Biomedical subjects

D Johnson

Publications and source records attributed to D Johnson.

At least 19 recordsLinked to original sources

PubMed1992

The C/EBP family of transcriptional activators is functionally important for Ig VH promoter activity in vivo and in vitro.

We have examined the functional importance of binding sites for C/EBP family members (E sites), in two Ig VH promoters: VH1, a member of the S107 family, and BCL1, a member of the J558 family. Mutation of the E site in the VH1 promoter diminishes transcription in vivo to 59% of wild-type and transcription from the BCL1 promoter in vitro is inhibited to an average of 39% of wild-type by competition with E site oligonucleotides. Purified E site binding proteins from plasmacytoma cells stimulated BCL1 transcription in vitro 2.3-fold. Although five C/EBP family proteins are known which bind the E site, antibody ablation of DNA:protein complexes resolved by electrophoretic mobility shift assays showed that Ig/EBP-1 is the only E site binding protein detectable in early B cell lines; more mature B cells contain Ig/EBP-1 and NF-IL6. We also show by antibody-depletion that Ig/EBP-1 activates the BCL1 promoter in vitro.

Animals↗

PubMed1992

Inactivation of factor VIII by factor IXa.

Factor VIII (FVIII) is the nonproteolytic cofactor for FIXa in the tenase complex of blood coagulation. FVIII is proteolytically activated by thrombin and FXa in vitro to form a heterotrimer with full procoagulant activity. Activated protein C inactivates thrombin-activated FVIII through cleavage adjacent to position Arg 336 in the cofactor. We have investigated the interaction of FIXa and FVIII and subjected FVIII polypeptides to N-terminal amino acid sequence analysis. Contrary to previous reports, we were unable to demonstrate the activation of FVIII by FIXa. Incubation of these two proteins at equimolar or close to equimolar concentrations resulted in the inactivation of FVIII, coincident with cleavage of the FVIII heavy chain adjacent to Arg 336 and the light chain adjacent to Arg 1719. These cleavages were detected in the presence or absence of thrombin, indicating that FIXa does not stabilize thrombin-activated FVIIIa. APC cleaved FVIII at the same position in the heavy chain, and simultaneous incubation of FVIII, APC, and FIXa did not result in stabilization of the cofactor. We conclude that FIXa does not play a role in the stabilization or activation of FVIII.

Amino Acid Sequence↗

PubMed1992

Mutant prohead RNAs in the in vitro packaging of bacteriophage phi 29 DNA-gp3.

The 174-base prohead RNA encoded by bacteriophage phi 29 of Bacillus subtilis, essential for packaging of the DNA-gp3 (DNA-gene product 3) complex, was expressed efficiently from the cloned gene. Computer programs for RNA structure analysis were used to fold hypothetical RNA mutants and thus to target mutagenesis of the RNA for studies of structure and function. Five mutants of the RNA were then produced by oligonucleotide-directed mutagenesis that were altered in the primary sequence at selected sites; two of these mutants were predicted to be altered in secondary structure from a model established previously by a phylogenetic analysis. The binding of the 32P end-labeled mutant RNAs to RNA-free proheads was comparable with that of the wild-type RNA. However, the capability of the mutant RNAs to reconstitute RNA-free proheads for DNA-gp3 packaging in the defined in vitro system and for assembly of phage in RNA-free extracts was variable, depending upon the alteration. Changes of highly conserved bases that retained the predicted secondary structure of the RNA model were tolerated to a much greater extent than changes predicted to alter the RNA secondary structure.

Bacteriophages↗

PubMed1992

Choroid plexus carcinoma of childhood.

The presentation, growth patterns, and response to therapy of 11 consecutive children with choroid plexus carcinomas were analyzed, and the results were compared with the outcome reported in other series. Patients were a median of 26 months of age at diagnosis. Two patients had thalamic tumors, one had a posterior fossa primary, and the rest had ventricular lesions. Five of 11 (45%) children remain in continuous progression-free remission a median of 48 months from diagnosis. Four of the five in continuous remission had a "gross total" surgical resection, and only one received radiation therapy. Five of six patients with subtotal resections relapsed despite postoperative treatment with radiation therapy (three) and chemotherapy (one). The response to treatment with radiation therapy or chemotherapy at relapse was disappointing, with only one child (treated with etoposide) responding. In combination with other series, 11 of 14 children had prolonged progression-free survival after gross total resection (only two of whom received adjuvant therapy) compared with two of 20 after less than total resections, independent of the type of adjuvant therapy given. Adjuvant therapy for children with choroid plexus carcinomas is of unproven benefit, and this must be considered when analyzing innovative treatment trials for such children, especially for those with totally resected tumors. Patients with partially resected lesions fare poorly with present forms of treatment.

Child↗

PubMed1992

Intracoronary thrombolysis followed by directional atherectomy: a combined approach for thrombotic vein graft lesions considered unsuitable for angioplasty.

Eccentric complex vein graft lesions with abundant luminal thrombus have been generally considered unfavorable for balloon angioplasty. We present 3 patients in whom such lesions were successfully treated by a combined approach: intracoronary urokinase (1 million units over 1 hr) administered in the catheterization laboratory followed by directional atherectomy of the residual lesions in 2 separate procedures; with the patients maintained on heparin infusion between the 2 stages. No distal embolizations were encountered. Two of the 3 patients developed a groin hematoma without vascular compromise. This combined approach may prove to be an attractive alternative to reoperation in select patients with unfavorable vein graft lesions.

Aged↗

PubMed1992

Structural complexity and evolutionary conservation of the Drosophila homeotic gene proboscipedia.

Mutations of the homeotic gene proboscipedia (pb) of Drosophila cause striking transformations of the adult mouthparts, to legs or antennae. We report here an analysis of the gene structure of pb. Coding sequences across a 34 kb interval yield, by alternative splicing, four identified mRNA forms which differ immediately upstream of the homeobox. As a consequence, the homeodomain is expected to reside in four different contexts in the predicted protein isoforms. Mammalian homologs of pb, human HOX-2H and murine Hox-2.8, were identified based on the similarities of their homeodomains (95% identity) and several other conserved motifs. Examination of a collection of pb mutant alleles with antisera directed against the N-terminal region, the center or the C-terminal region of the protein showed that, surprisingly, several partial loss-of-function pb alleles appear to generate partially functional proteins truncated at their C-termini. This suggests that a significant portion of the protein contributes quantitatively to pb function, but is partially dispensable. Finally, evolutionary considerations suggest that pb may be one of several ancient genes which preceded the process yielding the modern homeotic gene complexes.

Amino Acid Sequence↗

PubMed1992

Bladder cancer, parity, and age at first birth.

The excess of bladder cancer in males (M:F ratio of 4:1 in the United States) is not explained fully by gender differences in smoking habits or occupational exposures. Laboratory studies suggest that some androgenic hormones stimulate (or do not inhibit) oncogenesis in bladder tissue, and that estrogenic hormones have the opposite effect. These observations suggest that bladder cancer risk in females may be modified by sex hormones which undergo profound changes during and following pregnancy. Mail-questionnaire data from 317 incident female cases, and 833 population-based controls in Iowa were used to measure the effect of parity and maternal age at first birth on bladder cancer risk. Parous women were at decreased risk relative to nulliparous women (odds ratio [OR] = 0.67, 95 percent confidence interval [CI] = 0.44-1.00), after adjustment for age, tobacco use, and previous bladder infection. The overall risk reduction was restricted to women who had never smoked (OR = 0.51, CI = 0.30-0.88), with no apparent effect of parity among ever-smokers (OR = 0.93, CI = 0.49-1.77). Risk appeared to decrease with increasing age at first birth, but did not vary with increasing parity after the first birth. Our findings are consistent with the hypothesis that oncogenesis in transitional cell tissue of the human bladder is influenced by sex hormones, and that hormonal changes related to pregnancy thereby can decrease risk.

Adult↗

PubMed1992

The short-term effect of patient health status assessment in a health maintenance organization.

This study was designed to test the short-term effects of health assessment on the process of care and patient satisfaction. The 29 Chart physicians used the Dartmouth COOP Charts to measure their adult patients' health status during a single clinical encounter; the 27 control clinicians used no measure of health status. We compared the change between baseline and post-intervention information for a sample of all study clinicians' patients. Most of the patients were female (67%), well educated (70% had at least a college education) and young (approximately 90% were aged 59 years or younger). We found that the ordering of tests and procedures for women was increased by exposure to the COOP Charts (52% vs. 35%; p < 0.01); the effect in men was not as significant (37% vs. 23%: p = 0.06). Although women reported no change in satisfaction with care, men claimed that the clinician helped in the management of pain (p = 0.02). We conclude that the use of health status measures during a single clinical encounter in an HMO changes clinician test ordering behaviour and may improve the help male patients receive for pain conditions. The long-term impact of these management changes is not known.

Episode of Care↗

PubMed1992

Interactions of mast cells with the nervous system--recent advances.

This article reviews recent advances in the understanding of mast cell-nervous system interactions. It is drawn largely from work published within the last ten years, and discusses the anatomical and biochemical evidence of a functional connection between mast cells and the nervous system, and the implications that such a relationship may have for normal and abnormal physiological functioning. Mast cells are found at varying levels of association with the nervous system; in CNS parenchyma (mainly thalamus), in connective tissue coverings (e.g. meninges, endoneurium), and in close apposition to peripheral nerve endings in a variety of tissues. There is, as yet, no clearly defined role for mast cells in nervous system function, or vice-versa, and it seems most likely that their interactions fulfil mutually modulatory roles. By extension, pathological situations where one of the partners in this relationship is overly stimulated may lead to a dysregulation of the other, and contribute to disease symptomatology.

Animals↗

PubMed1992

Astrocytes support mast cell viability in vitro.

Mast cells are normally found adjacent to blood vessels in the nervous system, and have been implicated in the development of inflammatory central nervous system (CNS) diseases such as experimental allergic encephalomyelitis. To further study mast cell-CNS interactions, we have developed a model in which viable rat peritoneal mast cells can be maintained in culture for up to 30 days on a monolayer of rat astrocytes. In this microenvironment, mast cells maintain their phenotype, morphology, and ability to degranulate in response to appropriate stimuli.

Animals↗

PubMed1992

"Tree-barking" of the ascending aorta. Syphilis or systemic lupus erythematosus?

A case of unsuspected classical aortitis with "tree-barking" of the ascending aorta in a young woman with systemic lupus erythematosus and inconclusive syphilitic serologic results is presented. At autopsy, no definite diagnostic clues as to syphilitic or lupic aortitis could be obtained. Although infrequent today, the possibility of complicated cardiovascular syphilis still should be considered. Involvement of the ascending aorta by other systemic diseases is well known and can imitate syphilitic aortitis. Although the possibility of two concomitant diseases cannot be ruled out, the young age of the patient, the weak syphilitic serologic result, and active systemic lupus erythematosus demonstrated in other organs favor a diagnosis of lupic aortitis of the ascending aorta.

Adolescent↗

PubMed1992

Biological actions of monoclonal luteinizing hormone/human chorionic gonadotropin receptor antibodies.

Several recent studies have elucidated the structure of the mammalian LH/hCG receptor; as reported in the present work, we have developed a series of monoclonal antibodies (mAbs) against the rat ovarian LH/hCG receptor using highly purified receptor as immunogen and by screening hybridomas with purified LH/hCG receptors. The mAbs were able to specifically immunoprecipitate LH/hCG receptors from solubilized preparations of rat ovarian membranes as well as from partially purified preparations. Western blotting with mAb P1B4 detected a probable receptor dimer and a receptor fragment in rat and porcine ovarian tissue but not in other tissues. This mAb also partially inhibited hCG binding to rat and porcine ovarian tissues. The receptor mAbs were able to inhibit hCG-induced progesterone synthesis in cultured human and porcine granulosa cells without affecting cAMP- and FSH-induced progesterone synthesis. The mAb P1B4 was used to demonstrate that the majority of ovarian receptors are internalized after hCG treatment and that in pseudopregnant rats receptors are present in the rough endoplasmic reticulum and in microvesicles. Bovine corpus luteal cells also contained P1B4 binding sites, as detected by immunohistochemical technique. Taken together, these results suggest that the mAbs are specific for the LH/hCG receptor, mAb P1B4 recognizes an epitope that is highly conserved among mammals, and this epitope is probably in the extracellular domain.

Animals↗

PubMed1992

Insufflated halothane increases venous admixture less than nitroprusside in canine atelectasis.

Although it generally is agreed that halothane is a pulmonary vasodilator, its effect on venous admixture and hypoxic pulmonary vasoconstriction are more controversial. The effects of 2.4% halothane on pulmonary vascular resistance and venous admixture were investigated in an isolated canine lobe made atelectatic. Halothane was administered by three different methods: insufflation, addition to the pulmonary artery blood through a bubble deoxygenator, or a combination of both techniques. Pulmonary vascular resistance was divided into arterial, venous, and middle segmental resistance by a vascular occlusion technique. Middle resistance increased with 3% O2 ventilation (0.0238 +/- 0.0092 cmH2O.ml-1.min-1) or after production of atelectasis (0.0225 +/- 0.0074 cmH2O.ml-1.min-1), compared to control ventilation in the nonatelectatic lung 0.01 +/- 0.0067 cmH2O.ml-1.min-1). Halothane by any delivery method variably decreased middle resistance, with increasing potency from addition of halothane through the bubble deoxygenator (0.0118 +/- 0.0047 cmH2O.ml-1.min-1) to halothane insufflation (0.0072 +/- 0.0058 cmH2O.ml-1.min-1), and finally to a combination of both techniques (0.0026 +/- 0.0041 cmH2O.ml-1.min-1). In contrast to vascular resistance, venous admixture in the atelectatic (8 +/- 5%) and nonatelectatic lobes (7 +/- 4%) was increased with halothane insufflation (11 +/- 4%), addition of halothane through the bubble deoxygenator (26 +/- 16%), and a combination of both techniques (22 +/- 13%). Compared to intravenous nitroprusside (26 +/- 12%), halothane insufflation was less potent in increasing venous admixture when total pulmonary vascular resistances were of similar magnitude (0.0526 +/- 0.0112 and 0.0484 +/- 0.0088 cmH2O.ml-1.min-1, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Detection of recurrent colon cancer with In-111 labeled MoAb B72.3 in a patient with normal CEA and TAG-72 levels.

The usefulness of radioimmunoscintigraphy with In-111 labeled MoAb B72.3 is illustrated in this case report of a patient with an aggressive cancer of the ascending colon. When used in conjunction with CT, ultrasound examination, and MRI, radioimmunoscintigraphy improved the specificity of these other imaging modalities, although the patient's serum CEA and TAG-72 levels remained within the normal ranges. In addition, MoAb imaging demonstrated superiority over CT in identifying an additional unsuspected lesion. Detection of occult disease by imaging modalities with or without elevated serum CEA levels is discussed.

Adult↗

PubMed1992

Prostacyclin (not nitroprusside) preserves venous admixture in the injured canine lung.

OBJECTIVE: To compare the effects of a prostaglandin vasodilator (prostaglandin I2 [PGI2]) with that of sodium nitroprusside in the isolated lung during 3% and 35% oxygen ventilation. BACKGROUND AND METHODS: Pulmonary vascular resistance was divided into arterial, middle, and venous segmental resistances. Left lower lobes were injured in a patchy (atelectasis) or diffuse (oleic acid-induced edema) manner. RESULTS: Nitroprusside diminished, but PGI2 ablated, the usual increase in middle segment resistance observed during 3% oxygen ventilation in atelectatic lobes. In the oleic acid-treated lobes, both nitroprusside and PGI2 ablated the increase in middle segment resistance during 3% oxygen ventilation. During nitroprusside administration, as pulmonary vascular resistance decreased, venous admixture proportionately increased, but this correlation was lost during PGI2 administration. CONCLUSIONS: We hypothesize that exogenous PGI2 dilates the vessels most constricted by hypoxia but to a lesser degree than does nitroprusside. Therefore, increases in venous admixture may be reduced during PGI2 administration, compared with nitroprusside administration.

Animals↗

PubMed1992

Benefits and obstacles of health status assessment in ambulatory settings. The clinician's point of view. The Dartmouth Primary Care COOP Project.

In the past decade physicians have identified the need to expand patient assessment to include global function and quality of life. During the same period, the busy clinic has evolved into the location where this assessment seems most appropriate. Integrating functional health assessment into a busy clinical practice is difficult because the necessary steps require time, thought, recording, and follow-up. Attention to the office ecosystem is very important before any patient care management method is introduced. The clinician must transform the results of health status screening into a specific functional diagnosis. The clinician has to understand the sensitivity, specificity, and predictive value of the measure for a preliminary diagnosis to be made. Often, additional measurements must be taken to establish a specific diagnosis. These steps encompass assessment linkage. Once the specific cause for the dysfunction is recognized, the clinician then has to determine the need for special resources. This is called the resource linkage. By following the steps outlined in this paper, the clinician should be able to overcome many obstacles for functional health status assessment in busy ambulatory settings.

Activities of Daily Living↗

PubMed1992

Gene expression during preimplantation mouse development.

To develop a resource for the identification and isolation of genes expressed in the early mammalian embryo, large and representative cDNA libraries were constructed from unfertilized eggs, and two-cell, eight-cell, and blastocyst-stage mouse embryos. Using these libraries, we now report the first stages at which the cytokines interleukin (IL)-6, IL-1 beta, and interferon (IFN)-gamma are transcribed in the developing embryo and the presence of IL-7 transcripts in the unfertilized egg. Transcripts for IL-1 alpha, -2, -3, -4, or -5 were not detected at these stages. To identify novel genes expressed on activation of the embryonic genome, the egg and eight-cell stage-specific cDNA libraries were subtracted from the two-cell library, yielding a specialized cDNA library enriched for transcripts expressed at the two-cell stage. Sequence and Southern blot analysis of several of these cDNAs expressed predominantly at the two-cell stage of embryogenesis revealed them to be from novel genes, thereby providing the first molecular tools with which to approach the study of gene expression in the early mammalian embryo.

Animals↗

PubMed1992

Histochemical and morphometric studies of peripheral muscle in bovine progressive degenerative myeloencephalopathy of brown Swiss cattle.

Histochemical and morphometric analysis of selected skeletal muscles was performed on 14 pure bred, Brown Swiss cattle. Nine cattle were clinically affected with bovine progressive degenerative myeloencephalopathy (BPDME) while five served as controls. Statistically significant trend differences were not observed for the parameters of mean cross sectional area, and mean fiber type percentages for types, I, IIA, and IIB fibers between affected and control test groups. In general, patterns of hypertrophy or atrophy, fiber type grouping, fiber type predominance, or fiber cross sectional profile alteration were not observed in the muscles examined from affected cattle. The findings suggest that BPDME, or weaver syndrome, is not a muscular dystrophy and that muscle pathology is not a primary part of the syndrome nor would muscle pathology be expected to contribute significantly to the clinical signs of the disease.

Animals↗