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Biomedical subjects

C Lawrence

Publications and source records attributed to C Lawrence.

At least 145 records · Page 8Linked to original sources
PubMed1986

Secondary structure model for mouse beta Maj globin mRNA derived from enzymatic digestion data, comparative sequence and computer analysis.

A model for the secondary structure of mouse beta Maj globin messenger RNA is presented based on enzymatic digestion data, comparative sequence and computer analysis. Using 5'-32P-end-labeled beta globin mRNA as a substrate, single-stranded regions were determined with S1 and T1 nucleases and double-stranded regions with V1 ribonuclease from cobra venom. The structure data obtained for ca. 75% of the molecule was introduced into a computer algorithm which predicts secondary structures of minimum free energy consistent with the enzymatic data. Two prominent base paired regions independently derived by phylogenetic analysis were also present in the computer generated structure lending support for the model. An interesting feature of the model is the presence of long-range base pairing interactions which permit the beta globin mRNA to fold back on itself, thereby bringing the 5'- and 3'-noncoding regions within close proximity. This feature is consistent with data from other laboratories suggesting an interaction of the 5'- and 3'-domains in the mammalian globin mRNAs.

Animals↗
PubMed1986

Visual cortical lesions abolish the use of motion parallax in the Mongolian gerbil.

Mongolian gerbils received lesions of either the visual cortex, pretectal nuclei, superior colliculus or a sham operation. Visual distance estimation was tested by means of a jumping task on which gerbils have previously been shown to employ motion parallax information generated by head movements. Videotaped jumps were analyzed to determine latency to jump, jump distance, and head movement frequency. While all of the lesion groups showed some changes in performance, the most severe deficits in jump accuracy were seen after the visual cortical lesions. In none of the lesion groups, however, were head movements abolished. The results suggest that the visual cortex subserves a critical aspect of dynamic distance estimation but that the motor program for generating head movements is located elsewhere.

Animals↗
PubMed1986

Erythrocyte sedimentation rate during steady state and painful crisis in sickle cell anemia.

To define its diagnostic utility in sickle crisis, the erythrocyte sedimentation rates of oxygenated blood were studied in patients with sickle cell anemia and healthy normal subjects using the Guest-Westergren method. A normal range for sedimentation rate as a function of hematocrit was established in 22 normal subjects. Twenty-seven asymptomatic patients with sickle cell anemia had abnormally low sedimentation rates in relation to their hematocrits. Those low sedimentation rates were not increased by substituting plasma from healthy control subjects, which suggests that the low sedimentation rate was a cell-related phenomenon. Sedimentation rates measured in 28 patients with sickle cell anemia at the end of uncomplicated painful crisis increased to levels appropriate for their degree of anemia. In patients with sickle crisis and medical complications, the sedimentation rates were even higher. At the end of an uncomplicated painful crisis, the mean plasma fibrinogen level was significantly higher than at the onset (p less than 0.005). When red cells from patients with sickle cell anemia at the end of crisis were suspended in normal plasma from control subjects, the sedimentation rates remained high. It is concluded that the erythrocyte sedimentation rate of asymptomatic patients with sickle cell anemia is abnormally low due to cellular factors, and the increase during painful crisis is due primarily to red cell changes, modified by plasma factors.

Adult↗
PubMed1986

Birefringent hemozoin identifies malaria.

The diagnosis of malaria is still sometimes difficult because of the insensitivity of microscopic screening at low levels of parasitemia. The malarial pigment, hemozoin, is a crystalline product of the digestion of hemoglobin by the parasites. Under polarized light at 500X magnification, brilliantly birefringent granules of the pigment were detected in Wright's stained smears, and the parasites easily localized, in 18 cases of malarial infection. Fresh, wet, coverslipped preparations of cultures of Plasmodium falciparum also were examined under polarized light. Serial dilutions of the cultures showed that, even at the very low level of 0.01% parasitemia, intracellular birefringent granules were detected in an average of 45 +/- 16 (SE) seconds at 500X magnification. Using polarized light is a simple, fast, sensitive, and specific method for localizing intracellular pigmented malaria parasites in wet preparations of blood.

Hemeproteins↗
PubMed1986

The influence of chemically-induced modifications of root surfaces on cell migration, attachment, and orientation.

Surface demineralization of tooth root surfaces has been shown to improve re-attachment of cells and to promote tissue reconstruction following periodontal surgery. Exposure of collagen fibers has been thought to facilitate migration, attachment, and orientation of fibroblasts on the root surface. However, using an in vitro assay, we have found that both attachment and orientation of human gingival fibroblasts on demineralized dentin surfaces are further improved following digestion of the exposed collagen with bacterial collagenase. In contrast, pronase and trypsin digestion of the surface collagen had no significant effect, whereas heat denaturation had an inhibitory effect. Dissociative extraction of the demineralized dentin slices with 4 mol/L guanidine hydrochloride (GuHCl) also improved attachment and orientation, and when undemineralized dentin was subjected to dissociative extraction, cell attachment was comparable and orientation superior to that on demineralized surfaces. These studies indicate that demineralization is not a prerequisite for facilitating attachment, and that enhanced attachment and orientation of cells are not dependent upon a collagenous substratum.

Animals↗
PubMed1985

Steroid-induced hypersegmentation in neutrophiles.

The effect of glucocorticoid administration on the nuclear segmentation of circulating granulocytes was studied in 13 patients with hematologic disorders and in two normal volunteers. In seventeen of eighteen courses, the granulocyte nuclear lobe count increased from 3.24 +/- 0.12 (SD) to 3.41 +/- 0.12 by the third day of treatment (P less than .001). Nuclear segmentation increased even further with continued therapy during a week of observation. Thus, like deficiencies of folate and of vitamin B12, glucocorticoid therapy causes neutrophil hypersegmentation. The cause of this effect is not known.

Asthma↗
PubMed1985

[Not Available].

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Diagnosis↗
PubMed1985

Red cell distribution width parallels dense red cell disappearance during painful crises in sickle cell anemia.

We reported previously that painful crises in patients with sickle cell anemia are accompanied by striking decreases in the percent of densest red cells (fraction 4) when studied with isopyknic Percoll-Stractan gradients. We report that an alternative to density gradients is the red cell distribution width (RDW), an estimate of red cell size variation measured with a Coulter counter. In 17 painful crises in 12 patients with homozygous sickle cell anemia the RDWs decreased in each crisis, from an initial mean of 16.2 +/- 1.8 SD to 12.8 +/- 1.3 (P less than 0.001). In patients in whom serial measurements of both RDW and fraction 4 (very dense) red cells were taken during crisis, the two measurements declined in parallel. The decrease of RDW is a readily observable and objective laboratory concomitant of painful sickle crisis.

Anemia, Sickle Cell↗
PubMed1984

Monitoring of the neonatal electroencephalogram using an infrared multichannel telemetry system.

A 3-channel neonatal medical monitoring system is described which uses infrared light instead of electrical leads to transmit physiological signals from the neonate to monitoring equipment. This system is especially applicable to situations where low level physiological signals such as the EEG need to be monitored in the vicinity of other life support and monitoring equipment that is likely to introduce electrical interference. Examples of EEG activity showing the progress of a neonate, who had experienced asphyxia, are presented.

Asphyxia Neonatorum↗
PubMed1984

Broken appointments at a neighborhood health center. Emphasis on weather.

Broken appointments have been a major problem at the Anthony L. Jordan Health Center since it opened in 1968. In an earlier 6-month study of broken appointments at the center the authors found 48% of pediatric appointments and 43% of medicine appointments to be broken. Daily broken appointment rates were correlated between the two departments and were associated with day and time scheduled and with certain weather conditions. Specifically, highest broken appointment rates were noted for Mondays, for afternoon and evening hours, and for days with precipitation.

Appointments and Schedules↗
PubMed1984

A randomized double-blind comparison of PUVA-etretinate and PUVA-placebo in the treatment of chronic plaque psoriasis.

Twenty-eight patients with chronic plaque psoriasis affecting 20-40% of their body surface were treated with either PUVA and placebo (thirteen patients) or PUVA and etretinate (0.75 mg/kg) (fifteen patients). PUVA was given three times a week for a maximum of 10 weeks after a 2-week period on placebo or etretinate alone. Four patients failed to clear with PUVA and placebo compared with one patient with PUVA and etretinate, and the mean total UV-A dose to clear was lower with etretinate (mean = 62.1 J/cm2) than with placebo (mean = 77.3 J/cm2) but none of these differences were significant. Because the additional response to etretinate was only marginal, whilst unwanted effects were common, we found no advantage in adding etretinate to PUVA.

Chronic Disease↗