Ergonomic assessment of a new hand tool design for laparoscopic surgery based on surgeons' muscular activity

Laparoscopic surgery techniques are customarily used in non-invasive procedures. That said traditional surgical instruments and devices used by surgeons suffer from certain ergonomic deficiencies that may lead to physical complaints in upper limbs and back and general discomfort that may, in turn, affect the surgeon's skills during surgery. A novel design of the laparoscopic gripper handle is presented and compared with one of the most used instruments in this field in an attempt to overcome this problem. The assessment of the ergonomic feature of the novel design was performed by using time-frequency analysis of the surface electromyography (sEMG) signal during dynamic activities. Singular Spectrum Analysis (SSA) was used to decompose the sEMG signal and extract the median frequency of each muscle to assess muscle fatigue. The results reveal that using the proposed ergonomic grip reduces the mean values of the muscle activity during each of the proposed tasks. The novel design also improves the ease of use in laparoscopic surgery as it minimises high-pressure contact areas, reduces large amplitude movements and promotes a neutral position of the hand, wrist and forearm. Furthermore, the SSA method for time-frequency analysis provides a powerful tool to analyse a prescribed activity in ergonomic terms. The proposed methodology to assess muscle activity during surgery activities may be useful in the selection of surgical instruments when programming extended procedures, as it provides an additional selection criterion based on the surgeon's biomechanics and the proposed activity.

Resistive Switching and Charge Transport in Laser-Fabricated Graphene Oxide Memristors: A Time Series and Quantum Point Contact Modeling Approach

This work investigates the sources of resistive switching (RS) in recently reported laser-fabricated graphene oxide memristors by means of two numerical analysis tools linked to the Time Series Statistical Analysis and the use of the Quantum Point Contact Conduction model. The application of both numerical procedures points to the existence of a filament connecting the electrodes that may be interrupted at a precise point within the conductive path, resulting in resistive switching phenomena. These results support the existing model attributing the memristance of laser-fabricated graphene oxide memristors to the modification of a conductive path stoichiometry inside the graphene oxide.

Design of Semirigid Wearable Devices Based on Skin Strain Analysis

Nowadays, both usability and comfort play a key role in the development of medical and wearable products. When designing any device that is in contact with the human body, the mechanical behavior of the embraced soft tissue must be known. The unavoidable displacement of the soft tissue during motion may lead to discomfort and, thus, the removal of the wearable product. This paper presents a new methodology to design and test a wearable device based on the measurement of the dynamic skin strain field. Furthermore, from this field, the anatomical lines with minimum strain (lines of nonextension (LoNEs)) are calculated to design the structural parts of the wearable device. With this new criterion, the resulting product is not only optimized to reduce the friction in skin-device interface, but fully personalized to the patient's morphology and motion. The methodology is applied to the design of an ankle-foot wearable orthosis for subjects with ankle dorsiflexors muscles weakness due to nervous system disorders. The results confirm that the use of LoNEs may benefit the design of products with a high interaction with the skin.

Glutaminase isoenzymes as key regulators in metabolic and oxidative stress against cancer

Cancer cells require a robust supply of reduced nitrogen to produce nucleotides, non-essential amino acids and a high cellular redox activity. Glutamine provides a major substrate for respiration as well as nitrogen for the production of proteins, hexosamines, and macromolecules. Therefore, glutamine is one of key molecules in cancer metabolism during cell proliferation. The notion of targeting glutamine metabolism in cancer, originally rationalized by the number of pathways fed by this nutrient, has been reinforced by more recent studies demonstrating that its metabolism is regulated by oncogenes. Glutamine can exert its effects by modulating redox homeostasis, bioenergetics, nitrogen balance or other functions, including by being a precursor of glutathione, the major nonenzymatic cellular antioxidant. Glutaminase (GA) is the first enzyme that converts glutamine to glutamate, which is in turn converted to alpha-ketoglutarate for further metabolism in the tricarboxylic acid cycle. Different GA isoforms in mammals are encoded by two genes, Gls and Gls2. As each enzymatic form of GA has distinct kinetic and molecular characteristics, it has been speculated that the differential regulation of GA isoforms may reflect distinct functions or requirements in different tissues or cell states. GA encoded by Gls gene (GLS) has been demonstrated to be regulated by oncogenes and to support tumor cell growth. GA encoded by Gls2 gene (GLS2) reduces cellular sensitivity to reactive oxygen species associated apoptosis possibly through glutathione-dependent antioxidant defense, and therefore to behave more like a tumor suppressor. Thus, modulation of GA function may be a new therapeutic target for cancer treatment.

Anticancer antioxidant regulatory functions of phytochemicals

Plant foods are not only a main source of nutrients, but they are also rich in physiologically bioactive bionutrients or phytochemicals. Consumption of fruit and vegetables is associated with a decreased risk of pathological status, including cancer. Reactive oxygen species play a key role in the genesis and development of cancer. Therefore, antioxidant functions of phytonutrients have been thoroughly investigated in the last years in relation to their crucial effect in the pathophysiology associated with neoplasia. This review discusses current knowledge on phytochemicals in relation to their potential as chemopreventive and/or chemotherapeutic molecule against human cancers. Finally, we will outline the use of bioactive phytochemicals on synergistic actions involved in the prevention and treatment of cancer as well as its future prospects.

Natural antioxidants: therapeutic prospects for cancer and neurological diseases

An all out war is continuously occurring between oxidants and antioxidants inside the cells. This mini-review will provide an updated revision of the function of some natural compounds having main roles in antioxidant function. We will point on some phytochemicals working at two outstanding targets, tumour cells and neurons.

Application of singular spectrum analysis to the smoothing of raw kinematic signals

Motion capture systems currently used in biomechanical analysis introduce systematic measurement errors that appear in the form of noise in recorded displacement signals. The noise is unacceptably amplified when differentiating displacements to obtain velocities and accelerations. To avoid this phenomenon, it is necessary to smooth the displacement signal prior to differentiation in order to eliminate the noise introduced by the experimental system. The use of singular spectrum analysis (SSA) is presented in this paper as an alternative to traditional digital filtering methods. SSA is a novel non-parametric technique based on principles of multivariate statistics. The original time series is decomposed into a number of additive time series, each of which can be easily identified as being part of the modulated signal, or as being part of the random noise. Several examples that demonstrate the superiority of this technique over other methods used in biomechanical analysis are presented in this paper.

[Anti-hypertensive effect of eprosartan in diabetic patients]

OBJECTIVE

Diabetes mellitus seems to induce an special difficulty to control the high blood pressure. This effect is more severe on the SBP. Previous reports suggest that a new angiotensin receptor blocker, eprosartan, might have a higher efficacy to reduce SBP. It has been evaluated the BP decrease obtained with eprosartan in a group of diabetics patients compared to non diabetic patients.

MATERIAL AND METHODS

81 patients were recruited of whom 65 have ended follow-up. 34 patients were diabetics (mean age 66.7+/-10.7 years, 15 men and 19 women) and 31 were non diabetics control patients (mean age 61.8+/-12,8 years, 13 men and 18 women). All patients were treated with (600 mg) once daily. The doses was ingested in the morning. They were made three follow up visits (1, 3 and 6 mo after the first visit).

RESULTS

SBP was significantly decreased both in diabetics (baseline 170.9+/-12.0, final 139.1+/-13.0 mmHg, p < 0.001) and in non diabetics group (baseline 169.9+/-18.0, final 142.0+/-13.3 mmHg, p < 0.001). DBP was also reduced in both groups (diabetics: baseline 92.9+/-9.7, final 78.4+/-8.5 mmHg, p < 0.001; non diabetics: baseline 95.6+/-7.9, final 79.1+/-7.4 mmHg, p < 0.001). Differences between the groups were not significant in any visit. Final BP reduction reached was -31.7/-14.6 mmHg in diabetics vs -27,6/-16,5 mmHg in non diabetics patients (difference is not significant) Pulse pressure changes were not different between the two groups (diabetics, 17.8+/-14.5, vs non diabetics, 11.1+/-13.2 mmHg). Two diabetic patients need a second drug to achieve BP goal and no one in non diabetic group. No adverse effects were reported.

CONCLUSIONS

Eprosartan seems to be an effective drug to reduce SBP, DBP and pulse pressure with the same effectiveness in diabetics and non diabetic patients.

An osmotic-sensitive taurine pool is localized in rat pancreatic islet cells containing glucagon and somatostatin

Previous reports have dealt with the hypoglycemic properties of taurine and its effects on insulin secretion by adult and fetal isolated islets. We have studied the presence and cellular distribution of taurine in rat islets, the conditions to evoke its release, and its possible modulatory action on insulin secretion. We localized taurine by techniques of double immunolabeling in most glucagon-positive cells and in some somatostatin-positive cells, whereas insulin-positive cells were not labeled with the taurine antibody. Although high-glucose stimulation did not evoke any taurine release, a hyposmotic solution (17% osmolarity reduction) induced a specific phasic release of taurine and GABA (34 and 52% increase on their basal release rate). On the other hand, taurine (10 mmol/l) application slightly reduced the second phase of insulin secretion induced by glucose stimulation. In conclusion, taurine is highly concentrated in glucagon-containing cells of the islet periphery. It is not liberated by glucose stimulation but is strongly released under hyposmotic conditions. All of these data suggest that taurine plays an osmoregulatory role in alpha-cells.

Immunohistochemical localization of taurine in the rat ovary, oviduct, and uterus

The distribution of the amino acid taurine in the female reproductive organs has not been previously analyzed in detail. The aim of this study was to determine taurine localization in the rat ovary, oviduct, and uterus by immunohistochemical methods. Taurine was localized in the ovarian surface epithelium. The granulosa cells and oocytes of primordial follicles were immunonegative. In primary and antral follicles, taurine was found mainly in theca cells and oocytes, whereas the zona pellucida, antrum, and most granulosa cells were unstained. However, taurine immunoreactivity in theca cells and oocytes decreased during follicular atresia. During corpora lutea development, the number of immunopositive theca lutein cells increased as these cells invaded the granulosa-derived region. Therefore, most luteal cells from the mature corpora lutea were stained. In the regressing corpora lutea, however, taurine staining in luteal cells decreased. In the fimbriae, infundibulum, and uterotubal junction, taurine was localized in most epithelial cells. In the ampullar and isthmic segments, taurine was found in the cilia of most ciliated cells and in the apical cytoplasm of some non-ciliated cells. In the uterus, most epithelial cells were immunopositive during diestrus and metestrus, whereas most of them were immunonegative during estrus and proestrus. Moreover, taurine immunoreactivity in the oviduct and uterus decreased with pregnancy. (J Histochem Cytochem 49:1133-1142, 2001)

Incorporation of stable organic radicals into cyclotriphosphazene: preparation and characterization of mono- and diradical adducts

Stable cyclotriphosphazenes 4 and 5, incorporating one and two carbon radical centers, respectively, have been easily prepared and characterized. EPR spectroscopic studies in fluid solution at room temperature were carried out for both compounds and also for diradical 5 in frozen solvent matrixes. Spectral results are consistent with a triplet or degenerate singlet triplet ground state for 5. Reductive cyclic voltammetry shows a redox couple, being monoelectronic for 4 and bielectronic for 5.

Taurine levels and localisation in the stratified squamous epithelia

The content and distribution of the amino acid taurine in squamous epithelia were studied using high-performance liquid chromatography and immunohistochemical methods. Quantitative analysis demonstrated that taurine was highly concentrated in the epidermis (5.49 mumol/g fresh tissue in the hairless skin of the hind footpad of the rat), although the values in the isolated stratum corneum were extremely low (< 0.073 mumol/g in the horny layer of the same skin area). No other analysed amino acid (such as glutamate, glutamine, glycine or alanine) showed this specific pattern of distribution. The immunohistochemical study revealed that in the dog and rat epidermis, taurine was present in the keratinocytes of the granular and upper spinous layers. The basal layer, lower spinous layer and stratum corneum were immunonegative. A similar immunostaining pattern was found in the epithelia of the different organs studied: the mouth, tongue and oesophagus of the dog and rat, the rat forestomach and the rat corneal epithelium. Other cell types, such as sebaceous and muscle cells, were immunolabelled. The existence of a circulating pool of taurine in the epidermis (via taurine release from keratinocytes before they reach the horny layer and its uptake by nearby cells) and its possible roles in these cells are discussed.

Ehrlich ascites tumor cells expressing anti-sense glutaminase mRNA lose their capacity to evade the mouse immune system

Glutaminase (EC 3.5.1.2) is a key enzyme in rapidly proliferating cells. Using anti-sense technology, an Ehrlich ascites tumor cell line (0.28AS-2) with reduced glutaminase activity has been obtained. We investigated the in vivo growth characteristics of the 0.28AS-2 cells. When injected i.p. into normal Swiss albino mice, the 0.28AS-2 cells were unable to grow. On the contrary, when injected into nude mice, they developed into solid tumors. Mice inoculated with 0.28AS-2 cells kept immunologic memory and rejected a second inoculation with parental Ehrlich ascites tumor cells. Expression of both polymorphic epithelial mucin-1 (MUC-1) and the enzyme N-acetyl-alpha-D-galactosaminidase, proteins implicated in host immune system escape, were markedly diminished in 0.28AS-2 cells. Study of the immune system response in mice inoculated with 0.28AS-2 cells revealed an increase in splenic CD18 cells and the presence of a large number of activated F4/80+ macrophages in the ascites cavity. These features, not observed in mice inoculated with parental Ehrlich ascites tumor cells, indicate that a distinctive, strong immune response occurred in animals inoculated with 0.28AS-2 cells. Our results suggest that inhibition of glutaminase expression using anti-sense technology induces phenotypic changes in Ehrlich ascites tumor cells that allow the development of an effective anti-tumor immune response, which makes the cells unable to develop in vivo tumors.

Inhibition of glutaminase expression by antisense mRNA decreases growth and tumourigenicity of tumour cells

Phosphate-activated glutaminase has a critical role in tumours and rapidly dividing cells and its activity is correlated with malignancy. Ehrlich ascites tumour cells transfected with the pcDNA3 vector containing an antisense segment (0.28 kb) of rat kidney glutaminase showed impairment in the growth rate and plating efficiency, as well as a shortage in the glutaminase protein and activity. The C-terminal segment used is well conserved in all glutaminase sequences known. The transfected cells, named 0.28AS-2, displayed remarkable changes in their morphology compared with the parental cell line. The 0.28AS-2 cells also lost their tumourigenic capacity in vivo. Control mice developed an ascitic tumour, with a lifespan of 16+/-1 days, when inoculated with 10(7) cells/mouse; on the contrary, animals inoculated with transfected cells up to 2.5 times the cell numbers of control mice did not develop tumours and behaved as healthy animals. The ability to revert the transformed phenotype of antisense-transfected cells confirms the relevance of glutaminase in the transformation process and could provide new ways for the study of gene therapy.

Functional implications of the noradrenergic-cholinergic switch induced by retinoic acid in NB69 neuroblastoma cells

Some neuroblastoma cell lines change their neurotransmitter phenotype from noradrenergic to cholinergic under retinoic acid treatment. Such "neurotransmitter switch" seems to be a consequence of changes in the expression and activity of the biosynthetic machinery for both neurotransmitters. In this study, we have characterized this "neurotransmitter switch" induced by retinoic acid in a human neuroblastoma cell line (NB69) showing catecholaminergic characteristics. Retinoic acid treatment reduced tyrosine hydroxylase activity and noradrenaline levels in NB69 cells but did not modify the expression of this enzyme. Moreover, the calcium-dependent release of [(3)H]noradrenaline in control cells was highly reduced by retinoic acid treatment. On the other hand, NB69 cells treated with retinoic acid enhanced the expression of choline acetyltransferase and acquired the capability to release [(3)H]acetylcholine in a calcium-dependent way. In addition, we found that the expression of the vesicular monoamine transporter 2 (VMAT2) and the vesicular acetylcholine transporter (VAChT) was increased in those cells treated with retinoic acid. Immunostaining revealed that retinoic acid treatment changed the cellular distribution of both vesicular monoamine transporter 2 and vesicular acetylcholine transporter. In conclusion, retinoic acid induces a noradrenergic to cholinergic switch in NB69 cells by acting at several levels of the neurotransmitter phenotypic expression.

A tomato peroxidase involved in the synthesis of lignin and suberin

The last step in the synthesis of lignin and suberin has been proposed to be catalyzed by peroxidases, although other proteins may also be involved. To determine which peroxidases are involved in the synthesis of lignin and suberin, five peroxidases from tomato (Lycopersicon esculentum) roots, representing the majority of the peroxidase activity in this organ, have been partially purified and characterized kinetically. The purified peroxidases with isoelectric point (pI) values of 3.6 and 9.6 showed the highest catalytic efficiency when the substrate used was syringaldazine, an analog of lignin monomer. Using a combination of transgenic expression and antibody recognition, we now show that the peroxidase pI 9.6 is probably encoded by TPX1, a tomato peroxidase gene we have previously isolated. In situ RNA hybridization revealed that TPX1 expression is restricted to cells undergoing synthesis of lignin and suberin. Salt stress has been reported to induce the synthesis of lignin and/or suberin. This stress applied to tomato caused changes in the expression pattern of TPX1 and induced the TPX1 protein. We propose that the TPX1 product is involved in the synthesis of lignin and suberin.

Levels, phosphorylation status and cellular localization of translational factor eIF2 in gastrointestinal carcinomas

The level of expression and the phosphorylation status of the alpha subunit of initiation factor 2 (eIF2alpha) protein have been determined by comparing samples from human stomach, colon and sigma-rectum carcinomas with normal tissue from the same patients. The unphosphorylated and phosphorylated levels of cytoplasmic eIF2alpha, as well as the percentage of phosphorylated factor over the total, were significantly higher in stomach, colon and sigma-rectum tumours compared with normal tissue. The expression of this factor was also studied by using immunocytochemical methods, where redistribution towards the nucleus in tumour cells as compared with normal tissue was observed. Our results support a likely implication of eIF2alpha in gastrointestinal cancer.

Immunohistochemical localization of taurine in the male reproductive organs of the rat

The amino acid taurine has been implicated in several aspects of reproductive system physiology. However, its localization in these organs has not been previously analyzed. The aim of this study was to characterize its distribution in male rat reproductive organs by immunohistochemical methods. Taurine was localized in the smooth muscle cells of the tissues studied and in the skeletal fibers of the cremaster muscle. In the testis, taurine was found in Leydig cells, vascular endothelial cells, and other interstitial cells. No immunoreactivity was observed in the cells of the seminiferous tubules, either in germ cells at all spermatogenic stages or in Sertoli cells. However, peritubular myoid cells were immunostained. Most epithelial cells of the efferent ducts were immunolabeled, whereas the epithelial cells of the rete testis (extratesticular segments), epididymis (caput, corpus, and cauda regions), and ductus deferens were unstained. However, most epithelial cells from the intratesticular segments of the rete were immunopositive. Some cells identified as intraepithelial macrophages and lymphocytes, apical cells, and narrow cells were intensely immunolabeled. Regional differences in the distribution of these cell types along the ducts studied were also noted. The possible functional roles for taurine in these cells are discussed.

Molecular cloning, sequencing and expression studies of the human breast cancer cell glutaminase

Phosphate-activated glutaminase (GA) is overexpressed in certain types of tumour but its exact role in tumour cell growth and proliferation is unknown. Here we describe the isolation of a full-length cDNA clone of human breast cancer ZR75 cells, by a combination of lambdagt10 cDNA library screening and the rapid amplification of cDNA ends ('RACE') technique. The cDNA of human GA is 2408 nt with a 1806-base open reading frame encoding a 602-residue protein with a predicted molecular mass of 66309 Da. The deduced amino acid sequence contains a putative mitochondrial import presequence of 14 residues at the N-terminal end. Heterologous expression and purification in Escherichia coli yielded a product of the expected molecular size that was recognized by using antibodies against the recombinant human GA. Sequence analyses showed that human GA was highly similar to the rat liver enzyme. Northern gel analysis revealed that the gene is present in human liver, brain and pancreas, in which a major transcript of 2.4 kb was demonstrated, but not in kidney, heart, skeletal muscle, lung or placenta. These results strongly suggest that the first human GA cloned, the GA from ZR-75 breast cancer cells, and presumably those from human liver and brain, are liver-type isoenzymes, in sharp contrast with the present view that considers the kidney type as the isoform expressed in all tissues with GA activity, with the exception of postnatal liver.

Immunocytochemical localization of taurine in different muscle cell types of the dog and rat

The presence and distribution of the amino acid taurine in different muscle cell types of the dog and rat was examined by immunocytochemical methods. The light microscope study revealed that smooth muscle cells were similarly immunoreactive for taurine, whereas skeletal muscle fibres showed wide differences in taurine immunoreactivity among individual cells. Some skeletal fibres were strongly immunoreactive whereas others did not display immunolabelling. Mononucleated satellite cells, found adjacent to skeletal fibres in a quiescent stage, were also immunostained. Other myoid cells, such as testicular peritubular cells showed a cytoplasmic and a nuclear pool of taurine. By means of electron microscope immunolabelling, the subcellular localization of taurine was studied in vascular and visceral smooth muscle cells. Taurine was present in most subcellular compartments and frequently appeared randomly distributed. Taurine was localized on myofilaments, dense bodies, mitochondria, the plasma membrane and the cell nucleus. Moreover, the labelling density within individual smooth muscle cells was variable and depended on the state of contraction of each single fibre. Contracted cells showed a higher density of gold particles than relaxed cells. Unmyelinated nerve fibres, found adjacent to smooth muscle cells from the muscularis mucosae and the lamina propria of the stomach, were unstained or poorly stained.

Cytochemical localization of calcium in prefusion myoblasts from the chick embryo myotome

Myoblast fusion is a Ca2+-dependent process. The aim of this report was to study the localization of Ca2+ in prefusion myoblasts from the brachial somites of chick embryos (51-108 h of incubation), using the potassium pyroantimonate cytochemical method. When observed under a transmission electron microscope, electron-dense precipitates of Ca2+-antimonate were found in the basement membrane of the myotome, which separates the myotome from the adjacent mesenchyma. Within myoblasts, triads and sarcoplasmic reticulum associated with the first newly formed sarcomeres were observed, but a T-tubule network was not found. Moreover, Ca2+-antimonate precipitates were not observed in structures resembling T-tubules or sarcoplasmic reticulum. The results suggest that sarcomerogenesis and sarcoplasmic reticulum development occur simultaneously and that prefusion myoblasts have neither a T-tubule network nor Ca2+ deposits on sarcoplasmic reticulum. Small Ca2+ pools were found in the myoblast nuclei, cytoplasmic vesicles and mitochondrias. Ca2+-antimonate precipitates periodically distributed at the cell periphery, close to the cell membrane, were observed. These precipitates could represent internal Ca2+ stores located in the peripheral couplings and it is proposed that these pools of Ca2+ could be mobilized before fusion, leading to the increase in free intracellular Ca2+ that precedes myoblast fusion.

Localization of eukaryotic initiation factor 2 in neuron primary cultures and established cell lines

Eukaryotic initiation factor 2 (eIF-2) is a heterotrimeric protein with subunits alpha, beta and gamma that forms a ternary complex with Met-tRNA and GTP. It promotes the binding of Met-tRNA to ribosomes and controls translational rates via phosphorylation/dephosphorylation mechanisms. By means of immunofluorescence and post-embedding immunocytochemistry of intact cells and quantitative immunoblotting of cell extracts, the cellular distribution of the initiation factor has been examined in primary neuronal cultures as well as in two established cell lines: PC12 phaeochromocytoma cells and rat pituitary GH4C1 cells. Our results indicated that the initiation factor is located not only in the cytoplasm but also in the nuclei of the cultured neurons and cell lines. In the cytoplasm, immunocytochemical studies reveal that the factor is present mainly in those areas that are rich in ribosomes. In the nucleus, the immunolabelling of eukaryotic initiation factor 2 verified the presence of gold particles in both nucleolar and extranucleolar areas. The specific distribution of this factor on both sides of the nuclear envelope suggests that it might have some nuclear-related function(s) besides its already known role in the control of translation.

Effect of dehydrodidemnin B on human colon carcinoma cell lines

Didemnins are cytotoxic agents belonging to a depsipeptide family isolated from marine tunicates. In the present study, a new member, dehydrodidemnin B (DDB), isolated from the mediterranean tunicate Aplidium albicans, was used. The effect of the drug on human colon cultured cell lines was tested using multiple approaches: proliferation studies, long term survival after three hours of exposure to DDB by means of a clonogenic assay and the decrease of the protooncogen, ornithine decarboxylase, activity. A dehydrodidemnin B concentration of 10(-8) M completely inhibited cell growth. The IC50 obtained using the MTT proliferation test, indicated that the most proliferative cell line (CT-2) was the most sensitive to the drug. Using a clonogenic assay a clear dose-response was obtained for the three cell lines used; HT-29 cell line showed the minimum survival after 3 hours of dehydrodidemnin B treatment. A dose-dependent decrease in ornithine decarboxylase activity was also observed in three cell lines assayed. The data presented indicate that the dehydrodidemnin B is a potent cytotoxic agent on rapidly dividing human colon cancer cells.

The G-cells in the dog: a light and electron microscope immunocytochemical study

An immunohistochemical study has been performed to analyse the distribution of gastrin cells in the gastrointestinal tract of the dog. This study revealed that G-cells immunoreactive for gastrin were almost exclusively present in the pyloric antral mucosa, mainly in the middle third of the pyloric mucosa. The calculated number of G-cells per surface unit area was 8.5 x 10(3)-1.2 x 10(4) cells cm-2. Some gastrin-immunopositive cells were found in the first 10 mm of the proximal duodenum, mainly in the villous region. The fundic area of the dog stomach, the oesophagus, small intestine, caecum, colon, rectum, salivary glands, liver and pancreas were all immunonegative for gastrin. At the ultrastructural level, three different types of granules (150-400 nm) were evident in G-cells: electron-dense, electron-lucent and intermediate forms. Most of them were located in the subnuclear region of the cell. The effect of fixation of the antral mucosa at different pH levels was studied. In samples fixed with acid solutions, most of the G-cell granules were of the electron-dense type and were strongly immunopositive for gastrin. Fixation of samples at a basic pH resulted in most of the gastrin granules losing their contents into the cytoplasm, and the positive reaction to gastrin was then located in the cytoplasm and at the periphery of the electron-lucent granules.

Bovine Reissner's fiber (RF) and the central canal of the spinal cord: an immunocytochemical study using a set of monoclonal antibodies against the RF-glycoproteins

The subcommissural organ secretes N-linked complex-type glycoproteins into the cerebrospinal fluid. These glycoproteins condense to form Reissner's fiber (RF), which extends along the fourth ventricle and central canal of the spinal cord. A set of three monoclonal antibodies (Mabs 3E6, 3B1, and 2A5) has been obtained using these glycoproteins as immunogens. Competitive and sandwich enzyme-linked immunoassay methods have demonstrated that the three monoclonal antibodies are directed against different epitopes, and that there is no competition among them for their binding to glycoproteins of RF. Mab 3E6 displays immunoblotting properties that are similar to those of a polyclonal antibody against the pool of glycoproteins from RF, but that are different from those of Mabs 3B1 and 2A5. All three antibodies immunostain the bovine subcommissural organ and RF. A population of ependymal cells is stained by the polyclonal antibody, and Mabs 2A5 and 3E6, but not by Mab 3B1. The material present in a population of ependymal cells of the central canal, and the glycoproteins secreted by the subcommissural organ thus probably have partial chemical identity. Some evidence suggests that the immunoreactive ependymal cells are secretory cells. The luminal surface of the central canal is coated by a thin layer of material with immunocytochemical characteristics different from those of the ependymal cells; such a coat may correspond to material released from RF.

Mouse placental cells secrete immunoreactive growth hormone-releasing factor

The initial objective of this study was to establish a placental cell culture system in which the secretion of mouse growth hormone-releasing factor (mGHRF) could be examined during a several-day period. To determine when during pregnancy placental cells begin to express mGHRF, Northern blot analysis was carried out on total RNA from placentas collected on Days 6, 9, 11, 13, 15, 17, and 18 of pregnancy. Mouse GHRF mRNA could be detected as early as Day 11 of pregnancy. Its steady-state levels increased to maximum values on Days 15-17 and then declined slightly on Day 18. Placentas from Day 12 of pregnancy were selected for cell culture. The basal zone and labyrinth were dispersed in collagenase, and the cells were fractionated on a Percoll gradient. Two bands of cells were selected for further study. Both released significant amounts of immunoreactive mGHRF during a 5-day culture period. Effects of prolonged exposure of the cells to 8-bromo-cAMP and to agents that elevate intracellular cAMP concentration were then examined. Treatment of the cells with 0.5 mM 8-bromo-cAMP resulted in a significant decrease in the mGHRF concentration of the medium by the second day of culture. Mouse GHRF secretion was also inhibited by treatment of the cells with 100 ng/ml cholera toxin or 0.1 mM forskolin. The effect of 8-bromo-cAMP was concentration-dependent, with 0.1 mM being the lowest concentration that was active. 8-Bromo-cAMP treatment also reduced the steady-state level of mGHRF mRNA in the cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphate-activated glutaminase expression during tumor development

Changes in phosphate-activated glutaminase activities determined in intact cells and isolated mitochondria have been followed during mouse Ehrlich ascites carcinoma development. Glutaminase activities parallel the levels of poly(A)+ RNAs encoding for the mitochondrial phosphate activated glutaminase. During the exponential growth phase, maximum activity was observed and the relative abundance of glutaminase mRNA significantly increased with regard to the stationary growth phase. The presented results show that tumor phosphate-activated glutaminase is subject to long-term regulation by differential gene expression.

Glycolysis and glutaminolysis in perifused Ehrlich ascites tumour cells

A perifusion system was designed in order to study glucose and glutamine metabolism by freshly harvested Ehrlich ascites tumour cells in steady state conditions. Cells were perifused in the presence of 5 mM glucose, 0.5 mM glutamine or 5 mM glucose and 0.5 mM glutamine. The results in steady state reveal that both substrates glucose and glutamine are continuously wasted by tumour cells, excreting two moles of lactate per mol of glucose and one mol of glutamate and ammonia per mol of glutamine consumed into the medium. Glutamine consumption in the presence of glucose was higher than with glutamine alone.