Plant growth analysis: an evaluation of experimental design and computational methods

Journal of Experimental Botany, Vol. 47, No. 302, pp. 1343–1351,September 1996 On page 1345, equation (2) should have read:      

Intracellular Calcium Dynamics and Cellular Energetics in Ischemic NG108-15 Cells Studied by Concurrent 31P/19F and 23Na Double-Quantum Filtered NMR Spectroscopy

Abstract: The role of voltage-sensitive Ca²⁺ channels in mediating Ca²⁺ influx during ischemia was investigated in NG108-15 cells, a neuronal cell line that does not express glutamate-sensitive receptor-mediated Ca²⁺ channels. Concurrent ³¹P/¹⁹F and ²³Na double-quantum filtered (DQF) NMR spectra were used to monitor cellular energy status, intracellular [Ca²⁺] ([Ca²⁺]_i), and intracellular Na⁺ content in cells loaded with the calcium indicator 1,2-bis-(2-amino-5-fluorophenoxy)ethane-N,N,N′,N′-tetraacetic acid (5FBAPTA) during ischemia and reperfusion. Cells loaded with 5FBAPTA were indistinguishable from unloaded cells except for small immediate decreases in levels of phosphocreatine (PCr) and ATP. Ischemia induced a steady decrease in intracellular pH and PCr and ATP levels, and a steady increase in intracellular Na⁺ content; however, a substantial increase in [Ca²⁺]_i (about threefold) was seen only following marked impairment of cellular energy status, when PCr was undetectable and ATP content was reduced to 55% of control levels. A depolarization-induced increase in [Ca²⁺]_i could be completely blocked by 1 µM nifedipine, whereas up to 20 µM nifedipine had no effect on the increase in [Ca²⁺]_i seen during ischemia. These data demonstrate that voltage-gated Ca²⁺ channels do not mediate significant Ca²⁺ flux during ischemia in this cell line and suggest an important role for Ca²⁺_i stores, the Na⁺/Ca²⁺ antiporter, or other processes linked to cellular energy status in the increase in cytosolic Ca²⁺ level during ischemia.     

Amyloid β Protein Primes Cultured Rat Microglial Cells for an Enhanced Phorbol 12-Myristate 13-Acetate-Induced Respiratory Burst Activity

Abstract: Activated microglia, often associated with neuritic amyloid plaques in the Alzheimer's disease brain, are likely to contribute to the progression of the disease process, e.g., by releasing neurotoxic reactive oxygen and/or nitrogen intermediates. In the present study, whether the amyloid β peptide (Aβ), the principal constituent of amyloid plaques, can stimulate microglial respiratory burst activity and/or microglial production of nitric oxide was examined. Using neonatal rat microglial cultures as a model, it was found that neither the spontaneous release of nitric oxide nor the lipopolysaccharide-induced production of nitric oxide was altered in cultures previously incubated with synthetic Aβ(1–40). for 24 h. In addition, no direct stimulatory effect of Aβ(1–40) on the respiratory burst activity was observed. Nevertheless, concomitant with an increase in the number of responsive cells, a profound priming of the phorbol 12-myristate 13-acetate-evoked production of superoxide anion was observed in Aβ(1–40)-treated cultures. Thus, both the maximal rate and the total phorbol 12-myristate 13-acetate-induced production of superoxide appeared to be statistically significantly higher as compared with untreated cultures. It is concluded that, as far as activation of the microglial respiratory burst is concerned, Aβ(1–40) may merely act as a priming rather than a triggering stimulus.     

Repression of cyclin D1 expression does not contribute to initiation or maintenance of cell transformation by adenovirus type 5 E1.

Expression of the gene encoding the cell cycle regulator cyclin D1 is strongly repressed in adenovirus type 5 E1 (Ad5E1)-transformed cells. Since cyclin D1 is a regulator of cell proliferation, modulation of its abundance may affect cell cycle control. Therefore, we studied the importance of cyclin D1 repression for cell transformation by Ad5E1. We found that forced expression of cyclin D1 does not affect the transforming potential of Ad5E1. Similarly, cyclin D1 overexpression did not affect the efficiency of colony formation, the proliferation rate, or the cell cycle distribution of Ad5E1-transformed cell lines, whereas the colony formation of untransformed cell lines was strongly inhibited. Thus, repression of cyclin D1 expression is not required for initiation or maintenance of cell transformation by Ad5E1. In addition, we show that the growth-suppressive effect of cyclin D1 correlates with cyclin D1 binding to cdk4 rather than to proliferating cell nuclear antigen PCNA.     

EPISTASIS AS A SOURCE OF INCREASED ADDITIVE GENETIC VARIANCE AT POPULATION BOTTLENECKS

The role of epistasis in evolution and speciation has remained controversial. We use a new parameterization of physiological epistasis to examine the effects of epistasis on levels of additive genetic variance during a population bottleneck. We found that all forms of epistasis increase average additive genetic variance in finite populations derived from initial populations with intermediate allele frequencies. Average additive variance continues to increase over many generations, especially at larger population sizes (N = 32 to 64). Additive-by-additive epistasis is the most potent source of additive genetic variance in this situation, whereas dominance-by-dominance epistasis contributes smaller amounts of additive genetic variance. With additive-by-dominance epistasis, additive genetic variance decreases at a relatively high rate immediately after a population bottleneck, rebounding to higher levels after several generations. Empirical examples of epistasis for murine adult body weight based on measured genotypes are provided illustrating the varying effects of epistasis on additive genetic variance during population bottlenecks.     

Perinatal Steroid Treatments Alter Alloparental and Affiliative Behavior in Prairie Voles

This experiment was designed to examine the hypothesis that perinatal manipulation of gonadal or adrenal steroids can alter the subsequent expression of juvenile parental (alloparenting) and affiliative behavior in prairie voles (Microtus ochrogaster). Corticosterone (PRECORT), testosterone (PRE-TP), or oil injections (PRESES) were given on Prenatal Days 12–20 or on Postnatal Days 1–6 (CORT6, TP6, or SES6, respectively). Alloparenting was reduced significantly in females in the CORT6 group and in males in the TP6 group. Sibling affiliative preferences were increased significantly in PRE-TP females and stranger preferences were increased in TP6 and CORT6 females. The results suggest timing is a critical factor determining whether hormones have a facilitative or inhibitory effect on alloparental and affiliative behavior in prairie voles. In this species, corticosterone and testosterone have similar organizational effects on affiliative behavior in females. Alloparental behavior is inhibited by postnatal corticosterone administration in females and by postnatal testosterone administration in males, whereas prenatal steroid administration had no significant effect on alloparenting in either gender.