Capillary electrophoretic analysis of cathepsin D action on hemoglobin

The action of purified cathepsin D on hemoglobin was examined using micellar electrokinetic chromatographic separation of peptide products. Purified cathepsin D was incubated with hemoglobin in 40 mM Na-formate pH 3.1 at 37 degrees C for varying lengths of time. The reaction was stopped by the addition of the inhibitor pepstatin, and the peptide products were isolated from the reaction mixture by ultrafiltration with a 10,000 molecular weight cut-off (MWCO) microfuge type filter. Filtered samples were then separated in 100 mM Tris-Cl pH 8.5 containing sodium dodecyl sulfate (SDS) or Na-deoxycholate at micellar concentrations using a 50-microns (i.d.) fused-silica capillary. Detection was performed at 214 nm. It was found that Na-deoxycholate containing separations were superior in resolution and required less time. This technique was used to determine initial velocity (expressed as peak area per unit time) for nine peptides. Several peptides resulted after very short incubation times (< 10 min). This suggests that this approach may be useful for the determination of cathepsin D activity.

Elevated plasma glycosaminoglycans in chickens with tibial dyschondroplasia induced by a Fusarium oxysporum isolate

Chicken plasma glycosaminoglycans (GAGs) were isolated and digested. Their building block molecules, namely, glucosamine and galactosamine, were quantified by gas chromatography. The levels of these two amino sugars were elevated in broiler chickens with tibial dyschondroplasia (TD) induced by culture material of Fusarium oxysporum (FO), a mold isolated from corn originated from the endemic region of Kaschin-Beck disease (KBD) in China. As the TD severity score changed from 1 (healthy) to 2, 3, and 4, glucosamine increased by 10%, 33%, and 57% and galactosamine by 9%, 13% and 48%, respectively. The elevated plasma GAGs correlated to TD severity but not to the amount of FO material in the diets. This correlation of plasma GAGs to TD in chickens parallels the reported correlation of urinary GAGs to KBD in humans. The possibility of TD as an animal model for KBD is discussed.

In vivo dynamics of myosin II in Dictyostelium by fluorescent analogue cytochemistry

We used fluorescent analogue cytochemistry to study in vivo dynamics of myosin II in Dictyostelium discoideum. We labeled myosin with biotin or tetramethyl-rhodamine iodoacetamide (IATR). The labeled myosin shows normal activities as reversible filament assembly and Ca2+ and actin-activatable Mg(2+)-ATPase. We used the biotin-myosin as a probe examining the effects of microinjection on the amoebae and the ability to associate with endogenous actin cytoskeleton. The biotin-myosin incorporates into certain actin populations and localizes to the cortex with the highest accumulation in the posterior end of polarized amoebae. The dynamics in live amoebae were probed by TR-myosin. We monitored the dynamics for a long period to determined the dynamic reorganization corresponding specific cellular behaviors. The TR-myosin converges into a discrete actin- and myosin-rich structure located at the posterior end ("myosin-organizing center"). The rod-shaped TR-myosin exhibits linear orderly arrays emanating from the organizing center which extend about two-thirds of the cell length. The myosin arrays show a dynamic reorganization when the amoebae move. To examine if the observed myosin dynamics are related to filamentous (F-) actin, we disrupted the F-actin by cytochalasin D. The ratioed image of TR-myosin (vs. FITC-dextran) demonstrates that myosin in these cells accumulates in the cortex but does not form the organizing center. Overall, the results suggest that the filamentous myosin organizes into orderly arrays in the live cytoplasm and its translocation occurs by means of F-actin cables, converging into the organizing center.

Determination of 3-methylhistidine by capillary electrophoresis

The post-translational methylation of histidine to form 3-methylhistidine (3MH) is a modification principally found in contractile proteins, and thus, the level of free 3MH has been used to monitor muscle protein turnover. This work describes procedures for the capillary electrophoretic separation and determination of the phenylthiohydantoin (PTH) derivative of 3MH using uncoated fused-silica capillaries. The procedure described here utilized UV detection and resulted in a linear standard curve in the range of 2-15 pmole, which is more sensitive than previously reported HPLC methods using fluorescent detection. In addition, good agreement for theoretical amounts of 3MH in hydrolyzed rabbit skeletal muscle actin and myofibril preparations from bovine skeletal muscle cells was found.

In vivo effects of peroxovanadium compounds in BB rats

Peroxovanadium compounds, each containing an oxo ligand, one or two peroxo anions, and an ancillary ligand in the inner coordination sphere of vanadium, were synthesized, crystallized and characterized by 51V NMR as > 95% pure. They markedly decreased plasma glucose in insulin-deprived diabetic BB rats, with a nadir occurring between 60 and 100 min after intravenous, intraperitoneal or subcutaneous administration. Plasma glucose was reduced after oral administration in insulin-treated and in insulin-deprived BB rats. When compared to sodium orthovanadate, peroxovanadium compounds exhibited a markedly greater potency on a molar basis, and in relation to their toxicity. The in vivo potency can be predicted by the degree of phosphotyrosine phosphatase inhibition observed in vitro. These are the first agents other than insulin that can acutely and markedly reduce plasma glucose in hypoinsulinemic diabetic BB rats.

Immortalization of distinct human mammary epithelial cell types by human papilloma virus 16 E6 or E7

Multiple mammary epithelial cell (MEC) types are observed both in mammary ducts in vivo and in primary cultures in vitro; however, the oncogenic potential of different cell types remains unknown. Here, we used human papilloma virus 16 E6 and E7 oncogenes, which target p53 and Rb tumor suppressor proteins, respectively, to immortalize MECs present in early or late passages of human mammary tissue-derived cultures or in milk. One MEC subtype was exclusively immortalized by E6; such cells predominated in late-passage cultures but were rare at early passages and apparently absent in milk. Surprisingly, a second cell type, present only in early-passage tissue-derived cultures, was fully immortalized by E7 alone. A third cell type, observed in tissue-derived cultures and in milk, showed a substantial extension of life span with E7 but eventually senesced. Finally, both E6 and E7 were required to fully immortalize milk-derived MECs and a large proportion of MECs in early-passage tissue-derived cultures, suggesting the presence of another discrete subpopulation. Identification of MECs with distinct susceptibilities to p53- and Rb-targeting human papillomavirus oncogenes raises the possibility that these cells may serve as precursors for different forms of breast cancer.

Induction of tibial dyschondroplasia and suppression of cell-mediated immunity in chickens by Fusarium oxysporum grown on sterile corn

An isolate of Fusarium oxysporum from corn associated with Kaschin-Beck disease in humans was tested for its ability to induce tibial dyschondroplasia (TD) and toxicity in chicks. Both leghorn and broiler chicks were fed diets in which corn was replaced with varied amounts (0% to 50%) of the F. oxysporum culture grown on sterile corn, or with known TD-inducing agents. F. oxysporum did not affect body weight in either type of chicks. In leghorn chicks, neither F. oxysporum nor the known TD-inducing agents (F. equiseti, 4%; tetramethylthiuram disulfide [Thiram], 35 ppm) caused TD. However, F. oxysporum at high levels (50%) and the two known TD-inducing agents reduced interdigital cutaneous response to phytohemagglutinin-P challenge. In addition, Thiram also reduced body-weight gain by more than 17%. In female broiler chicks (Cornish Rock), F. oxysporum not only decreased cell-mediated cutaneous response to phytohemagglutinin-P but also increased TD incidence; these same effects were observed with F. equiseti and Thiram. Histological examinations revealed similar pathological changes among dyschondroplastic lesions induced by F. oxysporum, F. equiseti, and Thiram. Results of this experiment indicate that the isolate of F. oxysporum from the region in which Kaschin-Beck disease is endemic can induce TD in broiler chicks and that it is immunosuppressive.

Tumor cell-specific loss of p53 protein in a unique in vitro model of human breast tumor progression

Mutations of the p53 gene are the most frequent genetic lesion in breast cancer. Here, we examined p53 expression in a unique in vitro model of tumor progression derived from a single breast cancer patient (21T series). While the normal mammary epithelial, fibroblast and mesothelial cells derived from this patient expressed easily detectable functional p53 protein, the primary as well as metastatic tumor cell lines demonstrated a lack of p53 protein synthesis. 21T tumor cells failed to exhibit G1 cell cycle arrest upon exposure to gamma-irradiation, and their growth was suppressed by transfection of a normal p53 cDNA, demonstrating a lack of p53-mediated function in these cells. No p53 gene deletion or rearrangements were detectable. PCR and sequence analysis of the entire coding region of p53 gene revealed a novel mutation, an insertion of a single T within codon 33, which resulted in a frame-shift and early termination. The same mutation was observed in all 21T tumor cell lines. These results demonstrate a tumor cell-specific loss of p53 protein due to a frame-shift mutation, and suggest that p53 loss may occur at a relatively early step in breast tumorigenesis before metastatic seeding or emergence of tumor heterogeneity. In addition, the availability of normal and tumor-derived epithelial cells with known p53 sequences from a single breast cancer patient should facilitate understanding of the p53 regulation in mammary cells.

Loss of p53 protein during radiation transformation of primary human mammary epithelial cells

The causative factors leading to breast cancer are largely unknown. Increased incidence of breast cancer following diagnostic or therapeutic radiation suggests that radiation may contribute to mammary oncogenesis. This report describes the in vitro neoplastic transformation of a normal human mammary epithelial cell strain, 76N, by fractionated gamma-irradiation at a clinically used dose (30 Gy). The transformed cells (76R-30) were immortal, had reduced growth factor requirements, and produced tumors in nude mice. Remarkably, the 76R-30 cells completely lacked the p53 tumor suppressor protein. Loss of p53 was due to deletion of the gene on one allele and a 26-bp deletion within the third intron on the second allele which resulted in abnormal splicing out of either the third or fourth exon from the mRNA. PCR with a mutation-specific primer showed that intron 3 mutation was present in irradiated cells before selection for immortal phenotype. 76R-30 cells did not exhibit G1 arrest in response to radiation, indicating a loss of p53-mediated function. Expression of the wild-type p53 gene in 76R-30 cells led to their growth inhibition. Thus, loss of p53 protein appears to have contributed to neoplastic transformation of these cells. This unique model should facilitate analyses of molecular mechanisms of radiation-induced breast cancer and allow identification of p53-regulated cellular genes in breast cells.

Decreased cell-mediated immunity and lack of skeletal problems in broiler chickens consuming diets amended with fusaric acid

Young female broiler chickens fed diets amended with 0, 35, 75, and 150 mg fusaric acid (FA)/kg diet for 3 weeks showed no aberrations in behavior, feed intake, weight gain, or appearance of the visceral organs. Furthermore, there was no correlation between the dietary concentration of FA and incidence of tibial dyschondroplasia and leg-shape deformities. Ash content of dry fat-free tibiae was not influenced by FA; thus, no rickets was present in these chickens. FA enhanced the humoral response to sheep erythrocytes but significantly reduced cell-mediated cutaneous response to phytohemagglutinin-P.

Tibial dyschondroplasia of chickens induced by Fusarochromanone, a mycotoxin

Chicks were fed for 3 weeks a practical broiler starter diet amended with fusarochromanone (FC), a mycotoxin. In Hubbard broiler chicks, the highest test dose of FC (75 ppm) suppressed body weight by 33% and humoral response to sheep erythrocytes by 34% to 50%, and increased the incidence of tibial dyschondroplasia (TD) to 100%. The intermediate dose (35 ppm) significantly increased the incidence of TD in both types of broiler chicks (Hubbard and Indian River), but its effect on humoral response to sheep erythrocytes was not consistent across several experiments. A minimum dietary concentration greater than 20 ppm was required to significantly increase the incidence of TD. Excessive dietary copper or zinc (200 ppm) alleviated the effect of FC on TD. However, activities of copper-dependent ceruloplasmin and superoxide dismutase was not affected by FC. Cartilage mineral profiles in FC- or Thiram-induced TD differed from that of 1-day-old hypertrophic embryonic cartilage core (less K and Mn). FC did not induce TD in leghorn chicks.