Dietary fatty acid modulation of events associated with mouse skin tumor promotion

Increasing levels of dietary corn oil have been correlated with inhibition of 12-O-tetradecanoylphorbol-13-acetate-(TPA) promoted skin tumorigenesis in mice (Leyton et al. Cancer Res. 51, 907-915, 1991). This study was undertaken to assess the effects of dietary corn oil on several events associated with tumor promotion. Three semipurified diets containing 15% (wt/wt) total fat with increasing levels of linoleate (0.8%, 4.5%, and 8.4%) supplied by corn oil were fed to mice for at least four weeks. Although incorporation of linoleate into epidermal phosphatidylcholine increased with increasing amounts of dietary corn oil, the elongated desaturated product of linoleate, arachidonate, was similar or decreased slightly in mice fed the three diets. Minimal activity of delta 6-desaturase, the rate-limiting enzyme in the conversion of linoleate to arachidonic acid, was found in the epidermis compared with the liver, suggesting that linoleate is not converted to arachidonic acid in the skin. Subcellular distribution of protein kinase C was altered in mice fed 0.8% linoleate, where 69% of protein kinase C activity was in the cytosol compared with 78% and 74% for groups fed 4.5% and 8.4% linoleate, respectively. Activation of partially purified protein kinase C isolated from mouse epidermis by linoleate was significantly lower (p < 0.01) than that isolated by arachidonic acid. TPA-induced vascular permeability was significantly greater (p < 0.05), whereas hyperplasia 48 hours after TPA treatment was significantly lower, in mice fed the 8.4% linoleate diet. However, TPA induction of ornithine decarboxylase activity did not appear to be significantly modified by dietary linoleate. These data suggest that cellular processes associated with carcinogenesis are affected by the level of dietary linoleate.     

Hypertension in paediatrics: can pre- and post-captopril technetium-99m dimercaptosuccinic acid renal scans exclude renovascular disease?

The presence of biogene monoamines in adult and larval Diphyllobothrium dendriticum (Cestoda) was investigated by high-performance liquid chromatography with electrochemical detection (HPLC-ED). The biogene amines serotonin (5-HT), dopamine (DA), noradrenaline (NA), and adrenaline (A) as well as many of their precursors and metabolites, comprising a total of 15 different substances, were analyzed. 5-HT, DOPA, DA, NA, and A were detected in the worm, with 5-HT, DOPA, and DA being the dominating amines. The DA metabolites DOPAC and 3-MT or the 5-HT precursor 5-hydroxytryptophan could not be detected, but two unidentified substances, believed to be catecholic, were present in the worm. A high concentration of DOPA was measured in the proglottids and especially in the eggs. This is the first report of A in a flatworm.     

Immobilisation of levansucrase on calcium phosphate gel strongly increases its polymerase activity

The goal of podiatric surgery in the older patient should be pain management with the highest degree of functional restoration. Thorough preoperative analysis, meticulous surgical technique, and careful postoperative planning are necessary to ensure a favorable surgical result. Each planned procedure must coincide with the specific needs of the individual patient while conforming to the body's physical limitations. A complete medical examination with laboratory studies is indicated due to the elderly patient's inherent diminished physical status. When the patient is deemed a proper candidate for surgery, the medical team, family, and friends should be consulted regarding immediate and long-term postoperative care. Strict adherence to these principles is in the best interest of both the practitioner and the older patient.     

Cardiac adaptation to increased systemic blood pressure in borderline hypertensive men

Two women, aged 28 and 32, presented with primary infertility and severe dysmenorrhea. The younger woman developed recalcitrant and recurrent firm vaginal, cervical and possibly endometrial lesions over a period of six years; the older patient had similar material in the cervix, endometrium and a fallopian tube. The lesions were composed of amorphous eosinophilic hyaline or necrotic material, shown by histochemical and immunoperoxidase stains to be partly fibrin. Pathologic examination showed that the lesions were similar to those of ligneous (pseudomembranous) conjunctivitis, a rare disease that may occasionally affect the lower female genital tract. However, neither patient had eye disease, and ligneous conjunctivitis has not previously been reported to involve the upper genital tract. Endometrial and tubal involvement could readily explain primary infertility and dysmenorrhea in these patients.     

Bidirectional long-term modification of synaptic effectiveness in the adult and immature hippocampus

Previously we showed that delivering 900 pulses to the Schaffer collateral-CA1 pathway at 1-3 Hz causes a lasting depression of synaptic effectiveness that is input specific and dependent on NMDA receptor activation (Dudek and Bear, 1992a). Here we describe experiments aimed at further characterizing this homosynaptic long-term depression (LTD) and comparing it with long-term potentiation (LTP). To address the question of whether depressed synapses can still be potentiated and vice versa, LTP was saturated with repeated high-frequency tetani, and then LTD was induced with low-frequency stimulation (LFS). A second strong tetanus then restored the potentiation, indicating that the same synapses whose transmission had been depressed by LFS were capable of subsequently supporting potentiation. In a complementary experiment, LTD was induced first and then a strong high-frequency tetanus was delivered. We found that the resulting LTP achieved the same absolute magnitude as that observed in control slices that had received the high-frequency stimulation alone. Next, the postnatal development of LTD was investigated in slices prepared from rats at 6-35 d of age. The consequences of LFS were far more pronounced in slices from young rats. LTD following 900 pulses at 1 Hz measured -45 +/- 4% in CA1 of rats less than 2 weeks old as compared with -20 +/- 4 in animals at 5 weeks postnatal. It was also found that LTD precedes the developmental onset of LTP in CA1. Finally, we addressed the question of whether LTD could be saturated by repeated episodes of LFS in slices prepared from 3-week-old rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Substrate requirements of bacterial phosphatidylinositol-specific phospholipase C

A series of symmetric short-chain phosphatidylinositols (PI), including dihexanoyl-PI, diheptanoyl-PI (racemic as well as D and L forms), and 2-methoxy inositol-substituted diheptanoyl-PI, have been synthesized, characterized, and used to investigate key mechanistic questions about phosphatidylinositol-specific phospholipase C (PI-PLC) from Bacillus thuringiensis. Key results include the following: (i) bacterial PI-PLC exhibits a 5-6-fold "interfacial activation" when its substrate is present in an interface as opposed to existing as a monomer in solution (in fact, the similarity to the activation observed with nonspecific PLC enzymes suggests a similarity in activation mechanisms); (ii) the 2-OH must be free since the enzyme cannot hydrolyze diheptanoyl-2-O-methyl-PI (this is most consistent with the formation of inositol cyclic 1,2-phosphate as a necessary step in catalysis); (iii) the inositol ring must have the D stereochemistry (the L-inositol attached to the lipid moiety is neither a substrate nor an inhibitor); and (iv) the presence of noninhibitory L-PI with the D-PI substrate relieves the diacylglycerol product inhibition detected at approximately 30% hydrolysis.     

Disulfide bonds in recombinant human platelet-derived growth factor BB dimer: characterization of intermolecular and intramolecular disulfide linkages

Interchain cystines of PDGF-BB dimer were characterized by Edman reaction and by SDS-PAGE analysis on the protein which was chemically cleaved at Trp-40. It was found that Cys-43 has a key role in dimer formation, asymmetrically cross-linked to a cysteine residue of another identical subunit. The remaining cystines participate in the intramolecular disulfide linkages. Pepsin digestion of PDGF-BB dimer generated several small peptides and one ubiquitous Cys-containing peptide. Sequence analyses of several Cys-containing peptides indicated the existence of three intramolecular disulfide linkages including Cys-16--Cys-60, Cys-49--Cys-97, and Cys-53--Cys-99. Two interchain disulfide bonds of Cys-43--Cys-52 between two subunits were deduced from the partial reduction and alkylation of PDGF-BB. This study provides chemically determined disulfide linkages of PDGF-BB.     

Sonolucent peripancreatic masses: differential diagnosis and related imaging

The third variable region (V3) of the HIV-1 gp120 envelope molecule appears to represent a target for naturally occurring neutralizing antibodies in HIV-1-infected individuals. In this report, we examined the extent of antibody cross-reactivity to a panel of V3-based synthetic peptides in six inbred strains of mice following repeated immunization with a baculovirus-derived recombinant gp160 (rgp160) preparation formulated with alum. The amino acid sequence of the rgp160 used in these immunizations was based upon the HIV-1 IIIB (LAI) isolate. Following five injections with rgp160, all six strains developed antibodies to the homologous IIIB-based V3 peptides, designated 304-321 and RP135. However, antibody cross-reactivity to the other nonhomologous V3 peptides was either undetectable or limited among the strains of mice examined. No in vitro neutralizing activity against HIV-1 was observed in sera from any of the six inbred strains of mice that were examined. These results suggest that repeated immunization of mouse strains with a rgp160/alum formulation leads to nonneutralizing antibodies directed against the V3 region which remain predominantly type specific.     

Radiation-induced DNA damage and repair in radiosensitive and radioresistant human tumour cells measured by field inversion gel electrophoresis

Radiation-induced DNA damage induction and repair was measured in two human squamous carcinoma cell lines with differing radiosensitive. Experiments were carried out with field inversion gel electrophoresis (FIGE), adapted to measure DNA double strand break (DSB) induction and repair in unlabelled cells. The sensitivity of the method was increased by introducing a hybridization membrane into the agarose gel. Damaged DNA accumulated on one spot on the membrane resulting in high local concentrations. This DNA was quantified using radioactively-labelled total human DNA as a probe. Dose response experiments for damage induction correlated well with the results using prelabelled cells. Linear DNA damage induction curves were observed with a sensitivity for the post-labelling method of 1 Gy. No differences in DSB induction were found, however, between the radiosensitive SCC61 and the radioresistant SQ20B cell line. Repair experiments were carried out with trypsinized cells with different doses and repair temperatures. The 10, 25 and 50 Gy doses resulted in 6, 13 and 50% of the DNA migrating out of the plug at 0 h. For both the cell lines 75-85% of the initial damage was repaired within 1 h at 37 degrees C at all three radiation doses, i.e. no significant differences were observed in repair rates or extent between the two cell lines. At 24 degrees C repair was slower than at 37 degrees C, and at 0 degree C no repair was observed. In summary, radiosensitivity differences at physiological temperatures could not be explained by differences in either induction or repair of DNA damage as measured by pulsed field gel electrophoresis.     

Quantitative brain SPECT in Alzheimer's disease and normal aging

To improve the diagnostic utility of brain single-photon emission computed tomography (SPECT) in Alzheimer's disease (AD), we have developed and evaluated an objective method of differentiating patients and healthy elderly controls using a quantitative image analysis protocol. HMPAO-SPECT image datasets from 29 patients with probable AD and 78 age-matched controls were registered to a common anatomic frame of reference. Activity levels within 120 standardized cortical volumes were determined by an automated procedure. Subjects were classified into normal and AD groups by quadratic discriminant analysis using two features: global average activity level and average normalized activity levels within the two clusters of standardized volumes identified as most significantly different in AD by analysis of covariance. The classification used split-half replication to ensure valid results. Classification performance quantified by the area under a binormal ROC curve fitted to the data was 0.923 +/- 0.036; at a threshold likelihood ratio of 1, the sample sensitivity was 91% and specificity was 86%. We conclude that quantitative SPECT accurately distinguishes AD patients from elderly controls.