A highly informative CA/GT repeat polymorphism in intron 38 of the human neurofibromatosis type 1 (NF1) gene

We describe a polymorphic microsatellite in intron 38 of the neurofibromatosis type 1 (NF1) gene. The microsatellite consists of a CA/GT dinucleotide repeat detecting 8 alleles; it has a heterozygosity of 82%.

Different feedback regulation of hepatic cholesterol and bile acid synthesis by glycodeoxycholic acid in rabbits

BACKGROUND

To explore the sexual difference in the feedback regulation of hepatic bile acid synthesis, glycodeoxycholic acid (GDCA) was administered to 15 male and 14 female rabbits.

METHODS

After bile diversion, GDCA equivalent to the hepatic bile acid influx was infused intraduodenally. Biliary cholic acid output represented bile acid synthesis. Hepatic 3-hydroxy-3 methylglutaryl coenzyme A (HMG-CoA) reductase and cholesterol 7 alpha-hydroxylase activities and steady state messenger RNA (mRNA) levels were determined.

RESULTS

GDCA inhibited bile acid synthesis less in female than in male rabbits. Hepatic HMG-CoA reductase activity decreased 39% in males, but increased 48% in females. Hepatic cholesterol 7 alpha-hydroxylase activity decreased similarly in males and females, and mRNA levels decreased 86% in males but were unchanged in females.

CONCLUSIONS

(1) Total bile diversion stimulated both hepatic cholesterol and bile acid synthesis by activating the rate-controlling enzymes and increasing mRNA levels. (2) GDCA decreased mRNA levels of HMG-CoA reductase and cholesterol 7 alpha-hydroxylase in males, but mRNA levels did not decrease in females. (3) Bile acid synthesis was sustained in females because continued biosynthesis of cholesterol provided a substrate for cholesterol 7 alpha-hydroxylase and stimulus for enzyme formation.

Method for group determination of total N-nitroso compounds and nitrite in fresh gastric juice by chemical denitrosation and thermal energy analysis

A method for the determination of total N-nitroso compounds (NOC) and nitrite in fresh human gastric juice is described, which is based on earlier methods. A freshly obtained gastric juice sample is injected directly into refluxing ethyl acetate containing glacial acetic acid, HCl and HBr to determine the total concentration (A) of nitrite, total NOC and thermo- and acid-labile thermal energy analyser (TEA)-responsive compounds (TAC). Another fresh sample of the same juice (with or without the addition of sulfamic acid) is injected directly into refluxing ethyl acetate containing glacial acetic acid and HCl for determining the TAC level (B) and the total level (C) of nitrite and TAC. The NO released from nitrite, TAC and NOC is detected by TEA acting as a chemiluminescence detector. The differences between A and C and between C and B represent the concentrations of total NOC and nitrite, respectively. The method is rapid, reproducible (relative standard deviation 1-6%) and sensitive (detection limit 1.0 pmol). The behaviour of nitrite and NOC in the analytical system was studied and relevant techniques for the direct analysis of fresh gastric juice samples and for stabilization of fresh samples have been developed.

[Determination of serum pancreatic polypeptide and its clinical significance in patients with end state renal failure]

Serum levels of pancreatic polypeptide (SPP) responding to 75g glucose (oral) challenge were observed in 27 patients with end state renal failure (ESRF) and 27 normal subjects as a control. The results showed that the levels of SPP were significantly higher in ESRF patients than in normal subjects. Dialysis therapy seemed to have no effect on the levels of SPP. The elevated levels of SPP could return to normality after kidney transplantation. There was no positive correlation between the levels of SPP, the blood sugar, and the serum insulin. It is suggested that kidneys are the important sites for the metabolism of PP. The elevated SPP concentration in patients with ESRF may result from their renal failure, and may contribute to some gastrointestinal symptoms which are frequently associated with ESRF.

Differential regulation of cellular activities by GTPase-activating protein and NF1

The regulation of the GTPase activity of the Ras proteins is thought to be a key element of signal transduction. Ras proteins have intrinsic GTPase activity and are active in signal transduction when bound to GTP but not following hydrolysis of GTP to GDP. Three cellular Ras GTPase-activating proteins (Ras-gaps) which increase the GTPase activity of wild-type (wt) Ras but not activated Ras in vitro have been identified: type I and type II GAP and type I NF1. Mutations of wt Ras resulting in lowered intrinsic GTPase activity or loss of response to cellular Ras-gap proteins are thought to be the primary reason for the transforming properties of the Ras proteins. In vitro assays show type I and type II GAP and the GAP-related domain of type I NF1 to have similar biochemical properties with respect to activation of the wt Ras GTPase, and it appears as though both type I GAP and NF1 can modulate the GTPase function of Ras in cells. Here we report the assembling of a full-length coding clone for type I NF1 and the biological effects of microinjection of Ras and Ras-gap proteins into fibroblasts. We have found that type I GAP, type II GAP, and type I NF1 show markedly different biological activities in vivo. Coinjection of type I GAP or type I NF1, but not type II GAP, with wt Ras abolished the ability of wt Ras to induce expression from an AP-1-controlled reporter gene. We also found that serum-stimulated DNA synthesis was reduced by prior injection of cells with type I GAP but not type II GAP or type I NF1. These results suggest that type I GAP, type II GAP, and type I NF1 may have different activities in vivo and support the hypothesis that while type I forms of GAP and NF1 may act as negative regulators of wt Ras, they may do so with differential efficiencies.

Perceptions of practice problems encountered by family physicians, pediatricians, and orthopedic surgeons

Information about physicians' practice problems was solicited through a structured questionnaire mailed to a group of family physicians, pediatricians, and orthopedic surgeons. Overall, a lack of personal time was the major concern across the three groups of physicians. Comparisons among the three types of physicians revealed two patterns: Family physicians reported more concerns in the "interpersonal" dimension, whereas orthopedic surgeons had more concerns in the "legal-economic" dimension. These patterns of differences persisted with two variables controlled: gender and time period in which they completed their residency program. These findings indicate that physicians' concerns in their practice vary among the specialties, and they imply that the changed economy and reimbursement system might have more impact on one than the other. Thus the effectiveness of residency training and continuing education might be improved by emphasizing the specialty-related problems in practice.

Drift of the sialyl-linkage specific recognition of the sialidase of influenza B virus isolates

Sialyl-linkage specificity of the sialidase of influenza B viruses isolated in different years from 1940 through 1990 (B/Lee/40,B/Setagaya/3/56,B/Tokyo/7/66,B/Kagoshima/1/68, B/Gifu/2/73, B/Kanagawa/3/76, B/Ibaraki/2/85, B/Yamagata/16/88, and B/Bangkok/163/90) was studied with N-acetylneuraminyl (alpha 2-3)- and (alpha 2-6)-lactoses, GM3 gangliosides containing the same sialyl-oligosaccharide sequences as sialyllactose, and also with type I and type II lacto-series gangliosides carrying Neu5Ac alpha 2-3Gal and NeuAc alpha 2-6Gal linkages as substrates. From an examination of up to nine strains, the sialidases of all viruses preferentially hydrolyze substrates with Neu5Ac alpha 2-3Gal linkage rather than the Neu5Ac alpha 2-6Gal linkage. It was found that the sialidase activity toward Neu5Ac alpha 2-6Gal linkage relative to Neu5Ac alpha 2-3Gal linkage is increased in later strains, whether sialyllactose or ganglioside is used as the substrate. These results suggested that the sialidase of influenza B virus isolates has shown a drift in linkage specificity which correlates with the year of isolation.

Evaluation of brain function in acute carbon monoxide poisoning with multimodality evoked potentials

The median nerve somatosensory evoked potentials (SEP), pattern reversal visual evoked potentials (VEP), and brain stem auditory evoked potentials (BAEP) were studied in 109 healthy adults and in 88 patients with acute carbon monoxide (CO) poisoning. The upper limits for normal values of peak and interpeak latencies of multimodalities of evoked potentials in the reference group were established by a stepwise multiple regression analysis. SEP changes selectively affecting N32 and N60 were found in 78.8% of patients. There was prolonged P100 latency of VEP in 58.2% of the cases examined. The prevalence of BAEP abnormalities in comatose patients (36%) was significantly higher than that (8.6%) in conscious patients. BAEP abnormalities were most frequently seen in comatose patients who had diminished brain stem reflexes (77.8%). It has been found that a consistent abnormality involving N20 and subsequent peaks in SEP, a remarkable prolongation of P100 latency in VEP, or a prolongation of III-V interpeak latency in BAEP as well as the reoccurrence of evoked potential abnormalities after initial recovery all indicate unfavorable outcomes in patients with acute CO poisoning. The multimodality evoked potentials have proved to be sensitive indicators in the evaluation of brain dysfunction and in the prediction of prognosis of acute CO poisoning and the development of delayed encephalopathy.

Plasma ascorbic acid concentrations relate inversely to blood pressure in human subjects

This study relates antioxidant status and blood pressure (BP) in 168 healthy residents of Augusta, GA, following usual diets. BP ranges were systolic (S) 84-152, mean 112 +/- 1 mm Hg, and diastolic (D) 52-96, mean 72 +/- 1 mm Hg. Plasma concentrations of ascorbic acid (AA) were significantly inversely related to SBP (r = -0.18, P < 0.05) and DBP (r = -0.20, P < 0.01); with regression equations SBP vs AA = -0.083C + 116 and DBP = -0.077C + 76. Highest and lowest quintiles of AA differed significantly in mean SBP (108 +/- 2, 113 +/- 2 mm Hg) and DBP (69 +/- 1, 74 +/- 2), P < 0.05. Plasma AA concentrations were significantly lower in the smokers. By deleting smokers, the inverse relations of SBP and DBP with plasma AA and the slopes of the equation were enhanced. Plasma selenium, alpha-tocopherol, alpha-tocopherol:cholesterol ratio, retinol and taurine were not related to BP; whereas male gender, body mass index, body fat distribution, plasma cholesterol, low density lipoprotein cholesterol, and triglycerides correlated.

Longitudinal comparison of the academic performances of Asian-American and white medical students

PURPOSE

To compare the academic performances of Asian-American medical students--before, during, and after medical school--with those of white students.

METHOD

The 140 Asian-American graduates and 2,269 white graduates from the classes of 1981-1992 at Jefferson Medical College were studied prospectively: data on academic performance, indebtedness, and delayed graduation were analyzed and compared for all the graduates. F-tests, chi-square tests, and regression models were used.

RESULTS

The Asian-Americans had statistically significantly higher scores on the SAT (Scholastic Aptitude Test) quantitative subtest and on the MCAT (Medical College Admission Test) chemistry, physics, and science problems subtests; the whites had significantly higher scores on the MCAT reading subtest; third-year grade-point averages for required clerkships; and scores on National Board of Medical Examiners Part I, II, and III examinations (NBME I, II, and III). No significant difference was found in the other performance measures, including ratings in the first year of residency. Regression analysis showed that the MCAT reading score was the major predictor of Asian-Americans' performances on the NBME I and II.

CONCLUSION

Because the MCAT reading score is the major predictor of later performance for Asian-American students, schools should consider employing different criteria in predicting and monitoring these students' performances.

Attendings' and residents' teaching role and students' overall rating of clinical clerkships

The study was conducted with a sample of third-year students (n = 584) at Jefferson Medical College to explore students' perception of patterns of differences between attending physicians and residents in their teaching behaviors during clinical clerkships. Attending physicians' teaching behaviors were perceived more in a mentorship mode whereas residents' teaching behaviors were equally divided between mentorship and preceptorship modes. Attending physicians and residents' teaching behaviors varied among clerkships. Results were discussed in terms of difference of teaching roles played by attending physicians and residents and relationship of the teaching behaviors to students' overall rating of clerkship.

Genotypic and antigenic identification of two new strains of spotted fever group rickettsiae isolated from China

Four isolates of spotted fever group rickettsiae isolated from ticks in China were compared with all known species and strains of spotted fever group rickettsiae by immunofluorescence assay, DNA polymerase chain reaction followed by restriction endonuclease fragment length polymorphism analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and Western immunoblot. The Chinese isolates belonged to three types, including a novel serotype which has not been described before. One isolate obtained from tick ova of Dermacentor nuttallii in Inner Mongolia was antigenically and genotypically identical to Rickettsia sibirica. Two isolates obtained from Dermacentor sinicus collected from Beijing were identical, different from other members of spotted fever group rickettsiae but apparently closely related to R. sibirica. HA-91, a strain isolated from Hyalomma asiaticum bv. kozlovi olenew, was antigenically and genotypically unique among spotted fever group rickettsiae, and we feel that data presented here should prompt consideration of it as a new species on the basis of current rickettsial taxonomy.

STE50, a novel gene required for activation of conjugation at an early step in mating in Saccharomyces cerevisiae

A new gene, STE50, which plays an essential role in cell differentiation in Saccharomyces cerevisiae was detected and analysed. STE50 expression is not cell type-specific and its expression in MATa and MAT alpha cells is unaffected by pheromones. When present on a high copy number plasmid, STE50 causes supersensitivity to alpha-pheromone, and increases the level of alpha-pheromone-induced transcription of FUS1 in haploid a cells. Mutants bearing either of the two gene disruptions, ste50-1 or ste50-2, are sterile and have a modulated sensitivity to alpha-pheromone. The overexpression of STE4 (G beta) in wild-type cells elicits a constitutive growth arrest signal, however this phenotype is suppressed by a C-terminal truncation mutation in STE50 (ste50-2). In contrast, the constitutive activation of the pheromone response pathway caused by disruption of GPA1 (G alpha) is not suppressed in ste50-2 mutants. The ste50-2 mutation partially suppresses the desensitisation defect of the sst2-1 mutation, and the resulting ste50-2 sst2-1 mutants restore fertility. Our results indicate that the ste50-2 mutant may have a defect in adaptation (hyperadaptation), and suggest a possible interaction of STE50-2 with the G alpha subunit of the G protein.

Hypoxia-mediated impaired differentiation by LLC-PK1 cells: evidence based on the protein kinase C profile

We recently reported that mild hypoxia in LLC-PK1 cells, grown in standard fashion under a still layer of overlying medium at 5% CO2/18% O2 environment, result in decreased oxidative metabolism and impaired differentiated functions in comparison to adequately oxygenated cultures maintained either under a higher oxygen (36% O2) environment or conditions of continuous rocking of the media fluid. In the present study, subcellular distribution of a regulatory enzyme protein kinase C (PKC) was examined between hypoxic still and normoxic rocked LLC-PK1 cells. Subconfluent cultures of hypoxic LLC-PK1 cells exhibited significantly lower and predominantly membrane-bound PKC activity in comparison to mostly cytosolic localization of this enzyme in normoxic rocked cells. One hour of exposure of adequately oxygenated-rocked LLC-PK1 cells with the phorbol ester TPA, a dedifferentiating agent that did not effect the cell ATP content, resulted in significant inhibition of dome formation and sodium-dependent glucose transport activity, a partial loss of pH-responsive ammoniagenesis, and almost complete translocation of protein kinase C activity from cytosol to the membrane pool; all of which resembles the behavior of hypoxic still cultured cells. In addition, acute re-oxygenation of hypoxic still cultures by rocking the media fluid for one hour resulted in an increase in cell ATP content to the cellular levels of ATP observed in normoxic rocked cells. However, all the parameters of differentiation were unaffected by re-oxygenation. These studies support the notion that hypoxia can act in some primary fashion, independent of its effects on energy metabolism, to impair cellular differentiation in LLC-PK1 cells. They also raise the possibility that activation of protein kinase C may act as an important mediator in this process.