A re-evaluation of plasma sialic acid determination using the periodate resorcinol method versus the enzymatic method.

The concentration of plasma sialic acid was estimated using the modified chemical method and the more sensitive enzymatic method in 20 subjects with impaired glucose tolerance and 20 control subjects. The mean sialic acid concentration values of the control subjects and subjects with impaired glucose tolerance using the enzymatic method were 1.747 +/- 0.047 and 2.583 +/- 0.070 mmole/l and 1.753 +/- 0.067 and 2.591 +/- 1.02 mmole/l for the chemical method. The intra-assay coefficient of variation for the control subjects and for the subjects with impaired glucose tolerance were 1.963% and 1.583%, respectively, for the enzymatic assay and 2.728% and 2.431%, respectively, for the chemical assay. The inter-assay coefficient of variation for the control subjects and for the subjects with impaired glucose tolerance were 2.686% and 2.723% for the enzymatic assay, and 3.819% and 3.95% for the chemical assay. Since the values do not differ significantly, the chemical assay is a cost effective method that can be used in large epidemiological studies.

Interleukin-1 beta stimulates phospholipase A2 activity in rat C6 glioma cells.

Phospholipase A2 activities could be detected in both cytosolic and membrane fractions prepared from rat C6 glioma cells. The activities in both fractions were significantly increased by human recombinant interleukin-1 beta in a dose-dependent manner. Such a stimulation required a long-time exposure over 72 h and was partially inhibited by cycloheximide, a potent protein synthesis inhibitor. These results suggested that interleukin-1 beta may stimulate phospholipase A2 activity through its gene activation.

Interleukin-1 beta induces cytosolic phospholipase A2 gene in rats C6 glioma cell line.

Treatment of the rat C6 glioma cell line with interleukin-1 beta (IL-1 beta) resulted in an accumulation of cytosolic phospholipase A2 (cPLA2) in mRNA level. The increase of cPLA2 in mRNA level was observed at 6 hours after treatment of IL-1 beta and reached to the maximal level at 12 hours. The accumulation also remained sustained for up to 72 hours. Dose response curve of IL-1 beta showed that as little as 40 units/ml concentration induced the accumulation of mRNA and 100 units/ml concentration showed the maximal effect. In contrast, cyclooxygenase 2 gene was not affected with treatment of IL-1 beta.

Development of mouse ovarian follicles from primary to preovulatory stages in vitro.

An in-vitro culture system was developed in which primary mouse follicles from 12-16-day-old mice grew to the preovulatory stage. The important determinants of growth in culture were the inclusion of stroma with the primary follicles, the age of the mouse, the presence of FSH and LH, the use of culture dishes with a hydrophobic membrane and the use of post-menopausal human serum to supply growth factors. During culture the pieces of ovarian tissue containing the primary follicles coalesced to form characteristic spherical clusters. The cultured follicles appeared to be normal as determined by the appearance and organization of the granulosa cells, the appearance of the antrum and the accompanying steroidogenesis, but the ova had not resumed meiosis. The results show that the growth of mouse follicles starting from the primary stage is critically dependent on adequate concentrations of FSH.

Diminished production of thromboxane B2 and prostaglandin E by stimulated polymorphonuclear leukocytes from insulin-treated diabetic subjects.

As an initial step to investigate the possibility that abnormal polymorphonuclear leukocyte (PMNL) function in diabetes might be related to abnormalities of arachidonic acid metabolism, product of the cyclooxygenase pathway were assayed in PMNL from 27 insulin-treated diabetic subjects and 27 age- and sex-matched nondiabetic subjects. It was found that the major prostanoid products formed were thromboxane B2 (TxB2) and prostaglandin E (PGE). Production of both these substances was greatly enhanced in PMNL from control and diabetic subjects by exposure to a killed preparation of Staphylococcus aureus (S. aureus) or to zymosan. There was a marked reduction in the production of TXB2 by PMNL from diabetic subjects in response to stimulation by both S. aureus [670 +/- 98 (SE) versus 1010 +/- 76 pg/10(6) PMNL/90 min, P less than 0.01] and zymosan (583 +/- 53 versus 1034 +/- 46 pg/10(6) PMNL/90 min, P less than 0.001). Similarly, production of PGE was significantly reduced in diabetics in response to both S. aureus (145 +/- 29 versus 232 +/- 16 pg/10(6) PMNL/90 min, P less than 0.05) and zymosan (181 +/- 21 versus 271 +/- 27 pg/10(6) PMNL/90 min, P less than 0.01). There was no relation between the plasma glucose at the time of the test and the production of either prostanoid. Diminished production of cyclooxygenase products of arachidonic acid metabolism should be added to the known abnormalities of PMNL in diabetes. In view of the demonstrated or inferred effects of cyclooxygenase products on aspects of PMNL function, this observation may be important in understanding the pathogenesis of PMNL dysfunction in diabetes.

Increased expression of actin-like protein in human and ethylnitrosourea-induced tumors of the nervous system.

Twenty-one human intracranial tumors comprising 15 astrocytomas and 6 meningiomas and 26 ethylnitrosourea-induced rat neural tumors comprising 7 astrocytomas and 9 schwannomas were examined by indirect immunofluorescence for reactivity with a human anti-actin antibody. In cryostat sections both human and rat astrocytomas showed an increased reaction with the anti-actin antibody compared to normal astrocytes, and the reaction with astrocytomas was greater than that with meningiomas. Malignant rat schwannomas also showed prominent anti-actin staining contrasting with the negative reaction in normal Schwann cells. These in vivo observations were paralleled by concurrent studies with impression films and in vitro monolayer cultures of tumor tissue. The results, reviewed in the light pfo previous studies of anti-actin antibody reactivity with other nonneural tumors, suggest that an enhanced actin expression in vivo may be a general feature of the neoplastic state and that this increased expression may be more pronounced in malignant than in benign tumors.

Transfer RNA and aminoacyl tRNA synthetases in hormone dependent and independent mammary tumors of GR mice: I. Comparative study of the amino acid accepting capacity of the tRNA's in the presence of the homologous and heterologous enzymes.

Transfer RNA and aminoacyl tRNA synthetases were obtained from hormone dependent and independent mammary tumors of GR mice. We have studied the possible changes in the tRNA level by comparing the specific activities of the hormone dependent and independent mammary tumor tRNA's, but no differences were observed. Differences were found in the ability of enzymes from normal male GR mice liver, independent mammary tumor and dependent mammary tumor to cross-react with heterologous tRNA.

Transfer RNA and aminoacyl tRNA synthetases in hormone dependent and independent mammary tumors of GR mice: II. Isoacceptor tRNA's in hormone dependent and independent mammary tumors of GR mice.

The chromatographic elution profiles of 15 aminoacyl tRNA's from dependent and independent mammary tumors of GR mice have been studied using the reversed phase chromatography (RPC 5). The seryl tRNA from the dependent tumor displayed three isoacceptor peaks while only two isoacceptor peaks were observed in the case of the independent tumor when the tRNA's were charged in the presence of the GR mice liver enzyme. Charging of the tRNA's with radioactive leucine by homologous and heterologous enzyme revealed major differences in the leucyl isoacceptor species. The homologous dependent tumor system charges five leucyl tRNA species while the independent system only charges four. The leucyl tRNA from the dependent tumor has a new peak which is only recognized by its own enzyme, but this peak is either suppressed or completely absent in the independent tumor.