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Infrared and Raman spectra have been used extensively for the characterisation of the mineral component of mineralised tissues, especially bone and teeth. Often the vibrational modes of hydroxy groups and hydrogen phosphate are masked in the presence of substituent anions such as carbonate. The inelastic neutron scattering (INS) spectra are dominated by the vibrations of groups with hydrogen or with hydrogen riding on groups. Two sets of bands have been assigned to the hydroxy librations related to the hexagonal and monoclinic polymorphs of hydroxyapatite. Of the phosphate bands in brushite only the HPO42- bands are seen in the INS spectrum. These INS studies of synthetic hydroxyapatites and brushite present new opportunities for studying aspects of biominerals not accessible by standard vibrational techniques.

We describe a polymerase chain reaction which amplifies part of the Eco RI repeat unit of the fowl W chromosome. The resulting 447 bp fragment enables DNA from female birds to be identified. The composition of this DNA is confirmed by a nested polymerase chain reaction which specifically amplifies a known internal 263 bp region in this fragment. Using this technique it is possible to follow the fate of female cells in male germline chimaeras. The polymerase chain reaction fragment can be traced in cells of the embryonic and hatchling gonad and in adult sperm implying that cells containing the W chromosome are capable of being processed through the avian testis.

In the past decade there has been increasing recognition of the ability of cells to transmit signals by means of transient pulses of calcium ions. The system can use both extracellular and intracellular calcium sources to generate these effects. The relationship of this signaling system to the more commonly discussed properties of calcium homeostasis and calcium transport offers interesting opportunities for future research.

Granules isolated from the snail Helix aspersa and the shore crab Carcinus maenas have been studied by using scanning electron microscopy, powder X-ray diffraction and solid-state nuclear magnetic resonance (NMR). These amorphous deposits are largely based on pyrophosphate (P$\_{2}$O$\_{7}{}^{4-}$) and orthophosphate (PO$\_{4}{}^{3-}$) respectively. NMR indicates that water is evenly distributed throughout the pyrophosphate granules and that the PO$\_{4}{}^{3-}$ ions occupy distorted lattice sites. The $^{1}$H NMR spectra of the orthophosphate granules of desiccated and normal deposits indicate that water can move in and out of these solids. This movement is probably facilitated by the organic component, identified by $^{1}$H-$^{13}$C NMR, particularly in the crab granules. The distorted lattice, the presence of hydrated ions and the interactions with the organic matrix probably account for many of the properties of these solids and are relevant to the interpretation of their biological significance.

The chemosterilant drug busulphan (1, 4-butanediol dimethane sulphonate) has been applied to embryos of the domestic fowl at doses of from 1 to 500 μg after 48 hours incubation. Direct application caused a number of teratological effects. These could be avoided by injecting the drug in sesame oil directly into the yolk. Embryos treated in this way could be sterilised with an efficiency of over 95 per cent with minimal side effects to the young embryo. The technique provides a method for destroying primordial germ cells that will facilitate studies of germ cell/stroma interactions in the gonad and facilitate the production of transgenic birds.

The uptake of anthropogenic chemicals by benthic bivalves may occur through the water phase and also by the ingestion of particles from both the suspended matter and bottom sediments. Many chemicals sorb to sediments and, subsequently, are released in the digestive tract of animals. The assessment of sediment-bound chemicals has been difficult because of the complexity of the association between these chemicals and natural particles. To simplify this complexity, we previously devised a test system using artificial particles with known chemical structures. In the present work, we improved this experimental design by adding humic materials as a source of organic matter. Bioassays were conducted by exposing the fingernail clam Sphaerium corneum to sublethal levels of pentachlorophenol (PCP) in the presence or absence of the artificial particles, treated with or without a commercial preparation of humic acids. The results showed that the bioavailability and bioaccumulation could be explained on the basis of the interactions of PCP with the active groups and/or the backbone of the resins, both in systems with or without humic acids. This model may constitute a useful approach to modeling and predicting the uptake and accumulation of chemicals bound to natural sediments.

Chicken primordial germ cells were infected with a defective retrovirus containing the Escherichia coli lacZ gene and injected into the heart of stage 15 embryos. DNA samples were isolated from various tissues of the injected embryos at different stages of development and were examined for the presence of the lacZ gene using the polymerase chain reaction. Integration of the retrovirus DNA was demonstrated with a 32P-labelled oligonucleotide in five-, 10- and 18-day embryos. This quick procedure provides an opportunity for the early detection of foreign DNA in small numbers of transfected cells and is a valuable tool in the detection of transgenic animals.

In the fowl the primordial germ cells accumulate in the germinal crescent to the anterior of the two-day embryo. A simple ballistic device has been used to fire tungsten particles (mean diameter 1.5 microns) into this region. By coating these projectiles with vector DNA it is possible to transfect these cells. Hatchlings produced by this technique were raised to sexual maturity and shown to contain the foreign DNA in their sperm. G1 offspring containing this DNA were also produced in roughly 20% of these cockerels. In the majority of cases the vector DNA disappeared from the G1 generation as they matured suggesting that in these cases it had been transmitted episomally.

1. Embryos of the domestic fowl have been partially sterilised by injecting the drug busulphan into 24-h incubated eggs. 2. Some of these embryos were injected with primordial germ cells (PGCs) after 55 h of incubation to attempt to repopulate the gonads. 3. Primordial germ cells transfected with a defective retrovirus containing the reporter gene lac Z were shown to settle in these sterilised gonads. 4. Quantitative histology of 6-d embryos showed that busulphan produced 75% sterilisation but that PGCs could repopulate these gonads. 5. The technique of producing such germ line chimaeras is of value in studying cell kinetics, gonad differentiation and the production of transgenics.

The drug busulphan is known to be cytotoxic to migrating primordial germ cells (PGCs). A technique is described in which doses of 0, 25, 50 and 250 micrograms busulphan in 40 microliters sesame oil were injected into the yolk of White Leghorn eggs incubated for 0, 24, 48 and 72 h. The percentage survival values of these embryos showed that the older the embryo at the time of injection, the greater the survival. Increasing the dose of busulphan decreased the survival. The percentage of embryos showing abnormalities increased with higher doses of busulphan. The number of germ cells in histological sections from gonads of 16-day embryos was estimated and in embryos treated with 50 micrograms and 250 micrograms busulphan the number of germ cells was significantly less than in the controls. Eggs were injected with 50 micrograms busulphan at 24-30 h, and at 50-55 h the embryos received an intravascular injection of a germinal crescent cell suspension containing PGCs from Rhode Island Red embryos. Twenty hatchlings from these experiments were raised to sexual maturity. All these birds were fertile and half of the breeding groups producing offspring from the transferred germ cells at a rate of about 35% of the total. The technique would improve the efficiency of producing transgenic gametes.

Primordial germ cells (PGCS) are the progenitor cells for the gametes. They can be obtained from avian embryos by dissociating the germinal crescent region, where they accumulate, or by sampling the blood at the time of their migration to the gonad. PGCS were obtained from these sources and transfected with defective retroviruses. These manipulated cells were injected into recipient embryos to form chimaeras which grew to sexual maturity and produced offspring, some of which contained the foreign DNA. This is the first example of the direct use of PGCS to produce transgenic offspring.

1. Experiments were undertaken to attempt to sterilise fowl embryos with ultraviolet light. Such sterilised embryos would be useful as recipients of genetically manipulated germ cells. 2. The germinal crescents of embryos were exposed to a calibrated UV source at stages 4 and 8 to 10 of incubation for 30 s, 3 min and 10 min. Teratological and sterility effects were studied at periods up to 6 d of incubation. 3. Simply exposing embryos by opening the shell produced a number of abnormalities and mortalities. These decreased with the age of the embryo but increased with the dosage of irradiation. 4. Although there was abundant evidence for UV‐induced cell damage, the sterility of the embryos was usually less than 75%.

Manganese, zinc and calcium diphosphates have been modelled using atomistic simulation techniques. The ionic model was used for the cation–anion interactions. Parameters for the short-range interatomic potentials previously calculated using the electron gas methods for the diphosphate anion of α-magnesium diphosphate, were used together with specific metal oxygen parameters. The structural data for each compound were reproduced well, indicating that the anion parameters were transferable. These studies present new opportunities for modelling important aspects of biominerals which are not readily accessible to experimental studies.

The water/water and water/gas interfaces of the developing embryo are described. During incubation three main compartments are present the subgerminal amniotic and allantoic fluids. The formation composition and regulation of these solutions are considered as examples of the water/water interfaces. Evaporative water loss across the eggshell is considered as an example of a water/gas interface. The effects of this phenomenon are considered as having been oversimplified in the past because they ignore phase changes (condensing of water vapour) and the ability of the embryo to regulate its development according to the supplies available.

The snail Helix aspersa has large numbers of calcium cells in its hepatopancreas which contain membrane-bound intracellular granules of CaMgP 2 O 7 . These inorganic deposits are the sites of accumulation of a wide variety of cations and act as a detoxification mechanism that traps a number of dietary metals once they have entered the animal. This study concentrates on the mechanism of incorporation of manganese ions into these deposits by using electron microscopy, ultra-low-angle X-ray scattering and extended X-ray absorption spectroscopy. The results show that manganese ions cause a localized corrosion of these intracellular granules with a consequent release of calcium ions. This release appears to overwhelm the calcium-regulatory mechanisms of these cells and leads to their death and subsequent shedding into the lumen of the alimentary tract. The concept of intracellular corrosion is a novel interpretation of a previously unsuspected biochemical lesion.

At the turn of the last century there was an ever increasing world demand for pearls while at the same time their known fishing grounds were becoming exhausted. Some way of artificially increasing their production was obviously desirable, and the problem attracted considerable effort. It was an attempt to exploit a scientifically poorly understood phenomenon, and it is interesting, in retrospect, to relate these attempts to recent concepts of biomineralisation. Pearls are, of course, the layers of aragonitic calcium carbonate secreted by molluscs.

CALCIUM carbonate can exist in three polymorphic forms, which in the order of their usual stabilities are calcite, aragonite and vaterite. Calcite is the most stable and the least soluble, and, therefore, the form in which calcium carbonate would be expected to precipitate from sea-water. It has been pointed out, however, that when carbon dioxide was removed from natural sea-water a precipitate of aragonite formed1. Since this discovery, much work has been performed which confirms the observation, and there are a number of suggestions as to the cause of this phenomenon2.