The progressive effects of a fat enriched diet on ventricular myocyte contraction and intracellular Ca2+ in the C57BL/6J mouse

The C57BL/6J mouse has a genetic susceptibility to develop diabetes when fed with a high-fat, high-sucrose diet. The general characteristics of diet-induced diabetes in this model include progressive development of hyperinsulinaemia, hyperglycaemia, insulin resistance and obesity, features that are frequently observed in the clinical setting. This study investigated the progressive effects of a fat enriched (FE) diet on contraction and intracellular Ca2+ in ventricular myocytes from the C57BL/6J mouse. The characteristics of the mice fed with the FE diet compared to mice receiving control diet included progressive increase in the rate of body weight gain, increased fasting blood glucose and time-dependent differences in the disposal of blood glucose after a glucose challenge. The ultrastructure of cardiac myocytes and associated capillaries did not show any gross morphological alteration after 27 weeks of FE diet compared to controls. At 5 months the resting cell length (RCL) and the kinetics of shortening were not significantly altered in ventricular myocytes from mice receiving the FE diet compared to age-matched controls. At 5 and at 7 months the amplitude of shortening was increased in myocytes receiving the FED diet compared to controls. At 7 months the time to half (THALF) relaxation of myocyte contraction was shortened in myocytes from mice receiving the FE diet compared to controls. Mean THALF relaxation in myocytes from mice fed the FE diet was 32.0 +/- 1.4 ms (n = 23) compared to 40.2 +/- 2.0 ms (n = 27) in controls. Neither resting intracellular Ca+ nor the kinetics or amplitude of the Ca2+ transient were altered by FE diet. Differences in myofilament sensitivity to Ca2+ might underlie the changes in contractility.

Rapid and reliable method for diagnostic electron microscopy of faeces

Four methods are described for examining viruses in faeces by electron microscopy using negative staining. Faeces samples from a total of 180 patients with diarrhoea illnesses were processed for electron microscopy by the direct staining technique, pseudoreplica technique, microsolute concentration technique and by ultracentrifugation. Virus particles (including rotaviruses and adenoviruses) were found in fifty-five (31%) samples when the results of all methods were combined. Bacteriophages were found in thirty of the samples which were read virus negative. Herpesviruses were also found in the faecal samples of two patients with diarrhoea illness. Parvovirus-like particles were identified in one sample which was rotavirus and adenovirus positive. Calicivirus-like particles were found in a sample which was adenovirus positive. With the direct staining technique thirty-six (20%) samples contain virus particles; with microsolute concentration technique forty-eight (27%) samples contain virus particles and with ultracentrifugation thirty-eight (21%) contain virus particles. It is believed the microsolute concentration technique is rapid and more reliable than the pseudoreplica technique and ultracentrifugation method, and is a more preferable method for the diagnosis of faecal sample by electron microscopy.

Ultrastructural changes in the heart of rats treated with chloroquine

Effects of prolonged chloroquine administration on ultrastructure of the heart was studied in albino rats. Chloroquine when administered orally (30-40 mg/kg/day) or subcutaneously (20 mg/kg/day) for two to four weeks, produced marked degenerative changes in the mitochondria and myofibrils of the myocardium. The mitochondria were more susceptible to the toxic effect of chloroquine than were other cell organelles. Moreover, the cytotoxic effect of the drug appeared to be related to total dose. Chloroquine-induced abnormalities were reversible on terminating medication. These results indicate that prolonged chloroquine administration impairs ultrastructure of the myocardium.

Improved rapid method for electron microscopy of macro- and micro-tissue cultures

A rapid method of embedding macro- and micro-tissue cultures is described. The procedure involves use of a preshaped BEEM capsule for pelleting, fixation and embedding of tissue culture cells for electron microscopy. To obtain good contrast specimens prepared by this rapid method need a rather longer staining time with uranyl acetate than specimens prepared by standard methods. THis procedure takes only about 200 min from fixation and embedding to double staining with uranyl acetate and lead citrate. It should be useful for both monolayer tissue cultures and organ cultures in diagnostic and research studies on viral agents.