Biomedical subjects
Publications and source records attributed to K E White.
Explore the source record for details and available documents.
Plasma membrane Ca(2+)-ATPase (PMCA) and the Na+/Ca2+ exchanger participate in regulating cell function by maintaining proper intracellular Ca2+ concentrations ([Ca2+]i). In renal epithelial cells these proteins have been additionally implicated in cellular calcium absorption. The purpose of the present studies was to determine the Ca2+ extrusion mechanisms in cells derived from the proximal tubule. Homology-based RT-PCR was used to amplify PMCA transcripts from RNA isolated from mouse cell lines originating from the S1, S2, and S3 proximal tubule segments. S1, S2, and S3 cells exhibited only PMCA1 and PMCA4 products. PCR product identity was confirmed by sequence analysis. Northern analysis of proximal tubule cell RNAs revealed appropriate transcripts of 7.5 and 5.5 kb for PMCA1 and 8.5 and 7.5 kb for PMCA4, but were negative for PMCA2 and PMCA3. Western analysis with a monoclonal antibody to PMCA showed that all proximal cell lines expressed a reacting plasma membrane protein of 140 kD, the reported PMCA molecular mas. Na+/Ca2+ exchanger (NCX1) mRNA expression, analyzed by RT-PCR, protein expression by Western analysis, and functional exchange activity were uniformly absent from all proximal tubule cell lines. These observations support the idea that immortalized cells derived from the proximal tubule express PMCA1 and PMCA4, which may serve as the primary mechanism of cellular Ca2+ efflux.
BACKGROUND: In September 1994, the Minnesota Department of Health detected an increase in the number of reports of Salmonella enteritidis infections. After a case-control study implicated a nationally distributed brand of ice cream (Schwan's) in the outbreak, the product was recalled and further epidemiologic and microbiologic investigations were conducted. METHODS: We defined an outbreak-associated case of S. enteritidis infection as one in which S. enteritidis was cultured from a person who became ill in September or October 1994. We established national surveillance and surveyed customers of the implicated manufacturer. The steps involved in the manufacture of ice cream associated with cases of S. enteritidis infection were compared with those of products not known to be associated with infection matched for the date of manufacture. Cultures for bacteria were obtained from ice cream samples, the ice cream plant, and tanker trailers that had transported the ice cream base (premix) to the plant. RESULTS: We estimate that S. enteritidis gastroenteritis developed in 224,000 persons in the United States after they ate Schwan's ice cream. The attack rate for consumers was 6.6 percent. Ice cream associated with infection contained a higher percentage of premix that had been transported by tanker that had carried nonpasteurized eggs immediately before (P = 0.02). S. enteritidis was isolated from 8 of 226 ice cream products (3 percent), but not from environmental samples obtained from the ice cream plant (n = 157) or tanker trailers (n = 204). CONCLUSIONS: This nationwide outbreak of salmonellosis was most likely the result of contamination of pasteurized ice cream premix during transport in tanker trailers that had previously carried nonpasteurized liquid eggs containing S. enteritidis. To prevent further outbreaks, food products not destined for repasteurization should be transported in dedicated containers.
In summary, DCT cells express multiple isoforms of the Na-Ca exchanger and exhibit functional exchange, and antisense oligonucleotides to a downstream region of the exchanger transcript inhibit activity. These experiments provide direct evidence for Na-Ca exchange in DCT cells mediated by NACA2, NACA3, or NACA6.
Ca2+ efflux from osteoblasts is thought to be mediated by Na+/Ca2+ exchange and by a plasma membrane Ca(2+)-ATPase. The presence of plasma membrane Na+/Ca2+ exchange was determined in rat UMR 106 osteosarcoma cells by functional and molecular studies. Na+/Ca2+ exchange activity was tested by measuring changes of [Ca2+]i in single cells. After Na+ loading the cells and removing extracellular Na+, the direction of exchange was reversed and [Ca2+]i increased by 100%. Multiple isoforms of the NCX1 gene product, encoding plasma membrane Na+/Ca2+ exchangers, were cloned from UMR 106 cells and a sample of primary human osteoblasts using homology-based RT-PCR. Isoforms NACA3, NACA7, and NACA10 were found in UMR 106 cells, whereas human osteoblasts expressed NACA3 and NACA7. Transcripts for NCX2 and the Na+/Ca2+, K+ exchanger were not detected. Northern analysis of UMR 106 cells with a probe to the NCX1 gene product revealed the presence of a transcript of 7 kb, the size of the exchanger message. Western analysis of UMR 106 cell membrane preparations with a polyclonal antibody specific for the NCX1 exchanger showed the presence of reacting proteins consistent with the reported masses of the exchanger at 125 and 85 kD. These results demonstrate Na(+)-dependent Ca2+ efflux from UMR 106 cells and the presence of several NACA isoforms in UMR 106 and primary human osteoblasts.
PURPOSE: To assess possible triggers and cofactors for chronic fatigue syndrome (CFS) and to compare levels of selected cytokines between cases and an appropriately matched control group. PATIENTS AND METHODS: We conducted a case-control study of 47 cases of CFS obtained through a regional CFS research program maintained at a tertiary care medical center. One age-, gender-, and neighborhood-matched control was identified for each case through systematic community telephone sampling. Standardized questionnaires were administered to cases and controls. Sera were assayed for transforming growth factor-beta (TGF-beta), interleukin-1 beta, interleukin-6, tumor necrosis factor-alpha, and antibody to Borrelia burgdorferi and Babesia microti. RESULTS: Cases were more likely to have exercised regularly before illness onset than controls (67% versus 40%; matched odds ratio (MOR) = 3.4; 95% CI = 1.2 to 11.8; P = 0.02). Female cases were more likely to be nulliparous prior to onset of CFS than controls (51% versus 31%; MOR = 8.0; 95% CI = 1.03 to 170; P = 0.05). History of other major factors, including silicone-gel breast implants (one female case and one female control), pre-morbid history of depression (15% of cases, 11% of controls) and history of allergies (66% of cases, 51% of controls) were similar for cases and controls. However, cases were more likely to have a diagnosis of depression subsequent to their diagnosis of CFS compared to a similar time frame for controls (MOR = undefined; 95% CI lower bound = 2.5; P < 0.001). Positive antibody titers to B burgdorferi (one case and one control) and B microti (zero cases and two controls) were also similar. CONCLUSIONS: Further investigation into the role of prior routine exercise as a cofactor for CFS is warranted. This study supports the concurrence of CFS and depression, although pre-morbid history of depression was similar for both groups.
Renal distal convoluted tubules (DCT) are a major site of hormone-regulated, active calcium absorption. Calcium exit across basolateral plasma membranes is thought to be mediated by Na+/Ca2+ exchange and a Ca(2+)-ATPase. In this report the presence and function of Na+/Ca2+ exchangers in DCT cells were assessed. cDNAs encoding a conserved region and the variable regions of three alternatively spliced isoforms of the Na+/Ca2+ exchanger, NACA2, NACA3, and NACA6, were isolated in a ratio of 7:12:1 using homology-based reverse transcription-polymerase chain reaction (RT-PCR) with RNA from an immortalized mouse DCT cell line. Northern blots probed with a 32P-labeled PCR product from a conserved region of the exchanger were positive for a single transcript of 7 kb in primary cultures of distal tubule cells (cortical ascending limb + DCT cells), consistent with the reported size of the exchanger in other tissues. Na+/Ca2+ exchange was assessed by measuring sodium-dependent changes of intracellular calcium ([Ca2+]i), in single cells. In the presence of an outward Na+ gradient, [Ca2+]i increased by 240%. Collapsing the Na+ gradient with monensin inhibited the rise of [Ca2+]i. Removal of extracellular Ca2+ or the addition of an Na+ ionophore inhibited the rise of [Ca2+]i. The intracellular Na+ concentration decreased upon removal of extracellular Na+ in parallel with the rise of [Ca2+]i. Western analysis performed on membranes prepared from DCT cells or primary cultures of distal tubule cells with a polyclonal antibody revealed bands at approximately 125 and 85 kDa, consistent with reported sizes for exchanger protein. These findings show that Na+/Ca2+ exchanger transcripts, protein, and activity are present in DCT cells and that Na(+)-dependent Ca2+ efflux may be mediated by NACA2, NACA3, and NACA6.
To determine the accuracy of school-based childhood immunization records and to describe the effects of their use on estimates of community-wide immunization coverage, we verified the immunizations to 72 months of age for children born in 1986 to residents in Dallas County, TX, and in Minnesota. Verified immunizations were compared with those documented in the school record. Major transcription errors accounted for fewer than 1% of discrepancies between school and provider records. For 99 subjects with 987 verified immunizations in Minnesota, age-appropriate immunization coverage estimated from the school records was within two percent of actual coverage. For 86 subjects with 981 verified immunizations in Dallas County, age-appropriate immunization coverage from the school records underestimated actual coverage by as much as 21%. The primary factor explaining the underestimate in Dallas was incomplete school immunization records for 33 (38%) subjects and 126 (13%) immunizations. Selective recording of immunizations related to the minimum state requirements in Texas contributed to incomplete school records in Dallas County. Verification of the completeness of records selected to estimate immunization coverage is essential if the estimates are used to monitor trends or to make public policy decisions.
Physician attitudes and practices regarding universal infant vaccination against hepatitis B virus infection in Minnesota were assessed approximately 1 year after publication of the Immunization Practices Advisory Committee recommendations. Four-hundred eighteen Minnesota family physicians and pediatricians were sent self-administered questionnaires, with follow-up by telephone. Among physicians who provide care to infants, 67 (29%) of 234 family physicians and 29 (50%) of 58 pediatricians routinely offered hepatitis B vaccine to all infants (overall 33%) (P = 0.002). The recommendations of the Immunization Practices Advisory Committee, the American Academy of Pediatrics and the American Academy of Family Physicians had the greatest positive influence on physicians' opinions regarding routine hepatitis B vaccination. The factors with the greatest negative influence on their opinions were the low prevalence of hepatitis B virus infection in Minnesota and the addition of three injections to the current childhood immunization schedule. Universal infant hepatitis B vaccination remains controversial among Minnesota family physicians and pediatricians. We believe, given the variability in hepatitis B virus incidence and prevalence in the United States and the relatively low risk of most infants, that a single national policy based solely on universal infant immunization may be difficult to implement.
Magnetic resonance imaging (MRI) has provided a clear view of the sella turcica and the pituitary gland, even on "routine" procedures that invariably include the sagittal T1-weighted sequence. A pituitary gland that does not fully occupy the sella is a common observation, even in normal individuals. Terms such as "empty sella" and "partially empty sella" have become more commonly used, occasionally giving rise to some confusion regarding their clinical significance. In a prospective study of 50 "near-normal" patients, based exclusively on the midsagittal T1-weighted image, we have found a statistically significant increase in sellar emptiness with age, a phenomenon that is more prominent in women. The finding of an empty or partially empty sella on routine MRI of the brain is therefore usually of no clinical significance.
OBJECTIVE: To determine the incidence of invasive Haemophilus influenzae type b disease in children living in Minnesota and Dallas County, Texas, before and since introduction of plain polysaccharide vaccine in 1985, and conjugate vaccine in 1988. Initially, use of these vaccines was limited to infants 18 months of age and older. DESIGN: Identification of culture-proven cases of H influenzae type b disease was through systems of active, laboratory-based surveillance. The mean incidence of disease (cases observed/100,000 child-years) for 1983 and 1984 served as a baseline for comparison with subsequent years through 1991. PARTICIPANTS: Children less than 5 years of age in Minnesota and Dallas County, Texas. Overall, there were 2557 confirmed age-eligible cases of invasive H influenzae type b disease from 1983 through 1991. RESULTS: Between the 1983-1984 baseline and 1991, the incidence of H influenzae type b disease decreased 85% in Minnesota and 92% in Dallas. Notably, declines in incidence were observed in children in the age group being vaccinated as well as in infants younger than 18 months of age prior to introduction of vaccination. CONCLUSION: In two widely separated areas of the United States, a profound decrease in the incidence of H influenzae type b disease has occurred. The data suggest that vaccination may be protecting against disease, as well as decreasing the spread of infection to unvaccinated infants.
The incidence of Salmonella enteritidis infections has increased in the eastern United States, and consumption of undercooked eggs has been associated with outbreaks of S. enteritidis. In Minnesota, the incidence of S. enteritidis infections doubled from 1980 to 1990; however, no egg-associated outbreaks were identified. A case-control study was conducted to examine potential exposures for S. enteritidis and Salmonella typhimurium infections in Minnesota adults. Sporadic cases of S. enteritidis (odds ratio [OR], 5.2; 95% confidence interval [CI], 1.9-14.2; P = .003) and S. typhimurium infection (OR, 2.4; CI, 1.1-5.5; P = .03) were more likely to have consumed undercooked eggs or egg-containing foods during the 3 days before onset of illness compared to a similar reference period for controls. In addition, the extent to which eggs were cooked was directly associated with illness (chi 2 test for trend, P < .001). These findings demonstrate that eggs are important vehicles for S. enteritidis and S. typhimurium, even in the absence of recognized outbreaks.
Explore the source record for details and available documents.
OBJECTIVE: To determine the source of an outbreak of Salmonella javiana and Salmonella oranienburg infections. DESIGN: Laboratory-based statewide surveillance for Salmonella infections and two separate case-control studies. SETTING: Community- and industry-based studies conducted from May through October 1989. PARTICIPANTS: Thirty-one culture-confirmed outbreak-associated cases of S javiana infection and 60 community controls matched for telephone prefix, gender, and age in case-control study I; 50 cases, 100 community controls, and 64 family member controls in case-control study II. RESULTS: One hundred thirty-six culture-confirmed cases of S javiana infection and 11 cases of S oranienburg infection were associated with the outbreak in Minnesota. Outbreak-associated cases were also identified in Wisconsin (15 cases), and in Michigan and New York (one case each). Cases were more likely than controls to have consumed mozzarella cheese manufactured at a single cheese plant (plant X) or cheese that had been shredded at processing plants that also shredded cheese manufactured at plant X (odds ratio [OR], 7.2; 95% confidence interval [CI], 1.7 to 23.2; P < .01). The outbreak-associated strains of both serovars were isolated from two unopened 16-oz (0.45-kg) blocks of mozzarella cheese produced at plant X. The most probable numbers of Salmonella organisms in these samples were 0.36/100 g and 4.3/100 g. CONCLUSIONS: The potential for bacterial pathogen contamination of cheese during manufacture and processing has important epidemiologic implications, particularly because cheese consumption has recently increased in the United States. Low-level contamination of a nationally distributed food product can cause geographically dispersed foodborne outbreaks that may be difficult to detect.
OBJECTIVE: To determine the source of an international outbreak of shigellosis associated with consumption of food served by a Minnesota-based airline. DESIGN: Cohort studies of players and staff of a Minnesota-based professional football team and passengers on flights with a confirmed case of outbreak-associated Shigella sonnei infection. SETTING: Community- and industry-based studies conducted from October through November 1988. PARTICIPANTS: Sixty-five football team players and staff, and 725 airline passengers in the cohort studies. RESULTS: Twenty-one (32%) of 65 football players and staff developed shigellosis that was associated with consumption of cold sandwiches prepared at the airline flight kitchen (relative risk [RR], 17.1; 95% confidence interval [Cl], 2.4 to 120; P < .001). Confirmed or probable shigellosis was identified among 240 passengers on 219 flights to 24 states, the District of Columbia, and four countries between September 14 and October 13. An outbreak-associated strain of S sonnei was isolated from football players and staff, airline passengers, and flight attendants. Thirty (4.1%) of 725 passengers on 13 flights with confirmed cases had confirmed or probable shigellosis. Illness was associated with consumption of cold food items served on the flights and prepared by hand at the airline flight kitchen (RR, 5.7; 95% Cl, 1.4 to 23.5; P < .01). CONCLUSIONS: This international outbreak of shigellosis was identified only because of the occurrence of an index outbreak involving a professional football team. Prevention of Shigella transmission in mass catering establishments may require reduction of hand contact in the preparation of cold food items or elimination of these items from menus.
The brush border membrane of the proximal tubule contains two efflux pathways for organic cations from the cell to the tubular fluid: a P-glycoprotein and an organic cation/H+ exchanger. There is evidence that they transport many of the same substrates. Their structural relatedness is unknown and is the subject of this report. The experimental approach was to identify the exchanger with photoaffinity labeling reagents. The rationale was that if the P-glycoprotein and the organic cation/H+ exchanger transport many of the same substrates, then they might be photoaffinity labeled by the same reagents. [125I]Iodoarylazidoprazosin and [3H]azidopine are two reagents, which have been used, to photoaffinity label the P-glycoprotein. We found that several polypeptides were photolabeled in a time- and concentration-dependent manner. The photoincorporation into only two of these polypeptides (41 and 28 kDa) was blocked extensively by the presence of known substrates for the exchanger. The photoaffinity labeling of only the 41-kDa polypeptide was affected by treatment with the chemical reagents, N-ethylmaleimide and dithiothreitol, which are known to affect the exchanger reaction. The findings are consistent with the interpretation that a 41-kDa polypeptide is, or is a component of, the exchanger.
During 1983 and 1984, 733 cases of invasive Haemophilus influenzae type b disease in children less than 5 years of age were identified in Minnesota and in Dallas County, Texas. The overall incidence of disease was lower in Minnesota than in Dallas County. However, among urban residents, the rates of disease for whites were similar in the two areas. A higher rate of disease among whites in urban Minnesota compared with rural Minnesota resulted from an increased rate of cases for diagnoses other than meningitis. Local practices might have affected the rate of certain diagnoses, since ascertainment of Hib disease other than meningitis is more dependent on diagnostic practices than is diagnosis of meningitis. These data suggest that the incidence of invasive H. influenzae type b disease is influenced by the racial composition of the population, the rates of disease in specific subgroups, and possibly by local medical practices. Understanding the factors that contribute to the incidence of disease is necessary to interpret variations in different populations and changes over time.
An outbreak of Escherichia coli O157:H7 hemorrhagic colitis at a Minnesota junior high school in October 1988 comprised 32 cases among 1562 students (attack rate, 2.0%). Four children were hospitalized; none developed hemolytic-uremic syndrome. Case children were more likely than controls to have eaten heat-processed meat patties (odds ratio, 6.2; 95% confidence interval, 2.0-20.1; P less than .001) in the school cafeteria on a specific day. The minimum estimated attack rate among students who ate these patties was 8%. The patties should have been sufficiently cooked by the manufacturer to destroy enteric pathogens before they were frozen and distributed. E. coli were cultured from frozen patties that were manufactured at the same plant on the same dates as the implicated patties, but serotype O157:H7 was not isolated. Heat-processed meat patties may serve as vehicles for E. coli O157:H7 infection, and currently there are no federal or state regulatory standards to ensure the safety of these products.