Towards a data transfer agreement for the South African research community: The empowerment approach.

The idea of a data transfer agreement (DTA) template for the South African (SA) research community is receiving increasing attention. While developing such a DTA template is certainly a worthwhile project, questions regarding the project's practical execution should be addressed, including how to best operationalise the envisioned DTA template, and the content of the envisioned DTA template. It is proposed that an empowerment approach be followed in operationalising the envisioned DTA template, which is contrasted with the regulatory approach followed with the material transfer agreement that the Minister of Health promulgated in 2018. While the regulatory approach would entail government making the use of the envisioned DTA template compulsory regardless of the quality of such a template, the empowerment approach, by contrast, entails a focus on developing a high-quality, professionally drafted DTA template for the SA research community and making the use thereof a matter of own choice. Regarding the content of the envisioned DTA template, four hot-button content provisions are analysed, and it is argued that SA research institutions and researchers should be empowered to: (i) have clarity and legal certainty regarding their ownership of data, where relevant; (ii) be able to commercialise their research findings without unnecessary contractual constraints; (iii) avoid falling into the trap of unlawful benefit sharing with research participants; and (iv) be aware that their legal role as responsible parties, where relevant, cannot be contracted out via a DTA.

Distribution of SchistoFLRFamide-like immunoreactivity in the adult ventral nervous system of the locust, Schistocerca gregaria.

SchistoFLRFamide (PDVDHVFLRF-NH2) is one of the major endogenous neuropeptides of the FMRFamide family found in the nervous system of the locust, Schistocerca gregaria. To gain insights into the potential physiological roles of this neuropeptide we have examined the distribution of SchistoFLRFamide-like immunoreactivity in the ventral nervous system of adult locusts by use of a newly developed N-terminally specific antibody. SchistoFLRFamide-like immunoreactivity in the ventral nerve cord is found in a subgroup of the neurones that are immunoreactive to an antiserum raised against bovine pancreatic polypeptide (BPP). In the suboesophageal ganglion three groups of cells stain, including one pair of large posterior ventral cells. These cells are the same size, in the same location in the ganglion and have the same branching pattern as a pair of BPP immunoreactive cells known to innervate the heart and retrocerebral glandular complex of the locust. In the thoracic and abdominal ganglia two and three sets of cells, respectively, stain with both the SchistoFLRFamide and BPP antisera. In the abdominal ganglia the immunoreactive cells project via the median nerves to the intensely immunoreactive neurohaemal organs.

Distribution of myomodulin-like immunoreactivity in the brain and retrocerebral complex of the locust, Schistocerca gregaria.

The distribution of myomodulin-like immunoreactivity is described for the brain and retrocerebral complex of an insect, the locust, Schistocerca gregaria. The locust brain contains 70-100 neuronal cell bodies and numerous neuropilar processes exhibiting myomodulin-like immunoreactivity. The most marked feature of the staining is a group of lateral tritocerebral neurones that form a highly immunoreactive tract that gives rise to a complex neuropile of stained processes in the dorsal tritocerebrum. This tract continues dorsally and bifurcates into a major branch that exists the brain via nervi corpora cardiaca 1 (NCC1) to innervate the corpora cardiaca and the corpora allata. A minor branch, consisting of several individual axons, combines with immunoreactive processes from the ventral nerve cord and generates a complex immunoreactive neuropile in the anterior and posterior regions of the protocerebrum. Immunoreactive processes are also found in the structured neuropile of the central body complex. Immunoreactive cell bodies are also found in the antennal lobes, in the lateral margins of the protocerebrum, in the optic lobes, and in a few cells in the pars intercerebralis. The results suggest that myomodulin-like neuropeptides may play roles as central neurotransmitters or neuromodulators in insects as well as being released into the circulation as neurohormones or acting as releasing agents for neurohormones in neurohaemal areas. They also further strengthen the idea that myomodulins, which were first identified in molluscs, may represent another interphyletic family of neuropeptides.

Distribution of myomodulin-like immunoreactivity in the adult and developing ventral nervous system of the locust Schistocerca gregaria.

The distribution of myomodulin-like immunoreactivity in the ventral nervous system of an insect, the locust Schistocerca gregaria, both in the adult and during development, is described. The results suggest the presence of a novel modulatory system in insects which uses myomodulin-like neuropeptides. The study also indicates that the myomodulins, which were first identified in mollusks, may represent another interphyletic family of neuropeptides. In the suboesophageal ganglion, immunoreactive cells occur in five groups. The processes from the two anterior ventral midline groups of cells project to the corpora allata via nervi corpora allata II. Thus myomodulin-like neuropeptides may be involved in the control of the release of juvenile hormone from the corpora allata. The thoracic ganglia contain three groups of immunoreactive cells, including a bilaterally symmetrical group of 12-15 posterior lateral cells, which project to the median nerve and its neurohaemal organs, suggesting a possible neurohaemal role for myomodulin-like peptides. Each thoracic neuromere also contains a single, intensely stained, dorsal unpaired median (DUM) cell that may correspond to the so-called H cell. In the abdominal ganglia, the staining shows sexual dimorphism, both in terms of the number of dorsal and ventral midline cells stained and in terms of the distribution of their immunoreactive processes. Myomodulin-like immunoreactivity is one of the earliest neurotransmitter/neurohormone phenotypes detectable during the development of the locust nervous system. It first appears in the single DUM cells in each of the thoracic neuromeres at 50% development, and the complete adult pattern of staining is present at 85-90% of development.

The differentiation between neuroglia and connective tissue sheath in insect ganglia revisited: the neural lamella and perineurial sheath cells are absent in a mesodermless mutant of Drosophila.

Two morphogenetic mutations, twist and Delta, that affect the embryonic development of Drosophila in known ways were used to examine the derivation and function of the outer layers of the central nervous system (CNS). Both the extracellular neural lamella, which ensheaths the CNS, and its source, the underlying perineurial sheath cell layer, fail to develop in Drosophila embryos that are homozygous for a loss of function mutation in the twist gene, and which thus lack mesodermal derivatives. The cell layer immediately below the perineurial sheath cells, here termed barrier glial cells, constitute the ion permeability barrier in wild-type embryos. They are present in twist mutant embryos, appear to be normal at the ultrastructural level, and function as a blood-brain ion barrier. The apparent derivation of perineurial sheath cells from mesodermal precursors distinguishes them from neurons, glia and other nonneural components of the CNS, such as tracheae, all of which are of ectodermal origin. We confirm Scharrer's interpretation of the relationship between the perineurium and underlying neuroglia. In embryos homozygous for the neurogenic mutant Delta, an embryonic lethal in which excess ventral blastoderm gives rise to neuroblasts, the CNS forms as an amorphous cell mass, with discontinuous perineurial sheath and barrier glial cell layers. We propose that the cell mass is permeable to lanthanum ions and fails to form a blood-brain barrier because volume growth prevents the formation of continuous surface cell layers.

Cell specific DNA-labelling in the repairing blood-brain barrier of the insect Periplaneta americana.

This study uses a recently developed technique for preserving the ultrastructure of cells in the insect CNS during immunohistochemical processing for 5-bromo-2-deoxyuridine incorporation into newly synthesised DNA. The results allow us to identify the proliferating cell classes in the regenerating blood-brain barrier. High resistance barrier cells do not label with the antibody but sheath cells clearly do. Intermediate cell types appearing during repair are identified. It is hypothesised that these cells generate matrix molecules for neural lamella repair and may represent transitional forms as invasive blood cells transdifferentiate into functional sheath cells.

The innervation of the closer muscle of the mesothoracic spiracle of the locust.

The closer muscle of the mesothoracic spiracle of the locust, Schistocerca gregaria is innervated by two excitatory motoneurones and also by processes of a peripherally located neurosecretory cell. Within the muscle, ultrastructural studies show the presence of two types of excitatory nerve terminal which differ in the content of dense cored vesicles and in their distribution. The ventral segment of the muscle is innervated predominantly by terminals with small clear vesicles and only an occasional dense-cored vesicle. The central part of the muscle is innervated predominantly by terminals with small clear vesicles and larger numbers of dense-cored vesicles. The dorsal segment of the muscle is innervated exclusively by a neurosecretory type innervation. The small neurohaemal organ of the median nerve close to the spiracle muscle is immunoreactive to an antibody raised against bovine pancreatic polypeptide but no immunoreactive processes enter the muscle itself. The muscle possesses specific octopaminergic receptors that increase cyclic AMP levels and the possibility that the neurosecretory input to the muscle is provided by either a central or peripheral octopamine containing neurone is discussed.

Secretion and movement of wingless protein in the epidermis of the Drosophila embryo.

The segment polarity gene wingless encodes a cysteine rich protein which is essential for pattern formation in Drosophila. Using polyclonal antibodies against the product of the wingless gene, we demonstrate that this protein is secreted in the embryo and that it is taken up by neighbouring cells. The protein can be found two or three cell diameters away from the cells in which it is synthesized. We discuss the possible mechanisms which are responsible for this spatial distribution and its regulation during embryogenesis.

Immunohistochemical localisation of the thymidine analogue 5-bromo-2-deoxyuridine in insect tissue: preservation of cellular ultrastructure.

The incorporation of the thymidine analogue 5-bromo-2-deoxyuridine and its detection by a specific monoclonal antibody, is proving a valuable tool in the study of cell kinetics and proliferation. To date, however, its use has been largely restricted to the light microscope level. The fixatives and processing required do not preserve the cellular ultrastructure. This paper details an immunohistochemical procedure which retains both structural details and preserves sufficient antigenicity for the use of the monoclonal at the electron microscopical level.

A concentration-dependent localization of octopamine-sensitive adenylate cyclase activity in locust skeletal muscle.

A concentration-dependent localization of octopamine-sensitive adenylate cyclase activity has been demonstrated in skeletal muscle of the locust, Schistocerca gregaria, using an histochemical technique. In the intermediate speed contracting muscle fibres from the fan region of the extensor-tibiae muscle of the locust hindleg, low concentrations of DL-octopamine (10(-8) M) induce reaction product preferentially in the sarcoplasmic reticular component of the dyads. At slightly higher concentrations (10(-7) and 10(-6) M) lower amounts of diffuse reaction product are also found in the non-dyad sarcoplasmic reticulum and at the sarcolemmal membrane, with occasional amounts of a less diffuse, punctuate product in the transverse tubule (T-tubule) component of the dyads. At higher concentrations (10(-5) and 10(-3) M) the predominant product is the dense, plaque-like accumulations of reaction product in the T-tubule component of the dyads. The results are discussed in terms of the likely physiological significance of the accumulation of reaction product in these different locations.

Histochemical localization of octopamine- and proctolin-sensitive adenylate cyclase activity in a locust skeletal muscle.

A histochemical technique for the localization of adenylate cyclase activity has been applied to the extensor-tibiae muscle of the hindleg of the locust, Schistocerca gregaria to localise the sites of action of the modulatory compounds octopamine and proctolin. Octopamine-sensitive adenylate cyclase activity can be demonstrated in fast and intermediate type muscle fibres but not in the limited number of purely slow muscle fibres (3-6) in the fan region at the proximal end of the muscle. In contrast the latter fibres are the only ones in the muscle to exhibit proctolin-sensitive adenylate cyclase activity. In both cases the bulk of the reaction product is localised in the sarcoplasmic reticulum component of the dyads, with lesser amounts occurring beneath the sarcolemmal membrane, in the non-dyad sarcoplasmic reticulum and in the T-tubule system. The results are consistent with physiological data suggesting that proctolin, but not octopamine, mediates its effects on the myogenic rhythm of contraction and relaxation in this muscle by changing the levels of cyclic AMP in the small group of slow muscle fibres which act as the pacemaker for this rhythm.

Enzyme effects on the connective tissues of an insect central nervous system.

The effect of various enzymes on the two connective tissue matrices of the cockroach central nervous system were investigated. Removal of the neural lamella, using collagenase, allows some of the cells which form the perineurium to pull out of this cell layer but the perineurial bracelet cells maintain an intact blood-brain barrier. Incubation of the nerve cord with hyaluronidase has little or no effect on the neural lamella and allows the selective removal of the matrix from the glial lacunar system. Partial removal of this matrix appears to have little effect on the ability of the axons to conduct action potentials at high frequencies. In addition to this difference in susceptibility of the neural lamella and lacunar matrices to different enzymes, there appears to be a difference between the lacunar matrix of the connectives and of the ganglia, the latter being more resistant to enzyme attack. There is no such difference in the neural lamella covering the ganglia and connectives.

Unusual structural features and assembly of gap and pleated septate junctions in embryonic cockroach CNS.

Junctional assembly in the developing CNS in cockroach embryos has been studied during the last half of neurogenesis. Atypical linear tracts of gap junctions are found to develop between attenuated cytoplasmic glial cell processes and their overlying perineurial cells during the last third of development. During both perineurial and glial gap-junctional formation, 13 nm E face (EF) intramembrane particles (IMPs), such as are characteristic of arthropod gap junctions, are seen initially as free IMPs; these then become arranged in loose irregular clusters or alignments and finally are aggregated in plaques. P face ridges (or EF grooves), typical of tight junctions, are found on the same perineurial membrane face as assembling gap-junctional PF pits (or EF particles). Pleated separate junctions also develop between adjacent perineurial processes during the last third of embryogenesis; these form by the apparent migration of individual 8 nm PF IMPs into meandering rows, which then become aligned in numerous orderly parallel stacks. Although all these junctions occur on the same perineurial membrane face, the IMPs that form the different junctional types never appear to be confused during junctional assembly. The cues to signal the advent of these precise patterns, however, are unknown.

X-ray analysis of Lymnaea stagnalis muscle fibres does not suggest that the sarcolemma is permeable to lanthanum ions.

The cross-striated muscle from the heart ventricle and the smooth penis retractor muscle of the freshwater snail Lymnaea stagnalis have been investigated by X-ray microanalysis to establish whether lanthanum can cross the plasma membrane, as has been reported by other investigators. Tissues were incubated in 1 mM ionic lanthanum before fixation in phosphate- or cacodylate-buffered fixative. X-ray mapping for emissions in the lanthanum energy range indicates a concentration of emissions that coincided only with the network of sub-surface transverse tubules formed by the invagination of the plasma membrane and with the plasma membrane/extracellular space interface. X-ray energy spectra were collected from various cell compartments; peak-to-background ratios were obtained and analysed statistically. Cacodylate buffer is less effective than phosphate buffer in precipitating lanthanum, but no evidence to suggest the redistribution of lanthanum in cacodylate-buffered preparations was found. Lanthanum is precipitated only in the sub-surface transverse tubules and at the plasma membrane/extracellular space interface in both heart ventricle muscle and penis retractor muscle, fixed in either phosphate or cacodylate buffer. There was no evidence of lanthanum precipitation in the background cytoplasm or on any cytoplasmic organelle. These results confirm our hypothesis that lanthanum does not cross the plasma membranes in these molluscan tissues.

Embryonic development of glial cells and their junctions in the locust central nervous system.

The embryonic development of the specialized glial cells that form the perineurial blood-brain barrier in the locust CNS has been studied by freeze-fracture and tracer uptake. These cells migrate to form bracelet cell arrangements around the nervous tissues between day 4 to day 10 of embryonic differentiation which lasts 14 days in toto. A number of different kinds of intercellular junction form between the bracelet cells from day 8 to day 13 of development. These include gap junctions with features characteristic of arthropods, which seem to assemble by lateral migration of 13-nm E face intramembranous particles (IMPs), which ultimately cluster to form a large number of mature plaques of varying diameters. Less numerous are tight junctions which serve to restrict entry of exogenous molecules, including lanthanum and cationic ferritin, thereby forming the blood-brain barrier; these appear to assemble by migration of individual 8- to 10-nm P face IMPs into ridges which are found between the overlapping fingers of the perineurial bracelet cell processes. Septate junctions also mature at this stage in embryonic development by apparent assembly of IMPs into characteristic aligned rows; these may serve to slow down the entry of positively charged molecules as well as being adhesive, although anionic ferritin may leak into the CNS even after septate and tight junction formation. The observed changes in cellular associations and the formation of the blood-brain barrier coincide with the onset of mature neuronal electrical properties and spontaneous synaptic input.

Glial cell contacts in insects: Effects of feeding on intercellular junctions.

The intercellular junctions associated with the modified glial cells of the perineurium have been examined in the ganglia and main abdominal nerves of the blood-sucking bug Rhodnius prolixus, both before and and after feeding, by means of freeze-fracture and tracer studies. It was found that the pleated septate junctions found in the main abdominal nerve have many fewer septa than those found in the ganglion. These junctions appear to provide the flexibility needed for the movement of cells which occurs to accommodate the tremendous increase in body size that takes place after a bloodmeal. On feeding and during the subsequent period of digestion the nerves stretch to double their length, yet the blood-brain barrier is maintained throughout. In the same manner as loosely interconnected tight junctions, septate junctions with fewer septa seem to form a junction which is able to respond readily to the stress of stretching. With feeding and afterwards the septate junctions become disorganized and disassemble, while the gap junctions and tight junctions remain intact. It is envisaged, therefore, that the primary function of the septate junction is adhesive.

Insect intercellular junctions: rapid freezing by jet propane.

The ventral nerve cord of the cockroach, Periplaneta americana, and that of the locust, Schistocerca gregaria, have been studied after rapid freezing by cryo-jet, using liquid propane. Such tissues, unfixed and uncryoprotected, have been compared with unfixed cryoprotected tissues, as well as with material fixed with glutaraldehyde and cryoprotected with glycerol or polyvinylpyrrolydone. The perineurial tight junctions in the cryo-jet-frozen tissues exhibit characteristic intramembranous P-face ridges, but frequently these are composed of smooth-surfaced strands, comparable to those seen with fast-freezing in mammalian tissues, rather than of bead-like fibres. The intramembranous PF ridges, characteristic of axonal and glial processes in the insect central nervous system, also display a smooth surface in rapidly frozen preparations. Prior fixation and/or cryoprotection produces a bead-like appearance in the ridges. The interglial gap junctions, after fast-freezing, exhibit both clustered connexon arrays in the E-face and loosely aggregated ones; hence the coupled state cannot be unequivocally associated with the latter configuration. The septate junctions between glial cells are unchanged after rapid freezing, exhibiting the typical rows of P-face intramembranous particles with complementary E-face pits that are found in replicas from fixed and cryoprotected tissues. The surfaces of the axons and glial processes exhibit pleiomorphic depressions and associated particles as well as PF pits with complementary EF mounds, both with associated IMPs. These structures are not usually seen after fixation or cryoprotection and may represent some kind of receptor structure, or axo-glial specialization.