were reconstructed with a Butterworth filter (cutoff frequency, 0.45-0.55 Nyquist; order, 7), and short-axis images were created. All GBPS studies were processed with a new GBPS program, and LVEF was computed from the isolated left ventricular chamber and compared with standard ERNA LVEF. Reproducibility of GBPS LVEF was evaluated, and right ventricular ejection fraction (RVEF) was computed in a subset of patients (n = 33). Using GBPS, RWM and image quality from 3D surface-shaded and volume-rendered cine displays were evaluated qualitatively in a subset of patients (n = 30).

RESULTS

The correlation between GBPS LVEF and planar LVEF was excellent (r = 0.92). Mean LVEF was 62.2% for GBPS and 54.1% for ERNA. The line of linear regression was GBPS LVEF = (1.04 x ERNA LVEF) + 6.1. Bland-Altman plotting revealed an increasing bias in GBPS LVEF with increasing LVEF (Y = 0.13x + 0.61; r = 0.30; mean difference = 8.1% +/- 7.0%). Interoperator reproducibility of GBPS LVEF was good (r = 0.92). RVEF values averaged 59.8%. RWM assessment using 3D cine display was enhanced in 27% of the studies, equivalent in 67%, and inferior in 7%.

CONCLUSION

GBPS LVEF was reproducible and correlated well with planar ERNA. GBPS LVEF values were somewhat higher than planar ERNA, likely because of the exclusion of the left atrium.

Clinical impact of arrhythmias on gated SPECT cardiac myocardial perfusion and function assessment

BACKGROUND

We reported previously that mean quantified cardiac functional parameters computed by one gated single photon emission computed tomography (SPECT) technique were not significantly altered by common gating errors. However, it is not known to what extent other gated SPECT approaches that are based on different ventricular modeling assumptions are influenced by arrhythmias, nor are the effects of gating errors on visual analyses and their subsequent clinical implications known.

METHODS

Projection data for 50 patients (aged 64 +/- 12 years; 68% men; 76% with myocardial perfusion defects) undergoing technetium-99m sestamibi gated SPECT who were in sinus rhythm during data acquisition were altered to simulate common arrhythmias. To determine quantitative effects, we performed calculations for original control and altered images by Gaussian myocardial detection (Quantitative Gated SPECT [QGS] program) and by wall thickening derived from gated perfusion polar maps (Emory Cardiac Toolbox program). To evaluate visual assessment in control and simulated-arrhythmia tomograms, 2 experienced blinded observers independently interpreted perfusion from polar maps and wall motion and thickening from tomographic cines, using a 4-point scale.

RESULTS

Although mean functional parameters were scarcely altered, paired t tests showed ejection fraction fluctuations to be significantly different from control values, causing patients to change between abnormal and normal ejection fraction categories (2% of patients by QGS and 14% by Emory Cardiac Toolbox). Visual examination of QGS polar perfusion and function maps showed changes for 72% of cases, although in only 4% were these considered to have potential clinical consequences. The kappa statistic for visual analysis of concordance between control and arrhythmia readings showed that agreement was "excellent" for perfusion, "good" for motion, and "marginal" for thickening.

CONCLUSIONS

As with quantitative measurements, thickening is the parameter most prone to error in the presence of arrhythmias. It is important to test data for gating errors to avoid potentially erroneous measurements and visual readings.

Artifactual reverse distribution pattern in myocardial perfusion SPECT with technetium-99m sestamibi

BACKGROUND

The reverse distribution pattern (RDP), in which resting perfusion imaging demonstrates a de novo or more marked regional defect than that present in stress images, is observed frequently in patients with a low likelihood of coronary artery disease.

METHODS AND RESULTS

To determine whether this scan pattern is artifactual and to investigate its causes, we retrospectively evaluated scans in 202 patients with a low likelihood of coronary artery disease (77 men and 125 women) undergoing single-day rest/stress technetium-99m sestamibi single photon emission computed tomography (SPECT). The presence and location of RDP was correlated with relevant body habitus parameters. RDP was observed in 15.3% of patients. The finding was significantly more frequent in patients who were obese (P<.02 in men, P<.03 in women), in men with abdominal protuberance (P<.05), and in women with prominent breast "shadows" observed on planar projection images (P<.008). RDP was most frequent in the right coronary artery territory in men and the left anterior descending coronary artery territory in women. It was demonstrated by means of a cardiac SPECT phantom experiment that soft tissue attenuation effects were most evident in low count density SPECT studies with localized soft tissue attenuation, accounting for the higher than clinical observation of RDP in obese patients undergoing low-dose rest/high-dose imaging.

CONCLUSIONS

RDP is a frequently encountered artifact in obese patients undergoing rest/stress Tc-99m sestamibi SPECT, particularly in men with abdominal protuberance and in women with large, dense breasts.

Overexpression of GLUT2 gene in renal proximal tubules of diabetic Zucker rats

Renal tubular reabsorption of glucose is substantially increased in humans and rats with diabetes mellitus. The influx of luminal glucose is mediated by Na+/glucose cotransporter system and glucose efflux from tubules to interstitium by facilitative glucose transporters (GLUT). In Zucker diabetic rats, GLUT2 protein levels of renal proximal tubules were higher than in control litter mates: 9.67 +/- 1.95 versus 4.72 +/- 1.55 (P = 0.0073). In the same proximal tubules, diabetes was associated with minor decreases in GLUT1 protein levels: 1.96 +/- 0.37 for diabetics and 2.37 +/- 0.34 for controls (P = 0.12). Na+/glucose cotransporter system protein levels were similar in both groups, whereas Na+/K+ ATPase levels were slightly decreased in diabetic rats, but the difference was not statistically significant. In this report, it is suggested that in long-term uncontrolled diabetes, GLUT2 transporters are overexpressed in renal tubules. This adaptation promotes low-affinity, high-capacity glucose efflux. The higher number of high K(m) GLUT2 ensures that glucose reabsorption is increased by promoting glucose efflux, which could be rate-limiting in the face of hyperglycemia.

Surface receptors and immune activity of purified human circulating mononuclear cells. V. Circulating null cells and a factor secreted by the null cells inhibit the synthesis of receptors for Fc mu by T cells in culture

Receptors for Fc mu (Fc mu R) were not detected on freshly isolated unfractionated circulating human mononuclear cells (MNC) or purified T cells. However, a significant percentage of the T cells (20% to 40%), but not of the unfractionated MNC, exhibited Fc mu receptors following culture for 24 h at 37 degrees C in medium enriched with fetal calf serum. These receptors were newly synthesized by the T cells since they were not detected on T cells cultured for 24 h with cycloheximide in a non-cytotoxic concentration. The absence of Fc mu R on the cultured unfractionated MNC (of which 70% are T cells) suggested that non-T cells within the MNC-B cells and/or null cells and/or monocytes suppressed the synthesis of Fc mu R by the T cells. These cells were individually assayed for their capacity to suppress Fc mu R synthesis by co-cultured T cells. The null cells were able to totally suppress Fc mu R synthesis whereas the B cells and monocytes exhibited no suppressive activity. Null cells cultured for 24 h at 37 degrees C secreted a factor which inhibited the synthesis of receptors for Fc mu by the cultured T cells. This factor is referred to as receptor synthesis suppressor factor or RSSF. On the basis of these findings, it is concluded that (a) the circulating T cells do not possess Fc mu R; these receptors are synthesized de novo by the T cells in culture, (b) the null cells, but neither the B cells nor the monocytes, suppress the synthesis of the Fc mu R by the T cells and (c) the null cells, but neither the B cells nor the monocytes, secrete a factor, receptor synthesis suppressor factor, which can suppress the synthesis of Fc mu R by the T cells.