Inhibitor of peritoneal mononuclear phagocyte colony forming cells

We investigated an inhibitory factor present in mouse L-cell conditioned medium. This soluble factor, colony inhibitory factor (CIF), selectively inhibits the clonal growth of mouse peritoneal exudate (PE) macrophages in vitro. CIF appears to be a non-dialyzable macromolecule which was eluted by Sephadex G200 gel filtration at post-albumin fractions. It can be fractionated by ammonium sulfate precipitation within the range of 60%--70% saturated solution at room temperature. CIF is moderately heat labile and is destroyed by incubation at high pH. CIF is more effective on PE cells from C57 mice than on those from C3H or DBA mice. It also inhibits the clonal growth of committed stem cells for both granulocytes and macrophages present in bone marrow but to a much lesser degree. CIF is not interferon since no antiviral activity is demonstrable in the CIF preparation.

Neuromuscular block by antibiotics: polymyxin B

Characteristics of neuromuscular block produced by polymyxin B (PXB) were examined in 12 anesthetized cats, using sciatic nervetibialis anticus muscle preparations. The ED50 was 6.7 (+/- 1.4, SD) PXB base/kg body weight. The ED95 was 10.8 (+/- 2.4) mg/kg. Spontaneous recovery from 25 percent of control to 75 percent of control required 72 (+/- 16) minutes. During a 50 percent block, train-of-four twitches elicited at 2 Hz faded with a train-of-four ratio of 0.42 (+/- 0.13), but the tetanus did not fade. Edrophonium Cl, neostigmine methylsulfate, and pyridostigmine Br at sub-clinical dosages weakly antagonized the block but enhanced the block at anti-curare dosages. All 3 cholinesterase inhibitors were short acting, lasting 10 to 15 minutes, and noncumulative on repeated injection. The potency ratio was approximately 20:10:1 in the order of edrophonium, neostigmine, and pyridostigmine on a weight-for-weight basis. Calcium partially antagonized the block. The authors conclude that neuromuscular blocks produced by various antibiotics differ from each other and from that produced by other groups of neuromuscular blocking agents, including curare.

Characteristics of nondepolarizing neuromuscular block: (I) post-junctional block by alpha-bungarotoxin

The characteristics of neuromuscular block produced by alpha-bungarotoxin, a post-junctionally active polypeptide toxin purified from snake venoms, have been studied in vivo in 12 anaesthetized cats, using the sciatic nerve-tibialis anterior muscle preparation. The onset of the neuromuscular block was slow and without fasciculation. The block was persitently progressive. The time course of the block depended on the dosage. In general, 0.1 mg/kg of alpha-BuTX appeared to approximate the threshold dosage while 0.2 mg/kg completely eliminated the twitch response in 2-5 hours. No recovery was observed in 8-30 hours. Larger doses accelerated the progression of the block. During the block, tetanic contractions and train-of-four twitches did not fade. The post-tetanic twitches were markedly facilitated. The block was antagonized by edrophonium, neostigmine, pyridostigmine, and succinylcholine, but the antagonism was less effective and shorter-lasting than that observed on curare-block, and the block always resumed the projected progression. Attempts were made to explain the observed difference between alpha-BuTX- and dTc-induced neuromuscular blocks by the practically permanent nature of block and the purely post-junctional site of action of alpha-BuTX. It was concluded that a pure post-junctional block is not characterized by fade, which rather might be a pre-junctional effect of some nondepolarizing neuromuscular blocking agents like d-tubocurarine.

Neuromuscular block by neomycin in the cat

The neuromuscular block produced by neomycin is unique. Despite nearly complete blockade of the twitch the tetanus is not blocked and does not fade. The pathognomonic post-tetanic exhaustion has not been reported previously. Anticholinesterases and calcium antagonize the block, but the antagonism may not be complete. Germine antagonizes the block in the cat, but its clinical value has not been tested. These characteristics of neuromuscular block by neomycin strongly suggest respiratory support and sedation to decrease the respiratory drive, rather than attempts at antagonism, as the rational management of patients suffering from toxic paralysis due to neomycin.

Spontaneous recovery of the thumb twitch from neuromuscular block by suxamethonium in anaesthetized man

The neuromuscular blocking effect of repeated bolus administration of suxamethonium 1 mg/kg was observed in 10 healthy surgical patients under enflurane-nitrous oxide-oxygen anaesthesia. Tachyphylaxis and slow recovery of the thumb twitch occurred in close dose-relationships with transition of Phase I block to Phase II, using train-of-four fade as an indicator of the transition. Failure of the thumb twitch to recover to 75% of control, and subsequent step-wise depression from additional doses of suxamethonium had a sudden onset shortly after establishment of marked train-of-four fade.

De Novo Biosynthesis of Deoxyribonucleic Acid Polymerase during Wheat Embryo Germination

An 8-fold enhancement in the activity of a DNA-dependent DNA polymerase was found in extracts from germinating wheat (Triticum vulgare var. Florence) embryos, as compared to the activity found in extracts from ungerminated embryos. The enhancement of this activity during the first hours of germination is concomitant to the increase of a Dnase activity. The two activities could be separated and the increased level of the DNA polymerase upon germination was observed in an enzymatic fraction which contains very low DNase activity. Addition of the protein synthesis inhibitor, blasticidin S, to germinating wheat embryos, reduced the increase in DNA polymerase. Incorporation of radioactive amino acids into a phosphocellulose preparation, which contains the DNA polymerase starts during the first 6 hours of germination. The amount of radioactivity incorporated is doubled in the next 6 hours, and the incorporation is continued between 12 and 18 hours of germination.

Offset prism for optical waveguide coupling

High refractive index prisms have been used to couple optical beams into the thin film waveguides. To scan through various propagating modes normally requires rotating and repositioning of the prism-waveguide assembly. We have found that the required adjustment of the prism-position can be eliminated during the scanning of the various modes if the prism is properly offset with respect to the rotational axis. An analysis and a computer program are given for the calculation of this prism offset position on the basis of minimum deviation within the specified limits of the prism rotational angle.

Subnanosecond Laser Recording on MnBi Thin Films

Thermomagnetic writing and erasure of binary information in MnBi thin films using 250-psec pulses are described. The ability to write with such short pulses could greatly improve data rates in optical memories. Repeated cycling of a single spot gave inconclusive results concerning possible retardation or inhibition of phase change in MnBi for very short heating pulses.

Magnetic materials for optical recording

Optical digital data storage using magnetic materials offers the combined advantages of magnetic recording and beam addressable technique. Recent progress in this technology is reviewed.

Deoxyribonucleic Acid polymerase from wheat embryos

A soluble DNA-dependent DNA polymerase was extracted from wheat embryos. In vitro, the incorporation of radioactive thymidine triphosphate into acid-insoluble material is dependent upon the presence of the enzyme, all four deoxyribonucleotide triphosphates, Mg(2+), and a DNA template. Incorporation occurs on native, alkali-denatured, and strictly double-stranded DNA. The in vitro synthesized product is a polydeoxynucleotide with a chain length shorter than the template; it has the same buoyant density as wheat embryo DNA when this DNA is used as template; and it forms a double-stranded complex with the DNA template. These data suggest that the in vitro DNA synthesis catalyzed by proteins extracted from wheat embryos occurs in a semiconservative way.

The antibody response to sporozoites of simian and human malaria parasites: its stage and species specificity and strain cross-reactivity

Attempts to vaccinate against malaria are currently being pursued in both simian hosts and human volunteers, using X-irradiated sporozoites as antigen. The present experiments provide information on the developmental stage during which simian malaria sporozoites acquire certain antigen(s) and become infective, and on the antigenic similarities between sporozoites of different strains and species of simian and human malaria parasites. Such knowledge should prove of value in the choice of sporozoite preparations for future attempts at vaccination.

Antibodies against Sporozoites of Human and Simian Malaria Produced in Rats

The various methods commonly used for the detection of antimalarial antibodies employ, in nearly all instances, the erythrocytic stages of these parasites as antigen source (1). The antigenic components of the different stages of development of the malaria parasites, however, differ considerably, in spite of the existence of some shared or common antigens (2, 3). Furthermore, the common antigens do not account for all of the antigenic components of the parasites, nor do they include the functional, i.e., protective, antigens of the various developmental stages. This is suggested by the finding that rodents immunized with attenuated sporozoites become totally resistant to an otherwise lethal sporozoite inoculum, but remain fully susceptible to challenge with erythrocytic stages of the same parasite strain (4).

Anti-sporozoite antibodies, i.e., antibodies directed against the infective stages of all malaria parasites, have previously been shown to occur in avian and rodent malaria. In both instances, these antibodies were observed upon immunization of the animals with attenuated, irradiated sporozoites.

Advanced optical storage techniques for computers

The growing demand for data storage in computing systems has stimulated the investigation of optical memory techniques because they offer a potential improvement in packing density of about two orders of magnitude over the apparent limits of conventional magnetic storage techniques. Physical properties and optical memory characteristics of magnetooptic thin-films of manganese bismuth have been investigated with regard to both bit-oriented and holographic memories. All the required technology for design of a bit-oriented memory appears to be available, but several key components required for a holographic memory still remain to be developed.

Onset of deoxyribonucleic Acid synthesis in germinating wheat embryos

Germinating wheat embryos (Triticum vulgare var. Florence) synthesize proteins before the onset of DNA synthesis. The onset of DNA replication occurs at about 15 hours of germination and was shown to depend on proteins synthesized before 9 hours of germination with the use of blasticidin S, a specific inhibitor of protein synthesis. A 10-fold increase in the activity of DNA-dependent DNA polymerase was found in extracts derived from germinated embryos, as compared to the activity found in extracts from ungerminated embryos.