Catastrophic storms, el nino, and patch stability in a southern california kelp community

Strong winter storms in southern California destroyed most of the canopy ofthe giant kelp Macrocystis pyrifera but not the patches of understory kelps in the Point Loma kelp forest near San Diego. Subsequent massive recruitment of Macrocystis juveniles and adults that survived the storms had low survival in the summer during the California El Ni?o of 1983. The combined disturbance may have long-lasting structural consequences for this community because, once established, the understory patches can resist invasion by Macrocystis.     

Effect of constitutive expression of porcine IGFBP-3 on proliferation and differentiation of L6 myogenic cells

We have previously shown that exogenous recombinant porcine IGFBP-3 (rpIGFBP-3) suppresses proliferation and differentiation of L6 myogenic cells in an IGF-I-dependent manner and suppresses proliferation of L6 myogenic cells via an IGF-I-independent mechanism. In order to assess the effects of endogenously produced IGFBP-3, we have transfected L6 myogenic cells with a pEF6/V5 vector containing pIGFBP-3 cDNA under the control of the human elongation factor 1alpha (hEF-1alpha) promoter and with the empty vector. We have isolated a cell population that constitutively produces porcine IGFBP-3 (tL6 cells) and a stable mock transfected cell population containing the empty vector (mtL6 cells). Constitutive expression of IGFBP-3 slightly reduced the expression of IGFBP-5 but had no effect on IGFBP-4 production by L6 myogenic cells. Immunoneutralization of IGFBP-3 increased both IGF-I- and Long-R3-IGF-I-stimulated proliferation of tL6 cells (58 and 33%, respectively) (P<0.01). These data indicate endogenous pIGFBP-3, like exogenous rpIGFBP-3, suppresses the proliferation of L6 myogenic cells via both IGF-I-dependent and -independent pathways. Immunoneutralization of IGFBP-3 also increased IGF-I-stimulated differentiation (21%, P<0.05) but had no effect on Long-R3-IGF-I stimulated differentiation of tL6 myogenic cells. Results indicate that exogenous and endogenous IGFBP-3 affect proliferation and differentiation of L6 myogenic cells in a similar way. Immunohistochemical localization data reveal that pre-incubation with anti-pIGFBP-3 dramatically reduces the level of intracellular IGFBP-3 in tL6 myogenic cells indicating that endogenously produced IGFBP-3 must first be secreted before it is internalized and that anti-pIGFBP-3 prevents internalization of IGFBP-3. TL6 and mtL6 cells provide a good system to further investigate the mechanisms by which IGFBP-3 affects proliferation and differentiation of myogenic cells.     

Successful Non-Surgical Transfer of Horse Embryos to Mule Recipients

Mules, hybrids resulting from the mating of a horse mare (Equus caballus, 2n = 64) to a Jack donkey (E. asinus, 2n = 62), are generally infertile. Five horse embryos were transferred non‐surgically to two cyclic and one acyclic recipient mules. In the mares and cycling mules, oestrus and ovulation were induced with, respectively, d ‐cloprostenol and human chorionic gonadotrophin (hCG). The acyclic mule, on the other hand, received oestradiol benzoate when the embryo donor was showing oestrus and progesterone after the donor had ovulated and until pregnancy diagnosis. Non‐surgical embryo collections were attempted on day 7 after ovulation and recovered embryos were transferred transcervically into the mules’ uteri. Mules that became pregnant were blood sampled serially for equine chorion gonadotrophin (eCG), progestagen and total conjugated oestrogen concentrations until around 6 months of gestation. The three embryos transferred to the acyclic mule did not produce any pregnancies whereas both embryos transferred to the cycling mules resulted in the birth of live foals. The peak concentration and duration of secretion of eCG differed markedly between the two pregnant mules, although both animals appeared to develop secondary corpora lutea beyond day 40 of gestation, as in normal intraspecies horse pregnancy. Moreover, the rise in serum oestrogen concentrations from around day 90 was also similar to that seen in normal pregnant mares. Parturition occurred spontaneously on day 348 of gestation in both mules and the resulting colt foals developed normally to weaning. Thus, cycling mules can carry a horse conceptus after non‐surgical embryo transfer and give birth to a normal mature foal.     

Functional analysis of CAR, the target sequence for the Rev protein of HIV-1

Expression of high levels of the structural proteins of the human immunodeficiency virus type 1 (HIV-1) requires the presence of the protein encoded by the rev open reading frame (Rev) and its associated target sequence CAR (cis anti-repression sequence) which is present in the env region of viral RNA. Extensive mutagenesis demonstrated that CAR has a complex secondary structure consisting of a central stem and five stem/loops. Disruption of any of these structures severely impaired the Rev response, but many of the stem/loops contain material that was unnecessary for Rev regulation and must be retained in these structures to avoid disturbing adjacent structures critical for CAR function. Probably no more than two of the described structural components are involved in sequence-specific recognition by regulatory proteins.     

Stem cell research. Reports give green light in Australia, Israel

BERLIN AND MELBOURNE--After 2 years of deliberation, an Australian government committee has endorsed legislation that would allow both human embryonic stem cell research and the derivation of ES cells from unwanted embryos created during fertility treatments. And in Israel, another country at the forefront of work on ES cells, a national bioethics committee has approved both the derivation of ES cells and research into therapeutic cloning.     

Geographically weighted regression estimation of the linear response and plateau function

Precision Agriculture - The objective of this paper is to modify the linear geographically weighted regression (GWR) estimator to accommodate the discontinuous join point, or “knot”, of...     

Effect of differentiation on levels of insulin-like growth factor binding protein mRNAs in cultured porcine embryonic myogenic cells

Insulin-like growth factor binding proteins (IGFBPs) have been shown to affect proliferation of several cell types via insulin-like growth factor (IGF)-dependent and IGF-independent mechanisms. The goal of this study was to determine if levels of IGFBP-2, -3, -4 and -5 mRNA changed during differentiation of cultured porcine embryonic myogenic cells. Total RNA was isolated from muscle cultures at various stages of differentiation and Northern blots of this RNA were probed with 32P-labeled cDNA probes specific for individual IGFBPs. Fusion, myogenin mRNA, and creatine phosphokinase activity were used as markers of differentiation. The level of IGFBP-3 mRNA in differentiating cultures (120 h in culture) was only one-third of the level in myogenin negative, nonfused cultures (72 h in culture) (P < 0.05, n = 4). In contrast, the level of IGFBP-3 mRNA in extensively fused cultures (144 h in culture) was increased by three-fold as compared to the level in myogenin negative, nonfused cultures (P < 0.05, n = 4) and approximately seven-fold as compared to the 120-h cultures (P < 0.05, n = 4). No significant change in the level of IGFBP-5 mRNA was observed during differentiation of myogenic cultures. IGFBP-2 mRNA levels were not significantly different at 72, 96 and 120 h, but at 144 h IGFBP-2 mRNA level was increased three-fold as compared to nonfused cultures (72 h) (P < 0.05, n = 4). IGFBP-4 mRNA was not detectable on Northern blots of total RNA from porcine myogenic cultures at any stage of differentiation. Changes in IGFBP-3 and IGFBP-2 mRNA levels are associated with differentiation of embryonic porcine myogenic cells in culture and this may indicate that these IGFBPs play a role in differentiation of these cells.