Removal of histone H1 from intact nuclei alters the digestion of nucleosome core DNA by staphylococcal nuclease

We have examined the gel profiles of staphylococcal nuclease digests of intact nuclei following different extents of removal of histone H1 by low pH. It was found that the submonomer fragment pattern (i.e. fragments less than 140 base pairs (bp) changed dramatically following removal of H1. The most striking feature of this change was a marked increase in the relative intensity of a band migrating at 102 +/- 4 bp when about 20-50% of the nuclear DNA is rendered acid soluble. All other submonomer bands decreased in relative intensity. There was no evidence for an approximately 100-bp repeat pattern accompanying the enhanced generation of the 102-bp fragment following H1 removal. This result, along with the comparisons of gel profiles for different extents of digestion, suggests that removal of histone H1 from nuclei results in an increased susceptibility of the DNA to staphylococcal nuclease at one or both ends of many of the core particles and that a strong block to further digestion occurs within these core particles resulting in the formation of a relatively stable 102-bp fragment.     

Effect of large oral doses of ascorbic acid on uric acid excretion by normal subjects

The effects of large and oral doses of ascorbic acid on renal clearance and excretion of uric acid were studied in nongouty subjects because ascorbic acid has been reported to increase renal uric acid clearance. Our results indicate that 4 or 12 gm ascorbic acid taken in divided doses had no effect on serum uric acid concentration or uric acid excretion and clearance by the kidney. Reasons for these results, which differ from previous reports, are discussed. We quantitated the magnitude of the interference of ascorbic acid in the measurement of uric acid by the nonspecific methods frequently used, since falsely elevated urine uric acid could lead to misinterpretation of screening tests.     

Zinc metabolism and homeostasis in rats fed a wide range of high dietary zinc levels

Zinc metabolism and homeostasis were studied in young growing rats fed a 38 ppm zinc diet with added zinc levels ranging from 0 to 8400 ppm for 21 days. High dietary zinc did not cause toxicity symptoms. Stable zinc in feces increased linearly with dietary zinc intake but fecal 65Zn, from a single oral dose, did not increase above the 1200 ppm dietary level. Stable zinc in liver, kidney, and tibia increased two to three times with 2400 ppm added zinc, but was not further elevated until 8400 ppm was fed. Stable zinc in muscle and heart was not affected appreciably by dietary zinc level. In all tissues, 65Zn retention was drastically reduced with 1200 ppm added dietary zinc. Additional dietary zinc reduced 65Zn in muscle and heart but had little effect on liver and kidney 65Zn. The data indicate that rats have fairly effective homeostatic control mechanisms for tissue zinc below about 7200 ppm dietary zinc. Whereas, with dietary zinc up to about 1200 ppm, decreasing absorption is the main route of homeostatic control, above this level, more rapid zinc turnover rates and increasing endogenous zinc excretion appear to have major importance.     

Reovirus-like agent associated with fatal diarrhea in neonatal pigs

Large numbers of a reovirus-like agent were visualized with electron microscopy in bacteria-free gut homogenates obtained from piglets with a fatal diarrhea resembling transmissible gastroenteritis. The syndrome, of vomiting, diarrhea, dehydration, and death, was reproduced in piglets artificially infected with these bacteria-free gut homogenates. Reovirus-like particles persisted in serial piglet passage and none was seen in uninfected, asymptomatic controls. Hyperimmune sera (made in recovered piglets) aggregated the reovirus-like particles, as judged by immunoelectron microscopy, and neutralized the infectious agent. The cytoplasm in enterocytes on infected intestinal epithelium fluoresced when this hyperimmune sera was used in an indirect fluorescent antibody test. Feeding cow colostrum or diets containing porcine gamma globulin protected infected piglets. No cytopathogenic effect was noted in infected tissue cultures, nor did this agent affect neonatal guinea pigs, hamsters, mice, and rats. The agent did not agglutinate human O or A erythrocytes.     

Capture myopathy in Elk in Alberta, Canada: a report of three cases

Acute capture myopathy was diagnosed in 3 elk (Cervus canadensis). In 2 of the elk, hindlimb lameness developed within 10 days of capture. Clinical signs were not observed in the third elk, which was found dead 7 days after its capture. Elks 1 and 2 were euthanatized and all 3 animals were necropsied. In elks 1 and 2, rupture of the semi-membranosus muscle was associated with massive hemorrhage and swelling. Microscopic findings included hemorrhage, edema, myofibril fragmentation, and evidence of attempted muscular regeneration. In elk 3, several of the large muscles of the hindlimbs as well as the biceps brachii muscles of the forelimbs appeared pale, dry, and friable. Except for lack of hemorrhage and edema, microscopic findings in this elk were similar to those of elks 1 and 2.     

Effects of various ambient temperatures and of heating and cooling the hypothalamus and cervical spinal cord on antidiuretic hormone secretion and urinary osmolality in pigs

1. Plasma ADH concentration, urinary and plasma osmolality and haematocrit were measured in young pigs placed in cold, thermoneutral, warm and hot ambient temperatures. In some experiments a thermode placed in the hypothalamus or over the cervical spinal cord was heated or cooled at various ambient temperatures. 2. Plasma ADH concentration remained at a low level (0-5--5 muu. ml.-1) over 2 hr or 3 hr periods when the pigs were in cold, thermoneutral or warm ambient temperatures. A hot environment, which caused a marked rise in the pigs' rectal temperature, was associated with a large rise in plasma ADH level. 3. The rise in plasma ADH level which occurred during an increase in body temperature was consistently and completely suppressed by simultaneous cooling of the thermode in the pre-optic region to 5 to 10 degrees C. When the thermode was in the region of the supraoptic nucleus the rise in ADH was only partly suppressed, and when it was over the cervical cord it was only sometimes suppressed. 4. Cooling the thermodes in any position at a cold or thermoneutral ambient temperature, or heating them at a thermoneutral or warm ambient temperature, caused no consistent change in ADH. 5. A diuresis, with a urinary flow-rate of at most 1 ml. min-1 and minimal urinary osmolality of 53 m-osmole kg-1, was observed on only three occasions, twice during cooling of a thermode in the hypothalamus and once after the end of a period when the thermode was heated. In each case, the plasma ADH was less than 2 muu. ml.-1. 6. A slight rise of haematocrit in cold ambient conditions and a slight fall in the warm were observed. Otherwise changes in haematocrit were trivial, and a shift of water between vascular system and interstitium could not be invoked to account for changes in ADH levels. Observed variation of plasma osmolality was also slight.