Calcium oxalate crystals inGeastrum

Calcium oxalate crystals are reported for the first time in fiveGeastrum species,G. badium, G. berkeleyi, G. pectinatum, G. pedicellatum andG. striatum, and are illustrated by SEM photographs. Crystal shape, distribution within the genus, precise position in the carpophore, and significance in respect to physiology and taxonomy are discussed.     

Calcium oxalate crystals in thyroid fine needle aspiration cytology

OBJECTIVE: To determine the occurrence, distribution and location of calcium oxalate crystals (COCs) in thyroid fine needle cytology specimens. STUDY DESIGN: Thyroid tissues from 60 fine needle aspiration cytology specimens (31 benign and 29 malignant lesions) were reviewed. These lesions were also histologically examined, and their pathologic diagnosis was confirmed. The cytologic slides were examined by normal and polarized light microscopy to determine their size, shape, occurrence, distribution and location. RESULTS: The size and shape of COCs varied from case to case. The total incidence was 45% (benign diseases, 68%; malignant lesions, 21%). No significant relationship between age and occurrence of COCs was found. Benign diseases showed more multifocal than focal distribution of COCs, unlike malignant diseases. Twenty-three (85%) of 27 cases with COCs revealed background location of COCs, especially within thyroid colloid. CONCLUSION: The occurrence of COCs in thyroid fine needle cytology was lower than that in histologic specimens reported in the literature, and COCs were more often identified in benign than malignant lesions. The presence of COCs may be a clue to benign lesions if their distribution is taken into consideration.     

Calcium oxalate crystals in benign cyst fluid from the breast. A case report

BACKGROUND: Two types of calcification have been observed in breast lesions. The more common is composed mostly of calcium phosphate and is detected in routine histologic tissue sections of frequently malignant lesions. The rare type is calcium oxalate and is found exclusively in benign cysts. CASE: In a 47-year-old female, strongly birefringent polyhedral crystals of calcium oxalate were detected in benign breast cyst fluid. CONCLUSION: Calcium oxalate is not clearly visible on routine histologic sections, and examination of the cytologic specimens under polarized light reveals them. Awareness of this potential pitfall might lead to conservative management.     

Calcium oxalate crystals and crystal cells in the leaves ofRhynchosia caribaea (Leguminosae: Papilionoideae)

Summary The development and distribution of calcium oxalate crystals, stomates and hairs were studied in the first trifoliolate leaf ofRhynchosia caribaea (Leguminosae: Papilionoideae, Phaseoleae). Using light and transmission electron microscopy, the crystals were shown to occur in both bundle sheath and mesophyll cells. Crystal distribution and shapes are characteristic forRhynchosia. Crystals develop late in leaf development in contrast to the stomates and hairs. As these latter two structures decrease in number per unit area with leaf age, crystal number increases.     

Calcium in plants

Calcium is an essential plant nutrient. It is required for various structural roles in the cell wall and membranes, it is a counter-cation for inorganic and organic anions in the vacuole, and the cytosolic Ca2+ concentration ([Ca2+]cyt) is an obligate intracellular messenger coordinating responses to numerous developmental cues and environmental challenges. This article provides an overview of the nutritional requirements of different plants for Ca, and how this impacts on natural flora and the Ca content of crops. It also reviews recent work on (a) the mechanisms of Ca2+ transport across cellular membranes, (b) understanding the origins and specificity of [Ca2+]cyt signals and (c) characterizing the cellular [Ca2+]cyt-sensors (such as calmodulin, calcineurin B-like proteins and calcium-dependent protein kinases) that allow plant cells to respond appropriately to [Ca2+]cyt signals.     

Calcium oxalate crystals in the mature seeds of Norway spruce, Picea abies (L.) Karst.

 The morphology and location of crystals encountered in the mature seeds of Norway spruce, Picea abies (L.) Karst., were examined using light and field emission scanning electron microscopy (FESEM). Crystals of various forms and sizes were discovered in different regions and tissues of seeds, particularly in the testa and the nucellus. Both solitary crystals and druses were occasionally enveloped by protrusions of the megaspore membranes or the cuticle of the megagametophyte. Histological studies and acid solubility tests coupled with analysis using energy dispersive X-ray microanalysis and X-ray diffraction evinced the crystals as calcium oxalate, but were unable to identify different hydration forms. Calcium oxalate crystals were most abundant in the damaged and infected tissues, and in the structures that desiccate during the development of the seed. Based on these observations we concluded that the accumulation of calcium oxalate is a regular process belonging to maturation and defense mechanism in spruce seeds. Received: 1 July 1998 / Accepted: 20 September 1998     

Calcium oxalate crystals in the red algaAntithamnion kylinii (Ceramiales): cytoplasmic and limited to indeterminate axes

Summary The red alga,Antithamnion kylinii Gardner, was found to have needle-shaped inclusions about 10 m long and less than 0.4 m thick. They ranged in abundance from one or a few in young cells to hundreds in fully enlarged cells. Under polarized light, the inclusions were birefringent, indicating crystallinity. Solubility tests suggested that the inclusions were composed of calcium oxalate: they dissolved in 1 N hydrochloric acid and in a saturated solution of aqueous cupric acetate, but they were not soluble in 10 N acetic acid or 5.25% sodium hypochlorite. X-ray microanalysis confirmed the presence of calcium. Calcium oxalate crystals were present in cells of indeterminate axes, but cells of determinate lateral filaments lacked them. Light and electron microscopic study demonstrated that the crystals were associated with the parietal cytoplasm. Calcium oxalate crystals were also present inA. defectum Kylin, but they were not found in ten more distantly related taxa.     

Calcium oxalate crystals in fetal bovine serum: implications for cell culture, phagocytosis and biomineralization studies in vitro

Cell culture methods and models are key investigative tools for cell and molecular biology studies. Fetal bovine serum (FBS) is commonly used as an additive during cell culture since its constituents promote cell survival, proliferation and differentiation. Here we report that commercially available FBS from different major suppliers consistently contain precipitated, calcium oxalate crystals-either in the monohydrate (COM) or dihydrate (COD) form. Mineral structure and phase identification of the crystals were determined by X-ray diffraction, chemical composition by energy-dispersive X-ray microanalysis, and imaging and measurement of crystal growth steps by atomic force microscopy-all identified and confirmed crystallographic parameters for COM and COD. Proteins binding to the crystals were identified by immunoblotting, revealing the presence of osteopontin and fetuin-A (alpha(2)HS-glycoprotein)--known regulators of crystal growth found in serum. Macrophage cell cultures exposed to calcium oxalate crystals showed internalization of the crystals by phagocytosis in a process that induced disruption of cell-cell adhesion, release of reactive oxygen species and membrane damage, events that may be linked to the release of inflammatory cytokines by these cells into the culture media. In conclusion, calcium oxalate crystals found in commercially available FBS are toxic to cells, and their presence may confound results from in vitro studies where, amongst others, phagocytosis, biomineralization, renal cell and molecular biology, and drug and biomaterial testing are being examined.     

Calcium oscillations in higher plants

There is considerable interest in the possibility that stimulus-induced oscillations in cytosolic free calcium encode information that is used to specify the outcome of the final response in calcium-based signalling pathways in plants. Recent results provide conclusive evidence that plant cells can decipher complex calcium signatures.     

Calcium messenger system in plants

The purpose of this review is to delineate the ubiquitous and pivotal role of Ca2+ in diverse physiological processes. Emphasis will be given to the role of Ca2+ in stimulus-response coupling. In addition to reviewing the present status of research, our intention is to critically evaluate the existing data and describe the newly developing areas of Ca2+ research in plants.     

Calcium channels in higher plants

Calcium channels are involved principally in signal transduction. Their opening results in increased cytoplasmic Ca(2+) concentration, and the spatial and temporal variations in this are thought to elicit specific physiological responses to diverse biotic and abiotic stimuli. Calcium-permeable channels have been recorded in the plasma membrane, tonoplast, endoplasmic reticulum, chloroplast and nuclear membranes of plant cells. This article reviews their electrophysiological properties and discusses their physiological roles. Emphasis is placed on the voltage-dependent and elicitor-activated Ca(2+) channels of the plasma membrane and the depolarisation-activated (SV), hyperpolarisation-activated, IP(3)- and cADPR-dependent Ca(2+) channels of the tonoplast. The closing of stomatal guard cells in the presence of abscisic acid (ABA) is used to illustrate the co-ordination of Ca(2+) channel activities during a physiological response.     

Calcium decoding mechanisms in plants

Ca²⁺ is a crucial second messenger that is involved in mediating responses to various biotic and abiotic environmental cues and in the regulation of many developmental processes in plants. Intracellular Ca²⁺ signals are realized by spatially and temporally defined changes in Ca²⁺ concentration that represent stimulus-specific Ca²⁺ signatures. These Ca²⁺ signatures are sensed, decoded and transmitted to downstream responses by a complex tool kit of Ca²⁺ binding proteins that function as Ca²⁺ sensors. Plants possess an extensive and complex array of such Ca²⁺ sensors that convey the information presented in the Ca²⁺ signatures into phosphorylation events, changes in protein-protein interactions or regulation of gene expression. Prominent Ca²⁺ sensors like, Calmodulins (CaM), Calmodulin-like proteins (CMLs), calcium dependent protein kinases (CDPKs), Calcineurin B-like proteins (CBLs) and their interacting kinases (CIPKs) exist in complex gene families and form intricate signaling networks in plants that are capable of robust and flexible information processing. In this review we reflect on the recently gained knowledge about the mechanistic principles of these Ca²⁺ sensors, their biochemical properties, physiological functions and newly identified targets proteins. These aspects will be discussed in the context of emerging functional principles that govern the information processing via these signaling modules.     

Calcium oxalate crystal morphology mutants from Medicago truncatula

Plants accumulate crystals of calcium oxalate in a variety of shapes and sizes. The mechanism(s) through which a plant defines the morphology of its crystals remains unknown. To gain insight into the mechanisms regulating crystal shapes, we conducted a mutant screen to identify the genetic determinants. This is the first reported mutant screen dedicated to the identification of crystal morphology mutants. A single leaf was harvested from individual Medicago truncatula L. plants that had been chemically mutagenized. Each leaf was visually inspected, using crossed-polarized light microscopy, for alterations in crystal shape and size. Seven different crystal morphology defective ( cmd) mutants were identified. Six cmd mutants were recessive and one dominant. Genetic analysis of the six recessive mutants suggested that each mutant was affected at a different locus. Each cmd mutant represents a new locus different than any previously identified. The plant phenotype of the cmd mutants appeared similar to that of the wild type in overall growth and development. This observation, coupled with the finding that several of the mutants had drastically altered the amount of calcium they partition into the oxalate crystal, questions current hypotheses regarding crystal function. Comparisons between the mutant crystals and those present in other legumes indicated the likelihood that simple point mutations contributed to the evolution of the variations in prismatic crystal shapes commonly observed in these plants today. The availability of cmd mutants provides the opportunity to investigate aspects of crystal shape and size that have been recalcitrant to previous approaches.