Effects of differentiated membranes on the developmental program of the cellular slime mold.

In the preceding paper isolated aggregation phase membranes (prepared from Dictyostelium discoideum cells which had proceeded through 12–14 hr of the developmental cycle) were found to be capable of preventing the aggregation and subsequent morphological development of vegetative cells when mixed with these and plated under normal conditions for slime mold development. In this paper we have extended the investigations on the nature of this interaction by monitoring the display of several developmentally controlled enzymes. It appears that exogenously applied aggregation phase membrane preparations are capable of influencing biochemical events inside D. discoideum cells through their interaction with the cell surface. This interaction leads to the induction or accumulation of some developmentally controlled enzymes, as well as the repression or excretion of others. The results suggest that the formation and maintenance of correct cell-cell contacts during normal development may be of crucial importance. They also show that changes in the specific activity of some developmentally controlled enzymes may in certain conditions be wholly divorced from both morphogenesis and the normal sequence of induction.     

Investigations of the toxic mechanisms of ammonia to fish–gas exchange in rainbow trout (Salmo gairdneri) exposed to acutely lethal concentrations

Exposure to acutely lethal un-ionised ammonia concentrations resulted in a 3.3-fold increase in oxygen consumption. This was associated with increases in ventilation volume, respiratory frequency and amplitude. 'Cough' frequency was not significantly affected. Heart rate and dorsal aortic blood pressure were increased and cardiac output was estimated to have more than doubled. Dorsal aortic blood Po₂ decreased but no significant changes in erythrocyte number, haematocrit, haemoglobin concentration, blood pH or P50 were observed. Possible toxic actions of ammonia were discussed and it was speculated that, as in mammals, ammonia may act by impairing cerebral energy metabolism.     

Acute toxicity effects of ibuprofen on behaviour and haematological parameters of African catfish Clarias gariepinus (Burchell, 1822)

Indiscriminate discharge of pharmaceutical waste into the aquatic ecosystem may pose serious health challenges to aquatic biota. The effect of acute exposure to ibuprofen was evaluated using changes in behaviour and haematological parameters under static bio-assay method in Clarias gariepinus. Test specimens were exposed to acute concentrations of ibuprofen (0.28, 0.33, 0.38, 0.43 and 0.48 mg l^?1) for 24, 48, 72 and 96 h durations respectively. Behavioural and phenotypic changes were observed in surviving fish. There were significant (p < 0.05) concentration and duration-dependent increases in erythrocyte (RBC), haemoglobin (Hb), pack cell volume (PCV) and leukocytes (WBC) in treated fish compared to the control. Insignificant decreases (p > 0.05) in mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) were observed in treated fish compared to the control. Ibuprofen elicited dose and duration- dependent decrease in neutrophil counts with the decreases being significant (p < 0.05) in the higher doses of 0.43 and 0.48 mg l^?1. Ibuprofen did not elicit any significant changes in monocytes, basophils and eosinophils. Changes observed in this study showed that ibuprofen negatively affected the health of the fish and we recommend that discharge of ibuprofen into the aquatic environment should be monitored and controlled.     

The Identity of “Chromium Malate”

Recently, several studies on the effects of a compound named “chromium malate,” with the proposed formula “Cr₂malate₃·xH₂O” where x = 3.5 or 5, on the health of healthy and diabetic rats have appeared. However, the compound is poorly characterized, and knowing the identity of this material could be important in the interpretation of the previous and of future studies on the effects of this compound in animals. Consequently, the synthesis, characterization, and identity of this material were explored. A combination of spectroscopic, magnetic, and elemental analyses and mass spectral studies reveal that the compound is probably a polymer, not a discrete molecule, and does not have the composition previously reported. The repeating unit of the polymer possesses an antiferromagnetically coupled trinuclear Cr(III) core. The current study suggests that previous reports on chromium malate and its effects in animals must be viewed with caution.

     

An artificial peptide with corticotropin-releasing factor receptor-2 (CRF-R2) selective properties: the role of primary structure in the induction of signal transduction pathways.

Considerable plasticity can occur within the amino acid sequence of amphiphilic peptide hormones. This is particularly evident within the corticotropin-releasing factor (CRF) family of peptides where, despite less than 15% sequence similarity among the four paralogous lineages, all are capable of acting as high affinity ligands to members of the CRF receptor family. This suggests that these peptides could undergo many mutational changes and remain as high affinity ligands to their receptors as long as the functional motifs do not change radically. Because paralogous peptide lineages are a product of genome duplications, additional genes encoding peptide-like sequences, which through mutation have lost their functional integrity, may exist. Function to these sequences may be restored if the appropriate motifs are reinserted into the primary structure. We screened rat genomic DNA with highly degenerate polymerase chain reaction (PCR) primers targeted to hybridize with the termini of CRF-related sequences. One set of sauvagine-based primers hybridized with a 120-bp sequence. The theoretical peptide sequence (SV4) showed similarity to the CRF family of peptides at the primary structure level. The encoded sequence was prepared by solid-phase synthesis and its activity assayed against mouse R1 and human R1/R2 receptors. SV4 did not bind to either mouse or human variants of the R1 receptor, but did bind to the R2 receptor with an affinity comparable to human CRF. SV4 exhibited a similar efficacy of cellular activation as CRF in trials quantifying the acidification rate of human R2alpha-transfected Chinese hamster ovary (CHO) cells, but not R1-transfected cells. SV4 utilizes adenylate cyclase as the principal secondary messenger of R2 signal transduction but, unlike urocortin or sauvagine, does not activate guanylate cyclase-, calcium- or mitogen-activated protein (MAP) kinase-mediated pathways. These data suggest that this artificial peptide may be useful to understand the cyclic adenosine monophosphate (cAMP)-dependent component of the CRF-R2 signal transduction cascade, and that additional sequences in the genome may be used to engineer bioactive peptides.     

The Ring Nematode,Criconemoides ornatus,on Peach and Centipede Grass

Criconemoides ornatus at 500, 1,000, and 10,000 specimens per 15-cm pot containing 1,500 cc of soil was not pathogenic or parasitic on "Loveli'' peach. The number of nematodes recovered was always less than the inoculum. Inocula of 1,000 and 10,000 specimens were pathogenic to centipede grass, but the 500 inoculum level was not. The number of nematodes recovered from parasitized centipede grass was considerably higher than the inoculum.