Calreticulin is transported to the surface of NG108-15 cells where it forms surface patches and is partially degraded in an acidic compartment

Although calreticulin (Crt) is primarily localized to the endoplasmic reticulum (ER), our results using biotinylation and immunocytochemical methods indicate that a small but significant amount of Crt is present and forms large patches on the surface of NG108-15 cells (a mouse neuroblastoma-rat glioma hybrid cell line). (35)S-labelled Crt molecules begin to reach the cell surface after only 10 min of labelling and disappear slowly from the cell surface. After 4 hr of labelling, approximately half of the newly synthesized Crt molecules are on the cell surface. We believe that some Crt molecules may escape from the KDEL receptor-mediated salvage pathway as they are synthesized and proceed through the secretory pathway to the cell surface. Immunoprecipitation from the culture medium shows that Crt is not released from the cell surface to the medium, suggesting tight binding to surface molecules. NH(4)Cl can block the degradation of Crt; therefore, Crt is presumably degraded in the lysosome pathway. However, blockage of the disappearance of surface Crt is less efficient than that of internal Crt. This suggests that the disappearance of Crt from the cell surface may not be due solely to its degradation, but may reflect transport into another cell compartment such as the ER.     

Effects of cataract and scotoma on visual acuity: a simulation study.

Central field loss (CFL) and cataract both decrease visual acuity. For patients with CFL, visual acuity is further reduced when the acuity target is more visually complex. We tested visual acuity for targets of varying complexity (letters alone, letters flanked by one or two x's on each side, and words) in subjects with normal vision and in the presence of a simulated cataract, simulated scotoma, and their combination (scotoma + cataract). Visual acuity was best with normal vision and worst with scotoma + cataract for all of the acuity targets. There was little difference in visual acuity between the letters alone and flanked letters, and visual acuity was best for words under all vision conditions. The cataract had a greater impact on visual acuity when the subject's central visual field was clear (normal vision) than when it was occluded by the simulated scotoma.     

STDs and family planning clinics: a regional program for Chlamydia control that works

Joint meetings between the members of the US Family Planning Services Program and the STD Program of Region X (comprising Alaska, Idaho, Oregon, and Washington) from fall 1986 through spring 1987 led to the screening and treatment of patients with chlamydia. Samples from patients were sent to state health department laboratories in Idaho, Washington, and Oregon. A direct fluorescent antibody (DFA) slide technique was used to process the cervical smears. Clinic visit record (CVR) information and laboratory results were collected by a central data management company, and sent to CDC and Region X researchers. 6 clinics in 3 of the states collected 2 cervical samples from each of 3000 patients, 1 for smear (DFA slide) and 1 for tissue culture over a 4-month period. During the 1988-1990 period, 136 clinics in the region supplied patient information and test results on over 300,000 samples. Overall, positive rates for chlamydia in the region went from a high of 10.9% in the 1st quarter of 1988 to 6.8% in the last quarter of 1990, with an overall declining trend. This amounted to an almost 37% decrease within the region. When analyzed by state, the positivity rates and decreases were relatively similar: Alaska, 12.2% to 10.0% positivity (18% decrease); Idaho, 10.5% to 8.0% (24% decrease); Oregon, 8.9% to 6.9% (22% decrease); and Washington, 9.3% to 6.6% (29% decrease). In patients 17 years of age and younger, positive rates for chlamydia fell 19%, from 12.2% in 1988 to 9.9% in 1990. In women 18-19 years old and women 20-24 years old, the rates fell 24% and 31%, respectively. Larger decreases in chlamydia rates were found among women in the 25-29 year age group (31% reduction) and in those 30 years old and older (44% reduction). Infection rates decreased in all race/ethnic groups, except Asians. Approximately 2/3 of the women with positive chlamydia tests had no apparent symptoms of disease. Conversely, the presence of certain clinical indicators seemed to correlate with the probability of a positive test result.     

Stimulation of Na+/H+ exchange is not required for induction of hypertrophy of renal cells in vitro.

Hypertrophy of renal proximal tubular cells is associated with an early increase in Na+/H+ antiport activity both in vivo and in vitro. The purpose of the study presented here was to determine whether functioning Na+/H+ antiport activity is required for hypertrophy to occur. LLC-PK1 cells deficient in Na+/H+ antiport activity were prepared by the "proton-suicide" method. Mutant cells had 28 to 40% of the normal Na+/H+ antiport activity. The addition of 50 nM methylisobutylamiloride to these cells decreased the antiport activity to less than 5% of the control value. In the mutant cells, steady-state intracellular pH was normal as was the protein content. After exposure of the wild-type cells for 72 h to 10(-6) M insulin and 10(-9) M insulin-like growth factor 1, cell protein content increased significantly. The increase in protein content induced by these growth factors in the mutant cells did not differ significantly from the response of the wild-type cells. Lowering the Na+/H+ exchange further by the addition of methylisobutylamiloride (50 nM) to less than 5% of the control value did not blunt the hypertrophic response in the mutant cells. These studies indicate that hypertrophy can be induced in LLC-PK1 cells by growth factors when basal Na+/H+ antiport activity is reduced to low levels by selective mutation or by competitive inhibition. The results suggest that stimulation of the Na+/H+ antiporter is not an essential prerequisite for the induction of hypertrophy in renal cells.     

Integration of new embryonic nephrons into the kidney

The current report summarizes our experiments exploring the feasibility of creating a chimeric kidney, that is, an organ constituted by cells derived from more than one fertilized ovum. The overall strategy has been to obtain donor renal tissue from avian and murine embryos and to implant this into the host avian mesonephric mesoderm or into the cortex of murine neonatal kidney. In both models, donor cells were distinguished from the host by the presence of characteristic nuclear or cytoplasmic markers. Examination of quail to chick transplants showed the tandem development of mesonephric tissue in the form of bilobed organ. In the mouse chimeric kidney, examined 2 to 4 weeks postnatally, transplanted metanephric tissue grew and developed glomeruli, proximal tubules, and cords of cells, which extended into the medulla of the host kidney. Before death, intravenous FITC-dextran was administered to the host mouse. Some transplanted tubules were connected to filtering glomeruli, as judged by the presence of fluorescein within their lumens. These experimental models provide novel means with which to study nephrogenesis in vivo. Finally, if the embryonic donor tissue could be genetically engineered before implantation, the prospect of "nephron therapy" arises, in which altered implanted nephrons could deliver therapeutically useful molecules into the urine or kidney interstitium.