BIRD-DISPERSAL OF PHYTOLACCA AMERICANA L. AND THE INFLUENCE OF FRUIT REMOVAL ON SUBSEQUENT FRUIT DEVELOPMENT

Characteristics of fruits, seeds, and ripening of Phytolacca americana were studied in New Jersey, USA to assess their importance in the dispersal strategy of this species. Removal by birds was directly related to the percent of ripe fruits available on a raceme. Fruit removal from a raceme resulted in lower fruit pulp and seed weights for fruits developing on the same raceme, but these differences probably do not influence probability for dispersal by birds. We demonstrate that characteristics of the fruit pulp may decrease seed availability for the primary seed predator, Peromyscus leucopus, and increase the time fruits are available for dispersal. We speculate on the significance of the sequential fruiting in Phytolacca and the relationship to availability of dispersal agents and high-lipid fruits. Sequential ripening and protection from predation result in seed dispersal from late August to early December.     

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A 65-year-old man undergoes a routine checkup before retiring. His wife has urged him to have his prostate examined, because she has read about testing for prostate cancer and a friend has just died of this disease. During the rectal examination, the man''s physician discovers some firmness in the right lobe of the prostate gland. The patient has had no urinary symptoms and is in excellent general health. Sexual function is normal. There is no history of prostate cancer; his father died of a stroke at age 86 years. Testing shows that the patient''s prostate-specific antigen level is 9.3 ng/mL, and he is referred to a urologist. Transrectal ultrasound-guided needle biopsy reveals adenocarcinoma with a Gleason score of 7 (intermediate grade). At a follow-up meeting with his physician, the patient says, "I have been doing some research, and it appears that I should have treatment. However, what is less clear to me is what form of therapy is best--surgery or radiation treatment. Please tell me what you can about the state of the art with respect to surgery."     

The Xenopus platelet-derived growth factor α receptor: cDNA Cloning and demonstration that mesoderm induction establishes the lineage-specific pattern of ligand and receptor gene expression

We have cloned the Xenopus PDGF α receptor cDNA and have used this clone, along with cDNA encoding PDGF A, to examine their expression pattern in Xenopus embryos and to determine the factors responsible for lineage specificity. Recombinant Xenopus α receptor expressed in COS cells exhibits PDGF-A-dependent tyrosine kinase activity. We find that receptor mRNA is present in cultured marginal zone tissue explants and in animal cap tissue induced to form mesoderm either by grafting to vegetal tissue or by treatment with recombinant activin A. In contrast, PDGF A mRNA is expressed in cultured, untreated animal cap tissue and is suppressed by mesoderm induction. These results suggest that ectodermally produced PDGF A may act on the mesoderm during gastrulation and that mesoderm induction establishes the tissue pattern of ligand and receptor expression. © 1993Wiley-Liss, Inc.     

The tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate enhances the proliferative response of Balb/c-3T3 cells to hormonal growth factors.

Stimulation of Balb/c-3T3 cell growth by TPA requires factors found in serum. We examined the interaction between TPA and serum growth factors in the stimulation of cell growth. The number of cells synthesizing DNA (incorporating 3H-thymidine) within 24 to 30 hours after the addition of TPA and the growth factors to density-inhibited Balb/c-3T3 cultures in serum-free medium was determined by autoradiography. With no additions or with TPA (30--300 ng/ml) alone, only 3--7% of cells synthesized DNA. However, TPA synergistically promoted DNA synthesis in combination with each of the defined serum growth fractions, platelet derived growth factor and platelet poor plasma. TPA also synergistically promoted DNA synthesis in combination with purified growth factors including fibroblast growth factor, insulin (10(-6)--10(-5)M), and epidermal growth factor. In all conditions, TPA enhancement of DNA synthesis also resulted in an increase in cell number. Because TPA synergistically enhanced the activity of each growth factor tested, it did not act identically to any of the growth factors.     

Recovery of Mycobacterium avium subspecies paratuberculosis from the natural host for the extraction and analysis in vivo-derived RNA

RNA has been extracted and analysed from in vivo-derived Mycobacterium avium subspecies paratuberculosis recovered from the natural host. The bacteria were selectively extracted from the intestinal tissue of two goats exhibiting clinical signs of Johne's disease. Small intestine was rapidly removed, luminal contents washed away and the mucosa and submucosa harvested. Mycobacteria in this material were released from the macrophages by isotonic lysis and differential centrifugation. RNA was extracted and compared with RNA extracted from bacteria grown in vitro. Real-time polymerase chain reaction was used to analyse the katG gene from the bacterial messenger RNA. The katG mRNA encoding the putative catalase/peroxidase showed differential expression in the in vivo and in vitro-derived samples. We hypothesize that the increase in katG expression for in vivo-derived M. paratuberculosis may represent a response to the oxidative stress encountered within the intra-macrophage environment.     

Simple method to identify bacteriocin induction peptides and to auto-induce bacteriocin production at low cell density

The production of some bacteriocins by lactic acid bacteria is regulated by induction peptides (IPs) that are secreted by a dedicated secretion system. The IP gene cbaX, for carnobacteriocin A production by Carnobacterium piscicola LV17A, and a presumptive IP gene (orf6), associated with the genetic locus for enterocin B production in Enterococcus faecium BFE 900, were fused to the signal peptide of the bacteriocin divergicin A from Carnobacterium divergens LV13 to access the general secretory pathway. The culture supernatants of C. piscicola UAL26 and Lactococcus lactis MG1363 containing either of these constructs were used to induce bacteriocin production by Bac(-) cultures of C. piscicola LV17A or E. faecium CTC492. The cbaX fusion product induced bacteriocin production by Bac(-) C. piscicola LV17A, but the orf6 fusion product did not induce bacteriocin production by E. faecium CTC492. This represents a relatively simple method of confirming the role of presumptive IPs. The transformation of C. piscicola LV17A with the CbaX gene under expression of the P32 promoter from L. lactis resulted in constitutive production of bacteriocin by either the dedicated transport apparatus or the general secretory pathway.     

Sterol carrier protein-2 expression alters phospholipid content and fatty acyl composition in L-cell fibroblasts

The effects sterol carrier protein-2 (SCP-2) expression on L-cell phospholipid levels and fatty acyl composition was assessed using L-cells transfected with the murine cDNA encoding for either the 15 kDa proSCP-2 or 13.2 kDa SCP-2. Expression of these proteins reduced total phospholipid mass (nmol/mg protein) by 24% and reduced the cholesterol to phospholipid ratio 60 and 28%, respectively. In 15 kDa proSCP-2 expressing cells, individual phospholipid class masses, excluding sphingomyelin (CerPCho), were reduced as follows: phosphatidylinositol (PtdIns) and phosphatidylserine (PtdSer) > ethanolamine glycerophospholipid (EtnGpl) > choline glycerophospholipid (ChoGpl). Furthermore, ethanolamine plasmalogen mass was decreased 25%, while choline plasmalogen mass was elevated 30% in 15 kDa proSCP-2 expressing cells. In 13.2 kDa SCP-2 expressing cells, phospholipid class mass was decreased as follows: PtdIns and PtdSer > ChoGpl. These changes in phospholipid mass resulted in altered cellular phospholipid composition. Expression of either protein differentially altered the type of fatty acid esterified onto the phospholipids. These effects included a greater proportion of polyunsaturated fatty acids and a reduction in saturated fatty acids, although 15 kDa proSCP-2 expression had a more robust effect on these parameters than did 13.2 kDa SCP-2 expression. In summary, expression of SCP-2 reduced individual phospholipid class mass, except for CerPCho, and altered the fatty acid composition of each phospholipid class examined.These results clearly demonstrate that SCP-2 expression altered basal phospholipid levels, suggesting that SCP-2 can alter the function of endoplasmic reticulum phospholipid synthetic enzymes.     

Four-point electrode measurement of impedance in the vicinity of bovine aorta for quasi-static frequencies

Results are presented here of experimental measurements using a four-point electrode technique to measure the complex impedance of bovine aorta submerged in Ringer's solution. Impedance measurements were taken at 250 microm intervals, ranging from 0 (the electrode directly on the surface of the tissue) to 10 mm. Frequencies ranged from 1 kHz to 10 MHz. Throughout this range, the measured impedance changed by an average of 400% when the electrode was 10 mm from the tissue as compared to when the electrode was in direct contact with the tissue. The change in impedance made it possible to determine when the electrode made contact with the arterial wall.