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Biomedical subjects

J Carlson

Publications and source records attributed to J Carlson.

At least 217 records · Page 12Linked to original sources
PubMed1990

Geographical distribution of Plasmodium falciparum erythrocyte rosetting and frequency of rosetting antibodies in human sera.

Uninfected erythrocytes bind spontaneously to those infected with certain strains of Plasmodium falciparum. This is known as spontaneous erythrocyte rosetting. We have studied the occurrence and frequency of rosetting in 75 fresh patient isolates and have identified rosetting strains from Africa, South America, and Asia. Rosetting was present in 49% of the isolates tested; the frequency of rosetting red blood cells (RBC) in individual isolates was 0-75% when scored during the first cycle of in vitro growth. Rosetting antibodies were found in 15 out of 73 (21%) Liberian sera as measured by disruption of rosettes in vitro. However, antibodies able to inhibit CD36 dependent cytoadherence of P. falciparum-infected RBC were not detected in these sera. Erythrocyte rosetting is a geographically widespread phenomenon. Rosetting antibodies seem to be induced by natural infection and the molecular mechanism of rosette formation seems distinct from that of endothelial cytoadherence.

Africa↗
PubMed1989

Plasmodium falciparum-infected erythrocytes form spontaneous erythrocyte rosettes.

Erythrocytes infected with trophozoites or schizonts of Plasmodium falciparum bind uninfected erythrocytes, leading to rosette formation. Both established laboratory strains and fresh isolates from patients form such rosettes, but at widely different frequencies. IgG preparations from the serum of some P. falciparum-immune donors and heparin inhibited rosette formation. The results indicate that cytoadherence of infected erythrocytes to endothelial cells and rosetting represent distinct genetic traits.

Animals↗
PubMed1989

Characterization of the larval olfactory response in Drosophila and its genetic basis.

Drosophila larvae are attracted to a wide variety of chemical stimuli. The olfactory response to ethyl acetate, a powerful attractant, was found to be surprisingly well conserved across a variety of different wild-type strains. Strain differences are documented, however, both in attraction to ethyl acetate and in another chemosensory behavior: avoidance of an aversive stimulus. As a means of analyzing the extent of genetic heterogeneity within strains, one wild-type population, Canton-S, was screened for variant X chromosomes. An enrichment procedure was characterized and used to make the screening more efficient. Lines homozygous for individual X chromosomes were established, and all were found to exhibit a strong olfactory response, although evidence was found for variation among them. The olfactory response was found to be conserved through an extended period of larval development, including the final period during which larvae leave the culture medium in preparation for metamorphosis. The results are discussed in terms of the genetic basis of the response and the use of single-gene mutations as a means of dissecting olfactory system function.

Animals↗
PubMed1989

Radiosensitivity of human prostate cancer and malignant melanoma cell lines.

The relative radioresponsiveness of human prostate cancer compared to malignant melanoma is well known. The effects of beta-estradiol or testosterone on the X-irradiation survival of several human cell lines were studied, including: human prostate carcinoma cell lines PC3 and DU145 and human malignant melanoma cell lines A375 and A875. Lines PC3 and DU145 demonstrated 55-61 fmol per 10(6) cells of androgen receptor with no detectable estrogen or progesterone receptor. Cells were irradiated at 120 cGy/min dose rate. There was no detectable toxicity of up to 10(-4) M testosterone or beta-estradiol on PC3 or DU145 cells in the absence of X-irradiation. At plating efficiencies from 11-13%, and plating densities of 1 x 10(4) cells per 60 cm2 flask, cell lines PC3 and DU145 demonstrated a Do of 108.5 +/- 6.5, n 2.1 +/- 0.7 cGy, and Do of 143.5 +/- 1.5 cGy, n 2.4 +/- 0.5, respectively. The addition of testosterone or beta-estradiol at 10(-4) to 10(-10) M prior to or after, X-irradiation did not alter radiosensitivity. At the same dose rate of 120 cGy/min, malignant melanoma cell lines A375 and A875 had a Do of 125 +/- 2.5 cGy, n 1.56 +/- 0.8 SF2 0.65 +/- 0.03 and line A875 demonstrated a Do of 129 +/- 4.5 cGy, n 1.58 +/- 0.4 SF2 0.55 +/- 0.04, respectively. The radiosensitivity of melanoma cell lines did not decrease at low dose rate 5 cGy/min. Thus, the in vitro radiosensitivity of androgen receptor positive prostate cancer cell lines is not necessarily altered by the presence of androgen before or after irradiation. The data support the concept that all malignant melanoma cell lines do not show a broad-shouldered cell survival curve in vitro and intrinsic cellular radioresistance.

Cell Survival↗
PubMed1989

Why do Plasmodium falciparumm-infected erythrocytes form spontaneous erythrocyte rosettes?

Plasmodium falciparum malaria is one o f the most widespread o f human parasitic diseases and is responsible for the deaths of several million people in subtropical and tropical regions o f the world. The interaction o f malarial merozoites with erythrocytes and the adherence o f infected erythrocytes to the endothelium are among the cellular interactions extensively studied to define candidate antigens for a blood stage vaccine. However, the exact mechanisms underlying the invasion o f erythrocytes by P. falciparum merozoites and their subsequent binding to endothelium are not yet understood. Here Mats Wahlgren, Johan Carlson, Rachonee Udomsangpetch and Peter Perlmonn discuss a novel cytoodherence phenomenon which may be o f great importance in this context, that is, the spontaneous binding o f uninfected erythrocytes to those infected with late-stage parasites (trophozoites/schizonts).

Journal Article↗
PubMed1989

A simple chemosensory response in Drosophila and the isolation of acj mutants in which it is affected.

Although the Drosophila visual system has been described extensively, little is known about its olfactory system. A major reason for this discrepancy has been the lack of simple, reliable means of measuring response to airborne chemicals. This paper describes a jump response elicited by exposing Drosophila to chemical vapors. This behavior provides the basis for a single-fly chemosensory assay. The behavior exhibits dose dependence and chemical specificity: it is stimulated by exposure to ethyl acetate, benzaldehyde, and propionic acid but not ethanol. Animals can respond repeatedly at short intervals to ethyl acetate and propionic acid. The response relies on the third antennal segments. To illustrate the use of this behavior in genetic analysis of chemosensory response, nine acj mutants defective in response are isolated (acj = abnormal chemosensory jump), and their responses to two chemicals are characterized. All of the acj mutants are normal in giant fiber system physiology, and two exhibit defects in visual system physiology.

Animals↗
PubMed1989

Genetic analysis of olfactory behavior in Drosophila: a new screen yields the ota mutants.

A simple means of measuring Drosophila olfactory response is described, and the behavior which it measures is characterized. The assay was used to screen for X-linked mutants defective in olfactory function. Six ota mutants were isolated and characterized (ota = olfactory trap abnormal). Four of the mutants were found to be abnormal in another chemosensory behavior as well. Two of the mutant phenotypes extend to include another sensory system: they are defective in visual system physiology. All were normal, however, in a test of giant fiber system physiology. Two of the mutations are dominant, and the recessive mutations define two complementation groups. Mutations representing each complementation group, as well as one of the dominant mutations, were mapped. For the mutants with defective visual system physiology, the visual defects were shown to cosegregate with olfactory phenotypes.

Analysis of Variance↗
PubMed1989

Effect of unilateral spinal adjustments on goniometrically-assessed cervical lateral-flexion end-range asymmetries in otherwise asymptomatic subjects.

A triple blinded, multiple-measure, experimental protocol was employed in order to investigate the effectiveness of unilateral cervical adjustments on goniometrically assessed cervical lateral-flexion asymmetries. On pretest, subjects selected for the experiments exhibited mean left-right lateral-flexion differences of approximately 14 degrees. In subjects which either received no intervention, or had been subjected only to preliminary palpatory and set-up procedures but no thrust, asymmetry magnitudes were found to be unchanged on goniometric posttesting done 30-45 min later. However, in subjects which received lower cervical adjustments performed on the side of most restricted end-range, there was a dramatic reduction in asymmetry magnitudes. Furthermore, the adjustment procedure used in this investigation appeared to be relatively side-specific, since adjustments, when delivered to the less restricted side, were only marginally effective in ameliorating the asymmetries. Potential clinical relevance as well as the possible structural or physiological mechanisms responsible for the results obtained in the study are discussed.

Adult↗
PubMed1989

Accessible magnetic resonance imaging.

The cost of magnetic resonance imaging (MRI) is driven by magnetic field strength. Misperceptions as to the impact of field strength on performance have led to systems that are more expensive than they need to be. Careful analysis of all the factors that affect diagnostic quality lead to the conclusion that field strength per se is not a strong determinant of system performance. Freed from the constraints imposed by high-field operation, it is possible to exploit a varied set of opportunities afforded by low-field operation. In addition to lower costs and easier siting, we can take advantage of shortened T1 times, higher contrast, reduced sensitivity to motion, and reduced radiofrequency power deposition. These conceptual advantages can be made to coalesce onto practical imaging systems. We describe a low-cost MRI system that utilizes a permanent magnet of open design. Careful optimization of receiving antennas and acquisition sequences permit performance levels consistent with those needed for an effective diagnostic unit. Ancillary advantages include easy access to the patient, reduced claustrophobia, quiet and comfortable operation, and absence of a missile effect. The system can be sited in 350 sq ft and consumes a modest amount of electricity. MRI equipment of this kind can widen the population base than can access this powerful and beneficial diagnostic modality.

Costs and Cost Analysis↗
PubMed1988

Seropositivity for HIV and the development of AIDS or AIDS related condition: three year follow up of the San Francisco General Hospital cohort.

The three year actuarial progression rate to the acquired immune deficiency syndrome (AIDS) in a cohort of men in San Francisco who were seropositive for the human immunodeficiency virus (HIV) was 22%. An additional 26 (19%) developed AIDS related conditions. Beta 2 Microglobulin concentration, packed cell volume, HIV p24 antigenaemia, and the proportion and number of T4 lymphocytes each independently predicted progression to AIDS. Beta 2 Microglobulin was the most powerful predictor. The 111 subjects tested who were normal by all predictors (40%) had a three year progression of 7%, and the 68 subjects who were abnormal by two or more predictors (24%) had a progression rate of 57%. Two thirds of all men who progressed to AIDS were in the last group. The median T4 lymphocyte count in subjects who did not progress to AIDS fell from 626 x 10(6) to 327 x 10(6)/l. HIV p24 antigenaemia developed in 7% of the subjects per year. The proportion who were abnormal by two or more predictive variables rose to 41%. At three years an estimated two thirds of the seropositive subjects showed clinical AIDS, an AIDS related condition, or laboratory results that were highly predictive of AIDS. It is concluded from the observed rates and the distribution of predictive variables at three years that half of the men who were seropositive for HIV will develop AIDS by six years after the start of the study, and three quarters will develop AIDS or an AIDS related condition.

AIDS-Related Complex↗