Changes in the tartrate-resistant acid phosphatase cell population in dental follicles and bony crypts of rat molars during tooth eruption

It was the aim of this study to determine the cellular changes that occur in the enamel organ, dental follicle, and surrounding bony crypt of the rat molar prior to and during tooth eruption. By use of light microscope histochemistry to detect cells containing tartrate-resistant acid phosphatase (TRAP), it was seen that TRAP-positive mononuclear cells were present in the dental follicle prior to the onset of eruption (e.g., three days postnatal age) and then declined in number during eruption. Concurrently, TRAP-positive osteoclasts were initially present in large numbers on the surface of the bony crypts surrounding the molars (three days postnatal age) and then declined in number as eruption progressed. Electron microscopy confirmed that these were mononuclear cells and osteoclasts. The results suggest that the mononuclear cells are either precursors of the osteoclasts or perhaps release cytokines that affect osteoclast formation or activity. Staining for alkaline phosphatase (ALP) activity indicated that at an early postnatal age (secretory stage of amelogenesis), ALP was detected only in the stratum intermedium of the enamel organ, whereas at a later age (maturation phase of amelogenesis), it was present only in the ameloblasts. These results, combined with a survey of the literature, strongly suggest that ALP moves from the base of the enamel organ to the enamel itself over a period of time ranging from pre- to post-eruption. Rat molars are teeth of limited eruption, and the cellular events that occur in eruption appear comparable with what is seen in dog and human dentition, especially in terms of the cellular events seen in the dental follicle prior to and during eruption.(ABSTRACT TRUNCATED AT 250 WORDS)

Multiple thermolabile and temperature-sensitive lesions in mutant tl17 of vesicular stomatitis virus

The vesicular stomatitis virus thermolabile mutant tl17 contains multiple lesions. The RNA-dependent RNA polymerase is temperature sensitive during primary transcription. The glycoprotein develops Endo H sensitivity more slowly at the nonpermissive temperature. Maturation or incorporation of the glycoprotein into progeny virions is also reduced. When virions of tl17 made at the permissive temperature are incubated in buffered medium at 39 degrees, their glycoprotein is cleaved, resulting in a product that resembles soluble glycoprotein. Compared to another glycoprotein mutant, ts 045, the glycoprotein of tl17 is only partially degraded to soluble G intracellularly and is more thermolabile. These properties of tl17 make it potentially useful for studies on glycoprotein synthesis, processing, and transport as well as for studies on pseudotype formation and viral maturation.

Locally and systemically derived natural killer cells participate in defense against intranasally inoculated influenza virus

Previous studies have indicated that the pulmonary natural killer (NK) cells are important in early defense against influenza virus (PR8/34) infection by the intratracheal route. Since the natural route of virus entry into the lung is via the upper respiratory tract, the present study was to elucidate the role of NK cells in early defense to intranasal (IN) inoculation of influenza virus. Rabbit anti-Asialo GM1 (RAGM1) serum was administered by IN, intravenous (IV), or both routes, 24 hours before IN infection with a median lethal dose (LD50) of PR8/34 previously shown to kill 50% of the inoculated mice (B6D2F1 or nu/nu) by day 8. IN or IV inoculation of 20 microliters of RAGM1 (whole rabbit serum) had no effect on the survival of the mice to virus administered by the IN route. When RAGM1 was given IV (10 microliters) and IN (10 microliters) 24 hours before PR8/34 IN, 60% of the mice (B6D2F1 or nu/nu) died by day 4. Influenza virus titers were at least one log higher in the lungs of B6D2F1 mice and two logs higher in IN/IV NK-depleted nu/nu mice than in lungs of mice who received RAGM1 by IV or IN route alone or who were untreated. NK activity was depleted in lungs but not blood of mice treated IN with RAGM1 and was depleted in both lungs and blood if RAGM1 was given IV. These data support the hypothesis that NK cells are important to early defenses against influenza virus in the upper respiratory tract and that they are derived from both a local and systemic population of NK cells.

Imipenem-cilastatin in the treatment of methicillin-sensitive and methicillin-resistant Staphylococcus aureus infections

Imipenem-cilastatin was evaluated for efficacy and toxicity as an antistaphylococcal agent in 23 patients; 11 of these patients were infected with methicillin-resistant Staphylococcus aureus (MRSA), and 12 were infected with methicillin-susceptible S. aureus (MSSA). There were 15 soft tissue, 5 endovascular, and 3 skeletal infections and a total of nine patients with bacteremia. As determined by in vitro susceptibility testing, the MICs for 90% of the MRSA and MSSA isolates tested were 6.25 and 0.39 micrograms/ml, respectively. Two MRSA isolates were resistant to a concentration of greater than 16 micrograms/ml. When 11 MRSA isolates and 7 MSSA isolates were incubated for 48 h the MICs for 90% of the isolates increased to greater than 50 micrograms/ml for the MRSA isolates and 6.25 micrograms/ml for the MSSA isolates. Three S. aureus isolates emerged resistant. Ten of 11 (91%) MRSA infections and 11 of 12 (92%) MSSA infections were clinically cured. Adverse reactions occurred in 25% of the imipenemcilastatin-treated patients. These reactions included gastrointestinal intolerance (7% of the patients), rash or pruritus (6%), eosinophilia (6%), thrombocytosis (4%), and a positive, direct Coomb test without hemolysis (3%). One of the two patients for whom therapy was discontinued because of gastrointestinal intolerance had antibiotic-associated colitis. Imipenem appears to be an effective antistaphylococcal agent against both MRSA and MSSA infections.