Modulation-instability-based fiber interferometer switch near 1.5 microm

We demonstrate a modulation-instability-based fiber interferometer switch, an ultrafast all-optical fiber switch operating near 1.5-microm wavelength with more than 40dB of small-signal gain. Switching is accomplished.by seeding the modulation instability in one arm of a Mach-Zehnder interferometer, thus destroying its balance. Computer simulations, which include the effects of Raman self-frequency shifts, suggest that as much as 74% of the power input to the interferometer can be transferred to its (initially nulled) output arm when cw pumps are used. Even with an 80% loss at the output analyzer, we have gated 184 mW of power from a color-center laser using only 4.4 microW from a semiconductor laser.

Amplifier/compressor fiber Raman lasers

We show that the chirp from cross-phase modulation (XPM) dominates the operation of fiber Raman lasers (FRL's). Thus a FRL in the anomalous group-velocity regime is best described as a XPM-chirped Raman amplifier followed by a linear fiber compressor. While the output of such a laser is generally a narrow pulse with a broad pedestal, we show both experimentally and by computer simulation that negligible background is achievable.

Cross-phase modulation in optical fibers

When pulse pairs copropagate in a fiber, each pulse chirps the other through cross-phase modulation (XPM). In particular, XPM causes spectral broadening of signal pulses during Raman or parametric optical pulse amplification. We have studied XPM experimentally in the fiber Raman amplification soliton laser. We show that experimentally observed spectra can be explained by a simple model that concentrates on the phase change as a function of pulse walk-off.

Use of anti-idiotypic antibodies as probes for the interaction of TSH subunits with its receptor

TSH is a heterodimeric glycoprotein hormone, whose dissociated subunits are without biological activity. This has precluded the assessment of the relative contribution of each subunit to hormone action. We have raised anti-idiotypes to monoclonal antibodies specific, respectively, for the alpha and beta hTSH subunits. The anti-beta anti-idiotype inhibited 125I-hTSH binding to the beta subunit-specific monoclonal quantitatively, whereas 125I-hTSH binding to the alpha subunit-specific monoclonal was not inhibited by anti-alpha anti-idiotypes, suggesting that only the former is an "internal image" anti-idiotype. Neither of the two anti-idiotypes nor equimolar mixtures thereof inhibited 125I-bTSH binding to thyroid membranes, even though radiolabelled anti-idiotypes showed saturable binding to thyroid plasma membrane which was inhibited 41-65% by bTSH. Each anti-idiotype alone caused 9% inhibition (compared to 50% by NRIgG) of thyroid plasma membrane adenylate cyclase. Equimolar mixtures (125 micrograms/ml IgG of each anti-idiotype) induced enzyme activity equivalent to 85% of that of 250 mU/ml of TSH. The TSH-like action of the two anti-idiotypes was also reflected in their capacity to increase (450% by 250 micrograms/ml IgG compared to normal rabbit IgG) the uptake of 131I into isolated thyrocytes and to promote the organization of such cells into follicular structures. At 250 micrograms/ml, anti-beta anti-idiotype promoted the organization of small follicles and only at a concentration of 500 micrograms/ml did it enhance 131I uptake.

Congenital meningocele-encephalocele in an experimental swine herd

Fourteen instances of meningocele-encephalocele in an experimental herd were recorded over a 5-year period. Thirteen of these affected animals were subjected to extensive pedigree analyses. Familial associations were strong, and clearly the meningocele-encephalocele in this herd was under genetic influence. However, additional studies are needed to clarify the mode of inheritance and, perhaps, to identify other factors that might be involved.

Self-selectivity problems in interregional and interindustry migration in Canada

This study is concerned with the role that inter-industry mobility plays in the decision to migrate in Canada, and also with the joint impact on earnings of inter-industry and interregional migration, corrected for selectivity bias. The data, for the period 1970-1971, are from a one percent random sample of a micro data base established by the Unemployment Insurance Commission. "Contrary to the commonly held belief that a migrant's decision to change his location is independent of his decision to change his industry of employment, this paper provides evidence that these movements are in fact interrelated."

Experimental demonstration of soliton propagation in long fibers: loss compensated by Raman gain

With sufficient Raman gain to compensate exactly for net fiber energy loss, we have demonstrated distortionless propagation of 10-psec FWHM fundamental (N = 1) soliton pulses (lambda = 1.56 microm) over a 10-km length of single-mode fiber. The implications of this experiment for development of an all-optical, high-bit-rate, long-distance telecommunications system are discussed briefly.

Structure of the porcine thyrotropin receptor: a 200 kilodalton glycoprotein heterocomplex

We have determined that the porcine thyroidal TSH receptor is a glycoprotein heterotetramer composed of two Mr approximately 35,000 (epsilon) covalently linked subunits which interact noncovalently with two copies of delta (Mr 66,000) chains.

Anti-idiotypic antibodies as probes for hormone-receptor interaction

On the premise that an antibody combining site is a mirror image of its antigen epitope, it is expected that an anti-idiotypic antibody (i.e., an antibody specific for the combining site of the first antibody) will be homologous to the epitope. Anti-idiotypic antibodies raised against hormones or drugs would, therefore, be anticipated to interact with their respective receptors. According to this schema, anti-idiotypic antibodies could either be antagonists or agonists. Most of the anti-idiotypic antibodies raised against hormones and neurotransmitters to date have proved, however, to be agonists. We have raised antithyrotropin (anti-TSH) anti-idiotypic antibodies and found these to interact with the high affinity binding site for TSH on thyroid plasma membranes and to induce cGMP-dependent adenylate cyclase activation and iodide transport into dispersed thyroid cells, as well as to promote their organization into follicular structures. The anti-TSH anti-idiotypic antibody interacted with a holoreceptor band of relative mass (Mr) approximately 200 000, resolved on sodium dodecyl sulfate-polyacrylamide gel electrophoresis from thyroid membranes and transferred to nitrocellulose paper. In another set of experiments we raised anti-idiotypic antibodies against monoclonal antibodies specific, respectively, for the alpha and beta subunits of TSH. Neither the alpha nor beta monoclonal antibody specific anti-idiotypic antibodies interacted with the TSH holoreceptor. The combinations of the two anti-idiotypic antibodies, however, did so and increased basal cyclase activity significantly compared with normal immunoglobulin G. As a result of the second set of experiments, we propose that the interaction of TSH with its receptor involves two signals delivered by the two subunits rather than a single signal requiring their combination. Anti-idiotypic antibodies raised against highly purified hormones can be obtained in large amounts. They facilitate simple isolation of hormone receptors and are useful as probes for hormone-receptor interactions.

Hepatitis-B virus infection in Dhaka, Bangladesh

Three thousand six hundred and ten patients with acute hepatitis in two large hospitals in Dhaka city were tested for HBsAg. Besides, 780 commercial blood donors, 126 doctors and 576 apparently healthy persons were also tested. Passive haemagglutination technique was applied for this test. Patients with post-transfusion hepatitis and doctors with acute hepatitis showed the highest incidence, being 60% and 65.5% respectively. HBsAg was detected only in 15.4% of children and 27.2% of adult patients with acute hepatitis.

Both TSH and thyroid-stimulating antibody of Graves' disease bind to an Mr 197,000 holoreceptor

Human and porcine thyroid plasma membranes were submitted to sodium-dodecyl sulphate polyacrylamide gel electrophoresis in the absence and presence of reductant and electrotransferred onto nitrocellulose paper. Native bovine TSH, IgG from all 10 patients with active Graves's disease tested, as well as rabbit anti-bTSH anti-idiotypic antibody were found to bind to a single Mr approximately 197,000 band present only in non-reduced gels. We conclude that TSH and Graves' IgG bind to the TSH holoreceptor.

Surface labeling of thyrocytes isolated by a new method combining enzymatic digestion and percoll gradient centrifugation

Thyrocytes were isolated from porcine thyroid glands using a new method entailing two-step collagenase digestion and Percoll gradient centrifugation. Good yield and a high percentage of viable thyrocytes free from other contaminating cells was achieved. Proteins present on the surface of thyroid cell plasma membranes were then specifically labeled using Iodogen and 125I-. Membrane lysates were separated by electrophoresis on 10% polyacrylamide gel, under reducing and nonreducing conditions, followed by autoradiography. When the gels were stained with silver nitrate some 30 bands were visualized in both the presence and absence of reductant. Only 9 bands were found to be labeled under nonreducing conditions and 12 in the presence of reductant. Two bands involved in the thyrotropin receptor structure--Mr = 66,000 and Mr = 70,000, respectively--were visualized in the absence of reductant. Upon reduction the Mr 66,000 band was retained and a new band (Mr = 33,000) was seen. The mild enzymatic treatment used in isolating thyrocytes and the lack of contamination with other cells allowed the consistent labeling of exposed plasma membrane components by the Iodogen method such that the orientation of thyrotropin receptor components in the plasma membrane could be deduced.

Biological activity of anti-thyrotropin anti-idiotypic antibody

Rabbit anti-rat anti-human thyrotropin anti-idiotypic antibodies have been raised. These antibodies were active at the thyrotropin (TSH) receptor, in that they inhibited 125I-labeled bovine TSH binding to thyroid plasma membranes, stimulated adenylate cyclase activity through a guanyl nucleotide-dependent mechanism, augmented radioiodide transport into isolated porcine thyroid follicular cells and induced such cultured cells to organize into follicles. Aside from substantiating the expectation that anti-hormone anti-idiotypic antibodies may possess properties of the original hormone, this work raised the possibility that thyroid-stimulating antibodies which cause the hyperthyroidism of Graves' disease may be anti-TSH anti-idiotypic antibodies.

Minimizing Salmonella Contamination on Broiler Carcasses with Poly (Hexamethylenebiguanide Hydrochloride)

Broiler carcasses, each inoculated with 30 cells of marker Salmonella heidelberg , were prechilled and chilled together with uninoculated carcasses in a simulated commercial chilling system. When either 10 or 25 ppm of PHMB [poly(hexamethylenebiguanide hydrochloride)] was added to the prechill water, cross-contamination (uninoculated carcasses showing contamination with marker Salmonella after chilling) was prevented, and no viable Salmonella were found on the inoculated carcasses. When carcasses, each inoculated with 60,000 cells of marker Salmonella , were similarly chilled, and 10 ppm of PHMB was added to the prechill water, cross-contamination was not prevented, and viable Salmonella were found on the inoculated carcasses. With 60,000 cells, and 25 ppm PHMB, cross-contamination was prevented, but viable Salmonella remained on the inoculated carcasses.

Aortocoronary Gore-Tex graft: 18-month patency

Despite widespread success with Gore-Tex (polytetrafluoroethylene) vascular grafts in peripheral artery operations, very little use has been made of this material in aortocoronary bypasses. We present the case of a 61-year-old woman with a 6-month history of angina who was found to have no suitable saphenous vein available at operation and who therefore underwent Gore-Tex bypass grafting to the right coronary artery. Coronary angiograms made 6 months and 18 months postoperatively showed patency of the 6 mm Gore-Tex replacement graft as well as the internal mammary artery placed to the left anterior descending coronary artery. Although frequent follow-up and close observation are recommended in patients with aortocoronary Gore-Tex grafting, the unique design of this material has made it the best alternative for synthetic coronary bypass conduit in the absence of the saphenous veins, particularly when these veins are found to be inadequate only at the time of operation.

Evidence for possible emergence of immunochemically distinct nucleotide-peptides in malignant transformation

Antibodies against nucleotide-peptides of beef heart do crossreact with nucleotide-peptides of other beef organs, but with nucleotide-peptides of Ehrlich tumor cells. Antibodies against the latter do not crossreact with nucleotide-peptides of normal organs, but do so with nucleotide-peptides of a rat hepatoma.

The prevalence of hepatitis-B antigen (HB S Ag) and its antibody (Anti-HB S) among London hemophiliacs and blood donors from London and two tropical areas

The prevalence of hepatitis-B antigen (HB s AG) and its antibody (anti-HBs) among 49 London hemophiliacs was compared with that among women attending an antenatal clinic and healthy blood donors from London and from two parts of the tropics (Mauritius and Zambia). The prevalence of HBsAG and anti-HBs was low in antenatal patients, London blood donors and blood donors from Mauritius. However, a high proportion of hemophiliacs (59%) were anti-HBs positive, this being comparable with Zambian blood donors (53%), although anti-HBs titers in hemophiliacs were much higher (GMT 1:342) than in Zambian blood donors (GMT 1:36). In contrast, HBsAG was detected in 29 of 250 (12%) Zambian donors but in only 3 of 49 (6%) hemophiliacs. Clinically overt hepatitis occurred in only two hemophiliacs. However, the presence of HBsAG-specific IgM in 7 of 29 (24%) anti-HBs-positive hemophiliacs suggests that a proportion of these patients recently experienced subclinical infection by hepatitis-B virus, Anti-HBs-positive hemophiliacs received a significantly higher number of- cryoprecipitate units than did those without anti-HBs(P less than 0.01). Five of seven hemophiliacs with high titers of anti-HBs (greater than 1:4,096) showed a decline in titer after 1972 which may have been associated with the introduction of screening of cryoprecipitate for HBsAG.

The incidence of hepatitis-B-antigen and anti-hepatitis-B among blood donors in Ndola, Zambia

Hepatitis-B antigen (HBsAG) was detected in the sera of 29 or 250 (11.6%) blood donors in Ndola, Zambia, most of whom were prisoners or students. The incidence among prisoners was 15.1%, among students only 1.6%. Thirteen sera were subtyped, nine carried the y and four the d antigenic determinant. Although there was a marked difference in the incidence of HBs antigen between prisoners and students, when donors were tested for antibody to HBsAg (anti-HBs) this positive. Overall, anti-HBs was detected in 132 of 250 blood donors (52.8%). The sensitivity of radioimmunoassay, counter-immunoelectrophoresis and a newly developed passive haemagglutination (PHA) test, employing tanned formalinised antibody coated turkey erythrocytes, was compared. Although radioimmunoassay provided the most sensitive method, the PHA test compared extremely favourably and was considered to be particularly suitable for use in the tropics.