Mutants of Yeast Sensitive to Ultraviolet Light

Six uvr mutants of Saccharomyces cerevisiae with hypersensitivity to ultraviolet (UV) light were isolated after mutagen treatment with ethylmethanesulfonate. UV sensitivity ranges from moderate to extreme, and four of the mutants are also sensitive to nitrous acid. Ranking in terms of UV sensitivity does not parallel ranking in terms of nitrous acid sensitivity. Homozygous diploid mutant strains are somewhat less sensitive than the corresponding haploids. All mutations are recessive. None of the mutants is sensitive to gamma rays, and each shows photoreactivation after UV radiation. Complementation tests and tetrad analysis indicate that each strain represents mutation in a different gene. Two of the uvr genes are linked, and two others are centromere-linked.     

Economic Aspects of “Whiplash” Injury

The term “whiplash,” used to describe a neck injury received in an automobile accident, has no foundation in medical science to support the complaints of persons suing for damages. The term is gaining unwarranted popularity as a term describing an injury, even though there are no clinical or pathological findings to support it.“Whiplash” cases today account for an estimated 30 per cent of all injuries in automobile accidents. Direct compensation for damages paid to persons injured in automobile accidents in the United States in 1961 amounted to approximately one billion, seven hundred million dollars. It has been estimated that five hundred and eighty million dollars of that amount was paid in compensation on allegation of neck injuries.     

Assay of the mycobactins by measurement of the growth of Mycobacterium johnei

A method is described for the assay of mycobactin P and T by turbidimetric measurement of the growth of Mycobacterium johnei. The assay agrees satisfactorily with spectroscopic determination of the iron complexes. The growth curves with mycobactins P and T differ somewhat in form. An approximate ratio of activities has been determined.     

Effect of Growth Stage and Initial Inoculum Level on Leaf Rust Development and Yield Loss Caused by Puccinia recondita f. sp. tritici

The effects of the combinations of leaf rust inoculation at different growth stages and initial inoculum levels on leaf rust development and yield of winter wheat cultivars, McNair 1003 and Coker 762 were evaluated. Disease onset stage and initial inoculum level affected the rate of leaf rust development and shape of the disease progress curves in both cultivars. Epidemics with common onset stages and different initial inoculum levels differed in area under the disease progress curve (AUDPC). Leaf rust epidemics initiated at Feeke's growth stages 5, 7, and 10 reduced yield in both cultivars. Leaf rust epidemics initiated early with high inoculum levels had the greatest deleterious effect on yield. Maximum losses due to leaf rust were 30–40 %. Yield loss was directly related to AUDPC when the AUDPC varied from 500 to 1700 in McNair 1003 and from 250 to 1700 in Coker 762. Yield reduction was mainly due to reduction in grain weight.     

Construction and characterization of the chimeric monoclonal antibody E48 for therapy of head and neck cancer

Data from an ongoing clinical radioimmunoscintigraphy trial indicate that^99mTc-labeled monoclonal antibody (mAb) E48 is highly capable of selectively targeting squamous cell carcinoma of the head and neck (HNSCC). The percentage of the injected dose per gram of tumor tissue was found to be high, rendering mAbE48 a promising candidate mAb for therapeutic purposes. We now describe the construction of a chimeric (moouse/human) mAb E48 by recombinant DNA technology. The genes encoding the variable domains of the heavy and light chain were cloned and ligated into experession vectors containing the human 1 heavy-chain gene and the human k lightchain gene respectively. Biological properties of the resulting chimeric mAb E48 were compared to the murine form in vitro and in vivo. The reactivities of chimeric (c)mAb and murine (m)mAb E48 with HNSCC, as assessed by immunohistochemical staining as well as immuno-blotting were shown to be similar. The affinity constant appeared to be 0.9×10¹⁰ M^–1 and 1.6×10¹⁰ M^–1 for the mmAb and cmAb respectively. The biodistribution of both antibodies was tested by simultaneous injection into nude mice bearing human HNSCC xenografts. cmAb E48 was found to be cleared more rapidly from the blood than mmAb E48, resulting in a 30% lower tumor uptake but similar tumor to non-tumor ratios, 3 days after injection. Moreover, it was shown that cmAb E48 is highly capable of lysing HNSCC targets in ADCC assays in vitro, whereas the mmAb appeared to be almost incative. These data indicate that cmAb E48 has potential as a targeting agent for the eradication of HNSCC in man.     

Genetic Evidence for Interaction between Nonhomologous Proteins in Yeast and a Case of Suppression at the HIS1 Locus

The HIS1 and THR4 loci are the structural genes for phosphoribosyl-ATP pyrophosphorylase and threonine synthetase, respectively. The allele his1–1S has no enzyme activity at 30°, but does have activity at 15° provided the cell contains the wild-type THR4 allele or a suppressing allele at another locus, designated SUP(his1–1S). Under these conditions, cells with the his1–1S mutation are capable of growth on minimal medium at 15°. Three kinds of reversions of a his1–1S thr4 sup(his1–1S) strain to histidine prototrophy have been obtained: (1) his1–1S locus reversions to HIS1 that restore growth without added histidine at 30°, (2) thr4 reversions to THR4 that simultaneously eliminate the requirement for threonine and restore the low-temperature effect on the his1-1S allele, and (3) mutations from sup to SUP. The SUP allele is not an ochre suppressor, and it is not linked to either HIS1, THR4 or a centromere. It may represent a missense suppressor. It is proposed that the effect of THR4 is caused by aggregation of the wild-type threonine synthetase with defective his1–1S monomers, causing a favorable conformational change in the histidine protein that restores limited enzymatic activity. This can be regarded as a case of complementation between nonhomologous proteins.