Biomedical subjects
B Howard
Publications and source records attributed to B Howard.
Positive chlamydial serology and its effect on factors influencing outcome of IVF treatment.
A retrospective study of 98 IVF treatment cycles from 49 couples has assessed the relationship between presence of antibodies to Chlamydia trachomatis and success with respect to fertilization, cleavage and pregnancy rate, both at nidation and term. No effect of prior infection on IVF outcome was noted.
Words and images in the time of AIDS.
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Nucleotide sequence of the trout metallothionein A gene 5' regulatory region.
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Evaluation of the accuracy of the home ovulation detection kit, Clearplan, at predicting ovulation.
A home ovulation testing kit, Clearplan, that detects the urinary luteinizing hormone (LH) surge was compared with basal body temperature (BBT) charts and cervical scoring as a method of ovulation prediction in 54 consecutive patients. The accuracy of all these methods was evaluated using daily serum LH measurements. Clearplan was shown to be significantly more accurate at timing ovulation than were BBT charts (P less than 0.0001) and cervical scoring (P less than 0.025). In 82%-88% of cases the kit predicted ovulation within one day and in 89%-96% of cases within two days of the serum LH surge. The kits were found to be easy to use and their potential place in clinical practice is discussed; home ovulation testing may ultimately replace serum LH assays as the method of choice in timing ovulation.
Antiproton annihilation at rest in nitrogen and deuterium gas.
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AHA Conference Report on Cholesterol. Basis for dietary treatment.
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Bacteria-lectin interactions in phytohemagglutinin-induced bacterial overgrowth of the small intestine.
The mechanism of phytohemagglutinin-induced bacterial overgrowth of the small bowel in the rat was studied. Interaction of the lectin with bacterial isolates selected at random from those that comprised the major population of the overgrowth was determined. In both bacterial agglutination assays and glycocalyx stabilization, no specific association between lectin and bacteria was seen. In three independent binding assays phytohemagglutinin was not found to increase bacterial adherence to washed intestinal mucosa. Phytohemagglutinin would not appear to act, therefore, as a direct ligand to mediate bacterial adherence or to modify the mucosal surface to increase bacterial adherence.
Spontaneous osteonecrosis of the tarsal navicular in adults: imaging findings.
We encountered five otherwise healthy adults with alterations of the tarsal navicular bone compatible with spontaneous osteonecrosis. Four women had bilateral involvement and one man had unilateral involvement. The patients were 23-71 years old. The disorder was initially described by Mueller and Weiss and should not be confused with Koehler disease (osteochondrosis of the tarsal navicular in children). This group of patients was compared with five other patients (29-74 years old) with similar radiographic and clinical changes in whom an underlying disease (rheumatoid arthritis, renal failure, trauma, and lupus erythematosus) associated with osteonecrosis was known. Routine radiography in both groups defined characteristic abnormalities of the navicular bone (decreased size, a comma-shaped configuration, increased radiodensity, fragmentation, and medial or medial and dorsal osseous protrusion). MR in three patients confirmed alterations consistent with osteonecrosis. Three of the patients without underlying disease had bilateral involvement on plain films, with flat feet and hindfoot valgus deformity, leading to local pain and deformity. In a fourth patient, bilateral distribution was documented by MR as marrow alterations. Although no certain pathogenic explanation for spontaneous osteonecrosis of the tarsal navicular is known, trauma and chronic stress changes caused by physiologic pressure on the medial longitudinal arch in hindfoot valgus and increased tension forces of the plantar aponeurosis during weight-bearing (in pes planus) may be important. Discrimination of primary from secondary osteonecrosis of the tarsal navicular bone is not possible by radiologic means alone, although bilateral distribution, particularly in women, favors the diagnosis of spontaneous disease.
Septic arthritis.
Infectious arthritis is a commonly encountered clinical problem which may result from articular contamination by a wide variety of organisms. Involvement of an articulation may occur by one of four mechanisms: hematogenous spread, spread from a contiguous source of infection, direct implantation, or postoperative contamination. Distribution is typically monoarticular with a swollen, erythematous, and painful joint. The radiographic differential diagnosis includes limited rheumatoid arthritis, gout, synovial osteochondromatosis, and pigmented villonodular synovitis. In order to prevent complications, including growth disturbances, articular destruction with ankylosis, osteomyelitis, or soft tissue extension, early diagnostic arthrocentesis is important. Radiographic abnormalities, which include soft tissue swelling, joint space loss, periarticular osteopenia, and central or marginal osseous erosions, may be delayed following clinical onset of infection. Advanced imaging techniques such as scintigraphy, CT, or MRI may allow accurate diagnosis of the infectious process at an earlier stage.
Arthrography, tenography, and bursography of the ankle and foot.
A brief description of normal anatomy and common arthrographic, tenographic, and bursographic procedures is presented. The described procedures are important diagnostic tools and do not carry major risk. Therefore, these procedures can be performed on an outpatient basis.
Primary rat embryo cells transformed by one or two oncogenes show different metastatic potentials.
Second-passage rat embryo cells were transfected with a neomycin resistance gene and the activated form of the c-Ha-ras I gene, or with these two genes plus the adenovirus type 2 E1a gene. Foci of morphologically transformed cells were observed in both cases; however, the frequency of transformation was at least ten times higher with two oncogenes than with the ras gene alone. All the transformed cell lines gave rise to rapidly growing tumors when injected subcutaneously into nude mice. All but one of the cell lines transformed by the ras oncogene alone formed metastatic nodules in the lungs of animals that had been injected subcutaneously with transformed cells. When transformed cells were injected intravenously, all the ras single-gene transformants gave rise to many metastatic lung nodules. In contrast, cell lines transformed with ras and E1a did not generate metastases after subcutaneous injection and gave rise to very few metastatic lung nodules after intravenous injection. These data demonstrate that a fully malignant cell with metastatic potential, as measured in an immunodeficient animal, can be obtained from early passage embryo cells by the transfection of the ras oncogene alone.
The 5'-flanking sequences of human globin genes contribute to tissue specific expression.
The specificity of expression of the isolated 5'-flanking sequences of the human beta- and epsilon-globin genes was examined in the K562 human erythroleukemia cell line, the murine erythroleukemia (MEL) cell, and in nonerythroid cell lines CV-1, HeLa-S3, and WI-38. Globin flanking sequences were active only in the erythroid K562 and MEL cell lines. Furthermore, the upstream sequence of the adult, beta-globin gene was active in MEL cells which express adult globin and not in K562 cells which express embryonic and fetal globins suggesting that tissue specificity resides in these upstream sequences. No expression was observed in K562 cells which have an embryonic-fetal hemoglobin phenotype.
Minichromosome assembly of non-integrated plasmid DNA transfected into mammalian cells.
The nucleoprotein structures formed on various plasmid expression vectors transfected into mammalian cells by both the calcium phosphate and DEAE-dextran methods have been studied. We demonstrate by a variety of means that mammalian cells are capable of rapidly assembling non-integrated circular plasmids (both replicating and non-replicating) into typical "minichromosomes" containing nucleosomes with a 190 bp repetitive spacing. Treatment of recipient cells with sodium butyrate for a short period of time (12-16 h) immediately following transfection markedly increased the DNase I digestion sensitivity of the newly assembled plasmid chromatin. Furthermore, minichromosomes isolated from such butyrate-treated cells are depleted in histone H1 and contain highly acetylated forms of histone H4. These findings are entirely consistent with our earlier speculation (Gorman et al., Nucleic Acids Res. 11, 1044; 1983) that appropriate butyrate treatment might stimulate transient expression of newly transfected genes by facilitating their assembly into an "active" type of chromatin structure.
Metabolism of ingested U and Ra.
The literature on metabolism of U and Ra for man relevant to deriving drinking water standards has been reviewed and summarized. Radium is well understood, but significant gaps remain in our knowledge about U metabolism. Limits should be based on an equilibrium model where a constant relationship between intake and organ burden is established, using the best and most likely metabolic parameters. For the skeleton we conclude that the best estimate of skeletal burden expressed in days equivalent intake are 25 days for 226Ra, 10 days for 228Ra, and 0.3 days for 224Ra. For long-lived isotopes of U, we chose 11 days, with a range between 1 and 35 days. The committee believes that intake of natural U in water should be limited by considerations of toxicity to the kidney, and we believe that the metabolic model of Spoor and Hursh with a modified gastrointestinal (GI) absorption (1.4%) should be used to infer kidney content. Our review and analysis of the world literature leads us to believe the average human GI absorption of U is most likely 1-2% and is probably reasonably independent of age or the mass of U ingested. Using a safety factor of 50-150, the committee recommends a limit of U in water of 100 micrograms/l in order to limit toxic effects in the kidney. One hundred micrograms/liter is equivalent to 67 pCi/l of long-lived alpha-emitting natural U isotopes. Further research into the distribution of U in the human body is desirable, especially at natural levels in kidney and skeleton, the time-dependent pharmacokinetics of U in animals, the GI absorption of U in man from water and food, toxicological and U distribution studies in animals under conditions of chronic oral U intake, and metabolic model error propagation.
In vivo incorporation of Drosophila H2a histone into mammalian chromatin.
Hybrid prokaryotic/eukaryotic expression vectors have been used to introduce Drosophila histone genes into CV-1 African green monkey tissue culture cells. Transfection of CV-1 cells with Drosophila genes under the control of insect DNA promoter sequences results in low level expression of histone genes. On the other hand, when the Drosophila H2a gene is juxtaposed downstream from the long terminal repeat sequence of Rous sarcoma virus (RSV) expression of the insect gene is considerably more efficient; both 3' polyadenylated insect histone messenger RNA and putative Drosophila H2a histone protein can be readily detected in the transduced cells. Using this RSV/H2a vector, we have been able to demonstrate the presence of Drosophila H2a histone in monomer nucleosome preparations isolated from transfected CV-1 cells. These results suggest the feasibility of 'remodeling' cellular chromatin in vivo in precisely defined ways. The techniques described may be generally applicable to other genes coding for chromosomal proteins.
Host-specific activation of transcription by tandem repeats from simian virus 40 and Moloney murine sarcoma virus.
The simian virus (SV40) 72-base pair (bp) tandem repeated sequences have recently been shown to function as activators or enhancers of early viral transcription. A recombinant viral genome was recently constructed by inserting 72-bp tandem repeats from the Moloney murine sarcoma virus (MSV) in place of the 72-bp repeats of SV40. Although this genome replicates in monkey kidney cells, its rate of large tumor antigen expression and replication is considerably slower than that of wild-type SV40. In mouse cells, however, equivalent levels of large tumor antigen appear to be expressed from both wild-type and recombinant genomes, suggesting a relationship between the level of enhancer activity and the host cell. To confirm this observation, we have applied a sensitive quantitative assay for gene expression based on the conversion of chloramphenicol to its acetylated forms. The gene encoding the enzymatic function chloramphenicol acetyltransferase was inserted into two vectors in which the enhancer sequences from SV40 or MSV were placed adjacent to the early SV40 promoter. The SV40 tandem repeats appear to activate gene expression to significantly higher levels in monkey kidney cells, but the MSV repeats are more active in two lines of mouse cells. These findings suggest that the tandem repeat elements may interact with host-specific molecules and, furthermore, may constitute one of the elements determining the host range of these eukaryotic viruses.
Report of the topic study group on graduate education in medical technology.
The reported study indicates that individuals are motivated for personal reasons to obtain advanced education. Tangible benefits of more challenging employment opportunities and greater financial rewards were achieved by some of the respondents. There is apparently a deficiency in financial support of graduate education for this group of health professionals because many of the individuals reported attending graduate school on a part-time basis. However, it is possible that some part-time students elected this route to keep in contact with current laboratory practice. In addition, the external degree program was a welcome and only possible route for one-fifth of the sample. A tendency to be interested in leaving the health field is noted with concern.