The infection ofGlossina morsitans weid byTrypanosoma brucei in relation to the parasitaemia in the mouse host

Summary G. morsitans were fed upon white mice infected withT. brucei TREU667, within 24 hours of emergence from the puparium. Infection rates in the flies averaged 5.8 per cent mature infections with a maximum of 15.4 per cent in one experiment. Irradiation of mice with 400r X-rays 24 hours before infection was found to slightly enhance the infection rate in flies. Flies are more readily infected when the blood-meal contains 50–20,000 trypanosomes per mm³ and 10–20,000 short stumpy forms per mm³. With the strain ofT. brucei used, suitable conditions in the mouse occur subsequent to 12 days after infection.

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Sumario MoscasG. morsitans fueron alimentadas sobre ratones blancos infectados conT. brucei TREU 667, dentro de las 24 horas de su emergencia del puparium. Las tasas de infección en las moscas promediaron 5.8 por ciento de infecciones maduras con un maximo de 15.4 por ciento en un experimento. La irradiación de ratones con 400r de rayos X por 24 horas antes de la infección acrecentó ligeramente la tasa de infección en las moscas. Las moscas son mas facilmente infectables cuando la sangre de los ratones contiene de 50–20,000 tripanosomas por mm³ y 10–20,000 formas cortas de mu?ón por mm³. Con la cepa deT. brucei usada, las condiciones adecuadas en el ratón occurren subsecuente a los 12 dias despues de la infección.

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Résumé DesG. morsitans écloses depuis moins de 24 heures ont été nourries sur souris blanche infectée avecTrypanosoma brucei. Les taux d'infection chez les mouches ont atteint une moyenne de 5,8 p. 100 de formes infectantes avec un maximum de 15,4 p. 100 dans une expérience. L'irradiation des souris aux rayons X à la dose de 400 r, 24 heures avant l'infection, a augmenté légèrement le taux d'infection chez les mouches. Les mouches sont plus aisément infectées quand le repas de sang contient de 50 à 20,000 trypanosomes par mm³ et 10 à 20,000 formes courtes et trapues par mm³. Avec la souche deT. brucei utilisée, ces taux d'infection favorables apparaissent chez la souris 12 jours après l'infection.

     

A comparison of the efficacy against Marek's disease of cell-free and cell-associated turkey herpesvirus vaccine.

One-day-old White Leghorn and broiler chicks with maternal antibody to turkey herpesvirus (HVT) were vaccinated with 300 or 1,000 plaque-forming units (PFU) of cell-free or cell-associated HVT vaccine and challenged with virulent Marek's disease virus (MDV) by contact exposure. Broiler chicks receiving 300 PFU of cell-associated HVT had a 3.3% incidence of MD lesions, whereas only 2.0% of those receiving 1,000 PFU had macroscopic lesions. Broiler chicks vaccinated with 300 PFU of cell-free vaccine had 6.8% gross lesions, and 0.67% of the birds receiving 1,000 PFU had MD lesions. Unvaccinated broiler chickens had a 28.3% incidence of MD lesions. Unvaccinated White Leghorn chickens had a 48.9% incidence of macroscopic lesions, whereas 5.4% of the birds receiving 300 PFU of cell-associated HVT had gross lesions, and 8.3% of the birds vaccinated with 1,000 PFU had lesions. In contrast, 6.7% of the chicks vaccinated with 300 PFU of cell-free HVT had MD lesions, and only 4.0% of those receiving 1,000 PFU of cell-free HVT had macroscopic lesions.     

Feline vaccine-associated sarcomas

Feline vaccine-associated sarcomas have presented many challenges. Initially, the etiopathogenesis and biological behavior of these tumors had to be characterized, and strategies implemented to move tumors away from problematic sites. Next, diagnostic and treatment recommendations evolved as the biologic behavior of vaccine-associated sarcomas forced early and aggressive intervention. Current therapeutic strategies are expensive, at times debilitating, and frequently fail to effect tumor control. This review summarizes the known history, epidemiology, etiology, and clinical management of vaccine-associated sarcomas after a decade of work. The next challenges must be to find more practical and effective solutions, and to eliminate the cause of vaccine-associated sarcomas.     

A survey of beef muscle color and pH

The objectives of this study were to define a beef carcass population in terms of muscle color, ultimate pH, and electrical impedance; to determine the relationships among color, pH, and impedance and with other carcasses characteristics; and to determine the effect of packing plant, breed type, and sex class on these variables. One thousand beef carcasses were selected at three packing plants to match the breed type, sex class, marbling score, dark-cutting discount, overall maturity, carcass weight, and yield grade distributions reported for the U.S. beef carcass population by the 1995 National Beef Quality Audit. Data collected on these carcasses included USDA quality and yield grade data and measurements of muscle color (L*, a*, b*), muscle pH, and electrical impedance of the longissimus muscle. About one-half (53.1%) of the carcasses fell within a muscle pH range of 5.40 to 5.49, and 81.3% of the carcasses fell within a longissimus muscle pH range of 5.40 to 5.59. A longissimus muscle pH of 5.87 was the approximate cut-off between normal and dark-cutting carcasses. Frequency distributions indicated that L* values were normally distributed, whereas a* and b* values were abnormally distributed (skewed because of a longer tail for lower values, a tail corresponding with dark-cutting carcasses). Electrical impedance was highly variable among carcasses but was not highly related to any other variable measured. Color measurements (L*, a*, b*) were correlated (P < 0.05) with lean maturity score (-.58, -.31, and -.43, respectively) and with muscle pH (-.40, -.58, and -.56, respectively). In addition, fat thickness was correlated with muscle pH and color (P < 0.05). There was a threshold at approximately .76 cm fat thickness, below which carcasses had higher muscle pH values and lower colorimeter readings. Steer carcasses (L* = 39.62, a* = 25.20, and b* = 11.03) had slightly higher colorimeter readings (P < 0.05) than heifer carcasses (L* = 39.20, a* = 24.78, and b* = 10.80) even though muscle pH was not different between steer and heifer carcasses. Dairy-type carcasses (pH = 5.59, L* = 37.56, a* = 23.40, and b* = 9.68) had higher muscle pH values and lower colorimeter readings than either native-type (pH = 5.50, L* = 39.55, a* = 25.13, and b* = 11.00) or Brahman-type (pH = 5.46, L* = 39.75, a* = 25.17, and b* = 11.05) carcasses (P < 0.05).