The chronic course of a probable monensin toxicosis in cattle.

Feedlot calves given monensin in their feed developed an excessive mortality which peaked 3-4 mo after monensin was withdrawn. Typically the calves died suddenly and necropsy revealed areas of paleness in the skeletal muscles (early cases) and in the myocardium (more chronic cases). Histology (in 19 calves) showed swollen myocytes with loss of striation and sarcoplasmic vacuolization, followed by the appearance of necrotic fibres and infiltration with macrophages and neutrophils, and finally local and generalized fibrosis. Calcification was not evident. A differential diagnosis ruled out an etiology of nutritional and toxicological origin, thus leaving the probability of atypical (chronic) monensin toxicosis.

Variety x line cross - A suggested breeding procedure for maize in developing countries.

Phra-Phutthabat No.5 (PB5), a widely grown local variety in Thailand, was crossed with open-pollinated varieties, S3 and S6 lines from different parts of the world. The resulting hybrids were tested in the dry season in Thailand, Laos and Israel with PB5 as the control. A number of hybrids were also tested in the wet season in Thailand and Laos. Hybrids giving significantly higher yields than PB5 were found in both the dry and the wet seasons. The variety x line crosses were superior to the variety x variety crosses at all locations. The hybrids with the South African germ plasm were intermediate, and those with the African and Asian germ plasm gave the lowest yields. The variety x line cross is suggested as a simple and rapid breeding procedure for the developing countries.

An ems-sensitivity factor in maize conditioning albino leaf stripes.

A description is given for a recessive EMS-sensitivity factor conditioning albino leaf stripes. In the homozygous condition, there is low frequency of spontaneous leaf stripes. EMS, depending on the concentration, increases markedly the frequency of the stripes in 100% of the treated plants. The effects of EMS, given to the seeds, starts to appear from the 6th to 7th leaf and persists in all the leaves throughout the life cycle of the M(1) plants. Only about 20-25% of the M(2) plants showed some variegation. These variegated M(2) plants were not distributed at random among the different ear-to-row M(2) rows.

Inheritance studies with inbred lines of maize having different activity levels of the AP 1 controlled acid phosphatase isozymes.

The genetic control of acid phosphatase-1 (AP 1) activity in pollen of maize was studied by crossing inbred lines having different AP 1 isozymes and different activity levels of the A P 1 enzyme. Usually, the intensities of the SS and FF isozyme bands were not equal in pollen of A P 1 (S) /A P 1 (F) heterozygous F 1 hybrids, but the relative intensities of the two bands were not correlated to the activity levels of the parental lines. The A P 1 (S) /A P 1 (S) and A P 1 (F) /A P 1 (F) F 2 populations differed in their mean level of activity. Both populations showed segregation in the activity levels indicating single gene control. The intensity ratios of the SS and FF bands in the different heterozygous A P 1 (S) /A P 1 (F) F 2 plants did not segregate. The results support the competition model for gene regulation proposed by Schwartz (1971).

Alcohol dehydrogenase in maize: genetic control of enzyme activity.

A gene (Adhr(r)) which controls the activity of alcohol dehydrogenase in the scutellum of maize has been found. This gene is not allelic to the Adh(1) locus, which specifies the charge of the enzyme molecule and hence its migration rate. The two genes are linked and located about 17 crossover units apart. The Adh(r)(N) allele specifies equal activities of both the Adh(1)(S) and Adh(1)(F) products. The Adh(r)(L) allele gives lower activities of the Adh(1)(S) products only and operates in both the cis and the trans configurations.