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Strain compensated 1.3 μm InAsP/InGaAsP laser structures have been grown by using gas source MBE and the ridge waveguide laser diodes have been fabricated. The temperature characteristics of those laser chips have been investigated in detail. The ridge type laser chips show threshold current about 10 mA at room temperature, with slope efficiency greater than 0.35 W/A/un-coated facet. The characteristic temperature of the threshold current were greater than 90 K from 25°C to 90°C. The spectral and far field characteristics of those laser chips also have been investigated.

We prepared In 0.53 Ga 0.47 As/InP electron waveguides with in-plane side gates by deep etching through a two-dimensional electron gas. In these structures we investigated the conductance dependent on the voltages applied at both gates. Our experiments show a remarkable asymmetry in the gate efficiency: negative gate voltages seem to be more efficient than positive ones, and the pinch-off voltage of the waveguide depends mainly on the more negative of the two gate voltages. A model is given which takes the etched surfaces into account. The conductance in the waveguide is essentially determined by the potentials at the etched surfaces, which are via Schottky-diode transitions coupled with the gates and the channel. With the help of this model we are able to explain the behavior of the electron waveguides.

Spherulocytes were purified from the haemolymph of two lepidopteran species, Heliothis virescens and Malacosoma disstria . Analysis by polyacrylamide gel electrophoresis revealed the presence of two to four major polypeptides of relatively low molecular weight in purified M. disstria cells and one or two in H. virescens spherulocytes. A sulphated glycosaminoglycan-like substance was extracted from the purified cells.

Parasitization by Campoletis sonorensis consistently results in the appearance of a new polypeptide, a glycoprotein, in several habitual host species. This occurs prior to the hatching of parasitoid eggs, and can be duplicated by the injection of either calyx fluid or purified C. sonorensis virus. Oviposition in two non-permissive hosts. Anticarsia gemmatalis and Mamestra configurata, leaves haemolymph polypeptide profiles unchanged.

The particulate fraction of the calyx fluid of the endoparasitoid, Campoletis sonorensis, reduces host weight gain when manually injected into healthy Heliothis virescens larvae. Reduced weight gain of the host, H. virescens, is normally associated with parasitism by C. sonorensis. Electron microscopy has confirmed that the particulate fraction of the calyx fluid is composed of virus particles and it appears that this virus, injected with the egg at oviposition, actually reduces host weight gain. The effect of the virus is negated when the calyx fluid is exposed to ultraviolet light prior to injection. Furthermore, the calyx fluid is effective only if injected into hosts; there is no effect on host weight gain when hosts are fed or topically treated with the virus-containing calyx fluid.

Polydnaviruses are thought to replicate only in the ovaries of certain hymenopteran species. Nevertheless, in the present study, polydnaviral DNA was found to exist in males of the braconid parasitoid species Cotesia melanoscela and in both male and female non-ovarian tissue of an ichneumonid, Hyposoter fugitivus; preliminary results suggest that viral DNA may be present in an unintegrated form, but whether or not it is encapsidated is unknown. Using interstrain genetic crosses, we demonstrated that C. melanoscela males can apparently transmit at least some viral DNA to female progeny. We suggest that polydnavirus DNAs may be present in most if not all tissues of certain parasitoid species, and are probably maintained within parasitoid populations by vertical transmission through the germ line. In parallel experiments, manually injected eggs of the ichneumonid parasitoid (H. fugitivus) survived and hatched in Malacosoma americanum larvae in the apparent absence of exogenous polydnavirus; female parasitoids reared in this manner nevertheless carried virus in their ovaries. Experiments utilizing different strains of C. melanoscela also suggest that per os transmission of polydnaviruses (to parasitoid larvae) does not occur, despite the fact that inoculum viral DNA can be shown to persist for several days in the tissues of parasitized host larvae.

The icheneumonid wasp, Hyposoter fugitivus , is an habitual parasitoid of tent caterpillar ( Malacosoma disstria ) larvae. Successful parasitism is associated with an apparent behavioural transformation of certain host haemocytes, and is in addition characterized by a suppression of immunity to foreign objects such as parasitoid eggs, yeast, and Sephadex beads; it is suggested that transformation of haemocytes renders them incapable of participating in normal immune responses. Inhibition of some aspects of cellular immunity in host insects can also be induced by manual injection of a polydnavirus isolated from the ovaries of the parasitoid. It was observed that haemolymph from parasitized larvae does not melanize in vitro; this phenomenon may be associated with a greatly increased stability of oencytoids.

Certain strains of the braconid parasitoid Cotesia melanoscela carry two different viruses within their ovaries, one of which (here designated CmV2) is apparently not a polydnavirus. Virus replication occurs in the ovarian calyx and in some other tissues of both male and female parasitoids; as yet, no replication has been observed in the testis, however. In addition, CmV2 is one of only two parasitoid viruses known to replicate in host insect larvae, and we now show that this virus is also capable of replicating in vitro ; the virus is nevertheless nonpathogenic for gypsy moth larvae. The virus is not transmissible per os , either to host animals or to larvae of parasitoid strains lacking it. CmV2 is stably maintained within strains carrying it apparently by a vertical transmission mode involving the maternal line; transmission via the male germ line could not be demonstrated. While purification of the virus was not achieved, preliminary work allows us to suggest that the genome consists of a single double-stranded DNA molecule of approximately 125 kb.

The use of a small ultrafast electrical signal differentiator is described. Its application in conjunction with photoconductive elements in the measurement of mode-locked laser pulses with picosecond resolution has been investigated.

Cellular responses to the introduction of foreign objects into the haemocoele of both control and parasitized tussock moth larvae were examined. In normal larvae, the response to large foreign objects such as Hyposoter fugitivus eggs and Sephadex beads was encapsulation, accompanied by a rapid and sustained increase in the total haemocyte count. Smaller objects such as yeast cells were cleared into nodules within a matter of minutes; nodulation too was accompanied by an increased total haemocyte count. In larvae parasitized by the braconid wasp Cotesia melanoscela, both encapsulation and nodulation were permanently suppressed. Inhibition of these normal cellular defence reactions was accompanied by a reduction in the total haemocyte count, the appearance of debris in the haemocoele, and by nuclear pycnosis in an unidentified population of cells; however, since extensive nuclear pycnosis also occurred in haemopoietic tissue, it is assumed that prohaemocytes may represent a target cell population. All of the observed effects required the presence of both C. melanoscela calyx fluid and venom in the host animal. Phagocytosis as an immune response remained essentially intact, and was capable of completely clearing both yeast and Escherichia coli cells injected into the haemocoele.

Virus-like particles have been isolated from the oviducts of a parasitoid wasp, Hyposoter exiguae (Hymenoptera: Ichneumonidae). Particles are readily purified by centrifugation on either Ficoll or sucrose gradients. Double-stranded circular DNA isolated from purified particles is heterodisperse in terms of molecular weight; none of the molecules are sufficiently large to code for the aggregate of structural proteins comprising the particles. Preliminary Southern blot hybridization data suggest that there is minimal sequence homology between the different size classes of DNA examined.

A detailed comparative ultrastructural study has been made on several icosahedral cytoplasmic deoxyriboviruses (ICDV) of insects and one of vertebrates. The available evidence now seems to indicate that ICDV particles contain only a single structural unit membrane, associated with the viral nucleoid. ICDV shells are therefore redefined entirely in terms of icosahedral lattices, in contrast to an earlier model. A partial explanation is offered for the variability in appearance of ICDV shell surfaces. Previous evidence for the structural relatedness of ICDV's of different sizes and from different hosts is corroborated by the following additional observations: triangular arrays of capsomers (trisymmetrons) are present in mosquito iridescent virus (MIV) shells; mosquito and Corethrella iridescent virus (CoIV) cores are identical in morphology and are uncoated in an apparently intact form under similar conditions; sectioned MIV and frog virus (FV3) particles reveal definite structural homology; the morphogenesis of all ICDV's studied appears basically identical. Proposals concerning the nomenclature and classification of this group of viruses are briefly discussed.

An account is given of the ultrastructure of a poxvirus infecting larvae of a midge, Chironomus attenuatus. The virus appears to replicate only in hemocytes, and is of the occluded type. Immature virions are formed in association with an amorphous virogenic stroma, portions of which are sequestered into the developing particles. Further maturation of virions occurs either free in the cytoplasm or during (or after) occlusion within the crystalline matrix of polyhedra. A new intermediate in the development of cores from nucleoids is described. In addition, the presence of a unit membranelike structure in the poxvirus core is indicated. A possible nucleation site for the deposition of polyhedron protein is described.