SnRK1/TOR/T6P: three musketeers guarding energy for root growth

Sugars derived from photosynthesis, specifically sucrose, are the primary source of plant energy. Sucrose is produced in leaves and transported to the roots through the phloem, serving as a vital energy source. Environmental conditions can result in higher or lower photosynthesis, promoting anabolism or catabolism, respectively, thereby influencing the sucrose budget available for roots. Plants can adjust their root system to optimize the search for soil resources and to ensure the plant's adaptability to diverse environmental conditions. Recently, emerging research indicates that SNF1-RELATED PROTEIN KINASE 1 (SnRK1), trehalose 6-phosphate (T6P), and TARGET OF RAPAMYCIN (TOR) collectively serve as fundamental regulators of root development, together forming a signaling module to interpret the nutritional status of the plant and translate this to growth adjustments in the below ground parts.

Production of Recombinant Proteins in Transgenic Tobacco Plants

Nicotiana tabacum (the tobacco plant ) has numerous advantages for molecular farming, including rapid growth, large biomass and the possibility of both cross- and self-fertilization. In addition, genetic transformation and tissue culture protocols for regeneration of transgenic plants are well-established. Here, we describe the production of transgenic tobacco using Agrobacterium tumefaciens and the analysis of recombinant proteins, either in crude plant extracts or after purification, by enzyme-linked immunosorbent assays, sodium dodecyl sulfate polyacrylamide gel electrophoresis with western blotting and surface plasmon resonance.

Contributions of the international plant science community to the fight against infectious diseases in humans-part 2: Affordable drugs in edible plants for endemic and re-emerging diseases

The fight against infectious diseases often focuses on epidemics and pandemics, which demand urgent resources and command attention from the health authorities and media. However, the vast majority of deaths caused by infectious diseases occur in endemic zones, particularly in developing countries, placing a disproportionate burden on underfunded health systems and often requiring international interventions. The provision of vaccines and other biologics is hampered not only by the high cost and limited scalability of traditional manufacturing platforms based on microbial and animal cells, but also by challenges caused by distribution and storage, particularly in regions without a complete cold chain. In this review article, we consider the potential of molecular farming to address the challenges of endemic and re-emerging diseases, focusing on edible plants for the development of oral drugs. Key recent developments in this field include successful clinical trials based on orally delivered dried leaves of Artemisia annua against malarial parasite strains resistant to artemisinin combination therapy, the ability to produce clinical-grade protein drugs in leaves to treat infectious diseases and the long-term storage of protein drugs in dried leaves at ambient temperatures. Recent FDA approval of the first orally delivered protein drug encapsulated in plant cells to treat peanut allergy has opened the door for the development of affordable oral drugs that can be manufactured and distributed in remote areas without cold storage infrastructure and that eliminate the need for expensive purification steps and sterile delivery by injection.

Contributions of the international plant science community to the fight against human infectious diseases - part 1: epidemic and pandemic diseases

Infectious diseases, also known as transmissible or communicable diseases, are caused by pathogens or parasites that spread in communities by direct contact with infected individuals or contaminated materials, through droplets and aerosols, or via vectors such as insects. Such diseases cause ˜17% of all human deaths and their management and control places an immense burden on healthcare systems worldwide. Traditional approaches for the prevention and control of infectious diseases include vaccination programmes, hygiene measures and drugs that suppress the pathogen, treat the disease symptoms or attenuate aggressive reactions of the host immune system. The provision of vaccines and biologic drugs such as antibodies is hampered by the high cost and limited scalability of traditional manufacturing platforms based on microbial and animal cells, particularly in developing countries where infectious diseases are prevalent and poorly controlled. Molecular farming, which uses plants for protein expression, is a promising strategy to address the drawbacks of current manufacturing platforms. In this review article, we consider the potential of molecular farming to address healthcare demands for the most prevalent and important epidemic and pandemic diseases, focussing on recent outbreaks of high-mortality coronavirus infections and diseases that disproportionately affect the developing world.

Pathological response and clinical outcomes in operable triple-negative breast cancer with cisplatin added to standard neoadjuvant chemotherapy

BACKGROUND

Response to neoadjuvant chemotherapy is associated with improved outcomes for patients with triple negative breast cancer (TNBC). Patients with residual disease are at increased risk of relapse and death from breast cancer. In this retrospective study, we aimed to evaluate the efficacy and safety of cisplatin added to standard neoadjuvant chemotherapy for locally advanced TNBC.

MATERIALS AND METHODS

All TNBC treated with neoadjuvant cisplatin 60mg/m2 once in 3 weeks with weekly paclitaxel for 12 weeks, following 8 weeks of dose-dense epirubicin 90mg/m2 or doxorubicin 60mg/m2 with cyclophosphamide 600mg/m2 were analyzed retrospectively. The data related to pathological complete response, adherence to planned therapy, disease-free survival and overall survival were collected.

RESULTS

Eighty-three patients were included, of whom 80% had stage III disease. Pathological complete response in both breast (T0/Tis) and axilla (N0) was observed in 48.1% of patients. Miller Payne grade 5 pathological response in the breast was seen in 61% of patients. Good partial responses (Miller Payne grades 3,4) were observed in 32.5% of patients. The remaining 6.5% were poor responders. Seventy-seven patients underwent surgery. The disease-free survival at 1 and 3 years for those who had a pathological complete response was 96.7% and 77.6%, respectively, and 92.3% and 62.7% for those who did not, respectively. The predominant adverse events were hematological, with anemia being the most common one.

CONCLUSION

The addition of cisplatin to neoadjuvant chemotherapy with anthracycline and taxane in TNBC was tolerable and produced a high rate of pathological complete response. Cisplatin added to standard chemotherapy in patients with locally advanced TNBC could improve clinical outcomes.

Papillary Thyroid Carcinoma in Children: Clinicopathological Profile and Outcomes of Management

BACKGROUND

We aim to analyze the clinicopathological profile and outcomes of management for children with papillary thyroid carcinoma (PTC).

METHODS

Relevant clinical data of children ≤ 18 years of age managed for PTC between January 2006 and July 2018 as well as details of their follow-up till December 2019 were retrospectively collected and analyzed.

RESULTS

There were 82 children with PTC that were managed during the study period. At presentation, 39 (47.6%) had cervical lymphadenopathy, while 9 (11%) had systemic metastasis. Majority of patients 39 (47.6%) underwent total thyroidectomy with a selective neck dissection, while total thyroidectomy alone was performed in 26 (31.7%). Following surgery, hypocalcemia was seen in 39 (47.6%): 28 (34.1%) were temporary, while 11 (13.4%) were permanent. Twenty-eight (34%) developed persistent disease after surgery and ¹³¹I therapy. Significant risk factors for persistence and metastatic disease were metastatic cervical lymph node at presentation (p = 0.002) and tumor size (p = 0.014), respectively. The mean duration of follow-up was 60.3 (range 12-150) months with a mean overall disease-free survival of 60 months (95% CI 57.11, 77.95).

CONCLUSION

Children with papillary thyroid cancers present with aggressive disease, 47.6% with cervical nodal metastasis and 11% with distant metastasis in this cohort. The rate of post-thyroidectomy hypocalcemia in this study is substantial, and efforts to reduce it are actively being pursued. The presence of metastatic cervical lymph node at presentation (p = 0.002) and tumor size (p = 0.014) were the only significant risk factors for persistent and metastatic disease, respectively, in this study.

Engineering the interactions between a plant-produced HIV antibody and human Fc receptors

Plants can provide a cost-effective and scalable technology for production of therapeutic monoclonal antibodies, with the potential for precise engineering of glycosylation. Glycan structures in the antibody Fc region influence binding properties to Fc receptors, which opens opportunities for modulation of antibody effector functions. To test the impact of glycosylation in detail, on binding to human Fc receptors, different glycovariants of VRC01, a broadly neutralizing HIV monoclonal antibody, were generated in Nicotiana benthamiana and characterized. These include glycovariants lacking plant characteristic α1,3-fucose and β1,2-xylose residues and glycans extended with terminal β1,4-galactose. Surface plasmon resonance-based assays were established for kinetic/affinity evaluation of antibody-FcγR interactions, and revealed that antibodies with typical plant glycosylation have a limited capacity to engage FcγRI, FcγRIIa, FcγRIIb and FcγRIIIa; however, the binding characteristics can be restored and even improved with targeted glycoengineering. All plant-made glycovariants had a slightly reduced affinity to the neonatal Fc receptor (FcRn) compared with HEK cell-derived antibody. However, this was independent of plant glycosylation, but related to the oxidation status of two methionine residues in the Fc region. This points towards a need for process optimization to control oxidation levels and improve the quality of plant-produced antibodies.

Migration of noble gas tracers at the site of an underground nuclear explosion at the Nevada National Security Site

As part of an underground gas migration study, two radioactive noble gases (³⁷Ar and ¹²⁷Xe) and two stable tracer gases (SF₆ and PFDMCH) were injected into a historic nuclear explosion test chimney and allowed to migrate naturally. The purpose of this experiment was to provide a bounding case (natural transport) for the flow of radioactive noble gases following an underground nuclear explosion. To accomplish this, soil gas samples were collected from a series of boreholes and a range of depths from the shallow subsurface (3 m) to deeper levels (~160 m) over a period of eleven months. These samples have provided insights into the development and evolution of the subsurface plume and constrained the relative migration rates of the radioactive and stable gas species in the case when the driving pressure from the cavity is low. Analysis of the samples concluded that the stable tracer SF₆ was consistently enriched in the subsurface samples relative to the radiotracer ¹²⁷Xe, but the ratios of SF₆ and ³⁷Ar remained similar throughout the samples.

Prepubertal ovarian inhibition of Light/Dark Box exploration and novel object investigation in juvenile Siberian hamsters

The overwhelming majority of research on the role of gonadal hormones in behavioral development has focused on perinatal, pubertal, or adult life stages. The juvenile period has been overlooked because it is thought to be a time of gonadal quiescence. In the present study, we tested whether prepubertal gonadectomy impacts the behavior of male and female juvenile hamsters on the Light/Dark Box, Novel Object, and Social Approach tests (Experiment 1) and compared these findings to those obtained after adult gonadectomy (Experiment 2). Prepubertal ovariectomy increased exploration (i.e. time spent in the light zone of the Light/Dark Box) and novel object investigation of juveniles indicating an inhibitory role for the juvenile ovary; social approach was unaffected. In contrast, adult ovariectomy and castration (both prepubertal and adult) had no effect on any behavioral measure. Experiment 3 tested whether rearing hamsters in a short day length (SD), which delays puberty in this species, extends the interval of juvenile ovarian inhibition on exploration and novelty seeking. We also tested whether provision of estradiol reverses the effects of prepubertal ovariectomy. Hormonal manipulations and behavioral tests of Experiment 3 were conducted at ages when long day-reared hamsters are adult (as in Experiment 2), but SD-reared hamsters remain reproductively immature. Ovariectomy again increased exploration in the SD-reared juveniles despite the older age of surgery and testing. Estradiol treatment had no effect. These findings reveal a novel role for the juvenile ovary in exploration and novelty seeking that is unlikely to be mediated exclusively by estradiol.

Inactivated Lactobacillus plantarum Carrying a Surface-Displayed Ag85B-ESAT-6 Fusion Antigen as a Booster Vaccine Against Mycobacterium tuberculosis Infection

Vaccination is considered the most effective strategy for controlling tuberculosis (TB). The existing vaccine, the Bacille Calmette-Guérin (BCG), although partially protective, has a number of limitations. Therefore, there is a need for developing new TB vaccines and several strategies are currently exploited including the use of viral and bacterial delivery vectors. We have previously shown that Lactobacillus plantarum (Lp) producing Ag85B and ESAT-6 antigens fused to a dendritic cell-targeting peptide (referred to as Lp_DC) induced specific immune responses in mice. Here, we analyzed the ability of two Lp-based vaccines, Lp_DC and Lp_HBD (in which the DC-binding peptide was replaced by an HBD-domain directing the antigen to non-phagocytic cells) to activate antigen-presenting cells, induce specific immunity and protect mice from Mycobacterium tuberculosis infection. We tested two strategies: (i) Lp as BCG boosting vaccine (a heterologous regimen comprising parenteral BCG immunization followed by intranasal Lp boost), and (ii) Lp as primary vaccine (a homologous regimen including subcutaneous priming followed by intranasal boost). The results showed that both Lp constructs applied as a BCG boost induced specific cellular immunity, manifested in T cell proliferation, antigen-specific IFN-γ responses and multifunctional T cells phenotypes. More importantly, intranasal boost with Lp_DC or Lp_HBD enhanced protection offered by BCG, as shown by reduced M. tuberculosis counts in lungs. These findings suggest that Lp constructs could be developed as a potential mucosal vaccine platform against mycobacterial infections.

Viral rescue of magnocellular vasopressin cells in adolescent Brattleboro rats ameliorates diabetes insipidus, but not the hypoaroused phenotype

Dysregulated arousal often accompanies neurodevelopmental disorders such as attention deficit hyperactivity disorder and autism spectrum disorder. Recently, we have found that adolescent homozygous Brattleboro (Hom) rats, which contain a mutation in the arginine vasopressin (AVP) gene, exhibit lower behavioral arousal than their heterozygous (Het) littermates in the open field test. This hypoaroused phenotype could be due to loss of AVP in magnocellular cells that supply AVP to the peripheral circulation and project to limbic structures or parvocellular cells that regulate the stress axis and other central targets. Alternatively, hypoarousal could be a side effect of diabetes insipidus - polydipsia and polyuria seen in Hom rats due to loss of AVP facilitation of water reabsorption in the kidney. We developed a viral-rescue approach to "cure" magnocellular AVP cells of their Brattleboro mutation. Infusion of a recombinant adeno-associated virus (rAAV) containing a functional Avp gene and promoter (rAAV-AVP) rescued AVP within magnocellular cells and fiber projections of the paraventricular nucleus of the hypothalamus (PVN) of male and female adolescent Hom rats. Furthermore, water intake was markedly reduced, ameliorating the symptoms of diabetes insipidus. In contrast, open field activity was unaffected. These findings indicate that the hyporaoused phenotype of adolescent Hom rats is not due to the loss of AVP function in magnocellular cells or a side effect of diabetes insipidus, but favors the hypothesis that central, parvocellular AVP mechanisms underlie the regulation of arousal during adolescence.

Mutation in the vasopressin gene eliminates the sex difference in social reinforcement in adolescent rats

The neuropeptide, arginine vasopressin (AVP), is thought to contribute to sex differences in normative and pathological social development by regulating social motivation. Recent studies using Brattleboro rats that have a mutation in the Avp gene, however, have suggested that AVP impacts adolescent social behaviors of males and females in a similar manner through actions on behavioral state (i.e., arousal). In the present study, we made use of a recently developed operant conditioning paradigm to test whether the chronic, lifelong AVP deficiency caused by the Brattleboro mutation impacts the reinforcement value of social stimuli during adolescence. Operant responding for access to a familiar conspecific was assessed in male and female adolescent wild type (WT; normal AVP), heterozygous Brattleboro (HET), and homozygous Brattleboro (HOM) rats. Following the social reinforcement test, rats were tested in the same operant paradigm except that the social reinforcer was replaced with a light reinforcer to determine whether effects of the Brattleboro mutation were specific to social stimuli or a general characteristic of operant conditioning. WT males directed a greater proportion of their responding toward the social and light stimuli than WT females; only males exhibited a preference for these reinforcers over unreinforced ports. The sex difference in social reinforcement was absent in HOM rats, whereas the sex difference in light reinforcement was present in all genotypes. These data indicate that adolescent males are more sensitive to the reinforcing properties of social and light stimuli, and that the sex difference in social, but not light, reinforcement depends upon normal levels of AVP. These findings support the hypothesis that AVP plays a critical role in sex differences in social development by acting on factors that influence social motivation.

A polymeric immunoglobulin-antigen fusion protein strategy for enhancing vaccine immunogenicity

In this study, a strategy based on polymeric immunoglobulin G scaffolds (PIGS) was used to produce a vaccine candidate for Mycobacterium tuberculosis. A genetic fusion construct comprising genes encoding the mycobacterial Ag85B antigen, an immunoglobulin γ-chain fragment and the tailpiece from immunoglobulin μ chain was engineered. Expression was attempted in Chinese Hamster Ovary (CHO) cells and in Nicotiana benthamiana. The recombinant protein assembled into polymeric structures (TB-PIGS) in N. benthamiana, similar in size to polymeric IgM. These complexes were subsequently shown to bind to the complement protein C1q and FcγRs with increased affinity. Modification of the N-glycans linked to TB-PIGS by removal of xylose and fucose residues that are normally found in plant glycosylated proteins also resulted in increased affinity for low-affinity FcγRs. Immunization studies in mice indicated that TB-PIGS are highly immunogenic with and without adjuvant. However, they did not improve protective efficacy in mice against challenge with M. tuberculosis compared to conventional vaccination with BCG, suggesting that additional or alternative antigens may be needed to protect against this disease. Nevertheless, these results establish a novel platform for producing polymeric antigen-IgG γ-chain molecules with inherent functional characteristics that are desirable in vaccines.

Xenon adsorption on geological media and implications for radionuclide signatures

The detection of radioactive noble gases is a primary technology for verifying compliance with the pending Comprehensive Nuclear-Test-Ban Treaty. A fundamental challenge in applying this technology for detecting underground nuclear explosions is estimating the timing and magnitude of the radionuclide signatures. While the primary mechanism for transport is advective transport, either through barometric pumping or thermally driven advection, diffusive transport in the surrounding matrix also plays a secondary role. From the study of primordial noble gas signatures, it is known that xenon has a strong physical adsorption affinity in shale formations. Given the unselective nature of physical adsorption, isotherm measurements reported here show that non-trivial amounts of xenon adsorb on a variety of media, in addition to shale. A dual-porosity model is then discussed demonstrating that sorption amplifies the diffusive uptake of an adsorbing matrix from a fracture. This effect may reduce the radioxenon signature down to approximately one-tenth, similar to primordial xenon isotopic signatures.

Mucosal Delivery of Fusion Proteins with Bacillus subtilis Spores Enhances Protection against Tuberculosis by Bacillus Calmette-Guérin

Tuberculosis (TB) is the most deadly infectious disease in existence, and the only available vaccine, Bacillus Calmette-Guérin (BCG), is almost a century old and poorly protective. The immunological complexity of TB, coupled with rising resistance to antimicrobial therapies, necessitates a pipeline of diverse novel vaccines. Here, we show that Bacillus subtilis spores can be coated with a fusion protein 1 (“FP1”) consisting of Mycobacterium tuberculosis (Mtb) antigens Ag85B, ACR, and HBHA. The resultant vaccine, Spore-FP1, was tested in a murine low-dose Mtb aerosol challenge model. Mice were primed with subcutaneous BCG, followed by mucosal booster immunizations with Spore-FP1. We show that Spore-FP1 enhanced pulmonary control of Mtb, as evidenced by reduced bacterial burdens in the lungs. This was associated with elevated antigen-specific IgG and IgA titers in the serum and lung mucosal surface, respectively. Spore-FP1 immunization generated superior antigen-specific memory T-cell proliferation in both CD4⁺ and CD8⁺ compartments, alongside bolstered Th1-, Th17-, and Treg-type cytokine production, compared to BCG immunization alone. CD69⁺CD103⁺ tissue resident memory T-cells (Trm) were found within the lung parenchyma after mucosal immunization with Spore-FP1, confirming the advantages of mucosal delivery. Our data show that Spore-FP1 is a promising new TB vaccine that can successfully augment protection and immunogenicity in BCG-primed animals.

Outcome of Treatment for Medullary Thyroid Carcinoma-a Single Centre Experience

We conducted this study to evaluate the demography, clinical presentation, management and outcomes of medullary thyroid carcinoma (MTC) from the Indian context. This was a retrospective study of patients with MTC managed between January 2008 and December 2016. All pertinent data was collected and the results were analysed using STATA (v.13.1). MTC accounted for 90/2022 (4.45%) patients managed with thyroid cancer during the study period. The mean age of presentation was 40 years (range 14-70 years) with 47 males and 43 females. The most common presentation included goitre with cervical lymphadenopathy seen in 60 patients (66.7%). There were 11 patients (12.2%) with systemic metastasis at presentation. Rearranged during transfection (RET) testing was performed in 71 patients and was positive in 25 (35.2%). The mutations among these patients were seen in the following codons: 634 (12), 804 (8), 790 (3) and 618 (2). Persistent hypercalcitoninemia (calcitonin > 50 pg/ml) was observed in 62/80 (77.5%) patients. Forty patients underwent a meta-iodo-benzyl-guanidine (MIBG) scan in the postoperative period, 10 were positive. The mean duration of follow-up was 32 months and 10 patients defaulted from follow-up. Sixteen patients developed metastasis during the period of follow-up while eight patients expired. The mean survival was 85.75 months (95% CI 78.7-92.7). MTC accounted for 4.5% of thyroid carcinomas in this cohort among which 35% were hereditary. Persistent hypercalcitoninemia following surgery is seen in more than 70% of patients but this does not affect survival. RET screening should be performed for all patients with MTC as curative surgery can be offered for mutation positive offspring.

Dermatofibrosarcoma Protuberans of the Breast-a Rare Entity

Dermatofibrosarcoma protuberans (DFSP) represents about 1% of soft-tissue sarcomas with an estimated incidence of 0.8 to 5.0 cases per million per year. This lesion may occur anywhere in the body but more than 50% occur on the trunk, 20% on the head and neck and 30% on the extremities. DFSP of the breast is an extremely uncommon site of presentation. Data regarding DFSP of the breast is limited and mostly in the form of case reports. Clinical presentation is not uniform and may mimic benign skin lesions [1]. However, it typically presents as a nodular cutaneous mass in early or mid-adult life. We herein report a case of DFSP of the breast in a 33-year-old lady who was managed successfully in our institute and review the literature associated with it.

Radiotherapy in Phyllodes Tumour

INTRODUCTION

Phyllodes Tumour (PT) of the breast is a relatively rare breast neoplasm (<1%) with diverse range of pathology and biological behaviour.

AIM

To describe the clinical course of PT and to define the role of Radiotherapy (RT) in PT of the breast.

MATERIALS AND METHODS

Retrospective analysis of hospital data of patients with PT presented from 2005 to 2014 was done. Descriptive statistics was used to analyze the results. Simple description of data was done in this study. Age and duration of symptoms were expressed in median and range. Percentages, tables and general discussions were used to understand the meaning of the data analyzed.

RESULTS

Out of the 98 patients, 92 were eligible for analysis. The median age of presentation was 43 years. A total of 64/92 patients were premenopausal. There was no side predilection for this tumour but 57/92 patients presented as an upper outer quadrant lump. Fifty percent of the patients presented as giant (10 cm) PT. The median duration of symptoms was 12 months (range: 1-168 months). A 60% of patients had Benign (B), 23% had Borderline (BL) and 17% had malignant (M) tumours. The surgical treatment for benign histology included Lumpectomy (L) for 15%, Wide Local Excision (WLE) for 48%, and Simple Mastectomy (SM) for 37%. All BL and M tumours were treated with WLE or SM. There was no recurrence in B and BL group when the margin was ≥1 cm. All non-metastatic M tumours received adjuvant RT irrespective of their margin status. Total 3/16 patients with M developed local recurrence. Total 6/16 M patients had distant metastases (lung or bone). Our median duration of follow up was 20 months (range: 1-120 months).

CONCLUSION

Surgical resection with adequate margins (>1 cm) gave excellent local control in B and BL tumours. For patients with BL PT, local radiotherapy is useful, if margins are close or positive even after the best surgical resection. There is a trend towards improved local control with adjuvant radiotherapy for malignant PT. Metastatic malignant PT has a poor outcome.

Can New Ultrasound Signs Help in Identifying Follicular Variant of Papillary Carcinoma of Thyroid? - A Pilot Study

AIM

To describe two new ultrasound signs for thyroid nodules - "nodule in nodule" and "hypoechoic internal septae" and assess their usefulness in differentiating follicular variant of papillary thyroid carcinoma (FVPTC) from benign thyroid nodules (BTN).

METHODOLOGY

Ultrasound findings of 210 patients with histopathologically proven FVPTC (68 nodules, M:F=13:47 with mean age of 39.5±11.9 years) and BTN (165 nodules, (M:F=41:109 with mean age of 44±11.3 years) were retrospectively reviewed from PACS by a single radiologist blinded to the final diagnosis. Logistic regression analysis was performed to identify the best predictors of FVPTC and their diagnostic performance was assessed.

RESULTS

The "nodule in nodule" sign was seen in 80.9% of FVPTC and only 12.1% of BTN. The "hypoechoic internal septae" sign was seen in 44.1% of FVPTC and 17% of BTN. Younger patients, heterogeneous echotexture, nodule in nodule sign, thick incomplete non-uniform halo and presence of significant nodes were the best predictors of FVPTC (p<0.05). The sensitivity, specificity, positive predictive value, negative predictive value, accuracy and relative risk for FVPTC given as odds ratio (95% CI) for heterogeneous echotexture and nodule in nodule sign which were the best 2 predictors of FVPTC were 91.2%, 81.8%, 67.3%, 95.7%, 84.5%, 46.5 (18.5-117.4) and 80.9%, 87.7%, 74.3%, 91.2%, 86.2%, 32.5 (15.04-70.2), respectively. There was improvement in the specificity (91.5%) and accuracy (86.6%) when a combined criterion of heterogeneous echotexture and nodule in nodule sign was applied to predict FVPTC.

CONCLUSION

The "nodule in nodule" sign is common in FVPTC and when combined with heterogeneous echotexture can differentiate FVPTC and BTN with high specificity.

Recombinant biologic products versus nutraceuticals from plants - a regulatory choice?

Biotechnology has transformed the potential for plants to be a manufacturing source of pharmaceutical compounds. Now, with transgenic and transient expression techniques, virtually any biologic, including vaccines and therapeutics, could be manufactured in plants. However, uncertainty over the regulatory path for such new pharmaceuticals has been a deterrent. Consideration has been given to using alternative regulatory paths, including those for nutraceuticals or cosmetic agents. This review will consider these possibilities, and discuss the difficulties in establishing regulatory guidelines for new pharmaceutical manufacturing technologies.

Malignant Peripheral Nerve Sheath Tumour of the Male Breast with Nodal Metastasis

Malignant peripheral nerve sheath tumour (MPNST) is a rare soft tissue sarcoma with high rate of local recurrences and metastases. Common sites include deeper soft tissues, usually in the proximity of a nerve trunk. MPNST of breast is a rare occurrence. To our knowledge there are only less than 10 case reports of MPNST of breast. We present a young male patient with MPNST and lymph node metastases and also discuss diagnostic modes and management challenges in such rare difficult scenarios.

Regulatory approval and a first-in-human phase I clinical trial of a monoclonal antibody produced in transgenic tobacco plants

Although plant biotechnology has been widely investigated for the production of clinical-grade monoclonal antibodies, no antibody products derived from transgenic plants have yet been approved by pharmaceutical regulators for clinical testing. In the Pharma-Planta project, the HIV-neutralizing human monoclonal antibody 2G12 was expressed in transgenic tobacco (Nicotiana tabacum). The scientific, technical and regulatory demands of good manufacturing practice (GMP) were addressed by comprehensive molecular characterization of the transgene locus, confirmation of genetic and phenotypic stability over several generations of transgenic plants, and by establishing standard operating procedures for the creation of a master seed bank, plant cultivation, harvest, initial processing, downstream processing and purification. The project developed specifications for the plant-derived antibody (P2G12) as an active pharmaceutical ingredient (API) based on (i) the guidelines for the manufacture of monoclonal antibodies in cell culture systems; (ii) the draft European Medicines Agency Points to Consider document on quality requirements for APIs produced in transgenic plants; and (iii) de novo guidelines developed with European national regulators. From the resulting process, a GMP manufacturing authorization was issued by the competent authority in Germany for transgenic plant-derived monoclonal antibodies for use in a phase I clinical evaluation. Following preclinical evaluation and ethical approval, a clinical trial application was accepted by the UK national pharmaceutical regulator. A first-in-human, double-blind, placebo-controlled, randomized, dose-escalation phase I safety study of a single vaginal administration of P2G12 was carried out in healthy female subjects. The successful completion of the clinical trial marks a significant milestone in the commercial development of plant-derived pharmaceutical proteins.

Site-specific proteolytic degradation of IgG monoclonal antibodies expressed in tobacco plants

Plants are promising hosts for the production of monoclonal antibodies (mAbs). However, proteolytic degradation of antibodies produced both in stable transgenic plants and using transient expression systems is still a major issue for efficient high-yield recombinant protein accumulation. In this work, we have performed a detailed study of the degradation profiles of two human IgG1 mAbs produced in plants: an anti-HIV mAb 2G12 and a tumour-targeting mAb H10. Even though they use different light chains (κ and λ, respectively), the fragmentation pattern of both antibodies was similar. The majority of Ig fragments result from proteolytic degradation, but there are only a limited number of plant proteolytic cleavage events in the immunoglobulin light and heavy chains. All of the cleavage sites identified were in the proximity of interdomain regions and occurred at each interdomain site, with the exception of the VL /CL interface in mAb H10 λ light chain. Cleavage site sequences were analysed, and residue patterns characteristic of proteolytic enzymes substrates were identified. The results of this work help to define common degradation events in plant-produced mAbs and raise the possibility of predicting antibody degradation patterns 'a priori' and designing novel stabilization strategies by site-specific mutagenesis.

Mutations seen among patients with pheochromocytoma and paraganglioma at a referral center from India

Determining the mutational status of susceptibility genes including RET, VHL, SDHx (SDHB, SDHC, SDHD) among patients with pheochromocytoma/paraganglioma (PCC/PGL) is gaining importance. These genes have not been systematically characterized among patients with PCC/PGL from India. The aim of the work was to screen the most frequently mutated genes among patients with PCC/PGL to determine the frequency and spectrum of mutations seen in this region. Fifty patients with PCC/PGL treated at our tertiary care hospital between January 2010 and June 2012 were screened for mutations in susceptibility genes using an algorithmic approach. Thirty-two percent (16/50) of patients were found to be positive for mutations including mutations among RET (n=4), VHL (n=6), SDHB (n=3), and SDHD (n=3) genes. None of these patients were positive for SDHC mutations. A significant association was found between young patients with bilateral tumors and VHL mutations (p=0.002). Two of the 3 patients with extra-adrenal SDHB associated tumors, had unique mutations, viz., c.436delT (exon 5) and c.788_857del (exon 8), one of which was malignant. High frequency of mutations seen among patients in this study emphasizes the need to consider mutational analysis among Indian patients with PCC/PGL.

Target product selection - where can Molecular Pharming make the difference?

Four major developments have taken place in the world of Molecular Pharming recently. In the USA, the DARPA initiative challenged plant biotechnology companies to develop strategies for the large-scale manufacture of influenza vaccines, resulting in a successful Phase I clinical trial; in Europe the Pharma-Planta academic consortium gained regulatory approval for a plant-derived monoclonal antibody and completed a first-in-human phase I clinical trial; the Dutch pharmaceutical company Synthon acquired the assets of Biolex Therapeutics, an established Molecular Pharming company with several clinical candidates produced in their proprietary LEX system based on aquatic plants; and finally, the Israeli biotechnology company Protalix Biotherapeutics won FDA approval for the commercial release of a recombinant form of the enzyme glucocerebrosidase produced in carrot cells, the first plant biotechnology-derived biopharmaceutical in the world approved for the market. Commercial momentum is gathering pace with additional candidates now undergoing or awaiting approval for phase III clinical trials. Filling the product pipeline is vital to establish commercial sustainability, and the selection of appropriate target products for Molecular Pharming will be a critical factor. An interesting feature of the four stories outlined above is that they span the use of very different platform technologies addressing different types of molecules which aim to satisfy distinct market demands. In each case, Molecular Pharming was an economically and technically suitable approach, but this decisionmaking process is not necessarily straightforward. Although the various technologies available to Molecular Pharming are broad ranging and flexible, competing technologies are better established, so there needs to be a compelling reason to move into plants. It is most unlikely that plant biotechnology will be the answer for the whole biologics field. In this article, we discuss the current plant biotechnology approaches that appear to hold the greatest promise and in doing so attempt to define the product areas that are most likely to benefit from different Molecular Pharming technologies.

How 'informed' is informed consent? Findings from a study in South India

A qualitative study using in-depth interviews was carried out among patients and doctors working in a private hospital in Tamil Nadu, to understand perceptions of informed consent. Audio-recorded interviews were transcribed verbatim and a framework analytical approach was used in analysis. Emergent themes ranged from perceptions on informed consent, and discussing health concerns and decision making, to information provided by and expectations from doctors, and suggestions for improvement. Most patients were unfamiliar with the kind of information provided in the informed consent process; a few felt that the information was inadequate. Decision making about surgery was left mostly to the doctor. Poor literacy in patients was seen as a barrier to effective communication by doctors. Developing local language versions of consent forms supported by audiovisual aids is needed for patients to take a proactive role in their treatment process, and for doctors to be receptive to patients' needs and capacities.

An epidermal cyst in the floor of the mouth: a rare presentation

Epidermal cysts rarely occur in the head and neck region as compared to the dermoid cysts and when they do occur in this region, they present in the floor of the mouth. We are reporting a rare case of an epidermal cyst in the floor of the mouth, with a brief review of the literature.

Recombinant monoclonal antibody yield in transgenic tobacco plants is affected by the wounding response via an ethylene dependent mechanism

Variability in recombinant IgG yield in transgenic tobacco plants has previously been observed in relation to leaf position, and is interpreted as a function of ageing and the senescence process, leading to increasing protein degradation. Here, similar findings are demonstrated in plants of different ages, expressing IgG but not IgG-HDEL, an antibody form that accumulates within the endoplasmic reticulum. Antibody yields declined following wounding in young transgenic plants expressing IgG but not in those expressing IgG-HDEL. However, in mature IgG plants, the opposite was demonstrated, with significant boosts in yield, while mature IgG-HDEL plants could not be boosted. The lack of response in IgG-HDEL plants suggests that the changes induced by wounding occur post-translationally, and the findings might be explained by wounding responses that differ in plants according to their developmental stages. Plant mechanisms involved in senescence and wounding overlap to a significant degree and compounds such as ethylene, jasmonic acid and salicylic acid are important for mediating downstream effects. Treatment of transgenic plants with ethylene also resulted in a decrease in recombinant IgG yield, which was consistent with the finding that wounded plants could induce lower IgG yields in neighbouring non-wounded plants. Treatment with 1-MCP, an ethylene antagonist, abrogated the IgG yield drop that resulted from wounding, but had no effect on the more gradual IgG yield loss associated with increasing plant age.

Incidence and estimated annual cost of emergency laparotomy in England: is there a major funding shortfall?

Significant recent interest has focussed on improving outcomes after emergency laparotomy. This retrospective database analysis estimated the annual incidence and associated inpatient costs of emergency laparotomy in England. Demographic, process and outcome data were collected for all patients undergoing emergency laparotomy in Brighton for two calendar years (2009-2010). Cost analysis assumed £16 per minute theatre time, and £282 per day ward bed and £1382 per day critical care bed costs. National incidence was confirmed from Hospital Episode Statistics and Office of National Statistics mid-year population data. In total, 768 patients underwent 850 emergency laparotomies. The incidence of emergency laparotomy was estimated as ∼1:1100 population. Thirty-six percent (276 patients) were admitted for a median (IQR [range]) of 5 (3-11 [1-76]) days of critical care. Postoperative median (IQR [range]) length of stay was 13 (8-24 [1-176]) days. Our estimated annual inpatient cost of emergency laparotomy for Brighton was ∼£5 million, equivalent to ∼£13 000 per patient, and for England, an annual estimated cost of ∼£650 million. However, 'Payment by Results' reimbursement amounted to a mean (SD) hospital income of just £6905 (2639) per patient, a net financial loss of ∼£6100 per patient, equivalent to a reimbursement shortfall nationally of ∼£300 million. We also found that patients > 70 years (46%) had significantly higher 30-day postoperative mortality (18% vs 6%, p < 0.0001), significantly prolonged median (IQR [range]) length of stay (15 (10-26 [1-123]) days vs 12 (7-22 [1-176]) days, p < 0.001) and incurred higher costs (median (IQR [range]) £9667 (6620-15 732 [1920-103 624]) vs £7467 (4975-14 251 [1178-118 060]), p < 0.001). Emergency laparotomy is a common procedure associated with considerable cost, particularly among elderly patients. A National Emergency Laparotomy Database will help provide an evidence base on which to improve clinical outcome and cost efficiency.

Factors predicting local recurrence in phyllodes tumor of the breast

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Background: Phyllodes tumor of the breast (PT) has local recurrences resulting in higher morbidity and disfiguring reoperations. Aim to find factors predicting local recurrences in PT. Methods: Retrospective data analyzed with SPSS v.17 (Pearson Chi square test, Logistic regression test for multivariate analysis) done on patients with PT managed during 2000-2010. Results: In total 141 patients with PT, mean age was 40.44 years (+0.98) and mean tumor size 11.07 cm (+0.57). Preoperatively cytology done in 96 % and was suggestive of PT in 59%; core biopsy done in 58 % and was suggestive of PT in 93% Imaging done in 65%. The mean duration of lump- 2.2 years (+0.23). Thirty two patients (23%) presented with recurrence post lumpectomy done elsewhere. Adjuvant radiotherapy was given in 28% patients. In multivariate analysis, high stromal cellularity ( p 0.002), surgery type (p= 0.000) and recurrent status (p=0.05) at first time presentation showed statistically significant p values for odd’s ratios. Conclusions: Tumor size, margins, surgery type, histological features of high stromal hypercellularity, necrosis with high mitotic rates predicted recurrence in PT. Core biopsy is more accurate than fine needle biopsy in diagnosis and recommended in suspected cases to permit the correct initial surgery. [Table: see text]

Role of cortical sparing adrenalectomy and novel variant of mutation in patient with von Hippel-Lindau disease

Neurofibromatosis type 1 is the most common phakomatoses and is inherited in autosomal dominant fashion with complete penetrance. Secondary hypertension is common in these patients due to various causes including adrenal tumors. Pheochromocytoma is a rare catecholamine producing tumor seen in 0.5% to 5% of patients with neurofibromatosis. The combination of pheochromocytoma with neurofibromatosis is rarely reported in the literature. We recently encountered an elderly lady with this combination who successfully underwent adrenalectomy. We report the case for the uncommon occurrence and to highlight the relevant literature review about pheochromocytoma in neurofibromatosis.

Exploring the vaccine potential of Dec-205 targeting in Mycobacterium tuberculosis infection in mice

Protein subunit vaccines are an attractive mode of immunisation against infectious diseases but the approach is hampered by the lack of suitable adjuvants for human use. We investigated if antigen targeting to the endocytic cell receptor Dec-205 on dendritic cells (DCs) could induce a protective immune response to Mycobacterium tuberculosis (MTB) infection in the absence of conventional adjuvants. Dec-205 receptor expressed by several subsets of DC has been shown in previous studies to be an efficient endocytic receptor for inducing both humoral and cellular immune responses, but this immunisation approach has not been tested in an experimental model of infection. We therefore prepared chemical conjugates of an anti-mouse Dec-205 monoclonal antibody (mAb) and the highly immunogenic antigen 85B (Ag85B) of MTB and showed that they bound efficiently to bone-marrow derived DC. Moreover, DC stimulated in vitro with Dec-205 conjugates could induce proliferation of splenocytes from Ag85B-immunised mice, while the negative control conjugates failed to do so. Following immunisation of mice with the anti-Dec-205-Ag85B conjugates administered together with a co-stimulatory anti-CD40 mAb, antigen-specific humoral and cellular responses were detected. Although the conjugates induced a strong Ag85B-specific humoral response, T cell proliferation and interferon-γ production were observed only when the conjugates were used to boost BCG vaccine. Importantly though, the conjugate vaccine did not offer significant protection against MTB challenge when used on its own or as a boost to BCG. Therefore, we conclude that Ag85B-based vaccine targeting to Dec-205 alone is not a sufficiently robust vaccination strategy for tuberculosis, although this approach might be more successful with other antigens or infections.

Terahertz imaging and spectroscopy of large-area single-layer graphene

We demonstrate terahertz (THz) imaging and spectroscopy of a 15 × 15-mm2 single-layer graphene film on Si using broadband THz pulses. The THz images clearly map out the THz carrier dynamics of the graphene-on-Si sample, allowing us to measure sheet conductivity with sub-mm resolution without fabricating electrodes. The THz carrier dynamics are dominated by intraband transitions and the THz-induced electron motion is characterized by a flat spectral response. A theoretical analysis based on the Fresnel coefficients for a metallic thin film shows that the local sheet conductivity varies across the sample from σ(s) = 1.7 × 10(-3) to 2.4 × 10(-3) Ω(-1) (sheet resistance, ρ(s) = 420 - 590 Ω/sq).

Photic and nonphotic seasonal cues differentially engage hypothalamic kisspeptin and RFamide-related peptide mRNA expression in Siberian hamsters

Seasonally breeding animals use a combination of photic (i.e. day length) and nonphotic (e.g. food availability, temperature) cues to regulate their reproduction. How these environmental cues are integrated is not understood. To assess the potential role of two candidate neuropeptides, kisspeptin and RFamide-related peptide-3 (RFRP), we monitored regional changes in their gene expression in a seasonally breeding mammal exposed to moderate changes in photoperiod and food availability. Adult male Siberian hamsters (Phodopus sungorus) were housed under a long (16 h light/day; 16 L) or intermediate (13.5 L) photoperiod and fed ad lib. or a progressive food restriction schedule (FR; reduced to 80% of ad lib.) for 11 weeks. Gonadal regression occurred only in FR hamsters housed under 13.5 L. Immunohistochemistry was used to identify diencephalic populations of kisspeptin- and RFRP-immunoreactive cells, and quantitative PCR was used to measure gene expression in adjacent coronal brain sections. Photoperiod, but not food availability, altered RFRP mRNA expression in the dorsomedial sections, whereas food availability but not photoperiod altered Kiss1 expression in the arcuate sections; intermediate photoperiods elevated RFRP expression, and food restriction suppressed Kiss1 expression. Regional- and neuropeptide-specific activity of RFamides may provide a mechanism for integration of multi-modal environmental information in the seasonal control of reproduction.

Heat-shock protein 70 gene polymorphism is associated with the severity of diabetic foot ulcer and the outcome of surgical treatment

Background

Foot ulcer is a significant cause of morbidity in diabetics. Genetic make-up can determine inflammatory and healing responses. This study examined the hypothesis that specific polymorphisms of the heat-shock protein 70 gene could predispose to the severity of diabetic foot ulceration.

Methods

Some 106 consecutive diabetic patients (101 evaluable) with foot ulceration admitted to a tertiary care hospital were managed according to a standard protocol. DNA was extracted from venous blood and examined by polymerase chain reaction–restriction fragment length analysis for two specific polymorphisms: G1538A in the HSPA1B and C2437T in the HSPA1L gene.

Results

HSPA1B genotyping showed that 70 patients were AG and 30 GG (one not amplified). The AG genotype was significantly associated with the severity of foot ulceration (Wagner grade) (P = 0·008, χ2 test), need for amputation (relative risk 2·02, 95 per cent confidence interval 1·02 to 4·01; P = 0·025) and median length of hospital stay (8 versus 5 days for GG; P = 0·043). HSPA1L genotypes (78 TT, 22 CT, one CC) did not show any significant association with these parameters.

Conclusion

The HSPA1B genotype, was associated with the severity of diabetic foot ulceration, need for amputation and duration of hospitalization in these patients.

Pheochromocytoma and haemophilia: an unusual combination

We report pheochromocytoma and haemophilia occurring in a 19-year-old South Indian man. To the best of our knowledge, this case is the first of its kind to be reported in the medical literature. The patient had bilateral adrenal pheochromocytomas with an extradrenal pheochromocytoma on the left side, and was successfully operated on after optimal preoperative blood pressure control and factor VIII support.

On the chronobiology of cohabitation

Social regulation of animal circadian rhythms may enable individuals in a population to temporally synchronize or segregate their activities within the community. Relatively little is known about the mechanisms for such interindividual temporal adaptations or how the circadian system might be involved. The literature suggests that actual prolonged cohabitation might lead to robust effects on the rhythmicity of cohoused individuals but that these effects are not easily reproduced by indirect or pulsatile social contacts. We have begun to study the conditions under which such cohabitation effects might be revealed in the laboratory, and we present and discuss initial data that cohousing pairs of golden hamsters can result in a persistent change in the free-running circadian period of one of the two hamsters of the pair. We believe that analyzing the societal level of temporal organization, and ultimately dissecting its underlying mechanisms, will enrich our understanding of the circadian clock and its role in establishing ecological communities.

Products of leaf primary carbon metabolism modulate the developmental programme determining plant morphology

Considerable effort has been expended on understanding the genetic networks that regulate leaf development and morphology, however, less attention has been given to the role of leaf carbon status in modulating the plant developmental programme. Unexpected changes in plant development have been observed in response to changes in leaf metabolism. The focus of this review will be to discuss how manipulation of leaf carbon metabolic pathways, such as the photosynthetic carbon reduction cycle and trehalose biosynthesis, has provided insights into links between metabolism and development.

Effect of temozolomide on central nervous system relapse in patients with advanced melanoma

Temozolomide has shown efficacy in the treatment of metastatic melanoma similar to that of dacarbazine (DTIC), the standard chemotherapy, but with the added benefit of penetration into the central nervous system (CNS). Isolated CNS relapse is increasingly a problem for patients who respond to biochemotherapy. By replacing DTIC with temozolomide in treatment regimens, the incidence of CNS relapse might be reduced. This hypothesis is difficult to test in a prospective randomized controlled trial because of the large number of patients that would be required. We have examined this question in a retrospective case control study, observing the rates of CNS relapse in advanced metastatic melanoma patients responding to DTIC- or temozolomide-based chemotherapy in three institutions. Twenty-one DTIC and 20 temozolomide responders were identified, and have been followed up for a median of 19.0 months (range 6.0-74.3 months). CNS relapse occurred in nine DTIC- and two temozolomide-treated patients, a statistically significant difference in favour of the new agent (P = 0.03). These results support the investigation of temozolomide as a replacement for DTIC in systemic treatment regimens for melanoma.

Sink regulation of photosynthesis

The concept that photosynthetic flux is influenced by the accumulation of photo-assimilate persisted for 100 years before receiving any strong experimental support. Precise analysis of the mechanisms of photosynthetic responses to sink activity required the development of a battery of appropriate molecular techniques and has benefited from contemporary interest in the effects of elevated CO2 on photosynthesis. Photosynthesis is one of the most highly integrated and regulated metabolic processes to maximize the use of available light, to minimize the damaging effects of excess light and to optimize the use of limiting carbon and nitrogen resources. Hypotheses of feedback regulation must take account of this integration. In the short term, departure from homeostasis can lead to redox signals, which cause rapid changes in the transcription of genes encoding photosystems I and II. End-product synthesis can exert short-term metabolic feedback control through Pi recycling. Beyond this, carbohydrate accumulation in leaves when there is an imbalance between source and sink at the whole plant level can lead to decreased expression of photosynthetic genes and accelerated leaf senescence. In a high CO2 world this may become a more prevalent feature of photosynthetic regulation. However, sink regulation of photosynthesis is highly dependent on the physiology of the rest of the plant. This physiological state regulates photosynthesis through signal transduction pathways that co-ordinate the plant carbon : nitrogen balance, which match photosynthetic capacity to growth and storage capacity and underpin and can override the direct short-term controls of photosynthesis by light and CO2. Photosynthate supply and phytohormones, particularly cytokinins, interact with nitrogen supply to control the expression of photosynthesis genes, the development of leaves and the whole plant nitrogen distribution, which provides the dominant basis for sink regulation of photosynthesis.

Low sink demand limits photosynthesis under P(i) deficiency

The role of the demand for carbon assimilates (the 'sink') in regulating photosynthetic carbon assimilation (Pn: the 'source') in response to phosphate (P(i)) deficiency was examined in tobacco (Nicotiana tabacum L.). P(i) supply was maintained or withdrawn from plants, and in both treatments the source/sink ratio was decreased in some plants by darkening all but two source leaves (partially darkened plants). The remaining plants were kept fully illuminated. P(i)-sufficient plants showed little variation in rate of Pn, amounts of P(i) or phosphorylated intermediates. Withdrawal of P(i) decreased Pn by 75% under the growing conditions and at both low and high internal CO2 concentration. Concomitantly, P(i), phosphorylated intermediates and ATP contents decreased and starch increased. RuBP and activity of phosphoribulokinase closely matched the changes in Pn, but Rubisco activity remained high. Partial darkening P(i)-deficient plants delayed the loss of photosynthetic activity; Rubisco and phosphoribulokinase activities and amounts of sucrose and metabolites, particularly RuBP and G6P, were higher than in fully illuminated Pi-deficient plants. Rates of sucrose export from leaves were more than 2-fold greater than in fully illuminated P(i)-deficient plants. Greater sucrose synthesis, facilitated by increased G6P content, an activator of SPS, would recycle P(i) from the cytosol back to the chloroplast, maintaining ATP, RuBP and hence Pn. It is concluded that low sink strength imposes the primary limitation on photosynthesis in P(i)-deficient plants which restricts sucrose export and sucrose synthesis imposing an end-product synthesis limitation of photosynthesis.

Decrease of phosphoribulokinase activity by antisense RNA in transgenic tobacco: definition of the light environment under which phosphoribulokinase is not in large excess

To test the hypothesis that the contribution of phosphoribulokinase (PRK) to the control of photosynthesis changes depending on the light environment of the plant, the response of transgenic tobacco (Nicotiana tabacum L.) transformed with antisense PRK constructs to irradiance was determined. In plants grown under low irradiance (330 micromol m(-2) s(-1)) steady-state photosynthesis was limited in plants with decreased PRK activity upon exposure to higher irradiance, with a control coefficient of PRK for CO2 assimilation of 0.25 at and above 800 micromol m(-2) s(-1). The flux control coefficient of PRK for steady-state CO2 assimilation was zero, however, at all irradiances in plant material grown at 800 micromol m(-2) s(-1) and in plants grown in a glasshouse during mid-summer (alternating shade and sun 300-1600 micromol m(-2) s(-1)). To explain these differences between plants grown under low and high irradiances, Calvin cycle enzyme activities and metabolite content were determined. Activities of PRK and other non-equilibrium Calvin cycle enzymes fructose-1,6-bisphosphatase, sedoheptulose-1,7-bisphosphatase and ribulose-1,5-bisphosphate carboxylase-oxygenase were twofold higher in plants grown at 800 micromol m(-2) s(-1) or in the glasshouse than in plants grown at 330 micromol m(-2) s(-1). Activities of equilibrium enzymes transketolase, aldolase, ribulose-5-phosphate epimerase and isomerase were very similar under all growth irradiances. The flux control coefficient of 0.25 in plants grown at 330 micromol m(-2) s(-1) can be explained because low ribulose-5-phosphate content in combination with low PRK activity limits the synthesis of ribulose-1,5-bisphosphate. This limitation is overcome in high-light-grown plants because of the large relative increase in activities of sedoheptulose-1,7-bisphosphatase and fructose-1,6-bisphosphatase under these conditions, which facilitates the synthesis of larger amounts of ribulose-5-phosphate. This potential limitation will have maintained evolutionary selection pressure for high concentrations of PRK within the chloroplast.