Cyclic AMP inhibits increased collagen production by cyclically stretched smooth muscle cells

Rabbit arterial smooth muscle cells, grown on elastin membranes which were cyclically elongated and relaxed, responded by increasing their rates of synthesis of protein and, in particular, of collagen, compared to stationary controls. Raising intracellular cyclic AMP (cAMP) levels by adding theophylline or dibutyryl cAMP to the culture medium prevented the synthetic response to cyclic stretching, but did not alter the rates of protein or collagen synthesis by stationary controls. Both synthesis and degradation of collagen by cyclically stretched cells increased in parallel such that the proportion of synthesized collagen that was degraded was similar to that found in the stationary cultures. Collagen degradation was not affected by theophylline administration to stationary cell cultures but the drug increased degradation of collagen by cyclically stretched cells. We conclude that the net production of protein, and in particular of a structural protein, collagen, by arterial smooth muscle cells subjected to the mechanical force of stretching was inhibited when intracellular levels of cAMP were raised. The results suggest that cAMP may play a role in the modulation of structural protein content of artery walls in response to changes in tensile stress.     

Filamentous actin bundles in the kidney

The distribution of filamentous actin bundles in the rat kidney was studied using a fluorescent phallotoxin label and transmission electron microscopy. The microvillous brush border lining proximal tubules, smooth muscle in renal vessels, and renal corpuscles were the structures most intensely labeled with rhodamine phalloidin. Closer evaluation of renal corpuscles revealed intense labeling of filamentous actin within podocyte foot processes enveloping the glomerular capillary loops. Rhodamine phalloidin also labeled basal bands of filamentous actin in the parietal epithelium and basal bands of actin in proximal and distal tubules. Finally, a band of filamentous actin was evident along the innermost aspect of the kidney capsule, within cells which often joined to form sinus-like compartments.     

Origin and filiation of human plasmacytoid dendritic cells

Human plasmacytoid dendritic cells represent a rare population of leukocytes which produce high amounts of type I interferon in response to certain viruses. Although those cells were first described in 1958, there are still unsolved issues related to their origin and function. Recently, a leukemic counterpart of plasmacytoid dendritic cells was identified. Molecular approaches using either normal or leukemic plasmacytoid dendritic cells provide some new insights into the controversial lymphoid origin of those cells. The need for specific markers is still a critical aspect for the identification of plasmacytoid dendritic cells, whatever stage of differentiation, in normal as well as in pathological conditions. Hopefully, novel markers will allow delineation of the relationships between dendritic cells at different stages of differentiation/maturation along the myeloid and lymphoid lineages.     

Calcitonin determination by a fast and highly sensitive enzyme amplified immunoassay

A colorimetric enzyme amplification system was used to develop an immunoassay for human calcitonin (hCT) with a sensitivity of 6 pmol/l, and intra- and inter-assay CVs of 12% and 11.8% respectively for the low pool, and 10% and 11.2% for the high pool. The mean recovery of added synthetic hCT (58.5 pmol) from the plasma of 10 patients was 110% (64.4 pmol). The correlation coefficient between radioimmunoassay (RIA) and amplified enzymo-immunoassay was found to be 0.96 (p 0.001). The assay was successfully applied to the measurement of elevated calcitonin levels in plasma from patients with medullary carcinoma of the thyroid (MCT). AEIA offered a reliable and sensitive alternative to RIA for calcitonin determination with the added advantage of convenience as the label employed was much more stable.     

Surveillance of antibiotic resistance in invasive isolates of Neisseria meningitidis in Australia 1994-1999

A total of 1434 strains of Neisseria meningitidis isolated from cases of invasive meningococcal disease (IMD) in Australia between 1994 and 1999 were examined by standard methods for susceptibility to antibiotics used for treatment and prophylaxis. The proportion of isolates fully susceptible to penicillin decreased from 45% in 1994 to 26% in 1999 (P<0.001). All the other isolates were less sensitive to penicillin except for two meningococci with a penicillin MIC of 1 mg/l. The geometric mean penicillin MIC increased from 0.045 to 0.065 mg/l from 1994 to 1999. There was no significant difference in the geometric mean penicillin MICs of serogroup B and serogroup C meningococci. Penicillin susceptibility was significantly associated with a poorer outcome. Isolates from survivors of IMD had a higher geometric mean penicillin MIC (0.06 mg/l) than those from fatal cases (0.048 mg/l) (P< 0.001). This suggests that factors other than the decrease in susceptibility to penicillin observed were more relevant to outcome in IMD. All isolates were fully susceptible to ceftriaxone. Rifampicin resistance was infrequent (eight isolates in 6 years) and sporadic. A single isolate had decreased quinolone susceptibility. Despite the significant shift in susceptibility to penicillin recorded, this group of antibiotics remains a suitable treatment for IMD in Australia.