Interplay of lattice-spin-orbital coupling and Jahn-Teller effect in noncollinear spinel TixMn1-x(FeyCo1-y)2O4: a neutron diffraction study.

Local magnetostructural changes and dynamical spin fluctuations in doubly diluted spinel TixMn1‒x(FeyCo1‒y)2O4has been reported by means of neutron diffraction and magnetization studies. Two distinct sets of compositions (i)x(Ti) = 0.20 andy(Fe) = 0.18; (ii)x(Ti) = 0.40 andy(Fe) = 0.435 have been considered for this study. The first compound of equivalent stoichiometry Ti0.20Mn0.80Fe0.36Co1.64O4exhibits enhanced tetragonal distortion across the ferrimagnetic transition temperatureTC= 258 K in comparison to the end compound MnCo2O4(TC∼ 180 K) with a characteristic ratioct/√2atof 0.99795(8) demonstrating robust lattice-spin-orbital coupling. However, in the second case Ti0.40Mn0.60Fe0.87Co1.13O4with higherB-site compositions, the presence of Jahn-Teller ions with distinct behavior appears to counterbalance the strong tetragonal distortion thereby ceasing the lattice-spin-orbital coupling. Both the investigated systems show the coexistence of noncollinear antiferromagnetic and ferrimagnetic components in cubic and tetragonal settings. On the other hand, the dynamical ac-susceptibility,χac(T) reveals a cluster spin-glass state with Gabay-Toulouse (GT) like mixed phases behaviour belowTC. Such dispersive behaviour appears to be sensitive to the level of octahedral substitution. Further, the field dependence ofχac(T) follows the weak anisotropic GT-line behaviour with crossover exponent Φ lies in the range 1.38-1.52 on theH-Tplane which is in contrast to theB-site Ti substituted MnCo2O4spinel that appears to follow irreversible non-mean-field AT-line behaviour (Φ âˆ¼ 3 +δ). Finally, the Arrott plots analysis indicates the presence of a pseudo first-order like transition (T< 20 K) which is in consonance with and zero crossover of the magnetic entropy change within the frozen spin-glass regime.

Magnetic exchange interactions and non-Debye relaxation in spin-3/2 frustrated Kagomé magnet Co3V2O8.

We report the experimental determination of the magnetic exchange parameter (J/kB= 2.88 ± 0.02 K) for the Spin-3/2 ferromagnetic (FM) Kagomé lattice system: Co3V2O8using the temperature dependence of dc-magnetic susceptibilityχ(T) data by employing the fundamental Heisenberg linear chain model. Our results are quite consistent with the theoretically reported nearest neighbor dominant FM exchange coupling strengthJex-NN∼2.45 K. Five different magnetic phase transitions (6.2-11.2 K) and spin-flip transitions (9.6-7.7 kOe) have been probed using the∂(χT)/∂Tvs.T, heat capacity (CP-T) and differential isothermal magnetization curves. Among such sequence of transitions, the prominent ones being incommensurate antiferromagnetic (AFM) state at 11.2 K, commensurate AFM state at 8.8 K, and commensurate FM state across 6.2 K. All the successive magnetic phase transitions have been mapped onto a single H-T plane through which one can easily distinguish the above-mentioned different phases. The magnetic contribution of theCP-TnearTN(11.2 K) has been analyzed using the power-law expressionCM=A|T-TN|-αresulting in the critical exponentα= 0.18 ± 0.01 (0.15 ± 0.003) forTTN), respectively for the Co3V2O8. It is interesting to note that non-Debye type dipole relaxation is quite prominent in Co3V2O8and was evident from the Kohlrausch-Williams-Watts analysis of complex modulus and impedance spectra (0⩽ß⩽1). Mott's variable-range hopping of charge carriers process is evident through the resistivity analysis (ρac-T-1/4) in the temperature range 275 ∘C-350 ∘C. Moreover, the frequency-dependent analysis ofσac(ω) follows Jonscher's power law yielding two distinct activation energies (Ea∼0.37 and 2.29 eV) between the temperature range 39 ∘C-99 ∘C and 240 ∘C-321 ∘C.

Spin glass states in multicomponent layered perovskites.

Temperature-dependent dc-magnetization and ac-susceptibility curves have been recorded for series of single and double layered Ruddlesden-Popper multicomponent perovskites with chemical formula A2BO4 and A3B2O7, respectively, with (La, Sr) on A-sites and up to 7 different cations on the B-sites (Ti, Cr, Mn, Fe, Co, Ni, Cu). The phase purity and chemical homogeneity of the compounds were investigated by X-ray diffraction and energy dispersive X-ray spectroscopy. Independently of the composition, spin glassiness is observed in both systems. Scaling analyses suggest the materials undergo spin glass phase transitions at low temperatures. Yet, qualitative differences are observed between the single-layered and double-layered systems, which are discussed in the light of the spatial dimensionality and magnetic interaction in layered oxide perovskites.

Reentrant canonical spin-glass dynamics and tunable field-induced transitions in (GeMn)Co2O4Kagomé lattice.

We report on the reentrant canonical semi spin-glass characteristics and controllable field-induced transitions in distorted Kagomé symmetry of (GeMn)Co2O4. ThisB-site spinel exhibits complicated, yet interesting magnetic behaviour in which the longitudinal ferrimagnetic (FiM) order sets in below the Néel temperatureTFN∼ 77 K due to uneven moments of divalent Co (↑ 5.33µB) and tetravalent Mn (↓ 3.87µB) which coexists with transverse spin-glass state below 72.85 K. Such complicated magnetic behaviour is suggested to result from the competing anisotropic superexchange interactions (JAB/kB∼ 4.3 K,JAA/kB∼ -6.2 K andJBB/kB∼ -3.3 K) between the cations, which is extracted following the Néel's expression for the two-sublattice model of FiM. Dynamical susceptibility (χac(f, T)) and relaxation of thermoremanent magnetization,MTRM(t) data have been analysed by means of the empirical scaling-laws such as Vogel-Fulcher law and Power law of critical slowing down. Both of which reveal the reentrant spin-glass like character which evolves through a number of intermediate metastable states. The magnitude of Mydosh parameter (Ω âˆ¼ 0.002), critical exponentzυ= (6.7 ± 0.07), spin relaxation timeτ0= (2.33 ± 0.1) × 10-18s, activation energyEa/kB= (69.8 ± 0.95) K and interparticle interaction strength (T0= 71.6 K) provide the experimental evidences for canonical spin-glass state below the spin freezing temperatureTF= 72.85 K. The field dependence ofTFobtained fromχac(T) follows the irreversibility in terms of de Almeida-Thouless mean-field instability in which the magnitude of crossover scaling exponent Φ turns out to be ∼2.9 for the (Ge0.8Mn0.2)Co2O4. Isothermal magnetization plots reveal two field-induced transitions across 9.52 kOe (HSF1) and 45.6 kOe (HSF2) associated with the FiM domains and spin-flip transition, respectively. Analysis of the inverse paramagnetic susceptibilityχp-1χp=χ-χ0after subtracting the temperature independent diamagnetic termχ0(=-3 × 10-3emu mol-1Oe-1) results in the effective magnetic momentµeff= 7.654µB/f.u. This agrees well with the theoretically obtainedµeff= 7.58µB/f.u. resulting the cation distributionMn0.24+↓A[Co22+↑]BO4in support of the Hund's ground state spin configurationS=3/2andS= 1/2of Mn4+and Co2+, respectively. TheH-Tphase diagram has been established by analysing all the parameters (TF(H),TFN(H),HSF1(T) andHSF2(T)) extracted from various magnetization measurements. This diagram enables clear differentiation among the different phases of the (GeMn)Co2O4and also illustrates the demarcation between short-range and long-range ordered regions.

Neutron diffraction evidence for local spin canting, weak Jahn-Teller distortion, and magnetic compensation in Ti1-x Mn x Co2O4 spinel.

A systematic study using neutron diffraction and magnetic susceptibility is reported on Mn substituted ferrimagnetic inverse spinel Ti1-x Mn x Co2O4 in the temperature interval 1.6 K [Formula: see text] T [Formula: see text] 300 K. Our neutron diffraction study reveals cooperative distortions of the TO6 octahedra in the Ti1-x Mn x Co2O4 system for all the Jahn-Teller active ions T = Mn3+ , Ti3+ and Co3+ , having the electronic configurations 3d 1, 3d 4 and 3d 6, respectively which are confirmed by the x-ray photoelectron spectroscopy. Two specific compositions (x = 0.2 and 0.4) have been chosen in this study because these two systems show unique features such as; (i) noncollinear Yafet-Kittel type magnetic ordering, and (ii) weak tetragonal distortion with c/a < 1, in which the apical bond length d c (T B -O) is longer than the equatorial bond length d ab (T B -O) due to the splitting of the e g level of Mn3+ ions into [Formula: see text] and [Formula: see text]. For the composition x = 0.4, the distortion in the T B O6 octahedra is stronger as compared to x = 0.2 because of the higher content of trivalent Mn. Ferrimagnetic ordering in Ti0.6Mn0.4Co2O4 and Ti0.8Mn0.2Co2O4 sets in at 110.3 and 78.2 K, respectively due to the presence of unequal magnetic moments of cations, where Ti3+ , Mn3+ , and Co3+ occupy the octahedral, whereas, Co2+ sits in the tetrahedral site. For both compounds an additional weak antiferromagnetic component could be observed lying perpendicular to the ferrimagnetic component. The analysis of static and dynamic magnetic susceptibilities combined with the heat-capacity data reveals a magnetic compensation phenomenon (MCP) at T COMP = 25.4 K in Ti0.8Mn0.2Co2O4 and a reentrant spin-glass behaviour in Ti0.6Mn0.4Co2O4 with a freezing temperature of ∼110.1 K. The MCP in this compound is characterized by sign reversal of magnetization and bipolar exchange bias effect below T COMP with its magnitude depending on the direction of external magnetic field and the cooling protocol.

An indigenous strain of potassium-solubilizing bacteria Bacillus pseudomycoides enhanced potassium uptake in tea plants by increasing potassium availability in the mica waste-treated soil of North-east India.

AIM: Potassium (K) is one of the three major nutrients required of plant growth and muriate of potash (MoP) is the only recognized chemical fertilizer used in agriculture. In many countries, 100% of the applied MoP is imported costing huge revenue. Application of suitable potassium-solubilizing bacteria (KSB) as biofertilizer could be an integral part of K management in arable soil. The object of this study was to evaluate K-solubilizing ability of a ubiquitous micro-organism as KSB to supplement K in soil. METHODS AND RESULTS: Strain (O-5) was isolated from tea-growing soil and identified as Bacillus pseudomycoides. Phylogenetic analysis revealed that the nearest neighbours of B. pseudomycoides strain O-5 were Bacillus cereus, Bacillus thuringiensis and Bacillus toyonensis. Though the species was first identified in 1998 and is ubiquitous in soil, the role of this group of micro-organisms in nutrient cycling in soil has not been studied before. Strain solubilized 33·32 ± 2·40 µg K ml-1 in mica waste (MW; muscovite type mineral)-amended broth after 7 days incubation at 30 ± 1°C. In a soil microcosm study under laboratory condition, B. pseudomycoides strain O-5 increased K availability by 47·0 ± 7·1 mg kg-1 after 105 days incubation, while the strain released 104·9 ± 15·3 mg K kg-1 in MW-treated soil. In this study, application of isolated B. pseudomycoides with MW significantly increased K availability in soil, and that in turn facilitated K uptake by tea plants. CONCLUSION: Based on the data, it could be inferred that B. pseudomycoides could mobilize K from bound form in soil and can be utilized as K-solubilizing biofertilizer especially in combination with MW for supplementing K in soil. SIGNIFICANCE AND IMPACT OF THE STUDY: Bacillus pseudomycoides strain O-5 has potential to be used as K-solubilizing biofertilizer in agriculture.

Effect of elevated carbon dioxide on soil hydrothermal regimes and growth of maize crop (Zea mays L.) in semi-arid tropics of Indo-Gangetic Plains.

To see the effect of climate change on the variation of soil hydrothermal regimes and growth of maize crop, an experiment was conducted in free-air carbon dioxide enrichment (FACE) facility during the kharif season of 2015 at Climate Change Facility of Indian Agricultural Research Institute, New Delhi, India. Under elevated CO2 and ambient condition, surface bulk density (BD) were 1.38 Mgm-3 and 1.44 Mgm-3, respectively but BD were not significantly different. During different days after sowing (DAS), in 0 to 10-cm soil depth, soil water content (SWC) in FACE varied between 14.58-20.70%, whereas in ambient condition, SWC variations were in between 19.33-22.94%. In 10 to 20-cm soil depth, SWC ranged in between 20.47-27.14% in FACE and 23.57-25.42% in ambient condition for different DAS. It is also observed that the arrival of peak surface ST was 1 h early in elevated CO2 condition. Photosynthetic rate increased by 5.7% on 44 DAS and 18.1% on 70 DAS under elevated carbon dioxide condition. Elevated carbon dioxide had reduced the stomatal conductance but the reduction was not significant. Like variation in air temperature for climate change, more intensive study is required to see the effect of climate change on soil temperature and its effect on crop growth.

Effect of elevated temperature on soil hydrothermal regimes and growth of wheat crop.

An attempt has been made to study the effect of elevated temperature on soil hydrothermal regimes and winter wheat growth under simulated warming in temperature gradient tunnel (TGT). Results showed that bulk density (BDs) of 0, 0.9, and 2.5 °C were significantly different whereas BDs of 2.8 and 3.5 °C were not significantly different. Water filled pore space (WFPS) was maximum at 3.5 °C temperature rise and varied between 43.80 and 98.55%. Soil surface temperature (ST) at different dates of sowing increased with rise in sensor temperature and highest ST was observed at S5 sensors (3.5 °C temperature rise). Temperature and its difference were high for the top soil, and were stable for the deep soil. Photosynthesis rate (µmol CO2 m-2 s-1) of wheat was lower at higher temperature in different growth stages of wheat. In wheat, stomatal conductance declined from 0.67 to 0.44 mol m-2 s-1 with temperature rise. Stomatal conductance decreased with increase in soil temperature and gravimetric soil moisture content (SWC). In TGT, 0 °C temperature rise showed highest root weight density (RWD) (5.95 mg cm-3); whereas, 2.8 and 3.5 °C showed lowest RWD (4.90 mg cm-3). Harvest index was maximum (0.37) with 0 °C temperature rise, and it decreased with increase in temperature, which indicated that both grain and shoot biomass decreased with increase in temperature. Intensive studies are needed to quantify the soil hydrothermal regimes inside TGT along with the crop growth parameters.

Effect of limited nickel availability on methane emission from EDTA treated soils: coenzyme M an alternative biomarker for methanogens.

Methanogens utilize simple carbon compounds to produce methane (CH(4)) under strictly anaerobic condition. During methanogenesis, methyl coenzyme M (MeCoM) is reduced by MeCoM reductase enzyme to CH(4) involving a nickel-containing cofactor F(430). In this experiment, strong chelating agent like ethylenediaminetetraacetic acid (EDTA) was applied in soil to study its feasibility for suppressing methanogen activity and CH(4) production in soil. Application of EDTA significantly (P≤0.05) reduced CH(4) production in soil. Application of 60 ppm EDTA (soil weight basis) was the most effective among all treatments. Applied EDTA forms complex compounds with heavy metals like nickel (Ni) and increases Ni concentration in soil solution. Since methanogenesis is intracellular process, it is necessary for methanogens to assimilate those Ni-EDTA complexes inside cell to utilize Ni in EDTA treated soils. Results indicated that methanogens cannot utilize Ni in the presence of EDTA and that significantly (P≤0.05) reduced mcrA gene (coding MeCoM reductase enzyme) copy number and Co-M concentration in soil. Due to high correlation (r=0.901(*)) between Co-M concentration and mcrA gene copy numbers, Co-M concentration could be used as an alternative biomarker for methanogens. Therefore, it could be propose that 60 ppm EDTA could be an optimum dose to suppress CH(4) emission from soil by restricting Ni availability to methanogens.

Surface-modified cobalt oxide nanoparticles: new opportunities for anti-cancer drug development.

The development of smart nanoparticles that can exhibit the anti-cancer activity, introduces better efficacy and lower toxicity for treatment. The present study was aimed to evaluate the anti-cancer activity of surface functionalized CoO nanoparticles against Jurkat (T-cell lymphoma) and KB (oral carcinoma) cell lines. The nano-sized cobalt oxide nanoparticles (CoO) was prepared by thermal decomposition method followed by surface modification using phosphonomethyl iminodiacetic acid (PMIDA). The PMIDA-coated CoO nanoparticle was characterized by X-ray diffraction, dynamic light scattering, and transmission electron microscopy; and the conjugation was analyzed by Fourier transform infrared spectroscopy. The resultant nanoparticles with an average size less than 100 nm measured by dynamic light scattering and transmission electron microscopy. Cytotoxicity study, flow cytometric analysis and scanning electron micrographs have been revealed that PMIDA-coated nanoparticles significantly enhances the cellular uptake of the nanoparticle and thus facilitates apoptosis of cancer cell (Jurkat and KB). For the application of PMIDA-coated CoO nanoparticles in the medical field, doxorubicin, a potent anti-cancer drug, has been used in similar fashion in this experimental design and all these effects or patterns were observed.

Changes in enzymatic activities and microbial properties in vermicompost of water hyacinth as affected by pre-composting and fungal inoculation: a comparative study of ergosterol and chitin for estimating fungal biomass.

In this experiment, three different fungal species, viz. Trichoderma viridae, Aspergillus niger and Phanerochaete chrysosporium, were inoculated in 7 day and 15 day partially decomposed water hyacinth to study their effect on enzymatic activities, microbial respiration and fungal biomass of the final stabilized product. The results suggested that increasing the duration of pre-composting from 7 days to 15 days did not show any significant effect on the activities of hydrolytic enzymes. Inoculation of fungi significantly (P < or = 0.05) increased cellulase, protease and acid and alkaline phosphatase activities. The highest value of ergosterol was recorded in A. niger-inoculated vermicomposts. Inoculation of P. chrysosporium in initial organic waste registered the highest chitin content in vermicompost. A comparison of fungal biomass and chitin content revealed a conversion factor of 2.628 with a standard deviation of 0.318. Due to significant correlation (r = 0.864), this conversion factor allows for the calculation of fungal biomass from chitin, which is comparatively more stable than ergosterol.

Changes in microbial properties and nutrient dynamics in bagasse and coir during vermicomposting: quantification of fungal biomass through ergosterol estimation in vermicompost.

In this experiment, different microorganisms viz., Trichoderma viridae, Aspergillus niger and Bacillus megaterium were inoculated in bagasse and coir with the objective to study their effect on nutrient dynamics and microbial properties, specially effect on fungal status in these waste materials. Fungal biomass (FBC) was calculated from the ergosterol content in the vermicompost samples. Inoculation of B. megaterium registered comparatively higher TP content in the final stabilized product. Vermicomposting increased microbial biomass carbon (MBC) and nitrogen (MBN) content in bagasse and coir. Microbial biomass carbon to nitrogen ratio (MBC/ MBN) was comparatively narrower in fungi inoculated vermicomposts and FBC/MBC ratio was increased up to 11.69 from 9.51 of control during vermicomposting.

Effect of microbial inoculation during vermicomposting of different organic substrates on microbial status and quantification and documentation of acid phosphatase.

In this experiment, three microbial strains were inoculated in two different organic wastes to study their effect on the humic acids content, acid phosphatase activity and microbial properties of the final stabilized products. Pyrophosphate extract of vermicomposts were analyzed through polyacrylamide gel electrophoresis to study the nature of a isozymes in different treatments. Results suggested that vermicomposting increased humic acids content and acid phosphatase activity in organic substrates and microbial inoculation further enhanced the rate of humification and enzyme activity. Although humic acids content in different microorganism-inoculated vermicomposts were statistically at par, acid phosphatase activity in these treatments was significantly (P<0.05) different. Results revealed that microbial respiration was increased due to vermicomposting, but a reduction in microbial biomass was recorded after stabilization of organic wastes. Although vermicomposting increased the value of microbial quotient (qCO(2)), microbial inoculation did not show any significant effect on qCO(2). The zymogram revealed that two isozymes of acid phosphatase (group II and group III) were present in all vermicompost samples and higher acid phosphatase activity in fungi-inoculated vermicomposts might be due to the presence of an additional isozyme (group I) of acid phosphatase.

Bio-functionalization of magnetite nanoparticles using an aminophosphonic acid coupling agent: new, ultradispersed, iron-oxide folate nanoconjugates for cancer-specific targeting.

The present study describes a systematic approach towards the design and development of novel, bio-functionalized, magneto-fluorescent nanoparticles for cancer-specific targeting. Biocompatible, hydrophilic, magneto-fluorescent nanoparticles with surface-pendant amine, carboxyl or aldehyde groups, to be later used for bio-conjugation, were designed using an aminophosphonic acid coupling agent. These magneto-fluorescent nanoparticles were further functionalized with folic acid, using diverse conjugation strategies. A series of new iron-oxide folate nanoconjugates with excellent aqueous dispersion stability and reasonably good hydrodynamic sizes under a wide range of physiological conditions were developed. These ultradispersed nanosystems were analyzed for their physicochemical properties and cancer-cell targeting ability, facilitated by surface modification with folic acid. The nanoparticle size, charge, surface chemistry, magnetic properties and colloidal stability were extensively studied using a variety of complementary techniques. Confocal microscopy, performed with folate receptor positive human cervical HeLa cancer cells, established that these non-cytotoxic iron-oxide folate nanoconjugates were effectively internalized by the target cells through receptor-mediated endocytosis. Cell-uptake behaviors of nanoparticles, studied using magnetically activated cell sorting (MACS), clearly demonstrated that cells over-expressing the human folate receptor internalized a higher level of these nanoparticle-folate conjugates than negative control cells.

A mathematical model on the effect of M. denticulata weed on different winter crops.

Many weeds interfere with the productivity of wheat and other winter annual crops; however, one common weed Medicago denticulata, appears to have a beneficial effect. An experiment was conducted at Agricultural Experimental Farm of the Indian Statistical Institute, Giridih, Jharkhand to observe the effect of M. denticulata (a legume) on different crops yield of barley (Hordeum vulgare Sensu lato), linseed (Linum usitatissimum L.), Indian mustard [Brassica juncea (L.) Czernj. & Cosson] and wheat (Triticum aestivum L.). The commensalisms interaction was studied, in which one species benefits, while the other is unaffected, between the crops, M. denticulata and other weeds, to observe the role of medicago as biological control agent of other weeds for enhancement of crop productivity. Further, a statistical test was performed to establish the effect of M. denticulata and weed infestations based on one-step Markov structure of the covariance matrix of the biomass. This permitted development of a mathematical model of a crop-M. denticulata-other weeds system and their interactions through direct and indirect competition for resources. Crops yield decreased considerably due to the presence of other weeds, while it increased due to introduction of medicago and hence medicago acted as a controlling agent in a crop-M. denticulata-other weeds system. Our mathematical analysis supported the experimental findings. The model parameters are estimated through a nonlinear least square and stochastic differential equations. Moreover, some thresholds for the growth of medicago population came out from our analysis that may be used as a biological control threshold for the enhancement of crop productivity.

Changes in organic - C, N, P and K and enzyme activities in vermicompost of biodegradable organic wastes under liming and microbial inoculants.

The aim of this work was to study the effect of different organic wastes, viz. cow dung, grass, aquatic weeds and municipal solid waste with lime and microbial inoculants on chemical and biochemical properties of vermicompost. Cow dung was the best substrate for vermicomposting. Application of lime (5 g/kg) and inoculation of microorganisms increased the nutrient content in vermicompost and also phosphatases and urease activities. Bacillus polymyxa, the free-living N-fixer, increased N-content of vermicompost significantly (p < or = 0.01) as compared to other inoculants.

Preparation of nanocrystalline alpha-Al2O3 using plant fiber.

Nanocrystalline alpha-Al2O3 ceramic powders have been prepared from aqueous poly vinyl alcohol (PVA)-aluminum nitrate solution and jute (plant fiber). Soluble Al-ion-PVA solution formed a uniform coating on the surface of jute once it dried completely. Slow hydrolysis of aluminum ion with ammonium hydroxide deposited aluminum hydroxide on the jute surface. Decomposition of the dried aluminum hydroxide-coated jute at high temperature (1150 degrees C/2 hrs) resulted in the formation of single-phase, nanocrystalline alpha-Al2O3 with the corresponding average X-ray and TEM particle size approximately 50 nm. Precursor and heat-treated powders have been characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analysis. This method can be used to produce high-temperature as well as low-temperature nanocrystalline oxides.

A comparative study of classical vs. desmoplastic medulloblastomas.

Classical and desmoplastic medulloblastomas (MBs) have been suspected to be biologically different, though comparative studies on markers of biological aggressiveness in these two variants are sparse in the literature. 87 classical and 43 desmoplastic variants of MB were studied with respect to clinical and histological characteristics, MIB-1 labeling index (MIB-1 LI), apoptotic index (AI), ratio of AI to MIB-1 LI, expression of p53 and Bcl-2 protein and 3-year progression-free survival. The only differences documented between the variants were with regard to age distribution and location. Thus, classical histology cases occurred predominantly in children and 80% were midline in location. In contrast, lateral location was seen more frequently with tumors of desmoplastic histology, which occurred in an almost equal distribution between children (56%) and adults (44%). No difference was noted between the variants with regard to proliferation index, apoptotic index, their ratio on or their molecular controls (p53 and Bcl-2). This was reflected in the clinical outcome wherein no significant difference was observed in the 3-year progression-free survival between the variants. It is concluded that the two histological variants of medulloblastoma are not different with regard to biological parameters of aggressiveness. The growth rate and clinical outcome in medulloblastomas have no correlation with the histological variant.

High-lipid diet intake is a possible predisposing factor in the development of hypogonadal osteoporosis.

The effects of a high-lipid diet on the intestinal transference of Ca2+ and the activities of intestinal enzymes were studied in ovariectomized rats. The plasma Ca2+ level and urinary loss of Ca2+ were also observed. Ovariectomy decreased both alkaline phosphatase (AP) and calcium ATPase (Ca(2+)-ATPase) activity, and also reduced the mucosal transference of Ca2+ in all parts of the small intestine. Although the plasma Ca2+ level did not change significantly, the urinary loss of Ca2+ was enhanced. A high-lipid diet supplement enhanced all these parameters in ovariectomized rats. It is therefore believed that a high-lipid diet may promote osteoporosis in ovariectomized rats as the result of Ca2+ transfer and enhanced urinary Ca2+ loss.

Mechanism of chloramphenicol-induced modulation of mouse ileal motility.

The effect of chloramphenicol (CAP) on the intestinal motility of mice was studied. Acute and chronic CAP treatment significantly increased the food transit time. CAP produced concentration-dependent inhibition of motility of the isolated ileum of mice. Prazosin, propranolol, atropine, ouabain and chlorpromazine all failed to modulate or counteract the CAP-induced inhibition of ileal motility. However, naloxone and hexamethonium slightly modified the inhibitory response of CAP. The inhibitory response of CAP was markedly counteracted by cystine, a guanylate cyclase inhibitor. CAP increased the activity of Ca(++)-ATPase in the ileum in all experiments. Our results suggest that the CAP-induced inhibition of the intestinal motility is not mediated through adrenergic, cholinergic and cAMP or through inhibition of the electrogenic pump. Compared to thiamphenicol (TAP), CAP, with a p-NO2 group in its structure, exhibited more pronounced alteration of both intestinal motility and Ca(++)-ATPase activity. We, therefore, suggest that greater inhibition of ileal motility induced by CAP is possibly a p-NO2-cGMP-Ca(++)-ATPase-mediated mechanism.