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Biomedical subjects

D M Williams

Publications and source records attributed to D M Williams.

At least 307 records · Page 17Linked to original sources

Effects of repetition on short-term retention of order information.

Two experiments examined the effects of repetition on the short-term retention of order information. A partial report procedure was coupled with the distractor paradigm to vary which one of two 4-letter sequences was tested after a digit-filled retention interval. Repeatedly presenting the stimulus but not its testing did not increase recall, but recall did increase when both presentation and testing were repeated. Recall was also improved by precues that informed subjects in advance which sequence was to be recalled. The perturbation model of Estes (1972; Lee & Estes, 1981) was able to account for the qualitative and quantitative aspects of the results by making an explicit distinction between two types of rehearsal: the reactivation process, which corresponds to a passive, automatic rehearsal process; and an active, conscious rehearsal process that crystallizes the memory structure and makes perturbations less likely.

Adult↗

Lithium carbonate treatment in familial cyclic neutropenia.

A patient with previously documented cyclic neutropenia was followed for 48 days on no treatment. Blood counts obtained at 3-day intervals confirmed the presence of cyclic neutropenia with virtually complete disappearance of neutrophils at the nadir of cycles with a periodicity of 21 days. Lithium carbonate treatment was begun on day 49. Serum lithium levels remained in the therapeutic range throughout the study interval of 58 days. Periodicity and depth of neutropenia were not diminished during the study period.

Adult↗

Cellular immunity to the mouse pneumonitis agent.

During infection with the mouse pneumonitis biovar of Chlamydia trachomatis, heterozygous (nu/+) mice with relatively intact T cell function develop both delayed hypersensitivity to C trachomatis antigen and antigen-specific lymphocyte transformation, whereas athymic nude (nu/nu) mice do not. Nu/nu mice are protected against death from mouse pneumonitis by transfer of immune T cells from nu/+ mice, which are more resistant to C trachomatis. While this enables athymic mice to make antibody to C trachomatis (which does not occur without reconstitution), resistance correlates best with development of antigen-specific lymphocyte transformation in the recipient animals. During infection nu/+ mice develop activated alveolar macrophages (by both morphological and functional criteria) while nu/nu mice do not. Nu/+ mice that have been preinfected with Histoplasma capsulatum to activate cellular immunity become more resistant to C trachomatis than do nu/+ controls. Cell-mediated immunity to C trachomatis pneumonia is T cell dependent and is important in host defense.

Animals↗

The relationship between linear IgA disease and benign mucous membrane pemphigoid.

Nine out of thirty-four patients with linear IgA disease (LAD) had oral ulceration. Four out of seven of these patients who were examined by an ophthalmologist had changes of a cicatrising conjunctivitis indistinguishable from those of benign mucous membrane pemphigoid (BMMP). Three of these patients gave no history of ocular symptoms up to the time of examination. These findings indicate a need for oral and ophthalmological assessment in all patients with LAD. Twenty-seven patients with a diagnosis of BMMP were also studied. Nine presented with oral symptoms alone, nine with ocular symptoms alone, seven with oral and ocular symptoms, and two with cutaneous lesions in addition to oral and ocular symptoms. All the patients were examined by the same ophthalmologist. Six of the nine patients who presented with oral symptoms alone had signs of a cicatrising conjunctivitis. Four of these six patients had the clinical pattern of erosive gingivitis which was not previously thought to be associated with a cicatrising conjunctivitis. There is a similar need, therefore, for an ophthalmological assessment in all patients presenting with oral BMMP. Three of the twenty-seven patients with BMMP had homogeneous-linear deposits of IgA in uninvolved skin. The finding of linear IgA deposits in the skin of these patients with only mucous membrane lesions, and the finding that patients with LAD have a high incidence of oral and conjunctival lesions, raise the possibility of a common pathogenic pathway but with varying clinical expressions in these two groups.

Adult↗

Antibody in host defense against mouse pneumonitis agent (murine Chlamydia trachomatis).

In a murine model of chlamydial pneumonia employing murine Chlamydia trachomatis, immune serum given intranasally delayed death in nude (nu/nu) mice and prevented death in nu/+ mice. Serum-derived immunoglobulin G and A fractions and immune lavage fluid fractions containing immunoglobulins G and A were effective in producing protection when used to opsonize the murine C. trachomatis inoculum. In hyperclean mice (previously made germfree and then colonized with a limited flora nonpathogenic to mice) antibody given intravenously was ineffective. The effects of antibody and nonspecific stimulation of cell-mediated immunity (after previous infection with Histoplasma capsulatum) were additive in increasing host resistance to murine C. trachomatis.

Animals↗

Regulatory regions that control expression of two chloramphenicol-inducible cat genes cloned in Bacillus subtilis.

Plasmid pPL603 is a promoter cloning vector for Bacillus subtilis and consists of a 1.1-kilobase fragment of Bacillus pumilus DNA inserted between the EcoRI and BamHI sites of pUB110. The gene cat-86, specifying chloramphenicol-inducible chloramphenicol acetyltransferase, is located on the 1.1-kilobase cloned DNA. When pPL603 is present in B. subtilis, cat-86 is unexpressed during vegetative growth but expressed during sporulation. The regulation of cat-86 in pPL603 is due to sequences within two restriction fragments, designated P1 and R1, that precede the main coding portion of the gene. The P1 fragment promotes transcription of cat-86 only during sporulation, whereas the adjacent R1 fragment lacks promoter function but contains sequences essential to chloramphenicol inducibility. A second B. pumilus gene, cat-66, was cloned in B. subtilis and is expressed throughout the vegetative growth and sporulation cycle. The cat-66 coding region is preceded by two adjacent restriction fragments designated as P2 and R2. P1 and P2 are identical in size and share 95% conservation of base sequence. R1 and R2 are also identical in size and share 91% conservation of base sequence. Fragment substitution experiments demonstrate that R2 can functionally replace R1. The substitution of P2 for P1 promotes cat-86 expression throughout vegetative growth and sporulation. Analysis of a derivative of pPL603 in which P2 has replaced P1 demonstrates that P2 promotes transcription of cat-86 during vegetative growth and that P2 contains the start site for transcription of cat-86. Thus, P1 and P2 differ strikingly in vegetative promoter function, yet they differ by single-base substitutions at only 11 positions of 203.

Bacillus subtilis↗

Ossification in the cephalic attachment of the ligamentum flavum. An anatomical and CT study.

A review of 50 anatomical specimens and 100 routine CT scans of the chest and abdomen demonstrated that ossification in the cephalic attachment of the ligamentum flavum is a common anatomical finding, but not as common on CT. Examination of hospital charts and plain radiographs of 26 patients with such ossification suggests that it is probably a normal variant; there was no evidence that it is related to diffuse idiopathic skeletal hyperostosis (DISH) or inflammatory arthropathy. Marked ossification may cause or contribute to neurological symptoms.

Adolescent↗

Transcatheter embolization with sodium tetradecyl sulfate. Experimental and clinical results.

Sodium tetradecyl sulfate (Sotradecol), which has been employed for sclerotherapy of varicose veins, was evaluated in dogs and humans as an agent for selective arterial embolization. In dogs, intraarterial injection of Sotradecol 3% into the proximally occluded renal, hepatic, splenic, and deep femoral arteries produced arterial occlusion and tissue destruction. Transcatheter embolization with Sotradecol was performed in 11 patients and was successful in 10; in the remaining patient, failure was attributed to rapid dilution by unobstructed blood flow in arteriovenous malformations of the neck. The authors conclude that Sotradecol is a safe and efficient agent for selective arterial embolization.

Adenocarcinoma↗

Venous involvement in islet cell tumors of the pancreas.

Peripancreatic venous abnormalities were demonstrated angiographically in 10 patients with islet cell tumor: six nonfunctioning, two gastrin-producing, one glucagon-producing, and one pancreatic polypeptide-producing. Venous involvement recognized included venous occlusion, venous encasement, and intraportal tumor growth. Seven patients had islet cell carcinoma with hepatic metastases while the other three had benign tumors. Three patients had arteriographic evidence of intraportal tumor growth with the "thread and streaks" sign, similar to that of portal venous extension of hepatocellular carcinoma.

Adenoma, Islet Cell↗

Enhanced expression of mouse dihydrofolate reductase in Bacillus subtilis.

pPL608-TR1 is a high-copy plasmid that permits phenotypic expression of the mouse dihydrofolate reductase (DHFR) gene in Bacillus subtilis. A plasmid mutation has been identified that increases expression of mouse DHFR more than ten-fold. The mutation is located in a 0.2-kb segment that intervenes between the DHFR gene and the 0.3-kb promoter fragment needed for transcriptional activation of DHFR. Nucleotide sequence analysis suggests that the effect of the mutation is to facilitate translation, initiated within the promoter fragment, through the 0.2-kb segment to the site of insertion of the DHFR-containing fragment. Additional promoter-containing fragments selected by their ability to promote expression of a plasmid gene located downstream from DHFR, the CAT gene, promote either high, intermediate or no phenotypic expression of DHFR. The results indicate that promoter fragments that allow phenotypic expression of the mouse DHFR gene contain two regulatory signals. One signal is essential to transcription of both DHFR and CAT and therefore functions as a promoter. The second signal may be necessary for translation of that portion of the mRNA specifying mouse DHFR.

Animals↗

Nucleotide sequence of a Bacillus pumilus gene specifying chloramphenicol acetyltransferase.

Gene cat-86 of Bacillus pumilus, specifying chloramphenicol-inducible chloramphenicol acetyltransferase, was previously cloned in Bacillus subtilis on plasmid pUB110. The nucleotide sequence of cat-86 indicates that the gene encodes a protein of 220 amino acids and contains TTG as the translations-initiation codon. The proteins specified by cat-86 and the cat genes present on pC194, pC221 and Tn9 appear to share regions of amino acid sequence similarity. cat-86 is a structural gene on the B. subtilis expression plasmid pPL608. Restriction sites exist within the gene that should permit the product of inserted heterologous coding sequences to be synthesized in B. subtilis as fusion proteins.

Acetyltransferases↗

Chloramphenicol-inducible gene expression in Bacillus subtilis.

A cloned Bacillus pumilus cat gene expresses chloramphenicol-inducible chloramphenicol acetyltransferase activity in Bacillus subtilis. The chloramphenicol inducibility trait was shown to be determined by a 234-bp region of the cloned DNA. Nucleotide sequence analysis of this 234-bp segment indicated that the cat ribosome-binding site occurs within a 40-bp region containing 14-bp terminal inverted repeat sequences. Transcription of this region into RNA should sequester the cat ribosome-binding site in a stable stem-loop conformation. Chloramphenicol-mediated destabilization of the stem-loop is suggested as the basis for the chloramphenicol inducibility phenotype.

Acetyltransferases↗

Hepatic iron accumulation in copper-deficient rats.

Studies of anaemia and tissue iron distribution were carried out in copper-deficient rats and pair-fed control animals given Fe orally or parenterally in varying doses. The anaemia of Cu deficiency was partially but incompletely corrected by oral Fe supplementation of one- to five-fold normal dietary levels or by intramuscular Fe supplementation. Serum Fe increased in Cu-deficient animals as the dose of supplemental Fe was increased. Hepatic Fe accumulation occurred in Cu-deficient rats which were administered with either oral Fe in two- to five-fold excess or low doses of intramuscular Fe. This difference was not seen in animals receiving high doses of intramuscular Fe, but similar relative differences were seen in Cu-deficient and Cu-replete rats which had been given no Fe supplementation. Duodenal Fe was not increased in Cu deficiency. Bone marrow Fe was present in Cu-deficient animals receiving either parenteral or oral Fe supplementation. Present studies suggest that a decrease in caeruloplasmin (EC 1.16.3.1) activity does not wholly explain the anaemia of Cu deficiency. Fe accumulation may be restricted to the liver, suggesting that Cu may be required for normal intracellular Fe metabolism.

Administration, Oral↗

Copper deficiency in humans.

Copper is an essential trace element that is required for a number of enzymes which are necessary for normal metabolic function. Metabolic balance studies have demonstrated that daily copper losses are approximately 1.3 mg/day. In order to remain in copper balance, the average adult male must consume a diet which contains at least 2 mg copper/day. It has been assumed that most diets satisfy this requirement because of the ubiquitous presence of copper in most foodstuffs. Recent studies, however, have shown that dietary copper may often fall below the estimated daily needs. Nevertheless, clinically evident copper deficiency has been documented in only a few situations. Of these disorders. Menkes' syndrome has been most intensively studied. This x-linked abnormality is associated with copper deficiency due to impaired gastrointestinal copper absorption. However, the clinical disorder cannot be corrected readily with copper replacement, thus suggesting that Menkes' syndrome may reflect more than simple copper deficiency. Nutritional copper deficiency appears to be well documented in two situations: (1) the newborn, usually premature, undergoing rapid growth on a diet poor in copper, and (2) the patient maintained on total parenteral nutrition for long periods of time without copper supplementation. In both of these situations, anemia and neutropenia are the most striking hematologic abnormalities associated with copper deficiency. Sideroblastic changes as well as nuclear maturation defects observed in erythroid precursors. However, suggest that there is an effect of copper deficiency on the hematopoietic system which cannot be explained solely by defective plasma iron transport.

Adolescent↗

Kinetics of osteoclast formation: the significance of blood monocytes as osteoclast precursors during 1 alpha-hydroxycholecalciferol-stimulated bone resorption in the mouse.

The significance of blood monocytes as a source of osteoclast precursors was investigated during 1 alpha-hydroxycholecalciferol-stimulated bone resorption in mice. Animals were given three injections of tritiated thymidine at 8 hourly intervals in order to label blood monocytes. The proportion of labelled monocytes was then compared with the proportion of labelled nuclei in osteoclasts, the formation of which was provoked by daily injections of 1 alpha-hydroxycholecalciferol, beginning 48 hours after the first injection of isotope. Although more than 60% of blood monocytes were labelled during the period of peak osteoclast formation, labelling of osteoclast nuclei in the metaphyseal endosteum of the femur never exceeded 8%. These results suggest strongly that the majority of osteoclast nuclei were derived from a source of unlabelled precursors, and that very few osteoclasts were derived directly from blood monocytes. Although few labelled osteoclasts were found, the proportion of labelled spindle shaped cells in the metaphyseal endosteum rose gradually to 16%. It is likely, therefore, that labelled mononuclear cells, possibly blood monocytes, were attracted to the endosteum where they formed a population of tissue macrophages. At this site they may participate in bone resorption, either individually or by providing a local pool of osteoclast precursors.

Animals↗