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Non-parabolic growth of intermediate phases in CuSn binary diffusion couples has been observed at 220° C. The deviation from parabolic behaviour may be attributed to grain boundary diffusion. Diffusion coefficients for both the?-(Cu3Sn) and?-(Cu6Sn5) phases are typically of the order of 2×10-11 cm2 sec-1, and are in general agreement with other published values.

Certain nonlinear properties of molluscan neurones suggest that network activity could be described in relation to nonlinear relaxation oscillators. A specific example is fitted by the Van der Pol equation with an exponentially decaying damping coefficient, and changes in the associated energy and sensitivity are considered. More precise details of the interaction pattern are determined by analysis of a single cycle of burst activity, and it is shown that there are two states of activity, depending on the balance of presumed inhibitory components. Previous results are discussed in relation to an overall decaying oscillation. Changes in subcomponents of a cycle are described for decaying sequences and the constancy of synaptic interaction is demonstrated. The results are briefly discussed in relation to catastrophe theory and learning.

The central generation of burst activity was investigated in the buccal ganglia of Lymnaea. Eight different patterns of burst activity were generated by one or two consecutive phases of compound synaptic potentials resulting from activity of neurones outside the population of recorded neurones. These inputs acted upon the different endogenous properties of buccal neurones such as post-inhibitory rebound and spike adaptation. Effects of synaptic inputs were reinforced by electrotonic coupling of some buccal neurones of the same type.

Electromyographic recordings from the buccal muscles of Lymnaea during feeding has shown that there are 4 component phases in the feeding cycle. Cinephotography of feeding cycles has confirmed that these correspond to protraction, 2 phases of retraction, and an inactive phase. The 4 phases of muscle activity can also be related to the cycle of neural activity described previously (Benjamin & Rose, 1979). Thus types 6, 4 group, and type 8 cells are motoneurones involved in protraction and the two retraction phases, while the type 5 cell fires in the inactive period. The combination of physiological and anatomical approaches has led to the suggestion that the single and double input cells described by Benjamin & Rose (1979) are involved with the control of buccal and oesophageal activity respectively.

The morphology of seven types of identified neurones in buccal ganglia of Lymnaea was investigated by intracellular injection of Procion Yellow and retrograde injection of cobaltous chloride into the nerve roots of the buccal ganglia. The results provided anatomical support for the electrophysiological findings that some cells are motoneurones for muscles of the buccal mass (type 4-group cells, types 6 and 8 cells). Others project to nerves innervating oesophageal tissue (types 2, 3 and 5 cells) and to pro-oesophageal tissue (types 3 and 5 cells). The type-i cells project to the salivary gland ducts and are similar to the salivary gland motoneurones found in other molluscan species.

In-process and off-line rheometry studies are reported for compounds based on Mg(OH)2filled low density polyethylene, some of which were first subjected to a range of strain histories in typical compounding operations. In the study reported here, the compounds were processed using an instrumented, computer monitored single screw extruder in the IRC laboratories, fitted with in line rheometers (ILR). In initial experiments a four sensor ILR slit die was used for the in-process shear rheometry, and a Rosand RH7 twin bore capillary rheometer for off-line shear and entry pressure measurements. Off line and in-line results are compared, showing good agreement for shear. Estimates have been obtained for the sensitivity to filler loading of the off line rheometer (shear flow and entry pressure measurements), and the 4 sensor ILR (shear flow measurements), which indicate that the ILR offers similar resolution of filler level to the off line rheometer at the higher loadings, although the ILR appears to have much lower sensitivity at higher shear rates at lower loadings, an effect which appears to be related to processing effects on the rheology of the compound rather than the measurement ability of the ILR. The ILR was also able to discriminate between samples with differing processing histories. Results from a six-sensor ILR die have shown good agreement in shear flow measurements, and have added the ability to measure entry pressures, which are compared with off-line measurements.

The feeding cycle of Lymnaea is generated by a network of three types of interneurone, N1, N2 and N3. This network is driven by the slow oscillator (SO) interneurone described in the previous paper. Interaction between the different interneurones is dependent on both connectivity and endogenous properties, and utilizes such properties as post-inhibitory rebound and self-feedback within electrically-coupled populations. Each of the four components of the interneuronal network (SO, N1, N2 and N3) is responsible for a different phase of synaptic input to the follower cell population which was previously shown to directly control feeding movements.

Concentrations of cortisol and testosterone in the plasma of adult male rhesus monkeys living in social groups were determined during a 27-h period. Capture and venipuncture of experienced, conditioned animals did not lead to a fall in the concentration of testosterone in the plasma during the 90 min immediately after removal from the group. Both plasma cortisol and plasma testosterone concentrations showed a significant fall and rise in samples collected every 3 h during a 27-h period, even though there was considerable individual variation. During the autumn breeding season, animals showed higher concentrations of testosterone at both 10.00 and 22.00 h compared with those observed at the same times during the summer. Even though animals demonstrated significant diurnal changes, testosterone samples withdrawn at the same time of day (10.00 h) on consecutive days were significantly correlated with one another (r= 0·65, n= 27, P< 0·01), suggesting the usefulness of sampling once a day to study potential environmental influences on plasma testosterone concentrations.

A fast-acting inhibitor of serine elastase has been detected at high levels in human neutrophils, fresh monocytes, matured monocytes, and macrophages. The elastase inhibitor was isolated from large scale cultures of the monocyte-like cell line U937 by DNase chromatography, disulfide exchange, Phenyl-Sepharose, Red A-agarose, and DEAE HPLC chromatography with an average yield of 480 micrograms from 1.8 x 10(10) cells. The isolated polypeptide was verified as elastase inhibitor by its ability to (a) form a covalent complex with elastase; and (b) inhibit the elastinolytic activity of elastase. The purified elastase inhibitor molecule is unique, i.e., physiochemical and/or functional properties distinguish it from all other serine proteinase inhibitors. Treatment with iodoacetamide abrogates the ability of the molecule to form a complex with elastase, thereby providing evidence for the presence of an essential cysteine residue. Based on functional criteria, this elastase inhibitor has been grouped with the proteinase inhibitors of the serpin superfamily. The purified elastase inhibitor is a single polypeptide of Mr approximately 42,000. The NH2 terminus appears to be blocked. Compositional analyses indicates five cysteine residues per molecule of approximately 360 amino acid residues. Negligible levels of carbohydrate were detected on gas-liquid chromatography. This finding and the insensitivity of the molecule to peptide N-glycosidase F treatment strongly indicate that the elastase inhibitor is a nonglycosylated protein.

The ability of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) and gamma interferon (IFN-gamma) to modify human immunodeficiency virus (HIV; also called HTLV-III/LAV) infection in the monocytic cell line U-937 was examined. When added to persistently infected cell cultures, GM-CSF at 30-300 units per ml produced maximal reductions in reverse transcriptase activity of 37-55% 10-14 days after its addition, whereas IFN-gamma produced reductions of 64-68% 10-17 days after addition. When used prior to acute HIV infection and maintained in the cell culture system, these cytokines reduced reverse transcriptase activity 90-100% and nearly eliminated viral antigen expression but did not prevent return of productive infection after their removal. These results indicate that, in a monocyte model of HIV infection, GM-CSF and IFN-gamma substantially restrict HIV expression and that these cytokines deserve further evaluation as therapeutic alternatives in HIV-related disorders.

The activity of the buccal ganglion of Aplysia depilans is manifested as regular and sequential bursts of nerve impulses. Regularly firing bursts are seen in the absence of feeding movements. Sequences of bursts lasting for several minutes have been recorded during feeding movements induced by a natural stimulus. A feed-back system has been used to produce bursts in certain other cells synchronous with the regularly firing units. During sequences of bursts there is an alternation of activity between the two groups of neurones. One group is made up of four cells discharging synchronously but within different ranges of frequency. A mathematical model of this activity will be presented in another paper.