A mass mortality of fishes caused by receding water levels in the vegetated littoral zone of the West Kleinemonde Estuary,South Africa

On 15 November 2017 the mouth of the West Kleinemonde Estuary breached following heavy catchment rains and increased river flow. The water level in the estuary following mouth opening decreased by 1.65 m within 24 h, resulting in an almost complete draining of the littoral zone where large beds of the aquatic macrophyte Ruppia cirrhosa and mats of the associated filamentous algae were present. As the water depth within the plant beds decreased, the macrophytes, together with the algal filaments, created an increasingly dense mat, trapping fish that were resident, foraging or passing through the littoral zone. By 16 November 2017 large numbers of fishes belonging to at least 20 species were trapped in pools and depressions within the littoral, as well as within the R. cirrhosa beds and filamentous algal mats in the lower reaches of this system. Other affected taxa included crustaceans, especially isopods, and large numbers of small bivalves attached to macrophyte vegetation. Beneficiaries of the fish kill, in terms of unexpected food availability, included a variety of piscivorous bird species and the Cape clawless otter Aonyx capensis. This is the first documented account of a diverse species fish kill associated with estuary mouth breaching.     

A longitudinal study of unsaturated iron-binding capacity and lactoferrin in unstimulated parotid saliva

Availability of iron is one important nutritional parameter for microbial growth in saliva. This longitudinal study measured the diurnal and day-to-day variations in the total iron (TI), total ironbinding capacity (TIBC), unsaturated iron-binding capacity (UIBC), and lactoferrin (LF) in unstimulated human parotid saliva. Saliva was collected from 15 young male subjects in the morning and afternoon hours each day for five consecutive days. The TI and TIBC were determined by flameless atomic absorption spectroscopy, and UIBC was determined by subtraction of TI from TIBC. The LF was determined by “sandwich” enzyme-linked immunosorbent assay (ELISA). One peripheral blood sample of each subject was also analyzed for TI, TIBC, and ferritin. The results showed no significant diurnal or day-to-day variation of TI, TIBC, UIBC, or LF in saliva for most subjects. However, significant between-subject variations were observed for most parameters. Variations ranged from subjects with constantly positive UIBC values to subjects with constantly negative UIBC values. The relationship between the LF values and the TI and TIBC values suggests that other iron-binding protein(s) are present in saliva. Also, saliva had significantly lower TIBC values than serum. This finding indicated that iron may be easily available in saliva. However, further studies are required to determine the relationship between UIBC value of saliva and oral and dental diseases, and also to detect the presence of other iron-binding proteins in saliva.     

Simulation of Gamma Rhythms in Networks of Interneurons and Pyramidal Cells

Networks of hippocampal interneurons, with pyramidal neuronspharmacologically disconnected, can generate gamma-frequency(20 Hz and above) oscillations. Experiments and models have shownhow the network frequency depends on excitation of the interneurons,and on the parameters of GABA_{{\rm A}}-mediated IPSCs betweenthe interneurons (conductance and time course). Herewe use network simulations to investigate how pyramidal cells, connected tothe interneurons and to each other throughAMPA-type and/or NMDA-type glutamatereceptors, might modify the interneuron network oscillation. With orwithout AMPA-receptor mediated excitation of the interneurons, the pyramidal cells and interneurons fired in phaseduring the gamma oscillation. Synaptic excitation of the interneuronsby pyramidal cellscaused them to fire spike doublets or short bursts at gammafrequencies, thereby slowing the population rhythm.Rhythmic synchronized IPSPs allowed the pyramidal cells toencode their mean excitation by their phase of firing relativeto the population waves.Recurrent excitation between the pyramidal cells couldmodify the phase of firing relative to the population waves.Our model suggests that pools of synaptically interconnectedinhibitory cells are sufficient to produce gamma frequency rhythms,but the network behavior can be modified by participation ofpyramidal cells.     

The respiratory chain of Helicobacter pylori: identification of cytochromes and the effects of oxygen on cytochrome and menaquinone levels

Abstract The quinone and cytochrome components of the respiratory chain of the microaerophilic bacterium Helicobacter pylori have been investigated. The major isoprenoid quinone was menaquinone-6, with traces of menaquinone-4; no methyl-substituted or unusual menaquinone species were found. Cell yield was highest after growth at 10% (v/v) oxygen and menaquinone levels (per dry cell mass) were maximal at 5–10% (v/v) oxygen. Helicobacter pylori cells and membranes contained b -and c -type cytochromes, but not terminal oxidases of the a -or d -types, as judged by reduced minus oxidised difference spectra. Spectra consistent with the presence of a CO-binding terminal oxidase of the cytochrome b -or o -type were obtained. The soluble fraction from disrupted cells also contained cytochrome c . There were no significant qualitative differences in the cytochrome complements of cells grown at oxygen concentrations in the range 2–15% (v/v) but putative oxidases were highest in cells grown at 5–10% (v/v) oxygen.     

Morphological correlates of locomotor performance in hatchling Amblyrhynchus cristatus

Previous studies of locomotor performance from a variety of perspectives often assumed that speed and limb length were strongly correlated. Despite support of this assumption from biomechanical models, few empirical studies have demonstrated a significant relationship between measures of locomotor capacity, such as maximum velocity, and length of the hindlimb at either the inter- or intra-specific level. We examined whether one measure of locomotor performance, maximum velocity, correlates with body size and elements of the hindlimb in hatchling marine iguanas (Amblyrhynchus cristatus). Larger hatchlings ran faster. Removing the effects of body size revealed that relative lengths of the tibia and hindfoot correlated with size-adjusted maximum velocity. Individuals with relatively long tibia and short pes were relatively faster than individuals with short tibia and long pes. Functional morphological analyses predict that femur length should correlate with maximum velocity. However, our analyses failed to support this prediction. Because hatchling marine iguanas exploit relatively open habitats, the relationship between maximum velocity and limb morphology may be interpreted as an adaptation enhancing escape from predators.     

Synthesis and antitumor activity of platinum complexes of protonated diamines

Complexes of the formula cis-[Pt(H$\text{N}\text{+}$^～N)(L)Cl₂], where (H$\text{N}\text{+}$^～N) are the protonated diamines including 3-aminoquinuclidine, N-aminopiperidine, piperazine, N-methylpiperazine, 1,1,4-trimethylpiperazine, and N-methyl-1,4-diazabicyclo [2,2,2] octane (N-methyl-dabco) and L = SCN^?, NO₂^?, Br^?, and F^?, were synthesized from the protonated diamine complexes, [Pt(H$\text{N}\text{+}$^～N)Cl₃]. The antitumor activities of the complexes were evaluated in vitro against L1210 murine leukemia cells, and ID₅₀ values for the L-substituted complexes were compared to values of the parent complexes. In each case it was found that replacement of a chloride ion by SCN^?, NO₂^?, Br^?, or F^?, either reduced or completely eliminated antitumor activity. This effect is explained in terms of the trans-directing ability of the ligand, L, compared to chloride. The NO₂-substituted complex of 3- aminoquinuclidine was tested in vivo and found to exhibit little or no antitumor activity.     

Foraging on patchily distributed prey by a cichlid fish (Teleostei,Cichlidae): A test of the ideal free distribution theory

Cichlid fish (Aequidens curviceps) distributed themselves and allocated their foraging time between two drift food patches in close approximation to the patch profitability ratio, as predicted by the ideal free distribution theory. The fish thereby achieved similar average feeding rates in the two patches, in two of three patch profitability ratio experiments. However, one major assumption of the ideal free model was violated, since individual fish differed in their competitive abilities for limited food resources, which resulted in unequal payoffs among individuals within each patch. Individual variation in feeding rates, and thus in competitive ability, was not related to despotism, but perhaps rather to individual differences in perceptual ability and in the ability to learn which patch was currently the more profitable. The strategy used by the fish to assess patch profitability included sampling available patches. However, individual fish switched (sampled) patches with varying frequency. Sampling had an associated cost, since high-frequency switchers had lower feeding rates on average than low-frequency switchers. Differences in foraging strategy among the fish therefore contributed to the observed in-equality in individual payoffs within patches.     

Regulation of glucose turnover at the onset of exercise in the dog.

The early responses of endogenous glucose production (Ra), glucose utilization (Rd), and glucoregulatory hormones to moderate treadmill exercise (12% incline, 100 m/min, 60 min) were examined in dogs. Rd increased rapidly and progressively from the start of exercise. The change in Ra, as estimated with a variable-volume model of glucose kinetics, was biphasic, with an abrupt increase by 8.5 +/- 2.3 mumol.min-1.kg-1, followed by a delayed further increase that matched Rd 11-22 min after the onset of exercise. The plasma glucagon-to-insulin molar ratio fell slightly at the onset of exercise and then increased gradually. The glucagon-to-insulin ratio was correlated with Ra over the entire exercise period (r = 0.63, P less than 0.0001), but not during the early part of exercise, when Ra increased rapidly. The catecholamine- (epinephrine plus norepinephrine) to-insulin molar ratio was correlated with Ra during the early period (r = 0.52, P less than 0.01) and over the entire period of exercise (r = 0.66, P less than 0.0001). Our results confirm previous demonstrations that the glucagon-to-insulin molar ratio is an important regulator of Ra during exercise. We hypothesize that the catecholamine-to-insulin molar ratio is important during the early period of exercise and possibly during late exercise as an additional regulatory factor to the glucagon-to-insulin molar ratio.