Independent control of mean and noise by convolution of gene expression distributions

Gene expression noise can reduce cellular fitness or facilitate processes such as alternative metabolism, antibiotic resistance, and differentiation. Unfortunately, efforts to study the impacts of noise have been hampered by a scaling relationship between noise and expression level from individual promoters. Here, we use theory to demonstrate that mean and noise can be controlled independently by expressing two copies of a gene from separate inducible promoters in the same cell. We engineer low and high noise inducible promoters to validate this result in Escherichia coli, and develop a model that predicts the experimental distributions. Finally, we use our method to reveal that the response of a promoter to a repressor is less sensitive with higher repressor noise and explain this result using a law from probability theory. Our approach can be applied to investigate the effects of noise on diverse biological pathways or program cellular heterogeneity for synthetic biology applications.

Overlaid positive and negative feedback loops shape dynamical properties of PhoPQ two-component system

Bacteria use two-component systems (TCSs) to sense environmental conditions and change gene expression in response to those conditions. To amplify cellular responses, many bacterial TCSs are under positive feedback control, i.e. increase their expression when activated. Escherichia coli Mg²⁺ -sensing TCS, PhoPQ, in addition to the positive feedback, includes a negative feedback loop via the upregulation of the MgrB protein that inhibits PhoQ. How the interplay of these feedback loops shapes steady-state and dynamical responses of PhoPQ TCS to change in Mg²⁺ remains poorly understood. In particular, how the presence of MgrB feedback affects the robustness of PhoPQ response to overexpression of TCS is unclear. It is also unclear why the steady-state response to decreasing Mg²⁺ is biphasic, i.e. plateaus over a range of Mg²⁺ concentrations, and then increases again at growth-limiting Mg²⁺. In this study, we use mathematical modeling to identify potential mechanisms behind these experimentally observed dynamical properties. The results make experimentally testable predictions for the regime with response robustness and propose a novel explanation of biphasic response constraining the mechanisms for modulation of PhoQ activity by Mg²⁺ and MgrB. Finally, we show how the interplay of positive and negative feedback loops affects the network’s steady-state sensitivity and response dynamics. In the absence of MgrB feedback, the model predicts oscillations thereby suggesting a general mechanism of oscillatory or pulsatile dynamics in autoregulated TCSs. These results improve the understanding of TCS signaling and other networks with overlaid positive and negative feedback.

Feedback loops are commonly observed in bacterial gene-regulatory networks to enable proper dynamical responses to stimuli. Positive feedback loops often amplify the response to stimulus, whereas negative feedback loops are known to speed-up the response and increase robustness. Here we demonstrate how combination of positive and negative feedback in network sensing extracellular ion concentrations affects its steady-state and dynamic responses. We utilize published experimental data to calibrate mathematical models of the gene regulatory network. The resulting model quantitatively matches experimentally observed behavior and can make predictions on the mechanism of negative feedback control. Our results show the advantages of such a combination of feedback loops. We also predict the effect of their perturbation on the steady-state and dynamic responses. This study improves our understanding of how feedback loops shape dynamical properties of signaling networks.

Dysregulated mitogen-activated protein kinase pathway mediated cell cycle disruption in sporadic parathyroid tumors

OBJECTIVES

The study was designed to evaluate expression profiling of mitogen-activated protein kinase (MAPK) signalling pathway genes in sporadic parathyroid adenoma.

METHODS

Expression of MAPK signalling pathway genes including activated transcription factors and cell cycle regulatory genes was analysed by real-time PCR- based array in parathyroid adenoma (N = 20) and normal parathyroid tissue (N = 4).

RESULTS

MAPK signalling pathway as studied by PCR array revealed that a total of 22 genes were differentially expressed (≥ twofold change, p ≤ 0.05) in parathyroid adenoma. Up-regulated genes were ARAF, MAPK12, CREBBP, MYC, HSPB1, HRAS, CDK4, CCND1, and E2F1, and down-regulated genes were MAP4K1, DLK1, MAP3K4, MAPK10, MAPK8, ATF2, SMAD4, MEF2C, LAMTOR3, FOS, CDKN2A CDKN2B, and RB1. The present study revealed that ERK1/2 signalling pathway with up-regulation of HRAS, ARAF, and MEK1 genes and up-regulation of positive regulators of cell cycle (CCND1, CDK4, and E2F1) and down-regulation negative regulators of cell cycle (CDKN2A, CDKN2B, and RB1) made highly dysregulated MAPK signalling pathway in parathyroid adenoma. Expression of CDK4 was positively associated with plasma PTH level (r = 0.60, p = 0.04) and tumor weight (r = 0.80, p = 0.02) of the adenoma patients, respectively. Expression of CDKN2A was correlated negatively with PTH level (r = - 0.52, p = 0.04) of the adenoma patients.

CONCLUSION

The current study revealed that ERK pathway and associated cell cycle regulator genes are dysregulated in sporadic parathyroid adenoma.

Quantitative proteomics analysis of sporadic parathyroid adenoma tissue samples

OBJECTIVE

Molecular pathogenesis of parathyroid tumors is incompletely understood. Identification of novel molecules and understanding their role in parathyroid tumorigenesis by proteomics approach would be informative with potential clinical implications.

METHOD

Adenomatous (n = 5) and normal (n = 2) parathyroid tissue lysates were analyzed for protein profile by LC-MS/MS method and the proteins were classified using bioinformatics tools such as PANTHER and toppfun functional enrichment tool. Identified proteins were further validated by western blotting and qRT-PCR (n = 20).

RESULT

Comparative proteomics analysis revealed that a total of 206 proteins (74 upregulated and 132 downregulated) were differentially expressed (≥ twofold change) in adenomas. Bioinformatics analysis revealed that 48 proteins were associated with plasma membrane, 49 with macromolecular complex, 39 were cytoplasm, 38 were organelle related, 21 were cell junction and 10 were extracellular proteins. These proteins belonged to a diverse protein family such as enzymes, transcription factors, cell signalling, cell adhesion, cytoskeleton proteins, receptors, and calcium-binding proteins. The major biological processes predicted for the proteins were a cellular, metabolic and developmental process, cellular localization, and biological regulation. The differentially expressed proteins were found to be associated with MAPK, phospholipase C (PLC) and phosphatidylinositol (PI) signalling pathways, and with chromatin organization. Western blot and qRT-PCR analysis of three proteins (DNAJC2, ACO2, and PRDX2) validated the LC-MS/MS findings.

CONCLUSION

This exploratory study demonstrates the feasibility of proteomics approach in finding the dysregulated proteins in benign parathyroid adenomas, and our preliminary results suggest that MAPK, PLC and PI signalling pathways and chromatin organization are involved in parathyroid tumorigenesis.

Primary hyperparathyroidism: review and recommendations on evaluation, diagnosis, and management. A Canadian and international consensus

The purpose of this review is to assess the most recent evidence in the management of primary hyperparathyroidism (PHPT) and provide updated recommendations for its evaluation, diagnosis and treatment. A Medline search of "Hyperparathyroidism. Primary" was conducted and the literature with the highest levels of evidence were reviewed and used to formulate recommendations. PHPT is a common endocrine disorder usually discovered by routine biochemical screening. PHPT is defined as hypercalcemia with increased or inappropriately normal plasma parathyroid hormone (PTH). It is most commonly seen after the age of 50 years, with women predominating by three to fourfold. In countries with routine multichannel screening, PHPT is identified earlier and may be asymptomatic. Where biochemical testing is not routine, PHPT is more likely to present with skeletal complications, or nephrolithiasis. Parathyroidectomy (PTx) is indicated for those with symptomatic disease. For asymptomatic patients, recent guidelines have recommended criteria for surgery, however PTx can also be considered in those who do not meet criteria, and prefer surgery. Non-surgical therapies are available when surgery is not appropriate. This review presents the current state of the art in the diagnosis and management of PHPT and updates the Canadian Position paper on PHPT. An overview of the impact of PHPT on the skeleton and other target organs is presented with international consensus. Differences in the international presentation of this condition are also summarized.

Multiple nodules on the face and trunk in metastatic adenocarcinoma of unknown primary origin

Metastatic cancer of unknown primary (CUP) may unexpectedly manifest on the skin and subcutaneous tissue, prompting the patient to first visit a dermatologist. We describe an interesting case of cutaneous metastases from poorly differentiated adenocarcinoma of an unknown primary site in a 57-year-old man. The CUP had an unusually long period of indolence between presentation as a solitary axillary lymph node metastasis and rapid cutaneous dissemination. The possible causes of such a presentation are reviewed, and the management is briefly discussed. Diagnosis of unusual cutaneous manifestations of occult systemic malignancies could pose a diagnostic challenge to dermatologists.

Onycholysis caused by Candida krusei

Onycholysis caused by Candida krusei is rare. A 21 years old male patient presented with grayish discolouration and elevation of all fingernails since one year. Patient was refractory to treatment with fluconazole. Potassium hydroxide preparation of subungual debris revealed fungal elements. Growth on Sabouraud dextrose agar was identified by cultural characteristics, morphotyping, microscopy and biochemical tests as Candida krusei. The isolate was resistant to fluconazole and amphotericin-B but susceptible to nystatin and clotrimazole. Patient responded well to clotrimazole and terbinafine.

Keratomycosis due to Exserohilum rostratum - a case report

We report here a case of keratomycosis by Exserohilum rostratum. An 18-year old female patient presented with pain and watery discharge from the left eye since 10 days. Clinically the case was diagnosed as keratomycosis. Gram stain and KOH preparation of corneal scrapings revealed fungal elements. Fungal isolate was identified as Exserohilum rostratum by standard techniques.

Development of a novel immunoradiometric assay exclusively for biologically active whole parathyroid hormone 1-84: implications for improvement of accurate assessment of parathyroid function

We developed a novel immunoradiometric assay (IRMA; whole parathyroid hormone [PTH] IRMA) for PTH, which specifically measures biologically active whole PTH(1-84). The assay is based on a solid phase coated with anti-PTH(39-84) antibody, a tracer of 125I-labeled antibody with a unique specificity to the first N-terminal amino acid of PTH(1-84), and calibrators of diluted synthetic PTH(1-84). In contrast to the Nichols intact PTH IRMA, this new assay does not detect PTH(7-84) fragments and only detects one immunoreactive peak in chromatographically fractionated patient samples. The assay was shown to have an analytical sensitivity of 1.0 pg/ml with a linear measurement range up to 2,300 pg/ml. With this assay, we further identified that the previously described non-(1-84)PTH fragments are aminoterminally truncated with similar hydrophobicity as PTH(7-84), and these PTH fragments are present not only in patients with secondary hyperparathyroidism (2 degrees -HPT) of uremia, but also in patients with primary hyperparathyroidism (1 degrees -HPT) and normal persons. The plasma normal range of the whole PTH(1-84) was 7-36 pg/ml (mean +/- SD: 22.7 +/- 7.2 pg/ml, n = 135), whereas over 93.9% (155/165) of patients with 1 degrees -HPT had whole PTH(1-84) values above the normal cut-off. The percentage of biologically active whole PTH(1-84) (pB%) in the pool of total immunoreactive "intact" PTH is higher in the normal population (median: 67.3%; SD: 15.8%; n = 56) than in uremic patients (median:53.8%; SD: 15.5%; n = 318; p < 0.001), although the whole PTH(1-84) values from uremic patients displayed a more significant heterogeneous distribution when compared with that of 1 degrees -HPT patients and normals. Moreover, the pB% displayed a nearly Gaussian distribution pattern from 20% to over 90% in patients with either 1 degrees-HPT or uremia. The specificity of this newly developed whole PTH(1-84) IRMA is the assurance, for the first time, of being able to measure only the biologically active whole PTH(1-84) without cross-reaction to the high concentrations of the aminoterminally truncated PTH fragments found in both normal subjects and patients. Because of the significant variations of pB% in patients, it is necessary to use the whole PTH assay to determine biologically active PTH levels clinically and, thus, to avoid overestimating the concentration of the true biologically active hormone. This new assay could provide a more meaningful standardization of future PTH measurements with improved accuracy in the clinical assessment of parathyroid function.

Ergotamine/caffeine treatment of orthostatic hypotension in parkinsonism with autonomic failure

Eight patients with parkinsonism who developed severe orthostatic hypotension, were treated with oral ergotamine/caffeine. Significant long-term improvement in standing systolic blood pressure and symptoms of syncope and light-headedness were observed in four of these patients. One patient in whom the drug was effective discontinued it because of nausea. Another lost benefit after 2 weeks of successful therapy. Significant supine systolic hypertension occurred in only one patient, which was easily managed by nifedipine given at night. Symptoms or signs of ergotism were not observed. Oral ergotamine/caffeine should be considered as a cost-effective treatment for refractory orthostatic hypotension in carefully selected patients with parkinsonism. Copyright 1998 Lippincott Williams & Wilkins

Growth hormone-releasing hormone immunoreactivity in the brain, pituitary, and pineal of the goldfish, Carassius auratus

Using antisera directed against carp growth hormone-releasing hormone (cGHRH), the distribution of immunoreactive (ir) structures in the brain, pituitary, and pineal of the goldfish, Carassius auratus, was investigated. The antisera were produced in rabbits by administration of cGHRH(1-44)-NH(2) followed by cGHRH(1-45)-OH for different periods of time, both coupled to human alpha-globulins via bisdiazotized benzidine as immunogen. Immunoreactive perikarya were visualized in the nucleus preopticus periventricularis (NPP), nucleus lateralis tuberis (NLT), nucleus of the lateral lemniscus (NLL), and the pineal. The preoptic area and area ventralis telencephali seemed to receive innervation from the NPP cells. The fibers of the NLT cell bodies extended caudally along the infundibular floor and innervated the hypophysis. The processes of the NLL perikarya extended rostrally along the lateral lemniscus, curved ventrally along the outer margin of the glomerular nuclear complex, and extended to the dorsal area of the lateral recess, while issuing fascicles that branched off and fanned out to innervate extensively the nucleus diffusus of the hypothalamic inferior lobes and the nucleus lateralis tori; several fiber bundles branched off and extended toward the lateral areas of the paraventricular organ area and even into the rostral region of the hypothalamic inferior lobes. A small percentage of the corticotrophs of the rostral pars distalis, a few cells in the central area of the pars intermedia (PI), and neurohypophysial fibers in the peripheral area of the PI of the pituitary gland had colocalization of GHRH-ir; GHRH-ir fibers in the rostral and proximal pars distalis were sparse. It is suggested that the GHRH-ir perikarya of the diencephalon may stimulate growth hormone release either by modulating the activity of somatotrophs or of other hypothalamic neurosecretory neurons. The innervation of the hypothalamic inferior lobe by GHRH-ir perikarya of the NLL suggests some influence on feeding processes. Presence of GHRH in the pineal implies involvement in some daily cyclic activity.

Comparison of rectal and axillary temperatures in neonates admitted to a neonatal unit

To determine whether axillary temperature could be used as an alternative to rectal temperature, 45 neonates were subjected to simultaneous rectal temperature and axillary temperature recordings. Each baby had an average of 10 recordings over the first 72 hours. The mean of these readings was taken and subjected to regression analysis and the 't' paired test. The overall mean difference between the rectal and axillary temperature was 0.3 degrees F. The mean difference was least in preterm small for date (SFD) babies (0.2 degrees F) and most in preterm appropriate for date (AFD) babies (0.5 degrees F). The mean difference was less in incubator babies (0.2 degrees F) compared to those in warmer cradles (0.4 degrees F). The regression analysis showed that the correlation was good in all groups except the term small for date babies. We conclude that axillary temperature could be used as an alternative to rectal temperature in neonates.

Hyperparathyroidism following head and neck irradiation

A history of head and neck irradiation in childhood or adolescence was found in 22 of 130 patients with primary hyperparathyroidism compared with only 12 of 400 control patients, a significant difference (P less than .025). Among 200 patients with a known history of childhood irradiation, biochemical or surgical evidence of hyperparathyroidism was found in ten, a prevalence of 5%. This is at least 30 times the prevalence of hyperparathyroidism in the general population (P less than .025). The data indicate that head and neck irradiation should be regarded as an important risk factor in the subsequent development of hyperparathyroidism.