Publications of Anthony Calhoun Clement (1909–1984)

Summary

Two zoeae and the megalopa of the majid crab Macropodia parva were obtained from laboratory material. At 25±1°C and 35% salinity, the first crab appeared 12 days after hatching; survival to the first crab instar was 27%. The larval stages are described in detail and compared with those of the previously described species of the genus Macropodia. Zoeal characteristics of M. parva that differentiate it from other known Macropodia larvae are the naked telson furcae and the absence, in zoea II, of the exopodal setae on the basis of the maxillule.     

Reproductive cycle of the winged pearl oyster,Pteria penguin (Röding 1793) (Pteriidae) in north-eastern Australia

The spawning cycle of the winged pearl oyster, Pteria penguin, was studied at Orpheus Island, north-eastern Queensland to observe seasonal changes in gonad development, mean oocyte diameter and sex ratio over time. A total of 201 oysters were collected over 10 sampling periods, approximately every 5–6 weeks (mean?=?20 oysters/sample). Histological analysis of gonads showed that spawning activity occurred mainly through the austral mid-spring to late summer (November to March), when mean monthly water temperature ranged between 27.5°C and 29.4°C. There was a primary spawning peak at the beginning of the spawning season in December, followed by a secondary peak in March. Mean oocyte diameter (µm) was highest during the warmer months, ranging from 31.2?±?2.4 in November to 36.2?±?3.2 in March, and sex ratio analysis showed the percentage of females in the population also peaked between 30% and 50% during this period.     

The larvae of Diadema setosum (Leske, 1778) (Camarodonta: Diadematidae) from South China Sea

Abstract

Diadema setosum (Leske, 1778) develops from small isolecithal eggs with a diameter of 84 ± 3 μm. Embryonic development took about 6.5–7 h and finished when a blastula left the fertilization envelope and became a larva. At this stage, the first pigment cells had appeared. At 23 h a prism developed; at 44 h a pluteus with one pair of arms had appeared; at 45 h of development plutei had two pairs of arms. The pigment cells colour the pluteus of D. setosum dark red. When 20-day-old larvae were mechanically stimulated, they flared their arms which may be defensive behaviour. During further development, the post oral arms of plutei grew to 1900 μm or more. Metamorphosis took place at about 40–45 days. At this time, five primary ambulacral podia were visible within the larval body. The duration of metamorphosis from the moment of larval settlement until the juvenile sea urchins began to move along the bottom was 40–60 min. The diameter of the test of the newly metamorphosed juvenile sea urchins was about 500 μm.     

Varied development of trunk segmentation in three related Upper Devonian phacopine trilobites

In many arthropods, the development of the trunk region is a complex part of post-embryonic development. Consideration of fossil ontogeny provides an additional source of data and a broader evolutionary perspective on the evolution of arthropod body patterning. Here, I examine the development of the thoraco-pygidial exoskeleton of three related phacopine trilobites from the Upper Devonian according to the integrated ontogenetic scheme proposed by Hughes et al. Pygidial shields assigned to three ontogenetic series gave us the opportunity to further explore the evolutionary pattern of the trilobite segmentation. The analysis showed a different mode of development in two of three species and thus reveals variability between the related taxa. Comparison of the boundaries of different aspects of ontogenesis ratifies the diversity of the segmentation process among trilobites and even among related phacopine species. Results include (i) in a synarthromeric trunk condition recorded to date, there has consistently been a preceding ‘equilibrium’ phase for the late meraspid pygidium and (ii) two developmental modes, i.e. both hypoprotomeric development and synarthromeric development, occur contemporaneously in closely related taxa. Such developments suggest that aspects of segmental development such as segment accretion and segment articulation were able to vary in a labile manner.     

Influence of solids retention time on membrane fouling: characterization of extracellular polymeric substances and soluble microbial products

The objective of this study was to investigate the influence of solids retention time (SRT) on membrane fouling and the characteristics of biomacromolecules. Four identical laboratory-scale membrane bioreactors (MBRs) were operated with SRTs for 10, 20, 40 and 80 days. The results indicated that membrane fouling occurred faster and more readily under short SRTs. Fouling resistance was the primary source of filtration resistance. The modified fouling index (MFI) results suggested that the more ready fouling at short SRTs could be attributed to higher concentrations of soluble microbial products (SMP). Fourier transform infrared (FTIR) spectra indicated that the SRT had a weak influence on the functional groups of the total extracellular polymeric substances (TEPS) and SMP. However, the MBR under a short SRT had more low-molecular-weight (MW) compounds (<1 kDa) and fewer high-MW compounds (>100 kDa). Aromatic protein and tryptophan protein-like substances were the dominant groups in the TEPS and SMP, respectively.     

Mathematical modelling and computer simulation of Brownian motion and hybridisation of nanoparticle–bioprobe–polymer complexes in the low concentration limit

A wide variety of nano-biotechnological applications are being developed for nanoparticles based on in vitro diagnostic and imaging systems. Some of these systems allow highly sensitive detection of molecular biomarkers. Frequently, the very low concentration of the biomarkers makes very difficult the mathematical simulation of the motion of nanoparticles based on classical, partial differential equations. We address the issue of incubation times for low concentration systems using Monte Carlo simulations. We describe a mathematical model and computer simulation of Brownian motion of nanoparticle–bioprobe–polymer contrast agent complexes and their hybridisation to immobilised targets. We present results for the dependence of incubation times on the number of particles available for detection, and the geometric layout of the DNA-detection assay on the chip.     

Note: NAMD–LP: Filtering and Translating NAMD-generated Files

Abstract

We have empirically tested limits of the magnitude of multiple time steps in molecular dynamics simulations of aqueous systems, and the extent to which these offer a means to shorten computation time. Three different steps were employed, δ₀t for calculation of “bonded” forces, δ₁t for calculations of short-range (< 6 Å) non-bonded forces, and δ₂t for long-range (< 10 Å) non-bonded forces. Each longer step was a multiple of the shortest one. The leap-frog integration algorithm was used with SHAKE for restraint of all bond lengths and water molecules. For a system of SPC water molecules, calculation of short-range non-bonded forces could be done with a time step δ₁t = 10 fs, without appreciable change of the average temperature and energy, radial distribution function or diffusion coefficient. These properties were found to be insensitive to the inclusion of long-range non-bonded forces. A multiple-step protocol with δ₀t = 2, δ₁t = 4 and δ₂t = 16 fs has been compared with a single-step procedure with δt 2 fs for small polypeptides in water. The exploration of conformation space, with crossing of low energy barriers, was tested with the glycine dipeptide and was found to proceed at similar rates. Mean, hysteresis and statistical error of the free energy for changing alanine to α-amino butyric acid in the dipeptide, calculated by the slow-growth method, proved independent of the cutoff distance or exact protocol, within 1 kJ/mol. In conclusion, we recommend, instead of use of a single time step of 2 fs at a 10 Å cutoff, use of a time step δ_t = 4 fs for short-range nonbonded forces and a time step δ₂t = 16 fs for long-range nonbonded forces for a 60% reduction of computation time.     

Computer Simulation of Liquid Methanol II. System Size Effects

Abstract

A series of molecular dynamics simulations of liquid methanol has been carried out on a supernode transputer array. Four system sizes from 125 to 512 molecules have been considered, in order to study the effect of system size on the calculated structural, orientational and dynamic properties. The dielectric constant and the dielectric relaxation time are compared with experimental data.     

Glycosylation: impact,control and improvement during therapeutic protein production

Abstract

The emergence of the biopharmaceutical industry represented a major revolution for modern medicine, through the development of recombinant therapeutic proteins that brought new hope for many patients with previously untreatable diseases. There is a ever-growing demand for these therapeutics that forces a constant technological evolution to increase product yields while simultaneously reducing costs. However, the process changes made for this purpose may also affect the quality of the product, a factor that was initially overlooked but which is now a major focus of concern. Of the many properties determining product quality, glycosylation is regarded as one of the most important, influencing, for example, the biological activity, serum half-life and immunogenicity of the protein. Consequently, monitoring and control of glycosylation is now critical in biopharmaceutical manufacturing and a requirement of regulatory agencies. A rapid evolution is being observed in this context, concerning the influence of glycosylation in the efficacy of different therapeutic proteins, the impact on glycosylation of a diversity of parameters/processes involved in therapeutic protein production, the analytical methodologies employed for glycosylation monitoring and control, as well as strategies that are being explored to use this property to improve therapeutic protein efficacy (glycoengineering). This work reviews the main findings on these subjects, providing an up-to-date source of information to support further studies.     

Behavioral and Morphological Studies of Fetal Neural Transplants into SCN-Lesioned Rats

We have studied the effects of fetal neuronal grafts on the temporal pattern of drinking behavior of suprachiasmatic nuclei (SCN)-lesioned adult rats. Additionally, in an independent set of animals, the immunohistochemical staining for vasopressin, vasoactive intestinal polypeptide, and neuropeptide Y and the retinal connections to the hypothalamus were studied. The behavioral experiments indicate that anterior hypothalamic transplants induced reorganization of the temporal pattern of drinking behavior when placed in the third ventricle of adult hosts bearing complete SCN lesions, but not when placed in a cavity in the occipital cortex. Such rhythmicity persists only when the animals were recorded under constant darkness but not under constant light, indicating that the restored rhythmicity was generated endogenously but that the oscillator was extremely sensitive to light. Fetal occipital cortex induced reorganization of the temporal pattern of previously arrhythmic hosts, but it disappeared when the animals were recorded under constant light or constant darkness. It is clear that this rhythmicity was exogenous. In contrast to the cortical transplants, the hypothalamic transplants showed a morphological organization similar to that found in the normal hypothalamus regardless of their placement in the host brain. From these observations it is concluded that development of neocortex is more affected by environmental factors than that of the hypothalamus. Both hypothalamic and cortical transplants induced sprouting of retinal fibers into the anterior hypothalamus and the grafted tissue. It is possible that such fibers could be the neuroanatomical substrate by which rhythmicity is induced by cortical tissue.